Interface electronics design for POSFET devices based tactile sensing systems

Abstract

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

Device Modelling for Bendable Piezoelectric FET-Based Touch Sensing System

“…In some cases, the range of force experienced by the sensor is not defined and hence we need the sensor to maintain reliable functionality in a wide range of applied contact force. For this reason, in past we biased the POSFET device in common drain mode, popularly known as source follower configuration [14,39]. The major advantages of this configuration are simplicity, stability and predictability with very high input impedance and low output impedance.…”

Measurement of piezoelectric based tactile sensor using low cost setup

“…The system for analog stage consists of POSFET board and analog unit whose specification is given in Table II. The specification for the digital stage is as fo llows, [15], [16] • Sampling rate of one channel: 2fH…”

Design of an advanced signal conditioning unit for sensor with reduced off-the-shelf components

“…In the interface circuitry the main role is played by the signal conditioning unit, in optimizing the sensed signal for better processing at higher level [I]. In recent years proposals have been made for single supply from conditioning electronics to data processing [2]. Such an arrangement can reduce the size of Printed Circuit Board (PCB), by reducing the number of off-the-shelf compon ents.…”