Linear actuator torque control

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1

Hi,

I want to build aplication where I will provide defined force with linear actuator. DC motor is going to be stalled most of the time and and controlled torque should be applied. So at the actuator shaft I would like to then to have controlled force. If I apply bigger opposite force on shaft it should go down, if smaller then it should move forward to the end… this application is analog: https://www.youtube.com/watch?v=paohnDXfj6U

At the end I want to connect force sensor into closed loop and control it with PID.

So…my question is how to make cuircuit (I want to use arduino) that would be able to do it. On internet I was able to find a lot of examples how to control linear actuators or DC motor, but 99% of it is about speed control, position control…but about torque control in stalled state I didnt find actually nothing…

Is it possible to make it with basic linear actuator at all or I need some other actuator?

Can I use normal motor drivers, or even simpler configuration with N-Mosfet + PWM signal…?

Any comment, suggestion on this topic?

Regards,

Damir

2

If the motor is stalled, the torque is proportional to the average current.

Either PWM of the appropriate frequency or a variable voltage regulator will work to control the current through a stalled motor, but don’t expect the motor to last very long.

3

thanks for your reply,

Ok…why? what means now very long? …there are many tensile machines that have actuator that pull of press with many tons of force

…like http://www.testresources.net/test-machines/174-family

and I dont think life expectancy is short…what kind of actuator are they then using?

Regards,

Damir

4

Those machines are built by electromechanical engineers who know what they are doing.

The small DC motors used in consumer grade linear actuators are not intended to be stalled.

In general, small DC motors should not be used to provide more than about 25% of the stall torque, otherwise they burn out very quickly. Problems include brush burnout due to over current and no air motion to cool the windings.