Crawling welding robot and welding position tracking method

Abstract

The present disclosure provides a crawling welding robot and a welding position tracking method. The crawling welding robot includes a body, wheels, a welding gun and a laser sensor. The welding gun and the laser sensor are fixed on the body, facing the front of the body and located on the same central axis. The laser sensor is used to detect the midpoint of the weld. The tracking method includes: determining the initial coordinates of the midpoint of the weld as a target value; and based on the deviation between the subsequent coordinates of the midpoint of the weld and the target value, calculating a voltage signal for controlling the differential of the wheels to control the crawling welding robot to track the target value.

Description

Technical Field

[0001] The present disclosure relates to the field of welding technology, and more specifically, to a crawling welding robot and a welding position tracking method. Background Art

[0002] In recent years, with the development of welding automation, more and more large structures need automated welding. The railless all-position crawling welding robot has a unique competitive advantage, making automated welding of large structures possible. This type of crawling welding robot is mainly composed of a mobile mechanism, a weld sensor, a control circuit and an information processing system. The weld sensor is mainly used to detect the deviation between the welding gun and the center position of the weld, and provide input information for the weld tracking control system.

[0003] In the prior art, weld sensors are often installed on the central axis of the side of the crawling welding robot. When the crawling welding robot deviates, the position deviation of the weld sensor caused by the steering of the vehicle body is very small, so that the weld sensor cannot timely know the offset of the welding position, resulting in the crawling welding robot being unable to accurately track the welding position. Summary of the invention

[0004] In view of this, the present disclosure provides a crawling welding robot and a welding position tracking method to solve or alleviate the problem of low sensitivity and poor accuracy of welding position tracking caused by the side placement of the weld sensor in the prior art.

[0005] According to one aspect of the present disclosure, a crawling welding robot is provided, comprising a vehicle body, a laser sensor and a welding gun, wherein the laser sensor and the welding gun are fixed on the vehicle body, facing the front of the vehicle body and located on the same central axis.

[0006] Furthermore, the laser sensor can be used to detect the midpoint of the weld.

[0007] Furthermore, the laser sensor and the welding gun may be fixed at the front end of the vehicle body.

[0008] Furthermore, the crawling welding robot may also include wheels, and the differential speed of the wheels enables the crawling welding robot to turn and track the midpoint of the weld.

[0009] Furthermore, the crawling welding robot may also include a posture sensor for collecting the posture angle of the crawling welding robot during the crawling process.

[0010] According to another aspect of the present disclosure, a welding position tracking method of a crawling welding robot is also provided, wherein the crawling welding robot comprises a body, wheels, a welding gun and a laser sensor, wherein the welding gun and the laser sensor are fixed on the body, facing the front of the body and located on the same central axis, and the laser sensor is used to detect the midpoint of the weld, and the tracking method comprises:

[0011] determining the initial coordinates of the midpoint of the weld as target values; and

[0012] Based on the deviation between the subsequent coordinates of the midpoint of the weld and the target value, a voltage signal for controlling the differential speed of the wheels is calculated to control the crawling welding robot to track the target value.

[0013] Furthermore, the coordinate may be a lateral coordinate of the midpoint of the weld relative to the crawling welding robot.

[0014] Furthermore, the welding position tracking method may be executed by a PID controller.

[0015] Further, the subsequent coordinates of the midpoint of the weld may be the current coordinates.

[0016] Furthermore, the subsequent coordinates of the midpoint of the weld may be a series of midpoint coordinates of the weld detected in sequence by the laser sensor at each time point obtained by averaging the time for the welding gun to move to the laser line of the laser sensor. The tracking method may further include: after the welding gun moves to the initial detection position of the laser sensor, using the series of coordinates in sequence to track the target value.

[0017] Furthermore, the subsequent coordinates of the weld midpoint may be a series of weld midpoint coordinates detected in sequence by the laser sensor at various position points that evenly divide the distance from the welding gun to the laser line of the laser sensor. The tracking method may further include: after the welding gun moves to the initial detection position of the laser sensor, using the series of weld midpoint coordinates in sequence to track the target value.

[0018] Furthermore, if the target value is tracked to reach a steady state and lasts for a period of time, the average value of the steady-state posture angle of the crawling welding robot within the period of time is recorded; and when the deviation between the subsequent coordinates of the midpoint of the weld and the target value is greater than a threshold value, the crawling welding robot is controlled to track the average value of the steady-state posture angle.

[0019] Furthermore, the crawling welding robot is controlled to track the average value of the steady-state attitude angle. Specifically, the current attitude angle is subtracted from the average value of the steady-state attitude angle, and a fuzzy coefficient matching the difference is called to associate the fuzzy coefficient with the differential control of the wheel.

[0020] As described above, the crawling welding robot and welding position tracking method provided by the present invention can sensitively obtain the offset of the weld position by setting the laser sensor and the welding gun at the front end of the crawling welding robot body, and can achieve high-precision tracking of the welding position by fine-tuning the body. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the specific implementation manner of the present disclosure, the drawings required for use in the description of the specific implementation manner will be briefly introduced below. Obviously, the drawings described below are one implementation manner of the present disclosure, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1A An example block diagram of a crawling welding robot provided in an embodiment of the present disclosure;

[0023] Figure 1B An exemplary perspective view of a crawling welding robot provided by an embodiment of the present disclosure;

[0024] Figure 2 A schematic flow chart of a welding position tracking method provided by an embodiment of the present disclosure;

[0025] Figure 3 A schematic diagram of a control circuit of a welding position tracking method provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0027] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The words "a", "an (kind)" and "the" used herein should also include the meanings of "multiple" and "multiple", unless the context clearly indicates otherwise. In addition, the terms "including", "comprising" and the like used herein indicate the presence of the features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0028] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0029] The prior art usually installs the sensor on the side of the crawling welding robot. In this case, the deviation of the sensor in the lateral direction caused by the turning of the crawling welding robot is very small. According to the present disclosure, when the sensor is installed in the front, it has a sensing effect several times greater than that in the side, which allows the system to sense the changes of the weld earlier and faster, so that the crawling welding robot can adjust the tracking direction more timely to achieve a faster, more accurate and non-oscillating effect.

[0030] Embodiment 1:

[0031] Figure 1A A schematic structural diagram of a crawling welding robot 100 according to an embodiment of the present disclosure is shown; Figure 1B An example perspective view of a crawling welding robot according to an embodiment of the present disclosure is shown. As shown in the figure, the crawling welding robot 100 includes a body 110, wheels 120, a laser sensor 130, a welding gun 140, and a posture sensor 150. The laser sensor 130 and the welding gun 140 are fixed to the front end of the body 110, facing the front of the body 110 and located on the same central axis. In this embodiment, the laser sensor 130 is used to detect the midpoint of the weld.

[0032] In this embodiment, the laser sensor 130 and the welding gun 140 are fixedly arranged on the vehicle body 110 and are located on the same central axis. Therefore, when the laser sensor 130 is offset, the position of the welding gun 140 is also offset, and the two are still on a straight line without any unnecessary lateral offset. In this way, the laser sensor 130 and the welding gun 140 can be spaced only in the longitudinal direction.

[0033] The laser sensor 130 used in this embodiment is composed of a laser generator and a CCD camera. It is an active visual sensor that uses structured light as an auxiliary light source. Its specific working principle is: a light beam is projected onto the weld. The uneven surface of the workpiece causes the light to deform on the weld. The deformed structured light is captured by a camera. The deformation position of the light band in the image is detected, and the shape of the weld can be calculated. After calibrating the distance between the camera, the light source and the workpiece, the actual three-dimensional position of the weld can be calculated. The laser sensor 130 has the advantages of rapid information collection and high accuracy, but any other device that can collect the width of the weld is also within the scope of protection of the present invention.

[0034] The crawling welding robot provided in this embodiment also includes wheels 120, and the differential speed of the wheels 120 enables the crawling welding robot 100 to turn and track the midpoint of the weld. The crawling welding robot 100 provided in this embodiment can be a double-track structure with two wheels driven independently. Since the DC motor has a series of advantages such as large starting torque, good dynamic performance, wide speed regulation range and relatively simple control, two DC servo motors can be used as driving units of two track wheels in this embodiment, including a DC motor with a reduction gear, a servo amplifier and a rotating optical encoder disk used as speed feedback. They provide the speed and torque required for rotation. The running speed and rotation angular velocity of the vehicle body are controlled by adjusting the speed of the two track wheels, so that the crawling welding robot can move in the required direction and speed.

[0035] The crawling welding robot 100 further includes a posture sensor 150 ( Figure 1B (not shown) is used to collect the attitude angle of the crawling welding robot during the crawling process, and the attitude angle can be used to control the crawling welding robot to track the weld.

[0036] Figure 2 FIG. 2 is a flow chart of a welding position tracking method 200 according to an embodiment of the present disclosure. Figure 2 As shown, the tracking method includes:

[0037] 210: Determine the initial coordinates of the midpoint of the weld as target values; and

[0038] 220: Based on the deviation between the subsequent coordinates of the midpoint of the weld and the target value, calculate a voltage signal for controlling the differential speed of the wheels to control the crawling welding robot to track the target value.

[0039] In this embodiment, for example, a dynamic coordinate system can be established with the position of the crawling welding robot as the origin, the right direction of the crawling welding robot as the X-axis, and the forward direction as the Y-axis.

[0040] Since the laser sensor and the crawling welding robot are fixedly mechanically connected, the deviation of the crawling welding robot body will cause the laser sensor to deflect in the X and Y axis directions. The laser sensor is installed in front of the central axis of the crawling welding robot, where the deviation of the crawling welding robot body causes a larger deflection in the X axis direction and a smaller deflection in the Y axis direction. Therefore, in this embodiment, the horizontal coordinate of the midpoint of the weld relative to the crawling welding robot is used as its coordinate value.

[0041] In this embodiment, for example, the initial coordinate of the midpoint of the weld in the initial state is 0 (not limited thereto), and after the tracking starts, the laser sensor collects the subsequent coordinates of the midpoint of the weld in real time at a certain time interval, and the subsequent coordinates are the current coordinates X t .

[0042] Figure 3 The schematic diagram of the control circuit for implementing the welding position tracking method of the embodiment of the present disclosure is shown. In this embodiment, the welding position tracking method can be executed by a control circuit such as a PID controller. Specifically, after the industrial computer 302 receives the signal to start welding tracking, it triggers the laser sensor 301 to scan the weld position. The laser sensor 301 stores the initial coordinates of the weld midpoint obtained in the initial state into the PID controller 304 through the industrial computer 302 and the single-chip microcomputer 303 as the target value, and then stores the current coordinates X of the weld midpoint obtained at each moment. t As the input value of PID controller 304. PID controller 304 calculates the deviation e between the current coordinates of the midpoint of the weld and the target value, and then obtains the final differential value ΔV through linear conversion. The differential value ΔV is transmitted to servo driver 307 through DA module 306. Servo driver 307 controls the action of servo motors 308 of the left and right wheels of the vehicle body to achieve differential control of the left and right wheels of the vehicle body. Among them, the vehicle body steering adopts double-wheel differential. If the current speed of the crawling welding robot is V1, the speed of the right wheel of the vehicle body is V R =V1-ΔV, the speed of the left wheel of the vehicle is V L =V1+ΔV, where

[0043] When V R >V L When , the vehicle turns to the left;

[0044] When V R <V L When , the vehicle turns to the right;

[0045] When V R =V L , the vehicle moves straight ahead.

[0046] Since the crawling welding robot body and the laser sensor 301 are fixedly connected, the laser sensor 301 will be deflected when the body turns, and the corresponding collected weld midpoint coordinate value will also be offset. The weld midpoint coordinate value is collected again, and the above steps are repeated until the current coordinate of the weld midpoint is consistent with the initial coordinate.

[0047] This method compensates for the position deviation between the vehicle body and the weld by controlling the crawling welding robot to produce motion offset, so that the vehicle body and the weld are continuously approached until the position deviation is 0, thereby achieving the purpose of real-time adjustment of the welding position.

[0048] Embodiment 2:

[0049] On the basis of the technical solution provided in the first embodiment, this embodiment also takes into account the welding delay caused by the distance between the laser sensor and the welding gun on the longitudinal axis, and is specifically described as follows:

[0050] Since the laser sensor is located at the front end of the welding gun, there is a distance between the laser sensor and the welding gun on the longitudinal axis. The crawling welding robot cannot directly use the midpoint position of the weld collected by the laser sensor at a certain moment to adjust its own position.

[0051] In this embodiment, the time taken from the welding gun position to the laser sensor position can be calculated by the vehicle speed, and the weld position coordinates collected by the laser sensor are calculated using the time lag method and then input into the controller that controls the movement of the crawling welding robot body.

[0052] In this embodiment, the subsequent coordinates of the midpoint of the weld are a series of midpoint coordinates of the weld detected in sequence by the laser sensor at each time point averaged over the time for the welding gun to move to the laser line of the laser sensor. After the welding gun moves to the initial detection position of the laser sensor, the series of coordinates are used in sequence to track the target value.

[0053] In this embodiment, the distance between the laser line of the laser sensor and the welding gun can be set to d, and the running speed of the crawling welding robot can be set to v. From this, the time t required from the laser sensor to the welding gun can be calculated, and the time t is evenly divided into N time periods, each time period is t / N. From the initial time, the coordinate value X of the midpoint of the weld collected by the current laser collector is recorded every time period t / N until time t. When the welding gun moves to the initial recording point, it starts to track the weld, and then reads the coordinate values ​​of the midpoint of the weld collected in chronological order, and inputs them as input to the PID controller that controls the movement of the crawling welding robot body.

[0054] In this embodiment, the distance interval method can also be directly used to correspond the weld position coordinates collected by the laser sensor to the subsequent crawling welding robot body control.

[0055] In this embodiment, the subsequent coordinates of the midpoint of the weld are a series of midpoint coordinates of the weld detected in sequence by the laser sensor at various position points that evenly divide the distance that the welding gun moves to the laser line of the laser sensor. After the welding gun moves to the initial detection position of the laser sensor, the series of midpoint coordinates of the weld are used in sequence to track the target value.

[0056] In this embodiment, the distance between the laser line of the laser sensor and the welding gun can be set to d, and the distance d can be divided into N equal parts, and the coordinate value of the current weld midpoint of each equal part is recorded until the N equal parts are recorded. When the welding gun moves to the initial recording point, it starts to track the weld, and then reads the collected coordinate values ​​of the weld midpoint in chronological order, and inputs them into the PID controller that controls the movement of the crawling welding robot body as input.

[0057] Embodiment three:

[0058] On the basis of the technical solutions disclosed in the first and second embodiments, this embodiment further considers the situation where the midpoint position of the weld deviates greatly from the crawling welding robot.

[0059] When the welding position tracking method disclosed in the first and second embodiments is applied and a steady state is reached and the time lasts for t seconds (t is a positive constant), the average value of the steady-state posture angle in this time period is recorded as the angle target value for vehicle body posture tracking.

[0060] When the absolute value of the difference between the real-time weld midpoint coordinates collected by the laser sensor and the target value of PID tracking is greater than a threshold, the posture tracking mode is triggered to control the crawling welding robot to track the average value of the steady-state posture angle.

[0061] In this embodiment, the crawling welding robot is controlled to track the average value of the steady-state posture angle, specifically: the posture sensor collects the current posture angle of the crawling welding robot, and makes a difference between the current posture angle and the angle target value. In this embodiment, the system is provided with an M-level fuzzy control table, and the fuzzy control table stores the fuzzy coefficient corresponding to the difference.

[0062] The fuzzy coefficient corresponding to the difference is called from the fuzzy control table, so that the fuzzy coefficient is associated with the differential value of the left and right wheels of the crawling welding robot. Finally, the target posture angle is tracked by controlling the differential speed of the left and right wheels.

[0063] The technical solution provided in this embodiment can use the posture sensor to collect the current posture angle of the crawling welding robot when the weld position deviates greatly from the crawling welding robot, and use posture fuzzy tracking to achieve rapid adjustment of the position of the crawling welding robot. It is an effective supplement to the high-precision small-deviation welding position tracking method provided in embodiments one and two.

[0064] Although example embodiments have been described, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present disclosure. Therefore, it should be understood that the above example embodiments are not restrictive, but illustrative.

Claims

1. A welding position tracking method of a crawling welding robot, the crawling welding robot comprising a body, wheels, a welding gun and a laser sensor, the laser sensor and the welding gun being fixed at the front end of the body, the welding gun and the laser sensor being fixed on the body, facing the front of the body and being located on the same central axis of the crawling welding robot, the laser sensor being used to detect the midpoint of a weld, the tracking method comprising: Determine the initial coordinates of the weld midpoint as the target value; as well as Based on the deviation between the subsequent coordinates of the midpoint of the weld and the target value, calculating a voltage signal for controlling the differential speed of the wheels to control the crawling welding robot to track the target value; Among them, the subsequent coordinates of the midpoint of the weld are a series of midpoint coordinates of the weld detected in sequence by the laser sensor at each time point averaged over the time for the welding gun to move to the laser line of the laser sensor; the tracking method also includes: after the welding gun moves to the initial detection position of the laser sensor, using the series of midpoint coordinates of the weld in sequence to track the target value.

2. The tracking method according to claim 1, wherein: The coordinates are the lateral coordinates of the midpoint of the weld relative to the crawling welding robot.

3. The tracking method according to claim 1, wherein: The subsequent coordinates of the midpoint of the weld are replaced by a series of midpoint coordinates of the weld detected in sequence by the laser sensor at each position point that evenly divides the distance the welding gun moves to the laser line of the laser sensor, The tracking method further includes: after the welding gun moves to the initial detection position of the laser sensor, using the series of weld midpoint coordinates in sequence to track the target value.

4. The tracking method according to claim 1, further comprising: If the target value is tracked to reach a steady state and lasts for a period of time, an average value of the steady-state posture angle of the crawling welding robot in the period of time is recorded; as well as When the deviation between the subsequent coordinates of the midpoint of the weld and the target value is greater than a threshold value, the crawling welding robot is controlled to track the average value of the steady-state posture angle.

5. According to the tracking method of claim 4, the crawling welding robot is controlled to track the average value of the steady-state attitude angle, specifically, the current attitude angle is subtracted from the average value of the steady-state attitude angle, and the fuzzy coefficient matching the difference is called to associate the fuzzy coefficient with the differential control of the wheel.

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