Overtravel Conditions

The PLCopenClosedA vendor -and product- independent worldwide association active in Industrial Control and aiming at standardizing PLC file formats based on XML and PipeNetwork motion engines can respond to overtravel conditions from the AKD and AKD2G drive family. As a safety feature, AKD and AKD2G drives ignore motion commands once an overtravel is detected in the direction of a hardware limit switch. The PLCopen or PipeNetwork motion engine applies a stop action to axes when these overtravel conditions occur.

PLCopen Behavior

A PLCopen axis issues an emergency stop of the axis when it experiences an overtravel condition. The axis remains enabled under servo control once the emergency stop action completes. This action puts the axis into the "ErrorStop" state (see PLCopen State Machine).

To recover from this state:

  1. Call MC_ResetError on the axis.
  2. Command motion in the direction opposite to what was previously commanded.

    If you are uncertain about which direction the axis was traveling in, check the states of the I/O points configured for the positive and negative limit switches on the drive.

Coordinated Motion Behavior

An axis that is part of an axes group issues an emergency stop on the axes group when it experiences an overtravel condition. All axes remain enabled under servo control once the emergency stop action completes. This action puts the axes group into an error state.

To recover from this state:

  1. Call MC_GrpReset on the axes group
  2. Check the states of the I/O points configured for the positive and negative limit switches on the drives associated with the axes to figure out which axis and which limit switch cause the error.
  3. Command motion in the direction opposite to what was previously commanded.

PipeNetwork Behavior

A PipeNetwork axis issues a stop action on the axis when it experiences an overtravel condition. This is similar to calling MLAxisStop. Bit 11 of MLAxisStatus is set and the axis remains enabled under servo control once the emergency stop action completes. The axis will no longer be accepting pipe positions. The pipe that the axis is connected to will continue functioning as before and any master will continue generating new positions. The axis which experienced overtravel simply no longer responds to new pipe positions.

To recover from this state, call MLAxisReAlign to realign the axis with the pipe. See the page Restarting Motion with PipeNetwork to understand how to accomplish this.


  • If a hardware limit flag is being triggered at the program startup by a PipeNetwork axis, MLAxisReAlign may need to be called immediately before motion occurs. In this case, the distance to travel should be at least as long as the maximum distance the hardware limit flag can remain active.

Configuring Generation 1 AKD Drives

When using generation 1 AKD drives, bit 14 of the parameter FBUS.PARAM05 (see FBUS.PARAM1 TO FBUS.PARAM10 must be set high to allow KAS IDEClosed"Integrated development environment" An integrated development environment is a type of computer software that assists computer programmers in developing software. IDEs normally consist of a source code editor, a compiler and/or interpreter, build-automation tools, and a debugger to respond to the hardware limit switches,

If FBUS.PARAM05 originally had a value of 0, typing FBUS.PARAM05 16384 would turn on bit 14. Remember to save your drive parameters to flash memory once bit 14 is set, otherwise the behavior will turn off once the drive is power cycled.