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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.

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.

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 impact, as an alternative to well-known paraffin waxes. The proposed heat sink has been applied to the real case study of a thermoelectric energy harvester 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.

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.

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.

In this work, a Radio Frequency (RF) Energy Harvester comprised of a differential Radio Frequency-to-Direct Current (RF-DC) converter realized in ST130 nm Complementary Metal-Oxide-Semiconductor (CMOS) technology and a customized broadband Printed Circuit Board (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.

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 &micro, m in case of a carbon steel target when operated with a supply voltage of 200 mV and with a power consumption of 150 &micro, W. By accepting a resolution of 12 &micro, m, it is possible to further reduce the power consumption of the sensor to less than 10 &micro, W. 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.

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 when subjected to repetitive impacts with a contact force of 65N.

In this paper we present a triboelectric generator realized with ultra-low cost materials, assembled using 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 have been characterized in various working conditions generating up to 25µW output power with variable resistive load, making this technology solution very attractive for embedded energy-autonomous sensors.

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 diagnosis 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.

chap 6; International audience; Vibration‐powered generators are typically inertial spring and mass systems which employ three main transduction mechanisms to extract energy from vibrations: piezoelectric, electromagnetic and electrostatic. This chapter presents a short overview of the microelectromechanical systems (MEMS) energy harvesters employing both piezoelectric and electromagnetic effects both proposed in the literature and developed in the framework of the Nanofunction project. It presents a short overview of state‐of‐the‐art vibration energy transducers employing the piezoelectric effect. The chapter illustrates the near‐field characterization techniques as well as electromechanical modeling and simulation required for the design of the energy harvesting transducers. It reviews the electromagnetic generators presented in the literature including large‐scale discrete devices and integrated versions, where the results achieved on vibration energy harvester exploiting both electromagnetic and piezoelectric effects are derived. Modeling and simulation results are presented to demonstrate the feasibility of the proposed device concepts.

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.

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 130 nm, provide a regulated output voltage of ~2 V when working at 868 MHz, with a -21 dBm sensitivity. The circuit efficiency peaks at 60%, remaining above the 40% for a 18 dB input power range.

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.

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 0.130μm 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%.

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.

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.

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.

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).

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.

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 300?V and an output power up to 0.4 pW for single MEMS device.

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.

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.

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.