Lead Compensator - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 13.1

Controller Tool Help

Brand
Johnson Controls
Metasys
Product name
Controller Configuration Tool
Document type
User Guide
Document number
LIT-12011147
Version
13.1
Revision date
2019-12-04
Language
English

The Lead Compensator block attempts to remove some of the dynamics of a control loop. This process results in forward-looking predictions and speeds up controller responses. The effect is similar to adding derivative action to the controller. Lead compensation is incorporated into most zone temperature control processes where oversized or nonlinear valves might be applied. The Lead Compensator block only exists within a Control Sequence or Control Activity within a Control Sequence.

The Lead Compensator primitive provides the following reliability values: Reliable, Input Out of Range, or Math Error. The Present Value retains its previous value on Math Error. The block remains Reliable if the Input is not Reliable (ignores unreliability of the input).

The following table describes the inputs and outputs of the Lead Compensator logic block.

Table 1. Lead Compensator Block Inputs and Outputs

Name

Data Type

Exposed for Connection by Default

Description

Default Value

Inputs

Count

Float

Yes

Indicates the number of executions performed by the PID. This value is used to ensure that this block only runs its execute method when the PID that drives the block runs.

0.0

Input

Float

Yes

Provides an input to this logic block from the connected PID. This input is referred to as u k in the equations defined in the Present Value description. If the input is less than the Low Limit, the Low Limit value is used. If the input is greater than the High Limit, the High Limit value is used.

0.0

High Limit

Float

Yes

Indicates the maximum value the Lead Compensator Present Value can assume. If the High Limit is set to a value less than the Low Limit, the block’s reliability is set to Input Out of Range and the logic continues to use the last reliable pair of values. See the Low Limit description for the behavior when High Limit equals Low Limit.

100.0

Low Limit

Float

Yes

Indicates the minimum value that the Lead Compensator Present Value can assume. The Low Limit must be less than or equal to the High Limit. If the Low Limit is set to a value greater than the High Limit, the block’s reliability is set to Input Out of Range, the logic sets the Present Value to the Low Limit, and behaves the same as if the limits are equal. If the Low Limit is set to the same value as the High Limit, the logic sets the Present Value to this value. These inputs may be equal, therefore, the block’s Reliability is not set to Input Out of Range.

0.0

Time Constant

Float

Yes

Indicates the time constant of the process being controlled. This value usually comes from a PID Pre-Processor.

900

Outputs

Present Value 1

Float

Yes

Provides an output from the Lead Compensator logic block, calculated by the following equations:

0.0

Properties

Actual Period

Float

N/A

Indicates the length of time since the last execution of this block.

1.0 second

Lambda

Float

N/A

Indicates the value used by the block. See the equations defined in the Present Value description.

0.8758

Last Input

Float

N/A

Indicates the input at the time of the last execution of this block. This value is the same as the Input on the first execution of this block on startup, or on an enable after a disable.

0.0

Last Output

Float

N/A

Indicates the output at the time of the last execution of this block. This value is the same as the Input on the first execution of this block on startup, or on an enable after a disable.

0.0

1 This input or output is the Default Element of the block.