Quantized control for networked control systems with communication delay and packet dropouts

Abstract

In the past few decades, the study of NCSs has been of great interest since networked control modeling has come to play an important role in modern engineering applications. NCSs are systems where sensors, actuators, estimation units and control units are interconnected by communica -tion networks. In NCSs, data transmission through communication channels can reduce the costs of the wring and maintenance, simplify the installation, etc. However, some new problems occur because all signals are transmitted through a network, such as communication delays and packet dropouts caused by data transmission limitations or errors always happen. Communication delays and packet dropouts deteriorate the performance and may destabilize the systems[1-3]. Another important aspect, which is well known in the signal processing area, is signal quantization. In NCSs, because of the limited transmission capacity, the data should be quantized before they are transmitted to the next nodes. Then quantization errors have adverse effects on the NCSs performance. All of these bring some new challenges in the NCSs analysis and controller design [4][5][6]. Quantizers are divided into linear quantizer, logarithmic quantizer, dynamical quantizer and nonlinearity quantizer. The characteristic of linear quantizer is fixed sector bound. In [7] that the optimal quantizer is a logarithmic in discrete time single-input-single-output system (SISO). In [8] and [9], the authors proposed the idea of sector-bounded nonlinearities. In [10], the authors dealt with the problem of feedback control for networked systems with discrete and distributed delays subject to quantization and packet dropout, and a compensation scheme was proposed to deal with the effect of random packet dropout through communication network. In [11], a unified control law This work is supported by Grant No.L2012414 of College Research Project of Liaoning Province, China.model is proposed to take the network-induced delay, random packet dropout and measurement quantization into consideration simultaneously. Then, a less conservative stability condition is derived, which depends on packet dropout probability, the lower and upper bounds of the delay and quantization density. To the best of the authors' knowledge, the quantized ∞ H feedback stabilization for NCSs with simultaneous consideration of the random communication delay, packet dropout and measurement quantization has not been fully investigated. In contrast with the above previous works, in this paper, based on Logarithmic quantization, the discrete-time NCSs model is described under the concerns of the synthesis effect of quantized signal, random communication delays and packet dropouts. By choosing appropriate Lyapunov functional, a sufficient condition for the existence of quantized ω , are the state vector , control input vector, measured output vector, controlled output, and disturbance Abstract: This paper is concerned with the problem of quantized ∞ H control for discrete-time networked control systems (NCSs) with random c...