speed and position control in a servo system?

[victorjiem]

 i need to be able to manually control the speed and position of a servo motor while the motor is working. the manual part is operating some sort of position switch or sensor. basically i want to move the position switch or sensor to a position and have the motor shaft go to a certain position. the motor needs a very quick response time between when i move the switch to when the motors shaft gets to its position. for example.....say i have a rotary position switch or sensor, i need the motors shaft to rotate 1 degree for every 1 degree that i manually rotate the position switch or sensor. it has to be able to go in both directions. if i rotate the switch or sensor 1 or more degrees in a clockwise direction then the motors shaft should rotate the equal number of degrees also in a clockwise direction. if i manually rotate the switch or sensor 1 or more degrees in a counter clockwise position then the motors shaft needs to rotate an equal number of degrees also in a counter clockwise direction. now with speed...i need to be able to adjust the motors velocity occationaly. i know i can use a potentiometer for this but will that reduce the motors power or torque? the motor needs to retain at least its rated power and torque specs. i'm totally lost with this. please help!? i clearly don't even know if its a position sensor or switch that i need. plus i need to fiqure out where to buy this stuff once i learn what i need to make this system. i believe i'm looking at an open loop set up. i know that i need several components to do this. i just don't know for sure what they are and what gets hooked up to what. also this set up needs to run independantly without being permanatly connectected to a computer. for the purpose of programming some sort of drive or control would be ok as long as i can remove the computer when programming is complete. thanks for any help.

[AndyClegg]

Hi,

Sounds like you need:

1) a feedback position controller, where your "position switch" is the reference (or setpoint), and the controller adjusts the signal sent to the motor to drive it forward or back. You need a sensor that measures the position of the motor, which is the measurement the controller tries to match to the reference. The performance of what you get out of this the performance of the motor, controller tuning, controller structure, sample rate etc.

2) to "adjust the motors velocity" you probably need a switch to bypass the above loop and operate the motor open loop - where the user input is directly connected to the signal passed to the motor.

3) to achieve this without the computer, you will need some hardware to execute the control algorithm.

Of course this all depends upon exactly what type of servo motor you have. There functionality should be standard within the Motion Control software and hardware tools available for use with LV - and I am sure there are some relevant examples. Unfortunatley that suite of sofware and hardware is not something I'm familiar with - but I am sure there are others here who are.