Open Loop Halt

The Open Loop Halt is one of the four types of RMC Halts. Use the Open Loop Halt to halt the axis in open loop control.

When an Open Loop Halt occurs, it takes the following steps:

It puts the axis in open loop and ramps down the Control Output to the Output Bias using the Open Loop Halt Ramp parameter.
The Halted status bit is set and the axis is said to be in the halted state.
If the axis is part of a Halt Group, it starts an Open Loop Halt on all axes in the group.

Pressure/Force Limit

The Open Loop Halt will ramp the Control output to zero, but will not remove the axis from pressure/force limit. The Direct Output Halt (3) and Fault Controller (8) commands will remove it from pressure/force limit.

Tip:
The Halts do more than just stop the axis. If you simply wish to stop the motion in open loop control, use the Stop (Open Loop) (22) or Open Loop Rate (10) commands. If you wish to stop the motion in closed loop control, use the Stop (Closed Loop) (6) command instead.

Triggering an Open Loop Halt

An Open Loop Halt can be triggered in two ways:

By issuing the Open Loop Halt (2) command.
Via Auto Stops.

After a Halt has Occurred

If the halt was caused by an Auto Stop, you should first make sure the error condition that caused it has been resolved before continuing. Once it has been fixed, you can clear the Halted status bit by issuing the Clear Faults (4) command. Issuing a valid motion command will also clear the Halted status bit.

Why Bother?

This halt is useful when you want to set the Control Output to zero because of a potentially dangerous error. The Open Loop Halt Ramp parameter is used to avoid an abrupt (and potentially damaging) stop. If you just want to stop the axis but still have closed loop control over it, use the Closed Loop Halt.

The Auto Stops can be set up to cause this halt when an error bit turns on.