I have a robot that uses brushed motors in its servo system. These are Maxon 3W motors, with 131:1 planetary gearboxes. The motors are controlled by a PIC microcontroller, running a 1kHz PID controller. The servos are for a low speed high torque application. There is significant backlash between the sensor and the motor.
Maxon offer 12W brushless motors which are the same size. These are better in many ways: double the torque, better heat dissipation, higher efficiency.
The problem, obviously, is that they require more complex drive electronics. Also, I have heard a couple of people mention that brushed motors are better for servo applications, though they never explained why.
- Has anyone else implemented this kind of system?
- Are there any gotchas when using brushed motors for servos?
- Is it possible to servo it at low speeds if I only have the 3 integral digital Hall sensors, and no encoder? (I would prefer not to add an encoder because of the money and space cost)
- It torque ripple likely to be a problem?