Study On Open Architecture Controller And Its Application In Piston Machining

NC is the foundation and core technology of advanced manufacturing, and reflects a nation's manufacturing and industry level. Nowadays, open architecture controller and fieldbus for motion control are the hotspots in the area of numerical control system. In order to win the new competition of NC technology in the world, we must develop advanced NC system with our own intellectual property. Hence, the paper focuses on the research of open architecture controller and fieldbus for motion control.The architecture of open controller projects, such as OSACA, OMAC, OSEC, is systematically analyzed and compared. The differences in the architecture and implementation among them are elaborated from the view of the reference architecture, classification of function modules, module's behavior expression, communication system, configuration system etc. Based on the above analysis, a methodology is proposed for building an open architecture controller.Taking advantages of typical open architecture projects and combining with advanced PC technology, communication technology, control technology and typical application in controller, a new Soft Open Architecture Platform for controller (SOAP) is presented. SOAP is described by the distributed microkernel pattern of the software architecture theory. The microkernel pattern divides the platform into microkernel module, internal application module and external application module. The microkernel pattern separates the minimal functional core from extended functions and specific functions. Because this description is based on the CORBA component model, the platform is distributed logically, but centralized or distributed physically. Based on the classification of functional modules in OMAC, the design patterns and their structures are described for motion control module, logic control module, axis control module, schedule and update module, human machine control module. The RTCORBA middleware acts as communication system. Therefore, by the means of modularization, loose coupling and tight function cohesion, separation of policy and implementation, separation of interface and implementation, and separation of data stream and control stream, new functions can be added to the system and the function can also be updated in the future; the system can support the third party's components and libraries; at the same time, the new requirements brought forward by users can also be met during the process of system design and implementation.One of important characteristics of open architecture controller is that user can select and configure hardware optionally in a large range. And fieldbus has brought renovation in theautomatic control system. On reference of three typical fieldbuses in motion control, such as SERCOS, MACRO, FireWire, and China standard Electrical equipment of industrial machines—Serial data link for real-time communication between controls and drives, a new fieldbus in motion control—Serial COmunication system in Motion control (SCOM) is presented. A broadcasting bus topology is applied to the net structure. According to ISO/OSI model, reference model for fieldbus interconnection is established. The protocol for physical layer is UART. And based on the high data link control (HDLC) of OSI, the message structure and contents of SCOM are defined. The bus timing, synchronization, error dealing, initialization are also provided. SCOM master and slave card is implemented. The API for application layer of SCOM is provided, and the driver for SCOM master card is also described on the RTLinux. SCOM brings an approach to reform the traditional controller structure, and also eliminates the controller's timing shifts caused by jitters of RTOS. It is a solution for next generation controller with the excellent performance of high speed and high precision. Because the working condition of engine piston is extremely harsh, piston surface is composed by complex 3D curved surface. Analyzing the piston curves, two type of kinemics models are established. One is signal-separating model, the other is signal-synthesizing model. The transverse section curve is given by formula or irregular discrete points. The controller adopts cubic non-uniform B spline to fit the discrete points, afterwards the curve is divided into discrete points by equal angle interval.The frequency range of general servo-drive feed system in the NC machine is about 10~20Hz, but the frequency of tool motion in piston machining is about 1 OOHz, so the special servo system for piston machining must be developed. The electro hydraulic servo drive system is selected for piston machining in the paper. The tool's physical model, i.e. a Bernoulli- Euler beam, is established with complex boundary condition: one fixed end and one free end with an affixed mass. According to functional analysis, the tool's stiffness and 1st order inherent frequency are solved. The tool's dynamics model is 2nd order system on the basis of its physical model. As the result, the tool system is a hydraulic servo system with spring load. Finally, according to the principle of flow continuity, the characteristics of four-path slide valve linearity, and the equation of force-equilibrium, the dynamics model of the tool system is a 3rd order system consisted of a 1st order inertia element and 2nd order oscillating element in series.The hardware platform based on PC can meet the open requirement in open architecture controller. According to the kinemics analysis of piston machining, the controller for piston machining is comprised by two parts. One is for lathe control, which is consisted of PC...