1、PDF外文：http:/ Development of a 3-axis Desktop Milling Machine and a CNC System Using Advanced Modern Control Algorithms Byung-Sub Kim， Seung-Kook Ro and Jong-Kweon Park 1Nano Convergence Manufacturing Systems Research Division, Korea Institute of Machinery & Materials, Daejeon, South Korea,
2、 305-343 Corresponding Author / E-mail: bkimkimm.re.kr, TEL: +82-42-868-7109, FAX: +82-42-868-7180 In this paper, we introduce a desktop-size 3-axis milling machine and a CNC system which was developed to operate the 3-axis milling machine. The 3-axis milling machine has a mini-desktop size of 20030
3、0200 mm3 and its cutting volume is 202020 mm3. The vertically installed XY stage is driven by voice-coil motors, and for the z-axis, a magnetically preloaded air bearing and a linear motor are used. The air spindle runs at up to 160,000 rpm. The gravity force is acting on the y-direction, so a weigh
4、t balancer using an air bearing cylinder is installed to cancel out the gravity force acting on the XY stage in the y-direction. The CNC system designed for the 3-axis milling machine consists of two parts. The one is a graphical user interface program which runs under Microsoft Windows and the othe
5、r is a DSP program which is implemented on a DSP board with TI TMS320C6701 chips. A G-code interpreter is included in the CNC system which can interpret and interpolate a basic set of G-codes and M-codes in real-time. To improve the performance of servo control loop in the CNC system beyond the trad
6、itional PID-type control, several modern control algorithms have been tested including control, input shaping control, disturbance observer and cross-coupled control on the 3-axis milling machine. Experimental results show the effectiveness and drawbacks of each control scheme when they are ap
7、plied to the 3-axis desktop milling machine. KEYWORDS: 3-axis milling machine, CNC system, H control, Input shaper, Cross-coupled control 2 1. Introduction As new fields such as IT(Information Technology), BT(Bio Technology) and NT(Nano Technology) emerge as a driving force in the industry, th
8、e interests in micro-factory system have been growing. The micro-factory is a miniaturized flexible manufacturing system which consumes minimal space and energy compared to the conventional one, and it is desired to produce micro/meso size mechanical components necessary for IT, BT and NT applicatio
9、ns. Major technical units contributing to micro mechanical machining systems are, to name a few, high speed spindle systems, micro high precision feeding systems, control systems to generate coordinated motions, tooling and chucking systems, frame design and module allocation schemes based upon opti
10、mization for high stiffness. Researchers have been trying to put micro technologies together to build micro-factory systems which make micro/meso size precision parts to meet the needs from the manufacturing industry.1 In this paper, we present a miniaturized 3-axis milling machine and a dedicated C
11、NC system for the machine. The 3-axis milling machine is constructed as one of micro-factory module and designed to produce high precision micro parts. It has a desktop size of 200300200 mm3 and is serving as our testbed machine. From finite element analysis and an impact hammer test, we have verifi
12、ed that it has a good structural stiffness and high natural frequencies. A high speed air turbine spindle on the horizontal z-axis can run at up to 160,000 rpm. This 3-axis milling machine was put under real machining tests and it successfully demonstrated its machining capabilities. A CNC system wa
13、s developed for operation of the 3-axis desktop milling machine. The CNC system includes a G-code interpreter which can process a basic set of G-codes and M-codes in real-time. The CNC system consists of two parts. The one is a graphical user interface which runs under Microsoft Windows, and the oth
14、er is a DSP program which interpolates commands and executes a real-time servo control. 3 Two parts communicate each other through a dual port RAM(Random Access Memory). Job assignments for the two parts are discussed in detail in this paper. To improve the performance of the CNC system for th
15、e 3-axis milling machine beyond the traditional PID-type control, different control schemes have been tested including control, input shaping control, disturbance observer and cross-coupled control on the 3-axis milling machine. The rest of this paper is organized as follows. Sec. 2 presents t
16、he design of the 3-axis milling machine. The results of the finite element analysis and the natural frequencies obtained from the impact hammer test are given in this section. In Sec 3, a PC-based CNC system developed for the 3-axis milling machine is discussed. Several modern control schemes includ
17、ing control design, input shaping control, disturbance observer, and cross-coupled control are discussed with their experimental results to show their effectiveness and drawbacks in Sec 4. The concluding remarks will be given in Sec. 5. 2. Design of a 3-axis Milling Machine Micro machine tools
18、 are required to have high machining accuracy while providing enough stiffness. To estimate basic machining performance and stiffness of a micro machine tool, a miniaturized 3-axis milling machine was built and used as a testbed. Fig. 1 shows the 3-axis milling machine and its specifications. It has a mini-desktop size of
