A dc motor controller is a device that works alongside a microcontroller, the batteries and motors. Most controllers have under-voltage, over-voltage, short circuit protection, current limit protection, thermal protection and voltage transients. Without these protections, the motor is exposed to threats that can result in permanent electrical or mechanical damage.
Some DC Motor Controllers control two motors independently and often only one supply voltage can be used to supply both motors
The benefits of using a controller.
Electrical protection of the motor
Maintains constant speed
Dynamic response to changing system demands
Monitoring to evaluate machine performance / diagnostics
Accurate speed control