Motion Planning Algorithms of Redundant Manipulators Based on Self-motion Manifolds

The current motion planning approaches for redundant manipulators mainly includes two categories： improved gradient-projection method and some other efficiency numerical methods. The former is excessively sensitive to parameters, which makes adjustment difficult; and the latter treats the motion planning as general task by ignoring the particularity, which has good universal property but reduces the solving speed for on-line real-time planning. In this paper, a novel stepwise solution based on self-motion manifold is proposed for motion planning of redundant manipulators, namely, the chief tasks and secondary tasks are implemented step by step. Firstly, the posture tracking of end-effector is achieved accurately by employing the non-redundant joint. Secondly, the end-effector is set to keep stationary. Finally, self-motion of manipulator is realized via additional work on the gradient of redundant joint displacement. To verify this solution, experiments of round obstacle avoiding are carried out via the planar 3 degree-of-~eedom manipulator. And the experimental results indicate that this motion planning algorithm can effectively achieve obstacle avoiding and posture tracking of the end-effector. Compared with traditional gradient projection method, this approach can accelerate the problem-solving process, and is more applicable to obstacle avoiding and other additional work in displacement level.

Self-motion Manifolds of an 8-DOF Non-holonomic Mobile Manipulator

For the non-holonomic constraint robot,determining the pose of its end-effector will rely on its joints' displacement and the velocity of its non-holonomic constraint joints as well.Therefore,it becomes increasingly difficult to obtain the analytic solution of its self-motion manifold in the traditional way for solving matrix equation.In this paper,we take the pose of end manipulator as the result of the joint sequential motion based on the mentality of motion equivalence,the structure and the reference velocity which correspond precisely to the points in self-motion manifold as self-motion variable.Thus an analytical solution for the self-motion manifold of the 8 degree of freedom wheeled mobile manipulator is presented by taking vector algebra as a tool,which facilitates deriving the closed solution of its self-motion manifold.In the closing part of this paper,calculating examples of self-motion manifold and mechanism self-motion simulation are proposed,which proves the validity of solution algorithm for self-motion manifold.

A Coordinate-Free Approach to the Design of Generalized Griffis-Duffy Platforms

Architectural singularity belongs to the Type II singularity,in which a parallel manipulator(PM)gains one or more degrees of freedom and becomes uncontrollable.PMs remaining permanently in a singularity are beneficial for linearto-rotary motion conversion.Griffis-Duffy(GD)platform is a mobile structure admitting a Bricard motion.In this paper,we present a coordinate-free approach to the design of generalized GD platforms,which consists in determining the shape and attachment of both the moving platform and the fixed base.The generalized GD platform is treated as a combination of six coaxial single-loop mechanisms under the same constraints.Owing to the inversion,hidden in the geometric structure of these single-loop mechanisms,the mapping from a line to a circle establishes the geometric transformation between the fixed base and the moving platform based on the center of inversion,and describes the shape and attachment of the generalized GD platform.Moreover,the center of inversion not only identifies the location of rotation axis,but also affects the shape of the platform mechanism.A graphical construction of generalized GD platforms using inversion,proposed in the paper,provides geometrically feasible solutions of the manipulator design for the requirement of the location of rotation axis.

Gravitation and the Unified Nature of All Kinds of Motion in Non-Empty Space (Part 1)

The presented work examines the mechanism and conditions of self-motion in bodies as systems of interacting elements. It is shown how the oscillation parameters of these elements determine the mode of motion of the system (body). In this case, the motion is considered as a consequence of symmetry breaking of forces in the systems themselves, and not as a reaction of individual elements to external influences. It is shown that such a violation takes place both in the gravitational field and when the system moves by inertia. Examples of the influence of changes in phase (φ) and frequency (f) parameters of the system elements on the velocity mode of its motion in space are considered. The identity of the causes of self-motion is revealed both in the case of gravitation and inertial motion.

WNBTE网页正文抽取方法研究

WNBTE是一种基于文本字数统计信息,从网页中抽取正文内容的方法。该方法分析网页上存在的各种文字及其特点,寻找网页中包含字符数最多的结点,去掉该结点内的布局文字和说明文字,从而得到正文信息。该方法不需要人工参与,也不需要样本学习,克服了传统网页内容抽取方法中需要根据不同数据源构造不同抽取器的问题。

体育绘图课教学中如何培养学生的教育能力

针对目前教学中只努力教会学生,而忽略使学生会教的教学现象,提出如何在教学中培养学生的教育能力,从而对教育能力和自我教育有个再认识。

Cortical Mechanisms of Multisensory Linear Self-motion Perception

Accurate self-motion perception,which is critical for organisms to survive,is a process involving multiple sensory cues.The two most powerful cues are visual(optic flow)and vestibular(inertial motion).Psychophysical studies have indicated that humans and nonhuman primates integrate the two cues to improve the estimation of self-motion direction,often in a statistically Bayesian-optimal way.In the last decade,single-unit recordings in awake,behaving animals have provided valuable neurophysiological data with a high spatial and temporal resolution,giving insight into possible neural mechanisms underlying multisensory self-motion perception.Here,we review these findings,along with new evidence from the most recent studies focusing on the temporal dynamics of signals in different modalities.We show that,in light of new data,conventional thoughts about the cortical mechanisms underlying visuo-vestibular integration for linear self-motion are challenged.We propose that different temporal component signals may mediate different functions,a possibility that requires future studies.

Sensitivity of LS neurons to optic flow stimuli

LS (lateral suprasylvian area) is an important area in the extrastriate visual cortex of the cat.The receptive fields of cells in LS are much larger than those of primary visual cortex. MostLS neurons can give strong responses to moving stimuli and about 80% of the cells are sensi-tive to the direction of motion. LS is mainly involved in the analysis of moving informationand is thought to be analogous in function to the middle temporal area (MT) of macaque mon-