Patent Description:
Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

Unmanned Aerial Vehicles (UAV) are being increasingly employed for situations where direct human contact could be dangerous, difficult or economically and technically unfeasible to say the least. In such situations, an UAV could technically provide more than an "eye" to operator(s) among other associated individuals relying thereon. While promising far reaching coverage and communication of target areas/locations to base station, on account of different sensor(s) and payload(s), UAVs, at times, could prove to be dangerous for life and property on loss or complete failure of communication.

In particular, smaller UAVs must have access to communications and navigation signals for some parts of their missions, including (safe) landing. In general, planning for a nominal mission typically makes use of a pre-programmed flight path that includes consideration of where and when these signals can be available and where and when they are expected to be blocked. This finds significance since flight, in-absence of regular human feedback, may lead to increased changes of an avertable incident.

However, sometimes communication or navigation signals can be unexpectedly blocked for one or more reasons such as, for example but need not necessarily, by jamming or by landform factors (i.e. terrain) or due to some other contingency forces like flying an improvised route to pursue a suspect that may force departure from nominal mission path andthereby increase possibility of unforeseen collision and like incidents.

<CIT> discloses an auto-return function for an UAV that is triggered, inter alia, under condition of loss of communication with a remote controller The auto-return function includes recording a plurality of waypoints corresponding to previously traveled positions as the UAV navigates within the environment, and travelling the stored waypoints in reverse order in order to cause the UAV to return to the initial location.

<CIT> discloses an autonomous aerial system having an aerial vehicle configured to communicate with an operating base and receive mission plan data from the operating base, and a supervisory control system operatively coupled with the aerial vehicle that is configured to generate flight control signal data via a sensor package that detects obstacles and perceive physical features. Besides other things, the supervisory control system is also configured with a lost communications contingency catering to situation when communication is lost with both the operating base.

<CIT> discloses computer implemented system for providing communication links to unmanned aerial vehicles that enhances the duration of connectivity and coverage. The system includes a plurality of nodes which communicate with each other and with the unmanned aerial vehicle to allow exchange of data. A 3D signal coverage model is created which determines signal coverage provided by the plurality of nodes. A navigator present in the system navigates the unmanned aerial vehicle to follow a stored flight path based on the 3D model. Besides other things, the system identifies waypoints present in the path of the unmanned aerial vehicle and suitable waypoints are selected from where sensed pre-stored data is collected. A suitable node is then selected based on the stored 3D signal coverage model, location of the unmanned aerial vehicle and the nodes, and the signal strength of the nodes and the collected data is transmitted to the suitable node through the unmanned aerial vehicle to provide robust communication.

Thus, there have been efforts in the past to address aforementioned issues but with limited success and impractical viability. One solution could be to pre-program desired behavior of a UAV for events that involve emergency such that when the UAV loses communication, it executes a path pre-programmed to return to its home location by its operator as configured therein prior to the flight. This pre-programmed emergency route is usually planned to have the shortest distance (i.e. linear flight path) from the point of UAV's event of loss of communication to the home location. However, a disadvantage of such a linear flight path is the possibility of having obstacles in the way, since factors such as properline-of-sight cannot not be properly taken into consideration. Alternatively, to avoid this, the pre-programmed emergency path may use the same pre-programmed flight path as traced by the UAV for the mission i.e. re-trace the path travelled by the UAV, but in this case the amount of time taken for the UAV to return to the home location can be more, and further, this would prove to be a hassle as the battery tested for a UAV during emergency is generally calculated based on time corresponding to the shortest distance, among other possible relevant factors.

There is therefore a need to provide emergency path planning for a UAV (or a system therefor) to safely return back to home location during an emergency situation/communication failure, wherein such planning ensures shortest distance flight path, while avoiding the possibility of colliding with any obstacle(s). Further, it would be an additional benefit in case there is a provision to regain control of the UAV, by its operator, even after one or more event(s) of communication failure.

In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term "about. " Accordingly, in some embodiments, the numerical parametersset forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specificationas if it were individually recited herein. The use of any and all examples, or exemplary language (e.g. "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

A general object of the present disclosure is to provide simple, safe, and fast UAV emergency path planning that does not have shortcomings of conventional communication failure path planning techniques.

An object of the present disclosure is to provide a safety-centered UAV path planning method for events involving loss of communication with home location.

Another object of the present disclosure is to provide a shortest-distance flight path for emergency return journey of a UAV while taking into account probability of obstacle(s).

Aspects of the present disclosure generally relate to the field of unmanned aerial vehicles (UAVs), and in particular, to communication failure(s) during flight of a UAV. More specifically, the present disclosure relates to shortest and safest emergency path planning upon communication failure of the UAV.

In an aspect, the present disclosure relates to a method for executing safe-return of an Unmanned Aerial Vehicle (UAV) moving along a path having a plurality of communication waypoints in an event of failure of communication with a home location due to an obstacle, in line of sight between the UAV and the home location, the method including the steps of: detecting, at the UAV, a communication failure; enabling the UAV to return to last healthy communication waypoint location; and returning back to the home location if the communication does not return within a defined time period. In an aspect, the last healthy communication waypoint location being a communication waypoint out of the plurality of communication waypoints with healthy signal and selected based on one or more factors selected from the group of battery power staus, on-board sensor status/condition and nominal mission parameters comprising total time, total distance, distance travelled, payload weight, payload condition/health.

In an aspect, the UAV returns back to the home location using linear shortest flight path from the last healthy communication waypoint location to the home location. In another aspect, in case the communication returns within the defined time period, the UAV waits for user command.

The present disclosure further relates to a system configured to enable safe-return of a UAV moving along a path having a plurality of communication waypoints in an event of failure of communication with a home location due to an obstacle, in line of sight between the UAV and the home location, said system having a communication module; and a flight control system operatively coupled with the communication module so as to detect a communication failure and, based on such detection, return to last healthy communication waypoint location, wherein the flight control system is configured to enable the UAV to return to its home location if the communication does not return within a defined time period. In an aspect, the last healthy communication waypoint location being a communication waypoint out of the plurality of communication waypoints with healthy signal and selected based on one or more factors selected from the group of battery power status, on-board sensor status/condition and nominal mission parameters comprising total time, total distance, distance travelled, payload weight, payload condition/health.

In another aspect, the flight control system-is further configured to, using one or more sensors, monitor UAV parameters selected from any or a combination of location, payload, speed, height, direction, path traversed, and fuel level.

In yet another aspect, the communication failure is detected based on status of wireless radio link.

The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.

Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

In an aspect, the present disclosure relates to a method for executing safe-return of an Unmanned Aerial Vehicle (UAV) moving along a path having a plurality of communication waypoints in an event of failure of communication with a home location due to an obstacle, in line of sight between the UAV and the home location, the method including the steps of: detecting, at the UAV, a communication failure; enabling the UAV to return to last healthy communication waypoint location; and returning back to the home location if the communication does not return within a defined time period.

The present disclosure further relates to a system configured to enable safe-return of a UAV moving along a path having a plurality of communication waypoints, said system including a communication module; and a flight control system (<NUM>) operatively coupled with the communication module so as to detect a communication failure and, based on such detection, return to last healthy communication waypoint location, wherein after waiting for_ a defined time period for communication to return, the flight control system is configured to enable the UAV to return to its home location.

In an aspect, the UAV returns back to the home location using linear shortest flight path from the last healthy communication waypoint location to the home location. In another aspect, the UAV returns back to the home location if the communication does not return within the defined time period, wherein in case the communication returns within the defined time period, the UAV waits for user command.

In another aspect, the flight control system is further configured to, using one or more sensors, monitor UAV parameters selected from any or a combination of location, payload, speed, height, direction, path traversed, and fuel level.

Embodiments of the present disclosure generally relate to the field of unmanned aerial vehicles (UAVs), and in particular, to communication failure during flight of UAV. More specifically, the present disclosure relates to shortest and safest emergency path planning on the communication failure of the UAV.

In an aspect, the present disclosure provides a method for executing safe-return for an UAV (also referred to as a "vehicle" and both these terms used interchangeably hereinafter) moving along a path with a plurality of waypoints for a nominal mission, wherein method includes the steps of detecting an event of communication failure by the UAV, self-directing the UAV to a waypoint with last healthy signal (LHS) of the plurality of waypoints, and planning, by the UAV, an emergency mission with linear flight path (alternatively, flight path) from a source to a destination, wherein the source is the waypoint with the LHS and the destination (say home location) is pre-configured in the UAV.

In an aspect, method of the present disclosure further includes the step of communicating, by UAV, with home location to check for a healthy signal after moving to the waypoint with the LHS such that, upon successful communication from the home location, the UAV establishes a healthy signal while communicating with the home location, wherein the next step is of detecting, by the UAV, a user command for further proceedings.

In an aspect, method of the present disclosure further includes the step of self-flying of UAV along linear flight path of emergency mission to a destination, wherein the destination is any of a plurality of waypoints with a healthy signal.

In an aspect, communication failure, as detected by UAV, takes place due to obstruction by an obstacle present substantially along line-of-sight from operator or home location to the UAV.

In an aspect, destination is pre-configured before start of nominal mission based upon conditionality with reference to a threshold value for waypoint with a healthy signal. Alternatively, the destination is pre-configured in-flight by UAV on communication failure based on any or a combination of obstacle features, battery power status, on-board instrument health, and distance travelled of total path of nominal mission.

In an aspect, selection of the waypoint with last healthy signal (LHS) is done with any or a combination of one or more of the factors selected from the group of batter power status, nominal mission parameters (total time, total distance, distance travelled, payload weight and the like), payload condition/health, on-board sensor status/condition.

Although the present disclosure takes the example of an UAV while referring to various aspects thereof, it to be appreciated that any aerial vehicle enabled with provision of autonomous operation, for whole or a part of its flight, readily makes use of the present disclosure, from one or more considerations such as safe retrieval, for instance. Further, vehicles other than aerial-based vehicles, such as but not limited to land-based vehicles also implement the present disclosure with minimum or no modifications, and all such variations have been well thought of and are well within the scope of the present disclosure.

<FIG> illustrates an exemplary architecture diagram of UAV <NUM> in accordance with an aspect of the present disclosure. As illustrated, UAV <NUM> includes a flight control system <NUM> in communication with modules/components such as a sensor module <NUM>, a communication module <NUM>, control actuators and propulsion <NUM>, and payload <NUM>. In an aspect, the control system <NUM> is responsible for integration and/or management of such modules/components. Further, an antenna <NUM> is in communication with the sensor module <NUM> and the communication module <NUM> such that the antenna <NUM> continuously interacts with base/home location. While in flight, the sensor module <NUM> utilizes one or more transducers such as, but need not necessarily, IMU (Inertia Measurement Unit) <NUM>, GPS (Global Positioning System) <NUM>, accelerometer, gyroscope, IR sensors and the like.

With respect to <FIG>, in an aspect, a nominal mission for UAV <NUM> includes a path with a plurality of waypoints with variation in signal strength on account of communication failure due to component(s) malfunction or due to presence of obstacle(s). Generally, when UAV <NUM> needs to perform nominal mission that is pre- programmed into it or is dynamically commanded, control system <NUM> directs the nominal mission functions and keeps track of the vehicle state, i.e., location, speed, fuel level, etc. by acquiring data from sensors (sensor module <NUM>). During execution of the nominal mission, the control system <NUM> also keeps checking health of wireless radio link from GCS (Ground Control Station, or alternatively Ground Station/Home Location). If the wireless radio link is connected, the flight control system <NUM> continues to guide the UAV 202through its nominal mission. However, if wireless radio link communication (or simplycommunication) is lost, the flight control system <NUM> directs the UAV <NUM> to its last healthy signal (LHS) communication waypoint location.

In an aspect, flight control system <NUM>, not only stores home/original takeoff location in its memory, but also stores last known healthy communication waypoint (A4 as illustrated in <FIG>) location. This data is_repeatedly updated as UAV <NUM> is in- flight and moves from one waypoint to the other of a plurality of waypoints for a nominal mission. Furthermore, the UAV <NUM> is configured to send status/updates with sensor data such as GPS coordinates, altitude, velocity, acceleration, wind speed and other instrumental or environmental data that is warranted to successfully undertake such mission, on reaching each waypoint of the plurality of waypoints. Notably, flight control system <NUM> is configured to calculate and analyze underlying flight parameters to notify user, on being queried, desirable information such as ETA (Estimated Time of Arrival) to next waypoint, average flight velocity, distance to empty or any other analysis as cold be required.

<FIG> illustrate exemplary flight paths of an UAV <NUM> in accordance to an embodiment of the present disclosure. In particular, <FIG> relates to nominal mission that enables UAV <NUM> to move along a path with a plurality of waypoints, such as waypoints A1, A2, A3, A4, and A5 (more waypoints possible while only these have been shown for better clarity and understanding). Herein, A1 is "Home Location" from where the UAV <NUM> starts its nominal mission while moving to other waypoints A2 and onwards. As elaborated earlier also, during the nominal mission, a situation could arise such that there is a communication failure, as detected by the UAV <NUM>, which happens due to various reasons such as UAV <NUM> onboard-instrument malfunction/failure, inclement weather, and obstacle(s) among other possible reasons.

In an aspect, the present disclosure provides a method for executing conditional safe-return for an UAV <NUM> (Unmanned Aerial Vehicle) moving along a path with a plurality of waypoints (herein A1 to A5) for a nominal mission, wherein the method includes the steps of detecting an event of communication failure (near A5) by the UAV <NUM>; self- directing the UAV <NUM> to a waypoint with last healthy signal (A4) of the plurality of waypoints; and planning, by the UAV <NUM>, an emergency mission with linear flight path from a source to a destination, wherein the source is the waypoint with the last healthy signal and the destination (say home location A1) is pre-configured in the UAV <NUM>. Notably, the communication failure takes place due to obstruction of line-of-sight from A5 to the UAV <NUM> by an obstacle <NUM>.

In an aspect, <FIG> illustrate conditions for communication failure due to obstacle <NUM>. Herein, UAV <NUM> is in a nominal mission mode while origination from A1 (Home Location) but somewhere during the flight, say at waypoint A5, there is obstruction to radio link/signal from the A1 due to presence of obstacle <NUM> in line-of-sight to the UAV <NUM>/A5. For reasons foretold in the present disclosure, retracing the nominal path or moving directly from A5 to A1 leads to a security challenge for the UAV <NUM> from any obstacle(s) in linear path from A5 to A1. Retracing the nominal path leads to an undesirably long time lapse with implications to on-board battery life of the UAV <NUM>.

In an aspect, as would be evident, for one or more reasons relating to outside environment of UAV <NUM>, while flying from Home Location (A1) to further waypoints A2 and thereon, it is possible for the USV <NUM> to have (while receiving through antenna <NUM>) varying quality, magnitude, or clarity of communication/radio link signal that is required for proper human assisted flight thereof. Such difference in quality of the signal would warrant proper differentiation from considerations such as safety, so as to set a threshold value for a healthy signal while taking into account user preference and other parameters as dynamically read and managed by flight control system <NUM>.

In an aspect, say for communication failure at A5, UAV <NUM> is configured to move back to waypoint with last healthy signal, in this case waypoint A4. Here, since the communication failure is due to obstacle <NUM> obstructing the line-of-sight from A1 to A5, the UAV <NUM> (or more particularly flight control system <NUM>) plans a linear flight path (marked with dotted line in <FIG>) from A4 to A1, for which the line-of-sight is expected to be free of any obstacles. Moreover, this would prove to be a better option at least from time and safety considerations, when compared to other conventional options as elaborated earlier.

In an aspect, linear flight path (as illustrated in <FIG>) is not exactly linear from consideration such as change in height of UAV while in-flight for emergency mission. Even otherwise, a constant-height flight could require slight detour(s) from normal straight line of the linear flight path in view of some obstacle(s) and the like that could be readily detected by sensors as elaborated in some aspects of the present disclosure. It could also happen that such detour(s) put the UAV back on path of nominal mission thereafter the UAV reconnects/re-communicates with Home Location, for directions such as rerouting to original pursuit on the nominal mission, or any other command from user.

In an aspect, selection of waypoint with last healthy signal (LHS) is done (by UAV) with any or a combination of one or more of the factors selected from the group of battery power status, nominal mission parameters (total time, total distance, distance travelled, payload weight and the like), payload condition/health, on-board sensor status/condition among other factors. Moreover, the UAV is configured to automatically share crucial data pertaining to the waypoint with the LHS as soon as the UAV reconnects with Home Location/user.

In an aspect, UAV is configured to scan areas in vicinity of path (with a plurality of waypoints) of nominal missions so as to execute a preemptive action in order to prevent or lessen events of communication failure. Such scan would enable the UAV to automatically check for presence of obstacles, by comparing characteristics of objects scanned in the path (or adjoining areas) with pre-stored characteristics/image of obstacles as is accessed through a database. The database is mission specific so as to take into account geographical and climatic features among other relevant factors such that there is a higher probability to timely predict and judge presence of obstacle(s). Further, the UAV is configured to dynamically update a relevant part of such database as pertains to current and/or upcoming section of the path, keeping in mind constraints of storing large amount of data and various hardware required therefore, among other relevant factors as would be obvious to a person having ordinary knowledge in the art. Thus, timely detection of obstacles, primarily by comparison with database, enables the UAV to automatically maneuver around immediate obstacles or allow timely sharing of such possibilities with user (Home Location) so as to take command from the user. Moreover, UAV is configured with a selection of different maps of target areas whether in a dynamic fashion or pre-stored in its memory. Further, online weather updates is provided for the UAV to better equip it for handling of possible communication failures, mainly due to weather and related phenomenon.

In an aspect, UAV is equipped with an image capturing means such cameras to regularly send images of vicinity of in-flight locations for nominal mission so as to enable a user to proceed accordingly, especially for events such as communication failure where such images is highly beneficial. Moreover, images of areas around the UAV is possibly helping in better judging characteristics/features of obstacle(s) that might have resulted in loss/failure of communication with Home Location. Further, images with geo- tags prove to be more beneficial to allow a user to plan SOP, such as from preliminary analysis the situation appears to warrant relocating/moving Home Location/user so as to reconnect for short time period with better line-of-sight.

<FIG> illustrates an exemplary flowchart <NUM> for planning an emergency path for UAV <NUM> on communication failure, in accordance to an embodiment of the present disclosure. At step <NUM>, the method includes the step of detecting, at the UAV, a communication failure; at step <NUM>, enabling the UAV to return to last healthy communication waypoint location; and at step <NUM>, based on status of the communication failure, i.e., if the communication returns or not, enabling the UAV to return to its home location.

Since, the present disclosure takes advantage of high probability of absence of obstacle(s) while flying/planning path from waypoint with last healthy signal (LHS) when encountering a communication failure (around further waypoint due to obstacle blocking direct line-of-sight to UAV), the present disclosure has made various references to emergency mission with reference to the waypoint with the LHS since it provides a balance of safety and efficiency of time. While it shall be well understood that any waypoint (say A2 or A3 for instance) even before the waypoint with the LHS is preferred, for one or more reasons such as a user defined threshold for healthy signal strength and the like, over and above the waypoint with the LHS (A4 of <FIG>) and all such variations are well within the scope of the present disclosure.

Thus, the present disclosure provides method for planning a safety and shortest-distance based emergency path for a UAV, particularly for conditions involving communication failure. Notably, there is also a provision to allow re-gaining of control by user/home station on conditional basis, as elaborated through various aspects of the present disclosure.

The present disclosure provides a simple, safe and fast UAV emergency path planning that does not have shortcomings of conventional communication failure path planning techniques.

The present disclosure provides a safety-centered UAV path planning method for events involving loss of communication with Home Location.

Claim 1:
A method for executing safe-return of an Unmanned Aerial Vehicle (UAV) (<NUM>) moving along a path having a plurality of communication waypoints, in an event of failure of communication with a home location due to an obstacle, in line of sight between the UAV and the home location, the method comprising the steps of:
detecting, at the UAV (<NUM>), a communication failure;
enabling the UAV (<NUM>) to return to last healthy communication way point location (A4), the last healthy communication waypoint location being a communication waypoint out of the plurality of communication waypoints with healthy signal and selected based on one or more factors selected from the group of battery power status, on-board sensor status/condition and nominal mission parameters comprising total time, distance travelled, payload weight, payload condition/health; and
returning back to the home location (A1) if the communication does not return within a defined time period.