System and method for landing and takeoff guidance

Abstract

The present invention is entitled "System and method for landing and takeoff guidance". The present invention discloses a technique for using radar echo images of a landing site to allow a vehicle equipped with at least one radar to take off and land. At least one radar generates one or more radar echo images of the landing site, in particular one or more radar echo images of reflection symbols attached to the landing site, thereby allowing the vehicle to orient itself to the landing site and provide information specific to the landing site. At least one radar and a guidance and landing system can be used to determine a position and velocity relative to the landing site. Using the position and velocity information, the guidance and landing system can guide the vehicle to and from the landing site and / or determine whether obstacles require the use of an alternative landing site.

Description

Background Art

[0001] Emerging technologies allow for the operation of vehicles (e.g., air taxis, delivery drones) that require reliable, safe, and accurate means for landing and takeoff in the absence of primary position information, such as provided by a Global Navigation Satellite System (GNSS) receiver. However, GNSS receivers may provide position information of reduced accuracy or may not provide any position information at all (e.g., because the GNSS signal is blocked by structures or is interfered with). For vehicles during landing or takeoff, even a momentary degradation or loss of position information may result in a collision with the landing site or adjacent obstacles. Vehicles performing takeoffs or landings require extreme navigation accuracy to operate when the landing site is in an urban environment.

[0002] While the above problems can occur when a human is operating a vehicle, the problem can be more severe for an autonomous vehicle. In some cases, an autonomous vehicle lacks an auxiliary system (other than a GNSS receiver) to determine its position. In addition, some autonomous vehicles cannot determine when their GNSS receivers are generating inaccurate position data (e.g., because of interference or multipath of satellite signals caused by obstacles (such as buildings)). This is particularly problematic when the vehicle relies on GNSS during takeoff and landing, as accuracy is required to prevent collisions with the environment.

[0003] Visual aids and passive optical image sensors can be used to determine the position of a vehicle when GNSS position information is degraded or unavailable. Optical image sensors allow for accurate identification of objects and structures and can provide insight into the position of the optical image sensor relative to said objects and structures. However, optical image sensors can be unreliable due to external variables (i.e., weather that affects optical imaging). Therefore, a more robust device is needed to assist in takeoff and landing of vehicles where optical image sensors may be affected or rely solely on GNSS for guidance. Summary of the invention

[0004] The present invention provides a method, which includes: transmitting a radar signal from a vehicle toward a landing site; receiving a radar echo signal reflected from a reflection symbol at the landing site at the vehicle; using the radar echo image of the reflection symbol to determine a guidance indicator, a distance, and a relative speed relative to the landing site; and guiding the vehicle to the landing site using the guidance indicator, the distance, and the relative speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Understanding that the drawings depict only some embodiments and are therefore not to be considered limiting of the scope of the invention, exemplary embodiments will be described with additional specificity and detail using the accompanying drawings, in which:

[0006] Figure 1A is a schematic diagram of a vehicle having a guidance and landing system as it approaches a landing site according to one embodiment of the present invention;

[0007] Figure 1B is a schematic diagram of a landing site according to one embodiment of the present invention;

[0008] Figure 2 is a block diagram of an exemplary embodiment of a vehicle equipped with the takeoff and landing system of the present disclosure; and

[0009] Figure 3 is a flow chart illustrating an exemplary embodiment of a method for implementing radar-assisted landing and takeoff using reflection symbols at a landing site.

[0010] According to common practice, the various features described are not necessarily drawn to scale, instead emphasis is placed on specific features relevant to the exemplary embodiments. DETAILED DESCRIPTION

[0011] In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific illustrative embodiments. It is to be understood, however, that other embodiments may be utilized and that logical, mechanical, and electrical changes may be made.

[0012] Embodiments of the present disclosure provide systems and methods that allow a vehicle's radar-based landing and takeoff system (using reflection signatures) to determine the vehicle's three-dimensional position during takeoff and landing. That is, when the vehicle attempts to land on a particular landing site, it uses radar to scan the area below the vehicle. When the vehicle is within range of the landing site, the radar will receive a radar return signal corresponding to the reflection signature of the landing site. Each radar can be a scanning or non-scanning radar as will be described later.

[0013] In some cases, the reflected symbol may include a data symbol that is compared with a database of data symbols, and based on the association of the data symbol with the data symbol in the database corresponding to the landing site, the vehicle may identify the landing site as a specific landing site. The system within the vehicle may use the information about the specific landing site stored in the database to further assist in landing. When the vehicle approaches the landing site, the vehicle uses the radar echo signal to determine the three-dimensional position of the vehicle relative to the landing site and optional other kinematic information, i.e., the speed and attitude of the vehicle. In addition, based on the radar echo signal, the vehicle can determine whether there is an obstruction on the landing site, whether it is due to the detection of foreign objects on the landing site or due to the obstruction of the data symbol. Using this information, the vehicle can land on the landing site without relying on (even partially relying on) a system that provides position information, such as a GNSS receiver or one or more inertial measurement units (IMUs). The system and associated method can also be used in a similar manner during takeoff. The reflected symbol and the data symbol are composed of a specific material that reflects the radar signal more than the material surrounding such symbols, so that the radar can distinguish the reflected symbol and the data symbol from its surrounding area.

[0014] Figure 1A 1 is a schematic diagram of a vehicle with a guidance and landing system when approaching a landing site according to one embodiment of the present invention 100. For educational purposes, the vehicle 101 shown herein is an autonomous aerial vertical take-off and landing vehicle, such as an aerial drone; however, the vehicle 101 may be any other type of vehicle, including but not limited to space-based or land-based vehicles. Such other types of vehicles may be non-aeronautical vehicles (including drones). The vehicle 101 includes at least one radar, such as a forward-facing radar. In such cases, the landing site 110 may be more generally referred to as a departure point or an arrival point. In addition, the vehicle 101 may be driven by one or more vehicle operators.

[0015] A forward-facing radar 102, a downward-facing radar 104, and at least one or more radars (collectively referred to as “radars”) facing other directions in some examples are mounted on the vehicle 100. In some examples, the forward-facing radar 102 and the downward-facing radar 104 are separate from the vehicle 100. In other examples, the forward-facing radar 102 and the downward-facing radar 104 are integrated into the vehicle 100. Reflection symbol 112. However, in other embodiments, a single radar may be employed, for example, which may effectively function as both a forward-facing radar and a downward-facing radar.

[0016] Figure 1B1 is a schematic diagram of a landing site 110 according to one embodiment of the present invention. Landing site 110 includes an area, such as a surface, where vehicle 101 can land. Reflection symbol 112 is located on landing site 110. Reflection symbol 112 is used to orient vehicle 101 using a radar echo image of reflection symbol 112. The radar echo image is formed by, for example, radar echo signals received over a period of time for all or part of the field of view of one or more corresponding radars. Optionally, landing site 110 includes data symbol 114. Data symbol 114 is used to identify landing site 110 from a set of landing sites 110 and may correspond to data accessible to guidance and navigation system 107. Optionally, reflection symbol 112 and data symbol 114 may be combined into one symbol or may not be combined into one symbol. Reflection symbol 112 and data symbol 114 may be embedded in landing site 110 itself. In such embodiments, reflective symbols 112 and data symbols 114 may include corner reflectors of a reflective material (e.g., metal) so that while the symbols are not visible to the eye, they still reflect radar signals such that the symbols are recognizable as reflective symbols 112 and data symbols 114 in a radar return image of landing site 110. In other examples, reflective symbols 112 and data symbols 114 may include a combination of reflective materials on the surface of landing site 110 and / or embedded in landing site 110. Embedded materials offer the advantage of being less susceptible to damage and degradation.

[0017] Back to Figure 1A , for educational purposes, two radars will be shown: a forward-facing radar 102 and a downward-facing radar 104. However, one, three, or more than three radars may alternatively be used. The forward-facing radar 102 generates information, such as about the landing site and obstacles in front of the vehicle 101. The downward-facing radar 104 generates information, such as about the landing site and objects below the vehicle 101. The vehicle 101 can use such information to land and take off from a landing site in an urban environment, for example. Using reflective material attached to the reflective symbol 112 of the landing site, the guidance and landing system 107 can process radar echo images from one or more radars to determine the distance to the landing area and the attitude and speed of the possible vehicle, and use such information to adjust the flight control and actuator 108 of the vehicle 101 to guide the vehicle 101 when taking off from or landing at the landing site 110, while avoiding potential physical obstacles, such as another vehicle blocking the landing area. Guidance and landing system 107 may control flight controls and actuators 108 to guide vehicle 101 during travel between landing sites.

[0018] However, in some examples, one or more radars facing directions other than forward or downward may be employed in vehicle 101. The one or more radars may be collectively referred to as "radars." Multiple radars may be used to increase the field of view, for example, up to 360°. Such radars may be mounted on and / or in vehicle 101. The description of forward-facing radar 102 and downward-facing radar 104 applies to all radars employed in vehicle 101.

[0019] The forward-facing radar 102 and the downward-facing radar 104 are configured to transmit radar signals and receive echo radar signals. Radar signals are reflected from objects in the environment. The reflectivity of an object depends on many factors, including the shape of the object, the material of the object, and the proximity of different materials. The reflected echo radar signals from the radars 102 and 104 can be used to determine the position of an object in the field of view based on the intensity, direction, and delay of the corresponding echo radar signal. For example, the corner of a building will be easier to identify than a flat window pane. Therefore, certain features of objects in an urban environment will be easier to identify than other features. The landing site 110 includes a reflection symbol 112 that is specially designed to highly reflect radar signals.

[0020] exist Figure 1A In the example shown, the forward-facing radar 102 is mounted on the vehicle 101 (e.g., in front of the vehicle) so that the forward-facing radar 102 provides a radar echo image of the volume in front of the vehicle 101. The forward-facing radar 102 is configured to transmit radar signals in at least one directional beam. In some examples, the forward-facing radar 102 is configured to transmit at least one radar signal in each of at least one narrow beam and receive a corresponding reflected radar signal.

[0021] exist Figure 1AIn the example shown, the downward facing radar 104 is mounted on the vehicle 101 (e.g., on the bottom of the vehicle) so that the downward facing radar 104 provides a radar echo image of the volume below the vehicle 101. The downward facing radar 102 is configured to transmit radar signals with at least one directional beam. In some examples, the downward facing radar 104 is configured to transmit at least one narrow beam radio signal with each narrow beam in at least one narrow beam and receive the corresponding reflected radio signal. For example, the downward directional beam will, for example, electronically scan a wide (e.g., hemispherical) volume in front of the vehicle 101. In the downward directional beam, a downward radar signal is emitted, and if the downward radar signal is reflected from the reflected symbol 112 incident by the downward radar signal, the downward echo signal is received. In some examples, the downward facing radar 104 is configured to transmit and receive radio signals with at least one beam. One or more beams are electronically scanned, for example, to generate a radar echo image of the reflected symbol in the volume below the vehicle 101 by the radar echo signal. For example, the downward directional beam will scan (e.g., electronically) across a wide (e.g., hemispherical volume) in front of the vehicle 101. In the downward directional beam, a downward radar signal is transmitted, and if the downward radar signal is reflected from the reflection symbol 112 incident on the downward radar signal, a downward radar return signal is received. In some examples, the downward facing radar 104 is configured to transmit radar signals with at least one beam and receive radar return signals. One or more beams are electronically scanned, for example, to image the reflection symbol 112 within the volume below the vehicle 101.

[0022] In some examples, each radar is a scanning radar (e.g., a phased array radar) or a non-scanning radar (e.g., a synthetic aperture radar (SAR) or inverse SAR). Phased array radars can be implemented as described in U.S. Patent No. 8,633,851 (the '851 patent), issued on January 21, 2014, which is incorporated herein by reference in its entirety. Phased array radars are suitable for vehicles because they can scan a volume electronically, thereby eliminating the need for cumbersome and bulky mechanical scanning hardware. Unlike mechanically scanned radars, electronically scanned phased array radars can change beam directions almost instantaneously. Therefore, electronically scanned phased array radars facilitate extremely fast scan rates - and therefore extremely quickly updated radar return images, which are beneficial for landing and collision avoidance applications as described herein.

[0023] The phased array radar described in the '851 patent includes multiple radar units, a clock, and a processing system. The radar signal transmitted by each radar unit is phase locked to the clock. Each radar unit can then adjust the phase and amplitude of the radar signal it transmits. In this way, the phased array radar can be customized to transmit one or more beams and scan the one or more beams. The phased array radar described in the '851 patent is only one example of how the radar in embodiments of the present invention can be implemented.

[0024] Optionally, the field of view may be divided into more than one region. Each region may be scanned by one or more beams from one or more radars. Optionally, single pulse processing may be used to improve radar echo image resolution.

[0025] Alternatively, as an alternative to scanning radar, a non-scanning radar, such as SAR or inverse SAR, can be used. SAR or inverse SAR systems utilize a single non-scanning radar on a vehicle and the respective motion of the vehicle or target to produce, for example, a detailed image of an urban environment. The radar image produced provides a three-dimensional image of the radar echo by calculation. In some examples, SAR and ISAR radars process radar echo signals and provide radar echo images for the guidance and landing system 107. In other examples, the radar echo signals described herein are provided to the guidance and landing system 107, and the guidance and landing system 107 is configured to process the radar echo signals into radar echo images. In one example, the forward-facing radar 102 and / or the downward-facing radar 104 are implemented as non-scanning radars.

[0026] In one example, the forward-facing radar 102 and / or the downward-facing radar 104 are implemented as scanning radars, such as phased array radars. In this example, the forward-facing radar 102 transmits one or more beams that scan the area in front of the vehicle 101 to generate a forward radar echo image derived from the forward echo signal; the downward-facing radar 104 transmits one or more beams that scan the area below the vehicle 101 to generate a downward radar echo image derived from the forward echo signal.

[0027] exist Figure 1A In the example shown, guidance and landing system 107 is configured to receive radar return signals from forward facing radar 102 and downward facing radar 104. One or more radar return signals are combined to form a radar return image.

[0028] In some examples, the guidance and landing system 107 is configured to send and receive information with other navigation components such as a GNSS receiver, an altimeter, and an attitude and heading reference system (AHRS). Figure 1AIn the example shown, the guidance and landing system 107 is configured to determine the position and trajectory of the vehicle 101 relative to the reflective symbol 112. In addition, the guidance and landing system 107 is coupled to the vehicle flight control and actuator 108. The flight control and actuator 108 includes, for example, control surfaces (e.g., one or more rudders, one or more elevators, and / or one or more ailerons), one or more propulsion systems (e.g., one or more jets, one or more rockets, and / or one or more propeller systems), and systems for controlling the aforementioned components. The flight control and actuator 108 is used to control the speed (rate and direction) and acceleration of the vehicle.

[0029] Using the relative position and trajectory of vehicle 101 with respect to reflective symbol 112 , guidance and landing system 107 is configured to operate flight controls and actuators 108 during takeoff of vehicle 101 from or landing on landing site 110 .

[0030] exist Figure 1A In the example shown, dashed line 103 represents the center of the reflection symbol 112 and the tracking directly below the vehicle. Arc angle "x" 105 shows the arc angle between the center of the reflection symbol 112 and directly below the vehicle. Guidance and landing system 107 is configured to use AHRS to orient the vehicle 101 along three axes, and can guide the downward facing radar 104 so that it is orthogonal to the landing site 110 even when the vehicle 101 is uneven. In some examples, the downward facing radar 104 and landing system 107 are configured to track a specific point, such as the center of the reflection symbol 112. When the vehicle 101 changes position, the landing system 107 updates the direction of the downward facing radar 104 so that it continues to point to the reflection symbol (e.g., the center of the reflection symbol). In some examples, the center of the reflection symbol 112 can be detected by its relationship with the rest of the reflection symbol 112, and the downward facing radar tracks the center of the reflection symbol 112 through continuous radar scanning of the reflection symbol 112. Arc angle "x" is zero, and reflective symbol 112 is directly below vehicle 101. When reflective symbol 112 is directly below vehicle 101, vehicle 101 can descend vertically onto reflective symbol 112. However, in other embodiments, vehicle 101 can descend at an arc angle that is not equal to zero. Guidance and landing system 107 can also use direction indicator 118 to determine the direction of vehicle 101, and can change the attitude and heading of vehicle 101 so that vehicle 101 lands facing the appropriate direction (e.g., in the direction of direction indicator 118). Direction indicator 118 may or may not be visible to the eye. In some examples, direction indicator 118 is embedded in landing site 110 and is therefore not visible.

[0031] exist Figure 1AIn the example shown, dashed line 106 represents the tracking of edge 113 of reflection symbol 112. Arc angle "y" 109 represents the arc angle between two opposite edges of reflection symbol 112 relative to forward-facing radar 102 or downward-facing radar 104. Arc angle "y" 109 and the known distance between radar 102, 104 and the edge of reflection symbol 112 can be used to determine the distance between VTOL vehicle 101 and the landing site. Downward-facing radar 104 is configured to determine the distance between it and physical objects. If the determined distance between downward-facing radar 104 and reflection symbol 112 is different from the distance between vehicle 101 and reflection symbol 112 as determined by arc angle "y" 109, vehicle 101 can determine that there is an object obscuring or blocking reflection symbol 112.

[0032] Landing site 110 may include reflective symbols 112 , data symbols 114 , direction indicators 118 , and in some examples a windsock 116 .

[0033] exist Figure 1A and Figure 1B In the example shown, when the guidance and landing system 107 detects the reflective symbol 112, the guidance and landing system 107 is configured to determine that the area containing the reflective symbol 112 is the landing site 110. The reflective symbol 112 may or may not be visible to the human eye. In some examples, the reflective symbol 112 includes a ring around the preferred landing site of the vehicle 101. In some examples, the reflective symbol 112 is a geometric pattern that may or may not be circular and / or symmetrical. In some examples, the reflective symbol 112 has a plurality of reflective features around the perimeter of the reflective symbol 112. In some examples, the reflective features are symmetrical along the perimeter of the reflective symbol 112. For example, a reflective symbol 112 in the shape of an octagon may have a reflective feature at each of the eight corners.

[0034] The data symbol 114 may be within the reflective symbol 112. The data symbol 114 may or may not be part of the reflective symbol 112. The data symbol 114 is a reflective identifier of the landing site 110, such as a QR code, a reflective dot pattern, and / or a unique pictogram. Each data symbol 114 may be used to identify a specific landing site 110, so that the data symbol 114 may be used to distinguish one landing site 110 from another landing site 110. In some examples, the data symbol 114 corresponds to a data entry that includes further information about the landing site 110 and the reflective symbol 112. The further information may or may not include the dimensions of the landing site 110 and the reflective symbol 112, a schedule for the landing site 110, information about nearby alternative landing sites 110, and / or information about the ownership of the landing site 110. In a complex (e.g., a helipad) that includes multiple landing sites 110, each landing site may be uniquely identified so that a vehicle may be assigned to a specific landing site. For example, multiple landing sites 110 may exist within a smaller neighborhood. Each landing site 110 will have a data symbol 114 so that the guidance and landing system 107 can be instructed to land on a specific landing site 110 with a specific data symbol 114. In addition, when the data symbol 114 is unique to the landing site, information about the landing site can be associated with the data symbol 114. In some examples, the data symbol 114 is associated with information about the landing site 110, the direction indication 118, and / or the reflective symbol 112 (e.g., location, owner name, delivery instructions, size of the reflective symbol 112). The data symbol 114 may or may not be visible to the eye. In other examples, the data symbol 114 is embedded in the landing site 110 and is therefore not visible.

[0035] exist Figure 1BIn the example shown, the windsock 116 provides landing system information about the conditions around the landing site 110. In some examples, the windsock 116 includes radar reflective material. In some examples, the windsock mounting piece (e.g., a pole) also includes radar reflective material. When the wind at the landing site 110 is strong enough, the windsock 116 changes direction with the wind. Radar imaging of the windsock can be used to detect the wind direction at the landing site 110. In addition, the stronger the wind, the higher the windsock 116 rises on its mounting piece. The higher the windsock 116 rises, the farther it is from the ground around it, and the closer it is to the vehicle 101 and its one or more radars. Therefore, radar imaging of the windsock can also be used to determine the wind strength or speed at the landing site 110. The forward-facing radar 102 and the downward-facing radar 104 are configured to generate radar echo images, which can be processed, for example, by the guidance and landing system 107 to detect the height and orientation of the windsock 116 above the surface and thus detect the wind speed or strength and direction. Using this information, guidance and landing system 107 uses flight controls and actuators 108 to compensate for the effects of wind when landing at touchdown site 110 .

[0036] Figure 1B The direction indication 118 shown may include a general indication of direction, such as a cardinal direction. The direction indication 118 may or may not be integrated into the reflective symbol 112. The direction indication 118 will be known, so the guidance and landing system 107 can use the direction indication 118 to orient the vehicle as it descends onto the landing site 110.

[0037] For educational purposes, as vehicle 101 approaches landing site 110, forward-facing radar 102 and downward-facing radar 104 scan for reflection symbol 112. When the radar return indicates reflection symbol 112, guidance and landing system 107 maneuvers the vehicle so that downward-facing radar 104 can detect reflection symbol 112. Using downward-facing radar 104, guidance and landing system 107 maneuvers vehicle 101 so that the vehicle is directly above reflection symbol 112. Vehicle 101 lands vertically on landing site 110.

[0038] In some examples, vehicle 101 is configured to land on landing site 110 using reflection symbol 112 as a reference. In some examples, vehicle 101 lands vertically, and in other examples, the vehicle lands from a non-vertical angle (i.e., never directly above landing site 110). Guidance and landing system 107 uses the attitude of the vehicle to compensate when the vehicle tilts off-axis.

[0039] In one example of landing, compensation is performed as vehicle 101 approaches landing site 110 from above. Guidance and landing system 107 uses radars (i.e., forward-facing radar 102 and downward-facing radar 104) to track reflection symbols 112. Vehicle 101 continues to move horizontally toward landing site 110 when transitioning from using forward-facing radar 102 to using downward-facing radar 104 alone. When vehicle 101 is positioned directly above landing site 110, vehicle 101 descends by determining the distance between vehicle 110 and the landing site using the radar echo image of reflection symbols 112. In other embodiments, guidance and landing system 107 may track reflection symbols using only downward-facing radar 104.

[0040] The vehicle 101 is also configured to take off using the reflected symbol 112 as a reference as during landing. During takeoff, sensors (such as GNSS receivers) that are typically used for navigation may be less accurate due to interference caused by nearby structures. For example, in an urban environment, multipath errors occur when GNSS signals reflect off nearby structures, reducing the accuracy of the GNSS positioning information by more than the allowable tolerance for takeoff and landing. In one example of takeoff, during takeoff, the guidance and landing system 107 operates in the opposite direction of landing by first using the radar echo image of the landing symbol 112 to determine the distance between the vehicle 101 and the landing site 110. When the vehicle 101 reaches the desired altitude or distance from the landing site 110, the radar on the vehicle 101 can be used to determine the three-dimensional position of the vehicle 101 when near other structures.

[0041] Figure 2 is a block diagram of one example of guidance and landing system 207. Descriptions of components with similar names and numbers (ie, guidance and landing system 207) apply to previous iterations of those components, and vice versa.

[0042] Guidance and landing system 207 is configured to operate on and / or in vehicle 101. Guidance and landing system 207 uses one or more radar return images of the landing site to assist in navigation of vehicle 101. Guidance and landing system 207 includes processing system 221, which includes symbol database 222 and radar return images 226. Processing system 221 is configured to couple to one or more radars (e.g., forward facing radar 102 and downward facing radar 104) and flight controls and actuators 108.

[0043] Optionally, the guidance and landing system 207 includes an air data unit 223, a GNSS receiver 225, and / or an AHRS 224 coupled to the processing system 221. The GNSS receiver 225 may be a GPS receiver. The air data unit 223 is configured to provide data about the altitude of the vehicle above the ground or sea level to the processing system 223. The AHRS 224 is configured to provide data about the heading and attitude (including roll, pitch, and yaw) of the vehicle 101 to the processing system 223; such information can be used to determine the three-dimensional position and velocity of the vehicle. The AHRS 224 is typically much cheaper than an inertial navigation system (INS) or an inertial reference system (IRS). The attitude of the vehicle 101 refers to the orientation of the vehicle 101 relative to an inertial reference system (e.g., relative to the earth).

[0044] The processing system 221 (also referred to as the processor 221) is configured to determine the three-dimensional position, attitude, and / or velocity of the vehicle from the radar echo image of the reflected symbol 112 and the AHRS 224. The processing system 221 uses an edge detection algorithm to determine the edge 113 of the reflected symbol 112. The processing system 221 is configured to identify the reflected symbol 112 and the data symbol 114 by referencing the symbols stored in the symbol database 222. In some examples, the processing system 221 is pre-programmed with the size of the reflected symbol 112. In some examples, the processing system 221 determines the size of the reflected symbol 112 by associating the data symbol 114 with the symbol database 222. The AHRS 224 provides the processing system with the attitude of the vehicle 110. The radar echo image of the reflected symbol 112 is used as a reference in three-dimensional space to determine the three-dimensional position and / or velocity of the vehicle 101 by using the attitude of the vehicle 101 to compensate for the vehicle off-axis tilt. By continuously updating the three-dimensional position and / or velocity of the vehicle 101 with respect to the reflection symbol 112, the processing system 221 can guide the vehicle 101 to the associated landing site 110. To this end, the processing system 221 is configured to generate control signals. The flight control actuator 108 is configured to be coupled to the processing system 221 and receive control signals from the guidance and landing system 107. With the knowledge of the three-dimensional position of the vehicle, the guidance and landing system 207 can modify the velocity and therefore the future three-dimensional position of the vehicle 101 so as to avoid one or more collisions with one or more obstacles when landing at the landing site 110.

[0045] Symbol database 222 contains information about data symbol 114 and reflected symbol 112. For example, symbol database 222 may contain an index of data symbol 114 with corresponding information about associated landing site 110, i.e., location of landing site 110, ownership information, alternative landing sites, delivery schedule, size of reflected symbol 112. Processor 221 is configured to access symbol database 222 and compare the radar echo image of data symbol 114 with symbol database 222 to extract information. In some examples, symbol database 222 is stored within processor 221.

[0046] When utilizing the GNSS receiver 225, the vehicle 101 primarily uses the GNSS receiver 225 to determine its three-dimensional position and velocity until the vehicle is in the vicinity of the landing site 110. When the guidance and landing system 207 determines that the reflection symbol 112 is present at the landing site 110, the guidance and landing system 207 may begin tracking the reflection symbol 112. Optionally, the processing system 221 may use the three-dimensional position data from the GNSS receiver 225 and the radar echo image of the landing symbol 112 to determine the three-dimensional position and velocity. In such an example, the three-dimensional position information may be compared with the position information from the GNSS receiver 225. This may be particularly advantageous when the reflection symbol 112 is obscured by an obstacle. For example, if another vehicle temporarily obscures the reflection symbol 112 from view by the vehicle 101, the guidance and navigation system 207 continues to rely on the GNSS receiver 225 until the location of the landing site 110, and switches back to radar navigation once the temporary obstacle is removed. In addition, using data from both the GNSS receiver 225 and the radar return image can be used to generate more accurate relative three-dimensional position and / or velocity data, and / or identify obstacles that partially obscure the landing site 110. When the GNSS receiver 225 is used in conjunction with one or more radars, the one or more radars can focus on the known location of the reflection symbol 112. When the radar return signal indicates that the reflection symbol 112 is not where it should be based on the position information from the GNSS receiver 225, the reflection symbol 112 may be completely obstructed by an obstacle. The combination of GNSS receiver position data and position data using radar return images can be used, for example, with a Kalman filter in and executed by the processing system 221 to more accurately determine the three-dimensional position and / or velocity of the vehicle 101 relative to the reflection symbol 112.

[0047] Processing system 221 includes processing circuitry coupled to memory circuitry. Processing system 221 may be implemented with analog and / or digital circuitry. For example, processing circuitry may be implemented with electronic analog circuitry, including circuitry for implementing an electronic analog computer. In some examples, processing system 221 is configured to associate the output of one or more radars with data from symbol database 222, air data unit 223, AHRS 224, and GNSS receiver 225. In some examples, processing system 221 is incorporated into other components within guidance and landing system 207.

[0048] exist Figure 2 In the example shown, radar echo image 226 is stored in processing system 221. It should be understood that radar echo image 226 can be stored in another system in the vehicle and / or in an external system. In some examples, radar echo image 226 is stored in a memory circuit. Radar echo image 226 includes radar echo signals from radars 102, 104 that have been processed to form an image of the environment around vehicle 101.

[0049] exist Figure 2 In the example shown, the air data unit 223 is configured to be coupled to the processing system 221 and provide the altitude of the vehicle 101 and optionally the rate of change of the altitude of the vehicle 101. In some examples, the air data unit 223 includes a barometric altimeter that provides information about the altitude of the vehicle 101 above the ground or sea level based on the air pressure measured by the barometric altimeter. For example, when the air data unit 223 determines that the altitude of the vehicle 101 is higher than the maximum altitude of all obstacles in the area where the vehicle 101 is traveling (or higher than the maximum altitude plus an offset), then the guidance and landing system 207 and the processing system 221 do not need to use data from one or more radars 202, 204 to perform guidance and landing functions. The offset value can be used to account for error margins in the measurement data from the air data unit 223. Additionally, if the vehicle detects no obstacles in its path, such as if the vehicle is above the maximum altitude of all obstacles, the guidance and landing system 207 may be configured to adjust the scanning strategy, such as focusing on detecting and avoiding other moving objects or switching to long-range scanning and / or mapping.

[0050] exist Figure 2In the example shown, AHRS 224 provides information about the attitude and heading of vehicle 207 to other components. In some examples, AHRS 224 includes at least one accelerometer, at least one gyroscope, and at least one magnetometer. Each accelerometer measures acceleration along an axis. Each gyroscope measures angular rotation around an axis. Each magnetometer determines the direction of the ambient magnetic field. Data from AHRS 224 can be used to determine the attitude of vehicle 101 and therefore the orientation of the radar return image of landing site 110. In addition, AHRS 224 can be used together with direction indication 118 to determine the horizontal direction of the vehicle relative to landing site 110.

[0051] When vehicle 101 is oriented off-axis, the radar echo image must be corrected with attitude information prior to processing. Processing system 221 uses the output of AHRS 224 to determine the attitude and / or heading of vehicle 101 relative to the reference frame of landing site 110 represented by radar echo image 226 (e.g., relative to reflection symbol 112). When vehicle 101 is oriented off-axis without reference frame correction of the radar echo image, processing system 221 cannot accurately determine the three-dimensional position and / or velocity of the vehicle relative to reflection symbol 112 because radar echo image 226 may result in an inaccurate determination of the three-dimensional position and / or velocity (relative to landing site 110) dependent on the attitude of the vehicle.

[0052] Figure 3 An exemplary process 300 for performing vehicle landing using at least one radar is shown. The process 300 includes: Figure 3 1 and described herein as comprising discrete elements. Such illustrations are for ease of description, and it should be appreciated that the functions performed by these elements may be combined in one or more components, such as implemented in software and / or hardware.

[0053] if Figure 3 The method 300 shown is described herein as being in the above relative Figure 1A , Figure 1B and Figure 2 If the method is implemented in the device described, it should be understood that other embodiments can be implemented in other ways. For ease of explanation, the blocks of the flowchart are arranged in a generally sequential manner; however, it should be understood that this arrangement is merely exemplary, and it should be recognized that the processing associated with these methods (and the blocks shown in the figure) can occur in a different order (for example, where at least some of the processing associated with these blocks is performed in parallel and / or in an event-driven manner).

[0054] In box 330, a radar signal is transmitted toward the landing site. In some examples, the guidance and navigation system continuously scans for reflected symbols close to the vehicle. In other examples, when it is determined that the vehicle is near the landing site (e.g., as determined by the guidance and landing system using position data from a GNSS receiver), the guidance and navigation system begins to scan reflected symbols indicating the landing site. One or more radars may project at least one directional beam from at least one radar on the vehicle toward the landing site and the area where the reflected symbol is expected to be located. Each radar periodically transmits a radar signal with each directional beam and can receive radar return signals with a directional beam. Optionally, at least one of the at least one directional beam is used to scan at least a portion of the field of view of at least one radar (the landing site and the expected location of the reflected symbol). For example, a single radar (such as a forward-facing radar) can use progressive scanning to scan the directional beam. However, other scanning techniques may be used, such as interlaced scanning of two directional beams emitted by one or more radars. If the directional beam is not scanned, for example, the directional beam may be fixedly pointed at a particular area in the radar's field of view, at least for a period of time, which may provide for detection of a landing site in the corresponding field of view and determination of the distance to the landing site.

[0055] In box 332, determine whether the reflection symbol is detected in the reflected echo signal. A radar echo image is generated by one or more reflected echo signals. Since the reflection symbol is designed to highly reflect the radar signal, the reflection symbol can be easily detected in the radar echo image. In one embodiment, the reflection symbol is determined to be in the radar echo image by comparing the radar echo image with the symbol database containing the reflection symbol. In other embodiments, the guidance and landing system is trained to find the reflection symbol at a specific location. If the guidance and landing system finds a specific landing site and cannot detect the associated reflection symbol when the vehicle is located near the landing site, the landing site and / or the reflection symbol may be blocked by obstacles. In some examples, a data symbol (with a reflection characteristic similar to the reflection symbol) accompanies the reflection symbol or is included in the reflection symbol. In such examples, the data symbol can be compared with the symbol database to determine information about the landing site, such as the size of the reflection symbol, the landing site designation, and / or the landing and / or take-off instructions. The landing and / or takeoff instructions may include information useful to the vehicle, such as speed limits and known potential hazards (such as power lines) in the immediate vicinity of the landing site. The navigation and guidance system may continue to drive near the landing site, find an alternative landing site, or abort the landing altogether. Generally speaking, if the reflected symbol cannot be detected, the method returns to block 334. If the reflected symbol can be detected, the method continues to block 336.

[0056] In block 334, the vehicle determines a path to an alternate landing site. In some examples, an alternate landing site is available that provides the same service as the initial landing site, i.e., allows product delivery to the same individual. For example, the initial landing site may be one of a set of landing sites, and when one landing site is blocked, the vehicle may seek one of the other unobstructed landing sites. In another example, if other acceptable landing sites are not available, the vehicle may be programmed to return to the predetermined landing site to await further instructions. In some examples, an alternate path to a landing site is determined based on information in a symbol database.

[0057] In block 336, the three-dimensional position and / or velocity of the vehicle relative to the landing site is determined. In each radar echo image, a reflection symbol with a known size is depicted. The radar echo image, the known size of the reflection symbol, and the attitude information of the vehicle can be used to geometrically determine the three-dimensional position of the vehicle. In examples where the reflection symbol includes a data symbol, further information about the landing site can convey the determination of the three-dimensional position and / or velocity. The data symbol may or may not provide updated information about the size of the reflection symbol. In such cases, the updated size of the landing symbol is used to determine the three-dimensional position and / or velocity of the vehicle.

[0058] In box 338, determine whether the landing site is obstructed. The guidance and landing system 200 is configured to detect obstructions on the landing site using several different methods. One method for detecting obstructions is partial obstruction of the reflection symbol 112. Once the reflection symbol 112 and the corresponding data symbol 114 have been identified, the guidance and landing system 200 can detect when a portion of the reflection symbol 112 is obscured and not seen by the radar 102, 104. Another method for detecting obstructions is Doppler echoes that indicate a motion (e.g., rotation) mechanism. When an object on the reflection symbol 112 is moving, this causes a Doppler effect by the radar signal reflected from the object. The guidance and landing system is configured to recognize these Doppler effects and perceive them as obstructions on the reflection symbol 112. Another method for detecting obstructions is when the timing echo of the radar indicates that a solid body is located above the symbol. This method may be particularly useful when a person is obstructing the landing site, where the person may not be large enough to obscure the reflective symbol 112, or the person may not be dense enough to obscure the reflective symbol 112 from being visible to the radar. Radar signals may be delayed when passing through solid objects, such as solid objects of living matter. If it is determined that the landing site is obstructed, the method continues to block 340. If it is determined that there is no obstruction, the method continues to block 342.

[0059] In box 340, determine the alternative path to the landing site. When the reflective symbol 112 is blocked, the guidance and landing system 200 is configured to determine the alternative flight path of the vehicle to avoid collision with the obstruction. In some examples, the alternative flight path is an alternative driving path to the reflective symbol 112 that can avoid the obstruction. When the obstruction is away from the reflective symbol 112, but between the vehicle 100 and the reflective symbol 112, such an alternative flight path will be advantageous. In another example, the guidance and landing system 200 can determine that landing is impossible at the reflective symbol 112, and an alternative landing site is required. In this case, the guidance and landing system will start searching for the landing site again, using its known position related to the known position of another landing site to determine the proposed driving (e.g., flight) path. In another example, the guidance and landing system 200 can determine that the obstruction to the reflective symbol 112 can be temporary, and the vehicle should maintain its position while waiting to remove the obstruction from the reflective symbol 112. These alternative flight paths are intended to be examples of options that may be used by guidance and landing system 200 and are not an exhaustive list of available options.

[0060] If it is determined that the alternate path is not available, the vehicle may find another landing site by another iteration of the method to find another landing site. Alternatively, the guidance and landing system may determine that there is no unobstructed landing site in the area and may instruct the vehicle to abort the landing procedure.

[0061] In box 342, the vehicle is guided based on the relative position, distance and speed of the vehicle. Using one or more of the radars 102, 104, the guidance and landing system 200 identifies where the identified reflection symbol 112 exists within the entire field of view of the radar echo. If the data symbol 114 accompanies the reflection symbol 112, the data symbol 114 detected in the radar echo image is used as a reference to the symbol database 222 to determine whether the landing point 110 is an appropriate landing point. If the landing point 110 is specified for the vehicle, the guidance and landing system 200 begins physical landing. In some examples, the information in the data symbol database changes the landing and / or takeoff scheme, such as providing a rate limit when near the landing point. In an alternative embodiment, the reflection symbol 112 is associated with the information in the symbol database 222, in which case, the symbol database 222 is used as a reference to determine whether the landing point 110 is an appropriate landing point. The echoes of multiple radar signals allow the guidance and landing system to triangulate the location of a specific reflection point. The timing of the echoes from the symbol region is used to determine the distance and rate of change of the vehicle from the reflected symbol 112. Using the position of the vehicle relative to the reflected symbol 112 and the relative motion of the vehicle relative to the reflected symbol 112, the navigation sensor calculates the forward, lateral and vertical range and velocity of the vehicle.

[0062] Exemplary embodiments

[0063] Embodiment 1 includes a method for landing and taking off a vehicle, the method comprising: transmitting a radar signal from the vehicle toward a landing site; receiving at the vehicle a radar echo signal reflected from a reflection symbol at the landing site; using the radar echo image of the reflection symbol to determine a guidance vector, a distance, and a relative speed relative to the landing site; and using the guidance vector, the distance, and the relative speed to guide the vehicle to the landing site.

[0064] Embodiment 2 includes the method of embodiment 1, wherein the at least one radar signal is transmitted by at least one of a phased array radar, a synthetic aperture radar, and an inverse synthetic aperture radar.

[0065] Embodiment 3 includes a method according to any one of embodiments 1 to 2, further comprising: receiving at a vehicle at least one radar signal reflected from a data symbol at a landing site; comparing the data symbol with a symbol database; determining from the symbol database at least one of a size of the reflected symbol, a landing site designation, a landing instruction, and a takeoff instruction; and wherein guiding the vehicle further comprises guiding the vehicle using at least one of the size of the reflected symbol, the landing site designation, the landing instruction, and the takeoff instruction.

[0066] Embodiment 4 includes the method according to any one of embodiments 1 to 3, wherein the vehicle is a vertical take-off and landing vehicle.

[0067] Embodiment 5 includes the method of any one of Embodiments 1 to 4, wherein the at least one radar signal includes at least two radar signals configured to be directed in different directions.

[0068] Embodiment 6 includes a method according to any one of embodiments 1 to 5, further comprising: receiving a radar echo signal reflected from a wind direction bag at a landing site at a vehicle; and using the at least one radar echo signal to determine at least one of the direction and strength of the wind at the landing site.

[0069] Embodiment 7 includes a method according to any one of embodiments 1 to 6, further comprising: identifying an obstacle on the landing site; determining an alternative landing path to avoid collision with the obstacle; and searching for an alternative landing site if an alternative landing path cannot be determined.

[0070] Embodiment 8 includes the method according to any one of embodiments 1 to 7, wherein the vehicle is an autonomous vertical take-off and landing vehicle.

[0071] Embodiment 9 includes a system comprising: a vehicle; at least one radar system attached to the vehicle, the at least one radar system configured to transmit a radar signal and receive one or more radar return signals; a landing site having a reflection symbol; a processing circuit within the vehicle, the processing circuit configured to process the received radar return signals to generate at least one radar return image, wherein the processing circuit is configured to determine at least one of a guidance vector, a distance, and a closing speed of the vehicle relative to the landing site based on an association of the at least one radar return image.

[0072] Embodiment 10 includes a system according to embodiment 9, further comprising: a symbol database, the symbol database comprising entries having information about at least one of the size of the reflection symbol, the identification of the landing site, and the landing instructions; and wherein the landing site also includes a data symbol, wherein the data symbol corresponds to at least one entry in the symbol database.

[0073] Embodiment 11 includes the system of any one of embodiments 9-10, further comprising an attitude and heading reference system (AHRS) comprising at least one accelerometer, at least one gyroscope, and at least one magnetometer.

[0074] Embodiment 12 includes the system of any one of Embodiments 9 to 11, wherein the processing circuit is further configured to use attitude information from the AHRS to adjust a reference frame of the one or more radar return signals relative to the reflection symbols.

[0075] Embodiment 13 includes the system of any one of Embodiments 9 to 12, wherein the at least one radar system includes a forward facing radar system and a downward facing radar system.

[0076] Embodiment 14 includes a system according to any one of Embodiments 9 to 13, wherein the at least one radar system includes at least one phased array radar configured to transmit at least one directional beam, wherein a radar signal is transmitted with each directional beam and a radar return signal can be received with each directional beam.

[0077] Embodiment 15 includes a system according to any one of embodiments 9 to 14, wherein the processing circuit is further configured to: determine whether the landing site is obstructed; and if the landing site is obstructed, determine an alternative landing path.

[0078] Embodiment 16 includes the system of any one of Embodiments 9 to 15, wherein the vehicle is an autonomous vertical take-off and landing vehicle.

[0079] Embodiment 17 includes a system comprising: a landing site for a vehicle; and a reflective symbol at the landing site, wherein the reflective symbol includes a pattern of radar reflective material, the pattern including geometric shapes of known dimensions.

[0080] Embodiment 18 includes the system of Embodiment 17, further comprising a windsock attached to the mount on the landing site, wherein the windsock is made of a radar reflective material.

[0081] Embodiment 19 includes the system of any one of Embodiments 17-18, wherein the reflective symbol further includes an indication of a cardinal direction.

[0082] Embodiment 20 includes a system according to any of Embodiments 17 to 19, further comprising a data symbol comprising a reflective material, wherein the data symbol corresponds to an entry in a symbol database comprising at least one of a size of the reflective symbol, an identification of a landing site, and landing instructions.

[0083] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. Therefore, it is manifestly intended that the present invention be limited only by the claims and the equivalents thereof.

Claims

1. A system for facilitating landing and takeoff of a vertical take-off and landing (VTOL) vehicle, the system comprising: at least one radar system attached to the VTOL vehicle, the at least one radar system configured to transmit radar signals and receive at least one radar return signal from a reflection symbol at a landing site; processing circuitry configured to be attached to the VTOL vehicle and configured to process the at least one radar return signal to generate at least one radar return image, wherein the processing circuitry is configured to determine a guidance indicator, a distance, and a velocity of the VTOL vehicle relative to the landing site based on the at least one radar return image, and wherein the processing circuitry is further configured to guide the VTOL vehicle to vertically land on or vertically take off from the landing site using the guidance indicator, distance, and velocity; and wherein the processing circuit further comprises a symbol database, the symbol database comprising entries, wherein each entry corresponds to a data symbol at a particular landing site, wherein each entry comprises information of a size of the reflected symbol, an identification of the landing site, at least one of takeoff instructions and landing instructions, wherein the takeoff instructions are configured for directing the VTOL vehicle to take off vertically from the landing site, and wherein the landing instructions are configured for directing the VTOL vehicle to land vertically at the landing site; The processing circuit is further configured to use information of at least one of the size of the reflected symbol, the takeoff instruction, and the landing instruction to guide the VTOL vehicle.

2. The system of claim 1 , wherein the processing circuit is further configured to: determining whether the landing site is obstructed based on the at least one radar return signal; and When it is determined that the landing location is obstructed, an alternate landing path is determined.

3. The system according to claim 1, further comprising: an attitude and heading reference system AHRS, the attitude and heading reference system AHRS comprising at least one accelerometer, at least one gyroscope and at least one magnetometer; The processing circuit is further configured to use attitude information from the attitude and heading reference system (AHRS) to adjust a reference frame of the at least one radar return signal relative to the reflection symbol.

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