Patent Description:
Aircrafts are typically driven by a propulsion system having a fuel-powered engine, such as a reciprocating engine and/or a turbine engine. These engines generally ignite fuel to provide power to propel the aircraft. Such fuel-powered systems may be expensive to operate and/or maintain, emit higher levels of noise during operation, and/or have a harmful effect on the environment.

<CIT> discloses a purebred and hybrid electric Vertical Takeoff and Landing ("VTOL") tilt rotor aircraft. Contemplated VTOL aircraft can include one or more electrical energy stores capable of delivering electrical power to one or more electric motors disposed within one or more rotor housings, where the motors can drive the rotors. The VTOL aircraft can also include one or more sustainer energy/power sources (e.g., batteries, engines, generators, fuel-cells, semi-cells, etc.) capable of driving the motors should the energy stores fail or deplete. Various VTOL configurations are presented including an all-battery purebred design, a light hybrid design, and a heavy hybrid design. The contemplated configurations address safety, noise, and outwash concerns to allow such designs to operate in built-up areas while retaining competitive performance relative to existing aircraft.

In some instances, it may be desirable to provide an electric propulsion system for aircrafts, such as mutli-rotor aircraft, instead of a fuel-powered propulsion system. Such electric propulsion systems use electricity instead of fuel to propel the aircraft, which may decrease costs for operating and/or maintaining the system, decrease noise emitted from the system, and/or decrease the effect on the environment. Accordingly, an electronic propulsion system is described herein for operating aircrafts, such as a multi-rotor aircraft.

Aspects of the present disclosure provide an aircraft comprising a plurality of rotors and a propulsion system and a method of operating a propulsion system as defined in the appended claims. Optional features are defined in the dependent claims.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.

For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:.

Referring now to <FIG> and <FIG>, an exemplary tiltrotor aircraft <NUM> is shown that includes ducted rotors (or fans). The tiltrotor aircraft <NUM> is convertible between a helicopter mode (shown in <FIG>), which allows for vertical takeoff and landing, hovering, and low speed directional movement, and an airplane mode (shown in <FIG>), which allows for forward flight as well as horizontal takeoff and landing. Aircraft <NUM> comprises a fuselage <NUM> with a fixed wing <NUM> that extends therefrom and a plurality of rotatable ducts <NUM>. Each duct <NUM> houses a power plant for driving an attached rotor <NUM> in rotation. Each rotor <NUM> has a plurality of blades <NUM> configured to rotate within ducts <NUM>.

In the illustrated version, aircraft <NUM> is configured with four ducts <NUM>, including a first duct 107a and a second duct 107b that form a forward pair of ducts and a third duct 107c and a fourth duct 107d that form an aft pair of ducts. Each duct <NUM> is rotatably coupled to fuselage <NUM> of aircraft <NUM> via a spindle. Ducts 107a and 107b are coupled directly to fuselage <NUM> by a respective spindle <NUM>. Ducts 107c and 107d are each independently coupled to a corresponding end of wing <NUM> via a respective spindle <NUM>. As shown, each of ducts 107c and 107d includes a winglet <NUM> that is coupled thereto. It should be appreciated that aircraft <NUM> is not limited to the illustrated configuration having four ducts <NUM>, and that aircraft <NUM> may alternatively be implemented with more or fewer ducts <NUM>.

The position of ducts <NUM>, and optionally the pitch of blades <NUM>, can be selectively controlled to control direction, thrust, and lift of rotors <NUM>. For example, ducts <NUM> are repositionable to convert aircraft <NUM> between a helicopter mode and an airplane mode. As shown in <FIG>, ducts <NUM> are positioned such that aircraft <NUM> is in helicopter mode, which allows for vertical takeoff and landing, hovering, and low-speed directional movement. As shown in <FIG>, ducts <NUM> are positioned such that aircraft <NUM> is in airplane mode, which allows for high-speed forward-flight. In particular, in airplane mode, ducts <NUM> direct their respective thrusts in the aft direction to propel aircraft <NUM>. Aircraft <NUM> is operable to fly in all directions during the vertical takeoff and landing (i.e., helicopter) mode configuration of <FIG>, although faster forward flight is achievable while in the forward flight (i.e., airplane) mode configuration of <FIG>. Ducts <NUM> may be tiltable between the vertical and horizontal positions by spindles <NUM>, <NUM>, which are rotatable in response to commands originating from a pilot and/or a flight control system of the aircraft <NUM>.

Rotors <NUM> of aircraft <NUM> can be driven by a redundant electric propulsion system to provide propulsion to aircraft <NUM>. Such a redundant electric propulsion system can include a propulsion control system for controlling movement of rotors <NUM> and a power system for providing power to the propulsion control system. The propulsion control system can include at least two electric motors coupled with each rotor <NUM> to provide redundancy in driving each respective rotor <NUM>. Each electric motor can include an overrun clutch for coupling the respective electric motor with the respective rotor <NUM>. This may mitigate jamming of the respective electric motor, as will be discussed in more detail below. The propulsion control system can further include a propulsion control unit for each electric motor to actuate the respective electric motor based on a desired torque level provided by a flight control system. The power system can include a battery for each propulsion control unit and each electric motor to provide power to the respective propulsion control units and electric motors. In some versions, each propulsion control unit and each battery are coupled with a pair of electric motors positioned on opposite sides of aircraft <NUM>. This may provide a distributed propulsion system for aircraft <NUM> such that a failure of a single component of the redundant electric system inhibits aircraft un-balance and/or loss of control, as will be discussed in more detail below.

Referring to <FIG>, a preferred embodiment of an exemplary redundant electric propulsion system <NUM> is shown having a propulsion control system and a power system to provide propulsion to aircraft <NUM> (see <FIG>). The propulsion control system of system <NUM> includes at least two electric motors <NUM> coupled with each rotor <NUM> to provide redundancy in driving each respective rotor <NUM>. In the illustrated version, each electric motor <NUM> interface to a gearbox <NUM> of a rotor <NUM> via an over-run clutch <NUM>. The propulsion control system further includes a Propulsion Motor Control Electronic unit (PMCE) <NUM> for actuating each electric motor <NUM> based on a desired torque level provided by a Flight Control Computer (FCC) <NUM>. The power system of system <NUM> includes a battery <NUM> for providing power to each PMCE <NUM> and electric motors <NUM>. In the illustrated version, one PMCE <NUM> and one battery <NUM> feed two electric motors <NUM> located at opposite sides of aircraft <NUM> (see <FIG>), as will be discussed in more detail below.

As shown in <FIG>, system <NUM> comprises at least one electric motor <NUM>, a propulsion motor control <NUM>, and a flight control <NUM>. The at least one electric motor <NUM> is coupled with at least one duct <NUM> of aircraft <NUM> (see <FIG>) for driving rotor <NUM> of the at least one duct <NUM>. In the illustrated version, each duct <NUM> is coupled with a plurality of electric motors <NUM>, such as three electric motors <NUM>. Any two or more of the plurality of motors <NUM> is configured to drive the attached rotor <NUM> of a respective duct <NUM> via a gearbox <NUM>. This may provide a triple redundancy for operating a respective rotor <NUM> such that rotor <NUM> may continue to be driven in the event of a failure of a motor <NUM>. Each motor <NUM> of the illustrated version comprises an overrun clutch <NUM> for mechanically coupling each motor <NUM> with a respective gearbox <NUM>. Each overrun clutch <NUM> is configured to transmit torque from a respective motor <NUM> to rotor <NUM> in only one direction and permits rotor <NUM> to freewheel, or continue rotating, when the respective motor <NUM> is rotating at a slower speed than rotor <NUM> and/or is stopped. Overrun clutch <NUM> may thereby mitigate motor jam of system <NUM>.

Accordingly, first duct 107a includes a first motor 122a<NUM> coupled to a first gearbox 121a via a first overrun clutch 123a<NUM>, a second motor 122a<NUM> coupled to first gearbox 121a via a second overrun clutch 123a<NUM>, and a third motor 122a<NUM> coupled to first gearbox 121a via a third overrun clutch 123a<NUM>. Second duct 107b includes a first motor 122b<NUM> coupled to a second gearbox 121b via a first overrun clutch 123b<NUM>, a second motor 122b<NUM> coupled to second gearbox 121b via a second overrun clutch 123b<NUM>, and a third motor 122b<NUM> coupled to second gearbox 121b via a third overrun clutch 123b<NUM>. Third duct 107c includes a first motor 122c<NUM> coupled to a third gearbox 121c via a first overrun clutch 123c<NUM>, a second motor 122c<NUM> coupled to third gearbox 121c via a second overrun clutch 123c<NUM>, and a third motor 122c<NUM> coupled to third gearbox 121c via a third overrun clutch 123c<NUM>. Fourth duct 107d includes a first motor 122d<NUM> coupled to a fourth gearbox 121d via a first overrun clutch 123d<NUM>, a second motor 122d<NUM> coupled to fourth gearbox 121d via a second overrun clutch 123d<NUM>, and a third motor 122d<NUM> coupled to fourth gearbox 121d via a third overrun clutch 123d<NUM>. Still other suitable configurations for ducts <NUM> can be used. For instance, each duct <NUM> may alternatively be implemented with more or fewer motors <NUM> and/or overrun clutches <NUM>. For example, the redundant propulsion system described herein would be easily adaptable to any electric aircraft with an even number of rotors such as six, eight or more.

Propulsion motor control <NUM> is electrically coupled with motors <NUM> to actuate motors <NUM>. Propulsion motor control <NUM> of the illustrated version comprises one or more Propulsion Motor Control Electronic units (PMCE) <NUM> and one or more batteries <NUM>. Each PMCE <NUM> includes a processor having a command module (COM) that is electrically connected with one or more motors <NUM> of one or more ducts <NUM> such that each PMCE <NUM> is configured to send and/or receive signals from the one or more motors <NUM>. Each battery <NUM> is electrically connected with one or more PMCEs <NUM> and/or motors <NUM> such that each battery <NUM> is configured to provide power to the one or more PMCEs <NUM> and/or motors <NUM>. For instance, each battery <NUM> may provide about <NUM> Volts to a respective PMCE <NUM> and/or about <NUM> Volts to a respective motor <NUM>, though any other suitable amounts of power can be used.

In the illustrated version, each PMCE <NUM> is coupled with two motors <NUM> that are diagonally positioned relative to each other such that one PMCE <NUM> is coupled with a motor <NUM> of a duct 107a, 107b in the forward position on one side of aircraft <NUM> (see <FIG>) and with a motor <NUM> of a duct 107c, 107d in the aft position on an opposite side of aircraft <NUM> (see <FIG>). Accordingly, if one PMCE <NUM> fails, the effected motors <NUM> of such a failure are distributed on opposite sides of aircraft <NUM> (see <FIG>). One battery <NUM> of the illustrated version is also coupled with two motors <NUM> that are diagonally positioned relative to each other such that one battery <NUM> is coupled with a motor <NUM> of a duct 107a, 107b in the forward position on one side of aircraft <NUM> (see <FIG>) and with a motor <NUM> of a duct 107c, 107d in the aft position on an opposite side of aircraft <NUM> (see <FIG>). Accordingly, if one battery <NUM> fails, the effected motors <NUM> of such a failure are distributed on opposite sides of aircraft <NUM> (see <FIG>). This may inhibit aircraft un-balance or loss of control in the event of a failure of a component of propulsion motor control <NUM>.

Accordingly, as shown in <FIG>, a first PMCE 132a is coupled with first motor 122b<NUM> of second duct 107b and first motor 122c<NUM> of third duct 107c. A first battery 134a is then coupled with first PMCE 132a and first motors 122b<NUM>, 122c<NUM>. A second PMCE 132b is coupled with second motor 122b<NUM> of second duct 107b and second motor 122c<NUM> of third duct 107c. A second battery 134b is then coupled with second PMCE 132b and second motors 122b<NUM>, 122c<NUM>. A third PMCE 132c is coupled with third motor 122b<NUM> of second duct 107b and third motor 122c<NUM> of third duct 107c. A third battery 134c is then coupled with third PMCE 132c and third motors 122b<NUM>, 122c<NUM>. A fourth PMCE 132d is coupled with first motor 122a<NUM> of first duct 107a and first motor 122d<NUM> of fourth duct 107d. A fourth battery 134d is then coupled with fourth PMCE 132d and first motors 122a<NUM>, 122d<NUM>. A fifth PMCE 132e is coupled with second motor 122a<NUM> of first duct 107a and second motor 122d<NUM> of fourth duct 107d. A fifth battery 134e is then coupled with fifth PMCE 132e and second motors 122a<NUM>, 122d<NUM>. A sixth PMCE 132f is coupled with third motor 122as of first duct 107a and third motor 122d<NUM> of fourth duct 107d. A sixth battery 134f is then coupled with sixth PMCE 132f and third motors 122a<NUM>, 122d<NUM>. Still other suitable configurations for propulsion motor control <NUM> can be used. For instance, propulsion motor control <NUM> may alternatively be implemented with more or fewer PMCEs <NUM> and/or batteries <NUM>. Further, components of propulsion motor control <NUM> may be housed in a single enclosure or alternatively in two or more separate enclosures.

Flight control <NUM> is electrically connected with propulsion motor control <NUM> to transmit a desired torque or speed to propulsion motor control <NUM> for actuating motors <NUM> to drive rotors <NUM> at the desired torque or speed. Flight control <NUM> can further be configured to control the direction, thrust, and/or lift of ducts <NUM>. As shown in <FIG>, flight control <NUM> comprises a first FCC 142a and a second FCC 142b that each include a processor having a command module (COM) and a monitoring module (MON) that is electrically connected one or more PMCEs <NUM> of propulsion motor control <NUM> such that each FCC <NUM> is configured to send, receive, and/or monitor signals from the one or more PMCEs <NUM>. While each FCC <NUM> is shown as being coupled with each PMCE <NUM>, other suitable configurations for flight control <NUM> can be used. For instance, flight control <NUM> may alternatively be implemented with more or fewer FCCs <NUM>. Further, components of flight control <NUM> may be housed in a single enclosure or alternatively in two or more separate enclosures.

In some versions, system <NUM> is configured to inhibit failure of system <NUM> by providing components that are dissimilar from each other, such as having different types of parts and/or being provided by different manufacturers. For instance, first and second FCCs 142a, 142b may include one or more components that differ from each other to provide a dual dissimilar flight control <NUM>. Propulsion motor control <NUM> may also include PMCEs <NUM> having one or more components that differ from each other. In the illustrated version, first and fourth PMCEs 132a, 132d may include one or more components that differ from second and fifth PMCEs 132b, 132e, which may include one or more components that differ from third and sixth PMCEs 132c, 132f to provide a triple dissimilar propulsion. Likewise, first motors 122a<NUM>, 122b<NUM>, 122c<NUM>, 122d<NUM> may include one or more components that differ from second motors 122a<NUM>, 122b<NUM>, 122c<NUM>, 122d<NUM>, which may include one or more components that differ from third motors 122as, 122b<NUM>, 122c<NUM>, 122d<NUM>. Still other suitable configurations for system <NUM> will be apparent to one with ordinary skill in the art in view of the teachings herein. Referring to <FIG>, a method <NUM> is shown for operating redundant electric propulsion system <NUM> to control propulsion of ducts <NUM> of aircraft <NUM> (see <FIG>). Method <NUM> comprises a step <NUM> of transmitting a desired torque level, such as a desired speed and/or revolutions per minute (rpm) for the rotors <NUM> and/or motors <NUM>, from flight control <NUM> to propulsion motor control <NUM>. For instance, one or more FCCs <NUM> of flight control <NUM> may transmit the desired torque level to one or more PMCEs <NUM> of propulsion motor control <NUM>. In the illustrated version, each of first and second FCCs 142a, 142b is configured to transmit the desired torque level to each PMCE <NUM>. Method <NUM> further comprises a step <NUM> of actuating motors <NUM> to drive a respective rotor <NUM> based on the desired torque level via propulsion motor control <NUM>, to provide propulsion of the aircraft <NUM>. The PMCEs <NUM> of propulsion motor control <NUM> actuate the motors <NUM> based on the desired torque level. Each PMCE <NUM> is configured to actuate a pair of motors <NUM>, one motor <NUM> in a forward duct 107a, 107b and one motor <NUM> in an aft duct 107c, 107d on an opposite side of the aircraft to the other motor. System <NUM> can be configured to transmit one or more desired torque levels such that rotors <NUM> can be operated at the same torque level and/or one or more rotors <NUM> can be operated at a varying torque level relative to the other rotors <NUM>.

In some versions, ducts <NUM> and/or motors <NUM> include one or more sensors (not shown) that are configured to measure one or more drive characteristics of rotors <NUM> and/or motors <NUM>, such as a torque, a speed, a temperature, a pitch angle, a thrust, a position, and/or other drive characteristic. Accordingly, method <NUM> may include a step <NUM> to measure one or more drive characteristics of rotors <NUM> and/or motors <NUM>. For instance, system <NUM> can be configured to transmit the measured drive characteristic to PMCEs <NUM> of propulsion motor control <NUM> and/or FCCs <NUM> of flight control <NUM> to provide a closed-loop propulsion control. Method <NUM> may further include a step <NUM> of analyzing the measured drive characteristic. For instance, propulsion motor control <NUM> and/or flight control <NUM> can be configured to analyze the measured drive characteristic. Accordingly, propulsion motor control <NUM> and/or flight control can determine whether rotors <NUM> and/or motors <NUM> are sufficiently operating at the desired torque level and/or whether a fault, such as a discrepancy and/or failure, of one or more of components of system <NUM> has occurred.

As shown in Table <NUM> below, system <NUM> can be configured to detect a fault of one or more of components of system <NUM>. For instance, whether a gearbox <NUM>, a rotor <NUM>, a motor <NUM>, and/or a clutch <NUM> has jammed, disconnected, and/or failed. System <NUM> can also be configured to determine whether one or more of sensors, PMCEs <NUM>, batteries <NUM>, and/or FCCs <NUM> has an error and/or has failed. These faults can have an immediate effect on system <NUM> and/or aircraft <NUM> (see <FIG>). Some examples of such effects are provided in Table <NUM>. System <NUM> can then be configured to provide a system response based on the detected fault to have an aircraft level effect to thereby minimize the criticality of the fault. For instance, in the event of a motor, sensor, clutch, PMCE, and/or battery failure on one rotor <NUM>, system <NUM> can adjust power on the remaining rotor motors in order to re-establish control to minimize the criticality of such failure to a major hazard at the aircraft level. In the event of a motor and/or FCC fault, system <NUM> can reduce the thrust margin on the one rotor and/or provide commands via the healthy FCC to minimize the criticality of such fault to a minor hazard at the aircraft level. Still other suitable faults will be apparent to one with ordinary skill in the art in view of the teachings herein.

Method <NUM> may comprise a step <NUM> of adjusting the desired torque level based on the analyzed drive characteristic. For instance, propulsion motor control <NUM> and/or flight control <NUM> can adjust the desired torque level by increasing or decreasing the desired torque level to actuate motors <NUM> based on the analyzed drive characteristic. Propulsion motor control <NUM> and/or flight control <NUM> can further adjust operation of system <NUM> based on whether a fault has been detected for one or more of components of system <NUM>. For instance, propulsion motor control <NUM> and/or flight control <NUM> can be configured to disconnect and/or shutdown a motor <NUM> in the event of a fault in the propulsion control of such a motor <NUM>. Propulsion motor control <NUM> and/or flight control <NUM> can further be configured to adjust the desired torque levels of the remaining rotors <NUM> and/or motors <NUM> that have not been disconnected and/or shutdown. In some versions, system <NUM> is configured to provide an alert upon the detection of a fault of system <NUM>. Still other suitable methods for operating system <NUM> will be apparent to one with ordinary skill in the art in view of the teachings herein.

Accordingly, the redundancy provided by system <NUM> is configured to inhibit a catastrophic failure of aircraft <NUM> in the event of a failure of a single component of system <NUM>, apart from a rotor <NUM> separation, such that a failure of any component of system <NUM> does not cause aircraft <NUM> to un-balance or experience a loss of control. System <NUM> is further configured to provide a minimum number of control units and/or computational lanes to lower the cost of system <NUM> while allowing sufficient functional independence and safety of system <NUM>. Accordingly, system <NUM> may be lightweight to improve the efficiency of aircraft <NUM>.

Claim 1:
An aircraft (<NUM>) comprising a plurality of rotors (<NUM>) and a propulsion system (<NUM>) for controlling propulsion of the aircraft (<NUM>), wherein the propulsion system (<NUM>) comprises:
a plurality of electric motors (<NUM>) including for each rotor (<NUM>) of the plurality of rotors, two or more electric motors coupled therewith, for driving the rotors;
a propulsion motor control (<NUM>) comprising:
a plurality of propulsion control units (<NUM>), wherein each propulsion control unit (<NUM>) is electrically coupled to a pair of electric motors of the plurality of electric motors (<NUM>), wherein one of the electric motors of the pair of electric motors is coupled with a first rotor and wherein the other of the electric motors of the pair of electric motors is coupled with a second rotor positioned on an opposite side of the aircraft relative to the first rotor, wherein each propulsion control unit (<NUM>) is configured to actuate a respective pair of the electric motors (<NUM>), and
at least one battery (134a-f) electrically connected with at least one of the plurality of propulsion control units (<NUM>) of the propulsion motor control (<NUM>) and at least one electric motor of the plurality of electric motors (<NUM>), wherein the at least one battery (134a-f) is configured to provide power to the at least one propulsion control unit and the at least one electric motor; and
a flight control (<NUM>) coupled with the plurality of propulsion control units (<NUM>), wherein the flight control (<NUM>) is configured to transmit a desired torque level to the plurality of propulsion control units (<NUM>);
wherein the propulsion motor control (<NUM>) is configured to actuate the plurality of electric motors (<NUM>) based on the desired torque level to drive each rotor (<NUM>) to provide propulsion of the aircraft (<NUM>).