Relations are derived that allow standard MATLAB routines to be used to solve the static output-feedback control problem for a periodic discrete-time system. The efficiency of the approach proposed to design optimal static output-feedback controllers is demonstrated by examples Keywords: periodic discrete-time system, static output feedback, objective function Introduction. The optimization problem for linear periodic systems has a wide range of applications [2, 3, 6, 9-12, 14, 15, 18, 19, 30-32]. One of such is the synthesis of stabilization systems for walking and hopping robots [20][21][22][23][24][25][27][28][29]. It is known (see, e.g., [13]) that for a nonstationary linear system whose phase vector can only partially be observed, the feedback design procedure reduces to solving two matrix differential Riccati equations.One of these equations describes a filter that generates an estimate of the whole phase vector, and the other equation produces a controller matrix that relates this estimate and the control. This is the so-called case of dynamic feedback design. Designing static feedback is a more complicated problem because it requires determining constant matrices that form the control directly from the observable portion of the phase vector. Even if the system is stationary, this problem is very complicated [16,33,35]. To solve it, numerical algorithms based on the gradient of the objective function were proposed in [7,8,[33][34][35].Moreover, if the system is unstable, these algorithms additionally require an initial approximation, i.e., a stabilizing matrix. Forming this matrix is an independent problem [33]. Various approaches to its solution were proposed in [4,8,26,33,36].Here, we outline an algorithm for design of the optimal (i.e., minimizing a quadratic performance criterion) static output-feedback controller for a periodic discrete(-time) system. This algorithm generalizes the approach from [4,26] to periodic discrete-time systems, which substantially simplifies the procedure of selecting an initial approximation. The relations describing the objective function and its gradient are also generalized appropriately. We will show that standard MATLAB routines can be used to implement this algorithm.1. Problem Formulation. Consider a p-periodic discrete-time system described by the following difference relations: