KR20170137353A - Apparatus and method for cable robot calibration - Google Patents

Abstract

The present invention suggests a cable robot calibration device and method. According to the present invention, a cable robot calibration device comprises: a laser distance measuring sensor attached to a center of an end-effector of a cable robot, measuring a distance to a target plate using a laser; a target plate to prevent the laser from reaching and passing therethrough; and a calibration algorithm portion to perform calibration of the cable robot using data measured by the laser distance measurement sensor. According to the present invention, as a laser distance measuring sensor is used for calibration of a cable robot, the present invention is able to perform calibration operation at low costs and with high accuracy, and be also be applied in case where a work space is large.

Description

[0001] APPARATUS AND METHOD FOR CABLE ROBOT CALIBRATION [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for calibrating a cable robot, and more particularly, to a technique for calibrating the shape of a parallel cable-driven robot using a laser distance measuring sensor.

The cable robot is a parallel type robot consisting of a plurality of cables unlike a conventional robot composed of a rigid skeleton. Since the cable robot is operated only by a cable, the body is light and has high speed and low power consumption. In addition, while the existing robot has a fixed radius of motion, the cable robot can be driven only when the cable is installed, so that there is no limit to the working area, so that a huge vessel work and desert operation can be performed.

In a cable robot, the position of the pulleys that make up the shape of the winch and cable must be fixed to the frame by changing the direction of the cable pulling pull cable, and this position greatly affects the overall performance of the robot. Recently, many researches have been made to change the shape of the winch or pulley and to easily attach and detach the pulley instead of using only one fixed position. The attachment and detachment of the winch or pulley allows the cable robot to be used in various fields, but in order to maintain high precision every time the shape changes, the calibration of the cable robot structure or the calibration of the position of the connection points of the cable You must proceed.

The existing calibration method can be roughly divided into the calibration using the external sensor and the calibration using the own sensor. In the case of calibration using an external sensor, an optical measuring device using an infra-red (IR) or a laser measuring device is used. In the IR-based measuring device, the work space is limited and it is difficult to apply to a large cable robot. The optical measuring device used has a disadvantage of high cost. Recently, there have been many researches on calibration using self-sensors, but in this case, it is difficult to make high-precision calibration due to the characteristics of cable robots.

Korean Patent Laid-Open No. 10-2005-0083473 (Robot position correction control device and method)

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a cable robot calibration method and apparatus, which can quickly and precisely calibrate a changed position when changing a frame shape, a pulley position, And an object of the present invention is to provide an apparatus and a method.

A cable robot calibration apparatus according to one aspect of the present invention is a cable robot calibration apparatus for correcting a shape of a cable robot, comprising: a target plate for preventing an arriving laser from passing therethrough; A laser distance measuring sensor attached to the center of the end-effector of the cable robot and measuring a distance to the target plate using a laser; And a calibration algorithm unit for performing calibration of the cable robot using data measured by the laser distance measurement sensor.

Preferably, the calibration algorithm unit may perform calibration of the cable robot using a cable robot calibration algorithm using data measured by the laser distance measurement sensor.

According to another aspect of the present invention, there is provided a method of calibrating a robot, the method comprising: changing a position of an end-effector of a cable robot due to a positional change of at least one of a winch, a pulley, and a cable; A data measuring step of measuring distance data from the laser distance measuring sensor to the target plate by a laser distance measuring sensor attached to the center of the end-effector of the cable robot; And a calibration step in which the calibration algorithm unit performs a calibration of the cable robot using a cable robot calibration algorithm using the data.

According to the present invention, since a laser distance measuring sensor is used for calibration of a cable robot, it is possible to perform a calibration operation with a low cost and high precision, and can be applied even when the work space is large. Further, by using the present invention, it is also possible to calibrate a cable robot of a variable cable structure in which the position of the cable robot or the winch is changed.

1 is a configuration diagram of a cable robot calibration apparatus according to an embodiment of the present invention.
FIG. 2A is a view showing the kinematics of a cable robot to which an apparatus for calibrating a cable robot according to an embodiment of the present invention is applied.
FIG. 2B is a diagram illustrating a basic assumption for utilizing a cable robot calibration apparatus according to an embodiment of the present invention.
FIG. 2C is a view showing a distance between the laser distance measuring sensor and the target plate according to an embodiment of the present invention. FIG.
FIG. 3 is a diagram illustrating a procedure of a cable robot calibration algorithm used by a calibration algorithm of a cable robot calibration apparatus according to an exemplary embodiment of the present invention to perform cable robot calibration.
Figure 4 is an illustration of a system that illustrates an actual implementation of a cable robot calibration device in accordance with an embodiment of the present invention.
5 is a flowchart of a cable robot calibration method according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference symbols in the drawings denote like elements.

FIG. 1 is a block diagram of a cable robot calibration apparatus 1 according to an embodiment of the present invention. Referring to FIG. As shown, the cable robot calibration apparatus 1 includes a laser distance measurement sensor 10, a target plate 20, and a calibration algorithm unit 30. [

The laser distance measuring sensor 10 is attached to an end-effector and can measure the distance from the end-effector to the target plate using a laser. To allow more accurate and precise cable robot calibration. The laser distance measuring sensor 10 is a commonly used laser sensor, which is composed of a photodetector for detecting a returned laser reflected from a target and a counter for calculating time, and a laser is emitted toward the target It is a device that measures the exact distance by detecting the back reflected laser and is a low-cost and high-accuracy measuring device.

The target plate 20 may serve as a wall for preventing the laser from passing through to the laser reaching the laser distance measuring sensor 10. The target plate 20 is generally made of wood, cement, reinforcing steel or concrete, and may be made of various materials and shapes.

The calibration algorithm unit 30 can perform cable robot calibration using the data measured by the laser distance measurement sensor 10. [ The calibration algorithm unit 30 may be manufactured as a robot controller and used in combination with a PC, a smart phone, or the like. A procedure and a method by which the calibration algorithm unit 30 performs the robot calibration will be described in detail with reference to FIGS. 2A to 2C. FIGS. 2A to 2C are diagrams showing the kinematics of a cable robot to be applied to the cable robot calibration apparatus 1 according to an embodiment of the present invention, a basic assumption, a distance between the laser distance measurement sensor and the target plate, .

The calibration algorithm unit 30 can perform the calibration of the cable robot using the cable robot calibration algorithm using the data measured by the laser distance measurement sensor 10 on the basis of the following description.

Although the method described below is applicable to all cable robots, it is described as an example applied to a planar cable robot for convenience of explanation.

FIG. 2A shows the kinematics of a 6-degree-of-freedom space-type cable robot to which a cable-cable calibration apparatus according to an embodiment of the present invention is applied.

는 풀리의 위치(q3),

는 케이블과 연결된 엔드-이펙터 상의 포인트(q4),

는 전체 기준 좌표계 {0}에서 본

의 위치벡터(q5),

는 좌표계 {P}에서 본

의 위치벡터(q6),

는 전체 기준 좌표계 {0}에서 본 엔드-이펙터의 위치 벡터(q7),

는 회전 행렬(q8)을 나타낸다. Referring to FIG. 2A, {P} is an end-effector coordinate system q1, {0} is an overall reference coordinate system q2,

(Q3) of the pulley,

(Q4) on the end-effector connected to the cable,

Is viewed from the entire reference coordinate system {0}

The position vector q5,

Is viewed from the coordinate system {P}

The position vector q6,

(Q7) of the end-effector viewed from the entire reference coordinate system {0},

Represents a rotation matrix q8.

는 i번째 케이블 길이를 나타내는데, 캘리브레이션을 위해서는 이론상의 케이블 길이와 측정된 케이블 길이를 구분하기 위하여, 이론상의 예측된 케이블 길이는

라 정의하고, 측정된 케이블 길이는

으로 정의한다, 여기서 문자 i와 j는 i번째 케이블 길이를 j번째 희망 위치에서 측정하였음을 의미한다. 만약 엔드이펙터의 포즈

(위치

, 회전량

를 포함하는 정보임)이 결정되면 i번째 케이블을 j번째 측정 위치에서 이론상의 예상된 케이블 길이

는 식(1)을 사용하여 예측할 수 있다.

에서 M는 케이블의 개수를 표시하고

에서 N은 측정 하는 pose 개수를 표시한다.

Represents the i-th cable length. To distinguish the theoretical cable length from the measured cable length for calibration, the theoretical predicted cable length is

And the measured cable length is

, Where the letters i and j mean that the i-th cable length is measured at the j-th desired position. If the end effector pose

(location

, The amount of rotation

Is determined, the i < th > cable is routed to the theoretical expected cable length < RTI ID = 0.0 >

Can be estimated using equation (1).

Where M represents the number of cables

Where N is the number of pose to be measured.

=

식(1)

=

Equation (1)

(q5)의 오차를 최소화하여 케이블 로봇 기구학 식(1)의 정밀성을 개선하는 것을 통해 케이블 로봇의 제어성능을 향상시키는 것이다.The purpose of the cable robot calibration according to one aspect of the present invention is to use the laser length measuring sensor 10 to measure the cable contact

(q5) to improve the control performance of the cable robot by improving the precision of the cable robot kinematic equation (1).

First, some assumptions (a) to (d) are needed to use the cable robot calibration algorithm.

은 {0}에 놓여 있고, (b)

는

과 같은 y축에 놓여 있으며, (c)레이저 거리 측정 센서는 엔드-이펙터의 중앙에 장착되고. (d) 엔드-이펙터의 크기

(q6)를 알고 있다.Referring to FIG. 2B, (a)

Is placed at {0}, (b)

The

(C) The laser range finder is mounted at the center of the end-effector. (d) Size of end-effector

(q6).

이면 레이저 빔의 직선 방정식은 식(2)와 같다. 2C, the position of the laser distance measurement sensor 10 attached to the center of the end-

The linear equation of the laser beam is given by Equation (2).

식(2)

Equation (2)

The equation of the laser target plate is shown in Equation (3).

식(3)

Equation (3)

는 식 (4)와 같다.Therefore, the intersection between the laser beam from the laser distance measurement sensor 10 and the target plate 20

(4).

식(4)

Equation (4)

The formula for obtaining the distance from the end-effector to the target plate 20 measured by the racer distance measuring sensor 10 in order from Eqs. (1) to (4) is equation (5).

식(5)

Equation (5)

와 풀리에서 나오는 케이블 접점 예상치

(실제값

과 error가 존재함)를 알고 또한 가정 (d)에 의하여

(q6)를 알고 있으므로 forward kinematics를 numerical 방법으로 풀어서 현재 pose

(위치

, 회전량

)를 구하고 식(6)에 대입하여

를 구할 수 있다. That is, the current cable length measured through the cable robot calibration algorithm used by the calibration algorithm unit 30

And cable contacts expected from the pulley

(Actual value

And error exists) and also by assumption (d)

(q6), we solve the forward kinematics using the numerical method,

(location

, The amount of rotation

) And substituting it into the equation (6)

Can be obtained.

가 실제값

와 동일한 경우, 매우 정확한 결과를 도출해 내지만, 두 값이 동일하지 않은 경우, 두 값에 차이가 나게 되고, 이 차이를

로 정의할 수 있다. 추가로, 엔드-이펙터의 Pose

는 평면형 케이블 로봇의 경우

,

와 같이 계산 할 수 있다.Forward kinematics can be solved using the Numerical Iterative Method, which can be obtained by a general numerical iterative method including the Newton-Raphson iterative method. Forward kinematics using numerical iterative methods

Is the actual value

, But if the two values are not the same, the two values will differ, and the difference

. In addition, the end-effector Pose

In the case of a planar cable robot

,

Can be calculated as follows.

(희망 엔드-이펙터 이동 위치)를 식(5)에 대입하여 이론적인 레이저 거리 측정 센서(10)로부터 표적판(20)까지의 거리(

)를 구한 다음 두 값의 차인

를 식(7)과 같이 구할 수 있다.Also,

(The desired end-effector moving position) is substituted into the equation (5), and the distance from the theoretical laser distance measuring sensor 10 to the target plate 20

), And then the difference between the two values

Can be obtained as shown in equation (7).

식(6)

Equation (6)

식(7)

Equation (7)

Then, we combine the two error functions into ErrorFn to form Eq. (8).

식(8)

Equation (8)

의 x좌표,

의 x좌표 및 y좌표,

의 x좌표 및 y좌표 총 5개로서 독립 변수의 수를 K라고 한다면

가 된다. In the equation (8), V represents the independent variable to perform the calibration. In the planar cable robot according to the assumptions (1) and (2)

The x coordinate,

The x coordinate and y coordinate,

The total number of x and y coordinates is 5, and the number of independent variables is K

.

그리고 B는 엔드이펙터(end-effector)의

를 나타내고 Cable은 케이블의 측정값, Laser는 Laser의 측정값,

는

관련 값들을 의미한다. Expression

And B is an end-effector

Cable is the measured value of the cable, Laser is the measured value of the laser,

The

And related values.

)의 절대값이 기 설정한

이하가 되는(

)

(q5)의 최종 값을 구할 수 있다.Using this, Jacobian matrix can be constructed as Eq. (9)

) Is greater than the absolute value of

Or less

)

(q5) can be obtained.

은 가변적인 값이며 미리 설정할 수 있으며, 0에 가까운 값으로 설정하는 것이 바람직하다.

Is a variable value and can be set in advance, and is preferably set to a value close to zero.

식(9)

Equation (9)

Therefore, it is possible to calibrate cable robots at a low cost and with high precision by using the laser distance measuring sensor 10 through the above-described cable robot calibration algorithm.

FIG. 3 shows a procedure of a cable robot calibration algorithm used by the calibration algorithm unit 30 of the cable robot calibration apparatus 1 according to the embodiment of the present invention to perform calibration of a cable robot. The cable robots calibration algorithm will be described again in detail.

)를 생성(s2)한다, First, the expected shape information of the cable robot is set (s1), and the desired EE (end-effector) movement position information

(S2) is generated,

)을 계산(s3)한다. 도 5의 데이터 측정 단계(s502)에서 측정된 현재 케이블 길이값 (

)을 읽어들인(s4) 후 두 값의 차인 케이블 길이 에러를 구한다(s5). 이 때, 현재 케이블 길이값을 측정하기 위해서는 도 5와 같이 케이블 로봇 위치 변경 단계(s501)가 필요하며, 로봇 변경을 위해서는 희망 EE이동 위치설정 단계(s2)에서 정의한 희망 위치(

)와 동일한 위치를 사용한다. 정기구학을 통한 예상 엔드-이펙터 위치

를 정한 뒤(s6) 레이저 거리 측정 센서(10)로부터 표적판(20)까지의 이론적인 거리값(

) 계산(s7) 및 실제 측정된 레이저 거리 측정 센서(10)로부터 표적판(20)까지의 거리값(

) 계산(s8) 후 두 값의 차인 레이저 거리 에러를 구한다(s9). Inverse Kinematics is performed from the desired position information to obtain the theoretical cable length value (

Is calculated (s3). The current cable length value measured in the data measurement step (s502) of FIG. 5

(S4), the cable length error which is a difference between the two values is obtained (s5). In this case, in order to measure the current cable length value, a cable robot position changing step (s501) is required as shown in FIG. 5, and in order to change the robot, a desired position

) Is used. Estimated end-to-end position of the effector

(S6) and the theoretical distance value from the laser distance measurement sensor 10 to the target plate 20

) Calculation s7 and a distance value from the actually measured laser distance measurement sensor 10 to the target plate 20

) After calculation (s8), the laser distance error which is the difference between the two values is obtained (s9).

값을 구한다(ErrorFn)(s10). Then, based on the above-mentioned two errors, using the above-mentioned equations (1) to (9)

(ErrorFn) (s10).

의 절대값이 기 설정한

값 이하로 만드는

의 값을 찾았다면 적용한 뒤(s11) 알고리즘을 종료하게 되고,

의 절대값이 기 설정한

값 보다 크다면 다시 jacobian matrix 계산(s12)을 통해 형상정보 갱신 후(s13) 이전 절차를 계속한다.if

The absolute value of

Less than

(S11), the algorithm is terminated,

The absolute value of

If it is larger than the value, the procedure before the step (s13) after the update of the shape information is continued through the jacobian matrix calculation (s12).

FIG. 4 is an exemplary view of an actual implementation of a cable robot calibration apparatus 1 according to an embodiment of the present invention, and will be described with reference to FIG.

4, a plurality of cables 401, a plurality of winch 402, a pulley 403, and an end-effector 404, which serve to fix the cable 401, Is installed. A laser distance measuring sensor 41 attached to the center of the end-effector 404; a target plate 42 for preventing the laser output from the laser distance measuring sensor 41 from reaching and passing therethrough; And a shape correcting computer 44 for performing calibration of the cable robots to which the cable robot controller 43 and the laser distance measuring sensor 10 and the cable robot controller 43 are connected.

When the position of the cable robot is changed, the shape correcting computer 44 may perform a cable robot calibration algorithm using the data value measured by the laser distance measuring sensor 41 to perform calibration for the cable robot.

FIG. 5 is a flowchart illustrating a method of calibrating a cable robot according to an embodiment of the present invention. Referring to FIG.

The cable robot calibration method according to the present embodiment includes a cable robot position changing step s501, a data measuring step s502, and a calibration step s503.

The cable robot position changing step s501 is a step of changing the position of the winch, cable and pulley of the cable robot which may include a winch, a cable, a pulley, an end-effector and a laser distance measuring sensor 10 attached to the center of the end- And the end-effector position of the cable robot is changed due to at least one or more positional deformation. The winch, the cable and the pulleys may be plural.

The data measurement step s502 refers to a step in which the laser distance measurement sensor 10 attached to the center of the end-effector measures distance data from the laser distance measurement sensor to the target plate 20. [

의 절대값이 기 설정된

이하가 되도록 하는 케이블 로봇 캘리브레이션 알고리즘을 수행하는 단계를 말하며 도3에 기술한 과정 전체를 의미한다.The calibration step (s503) is a step in which the calibration algorithm unit 30 uses the data to calculate the above-

The absolute value of

Or less, and means the entire procedure described in FIG. 3.

The present invention has been described in detail with reference to preferred embodiments. It will be apparent to those skilled in the art that the present invention is not limited to the embodiments described above and that various modifications and changes may be made by one of ordinary skill in the art without departing from the scope of the present invention, It is to be understood that the technical idea of the present invention extends to the extent possible.

Claims (4)

A cable robot calibration apparatus for correcting a shape of a cable robot,
A target plate that prevents the laser from reaching the laser;
A laser distance measuring sensor attached to the center of the end-effector of the cable robot and measuring a distance to the target plate using a laser;
And a calibration algorithm unit for performing calibration of the cable robot using data measured by the laser distance measurement sensor.
The method according to claim 1,
The calibration algorithm compares the difference between the measured cable length value and the theoretical cable length value and the actual measured distance value from the laser distance measurement sensor to the target plate and the theoretical distance value from the laser distance measurement sensor to the target plate Wherein a cable robot calibration algorithm is implemented that minimizes the error through the cable.
Changing the position of the cable robot end-effector due to the deformation of at least one of the winch, the pulley, and the cable;
A data measuring step of measuring distance data from the laser distance measuring sensor to the target plate by a laser distance measuring sensor attached to the center of the end-effector of the cable robot; And
And performing a calibration of the cable robot using a cable robot calibration algorithm using the data.
The method of claim 3,
The calibration step may include comparing the measured cable length value to the theoretical cable length value and comparing the actual measured distance value from the laser distance measurement sensor to the target plate and the theoretical distance value from the laser distance measurement sensor to the target plate And performing a cable robot calibration algorithm that minimizes errors.

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