CA6140車(chē)床主軸加工工藝規(guī)程設(shè)計(jì)含CAD圖,CA6140,車(chē)床,主軸,加工,工藝,規(guī)程,設(shè)計(jì),CAD Monitoring Computer Numerical Control Machining Progress Based on Information Fusion TONG Liang1, 2, *,YAN Ping1, 2, and LIU Fei, 2 1 State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400030, China 2 Chongqing Engineering Research Center of Networked Manufacturing, Chongqing University, Chongqing 400030, China Received March 3, 2010; revised March 17, 2011; accepted April 7, 2011; published electronically April 12, 2011 Abstract: To cope with the market demand dynamically, enterprise needs to obtain the production status of work in process real-timely, but the information of machining progress has feature of uncertainty and can not reflect the status of production field effectively. In this work, to overcome the ineffectiveness of computer numerical control (CNC) machining progress information extraction and its application restriction in practice because of heterogeneous system of CNC machine, based on information fusion by analyzing multi-sources information, estimating CNC machining status and predicting the machining progress through tracking tool coordinates, a CNC machining progress monitoring method is presented. The multi-sources heterogeneous information includes machining path, real-time spindle power information, manual input data and tool position. On the method of obtaining this multi-sources heterogeneous information, the method which helps explore numerical control (NC) program, monitor spindle power of CNC, collect human-computer interaction(HCI) information, obtain real-time tool coordinates and express the knowledge concerned in this field is analyzed; The decision rule of CNC machining status in the way of fusing multi-sources information in manufacturing process is summarized, as well as the machining progress tracking method in accordance with real-time tool coordinates and machining path is presented. Finally, the method discussed is proved feasible by the verification of machining progress tracking through simulation experiment. The proposed research realizes the effective integration of CNC machining progress information, and enables enterprises an efficient way to share CNC information and configure CNC resources optimally. Key words: machining progress, information fusion, machining path, CNC machining, process track 1 Introductio To monitor the machining progress of computer numerical control (CNC) machines, the most important manufacturing resources, is the foundation of promoting productivity and tracking manufacturing process[1–3]. Yet in the machining process, there are many situations that lead decision-makers fail to acknowledge the production status, especially the production of some complex parts which have a long time to be manufactured. For instance, simultaneous execution of tasks in heterogeneous CNC machines, the uncertainty of information that results in status delivery inefficiency. Monitoring CNC machining progress in workshop is always of great importance in terms of research on manufacturing process informatization. Up till now, on one hand, reporting manufacturing process according to manual * Corresponding author. E-mail: toli1226@163.com This project is supported by National Natural Science Foundation of China (Grant No. 50775228), Municipality Key Scientific & Technological Program of Chongqing, China (Grant No. CSTC2007AA2013), and Fundamental Research Funds for the Central Universities of China (Grant No. CDJXS11111136), and Program for New Century Excellent Talents in University of Ministry of Education of China statistics is still taken by most enterprises, the way which is both inaccurate and error-oriented. On the other, machining progress can not be guaranteed with human-computer interaction (HCI) which is also influenced by human being. With the deepening of network manufacturing in workshop, monitoring CNC machining progress gradually becomes the focus of research. To illustrate, OKAZAKI [4] introduced the method of collecting machining progress though monitoring NC program instantaneously; MAHAYO- TSANUN, et al [5] , introduced the tooling-integrated sensing systems for the on-line observability of the stamping process; OLIVEIRA, et al [6] , brought the method of monitoring machining process on open CNC system, which collects information by HCI or sensors; WANG, et al [7] , suggested macro instruction in order to obtain CNC status and machining progress information; and HOU [8] established the manufacturing process control framework with STEP-NC compatibility. Owing to the heterogeneity of CNC machine or numerical control(NC) system that made by different manufacturers, the diversity of their way as to get machining process information, and high cost of obtainment of system interfaces, these methods can not apply to the most situations. To solve these problems, or rather, to get rid of the application restriction, an automatic collection method of machining progress information for large-size work pieces based on reference power curve [9] is presented. But the observation error from single source may lead to incorrect results, and can make machining progress invalidated, moreover, in machining, there are various information can reflex machining process from different sides, and the current machining status can be synthetically determined.So machining status and progress should be analyzed and estimated based on the way of information fusion. It is after all the considerations of factors as universality, practicability and cost had this method of monitoring CNC machining progress based on information fusion developed. As stated previously, it is such a mean that (obtains machining status and progress through fusing various manufacturing process information that includes machining path, real-time spindle power information, manual input data and tool coordinates; estimates and predicts the machining progress through tracking real-time position of tool dynamically in processing) can track CNC machining progress efficiently so as to enable enterprises act upon changes in market according to the conditions in production field. 2 Structure of the Method Machining progress of simultaneously executing tasks in heterogeneous CNC machines is a matter of dynamic multiple targets tracking. It is the process of handling, analyzing and estimating the metrical information received from sources, and mapping the targets from physical conditions in reality to logical conditions in the system [10]. first problem to solve, in the process of tracking multiple tasks, is track of singular task. To overcome the ineffectiveness of CNC machining progress information extraction and its application restriction in practice due to the heterogeneous system of CNC machine, CNC machining progress monitoring method based on information fusion is hereby presented. See structure of the method in Fig. 1. Fig. 1. Structure of the method The structure goes from information collection that relevant to machining progress to its logical schema integration. Information includes the following. (1) NC program. It is obtained from database or file system in CAX(CAD, CAE, CAM, etc) or product data (PDM), so as to it can be applied to analyze machining path; (2) Spindle power of CNC. It collects spindle real-time power from sensor and draw power curve; (3) Manual input data. Operator inputs current status and machining progress directly though the interface of HCI in network terminal; (4) Real-time position of tool. It reflects machining progress and status; and should be collected accordingly to the difference of CNC interface. Information is then analyzed by fusion center (IFC). In the process of CNC machining, various information which reflects machining progress are associated and fused according to the machining path defined by NC program. After all, information as current machining status, progress and remaining time estimated by IFC would be sent to decision-makers, to make appropriate policy in time. Knowledge center (KC) provides essential knowledge support for information integration and fusion in machining. Information base (IB) saves the important process data and results; rule base (RB) provides reasoning mechanism and calculation method for multi-sources information fusion; experience base (EB) is created from knowledge and experiences that accumulated in the all machining process and would enrich KC. Data need to fuse always exist in different sources with different forms. In IFC, the characteristics of physical status are abstracted as matrix of status though their own information model, and then generate the status data of the target according to the fusion rule of machining status. In machining status, current state and prediction state are determined by the results of the fusion and estimation from the target status, theoretical machining path, fusion algorithm, and the prediction made by previous fusion. Current logical status can influence the next estimation until machining stops. It is observed that the key problems of monitoring CNC machining progress based on information fusion are as follows: (1) collection and integration of multi-sources information and expression of knowledge concerned; (2) measure of machining status and track algorithm of machining progress with multi-sources information fused. 3 Information Integration and Expression 3.1 Multi-sources information integration 3.1.1 NC program The majority of NC programs are created and managed by enterprise information system, such as CAX, PDM, etc. Only by integrating these systems efficiently can the NC program be worked out. Traditional tightly-coupled way applied to information integration mainly depends on component technology, such as CORBA, COM/COM+/ DCOM, Java RMI, etc. It ensures reusability, portability and interoperability of software, and functions well when managing communication and distributional processes. System based on these technologies is characterized by independent component, transparent network, unified data and interface, etc. However, with the development of network service and the growing demands of system interaction, loose coupling becomes the trend. Service-oriented integration organizes the business processes based on loosely-coupled web service to promote reusability of resources and development efficiency, so much so it turns out the most valuable application. Therefore, when integrate CAX and PDM, it is necessary to adopt either way discussed above so as to integrate NC program by encapsulating and calling the system interface. 3.1.2 Power information of CNC spindle The result of collecting machining task progress through power information of machine tool spindle is fairly satisfactory, for the product which spindle power curve enjoys the feature of similarity and repeatability in mass production. Although power of complex parts which characterized by long machining period, single piece or small quantities of manufacturing are not repetitive, it is feasible to collect some key information in machining process from the curve which is shown in Fig. 2 [9], and the information includes: start machining (a), idle (b, d, f ), cutting (c, e), stop machining (g). In machining, every obvious salient compared with idle power on the curve means one cutting, and the shape of salient is different in cutting mode. There are the same salients when spindle starts and stops, and the salients are named as shape in this paper. Although these information can not reflect the whole machining process but describe some key points in machining process, it can determine the minute to start or stop machining, and estimate whether it is being cutting or not. Fig. 2. Shape of power curve of machine tool spindle 3.1.3 Manual input information Operator and device are two main bodies in manufacturing process. Device information can be collected by sensors, and operator may input observed information into system through HCI. In comparison, it is easier to display subjective initiative to learn and estimate phenomenon observed so that the system can be provided with more accurate information. However, Manual input information has lower real-time and higher delay.Therefore, HCI must make the operation easy and rapid, with minimal time to input maximal information. 3.1.4 Real-time position of tool The way to collect real-time position of tool varies with different NC system. It is easy for newly developed NC system to collect machining process information from interfaces thanks to its higher openness, some machines with universal-Operating-System-controlled NC system can even collect position through application program interface (API) of OS. While the interfaces are not provided on old-fashioned CNC machines, the position of tool can not be read directly from their NC system, and are obtained form CNC producer with high cost. 3.2 Knowledge representation Information collection and integration comes the first in the process of multi-sources information fusion, that is, to unify the logical expression modes of data from various sources. Features of XML such as openness, portability, extendibility help describe complex information, and separation of content from form relieves XML data from being restricted by its own expression but enables multi-sources information integration and share by conveying semantic information [11]. After all, KC can be built to store useful data in knowledge base, taking the following into consideration: (1) reasonable structure adopted to organize and manage knowledge; (2) express knowledge in related field effectively to form reasoning process. There are many advantages to express various information related with machining progress by XML. For one thing, it can unify multi-sources heterogeneous information, for another, important process data and results can be stored in IB for further use. It can be descript as: KIB={ID, St, V, T}, where ID is the index of record in KIB, St is the set of the data styles, V is the set of values, T is the set of time when records being obtained. The rule base in CNC machining can be descript as: KRB={S, R, }, where S={S1S2 , Sn} is the set of all status in process. Then the status can be divided into input status set SI={siii=1, 2, , nsi} and output status set SO={soi|i=1, 2, , nso}, where sii and soi here are an order in S. R={r1r, , rm} is the set of status rules; is the relation of status rules, and use Production rules to express knowledge: It shows that the set of status rules sono can be derived from r(sii. As each production rule applies identical format and is managed as one module, it is easy to index, add, delete, modify, and query from the knowledge base. In the process of information fusion, the experience can be made constant improvements ever after through making use of various information integrated by rule mechanism and modifying results produced by them continuously by self-learning machines and accumulating. 4 Fusion Algorithm of Progress Track 4.1 Analysis of machining path The machining path described as f (x, y, z)=0 and defined by NC program is consist of many continuous arcs. The machining path can also be expressed as G={N, E(l, f)}, where N={Ni|i=0, 1, 2, , n} is the set of nodes; E={e(li, fi|i=1, 2, , n} the vector between two continuous nodes, where li is length of the curve from Ni-1 to Ni, and unit mm, i is assigned by NC program the feed rate on li, and unit mm/min. Today, most CNC machines in workshop still apply the technique of machining complex curved surface by incorporating line with arc interpolation. Analyzing NC program can obtain the matrix of machining path Rn+1, it can be defined as The expression of the parameters in Rn+1 is given in Table 1. 4.2 Fusion rule of machining status The discrimination of time points as start, end, break and resume is of significant meaning for judging current machining status in the track of CNC machining. Once machining begins, status can be judged roughly by following information: constantly changing position of tool, shape of spindle power curve, and possible human input information. According to the method in section 3.2, the fusion rule of machining status goes as follows: where g(w) is the path formed with consecutive nodes in amount of w, is the shape information of spindle power curve, is manual input information, Pstate Cstate are the status of previous and current time. ={ , , , }, where is machining start, is machining end, is break, and is in machining. Status of are given in Table 2. According to the features of different state, concrete determining rule is conducted in Table 3. 44 If machine is working or not is the key point of machining tracking. When it is not, method of judging the starting point of machine begins with the set of w=u indicated as coordinates P1 Puthat collected on timelineconsecutively in the cycle of T can be matched up with its counterpart Q1 Qu in equal intervals in path G, and then spindle power reflects the shape of input information occurs as possible. Tracking and calculating can hereby be carried out while time points of end, break, resume are executed by the same rule. 4.3 Tracking machining progress 4.3.1 Estimation of machining progress It is until now that the concrete machining progress, including current progress and remaining machining time, can be tracked by real time position of tool. Theoretically, the total machining time Tn, according to the