Small unmanned aerial vehicle

Abstract

To provide a small-sized unmanned aircraft capable of travelling on the surface of a structure stably by an endless track, and executing stable flight after the travelling as well.SOLUTION: A small-sized unmanned aircraft having an endless track and a rotor includes: a body part 11; a flying means part 120 in which a rotor 12 is attached to each of a plurality of arms 11a overhung in the horizontal direction from the body part; a moving means part 2 having a crawler 21 provided above the body part; and a flight control part for controlling the posture of the body part. In the flight control part, control of the flying means part is executed by feedback control combining proportional control, integral control, and differential control, and an oblivion part is provided for reducing an integral value of the integral control.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a small unmanned aerial vehicle having tracks and a rotor. [Background technology]

[0002] As disclosed in Patent Documents 1 and 2, an inspection system using a drone has been developed that can approach structures located at high altitudes and perform various inspections. This drone is equipped with a camera, a hammering inspection device, a rebar detection device, etc., and can perform various inspections.

[0003] In addition, the drones of the inspection systems disclosed in Patent Documents 1 and 2 are equipped with endless tracks (crawlers) for traveling on structural surfaces in addition to rotors, so that they can travel stably on structural surfaces such as wall surfaces. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6864644 [Patent Document 2] Patent No. 6363632 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the provision of tracks enables the drone to travel stably on the surface of structures such as walls, but if the drone is operated while attached to a wall, the crawlers in contact with the wall will restrain the drone, contrary to the control information (target) from the drone's aircraft control device, and prevent it from changing its attitude.

[0006] If this situation continues for a long time, the deviation (integral error) between the target value and output value of the drone's feedback control (PID control) will accumulate, which may lead to a control breakdown.If control fails, the drone will behave in an unexpected way, so measures to address this will be required.

[0007] Therefore, the present invention aims to provide a small unmanned aircraft that can run stably on the surface of a structure using caterpillar tracks and can also fly stably after running. [Means for solving the problem]

[0008] In order to achieve the above object, the miniature unmanned aerial vehicle of the present invention is a miniature unmanned aerial vehicle having tracks and a rotor, and is provided with a main body, a flight means unit in which a rotor is attached to each of a plurality of arms extending laterally from the main body, a transportation means unit having tracks provided above the main body, and a flight control unit that controls the attitude of the main body, wherein the flight control unit controls the flight means unit by feedback control that combines proportional control, integral control, and differential control, and is provided with a forgetting unit that reduces the integral value of the integral control. Here, it is preferable that the forgetting unit is configured to function when the transportation means unit is traveling.

[0009] In addition, the moving means unit can be configured to include a plurality of pillars extending upward from the main body unit, a frame unit supported on the upper ends of the pillars and extending laterally, and a pair of approximately parallel crawlers attached to the frame unit, and the frame unit can be configured to have an elastic movable part that allows the crawlers to tilt relative to the main body unit.

[0010] Furthermore, the pillar portions are each provided at a position that forms a corner of a rectangle relative to the main body portion, and the frame body portion comprises a pair of stationary beams that are spanned approximately parallel between the upper ends of the pillar portions, a first movable beam whose center is elastically rotatably connected to the center of each of the stationary beams, a pair of approximately parallel connecting beams that connect both ends of the pair of first movable beams, and a second movable beam whose center is elastically rotatably connected to the center of each of the connecting beams, and the pair of approximately parallel crawlers are provided to connect both ends of the pair of second movable beams. [Effects of the Invention]

[0011] The miniature unmanned aerial vehicle of the present invention configured in this manner comprises a flight means unit having a rotor, a moving means unit having tracks, and a flight control unit that controls the attitude of the main body unit. The flight control unit controls the flight means unit using feedback control that combines proportional control, integral control, and differential control, and is provided with a forgetting unit that reduces the integral value of the integral control.

[0012] As a result, the endless tracks allow the robot to travel stably on the surface of the structure, and the forgetting section prevents the accumulation of integral errors caused by travel involving adhesion, making it possible to fly stably even after travel.

[0013] Furthermore, if the frame body to which the crawler of the moving means unit is attached is provided with an elastic movable part that allows the crawler to tilt relative to the main body unit, the constraint of the small unmanned aircraft by the crawler's running surface can be made more flexible, and the increase in feedback control deviation itself can be reduced. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view showing the configuration of a small unmanned aerial vehicle according to an embodiment of the present invention. [Figure 2] 2 is a block diagram illustrating the configuration of a flight control unit of the small unmanned aerial vehicle of the present embodiment. FIG. [Figure 3]1 is an enlarged perspective view showing the configuration of a small unmanned aerial vehicle according to an embodiment of the present invention. FIG. [Figure 4] These figures explain the operation of the small unmanned aerial vehicle of this embodiment when rolling, where (a) is an explanatory diagram when stable, (b) is an explanatory diagram when tilting downward to the right, and (c) is an explanatory diagram when tilting downward to the left. [Figure 5] These figures explain the pitching behavior of the small unmanned aerial vehicle of this embodiment, where (a) is an explanatory diagram when stable, (b) is an explanatory diagram when pitching downward to the right, and (c) is an explanatory diagram when pitching downward to the left. [Figure 6] 10A and 10B are explanatory diagrams showing the results of flight experiments of the small unmanned aerial vehicle of the present embodiment. [Figure 7] 10 is an explanatory diagram showing the results of another flight experiment of the small unmanned aerial vehicle of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will now be described with reference to the drawings. Figures 1 and 3 are perspective views illustrating the configuration of a miniature unmanned aircraft 1 according to this embodiment, and Figure 2 is a block diagram illustrating the configuration of a flight control unit 13 of the miniature unmanned aircraft 1.

[0016] By using the small unmanned aerial vehicle 1 of this embodiment, it becomes possible to inspect high places where there is no foothold or places that are difficult for workers to reach. For example, it becomes possible to perform inspections such as hammering inspections and rebar detection on the surfaces (structural surfaces) of the undersides and sides of structures such as bridges, buildings, and retaining walls.

[0017] The small unmanned aircraft 1 comprises a main body 11, a flight means 120 to which multiple rotors 12 are attached, a moving means 2 having an endless track provided above the main body 11 via a support 3, and a flight control unit 13 that controls the attitude of the main body 11.

[0018] In this embodiment, the main body 11 has a base 110 formed, for example, in a rectangular shape when viewed from above, and is equipped with a flight control unit 13 for controlling the flight of the small unmanned aerial vehicle 1, a driving power supply unit such as a battery or converter, and an inspection device 4 according to the intended use.

[0019] Arms 11a extend in all four directions from main body 11, and rotors 12 are attached to each of the four arms 11a. In miniature unmanned aerial vehicle 1 of this embodiment, rotors 12 having propellers that are rotated by the drive of a motor are disposed below arms 11a.

[0020] The rotor 12 is attached to the middle of the arm 11a, and legs 11c are provided at the tips of the arms 11a, which extend downward. The tips of the arms 11a, which extend in all directions, are connected by rod-shaped guards 11b. This connection by guards 11b not only prevents deformation of the arms 11a, but also prevents the rotor 12 and main body 11 from colliding with or interfering with foreign objects.

[0021] The flight control unit 13 mounted on the main body 11 controls the rotation speed of each rotor 12, thereby controlling the flight of the miniature unmanned aircraft 1, such as lift-off, movement, and turning. The flight control unit 13 has flight sensors such as gyros, which detect the attitude of the miniature unmanned aircraft 1 and use the detected attitude for flight control.

[0022] In addition, the small unmanned aircraft 1 can be equipped with a GPS antenna on the main body 11, and the flight control unit 13 can perform attitude control and flight control of the small unmanned aircraft 1 based on information from a GPS communication satellite received via the GPS antenna.

[0023] Furthermore, the flight control unit 13 has a wireless communication unit, and performs wireless communication with a ground-based control device (not shown) to send and receive various signals and information. Flight data such as route can be stored in advance in the flight control unit 13, but it can also be operated from the ground via a control device.

[0024] In the flight control unit 13 of this embodiment, as shown in the block diagram of Figure 2, the flight means unit 120 is controlled by feedback control (PID control) that combines proportional control (P), integral control (I), and differential control (D).

[0025] In PID control, the deviation between the target value (131) calculated by the calculation processing of the flight control unit 13 and the output value (139) at which the small unmanned aircraft 1 actually operates is fed back and reflected in continuous flight control.

[0026] In the PID control, a control is performed that combines proportional control based on a proportional gain Kp (132), integral control based on an integral gain Ki (133), and differential control based on a differential gain Kd (134).

[0027] Each parameter (Kp, Ki, Kd) of the PID control can be set arbitrarily. On the other hand, when inspecting the wall surface (structural surface) of a structure such as a bridge by traveling while attached to a caterpillar, the behavior of small unmanned aerial vehicle 1 is restricted (constrained) by friction with the attached surface, making it impossible to correct the attitude according to the target value (131), resulting in a discrepancy between the control and the aircraft behavior.

[0028] If the discrepancy continues for a long time, the integral value of the deviation between the target value (131) and the output value (139) in the PID control may accumulate and increase in the integrator (135). Therefore, a forgetting unit (137) that reduces the integral value is provided in the integral control to prevent the control from failing.

[0029] That is, in order to prevent the integral error of the PID control from increasing, a control law is used that introduces a forgetting factor γ (138) to eliminate the increasing integral error when controlling the small unmanned aerial vehicle 1 during flight or adhesion running.

[0030] In the PID control of the flight control unit 13 of this embodiment, the integral value of the deviation is not adjusted only by the integral gain Ki (133), but a "forgetting factor γ (138)" is introduced into the control to intentionally reduce it, thereby preventing an increase in the integral value of the deviation between the target value (131) and the output value (139) and preventing a control breakdown. Specific setting values ​​of each parameter (Kp, Ki, Kd) will be described later together with an explanation of the flight experiment.

[0031] Furthermore, a camera (not shown) for observing the surface of a structure, for example, can be attached to the main body 11 of the miniature unmanned aerial vehicle 1. Images captured by the camera are transmitted to the piloted aircraft via the flight control unit 13. Furthermore, depending on the purpose of the inspection, an inspection device 4 such as a hammering inspection device or a rebar detection device can be mounted on the miniature unmanned aerial vehicle 1.

[0032] Next, the detailed configuration of the moving means unit 2 will be described with reference to the enlarged perspective view of the miniature unmanned aerial vehicle 1 shown in Figure 3. The moving means unit 2 includes a plurality of pillars 31 extending upward from the main body 11, a frame body 32 supported on the upper ends of the pillars 31 and extending laterally, and a pair of crawlers 21 attached to the frame body 32, each of which forms a substantially parallel endless track.

[0033] The pillars 31 are provided at four positions that become the corners of the base 110, which is substantially square in plan view, of the main body 11. The frame 32 is supported by these four pillars 31.

[0034] The frame body portion 32 comprises a pair of stationary beams 321 that are spanned approximately parallel between the upper ends of the column portions 31, a first movable beam 322 whose center is elastically rotatably connected to the center of each stationary beam 321, a pair of approximately parallel connecting beams 323 that connect both ends of the pair of first movable beams 322, and a second movable beam 324 whose center is elastically rotatably connected to the center of each connecting beam 323.

[0035] A pair of approximately parallel crawlers 21 are provided to connect both ends of the pair of second movable beams 324. Here, the connection between both ends of the second movable beams 324 may be performed by a connecting beam that constitutes the frame body portion 32, and then the crawler 21 may be attached parallel to the connecting beam, or the connection between both ends of the second movable beams 324 may be performed directly by a rod-shaped member that constitutes the crawler 21.

[0036] The crawler 21 that serves as an endless track includes a belt, a plurality of pulleys around which the belt is wound, and a motor and gearbox that are connected to one of the pulleys to rotate it.

[0037] When the pulley is rotated while the surface of the crawler 21 is in contact with the surface (structural surface) of a structure or the like, the belt wrapped around the pulley moves, thereby allowing the small unmanned aerial vehicle 1 to move (self-propel) along the length of the crawler 21.

[0038] The movement means unit 2 is controlled by, for example, a control unit (not shown) provided separately from the flight control unit 13. In addition, data on the distance traveled by the movement means unit 2 of the miniature unmanned aerial vehicle 1 can be obtained by measuring the amount of rotation of the pulley using a rotation sensor or the like.

[0039] Here, the surface of crawler 21 is formed to have a high coefficient of friction. In other words, a certain degree of frictional resistance is required to move miniature unmanned aerial vehicle 1 pressed against the surface of a structure by buoyancy using the rotational drive of crawler 21. The surface of crawler 21 can be made to have a structure with high adhesive properties, such as rubber, a fine suction cup structure, or an ultra-fine hair structure (using van der Waals forces).

[0040] Further, frame unit 32 is provided with elastic movable units 33A and 33B that allow crawler 21 to tilt relative to main body unit 11. In other words, a suspension mechanism that is movable on two axes (in multiple directions) is provided between main body unit 11, to which flight means unit 120 is attached, and crawler 21.

[0041] That is, the elastic movable part 33A is a suspension mechanism in which a member having a restoring force, such as a spring, is incorporated into an oscillation shaft that allows the first movable beam 322 to oscillate relative to the stationary beam 321. Similarly, the elastic movable part 33B is a suspension mechanism in which a member having a restoring force, such as a spring, is incorporated into an oscillation shaft that allows the second movable beam 324 to oscillate relative to the connecting beam 323.

[0042] The use of a suspension mechanism such as elastic movable parts 33A and 33B can flexibly restrict the constraint of miniature unmanned aerial vehicle 1 by the surface of the structure on which it travels. This allows for a margin of response of main body 11 to control signals, and reduces the increase in the deviation between target value (131) and output value (139) in the PID control described above.

[0043] 4 is a diagram illustrating the rolling operation of miniature unmanned aerial vehicle 1 according to this embodiment. This diagram is for explaining the range of swinging motion during rolling, and does not show the actual flight attitude.

[0044] That is, Fig. 4(a) is an explanatory diagram of a stable state in which no force is acting on the pair of crawlers 21, 21, or downward forces of the same magnitude are acting on them. The explanatory diagram of the downward movement to the right shown in Fig. 4(b) shows a state in which a larger downward force is acting on the right crawler 21 than on the left crawler 21. Conversely, the explanatory diagram of the downward movement to the left shown in Fig. 4(c) shows a state in which a larger downward force is acting on the left crawler 21 than on the right crawler 21. In reality, if the traveling surface of the crawlers 21, 21 is horizontal, the main body 11 will be the one that tilts.

[0045] Such rolling inclination occurs when the second movable beam 324 connected to the connecting beam 323 via the elastic movable portion 33B rotates at a hinge having rotational rigidity of the elastic movable portion 33B.

[0046] On the other hand, Figure 5 is a diagram illustrating the motion of the miniature unmanned aerial vehicle 1 during pitching, viewed from a direction perpendicular to that of Figure 4. This diagram is also used to explain the range of motion during pitching, and does not show the actual flight attitude.

[0047] That is, Fig. 5(a) is an explanatory diagram of a stable state in which no force is acting on the crawler 21 or a downward force of the same magnitude is acting along the entire length. The explanatory diagram of Fig. 5(b) when the crawler 21 is tilting downward to the right shows a state in which a larger downward force is acting on the right end of the crawler 21 than on the left end. Conversely, the explanatory diagram of Fig. 5(c) when the crawler 21 is tilting downward to the left shows a state in which a larger downward force is acting on the left end of the crawler 21 than on the right end. In reality, if the running surface of the crawler 21 is horizontal, the main body 11 will be tilted.

[0048] Such pitching (pitch) inclination occurs when the first movable beam 322 connected to the stationary beam 321 via the elastic movable part 33A rotates on a hinge having rotational rigidity of the elastic movable part 33A.

[0049] In short, the crawler 21 is supported on the main body 11 via the elastic movable parts 33A, 33B of the frame body 32, so that roll and pitch movements (swaying) of the main body 11 are permitted even when the crawler 21 is attached to the surface of the structure.

[0050] However, the range of movement of the elastically movable parts 33A and 33B in the forward, backward, leftward, and rightward directions must be limited to a range in which the guard 11b, rotor 12, etc. of the miniature unmanned aerial vehicle 1 do not collide with the surface to be inspected (the surface of the structure) or the crawler 21. For this reason, although not shown, stoppers that limit the movement range are provided on the elastically movable parts 33A and 33B.

[0051] In addition, the crawler 21 of the small unmanned aerial vehicle 1 may be left attached to the surface of a structure and the body may be rotated by changing the speed of the pair of crawlers 21, 21, but the operating range of the elastic movable parts 33A, 33B is restricted to a range in which the moment generated during this rotation does not cause the crawler 21 to move away from the surface of the structure or change the distance between the inspection device 4 and the surface to be inspected.

[0052] On the other hand, when crawler 21 is attached to the surface to be inspected (structure surface) by miniature unmanned aerial vehicle 1 and travels on it, it is necessary to prevent the inspection siding from bending or shaking, so the degree of freedom of rotation (yaw) relative to the traveling direction is restricted. That is, since immobile beam 321 is fixed to the upper end of column 31 fixed to main body 11 so as not to rotate within the upper end surface, crawler 21 does not rotate in a direction intersecting base 110 of main body 11 in a plan view.

[0053] Next, flight experiments using the miniature unmanned aircraft 1 of the present embodiment will be described with reference to Figures 6 and 7. Figures 6 and 7 are explanatory diagrams showing the results of two flight experiments using the miniature unmanned aircraft 1 of the present embodiment.

[0054] In the flight experiment, the small unmanned aircraft 1 was made to hover, and then a crawler 21 was attached to the ceiling surface, which represented the surface to be inspected.A test flight was conducted in which the crawler 21 was driven, and then stopped to perform a tapping inspection using the inspection device 4, and stability was confirmed during the test flight.

[0055] Here, we will explain the PID control parameters in flight control unit 13 of small unmanned aerial vehicle 1 when flight experiments were conducted. Proportional gain Kp (132, see Figure 2) for proportional control was set to 1.8 for roll and pitch, and 1.9 for yaw. Furthermore, differential gain Kd (134) for differential control was set to 0.066 for roll and pitch, and 0 for yaw.

[0056] The integral control provided with the forgetting unit (137) was set as follows: First, the integral gain Ki (133) was set to 7 for roll and pitch, and to 4.4 for yaw. Furthermore, the forgetting coefficient γ (138) of the forgetting unit (137) was set to 0.001 for roll and pitch, and to 0 for yaw.

[0057] Looking at the results of the first flight test shown in Figure 6, during the ceiling contact period when the altitude was from 2.39 m to 2.51 m, the fluctuation range due to the swing axis of the elastic movable parts 33A and 33B fell within the range of -0.52 degrees to 0.80 degrees during roll, and also fell within the range of -0.57 degrees to 0.80 degrees during pitch.

[0058] Furthermore, looking at the results of the second flight test shown in Figure 7, during the ceiling contact period when the altitude was from 2.30 m to 2.36 m, the fluctuation range due to the swing axis of the elastic movable parts 33A and 33B fell within the range of -0.86 degrees to 0.75 degrees during roll, and within the range of -0.57 degrees to 0.80 degrees during pitch.

[0059] From the results of these two flight experiments, it was found that by setting the forgetting coefficient γ (138) in the forgetting unit (137), even when an inspection is performed in which the crawler 21 of the small unmanned aerial vehicle 1 is attached to the surface to be inspected and moves, the integral value of the integral control is reduced in the forgetting unit (137), so that the flight of the small unmanned aerial vehicle 1 does not fall into a state where it breaks down, and stable flight can be continued.

[0060] Next, the operation of miniature unmanned aerial vehicle 1 according to this embodiment will be described. The small unmanned aircraft 1 of this embodiment configured as described above comprises a flight means unit 120 having a rotor 12, a moving means unit 2 having a crawler 21, and a flight control unit 13 that controls the attitude of the main body unit 11.

[0061] The flight control unit 13 controls the flight means unit 120 using feedback control (PID control) that combines proportional control, integral control, and differential control, and is provided with a forgetting unit (see 137 in Figure 2) that reduces the integral value of the integral control.

[0062] Therefore, crawler 21 can travel stably on the surface of the structure, and the forgetting coefficient γ (138) set in forgetting unit 137 can prevent the accumulation of integral error due to travel accompanied by adhesion, allowing stable flight even after travel. In particular, when crawler 21 detaches from the adhesion surface, the influence of the accumulated integral error increases the possibility of control of miniature unmanned aerial vehicle 1 failing, but even under such circumstances, miniature unmanned aerial vehicle 1 of this embodiment can continue to fly stably because the accumulation of integral error does not become excessive.

[0063] On the other hand, in order to appropriately control the attitude of the miniature unmanned aerial vehicle 1 during flight, it is necessary to perform control using the deviation between the target value (131) and the output value (139) through PID control. Therefore, it is preferable to set the forgetting factor γ (138) to a value with a high forgetting effect during takeoff and adhesion running, and to perform control without using the forgetting factor γ (138) during other free flight situations.

[0064] In this way, by incorporating the forgetting unit (137) into the flight control unit 13 in PID control, it is possible to prevent a control breakdown of the small unmanned aerial vehicle 1. As a result, even if the crawler 21 is attached to and travels on the surface to be inspected for a long period of time, the small unmanned aerial vehicle 1 will not exhibit abnormal behavior, and inspection work can be carried out continuously. It is also possible to prevent accidents such as the crash of the small unmanned aerial vehicle 1.

[0065] Furthermore, if the frame body part 32 to which the crawler 21 of the moving means part 2 is attached is provided with elastic movable parts 33A, 33B that allow the crawler 21 to tilt relative to the main body part 11, the constraint of the small unmanned aerial vehicle 1 by the running surface of the crawler 21 can be made more flexible, and the increase in the deviation of the PID control itself can be reduced.

[0066] Furthermore, if the effect of the suspension mechanism of the elastic movable parts 33A, 33B provided on the frame part 32 can sufficiently suppress an increase in the deviation between the target value (131) and the output value (139), long-term adhesion running by the crawler 21 is possible even if the forgetting effect due to the forgetting factor γ (138) is suppressed. In this case, since it is possible to control the aircraft during adhesion running without applying an excessively large forgetting factor γ (138), the forgetting factor γ (138) is set in advance in a flight experiment according to the effect of the suspension mechanisms (33A, 33B) and a control law is constructed.

[0067] The embodiments of the present invention have been described above in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes that do not deviate from the gist of the present invention are included in the present invention.

[0068] For example, in the above embodiment, a small unmanned aircraft 1 was described as being used to inspect the surfaces of structures such as bridges and high-rise buildings, but this is not limited to this, and the small unmanned aircraft 1 of the present invention can also be applied for purposes other than inspection. [Explanation of symbols]

[0069] 1: Small unmanned aerial vehicle 11: Main body 11a: Arm 120: Flight means department 12: Rotor 13: Flight control unit 137: Oblivion Department 2: Transportation section 21: Crawler (Crawler) 31:Column part 32: Frame body part 321: Fudoryo 322: 1st movable beam 323: Connecting beam 324: 2nd movable beam 33A, 33B: Elastic movable part

Claims

[Claim 1] A small unmanned aerial vehicle having tracks and a rotor, a main body; a flight means unit having a rotor attached to each of a plurality of arms extending laterally from the main body unit; a moving means unit having an endless track provided above the main body unit; A flight control unit that controls the attitude of the main body unit, The flight control unit controls the flight means unit by feedback control that combines proportional control, integral control, and differential control, and is provided with a forgetting unit that reduces an integral value of the integral control, the forgetting unit functions when the moving means unit is traveling, the movement means unit includes a plurality of pillars extending upward from positions that form corners of a rectangle relative to the main body unit, a frame unit supported on upper ends of the pillars and extending laterally, and a pair of approximately parallel crawlers attached to the frame unit; the frame body portion includes a pair of stationary beams spanning the upper ends of the column portions in a substantially parallel relationship, a first movable beam whose center is elastically rotatably connected to the center of each of the stationary beams, a pair of substantially parallel connecting beams connecting both ends of the pair of first movable beams, and a second movable beam whose center is elastically rotatably connected to the center of each of the connecting beams, the pair of substantially parallel crawlers are provided to connect both ends of the pair of second movable beams, and A small unmanned aerial vehicle, characterized in that the elastic rotation of the first movable beam and the second movable beam is limited within a movement range by a stopper.

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