Integration Sample Questions

1. A closed-loop control system utilizes an amplifier in the current mode. If the system parameters are changed as indicated and assuming a steady-state gain under step response, what is the overall effect on the loop gain?

1. increase by a factor of 2
2. increase by a factor of 8
3. increase by a factor of 4
4. no change
5. decrease by a factor of 2

2. It is required to compare two similar motor/drive systems from two different manufacturers. You have torque versus speed information for both systems, but the assumed temperatures are different. For motor/drive system A, the assumed rotor temperature is 155C with an ambient temperature of 25C. On the other hand, for motor/drive system B, the assumed rotor temperature is 100C with ambient temperature was 40C. Assuming all other factors being equal, approximately how much should you derate system A in order to make a valid comparison?

1. 32%
2. 68%
3. 46%
4. 63%
5. 27%

3. You are designing a ball-screw driven positioning system (using a 5 pitch screw) that requires a linear encoder be mounted on the table. The linear encoder has 1000 lines per inch. In order to achieve stability at zero speed, you've chosen to use a stepper motor drive and will use a count and compare type motion controller to close the position loop. The motion controller accepts quadrature signals form the linear encoder. In order to take full advantage of the available resolution of the linear encoder, what is the minimum steps per revolution that you recommend?

1. 3200 steps per revolution
2. 400 steps per revolution
3. 200 steps per revolution
4. 800 steps per revolution
5. 20,000 steps per revolution

4. The torque versus speed curve for typical brushless servo motor-drive systems have two different operating regions: a continuous duty region and a intermittent duty region. In both regions most systems have relatively flat torque curves up to a relatively high speed, then the torque decreases linearly up to the maximum speed, where it drops to zero. To what is the drop-off in available torque at higher speeds attributed?

1. voltage available from the amplifier
2. motor thermal characteristics
3. current available from the amplifier
4. motor rotor balance and centrifugal force considerations
5. commutation limits due to brush arching

Page Revised: July 14, 2003