I am running a linear actuator using the Pololu Jrk 12v12 USB Motor Controller with Feedback. While performing collision tests with the actuator I noticed that the controller was still drawing current even after the actuator had collided and was not moving anymore. I am wondering if there is a setting in the Pololu software that could control the current drawn after the actuator collides and is no longer moving? Currently the system is still drawing .6 A after the actuator has collided. Are there any settings in the Pololu JRK configuration Utility to change the current draw to 0 when a collision occurs?
Hello.
It sounds like when you refer to a collision, you are talking about the actuator hitting an object and stalling. If that is the case, you will need some way of detecting this condition. If your actuator draws less than 0.6A when operating normally in your application, you might try setting the “Max. current (A)” setting in the “Motor” tab of the Jrk Configuration Utility to 0.6 (or just under) and changing the mode for the “Max. current exceeded” error in the “Errors” tab to “Enabled and latched” to have the jrk stop driving the motor and wait for another set target command.
Brandon
I tried this solution by setting the Max current to 1 A. The problem with this solution is that the inrush current to get the actuator to start to move is greater than 1 A, so it trips the Max Current (A) error and the actuator does not even start to move sometimes. I have a potentiometer connected to the JRK 12V12 to control the actuator and there is also there is the problem that when the error is latched I have to go back into the Pololu Software utility to run the Motor again once the error is tripped, not just adjust the potentiometer to retract the actuator. Do you have any other suggestions?
If you can give me more specifics about your project, I might have additional suggestions. Can you describe what your application is? Are you using an actuator that has position feedback (e.g. a built-in potentiometer)? Is it colliding with something that is always in the same place (e.g. when it is extended 80%)?
Brandon
The project I am working on is controlling hydrofoils on a boat using actuators controller by the JRK 12V12. The actuators do have potentiometers in them, but I am creating a mechanical stop in case there is some slip in the potentiometer. It is desired that if there is a glitch in the potentiometers and the actuators collide with the mechanical stop that they do not continue to draw power. This is why I cannot just simply change the max and min positions of the actuators.
Thank you for the additional information. The closest thing the jrk has to stall detection is the max. current limit. Since it sounds like you are mainly using it as a fail safe and it should only trigger if something goes wrong, it might work if you can limit the start-up current of your actuator. You might try adding an acceleration limit in the “Motor” tab of the Jrk Configuration Utility (maybe test with something low like 10 or 20).
Alternatively, you might consider adding some limit switches near the mechanical stop. Since the jrk does not support limit switches directly, you would need to add a separate microcontroller to process the limit switches (as well as your potentiometer input) and send TTL serial commands to the jrk to control the actuator. This way, if the limit switch gets triggered, you can ignore the potentiometer and command the actuator to close or have the microcontroller adjust an offset until the switch is no longer triggered.
Brandon