Need help with and if else statement to be entered into a state space set up

clc
clear

Mb = 1200; %kg
Mt = 15;   %kg
ks = 30000; %N/m
kt = 100000; %N/m
Cs = 3000; %N*s/m
b = 2;    %m
c = 0.3;  %m
d = 1.5;  %m
e = 1;    %m
% Speed bump is half a sine wave

v1 = 5;  %m/s
v2 = 10;  %m/s
v3 = 20;  %m/s
v4 = 30;  %m/s

t = [0:0.1:4];

if t>=0 && t < (e/v1)
    y = 0;
elseif t>=(e/v1) && t < (e+d)/v1  
    y = (c*sin(((pi*v1)/d)*(t-(e/v1))));
elseif t>=((e+d)/v1) && t < (e+d+b)/v1 
    y = 0;
elseif t>=((e+d)/v1) && t < (e+d+b)/v1 
    y = (c*sin(((pi*v1)/d)*(t-((e+d+b)/v1))));
end

A = [0 0 1 0; 0 0 0 1; -((ks+kt)/Mt) ks/Mt -Cs/Mt Cs/Mt; ks/Mb -ks/Mb Cs/Mb -Cs/Mb]
B = [0; 0; (kt/Mt).*y; 0]
C = [1 0 0 0; 0 1 0 0]
D = zeros(1)

sys = ss(A,B,C,D)

Above is my code im working on for a state space problem. in matrice B im multyplying by variable y which is in described in my if statement. Y changes with time and the if statement on wants scalar. Here is the error code:

Operands to the || and && operators must be convertible to logical scalar values

Any help with this would be grateful. also can I do an array for v values or would 4 if statements be easier to do. I need 4 different plots for the 4 different v values.

Answer 1

[Walter Roberson]

You assign a vector to t. You then try to test

if t>=0 && t < (e/v1)

With t being a vector, this is

if logical_vector && logical_vector

however, the && operator can only be used when both sides are scalars.

You could try changing the && to & so that you had

if logical_vector & logical_vector

which would then calculate down to

if logical_vector

but remember that is only considered to be true if all of the elements of the vector are non-zero, same as if you had written

if all(t>=0 & t < (e/v1))

This will be false because some of your t are not < e/v1

It looks to me as if you have a state space model that you want to have act differently depending on the time. That is not possible with typical transfer functions or typical ss . I am not sure if it is possible if you use genmat() inputs to ss() or if you use genss() . genmat() and genss() permit you to use tunable parameters, but at any one point the tunable parameters always have a specific value, not a formula, so I do not think you can make time a component of the tunable matrices.