A question which surfaces from time to time on the Zone relates to whether stepper motor control systems provide a full closed-loop facility.
I must confess to having a preference for Servo systems and have spent a considerable amount of time developing a closed-loop servo motor controller. The system works well with a variaty of controllers for brushed /brushless DC motors, but could a stepper motor be hooked-up to replicate the response of the DC motor ???
The fundamental theory behind closed-loop control, is the generation of an outout signal which is proportional to the difference between the actual & required positions. In many controls this signal is an analoque command voltage of +/- 10volts and is used to vary the speed of the DC motor, whilst driving it to the 'requested posiotion'.
IF---- the +/- 10volt command signal is processed by a voltage to frequency converter (LM331 or AD625) a PULSE TRAIN whose frequency is proportional to the input voltage is produced.
Would the stepper motor speed respond to this change in pulse frequency and perform similarly to a DC motor?
My experience with stepper motors is very limited (well a bit less than that !! ) so I look forward to reading some of your comments on this theory.