PID Gains Store and Update

Store and update tuned PID gains tuned using Closed-Loop PID Autotuner

Since R2023b

• 

Libraries:
Simulink Control Design / Autotuning

Description

The PID Gains Store and Update block lets you write the gains obtained from the Closed-Loop PID Autotuner block to a memory location or route them as a signal. Use this block to manage the gains obtained at various operating points during the autotuning process.

Typically, tuning a gain-scheduled controller is a complex process. It requires you to run multiple simulations for tuning at each operating point and provide a logic to store PID gains at that operating point. Using this block, along with the Change Operating Points and PID Gain Scheduler blocks, helps you implement a streamlined workflow for autotuning gain-scheduled PID controllers over an operating range in a single run. To do so, use this workflow.

1. Switch between predefined or snapshot operating point data during the simulation using the Change Operating Points block.

2. Perform autotuning at the operating points using Closed-Loop PID Autotuner.

3. Store the PID gains corresponding to the operating point in an array using PID Gains Store and Update block.

4. Perform lookup table based gain scheduling from the array using the PID Gain Scheduler block.

On a high level, you can use these blocks to implement the gain-scheduled workflow as shown in this diagram.

Ports

Input

tuned Gains — Tuned PID gains

bus

Specify the tuned PID gain values to store and route. Typically, you obtain these tuned gains from the Closed-Loop PID Autotuner block.

This 4-element bus signal must contain the tuned PID gains P, I, D, and the filter coefficient N. These values correspond to the P, I, D, and N parameters in the expressions given in the Controller type parameter. During autotuning, initially, the values are 0, 0, 0, and 100, respectively. The Closed-Loop PID Autotuner block updates the values when the experiment ends. This bus signal always has four elements, even if you are not tuning a PIDN controller.

scheduling Variable — Scheduling variable

scalar

Specify the scheduling variable. This signal indicates where in the operating range the system is at a given time.

This signal also dictates when the gains change in a gain-scheduled control application.

Dependencies

To enable this port, select Use for gain scheduling.

Breakpoints — Breakpoint data

vector

Breakpoint data for gain scheduling, specified as a vector.

Dependencies

To enable this port, select Use external signal.

Update Trigger — Trigger control signal

scalar

Control signal to trigger the update of gains.

Dependencies

To enable this port, set Method to trigger gain update to External trigger.

Output

PID Gains Out — PID gain array

bus

Stored PID gain array. Use this gain array along with the breakpoint data to implement lookup table based gain scheduling.

Use this port to specify a custom logic to route the gain array.

To enable this port, set Method of storing gains to Output from block.

Parameters

Controller type — PID controller type

P (default) | I | PI | PD | PDN | PID | PIDN

Specify the type of the PID controller in your system. The controller type indicates what actions are present in the controller. The following controller types are available:

• P — Proportional only

• I — Integral only

• PI — Proportional and integral

• PD — Proportional and derivative

• PDN — Proportional and derivative with derivative filter

• PID — Proportional, integral, and derivative

• PIDN — Proportional, integral, and derivative with derivative filter

When you update a PID Controller block or custom PID controller with tuned parameter values, make sure the controller type matches.

Programmatic Use

Block Parameter: ControllerType

Type: string

Values: "P" | "I" | "PI" | "PD" | "PDN" | "PID" | "PIDN"

Default: "PID"

Use for gain scheduling — Enable block for gain scheduling

on (default) | off

Use this option to enable the block for gain-scheduling applications. Doing so allows you to specify breakpoints used with gain lookup.

Programmatic Use

Block Parameter: UseGainScheduling

Type: string

Value "off" | "on"

Default: "on"

Save breakpoints in gain array — Save breakpoints along with PID gains

off (default) | on

Use this option to save breakpoints along with the stored gain array. The PID Gain Scheduler block can interpret this combined data for gain-scheduling applications.

Dependencies

To enable this parameter, select Use for gain scheduling.

Programmatic Use

Block Parameter: SaveBreakpoints

Type: string

Value "off" | "on"

Default: "off"

Breakpoints — Gain scheduling breakpoints

[1 2 3] (default) | vector

Specify the gain-scheduling breakpoint data.

Dependencies

To enable this parameter, select Use for gain scheduling.

Programmatic Use

Block Parameter: NumBreakpoints

Type: vector

Values: vector of at least two elements

Default: "[1 2 3]"

Number of breakpoints — Number of breakpoints

3 (default) | positive scalar

Specify the number of breakpoints in the external breakpoints signal.

Dependencies

To enable this parameter, select Use for gain scheduling and Use external signal.

Programmatic Use

Block Parameter: NumBreakpoints

Type: scalar

Values: positive scalar

Default: 3

Use external signal — Specify breakpoints from input port

off (default) | on

Specify breakpoints from the block input port.

Dependencies

To enable this parameter, select Use for gain scheduling.

Programmatic Use

Block Parameter: UseExternalBreakpoints

Type: string

Value "off" | "on"

Default: "off"

Gain index tolerance — Gain index tolerance

1e-3 (default) | nonegative scalar

Specify the tolerance between the scheduling variable and the breakpoints. To determine which breakpoint to update in the array, the block compares the scheduling variable with the breakpoint array and uses this tolerance value to determine the closest value.

Dependencies

To enable this parameter, select Use for gain scheduling.

Programmatic Use

Block Parameter: GainIndexTolerance

Type: scalar

Values: nonnegative scalar

Default: 1e-3

Method of storing gains — Method of storing gains

Data store memory (default) | Goto/from | Output from block

Specify the method of storing gains.

• Data store memory — Use Data Store Memory blocks to store the gains. To create the data store blocks, first specify a name for the data store using Parameter Name parameter for each gain, then click the Add Data Store Memory blocks to model button. The PID Gains Store and Update block creates Data Store Memory blocks in the top-level of the model. You can specify these data store names directly in the PID Gain Scheduler block to perform lookup table based gain scheduling.

• Goto/from — Use Goto and From blocks to route the gains. To specify a Goto tag, use the Parameter Name parameter for each gain. You can specify these Goto tags directly in the PID Gain Scheduler block to read and lookup the gains.

• Output from block — Use the PID Gains Out output port. You can feed this output signal directly into the PID Gain Scheduler block.

Use the Gain initial conditions parameters to specify the initial values of gains. The block uses the initial values when the tuned gained are not available.

Programmatic Use

Block Parameter: TriggerUpdateMethod

Type: string

Values: "Data store memory" | "Goto/from" | "Output from block"

Default: "Data store memory"

P Gain Parameter Name — Proportional gain data name

PGain (default) | string

Specify the name of the data store or goto tag for the proportional gain data.

Dependencies

To enable this parameter, set

• Controller type to a controller type that has proportional action.

• Method of obtaining gains to Data store memory or Goto/from.

Programmatic Use

Block Parameter: StoreGainsPParamName

Type: string

Default: "PGain"

P Gain initial conditions — Proportional gain initial value

0 (default) | scalar | vector

Specify the initial value of the proportional gain as a scalar or vector. The block uses this value when tuned gains data from the external sources (like Closed-Loop PID Autotuner) is not available.

• Scalar — The block uses this value for all breakpoints.

• Vector — Specify a vector of same length as Breakpoints. The block uses the initial value at the index corresponding to the current breakpoint.

Dependencies

To enable this port, set Controller type to a controller type that has proportional action.

Programmatic Use

Block Parameter: PGainInitialConditions

Type: scalar | vector

Default: 0

I Gain Parameter Name — Integral gain data name

IGain (default) | string

Specify the name of the data store or goto tag for the integral gain data.

Dependencies

To enable this parameter, set

• Controller type to a controller type that has integral action.

• Method of obtaining gains to Data store memory or Goto/from.

Programmatic Use

Block Parameter: StoreGainsIParamName

Type: string

Default: "IGain"

I Gain initial conditions — Integral gain initial value

0 (default) | scalar | vector

Specify the initial value of the integral gain as a scalar or vector. The block uses this value when tuned gains data from the external sources (like Closed-Loop PID Autotuner) is not available.

• Scalar — The block uses this value for all breakpoints.

• Vector — Specify a vector of same length as Breakpoints. The block uses the initial value at the index corresponding to the current breakpoint.

Dependencies

To enable this port, set Controller type to a controller type that has integral action.

Programmatic Use

Block Parameter: IGainInitialConditions

Type: scalar | vector

Default: 0

D Gain Parameter Name — Derivative gain data name

DGain (default) | string

Specify the name of the data store or goto tag for the derivative gain data.

Dependencies

To enable this parameter, set

• Controller type to a controller type that has derivative action.

• Method of obtaining gains to Data store memory or Goto/from.

Programmatic Use

Block Parameter: StoreGainsDParamName

Type: string

Default: "DGain"

D Gain initial conditions — Derivative gain initial value

0 (default) | scalar | vector

Specify the initial value of the derivative gain as a scalar or vector. The block uses this value when tuned gains data from the external sources (like Closed-Loop PID Autotuner) is not available.

• Scalar — The block uses this value for all breakpoints.

• Vector — Specify a vector of same length as Breakpoints. The block uses the initial value at the index corresponding to the current breakpoint.

Dependencies

To enable this port, set Controller type to a controller type that has derivative action.

Programmatic Use

Block Parameter: DGainInitialConditions

Type: scalar | vector

Default: 0

N Gain Parameter Name — Filter gain data name

NGain (default) | string

Specify the name of the data store or goto tag for the derivative filter gain data.

Dependencies

To enable this parameter, set

• Controller type to a controller type that has a filtered derivative.

• Method of obtaining gains to Data store memory or Goto/from.

Programmatic Use

Block Parameter: StoreGainsNParamName

Type: string

Default: "NGain"

N Gain initial conditions — Filter gain initial value

100 (default) | scalar | vector

Specify the initial value of the derivative filter gain as a scalar or vector. The block uses this value when tuned gains data from the external sources (like Closed-Loop PID Autotuner) is not available.

• Scalar — The block uses this value for all breakpoints.

• Vector — Specify a vector of same length as Breakpoints. The block uses the initial value at the index corresponding to the current breakpoint.

Dependencies

To enable this port, set Controller type to a controller type that has a filtered derivative.

Dependencies

To enable this parameter, set Method of storing gains to Data store memory or Goto/from.

Programmatic Use

Block Parameter: NGainInitialConditions

Type: scalar | vector

Default: 100

Method to trigger gain update — Update trigger method

Detect change in PID gains (default) | External trigger

Specify the method to trigger gain update.

• Detect change in PID gains — Update the gains automatically when there is a change in the input gains.

• External trigger — Use an external signal to trigger the gains update.

Programmatic Use

Block Parameter: TriggerUpdateMethod

Type: string

Values: "Detect change in PID gains" | "External trigger"

Default: "Detect change in PID gains"

Number of samples to delay update — Number of samples to delay update

1 (default) | nonnegative scalar

Number of samples to delay the gains update following the trigger event. Use this option to delay updating the gains in order to give the autotuning algorithm enough time to calculate the gains.

Programmatic Use

Block Parameter: NumUpdateDelays

Type: scalar

Values: nonnegative scalar

Default: 1

Sample time (-1 for inherited) — Sample time

-1 (default) | positive scalar

Specify the sample time. In your autotuning applications, this sample time must match with the controller sample time specified in the PID Controller and Closed-Loop PID Autotuner blocks.

Programmatic Use

Block Parameter: SampleTime

Type: scalar

Values: positive scalar | –1

Default: –1

Data Type — Floating point precision

Double (default) | Single

Specify the floating-point precision based on simulation environment or hardware requirements.

Programmatic Use

Block Parameter: BlockDataType

Type: string

Values: "Double" | "Single"

Default: "Double"

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2023b