Write code and driver MR damper

@function function ret= MR(t,y)

ret=zeros(4,1);

alva=y(1);

c1=y(2);

co=y(3);

u=y(4);

coa=784; cob=1803;

c1a=14649; c1b=34622;

alvaa=12441; alvab=38430;

eff=190;

ret(1) = alvaa+alvab*u;

ret(2) = c1a+c1b*u;

ret(3) = coa+cob*u;

ret(4) = -eff*(u-v);

end

@driverclear all

clc

tRange = [-750,750];

yZero = [0,0.2,2];

[myT, myY]=ode45(@MR,tRange,yZero);

a = myY(:,1);

b = myY(:,2);

c = myY(:,3);

d = myY(:,4);

figure(1)

plot(myT,myY);

xlabel('time(s)');

ylabel('Force(N)');

z1=a.*d;

z2=b.*d;

z3=c.*d;

And here is the error message I get :

Attempted to access y(4); index out of bounds because numel(y)=3.

Error in MR (line 6)

u=y(4);

Error in odearguments (line 87)

f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Error in ode45 (line 113)

[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...

Error in driveMR (line 7)

[myT, myY]=ode45(@MR,tRange,yZero);

Answer 1

[Sam Chak]

Hi @kerollos

The code can run now. However, you have to review the initial values and define for v.

The system looks unstable. Is the instability part of the intended design?

tRange = [-750, 750]; 
yZero  = [0, 0.2, 2, 0];    % <-- there are 4 states, so there must be 4 initial values
[myT, myY] = ode45(@MR, tRange, yZero); 
a = myY(:,1);
b = myY(:,2);
c = myY(:,3);
d = myY(:,4);

figure(1)
plot(myT, myY), grid on
xlabel('time(s)');
ylabel('Force(N)');

function ret = MR(t, y)
    ret    = zeros(4,1);
    alva   = y(1);
    c1     = y(2);
    co     = y(3);
    u      = y(4);
    coa    = 784; 
    cob    = 1803;
    c1a    = 14649; 
    c1b    = 34622; 
    alvaa  = 12441; 
    alvab  = 38430; 
    eff    = 190; 
    v      = 0;         % <-- you need to define for v
    ret(1) = alvaa + alvab*u;
    ret(2) = c1a + c1b*u;
    ret(3) = coa + cob*u;
    ret(4) = - eff*(u - v);
end