Three methods of zeroing a servo motor

Zeroing is a big issue in servo control. There are a variety of system requirements for zeroing, different zeroing methods supported by each manufacturer's motion controller or driver, and a variety of feedback types for servo motors, resulting in a variety of zeroing methods. In addition, the description of key terms related to zero return varies from manufacturer to manufacturer, so there are many topics and discussions related to servo zero return.

There are various methods of real zeroing, which can be selected according to the required accuracy and actual requirements. It can be completed by the servo motor itself (some brands of servo motors have a complete return to zero function), or through the upper computer with the servo to complete, but the principle of return to zero is basically common in the following ways.

First, the servo motor to find the origin, when it touches the origin switch, immediately decelerate and stop, this point for the origin. This method of returning to the origin, whether you choose a mechanical proximity switch, or light sensor switch, back to the original precision is not high, as a netizen said, by the temperature and power fluctuations and so on the impact of the signal response time will be different every time, coupled with the high speed from back to the origin of the sudden deceleration and stopping the process, it can be said that 100%, even if you exclude the mechanical reasons, each time back to the origin of the difference between the silk level or more.

Second, when returning to the home position, directly look for the Z signal of the encoder, and decelerate and stop immediately when there is a Z signal. This method of returning to the origin is generally only applied to the rotary axis, and the speed of return to the origin is not high, and the accuracy is not high.

Third, this kind of back to the original method is the most accurate, mainly used in CNC machine tools: the motor first to the first section of high-speed to find the origin switch, the origin switch signal, the motor immediately to the second section of the speed to find the motor's Z believe the signal, the first Z believe the signal must be in the origin of the gear block (so you can notice, in fact, high-grade CNC machine tools and the center of the origin of the gear block are mechanical and will not be the inductive, and its length must be greater than the motor a circle converted to the origin of the encoder, and its length must be greater than the motor a circle converted to the origin of the encoder. Length must be greater than the length of the motor to convert a circle into a straight line distance). After finding the first Z believe the number, at this time there are two ways to try, one is the gear block before the return to the origin, one is the gear block after the return to the origin (gear block before the return to the origin of the safer, European system used, the gear block after the return to the origin of the work stroke will be longer, the Japanese system used). Take the gear block back to the original as an example, after finding the first Z signal on the gear block, the motor will continue to rotate in the same direction to find the first Z signal after disengaging the gear block. Generally, this is the real origin, but because sometimes this point is exactly in the middle of the origin of the action of the gear block, prone to malfunction, and coupled with other process requirements, can be set to an offset; at this point, this point is the real mechanical origin. This method is the most accurate, and repeat the original high precision.

The zero point should be determined before running the servo motor. The position coordinates of the servo motor are established based on the zero point.

Incremental encoders require a zero return each time they are powered up, and absolute encoders determine whether a zero return is required on a case-by-case basis. However, the machinery should be put into use for the first time to perform a return to zero, in order to determine the mechanical origin.

Zeroing is the process of finding a repeatable position near an "anchor" point that can be used as the zero point.

The crawl speed index pulse finding process is implemented within the drive and the index pulse does not need to be mapped to the controller side. There are a variety of zeroing methods, which can be flexibly determined based on the zeroing method supported by the specific product, the IO signals provided by the mechanism, and the specific application requirements.