Priority

[0001] This application claims priority to U.S. provisional application having serial number 63/387,358 (filed December 14th, 2022). These and all other extrinsic material discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

Field of the Invention

[0002] The field of the invention is position sensing.

Background

[0003] Many conventional linear actuation systems use resolvers. That is, one or more resolvers are configured to rotate in relation to the linear travel of the actuator. For example, in a lead screw type actuator, the resolver can be geared to the lead screw nut. However, many rotary feedback sensors have a range limited to three-hundred and sixty degrees. After each full revolution the sensor reading returns to zero.

[0004] In most linear motion systems comprising resolvers, the resolvers will undergo several full revolutions throughout the stroke of the linear actuator. The actuator can lose knowledge of where the moving portion of the linear actuator is, especially in applications where the actuator can be moved during power off mode. As a result, each time the actuator is powered up, the actuator must undergo a homing sequence to identify an absolute location/reference location for each revolution.

Summary

[0005] In one aspect, presented herein is a linear position sensor system comprising two or more rotary feedback sensors. The system can determine the absolute the position of a device along a path after a power cycle without requiring a homing sequence or an alternative external input. [0006] Furthermore, using principles described herein, embodiments of a multiple rotary feedback sensor linear position sensor can use two or more rotary position sensors to achieve position determination across a large range of motion in a computationally efficient manner.

Brief Description of the Drawings

[0007] Figure 1 illustrates aspects of a linear actuator comprising three rotary feedback sensors.

[0008] Figure 2 illustrates aspects of an alternative linear actuator comprising two rotary feedback sensors.

[0009] Figure 3 illustrates a linear actuator system.

[0010] Figure 4 illustrates steps that can be executed by a linear position computing module.

[0011] Figure 5 illustrates a linear actuator system comprising three rotary feedback sensors.

[0012] Figure 6 illustrates the steps which can be executed by the linear position computing module of Figure 5.

[0013] Figure 7 illustrates a hardware environment for implementing one embodiment of concepts described herein.

[0014] Figure 8 illustrates a conceptual diagram of an embodiment of a virtual rotary position sensor gear shown engaged with an idler sun gear that is also engaged with rotary position sensor gears.

[0015] Figure 9 illustrates an aircraft comprising an embodiment of the concepts described herein.

Detailed Description

[0016] Many conventional linear actuation systems use resolvers. That is, one or resolvers are configured to rotate in relation to the linear travel of the actuator. For example, in a lead screw type actuator, the resolver can be geared to the lead screw nut. However, many rotary feedback sensors have a range of only three-hundred and sixty degrees. After each full revolution the sensor reading returns to zero. In most linear motion systems comprising rotary feedback sensors, the rotary feedback sensors will undergo several full revolutions throughout the stroke of the linear actuator. Especially in applications where the actuator can be moved during power off mode, the actuator can lose knowledge of where the moving portion of the linear actuator is. As a result, each time the actuator is powered up, the actuator must undergo a homing sequence to identify an absolute location/reference location for each revolution.

[0017] One conventional rotary actuator feedback system comprises two resolvers. However, those rotary actuator feedback systems are not capable of being configured for use of more than two rotary feedback sensors. Useable travel depends on common multiple of revolutions of resolvers. Thus, the useable travel for which the linear position system can function is relatively limited with only two resolvers.

[0018] Some embodiments described herein comprise three rotary position sensors — thereby more usable travel can be achieved. Furthermore, relatively large amounts of computing power are required to determine position in conventional systems.

[0019] In one aspect, presented herein is a linear position sensor system comprising two or more rotary feedback sensors. The system can address a desire to efficiently determine absolute position over a large range without requiring a homing sequence for each power cycle.

[0020] Furthermore, using principles described herein, embodiments of a multiple rotary feedback sensor linear position sensor can use 3 or more rotary position sensors to achieve a large range of travel in a computationally efficient manner.

[0021] Illustrated in Figure 1 are aspects of a linear actuator 100a comprising an embodiment of a multiple rotary position sensor system 106. In the embodiment of Figure 1, multiple rotary position sensor system 106 comprises a first rotary position sensor 101a, a second rotary position sensor 101b, and a third rotary position sensor 101c. First rotary position sensor gear 102a is connected to first rotary position sensor 101a. Second rotary position sensor gear 102b is connected to second rotary position sensor 101b. Third rotary position sensor gear 102c is connected to third rotary position sensor 101c. Main position sun gear 103 is configured to rotate with rotary nut 104. Idler sun gear 107 is interposed between the main position sun gear 103 and rotary position sensor gears 102a, 102b, and 102c. Roller screw nut 104 is threaded onto roller screw shaft 105 — shown in Figure 1.

[0022] The roller screw nut 104 is configured to translate along roller screw shaft 105 as torque is applied to roller screw nut 104 — forcing the movable portion 108 of the linear actuator 100a to move. Since the main position sun gear 103 is configured to rotate with roller screw nut 104, the distance travelled by roller screw shaft 105 — and thus the distance moved by the entire moving portion 108 — is directly proportionate to the rotation of the main position sun gear 103 and idler sun gear 107.

[0023] Rotary position sensor gears 102a, 102b, and 102c are engaged with idler sun gear 107.

[0024] Figure 2 illustrates an alternate embodiment of a linear actuator — linear actuator 100b. The embodiment of Figure 2 differs from the embodiment of Figure 1 in that the embodiment of Figure 2 comprises only two rotary position sensors.

[0025] In the embodiment of Figure 2, rotary position sensor gear 101a comprises a different number of gear teeth than rotary position sensor gear 101b.

[0026] Figure 3 illustrates a linear actuator system 300. The linear actuator system 300 comprises linear actuator 100b, first rotary position sensor 101a, second rotary position sensor 101b, position computing module 301, and flight control computer 302.

[0027] Figure 4 illustrates steps that can be executed by position computing module 301 to determine the linear position of actuator shaft 105 — shown in Figure 2.

[0028] In step 401, linear position module 301 receives a first raw rotary position sensor angle reading from the first rotary position sensor 101a. In step 402, linear position module 301 receives a second raw rotary position sensor angle reading from the second rotary position sensor 101b. In step 403, the linear position module 301 computes a revolution pair index using the first raw rotary position sensor angle reading, the second raw rotary position sensor angle reading, and the ratio of a first rotary position sensor gear ratio to a second rotary position sensor gear ratio. [0029] In the embodiment of Figure 2, the rotary position sensor gear ratio is the gear reduction ratio between the rotary position sensor 101 shaft and the roller screw nut 104.

[0030] A revolution pair index can be computed using the algorithm y _AB = ( ^{9b a 0A} wherein y _AB represents the revolution pair index, “b” and “a” are the smallest natural d R R numbers that satisfy the relation - = — . — is ratio of the radii of the rotary position b sensor gears A and B. 0 _A and 0 _B are the raw rotary position sensor angle of the first and second rotary position sensor, respectively.

[0031] In step 404, the linear position module 301 computes, using the computed revolution pair index, the number of completed revolutions from a home position for each of the rotary position sensors 101a and 101b. In the embodiment of Figure 4, the revolution pair index is used to compute the number of full rotations that the first rotary position sensor and second rotary position sensor have made respectively. The absolute angle from home of the first rotary position sensor and second rotary position sensor can then easily be computed. The pitch of the roller screw is then used to compute the absolute distance travelled by the moving portion of the linear actuator.

[0032] In the embodiment of Figure 4, the number of full rotations of the first rotary position sensor and second rotary position sensor can be computed using the computed revolution pair index. Each unique y _AB corresponds to a unique m _A and m _B . The unique pair of m _A and m _B can be computed using a look up table after y _AB is determined. The lookup table can be preloaded onto the linear position module 301 at the time of manufacture. The lookup table can be generated by counting the number turns of actual resolvers and computing the corresponding y _AB using the equation:

[0033] In step 405, the linear position module 301 computes, using the first absolute angle for the first rotary position sensor 101a, the absolute position of the traveling portion of the linear actuator. The linear position can be computed by multiplying the number of turns of the roller screw nut 104 by the linear distance corresponding to each revolution of the roller screw nut 104. The number of turns the roller screw nut has turned relative to an absolute home position can be computed by using the known ratio of first rotary position sensor gear 102a revolutions to the main sun gear 103. In the embodiment of Figure 2, the main sun gear turns at a 1 : 1 ratio to roller screw nut 104.

[0034] Figure 5 illustrates an embodiment of linear actuator 100a comprising three rotary feedback sensors 101a, 101b, and 101c. Figure 6 illustrates steps that the linear position module 301b of the embodiment of Figure 5 can execute to determine position of the moving portion 108.

[0035] In step 601, linear position module 301b receives a first raw rotary position sensor angle reading from the first rotary position sensor 101a.

[0036] In step 602, linear position module 301b receives a second raw rotary position sensor angle reading from the second rotary position sensor 101b.

[0037] In step 603, the linear position module 301 computes a revolution pair index using: first raw rotary position sensor angle reading; a second raw rotary position sensor angle reading; and a ratio of the first rotary position sensor gear ratio to a second rotary position sensor gear ratio.

[0038] In step 604, the linear position module 301 computes, using the computed revolution pair index, a first absolute angle for the first rotary position sensor 101a and a second absolute angle for the second rotary position sensor 101b.

[0039] In step 605, the linear position module 301 generates a virtual rotary position sensor such that the virtual rotary position sensor completes one full revolution each time the first rotary position sensor completes b revolutions, and the second rotary position sensor completes a revolutions.

[0040] In step 606, the linear position module 301 receives a third raw rotary position sensor angle from a third rotary position sensor.

[0041] In step 607, the linear position module 301 computes a second revolution pair index using the virtual rotary position sensor raw rotary position sensor angle and the third raw rotary position sensor angle. The process is similar to the process used to compute the first revolution pair index but the virtual rotary position sensor raw rotary position sensor angle and the third raw rotary position sensor angle are used as the inputs.

[0042] In step 608, the absolute angle for the third rotary position sensor is computed using the computed revolution pair index.

[0043] In step 609, the linear position of the moving portion of the actuator is computed using the absolute angle of the third rotary position sensor and the computed absolute angle of the virtual rotary position sensor.

[0044] Figure 7 illustrates an environment for implementing portions of an embodiment of a multi-rotary position sensor system. The system comprises rotary position sensors 101a, 101b, and 101c. The rotary position sensors lOla-c, are connected to position module 301. Position module 301 comprises processor 701, main memory 702, and MCU 703. The position module 301 is connected to flight control computer 302. Flight control computer 302 comprises flight control processor 704, flight control MCU 705, and flight control main memory 706. The flight control computer 302 is connected to actuator driver 707, and actuator drive motor 708.

[0045] Figure 8 illustrates a conceptual diagram of virtual rotary position sensor 801, sun idler gear 107, first rotary position sensor gear 101a, second rotary position sensor gear 101b, and third rotary position sensor gear 101c.

[0046] Figure 9 illustrates aircraft 901. In the embodiment of Figure 9, aircraft 901 comprises an electric vertical takeoff and landing (eVTOL) aircraft. Aircraft 901 comprises tilting proprotors 902, nacelles 903 and fuselage 904. The aircraft comprises linear actuators 100a that are configured to actuate the proprotors 902 to tilt. In other embodiments the aircraft may be any sort of aircraft including fuel consuming aircraft, rotary wing aircraft, fixed wing aircraft or any other type of aircraft.

[0047] Some embodiments described herein include an idler sun gear 107 engaged with a main sun gear that is driven directly by the roller screw nut. The idler sun gear 107 is engaged with rotary position sensor gears that directly drive the rotary position sensors. However, it should be understood that other embodiments can comprise any geartrain between the roller screw nut — or the final rotary drive mechanism in other embodiments — and the individual rotary position sensors. For example, each rotary position sensor could have individual geartrains or portions of a geartrain between the rotary position sensor and the roller screw nut. Additionally other embodiments can have the rotary position sensors engaged directly with main position sun gear 103 — that is without an intermediary sun gear as shown in the embodiment of Figure 1 herein. In such alternative embodiments, the first, second, third, and consecutive gear ratios would be the drive ratios between the corresponding rotary position sensor shaft — that is the shaft of the first rotary position sensor, the shaft of the second rotary position sensor, etc. — and the final rotating element — for example the roller screw nut in a travelling shaft roller screw actuator.

[0048] It should be understood that while some embodiments herein comprise gears, other embodiments may comprise any known torque transfer device, for example belts or smooth wheels.

[0049] It should be understood that the rotary position sensor gear ratios of the first, second, and any consecutive rotary position sensor gear ratios differ from each other such that each rotary position sensor completes a full rotation at a frequency different than the other rotary position sensors.

[0050] While some embodiments herein comprise roller screw systems, other embodiments may comprise other devices, for example: ball-screw devices, rack and pinion, lead screw, or any suitable mechanism.

[0051] Different embodiments may use any type of rotary position sensor including resolvers, encoders, hall sensor arrays, capacitive disks, inductive disks, optical disks, RVDTs, magnetic disks, magnetic field sensors, or any other suitable sensor.

[0052] One embodiment herein uses a lookup table to compute m _A and m _B . However, in other embodiments, linear position module 301 can be configured to compute m _A and m _B by executing the algorithms: m _A = mod(y _AB ■ f _A , b) and m _B = mod — y _AB • f _B , a). Wherein mod is a modulo function, f _A and f _B are constants that can be computed at the time of system design. The constants can be computed by trying a range of values until a value that works is identified. The advantage of computing m _A and m _B using the above equations can be improved computational efficiency while the system is in service. A system configured to use the above algorithms avoids the need for lookup tables while in service. [0053] An alternate method for determining values f _A , f _B at the time of design is described next. f _A is the smallest natural number of the form f _A = k _A x b + 1 and f _A is an integer multiple of a (k _A is an integer). Similarly, f _B is the smallest natural number of the form f _B = k _B x a + 1 and f _B is an integer multiple of b (k _B is an integer).

[0054] In some embodiments herein the rotary position sensor gear ratio is the gear reduction ratio between the rotary position sensor shaft and the roller screw nut. However, in other embodiments comprising a travelling nut, the rotary position sensor gear ratio will be the ratio between the rotary position sensor shaft and the roller screw shaft. In other embodiments still, the rotary position gear ratio is the ratio between the rotary position sensor shaft and the actuator element that drives the linear motion by rotating. That is the rotary position sensor gear ratio is equal to the drive ratio between the shafts of the respective rotary position sensors and the final rotary drive element.

[0055] While some embodiments herein describe a system for determining the absolute position of a linear actuator, other embodiments can be configured to determine the absolute position of a rotary output actuator. This is useful for applications in which the final output is rotary actuation. In such application, a rotary position module would carry out similar steps to the linear actuator module in the embodiment of Figure 4 or Figure 6, except the steps of determining a linear position of the linear actuator would not be necessary.

[0056] While some embodiments herein describe tilt actuators for an aircraft, other embodiments may be configured to be used in actuation systems for different aspects of an aircraft or even non-aircraft applications, for example: factory automation applications; robotics; automation, machine tools; 3D printers; medical devices; or any other suitable application.

[0057] Some embodiments may use any number of rotary position sensors greater than 2, including 4, 5, 6 or more.

[0058] It should be understood that concepts described herein may be used separate from an actuation system — for example in a system that merely measures position.

[0059] It should be noted that any language directed to a linear position module or flight control computer should be read to include any suitable combination of computing devices, including servers, interfaces, systems, databases, agents, peers, engines, controllers, or other types of computing devices operating individually or collectively. The computing devices may comprise a processor configured to execute software instructions stored on a tangible, non-transitory computer readable storage medium (e.g., hard drive, solid state drive, RAM, flash, ROM, etc.). The software instructions preferably configure the computing device to provide the roles, responsibilities, or other functionality as discussed above with respect to the disclosed apparatus. In some embodiments, various servers, systems, databases, or interfaces may exchange data using standardized protocols or algorithms, possibly based on HTTP, HTTPS, AES, public-private key exchanges, web service APIs, known financial transaction protocols, or other electronic information exchanging methods. Data exchanges preferably are conducted over a packet-switched network, the Internet, LAN, WAN, VPN, or other type of packet switched network. Furthermore, the aircraft controller may include any suitable combination of computing devices, including servers, interfaces, systems, databases, agents, peers, engines, controllers, or other types of computing devices operating individually or collectively.

[0060] Aspects of the linear position module may be located somewhere on the aircraft on which the rotary position sensors are located or anywhere else including in components of an actuator. Furthermore, in some embodiments the linear position module and the flight control computer may be implemented in distinguishable units or may be combined in one unit.