Optimal State Feedback Control in Operator Domain for Multi-Rate
Networked Control Systems with Long Time Delay
YANPING Wang
1, a
, QIXIN Zhu
2,b
and ZHIPING Li
2,c
1
College of Information Engineering, Beijing Institute of Clothing, Beijing, 100029, China
2
School of Electrical &Electronics Engineering, East China Jiaotong University, Nanchang,
330013,China
a
wangyp821@sina.com,
b
bob21cn@163.com,
c
lizhiping704@163.com
Keywords: multi-rate networked control systems,
operator, dynamic programming
Abstract. By multi-rate networked control systems (NCS), we mean the sampling periods of the
sensor, the controller and the actuator in networked control systems are not the same, that is to say
there are more than one sampling rate in networked control systems. For the long time delay
multi-rate NCS with event-driven controller and actuator, a stochastic discrete model is established
under
operator. The state feedback control laws for the multi-rate NCS in
operator domain are
designed by using a dynamic programming approach. The derived optimal LQG controller can be
used as a delay-compensator for multi-rate NCS with long time delays. An example is given to verify
the theory results of this paper.
Introduction
Feedback control systems wherein the control loops are closed through a real-time network are called
networked control systems. Networked control architecture has many advantages over a traditional
point-to-point design including low cost of installation, ease of maintenance, lower cost and greater
flexibility. For these reasons the networked control architecture is already used in many applications,
particularly where weight and volume are of consideration. NCS received more and more attentions
and has been a very hot research topic.
The insertion of the communication network in the feedback control loop makes the analysis and
design of an NCS very complex. Network-induced delay occurs while exchanging data among
devices connected to the shared medium. This delay can degrade the performance of control systems
designed without considering the delay and can even destabilize the system. The performance of
controllers that were designed without network inserted must be demonstrated again. Therefore, it is
important to study NCS with network-induced delay. So far, various methodologies have been
proposed to deal with the problem of network-induced delay. The stochastic control of integrated
communication and control systems was discussed and the format and structure of controller was
proposed in [1]. The derived optimal LQG controller can be used as a delay-compensator for
networked control systems with long time delays in [2].The LQG controller of NCS is given in [3]
when the data packet dropout is not considered and network-induced delay is shorter than a sampling
period. The results of [3] are extended to the case that the network-induced delay is longer than a
sampling period in [4].
However, these papers are all under the assumption that NCS work in the single rate mode. For
multi-rate networked control systems, there are some papers published. Model of multi-rate
networked control systems is set up when sensor, controller and actuator are all time driven in [5] and
[6]. LQG state feedback controllers of multi-rate networked control systems are designed in the case
of full state information. The controllers are proved to render corresponding networked control
systems exponentially mean square stable in [7]. A kind of MIMO networked control systems, in
which the sensors and controller are interconnected by network and the state of control object is
feedback to the controller and each loop is controlled at different sampling period, is studied in [8].
Papers [9]and [10] the simple extension to [8].
Applied Mechanics and Materials Vols. 241-244 (2013) pp 1672-1676
© (2013) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMM.241-244.1672
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,
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