Hoisting welding robot and path planning method thereof

Abstract

The invention discloses a hoisting welding robot and a path planning method thereof.The hoisting welding robot comprises a welding robot base, a welding mechanical arm and an auxiliary mechanical arm, the welding mechanical arm and the auxiliary mechanical arm are four-degree-of-freedom mechanical arms, the welding mechanical arm is driven and controlled by five steering engines, a second joint is driven by double steering engines, and a second joint is driven by double steering engines; the top end of the mechanical arm is connected with a welding spray gun. An auxiliary manipulator is arranged at the top of the robotic arm, and a steering engine drives a connecting rod to control opening and closing of the manipulator nippers. The fixed base is provided with three hydraulic systems for controlling opening and closing of the base. The hoisting welding robot adopts a dynamic updating weighting A * algorithm to realize path planning of a mechanical arm, and a simulation result shows that the dynamic updating weighting A * algorithm has advantages compared with a traditional A * algorithm. The device has the high-precision and high-quality welding capacity, meanwhile, the labor intensity of workers and the influence on body health are reduced, and the device can adapt to arch bridge arch rib structures of various forms and has wide application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of steel structure arch bridge construction equipment, and in particular to a hoisting welding robot and a path planning method thereof. Background Art

[0002] One of the most important processes in the construction of the arch ribs of steel tube concrete arch bridges is arch rib welding. Due to limited conditions on the construction site, traditional welding methods at home and abroad currently rely on workers working at high altitudes, which is not only labor-intensive, but also unable to guarantee the safety of workers during the welding process. In addition, the welding efficiency and quality of manual welding are directly affected by the workers' technical level, and the progress of the arch bridge is affected by the weather environment. The existing path planning algorithm is slow in efficiency and low in accuracy, which seriously limits the efficiency of the welding robot. Summary of the invention

[0003] In order to solve the problems existing in the background technology, the present invention provides a hoisting welding robot and a path planning method thereof, which solves the problems of high intensity of workers' high-altitude welding work, low welding precision and poor welding quality, improves welding work efficiency, increases the safety of high-altitude operations, and improves the accuracy of welding robot path planning.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The hoisting welding robot described in the present invention comprises a welding robot arm, a welding robot base, a welding arch rib, a hydraulic mechanism and an auxiliary robot arm. The welding robot arm and the auxiliary robot arm are fixed to the welding robot base by bolt connection, and are responsible for welding and adjusting the working posture of the robot. A hydraulic mechanism is provided under the base connection cover of the welding robot base, and the hydraulic mechanism is used to control the posture of the welding robot base and complete its tightening work on the welding arch column.

[0006] As a preferred welding robot arm, the robot arm is a four-degree-of-freedom robot arm with a servo for closed-loop drive control to ensure that the stability, accuracy, torque and speed requirements of the robot arm during movement are met. The welding robot arm is fixed to the welding robot base by bolts; the upper side of the robot arm base is equipped with a first servo, the output shaft of the first servo is engaged with the steering wheel, and the steering wheel is connected to the driving first rotating joint; the second and third servos are respectively installed on both sides of the first joint, the output shafts of the second and third servos are engaged with the servo, and the servo is connected to the second joint by bolts; the second joint is connected to the fourth servo on one side, the output shaft of the fourth servo is engaged with the steering wheel, and the steering wheel is connected to the third joint; the third joint is connected to the fifth servo on one side, the output end of the fifth servo is engaged with the steering wheel, and the steering wheel is connected to the fourth joint; the fourth joint is connected to a welding gun, and welding is performed through the welding gun.

[0007] As an optimal welding robot base, it is composed of three base connection covers, two base side grips, and two base half-side grips. A hydraulic mechanism is installed on the lower side of each base connection cover, and the two ends of the hydraulic mechanism are respectively connected to the side grip or the half-side grip. By controlling the opening and closing of the side grip and the base half-side grip, the welding robot base is controlled to hold the arch rib tightly.

[0008] As a preferred auxiliary robot, the auxiliary robot is a four-degree-of-freedom robot arm, but the fourth joint thereof is connected to a robot device. The robot device is driven by a robot control steering gear, which is transmitted to a robot connecting rod through a robot control steering wheel, and the opening and closing of the robot claw is controlled by the swing of the robot connecting rod.

[0009] As a preferred hydraulic mechanism, a hydraulic cylinder and a hydraulic rod are installed inside the base link cover to form a hydraulic mechanism.

[0010] The construction method of the hoisting welding robot has the following specific steps: hoisting the hoisting welding robot to the arch bridge welding working position, using a hydraulic mechanism to fasten the welding robot base to the welding arch rib, using an auxiliary robot arm to position and align the robot, and adjusting the welding robot arm to the working position, and then welding. The above steps realize the fully automatic welding of the high-altitude arch bridge.

[0011] The hoisting welding robot adopts a dynamic weighted A* algorithm, which is based on the traditional A* algorithm, and its cost function is optimized as shown in the following formula:

[0012] f * (n) = g * (n)+ω(p)*h(n)

[0013] Among them, f * (n) is the optimized cost estimation function, g * (n) is the cost from the incremental starting target to the target n. Compared with the traditional function, this function dynamically updates the starting point position in each algorithm iteration, and takes the position five iterations ago as the dynamic starting point. ω(p) is a weighting function, and its value is between 0 and 1. The function adopts a dynamic weighting method, and the core idea of ​​the Dijsktra algorithm is to find the shortest path from the starting point to all other nodes by gradually expanding the shortest path tree and the greedy best first search algorithm for smooth interpolation.

[0014] Manhattan distance is used as the heuristic function, as shown below:

[0015] d(x,y)=|x i -x j |+|y i -y j |

[0016] The specific meanings of each parameter are as follows:

[0017] d(x,y) is the Manhattan distance, x i is the horizontal coordinate of point i, y i is the vertical coordinate of point i, x j is the horizontal coordinate of point j, y j is the vertical coordinate of point j.

[0018] The path planning method of a hoisting welding robot comprises the following steps:

[0019] S1: Obtain the initial information of the robot in three-dimensional space and determine the geometric structure and kinematic parameters of the robot, including the number of joints, link length, joint limits, etc.

[0020] S2: Determine the position and posture of the end effector according to the target setting.

[0021] S3: Use the dynamic weighted A* algorithm for path planning. After finding the path, use B-spline curves to optimize the path to make it smoother and reduce unnecessary turns and corners.

[0022] S4: Through inverse kinematics calculation, a mathematical model is established using DH parameters to obtain the coordinate transformation from the end effector to each joint. The path is converted into a specific trajectory through cubic spline interpolation, and the velocity and acceleration of each joint on the path are configured using the gradient velocity profile.

[0023] S5: Input the planned trajectory into the control system to control the robot arm to move according to the planned trajectory.

[0024] Compared with the traditional A* algorithm, the improved A* algorithm uses a dynamic starting node in the calculation, optimizes the defect of the traditional A* algorithm of over-calculating the starting point, greatly shortens the calculation process of the g(n) function, reduces the number of node traversals, and solves the defects of the traditional A* algorithm of large memory usage and high computational complexity.

[0025] As a heuristic function, h(n) is used in the A* algorithm to add the greedy algorithm to guide the correct expansion direction. If the weight is 0, the A* algorithm degenerates into the Dijkstra algorithm. By dynamically weighting it, the proportion of the greedy algorithm in the A* algorithm can be controlled. At the beginning of the algorithm, the weight ratio of the h(n) function is reduced, and the Dijkstra algorithm is used to ensure the shortest path to perform global planning of the algorithm and optimize the accuracy of the algorithm. At the end of the algorithm, the weight is increased, the current node to the target node valuation is increased, and the influence of the local optimal solution on the algorithm is enhanced to obtain the optimized calculation results more quickly.

[0026] The beneficial effects obtained by the present invention are:

[0027] 1. The invention uses a hydraulic mechanism to fasten the welding robot base to the welding arch rib, uses an auxiliary robot arm to perform operations such as positioning and alignment on the robot, and adjusts the welding robot arm to the working position to achieve fully automatic welding of high-altitude arch bridges.

[0028] 2. The robot arm of the invention is driven by a servo, which has a fast response speed and can be quickly adjusted to the target position, which makes the robot arm have a fast welding speed and high completion efficiency during welding operations.

[0029] 3. The welding robot arm of the invention is a four-degree-of-freedom robot arm with excellent flexibility and functionality, allowing it to move and position freely in the workspace, thereby improving welding efficiency. The setting of two welding robot arms can complete the welding of a circle of arch ribs in one fixation, without the need to frequently adjust the position of the welding robot. In addition, the auxiliary robot arm can realize auxiliary welding, more accurately locate and adjust the position and posture of the robot and the welding arch rib.

[0030] 4. The welding quality of this invention is high, and the welding robot arm can accurately control the welding position, speed and strength to ensure stability and consistency during the welding process.

[0031] 5. The invention is easy to operate and uses the A* algorithm after dynamic weighted optimization to perform path search, reducing the workload of operators.

[0032] 6. This invention realizes intelligent high-altitude welding. This invention introduces a welding robot into the welding system, which can complete welding tasks in complex spaces. It can also realize real-time programming of the servo, and achieve precise control and adjustment of welding by adjusting the position of the welding robot. The A* algorithm after dynamic weighted optimization is adopted to improve the efficiency of robot tracking.

[0033] 7. The invention reduces the impact on the health of workers, realizes the fully automatic welding of the arch ribs of high-altitude arch bridges, and significantly reduces the need for manual high-altitude welding operations. This not only greatly reduces the labor intensity of workers, but also effectively ensures the safety of workers and further reduces the health risks that may be caused by high-altitude operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the structure of a hoisting welding robot provided in an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of a portion of the structure of a welding robot provided in an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the structure of a welding robot base and a hydraulic mechanism provided in an embodiment of the present invention;

[0037] Figure 4 A schematic diagram of the structure of an auxiliary robot arm provided by an embodiment of the present invention;

[0038] Figure 5 It is a schematic flow chart of the path planning method of the robot arm of the present invention;

[0039] Figure 6 This is a diagram of a MATLAB algorithm simulation example.

[0040] In the figure: a welding robot arm 1; a welding robot base 2; a welding arch rib 3; a hydraulic mechanism 4; an auxiliary manipulator 5; a robot arm base 11; a first steering gear 12; a second steering gear 13; a third steering gear 14; a second joint 15; a fourth steering gear 16; a third joint 17; a fifth steering gear 18; a fourth joint 19; a welding gun 110; a first rotary joint 111; a base link cover 21; a base side claw 22; a base half-claw 23; a base connecting plate 24; a hydraulic cylinder 41; a hydraulic rod 42; a manipulator control steering gear 51; a manipulator control steering wheel 52; a manipulator connecting rod 53; a manipulator claw piece 54, and a manipulator palm plate 55. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0042] Embodiment 1:

[0043] The hoisting welding robot described in the present invention comprises a welding robot arm 1, a welding robot base 2, a welding arch rib 3, a hydraulic mechanism 4 and an auxiliary robot arm 5.

[0044] Wherein: the robot arm is a four-degree-of-freedom robot arm, and the robot arm base 11 is connected to the welding robot base 2 by bolts; a first steering gear 12 is installed on the upper side of the robot arm base 11, and the output shaft of the first steering gear 12 is buckled with the steering wheel, and the steering wheel is connected to the driving first rotating joint 111; a second steering gear 13 and a third steering gear 14 are respectively installed on both sides of the first joint 111, and the output shafts of the second steering gear 12 and the third steering gear 13 are buckled with the steering gear, and the steering gear is connected to the second joint 15 by bolts; one side of the second joint is connected to the fourth steering gear 16, and the output shaft of the fourth steering gear 16 is buckled with the steering wheel, and the steering wheel is connected to the third joint 17; one side of the third joint 17 is connected to the fifth steering gear 18, and the output end of the fifth steering gear is buckled with the steering wheel, and the steering wheel is connected to the fourth joint 19; the fourth joint 19 is connected to the welding gun 110, and the welding operation is performed through the welding gun.

[0045] A hydraulic mechanism 4 is installed under the base connection cover 21. The hydraulic mechanism 4 consists of a hydraulic cylinder 41 and a hydraulic rod 42. The two ends of the hydraulic mechanism 4 are respectively connected to the base side grip 22 or the base half side grip 23. By controlling the opening and closing of the base side grip 22 and the base half side grip 23, the welding robot base is controlled to hold the arch rib 3 tightly.

[0046] The auxiliary robot 5 is driven by a robot control steering gear 51 , which is transmitted to a robot connecting rod 53 through a robot control steering wheel 52 , and the opening and closing of a robot claw 54 is controlled by the swing of the robot connecting rod 53 .

[0047] Embodiment 2:

[0048] The construction method of the hoisting welding robot comprises the following steps:

[0049] S1 hoists the hoisting welding robot to the arch bridge welding work position;

[0050] S2 uses a hydraulic mechanism to fasten the welding robot base to the welding arch rib 3, uses the auxiliary robot 5 to position and align the robot, and fastens the base connection plate to complete the welding robot's fixation work on the arch rib; hoists the welded part to the vicinity of the welding position, and uses the auxiliary robot 5 to clamp the welded part and maintain stability;

[0051] S3 adjusts the welding robot arm 1 to the working position, and then the two welding robot arms perform welding in their respective working areas;

[0052] The above steps realize the fully automatic welding of the high-altitude arch bridge. The purpose of setting two welding robot arms is to speed up the welding speed and facilitate welding so that the tilt direction of the welding gun is basically consistent to ensure the welding quality. The setting of the auxiliary robot arm 5 can reduce the work intensity of workers during high-altitude operations.

[0053] The path planning method is carried out in the following steps:

[0054] S1: Obtain the initial information of the robot in three-dimensional space and determine the geometric structure and kinematic parameters of the robot, including the number of joints, link length, joint limits, etc.

[0055] S2: Determine the position and posture of the end effector according to the target setting.

[0056] S3: Use the heuristic A* algorithm for path planning. After finding the path, use B-spline curves to optimize the path to make it smoother and reduce unnecessary turns and corners.

[0057] S4: Through inverse kinematics calculation, a mathematical model is established using DH parameters to obtain the coordinate transformation from the end effector to each joint. The path is converted into a specific trajectory through cubic spline interpolation, and the velocity and acceleration of each joint on the path are configured using the gradient velocity profile.

[0058] S5: Input the planned trajectory into the control system to control the robot arm to move according to the planned trajectory.

[0059] The present invention adopts a dynamic weighted update A* algorithm, which is based on the traditional A* algorithm. After optimization, its cost function is shown as follows:

[0060] f * (n) = g * (n)+ω(p)*h(n)

[0061] Among them, f * (n) is the optimized cost estimation function, g * (n) is the cost from the incremental starting target to the target n. Compared with the traditional g(n) function, this function dynamically updates the starting point position in each algorithm iteration, and takes the position five iterations ago as the dynamic starting point. ω(p) is a weighting function, and its value is between 0 and 1. The h(n) function uses a dynamic weighting method to combine the core idea of ​​the Dijsktra algorithm by gradually expanding the shortest path tree to find the shortest path from the starting point to all other nodes with the greedy best first search algorithm for smooth interpolation.

[0062] Use Manhattan distance as the heuristic function, as shown below:

[0063] d(x,y)=|x i -x j |+|y i -y j |

[0064] The specific meanings of each parameter are as follows:

[0065] d(x,y) is the Manhattan distance, x i is the horizontal coordinate of point i, y i is the ordinate coordinate of point i, similarly x j is the horizontal coordinate of point j, y j is the vertical coordinate of point j.

[0066] Compared with the traditional A* algorithm, the improved A* algorithm optimizes the excessive overhead of the traditional algorithm in the calculation of the starting point by introducing a dynamic starting node. This improvement significantly shortens the calculation process of the g(n) function and reduces the number of node traversals, thus effectively solving the shortcomings of the traditional A* algorithm in terms of memory usage and computational complexity.

[0067] In the traditional A* algorithm, the role of the heuristic function h(n) is to guide the greedy algorithm in the correct expansion direction. When the weight of h(n) is set to 0, the A algorithm degenerates into the Dijkstra algorithm; by dynamically weighting h(n), the influence ratio of the greedy algorithm in the A* algorithm can be adjusted. Specifically, the weight of h(n) is reduced at the beginning of the algorithm, and the global planning ability of the Dijkstra algorithm is used to ensure that the shortest path is found, thereby improving the overall accuracy of the algorithm. As the algorithm proceeds, the weight of h(n) is gradually increased to enhance the valuation from the current node to the target node, which can increase the influence of the local optimal solution in the final stage, thereby obtaining the optimized calculation results more quickly.

[0068] To verify the superiority of the algorithm, MATLAB was used to generate random maps to compare the algorithm with the traditional A* algorithm. The calculation results show that compared with the traditional A* algorithm, the algorithm has significantly improved the path planning accuracy and speed. The results are visualized as follows: Figure 6 shown.

[0069] The above only describes certain exemplary embodiments of the present invention by way of illustration. It is undoubted that those skilled in the art can modify the described embodiments in various different ways without departing from the spirit and scope of the present invention.

Claims

1. A hoisting welding robot, characterized in that: include: A welding robot arm (1), a welding robot base (2), a hydraulic mechanism (4) and an auxiliary robot arm (5); the welding robot arm (1) is a four-degree-of-freedom robot arm, the welding robot arm (1) is fixed to the welding robot base (2); the hydraulic mechanism is connected and fixed to the welding robot base (2); the auxiliary robot arm (5) is driven by a robot arm control steering gear (51), and is transmitted to a robot arm connecting rod (53) through a robot arm control steering wheel (52), and the opening and closing of a robot arm claw piece (54) is controlled by the swing of the robot arm connecting rod (53).

2. The hoisting welding robot according to claim 1, characterized in that: The welding robot arm (1) comprises: A first rotary joint (111), the first rotary joint is driven by a first steering gear (12); a second rotary joint (15), the second rotary joint is driven by a second steering gear (13) and a third steering gear (14); a third rotary joint (17), the third rotary joint is driven by a fourth steering gear (16); a fourth rotary joint (19), the fourth rotary joint is driven by a fifth steering gear (18); and a welding gun (110), the welding gun is connected to the end of the fourth rotary joint (19).

3. The hoisting welding robot according to claim 1 or 2, characterized in that: The welding robot arms (1) are provided with two, and the two auxiliary robot arms are arranged at different positions on the welding robot base (2).

4. The construction method for hoisting a welding robot according to claim 3, characterized in that: The following steps are involved: S1: hoisting the single-side hoisting three-arm welding robot to the arch bridge welding working position; S2: Using a hydraulic mechanism (4), the welding robot base (2) is fastened to the welding arch rib (3); then the auxiliary manipulator further fine-tunes the arch rib and the robot position so that the welding robot arm is located in its working area; and the welding robot fixes the arch rib with the help of the auxiliary manipulator (5); S3: The welding robot arm (1) is adjusted to the working position, and then the two welding robot arms perform welding in their respective working areas.

5. The path planning method for the hoisting welding robot according to claim 4, characterized in that: The following steps are involved: S1: Obtain the initial information of the robot in three-dimensional space and determine the geometric structure and kinematic parameters of the robot; S2: Determine the position and posture of the end effector according to the target setting; S3: Use heuristic dynamically updated weighted A* algorithm for path planning. After finding the path, use B-spline curve to optimize the path. S4: Through inverse kinematics calculation, a mathematical model is established using DH parameters to obtain the coordinate transformation from the end effector to each joint; S5: Input the planned trajectory into the control system to control the robot arm to move according to the planned trajectory.

6. The path planning method for a hoisting welding robot as claimed in claim 5, characterized in that: The dynamic weighted update A* algorithm has a cost function as shown below: f * (n)=g * (n)+ω(p)*h(n) Among them, f * (n) is the optimized cost estimation function, g * (n) is the cost from the incremental starting target to the target n. Compared with the traditional g(n) function, this function dynamically updates the starting point position in each algorithm iteration, and takes the position five iterations ago as the dynamic starting point; ω(p) is a weighting function, and its value is between 0 and 1; the h(n) function adopts a dynamic weighting method, which combines the core idea of ​​the Dijsktra algorithm by gradually expanding the shortest path tree to find the shortest path from the starting point to all other nodes and the greedy best first search algorithm for smooth interpolation.

7. The dynamic weighted update A* algorithm as claimed in claim 6, characterized in that: The distance calculation formula using Manhattan distance as the heuristic function is as follows: d(x,y)=|x i -x j |+|and i -and j | The specific meanings of each parameter are as follows: d(x,y) is the Manhattan distance, x i is the horizontal coordinate of point i, y i is the vertical coordinate of point i, x j is the horizontal coordinate of point j, y j is the vertical coordinate of point j.

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