I’m planning on using a brushless motor for the weapon, and possibly two brushed motors for the wheels, so do I need more than one speed controller? Do I need a speed controller for brushed motors? Can one speed controller be used for multiple motors?
If you have any recommendations in general that would be helpful. Thanks.
Brushless DC motors don’t self commutate and so need electronics to "emulate" the brushes. Controllers for them take the position of the motor, combine it with a desired speed and use that to alter the flow of current in the wires feeding power to the motor.
Brushed motors don’t need to emulate the brushes, and so a very simple on/off switch will function as a very basic speed controller for a brushed motor. ie off=0 rpm. On=max rpm. Switching such a motor on/off fast, is called PWM, and allows the speed of a brushed motor to be altered between on and full, using only a single transistor. If you want option of reverse you’ll need some more electronic switches (transistors) to form a H-bridge.
I’d probably use a pic uC to generate control signals for the switches. Transistors convert those low power signals into power feeds for the motors. This could all be fit on single PCB and would constitute a motor control board. Best to have some decent heat sinks on the transistors! Once the circuit is running/tested, it might be worthwhile potting the board up (make sure the heat can still escape from the transistors) If the resulting box (filled with potting compound) is strong enough you could perhaps use the box as a structural member, in much the same way as F1 cars use the engine to connect the rear suspension to the rest of the car.
You need some kind of controller/switch for each motor you want independant control of.