Information and Computer Technologies
210
Computer Modelling and New Technologies, 2013, Vol.17, No. 4, 210-216
Transport and Telecommunication Institute, Lomonosov 1, LV-1019, Riga, Latvia
ANALYSIS AND SIMULATION OF NETWORKED CONTROL
SYSTEMS DELAY CHARACTERISTICS BASED ON TRUETIME
Y. Wang
a
, L. He
b
a
The Physics and Electronics Science College
Guizhou Normal University, Guiyang, China, 550025
Phone: (+086)-13007888851. E-mail: wyigz@126.com
b
The Science College, Guizhou University
Guiyang, China, 550025
E-mail: 630897810@qq.com
The network-induced delay in networked control system is the most important reason of system performance degradation
or even instability. In this paper, based on the analysis of structure of networked control system, the causes and integral part of delay
was studied. Adopted the network control system simulation tool Truetime to build the simulation model of network control system
delay. Discussed the effects of network delay on the performance of the control system in three cases. Then draw a conclusion that
reduce the proportion of forward delay in total delay of the network can effectively improve the performance of networked control
system.
Keywords:
network delay, control performance, truetime, stability
1. Introduction
Recent years, with the increasing complexity of control object and continue expand of distribution
area, the complex wiring, difficult to maintain, poor scalability, and other issues that brought by
traditional point-to-point control system structure, has become increasingly prominent. It is difficult to
meet the rapid development of the control system performance requirements. Thus the networked control
systems (NCS) that exchange information between controller and actuator, sensor through a shared
communication network has come into being. It is a complex fully distributed control system that
combined communication network and control system as one unit. In addition, it reflects the development
trend of networked, integration, distribution and intelligent. Compared with the point-to-point control,
NCS has advantages of shared information resources, system wiring, reliability and flexibility, easy to
extend and maintain, etc. So that it has rapidly develop and application, and catch more attention and
applications in industrial control.
CAN bus control system is a kind of NCS that widely used. It has inevitable bring about some
uncertain factors as the introduction of network. Moreover, mainly problem is performance degradation
or even instability that caused by network-induced delay in NCS. In order to ensure the stability of
control system, it is necessary to do an in-depth theoretical study to delay issue in NCS. In paper [1], in
order to research stability issue, the discrete model of NCS was built. In addition, in paper [2], using the
random delay modelling method to analysis the delay issues in NCS, and verify the effectiveness of
algorithm by simulation results. While in article [3], it proposed a delay compensation strategy of
segmentation dynamic matric to compensate the delay in the network transmission. Paper [4] put forward
an adaptive PID control method based on BP neural network compensation. That can achieve online
adaptive compensation network delay. Based on the analysis of the delay issues in the NCS, the paper [5]
discussed and summarized the findings of delay problem. At last, this paper mainly studies the effects of
forward and feedback delay in NCS to the performance of control system. Then draw a conclusion that
there are some references value to the design of NCS.
2. Relationship of Delay and Sampling Period in NCS
NCS is a real-time closed-loop feedback control system that transmit data thought network. The
typical structure is shown in figure 1.