Positive Travel Limit

Type:	Axis Parameter Register
Address:	RMC75: %MDn.92, where n = 12 + the axis number RMC150: %MDn.92, where n = 24 + the axis number RMC200: %MDn.400, where n = 384 + the axis number
System Tag:	_Axis[n ].PosTravelLimit, where n is the axis number
How to Find:	Axes Parameters Pane, Setup tab: Primary Control Setup
Data Type:	REAL
Units:	pu
Range:	any
Default Value:	0

Description

The Positive Travel Limit and the Negative Travel Limit specify the position boundaries in which the axis is allowed to operate. The Positive Travel Limit must be greater than or equal to the Negative Travel Limit. These limits are not available on Rotary axes.

In Closed Loop Control

If the Target Position exceeds the Positive Travel Limit, the Positive Overtravel error bit will be set. If the Target Position is less than the Negative Travel Limit, the Negative Overtravel error bit will be set. While the axis is in an overtravel condition, motion commands that move the axis toward the valid range will be accepted, even if they don't move the axis entirely into the valid range.

In Open Loop Control

If the Actual Position exceeds the Positive Travel Limit, the Positive Overtravel error bit will be set. If the Actual Position is less than the Negative Travel Limit, the Negative Overtravel error bit will be set. While the axis is in an overtravel condition, motion commands that move the axis toward the valid range will be accepted, even if they don't move the axis entirely into the valid range.

The error bits will cause a Halt to occur if the corresponding Auto Stops are configured to do so and the Direct Output Status bit is off.

Note:
If the Direct Output Status bit is on, the Overtravel bits will not be set.

Moving Toward the Valid Travel Range

While the axis is outside the valid travel range, as defined by the Travel Limits, any motion commands the move the axis toward the valid travel range will be accepted, even if they don't move the axis entirely into the valid range.

Notice that if the axis is outside the valid travel range, in open loop, and is drifting slightly away from the valid range, issuing a closed loop motion command may again trigger an overtravel error. This is because the target position starts at the actual position, velocity and acceleration at the time the command is issued. This means the target will continue moving away from the valid range while accelerating to turn around. This will trigger an overtravel error. To avoid this, first issue a Hold Current Position (5) command, then the motion command. Or, simply use an open loop move to move into the valid range.

Truncating a Motion Command

Any motion command issued with a Requested Position that is outside of the travel limits will be set to the closest travel limit, and the Command Modified error bit will be set. The error bit will cause a Halt to occur if the Command Modified Auto Stop is configured to do so and the Direct Output Status bit is off. If the axis is outside of the travel limits when a move command is issued, the axis will only be allowed to move in the direction that brings it closer to the limit.