Using a neural network for predicting the average grain size in friction stir welding processes

In the paper the microstructural phenomena in terms of average grain size occurring in friction stir welding (FSW) processes are focused. A neural network was linked to a finite element model (FEM) of the process to predict the average grain size values. The utilized net was trained starting from experimental data and numerical results of butt joints and then tested on further butt, lap and T-joints. The obtained results show the capability of the AI technique in conjunction with the FE tool to predict the final microstructure in the FSW joints.     

Conceptual design and analysis of the 2T1R mechanism for a cooking robot

This paper deals with the design and analysis of a two-translation and one-rotation (2T1R) mechanism for a novel cooking robot. Firstly the motions involved in stir-fry, the most representative operation in the cooking processes used in Chinese cuisine, are analyzed in details. Then the featured motions are decomposed into four main movements that are used as a design base for a wok motion mechanism. Several three-degrees-of-freedom (DOF) parallel manipulators are considered. From these, a 2T1R mechanism is selected as an ideal candidate. A 4-DOF (2T1R+1T) cooking robot is constructed by combining the 2T1R parallel manipulator with a 1-DOF linear feed mechanism. It is shown that the combined 4-DOF robot can perform the required cooking operations, particularly the stir-fry. The analysis conducted on the proposed 2T1R parallel manipulator includes inverse kinematics, forward kinematics, the velocity analysis, the constant orientation workspace, and the total orientation workspace. A prototype of the cooking robot is developed. The experiments verify that the proposed cooking robot is suitable for performing the required operations.     

Preliminary design and manufacturing planning integration using web-based intelligent agents

Software agents have been increasingly used in the product and process development in industry over the past years due to the rapid evolvement of the Internet technology. This paper describes agents for the integration of conceptual design and process planning. Agents provide mechanisms to interact with each other. This mechanism is important since both of those processes involve negotiations for optimization. A set of design and planning software agents has been developed. These agents are used in a computer-based collaborative environment, called a multi-agent platform. The main purpose of developing such a platform is to support product preliminary design, optimize product form and structure, and reduce the manufacturing cost in the early design stage. The agents on the platform have access to a knowledge base that contains design and planning rules. These rules are derived from an analysis of design factors that influence process and resource planning, such as product material, form, shape complexity, features, dimension, tolerance, surface condition, production volume, and production rate. These rules are used by process planning agents to provide process planners with information regarding selecting preliminary manufacturing processes, determining manufacturing resources, and constructing feedback information to product designers. Additionally, the agents communicate with WEB servers, and they are accessible by users through Internet browsers. During performing design and planning tasks, agents access the data pertinent to design and manufacturing processes by the programming interfaces of existing computer-aided design (CAD) and manufacturing system. The agents are supported by a developed prototype agent platform. The agents and the platform enable the information exchange among agents, based on a previously developed integrated design and manufacturing process object model.     

A shape optimization study for tool design in resistance welding

The purpose of this study is to apply shape optimization tools for design of resistance welding electrodes. The numerical simulation of the welding process has been performed by a simplified FEM model implemented in COMSOL. The design process is formulated as an optimization problem where the objective is to prolong the life-time of the electrodes. Welding parameters like current, time and electrode shape parameters are selected to be the design variables while constraints are chosen to ensure a high quality of the welding. Surrogate models based on a Kriging approximation has been used in order to simplify the calculation of shape sensitivities and to generate a generic tool that can be interfaced with other simulation tools. An example numerical study shows the potential of applying optimal design techniques in this area. Part of this work was presented at WCSMO7 in Seoul Korea, May 21–25, 2007, in the paper titled ‘Some optimization aspects of resistance welding’ (CD-ROM, pp 2687–2695).     

A Scalable Intelligent Takeoff Controller for a Simulated Running Jointed Leg

Running with jointed legs poses a difficult control problem in robotics. Neural controllers are attractive because they allow the robot to adapt to changing environmental conditions. However, scalability is an issue with many neural controllers. This paper describes the development of a scalable neurofuzzy controller for the takeoff phase of the running stride. Scalability is achieved by selecting a controller whose size does not grow with the dimensionality of the problem. Empirical results show that with proper design the takeoff controller scales from a leg with a single movable link to one with three movable links without a corresponding growth in size and without a loss of accuracy.     

Optimal design and workspace analysis of a mobile welding robot with a 3P3R serial manipulator

This paper presents the design optimization of a mobile welding robot based on the analysis of its workspace. A welding robot has been developed to be used inside the double-hull structure of ships, and it shows good welding functionality. But there is a need to optimize the kinematic variables ensuring that the required welding functions inside the ships are satisfied. The task-oriented workspace, which is the workspace enabling specific rotations, has been defined in order to validate the welding ability of the robot, and incorporating the required rotational capabilities. To calculate the workspace, a geometric approach is adopted which considers the pitching and yawing angles simultaneously. Based on the workspace analysis, a scenario is compiled for considering a mass reduction, and a ratio between the design parameters and the workspace, with constraints on the workspace margins. The proposed optimization procedure is composed of two steps of coarse and fine searching. In the coarse searching step, a feasible parameter region (FPR) is defined, which satisfies the geometrical design constraints, and can be obtained without any considerations of the objective functions. In the fine searching step, the design parameters are determined by using the optimization technique of the conjugate gradient method in the overall FPRs. The suggested approach to calculating the task-oriented workspace, and the procedure of optimal design, are expected to be applied to general industrial robots.     

焊接机器人图像传感器噪声分析

焊接机器人获取焊缝的计算机视觉信息过程中,由于工件表面的反光系数,光学镜头性能的非线性,光电转换时叠加了随机噪声;信号电荷的存储、传输和输出存在暗电流等噪声;视频信号传输时存在噪声;视频信号模数转换存在量化噪声,导致获取的二维数字图像信号有一定的误差。为了减小此误差对后续的图像处理的影响,对图像传感器的图像噪声进行了分析,并得到了一个经验的图像噪声模型,实验结果表明:该模型有效且实用。     

两轮自平衡机器人控制系统的设计

针对自行设计的两轮自平衡机器人Opyanbot建立了动力学模型,应用最优控制和两轮差动等控制方法设计了控制器,提出了针对两轮自平衡机器人平衡和行进的新策略。为了提高两轮自平衡机器人的控制效果,利用基于DSP数字电路的全数字智能伺服驱动单元IPM100分别精确控制左右轮电机,并利用上位机实时控制机器人的运动状态,提高了控制精度、可靠度和集成度,得到了很好的控制效果。     

Artificial Neural Network Application to the Friction Stir Welding of Al 6061 Alloy to Stainless Steel 304

The joining of a 6-mm thickness Al 6061 to Stainless steel 304 has been performed by solid state welding. A selection method of optimum friction welding condition using neural networks is proposed. The data used for analyses are the friction stir welding condition, the input parameters of the model consist of welding speed and tool rotation speed. The outputs of the ANN (Artificial Neural Network)model includes resulting parameters, namely, maximum reached temperature,and heating rate for both aluminum allo...     

Design of a teaching pendant program for a mobile shipbuilding welding robot using a PDA

Teaching pendant is a handheld device by which a human can control a robot. The main functions of a teaching pendant are moving the robot, teaching it about the locations, running robot programs, and jogging the axes. A teaching pendant is usually connected to the robot by a cable. The cable connection and the size of the teaching pendant generally do not pose a problem when the robot controller is separate from the robot. However, a large teaching pendant connected by a cable is not suitable for a self-propelled mobile robot with an internal controller. This paper describes the communication network of a personal data assistant (PDA) as a wireless teaching pendant for a mobile shipbuilding welding robot with embedded controller system that welds and moves autonomously inside the double hull structure of a ship. A double hull is a closed structure that has only a few access holes. It is very difficult and dangerous to weld components inside a double hull structure because of fumes, poisonous gas, and high temperatures. Using a wireless teaching pendant has the following advantages: (1) there are no limits to the welding activities that can take place, (2) the safety level increases because no workers are in close proximity to the robot, (3) workers are far away from the dangerous environmental conditions, (4) it is possible to reduce the weight of the cable connected to the robot, and (5) it is possible to reduce the weight of the robot because of the reduced load of the teaching pendant and the cable. We demonstrate the functionality and performance capabilities of our wireless teaching pendant through field-testing experiments.     

Experimental control of a single-link flexible robot arm using energy shaping

Flexible-link robotic manipulators are mechanical devices whose control can be rather challenging, among other reasons because of their intrinsic under-actuated nature. This paper presents the application of an energy-based control design methodology (the so-called IDA-PBC, interconnection and damping assignment passivity-based control) to a single-link flexible robotic arm. It is shown that the method is well suited to handle this kind of under-actuated device not only from a theoretical viewpoint but also in practice. A Lyapunov analysis of the closed-loop system stability is given and the design performance is illustrated by means of a set of simulations and laboratory control experiments, comparing the results with those obtained using conventional control schemes for mechanical manipulators.     

Development and application of an intelligent welding robot system for shipbuilding

Over the last few decades, there have been a large number of attempts to automate welding in the shipbuilding process. However, there are still many non-automated welding operations in the double-hulled blocks, even though it presents an extremely hazardous environment for the workers. And, the hazards come about mainly because of the dimensional constraints of the access-hole. Thus, much effort has been recently directed toward the research on compact design of the fully-autonomous robot working inside of the double-hulled structures. This paper describes the design, integration, simulations, and field testing trials of a new type of welding robotic system, the RRXC, which is composed of a 6-axis modularized controller, a 3P3R serial manipulator, and an auxiliary transportation device. The entire cross section of the RRXC is small enough to be placed inside the double-hulled structures via a conventional access hole of 500×700 mm², from the outside shipyard floor. The weight of the manufactured RRXC is 60 kg, with a 6-axis manipulator and modularized controller, and the weight of an auxiliary transportation device is 8 kg, with a 2.5 m steel wire of 6Φ. Throughout the field tests in the enclosed structures of shipbuilding, the developed RRXC has successfully demonstrated welding functions without the use of any additional finishing by manual welders, and has shown good mobility using an auxiliary transportation device in double-hulled structures.     

Information management for integrated design environments

This paper identifies requirements for an engineering design information management system. Future CAD systems must support a wide range of activities — such as definition, manipulation and analyses of complex product information models. These models represent not only conventional data associated with current CAD applications, but also design information characterizing the correlations between the requirements, functions, behaviors and physical form of the product. Such functionality is important for both the individual designer and the design organization, as the need to manage information as a corporate asset is becoming a critical component of business strategy. This paper explores these needs using two design studies. The first study illustrates some major concepts relative to non-routine design activities, while the second study focuses on the routine design activities relative to organization interactions. These studies were used to elicit high level requirements which serve as the basis for the development of prototype software systems. These prototypes are briefly introduced here.     

Developing an expert system to assist in control system design

This paper addresses the problem of how to develop an expert system that is able to design or to assist in the design of a control system. The discussion includes how to structure the expert system, how to choose the relationship between the symbolic and numerical processor and how to divide the work among the expert system, the computer aided control systems analysis package and the design engineer. A prototype intelligent design associated is presented and an example of a compensator design is given.     

A form verification system for the conceptual design of complex mechanical systems

This paper presents a summary of research into the development and implementation of a domain-independent, computer-based model for the conceptual design of complex mechanical systems [1]. The creation of such a design model includes the integration of four major concepts: (1) the use of a graphical display for visualizing the conceptual design attributes: (2) the proper representation of the complex data and diverse knowledge reguired to design the system; (3) the integration of quality design methods into the conceptual design: (4) the modeling of the conceptual design process as a mapping between functions and forms. Using the design of an automobile as a case study, a design environment was created which consisted of a distributed problem-solving paradigm and a parametric graphical display. The requirements of the design problem with respect to data representation and design processing were evaluated and a process model was specified. The resulting vehicle design system consists of a tight integration between a blackboard system and a parametric design system. The completed system allows a designer to view graphical representations of the candidate conceptual designs that the blackhoard system generates.     

Impact of CAD tools on creative problem solving in engineering design

This paper presents the results of a survey of CAD users that examined the ways in which their computational environment may influence their ability to design creatively. This extensive online survey builds upon the findings of an earlier observational case study of the use of computer tools by a small engineering team. The case study was conducted during the conceptual and detailed stages of the design of a first-to-world product. Four mechanisms by which CAD tools may influence the creative problem solving process were investigated: enhanced visualisation and communication, circumscribed thinking, premature design fixation and bounded ideation. The prevalence of these mechanisms was examined via a series of questions that probed the user’s mode of working, attitudes, and responses to hypothetical situations. The survey showed good support for the first three mechanisms and moderate support for the fourth. The results have important implications for both the users and designers of CAD tools.     

Adaptive bearing friction compensation based on recent knowledge of dynamic friction

Gimbal bearing friction is a major source of stabilization errors for airborne pointing and tracking systems. This paper describes a novel addition to conventional stabilization techniques which has recently been incorporated in such a system to greatly improve stabilization performance. This addition contains a model in system software which predicts realtime friction torque values. This new, dynamic friction model, which is the result of recent investigations into dynamic friction characteristics, is adaptively adjusted into agreement with actual friction behavior by processing inputs from conventional system sensors. Measurements from these sensors cause on-line adjustment of model parameters, resulting in ‘adaptive’ compensator action. The model's output is used to generate an addition to conventional stabilization subsystem commands. The resulting additional gimbal motor torque is equal and opposed to the actual friction disturbance such that the residual torque, and hence stabilization errors, are a small fraction of those for an uncompensated system. The model-referenced compensator thus operates in a predictive, adaptive, feedforward manner to pre-condition the stabilization subsystem, reducing stabilization errors well below levels which are achievable through conventional feedback operation alone.     

搅拌摩擦焊接机器人大型薄壁零件空间曲线焊缝测量与轨迹生成

针对大型金属薄壁零件制造、装夹变形后的空间曲线焊缝加工轨迹尤其是零件空间法矢难以确定的问题,提出了一种通过测量焊缝上离散点计算刀位点并估计空间法矢的方法.首先,利用搅拌摩擦焊接(FSW)机器人末端安装的接触式测头碰触焊缝进行测量,再利用三次样条拟合一系列测得的空间点,得到一条与真实焊缝距离为1倍测头球心半径的空间曲线;其次,通过最小二乘法求出众多测量点的最小二乘平面;以最小二乘平面内焊缝曲线投影的面内法矢估计实际焊缝曲线的空间法矢.最后,将拟合曲线上用弦高差法离散得到的伪刀位点沿其空间法矢的负向平移1倍测头球心半径的距离,作为真正的刀位点.仿真实验表明本文的研究为大型复杂薄壁回转体零件的搅拌摩擦焊接提供了一种不必测量整个曲面便可得到焊接刀位点和法矢的有效方法.