Enhanced vibration isolation solution for sensitive multirotor drone components

Abstract

A vibration isolating plate, suitable for multirotor drones, has a low vibration area 5 with connections 9 to the drone’s body 2 at nodal points (fig.4,7) associated with specific modes of vibration,

Description

DESCRIPTION: Unmanned aerial vehicles, otherwise known as drones, require precise measurements of their movement to operate effectively. To take precise measurements of the orientation and rotational velocity of a drone sensors such as accelerometers and gyroscopes are installed within the drone. Drones may also be fitted with camera systems or other components that require a low level of vibration in order to function effectively. Vibrations created by motors, propellers or aerodynamic effects such as buffeting, or turbulence can interfere with the measurement of the movements of the drone or with the functionality or performance of other vibration sensitive components such as cameras. Existing methods to address this issue involve hardware-based solutions, such as vibration-absorbing rubber components placed between the drone body and the sensitive components, and softwarebased techniques like low-pass filtering of the sensor data before it is used to control the drone. However, filtering using a hardware or software-based approach comes with drawbacks. Filtering adds additional time delay between the drone moving and the sensor detecting the movement of the drone. This increases the delay between an unexpected movement and a corrective control action. Hardware-based filtering may also add weight, additional components, and cost which are often undesirable. Software-based filtering increases the computational requirement to process the sensor data. This may necessitate using a more powerful processor or reducing the data rate which is also undesirable. Software based filtering is also not suitable for every type of sensor. To overcome these challenges, this patent introduces a novel vibration isolating plate. The plate is designed to reduce the transmission of vibrations from the drone's body to vibration-sensitive components whilst ensuring rigid body rotations and translations of the drone are transmitted. This is achieved by establishing a low vibration area within the plate to house the sensitive components. Importantly, the plate is substantively connected to the drone's body at nodal points associated with specific modes of vibration of concern, while maintaining substantive disconnection from the rest of the drone body. This configuration effectively minimizes the impact of vibrations on the sensitive components while still tightly coupling the movement of the sensitive components to the rigid body movements of the drone. The invention will now be described by way of example and with reference to the accompanying drawings. Figure 1 shows a simplified schematic diagram of a multirotor drone in plan view. Figure 2 shows a simplified schematic diagram of a multirotor drone in side view. Figure 3 shows a schematic example of a resonant mode of vibration of a multirotor drone. Figure 4 shows a schematic example of nodal and antinodal areas of the body of a multirotor drone for one mode of vibration. Figure 5 shows a vibration isolating plate designed according to the current invention. Figure 6 shows a vibration isolating plate designed according to the current invention which uses separate parts to connect the low vibration area to the body of the drone. 09 10 23 Figure 7 shows a vibration isolating plate designed according to the current invention created with two parts. Figure 8 shows a simplified schematic diagram of a tricopter drone in plan view. Figure 9 shows a vibration isolating plate designed according to the current invention for a tricopter drone. Figure 10 shows a simplified schematic diagram of a hexacopter drone in plan view. Figure 11 shows a vibration isolating plate designed according to the current invention for a hexacopter drone. Figure 12 shows a simplified schematic diagram of a octacopter drone in plan view. Figure 13 shows a vibration isolating plate designed according to the current invention for a octacopter drone. Figure 14 shows a vibration isolating plate designed according to the current invention with two vibration sensitive components attached to the vibration isolating plate and also attached to the body of the drone. In Figure 1 a schematic of a multirotor drone is shown consisting of a vibration sensitive component 1 mounted within the drone body 2. The drone has a plurality of arms 3 which connect the drone body 2 to a plurality of motors 4. In this typical drone design the spinning motors and attached propellers are a substantial source of vibration. Figure 2 shows the same schematic in a side view. The whole structure of the drone has a plurality of resonant modes of vibration. Figure 3 shows a schematic example of a mode of vibration for a multirotor drone structure. The motors 4 are moving up and down, the arms 3 are bending, and the body of the drone 2 is bending as a result of the resonant vibration. The bending of the body of the drone 2 transmits vibrations to the vibration sensitive component 1 which is undesirable. It is possible to analytically determine the resonant modes of vibration for a drone structure up to and including a maximum frequency of interest. This can be done in several ways including experimental testing or finite element simulation of the structure. Typically, the resonant modes of vibration with lower natural frequencies are of more concern when the vibration sensitive component 1 is a sensor used to determine the orientation or rotation rate of the drone. However, this may not always be the case and will depend on the drone structure and the nature of the vibration sensitive component 1. Once a resonant mode of vibration is determined it is possible to identify areas of the drone body which move more as a result of the vibration and areas of the drone body which move less as a result of the vibration. Figure 4 shows the drone body of Figure 3 in plan view. Darker shading indicates the areas of the drone body which move more as a result of the resonant mode of vibration shown in Figure 3. Areas which move more will be called antinodes of vibration 6 and areas which move less will be called nodes of vibration 7. The vibration isolating plate described in this disclosure is used to reduce the transmission of vibrations from one or more identified modes of vibration from the body of the drone 2 into the vibration sensitive component 1. Figure 5 shows a vibration isolating plate designed according to the description in this disclosure. It consists of a low vibration area 5 where one or more vibration sensitive components can be secured. 09 10 23 This area is substantially connected to the body of the drone 2 by one or more connecting features 9 at one or more locations which have been identified as nodes of vibration 7 for the resonant modes of concern. The area 5 is also substantially disconnected from the rest of the body of the drone 2 by separating features 8. The substantial connecting features 9 may be formed by the material between two separating features 8 as shown in Figure 4. The substantial connecting features 9 may also be formed using one or more separate parts that are connected to the body of the drone 2 and to the low vibration area 5 as shown in Figure 6. The substantial connecting features 9 may also be formed using one or more features of one or more separate parts connected to the body of the drone 2 close to the nodes of vibration 7. The substantial connecting features 9 may be formed in other ways that perform the function of connecting the low vibration area to the body of the drone. The separating features 8 may be formed from the separation between the drone body and the vibration isolating plate or the separation between two other parts. The separating features 8 may be achieved by having less material in locations around the low vibration area for example creating slots or substantially thinning the material compared to the connecting features 9. The separating features 8 may also be achieved by using a material that is substantially less rigid than the material used to form the connecting features 9 for example a soft rubber or plastic if the connecting features 9 are formed from rigid plastic or metal. The separating features 8 may be achieved in other ways that perform the function of separating the low vibration area from the body of the drone. The separating and connecting features may be created using multiple parts. Figure 7 shows a vibration isolating plate according to the current invention created by attaching a separate part to the body of the drone 2 which is connected at four nodes of vibration which move less as a result of a resonant mode of vibration. The separating features 8 and connecting features 9 may be formed in the same part for example by machining or moulding. For multirotor drones that have four arms the preceding examples provide a reduction to practice for a vibration isolating plate according to the current invention. Multirotor drones with multiple arms may have many nodes of vibration throughout the structure. It is not necessary to connect to all the suitable nodes of vibration. Usually, one to four connections spaced around the low vibration area 5 are sufficient. For multirotor drones the nodes for low frequency vibrations can typically be found midway between adjacent arms. In most cases the low frequency vibrations are of greatest concern and therefore it is advantageous to connect the vibration isolating plate at the midpoints between adjacent arms. The application of the current invention to drones with three, six and eight arms will now be described by way of further examples. Figure 8 shows a tricopter drone with three arms in plan view. 09 10 23 Figure 9 shows a vibration isolating plate according to the current invention suitable for a tricopter drone. The low vibration area 5 is connected to the body of the drone 2 at the nodes of vibration found between adjacent arms using substantial connecting features 9 and separated from the rest of the drone body 2 by separating features 8. Figure 10 shows a hexacopter drone with six arms in plan view. Figure 11 shows a vibration isolating plate according to the current invention suitable for a hexacopter drone. The low vibration area 5 is connected to the body of the drone 2 at three nodes of vibration found between adjacent arms using substantial connecting features 9 and separated from the rest of the drone body 2 by separating features 8. Figure 12 shows an octacopter drone with eight arms in plan view. Figure 13 shows a vibration isolating plate according to the current invention suitable for an octacopter drone. The low vibration area 5 is connected to the body of the drone 2 at four nodes of vibration found between adjacent arms using substantial connecting features 9 and separated from the rest of the drone body 2 by separating features 8. Although it is usually preferable to mount the vibration sensitive component entirely on the vibration isolating plate this may not always be possible due to other design constraints. A significant reduction in vibration can still be achieved by locating one or more of the attachment points for the vibration sensitive component within the low vibration area of the vibration isolating plate. The remaining attachment points are located elsewhere on the drone. Figure 14 shows a vibration isolating plate according to the current invention with two vibration sensitive components 1. Each vibration sensitive component is attached within the low vibration area of the vibration isolation plate 5 and also attached to the body of the drone 2. Each vibration sensitive component benefits from a reduction in vibration compared to being mounted only to the body of the drone. This approach is useful in applications where design constraints limit the number or size of vibration isolating plates that can be implemented. When there is insufficient space to mount all the vibration sensitive components entirely within the low vibration area locating one or more attachment points for each of the vibration sensitive components within the low vibration area can still provide a reduction in vibration for those components.

Claims

1. A vibration isolating plate for multirotor drones, comprising a low vibration area substantially connected to the drone's body at nodal points associated with specific modes of vibration, while maintaining substantial disconnection from the remaining parts of the drone body.

2. The vibration isolating plate of claim 1, where the points of connection are positioned midway between adjacent arm attachment points on the drone body.

3. The vibration isolating plate of claim 1, wherein there is more than one point of substantial connection between the low vibration area and the drone's body.

4. The vibration isolating plate of claim 1, wherein there are between 1 and 8 points of substantial connection between the low vibration area and the drone's body.

5. The vibration isolating plate of claim 1, wherein there are between 1 and 4 points of substantial connection between the low vibration area and the drone's body.

6. The vibration isolating plate of claim 1, wherein there are more than 8 points of substantial connection between the low vibration area and the drone's body.

7. The vibration isolating plate of claim 1, wherein the separating features are engineered to minimize energy transfer from the drone's body to the low vibration area.

8. The vibration isolating plate of claim 1, wherein the substantial connections are engineered to tightly couple the rigid body movements of the drone to the low vibration area.

9. The vibration isolating plate of claim 1, wherein the separation between the vibration isolating plate and the drone's body forms the separating feature.

10. The vibration isolating plate of claim 1, wherein the separating features are characterized by a softer or more flexible material compared to the substantial connecting features.

11. The vibration isolating plate of claim 1, wherein the vibration isolating plate comprises one or more separate parts.

12. The vibration isolating plate of claim 1, wherein the vibration isolating plate is integrally formed as part of the drone's body.

13. The vibration isolating plate of claim 1, wherein the separating features are characterized by thinner material compared to the substantial connecting features.

14. The vibration isolating plate of claim 1, wherein the separating features and connecting features are both formed in the same part of the drone's body.

15. The vibration isolating plate of claim 1, wherein the separating features are formed by slots.

16. The vibration isolating plate of claim 1, wherein the connecting features are formed from material between two separating features.

17. The vibration isolating plate of claim 1, wherein the separating features are implemented through a material composition that differs in rigidity compared to the material composition used for the substantial connecting features.

18. The vibration isolating plate of claim 1, wherein the nodal points of connection are determined based on resonant modes of the drone's body structure, allowing for effective vibration attenuation for specific modes of vibration.

19. A vibration isolating plate as described in any of claims 1-18, wherein the vibration isolating plate is specifically designed and configured for application in multirotor drones comprising a drone body with multiple arms and vibration-sensitive components requiring enhanced vibration isolation.

20. A vibration isolating plate as described in any of claims 1-18, wherein the vibration isolating plate is configured to reduce the transmission of vibrations generated by spinning motors and attached propellers of the multirotor drone to vibration-sensitive components, including but not limited to sensors, cameras, and other precision instruments.

21. A vibration isolating plate as described in any of claims 1-18, wherein one or more vibration sensitive components are mounted within the low vibration area of the vibration isolating plate22. A vibration isolating plate as described in any of claims 1-18, where one or more vibration sensitive components have one or more of their attachment points within the low vibration area of the vibration isolating plate and one or more of their attachment points elsewhere on the drone.

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