Applied Mechanics and Materials Vol. 162

Abstract: Starting from the analysis of the modern robotic arc welding system from the kinematic point of view, the paper presents an original concept of the systems structure. Instead a combination of two open chains, as it is generally seen, the author proposes one single closed kinematic chain. The main element of this chain is the electric arc employed for welding, virtually seen as a vector which connects the two open chains, the robot and the part manipulator. This new approach could possibly change and simplify the way arc welding robots are programmed today.

Abstract: In this article, the authors aim to develop a method for determining the components errors of a robotic welding cell, using coordinate transformations between the reference systems attached to the cells components. Errors are expressed as matrices, as it is usual in the mathematical expressions used in robotics. Errors mathematical modeling refers to the positioning error and also to the orientation error. Therefore, a test cube is used. The experiments presented in the paper, approaches only the positiong error (AP). The method is used for measuring the pose errors of a welding cell, using two theodolits. The method is based on measuring the coordinates of a target characteristic point TCP, the corner of a test cube, relative to a coordinate system attached to one of the two theodolits. It is part of the no contact measurement methods. The main principles of the method and its theoretical basis are validated by experiments, conducted in a welding cell, using a robot CLOOS-Romat in the Robotics Laboratory of the University "Politehnica" of Timisoara.

Abstract: This paper deals with electric arc robotic welding, the main objective being the optimal structure configuration of the flexible Robotic Welding Cells (RWC). To this purpose, the authors propose a new algorithm for the configuration of the cell structure based on a set of optimization criteria. Thus, to determine the optimum RWC structure, the working cycle of the technological welding process and some process parameters influencing the welded ensemble are improved as well.

Abstract: This paper presents current technologies used for pipe welding. Welding processes such as Tandem and Hybrid (Laser-GMAW) welding are compared to regular 1-wire GMAW. The device used for positioning the welding head is an anthropomorphic robot, as this type of robot provides everything needed for the application: low cost, flexibility, sufficient payload and precision.

Abstract: This paper describes a tactile display for softness feelings with a function of controlling contact area and pressure distribution. Contact area between a fingertip and a display is controlled by wrapping a flexible film around a finger. An active tensioner controls the tension of the flexible film to modify the contact pressure distribution. Controlling both area and pressure distribution realizes rendering of wider range of softness feelings. The effect was verified using photoelastic phenomenon. The experimental results show that the display can render the different contact conditions that arise from two differently-felt sponge samples with different thicknesses.

Abstract: This paper describes high speed non-contact object handling with one degree-of-freedom magnetic levitation. Feed-forward tilt control using an industrial robot realizes large acceleration and tilt angle. Experimental results demonstrate the transportation with the maximum acceleration of 7.31 m/s² and maximum tilt angle of 36^o. This acceleration is seven times higher than the previously performed experiments. Tracking error associated with high speed motion causes lateral vibration of the object. This paper also introduces iterative learning control (ILC) to improve trajectory tracking. Experimental results show that ILC reduces the tracking error; nevertheless the lateral vibration still remains.

Abstract: The capabilities of a biaxial camera system to verify control loops are investigated here with the verification of a Cartesian robot. The biaxial camera system will serve in the future as a tool to investigate the three-dimensional trajectories of insects, projectiles and other airborne devices. Three-dimensional motion is measured by means of two cameras arranged at right angles to each other with a common focal point. Control loop instructions to the robot allow it to simulate a circular orbit. The control system for the Cartesian robot is documented. The biaxial camera system allows an elliptical least-squares minimization algorithm to be employed to measure the phenomenon produced by the Cartesian robot.

Abstract: Among region-based descriptors, geometric moments have been widely exploited to design visual servoing schemes. However, they present several disadvantages such as high sensitivity to noise measurement, high dynamic range and information redundancy (since they are not computed onto orthogonal basis). In this paper, we propose to use a class of orthogonal moments (namely Legendre moments) instead of geometric moments to improve the behavior of moment-based control schemes. The descriptive form of the interaction matrix related to the Legendre moments computed from a set of points is rst derived. Six visual features are then selected to design a partially-decoupled control scheme. Finally simulated and experimental results are presented to illustrate the validity of our proposal.

Abstract: A fabric defect detection system based on single-point photoelectric sensing, was proposed and developed. The performance of the system was enhanced by using wavelet denoising algorithm to reduce the negative effect of noise and the environment disturb, such as fluorescent light in the factory. Instead of detection of light reflection from fabric, a light transmission technique with higher signal-to-noise rate was employed in the system for evaluating the fabric defect. A Si photodiode was used to record the defect signal of fabric. The signal was enhanced by stationary wavelet transform. The signal was quantitatively evaluated and finally a defect alarm was triggered. From the experimental results, the timeliness, robustness and detection precision of the system were demonstrated, therefore, it could be recommended for the applications in fabric industries.

Abstract: In this paper, an algorithm dedicated to light ATVs, which estimates and anticipates the rollover, is proposed. It is based on the on-line estimation of the Lateral Load Transfer (LLT), allowing the evaluation of dynamic instabilities. The LLT is computed thanks to a dynamical model split into two 2D projections. Relying on this representation and a low cost perception system, an observer is proposed to estimate on-line the terrain properties (grip conditions and slope), then allowing to deduce accurately the risk of instability. Associated to a predictive control algorithm, based on the extrapolation of riders action, the risk can be anticipated, enabling to warn the pilot and to consider the implementation of active actions.