MC_GearInPos

Description

This function block performs a slave axis move which follows the master axis based on the ratio specified by RatioNumerator and RatioDenominator.

SlaveCommandPosition = MasterActualPosition * RatioNumerator / RatioDenominator

This function block also 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 JerkIn physics, jerk is the rate of change of acceleration; more precisely, the derivative of acceleration with respect to time, 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:

Abort the gearing function with an MC_GearOut with higher accelerations and/or Jerk values (or zero jerkIn physics, jerk is the rate of change of acceleration; more precisely, the derivative of acceleration with respect to time value),
Execute the next MC motion function block such as 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:

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 such as MC_Halt.

MC_GearInPos

Figure 8-151: MC_GearInPos

Time Diagram

MC_GearInPos: Timing Diagram

This function block starts a motion-related action and therefore stores data for calculations and error checking. Please see Calling Function Blocks Multiple Times in the Same Cycle if you are using a dual-core controller.

Arguments

For more detail on how inputs and outputs work, refer to PLCopen Function Blocks - General Rules

Input

Execute	Description	Requests to queue the slave gear ratio move
	Data type	BOOL
	Range	0, 1
	Unit	N/A
	Default	—
Master	Description	Name of a declared instance of the AXIS_REF library function (for more details,About Axis Name and Number)
	Data type	AXIS_REF
	Range	[1,256]
	Unit	N/A
	Default	—
Slave	Description	AXIS_REF.AXIS_NUM is the slave axis number
	Data type	AXIS_REF
	Range	[1,256]
	Unit	N/A
	Default	—
RatioNumerator	Description	Numerator of master/slave ratio. The sign (+ or -) indicates the direction for the slave axis.
	Data type	DINT
	Range	[-2147483648, 2147483647]
	Unit	N/A
	Default	—
RatioDenominator	Description	Denominator of master/slave ratio. The sign (+ or -) 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. For a master moving in the negative direction, use a negative RatioDenominator.
	Data type	DINT
	Range	[-2147483648, 2147483647]
	Unit	N/A
	Default	—
MasterSyncPosition	Description	Master axis sync position
	Data type	LREAL
	Range	-1.7³⁰⁸ to 1.7³⁰⁸ (14 to 15 significant digits of accuracy)
	Unit	N/A
	Default	—
SlaveSyncPosition	Description	Slave axis sync position
	Data type	LREAL
	Range	-1.7³⁰⁸ to 1.7³⁰⁸ (14 to 15 significant digits of accuracy)
	Unit	N/A
	Default	—
SyncMode	Description	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. In the case of axes that have a non-zero rollover, the MC_GearInPos function block will always assume 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 will ramp 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. If the conditions of SyncMode = 0 are not met, Synchronization is allowed even though the axis positions may be beyond their respective Sync Positions. The MasterStartDistance may be 0. If the MasterStartDistance is zero, the Slave axis will synchronize 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 will immediately synchronize to the master axis. If the master start distance and the slave axis distance from the SlaveSyncPosition are sufficiently large enough, the slave axis will ramp to the sync position. If not sufficiently large enough or immediate synchronization occurs, slave axis acceleration may be excessive. Excessive slave acceleration may also 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 will move backwards.
	Data type	INT
	Range	0-1
	Unit	N/A
	Default	—
MasterStartDistance	Description	When the master axis reaches this distance before MasterSyncPosition, the slave axis begins its lock-on process. 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 will be generated.
	Data type	LREAL
	Range	1.7^-308 to 1.7³⁰⁸ (14 to 15 significant digits of accuracy)
	Unit	User unit
	Default	—
BufferMode	Description	1 = buffer See table in Buffer Modes
	Data type	SINT
	Range	[1]
	Unit	N/A
	Default	—

Output

StartSync	Description	Indicates that the master axis has reached the MasterStartDistance from the MasterSyncPosition and the lock-on process has begun
	Data type	BOOL
InSync	Description	Indicated the slave axis is locked on to the master axis
	Data type	BOOL
Busy	Description	High from the moment the Execute input goes high until the time the move is ended
	Data type	BOOL
Active	Description	Indicates this move is the Active move
	Data type	BOOL
CommandAborted	Description	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
	Data type	BOOL
Error	Description	Indicates an invalid input was specified or the move was terminated due to an error
	Data type	BOOL
ErrorID	Description	Indicates the error if Error output is set to TRUE See table in PLCopen Function Block ErrorID Output
	Data type	INT

Example

Example Description

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

Structured Text

            (* 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

Ladder Diagram

MC_GearInPos: LD example

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