Beifu PLC realizes zero point power-off hold of absolute value encoder -- use of bias

In this paper, Position Bias How the TC3 The program sets the absolute value of the encoder . How to complete the calibration of absolute position and equipment . Ensure that the position is still maintained after power failure .

1. Operation process
   1.1. Biff Beckhoff
   Configuration settings bias value ： First move the axis to the origin of the device （ If you use MC_Home After execution, you must perform absolute positioning to move to 0）, stay Position Bias The default is 0 when , Get record current NC The value in the position value （ After searching the origin, the device must be restarted to obtain ）, Take the negative value and put it in Position Bias Post activation , The absolute position and equipment calibration can be completed . The effect is after power failure , The displayed position value after restart is compensated with the set value , So the origin is still only valid .

give an example ：

When the axis stops at the origin position, it is displayed as 500, that position bias It needs to be set to -500, After the device restarts , If the axis reads in a new position 1000 Words , It indicates the coordinate relationship between the current position and the origin +1000, The principle is that the encoder feeds back NC The value of 1500, Because the reference position of the origin is changed -500 The compensation .

Program settings Position Bias：
Use instruction mc_writeparameterpersistent; The order TC3 Unique , The feature is saved to the configuration after modification , Power failure is still effective . The modification is effective when the shaft is not enabled . If it is TC2 If you want to rely on instruction modification, you can use mc_writeparameter, The command write value will be lost after power failure , Therefore, it is necessary to re trigger each time when it is powered on .
mc_writepar