Abstract:
Future advanced artificial hands will require the automatic holding of objects using
feedback control. To achieve this aim will require sensors of various types, one of which
should be capable of detecting the relative movement between the surface of a grasped object
and the hand (slip). A low-cost sensor, using thick-film technology, has been developed
which detects slip using the piezoelectric effect. Experimental evaluation of the sensor has
been carried out using a test apparatus whereby a block of aluminium representing an object
slides past the sensor. Attached to the object surface is a Perspex sheet with repeating groves
cut into the surface. Two different separations of the groves have been tested. The results
show that the slip sensor detects the relative velocity between a moving object and the sensor
surface. The sensor has a frequency response into the kilohertz which makes it an excellent
candidate for a slip sensor. The sensor is able to detect slip with and without a cosmetic
material covering the sensor. Computer simulations of the mechanical modes of vibration
have shown that the frequency of the lowest fundamental mode is much higher than the
electronic signal output from the sensor.
