# Inner matrix dimensions must agree. error

조회 수: 1 (최근 30일)
Khoa . 2012년 12월 4일
Hi everybody. I'm very news in matlab. I try to design kalman filter but the error occurred 'Inner matrix dimensions must agree' in matlab function
function [ x, P] = kalman( z, Q, R, x_old, P_old, A, H)
I = eye(3);
% Measurement update
K = (P_old * H') / (H*P_old*H'+R);
x = x_old + K * (z - H*x_old);
P = (I-K*H)*P_old;
% Time update
x = A * x ;
P = A * P * A' + B*Q*B';
Maybe initial estimates of P_old and x_old is not set I think. How to set that value? I want to set the first value for x and P are [0 ; 0 ;0 ] and [0.1 0 0; 0 0.1 0; 0 0 0.1] but dont know how to do.
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Walter Roberson 2012년 12월 4일
Please go in with the debugger, with dbstop if error, run until the problem occurs, and then try the subexpressions to see which part is generating the error
(P_old * H')
(H*P_old*H'+R)
and then if neither of those, finally
(P_old * H') / (H*P_old*H'+R)
With the array sizes you report, I do not reproduce the error.
I have to wonder about possibilities such as on the first iteration, something might be empty or an unexpected size.

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### 채택된 답변

Azzi Abdelmalek 2012년 12월 4일
편집: Azzi Abdelmalek 님. 2012년 12월 4일
As you said in your question, in your delay block you must set initials conditions to x0 and P0, where x0=zeros(n,1); n is your system order, and P0=0.1*eye(n). in your case n=3
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Azzi Abdelmalek 2012년 12월 6일
편집: Azzi Abdelmalek 님. 2012년 12월 6일
What is B in your code?, it should be H.
Corrected function
function [ x, P] = kalman( z, Q, R, x_old, P_old, A, H)
I = eye(3);
% Measurement update
K = P_old * H'/(H*P_old*H'+R);
x = x_old + K * (z - H*x_old);
P = (I-K*H)*P_old;
% Time update
x = A * x;
P = A * P * A' + H*Q*H';
Also, In the constant block H uncheck Interpret Vector as 1-D

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### 추가 답변 (1개)

Khoa 2012년 12월 24일
편집: Khoa 님. 2012년 12월 24일
Sorry for reply late. I followed you and it worked correctly. But the output of kalman filter is not correct. My input of kalman filter is measurement position and I want to output position, velocity and acceleration. You can see it from scope1 and scope2(position input and velocity). I dont know how to fix kalman output. In other hand, My kalman block show bad result for output velocity and acceleration (scope5,6). I post my simulink below: http://www.mediafire.com/?l4mfgcupgmge4ij http://www.mediafire.com/?laa26ib5bgsco88

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