CN103386554B - Tracking system for movable welding line stress eliminating robot - Google Patents

Abstract

The invention discloses a tracking system for a movable welding line stress eliminating robot. The tracking system comprises movable welding equipment for welding a welding line and the movable welding line stress eliminating robot for eliminating welding line stress, wherein a synchronous motor is fixedly placed outside the welding line, and the axis of a rotary shaft of the synchronous motor is used as a reference point; two reflection type distance measuring sensors are fixed on a motor shaft and coaxially rotate with the motor shaft; a distance is formed between the two sensors; and reflector plates are stuck on a welding initial point, a welding nozzle of the movable welding equipment and the tail end of the movable welding line stress eliminating robot. The tracking system disclosed by the invention is simple in structure, high in automation degree and high in tracking precision of the welded welding line, and is not suffered from the influences to the welded welding line by welding dregs or welding defects.

Description

Weld seam stress relief mobile robot tracking system

This application is a divisional application with application number 201210401736.0, application date: 2012.10.19, and the name "Constant Speed Scanning and Positioning Post-Weld Seam Tracking and Residual Stress Relief System".

technical field

The invention relates to an automatic control system for welding stress relief, which belongs to the technical field of sensing and measurement and control.

Background technique

In the fields of large structural parts welding, thin plate welding, dissimilar metal welding, superalloy welding, and high-precision special equipment welding, welding deformation needs to be effectively controlled, otherwise it will affect the size and shape of the welded parts, and will reduce the structure. Carrying capacity. For example, in the aluminum alloy shipbuilding industry, due to the large heat input during the welding process, the plate is deformed greatly and the performance of the welded joint is poor. When building a hull, about 25% of the work is shaping and hammering the planks to achieve the required flatness and curvature so that the planks can be held together. This not only affects the efficiency of ship production, but also greatly reduces the quality of the ship. Even laser welding with small heat input and small deformation still has the problem of welding deformation. Welding stress is the main cause of welding deformation. There are many ways to eliminate welding stress and control welding deformation. At present, several post-weld treatment methods commonly used in engineering include ultrasonic impact, welding toe grinding, shot peening, hammering, TIG melting, and application of low phase change point electrode method, etc. . Impact, hammering, and rolling during or after welding are effective ways to reduce welding stress and prevent welding deformation. Among them, ultrasonic impact technology is a novel and effective method to eliminate harmful residual tensile stress on the surface of components or weld area and introduce beneficial compressive stress. Compared with other methods, its advantages are outstanding. Ultrasonic impact equipment uses high-power energy to push the impact head to impact the surface of metal objects at a frequency of about 20,000 times per second. The high-frequency, high-efficiency, and large energy under focus cause large compressive plastic deformation on the metal surface; at the same time, ultrasonic impact changes The original stress field is eliminated, and beneficial compressive stress is generated; under the high-energy impact, the metal surface temperature rises rapidly and then cools down rapidly, so that the surface metal structure of the action area changes, and the impact part is strengthened.

Although the welding/post-welding stress relief equipment carried by the mobile trolley has been developed at home and abroad, none of them have the automatic tracking function of long welds and curved welds after welding. To enable the welding/post-weld stress relief equipment to automatically perform operations, it is necessary to have a post-weld seam tracking function. Advanced post-weld seam tracking is used in weld quality inspection, and the methods used are mostly machine vision, see literature (Lu Changfu. Research on post-weld inspection technology based on laser vision sensing [D]. [Master's Dissertation ]. Harbin: Harbin Institute of Technology, School of Materials Science and Engineering, 2007.7.; Jean-Paul Boillot, Koichi Uota, Etienne Berthiaume, et al.Tracking and inspection for laser welding[J].Proceeding of SPIE,2002(4):165 -170.), due to the disappearance of groove features after welding, welding defects, residual flux slag and spatter, etc., all directly affect the visual inspection. It will be of great practical value to explore a fully automatic post-weld seam tracking method with high precision and not affected by post-weld working conditions, and apply it to the post-weld stress relief system.

Contents of the invention

The object of the present invention is to provide a tracking system for a mobile robot tracking system for real-time recording of the moving track of the welding nozzle and good effect of stress relief.

Technical solution of the present invention is:

A welding seam stress relief mobile robot tracking system is characterized in that: it includes mobile welding equipment for welding the weld seam, a welding stress relief mobile robot for eliminating welding stress, and a synchronous motor is fixedly placed outside the weld seam to synchronize The axis of the motor shaft is used as a reference point; two reflective ranging sensors are fixed on the motor shaft and rotate coaxially with the motor, and there is a distance between the two sensors; Stress relief mobile robots are attached with reflective sheets at the end of the operation, and cooperate with the above distance measuring sensors for distance measurement. One of the distance measurement sensors detects the distance between the reference point and the initial point of welding, and the distance between the reference point and the welding nozzle, and the other distance measurement sensor Detect the distance between the reference point and the initial point of welding, the reference point and the end of the welding stress relief mobile robot; during the operation of the system, the motor keeps rotating at a constant speed, and the ranging sensor continuously detects the distance between the welding nozzle and the reference point. And take the reference point as the center of the circle, the angle formed by the reference point, the initial welding point, and the welding nozzle, so as to obtain the moving track of the welding nozzle relative to the reference point; at the same time, the ranging sensor detects the distance between the working end of the welding stress elimination mobile robot and the reference point in real time distance, and with the reference point as the center of the circle, the angle formed by the reference point, the initial welding point, and the end of the welding stress relief mobile robot, so as to obtain the moving trajectory of the welding stress relief mobile robot operation end relative to the reference point, and carry out the above two trajectories By comparison, the distance and direction of the deviation of the working end of the welding stress relief mobile robot from the welded seam can be obtained, and the deviation can be corrected by the control system.

Set two reflectors up and down on the initial point of welding, and there is a distance between the two reflectors; the center of the reflector at the welding nozzle, the center of a reflector on the initial point of welding and a distance sensor are on the same horizontal plane; welding The center of the reflective sheet at the working end of the stress relief mobile robot, the center of another reflective sheet at the initial point of welding, and the other distance measuring sensor are on the same horizontal plane.

The distance measuring sensor is installed higher than the welding nozzle, and the modulation frequency is used to avoid the interference of arc light and plasma radiation.

The pose detection sensor is installed on the welding stress relief mobile robot to obtain the pose of the robot relative to the reference point at any time, and the deviation is corrected through the control system.

The mobile robot for welding stress relief uses a wheeled mobile robot as its main body, and realizes rough positioning of the robot position through two-wheel differential, and uses a cross slider as the positioning drive mechanism of the stress relief operation end to realize precise positioning of the end of the stress relief operation.

The invention has the advantages of simple structure, high degree of automation, high accuracy of seam tracking after welding, and is not affected by welding slag or welding defects on seam tracking after welding. Looking at the existing domestic automation systems and equipment in the field of welding, no unit has realized the design goal proposed by the present invention.

The invention uses a constant-speed rotating motor as a reference position, adopts a method combining distance measurement and angle measurement (angle measurement adopts high-frequency pulse linear interpolation subdivision) to record the moving track of the welding nozzle in real time, and controls the welding stress to eliminate the position and posture adjustment of the mobile robot , implement stress relief along the welding nozzle trajectory.

Description of drawings

The present invention will be further described below in conjunction with drawings and embodiments.

Fig. 1 is a structural diagram of the constant-speed scanning positioning type post-weld seam tracking and residual stress elimination system of the present invention.

Fig. 2 is a structural diagram of the control system of the welding stress relieving mobile robot in the constant-speed scanning positioning type post-weld seam tracking and residual stress relieving system of the present invention.

Fig. 3 is a schematic plan view of the measurement principle of the post-weld seam tracking system in the constant-speed scanning positioning type post-weld seam tracking and residual stress relief system of the present invention.

Fig. 4 is a timing diagram of the measurement principle of the post-weld seam tracking system in the constant-speed scanning positioning type post-weld seam tracking and residual stress elimination system of the present invention.

Detailed ways

A welding seam stress relief mobile robot tracking system, including a mobile welding equipment 1 for welding the weld seam, a welding stress relief mobile robot 2 for eliminating welding stress, a synchronous motor 3 fixedly placed outside the weld seam, and a synchronous motor The axis of the rotating shaft is used as a reference point; two reflective ranging sensors 4 and 5 are fixed on the motor shaft and rotate coaxially with the motor, and there is a distance between the two sensors; at the welding initial point and the welding nozzle of the mobile welding equipment , The end of the welding stress relief mobile robot is respectively pasted with reflective sheet C, reflective sheet D, reflective sheet A, and reflective sheet B, which cooperate with the above-mentioned distance measuring sensors for distance measurement, and one of the distance measurement sensors detects the reference point and the welding initial point, respectively. The distance between the reference point and the welding nozzle, another ranging sensor respectively detects the distance between the reference point and the initial point of welding, the distance between the reference point and the end of the welding stress relief mobile robot; during the operation of the system, the motor keeps constant speed Rotating, the ranging sensor continuously detects the distance between the welding nozzle and the reference point, and the angle formed by the reference point, the initial welding point, and the welding nozzle with the reference point as the center, so as to obtain the moving track of the welding nozzle relative to the reference point; The sensor detects the distance between the working end of the welding stress relieving mobile robot and the reference point in real time, and the angle formed by the reference point, the initial welding point, and the working end of the welding stress relieving mobile robot with the reference point as the center, so as to obtain the welding stress relieving mobile robot The moving trajectory of the working end relative to the reference point, by comparing the above two trajectories, the distance and direction of the welding stress relief mobile robot working end deviating from the welded seam can be obtained, and the deviation can be corrected by the control system. The mobile robot for welding stress relief uses a wheeled mobile robot as the main body, and realizes the rough positioning of the robot position through two-wheel differential, and uses the cross slider as the positioning drive mechanism of the stress relief operation end to realize the precise positioning of the end of the stress relief operation.

The details are as follows: Take a two-dimensional planar curved or straight weld as an example, as shown in Figure 1. Among them are synchronous motors, distance measuring sensors F, distance measuring sensors E, reflectors A, B, C, D, mobile welding equipment (including welding nozzles), stress relief mobile robots (including electronic compass, and stress relief equipment at the end of the operation. Using electromagnetic hammer or ultrasonic impact head, etc.). The ranging sensors E and F are fixed on the motor shaft and rotate coaxially with the motor, and there is a distance between E and F. E, F and the corresponding reflectors are installed at different heights to avoid mutual interference, and lasers or infrared light with different modulation frequencies are used to avoid interference. The welds are planar two-dimensional welds, the black filled lines are welded welds, and the rest are unwelded welds. A benchmark is erected at the initial point of welding, and reflectors C and D are fixed on the benchmark, with a certain distance between C and D. The centers of the reflective sheets A and C are on a horizontal plane with the distance measuring sensor F. When the distance measuring sensor F is directly opposite to the reflective sheets A and C, the distance between FA and FC can be measured. The centers of the reflective sheets B and D are on a horizontal plane with the distance measuring sensor E. When the distance measuring sensor E is directly opposite to the reflective sheets B and D, the distances of EB and ED can be measured. In order to avoid interference such as arc light during the laser welding process, the distance measuring sensor is installed at a height higher than the welding nozzle, and a specific modulation frequency is used to avoid interference from arc light and plasma radiation.

For the convenience of analysis, draw a schematic top view of the measurement principle as shown in Figure 3. It is assumed that the synchronous motor drives the ranging sensors E and F to rotate clockwise, and the moving point A moves counterclockwise. The initial position of the moving point A is A0, and the ranging sensor continuously rotates and scans at a high speed during the welding equipment moving along the weld seam.

The distance L0 between point A0 and point F can be obtained. Assuming that the light emitted by F passes through points C and A0, two high-level pulses can be output through the interface circuit as shown in Figure 4. Assume that initially, the welding nozzle is still at position A0, and the initial phase angle ∠CFA ₀ is denoted as α ₀ . When the light passes through A, the high-frequency pulse counting is started, and when it reaches C, the counting is stopped. Assume that the motor rotates at a constant speed, and there are N high-frequency pulses filled in one revolution. And the number N0 of high-frequency pulses represented by the angle between A0 and C can be recorded by the controller, then it can be calculated as follows:

In the same way, L ₁ , ∠CFA ₁ , L ₂ , ∠CFA ₂ . . . can be measured. Therefore, the distance change trajectory (L1, L2, L3...) and angle change trajectory (∠CFA ₀ , ∠CFA ₁ , ∠CFA ₂ ...) of the welding nozzle relative to the reference position can be recorded in real time, and the weld seam can be obtained by fitting The trajectory of the center (provided that the welding nozzle has high seam tracking accuracy by default).

Using the above method, the sensor E cooperates with the reflectors B and D to detect the position of the working end of the stress relief equipment in real time, and the distance change track and the angle change track of the work end of the stress relief equipment relative to the reference position can be obtained. Comparing the trajectory of the working end of the stress relief equipment with the trajectory of the welding nozzle, the angle and distance (based on the reference position) of the working end of the stress relief equipment from the center of the weld can be obtained. At the same time, an electronic compass is installed on the stress relief mobile robot to obtain the pose of the robot relative to the reference position. At this time, the deviation between the current position of the robot and the fitted trajectory can be reduced by controlling the motion of the robot, so that the end of the stress relief equipment operation Always aim at the weld (when hammering is used, the hammer head of the electromagnetic hammer applies a hammering force of a certain frequency to the weld toe and the metal in the weld zone that are still in a high temperature state after welding. When ultrasonic impact is used, the ultrasonic impact head to achieve weld toe or full weld bead coverage impact. Therefore, whether the moving track of the end of the stress relief equipment operation is along the center of the weld or the track of the weld toe depends on the specific stress relief method.)

In the constant-speed scanning positioning type post-weld seam tracking and residual stress elimination system of the present invention, under laser welding conditions, E and F can use infrared distance measuring sensors with a small range. Because the cooling rate of the weld metal during laser welding is much faster than that of conventional welding, up to 106°C/s, the distance between the welding torch and the stress relief equipment can be closer, and hammering, impact, etc. can be performed after a short time after welding. In other welding methods, E and F can use laser sensors to achieve long-range tracking of weld seams.

Claims (1)

1. a weld stress eliminates mobile robot tracking system, it is characterized in that: comprise the Mobile welding equipment that butt welded seam carries out welding, the welding stress elimination mobile robot eliminating welding stress, a synchronous motor fixed placement is outside weld seam, as a reference point with synchronous motor rotating shaft core; Two reflective distance measuring sensors are fixed on motor shaft, rotate with motor coaxle, a segment distance of being separated by between two sensors; Eliminate mobile robot's operation end all post reflector plate at welding initial point, the welding tip place of Mobile welding equipment, welding stress, coordinate with above-mentioned distance measuring sensor and find range, one of them distance measuring sensor detects reference point respectively and welds initial point, distance between reference point and welding tip, and another distance measuring sensor detects reference point respectively and welds initial point, reference point and welding stress and eliminate distance between mobile robot's operation end; In system operation, motor is constant speed rotary ceaselessly, and distance measuring sensor constantly detects the distance of welding tip and reference point, and is the center of circle with reference point, the angle that reference point, welding initial point, welding tip are formed, thus obtain the motion track of welding tip relative to reference point; Distance measuring sensor detects the distance that welding stress eliminates mobile robot's operation end and reference point in real time simultaneously, and be the center of circle with reference point, reference point, welding initial point, welding stress eliminate the angle that mobile robot's operation end is formed, thus obtain the motion track of welding stress elimination mobile robot operation end relative to reference point, above-mentioned two tracks are compared, the Distance geometry direction that welding stress elimination mobile robot operation end departs from welding line can be obtained, and rectified a deviation by control system; Welding initial point arranges upper and lower two reflector plates, and a segment distance of being separated by between two reflector plates; A reflector plate center on the reflector plate center at welding tip place, welding initial point and a distance measuring sensor are in same level; Welding stress eliminates another reflector plate center on the reflector plate center of mobile robot operation end, welding initial point and another distance measuring sensor in same level; Distance measuring sensor setting height(from bottom), higher than welding tip, adopts modulating frequency to avoid the interference of arc light and plasma resonance; Welding stress is eliminated mobile robot and is adopted wheeled mobile robot as body, realizes robot location's coarse positioning by two-wheeled is differential, adopts crosshead shoe as stress elimination operation end positioning drive mechanisms, realizes the precision positioning of stress elimination operation end.