PID Controller (Universal)

Symbol (samples)

[A]

Without limit controller output

[B] Disturbance feed forward and with limit inputs

[C] Disturbance feed forward

[D]

The function block PID Controller (Universal) contains the following elements:

- proportional term

- integral term

- differential term

- integral wind-up avoidance logic

- setup of controller output; with auto/manual selection

The function block supports four types of PID controllers. Depending on the selection, there are different input and output connectors available.

Type 1 [a]	Shared error input for P-, I- and D-term
Type 2 [b]	Individual error input for P-, I- and D-term
Type 3 [c]	Setpoint and controlled variable as input, the error input d (d=W-X) is set in the controller
Type 4 [d]	Setpoint and controlled variable as input, the error input d (d=W-X) for the P- and I-term is set in the controller, for the D-term it is calculated from the change of the controlled variable.

The input pins must be connected. The controller subtracts the disturbance (Z) from the controller output before it is limited.

The controller can be tuned by the multiplier (Kr) and by the multipliers (Ki, Kd) or by the time constants (Tn, Tv). Internally, a calculation with the coefficients is taking place. If the reset time Tn turns to 0, the I-proportion is turned off.

If parameter pins for the limitation are activated, they have to be connected. The limitation takes place inside the block. The output limitation is used to prevent a wind-up. If the output limitation is not done properly, the integration sum will be frozen.

If the input disturbance (Z) activated, the preset input (PS) will be available. Setting it means the the input disturbance (Z) is set on the output.

Setting the manual mode (H) will lead to the manual set input (Yh) on the output. The manual mode is dominant over the preset input.

A limitation of the setpoint will also be effected, if the preset or manual input is set.

At the output, either the Controller output (Y) or the change of the output (dY) can be output.

If the limitations are exceeded, the outputs SYu or SYo are set.

Parameters

The parameter dialog can be used to select the type of the PID controller and several variations within each type. The available input and output connectors can be selected and the interpretation of the input parameters (time based or coefficient) as well as the terms, which have an effect on controlling (PID, PI, PD), can be defined.

Operations

Legend:

T Cycle time

Signals

Name	I/O	Type(s)	Function
d	I	FLOAT	Error input [a]
dP	I	FLOAT	Error input; P-term [b]
dI	I	FLOAT	Error input; I-term[b]
dD	I	FLOAT	Error input; D-term [b]
W	I	FLOAT	Setpoint [c], [d]
X	I	FLOAT	Controlled variable (sensor input) [c], [d]
Z	I	FLOAT	Disturbance (disturbance feed forward)
Iu	I	FLOAT	Lower limit inputs
Io	I	FLOAT	Upper limit inputs
Kr	I	FLOAT	Proportional multiplier
Ki, Tn	I	FLOAT	Integral multiplier, term integral time constant in [s]
Kd, Tv	I	FLOAT	Differential multiplier, term differential time constant in [s]
Yh	I	FLOAT	Manual set input
H	I	BIT	Manual mode
PS	I	BIT	Disturbance mode, Preset (disturbance feed forward)
Yu	I	FLOAT	Lower limit controller output, wind-up
Yo	I	FLOAT	Upper limit controller output, wind-up
SIu	O	BIT	Lower limit (error W-X) reached
SIo	O	BIT	Upper limit (error W-X) reached
SYu	O	BIT	Lower controller output limit (Yu) reached
SYo	O	BIT	Upper controller output limit (Yu) reached
Y	O	FLOAT	Controller output
dY	O	FLOAT	Controller output (y[n] - y[n-1])

Parameters

Ki	= 0	I-term is off
Tn	= 0	I-term is off
Kd	= 0	D-term is off
Tv	= 0	D-term is off
H	= 1	Manual mode - Yh is channeled directly to Y (dominant)
PS	= 1	Disturbance mode – The signal Z is channeled directly to Y