MATLAB: Error: Array indices must be positive integers or logical values.

array indicieserrorlogical valuesMATLABpostive integers

I have looked at past threads and cannot find the issue of my problem. The error is in the last line with description "Array indices must be positive integers or logical values"

q=10; % W/m^3

km=100; %W/Km

kw=500; %W/Km

R1=1;

R2=1.2;

N=5;

Tr=300;

dr=R1/(N+1);

M=zeros(N+N,N+N);

M(N+1,N+1)=-km/((N+1)*dr^2)-kw((N+1)*dr^2);

Best Answer

the expression

kw((N+1)*dr^2)

is the problem. I suspect a missing * or / - for example:

kw*((N+1)*dr^2)

Related Solutions

MATLAB: Iteration output won’t show in a plot

Try this:

format long;
disp('Number of Iterations            Approximate Value')
xData=1;
n=1;
fprintf('\n%d                                  %.12f. \n\n',1,xData)
for n=2:5
    x=0.5*(xData(n-1)+2/xData(n-1));
    xData(n)=x;
    fprintf('\n%d                                  %.12f. \n\n',n,xData)
end
figure
plot(1:1:5,xData)

MATLAB: I need to find the displacement and velocity characteristics of a suspended mass on a boat. I am struggling to develop a state space expression that can take a sinusoidal input, and then to plot graphs of displacement and velocity from this.

You need to define your outputs(with C matrix) correctly. Since you would like to see both displacement and velocity, then C matrix has to be

C=[1 0;0 1];

Also, to simulate the system under a sine input, you need to use lsim command:

lsim(sys,x,t);

The overall code:

clear
t=0:0.1:10;                                          %time peroid
Y0= input('wave amplitude ') ;                        %Wave amplitude
l= input('length of wave ') ;                        %length of the wave
u=10;                                                %Boat Velocity
w=u/l;                                               %frequency of wave
y=Y0*sin(w*t);                                        %wave height model
Dr= input('damping ratio ');                         %Required Damping Ratio
if (Dr<0 || Dr>=1)                                   % test for acceptable damping ratio.
error('Damping ratio not in acceptable range!')
end
k=17000;                                             %Spring Constant of suspension
m=100;
wn=(k/m)^0.5;
wd=wn*(1-Dr^2)^0.5;
if (wd<6)
    error('Suspension excessively soft')            %test  for suspension softness
end
r=w/wn;                                             %Frequency ratio 
b=2*Dr*(k*m)^(0.5);                                 %Damping coefficient
i=(1-r^2)^2+(2*Dr*r)^2;                             
X0=(r^2)*Y0/(i^0.5);                                %Maximum amplitude of displacement
T=atan((2*Dr*r)/(1-r^2));                           %Spatial Frequency
x=X0*sin(w*t-T);                                    %Displacement of sprung mass
A = [0 1; -k/m -b/m];                            %state space matrices
B = [0 1/m]';
C = [1 0;0 1];                                       %I have put y into the input matrix as that is the wave input  
D = [0];
sys=ss(A,B,C,D);
lsim(sys,x,t)

Best Answer

Related Solutions

MATLAB: Iteration output won’t show in a plot

MATLAB: I need to find the displacement and velocity characteristics of a suspended mass on a boat. I am struggling to develop a state space expression that can take a sinusoidal input, and then to plot graphs of displacement and velocity from this.

Related Question