1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2006 SAE International All rights reserved. No part of this publication m
3、ay be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA)
4、 Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org ARP4895 REV. A AEROSPACE RECOMMENDED PRACTICE Issued 1994-02 Revised 2006-05 Superseding ARP4895 (R) Flight Control Actuators - Dynamic Seals, Collection of Duty Cycle Data RATIONALE There is a trend to design airpla
5、nes with less natural stability than before, now relying on stability augmentation systems. Reduction of the size of the vertical and horizontal stabilizers is considered as a major weight and drag reduction opportunity, therefore making stability augmentation systems more and more active, depending
6、 on the degree of stability relaxation or instability left to the natural aircraft. Moreover it is to be noted that imperfections of the control laws, non-linearities in hydro mechanical equipment etc. may generate control surface position servo loop limit cycles, detrimental to the dynamic seal lif
7、e. The two most significant factors affecting seal life are the number of small amplitude reversals and the total stroke distance. This is the reason why an automatic, cost effective method for assessing hydraulic actuator dynamic seal duty cycle data at different stages of development of an aircraf
8、t project becomes a very useful tool. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 2 - 1. SCOPE This SAE Aerospace Recommended Practice (ARP) provides an algorithm aimed t
9、o analyse flight control surface actuator movements with the objective to generate duty cycle data applicable to hydraulic actuator dynamic seals. This algorithm can be used to process digitally recorded actuator positions, generated either by pure simulation, or hardware-in-the-loop simulation, or
10、flight test of full scale demonstrator of new aircraft, of new aircraft models in development, or of in-service aircraft, depending on what is available at different stages of the aircraft development and the purpose of the duty cycle investigation. This generated duty cycle data can be used as a ba
11、sis for defining dynamic seal life requirements, dynamic seal life testing, or to assess the impact of control law or other changes to dynamic seal behavior. 2. REFERENCES 2.1 Applicable Documents 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0
12、001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. There are no applicable documents. 2.2 Other Applicable References Royal Aircraft Establishment Report 69096 - An Investigation into the Duty Cycle of Powered Flying Controls, F. Holombek, May 1969 3. BACKGROU
13、ND 3.1 Past Practice Actuator displacement duty cycle requirements used in the qualification of past fly-by-wire aircraft have been established analytically from a limited amount of flight test data. Studies analyzing flight test data have been very limited in scope. A Royal Aircraft Establishment s
14、tudy in the late 1960s indicated that the control actuator usage for aircraft with unaugmented mechanical control systems was less “arduous“ than the design requirements. No systematic, quantified investigation into the flight control demands has been undertaken for highly augmented or totally fly-b
15、y-wire aircraft. A major concern in the development of actuators for this type aircraft is actuator endurance and particularly seal life. 3.2 Recommended Practice Displacement duty cycle data should be collected from aircraft that are advanced technology demonstrators and full-scale development prog
16、rams. The collection of data during the development testing phase of new aircraft is very cost-effective because these aircraft are normally highly instrumented and all the data are recorded on-board the aircraft and/or in a telemetry ground station. Normally, several flight control system parameter
17、s are monitored on all test aircraft to assure safety of flight. The parameters typically include: aircraft rates and accelerations, pilot primary control inputs and control surface positions. The duty cycle collection method identified in this ARP makes use of a computer algorithm which can run rea
18、l time in a telemetry ground station. Data recorded on board the aircraft can be postflight processed if a real time telemetry ground station is not available. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from
19、 IHS-,-,-SAE ARP4895 Revision A - 3 - Limitations for real time data processing are telemetered parameters, data sample rate, and ground station capability. If small reversals are considered important, sample rates and timing of the sampling may be statistically important. Limitations for postflight
20、 nonreal time processing of data are the cost and logistics of replaying hundreds of hours of data tapes. However the described algorithm can also be used in other contexts as mentioned in the scope 4. ACTUATOR DISPLACEMENT DATA ACQUISITION 4.1 Digital Data Acquisition The position data sampling fre
21、quency shall be selected high enough, not to lose information. Theoretical minimum is twice the frequency of the movement to be analyzed. If the movement frequency is not precisely known it is safe to consider a margin, typically a factor of five rather than two . 4.2 Data Identification and Collect
22、ion In order to manage the collection of actuator displacement data, all of the actuator reversals shall be counted and the displacement amplitudes be lumped in a limited number of levels based on percent of stroke ranges. Because the effects of an augmentation system is a major area of interest, th
23、e number of smaller reversals should have better resolution than the larger amplitude reversals. The data should be segregated by flight phase; e.g., ground operation, takeoff/landing configuration, and other regimes through the flight envelope Data Analysis: An actuator displacement usage algorithm
24、 should operate as shown in Figure 1. The algorithm is based on a three point approach to determine the existence of a peak or valley. The algorithm identifies a peak when the middle point has a value greater than or equal to the preceding point and has a value greater than the succeeding point. Lik
25、ewise, a valley is identified when the middle point has a value less than the preceding point and has a value less than or equal to the succeeding point. The stroke can then be determined by calculating the displacement between the peak and the valley. To eliminate the possibility of identifying inc
26、orrect peaks or valleys, for instance due to data dropouts, the algorithm calculates the actuator rate between successive points. If the calculated rate exceeds the actuator maximum rate capability, the algorithm ignores that data point. Data processed by the algorithm either in real time or by repl
27、ay can be stored and sorted into displacement “bins“ i.e., 0-2%, 2-5%, 5-10%, 10-25%, 25-50%, 50-75%, 75-100%. The data can then be presented in a histogram format. The number of displacement bins in this example was chosen to be similar to the duty cycle recommendation presented in ARP1281. The use
28、r of this algorithm can select any number displacement range bins. A flow chart for the Actuator Reversal Calculation Program is presented in Figure 2. 4.3 Data Sample An example of flight test data that has been processed by the algorithm is shown in Figures 3 and 4. The data for this example was c
29、hosen because Parade Formation is a nonmaneuvering flight phase that requires highly precise pilot inputs and results in a larger number for small actuator displacements. The symbols shown on the plots in Figure 3 shows points which are picked by the algorithm without a minimum displacement window.
30、Figure 4 shows the results of incorporating a 0.25% (0.09) minimum displacement window. The minimum displacement window is a user defined parameter which can be set at any value to prevent the algorithm from processing noise in the instrumentation system. It may be based on the knowledge of the qual
31、ity of the acquisition chain, in terms of noise or resolution, or actual actuator position servo loop performance. It shall not be ignored that actual position threshold may be lower than specified. The 0.25% minimum displacement was chosen for the example because it corresponds to the actuator thre
32、shold. Histograms of the data from Figures 3 and 4 are presented in Figure 5. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 4 - FIGURE 1 - VALLEY-PEAK ALGORITHM Copyright S
33、AE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 5 - FIGURE 2 - ACTUATOR REVERSAL CALCULATION PROGRAM Copyright SAE International Provided by IHS under license with SAENot for ResaleNo r
34、eproduction or networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 6 - FIGURE 2A - ACTUATOR REVERSAL CALCULATION PROGRAM Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP
35、4895 Revision A - 7 - FIGURE 2B - ACTUATOR REVERSAL CALCULATION PROGRAM Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 8 - FIGURE 2C - ACTUATOR REVERSAL CALCULATION PROGRAM
36、Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 9 - FIGURE 2D - ACTUATOR REVERSAL CALCULATION PROGRAM Copyright SAE International Provided by IHS under license with SAENot fo
37、r ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 10 - FIGURE 2E - ACTUATOR REVERSAL CALCULATION PROGRAM Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IH
38、S-,-,-SAE ARP4895 Revision A - 11 - FIGURE 2F - ACTUATOR REVERSAL CALCULATION PROGRAM Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 12 - FIGURE 2G - ACTUATOR REVERSAL CALCU
39、LATION PROGRAM Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 13 - FIGURE 2H - ACTUATOR REVERSAL CALCULATION PROGRAM Copyright SAE International Provided by IHS under licens
40、e with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 14 - FIGURE 3 - LEFTSTAB VERSUS TIME WITHOUT A MINIMUM DISPLACEMENT WINDOW LEFTSTAB Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or
41、 networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 15 - FIGURE 4 - LEFTSTAB VERSUS TIME INCORPORATING 0.25% MINIMUM DISPLACEMENT WINDOW LEFTSTAB Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without li
42、cense from IHS-,-,-SAE ARP4895 Revision A - 16 - FIGURE 5 - 7 BUCKETS PARADE FORMATION (1 MIN) # OCCURENCES Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE ARP4895 Revision A - 17 - 5. APPLICABIL
43、ITY The proposed method of data reduction is intended to capture the number of reversals and the total stroke distance which are the most significant factors affecting the hydraulic actuator dynamic seal life. The collected data is therefore particularly appropriate for defining seal life requiremen
44、ts or verification tests. However some information is lost in this process: absolute positions of the actuator output and time related data, like particular sequences, rate, dwell periods etc. This means that this displacement duty cycle data cannot be associated to a load profile and therefore is n
45、ot appropriate for covering rod end bearing or actuator structural fatigue life requirement, or actuator thermal behavior requirements. 6. NOTES 6.1 Key Words Flight controls, actuator, hydraulic, dynamic seal, life, duty cycle, collection, algorithm 6.2 Change Summary Purpose of RevA is the introdu
46、ction of the algorithms shown in Figures 2D and 2F as a correction to an anomaly identified by users of the original program. It has also been the opportunity to add the Rationale paragraph and many improvements of the original wording. 6.3 The change bar ( l ) located in the left margin is for the
47、convenience of the user in locating areas where technical revisions, not editorial changes, have been made to the previous issue of this document. An (R) symbol to the left of the document title indicates a complete revision of the document. PREPARED BY SAE SUBCOMMITTEE A-6A3, FLIGHT AND UTILITY CONTROL SYSTEM OF COMMITTEE A-6, AEROSPACE ACTUATION, CONTROL AND FLUID POWER SYSTEMS Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
