Method and system for determining a minimum-thrust synchronous descent and rejoining profile for an aircraft

• US 10,089,893 B2
• Filed: 10/06/2017
• Issued: 10/02/2018
• Est. Priority Date: 10/20/2016
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Dacre-Wright, Benoit, Sacle, Jerome, D'Silva, Cedric
• Primary Examiner(s): Nguyen, Tan Q
• Application Number:
  US15/727,468
• Publication Number:
  US 20180114452A1
• Time in Patent Office: 361 Days
• Field of Search: 701121
• CPC Class Codes: B64C 39/024 of the remote controlled vehicle type, i.e. RPV
• CPC Class Codes: B64U 10/13 Flying platforms
• CPC Class Codes: G05D 1/0005 with arrangements to save energy
• CPC Class Codes: G05D 1/0676 specially adapted for landing
• CPC Class Codes: G08G 5/0013 with a ground station
• CPC Class Codes: G08G 5/0021 located in the aircraft
• CPC Class Codes: G08G 5/0039 Modification of a flight plan
• CPC Class Codes: G08G 5/0052 for cruising combined instruments indicating more than one navigational value G01C23/00
• CPC Class Codes: G08G 5/0069 specially adapted for an unmanned aircraft
• CPC Class Codes: G08G 5/0091 for monitoring atmospheric conditions radar or analogous systems specially adapted for meteorological use G01S13/95; meteorology G01W
• CPC Class Codes: G08G 5/025 Navigation or guidance aids radar or analogous systems specially adapted for landing purposes G01S13/913

Abstract

A method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft comprises a first step of computing an energy differential of the aircraft in the air ΔE_a between a first initial state of the aircraft at an initial geodesic point Qi and a second final state of the aircraft at the final arrival target point Qf. The method comprises a second step of adjusting an adjustable modelled profile of altitude h_m(t) and of air speed Va_m(t) of the aircraft with the aid of parameters so the adjusted modelled profile of altitude h(t) and of air speed Va(t) of the aircraft ensures the consumption of the variation of energy of the aircraft in the air ΔE_a in a fixed required timespan Δt_required and a fixed required altitude variation t_f−t_i in the required time timespan, the aircraft operating permanently in an engine regime with constant and minimum thrust. The method comprises a third step of determining a lateral geodesic trajectory of the aircraft on the basis of the adjusted altitude profile h(t), of the adjusted air speed profile Va(t) and of the knowledge of the speeds of the winds in the aircraft'"'"'s scheduled geographical traversal zone.

Claims

1. A method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft,

the permanently minimum-thrust descent profile being defined from a first initial state of the initial aircraft up to a second final state of the aircraft temporally constrained,

the first initial state of the aircraft comprising a first geodesic position Qi of departure, an initial time ti, a first initial altitude hi, a first initial speed of the aircraft {right arrow over (Vι

)} relative to the ground and a first wind speed {right arrow over (Wι

)},

the second final state of the aircraft comprising a second geodesic position Qf of arrival at the target point, a final constraint time tf, a second final altitude hf, a second final speed of the aircraft {right arrow over (Vf)} relative to the ground and a second wind speed {right arrow over (Wf)}, the method comprising

a first step of computing an energy differential of the aircraft in the air Δ

E_a between the first initial state of the aircraft and the second final state of the aircraft; and

a second step, subsequent to the first step of

providing an adjustable modelled profile of altitude h_m(t) and of air speed Va_m(t) of the aircraft, corresponding to an air descent strategy which permanently ensures an engine regime at minimum thrust and using one or more adjustable parameters, and then

adjusting the adjustable parameter or parameters so that an adjusted profile of altitude h(t) and of air speed va(t) of the aircraft ensures the consumption of the variation of energy of the aircraft in the air Δ

E_a within the required timespan Δ

t_required, and the required altitude variation h_i−

h_f within the required timespan with permanently an engine regime with constant and minimum thrust; and

a third step, subsequent to the second step, of determining a lateral geodesic trajectory P(t) of the aircraft on the basis of the adjusted altitude profile h(t), of the adjusted air speed profile Va(t) and of the knowledge of the speeds of the winds in the aircraft'"'"'s scheduled geographical traversal zone.

2. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 1, wherein

the first step consists in determining the differential of the energy of the aircraft in the air Δ

E_a as the difference E_ai−

E_af between the energy of the aircraft in the air in the initial state E_ai and the energy of the aircraft in the air in the final state E_af,

the energy of the aircraft in the air E_ai in the initial state being equal to the sum E_Ti+E_Wi of the total energy E_Ti of the aircraft in the initial state and of a first corrective term E_Wi for the effect of the winds in the initial state on the air slope followed by the aircraft, and

the energy of the aircraft in the air E_af in the final state being equal to the sum E_Tf+E_Wf of the total energy E_Tf of the aircraft in the final state and of a second corrective term E_Wf for the effect of the winds in the final state on the air slope followed by the aircraft, with

3. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 1, wherein

the adjustable modelled profile of altitude h_m(t) and of air speed Va_m(t) of the aircraft is decomposed into a temporal succession of a number N, greater than or equal to 2, of adjustable elementary profiles of altitude h_m(k,t) and of air speed Va_m(k,t) of the aircraft, the index k being an identification index identifying the order of temporal succession of the adjustable elementary profiles h_m(k, t), Va_m(k,t) lying between 1 and N;

and

the elementary profile h_m(1, t) and Va_m(1, t) evolves over a first elementary time interval IT(1) lying between the initial time ti and a first intermediate time t(2) forming respectively the times associated with the first initial state and with a first intermediate state of the aircraft; and

for k varying between 2 and N−

1, the elementary profile h_m(k, t) and Va_m(k, t) evolves over a k-th elementary time interval IT(k) lying between a (k−

1)-th intermediate time t(k) and a k-th intermediate time t(k+1) forming respectively the times associated with the (k−

1)-th intermediate state and with the k-th intermediate state of the aircraft; and

the elementary profile h_m(N, t) and Va_m(N, t) evolve over an N-th elementary time interval IT(N) lying between the (N−

1)-th intermediate time t(N) and the final time tf forming respectively the times associated with the (N−

1)-th intermediate state and with the second final state of the aircraft; and

two consecutive intervals IT(k), IT(k+1) for k varying from 1 to N−

1 are contiguous,

the adjustable profiles h_m(k,t) and Va_m(k,t), for k varying from 1 to N correspond to phases Φ

(k) of descent under constant and minimum engine regime, the phases of descent under constant and minimum engine regime included in the set formed by the descent phases with constant speed CAS, the constant-acceleration phases and the deceleration phases with constant energy ratio ER.

4. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 3, wherein

for each descent phase Φ

(k) and the corresponding adjustable profile h_m(k, t) and Va_m(k,t), k varying from 1 to N, the start instant of the interval IT(k), t(k), the end instant of the interval IT(k), t(k+1), the altitudes h_m(t(k)), and h_m(t(k+1)), the air speeds of the aircraft Va_m(k, t(k)) and Va_m((k,t(k+1)), the excess powers SEP_m(k, t(k)), SEP_m(k, t(k+1)), corresponding respectively to the two instants t(k) and t(k+1) are linked by the relation;

5. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 3, wherein, for k varying from 1 to N,

when the adjustable profiles h_m(k, t) and Va_m(k,t) correspond to a phase ϕ

(k) of descent with bounded constant acceleration and under constant and minimum engine regime, the duration Δ

t_m(k) of the k-th elementary interval IT(t) and the altitude variation Δ

h_m(k) over the said interval IT(k) satisfy the equations;

6. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 3, wherein the parametric model of profile of altitude h(t) and of air speed va(t) of the aircraft to be adjusted comprises three successive phases:

a first phase of acceleration/deceleration to a desired speed CAS, and then

a second phase at the constant desired speed CAS, and then

a third phase of acceleration/deceleration to the final speed,

the desired speed CAS and the durations of the three phases being adjusted so as to satisfy the total duration constraint Δ

t_required as well as the duration of the altitude variation constraint h_i−

h_f.

7. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 3, wherein the modelled profile of altitude h(t) and of air speed Va(t) of the aircraft to be adjusted comprises three successive phases:

a first phase at the initial speed CAS on a first altitude slice Δ

h(1) with an adjustable duration making it possible to vary a deceleration start instant, and then

a second phase of deceleration from the initial speed CAS to the final speed CAS, and then

a third phase of descent at the final speed CAS until the final altitude,

the altitude variation Δ

h(1) before the deceleration is adjusted iteratively to obtain the duration of the first phase.

8. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 1, wherein the third step comprises

a first sub-step in the course of which, horizontal positions of departure and arrival, P_ai and P_af, within the air mass are determined on the basis of departure and arrival horizontal geodesic positions, Pi and Pf, and of the horizontal speed of the wind {right arrow over (W_hor(h))} by assuming that the speed and the direction of the wind depend only on the altitude h and by using the relation:

{right arrow over (P_aι

P_af)}={right arrow over (P_ι

P_f)}−

∫

_ti^tf{right arrow over (W_hor)}(h(t))dt

and

a second sub-step of determining a required lateral distance in the air to be travelled D_a on the basis of the air speed profile of the aircraft Va(t) and of the air slope γ

(t) by using the equation;

D_a=∫

_t1^t2V_a(t)·

cos(γ

(t))dt

a third sub-step of determining a lateral trajectory in the air Pa(t) joining the departure and arrival horizontal positions, Pai and Paf and taking into account the vectors of initial and final air speed, the length of the lateral trajectory in the air Pa(t) being constrained by being set equal to the required lateral distance in the air to be travelled D_a,

a fourth sub-step of computing a geodesic lateral trajectory Pa(t) deduced on the basis of lateral trajectory in the air Pa(t) and of the wind chart.

9. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 1, wherein the third step comprises

a first sub-step of providing a preliminary lateral trajectory of a predetermined type adjustable by modification of a parameter, and a wind model dependent on the altitude and optionally the horizontal position and optionally the time, and

a second sub-step of adjusting the at least one parameter of the preliminary lateral trajectory in the course of which the at least one adjustment parameter is modified so that the horizontal geodesic distance travelled along the preliminary lateral trajectory, adjusted by taking account of the winds, terminates precisely at the final geodesic position P_f, and

a third sub-step of determining a required horizontal geodesic distance on the basis of the profiles of altitude h(t) and of air speed of the aircraft Va(t), by evaluating at each instant t the modulus ∥

{right arrow over (V_g,hor)}∥

of the horizontal geodesic speed of the aircraft on the basis of the air speed Va(t) and of components of the speed of the wind (XW(t), TW(t)), and by integrating over time the modulus of the horizontal geodesic speed according to the equations;

D=∫

_t1^t2∥

{right arrow over (V_g,hor)}∥

dt=∫

_t1^t2(√

{square root over (V_a²−

XW²(t))}+TW(t))dt

XW(t) and TW(t) denoting respectively the transverse component and the longitudinal component of the wind at the instant T.

10. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 1, further comprising a fourth step, subsequent to the third step, of corrections of the profiles of altitude h(t) and of air speed of the aircraft Va(t), and of the lateral geodesic trajectory, determined respectively in the second and third steps, which take into account, a first effect ε

₁(t) of the wind gradients in the computation of the excess power in the air SEP and/or a second effect ε

₂(t) of the turning manoeuvres on the load factor which modifies the apparent mass in the computation of the variation of the excess power in the air SEP(t), the general expression for the excess power in the air SEP(t) being written in the form;

11. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 10, wherein

the fourth step is an iterative process, comprising first, second, third, fourth sub-steps executed in a loop;

and

the first sub-step, executed initially at the end of the third step and subsequent to the fourth sub-step when at least one iteration has been decided in the course of the third sub-step, wherein determining in a conventional manner a temporal evolution of a state vector of the aircraft including at least the altitude h(t), the air speed of the aircraft Va(t), the geodesic distance travelled D(t) along the current geodesic trajectory P(t), initially determined at the start of a first iteration in the third step or determined in the course of the fourth sub-step of the fourth step, by taking into account the wind gradients and the load factor of the turning manoeuvres in the computation of the excess power variation SEP(t) until either the final position, or the final altitude is reached at a stopping point of the current geodesic trajectory; and

the second sub-step, executed subsequent to the first sub-step, wherein the fact that raw disparities δ

D₁, δ

t₁, δ

h, δ

V_a, relating to the geodesic distance travelled, the time, the altitude, the air speed, are evaluated between the state of the aircraft, considered at the stopping point and computed by taking into account the correction effects, and the desired final state, and wherein the fact that refined disparities δ

D₂, δ

t₂, relating to geodesic distance travelled and time, are evaluated as a function of the raw disparities δ

D₁, δ

t₁, between the state of the aircraft, considered at the stopping point and computed by taking into account the correction effects, and the desired final state,

the third sub-step of test and decision of execution of an iteration of the loop, executed subsequent to the second sub-step, wherein the fact that the refined disparities δ

D₂, δ

t₂ of geodesic distance travelled and of time of arrival at the stopping point are compared with a loop exit stopping threshold ε

, a branching is carried out to the fourth sub-step when at least one of the refined disparities δ

D₂, δ

t₂ is greater than or equal to the stopping threshold, and a stopping of the fourth step is carried out when the two refined disparities δ

D₂, δ

t₂ are strictly less than the threshold, the fourth step is terminated; and

the fourth sub-step, executed when at least one of the refined disparities δ

D₂, δ

t₂ is greater than or equal to the stopping threshold, wherein the fact that the current profile of altitude h(t) and of air speed Va(t) is readjusted by taking into account the refined time disparity and by reusing the method for adjusting the profile of the second step, and then the lateral trajectory manoeuvre is readjusted by taking into account the refined distance disparity and by reusing the method for adjusting the lateral trajectory of the third step to obtain an updated current geodesic trajectory.

12. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 11, wherein the refined disparities δ

D₂, δ

t₂ of geodesic distance travelled and of time of arrival at the stopping point are functions of the raw disparities δ

D₁, δ

t₁, between the state of the aircraft, considered at the stopping point and computed by taking into account the correction effects, and the desired final state, according to the relations;

13. The method for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 1, wherein

the aircraft is included in the set of aeroplanes piloted on-board manually or in automatic mode and of drones piloted remotely manually or in automatic mode.

14. A system for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft, the permanently minimum-thrust descent profile being defined from a first initial state of the initial aircraft up to a second final state of the aircraft constrained temporally by a final arrival time tf or a required temporal timespan Δ

t_required,

the first initial state of the aircraft comprising a first geodesic position Qi of departure, an initial time ti, a first initial altitude hi, a first initial speed of the aircraft {right arrow over (Vι

)} relative to the ground and a first wind speed {right arrow over (Wι

)},

the second final state of the aircraft comprising a second geodesic position Qf of arrival at the target point, a final constraint time tf, a second final altitude hf, a second final speed of the aircraft {right arrow over (Vf)} relative to the ground and a second wind speed {right arrow over (Wf)},

the said determining system comprising a database of the performance of the aircraft, a means for providing meteorological data of the environment wherein the aircraft is deploying, a ground station for providing the required final time or a required temporal timespan to the aircraft, and one or more electronic computers for computing the minimum-thrust descent and rejoining profile in respect of a target point,

the said determining system being configured to

in a first step, compute an energy differential of the aircraft in the air Δ

E_a between the first initial state of the aircraft and the second final state of the aircraft, and then

in a second step, provide an adjustable modelled profile of altitude h_m(t) and of air speed V_am(t) of the aircraft corresponding to an air speed strategy with permanently a minimum engine thrust, and then adjust parameters of the said adjustable modelled profile so that the adjusted modelled profile obtained of altitude h(t) and of air speed Va(t) of the aircraft ensures the consumption of the variation of energy of the aircraft in the air Δ

E_a within the required timespan Δ

t_required, and the required altitude variation h_i−

h_f in the required time with permanently a minimum engine thrust; and

then

in a third step, determine a geodesic trajectory of the aircraft and a lateral geodesic trajectory on the basis of a type of lateral manoeuvre, of the adjusted altitude profile h(t), of the adjusted air speed profile va(t) and of the knowledge of the speeds of the winds in the aircraft'"'"'s scheduled geographical traversal zone.

15. The system for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 14, wherein

the at least one electronic computer for determining a computation of a minimum-thrust descent and rejoining profile is

an electronic computer integrated into a flight management system FMS,

an EFB or any embedded computer for aiding navigation but not integrated into the avionics of the aircraft,

a computer integrated into an air traffic control ground station, as decision aid for a controller,

a computer integrated into a drone'"'"'s mission management ground station.

16. The system for determining a minimum-thrust descent and rejoining profile in respect of a target point by an aircraft according to claim 14, wherein

according to a first configuration, the aircraft comprises a first computer, configured to compute on-board a required intermediate descent speed CAS and a required flight distance, and first transmission means for dispatching these two prerequisite parameters, and the air traffic control station comprises second transmission means for receiving the required intermediate descent speed CAS and the required flight distance and dispatching to the aircraft setpoints for defining a lateral trajectory and a speed, the said setpoints being determined by a second computer of the ground station so as to ensure the flight distance and the intermediate speed required, or

according to a second configuration, the ground station is configured to dispatch to the aircraft as a supplement to the required timespan, a point of convergence along the flight plan, and the first computer of the aircraft is configured to determine the required intermediate speed CAS and the required geodesic distance, and to identify a turning point, either along a holding of current heading by a trajectory alignment, or along the current flight plan, by trajectory shortening, followed by direct flight towards the convergence point.