System and method for providing a simple and reliable inertia measurement unit (IMU)

• US 10,030,974 B2
• Filed: 11/11/2016
• Issued: 07/24/2018
• Est. Priority Date: 04/07/2015
• Status: Active Grant

• Current Assignee: SZ DJI Technology Co., Ltd. (d/b/a DJI) (iFlight Technology Company Limited)
• Original Assignee: SZ DJI Technology Co., Ltd. (d/b/a DJI) (iFlight Technology Company Limited)
• Inventors: Feng, Jiangang, Tang, Yin
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US15/349,980
• Publication Number:
  US 20170059319A1
• Time in Patent Office: 620 Days
• CPC Class Codes: B64C 39/024 of the remote controlled vehicle type, i.e. RPV
• CPC Class Codes: B64U 2201/10 autonomous, i.e. by navigating independently from ground or air stations, e.g. by using inertial navigation systems [INS]
• CPC Class Codes: B64U 50/10 Propulsion rotors specially adapted for rotorcraft or VTOL B64U30/20
• CPC Class Codes: G01C 19/00 Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
• CPC Class Codes: G01C 19/5628 Manufacturing; Trimming; Mounting; Housings
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems
• CPC Class Codes: G01C 21/265 constructional aspects of navigation devices, e.g. housings, mountings, displays G01C21/3688 takes precedence
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G01P 1/003 used for damping
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: H01L 23/345 Arrangements for heating thermal treatment apparatus H01L21/00
• CPC Class Codes: H05K 1/189 characterised by the use of a flexible or folded printed circuit H05K3/326 takes precedence
• CPC Class Codes: H05K 2201/10151 Sensor
• CPC Class Codes: H05K 7/20 Modifications to facilitate cooling, ventilating, or heating

Abstract

System and method can support a measurement module on a movable object. The measurement module includes a first circuit board with one or more sensors. Additionally, the measurement module includes a weight block assembly, wherein the weight block assembly is configured to have a mass that keeps an inherent frequency of the measurement module away from an operation frequency of the movable object. Furthermore, said first circuit board can be disposed in an inner chamber within the weight block assembly.

Claims

1. An inertia measurement module for an unmanned aircraft, said inertia measurement module comprising:

a weight block assembly comprising a first weight block and a second weight block coupled together to form an inner chamber therein;

a first circuit board comprising one or more sensors, said first circuit board being supported within the inner chamber of the weight block assembly;

a housing assembly configured to support the weight block assembly therein, wherein the housing assembly is mounted onto a second circuit board located outside of said housing assembly; and

a signal line that connects the first circuit board with the second circuit board, wherein the signal line is (1) coupled to a first edge of the first circuit board and (2) extends out of openings from the weight block assembly and the housing assembly to the second circuit board, wherein said openings are located proximal to a second edge of the first circuit board that is different from the first edge of the first circuit board.

2. The inertia measurement module of claim 1, wherein:

at least one of said sensors is an inertia sensor, which includes one or more velocity measurement instruments, one or more acceleration measurement instruments, one or more gyroscopes, and/or one or more gravity gradiometers.

3. The inertia measurement module of claim 1, further comprising:

one or more vibration damping elements for reducing vibrations experienced by the one or more sensors, wherein said vibrations are produced by one or more propulsion units located distally on the unmanned aircraft.

4. The inertia measurement module of claim 1, further comprising:

a thermal interfacing material, which is filled in a gap in the inner chamber within the weight block assembly, wherein the thermal interfacing material is adapted to conduct heat away from the first circuit board, and to prevent the first circuit board from moving inside the inner chamber within the weight block assembly such that the first circuit board abuts against an inner surface of the first weight block via the thermal interfacing material.

5. The inertia measurement module of claim 4, wherein:

the thermal interfacing material is selected from a group consisting of silica gel, thermal gel, epoxy, phase change materials, polyimide, graphite, aluminum tapes, and silicone-coated fabrics.

6. The inertia measurement module of claim 5, wherein the first and second edges of the first circuit board are opposite to each other.

7. The inertia measurement module of claim 1, wherein the signal line comprises (1) a first bent portion located near the first edge of the first circuit board inside the housing assembly, and (2) a second bent portion located near the second edge of the first circuit board outside of the housing assembly.

8. The inertia measurement module of claim 1, wherein the openings comprise a first opening in the weight block assembly and a second opening in the housing, and the signal line is stabilized on an outside surface of the weight block assembly.

9. The inertia measurement module of claim 6, wherein a portion of the signal line extends longitudinally across a surface of the first circuit board between the first and second edges of the first circuit board.

10. The inertia measurement module of claim 3, wherein the one or more propulsion units are located on a plurality of arms that extend from a central body of the unmanned aircraft, the inertia measurement module is located at the central body of the unmanned aircraft, and the vibrations propagate from the one or more propulsion units along the plurality of arms towards the inertia measurement module at the central body during operation of said unmanned aircraft.

11. The inertia measurement module of claim 9, wherein said portion of the signal line is in contact with the thermal interfacing material.

12. The inertia measurement module of claim 1,

wherein the housing assembly comprises a first housing member and a second housing member, which are adapted to be locked together to thereby form a cavity therebetween,

wherein a first surface of the weight block assembly abuts against a first inner surface of the cavity via an adhesive layer, and a second surface of the weight block assembly abuts against a second inner surface of the cavity via a foam layer.

13. The inertia measurement module of claim 12, wherein:

the weight block assembly is positioned within the housing assembly using a positioning device, and affixed in the housing assembly using the adhesive layer and/or the foam layer.

14. The inertia measurement module of claim 3, wherein:

the one or more vibration damping elements comprise one or more foam layers that are configured such that the inertia measurement module operates within a predetermined humidity and temperature range.

29. The inertia measurement module of claim 12, wherein the first and second surfaces of the weight block assembly are located on opposite sides of the weight block assembly, wherein the first inner surface of the cavity is located on the first housing member and the second inner surface of the cavity is located on the second housing member.

15. A method for assembling an inertia measurement module for an unmanned aircraft, said method comprising:

providing a first circuit board comprising one or more sensors;

providing a weight block assembly that is formed by coupling a first weight block and a second weight block together to form an inner chamber therein, and supporting the first circuit board comprising the one or more sensors within the inner chamber of the weight block assembly;

providing a housing assembly and supporting the weight block assembly therein, wherein the housing assembly is mounted onto a second circuit board located outside of said housing assembly; and

providing a signal line that connects the first circuit board with the second circuit board, wherein the signal line is (1) coupled to a first edge of the first circuit board and (2) extends out of openings from the weight block assembly and the housing assembly to the second circuit board, wherein said openings are located proximal to a second edge of the first circuit board that is different from the first edge of the first circuit board.

16. The method of claim 15, wherein:

at least one of said sensors is an inertia sensor, which includes one or more velocity measurement instruments, one or more acceleration measurement instruments, one or more gyroscopes, and/or one or more gravity gradiometers.

17. The method of claim 15, further comprising:

providing one or more vibration damping elements for reducing vibrations experienced by the one or more sensors, wherein said vibrations are produced by one or more propulsion units located distally on the unmanned aircraft.

18. The method of claim 15, further comprising:

filling a thermal interfacing material in a gap in the inner chamber within the weight block assembly, wherein the thermal interfacing material is adapted to conduct heat away from the first circuit board, and to prevent the first circuit board from moving inside the inner chamber within the weight block assembly such that the first circuit board abuts against an inner surface of the first weight block via the thermal interfacing material.

19. The method of claim 18, wherein:

the thermal interfacing material is selected from a group consisting of silica gel, thermal gel, epoxy, phase change materials, polyimide, graphite, aluminum tapes, and silicone-coated fabrics.

20. The method of claim 19, wherein the first and second edges of the first circuit board are opposite to each other.

21. The method of claim 15, wherein the signal line comprises (1) a first bent portion located near the first edge of the first circuit board inside the housing assembly, and (2) a second bent portion located near the second edge of the first circuit board outside of the housing assembly.

22. The method of claim 21, wherein the openings comprise a first opening in the weight block assembly and a second opening in the housing, and the signal line is stabilized on an outside surface of the weight block assembly.

23. The method of claim 20, wherein a portion of the signal line extends longitudinally across a surface of the first circuit board between the first and second edges of the first circuit board.

24. The method of claim 17, wherein:

the one or more propulsion units are located on a plurality of arms that extend from a central body of the unmanned aircraft, the inertia measurement module is located at the central body of the unmanned aircraft, and the vibrations propagate from the one or more propulsion units along the plurality of arms towards the inertia measurement module at the central body during operation of said unmanned aircraft.

25. The method of claim 23, wherein said portion of the signal line is in contact with the thermal interfacing material.

26. The method of claim 15,

wherein the housing assembly comprises a first housing member and a second housing member, which are adapted to be locked together to thereby form a cavity therebetween,

wherein a first surface of the weight block assembly abuts against a first inner surface of the cavity via an adhesive layer, and a second surface of the weight block assembly abuts against a second inner surface of the cavity via a foam layer.

27. The method of claim 26, further comprising:

using a positioning device to position the weight block assembly within the housing assembly, and using the adhesive layer and/or the foam layer to affix the weight block assembly in the housing assembly.

28. The method of claim 17, wherein the one or more vibration damping elements comprise one or more foam layers that are configured such that the inertia measurement module operates within a predetermined humidity and temperature range.

30. The method of claim 26, wherein the first and second surfaces of the weight block assembly are located on opposite sides of the weight block assembly, wherein the first inner surface of the cavity is located on the first housing member and the second inner surface of the cavity is located on the second housing member.