Controller Area Network Network Research Articles

An Active Star Topology for Improving Fault Confinement in CAN Networks

The controller area network (CAN) is a field bus that is nowadays widespread in distributed embedded systems due to its electrical robustness, low price, and deterministic access delay. However, its use in safety-critical applications has been controversial due to dependability limitations, such as those arising from its bus topology. In particular, in a CAN bus, there are multiple components such that if any of them is faulty, a general failure of the communication system may happen. In this paper, we propose a design for an active star topology called CANcentrate. Our design solves the limitations indicated above by means of an active hub, which prevents error propagation from any of its ports to the others. Due to the specific characteristics of this hub, CANcentrate is fully compatible with existing CAN controllers. This paper compares bus and star topologies, analyzes related work, describes the CANcentrate basics, paying special attention to the mechanisms used for detecting faulty ports, and finally describes the implementation and test of a CANcentrate prototype.

Design and Implementation of a Vehicular Controller Area Network Bus System with an Application of Active Noise Control for Engine Exhaust System

This paper describes the design of a vehicular controller area network (CAN) bus system with an application of active noise control (ANC) for engine exhaust systems. The work includes two parts: the first part is the design and implementation of a CAN bus platform system; the second is an application of ANC to an engine exhaust system which utilizes the CAN network implementation. The proposed ANC uses the adaptive control algorithm with engine speed as a reference. Most of the conventional methods for ANC involve primarily an adaptive filter with the least-mean-square (LMS) error algorithm. Unfortunately, convergence speed is often limited when a sound source or a filtering plant varies, because the learning process of the adaptive algorithm fails to respond quickly to the changing operational conditions. In this study, a variable step-size affine-projection algorithm (VSS-APA) is proposed. The proposed VSS-APA filtering algorithm is a combination of the variable step-size convergence algorithm and the affine-projection algorithm (APA). The controller is implemented on the proposed CAN bus system. Experiments are carried out to evaluate the noise attenuation performance at various engine speeds. The experimental results indicated that the ANC system achieved the noise attenuation in an engine exhaust system by using the proposed CAN bus system.

Performance evaluation of the distributed implementation of a car suspension system

Abstract In a wide category of embedded systems, sensors, controllers and actuators are located in distant locations. To ensure the control functions, these components need to be interconnected. Usually, communication networks are chosen to support the required communication exchange. In the context of the automotive industry, the Controller Area Network (CAN) bus is yidely used because of its interesting properties. In theory, a CAN network can ensure real-time communications, when no transmission errors are detected. However, an incrpasing numher of applications are sharing this hus, generating jitter and delays on the exchanged messages, which can degrade the performance of control applications. In this paper, the distributed implementation of an active suspension controller is modelled in Simulink thanks to the use of the tool box TRUETIME. The network traffic is generated using the well-known SAE benchmark. Using this simulation model, the control performance of the active suspension system is studied as a function of the available network bandwidth

Delay analysis of priority promotion systems

Distributed real-time systems are often characterised by tight timing requirement on data exchanges, which should take place within precise deadlines in order to ensure that the system operates correctly. In this paper, a new priority promotion mechanism is introduced which is based on the medium access technique of the Controller Area Network (CAN) protocol and which offers a higher degree of robustness and responsiveness than token-based networks. At the same time, unlike conventional CAN networks, the one proposed is very fair and provides a means by which the schedule for the different real-time message streams in the system can be defined precisely. The priority promotion mechanism is analysed in detail and an analytical expression for an upper bound on the worst case transmission time is found.

Design and implementation of efficient message scheduling for controller area network

The Controller Area Network (CAN) is being widely used in real-time control applications such as automobiles, aircraft, and automated factories. In this pacer, we present the mixed traffic scheduler (MTS) for CAN, which provides higher schedulability than fixed-priority schemes like deadline-monotonic (DM) while incurring less overhead than dynamic earliest-deadline (ED) scheduling. We also describe how MTS can be implemented on existing CAN network adapters such as Motorola's TouCAN. In previous work, we had shown MTS to be far superior to DM in schedulability performance. In this paper, we present implementation overhead measurements showing that processing needed to support MTS consumes only about 5 to 6 percent of CPU time. Considering its schedulability advantage, this makes MTS ideal for use in control applications.

FastCAN: a high-performance enhanced CAN-like network

The controller area network (CAN) is a real-time fieldbus network which today is very popular in industrial environments because of its very appealing characteristics and low implementation costs. It has, however, serious limitations regarding the network extension and the transmission speed which may rule out this protocol in the next few years, at least for the use in high-performance automation systems. This paper presents a modification to the conventional CAN protocol based on a dual channel topology, which overcomes those limitations and exhibits a behavior that is very similar to the original standard protocol. FastCAN features very high communication performance and ensures a certain degree of compatibility with the existing devices and applications developed for the conventional CAN networks.

Design of Reliable Real-Time Applications Distributed Over CAN (Controller Area Network)

Real-time applications distributed over the CAN network are characterized by stringent temporal and dependability constraints. Our goal is to take account of transmission errors in the design of real-time distributed applications because in practice the consequences of such disturbances are potentially disastrous. In the paper, we propose, on the one hand, a method for computing for each message the tolerable threshold of transmission errors guaranteeing the timing constraints to be met. On the other hand, we also suggest an error model enabling us to consider both error frequency and error gravity. Our error model follows a generalized poisson process and its stochastic parameters have been derived. The analysis has been applied to an industrial case-study to compute the probability that the deadlines will be respected.