servodrift

Servodrift is the term used to describe the deviation between a commanded servo position and the actual position reached by the servo over time. It can occur in both hobby RC servos and industrial closed-loop systems, and it may appear as a steady offset, a gradual change, or intermittent fluctuation under constant input.

Mechanical factors commonly contributing to servodrift include gear backlash, stiction, wear in bearings, and flex in mounting or linkages. Temperature-induced expansion and contraction of components can also shift the effective geometry, leading to positional errors, especially in systems with small tolerances or heavy loads.

Electrical and control-related factors include insufficient torque or stall under load, voltage supply fluctuations, noise in the feedback potentiometer or position sensor, and PWM jitter. Control-loop issues such as improper PID gains, integral windup, or deadband can also cause drift, particularly in systems operating near their limits or with changing load profiles.

Drift may be static, presenting as a fixed offset, or dynamic, appearing as creeping or oscillatory behavior. It is typically diagnosed by repeated position checks with a known reference, under controlled load, and by monitoring torque, temperature, and supply voltage.

Mitigation strategies focus on reducing mechanical play, improving calibration, and refining control parameters. Approaches include reducing backlash with stiffer mounts or direct-drive options, ensuring clean, stable power supplies, selecting higher-torque servos, and tuning the control loop (PID gains, anti-windup, feed-forward). Regular maintenance, components replacement, and temperature compensation can also minimize drift over time.

In practice, servodrift is a common design consideration in robotics, RC applications, and automated systems that rely on precise positional control. See also: backlash, creep, hysteresis, closed-loop servo.