Patent Publication Number: US-11661185-B2

Title: Redundant electric propulsion system

Description:
TECHNICAL FIELD 
     The present disclosure is directed to in general to the field of aircraft and, more particularly, though not exclusively, to a redundant electric propulsion system for use in connection with such aircraft. 
     BACKGROUND OF THE INVENTION 
     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. 
     BRIEF SUMMARY OF THE INVENTION 
     In some instances, it may be desirable to provide an electric propulsion system for aircrafts, such as mutli-rotor aircrafts, 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. 
     In one embodiment, a propulsion system for controlling propulsion of an aircraft having two or more rotors can comprise: a plurality of electric motors coupled with each rotor of the two or more rotors for driving the two or more rotors, a propulsion motor control, and a flight control. The propulsion motor control can comprise at least one propulsion control unit electrically connected with at least one electric motor of the plurality of electric motors, wherein the at least one propulsion control unit is configured to actuate the at least one electric motor, and at least one battery electrically connected with the at least one propulsion control unit of the propulsion motor control and at least one electric motor of the plurality of electric motors, wherein the at least one battery is configured to provide power to the at least one propulsion control unit and the at least one electric motor. The flight control is coupled with the least one propulsion control unit and is configured to transmit a desired torque level to the at least one propulsion control unit. The propulsion motor control is configured to actuate the plurality of electric motors based on the desired torque level to drive two or more rotors to provide propulsion of the aircraft. 
     In another embodiment, a method of operating a propulsion system for controlling propulsion of an aircraft having two or more rotors, wherein the propulsion system comprises a plurality of electric motors coupled with each rotor of the two or more rotors, a propulsion motor control having at least one propulsion control unit electrically connected with at least one electric motor of the plurality of electric motors and at least one battery electrically connected with the at least one propulsion control unit of the propulsion motor control and at least one electric motor of the plurality of electric motors, and a flight control coupled with the propulsion motor control, can comprise the steps of: transmitting a desired torque level from the flight control to the propulsion motor control; and actuating the plurality of electric motors via the propulsion motor control based on the desired torque level to drive each rotor to provide propulsion of the aircraft. 
     In another embodiment, a propulsion system for providing propulsion for an aircraft can comprise: a plurality of electric motors coupled with at least one rotor of the aircraft such that each electric motor of the plurality of electric motors is configured to drive the at least one rotor; and a propulsion motor control electrically connected with each electric motor of the plurality of electric motors. The propulsion motor control is configured to actuate each electric motor of the plurality of electric motors based on a desired torque level. The plurality of electric motors are configured to drive the at least one rotor based on the desired torque level to provide propulsion of the aircraft. 
     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. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG.  1    is a perspective view of an exemplary tiltrotor aircraft, showing the aircraft operating in a helicopter mode. 
         FIG.  2    is a perspective view of the aircraft of  FIG.  1   , showing the aircraft operating in an airplane mode. 
         FIG.  3    is a schematic of an exemplary redundant electric propulsion system that may be incorporated into the aircraft of  FIG.  1    for controlling the propulsion of the aircraft. 
         FIG.  4    is a schematic of an exemplary method of operating the redundant electronic propulsion system of  FIG.  3   . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIGS.  1  and  2   , an exemplary tiltrotor aircraft  101  is shown that includes ducted rotors (or fans). The tiltrotor aircraft  101  is convertible between a helicopter mode (shown in  FIG.  1   ), which allows for vertical takeoff and landing, hovering, and low speed directional movement, and an airplane mode (shown in  FIG.  2   ), which allows for forward flight as well as horizontal takeoff and landing. Aircraft  101  comprises a fuselage  103  with a fixed wing  105  that extends therefrom and a plurality of rotatable ducts  107 . Each duct  107  houses a power plant for driving an attached rotor  109  in rotation. Each rotor  109  has a plurality of blades  111  configured to rotate within ducts  107 . 
     In the illustrated version, aircraft  101  is configured with four ducts  107 , including a first duct  107   a  and a second duct  107   b  that form a forward pair of ducts and a third duct  107   c  and a fourth duct  107   d  that form an aft pair of ducts. Each duct  107  is rotatably coupled to fuselage  103  of aircraft  101  via a spindle. Ducts  107   a  and  107   b  are coupled directly to fuselage  103  by a respective spindle  113 . Ducts  107   c  and  107   d  are each independently coupled to a corresponding end of wing  105  via a respective spindle  115 . As shown, each of ducts  107   c  and  107   d  includes a winglet  117  that is coupled thereto. It should be appreciated that aircraft  101  is not limited to the illustrated configuration having four ducts  107 , and that aircraft  101  may alternatively be implemented with more or fewer ducts  107 . 
     The position of ducts  107 , and optionally the pitch of blades  111 , can be selectively controlled to control direction, thrust, and lift of rotors  109 . For example, ducts  107  are repositionable to convert aircraft  101  between a helicopter mode and an airplane mode. As shown in  FIG.  1   , ducts  107  are positioned such that aircraft  101  is in helicopter mode, which allows for vertical takeoff and landing, hovering, and low-speed directional movement. As shown in  FIG.  2   , ducts  107  are positioned such that aircraft  101  is in airplane mode, which allows for high-speed forward-flight. In particular, in airplane mode, ducts  107  direct their respective thrusts in the aft direction to propel aircraft  101 . Aircraft  101  is operable to fly in all directions during the vertical takeoff and landing (i.e., helicopter) mode configuration of  FIG.  1   , although faster forward flight is achievable while in the forward flight (i.e., airplane) mode configuration of  FIG.  2   . Ducts  107  may be tiltable between the vertical and horizontal positions by spindles  113 ,  115 , which are rotatable in response to commands originating from a pilot and/or a flight control system of the aircraft  101 . 
     Rotors  109  of aircraft  101  can be driven by a redundant electric propulsion system to provide propulsion to aircraft  101 . Such a redundant electric propulsion system can include a propulsion control system for controlling movement of rotors  109  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  109  to provide redundancy in driving each respective rotor  109 . Each electric motor can include an overrun clutch for coupling the respective electric motor with the respective rotor  109 . 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  101 . This may provide a distributed propulsion system for aircraft  101  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.  3   , a preferred embodiment of an exemplary redundant electric propulsion system  120  is shown having a propulsion control system and a power system to provide propulsion to aircraft  101  (see  FIG.  1   ). The propulsion control system of system  120  includes at least two electric motors  122  coupled with each rotor  109  to provide redundancy in driving each respective rotor  109 . In the illustrated version, each electric motor  122  interface to a gearbox  121  of a rotor  109  via an over-run clutch  123 . The propulsion control system further includes a Propulsion Motor Control Electronic unit (PMCE)  132  for actuating each electric motor  122  based on a desired torque level provided by a Flight Control Computer (FCC)  142 . The power system of system  120  includes a battery  134  for providing power to each PMCE  132  and electric motors  122 . In the illustrated version, one PMCE  132  and one battery  134  feed two electric motors  122  located at opposite sides of aircraft  101  (see  FIG.  1   ), as will be discussed in more detail below. 
     As shown in  FIG.  3   , system  120  comprises at least one electric motor  122 , a propulsion motor control  130 , and a flight control  140 . The at least one electric motor  122  is coupled with at least one duct  107  of aircraft  101  (see  FIG.  1   ) for driving rotor  109  of the at least one duct  107 . In the illustrated version, each duct  107  is coupled with a plurality of electric motors  122 , such as three electric motors  122 . Any two or more of the plurality of motors  122  is configured to drive the attached rotor  109  of a respective duct  107  via a gearbox  121 . This may provide a triple redundancy for operating a respective rotor  109  such that rotor  109  may continue to be driven in the event of a failure of a motor  122 . Each motor  122  of the illustrated version comprises an overrun clutch  123  for mechanically coupling each motor  122  with a respective gearbox  121 . Each overrun clutch  123  is configured to transmit torque from a respective motor  122  to rotor  109  in only one direction and permits rotor  109  to freewheel, or continue rotating, when the respective motor  122  is rotating at a slower speed than rotor  109  and/or is stopped. Overrun clutch  123  may thereby mitigate motor jam of system  120 . 
     Accordingly, first duct  107   a  includes a first motor  122   a   1  coupled to a first gearbox  121   a  via a first overrun clutch  123   a   1 , a second motor  122   a   2  coupled to first gearbox  121   a  via a second overrun clutch  123   a   2 , and a third motor  122   a   3  coupled to first gearbox  121   a  via a third overrun clutch  123   a   3 . Second duct  107   b  includes a first motor  122   b   1  coupled to a second gearbox  121   b  via a first overrun clutch  123   b   1 , a second motor  122   b   2  coupled to second gearbox  121   b  via a second overrun clutch  123   b   2 , and a third motor  122   b   3  coupled to second gearbox  121   b  via a third overrun clutch  123   b   3 . Third duct  107   c  includes a first motor  122   c   1  coupled to a third gearbox  121   c  via a first overrun clutch  123   c   1 , a second motor  122   c   2  coupled to third gearbox  121   c  via a second overrun clutch  123   c   2 , and a third motor  122   c   2  coupled to third gearbox  121   c  via a third overrun clutch  123   c   3 . Fourth duct  107   d  includes a first motor  122   d   1  coupled to a fourth gearbox  121   d  via a first overrun clutch  123   d   1 , a second motor  122   d   2  coupled to fourth gearbox  121   d  via a second overrun clutch  123   d   2 , and a third motor  122   d   2  coupled to fourth gearbox  121   d  via a third overrun clutch  123   d   3 . Still other suitable configurations for ducts  107  can be used. For instance, each duct  107  may alternatively be implemented with more or fewer motors  122  and/or overrun clutches  123 . 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  130  is electrically coupled with motors  122  to actuate motors  122 . Propulsion motor control  130  of the illustrated version comprises one or more Propulsion Motor Control Electronic units (PMCE)  132  and one or more batteries  134 . Each PMCE  132  includes a processor having a command module (COM) that is electrically connected with one or more motors  122  of one or more ducts  107  such that each PMCE  132  is configured to send and/or receive signals from the one or more motors  122 . Each battery  134  is electrically connected with one or more PMCEs  132  and/or motors  122  such that each battery  134  is configured to provide power to the one or more PMCEs  132  and/or motors  122 . For instance, each battery  134  may provide about 28 Volts to a respective PMCE  132  and/or about 600 Volts to a respective motor  122 , though any other suitable amounts of power can be used. 
     In the illustrated version, each PMCE  132  is coupled with two motors  122  that are diagonally positioned relative to each other such that one PMCE  132  is coupled with a motor  122  of a duct  107   a ,  107   b  in the forward position on one side of aircraft  101  (see  FIG.  1   ) and with a motor  122  of a duct  107   c ,  107   d  in the aft position on an opposite side of aircraft  101  (see  FIG.  1   ). Accordingly, if one PMCE  132  fails, the effected motors  122  of such a failure are distribute on opposite sides of aircraft  101  (see  FIG.  1   ). One battery  134  of the illustrated version is also coupled with two motors  122  that are diagonally positioned relative to each other such that one battery  134  is coupled with a motor  122  of a duct  107   a ,  107   b  in the forward position on one side of aircraft  101  (see  FIG.  1   ) and with a motor  122  of a duct  107   c ,  107   d  in the aft position on an opposite side of aircraft  101  (see  FIG.  1   ). Accordingly, if one battery  134  fails, the effected motors  122  of such a failure are distribute on opposite sides of aircraft  101  (see  FIG.  1   ). This may inhibit aircraft un-balance or loss of control in the event of a failure of a component of propulsion motor control  130 . 
     Accordingly, as shown in  FIG.  3   , a first PMCE  132   a  is coupled with first motor  122   b   1  of second duct  107   b  and first motor  122   c   1  of third duct  107   c . A first battery  134   a  is then coupled with first PMCE  132   a  and first motors  122   b   1 ,  122   c   1 . A second PMCE  132   b  is coupled with second motor  122   b   2  of second duct  107   b  and second motor  122   c   2  of third duct  107   c . A second battery  134   b  is then coupled with second PMCE  132   b  and second motors  122   b   2 ,  122   c   2 . A third PMCE  132   c  is coupled with third motor  122   b   3  of second duct  107   b  and third motor  122   c   3  of third duct  107   c . A third battery  134   c  is then coupled with third PMCE  132   c  and third motors  122   b   3 ,  122   c   3 . A fourth PMCE  132   d  is coupled with first motor  122   a   1  of first duct  107   a  and first motor  122   d   1  of fourth duct  107   d . A fourth battery  134   d  is then coupled with fourth PMCE  132   d  and first motors  122   a   1 ,  122   d   1 . A fifth PMCE  132   e  is coupled with second motor  122   a   2  of first duct  107   a  and second motor  122   d   2  of fourth duct  107   d . A fifth battery  134   e  is then coupled with fifth PMCE  132   e  and second motors  122   a   2 ,  122   d   2 . A sixth PMCE  132   f  is coupled with third motor  122   a   3  of first duct  107   a  and third motor  122   d   3  of fourth duct  107   d . A sixth battery  134   f  is then coupled with sixth PMCE  132   f  and third motors  122   a   3 ,  122   d   3 . Still other suitable configurations for propulsion motor control  130  can be used. For instance, propulsion motor control  130  may alternatively be implemented with more or fewer PMCEs  132  and/or batteries  134 . Further, components of propulsion motor control  130  may be housed in a single enclosure or alternatively in two or more separate enclosures. 
     Flight control  140  is electrically connected with propulsion motor control  130  to transmit a desired torque or speed to propulsion motor control  130  for actuating motors  122  to drive rotors  109  at the desired torque or speed. Flight control  140  can further be configured to control the direction, thrust, and/or lift of ducts  107 . As shown in  FIG.  3   , flight control  140  comprises a first FCC  142   a  and a second FCC  142   b  that each include a processor having a command module (COM) and a monitoring module (MON) that is electrically connected one or more PMCEs  132  of propulsion motor control  130  such that each FCC  142  is configured to send, receive, and/or monitor signals from the one or more PMCEs  132 . While each FCC  142  is shown as being coupled with each PMCE  132 , other suitable configurations for flight control  140  can be used. For instance, flight control  140  may alternatively be implemented with more or fewer FCCs  142 . Further, components of flight control  140  may be housed in a single enclosure or alternatively in two or more separate enclosures. 
     In some versions, system  120  is configured to inhibit failure of system  120  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  142   a ,  142   b  may include one or more components that differ from each other to provide a dual dissimilar flight control  140 . Propulsion motor control  130  may also include PMCEs  132  having one or more components that differ from each other. In the illustrated version, first and fourth PMCEs  132   a ,  132   d  may include one or more components that differ from second and fifth PMCEs  132   b ,  132   e , which may include one or more components that differ from third and sixth PMCEs  132   c ,  132   f  to provide a triple dissimilar propulsion. Likewise, first motors  122   a   1 ,  122   b   1 ,  122   c   1 ,  122   d   1  may include one or more components that differ from second motors  122   a   2 ,  122   b   2 ,  122   c   2 ,  122   d   2 , which may include one or more components that differ from third motors  122   a   3 ,  122   b   3 ,  122   c   3 ,  122   d   3 . Still other suitable configurations for system  120  will be apparent to one with ordinary skill in the art in view of the teachings herein. 
     Referring to  FIG.  4   , a method  150  is shown for operating redundant electric propulsion system  120  to control propulsion of ducts  107  of aircraft  101  (see  FIG.  1   ). Method  150  comprises a step  152  of transmitting a desired torque level, such as a desired speed and/or revolutions per minute (rpm) for a respective rotor  109  and/or motor  122 , from flight control  140  to propulsion motor control  130 . For instance, one or more FCCs  142  of flight control  140  may transmit the desired torque level to one or more PMCEs  132  of propulsion motor control  130 . In the illustrated version, each of first and second FCCs  142   a ,  142   b  is configured to transmit the desired torque level to each PMCE  132 . Method  150  further comprises a step  154  of actuating motors  122  to drive a respective rotor  109  based on the desired torque level via propulsion motor control  130 . For instance, one or more PMCEs  132  of propulsion motor control  130  can actuate one or more motors  122  based on the desired torque level. In the illustrated version, each PMCE  132  is configured to actuate a pair of motors  122 , one motor  122  in a forward duct  107   a ,  107   b  and one motor  122  in an aft duct  107   c ,  107   d . System  120  can be configured to transmit one or more desired torque levels such that rotors  109  can be operated at the same torque level and/or one or more rotors  109  can be operated at a varying torque level relative to the other rotors  109 . 
     In some versions, ducts  107  and/or motors  122  include one or more sensors (not shown) that are configured to measure one or more drive characteristics of rotors  109  and/or motors  122 , such as a torque, a speed, a temperature, a pitch angle, a thrust, a position, and/or other drive characteristic. Accordingly, method  150  may include a step  156  to measure one or more drive characteristics of rotors  109  and/or motors  122 . For instance, system  120  can be configured to transmit the measured drive characteristic to PMCEs  132  of propulsion motor control  130  and/or FCCs  142  of flight control  140  to provide a closed-loop propulsion control. Method  150  may further include a step  158  of analyzing the measured drive characteristic. For instance, propulsion motor control  130  and/or flight control  140  can be configured to analyze the measured drive characteristic. Accordingly, propulsion motor control  130  and/or flight control can determine whether rotors  109  and/or motors  122  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  120  has occurred. 
     As shown in Table 1 below, system  120  can be configured to detect a fault of one or more of components of system  120 . For instance, whether a gearbox  121 , a rotor  109 , a motor  122 , and/or a clutch  123  has jammed, disconnected, and/or failed. System  120  can also be configured to determine whether one or more of sensors, PMCEs  132 , batteries  134 , and/or FCCs  142  has an error and/or has failed. These faults can have an immediate effect on system  120  and/or aircraft  101  (see  FIG.  1   ). Some examples of such effects are provided in Table 1. System  120  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  109 , system  120  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  120  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. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Redundant Electric Propulsion System Fault Isolation Table 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Single 
                 Immediate 
                   
                 System 
                 Aircraft 
                   
               
               
                 Part 
                 Fault 
                 Effect 
                 Detection 
                 Response 
                 Level Effect 
                 Criticality 
               
               
                   
               
               
                 Gearbox/ 
                 Jam 
                 Loss of one 
                 FCC Propulsion 
                 None possible 
                 Loss of one 
                 Catastrophic 
               
               
                 Rotor 
                   
                 duct out of 
                 Motor No 
                   
                 duct out of 
               
               
                 shaft 
                   
                 four 
                 Response monitor 
                   
                 four 
               
               
                   
                   
                   
                 trip on all three 
               
               
                   
                   
                   
                 motors on a given 
               
               
                   
                   
                   
                 duct 
               
               
                 Electric 
                 Jam 
                 Failed 
                 PMCE Current 
                 Power 
                 No thrust 
                 Major 
               
               
                 motor 
                   
                 motor can 
                 monitor trip (high 
                 adjusted on all 
                 margin on one 
               
               
                   
                   
                 no longer 
                 threshold) on 
                 remaining duct 
                 of the four 
               
               
                   
                   
                 transmit 
                 faulty motor and 
                 motors in 
                 ducts, 130- 
               
               
                   
                   
                 power to 
                 FCC Propulsion 
                 order to re- 
                 140% thrust 
               
               
                   
                   
                 rotor 
                 Motor No 
                 establish 
                 capability on 
               
               
                   
                   
                   
                 Response monitor 
                 control 
                 the remaining 
               
               
                   
                   
                   
                 trip on one motor 
                   
                 three ducts 
               
               
                   
                   
                   
                 on a given duct 
               
               
                 Electric 
                 Shaft 
                 Failed 
                 PMCE Current 
                 Power 
                 No thrust 
                 Minor 
               
               
                 motor 
                 disconnect 
                 motor can 
                 monitor trip (low 
                 increased on 
                 margin on one 
               
               
                   
                   
                 no longer 
                 threshold) on 
                 the two other 
                 of the four 
               
               
                   
                   
                 transmit 
                 faulty motor 
                 duct motors 
                 ducts, 130- 
               
               
                   
                   
                 power to 
                   
                   
                 140% thrust 
               
               
                   
                   
                 rotor 
                   
                   
                 capability on 
               
               
                   
                   
                   
                   
                   
                 the remaining 
               
               
                   
                   
                   
                   
                   
                 three ducts 
               
               
                 Electric 
                 Winding 
                 Max power 
                 Electric motor 
                 Current 
                 Reduced thrust 
                 Minor 
               
               
                 motor 
                 Open 
                 capability 
                 Phase Loss 
                 increased in 
                 margin on one 
               
               
                   
                   
                 reduced on 
                 monitor trip 
                 two other 
                 of the four 
               
               
                   
                   
                 failed 
                   
                 motor phases 
                 ducts 
               
               
                   
                   
                 motor due 
               
               
                   
                   
                 to lost 
               
               
                   
                   
                 phase 
               
               
                 Electric 
                 Winding 
                 Max power 
                 Electric motor 
                 Current 
                 Reduced thrust 
                 Minor 
               
               
                 motor 
                 Short 
                 capability 
                 Phase Loss 
                 increased in 
                 margin on one 
               
               
                   
                   
                 reduced on 
                 monitor trip 
                 two other 
                 of the four 
               
               
                   
                   
                 failed 
                   
                 motor phases 
                 ducts 
               
               
                   
                   
                 motor due 
               
               
                   
                   
                 to Back 
               
               
                   
                   
                 EMF 
               
               
                 Electric 
                 Position 
                 Failed 
                 FCC Propulsion 
                 Power 
                 No thrust 
                 Major 
               
               
                 motor 
                 Sensor 
                 motor 
                 Motor No 
                 adjusted on all 
                 margin on one 
               
               
                   
                 Disconnect 
                 cannot 
                 Response monitor 
                 remaining duct 
                 of the four 
               
               
                   
                   
                 properly 
                 or Underspeed 
                 motors in 
                 ducts, 130- 
               
               
                   
                   
                 commutate 
                 trip on one motor 
                 order to re- 
                 140% thrust 
               
               
                   
                   
                   
                 on a given duct 
                 establish 
                 capability on 
               
               
                   
                   
                   
                   
                 control 
                 the remaining 
               
               
                   
                   
                   
                   
                   
                 three ducts 
               
               
                 Electric 
                 Position 
                 Failed 
                 FCC Propulsion 
                 Power 
                 No thrust 
                 Major 
               
               
                 motor 
                 Sensor 
                 motor 
                 Motor No 
                 adjusted on all 
                 margin on one 
               
               
                   
                 Failed 
                 cannot 
                 Response monitor 
                 remaining duct 
                 of the four 
               
               
                   
                   
                 properly 
                 or Underspeed 
                 motors in 
                 ducts, 130- 
               
               
                   
                   
                 commutate 
                 trip on one motor 
                 order to re- 
                 140% thrust 
               
               
                   
                   
                   
                 on a given duct 
                 establish 
                 capability on 
               
               
                   
                   
                   
                   
                 control 
                 the remaining 
               
               
                   
                   
                   
                   
                   
                 three ducts 
               
               
                 Over-run 
                 Jam 
                 None, 
                 FCC IBIT test of 
                 N/A (IBIT and 
                 N/A (IBIT and 
                 NSE (no 
               
               
                 clutch 
                   
                 however 
                 activating each 
                 Maintenance 
                 Maintenance 
                 safety 
               
               
                   
                   
                 next failure 
                 duct motor 
                 action) 
                 action) 
                 effect) 
               
               
                   
                   
                 (motor 
                 separately to 
               
               
                   
                   
                 jam) can 
                 confirm clutch 
               
               
                   
                   
                 lead to 
                 function 
               
               
                   
                   
                 rotor jam 
               
               
                 Over-run 
                 Open 
                 Associated 
                 PMCE Current 
                 Power 
                 No thrust 
                 Major 
               
               
                 clutch 
                   
                 motor can 
                 monitor trip (low 
                 increased on 
                 margin on one 
               
               
                   
                   
                 no longer 
                 threshold) on 
                 the two other 
                 of the four 
               
               
                   
                   
                 transmit 
                 faulty motor 
                 duct motors 
                 ducts, 130- 
               
               
                   
                   
                 power to 
                   
                   
                 140% thrust 
               
               
                   
                   
                 rotor 
                   
                   
                 capability on 
               
               
                   
                   
                   
                   
                   
                 the remaining 
               
               
                   
                   
                   
                   
                   
                 three ducts 
               
               
                 PMCE 
                 Erroneous 
                 Associated 
                 FCC Rotor 
                 FCC 
                 No thrust 
                 Major 
               
               
                 (Single 
                 (Runaway) 
                 motor 
                 Overspeed 
                 disengages the 
                 margin on two 
               
               
                 channel) 
                   
                 transmits 
                 monitor trip on 
                 two associated 
                 of the four 
               
               
                   
                   
                 increased 
                 two opposed ducts 
                 motors - 
                 ducts, 130- 
               
               
                   
                   
                 power to 
                 combined with 
                 Power 
                 140% thrust 
               
               
                   
                   
                 rotor on 
                 higher power 
                 increased on 
                 capability on 
               
               
                   
                   
                 two 
                 draw on faulty 
                 the two other 
                 the remaining 
               
               
                   
                   
                 opposed 
                 motors 
                 duct motors on 
                 two ducts 
               
               
                   
                   
                 ducts 
                   
                 two opposed 
               
               
                   
                   
                   
                   
                 ducts 
               
               
                 PMCE 
                 Failed 
                 Associated 
                 FCC PMCE 
                 Power 
                 No thrust 
                 Major 
               
               
                 (Single 
                 (Passive) 
                 motor can 
                 monitor trip 
                 increased on 
                 margin on two 
               
               
                 channel) 
                   
                 no longer 
                   
                 the two other 
                 of the four 
               
               
                   
                   
                 transmit 
                   
                 duct motors on 
                 ducts, 130- 
               
               
                   
                   
                 power to 
                   
                 two opposed 
                 140% thrust 
               
               
                   
                   
                 rotor on 
                   
                 ducts 
                 capability on 
               
               
                   
                   
                 two 
                   
                   
                 the remaining 
               
               
                   
                   
                 opposed 
                   
                   
                 two ducts 
               
               
                   
                   
                 ducts 
               
               
                 PMCE 
                 Generic 
                 Associated 
                 FCC Rotor 
                 FCC 
                 No thrust 
                 Major 
               
               
                 (Single 
                 failure (one 
                 motor 
                 Overspeed 
                 disengages the 
                 margin at the 
               
               
                 channel) 
                 type) 
                 transmits 
                 monitor trip on all 
                 four associated 
                 vehicle level 
               
               
                   
                   
                 increased 
                 ducts 
                 motors 
               
               
                   
                   
                 power to 
               
               
                   
                   
                 rotor on all 
               
               
                   
                   
                 ducts 
               
               
                 Battery 
                 Erroneous 
                 Over- 
                 BMS Battery 
                 BMS 
                 Same as loss 
                 Major 
               
               
                   
                 (Runaway) 
                 voltage and 
                 Health monitor 
                 passivates 
                 of one PMCE 
               
               
                   
                   
                 thermal 
                 trip 
                 battery 
                 (No thrust 
               
               
                   
                   
                 runaway 
                   
                   
                 margin on two 
               
               
                   
                   
                   
                   
                   
                 of the four 
               
               
                   
                   
                   
                   
                   
                 ducts, 130- 
               
               
                   
                   
                   
                   
                   
                 140% thrust 
               
               
                   
                   
                   
                   
                   
                 capability on 
               
               
                   
                   
                   
                   
                   
                 the remaining 
               
               
                   
                   
                   
                   
                   
                 two ducts) 
               
               
                 Battery 
                 Failed 
                 Loss on 
                 BMS Battery 
                 Power 
                 Same as loss 
                 Major 
               
               
                   
                 (Passive) 
                 one PMCE 
                 Health monitor 
                 increased on 
                 of one PMCE 
               
               
                   
                   
                 and its two 
                 trip and FCC 
                 the two other 
                 (No thrust 
               
               
                   
                   
                 associated 
                 PMCE monitor 
                 duct motors on 
                 margin on two 
               
               
                   
                   
                 motors 
                 trip 
                 two opposed 
                 of the four 
               
               
                   
                   
                   
                   
                 ducts 
                 ducts, 130- 
               
               
                   
                   
                   
                   
                   
                 140% thrust 
               
               
                   
                   
                   
                   
                   
                 capability on 
               
               
                   
                   
                   
                   
                   
                 the remaining 
               
               
                   
                   
                   
                   
                   
                 two ducts) 
               
               
                 FCC 
                 Erroneous 
                 FCC Com 
                 FCC Com/Mon 
                 FCC 
                 No functional 
                 Minor 
               
               
                 (Com/ 
                 (Runaway) 
                 or Mon 
                 Miscompare 
                 passivates its 
                 or 
               
               
                 Mon) 
                   
                 erroneous 
                   
                 output and 
                 performance 
               
               
                   
                   
                 velocity 
                   
                 declare itself 
                 impact 
               
               
                   
                   
                 command 
                   
                 failed - 
               
               
                   
                   
                 on one 
                   
                 Commands 
               
               
                   
                   
                 FCC 
                   
                 provided by 
               
               
                   
                   
                   
                   
                 healthy FCC 
               
               
                 FCC 
                 Failed 
                 One of two 
                 Healthy FCC 
                 Commands 
                 No functional 
                 Minor 
               
               
                 (Com/ 
                 (Passive) 
                 FCC is no 
                 detects loss 
                 provided by 
                 or 
               
               
                 Mon) 
                   
                 longer 
                   
                 healthy FCC 
                 performance 
               
               
                   
                   
                 available 
                   
                   
                 impact 
               
               
                   
               
            
           
         
       
     
     Method  150  may comprise a step  160  of adjusting the desired torque level based on the analyzed drive characteristic. For instance, propulsion motor control  130  and/or flight control  140  can adjust the desired torque level by increasing or decreasing the desired torque level to actuate motors  122  based on the analyzed drive characteristic. Propulsion motor control  130  and/or flight control  140  can further adjust operation of system  120  based on whether a fault has been detected for one or more of components of system  120 . For instance, propulsion motor control  130  and/or flight control  140  can be configured to disconnect and/or shutdown a motor  122  in the event of a fault in the propulsion control of such a motor  122 . Propulsion motor control  130  and/or flight control  140  can further be configured to adjust the desired torque levels of the remaining rotors  109  and/or motors  122  that have not been disconnected and/or shutdown. In some versions, system  120  is configured to provide an alert upon the detection of a fault of system  120 . Still other suitable methods for operating system  120  will be apparent to one with ordinary skill in the art in view of the teachings herein. 
     Accordingly, the redundancy provided by system  120  is configured to inhibit a catastrophic failure of aircraft  101  in the event of a failure of a single component of system  120 , apart from a rotor  109  separation, such that a failure of any component of system  120  does not cause aircraft  101  to un-balance or experience a loss of control. System  120  is further configured to provide a minimum number of control units and/or computational lanes to lower the cost of system  120  while allowing sufficient functional independence and safety of system  120 . Accordingly, system  120  may be lightweight to improve the efficiency of aircraft  101 . 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.