扩径机零部件工艺定型方案设计【说明书+CAD】
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扩径机零部件工艺定型方案设计【说明书+CAD】,扩径机,零部件,工艺,定型,方案设计,说明书,CAD
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International Conference on Control, Automation and Systems 2010 Oct. 27-30, 2010 in KINTEX, Gyeonggi-do, KoreaVibration Control of a High-Speed Air-Bearing Spindle using an Active Aerodynamic BearingHiroshi Mizumoto1 ShiroArii1 Yoshito Yabuta1 and Yoichi Tazoe2 1 Department of Electrical Engineering, Tottori University, Tottori, Japan (Tel : +81-857-31-5214; E-mail: mizuike.tottori-u.ac.jp)2 Department of Mechanical Engineering, Nachi-Fujikoshi Corp., Toyama, Japan(Tel : +81-76-471-2104; E-mail: tazoe)Abstract: A novel high speed air-bearing spindle is proposed as a tool spindle for small diameter of cutting and grinding tools. The spindle vibration at high rotational speed is suppressed by an active aerodynamic bearing incorporated into the spindle. For generating aerodynamic damping force, the wedge angle on the aerodynamic bearing surface is controlled by piezoelectric actuators. By using several control tactics, the effect of the active control of the aerodynamic bearing on the spindle vibration is analyzed. Experimental result shows that the amplitude of the spindle vibration can be suppressed to be 0.1 m at the rotational speed of 50,000min-1 (833Hz). Final goal of the study is to suppress the amplitude of spindle vibration less than 0.1 m at the rotational speed of 120,000min-1 (2kHz).Keywords: active control, aerodynamic bearing, aerostatic bearing, air-bearing spindle, piezoelectric actuator3 INTRODUCTION OF HYBRID AIR-BEARING SPINDLEFor small diameter of cutting tools used in ultraprecision machining, a high speed tool spindle is a vital element 1. Aerostatic bearings is suitable for such tool spindle, however, the spindle vibration of the conventional air-bearing spindle inevitably increases as the rotational speed increases. For suppressing the vibration at higher rotational speed of the air-bearing spindle, we proposed a control system using an active aerodynamic bearing 2, 3. The active aerodynamic bearing is incorporated at the top end of the air-bearing spindle shown in Fig. 1. As shown in the cross sectional view of this hybrid air-bearing spindle in Fig. 2, the spindle is supported by conventional aerostatic thrustBuilt-in motorAerostatic bearingSpindleAir supplyCoolant in/outActive aerodynamic bearingand radial bearings and the proposed active aerodynamic radial bearing. The spindle is driven by a built-in induction motor, maximum driving speed of which is 2kHz (120,000min-1).Because the load carrying capacity of the aerodynamic bearing increases as the rotational speed increases, the spindle vibration in the high speed range can be suppressed by the active control of the aerodynamic bearing. In the present paper, the performance of this hybrid air-bearing spindle in the higher rotational speed is analyzed under various control tactics; the feedback control using internal or external sensors, and the feedforward control. It is also shown that the positioning of the spindle with nanometer resolution can be performed by the feedback controlling of the active aerodynamic bearing.4 CONTROL SYSTEM FOR ACTIVE AERODYNAMIC BEARINGFront view of the proposed active aerodynamic radial bearing and the feedback control system using internal sensors is shown in Fig. 3. On the circular bearingFig. 1Hybrid air-bearing spindle employingaerostatic and aerodynamic bearingsFig. 2 Cross sectional view of hybrid air-bearing spindle incorporating active aerodynamic radial bearingsurface, there are four elastic regions formed by a circular and a oval notches. A piezoelectric actuator (PZT) embedded behind each elastic region deforms the bearing surface to form a wedge region in the air gap. As the spindle rotates, this wedge region generates aerodynamic force.According to the spindle vibration detected by an978-89-93215-02-1 98560/10/$15 ICROS2261Fig.3ro stdyn ema usFro andntfview of active aemic bearing eedback control sying internalsensorsinternal capacitance sensor adjacent to the elastic region, (phase advance of /8), a microcomputer (PC) controls the wedge angle of the elastic region. When the spindle approaches to the elastic region, the wedge angle of this region is increased and the spindle is pushed back by the generated aerodynamic force. Phase advance of the sensor position is effective when the processing time in the PC is considerable.Supposing the use of a rotational tool, we also adopted another control system shown in Fig. 4. A reference bar (dummy tool) is attached to the spindle end and two external capacitance sensors detecting the horizontal and the vertical vibration of the bar are arranged in phase with the PZT. Such arrangement is effective when the processing time in the PC is negligible.5 EFFCT OF ACTIVE CONTROL Stroke of active aerodynamic bearingFig. 4Feedback control system for active aerodynamic bearing using external sensors1200Displacement of spindle nm10008006002According to the impressed voltage for the PZT increases, the wedge angle on the bearing surface of the active aerodynamic bearing increases and the generated aerodynamic force displaces the spindle. For the400200ADE2 for PZT2with 150V978-89-93215-02-1 98560/10/$15 ICROSmaximum impressed voltage of 150V to one of the PZT, the displacement of the spindle detected by the external sensor is shown in Fig. 5. As the rotational speed increases, the spindle displacement is expected to be increased because the aerodynamic force increases. However, Fig. 5 shows that the measured spindle displacement is saturated when the rotational speed is higher than 300Hz. It is considered that the generated aerodynamic force on the bearing surface may suppress the deformation of the PZT and the displacement of the spindle cannot be increased as expected. Active control using internal sensorFigure 6 shows the effect of feedback control of the aerodynamic bearing on the spindle vibration, where the internal sensor is used for detecting the spindle00200400600800Rotational speedHzFig. 5Stroke of active aerodynamic radial bearingFig. 6 Effect of feedback control of active aerodynamic bearing using internal sensordisplacement.Therotationalspeedis500Hz (30,000min-1) and the period of rotation is 2ms. Theprocessing time in the PC is several milli-second, and the delay in the controlling is considerable. Therefore, the processing time is adjusted so that the time delay is equal to the period of the spindle rotation. Such delayed control is effective for the repeative ron-out (rro) component of the spindle vibration, however, the effect of active control can not be expected for the non-repeatative run-out(nrro) component.Without active control (left of Fig. 6), the amplitude of the spindle vibration is larger than 0.5 m. Under control (right of Fig. 6), the amplitude of the vibration can be decreased to as large as 0.3 m. Thus the effect of the active control can be observed, however, the effect is restrictive. For improving the effect of the active control, the processing time in the PC should be reduced. Active control using external sensorBy using the control system shown in Fig. 4 and another PC, the processing time in the PC can be reducedFig. 7 Changes in spindle vibration and impressed voltage at beginning of active control using external sensorto be 30 s. As the result of reduction in theprocessing time, the external sensors and the PZTs for the active control can be arranged at the same phase of the spindle revolution.The effect of active control with the control system of shorter processing time is shown in Fig. 7, where the spindle vibration in the horizontal and vertical directions detected by the external sensors and the impressed voltages for the PZTs are indicated. The rotational speed is 500Hz, therefore the delay angle of the feedback control is only about 5degrees. Without active control, the amplitude of the spindle vibration is 0.3 m and some beat is observed. When the active controlMTI-1MTI-2 MTI-3ADE-110ms313nmMTI-4 ADE-2MTI-1 MTI-2 MTI-3MTI-4ADE-110ms313nmADE-2Without control (N=300Hz)Active control (N=300Hz)Without control (N=300Hz)NRRO=73nmMTI-3MTI-2250nmActive control (N=300Hz)NRRO=52nmMTI-3starts, the impressed voltages for the PZTs fluctuate and the spindle vibration of both the rro and nrro components reduces. The total amplitude of theMTI-2250nmvibration under active control is 0.1 m. The spindle displacements detected by both the internal and external sensors are shown in Fig. 8. WithoutFig. 8Effect of active control on spindle vibration detected by internal and external sensorsboth the rro and the nrro components is reduced. Further978-89-93215-02-1 98560/10/$15 ICROSactive control (upper), the amplitude of the spindle isabout 0.3 m in all directions. The Lissajous figure (xy-representaion of horizontal and vertical vibration detected by the internal sensors) indicates that the nrro of the spindle vibration is 73nm.Under active control using the external sensors (Fig. 8 lower), the amplitude of the spindle vibration detected by the external sensors (ADE-1 and 2) can be less than 0.1 m, however the amplitude detected by the internal sensors seem to be unchanged. The Lissajous figure of internal sensors shown in Fig. 8 (lower right) indicates that the nrro of the spindle vibration reduces to 52nm. Thus the active control stabilizes the spindle rotation andexperiment shows that the active control can not be effective for the rotational speed higher than 600Hz. This is because the delay in the PZT control owing to the finite signal processing time in the control PC.For improving the delay in the control, the feedforward control is effective. A sinusoidal signal synchronized with the rotational speed is supplied to thePZT. For the rotational speed of 835Hz (50,000min-1),the effect of the feedforward control is shown in Fig. 9. Without active control, the amplitude of the spindle vibration is as large as 0.5 m. The feedforwad control of the aerodynamic bearing suppresses the spindle vibrationtobe lower than 0.2 m. The feedforward control is effective on the rro component of the spindle vibration, however it is not effective on the nrro component. Therefore, further improvement of the spindle vibration can not be expected by the feedforwar control.4STEP POSITIONING OF SPINDLEWhen the spindle rotates, the spindle position in the radial direction can be controled by the feedback control of the aerodynamic bearing.Fig. 9Effect of feedforward control on spindle vibrationFigure 10 shows the result of the step positioning of the spindle; the rotational speed of the spindle is 300Hz (18,000min-1), and a lowpass filter is used for eliminating the dominant spindle vibration at the rotational speed. The stroke of the positioning is larger than 200nm and the positioning resolution is in the order of nanometer. Such positioning function can be utilized in the micro cutting as the FTS.6 CONCLUSIONSThe results of the experiments show that the proposed hybrid air-bearing spindle is effective for suppressing the1002000-100-20-200-4000.81.6 2.43.24.000.81.62.43.24.0Displacement nm200Displace
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