Hi @axppxsky,
The Newton Gripper uses a brushed DC motor[1], and has no included sensor to estimate its position / rotation angle. It’s only possible for it to detect when it’s fully opened (or closed against something) because the driving current spikes at those points, which the firmware takes note of and stops trying to push further.
There’s no reliable way to do this with software alone, unless your application has a highly consistent load on the motor, in which case you could command movement in the desired direction for a set amount of time, but even then the control may not be very precise.
To achieve reliable and precise movement limits your options are:
- Make physical end-stops that prevent the motor/linear actuator from moving beyond the desired region
- in this case the existing firmware will detect that the motor has reached a stopping point and will avoid trying to push beyond it
- you could potentially design some custom jaws that would achieve such an effect, or add some parts to the existing jaws so they push against something at your desired limits
- Add a positioning sensor to the motor, and feed its signal back to whatever you’re using to control the motor
- this would be significantly more complicated, especially if you’re trying to put the sensor inside the existing gripper housing.
Not a servo motor - we just set the motor controller up to take PWM signals with pulse durations in the standard servo range, for ease of integration with hardware that is normally set up to control servo-style motors or ESCs. ↩︎