MC_GearInPos

 Function Block - Performs a slave axis move which follows the master axis based on the ratio specified by RatioNumerator and RatioDenominator.

Inputs

Input	Data Type	Range	Unit	Default	Description
Execute	BOOL	0, 1	N/A	No default	On the rising edge, request to queue the slave gear ratio move.
Master	AXIS_REF	1 to 256	N/A	No default	Name of a declared instance of the AXIS_REF library function. See Axis Name and Number. See AXIS_REF Structure.
Slave	AXIS_REF	1 to 256	N/A	No default	AXIS_REF.AXIS_NUM is the slave axis number. See AXIS_REF Structure.
RatioNumerator	DINT	-2147483648 to 2147483647	N/A	No default	Numerator of master/slave ratio. The + or - sign indicates the direction for the slave axis.
RatioDenominator	DINT	-2147483648 to 2147483647	N/A	No default	Denominator of master/slave ratio. The + or - sign indicates the direction for the master axis. The direction determines the sync trigger comparison direction for the slave. For a master moving in the: positive direction, use a positive RatioDenominator. negative direction, use a negative RatioDenominator.
MasterSyncPosition	LREAL	-1.7E308 to 1.7E308	N/A	No default	Master axis sync position. 14 to 15 significant digits of accuracy.
SlaveSyncPosition	LREAL	-1.7E308 to 1.7E308	N/A	No default	Slave axis sync position. 14 to 15 significant digits of accuracy.
SyncMode	INT	0, 1	N/A	No default	SyncMode determines the allowed conditions for synchronization. 0 = Normal Synchronization Prior to executing the MC_GearInPos function block, the Master axis position must be before the MasterSyncPosition by a distance greater than the MasterStartDistance. The Slave axis position must be before the SlaveSyncPosition. Axes that have a non-zero rollover, the MC_GearInPos function block always assumes the axes meet these conditions by assuming the sync point is in the next occurrence of the sync position. MasterStartDistance must be positive and greater than the distance the master axis is currently moving per axis update. If the master start distance and the slave axis distance from the SlaveSyncPosition are sufficiently large enough, the slave axis ramps to the sync position. If not sufficiently large enough, acceleration of the slave axis may be excessive. 1 = Immediate Synchronization Allowed This mode is only allowed if both the master and slave axes have rollover = 0 (zero). If the conditions of SyncMode = 0 (zero) are not met, Synchronization is allowed even though the axis positions may be beyond their respective Sync Positions. The MasterStartDistance may be 0 (zero). If the MasterStartDistance is 0 (zero), the Slave axis synchronizes with the master the instant the master axis crosses the MasterSyncPosition. If either the master or slave axis are beyond their respective sync start positions, the slave axis immediately synchronizes to the master axis. If the master start distance and the slave axis distance from the SlaveSyncPosition are sufficiently large enough, the slave axis ramps to the sync position. If not sufficiently large enough or immediate synchronization occurs, slave axis acceleration may be excessive. Excessive slave acceleration may occur if the master axis velocity is large or the master and slave axes have disproportionally different distances to their respective sync positions. If the slave axis is ahead of the master axis at the time of synchronization, the slave axis moves backwards.
MasterStartDistance	LREAL	-1.7E308 to 1.7E308	User units	No default	When the master axis reaches this distance before MasterSyncPosition, the slave axis begins its lock-on process. 14 to 15 significant digits of accuracy. The MasterStartDistance * (RatioNumerator/RatioDenominator) should be greater than (or equal to) the slave sync distance. The slave sync distance is defined as the distance between the slave position when MC_GearInPos executes and the SlaveSyncPosition. If the MasterStartDistance is too short, the MC_GearInPos may have excessive acceleration and a warning log message is generated.
BufferMode	SINT	1	N/A	No default	1 = Buffer. See Buffer Modes for detailed information.

Outputs

Output	Data Type	Range	Unit	Description
StartSync	BOOL	No range	N/A	Indicates the master axis has reached the MasterStartDistance from the MasterSyncPosition and the lock-on process has begun.
InSync	BOOL	No range	N/A	Indicated the slave axis is locked on to the master axis.
Busy	BOOL	No range	N/A	High from the moment the Execute input goes high until the time the move is ended.
Active	BOOL	No range	N/A	Indicates this move is the Active move.
CommandAborted	BOOL	No range	N/A	Indicates the move was aborted. If the abort arises because the inputs cause inconsistent motion, then this FB: Performs no motion. Sets an error flag. Set the ErrorID to 13.
Error	BOOL	No range	N/A	Indicates either: An invalid input was specified. The move was terminated due to an error.
ErrorID	INT	No range	N/A	Indicates the error if the Error output is set to TRUE. See PLCopen Function Block ErrorIDs.

Remarks

SlaveCommandPosition = MasterActualPosition * RatioNumerator / RatioDenominator

• 
  
• This function block starts a motion-related action and stores data for calculations and error checking.
  If using a dual-core controller, see Call Function Blocks Multiple Times in the Same Cycle.

• See Function Blocks - General Rules about how inputs and outputs work.
• This function block allows the application to specify sync positions for the master and slave axes.
  • It is the point in which the master and slave axes become engaged in synchronous motion.
• When the master axis reaches the MasterStartDistance from the MasterSyncPosition, the slave axis begins to accelerate to the target velocity determined by the master axis velocity and the ratio.
  • The slave axis arrives at the target velocity and the SlaveSyncPosition at the same time the master axis arrives at the MasterSyncPosition.
  • At that time, the slave is locked on to the master and follows the master at the ratio specified.
  • The slave axis continues to follow the master axis until this move is aborted.

Aborting Gearing

Gearing functions can generate large accelerations while following the master.

• If the aborting function block has small, non-zero Jerk, or small acceleration values, it can take a long time for an accelerating axis to reach the target velocity, or position of the aborting function block.
  • If the Jerk and/or acceleration of the aborting function cannot be increased to suitable values, it may be desirable to either:
    • Abort the gearing function with an MC_GearOut with higher accelerations and/or Jerk values (or zero jerk value).
    • Execute the next MC motion function block (e.g., MC_Halt).

Time to Reach the Target Velocity

While following the master, gearing functions can generate large accelerations.

• If the gearing function is aborted while the axis is currently accelerating, and the aborting function block has small non-zero Jerk or small acceleration values, it can take a long time to reach the target velocity, or position of the aborting function block.
  • If the Jerk and/or acceleration of the aborting function cannot be increased to suitable values, it may be desirable to either:
    • Abort the gearing function with an MC_GearOut with higher accelerations and/or Jerk values (or zero jerk value).
    • Execute the next MC motion function block (e.g., MC_Halt).

Figure 1: MC_GearInPos

Time Diagram

Figure 2: Time Diagram

Example

• Master and Slave are rotary axes with rollovers at 360 degrees.
• The Master initial position is 0 degrees and the slave initial position is 45 degrees.
• The GearInPos FB commands the slave to accelerate up to the geared ratio (1:1) during the master start distance (90 degrees) and be synchronized with the master at the master and slave sync positions.

 

Master Axis Slave Axis Master Start Distance Slave starts to accelerate Master Sync Position Slave Sync Position

FBD Language Example

Not available.

FFLD Language Example

IL Language Example

Not available.

ST Language Example

            (* MC_GearInPos ST example *)
            
Inst_MC_GearInPos( GearInPosReq, Axis1, Axis2, 2, 1, 0, 0, 0, 100.0, 1 );
//Inst_MC_GearInPos is instance of MC_GearInPos
GearInPosSync:= Inst_MC_GearInPos.InSync;       
//store InSync output into user defined variable