Servo Controllers
Servo controllers are a wide category of motor control. Common features are:
- precise closed loop position control
- fast acceleration rates
- precise speed control Servo motors may be made from several motor types, the most common being:
- brushed DC motor
- brushless DC motors
- AC servo motors
Servo controllers use position feedback to close the control loop. This is commonly implemented with encoders, resolvers, and Hall effect sensors to directly measure the rotor's position.
Other position feedback methods measure the back EMF in the undriven coils to infer the rotor position, or detect the Kick-Back voltage transient (spike) that is generated whenever the power to a coil is instantaneously switched off. These are therefore often called "sensorless" control methods.
A servo may be controlled using pulse-width modulation (PWM). How long the pulse remains high (typically between 1 and 2 milliseconds) determines where the motor will try to position itself. Another control method is pulse and direction.
Read more about this topic: Motor Controller