A test method capable of quantitatively indicating the rigidity of a multicopter

Abstract

In the development of drones, with regard to strength, it has become possible to conduct strength studies almost accurately through FEM analysis. However, in drones, rigidity is more important than strength, and there was no method to accurately and quantitatively judge rigidity. 【Solution means】Place a vertical cylindrical jig on a vibration testing machine, fix the drone's motor mount at the center of the plate thickness that constitutes the side surface of the upper part of the jig, and conduct a variable vibration test to obtain the natural frequency of the drone, enabling accurate and quantitative judgment of rigidity.

Description

Technical Field

[0001] The present invention relates to a test method for determining the rigidity of a multicopter that performs flight by mounting three or more propellers upward or downward, or a fixed-wing aircraft (hereinafter referred to as a drone) with the function of a multicopter added.

Background Art

[0002] As the advantages of drones are evaluated and their popularity spreads, there is a need to extend the flight time of drones. To extend the flight time, weight reduction is necessary. When developing a drone, regarding strength, strength studies can be carried out almost accurately by FEM analysis. However, in a drone, rigidity is more important than strength, and there has been no method to accurately and quantitatively determine rigidity.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When attempting to design the strength of a drone, the problem lies not in strength but in rigidity. This is because even if the strength is sufficient, if the rigidity is weak, vibrations will occur, which will have an adverse effect on the control equipment of the drone and attached equipment such as cameras. Therefore, sufficient rigidity is required. However, the structure of the drone is complex, and in order to achieve weight reduction, cutouts are made in various places, so it cannot be obtained by ordinary calculations. Also, even if we try to obtain it by FEM analysis, the parameters and Young's modulus differ from part to part, and there are also variations in physical properties, so it was necessary to conduct experiments to verify whether the calculation results were correct. Therefore, the strength or weakness of rigidity cannot be determined solely by FEM analysis.

Means for Solving the Problem

[0005] In the invention of claim 1, in order to solve the above problems, in a multicopter having a plurality of motor arms extending radially, the motor center of the motor mount at the tip of the motor arm is fixed in accordance with a predetermined position at the upper part of the jig, the lower part of the jig is attached to a vibration tester to perform a variable frequency vibration test, and by measuring the natural frequency of the multicopter, the rigidity of the multicopter can be quantitatively expressed numerically. Here, it is necessary to apply the jig to the vibration tester as well, measure the natural frequency, and confirm that the natural frequency of the drone and the natural frequency of the jig are far apart. If they are far apart, the measurement error of the natural frequency of the drone can be reduced.

Effect of the Invention

[0006] When using this test method, once the assembly of the main components is completed, the rigidity can be expressed as a numerical value by measuring the natural frequency. Here, if the natural frequency increases, it can be judged that the rigidity has increased, and if the natural frequency decreases, it can be judged that the rigidity has decreased. Based on the numerical value, it becomes possible to judge how much it has decreased or increased. When the rigidity of the drone can be quantified, even a small change can determine the strength or weakness of the drone's rigidity, and the efficiency of drone development can be improved dramatically.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0008] The most important thing in the development of the drone is to reduce the weight within the allowable vibration range. First, based on past experience, a No. 1 drone is manufactured and flown to confirm that it can fly. The natural frequency at that time is also measured. If you want to reduce the weight of this No. 1 drone, you may try to change the material of each part that makes up the drone or change the plate thickness (make it thinner) to reduce the weight. However, how such changes actually affect the rigidity of the drone cannot be known until the drone is manufactured, flown, and the vibration during flight is measured, and it cannot be judged quantitatively. In this embodiment, the jig is described as being in the shape of a standing cone, but it may also be in the shape of a standing cylinder. FIG. 1 and FIG. 2 show a plan view and an elevation cross-sectional view of an example drone mounted on a vibration testing machine. Reverse the motor mount of the drone and fix the motor center to the plate thickness surface at the upper end of the cylindrical part of the standing cylindrical jig. Also, close the lower part of the jig and attach it to the vibration testing machine. Change the vibration frequency of the vibration testing machine to find the peak of the vibration frequency at which the vibration suddenly becomes large, and use it as the natural frequency of the drone. The vibration testing jig needs to be measured and confirmed in advance so that its natural frequency is far from that of the drone. The weight of the drone at this time needs to be compared with the maximum takeoff weight of the actually manufactured drone. For example, Change the plate thickness and the cut-out shape of the drone body. Change the material of the drone body. Change the plate thickness of the motor arm. Change the material of the motor arm. Change the plate thickness of the motor mount. Change the material of the motor mount. It is confirmed that even if these conditions are slightly changed, the natural frequency reacts sensitively and changes, enabling a design that reduces the weight of the drone and increases its rigidity.

Explanation of symbols

[0011] 1 Drone body 2 Motor arm 3 Motor mount 4 Vertical conical jig 5 Vibration testing machine 6 Upper frame of the drone body 7 Lower frame of the drone body 8 Closing plate on the lower surface of the jig 9 Fixture for fixing the jig and the vibration table

Claims

[Claim 1] A testing method for a multicopter having multiple motor arms extending radially from a main body, comprising: fixing the motor center of the motor mount at the end of the motor arm to a predetermined position on the upper part of a jig; attaching the lower part of the jig to a vibration testing machine; and quantitatively determining the rigidity of the multicopter by measuring the natural frequency of the multicopter.

Images