#37 - Rockwell program with Servo Motor

In the previous post,  we configured two virtual servo motor axes to simulate one axis in rotation and the other in translation. In this post we will make a program with two rotating axes in RSLogix5000 and use the available Motion Control commands. As we are using axes whose Data Type is VIRTUAL_AXIS, with no real hardware present, the available commands are limited. Virtual axes can be used in a project for several purposes, such as synchronizing axes, multiplying input and output ratios (virtual gear box) and even to do virtual tracking of objects in applications in motion.

Testing Motion State and Motion Move commands via Motion Direct Commands:

Error 16 # 0026 is due to the fact that it is a virtual axis. Even without all the commands available, it is possible to make a program and test important points. 

Motion State commands available: MASD, MASR

Motion Move commands available (all): MAS, MAH, MAJ, MAM, MAG, MCD, MRP

• The program structure is made using EQU - MOV rungs, which is a simple way of representing a sequential system, such as GRAFCET, in LAD language. The transition from one stage to another, is done with the validation of State Bits that confirm that the current stage has been completed. 
• In the example below, a virtual axis is jogged, with the possibility of updating the running speed. The axis is stopped with the MASD command, and MARS resets after MASD. The first movement is a Homing operation to the established Home position. 

A UDT was created with the main commands and is instantiated as Axis1_CMD:

The MAJ command makes the jog and the MCD update the speed:

Visualizing the Trend with the current position and speed of the axis and simulating a speed change from 100 degrees / s to 150 degrees / s:

There is also the possibility to synchronize the second virtual axis and to change the virtual gear box between these two axes. Dynamic results are represented with Trends that help in visualization. 

Proposed sequence of actions / transitions could be:

• Reset from Shutdown or Fault: MASR/MAFR (NEQ .AxisFault, XIO .ShutdownStatus)
• Homing: MAH (.PC transition)
• Move to specified position: MAM (.PC transition)
• Jog: MAJ (.IP transition as no .PC when jogging)
• Change dynamics (e.g. change speed) on MAM/MAJ: MCD (executes when MCD.EN edge falls and edge rises)
• Stop: MAS (.PC transition)
• Shutdown: MASD (.ShutdownStatus)

Axis commands On/Off (MSO, MSF) are not available for virtual axis, but typically the axis is turned Off then On after resetting and before homing. 

Worth checking out the instructions help for these commands to see in more details the configurations and possibilites.