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Torque, Velocity & Position Loops

The Gemini and Dynaserv can be operated in Torque, Velocity, or Position Mode. Other drives are either Torque (OEM670/675/770 and TQ10) or Velocity (TQ10V) drives. Some, like the APEX drives, can be either Torque or Velocity drives.

+/-10V into the drive commands torque. +0V means that no torque is being commanded and the motor can free-wheel or just spin freely. Any voltage will apply current to the motor, thus causing the motor to create torque. Torque has a direct relationship with acceleration, so the more torque that is being commanded, the higher the acceleration. If a Velocity or Position loop is to be closed, the encoder information must go back to a controller that will control how much torque is required to get to a desired velocity or position. All tuning is done within the controller.

+/-10V into the drive commands velocity. +0V means that a zero velocity is being commanded. Turning the shaft by hand is very difficult because torque will be commanded to keep the motor at zero velocity. To close the Position loop requires that the encoder information goes back to the controller so that the correct amount of velocity can be commanded to get to the correct position. Some tuning is required in a Velocity drive. Analog drives will have potentiometers while digital drives, like the Gemini, will have software commands for tuning.

Few drives have a Position Mode. Instead of taking +/-10V, the drive requires Step & Direction like a stepper drive. A controller is not required for closing any loops. But, unless the encoder information is returned to the controller in this case, the controller can only assume that the motor is in it commanded position. Without the feedback, the controller will not know exactly where the motor is. This is the case with using a 6K and GV in Position Mode. The tuning is all done within the drive when it is in Position Mode.