The controller is not a motor nor does it contain one. It is an electrical device that controls the sewing machine motor. The ones I've worked on have a system that modulates/controls the amount of electricity that the motor gets, therefore controlling the speed of the sewing machine motor. As you press your foot on the controller, the insides become closer together and more electricity flows through the device. The older American ones are basically the same on the inside.
If your controller is like the American ones, you can adjust the insides to sew a little faster, slower or just allow more variation in speed. You can replace it with an electronic controller, if you don't want to mess with adjusting the one you have.
bkay