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[January 2005]
Piezo Motor Walks Round in Circles
A rotary version of the Piezo Legs motor is now available from Unimatic Engineers Ltd (London, England) which the company is introducing as a companion to the Piezo Legs linear motor/actuator. It uses a similar operating principle to the original Piezo Legs linear motor, i.e. tiny piezoelectric legs are made to 'walk', in this case driving around a shaft instead of creating linear motion.
Each leg is made of a ceramic laminate cantilevered from a base plate. When subjected to an electrical impulse the leg deflects rather like a bimetallic strip. By sequencing the pulses to a number of legs, a walking effect is created. Like the legs, the electrical impulse is very small - so small in fact that they cannot spark, even in an explosive atmosphere.
It is a characteristic of the piezoceramic material that the legs are bistable and will maintain both the resting and extended position with no need for a constant electrical signal, further enhancing the intrinsic safety of the motor.
Unimatic says that the low speed performance of the motor is phenomenal, with one rotation per week being achievable while maintaining accuracy to one ten millionth of a turn. Maximum speed is 20rev/min.
Torque output is up to 0.08Nm, representing a considerable power density considering that it is 32mm long and 23mm in diameter. With no gearbox and no minimal moving within the motor, a long maintenance-free working life is guaranteed according to the company.
Potential applications include crystal growing, electronics manufacture and assembly, medical and robotic tools for microsurgery, intrinsically safe machinery for explosive atmospheres, hygienic and sterile environments etc.
www.unimatic.com
ENDS