This paper addresses the set-point control problem of a heat equation with in-domain actuation. The proposed scheme is based on the framework of zero dynamics inverse combined with flat system control. Moreover, the set-point control is cast into a motion planing problem of a multiple-input, multiple-out system, which is solved by a Green's function-based reference trajectory decomposition. The validity of the proposed method is assessed through the convergence and solvability analysis of the control algorithm. The performance of the developed control scheme and the viability of the proposed approach are confirmed by numerical simulation of a representative system. functional analytic setting based on semigroup and other related tools can be applied (see, e.g., [1,2,3,4]). It is interesting to note that in recent years, some methods that were originally developed for the control of finite-dimensional systems have been successfully extended to the control of parabolic PDEs, such as backstepping (see, e.g.,
10[5, 6, 7]), flat systems (see, e.g., [8,9, 10,11,12,13,14]), as well as their variations (see, e.g., [15,16,17]).This paper addresses the in-domain (or interior point) control problem of a heat equation, which may arise in application related concerns for, e.g., the enhancement of control efficiency. Integrating a number of control inputs acting in the domain will lead 15 to non-standard inhomogeneous PDEs [1,18], which should be treated differently than the standard boundary control problem. The control scheme developed in the present work is based-on the framework of zero-dynamics inverse (ZDI), which was introduced by Byrnes and his collaborators in [19] and has been exploited and developed in a series of work [20,21,22,23,24]. It is pointed out in [23] that "for certain boundary control 20 systems it is very easy to model the system's zero dynamics, which, in turn, provides a simple systematic methodology for solving certain problems of output regulation."Indeed, the construction of zero dynamics for output regulation of certain in-domain controlled PDEs is also straightforward (see, e.g., [22]) and hence, the control design can be carried out in a systematic manner. A main issue related to the ZDI design is that 25 the computation of dynamic control laws requires resolving the corresponding zero dynamics, which may be very difficult for generic regulation problems, such as set-point control. To overcome this difficulty, we leverage one of the fundamental properties of flat systems, that is if a lumped or distributed parameter system is differentially flat (or flat for short), then its states and inputs can be explicitly expressed by the so-called flat 30 output and its time-derivatives [25,13]. In the context of ZDI design, the control can be derived from the flat output without explicitly solving the zero dynamics. Moreover, in the framework of flat systems, set-point control can be cast into a problem of motion planning, which can also be carried out in a systematic manner.The system model used in this ...