Cyclorotor thrust control, transmission and mounting system

A device for controlling the orientation and magnitude of cyclorotor thrust and for providing mechanical power to that cyclorotor including a system of linear actuators to position a cam or eccentric around a geared shaft. The invention includes a frame which supports the main cyclorotor shaft, provides mounting for the linear actuators, and contains the mechanical gearing system.

SUMMARY

This invention provides control of the pitch of cyclorotor blades and a transmission system to power them. These capabilities enable powering and controlling cyclorotor thrust. Linear actuators are used to modify cyclorotor blade pitch kinematics pseudo-sinusoidally in phase and amplitude. This enables the rapid vectoring of cyclorotor thrust in the plane perpendicular to cyclorotor rotation without varying the rotational speed or orientation of the cyclorotor. A transmission including a pinion gear on a motor and a main gear on a cyclorotor shaft is integrated within this system to provide high torque power to the cyclorotor. These transmission and blade pitch control systems are integrated on a frame which translates cyclorotor aerodynamic forces to a flying or marine vehicle.

BACKGROUND

Cyclorotors are fluid propulsion and control devices that convert mechanical rotation into vectorable thrust by fluid acceleration. They incorporate blades10whose span is parallel to the cyclorotor axis of rotation, as shown inFIG. 1. As the cyclorotor100rotates39these blades are oscillated once per revolution so that the individual blade aerodynamic lift42produces a net thrust40in a unified direction. Altering the function of blade motion changes the thrust direction and magnitude anywhere in the plane perpendicular to the cyclorotor axis of rotation (FIG. 2). This contrasts traditional propulsion systems38(helicopter rotors, propellers, jet engines, etc.) that can only produce thrust along their axis of rotation. Certain blade motions can extract power from a moving fluid and in these cases the device is known as a cycloturbine.

Cyclorotors are useful for propulsion, control and aerodynamic lift in aerial and marine applications that require rapid thrust direction control. They are commercially found on tugboats and ferries which leverage this capability for precise docking. Other practical advantages of the cyclorotor include low aerodynamic noise, simple transition between operation in a stationary and moving fluid, efficient thrust production at low Reynolds numbers, and ease of mounting on a planar surface. Researched applications leveraging these characteristics include airship propulsion and control, micro air vehicles, highly maneuverable unmanned aerial vehicles (UAVs), and manned high speed vertical take-off and landing aircraft. Aircraft using cyclorotors as the primary source of lift, propulsion, and control are known as cyclogyros.FIG. 7. shows an example of a quad-rotor cyclogyro47and a twin-rotor cyclogyro48.

Further detailed background on cyclorotors and cycloturbines can be found in “Fundamental Understanding of the Cycloidal-Rotor Concept for Micro Air Vehicle Applicaions” and “Development of Advanced Blade Pitching Kinematics for Cyclorotors and Cycloturbines.” These dissertations include an extensive discussion of cyclorotor applications and aerodynamics.

For operation, cyclorotors require a mechanism to oscillate the blades in sync with cyclorotor rotation and vary this motion for control of thrust direction and magnitude. Cyclorotors must also incorporate a geared drivetrain to provide the high torque they require. This control system and drivetrain must be incorporated by a support structure that transmits the cyclorotor aerodynamic forces to the host vehicle.

This invention accomplishes these objectives in a way appropriate for a wide range of cyclorotor applications. It could be used in tandem with the inventor's prior awarded patent “Ring cam and ring cam assembly for dynamically controlling pitch of cycloidal rotor blades (U.S. Pat. No. 9,346,535 E1)” to provide more efficient cyclorotor control under a wide range of fluid speeds. The blade pitch control subsystem of this invention serves as an alternative to the inventor's patent application “Thrust vectoring control of a cyclorotor” (U.S. patent application Ser. No. 15/830,581).

To assist in the understanding of the present disclosure the following list of components and associated numbering found in the drawings is provided herein:

ComponentNumberFrame1Rotating pitch link2Eccentric bearing3Cam attach bracket4Central rotating shaft5Spoke6Blade pitch link7Pinned cam linear actuator8Fixed cam linear actuator9Cyclorotor blade10Blade shaft11Blade pitch link shaft12Blade pitch link bearing13Pinned connection of pitch link14Motor15Pinion gear16Main shaft gear17Main shaft bearing18Cyclorotor mounting bracket19Cyclorotor axis of rotation20Pinned connections of linear actuators21Rigid attach point for fixed cam linear actuator22Pinned attach point for pinned cam linear actuator23Magnet24Hall effect sensor25Hall effect sensor electrical conection26Microcontroller27Electronic speed control electrical connection28Pinned cam linear actuator electric control signal29Fixed cam linear actuator electric control signal30Pilot/system control signal31Zero displaced cam (No net thrust)32Cyclootor with cam displaced down and to right33(thrust generated up and left)Cyclorotor with cam attach bracket displaced left34(thrust generated right)Cyclorotor with cam attach bracket displaced right35(thrust generated left)Cyclorotor with cam attach bracket displaced up36(thrust generated down)Cyclorotor with cam attach bracket displaced down37(thrust generated up)Traditional propulsion systems38Direction of cyclorotor rotation39Cyclorotor thrust40Air moving through cyclorotor from flight or wind41Cyclorotor blade aerodynamic lift42Cyclorotor blade shaft bearing43Longitudinal frame member44Electronic speed control45Cyclorotor aircraft fuselage46Quad-rotor cyclogyro47Twin-rotor cyclogyro48Cam49Cam following bearing50Linear Slider51Cyclorotor100Cyclorotor150

DETAILED DESCRIPTION

Referring toFIG. 3, the components of this invention are supported on a frame1. The frame1is composed of two parallel plus shaped pieces of material (seeFIG. 5) that extend outward perpendicular to the cyclorotor axis of rotation. These plus-shaped frames1are connected by longitudinal frame members44to form a rigid skeleton. This rigid skeleton supports several stationary, rotating, and translating components as highlighted in the breakout blocks ofFIG. 3. Main shaft bearings18are positioned at the center of each of these frames1. These bearings hold the central rotating shaft5which extends through and out of one side of the frame1. Referring toFIG. 3andFIG. 7, this frame1is attached on the opposite side of the cyclorotor150to the cyclorotor aircraft fuselage46by a cyclorotor mounting bracket19or other means.

A motor15is attached to the frame1on the same side as the aircraft fuselage46and the motor shaft extends to the inside of the frame1and rotates a pinion gear16. This pinion gear16meshes with a main shaft gear17connected to and centered on the central rotating shaft5. This gearing provides the lower rotational speed, high torque power required to turn the cyclorotor150in the direction of cyclorotor rotation39.

Referring now toFIG. 4, digital feedback control loop is used to maintain the rotational speed of the cyclorotor150. A magnet24is contained on the outer edge of this main shaft gear17. Passage of this magnet24is counted by a hall effect sensor25mechanically connected to the frame1and electrically connected26to a microcontroller27. The microcontroller27is also electrically connected28to the electronic speed control45for the motor15. Software on the microcontroller27measures the rotational speed of the cyclorotor150via the hall effect sensor25and then modulates motor power through the electronic speed controller45to attain or maintain a desired cyclorotor rotational speed. Cyclorotor speed does not need to change in order to adjust cyclorotor thrust40magnitude.

Referring now toFIGS. 3 and 5, opposite from the cyclorotor aircraft fuselage46the central rotating shaft5protrudes from the frame1. One or more spokes6are rigidly attached to the central rotating shaft5and extend outward to just beyond the radius of the cyclorotor150. Blade shaft bearings43at the tip of these spokes hold blade shafts11fastened in the blades10. These blade shaft bearings43transmit the aerodynamic and centrifugal forces of the blades10to the spokes6while allowing the angle between the spokes6and the blades10(blade pitch) to be adjusted by a blade pitch link7.

The pinned cam linear actuator8and fixed cam linear actuator9are connected to the frame by pinned connections21. These actuators may be electro-mechanical, hydraulic, pneumatic, shape-memory alloy or pizo-electric depending on the application. Electromechanical and pizo-electric actators are appropriate for small aircraft. Hydraulic actuators are likely more appropriate on larger air and marine vehicles. Pneumatic actuators may also be appropriate on marine vehicles. Shape-memory alloy actuators may be best suited for micro-air vehicles. Other actuator types may also be appropriate.

The pinned cam linear actuator8and fixed cam linear actuator9are mounted on the same side of the frame1as the spokes6and oriented so that they extend inward from the outer edges of the frame1towards the cyclorotor axis of rotation20. The axis of elongation of the pinned cam linear actuator8is generally perpendicular to the axis of elongation of the fixed cam linear actuator9and the cyclorotor axis of rotation20. Both the pinned cam linear actuator8and fixed cam linear actuator9are connected to a cam attach bracket4on the side closest to the cyclorotor axis of rotation20. The cam attach bracket4is manufactured so that it sandwiches the plus-shaped frame1. The cam attach bracket4is thus permitted to slide freely in the plane perpendicular to the cyclorotor axis of rotation20, but is constrained to prevent motion along the cyclorotor axis of rotation20. The fixed cam linear actuator9is rigidly attached22to the cam attach bracket4so that the cam attach bracket4cannot rotate with respect to the fixed cam linear actuator9. The pinned cam linear actuator8is attached to the cam attach bracket4via a pinned connection23. A pinned connection allows free rotation about the joint, but constrains elongation and contraction. Extension of the pin cam linear actuator8translates the cam attach bracket4, but prevents mechanical binding by allowing rotation of the cam attach bracket4relative to the pinned cam linear actuator8.

Referring now toFIG. 6, extension of the pinned cam linear actuator8and fixed cam linear actuators9in tandem translates the cam attach bracket4in the plane perpendicular to the cyclorotor axis of rotation20. Referring to subfigure34ofFIG. 6, retraction of the fixed cam linear actuator9translates the cam attach bracket4left. In turn this causes a change in the cyclorotor blade pitching motion (by way of a linkage system discussed above) and vectors cyclorotor thrust40generally right. Referring to subfigure35ofFIG. 6, extension of the fixed cam linear actuator9moves the cam attach bracket4right, which results in a blade pitch motion that vectors cyclorotor thrust40generally left. Referring to subfigure37ofFIG. 6, extension of the pinned cam linear actuator8displaces the cam attach bracket4downward causing a cyclorotor thrust40generally upward. Referring to subfigure36ofFIG. 6, retraction of the pinned cam linear actuator8moves the cam attach bracket4upward and causes a cyclorotor thrust40generally downward. Simultaneous movement of the pinned cam linear actuator8and fixed cam linear actuator9can move the cam attach bracket4in plane allowing cyclorotor thrust40to be vectored a full 360 degrees. Subfigure33ofFIG. 6shows an example that simultaneous extension of of the pinned cam linear actuator8and fixed cam linear actuator9causes a cyclorotor thrust40generally up and to the left. Subfigure32ofFIG. 6shows a neutral position where there is no cyclorotor thrust40.

Referring back toFIG. 4, a microcontroller27transforms an electric signal representing the desired cyclorotor thrust condition31into electrical signals29,30. Referring again toFIG. 6, these signals command the proper pinned cam and fixed cam linear actuators8,9extensions which vector cyclorotor thrust40anywhere in the plane of cam attach bracket4motion. Thus, small adjustments to the pinned cam linear actuator8and fixed cam linear actuator9extension lengths rapidly vectors cyclorotor thrust40.

Referring toFIG. 8, translation of this cam attach bracket4can produce variation in blade pitching motion by a variety of existing designs. The only requirement is that the cyclorotor blade pitch vary pseudo-sinusoidally with displacement of the cam attach bracket4from the cyclorotor axis of rotation20. Specifically, the radial displacement of the cam attach bracket4must proportionally increase the amplitude of cyclorotor blade pitching motion and the angle of this radial displacement must alter the phase of the pitching motion. Several implemented and proposed designs provide mechanisms to accommodate this task. In one method, which is known in the art, a cam49can be used in conjunction with a cam following bearing50and slider51as described in “Optimization of Vertical Axis Wind Turbine Blade Pitching Kinematics via Fluxline Theory with Experimental and Computational Verification.” Alternatively, and also known in the art, a cam bearing50directly attached to the blade can follow a cam49similar in radius to the cyclorotor radius as described in “Design, Development, and Flight Test of a Small-Scale Cyclogyro UAV Utilizing a Novel Cam-Based Passive Blade Pitching Mechanism.” Another design, also known in the art, is a 5-bar linkage system which is described in “Fundamental Understanding of the Cycloidal-Rotor Concept for Micro Air Vehicle Applicaions,” where a pitch link7is attached to a rotating pitch link2via a pinned connection of pitch link14. A further common design, known in the art, is a 4-bar linkage system, where all of the linkages are rotating pitch links2, which is described in “Flow Field Studies on a MAV scale Cycloidal Rotor in Forward Fight”. In each of these designs the cam49is fixed or the rotating pitch link2is allowed to rotate on the cam attach bracket4. Moving the cam attach bracket4position in the plane perpendicular to the cyclorotor axis of rotation20moves the cam49or rotating pitch link2, producing a pseudo-sinusoidal variation in blade pitching kinematics. Examples of how the cam attach bracket4position affects the blade pitching motion are shown inFIG. 6.

A simple mixed 4-bar and 5-bar linkage system appropriate for smaller-scale cyclorotors is pictured inFIGS. 3, 5, and 6. In this design variation, known in prior art, the cam attach bracket4holds an eccentric bearing3as shown inFIG. 5. This eccentric bearing3holds a single rotating pitch link2having an extension attached to one of the blades10forming a 4-bar linkage system. Rotation of the blade10attached to the rotating pitch link2also rotates the rotating pitch link2and the interior of the eccentric bearing3. The remaining blade pitch links7are attached as near to the center of the rotating pitch link2as possible via a pinned connection14. Thus only the rotating pitch link2rotates the eccentric bearing3, and the remaining pitch links7will produce a pitch motion closely approximating that of the rotating pitch link2. The blade pitch links7and the rotating blade pitch link2are attached to the cyclorotor blades10by a blade pitch link bearing13and blade pitch link shaft12. This design obviates the need to have several heavy bearings attached to the cam attach bracket4as usually required on an exclusively 4-bar mechanism. The mixed 4-bar and 5-bar mechanism is also described in “The research on the performance of cyclogyro.”

FIG. 9shows a flowchart summarizing a method200of controlling the thrust vector of a cyclorotor implementing the previously described mechanism. Understand that the process blocks displaying the steps in the method200may be accomplished separately, or simultaneously. As an example, both the pinned cam linear actuator205and the fixed cam linear actuator206may be extended/contracted in tandem to position the cam attach bracket207.

The method200may provide a controller201possessing a processor and memory. This controller may read signals202that includes sensor inputs that observe the current state of the pinned cam and fixed cam linear actuators8,9(position, velocity, etc), from the motor15, and from the hall effect sensor25. It may also read signals202from other sensors including environmental sensors. Environmental sensors may include pitot-static velocity, hotwire velocity, temperature, pressure, humidity, dewpoint, and other instruments. The controller may also receive signals202from a pilot or autopilot. The controller may implement feedback control to vary the cam attach bracket4position based on input of these signals202to achieve a desired cyclorotor thrust40.

The controller may extend/contract the pinned cam linear actuator205and extend/contract the fixed cam linear actuator206in order to position the cam attach bracket207. Positioning the cam attach bracket controls the cyclorotor blade pitching motion208by varying the amplitude and phase of the pitching motion. In concert with control of cyclorotor rotational speed204, controlling the cyclorotor blade pitching motion208, controls the cyclorotor thrust vector209.

The controller may also change the motor torque203in order to control the cyclorotor rotational speed204. For instance, the commanded motor torque may be increased to maintain a constant cyclorotor rotational speed when the pinned cam linear actuator8is extended, which increases cyclorotor thrust40and aerodynamic torque on the cyclorotor150. The controller may also vary cyclorotor rotational speed204to increase or decrease cyclorotor thrust40without varying the cam attach bracket position. In one example, the cyclorotor rotational speed might be increased to provide more thrust when the cam attach bracket4is already displaced to the maximum thrust position.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. It will be understood by those skilled in the art that many changes in construction and widely differing embodiments and applications will suggest themselves without departing from the scope of the disclosed subject matter.