I am building a robot, and the motors are DC. In my project, the reference inputs of lower controller are torque. I can not find articles about how to control DC torque,though there are a lot of articles about DC speed/position control.I want some articles about how to make a joint and to control DC torque.Please help me!!!my email is [email protected] or [email protected] you!

 

If you control the voltage applied to a DC motor, then you will be approximately controlling speed. If you want to control torque, then you will have to control the current. This is a little harder than controlling voltage because, depending on the speed and back EMF, different amounts of voltage are needed to achieve the same current (i.e. torque). You could construct a circuit that measures current in a small sense resistor, and then varies the voltage, or the duty cycle, in order to achieve the level of current/torque that you want.

-Robert Scott
Real-Time Specialties
Embedded Systems Consulting

 

Almost exactly -
Torque=Power/rpm in an ideal motor. To control torque exactly you need to
know:
A. Shaft speed - can be measured on shaft (Tachometer) or deduced from back
EMF measured in PWM circuit when input power is momentarily off.
B. Armature resistance (to deduct internal losses = I * I *R).
Meir

 

Basically, DC motor torque is proportional to current.

For DC motor current control, add current error PI amplifier with output voltage limitation for processing current command and current feedback to H-bridge PWM voltage amplifier described in "Advanced Unipolar PWM Technique" article at

http://www.drbrushless.com/cgi-bin/articles.phtml

 

On October 17, 2003 11:54, xianglj wrote:
<clip>
> I am building a robot, and the motors are DC. In my project, the reference
> inputs of lower controller are torque. I can not find articles about how to
> control DC torque,though there are a lot of articles about DC
> speed/position control.I want some articles about how to make a joint and
> to control DC torque.
<clip>

If this is a conventional DC motor, torque is proportional to current. To
control torque, you need to control the current rather than the voltage.

Michael Griffin
London, Ont. Canada

 

Almost exactly - Torque=Power/rpm in an ideal motor. To control torque exactly you need to know:
A. Shaft speed - can be measured on shaft (Tachometer) or deduced from back EMF measured in PWM circuit when input power is momentarily off.
B. Armature resistance (to deduct internal losses = I * I *R).

Meir

 

Commercial BLDC drives have an internal current loop that regulates the torque depending on the motor load. There are provision to get at the current loop input to regulate torque if required for such things as limiting the torque in special cases. I have a document that shows how the current loop works in a BLDC drive if you are interested.

George W. Younkin, PE, IEEE Fellow
Staff Engineer
Industrial Controls Consulting
A division of Bull's Eye Marketing, Inc.
104 S. Main St., Suite 320
Fond du Lac, WI 54935
Ph: 920: 929-6544
Fax: 920: 929-9344
E-mail: [email protected]

 

If you use lower controller (current or torque controller) inside outer speed or position loop, than current or torque will be controlled by PI speed or PID position filter. Independent torque control is used mainly for tension control.

Leonid Gannel

 

COMPLETE EXACT:TORQUE=(mg-F)r(Nm)