Online Real-Time Estimation of Response Time for Periodic Messages in Controller Area Networks

Mathematical Problems in Engineering, Dec 2015

The Controller Area Networks (CAN) are widely used in industrial Networked Control Systems (NCSs), such as construction machineries, hybrid vehicles, robotics, and other applications. The message response time (MRT) or communication delay is the main issue to degrade the performance of CAN-based NCSs since its exact value is time-varying and unpredictable. The online acquisition of exact MRT can be quite helpful for the delay compensation of NCSs. However, since the clocks on different nodes are asynchronous, the MRT acquisition in CAN is a challenging work. The current delay acquisition methods for asynchronous systems are not suitable for the delay compensation in CAN-based NCSs because they either increase the bus load of CAN or cannot acquire the exact MRT in real time. In this paper, we propose a novel online real-time MRT estimation method for periodic CAN messages based on the analysis of message traces on CAN bus. The proposed method can estimate the exact MRT of the received message instance in real time without increasing the bus load and can be conveniently embedded into the CAN nodes without requiring additional equipment. In order to validate the proposed method, practical experiments are carried out and the experimental results show that the proposed method can effectively estimate the exact MRT of periodic CAN messages.

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Online Real-Time Estimation of Response Time for Periodic Messages in Controller Area Networks

Online Real-Time Estimation of Response Time for Periodic Messages in Controller Area Networks Dahui Gao,1,2 Qingfeng Wang,1 Yong Lei,1 Zheng Chen,3 and Linying Shangguan1 1State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China 2Ocean College, Zhejiang University, Hangzhou 310027, China 3Nanjing Research Institute of Electronics Technology, 8 Guorui Road, Nanjing 210039, China Received 19 August 2015; Revised 22 November 2015; Accepted 23 November 2015 Academic Editor: Anna Vila Copyright © 2015 Dahui Gao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract The Controller Area Networks (CAN) are widely used in industrial Networked Control Systems (NCSs), such as construction machineries, hybrid vehicles, robotics, and other applications. The message response time (MRT) or communication delay is the main issue to degrade the performance of CAN-based NCSs since its exact value is time-varying and unpredictable. The online acquisition of exact MRT can be quite helpful for the delay compensation of NCSs. However, since the clocks on different nodes are asynchronous, the MRT acquisition in CAN is a challenging work. The current delay acquisition methods for asynchronous systems are not suitable for the delay compensation in CAN-based NCSs because they either increase the bus load of CAN or cannot acquire the exact MRT in real time. In this paper, we propose a novel online real-time MRT estimation method for periodic CAN messages based on the analysis of message traces on CAN bus. The proposed method can estimate the exact MRT of the received message instance in real time without increasing the bus load and can be conveniently embedded into the CAN nodes without requiring additional equipment. In order to validate the proposed method, practical experiments are carried out and the experimental results show that the proposed method can effectively estimate the exact MRT of periodic CAN messages. 1. Introduction The Networked Control Systems (NCSs) based on Controller Area Networks (CAN) have been widely used in construction machineries, hybrid vehicles, robotics, and other applications. In these NCSs, the feedback signals and control commands carried by CAN messages will suffer from time-varying and unpredictable communication delay or message response time (MRT). When using the random delayed feedback signals and control commands in the control loop, the performance of NCSs will be degraded, and, ultimately, the comfortability, operability, and service life of the equipment will be significantly degraded [1, 2]. How to reduce the adverse impacts of random communication delay in NCSs has become an important research issue. In recent years, many studies have been devoted to the delay in NCSs. In the communication aspect, new protocols (e.g., TTCAN [3] and FlexRay [4]), new encoding mechanism [5], new scheduling policy [6], and queuing/buffering method [7] are proposed to reduce the delay and its variation. However, since these solutions will cause some new drawbacks, such as side effects in fault tolerant ability, complexity of hardware and software, and artificial increase of delays, the conventional CAN are still widely used in industrial applications. The delay is inevitable for CAN-based NCSs. In the control aspect, various control methods are proposed to compensate the delay in NCSs. The robust control [8, 9], predictive control [10, 11], stochastic optimal control [12], and switched system approach [13] are some of the most popular methods. However, in order to improve the performance of the NCSs when using these methods, diverse key issues need to be solved for each method. For real-time delay compensation methods, such as predictive control method, one of the most important issues is to obtain the exact delay of the received data packet in real time. In order to achieve the real-time delay compensation, the delay acquisition should satisfy the following requirements:(i)The delay should be acquired in real time. That means the delay of a received message instance should be identified immediately after its receiving completion.(ii)The acquired delay should be accurate enough. If the acquired delay is too inaccurate, the NCSs’ performance may be degraded further by the delay compensation. The more accurate the delay is, the better the compensation effect can be achieved.(iii)The delay acquisition method should not increase the bus load since the communication performance of CAN is greatly affected by its bus load due to the limited bandwidth. However, due to some limitations, it is a challenging work to acquire the exact delay in the case of meeting the above requirements. As the traffic congestion on CAN bus, which greatly affects the delay, is random, the exact MRT of a data p (...truncated)


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Dahui Gao, Qingfeng Wang, Yong Lei, Zheng Chen, Linying Shangguan. Online Real-Time Estimation of Response Time for Periodic Messages in Controller Area Networks, Mathematical Problems in Engineering, 2015, 2015, DOI: 10.1155/2015/659623