Q: How to implement closed-loop motor control using encoders and PID position control?
Answer
Closed-loop motor control system: motor + encoder + controller + driver. Encoder types: incremental (A/B quadrature signals) or absolute (SSI SPI BiSS). Position control: implement cascaded PID: outer loop (position error -> velocity command) inner loop (velocity error -> torque/current command) current loop (PI control -> PWM duty cycle). Tune with Ziegler-Nichols: set I=D=0 increase P until oscillation then set P=P_critical/2 I=2*P_critical/T_c D=P_critical*T_c/6. For digital implementation use fixed-point arithmetic and anti-windup on the I term. Run control loops at constant rate (1-10 kHz) using hardware timer interrupt. Use feedforward (friction and inertia compensation) to improve tracking performance. For high-performance: use space vector PWM (SVPWM) and field-oriented control (FOC) for ACIM/PMSM.
Filed under: FAQ