Thick-film piezoceramic “slip sensors” for a multifunctional prosthetic hand

The majority of prosthetic hands lack an intelligent feedback control system meaning that the user has to rely on visual feedback to detect whether an object is being crushed or if it is slipping out of the hand. Recently, a new type of fingertip for the Southampton Hand has been developed encompassing an array of thick-film sensors to measure grip force and the onset of object slip. There are three types of sensor used: piezoresistive thick-film sensors to detect the force on a finger, a piezoelectric thick-film sensor to detect the onset of slip and a thick-film thermistor to monitor temperature. Some initial results are presented for the “slip” signals produced from the thick-film piezoelectric sensor. The sensor has already shown its ability to differentiate between the initial contact with an object and the object sliding past the fingertip. It may also be able to determine several variables and parameters such as: object acceleration, the coefficient of friction between the sliding surfaces and the force applied by the fingertip to the sliding object. There characteristics could then be used in a closed loop control system