英文原文Evolutionary programming of CNC machinesAbstractThe paper proposes a new concept for programming of CNC machines. The concept based on genetic algorithms assures evolutionary generation and optimization of NC programs on the basis of CAD models of manufacturing environment. The structure, undergoing simulated evolution, is the population of NC programs. The NC programs control the machine which performs simple elementary motions. During the evolution the machine movement becomes more and more complex and intelligent solutions emerge gradually as a result of the interaction between machine movements and manufacturing environment. The examples of evolutionary programming of CNC lathe and CNC milling machine tool for different complexities of the blanks and products are presented. The proposed concept showed a high degree of universality, efficiency, and reliability and it can be also simply adopted to other CNC machines. 2005 Elsevier B.V. All rights reserved.Keywords: Manufacturing systems; NC programming; CNC machines; Genetic algorithm.1. IntroductionSince the CNC machines are already present in almost all manufacturing systems, the automatic programming of CNC machines became widespread in the last two decades 1,4,6,7. Thus, nowadays numerous commercial programming solutions, including automatic generation of NC programs, are available. The solutions differ in reliability, ef-ficiency, flexibility and universality. So far, it has not been possible to trace a universal solution for the programming of NC machines. In this paper we used the genetic algorithms (GA) 2 based approach for programming of CNC lathe and milling machine tool. The proposed concept can be adopted also to other CNC machines for example coordinate measuring machines 5, welding machines, laser and plasma cutting machines 4, robots and manipulators. The concept imitates the natural evolution of living organisms, where in the struggle for natural resources the successful individuals gradually become more and more dominant, and adaptable to the environment in which they live, whereas the less successful ones are present in the next generations rarely. In the proposed concept the NC programs, represented as weighted graphs, undergo adaptation. During the simulated evolution more and more successful organisms (the NC programs) emerge on the basis of given data on manufacturing environment. Researches have shown that the proposed concept is universal, flexible, reliable, and efficient. For the paper to be self-contained the basic terms on turning and milling processes are stated in the beginning of theSection 2. Afterwards the idea of the proposed concept is presented. The coding (i.e., genotype) of the individual NC program (organism), the evaluation of organisms, and the genetic operations used are described. Sections 3 and 4 showfunctioning of the proposed system. The examples of programming of CNC lathe and CNC milling machine tool for different combinations of exactingness of the blank and product are given. Section 5 summarizes the main contributions ofthe performed research and also gives guidelines for further researches.2. Programming of CNC lathe and milling machine tool with GAThe objective of turning and milling process is to assure relative motion of the tool with respect to the workpiece. The consequence of the relative motion is moving of the tool reference point and, consequently, forming of the desired shape of the product. The tool movement consists of the working and feeding motions. Machining of material takes place in several cuts whose optimum sequence is known in general only for very simple products. Each working motion takes off a certain quantity of material and thus it produces the cuttings.2.1. Main algorithmThe basic idea of the proposed concept will be demonstrated on simple examples. Figs. 1 and 2 show the blank, product and the relevant chips in turning and milling process, respectively. The area of the possible tool (blade) motion isdiscretized into squares in case of turning and boxes in case of milling. The tool of one square thickness in turning can move discretely up, down, to left and to right, whereas it cuts only to right or downwards. In case of milling the tool canmove and cut in the positive and negative directions of axes x, y and z. Due to the discretization of the machining field the tool reference point is in the middle bottom of the cutting tool (Figs. 1 and 2).The material to be taken off is divided into several cuts consisting of chips. For example, the cut-1 in the bottom diagram of Fig. 1 consists of nine chips, the cut-2 and the cut-3 consist of four chips each, the cut-4 of two chips, etc.Diagrams at the right of Fig. 1 show the types of machining. Due to the discrete nature of the system it is possible to select horizontal, vertical or combined cuts.Fig. 3 shows the main algorithm for programming of the CNC machine tool in the pseudo c