Finite memory output sliding mode control under the round-robin protocol: variable scheduling frequency
摘要
In static delayed output feedback control, the problem of simultaneously scheduling current and historical sampled outputs for data reusing has been rarely discussed. To solve this issue, this study proposes the integrated design of the static delayed output sliding mode control (SMC) with finite memory and the round-robin protocol (RRP) for a networked control system (NCS) with an arbitrary system order n. The key advantage of this design is the co-selection of the scheduling frequency and the tokens to generate sampling sequences for reducing the transmission burden and improving the controller performance. First, the NCS, composed of the plant, the controller, the scheduler, the buffer, and the zero-order or first-order hold (FOH), is taken into account. For such a system, a token-dependent static delayed output sliding surface is designed by inserting a series of current and historical measurements into the surface. Moreover, the estimation of xn(t) under FOH is constructed to further reduce the truncated errors arising from the sampler-and-hold mechanism. On this basis, the static delayed output SMC law, requiring at most three sensors, is designed for the nth-order NCS under RRP scheduling between the sensors and controllers. Sufficient conditions are derived to determine the reasonable scheduling period under a predetermined circular order. Finally, a numerical example is presented to illustrate the effectiveness and merits of the finite memory output SMC of a fourth-order NCS under RRP scheduling.