EPOS using absolute encoders can be calibrated by software, but due to motor reinstallation, device replacement, etc., sometimes this function needs to be provided in the PLC program instead of being operated by Starter/SCOUT software. Therefore, this article describes the steps and basic methods for calibration operations of absolute encoders via PLC (S7-1516 DP/PN).
1 Overview
When using the EPOS (Basic Positioning) function of the S120 inverter, calibration of the encoder is required if an absolute encoder type is used. After calibrating the absolute encoder operation, the S120 drive can establish a correlation between the absolute encoder data and the mechanical zero point. And when the position is detected with an absolute encoder, the position value is not lost after a power failure.
In general, the calibration operation of the absolute encoder can be carried out by the STARTER/SCOUT software, that is, after opening the STARTER/SCOUT software, the following steps are performed:
(1) Move the axis to the reference point position on the machine by the jog function, or know the coordinate position of the current machine.
(2) Check the dialog “Homing” (Technology->Basic positioner-> Homing under Drive).
(3) If online, enter the current coordinate location in the Home position coordinate dialog box:
Figure 1-1 Mechanical coordinate position input
(4) In the online case, the correction can be performed by the button “Perform absolute value calbration”, followed by the “Copy RAM to ROM” operation.
However, due to motor reinstallation, equipment replacement, etc., sometimes it is necessary to provide this function in the PLC program, rather than through the Starter software to operate. Therefore, this article describes the steps and basic methods for calibration operations of absolute encoders via PLCs (S7-315 and S7-1516).
For absolute encoder calibration operations, three parameters are mainly used, and encoder calibration operations can be achieved by modifying the parameter values through non-periodic communication:
(1) Set the p2599 of the drive, this parameter is the position value of the current machine, that is, the position of the equipment after calibration. Usually move the device to the location reference point and then set p2599=0.
Modify the driver P2507, this parameter is set to 2 when the calibration operation is started, and when this parameter is equal to 3, the calibration is complete.
Set the CU to p977, when this parameter equals 1, store the parameters to the CF card.
2 Project configuration
2.1 Hardware and software used in this document
l TIA Portal V13 SP1 Update4
l S7-1516 PN/DP V1.8
l S120 CU320-2DP V4.6 with CBE20 board
2.2 Project configuration steps using Portal V13 SP1 DP/PN communication
Table 2-3 describes the project configuration steps.
1.
Select in the network view
Configuration S120 DP (in PROFIBUS DPSIEMENS AGDrivesSINAMICS under Other field devices in the hardware catalog):
Configuration of the S120 PN (located in PROFINET IOSIEMENS AGDrivesSINAMICS under Other field devices in the hardware catalog):
Connect the DP or PN interface of the S120 to the DP interface of the PLC by dragging and dropping, and set the DP address or IP and device name:
Or the configuration of PN is as follows:
2.
Configure communication messages in the hardware view of the S120:
3.
Query the HW ID of the drive message through the properties of the message for programmatic use (276 in this article):
Query the HW ID of CU packets through the properties of the packet for programmatic use (280 in this article):
4.
Write the program as shown in the following figure:
Parameter description:
1. Start: The rising edge of start will start the parameter operation task during the parameter operation.
2. ReadWrite: Parameter =0 indicates the read operation, if equal to 1 corresponds to the write operation.
3. Parameter: The parameter number that needs to be read and written.
4. INDEX: Fixed setting is 0.
5. ValueWrite: Set to the parameter value that needs to be written, note that it is in floating-point format.
6, AxisNo: The driver number, which can be queried in the starter Overview.
7, ERROR: error flag bit.
8. ErrorID: Return value.
9. BUSY: 1 when the write parameter is executed, and becomes 0 if it is completed or fails.
10. DONE: The task execution is completed, which can be used for reset requests when writing programs.
11, DiagId: Return value.
The specific procedure can refer to the attached routine.
Table 2-3 Project configuration steps