A VERY HIGH-SPEED PIEZOELECTRICALLY ACTUATED CLUTCHING DEVICE

Piezoelectric multilayer actuators can rapidly generate very large sta ll forces. A typical device measuring 18 mm long by 5 mm square will p roduce an 800 N stall force in less than 100 mus, however the small ou tput movement obtained, typically 15 mum, is almost unusable in medium or low precision machines. Efficient amplification or transformation of such movement, with optimization of the force-displacement product at the output, makes it advantageous to employ piezoelectric multilaye r actuators in lower precision, lower cost high-speed machines, such a s those involving clutching or gripping. The mechanism described in th is paper is one design in a series of monolithically constructed devic es designed around flexure hinges. It generates a 30 N stall force, wi th an unrestrained movement of over 110 mum, derived from a piezoelect ric device which only extends by 15 mum. Although the device cannot be considered highly efficient, it transforms the output movement up to a level which can be used directly with components produced to moderat e degrees of surface finish. This paper describes a prototype device w hose purpose is to rapidly clutch a thin metal strip. This paper detai ls the device and shows performance data including speed of response, electrical clutching energy and mechanical performance. The efficient displacement amplification of piezoelectric devices is seen as a gatew ay to many differing applications, currently dominated by the solenoid . Many potential applications exist in the field of robot actuation.