Aeronautical apparatus

An aeronautical apparatus is disclosed that has two pairs of wings. Each wing has a thrust-angle motor. A propeller and propeller motor are coupled to each thrust-angle motor. Propeller pitch is controlled by a propeller-pitch motor. The thrust-angle motor allows the propeller axis of rotation to be parallel to the fuselage's longitudinal axis; vertical (perpendicular to longitudinal axis, as in well-known fixed-position, four-propeller drones); and any position between as well as a given range exceeding these bounds which is used for control. An electronic control unit is electronically coupled to the thrust-angle motors, propeller motors, and propeller-pitch motors, which can be independently controlled, to provide the desired thrust and trajectory. Such an apparatus can provide efficient operation in vertical take-off/landing (hovering) and forward (translational) flight modes. Control surfaces, such as ailerons, which are provided on airplanes, are unnecessary due to the many degrees of freedom in control.

FIELD

The present disclosure relates to vertical take-off and landing (VTOL) aircraft, in particular aeronautical vehicles, commonly referred to as unmanned aerial vehicles (UAVs) or drones.

BACKGROUND

UAVs, more commonly called drones, particularly for aerial reconnaissance and small package delivery, are presently often covered by the press and are being designed and built by many researchers and developers. Such drones are typically powered by onboard batteries. One of the significant hurdles to overcome is range limitation due to the well-understood tradeoff between including more batteries to extend range, and the additional weight of those batteries requiring more lift, causing them to drain energy at a faster rate. Although the U in UAV stands for unmanned, the present disclosure applies to aeronautical vehicles that include passengers and/or crew. Herein, UAV and drone both refer to manned or unmanned aeronautical vehicles.

Drones for many purposes are VTOL devices. A common prior-art drone10configuration, as shown inFIG. 1, has a body12with four arms14extending outwardly in a plane, approximately evenly radially displaced. Each arm has a propeller motor housed within a nacelle16. The propeller motor (not visible inFIG. 1) drives a propeller18. The propellers are arranged to provide an upward thrust to drone10by pushing air downward in a direction that gravity nominally acts, as indicating by arrow20. Drone10has landing feet22.

A drone, such as the one shown inFIG. 1, takes-off, lands, hovers or adjusts its altitude by applying equal power to all propeller motors; adjusts its yaw rate by applying more power to propeller motors rotating in one direction and/or less to the ones rotating in the opposite direction; and adjusts its pitch or roll rates by applying more power to certain propeller motors and less power to those diametrically opposite. Thrust is varied by varying propeller speed in response to propeller motor power. The drone ofFIG. 1is a simple, light-weight device that hovers, takes-off, and lands well. However, in terms of energy, is inefficient. It has no airfoils that provide lift, thus the propellers provide the upward thrust to keep the drone inefficiently aloft as well as provide thrust for forward motion. In level flight, the direction of gravity is substantially normal to the plane in which the four arms14sit. To maneuver forward (or other maneuvers perpendicular to the direction of gravity), the drone is angled slightly by differing the power of diametrically opposite propeller motors so that the imbalance causes the direction of gravity to no longer be substantially normal to the plane in which the four arms sit.

A prior-art drone30that overcomes some of the disadvantages associated with the type of drone illustrated inFIG. 1is shown inFIG. 2. Drone30has a fuselage32and four wings: right aft, left aft, right fore, and left fore. At tips of wing34, a propeller motor is coupled. The propeller motor is not separately visible because it is housed within a nacelle36. The propeller motors drive propellers38. A thrust-angle position (which is to say an angle that the axis of rotation of a propeller or propeller motor makes with a longitudinal axis of a fuselage) of propellers38, inFIG. 2, is shown in an intermediate thrust-angle position between a hovering thrust-angle position and a translational flight thrust-angle position. Propellers38(and propeller motors) ofFIG. 2can change their thrust-angle position to a hovering thrust-angle position similar to propellers'18thrust-angle position ofFIG. 1. InFIG. 1, blades of propellers18rotate in a plane substantially parallel with the geometric plane in which arms14are located. Or stated another way, the axis of rotation of propellers18is substantially parallel to arrow20in level flight. Referring back toFIG. 2, the translational flight thrust-angle position of propellers38is what is the familiar thrust-angle position for a propeller-equipped airplane50, as shown inFIG. 3. The airplane ofFIG. 3has a fuselage52with two wings54extending outward from fuselage52. Wings54have engines56that drive propellers58. The axis of rotation of engines56and propellers58is substantially parallel with the longitudinal axis of the fuselage. Referring back toFIG. 2, the axes of rotation of propellers38are about halfway between the axes of rotation of the propellers shown inFIGS. 1 and 3.

Not visible inFIG. 2is a thrust-angle motor, i.e., motor that change the propeller motors' and propellers'38thrust-angle position between the hovering and translational flight thrust-angle positions. In drone30ofFIG. 2, a single thrust-angle motor controls all propellers' thrust-angle positions synchronously, i.e., they are ganged together with their thrust-angle positions mechanically linked.

Drone30ofFIG. 2can take-off vertically, hover, and land vertically when propellers'38thrust-angle positions are in the hover thrust-angle position. When propellers'38thrust-angle positions are changed to like that of propellers58inFIG. 3, drone30is in translational flight. When in translational flight, wings34act as airfoils to provide lift. If the thrust-angle position of propellers18inFIG. 1were to be similarly changed, there would be no lift produced and drone10would descend.

To control the trajectory of aeronautical apparatuses, such as drone30inFIG. 2and airplane50inFIG. 3, there must be a number of control surfaces. Examples of such control surfaces are elevons42on drone30inFIG. 2. Airplane50inFIG. 3has ailerons60, elevators62, and rudders64. Such control surfaces penalize flight by increasing weight, drag and mechanical complexity of the aeronautical apparatus.

An aircraft or drone that has a high degree of control over trajectory and does so in a mechanically and energy efficient manner is desired.

SUMMARY

To overcome at least one of the disadvantages of the prior art, an aerodynamic apparatus is disclosed that provides at least one additional degree of freedom in controlling the propellers thrust-angle position so that much of the typically used control surfaces can be eliminated to reduce weight and drag while flying, thereby allowing for greater endurance, faster flight, and/or increased range per charge of the batteries, and doing so while only using hardware that is already in place to transition between hover and translational flight when airborne. Furthermore, mechanical complexity is reduced when control surfaces are eliminated.

An aeronautical apparatus is disclosed that includes: a fuselage having a longitudinal axis and a transverse axis; first and second wings coupled to a fore section of the fuselage at the same axial location as each other with the second wing being a mirror image of the first wing; third and fourth wings coupled to an aft section of the fuselage at the same axial location as each other but behind the axial location of the first and second wings with the fourth wing being a mirror image of the third wing; first, second, third, and fourth thrust-angle motors having an axis of rotation substantially parallel to the transverse axis of the fuselage with the first, second, third, and fourth thrust-angle motors coupled proximate a tip of the first, second, third, and fourth wings, respectively; and first, second, third, and fourth propeller motors coupled to the first, second, third, and fourth thrust-angle motors, respectively; and first, second, third, and fourth propellers coupled to the first, second, third, and fourth propeller motors, respectively.

A propeller assembly is comprised of a propeller coupled to a propeller motor.

Each thrust-angle motor controls the thrust-angle position of its associated propeller assembly.

In some embodiments, the first, second, third, and fourth wings are unitary, i.e., without control surfaces such as ailerons or elevons.

In some embodiments, the aeronautical apparatus also includes at least one stabilizer. It is typical, for example, for vertical stabilizers at the aft of an aircraft to have controllable rudders. In some embodiments of the present disclosure, a stabilizer, such as a vertical stabilizer is included, although as a non-controllable stationary vertical stabilizer, i.e., without a rudder.

The aeronautical apparatus also includes an electronic control unit (ECU).

The ECU is in electronic communication with the first, second, third and fourth thrust-angle motors. The ECU determines desired first, second, third, and fourth thrust-angle positions for the first, second, third, and fourth propeller assemblies, respectively, based at least on a desired trajectory. The ECU commands the first, second, third, and fourth thrust-angle motors to attain the desired first, second, third and fourth thrust-angle positions, respectively.

The ECU is in electronic communication with the first, second, third and fourth propeller motors. The ECU determines desired first, second, third, and fourth propeller speeds for the first, second, third and fourth propellers, respectively, based at least on the desired trajectory. The ECU commands the first, second, third, and fourth propeller motors to attain the desired first, second, third, and fourth propeller speeds, respectively.

The ECU determines actual trajectory of the aeronautical apparatus based on data from a sensor and determines desired trajectory of the aeronautical apparatus based on at least one input signal. The input signal, in some embodiments, is used to communicate a desired flight path, a desired maneuver, or a desired end point. In some embodiments, the input signal is updated during the flight, maybe in real time. In other embodiments the input signal is used only before flight. Commands to the first, second, third, and fourth thrust-angle motors and the first, second, third, and fourth propeller motors are based on the actual trajectory and the desired trajectory. The sensor comprises at least one of: air speed, ground speed, radar altimeter, barometric pressure, thermometer, magnetometer, global position, accelerometer, gyroscope, radar, LIDAR, sonar, infrared camera, visible wavelength camera, energy consumption rate, energy generation rate, and battery charge state.

In some embodiments at least two of the propellers are variable pitch having a propeller-pitch motor. Propeller-pitch angle (which is to say the angle the propeller blade makes with the plane of the propeller's rotation, or stated differently, the propeller blade's angle of attack in still air) is controlled by the propeller-pitch motor. In other embodiments, all the propellers have propeller-pitch motors.

The ECU is in electronic communication with the first and second propeller-pitch motors. The ECU determines the desired first and second propeller-pitch angles for the first and second propellers, respectively, based at least on the desired trajectory. The ECU commands the first and second propeller-pitch motors to attain the desired first and second propeller-pitch angles, respectively.

Thrust-angle positions are comprised of thrust-angle base positions that have a range of 90 degrees and thrust-angle control positions that have a range of at least 10 degrees. Thrust-angle control positions allow the aeronautical apparatus to be controllable about the yaw axis and in the longitudinal direction while hovering and controllable about the roll and pitch axes while in translational flight.

Propeller-pitch angles are comprised of propeller-pitch base angles and propeller-pitch control angles. Propeller-pitch control angles allow the aeronautical apparatus to be controllable about the roll and pitch axes while hovering and controllable about the yaw axis while in translational flight.

The ECU bases the desired first, second, third, and fourth thrust-angle positions, the desired first, second, third, and fourth propeller speeds and the desired first and second propeller-pitch angles on data from sensors. The sensors include at least one of: air speed, ground speed, radar altimeter, barometric pressure, thermometer, magnetometer, global position, accelerometer, gyroscope, radar, LIDAR, sonar, infrared camera, visible wavelength camera, energy consumption rate, energy generation rate, and battery charge state.

The ECU obtains data on an actual trajectory for the aeronautical apparatus. The ECU computes a trajectory discrepancy based on a difference between the desired trajectory and the actual trajectory. The ECU computes updated first, second, third, and fourth thrust-angle positions; first, second, third and fourth propeller speeds; and first and second propeller-pitch angles based on the trajectory discrepancy. The ECU commands first, second, third, and fourth thrust-angle motors; first, second, third and fourth propeller motors; and first and second propeller-pitch motors to attain the updated first, second, third and fourth thrust-angle positions; first, second, third and fourth propeller speeds; and the first and second propeller-pitch angles, respectively.

The fore wings are angled downward with anhedral, and the aft wings are angled upward with dihedral, where the aft wings have a larger projected area than the fore wings. Landing feet provided near the tips of the fore wings touch the ground before the fuselage would touch the ground due to the anhedral wings.

The first and second wingtips are below the transverse axis by the same amount that the third and fourth wingtips are above the transverse axis. The first and second thrust-angle motor are coupled to the first and second wingtips respectively such that the first and second propeller motors (which are coupled to the first and second thrust-angle motors, respectively) are the same distance below the transverse axis that the third and fourth propeller motors (which are coupled to the third and fourth thrust-angle motors which are in turn coupled to the third and fourth wingtips, respectively) are above the transverse axis, and, the first and second propeller motors are in front of the transverse axis by the same amount that the third and fourth propeller motors are behind the transverse axis.

The aeronautical apparatus also has at least one stabilizer coupled to the fuselage and extending downwardly from the fuselage. A tip of the first wing, a tip of the second wing, and the stabilizer support the aeronautical apparatus when on the ground.

Also disclosed is an aeronautical apparatus with a fuselage having a longitudinal axis and a transverse axis; a first wing coupled to a right side of the fuselage; a second wing coupled to a left side of the fuselage; first and second thrust-angle motors having an axis of rotation substantially parallel to the transverse axis of the fuselage with the first and second thrust-angle motors coupled proximate a tip of the first and second wings, respectively; a first propeller motor coupled to the first thrust-angle motor; a second propeller motor coupled to the second thrust-angle motor; a first propeller coupled to the first propeller motor; and a second propeller coupled to the second propeller motor.

The aeronautical apparatus includes a third propeller motor coupled to the fuselage; and a third propeller coupled to the third propeller motor.

Some embodiments of the aeronautical apparatus include: a third wing coupled to a right side of the fuselage; a fourth wing coupled to a left side of the fuselage; third and fourth thrust-angle motors having an axis of rotation substantially parallel to the transverse axis of the fuselage with the third and fourth thrust-angle motors coupled proximate a tip of the third and fourth wings, respectively; a third propeller motor coupled to the third thrust-angle motor; a fourth propeller motor coupled to the fourth thrust-angle motor; a third propeller coupled to the third propeller motor; and a fourth propeller coupled to the fourth propeller motor.

In some embodiments at least two of the propellers are variable pitch having propeller-pitch motors. Propeller-pitch angle is controlled by the propeller-pitch motors. In other embodiments, all the propellers have propeller-pitch motors.

The aeronautical apparatus includes an ECU in electronic communication with the first and second thrust-angle motors, first and second propeller motors, and first and second propeller-pitch motors. The ECU commands thrust-angle positions to the first and second thrust-angle motors, propeller speeds to the first and second propeller motors, and propeller-pitch angles to first and second propeller-pitch motors based at least on a desired trajectory.

The aeronautical apparatus includes a plurality of sensors in electronic communication with the ECU. The ECU commands to the first and second thrust-angle motors, first and second propeller motors and first and second propeller-pitch motors are further based on data from the plurality of sensors.

The aeronautical apparatus includes a stabilizer extending downwardly from the fuselage. When on the ground, the aeronautical apparatus is supported by a wingtip of the first wing, a wingtip of the second wing, and the stabilizer.

According to embodiments disclosed herein, inefficient flying configurations are avoided and components that increase drag are omitted as their function is supplanted by the high degree of control over the aeronautical apparatus afforded by individual control of thrust-angle position of the propellers via thrust-angle motors, speed of the propellers, and pitch of propeller blades, depending on the embodiment.

When hovering, lift is provided solely by the action of the propellers. When in translational flight, lift is provided solely by the wings. Of course, to obtain lift using wings, the aeronautical apparatus must be moving through the air. The power required to drive the propellers during translational flight while maintaining the same lift is less than the power required to drive the propellers while hovering. To improve endurance, it is useful to switch to translational flight as soon as practical. Additionally, for some hovering operations, it may be suitable to translate in a small radius ellipse for pseudo hovering at greater efficiency than a true hover. The aeronautical apparatus disclosed herein is particularly suitable for drone applications in which much of the flight plan includes translation due to the significant energy savings, which equates to greater endurance, that such a drone affords. Furthermore, the greater endurance provided by translational flight increases the range of such a drone by allowing it to remain airborne longer. Also, it is necessary for the minimum airspeed to be higher for translational flight when compared to hovering, and this higher speed coupled with the ability to remain airborne longer compounds the effects on range increasing it even further.

DETAILED DESCRIPTION

As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce alternative embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. Those of ordinary skill in the art may recognize similar applications or implementations whether or not explicitly described or illustrated.

InFIG. 4, an isometric view of an aeronautical apparatus (UAV or drone)70is shown. Drone70has a fuselage72with a nose76at its fore. Fuselage72has a longitudinal axis74. Four wings are coupled to fuselage72: right fore78, left fore (not visible), right aft82, and left aft84. In the embodiment inFIG. 4, fore wings are attached to fuselage72located below longitudinal axis74(or below a plane that includes longitudinal axis74and which the direction of gravity is normal to) with anhedral (wings pointing downward); and aft wings are attached to fuselage72above longitudinal axis74(or above a plane that includes longitudinal axis74and which the direction of gravity is normal to) with dihedral (wings pointing upward).

Coupled to a tip of right aft wing82inFIG. 4is a thrust-angle motor (not visible) which is contained within a tip92of wing82. A propeller motor102is coupled to the thrust-angle motor (not shown) within tip92and a propeller112is coupled to propeller motor102. Assembly130ofFIG. 5shown in an exploded view are provided at the tips of each of the wings: right fore, right aft, left fore, and left aft, with those on the left being of a mirror-image configuration. InFIG. 5, an exploded view illustrates that a thrust-angle motor121is coupled to tip92of a wing (not shown). A slewing ring124has an adapter122provided between thrust-angle motor121and slewing ring124. Typically, propeller motor102is contained within a nacelle (a streamlined housing), not shown inFIG. 5. An adaptor126is provided between slewing ring124and propeller motor102. Coupled to propeller motor102is shaft128. Propeller blades (not shown) are mounted on shaft128.

An alternative configuration of an aeronautical apparatus (drone)200, is shown inFIG. 6. Drone200has a fuselage202that has a longitudinal axis204and a nose206at its fore. A right wing208is equipped with a thrust-angle motor (not shown) behind a slewing ring210. Thrust-angle motor is coupled to a propeller motor212via the slewing ring210to change the thrust-angle position of propeller motor212(an assembly similar to assembly130ofFIG. 5is provided on each of the right and left wings, but mirror on the left). Propeller motor212is shown with an axis of rotation that is substantially perpendicular with longitudinal axis204and parallel with the direction gravity acts in level flight, which is a thrust-angle position for take-off, hovering and landing. The axis of rotation of propeller motor212can be positioned such that it is substantially parallel with longitudinal axis204for translational flight. Propeller motor212is coupled to shaft214to which a propeller216is mounted. The wing assembly (208,210,212,214,216, and the thrust-angle motor which is not visible) on the right side of fuselage202is provided on the left side of fuselage202, although in a mirror-image configuration. The only parts of the left-wing assembly visible inFIG. 6are shaft224and a propeller226. A third propeller assembly is provided on fuselage202. A propeller motor232housed within fuselage202is shown in phantom. Propeller motor232drives shaft234that has a propeller236mounted thereto. Propeller motor232is fixed, meaning that it does not have a thrust-angle motor. In some embodiments, it is provided with a propeller-pitch motor that changes the propeller-pitch angle of the blades. Propeller236is utilized primarily during take-offs, landings, and hovering. In some embodiments propeller motor232, shaft234and propeller236are placed in front of right wing208and left wing (not visible) on the fuselage202. During translational flight, propeller motor232is deactivated and propeller236presumably assumes a configuration in which the blades are substantially parallel with longitudinal axis204. Propeller236becomes drag during forward flight. To avoid significant drag, propeller236has two blades that can assume a fore and aft configuration when in forward flight. In alternative embodiments, propeller236may have other blade numbers and configurations.

As described above, some embodiments include mechanisms to change the pitch of the blades of the propeller, such as that shown inFIG. 7. A propeller motor250has a propeller motor output shaft252to which propeller blades254are coupled. Propeller motor output shaft252is hollow to allow a control shaft260to extend there through. Control shaft260is attached to a yoke262. Yoke262has pins at its periphery that engage with control links264. There is one pin and one control link per propeller blade. Control links264couple to yoke262at one end and at a bell crank266attached to the root of the propeller blades254at the other. Propeller blades254have a centerline256. Control links264couple to bell crank266away from the centerline256so that when control links are moved, blade254, which is attached to bell crank266, rotates around a propeller drive shaft268. Propeller drive shaft268is integrally formed with propeller motor output shaft252in the example shown inFIG. 7. When control shaft260is pulled downward, propeller blades254rotate around centerline256; when control shaft260is pushed upward, propeller blades254rotate about centerline256in an opposite direction of that when shaft260is pulled downward. Rotation of an actuator270causes linear motion of control shaft260. The mechanism for changing pitch of propeller blades shown inFIG. 7is not intended to be limiting and is simply one example of a pitch control actuator.

Airplanes have landing gear. An aeronautical device with hovering capability need not have wheels for landing gear, instead, just stable surfaces. A side view of drone70on the ground138is shown inFIG. 8. The right fore wing78is partially visible inFIG. 8. Associated with the tip of wing78is a landing foot136. Both right fore wing78and left fore wing (not visible inFIG. 8) have such a landing foot. In some embodiments, there are two stabilizers120that rest on ground138. In alternative embodiments, only one stabilizer is provided at the aft with drone70resting on two landing feet136and stabilizer120in a triangular formation. Drone70has the right fore wing78and the left fore wing (not visible) coupled to the aircraft at a lower point on the fuselage72. Because the axes of rotation of propellers112,114,116, and118ofFIG. 4can be positioned such that they are parallel to the direction of gravity, propellers112,114,116, and118ofFIG. 4do not run the danger of hitting the ground138ofFIG. 8and causing damage or throwing drone70out of its desired attitude. Drone70has an advantage in that stabilizer120and tip of right fore wing78and tip of left fore wing (not visible inFIG. 8) double as landing feet, presenting a minimal increase in weight and drag, particularly when compared to the prior-art landing wheels, such as those shown inFIGS. 2 and 3.

InFIG. 9, a plan view of drone70is shown. Both the longitudinal axis74and a transverse axis75are shown. The center of mass77is located at the intersection of axes74and75. Fore wings78and80are shorter than aft wings82and84. It is desirable for the center of mass77of drone70to be at the center of lift while hovering and ahead of the center of lift while in translational flight. Stated another way, it is desirable for the center of mass77to be longitudinally equidistant between the fore and aft propeller's axis of rotation and laterally (transversely) equidistant between the left and right propeller's axis of rotation while hovering, and directly ahead of the aerodynamic center while in translational flight. While hovering, lift is provided by propellers112,114,116, and118only. Thus, the location of the propellers112,114,116, and118is such that the centroid of the propellers112,114,116, and118is substantially coincident with the center of mass77. In translational flight, wings78,80,82, and84provide the lift. To make the aerodynamic center behind the center of mass77for stable forward flight, the projected wing area of aft wings82and84is greater than the projected wing area of fore wings78and80.

Referring now toFIG. 10, the basics of the control hardware is shown for drone70. A laptop or other device250may be used to provide a desired route before taking off or an updated route while in flight (such as real-time control). Device250may be communicating wirelessly through Bluetooth (when in range), radio, Wi-Fi, or any suitable system. Device250may use telephone cellular communication as well. Control of drone70may use other sensors252, such as those that communicate weather information, wind speed, barometric pressure, etc. that can be transmitted wirelessly. Both device250and sensors252provide input data to electronic control unit (ECU)260onboard drone70. In other alternatives, the ECU can be located remotely. ECU260is provided sensor data from a host of sensors262based on output from one or more of sensors detecting: air speed, ground speed, radar altimeter, barometric pressure, thermometer, magnetometer, global position, accelerometer, gyroscope, radar, LIDAR, sonar, infrared camera, visible wavelength camera, energy consumption rate, energy generation rate, and battery charge state. Based on the desired trajectory and the information from a plethora of sensors262, ECU260determines what to command to the various motors: thrust-angle motors (not visible) to control the propellers'112,114,116, and118and propeller motors'102,104,106and108thrust-angle positions at the tips of the wings82,78,84and80(wing80not visible inFIG. 10; refer toFIG. 9to see wing80) respectively, and propeller-pitch motors (not visible) and propeller motors102,104,106and108to control the thrust produced by each of the propellers112,114,116, and118, respectively. ECU260provides control signals264to the various motors. In some embodiments, ECU260includes motor drivers with sufficient current capability to drive the motors. In some embodiments, ECU260simply provides control signals that are sent to motor drivers which are electrically coupled to the motors. ECU260may communicate back to device250to provide images or other information, such as the state of battery charge.

It is desirable to have the ability to extend the thrust-angle position's range somewhat beyond the thrust-angle base positions shown inFIG. 9(hovering thrust-angle base position) andFIG. 10(translational thrust-angle base position) for control purposes. Approximately 10 degrees of additional thrust-angle control position near each end of travel allows the aeronautical apparatus to be controllable about the yaw axis and longitudinal direction while hovering (i.e. thrust-angle motors are substantially in the hovering thrust-angle base position) and controllable about the roll and pitch axes while in translational flight (i.e. thrust-angle motors are substantially in the translational flight thrust-angle base position).

InFIG. 11, one example of many possible combinations of thrust-angle positions is shown that causes drone70to undergo a maneuver. As shown inFIG. 11, drone70is in a level transitional attitude. Propellers112and118are in a translational thrust-angle base position with no thrust-angle control position, i.e., with an axis of rotation parallel to longitudinal axis74. Propeller114is rotated backward, i.e., the axis of rotation is displaced from being parallel to the longitudinal axis by a thrust-angle control position denoted by314. Propeller116is rotated forward, i.e., the axis of rotation is displaced from being parallel to the longitudinal axis by a thrust-angle control position denoted by316. Drone70rolls left and pitches upward in response to the propellers being at the thrust-angle positions shown inFIG. 11. In some embodiments thrust-angle control positions314and316may be equal to each other in magnitude.

InFIG. 12, another example combination of thrust-angle positions is shown. When hovering, all of propellers112,114,116, and118have a thrust-angle base position such that their axes of rotation are perpendicular to longitudinal axis74and parallel to the direction of gravity in level flight (should no thrust-angle control positions be present). InFIG. 12, propellers112and114are rotated backward by thrust-angle control positions312and314, respectively, from the hovering thrust-angle base position. Propellers116and118are rotated forward by thrust-angle control positions316and318, respectively, from the hovering thrust-angle base position. Drone70yaws to the right in response to the propellers being at the thrust-angle positions shown inFIG. 12. In some embodiments all four of these thrust-angle control positions may be equal to each other in magnitude.

The desired range of authority of thrust-angle motors is greater than the range between the hovering thrust-angle base positions and the translational thrust-angle base position (90 degrees). InFIG. 11, the thrust-angle position of propeller116is rotated forward from the translational thrust-angle base position to undergo a maneuver. As such the thrust-angle position of propeller116causes a slight negative lift, this is not a thrust-angle position that is sustained for a substantial period of time, mainly employed to complete a maneuver. InFIG. 12, another propeller thrust-angle position is shown that is outside of the range between the hovering and translational thrust-angle base positions. In particular, the thrust-angle position of propellers112and114are rotated backward from the hovering thrust-angle position, which results in the thrust being slightly reversed from the direction of what is normally set for translational flight. Again, some thrust-angle positions that are accessible via thrust-angle motors may be employed for brief periods to cause a particular maneuver. A range of 90 degrees plus at least 10 degrees on each end of the hovering and translational thrust-angle base positions yields a total range of control authority of at least 110 degrees for the thrust-angle motors to provide the desired functionality. The example of 10 degrees of rotation beyond the thrust-angle base hovering and translational positions is not intended to be limiting. Depending on the application, greater or lesser ranges of authority may be desirable. Also, depending on the application, it may be useful to allow a greater range beyond the translational thrust-angle base position than the hovering thrust-angle base position and vice versa in other applications.

While the best configuration has been described in detail with respect to particular embodiments, those familiar with the art will recognize various alternative designs and embodiments within the scope of the following claims. While various embodiments may have been described as providing advantages or being preferred over other embodiments with respect to one or more desired characteristics, as one skilled in the art is aware, one or more characteristics may be compromised to achieve desired system attributes, which depend on the specific application and implementation. These attributes include, but are not limited to: cost, efficiency, strength, durability, life cycle cost, marketability, speed, endurance, range, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. The embodiments described herein that are characterized as less desirable than other embodiments or prior-art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.