Discussion on Control Accuracy of Stepper Motor Control
A stepper motor is a device that converts an electrical pulse signal into an angular displacement or a linear displacement. In the case of no overload, the speed and distance of the stepper motor depend on the frequency and number of control electrical pulses.
Its control accuracy is mainly determined by two aspects:
1. The accuracy of each step of the stepping motor is taken as an example of a 2-phase hybrid stepping motor. The stepping motor of a 200 step step is: 360°/200=1.8° without splitting. That is, the minimum distance that the stepping motor walks alone is 1.8°. However, in actual use, the number of steps is generally subdivided. Take 2 subdivision as an example. At this time, the stepping motor walks two steps, which is equivalent to the original one step. Now the step distance of the single step is: 360°/(200*2)=0.9°; similarly, under 4 subdivisions, Single step: 360°/(200*4)
= 0.45 °; 8 subdivision, single step step: 360 ° / (200 * 8) = 0.225 °; 16 subdivision, single step step: 360 ° / (200 * 16) = 0.1125 °; Under the 32 subdivision, the single step is 360°/(200*32)=0.05625°. Therefore, under the driving subdivision, the stepping motor single step step angle calculation formula is: 360 / (stepping motor inherent step number * subdivision number).
It can be seen that to reduce the stepping angle of the stepping motor to achieve higher precision, it is necessary to start from two aspects. One is to increase or adopt a stepping motor with more inherent steps to obtain a smaller single step. The angle of view, such as 0.9 °. The second is to increase the degree of step breakdown.
2. Calculation accuracy. When controlling the stepper motor to operate, the calculation system should ensure that the calculation accuracy is higher than the stepper motor step accuracy when converting the angular displacement or line displacement to be calculated into the step motor step. For example, the stepping angle of the stepping motor is 0.1125° per step, the angular displacement to be moved is 143.45°, and the number of steps to be taken should be =143°/0.1125°, and the calculation result is 1273.11.....step, The actual result is 1275 steps, and the movement error is: 0.11111*0.1125
=0.0125°. If the angular displacement of the calculated movement is in 1°, 143.45° = 143°, the fractional part is discarded. 143/0.1125=1271.1111 step, then compare the previous movement, the error is: (1275-1271) * 0.1125 °
=0.45°. The reason why this is proposed here is mainly because in the embedded system, because of the limitation of the data type, if the calculation is not performed using float or double, the fractional part is generally discarded, resulting in a large calculation error.
Stepper motor can be used as a bank device motor、spraying machine motor、machinery device motor、industrial control system motor.
