1、 Institute of Environmental Sciences and Technology Design, Test, and Evaluation Division IEST-RP-DTE019.1 Recommended Practice 19.1 Vibration Controller Selection Arlington Place One 2340 S. Arlington Heights Road, Suite 100 Arlington Heights, IL 60005-4516 Phone: (847) 981-0100 Fax: (847) 981-4130
2、 E-mail: informationiest.org Web: www.iest.org 2 IEST 2011 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-DTE019.1 IEST 2011 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-DTE019.1 3 This Recommended Practice is published by the INSTITU
3、TE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY to advance the technical and engineering sciences. Its use is entirely voluntary, and determination of its applicability and suitability for any particular use is solely the responsibility of the user. Use of this Recommended Practice does not imply any wa
4、rranty or endorsement by IEST. This Recommended Practice was prepared by and is under the jurisdiction of Working Group 019 of the IEST De-sign, Test, and Evaluation Division. Copyright 2011 by the INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY First printing, April 2011 ISBN 978-0-9841330-4-8 P
5、ROPOSAL FOR IMPROVEMENT: The Working Groups of the Institute of Environmental Sciences and Tech-nology are continually working on improvements to their Recommended Practices and Reference Documents. Suggestions from users of these documents are welcome. If you have a suggestion regarding this docume
6、nt, please use the online Proposal for Improvement form found on the IEST website at www.iest.org. INSTITUTE OF ENVIRONMENTAL SCIENCES AND TECHNOLOGY Arlington Place One 2340 S. Arlington Heights Road, Suite 100 Arlington Heights, IL 60005-4516 Phone: (847) 981-0100 Fax: (847) 981-4130 E-mail: infor
7、mationiest.org Web: www.iest.org 4 IEST 2011 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-DTE019.1 IEST 2011 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-DTE019.1 5 Vibration Controller Selection IEST-RP-DTE019.1 Contents SECTION 1
8、SCOPE AND LIMITATIONS 6 2 REFERENCES 7 3 TERMS AND DEFINITIONS 7 4 BACKGROUND . 7 5 RECOMMENDED FEATURES. 8 6 ADDITIONAL CONSIDERATIONS . 14 7 RECOMMENDED ORDER OF TEST PROCESSES 14 8 TEST DATA AND REPORTING 14 9 BIBLIOGRAPHY . 15 6 IEST 2011 All rights reserved Institute of Environmental Sciences a
9、nd Technology IEST-RP-DTE019.1 Institute of Environmental Sciences and Technology Design, Test, and Evaluation Division Recommended Practice 019.1 Vibration Controller Selection IEST-RP-DTE019.1 1 SCOPE AND LIMITATIONS 1.1 Purpose This Recommended Practice (RP) is meant to provide rudimentary guidel
10、ines for those tasked with selecting a closed-loop digital shaker control system (DSCS) for use in vibration or shock testing, or both. This RP is concerned with single shaker operation only. It is not meant to be a specification for a specific purchase, but rather a focused treatise on factors that
11、 should be con-sidered when setting out to specify a new vibration control system. It is assumed this system will be used for critical qualification of military or commercial products, for example, according to MIL-STD-810, and will be based on valid engineering design and ex-hibit robust performanc
12、e. 1.2. Basic Control Concepts In a professional closed-loop digital shaker control system, a desired power spectral density (PSD), sine profile, transient waveform, or shock response spec-trum (SRS) is stored as a reference and compared, on-line, with one or more measured control responses. The dri
13、ve signal is updated as necessary, each control loop, to maintain the specified test function. Typically, the control loop gain is measured prior to random or sine tests. When performing transient or SRS tests, both gain and phase of the control loop should be measured during system characterization
14、 to avoid un-wanted pulse distortion during testing. In random con-control, both the spectrum shape and the root-mean-square (RMS) value of the test should be simulta-neously controlled. In random and sine tests, control may be established using multiple control transducers to control to the average
15、, the maximum, or the mini-mum of the measured responses. Also, limit channels may be specified to avoid over testing of sensitive test articles. A combination of sine-on-random, random-on-random, or sine plus random-on-random may also be required. In these tests, control of all test componentsinclu
16、ding tones, bands, and broadband randomshould be specified to avoid out of control conditions. Occasional independent analysis of the control loop performance is encouraged as a means to assure uni-form test results from a variety of available shakers and control systems. A multi-pole, analog, anti-
17、aliasing filter should be fur-nished at the input of each control channel of the DSCS to avoid downstream aliasing of measured con-trol signals. Similarly, an analog anti-imaging filter should be present in the drive signal path from the DSCS digital/analog (D/A) to the shaker power am-plifier to re
18、duce or eliminate transition steps from the output D/A converter as well as unwanted low fre-quency drive energy. The basic block concept of a closed-loop, controlled vibration test is shown in Figure 1. IEST 2011 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-DTE019.
19、1 7 Figure 1 Block concept of a closed-loop vibration test using a DSCS. 2 REFERENCES IEST-RD-DTE046 Terms Commonly Used in the Digital Analysis of Dynamic Data MIL-STD-810G, Test Method Standard for Environ-mental Engineering Considerations and Laboratory Tests Military Standards Standardization Do
20、cument Order Desk 700 Robbins Avenue Bldg #4, Section D Philadelphia, PA 19111, USA http:/dodssp.daps.dla.mil/ 3 TERMS AND DEFINITIONS 3.1 Glossary See IEST-RD-DTE046 (provided with this document). 3.2 Additional Terms and Concepts The following terms refer specifically to the systems described in t
21、his RP. adaptive control A closed loop control approach that updates the Sys-tems Impedance Function (SIF) at every control loop iteration to assure the control of non-linear or time varying system responses, rather than updating the SIF only at the beginning of the test and using this fixed model o
22、f the dynamics of the system under test for its control during the entire test. control dynamic range A digital shaker control system (DSCS) is designed to produce a desired control response at a selected loca-tion (or averaged locations) on a test article, fixture, or shaker. The desired test may b
23、e random, sine, shock, or some combination of these, but regardless of the dynamics in the shaker, fixture, test article, transduc-ers, cables, etc., the DSCS should be able to maintain the desired control level and shape within the specified tolerance bands. Thus the DSCS should adjust its drive le
24、vel to accommodate all the dynamics encountered in the control loop as the test progresses. If a known vari-ation in peak to notch dynamics of X dB is placed in the feedback path of the DSCS, and the DSCS is able to control the response signal to within the test toler-ance bands, the DSCS can be sai
25、d to have a control dynamic range of X dB. This definition of control dy-namic range is independent of the amount of drive swing from peak to notch that is required to achieve control of the X dB dynamic load. Some DSCS de-signs may perform input and output auto ranging, which will affect total driv
26、e swing. Also, this means that a true test of DSCS dynamic range cannot be achieved simply by performing a closed-wire test be-cause a wire has no dynamic range. 4 BACKGROUND Those charged with specifying or selecting a DSCS have many factors to consider in making this selection. The specified DSCS
27、may be used with a variety of different shakers, on widely varying tests, perhaps with many different data requirements, and by users with varying backgrounds and experience. Some of the cat-egories or criteria that should be considered include: a) Upper and lower frequency range of operation. b) Ma
28、ximum and minimum sampling rate pro-videdmay be critical for shock control. c) Input accuracy (not resolution) Many transduc-ers that will be used with the DSCS have a stated accuracy of 1% to 5% over a given frequency range. 8 IEST 2011 All rights reserved Institute of Environmental Sciences and Te
29、chnology IEST-RP-DTE019.1 The DSCS should have an accuracy at least 10 times better than that, or typically 0.2% of reading or better. d) Calibration Provisions should be included for offset removal and linearity calibration of the input A/D and output D/A converters. Any necessary soft-ware and har
30、dware should be available from the DSCS vendor to effect a calibration traceable to National Institute of Science and Technology (NIST) standards. e) Types of tests to be performed, such as random or sine-on-random. f) Types of transducers that may be used with the DSCS. 5 RECOMMENDED FEATURES 5.1 G
31、eneral The DSCS is to be used for measurement, analysis, and closed-loop control of random, sine, and shock, as well as expansion to more complex control methods such as shock synthesis, sine-on-random, and random-on-random. The system should be based on fast Fouri-er transform (FFT) and digital sig
32、nal analysis algorithms. The system should be capable of simulta-neously acquiring and controlling vibration data on at least two analog input channels but be expandable to include at least N channels without degrading mea-surement or control performance. The control should be based on any of the ch
33、annels as well as combina-tions of channels with average, minimum, maximum, and limit control strategies. The system should be con-structed on a modular basis, using standard production assemblies and subassemblies. The system capabilities should be easily expandable by standard, off-the-shelf, soft
34、ware and hardware option modules. Each input channel should provide user-selectable coupling of AC, DC, and ICP. The DSCS should have a menu and computer mouse-driven mode of test setup with simple setup file storage and retrieval capability. It should be possible to store and retrieve named test se
35、tups with simple mouse operation. Similarly, it should be possible to store and retrieve for post-test observation, test data, using simple mouse operations. Calibration software should be furnished and calibra-tion hardware recommended by the vendor to permit the DSCS user to perform an in-situ cal
36、ibration of the entire control system. Either as a standard or an op-tional feature, the DSCS should provide the ability to measure frequency response functions (FRF) between the drive and a response or between two responses. Displays of magnitude and phase should be specified. Storage of displays a
37、nd graphical data, directly from the controller, is also desirable. 5.2 Graphical User Interface (GUI) Application software should be based on industry standard multiple-windows display or equivalent graphical user interface. The ability to display control channel(s) during the test is required. In
38、addition, at least four display windows should be furnished for real-time observation of drive, control, and response parameters as desired. Tagging of selected display values should be furnished with a means to maintain their shown values on hardcopy. Display of at least two overlaid traces should
39、be furnished. It should be possible to quickly print any displayed parameter through a simple print control. 5.3 Safety considerations The following safety features should be provided: Noise check of all control channels prior to test Loop check of all control channels prior to raising test level Si
40、mple user manual abort control Loss of control signal abort Remote abort control Adjustable alarm and abort values for each test setup Emergency hardware abort switch option 5.4 Random testing See Figure 2. The following features and parameters should be considered: Frequency ranges of operation Num
41、ber of control lines of resolution Number of breakpoints for PSD definition Type of breakpoint elements (values, lines, slopes, etc.) Control dynamic range (see 3.2) Real Gaussian noise, or a possible non-Gaussian signal requirement Number of control degrees-of-freedom (DOF) specification IEST 2011
42、All rights reserved Institute of Environmental Sciences and Technology IEST-RP-DTE019.1 9 Figure 2 Typical random test profile and control results. Figure 3 Typical swept sine test profile with constant D and sloped acceleration segments. Manual and automatic startup modes Selectable increment step
43、size, in dB, during startup Selectable startup and shutdown rate in dB/sec All input channels available for control PSD rescaling from user-entered g RMS or dB value Limit channel definition with independent limit profile per channel Stop and resume a test manually Manually change test level Display
44、 any active channel during a test Clipping selectable in sigma (RMS value multiples), g, or volt (V) values Specification of adaptive control (see 3.2) Selectable measurements with linear or expo-nential averaging and selectable number of averages and reset 5.5 Swept sine testing See Figure 3. The f
45、ollowing features and parameters should be considered: Smooth, continuous sine sweep with no dis-cernible steps 10 IEST 2011 All rights reserved Institute of Environmental Sciences and Technology IEST-RP-DTE019.1 Amount of acceptable distortion on the sine control output, typically less than 1% Broa
46、d selection of linear, logarithmic, and in-teger sweep rates Number of sweeps to test completion Wide frequency range of operation Limit channel definition with independent limit profile and alarm/abort tolerances per limit channel Control dynamic range Number of breakpoints furnished to define the
47、test Type of breakpoints furnished; such as acce-leration, velocity, displacement (A, V, D); log-log line Sweep up, sweep down, sweep up and down, sweep hold, sweep resume Selectable control signal processing; broad-band peak, broadband RMS, or tracking filter Wide selection of tracking filter bandw
48、idths Provision of Constant Output Level Adapter (COLA) signal of nominal 1-V peak as a sep-arate output Ability to control correction rate (compres-sion speed) as a function of frequency Manually change test level during sweep Specify test duration in number of sweeps, cycles, or time Furnish optio
49、n of stepped sine testing to meet MIL-STD-167 Resonant dwell testing including manual dwell, auto search and dwell, phase tracking, frequency limits, and automatic frequency re-sponse measurements during test sweep 5.6 Classical shock pulse testing See Figure 4. The following features and parameters should be considered: Types of test pulses to be furnished, including half-sine, initial, and terminal peak sawtooth, rectangular, trapezoidal, etc. Number of pulses
