Fourier Descriptors with Different Shape Signatures:a Comparative Study for Shape Based Retrieval of Kinematic Constraints

Fourier Descriptors（FD） has been widely used in image analysis and computer vision for shape recognition as they can be made independent of translation,rotation,as well as scaling.They have also been used for developing methods for the analysis and synthesis of four-bar linkages for path generation.This paper focuses on a comparative study of Fourier descriptors derived from various shape signatures of planar closed curves.This includes representations based on Cartesian coordinates,centroid distance,cumulative angle,and curvature.The comparison is conducted not only using commonly used criteria for shape representation and identification but also in the context of shape based retrieval of kinematic constraints for task centered mechanism design.Examples are provided to seek to extract geometric constraints such as circle,circular arc,ellipse and line-segment from a given motion.

STABLE PROGRAMMED MANIFOLD SOLVER FOR VIRTUAL PROTOTYPING MOTION SIMULATION

Based on constructing programmed constraint and constraint perturbation equation, a kinematics and dynamics numerical simulation model is established for virtual mechanism, in which the difference scheme guarantee precision in simulation procedure and its mtmerical solutions satisfy programmed manifold stability. A crank-piston mechanism in a car engine, a steering mechanism and a suspension mechanism are simulated in a virtual environment, then comparing the simulation results with those obtained in ADAMS under the same circumstances proved the solver valid.

A Fast Approach for Time Optimal and Smooth Trajectory Planning of Robot Manipulators

In this paper, a fast approach to generate time optimal and smooth trajectory has been developed and tested. Minimum time is critical for the productivity in industrial applications. Meanwhile, smooth trajectories based on cubic splines are desirable for their ability to limit vibrations and ensure the continuity of position, velocity and acceleration during the robot movement. The main feature of the approach is a satisfactory solution that can be obtained by a local modification process among each intermal between two consecutive via-points. An analytical formulation simplifies the approach to smooth trajectory and few,iterations are enough to determine the correct values. The approach can be applied in many robot manipulators which require high performance on time and smooth. The simulation and application of the approach on a palletizer robot are performed, and the experimental results provide evidence that the approach can realize the robot manipulators more efficiency and high smooth performance.

Dynamic Simulation Analysis of the Flexible Swap Device

With the development of space science and technology,the on-orbit servicing technologies of spacecraft get more and more attention.According to the design criterion of existing spacecraft in orbit module replacement technology,the flexible swap device is designed and the dynamics simulation of institutions by the automatic dynamic analysis of mechanical systems(ADAMS)simulation software is analyzed.Throughout the analysis process,this paper studies the effect of collision force of flexible mechanism and provides a basis for the optimization of flexible plug agencies.

Dynamic Effect Research of Cable-Lead-In Rod on Towed System

This paper aims to research the cable-lead-in rod effect on a towed system through mathematical modeling and numerical simulations.The rod dynamics,as a key part of this study,is modeled using the combination of cable node governing equations and kinematic constraint conditions.As the first attempt to analyze such a problem,the rod is simply treated as an elastic cable segment so as to be incorporated into the dynamics of the cable,and a set of algorithm is then proposed based on the kinematic constraint conditions to fully describe its motions.Meanwhile,the cable and the underwater vehicle are modeled by the traditional lumped mass method and the 6 degree-of-freedom maneuverability equations for submarines respectively;the coupling boundary conditions besides the rod dynamics are also given to form the whole system's model.Several numerical cases are performed to investigate the rod effect on the system in different maneuver situations.Some meaningful conclusions are drawn through comparative analysis.