references - cern · 200 answers and hints to exercises 1.10. (1.35) can be verified by a direct...
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References
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Answers and Hints to Exercises
Chapter 1
1.1. Since most of the properties can be verified directlyby using the definition of the trace, we only considertrAB = trBA. Indeed,
1.2.
1.3.
A=[~ ;], B=[~ ~].1.4. There exist unitary matrices P and Q such that
andn n
LA~ ~ LJl~'k=l k=l
Let P = [Pij]nxn and Q = [qij]nxn. Then
Pin + P~n + + P;n = 1 , qrl + q~l + + q~l = 1,
q~2 + q~2 + + q~2 = 1 , ... ,q~n + q~n + + q~n = 1 ,
and
198 Answers and Hints to Exercises
tr P~lAi + P~2A~+ ... +P~nA;
*
P~lAi + P~2A~* + ... +P~nA~
= (pil + P~l + ... + p;l)Ai + ... + (Pin + P~n + ... + P;n)A;
= Ai + A~ + ... + A~.
Similarly, trBBT = JLi + JL~ + ... + JL~. Hence, trAAT ~ trBBT .
1.5. Denote
100 2
1= e-Y dy.-00
Then, using polar coordinates, we have
1.6. Denote
100 2
I(x) = -00e-xydy.
Then, by Exercise 1.5,
1 100 2I(x) = - e-(VXY) d( yXy) = V1r / x .Vi -00
Hence,
100 2 d Iy2e- Y dy = --I(x)-00 dx x=l
= -!-(~)I = ~V1f.dx x=l 2
1.7. (a) Let p be a unitary matrix so that
R = pTdiag[Al,···, An]P,
Answers and Hints to Exercises 199
and define
Then
E(X) =1:xf (x)dx
=1:~ + y'2p-l diag[ 1/-1>.1> ... ' l/-I>.n ]y)f(x)dx
=~l:f(X)dX
00 00 [Yl]+ const·loo
... loo ~n e-yr . .. e-Y;dYl ... dYn
=l!:·1+0=l!:.
(b) Using the same substitution, we have
Var(X)
=1:(x - ~)(x - ~)T f(x)dx
=1:2R1/
2yyT R 1/
2f(x)dx
= (~~n/2Rl/2{1: ...1: [~rYnYl
2 2 } 1/2. e-Yl ... e-YndYl ... dYn R
= R l/
2 IRl/2 = R.
1.8. All the properties can be easily verified from the definitions.
1.9. We have already proved that if Xl and X 2 are independent then CoV(Xl ,X2 ) = o. Suppose now that R 12 =Cov(Xl , X 2 ) = o. Then R2l = COV(X2 , Xl) = 0 so that
1f(Xl ,X2 ) = /(21l")n 2detRlldetR22
. e-~(Xl-~l)TRll(Xl-~1)e-~(X2-~2)T R 22(X2 -E:2)
= fl(Xl ) . f2(X2 ).
Hence, Xl and X 2 are independent.
200 Answers and Hints to Exercises
1.10. (1.35) can be verified by a direct computation. First, thefollowing formula may be easily obtained:
This yields, by taking determinants,
and
det [RxxRyx
~Xy] = det [Rxx - RxyR;;R yx ] . detRyyyy
([;J -[~x ]) T [~: ~:r\[;J -[~x ])-y -y
=(x - i!:.)T [Rxx - RxyR;;Ryxr\x - i!:.) + (y - !!:.)TR;;(y -!!:.)'
whereI!:. = l!.x + RxyR;yl(y -l!.y) .
The remaining computational steps are straightforward.1.11. Let Pk = ClWkZk and 0-
2 = E[pr (ClWkCk)-lpk]. Then itcan be easily verified that
FromdFd(Yk) = 2(CIWkCk)Yk - 2Pk = 0,
Yk
and the assumption that the matrix (CJWkCk) is nonsingular, we have
1.12.EXk = (Cl R;lCk)-lC~R;lE(Vk - DkUk)
= (cl R;lCk)-lC~R;lE(CkXk + !lk)
=EXk·
Answers and Hints to Exercises 201
Chapter 2
2.1.
Wk- kl_l = VarC~k k-l) = E(fk k-Ifl k-l), , "
= E(Vk-1 - Hk,k-lXk)(Vk-l - Hk,k-lXk) T
] [
Co E~=l iPOiri-1{i_l ]
+Var :
Rk-l Ck-l iPk-l,krk-l{k_1
2.2. For any nonzero vector x, we have x T Ax > 0 and x T Bx ~ 0so that
X T (A + B)x = X T Ax + X T Bx > 0 .
Hence, A + B is positive definite.2.3.
W - 1k,k-l
= E(fk k-lfl k-l), ,
= E(fk-l,k-l - Hk,k-lrk-l{k_l)(fk-l,k-l - Hk,k-lrk-l~k_I)T
= E(fk-l,k-Ifl-l,k-l) + Hk,k-lrk-IE({k_I{~_I)rl-IH~k-1
= Wk"!l,k-l + Hk-l,k-Iq>k-l,krk-IQk-lrl-liPl-l,kH"[-l,k-l'
2.4. Apply Lemma 1.2 to All = Wk"!I,k-I,A22 = Qk~l and
2.5. Using Exercise 2.4, or (2.9), we have
H~k-lWk,k-l
=iPl- 1 kH"[-1 k-lWk-1,k-1, ,
- q>l-l,kH"[-I,k-1Wk,k-IHk,k-l iPk-l,krk-1
· (Qk~l + rl-1q>l-l,kH"[-l,k-lWk-l,k-lHk-l,k-l iPk-1,krk-l)-1
· rl-1iPl-1 kH"[-1 k-lWk-l,k-l, ,
=q>l-l,k{I - H"[-l,k-lWk-l,k-lHk-l,k-l iPk-l,krk-l
· (Qk~l + rl- 1q>l-l,kH"[-l,k-lWk-l,k-lHk-l,k-l iPk-l,krk-l)-l
· rl- 1q>l-l k}H"[-l k-lWk-l,k-l ., ,
202 Answers and Hints to Exercises
2.6. Using Exercise 2.5, or (2.10), and the identity Hk,k-1Hk-1,k-1~k-1,k, we have
(H~k-1Wk,k-1Hk,k-1)~k,k-1
· (H"!-1,k-1 Wk-1,k-1Hk-1,k-1)-1 H~-1,k-1Wk-1,k-1
= ~l-l,k{I - H~-1,k-1Wk-1,k-1Hk-1,k-1 ~k-1,krk-1
· (Q;;~l + rl-1~l-1,kH~-1,k-1Wk-1,k-1Hk-1,k-1 ~k-1,krk-1)-1
· rl-1~l-1,k}H~-1,k-1Wk-1,k-1
= H~k-1Wk,k-1 .
2.7.
Pk,k-1C~ (CkPk,k-1CJ + Rk)-l
=Pk,k-1C~(R;;l - R;;lCk(Pk~~_l + C~R;;lCk)-lC~R;;l)
=(Pk,k-1 - Pk,k-1C~R;;lCk(Pk~_l + C~R;;lCk)-l)C~R;;l,
=(Pk,k-1 - Pk,k-1C~ (CkPk,k-1C~ + Rk)-l
· (CkPk,k-1C~ + Rk)R;;lCk(Pk~_l + c~R"k1Ck)-1)C"! R"k 1,
=(Pk,k-1 - Pk,k-1C~ (CkPk,k-1C~ + Rk)-l
· (CkPk,k-1C~R"k1Ck + Ck)(Pk,~-l + C~R"k1Ck)-1)C~R"k1
=(Pk,k-1 - Pk,k-1C~ (CkPk,k-1C~ + Rk)-lCkPk,k-1
· (C~R;;lCk + Pk~~-l)(Pk,~-l + c~R"k1Ck)-1)C~R;;l
=(Pk,k-1 - Pk,k-1C~ (CkPk,k-1C~ + Rk)-lCkPk,k-1)C~R"k1
=Pk,kCJ R;;l
=Gk·
2.8.
Pk,k-1
=(H~k-1Wk,k-1Hk,k-1)-1
=(~l-1,k(H"!-1,k-1Wk-1,k-1Hk-1,k-1
- H~-1,k-1Wk-1,k-1Hk-1,k-1 ~k-1,krk-1
· (Q;;~l + rl-1~J-1,kH"!-1,k-1Wk-1,k-1Hk-1,k-1 ~k-1,krk-1)-1
· rl-1~J-1 kH~-l k-1 Wk-1,k-1Hk-1,k-1)~k-1,k)-1, ,
=(~l-1,kPk-.!1,k-1~k-1,k - ~l-1,kPk.!1,k-1 ~k-1,krk-1
· (Q"k~l + rJ-1 ~J-1,kPk.!1,k-1~k-1,krk-1)-1
r T m.T p-1 m. )-1· k-1 '*'k-1,k k-1,k-1 '*'k-1,k
=(~l-1,kPk!1,k-1~k_1,k)-1+ rk-1Qk-1rl-1
=Ak-1Pk-1,k-1Al-1 + rk-1Qk-1rl-1 .
Answers and Hints to Exercises 203
2.9.
E(Xk - Xklk-l)(Xk - Xklk-l) T
=E(Xk - (H~k-lWk,k-lHk,k-l)-lH~k-lWk,k-lVk-l)
o (Xk - (H~k-lWk,k-lHk,k-l)-lH~k-lWk,k-lVk-l) T
=E(Xk - (H~k-lWk,k-lHk,k-l)-lH~k-lWk,k-l
o (Hk,k-lXk + fk,k-l))(Xk - (H~k-lWk,k-lHk,k-l)-l
o H~k-lWk,k-l(Hk,k-lXk + f.k,k-l)) T
=(H~k-lWk,k-lHk,k-l)-lH~k-lWk,k-lE(fk,k-lfr,k-l)Wk,k-l
o Hk,k-l(H~k-lWk,k-lHk,k-l)-l
=(H~k-lWk,k-lHk,k-l)-l
=Pk,k-l o
The derivation of the second identity is similar.2.10. Since
a 2 = Var(xk) = E(axk-l + ~k_l)2
= a2Var(xk_l) + 2aE(xk-l~k-l) + E(~~-l)
= a2a2 + J.-l2 ,
we have
For j = 1, we have
E(XkXk+l) = E(Xk(axk + ~k))
= aVar(xk) + E(Xk~k)
= aa20
For j = 2, we have
E(XkXk+2) = E(Xk(axk+l + ~k+l))
= aE(xkxk+l) + E(Xk + ~k+l)
= aE(xkxk+l)
= a2a 2,
etc. If j is negative, then a similar result can be obtained.By induction, we may conclude that E(XkXk+j) = a1j1 a 2 forall integers j.
204 Answers and Hints to Exercises
2.11. Using the Kalman filtering equations (2.17), we have
Po,o = Var(xo) = J.L2 ,
Pk,k-l = Pk-l,k-l ,
( )-1 Pk-l,k-l
Gk = Pk,k-l Pk,k-l + Rk = P 2 'k-l,k-l + a
and
()a2Pk-lk-l
Pk,k = 1 - Gk Pk,k-l = 2 p' .a + k-l,k-l
Observe that
Hence,
GPk-l,k-l
k=Pk-l,k-l + 0'2
so that
Xklk = xklk-l + Gk(Vk - xklk-l)
'" J.L2 '"= Xk-llk-l + 2 k 2 (Vk - Xk-llk-l)a + J.L
with xOlo = E(xo) = o. It follows that
for large values of k.2.12.
N'" I" TQN = N L...J(VkVk)k=l
1 1 N-l
= N(VNvl.) + N L(VkVJ)k=l
1 T N-1 '"= N(VNVN) + -yv-QN-l
'" 1 T '"= QN-l + N[(VNVN) - QN-l]
with the initial estimation Ql = vlvT.
Answers and Hints to Exercises 205
2.13. Use superimposition.2.14. Set Xk = [(xl) T ... (xf)T]T for each k, k = 0,1, ... , with Xj = 0
(and Uj = 0) for j < 0, and define
Then, substituting these equations into
yields the required result. Since Xj = 0 and Uj = 0 for j < 0,it is also clear that Xo = o.
Chapter 3
3.1. Let A = BBT where B = [bij ] =1= o. Then trA = trBBT =
Ei,j b;j > O.3.2. By Assumption 2.1, TU is independent ofxo, {o' ... , {j-I' !la '
!l.j -1' since f ~ j. On the other hand,
ej = Cj(Xj - Yj-l)
j-l
= C j (Aj-IXj-1 + rj-IE. 1 - ""'" Pj - l i(CiXi + "7,))-J- ~, -'I,
i=O
j-l j-l
= Boxo +E Bli~i + E B 2i'!1.ii=O i=O
for some constant matrices Ba, B li and B 2i • Hence, (TU, ej)= Oqxq for all f ~ j.
3.3. Combining (3.8) and (3.4), we have
j-l
ej = IIzjll;lzj = IIzjll;lvj - E(llzjll;lCjPj-1,i)vi;i=O
206 Answers and Hints to Exercises
that is, ej can be expressed in terms of vD, VI,· .. ,Vj. Conversely, we have
Vo =Zo = Ilzollqeo,
VI =ZI + CIYo = ZI + CIPO,OVo
=llzIllqel + CIPo,ollzollqeo,
that is, Vj can also be expressed in terms of eo, el, ... , ej.Hence, we have
3.4. By Exercise 3.3, we have
i
Vi = LLlell=O
for some q x q constant matrices Ll' f = 0,1,· .. , i, so that
i
(Vi, Zk) = LLl(el, ek)llzkll; = Oqxq,l=O
i = 0,1, ... ,k - 1. Hence, for j = 0,1, ... ,k - 1,
j
= LPj,i(Vi' Zk)i=O
= Onxq.
3.5. Since
Xk = Ak-IXk-1 + rk-l~k_1
= A k - I (Ak-2 X k-2 + rk-2~k_2) + rk-l~k_1
k-I
= Boxo + L BIi~ii=O
for some constant matrices Bo and B Ii and ~k is independent of Xo and ~i (0::; i ::; k - 1), we have (Xk' ~k) = o. Therest can ·be shown in a similar manner.
Answers and Hints to Exercises 207
3.6. Use superimposition.3.7. Using the formula obtained in Exercise 3.6, we have
{
~klk = dk-llk-l + hWk-l + Gk(Vk - fldk - dk-llk-l - hWk-l)
dOlo == E(do) ,
where Gk is obtained by using the standard algorithm(3.25) with A k == Ck == rk == 1.
3.8. Let
C==[100].
Then the system described in Exercise 3.8 can be decomposed into three subsystems:
{
Xk+l = Ax~ + r~i~
vk == CXk + 1]k ,
i == 1,2,3, where for each k, Xk and ~k are 3-vectors, Vk and1]k are scalars, Qk a 3 x 3 non-negative definite symmetricmatrix, and Rk > 0 a scalar.
Chapter 4
4.1. Using (4.6), we have
L(Ax+ By, v)
== E(Ax + By) + (Ax + By, v) [Var(v)] -l(v - E(v))
= A{E(x) + (x, v) [Var(v)]-l(v - E(v))}
+B{E(y)+(y, v)[Var(v)]-l(v-E(v))}
== AL(x, v) + BL(y, v).
208 Answers and Hints to Exercises
4.2. Using (4.6) and the fact that E(a) = a so that
(a, v) = E(a - E(a)) (v - E(v)) = 0,
we have
L(a, v)=E(a)+(a, v)[Var(v)]-l(v-E(v))=a.
4.3. By definition, for a real-valued function j and a matrixA = [aij], dj /dA = [aj /aaji]. Hence,
o= 8~ (trllx - YII~)a
= 8HE((x - E(x)) - H(v - E(v))) T ((x - E(x)) - H(v - E(v)))
a= E 8H((x - E(x)) - H(v - E(v)))T ((x - E(x)) - H(v - E(v)))
= E( -2(x - E(x)) - H(v - E(v))) (v - E(v)) T
= 2(H E(v - E(v)) (v - E(v))T - E(x - E(x)) (v - E(v))T)
=2(Hllvll~-(x, v)).
This gives
so that
x* = E(x) - (x, v) [IIVII~] -1 (E(v) - v).
4.4. Since v k - 2 is a linear combination (with constant matrixcoefficients) of
xa, {a' ... , {k-3' '!la' ... , '!lk-2
which are all uncorrelated with {k-l and '!lk-l' we have
and
Similarly, we can verify the other formulas [where (4.6)may be used].
4.5. The first identity follows from the Kalman gain equation(cf. Theorem 4.1(c) or (4.19)), namely:
Answers and Hints to Exercises 209
so thatGkRk = Pk,k-lCJ - GkCkPk,k-lCJ
= (1 - GkCk)Pk,k-lCJ .
To prove the second equality, we apply (4.18) and (4.17)to obtain
(Xk-l - Xk-llk-l, rk-l~k_l - Kk-l!lk_l)
(Xk-1 - Xk-1Ik-Z - (x#k-l, v#k-1) [lIv#k_IiIZ
] -1V#k-1,
rk-l~k_l - Kk-l!lk_l)
(X#k-1 - (X#k-1, V#k-1) [llv#k-IIIzr\Ck- 1X#k-1 + !lk-1)'
rk-l~k_l - Kk-l!lk_l)
= -(X#k-b V#k-1) [lIv #k-1Il zr\SJ-1fL1 - Rk-1KJ-1)
= Onxn,
in which since Kk-l = rk-ISk-lRk~I' we have
sJ-Irl- 1 - Rk-IKJ-I = Onxn·
4.6. Follow the same procedure in the derivation of Theorem4.1 with the term Vk replaced by Vk - DkUk, and with
xklk-l = L(Ak-IXk-l + Bk-lUk-l + rk-l~k_I' Vk
-1
)
instead of
xklk-I = L(Xk' v k-
1) = L(Ak-IXk-1 + rk-I~k_l' V
k-
1).
4.7. LetWk = -alVk-I + bl Uk-I + CIek-1 + Wk-I ,
Wk-I = -a2Vk-2 + b2Uk-2 + Wk-2 ,
and define Xk = [Wk Wk-I Wk_2]T. Then,
{
Xk+1 = AXk + BUk + rek
Vk = CXk + DUk + D..ek ,
where
A = [=;; ~ n,C=[l 00], D = [bo] and D.. = [co].
210 Answers and Hints to Exercises
4.8. LetWk = -alVk-l + bl Uk-l + clek-l + Wk-l ,
Wk-l = -a2vk-2 + b2U k-2 + C2 ek-2 + Wk-2 ,
where bj = 0 for j > m and Cj = 0 for j > f, and define
Xk = [Wk Wk-l ... Wk_n+I]T.
Then
{
Xk+l = AXk + BUk + rek
Vk = CXk + DUk + flek ,
where-al 1 0 0-a2 0 1 0
A=
-an-l 0 0 1-an 0 0 0
bl - albo Cl - alcO
B=bm - ambo r= Cl - alcO-am+lbo -al+l
C=[10 0],
Chapter 5
D = [bo], and fl = [co].
5.1. Since v k is a linear combination (with constant matricesas coefficients) of
Xo, !lo' 10, ... , 'lk' io' f!..o' ... , f!..k-l
which are all independent of fik
, we have
(f!..k' vk
) = o.
On the other hand, fik
has zero-mean, so that by (4.6) wehave
L(1!-k' vk
) = E(1!-k) - (1!-k' vk
) [lIvk l1 2r1
(E(vk) - vk
) = o.
Answers and Hints to Exercises 211
5.2. Using Lemma 4.2 with v = V k- I , VI = V k - 2 , V 2 = Vk-I and
# - L( k-2)V k-I - Vk-I - Vk-I, V ,
we have, for x = Vk-I,
L(Vk-l, v k-
I)
= L(Vk-ll vk
- 2) + (V#k-ll V#k-l) [IIV #k_ 1 11 2] -1V#k-l
= L(Vk-l, v k- 2) + Vk-I - L(Vk-l, v k- 2
)
= Vk-I .
The equality L(lk' v k - I ) = 0 can be shown by imitatingthe proof in Exercise 5.1.
5.3. It follows from Lemma 4.2 that
Zk-I - Zk-I
= Zk-I - L(Zk-l, Vk
-I
)
=Zk-l - E(Zk-l) + (Zk-ll v k - 1) [lIvk - 1 11 2] -1 (E(vk- 1) _ v k -
1)
_ [Xk-I] _ [E(Xk-I)]- ~k-I E(~k_l)
+ [(Xk-l, V:=~)] [llvk - 1112]-1 (E(Vk- 1 ) _ vk - 1)({k_I'V )
whose first n-subvector and last p-subvector are, respectively, linear combinations (with constant matrices as coefficients) of
Xo, ~o' f!..o' ... , f!..k-2' !lo' 10, ... , lk-I'
which are all independent of lk. Hence, we have
5.4. The proof is similar to that of Exercise 5.3.5.5. For simplicity, denote
B = [CoVar(xo)cri +RO]-I.
212 Answers and Hints to Exercises
It follows from (5.16) that
Var(xo - xo)
= Var(xo - E(xo)
- [Var(xo)]cri [CoVar(xo)cri + RO]-I(vO - CoE(xo)))
= Var(xo - E(xo) - [Var(xo)]cri B(Co(xo - E(xo)) + ~o))
= Var((1 - [Var(xo)]criBCo)(xo - E(xo)) - [Var(xo)]C~B!lo)
= (I - [Var(xo)]C~BCo)Var(xo) (I - criBCo[Var(xo)])
+ [Var(xo)]Cri BRoBCo[Var(xo)]
= Var(xo) - [Var(xo)]cri BCo[Var(xo)]
- [Var(xo)]Cri BCo[Var(xo)]
+ [Var(xo)]cri BCo[Var(xo)]C~BCo[Var(xo)]
+ [Var(xo)]Cri BRoBCo[Var(xo)]
= Var(xo) - [Var(xo)]C~BCo[Var(xo)]
- [Var(xo)]Cri BCo[Var(xo)] + [Var(xo)]C~BCo[Var(xo)]
= Var(xo) - [Var(xo)]C~BCo[Var(xo)].
5.6. From ~o == 0, we have
Xl == Aoxo + GI(VI - CIAoxo)
and ~l == 0, so that
X2 == AIXI + G2(V2 - C2AIXI) ,
etc. In general, we have
Xk == Ak-IXk-1 + Gk(Vk - CkAk-IXk-l)
== xklk-l + Gk(Vk - CkXklk-l) .
Denote
and
Then
Answers and Hints to Exercises 213
Pl = ([~o ~o] -Gl[ClAo CIf0]) [Pg,O ~oJ [:f ~]
+[~ ~J= [[ In - Pl,ocl (ClPl'gCl +Rd-lCl ]Pl,o 31]'
and, in general,
Gk = [Pk,k-l C;[ (CkPkt-lC;[ + Rk)-l] ,
Pk = [[ In - Pk,k-lC;[(CkPk,kOlC;[ + Rd-lCk]Pk,k-l 3J.Finally, if we use the unbiased estimate :Ko = E(xo) of xoinstead of the somewhat more superior initial state estimatei o = E(xo) - [Var(xo)]C~[CoVar(xo)C~ + Ro]-l[CoE(xo) - vo],
and consequently set
Po =E([XO] _ [E(Xo)]) ([xo] _[E(Xo)])T
~o E~o) ~o E~o)
= [var~xo) 30]'then we obtain the Kalman filtering algorithm derived inChapters 2 and 3.
5.7. Let
andHk-l = [ CkAk-l - Nk-lCk-l ].
Starting with (5.17b), namely:
Po = [( [var(xo)]-lo+ COR01CO)-1 0] [Po 0]Qo 0 Qo '
we have
Gl= [~o ~o] [~o ~oJ [f¥~l].([Ho Clfo][~O ~o][f¥~l]+Rl)-l
= [(AoPoH~ +foQofri Cl) (Ho~oH~ +ClfoQofricl +RI) -1]:= [~l]
o ] [AT 0]Qo rJ 0
214 Answers and Hints to Exercises
and
PI = ([~o ~o] - [~l][Ho GIrO l) [~o
+[~ 3J= [(Ao - G1Ho)PoAJ -;; (I - G1G1)roQorJ
:= [~l 3J.In general, we obtain
Xk = Ak-1Xk-1 + Ok(Vk - Nk-1Vk-1 - Hk-1Xk-1)
Xo = E(xo) - [Var(xo)] cri [CoVar(xo)Cri + Ro]-l[CoE(xo) - vo]
Hk-1 = [ CkAk-1 - Nk-1Ck-1 ]- -- - T - T
Pk = (Ak- 1 - GkHk-1)Pk-1Ak-1 + (1 - GkCk)rk-1Qk-1rk-1- - -T T T
Gk = (Ak-1Pk-1Hk-1 + fk-1Qk-1fk-1Ck ).- - -T T T 1
(Hk-lPk-1Hk-1 + Ckrk-1Qk-1rk-1ck + Rk-1)-
Po = [ [Var(xo)]-l + criRa1Co]-1
k = 1,2,··· .
By omitting the "bar" on Hk, Ok, and Pk , we have (5.21).
5.8. (a)
{Xk+1 = AcXk + ~k
Vk = CcXk ·
(b)
[
var(xo)Po,o = 0
o00]
Var(~o) 0 ,o Var(1Jo)
oo
rk-1
Answers and Hints to Exercises 215
(c) The matrix CJPk,k-l Cc may not be invertible, and theextra estimates ~k and r,k in Xk are needed.
Chapter 6
6.1. Since
and
Xk-l = A n [N6ANcA]-I(CT Vk-n-l + AT CTvk-n
+ ... + (AT)n-IcT Vk-2)
= An[N6ANcA]-I(CTCXk-n-1 + AT C T CAXk-n-1
+ ... + (AT)n-IcT CAn-Ixk_n_1 + nOise)
= A n [N6ANcA]-I[N6ANCA]Xk-n-1 + noise
= AnXk_n_1 + noise,
we have E(Xk-l) = E(AnXk _n_ l ) = E(Xk-I).6.2. Since
we have
Hence,
~A-l(S) = -A-1(S)[:sA(s)]A- 1(s).
6.3. LetP=Udiag[AI,···,An]U- I . Then
P - AminI = Udiag[ Al - Amin,···, An - Amin ]U- I 2: o.
6.4. Let AI,···, An be the eigenvalues of F and J be its Jordancanonical form. Then there exists a nonsingular matrix Usuch that
U-IFU = J =
216 Answers and Hints to Exercises
with each * being 1 or o. Hence,
A~ * *A~ * *
F k = UJkU- 1 = U
where each * denotes a term whose magnitude is boundedby
p(k)IAmaxl k
with p(k) being a polynomial of k and IAmaxl = max( IAII,· .. ,IAnl ). Since IAmaxl < 1, F k ~ 0 as k ~ 00.
6.5. Since
we have
Hence,
(A+B) (A+B)T =AAT +ABT +BAT +BBT
:S 2(AAT + BBT).
6.6. Since Xk-l = AXk-2 + r~k_2 is a linear combination (withconstant matrices as coefficients) of xO'~o,··· '~k-2 and
Xk-l = AXk-2 + G(Vk-1 - CAXk-2)
= AXk-2 + G(CAXk-2 + cr~k_2 + '!lk-l) - GCAXk-2
is an analogous linear combination of Xo, ~o' ... '~k-2 and'!lk-l' which are uncorrelated with ~k-l and '!lk' the twoidentities follow immediately.
6.7. Since
Pk,k-I C-:Gl - GkCkPk,k-I C-:al=CkCkPk,k-IC"[cl + CkRkCl - CkCkPk,k-I C"[cl
=GkRkGl,
we have
Answers and Hints to Exercises 217
Hence,
Pk,k = (1 - GkC)Pk,k-1
= (1 - GkC )Pk,k-I(1 - GkC )T + GkRGl
= (1 - GkC) (APk_l,k_IAT + rQrT) (1 - GkC)T + GkRGl
= (1 - GkC)APk_l,k_IAT (1 - GkC) T
+ (1 - GkC)rQrT (1 - GkC )T + GkRGl.
6.8. Imitating the proof of Lemma 6.8 and assuming that IAI ~1, where A is an eigenvalue of (1 - GC)A, we arrive at acontradiction to the controllability condition.
6.9. The proof is similar to that of Exercise 6.6.6.10. From
o < (E.-8. E.-8.)- -J -J'-J -J
= (fj' fj) - (fj' ~j) - (~j' fj) + (~j' ~j )
and Theorem 6.2, we have
(fj' ~j) + (~j' fj)
< (fj, fj) + (~j' ~j )
(Xj -Xj +Xj -Xj,Xj -Xj +Xj -Xj) + IIxj -Xjll~
- Ilx· - x·11 2 + (x· - x· x· - x·)- J J n J J' J J
+ (Xj - Xj,Xj - Xj) + 211xj - Xjll;
:S 211 x j - Xj 11; + 311 x j - Xj 11;-+ 5(P- 1 + CT R-IC)-I
as j -+ 00. Hence, Bj = (fj'~j)ATc T are componentwiseuniformly bounded.
6.11. Using Lemmas 1.4, 1.6, 1.7 and 1.10 and Theorem 6.1,and applying Exercise 6.10, we have
tr[PBk-I-i(Gk-i - G) T + (Gk-i - G)BJ_I_iPT ]
:S(n trPBk-I-i(Gk-i - G)T (Gk-i - G)BJ_I_iPT)I/2
+ (n tr(Gk-i - G)BJ_I_ipTPBk-I-i(Gk-i - G) T)I/2
:S(n trppT . trBk-I-iBJ_I_i· tr(Gk-i - G)T (Gk-i - G))1/2
+ (n tr(Gk-i - G) (Gk-i - G)T . trBJ_I_iBk-I-i . trpT p)I/2
=2(n tr(Gk- i - G) (Gk- i - G) T . trBJ_I_iBk-I-i . trFT F)I/2
<C r k +l - i- I I
for some real number rI, 0 < rl < 1, and some positiveconstant C independent of i and k.
218 Answers and Hints to Exercises
6.12. First, solving the Riccati equation (6.6); that is,
c2p2 + [(1 - a2)r - c2,2q]p - rq,2 = 0,
we obtain
1p = 2c2 {c2
,),2q + (a2- l)r + V[(l - a2 )r - c2')'2q]2 + 4C2')'2 qr }.
Then, the Kalman gain is given by
9 = pcj(c2p + r) .
Chapter 7
7.1. The proof of Lemma 7.1 is constructive. Let A = [aij]nxnand AC = [Rij]nxn. It follows from A = AC(AC)T that
and
i
aii = LR;k,k=1
j
aij = L RikRjk , j =1= i ;k=1
i = 1,2,' .. , n,
i,j = 1,2,···,n.
Hence, it can be easily verified that
i-I 1/2
f ii = (aii - L f;k) , i = 1, 2, ... ,n,k=1j-l
fij = (aij - L fikfjk) / fj j , j = 1,2, ... ,i - 1; i = 2, 3, ... , n,k=1
and
j = i + 1, i + 2, ... , n; i = 1,2, ... , n.
This gives the lower triangular matrix AC. This algorithmis called the Cholesky decomposition. For the generalcase, we can use a (standard) singular value decomposition (8VD) algorithm to find an orthogonal matrix U suchthat
U diag[sl,···,Sr,o, ... ,O]UT =AAT ,
Answers and Hints to Exercises 219
where 1 :::; r :::; n, 81,'" ,8r are singular values (which arepositive numbers) of the non-negative definite and symmetric matrix AAT, and then set
A = U diag[JS1 ... VS; 0 ... 0], , r" , .
7.2.
L = [~0
n· [J20
o ](a) 2 (b) L = J2/2 m o .-2 J2/2 1.5/m J2]
7.3.(a)
[ l/f l1 0o ]L- 1 = -£21/£11£22 1/£22 o .
-£31/£11£33 + £32£21/£11£22£33 -£32/£22£33 1/£33
(b)
[bl1 0 0
)JL- 1 = b~lb22 0
bn1 bn2 bn3
where
i = 1,2,"" n;i
bij = -£711 L bik£kj,
k=j+1
j = i - 1, i - 2, ... ,1; i = 2,3, ... ,n.
7.4. In the standard Kalman filtering process,
which is a singular matrix. However, its "square-root" is
p1/2 _ [E/~ 0] [E 0]k,k - 0 1 ~ 0 1
which is a nonsingular matrix.
220 Answers and Hints to Exercises
7.5. Analogous to Exercise 7.1, let A == [aij]nxn and AU == [£ij]nxn.
It follows from A == AU(AU)T that
and
n
aii == L£;k'k=i
n
aij == L fikfjk ,
k=j
i == 1,2.···, n,
j =I i; i, j == 1,2,· .. ,n.
Hence, it can be easily verified that
i == 1,2,· .. , n,
n
f ij = (aij - L fikfjk )/fjj ,
k=j+l
j == i + 1, ... ,n; i == 1,2, ... ,n.
andj == 1,2, ... ,i - 1; i == 2,3, ... ,n.
This gives the upper-triangular matrix AU.7.6. The new formulation is the same as that studied in this
chapter except that every lower triangular matrix withsuperscript c must be replaced by the corresponding uppertriangular matrix with superscript u.
7.7. The new formulation is the same as that given in Section7.3 except that all lower triangular matrix with superscriptc must be replaced by the corresponding upper triangularmatrix with superscript u.
Chapter 8
8.1. (a) Since r 2 ==x2 +y2, we have
. x. y.r == -x + -y,
r r
so that r == v sinB and
r == iJ sinB + vB cosB.
Answers and Hints to Exercises 221
On the other hand, since tane = yjx, we have 8sec20 =(xy - xy)jx2 or
. xy - xy xy - xy vo= 2 20 = 2 = -cosO ,
x sec r r
so that.. . v2
r = a s~nO + -cos20r
and.. (iJr-vi') v·o= r 2 cosO - ;:OsinB
(ar - v2sinO) v2
= r 2 cosB - r 2sinOcosB .
(b)
[
V sinB ]x = f(x) := a sinO + vr
2cos2B .
(ar - v2sinO)cosfJ j r 2 - v2sinfJ cosO j r 2
(c)
xk[l] + hv sin(xk[3])
xk[2] + ha sin(xk[3]) + v2cos2(xk[3])jxk[1]
vcos (xk [3] ) j Xk [1]
(axk[l] - v2sin(xk[3]))cos(xk[3])jxk[l]2-v2sin(Xk [3])COS(Xk [3])/xk[1]2
andVk = [1 0 0 0 ]Xk + TJk ,
where Xk := [xk[l] xk[2] xk[3] xk[4]]T.(d) Use the formulas in (8.8).
8.2. The proof is straightforward.8.3. The proof is straightforward. It can be verified that
8.4. Taking the variances of both sides of the modified "observation equation"
Vo - Co(fJ)E(xo) = Co(O)xo - Co(B)E(xo) + '!lo'
222 Answers and Hints to Exercises
and using the estimate (vo - Co(B)E(xo))(vo - Co(B)E(xo))Tfor Var(vo - Co(B)E(xo)) on the left-hand side, we have
(vo - Co(B)E(xo))(vo - Co(B)E(xo))T
=Co(B)Var(xo)Co(B)T + Ro.
Hence, (8.13) follows immediately.8.5. Since
E(Vl) = Cl(B)Ao(B)E(xo) ,
taking the variances of both sides of the modified "observation equation"
VI - Cl (B)Ao(B)E(xo)
=Cl(B)(Ao(B)xo - Cl(B)Ao(B)E(xo) + r(B)~o) + '!1.l '
and using the estimate (VI -Cl(B)Ao(B)E(xo))(Vl -Cl(B)Ao(B)·E(xo))T for the variance Var(vl - Cl(B)Ao(B)E(xo)) on theleft-hand side, we have
(VI - Cl (B)Ao(fJ)E(xo))(Vl - Cl (B)Ao(B)E(xo)) T
=Cl(B)Ao(B)Var(xo)A~ (B)Ci (B) + Cl(B)ro(B)Qor~ (B)Ci (B) + RI·
Then (8.14) follows immediately.8.6. Use the formulas in (8.8) directly.8.7. Since fl. is a constant vector, we have Sk := Var(fl.) = 0, so
thatp, = V (x) = [var(xo) 0]
0,0 ar fl. 0 o·
It follows from simple algebra that
Pk,k-l = [~~] and Gk = [~]
where * indicates a constant block in the matrix. Hence,the last equation of (8.15) yields ~klk == ~k-llk-l·
8.8.
p, _ [po 0 ]0,0 - 0 So
Answers and Hints to Exercises 223
where ca is an estimate of Co given by (8.13); that is,
Chapter 9
{
Xk = -(a + /3 - 2)Xk-l - (1 - a)Xk-2 + aVk + (-a + (3)Vk-l
:h = -(a + (3 - 2)Xk-l - (1 - a)Xk-2 + kVk - kVk-l .
2(b) 0 < a < 1 and 0 < /3 < l~a.
9.2. System (9.11) follows from direct algebraic manipulation.9.3. (a)
(b)
[
I-a
<P = -/3lh-,lh2
-()
(1 - a)h (1 - a)h2 /21 - /3 h - /3h12
1 -,Ih 1 -,/2-()Ih -()h2 /2
-sa]-s/3/h-s,lh2
s(l - ())
det[zI - <1>] =z4 + [(a - 3) + /3 + ,/2 - (() - 1)s]z3
+ [(3 - 2a) - /3 +,/2 + (3 - a - /3 -,/2 - 3())s]z2
+ [(a - 1) - (3 - 2a - /3 + ,/2 - 3())s]z + (1 - a - ())s.
- zV(z-s) 2Xl = det[zI _ Ill] {az + h'/2 + (3 - 2a)z + (,/2 - j1 +an,X = zV(z - l)(z - s) {/3 - /3 }/h
2 det[zI _ <1>] z +, ,x = zV{z - 1)2(z - s) Ih2
3 det[zI _ <p] , ,
andw= zV(z-1)3 ().
det[zI - 4.>]
224 Answers and Hints to Exercises
Xk = alXk-1 + a2 Xk-2 + a3x k-3 + a4Xk-4 + aVk
+ (-2a - sa + ,8 + , /2)Vk-1 + [a - ,8 +,/2+ (2a - ,8 - , /2)S]Vk-2 - (a - ,8 +,/2)SVk-3 ,
Xk = alxk-l + a2x k-2 + a3x k-3a4x k-4 + (,8/h)Vk
- [(2 + s),8/h - ,/h]Vk-1 + [,8/h - ,/h
+ (2,8 - ,)S/h]Vk-2 - [(,8 - ,)S/h]Vk-3,
Xk = alxk-l + a2x k-2 + a3x k-3 + a4x k-4 + (,/h)Vk
- [(2 + ,),/h2]Vk_1 + (1 + 2S)Vk-2 - SVk-3,
Wk = alwk-l + a2Wk-2 + a3Wk-3 + a4Wk-4
+ (,/h2)(Vk - 3Vk-1 + 3Vk-2 - Vk-3),
with the initial conditions X-I = X-I = X-I = Wo = 0,where
al = -a - ,8 -,/2 + (0 - l)s + 3,
a2 = 2a + {3 - ,/2 + (a + ,8h + ,/2 + 38 - 3)s - 3 ,a3 = -a + (-2a - ,8 +,/2 - 38 + 3)s + 1 ,
and
a4 = (a + 8 - l)s.
(d) The verification is straightforward.9.4. The verifications are tedious but elementary.9.5. Study (9.19) and (9.20). We must have ap,av,aa 2: 0, am >
0, and p > o.9.6. The equations can be obtained by elementary algebraic
manipulation.9.7. Only algebraic manipulation is required.
Chapter 10
10.1. For (1) and (4), let * E {+,-, .,/}. Then
X * Y = {x * ylx E X,y E Y}
= {y * xly E Y,x E x}=y*x.
The others can be verified in a similar manner. As to part(c) of (7), without loss of generality, we may only consider
Answers and Hints to Exercises 225
the situation where both x 2 0 and y 2 0 in X = [;f, x] andy = [y, y], and then discuss different cases of ± 2 0, z :::; 0,and ±--Z < o.
10.2. It is straightforward to verify all the formulas by definition. For instance, for part (j.1), we have
A1(BC) = [~AI(i,j) [~BjlClk]]
~ [~~AI(i,j)BjlClk]
= [t [tA1(i,j)Bjl] Clk]l=l J=l
= (A1B)C.
10.3. See: Alefeld, G. and Herzberger, J. (1983).10.4. Similar to Exercise 1.10.10.5. Observe that the filtering results for a boundary system
and any of its neighboring system will be inter-crossingfrom time to time.
10.6. See: Siouris, G., Chen, G. and Wang, J. (1997).
Chapter 11
11.1.1 2-t2
2 3-t + 3t --2
1 2 9-t -3t+2 2
o1 3-t6
1 3 2 2- - t + 2t - 2t + -2 3
1 3 2 22- t - 4t + lOt - -2 3
1 3 2 32- - t + 2t - 8t + -6 3
o
O:::;t<l
1:::;t<2
2:::;t<3
otherwise.
O:::;t<l
1::;t<2
2:::;t<3
3:::;t<4
otherwise.
226 Answers and Hints to Exercises
11.2.;j;;,(w) = C-i:-iW)n= e-inw/2 (si~1f2))n.
11.3. Simple graphs.11.4. Straightforward algebraic operations.11.5. Straightforward algebraic operations.
Subject Index
adaptive Kalman filtering 182
noise-adaptive filter 183
adaptive system
identification 113,115
affine model 49
a - {3 tracker 140
a - {3 - , tracker 136
a - {3 - , - () tracker 141,180
algorithm for real-time
application 105
angular displacement 111,129
ARMA (autoregressive
moving-average) process 31
ARMAX (autoregressive
moving-average model
with exogeneous inputs) 66
attracting point 111
augmented matrix 189
augmented system 76
azimuthal angular error 47
Bayes formula 12
Cholesky factorization 103
colored noise (sequence
or process) 67,76,141
conditional probability 12
controllability matrix 85
controllable linear system 85
correlated system and
measurement noise processes 49
covariance 13
Cramer's rule 132
decoupling formulas 131
decoupling of filtering
equation 131
Descartes rule of signs 140
determinant preliminaries 1
deterministic input sequence 20
digital filtering process 23
digital prediction process 23
digital smoothing estimate 178
digital smoothing process 23
elevational angular error 47
estimate 16
least-squares optimal
estimate 17
linear estimate 17
minimum trace variance
estimate 52
minimum variance
estimate 17,37,50
optimal estimate 17
optimal estimate
operator 53
unbiased estimate 17,50
event 8
simple event 8
expectation 9
conditional expectation 14
228 Subject Index
extended Kalman filter 108,110,115
FIR system 184
Gaussian white noise sequence 15,117
geometric convergence 88
IIR system 185
independent random variables 14
innovations sequence 35
inverse z-transform 133
Jordan canonical form 5,7
joint probability
distribution (function) 10
Kalman filter 20,23,33
extended Kalman filter 108,110,115
interval Kalman filter 154
limiting Kalman filter 77,78
modified extended Kalman filter 118
steady-state Kalman filter 77,136
wavelet Kalman filter 164
Kalman-Bucy filter 185
Kalman filtering equation
(algorithm, or process)
23,27,28,38,42,57,64,72-74,76,108
Kalman gain matrix 23
Kalman smoother 178
least-squares preliminaries 15
limiting (or steady-state)
Kalman filter 78
limiting Kalman gain matrix 78
linear deterministic/ stochastic
system 20,42,63,143,185
linear regulator problem 186
linear state-space (stochastic) system
21,33,67,78,182,187
LU decomposition 188
marginal probability
density function 10
matrix inversion lemma 3
matrix Riccati equation 79,94,132,134
matrix Schwarz inequality 2,17
minimum variance estimate 17,37,50
modified extended Kalman filter 118
moment 10
nonlinear model (system) 108
non-negative definite matrix 1
normal distribution 9
normal white noise sequence 15
observability matrix 79
observable linear system 79
optimal estimate 17
asymptotically optimal estimate 90
optimal estimate operator 53
least-squares optimal estimate 17
optimal prediction 23,184
optimal weight matrix 16
optimality criterion 21
outcome 8
parallel processing 189
parameter identification 115
adaptive parameter
identification algorithm 116
positive definite matrix 1
positive suqare-root matrix 16
prediction-correction 23,25,31,39,78
probablity preliminaries 8
probablity density function 8
conditional probability
density function 12
joint probability
density function 11
Gaussian (or normal) probability
density function -9,11
probability distribution 8,10
function 8
joint probability
distribution (function) 10
radar tracking model
(or system) 46,47,61,181
random sequence 15
randon signal 170
random variable 8
independent random variables 13
uncorrelated random variables 13
random vector 10
range 47,111
real-time application 61,73,93,105
real-time estimation/decomposition 170
real-time tracking 42,73,93,134,139
sample space 8
satellite orbit estimation 111
Schur complement technique 189
Schwarz inequality 2
matrix Schwarz inequality 2,17
vector Schwarz inequality 2
separation principle 187
sequential algorithm 97
Subject Index 229
square-root algorithm 97,103
square-root matrix 16,103
steady-state (or limiting)
Kalman filter 78
stochastic optimal control 186
suboptimal filter 136
systolic array 188
implementation 188
Taylor approximation 47,122
trace 5
uncorrelated random variables 13
variance 10
conditional variance 14
wavelets 164
weight matrix 15
optimal weight matrix 16
white noise sequence (process)
15,21,130
Gaussian (or normal) white
noise sequence 15,130
zero-mean Gaussian white
noise sequence 21
Wiener filter 184
z-transform 132
inverse z-transform 133