JPH0324384B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Purpose of the Invention [Field of Industrial Application] This invention relates to a levitation machine such as a helicopter or a hovercraft, in particular, to a levitation machine such as a helicopter or a hovercraft, in which four or more fans (including propellers and rotors) are rotated vertically. This invention relates to a mechanism for stabilizing the attitude of a levitator while hovering.

Helicopters and hovercrafts are familiar vehicles that can be used to perform forestry work on rough or sloping land, rescue operations, etc. from the air.

[Prior Art] However, when a helicopter has complex terrain near the ground, it becomes difficult to maneuver due to complex aerodynamic ground effects. I have no choice but to do the work. On the other hand, in the case of hovercraft,
A hovercraft for use on rough terrain has not been realized because the flying height is low, and in order to increase the flying height, it has to be large, and the flexible skirt wears out.

In such cases, in order to ascend at a relatively high altitude, and to deal with complex ground effects, a large number of fans are rotated downward to obtain thrust. It has been considered that adjustments can be made to balance complex ground effects, and in recent years, research has been conducted on linking multiple helicopters together to transport heavy loads.
In either case, a particularly important consideration is the attitude control of the aircraft. Attitude control of these aircraft has conventionally been performed mainly by manipulating the fan's cyclic pitch, collective pitch, and rotation speed, but the equipment is complex and difficult to apply to simple levitators. Not necessarily suitable. For this reason, there is a desire to develop a levitator equipped with an attitude control mechanism that is simple in structure and operation.

[Problems to be Solved by the Invention] This invention has been made in view of the above circumstances, and is an object of the present invention to correct the attitude stabilization of a vehicle levitated by a large number (four or more) of fans or rotors. The object of the present invention is to provide a levitator having an attitude control mechanism that can be controlled only by controlling the pitch or rotation speed.

(b) Structure of the invention [Means for solving the problem] In response to this purpose, the air levitation aircraft having an attitude stabilization mechanism of the present invention has four or more fans attached to the aircraft body facing downward. The air levitation vehicle rotates and hovers, and the direction of rotation of some of the four or more fans is opposite to the direction of rotation of the remaining fans, and the rotation axis of the fans is aligned with the center axis of the body. The fan is characterized in that it is arranged so as to be inclined in a circumferential direction around the center in a direction that increases the moment received as a reaction to the rotation of the fan.

Hereinafter, details of the present invention will be explained with reference to the drawings showing one embodiment.

In FIG. 1, FIG. 2, and FIG. 3, 1 is a levitator, and the levitator 1 is equipped with a body 2. However, FIG. 2 is a cross-sectional view of the negative part in FIG. 1, and FIG. 3 is a cross-sectional view of the negative part in FIG. 1. The fuselage 2 has four holes 3 cut out in the direction of the fuselage center axis G, and the holes 3 serve as ducts for the fans 4a to 4d. The four fans 4a to 4d are attached to the rotating part of the rotating device 5. Further, the rotating device 5 is fixed to the body 2 by a fixing device 6. To drive the rotating device 5, an engine may be attached directly to the rotating device 5 and rotated, the engine may be placed in the center of the body and driven by a belt, or a pneumatic motor may be attached to the rotating device and driven. It's okay. Furthermore, an electric motor may also be used. When using a pneumatic motor and a pneumatic motor, it can also be used for work in a factory by installing a pump and power source externally.

It is particularly important to note that the four fans 4a-4
As shown in FIG. 3, the rotation axis 7 of d is inclined by a certain angle (for example, by an angle θ in the cross section of FIG. 3) with respect to the central axis G of the body 2. When viewed from the center of the aircraft 2, the directions of inclination are the same for fans 4a and 4c, and the same for fans 4b and 4d.
It is tilted in the opposite direction to a and 4c. In this embodiment, the tilt angle θ is the same for all the fans 4a to 4d, but does not necessarily have to be the same.

As shown in FIG. 2, the duct 3 has a rounded top to generate negative pressure when air is sucked in, thereby increasing propulsion efficiency. 8 is the ground.

[Function] The function of the levitator 1 configured as described above is as follows.

When the rotating device 5 is driven to rotate the fans 4a to 4d, thrust is generated. In other words, the streamlines 11 expand downward near the ground, so the thrust increases compared to when there is no ground. In other words, it is a ground effect. When one fan (diameter D) is placed at a height h above the ground, the thrust L has the characteristics shown in Figure 4, compared to the thrust L _∞ when there is no ground.
Known for research by NASA. Furthermore, when using multiple fans, ground effects due to mutual interference also occur. Like the streamline at the bottom near the center of Figure 2,
A pushing air flow is created, increasing the thrust. This is the so-called air action effect.
Furthermore, there is also an influence due to the shape of the aircraft. For example, if there is a bulge around the fuselage, air flows downward from the outside, reducing thrust. Therefore, it is preferable to arrange the fans 4a to 4d at the periphery. The above is a well-known fact and should be considered during design.

Now, the thrust of each of the fans 4a to 4d can be controlled by changing the rotation speed. It can also be operated by changing the pitch.
Generally speaking, it is desirable to change both the rotation and pitch. In other words, the optimum pitch is determined depending on the rotational speed. Generally, in the case of engine drive, it is difficult to vary the rotational speed in short periods, so control is performed by operating the pitch in order to stabilize the attitude. In the case of electric motors or pneumatic motors, the rotational speed can be controlled by adjusting current or valves. Therefore, in this invention, it is only stated that the thrust is manipulated, but this is done by either changing the pitch or changing the number of rotations. It should be emphasized here that the present invention does not require the cyclic pitch mechanism found in ordinary helicopters.

Next, let's talk about stability. Generally, the levitator 1 has six degrees of freedom. If we take the X, Y, and Z coordinate axes as shown in the lower left corner of FIG. 1, these are movements in the X, Y, and Z directions, and rotations around the X, Y, and N axes. However, regarding the movement of X and Y,
The effect of rotation around the X, Y axes, the aircraft tilts, and the thrust vector of each fan tilts, creating a horizontal force and moving, so in reality, the X, Y, Z It is sufficient to be able to control the four components of rotation around and movement in the Z direction. Therefore, the required minimum number of fans is four.

Stability includes static stability and dynamic stability. Static stability is the ability of an aircraft to recover when it deviates from its normal position or attitude. Dynamic stability is stability when temporal fluctuations are considered. In order to obtain dynamic stability, it is first necessary to have static stability.

The levitator, which is the subject of this invention, essentially cannot achieve static stability unless it is controlled. Therefore, the attitude control mechanism according to the present invention is a mechanism that can obtain static stability through control.

To control the rotation around the X axis, the thrust of the fans 4b and 4d in FIG. 1 can be adjusted. For example, when the aircraft tilts in the positive direction around the X-axis, the thrust of the fan 4b may be increased, the thrust of the fan 4d may be decreased, or both may be adjusted at the same time. Similarly, to manipulate rotation around the Y axis,
It is only necessary to adjust the thrust of the fans 4a and 4c. Such operations are commonly carried out in a two-rotor tandem helicopter and are well known. Furthermore, in order to move in the Z direction, the overall thrust may be adjusted. This is also well known.

The problem is rotation around the Z axis. Now, assuming that each fan is installed horizontally, the sum of the torque reactions of each fan acts as the moment around the Z axis. For example, even if the torque is manipulated by increasing or decreasing the rotation speed, stability cannot be achieved. Because the torque is minute,
Due to the slight inclination of each fan and the ground effect, the acting moment cannot be canceled out. Normally, a helicopter rotates around the Z axis by a tail rotor, but in the case of a tandem type, moment is generated by a cyclic pitch. Although the levitator to which this invention is applied does not have a cyclic pitch mechanism or a tail rotor, rotation around the Z-axis can be controlled by a mechanism in which the rotation axis of the fan is inclined.

That is, two opposing moments are generated by a mechanism in which the rotation axis of each fan is intentionally tilted several degrees, but the thrust is adjusted to balance them. That is, in FIG. 1, since the fans 4a and 4c rotate clockwise, they receive a counterclockwise moment as a reaction, but they are tilted to increase the counterclockwise moment. By tilting in a direction that increases the torque reaction in this way, the angle of inclination can be made smaller than when tilting in the opposite direction, and the reduction in the vertical component of the thrust due to the tilt can be minimized. In Figure 1,
If the broken line circle represents the bottom surface of the duct and the solid line circle represents the top surface, such a moment will occur. Conversely, the fans 4a and 4d are tilted so as to generate a clockwise rotation moment. In the above manner, Z
Stable rotation around the axis can be obtained.

FIG. 5 is a plan view of a levitator having eight fans as another embodiment of the present invention. For example, if each fan is assumed to rotate in the direction indicated by an arrow in FIG. 5, it is divided into a group of fans 4a, 4c, 4e, and 4g and a group of fans 4b, 4d, 4f, and 4h. In the first group, the rotation axis is tilted as indicated by the broken line circle so as to generate a clockwise rotation moment. The second group tilts the axis of rotation to generate a moment of left rotation.
Increasing the number of fans in this manner provides better stability. For example, as shown in Figure 5,
If we consider a case in which an axis is determined and a tilted object must be rotated in the positive direction around the Y axis to return it to horizontal, it is necessary to increase the thrust on the positive side of X and reduce the thrust on the negative side. At this time, when increasing or decreasing the thrust without destroying the balance around the X-axis and the Z-axis, since the number of fans is large, the range of increase or decrease becomes small, and smooth stabilization control can be performed.

In order to stabilize the posture in this way, at least four fans are required, but a stabilization mechanism using four or more fans is an extension of the four fans case.
All you have to do is subdivide it.

[Example] Next, an experimental example of the present invention using a model will be described.

() Experimental system As shown in Figure 6, the model consists of four fans (diameter 15, made of styrofoam) powered by a DC motor (Mabuchi).
RE140) to rotate and float. The rotation direction of the fans 4a and 4c is counterclockwise, and the rotation direction of the fans 4b and 4d is clockwise. Drop the wire down through the hole in the center of the frame. Total weight is 100g.

The position and posture of the model are determined by the eight posts 13a to 1.
3h are the conductive tips 14a to 14d of the model, respectively.
Detection is done based on whether or not the person is in contact with the object. The purpose of the experiment was to adjust the rotation speed of each fan so that it did not touch any post. For this purpose, aluminum foil is pasted on the post and the conductive tip, and the tip is grounded.

Fig. 7 shows the electrical connections including the computer. Since the post and the conductive tip repeat contact and non-contact in short cycles, the input is input to the flip-flop, and the judgment is made by whether the flip-flop turns on within a certain period of time (0.2 seconds in the experiment). The motor drive amplifier has a maximum output of 1.65A according to the specifications, but in order to increase the flying height and give the experiment more margin, it draws 2A. On the other hand, the rated current of the motor is 0.6A. Therefore, although the experiment time is set at about one minute, the characteristics will change as described later if the experiment is used beyond this limit.

The rotation speed of the fan is 2600 rpm, and the levitation height is 1.5 cm.

() Basic aerodynamic characteristics The aerodynamic characteristics of propellers have already been well studied, and the following relational expression holds.

T=C _T ρn ² D ⁴ (1) Q=C _Q ρn ² D ⁵ (2) P=C _P ρn ³ D ⁵ (3) where ρ: air density, n: propeller rotation speed D: propeller diameter, T : Thrust Q: Torque, P: Power, C _Q : Torque coefficient _CT : Thrust coefficient, C _P (2πC _Q ): Power coefficient.

Also, regarding the influence of the ground, that is, the ground effect,
The case where the ground is horizontal has been investigated. According to this, if h is the hovering altitude, L _∞ is the thrust when there is no ground effect, and L is the thrust including the ground effect, then L/L _∞ increases rapidly as the altitude becomes lower, as shown in Figure 4. increases to

Figure 8 shows the aerodynamic characteristics of the experimental system. Ptotal on the horizontal axis is the total power consumed, but nearly 90% is consumed as copper loss in the motor. The numbers near the circle are the values after subtracting the copper loss Pcopper. This kind of inefficiency is caused by the fact that it is used far beyond its rated value. In the figure, the circle indicates the rotation speed n of the fan, which was measured using a strobe.
From the figure, it can be seen that it agrees well with equation (3).
The △ mark is the flying height h. The flying height varies depending on not only the diameter of the fan but also the area and pitch of the fan. It has been experimentally confirmed that the larger the pitch, the higher the levitation height, and the greater the minimum power required for levitation. Therefore, it is necessary to reduce energy consumption by changing the pitch depending on the altitude.

() Control method and experimental results Control is performed by manipulating the rotation speed of each fan. Movement in the X-axis and Y-axis directions is performed by fans 4a and 4, respectively.
Balance is achieved by adjusting the thrusts c, 4b and 4d.

Regarding rotation around the Z-axis, since the torque is determined by equation (2), it is first considered to rotate the fans 4a and 4c and 4b and 4d in opposite directions to adjust the rotation speed. However, experiments have shown that such a method is difficult.
The reason is that the torque acting as a reaction to the rotation of the fan is much smaller than the moment generated by the inclination of the thrust vector. Even if the motor and fan were installed precisely, it would not solve the problem because moments would be generated due to uneven terrain.

Therefore, in this experiment, we were able to achieve balance using the following mechanism. That is, the fan is intentionally tilted slightly (several degrees) to generate a moment. Moreover, the fans 4a and 4c are tilted so as to generate a clockwise moment, and the fans 4b and 4d
is tilted to generate a counterclockwise moment. Balance can be achieved by adjusting moments in opposite directions.

Now, when the rotational speed of fan i is increased by n _i , the total thrust, force in the X and Y directions, and moment around the Z axis become 4T, 2x, 2y, and 4N, respectively.
Suppose that only . At this time, the following equation approximately holds true.

4T=n ₁ +n ₂ +n ₃ + ₄ (4) 2x=n ₂ −n ₃ (5) 2y=n ₂ −n ₄ (6) 4N=n ₂ +n ₄ −n ₁ −n ₃ (7) However, So that the coefficient of each term on the right side is 1,
It is assumed that T, x, y, and N have been normalized.

Conversely, from equations (4) to (7), we get n ₁ =T-N+x (8) n ₂ =T+N+y (9) n ₃ =T-N-x (10) n ₄ =T+N-y (11) It will be done. That is, to balance
If you want to generate forces and moments of 4T, 2x, 2y, and 4N, n _i can be determined from equations (8) to (11).

In the experimental system, only N, x, and y are adjusted, assuming that there is no increase or decrease in thrust because the floor is flat.
Also, direct measurements of N, x, and y are not possible; only their sign is known through contact with the post. Therefore, an attempt is made to stabilize it by sequentially changing n _i . If the minimum unit of n _i is ±1, the minimum units of x, y, and N are also ±1. Therefore, 1 or -1 is taken depending on the sign of N, x, and y, and n _i is determined according to equations (8) to (11), and this is repeated at each sample time.

Next, the correspondence between the contact state with the post and N, x, and y is determined as follows. The state of post i (i=a to h) is represented by Si and determined by the following equation. (Contact when Si=1, non-contact when Si=0) IF(S _{a f} +S _{c h} +S _{e b} +S _{g d} )N=1 (12) IF(S _{b e} +S _{d g} +S _{f a} +S _{h c} ) N=-1
(13) IF (S _{c g} + S _{h d} ) x = 1 (14) IF (S _{d h} + S _{g c} ) x = -1 (15) IF (S _{b f} + S _{e a} ) y = 1 (16) IF (S _{a e} + S _{f b} )×=−1 (17) However, the value in parentheses is a logical expression, which specifies that if there is a post that comes into contact with it, the object will move away from the post.

FIG. 9 shows the results of an experiment using the above mechanism and control method, and is a graph of the output values to each motor. However, the sampling period is approximately
It is 0.2 seconds. At first, the same value is output to the motor, but the difference in characteristics creates a balance, so it can be seen that it is successively adjusted. In the figure, the part where no output changes corresponds to the state where there is no contact with any post.

Areas where there is no contact for 2 seconds or more are indicated by diagonal lines. Due to changes in the characteristics of the fan drive unit, it is difficult to maintain a stable state, but after 40 seconds it has remained stable for a fairly long time. In an actual levitator, if a highly accurate accelerometer, etc. used in a normal aircraft is used instead of a post, a stable state can be quickly reached, and it is essential to maintain a stable state. This will become clear through experimental examples.

(C) Effects of the Invention As is clear from the above explanation, according to the attitude control mechanism for a levitator of the present invention, the cyclic pitch can be adjusted by controlling only the thrust generated by controlling the collective pitch or rotation speed of the fan. Therefore, it is possible to obtain a levitator equipped with an attitude control mechanism that is simple in structure and operation.

[Brief explanation of the drawing]

Fig. 1 is a plan explanatory diagram of a levitator according to an embodiment of the present invention, Fig. 2 is a sectional view at the - part in Fig. 1, Fig. 3 is a sectional view at the - part in Fig. 1, and Fig. 4 is a sectional view at the - part in Fig. 1. 5 is a plan view of a levitator according to another embodiment of the present invention; FIG. 6 is an explanatory plan view of an experimental model; and FIG. 7 is a block diagram showing a control system. , FIG. 8 is a graph showing the aerodynamic characteristics of the experimental system, and FIG. 9 is a graph showing the experimental results showing the output values to each motor. 1... Levitation machine, 2... Aircraft, 3... Hole (duct), 4
a to 4d... Fan, 5... Rotating device, 6... Fixing device, 7... Rotating shaft, 8... Ground, 11... Streamline, 13a
~13h...Conductive post, 14a-14d...Conductive tip.

Claims (1)

[Claims] 1. An air levitation vehicle that hovers by rotating four or more fans attached to the aircraft body downward, where the rotational direction of some of the four or more fans is opposite to the rotational direction of the remaining fans. and the rotational axis of the fan is disposed so as to be inclined in a circumferential direction around the central axis of the aircraft body in a direction that increases the moment received as a reaction to the rotation of the fan. An air levitation machine with a floating mechanism.