Document
[I11 4,261,537
United States Patent [I91
1451 Apr. 14, 1981
Tisdale, Sr. et al.
VELOCITY VECTOR CONTROL SYSTEM [561 References Cited AUGMENTED WITH DIRECT LIFT U.S. PATENT DOCUMENTS CONTROL 3,167,276 1/1965 Moosbrugger et al. ......... 318/584 X 244/181 X 3,237,107 2/1966 Bresenoff et al. ...............
Inventors: Robert A. Frosch, Administrator of
3,399,849 9/1968 Hendrick ......................... 244/187 X
3,618,878 11/1971 Klein et al. .......................... 244/188 the National Aeronautics and Space
3,860,800 1/1975 Simpson ........................... 364/434 X
Administration, with respect to an
3,945,590 3/1976 Kennedy, Jr. et al. .......... 244/181 X
invention of Henry F. Tisdale, Sr., Oakhurst, N.J.; Wendell W. Kelley, Primary Examiner-J. D. Miller Newport News, Va.
Assistant Examiner-Reinhard J. Eisenzopf Attorney, Agent, or Firm-William H. King; John R.
Manning; Howard J. Osborn Assignee: The United States of America as represented by the Administrator of [571 ABSTRACT the National Aeronautics and Space A pilot controlled stability control system that employs Administration, Washington, D.C.
direct lift control (spoiler control) with elevator control to control the flight path angle of an aircraft. A com- Appl. No.: 15,996 puter on the aircraft generates an elevator control signal and a spoiler control signal, using a pilot-controlled pitch control signal and pitch rate, vertical velocity, roll Filed: Feb. 28, 1979 angle, groundspeed, engine pressure ratio and vertical acceleration signals which are generated on the aircraft.
The direct lift control by the aircraft spoilers improves
Int. Cl.3 ............................................... G05D 1/08
the response of the aircraft flight path angle and pro- U S . Q. .................................... 244/181; 244/195; 318/584; 364/434 vides short term flight path stabilization against envi- Field of Search ................................ 244/180-182, ronmental disturbances.
244/186-188, 177, 195; 318/580, 584; 73/178 R; 364/433,434,435 10 Claims, 2 Drawing Figures PILOT ------c --+
CONTROLLED . ANALOG -
DIGITAL FLIGHT PITCH TO TO b CONTROL TRANSDUCER
DIGITAL -
ANALOG COMPUTER
’ CONVERTERS ------)
CONVERTERS 4 t - - m PITCH GYRO CONTROL I I DATA SPOILERS ELEVATORS SYSTEM
7 1 AIRCRAFT EPR
ENGINE INSTRUMENTATION
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U.S. Patent Apr. 14, 1981 Sheet 1 of 2
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Sheet 2 of 2 4,261,537
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DETAILED DESCRIPTION O F THE VELOCITY VECTOR CONTROL SYSTEM INVENTION AUGMENTED WITH DIRECT LIFI: CONTROL Turning now to the embodiment of the invention 5 selected for illustration in the drawings the number 11 ORIGIN OF THE INVENTION
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in FIG. 1 designates a pilot controlled pitch transducer The invention described herein was made in the per-
which generates a pitch x. In Operating
formant- of work under a NASA contract and is sub- this invention the pilot views the flight path angle on ject to the provisions of Section 305 of the National the aircraft cockpit display and he changes the value of Aeronautics and Space Act of 1958, public L~~ 85-568 10 the pitch control signal X to change the flight path (72 Stat. 435; USC 2457).
angle to some new commanded value. This invention
-
quickens the response time between the time of a BACKGROUND OF THE INVENTION change of the pitch control signal X and the time the The invention relates generally to aircraft control change is shown on the aircraft display as a change in systems and more particularly concerns an aircraft 15 the flight path angle. Moreover, this invention provides flight path angle control system that employs direct lift a well-damped, highly stable response, control.
Instrumentation on the aircraft generate feedback is the The flight path between the air- control sigqals: a pitch rate gyro 12 generates a pitch craft's inertial velocity vector and the local horizontal rate signal 6; an air data computer 13 generates a verti- reference plane. In the past, pilot-controlled Stability 20 cal velocity signal h; an aircraft engine instrumentation Augmentation Systems (SASI designed to control the 15 generates an EPR signal; and an inertial navigation flight Path angle have utilized the aircraft's elevators (or system 14 generates 3 groundspeed signal V , , a vertical horizontal stabilizers) for the control. The main disad- acceleration signal h, and a roll angle signal 4. The vantage with these systems is there is a delay between pitch control, pitch rate, vertical velocity, ground- the time the pilot changes the position of the elevators 25 speed, vertical acceleration, roll angle and EPR signals and the time the flight Path angle changes in response are all applied to analog-to-digital converters 16 where thereto. Also with elevator control there is limited abil- they are converted to digital signals. These digital sig- itY to counteract short term flight Path fluctuation due nals are applied to a flight control computer 17 which to environmental disturbances.
generates an elevator control signal and a spoiler con- It is the primary object of this invention to Provide a 30 trol signal. These elevator control and spoiler control pilot-controlled SAS that decreases the delay between digital signals are applied to digital-to-analog convert- the time that the pilot actuates his control until the time ers 18 which convert them to analog signals. The analog that the flight path angle changes in response thereto. elevator control signal is applied to elevator power Another object of this invention is to provide short control units 19 to control the elevators 20 on the air- term flight path angle stabilization due to environmental 35 craft; and the analog spoiler control signal is applied to disturbances.
spoiler power control units 21 to control the spoilers 22.
Flight control computer 17 as shown in FIG. 2 in- Other objects and advantages of this invention will become apparent hereinafter and in the drawings. cludes a divider 30 which receives the vertical velocity and groundspeed signals and generates a flight path SUMMARY OF THE INVENTION 4 0 angle signal y by dividing the groundspeed signal into This invention is a pilot controlled SAS that employs the vertical velocity signal. The pitch control signal X direct lift control in conjunction with the aircraft eleva- from the pilot-controlled transducer 11 is applied tors to control the flight path angle. The direct lift through a gain and noise filter 31 to a summing device 45 32. The output of summing device 32 is the elevator control provides lift quickening and thus improves the response of the aircraft flight path to pilot commands. control signal. The signal from the gain and noise filter Also the direct lift control augments elevator control in 31 initiates pitch response through the elevators. The providing short term flight path stabilization due to characteristics of the gain and noise filter 31 is defined environmental disturbances. Long term flight path con- by the expression: trol is maintained by a high performance closed loop 5o elevator control system. KPDE A transducer generates a pitch control signal in re-
72s + 1
sponse to pilot inputs and instruments on the aircraft generate signals ProPortional to pitch rate, vertical ve- where KPDEis a constant determined by the character- locity, groundspeed, and vertical acceleration. A com- 55 istics of the aircraft on which the system is used. 7 2 is a puter on board the aircraft receives these signals and time constant and s is a Laplace operator. The pitch generates an elevator control signal and a direct lift control signal X is also applied to a constant multiplier control signal for controlling the elevators and spoilers 33 which multiplies X with a constant Kpp. The output on the aircraft. In addition, a roll angle signal is gener- multiplier 33 is applied through a summing device 34 to ated on the aircraft and applied to the computer to 60 a spoiler command limiter 35 the output of which is the cancel a loss of the vertical component of lift due to spoiler control signal. The signal at the output of limiter bank xgles.
35 provides an immediate lift increment to start chang-
ing the flight path angle in a favorable direction. To
DESCRIPT1oN OF THE counteract the moiler Ditching moment. the moiler FIG. 1 is a block diagram of the preferred embodi- 65 control signal at 'the output oflimiter 35 is crok fed through a constant multiplier 36 which multiplies the ment of the invention; and FIG. 2 is a block diagram of the flight control com- signal by a constant KCF to a summing device 32 to puter shown in FIG. 1.
provide additional elevator control.
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At the instant the system is activated (turned on) by summing device 47 is multiplied by a constant KEPR by the pilot the flight path angle signal y at the output of means of a constant multiplier 48 and then applied to divider 31 is applied to an integrator 37 to set the inte- summing device 32. Two benefits are immediately grator to the initial value of 7. The pitch control signal available from this scheme: pitch disturbances due to X is then integrated by the integrator 37 to form the 5 thrust changes are cancelled, and an elevator bias signal commanded flight path angle signal Y C at the output of is provided downstream of the washout integrator 40 the integrator. This signal is compared with the com- allowing a reduction in the integrator gain and thereby puted A signal at the output of divider 30 by means of a contributing to an increase in system stability.
summing device 38 to produce an error signal A65.
All of the constants shown in the block diagram in The primary elevator stabilization signal is derived 10 FIG, 2 are determined by the particular aircraft on by passing the error signal AY through a high gain lead which the invention is used. A good estimate of each lag filter 39 the output of which is applied to summing constant can be determined from the available data on device 32. The characteristic of filter 39 is defined by the aircraft and thereafter the constants can be adjusted the expression: to obtain the desired responses.
l 5 This invention has been used on a flight simulator by
Ki(s + K2
Langley Research Center in Hampton, Va. The simula-
s + K3
tor represents a twin-engine medium jet transport that was modified to include an advanced research cockpit, where K1, K2 and K3 are constants. This Part of the direct lift control capability, and onboard flight re- elevator control signal is the primary elevator stabiliza- 20 search equipment. The values of the constants in FIG. 2 tion signal. Filter 39 is the part of the invention that that were used are as follows: optimizes stability and response. The AA signal is also Kh=4.9 applied through an integrator 40 the output of which is Kpsp=2.4 applied to the summing device 32. This part of the ele- Limiter 35= +8" vator control signal takes care of possible steady-state 25 KcFo.35 standoff errors which would occur due to bias error Kc=o.33 signals or elevator trim requirements. In addition the Khy=8.O signal Ay is applied through a constant multiplier 41, KpDE=1*3 which multiplies the signal by a constant K A ~ , to sum- 72=0'09 ming device 34 to provide long term spoiler corrections 30 K1=20.0 for the flight path angle errors. The vertical accelera- Kz=o*8 tion signal h from the inertial navigation system 14 is K3=2.5 applied through a constant multiplier 42, which multi- KI=0.3 plies the signal by a constant Ki, to the summing device
Ki=4.0
34. This part of the spoiler control signal essentially 35 provides a signal for stabilization. ~ 1 = 1 6 Kb=o.oo4 The Ditch rate signal 6 from the Ditch rate gvro 12 is "I KEPR = 8.2 applied through a constant multiplier 49, which multi- The advantages of this invention over previous pilot plies the signal by a constant Ki, to a washout filter 43.
40 controlled stability augmentation systems are numer- The characteristic of filter 43 is defined by the expres- ous. It provides lift quickening and thus improves the sion: response of the aircraft flight path angle to pilot com- mands; it provides short term flight path stabilization 71s against environmental disturbances; it improves the ride
71s + 1
45 quality of the aircraft; it improves the pilot accuracy in tracking a glide slope; and it improves flare and touch- where 71 is a time constant. The output of filter 43 is down performance of the aircraft.
applied to summing device 32 to provide short period What is claimed is: mode dampening in the elevator control signal. The roll 1. An aircraft flight path angle control system that
angle signal 4 from the inertial navigation system 14 is
50 employs direct lift control comprising: squared by a multiplier 44 and applied through a con- a pilot controlled means for generating a pitch con- stant multiplier 45 to the summing device 32. Multiplier trol signal; 45 multiplies the roll angle signal by a constant K+ to means on the aircraft for generating feedback. signals cancel a loss of the vertical component of lift due to proportional to the vertical velocity, and the bank angles.
55 groundspeed; Another feature of the invention which is claimed in first computer means receiving said pitch control a co-pending application is the use of the EPR feedback signal for generating a direct lift control signal; for cancelling pitching moments due to thrust changes.
second computer means receiving said pitch control, The technique is based upon knowledge of the relation- ship between engine location, engine thrust, EPR, and vertical velocity, and groundspeed signals for gen- elevator effectiveness. An analysis of these factors pro- erating an elevator control signal said second com- 60 duces a gain of KEPR which when applied to the EPR puter means including means for generating a pri- feedback signal commands the proper amount of eleva- mary elevator stabilization signals, means for gen- tor to cancel thrust induced pitching moments. To im- erating a signal for initiating pitch response, means plement this part of the elevator control signal the EPR for generating a possible standoff errors signal and signal initially sets the reference EPR 46 at the time the means for summing the last three mentioned gener- 65 pilot engages the system. Thereafter the generated EPR ated signals to generate the elevator control signal; signal is compared with the reference EPR signal by means responsive to said elevator control signal for means of a summing device 47. The difference output of controlling the elevators on said aircraft; and
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a gain and noise filter means receiving said pitch means responsive to said lift control signal for con- control signal for producing said signal for initiat- trolling the direct lift controls on said aircraft.
ing pitch response; 2. An aircraft flight path control system according to a second constant multiplier receiving said direct lift claim including on the aircraft for generating a control signa1for providing an feedback signal proportional to pitch rate that is applied control signal; and to said second computer means which includes means the first said summing means for combining said pri- for generating a short-period mode damping signal that mary elevator stabilization, possible standoff er- is applied to said summing means.
rors, initiating pitch response and additional eleva- 3. An aircraft flight path control system according to 10 tor control signals to form said elevator control claims 1 or 2 including means on the aircraft for gener- signal.
ating a feedback signal proportional to vertical aCCeler- 7. An aircraft flight path angle control system ac- ation that is applied to said first computer means which cording to claim 6 including a third constant multiplier includes means for combining a stabilization signal with receiving said error signal for producing a long-term said direct lift control signal. 15 spoiler corrections signal, and a third summing means receiving the long-term spoilor corrections signal and 4. An aircraft flight path control system according to the signal at the output of said first constant multiplier claims 1 or 2 including means on the aircraft for gener- for combining the two signals to form said direct lift sting a feedback signal porportional to roll angle that is applied to said second computer means which includes system ac- 8. An aircraft flight path angle
means for combining with the elevator control signal a 2o
cording to claim 7 including means on the aircraft for signal to cancel a loss of the vertical component of lift generating a vertical acceleration feedback signal, a due to bank angles.
fourth constant multiplier receiving said vertical accel-
'' An aircraft flight path system
eration feedback signal for producing a spoiler stabiliza- cording to clairn 1 wherein said first computer means 25 tion signal and provided with said third summing includes a first constant multiplier for multiplying said for combining said spoiler stabiiization signal pitch control signal by a constant to form said direct lift with long-term spoiler corrections signal and the signal control signal.
at the output of said first constant multiplier to form said 6. An aircraft flight path angle control system ac- direct lift control signal.
cording to claim 5 wherein said second computer means 30 9. An aircraft flight path angle control system ac- comprises: cording to claims 7 or 8 including means on the aircraft for generating a feedback pitch rate signal, a fifth con- a divider receiving said vertical velocity and ground- stant multiplier receiving said pitch rate signal for multi- speed signals for dividing the groundspeed signal plying it with a constant, a washout filter means receiv- into the vertical velocity signal to form a computed 35 ing an output of said fifth constant multiplier for pro- flight path angle signal; ducing a short-period mode and a first integrator means receiving said pitch control for combining said short-period mode damping signal signal for forming a commanded flight path angle with said elevator control signal.
signal; 10. An aircraft flight path angle control system ac- a second summing for Obtaining an error signa1 40 cording to claim 9 including means on said aircraft for which is the difference between the computed and generating a feedback roll angle signal, means for squar- commanded flight path angle signals; ing said roll angle signal and multiplying it by a constant a lead-lag filter means receiving said error signal for to form a signal for a loss of the vertical Producing Said Primary elevator stabilization Sig- component of the lift due to bank angles and means for nal; 45 combining the last mentioned signal with the elevator a second integrator means receiving said error signal control signal.
* * * * *
for producing said possible standoff errors signal;