The code for nmpc is not working even if i put it in same folder ?

nx = 4; %no. of states
ny = 2; %no. of outputs
nu = 2; %no. of inputs
n1 = nlmpc(nx,ny,nu);
n1.Model.StateFcn="statefunctiontank";
n1.Model.OutputFcn="outputtank";
n1.PredictionHorizon=400;
n1.ControlHorizon=50;
Ts = 0.25;
n1.Ts = Ts

n1 = 
  nlmpc with properties:

                      Ts: 0.2500
       PredictionHorizon: 400
          ControlHorizon: 50
              Dimensions: [1×1 struct]
                   Model: [1×1 struct]
                  States: [1×4 struct]
         OutputVariables: [1×2 struct]
    ManipulatedVariables: [1×2 struct]
    MeasuredDisturbances: []
                 Weights: [1×1 struct]
            Optimization: [1×1 struct]
                Jacobian: [1×1 struct]
               Passivity: [1×1 struct]

%setting constraints on states
n1.States(1).Max=40;
n1.States(1).Min=0;
n1.States(2).Max=40;
n1.States(2).Min=0;
n1.States(3).Max=40;
n1.States(3).Min=0;
n1.States(4).Max=40;
n1.States(4).Min=0;
%setting constraints on output
n1.Ov(1).Max=40;
n1.Ov(1).Min=0;
n1.Ov(2).Max=40;
n1.Ov(2).Min=0;
%setting constraints on input
n1.Mv(1).Max=10;
n1.Mv(1).Min=0;
n1.Mv(2).Max=10;
n1.Mv(2).Min=0;

%Validate model fucntion at arbitrary point
x0=[10;15;13;15]

x0 = 4×1

10 15 13 15

u=[5;07]

u = 2×1

5 7

validateFcns(n1,x0,u)

Error using nlmpc/validateFcns
Function statefunctiontank does not exist.

function dxdt= statefunctiontank(x,u)
A1 = 28;
A2 = 32;
A3 = 28;
A4 = 32;
a1 = 0.071;
a2 = 0.057;
a3 = 0.071;
a4 = 0.057;
gamma1 = 0.70;
gamma2 = 0.60;
g = 981;
dxdt(1) = -a1/A1*sqrt(2*g*x(1)) + a3/A1*sqrt(2*g*x(3))+(gamma1/A1)*u(1);
dxdt(2) = -a2/A2*sqrt(2*g*x(2)) + a4/A2*sqrt(2*g*x(4))+(gamma2/A2)*u(2);
dxdt(3) = -a3/A3*sqrt(2*g*x(3)) + ((1-gamma2)/A3)*u(2);
dxdt(4) = -a4/A4*sqrt(2*g*x(4)) + ((1-gamma1)/A4)*u(1);
end
function [y] = outputtank(x)
y=[x(1);x(2)];
end

these functions i was using as different code and called these in above code but i was not able to get what i should do to correct it.

Answer 1

[Emmanouil Tzorakoleftherakis]

I wasn't able to reproduce the error. Both state and output functions must be in different .m files. I did that and put everything on the same folder and did not get the error you are seeing (once you get it to work you will get a different error because you need to transpose the output dimensions of the state function).

[AMAN]

thanks for helping. can you change or give me what is required to be changed.Yeah it's giving me some error and i will update the code here however i am new in this type of coding so can you help me troubleshoot this.

nx = 4; %no. of states
ny = 2; %no. of outputs
nu = 2; %no. of inputs
n1 = nlmpc(nx,ny,nu);
n1.Model.StateFcn="statefunctiontank";
n1.Model.OutputFcn="outputtank";
n1.PredictionHorizon=400;
n1.ControlHorizon=50;
Ts = 0.25;
n1.Ts = Ts
%setting constraints on states
n1.States(1).Max=40;
n1.States(1).Min=0;
n1.States(2).Max=40;
n1.States(2).Min=0;
n1.States(3).Max=40;
n1.States(3).Min=0;
n1.States(4).Max=40;
n1.States(4).Min=0;
%setting constraints on output
n1.Ov(1).Max=40;
n1.Ov(1).Min=0;
n1.Ov(2).Max=40;
n1.Ov(2).Min=0;
%setting constraints on input
n1.Mv(1).Max=10;
n1.Mv(1).Min=0;
n1.Mv(2).Max=10;
n1.Mv(2).Min=0;



%Validate model fucntion at arbitrary point
x0=[10 15 20 25]
u=[5;07]
validateFcns(n1,x0,u)

function dxdt= statefunctiontank(x,u)
A1 = 28;
A2 = 32;
A3 = 28;
A4 = 32;
a1 = 0.071;
a2 = 0.057;
a3 = 0.071;
a4 = 0.057;
gamma1 = 0.70;
gamma2 = 0.60;
g = 981;
dxdt(1) = -a1/A1*sqrt(2*g*x(1)) + a3/A1*sqrt(2*g*x(3))+(gamma1/A1)*u(1);
dxdt(2) = -a2/A2*sqrt(2*g*x(2)) + a4/A2*sqrt(2*g*x(4))+(gamma2/A2)*u(2);
dxdt(3) = -a3/A3*sqrt(2*g*x(3)) + ((1-gamma2)/A3)*u(2);
dxdt(4) = -a4/A4*sqrt(2*g*x(4)) + ((1-gamma1)/A4)*u(1);
end
function [y] = outputtank(x)
y=[x(1);x(2)];
end

[Emmanouil Tzorakoleftherakis]

You mean for the error I mentioned with the dimensions of the state function output? Just transpose dxdt

dxdt=dxdt';

[AMAN]

it worked but now giving error in Output function how i should troubleshoot this

[Emmanouil Tzorakoleftherakis]

The error looks self-explanatory - take a look at the definition of the output function and make sure it's consistent with what the nlmpc object requires. Looks like there should be one more argument in there. This page provides more information on how to define state and output functions:

https://www.mathworks.com/help/mpc/ug/specify-prediction-model-for-nonlinear-mpc.html

[AMAN]

I Got it now thank you for your help very much sir.