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Alessandro BERTACCHINI

Ricercatore Universitario
Dipartimento di Scienze e Metodi dell'Ingegneria

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Pubblicazioni

2024 - Pre-processing techniques to enhance the classification of lung sounds based on deep learning [Articolo su rivista]
Fava, Alessandra; Dianat, Behnood; Bertacchini, Alessandro; Manfredi, Andreina; Sebastiani, Marco; Modena, Marco; Pancaldi, Fabrizio
abstract

2023 - An IoT Toolchain Architecture for Planning, Running and Managing a Complete Condition Monitoring Scenario [Articolo su rivista]
Montori, Federico; Zyrianoff, Ivan; Gigli, Lorenzo; Calvio, Alessandro; Venanzi, Riccardo; Sindaco, Simone; Sciullo, Luca; Zonzini, Federica; Zauli, Matteo; Testoni, Nicola; Bertacchini, Alessandro; Londero, Elisa; Alessi, Enrico; Felice, Marco Di; Bononi, Luciano; Bellavista, Paolo; De Marchi, Luca; Marzani, Alessandro; Azzoni, Paolo; Cinotti, Tullio Salmon
abstract

Condition Monitoring (CM) is an extremely critical application of the Internet of Things (IoT) within Industry 4.0 and Smart City scenarios, especially following the recent energy crisis. CM aims to monitor the status of a physical appliance over time and in real time in order to react promptly when anomalies are detected, as well as perform predictive maintenance tasks. Current deployments suffer from both interoperability and management issues within their engineering process at all phases – from their design to their deployment, to their management –, often requiring human intervention. Furthermore, the fragmentation of the IoT landscape and the heterogeneity of IoT solutions hinder a seamless onboarding process of legacy devices and systems. In this paper, we tackle these problems by first proposing an architecture for CM based on both abstraction layers and toolchains, i.e., automated pipelines of engineering tools aimed at supporting the engineering process. In particular, we introduce four different toolchains, each of them dedicated to a well-defined task (e.g., energy monitoring). This orthogonal separation of concerns aims to simplify both the understanding of a complex ecosystem and the accomplishment of independent tasks. We then illustrate our implementation of a complete CM system that follows said architecture as a real Structural Health Monitoring (SHM) pilot of the Arrowhead Tools project, by describing in detail every single tool that we developed. We finally show how our pilot achieves the main objectives of the project: the reduction of engineering costs, the integration of legacy systems, and the interoperability with IoT frameworks.

2023 - Combined Effects of Different LED Light Recipes and Slow-Release Fertilizers on Baby Leaf Lettuce Growth for Vertical Farming: Modeling through DoE [Articolo su rivista]
Barbieri, Francesco; Barbi, Silvia; Bertacchini, Alessandro; Montorsi, Monia
abstract

The modern agriculture system based on open-field crops requires a lot of energy and resources in terms of soil, water, and chemicals. Vertical farming (VF) systems could be a viable alternative for some types of cultivation that are receiving interest thanks to their high modularity, optimized water and nutrients use, and LEDs employment as an energy-efficient light source. However, VF design and installation are expensive and require well-tailored optimization depending on the specific crop to increase its competitiveness. This work analyzed the effects of different combinations of NPK (nitrogen-phosphorus-potassium) slow-release fertilizers and LED-based light recipes on the growth of baby leaf lettuce (Lactuca sativa L.), taking advantage of the Design of Experiments (DoE) methodology. The type of slow-release fertilizer, its quantity measured as the number of aggregates from 0 to 6, and the type of light recipe were considered as input factors, and their possible influence on the growth of lettuce (in terms of morphological parameters) in a controlled indoor farming system was measured. Results suggest that using higher fertilizer inputs equal to six aggregates leads to an increase of average leaf area equal to 46% (from 13.00 cm2 to 19.00 cm2), while the fresh weight of lettuce increases by 65% (from 1.79 g to 2.96 g). However, the height of plants also depends on the combination of the light recipes. In particular, the separate coupling of higher inputs of two fertilizers and light recipes leads to an increase in the height of lettuce equal to 33% (from 6.00 cm to 8.00 cm).

2023 - Design-Time Tool for Energy Harvesting Applications [Capitolo/Saggio]
Bertacchini, A.; Ricci, Y.
abstract

A Matlab-LTSpice based tool is presented in this paper. It has been developed to help the designer to add Energy Harvesting (EH) capabilities to a generic electronic device that is being developed. The realized easy-to-use tool allows to quick evaluate several EH solutions at design time, contributing to considerably reduce both design time and costs because no hardware prototypes are needed. The tool is based on a set of pre-designed EH circuits covering all the main EH sources available in industrial applications (i.e. light, thermal gradients and vibrations) and drives the designer in the choice of the most suitable one accordingly with both the estimated environmental working conditions and the estimated power consumption profile of the specific electronic device that is being developed.

2023 - Quantitative Calculation of the Most Efficient LED Light Combinations at Specific Growth Stages for Basil Indoor Horticulture: Modeling through Design of Experiments [Articolo su rivista]
Barbi, Silvia; Barbieri, Francesco; Taurino, Claudia GERARDO; Bertacchini, Alessandro; Montorsi, Monia
abstract

Indoor farms are a promising way to obtain vegetables in standard quantity and quality. As opposed to previous studies, this study attempts to calculate optimized LED light conditions for different growth stages (five-days time step) of basil (Ocimum basilicum) to enhance its indoor growth through a statistical approach. Design of Experiments (DoE) was used to plan a limited number of experiments (20) and to calculate quantitatively the effect of different light recipes on four responses: the number of plants, their height, the Leaf Area Index, and the amount of water used. Different proportions (from 25% to 77%) of Hyper Red (660 nm) and Deep Blue (451 nm), intensities in terms of LEDs–plant distance (60, 70 and 80 cm), and the addition of Warm White (3000 K) LEDs were considered as independent variables. The obtained models suggest that a light recipe tailored for every growth step in the plant’s life is beneficial. Appropriate LEDs must be carefully chosen at the beginning of growth, whereas distance becomes relevant at the end. This is confirmed by the results analysis carried out at the end of an additional growth test where the optimal light recipe extracted from the DoE’s results were used.

2022 - Effects of Different LED Light Recipes and NPK Fertilizers on Basil Cultivation for Automated and Integrated Horticulture Methods [Capitolo/Saggio]
Barbi, Silvia; Barbieri, Francesco; Bertacchini, Alessandro; Barbieri, Luisa; Montorsi, Monia
abstract

2022 - Statistical Optimization of a Hyper Red, Deep Blue, and White LEDs Light Combination for Controlled Basil Horticulture [Capitolo/Saggio]
Barbi, Silvia; Barbieri, Francesco; Bertacchini, Alessandro; Montorsi, Monia
abstract

2022 - Suitability of Porous Inorganic Materials from Industrial Residues and Bioproducts for Use in Horticulture: A Multidisciplinary Approach [Articolo su rivista]
Righi, Claudia; Barbieri, Francesco; Sgarbi, Elisabetta; Maistrello, Lara; Bertacchini, Alessandro; Andreola, Nora Maria; D’Angelo, Antonio; Catauro, Michelina; Barbieri, Luisa
abstract

This study follows a circular economy approach through the preliminary implementation of a coated porous inorganic material (PIM), studied as sustainable controlled release fertilizer, and its application for lettuce Lactuca sativa L. cultivar Chiara growth. The PIM was made of pumice scraps that partially replaced clay as a natural raw material, spent coffee grounds as a porous agent, bovine bone ash and potassium carbonate to provide phosphorus (P) and potassium (K) nutrients, respectively. A coating made with defatted black soldier fly prepupae biomass was used as a nitrogen (N) source. Most of the ingredients used were industrial residues, with the aim of valorizing the raw waste materials present locally. The suitability of PIMs as a fertilizer was investigated with an interdisciplinary approach, which included the first chemical and physical characterization of the material, the evaluation of its antibacterial properties and of its use in horticulture through lettuce growth tests. As tests were carried out indoors, a specific LED lighting device was used to grow the lettuce. The release of nutrients into the soil was estimated by measuring the main elements in the fertilizers before and after their use in the soil. The first results from this characterization study support PIMs’ suitability for agronomic applications. The use of the PIMs suggested average higher dry weight (49%), fresh weight (112%), and leaf area (48%), compared to those with the use of a standard fertilizer soil, without the release of any dangerous element for the plant in the soil. These results are a promising beginning for the development of further studies already in progress on sustainable controlled-release fertilizers.

2021 - A simple multiparametric analysis to guide, compare and optimize the design of 'lensless' LED illuminators [Relazione in Atti di Convegno]
Cattini, S.; Pancaldi, F.; Bertacchini, A.; Parmeggiani, A.
abstract

LED lighting is becoming increasingly pervasive in many areas ranging from ambient lighting, up to applications such as microscope illumination, UV-LED curing and, UV disinfection for air, surfaces, and water. Irradiance uniformity is often a fundamental parameter for guiding the design, comparison, and optimization of the illuminator. To this end, many methods and procedures have been proposed to guide the arrangement of the LED sources, as well as to guide the design of ad-hoc lenses. Nevertheless, there are many applications in which it is important to be able to consider other aspects as well as the uniformity of the irradiance. For this purpose, we propose both a method that allows calculating the irradiance generated by the used LED sources and, performance indicators for guiding the design and comparing different optical layouts.

2021 - Effects of Different LED Light Recipes and NPK Fertilizers on Basil Cultivation for Automated and Integrated Horticulture Methods [Articolo su rivista]
Barbi, Silvia; Barbieri, Francesco; Bertacchini, Alessandro; Barbieri, Luisa; Montorsi, Monia
abstract

This study aims to optimize the conditions for “Genovese” basil (Ocimum Basilicum) germination and growth in an indoor environment suitable for horticulture through a synergic effect of light and fertilizers addition. In fact, several studies determined that specific light conditions are capable of enhancing basil growth, but this effect is highly dependent on the environmental conditions. In this study, the effect of different light sources was determined employing a soil with a negligible amount of fertilizer, demonstrating substantial improvement when light-emitting diode (LED) lights (hyper red and deep blue in different combinations) were applied with respect to daylight (Plants height: +30%, Total fresh mass: +50%). Thereafter, a design of experiment approach has been implemented to calculate the specific combination of LED lights and fertilizer useful to optimize the basil growth. A controlled-release fertilizer based on nitrogen, phosphorus, and potassium (NPK) derived from agro-residues was compared with a soil enriched in macronutrients. The results demonstrate significant improvements for the growth parameters with the employment of the controlled-release NPK with respect to enriched soil combined with a ratio of hyper red and deep blue LED light equal to 1:3 (Total fresh mass: +100%, Leaves number: +20%).

2021 - Evaluation of VTH and RON Drifts during Switch-Mode Operation in Packaged SiC MOSFETs [Articolo su rivista]
Cioni, Marcello; Bertacchini, Alessandro; Mucci, Alessandro; Zagni, Nicolò; Verzellesi, Giovanni; Pavan, Paolo; Chini, Alessandro
abstract

In this paper, we investigate the evolution of threshold voltage (VTH) and on-resistance (RON) drifts in the silicon carbide (SiC) power metal-oxide-semiconductor field-effect transistors (MOSFETs) during the switch-mode operation. A novel measurement setup for performing the required on-the-fly characterization is presented and the experimental results, obtained on commercially available TO-247 packaged SiC devices, are reported. Measurements were performed for 1000 s, during which negative VTH shifts (i.e., VTH decrease) and negative RON drifts (i.e., RON decrease) were observed. To better understand the origin of these parameter drifts and their possible correlation, measurements were performed for different (i) gate-driving voltage (VGH) and (ii) off-state drain voltage (VPH). We found that VTH reduction leads to a current increase, thus yielding RON to decrease. This correlation was explained by the RON dependence on the overdrive voltage (VGS–VTH). We also found that gate-related effects dominate the parameter drifts at low VPH with no observable recovery, due to the repeated switching of the gate signal required for the parameter monitoring. Conversely, the drain-induced instabilities caused by high VPH are completely recoverable within 1000 s from the VPH removal. These results show that the measurement setup is able to discern the gate/drain contributions, clarifying the origin of the observed VTH and RON drifts.

2021 - Investigation on VTH and RON Slow/Fast Drifts in SiC MOSFETs [Relazione in Atti di Convegno]
Cioni, M.; Bertacchini, A.; Mucci, A.; Verzellesi, G.; Pavan, P.; Chini, A.
abstract

RON and VTH drifts in TO-247 SiC packaged MOSFETs are investigated in this paper. The use of a novel on-the-fly measurement setup able to capture their variation over a 100µs to 1000s time range revealed the presence of two separated fast and slow mechanisms affecting the VTH and RON stability. Particularly, fast drain-induced mechanisms were found to negatively shift VTH, whereas no appreciable fast drifts were observed on RON. Conversely, slow drifts were found on both parameters, yielding a decrease in VTH and an RON increase. To investigate their origin, measurements were carried out for either i) different Duty Cycles and ii) several on-state current levels, proving that device self-heating (i.e., temperature increase) is responsible for the observed slow instabilities.

2021 - Statistical Optimization of a Hyper Red, Deep Blue, and White LEDs Light Combination for Controlled Basil Horticulture [Articolo su rivista]
Barbi, Silvia; Barbieri, Francesco; Bertacchini, Alessandro; Montorsi, Monia
abstract

2020 - Effects of the target on the performance of an ultra-low power eddy current displacement sensor for industrial applications [Articolo su rivista]
Bertacchini, A.; Lasagni, M.; Sereni, G.
abstract

The demand for smart, low-power, and low-cost sensors is rapidly increasing with the proliferation of industry automation. In this context, an Ultra-Low Power Eddy Current Displacement Sensor (ULP-ECDS) targeting common industrial applications and designed to be embedded in wireless Industrial Internet of Things (IIoT) devices is presented. A complete characterization of the realized ULP-ECDS operating with different metallic targets was carried out. The choice of the considered targets in terms of material and thickness was inspired by typical industrial scenarios. The experimental results show that the realized prototype works properly with extremely low supply voltages, allowing for obtaining an ultra-low power consumption, significantly lower than other state-of-the-art solutions. In particular, the proposed sensor reached the best resolution of 2 µm in case of a carbon steel target when operated with a supply voltage of 200 mV and with a power consumption of 150 µW. By accepting a resolution of 12 µm, it is possible to further reduce the power consumption of the sensor to less than 10 µW. The obtained results also demonstrate how the performances of the sensor are strongly dependent on both the target and the demodulation technique used to extract the displacement information. This allowed for defining some practical guidelines that can help the design of effective solutions considering application-specific constraints.

2020 - Improved Heat Sink for Thermoelectric Energy Harvesting Systems [Capitolo/Saggio]
Bertacchini, Alessandro; Barbi, Silvia; Montorsi, Monia
abstract

Abstract. This paper is focused on the improvement of the heat sink system of a thermal energy harvester by using organic and inorganic Phase Change Materials (PCM), considering solutions with the lowest environmental im-pact, as an alternative to well-known paraffin waxes. The proposed heat sink has been applied to the real case study of a thermoelectric energy har-vester to supply a wireless sensor node placed in the engine compartment of a vehicle and used for the continuous monitoring of the engine’s vibrations. Different hydrated salts (nitrate mixtures) have been evaluated as PCM, trough design of experiments techniques, working in a restrained well-tailored temperature ranges (±5°C) depending on mixtures’ composition, and compared with acetamide as best organic alternative. The realized PCM-based heat sink shown better performance compared with a classic heat sink in both steady-state and dynamic conditions.

2020 - Ultra-High Frequency (500 MHz) Capacitance Spectroscopy for Nanobiosensing [Abstract in Atti di Convegno]
Cossettini, Andrea; Brandalise, Denis; Palestri, Pierpaolo; Bertacchini, Alessandro; Ramponi, Michele; Widdershoven, Frans; Benini, Luca; Selmi, Luca
abstract

Abstract—We report unprecedented ultra high frequency capacitance spectroscopy measurements up to 500 MHz on a nanoelectrode array for biosensing applications, which extends considerably the previous 70 MHz limit. To achieve this goal, a high-frequency adapter board and measurement system are designed to drive the sensing nanoelectrodes of an existing biochip with appropriate clocks generated by an advanced highspeed pulser. Experimental results in dry and in electrolyte conditions are reported. The extended frequency range enables to overcome the Debye screening cut-off frequency of electrolytes at physiological salt concentrations, thus disclosing new perspectives for single molecule detection.

2020 - Ultra-Low Power Displacement Sensor [Capitolo/Saggio]
Bertacchini, Alessandro; Lasagni, Marco; Sereni, Gabriele
abstract

In this paper a proof of concept of ultra-low power Eddy-Current Displacement Sensor (EDCS) is presented. Measurements carried out on the realized prototype, show that the sensor has a resolution up to 6 µm, with a power consumption of 28µW. The ultra-low power consumption of the sensor could pave the road towards the realization of a new generation of smart wireless displacement and proximity sensors able to gather the needed energy directly from the environment where they operate thanks to the introduction of energy harvesting-based devices.

2019 - An Ultra-Low Cost Triboelectric Flowmeter [Capitolo/Saggio]
Bertacchini, A.; Pavan, P.
abstract

In this paper, we present an ultra-low cost flowmeter suitable for both gases and fluids. Differently from other flowmeters presented in the literature, the prototype is based on the triboelectric effect. The realized device is extremely low cost because it uses commercial silicone as triboelectric material. The comparison between experimental measurements and output data of a commercial flowmeter, used as reference, demonstrates the effectiveness of the proposed solution in both constant and variable flow conditions. Moreover, thanks to its reconfigurable architecture, the realized device can be used for both redundant measurements and triboelectric energy harvesting purposes.

2018 - Characterization and Modeling of Low-Cost Contact-Mode Triboelectric Devices for Energy Harvesting [Relazione in Atti di Convegno]
Bertacchini, A.; Lasagni, M.; Sereni, G.; Larcher, L.; Pavan, P.
abstract

In this paper we investigate the effect of the contact force in Contact-Mode TriboElectric Devices (CM-TED). In this kind of devices, the generated output voltage and the electrical energy harvested from mechanical impacts depend on the contact force. The number of impacts and the contact force influences also the surface charge density of the triboelectric layers of CM-TED. This is confirmed by the measurements carried out on the low-cost CM-TED prototypes we realized using commercial silicone as triboelectric material. The effect of the impact force has been included into a device model suitable for both dielectric-to-dielectric and contact-to-dielectric triboelectric devices. The model predicts the output voltage and power at given conditions and it can be used to design ultra-low cost triboelectric energy harvesters. The realized prototypes provide up to 5.5µW when subjected to repetitive impacts with a contact force of 65N.

2018 - Design and Simulation of Out-of-Plane Nanomaterial-Based Thermocouples [Relazione in Atti di Convegno]
Falco, A.; Lugli, P.; Loghin, F.; Rivadeneyra, A.; Larcher, L.; Bertacchini, A.
abstract

Our contribution indicates a novel solution for the development of the field of low-cost, printed thermocouples for energy harvesting and autonomous thermal sensors. Particularly, our work stems from the observation that the totality of printed thermocouples presented in literature relies on the conversion of a thermal gradient parallel to the plane of material deposition. This strategy is inherently inefficient and rarely applicable in real life scenarios. To overcome these issues, we introduced a novel concept of printed thermocouples, which use 3D-printing to define a vertical structure, upon which an out-of-plane thermal gradient can form and be harvested. Here, we perform thermoelectrical multi-physics simulations, employing parameters of nanomaterials extracted from literature, to show how this approach can lead to generate hundreds of microwatt in typical work conditions. Given their elevated thermopower, these structures could be employed both as autonomous sensors and energy harvesters in Internet of Things applications.

2016 - Force Impact Effect in Contact-Mode Triboelectric Energy Harvesters: Characterization and Modeling [Relazione in Atti di Convegno]
Lasagni, Marco; Pavan, Paolo; Bertacchini, Alessandro; Larcher, Luca
abstract

In this paper we investigate the effect of the contact force on the voltage generated by Contact-Mode Triboelectric Energy Harvesting Devices (CM-TEHD). The electrical energy harvested from mechanical shocks increases with the contact force. In order to investigate the role of the contact force in the triboelectric energy generation, we developed a physical model, which allows understanding the physical mechanisms of this process, while predicting the output voltage and power at given conditions. Prototypes of the CM-TEHD made of low-cost commercial silicone were fabricated using a very low cost process. The prototypes provide up to 5.5µW when subjected to repetitive impacts with a contact force of 65N.

2016 - System With RF Power Delivery Capabilities for Active Safety Enhancement in Industrial Vehicles Using Interchangeable Implements [Articolo su rivista]
Bertacchini, Alessandro; Napoletano, Giacomantonio; Scorcioni, Stefano; Larcher, Luca; Pavan, Paolo
abstract

In this paper, an active system for safety enhancement in industrial and off-highway vehicles using interchangeable implements is presented. The system, applied to the real case study of automatic identification of implements connected to a telehandler, is developed by adopting a hardware–software codesign approach. It is comprised of two devices: the Illuminator-Gateway Device (IGD) and the End Device (ED). Differently from other similar solutions, the system embeds a complete radio frequency (RF) power delivery system that is compliant with the regulations in force in Europe and in North America to extend the battery lifetime of the ED. In particular, the IGD, positioned on the free end of the telescopic arm of the telehandler, supplies the RF energy required for the operations of the ED and acts as a gateway sending the data received from the ED to the other Electronic Control Units (ECUs) of the vehicle. The ED, instead, is mounted on the connected implement, collects the RF energy delivered by the IGD, and wirelessly sends the unique identifier, the key parameters, and the calculated effective working time of the implement. This information can be used by the main ECU of the vehicle for safety-related purposes and programmed maintenance. Experimental results show that the implemented RF power delivery system is able to gather up to 63% of the power required by the ED when it is on duty, thus significantly extending its battery lifetime.

2016 - Wireless sensor systems with energy harvesting capabilities for safety enhancement in agricultural vehicles [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Larcher, Luca
abstract

This paper presents an overview of a multi-sensor wireless system applied to agricultural vehicles. The data provided by the different kinds of ad-hoc developed wireless sensors can be used as starting point for the implementation of an automatic system for the active safety enhancement of the vehicles. In order to guarantee a lifetime comparable with the one of the implement or trailer where they are mounted, each sensor has his own energy harvesting system able to gather energy from the vibrations occurring in the environment where the sensor operates.

2015 - A novel ball joint wear sensor for low-cost structural health monitoring of off-highway vehicles [Articolo su rivista]
Castagnetti, Davide; Bertacchini, Alessandro; Spaggiari, Andrea; Lesnjanin, A.; Larcher, Luca; Dragoni, Eugenio; Arduini, M.
abstract

Mechatronic agricultural machines and equipment are continuously increasing their complexity and cost. In order to ensure their efficiency and reliability and preserve their value, it is important to actively monitor damaging and wear occurring on critical components. This approach needs the introduction of sensors on the machine, which allow continuous monitoring of the residual life of components. This work presents the development and testing of a wear sensor for a ball joint which can be applied for monitoring and diagnostic in off-highway vehicles, automotive and the industrial fields. Many peculiar features make this sensor innovative and contribute to the advance of the technology in the sector: there are no other active sensors for this specific and safety-critical joint; it has an ultra-low power consumption and can be self-powered through energy harvesting; it implements wireless connectivity; it is simple, small size and low cost. This wear sensor for the ball joint is firstly aimed at monitoring the damage of the ball joint placed between the steering actuator and the wheel spindle, since failure of the joint leads to complete loss of steering action. However, the sensor can be applied to any application involving a safety-critical ball joint (e.g. the front suspension of a vehicle). The present work describes the conceptual design and development of the whole mechatronic sensor, which includes the mechanical joint sensor and the electronic board which manages the system. Validation of the ball joint wear sensor, which was performed on an agricultural tractor through tests on a track, proved the reliability of the proposed solution.

2015 - Reconfigurable RF Energy Harvester with Customized Differential PCB Antenna [Articolo su rivista]
Bertacchini, Alessandro; Larcher, Luca; Maini, Moreno; Vincetti, Luca; Scorcioni, Stefano
abstract

In this work, a RF Energy harvester comprised of a differential RF-DC CMOS converter realized in ST130nm CMOS technology and a customized broadband PCB antenna with inductive coupling feeding is presented. Experimental results show that the system can work with different carrier frequencies and thanks to its reconfigurable architecture the proposed converter is able to provide a regulated output voltage of 2 V over a 14 dB of RF input power range. The conversion efficiency of the whole system peaks at 18% under normal outdoor working conditions.

2015 - Ultra low cost triboelectric energy harvesting solutions for embedded sensor systems [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Larcher, Luca; Lasagni, Marco; Pavan, Paolo
abstract

In this paper we present a triboelectric generator realized with ultra-low cost materials, assembled through a very simple in-house fabrication facility. The triboelectric generator is designed to harvest the mechanical energy from shocks. Different combinations of low-cost materials such as acetic, neutral and acrylic silicone was explored to increase device performances. The device prototypes, characterized under various working conditions show a generated output power of 25µW with an applied load of 50 MΩ, which makes this technology solution very attractive for embedded energy-autonomous sensors system solutions.

2014 - Active Safety System with RF Energy Harvesting Capabilities for Industrial Applications using Interchangeable Implements [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Napoletano, Giacomantonio; Scorcioni, Stefano; Larcher, Luca; Pavan, Paolo
abstract

In this paper a system for the remote powering of low power electronic devices is presented. The system has been applied to a real industrial application allowing to enhance active safety in industrial vehicles. It is comprised of two main devices: i) the End Device (ED) with an embedded Radio Frequency (RF) energy harvester; ii) the Illuminator-Gateway Device (IGD) with an embedded RF power transmitter. Thanks to the optimization of the customized dual band Planar Inverted Folded Antenna (PIFA) used, the ULP architecture of the ED, the hardware-software co-design approach used and the optimization of the ED firmware, the proposed system is able to provide up to the 63% of the power required by the ED when it is on duty.

2014 - Integrated RF-DC converter and PCB antenna for UHF wireless powering applications [Relazione in Atti di Convegno]
Vincetti, Luca; Maini, M.; Scorcioni, Stefano; Larcher, Luca; Bertacchini, Alessandro; Tacchini, Alessandro
abstract

In this work, a broadband differential RF-DC CMOS converter realized in CMOS 130 nm technology with a customized PCB antenna with inductive coupling feeding for RF energy scavenging is presented. Experimental results show that output DC voltage higher than 1V from 800MHz to 970MHz can be obtained with a load of 1kohm.

2014 - Optimized Energy-Aware Wireless System for Identification of the Relative Positioning of Articulated Systems in the Free Space [Articolo su rivista]
Bertacchini, Alessandro; Napoletano, Giacomantonio; Dondi, Denis; Larcher, Luca; Pavan, Paolo
abstract

In this paper, a low-cost solution to identify the relative positioning of articulated systems in the free space is presented. To prove the effectiveness of the proposed solution, the system has been applied to a real case study of a tractor connected with a baler. Differently from other solutions, the implemented system can monitor the working conditions of the whole machinery while warning the driver when the machinery gets into a dangerous situation. The system is comprised of two wireless devices called Wireless Master Device (WMD) and Wireless End Device (WED) installed on the tractor and on the baler, respectively. To identify instantaneously the dangerous working conditions, each of the two wireless devices exploits a MEMS inertial sensor measuring 3-D linear accelerations and 3-D magnetic fields components integrated in the devices. Very low power consumption has been obtained by exploiting a hardware–software codesign approach implementing an optimized algorithm combined with a smart task manager. Furthermore, a vibrational energy harvester has been designed and integrated on the WED in order to make the device autonomous from an energetic point of view.

2014 - Vibrational Energy Harvesting [Capitolo/Saggio]
Larcher, Luca; Roy, Saibal; Mallick, Dhiman; Podder, Pranay; De Vittorio, Massimo; Todaro, Teresa; Guido, Francesco; Bertacchini, Alessandro; Hinchet, Ronan; Keraudy, Julien; Ardila, Gustavo
abstract

Energy harvesting is an attractive way to power electronic systems such as wireless sensors without using batteries or other energy storages with limited lifetime. Among the energy harvesters proposed from different sources (e.g. light, thermal gradient, strain, vibrations, electromagnetic field, air flow and pressure variations), vibrations pervasively available in different environments (indoor and outdoor) represent an attractive option for the development of adequate sources for low power supplying or for extending the autonomy of remote sensors and portable electronics. Power harvested from mechanical vibrations represents a very promising energy source with estimated power in the μW–mW range [ROU 04a]. Vibration-powered generators are typically inertial spring and mass systems (Figure 6.1) which employ three main transduction mechanisms to extract energy from vibrations: piezoelectric, electromagnetic and electrostatic. Piezoelectric generators employ active materials that generate a charge and, therefore, a voltage when mechanically stressed. Electromagnetic generators harvest energy from vibrations by employing the electromagnetic induction arising from the relative motion between a magnetic flux gradient and a conductor. Electrostatic generators use the vibration-induced relative movement between electrically isolated charged capacitor plates against the electrostatic force to generate energy. Other solutions employing either electrets or magnetostrictive materials for the mechanical energy conversion were also proposed [WAN 08, KAR 08a]. Microelectromechanical systems (MEMS) technology was largely investigated to achieve vibration energy harvesters that can be potentially integrated with low power applications such as wireless sensor networks (WSN) nodes [AMM 05,ERI 05, JEO 05, BEE 06, ROU 03]. Piezoelectric transducers have often been proposed to implement easily exploitable energy harvester solutions mainly because of their low-cost manufacturing process and the potential integration with complementary metal–oxide semiconductor (CMOS) technology. Nevertheless, electromagnetic transducers were also explored due to their complementary advantages compared to piezoelectric transducers, and solutions combining both transduction harvesters were proposed to improve the energy density and the conversion efficiency [BEE 07a]. In order to be used in practical applications, the energy harvesters have to deliver a minimum output power and voltage, which are required by power converters to operate with acceptable efficiency. Unfortunately, this is not always the case, and several energy harvesters proposed in the literature have low output power and voltages, were large and bulky, and their efficiency was shown to peak only in a very narrow frequency range, thus making such devices unsuitable to scavenge energy from actual ambient vibrations. For this reason, research activities have been oriented to improve the power efficiency and the output power of the vibration energy harvester, to decrease the size of the transducers, to decrease the operating frequency, to match the low frequency ambient vibrations and to widen their bandwidth to maximize the energy collection (ambient vibrations rarely never occur at exact frequencies) [MUR 09]. This chapter will present a short overview of the MEMS energy harvesters employing both piezoelectric and electromagnetic effects both proposed in the literature and developed in the framework of the Nanofunction project. A short overview of state-of-the-art vibration energy transducers employing the piezoelectric effect is presented in section 6.2, where MEMS prototypes realized in the framework of the Nanofunction project will also be presented. Near-field characterization techniques as well as electromechanical modeling and simulation required for the design of the energy harvesting transducers will be illustrated. Electromagnetic generat

2013 - A Reconfigurable Differential CMOS RF Energy Scavenger With 60% Peak Efficiency and -21dBm Sensitivity [Articolo su rivista]
Scorcioni, Stefano; Larcher, Luca; Bertacchini, Alessandro
abstract

A differential RF-DC CMOS converter for RF energy scavenging based on a reconfigurable voltage rectifier topology is presented. The converter efficiency and sensitivity are optimized thanks to the proposed reconfigurable architecture. Prototypes realized in 130nm provide a regulated output voltage of ~2V when working at 868MHz, with a -21dBm sensitivity. The circuit efficiency peaks at 60%, remaining above the 40% for a 18dB input power range.

2013 - An Integrated RF Energy Harvester for UHF Wireless Powering Applications [Relazione in Atti di Convegno]
Scorcioni, Stefano; Larcher, Luca; Bertacchini, Alessandro; Vincetti, Luca; Maini, Moreno
abstract

A RF energy harvester comprised of an integrated differential RF-DC converter and a differential PCB custom antenna is presented for wireless powering applications in the UHF band. The RF-DC converter, based on a reconfigurable voltage rectifier directly connected to a matched PCB antenna, is designed for high efficiency and sensitivity. Prototypes of the RF-DC converter realized in CMOS 130nm technology show a -16dBm sensitivity and a 60% peak efficiency. The RF-DC converters operate within the -16dBm÷0dBm input power range with an efficiency which remains above the 40% for more than 10dB. The RF energy harvester operates on the 840MHz÷975MHz band thanks to the ad-hoc designed wide-band differential antenna.

2013 - Exploration of new Materials, Devices and Technologies for Energy Harvesting: the NANOFUNCTION Experience [Abstract in Atti di Convegno]
M. Tartagni, A. G. Nassiopoulou; Costache, M. V.; Svalenzuela, S. Valenzuela; Torres, S.; Wwang, W. Wang; Wang, N.; Rohan, J.; Hayes, M.; Roy, S.; Flandre, D.; Kaminski Cachopo, A.; Ardila, G.; Mouis, M.; Aberg, M.; Parker, E.; Bertacchini, Alessandro; Larcher, Luca; Romani, A.; Fiegna, C.; Zanuccoli, M.
abstract

The concurrent decrease of energy demanded by electronic systems with the increase of the energy stored and/or harvested by generation systems give the opportunity for novel approaches in a large amount of applications. Some of them already reached the market, however, the real limits of the issues should be carefully analyzed on a case-by-case basis. Energy harvesting entails conversion of ambient energy sources into usable energy and will become a critical technology for applications such wireless sensor networks, wireless security systems, in situ monitoring for mobile/moving systems, body area networks, biomedical devices, portable power generation for mobile electronics. This paper shows the recent results achieved by research groups within the NANOFUNCTION FP7 Network of Excellence working in the energyharvesting field. The collaboration provided advanced solutions in energy harvesting systems thanks to the interdisciplinary research performed at the level of materials, devices and architectures. The objective of the joint group is twofold: to investigate the potential of nano-materials and nano-devices capable to scale to micro- and nano-system level the energy harvesting and energy storage functions, and to devise innovative, integrated and efficient systems able to manage and deliver the harvested and stored energy.

2013 - Single-Ended Broadband Antenna for Radiofrequency Energy Harvesting [Relazione in Atti di Convegno]
Vincetti, Luca; Maini, M.; Bompani, M.; Larcher, Luca; Scorcioni, Stefano; Bertacchini, Alessandro; Grossi, D.; Tacchini, Alessandro
abstract

A single-ended broadband UHF antenna with high inductive input impedance for radiofrequency energy harvesting is here presented. It consists of a small feeding loop and a conical radiating monopole. A prototype has been fabricated on a FR4 substrate and tested. Experimental results show a -3dB power transmission bandwidth of about 130MHz (860MHz−990MHz).

2012 - A WSN System Powered by Vibrations to Improve Safety of Machinery with Trailer [Relazione in Atti di Convegno]
Dondi, Denis; Napoletano, Giacomantonio; Bertacchini, Alessandro; Larcher, Luca; Pavan, Paolo
abstract

In this paper we present an energetically autonomous wireless sensor system designed to enhance safety in industrial machinery comprising a main vehicle with an attached trailer. The proposed system establishes a wireless link between the vehicle ECU and our sensors to provide motion dynamic data of trailer to the vehicle stability control algorithm. The wireless sensor devices we implemented comprise a 3-axial accelerometer and a 3-axial magnetometer to detect the trailer operating conditions. Such motion data are elaborated using an ultra-low power MCU, which communicates to vehicle’ ECU using an IEEE 802.15.4 channel at 2.4GHz. To enable perpetual operation of the system, we developed a vibrational energy harvesting system, VIBester, capable to gather kinetic energy from trailer natural vibrations and convert such energy in electrical energy for the system power supply. The vibrational energy harvester adopts a piezoelectric (PZT) transducer to convert the kinetic energy and a custom AC/DC converter to supply the wireless sensor device.

2012 - A 868MHz CMOS RF-DC Power Converter With -17dBm Input Power Sensitivity and Efficiency Higher Than 40% Over 14dB Input Power Range [Relazione in Atti di Convegno]
Scorcioni, Stefano; Bertacchini, Alessandro; Larcher, Luca
abstract

In this paper we present a novel CMOS RF-DC converter circuit, operating at 868MHz, for RFID and remote powering applications. The novel reconfigurable architecture of the converter allows the circuit to operate over a very wide input power range with very high efficiency compared with previous art works. Prototypes realized in STM 0.130ìm CMOS technology provide a regulated output voltage ~2V with a -17dBm input power sensitivity. The circuit efficiency, higher than 40% over a 14dB input power range, peaks at 60%.

2012 - An autonomous wireless sensor network device powered by a RF energy harvesting system [Relazione in Atti di Convegno]
Dondi, Denis; Scorcioni, Stefano; Bertacchini, Alessandro; Larcher, Luca; Pavan, Paolo
abstract

In this paper, we present an energetically autonomous wireless sensor network (WSN) device designed to enhance safety in vehicles capable to connect extra gear/equipment to the main chassis. The proposed system allows the vehicle stability control system to automatically recognize the connected trailer or implement through a purposely designed WSN device, which is integrated into trailer /implement and wirelessly sends its identification number. The WSN device we developed integrates also a novel RF energy harvesting circuit which gathers the energy from an 868MHz RF signal source, which is purposely transmitted from the vehicle towards the trailer or implement for remote powering. Measurements performed on fabricated WSN system prototypes show that the RF harvester can gather up to ≈50uW@3m from the RF power source with efficiency higher than 30% over a range of 10dBm. The combination of the RF energy harvesting circuit with the ultra-low power architecture and a custom task manager designed for the WSN system allows to further increase primary battery lifetime, making the wireless system capable to operate autonomously for several years.

2012 - Broadband Printed Antenna for Radiofrequency Energy Harvesting [Relazione in Atti di Convegno]
Vincetti, Luca; Maini, Moreno; E., Pinotti; Larcher, Luca; S., Scorcioni; Bertacchini, Alessandro; D., Grossi; A., Tacchini
abstract

In this work a broadband UHF antenna with high inductive input impedance for radiofrequency energy harvesting is presented. It consists of a small feeding loop and a biconical radiating dipole. A prototype has been fabricated on a FR4 substrate and tested. Experimental results show a - 3dB power transmission bandwidth of about 135MHz (840MHz−975MHz).

2012 - Enhancing Safety in Vehicles with Implement or Trailer using an Autonomous Wireless Sensor Network System [Relazione in Atti di Convegno]
Dondi, Denis; Bertacchini, Alessandro; Scorcioni, Stefano; Larcher, Luca; Pavan, Paolo
abstract

In this paper, we present an autonomous wireless sensor network system to enhance safety in vehicles with connected implement or trailer. Today’s vehicle stability control algorithms are used to enhance safety and prevent accidents, but they do not take into account if a trailer or an implement is connected to the front/rear of the vehicle. The proposed system allows overcoming this limitation by advertising to the vehicle’ electronic control unit the presence of the connected implement. This allows the stability control algorithm adjusting the vehicles parameters to current real conditions. The developed system comprises two wireless devices: a Wireless Master Device (WMD), mounted on the vehicle, and an autonomous Wireless End Device (WED), installed on the connected implement or trailer. The WED gathers energy from implement’ or trailer’ natural vibrations by using a vibrational energy harvester and a piezoelectric transducer. Thus, avoiding the need of frequent battery replacement and leading the wireless system to autonomously work for several years.

2012 - Optimized CMOS RF-DC converters for remote wireless powering of RFID applications [Relazione in Atti di Convegno]
Scorcioni, Stefano; Larcher, Luca; Bertacchini, Alessandro
abstract

In this paper, we present for the first time a novel optimization procedure which allows to maximize the efficiency of RF-DC energy harvester converters, taking into account the contributions of the matching network. Thanks to this procedure, we have designed and realized a CMOS RF-DC converter operating in a very wide range of input power -14÷+1dBm with a peak efficiency of 45%. The RF-DC converter provides a constant output voltage ~2V in the whole input power range thanks to a smart voltage regulator integrated with the converter.

2012 - RF to DC CMOS rectifier with high efficiency over a wide input power range for RFID applications [Relazione in Atti di Convegno]
Scorcioni, Stefano; Bertacchini, Alessandro; Larcher, Luca; Ricciardi, Antonio; Dondi, Denis; Pavan, Paolo
abstract

In this paper we present a RF-DC rectifier which operates over a wide range of input power by providing a regulated output DC voltage. The circuit solution we propose is based on a novel active load circuit which adjusts the output current as a function of the incoming RF power. This allows maximizing both the efficiency and sensitivity of the circuit. Circuit prototypes fabricated in 130nm CMOS technology start to operate at -14dBm, providing a regulated output voltage of 1.6÷1.8V in the -14÷1dBm RF input power at 868MHz. Noticeably, the circuit efficiency of the rectifier peaks at 45%, remaining above 30% in the -12÷+1dBm input power range.

2012 - Self Powered Wireless Sensors for Chassis, Powertrain, Working Equipment and Trailed Implements [Relazione in Atti di Convegno]
Carli, Davide; Dondi, Denis; Bertacchini, Alessandro; Larcher, Luca; Ruggeri, Massimiliano
abstract

Performance request, needs for fleet management, vehicle safety and diagnosis control strategies, ask for a continuous increase in vehicle functionalities and work variables observability and controllability. Self-powered wireless sensors, capable of collecting the power they consume directly from the vibrations available on the spot, could play a key role in enabling the sensorization of all those parts of heavy duty machines and trailed vehicles which cannot be connected through wires. This paper investigates the applicability of self-powered wireless sensor nodes to heavy duty machinery by analyzing the energy budget which can be reached by these devices in such operating environment. A survey of possible sensor design is presented, to examine the energy requirements for signal transduction and wireless data transmission, and to highlight most relevant design issues affecting power consumption. Two representative case studies are then considered, to estimate with the support of original experimental data the amount of energy that can be generated by placing state-of-the-art off-the-shelf energy transducers on the gearbox of a baler and on the rear chassis of a tractor. By comparing the amounts of generated and required energy, this paper demonstrates the feasibility of self-powered wireless sensors in the context of heavy duty machines.

2012 - Wireless self-powered transponders and multi-sensing unit to enable ISOBUS identification of mechanical implements [Relazione in Atti di Convegno]
Mainardi, Gino; Ferretti, Marco; Marzani, Stefano; Scorcioni, Stefano; Bertacchini, Alessandro; Larcher, Luca; Dondi, Denis; Fantesini, Lorenzo
abstract

In this paper we present an ISOBUS-based system for the automatic identification of implements or trailers without electronics on board. This allows, firstly, to improve the pre-crash prevention because the performances of existing vehicle dynamics control systems can now take into account data coming from the implements or trailers connected to the tractor. Secondly, publishing on the ISOBUS network the information of all the implements, including the ones without electronics, permits a full deployment of precision farming techniques. The absence of electrical or electronic equipment on implements forces the use of wireless solutions, which in turn are limited by their battery lifetime, which is not comparable with the typical lifetime of trailers or implements. To overcome this limiting factor we added energy harvesting capabilities to the developed transponder, which is able to store energy coming from mechanical vibrations occurring during the normal implement working conditions.

2011 - A Vibration-Powered Wireless System to Enhance Safety in Agricultural Machinery [Relazione in Atti di Convegno]
Scorcioni, Stefano; Bertacchini, Alessandro; Dondi, Denis; Larcher, Luca; Pavan, Paolo; G., Mainardi
abstract

In this paper, we present a wireless sensing system capable to enhance safety in agricultural machinery. Modern farm tractors adopt vehicle stability control algorithms to enhance safety and prevent accidents. The main limitation in current approach is that the tractor has no information about the implement connected on the front/rear. The system we propose provides information on the connected implement to the tractor control unit allowing the vehicle characteristics update, which allows enhancing vehicle safety. The system we developed is comprised of two wireless devices. The first one, called Master Device (MD), is mounted on the tractor and receives power supply from on-board electrical system. The second one, called End-Device (ED), is mounted on the implement and gathers the supply energy from implement natural vibrations by using a vibrational energy harvester and a piezoelectric transducer. With this approach, the device can recharge an energy reservoir (e.g. a battery) during the implement usage, thus avoiding the need of frequent battery replacement and leading the wireless system to autonomously work for several years.

2011 - AlN-based MEMS devices for vibrational energy harvesting applications [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Scorcioni, Stefano; Dondi, Denis; Larcher, Luca; Pavan, Paolo; M. T., Todaro; A., Campa; G., Caretto; S., Petroni; A., Passaseo; M., De Vittorio
abstract

This paper presents a new AlN-based MEMS devices suitable for vibrational energy harvesting applications. Due to their particular shape and unlike traditional cantilever which efficiently harvest energy only if subjected to stimulus in the proper direction, the proposed devices have 3D generation capabilities solving the problem of device orientation and placement in real applications. Thanks to their particular shape, the realized devices present more than one fundamental resonance frequencies in a range comprised between 500 Hz and 1.5 kHz, with a voltage generation higher than 300μV and an output power up to 0.4 pW for single MEMS device.

2011 - Bent AlN Piezoelectric Resonators for Vibrational Energy Harvesting [Relazione in Atti di Convegno]
M. T., Todaro; G., Caretto; G., Epifani; A., Campa; Bertacchini, Alessandro; Larcher, Luca; A., Passaseo; M., De Vittorio
abstract

Advances in the areas of wireless technology and low-power electronics stimulated extensively research in energy harvesting from environmental vibration sources. Aluminium nitride (AlN) thin films are promising for piezoelectric microsensors/ microactuators as well as for energy harvesting devices, due to their interesting material properties including good piezoelectric and electromechanical coupling coefficients, low permittivity and high Young's modulus. Despite this, few works reported on the AlN employment for the realization of micro power generators. In such cases, devices have a typical flat cantilever shape (M. Marzencki et al. 2008, R. Elfrink et al. 2009) and sizes are larger than that of most typical MEMS devices. This paper reports on the fabrication and analysis of bent AlN cantilever resonators based on a novel and simple fabrication process without additional proof masses for energy harvesting at frequencies around 2 KHz.

2011 - Freestanding piezoelectric rings for high efficiency energy harvesting at low frequency [Articolo su rivista]
A., Massaro; S., De Guido; I., Ingrosso; R., Cingolani; M., De Vittorio; M., Cori; Bertacchini, Alessandro; Larcher, Luca; A., Passaseo
abstract

Energy harvesting at low frequency is a challenge for microelectromechanical systems. In this work we present a piezoelectric vibration energy harvester based on freestanding molybdenum (Mo) and aluminum nitride (AlN) ring-microelectromechanical-system (RMEMS) resonators. The freestanding ring layout has high energy efficiency due to the additional torsional modes which are absent in planar cantilevers systems. The realized RMEMS prototypes show very low resonance frequencies without adding proof masses, providing the record high power density of 30.20 μW mm-3 at 64 Hz with an acceleration of 2g. The power density refers to the volume of the vibrating RMEMS layout.

2010 - A Micro Fuel Cell Power Supply Module for Low Power Portable Applications [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Scorcioni, Stefano; Cori, Marco Maria; Larcher, Luca; Pavan, Paolo; J. P., Esquivel; N., Torres Herrero; N., Sabaté; J., Santander
abstract

This paper presents a power supply module targeted for low-power applications in the sub-mW range incorporating a passive µDMFC fuel cell (µFC) acting as energy source and a customized boost converter for the energy conversion. The low power budget of such energy sources mandates the adoption of efficient circuit solutions, hence the design of the boost converter is challenging. To maximize the lifetime of the micro fuel cell, the module has been designed to keep constant the µFC operating point and it has been optimized to work with µFC providing a voltage in the range 280mV-320mV, reaching a maximum efficiency higher than 65% with an output power of 350 μW.

2010 - Investigation of trapping/detrapping mechanisms in Al2O3 electron/hole traps and their influence on TANOS memory operations [Relazione in Atti di Convegno]
Larcher, Luca; Padovani, Andrea; Vincenzo della, Marca; Pavan, Paolo; Bertacchini, Alessandro
abstract

The purpose of this work is to investigate the physics of electron/hole trapping/detrapping mechanisms in Al2O3. Combining I-V and C-V measurements with a physical model we derive the energy levels of electron/hole traps and the location of electron/hole charge. The influence of electron/hole alumina traps on TANOS operations and reliability is investigated.

2010 - 250mV Input Boost Converter for Low Power Applications [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Scorcioni, Stefano; Cori, Marco Maria; Larcher, Luca; Pavan, Paolo
abstract

This paper presents a novel low power boost converter designed and optimized to operate with a minimum input voltage as low as 250mV, which is the typical voltage range of novel micro energy sources. The low power budget of such energy sources (at most few hundreds of μWs) mandates the adoption of very efficient circuit solutions. The realized PCB prototype provides a regulated maximum output voltage 3.3V with 70% maximum efficiency, thus making the proposed converter topology very attractive for low power application power supply. Noticeably the converter operates without any external power supply of the control logic.

2009 - Photovoltaic scavenging systems: Modeling and optimization [Articolo su rivista]
Brunelli, D.; Dondi, Denis; Bertacchini, Alessandro; Larcher, Luca; Pavan, Paolo; Benini, L.
abstract

The interest in embedded portable systems and wireless sensor networks (WSNs) that scavenge energyfrom the environment has been increasing over the last years. Thanks to the progress in the design oflow-power circuits, such devices consume less and less power and are promising candidates to performcontinued operation by the use of renewable energy sources. The adoption of maximum power pointtracking (MPPT) techniques in photovoltaic scavengers increases the energy harvesting efficiency andleads to several benefits such as the possibility to shrink the size of photovoltaic modules and energyreservoirs. Unfortunately, the optimization of this process under non-stationary light conditions is still akey design challenge and the development of a photovoltaic harvester has to be preceded by extensivesimulations. We propose a detailed model of the solar cell that predicts the instantaneous powercollected by the panel and improves the simulation of harvester systems. Furthermore, the paperfocuses on a methodology for optimizing the design of MPPT solar harvesters for self-poweredembedded systems and presents improvements in the circuit architecture with respect to our previousimplementation. Experimental results show that the proposed design guidelines allow to incrementglobal efficiency and to reduce the power consumption of the scavenger.

2008 - A Solar Energy Harvesting Circuit for Low Power Applications [Relazione in Atti di Convegno]
Dondi, Denis; Bertacchini, Alessandro; Larcher, Luca; Pavan, Paolo; D., Brunelli; L., Benini
abstract

In this paper we present a solar energy harvesting circuit for low-power applications describing circuit architecture and guidelines for an optimal design. We evaluate the performance of two implemented prototypes intended to power a wireless embedded system under different light intensities and different switching frequencies. Measurements show that higher switching frequencies allow reaching the maximum efficiency (90%) at higher light intensities, whereas lower operating frequencies perform better under lower irradiance. Experimental results show that circuit optimization depends on light conditions and the proposed solar energy harvester can autonomously supply the nodes of a wireless sensor network WSN.

2008 - Modeling and Optimization of a Solar Energy Harvester System for Self Powered Wireless Sensor Networks [Articolo su rivista]
Dondi, Denis; Bertacchini, Alessandro; D., Brunelli; Larcher, Luca; L., Benini
abstract

In this paper we propose a methodology for optimizing a solar harvester with maximum-power point tracking for self powered wireless sensors networks (WSN) nodes. We focus on maximizing the harvester’s efficiency in transferring energy from the solar panel to the energy storing device.A photovoltaic panel analytical model, based on a simplified parameter extraction procedure is adopted. This model predicts the instantaneous power collected by the panel helping the harvester design and optimization procedure. Moreover, a detailed modeling of the harvester is proposed to understand basic harvester behavior and optimize the circuit. Experimental results based on the presented design guidelines demonstrate the effectiveness of the adopted methodology. This design procedure helps in boosting efficiency, allowing to reach a maximum efficiency of 85% with discrete components. The application field of this circuit is not limited to self powered WSN nodes, but it can be easily extended also in embedded portable applications to extend battery life.

2008 - Performance Analysis of Solar Energy Harvesting Circuits for Autonomous Sensors [Relazione in Atti di Convegno]
Bertacchini, Alessandro; D., Dondi; Larcher, Luca; Pavan, Paolo
abstract

In this paper we present two different energy harvesting circuits for solar powered autonomous sensors.Both circuits are able to supply several types of sensor nodes. Performance of these circuits under different light conditions and different loads have been evaluated by experimental results conducted on implemented prototypes.Moreover, starting from the estimated working conditions of the sensor in terms of power requirements and light irradiance, the comparison between these circuits provides useful insights to help a designer in choosing of the optimal harvesting implementation.

2008 - Solar Energy Harvesting: applicazioni a bassa potenza [Altro]
Dondi, Denis; Bertacchini, Alessandro; Larcher, Luca; Pavan, Paolo; D. Brunelli e. L., Benini
abstract

Negli ultimi anni si sono sempre più utilizzate reti wireless a elevata velocità per scambiare dati su larga scala con centinaia e migliaia di nodi. I nodi di queste reti sono dei sistemi embedded, che devono essere in grado di connettersi utilizzando solo la quantità di energia fornita dalle batterie. Proprio questo è uno tra i maggiori limiti al loro funzionamento, dato che tali batterie sono in grado di alimentare questi sistemi solo per poco tempo e non continuativamente. Per questo, l’obiettivo dei recenti lavori di ricerca sia aziendale che accademico è quello di ridurre la dissipazione di potenza per aumentare la vita operativa dei nodi. In questo senso, sono state studiate architetture a bassissimo consumo di potenza e applicazioni che necessitano di bassissimo duty cycle di alimentazione. Sfortunatamente, queste tecniche non sono adatte per le applicazioni con requisiti più severi, come, ad esempio, quelle che richiedono elaborazioni di dati intensive e trasmissione di dati a una distanza e velocità superiori. Inoltre, più di recente, la ricerca scientifica sta studiando la possibilità di estrarre l’energia necessaria al funzionamento dei nodi della rete di sensori wireless da fonti alternative, ad esempio sotto forma di luce solare, vento o vibrazioni. Questo ha spinto i ricercatori a progettare sistemi di energy harvesting. L’energy harvesting non è una novità, tuttavia, mediante una metodologia efficace di progetto, la realizzazione e l’integrazione di energy harvester efficienti nei moderni sistemi embedded rimane tuttora un argomento molto stimolante. In questo scenario, questo articolo presenta un sistema di harvesting da energia solare progettato per alimentare sistemi embedded wireless a bassa potenza. Saranno analizzate l’efficienza del circuito realizzato per valori realistici di duty cycle e l’intensità luminosa del sensore. L’analisi dimostra che la scelta migliore per la configurazione operativa del sistema di energy harvesting non è unica. In particolare, una configurazione con dispositivi a bassissimo consumo di potenza (ULP) è più efficiente in condizioni di bassa intensità luminosa, mentre architetture ad alta frequenza sono ideali in condizioni di luminosità elevata.

2008 - Solar harvesting per reti di sensori wireless [Altro]
Bertacchini, Alessandro; Dondi, Denis; Larcher, Luca; Pavan, Paolo; D., Brunelli; L., Benini
abstract

Lo sviluppo di sistemi ad alimentazione perpetua, in grado di evitare la frequente sostituzione e/o ricarica delle batterie, è uno degli obiettivi di ricerca più importanti nella progettazione di sistemi embedded distribuiti e delle reti wireless di sensori. Nonostante i progressi tecnologici nella progettazione di dispositivi low-power, che possono contribuire a prolungare la durata delle batterie, la ridotta capacità degli accumulatori di energia (batterie, supercapacitor, ecc.) limita severamente l’autonomia di sistemi quali le Wireless Sensor Networks (WSN). Recentemente circuiti che convertono fonti energetiche ambientali,come l'energia solare o termica, in energia elettrica si stanno diffondendo nella comunità dei progettisti di sistemi embedded e solitamente assumono il nome di energy scavenger o energy harvester. In particolare scavengerche utilizzano piccole celle solari sono stati proposti per alimentare perpetuamente le reti di sensori. Rispetto ai tradizionali sistemi fotovoltaici su larga scala (decine o centinaia di kW), che riescono agevolmente a operare nel punto di massima potenza delle celle (maximum power point - MPP), i circuiti di gestione dell’energia elettrica generata da pannelli fotovoltaici di piccole dimensioni devono affrontare problemi aggiuntivi: (a) una ridotta quantità di energia dovuta alla dimensione delle celle; (b) la realizzazione di circuiti efficienti in grado di operare nel punto di massima potenza (MPP) di norma richiede un’alta percentuale dell’energia fornita dalla cella stessa (riducendo in pratica la potenza disponibile al sistema);(c) è presente un’interazione sostanziale fra circuiti di conversione e immagazzinamento dell’energia e i dispositivi alimentati. La progettazione deve quindi essere supportata da simulazioni, in particolare quando l’efficienza della conversione deve essere ottimizzata per basse intensità di radiazione solare. La definizione di un flusso di progettazione chiaro è perciò fondamentale per lo sviluppo di soluzioni circuitali con buone prestazioni. Simulazioni circuitali dell’intero sistema elettronico di gestione dell’energia generata dai pannelli fotovoltaici sono tipicamente disponibili per sistemi fotovoltaici a larga scala, ma si rendono fondamentali e necessarie per l’efficienza di reti di sensori wireless e sistemi low-power. Per ottenere simulazioni affidabili, è opportuno sviluppare modelli compatti e accurati e la validazione di un modello delle caratteristiche I-V non lineari dei moduli PV diventano cruciali per la progettazione dei sistemi di energy harvesting efficienti.

2007 - Photovoltaic Cell Modeling for Solar Energy Powered Sensor Networks [Relazione in Atti di Convegno]
Dondi, Denis; D., Brunelli; L., Benini; Pavan, Paolo; Bertacchini, Alessandro; Larcher, Luca
abstract

Photovoltaic scavenging circuits have been presentedto reduce installation and maintenance costs of wirelesssensor networks. When small-size photovoltaic modules areadopted, optimizing the efficiency of the harvesting process andtracking theMaximum Power Point (MPP) becomes very difficult,and the development of a photovoltaic harvester has to bepreceded by extensive simulations. The paper focuses on thedefinition of the model for a small PV cell allowing the simulationof harvester systems. The model is validated on a case study ofMPPT circuit for sensor networks.

2006 - Force Feedback in Steer-by-Wire Systems: Architecture and Experimental Results [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Tamagnini, Luca; Pavan, Paolo
abstract

In this paper a preliminary architecture of a force-feedback subsystem in steer-by-wire (SBW) systems is proposed. In SBW applications, a force feedback control is needed to recreate on a steering wheel (or another man-machine interface) a drive feeling like the one produced by a traditional mechanical steering system. In this case a brushless motor is used as force feedback actuator. To validate the proposed architecture we adopted a Hardware-in-the-Loop (HIL) approach. HIL is a powerful development tool. In particular, a dynamic model of the vehicle is implemented in virtual hardware. The model is needed to evaluate the realized hardware (ECU and inverter needed to operate the motor) and to validate the force feedback control algorithms before the real implementation of the complete SBW system.Experimental results show as the realized ECU and the implemented control algorithm based on a field oriented control technique are correct and particularly suitable for steer-by-wire applications.

2006 - Hardware-in-the-Loop Approach for Redundant Brushless Motor Control System [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Pavan, Paolo; Tamagnini, Luca; M., Mistrorigo; M., Morandi
abstract

Brushless motors can be used in a very large range of industrial applications, including force feedback actuators in steer-by-wire systems. Due to the safety critical requirements of this kind of applications, a fault tolerant architecture is needed and it is implemented here using a Hardware-in-the-Loop (HIL) approach.To obtain a reliable control system a classic Triple Modular Redundancy (TMR) architecture has been designed. The very same basic principles to control the motor have been implemented exploiting three different hardware platforms (8-bit, 16-bit and hybrid microcontrollers). All these three hardware modules execute the control algorithm and it will be the voter of the TMR architecture to determine the effective signals (PWM signals) needed to control the motor.This means that redundancy is not limited to the determination of the position of the drive shaft of the motor, but extended to the entire electronic control of the brushless motor

2006 - XBW s.r.l. - Mechatronic Solutions [Spin Off]
Pavan, Paolo; Bertacchini, Alessandro; L., Tamagnini; M., Mistrorigo; M., Morandi
abstract

2005 - Control of brushless DC motor with static redundancy for force-feedback in steer-by-wire applications [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Pavan, Paolo; Tamagnini, Luca; M., Mistrorigo
abstract

In this paper we propose a Hardware-in-the-Loop (HIL) approach to implement a preliminary architecture for force-feedback control in steer-by-wire (SBW) applications. A brushless DC motor (BLDC) is used as force feedback actuator. The determination of the position of the BLDC rotor plays a key role in the control algorithm.To obtain a reliable rotor position a classic triple static redundancy (TMR) is implemented. The position signals from the encoder integrated on the motor are computed in three different ways: using a 8-bit microcontroller, a 16-bit microcontroller, and, last, using the software module integrated in a virtual hardware development tool. The virtual hardware platform operates as voter, too. The position is the output of the voting algorithm and it is sent to the 16-bit platform that controls the motor and provides the correct output PWM signals.The communication between virtual hardware and real hardware uses CAN bus. The bus is monitored by a dedicated development tool. Steer-by-wire is a safety critical application and therefore requires time-triggered protocols. In this preliminary architecture a dedicated network has been implemented and therefore the disadvantages of the event-triggered protocol are considerably reduced.Experiments at different baudrates confirm that the voting algorithm produces correct results also in case of failure in one of the modules of the TMR architecture and it is not conditioned by bus loads. This means that the torque control algorithm of the BLDC motor can generate on the steering wheel (directly connected to the motor) a drive feeling like the one produced by a traditional steering system also in this fail-mode.

2005 - Control of Brushless Motor with Hybrid Redundancy for Force Feedback in Steer-by-Wire Applications [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Tamagnini, Luca; L., Fergnani; Pavan, Paolo
abstract

In this paper we propose a Hardware-in-the-Loop (HIL) approach to implement a preliminary architecture for force-feedback control in steer-by-wire (SBW) applications. A brushless motor is used as force feedback actuator. The determination of the position of the rotor plays a key role in the control algorithm.To obtain a reliable rotor position a hybrid redundancy has been implemented. The position signals of the encoder integrated on the motor are computed in three different ways: using a 8-bit microcontroller, a 16-bit microcontroller, and, last, using a FPGA. A virtual hardware platform operates as voter. The position estimated by the voter is used by the 16-bit platform to generate the PWM signals needed to control the motor.The voter executes a simple self diagnostic process, too and in case of failure in more than one module performs a reconfigurations of the system and the position estimated by a fourth back-up module is used by the 16-bit microcontroller to implement the motor control algorithm.In particular, the results of Hardware-in-the-Loop experiments show as using a redundant architecture like the one proposed in this paper, it is possible to control the motor in order to recreate on a steering wheel (directly connected to the motor) a drive feeling like the one produced by a traditional steering system also in case of failure in one, or more than one module, of the system.

2005 - Sperimentando con CANbus - Controllo di un motore brushless con ridondandza statica per applicazioni di force-feedback in sistemi steer-by-wire [Altro]
Bertacchini, Alessandro; L., Tamagnini; M., Mistrorigo; Pavan, Paolo
abstract

In questo articolo viene proposto un approccio Hardware-in-the-Loop (HIL) per la realizzazione di una architettura preliminare di controllo di force feedback in applicazioni Steer-by-Wire (SBW). Come attuatore è stato scelto un motore brushless. La determinazione della posizione dell’albero motore gioca un ruolo chiave nell’algoritmo di controllo.Per ottenere una posizione affidabile dell’albero motore si è scelto di implementare una classica ridondanza statica tripla (TMR – Triple Modular Redundancy). I segnali provenienti dall’encoder integrato nel motore sono stati elaborati sfruttando tre differenti piattaforme HW: la prima basata su microcontrollore a 8-bit, la seconda basata su microcontrollore a 16-bit mentre la terza sfrutta un modulo software integrato nel tool di sviluppo utilizzato come HW virtuale. La piattaforma di HW virtuale è utilizzata anche come voter. La posizione effettiva dell’albero motore, risultato dell’ algoritmo di voting, è inviata via bus CAN alla piattaforma a 16-bit che implementa l’algoritmo di controllo del motore e genera i segnali PWM necessari all’alimentazione del motore.La comunicazione tra HW virtuale e reale avviene attraverso bus CAN. Esperimenti condotti a diverse baudrates confermano la validità dell’algoritmo di voting implementato, che produce risultati corretti anche in caso di guasto in uno dei moduli dell’architettura TMR e non è influenzato da condizioni di alto carico del bus di comunicazione.

2003 - Control Structures and Physical Requirements for Steer-By-Wire Systems [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Morselli, Riccardo; Zanasi, Roberto; Pavan, Paolo; Bertoli, A.
abstract

Starting from the dynamic model of a conventional steering system, this paper proposes some hardware-independent control structures for the implementation of a steer-by-wire system for ground vehicles. Moreover the proposed approach allows the definition of the physiscal requirements on the real implementation and it can be used as a desgin tool fore the evaluation of the dynamic behaviour of al the steer-by-wire mechatronic devices.

2003 - Energetic Approach for Steer-by-Wire in Off-highway Vehicles [Relazione in Atti di Convegno]
Morselli, Riccardo; Bertacchini, Alessandro; Reggiani, W.; Pavan, Paolo; Zanasi, Roberto
abstract

Starting from an energetic model of a traditional steering system, this paper proposes three different kinds of architecture for the implementation of a steer-by-wire system on off-highway vehicles. The force feedback and the rack hydraulic control cannot be ideal systems and this affects the overall vehicle dynamics, moreover the effects on the vehicle behavior depends on the chosen architecture. The hardware independent approach proposed in the paper drives the definition of the control requirements on the steering wheel control and on the rack control subsystems and it allows to appreciate the effects of the architecture on the implementation of a steer-by-wire system.

2003 - Testing Steer-by-Wire Controllers for Off-Highway Vehciles by Hardware-in-the-Loop Experiments [Capitolo/Saggio]
Bertacchini, Alessandro; Morselli, Riccardo; Pavan, Paolo; Zanasi, Roberto
abstract

The control laws and the hardware architecture for the implementation of a steer-by-wire system for off-highway vehicles are proposed. This paper describes how the hardware-independent control laws for the steer-by-wire actuators have been obtained, it explains the motivations for the choice of the force feedback actuator and of the steering rod electro-hydraulic actuator and finally it presents some hardware-in-the-loop simulation results that test the electro-hydraulic rod actuator and the electronic control unit dedicated to the steering rod

2003 - Testing Steer-by-Wire Controllers for Off-Highway Vehicles by Hardware-in-the-Loop Experiments [Relazione in Atti di Convegno]
Bertacchini, Alessandro; Morselli, Riccardo; Pavan, Paolo; Zanasi, Roberto
abstract

The control laws and the hardware architecture for the implementation of a steer-by-wire system for off-highway vehicles are proposed. This paper describes how the hardware-independent control laws for the steer-by-wire actuators have been obtained, it explains the motivations for the choice of the force feedback actuator and of the steering rod electro-hydraulic actuator and finally it presents some hardware-in-the-loop simulation results that test the electro-hydraulic rod actuator and the electronic control unit dedicated to the steering rod.