Research on motion planning system for wall-climbing mobile manipulator for large steel structures welding operation

Mobile manipulator combines the mobility of mobile platform and the dexterity of manipulator, which has the great application potential in industry scenarios. In practical applications, efficiently planning a path in a given environment is the main objective, but the high degrees of redundancy, which is caused by the coupling of platform and manipulator, will make the planning problem more challenging. Therefore, the motion planning based on the RRT-GoalBias algorithm and path smoothing is proposed in this paper, where the kinematics of mobile manipulator is modeled, and the constraints of configuration and obstacle avoidance are analyzed. Subsequently, the RRT-GoalBias algorithm is applied and modified to generate an initial path for mobile manipulator in a given site, and a novel post-processing algorithm is proposed to smooth and optimize the initial path. Comparative Simulations are carried out with MATLAB and V-REP to verify the effectiveness of the proposed path planning algorithm for mobile manipulator under the given environment.

As the demand for service robots increases, a mobile manipulator robot which can perform various tasks in a dynamic environment attracts great attention. There are some controllers that control mobile platform and manipulator arm simultaneously for efficient performance, but most of them are difficult to apply universally since they are based on only one mobile manipulator model. This lack of versatility can be a big problem because most mobile manipulator robots are made by connecting a mobile platform and manipulator from different companies. To overcome this problem, this paper proposes a simultaneous controller which can be applied not only to one model but also to various types of mobile manipulator robots. The proposed controller has three main characteristics, which are as follows: (1) establishing a pose that motion planning can be carried out in any position, avoiding obstacles and stopping in a stable manner at the target coordinates, (2) preventing the robot from collision with surrounding obstacles while driving, (3) defining a safety area where the manipulator does not hit the obstacles while driving and executing the manipulation accordingly. Our controller is fully compatible with Robot Operating System (ROS) and has been used successfully with three different types of mobile manipulator robots. In addition, we conduct motion planning experiments on five targets, each in two simulation worlds, and two motion planning scenarios using real robots in real-world environments. The result shows a significant improvement in time compared to existing control methods in various types of mobile manipulator and demonstrates that the controller works successfully in the real environment. The proposed controller is available on GitHub.

JL-II is a reconfigurable multi-robot system, which consists of three modules with mobile manipulator. To reveal the kinematic cooperation among modules, this paper analyzes the mechanism of each part, including the mobile platform and docking manipulator. The kinematic models are established to present the 3DOF docking manipulator and mobile body in unconnected and connected states. Finally, the paper obtains a suitable and definite inverse solution through presenting a motion planning of a grasping task.

The determination of wind‐induced fatigue load in large structures and buildings with complex geometries, which do not fall in typical cases of building codes and standards, represents a consuming task, and it is usually evaluated through the aid of wind tunnel tests, while computational approaches do not yet have a large application.The practical use of computational fluid dynamics (CFD) techniques in civil engineering applications has in fact been rare outside the framework of steady‐state analyses, because of the limitations of RANS approaches and of the higher cost of LES, but with the increase in computing resources and with the introduction of new and more efficient turbulence models, the practical use of CFD to evaluate fluctuating features of wind flow is much more feasible now. With it, it is possible to foresee the possibility for the evaluation of wind‐induced fatigue loads in steel structures by using CFD. This paper has the purpose to discuss the feasibility of a procedure that uses CFD as the first step in a chain of numerical simulations that leads to the fatigue calculation of a large, complex structure.The state of the art of turbulence models for CFD is here shown by performing literature review, with particular attention to their application to case studies related to large steel structures. A special focus in this paper lies in the use of PANS models, which reduce computational cost and grid sensitivity compared with LES, while providing comparable accuracy.

To achieve efficient and accurate thick plate welding, as well as to precisely extract and plan the paths of complex three-dimensional weld seams in large steel structures, this study introduces a novel vision-guided approach for robotic welding systems utilizing a constant-focus laser sensor. This methodology specifically targets and mitigates several critical shortcomings inherent in conventional vision-guided welding techniques, including limited detection ranges, diminished precision in both detection and tracking, and suboptimal real-time performance. For preprocessed weld images, an improved grayscale extreme centroid method was developed to extract the center of the light stripe. Furthermore, a sophisticated feature point extraction algorithm, which integrates a maximum distance search strategy with a least-squares fitting procedure, was developed to facilitate the precise and timely identification of weld seam characteristic points. To further optimize the outcomes, a cylindrical filtering mechanism was employed to eliminate substantial discrepancies, whereas local Non-Uniform Rational B-Spline (NURBS) curve interpolation was utilized for the generation of smooth and accurate trajectory plans. A spatial vector-based pose adjustment strategy was then implemented to provide robust guidance for the welding robot, ensuring the successful execution of the welding operations. The experimental results indicated that the proposed algorithm achieved a tracking error of 0.3197 mm for welding workpieces with a thickness of 60 mm, demonstrating the method’s substantial potential in the manufacturing sector, especially in the domain of automated welding.

This paper investigates a new method of modeling and simulation of a two wheeled Mobile Manipulators (MMs) system each equipped with a 6 DOF arm. Such system modeled in Matlab/Simulink (Simmechanic) environment is used to transport objects without explicit communication between the MMs. MMs cooperation control has received big interest in the last few years and has been suggested for various applications such as tasks involving hazardous environments, explosive handling, and space operations. However most research in MMs cooperation has been performed within 2D flat terrain environment. In this paper MMs are considered working in 3D space and we use the nonholonomic characteristics of the robotic manipulators which has been neglected in previous work. This paper describes a control algorithm for two MMs cooperation executing cooperation’s tasks. The proposed approach uses common MM sensors. The paper includes the description of the proposed control mechanism that enables ground mobile manipulators to execute complex tasks in cooperation’s.

This paper introduces a novel and general real-time adaptive motion planning (RAMP) approach suitable for planning trajectories of high-DOF or redundant robots, such as mobile manipulators, in dynamic environments with moving obstacles of unknown trajectories. The RAMP approach enables simultaneous path and trajectory planning and simultaneous planning and execution of motion in real time. It facilitates real-time optimization of trajectories under various optimization criteria, such as minimizing energy and time and maximizing manipulability. It also accommodates partially specified task goals of robots easily. The approach exploits redundancy in redundant robots (such as locomotion versus manipulation in a mobile manipulator) through loose coupling of robot configuration variables to best achieve obstacle avoidance and optimization objectives. The RAMP approach has been implemented and tested in simulation over a diverse set of task environments, including environments with multiple mobile manipulators. The results (and also the accompanying video) show that the RAMP planner, with its high efficiency and flexibility, not only handles a single mobile manipulator well in dynamic environments with various obstacles of unknown motions in addition to static obstacles, but can also readily and effectively plan motions for each mobile manipulator in an environment shared by multiple mobile manipulators and other moving obstacles.

Mobile manipulators have attracted a lot of interest recently. This paper discusses the development of mobile manipulators in recent years in the aspect of motion planning and coordinated control between mobile platform and manipulator. An intelligent controller based on RBF neural network is introduced for the coordinating control of the mobile manipulator, which mimics human behavior. Simulation results was given out and the method has been applied on the Hebut-II mobile robot platform. Experimental results verified the validity of the method.

This paper is a summary of an effort to develop a powerful motion planning algorithm for the mobile manipulator. The mobile manipulator is expected to work in partially defined or unstructured environments. In our global/local approach to path planning, joint trajectories are generated for a desired Cartesian space path, designed by the global path planner. For local path planner, inverse kinematics for a redundant system is used. Obstacle avoidance and joint displacement limits for the manipulator links are considered in the motion planner. In an event of failure to obtain feasible trajectories, the task can not be accomplished. In the case of the joint constraint violation, use of Jacobian matrix element as gradient is proposed. At the point of failure, a derivation in the Cartesian space path is obtained and the re-planner gives a new path that would achieve the goal position. To calculate the deviation, a non-linear optimization problem is formulated and solved by standard sequential quadratic programming (SQP) method.

Objectives. The work analyzes features of one of the most promising approaches to solve the problems for motion planning of autonomous robotic manipulators of various types and purposes using the rapidly exploring random tree (RRT) method. The development of modern robotics is shown to be inextricably linked with the improvement of the designs of the created samples, for which the placement of a manipulator on platform becomes a typical layout option. Prospects for using the RRT method as a constructive basis for creating a universal motion planner are evaluated for mobile and robotic manipulators, including autonomous robotic systems with a manipulator on a moving platform.Methods. The object of the research is the RRT method and its well-known modifications RRT* and RRT-Connect. The effectiveness of applying such methods for solving problems associated with planning the motions of robotic manipulators of various types was evaluated using computer and natural simulation methods.Results. Based on a review of the literature and the results of the research, the wide possibilities of the RRT method can be used for solving motion planning problems not only for mobile and robotic manipulators, but also for robotic systems on whose transport platform an onboard manipulator has been installed (including those having a redundant or reconfigurable structure). The effectiveness of the applied application of the RRT method is confirmed by examples of modeling a mobile platform with an onboard manipulator and the results of full-scale experiments with a prototype of the ARAKS reconfigurable mechatronic-modular robotic manipulators (RTU MIREA, Russia). It can be experimentally demonstrated and theoretically substantiated that the final dimension of the exploring tree, and hence the time of its construction up to reaching a given target state, is largely determined by the value of the growth factor.Conclusions. The generalization of the results obtained opens up real prospects for using the RRT method as a constructive basis not only for creating universal means for motion planning mobile robotic systems with an onboard manipulator, but also for solving the problems of automating the docking of autonomous mobile platforms.

VLSI-efficient schemes for high-speed construction of tangent graph

Collapse of the spatial double-layer cylinder shell by experimental study

Ocean large steel structures are usually constructed on the slide site, being prone to forming large deformation because of its features such as heavy weight, large bulk and great span. However, the 18 large-scale steel structures of a nickel ore project are need to building on the non-slide foundation, resulting in different settlements of foundation. Moreover, the earthquake load is one of main load of the high-level structure. And the earthquake often happens suddenly and is out of control, with devastating destructive power. To ensure the safety of construction, it’s necessary to analyze the influence of large steel structure responding to the seismic load. This paper expounds the analyzing method on the response of the large steel structure based on non-slide site to the earthquake load. This article has analyzed responses of three-dimensional finite element model to the earthquake load with ANSYS analysis of finite element, such as the stress, deformation analysis, modal analysis and transient dynamic analysis, and assessed the risk of earthquake. This paper provides a feasible and effective analyzed method for researching the response of structure built on non-slide site to the earthquake load, which has important significance for the seismic design of the structure.

Fil: Roberti, Flavio. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - San Juan. Instituto de Automatica. Universidad Nacional de San Juan. Facultad de Ingenieria. Instituto de Automatica; Argentina

The current physical pre-assembly method of large steel structures is time consuming and costly and requires large sites. Thus, the pre-assembly of large steel structures in a virtual way, starting from building information modeling (BIM), is an interesting alternative to the physical one. In this study, an innovative method for virtual pre-assembly is proposed on the basis of BIM, plane-line-point algorithm, and 3D measurement. This method determines the optimal analytical least squares of the various built components. The technique verifies the feasibility of the steel structure assembly and the fulfillment of the design geometries, starting from the real data obtained by an accurate metric survey of the fabricated steel elements. The method is applied to a real case, and obtained results largely satisfy the prefixed research objectives. Suggestions to improve the proposed method are also discussed.