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How Do I Implement Closed-Loop Position Control on a PA Actuator with Arduino?

Closed-loop control uses continuous position feedback to automatically correct errors and maintain a target position. This article walks through a practical proportional (P) controller — the most useful and approachable control method for linear actuators.

Open-Loop vs Closed-Loop

Type How it works Accuracy Use when
Open-loop Run motor for a fixed time; assume position from timing Poor — drifts with load and temperature End-of-stroke only, no mid-stroke needed
Closed-loop (P) Continuously read position, adjust motor power to reduce error Good — ±1–3 mm with potentiometer Any application requiring consistent mid-stroke stops

Proportional Controller (P Control)

A proportional controller drives the motor at a speed proportional to the distance from the target. Far away → fast. Near the target → slow. At the target → stop. This naturally provides deceleration and reduces overshoot.

Captura de Pantalla 2026-03-10 a la(s) 13.58.36

Tuning the Controller

  • KP too low:Actuator is slow to reach target; final approach is sluggish
  • KP too high:Actuator oscillates around the target (hunts back and forth). Reduce KP or increase DEADBAND.
  • MIN_PWM too low:Motor stalls in the slow-down zone before reaching the deadband. Increase MIN_PWM until the actuator reliably completes its final approach.
  • Good starting point:KP = 3, DEADBAND = 2 mm, MIN_PWM = 60 for PA-14P under light load

📖  PA code library PA's Arduino Coding page includes downloadable sample sketches for position control, timing control, and sensor-triggered motion with PA actuators.