The Design And Implementation Of Autonomous Decentralized Sub-System Based On Linux

The technique of Autonomous Decentralized System which was widely used resolved some online expanding or maintaining problems in traditional decentralized control system. At 2003, the network protocol standard Autonomous Decentralized Protocol(ADP) was adopted as international standard (ISO15745-4). This will make Autonomous Decentralized System being easily constructed and realized.The article research a scheme of constructing Autonomous Decentralized Sub-system (node). This scheme realized Autonomous Control Process which is base the function of Autonomous Decentralized System based upon Linux's TCP/IP protocol and Autonomous Decentralized Protocol, designed program interface of ACP to develop the Aplication on Autonomous Decentralized Sub-system, and provided common developing steps. To verify the scheme, we developed a ADS application example on Linux system which was running ACP.ADP is an application layer protocol realized upon TCP/IP protocol.The content of ADP can completely realized by Linux network Programme technology. Adding or Removing from a Muliticast Group can be accomplished in a way of binding or releasing a UDP port which is corresponding to a Multicast Group Number. ADP multicast communication works in a way of UDP broadcast. We make use of Linux socket interface function to receive or send message. The communication reliability was controlled by message sequence number and version number. We can realize message priority control inside a node by Linux message quenen's type property which is corresponding to seven priorities of ADP message.ADS node software comprises of ACP,ADF and application.ACP is multi-process module which includes message receiving and sengding processes. Receiving process works to receiving and processing message. The receiving message task calls 'select'which is Linux system function to receive message from more than one MG. We use thread poll technique to enhance message handling efficiency.Alive signal is transefered by sending process.ADF is designed with Linux IPC technique. We divide ADF into input part which using Linux message quenen and output which using Linux shared memory. ACP-API is designed with Shared Object technique of Linux. We designed interface function into Shared Object Library which can be dynamically linked. When programming application, the programmer could directly call ACP-API function if the header file of Shared Object Library was included. The function ap_reginfo() of ACP-API work to realize the online extention of AP in one node with the server and client mode of Linux FIFO.This paper constructed a simple temperature monitor ADS on Linux enviroment according to the design scheme. The running result proved that the scheme is feasible, system can run ADP's base communication function, can support the AP online extention of ADS node.