Rigid-flexible combined folding inertial measurement device and system

Abstract

The invention discloses a rigid-flexible combined folding inertial measurement device and system, and belongs to the technical field of inertial measurement. The device comprises a flexible circuit board and at least one sensor arranged on the flexible circuit board, and the flexible circuit board can be folded to form a laminated structure. In some embodiments, the flexible circuit board comprises a central main circuit area and at least two branch extension areas, and rigid-flexible combination is realized through a reinforcing plate. After folding, an interlayer gap is formed by using the thickness difference between the reinforcing plate and the flexible circuit board, and a damping material can be filled to wrap the sensor. Through the rigid-flexible combined structural design, the stacked integrated structural design, the gap and vibration reduction design and the flexible customization design, the ultra-small size, light weight, high impact resistance and flexible customization of the device are achieved, and the problems of large size, large weight, impact transmission, data lag and the like caused by an existing balancing weight design scheme are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inertial measurement technology, in particular to a micro inertial measurement device and system based on rigid-flex folding structure. BACKGROUND

[0002] Inertial measurement device (IMU) is the core perception component in the fields of model aircraft, aircraft, unmanned aerial vehicle, robot, etc. With the upgrading of application scenarios to miniaturization and high integration, the existing technical solutions gradually fail to meet the requirements of volume, weight and impact resistance. The most relevant inertial measurement device patents to the present application all adopt the design of connecting sensor with weight block, and optimize vibration isolation by adjusting the weight of the weight block. However, this design is limited by physical laws and has the following core defects: structural redundancy, high proportion of weight block or multi-circuit board splicing, resulting in excessive volume and weight, which cannot adapt to micro scenarios, for example, CN201110260585 specification

[0036] records that the weight of the weight block 5 is 1g-30g, preferably, 15g, 17.5g, 20g or 25g can be selected. The weight block significantly increases the overall weight, and CN201580077627 specification

[0032] describes that the weight block assembly surrounds the sensor, forming a multi-component splicing structure; the weight block transmits impact, and the weight block generates inertial force under strong impact, increasing the risk of sensor damage. According to the formula of inertial force (the negative sign indicates that the direction is opposite to the acceleration), the greater the mass m of the weight block, the greater the impact force F, for example, CN201110260585 and CN202010269676 both adopt the design of recessed weight block surrounding the sensor. In the automobile crash test scenario (impact acceleration of 9.5g~142g), the inertial force of the weight block may be transmitted to the sensor; data lag, according to the formula of dynamic response delay (where depends on the current flight speed of the unmanned aerial vehicle, usually depends on the support force of the damping material on the sensor), it can be known that the dynamic response delay is proportional to the mass of the weight block. The weight block increases the total mass of the system, resulting in lag of dynamic response delay and phase difference, which cannot meet the high-frequency acquisition requirement (such as 10KHz acquisition requirement). Therefore, a rigid-flex folding structure without weight block is needed to solve the above-mentioned defects. SUMMARY

[0003] The present application aims to solve the problems of structural redundancy (excessive volume and weight), transmission of impact by weight block (easy to damage the sensor in strong impact scenario), data lag, etc. of the existing inertial measurement device, and provides a rigid-flex folding structure to realize the structure of the inertial measurement device with ultra-small size, light weight, flexible customization, strong impact resistance and high reliability.

[0004] To achieve the above object, the present application provides a rigid-flexible combined folding inertial measurement device and system. The device comprises a flexible circuit board and at least one sensor disposed on the flexible circuit board; the flexible circuit board is configured to be folded to form a stacked structure.

[0005] In some embodiments, the flexible circuit board comprises a central main circuit area and at least two branch extension areas extending from the central main circuit area.

[0006] In some embodiments, the device further comprises a reinforcing plate bonded to the flexible circuit board. The reinforcing plate is configured to provide rigid support in the non-folded area of the branch extension area.

[0007] Optionally, the branch extension area is configured to be folded towards the central main circuit area, so that the folded device forms a cubic structure.

[0008] To achieve the above object, the present application provides a structure design of a rigid-flexible combined folding inertial measurement device, which comprises: rigid-flexible combined structure design; stacked integrated structure design; gap and vibration reduction design; and flexible customization design.

[0009] The rigid-flexible combined structure design comprises: a flexible circuit board body comprising a central main circuit area 111 and N branch extension areas 112 and a flexible extension part 113, wherein N≥2, preferably N=2, 3 or 4, the overall shape is like multiple square petals, N=4 is a cross shape, N=3 is a T shape, and N=2 is a 1 shape, the flexible circuit board is made of polyimide or polyester film as the base material, the thickness is 0.11-0.2mm, the total thickness of the upper and lower layer characters ink, solder mask, copper foil and base insulating layer is included, and the flexible circuit board has the characteristics of light weight, thin thickness and free bending and folding; a plurality of reinforcing plates 102 made of rigid material, preferably 1.6mm thick epoxy resin-based composite material, are bonded to the edges of the flexible circuit board by adhesive, preferably 3M9077 glue or 3M468 glue, but the flexible extension part has no reinforcing plate, forming a rigid-flexible combined structure which retains folding flexibility and provides structural rigidity.

[0010] The stacked integrated structure design comprises: the flexible extension part 113 is used for folding, the branch extension area 112 and the central main circuit area 111 are stacked by 180° to form a three-dimensional structure, each flexible extension part has a different length and a preset stacked level position; the upper and lower reinforcing plates 102 are bonded and fixed after stacking to form a cubic structure, the total number of stacked layers is N+1, the bottom area after stacking is only the bottom area of the central main circuit area, and the bottom area before stacking is N+1 times the bottom area after stacking; optionally, a plurality of through holes 121 are provided in the central main circuit area and the branch extension area, which are coaxial after stacking and are used for fixing or connecting other devices.

[0011] The gap and damping design includes: the interlayer gap is formed by the thickness difference between the reinforcing plate 102 and the flexible circuit board, and the interlayer gap is filled with a plurality of layers of damping material 201, preferably, silicone or sponge with a Shore A hardness of 15-45 degrees is selected, the number of layers of the damping material is greater than the number of layers of the branch extension area 112 where the sensor 132 is located, for example, 2 layers of sensor require 3 layers of damping material, the sensor is wrapped by the damping material, the vibration energy is absorbed by damping to reduce mechanical impact stress, and heat is transferred by the heat conductivity of the material.

[0012] The flexible customization design includes: the number of branches N is adjustable, different scenes are adapted by adjusting the number of branch extension areas 112, N=2, 3, 4, N=2 is a 1-shaped structure (stacked 3 layers), preferably adapted to a micro unmanned aerial vehicle, N=3 is a T-shaped structure (stacked 4 layers), preferably adapted to a model aircraft, N=4 is a cross-shaped structure (stacked 5 layers), preferably adapted to a general robot; the sensor is modular and replaceable, the branch extension area is provided with a standardized welding or plug-in interface, different range sensors 132 such as ADIS16470, ADXL1003, and ICM42688 can be replaced without damaging the structure; the function is expanded and adapted, the processor chip 131 of the center main circuit area 111 is provided with a communication interface, and optional interfaces such as I2C, SPI, and UART can be externally connected to a functional module; optionally, the through hole 121 supports M2 screw fixation or non-hole sealing design.

[0013] The beneficial effects of the embodiment of the application are: ultra-small size and light weight, through rigid and flexible folding, the volume after stacking is 28mmx28mmx17.09mm, without additional counterweight and rigid shell, the weight is ≤25g, suitable for micro scenes, compared with CN202010269676 (including a counterweight assembly), the volume is reduced; flexible customization, the number of branches N is adjustable, the sensor is modular and replaceable, the through hole 121 design supports diversified installation, and is suitable for different scenes such as unmanned aerial vehicles, automobiles, and robots; strong impact resistance, there is no rigid structure around the sensor 132, the impact resistance performance depends on the range of the sensor, optionally, a sensor with a range of ±200g of ADXL1003 is used, which does not exceed the range of the sensor in the automobile crash test (impact acceleration 9.5g~142g) environment, while CN202010269676 may generate inertial force under strong impact because the sensor is associated with the counterweight assembly; high reliability, the damping material wraps and the modular design, the structure is simple, there is no extra shell and counterweight, production and assembly are convenient, and the cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to further illustrate the structure of the application, the drawings of the specification include:

[0015] Figure 1 : The exploded structural diagram of the N=4 cross-shaped rigid-flexible combined structure in the unfolded state.

[0016] Figure 2 : The unfolded state of the folding integrated structure, showing the layout of the central main circuit area and the branch extension area;

[0017] Figure 3 : The perspective view of the folded cubic structure;

[0018] Figure 4 : Step 1 from folding to Figure 1 ; Figure 3

[0019] Figure 5 : Step 2 from folding to Figure 1 ; Figure 3

[0020] Figure 6 : Step 3 from folding to Figure 1 ; Figure 3

[0021] Figure 7 : Figure 3 : The front cross-sectional view of , showing the position relationship of the interlayer gap, damping material and sensor;

[0022] Figure 8 : Figure 3 : The right cross-sectional view of , showing the position relationship of the interlayer gap, damping material and sensor.

[0023] Explanation of reference numerals:

[0024] 102, reinforcing plate

[0025] 111, central main circuit area

[0026] 112, branch extension area

[0027] 113, flexible extension part

[0028] 121, through hole

[0029] 131, processor chip

[0030] 132, sensor

[0031] 201, damping material DETAILED DESCRIPTION

[0032] The present application will be further described below in conjunction with specific embodiments, which are only for clearly showing the technical solutions of the present application and are not a limitation of the present application. Taking the cross-shaped structure with N=4 as an example, the key implementation details of N=2 and N=3 are supplemented.

[0033] ​Rigid-flex structure design: The main body of the flexible circuit board adopts a 0.2mm thick flexible circuit board, which includes photocured character ink, solder mask film, copper foil and polyimide insulating layer substrate. The overall structure is cross-shaped, including one central main circuit area 111 and four branch extension areas 112. Each branch extension area has a reserved flexible extension part 113, with lengths of 3mm, 3mm, 6mm and 9mm respectively, which are used to match the layer height. The shape of the central main circuit area and each branch extension area is the same, which is a rounded rectangle with a side length of 28mm. The reinforcing plate 102 adopts multiple 1.6mm thick epoxy glass cloth laminates, which are pasted on the edge area of the flexible circuit board in blocks. However, there is no reinforcing plate around the flexible extension part to avoid folding interference. The paste between the reinforcing plates is pasted with acrylic adhesive, with a glue layer thickness of 0.13mm. After 12 hours of room temperature curing, the peel strength is 74-76N / 100mm.

[0034] Stacked integrated structure design: The stacking method is used, and the four branch extension areas 112 are folded by 180° to the central main circuit area 111 in the planned order, with the reinforcing plate 102 attached. The total stacking is 5 layers (1 central main circuit area + 4 branch extension areas), and the reinforcing plate is 9 layers (2 layers in the central area, 2 layers in each of the three branch areas, and 1 layer in one branch area). The glue layer is 13 layers (9 layers of reinforcing plate - flexible circuit board paste + 4 layers of reinforcing plate paste). The fixing method is used, and after folding, a cubic structure with dimensions of 28mm x 28mm x 17.09mm is formed. The height calculation is: reinforcing plate 1.6mm x 9 layers + glue layer 0.13mm x 13 layers + flexible circuit board 0.2mm x 5 layers = 17.09mm. The connection logic is that the central main circuit area is located on the 2nd layer (from bottom to top), and the branch extension areas are located on the 1st, 3rd, 4th and 5th layers respectively. The different lengths of the flexible extension parts 113 are used to distinguish the levels. The functional division is that the 1st layer branch extension area reserves the connector (for power supply and communication), the 3rd layer branch extension area is for bearing the sensor 132, the 4th layer branch extension area is for bearing the redundant sensor, and the 5th layer branch extension area bears the memory chip. The through-hole design is that each branch extension area or central main circuit area reserves 4 through-holes with a diameter of 2mm. The hole center horizontal distance is 20mm (4mm from the edge), and the coaxiality error after stacking is ≤0.1mm, which is suitable for M2 screws to fix the entire stacked structure.

[0035] Gap and vibration reduction design: Gap formation, the reinforcing plate 102 is 1.6mm thick, and the flexible circuit board is 0.2mm thick. After folding, the interlayer gap is about 2.8mm (reinforcing plate thickness 1.6mm x 2 layers - flexible circuit board thickness 0.2mm x 2 layers = 2.8mm). The damping material 201 adopts a sponge with a Shore A hardness of 25 degrees, with dimensions of 10mm x 10mm x 1mm, covering the sensor 132. Since there are two branch extension areas containing sensors, three layers of sponge are used to wrap from top to bottom. It is measured that the sponge can absorb vibration and transfer heat.

[0036] Flexible customization design: branch number adaptation, N=2 (1-shaped) flexible extension part 113 length 3mm (1st layer), 6mm (3rd layer), 3 layers, suitable for automobile transmission shaft detection (space ≤20mm×30mm×15mm), N=3 (T-shaped) flexible extension part length 3mm (1st layer), 3mm (3rd layer), 6mm (4th layer), 4 layers, suitable for small robot joints (anti-torsion requirement), N=4 (cross-shaped) as described above, suitable for micro unmanned aerial vehicle (cabin space 28mm×28mm×18mm); sensor modular replacement, branch extension area 112 uses 14-pin LGA package interface, when replacing the sensor, use a hot air gun (temperature 280℃, air speed 1 level) to disassemble and weld, without damaging the structure; function expansion, the processor chip 131 of the center main circuit area 111 reserves an SPI interface, which can be externally connected with a barometer and other modules to expand the function.

[0037] While the preferred embodiments of the application have been shown and described herein, it will be apparent to those skilled in the art that many changes, modifications, and substitutions can be made thereto without departing from the application. It is to be understood that various alternatives to the embodiments of the application described herein can be employed in practicing the application. It is intended that the following claims define the scope of the application and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

1. A rigid-flexible foldable inertial measurement device, characterized in that, include: A flexible circuit board having at least one sensor disposed thereon; the flexible circuit board is configured to be folded to form a stacked structure.

2. The rigid-flexible foldable inertial measurement device according to claim 1, characterized in that, The flexible circuit board includes a central main circuit area and at least two branch extension areas extending from the central main circuit area.

3. The rigid-flexible foldable inertial measurement device according to claim 2, characterized in that, It also includes a reinforcing plate bonded to the flexible circuit board; the reinforcing plate is configured to provide rigid support in the non-folded area of ​​the branch extension region.

4. The rigid-flexible foldable inertial measurement device according to claim 3, characterized in that, The branch extension area is configured to fold toward the central main circuit area, such that the folded device forms a cubic structure.

5. The rigid-flexible foldable inertial measurement device according to claim 4, characterized in that, After folding, an interlayer gap is formed between the reinforcing plate and the flexible circuit board. A vibration damping material is disposed in the interlayer gap, and the vibration damping material at least partially encapsulates the sensor.

6. The rigid-flexible foldable inertial measurement device according to claim 2, characterized in that, The number N of the branch extension regions is greater than or equal to 2, and N can be adjusted to adapt to different application scenarios.

7. The rigid-flexible foldable inertial measurement device according to claim 3, characterized in that, The reinforcing plate has a thickness.

8. The rigid-flexible foldable inertial measurement device according to claim 5, characterized in that, The vibration damping material is an elastic material.

9. An inertial measurement system, characterized in that, Includes the rigid-flexible folding inertial measurement device as described in any one of claims 1 to 8.

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