MC_GearInPos (FB)¶

FUNCTION_BLOCK MC_GearInPos

MC_GearInPos couples the slave axis to the master axis taking into account a specific positional relationship.

Important

In certain cases, it may be impossible to avoid a reversal of the slave. (Even if the slave velocity is not opposite to the master.) One example is a slave with a small positive velocity and a large negative acceleration. It may not be possible to ramp down the acceleration fast enough to prevent the velocity from becoming negative.

Note

MC_GearInPos should be called after the motion FB controlling the Master axis has been called. Otherwise, the Slave axis will lag behind the Master axis.

Timing diagram

With BufferMode Aborting, any previous motion is continued until the master crosses the position MasterSyncPosition – MasterStartDistance in the correct direction. At that point in time the output StartSync is set. When a stop command is executed on the slave axis before the synchronization has happened, it will inhibit the synchronization and the function block issues CommandAborted = TRUE.

If the MasterStartDistance is not specified (indicated by a non-positive value), the function block calculates the setting start distancepoint so that synchronization starts at the current master position.

With BufferMode Buffered or BlendingPrevious, the input MasterStartDistance cannot be provided (i.e. must be set to 0). The reason for this is that as soon as the previous movement finished, MC_GearInPos must take over the axis and continue the movement, it cannot wait until the master sync position has been reached. (If the master is in standstill when the previous movement is finished, then an error SMC_GIP_CANNOT_START_SYNC is reported.)

../../../../_images/GearInPos1.png — Timing Diagram of `MC_GearInPos`¶

../../../../_images/GearInPos2.png — Different examples of gearing¶

InOut:

Scope	Name	Type	Initial	Comment
Inout	`Master`	AXIS_REF_SM3		Reference to master axis
Inout	`Slave`	AXIS_REF_SM3		Reference to slave axis
Input	`Execute`	`BOOL`		Rising edge: Starts the execution of the function block.
	`RatioNumerator`	`DINT`	1	Gear ratio numerator
	`RatioDenominator`	`DINT`	1	Gear ratio denominator
	`MasterSyncPosition`	`LREAL`		Master position where the axes run in sync.
	`SlaveSyncPosition`	`LREAL`		Slave position where the axes run in sync.
	`MasterStartDistance`	`LREAL`		Master distance for the gear in procedure (where the slave axis will be started for getting into synchronization). In other words, the slave is brought into sync with the master during this distance, i.e. from `MasterSyncPosition - MasterStartDistance` until `MasterSyncPosition`. If `MasterStartDistance` is 0 (or negative), then the slave movement is started immediately, provided that the master is not in standstill. If BufferMode <> Aborting, then the MasterStartDistance must be 0 (or negative).
	`BufferMode`	`MC_BUFFER_MODE`		Defines the chronological sequence of the FB relative to the previous block. Only the BufferModes `Aborting`, `Buffered` and `BlendingPrevious` are supported. `BlendingPrevious` means that the configured velocity (including the direction) of the previous movement is used as the blending velocity, even if this movement has the opposite direction. If the function block is Busy, then only BufferMode=Aborting is allowed.
	`AvoidReversal`	`BOOL`		`FALSE`: Signals that the reversal of the slave is physically possible and acceptable. `TRUE`: Signals that a reversal of the modulo slave has to be avoided, e.g. because it is physically impossible or might lead to damage. It works only with modulo slave axes. If a reversal cannot be avoided, the axis is stopped with an error. Behavior: If the slave axis is a modulo axis and the master velocity (times the sign of the gear ratio) is not opposite to the `slave velocity`, then `MC_GearInPos` tries to avoid a reversal of the slave. It tries to “stretch” the slave movement by increasing the distance the slave travels by up to 5 slave periods. If this “stretching” is not successful, an error is reported. If the slave velocity is opposite to the master velocity times the sign of the gear ratio, an error is reported. If the slave axis is not a modulo axis, an error is reported on the rising edge of the Execute input.
Output	`StartSync`	`BOOL`		`TRUE`: Commanded gearing has been started.
	`InSync`	`BOOL`		`TRUE`: Cmmanded gearing has been completed.
	`Busy`	`BOOL`		`TRUE`: Execution of the function block has not been finished.
	`Active`	`BOOL`		Indicates that the FB has control on the axis
	`CommandAborted`	`BOOL`	FALSE	`TRUE`: Execution has been interrupted by another function block instance operating on the axis.
	`Error`	`BOOL`		`TRUE`: Error has occurred within the function block.
	`ErrorID`	`SMC_ERROR`		Error identification