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Research Papers

Design, Modeling, and Motion Control of the Noncircular Turning Process for Camshaft Machining

[+] Author and Article Information
Tsu-Chin Tsao

Mechanical and Aerospace Engineering Department, University of California Los Angeles, 137-30 Engineering IV 420 Westwood Plaza, Los Angeles, CA 90095-1597

Zongxuan Sun

Mechanical Engineering Department, University of Minnesota, Twin Cities Campus, 111 Church Street S.E., Minneapolis, MN 55455

Reed D. Hanson

 Seagate Technologies, 1280 Disc Drive, Shakopee, MN 55379

Alexanda Babinski

 Western Digital Corporation, 20511 Lake Forest Drive, Lake Forest, CA 92630

J. Dyn. Sys., Meas., Control 130(3), 031005 (Apr 18, 2008) (7 pages) doi:10.1115/1.2907350 History: Received November 19, 2002; Revised December 14, 2007; Published April 18, 2008

This paper presents the design, modeling, and motion control of the noncircular turning process for camshaft machining. The cam profile tracking performance requirements are first characterized to meet industry standards. Based on these requirements, a unique test fixture using state-of-the-art actuation and sensing technologies is designed for the noncircular turning process. Modeling of the electrohydraulic servo valve, actuator, and sensors is conducted based on their frequency responses. Digital motion control that achieves asymptotic cam profile tracking while maintaining system robust stability is designed and implemented on the turning test fixture. Spindle speed can be chosen depending on the required profile tracking accuracy with higher speed rendering higher machining rate for rough turning and lower speed rendering higher accuracy for finish turning. Experimental results of turning a variety of cam profiles show that the tracking error is less than 30μm for spindle speed at 300rpm and is less than 60μm for spindle speed at 600rpm or 1200rpm.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Maximum speed and acceleration requirements for cam profile motion

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Figure 2

Picture of the experimental system

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Figure 3

Control system hardware configuration

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Figure 4

Frequency response of the servo valve

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Figure 5

Frequency response of the actuator

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Figure 6

Frequency response of the stabilized electrohydraulic actuator using LVDT

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Figure 7

Frequency response of the stabilized electrohydraulic actuator (solid line) and the model (dash line) using laser sensor

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Figure 8

Actuator stiffness by the impact hammer test

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Figure 9

Block diagram of the control system

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Figure 10

Frequency responses of Q filter (lower curve) and inverse of the unmodeled dynamics (upper curve)

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Figure 11

Sensitivity function of the repetitive control system

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Figure 12

Simulated cam profile tracking performance in four spindle revolutions; top: cam profile and bottom: tracking errors at 1200rpm

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Figure 13

Experimental results of Profile 1; top: Cam Profile 1, middle: tracking error at 300rpm, and bottom: tracking error at 600rpm

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Figure 14

Experimental results of Profile 2; top: Cam Profile 2, middle: tracking error at 600rpm, and bottom: tracking error at 1200rpm

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Figure 15

Experimental results of a half lobe of Profile 1; top: half lobe of Cam Profile 1 and bottom: tracking error at 600rpm

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Figure 16

Experimental results of a half lobe of Profile 2; top: half lobe of Cam Profile 2 and bottom: tracking error at 1200rpm

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Figure 17

Sample of machined camshaft for Cam Profile 1

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Figure 18

Sample of machined camshaft for Cam Profile 2

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