A(I) = B error.
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This is what the error says "In an assignment A(I) = B, the number of elements in B and I must be the same.
Error in KF (line 6)
Xhat(i) =zeros(3,1);
How do I solve this.
A = [0.7474 0.453 0.0735; -0.441 -0.06106 0.01205; -0.0723 -0.5735 -0.1334];
B = [0.0421 0.0735 0.01205]';
C = [20 9 1];
U = 0; H = 1;
z = -0.37727 + 0.1*randn(50,1)
Xhat(i) =zeros(3,1);
P = eye(3,3);
Q = 0.00001
R = 0.01
for(i=2:50)
X_(i) = A*Xhat(i-1) + B*U;
P = A*P*A' + Q;
K = P*H'*inv(H*P*H' + Q)
Xhat(i) = X_(i) + K*(z(i)-H*X_(i));
P = (eye(1,1)-K*H)*P;
end
figure
plot([1:50],z,'rs')
hold on
plot([1:50], -0.37727*ones(1,50),'k')
plot([1:50], Xhat,'g')
采纳的回答
Star Strider
2015-4-19
That’s actually fairly straightforward. You’re assigning a (3x1) vector vector of zeros to a scaler Xhat(i). That won’t work. Either:
Xhat(i) = 0; % Scalar Assignment
or:
Xhat(i,:) = zeroes(3,1); % Vector Assignment
You later refer to a subscripted ‘Xhat’. so the second version is likely what you want.
4 个评论
PVR
2015-4-19
Star Strider
2015-4-19
Your current error is similar to your previous one. Since ‘B’ is a (1x3) vector as well, see if changing it to:
X_(i,:) = A*Xhat(i-1,:) + B*U;
... CODE ...
Xhat(i,:) = X_(i,:) + K*(z(i)-H*X_(i));
helps. (I think that’s all of them. Your ‘A’ matrix seems to be commented-out.)
PVR
2015-4-19
Star Strider
2015-4-20
It took me a few minutes to figure out that Xhat(:,i-1) is the correct way to reference it even though Xhat(i-1) is a column vector. (I’ve been working with MATLAB since 1994 when I was introduced to it in a modern control course and never encountered this problem before.) However, I usually use the form: y=(C*expm(A*t)*B+D)*U. It’s easier.
This works:
A = [0.7474 0.453 0.0735; -0.441 -0.06106 0.01205; -0.0723 -0.5735 -0.1334];
B = diag([0.0421 0.0735 0.01205]');
C = [20 9 1];
U = zeros(3,1);
H = 1;
z = -0.37727 + 0.1*randn(50,1);
Xhat(:,1) =zeros(3,1);
P = eye(3,3);
Q = 0.00001;
R = 0.01;
for(i=2:50)
Q2 = B*U;
Q1 = A*Xhat(:,i-1);
X_(:,i) = A*Xhat(:,i-1) + B*U;
P = A*P*A' + Q;
K = P*H'/(H*P*H' + Q);
Xhat(:,i) = X_(:,i) + K*(z(i)-H*X_(:,i));
P = (eye(1,1)-K*H)*P;
end
figure
plot([1:50],z,'rs')
hold on
plot([1:50], -0.37727*ones(1,50),'k')
plot([1:50], Xhat,'g')
hold off
You may have to experiment with it to get the result you want. All I know is that it runs successfully.
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