# Error: Not enough input arguments

조회 수: 1 (최근 30일)
Sam Butler 2023년 1월 6일
댓글: Sam Butler 2023년 2월 7일
Hello,
I am using the ode45 function to solve three second order equations (theta_double dot 1, theta_double dot 2 and theta_double dot n) to produce torque deflection characteristics. I have typed this code following a few tutorials on youtube.
Does anyone know why I am getting an error saying 'Not enough input arguments'?
*I am quite new to MATLAB*
Code:
syms J1 J2 Jn c1 c2 cn k1 k2 kn knl q w x(t) y(t) z(t) T Y
% let ddtheta(1)=x, ddtheta(2)=y, ddtheta(n)=z, dtheta_out=q. theta_out=w
Eq1 = diff(x,2) == (-c1*((diff(x)-q) - k1*(x-w) ...
+ c2*(diff(y)-diff(x)) + k2*(y-x) + cn*(diff(z)-diff(x))...
+ kn*(z-x) + knl*(z-x)^5))/J1;
Eq2 = diff(y,2) == ((-c2*(diff(y)-diff(x)))-(k2*(y-x)))/J2;
Eq3 = diff(z,2) == ((-cn*(diff(z)-diff(x)))-(kn*(z-x))-(knl*(z-x)^5))/Jn;
[VF,Sbs] = odeToVectorField(Eq1,Eq2,Eq3);
coupled_vanderpol = matlabFunction(VF, 'Vars',{J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y});
%Parameters
J1 = 2.08e-4;
J2 = 2.931e-3;
Jn = 4.0085e-4;
c1 = 0.15;
c2 = 0.2;
cn = 0.015;
k1 = 270;
k2 = 8500;
kn = 10.89;
knl = 38870;
%Velocity input
tspan = [0,100];
thetadot0 = 800; % mean motor speed (rpm)
q = thetadot0 + theta1dot*cos(36*2*pi*f_mech*tspan) ...
+ theta2dot*cos(2*36*2*pi*f_mech*tspan);
C=0;
w = thetadot0*tspan + (theta1dot*sin(72*pi*f_mech*tspan))/(72*pi*f_mech) ...
+ (theta2dot*sin(144*pi*f_mech*tspan))/(144*pi*f_mech) + C;
%Initial Conditions
%Plot
[t,v_z] = ode45(@(T,Y)coupled_vanderpol({J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y}),tspan,t0);
figure
plot(t, v_z)
grid
Error:
Not enough input arguments.
Error in symengine>@(J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y)[Y(2);-(c2.*(Y(2)-Y(4))+k2.*(Y(1)-Y(3)))./J2;Y(4);(c1.*(q+knl.*(Y(3)-Y(5)).^5-Y(4)-k1.*(w-Y(3))-c2.*(Y(2)-Y(4))+cn.*(Y(4)-Y(6))-k2.*(Y(1)-Y(3))+kn.*(Y(3)-Y(5))))./J1;Y(6);(knl.*(Y(3)-Y(5)).^5+cn.*(Y(4)-Y(6))+kn.*(Y(3)-Y(5)))./Jn]
Error in trial>@(T,Y)coupled_vanderpol({J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y}) (line 41)
[t,v_z] = ode45(@(T,Y)coupled_vanderpol({J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y}),tspan,t0);
Error in odearguments (line 92)
f0 = ode(t0,y0,args{:}); % ODE15I sets args{1} to yp0.
Error in ode45 (line 107)
odearguments(odeIsFuncHandle,odeTreatAsMFile, solver_name, ode, tspan, y0, options, varargin);
Error in trial (line 41)
[t,v_z] = ode45(@(T,Y)coupled_vanderpol({J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y}),tspan,t0);
Thank you!!

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### 답변 (1개)

Bora Eryilmaz 2023년 1월 6일
편집: Bora Eryilmaz 2023년 1월 6일
There are probably other array concatenation issues in your equation definitions, but regarding your current issue, remove the curly braces inside the coupled_vanderpol(...) call:
% Not this
%[t,v_z] = ode45(@(T,Y)coupled_vanderpol({J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y}),tspan,t0);
% But this
%[t,v_z] = ode45(@(T,Y)coupled_vanderpol(J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y),tspan,t0);
See the updated example below:
syms J1 J2 Jn c1 c2 cn k1 k2 kn knl q w x(t) y(t) z(t) T Y
% let ddtheta(1)=x, ddtheta(2)=y, ddtheta(n)=z, dtheta_out=q. theta_out=w
Eq1 = diff(x,2) == (-c1*((diff(x)-q) - k1*(x-w) ...
+ c2*(diff(y)-diff(x)) + k2*(y-x) + cn*(diff(z)-diff(x))...
+ kn*(z-x) + knl*(z-x)^5))/J1;
Eq2 = diff(y,2) == ((-c2*(diff(y)-diff(x)))-(k2*(y-x)))/J2;
Eq3 = diff(z,2) == ((-cn*(diff(z)-diff(x)))-(kn*(z-x))-(knl*(z-x)^5))/Jn;
[VF,Sbs] = odeToVectorField(Eq1,Eq2,Eq3);
coupled_vanderpol = matlabFunction(VF, 'Vars',{J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y});
%Parameters
J1 = 2.08e-4;
J2 = 2.931e-3;
Jn = 4.0085e-4;
c1 = 0.15;
c2 = 0.2;
cn = 0.015;
k1 = 270;
k2 = 8500;
kn = 10.89;
knl = 38870;
% Similar to what ode45 is doing
T = 0;
Y = 1:6;
% Not this:
% coupled_vanderpol({J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y})
% But this
coupled_vanderpol(J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y)
ans =
ode45 is probably calling the function with a Y vector that has a different size than 6, which results in array concatenation issues like this:
Y = 1:5;
coupled_vanderpol(J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y)
Index exceeds the number of array elements. Index must not exceed 5.

Error in symengine>@(J1,J2,Jn,c1,c2,cn,k1,k2,kn,knl,q,w,T,Y)[Y(2);-(c2.*(Y(2)-Y(4))+k2.*(Y(1)-Y(3)))./J2;Y(4);(c1.*(q+knl.*(Y(3)-Y(5)).^5-Y(4)-k1.*(w-Y(3))-c2.*(Y(2)-Y(4))+cn.*(Y(4)-Y(6))-k2.*(Y(1)-Y(3))+kn.*(Y(3)-Y(5))))./J1;Y(6);(knl.*(Y(3)-Y(5)).^5+cn.*(Y(4)-Y(6))+kn.*(Y(3)-Y(5)))./Jn]
I believe ode45 can call the function for Y values corresponding to multiple time points, in which case your code needs to be able to handle a matrix of Y values, which would have 6 columns and as many rows as the time points.
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Bora Eryilmaz 2023년 1월 6일
You will have to figure out how to structure the equations' output yourself.
For ode45, if you have three equations and three variables, you need to return a Y matrix with 3 columns and as many rows as in T that was passed in by ode45.
You also don't need to use symbolic math here. Just create a regular MATLAB function to encode your differential equations. Also, please read the examples more carefully: https://www.mathworks.com/help/matlab/ref/ode45.html#bu00_4l_sep_shared-odefun
Sam Butler 2023년 2월 7일
I have spent more time trying to do this however I have not made a great deal of progress. Would it be possible to speak further with you about this? possibly over a call.

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