Documentation

Three Point P-Controller (T8)

Block name

T8_THREE_POINT_CONTROLLER

ST call

PROGRAM TEST_T8
	VAR 
		REAL1,REAL2,REAL3,REAL4,REAL5,REAL6: REAL;
		TIME1,TIME2,TIME3,TIME4,TIME5,TIME6   :TIME;
		BOOL1,BOOL2,BOOL3,BOOL4,BOOL5,BOOL6:BOOL;
		FB: LIB.HVAC.V1_0.T8_THREE_POINT_CONTROLLER;
	END_VAR
	FB(X:= REAL1, W:= REAL2, BCRASH:= BOOL1, BR:= BOOL2, ENABLED:= BOOL3, BSP:= BOOL4, TOLMIN:= REAL3, TOLMAX:= REAL4, TROPEN:= TIME1, TRCLOSE:= TIME2, T0:= TIME3, TIMPMIN:= TIME4, TIMPMAX:= TIME5, CLOSE=>BOOL5, OPEN=>BOOL6, OUT=>REAL5, TIMEPERIOD=>TIME6);
END_PROGRAM

Library

LIB\HVAC

Version

V1.0

Description

The block is a P-controller with a three-point output.

Inputs

Input	Typ	Description	Default value
X	REAL	Real (measured) value	0
W	REAL	Setpoint value	0
BCRASH	BOOL	Signal for fast travel to a safe position, when activated, the safe position output is active permanently	False
BR	BOOL	Reset (sync) input to travel to a safe position and reset the internal position counter	False
ENABLED	BOOL	Synchronisation enabled	False
T0	TIME	Length of gap (pause) between the pulses	4s
TIMPMAX	TIME	Max. length of output pulse	2,5s
TIMPMIN	TIME	Min. length of output puls	1,5s
TOLMAX	real	Upper tolerance limit \|X-W\|>TOLMAX – the control pulse length is TIMPMAX, TOLMIN<=\|X-W\|<=TOLMAX – the control pulse length changes between TIMPMIN and TIMPMAX.	2
TOLMIN	REAL	Lower tolerance limit - at \|X-W\|<TOLMIN the outputs are inactive	1
TRCLOSE	TIME	Travel time 100 % to 0 %	65s
TROPEN	TIME	Travel time 0 % to 100 %	65s

Outputs

Output	Typ	Description
CLOSE	BOOL	Command to open
OPEN	BOOL	Command to close
OUT	REAL	Expected (calculated) position (0%...100%)
TIMEPERIOD	TIME	Auxiliary value - calculated length of the control pulse period

Function

The block is used where a 3-point actuator has to be controlled using a P algorithm. The output pulse length is proportional to the difference between real and setpoint values. Parameters T0, TIMPMAX, and TIMPMIN are set instead of the bandwidth or gain.

Application example

Similar to T2, however, the P controller is part of the three-point control block, and not a separate function block.