The main potential advantage of electro-rheological fluid when used as the interface medium between electronics and actuators in high speed machines is its ability to respond quickly to a change in the control signal. The analysis reported in this paper shows that over the operating speed range the system has a time constant of less than one millisecond and for most practical applications it can be assumed that when a suitable control strategy is employed the output torque would be proportional to the control signal.
Most electro-mechanical torque transducers have time constant of over 10 milliseconds and therefore direct measurement of the torque produced by the electro-rheological clutch would be very expensive if not impractical. This paper reports a numerical method of identifying the torque response from the output of a conventional torque transducer which has a natural frequency of 110 Hz. The transfer function is first identified from a standard step input test, and the torque response of the clutch then is estimated from the measured signal. Although the noise on the signal will be always amplified with this method the use of a digital filter makes it possible to obtain an accurate estimate of the torque response.