阅读说明：本技术 一种载油储罐底板检测机器人的定位方法 (Positioning method of oil-carrying storage tank bottom plate detection robot ) 是由 胡斌 沈功田 戴晓峰 沈永娜 于 2021-11-08 设计创作，主要内容包括：本发明公开了一种载油储罐底板检测机器人的定位方法,首先通过安装在检测机器人中心的惯性传感器获取所述检测机器人的行进方向,再利用安装在检测机器人前端和后端的超声传感器进行声速估计和回波测距,通过将距离之和与检测机器人的行进方向进行结合,从而计算获得检测机器人的位置。本发明所述定位方法利用了储罐底板的几何形状,不需要在储罐外部额外布置的传感器,仅通过惯性传感器和超声传感器,即可确定载油储罐底板内的检测机器人的位置,具有定位简便、快捷、准确的优点。(The invention discloses a positioning method of a detection robot for a bottom plate of an oil-carrying storage tank. The positioning method of the invention utilizes the geometric shape of the bottom plate of the storage tank, does not need a sensor arranged outside the storage tank additionally, can determine the position of the detection robot in the bottom plate of the oil-carrying storage tank only by the inertial sensor and the ultrasonic sensor, and has the advantages of simple, convenient, rapid and accurate positioning.)

1. A positioning method of a detection robot for a bottom plate of an oil-carrying storage tank is characterized in that position information is obtained through an ultrasonic sensor arranged on the detection robot, and the positioning method comprises the following steps:

step 1, laying sensors; establishing a global coordinate system by taking the circle center of the storage tank bottom plate as an origin, the south-north as a y axis and the east-west as an x axis, placing an inertial sensor at the central part of the detection robot, and setting the north angle of the inertial sensor to zero; respectively placing ultrasonic sensors at the front end and the rear end of the detection robot, wherein the connecting line of the front end and the rear end corresponding to the sensors is parallel to the central axis of the detection robot;

step 2, establishing a rotating coordinate system; recording the position of the detection robot entering the storage tank, acquiring an included angle alpha between the orientation of the detection robot and the y-axis direction of the global coordinate system by using an inertial sensor, and rotating the global coordinate system counterclockwiseObtaining a rotating coordinate system;

step 3, setting a positioning area; the radius of the oil-carrying storage tank bottom plate is r, according to the prior position of the detection robot, namely the position of the detection robot at the last moment, a semicircular area where the detection robot is located in the rotating coordinate system is set as a positioning area, namely the oil-carrying storage tank bottom plate is divided into two semicircular areas by taking an x axis of the rotating coordinate system as a boundary, and the semicircular area where the detection robot is located is the positioning area;

step 4, actually measuring sound velocity estimation; the actual sound velocity of the ultrasonic waves in a liquid medium carried at the bottom of the oil-carrying storage tank is obtained through the ultrasonic sensor based on the receiving and sending of the ultrasonic waves;

step 5, solving the positioning position;

step 5.1, solving chord length; a chord is formed by connecting intersection points of an axis extension line and the circular boundary of the positioning area in the detection robot, the chord length d of the chord is obtained according to the echo ranging of the ultrasonic sensors at the front end and the rear end of the detection robot, and the half-angle corresponding to the chord length can be obtained according to a chord length formula

Step 5.2, solving the position of the detection robot; the coordinates of the ultrasonic sensors at the front end and the rear end under a rotating coordinate system are obtained by theta calculationWherein d is₀Distance between the ultrasonic sensors at the front and rear ends, d₁、d₂The echo distance measured by the front and rear ultrasonic sensors is one half of the echo sound distance formed after the front and rear ultrasonic sensors transmit sound waves to the wall plate of the storage tank and reflect the sound waves;

5.3, solving the positioning coordinates in the global coordinate system,

and (3) converting the coordinate system of the ultrasonic sensor in the rotating coordinate system, wherein the rotating formula is as follows:

wherein, (x ', y') is the ultrasonic sensor coordinate in the global coordinate system, and (x, y) is the ultrasonic sensor coordinate in the rotating coordinate system, and the known alpha and x are₁、y₁、x₂、y₂Substituting the formula (1) into the formula (1), and calculating to obtain the coordinate M of the front and rear ultrasonic sensors in the global coordinate system₁(x₁',y₁')、M₂(x₂',y₂') to obtain a specific position of the inspection robot.

2. The method of claim 1, wherein the method is adapted for use with a cylindrical tank.

3. The method as claimed in claim 1 or 2, wherein the step 4 is implemented by two sets of four ultrasonic sensors disposed at the front end and the rear end of the inspection robot and located on the same straight line parallel to the central axis of the inspection robot, one set of ultrasonic sensors is located at the outer side of the inspection robot and the detection surface is outward, the other set of ultrasonic sensors is located at the inner side of the inspection robot and the detection surfaces are oppositely disposed and spaced by a distance d₀The sound wave is obtained in a transmitting-receiving mode through two opposite ultrasonic sensorsTime delay t of propagation between two sensors₀And the actually measured sound velocity v is calculated by the formula (2).

4. The method as claimed in claim 3, wherein the distance d between the ultrasonic sensors and the wall plate of the storage tank is obtained based on the echo sound distance₁And d₂So that the chord length in said step 5.1 is d ═ d₀+d₁+d₂。

Technical Field

The invention relates to the technical field of nondestructive testing of special equipment, in particular to the field of a detection robot suitable for storage tank detection.

Background

The large vertical metal storage tank is used as an international and domestic common oil storage container, and is inevitably corroded due to the influence of factors such as silt, water, air and the like all the year round, and particularly, the corrosion degree of a storage tank bottom plate is serious. Because the defects of high cost, long period and the like exist in manual tank opening detection, the existing advanced storage tank bottom plate corrosion condition detection method is to carry out corrosion detection on the storage tank bottom plate by utilizing the fact that a detection robot enters the storage tank under a load state. In order to ensure the safe operation of the detection robot, namely, the detection robot does not collide with the tank inner structure, the online detection robot has a real-time positioning function. At present, a positioning method of a detection robot is to arrange a plurality of sensor ultrasonic receiving sensors on the outer wall or the top of a storage tank to form a receiving array with a known spatial position, and calculate the position of a sound source by the time difference when sound waves emitted by an ultrasonic emitting sensor installed on the detection robot reach each ultrasonic receiving sensor in the receiving array, so as to obtain the position of the detection robot. To ensure accurate positioning, the known prior art is as follows:

alawi Salem Alwi Abdula et al (Alawi Salem Alwi Abdula, Alaa major Aboud Khalil, et al. localization of approximate mobile interaction platform in an oil storage tank [ C ]. proceedings of the 7th International Symposium on mechanics and Applications, Sharjah, UAE,2010:1-6) propose a sensing system consisting of three distance measuring sensors and an electronic compass, which works by solving the position of a detection robot from information measured by the distance sensors using the trilateration principle and solving the direction angle of the detection robot using the electronic compass. The method is a common method at present, but the arrangement error of the external sensor is introduced to influence the positioning precision, and when the storage tank is large, a large number of external receiving sensors need to be arranged, so that the complexity of the system is increased. Patent CN201710815328 discloses a positioning method suitable for a floating roof type storage tank, which does not have universality for storage tanks with other structures by arranging an intrusive receiving sensor in a floating roof part depending on the special structure of the floating roof. Patent CN201810752199 discloses a positioning method for a storage tank detection robot combining a camera and a distance measurement sensor, but the method substantially requires distance measurement by means of a manhole on a storage tank, and the detection precision is limited by requirements on the structure of the storage tank, factors such as accurate measurement of the position of the manhole, whether the height of a medium is higher than the manhole, and the like.

Therefore, the current detection robot positioning method has the following problems:

(1) in order to ensure the calculation accuracy of triangulation, the spatial position of the receiving array needs to be accurately set, and for a storage tank of thousands of cubic meters, the arrangement of dozens of ultrasonic receiving sensors is complex and the operation workload is large;

(2) the accuracy of the positioning result is affected by measurement errors of the position of the receiving sensor arranged on the outer wall of the storage tank, sensor sliding during the measurement process and other factors.

(3) The positioning method using the floating roof intervention or manhole distance measurement principle to improve the positioning accuracy has the problems of no universality or low positioning accuracy, and does not have universality for ensuring high positioning accuracy.

In summary, because the existing positioning method has the above disadvantages, a positioning method with simple operation and high positioning accuracy is urgently needed. The invention designs a positioning method which has stronger universality and simple structure and can provide the accurate position of the detection robot without arranging an additional sensor outside the storage tank by utilizing the geometric shape of the bottom plate of the storage tank and combining the inertial sensor and the ultrasonic distance measurement sensor.

Disclosure of Invention

The invention aims to solve the defects that the existing storage tank detection robot positioning system is easily influenced by a receiving sensor and the arrangement is complex when more sensors are arranged, so that the positioning accuracy is limited.

In order to achieve the purpose, the invention adopts the following technical scheme:

a positioning method of a detection robot for a bottom plate of an oil-carrying storage tank obtains position information through an ultrasonic sensor arranged on the detection robot, and comprises the following specific positioning steps:

a positioning method of a detection robot for a bottom plate of an oil-carrying storage tank is characterized in that position information is obtained through an ultrasonic sensor arranged on the detection robot, and the positioning method comprises the following steps:

step 1, laying sensors; establishing a global coordinate system by taking the circle center of the storage tank bottom plate as an origin, the south-north as a y axis and the east-west as an x axis, placing an inertial sensor at the central part of the detection robot, and setting the north angle of the inertial sensor to zero; respectively placing ultrasonic sensors at the front end and the rear end of the detection robot, wherein the connecting line of the front end and the rear end corresponding to the sensors is parallel to the central axis of the detection robot;

step 2, establishing a rotating coordinate system; recording the position of the detection robot entering the storage tank, acquiring an included angle alpha between the orientation of the detection robot and the y-axis direction of the global coordinate system by using an inertial sensor, and rotating the global coordinate system counterclockwiseObtaining a rotating coordinate system;

step 3, setting a positioning area; the radius of the oil-carrying storage tank bottom plate is r, according to the prior position of the detection robot, namely the position of the detection robot at the last moment, a semicircular area where the detection robot is located in the rotating coordinate system is set as a positioning area, namely the oil-carrying storage tank bottom plate is divided into two semicircular areas by taking an x axis of the rotating coordinate system as a boundary, and the semicircular area where the detection robot is located is the positioning area;

step 4, actually measuring sound velocity estimation; the actual sound velocity of the ultrasonic waves in a liquid medium carried at the bottom of the oil-carrying storage tank is obtained through the ultrasonic sensor based on the receiving and sending of the ultrasonic waves;

step 5, solving the positioning position;

step 5.1, solving chord length; a chord is formed by connecting intersection points of an axis extension line and the circular boundary of the positioning area in the detection robot, the chord length d of the chord is obtained according to the echo ranging of the ultrasonic sensors at the front end and the rear end of the detection robot, and the half-angle corresponding to the chord length can be obtained according to a chord length formula

Step 5.2, solving the position of the detection robot; calculating the rotation coordinate system of the ultrasonic sensor at the front end and the rear end according to thetaThe coordinates ofWherein d is₀Distance between the ultrasonic sensors at the front and rear ends, d₁、d₂The echo distance measured by the front and rear ultrasonic sensors is one half of the echo sound distance formed after the front and rear ultrasonic sensors transmit sound waves to the wall plate of the storage tank and reflect the sound waves;

5.3, solving the positioning coordinates in the global coordinate system,

and (3) converting the coordinate system of the ultrasonic sensor in the rotating coordinate system, wherein the rotating formula is as follows:

wherein, (x ', y') is the ultrasonic sensor coordinate in the global coordinate system, and (x, y) is the ultrasonic sensor coordinate in the rotating coordinate system, and the known alpha and x are₁、y₁、x₂、y₂Substituting the formula (1) into the formula (1), and calculating to obtain the coordinate M of the front and rear ultrasonic sensors in the global coordinate system₁(x₁',y₁')、M₂(x₂',y₂') to obtain a specific position of the inspection robot.

Further, the method is suitable for cylindrical oil-carrying storage tanks.

Further, in step 4, there are four sets of ultrasonic sensors disposed at the front end and the rear end of the inspection robot, and the four sets of ultrasonic sensors are disposed on the same straight line parallel to the central axis of the inspection robot, one set of ultrasonic sensor is disposed at the outer side of the inspection robot and the inspection surface is outward, and the other set of ultrasonic sensor is disposed at the inner side of the inspection robot and the inspection surfaces are disposed opposite to each other and spaced by a distance d₀The time delay t of the sound wave propagating between two ultrasonic sensors is obtained by the two ultrasonic sensors in a pitch-catch mode₀And the actually measured sound velocity v is calculated by the formula (2).

Furthermore, in step 4, the detection surfaces of the ultrasonic sensors are outward, and the distances between the two sensors and the storage tank wall plate are obtained based on echo sound distances and are d respectively₁And d₂So that the chord length in said step 5.1 is d ═ d₀+d₁+d₂。

Compared with the prior art, the invention has the beneficial effects that:

1. the sound velocity is actually measured by the two ultrasonic sensors, so that the sound velocity in the positioning environment does not need to be measured in advance or the empirical sound velocity is not used before positioning, and the positioning precision is improved;

2. because the invention only needs to install the sensor on the detection robot, the invention fundamentally overcomes the error brought by the external sensor and has stronger applicability;

3. by utilizing the geometric shape of the bottom plate of the storage tank, the position of the detection robot in the bottom plate of the oil-carrying storage tank can be determined only by the inertial sensor and the ultrasonic sensor which are arranged on the robot without additionally arranging a sensor outside the storage tank, so that the difficulty of arranging an external sensor is reduced, and the cost is saved.

Drawings

FIG. 1 is a schematic diagram of a sensor layout according to the positioning method of the present invention;

FIG. 2 is a schematic diagram illustrating a coordinate system transformation principle of the positioning method according to the present invention;

FIG. 3 is a block diagram of the positioning algorithm steps of the positioning method of the present invention;

the labels in the figure are:

1-four ultrasonic sensors with 1#, 2#, 3#, and 4# respectively,

2-the mass of the inertial sensor,

3-detection robot.

Detailed Description

The technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

A detection robot positioning method suitable for storage tank detection obtains position information through an ultrasonic sensor arranged on the detection robot, and comprises the following specific positioning steps:

step 1, laying sensors; as shown in fig. 1, a global coordinate system is established with the center of circle of the storage tank bottom plate as an origin, the south-north as a y-axis, and the east-west as an x-axis, an inertial sensor is placed at the central part of the detection robot, and the north angle of the inertial sensor is set to zero; respectively placing ultrasonic sensors at the front end and the rear end of the detection robot, wherein the connecting line of the front end and the rear end corresponding to the sensors is parallel to the central axis of the detection robot;

step 2, establishing a rotating coordinate system; recording the position of the detection robot entering the storage tank, acquiring an included angle alpha between the orientation of the detection robot and the y-axis direction of the global coordinate system by using an inertial sensor, and rotating the global coordinate system counterclockwiseObtaining a rotating coordinate system;

step 3, setting a positioning area; the radius of the oil-carrying storage tank bottom plate is r, according to the prior position of the detection robot, namely the position of the detection robot at the last moment, a semicircular area where the detection robot is located in the rotating coordinate system is set as a positioning area, namely the oil-carrying storage tank bottom plate is divided into two semicircular areas by taking an x axis of the rotating coordinate system as a boundary, and the semicircular area where the detection robot is located is the positioning area;

step 4, actually measuring sound velocity estimation; the actual sound velocity of the ultrasonic waves in the liquid medium carried by the oil-carrying storage tank is obtained through the ultrasonic sensor based on the receiving and sending of the ultrasonic waves;

four ultrasonic sensors arranged at the front end and the rear end of the detection robot are arranged on the same straight line parallel to the central axis of the detection robot, one group of ultrasonic sensors (sensor numbers 1#, 2#) are arranged at the outer side of the detection robot, the detection surfaces of the ultrasonic sensors are outward, and the other group of ultrasonic sensors (sensor numbers 3#, 4#)Is positioned at the inner side of the detection robot, the detection surfaces are oppositely arranged and have a distance d₀The time delay t of the sound wave propagating between two ultrasonic sensors is obtained by the two ultrasonic sensors in a pitch-catch mode₀And the actually measured sound velocity v is calculated by the formula (2).

The ultrasonic sensors are provided with a group of outward detection surfaces, and the distances between the two sensors and the storage tank wall plate are respectively d based on echo acoustic distances₁And d₂That is, the two sensors of the group both adopt a self-sending and self-receiving mode to obtain the echo time delays t respectively₁、t₂Thereby obtaining d according to the following formula₁、d₂

Step 5, solving the positioning position;

step 5.1, solving chord length; a chord is formed by connecting intersection points of an axis extension line and the circular boundary of the positioning area in the detection robot, the chord length d of the chord is obtained according to the echo ranging of the ultrasonic sensors at the front end and the rear end of the detection robot, and the half-angle corresponding to the chord length can be obtained according to a chord length formula

Step 5.2, solving the position of the detection robot; the coordinates of the ultrasonic sensors at the front end and the rear end under a rotating coordinate system are obtained by theta calculationWhere d0 is the distance between the front and rear ultrasonic sensors, d₁、d₂For the echo distances measured by the front and rear ultrasonic transducers, i.e. emitted by the front and rear ultrasonic transducersThe sound waves are reflected to the wall plate of the storage tank to form one half of echo sound distance;

step 5.3, solving the position of the detection robot; the coordinates of the ultrasonic sensors at the front end and the rear end under a rotating coordinate system are obtained by theta calculation according to a trigonometric formulaWherein d is₀Distance between the ultrasonic sensors at the front and rear ends, d₁、d₂The echo distance measured by the front and rear ultrasonic sensors is one half of the echo sound distance formed after the front and rear ultrasonic sensors transmit sound waves to the wall plate of the storage tank and reflect the sound waves;

5.4 solving the positioning coordinates in the global coordinate system,

and (3) converting the coordinate system of the ultrasonic sensor in the rotating coordinate system, wherein the rotating formula is as follows:

wherein, (x ', y') is the ultrasonic sensor coordinate in the global coordinate system, and (x, y) is the ultrasonic sensor coordinate in the rotating coordinate system, and the known alpha and x are₁、y₁、x₂、y₂Substituting the formula (1) into the formula (1), and calculating to obtain the coordinate M of the front and rear ultrasonic sensors in the global coordinate system₁(x₁',y₁')、M₂(x₂',y₂') to obtain a specific position of the inspection robot.

The method of the invention is suitable for all oil-carrying storage tanks with circular cross sections.

Uniqueness and accuracy of the solution of the location. There may be multiple chord locations within the circular region of the tank corresponding to a known chord length d, i.e., the solutions for the chord locations are not unique, but the method incorporates inertial sensors such that the two-dimensional location corresponding to the chord length has a unique solution.

First, the angle a determined by the initial entry direction of the inertial sensor,the chord length is parallel to the x axis of the rotating coordinate system, so that the calculation of the chord length is facilitated; furthermore, from the a priori position of the inertial sensor, the position of the inertial sensor in the rotating coordinate system at the previous moment, the positioning area (upper or lower semicircle), i.e. the range of the y-axis (y) corresponding to the chord is determined>Whether 0 or y<0) (ii) a Finally, the deflection angle of the chord, i.e. the half angle corresponding to the chord length, is determined according to the chord lengthAnd further determines the specific coordinates of x and y.

The calculation process is simple, iterative calculation and calibration of array sensor triangulation adopted in the prior art are not needed, auxiliary measurement of the position of an external manhole is also not needed, the calculation of the chord length can be realized by only four ultrasonic sensors, the operation is convenient, and the calculation precision is high; the determination of the angle of the chord is realized by introducing an inertial sensor, the arrangement is convenient, and the measurement precision is high. Therefore, the method has the characteristics of convenient operation and high calculation precision, utilizes the circular shape of the bottom surface of the storage tank during calculation, is suitable for all oil-carrying storage tanks with circular cross sections, and has wide application range.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.