New ultrasonic torque motor

Assembly Automation

ISSN: 0144-5154

Article publication date: 1 March 2000




(2000), "New ultrasonic torque motor", Assembly Automation, Vol. 20 No. 1.



Emerald Group Publishing Limited

Copyright © 2000, MCB UP Limited

New ultrasonic torque motor

New ultrasonic torque motor

Keywords: Electromagnetic torque, Ultrasonic

Providing high torque in a small package size is a big advantage of the new PMR40 motor over current electromagnetic motor designs. Even in a power off state the motor locks with 20Ncm of holding torque making it ideal for applications where a position has to be maintained for a long period without power consumption. Driven by a vibrating piezoelectric ring the motor does not produce any sparks or stray magnetic fields and can, therefore, be safely used in an explosive environment. Other typical applications will include belt drives and medical equipment.

The PMR40 offers unidirectional operation with a maximum torque of 10Ncm and a maximum variable speed of 100rpm. A fast start and stop response of 50ms is controlled by a TTL input and the power consumption of the motor, when in operation, is less than 2W. The mounting flange of the motor is 40mm square and the depth of the body, including flange, is 17.5mm (see Plate 5).

Plate 5The PMR40 - new ultrasonic torque motor

The PMR40, available through Lambda Photometrics, in the UK, employs a new operating principle. The piezoelectric ring is excited to its radial resonant frequency of 53kHz. Eight radially attached flexible steel blades transfer the oscillations to the rotor through friction. Each motor is supplied with a driver board equipped with the circuitry required to generate the operating frequency. The resonant frequency of the piezo element determines the vibration frequency of the circuit, independent of working conditions, temperature and ageing effects. A 12V DC source providing up to 0.15A is all that is required to drive the motor.

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