JP4590494B2 - Micro air vehicle - Google Patents

Description

  The present invention relates to a micro air vehicle, and more particularly to a micro air vehicle that flies by a fixed thin plate wing in a region where the Reynolds number is 10 5 or less with a chord length as a reference length. INDUSTRIAL APPLICABILITY The present invention is suitable for a micro air vehicle for research and exploration activities in which unmanned flight is performed by remote radio control.

  In recent years, with the miniaturization of industrial products, research and development of ultra-compact aircraft using ultra-compact, precision and lightweight parts has been actively performed in the industry. However, even if it is possible to realize an ultra-small aircraft from an electromechanical point of view, there is no expectation for the expected micro-aircraft industry unless the various hydrodynamic problems associated with the miniaturization of the aircraft are solved. It can be said that the use of is difficult. In the field of fluid mechanics, the Reynolds number defined by the contrast between inertia and viscosity in fluid phenomena dominates. In the field of hydrodynamics, downsizing will bring about a decisive decrease in the flight performance of the aircraft due to an increase in the effect of fluid viscosity due to a decrease in Reynolds number. For example, as shown in FIG. 7, the flow around the fixed thin plate blade 20 provided with an angle of attack of 5 degrees in the flow having a Reynolds number of 3500 is thicker than the thickness of the fixed thin plate blade 20 due to the influence of viscosity. It can be said that the dead water area 23 is formed and at the same time the viscosity resistance is remarkably increased, which impedes the realization of the high-speed flight of the micro air vehicle using the fixed thin wing 20.

  On the other hand, when considering the flight of a micro air vehicle in a natural wind environment, although the flight speed of the micro air vehicle is orders of magnitude smaller than that of a large aircraft, the natural wind environment Is not related to the size of the aircraft, the change in the angle of attack caused by the natural wind environment is relatively large in the micro air vehicle, and the flow around the fixed thin wing 20 shown in FIG. As described above, since the boundary layer peels off from the wing in the separation region 24, the fixed thin plate blade 20 is easily stalled. Therefore, the micro air vehicle is stable in a natural wind environment including strong winds and gusts. It can be said that it is basically difficult to continue flying. Furthermore, since the micro air vehicle is required to fly under the extremely low wind environment affected by the shape of the ground surface by remote control, etc. In order to avoid the crash of the micro air vehicle that is performed, it can be said that the micro air vehicle is required to have extremely high angle-of-attack flight characteristics and excellent maneuverability as compared with a normal aircraft. .

  However, in the fields of fluid mechanics and aeronautical engineering, which are responsible for these problems, the research and development of manned large aircraft, where industrial demand is concentrated, has been prioritized so far. It can be said that research and development of micro air vehicles have been left behind. For this reason, the inventor of the present invention returns to the origin of hydrodynamics and builds a flow around a rotating cylinder placed in a low Reynolds number flow in order to build aeronautical engineering in the low Reynolds number region that solves these problems. The starting point is to promote research and development activities in the field of aeronautical engineering related to low Reynolds number flow.

On the other hand, as a technique for improving the flow on the blade surface using a rotating cylinder that targets a conventionally known high Reynolds number flow, the invention related to the improvement of the performance of the rotating blade of a blower using the rotating cylinder disclosed in Patent Document 1 Is known (see Patent Document 1). The rotor blade of the blower disclosed in Patent Document 1 is a state in which a cylindrical rotor is exposed on the front edge or blade surface of the rotor blade and a part of the rotor is partially exposed on the blade surface. Generation of operating noise and blowing efficiency in the blower by preventing the separation of the boundary layer on the blade surface by the acceleration flow generated in the upward flow of the cylindrical rotating body that is buried and partially exposed on the blade surface It is supposed to prevent the decline of However, of course, the invention related to the improvement of the rotor blades of the blower disclosed in Patent Document 1 is a technology for rotating rotor blades rotating at high speed, that is, for a high Reynolds number flow, and the cylindrical shape. This invention is intended for large and thick blades that can be embedded in the rotor blades, and is superfluous in the low Reynolds number region using the fixed thin plate blade that is the subject of the present invention hydrodynamically. It does not contribute to the improvement of wing performance of small aircraft.
Japanese Patent No. 3503604

  For this reason, in order to enable the inventor of the present invention to observe the state of flow in a low Reynolds number region that cannot be easily observed by ordinary observation means because the flow is fine, We have developed a new flow visualization water tank that can expand and visualize the low Reynolds number flow with a similarity law, and target many flows around a rotating cylinder in the low Reynolds number region. We have succeeded in making detailed observations. As a result, the flow around the rotating cylinder in the low Reynolds number region is very different from that in the high Reynolds number region, and under constant flow conditions, It has been found that it is possible to generate a jet jet 22 having a speed much higher than the mainstream speed as shown in FIG. In a low Reynolds number flow that is a fine flow, the jet jet 22 behind the rotating cylinder 21 caused by the influence of a large viscosity in the low Reynolds number flow is much larger and more powerful than an acceleration flow in a high Reynolds number flow. It can be said that it has a large dominance in a low Reynolds number flow.

  Based on this novel discovery, the present invention provides a low Reynolds generated in the rear flow of a rotating cylinder rotating at high speed in a low Reynolds number flow region in which the chord length is defined as a reference length and the Reynolds number is 10 5 or less. By utilizing the powerful jet jets that are unique to several flows in an appropriate positional relationship with the flow around the wings in a fixed thin plate wing that is also used in the low Reynolds number region, the wing performance and flight performance of the micro air vehicle can be reduced. It aims to improve.

  Specifically, the dead water region 23 shown in FIG. 7 formed with a region thicker than the fixed thin plate wing in the flow around the fixed thin plate wing included in the micro air vehicle due to the influence of the viscosity in the low Reynolds number flow, and the By reducing the viscous resistance that increases due to the influence of viscosity, the low resistance flight characteristics of the micro air vehicle will be improved, especially under conditions of low angle of attack, and the flight speed of the micro air vehicle will be significantly improved. With the goal.

  Also, the separation region 24 shown in FIG. 8 can be easily generated by a large variation in the angle of attack of the fixed thin plate wing included in the micro air vehicle that changes suddenly in a natural wind environment including strong winds and gusts. It realizes a high angle of attack flight characteristic in the ultra-compact aircraft that does not stall, and has a powerful maneuvering characteristic that can exhibit sufficient maneuverability even in the natural wind environment. The purpose is to realize an excellent micro air vehicle equipped with.

The present invention has the following configuration in order to solve the above problems. That is, the flying object according to the present invention is a micro-aircraft that flies by a fixed thin plate wing in a region where the Reynolds number is 10 5 or less with the chord length as a reference length, and is close to the leading edge of the fixed thin wing. A rotating rod having a circular cross section having a smooth surface at a position ranging from 45 degrees forward and lower 45 degrees to the rear upper edge of the leading edge of the stationary thin plate blade, and the leading edge of the stationary thin plate blade and the rotational axis of the rotating rod. Are arranged in parallel, and the rotating rod is rotated in the same rotational direction as the blade circulation direction of the fixed thin plate blade so that the peripheral speed of the rotating rod is at least twice the uniform flow velocity. It is characterized by realizing low resistance flight and large attack angle flight.

  Further, the micro air vehicle according to the present invention is provided with a pair of left and right rotating rods independently only at the wing tip of the fixed thin plate wing, and the rotational speed of the rotating rod is independently changed on the port side and starboard side. It is characterized by performing flight control.

  According to the present invention, in the region of the low Reynolds number flow in which the Reynolds number is defined as the chord length as a reference length and the Reynolds number flow is 10 5 or less, the micro air vehicle is provided with the influence of the viscosity in the low Reynolds number flow. The dead water region 23 shown in FIG. 7 formed with a region thicker than the fixed thin plate wing in the flow around the fixed thin plate wing and the viscous resistance increased by the influence of the viscosity are close to the front edge of the fixed thin plate wing. Uniformity provided in a positional relationship in which the front edge of the fixed thin plate blade and the rotation axis of the rotating rod are substantially parallel to each other at a position in the range of 45 degrees from the front lower side to the rear upper 45 ° of the front edge of the fixed thin plate blade. Occurs in the backward flow of the rotating rod having a circular cross section having a generally smooth surface that rotates at high speed in the same rotational direction as the blade circulation direction of the stationary thin plate blade at a peripheral speed of twice or more the flow speed. Since the flow around the fixed thin plate blade can be improved to the ideal flow shown in FIG. 4 by reducing it using a powerful jet jet peculiar to a low Reynolds number flow, the flow is particularly suitable under the condition of a low angle of attack. The low resistance flight characteristics of the micro air vehicle can be improved, and the flight speed of the micro air vehicle can be remarkably improved.

  Further, according to the present invention, the backward flow of the rotating rod is also caused by a large variation in the angle of attack of the fixed thin plate wing provided in the micro air vehicle that changes suddenly in a natural wind environment including strong winds and gusts. 8 can be controlled so that the boundary layer is peeled off at the upper surface of the fixed thin plate blade due to the effect of the powerful jet jet peculiar to the low Reynolds number flow generated in FIG. Even under conditions of large angle of attack, the fixed thin plate wing does not stall, and the flow around the fixed thin plate wing is improved to an ideal flow to create high lift. A small aircraft can be realized. Here, FIG. 5 shows the result of the experiment using the circulating type visualization water tank by the inventors of the present invention. In the experiment using the circulating visualization water tank shown in FIG. 5, the fixed thin plate blade 20 having a large angle of attack of 30 degrees with respect to the uniform flow under the condition that the Reynolds number is about 3500 with the chord length as the reference length. A rotating cylinder 21 whose diameter is exactly 10% of the chord length is provided close to the front edge of the rotating cylinder 21, and the peripheral speed in the rotation of the rotating cylinder 21 is five times the uniform flow speed, That is, when the rotating cylinder 21 was driven to rotate in a driving state where the peripheral speed ratio was 5, it was confirmed that an ideal flow that does not cause separation of the flow can be realized even under the condition of the large angle of attack. In addition, about this result, it is confirmed by the experiment using the circulation type visualization water tank by the inventor of this invention that it is not greatly influenced by the difference of the said airfoil.

  Further, according to the present invention, the rotating rods are provided in a pair of left and right sides independently of each other only at the blade end portions of the fixed thin plate blades, and the rotational speed of the rotating rods is independently changed and controlled on the port side and starboard side. In addition, since suppression and generation of boundary layer separation on the upper surface of the fixed thin plate wing can be independently and freely controlled on the port side and starboard side, a spoiler for aircraft control that is conventionally known in the micro air vehicle of the present invention It is possible to realize an excellent micro air vehicle having powerful maneuvering characteristics capable of exhibiting sufficient maneuverability even in the natural wind environment similar to that provided with the maneuvering device.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is an explanatory view of the micro air vehicle shown in the present embodiment as viewed from above the left wing, and FIG. 2 is an explanatory view of the micro air vehicle shown in the same embodiment from the lower front of the left wing. The micro air vehicle of the present embodiment shown in FIGS. 1 and 2 has a basic specification of a total width (total span length) of 250 mm, a total length of 280 mm, a chord length of 35 mm, a mass of about 25 g, and a flight speed of about 6 m per second. A control comprising a CFRP front wing 1 and a rear wing 2 according to the arrangement, and comprising a shock absorber 3 made of EPP (Expanded Poly Propylene), a lithium ion battery covered with an EPP sheet, and a wireless communication control device And a propeller propulsion device 9 including a propulsion motor 7 and a propeller 8. In the micro air vehicle shown in this embodiment, the front wing 1 and the rear wing 2 provided by the close tandem wing arrangement have a planar shape with a high aspect ratio, so that induction resistance is reduced and a high lift-drag ratio is realized. Can do. The rear wing 2 is provided with a reverse camber for obtaining a trim in the pitching direction in the micro air vehicle shown in the present embodiment with the close tandem wing arrangement. Further, the flight Reynolds number of the micro air vehicle shown in the present embodiment is about 2 × 10 4.

  In addition to the above configuration, a rotating rod 10 having a cylindrical shape with a diameter of 3 mm and the rotating rod are provided at the left and right wing ends of the front wing 1 of the micro air vehicle of the present embodiment shown in FIGS. 1 and 2. A rotating rod drive motor 11 is provided for directly driving and rotating 10 in a rotation direction that is the same as the blade circulation direction in the flow around the front blade 1 at a maximum of about 60,000 revolutions per minute. The rotating rod 10 shown in the present embodiment is attached only at the tip of the front wing 1 of the micro air vehicle of the present embodiment, and the length of the rotating rod 10 is the span length of one wing of the front wing 1. The rotating rod 10 is formed over the entire width of the single wing span length of the front wing 1 by a number of water tank experiments and flight experiments conducted by the inventors of the present invention. Even if it is not provided, this is due to the fact that it is confirmed that the intended effect of the present invention can be sufficiently obtained. Of course, the rotating rod 10 may be provided over the entire width of the one-wing span length of the front wing 1, and the rotating rod 10 and the rotating rod are driven not only in the front wing 1 but also in the rear wing 2. The motor 11 may be provided.

  However, in the micro air vehicle shown in the present embodiment, the length of the rotating rod 10 is provided as a half length of the one wing span length of the front wing 1. This is because the total weight of the rotating rod 10 and the rotating rod driving motor 11 provided in a pair only at the end portions, the driving wiring attached to these, and the control components, etc. is contained in 5 g or less. In general, when the total weight of a micro air vehicle is divided into a structural system and a propulsion drive system, the smaller the aircraft, the less weight that can be allocated to the structural system. In the case of a micro air vehicle having a weight of 20 g, the weight that can be allocated to the structure system usually occupies about 50% (about 10 g) of the total weight. In such a case, even if a low-resistance flight device, a large angle-of-attack flight device, a steering control device, an accessory device, or the like can be additionally installed, the total weight of the structural system is increased by 50% (about 5 g). The extent is the limit. Due to such weight constraints, it is currently not possible to mount sophisticated low-resistance flying devices or large-attack flying devices and steering control devices that have complicated mechanisms that can be installed in large aircraft in micro-aircraft. According to the present invention, the flight performance improvement device can be mounted with a minimum weight increase by utilizing the hydrodynamic characteristics in the low Reynolds number region. Can be said.

  In the micro air vehicle shown in the present embodiment, the rotating rod 10 is disposed and provided so that the rotation center axis of the rotating rod 10 is positioned at a position 45 degrees above the front edge of the front wing 1. Yes. This is a result of an experiment using a circulating visualization water tank by the inventors of the present invention, and a strong jet jet generated in the flow behind the rotating cylinder in the low Reynolds number flow and the fixed thin plate disposed in the vicinity of the rotating cylinder. In the positional relationship with the wing, the range of the positional relationship in which the effect of improving the flight performance of the micro air vehicle according to the present invention can be obtained. The Reynolds number with the chord length as the reference length is 10 as shown in FIG. In the case of a micro air vehicle flying by the fixed thin plate wing 20 in the region of the fifth power or less, the rotating cylinder is located at a position in the range from 45 degrees forward and 45 degrees below the front edge of the fixed thin plate wing 20. 21 (corresponding to the rotating rod 10 in the embodiment) is clarified to correspond to a range in which the rotation center axis is located.

  For reference, in place of the rotary rod 10 having the circular cross section used in the micro air vehicle shown in the present embodiment, conventionally, in a fluid machine such as a Magnus windmill using the Magnus effect in a high Reynolds number region. Visualization in the case of using a rotating rod with a concave-convex cross-sectional shape of a gear shape that is considered to be effective and is being promoted for research and development as a rotating rod in the micro air vehicle shown in this embodiment as well. When a flow visualization experiment was performed using a water tank, the flow around the fixed thin plate blade adjacent to the rotating rod was greatly disturbed by the rotation of the rotating rod having the gear-shaped cross-sectional shape. The generation of the powerful jet jet 22 shown in FIG. 3 generated in the backward flow when the cylindrical rotating rod 10 shown in FIG. It was confirmed never completely occur in the case of using a rotating rod consisting by the uneven cross-sectional shape. For this reason, it can be said that the cross-sectional shape of the rotating rod 10 used in the present invention should be a smooth cross-sectional shape having a substantially circular cross section without irregularities. From the comparison of the experimental results, it is possible to know the dissimilarity between the flow around the rotating cylinder in the high Reynolds number region and the flow around the rotating cylinder in the low Reynolds number region.

  Since the micro air vehicle shown in the present embodiment has the above-described configuration, it can realize excellent low-resistance flight characteristics and large angle-of-attack flight characteristics. It is possible to perform horizontal flight at a high speed more than twice as fast as the flight speed, and to allow stalling etc. by allowing instantaneous high angle of attack flight even in natural wind environments including strong winds and gusts. It is confirmed by a flight test by the inventor of the present invention that a stable level flight can be performed stably even at a large angle of attack exceeding 30 degrees of attack angle in a calm outdoor environment. Has been.

  Further, since the rotating rod 10 and the rotating rod driving motor 11 are provided in a pair of left and right sides independently only at the left and right blade ends of the front wing 1, the rotational speed of the rotating rod 10 is set to the port side and By controlling the change on the starboard side independently, the suppression and generation of boundary layer separation on the upper surface of the fixed thin blade can be controlled independently and freely on the port side and starboard side. In the flying body, it has excellent maneuvering characteristics that can exhibit sufficient maneuverability even in natural wind environments including the strong winds, gusts, etc. that are the same as those equipped with a conventionally known spoiler control device for aircraft control A micro air vehicle can be realized.

  The specific embodiment according to the present invention has been described in detail above. However, the technical scope of the present invention is not limited by the specific embodiment disclosed as the example. Of course, the present invention is also applicable to the case where the cross-sectional shape of the rotating rod disclosed as a circular cross-section in the example is an extremely gentle elliptical cross-sectional shape that can be regarded as almost a circular cross-section or a gear-shaped cross-sectional shape provided with extremely minute irregularities. It can be said that this is equivalent to the scope of disclosure of the invention.

  According to the present invention, it is possible to operate an unmanned micro air vehicle operated by radio control outdoors in a natural wind environment, and therefore can exist within the range of conventional aircraft operating conditions. Has unexplored industrial applicability. In addition, the present invention makes it possible to manufacture and operate an ultra-compact aircraft that does not require any complicated steering drive mechanism at a low cost, and conventionally, it is difficult to use an aircraft in light of the operation cost. It has undeveloped industrial applicability in the areas that have been developed. Specific examples include detailed surveys of weather and air environment, search and observation of narrow danger zones by unmanned aircraft, scientific research and support for various activities, hobby applications, and so on. In addition, as a planetary probe that is resistant to disturbance in the Martian environment where the Reynolds number of the atmosphere is an order of magnitude lower than on the Earth, the micro air vehicle according to the present invention is considered to be an optimal candidate.

It is explanatory drawing which shows the micro air vehicle by this invention seeing from upper left back. It is explanatory drawing which shows the micro air vehicle by this invention seeing from the lower left front. It is explanatory drawing which shows the flow around the rotation cylinder in a low Reynolds number area | region. It is explanatory drawing which shows the flow around the wing | blade of the micro air vehicle by this invention. It is explanatory drawing which shows the flow around the wing | blade of the micro air vehicle by this invention. It is explanatory drawing which shows the arrangement position of the rotating rod for obtaining the effect of this invention. It is explanatory drawing which shows the flow around a flat blade in a low Reynolds number area | region. It is explanatory drawing which shows the flow around a flat blade in a low Reynolds number area | region.

Explanation of symbols

1: front wing 2: rear wing 3: shock absorber 4: control unit 5: fuselage 6: mass ballast 7: propulsion motor 8: propeller 9: propeller propulsion device 10: rotating rod 11: rotating rod driving motor 20 : Fixed thin plate blade 21: Rotating cylinder 22: Jet jet 23: Dead water area 24: Separation area

Claims (2)

In a micro air vehicle flying with a fixed thin plate wing in a region where the Reynolds number is 10 5 or less with a chord length as a reference length, the leading edge of the fixed thin plate wing is adjacent to the front edge of the fixed thin plate wing. A rotary rod having a circular cross section having a smooth surface in a position ranging from 45 degrees forward and lower 45 degrees to a rear upper 45 degrees in a positional relationship in which the front edge of the fixed thin plate blade and the rotation axis of the rotary rod are parallel to each other, Low resistance flight and large angle of attack flight by rotating the rotating rod in the same direction of rotation as the blade circulation direction of the fixed thin plate blade so that the peripheral speed of the rotating rod is twice or more the uniform flow velocity. An ultra-compact air vehicle characterized by realizing   A pair of left and right rotating rods are provided independently only at the blade tips of the fixed thin plate wings, and flight control is performed by independently changing and controlling the rotation speed of the rotating rods on the port side and starboard side. The micro air vehicle according to claim 1.

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