WO2010027127A1

WO2010027127A1 - Underwater vehicles controlled by using gyro momentum approach

Info

Publication number: WO2010027127A1
Application number: PCT/KR2008/007634
Authority: WO
Inventors: Soon Hee Han; Jin Seong Lee
Original assignee: Industry Foundation of Chonnam National University
Current assignee: Industry Foundation of Chonnam National University
Priority date: 2008-09-04
Filing date: 2008-12-24
Publication date: 2010-03-11
Anticipated expiration: 2011-03-04
Also published as: KR20100028376A

Abstract

The present invention relates generally to an underwater robot, and, more particularly, to an underwater robot using gyro momentum, the attitude of which can be controlled using the momentum of a pyramid gyro, including four gyros, without using a separate external propelling device.

Description

UNDERWATER VEHICLES CONTROLLED BY USING GYRO

MOMENTUM APPROACH

Technical Field

[1] The present invention relates generally to an underwater robot, and, more particularly, to an underwater robot using gyro momentum, the attitude of which can be controlled using the momentum of a pyramid gyro, including four gyros, without using a separate external propelling device. Background Art

[2] Attitude control of an underwater robot which performs underwater exploration has been conducted using a plurality of external propelling devices attached to the outside of the body of the underwater robot.

[3] That is, in a conventional underwater robot, all variations in position in a vertical direction, a left-right lateral direction and a front-back lateral direction, including the directions of roll, pitch and yaw, have been implemented by the external propelling devices.

[4] Therefore, in the case of the conventional underwater robot, since propulsive forces obtained by the external propelling devices have non-linearity, and the modeling of a plurality of external propelling devices is complicated when the external propelling devices are mounted, it is very difficult to control the attitude of an underwater robot.

[5] Further, such external propelling devices become factors destroying the natural environment by such actions as destroying an ecosystem and causing underwater organisms to wither and die.

[6] In particular, in the case of pen-up nurseries or fishing grounds, it is difficult to raise fish due to the vibration or noise of external propelling devices.

[7] Therefore, in underwater robots which observe the environment of nurseries or fishing grounds, being required is research into underwater robots capable of reducing vibration or noise in attitude control, and capable of switching the attitude and rapidly avoiding obstacles in narrow spaces in consideration of both the environment of fishing grounds, having a plurality of obstacles such as seaweed or fish, and submarine topography.

Disclosure of Invention

Technical Problem

[8] The present inventors devised the present invention because they developed a technical construction capable of obtaining an underwater robot, the attitude of which can be accurately controlled without using an external propelling device, as a result of efforts put into research into the development of an underwater robot capable of eliminating vibration or noise in attitude control and rapidly avoiding obstacles such as seaweed or fish.

[9] Accordingly, an object of the present invention is to provide an underwater robot, the attitude of which can be controlled without using an external propelling device.

[10] Another object of the present invention is to provide an underwater robot, the attitude of which can be stably controlled in spite of external resistance such as the flow of water.

[11] The objects of the present invention are not limited to the above-described objects, and other objects, not described here, will be more clearly understood by those skilled in the art from the following description. Technical Solution

[12] In order to accomplish the above objects, the present invention provides an underwater robot, comprising an underwater robot body, a pyramid gyro provided in a predetermined portion of the underwater robot body, and a gyro controller configured to control attitude of the underwater robot body by operating the pyramid gyro, wherein the pyramid gyro comprises four gyros, each of the four gyros comprising a gimbal rotating around its own gimbal axis and a wheel rotating around a wheel axis perpendicular to the gimbal axis within the gimbal, wherein the gyros are respectively provided at centers of sides of a bottom surface of an imaginary quadrangular pyramid so that the gimbal axes are perpendicular to side surfaces of the imaginary quadrangular pyramid, and wherein the gyro controller rotates the underwater robot body in a roll, pitch or yaw direction by rotating the gimbals and the wheels.

[13] In a preferred embodiment, the gyro controller comprises a control torque input vector generation unit for receiving a commanded rotation angle from the underwater robot body, calculating Euler angles ( θ i

σ2 and θ₃

), deriving a quaternion from the Euler angles, and then generating a control torque input vector ( ), a gimbal angle derivation unit for deriving gimbal angles (

S₃ and δ₄ ) of the respective gimbals using the following Equation (1), in which a function ( h=h(β}

) representing a relationship between angular momentums ( h

) of the wheels and gimbal angles (

T δ = ( δ j, δ₂, δ₃, δ₄)

), that is, rotation angles of the gimbals, is differentiated, in order to derive an angular momentum (

) of each of the gyros corresponding to the control torque input vector (

), and a gimbal driving unit for rotating the respective gimbals using the gimbal angles,

^¹⁵J : -cβcos δ j sin δ ₂ cβcos δ₃ - sin δ ₄ ;

^ = Ii -SIn O₁ -cpcos δ ₂ sin. δ ₃ cβcos δ₄| J 5|3cos δ _J 5βcos δ₂ 5βcos 6₃ -S¹PcOS e₄P;

(1)

[16] In a preferred embodiment, the gyro controller further comprises a feedback unit for detecting actual rotation angles of the gimbals driven by the gimbal driving unit and adding the actual rotation angles to the commanded rotation angle.

Advantageous Effects

[17] The present invention has the following excellent advantages. [18] First, according to the underwater robot of the present invention, an underwater robot, the attitude of which can be controlled using the gyro momentum of a pyramid gyro without using an external propelling device, can be provided.

[19] Further, according to the underwater robot of the present invention, an underwater robot, the attitude of which can be stably controlled in spite of external disturbances, such as the flow of water, can be provided.

[20]

Brief Description of Drawings

[21] Fig. 1 is a view showing an underwater robot according to an embodiment of the present invention;

[22] Fig. 2 is a view showing the pyramid gyro of the underwater robot according to an embodiment of the present invention;

[23] Fig. 3 is a control block diagram of the underwater robot according to an embodiment of the present invention; and

[24] Figs. 4 to 10 are views showing the results of a simulation of the attitude control of the underwater robot according to embodiments of the present invention.

[25] <Description of reference characters of important parts>

[26] 100: underwater robot 110: underwater robot body

[27] 120: pyramid gyro 121, 122, 123, 124: gyro

[28] 121a, 122a, 123a, 124a: gimbal 121b, 122b, 123b, 124b: wheel

[29] 130: gyro controller 131: control torque input vector generation unit

[30] 132: gimbal angle derivation unit 133: gimbal driving unit

[31] 134: feedback unit

Best Mode for Carrying out the Invention

[32] As terms used in the present invention, general terms that are currently and widely used were selected if possible, but, in special cases, the present applicant arbitrarily selected some terms. In this case, the meaning of these terms should be interpreted in consideration of the meaning of the terms described or used in the detailed description of the invention rather than per the common interpretation of the terms.

[33] Hereinafter, the technical construction of the present invention will be described in detail with reference to preferred embodiments shown in the drawings (attached drawings and preferred embodiments).

[34] However, the present invention is not limited to the embodiments described here, and may be implemented in other forms. The same reference numerals used throughout the present specification designate the same components.

[35] Fig. 1 is a view showing an underwater robot according to an embodiment of the present invention, and Fig. 2 is a view showing the pyramid gyro of the underwater robot according to an embodiment of the present invention.

[36] Referring to the drawings, an underwater robot 100 according to an embodiment of the present invention includes an underwater robot body 110, a pyramid gyro 120 and a gyro controller 130.

[37] The underwater robot body 110 is a main body defining the external appearance of the underwater robot 100, and may be the main body of any one of various types of underwater robots, such as well-known submarines, midget submarines, unmanned submarines, and Autonomous Underwater Vehicles (AUVs), capable of exploring underwater areas.

[38] The pyramid gyro 120 is a driving device provided in a predetermined portion of the underwater robot body 110 and configured to control the attitude of the underwater robot 100, and, in more detail, the attitude of the underwater robot body 110.

[39] Further, the pyramid gyro 120 includes four gyros 121, 122, 123 and 124 provided at regular locations, and each of the gyros 121, 122, 123 and 124 includes a gimbal 121a, 122a, 123a or 124a rotating around its own gimbal axis g, and a wheel 121b, 122b, 122c or 122d rotating around a wheel axis h perpendicular to the gimbal axis g of the corresponding gimbal 121a, 122a, 123a or 124a within the gimbal 121a, 122a, 123a or 124a.

[40] Further, the gyros 121, 122, 123 and 124 are respectively provided to face one another on the sides of the bottom surface 'b' of an imaginary quadrangular pyramid 'a', and are installed, more preferably, at the centers of the sides of the bottom surface 'b'.

[41] Furthermore, the gimbal axes g of the respective gimbals 121a, 122a, 123a, and 124a are provided to be perpendicular to the side surfaces of the imaginary quadrangular pyramid 'a'.

[42] That is, torques t generated in a direction perpendicular to the wheel axes h of the respective wheels 121b, 122b, 122c and 122d are provided to be parallel with the side surfaces of the quadrangular pyramid 'a'.

[43] In other words, the gyros 121, 122, 123 and 124 are arranged such that the vectors of the torques t are formed on the side surfaces of the quadrangular pyramid 'a'.

[44] The gyro controller 130 controls the gyros 121, 122, 123 and 124 so that the underwater robot body 110 rotates in the directions of roll, pitch and yaw.

[45] In more detail, the gyro controller 130 generates gyro momentum which is the sum of the vectors of the torques t generated by the respective gyros 121, 122, 123 and 124 by rotating the gimbals 121a, 122a, 123a and 124a and the wheels 122a, 122b, 122c and 122d of the gyros 121, 122, 123 and 124, thus enabling the underwater robot body 110 to be rotated.

[46] Further, the gyro controller 130 includes a control torque input vector generation unit

131, a gimbal angle derivation unit 132, a gimbal driving unit 133, and a feedback unit 134.

[47] A detailed description will be made with reference to Fig. 3.

[48] Fig. 3 is a control block diagram of the underwater robot according to an embodiment of the present invention.

[49] Referring to Fig. 3, when a commanded rotation angle

=+= δ which is a desired rotation angle of the underwater robot 100 is input to the control torque input vector generation unit 131, the control torque input vector generation unit 131 applies Euler angle rotation to the commanded rotation angle

=+= δ

, thus deriving Euler angles θ l

θ 2 and θ

[50] Further, the final matrix of the Euler angles θ l

θ 2 and θ and is given by the following Equation (2),

(2)

[52] where denotes the components of reference coordinates of the commanded rotation angle δ

, and

denotes the components of the relative coordinates thereof. Further,

C_n denotes the Direction Cosine Matrix (DCM) which defines the rotation of the relative coordinates, and is represented by the following Equation (3).

(3)

[54] Further, the control torque input vector generation unit 131 derives the components and round angle φ of a quaternion using the Euler angles θ l

θ₂ and θ₃

, as given by the following Equation (4).

^[55] q _γ = e _{l S}in(φ/2) q ₂ - = e ₂ sin(φ/2)

<7 ₃ ^{= e} ₃ sin(φ/2) ^ ₄= cos (φ/2)

[56]

(4)

[57] Further, the components of the quaternion have the relationships, given by the following Equation (5), with an angular velocity vector ω( ω _{1 ?} ω ₂, ω ₃)

[58] j j

1 r

(5)

[59] When the underwater robot 100 is assumed to be a rigid body, the following

Equation (6) is established by kinetic equations. The control torque input vector

can be derived and the angular acceleration vector

of the moving body of the underwater robot 100 can be obtained by Equation (6),

(6) [61] where

is a matrix indicating the moment of inertia of the rigid body, ω( ω _{1 ?} ω _{2 ?} ω ₃) is the angular velocity vector of the moving body of the underwater robot 100, and u( U ₁ , U ₂ , U ₃ ) is the control torque input vector. [62] The gimbal angle derivation unit 132 derives gimbal angles ^ ₂

⁶ ₃ and

, that is, are angles at which the respective gimbals 121a, 122a, 123a and 124a rotate around their own gimbal axes g according to the control torque input vector

[63] In other words, the gimbal angle derivation unit 132 calculates the momentums

of the respective wheels 121b, 122b, 123b and 124b provided in the gyros 121, 122, 123 and 124 and the gimbal angles

S i

υ 3 and

S ₄ of the respective gimbals 121a, 122a, 123a and 124a so that each of the gyros 121, 122, 123 and 124 can generate angular momentum

H corresponding to the control torque input vector u

[64] Further, a process in which the gimbal angle derivation unit 132 derives the gimbal angles & 2

S ₃ and

is described in brief. First, the relationship between the angular momentum

of each of the wheels 121b, 122b, 123b and 124b and the angular momentum

of each of the gyros 121, 122, 123 and 124 on the entire system is represented by the following Equation (7).

^[65] H =Jω+h

(7)

[66] Further, when Equation (7) is represented by a relational expression for the control torque input vector

, the following Equation (8) is obtained.

(8) [70] A function representing the relationship between the gimbal angles

S ₂

& 3 and and the angular momentums h of the wheels 121b, 122b, 123b and 124b can be represented by the following Equation (9). [71]

W=A(ββ>

(9)

[73] Further, when Equation (9) is represented with respect to the pyramid gyro 120, the matrix

JL can be given by the following Equation (10).

^⁷⁴^ : -cβcos S₁ sin δ₂ cβcos δ₃ -sin δ₄ ;

_^4 = § -sin δ_x -cβcos δ₂ sin δ₃ cβcos δ₄i

J Λ-βCOS δ_! Λ-βCOS δ₂ ΛrβCOS δ₃ ^βCOS δ₄|^

(10)

[75] Since Equation (10) is not a square matrix, the gimbal angles are derived using the following Equation (11) by applying a pseudo inverse matrix to Equation (10).

(H) [77] That is, when the matrix

A. is known, the gimbal angle

S corresponding to the control torque input vector

can be derived. Therefore, through the use of the derived gimbal angle δ

, the attitude of the underwater robot corresponding to the control torque input vector

can be controlled. [78] Further, when the number of dimensions of the matrix

Jl is less than 3, an inverse matrix is not present. Therefore, in order to avoid this particularity, the control torque input vector

and each gimbal angle δ are defined using null vectors and their weight coefficients y

, as shown in the following Equation (12), [79] sat u = - [Ksat(P q _E)+Cø] σ

A ^#= A^T(AA^T+U)^'1

[80]

^'=A *(-U-®Sh)+y[I-A *A](b*-b)

l= ^s ss^maatt σ iW)

(12)

[81] where

is the coefficient of

C is the scalar coefficient of an angular velocity vector, and

A, and

^■y are weight scales.

[82] Further, as shown in Equation (12), stable attitude control is possible by taking into consideration non-linear saturation characteristics (sat) indicating that, when values deviate from the range of limits of hardware characteristics, they do not increase or decrease any longer.

[83] The gimbal driving unit 120 controls the attitude of the underwater robot body 110 by rotating the respective gimbals 121a, 122a, 123a and 124a of the pyramid gyro 120 at the gimbal angles

S derived by the gimbal angle derivation unit 132.

[84] The feedback unit 134 receives the current attitude of the underwater robot body 100 from an attitude measurement sensor (not shown), which is provided in the underwater robot body 100 and configured to measure the current attitude of the underwater robot body 100, and then feeds the current attitude back to the commanded rotation angle * δ

, thus correcting the gimbal angles

8 of the respective gimbals 121a, 122a, 123a and 124a.

[85] Figs. 4 to 10 are views showing the results of an attitude control simulation of the underwater robot according to embodiments of the present invention.

[86] Figs. 4 and 5 are views showing responses to the rotation attitude angles (roll, pitch and yaw) of the underwater robot 100 and the gimbal angles CMGl, CMG2, CMG3 and CMG4 of the gyros 121, 122, 123 and 124 when the commanded rotation angle is small (5, 4, and -5 degrees), and Figs. 6 and 7 are views showing responses to the rotation attitude angles (roll, pitch and yaw) of the underwater robot 100 and the gimbal angles CMGl, CMG2, CMG3 and CMG4 of the gyros 121, 122, 123 and 124 when the commanded rotation angle is large (10, 20, and 30 degrees).

[87] As shown in Figs. 4 to 7, it can be seen that, in the case where the commanded rotation angle is large (10, 20, and 30 degrees), the time required for convergence was longer than that of the case where the commanded rotation angle is small (5, 4, and -5 degrees), but, convergence was stably realized in both the case where the commanded rotation angle is large and the case where the commanded rotation angle is small.

[88] Fig. 8 is a view showing the rotation attitude angles of the underwater robot 100 when the external disturbance is applied to the underwater robot 100 in the state in which the gyro controller 130 of the underwater robot 100 is not operated according to an embodiment of the present invention. Figs. 9 and 10 are views showing the rotation attitude angles and gimbal angles of the underwater robot 100 when external disturbance is applied to the underwater robot 100 in the state in which the commanded rotation angle is set to 10, 20 and 30 degrees. [89] As shown in Figs. 8 to 10, when the gyro controller 130 according to the embodiment of the present invention is not operated, the rotation attitude angles of the underwater robot 100 attributable to the external disturbance are not stabilized even with the passage of time. In contrast, when the gyro controller 130 is operated, the rotation attitude angles of the underwater robot 100 are gradually stabilized after a predetermined time has passed even if some vibrations or overshoots are present.

[90] As described above, although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that the present invention is not limited to the above embodiments, and various modifications and changes are possible, without departing from the scope and spirit of the invention. Industrial Applicability

[91] The present invention can be variously used in the fields of attitude control of underwater robots for the observation of nurseries or inshore fishing grounds, or the exploration of submarine areas.

Claims

[ 1 ] An underwater robot, comprising: an underwater robot body; a pyramid gyro provided in a predetermined portion of the underwater robot body; and a gyro controller configured to control attitude of the underwater robot body by operating the pyramid gyro; wherein the pyramid gyro comprises four gyros, each of the four gyros comprising a gimbal rotating around its own gimbal axis and a wheel rotating around a wheel axis perpendicular to the gimbal axis within the gimbal; wherein the gyros are respectively provided at centers of sides of a bottom surface of an imaginary quadrangular pyramid so that the gimbal axes are perpendicular to side surfaces of the imaginary quadrangular pyramid; and wherein the gyro controller rotates the underwater robot body in a roll, pitch or yaw direction by rotating the gimbals and the wheels.

[2] The underwater robot according to claim 1, wherein the gyro controller comprises: a control torque input vector generation unit for receiving a commanded rotation angle from the underwater robot body, calculating Euler angles (

Θ.

θ₂ and

), deriving a quaternion from the Euler angles, and then generating a control torque input vector (

); a gimbal angle derivation unit for deriving gimbal angles ( and

) of the respective gimbals using the following Equation (13), in which a function (

/z=/z(δ)

) representing a relationship between angular momentums (

) of the wheels and gimbal angles ( δ = ( S₁, δ₂, δ₃, δ₄)

) of each of the gyros corresponding to the control torque input vector (

);and a gimbal driving unit for rotating the respective gimbals using the gimbal angles,

_A= θh r ^{& h}ι i

3δ [ øδ, ]

: -cpcos δ _χ ssiinn 55₂₂ σσppccooss δδ ₃ - sin 5₄ ;

>l=l - sin 5 -cpcos 6₂ sin ό ₃ cβcos β j

J ^COS δ ₁ ^pcos δ ₂ -s-βcos δ ₃ 4cos δ ₄μ;

(13)

[3] The underwater robot according to claim 2, wherein the gyro controller further comprises a feedback unit for detecting actual rotation angles of the gimbals driven by the gimbal driving unit and adding the actual rotation angles to the commanded rotation angle.