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U. Arora, S. Singh, V. Vijayakumar, A. Shukla / IJOCTA, Vol.15, No.3, pp.483-492 (2025)
            therefore u is measurable. So, we can extract     Definition 10. [43] “A function x(·) ∈ C(I; Y)
            v(ϱ) from B(ϱ, v(ϱ)) so that for this control, the  is said to be the mild solution of (11)-(12) if it
            mild solution of the considered system equals to  satisfies
            the prescribed trajectory z(ϱ), which concludes                             Z  ϱ
            T-controllability of (1)-(2).                     y(ϱ) =C ν (ϱ)y 0 + S ν (ϱ)z 0 +  P ν (ϱ − α)B(α, v(α))dα
                                                                                         0
                                                                       Z  ϱ                  Z  ϱ
            3. Fractional differential systems of                    +    P ν (ϱ − α)G α, x(s),   g(ϱ, α, y(α))dα }ds
                order ν ∈ (1, 2]                                        0                       0
                                                                                                         (15)
            We are primarily focusing on the trajectory con-
            trollability of the subsequent fractional semilinear  where S ν (ϱ) and P ν (ϱ) are the fractional SF
            integrodifferential system of order ν ∈ (1, 2]    and fractional R-L family, respectively, associ-
                                                              ated with strongly continuous CF C ν (ϱ) as defined
              c  ν
               D y(ϱ) =Ay(ϱ) + B(ϱ, v(ϱ))                     above.”
                 ϱ
                                        ϱ
                                    Z
                         + G ϱ, y(ϱ),    g(ϱ, α, y(α))dα ,        Assume that P be the set of all functions de-
                                       0                                                 ′
                                                              fined on I with z(0) = y 0 , z (0) = z 0 , z(b) = y 1
                           ϱ ∈ I, ν ∈ (1, 2],                                             c  ν
                                                              and the fractional derivative D z exists almost
                                                                                             ϱ
                                                       (11)   everywhere for ν ∈ (1, 2]. Note that P be the set
                                    ′
                         y(0) = y 0 , y (0) = z 0 .    (12)
                                                              of all feasible trajectories for (11)-(12).
            Here,   A is the infinitesimal generator of           We prove the trajectory controllability of the
            the strongly continuous cosine family (CF)        system (11)-(12) in two cases.
            {C ν (ϱ), t ≥ 0} and y 0 , z 0 ∈ Y.                   Case-I: If the control appears linearly:
                To define the mild solution of (11)-(12), we      Consider the system (11)-(12) with the con-
            assume the subsequent system                      trol appears linearly, i.e. , B(ϱ, v(ϱ)) = b(ϱ)v(ϱ),
                c  ν                        ′                 where b : IR and u : IV, then the system (11)-(12)
                 D y(ϱ) = Ay(ϱ), y(0) = η y (0) = 0.   (13)
                   ϱ
                                                              becomes
            In the above, ν ∈ (1, 2]; A : D(A) ⊆ Y → Y is
                                                                  ν
                                                               c D y(ϱ) = Ay(ϱ) + b(ϱ)v(ϱ)
            a closed and densely defined operator in Y. Tak-      ϱ
                                                                                   Z  ϱ
            ing Riemann fractional integral of order ν on both
                                                                       + G ϱ, y(ϱ),    g(ϱ, α, y(α))dα , (16)
            sides of (13), one can attain
                                                                                     0
                            1  Z  ϱ                                    ϱ ∈ I, ν ∈ (1, 2],
               y(ϱ) = η +         (ϱ − α) ν−1 Ax(α)dα  (14)
                          Γ(ν)  0
                                                                                       ′
            Definition 7.    [43] “Let ν ∈ (1, 2]. A family             y(0) = y 0 and y (0) = z 0 .     (17)
            {C ν (ϱ)} t≥0 ⊂ L(Y) is called a solution operator    Assumptions [III].
            (or a strongly continuous ν-order fractional CF)
            for (13) if the following conditions are satisfied:  (1) A generates a strongly continuous CF
                                                                     {C ν (ϱ) : t ≥ 0} on Y.
                (1) C ν (ϱ) is strongly continuous for t ≥ 0 and
                                                                 (2) b(ϱ) does not disappear on I.
                    C ν (0) = I;
                                                                 (3) G and h are Lipschitz continuous in a sim-
                (2) C ν (ϱ)D(A) ⊂ D(A) and AC ν (ϱ)η =
                                                                     ilar manner as in Assumptions [I] of Sec-
                    C ν (ϱ)Aη for all η ∈ D(A), t ≥ 0;
                                                                     tion 2.
                (3) C ν (ϱ)η is a solution of (13),∀ η ∈ D(A),
                    ϱ ≥ 0.                                        By referring these two assumptions, we
            A is called infinitesimal generator of C ν (ϱ). The  may create the control explicitly to verify T-
            strongly continuous ν-order fractional CF is also  controllability of (16)-(17). For verifying this, we
            called ν-order CF.”                               continue in the following way:
                                                                  For every v ∈ L 2 (I, V), the existence and
            Definition 8. The sine family (SF) S ν         :  uniqueness of (16)-(17) follows from Assumptions
            [0, ∞) → L(Y) connected with C ν is presented as  [III] by employing the Lipschitz continuity of
                                ϱ                             functions G and h.
                              Z
                      S ν (ϱ) =  C ν (α)dα, ϱ ≥ 0.                Assume that z(ϱ) be the given trajectory in
                               0
                                                              P. We present v(ϱ) as
            Definition 9. The fractional R-L family P ν :
                                                                                            Z  ϱ
            [0, ∞) → L(Y) connected with C ν is presented as        c D z(ϱ) − Az(ϱ) − G ϱ, z(ϱ),  g(ϱ, α, z(α))dα
                                                                      ν
                                                                      ϱ
                          P ν (ϱ) = J ϱ ν−1 C ν (ϱ).          v(ϱ) =                   b(ϱ)   0
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