Three-point P controller
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.