A Wire-Driven Series Elastic Mechanism Based on Ultrasonic Motor for Walking Assistive System

In order to improve the elderly people's quality of life,supporting their walking behaviors is a promising technology.Therefore,based on one ultrasonic motor,a wire-driven series elastic mechanism for walking assistive system is proposed and investigated in this research.In contrast to tradition,it innovatively utilizes an ultrasonic motor and a wire-driven series elastic mechanism to achieve superior system performances in aspects of simple structure,high torque/weight ratio,quiet operation,quick response,favorable electromagnetic compatibility,strong shock resistance,better safety,and accurately stable force control.The proposed device is mainly composed of an ultrasonic motor,a linear spring,a steel wire,four pulleys and one rotating part.To overcome the ultrasonic motor's insufficient output torque,a steel wire and pulleys are smartly combined to directly magnify the torque instead of using a conventional gear reducer.Among the pulleys,there is one tailored pulley playing an important role to keep the reduction ratio as 4.5 constantly.Meanwhile,the prototype is manufactured and its actual performance is verified by experimental results.In a one-second operating cycle,it only takes 86 ms for this mechanism to output an assistive torque of 1.6 N·m.At this torque,the ultrasonic motor's speed is around 4.1 rad/s.Moreover,experiments with different operation periods have been conducted for different application scenarios.This study provides a useful idea for the application of ultrasonic motor in walking assistance system.

A new passive transfemoral prosthesis mechanism based on 3R36 knee and ESAR foot providing walking and squatting

Researchers have proposed various linkage mechanisms to connect knee and ankle joints for above-knee prosthe-ses,but most of them only offer natural walking.However,studies have shown that people assume a squatting posture during daily activities.This paper introduces a novel mechanism that connects the knee joint with the foot-ankle joint to enable both squatting and walking.The prosthetic knee used is the well-known 3R36,while the energy storing and return(ESAR)prosthetic foot is used for the ankle-foot joint.To coordinate knee and ankle joint movements,a six-bar linkage mechanism structure is proposed.Simulation results demonstrate that the proposed modular transfemoral prosthesis accurately mimics the motion patterns of a natural human leg during walking and squatting.For instance,the prosthesis allows a total knee flexion of more than 140°during squatting.The new prosthesis design also incorporates energy-storing mechanisms to reduce energy expenditure during walking for amputees.

Kinematics and Dynamics Analysis of a Quadruped Walking Robot with Parallel Leg Mechanism

It is desired to require a walking robot for the elderly and the disabled to have large capacity,high stiffness,stability,etc.However,the existing walking robots cannot achieve these requirements because of the weight-payload ratio and simple function.Therefore,Improvement of enhancing capacity and functions of the walking robot is an important research issue.According to walking requirements and combining modularization and reconfigurable ideas,a quadruped/biped reconfigurable walking robot with parallel leg mechanism is proposed.The proposed robot can be used for both a biped and a quadruped walking robot.The kinematics and performance analysis of a 3-UPU parallel mechanism which is the basic leg mechanism of a quadruped walking robot are conducted and the structural parameters are optimized.The results show that performance of the walking robot is optimal when the circumradius R,r of the upper and lower platform of leg mechanism are 161.7 mm,57.7 mm,respectively.Based on the optimal results,the kinematics and dynamics of the quadruped walking robot in the static walking mode are derived with the application of parallel mechanism and influence coefficient theory,and the optimal coordination distribution of the dynamic load for the quadruped walking robot with over-determinate inputs is analyzed,which solves dynamic load coupling caused by the branches’ constraint of the robot in the walk process.Besides laying a theoretical foundation for development of the prototype,the kinematics and dynamics studies on the quadruped walking robot also boost the theoretical research of the quadruped walking and the practical applications of parallel mechanism.

Research of 6-DOF Serial-Parallel Mechanism Platform for Stability Training of Legged-Walking Robot

The concept of legged-robot stability training with a training platform is proposed and a serial-parallel mechanism platform with 6 degrees of freedom is designed for this target. The designed platform is composed of 4-DOF parallel mechanism with spherical joints and prismatic pairs,and 2-DOF serial mechanism with prismatic pairs. With this design,the platform has advantages of low platform countertop,big workspace,high carrying capacity and high stiffness. On the basis of DOF analysis and computation of space mechanism,weight supporting auxiliary mechanism and raceways-balls supporting mechanism are designed,so as to improve the stiffness of designed large platform and payload capacity of servo motors. And then the whole structure design work of the platform is done. Meanwhile,this paper derives the analytical solutions of forward kinematics, inverse kinematics and inverse dynamics. The error analysis model of position and orientation is established. And then the simulation is done in ADAMS to ensure the correctness and feasibility of this design.

Structure design and analysis of aid walking mechanism for a lower limb rehabilitation robot

In order to improve the rehabilitative effect of users＇ recovery training and reduce the production cost of rehabilitation institution, this paper designs an aid walking mechanism for a lower limb rehabilitation robot which achieves the movement of transmission by use of the interrelationship between hip and knee. Using single chip micyoco （SCM） control technology to achieve the coordinated operation of the entire mechanical institution, this aid walking mechanism simulates the walking gait. Besides, this paper also verifies that materials＇ strength meet the design requirements by Solidworks simulation stress-strain analysis module.

STUDIES ON MECHANICS PROBLEM OF DYNAMIC WALKING OF ANTHROPOMORPHIC BIPED ROBOTS

This paper deals with the mechanics problem of dynamic walking of anthropomorphic biped robots. Through analysing the mechanics system of this kind of robots in detail, the motion constraint equations are established, three mechanics laws describing the r

The effects of total ankle replacement on ankle joint mechanics during walking

Background:End-stage ankle arthritis impairs joint function and patients' mobility.Total ankle replacement is a surgical procedure to treat severe ankle arthritis.Salto Talaris Anatomic Ankle^(TM)(STAA) was designed to mimic the normal ankle anatomy and flexion/extension of the ankle movement.The purpose of this study was to examine the effect of an STAA ankle replacement on ankle joint function and mechanics during gait.Methods:Five patients with end-stage unilateral ankle arthritis were recruited.Patients performed level walking in a laboratory setting on 2occasions,prior to and 3 months after the STAA ankle surgeries.American Orthopedic Foot and Ankle Society(AOFAS) hindfoot score was obtained.A 12-camera motion capture system was used to perform walking analysis.Gait temporo-spatial parameters and ankle joint mechanics were evaluated.Paired Student's t tests and non-parametric Wilcoxon matched tests were performed to examine the differences in biomechanical variables between the pre-and post-surgery walking conditions.Results:Compared to the pre-surgical condition,at 3 months of post-STAA surgery,patients experienced greater improvement in AOFAS hindfoot score(p = 0.0001);the STAA ankle demonstrated a 31% increase in ankle joint excursion(p = 0.045),a 22% increase in ankle plantarflexor moment(p = 0.075),a 60% increase in ankle power absorption(p = 0.023),and a 68% increase in ankle power production(p = 0.039).Patients also demonstrated a 26% increase in walking speed(p = 0.005),a 20% increase in stride length(p = 0.013),a 15% decrease in double support time(p = 0.043),and a 5% decrease in total stance time(p = 0.055).Conclusion:Three months after surgeries,the STAA patients experienced improvements in ankle function and gait parameters.The STAA ankle demonstrated improved ankle mechanics during daily activities such as walking.

Turn Control of a Three-Dimensional Quasi-Passive Walking Robot by Utilizing a Mechanical Oscillator

A turn control strategy is proposed in order to improve environmental adaptability of a quasi-passive walking robot by utilizing a mechanical oscillator. The target trajectory of the fmechanical oscillator is determined by online planning of its period, phase, amplitude and angle of the central axis of oscillation. The motion of the mechanical oscillator is always entrained with the rocking motion of the robot based on forced entrainment in order to stabilize the robot. The turn radius can be controlled by adjusting the inclination angle of the central axis of the mechanical oscillator movement, and the control method is numerically and experimentally examined. Results show that the robot can turn with different radius and it is possible for the robot to walk in various environments. Finally, the gait of turn is compared with that of straight walking and analyzed in terms of mechanical work and energy.

Description of a Propulsion Unit Used in Guiding a Walking Machine by Recognizing a Three-point Bordered Path

A reconfigurable propulsion unit based on the Peaucellier-Lipkin mechanism has the ability to describe exact straight or curved paths depending on the selected ratio between the lengths of two of its links. The Peaucellier-Lipkin mechanism with one degree of freedom is transformed into a more sophisticated parallel kinematic chain by including four more degrees of freedom. The resulting propulsion unit is able to adapt its kinematic structure and reach instant centers of rotation, in accordance with the presence of three points that border a geometric path. A laser sensor mounted on the body of the machine detects each point. Once the machine has detected the exact location of the border of the road, it walks along a curve parallel to that border. Although the proposed research describes only one propulsion unit or leg, the methodology can be applied to all the legs of the walking machine. The novel 5-DOF leg is able to reach different centers of rotation, providing either the concave or convex arcs that satisfy the basic principle of displacement of walking machines.

Modeling Walking with an Inverted Pendulum Not Constrained to the Sagittal Plane. Numerical Simulations and Asymptotic Expansions

Inverted pendulum models are commonly used to study the bio-mechanics of biped walkers. In its simplest form, the inverted pendulum consists of a point mass attached to two straight mass-less legs. Most works constrain the motion of the mass to the sagittal plane, i.e. the plane perpendicular to the ground that contains the direction toward the biped is walking. In this article, we remove this constrain to study the oscillations, the mass experiences in the direction perpendicular to the sagittal plane as the biped walks. While small, these lateral oscillations are unavoidable and of importance in the understanding of balance and stability of walkers, as well as walkers induced oscillations in pedestrian bridges.

Optimal trajectory planning for natural biped walking locomotion

An optimal trajectory planning method has been proposed for the walking locomotion of a biped mechanical system with thighs, shanks and small feet, which is modelled as a 3 DOF link system consisting of an inverted pendulum and a 2 DOF swing leg. The locomotion of swing and supporting legs is solved by the optimal trajectory planning based on function approximation. The optimal trajectory planning based on function approximation. The optimal walking locomotion solution with minimum square of input torque exhibits a natural walking gait with one step period of 0.64 s similar to the human walking gait by using the link parameters of an adult’s leg. It is concluded from the computation results that the method proposed in this paper has been proved to be an effective tool for solving the optimal walking locomotion and joint control torque problems for a 3 DOF biped mechanism; when the ankle joint of the supporting leg is a passive joint, a nearly, optimal walking solution can be obtained at t 1=0.49 s and t 2=10 s, and however, when the knee is a passive joint, it is impossible to obtain a solution which satisfies the constraint condition; for the link parameters used in this paper, the length of an optimal stride is 0.3 m.

煤矿巡检机器人可变形行走机构设计

针对灾后井下复杂的非结构化环境,结合对煤矿巡检工作的要求,以简化机器人的越障动作与增强机器人对复杂地形的适应能力为目标,设计一种平行四边形连杆机构机器人行走机构。采用Solidworks建立巡检机器人行走机构的三维结构模型,对机器人进行越障能力和倾覆稳定性分析。研究结果表明,该巡检机器人行走机构具有更好的越障性能和稳定性。

水稻无人机直播产量、效益分析及技术要点

以常规水稻品种秀水14为供试品种,比较了机械插秧、行走式机械直播和无人机直播3种种植方式的产量、成本和效益,分析了不同种植方式的工作效率与群体均匀性。结果表明,无人机直播的产量与机械插秧、行走式机械直播无显著差异,但其具有播种效率高、群体生长均衡、种植成本低的特点。最后小结了无人机直播技术要点。

Attention-Based CNN Fusion Model for Emotion Recognition During Walking Using Discrete Wavelet Transform on EEG and Inertial Signals

Walking as a unique biometric tool conveys important information for emotion recognition.Individuals in different emotional states exhibit distinct walking patterns.For this purpose,this paper proposes a novel approach to recognizing emotion during walking using electroencephalogram(EEG)and inertial signals.Accurate recognition of emotion is achieved by training in an end-to-end deep learning fashion and taking into account multi-modal fusion.Subjects wear virtual reality head-mounted display(VR-HMD)equipment to immerse in strong emotions during walking.VR environment shows excellent imitation and experience ability,which plays an important role in awakening and changing emotions.In addition,the multi-modal signals acquired from EEG and inertial sensors are separately represented as virtual emotion images by discrete wavelet transform(DWT).These serve as input to the attention-based convolutional neural network(CNN)fusion model.The designed network structure is simple and lightweight while integrating the channel attention mechanism to extract and enhance features.To effectively improve the performance of the recognition system,the proposed decision fusion algorithm combines Critic method and majority voting strategy to determine the weight values that affect the final decision results.An investigation is made on the effect of diverse mother wavelet types and wavelet decomposition levels on model performance which indicates that the 2.2-order reverse biorthogonal(rbio2.2)wavelet with two-level decomposition has the best recognition performance.Comparative experiment results show that the proposed method outperforms other existing state-of-the-art works with an accuracy of 98.73%.

新型聚乙烯弹性体导向的α-二亚胺镍配合物催化剂的研究进展

乙烯与α-烯烃共聚所制备的聚烯烃弹性体是聚烯烃材料的热点,可广泛应用于塑料相容剂、鞋底基材、光伏封装胶膜、微电子封装材料和弹性体纤维等高附加值产品领域。在我国缺少α-烯烃单体的形势下,迫切需要跨越传统共聚体系的新型催化剂。Brookhart型α-二亚胺镍(Ⅱ)配合物催化剂能够实现单一乙烯聚合制备聚乙烯弹性体,是特别值得重视和推进产业化的催化剂体系。该类催化剂在催化乙烯聚合过程中采用“链行走”机理,“通过调控催化剂结构,不仅可以调节催化活性,更重要地可实现对所得聚乙烯支链的有效剪裁”;这些微观结构可控的聚乙烯弹性体在具有窄分子量分布特点的基础上,涵盖了从低分子量(降凝剂)、中等分子量(膜材)到高分子量(高强度树脂)各个范围的聚合产物。综述了可制备乙烯低聚物,油性低分子量、中等分子量、高分子量甚至超高分子量全系列支化聚乙烯的α-二亚胺镍(Ⅱ)配合物的最新结构演变进展,对结构的改性包括N-芳基取代基的修饰、配体骨架结构的修饰和双核配体的利用三个部分;从空间效应和电子效应两方面探讨了配合物结构与催化性能的关系。α-二亚胺镍(Ⅱ)催化剂合成简单,具有中试放大基础和产业化推进的潜能,为单一乙烯聚合制备多品种新型聚乙烯弹性体奠定了良好基础。

基于分群游走机制的灰狼优化算法的FPRM逻辑电路面积优化

针对基于XNOR/OR的固定极性Reed-Muller电路(FPRM)逻辑电路面积优化方法搜索最优解速度较慢,易陷入局部最优等问题,提出一种新的FPRM逻辑电路面积优化方法,利用基于分群游走机制的灰狼优化算法(GDGWO)搜索电路面积最小的FPRM电路.GDGWO在初始化种群后,采取“轮盘赌”选择算法选出合适的新群体头狼,以提高种群多样性;执行种群分裂机制,防止因原始种群陷入局部最优而降低算法的鲁棒性;在分群搜索开发过程中引入改进后的随机游走策略,使灰狼种群能够更快地包围猎物,提高算法的收敛速度.基于北卡罗来纳微电子中心Benchmark测试电路的实验结果表明,GDGWO与粒子群算法相比,电路面积优化率提升57.42%;与黑猩猩算法相比,提升41.94%;与原始灰狼优化算法相比,提升43.68%.

Walker256乳腺癌细胞构建大鼠胫骨骨癌痛模型

目的：探讨以Walker256大鼠乳腺癌腹水瘤细胞制备大鼠胫骨骨癌痛模型，为骨癌痛机制和治疗研究提供有用的工具。方法：以Walker256乳腺癌细胞接种幼年雌性SD鼠腹腔制备腹水瘤细胞，将15μl腹水瘤细胞注入雌性成年SD鼠左侧胫骨骨髓腔制备骨癌痛模型；以注射加热灭活瘤细胞的SD鼠为假手术对照鼠，以正常鼠为正常对照鼠。造模后1-4周观察模型鼠自由行走痛评分、辐射热痛觉阈值[缩爪反应潜伏期（paw withdrawal latency，PWL）]和机械刺激诱发痛觉阈值[缩爪反应阈值（paw withdrawal threshold，PWT）]改变，并对痛觉行为改变明显的模型鼠进行影像学检测。结果：本方法制备模型的成瘤率为67．3％。模型鼠在造模后15d自由行走痛评分显著高于正常鼠和假手术鼠（P〈0．01）；模型鼠的模型后肢对热刺激痛觉阈值和对机械刺激诱发痛觉阈值分别在造模后21d和18d明显低于正常鼠和假手术鼠（P〈0．01），同时也明显低于模型肢对侧后肢（P〈0．05）。影像学结果显示，痛行为改变明显的模型鼠模型后肢胫骨骨质结构遭到明显破坏。结论：采用Walker256乳腺癌腹水瘤细胞可成功制备与人类骨癌痛体症相似的大鼠胫骨骨癌痛模型。

烯烃聚合用二亚胺催化剂的研究进展

综述了近几年烯烃聚合用α-二亚胺催化剂的研究进展,聚焦于配体结构的修饰,包括空间效应和电子效应的调控策略,以及配体结构变化对催化剂活性和热稳定性的影响。调控α-二亚胺配体的轴向位阻可达到提高催化剂活性、热稳定性,聚合物相对分子质量,以及调节支化度的目的。在适当的空间位阻下,引入不同电子效应的取代基对配体进行结构修饰同样也可提高α-二亚胺催化剂的性能。

基于知识子图与注意力机制的在线课程推荐模型

推荐系统可以帮助用户在海量的资源中筛选出满足其需求的项目,不断发展的推荐系统为在线教育提供了新的思路。在线课程资源推荐作为在线教育领域中的重要一环,目前存在课程资源过载和课程推荐结果缺乏可解释性的问题。对此,该文提出了一种基于知识子图与注意力机制的在线课程推荐模型,以利用知识子图进行推荐。有别于直接利用知识图谱进行推荐而忽略了知识表示不准确问题的模型,该模型首先采用Node2vec随机游走方法从知识图谱中提取连接用户-课程对的连通子图,然后通过分层注意网络对子图进行编码,以生成用于用户所需课程预测的子图嵌入,最后生成Top-N推荐课程列表,并给出模型的可解释性说明。为验证模型的有效性,以“中国大学MOOC(慕课)”上的数据为样本构建数据集,实验结果表明,相较于KGCN-PN、GAT、KGAT以及POCR模型,文中模型在NDCG、HR以及MRR评价指标上分别提升了10.6%,9.41%,13.7%。

基于Pro/MECHANICA Motion的四足步行机构运动仿真研究与优化

探讨了四足步行机构的行走问题。在Pro/MECHANICA Motion环境下对单腿八连杆机构进行了运动仿真,并且以机构的受力最佳为优化目标,建立了满足约束要求的数学模型,求出了满足结构的杆件参数。