On Controllability of Linear Systems 1
|
|
- Shannon Lester
- 5 years ago
- Views:
Transcription
1 On Controllability of Linear Systems 1 M.T.Nair Department of Mathematics, IIT Madras Abstract In this article we discuss some issues related to the observability and controllability of linear systems. Mainly we consider the system in the setting of finite dimensional Euclidean spaces. We do make some remarks about the applicability of the methods in the setting of infinite dimensional Hilbert space as well. The content of this article is essentially taken from project report (cf. [2]) based on a series of lectures the author had given in the Department of Mathematics, IIT Bombay, in For the lectures I had essentially used the book by Russel [6]. For the expositions on infinite dimensional controllability in this article, I referred some portions from book by Pazy [5] and the recent book by Curtain and Zwart [1] were used. Key-Words: Observability, Controllability, Linear System, Transition matrix, Controllability Grammian. CONTENTS 1. Solution of a Linear System (a) Solution of homogeneous system (b) Solution of non-homogeneous system using transition matrix 2. Controllability: In Finite Dimensional Setting (a) Definition of controllability (b) Control operator and reachable set (c) Kalman s condition for controllability (d) Controllability Grammian and steering operator 3. Controllability: In Infinite Dimensional Setting (a) Some basics of semigroup theory (b) Mild solution and controllability (c) Least-square control (d) Approximate controllability 4. Observability 1 Lectures at IIST Trivandrum on Novemebr 28-29, 212, under the auspices of NPDE-TCA 1
2 1 Solution of a Linear System Consider a linear system ẋ(t) = A(t)x(t) + f(t), (1.1) where A(t) R n n, f(t) R m and x(t) R n for each t I := (a, b). THEOREM 1.1. (Existence and Uniqueness) If A( ) is continuous and f is locally integrable on I, then for every (, x ) I R n, there exists a unique absolutely continuous function x such that (1.1) is satisfied a.e. with x( ) = x. Proof. (Sketch) Existence: For each closed and bounded interval J I, use Picard s-type iterations to obtain x L 2 (J, R n ) satisfying x(t) = x + [A(s)x(s) + f(s)]ds, t J, and use fundamental theorem of Lebesgue integration to see that ẋ(t) = A(t)x(t) + f(t), x( ) = x. Uniqueness: First observe that ẏ(t) = A(t)y(t), ż(t) = A(t) z(t) = y(t), z(t) constant. Suppose x and x are solutions, and let y = x x. For τ J, let z as above with z(τ) = y(τ). Then we have x(τ) x(τ) 2 = y(τ), z(τ) = y( ), z( ) =. This is true for all τ J sothat x = y. Then the solution can be extended to all of I, by using the fact that I is a union of an increasing sequence of closed and bounded intervals. Throughout this article, we shall assume the conditions on A( ) and f as prescribed in the above theorem. In applications the forcing function f may be of the form f(t) = F (t, u(t)), t I, for some control function u belonging to some admissible set Ũ of functions defined on I so that by choosing it appropriately the state function would behave in a specified manner. In engineering and science applications, the function u also represent certain intrinsic property of the system - such as density, specific heat etc. Another issue of practical interest would be the following: Suppose we do not know the initial state x ; but we may be knowing an observation on x, namely, an output function w based on the state function x. Then the question of interest is: 2
3 From the knowledge of the out function w can we determine the state function x uniquely? We shall see that both the above issues are related to each other. First, let us recall some preliminaries on ODE. 1.1 Solution of homogeneous system Consider the system ẋ(t) = A(t)x(t), t (a, b). (1.2) THEOREM 1.2. The following hold: (i) There exists solutions ϕ 1,..., ϕ n for (1.2) such that they are linearly independent. (ii) For every s I, ϕ 1 (s),..., ϕ n (s) are linearly independent vectors in R n. (iii) Every solution of (1.2) is a linear combination of ϕ 1,..., ϕ n. Proof. (i) Let {e 1,..., e n } be the standard basis for R n. Then, by Theorem 1.1, for each j {1,..., n}, there exists a unique solution ϕ j for (1.2) such that ϕ j ( ) = e j. Since rank[ϕ 1 ( ) ϕ 2 ( ) ϕ n ( )] = rank[e 1 e 2 e n ] = n, it can be shown that ϕ 1,, ϕ n are linearly independent. (ii) Let ϕ 1,, ϕ n be as in (i), and let s (a, b). We show that ϕ 1 (s),, ϕ n (s) are linearly independent. Assume, for a moment, that ϕ 1 (s),, ϕ n (s) are linearly dependent or some s I. Then there exists non-zero (α 1,..., α n ) R n such that n i=1 α iϕ i (s) =. Note that ϕ := n i=1 α iϕ i is a solution of (1.2) which satisfies ϕ(t) = A(t)ϕ(t), ϕ(s) =. Hence, by Theorem 1.1, ϕ is the zero function. Consequently, ϕ 1,..., ϕ n are linearly dependent; a contradiction. Thus, we have shown that ϕ 1 (s),, ϕ n (s) are linearly independent. (ii) Suppose that ψ is any solution of (1.2) and x = ψ( ) for some (a, b). By (ii), ϕ 1 ( ),..., ϕ n ( ) are linearly independent in R n, and hence they form a a basis of R n. Let α 1,..., α n be in R such that ψ( ) = α 1 ϕ 1 ( ) + + α n ϕ n ( ). Note that ϕ := n i=1 α iϕ i is a solution of (1.2) which satisfies ϕ( ) = ψ( ). Again, by Theorem 1.1, ψ(t) = ϕ(t) for all t (a, b). Thus, ψ is a linear combination of ϕ 1,..., ϕ n. Thus, we have shown that {ϕ 1,..., ϕ n } is a basis for mathcalx. By the above theorem, the set of all solutions of (1.2), i.e., X := {x C 1 (a, b) : x is a solution of (1.2)} 3
4 is a vector space over R with dim(x ) = n. Consider the matrix Φ(t) := [ϕ 1 (t),..., ϕ n (t)], t I where ϕ 1,..., ϕ n are as in Theorem 1.2. By Theorem 1.2, Φ(t) is non-singular for every t I. Also, we hve Φ(t) = A(t)Φ(t). Definition 1.3. The matrix Φ(t) is called a fundamental matrix for the system (1.2). 1.2 Solution of non-homogeneous system using transition matrix Let Φ(t) be a fundamental matrix for the system (1.2). Abusing the notation, let us denote Φ(t, s) := Φ(t)Φ(s) 1 THEOREM 1.4. The function x(t) := Φ(t, )x is the solution of (1.2) satisfying x( ) = x. Proof. Clearly, and x( ) := Φ(, )x = x. ẋ(t) = Φ(t, )x = Φ(t)Φ( ) 1 x = A(t)Φ(t)Φ( ) 1 x = A(t)x(t) Definition 1.5. The matrix Φ(t, ) is called the transition matrix for (1.2). Observe that Φ(t, t) = I, Φ(t 1, t 2 )Φ(t 2, t 3 ) = Φ(t 1, t 3 ), d dtφ(t, s) = A(t)Φ(t, s). We may observe that if A(t) is a constant matrix, say A, then Φ(t, s) := e (t s)a. Remark 1.6. For a matrix A R n n and α R n, we define e A α = k= A k α. k! Of course one has to show the convergence of the above series: 4
5 Note that, if A = [a ij ], then so that Hence, Thus, This implies that (Aα) i (Aα) i = n a ij α j j=1 n ( n a ij α j a ij 2) 1/2( n α j 2) 1/2 ( n = a ij 2) 1/2 α. j=1 Aα 2 = j=1 i=1 Hence, for every m, l with l > m, l A k α k! j=1 i=1 j=1 j=1 n [ n n (Aα) i 2 a ij 2] α 2. [ n n Aα M α, M := a ij 2] 1/2. k=m i=1 j=1 A k α M k α k N. l k=m A k α k! k= ( l k=m M k ) α. k! Thus, the series k= Ak α k! is convergent in R n, and hence the linear transformation e A : R n R n is well defined as ( N ) e A A k α := lim α. N k! THEOREM 1.7. The function is the solution of (1.1) with x( ) = x. t x(t) := Φ(t, )x + Φ(t, s)f(s)ds Proof. Let x(t) be as in the theorem. Since Φ(t, s) = Φ(t, )Φ(, s), we have Hence, t x(t) = Φ(t, )x + Φ(t, ) Φ(, s)f(s)ds. t ẋ(t) = Φ(t, )x + Φ(t, ) Φ(, s)f(s)ds + Φ(t, )Φ(, t)f(t) = A(t)Φ(t, )x + A(t)Φ(t, ) = A(t)x(t) + f(t), a.e.. t Φ(, s)fu(s)ds + f(t) 5
6 Thus, is the solution of (1.1) with x( ) = x. t x(t) := Φ(t, )x + Φ(t, s)f(s)ds 2 Controllability: In Finite Dimensional Setting 2.1 Definition of controllability As pointed out in the last section, in applications the forcing function f(t) may be of the form f(t) = F (t, u(t)), t I for some control function u(t) R m belonging to some admissible set Ũ of functions. We shall deal only the case when u F (t, u) is linear, i.e., there exists B(t) R n m such that F (t, u(t)) = B(t)u(t), t I. Also, we shall take Ũ to be the space L2 := L 2 (J, R m ), where J = [, t 1 ]. 2.2 Control operator and reachable set Definition 2.1. The system ẋ(t) = A(t)x(t) + B(t)u(t) (2.3) is said to be controllable over J := [, t 1 ] if for every x, x 1 R n, there exists u L 2 (J, R m ) such that x( ) = x, x(t 1 ) = x 1, and in that case u is called a control. By Theorem 1.7, the solution x(t) of (2.3) with x( ) = x is given by t x(t) := Φ(t, )x + Φ(t, s)f(s)ds For a give, t 1 I, let us define an operator from C : L 2 (J, R m ) R n by Cu := Φ(t 1, s)b(s)u(s)ds. THEOREM 2.2. The system (2.3) is controllable if and only if the operator C is onto, and in that case any u L 2 (J, R m ) such that Cu = x 1 Φ(t 1, )x is a control. 6
7 Proof. Recall that for a give u L 2 (J, R m ), the solution of ẋ(t) = A(t)x(t) + B(t)u(t) with x( ) = x is given by t x(t) := Φ(t, )x + Φ(t, s)b(s)u(s)ds. Hence, (2.3) is controllable if and only if there exists u L 2 (J, R m ) such that Cu = x 1 Φ(t 1, )x. In view of the above theorem, we have the following definition. Definition 2.3. The operator C defined above is called the control operator, and the set R(C), the range of C, is called the reachable set corresponding to the system (2.3). We have already observed that if A(t) is a constant matrix A, then Φ(t, s) = e (t s)a. Thus, if A(t) and B(t) are constant matrices A and B, respectively, then the system (2.3) takes the form and the operator C is given by Cu := ẋ(t) = Ax(t) + Bu(t) Example 2.4. (i) Consider the differential equation e (t1 s)a Bu(s)ds. ẋ(t) = x(t) + u(t). Then we know that the the solution x(t) satisfying x( ) = x is given by t x(t) = x e t t + e t s u(s)ds. Thus, the control problem is to find a function u such that That is to find u such that x 1 := x(t 1 ) = x e t1 t + e t1 s u(s)ds. e s u(s)ds = e t1 [x 1 x e t1 t ]. Note that F : u t 1 e s u(s)ds is a nonzero linear functional on L 2 (J, R), and hence it is surjective. Hence, there exists u L 2 (J, R) such that F (u) = e t1 [x 1 x e t1 t ]. (ii) Consider the system ẋ(t) = Ax(t) + Bu(t), [ ] [ ] 1 1 where A = and B =. Equivalently, 1 ẋ 1 (t) = x 1 (t) + u ẋ 2 (t) = x 2 (t). 7
8 In this case the system is not controllable: [ Suppose that the requirement on u is such that x( ) = [ ] and β 1 β 2 α 1 α 2 ] and x(t 1 ) = [ β 1 β 2 ] for some given. We know that there exists u such that x 1 ( ) = α 1 and x 1 (t 1 ) = β 1, and x 2 (t) = α 2 e t t. Hence, x 2 (t 1 ) = α 2 e t1 t. This quantity need not be equal to β 2. [ α 1 α 2 ] 2.3 Kalman s condition for controllability The above examples shows the necessity of prescribing conditions on (A, B) so that the system is controllable. We prescribe one such condition now. THEOREM 2.5. (Kalman s condition) Suppose A(t) and B(t) are constant matrices A and B, respectively. Then the system (2.3) is controllable if and only if rank[b AB A 2 B A n 1 B] = n. Proof. Let K = [B AB A 2 B A n 1 B]. Then rank(k) = n if and only if K : R mn R n is onto, if and only if K is one-one; i.e., if and only if, for y R n, K y = implies y =, i.e., if and only if y K = implies y =. Now, suppose that C is not onto, i.e., R(C) {}. Then there exists nonzero β R n such that Cu, β R n = for all u L 2 (J, R m ) i.e., In particular, taking u(s) = B e (t1 s)a β, we get e (t1 s)a Bu(s), β R nds = u L 2 (J, R m ). i.e., e (t1 s)a BB e (t1 s)a β, β R nds = u L 2 (J, R m ), B e (t1 s)a β, B e (t1 s)a β R nds = u L 2 (J, R m ), i.e., the function z(s) = B e (t1 s)a β satisfies z, z L 2 =. Hence z =, i.e., β e (t1 s)a B =. Since e (t1 s)a (t 1 s) k = I + A k, k! k=1 ( ) we have Thus, β e (t1 s)a B = β (t 1 s) k B + β A k B. k! k=1 β e (t1 s)a B = = y A k B = k N = β K = 8
9 so that K α, β = β K α = α R mn. Thus, K is not onto. Conversely, suppose K is not onto. Then there exists β such that y K =. Hence, using Cayley-Hamilton theorem and ( ), we obtain y K = = y A k B = k N = y e (t1 s)a B =. Hence, for every u L 2 (J, R m ), y e (t1 s)a Bu(s)ds =, i.e., Cu, y = for every u L 2. Thus, C is not onto. Note that in Example 2.4, we have [[ ] [ ] [ ]] [ ] K = [B AB] = =, 1 1 so that rank(k) = 1 < 2. Example 2.6. Consider the equation of the harmonic oscillator: ÿ + y = u, [ ] [ ] [ ] y 1 i.e., ẋ = Ax + Bu, where x =, A = and B =. In this case, y 1 1 [ ] 1 K = [B AB] = 1 so that rank(k) = 2. Hence, the system is controllable. 2.4 Controllability Grammian and steering operator We observe that CC is a non-negative self-adjoint linear operator from R n to itself. THEOREM 2.7. The system (2.3) is controllable over [, t 1 ] if and only if CC is positive definite, and in that case u = C (CC ) 1 [x 1 Φ(t 1, )x ] defines a control. Further, this control is the one having least norm. Proof. Since R(C ) is closed, by Projection Theorem, for every u L 2 (J, R m ), Cu = C(u 1 + u 2 ) 9
10 with u 1 R(C ), u 2 R(C ) = N(C). Hence, Cu = Cu 1 R(CC ) u L 2 (J, R m ). Thus, R(C) = R(CC ). Since CC is a linear operator from R n to itself, we have C is onto CC is bijective CC positive defiite. Thus, (2.3) is controllable if and only if CC is bijective, and in that case u := C (CC ) 1 [x 1 Φ(t 1, )x ]. satisfies Note that Cu = CC (CC ) 1 [x 1 Φ(t 1, )x ] = x 1 Φ(t 1, )x. u R(C ) = N(C). Hence, by projection theorem for Hilbert spaces, This completes the proof. u L 2 = inf{ v L 2 : v L 2, Cv = x 1 }. Let us see how C looks: Recall that Cu := Then for every β R n, Cu, β R n = = Φ(t 1, s)b(s)u(s)ds, u L 2. = u, C β. Φ(t 1, s)b(s)u(s), β R n ds u(s), B(s) Φ(t 1, s) β R n ds Thus, and hence i.e., CC β = CC = (C β)(s) = B(s) Φ(t 1, s) β, Φ(t 1, s)b(s)b(s) Φ(t 1, s) β ds, Φ(t 1, s)b(s)b(s) Φ(t 1, s) ds. 1
11 Definition 2.8. The matrix CC = Φ(t 1, s)b(s)b(s) Φ(t 1, s) ds. is called the controllability grammian for (2.3). Example 2.9. Consider the Example 2.4: ẋ(t) = x(t) + u(t). In this case, Thus, Φ(t, s) = e t s, B = [1]. (C β)(s) = e t1 s β, β R n CC = Φ(t 1, s)b(s)b(s) Φ(t 1, s) ds = e 2(t1 s) ds, (CC ) 1 α α = e 2(t1 s) ds, α Rn u(s) = C (CC ) 1 [x 1 Φ(t 1, )x ](s) = C (CC ) 1 [x 1 e t1 t x ](s) = et1 s [x 1 e t1 t x ] e 2(t1 s) ds Of course, in this case, we obtain the control from the definition of C, since is satisfied for We observe that whereas Note that so that Cu := Φ(t 1, s)b(s)u(s)ds = u(s) 2 ds = ũ(s) 2 ds = ( t 1 ũ := x 1 e t1 t x e t1 s ds. e t1 s u(s)ds = x 1 e t1 t x e 2(t1 s) x 1 e t1 t x 2 ( t 1 = x 1 x et1 t 2 e 2(t1 s) ds) 2 t1 e 2(t1 s) ds, x 1 e t1 t x 2 ( t 1 = x 1 et1 t x 2 (t 1 ) e t1 s ds) 2 ( t 1. e t1 s ds) 2 ) 2 e t1 s ds ( e 2(t1 s) ds)(t 1 ) u(s) 2 ds ũ(s) 2 ds. 11
12 LEMMA 2.1. The function y(t) := Φ(τ, t) x τ is the solution of ẏ(t) = A(t) y(t), y(τ) = x τ. Proof. For α R n, let x(t) = Φ(t, τ)α and let y(t) = Φ(τ, t) x τ. Note that But, x τ, α = x τ, Φ(τ, t)φ(t, τ)α = Φ(τ, t) x τ, Φ(t, τ)α = y(t), x(t). d y(t), x(t) dt = ẏ(t), x(t) + y(t), ẋ(t) = ẏ(t), x(t) + y(t), A(t)x(t) = ẏ(t), x(t) + A(t) y(t), x(t) = ẏ(t) + A(t) y(t), Φ(t, τ)α = Φ(t, τ) [ẏ(t) + A(t) y(t)], α. Thus, Φ(t, τ) [ẏ(t) + A(t) y(t)], α = for every α R n so that Φ(t, τ) [ẏ(t) + A(t) y(t)] =. Since Φ(t, τ) is an invertible matrix, we have This completes the proof. ẏ(t) + A(t) y(t) =. Definition The system ẏ(t) = A(t) y(t) (2.4) is called the dual of the system ẋ(t) = A(t)x(t). THEOREM The following are equivalent: 1. The system (2.3) is controllable over [, t 1 ]. 2. There exists c > such that B(s) Φ(t 1, s) α 2 ds c α 2 α R n. 3. The columns of B(t) Φ(t 1, t) are linearly independent functions. Proof. By Theorem 2.7, The system (2.3) is controllable over J if and only if CC is positive definite. Observe that for α R n, CC α, α = Φ(t 1, s)b(s)b(s) Φ(t 1, s) α, α ds = From the above relation, we obtain the equivalence. B(s) Φ(t 1, s) α 2 ds. 12
13 Recall that the adjoint of the operator C : L 2 (J, R m ) R n, is given by Cu := Φ(t 1, s)b(s)u(s)ds, u L 2. (C β)(s) = B(s) Φ(t 1, s) β, Hence, the inequality in Theorem 2.12 can be written as i.e., i.e., the operator C is bounded below. C α)(s) 2 ds c α 2 α R n, C α 2 L 2 (J,R m ) c α 2 R n α Rn, We know that the system (2.3) is controllable over J if and only if CC is positive definite. What can we say if it is not controllable? THEOREM The operator S = (C C) 1 C is well-defined. Given x 1 R n, let x 1 := x 1 Φ(t 1, )x and let u = S x 1. Then equivalently, and Cu x 1 = inf{ Cu x 1 : v L 2 (J, R m )}; C Cu = C x 1, u = inf{ v : C Cv = C x 1 }. Proof. We observe that, since R(C ) = N(C), the operator C C is injective on R(C ). Hence, the operator S = (C C) 1 C is well-defined. Also, u := Su satisfies C Cu = C x 1. Hence, equivalently, Cu x 1 = inf{ Cu x : v L 2 (J, R m )}. Further, since u R(C ) = N(C), we have u = inf{ v : C Cu = C x 1 }. Definition The operator S := (C C) 1 C is called the steering operator for the control system (2.3). Remark Note that the steering operator S defined above is the Moore-Penrose generalized inverse of the operator C. 13
14 3 Controllability: In Infinite Dimensional Setting Let us consider the system (2.3), when the space of values of the state function and control function are infinite dimensional. We shall consider only the time-independent case. More precisely, we consider the system ẋ(t) = Ax(t) + Bu(t), x() = x (3.5) for some given x X, where A : D(A) X X is a densely defined closed linear operator defined in a Hilbert space X and B : X U is a bounded linear operator between Hilbert spaces X and U, and t J := [, τ] for some τ >. Example 3.1. Consider the PDE: w t = 2 w + v(s, t), < s < l, t >, s2 with boundary conditions: w(, t) = = w(l, t). Taking X = U = L 2 (, l), and writing x(t) = w(, t), u(t) = v(, t), [Ax(t)](s) = 2 w s 2, the above PDE can be written as ẋ(t) = Ax(t) + u(t), where D(A) = {z L 2 (, l) : z L 2 (, l), z() = = z(l)}. Definition 3.2. The system (3.5) is said to be exactly controllable if for every x τ X, there exists u L 2 (J, U) such that there exists a differentiable function x L 2 (J, X) satisfying (3.5) and the condition x(τ) = x τ. 3.1 Some basics of semigroup theory To address the controllability issues in the above setting, we may recall certain results from the theory of semi-groups (cf. Pazy [5]): Definition 3.3. Let X be a Banach space over K which is either R or C. A family T := {T (t) : t } of bounded linear operators on X is called a strongly continuous semi-group or C -semi-group if 1. T () = I, 2. T (t + s) = T (t)t (s) t, s, 14
15 3. T (t)x x as t for every x X. Example 3.4. If X = R n and A R n n, then T (t) = e ta := I + k=1 t k k! Ak defines a C -semigroup. Further, it may be observed that if A is a diagonal matrix with diagonal entries as λ 1,..., λ n, then A k e j = λ k j e j for j = 1,..., n and for evert k N. Hence, in this case, T (t)e j = e ta e j = e j + k=1 t k k! Ak e j = e tλj e j. Thus, for every α R n, and n T (t)α = e ta α = e tλj α j e j. j=1 Example 3.5. If X be a Banach space and A : X X be a bounded linear operator. As in the last example, let T (t) = e ta := I + k=1 t k k! Ak. Then {T (t) : t } defines a C -semigroup. Since A k A k for every k N, it can be shown that e ta is well-defined bounded linear operator on X. THEOREM 3.6. If {T (t) : t } is a strongly continuous semi-group on X and if then A : D X defined by D := {x X : lim t T (t)x x t exists }, T (t)x x Ax = lim, x D, t t is a closed densely defined linear operator. Further, we have the following: 1. For every x D, t T (t)x is differentiable on (, ) and 2. There exists M 1 ω such that d T (t)x = AT (t)x, t >. dt T (t) Me ωt t. 15
16 By the above theorem, for every x D, the function x(t) := T (t)x, t, is a solution of the homogeneous differential equation ẋ(t) = Ax(t), x() = x. Definition 3.7. The operator A defined in Theorem 3.6 is called the infinitesimal generator of the semi-group T. Example 3.8. Let X be a separable Hilbert space and {v n : n N} be an orthonormal basis for X. Let (λ n ) be a sequence of positive real real numbers. For t, define T (t)x = e λnt x, v n v n, x X. n=1 Then, it can be seen that {T (t) : t } is a strongly continuous semigroup and its infinitesimal generator A is defined by Ax = λ n x, v n v n, x D, where D := {x X : λ 2 n x, v n 2 < }. n=1 n=1 Any mention of semi-group would be incomplete if one does not mention Hill-Yosida theorem which states a necessary and sufficient condition for a linear operator to be the infinitesimal generator of a strongly continuous semi-group. THEOREM 3.9. (Hille-Yosida theorem) A linear operator A : D(A) X X is the infinitesimal generator of a strongly continuous semi-group {T (t)} satisfying T (t) Me ωt for some M 1 and ω if and only if A is a closed densely defined operator, the resolvent set ρ(a) contains (ω, ) and (λi A) n M (λ ω) n λ > ω, n N. In view of Theorem 3.6, for every x D, the function x : J X defined by x(t) := T (t)x, t > is a solution of ẋ(t) = Ax(t), x() = x, (3.6) where A is the infinitesimal generator of {T (t)}. In fact, it is known that the solution of the Cauchy problem (3.6) is unique. 16
17 3.2 Mild solution and controllability In the following we assume that X is a Hilbert space. Now, let A be the infinitesemial generator A of a strongly continuous semi-group {T (t) : t }. For f L 2 (J, X), consider the non-homogeneous system ẋ(t) = Ax(t) + f(t), x() = x. (3.7) THEOREM 3.1. If (3.7) has a solution x, then it is given by x(t) = T (t)x + t T (t s)f(s) ds, t J. Definition For f L 2 (J, X), the function x defined by x(t) = T (t)x + is called a mild solution of (3.7). t T (t s)f(s) ds, t J, (3.8) Facts: A mild solution need not be a solution. If f L 2 (J, X) C 1 (J, X), then every mild solution is a solution. Now, let us consider the control system for u L 2 (J, U). Define K : L 2 (J, U) X by ẋ(t) = Ax(t) + Bu(t), (3.9) Let and Ku = τ T (τ s)bu(s) ds, u L 2 (J, U). L 2 (J, U) := {u L 2 (J, U) : T ( )x + Ku is a solution of (3.9)}. K u = Ku for u L 2 (J, U). THEOREM The system (3.9) is controllable if and only if K is surjective. Although a mild solution of (3.7) need not be a solution, most often, in the infinite dimensional setting, one looks for a control function u such that x(τ) = T (τ)x + So, we introduce the following definition. τ T (τ s)bu(s) ds. 17
18 Definition The system (3.9) is said to be controllable if for every x τ X, there exists u L 2 (J, U) such that x(τ) = T (τ)x + τ T (τ s)bu(s) ds. THEOREM The system (3.9) is controllable if and only if K is surjective. THEOREM The system (3.9) is controllable if and only if there exists c > such that K x L2 (J,U) c x X x X, and in that case, u := K (KK ) 1 [x τ T (τ)x ] defines a a control. Proof. First we recall the following relations R(K) = N(K ), R(K) = N(K ) and the fact, known as closed range theorem (cf. Nair [3], Theorem 11.5, page 355), that R(K) closed R(K ) closed. Suppose the system (3.9) is controllable. Then K : L 2 (J, U) X is surjective, so that its adjoint K : X L 2 (J, U) is injective and R(K ) is closed. Hence, by bounded inverse theorem, inverse of K is a bounded operator. Therefore, there exists c > such that K x c x for all x X. Conversely, suppose there exists c > such that K x c x for all x X. Then, K is injective and R(K ) is closed. Hence, R(K) is closed and R(K) = R(K) = N(K ) = {} = X. Thus, the system (3.9) is controllable. To see the expression for a control, we observe that, for x X, K x c x KK x, x c 2 x 2. Hence, KK is injective, so that R(KK ) dense. Also, since R(K ) is closed, for every u L 2 (J, U), Ku = K(u 1 + u 2 ) with u 1 R(K ), u 2 R(K ) = N(K) so that Thus, Ku = Ku 1 R(KK ). R(KK ) = R(K) = X. Therefore, KK : X X is bijective. Thus, u is well-defined and and hence, x τ = T (τ)x + Ku. Ku = KK (KK ) 1 [x τ T (τ)x ] = x τ T (τ)x 18
19 Now, let us give an expression for K and KK Note that for every u L 2 (J, U) and x X, Hence, Ku, x = = τ τ T (τ s)bu, x ds u, B T (τ s) x ds. (K x)(s) = B T (τ s) x, s J, and KK x = τ T (τ s)bb(s) T (τ s) x ds, x X. The above operator is also called the controllability grammian for the system (3.9). Thus the condition for mild controllability in Theorem 3.15 can be written as τ 3.3 Least-square control B(s) T (τ s) x 2 ds c 2 x 2, x X. Suppose the system (3.9) is not controllable. Then the range of the control operator is not the whole of X. More over R(K) need not be closed. Then what we look for is a function u L 2 (J, U) such that where x τ := x τ T (τ)x. Ku x τ = inf Kv x τ, v L 2 (J,U) In this regard, we have the following result from Hilbert-space theory: THEOREM Let x τ := x τ T (τ)x and u L 2 (J, U). Then the following are equivalent: 1. Ku x τ = inf v L 2 (J,U) Kv x τ, 2. K Ku = K x τ, 3. x τ R(K) + R(K). Definition A function u L 2 (J, U) is called a least-square control for the system (3.9) if Ku x τ = inf Kv x τ, v L 2 (J,U) where x τ := x τ T (τ)x. THEOREM If x τ R(K) + R(K), then there exists a unique least-square control ũ which minimizes the norm, and it is given by ũ = (K K) 1 K x τ. 19
20 3.4 Approximate controllability As in last section consider the control system ẋ(t) = Ax(t) + Bu(t), x() = x (3.1) for some given x X, where A : D(A) X X is a densely defined closed linear operator defined in a Hilbert space X which is the infinitesimal generator of a strongly continuous semi-group {T (t) : t }, B : X U is a bounded linear operator between Hilbert spaces X and U, and t J := [, τ] for some τ >. We have seen that the system (3.1) is controllable if and only if K is surjective, where Ku = τ T (τ s)bu(s) ds, u L 2 (J, U). Suppose (3.1) is not controllable. Definition The system (3.1) is approximately controllable if for every ε >, there exists u ε L 2 (J, U) such that the corresponding mild solution x ε (τ) := Ku ε + T (τ)x satisfies x ε (τ) x τ < ε, i.e., if and only if R(K) is dense in X. 4 Observability We shall link controllability of (2.3) with another concept, namely, the observability of another system. Definition 4.1. The system along with an output function ẋ(t) = A(t)x(t) + f(t) (4.11) w(t) = H(t)x(t). (4.12) is said to be observable if and only if w = = x =. Note that observability is about the reconstruction of the state x(t) in a unique manner from some attribute of it in the form of an output function w(t). Since the state function x(t) in (4.11) is completely determined by the initial state x := x( ), 2
21 THEOREM 4.2. The system (4.11)-(4.13) is observable if and only if w = = x( ) =. In particular, we have the following: THEOREM 4.3. The system ẋ(t) = A(t)x(t), w(t) = H(t)x(t) (4.13) is observable if and only if the columns of H(t)Φ(t, ) are linearly independent. Proof. Recall that the solution x(t) of ẋ(t) = A(t)x(t), x( ) = x, is given by x(t) = Φ(t, )x. Hence, the observability condition given in Theorem 4.2 is satisfied if and only if columns of H(t)Φ(t, ) are linearly independent. Let us define the operator O : R n L 2 (J, R n ) by (Oα)(t) := H(t)Φ(t, )α, α R n, t J. In terms of the operator O we have the following characterization: THEOREM 4.4. The system (4.13) is observable if and only if O is injective. How do we recover the state function x from the output function? Let us compute the adjoint of O: For every α R n, v L 2 (J, R n ), we have Oα, v = H(t)Φ(t, )α, v(t) dt J = α, Φ(t, ) H(t) v(t) dt J = α, Φ(t, ) H(t) v(t)dt. Thus, O v = Φ(t, ) H(t) v(t)dt. J J THEOREM 4.5. The system The system (4.13) is observable if and only if O O is positive definite and in that case for w R(O), α := (O O) 1 O w satisfies Oα = w. 21
22 Proof. By Theorem 4.4, (4.13) is observable if and only if O is injective. But, O is injective if and only if O is surjective, and in that case O O is positive definite. For w R(O), let α := (O O) 1 O w. Then we have (O O)α = O w. But, O is injective on R(O): (O O)β = = β = = Oβ =. Hence, we have Oα = w. This completes the proof. Definition 4.6. The operator R : L 2 (J, R m defined by Rw := (O O) 1 O w is called the reconstruction operator for the system (4.13). Remark 4.7. Note that the reconstruction operator is the Moore-Penrose generalized inverse of the operator O. 5 Relation Between Controllability and Observability THEOREM 5.1. The system (2.3) is controllable over [, t 1 ] if and only if the system y(t) = A(t) y(t), w(t) = B(t) y(t) is observable. Proof. By Lemma 2.1, is the solution of Hence, y(t) = Φ(t 1, t) α y(t) = A(t) y(t), y(t 1 ) = α. w(t) = B(t) Φ(t 1, t) α. Hence, By Theorem 4.3, y(t) = A(t) y(t), w(t) = B(t) y(t) is observable if and only if the columns of B(t) Φ(t 1, t) are linearly independent functions, and by Theorem 2.12, columns of B(t) Φ(t 1, t) are linearly independent functions if and only if (2.3) is controllable over [, t 1 ]. 22
23 References [1] Ruth F. Curtain, Hans Zwart, An Introduction to Infinite-Dimensional Linear Systems Theory, Springer Verlag, [2] M.T. Nair, Observability and Controllability of Linear Systems, Lecture Notes, IIT Bombay, 1986 (Pre-Print) [3] M.T. Nair, Functional Analysis: A First Course, Printice-Hall of India, New Delhi, 22. [4] M.T. Nair, Linear Operator Equations: Approximation and Regularization, World Scientific, Singapore, May 29. [5] A. Pazy, Semigroups of Linear Operators and Applications to Partial Differential Equations, Springer-Verlag, New York, [6] D.L. Russel, Mathematics of finte dimensional Control Systems, Marcel Decker Inc., New York,
Control, Stabilization and Numerics for Partial Differential Equations
Paris-Sud, Orsay, December 06 Control, Stabilization and Numerics for Partial Differential Equations Enrique Zuazua Universidad Autónoma 28049 Madrid, Spain enrique.zuazua@uam.es http://www.uam.es/enrique.zuazua
More informationANALYTIC SEMIGROUPS AND APPLICATIONS. 1. Introduction
ANALYTIC SEMIGROUPS AND APPLICATIONS KELLER VANDEBOGERT. Introduction Consider a Banach space X and let f : D X and u : G X, where D and G are real intervals. A is a bounded or unbounded linear operator
More informationMath Ordinary Differential Equations
Math 411 - Ordinary Differential Equations Review Notes - 1 1 - Basic Theory A first order ordinary differential equation has the form x = f(t, x) (11) Here x = dx/dt Given an initial data x(t 0 ) = x
More informationControl Systems Design, SC4026. SC4026 Fall 2009, dr. A. Abate, DCSC, TU Delft
Control Systems Design, SC4026 SC4026 Fall 2009, dr. A. Abate, DCSC, TU Delft Lecture 4 Controllability (a.k.a. Reachability) vs Observability Algebraic Tests (Kalman rank condition & Hautus test) A few
More informationGrammians. Matthew M. Peet. Lecture 20: Grammians. Illinois Institute of Technology
Grammians Matthew M. Peet Illinois Institute of Technology Lecture 2: Grammians Lyapunov Equations Proposition 1. Suppose A is Hurwitz and Q is a square matrix. Then X = e AT s Qe As ds is the unique solution
More informationDeterministic Dynamic Programming
Deterministic Dynamic Programming 1 Value Function Consider the following optimal control problem in Mayer s form: V (t 0, x 0 ) = inf u U J(t 1, x(t 1 )) (1) subject to ẋ(t) = f(t, x(t), u(t)), x(t 0
More informationControl Systems Design, SC4026. SC4026 Fall 2010, dr. A. Abate, DCSC, TU Delft
Control Systems Design, SC4026 SC4026 Fall 2010, dr. A. Abate, DCSC, TU Delft Lecture 4 Controllability (a.k.a. Reachability) and Observability Algebraic Tests (Kalman rank condition & Hautus test) A few
More informationA Spectral Characterization of Closed Range Operators 1
A Spectral Characterization of Closed Range Operators 1 M.THAMBAN NAIR (IIT Madras) 1 Closed Range Operators Operator equations of the form T x = y, where T : X Y is a linear operator between normed linear
More information2. Review of Linear Algebra
2. Review of Linear Algebra ECE 83, Spring 217 In this course we will represent signals as vectors and operators (e.g., filters, transforms, etc) as matrices. This lecture reviews basic concepts from linear
More informationThe first order quasi-linear PDEs
Chapter 2 The first order quasi-linear PDEs The first order quasi-linear PDEs have the following general form: F (x, u, Du) = 0, (2.1) where x = (x 1, x 2,, x 3 ) R n, u = u(x), Du is the gradient of u.
More informationApplied Math Qualifying Exam 11 October Instructions: Work 2 out of 3 problems in each of the 3 parts for a total of 6 problems.
Printed Name: Signature: Applied Math Qualifying Exam 11 October 2014 Instructions: Work 2 out of 3 problems in each of the 3 parts for a total of 6 problems. 2 Part 1 (1) Let Ω be an open subset of R
More informationZ i Q ij Z j. J(x, φ; U) = X T φ(t ) 2 h + where h k k, H(t) k k and R(t) r r are nonnegative definite matrices (R(t) is uniformly in t nonsingular).
2. LINEAR QUADRATIC DETERMINISTIC PROBLEM Notations: For a vector Z, Z = Z, Z is the Euclidean norm here Z, Z = i Z2 i is the inner product; For a vector Z and nonnegative definite matrix Q, Z Q = Z, QZ
More informationALMOST PERIODIC SOLUTIONS OF HIGHER ORDER DIFFERENTIAL EQUATIONS ON HILBERT SPACES
Electronic Journal of Differential Equations, Vol. 21(21, No. 72, pp. 1 12. ISSN: 172-6691. URL: http://ejde.math.txstate.edu or http://ejde.math.unt.edu ftp ejde.math.txstate.edu ALMOST PERIODIC SOLUTIONS
More informationTHE PERRON PROBLEM FOR C-SEMIGROUPS
Math. J. Okayama Univ. 46 (24), 141 151 THE PERRON PROBLEM FOR C-SEMIGROUPS Petre PREDA, Alin POGAN and Ciprian PREDA Abstract. Characterizations of Perron-type for the exponential stability of exponentially
More informationThe goal of this chapter is to study linear systems of ordinary differential equations: dt,..., dx ) T
1 1 Linear Systems The goal of this chapter is to study linear systems of ordinary differential equations: ẋ = Ax, x(0) = x 0, (1) where x R n, A is an n n matrix and ẋ = dx ( dt = dx1 dt,..., dx ) T n.
More informationChapter 4 Optimal Control Problems in Infinite Dimensional Function Space
Chapter 4 Optimal Control Problems in Infinite Dimensional Function Space 4.1 Introduction In this chapter, we will consider optimal control problems in function space where we will restrict ourselves
More informationLeft invertible semigroups on Hilbert spaces.
Left invertible semigroups on Hilbert spaces. Hans Zwart Department of Applied Mathematics, Faculty of Electrical Engineering, Mathematics and Computer Science, University of Twente, P.O. Box 217, 75 AE
More informationECEN 605 LINEAR SYSTEMS. Lecture 7 Solution of State Equations 1/77
1/77 ECEN 605 LINEAR SYSTEMS Lecture 7 Solution of State Equations Solution of State Space Equations Recall from the previous Lecture note, for a system: ẋ(t) = A x(t) + B u(t) y(t) = C x(t) + D u(t),
More informationCriterions on periodic feedback stabilization for some evolution equations
Criterions on periodic feedback stabilization for some evolution equations School of Mathematics and Statistics, Wuhan University, P. R. China (Joint work with Yashan Xu, Fudan University) Toulouse, June,
More informationOn Semigroups Of Linear Operators
On Semigroups Of Linear Operators Elona Fetahu Submitted to Central European University Department of Mathematics and its Applications In partial fulfillment of the requirements for the degree of Master
More informationA Concise Course on Stochastic Partial Differential Equations
A Concise Course on Stochastic Partial Differential Equations Michael Röckner Reference: C. Prevot, M. Röckner: Springer LN in Math. 1905, Berlin (2007) And see the references therein for the original
More informationSEMIGROUP APPROACH FOR PARTIAL DIFFERENTIAL EQUATIONS OF EVOLUTION
SEMIGROUP APPROACH FOR PARTIAL DIFFERENTIAL EQUATIONS OF EVOLUTION Istanbul Kemerburgaz University Istanbul Analysis Seminars 24 October 2014 Sabanc University Karaköy Communication Center 1 2 3 4 5 u(x,
More informationAPPROXIMATE CONTROLLABILITY OF DISTRIBUTED SYSTEMS BY DISTRIBUTED CONTROLLERS
2004 Conference on Diff. Eqns. and Appl. in Math. Biology, Nanaimo, BC, Canada. Electronic Journal of Differential Equations, Conference 12, 2005, pp. 159 169. ISSN: 1072-6691. URL: http://ejde.math.txstate.edu
More informationTheorem 1. ẋ = Ax is globally exponentially stable (GES) iff A is Hurwitz (i.e., max(re(σ(a))) < 0).
Linear Systems Notes Lecture Proposition. A M n (R) is positive definite iff all nested minors are greater than or equal to zero. n Proof. ( ): Positive definite iff λ i >. Let det(a) = λj and H = {x D
More information3 Compact Operators, Generalized Inverse, Best- Approximate Solution
3 Compact Operators, Generalized Inverse, Best- Approximate Solution As we have already heard in the lecture a mathematical problem is well - posed in the sense of Hadamard if the following properties
More informationIntroduction to Optimal Control Theory and Hamilton-Jacobi equations. Seung Yeal Ha Department of Mathematical Sciences Seoul National University
Introduction to Optimal Control Theory and Hamilton-Jacobi equations Seung Yeal Ha Department of Mathematical Sciences Seoul National University 1 A priori message from SYHA The main purpose of these series
More information1.4 The Jacobian of a map
1.4 The Jacobian of a map Derivative of a differentiable map Let F : M n N m be a differentiable map between two C 1 manifolds. Given a point p M we define the derivative of F at p by df p df (p) : T p
More informationExamples include: (a) the Lorenz system for climate and weather modeling (b) the Hodgkin-Huxley system for neuron modeling
1 Introduction Many natural processes can be viewed as dynamical systems, where the system is represented by a set of state variables and its evolution governed by a set of differential equations. Examples
More informationStabilization of Heat Equation
Stabilization of Heat Equation Mythily Ramaswamy TIFR Centre for Applicable Mathematics, Bangalore, India CIMPA Pre-School, I.I.T Bombay 22 June - July 4, 215 Mythily Ramaswamy Stabilization of Heat Equation
More informationLinear System Theory
Linear System Theory Wonhee Kim Chapter 6: Controllability & Observability Chapter 7: Minimal Realizations May 2, 217 1 / 31 Recap State space equation Linear Algebra Solutions of LTI and LTV system Stability
More informationObservability and state estimation
EE263 Autumn 2015 S Boyd and S Lall Observability and state estimation state estimation discrete-time observability observability controllability duality observers for noiseless case continuous-time observability
More information1 Math 241A-B Homework Problem List for F2015 and W2016
1 Math 241A-B Homework Problem List for F2015 W2016 1.1 Homework 1. Due Wednesday, October 7, 2015 Notation 1.1 Let U be any set, g be a positive function on U, Y be a normed space. For any f : U Y let
More informationApproximate controllability of impulsive neutral functional differential equations with state-dependent delay via fractional operators
International Journal of Computer Applications (975 8887) Volume 69 - No. 2, May 23 Approximate controllability of impulsive neutral functional differential equations with state-dependent delay via fractional
More informationCONTROLLABILITY OF MATRIX SECOND ORDER SYSTEMS: A TRIGONOMETRIC MATRIX APPROACH
Electronic Journal of Differential Equations, Vol. 27(27), No. 8, pp. 4. ISSN: 72-669. URL: http://ejde.math.txstate.edu or http://ejde.math.unt.edu ftp ejde.math.txstate.edu (login: ftp) CONTROLLABILITY
More informationWELL-POSEDNESS FOR HYPERBOLIC PROBLEMS (0.2)
WELL-POSEDNESS FOR HYPERBOLIC PROBLEMS We will use the familiar Hilbert spaces H = L 2 (Ω) and V = H 1 (Ω). We consider the Cauchy problem (.1) c u = ( 2 t c )u = f L 2 ((, T ) Ω) on [, T ] Ω u() = u H
More informationLecture 19 Observability and state estimation
EE263 Autumn 2007-08 Stephen Boyd Lecture 19 Observability and state estimation state estimation discrete-time observability observability controllability duality observers for noiseless case continuous-time
More informationPerturbation theory of boundary value problems and approximate controllability of perturbed boundary control problems
Proceedings of the 47th IEEE Conference on Decision and Control Cancun, Mexico, Dec. 9-11, 28 TuC7.6 Perturbation theory of boundary value problems and approximate controllability of perturbed boundary
More informationACM/CMS 107 Linear Analysis & Applications Fall 2016 Assignment 4: Linear ODEs and Control Theory Due: 5th December 2016
ACM/CMS 17 Linear Analysis & Applications Fall 216 Assignment 4: Linear ODEs and Control Theory Due: 5th December 216 Introduction Systems of ordinary differential equations (ODEs) can be used to describe
More information2 Statement of the problem and assumptions
Mathematical Notes, 25, vol. 78, no. 4, pp. 466 48. Existence Theorem for Optimal Control Problems on an Infinite Time Interval A.V. Dmitruk and N.V. Kuz kina We consider an optimal control problem on
More informationSolution of Linear State-space Systems
Solution of Linear State-space Systems Homogeneous (u=0) LTV systems first Theorem (Peano-Baker series) The unique solution to x(t) = (t, )x 0 where The matrix function is given by is called the state
More informationMathematical Journal of Okayama University
Mathematical Journal of Okayama University Volume 46, Issue 1 24 Article 29 JANUARY 24 The Perron Problem for C-Semigroups Petre Prada Alin Pogan Ciprian Preda West University of Timisoara University of
More informationNon-stationary Friedrichs systems
Department of Mathematics, University of Osijek BCAM, Bilbao, November 2013 Joint work with Marko Erceg 1 Stationary Friedrichs systems Classical theory Abstract theory 2 3 Motivation Stationary Friedrichs
More informationElliptic Operators with Unbounded Coefficients
Elliptic Operators with Unbounded Coefficients Federica Gregorio Universitá degli Studi di Salerno 8th June 2018 joint work with S.E. Boutiah, A. Rhandi, C. Tacelli Motivation Consider the Stochastic Differential
More information21 Linear State-Space Representations
ME 132, Spring 25, UC Berkeley, A Packard 187 21 Linear State-Space Representations First, let s describe the most general type of dynamic system that we will consider/encounter in this class Systems may
More informationAnalysis Preliminary Exam Workshop: Hilbert Spaces
Analysis Preliminary Exam Workshop: Hilbert Spaces 1. Hilbert spaces A Hilbert space H is a complete real or complex inner product space. Consider complex Hilbert spaces for definiteness. If (, ) : H H
More informationMassera-type theorem for the existence of C (n) -almost-periodic solutions for partial functional differential equations with infinite delay
Nonlinear Analysis 69 (2008) 1413 1424 www.elsevier.com/locate/na Massera-type theorem for the existence of C (n) -almost-periodic solutions for partial functional differential equations with infinite
More informationNonlinear Control Systems
Nonlinear Control Systems António Pedro Aguiar pedro@isr.ist.utl.pt 3. Fundamental properties IST-DEEC PhD Course http://users.isr.ist.utl.pt/%7epedro/ncs2012/ 2012 1 Example Consider the system ẋ = f
More informationSemigroup Generation
Semigroup Generation Yudi Soeharyadi Analysis & Geometry Research Division Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung WIDE-Workshoop in Integral and Differensial Equations 2017
More informationSPECTRAL THEOREM FOR SYMMETRIC OPERATORS WITH COMPACT RESOLVENT
SPECTRAL THEOREM FOR SYMMETRIC OPERATORS WITH COMPACT RESOLVENT Abstract. These are the letcure notes prepared for the workshop on Functional Analysis and Operator Algebras to be held at NIT-Karnataka,
More informationΨ-asymptotic stability of non-linear matrix Lyapunov systems
Available online at wwwtjnsacom J Nonlinear Sci Appl 5 (22), 5 25 Research Article Ψ-asymptotic stability of non-linear matrix Lyapunov systems MSNMurty a,, GSuresh Kumar b a Department of Applied Mathematics,
More informationExponential stability of families of linear delay systems
Exponential stability of families of linear delay systems F. Wirth Zentrum für Technomathematik Universität Bremen 28334 Bremen, Germany fabian@math.uni-bremen.de Keywords: Abstract Stability, delay systems,
More informationStability of Linear Distributed Parameter Systems with Time-Delays
Stability of Linear Distributed Parameter Systems with Time-Delays Emilia FRIDMAN* *Electrical Engineering, Tel Aviv University, Israel joint with Yury Orlov (CICESE Research Center, Ensenada, Mexico)
More informationDichotomy, the Closed Range Theorem and Optimal Control
Dichotomy, the Closed Range Theorem and Optimal Control Pavel Brunovský (joint work with Mária Holecyová) Comenius University Bratislava, Slovakia Praha 13. 5. 2016 Brunovsky Praha 13. 5. 2016 Closed Range
More informationProve that this gives a bounded linear operator T : X l 1. (6p) Prove that T is a bounded linear operator T : l l and compute (5p)
Uppsala Universitet Matematiska Institutionen Andreas Strömbergsson Prov i matematik Funktionalanalys Kurs: F3B, F4Sy, NVP 2006-03-17 Skrivtid: 9 14 Tillåtna hjälpmedel: Manuella skrivdon, Kreyszigs bok
More informationEXISTENCE THEOREMS FOR FUNCTIONAL DIFFERENTIAL EQUATIONS IN BANACH SPACES. 1. Introduction
Acta Math. Univ. Comenianae Vol. LXXVIII, 2(29), pp. 287 32 287 EXISTENCE THEOREMS FOR FUNCTIONAL DIFFERENTIAL EQUATIONS IN BANACH SPACES A. SGHIR Abstract. This paper concernes with the study of existence
More informationLinear System Theory
Linear System Theory Wonhee Kim Lecture 3 Mar. 21, 2017 1 / 38 Overview Recap Nonlinear systems: existence and uniqueness of a solution of differential equations Preliminaries Fields and Vector Spaces
More informationAnalysis Comprehensive Exam Questions Fall 2008
Analysis Comprehensive xam Questions Fall 28. (a) Let R be measurable with finite Lebesgue measure. Suppose that {f n } n N is a bounded sequence in L 2 () and there exists a function f such that f n (x)
More informationRelative Controllability of Fractional Dynamical Systems with Multiple Delays in Control
Chapter 4 Relative Controllability of Fractional Dynamical Systems with Multiple Delays in Control 4.1 Introduction A mathematical model for the dynamical systems with delayed controls denoting time varying
More informationME 234, Lyapunov and Riccati Problems. 1. This problem is to recall some facts and formulae you already know. e Aτ BB e A τ dτ
ME 234, Lyapunov and Riccati Problems. This problem is to recall some facts and formulae you already know. (a) Let A and B be matrices of appropriate dimension. Show that (A, B) is controllable if and
More informationSemigroups of Operators
Lecture 11 Semigroups of Operators In tis Lecture we gater a few notions on one-parameter semigroups of linear operators, confining to te essential tools tat are needed in te sequel. As usual, X is a real
More information16 1 Basic Facts from Functional Analysis and Banach Lattices
16 1 Basic Facts from Functional Analysis and Banach Lattices 1.2.3 Banach Steinhaus Theorem Another fundamental theorem of functional analysis is the Banach Steinhaus theorem, or the Uniform Boundedness
More informationA Second Course in Elementary Differential Equations
A Second Course in Elementary Differential Equations Marcel B Finan Arkansas Tech University c All Rights Reserved August 3, 23 Contents 28 Calculus of Matrix-Valued Functions of a Real Variable 4 29 nth
More informationAN EFFECTIVE METRIC ON C(H, K) WITH NORMAL STRUCTURE. Mona Nabiei (Received 23 June, 2015)
NEW ZEALAND JOURNAL OF MATHEMATICS Volume 46 (2016), 53-64 AN EFFECTIVE METRIC ON C(H, K) WITH NORMAL STRUCTURE Mona Nabiei (Received 23 June, 2015) Abstract. This study first defines a new metric with
More information6 Linear Equation. 6.1 Equation with constant coefficients
6 Linear Equation 6.1 Equation with constant coefficients Consider the equation ẋ = Ax, x R n. This equating has n independent solutions. If the eigenvalues are distinct then the solutions are c k e λ
More informationIntroduction to Exact Controllability and Observability; Variational Approach and Hilbert Uniqueness Method 1
Introduction to Exact Controllability and Observability; Variational Approach and Hilbert Uniqueness Method 1 A. K. Nandakumaran 2 We plan to discuss the following topics in these lectures 1. A brief introduction
More informationHille-Yosida Theorem and some Applications
Hille-Yosida Theorem and some Applications Apratim De Supervisor: Professor Gheorghe Moroșanu Submitted to: Department of Mathematics and its Applications Central European University Budapest, Hungary
More informationLecture 4 and 5 Controllability and Observability: Kalman decompositions
1 Lecture 4 and 5 Controllability and Observability: Kalman decompositions Spring 2013 - EE 194, Advanced Control (Prof. Khan) January 30 (Wed.) and Feb. 04 (Mon.), 2013 I. OBSERVABILITY OF DT LTI SYSTEMS
More informationAn Operator Theoretical Approach to Nonlocal Differential Equations
An Operator Theoretical Approach to Nonlocal Differential Equations Joshua Lee Padgett Department of Mathematics and Statistics Texas Tech University Analysis Seminar November 27, 2017 Joshua Lee Padgett
More informationA BRIEF INTRODUCTION TO HILBERT SPACE FRAME THEORY AND ITS APPLICATIONS AMS SHORT COURSE: JOINT MATHEMATICS MEETINGS SAN ANTONIO, 2015 PETER G. CASAZZA Abstract. This is a short introduction to Hilbert
More informationAPPROXIMATE CONTROLLABILITY OF NEUTRAL SYSTEMS
APPROXIMATE CONTROLLABILITY OF NEUTRAL SYSTEMS WITH STATE AND INPUT DELAYS IN BANACH SPACES Said Hadd and Qing-Chang Zhong Dept. of Electrical Eng. & Electronics The University of Liverpool Liverpool,
More informationOn the Ψ - Exponential Asymptotic Stability of Nonlinear Lyapunov Matrix Differential Equations
DOI: 1.2478/awutm-213-12 Analele Universităţii de Vest, Timişoara Seria Matematică Informatică LI, 2, (213), 7 28 On the Ψ - Exponential Asymptotic Stability of Nonlinear Lyapunov Matrix Differential Equations
More informationFractional Evolution Integro-Differential Systems with Nonlocal Conditions
Advances in Dynamical Systems and Applications ISSN 973-5321, Volume 5, Number 1, pp. 49 6 (21) http://campus.mst.edu/adsa Fractional Evolution Integro-Differential Systems with Nonlocal Conditions Amar
More informationA Smooth Operator, Operated Correctly
Clark Department of Mathematics Bard College at Simon s Rock March 6, 2014 Abstract By looking at familiar smooth functions in new ways, we can make sense of matrix-valued infinite series and operator-valued
More informationChapter III. Stability of Linear Systems
1 Chapter III Stability of Linear Systems 1. Stability and state transition matrix 2. Time-varying (non-autonomous) systems 3. Time-invariant systems 1 STABILITY AND STATE TRANSITION MATRIX 2 In this chapter,
More informationNON-AUTONOMOUS INHOMOGENEOUS BOUNDARY CAUCHY PROBLEMS AND RETARDED EQUATIONS. M. Filali and M. Moussi
Electronic Journal: Southwest Journal o Pure and Applied Mathematics Internet: http://rattler.cameron.edu/swjpam.html ISSN 83-464 Issue 2, December, 23, pp. 26 35. Submitted: December 24, 22. Published:
More information2.1 Dynamical systems, phase flows, and differential equations
Chapter 2 Fundamental theorems 2.1 Dynamical systems, phase flows, and differential equations A dynamical system is a mathematical formalization of an evolutionary deterministic process. An evolutionary
More informationSome recent results on controllability of coupled parabolic systems: Towards a Kalman condition
Some recent results on controllability of coupled parabolic systems: Towards a Kalman condition F. Ammar Khodja Clermont-Ferrand, June 2011 GOAL: 1 Show the important differences between scalar and non
More informationThe Dirichlet-to-Neumann operator
Lecture 8 The Dirichlet-to-Neumann operator The Dirichlet-to-Neumann operator plays an important role in the theory of inverse problems. In fact, from measurements of electrical currents at the surface
More informationStabilization of Distributed Parameter Systems by State Feedback with Positivity Constraints
Stabilization of Distributed Parameter Systems by State Feedback with Positivity Constraints Joseph Winkin Namur Center of Complex Systems (naxys) and Dept. of Mathematics, University of Namur, Belgium
More informationFredholm Theory. April 25, 2018
Fredholm Theory April 25, 208 Roughly speaking, Fredholm theory consists of the study of operators of the form I + A where A is compact. From this point on, we will also refer to I + A as Fredholm operators.
More informationAnalysis of undamped second order systems with dynamic feedback
Control and Cybernetics vol. 33 (24) No. 4 Analysis of undamped second order systems with dynamic feedback by Wojciech Mitkowski Chair of Automatics AGH University of Science and Technology Al. Mickiewicza
More informationHigher Order Averaging : periodic solutions, linear systems and an application
Higher Order Averaging : periodic solutions, linear systems and an application Hartono and A.H.P. van der Burgh Faculty of Information Technology and Systems, Department of Applied Mathematical Analysis,
More informationLecture 3: Review of Linear Algebra
ECE 83 Fall 2 Statistical Signal Processing instructor: R Nowak Lecture 3: Review of Linear Algebra Very often in this course we will represent signals as vectors and operators (eg, filters, transforms,
More informationDifferential Equations Preliminary Examination
Differential Equations Preliminary Examination Department of Mathematics University of Utah Salt Lake City, Utah 84112 August 2007 Instructions This examination consists of two parts, called Part A and
More informationLecture 3: Review of Linear Algebra
ECE 83 Fall 2 Statistical Signal Processing instructor: R Nowak, scribe: R Nowak Lecture 3: Review of Linear Algebra Very often in this course we will represent signals as vectors and operators (eg, filters,
More informationEXISTENCE AND UNIQUENESS OF SOLUTIONS FOR FOURTH-ORDER BOUNDARY-VALUE PROBLEMS IN BANACH SPACES
Electronic Journal of Differential Equations, Vol. 9(9), No. 33, pp. 1 8. ISSN: 17-6691. URL: http://ejde.math.txstate.edu or http://ejde.math.unt.edu ftp ejde.math.txstate.edu EXISTENCE AND UNIQUENESS
More informationConservative Control Systems Described by the Schrödinger Equation
Conservative Control Systems Described by the Schrödinger Equation Salah E. Rebiai Abstract An important subclass of well-posed linear systems is formed by the conservative systems. A conservative system
More informationStudy of Existence and uniqueness of solution of abstract nonlinear differential equation of finite delay
Study of Existence and uniqueness of solution of abstract nonlinear differential equation of finite delay Rupesh T. More and Vijay B. Patare Department of Mathematics, Arts, Commerce and Science College,
More information1 Compact and Precompact Subsets of H
Compact Sets and Compact Operators by Francis J. Narcowich November, 2014 Throughout these notes, H denotes a separable Hilbert space. We will use the notation B(H) to denote the set of bounded linear
More informationNewtonian Mechanics. Chapter Classical space-time
Chapter 1 Newtonian Mechanics In these notes classical mechanics will be viewed as a mathematical model for the description of physical systems consisting of a certain (generally finite) number of particles
More informationExercise Sheet 1.
Exercise Sheet 1 You can download my lecture and exercise sheets at the address http://sami.hust.edu.vn/giang-vien/?name=huynt 1) Let A, B be sets. What does the statement "A is not a subset of B " mean?
More informationFunctional Analysis. Martin Brokate. 1 Normed Spaces 2. 2 Hilbert Spaces The Principle of Uniform Boundedness 32
Functional Analysis Martin Brokate Contents 1 Normed Spaces 2 2 Hilbert Spaces 2 3 The Principle of Uniform Boundedness 32 4 Extension, Reflexivity, Separation 37 5 Compact subsets of C and L p 46 6 Weak
More informationConvexity of the Reachable Set of Nonlinear Systems under L 2 Bounded Controls
1 1 Convexity of the Reachable Set of Nonlinear Systems under L 2 Bounded Controls B.T.Polyak Institute for Control Science, Moscow, Russia e-mail boris@ipu.rssi.ru Abstract Recently [1, 2] the new convexity
More informationLinear Algebra 1. M.T.Nair Department of Mathematics, IIT Madras. and in that case x is called an eigenvector of T corresponding to the eigenvalue λ.
Linear Algebra 1 M.T.Nair Department of Mathematics, IIT Madras 1 Eigenvalues and Eigenvectors 1.1 Definition and Examples Definition 1.1. Let V be a vector space (over a field F) and T : V V be a linear
More informationLinear ODEs. Existence of solutions to linear IVPs. Resolvent matrix. Autonomous linear systems
Linear ODEs p. 1 Linear ODEs Existence of solutions to linear IVPs Resolvent matrix Autonomous linear systems Linear ODEs Definition (Linear ODE) A linear ODE is a differential equation taking the form
More informationSPACES ENDOWED WITH A GRAPH AND APPLICATIONS. Mina Dinarvand. 1. Introduction
MATEMATIČKI VESNIK MATEMATIQKI VESNIK 69, 1 (2017), 23 38 March 2017 research paper originalni nauqni rad FIXED POINT RESULTS FOR (ϕ, ψ)-contractions IN METRIC SPACES ENDOWED WITH A GRAPH AND APPLICATIONS
More informationHerz (cf. [H], and also [BS]) proved that the reverse inequality is also true, that is,
REARRANGEMENT OF HARDY-LITTLEWOOD MAXIMAL FUNCTIONS IN LORENTZ SPACES. Jesús Bastero*, Mario Milman and Francisco J. Ruiz** Abstract. For the classical Hardy-Littlewood maximal function M f, a well known
More informationPREPRINT 2009:10. Continuous-discrete optimal control problems KJELL HOLMÅKER
PREPRINT 2009:10 Continuous-discrete optimal control problems KJELL HOLMÅKER Department of Mathematical Sciences Division of Mathematics CHALMERS UNIVERSITY OF TECHNOLOGY UNIVERSITY OF GOTHENBURG Göteborg
More informationON PERIODIC SOLUTIONS TO SOME LAGRANGIAN SYSTEM WITH TWO DEGREES OF FREEDOM
ON PERIODIC SOLUTIONS TO SOME LAGRANGIAN SYSTEM WITH TWO DEGREES OF FREEDOM OLEG ZUBELEVICH DEPT. OF THEORETICAL MECHANICS, MECHANICS AND MATHEMATICS FACULTY, M. V. LOMONOSOV MOSCOW STATE UNIVERSITY RUSSIA,
More informationDecay rates for partially dissipative hyperbolic systems
Outline Decay rates for partially dissipative hyperbolic systems Basque Center for Applied Mathematics Bilbao, Basque Country, Spain zuazua@bcamath.org http://www.bcamath.org/zuazua/ Numerical Methods
More information