Leonardo Barboni

Towards Tactile Sensing System on Chip for Robotic Applications

This paper presents the research on tactile sensing system on chip. The tactile sensing chips comprise of 5 × 5 array of Piezoelectric Oxide Semiconductor Field Effect Transistor (POSFET) devices and temperature sensors. The POSFET devices are obtained by spin coating piezoelectric polymer, poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), films directly on to the gate area of Metal Oxide Semiconductor (MOS) transistors. The tactile sensing chips are able to measure dynamic contact forces and temperatures. The readout and the data acquisition system to acquire the tactile signals are also presented. The chips have been extensively tested over wide range of dynamic contact forces and temperatures and the experimental results are presented. The paper also reports the research on tactile sensing chips with POSFET array and the integrated electronics.

Evaluating Energy Consumption in Wireless Sensor Networks Applications

Wireless sensor networks (WSNs) simulation is essential for the development and optimization of such kind of networks. In this paper we present modifications made to prowler, a WSNs simulator, making its MAC protocol model compliant with the crossbow MICAz mote running on Tiny OS. Moreover, we added radio propagation models to the simulator and, most important, we implemented an energy consumption estimation model of the CC2420 radio chip. Then, the simulator is addressed to the development of WSNs applications with a particular emphasis on energy consumption optimization (and consequently battery lifetime). We present as case study the comparison between simulated results of two different physical deployments, showing how real operating conditions can affect and modify the system behavior in comparison with the results predicted by theoretical analysis.

Experimental Analysis of Wireless Sensor Nodes Current Consumption

Wireless sensor node (WSN) lifetime is correlated with the battery current usage profile. State of the art in wireless sensor nodes current consumption shows that available models have not been extensively tested and experimentally validated. This work aims to seek answers to the following questions: is it accurate the node lifetime prediction obtained with available models? Moreover, is the radio transceiver always responsible for depleting the battery? In order to perform experimental evaluations, we implemented a prototype board that enables to visualize charge extracted from batteries and battery current consumption waveforms of wireless sensor nodes. We selected benchmarks that represent usual tasks in WSN applications and we made experimental evaluations of battery current consumption. Finally, a battery full-depletion time measurement has been performed. Overall results are presented and discussed.

Interface electronics design for POSFET devices based tactile sensing systems

This work presents the development of novel POSFET (Piezoelectric Oxide Semiconductor Field Effect Transistor) devices based tactile sensing system. The tactile sensing system, primarily developed for the robotic applications, consists of 5×5 POSFET touch sensing array and the associated read out and data acquisition system. The POSFET touch sensing devices are obtained by spin coating piezoelectric polymer P(VDF-TrFE), poly(vinylidene fluoride - trifluoroethylene), film on the gate area of MOS (Metal Oxide Semiconductor) devices and polarizing the film in situ. To detect contact events, the taxels utilize the contact forces induced change in the polarization level (and hence change in the induced channel current) of piezoelectric polymer. Both, individual taxels and the array are designed to match spatio-temporal performance of the human fingertips. The data acquisition system is implemented with off-the-shelf electronic components and its design takes into account both the application related requirements as well as the constraints posed by existing hardware on the humanoid robot ‘iCub’. The biasing scheme for using POSFET devices and the problems thereof are also been discussed.

Assessment of the MAC layer behavior of wireless sensor networks simulators using experimental testbeds

In general, wireless sensor networks applications design requires the assistance of a reliable simulator. The comparison of simulated versus measured behavior is undoubtedly a good measure of the simulators reliability. The goal of this paper is to evaluate a wireless sensor network simulator (i.e. Prowler) by comparing its behavior with the measurements obtained from experimental testbeds consisting of MICAz motes. To this aim, the simulator parameters have been tuned to match the testbeds features. Moreover, representative testbeds have been developed and appropriate metrics have been defined, in order to assess the comparison. The results show that the simulator under evaluation can effectively approximate, at MAC layer, the behavior of a wireless sensor network in terms of the numbers of sent and received packets and detected collisions.

Wireless Sensor Networks Power-Aware Deployment

Wireless sensor networks (WSNs) are composed by battery supplied nodes. Node lifetime is defined as the time when the node works properly, before battery depletion. Distances between nodes determine the required radio output power level to ensure reliable connectivity among them, affecting then the node battery current consumption. If some node runs out, it could make unreliable network function. For this, it is important to implement a deployment which assures longer node lifetime; however, this problem is a very constrained and non-lineal one. In this paper, we propose a heuristic algorithm for searching network deployments. The algorithm predicts number of nodes, nodes distances and nodes output power level in order to give a deployment that reaches maximum battery lifetime and compliant with user specifications.

Smart readout design for tactile sensing devices

This article discusses the electronic readout design for tactile sensing transducers based on POSFETs (Piezoelectric Oxide Semiconductor Field Effect Transistors). The design approach, the proposed electronic architecture and the experimental results for validating the proof of concept are presented. This readout features a reduced number of circuits and is implemented with off-the-shelf electronic components. The design takes into account the application related requirements as well as the constraints posed by existing hardware on the humanoid robot ‘iCub’ [1].

Tactile Sensing Systems Based on POSFET Sensing Arrays

This work presents current research achievements on POSFET sensing arrays based tactile sensing system. The tactile sensing chips implement POSFET (Piezoelectric Oxide Semiconductor Field Effect Transistor) devices arrays and temperature sensors. This work presents quantitative evaluation of the tactile sensing chip and a proposal for the electronic data acquisition system. Our goal is to integrate the POSFET arrays into the hands of humanoid robots.

POSFET Touch Sensing Devices: Bias Circuit Design Based on the ACM MOS Transistor Compact Model

In this article we present a common-drain floating gate bias circuit design for POSFET (Piezoelectric Oxide Semiconductor Field Effect Transistor) touch sensing devices. A graphical-aided methodology, intended to furnish a criterion that assures the selection of the most appropriate bias resistance value, is presented

Signal Conditioning System Analysis for Adaptive Signal Processing in Wireless Sensors

In this work it is deduced an extended signal-to-noise (SNR) expression for embedded wireless sensor nodes. The expression can be included onto system level design methodologies for adaptive power-aware sensor acquisition design. In contrast to the conventional approach, it enables designers to estimate the achievable SNR regardless of sensor signal variations and battery voltage droop due to the depletion process. It is offered the theoretical discussion and expression usage examples.