METHOD AND DEVICE FOR PRODUCEING PATHS FOR A MOBILE DEVICE

Abstract

The invention relates to a method and device for generating, for a mobile apparatus, one or more paths, meeting a predetermined time constraint, between a start point and an end point, in a given spatial perimeter, the path being generated using a chosen method for computing a diverted path, on the basis of a selected diversion point. This method comprises determining (42) a first set of first diversion points in said given spatial perimeter, and for each of the first diversion points, computing (44) a computed diverted-path time obtained using said chosen method for computing a diverted path passing through the first diversion point, and determining (46) a second set of second diversion points, each having an associated estimated diverted-path time, said estimated time being computed (50) based on times associated with first diversion points neighbouring said second diversion point.

Description

[0001] TITLE: Method and device for generating trajectories of a mobile device

[0002] The present invention relates to a method for generating trajectory(ies) of a mobile device, respecting a predetermined time constraint, between a starting point and an arrival point, said mobile device having predetermined movement constraints. The invention also relates to an associated device, and an associated computer program product.

[0003] The invention lies in the field of controlling the movement of mobile devices, for example aerial, marine or underwater, and in particular of generating movement trajectories for mobile devices which comply with time constraints, also called synchronized trajectories.

[0004] For two distinct mobile devices, two trajectories are said to be synchronized if they respect a temporal constraint, for example arrival at the same point, called the arrival point, within a predetermined time range, or within successive predetermined ranges. Of course, this can be generalized to any number of mobile devices greater than two.

[0005] Subsequently, a duration of travel of a trajectory by a mobile device will be called trajectory duration.

[0006] For a single mobile device, synchronization consists of setting an arrival time range, for example relative to a target to be reached, or, equivalently, a given trajectory duration range. Thus, for each mobile device having movement constraints, for example a minimum movement speed and a maximum movement speed, or, in certain applications, a constant movement speed, it is appropriate to generate a trajectory of duration included in a trajectory duration range, to ensure an arrival in accordance with a time constraint.

[0007] The invention finds a particular application in particular in the field of cooperative trajectory planning for mobile devices, for example aircraft, with or without a pilot on board, for given missions. For example, for a given mission, civil or military, the aircraft without a pilot on board must travel to an arrival point in a temporally coordinated manner, starting from distinct starting points. Alternatively, several mobile devices of different types are to be coordinated, for example mobile devices having different movement constraints (e.g. minimum speed, maximum speed). In addition to the movement constraints, constraints relating to the possible routes are imposed, these constraints being able to be due to natural conditions (relief, currents, weather) or to imposed external conditions (e.g. passage zones, zones to be avoided, zones to be overflown).

[0008] A problem then consists of generating synchronized trajectories for one or more mobile devices considered. In the particular case of a coordinated arrival at an arrival point, the synchronization takes into account the slowest mobile device. For the other devices, a detour trajectory, of increased duration, is calculated.

[0009] Various methods are known for calculating a diverted trajectory based on a chosen detour point, between a starting point and an arrival point, the diverted trajectory being a trajectory of longer duration (i.e. slowed down). For example, a trajectory between a starting point A and an arrival point B, diverted based on a detour point C, can be constructed by concatenating two half-trajectories formed between the starting point A and the detour point C on the one hand, and from the detour point C to the arrival point B on the other hand.

[0010] In addition to the method chosen for calculating trajectories, for example using mathematical models, one of the problems that arises is the judicious choice of one or more detour point(s) C to respect the imposed time constraint.

[0011] It is understood that in a given spatial perimeter, in particular for an air or maritime mobile device, a large number of candidate detour points are available, and the selection of one or more detour points respecting the time constraint has a high computational cost.

[0012] The object of the invention is to propose a method for finding one or more detour points making it possible to respect the imposed time constraint more efficiently.

[0013] To this end, the invention proposes, according to one aspect, a method for generating trajectory(ies) of a mobile device, respecting a predetermined time constraint, between a starting point and an arrival point, in a given spatial perimeter, the trajectory generation implementing a chosen method for calculating a detour trajectory, on the basis of a selected detour point, connecting the starting point and the arrival point.This method being implemented by a processor of a programmable computing device and comprises steps of: determining a first set of first detour points in said given spatial perimeter, and for each of the first detour points, calculating a calculated duration of detour trajectory obtained by said chosen method of calculating detour trajectory on the basis of said first detour point, determining a second set of second detour points, each second detour point having an associated estimated duration of detour trajectory, respecting said time constraint, said estimated duration being calculated from durations associated with first detour points neighboring said second detour point.

[0014] Advantageously, the method of the invention, thanks to the determination of second detour points, obtained using an estimate of the duration of the associated detour trajectory, calculated from the calculated durations associated with first detour points neighboring said second detour point, makes it possible to reduce the computational load for obtaining candidate detour points, respecting the time constraint.

[0015] The method for generating trajectory(ies) according to the invention may also have one or more of the characteristics below, taken independently or in all technically conceivable combinations.

[0016] The method further comprises determining a third set of third detour points, comprising at least one third detour point, each third detour point being selected from said second detour points and being such that the calculated duration of the detoured trajectory obtained by said chosen method of calculating the detoured trajectory on the basis of said third detour point respects the time constraint.

[0017] The calculation of the estimated duration of the detour trajectory associated with a second candidate detour point implements an interpolation of calculated durations associated with first neighboring detour points, taking into account a distance between said second candidate detour point and each of the first neighboring detour points.

[0018] Determining a second set of second detour points includes selecting candidate second detour points and, for each candidate second detour point, determining neighboring first detour points.

[0019] The first set comprises first detour points distributed on a first regular grid of predetermined first grid spacing, and the second set of second detour points is obtained from second candidate detour points, distributed on a second regular grid of second grid spacing, the second grid spacing being less than the first grid spacing.

[0020] The first detour points and the second detour points are distributed randomly or pseudo-randomly in at least part of said spatial perimeter.

[0021] The method further comprises, for each first detour point, a calculation and storage of at least one associated figure of merit, and, for each second detour point, a calculation of at least one associated estimated figure of merit, the determination of a third set of third detour points being furthermore a function of said estimated figures of merit.

[0022] The method comprises ordering the second detour points according to an associated figure of merit and the selection of a third detour point being carried out in descending order of the figure of merit values.

[0023] According to another aspect, the invention relates to a device for generating trajectory(ies) of a mobile device, respecting a predetermined time constraint, between a starting point and an arrival point, in a given spatial perimeter, comprising a module configured for trajectory generation implementing a chosen method of calculating a detour trajectory, on the basis of a selected detour point, connecting the starting point and the arrival point.This device comprises at least one processor configured to implement: a module configured to determine a first set of first detour points in said given spatial perimeter, and for each of the first detour points, calculate a calculated duration of detour trajectory obtained by said chosen method of calculating detour trajectory on the basis of said first detour point, a module configured to determine a second set of second detour points, each second detour point having an associated estimated duration of detour trajectory, respecting said time constraint, said estimated duration being calculated from calculated durations associated with first detour points neighboring said second detour point.

[0024] According to one embodiment, the device further comprises a module for determining a third set of third detour points, comprising at least one third detour point, each third detour point being selected from said second detour points and being such that the calculated duration of the detoured trajectory obtained by said chosen method of calculating the detoured trajectory on the basis of said third detour point respects the time constraint.

[0025] Advantageously, the trajectory generation device is configured to implement the trajectory generation method, according to all its envisaged variants.

[0026] According to another aspect, the invention relates to a computer program comprising software instructions which, when executed by a programmable electronic device, implement a method for generating trajectory(ies) as briefly described above. Other characteristics and advantages of the invention will emerge from the description given below, for information purposes and in no way limiting, with reference to the appended figures, among which:

[0027] [Fig 1] Figure 1 is a schematic example of synchronized trajectories of mobile devices;

[0028] [Fig 2] Figure 2 is a mobile device guidance system comprising a device for generating trajectory(ies) respecting a time constraint;

[0029] [Fig 3] Figure 3 is a flowchart of the main steps of a trajectory generation method according to a first embodiment;

[0030] [Fig 4] Figure 4 is a first schematic example of a detoured trajectory obtained by a first trajectory calculation method;

[0031] [Fig 5] Figure 5 is a second schematic example of a detoured trajectory obtained by a second trajectory calculation method;

[0032] [Fig 6] Figure 6 schematically illustrates a first set of first detour points and a second set of second candidate detour points according to a variant;

[0033] [Fig 7] Figure 7 schematically illustrates a neighborhood of a second candidate detour point according to one embodiment;

[0034] [Fig 8] Figure 8 is a flowchart of the main steps of a trajectory generation method according to a second embodiment.

[0035] Figure 1 schematically illustrates an application scenario of the invention. Two mobile devices 2, 4, for example aircraft, with or without a pilot on board, move from a starting point A to an arrival point B, with time constraints to achieve synchronization.

[0036] It is understood that the invention is not limited to a particular type of mobile device, and finds applications for aerial, marine, underwater and terrestrial mobile devices.

[0037] The trajectory generation process applies to each mobile device, with time constraints, including a trajectory duration constraint, being applied to each mobile device, depending on a mission to be carried out.

[0038] Each device 2, 4 of the example of figure 1 moves according to a calculated trajectory Traji, Trajs, passing through a detour point Ci, C2 introduced to respect a given time constraint. The trajectories Traji, Trajs, and the detour points C1, C2 are obtained according to a method described in more detail below. Figure 2 schematically illustrates an example of a guidance system 10 for a mobile device 2 in which the invention is applied.

[0039] The mobile device 2 is, for example, an aircraft, of the type with or without a pilot on board.

[0040] The mobile device has movement constraints, which are either due to mechanical or aerodynamic limitations, or due to limitations of acceptability for the pilot or for the mission being performed. Movement constraints include, in particular, a minimum speed and a maximum speed.

[0041] In the guidance system 10, the mobile device 2 receives guidance commands from a computing device 12. For example, the computing device 12 is located in a ground computing center, and the guidance commands are communicated to the mobile device 2 via a wireless communication link. Alternatively, the computing device 12 is carried by the mobile device 2.

[0042] The calculation device 12 is configured to calculate one or more trajectories according to the method for generating trajectory(ies) described in more detail below.

[0043] For example, trajectory generation is performed as part of mission planning of the mobile device 2, for example for collaborative planning with other mobile devices not shown.

[0044] Mission planning involves consideration of many operating and environmental conditions.

[0045] The time constraint is satisfied if for a mobile device, the movement trajectory between a starting point A and an arrival point B has a duration T included in a given time range, for example between T min and T ma x, the mobile device having a speed between V min and V max . The length of the corresponding trajectory is included in the range of lengths:

[0046] [MATH1]

[0047] [^min min> ^max * ^maxl ■

[0048] To satisfy a time constraint, at constant travel speed or within a speed interval, a trajectory diverted by a detour point is calculated.

[0049] The computing device 12 is configured to generate one or more trajectories respecting the time constraint, each generated trajectory being a detour trajectory, calculated on the basis of a selected detour point. The detour point is selected within a given spatial perimeter.

[0050] A trajectory is defined by a list of points to be traveled, the points being defined by spatial coordinates in a given spatial reference frame, and by a path, for example modelable by straight lines / curves, between the successive points. The mobile device 2 comprises in particular an on-board computer 14 and a movement control system 16. For example, the on-board computer 14 transforms the diverted trajectory into guidance commands, for example longitudinal acceleration commands, steering movements, etc., which are transmitted to the movement control system 16.

[0051] The computing device 12 is for example a computer system composed of one or more programmable electronic devices, i.e. computers.

[0052] To simplify the explanation, it is considered that the calculation device 12 is a computer comprising a processor 18 and an electronic memory unit 20, adapted to communicate via a communication bus 22. This calculation device 12 is configured to implement the invention.

[0053] The processor 18 of the computing device 12 is configured to implement:

[0054] - a module 24 for calculating the duration of the detour trajectory obtained by a chosen method of calculating the detour trajectory on the basis of a detour point;

[0055] - a module 26 for determining a first set 25 of first detour points in the given spatial perimeter;

[0056] - a module 28 for determining a second set 27 of second detour points, each second detour point having an associated estimated duration of detoured trajectory, respecting said time constraint, the duration estimate being calculated from the calculated durations of detoured trajectory, associated with first detour points neighboring said second detour point,

[0057] - a module 30 for determining a third set 29 of third detour points, comprising at least one third detour point, each third detour point being selected from among said second detour points and being such that the calculated duration of the detoured trajectory obtained by the chosen method of calculating the detoured trajectory on the basis of the third detour point respects the time constraint,

[0058] - a module 32 for calculating a trajectory based on a third selected detour point.

[0059] The first, second and third sets of detour points are stored in the electronic memory unit 20.

[0060] The modules 24, 26, 28, 30 and 32 are adapted to cooperate, as described in more detail below, to implement a method for generating trajectory(ies) respecting a predetermined time constraint.

[0061] In one embodiment, the modules 24, 26, 28, 30 and 32 are implemented in the form of software instructions forming a computer program, which, when executed by a computer, implements a trajectory generation method according to the invention. In a variant not shown, the modules 24, 26, 28, 30 and 32 are each implemented in the form of programmable logic components, such as FPGAs (Field Programmable Gate Array), microprocessors, GPGPII components (General-purpose processing on graphics processing), or dedicated integrated circuits, such as ASICs (Application Specific Integrated Circuit).

[0062] The computer program comprising software instructions is further capable of being recorded on a computer-readable medium, not shown. The computer-readable medium is, for example, a medium capable of storing electronic instructions and of being coupled to a bus of a computer system. For example, the readable medium is an optical disk, a magneto-optical disk, a ROM memory, a RAM memory, any type of non-volatile memory (for example EPROM, EEPROM, FLASH, NVRAM), a magnetic card or an optical card.

[0063] Figure 3 is a flowchart of the main steps of a first embodiment of a method for generating trajectory(ies) respecting a time constraint, implemented by a processor of a programmable computing device.

[0064] The input to the process is provided: the spatial perimeter considered, which is a 2D or 3D perimeter depending on the application case, a starting point A, defined by its coordinates in a chosen 2D or 3D reference frame, and an arrival point B, also defined by its coordinates in the chosen reference frame.

[0065] Each mobile device trajectory, starting from the starting point (point A) to the ending point (point B), and diverted based on a detour point C, is generated by implementing a chosen method of detour trajectory calculation.

[0066] In one embodiment, the chosen method is a method using a mesh of the chosen spatial perimeter and calculated cost maps, associated respectively with the starting point A and the arrival point B, and a wavefront propagation method, described in patent application FR 20 12674. This method makes it possible to generate a detour trajectory passing through a selected detour point C, from a half-trajectory connecting the starting point A to the detour point C, and a second half-trajectory connecting the detour point C to the arrival point B.

[0067] Figure 4 schematically illustrates a detour trajectory Traj obtained by such a method.

[0068] Alternatively, any other method of calculating a trajectory between the starting point A and the arrival point B via a selected detour point C can be used.

[0069] In one embodiment, the trajectory is generated using the selected detour point C, without actually passing through the detour point C. For example, as schematically illustrated in Figure 5, a detour trajectory Traj is obtained by an asymptotic construction or a parametric curve, for example, of the Bézier (or B-spline) type, one control point of which is the detour point C.

[0070] The method for generating trajectory(ies) comprises a step 40 of acquiring input data comprising the coordinates of the starting and arrival points, the spatial perimeter and the time range [T min , T ma x] representative of the time constraint. Alternatively, a corresponding range of lengths (see equation [MATH 1]) is obtained.

[0071] Then, the method comprises a step 42 of determining a first set E1 of first detour points, and a step 44 of calculating and storing a calculated trajectory duration (or, equivalently, trajectory length) associated with each first detour point.

[0072] Several embodiments of step 42 of determining a first set E1 of first detour points are envisaged.

[0073] According to one embodiment, the first set E1 is defined by a regular grid, with a given first step.

[0074] According to a variant, the first set E1 is made up of a number N1 of points distributed randomly or pseudo-randomly in the spatial perimeter or in a part of the spatial perimeter, such a part being for example selected on a contextual criterion, for example according to meteorological or geographical information. This deepens the search for detours in an a priori preferred area.

[0075] Step 44 of calculating the duration associated with the first detour points implements the chosen method of calculating the detour trajectory, for each of the first detour points of the first set E1. Indeed, at this step, the actual trajectory duration is calculated and stored. In one embodiment, the method of generating the detour trajectory described in patent application FR 20 12674 is used.

[0076] Alternatively, any method of calculating a path from A to B diverted based on a detour point is applicable, for example, a mathematical modeling method using Bézier curves. The effective travel time of such a trajectory is calculated, knowing the speed of the mobile device.

[0077] At the end of step 44, the first detour points are defined by their coordinates, and information on the calculated trajectory duration (e.g. trajectory duration or length), called calculated duration in the following, associated with each first detour point. This information is stored in association with each first detour point.

[0078] Then, the method comprises a step 46 of determining a second set E2 of second detour points noted Q 2This determination step 46 comprises a selection 48 of second candidate detour points, and for each of these second candidate detour points, an estimate 50 of the associated trajectory duration, called the estimated duration, the estimate being carried out by a calculation based on the durations associated with neighboring first detour points.

[0079] In addition, it is checked at a verification step 52 whether the estimated duration is compatible with the time constraint, and the second candidate detour point is maintained in the second set E2 of detour points only if the duration estimated by calculation is compatible with the time constraint. For example, it is checked whether the estimated duration is included in the time range representative of the time constraint.

[0080] In one embodiment, the second candidate detour points are distinct from the first detour points.

[0081] Alternatively, at least some of the first detour points are considered among the candidate second detour points.

[0082] In one embodiment, the first detour points are points in a first regular grid defined by a first grid spacing, and the second candidate detour points are selected from a second regular grid, of second grid spacing, smaller than the first grid spacing.

[0083] For example, the second grid step is chosen based on a number N2 of second candidate detour points to be tested. This can for example be done by successive iterations on the second grid step, which is reduced until the resulting number of points E2 is deemed sufficient.

[0084] According to a variant, a number N2 of second candidate detour points is distributed randomly or pseudo-randomly in the spatial perimeter or in a part of the spatial perimeter, such a part being for example selected on a contextual criterion, for example based on meteorological or geographical information.

[0085] In another variant, the second candidate detour points are positioned on sub-grids of third grid spacing, around first detour points chosen using a multi-resolved grid generation algorithm, such as the Maubach algorithm, described in the article "Local bisection refinement for n-simplicial grids generated by reflection", JM Maubach, SIAM Journal on Scientific Computing, 1995.

[0086] For example, Figure 6 illustrates a first set E1 of randomly positioned first detour points, represented by circles, and having a calculated duration of associated detour trajectory, and a set E'2 of second candidate detour points represented by squares, positioned pseudo-randomly, in a part of the spatial perimeter. The duration estimation carried out in step 50 is for example carried out, for a second candidate detour point q 2 , by interpolation of the calculated duration values ​​associated with a number K of first detour points q 1 neighbors of the second candidate detour point q 2 .

[0087] According to a first embodiment, for a second candidate detour point q 2 , the first K detour points q 1 , nearest neighbors of q 2, are selected, and the respective distances between the second candidate detour point and each of the first neighboring detour points are taken into account in the calculation formula. The distances are preferably Euclidean distances.

[0088] For example, the estimated duration is calculated by the following interpolation formula: is the estimated detour trajectory duration associated with the second candidate detour point q 2 , Tt is the calculated trajectory duration associated with the first detour point q 1 and V denotes the set, of cardinal K, of indices of the first detour points forming the neighborhood of the second candidate detour point.

[0089] According to a second embodiment, the estimated duration is calculated by the following interpolation formula:

[0090] Where d 2 ( is the square of the Euclidean distance d id .

[0091] Advantageously, the calculation of estimated duration by an interpolation formula is fast and requires few computing resources.

[0092] The number K of neighbors is any number, for example determined according to the available computing power. For example, K=5. We will then take, for example, the 5 points of E1 closest to each point of E'2.

[0093] According to one variant, the number K of neighbors is not fixed, but all the first detour points located inside a circle of given radius R are considered to be points of the neighborhood. In other words, in this variant, the neighborhood is defined by a circle of given radius around the second candidate detour point. When the second candidate detour points are located on a second regular grid of given second pitch P2, the radius is for example chosen according to the second pitch P2, for example R=2P2. According to another variant, more particularly adapted to the case where the distribution of the first detour points and the second detour points is random or pseudorandom, the radius of the circle defining the neighborhood is not fixed, but variable, so that the neighborhood includes a given number of first detour points, or respects a distribution of the first detour points.For example, the distribution consists of ensuring that the circle includes at least one first detour point in each quadrant Q1, Q2, Q3, Q4 around the second candidate detour point. 2 , as schematically illustrated in Figure 7.

[0094] Returning to Figure 3, step 46 of determining a second set E2 of second detour points is followed by a step 54 of determining a third set E3 of third detour points, comprising a selection 56 of third candidate detour points from among the second detour points of the second set E2, and a calculation 58, for each third candidate detour point, of the trajectory duration generated by the chosen method of calculating the diverted trajectory on the basis of this third detour point. Finally, a verification 60 of compliance with the time constraint is applied, in order to retain, in the third set E3, only the third detour points whose calculated duration, and no longer only estimated, complies with the time constraint.

[0095] Thus, the third set E3 of third detour points is a subset of the second set of detour points, and this third set can be reduced to a single element.

[0096] The third set E3 comprises only third detour points for which the associated trajectory duration calculated, i.e. diverted on the basis of this third detour point, actually respects the time constraint. Indeed, there may be a difference between the duration estimated in the duration estimation step 50 and the duration calculated in step 58 for a trajectory generated on the basis of the detour point considered by the chosen method of calculating the diverted trajectory.

[0097] Finally, the method comprises obtaining 62 a diverted trajectory based on a third selected detour point or several diverted trajectories based on several third selected detour points, depending on the application.

[0098] For example, in a complex mission advance planning scenario, multiple third detour points are selected and multiple detour trajectories are generated. In one embodiment, the plurality of detour trajectories are then presented to an operator to select the detour solution that they deem best suited to their intent. For example, in an operational context, a trajectory is generated based on a selected third detour point, and this trajectory is transmitted to control the movement of a mobile platform.

[0099] Figure 8 is a flowchart of the main steps of a second embodiment of a method for generating trajectory(ies) respecting a time constraint, implemented by a processor of a programmable computing device.

[0100] This second embodiment comprises steps similar to the steps of the first embodiment described with reference to FIG. 3, and specific steps.

[0101] In this second embodiment, the method comprises a step 70 of acquiring input data similar to step 40, and a step 72 of determining a first set E1 of first detour points similar to step 42.

[0102] It further comprises a step 74 of calculating and storing a calculated trajectory duration (or, equivalently, trajectory length) associated with each first detour point, as well as an associated figure of merit. The calculation of the trajectory duration is carried out according to the chosen method of calculating the detoured trajectory, as explained above with reference to step 44 of FIG. 3.

[0103] The figure of merit is calculated based on application context or functional context considerations, for example based on geographical data (relief, currents), weather forecasts, safety conditions, and any restrictions imposed. The figure of merit calculated for each first detour point is stored in association with the first detour point and the associated calculated detour trajectory duration.

[0104] For example, the figure of merit could be defined as where dT is the time spent navigating in clouds. This time dT would be limited between 1 s and 1000s (considering that there is no more merit in navigating 1100s than 1300s in a cloudy area). The merit factor here is a numerical value between 0.001 and 1, the higher the merit factor, the more the corresponding detour point is considered satisfactory according to the context values ​​used for the calculation.

[0105] The method comprises a step 76 of determining a second set of second detour points, analogous to step 46 described above, comprising steps 78, 80, 82 analogous to steps 48, 50 and 52 described above, as well as a step 84 of calculating an estimated figure of merit, associated with each second detour point of the second set E2 of detour points.

[0106] For example, an interpolation calculation method similar to that used in step 80 is applied to the merit factor values ​​of the first detour points of the chosen neighborhood, to obtain, for each second detour point, an associated estimated merit factor.

[0107] The mathematical formulas [MATH 2] and [MATH 3] are easily transposable, by replacing the calculated duration by the figure of merit calculated for each first detour point in the neighborhood.

[0108] Thus, an estimated figure of merit is obtained and stored for each second detour point retained.

[0109] In a variant, the figure of merit used is a composite value of an initial set of figures of merit. For example, using the example mentioned above, the composite figure of merit combines a figure of merit penalizing the time spent in clouds, and a figure of merit penalizing the time spent above habitable zones, the composite figure of merit being calculated by a combination of these two figures of merit: - F- — . Of course, other formulas for combining or aggregating figures of merit to calculate a composite figure of merit are possible.

[0110] Then, the method comprises a step 85 of determining a third set of third detour points, comprising a step 86 of ordering the second detour points of the second set E2 in an order dependent on the merit factors, by the decreasing order of the merit factors, a step 88 of calculating the trajectory duration generated by the chosen method of calculating the diverted trajectory, in this decreasing order of merit factor, and a step 90 of verifying compliance with the time constraint, similar to step 60.

[0111] In one embodiment, as soon as a number L of third detour points is obtained, for example L between 3 and 6, step 85 is stopped and followed by step 92 similar to step 62 previously described. In this example, the system would return to the operator 3 to 6 possible detour solutions, and it is the operator who would select the one closest to his intention.

[0112] In one embodiment, L=1 and thus, the third detour point which has the highest figure of merit while being associated with a calculated duration of detoured trajectory respecting the time constraint is chosen for trajectory generation.

[0113] Advantageously, in addition to respecting the time constraint, at least one other criterion is satisfied for this third selected detour point, which ensures obtaining an optimized detour trajectory.

[0114] Advantageously, the method of the invention makes it possible to quickly obtain, at low computational cost, a second set of second detour points, for which the estimated duration of the diverted trajectory respects the time constraint. Advantageously, the calculation of an estimated duration of the diverted trajectory is rapid and of low complexity, because it does not require the actual generation of this diverted trajectory.

Claims

DEMANDS 1. A method for generating trajectory(ies) of a mobile device, respecting a predetermined time constraint, between a starting point and an arrival point, within a given spatial perimeter, the trajectory generation implementing a chosen method for calculating a detoured trajectory, based on a selected detour point, connecting the starting point and the arrival point, the method being implemented by a processor of a programmable computing device and being characterized in that it comprises the steps of: determining (42, 72) a first set of first detour points within said given spatial perimeter, and for each of the first detour points, calculating (44, 74) a calculated duration of the detoured trajectory obtained by said chosen method for calculating a detoured trajectory based on said first detour point, determining (46, 76) a second set of second detour points,each second detour point having an associated estimated detour trajectory time, respecting said time constraint, said estimated time being calculated (50, 80) from times associated with first detour points neighboring said second detour point.

2. A method according to claim 1, further comprising a determination (54, 85) of a third set of third detour points, comprising at least one third detour point, each third detour point being selected from said second detour points and being such that the calculated duration of detoured trajectory obtained by said chosen method of calculating detoured trajectory on the basis of said third detour point complies with the time constraint.

3. Method according to claim 1 or 2, wherein the calculation (50, 80) of estimated diverted trajectory time associated with a second candidate divert point implements an interpolation of calculated times associated with first neighboring divert points, taking into account a distance between said second candidate divert point and each of the first neighboring divert points.

4. A method according to any one of claims 1 to 3, wherein the determination (46, 76) of a second set of second detour points comprises a selection (48, 78) of candidate second detour points and, for each candidate second detour point, a determination of neighboring first detour points.

5. A method according to any one of claims 1 to 4, wherein said first set comprises first detour points distributed on a first regular grid of predetermined first grid spacing, and said second set of second detour points is obtained from candidate second detour points, distributed over a second regular grid of second grid step, the second grid step being smaller than the first grid step.

6. A method according to any one of claims 1 to 5, wherein said first detour points and said second detour points are distributed randomly or pseudo-randomly in at least a part of said spatial perimeter.

7. A method according to any one of claims 1 to 6, further comprising, for each first detour point, a calculation and storage (74) of at least one associated merit factor, and, for each second detour point, a calculation (84) of at least one associated estimated merit factor, the determination (85) of a third set of third detour points being further a function of said estimated merit factors.

8. Method according to claim 7, comprising a scheduling (86) of the second detour points according to an associated merit factor and the selection of a third detour point being carried out in descending order of merit factor values.

9. Computer program comprising software instructions which, when executed by a programmable electronic device, implement a trajectory generation method in accordance with claims 1 to 8.

10. A device for generating trajectory(ies) of a mobile device, respecting a predetermined time constraint, between a starting point and an arrival point, within a given spatial perimeter, comprising a module configured for trajectory generation implementing a chosen method for calculating a detoured trajectory, based on a selected detour point, connecting the starting point and the arrival point, the device being characterized in that it comprises at least one processor configured to implement: a module (26) configured to determine a first set of first detour points within said given spatial perimeter, and for each of the first detour points, to calculate a calculated duration of the detoured trajectory obtained by said chosen method for calculating a detoured trajectory based on said first detour point, a module (28) configured to determine a second set of second detour points,each second detour point having an associated estimated detour trajectory time, respecting said time constraint, said estimated time being calculated from calculated times associated with first detour points neighboring said second detour point.

11. Device according to claim 10, further comprising a module (30) for determining a third set of third detour points, comprising at 18 less a third detour point, each third detour point being selected from said second detour points and being such that the calculated duration of the detoured trajectory obtained by said chosen method of calculating the detoured trajectory on the basis of said third detour point respects the time constraint.