Single arm failure redundancy in a multi-rotor aerial vehicle with least rotors/propellers

Abstract

A multi-rotor Aerial Vehicle with least rotors/propellers and having single arm failure redundancy is disclosed. The AV comprises at least five arms with at least one arm having a co-axial pair of contra rotating rotors/propellers. To maintain yaw stability under normal conditions, half of rotors/propellers are rotated in one direction and other half in opposite direction. In the event of failure of any one of the rotors/propellers located adjacent to the pair of contra rotating rotors/propellers, the one propeller/rotor out of the contra rotating rotor/propeller that is rotating opposite to the failed rotor/propeller is shut off. In the event of failure of a rotor/propeller belonging to contra rotating rotors/propellers, other rotor/propeller of the pair is shut off. In the event of failure of any one of rotors/propellers not adjacent to contra rotating rotors/propellers, the RPMs of other rotors/propellers is adjusted to maintain stability and navigate the Aerial Vehicle.

Claims

1. A multi-rotor Aerial Vehicle comprising: a frame having at least five arms, wherein total number of arms is an odd number; a plurality of rotors/propellers configured on the at least five arms; wherein at least-one arm, but not all arms out of the at least five arms incorporates a co-axial pair of contra rotating rotors/propellers; a control system incorporating an autopilot configured to control operation of the plurality of rotors/propellers including throttle of the plurality of rotors/propellers based on operating condition of the Aerial Vehicle and functional systems of the Aerial Vehicle to maintain yaw stability, lift stability and tilt stability; wherein, in the event of failure of any one of the plurality of rotors/propellers, the autopilot controls operation the plurality of rotors/propellers to maintain yaw stability, lift stability and tilt stability.

2. The Aerial Vehicle of claim 1, wherein the rotors/propellers are configured such that lines joining the adjacent rotors/propellers define an irregular convex polygon of a configuration such that in event of failure of any one arm, centre of gravity of the Aerial Vehicle still lies within a polygon formed by remaining arms that are functional.

3. The Aerial Vehicle of claim 1, wherein the co-axial pair of contra rotating rotors/propellers have individual motors to enable independent operation of the contra rotating rotors/propellers.

4. The Aerial Vehicle of claim 1, wherein to maintain yaw stability under normal conditions, half of the plurality of rotors/propellers are configured to rotate in one direction and other half are configured for rotation in opposite direction.

5. The Aerial Vehicle of claim 4, wherein to maintain yaw stability under normal conditions when total of the plurality of rotors/propellers is an odd number, an appropriate propeller/rotor out of a co-axial pair of contra rotating rotors/propellers is kept off to have equal numbers rotating in two opposite directions.

6. The Aerial Vehicle of claim 1, wherein, in the event of failure of any one of the plurality of rotors/propellers on an arm located adjacent to the at least one arm having the co-axial pair of contra rotating rotors/propellers, the auto pilot shuts one propeller/rotor out of the pair of contra rotating rotor/propeller that has direction of rotation opposite to direction of rotation of the failed rotor/propeller to maintain yaw stability.

7. The Aerial Vehicle of claim 1, wherein in the event of failure of any one of the rotor/propeller belonging to the co-axial pair of contra rotating rotors/propellers, other rotor/propeller of the pair is shut off to maintain yaw stability.

8. The Aerial Vehicle of claim 1, wherein, in the event of failure of any one of the plurality of rotors/propellers on an arm that is not adjacent to the at least one arm having the co-axial pair of contra rotating rotors/propellers, the auto pilot reduces RPMs of the rotors/propellers adjacent to the failed propeller.

9. The Aerial Vehicle of claim 8, wherein, in the event of failure of any one of the plurality of rotors/propellers on an arm that is not adjacent to the at least one arm having the co-axial pair of contra rotating rotors/propellers, the auto pilot increases RPMs of propeller out of pair of contra rotating propellers and another propeller on an arm adjacent to the pair of contra rotating propellers that are rotating in same direction as the failed propeller.

10. The Aerial Vehicle of claim 9, wherein, in the event of failure of any one of the plurality of rotors/propellers on an arm that is not adjacent to the at least one arm having the co-axial pair of contra rotating rotors/propellers, the auto pilot adjusts RPMs of the contra rotating propellers such that the net torque about the body frame of the Aerial Vehicle is zero.

11. The Aerial Vehicle of claim 10, wherein in the event of failure of any one of the plurality of rotors/propellers on an arm that is not adjacent to the at least one arm having the co-axial pair of contra rotating rotors/propellers, movement of the Aerial Vehicle in any direction other than direction of the failed rotor/propeller, is enabled by making an appropriate yaw movement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1 illustrates a conventional multi-rotor Unmanned Aerial Vehicles (UAV) with each arm fitted with a pair of contra rotating propellers and providing single arm redundancy with minimum number of arms.

(3) FIG. 2 illustrates an exemplary perspective view of a five armed UAV with six propellers to get single arm redundancy with least rotors/propellers in accordance with an embodiment of the present disclosure.

(4) FIG. 3 illustrates an exemplary representation of a five armed UAV with propeller on an arm adjacent to arm having pair of contra rotating propellers failing in accordance with an embodiment of the present disclosure.

(5) FIG. 4 illustrates an exemplary perspective view of a five armed UAV with propeller on an arm non adjacent to arm having pair of contra rotating propellers failing in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

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

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

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

(9) The term ‘yaw’ as used herein refers to aside to side movement of the nose or rotation or heading of a multi-rotor UAV about its vertical axis passing through its centre of gravity

(10) The term ‘lift force’ as used herein refers to various forces in an UAV enabling it to be lifted up.

(11) The term ‘centre of lift’ as used herein refers to the point on an UAV where sum total of all lift forces generated by all rotors can be represented as an aggregate force with its direction.

(12) The term ‘throttle’ as used herein refers to a mechanism to vary the lift forces of a UAV, generally by varying speed of its rotor assemblies that drives its propellers.

(13) The term ‘moment of force’ as used herein refers to the tendency of a force to rotate an object about an axis, fulcrum, or pivot.

(14) Embodiments explained herein relate to a rigid frame multi-rotor aerial vehicle that provides single arm redundancy with least number of rotors. Thus the disclosure provides most economical configuration for an Aerial Vehicle which can operate even if one of its rotor assembly and/or associated components fail for any reason.

(15) It is to be appreciated that though various embodiments of the present disclosure have been described with reference to five armed configuration with one arm having a pair of contra rotating propellers, embodiments of the present disclosure can be applied to other configurations as well, such as to AVs having more than five but odd numbered arms, and with those having more than one arm with pairs of contra rotating propellers, as would be explained in subsequent paragraphs, and all such variations departing from the embodiments explained in the present disclosure are well within the scope of the present disclosure without any limitations. In that respect, the present disclosure provides a system for achieving single arm failure redundancy with least number of propellers/rotors for a configuration having a given number of arms.

(16) FIG. 2 illustrates an exemplary perspective view of a fixed/rigid frame five armed UAV 200 with six propellers to get single arm redundancy in accordance with an embodiment of the present disclosure. As shown the UAV 200 incorporates six rotors/propellers with one arm having a pair of contra rotating propellers, and other four arms having single propellers/rotors. In an aspect, feature of single arm redundancy can be achieved in a five armed UAV even with number of propellers less than ten as was the case with conventional arrangement as shown in FIG. 1, and reduction of number of rotors can have a significant impact on cost.

(17) In an embodiment, the five armed UAV 200 can comprise four rotors each having a single propeller such as P1, P2, P3 and P4, and a coaxial set of propellers P5-1 and P5-2 on its fifth arm as shown in FIG. 2. The four arms can have propellers P1 to P4 arranged to rotate in clockwise and counter-clockwise direction alternately to maintain yaw stability under normal conditions. The co-axial propeller pair can comprise two contra rotating propellers. Thus the UAV 200 can have only six propellers, three out of these six can rotate in one direction and other three rotate in opposite direction giving overall yaw stability. As can be appreciated, reduction in number of propellers from ten to six can bring in considerable cost benefits.

(18) In an aspect, coaxial set of contra-rotating propellers P5-1 and P5-2 can have independent motors so as to enable their independent operation.

(19) In an aspect, the UAV 200 can further include a control system that incorporates an auto pilot configured to control operation of the rotors including their throttle based on operating condition of the UAV 200 and its functional systems. For example, the auto pilot can start or stop rotation of a rotor, and throttle up or throttle down different rotors to maintain tilt stability, increase/decrease altitude or maintain yaw stability of the Aerial Vehicle.

(20) In an aspect, the system of the disclosed UAV 200 can also comprise means to detect location of a failed arm/propeller/rotor, and based on the detected location, the autopilot can stop and or stop one or more of other rotors, throttle up or throttle down other rotors based on their relative vector position in relation with the failed rotor to maintain stability of the AV.

(21) In an embodiment of implementation for maintaining stability of the disclosed UAV 200, referring to FIG. 3, in the event of mid-flight failure of any one of the rotors/propellers out of P1 and P4, i.e. those located adjacent to the contra rotating pair of propellers i.e. P5-1 and P5-2, one of the propellers out of pair of contra rotating propellers i.e. P5-1 or P5-2, that is rotating in direction opposite to the failed rotor/propeller can be shut off In such a scenario the UAV 200 would get reconfigured as a quadcopter and work accordingly to maintain stability.

(22) In another embodiment of implementation for maintaining stability of the disclosed UAV 200, if the failed rotor/propeller is one out of pair of contra rotating rotors/propellers i.e. P5-1 or P5-2, the functional contra rotating rotor/propeller can be shut off to maintain yaw stability. Thus, in this condition also four out of five arms shall continue to have functioning propellers to make the AV configuration similar to a typical quadcopter and works accordingly.

(23) In yet another embodiment of implementation for maintaining stability of the disclosed UAV 200, referring to FIG. 4, in the event of mid-flight failure of any one of the rotors/propellers such as P-2 or P-3 that is not located adjacent to the contra rotating pair of propellers, one of the contra rotating propellers i.e. P5-1 or P5-2 cannot be shut down. Though shutting down P5-1 or P5-2 can result in immediate yaw stability, it will result in problem in navigating the UAV 200. Therefore, it is proposed not to shut one of the pair of contra rotating propellers, and maintain yaw stability by reducing RPMs of the rotors/propellers adjacent to the failed propeller i.e. P2 and P4 in case of failure of P3 or P1 and P3 in case of failure of P2. Since both of such propellers/rotors are rotating in direction opposite to the failed propeller, reducing their RPM can result in compensating torque of failed propeller/rotor and thereby contribute to yaw stability. Simultaneously, for same reason, RPMs of a propeller out of pair of contra rotating propellers and another propeller on its adjacent arm, that are rotating in same direction as the failed propeller(i.e. P5-1 and P1 in case of failure of P2; or P5-2 and P4 in case of failure of P3) can be increased. In addition, RPMs of the contra rotating propellers can be adjusted such that the net torque about the body frame of the AV is zero. These actions can result in establishing yaw stability after mid-air failure of a rotor/propeller such as P2 or P3. In addition, adjustment of RPMs of the contra rotating propellers can also be used for yaw movement of the UAV 200 and thereby navigating the UAV 200 in different directions (refer to paragraph below).

(24) Thus, with this configuration after mid-air failure of a rotor/propeller that is not adjacent to the arm having pair of contra rotating propellers, UAV 200 shall be capable of controlled pitch in both positive and negative directions but shall have controlled yaw only in one direction either positive or negative about axis perpendicular to failed rotor depending on configuration of the failed rotor/propeller. Movement of the UAV 200 in any other direction such as direction opposite to the failed rotor/propeller can be enabled by making an appropriate yaw movement such as by 180 degree for movement in opposite direction, and then proceeding. This is because movement of the UAV in any other direction with fixed yaw would not be possible as that shall make the net torque non-zero. Thus, it will be capable of maintaining the assigned mission with complete control in the axis along the failed rotor direction by adjusting the RPMs of the remaining rotors.

(25) In an embodiment, if total number of propellers is an odd number (which is possible in case an even number of arms such as two arms incorporate pairs of coaxial contra rotating propellers), one of the propellers of the pair of contra rotating propellers can be kept off under normal conditions so as to meet limitations of the configuration described above, i.e. having even number of functional rotors under normal condition—half of them rotating in one direction and other half in opposite direction thus providing yaw stability. Principles underlying the present disclosure can still be applied to maintain stability of the AV with additional benefit that the propeller that is kept off under normal condition can be made operational in certain conditions. Besides, the contra rotating propellers can be positioned judiciously so that more arms that have a single propeller are adjacent to an arm having a pair of contra rotating propellers.

(26) It is to be appreciated that while the embodiments of the present disclosure have been explained with fixed pitch propeller mechanism, principle of the disclosure can be implemented with a variable pitch propeller system as well without any limitation whatsoever.

(27) It is contemplated that various combinations and/or sub-combinations of the specific features and aspects of the above embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments may be combined with or substituted for one another in order to form varying modes of the disclosed invention. Further it is intended that the scope of the present invention herein disclosed by way of examples should not be limited by the particular disclosed arrangements described above.

(28) While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION

(29) The present disclosure provides a reliable and cost effective multi-rotor rigid frame Aerial Vehicle.

(30) The present disclosure provides a multi-rotor Aerial Vehicle with in built single arm failure redundancy so as to improve its reliability.

(31) The present disclosure provides single arm failure redundancy in a multi-rotor Aerial Vehicle keeping number of rotors to a minimum.

(32) The present disclosure provides inbuilt single arm failure redundancy that takes care of lift, yaw, pitch and roll requirements of the multi-propeller UAV.