Lift fan position lock mechanism

Abstract

Lift fan position locking mechanisms are disclosed. In various embodiments, a position locking mechanism includes a ring structure having a first surface, the ring structure including one or more detents defined in the first surface of the ring structure. For each detent, the locking mechanism includes a fixed magnet fixedly coupled to the ring structure at a location adjacent to the detent. The locking mechanism also includes a rotating magnet assembly including a magnet having an opposite magnetic polarity to at least one of the fixed magnets and a mechanical stop structure having a size and shape that fits into a corresponding detent and mechanically engages a surface bounding at least one of the corresponding detent when the rotating magnet assembly is in a locked position.

Description

[0001] This application is a continuation-in-part of the patent application with application number 201780085648.5 (PCT application number PCT / US2017 / 060335), filing date November 7, 2017, and titled "Lift Fan Position Locking Mechanism." TECHNICAL FIELD

[0002] Lift fans, and other rotors, collectively referred to herein as "lift fans," can be used to provide lift to manned or unmanned multi-rotor aircraft, such as personal aircraft and drones. Hybrid flight mode aircraft can use lift fans to provide lift in a vertical flight mode (e.g., takeoff, hovering, or landing). Such aircraft can transition after takeoff into a forward flight mode in which one or more forward flight propellers can be used to propel the aircraft through the air. Lift can be generated in the forward flight mode by one or more wings included by the aircraft.

[0003] In the forward flight mode, the lift fan can generate drag and / or other undesirable forces unless locked. It can be impractical to use conventional mechanisms to lock the lift fan rotor, for example, due to weight considerations, uncertainty about the rotor position when the aircraft transitions into forward flight, and / or other factors. BRIEF DESCRIPTION OF DRAWINGS

[0004] Various embodiments of the application are disclosed in the detailed description and drawings below.

[0005] Figure 1 is a diagram illustrating an embodiment of a multicopter aircraft.

[0006] Figure 2A is a diagram illustrating a perspective view of an embodiment of a fixed ring portion of a lift fan locking mechanism.

[0007] Figure 2B is a diagram illustrating a top view and a side view of an embodiment of a fixed ring portion of a lift fan locking mechanism.

[0008] Figure 3A is a diagram illustrating a perspective view of an embodiment of a fixed ring portion of a lift fan locking mechanism, with a rotor magnet assembly in a lift fan locked position.

[0009] Figure 3B is a diagram illustrating a perspective view of an embodiment of a fixed ring portion of a lift fan locking mechanism, with a rotor magnet assembly in a lift fan unlocked position.

[0010] Figure 4Ais a diagram illustrating an embodiment of a lift fan locking mechanism in a locked configuration.

[0011] Figure 4B is a diagram illustrating an embodiment of a lift fan locking mechanism in an unlocked but not fully disengaged state.

[0012] Figure 4C is a diagram illustrating an embodiment of a lift fan locking mechanism in an unlocked and fully disengaged state.

[0013] Figure 4D is a diagram illustrating an embodiment of a lift fan locking mechanism in a locked configuration.

[0014] Figure 5 is a flowchart illustrating an embodiment of a process of transitioning a lift fan from a locked state to an unlocked state.

[0015] Figure 6 is a flowchart illustrating an embodiment of a process of transitioning a lift fan from an unlocked transition state to a locked state.

[0016] Figure 7 is a flowchart illustrating an embodiment of a process for stopping and locking a lift fan.

[0017] Figure 8 is a diagram illustrating an embodiment of a system for controlling a lift fan through a lock / unlock sequence. DETAILED DESCRIPTION

[0018] The application can be implemented in numerous ways, including as a process; an apparatus; a system; a composition of matter; a computer program product of a computer readable storage medium; and / or a processor, such as a processor configured to, or a processor configured by, execute instructions stored on, or provided by, a memory coupled to the processor. In this specification, these implementations, or any other form that the application can take, can be referred to as techniques. Generally, the order of the steps of disclosed processes can be altered, unless otherwise specified. Unless otherwise stated, components that are described as being configured to perform a task can alternatively be implemented as components that are temporarily configured to perform the task at a given time or a special purpose component configured to perform the task. As used in this document, the term ‘processor’ refers to one or more devices, circuits, and / or processing cores configured to process data, such as computer program instructions.

[0019] A detailed description of one or more embodiments of the application is provided in the following description with reference to the accompanying drawings. The application is described in connection with these embodiments, but the application is not limited to any embodiment. The scope of the application is limited only by the claims and the application encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the application. These details are provided for the purpose of example and the application can be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the application has not been described in detail so that the application is not unnecessarily obscured.

[0020] A lift fan position locking mechanism is disclosed. In various embodiments, a lift fan rotor is held in place by rotor magnets attached to the rotor and which are magnetically engaged and held in place in a locked position by corresponding stationary magnets mounted on a stationary structure such as a stator, housing, or other non-rotating structure that does not rotate when the lift fan rotor is rotating. In some embodiments, the stationary magnets are mounted on tabs extending inward from a metal or other ring structure. The ring structure provides a surface on which the assembly including the rotor magnets can slide, for example, when the rotor is first moved out of the locked position by application of a start-up torque via an associated motor. In some embodiments, as the rotational speed of the rotor increases, centrifugal forces are generated and cause the rotor magnets to rotate about a pivot axis as the rotor magnets move upward and outward away from the ring structure.

[0021] In various embodiments, a lift fan locking routine or procedure follows to lock the lift fan using a locking mechanism as disclosed herein. The lift fan speed is reduced, for example, by ceasing application of torque via the lift fan motor and / or by applying a counter torque. The position of the lift fan rotor relative to the locked position is determined, and a corresponding electrical excitation associated with causing the lift fan rotor to rotate at least to the locked position is determined and applied to the lift fan motor. In various embodiments, a torque less than the escape torque required to drive the lift fan rotor away from the locked position is applied. During the locking routine, the rotor magnets can be attracted to and can lock into position adjacent to the corresponding stationary magnets, causing the rotor to be locked in place.

[0022] In some embodiments, two pairs of magnets (i.e., two rotating and two stationary) can be used. In some such embodiments, the rotating and stationary magnets can have opposite magnetic polarity, such that the rotating magnets are attracted to corresponding stationary magnets having opposite magnetic polarity, but are repelled by stationary magnets having the same magnetic polarity. In some embodiments, use of magnets having alternating polarity results in the lift fan being locked in only one position.

[0023] Figure 1 is a diagram showing an embodiment of a multicopter. In various embodiments, a lift fan position locking mechanism as disclosed herein can be included in a multicopter as shown in Figure 1 . In the example shown, the aircraft 100 includes a fuselage 102 and wings 104. A set of three underwing booms 106 is provided under each wing. Each boom 106 has two lift fans 108 mounted thereon, one forward of the wing and one aft of the wing. Each lift fan 108 can be driven by an associated drive mechanism, such as a dedicated electric motor. One or more batteries (not shown) and / or an onboard power generator (e.g., a small gas turbine) can be used to drive the lift fans 108 and / or to charge / recharge the onboard batteries.

[0024] In various embodiments, each boom 106 can be positioned at an angle relative to a vertical axis of the aircraft such that the lift fans 108 are mounted thereon at the associated angle. The angle can be determined, at least in part, to satisfy design objectives and / or associated constraints to provide yaw control and / or to avoid the rotational plane of any lift fan intersecting with a portion of the fuselage 102 that is occupied by a person or otherwise critical.

[0025] In the example shown in Figure 1 , a propeller 110 is mounted on the fuselage 102 and is configured to push the aircraft through the air in a forward (e.g., x-axis) direction when in forward flight mode. The propeller 110 is positioned between a pair of aft booms 112 that extend rearward and are joined at their aft ends by an aft structure on which are mounted aerodynamic control surfaces including elevators 116 and rudders 118. In various embodiments, each of the inboard booms 106 at least partially forms an integrated part of the corresponding port / starboard aft boom 112. In some embodiments, the aft booms 112 include an extension rearward from the respective inboard boom 106. For example, the aft boom 112 can be formed as part of or fastened (e.g., bolted) to the aft end of the corresponding inboard boom 106. Additional control surfaces include ailerons 114 mounted on the trailing edges of the wings 104.

[0026] In various embodiments, the lift fan 108 can be used to provide lift, enabling the multirotor aircraft 100 to take off, hover, and / or land vertically (or over a short horizontal distance) in a vertical flight mode. The multirotor aircraft 100 can be configured to use the lift fan 108 for example, vertical takeoff, and then transition to a forward flight mode in which the propeller 110 propels the aircraft through the air and the wing 104 provides lift. In the forward flight mode, in various embodiments, a lift fan locking mechanism, as disclosed herein, is used to lock the lift fan 108 in a locked position. In some embodiments, the locked position can be a low (or relatively low) drag position. For example, in some embodiments, the lift fan 108 can be locked as in... Figure 1 In the positions shown, the corresponding blades of each lift fan (where, in this example, each lift fan has two blades) are substantially aligned with the longitudinal axis of one or both of the aircraft 100 and the boom 106. For different... Figure 1 The aircraft configuration of aircraft 100 and / or compared to Figure 1 The lift fan 108 is a lift fan with a different number and / or arrangement of blades, and a locking mechanism as disclosed herein can be used to lock the lift fan in contact with... Figure 1 The examples shown are compared to different low or relatively low resistance locations.

[0027] A lift fan locking mechanism is disclosed. In various embodiments, such as during forward flight, the lift fan locking mechanism disclosed herein can be used to lock and hold the lift fan in a low-drag or other stored position. In various embodiments, the lift fan lock disclosed herein may include a retaining ring that is securely mounted to the aircraft, for example, by bolting or other means to the stator, housing, or other non-rotating part of the lift fan assembly.

[0028] In some embodiments, such as Figure 1 The lift fan assembly of the lift fan 108 may include a lift fan rotor and a lower rotating cup or housing, with a non-rotating stator, control circuitry, and other stationary components sandwiched between the lift fan rotor and the lower rotating cup or housing. The lift fan rotor and lower rotating cup may be attached to a shaft extending through but not fixed to the stator. The lift fan rotor and lower rotating cup may include rotor elements for driving a generally flat brushless DC motor of the lift fan. The rotor elements may have magnets attached to and / or integrated therein. Current is supplied to the stator in a prescribed manner to cause the rotor elements to rotate.

[0029] In various embodiments, one or more rotor magnet assemblies including a lift fan locking mechanism as disclosed herein are attached to each rotor element. Corresponding stationary magnets are attached directly or indirectly to a stationary non-rotating element such as a stator, motor / lift fan housing, etc. In the locked position, the magnets of the rotating magnet assemblies are magnetically attracted and pulled into an engagement position with the corresponding stationary magnets having opposite magnetic polarity. The magnetic force between the respective rotating magnets and each corresponding stationary magnet holds the lift fan in place, i.e., prevents rotation, unless sufficient torque is applied by the lift fan motor. The torque required to release from the locked position is sometimes referred to herein as the "release" torque.

[0030] Figure 2A is a diagram illustrating a perspective view of an embodiment of the stationary ring portion of a lift fan locking mechanism. In the example shown, the stationary ring portion 200 of the lift fan locking mechanism includes an annular metal ring 202 having an upper surface (the top surface as shown) and a lower surface. In the example shown, the ring 202 includes a generally flat ring. In some alternative embodiments, rings having other shapes (e.g., tapered rings) and / or features (e.g., inner / outer diameters, materials, thicknesses, etc.) can be used. The ring 202 has notches or detents 204 and 206 formed therein on the sliding surface of the ring 202. In some embodiments, the notches 204 and 206 are V-shaped notches into which rigid stop portions of the rotating magnet assemblies, such as balls, posts, pins, or other structures, can be received and held when the lift fan is in the locked position. In various embodiments, a combination of one or more of magnetic force, spring force (e.g., from a helical torsion spring or other spring), and frictional force (e.g., frictional force of the stop structures against the detent surface) can be used to hold the rotating magnet assemblies in place when the lift fan is in the locked position.

[0031] Further reference is made to Figure 2A , the notches 204 and 206 each have a metal (or other) tab portion (208, 212) associated therewith on which a stationary magnet (210, 214) is mounted. In various embodiments, the magnets 210 and 214 can have opposite polarity. Thus, only one of the two rotating magnet assemblies can be magnetically attracted to a given one of the magnets 210, 214, while the other rotating magnet assembly will be repelled. In some embodiments, the different polarity causes the lift fan locking mechanism to lock the lift fan in only a single, same locked position, i.e., the locked position in which each rotating magnet assembly is engaged with a corresponding stationary magnet of opposite polarity (and associated structure, such as the associated notches 204, 206).

[0032] Figure 2Bare simplified diagrams showing top and side views of an embodiment of the fixed ring portion of the lift fan locking mechanism. In the example shown, Figure 2A The fixed ring portion 200 includes notch (204, 206), tab (208, 212), and magnet (210, 214) structures on diametrically opposite sides of the ring 202. The notches (204, 206) and tabs (208, 212) can be seen to include material extending below the lower surface of the ring 202, e.g., to provide mechanical strength and support.

[0033] In some embodiments, an insert made of Teflon™ or other durable material can be integrated with the notches (204, 206) to reduce wear associated with locking and unlocking operations during which the rotating magnet assemblies can slide into and / or out of the notches (204, 206), potentially causing excessive wear.

[0034] Figure 3A are simplified diagrams showing perspective views of an embodiment of the fixed ring portion of the lift fan locking mechanism with the rotor magnet assemblies in the lift fan locked position. In the example shown, the rotating magnet assemblies 302 and 304 are shown in the locked position in which the magnets on the bottom side of the rotating magnet assemblies 302 and 304 (not shown in Figure 3A engage physically and magnetically with the corresponding ones of the magnets 210 and 214 of the Figure 2A and Figure 2B the physical stop structures on the bottom side of the rotating magnet assemblies 302 and 304 (not shown in Figure 3A engage physically and mechanically with the corresponding ones of the notches 204 and 206 of the Figure 2A and Figure 2B

[0035] In the example shown, the rotating magnet assemblies 302 and 304 have pins extending through portions of the rotating magnet assemblies 302 and 304, the pins extending outwardly from and outside of the ring 202. In various embodiments, the rotating magnet assemblies 302 and 304 can be coupled to rotating elements associated with the lift fan assembly in a manner such that the respective pins are held in fixed positions relative to the rotating elements of the lift fan assembly, and the rotating magnet assemblies 302 and 304 are each held free to rotate about their associated pins, enabling the magnets and stop portions (not shown in Figure 3A to rotate upwardly and away from the top surface of the ring 202, e.g., during and after an unlocking sequence or operation and / or during normal operation of the lift fan when it is not locked.

[0036] Figure 3B ​is a diagram illustrating a perspective view of an embodiment of the fixed ring portion of the lift fan locking mechanism, with the rotor magnet assemblies in the lift fan unlocked position. In the example shown, torque has been applied to the rotating element 306 of the lift fan assembly to cause the rotating magnet assemblies 302 and 304 to release from the locked position in which they have been held, enabling the rotating element 306 to rotate in a clockwise direction (as shown), as indicated by the large arrow adjacent to the rotating magnet assemblies 302 and 304.

[0037] In some embodiments, the torque required to be applied by the motor to exit the locked orientation is approximately + / - 20 N*m. The peak torque capability of the motor is approximately + / - 150 N*m. The expected aerodynamic torque when the fan is not in use and when the fan is in the locked position (i.e., the torque associated with the aerodynamic forces acting on the surfaces of the lift fan when in the locked position) is approximately + / - 5 N*m. The peak speed of the motor is approximately 3500 rpm. The speed necessary to avoid the mechanism clacking on the detents is approximately 500 rpm. In normal operation, when the lift fan is expected to remain in the unlocked position, the flight control system will command torque from +150 N*m all the way to -150 N*m, but the lift fan remains above 500 rpm, and thus the rotating portion(s) of the locking mechanism do not contact the fixed portion(s). In other embodiments, the torque required to unlock and / or the speed below which contact with the fixed portion(s) of the locking mechanism and / or accidental locking can occur can differ from the values mentioned above, depending on design requirements.

[0038] In various embodiments, when a torque sufficient to release from the locked position is applied to the rotating element 306, the rotating magnet assemblies 302 and 304 release from the corresponding locked position in which they are held by the magnetic and mechanical forces described above. Initially, the stops or other rigid structures on the underside of the rotating magnet assemblies 302 and 304 can ride up or slide along the top surface of the fixed ring 202 until the rotating element 306 rotates at a sufficient rotational speed that the rotating magnet assemblies 302 and 304 rotate upward and away from the fixed ring 202 due to centrifugal force, causing each to rotate about its pin (or other rotational axis) structure as the rotating element 306 continues to rotate. In some embodiments, the stops or other structures skim the notches 204, 206, or can slide slightly into the notches 204, 206, but under sufficient speed and / or under sufficient torque, the rotating magnet structures do not engage and lock into the locked position, but instead continue through and / or over the notches (204, 206) and associated tab / magnet structures (208 / 210, 212 / 214).

[0039] Figure 4A is a diagram showing an embodiment of a lift fan locking mechanism in a locked configuration. In the example shown, a rotating magnet assembly 400 comprising the lift fan locking mechanism is shown in front cross-section and side view. The rotating magnet assembly 400 is shown as comprising an arm 404 integrated with a generally cylindrical mechanical stop portion 406, the arm 404 being attached to a mount portion 408 by a pin 410 such that the arm 404 and stop 406 can rotate relative to the mount portion 408 about the longitudinal axis of the pin 410 (out of the page as shown). The mount 406 is shown as being fixedly mounted to the lift fan rotating element 306. In some embodiments, a spring element (not shown in Figure 4A ) such as a helical or other torsion spring configured to apply a counterclockwise torsion spring force about the longitudinal axis of the pin 410 can be provided to tend to hold the rotating magnet assembly 400 in the position shown.

[0040] In the example shown, in the locked position, the magnetic force between the magnet 412 attached to the underside of the arm 404 and the magnet 214 attached to the fixed tab 212 of the fixed ring 202 tends to hold the rotating magnet assembly 400 in the locked position as shown in Figure 4A . The magnetic and spring forces described above result in a normal force being applied to the stop 406, which results in a force tending to prevent the stop 406 from sliding upward and away from the notch 206.

[0041] Figure 4B is a diagram showing an embodiment of a lift fan locking mechanism in an unlocked but not fully disengaged state. In the example shown, a motive force Fm has been applied to the rotating element 306. In some embodiments, the rotating element 306 can integrally comprise and / or can be fixedly attached to the rotor portion of a brushless motor provided to drive the lift fan. In the position shown in Figure 4B , sufficient torque has been applied to cause the rotating magnet assembly 400 to release from the notch 206 and magnet 214 and to begin sliding away from the notch 206 and magnet 214 as in the example shown in Figure 3B (see, e.g., rotating magnet assembly 304).

[0042] In the example shown in Figure 4B , the mechanical stop portion 406 extends at a downward angle relative to the arm 404 below the arm 404 such that when the rotating magnet assembly 400 is in the position shown in Figure 4BWhen the magnet 412 is in the position shown in FIG. 6 (where the stop 406 rides on the top surface of the fixed ring 202), the magnet 412 is held at an angle upward and away from the ring 202 and the tab 212 and magnet 214. In some embodiments, this arrangement further reduces the proximity of at least a substantial portion of the magnet 412 to the magnet 214, and orients the respective magnetic fields relative to each other in such a way that, when the rotating magnet assembly 400 is rotated in Figure 4B When the rotating magnet assembly 400 is rotated in the position shown in FIG. 6 around the ring 202, it causes the rotating magnet assembly 400 to experience less magnet attraction.

[0043] In the position as shown in FIG. 6, the mechanical stop portion 406 is shown engaged with and riding on the top surface of the fixed ring 202. In the position as shown in FIG. 6, the arm 404 is shown in a position where the stop 406 is engaged with and riding on the top surface of the fixed ring 202. Figure 4B In the position as shown in FIG. 6, the mechanical stop portion 406 is shown engaged with and riding on the top surface of the fixed ring 202. In the position as shown in FIG. 6, the arm 404 is shown in a position where the stop 406 is engaged with and riding on the top surface of the fixed ring 202. Figure 4B In the state and position shown in FIG. 6, the rotating magnet assembly 400 experiences a centrifugal force Fcl, but the centrifugal force Fcl has not yet reached a size sufficient to cause the arm 404 to rotate further around the longitudinal axis of the pin 410 (or more precisely, the longitudinal axis of the hole(s) in the mounting 408 through which the pin 410 extends). As shown, the force Fcl causes a moment that is proportional to the moment arm / distance dl. In various embodiments, as the rotational speed of the rotating element 306 increases, the size of the centrifugal force increases to a value such that the resulting moment is sufficient to begin causing the arm 404 to rotate further around the pin 410, resulting in the stop portion 406 becoming disengaged from the surface of the fixed ring 202.

[0044] Figure 4C is a diagram showing an embodiment of the lift fan locking mechanism in an unlocked and fully disengaged state. In the example shown, the centrifugal force experienced by the rotating magnet assembly 400 has become strong enough to cause the arm 404 to rotate further around the pin 410, causing the stop 406 to become disengaged from the fixed ring 202 and the magnet 412 to move further away from the fixed magnet as the rotating element 306 continues to rotate. In some embodiments, a mechanical stop is provided to prevent the arm 404 from rotating beyond a designed maximum displacement relative to the fixed ring 202.

[0045] Figures 4A-4C An unlock sequence of an embodiment of the lift fan locking mechanism as disclosed herein is shown. In some embodiments, the lock sequence can be shown by considering the Figures 4A-4C unlock sequence in reverse order. For example, in some embodiments, the lock sequence can include reducing the torque applied to the rotating element 306, causing the rotational speed of the element to decrease to a point at which the centrifugal force applied to the rotating magnet assembly 400 is reduced to a size that is less than the size of other forces applied to the rotating magnet assembly 400, such as gravity, a torsion spring as described above, etc. Thus, the rotating magnet assembly 400 can become disengaged from the fixed magnet 214 and the fixed ring 202, and the arm 404 can rotate further around the pin 410, causing the stop 406 to become disengaged from the surface of the fixed ring 202. Figure 4Cto the position shown in Figure 4B

[0046] Pneumatic and / or other forces can cause the rotating element 306 to remain unlocked. In some embodiments, a locking sequence as disclosed herein can be performed to cause the lift fan to move into and remain in the locked position as shown in Figure 4A

[0047] Figure 4D is a diagram showing an embodiment of a lift fan locking mechanism in a locked configuration. In the example shown, an insert 420 made of Teflon™ or other durable material is integrated with the notch 206 to reduce wear associated with locking and unlocking operations during which the rotating magnet assembly 400 can slide into and / or out of the notch 206, potentially causing excessive wear.

[0048] Figure 5 is a flowchart showing an embodiment of a process to transition a lift fan from a locked state to an unlocked state. In various embodiments, the unlocking routine or sequence of Figure 5 may be implemented by a controller or other computer or processor, such as a flight control computer or module, a motor controller, etc. In the example shown, an indication is received to rotate and use the lift fan (502). For example, an explicit command to start the lift fan can be received, or an indication of takeoff can be received, or an indication to transition from forward flight mode to vertical flight mode can be received. A start (unlock) sequence is performed to release the lift fan rotor from the locked position (504). In some embodiments, the start sequence includes applying a prescribed torque associated with releasing the lift fan rotor from the locked position by overcoming forces, such as magnetic, spring, and friction forces described above, that tend to keep the lift fan in the locked position according to design. Once the lift fan rotor has been released from the locked position, the torque is increased to a desired level, for example, a level associated with a desired lift fan rotational speed, lift, etc.

[0049] Figure 6 is a flowchart showing an embodiment of a process to transition a lift fan from an unlocked state to a locked state. In various embodiments, the locking routine or sequence of Figure 6 ​​lock routine or sequence. In the illustrated example, an indication is received to stop and lock the lift fan (602). For example, an indication can be received to stop and lock the lift fan in conjunction with transitioning from a vertical flight mode to a forward flight mode. The lift fan rotor is allowed to coast (604). For example, the torque applied using the lift fan rotor can be reduced to zero. Alternatively, a motor can be used to apply a braking force to slow the lift fan rotor. Eventually, a stop and lock sequence is performed (606). For example, as the aircraft moves through the air, the lift fan rotor can first coast to a lower rotational speed, and eventually can coast inertially under the influence of aerodynamic forces applied to the lift fan rotor. The stop and lock sequence can include estimating the position of the lift fan rotor, e.g., relative to a fixed component of the lift fan locking mechanism, and applying a sequence of voltages to the lift fan motor at a prescribed level that is associated with driving the motor from the estimated position to a locked position by applying a torque that is less than a "release" torque associated with transitioning from a locked state to an unlocked state. In some embodiments, performing the stop and lock sequence creates an opportunity for magnetic attraction between the rotating magnet(s) and corresponding fixed magnets to pull and hold the lift fan rotor into the locked position.

[0050] In some embodiments, the stop and lock sequence increases the likelihood that the lift fan rotor will pass through the locked position at a torque / speed condition at which the rotating magnet assembly can be modified to engage with the corresponding fixed structure, but does not necessarily ensure that the lift fan rotor is driven to the locked position. For example, aerodynamic forces can overcome the forces applied using the lift fan rotor. However, in various embodiments, performing the stop and lock sequence makes it very likely that the lift fan rotor will eventually rotate to and remain in the locked position, either by being driven to the locked position by the motor or as a result of other forces such as aerodynamic forces applied under the favorable conditions created by performing the stop and lock sequence.

[0051] Figure 7 is a flowchart illustrating an embodiment of a process for stopping and locking a lift fan. In some embodiments, Figure 7 The process of Figure 6 Step 606 of the process of In the illustrated example, an angular offset of the lift fan rotor relative to the locked position is estimated (702). In some embodiments, the lift fan rotor is driven by a three-phase brushless motor, and no angular position sensor is provided, so instead the angular position is estimated. In some alternative embodiments, a sensor is used to determine the position of the rotor and / or motor shaft, and the determined position is used as the starting position for the stop and lock sequence.

[0052] The motor is cycled through at least one full revolution (704) with less than the "escape" torque required to escape the locked position. In some embodiments, a voltage sequence is applied that will be sufficient to cycle the lift fan through two full revolutions. At some point during the application of this voltage, the lift fan will be expected to enter and be locked in the locked position. Any torque applied through the remainder of the voltage sequence will be less than the torque necessary to escape the rotor back from the locked position. For example, in some embodiments, the motor comprises a three-phase brushless motor. An open loop voltage sequence is applied to each of the three phases such that the rotor will tend to rotate for at least one revolution. The open loop voltage applied will not produce more torque than necessary to exit the locked position. Thus, as the rotor passes the locked position in its open loop rotation, it becomes locked and does not exit the lock.

[0053] Figure 8 is a diagram illustrating an embodiment of a system for controlling a lift fan through a lock / unlock sequence. In various embodiments, Figure 8 The lift fan control system 800 of Figure 5 may implement one or more of the processes of Figure 6 and Figure 7 In the example shown, the lift fan control system 800 includes a motor controller 802 configured to provide control signals 804 to an inverter 806 configured to convert a DC voltage 808 received from a DC voltage source such as a battery into AC voltages 810 applied to respective phases of a three-phase brushless motor 812 which in turn is configured to drive a lift fan having a position locking mechanism as disclosed herein. In various embodiments, the controller 802 can include one or more of circuitry and processors configured to execute computer instructions. In various embodiments, the controller 802 can be configured (e.g., by hardware, software, or both) to execute the processes of Figure 5 to cause a lift fan driven by the motor 812 to change from a locked state to an unlocked state, and / or configured to execute the processes of Figure 6 and Figure 7 to cause the lift fan to transition to a locked state.

[0054] While certain embodiments disclosed above can use a particular motor and / or controller, in various embodiments, the locking mechanism as disclosed herein can be used with other or different motors, controllers, and / or other elements and / or with components having different features (e.g., unlock torque, lock sequence, etc.) than those described in detail above.

[0055] In various embodiments, the technology disclosed herein can be used to lock a lift fan in a low-drag or other stowed position. The lift fan locking mechanisms as disclosed herein enable a reliable locking mechanism to be provided using relatively few components in a relatively uncomplicated arrangement. Despite the aerodynamic or other forces experienced by the lift fan rotor, the magnetic and mechanical forces hold the lift fan in place unless / until the torque is greater than or equal to the "escape" force exerted using the lift fan motor. Similarly, stopping and locking the lift fan rotor can be achieved without providing more complex braking mechanisms and, in some embodiments, without requiring a shaft angular position sensor.

[0056] While the forgoing embodiments have been described in some detail for purposes of clarity and the present application, it is not limited to the details provided. There are many alternative ways of implementing both the present application. The disclosed embodiments are illustrative in nature and are not to be considered as limiting.

Claims

1. A rotor lock mechanism, comprising: a ring structure having a first surface, the ring structure including one or more detents defined in the first surface of the ring structure; for each detent, a fixed magnet fixedly coupled to the ring structure at a location adjacent to the detent; and a rotating magnet assembly including a magnet having a magnetic polarity opposite to at least one of the fixed magnets and a mechanical stop structure having a size and shape that fits into a corresponding detent and mechanically engages a surface defining at least one boundary of the corresponding detent when the rotating magnet assembly is in a locked position; wherein the rotating magnet assembly is configured to be fixedly attached to a rotor via a base structure, at least a portion of the rotating magnet assembly including the magnet and the mechanical stop structure being connected relative to the base structure via a pin in a manner such that at least the portion remains free to rotate about an axis associated with the pin.

2. The rotor locking mechanism of claim 1, wherein, A center of mass of the portion of the rotating magnet assembly is approximately aligned with the axis in a plane approximately parallel to a plane of the ring structure when the rotating magnet assembly is in the locked position.

3. The rotor lock mechanism of claim 2, wherein, The center of mass of the portion of the rotating magnet assembly is positioned at a non-zero distance d from the plane approximately parallel to a plane of the ring structure when the rotating magnet assembly is in an unlocked position in which the mechanical stop structure is no longer in the detent.

4. The rotor locking mechanism of claim 1, wherein, The rotor lock mechanism includes a plurality of fixed magnets including a first subset having a first magnetic polarity and a second subset having a second magnetic polarity opposite to the first magnetic polarity.

5. The rotor locking mechanism of claim 1, wherein, The rotating magnet assembly includes a spring configured to exert a spring force in a direction associated with the locked position.

6. The rotor locking mechanism of claim 1, wherein, The rotating magnet assembly is attached to a rotor of an aircraft lift fan and the ring structure is fixedly attached to a non-rotating element of the aircraft lift fan.

7. The rotor locking mechanism of claim 6, wherein, The aircraft lift fan is operated under control of a control module.

8. The rotor locking mechanism of claim 7, wherein, The control module includes a processor configured to execute an unlock sequence to transition the aircraft lift fan from a locked state in which the rotor lock mechanism is in a locked position to an unlocked state in which the rotor lock mechanism is not in the locked position.

9. The rotor locking mechanism of claim 8, wherein, Executing the unlock sequence includes exerting a torque equal to or greater than a release torque associated with the rotor lock mechanism.

10. The rotor locking mechanism of claim 7, wherein, The control module includes a processor configured to execute a lock sequence to transition the aircraft lift fan from an unlocked state in which the rotor lock mechanism is not in a locked position to a locked state in which the rotor lock mechanism is in the locked position.

11. The rotor locking mechanism of claim 10, wherein, Executing the lock sequence includes causing the rotor to rotate through one or more revolutions at a torque less than a release torque associated with the rotor lock mechanism.

12. The rotor locking mechanism of claim 11, wherein, Executing the lock sequence includes estimating an angular position of the rotor.

13. The rotor locking mechanism of claim 1, wherein, The ring structure comprises one or more of: an axisymmetric ring; a substantially flat ring; and a conical ring.

14. A rotor lock mechanism, the rotor lock mechanism comprising: a ring structure having a first surface, the ring structure comprising one or more detents defined in the first surface of the ring structure; for each detent, a fixed magnet fixedly coupled to the ring structure at a location adjacent to the detent; and a rotating magnet assembly comprising a magnet having a magnetic polarity opposite to at least one of the fixed magnets, and a mechanical stop structure having a size and shape that fits into a corresponding detent and mechanically engages a surface defining at least one boundary of the corresponding detent when the rotating magnet assembly is in a locked position; wherein the mechanical stop structure comprises a substantially cylindrical element extending out of a plane associated with the magnet comprised by the rotating magnet assembly.

15. The rotor locking mechanism of claim 14, wherein, A longitudinal axis of the substantially cylindrical element is oriented at an acute angle relative to the plane associated with the magnet comprised by the rotating magnet assembly.

16. The rotor locking mechanism of claim 14, wherein, In the first surface of the ring structure, the detents comprise V-shaped notches.

17. The rotor locking mechanism of claim 14, wherein, The rotating magnet assembly comprises an arm integrated with the mechanical stop structure, wherein the arm is attached to a mount portion of the rotating magnet assembly such that the arm and the mechanical stop structure are configured to rotate relative to the mount portion.

18. The rotor locking mechanism of claim 14, wherein, When the rotating magnet assembly is in an unlocked position, the mechanical stop structure rides on a top surface of the ring structure, and the magnet of the rotating magnet assembly is positioned at an angle away from the ring structure.

19. The rotor locking mechanism of claim 14, wherein, When the rotating magnet assembly is in an unlocked and fully disengaged position, the mechanical stop structure is disengaged from the ring structure, and the magnet of the rotating magnet assembly is positioned at an angle away from the ring structure.

20. The rotor locking mechanism of claim 19, wherein, The rotating magnet assembly is configured to be fixedly attached to a rotor via a base structure, at least a portion of the rotating magnet assembly comprising the magnet and the mechanical stop structure is connected relative to the base structure via a pin in such a way that at least the portion remains free to rotate about an axis associated with the pin.

21. The rotor locking mechanism of claim 20, wherein, When the rotating magnet assembly is in the locked position, a center of mass of the portion of the rotating magnet assembly is substantially aligned with the axis in a plane substantially parallel to a plane of the ring structure.

22. The rotor locking mechanism of claim 21, wherein, When the rotating magnet assembly is in an unlocked position in which the mechanical stop structure is no longer in the detent, the center of mass of the portion of the rotating magnet assembly is positioned at a non-zero distance d from the plane substantially parallel to a plane of the ring structure.

23. The rotor locking mechanism of claim 14, wherein, The rotor lock mechanism comprises a plurality of fixed magnets comprising a first subset having a first magnetic polarity, and a second subset having a second magnetic polarity opposite to the first magnetic polarity.

24. The rotor locking mechanism of claim 14, wherein, The rotating magnet assembly comprises a spring configured to exert a spring force in a direction associated with the locked position.

25. The rotor locking mechanism of claim 14, wherein, The rotating magnet assembly is attached to a rotor of an aircraft lift fan, and the ring structure is fixedly attached to a non-rotating element of the aircraft lift fan.

26. The rotor locking mechanism of claim 25, wherein, The aircraft lift fan is operated under control of a control module including a processor configured to execute an unlock sequence to transition the aircraft lift fan from a locked state to an unlocked state in which the rotor locking mechanism is not in the locked position, and a lock sequence to transition the aircraft lift fan from the unlocked state to the locked state in which the rotor locking mechanism is in the locked position.

27. The rotor locking mechanism of claim 26, wherein, Executing the unlock sequence includes applying a torque equal to or greater than a release torque associated with the rotor locking mechanism.

28. The rotor locking mechanism of claim 26, wherein, Executing the lock sequence includes causing the rotor to rotate through one or more revolutions at a torque less than a release torque associated with the rotor locking mechanism.

29. The rotor locking mechanism of claim 28, wherein, Executing the lock sequence includes estimating an angular position of the rotor.

30. The rotor locking mechanism of claim 14, wherein, The ring structure includes one or more of: an axisymmetric ring; a substantially planar ring; and a conical ring.

31. A lift fan control system, the lift fan control system comprising: an aircraft lift fan; a rotor locking mechanism, the rotor locking mechanism comprising: a ring structure having a first surface, the ring structure including one or more detents defined in the first surface of the ring structure; for each detent, a fixed magnet fixedly coupled to the ring structure at a location adjacent to the detent; and a rotating magnet assembly including a magnet having a magnetic polarity opposite to at least one of the fixed magnets, and a mechanical stop structure having a size and shape to fit into a corresponding detent and mechanically engage a surface defining at least one boundary of the corresponding detent when the rotating magnet assembly is in a locked position; wherein the mechanical stop structure includes a substantially cylindrical element extending out of a plane associated with the magnet included with the rotating magnet assembly; wherein the rotating magnet assembly is attached to a rotor of the aircraft lift fan, and the ring structure is fixedly attached to a non-rotating element of the aircraft lift fan.

32. The lift fan control system of claim 31, further comprising: a control module including a processor configured to execute an unlock sequence to transition the aircraft lift fan from a locked state in which the rotor locking mechanism is in a locked position to an unlocked state in which the rotor locking mechanism is released from the locked position, and a lock sequence to transition the aircraft lift fan from the unlocked state to the locked state.

33. A rotor locking mechanism, the rotor locking mechanism comprising: a ring structure having a first surface, the ring structure including one or more detents defined in the first surface of the ring structure; for each detent, a fixed magnet fixedly coupled to the ring structure at a location adjacent to the detent. A rotating magnet assembly including magnets and mechanical stop structures, the magnets having a magnetic polarity opposite to at least one of the stationary magnets, the mechanical stop structures having a size and shape that fit into corresponding detents and mechanically engage surfaces defining at least one boundary of the corresponding detents when the rotating magnet assembly is in a locked position; and An insert disposed into the detents, the insert made of a first material that is harder than a second material forming the ring structure.

34. The rotor locking mechanism of claim 33, wherein, The mechanical stop structures slide into corresponding detents when the rotating magnet assembly moves from an unlocked position to a locked position, and the mechanical stop structures slide out of corresponding detents when the rotating magnet assembly moves from the locked position to the unlocked position.

35. The rotor locking mechanism of claim 33, wherein, The rotating magnet assembly is configured to be fixedly attached to a rotor via a base structure, at least a portion of the rotating magnet assembly including the magnets and the mechanical stop structures is connected relative to the base structure via a pin in a manner such that at least the portion remains free to rotate about an axis associated with the pin.

36. The rotor locking mechanism of claim 35, wherein, A center of mass of a portion of the rotating magnet assembly is approximately aligned with the axis in a plane that is approximately parallel to a plane of the ring structure when the rotating magnet assembly is in the locked position.

37. The rotor locking mechanism of claim 36, wherein, The center of mass of the portion of the rotating magnet assembly is positioned at a non-zero distance d from the plane that is approximately parallel to a plane of the ring structure when the rotating magnet assembly is in an unlocked position in which the mechanical stop structures are no longer in the detents.

38. The rotor locking mechanism of claim 33, wherein, The rotor lock mechanism includes a plurality of stationary magnets including a first subset having a first magnetic polarity and a second subset having a second magnetic polarity opposite the first magnetic polarity.

39. The rotor locking mechanism of claim 33, wherein, The rotating magnet assembly includes a spring configured to exert a spring force in a direction associated with the locked position.

40. The rotor locking mechanism of claim 33, wherein, The rotating magnet assembly is attached to a rotor of an aircraft lift fan, and the ring structure is fixedly attached to a non-rotating element of the aircraft lift fan.

41. The rotor locking mechanism of claim 40, wherein, The aircraft lift fan is operated under control of a control module including a processor configured to execute an unlock sequence to transition the aircraft lift fan from a locked state to an unlocked state, and a lock sequence to transition the aircraft lift fan from the unlocked state to the locked state, in which the rotor lock mechanism is in a locked position, in which the rotor lock mechanism is not in the locked position.

42. The rotor locking mechanism of claim 41, wherein, Executing the unlock sequence includes exerting a torque equal to or greater than a release torque associated with the rotor lock mechanism.

43. The rotor locking mechanism of claim 41, wherein, Executing the lock sequence includes causing the rotor to rotate through one or more revolutions at a torque less than a release torque associated with the rotor lock mechanism.

44. The rotor locking mechanism of claim 43, wherein, Executing the lock sequence includes estimating an angular position of the rotor.

45. The rotor locking mechanism of claim 33, wherein, The ring structure includes one or more of: an axisymmetric ring; an approximately planar ring; and a conical ring.

46. A lift fan control system, the lift fan control system comprising: An aircraft lift fan; A rotor lock mechanism, the rotor lock mechanism comprising: A ring structure having a first surface, the ring structure comprising one or more detents defined in the first surface of the ring structure; For each detent, a fixed magnet fixedly coupled to the ring structure at a location adjacent to the detent; and A rotating magnet assembly comprising a magnet having a magnetic polarity opposite to at least one of the fixed magnets and a mechanical stop structure having a size and shape to fit into a corresponding detent and mechanically engage a surface defining at least one boundary of the corresponding detent when the rotating magnet assembly is in a locked position; and An insert disposed into the detent, the insert made of a first material that is harder than a second material forming the ring structure; Wherein the rotating magnet assembly is attached to a rotor of the aircraft lift fan and the ring structure is fixedly attached to a non-rotating element of the aircraft lift fan.

47. The lift fan control system of claim 46, further comprising: A control module comprising a processor configured to execute an unlock sequence to transition the aircraft lift fan from a locked state, in which the rotor lock mechanism is in a locked position, to an unlocked state, in which the rotor lock mechanism is released from the locked position.

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