why does ode45 happen this index error?
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I've been struggling with this program for a long time.
Is this ode45 being used incorrectly?
global d;
d=1;
tspan=[0;0.05];
xi=[1;2;pi];
vk=[3;5];
func=@(xi,vk) TwoWheel2(xi,vk);
[t,y]=ode45(func,tspan,0);
function dxi = TwoWheel2(xi,vk)
v1=speed(vk);
wk=toRadian(vk);
dxi = zeros(3,1);
dxi(1) = cos(xi(3)) * v1;
dxi(2) = sin(xi(3)) * v1;
dxi(3) = wk;
end
function u0=toRadian(vk)
global d;
vr=vk(1);
vl=vk(2);
u0=(vr-vl)/(2*d);
end
function v1=speed(vk)
vr=vk(1);
vl=vk(2);
v1=(vr+vl)/2;
end
>> testode
The index exceeds the number of array elements (1).
error: testode>speed (line 22)
vl=vk(2);
error: testode>TwoWheel2 (line 7)
v1=speed(vk);
error: testode>@(xi,vk)TwoWheel2(xi,vk) (line 4)
func=@(xi,vk) TwoWheel2(xi,vk);
error: odearguments (line 90)
f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.
error: ode45 (line 115)
odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);
error: testode (line 5)
[t,y]=ode45(func,tspan,0);
采纳的回答
Alan Stevens
2020-9-19
See the following:
global d;
d=1;
tspan=[0;0.05];
xi=[1;2;pi];
vk=[3;5];
[t,y]=ode45(@TwoWheel2,tspan,xi,[],vk);
function dxi = TwoWheel2(~,xi,vk)
v1=speed(vk);
wk=toRadian(vk);
dxi = zeros(3,1);
dxi(1) = cos(xi(3)) * v1;
dxi(2) = sin(xi(3)) * v1;
dxi(3) = wk;
end
function u0=toRadian(vk)
global d;
vr=vk(1);
vl=vk(2);
u0=(vr-vl)/(2*d);
end
function v1=speed(vk)
vr=vk(1);
vl=vk(2);
v1=(vr+vl)/2;
end
5 个评论
Tsubasa Mano
2020-9-19
Alan Stevens
2020-9-19
You were calling the function with a single initial value of zero. Ode45 needed to call it with the same size vector as is returned (one with three elements here).
Tsubasa Mano
2020-9-19
Alan Stevens
2020-9-19
编辑：Alan Stevens
2020-9-19
- Yes, [] is a placeholder for options.
- You would often have t, the time value there (more generally, the name of the independent variable); but, in your case, t is not used explicitly within TwoWheel2, so MATLAB suggests replacing it by ~. If it did make explicit use of the value of t, then ~ would need to be replaced by t. The ~ isn't essential; the routine would still work if you did replace it with t.
Tsubasa Mano
2020-9-19
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