KR101622277B1 - Modularized Quad-Rotor control system and control method thereof - Google Patents

Abstract

The present invention discloses a modular quadrotor control system and a control method thereof. That is, the present invention measures the attitude and motion of a vehicle using a 9-axis inertial navigation device based on a quadrotor equipped with four motors, and controls a modularized controller to realize a system with a high efficiency as well as a performance , Which increases the stability of the quad rotor, which makes it easier to adjust / control the quad rotor, which can improve hovering performance in particular.

Description

Modularized quadrotor control system and control method thereof [0002]

The present invention relates to a modular quadrotor control system and a control method thereof.

Small unmanned aerial vehicles are used in various fields such as traffic control, video shooting, reconnaissance missions, and fire surveillance. With the development of processors, sensors and communication technologies, performance and functions have been improved, and as they have become smaller and more cost-effective, they have expanded their presence in various fields and will accelerate in the future.

Especially, in case of multi - copter, it is considered to be suitable as a platform of small unmanned aerial vehicle because it is free to move up, down, left and right. Although the multi-copter maintains the attitude by the output of each motor and the motor output of each axis is assisted by the automatic control system according to the attitude, it is relatively easy to control compared to other airplanes, It is never easy to steer to the desired behavior.

In other words, in order to make the multi-copter more useful and easy to use, it is necessary to provide a control system that can prevent the flow phenomenon, which makes the flight difficult. Flow stabilization is required to control this flow.

Korean Patent Laid-Open No. 10-2013-0081260 [entitled: Unmanned Aerial Vehicle Control Device and Unmanned Aerial Vehicle Having the Same]

The object of the present invention is to provide a system for measuring the attitude and motion of a vehicle using a 9-axis inertial navigation system based on a quadrotor equipped with four motors, A modular quadrotor control system and a control method thereof.

The modulated quadrotor control system according to an embodiment of the present invention is a quadrotor control system in which a position control function and an attitude control function are modularized. The quadrotor control system receives a reference value and a previous displacement value on the basis of X axis, Y axis and Z axis, respectively A setta reference value for the position control of the quadrotor, a theta value in the previous loop, a sipe reference value, a sipe value in the previous loop and a pie reference value in the previous loop through the PID control function for the received reference value and the previous displacement value, A position control unit for outputting pi values; And a PID control function for theta reference value output from the position control unit, theta value in the previous loop, the sipe reference value, the sipe value and the pie reference value in the previous loop, and the pi value in the previous loop, And a posture control unit for outputting a control signal.

A control method of a modular quadrotor control system according to an embodiment of the present invention is a control method of a quadrotor control system in which a position control function and an attitude control function are modularized, Receiving a reference value and a previous displacement value, respectively; The position control unit controls the PID control function for the received reference value and the previous displacement value to determine the setta reference value for the position control of the quadrotor, the theta value in the previous loop, the sipe reference value, the sipe value in the previous loop, And a pie value in a previous loop, respectively; And the attitude control unit, the PID control function for theta reference value output from the position control unit, theta value in the previous loop, the cy reference value, the cy value in the previous loop, and the pie reference value in the previous loop, And outputting a control signal for attitude control of the vehicle.

The present invention is based on a quadrotor equipped with four motors, measures the attitude and motion of a vehicle using a 9-axis inertial navigation system, and controls a modular controller to realize a system having a high efficiency as well as a performance, This increases the stability of the rotor, which makes it easier to adjust / control the quad rotor, and in particular, improves hovering performance.

1 is a diagram illustrating a quadrotor model according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a quadrotor control according to an embodiment of the present invention. Referring to FIG.
3 is a view for explaining a quadrotor control according to an embodiment of the present invention.
4 is a view for explaining control of the posture of the quadrotor according to the embodiment of the present invention.
5 is a view illustrating an inertial sensor of a quadrotor according to an embodiment of the present invention.
FIG. 6 is a block diagram showing a configuration of a flying body having a plurality of rotor blades according to an embodiment of the present invention.
7 is a view for explaining a modulated quadrotor attitude control system according to an embodiment of the present invention.
8 is a view illustrating an axial force in a tilted state in the quad rotor position control system according to the embodiment of the present invention.
9 is a flowchart illustrating a method of controlling a modular quadrotor control system according to an embodiment of the present invention.
10 is a diagram illustrating input / output data of a modular quadrotor attitude control system according to an embodiment of the present invention.

It is noted that the technical terms used in the present invention are used only to describe specific embodiments and are not intended to limit the present invention. In addition, the technical terms used in the present invention should be construed in a sense generally understood by a person having ordinary skill in the art to which the present invention belongs, unless otherwise defined in the present invention, Should not be construed to mean, or be interpreted in an excessively reduced sense. In addition, when a technical term used in the present invention is an erroneous technical term that does not accurately express the concept of the present invention, it should be understood that technical terms that can be understood by a person skilled in the art can be properly understood. In addition, the general terms used in the present invention should be interpreted according to a predefined or prior context, and should not be construed as being excessively reduced.

Furthermore, the singular expressions used in the present invention include plural expressions unless the context clearly dictates otherwise. The term "comprising" or "comprising" or the like in the present invention should not be construed as necessarily including the various elements or steps described in the invention, Or may further include additional components or steps.

Furthermore, terms including ordinals such as first, second, etc. used in the present invention can be used to describe elements, but the elements should not be limited by terms. Terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like or similar elements throughout the several views, and redundant description thereof will be omitted.

In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It is to be noted that the accompanying drawings are only for the purpose of facilitating understanding of the present invention, and should not be construed as limiting the scope of the present invention with reference to the accompanying drawings.

The multi-copter constructs the frame so that the motors can be arranged at the same distance with respect to the center axis, and attaches the motor and the rotor. Generally, the control unit, the power unit, and the battery are placed on the central axis to secure a space, and the weight is further concentrated on the central axis.

Especially, multi-copter is popular as a platform of small unmanned aerial vehicle because it is free to move up and down and left and right. In the case of multi-copter, since there are at least 4 power units, the loads that can be mounted are relatively large because of the good output relative to the mass.

Although the energy consumption is large, the efficiency of the brushless motor has been improved due to the development of battery technology.

As shown in FIG. 1, the multi-copter 10 is a quadrotor having four rotors and four motors. Since the quad rotor 11 has a shape in which the motor shafts are arranged at 90 degrees each, stable flight performance can be expected using a minimum motor. As for the motor rotation, the quadrotor reacts as shown in FIG.

The quadrotor adjusts the rotation speed of the four blades, and the output is controlled by the output. Fig. 2 illustrates how the attitude is controlled. FIGS. 2 (a) and 2 (b) show that the two motors rotating left and right rotate rapidly to rotate right or left, respectively. FIG. 2 (C) shows an elevation of the altitude by increasing the output of all the rotors. The remaining figures in FIG. 2 can also control the six-axis motion with this simple mechanical principle.

However, the quadrotor system usually used only controls the rotation. That is, depending on the feeling of the person who controls the ability to efficiently cope with the inertia and external force in order to accurately stop the quad rotor that is in motion, or hover at a fixed position.

In other words, for the automation or more convenient control of the quadrotor, it suggests the necessity of the controller that can control the quadrotor using the displacement instead of the control through the existing angle. In addition, external disturbance input should be able to counteract external shocks and noise.

Here, the entire system for dynamic modeling of the quadrotor may be set to the following assumption.

That is, the overall system follows the general assumptions considered when designing a quad rotor.

1. Quad rotors are rigid.

2. The origin of the inertial coordinate system is at the same position as the geometric center of the quad rotor.

3. The resistance and weight of the quad rotor are not affected by flight altitude and other factors.

4. The thrust in all directions is proportional to the square of propeller rotation speed.

As shown in Fig. 3, each variable according to the coordinate system is defined as follows.

3 is the angle between the X axis and the orthogonal axis Ox in the OXY plane and the pitch angle is the distance between the Z axis and the orthogonal Oz in the OXY plane And the roll angle (ψ) is the angle between the Y axis and Oxygen on the OXY plane.

Further, as shown in the equations (1) to (4), the quadrotor coordinate system B can be expressed by the inertia coordinate system E.

4 shows the relationship between the quadrotor and the inertial coordinate system.

R (φ, θ, ψ) is the coordinate system (B) of the transformed quadrotor for the inertial coordinate system (E).

In addition, the control variables and constants can be defined as follows.

That is, [Equation (5)] represents the disturbance received by the quadrotor.

Equation (6) represents the speed of the quadrotor.

Equation (7) represents the mass of the quad rotor.

Equation (8) represents the angular velocity of the center of the quad rotor.

Further, Equation (9) represents the resistance in each rotor.

Wherein the variable D represents a drag force, the variable Cd represents a coefficient of drag, the variable v represents a velocity of the quadrotor, the variable S represents an effective drag area, .

Further, the expression (10) represents the output of each rotor.

Wherein the variable Ct represents a trust coefficient, the variable p represents an air density, the variable A represents a rotor disk region, and the variable R represents a blade radius .

In addition, as shown in [Equation 11] to [Equation 14], elements capable of controlling motion based on each motion element are defined.

The above equations (11) to (14) are solved in the form of a matrix and are summarized as the following equation (15).

In addition, the second law and the dynamics equation of Newton of the quadrotor can be expressed in a vector form as shown in the following Equation (16).

는 외부에서 가해지는 힘, 즉 외란에 의한 힘을 나타낸다. 또한, 상기 변수 m은 쿼드로터의 잘량을 나타내고, 상기 변수

는 쿼드로터의 속력을 나타낸다.Here,

Represents the force exerted from outside, that is, the force due to disturbance. Further, the variable m represents a good amount of the quad rotor,

Represents the speed of the quad rotor.

)와 관성 좌표계에 의한 각운동량(

)은 다음의 [수학식 17]과 같은 형태로 나타낸다.Also, the moment of the quad rotor (

) And angular momentum by the inertial coordinate system (

) Is expressed by the following equation (17).

In addition, the forces on the respective axes are summarized by reflecting the characteristics of the system and the system, as shown in the following equations (18) to (20).

Further, based on the forces shown in the equations (18) to (20), the second law of motion equation of the quadrotor is expressed by the following equations (21) to (23).

은 공기 저항을 나타내며, 네 개의 로터를 가지고 있기 때문에 상기 [수학식 21] 내지 [수학식 23]과 같이 나타낼 수 있다.Here,

Represents the air resistance, and has four rotors, it can be expressed by the following equations (21) to (23).

In addition, the angular velocity relationship between the angle of the inertial coordinate system and the quadrotor coordinate system is expressed by the following equation (24).

In addition, the above equation (24) can be summarized by the following equation (25) and (26).

The following equation (27) can be obtained by summarizing the remainder using the above equation (26).

If the quad rotor has a symmetrical formation, the moment of inertia of the quadrotor can be represented by the following equation (28), which is a diagonal matrix.

Further, the relational expression of the moment, the angular velocity and the angular acceleration can be expressed by the following equations (29) to (31).

The above equations (29) to (31) can be summarized in a matrix form as shown in the following equation (32).

Also, the angular acceleration of the SISO system of the inertial system can be expressed by the following equation (33).

In addition, the equation of motion according to the equations (21) to (33) is summarized as the following equations (34) to (45).

The parameters according to the above equations (34) to (45) are used as input values of the modulated quadrotor control system 100.

In addition, the acceleration measured in the hovering state is expressed by the following equation (46).

At this time, the acceleration is not the acceleration in the axial direction. That is, as shown in Fig. 5, since the acceleration is measured in the horizontal direction of the inclination of the sensor (or the inertial sensor unit / acceleration sensor, IMU), the influence of gravity must be considered.

In addition, in order to consider the acceleration in the axial direction, the acceleration due to the rotation must be considered. However, when the sensor is mounted at the center of gravity, the acceleration in the axial direction is expressed by the following equation (47). However, it is assumed that the sensor calculates a very precise angle preset through filtering for each axis.

Based on this, the displacement caused by the disturbance can be obtained by integrating the acceleration generated in each axis twice.

Therefore, by adding a controller for compensating for the displacement, it is possible to compensate the flow phenomenon due to external force when hovering.

FIG. 6 is a block diagram illustrating the configuration of a modular quadrotor control system 100 according to an embodiment of the present invention, and FIG. 7 illustrates a detailed configuration of a modular quadrotor control system 100 according to an embodiment of the present invention. Fig.

As shown in FIG. 6, the modular quadrotor control system 100 includes a position control unit 110 and an attitude control unit 120. Not all of the components of the modular quadrotor control system 100 shown in FIG. 6 are required, and the quadrature control system 100 modularized by more components than the components shown in FIG. 6 is implemented Or a quadrotor control system 100 that is modularized by fewer components may be implemented.

As shown in FIG. 7, in order to compensate displacement due to disturbance in the modular quadrotor control system 100, the attitude controller 120 determines the attitude according to the displacement based on the displacement The control system must be able to expand.

In other words, when it is pushed backward, it is necessary to input the value to the posture control unit 120 by determining the posture in which the forward acceleration can be obtained by leaning forward so as to go forward.

Therefore, the modular quadrotor control system 100 shown in FIG. 7 can be used.

In addition, designing up to the position control system in the attitude control system is not so complicated and intuitive, and it is difficult to know which part of the verification has caused the problem, thereby causing maintenance and repair problems.

However, if the position control unit 110 and the posture control unit 120 are separately designed as shown in FIGS. 6 and 7, the design is simplified and it is easy to analyze the performance and reliability of each control unit. It is also easy to improve performance.

When the correlation between the position control unit 110 and the posture control unit 120 is analyzed, the position control unit 110 corresponds to an upper concept. That is, since the position control unit 110 performs hovering at a desired position using the posture control unit 120, the position control unit 110 can be considered to use the posture control unit 120. Therefore, the modular quadrotor control system 100 is not planar, but the position control unit 110 may include the posture control unit 120.

As shown in FIG. 8, in a quadrotor tilted on the ZX plane, if the force received by the four rotors in the X axis direction is F, the magnitude of F is expressed by the following equation (48) .

Here, the angle is an angle to the X axis.

Further, the Newton's two laws represented by the equation (49) can be expressed by the equation (50) by the Laplace transform.

In addition, by substituting the above expression (50) into the expression (48), the expression can be expressed as the following expression (51).

In addition, the above equation (51) is substituted for the angle and is summarized as the following equation (52).

The equation (52) indicates that the angle is determined by the distance to be moved and the output of four rotors. That is, when the distance to be moved is long, the angle becomes large, and when the output of the rotor is large, the angle becomes small.

Further, if the above expression (52) is defined for the X axis and the Y axis, the following expression (53) is obtained.

The above equation (53) is summarized for the two axes. Here, the phi angle is not considered, which should be discussed in terms of attitude control and is not discussed from the viewpoint of the flow phenomenon.

In addition, the altitude control is an important factor because the altitude is controlled by the resultant force of the four rotors and the posture of the aircraft is determined.

Also, in the embodiment of the present invention, the altitude control is performed through the PID control.

Also, there is one problem in the above equation (53), which is meaningless as a stable control system because the angle is 90 degrees when the target distance to move is very long (there is no infinity). In other words, it means that the position control unit must remove the factor that can make the quad rotor unstable, which can be solved by limiting the derived value.

Also, by limiting the angle, the time to reach steady state can be reduced, but the system is able to completely resolve the sudden reaction. The limit value can be obtained by an accumulated experimental value rather than a numerical value.

The position control unit (or position control system) 110 receives (or receives) the first reference value and the previous displacement value (or the previous displacement value related to the X axis) based on the X axis.

Also, the position controller 110 outputs a first set of reference values for controlling the position of the quadrotor and a set of set values of the previous set through the PID control function based on the received first reference value and the previous set value.

Also, the position controller 110 receives the second reference value and the previous displacement value (or the previous displacement value related to the Y axis) based on the Y axis.

Also, the position controller 110 outputs a first Cy reference value for controlling the position of the quadrotor and a Cy value in the previous loop through the PID control function based on the received second reference value and the previous displacement value.

Also, the position controller 110 receives the third reference value and the previous displacement value (or the previous displacement value related to the Z axis) with reference to the Z axis.

Also, the position controller 110 outputs a first pi reference value for position control of the quadrotor and a pi value in the previous loop through the PID control function based on the received third reference value and the previous displacement value.

The posture control unit (or attitude control system) 120 receives the first theta reference value and the previous theta value output from the position control unit 110.

The posture controller 120 outputs a first motor control signal for controlling the posture of the quadrotor through the PID control function based on the first theta reference value and the previous theta value.

In addition, the posture control unit 120 controls the posture of the quadrotor through the PID control function based on the first Cy reference value output from the position control unit 110 and the Cy value in the previous loop, 2 Output the motor control signal.

In addition, the posture control unit 120 may control the posture of the quad rotor through the PID control function based on the first pie reference value output from the position control unit 110 and the pie value in the previous loop, 3 Output the motor control signal.

The posture controller 120 combines the first motor control signal for the X axis, the second motor control signal for the Y axis, and the third motor control signal for the Z axis to generate one motor control signal Output.

The PID coefficient used in the PID control of the position control unit 110 and the posture control unit 120 according to the present invention may be an optimized value based on physical properties such as a mass moment of inertia.

In this way, based on the quadrotor equipped with four motors, the 9-axis inertial navigation system is used to measure the attitude and motion of the vehicle, and the modularized controller can be controlled to realize a system that is both efficient in performance as well as in performance.

Hereinafter, a method of controlling a modular quadrotor control system according to the present invention will be described in detail with reference to FIGS. 1 to 10. FIG.

9 is a flowchart illustrating a method of controlling a modular quadrotor control system according to an embodiment of the present invention.

First, the position controller 110 receives (or receives) a first reference value and a previous displacement value with respect to the X axis.

Also, the position controller 110 outputs a first set of reference values for controlling the position of the quadrotor and a set of set values of the previous set through the PID control function based on the received first reference value and the previous set value.

10, the position controller 110 performs a PID control function for a first reference value 1011 including noise and a previous displacement value 1012 based on the X axis, And outputs a first theta reference value 1021 in accordance with the PID control function execution and a theta value 1022 in the previous loop.

Also, the position controller 110 performs a PID control function based on the second reference value, the third reference value, and the previous displacement values with respect to the Y axis and the Z axis, respectively, to calculate a first pie reference value, A 1-th reference value, a hypothetical value in the previous loop, and the like, respectively.

In this manner, the position controller 110 performs a function of hovering the quadrotor at a desired position (S910).

Then, the posture control unit 120 receives the first and second theta reference values output from the position control unit 110.

The posture controller 120 outputs a first motor control signal for controlling the posture of the quadrotor through the PID control function based on the first theta reference value and the previous theta value.

10, the posture control unit 120 may include a PID control function for a first theta reference value 1021 output from the position control unit 110 and a theta value 1022 in the previous loop, And outputs a first motor control signal 1031 according to the execution of the PID control function.

In addition, the posture controller 120 may calculate a first pie reference value, a pie value in the previous loop, a first scho reference value, a sie value in the previous loop, and the like, which are respectively output from the position controller 110 on the Y axis and the Z axis, And outputs a second motor control signal for the Y-axis and a third motor control signal for the Z-axis, respectively.

The posture controller 120 combines the first motor control signal for the X axis, the second motor control signal for the Y axis, and the third motor control signal for the Z axis to generate one motor control signal Output.

In this manner, the posture control unit 120 performs the posture control function of the quadrotor (S920).

As described above, the embodiment of the present invention measures a posture and a motion of a vehicle using a 9-axis inertial navigation device based on a quadrotor equipped with four motors, controls the modularized controller, By implementing an efficient system, it increases the stability of the quad rotor, which makes it easier to adjust / control the quad rotor, especially the performance of hovering.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or essential characteristics thereof. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

The present invention is based on a quadrotor equipped with four motors, measures the attitude and motion of a vehicle using a 9-axis inertial navigation system, and controls a modular controller to realize a system having a high efficiency as well as a performance, This makes it possible to adjust and control the quadrotor more easily, and in particular, to improve the performance of hovering. It can be widely used in the quadrotor field, the unmanned aerial vehicle (UAV) field, the aviation field, etc. .

Claims (2)

In a multilayered quadrotor control system in which the position control function and attitude control function are modularized,
A reference value and a previous displacement value on the basis of the X-axis, the Y-axis, and the Z-axis, respectively, and a set of theta reference values for the position control of the quadrotor through the PID control function for the received reference value and the previous displacement value, A position control unit for outputting a sine value, a pie reference value, and a pie value in the previous loop, respectively, in the previous loop; And
And outputs a first motor control signal for attitude control of the quadrotor through the PID control function for theta reference value output from the position controller and theta value in the previous loop based on the X axis, A second motor control signal for controlling the attitude of the quadrotor is output through the PID control function for the outputted Cy reference value and the Cy value in the previous loop, and the pie reference value outputted from the position control unit based on the Z axis and the And a posture control unit for outputting a third motor control signal for attitude control of the quad rotor through a PID control function for a pie value of the quadrotor. A control method of a multi-layered quadrotor control system in which a position control function and an attitude control function are modularized,
Receiving a reference value and a previous displacement value with respect to the X axis, the Y axis, and the Z axis, respectively, through the position control unit;
The position control unit controls the PID control function for the received reference value and the previous displacement value to determine the setta reference value for the position control of the quadrotor, the theta value in the previous loop, the sipe reference value, the sipe value in the previous loop, And a pie value in a previous loop, respectively; And
A first control signal for attitude control of the quadrotor is output through the attitude control unit through the PID control function for theta reference value output from the position control unit and theta value in the previous loop with respect to the X axis, A second control signal for controlling the attitude of the quadrotor is output through the PID control function for the Cy reference value output from the position control unit and the Cy value in the previous loop and the pie reference value output from the position control unit And outputting a third control signal for attitude control of the quadrotor through a PID control function for the pi value in the previous loop.

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