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In this paper, we propose an extension to mixed multidimensional constraints of the problem of state and input constrained control introduced in [7], where the admissible set, namely the subset of the state space where the state and input constraints can be satisfied for all times, was studied, with focus on its boundary. The latter may be divided in two parts, one of them being called barrier, a semipermeable surface. We extend this notion of barrier to the mixed case and prove that it can be constructed via a minimum-like principle involving the Karush-Kühn-Tucker multipliers associated to the constraints and a generalised gradient condition at its endpoints.

In this paper a novel approach is presented for control design with guaranteed transient performance for multiple-input multiple-output discrete-time linear polytopic difference inclusions. We establish a theorem that gives necessary and sufficient conditions for the state to evolve from one polyhedral subset of the state-space to another. Then we present an algorithm which constructs a time-varying output feedback law which guarantees that the state evolves within a time-varying polyhedral targettube specifying the system's desired transient performance. We present generalisations involving constraints on the control, and a bounded additive disturbance term. Our formulation is very general and includes reference tracking with any desired transient behaviour in the face of disturbances, as specified, for example, by the most popular step response specifications. The approach is demonstrated by an example involving the control of water levels in two coupled tanks.

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