Page 234 - Servo Motors and Industrial Control Theory -

232 Appendix C

The data in Chap. 9 are presented in graphical forms that you should use.
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1. Assume that it is required to move a load inertia of 0.2 kg·m referred to the
motor shaft, to a speed of 500 rpm in one second. Note that the time response is
made of a saturated time response where the motor generates maximum torque
and a dynamic time response. These data are separated for servo motors of a
maximum speed of 1500 rpm. Assume that at speed of 500 rpm and a torque
2 N m is applied to the motor.
Determine what kind of servo motors meets the above mentioned specifications.
Assume also that the transmission mechanism is rigid. Also determine the maxi-
mum dynamic velocity drop when the step input of external torque is applied,
even though it has not been specified as a requirement. Discuss all aspect of
selection procedure such as reliability, cost and weight.
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2. For a special application, it is required to move a load inertia of 0.5 kg·m
referred to the motor shaft to 1500 rpm in 2 s. The velocity drop when the maxi-
mum torque of 50 N m is limited to 50 rpm. Determine which of the servo motors
meet these specifications. There may be several types of servo motors that meet
these specifications, and then you should consider other criteria such as reliabil-
ity, cost, weight and availability. It is also possible that none of the servo motors
meet the required specifications. In this case the required specifications must be
relaxed a little bit and a compromise has to be made between the required perfor-
mance and availability of the servo motors.
It is also possible to refine the controller by using acceleration feedback or to
use state variable feedback control strategy if the problem is only the dynamic
behavior of the motor.