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Error coming as Not enough input arguments

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Arjun Gupta
Arjun Gupta 2022-7-3
评论： Arjun Gupta 2022-7-3
function dx = invpen(t,x)
M = 3;
m = 0.4;
I = 1.5;
g = 9.8;
b = 1;
U = 0;
dx=zeros(4,1);
dx(1)=x(2);
dx(2)=((-g*m*sin(x(3))*cos(x(3))) + (m*l*(x(4))^2*sin(x(3))) + (m*b*x(4)*cos(x(3))) + U)/(M+(1-(cos(x(3))*cos(x(3))))*m);
dx(3)=x(4);
dx(4)=(((M+m)*((b*x(4))-(g*sin(x(3))))) + (m*l*(x(4))^2^sin(x(3))+cos(x(3)))+ (U*cos(x(3))))/(l*((m*cos(x(3))*cos(x(3)))-M-m));
end
  2 个评论
Karan Kannoujiya
Karan Kannoujiya 2022-7-3
Hi Arjun,
Could you please send how you calling the function and the value of x and t you are passing in function.
Arjun Gupta
Arjun Gupta 2022-7-3
clc
clear all
close all
L = 1.5;
t = 0:0.01:10;
x0 = [0.5 0 pi/2 0];
[t x]=ode45('invpend',t,x0);
figure
subplot(2,2,1)
plot(t,x(:,1))
xlabel('Time(sec)'), ylabel('m')
title('x')
subplot(2,2,2)
plot(t,x(:,2))
xlabel('Time(sec)'), ylabel('m/s')
title('x^{.}')
subplot(2,2,3)
plot(t,x(:,3))
xlabel('Time(sec)'), ylabel('rad')
title('\theta')
subplot(2,2,4)
plot(t,x(:,4))
xlabel('Time(sec)'), ylabel('rad/sec')
title('\theta^{.}')
X0 = 0;
Y0 = 0;
for i = 1:length(t)
Xc = x(i,1);
Xp = x(i,1) + L * sin(pi - x(i,3));
Yp = L * cos(pi - x(i,3));
figure(2)
plot([-3 5], [0 0], 'linewidth', 6, 'color', 'g');
axis([-4 6 -4 4]);
line([Xc Xp], [Y0, Yp], 'linewidth', 2, 'color', 'b');
hold on
plot(Xc, Y0, 's', 'markersize', 30, 'markerfacecolor', 'y');
plot(Xp, Yp, 'o', 'markersize', 15, 'markerfacecolor', 'r');
hold off
end

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回答（1 个）

Raghav
Raghav 2022-7-3
编辑：Raghav 2022-7-3
Hi @Arjun Gupta,
There are a few problems in this function.
First input argument 't' is not used anywhere in the function, so you can remove it from input argument list to remove this warning.
Second, the variable 'l' used in the calculation of dx(2) and dx(4)is not defined, also the variable 'ɪ' you defined is not used anywhere in the function, so I guess in the original formula, there was 'ɪ' instead of 'l' like:
dx(2)=((-g*m*sin(x(3))*cos(x(3))) + (m*I*(x(4))^2*sin(x(3))) + (m*b*x(4)*cos(x(3))) + U)/(M+(1-(cos(x(3))*cos(x(3))))*m);
and
dx(4)=(((M+m)*((b*x(4))-(g*sin(x(3))))) + (m*I*(x(4))^2^sin(x(3))+cos(x(3)))+ (U*cos(x(3))))/(I*((m*cos(x(3))*cos(x(3)))-M-m));
If you still face the error- "Not enough input arguments", call the function "invpen" with proper x, x should be an array of size atleast 4.

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