T.C. Yang

Networked Control Systems: A Historical Review and Current Research Topics

It is widely recognised that research in Networks and Control is extremely important. Broadly speaking, this covers two research areas; one is control of computer/communication networks called control of communication networks (CCN)1, 2, 8, 16, i.e. to study how the application of control methods improve quality of service (QoS), for example, Internet congestion control, routing control caching and updating data at multiple locations, managing power levels for wireless networks, etc. CCN has received a great attention during the past few years. The general control structure of control of communication networks is shown in Figure 1. A generic review on the transmission control protocols, congestion control protocols, the various analytical models currently studied in the networking community and an optimisation-based framework are presented in ref16. The other research area is networked control systems (NCS)1,2,17,18,20,33 which represents a control system communicating with sensors and actuators over a communication network, i.e. to study how the communication (wire or wireless) networks influence control systems. The general control structure of networked control systems is shown in Figure 2. This paper focuses on the survey of networked control systems.

Research into quasi-decentralised control

Quasi-decentralised control for complex systems is proposed in the paper. Different forms of input-output participation factors (IOPFs) are also introduced mainly to help to determine a suitable decentralised or, if necessary, a quasi-decentralised stabilising scheme. IOPFs can be used to identify practically fixed modes which cannot be detected by the most existing mathematical tools, and to compare the effectiveness of different input-output pairs. The proposed concepts and approaches are illustrated by a power system stabiliser design problem for a sample system. Two other applications of IOPFs and some suggested future research are also presented.

Modelling and control of magnetic suspension systems

The paper discusses the modelling and control of DC magnetic suspension systems. The dynamic model of magnetic suspension systems is first developed by using the Euler-Lagranges formulation. The several important properties, which are very useful for the system analysis and controller design, are investigated. After reviewing several popular control approaches, two new control schemes are proposed. One is the cascade design method which has fully utilised the structure information of the magnetic suspension system. The other is the energy-based control design approach which uses the energy information of the system.

Stabilizing controller design for complex systems: Some new concepts and approaches

Abstract Quasi-decentralized control for complex systems is proposed in this paper. Different forms of ∼put-Output Participation Factors (IOPFs) are also introduced in this paper mainly to help to determine a suitable decentralized or, if necessary, a quasi-decentralized stabilizing scheme. IOPFs can be used to identify practically fixed modes which camiot be detected by the most existing mathematical tools, and to compare the effectiveness of different input-output pairs. The proposed concepts and approaches are illustrated by a power system stabilizer design problem for a sample system. Future research in quasi-decentralized control is also outlined.

A Novel AQM Scheme for Wireless Networks with BER Estimation

A novel active queue management(AQM) scheme is proposed to deal with the performance degradation of TCP in wireless scenario. One of the key sources causing performance degradation is the high bit error rate(BER), which is an intrinsic link characteristic of wireless network. A high-gain observer is constructed to estimate the effect of bit error of source data. With the estimated BER, the drop probability of queuing packets can be adapted to time-varying link conditions and network loads so that it reduces the queue oscillation and maintains good throughput. Simulation results show that the proposed scheme outperforms RED(Random Early Detection) algorithm with strong robustness to time-varying scenarios of wireless networks.

MODEL REFERENCE PARAMETRIC ADAPTIVE ITERATIVE LEARNING CONTROL

Abstract Most of iterative learning control (ILC) methods requires that the relative degree of the plant is less than 2 for a linear system or the plant is passive for a non-linear system. A new model reference parametric adaptive iterative learning control using the command generator tracker (CGT) theory is proposed in this paper. The method can be applied to control a plant with a higher relative degree and it only requires to iteratively adjust n m + 2 parameters for an SISO plant. Therefore, the ILC control system is very simple. The proposed method is in the spirit of simple adaptive control which has received intensive researches during past two decades. Simulation results show the effectiveness and usefulness of the proposed method.

Weighting function selection for H/sub /spl infin// based power system stabilizer design

Despite much progress in applying modern control technology to power system stabiliser (PSS) design with many different suggested PSS structures, many utilities still prefer a conventional PSS structure. The reasons may include ease of on-line tuning and lack of assurance on the stability related to some adaptive or variable structure schemes. Previously developed H/sub /spl infin// and related design methods lead to fixed-structure and fixed-parameter yet robust controllers. Their applications in other areas have showed great potential. In Asgharian (1994) and Chow et al. (1990), some investigations on applying H/sub /spl infin// methods to the PSS design are also presented. Both papers reported the importance and the difficulties in the selection of weighting functions for such design. In addition, the systems studied in both papers were restricted to single-(or two identical) machine infinite-bus power systems. This gives the author the motivation to study (1) a simple and effective way of selecting weighting functions; and (2) applying H/sub /spl infin// method for multi-machine power system PSS design. In this, the author reports a study on the first problem for single-machine infinite-bus systems and this can also be extended to multi-machine power systems.

Applying feedback to stock trading: Exploring a new field of research

Nowadays, feedback control is everywhere and, affects everything. Recently, a novel idea of applying, feedback control to stock trading is proposed. Some, interesting results are published in recent IEEE/IFAC, control conferences. Different from current statistical or, artificial neural network based approaches, this opens a new, research field in analytical strategies for stock trading. In, this paper we follow the scheme of “Simultaneous Long-, Short feedback control” and carry out a new study. In our, study, instead of one feedback gain for both long and short, trading, different trading gains are applied. Based on recent, stock prices over one year (from 2014/3/27 to 2015/3/26), we show our selected simulation results for two stocks. One, is the Apple Incorporated stock. The trend of its price over, the year is increasing. The other is the NASDAQ-100 index, and the trend of its price is decreasing. A number of new, research topics are also proposed in this paper.

Co-simulation framework for Networked Control Systems over multi-hop mobile ad-hoc networks M Shahidul Hasan

Networked Control Systems over mobile ad-hoc networks have drawn the attention of the researchers because of its suitability in various ad-hoc applications. This paper presents the investigation of such systems using both real wireless communication and co-simulation of MATLAB and OPNET. The plant and the wireless node models are simulated on a computer by MATLAB and OPNET, respectively. The controller runs on a laptop. These two computers communicate using a real wireless link. The interactive co-simulation is applied to a double-pendulum plant with two sensors and two actuators. Both the co-simulation technique and the results are presented and discussed.

Nonlinear adaptive control with unknown high frequency gains

Abstract This paper presents an algorithm for output feedback adaptive control of a class of minimum phase nonlinear systems with unknown parameters. A priori knowledge of the sign of the high frequency gain is not required, and control signals and adaptive laws are smooth. Asymptotic output tracking of smooth reference signals is achieved while all other variables remain bounded. The algorithm makes use of backstepping and tuning functions with K-filters, and it enlarges the class of nonlinear systems with unknown parameters for which asymptotic output tracking can be achieved using output feedback.