一种新型小波域运动估计算法

离散小波变换中的位移可变性严重影响了小波域运动估计的精度。为了克服位移可变性,该文采用了一种新的双通道高通滤波方法,提出了一种新型小波域运动估计算法。仿真实验结果表明这种新算法比现有其他同类算法具有更好的性能和更低的计算复杂度。     

在线考虑运动学限制的最小加速度的轨迹规划

提出了一种基于简化运动规划的机器人轨迹规划新方法,可用于多自由度的机器人操作臂系统。关键问题是找到最小加速度的轨迹规划,来优化操作臂的运动以减少抖动。此外,给出了轨迹规划的解存在的充分必要条件,并考虑了所有的关节位置、角速度、加速度、加加速度等运动学限制。而且这种方法能够在线应用,适合任意非零的关节初始状态和目标状态,以便使机器人能够在运动过程中进行实时路径修正。最后提出的方法应用于一个七自由度的仿人机器人手臂来验证方法的有效性。     

Multi-robot spot-welding cells for car-body assembly: Design and motion planning

Multi-robot cells for spot welding use coordinated robots to assemble metal panels via spot welding by coordinated robots, for instance in the construction of car doors. The design of multi-robot cells for spot welding required both cell design and off-line motion planning. Cell design involves resource selection (such as robots and welding guns) and resource configuration, while considering cell productivity, costs, flexibility and reconfigurability. Motion planning involves allocating welding points to each resource and calculating collision-free motion plan for each robot. Currently, cell design and motion planning are sequential and manual activities, managed by different and separate industrial functional units. This results in several cycles before the design converges to a feasible final solution. The proposed approach introduces a unified methodology, aiming at optimizing the holistic cell design and motion planning, that reduces design time and errors. The feasibility of the proposed approach has been demonstrated in several ad-hoc basic replicable cases and in one industrial case. The outcome of this research improves state of the art, reducing design and motion planning time over current technology. Moreover, the method has been integrated into a computerized approach which has the potential to accelerate the whole cell design and motion planning processes and to reduce human efforts.     

Motion artifact removal based on periodical property for ECG monitoring with wearable systems

Motion artifact removal (MR) is one of the essential issues in processing raw ECG signals since it could not be simply solved by using classic filtering. In this paper, a QRS detection based Motion Artifact Removal algorithm (QRSMR) is proposed. The proposed method detects the entire QRS complex and removes the noise between two QRS complexes, while recovering P and T-waves. As verified in the tests on simulated noisy ECG signals, QRSMR outputs with seriously contaminated ECG signals have an increase of the correlation with their original clean signals from 40% to nearly 80%, demonstrating the improved noise removal ability of QRSMR. Moreover, in the tests on real ECG signals measured on volunteers with a flexible wearable ECG monitoring device developed at Fudan University, QRSMR is able to recover P-wave and T-wave from the contaminated signal, which shows its enhanced performance on motion artifact reduction comparing with adaptive filtering method and other methods based only on empirical mode decomposition.     

Searching for variable-speed motions in long sequences of motion capture data

Motion capture data digitally represent human movements by sequences of body configurations in time. Subsequence searching in long sequences of such spatio-temporal data is difficult as query-relevant motions can vary in execution speeds and styles and can occur anywhere in a very long data sequence. To deal with these problems, we employ a fast and effective similarity measure that is elastic. The property of elasticity enables matching of two overlapping but slightly misaligned subsequences with a high confidence. Based on the elasticity, the long data sequence is partitioned into overlapping segments that are organized in multiple levels. The number of levels and sizes of overlaps are optimized to generate a modest number of segments while being able to trace an arbitrary query. In a retrieval phase, a query is always represented as a single segment and fast matched against segments within a relevant level without any costly post-processing. Moreover, visiting adjacent levels makes possible subsequence searching of time-warped (i.e., faster or slower executed) queries. To efficiently search on a large scale, segment features can be binarized and segmentation levels independently indexed. We experimentally demonstrate effectiveness and efficiency of the proposed approach for subsequence searching on a real-life dataset.     

Motion planning and tracking control for coupled flexible beam structures

A systematic flatness-based motion planning approach for a structure consisting of coupled flexible bending beams is introduced. The beams are equipped with in-domain piezoelectric macro-fiber composite (MFC) actuators and are coupled by an elastic string, modeled as spring, which connects the tip masses of adjacent beams. This setup provides a challenging benchmark experiment to evaluate control concepts. Hamilton’s principle leads to the equations of motion involving spatially varying parameters due to the different material characteristics of the carrier structure and the attached MFC-actuators. The flat output is constructed by exploiting the spectral system representation and enables a differential parameterization of the system states and inputs. This parameterization transfers the motion planning problem into a trajectory assignment problem for the flat output. The resulting flatness-based feedforward control law is analyzed and evaluated at an experimental setup. To increase the performance and the robustness w.r.t. model uncertainties and external disturbances the flatness-based feedforward control is amended by a feedback controller with observer in the spirit of the two-degrees-of-freedom control approach.     

The effect of motion on fuel diffusion and mixture preparation of a free-piston linear hydrogen engine

The most notable difference between linear hydrogen engine (LHE) and conventional crank hydrogen engine (CHE) is that the former supports variable motion operation for combustion optimizing. This article presents a study to reveal the effect of variable motion on hydrogen fuel diffusion and mixing of a direct injection LHE. A multi-dimensional model of coupled dynamics is proposed to describe the motion effect on mixture formation. The fuel mixing characteristic of the LHE is evaluated by comparing a corresponding CHE. Result indicates that compared with the CHE, the LHE behaves a slight lower uniformity of the hydrogen-air mixture during injection stage due to its slower motion, but the slower motion also provides longer time for hydrogen diffusion to form more homogeneous mixture before sparking ignition. Moreover, the effect of variable motion stroke on the hydrogen-air mixing of the LHE is also analyzed. Study reveals that the variable stroke has little effect on the hydrogen-air mixing during the injection stage, and the mixture uniformity varies in positive correlation with the stroke length at the occurrence of spark ignition. Suggesting that in order to achieve homogeneous combustion mode, the long motion stroke operation is a good choice for the LHE.     

An overview of optical flow-based approaches for motion segmentation

The goal of motion segmentation is to segregate a visual scene into independently moving objects. It is an indispensable pre-processing step for various tasks in computer vision and has evolved as an active and flourishing research area in the last few decades. In the sequences captured using a monocular camera, motion segmentation is typically performed by analyzing apparent motion of pixels in the image plane, i.e. the optical flow. Optical flow is generally contemplated as an appropriate representation of image motion. Numerous techniques for reliable flow estimation and subsequent advancements in their framework have been proposed in the last couple of decades and are outlined briefly in this work. The paper attempts to give a summary of diverse optical flow-based approaches used for robust segmentation of static or dynamic scenes containing rigidly moving objects and discusses in brief the shortcomings associated with them.     

DMC及其在开放式机器人控制器中的应用

本文介绍了DMC在建立开放式机器人控制器中的优势，提出了SCARA型机器人控制器的方案。工业控制计算机进行空间轨迹规划计算而DMC实现关节运动的控制。实验证明了控制器的可靠性。     

基于Motion Skeleton的2K-H型轮系速比计算方法研究

对2K-H型轮系机构进行了运动学仿真。对机构模型进行了介绍和简化处理,借鉴齿轮系机构理论,得到机构的数学模型并求解;借助Creo软件的Motion Skeleton模块,对不同的轮系状态进行运动学仿真分析,得到了2K-H型轮系的速比变化曲线。验证了独特的2K-H型轮系速比求解的正确性。