Q: Step or Servo Motors? I am trying to source two position control motors for two belt and pulley actuators. The motor must have a fast response for my application since this is a high throughput production machine. The first actuator motor needs to perform two 720 degree moves in 0.2 seconds. This move will be repeated three times in 1 second, with about 0.1 seconds of dwell time. A second actuator motor will need to perform a 10 revolution move in 0.3 seconds, with 0.5 seconds of dwell time. The required torque for both actuators is 0.40 Nm. The system inertia is 3.8 x 10^-4 kg-m^2 according to my 3D CAD software.
The motor must be at least dust protected and enclosed, and needs to be cost effective. I am trying to avoid having to gain tune a servo motor, and am not sure about stepping motor performance qualities. In either case, feedback from the motor is required so that it can trigger flags in the controller to perform other functions based on position. What does Oriental Motor have to offer?
A: The choice between a stepping motor and a servo motor usually comes down to the overall application requirements. For the first application, since the overall move is less than 3 revolutions in a short time, a stepping motor will have the advantage overall due to the system differences. With a stepping motor, the motor responds immediately from the pulse input to the motor driver since it is capable of operating in open loop. With a servo motor, the motor will start its move after the PID control process.
This takes extra time for this process to occur. For initial response, the stepping motor has the advantage. We also have to consider settling time. Since the dwell time is only 0.1 seconds, a stepping motor would also be better suited since it will settle faster than that of a servo motor typically. Again, this is due to the PID control characteristics. Since the belt and pulley actuator is a low rigidity application, the gain must be set for a low rigidity system.
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