Dc motor controller as motor of electrical energy into mechanical energy, depending on the load demand, to adjust the speed.
Below we said about the dc motor controller of speed adjustment ways.
The armature voltage control: using input armature voltage to speed adjustment.
Magnetic field control: by means of adjusting excitation current to speed.
Resistance: in the armature circuit, the use of adjusting resistance to controller of dc motor speed control.
Above is the dc motor speed control ways of the controller, I hope it can help you.