CMC_SIPosiLoop (FB)

FUNCTION_BLOCK CMC_SIPosiLoop

The function block can be used for a simple interpolation. Alternatively, the function block CMC_SInterpolation can be used. A “stand alone” position control loop

This function block has to be used along with function block CMC_SInterPolation

Note

This block has to be called within the REAL-TIME task

Behavior of inputs

InSync	Active	Behavior
FALSE	x	Output Position = ActualPosition
TRUE	FALSE	Interpolates output Position to reach TargetPosition with the given velocity and acceleration.
TRUE	TRUE	Ramps down to velocity = 0.

Behavior of outputs

InSync	Active	Behavior
FALSE	TRUE	Function block is activated, position and velocity is not yet reached.
TRUE	FALSE	Function block is activated, position is reached, output Position = TargetPosition.
FALSE	TRUE	Function block is either disabled or stopped, velocity

Different use cases for this block

Use in Combination with MC_MoveByExternalReference

A positioning axis can be created with modifying the parameters for positioning “on the fly”, without the need of a certain statemachine to follow.

Use in Combination with MCA_SetDynamicFollower

The function block will smooth the movement when a group has to follow a conveyor.

It will create defined ramps to accelerate to the conveyors position and also can be used to prevent a position jump when switching between 2 conveyors or before switching of the follower.

Use to Create a Simple, basic positioning Axis

A very basic, simple positioning axis can be created by using this blokc without the PLCopen blocks.

Be aware that there is not additional check if the axis really follows, also no scaling for the position is included.

If function block CMC_SIPosiLoop is used, it will check for position or velocity following error.

InOut:

Scope	Name	Type	Initial	Comment
Input	Enable	BOOL		Level triggered, close = 1, open = 0, a rising edge required to clear any error condition
	NewPara	BOOL		At least one rising edge required to set parameter, TRUE: internal values calculated from input parameters, level triggered
	Position	LREAL		[u] Reference position
	ActualPosition	LREAL		[u] Actual position
	Pos_Lag_Percentage	LREAL	100	[%] Allowed percentage for following error, 100% will be reached with constant velocity at Max_Rpm with FF_Percentage = 0. Zero will switch off the monitoring
	V_Check_Time	TIME	TIME#100ms	[ms] Tolerance time during which the velocity might deviate for 50%, zero will switch off the monitoring
	Control_Time	LREAL	100	[ms] Determines the gain for position control loop
	FF_Percentage	LREAL	0	[%] Percentage for feed forward part of the control loop
	Cycle	LREAL	10	[ms] Cycle time of the PLC program
	U_Per_Rev_Nominator	DWORD	1024	Units per motor revolution = U_Per_Rev_Nominator/U_Per_Rev_Denominator
	U_Per_Rev_Denominator	DWORD	1	Units per motor revolution = U_Per_Rev_Nominator/U_Per_Rev_Denominator
	Ref_Max	LREAL	32767	Maximum value for SpeedReference, has to be the value when Max_Rpm is reached
	Max_Rpm	WORD	1500	Maximum rotation per minute, has to be reached with SpeedReference = Ref_Max
Output	Closed	BOOL		Position control loop activated and closed
	ParaError	BOOL		Wrong parameter
	PosFollowingError	BOOL		Following error detected
	SpeedReference	LREAL		Speed reference. Range -Ref_Max <= SpeedReference <= Ref_Max
	VelFollowingError	BOOL		Velocity error detected