Timing Analysis of Real-Time Communication Under Electromagnetic Interference

In order to contrast and analyze the real-time performance of the powertrain system of a plug-in hybrid electric vehicle, a mathematical model of the system delay is established under the circumstances that the transmission adopts the CAN (controller area network) protocol and the TTCAN (time-triggered CAN) protocol, respectively, and the interior of the controller adopts the foreground-background mode and the OSEK mode respectively. In addition, an experimental platform is developed to test communication delays of messages under 4 different implementation models. The 4 models are testing under the CAN protocol while the controller interior adopts the foreground-background mode; testing under the CAN protocol while the controller interior adopts the OSEK mode; testing under the TTCAN protocol while the controller interior adopts the foreground-background mode, and testing under the TTCAN protocol while the controller interior adopts the OSEK mode. The theoretical and testing results indicate that the communication delay of the OSEK mode is a little longer than the one of the foreground-background mode. Moreover, compared with the CAN protocol, the periodic message has a better real-time performance under the TTCAN protocol, while the nonperiodic message has a worse one.

Digital avionics using line replaceable unit (LRU) and integrated module avionics (IMA) has been promoted into very simplified and flexible design supports in modern system. Digital data bus system using controller area network (CAN) for small aircrafts has improved the accidental event by adding time trigger (Lin et al., 2006). However, the predictability on data transmission requires enforced. The arbitration mechanism in CAN has awarded higher priority to those high frequency data or important real time data. Some deficiency may cause unpredictable delays on lower priority message and data lose when high bus load situation. To integrate time trigger into time triggered CAN (TTCAN) chip can improve the time scheduling in periodic data transmission (Shaheen et al., 2002). Consequently, the complexity in time sequence synchronization has brought in significant load in development. This research method classifies the data frequency and assigning the concept of time to integrate hybrid data bus system. The research goal uses concept of TTCAN on dual bus CAN system and improve disadvantage of CAN.

Basically, the controller area network (CAN) is an event-triggered control network. However, design of precise and safety-critical applications requires time-triggered protocols as the communication infrastructure to achieve hard real-time performance. Although the time-triggered controller area network (TTCAN) is suitable for synchronized applications, complexity and inflexibility of implementing the TTCAN cause limited applications in motion control. This paper implements CAN communication services on precise synchronized multi-axis motion control by introducing the event/time-triggered structure. A motion command estimator is implemented to estimate the lost messages caused by the network transmission rate. The proposed CAN-based motion control system achieves desirable performance even under a lower transmission rate with heavier message loading on the bus. Furthermore, the proposed event/time-triggered structure has been successfully applied to a DYNA MTYE 1007 CNC machine and experimental results indicate that tracking accuracy in different CAN transmission rate has been obtained

A number of methods have been proposed for the response-time analysis (RTA) of controller area networks (CANs), which are the industry standard for in-vehicle network protocols. However, most of these methods are unsuitable for analyzing nonperiodically transmitted messages because they assume a constant transmission period for each message. Moreover, the calculated evaluation criteria are limited and comprise many over-pessimistic estimations, such as the worst-case response time (WCRT). To tackle these problems, this paper proposes an RTA method for CANs with randomly occurring messages, which replaces the constant transmission period with the average number of transmission instances per unit time. This approach finds the approximate probability distribution of the response time to any message in a CAN, providing a more general measure than the WCRT. To this end, a mathematical model based on M/G/1 queueing theory is developed. The model accurately emulates the behavior of nonperiodic CAN messages and enables RTA with minimal pessimistic estimations. When tested against the benchmarks, the proposed method accurately obtained response time distributions within several seconds to several tens of seconds.

The response time distributions of the frames sent on a Controller Area Network (CAN) bus are of prime interest to dimension and validate automotive electronic architectures. However, the existing work on the timing behaviour of the CAN network does not take into account that all the data exchanges between the Electronic Control Units (ECUs) are driven by different and independent clocks which are subject to clock drifts. This paper proposes a model for clock drifts and describes their impact on the CAN frame response time distributions. By implementing the clock drifts in a CAN simulation tool, we show experimentally that the response time distributions converge, for drift values chosen randomly within the same range on all ECUs, whatever the initial phasings between the sending nodes. Furthermore, we show that, as a result of the clock drifts, the situations leading to the worst case response times are transient.

A probabilistic approach to determine response-time distribution for messages in Controller Area Network (CAN) is presented here. CAN is a field bus level communication network for exchanging short real-time messages. CAN is mostly used to carry periodic messages for control and automation systems. Traditional response-time analysis of CAN messages only gives worst-case response-times. This introduces pessimism in analysis, resulting in over designing and under utilization of resources. Response-time distribution is a probabilistic function. Response-time distribution provides a complete characterization of CAN message response-time. It can provide probability of meeting/missing any specified response-time limit. This probability is useful for system reliability and performance modeling. In this paper response-time model of CAN messages is discussed. Technique to derive probabilistic parameters of response-time model, for periodic CAN messages with deterministic transmission times is given. The method has been applied to a standard data set, results are compared with that of worst-case analysis and reasons for deviations are discussed.

Controller Area Network (CAN) is used extensively in automotive applications, with in excess of 400 million CAN enabled microcontrollers manufactured each year. In 1994 schedulability analysis was developed for CAN, showing how worst-case response times of CAN messages could be calculated and hence guarantees provided that message response times would not exceed their deadlines. This seminal research has been cited in over 200 subsequent papers and transferred to industry in the form of commercial CAN schedulability analysis tools. These tools have been used by a large number of major automotive manufacturers in the design of in-vehicle networks for a wide range of cars, millions of which have been manufactured during the last decade.This paper shows that the original schedulability analysis given for CAN messages is flawed. It may provide guarantees for messages that will in fact miss their deadlines in the worst-case. This paper provides revised analysis resolving the problems with the original approach. Further, it highlights that the priority assignment policy, previously claimed to be optimal for CAN, is not in fact optimal and cites a method of obtaining an optimal priority ordering that is applicable to CAN. The paper discusses the possible impact on commercial CAN systems designed and developed using flawed schedulability analysis and makes recommendations for the revision of CAN schedulability analysis tools.

In the present day scenario, industrial automation is the most prominent and very common phenomena. Normally, to establish communication among different modules, in industrial applications controlled area network (CAN) protocol is very popular. As the number of devices connected to CAN bus increases, response time also increases for devices connected to CAN, which may lead to catastrophic effects in the system. As CAN deals with electrical signals it may generate electromagnetic interference (EMI) in signal sensitive areas. To avoid EMI and to reduce response time due to CAN bus protocols, other alternatives are to be thought of. So, to overcome the limitations and to resolve the problems due to CAN bus in industrial controlling a novel idea is proposed by the authors for controlling and monitoring the remote plant using Li-Fi. Remote plant is a signal sensitive area, where first a communication link based on Li-Fi is developed to monitor various modules of the plant and then collected data is stored in a server using Wi-Fi module, and necessary control signals are also sent through the Wi-Fi protocol to the plant to control it.

The Controller Area Network (CAN) is widely employed in automotive control system networks. In the last few years, the amount of data has been increasing rapidly in these networks. With the purpose of improving CAN bandwidth efficiency, scheduling and analysis are considered to be particularly important. As an effective method, it has been known that assigning offsets to the CAN messages can reduce their worst case response time (WCRT). Meanwhile, the fact is that many commercial CAN controllers have been equipped with a priority or first-in-first-out (FIFO) queue to transmit messages to the CAN bus. However, previous researches for WCRT analysis of CAN messages either assumed a priority queue or did not consider the offset. For this reason, in this paper we propose a WCRT analysis method for CAN messages with assigned offset in the FIFO queue. We first present a critical instant theorem, then we propose two algorithms for WCRT calculation based on the given theorem. Experimental results on generated message sets and a real message set have validated the effectiveness of the proposed algorithms.

International audience

The Controller Area Network (CAN) dominates in-vehicle networking systems in modern vehicles. CAN was designed with low-latency and reliability as key features. Authenticity of a CAN frame was not considered in the design, thus, most in-vehicle network nodes inherently trust received messages as coming from a legitimate source. As a result, it is trivial to program (or hack) a network node to spoof traffic. Authentication is challenging for CAN and related protocols, such as SAE J1939, due to limited frame sizes and high bus utilization. Adding a message authentication code (MAC) as a separate message can unduly stress the real-time delivery of safety-critical messages. Although this stressor is well-known, the impact of authentication protocols on real-time message delivery in CAN has not yet been thoroughly examined. In this paper, we provide the first comprehensive analysis of realtime schedulability analysis applied to authentication schemes for CAN, CAN Flexible Data-rate (CAN FD), and CAN extra long payload (CAN XL). We formulate the response time analysis for addition of MACs and periodic transmission of MACs, and we examine their impact on two case studies and through evaluation with randomized schedulability experiments over a wide range of message sets.

The controller area network (CAN) system is one of the serial bus systems used in various applications, such as automobiles, airplanes, and industry. This study describes the analysis of electromagnetic interference (EMI) caused by a buck converter that is installed close to a CAN communication bus, and highlights the problems in a conventional EMI evaluation, followed by the development of an experimental EMI mitigation method. The experiments performed for verification show that the periodic switching noise of a buck converter causes data-transmission failure of CAN. Finally, this study proposes a novel control method for a buck converter, which can reduce the data-transmission failure of CAN.

This paper investigates the concept of share-driven scheduling of networks using servers with real-time properties. Share-driven scheduling provides fairness and bandwidth isolation between predictable as well as unpredictable streams of messages on the network. The need for this kind of scheduled real-time communication network is high in applications that have requirements on flexibility, both during development for assigning communication bandwidth to different applications, and during run-time to facilitate dynamic addition and removal of system components. We illustrate the share-driven scheduling concept by applying it to the popular controller area network (CAN). We propose a scheduling mechanism that we call simple server-scheduled CAN (S/sup 3/-CAN), for which we also present an associated timing analysis. Additionally, we present a variant of S/sup 3/-CAN called periodic server-scheduled CAN (PS/sup 2/-CAN), which for some network configurations gives lower worst-case response-times than S/sup 3/-CAN. Also for this improvement, a timing analysis is presented. Moreover, we use simulation to evaluate the timing performance of both S/sup 3/-CAN and PS/sup 2/-CAN, comparing them with other scheduling mechanisms.

The Controller Area Network (CAN) is widely used for distributed systems in automotive and other applications such as safety-critical applications. As such, it is necessary to evaluate the property of the continuous working ability of a CAN node. In this paper we setup a discrete time Malkov chain model based on the fault confinement mechanisms of CAN to calculate how long a CAN node can work normally before it goes into its "bus-off" state. An example will be given to show the theoretical conclusion finally.

Electromagnetic interference (EMI) on wired communication systems caused by a switched-mode power supply is often remarkable in practice. The EMI undermines the performance of the communication and robust operation of the system. In this paper, a test system where a buck converter and a controller area network (CAN) communication system are integrated enables to measure noise waveforms and analyze the EMI mechanism in the time-domain. The simulation model of the system also performs verification of the mechanism. In the system, the DC bus cables connected to the converter are closely adjacent to the communication cables and they have electromagnetic couplings. Hence, when the converter generates a switching noise in the DC bus, an induced noise happens in the communication cable, which results in communication failure. Based on the EMI mechanism, a noise elimination method is developed and implemented to the CAN of the test system to prevent communication failure. The proposed method is feasible in the converter controller and it does not require additional hardware components to reduce the communication failure. Through experimental verification, the proposed method enables to reduce communication failure.