im modelling for two mass drive train , i could not able to know why an index exceed error

function dy= two_mass2(ta,te,k,d,jt,jg,y)

x=y(1);

y=y(2);

dxdt=y(3);

dydt=y(4);

d2xdt2=((1./jt)*(ta-d*(dxdt-d*dydt)-k*(x-y)));

d2ydt2=((1./jg)*(-te-d*(dydt-d*dxdt)-k*(y-x)));

dy=[dxdt;dydt;d2xdt2;d2ydt2];

end

clc

clear all

close all

ta=11198;

te=11937;

jt=995.8;

jg=81.2;

d=30.3;

k=19720;

tspan=[0 5000];

y0=[ 125;125;100;100];

[Tsol,Ysol]= ode45(@(t,y)two_mass2(ta,te,d,k,jt,jg,y),tspan,y0);

plot(Tsol,Ysol(:,1))

Answer 1

[KSSV]

function dy= two_mass2(ta,te,k,d,jt,jg,y)
x=y(1);
y=y(2);
dxdt=y(3);
dydt=y(4);
d2xdt2=((1./jt)*(ta-d*(dxdt-d*dydt)-k*(x-y)));
d2ydt2=((1./jg)*(-te-d*(dydt-d*dxdt)-k*(y-x)));
dy=[dxdt;dydt;d2xdt2;d2ydt2];
end

In the above function your input y to the function is 4*1 and in this line:

y=y(2);

you are overwrititng y. Change the variable y at input to some other variable.

Like shown below:

ta=11198;
te=11937;
jt=995.8;
jg=81.2;
d=30.3;
k=19720;
tspan=[0 5000];
y0=[ 125;125;100;100];
[Tsol,Ysol]= ode45(@(t,y)two_mass2(ta,te,d,k,jt,jg,y),tspan,y0);
plot(Tsol,Ysol(:,1))


function dy= two_mass2(ta,te,k,d,jt,jg,Y)  %<----- y changed to Y 
x=Y(1);
y=Y(2);
dxdt=Y(3);
dydt=Y(4);
d2xdt2=((1./jt)*(ta-d*(dxdt-d*dydt)-k*(x-y)));
d2ydt2=((1./jg)*(-te-d*(dydt-d*dxdt)-k*(y-x)));
dy=[dxdt;dydt;d2xdt2;d2ydt2];
end