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PID Gains Store and Update

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

Since R2023b

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  • PID Gains Store and Update block

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.

Diagram of a gain-scheduled system, with Closed-Loop PID Autotuner, PID Controller, Change Operating Points, Gain Scheduler, and PID Gains Store and Update blocks.

Ports

Input

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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.

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.

Breakpoint data for gain scheduling, specified as a vector.

Dependencies

To enable this port, select Use external signal.

Control signal to trigger the update of gains.

Dependencies

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

Output

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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

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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 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"

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"

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]"

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

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"

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

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"

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"

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

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"

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

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"

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

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"

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

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 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

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

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

See Also

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