mpcsimopt

MPC simulation options

Description

When simulating an implicit or explicit MPC controller using the sim function, you can specify additional simulation options using an mpcsimopt object.

Creation

Syntax

options = mpcsimopt;

Description

options = mpcsimopt; creates a default set of options for specifying additional parameters for simulating an MPC controller with the sim function. To specify nondefault values for the properties, use dot notation.

Properties

PlantInitialState — Simulation plant model initial state

[] (default) | vector

Simulation plant model initial state, specified as a vector with length equal to the number states in the plant model used for the simulation. To use the default nominal state of the simulation plant model, set PlantInitialState to [].

If you do not specify the Model option, then the plant model used for the simulation is the internal plant model from the controller. In this case, the default initial controller state is equal to mpcobj.Model.Nominal.X.

If you specify the Model option, then the plant model used for simulation is Model.Plant. In this case, the default initial controller state is equal to Model.Nominal.X.

ControllerInitialState — MPC controller initial condition

[] (default) | mpcstate object

MPC controller initial condition, specified as an mpcstate object. Setting ControllerInitialState = [] is equivalent to setting ControllerInitialState = mpcstate(mpcobj).

UnmeasuredDisturbance — Unmeasured disturbance signal

[] (default) | array

Unmeasured disturbance signal for simulating disturbances occurring at the unmeasured disturbance inputs of the simulation plant model, specified as an array with N_ud columns and up to N_trows, where N_ud is the number of unmeasured disturbances, and N_t is the number of simulation steps. If you specify fewer than N_t rows, then the values in the final row of the array are extended to the end of the simulation.

InputNoise — Manipulated variable noise signal

[] (default) | array

Manipulated variable noise signal for simulating load disturbances occurring at the manipulated variable inputs to the simulation plant model, specified as an array with N_mv columns and up to N_trows, where N_mv is the number of manipulated variables, and N_t is the number of simulation steps. If you specify fewer than N_t rows, then the values in the final row of the array are extended to the end of the simulation.

OutputNoise — Measured output noise signal

[] (default) | array

Measured output noise signal for simulating disturbances occurring at the measured output of the simulation plant model, specified as an array with N_y columns and up to N_trows, where N_y is the number of measured outputs, and N_t is the number of simulation steps. If you specify fewer than N_t rows, then the values in the final row of the array are extended to the end of the simulation.

RefLookAhead — Option to use reference previewing

'off' (default) | 'on'

Option to use reference previewing during simulation, specified as one of the following:

• 'off' — Do not use reference previewing.

• 'on' — Use reference previewing.

When simulating an explicit MPC controller, you must set RefLookAhead to 'off'.

MDLookAhead — Option to use measured disturbance previewing

'off' (default) | 'on'

Option to use measured disturbance previewing during simulation, specified as one of the following:

• 'off' — Do not use measured disturbance previewing.

• 'on' — Use measured disturbance previewing.

When simulating an explicit MPC controller, you must set MDLookAhead to 'off'.

Constraints — Enable constraints

'on' (default) | 'off'

Option to enable constraints during simulation, specified as one of the following:

• 'on' — Use the constraints defined in the controller during simulation.

• 'off' — Simulate the controller without any constraints.

Model — Plant model to use for simulation

[] (default) | LTI system object | structure

Plant model to use for simulation, specified as one of the following:

• [] — Simulate the controller against its internal plant model (mpcobj.Model). In this case, there is no plant-model mismatch.

• LTI system object — Simulate the controller against the specified LTI plant. The specified plant must have the same input and output group configuration as mpcobj.Model.Plant. To set this configuration, use setmpcsignals.

• Structure with fields Plant and Nominal — Simulate the controller using the specified plant (Plant) and nominal conditions (Nominal).

Model sets the actual plant (not the internal prediction model of the controller) to be used in closed-loop or open-loop simulations. To test the controller robustness against a plant model mismatch, use this option to specify a plant that differs from the controller internal plant model.

If you do not specify nominal conditions, Model.Nominal.U and Model.Nominal.Y are inherited from mpcobj.Model.Nominal. Model.Nominal.X and Model.Nominal.DX are only inherited if both plants are state-space objects with the same state dimension.

To specify the initial state of this simulation plant model, use the PlantInitialState option.

StatusBar — Display the simulation status bar

'off' (default) | 'on'

Option to display the simulation status bar, specified as one of the following:

• 'off' — Do not display the status bar.

• 'on' — Display the status bar.

MVSignal — Sequence of manipulated variables

[] (default) | array

Sequence of manipulated variables to use during open-loop simulation, specified as an array with N_mv columns and up to N_trows, where N_mv is the number of manipulated variables, and N_t is the number of simulation steps. If you specify fewer than N_t rows, then the values in the final row of the array are extended to the end of the simulation. The specified manipulated variable signals must include any manipulated variable offsets. If MVSignal is an empty array (default) then a value of 0 is assumed for all the manipulated variables.

MVSignal is ignored if OpenLoop is set to 'off'.

OpenLoop — Run an open-loop simulation

'off' (default) | 'on'

Option to run an open-loop simulation, specified as one of the following:

• 'off' — Perform a closed-loop simulation.

• 'on' — Perform an open-loop simulation.

ShowOutputNoise — Include output noise in measured output plots

'off' (default) | 'on'

Option to include output noise in measured output plots, specified as one of the following:

• 'off' — Do not include output noise in plots

• 'on' — Include output noise in plots

Enable this option to view the output disturbance rejection behavior of the controller during closed-loop simulations.

Object Functions

sim	Simulate an MPC controller in closed loop with a linear plant

Examples

Simulate MPC Control with Plant Model Mismatch

Simulate the MPC control of a multi-input, multi-output (MIMO) system with a mismatch between the predicted and actual plant models. The system has two manipulated variables, two unmeasured disturbances, and two measured outputs.

Define the predicted plant model.

p1 = tf(1,[1 2 1])*[1 1;0 1];
plantPredict = ss([p1 p1]);
plantPredict.InputName = {'mv1','mv2','umd3','umd4'};

Specify the MPC signal types.

plantPredict = setmpcsignals(plantPredict,'MV',[1 2],'UD',[3 4]);

Create the MPC controller.

mpcobj = mpc(plantPredict,1,40,2);

-->"Weights.ManipulatedVariables" is empty. Assuming default 0.00000.
-->"Weights.ManipulatedVariablesRate" is empty. Assuming default 0.10000.
-->"Weights.OutputVariables" is empty. Assuming default 1.00000.

Define the unmeasured input disturbance model used by the controller.

distModel = eye(2,2)*ss(-0.5,1,1,0);
mpcobj.Model.Disturbance = distModel;

Define an actual plant model which differs from the predicted model and has unforeseen unmeasured disturbance inputs.

p2 = tf(1.5,[0.1 1 2 1])*[1 1;0 1];
plantActual = ss([p2 p2 tf(1,[1 1])*[0;1]]);
plantActual = setmpcsignals(plantActual,'MV',[1 2],'UD',[3 4 5]);

Configure the unmeasured disturbance and output reference trajectories.

dist = ones(1,3);
refs = [1 2];

Create and configure a simulation option set.

options = mpcsimopt(mpcobj);
options.UnmeasuredDisturbance = dist;
options.Model = plantActual;

Simulate the system.

sim(mpcobj,20,refs,options)

-->Converting model to discrete time.
-->Assuming output disturbance added to measured output #1 is integrated white noise.
-->Assuming output disturbance added to measured output #2 is integrated white noise.
-->"Model.Noise" is empty. Assuming white noise on each measured output.
-->Converting model to discrete time.
-->"PredictionHorizon" is empty. Assuming default 10.
-->"ControlHorizon" is empty. Assuming default 2.
-->"Weights.ManipulatedVariables" is empty. Assuming default 0.00000.
-->"Weights.ManipulatedVariablesRate" is empty. Assuming default 0.10000.
-->"Weights.OutputVariables" is empty. Assuming default 1.00000.

Version History

Introduced before R2006a