JP2016068692A - Multi-rotor craft posture stabilization control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drastically improve the responsiveness of posture control by performing the posture control by a gravitational center movement with respect to a rotor aound a roll axis and a pitch axis to permit the imbalance of a machine body or an individual difference or variation in rotor thrust or a motor output.SOLUTION: In a multi-rotor craft having rotors 4a to 4d arranged in a circumferential direction, a machine body 5 is connected below the center of a multi-rotor part via a rod 7 swingable around a roll axis or a pitch axis. A posture around the roll axis or the pitch axis is controlled based on the swing angle of the rod 7 around the roll axis or the pitch axis and by using the machine body 5 as a weight, and a posture around a yaw axis is controlled based on the rotational speeds of the rotors 4a to 4d.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a posture stabilization control device around a pitch axis and a roll axis of a rotor craft having two or more rotors (hereinafter referred to as “multi-rotor craft”), also called a multi-rotor or multi-copter. .

In recent years, commercial use of multi-rotor craft for aerial photography and surveying projects has been expanding. The basic attitude stabilization control of multi-rotor craft keeps the rotor rotation surface horizontal, keeps the roll axis and pitch axis horizontal, and controls the yaw angle to be constant without rotating the fuselage relative to the rotor surface. That is.
Regarding the roll axis and pitch axis, the number of rotations of the rotor (rotor at a position symmetrical to the roll axis) involved in the attitude around the roll axis and the rotor involved in the attitude around the pitch axis (with respect to the pitch axis) The rotational speed of the rotor at the left and right symmetrical positions is changed, and the yaw axis is controlled using the rotational speed difference between the forward rotating rotor and the reverse rotating rotor. The rise and fall of the airframe is controlled by increasing or decreasing the output of all the rotors while controlling the yaw axis, pitch axis, and roll axis.

As described above, since the difference in the rotational speed of the rotor is used for the attitude control of the multi-rotor craft, the response delay of the prime mover such as the electric motor that drives the rotor, the inertia of the drive system including the speed reducer, the air flow Due to the compressibility, an inevitable response delay occurs before the change in the rotational speed of the rotor is reflected in the change in thrust.
As a control technique in consideration of this response delay, Patent Documents 1 and 2 describe performing control of a secondary response delay system.

  Patent Document 3 describes that the pitch and the roll are stabilized by the tension of the wire by mooring with the wire extending from the machine body on the ground surface, which is the ground surface.

  Patent Document 4 describes the use of a weight shift for controlling the pitch angle and the roll angle, and a motor for driving the planetary gear for controlling the yaw axis, regarding the operation of the heavy-rotation single-seat helicopter. ing.

JP 2004-256020 A Japanese Patent Laid-Open No. 2004-256022 JP 2013-079094 A JP 2000-072095 A

As described above, in the conventional technology, the rotor rotational speed difference is used for posture control around all the axes of the multi-rotor craft, so that the rotor itself, the prime mover such as an electric motor, and the like If there is an individual difference in the speed reduction mechanism intervening in the rotor, even if the same power is supplied, the thrust generated by each rotor becomes non-uniform.
If the thrust is extremely uneven, it will be impossible to stabilize the attitude of the multi-rotor craft due to the inevitable response delay described above, so strict quality control is performed to minimize individual differences. In addition, since a high-speed arithmetic processing unit is required, the cost is greatly increased.

  Even if these individual differences can be set to a state close to zero, when a disturbance such as a gust of wind acts, in order to stabilize the posture, when feedback control is performed on the prime mover output, if the responsiveness is increased, Due to the response delay of the prime mover, the inertia of the drive system, and the compressibility of the air, hunting occurs and the behavior of the aircraft becomes unstable. On the other hand, if the responsiveness of the feedback control is lowered, the posture control is not in time when the posture is largely collapsed due to a sudden disturbance, which may cause a runaway or a crash.

By the way, when an engine such as an internal combustion engine is employed as the prime mover, the cruising distance can be made much longer compared to an electric motor that is limited by the battery capacity.
However, the engine has a large individual difference in output characteristics as compared with an electric motor, and is inferior in output response and control convergence, so that it is extremely difficult to use the engine as a drive source for a multirotor. On the other hand, in the case of an electric motor, although the control characteristics are better than those of an engine, the cruising distance depends on the battery capacity, so that there is a problem that continuous aerial photography cannot be performed over a wide area.

Moreover, if the rolling angle and pitch angle of the fuselage exceed the limit values, the thrust of each rotor will be in a state close to the horizontal direction, and not only can the posture be reestablished, but also runaway, leading to safety assurance All the rotors are immediately stopped and crashed on the spot.
As described above, in the conventional technology, there is an essential problem in that the attitude control is performed by the thrust control of the rotor in which the output control of the prime mover is interposed, and the expensive parts and the maintenance cost accompanying the change over time are included. Major issues remain in safe and easy use, such as cost increase associated with quality control, limit of responsiveness to disturbances, and complete destruction of the aircraft to ensure safety.

  Accordingly, an object of the present invention is to improve the responsiveness of posture control drastically by performing posture control by moving the center of gravity with respect to the rotor, not about the thrust control of the rotor about the roll axis and the pitch axis. At the same time, it is intended to realize a multi-rotor craft that drastically enhances safety at low cost by allowing individual differences and variations such as unbalance of the fuselage, rotor thrust, and motor power output.

In order to solve the above-described problems, the following technical means have been taken in the present invention.
That is, in a multi-rotor craft in which a plurality of rotors are arranged in the circumferential direction, weights are connected to the lower part of the center of the multi-rotor part via rods that can swing around the roll axis and pitch axis of the multi-rotor craft. And the attitude of the multi-rotor craft around the roll axis and the pitch axis is controlled by the swing angle of the rod around the roll axis and the pitch axis, and the attitude of the multi-rotor craft around the yaw axis is controlled by the rotor. The number of rotations or the thrust direction changing device provided below the rotor is controlled.

According to the present invention, the posture of the multi-rotor craft around the roll axis and the pitch axis is controlled by changing the center of gravity of the weight according to the rocking angle of the rod. The attitude is controlled by a rotation direction of the rotor and a thrust direction changing device provided below the rotor. By this control, individual differences and variations such as the unbalance of the fuselage, the thrust of the rotor, and the motor output can be eliminated with a simple algorithm. Moreover, even if inexpensive devices with large individual differences are used for each device, advanced fine adjustment is not required, and after-sales maintenance can be made almost unnecessary, regardless of the deterioration of the aircraft and each device. Safety can be ensured.
Furthermore, since the rotor speed change is not used for attitude control, it is possible to use power other than the electric motor, such as a reciprocating engine or a turbine engine, which has low responsiveness to the speed change. As a result, it is possible to expand the time limit of flight due to battery use, which is a drawback of current multicopters.

FIG. 1 is an overall view of a multi-rotor craft based on the first embodiment. FIG. 2 is an enlarged view of the central portion of the multi-rotor craft. FIG. 3 is a diagram modeling a mechanism for performing posture control around the roll axis based on the first embodiment. FIG. 4 is a diagram modeling a mechanism for performing attitude control around the pitch axis based on the first embodiment. FIG. 5 is a control block diagram for performing posture control around the roll axis, the pitch axis, and the yaw axis based on the first embodiment. FIG. 6 is a diagram comparing the control response and the attitude angle of the first embodiment when a disturbance occurs around the roll axis with the prior art. It is explanatory drawing regarding an inclination control limit angle. FIG. 8 is a diagram illustrating an arrangement of the thrust direction changing device based on the second embodiment. FIG. 9 is an overall view of a multi-rotor craft based on the second embodiment. FIG. 10 is an enlarged view of the power distribution device according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Example 1]
FIG. 1 shows an overall view of a multi-rotor craft based on the present embodiment. Four arm portions 2a to 2d extend in a horizontal direction at 90 ° intervals from a central portion 1, and a rotor is provided at each end. 3a to 3d and prime movers 4a to 4d (which may include a speed reducer) are mounted. The arm portions 2a to 2d are equal in length, and are arranged so that the center points of the rotors 3a to 3d mounted on the tips thereof are located on the same circumference in plan view. The structure including the central portion 1, the arm portions 2a to 2d, the rotors 3a to 3d, and the prime movers 4a to 4d constitutes a multi-rotor portion, and the center of gravity coincides with the central point of the rotors 3a to 3d.
In addition, the rotor 3a and the rotor 3c are rotated in the same direction, and the rotor 3b and the rotor 3d are rotated in the opposite directions so that the rotational moment is canceled and the deviation in the yaw axis direction is suppressed. Yes.

  The multi-rotor craft body 5 is provided with a rod 7 extending upward from its center of gravity. The upper end of the rod 7 is rotated around the roll axis around the roll axis and around the pitch axis via a rotation axis around the roll axis (axis in the direction of travel) and a rotation axis around the pitch axis (axis perpendicular to the direction of travel). Each of them is connected so as to be able to swing independently. A leg 6 is mounted on the bottom surface of the body 5.

As shown in FIG. 2, a central actuator 1 is equipped with a first actuator 8 that swings the rod 7 about the roll axis, and a second actuator 9 that swings the rod 7 about the pitch axis. The swing angle of each axis is controlled by a controller to which detection values of the roll axis rate gyro and the pitch axis rate gyro are input.
In this embodiment, a servo is used as the actuator, but if the multi-rotor is large, an electric motor may be used.

The body 5 is equipped with various controllers, cameras, communication equipment and other mounted equipment, and when the prime movers 4a to 4d are electric motors, a secondary battery or the like is mounted, the center of gravity is directly below the rod 7, and has a predetermined weight. The rod 7 becomes a pendulum rod.
When the multi-rotor craft body 5 and each rotor are subjected to a disturbance rotating around the roll axis due to a gust of wind, etc., the first actuator 8 causes the body 5 to swing around the roll axis in a direction to cancel the disturbance. Offset. Similarly, when subjected to a disturbance rotating around the pitch axis, the second actuator 9 causes the body 5 to swing around the pitch axis in a direction to cancel this, thereby performing posture control around the roll axis.

At that time, the mass of the body 5 and the length of the rod 7 and the swing angles obtained by the first actuator 8 and the second actuator 9 determine the magnitude of the moment that cancels the disturbance.
That is, as the rod 7 is longer, a larger control force can be generated. Therefore, the control force can be adjusted by adjusting the length of the rod 7.

FIG. 3 is a model in which the posture control is performed by the actuators 8 and 9 of FIG. 1 with respect to the roll axis.
Basically, the equation of motion of the pendulum is applied, and it is considered that the fulcrum of the pendulum is moved by an object having a large air resistance. In FIG. 3, the multi-rotor craft receives a disturbance Tz, and the attitude of the roll axis is inclined with respect to the horizontal plane at an angle of θ _{1. In} order to correct the attitude, the first actuator 8 is actuated and the airframe is at an angle of θ _2. The state where 5 is inclined is shown.

At this time, when the mass of the airframe 5 serving as a pendulum is M ₁ [kg] and the length of the rod 7 is l ₁ [m], the posture correcting moment acting around the roll axis is
M ₁ × l ₁ × sin (θ ₁ + θ ₂ ) can be expressed.
Since the actual disturbance Tz is set to an average wind speed of about 2 to 10 m / s, which is a range of normal safe operation, θ ₁ and θ ₂ also take values close to zero. Therefore, the posture correction moment is (θ ₁ + θ ₂ ) can be linearly approximated.

The same applies to the pitch axis shown in FIG. 4, disturbed T _Y, posture inclination at an angle of pitch axis gamma ₁ with respect to the horizontal, tilted in order to correct the attitude, the second actuator 9 is actuated by an angle of the body 5 gamma ₂ Shows the state. In contrast to the roll axis attitude control described above, since the pitch axis attitude control is the traveling direction, the resultant direction of the acceleration direction and the gravitational direction is the roll axis attitude control only during a slight acceleration period of forward / stop / reverse. It corresponds to the gravity direction.

However, since the motion is constant during the flight movement, the rotor surface is horizontal during the constant speed movement, and basically the pitch axis control is performed with exactly the same dynamics as the roll control.
Forward acceleration is performed by tilting forward by pendulum posture control as shown in FIG. 4 and is kept constant by pendulum stability control to perform constant speed motion. To stop from constant speed motion, the rotor surface is tilted backward by pendulum attitude control to decelerate or accelerate, and when stationary, the pendulum stability control is maintained again to keep the air in the air. All these motions are realized by controlling the pendulum motion in the pitch direction as shown in FIG.

  In this way, because of the pendulum motion control that uses the instantaneously acting force of gravity, there is no need for time delay control without using compressible air, and the roll axis and pitch axis are controlled by linear control. Attitude control is possible.

  About the yaw axis, posture control is performed by increasing or decreasing one or both of the rotational speed of the rotor 3a and the rotor 3c and the rotational speed of the rotor 3b and the rotor 3d in a direction to cancel the disturbance.

As described above, the stable attitude control of the multi-rotor craft around the roll axis, pitch axis, and yaw axis stabilizes the attitude by always operating during stationary (hovering) and constant speed movement, which occupies most of the flight time. Prevent crash.
When the multirotor is actually operated, the roll axis or pitch axis is tilted for a short time at a certain point, and instantaneous acceleration and instantaneous deceleration are performed before and after the left and right. Then, the movement by the constant speed movement is repeated until the next point is reached, and the movement is made to the target position by the control of moving the grid eyes.

At that time, at the intersection of the grid's eyes, the roll axis control and pitch axis control to keep the posture horizontal are released for a moment, and the roll axis and pitch axis tilts for acceleration and deceleration are shortened by pendulum control. Do time. During the other periods, the pendulum posture stabilization control that keeps the posture horizontal at constant speed motion or stationary state is activated.
Such a control algorithm is executed by the correlation function G in the control block diagram of FIG. FIG. 5 is based on the premise that the motors 4a to 4d have an electric motor with good control characteristics and capable of posture control around the yaw axis by the number of rotations of the rotor.

When the operator uses a graphical user interface (GUI) to issue a movement command in the form of designating a destination on a map, for example, coordinate conversion is performed, and route generation is performed by a command value conversion route control algorithm. Done.
The command value conversion path control algorithm is divided into roll axis, pitch axis, Z axis (altitude), and yaw axis control elements, and respective control target values are output.
For the roll axis and the pitch axis, the roll axis rate gyro, pitch, and pitch are determined by θr (t) and θp (t), which are G (rpzy) correlation functions, respectively, based on the control target value from the command value conversion path control algorithm. Performs feedback control using an axial rate gyro.
As a result, as described above, the roll axis and the pitch axis are tilted at a specific point for a short time, instantaneous acceleration and deceleration for a moment in the left and right, and then constant velocity movement until the next point is reached. Repeat the movement.

For example, the pendulum posture stabilization control is always operated when the direction is changed by the yaw control, and the pendulum posture stabilization control is continuously operated during the altitude control at the time of ascent and descent. Regarding the yaw control, the correlation function G has little involvement, but there are cases where it accelerates while rotating in the yaw direction or decelerates while ascending and is not zero, so the correlation function G performs altitude control and yaw control. To include.
The pilot is given a command target in the form of designation of the destination on the map by the GUI, the coordinates are converted, the route is generated, and from there, it is decomposed into roll, pitch, altitude and yaw control elements. The control command value is input.

FIG. 6 shows the control response and the posture angle when a disturbance occurs in the posture control on the roll axis. The upper side is according to the embodiment, the lower side is according to the prior art, the bottom stage is the generated disturbance, the vertical axis indicates the force such as the disturbance and the controlled variable and the angle of the posture angle, and the horizontal axis indicates the time. .
In the conventional control based on thrust by changing the rotor rotational speed, a response delay occurs because of the compressible air.
On the other hand, according to the roll angle control using the airframe 5 as a pendulum according to the present embodiment, it can be confirmed that the response speed is extremely high and a high response speed for posture angle correction can be obtained.

  As described above, the yaw angle of the multi-rotor craft is normally rotated around the yaw angle by rotating the rotors 3a and 3c in the same direction and rotating the rotors 3b and 3d in the reverse direction. Offset the rotation of When a disturbance around the yaw axis is applied, this is detected by the yaw axis rate gyro, and the rotational speeds of the rotors 3a and 3c or the rotors 3b and 3d having the same rotation direction are adjusted, so that Offset the disturbance.

At this time, swinging around the roll axis and the pitch axis occurs with the change in the rotational speed of the rotors 3a to 3d, but this is offset by the control of the first actuator 8 and the second actuator 9 described above.
As described above, according to the present embodiment, even if the characteristics of the rotors 3a to 3d and the output of the motor driving the rotors vary, stable control around the roll axis and the pitch axis is maintained using the machine body 5 as a pendulum. Therefore, from the standpoint of maintaining the stability around the yaw axis only by adjusting the rotational speeds of the rotors rotating in reverse, even if the posture around the roll axis and the pitch axis changes, It can be absorbed by the above-described roll axis control and pitch axis control.

  In the conventional technology, the postures around the roll axis, the pitch axis, and the yaw axis are all controlled by the rotational speed of the rotor, so that the optimum conditions satisfying the stability around all axes at the same time can be adjusted. High precision rotors, motors, reducers, and control devices had to be used, and advanced adjustments were required for these adjustments. In addition, since the adjustment around one axis affects the other axes, the control is diverged due to the response delay caused by the compressibility of the air, causing unstable flight.

  However, according to the present embodiment, the control around the yaw axis can be made independent, and the control responsiveness around the roll axis and the pitch axis is very high due to the movement of the center of gravity. Even if there are individual differences, it can be absorbed by posture stabilization control around the roll axis and pitch axis using the airframe 5 as a pendulum, and the cost required for quality control can be greatly reduced. .

Further, in the conventional multi-rotor craft, when the posture is largely inclined as shown in FIG. 7, the thrust direction becomes the lateral direction with the thrust of the rotor, and therefore there is a tilt limit angle at which posture stable control is impossible. In the prior art, the inclination limit angle is normally set to about 35 °.
According to the present embodiment, the stability of the pitch axis and the roll axis is not controlled by the thrust of the rotor, but by the posture stability control by the pendulum using gravity, so that a large inclination that is impossible with the normal rotor thrust is achieved. In this case, stable posture control is possible.
In addition, according to the present embodiment, according to the scale of the multi-rotor craft, the weight of the fuselage 5 can be increased, a small engine generator is mounted in the fuselage 5 to charge the secondary battery, You may make it drive the motor which drives the rotors 3a-3d.

[Example 2]
Due to the above-described advantages of the present invention, in the case of a large multi-rotor craft, a small reciprocating engine can be arranged directly below each rotor instead of the electric motor to serve as a drive source.
As described above, an internal combustion engine such as a reciprocating engine is inferior in terms of variation in output characteristics and control responsiveness as compared with an electric motor. However, a pendulum control with the fuselage 5 as a weight is used to drive a large multirotor craft. It becomes possible to use as.
However, since the posture around the yaw axis is not subject to pendulum control, as shown in FIG. 8, the yaw control fins 9a to 9a attached to the arms 2a to 2d so as to be positioned directly below the rotors 2a to 2d. This is done by controlling the slope of 9d. The yaw control fins 9a to 9d function as thrust direction changing devices for the rotors 2a to 2d.
That is, when a disturbance around the yaw axis is applied, this is detected by the yaw axis rate gyro, at least one of the yaw control fins 9a to 9d is changed, and the rotor positioned above the yaw axis rate gyro is changed with respect to the gravity direction. By changing and adjusting the thrust direction, disturbance around the yaw axis can be offset. In this case, the control objects for the yaw axis control in FIG. 6 are the yaw control fins 9a to 9d.

  Furthermore, it is possible to mount a single internal combustion engine inside the fuselage 5 and distribute power to the rotors 3a to 3d with bevel gears. That is, as shown in FIG. 9, the output of the internal combustion engine mounted on the airframe 5 is used as a drive shaft 8 via a flexible wire, a torque transmission rod, a universal joint, or the like, or inside the hollow rod 7 Is transmitted to the input shaft of a pair of upper and lower bevel gears 10 provided at the center of the rotors 3a to 3d.

  As shown in FIG. 10, the lower gear of the bevel gear 10 that is directly connected to the internal combustion engine and rotationally driven is screwed with a bevel gear that is integrally fixed to the arms 2 a and 2 c, and the upper side of the bevel gear 10. The gears are screwed together with bevel gears fixed to the integrated arms 2b and 2d, so that the arms 2a and 2c and the arms 2b and 2d are rotated in the reverse direction. 2a and 2c and the rotors 2b and 2d are rotated in the opposite directions. As a result, the rotational moment around the yaw axis is canceled, and the disturbance around the yaw axis is canceled using the yaw control fins 10a to 10d.

  In the above embodiment, the multi-rotor craft body is used as a weight. However, the present invention is not limited to this, and the body 5 is directly connected to the central portion 1 that is the starting point of each of the arms 2a to 2d. You may install a pendulum separately in a center part. Further, the number of rotors is not limited to four.

As described above, according to the present invention, individual differences and variations such as the unbalance of the fuselage, the thrust of the rotor, and the motor output can be eliminated with a simple algorithm. Moreover, even if an inexpensive device having a large individual difference is used for each device, advanced fine adjustment is not required, and after-sales maintenance can be made almost unnecessary.
In this way, since the safety of the posture is always ensured regardless of the deterioration of the airframe and each device, it can be expected to be widely adopted as a posture control device for multi-rotor craft in the future. In addition, since the rotor speed change is not used for attitude control, power that has low responsiveness to speed changes other than electric motors, such as reciprocating engines and turbine engines, is used to dramatically increase the cruising time of multi-rotor craft. And can contribute to an increase in size.

DESCRIPTION OF SYMBOLS 1 Center part 2a-2d Arm part 3a-3d Rotor 4a-4d Motor | power_engine 5 Body 6 Leg part 7 Rod 8 1st actuator 9 2nd actuator

Claims (6)

In multi-rotor craft with multiple rotors arranged in the circumferential direction,
Under the center of the multi-rotor part, a weight is connected via a rod that can swing around the roll axis and the pitch axis of the multi-rotor craft,
The attitude of the multi-rotor craft around the roll axis and the pitch axis is controlled by the swing angle of the rod around the roll axis and the pitch axis, and the attitude of the multi-rotor craft around the yaw axis is rotated. The multi-rotor craft attitude stabilization control device is controlled by a number or a thrust direction changing device provided below the rotor.   2. The multi-rotor according to claim 1, wherein each of the rotors is driven by an individual electric motor, and the attitude of the multi-rotor craft around the yaw axis is controlled by the number of rotations of the rotor. Craft stabilization control device.   The attitude stability of the multi-rotor craft according to claim 1, wherein the rotor is driven by an internal combustion engine, and the attitude around the yaw axis of the multi-rotor craft is controlled by the thrust direction changing device. Control device.   Based on the detected values of the angle / angular velocity / angular acceleration detector around the roll axis of the multi-rotor craft and the angle / angular velocity / angular acceleration detector around the pitch axis, the rod swings around the roll axis and the pitch axis. A yaw control fin for controlling the first actuator and the second actuator for controlling the angle and changing the rotational speed of the rotor or the direction of thrust from the rotor based on the detection value of the angle detector around the yaw axis The multi-rotor craft attitude stabilization control device according to any one of claims 1 to 3, further comprising a controller for controlling the position.   5. The multi-rotor craft posture stabilization control device according to claim 1, wherein the weight of the multi-rotor craft body is the weight. 6. The multirotor craft body is mounted at the center of the multirotor section, and the rod is connected to the center of the body so that the rod can swing around the roll axis and the pitch axis of the multirotor craft. The attitude stabilization control device for a multi-rotor craft according to any one of claims 1 to 5, characterized in that:

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