microstep

Microstep is a technique used to control stepper motors by subdividing each full step into smaller increments. By shaping the currents in the motor windings to follow a sine-like trajectory, a driver can position the rotor between conventional full-step positions. This yields smoother motion and higher effective resolution without changing the motor’s hardware.

Operation typically involves a two-phase bipolar stepper controlled by a current-regulated driver. The driver generates a sine/cosine current pattern for the two windings, producing intermediate rotor positions. The effective step angle equals the full-step angle divided by the chosen microstep count. For a common 1.8-degree motor, 1/2 microstep is 0.9°, 1/4 is 0.45°, 1/8 is 0.225°, and 1/16 is 0.1125°.

Benefits include smoother starts and stops, reduced torque ripple and vibration, and higher apparent resolution in open-loop systems. Microstepping can improve low-speed torque control and positioning accuracy in many applications such as CNC machines, 3D printers, and robotic actuators.

Limitations center on torque and accuracy. The available torque at microstep positions decreases as the current is divided among phases, and microsteps do not create new mechanical resolution beyond the motor’s inherent step structure. The actual positioning accuracy depends on the driver’s sine approximation, winding characteristics, supply voltage, and mechanical load. At very high microstep counts, torque can become too weak to move loaded axes reliably, and backlash or slippage may dominate.

Typical drivers offering microstepping include common hobbyist boards and industrial controllers. Microstepping is widely used to enhance motion smoothness and control in open-loop systems, though closed-loop feedback may still be preferred for demanding precision.