Starting from human ?sense of touch,? this paper reviews the state of tactile sensing in robotics. The physiology, coding, and transferring tactile data and perceptual importance of the ?sense of touch? in humans are discussed. Following this, a number of design hints derived for robotic tactile sensing are presented. Various technologies and transduction methods used to improve the touch sense capability of robots are presented. Tactile sensing, focused to fingertips and hands until past decade or so, has now been extended to whole body, even though many issues remain open. Trend and methods to develop tactile sensing arrays for various body sites are presented. Finally, various system issues that keep tactile sensing away from widespread utility are discussed.

Tactile Sensing—From Humans to Humanoids

Interferometric measurements of electric field‐induced displacements in piezoelectric thin films using single‐beam and double‐beam optical detection schemes are reported. It is shown that vibrational response measured with a single‐beam interferometer includes a large contribution of the bending motion of substrate. Therefore, it is difficult to apply single‐beam technique for piezoelectric measurements in thin films. To suppress the bending effect a high‐resolution double‐beam interferometer is proposed. The sensitivity of the interferometer is significantly improved in comparison with previously reported system. The interferometer is shown to resolve small displacements without using a lock‐in technique. An example of the interferometric capabilities is demonstrated with experimental results on electric field, frequency, and time dependences of piezoelectric response for quartz and Pb(Zr,Ti)O3 thin film.

Interferometric measurements of electric field-induced displacements in piezoelectric thin films

A wide variety of tactile (touch) sensors exist today for robotics and related applications. They make use of various transduction methods, smart materials and engineered structures, complex electronics, and sophisticated data processing. While highly useful in themselves, effective utilization of tactile sensors in robotics applications has been slow to come and largely remains elusive today. This paper surveys the state of the art and the research issues in this area, with the emphasis on effective utilization of tactile sensors in robotic systems. One specific with the use of tactile sensing in robotics is that the sensors have to be spread along the robot body, the way the human skin is-thus dictating varied 3-D spatio-temporal requirements, decentralized and distributed control, and handling of multiple simultaneous tactile contacts. Satisfying these requirements pose challenges to making tactile sensor modality a reality. Overcoming these challenges requires dealing with issues such as sensors placement, electronic/mechanical hardware, methods to access and acquire signals, automatic calibration techniques, and algorithms to process and interpret sensing data in real time. We survey this field from a system perspective, recognizing the fact that the system performance tends to depend on how its various components are put together. It is hoped that the survey will be of use to practitioners designing tactile sensing hardware (whole-body or large-patch sensor coverage), and to researchers working on cognitive robotics involving tactile sensing.

Directions Toward Effective Utilization of Tactile Skin: A Review

https://ir.nctu.edu.tw:443/bitstream/11536/12727/1/000234982100017.pdf

Effects of doping concentration and annealing temperature on properties of highly-oriented Al-doped ZnO films

Piezoelectric materials have been integrated with silicon microelectromechanical systems (MEMS) in both microsensor and microactuator applications. Thin-film materials selection and processing routes are reviewed. Some recent and emerging applications of piezoelectric MEMS are presented including acoustic emission microsensors, vibration monitors, molecular recognition biosensors, precision positioners, micropumps, and linear stepper motors.

Processing and characterization of piezoelectric materials and integration into microelectromechanical systems

A multipurpose integrated-sensor chip has been fabricated for the simultaneous measurement of physical and chemical variables The multipurpose chip which measures 8 × 9 mm2contains conventional MOS devices for signal conditioning, array accessing, and output buffering along with the following on-chip sensors: a gas-flow sensor, an infrared-sensing array, a chemical-reaction sensor, cantilever-beam accelerometers, surface-acoustic-wave (SAW) vapor sensors, a tactile sensor array, and an infrared charge-coupled device imager The multisensing functions of this chip utilize both the pyroelectdc and piezoelectric effects in ZnO thin films Fabrication of the chip is carried out using a conventional 3-µm Si NMOS process combined with Si micromachining techniques Compatible fabrication technology and sensor properties are described

Integrated multisensor chip

A 64-element piezoelectric tactile-sensor array, integrated on a silicon chip, has been fabricated and tested. The sensor array consists of 1µm-thick sputtered ZnO piezoelectric capacitors in an 8 × 8 matrix with each sensing element measuring 70 × 70µm2and spaced with a pitch of 70µm. Each sensor element is connected to an on-chip NMOS buffer-amplifier. The measured piezoelectric coefficient d 33 in the ZnO films is 14.4 pCN-1. The measured voltage responsivity (at T=300K) is 5.2 mV/gm with a hysteresis-free linear response for loading to 200 gm.

Integrated Zinc oxide-on-silicon tactile-sensor array

Thin films of pyroelectric ZnO have been combined wlth NMOS planar tech nology to produce a fully integrated anemometer. The anemometer is based on the differential cooling rate of two heat sensors placed up- and downstream from a heat source. The heat sensors for the anemometer consist of 2 µm-thick sputtered ZnO pyroelectric capacitors encapsulated in silicon dioxide. Sense electrodes on the capacitors are connected directly to differentially coupled depletion-mode MOSFET pairs.

Monolithic integrated zinc-oxide on silicon pyroelectric anemometer

A fully-integrated, 64-element, pyroelectric infrared-detector array, fabricated on a thin-membrane structure by combining ZnO thin-film deposition technology, NMOS planar processing, and anisotropic backside etching of silicon is described. Incident thermal radiation on individual detector elements is sensed by the temperature change in a structure composed of a ZnO pyroelectric capacitor encapsulated in silicon dioxide and supported by a 25 µm-thick silicon membrane. Thai measured black-body responsivity at temperature T=300 K and frequency f=24 Hz is 4.3 × 104VW-1with a corresponding measured detectivity D*=3.1 × 107cm √ HzW-1.

Fully-integrated ZnO on silicon pyroelectric infrared detector array

A contactless optical modulation technique for the determination of photogenerated carrier lifetime in silicon is presented. The method is based on the measurement of the optically modulated free-carrier absorption in Si at 10.6 µm. The fractional change in transmitted intensity of a dc below band-gap probe beam (with ħω _{p} E_{g} ) due to a modulated pump beam (with ħω _{p} > E_{g} ) is proportional to the excess carrier lifetime. This optical modulation technique, which is relatively simple, contactless, and nondestructive, may have significant potential as a high-resolution high-sensitivity tool for Si wafer screening, crystal growth studies, and process evaluation.

D.L. Polla

Papers

Integrated multisensor chip

Integrated Zinc oxide-on-silicon tactile-sensor array

Monolithic integrated zinc-oxide on silicon pyroelectric anemometer

Fully-integrated ZnO on silicon pyroelectric infrared detector array

Determination of carrier lifetime in Si by optical modulation