The control of stepper motors is open-loop control. If the starting frequency is too high or the load is too large, it is easy to lose steps or stall. When the speed is too high, it is easy to overshoot. Therefore, to ensure accuracy, it should be handled well by the speed. When the device is out of step, the machine can't discover it, causing the displacement deviation of the pick and place machine, causing the overall displacement deviation of the placement effect, and the device can only be restarted and initialized.
The grating ruler displacement sensor (abbreviated as grating ruler) is a measurement feedback device that uses the optical principle of grating to work. The missing pulse can be automatically corrected through the cooperation of the grating ruler and the reading head, and feedback to the controller can be timely also when the rotor is locked.
Figure 1. The placement effect when the stepper motor loses steps
Figure 2. The final placement effect of adding the grating self-feedback closed-loop system to automatically correct the missing pulse
Figure3-5 is the grating ruler reading head which will give the feedback to the stepper motors. Stepper motors will adjust themselves in real time.
Figure 6 is the grating ruler.
1. When installing the reading head, first ensure that the base surface of the reading head meets the installation requirements, and then install the reading head. The installation method is similar to that of the grating strip. Finally, adjust the reading head so that the gap between the reading head and the grating strip is controlled within 1~1.5mm.
2. The grating strip must be installed horizontally and vertically without any bending.
3. The grating ruler is not easy to be too long, which leads to extremely high requirements for the installation of the grating strip.
4. The surface of the grating strip should be prevented from polluting the grating ruler surface by oil and water, so as not to damage the line stripe distribution of the grating ruler and cause measurement errors.