Design and Implementation of a Self-Configuring Instrument Control System

The trend in the design of complex instruments is toward distributed control systems implemented with networks of embedded devices. Historically these embedded networks have been implemented using field busses such as CAN, Lon Works, or Profi Net but the ubiquitous nature and low cost of Ethernet has made it the trend in embedded network applications. Ethernet, however, largely depends on DHCP and DNS servers or static IP addressing scheme to enable communication between devices on the network. This paper presents a service-oriented architecture for self-configuring Ethernet-based distributed control systems that is able to adapt to changes in network topology without manual intervention. The three core technologies used to enable self-configuration are all part of Zero Configuration Networking: link-local address auto-configuration for automatic IP address assignment, multicast DNS for automatic hostname resolution, and multicast DNS service discovery for automatic discovery of services. A temperature control system is developed as a case study implementation of the architecture using Java and SOAP web services. Programming web services is simplified using the Java API for XML-Web Services. Programmer productivity is also improved since Java enables the use of enterprise level development tools for debugging and deployment.