Servo Drive (Motor Driver)

The power-electronics board that turns control commands into motor current and runs low-level control loops.

A motor driver is the power-electronics module between the controller and the motor. The host computer or onboard compute platform only sends high-level commands — go to this position, at this speed, with this torque — and the driver reads the encoder, switches power transistors (such as MOSFETs) to energize the motor windings via PWM, and internally runs the current loop, velocity loop, and position loop (cascade control); for brushless motors it also performs field-oriented control (FOC). It communicates with the main controller over a bus such as CAN, EtherCAT, or RS-485. Selecting one comes down to voltage, continuous/peak current, control frequency, and communication interface. In humanoid robots, the driver is often integrated together with the motor and reducer into the joint module itself, an arrangement called a drive-integrated joint.

ExampleODrive and mjbots moteus are open-source brushless motor drivers commonly used by robotics hobbyists.

Also called

Motor Drive, Servo Amplifier

Related

Servo Motor · Field-Oriented Control · Integrated Drive and Control · EtherCAT (Ethernet for Control Automation Technology) · Controller Area Network (CAN) · ODrive

Sources

Servo drive - Wikipedia
ODrive Robotics