Micro Stepping in Stepper Motor

What is Micro Stepping in Stepper Motor

Stepper motors can be controlled by micro Stepping, which is typically done at low speeds to get better resolution or smoother motion.

In discrete steps or Fractions of a revolution, stepper motors rotate. For instance, a stepper motor that has a 1.8 degree step angle will complete 200 steps for each 360 degree Rotation of the motor. The motor’s Rotation is not completely smooth due to this Discrete motion, and the slower the Rotation, the less smooth it is because of the relatively large step size. Reducing the size of the motor’s steps is one way to solve this lack of Smoothness at low speeds. Herein lies the value of micro Stepping.

Micro stepping in Stepper Motor control divides each full step into smaller steps to help smooth out the motor’s rotation, especially at slow speeds. For example, a 1.8 degree step can be divided up to 256 times, providing a step angle of 0.007 degrees (1.8 ÷ 256), or 51,200 microsteps per revolution.

Pulse-width Modulated (PWM) voltage is used to control current to the motor Windings in order to achieve Microstepping. The motor windings receive two voltage sine waves that are 90 degrees out of phase from the driver. Current in one winding increases while Decreasing in the other winding. In Comparison to full- or Half-step control, this gradual transfer of current produces smoother motion and more consistent torque.

With Microstepping, resonance, low-speed motion, and torque Smoothness are all improved,. But they are still unable to reach their ideal states due to control and motor design restrictions. This is primarily due to the fact that Microstepping drives are only able to approximate a true sine wave;. Consequently, some torque ripple, resonance, and noise still exist, despite the fact. That each is significantly less than in full- and half-stepping modes. Furthermore, the torque generated by a stepper motor with Microstepping control is only about 70% of the torque generated by a stepper motor with full-step control.

Because it does not introduce backlash into the system or lower the system’s maximum speed, microstepping is occasionally regarded as a good substitute for mechanical gearing. The motor’s torque is multiplied by mechanical gearing, which also improves the motor’s ability to maintain position.

It’s crucial to prevent “empty resolution,” . Which occurs when the division level of the steps (i.e., the resolution) is higher than is practical given the constraints of the system. When the microstep’s torque is insufficient to overcome the friction torque of the component being driven (such as a leadscrew or ball screw),. This most frequently happens. The following equation yields the incremental torque per microstep:

Where:

T_INC = incremental torque produced with each microstep

T_HFS = holding torque (full-step operation)

SDR = step division ratio (number of microsteps per full step)

For a motor with 0.35 Nm holding torque using a 256 step division ratio (SDR),. The incremental torque produced by each microstep would be 0.002 Nm.

Tinc = 0.002 Nm

It will require 30 microsteps (0.06 ÷ 0.002) to produce enough torque to move the screw. If its friction torque is 0.06 Nm. Additionally, a higher frequency for the pulse train driving the motor is needed to operate at a higher steps per revolution. The motor rotates in 51,200 steps, or pulses, per revolution. When the 256 SDR is used (200 full steps per revolution x 256 microsteps per step). The required pulse frequency is greater than 5 MHz at a motor speed of 100 rpm (6000 rpm).