Analysis of timing properties from network control systems

Abstract

Due to the increased availability of low cost network technology, the use of networks to interconnect sensors, actuators and controllers is becoming widely accepted for the implementation of feedback control systems. Such type of feedback implementation, wherein the control loops are closed through a real-time network, is called Network Controlled Systems (NCS). When implementing a NCS, the underlying communication network must provide a timely communication service, which must be the adequate to fulfil the control application requirements. Therefore, the assessment of the network responsiveness to the realtime requirements of the control application is a fundamental issue. The CAN network is usually considered suitable to support small-scale NCS, due to their real-time capabilities. However, their temporal responsiveness is highly dependent on both the timing characteristics of the supported message streams, such as its periodicity and the related message lengths. In this paper, we analyse the timing properties of CAN control network. Basically, we assess their capability to support Network Controlled Systems, through the evaluation of the related worst-case messages response time. A small example of a NCS is then used to assess the capability of the CAN control network to fulfil control application requirements.