Basics of Stepper Motor Drive - Microstep Control Mode

Electromechanical Motors, Actuators, Solenoids and Drivers
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Stepper motors , Motor Drivers Technologies: Full-Step, Half-Step, and Microstep Control Modes

This article introduces the microstep control mode .

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Simplified 2-Phase Stepper Motor with Permanent Magnet Rotor (source: ADI)

Microstep Control Mode

Concept of Microstep Control

Microstep control is an advanced method that allows the motor to rotate to multiple intermediate positions between full steps, significantly improving positional resolution and enabling smoother low-speed rotation. This is achieved by subdividing each full step into a series of equally spaced microsteps.

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Simplified 2-Phase Stepper Motor with Permanent Magnet Rotor (source: ADI)

The figure above shows different states of the motor during microstep control, including the energization of coils A1, A2 and B1, B2, and the corresponding position changes of the rotor, visually presenting the working process of the motor under microstep control.*

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Comparison of Current Waveforms and Position Overshoot/Oscillation in Different Step Modes (source: ADI)

In the figure above, the green curve (Coil 1) and red curve (Coil 2) show the current changes of the two coils in different step modes. It is evident that the current changes in the full-step mode are steplike, the half-step mode has finer steps, and the microstep mode approximates a sine wave for smoother current changes.

The lower part is a position overshoot/oscillation diagram showing the rotor position changes in different step modes. The full-step mode has obvious overshoot and oscillation, the half-step mode improves this, and the microstep mode exhibits smoother position changes with almost no significant overshoot or oscillation, further illustrating the advantages of microstep control in improving motor performance.

Working Principle and Technical Implementation

Microstep control achieves optimal operating behavior by not only switching phases on and off but also applying different current values to them.

The two phases are controlled by approximate sine waves offset by 90°. A full step is divided into smaller units called microsteps. Microstep resolution is the number of intermediate positions into which a full step is divided.

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Operation of 1/16 Microstep (source: ADI)

Left diagram: Current change curves for two phases (Phase A and Phase B), showing approximate sine waves offset by 90°. The diagram marks 16 microsteps and 1 full step, indicating that one full step is subdivided into 16 microsteps, achieved by controlling the current changes of the two phases.

Middle diagram: An angle diagram showing that 1 full step is divided into 16 microsteps.

Right diagram: Demonstrates the application of microstep control in actual motor structures, illustrating how precise control of the current in the two-phase coils achieves precise rotor rotation with smaller step angles.

Performance Advantages and Limitations

  • Advantages:
    • Higher microstep resolution results in a smoother theoretical sine wave of phase current.
    • Transient effects are significantly reduced due to the much smaller movement distance compared to full-step operation.
  • Limitations:
    • In practice, specifying only sine wave setpoints is insufficient to obtain sine wave phase currents. Switching inductors and other interference effects require further measures to maintain very smooth operation.

Related Products

TMC2240 and TMC5240 are intelligent, high performance 2-phase stepper motor driver ICs integrated with motion controllers. The 8-point motion ramp function simplifies the system architecture, allowing users to easily program desired positions and motion profiles.

TMC2160 and TMC5160 are high power 2-phase stepper motor driver ICs supporting 256 microstep resolution and MicroPlyer microstep interpolation. They optimize driver performance using multiple Trinamic technologies, suitable for a wide range of scenarios from battery-powered systems to high-voltage industrial applications.

TMC2300 is a low voltage driver designed for 2-phase battery-powered stepper motors, featuring 256 microstep resolution and functions such as CoolStep, StealthChop2, StallGuard4, and SpreadCycle.

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