Source: http://www.google.com/patents/US7555371?dq=6,275,983
Timestamp: 2018-01-17 07:11:21
Document Index: 705183362

Matched Legal Cases: ['art 10', 'art 10', 'art 10', 'art 10', 'art 10', 'art 11']

Patent US7555371 - Automatic piloting device for rotary wing aircraft - Google Patents
An automatic piloting device utilizing a measurement of ground speed deduced from the measurements of acceleration originating from an AHRS attitude and heading platform which it readjusts by ground speed information provided by a T readjustment device: satellite-based positioning receiver or a Doppler...http://www.google.com/patents/US7555371?utm_source=gb-gplus-sharePatent US7555371 - Automatic piloting device for rotary wing aircraft
Publication number US7555371 B2
Application number US 11/353,243
Also published as US20070010920
Publication number 11353243, 353243, US 7555371 B2, US 7555371B2, US-B2-7555371, US7555371 B2, US7555371B2
Inventors Jean-Louis Lebrun, Jean Foisneau
Automatic piloting device for rotary wing aircraft
US 7555371 B2
An automatic piloting device utilizing a measurement of ground speed deduced from the measurements of acceleration originating from an AHRS attitude and heading platform which it readjusts by ground speed information provided by a T readjustment device: satellite-based positioning receiver or a Doppler radar exhibiting periods of unavailability. This automatic piloting device includes a preprocessing part with readjustment blocks based on estimator filters of the complementary type of second order with two branches one of the first order, the other of the second order which are momentarily transformed into first-order complementary filters, by action on their branch gains, with each return of availability of the readjustment device.
{ K 1 = 2 T K 2 = 1 2 T
T being a parameter lying between 5 and 10, whose value corresponds to the maximum tolerable duration of unavailability of the second device, expressed in seconds.
ψt=ψm +D m
and the longitudinal and transverse components Vlrec(L) and Vlrec(T) of the speed vector measured by the readjustment device by the relation:
[ V lrec ( L ) V lrec ( T ) ] = [ cos Ψ t sin Ψ t - sin Ψ t cos Ψ t ] × [ V lrec ( L ) V lrec ( T ) ] .
9. Automatic piloting device according to claim 7, wherein the means of calculation of speed compensations determine the speed compensations to be performed by means of the matrix relation:
[DV]=[Θ t]×[Φt ]×[GA^
[ DV ] = [ DVL DVT DVz ] ; [ GA ] = [ xa ya za ] ; [ Ω -> ] = [ p 1 q 1 r 1 ] [ Θ ] = [ cos Θ 0 - sin Θ 0 1 0 sin Θ 0 cos Θ ] ; [ Φ ] = [ 1 0 0 0 cos Φ sin Φ 0 - sin Φ cos Φ ] .
10. Automatic piloting device according to claim 9, wherein the means for calculation of speed compensations determine the longitudinal and transverse components Vrec-comp(L) and Vrec-comp(T) of the compensated measurement of speeds ground speed on the basis of the longitudinal and transverse components Vrec(L) and Vrec(T) of the measurement of ground speed delivered by the means of changing reference frames and the compensation components, by applying the relation:
V lrec-comp(L) =V lrec(L) +DVL
V lrec-comp(T) =V lrec(T) +DVT.
11. Automatic piloting device according to claim 7, wherein the means for calculation of the compensations of accelerations determine compensations to be applied to the measurements of longitudinal and transverse acceleration Γ(L) and Γ(T) originating from the attitude platform by subtracting from the horizontal component of the measured acceleration vector (Γ(L), Γ(T)), the vector product of the rate of rotation of change of heading □dot times the estimate of the horizontal projection (Vlest(L), Vlest(T)) of the speed vector delivered to the automatic piloting device in accordance with the matrix relation:
Γcomp=Γ=−
V lest
Γcomp being the projection of the compensated acceleration vector in the plane containing the longitudinal and transverse axes of the aircraft,
Γ comp = [ Γ comp ( L ) Γ comp ( T ) ] ; Γ [ Γ ( L ) Γ ( T ) ] ; Ω → H = [ 0 0 Ψ . ] .
12. Automatic piloting device according to claim 7, wherein the means for calculation of the rate of rotation of change of heading operate on the basis of the relation:
Ψ dot or Ψ . = r 1 * cos ( Φ ) + q 1 * sin ( Φ ) cos ( Θ ) .
13. Automatic piloting device according to claim 1, associated with an inertial platform and with a readjustment device of Doppler radar type delivering measurements of the components Vld(L), Vld(T) and Vld(Z) of the ground speed of the craft according to a reference frame tied to the aircraft, wherein its preprocessing part comprises, in addition to the estimator filter or filters:
[V rec-comp]=[Θt]×[Φt]×([V d ]+[GA
[ DV ] = [ DVL DVT DV z ] ; [ GA ] = [ xa ya za ] ; [ Ω → ] = [ p 1 q 1 r 1 ] [ Θ ] = [ cos Θ 0 - sin Θ 0 1 0 sin Θ 0 cos Θ ] ; [ Φ ] = [ 1 0 0 0 cos Φ sin Φ 0 - sin Φ cos Φ ] .
15. Automatic piloting device according to claim 13, wherein the means for calculation of the compensations of accelerations determine compensations to be applied to the measurements of longitudinal and transverse acceleration Γ(L) and Γ(T) originating from the attitude platform by subtracting from the horizontal component of the measured acceleration vector (Γ(L), Γ(T)), the vector product of the rate of rotation of change of heading ψdot times the estimate of the horizontal projection (Vlest(L), Vlest(T)) of the speed vector delivered to the automatic piloting device in accordance with the matrix relation:
Γcomp=Γ−
^ H V lest
16. Automatic piloting device according to claim 13, wherein the means for calculation of the rate of rotation of change of heading operate on the basis of the relation:
an inertial navigation platform providing accelerometric information and angular rates, as well as, depending on its degree of complexity, information regarding attitude, ground and vertical speeds referenced along the axes of the carrier, and information regarding heading followed and instantaneous position,
a Doppler radar delivering measurements of longitudinal and transverse ground speed in the axes of the carrier or
a satellite-based positioning receiver delivering measurements of ground speed along north and east geographical axes.
An inertial platform bears various names: IMU, IRS, AHRS, INS (acronyms standing for the expressions: “Inertial Measurement Unit, Inertial Reference System, Attitude and Heading Reference System, Inertial Navigation System”) which are dependent on its sophistication and on the diversity of the information provided. Its cost, which depends on its performance, on the precision of its information and on the drifting of the inertial and gyroscopic sensors used, spans a wide range of prices, so that any even slightly advanced flying machine is equipped with one. It has the advantage of not calling upon any outside assistance, of being able to be very precise over the short term and of always being available. However these advantages are counterbalanced by measurement bias and noise due to its inertial sensors and by medium- and long-term drifting, inherent in the mode of obtaining the speed and attitude information, by integration of measurements of acceleration or of angular rates, and in the mode of obtaining the position information by double integration of acceleration measurements.
Doppler radar, which also does not call upon any outside assistance, delivers speed information free of medium- and long-term drifting since the Doppler effect is manifested at the speed level. It is on the other hand prone to disturbances induced by abnormal “lock-ons” which sometimes cause its information not to be available.
Various methods for readjustment or hybridization have been proposed. Some of them call upon a so-called “Kalman” filtering technique which consists in modelling the dynamic behavior of the various errors encountered and of their dependency relations with the signals through which they are perceived from outside. This leads to adaptive filters which are lengthy and expensive to fine-tune on account of the difficulties of the modelling and which demand not inconsiderable calculation power in order to operate.
It is an object of this invention to provide an automatic piloting device for rotary wing aircraft utilizing a measurement of ground speed deduced from the measurements of accelerations provided by an inertial platform, for example a so-called AHRS attitude and heading platform, which it readjusts by means of ground speed information provided by a readjustment device, satellite-based positioning receiver or Doppler radar, not prone to drifting, but possibly noisy.
means for changing reference frames calculating the true heading ψt and the horizontal components Vlrec(L) and Vlrec(T) along the longitudinal and transverse axes of the carrier craft, of the ground speed vector of the carrier craft delivered by the readjustment device in the geographical axes,
means for calculation of compensations to be made to the longitudinal and transverse components Vlrec(L) and Vlrec(T) of the ground speed vector of the carrier craft delivered by the means for changing reference frames, compensations made necessary by the different locations, aboard the craft, of the sensors of the inertial platform and of those of the readjustment device,
Advantageously, when the automatic piloting device is associated with an inertial platform, and with a readjustment device of Doppler radar type delivering measurements of the components Vld(L), Vld(T) and Vld(Z) of the ground speed of the craft according to a reference frame tied to the aircraft, its preprocessing part comprises, in addition to the estimator filter or filters:
To simplify the diagrams, only the signals useful for the hybridization of the measurements of ground speed components along the longitudinal and transverse axes of the carrier craft are mentioned in the figures.
The piloting system shown in FIG. 1 is intended for a rotary wing aircraft. It comprises an automatic piloting device termed the “automatic pilot” 1 receiving diverse information on the attitude and the motion of the aircraft, from an inertial platform 2 of AHRS attitude and heading platform type, from a readjustment device 3 and from an electronic bank 4 of magnetic declinations that arises for example from a flight management system (FMS).
accelerometers providing, to the preprocessing part 10 of the automatic pilot, the longitudinal Γ(L) and transverse Γ(T) accelerations in a horizontal plane tied to the carrier,
gyros providing, to the preprocessing part 10 of the automatic pilot, the rates of rotation p1, q1, r1 of the carrier in the roll, pitch and yaw axes,
integrator circuits extracting by integration of the measurements of the gyros, the angles of attitude of the carrier in the roll Φ and pitch Θ axes, and
a magnetic compass providing the preprocessing part 10 of the automatic pilot with the magnetic heading ψm.
The readjustment device 3 (satellite-based navigation receiver or Doppler radar) provides diverse information to the preprocessing part 10 of the automatic pilot of which FIG. 1 depicts only information regarding ground speed Vlrec(N/S) of the carrier in the North-South direction and information regarding ground speed Vlrec(E/W) of the carrier in the East-West direction.
a block 110 for changing reference frames calculating the true heading ψt and the components Vlrec(L) and Vlrec(T) along the longitudinal and transverse axes of the carrier craft, of the ground speed vector delivered by the readjustment device 3 in the geographical axes,
a block 111 for calculating compensations to be made to the longitudinal and transverse components Vlrec(L) and Vlrec(T) of the speed vector of the carrier craft delivered by the reference frame changing block 110, compensations made necessary by the different locations, on board the craft, of the sensors of the attitude platform and of those of the readjustment device 3,
a block 112 for calculating the rate of change of heading Ψdot resulting from the roll attitude angle Φ and pitch attitude angle Θ and from their rates of evolution q1 and r1,
a block 113 for calculating compensations of the acceleration measurements Γ(L), Γ(T) originating from the AHRS platform 2, taking account of the rate of change of heading Ψdot,
and two readjustment blocks 114 and 115 providing, to the law of control of the selected mode of flight, the estimates of the longitudinal and transverse components Vlest(L) and Vlest(T) of the horizontal projection of the speed vector of the carrier craft.
The block for changing reference frames 110 determines the true heading ψt on the basis of the measured heading ψm delivered by the magnetic compass of the AHRS platform 2 and of the magnetic declination Dm read from the electronic database 4 of magnetic declination on the basis of the geographical positioning of the carrier craft known elsewhere:
In possession of the true heading A, the reference frame changing block 110 determines the longitudinal and transverse components Vlrec(L) and Vlrec(T) of the speed vector measured by the readjustment device 3 by the relation:
[ V lrec ( L ) V lrec ( T ) ] = [ cos Ψ t sin Ψ t - sin Ψ t cos Ψ t ] × [ V lrec ( L ) V lrec ( T ) ]
The block 111 for calculating speed compensations operates in a reference frame tied to the craft and centered on the sensors of the AHRS platform 2. It regards the speed compensations to be made as the vector product of the distance vector GA with components (xa, ya, za) separating the sensors of the readjustment device 3 from those of the AHRS platform 2. Then projects this vector product into the horizontal plane through two successive rotations, one of the opposite −Φ of the angle of pitch and the other of the opposite of the angle of roll −Θ so as to determine its longitudinal and transverse components DVL, DVT. These operations are summarized by the matrix relation:
[ DV ] = [ Θ t ] × [ Φ t ] × ⌊ GA ⋀ Ω -> ⌋ with [ DV ] = [ DVL DVT DVz ] ; [ GA ] = [ xa ya za ] ; [ Ω -> ] = [ p 1 q 1 r 1 ] [ Θ ] = [ cos Θ 0 - sin Θ 0 1 0 sin Θ 0 cos Θ ] ; [ Φ ] = [ 1 0 0 0 cos Φ sin Φ 0 - sin Φ cos Φ ]
The components of the vector product are expressed by the relation:
[ GA ⋀ Ω -> ] = [ DVx 1 DVy 1 DVz 1 ] = [ - q 1 * za + r 1 * ya p 1 * za - r 1 * xa - p 1 * ya + q 1 * xa ]
and the compensations DVL, DVT of the longitudinal and transverse speeds by the relations:
DVL=DVx1*cos(Θ)+DVy1*sin(Θ)*sin(Φ)+DVz1*sin(Θ)*cos(Φ)
DVT=DVy1*cos(Φ)−DVz1*sin(Φ)
V lrec-comp(T) =V lrec(T) +DVT
The block 112 calculates from the rate of rotation of change of heading Ψdot on the basis of the horizontal components of the rates of the rotational motions of the roll axis caused by yawing and pitching, by applying the relation:
Ψ dot or Ψ . = r 1 * cos ( Φ ) + q 1 * sin ( Φ ) cos ( Θ )
The block 113 calculates longitudinal and transverse acceleration compensations Γcomp(L) and Γcomp(T) correcting the effects of the rate of rotation of heading Ψdot on the measurements of longitudinal and transverse acceleration Γ(L) and Γ(T) originating from the AHRS platform 2 by subtracting from the horizontal component of the measured acceleration vector (Γ(L), Γ(T)), the vector product of the rate of rotation of change of heading Ψdot times the estimate of the horizontal projection (Vlest(L), Vlest(T)) of the speed vector delivered by the readjustment blocks 114, 115, in accordance with the relation:
Γ comp = Γ - Ω -> H ⋀ V lest with : Γ comp = [ Γ comp ( L ) Γ comp ( T ) ] ; Γ = [ Γ ( L ) Γ ( T ) ] ; Ω -> H = [ 0 0 Ψ . ] or else , Γ comp ( L ) = Γ L + V lest ( T ) * Ψ . Γ comp ( T ) = Γ T - V lest ( L ) * Ψ .
In order for the longitudinal and transverse compensated accelerations Γcomp(L) and Γcomp(T) to survive the fleeting unavailabilities of the readjustment device 3, the longitudinal and transverse speeds taken into account are not the longitudinal and transverse compensated speeds VLrec-comp(L) and Vlrec-comp(T) derived from the measurements of the readjustment device 3 but the longitudinal and transverse speeds Vlest(L) and Vlest(T) available at the output of the readjustment blocks 114 and 115.
FIG. 3 details the processing performed, in the preprocessing part 10 of the automatic pilot 1 in the case where the readjustment device 3 is a Doppler radar providing directly the longitudinal, transverse and perpendicular components Vld(L), Vdl(T) and Vld(z) of the ground speed vector [Vd] in a reference frame tied to the craft. The block 110 for changing reference frames has disappeared since there is no longer any need for it. The other blocks are retained and assigned a “prime” index. These operate in the same way as in the previous case with the exception of the block 111′ for calculating speed compensation which operates in a slightly different manner. Specifically, though it still determines the compensations in the reference frame tied to the craft, it no longer projects into the horizontal plane the compensation components but the longitudinal and transverse components of the compensated speed vector itself. The fact that the rotations are effected on the components of the compensated speed vector and not on the compensations alone is summarized by the matrix relation:
As shown in FIG. 4, each of the readjustment blocks 114 and 115 consists of an estimator filter of second-order complementary type which delivers the estimate of speed intended for the control laws part 11 of the automatic pilot 1, this speed estimate being either the estimate of longitudinal speed Vlest(L), or the estimate of transverse speed Vlest(T), according to the readjustment block considered 114 or 115.
a first branch comprising an amplifier stage 23 of gain K1 followed by a single integrator stage 20, and
a second branch having in common with the first branch, the amplifier stage 23 of gain K1 and the integrator stage 20, with, additionally, a second amplifier stage 24 of gain K2 and a second integrator stage 25 slipped in between the output of the integrator stage 23 and an auxiliary input of the adder 22.
The first branch (23, 22, 20) of the estimator filter is of first-order proportional integral type. Its inherent gain is the gain K1 afforded by the amplifier stage 23. It estimates a contribution of the speed bias to the readjustment and eliminates the noise of the GPS or Doppler radar signals.
{ K 1 = 2 T K 2 = 1 2 T with : 5 ≤ T ≤ 10
T being a parameter whose value corresponds to the maximum tolerable duration of unavailability of the second device, expressed in seconds.
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U.S. Classification 701/11, 701/3
European Classification G05D1/08B4, G05D1/10B2
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:LEBRUN, JEAN-LOUIS;FOISNEAU, JEAN;REEL/FRAME:017919/0579