Using NLMPC on vehicle dynamics

Question

Ragavendra Joshi 2023-4-28

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1954549-using-nlmpc-on-vehicle-dynamics

回答： Emmanouil Tzorakoleftherakis 2023-5-1

The code below generates NLMPC objects and uses greycar model for vehicle dynamics system. And also there is simulink implementation of the code. But there is an error. So, please help me with this.

%making grey car model

FileName = 'vehicle_c'; % File describing the model structure.

Order = [3 5 3]; % Model orders [ny nx nu].

Parameters = [1700; 1.5; 1.5; 404; 404; 0.5]; % Initial parameters.

InitialStates = [1; 0; 0]; % Initial value of initial states.

ts= 0;

sys = idnlgrey(FileName, Order, Parameters, InitialStates, ts, ...

'Name', 'vehicle model', 'TimeUnit', 's');

present(sys)

sys = Continuous-time nonlinear grey-box model defined by 'vehicle_c' (MEX-file): dx/dt = F(t, u(t), x(t), p1, ..., p6) y(t) = H(t, u(t), x(t), p1, ..., p6) + e(t) with 5 input(s), 3 state(s), 3 output(s), and 6 free parameter(s) (out of 6). Inputs: u(1) (t) u(2) (t) u(3) (t) u(4) (t) u(5) (t) States: Initial value x(1) x1(t) xinit@exp1 1 (fixed) in [-Inf, Inf] x(2) x2(t) xinit@exp1 0 (fixed) in [-Inf, Inf] x(3) x3(t) xinit@exp1 0 (fixed) in [-Inf, Inf] Outputs: y(1) (t) y(2) (t) y(3) (t) Parameters: Value p1 p1 1700 (estimated) in [-Inf, Inf] p2 p2 1.5 (estimated) in [-Inf, Inf] p3 p3 1.5 (estimated) in [-Inf, Inf] p4 p4 404 (estimated) in [-Inf, Inf] p5 p5 404 (estimated) in [-Inf, Inf] p6 p6 0.5 (estimated) in [-Inf, Inf] Name: vehicle model Status: Created by direct construction or transformation. Not estimated. More information in model's "Report" property. Model Properties

%non linear mpc parameters

nx=3; %no of states

nu=5; %no of parameters

ny=3; %no of outputs

%defining non linear mpc

nlobj= nlmpc(nx,ny,nu);

%defining parameters

Ts=0.1;

nlobj.Ts=Ts

nlobj =

nlmpc with properties: Ts: 0.1000 PredictionHorizon: 10 ControlHorizon: 2 Dimensions: [1×1 struct] Model: [1×1 struct] States: [1×3 struct] OutputVariables: [1×3 struct] ManipulatedVariables: [1×5 struct] MeasuredDisturbances: [] Weights: [1×1 struct] Optimization: [1×1 struct] Jacobian: [1×1 struct] Passivity: [1×1 struct]

nlobj.PredictionHorizon=10;

nl.ControlHorizon=2;

%parameters of mpc variables

nlobj.Weights.OutputVariables = [3,3,3];

nlobj.Weights.ManipulatedVariablesRate = [10,10,10,10,10];

nlobj.OV(1).Min = 1;

nlobj.OV(1).Max = 10;

nlobj.OV(2).Min = 1;

nlobj.OV(2).Max = 10;

nlobj.OV(3).Min = 1;

nlobj.OV(3).Max = 10;

nlobj.MV(1).Min = 1;

nlobj.MV(1).Max = 10;

nlobj.MV(2).Min = 1;

nlobj.MV(2).Max = 10;

nlobj.MV(3).Min = 1;

nlobj.MV(3).Max = 10;

nlobj.MV(4).Min = 1;

nlobj.MV(4).Max = 10;

nlobj.MV(5).Min = 1;

nlobj.MV(5).Max = 10;

%assigning values to mpc model

nlobj.Model.StateFcn = "sys";

nlobj.Model.IsContinuousTime = true;

nlobj.Model.NumberOfParameters = 6;

nlobj.Model.OutputFcn = @(x,u,Ts) [y(1) ;y(2) ;y(3)];

%initial state

x0=[0.1,0.2,-pi/2];

% Set the parameter values

mass = 1700;

lf = 1.5;

lr = 1.5;

car = 404;

caf = 404;

air = 0.5;

%createParameterBus(nlobj, 'myBusObject',Parameters

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Answer 1

Emmanouil Tzorakoleftherakis 2023-5-1

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1954549-using-nlmpc-on-vehicle-dynamics#answer_1226644

The error seems to be in your bus definition. You don't provide that so take a closer look and see if you set things properly. Also, since you are using parameters in your NMPC design, make sure that you provide the same parameters as input arguments to your model functions, cost function, constraint functions, and Jacobians. See example below for more details:

https://www.mathworks.com/help/mpc/ug/swing-up-control-of-a-pendulum-using-nonlinear-model-predictive-control.html#d124e30259