Position control without an encoder
Position control without an encoder
(OP)
I am relatively new to motor control and would like to move a mirror between 2 positions approx 90 degrees apart using a BLDC motor.
I want the mirror to flip between the 2 positions within a couple of seconds.
I hope to use limit switches to enable my control circuitry to know that it has almost reached either of the 2 positions.
At both of the positions/end points I plan to use stoppers. However, I want the motor to remain at the end point and not be disturbed by any vibration it may experience from the rest of the system.
At present, I am aware that I will need to reduce the current to the motor to stop it burning out, once it has reached an end point. However, I am unclear whether a minimal current is all I need to maintain this desired position, or whether there is an alternative approach.
I am reluctant to use a complete position feedback circuit, since I feel it is over-kill for what I am trying to achieve. Although, if you suggest otherwise..?
Also, for the application I am proposing, would a stepper motor be better, since they have a better holding torque?
I want the mirror to flip between the 2 positions within a couple of seconds.
I hope to use limit switches to enable my control circuitry to know that it has almost reached either of the 2 positions.
At both of the positions/end points I plan to use stoppers. However, I want the motor to remain at the end point and not be disturbed by any vibration it may experience from the rest of the system.
At present, I am aware that I will need to reduce the current to the motor to stop it burning out, once it has reached an end point. However, I am unclear whether a minimal current is all I need to maintain this desired position, or whether there is an alternative approach.
I am reluctant to use a complete position feedback circuit, since I feel it is over-kill for what I am trying to achieve. Although, if you suggest otherwise..?
Also, for the application I am proposing, would a stepper motor be better, since they have a better holding torque?





RE: Position control without an encoder
If your mechanical load is light, you may be able to use a damper motor. You can get faster action by using a linkage that uses only part of the stroke. It will hold your device tight on the stop at each end. No limit switches will be needed.
yours
RE: Position control without an encoder
RE: Position control without an encoder
TTFN
RE: Position control without an encoder
RE: Position control without an encoder
If you wanted to use a BLDC motor without position feedback to do this, you would actually have to run it like a (low-pole-count) stepper motor.
Curt Wilson
Delta Tau Data Systems
RE: Position control without an encoder
Plesae read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>
RE: Position control without an encoder
Mike Halloran
Pembroke Pines, FL, USA