Sensitivity of Buckling Load and Vibration Frequency with Respect to Shape of Stiffened and Unstiffened Plates

ABSTRACT

The method of calculating the sensitivities of buckling loads and vibration frequencies of nonlinear plates with respect to shape functions is presented. These shape functions describe the external shape of an unstiffened plate or the shape of a stiffener within the domain of a plate with fixed external boundaries. An adjoint variable method is used to determine the sensitivities. Thus, only one additional solution for an adjoint plate is required.     

Optimal strokes for axisymmetric microswimmers

We present a theory for low-Reynolds-number axisymmetric swimmers and a general strategy for the computation of strokes of maximal efficiency. An explicit equation characterizing optimal strokes is derived, and numerical strategies to obtain solutions are discussed. The merits of this approach are demonstrated by applying it to two concrete examples: the three linked spheres of Najafi and Golestanian and the pushmepullyou of Avron, Kenneth, and Oakmin.     

L'espace articulaire de la Robotique Industrielle est un espace vectorielIndustrial Robotics joint space is a vector space

The mathematical modelling of industrial robots is based on the vectorial nature of the n-dimensional joint space of the robot, defined as a kinematic chain with n degrees of freedom. However, in our opinion, the vectorial nature of the joint space has been insufficiently discussed in the literature. We establish the vectorial nature of the joint space of an industrial robot from the fundamental studies of B. Roth on screws. To cite this article: B. Tondu, C. R. Mecanique 331 (2003).     

Recognizing polygonal parts from width measurements

Automatic recognition of parts is an important problem in many industrial applications. One model of the problem is: given a finite set of polygonal parts, use a set of “width” measurements taken by a parallel-jaw gripper to determine which part is present. We study the problem of computing efficient strategies (“grasp plans”), with the goal to minimize the number of measurements necessary in the worst case. We show that finding a minimum length grasp plan is -hard, and give a polynomial time approximation algorithm that is simple and produces a solution that is within a log factor from optimal.     

机器人工程专业课程建设的思考与实践

我国自2015年开始机器人工程专业本科教育,目前开设机器人工程专业的高校已达301个,机器人工程专业教育呈现出快速发展的态势。与此同时,机器人工程专业在专业内涵、知识体系和课程体系建设上还存在一些矛盾和模糊之处,本文结合东北大学机器人工程专业建设、课程体系和机器人学课程建设等方面情况进行梳理,给出了机器人工程专业课程体系及机器人学课程建设的相关建议。     

Autonomous control of complex systems: robotic applications

One of the biggest challenges of any control paradigm is being able to handle large complex systems under unforeseen uncertainties. A system may be called complex here if its dimension (order) is too high and its model (if available) is nonlinear, interconnected, and information on the system is uncertain such that classical techniques cannot easily handle the problem. Soft computing, a collection of fuzzy logic, neuro-computing, genetic algorithms and genetic programming, has proven to be a powerful tool for adding autonomy to many complex systems. For such systems the size soft computing control architecture will be nearly infinite. Examples of complex systems are power networks, national air traffic control system, an integrated manufacturing plant, etc. In this paper a new rule base reduction approach is suggested to manage large inference engines. Notions of rule hierarchy and sensor data fusion are introduced and combined to achieve desirable goals. New paradigms using soft computing approaches are utilized to design autonomous controllers for a number of robotic applications at the ACE Center are also presented briefly.     

Applications of Optimization Strategies in the Design of Intelligent Laboratory Robotic Procedures

Abstract

Laboratory robots are being used to perform sample preparation and routine analytical determinations 1,2. In addition to these routine applications, laboratory robots should be able to analyze the analytical procedure itself and select the optimal experimental condition for any analytical method. The application of the fixed-sized SIMPLEX algorithm, the Nelder and Mead variable sized SIMPLEX algorithm and response surface fitting methods in analytical robotics is presented ³.     

The Erdős–Nagy theorem and its ramifications

Given a simple polygon in the plane, a flip is defined as follows: consider the convex hull of the polygon. If there are no pockets do not perform a flip. If there are pockets then reflect one pocket across its line of support of the polygon to obtain a new simple polygon. In 1934 Paul Erdős introduced the problem of repeatedly flipping all the pockets of a simple polygon simultaneously and he conjectured that the polygon would become convex after a finite number of flips. In 1939 Béla Nagy proved that if at each step only one pocket is flipped the polygon will become convex after a finite number of flips. The history of this problem is reviewed, and a simple elementary proof is given of a stronger version of the theorem. Variants, generalizations, and applications of the theorem of interest in computational knot theory, polymer physics and molecular biology are discussed. Several results in the literature are improved with the application of the theorem. For example, Grünbaum and Zaks recently showed that even non-simple (self-crossing) polygons may be convexified in a finite number of suitable flips. Their flips each take Θ(n²) time to determine. A simpler proof of this result is given that yields an algorithm that takes O(n) time to determine each flip. In the context of knot theory Millet proposed an algorithm for convexifying equilateral polygons in 3-dimensions with a generalization of a flip called a pivot. Here Millet's algorithm is generalized so that it works also in dimensions higher than three and for polygons containing edges with arbitrary lengths. A list of open problems is included.     

A task oriented haptic gait rehabilitation robot

This paper presents the concept, design process, and the prototype of a novel haptics-based lower-extremity rehabilitation robot for bed-ridden stroke patients. This system, named Virtual Gait Rehabilitation Robot (ViGRR), is required to provide the average gait motion training as well as other targeted exercises such as leg press, stair stepping and motivational gaming, in order to facilitate motor learning and enable the training of daily activities such as walking and maintaining balance. The system requirements are laid out and linked to the design of a redundant planar 4DOF robot concept prototype. An iterative design optimization loop was setup to obtain the robot kinematic and dynamic parameters as well as the actuators. The robot’s mechanical design, model, safety features, admittance controllers, and the architecture of the haptic controller are presented. Preliminary experiments were planned and performed to evaluate the capability of the system in delivering task-based virtual-reality exercises and trajectory following scenarios.