Distance control states and transitions

Alternative commanding via SPS interface

Basic condition: Distance control is enabled for the axis (see P-AXIS-00328).

In addition to the NC program, distance control can also be commanded via the PLC interface (see [HLI//Distance control]) by specifying the required status transitions (e.g. activating or deactivating) and specifying command positions via the DistanceControl control unit.

The current state of the distance control unit can be viewed in the state of the DistanceControl control unit. The control unit state also includes the current actual position of the workpiece surface, the current distance, the active command source (0=NC program,1=PLC) and the current output position offset.

Explanation of figure:

Distance control has 6 internal states which are depicted in the figure below together with the permitted transitions. Transitions, such as a transition to error state, are displayed automatically and cannot be commanded.

A change in the “Active” and “Active constant Distance” states is only permitted in the “Freeze” or “Inactive” states.

Distance control state graph and transitions

Defined states of distance control

State	Value	Meaning
HLI_DIST_CTRL_STATE_INACTIVE	0	Distance control is deactivated. The specified offset (“actual_offset”) is 0.
HLI_DIST_CTRL_STATE_ACTIVE	1	Distance control is active and adjusts the axis to the workpiece surface.
HLI_DIST_CTRL_STATE_FREEZE	2	Distance control is active. The offset (“actual_offset”) is frozen, i.e. the axis is not adjusted to the workpiece surface.
HLI_DIST_CTRL_STATE_TURNING_OFF	3	Distance control was deactivated. The actual active offset (“actual_offset”) is run out. As soon as the offset is 0, an automatic switch to INACTIVE state takes place.
HLI_DIST_CTRL_STATE_ACTIVE_CONST_DIST	4	Distance control is active and adjusts the axis to the workpiece surface. Continuous specification of the set distance of the tool to the workpiece surface.
HLI_DIST_CTRL_STATE_ERROR	5	Distance control is in error state, e.g. due to an incorrect state transition or due to an error in the position controller. Only a transition to TURNING OFF is possible to exit this state.
HLI_DIST_CTRL_STATE_DRYRUN_CONST_DIST	6	Distance control is active, however axis is not adjusted to workpiece surface. This allows the evaluation of data, for example filter effect without feedback from the control system. Continuous commanding of the set distance of the tool to the workpiece surface.
HLI_DIST_CTRL_STATE_DRYRUN_SETPOS	7	Distance control is active, however axis is not adjusted to workpiece surface. This allows the evaluation of data, for example filter effect without feedback from the control system.

Permissible transitions to command the distance control

Transition	Value	Meaning
HLI_DIST_CTRL_OFF	0	Distance control is deactivated. The program switches to the TURNING OFF state in which the position offset is run out. The state then switches automatically to the INACTIVE state.
HLI_DIST_CTRL_ON	1	Distance control is activated. When activated a command position for the workpiece surface must be transferred in the “position” datum. If no absolute encoder is used, distance control must first be referenced.
HLI_DIST_CTRL_FREEZE	2	The current position offset is frozen. Axis adjustment to the actual workpiece surface is ended.
HLI_DIST_CTRL_REF	3	Referencing distance control if no absolute encoder is used. Referencing is only permitted in the INACTIVE state. With this transition a reference position must additionally transferred in the “position” datum.
HLI_DIST_CTRL_ON_CONST_DIST	4	Activating distance control with continuous distance specification. On activation, a set position must be specified. If the distance sensor supplies no absolute values, distance control must be referenced in advance.
HLI_DIST_CTRL_DRYRUN	5	Activate distance control for pure evaluation of data. No axis tracking in case of changes to the workpiece surface. When activated a command position for the workpiece surface must be transferred in the “position” datum. If no absolute encoder is used, distance control must first be referenced.
HLI_DIST_CTRL_CONST_DIST	6	Activate distance control for pure evaluation of data. No axis tracking in case of changes to the workpiece surface. On activation, a set position must be specified. If the distance sensor supplies no absolute values, distance control must be referenced in advance.