January 1, 2021

#35 - Rockwell Servo motor configuration

In this post we will configure and send commands to two servo motor axes using the simulator in RSLogix5000. One will be a rotating axis and the other will be a translating axis. 

  • Create a periodic routine in the program (scan time of 20ms and increase the priority of the routine from index 10 to 5).

  • Set the Date / Time Enable time sync in the PLC properties:

  • On the Advanced tab, select the Reserve resources for system tasks option, as the Motion Control routine is periodic (not continuous).

  • Create a Motion Group and add the Driving Axes, in this case of Virtual type:

  • Edit the values ​​of the axis dynamics (speed, acceleration, deceleration, Jerk of acceleration and deceleration. The unit is specified by the programmer in the Units tab, in this case Degrees and the type of Linear or Rotation movement is selected in the Conversion tab.
The Conversion Constant value represents the feedback counter, for example the Encoder signal, and for Position Unwind the value is 360 degrees x 8000counts = 2880000 counts / unwind


With the two axes configured, we download the program and go online. Online it is possible to send a series of direct commands to the Servo Motor, such as Go to Home position, Jog, among others. The created tags whose Data Type is VIRTUAL_AXIS can be seen in the Controller Tags:


To send direct commands to the engine, just right-click on the Axis and click on Motion Direct Commands.
One way that helps in visualizing the movement is to create a Trend with the current values ​​of position, speed and acceleration, jerk, torque, error in the position:

When first running the servo motor it is important to verify that the configuration done in the software corresponds to the physical machine (gear box ratio of the motor reducer, parameters of the motor), i.e. n revolutions of the motor correspond to the expected course in mm in the right direction. In addition the homing and course limits signals, both in software and hardware, should be carefully verified and tuned.

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