Problem with a function

Question

Paul Rogers 2020-10-21

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https://ww2.mathworks.cn/matlabcentral/answers/621798-problem-with-a-function

评论： Paul Rogers 2020-10-24

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.

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madhan ravi 2020-10-21

what's your question? Are you asking if the way you defined the gamma function is correct?

Paul Rogers 2020-10-21

编辑：Paul Rogers 2020-10-21

I'd like to define gammaT as a function of the time, but I don't knwo how.

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Answer 1

Walter Roberson 2020-10-21

1
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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.

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Walter Roberson 2020-10-22

在 MATLAB Online 中打开

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