Non-Backdriving Arm

How do I stop a robot arm from backdriving under it’s own weight?

**This can be accomplished in several ways:

  1. Decrease the load of the arm - Try using rubber-bands, or some other kind of passive assistance to hold the arm up.

  2. Decrease the load on the motor - Increase the amount of gearing on the arm. This will cause the load “seen” by the motor to be reduced. When this load is decreased below the internal resistance of the motor/gearbox, then the arm will “stay”.

2a. Decrease the load on the motor - Try increasing the INefficiency in the gearing. Adding friction to the system will act as a brake on the arm. This will keep the arm where you want it. However, this load will also act on the arm when it is in motion. (i.e. when the arm is running, it will need to overcome this braking load.)

  1. Use some sort of torque transfer method, that does not backdrive (worm gear, or lead-screw). - Unfortunately, there are no current Vex pieces to accomplish this sort of thing. You would need to design your own.

  2. Apply some voltage to the motor, so it holds in place - This can be done through the use of software, or alternately, you can use the trim settings on the joysticks of your vex transmitter. (Simply set it, so the arm always wants to move upwards).

Note: #4 is not ideal, because in this case, the motor will opperate at a low-voltage stall-state for long periods of time. This is not good for the motor, and can potentially cause damage. **