Networked Control Systems Theory and Its Application Shanbin Li, PhD student NCS Research Group National Laboratory of Industrial Control Technology Zhejiang University 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Networked Control Systems Theory and Its Application Introduction State-of-the-arts of NCS Our results Current focus Future work Summary Questions and remarks 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

ZJU-NLICT-NCS Research Group By Shanbin Li Introduction What is networked control system? ? Do you know the fundamentals of NCS? Network has its positive side ,what is negative side? 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Development history of control system Analogous control system Centralized digital control system Decentralized control system Fieldbus control system (FCS) Networked control system (NCS) by Gregory C. Walsh 1998 Integrated communication and control systems (ICCS) by Ray Asok 1988 Partly Digital Partly Analogous Completely Distributed 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

ZJU-NLICT-NCS Research Group By Shanbin Li Introduction Reference 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

ZJU-NLICT-NCS Research Group By Shanbin Li Definition of NCS NCS is a completely distributed and networked real-time feedback control system. It is an integration of sensors, controllers (+estimators), actuators and communication network of certain local field and is used to provide data transmission between devices in order that users of different sites can realize resource sharing and coordinating manipulation. 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

QoS-parameters of network considered in the control loop Time-delay It varies with network topology, network protocol, network load, network bandwidth and package size Its value may be bounded, unbounded, time-varying, constant and random Packet losses 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

ZJU-NLICT-NCS Research Group By Shanbin Li Normal Sampling 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Vacant Sampling and Packet loss 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

State-of-the-arts of NCS Methodology One: From the view of guaranteeing network QoS. This is a scheduling methodology. Methodology Two: From the view of guaranteeing system QoP. This is a control methodology. Methodology Three: QoS and QoP co-consideration. This is an integrated scheduling and control methodology. Quality of Performance 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Methodology One: Scheduling Part Revise network MAC protocol Walsh ,Ye, Bushnell 1999 introduce an novel protocol TOD (Try-Once- Discard) and scheduling method MEF (Maximum-Error-First) based on the MATI (Maximal-Allowable-Transfer-Interval) which is denoted as  . In TOD, the node with the greatest weighted error from its last report value will win the competition for the network resource .If a data packet fails to win the competition for network access, it is discarded and new data is used next time. Again, the MATI constraint ensures at least one such transmission every  . This protocol can be realized by using CAN. 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Methodology One: Scheduling Part P-CSMA-CA: Level 1: highest priority, time-critical aperiodic data that is burst and cannot bear any loss, retransmission is required when the formal transmission is unsuccessful ; Level 2: time-critical periodic that can tolerate some loss, data that has not been sent will be discarded Level 3: lowest priority, consists of non-critical data which requires data integrity.Retransmission is implemented. If collisions occur, a random back-off is adopted . Revise network MAC protocol Ye, Walsh, Bushnell 2000 introduce a scheduling protocol P-CSMA/CA (Prioritized-CSMA-CA) based on IEEE 802.11 wireless standard. For the first time, they proposed and validated several new algorithms, a constant penalty, an estimated error order and a lag first order for dynamically scheduling the traffic of wireless networked control systems. 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Methodology One: Scheduling Part Sampling time scheduling Hong, 1995 presented a scheduling method of network bandwidth allocation and sampling period decision for multi-loop NCSs in virtue of the notion “window”, namely the service window of each transmission data in network. Hong & Kim 2000 extended this method to random delay networks such as CAN Kim, Kwon, and Park 1996, 1998 enhanced the concept of sampling time scheduling to develop another algorithm for multi-dimensional NCS. 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Methodology One: Scheduling Part Shaping 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Methodology Two: Control Part Augmented deterministic discrete-time method Halevi and Ray，1988 proposed a method to control a linear plant over periodic delay network Liou and Ray，1990 introduced a method to analyze the systems with multi-rate sampling sensor and control Evaluation: The complex of system is in proportion to the dimensions of the state and the input. The computation overhead increases with the dimensions. 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Methodology Two: Control Part Queuing Method Luck and Ray,1990;1994 deterministic delay compensation Chan and Ozguner, 1995 probabilistic delay compensation Evaluation: The dynamic model of the plant is required to be very precise. 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Methodology Two: Control Part Perturbation method Walsh et al.,1999a 1999b；2001 formulated the network delay effects in an NCS as the vanishing perturbation of a continuous-time system Branicky et al.,2000 , Zhang et al.,2001 use this method to compute upper value of MATI , which is far less than value obtained by simulation. (This method is conservative) Evaluation: - The dynamic model of the plant is not necessary to be very precise, may be non-linear - There is no network link between controller and actuator. 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Methodology Two: Control Part LQG/H2 Nilsson 1998 proposed the optimal stochastic control method to control an NCS on random delay networks. The optimal stochastic control method treats the effects of the random network delays in an NCS as a Linear –Quadratic-Gaussian (LQG) problem. Markovian delay case was also analyzed . Krtolica,1994 ，Montestruque,2002 Evaluation: - Better than the determinative method at dynamic performance -Storage overhead of past information. -Time delay less than one sampling period. 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Methodology Three: Control & Scheduling Seto et al. 1996 consider optimal sampling period selection for a set of digital controllers. The performance of each controller is described by a cost function (a performance index), which is approximated by an exponential function of the sampling frequency. An optimization problem is formulated, where the sum of the cost functions should be minimized subject to the schedulability constraint. Both fixed priority and earliest-deadline-first scheduling is considered. Evaluation: - Enhance the processor’s task schedulability by allowing the task frequencies to change in the context of real-time control system performance -Improve the overall system performance - do not consider the input-output latency in the controllers 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Methodology Three: Control & Scheduling Ryu and Hong 1997, 1998 proposed the sampling period optimization problem under the schedulability constraints. Main contribution: a systematic method to derive task-level timing constraints from system-level timing constraints establishing temporal relationship between the system’s external input and outputs maximum loop processing period, maximum allowable input-output latency period ,deadlines 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Methodology Three: Control & Scheduling Zhang 2002 formulated the optimal scheduling problem under both RM-schedulability constaints and NCS stability constraints. Anton Cervin 2003, two Matlab-based toolboxes Jitterbug , TrueTime. http://www.control.lth.se/~anton/ 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

ZJU-NLICT-NCS Research Group By Shanbin Li Our Results 1, Li Shanbin, Wang Zhi, Zhang Weidong, Sun Youxian, Research status and prospect of networked control systems (In Chinese), Journal of Information and Control, 2003. 2, Li Shanbin, Ren Xudong, Wang Zhi, Sun Youxian, Real-time analysis of CAN for networked control systems (In Chinese), Journal of chemical engineering automation and instrument, 2003 3,Li Shanbin,Wang Zhi, Sun Youxian, Fundamental Problems of Networked Control System from the view of Control and Scheduling, IEEE IECON'02, Spain，2002 4. Li Shanbin,Wang Zhi, Sun Youxian , A Novel Auto-tuning Robust PID Controller for Networked Control System, IEEE IECON'03, USA, 2003 5. Li Shanbin,Wang Zhi, Sun Youxian, Auto-tuning Robust Digital PID Controller for Networked Control System, Journal of Zhejiang Universtiy (Engineering), Accepted 6. Li Shanbin, Wang Zhi, Sun Youxian, Guaranteed cost control and its application to networked control systems, IEEE ISIE’04, France, 2004 7. Li Shanbin, Wang Zhi, Sun Youxian, Delay-Dependent Controller Design for Networked Control Systems with Long Time Delays :An Iterative LMI Method, IEEE WCICA, China, 2004 8. Xudong Ren, Shanbin Li, Zhi Wang, Mingze Yuan and Youxian Sun, “A QoS management scheme for paralleled Networked Control Systems,” IECON’03, USA, 2003 9. Xudong Ren , Shanbin Li ,Zhi Wang , Youxian Sun, A QoS management scheme for paralleled Networked Control Systems, Journal of Zhejiang University, Accepted. 10. Ren Xudong ,The Research on Real-time Scheduling Algorithms and its Applications to Paralleled Networked Control Systems, Master Thesis of Zhejiang Universtiy 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Current focus: packet losses Two reason for packet losses The network is unreliable The measurement is purposely dropped to stay within an allocated transmission rate, namely congestion control 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

ZJU-NLICT-NCS Research Group By Shanbin Li Packet losses model (m,k) Markov Chain Hidden Markov Chain 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

ZJU-NLICT-NCS Research Group By Shanbin Li Packet losses model (25-1) 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

ZJU-NLICT-NCS Research Group By Shanbin Li Packet losses model Independent losses Gilbert-Elliot losses Fixed-length burst losses (26-1) (26-2) (26-3) 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

NCS model with packet losses (1) (27-1) (27-2) 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

NCS model with packet losses (1) 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

NCS model with packet losses (1) (29-1) The details refer to Babak Azimi-Sadjadi "Stability of networked control systems in the presence of packet losses", IEEE CDC'03 Limitation: the model doesn’t take the delay into account 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

NCS model with packet losses (2) 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

NCS model with packet losses (2) (31-1) (31-2) 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

NCS model with packet losses (2) (32-1) (32-2) 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

NCS model with packet losses (2) (33-1) (33-2) 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

NCS model with packet losses (2) (34-1) The details refer to Hai Lin, Guisheng Zhai, Panos J.Antsaklis, Robust stability and disturbance attenuation analysis of a class of networked control systems, IEEE CDC’03 Limitation: Delay shorter than one sampling time. 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

Analysis fundament for NCS with packet losses Markov Jump Linear System Theory Dynamic Programming Stochastic System Theory, including estimation and filtering Soft Real-time Scheduling Theory Donglin Liu et al. Firm real-time system scheduling based on a novel QoS constraint, IEEE RTSS’03 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

My NCS model with packet losses Long time delay+ Hidden makovian packet losses Ongoing……… 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

ZJU-NLICT-NCS Research Group By Shanbin Li Future work Scheduling method for NCS in the presence of packet losses Congestion control The relationship between the parameters of network QoS and those of system QoP Stability analysis and controller design of NCS in the presence of packet losses 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

ZJU-NLICT-NCS Research Group By Shanbin Li Summary There is a challenge for better solution methods for the multidisciplinary systems combining control, communication, computation and other disciplines. Research groups: http://www.cwru.edu/cse/ncs/index.htm 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li

ZJU-NLICT-NCS Research Group By Shanbin Li Questions and remarks? Email: sbli@iipc.zju.edu.cn MSN: zjusbli@hotmail.com 2018/11/27 ZJU-NLICT-NCS Research Group By Shanbin Li