KR101981641B1 - Method and system for formation control of multiple mobile robots - Google Patents

Abstract

The present invention relates to a large control method of a multi-mobile robot, in which a virtual reader is set up, a minimum time velocity profile and a reference velocity profile are constructed, and a distribution kinematic equation and an error equation of a multi- And the control input is calculated.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a multi-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-sized control method and system for a multi-mobile robot.

In recent robotics, cooperative execution of work using multiple robots was the focus of robot research. Compared to the case of a single robot, the cooperative multiple robots provide a wide variety of target tasks as well as high flexibility and robustness in task execution.

Surveillance is a typical example of robotic work in which a team's multi-robots can be applied. In surveillance work, multiple robots must track and defeat the intruder. If the speed of the intruder is faster than each member of the multiple robots, the task of attacking the intruder is difficult to accomplish without controlling the cooperation of multiple robots to the target formation around the intruder. In this case, target tracking and large control are more important because the speed of the target object is not generally known. Another challenge is due to lack of wide area information, such as when each robot has to perform tracking and large control based on local information from the onboard sensors with limited or no communication link.

Much research has been conducted on target tracking and large - scale control of multiple mobile robots. In general, cooperative target tracking and large-scale mutual robots are achieved by controlling each mobile robot to a desired relative position with respect to a target and / or an adjacent mobile robot. Many researches have been made on the periodic tracking strategy for controlling the formation of multiple robots without a leader. These studies assume the acquisition of reference target position data and the exchange of control data between adjacent robots. On the other hand, a leader-follower-based control method has been developed to achieve the desired group formation by manipulating the follower robot to generate a limited inner shape for the leader.

KR 10-2010-0035531 A

Large-scale control of mobile robot for moving object tracking, The Transactions of the Korean Institute of Electrical Engineers v.60 no.4, 2011

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a large-sized control method and system for a multi-mobile robot that enables a team of mobile robots to visit a series of target positions within a minimum time while forming a desired size during navigation.

A large-scale control method of a multi-mobile robot according to an embodiment of the present invention includes a step of setting a virtual reader, a step of constructing a minimum time velocity profile of the virtual reader, a step of constructing a reference velocity profile of the virtual reader, Calculating a distribution kinematic equation of the robot and the virtual reader, calculating an error equation of the virtual reader and the multi-mobile robot, and calculating a control input based on the error equation.

According to the present invention, even if there is no distance and direction sensor and information can not be exchanged between the robots, the multiple mobile robots can achieve a desired size and can visit a series of target positions.

FIG. 1 is a diagram for explaining an example of a system to which a method for controlling a large-sized mobile robot according to an embodiment of the present invention is applied.
2 is a flowchart illustrating a method of controlling a multiple mobile robot according to an embodiment of the present invention.
3 is a schematic view for explaining a relationship between a mobile robot and a visiting position in a large control method according to an embodiment of the present invention.
4 is a schematic view for explaining a relationship between a mobile robot and a virtual reader in a large control method according to an embodiment of the present invention.
5 is a diagram illustrating a minimum time velocity profile of a mobile robot according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating a reference velocity profile for minimum time-and-size control according to an embodiment of the present invention.
7 to 10 are graphs showing experimental results using a large control method according to an embodiment of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents And variations are possible.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

FIG. 1 is a diagram for explaining an example of a system to which a method for controlling a large-sized mobile robot according to an embodiment of the present invention is applied. Although FIG. 1 shows one mobile robot for the sake of convenience, the present invention is applied to a large-sized control of a plurality of mobile robots.

Referring to FIG. 1, a system according to the present invention includes a mobile robot 100 and a robot controller 200 for controlling the mobile robot 100.

The robot controller 200 includes a target object modeling unit 201, a reference target modeling unit 203, an adder 205, a rotation matrix unit 207, an adaptation rule application unit 209, a velocity control unit 211, 213).

The target object modeling unit 201 calculates a kinematic model equation of the target object and outputs a corresponding signal. The reference target modeling unit 203 calculates a reference target model equation for tracking the target object based on the kinematic model equations of the target object, and outputs a corresponding signal. The adder 205 calculates the position error using the signal output from the reference target modeling unit 203 and the signal corresponding to the position information of the mobile robot 100 output through the integrator 213. [ The rotation matrix unit 207 rotates and converts the position error output through the integrator 213.

The speed control unit 211 outputs a control signal for controlling the travel of the mobile robot 100 based on signals output from the rotation matrix unit 207 and the adaptation rule application unit 209. [ At this time, the speed controller 211 adaptively converts the control signal according to a feedback signal including a signal transmitted from the adaptation rule application unit 209 and a signal corresponding to the position and the azimuth angle of the mobile robot 100.

According to this configuration, the control signal output from the speed control unit 211 is transmitted to the mobile robot 100, and the mobile robot 100 is allowed to cluster and traverse the target object in accordance with the received control signal have.

As a large control method according to an embodiment of the present invention, a reference model-based dynamic control scheme can be applied for cooperative target tracking of multiple mobile robots. In this embodiment, the reference model serves as a virtual reader for each mobile robot. The large control method according to the embodiment of the present invention includes two control algorithms. One is the relative distance control for the virtual target of the reference model and the other is the direction angle control. The reference model for each mobile robot is defined as a virtual target at a position substantially the same as the direction aligned with the connection line from the mobile robot to the target. In the reference model assigned to each mobile robot, the distributed control rule is designed using only the relative distance and direction angle information measured for the virtual target. According to this method, even if there is no communication link between the global position data collection and the mobile robot, large control can be achieved. Also, the target can be captured even if the mobile robot does not know the absolute position or moving speed of the target.

Hereinafter, a large control method according to an embodiment of the present invention will be described in more detail.

2 is a flowchart illustrating a method of controlling a multiple mobile robot according to an embodiment of the present invention.

First, n 2-degree-of-freedom wheeled mobile robots are expressed by the following equation (1).

[Equation 1]

는 각각 i 번째 로봇의 최대 속도 및 최대 가속도이다. 예를 들어 DC 모터로 구동되는 이동 로봇의 최대 속도는 DC 모터의 최대 RPM과 기어 비에 의존하고, 최대 가속도는 모터 토크와 로봇의 유효 관성(effective inertia)에 의존한다.here

Is the maximum speed and maximum acceleration of the i-th robot, respectively. For example, the maximum speed of a mobile robot driven by a DC motor depends on the maximum RPM and gear ratio of the DC motor, and the maximum acceleration depends on the motor torque and the effective inertia of the robot.

The kinematic model of each robot is expressed by the following equation (2).

&Quot; (2) "

에 대하여,

,

,

이다. 이때,

는 전역 참조 좌표계(global reference coordinate frame)

에서 i 번째 이동 로봇의 자세를 나타내고,

는 선속도 및 각속도이다.

는 각각 왼쪽 및 오른쪽 모터의 속도이고, (D, S)는 두 구동 바퀴의 직경과 두 모터를 연결하는 모터 축의 길이이다.here

about,

,

,

to be. At this time,

Is a global reference coordinate frame.

Represents the posture of the i-th mobile robot,

Is the linear velocity and angular velocity.

(D, S) are the diameters of the two drive wheels and the length of the motor shaft connecting the two motors, respectively.

3 is a schematic view for explaining a relationship between a mobile robot and a visiting position in a large control method according to an embodiment of the present invention.

As shown in FIG. 3, the cooperative large-scale control problem for search and tracking or monitoring tasks can be expressed by defining m visited locations as shown in the following equation (3).

&Quot; (3) "

는 전역 참조 좌표계에서 j 번째 방문 위치이다.here

Is the jth visited location in the global reference coordinate system.

The size of n robots for L is defined as: " (4) "

&Quot; (4) "

는 도 3에 도시한 것처럼 방문 위치에 대한 i 번째 로봇의 목표 상대 거리 및 방위각이다.here

Is the target relative distance and azimuth angle of the i-th robot with respect to the visited position as shown in Fig.

The goal of large-scale control is to find a minimum time-scale control strategy to control n robots in [Equation 1] to visit m locations in [Equation 3] for large conditions such as [Equation 4] . In the present embodiment, the visited position corresponds to the center position of the robot formation, but is not limited thereto and may be any position.

In the large control method according to the embodiment of the present invention, a virtual reader having a minimum time-velocity profile is set for each mobile robot at each visited location (S200). Then a distributed kinematic control framework is applied so that multiple robots track virtual readers.

The kinematic equation of the virtual leader is given by the following equation (5).

&Quot; (5) "

,

에 대하여

,

이다.here

,

about

,

to be.

4 is a schematic view for explaining a relationship between a mobile robot and a virtual reader in a large control method according to an embodiment of the present invention.

In FIG. 4, the virtual leader is designated as a visiting position and a moving coordinate system is set for each mobile robot. The x-axis is the direction of motion of the robot.

When the virtual reader is set, a minimum time velocity profile of the virtual reader is established (S210), and the multiple robots follow the leader while maintaining the large size.

과

는 대형 제어에 사용될 수 있다. 즉, 각 이동 로봇은 전역 참조 좌표계에 대하여 절대 선수각(absolute heading angle)과 함께 방위각 및 가상 리더에 대한 이동 좌표의 원점으로부터 상대적 거리를 측정 할 수 있다.As shown in Figure 4,

and

Can be used for large-scale control. That is, each mobile robot can measure a relative distance from an origin of a moving coordinate to an azimuth and a virtual leader together with an absolute heading angle with respect to a global reference coordinate system.

Then, the time optimal large control method capable of controlling the multiple mobile robots in a desired manner will be described in more detail.

First, a method for constructing a minimum time velocity profile for a virtual reader located at the center of multiple robots will be described.

The ability of a mobile robot in speed profile design is considered to be able to synchronize group movement during large control. Of course, the capabilities of each mobile robot are different. The first thing to consider for a large control synchronized around a virtual reader is the speed of the robot.

The pace of the mobile robot R _i can be expressed by a minimum time index required for moving the distance between two visited positions as shown in Equation (6).

&Quot; (6) "

는 두 개의 이웃 방문 위치 사이의 이동 거리이고,

.here

Is the travel distance between two neighboring visited locations,

.

5 is a diagram illustrating a minimum time velocity profile of a mobile robot according to an embodiment of the present invention.

Fig. 5 shows two different minimum time velocity profiles corresponding to [Equation 6], which depend on the travel distance and the maximum velocity and maximum acceleration of the i-th robot.

에 대하여 n 색인 사이의 최대 시간 지표를 결정한다.First, as shown in the following equation (7)

The maximum time index between n indexes is determined.

&Quot; (7) "

For m visited locations, there are m-1 maximum time indices such as Equation (8).

&Quot; (8) "

에 대하여 다음과 같이 구축한다(S220).The reference speed of the virtual reader with the maximum-minimum time index is

Is constructed as follows (S220).

을 충족하면 다음 [수학식 9]와 같고,The reference velocity profile

The following equation (9) is obtained,

&Quot; (9) "

을 충족하면 다음 [수학식 10]과 같고,Unlike

The following equation (10) is obtained,

&Quot; (10) "

을 충족하면 다음 [수학식 11]과 같다.other

The following equation (11) is obtained.

&Quot; (11) "

,

,

,

, 그리고

.here

,

,

,

, And

.

The angular velocity is defined by the following equation (12).

&Quot; (12) "

.here

.

Therefore, as in Equation (13), there exists m-1 minimum time-velocity profiles for m visited positions in the i-th robot.

&Quot; (13) "

FIG. 6 is a diagram illustrating a reference velocity profile for minimum time-and-size control according to an embodiment of the present invention. After the reference velocity profile is established, the mobile robots form a distributed formation and a distributed kinematic equation following the virtual reader is calculated (S230).

로 정의된다. 회전 변환을 이용하면 위치 에러는 이동 로봇 축 q에 대하여 다음 [수학식 14]로 표현될 수 있다.The location tracking error

. Using the rotation transformation, the position error can be expressed by the following equation (14) with respect to the mobile robot axis q.

&Quot; (14) "

,

는 회전 행렬이다.here

,

Is a rotation matrix.

If the robot kinematics equation of Equation (2) is combined with the reference model of Equation (5) of the virtual reader, the error equation can be calculated as Equation (15).

&Quot; (15) "

,

.here

,

.

The distance error is defined by the following equation (16).

&Quot; (16) "

,

.here

,

.

If [Expression 15] is differentiated according to the error system of the expression (14), the following expression (17) is calculated.

&Quot; (17) "

한편 도 4로부터

이므로,

그것은 [수학식 18]과 같이 된다.

On the other hand,

Because of,

(18).

&Quot; (18) "

는 원하는 대형에 대한 방향 에러이다.here

Is the direction error for the desired formation.

The new error system can then be described concisely as: < EMI ID = 19.0 >

&Quot; (19) "

,

.here

,

.

에 대하여 에러 변수

의 점근적 조절(asymptotic regulation)로 변환된다.In the new large system of (19), the control object of the large tracking

The error variable

Asymptomatic regulation of the immune system.

은 [수학식 9] 내지 [수학식 11]의 최소 시간 속도 프로파일을 충족하는 것으로 추정한다. 그러면 제어 입력은 다음 [수학식 20]과 같이 정의되어 산출된다(S250).The virtual speed input for the reference target model in deriving the distribution controller

Is estimated to satisfy the minimum time velocity profile of Equation (9) to Equation (11). Then, the control input is calculated and calculated as shown in the following equation (S250).

&Quot; (20) "

는 설계 파라미터이고,

는 싱크 함수(sync function)이고,

,

.here

Is a design parameter,

Is a sync function,

,

.

는 작은 상수

에 대하여 다음 [수학식 21]과 같이 정의된다.The projection function

Is a small constant

Is defined as < EMI ID = 21.0 >

&Quot; (21) "

는 양의 상수로 선택되며, 여기서

,

.Then,

Is chosen as a positive constant, where

,

.

에 대하여 다음 [수학식 22]가 산출된다.Applying this to (19)

The following equation (22) is calculated.

&Quot; (22) "

,

.here

,

.

에 대하여 수렴된다.According to this setting, the controller of Equation (19)

Lt; / RTI >

In order to verify the feasibility and effectiveness of the large control method according to the embodiment of the present invention, the proposed control system is applied to the cooperative large control problem. Experiments were carried out on the assumption of ideal velocity servo for each mobile robot. To reflect the physical characteristics of the robot within the maximum speed range, a nonlinear actuator model is used to generate the following velocity servo inputs:

,

는 최대 속도 제한 내에 있게 된다. {

,

}과 {

,

}는 각각 i 번째 로봇의 현재 선속도/각속도 및 명목상의 최대 선가속도/각가속도이다.here

,

Is within the maximum speed limit. {

,

} And {

,

} Are the current linear velocity / angular velocity and the nominal maximum linear velocity / angular velocity of the i-th robot, respectively.

The mobile robot used in the large control experiment was NRLAB02 (maximum linear velocity: 1.2m / s, maximum angular velocity: 0.224 rad / s, motor: BLDC (2) maximum 3000rpm) produced by Red One Technology and NRLAB04 Linear velocity: 0.9 m / s, maximum angular velocity: 0.169 rad / s, motor: BLDC (4) maximum 4000 rpm). Eight mobile robots participated in the experiment. Since all robots have no vision sensor and no absolute direction sensor, the approximate calculation of distance and direction angle for each mobile robot was performed using GPS sensor data.

7 to 10 are graphs showing experimental results using a large control method according to an embodiment of the present invention. The top of each figure is the simulation result, and the bottom photo shows the result of the actual experiment. Fig. 7 shows the transition from rhomboid to bell-shaped, Fig. 8 from longitudinal to lateral, and Fig. 9 from bell-shaped to rhombic. In each figure, a large change was made during the operation time of 40 seconds, and the cycle of large control was 10 ms. On the other hand, Fig. 10 shows that eight robots move while maintaining the formation from the initial position to the final position.

Although the GPS sensor is used instead of the distance and direction sensor for the control data collection, the controller according to the embodiment of the present invention operates well within the error tolerance of the GPS sensor data. As can be seen from these experimental results, according to the large control method according to the embodiment of the present invention, the multiple mobile robots cooperate with each other to achieve a desired size, and can visit a series of target positions.

Other embodiments of the invention include a computer readable medium having program instructions for performing various computer implemented operations. This medium records a program for executing the large control method of the multiple mobile robots described so far. The medium may include program instructions, data files, data structures, etc., alone or in combination. Examples of such media include magnetic media such as hard disks, floppy disks and magnetic tape, optical recording media such as CD and DVD, programmed instructions such as Floptical Disk and magneto-optical media, ROM, And a hardware device configured to store and execute the program. Or such medium may be a transmission medium, such as optical or metal lines, waveguides, etc., including a carrier wave that transmits a signal specifying a program command, data structure, or the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

100: mobile robot, 200: robot controller

Claims (1)

As a large control method for a multi-mobile robot,
Setting a virtual reader,
Establishing a minimum time velocity profile of the virtual reader,
Establishing a reference rate profile of the virtual reader;
Calculating a distribution kinematic equation that causes the multi-mobile robot to follow the virtual reader while forming a commanded size,
Calculating an error equation of the multi-mobile robot by combining the distribution kinematic equation, the minimum time velocity profile, and the reference velocity profile; and
Calculating a control input based on the error equation
/ RTI >
Wherein the minimum time velocity profile is calculated depending on the travel distance between the two visited locations, the maximum velocity and maximum acceleration of the virtual reader,
The reference velocity profile is calculated based on the minimum time index and maximum time index for each of the multiple mobile robots
A Large Control Method for Multiple Mobile Robots.

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