Measuring method for stepping motor speed change
The use of stepper motors is broadly divided into position control and speed control. The speed range of the speed control can be used from low speed to high speed shift control or constant speed, but there are speed changes. The figure below shows the definition of the rate of change of speed.
Now, the average speed of the stepper motor is expressed in ωm, and its speed changes from zero to the maximum value. If it is rotated by Δωm, the speed change rate VF is defined by the following formula:
This is the measurement of the rate of change of the speed, measured by the equivalent inertia or friction torque according to the actual load inertia, to be close to the actual use value. Especially when the inertia is large, the rate of change of speed (also called speed failure, jitter, swing, etc.) is also large. Therefore, we must pay attention to the speed running range of the stepping motor. The faster the speed, the smaller the speed change rate.
Such measurement methods are broadly classified into methods using an encoder and laser measurement methods. When using the encoder, be aware that the encoder is concentric with the shaft center of the stepper motor coupling, and also consider the effects of the encoder inertia. To calculate the rate of change of velocity, first count the number of pulses per unit time of the encoder, and then calculate the rate of change of speed. Instead of using a laser measurement method, a disc is mounted on a stepper motor that reflects the laser beam and reflects the light back. The speed change is calculated using the Doppler effect. This device is commercially available. Here, if the encoder measurement is not specifically required, it is best to use a laser measuring instrument.