Ode45 extra parameters

I would like to solve some equations with ode45.

The function is this:

function [ y_punto ] = bicicletta(t,y,a,b,u,delta,Ca,Cp,Iz,Fd)

v = y(1);
r = y(2);

alfaa = atan((v+a*r)/u)-delta;
alfap = atan((v-b*r)/u);

Fya = -Ca*alfaa;
Fyp = -Cp*alfap;

if (t>=tdon && t<=tdoff)
    Fyad=Fd;
else
    Fyad=0;
end

v_punto = 1/m*(Fya*cos(delta)+Fyp+Fyad)-ru;
r_punto = 1/Iz*(Fya*cos(delta)*a+Fyad*a-Fyp*b);

y_punto = [v_punto;r_punto];
end

Here is the script for starting simulation

clc
clear

a = 0.78;
b = 0.83;
Ca = 27537.5;
Cp = 27537.5;
Iz = 408.9;
u = 15*1000/3600;

delta = 5 * pi/180;
Fd = 100;

tf=5;
tspan = [0 tf];
y0 = [0;0];

[t,y] = ode45(bicicletta,tspan,y0);

The fact is that I need to pass extra parameters to the function. I don't know if I can define the function in this way

function [ y_punto ] = bicicletta(y)

and pass other parameters in another way for example declaring as global.

I did some search and I found this way of using ode45 but it gives me error

[t,y] = ode45(@(t,y)bicicletta(t,y,a,b,u,delta,Ca,Cp,Iz),tspan,y0);

[Stephen23]

Your last line of code, where you create an anonymous function:

 ode45(@(t,y)bicicletta(t,y,a,b,u,delta,Ca,Cp,Iz),tspan,y0);

is the correct approach to passing extra arguments. Please show us the complete error message (this means all of the red text).

Do not use globals: this is a slow and buggy way to write code.

[Stephen23]

SilverSurfer's "Answer" moved here:

Here his the error

    Error in odearguments (line 87)
    f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.

    Error in ode45 (line 115)
        odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

    Error in simulazione (line 18)
    [t,y] = ode45(@(t,y)bicicletta(t,y,a,b,u,delta,Ca,Cp,Iz),tspan,y0);

I attached also the scripts

Answer 1

[Star Strider]

You have to define ‘tdon’ and ‘tdoff’ in your ‘bicicletta’ ODE function. I have no idea what you want to do, so I cannot correct that for you.

[SilverSurfer]

Thanks, I didn't put them, anyway I still have the error. I attached the scripts.

[Star Strider]

The error your function call threw listed this line as being the problem:

[t,y] = ode45(@(t,y)bicicletta(t,y,a,b,u,delta,Ca,Cp,Iz),tspan,y0);

but the function you defined has one more argument, ‘Fd’:

function [ y_punto ] = bicicletta(t,y,a,b,u,delta,Ca,Cp,Iz,Fd)

You have to supply all them to your function.

[SilverSurfer]

I fixed the code. Now I supplied all the parameters used by the function. I'm still getting the error

Error in odearguments (line 87)
f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.

    Error in ode45 (line 115)
        odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);
    Error in simulazione (line 20)
    [t,y] = ode45(@(t,y)bicicletta(t,y,a,b,u,delta,Ca,Cp,Iz,Fd,tdon,tdoff),tspan,y0);

Here his the content of the latest script

a = 0.78;
b = 0.83;
Ca = 27537.5;
Cp = 27537.5;
Iz = 408.9;
u = 15*1000/3600;

delta = 5 * pi/180;
Fd = 100;

tdon=1;
tdoff=2;
tf=5;
tspan = [0 tf];
y0 = [0;0];

[t,y] = ode45(@(t,y)bicicletta(t,y,a,b,u,delta,Ca,Cp,Iz,Fd,tdon,tdoff),tspan,y0);

and function file.

function [ y_punto ] = bicicletta(t,y,a,b,u,delta,Ca,Cp,Iz,Fd,tdon,tdoff)

v = y(1);
r = y(2);

alfaa = atan((v+a*r)/u)-delta;
alfap = atan((v-b*r)/u);

Fya = -Ca*alfaa;
Fyp = -Cp*alfap;

if (t>=tdon && t<=tdoff)
    Fyad=Fd;
else
    Fyad=0;
end

v_punto = 1/m*(Fya*cos(delta)+Fyp+Fyad)-ru;
r_punto = 1/Iz*(Fya*cos(delta)*a+Fyad*a-Fyp*b);

y_punto = [v_punto;r_punto];
end

[Torsten]

m and ru (maybe you mean r*u ?) in the definition of v_punto are undefined.

Best wishes

Torsten.

[SilverSurfer]

Thanks. I seems my code is full of little errors.

I missed also m in the script.

Now it runs.

[Star Strider]

‘Now it runs.’

Congratulations!