Thread Starter

Ricardo Urbano

I,m currently working with brushless motors, and I still have many questions about the differences between force, speed, and position control amplifiers. I would apreciate it, if there is anybody out there, who can give some information or some resorces or sites about this topic. Thanks in advance.
Ricardo U.
Try American Institute of Motion Engineers ( Power Transmission Design magazine ( PTD has a yearly handbook covering all kinds of motor control basics. Also, Allen-Bradley (Electro-Craft) has a good engineering handbook. Also many textbooks
available on the subject.

Here is my idea but I'm not an engineer working on the amplifier. Just based on my experience...

Yes, most popular types of amplifier for brushless motor are Force (Torque), Speed and Position mode.

First two type (Torque and Speed) amplifier receive analog +/10DCV as a command input. Depend on the mode of amplifier this signal can be treated as torque or speed quantity. (Many of amplifers on the market today can be operated either Force or Speed mode depend on the internal parameter or jumper setting)

For "Force" mode amplifier, host controller should close internal velocity loop (usually means Derivative gain should not be set to Zero) as well as poistion loop. This mode amplifer doesn't close velocity loop and just close current loop and less determistic parameter make the user to set up the amplifier much easily. So I recommen you to use this mode amplifier if your host controller is enough smart and fast as most controller is.

Speed mode amplifier interprets incoming command signal (+/-10VDC usually) as a Speed quantity and it closes the velocity loop internally. Consequently, we have to adjust several amplifer parameter/or resistive pot to make the velocity loop works well with load attached. In this case host controller should not close the velocity loop, if possible.

Position mode amplifier, usually and we call it as stepper replacement amp., recieves pulse and direction signal just like stepper amplifier does. The amplifier closes all of servo loop; Position/ Velocity/ Current loop and host
controller just output pulse train, frequency determines speed and number of pulse determine position motor to go. I think only advantage of this amplifier is that you can use chipper host pulse-output controller. In this case you can't
close the real feedback loop on the host controller so never good for high reponse/precision machine.

Let me know for further information.
Hope this help you out.