Index in position 1 is invalid. Array indices must be positive integers or logical values. My Events
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I am currently working on an inverted pendulum problem. I have used the My event funtion to stop the penduum action at 45degree (please see code and function below). The highlighted line is causing problems. It is my understanding this is the strating conditions of the pendulum, but if i set to [0,0] it comes up with the above error. The current conditions are not correct but i am unable to change them and run the programme.
function zdot=crash(t,z,g,r,m,k,a)
zdot=zeros(2,1);
zdot(1)=z(2);
zdot(2)=(r^2*z(2)^2-r*a*cos(z(1))-r*g*sin(z(1)))/(k^2-2*r^2);
end
function [value,isterminal,direction] = dashboard(t,z)
minz = (pi/4); %for example
value = z(:,1) < minz;
isterminal = 1; %stops the integration
direction = 0; % The zero can be approached from either direction, -1 decreasing function, +1 increasing fucniton
end
clear;clc
%crash conditions
g=9.81; r=0.4; k=0.5; m=40; a=98.1;
tspan1=(0:0.002:5);
z0=[pi/2 0];
z0=[0, (a/r)^0.5]; <<<<<<<<<<<<<<<<<<<<----------------------------------------THIS LINE
Opt = odeset('Events', @dashboard);
[t,z]=ode45(@(t,z)crash(t,z,g,r,k,a,m),tspan1,z0,Opt);
ind = interp1(z(:,1),1:length(z(:,1)),pi/4,'nearest');
V_g=z(ind,2)*r
V_h=z(ind,2)*.75
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Ameer Hamza
2020년 4월 12일
The ode solver does not cause the issue. When z0 = [0 0], the pendulum never reaches the angle of pi/4, and then you run the line
ind = interp1(z(:,1),1:length(z(:,1)),pi/4,'nearest');
and that outputs NaN because pi/4 is not in the range of elements in z(:,1). Then you try to index using NaN value
z(ind,2)*r
and MATLAB's gives an error. You need to consider how to specify the maximum angle (instead of pi/4) for a given initial condition.
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