A direct algorithm for continuous path control of manipulators

This paper presents an algorithm for positioning and orientation of the hand for a redundant or non-redundant manipulator along a continuous path in space. This algorithm minimizes the distance between the actual position of the tip of the end-effector and the desired path. The algorithm does not use the Jacobian matrix for the inverse kinematics of the robot. It takes full advantage of the resolution of the joint drives, avoids singularity problems, and can be used for both redundant manipulators. The algorithm can be used in any situation where continuus motion of the end-effector is required in an open loop mode.     

Optimal robot task scheduling based on genetic algorithms

Industrial robots should perform complex tasks in the minimum possible cycle time in order to obtain high productivity. The problem of determining the optimum route of a manipulator's end effector visiting a number of task points is similar but not identical to the well-known travelling salesman problem (TSP). Adapting TSP to Robotics, the measure to be optimized is the time instead of the distance. In addition, the travel time between any two points is significantly affected by the choice of the manipulator's configuration. Therefore, the multiple solutions of the inverse kinematics problem should be taken into consideration.In this paper, a method is introduced to determine the optimum sequence of task points visited by the tip of the end effector of an articulated robot and it can be applied to any non-redundant manipulator. This method is based on genetic algorithms and an innovative encoding is introduced to take into account the multiple solutions of the inverse kinematic problem. The results show that the method can determine the optimum sequence of a considerable number of task points for robots up to six-degrees of freedom.     

Reducing the Complexity of Robot's Scene for Faster Collision Detection

In many real-life industrial applications such as welding and painting, the hand tip of a robot manipulator must follow a desired Cartesian curve while its body avoids collisions with obstacles in its environment. Collision detection is an absolutely essential task for any robotic manipulators in order to operate safely and effectively in cluttered environments. A significant factor that influences the complexity of the collision detection problem is the obstacles' density, i.e., the total number of obstacles in the robot's environment.In this paper, a heuristic algorithm for approximating the collision detection problem into a simpler one is presented. The algorithm reduces the number of obstacles that must be examined during the robot's motion by applying efficient techniques from computational geometry. The algorithm runs in time O(max(n ² log m, n m)) , and uses O(n ² + m n) space; with n being the number of obstacles in the robot's workspace, and m the total number of obstacles' vertices. Both costs are worst-case bounds.     

Task scheduling and motion planning for an industrial manipulator

In many robotic industrial applications, a manipulator should move among obstacles and reach a set of task-points in order to perform a pre-defined task. It is quite important as well as very complicated to determine the time-optimum sequence of the task-points visited by the end-effector's tip only once assuring that the manipulator's motion through the successive task-points is collision-free.     

An integrated mechatronic approach for the systematic design of force fields and programming of microactuator arrays for micropart manipulation

Micromanipulation is a hot topic in the rapidly emerging area of micromechatronics and particularly in the manufacturing and assembling of micromechatronic products. This paper introduces an integrated mechatronic approach for the systematic design and operation of flexible, sensorless, automated micromanipulation for a variety of microparts on microactuation arrays. This approach is a mechatronic synthesis of methods from different engineering areas such as solid modeling, electronics design, software for control and programming of mechanical actuation. It involves designing of programmable force fields for manipulation of convex or non-convex polygonal microparts on an array, hardware programmable circuitry for the activation of the array and a software algorithmic procedure for the programming. A detailed analysis is given, as well as several simulated experiments performed using the introduced approach on a cilia microactuator array for a variety of polygonal asymmetric and non-convex microparts and the results are presented and discussed. Finally, the advantages and limitations of this approach are analyzed and points for further research are raised.     

Torsional fatigue life reduction in turbogenerator shafts due to large scale disturbances under fast valving control

Contents The use of fast valving control may have a significant effect on life reduction due to torsional fatigue of rotor shafts. In this paper an analytical and numerical study has been applied to calculate the fatigue life reduction for large scale transient electrical disturbances under speed governor control of turbogenerator with reheater and under modern fast-valving control in the intercept valve after the reheater. —Finally, the fatigue life reduction was compared to the improvement of first swing stability under the two control systems.

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Torsionsalterung der Wellen von Turbogeneratoren infolge von Netzstörungen bei Einsatz eines schnellen Dampf-Zwischenventils

Übersicht Die Anwendung des Drehzahlregelsystems mit schnellem Dampfzwischenventil kann bedeutende Konsequenzen auf die Lebensminderung von Rotorachsen wegen Torsionsalterung haben. In dei vorliegenden Arbeit wird eine analytische-arithmetische Methode untersucht, die zur Berechnung der Lebensminderung der Wellen im Übergangszustand nach großen elektrischen Netzstörungen auftreten. —Außerdem wird ein Vergleich der Rechenergebnisse durchgeführt, die für ein Drehzahlregelsystem mit und ohne schnellem Zwischenventil festgestellt wurden.

     

Transformation and Normal Vector Calculation of Parametrically Defined Surfaces Based on Dual Vectors and Screw Theory: Application to Phong's Shading Model

This paper presents a new approach for the transformation and normal vector calculation algorithms of parametrically defined surfaces via dual vectors and line transformations. The surface is defined via dual points, the transformation is performed by rotations and translations based on screw theory while normal vector calculation is utilized for shading based on Phong's illumination model. The main benefit of this approach lies into the compactness of the surface's representation since geometrical characteristics, such as tangent vectors, that are necessary for shading algorithms, are included within its definition. An extensive comparison is performed between the proposed approach and the traditional homogeneous model, presenting the merits of our approach. Analytical and experimental determination of the computational cost via computer implementation of 3D surface transformation and shading is presented. Point‐based methods for the representation, transformation and shading of parametrically defined surfaces are compared to the introduced line‐based methods (dual quaternions and dual orthogonal matrices). It is shown that the simplified rendering procedure of 3D objects, is considerably faster using screw theory over the traditional point‐based structures.     

Collision-Free Cartesian Trajectory Generation Using Raster Scanning and Genetic Algorithms

An algorithm for Cartesian trajectory generation by redundant robots in environments with obstacles is presented. The algorithm combines a raster scanning technique, genetic algorithms and functions for interpolation in the joint coordinates space in order to approximate a desired Cartesian curve by the robot's hand tip under maximum allowed position deviation. A raster scanning technique determines a minimal set of knot points on the desired curve in order to generate a Cartesian trajectory with bounded position approximation error. Genetic algorithms are used to determine an acceptable robot configuration under obstacle avoidance constraints corresponding to a knot point. Robot motion between two successive knot points is finally achieved using well known interpolation techniques in the joint coordinates space. The proposed algorithm is analyzed and its performance is demonstrated through simulated experiments carried out on planar redundant robots.     

INTEGRATING PATH PLANNING,ROUTING, AND SCHEDULING FOR LOGISTICS OPERATIONS IN MANUFACTURING FACILITIES

This article considers the following manufacturing/logistics problem: an autonomous vehicle (AV) is requested to serve a set of pickup and delivery (P/D) stations in the shop floor of a modern factory providing P/D tasks while moving safely (i.e., avoiding any collision with obstacles) in its environment. A two-sided time window associated with each P/D station brackets the service time to within a specified interval. A tour for AV is considered legal if it (a) is collision free, (b) passes through each P/D station exactly once, and (c) satisfies the service time restrictions imposed by the P/D stations. A legal tour always starts and ends at a depot. The problem is thereby dual NP-hard because it combines the characteristics of path planning and those of vehicle routing and scheduling problems. The objective is to determine the shortest possible legal tour for AV. A new method is introduced to solve the problem accomplished in two successive phases: first, AV's environment is mapped into a 2D B-spline surface embedded in 3D Euclidean space using a robust geometric model. Then, the generated surface is searched using a genetic algorithm for an optimum legal tour that satisfies the requirements of the vehicle's mission. The performance of the proposed method is investigated and discussed through characteristic simulated experiments.     

Adaptive Tracking Controller for Rigid-Link Elastic-Joint Robots with Link Acceleration Estimation

This paper presents a adaptive switching control scheme for elastic joint robot manipulators. The characteristics of both flexible and rigid subsystems are assumed unknown except the joint stiffness. An adaptive estimator compensates the uncertainty due to the unknown robot characteristics. The actuators and links position, velocity and an estimation of the link acceleration are used as feedback to the control law. A filter is designed to estimate the links acceleration and its accuracy is insured by the linear control theory. Lyapunov theory is used to verify the asymptotic stability of the control law. The performance of the proposed control method is tested using a simulated planar robot with two rotational degrees of freedom for high and low joint stiffness.