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Problem with a function

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Paul Rogers
Paul Rogers on 21 Oct 2020
Commented: Paul Rogers on 24 Oct 2020
Hello everyone, I wrote this function:
function dz = nocontrol(v,z,parameters)
gammaT=??????????;
phi_0 =0.6;
psi_0 =0.6857;
psi_c0 = 0.3;
B=1.8;
Lc = 3; %m
W = 0.25;
H = 0.18;
C = 0;
dz = zeros(2,1);
dz(1)=(1/(4*B*B*Lc))*(z(2)-gammaT*(z(1))^0.5);
psi_c=psi_c0+H*(1+1.5*(z(2)/W-1)-0.5*(z(2)/W-1).^3);
dz(2) =(1/Lc)*(psi_c-z(1));
end
my problem is that I don't know how to write properly gammaT. I'd like to express it as a function, something like this:
gammaT_max = 0.8;
gammaT_min = 0.7;
A = (gammaT_max - gammaT_min)/2; %amplitude
b = gammaT_max - ((gammaT_max - gammaT_min)/2);
gammaT = A*sin(w*t)+b
but I don't know how.
  2 Comments
madhan ravi
madhan ravi on 21 Oct 2020
what's your question? Are you asking if the way you defined the gamma function is correct?
Paul Rogers
Paul Rogers on 21 Oct 2020
Edited: Paul Rogers on 21 Oct 2020
I'd like to define gammaT as a function of the time, but I don't knwo how.

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Accepted Answer

Walter Roberson
Walter Roberson on 21 Oct 2020
You have defined gammaT as a variable that you multiply by, but it needs to be a function of time. You will likely need something like
gammaT = @(t) A*sin(w*t)+b
dz(1)=(1/(4*B*B*Lc))*(z(2)-gammaT(SOMETHING)*(z(1))^0.5);
The SOMETHING would have to be replaced with your time variable, but it is not obvious that you have a time variable. Perhaps v is your time variable.
  3 Comments
Walter Roberson
Walter Roberson on 22 Oct 2020
You do not have a time variable, so I had to substitute the closest I could find.
function dz = nocontrol(v,z,parameters)
gammaT=parameters(1);
phi_0=parameters(2);
psi_0=parameters(3);
psi_c0=parameters(4);
B=parameters(5);
Lc=parameters(6);
W=parameters(7);
H=parameters(8);
C = 0;
gammaT_max = 0.8;
gammaT_min = 0.7;
A = (gammaT_max - gammaT_min)/2; %amplitude
b = gammaT_max - ((gammaT_max - gammaT_min)/2);
gammaT = @(t) A*sin(W*t)+b
dz = zeros(2,1);
dz(1)=(1/(4*B*B*Lc))*(z(2)-gammaT(v)*(z(1))^0.5);
psi_c=psi_c0+H*(1+1.5*(z(2)/W-1)-0.5*(z(2)/W-1).^3);
dz(2) =(1/Lc)*(psi_c-z(1));
end
Paul Rogers
Paul Rogers on 24 Oct 2020
thanks a lot, you really solved me something I couldn't figured out.
just the argument in the sin was't W but another variable w in radians.
It woorks now

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