solving differential riccati equation with a boundary condition

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Ifunanya
Ifunanya am 18 Aug. 2014
Kommentiert: Mingze Yin am 3 Dez. 2021
i would like to solve a riccati differential equation using matlab
  1 Kommentar
Esmail Alandoli
Esmail Alandoli am 3 Nov. 2016
see this link. it might be helpful for you https://www.mathworks.com/help/control/ref/care.html

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Aykut Satici
Aykut Satici am 18 Aug. 2014
Bearbeitet: Walter Roberson am 7 Nov. 2016
Since the Riccati equation is a first-order ordinary differential equation, you can do this easily with any of the ODE solvers available in MATLAB such as "ode45", see
http://www.mathworks.com/help/matlab/ref/ode45.html
The trick is to find the solution backwards in time.
As an example, let us consider the following example. Let the Riccati equation be given by
y'(t) = q0 + q1*y(t) + q2*y(t)^2,
y(tf) = yf
where q0, q2 are non-vanishing constants (these may be nontrivial functions of t, the fact that they are chosen to be constant is just for simplicity). The second line is the boundary condition that at the end time tf, the value of the solution must be yf. I have chosen, in particular, tf = 2 and yf = 1 in the example code below.
function riccatiEquationRunner()
par = [1;2;1]; % q0, q1, and q2
yf = 1;
ti = 0; tf = 2;
opt = odeset('AbsTol',1.0e-07,'RelTol',1.0e-07);
[t,y] = ode45( @riccatiEquation, [tf,ti], yf ,opt, par);
% Visualize
plot(t,y)
end
function dydx = riccatiEquation(x,y,parameters)
q0 = parameters(1);
q1 = parameters(2);
q2 = parameters(3);
dydx = q0 + q1*y + q2*y*y;
end
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jalal khodaparast
jalal khodaparast am 23 Okt. 2019
I apply ode45 to the complex differential riccati equation (solution is complex value) but I get unstable fluctuations in the results? Do you know how to solve this problem?
Mingze Yin
Mingze Yin am 3 Dez. 2021
Thanks so much for this. However, could you help me on how to write a code for solving a Riccati differential equation of the same form as u suggested, only when q1 and q2 are some function of t (instead of being fixed constants)?
so maybe for example:
y'(t) = q0 + q1*y(t) + q2*y(t)^2;
y(tf) = yf;
where q1 = t, q2 = t^2;
Thanks so much!

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Esmail Alandoli
Esmail Alandoli am 7 Nov. 2016
Bearbeitet: Walter Roberson am 7 Nov. 2016
Hi,
May you guys help me if you can please?
I have problem with the system below for solving the riccati equation for Y infinity. I always get the error of "Unable to solve the specified Riccati equation because the Hamiltonian spectrum is too close to the imaginary axis."
g = 40000;
A = [0 0 1 0; 0 0 0 1; 0 673.07 -35.1667 0; 0 -1023.07 35.1667 0];
B = [0; 0; 61.7325; -61.7325]';
B1 =[0 0 0 0]';
B2 = B;
C1 = [0 0 0 0]';
C2 = [1 1 0 0]';
C = [C1 , C2]
m1 = size(C1,2)
m2 = size(C2,2)
R = [-g^2*eye(m1) zeros(m1,m2) ; zeros(m2,m1) eye(m2)]
Y = care(A,C,B'*B,R)
can you please help?
Thank you so much
Esmail

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