MC_LoadSuperimposed (FB)

FUNCTION_BLOCK MC_LoadSuperimposed

This Function Block commands a controlled torque/force/pressure movement.

This function block commands a controlled load update (increase/decrease) of a specified relative value additional to an existing load. The existing load control operation is not interrupted, but is superimposed by the additional load.

• If MC_LoadSuperImposed is ‘Active’, then any other command in aborting mode except MC_LoadSuperImposed will abort both load commands: both the MC_LoadSuperImposed and the underlying load command. In any other mode, the underlying load command is not aborted

• If MC_LoadSuperImposed is ‘Active’ and another MC_LoadSuperImposed is commanded, only the ongoing MC_LoadSuperImposed command is aborted, and replaced by the new MC_LoadSuperImposed command, but not the underlying load command

• The values of ‘LoadRampIncrease’ and ‘LoadRampDecrease’ are additional values to the ongoing load control, and not absolute ones. With this, the underlying function block always finishes its job in the same period of time regardless of whether a MC_LoadSuperImposed function block takes place concurrently.

• The output ‘Active’ has a different behavior as in buffered function blocks.

• The load control will be activated when the axis is on position control at the start of this block. Any ongoing positioning movement will be interrupted.

Use Case Rational

The function block MC_LoadSuperImposed is intended to allow a superimposed load command to be issued on top of an existing load command without superceding the original load command. If not a load command but a position command is active when MC_LoadSuperimposed is enabled, the ongoing movement will be aborted and the axis be switched to load control. In case that no load control is active when the block is enabled, it will take the actual load value and increase or decrease the load staring from this. When disabled, it will return to this value.

Possible Application

Actuator

hydraulic cylinder with fluid pressure sensor actuates the press of plastic injection molding machine in a continuous load operation.

Request

prior to MC_LoadSuperImposed call, a MC_LoadControl block is ‘Active’ with a command of 7,500 kPa to press melted plastic into the mold. Once the MC_LoadControl

‘InLoad’ condition is achieved a superimposed pressure of 5,000 kPa is added several times to cause a hammering effect to relieve stresses in the plastic.

Result

The MC_LoadControl pressure command of 7,500 kPa is superimposed with a discrete pressure command of 5,000 kPa. Once the ‘LoadSuperImposed’ command is active the system pressure rises to 12,500 kPa. When the superimposed pressure command has been achieved the MC_LoadSuperImposed block is done and the original command given by the MC_LoadControl resumes the original pressure command. The MC_LoadSuperImposed block is executed several times without affecting the original pressure command given by the MC_LoadControl block.

Note

Busy and Active will remain TRUE after function block is disabled until Load is ramped down.

InOut:

Scope	Name	Type	Initial	Comment
Input	Enable	BOOL		Activate the Motion when Enable = TRUE.The axis will be controlled to Load=0 with falling edge, and be kept in load control.
	Load	LREAL		[u] = technical unit. Load that is to be superimposed. Torque/force/pressure
	LoadRampIncrease	LREAL		[u/s] = technical unit. Value of the load ramp increase of the additional load
	LoadRampDecrease	LREAL		[u/s] = technical unit. Value of the load ramp decrease of the additional load
	Direction	MC_Direction	Default	Supported direction: Positive, negative, current, default. The direction determines if just positive or negative load values are to be limited, or both (default)
Output	InLoad	BOOL		Commanded load finally reached
	Busy	BOOL		The function block is not finished
	Active	BOOL		Indicates that the function block has control on the axis
	CommandAborted	BOOL		Command is aborted by another command from other PLCopen function block
	Error	BOOL		Signals that error has occurred within function block
	ErrorID	AC500_MotionControl.ERROR_ID		Error identification. For error details refer to enumeration ERROR_ID from AC500_MotionControl library
Inout	Load_Axis	Load_Ref		Reference to axis