Electric motors convert electrical energy into mechanical motion. Motor control circuits regulate speed, torque, direction, and position using various power electronics techniques.
Understanding motor control is essential for robotics, automation, electric vehicles, and industrial applications.
Where τ is torque (N·m), Kt is torque constant, and I is armature current (A)
Where ω is angular velocity (rad/s), V is supply voltage, R is armature resistance, and Ke is back EMF constant
Mechanical power (Watts) = Torque × Angular velocity
The H-bridge is a circuit that allows bidirectional current flow through a motor, enabling forward/reverse operation and speed control.
Speed is controlled by varying PWM duty cycle:
Example: 12V supply with 75% duty cycle = 9V average to motor
Stepper motors move in discrete steps, typically 200 steps per revolution (1.8° per step).
Example: 200 steps/rev → 360°/200 = 1.8° per step
Example: 1000 steps/sec with 200 steps/rev = 300 RPM
Servo motors use closed-loop position feedback for precise angular control, typically 0-180° or continuous rotation.
Standard hobby servos use a 50Hz PWM signal (20ms period):
Where e(t) is position error, Kp is proportional gain, Ki is integral gain, Kd is derivative gain