Passive and active stability systems for ballistically launched multirotors

Patent metadata

Field	Value
Publication number	US-11780580-B2
Application number	US-202017067397-A
Country	US
Kind code	B2
Filing date	Oct 9, 2020
Priority date	Oct 9, 2019
Publication date	Oct 10, 2023
Grant date	Oct 10, 2023

Abstract

A ballistically launched foldable multirotor vehicle has a central body frame. A battery is located in an upper vertical location of the vehicle and positions a center of mass of the vehicle to provide aerodynamic stability during a launch. Fins are attached to the central body frame such that aerodynamic forces on the fins shift an aerodynamic center (AC) of the vehicle downward below the center of mass of the vehicle. Three or more foldable arms are attached to the central body frame via a hinge and exist in two states—a closed state where the foldable arms are parallel to a central body axis, and an open state (after launch) where the foldable arms extend radially outward perpendicular to the central body axis. Rotors mounted to each foldable arm are controlled by a motor to enable flight.

First claim

What is claimed is:

1. A launched multirotor vehicle, comprising:
(a) a central body frame;
(b) a battery that is located in an upper vertical location of the vehicle to position a center of mass of the vehicle to provide ballistic stability during a launch, wherein the vehicle is configured to be vertically oriented with respect to gravity at launch;
(c) fins attached to the central body frame, wherein the fins are configured such that aerodynamic forces on the fins provide for an aerodynamic center (AC) of the vehicle that is vertically downward below the center of mass of the vehicle;
(d) three or more foldable arms, wherein:
(i) each foldable arm is attached to the central body frame via a hinge;
(ii) the foldable arms exist in two states:
(1) a closed state wherein the foldable arms are parallel to a central body axis of the central body frame; and
(2) an open state wherein the foldable arms extend radially outward perpendicular to the central body axis; and

(iii) the foldable arms transition from the closed state to the open state subsequent to launch; and

(e) a rotor mounted to each of the three or more foldable arms, wherein the rotors are controlled by a motor to enable flight, and wherein each rotor is configured to continuously rotate during flight; and
wherein a configuration of the vehicle is ballistically stable during launch and actively stable during flight.

2. The vehicle of claim 1 , wherein:
the central body frame comprises a three-dimensional (3D) printed aeroshell structure.

3. The vehicle of claim 1 , wherein:
the central body frame comprises multiple plates that are separated by support columns that transmit a launch load via the central body frame.

4. The vehicle of claim 1 , further comprising:
a nosecone coupled to the central body frame, wherein the nosecone comprises a three-dimensional (3D) printed nosecone that reduces drag compared to drag resulting from a bluff body nose.

5. The vehicle of claim 1 , wherein:
the fins are fixed onto the central body frame; and
the fins comprise a ring-fin or the fins comprise a rigid fin.

6. The vehicle of claim 1 , wherein:
the fins comprise folding fins; and
feet attached to ends of the fins protect tips of the fins and serve as landing gear.

7. The vehicle of claim 1 , wherein:
the vehicle is configured to be launched from a launch tube;
the three or more foldable arms exist in the closed state by being constrained by the launch tube; and
the three or more foldable arms transition to the open state immediately after the vehicle leaves the launch tube via a torsional spring inside the hinge.

8. The vehicle of claim 1 , wherein:
transitioning to the open state of the foldable arms is controlled by a delay arm release mechanism.

9. The vehicle of claim 8 , wherein:
the delay arm release mechanism comprises a nichrome burn-wire trigger that cuts through a restraining loop of monofilament line.

10. The vehicle of claim 1 , further comprising:
a spring-loaded latch to keep the three or more foldable arms rigidly open after transitioning to the open state.

11. The vehicle of claim 1 , wherein:
the vehicle is configured to launch via a tube-launch into a ballistic trajectory.

12. The vehicle of claim 1 , further comprising:
sensors comprising a range finder, an IMU (inertial measurement unit), a barometer, and a camera;
the range finder autonomously triggering active stabilization that is controlled by an onboard computer;
the onboard computer comprising a processor and memory, wherein the onboard computer:
receives input from the sensors;
provides attitude control to stabilize the attitude based on the input from the IMU;
provides closed-loop altitude control to stabilize a z-position of the vehicle based on the input from the range finder; and
provides VIO (visual inertial odometry) initialization, and VIO convergence to stabilize an x-position and a y-position of the vehicle based on the input from the camera.

13. A launched multirotor vehicle, comprising:
(a) a central body frame;
(b) three or more foldable arms, wherein:
(i) each foldable arm is attached to the central body frame via a hinge;
(ii) the foldable arms exist in two states:
(1) a closed state wherein the foldable arms are parallel to a central body axis of the central body frame; and
(2) an open state wherein the foldable arms extend radially outward perpendicular to the central body axis; and

(iii) the foldable arms are configured to transition from the closed state to the open state subsequent to launch, wherein the vehicle is configured to be vertically oriented with respect to gravity at launch;

(c) a rotor mounted to each of the three of more foldable arms, wherein the rotors are controlled by a motor to enable flight, and wherein each rotor is configured to continuously rotate during flight;
(d) sensors mounted on the central body frame, wherein the sensors comprise a range finder, an IMU (inertial measurement unit), and a camera;
(e) the range finder configured to autonomously trigger active stabilization that is controlled by an onboard computer;
(f) the onboard computer comprising a processor and memory, wherein the onboard computer:
(i) receives input from the sensors;
(ii) provides attitude control to stabilize the attitude based on the input from the IMU;
(iii) provides closed-loop altitude control to stabilize a z-position of the vehicle based on the input from the rangefinder; and
(iv) provides VIO (visual inertial odometry) initialization, and VIO convergence to stabilize an x-position and a y-position of the vehicle based on the input from the camera; and

wherein a configuration of the vehicle is ballistically stable during launch and actively stable during flight.

14. The vehicle of claim 13 , wherein:
the central body frame comprises a three-dimensional (3D) printed aeroshell structure.

15. The vehicle of claim 13 , wherein:
the central body frame comprises multiple plates that are separated by support columns that transmit a launch load via the central body frame.

16. The vehicle of claim 13 , further comprising:
a nosecone coupled to the central body frame, wherein the nosecone comprises a three-dimensional (3D) printed nosecone that reduces drag compared to drag resulting from a bluff body nose.

17. The vehicle of claim 13 , wherein:
the vehicle is configured to be launched from a launch tube;
the three or more foldable arms exist in the closed state by being constrained by the launch tube; and
the three or more foldable arms transition to the open state immediately after the vehicle leaves the launch tube via a torsional spring inside the hinge.

18. The vehicle of claim 13 , wherein:
transitioning to the open state of the foldable arms is controlled by a delay arm release mechanism.

19. The vehicle of claim 18 , wherein:
the delay arm release mechanism comprises a nichrome burn-wire trigger that cuts through a restraining loop of monofilament line.

20. The vehicle of claim 13 , further comprising:
a spring-loaded latch to keep the three or more foldable arms rigidly open after transitioning to the open state.

21. The vehicle of claim 13 , wherein the onboard computer provides VIO initialization based on:
pitch and roll rates of the vehicle below a defined pitch-roll threshold;
a vertical velocity below a vertical velocity threshold; and
a lateral velocity below a lateral velocity threshold.

Assignees

• California Inst Of Techn

Inventors

• Izraelevitz Jacob S
• Kennedy Brett A
• Bouman Amanda R
• Pastor Moreno Daniel
• Anderson Matthew James Lindsay
• Nadan Paul M
• Burdick Joel W

Classifications

• B64U2101/30

  for imaging, photography or videography · CPC title

• B64U10/14

  with four distinct rotor axes, e.g. quadcopters · CPC title

• B64U30/20

  Rotors; Rotor supports · CPC title

• B64C39/024 Primary

  of the remote controlled vehicle type, i.e. RPV · CPC title

• B64C1/30

  Parts of fuselage relatively movable to reduce overall dimensions of aircraft · CPC title