[RATE_LIM] Rate-of-change limitation

Function block RATE_LIM limits the rate of change and the minimum and maximum values of the input signal.

RATE_LIM limits the rate of change and the minimum and maximum values of the input signal.

Functioning

The function calculates and limits the rate of change as follows:

Signal increase

Max. rate of change on signal increase = [MaxIn] - [MinIn] / [TiUp]

If the input signal [In] exceeds the maximum rate of change on signal increase, the rate of change for the output signal [Out] is limited. The output value [Out] thus only increases in a linear manner.

Signal decrease

Max. rate of change on signal decrease = [MaxIn] - [MinIn] / [TiDn]

If the input signal [In] exceeds the maximum rate of change on signal decrease, the rate of change for the output signal [Out] is exceeded. The output value [Out] thus only decreases in a linear manner.

Minimum and maximum values

[MinIn] and [MaxIn] limit the output value [Out].

Minimum value:

If input value [In] is smaller than [MinIn], output value is set to [Out] = [MinIn].

Maximum value:

If input value [In] is greater than [MaxIn], output value is set to [Out] = [MaxIn].

Enabling and disabling the function

  • When [EnFnct] = 1, the function is switched on.
  • When [EnFnct] = 0, the function is switched off. Input [In] is available at output [Out].
Pins

Input

Description

Data type

Default value
Value range

EnFnct

Enable function

Enables the function.

Boolean

1

0 - The function is disabled.
1 - The function is enabled.

In

Input

Real

0.0

TiUp

Rise time from InMin to InMax

Example: Valve rise time.

Time

0 ms

0 - No limitation of the signal increase.

TiDn

Fall time from InMax to InMin

Example: Valve fall time.

Time

0 ms

0 - No limitation of the signal decrease.

MaxIn

Maximum input signal

Defines the maximum output value [Out]. Example: Maximum valve position 100%.

Real

100.0 [%]

MinIn

Minimum input signal

Real

0.0 [%]

 

Output

Description

Data type

Default value
Value range

Out

Output

Real

0.0

Application
  • Adjustment of a manipulated variable to the valve runtime.
  • Limitation of the rotational speed of pumps and funs to avoid plant swinging and to conserve actuators.