Design and Realization of Bus-based Control Module

Along with the innovation of automatic control technology, the complexity of thecontrol system is increasing day by day. Traditional control system design processshows its disadvantages gradually, it is difficult to development the system and the cycleis too long, it also difficult in debugging and maintenance, design is inefficient, theability of reconfiguration is low. Based on these problems, the bus-based and networkedcontrol system emerges as the time requires. The centralized system becomes to severalnetwork nodes by bus. At the same time, it is also decoupled into many functionalmodules what are independent of each other. This way can solve the above problemeffectively.The purpose of this paper is designing such bus-based control module. The modulechooses the RS485bus as the primary connection channel. It makes the module havestandard and rich interfaces, realize the functional modules of the system in the platformconnecting with bus, and have generality.First of all, this paper put forward a overall design according to the input/outputsignal and interface that the function module need, communication mode of the system.It gives the detailed description about connections, network mode, and the functions andthe standard interfaces the control module should have.Secondly, according to the framework of the overall design, it gives the schematiccircuit diagram of the bus-based control module and designs the printed circuit board. Itbuilds the peripheral circuit about many functions such as several communicationinterfaces, radio frequency, AD, DA, and Motor Drive and so on with SAM3U4Csingle-chip microcomputer at the core.Thirdly, it describes the design of the RS485bus communication protocol. Itcontains the format of the data frames, the format and coding of the operatingcommands, mechanism of communication among the modules, query mode, and thehow to realize the program flow of the communication protocol.Finally, it brings several bus-based control modules into practical application. Theyare used in five control system called two-axis turntables. It describes how to realize the related function and some key critical points in detail. Then software of upper machineaiming at monitoring to the whole production control system is given. The systems canachieve the functions such as positioning, target tracking successfully with the help ofthe bus-based control modules. In addition, it tests the process of the buscommunication. And the result of using the control modules is showed after that. Itdemonstrates the validity of the design.