AdCtrlCascade (FB)

FUNCTION_BLOCK AdCtrlCascade

The Function Block AdCtrlCascade is based on the Pidt1 control algorithm and contains several structural enhancements to improve the performance for temperature control.

Several features to improve the behavior of reference input changes, speed up the settling time, mimimize the overshoot and to allow the optimization the controller for disturbance response has been incorporated.

A summary of the features are as follows:

• Deadbeat to speed up the reaction on large reference input changes

• Dynamic Feed-Forward with ramp for defined command response

• Optional cascade structure to overcome the limitations caused by integrating action of the temperature zones

• PT1-Filter to minimize the overshoot on reference input changes

• Static Feed-Forward as adaption to environment temperature

InOut:

Scope	Name	Type	Initial	Comment
Input	EnDeadbeat	BOOL	FALSE	1: Enable a deadbeat step, after a step change is applied to the setpoint
	EnDeadbeatPercent	BOOL	FALSE	2: Use a ramp at the transition from deadbeat to closed loop control, increases the deadbeat effect as closed loop and deadbeat run in parallel
	EnFeedForward	BOOL	FALSE	3: Enable a feed forward step after a step change is applied to the setpoint
	EnCascade	BOOL	FALSE	4: Enable a cascaded control structure
	EnFilter	BOOL	FALSE	5: Enable a filter for setpoint value
	EnStepControl	BOOL		6: The internal setpoint will follow the external setpoint in steps, to reduce overshoot
	ResetCtrl	BOOL	FALSE	7: Reset the controller, control variable will be set to zero.
	ActTemp	REAL	0	8: Actual temperature, controlled value
	RefTemp	REAL	0	9: Reference temperature, setpoint value
	EnvTemp	REAL	0	10: Environment temperature, just valid with KpPre >0
	FfDeltaPerCycle	REAL	0	11: Maximum rate of change for reference temperature per second, creates a dedicated ramp rather then the maximum ramp when EnFeedForward=TRUE
	FfTimeRatio	REAL	1	12: FfTimeRatio >=1, alternative for FfDeltaPerSec, prolonges the shortest possible ramp by the given factor
	FfGain	REAL	0.8	13: 0..1, gain for FeedForward part of controller
	DampCascade	REAL	1	14: Damping for inner loop, just valid when EnCascade=TRUE
	CtrlKp	REAL	0	15: Control parameter proportional gain
	CtrlTiCycles	REAL	0	16: Control parameter integration time
	CtrlTdCycles	REAL	0	17: Control parameter derivative time
	CtrlT1Cycles	REAL	0	18: Control parameter first order delay
	KpPre	REAL	0	19: Gain for a specific offset, applied to the control variable and related to the environment temperature
	MaxRef	REAL	32767	20: Maximum value for the control variable
	MinRef	REAL	0	21: Minimal value for the control variable equals zero means no cooling available or to use on/off cooling
	HysOn	REAL	50	22: Hysteresis used for on/off cooling, used to switch the cooling ON
	HysOff	REAL	0	23: Hysteresis used for on/off cooling, used to switch the cooling OFF
	FilterGain	REAL	0.5	24: Reduce the filter time for setpoint-filter, used time is AdaptTu*FilterGain
	CoolFact	REAL	1	25: Additional gain to be used when cooling is applied, refers to different strength of cooling/heating process
	AdaptKs	REAL	0	26: Value from AdCtrlAdapt Function Block
	AdaptTu	REAL	0	27: Value from AdCtrlAdapt Function Block
	AdaptTg	REAL	0	28: Value from AdCtrlAdapt Function Block
Output	Cv	REAL	0	1: control variable, value for actuator

Structure:

• AdCtrlCascade.zActionControl (ACT)
• AdCtrlCascade.zActionDeadbeat (ACT)
• AdCtrlCascade.zActionFf (ACT)
• AdCtrlCascade.zActionParameter (ACT)