Abstract

The Controller Area Network (CAN) protocol is widely used in distributed real-time, resource-constrained embedded systems. CAN uses “Non Return to Zero” (NRZ) coding and employs a bit-stuffing mechanism for clock synchronization. Such a mechanism causes a variation in the CAN frame length which may have a detrimental impact on the control behaviour of safety-critical systems employing this protocol. To address this issue, two techniques known as “byte-based XOR masking” and “software bit stuffing” were developed and achieved a jitter reduction of up to 20% and 40%, respectively, when employed in practical designs. This paper investigates the effectiveness of such techniques in a real-time control application; that is a simple furnace system case study based on a “hardware-in-the-loop” (HIL) testbed facility. The results show that reducing bit stuffing jitter has the potential to improve the control performance of distributed real-time systems employing CAN protocol.

Highlights

  • The Controller Area Network (CAN) protocol is widely used in distributed embedded control systems [1,2]

  • The main aim of this study is to show how much improvement in the control performance of such a furnace system can be achieved by reducing transmission jitter in the CAN network when applying “Nolte C” and software bit stuffing” (SBS) techniques

  • The case study considered was the CarboNitriding heat-treatment furnace system consisting of two communicating nodes where the nodes were connected physically via CAN hardware network protocol

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Summary

Introduction

The Controller Area Network (CAN) protocol is widely used in distributed embedded control systems [1,2]. CAN uses “Non Return to Zero” (NRZ) coding for bit representation, under which drift in the receiver’s clock may occur when a long sequence of identical bits has been transmitted. This drift might, in turn, result in message corruption. To avoid the possibility of this scenario, the CAN communication protocol (in its physical layer) employs a bit-stuffing mechanism which operates as follows. After five consecutive identical bits have been transmitted in a given frame, the sending node adds an additional bit of the opposite polarity.

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