Absolute positioning must have an origin, that is, a reference point or zero point. With the origin, all positions in the whole journey can be determined by reference to it. Under what circumstances must the back reference point be executed?
（80ST Flange servo motor 0.4-1.0kw）
1、 When you run the program for the first time, you need to go back to the origin.
The first time running the program, although the current position may be 0 and there is an origin signal input, the system does not know where the origin signal is. In order to perform absolute positioning, it is necessary to use the return to origin command to search for the origin signal in a specific way, which is the real return point.
2、 After many times of positioning, in order to eliminate the error, it is necessary to return to the origin.
The stepping system is an open-loop control system. It is easy to cause errors due to step loss or step-by-step in motion. There is also a gap in the machine itself. After repeated positioning for many times, the accumulated error will become larger and larger, which makes the positioning accuracy unable to meet the requirements. Therefore, it is necessary to carry out the operation of returning to the origin. Although the servo system is closed-loop control, there will not be out of step and over step phenomenon, but the pulse sent by PLC to the servo drive line may cause interference, as well as the error caused by mechanical clearance, which will also affect the positioning accuracy. Therefore, it is necessary to return to the original point after a period of time.
3、 If the position is changed or lost after power failure, it is necessary to return to the original point.
There is no encoder for the stepper motor, and the servo motor is usually installed with an incremental encoder. After power failure, the position can not be changed. Therefore, when the power is cut off, the position is changed due to human, gravity or inertia. PLC can no longer accurately know the current position. In order to ensure the accuracy of positioning, it is necessary to perform the operation of returning to the original point. If the motor position is not changed after power failure or the motor is installed with absolute value encoder, do you still need to return to the original point after power on again? Although the incremental encoder can not identify the position after power failure, we can store the current position in the address of PLC power-off holding storage area before power-off. Even if the power is off, the current position will not be lost, and it is not necessary to return to the origin after power on. Even if the absolute value encoder rotates after power failure, it can automatically identify the current position after power on, so it is not necessary to return to the original point. However, it is worth noting that the absolute value encoder is divided into single turn and multi turn. After power failure, the rotation position must be within the recognizable range, otherwise it also needs to return to the origin.
4、 Reset and other operations are performed to clear the current position.
When the program fails, in order to be able to restart, we need to reset all the States, including the current position, to the initial state. In this way, we must perform the operation of returning to the origin.
（B-4-2 200-220v Absolute servo driver）
Hxdwh absolute value servo motor adopts 17bit / 23bit absolute value encoder and ZSD absolute value servo driver. Different angles of absolute value encoder correspond to different codes, and there are absolute zero points, so it will automatically return to zero point. As long as the mechanical zero position is aligned with the coding zero point when the equipment is assembled, that is to say, align their respective benchmarks, then the mechanical zero position will return when the encoder returns to zero Fatal Frame.
Post time: Aug-25-2020