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Generate Code and Deploy Controller to Real-Time Targets

Model Predictive Control Toolbox™ software provides code generation functionality for controllers designed in MATLAB® or Simulink®.

Code Generation in MATLAB

After designing an MPC controller in MATLAB, you can generate C code using MATLAB Coder™ and deploy it for real-time control.

To generate code for computing optimal MPC control moves for an implicit or explicit linear MPC controller:

  1. Generate data structures from an MPC controller or explicit MPC controller using getCodeGenerationData.

  2. To verify that your controller produces the expected closed-loop results, simulate it using mpcmoveCodeGeneration in place of mpcmove.

  3. Generate code for mpcmoveCodeGeneration using codegen (MATLAB Coder). This step requires MATLAB Coder software.

For an example, see Generate Code to Compute Optimal MPC Moves in MATLAB.

You can also generate code for nonlinear MPC controllers that use the default fmincon solver with the SQP algorithm. To generate code for computing optimal control moves for a nonlinear MPC controller:

  1. Generate data structures from a nonlinear MPC controller using getCodeGenerationData.

  2. To verify that your controller produces the expected closed-loop results, simulate it using nlmpcmoveCodeGeneration in place of nlmpcmove.

  3. Generate code for nlmpcmoveCodeGeneration using codegen (MATLAB Coder). This step requires MATLAB Coder software.

Code Generation in Simulink

After designing a controller in Simulink using any of the MPC blocks, you can generate code and deploy it for real-time control. You can deploy controllers to all targets supported by the following products:

  • Simulink Coder

  • Embedded Coder®

  • Simulink PLC Coder™

  • Simulink Real-Time™

You can generate code for any of the Model Predictive Control Toolbox Simulink blocks.

Types of ControllersBlocks
Implicit MPC controllers

MPC Controller

Explicit MPC controllers

Explicit MPC Controller

Gain-scheduled MPC controllers

Multiple MPC Controllers

Multiple Explicit MPC Controllers

Adaptive MPC controllers

Adaptive MPC Controller

MPC controllers for automotive applications

Adaptive Cruise Control System

Lane Keeping Assist System

Path Following Control System

Nonlinear MPC controllers that use fmincon with SQP

Nonlinear MPC Controller

For more information on generating code, see Simulation and Code Generation Using Simulink Coder and Simulation and Structured Text Generation Using Simulink PLC Coder.

Note

The MPC Controller, Explicit MPC Controller, Adaptive MPC Controller, and Nonlinear MPC Controller blocks are implemented using the MATLAB Function (Simulink) block. To see the structure, right-click the block, and select Mask > Look Under Mask. Then, open the MPC subsystem underneath.

Note

If your nonlinear MPC controller uses optional parameters, you must also generate code for the Bus Creator block connected to the params input port of the Nonlinear MPC Controller block. To do so, place the Nonlinear MPC Controller and Bus Creator blocks within a subsystem, and generate code for that subsystem.

Sampling Rate in Real-Time Environment

The sampling rate that a controller can achieve in a real-time environment is system-dependent. For example, for a typical small MIMO control application running on Simulink Real-Time, the sample time can be as long as 1–10 ms for linear MPC and 100–1000 ms for nonlinear MPC. To determine the sample time, first test a less-aggressive controller whose sampling rate produces acceptable performance on the target. Next, decrease the sample time and monitor the execution time of the controller. You can further decrease the sample time as long as the optimization safely completes within each sampling period under normal plant operating conditions. To reduce the sample time, you can also consider using:

  • Explicit MPC. While explicit MPC controllers have a faster execution time, they also have a larger memory footprint, since they store precomputed control laws. For more information, see Explicit MPC Design.

  • A suboptimal QP solution after a specified number of maximum solver iterations. For more information, see Suboptimal QP Solution.

Tip

A lower controller sample time does not necessarily provide better performance. In fact, you want to choose a sample time that is small enough to give you good performance but no smaller. For the same prediction time, smaller sample times result in larger prediction steps, which in turn produces a larger memory footprint and more complex optimization problem.

QP Problem Construction for Generated C Code

At each control interval, an implicit or adaptive MPC controller constructs a new QP problem, which is defined as:

Minx(12xHx+fx)

subject to the linear inequality constraints

Axb

where

  • x is the solution vector.

  • H is the Hessian matrix.

  • A is a matrix of linear constraint coefficients.

  • f and b are vectors.

In generated C code, the following matrices are used to provide H, A, f, and b. Depending on the type and configuration of the MPC controller, these matrices are either constant or regenerated at each control interval.

Constant MatrixSizePurposeImplicit MPCImplicit MPC with Online Weight TuningAdaptive MPC or LTV MPC
HinvNM-by-NMInverse of the Hessian matrix, HConstantRegeneratedRegenerated
LinvNM-by-NMInverse of the lower-triangular Cholesky decomposition of H
AcNC-by-NMLinear constraint coefficients, AConstant
KxNxqp-by-(NM–1)Used to generate fRegenerated
Krp*Ny-by-(NM–1)
Ku1Nmv-by-(NM–1)
Kv(Nmd+1)*(p+1)-by-(NM–1)
Kutp*Nmv-by-(NM–1)
MlimNC-by-1Used to generate bConstantConstant, except when there are custom constraints
MxNC-by-NxqpRegenerated
Mu1NC-by-Nmv
MvNC-by-(Nmd+1)*(p+1)

Here:

  • p is the prediction horizon.

  • Nmv is the number of manipulated variables.

  • Nmd is the number of measured disturbances.

  • Ny is the number of output variables.

  • NM is the number of optimization variables (m*Nmv+1, where m is the control horizon).

  • Nxqp is the number of states used for the QP problem; that is, the total number of the plant states and disturbance model states.

  • NC is the total number of constraints.

At each control interval, the generated C code computes f and b as:

f=Kxxq+Krrp+Ku1ml+Kvvp+Kutut

b=(Mlim+Mxxq+Mu1ml+Mvvp)

where

  • xq is the vector of plant and disturbance model states estimated by the Kalman filter.

  • ml is the manipulated variable move from the previous control interval.

  • ut is the manipulated variable target.

  • vp is the sequence of measured disturbance signals across the prediction horizon.

  • rp is the sequence of reference signals across the prediction horizon.

Note

When generating code in MATLAB, the getCodeGenerationData command generates these matrices and returns them in configData.

Code Generation for Custom QP Solvers

You can generate code for linear MPC controllers that use a custom QP solver written in C or MATLAB code. The controller calls this solver in place of the built-in QP solver at each control interval.

For an example, see Simulate and Generate Code for MPC Controller with Custom QP Solver. For more information on custom QP solvers, see Custom QP Solver.

See Also

Functions

Blocks

Related Topics