Document
NASA Technical Memorandum 86728
NASA- TM-86728
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. Application of Frequency Domain
Handling Qualities Criteria to the
Longitudinal Landing Task
Shahan K. Sarrafian and Bruce G. Powers
L IS~ 'I"U, n"SA 'jllIVlPI L.N, VIKl.lr,IC, August 1985
NI\S/\
National Aeronautics and Space Administration
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3 1176 00187 9379
NASA Technical Memorandum 86728
Application of Frequency Domain
Handling Qualities Criteria to the
Longitudinal Landing Task
Shahan K. Sarrafian and Bruce G. Powers Ames Research Center, Dryden Flight Research FacIlity, Edwards, California
NI\S/\
National Aeronautics and Space Administration Ames Research Center Dryden Flight Research FacIlity Edwards, California 93523 APPLICATION OF FREQUENCY DOMAIN HANDLING QUALITIES CRITERIA TO THE LONGITUDINAL LANDING TASK Shahan K Sarraflan* and Bruce G Powerst NASA Ames Research Center, Dryden Fllght Research Faclllty Edwards, Callfornla Abstract Ka angle-of-attack feedback gaIn, deg/deg In recent years, advances In fllght controls KC command galn technology have resulted In the use of elaborate fly-by-wire systems that provlde stablllty augmen- KI Integral gaIn tatlon for both transport and hlgh-performance alrcraft wlth statlc lnstablilty Pltch-rate KL proportlonal galn command/attltude-hold systems are typlcally employed for thls purpose and are used on such Kp pIlot gaIn modern alrcraft as the F-16, X-29, and Shuttle In the flared landlng task, however, these systems Kq pltch rate feedback gaIn, deg/sec/deg/sec have exhIbIted floatIng and balloonIng tendencles WhICh result In handlIng qualItIes results that PIO pIlot-Induced osclilatlon are InconsIstent wIth classIcal predIctIve criteria q pItch rate, rad/sec Under NASA sponsorshIp, an In-flIght sImula- s Laplace operator tIon of the longItudInal handlIng qualltles of several confIguratIons for the approach and land- TIFS Total In-FlIght SImulator Ing task was performed on the USAF/AFWAL Total In-FlIght Slmulator by the Calspan CorporatIon T prefIlter lead tIme constant, sec Z The baSIC configuration was a generic transport aIrplane wIth statIc InstabIlIty The control TF prefIlter lag tIme constant, sec laws Included proportIonal plus Integral gaIn loops to produce pItch-rate command/attItude-hold TL : Neal-SmIth pllot model lead tIme systems whlch were evaluated wlth and wlthout constant, sec prefllters Conventlonal response characterlstlcs were obtalned by uSIng pItch-rate and angle-of- Te Neal-SmIth Pllot model lag tlme attack feedback loops The evaluatlon task was a constant, sec conventlonal vlsual approach to a flared touchdown at a deslgnated spot on the runway wlth a lateral Two washout fIlter tlme constant, sec offset a angle of attack, deg The general conclusIons were that the eXlst- lng crlterla are based on pltch-att1tude response A' real root due to augmentatIon system and that these character1st1cs do not adequately d1scr1mlnate between the good and bad conf1gura- e pItch attItude, deg tlons of thIS study. Thls paper descrlbes the work that has been done to further develop pitch attitude command, deg frequency-based crIterIa In an effort to provlde better correlatlon w1th the observed data w short perlod natural frequency, rad/sec nsp short perlod damplng ratIo Nomenclature /;sp -TS e pure tIme delay, sec longltud1nal stlck force, lb bandwIdth frequency, rad/sec alt1tude at pIlot statlon, ft p1tch rate numerator term due to 11ft altItude at p1lot statIon command, ft curve slope, sec- hp alt1tude rate at pllot statIon, ft/sec Introduct1on *Aerospace EngIneer. Member AIAA In recent years, advances 1n flIght controls tSenlor Aerospace EngIneer Member AIAA technology have resulted In the use of elaborate This paper IS declared a work of the U S Government and fly-by-wlre systems that provIde stabillty augmen- therefore IS In the public domain tatlon for both transport and hIgh-performance a1rcraft w1th stat1c 1nstab1llty. P1tch-rate dlagram form in Flg. 1. A summary of the conflg- command/attitude-hold systems are typlcally uratlons In terms of the q/Fes transfer functlon employed for th1S purpose and are used on such 1S presented In Table 1 Other transfer functlons modern a1rcraft as the F-16, X-29, and Shuttle. for these conflguratlons are presented In In the flared land1ng task, however, these systems Ref. 1. The pllot ratlngs asslgned to the con- have exhiblted float1ng and balloon1ng tenden- figuratlons are based upon the Cooper-Harper cies Longltudlnal PIO tendenc1es have also been ratlng scale (NASA TN 0-5153). A brlef descrlp- observed on occasion when p1lots attempt t1ght tlon of each conflguratlon set IS presented closed-loop control with such systems. The below. These conflguratlon sets are the prlmary result1ng a1rcraft characterLst1cs yielded han- database for the varlOUS frequency-domaln crlterla dllng qualLtLes results WhlCh have not been con- appllcatlons In thlS paper slstent w1th claSS1cai predlctlve crlterla.
Clearly, these longItudInal predIctIve crIterIa Set 1 Configuratlon need to be reflned for better correlatlon wlth Set 1 conslsted of three pltch-rate feedback handling qualitles results obtalned from the use conflguratlons wlth proportlonal plus Lntegral of such stability augmentatlon systems.
paths The short perlod was set at Under NASA sponsorshlp, an In-fllght slmula- W = 2 8 rad/sec and c = 0 8 The pltch- tion of the 10ngltudLnai handllng qualltles of r~~g numerator term (1/Te2~Pwas set at 0 38, 0 72, several conflgurat1ons for the approach and land- and 1.0 Lng task was performed on the USAF/AFWAL Total In-Flight Slmulator (TIFS) by the Cal span Corpora- Set 2 Conflguratlons tlon, Buffalo, NY The experLment descrlptlon and Set 2 contalned two pltch-rate feedback con- results are presented Ln Ref 1. The basLc con- flguratlons wlth proportlonal plus Integral flguratLon was a gener1c transport aLrplane wLth paths. The short perlod was set a~ statlc LnstabLllty Seven aerodynamlc conflgura- w = 1 8 rad/sec and C p = 0 6 The pltch- tions were obtalned by varylng the 11ft curve ns ratg numerator term (1/Te2~ was set at 0 38 and slope, statLc stabllLty, and 11ft due to elevator 0.72.
characterLstlcs. Elght var1atLons of control laws were used wlth the seven aerodynamlc models to produce 27 fl1ght-control/alrplane conf1guratlons Set 3 Conf1guratlons for the study. The control laws Included propor- t10nal plus 1ntegral gain loops to produce pltch- Set 3 Included two neutral-statlc-stablilty rate command/attitude-hold systems Wh1Ch were conflguratlons obtalned by removlng the lntegrator evaluated w1th and wlthout prefllters. Conven- In the forward path and modlfYlng the alrcraft t10nal response characterlstLcs were obtalned by model, WhlCh resulted In a flrst-order pltch-rate uS1ng pltch-rate and angle-of-attack feedback response 1/Te2 was set at 0 38 and 0 72 loops The evaluatlon task was a conventlonal visual approach to a flared touchdown at a deslg- Set 4 Conflguratlons nated spot on the runway A 300-ft lateral offset and a dlscrete vertlcal gust were used to Lncrease Set 4 conslsted of set 1 wlth the addltlon of p1lot workload a lead/lag prefllter deslgned to cancel the con- trol system zero at Kr and the augmented real The general concluslons of the study pre-
root A2 near 1/T . Conflguratlon 4-3-7-1
sented 1n Ref. 1 were that the eXlstLng crLterLa e2 added a washout fllter In serles wlth the lead/lag are generally based on pltch-attltude response and prefllter. The washout fllter canceled the Inte- that these characterlstlcs do not adequately dLS- grator root of the augmented system at frequencles crimlnate between the good and bad conflguratlons below 0 2 rad/sec.
of th1S study A tlme-domaln crlterlon was devel- oped based on angle of attack and normal accelera- Set 5 Conflguratlons t10n at the pilot station, and lmproved correla- t10n was shown A frequency-domaln crlterlon Set 5 conslsted of set 2 wlth the lead/lag based on slnk rate at the p1lot stat10n was also prefllter shown to be a Sllght Improvement over the pltch- attitude cr1ter1a ThlS paper descrlbes the work Set 6 Conflguratlons that has been done to further develop frequency- based crlterLa In an effort to provlde better Set 6 contalned four pltch-rate feedback correlatlon wlth the observed data conflguratlons wlth hlgh proportlonal plus Lnte- grator gaLn Ln the forward path. The basLc con- fLguratLon had a 1/Te2 = 0 38 The other conflg- Conflgurat1on Set Descr1ptlon uratLons conslsted of basLc plus washout, basLc plus prefLlter, and basLc plus washout and The conflgurat1ons evaluated durlng the prefLlter In-flIght slmulatlon used a fllght-control system of a generic transport Wh1Ch 1S presented Ln block Set 7 Configuration assumed). An example of a successful Neal-SmIth solution on a NIChols chart is shown In Fig 4 Set 7 Included one "conventional" configura- Once the closed-loop conditions are met, closed- tion obtained by using angle of attack and pitch- loop resonance and pilot lead/lag for a given rate feedback loops with one of the neutral-static bandwidth are plotted on a Neal-Smith parameter stability aIrcraft models.
plane (U8/8 ll vs pilot compensatIon) as shown In c Fig 5 and then correlated with the pIlot ratings Set 8 Configurations for a longItudInal task Figure 5 illustrates the revised Neal-Smlth boundarIes that were developed Set 8 consisted of five "Shuttle-lIke" con- in Ref. 3 for the longitudinal landing task figurations with a 1/T8 = 0.40. Four of the
models placed the pilot fo ft behind the center of
ApplicatIon of PItch-AttItude Frequency-Domain rotation. The fifth model was a canard confIgura- Cnterion tIon that placed the pilot 54 ft forward of the center of rotation. The first four models were The Neal-SmIth analYSIS performed on the also evaluated wIth the washout filter used In In-flIght simulatIon database showed that a number sets 4 and 6.
of confIguratIons were predicted by the crIterIon to be better than the actual pilot ratlngs had indicated. A bandWIdth of 2.0 rad/sec produced Pitch-AttItude Frequency-Domain CrIterIon the most representatIve correlatIon between the predicted and actual pIlot ratings in thIS analy- The Neal-SmIth theory2 is widely used to sis. Although the Neal-SmIth criterion IS a analyze the closed-loop pItch-attitude control of function of both closed-loop resonance and pilot aIrcraft. ThIS method assumed pitch-attItude lead/lag, at thIS bandWIdth the confIguratIons control to be the prImary task of the pIlot. An generally exhIbIted satIsfactory levels of closed- overview of the Neal-Smith theory IS presented loop resonance As a result, It appeared that the below. ThIS is Intended as a reVIew for those varIatIons In the actual pIlot ratIngs were prI- somewhat famillar WIth Neal-Smlth theory For a marIly dependent upon the amount of pllot lead more thorough explanation of the Neal-Smith compensatIon reqUIred to achieve the Neal-SmIth theory, see Ref. 2.
closed-loop reqUIrements. Figure 6 Illustrates the relatlonshlp between the actual pIlot ratings TechnIque DescrIptIon and the pIlot lead In pItch attItude reqUIred at a bandWIdth of 2 0 rad/sec In addition to the con- The Neal-SmIth theory IS based upon a slngle- fIgurations from Ref 1, selected confIguratIons loop closure performed on pItch attItude USIng a from Ref 4 comparable to those from Ref. 1 are pIlot model that employs a lead/lag fIlter WIth a shown In FIg. 6. These selected conflguratlons, gaIn and tIme delay. ThlS closure technIque lS those of a large aIrcraft wlth a short-aft tall, shown In FIg 2 The pIlot model operates on a are summarIzed In Table 2 The pllot ratIngs for pItch-attItude error SIgnal whlch IS the dlffer- these confIguratIons refer only to the landIng ~nce between the commanded attltude and the alr- performance The ±1 pIlot ratlng boundarles In craft's attItude The pIlot strategy for the FIg. 6 result In a data correlatlon of 55% Note Neal-SmIth theory IS shown In FIg 3. The pIlot, that FIg 6 shows a slgnlflcant amount of scatter through the flyIng parameters he is obserVIng, In the data for a wlde range of pllot lead tries to achleve a certaIn "standard of perfor- compensatIon mance" WhICh IS defIned by a certaln closed-loop bandWIdth The bandwldth IS deflned by the 90 The results from Flg. 6, however, dlsplay closed-loop phase reqUIrement. At frequenCIes some trends worth notIng The actual pIlot rat- below the bandwidth, the pIlot attempts to mlnl- Ings appear to degrade as the amount of lead com- mlze tracklng errors as defIned by a mInlmum low- pen~atlon reqUIred by the pllot Increases for the frequency droop (no more than -3 dB) The pllot glven bandWIdth ThIS IS to be expected, as the also attempts to mlnlmlze the closed-loop resonant pIlot would lIke to achIeve the hIghest pOSSIble peak 118/8 " ' WhICh mlnImlZeS osclllatory ten- max bandwldth WIth the least amount of compensatIon c dencies. The lead/lag fIlter (WhICh IS generally The baslc conflgurations WIth pItch rate feedback a pure lead term for most confIguratIons) and (sets 1,2,6-1) appear to reqUIre more lead compen- pIlot gaIn are adjusted such that the -3 dB droop satIon than the same confIguratIons WIth the and -90 of closed-loop phase condltlonS are met lead/lag prefIlter. The lead/lag prefIlter for a glven bandWIdth whIle the closed-loop reso- appears to reduce the amount of lead compensatIon nance IS mInImIzed These parameters then prOVIde requlred by the pIlot at the gIven bandWIdth a measure of compensatIon WIth WhICh the pIlot (sets 4,5,6-2) ThUS, as the prefIlter restores closes the loop The process of obtaInIng these the confIguratIon's orIgInal l/T 2' the amount of closed-loop condItIons IS readIly dIsplayed on a pIlot lead reqUIred IS reduced an~ thIS results In NIchols chart. The NIChols chart overlays the Improved pIlot ratIngs The conventIonal confIg- open-loop amplItude vs phase grId WIth the uratIon (set 7) WhICh consIstently produced closed-loop amplItude vs phase grId Thus, the level I pIlot performance reqUIred relatIvely NIChols chart prOVIdes Instant InformatIon regard- lIttle lead compensatIon, as dId some of the Ing the closed-loop performance (unIty feedback IS prefIlter conflguratlons. The Shuttle-lIke conf1gurat1ons (set 8) generally requ1red the shows an Improvement In the data scatter relative largest amount of lead compensat1on and displayed to the pltch-attltude data In Fig 6 degraded pilot ratings. Most of the configura- The altltude-rate lead requirements In Flg 8 tions that Included a washout filter (the four- appear to dlscrlmlnate a number of the conflgura- digit configurations) were rated better than would tlons. The baSlC conflguratlons wlth pitch-rate be expected based on the amount of pilot lead feedback (sets 1,2,6-1) generally requlre more required, this IS caused by the washout frequency lead In altitude rate than the same configurations range being below 0 2 rad/sec, which IS consider- With a lead/lag prefllter (sets 4,5,6-2) Thls ably below the given bandwidth for pitch atti- trend corresponds wlth the actual pllot ratings tude Most of the configurations from Table 2 The conventional conflguratlon (set 7) displayed correlated well with the trend In Fig. 6 The an altitude-rate lead representatlve of the pre- overall Ind1cations from Fig 6 pOint out that filter conflguratlons. The Shuttle-llke conflg- pitch-attitude characterlst1cs alone are not the uratlons (set 8) generally showed hlgher lead prlmary variable for the flared landlng task.
requirements and correlated well With the actual pllot ratlngs. The washout conflguratlons (the four-digit conflguratlons) were generally rated Alt1tude-Rate Frequency-Domain Crlterlon better than the altltude-rate lead requlrements Pilot comments Indicated that altitude rate would lndlcate, whlch lS again due to the low- control was a slgnlf1cant factor 1n the evaluation frequency feature of washout fllter The conflg- of touchdown performance. An attempt was made In uratlons from Table 2 showed poor correlatlon wlth Ref 1 to close the loop dlrectly on altitude rate the trend shown In Flg 8. Desplte thls pOlnt, at the pllot statlon uSing a pilot model which the trends mentloned above echoed those found wlth operated wlth a gain and time delay. A relatlon- the pltch-attltude lead requirements Sh1P was found between the altitude-rate bandwldth The relatlonshlp between the pilot ratlngs and the actual pllot ratings, which showed only a from thiS database and the results from the slight lmprovement over the pltch-attltude crl- Single-loop closure technlques have prOVided some terla As a result, an alternate method to evalu- Inslght lnto the flylng qualltles obtalned With ate altitude-rate control was developed as these conflguratlons. However, the results from descrlbed In the followlng sectlon these Single-loop closure techniques do not appear to glve an accurate picture of the longltudlnal Technique Descrlptlon landing task It lS pOSSible that control of more Assuming that the pllot closes the loop on than one parameter lS required by the pilot to altitude rate In a manner slmllar to pitch attl- achleve satlsfactory performance In thls tude, an Investlgatlon was made lnto the closed- lnstance, the pllot may elect to control one loop performance of altltude rate uSlng the Neal- parameter In serles wlth another durlng the longl- Smith technique Flgure 7 Illustrates the loop tudlnal landlng task.
closure In block diagram form Altltude rate at the pilot station IS controlled dlrectly uSlng a pilot model whlch employs a lead fllter with a Altitude Crlterlon Wlth Attltude Inner-Loop gain and time delay, as In Neal-Smlth theory The Closure closed-loop requirements, as before, were -3 dB of In an effort to obtaln a crlterlon that would droop and -90 of phase at the glven bandwldth better encompass the wlde range of characterlstlcs Thls method was then applied to the database found In thls database, an lnvestlgatlon was made lnto the closed-loop performance of the pilot Application of Altitude-Rate Criterion uSing multlloop control. Thls technlque assumes As with the Neal-Smith technique, thiS method that the pilot controls altitude through pitch uses a closed-loop bandwldth as one measure of attitude to prOVide satisfactory longitudinal pilot performance After several Iterations, an control durlng landlng.
altitude-rate bandWidth of 1.3 rad/sec appeared to best represent the data In general, the maximum Technlque Descrlptlon resonance at thiS bandWidth was low for the con- In the lnstance when the pllot deslres to figurations, and the amount of pilot lead for control altltude, thls task lS performed by clos- altitude-rate control appeared to be the domlnat- lng an lnner loop on pitch attltude and an outer lng factor In the pllot model Flgure 8 shows the loop on altltude In thls wayan altltude error relatlonshlp between the actual pllot ratlngs and lS translated lnto a pltch command Flgure 9 the amount of pllot lead In altltude rate Also shows the closure technlque In block dlagram Included In Flg 8 are the conflguratlons from form The pltch-attltude loop can be closed uSing Table 2 As wlth pltch-attltude lead, the actual the classlcal Neal-Smlth approach wlth a pllot pllot ratings appear to degrade as the requlrement model conslstlng of a lead/lag fllter wlth a galn for altitude-rate lead lncreases for the glven and time delay The altltude outer loop can then bandWidth The ±1 pilot ratings boundaries show a be closed through a pilot model operatlng w1th a data correlatlon of 60~, a slight Improvement over pure gain the pltch-attltude analysls Note that Flg 8 Followlng the closure of the pltch-attitude that the altitude performance characterlstics can loop, the altitude loop was closed to determine be defined by a single metrlc For the conflgura- the bandwldth available for altltude control The tions of this study, pllot lead compensation is altitude bandwidth is the frequency at which a required to improve the pltch-attltude control.
satisfactory level of closed-loop resonance However, lt is assumed that thlS pilot compensa- (2-4 dB) at -90° of closed-loop phase is tlon In pltch IS provlded to ensure good altltude achieved. A typical altitude outer-loop closure characterlstlcs rather than a good attitude is shown on a Nichols chart In Fig 10. "tracker," as such Therefore, In order to pro- vlde a conslstent inner-loop strategy between Application of Altitude Criterion with Attitude conflgurations, it IS assumed that the pilot will Inner-Loop Closure (Attitude Bandwldth Fixed) provlde an amount of lnner-Ioop pltch-attltude lead conslstent with level I handllng Quallties An example of this multlloop technlQue IS and then examlne the resulting altitude outer-loop found in Ref. 4. This method speclfles the inner performance. From Fig. 5, It can be seen that 25° loop as a result of the Neal-Smith attitude of lead compensatlon IS conslstent wlth level I closure at a given bandwidth. The multlloop tech- pllot ratlngs The lnner-Ioop pllot model (lead nlQue of Ref. 4 was applled to the observed data, and galn) was then determlned from the classlcal and the resultlng altitude bandwidths for the Neal-Smlth Solutlon that provlded 25° of lead conflguratlons were plotted against the corre- compensatlon (WhlCh corresponds to a bandwldth of spondlng actual pllot ratlngs, as shown In 1 8 rad/sec for the particular example ln Flg. 11 The Inner-Ioop attitude bandwldth Flg 5) Each conflguratlon wlil achleve a remalned at 2 0 rad/sec for all conflgurations different pltch-attltude bandwldth for the 25° (slnce thlS correlated best, as indlcated pllot model lead compensatlon Followlng the earller) Also included In Flg. 11 are the con- closure of the pltch-attltude loop, the altltude flguratlons from Table 2. Overall, the results loop was closed to determine the bandwldth from Flg. 11 show a data correlatlon of 64% wlthln avallable for altitude control These loop ±1 pllot ratlng This IS a Sllght Improvement closures are ldentlcal to the prevlously mentloned over the two prevlous slngle-Ioop closure tech- multlloop technlQue and are shown ln block dlagram nlQues However, the data In Flg 11 do not show form In Flg 9 adequate continulty and separatlon throughout the bandwidth range. The baS1C conflguratlons wlth The parameter of prlmary lnterest ln thlS technlQue, as before, lS the altltude bandwldth pltch-rate feedback (sets 1,2,6-1) do not ade- Quately show the Improvement (hlgher altltude The major feature of thlS technlQue, however, lS bandwldth) found In the actual pllot ratlngs wlth the ellmlnatlon of speclfylng an lnner-Ioop band- the addltlon of the lead/lag prefllter wldth and the emphasls upon level I lnner-Ioop (sets 4,5,6-2) The conventlonal conflguratlon attltude compensatlon If the pllot cannot attaln (set 7) dlsplayed one of the hlgher attalnable adequate altltude bandwldth wlth a reasonable bandwldths The Shuttle-Ilke conflguratlons amount of pltch-attltude compensatlon, the pllot (set 8) dlsplayed some of the lower bandwldths ratlngs wlil suffer Therefore, altltude band- Two of these conflguratlons (8-2-5, 8-3-5-1) wldth attalned wlth pllot compensatlon ln pltch devlated slgnlflcantly from the observed trends that corresponds to good flylng Qualltles wlli be The Shuttle-Ilke canard conflguratlon (8-4-6) was a measure of flare and landlng flylng Qualitles asslgned a pllot ratlng of 1 and had the hlghest Flgure 12 lliustrates the relatlonshlp between the attalnable bandwldth (2 75 rad/sec) Most of the altltude bandwldth uSlng thlS technlQue and the conflguratlons from Table 2 were not conslstent actual pllot ratlngs for thls database Agaln, wlth the trend observed In Flg 11 the conflguratlons from Table 2 are lncluded ln Flg 12 The results ln Flg 12 Indlcate a A posslble shortcomlng of thlS method lS that dlstlnct relatlonshlp between altltude bandwldth the lnner-Ioop attltude compensatlon lS based upon and actual pllot ratlngs. The ±1 pllot ratlng a glven bandwldth The pllot may not need all the bounds result ln a data correlatlon of 73%, WhlCh attltude compensatlon provlded by some of the lS slgnlflcantly hlgher than the pllot ratlng conflguratlons at thlS glven bandwldth Ideally, correlatlons found wlth altltude rate or pltch the pllot wlil attaln an lnner-Ioop bandwldth attltude. These results also show good contlnulty WhlCh provldes adequate lnner-Ioop control such and separatlon throughout the bandwldth range, that he may then control the outer loop The unllke the results ln Flg 11 whlch are based upon lnner-Ioop bandwldth wlil then vary for each con- the constant lnner-Ioop/bandwldth approach The flguratlon ThlS must be taken lnto account when baslc conflguratlons wlth pltch-rate feedback applYlng a multlloop technlQue of thlS type to (sets 1,2,6-1) show a lower altltude bandwldth handllng Qualltles data than the same conflguratlons wlth the lead/lag prefIlter (sets 4,5,6-2) The "conventlonal" Appllcatlon of Altltude Crlterlon wlth Attltude conflguratlon (set 7) dlsplayed one of the hlgher Inner-Loop Closure (Attltude Lead Compensatlon attaInable bandwldths The Shuttle-Ilke conflg- FlXed) uratlons (set 8) dIsplayed some of the lower band- wldths, wlth some exceptIons noted The Shuttle- The focal pOlnt of thlS paper lS the tech- llke canard conflguratlon (8-4-6) was aSSIgned a nlQue of deflnlng the lnner-Ioop pllot model such pIlot ratIng of 1 and had the hIghest attaInable altltude bandwldth (2.5 rad/sec). Another compensatlon requlred by the Neal-Smlth analysls Shuttle-like configuratlon wlth a washout fllter was compared wl~h the actual pllot ratlngs and a (8-3-5-1) was asslgned a pllot ratlng of 2, but data correlatlon of 60% wlthln ±1 pllot ratlng had a very low bandwidth The remalnlng washout resulted. ThlS IS Sllghtly better than that configuratlons appear to correlate well. The determlned from pitch attltude Desplte thlS conflguratlons from Table 2 correlated very well pOlnt, It appears that altltude rate control may with the other data In Flg. 12 The overall trend not be the prlmary task of the pllot In landlng a in Fig. 12 shows that a mlnlmum altltude bandWIdth hlghly augmented generlc transport alrcraft.
of 0 4 rad/sec appears to be necessary for level I pllot performance. It should also be noted that, 3) Altltude control performed by closlng an although the overall correlatlon of data wlth thls Inner loop on pItch attItude and closlng an outer technlque IS better than that of Ref. 4, the loop on altltude produced the most promlslng level I boundary for bandwldth IS s1mllar results. ThIS method assumed that the pllot WIll (0 5 rad/sec In Ref. 4) provlde an amount of Inner-Ioop pltch-attltude compensatIon conSIstent WIth level I handlIng The relatIonshIp between the Inner-Ioop quailtles and then examlne the resultIng altltude pltch-attltude bandWIdth and the outer-loop altI- outer-loop performance As a result, a data tude bandwldth from Flg 12 IS worth notlng, as correlatlon of 73% wlthln ±1 pllot ratlng was shown 1n Flg. 13 It appears that good altltude determlned from altltude bandwldth A mlnlmum bandwidth requlres good Inner-Ioop pltch attltude altltude bandwldth of 0 4 rad/sec appeared bandwldth, WhlCh IS to be expected. The capablll- necessary for level I performance.
tles of modern control systems allow conslderably more varlatlon In altitude bandwldth for a glven The capabliltles of modern control systems attltude bandwldth than has been posslble in the allow conslderably more varlatlon In altltude past. As a result, attItude control cannot be bandWIdth for a gIven attltude bandwldth than has used wlthout conslderation of the altltude been posslble In the past As a result, attItude response control cannot be used wlthout conslderatlon of the alt1tude response. Overall, it appears that control of altltude 1S a domlnant task for the Concluslons pllot during land1ng Three frequency-domaln handllng qualltles crlteria were applled to the observed data to References correlate the actual pllot ratlngs asslgned to generlc transport configuratlons WIth stablilty 1Berthe, C. J , Chalk, C. R., and Sarraflan, augmentatlon durlng the longltudlnal landlng S K., "Pltch Rate Fllght Control Systems In the task The crlterla were based on closed-loop Flared Landlng Task and Deslgn Crlterla Develop- technlques uSlng pltch attltude, altltude rate at ment," NASA CR-172491, Oct. 1984.
the pllot statlon, and altltude at the pllot sta- 2Neal , T. P. and SmIth, R. E., "An In-Fllght tion as domlnatlng control parameters durlng thlS Investlgatlon to Develop Control System Crlter1a task The appllcatlon of these crlterla to the for Flghter A1rplanes," AFFDL-TR-70-74, Vols I observed data have produced the followlng and II, Dec 1970.
concluslons 3Radford, R C , Sm1th, R E., and Balley, 1) The Neal-Smlth analysls uSlng pItch attl- R E, "Landing FlYlng Qualitles EvaluatlOn tude dId not correlate well wlth the observed Cn tena for Augmented Alrcraft," NASA CR-163097, data. The amount of pIlot lead compensatlon In Aug 1980 pltch attltude required by the Neal-Smlth analysis was compared wlth the actual pllot ratIngs and a 4We1ngarten, N C and Chalk, C. R , data correlatlon of 55% wlthln ±1 pllot ratlng "In-FlIght InvestIgatIon of Large AIrplane FlYIng resulted These results Indlcated that pltch- Qualitles for Approach and LandIng," attltude control may not be the prlmary task of AFWAL-TR-81-3118, Sept. 1981 the pllot In landlng a highly augmented generlc transport alrcraft 5"Mllltary Spec1flcatlon FlYlng Qualltles of P1loted Alrplanes," MIL-F-8785C, Nov 1980 2) Altltude rate was evaluated USIng the Neal-SmIth analYSIS Agaln, the amount of lead a Table 1 Conflguratlon Summary q/F Transfer Function es (s + KI}(s + 1/T ) (s + 11T ) s e2 z ~= (s + (s + F (s + ~2)(w • 11T ) 1lTwo) psp) F es nsp prefllter washout Cooper-Harper b ~ I Configuration 1/T pilot ratlngs (,u ' 1IT 1ITF KI 1ITe2 1;sp) wo z 2 nsp
1-1-1 2.0 o 44 0.8
0.38 2.79 5. 7 (1-2-2)
2.0 o 72 0.82 2.76 o 8 5 5. 7. 8
1-3-7 2.0 1 00 1. 19 2 73 o 8 4. 7
3.
2-1-1 2.0 0.38 o 50 1 78 0.6
5. 6. 7 2-2-2 2 0 4 5 o 72 0.93 1. 75 o 6 3.
3-1-3 0 2.50 0.38 0.036. 4.94 ~.5 • 6 3-2-4 0 2.50
o 72 o 063. 5 24 2 5. 5
4-1-1 0.44 2.0 0.38 2 79 0.8 0 43? 2.0 2 5. 5
4-2-2 2.0 0 1 19 2.73 o 8 0 821 2 0
72 2.3 ( 4-3-7) 2.0 1 00 1. 19 0.8 19 2.0 2 73 7 4-3-7-1 2.0 1 00 19 8 2 0 o 20 4 2 73 19 • 0
5 -1-1 2.0 o 50 2 0
0.38 1. 78 0 6 0.50 4.5. 4.5 5-2-2 2.0 o 72 o 93 1 75 0 6 0.931 2 0 2.
6-1-1 3 0 o 38 0.45 2 27 0 46 6 3. 5. 6.
6-1-1-1 o 38 o 45 2 27 o 46 0.20
3 0 3 6-2-1 0.45 3.0 0.38 2.27 0.46 0.448 3.0 2. 5 5.
6-2-1-1 3.0 o 38 o 45 2 27 o 448 3 0 0.20 • 0.46 3
7-1-4 o 72 0 2 84 0.80
2 5. 3
8-1-5 2 0 o 40 0.586 1 45 0 o 6 2 0 6
50 4. 5 5.
8-1-5 -1 2.0 0.40 o 586 1. 45 2
0.6 0 o 20 2
• 0 50 8-2-5 2.0 0.40 0 1 2 70 09 0 50 1.0 0 8. 8 7.
(8-2-5-1 )
2 0 0 40 0 70 1.09 50 0 2 0 o 20
• 0 8-3-5 2 0 0 40 0 586 45 0 50 2 0 8 5 5. 7. 7.
8-3-5 -1 2 0 0 40 0 586 45 2 0 o 20 50 5 3. 3 • 0 8-4-6 2 40 0 0 0 590 47 0 60 0 6 2 0 1 8-5-5 2 0 0.40 0 586 45 0 50 0 6 2 0 5. 7 a system
Feel (21 O. o 60)
Actuator (27.0. o 70)
bFlrst number of each conflguration refers to the set number ( ) IndIcate data consldered suspect. not Included In analysls Table 2 Large Alrcraft Conflguratlon Summary (Ref. 4) Cooper-Harper pllot ratln'Ssa conr 19urat JOn Descrlptlon ;x LA12 Short-aft tall, medlum feedback 10 LA13 Short-aft tall, hlgh feedback Cl 9, 8 a; LA13A Short-art tall, hlgh feedback 10 (clfferent 3~lCk feel sy'5tem than LA13) LA14 Short-art tall, 'lledlUm q feedback 9 LA15 Short-aft tall, hlgh q feedback 9 LA15A Short-aft tall, hlgh q feedback 6 (11fferent stlck feel system than LA15) aRpfer~ tu ratlng~ asslgned to landlng task onl; Gust a LJ"'....-.J Aircraft TS e- model q F~g. 1 P~tch-rate fL~ght-controL system (Ref. 1).
Pilot model
e
Aircraft T=025sec F~g. 2 CLasstcaL NeaL-Sm~th cLosure techn~que.
Minimize droop dB 0r-====~----'-----
<t :' -90
c deg -180L---------------~------ Log(w) F~g. 3 Neal-Smith p~lot strategy (closed-loop p~lot/veh~cle frequency response).
Closed loop gain, dB -3 Open loop gain, dB -9 -6 -12 -12 -15 -18 -18 _24L-~ __ -L __ ~L-L--ll __ ~~~== -240 -210 -180 -150 -120 -90 -60 -30 0 Open loop phase, deg F~g. 4 Neal-Sm~th solutLon. Bandw~dth 2.0 rad/sec. Dashed l~ne represents closed-loop p~lot/ veh~cle p~tch att~tude frequency response.
12 /PR=65 WBW=45~ :f , Clpsed loop ,
PR=7
resonance,
40~ /
dB 4 j / / " -2 _4~~~ __ L--L~ __ ~-L-J-l~-L~~ -30-20-10 0 10 20 30 40 50 60 70 80 90 Pilot compensation, deg F~g. 5 Neal-Sm~th solut~on (Neal-S~th paraneter plane).
Configurations
o Basehne
o Prefilter
o "Shuttle hke"
C::. Conventional aircraft I::. Neutral static D Washout o Large aircraft (ref 4) 8-3 50 ~8 2-5 OLA13
~~3
2 -l ~ 3-~8~2~5~
7 b
6-1-1 3-1-3 ~ LA15A
6 8- 8 <D6-1-1 I::. .021-1 0:1 PR
Actual 6-2-1 8-1 5 -!:-3-1-3 pilot 6-2-1 [[) 041-1 1-110 06-11 I::. 0 08-3-5 3-2-4 0 2-11 rating 13-7 0 22-2 8-1-5 5-2-2 8 3-5-1 i1 3 1 3-7 <DJ D 06-1-1 002-22 ""6-1-1-1 I::.
5-220 3-2-4 08-4-6 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 8 pilot compensation, deg Fig. 6 P~~ot rating as a function of a p~~ot compensation. WBWa 2.0 rad/sec.
Pilot model
T = 025 sec
F~g. 7 A~t~tude rate (pi~ot) c~osure technique.
LA120 Configurations :1 PR 0 Basehne 0 Prefilter 0 "Shuttle hke" Conventional aircraft C::.
7 1370 I::. Neutral static 1-110 L 021-1rLA15A D Washout 6 1 1 81-5 65 - - 8 5 ~31-3
6 6
Large aircraft (ref 4)
Actual 08-15 ,1-11 8-3- 7 2 1-1
pilot 006-1-1 rating ~8-3-5-1 D ~6-1-1 61-1 1 1::.3-2-4 052 Z 10 30 40 50 60 70 80 90 100 o 20 hp lead compensation, deg F~g. 8 P~~ot rat~ng as a funct~on of hp pi~ot compensat~on. WBWh 1.3 rad/sec.
p Outer· loop Inner loop pilot model pilot model h h P
e ee
c S + A'A Pe Kh TS CL + 1)
Kp e - --- r--- Aircraft J e
--,.:y- -- p
1.r0-
e TIs + 1
-
-
T = 025 sec Ftg. 9 Altttude outer-loop closure techntque Wtth attttude tnner-loop closure (6 lead 25°).
Closed loop gain, dB -3 Open loop gain, dB -6 -12 -12 -15 -18 -18 _24L1~L-~--L~~~~--~~==~ -240 -210 -180 -150 -120 -90 -60 -30 0 Open loop phase, deg Ftg. 10 Altttude outer-loop closure Wtth pttch- attttude tnner-loop closed (WBWh = 0.5 rad/sec).
p
10 o LA13A
Configurations o Baseline ~ LA15<J)LA13 o Prefilter ~5(:OLA13 825 (1) 825 0 "Shuttle like" 211u835 ~ Conventional aircraft 835VQA. 0111 0137 08 2 5 (::" Neutral static
~
LA15A ~2 1 1'),8.1 5 D Washout 6 "-..6 1 1 CID ~' (::" 3 1 3 o Large aircraft (ref 4) Actual 211~ 6110 313 pilot 5 835 ([]411 (::,,324 rating 621 ~ 222 1 1 1 8 1 5 5 1 1 2 2 2 '\~~~i;0~1;-:3;-:7-;- ____ D_4_3_7_'1 __ 835 1
742 r 522 7·1 4
3 Cl:I8351 6·110 0 0 rn; 01·37
4110 Ii 324(::" ~714
2 6210 L;6211 4~2DD 0522 6111 7 2 3 4 5 6 275 W ,rad/sec BW hp ctq. 11 ptlot rattng as a functton of altttude bandwtdth (6 tnner-loop results tn WBWe 2.0 rad/sec).
Configurations o Baseline o Prefilter
o "Shuttle like"
6 Conventional aircraft LA14 ~ Neutral static D Washout o Large aircraft (ref 4) 11-1 7 o 01-37 3-1-3 LA15A 0 2110 CD 8-1 5 Actual "-... 6-1-1 62_1,41-1 8-350 0 "",,-0 01-11 aD ~3 2-4 pilot 5 rating 2 1-1 6-1-1~2 2-2 62-1 D4 3 71 4 5-1-1 8-1 5 "- 0 1-3-7 8 3 51 52-2 62-1-1 ,42-2:-:-:-: ______ _ 3 m8351 6110 6-1_112-22 0 CI1D 67-1-4 4110 ~3-2-4 L1-3-7 67-1-4 "-.0 ~81-5-1 04-22 5-22 2 3 4 5 6 25 W ,rad/sec BW hp F~g. 12 P~lot rat~ng as a function of alt~tude band~dth (a ~nner-loop results ~n 25° lead cOT'7pensat~on).
Configurations o Baseline o Prefilter
o "Shuttle like"
6 Conventional aircraft ~ Neutral static 2-1-1 D Washout o Large aircraft (ref 4)
4 2-2 cf J:, 1-4
Flags denote averaged 25 - flYing qualilles levels One flag denotes levell, l-371 two flags, level II, and 5-11d
[a 1-5-1 three flags, level III
-
81V-
ds 6,.3-7
~
W ' BW 84-66 61-1-1
e
Flll rad/sec 5-110 1 5 cfs351
( t;22
31 3 LA15'@~ lA15A..... LA13 LA13A-'~ Level II lA12~ LA14 Level III 3 4 5 6 25 W ,rad/sec BW hp F~g. 13 WBWa as a funct~on of WBWh (results from Fig. 12).
P 1 Report No 2 Government Accession No 3 RecIpient's Catalog No NASA TM-86728 4 Title and Subtitle 5 Report Date August 1985 Application of Frequency Domain Handling Qualities Criteria 6 Performing Organization Code to the Longitudinal Landing Task Author(sl Performing Organization Report No 7 8 Shahan K. Sarrafian and Bruce G. Powers H-1288 10 Work Unit No 9 Performing Organization Name and Address RTOP 505-43-11 NASA Ames Research Center 11 Contract or Grant No Dryden Flight Research Facility P.O.
Box 273 Edwards, CA 93523-5000 13 Type of Report and Pertod Covered 12 Sponsoring Agency Name and Address Technical Memorandum National Aeronautics and Space Administration 14 Sponsormg Agency Code Washington, D.C. 20546 Supplementary Notes Prepared as AIAA Paper 85-1848 for presentation at the AIAA Guidance, Navigation, and Control Conference, Snowmass, Colorado, August 19-21, 1985.
16 Ahstract Under NASA sponsorship, an in-flight simulation of the longitudi- nal handling qualities of several configurations for the approach and landing task was performed on the USAF/AFWAL Total In-Flight Simulator by the Calspan Corporation.
The basic configuration was a generic transport airplane with static instability.
The control laws included proportional plus integral gain loops to produce pitch-rate and angle- of-attack feedback loops.
The evaluation task was a conventional visual approach to a flared touchdown at a designated spot on the run- way with a lateral offset.
The general conclusions were that the existing criteria are based on pitch-attitude response and that these characteristics do not ade- quately discriminate between the good and bad configuations of this study.
This paper describes the work that has been done to further develop frequency-based criteria in an effort to provide better correlation with the observed data.
17 Key Words (Suggested by Author(sll 18 DlStrtbutlon Statement Handling qualities Unclassified - Unlimited Control systems Landing task STAR category 08 19 Security ClasSif (of thIS report I 20 Security Classlf (of thIS pagel Pnce* 21 No of Pages
I 22
Unclassified Unclassified 13 A02 ~For sale by the Nat~ona1 Technical Informat~on Serv~ce, Spring£~e1d, V~rg~n~a 22161.