Building Light Weight CORBA Based Middleware for the CAN Bus Systems
Seongsoo Hong · Transaction on Control, Automation and Systems Engineering · 2001
The software components of embedded control systems get extremely complex as they are designed into distributed sys- tems consisting of a large number of inexpensive microcontrollers interconnected by low-bandwidth real-time networks such as the controller area network (CAN). While recently emerging middleware technologies such as CORBA and DCOM address the com- plexity of distributed programming, they cannot be directly applied to distributed control system design due to their excessive re- source demand and inadequate communication models. In this paper, we propose a CORBA -based middleware design for CAN- based distributed embedded control systems. Our design goal is to minimize its resource need and make it support group communica- tion without losing the IDL (interface definition language) level compliance to the OMG standards. To achieve this, we develop a transport protocol on the CAN and a group communication scheme based on the well-known publisher/subscriber model. The proto- col effectively realizes subject-based addressing and supports anonymous publisher/subscriber communication. We also customize the method invocation and message passing protocol, referred to as the general inter-ORB protocol (GIOP), of CORBA so that CORBA method invocations are efficiently serviced on a low-bandwidth network such as the CAN. This customization includes packed data encoding and variable-length integer encoding for compact representation of IDL data types. We have implemented our CORBA -based middleware on the mArx real-time operating system we have developed at Seoul National University. Our experiments clearly demonstrate that it is feasible to use CORBA in developing distributed embedded control sys- tems possessing severe resource limitations. Our design clearly demonstrates that it is feas ible to use a CORBA -based middleware in developing distributed embedded systems on real-time networks possessing severe resource limitations.