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数学中国总编辑
TA的每日心情 | 衰 2016-11-18 10:46 |
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签到天数: 206 天 [LV.7]常住居民III 超级版主
群组: 2011年第一期数学建模 群组: 第一期sas基础实训课堂 群组: 第二届数模基础实训 群组: 2012第二期MCM/ICM优秀 群组: MCM优秀论文解析专题 |
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发表于 2011-11-28 10:48
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matlab下面的kalman滤波程序- `4 x8 w2 U( _# \
clear N=200; w(1)=0; 3 I9 K9 W) H: q# H5 K. r) ~
w=randn(1,N) 1 _& J. i- _- b' o, o
x(1)=0;
& ~9 |: a( `9 _9 \. [" [a=1;
6 _8 O6 d) D* o6 ]for k=2:N; ; ^2 R, E( _4 D* j
x(k)=a*x(k-1)+w(k-1);
0 v* q5 h! s! \0 E$ \end
& i3 N$ m7 b8 Z9 S* {' [V=randn(1,N); 0 \5 @# X, c5 a/ F! Z( N
q1=std(V); 4 Y! l* j* K, J8 a
Rvv=q1.^2; , U* V) a- |# e2 r6 M# R; w
q2=std(x);
: k/ B4 X+ U+ ARxx=q2.^2; " Y/ y2 x8 V V0 L1 ?5 d! B2 a
q3=std(w); " M; s4 K1 i' @% K2 B: v
Rww=q3.^2; : {' d5 {& E0 F- ?( }
c=0.2; % R0 y* \9 U' l4 `5 \
Y=c*x+V;
: q3 U. [; [5 \p(1)=0;
$ j [# W2 M) a' }! @s(1)=0;
: g0 z7 _" E; P* S: k) N- \for t=2:N; 0 t/ X4 ~4 m! A5 x
p1(t)=a.^2*p(t-1)+Rww;
4 L7 Z, I7 C: t: R$ t3 ab(t)=c*p1(t)/(c.^2*p1(t)+Rvv); ' Z( b# P$ P& k
s(t)=a*s(t-1)+b(t)*(Y(t)-a*c*s(t-1));
/ y. `; c. B: Np(t)=p1(t)-c*b(t)*p1(t);
, @# [6 Z, h- [+ j" E2 c6 Zend
' k* S Z9 D i0 F' ot=1:N;
: B, Q6 n$ V. s9 f' @plot(t,s,'r',t,Y,'g',t,x,'b'); ; K# [2 z2 s, L5 W" \* e, n
function [x, V, VV, loglik] = kalman_filter(y, A, C, Q, R, init_x, init_V, varargin) 2 y* w0 |9 d4 B7 |# X4 A
% Kalman filter. / E3 {; q% \$ S( ~
% [x, V, VV, loglik] = kalman_filter(y, A, C, Q, R, init_x, init_V, ...)
( v$ Z( L7 [5 b8 F+ @2 ~7 e- h% 3 @+ T2 Y$ |8 y4 h, Q
% INPUTS: ' e( o4 j7 c$ [) Q) t
% y(:,t) - the observation at time t
" L. [0 |3 P; j. C% A - the system matrix
, J8 I; R3 A$ o$ Y# E' T% C - the observation matrix
' M. j; d5 f# b0 I% Q - the system covariance 3 O) n& U0 G8 o% j& g( \
% R - the observation covariance
3 q1 d7 G( p8 a& i7 b# e% init_x - the initial state (column) vector
6 b( x# V" r* x d% init_V - the initial state covariance , V/ y( e# C/ ]
% 7 D: q5 C* D, X# h3 W! f6 E/ T4 O1 o
% OPTIONAL INPUTS (string/value pairs [default in brackets])
8 Y3 _' e8 y* p0 `$ M3 j! }% 'model' - model(t)=m means use params from model m at time t [ones(1,T) ] % m4 ?& s, h) Y7 S' n: ^" R3 ^$ \
% In this case, all the above matrices take an additional final dimension, - t; P( n) ~5 ~3 }; h9 `1 `
% i.e., A(:,:,m), C(:,:,m), Q(:,:,m), R(:,:,m).
I0 C' e/ T4 C6 w3 {1 K# A% However, init_x and init_V are independent of model(1).
) P6 C% z1 L* T. y3 @8 }% 'u' - u(:,t) the control signal at time t [ [] ]
4 X% e3 k! l: f" C9 _% 'B' - B(:,:,m) the input regression matrix for model m
$ T+ R5 ^6 d c! j% P1 N4 a% ^% / J& _4 F- G& ]
% OUTPUTS (where X is the hidden state being estimated) 1 x, m+ r. t5 }8 B5 l% x4 R* s5 v
% x(:,t) = E[X(:,t) | y(:,1:t)]
' C/ R# `% e! k$ Q- z& |% V(:,:,t) = Cov[X(:,t) | y(:,1:t)]
( l4 r9 C, E: L `+ Z6 U% VV(:,:,t) = Cov[X(:,t), X(:,t-1) | y(:,1:t)] t >= 2 - @1 L) e7 k/ E
% loglik = sum{t=1}^T log P(y(:,t))
5 }' B1 ?* y$ H4 W* H" D: j) F8 w% 6 m k5 Q, M9 S' P1 h
% If an input signal is specified, we also condition on it:
5 z u3 ~9 y* d: T5 e, O- E& a% e.g., x(:,t) = E[X(:,t) | y(:,1:t), u(:, 1:t)] 6 Q/ p+ \4 _* W3 I
% If a model sequence is specified, we also condition on it:
8 |( {3 R6 d2 _4 H$ F1 L8 l! `% e.g., x(:,t) = E[X(:,t) | y(:,1:t), u(:, 1:t), m(1:t)]
% O8 \4 G! M; ~[os T] = size(y);
$ [0 I" w* V3 r8 L3 U# [ss = size(A,1); % size of state space , x- S" H; _* l. ~. J$ F* ~$ a
% set default params ( h% G2 Z0 m* ~+ f
model = ones(1,T); 5 {- X) S+ U. w
u = [];
0 B- o- b# s0 n% a8 O( OB = [];
2 y2 y" G5 a( v4 S. Y, Rndx = []; 1 u) J5 W, e' `3 _5 \3 `
args = varargin;
1 b( u6 o1 |0 Enargs = length(args);
. O% X7 T% H' ?2 }$ r7 Vfor i=1:2:nargs
7 ^9 n/ U0 h' P, y1 U9 Mswitch args
" t% n, T) k( ?case 'model', model = args{i+1}; 8 y3 i$ T- |; R0 p6 ~
case 'u', u = args{i+1}; 8 W; A2 g6 j9 K
case 'B', B = args{i+1};
( Y/ j0 p+ Y. u; D& u3 ]4 ]; ] rcase 'ndx', ndx = args{i+1}; ' R2 S' R+ B3 e4 [( k# P
otherwise, error(['unrecognized argument ' args])
4 M1 q5 r9 k; k5 t1 U. B4 K" j% _" [end + @5 `- Q+ i5 B4 `. _1 u
end ' W, Y% O6 N9 u& \/ N# w+ ]" y+ E
x = zeros(ss, T);
& x1 Z* o" g# ^; {V = zeros(ss, ss, T);
5 O( F% j, C- m3 _ E4 l; U4 ~$ ZVV = zeros(ss, ss, T); 1 @- v0 e4 n& ]; T
loglik = 0;
: w9 d `$ x- D% z+ Sfor t=1:T m = model(t);
6 } I4 U3 Y5 x( [$ O& x9 g) Hif t==1 %prevx = init_x(:,m); 5 \, a# u& J) _ E1 p& b6 r! M
%prevV = init_V(:,:,m);
0 A; V3 l# H0 Q8 b# x a* J4 Q, nprevx = init_x; 5 f/ T. B: p' C" N% \2 {+ `* ]
prevV = init_V;
4 W0 j' q9 w+ C6 W: pinitial = 1; 4 P8 G: K0 Y6 s; F. c
else prevx = x(:,t-1);
- K8 q) L* \. `: l; V$ LprevV = V(:,:,t-1); 4 n% g8 g3 S0 r
initial = 0; * ]3 Q8 }9 s0 v+ U& C* [: y$ C$ ^
end
# |/ l" `/ ?" {( {, h4 ]if isempty(u) * r' ^# u! S. f4 F( u7 @
[x(:,t), V(:,:,t), LL, VV(:,:,t)] = ... ! y+ D2 ^/ `$ H! D+ W& j9 z6 `
kalman_update(A(:,:,m), C(:,:,m), Q(:,:,m), R(:,:,m), y(:,t), prevx, prevV, 'initial', initial); else + S( O' |1 }0 m% C8 N' a
if isempty(ndx) [x(:,t), V(:,:,t), LL, VV(:,:,t)] = ... * O& _% T" M# q, C# a
kalman_update(A(:,:,m), C(:,:,m), Q(:,:,m), R(:,:,m), y(:,t), prevx, prevV, ... 'initial', initial, 'u', u(:,t), 'B', B(:,:,m));
9 o# `/ y* K# }3 n7 x* w; celse 8 E- ^8 U+ w0 {: k% @
i = ndx; 2 v( f: @* H7 q! s) ?/ f/ _
% copy over all elements; only some will get updated x(:,t) = prevx; ! Y7 y/ m1 {8 {4 {; N Z, u& J% B
prevP = inv(prevV);
& a4 y/ H7 d( n: tprevPsmall = prevP(i,i); * P' v4 ~/ @; N# a& _" Z
prevVsmall = inv(prevPsmall); ( V) U7 I8 D, O, E
[x(i,t), smallV, LL, VV(i,i,t)] = ... kalman_update(A(i,i,m), C(:,i,m), Q(i,i,m), R(:,:,m), y(:,t), prevx(i), prevVsmall, ... 'initial', initial, 'u', u(:,t), 'B', B(i,:,m));
- L) y0 m' J* I5 vsmallP = inv(smallV);
) k$ [ b& B% u9 S. A- M' gprevP(i,i) = smallP;
) K7 y* l, i: C% ^5 H% d# \: ]V(:,:,t) = inv(prevP); 4 o( K3 G3 N8 }( w1 K1 U! p
end
8 \8 V' X4 X! ^end 4 O' @7 \& s) f$ Y: Z$ I
loglik = loglik + LL; * N8 b- U* T* [3 G+ r1 W/ l
end |
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