Research On Windows-based Open Architecture Platform In Motion Control And Its Application

Nowadays, open architecture CNC (Computer Numerical Control) systems are becoming one of the most important directions of CNC technology. The purpose of open CNC system research is to build a modular, reconfigurable and expandable architecture of CNC systems to improve the system's flexibility, and enable the systems to be re-developed. As a result, CNC systems can be responsive to the market quickly and economically.As the de facto standard of desktops OS (Operating System), if the problem for using Windows (NT/2000/XP) in real-time system is solved in a method of economically and conveniently, it will be an ideal OS platform for industry control systems, and for the research of OA (Open Architecture) control system. And it spurs people to indulging with the study of using Windows in the domain of OA numerical control system. Fieldbus technology will provide an ideal platform for the openness of control system because of its openness, distributed architecture, suitability for control environment, smartness of each device and its interoperability. Hence this dissertation focuses on the researches of WOAP (Windows-based Open Architecture Platform for controller in motion control) developed with fieldbus technique. The aspects of the research include: the open method for control kernel of Widows OS, fieldbus technology, the real-time mechanism of Windows OS, etc. And the achievementes of the research is applied to a middle - convex and varying ellipse piston turning system. Following are the main work and results:Combining with modern advanced computer technology of hardware and software, communication technology, modern control technology, and according to the requirements of open characteristics of control system, a hiberarchy model for WOAP is presented. WOAP is separated into four layers of physical, operating system (including CNC real-time kernel and device drivers), open-interface and application control. The WOAP hybrid topology architecture is depicted and is implemented by fieldbus technique. The hardware of WOAP includes industry standard PC, fieldbus master control card, motor driver adapters, analog and digital I/O adapters. The software system is separated into three parts of hard real-time, soft real-time and non real-time according to the tasks real-time requirements. A technique is brought forward by implementing the hard real-time task, such as position controlling, real-time monitoring and fieldbus accessing, in the kernel of Windows. With the method of Object-Oriented Analysis (OOA), position control strategy is designed into assembled parts which can be configured by users at running time. The soft real-time tasks and non real-time tasks are implemented in Win32 processes by using Component Object Module (COM) criterion based modular structure. The software reusability, openness, configurable and scalability can be met by COM. The hard real-time kernel is opened by methods of kernel access COM or API (Application Program Interface). The IDL (Interface Definition Language) definition of real-time kernel access COM interface is presented. WOAP can achieve kernel level openness of OA system.Fieldbus has brought great renovation in the architecture of automatic control system, which provides a favorable method for users to select and configure hardware optionally in a large range for OA controller. On reference of SERCOS, and China standard Electrical equipment of industrial machines—Serial data link for real-time communication between controls and drives, by modifing the SCOM (Serial COmunication system in Motion control) presented by Wangheng, a new fieldbus in motion control--RTSB (Real-Time Serial comunication Bus) which is especially suitable for Windows OS is presented. The broadcasting bus topology is applied to the net structure. According to ISO/OSI model, the reference model for fieldbus interconnection is established. The protocol for physical layer is UART. The message structure and contents of RTSB are defined based on HDLC (High Data Link Control) of OSI. The bus timing, synchronization mechanism, error dealing, initialization are also provided. The RTSB master card electric scheme and API for the application layer of RTSB are provided, and Windows driver structure for RTSB master card is also described. A new method for enumerating fieldbus devices is presented which is convenient for allocating network address for fieldbus devices dynamically, and avoids the shortcomings of fixed address for adapter controllers. RTSB brings an approach to reform the traditional controller structure, solves the problem for general OS used in real-time control environment, 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.Windows NT (2000/XP) was originally based on a micro-kernel design. Interrupt handling is done in two steps in Windows NT. As in good real-time operating system, each interrupt service routine (ISR) executed in the immediate step is short. So interrupt latency in NT is comparable to the latencies of real-time operating systems. As an excellent general-purpose operating system, Windows NT consider sufficiently for the soft real-time on the aspects of interrupt handling, threads scheduling, virtual memory managing etc., with its mechanism of DPC (Deferred Procedure Call) and fully preempted kernel etc., Windows NT can provides very high throughput for data exchanging and very short interrupt latency. Since the interrupt latency in IRQL (interrupt request level) is comparable to the latencies of real-time operating systems, we can enhance the real-time capability by extension of Windows OS. The requirement of predictable interrupt latency can be met by extending Windows NT using device drivers which running in Windows kernel. The device driver of RTSB master card with PCI/ISA bus is programmed' by Windriver Kernel Plugin. The interrupt latency performance of Windows NT is evaluated by a series of tests, and the results show that the ISR latency time can be seen to be quite deterministic and predictable. By planning the responsive sequence of the driver properly according to characteristics of Windows interrupt acknowledgment, and cooperating with RTSB master controller, real-time capability of Windows NT can be enhanced greatly. The structure of WOAP micro-kernel, data exchange buffer and the method for openness of the real-time kernel is described. The numerical control platform constructed by Windows ISR, cooperating with RTSB controller, synchronous error is less than 250ns and hard real-time level is achieved. WOAP solved the problem of real-time performance capability for using Windows in real-time system in a method of economically and conveniently, which can meet the real-time requirements of CNC system.To improve the performance of engines, piston profile is composed by complex 3D curved surface to compensate the shape distortion of the piston in high temperature and high pressure environment. Based on the analyzing of pistons profiles now common in engine, a design mechanism of first resolving then composing pattern is proposed by analyzing the characteristics of piston shape. The Middle convex and varied elliptic surface is divided into the three basic characteristics of middle convex, ellipse and varied ellipse, and each was described in mathematical manners. To suit for the varying of piston shape, two additional characteristics of rotating and eccentricity is introduced. The transverse section curve is divided into regular curve and irregular curves. The analytical formulation is used to describe the regular curve and cubic non-uniform B spline is used to fit the irregular curve. The middle convex and varied ellipse characteristics are fitted by cubic spline. According to kinematic characteristic of the tools when machining the noncircular pistons, a hybrid kinematic model of signal-separating model with signal-synthesizing model is established. Although the basic characteristic of the piston is analyzed, the elements of the piston cannot be machined independently and they must be machined concurrently. All elements are composed to generate the machining data for controlling the motion track of cutting tool. By using a serial of ellipse cones, the middle-convex and varying ellipse can be approached, which can not only decrease the numbers of discrete sections and reduce file size, but also improve the precision of profile. According to the shape elements, shaping design software is programmed with modulization idea. This system has a few merits including powerful functions, friendly interface, easy use, good expansibility and so on, which can meet the shape design requirements of the pistons now common in engines. The design system is integrated with the CNC turning machining system organically, which is convenient for the turning module to receive the CNC information and integrative control of the lathe and turning module, and great flexible of the CNC system can be achieved.As a use case of WOAP, the lathe for abnormity circular piston machining is designed. 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 100Hz, so the special servo system for piston machining must be developed. GMA (Giant Magnetostrictive Actuator) system is selected for piston machining in the paper. According to the kinematic analysis of piston machining, the controller for piston machining is comprised by two parts. One is for lathe control and the other is for ellipse-machining control. Based on WOAP, an axis adapter is expanded to implement the control for ellipse-machining control. The dynamic model of the GMA system is analyzed which can be simplified to a system with 1^st order element and a delay element in series. The dynamics model of GMA tool system is identified by the method of frequency response. Vertical cross correlation method is used for data processing to deal with problems of identified error in condition of noise. After the amplitude and phase of the system is calculated out, the approximate transfer function of the system is presented. Amplitude-phase adjusting feed-forward control in the frequency domain and PID strategy are used to revise the GMA system. The control scheme is applied to the machining of pistons, and the accuracy of the work-piece can meets the design requirement which proves the effective of the scheme.