This research effort pursued the design, fabrication, and test of a robotic tactile sensor. The VLSI integrated circuit (IC) portion of the sensor included a 7 x 7 array of metal electrodes which were individually connected to identical MOSFET amplifiers. A 25 micrometers thick patch (6 mm x 6 mm) of piezoelectric polyvinylidene fluoride (PVDF) film was attached to the array with a non-conductive adhesive, thereby creating an array of taxels. Charge, generated by the PVDF film, was detected by the amplifiers. The outputs of these amplifiers were connected to onchip signal circuitry designed to produce a single stream of serial data. A problem with the signal processing circuit circumvented the proper operation of the entire IC. Therefore, an external multiplexer was used to analyze the performance of a 3 x 3 array of taxels located in the center of the 7 x 7 array. The key factor affecting the performance of the sensor was establishing a uniform initial charge state condition across the 3 x 3 array. Schemes for manifesting this condition were examined as well as characterization of taxel load response. A fundamental image recognition process successfully recognized an applied shape by comparing the pre-load, load, and post-load multiplexed output of the array.

The purpose of this research effort was to design, fabricate and test a robotic tactile sensor fabricated from polyvinylidend fluoride (PVDF) films coupled to a silicon substrate containing active amplification circuitry. The integrated circuit incorporated 25 sensor electrode pads (0.6mmx0.6mm each) arrayed in a 5x5 grid with a spacing of 0.6mm between electrodes (this corresponds to a spatial resolution four times greater than the human fingertip). The on-board amplification circuitry consisted of a dual MOSFET amplifier (with a gain of 5) for each sensor electrode. Four different sensor configurations were fabricated and tested. The configurations varied only in the thickness of the PVDF film used (25 microns, 40 microns, 52 microns, and 110 microns). The individual elements of each of the sensor configurations were tested and the sensor based on the 25 micron thick film was considered the optimal sensor of the four. Theses. (mjm).

The purpose of this research effort was to design, fabricate, and test a tactile sensor system consisting of an external high impedance switch circuit, an external multiplexing circuit, and a tactile sensor IC. In order to accomplish this objective, a hardware design and selection process was implemented along with a logical test methodology. An external multiplexer circuit samples all of the array elements in 50 ms. The current prototype sensor has linearity spanning loads of 0.8 g to 135 g, a load resolution of 20 g, and a maximum bandwidth of 25 Hz. Using an elementary shape recognition algorithm the sensor can recognize the shape of a contact load with a spatial resolution on the order of 700 micron. A comparison of three different adhesives used to bond the piezoelectric PVDF film to the surface of the electrode array was made and a urethane adhesive was selected for its superior electrical and physical properties.

Future robots are expected to work closely and interact safely with real-world objects and humans alike. Sense of touch is important in this context, as it helps estimate properties such as shape, texture, hardness, material type and many more; provides action related information, such as slip detection; and helps carrying out actions such as rolling an object between fingers without dropping it. This book presents an in-depth description of the solutions available for gathering tactile data, obtaining aforementioned tactile information from the data and effectively using the same in various robotic tasks. The efforts during last four decades or so have yielded a wide spectrum of tactile sensing technologies and engineered solutions for both intrinsic and extrinsic touch sensors. Nowadays, new materials and structures are being explored for obtaining robotic skin with physical features like bendable, conformable, and stretchable. Such features are important for covering various body parts of robots or 3D surfaces. Nonetheless, there exist many more hardware, software and application related issues that must be considered to make tactile sensing an effective component of future robotic platforms. This book presents an in-depth analysis of various system related issues and presents the trade-offs one may face while developing an effective tactile sensing system. For this purpose, human touch sensing has also been explored. The design hints coming out of the investigations into human sense of touch can be useful in improving the effectiveness of tactile sensory modality in robotics and other machines. Better integration of tactile sensors on a robot’s body is prerequisite for the effective utilization of tactile data. The concept of semiconductor devices based sensors is an interesting one, as it allows compact and fast tactile sensing systems with capabilities such as human-like spatio-temporal resolution. This book presents a comprehensive description of semiconductor devices based tactile sensing. In particular, novel Piezo Oxide Semiconductor Field Effect Transistor (POSFET) based approach for high resolution tactile sensing has been discussed in detail. Finally, the extension of semiconductors devices based sensors concept to large and flexile areas has been discussed for obtaining robotic or electronic skin. With its multidisciplinary scope, this book is suitable for graduate students and researchers coming from diverse areas such robotics (bio-robots, humanoids, rehabilitation etc.), applied materials, humans touch sensing, electronics, microsystems, and instrumentation. To better explain the concepts the text is supported by large number of figures.

The purpose of this research effort was to investigate the performance of a piezoelectric tactile sensor design and appropriately refine it. The sensor was fabricated from an 8 x 8 electrode array MOS integrated circuit. Each taxel in the array was 400 microns x 400 microns. A 6 mm x 6 mm piece of piezoelectric polyvinylidene fluoride was adhered to the electrode array using a urethane dielectric adhesive to form the active sensing area of the sensor. An amplifier was investigated to enhance the range of the tactile sensor's output signal. The amplifier is a high input' impedance differential amplifier with a linear range from 1 to 17 V. The unique feature of the differential amplifier was that it used a power supply of only 12 V. The spatial resolution of the sensor is 0.7 mm. The lower force limit of the sensor is 1 g while the upper limit, limited by a previous amplifier design with a range from 2.5 to 7 V, is 130 g. The dynamic range of the sensor is 130:1. The sensor's force sensitivity is 7.35 g. The pyroelectric bandwidth of the sensor is 0.083 Hz, and the temperature sensitivity of the sensor is 0.39 degrees Celsius. Tactile sensor, Sensors, Piezoelectric, Pyroelectric, PVDF, Thin film.