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Research Papers

Three Degrees of Freedom Active Control of Pneumatic Vibration Isolation Table by Pneumatic and Time Delay Control Technique

[+] Author and Article Information
Yun-Ho Shin

Shock and Vibration Team, System Engineering Research Division, Korea Institute of Machinery and Materials, 104 Sinseonguo, Yuseong-Gu, Daejeon 305-343, South Korea

Kwang-Joon Kim1

Center for NOVIC, KAIST, Daejeon 305-701, South Koreakjkim@kaist.ac.kr

Pyung-Hoon Chang, Dong Ki Han

Department of Mechanical Engineering, Robot Control Laboratory, KAIST, Daejeon 305-701, South Korea

1

Corresponding author.

J. Vib. Acoust 132(5), 051013 (Sep 10, 2010) (12 pages) doi:10.1115/1.4001509 History: Received July 06, 2009; Revised February 22, 2010; Published September 10, 2010; Online September 10, 2010

Based on previous feasibility study on one degree of freedom (1DOF) pneumatic active control of pneumatic springs, this paper presents procedures and results of a more realistic 3DOF active control of a pneumatic vibration isolation table. The 3DOF motion of the pneumatic table, consisting of heaving, rolling, and pitching, is controlled directly by adjusting air pressure in four pneumatic cylinders in a dynamic manner with pneumatic valves, without any external actuator such as an electromagnet or voice coil. The time delay control, which is a software chosen in this study, together with the hardware, i.e., the pneumatic actuator, is shown to be very powerful in enhancing the performance of vibration isolation for ground excitation as well as in settling time reduction for payload excitation through simulations and measurements on the 3DOF motion control system. New key results found in the experimental approach are that the pneumatic actuator shows a dynamic behavior of a second-order system, instead of a first-order system, which has been used in existing literatures so far, and that just feed-forward control of the pneumatic actuator by the second-order model can compensate for the inherently slow response characteristics of the pneumatic actuator very successfully. Effectiveness of the proposed active pneumatic control technique in the multi-input and multi-output system is shown via singular value decomposition analysis on the transmissibility matrix. Promising future of the proposed control and performance analysis technique is further discussed based on the results in the case of payload excitations as well.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 9

Frequency response functions between the desired and measured pressure applying feedforward control scheme only by second-order model: 5 Parms ––––; 10 Parms – – –; 50 Parms….; and 100 Parms−⋅−⋅

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Figure 10

Time response of the desired random pressure and actual pressure in chamber by feedforward control based on the second-order model (5 Parms): desired pressure −⋅−⋅; measured pressure –––

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Figure 11

Configuration and coordinate system for the dynamic analysis of the pneumatic vibration isolation table: (a) top view of the pneumatic table; (b) coordinate system

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Figure 13

Singular values of the transmissibility matrix of the pneumatic vibration isolation table: passive (maximum:–––, middle: −⋅−⋅, and minimum: −⋅⋅−⋯); active (maximum: – – –, middle: −⋅−⋅−⋅, and minimum: …….)

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Figure 14

Comparison of the responses of the passive and active pneumatic tables to the payload excitation based on the simulation: passive –––; active –––

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Figure 15

Location of the impact force to the payload

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Figure 16

Flow chart for generation of ground vibrations of the flat spectral shape by normalized weighting filter

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Figure 17

Narrow band power spectral density of ground vibrations generated by the exciter and floor system: background vibration …..; ground vibration w/o weighting filter by base excitation system −⋅⋅−⋅; ground vibration w/weighting filter by base excitation system pt. 1(zb1 in Fig. 2) –––, pt. 2 – – –, pt. 3 …., and pt. 4 −⋅−⋅

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Figure 18

Comparison of the transmissibilities of the passively and actively controlled pneumatic vibration isolation tables: passive –––; active …….

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Figure 19

Singular value of the transmissibility matrix of the pneumatic vibration isolation table: passive –––; active …….

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Figure 20

Responses of the actively controlled pneumatic vibration isolation table across turning-on of the controller: acceleration on the payload –––

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Figure 21

Location of the impact force to the payload for investigating the reduction in the settling time

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Figure 22

Input force to the pneumatic isolation table: passive –––; active …….

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Figure 23

Comparison of the responses of the passive and active pneumatic tables for direct payload excitation: passive –––; active …….

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Figure 1

Block diagram for the concept of the time delay controller

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Figure 2

Photograph and schematic diagram of the active pneumatic vibration isolation table and apparatus for generation of ground vibration: (a) photograph of the active pneumatic vibration isolation table and apparatus for generation of ground vibration; (b) schematic diagram of the active pneumatic vibration isolation table and apparatus for generation of ground vibration; (c) configuration of active pneumatic vibration isolation table

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Figure 3

Block diagram for the 3DOF time delay control of the pneumatic vibration isolation system

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Figure 4

Schematic diagram for the operation of the pneumatic valve

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Figure 5

Diagram of the experimental setup for the dynamic pressure actuator

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Figure 6

Measurement and fitted curve of the frequency response function between the input voltage and dynamic pressure in the chamber: experimental results–––––; fitted curve by second-order transfer function– – –; and fitted curve by first-order transfer function −⋅−⋅

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Figure 7

Block Diagram for the compensation of the response characteristics of the pneumatic actuator with feedback and feedforward controllers: (a) pressure actuation by the feedforward control using second-order transfer function; (b) pressure actuation by the feedforward control using first-order transfer function and feedback control

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Figure 8

Frequency response functions of the pneumatic actuator between the desired and measured pressure: feedforward control using the first-order transfer function only −⋅−⋅; both feedback and feedforward control using the first-order transfer function ……..; and feedforward control using the second-order transfer function only ––––

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Figure 12

Comparison of the transmissibilities of the passive and active pneumatic tables based on the simulation: passive –––; active …….

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