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.

Topology Search of 3-DOF Translational Parallel Manipulators with Three Identical Limbs for Leg Mechanisms

Three-degree of freedom（3-DOF） translational parallel manipulators（TPMs） have been widely studied both in industry and academia in the past decades. However, most architectures of 3-DOF TPMs are created mainly on designers＇ intuition, empirical knowledge, or associative reasoning and the topology synthesis researches of 3-DOF TPMs are still limited. In order to find out the atlas of designs for 3-DOF TPMs, a topology search is presented for enumeration of 3-DOF TPMs whose limbs can be modeled as 5-DOF serial chains. The proposed topology search of 3-DOF TPMs is aimed to overcome the sensitivities of the design solution of a 3-DOF TPM for a LARM leg mechanism in a biped robot. The topology search, which is based on the concept of generation and specialization in graph theory, is reported as a step-by-step procedure with desired specifications, principle and rules of generalization, design requirements and constraints, and algorithm of number synthesis. In order to obtain new feasible designs for a chosen example and to limit the search domain under general considerations, one topological generalized kinematic chain is chosen to be specialized. An atlas of new feasible designs is obtained and analyzed for a specific solution as leg mechanisms. The proposed methodology provides a topology search for 3-DOF TPMs for leg mechanisms, but it can be also expanded for other applications and tasks.

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.

Development of a Leg Mechanism for Soft Landing Based on Biological Motion

With jumping mechanisms,soft landing motion is important to protect loads and the mechanisms.This study proposes a leg mechanism for soft landing based on biological motion.Human jumping motion with a load suggests a unique motion for soft landing.The landing model consists of two periods.Jerk is minimized in the first period and force is minimized in the second period.In comparison with other landing models,this model is specialized for soft landing motion protecting an objective part.Given all mechanisms have mass,such model is useful in practical application.For the purpose of realizing soft landing motion,this study proposes a new leg mechanism.The mechanism achieves quick variable transmission with cam and wire.Design process of the cam is explained with dynamics and computation.With the calculated cam shape,the leg mechanism can be driven by constant input voltage for simple control.Robustness against height change is also verified with landing simulation.With 50mm falling experiment,prototype leg mechanism performed soft landing without bounce motion and large sound.The acceleration profile of the body also agrees with the proposed soft landing model.

The Kinematics and Force Analysis of a New Leg Mechanism for Multi-legged Wall-Climbing Robot

This paper presents a new kind of leg mechanism with which the wall climbing robot can easily perform the ground to wall transition by itself.To get its walking envelope and limit position,the forward/inverse kinematics and the statics of the mechanism are solved.All of these lay the foundation for ground to wall transition gait programing,mechanism parameter selection and optimization.

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.

Trajectory tracking control of the bionic joint of the musculoskeletal leg mechanism

Pneumatic artificial muscles(PAMs) have properties similar to biological muscles,which are widely used in robotics as actuators.It is difficult to achieve high-precision position control for robotics system driven by PAMs.A 3-DOF musculoskeletal bionic leg mechanism is presented,which is driven by PAMs for quadruped robots.PAM is used to simulate the compliance of biological muscle.The kinematics of the leg swing is derived,and the foot desired trajectory is planned as the sinusoidal functions.The swing experiments of the musculoskeletal leg mechanism are conducted to analyse the extension and flexion of joints.A proportional integral derivative(PID) algorithm is presented for controlling the flexion/extension of the joint.The trajectory tracking results of joints and the PAM gas pressure are obtained.Experimental results show that the developed leg mechanism exhibits good biological properties.

Development and Analysis of a Closed-Chain Wheel-Leg Mobile Platform

Current research concerning legged platforms and wheeled platforms primarily focuses on terrain adaptive capability and speed capability,respectively.Compared with wheeled platforms,legged platforms with a closed-chain mechanism still present deficiencies regarding speed ability.To integrate the advantages of these two types of platforms,a wheel-leg mobile platform with two modes based on a closed-chain mechanism is proposed.First,a closed-chain mechanism that generates a high-knee trajectory in legged mode is designed and analyzed based on kinematic analysis.To improve the platform’s obstacle-surmounting performance,the dimensional parameters of the closedchain mechanism are optimized and the design requirements for the platform’s frame are analyzed.In addition,the particular structure of the leg group is designed to realize transformation between legged mode and wheeled mode.The mobility of the constructed platform is calculated through an obstacle-surmounting probability analysis.The performances of the two motion modes are analyzed and compared by conducting dynamic simulations.Finally,experiments are carried out to verify both the theoretical analyses and the prototype performance.This study proposes a new approach to designing wheel-leg platforms with prominent speed ability and mobility based on a closed-chain mechanism.

Design of a Mobile Mechanism for Missing Miner Search Robots in Underground Mines

A mobile mechanism with four tracked-units for a missing miner search robot (MMSR) is presented, with a design based on the terrain features and atrocious environment of an underground mine. Its structure and working prin- ciple is discussed. The four tracked-units are controlled independently and driven cooperatively. By means of two DC motors being controlled respectively, one tracked-unit can accomplish two types of driving mode: tracked travel and in- tegral unit legged rotation (IULR), forming a track-legged compound function mechanism. Its capabilities of surmount- ing obstacles and its toppling stability in underground mines have also been analyzed. The results show that the mobile mechanism can directly surmount an obstacle of the height less than the length of one tracked-unit and get across a raceway with a span less than the length of one tracked-unit by using tracked travel and IULR. Its unstable slope angle is 51.3°. Toppling stability is determined by its structural size, moving direction and slope angle. IULR of four tracked-units can adjust the robot’s posture and then enhance toppling stability or assist in surmounting obstacles. Its track-legged compound function mechanism makes it suitable for working in underground mines.

Bionic Design and Simulation Analysis of Energy⁃Efficient and Vibration⁃Damping Walking Mechanism

African ostrich can run for 30 min at a speed of 60 km/h in the desert,and its hindlimb has excellent energy saving and vibration damping performance.In order to realize the energy⁃efficient and vibration⁃damping design of the leg mechanism of the legged robot,the principle of engineering bionics was applied.According to the passive rebound characteristic of the intertarsal joint of the ostrich foot and the characteristic of variable output stiffness of the ostrich hindlimb,combined with the proportion and size of the structure of the ostrich hindlimb,the bionic rigid⁃flexible composite legged robot single⁃leg structure was designed.The locomotion of the bionic mechanical leg was simulated by means of ADAMS.Through the motion simulation analysis,the influence of the change of the inner spring stiffness coefficient within a certain range on the vertical acceleration of the body centroid and the motor power consumption was studied,and the optimal stiffness coefficient of the inner spring was obtained to be 200 N/mm,and it was further verified that the inner and outer spring mechanism could effectively reduce the energy consumption of the mechanical leg.Simulation results show that the inner and outer spring mechanism could effectively reduce the motor energy consumption by about 72.49%.

Task-Oriented Topology System Synthesis of Reconfigurable Legged Mobile Lander Integrating Active and Passive Metamorphoses

To explore hostile extraterrestrial landforms and construct an engineering prototype,this paper presents the task-oriented topology system synthesis of reconfigurable legged mobile lander(ReLML)with three operation modes from adjusting,landing,to roving.Compared with our preceding works,the adjusting mode with three rotations(3R)provides a totally novel exploration approach to geometrically matching and securely arriving at complex terrains dangerous to visit currently;the landing mode is redefined by two rotations one translation(2R1T),identical with the tried-and-tested Apollo and Chang'E landers to enhance survivability via reasonable touchdown buffering motion;roving mode also utilizes 2R1T motion for good motion and force properties.The reconfigurable mechanism theory is first brought into synthesizing legged mobile lander integrating active and passive metamorphoses,composed of two types of metamorphic joints and metamorphic execution and transmission mechanisms.To reveal metamorphic principles with multiple finite motions,the finite screw theory is developed to present the procedure from unified mathematical representation,modes and source phase derivations,metamorphic joint and limb design,to final structure assembly.To identify the prototype topology,the 3D optimal selection matrix method is proposed considering three operation modes,five evaluation criteria,and two topological subsystems.Finally,simulation verifies the whole task implementation process to ensure the reasonability of design.

3-SRR腿履式调姿救援机器人优化设计与试验

为实现在复杂环境下对处于不同位姿伤员的精准施救及稳定转运,文中提出了一种3-SRR腿履式调姿救援机器人机构,并进行运动学分析、机构优化设计及试验研究。首先,基于闭环矢量法对其进行运动学分析,得到救援机器人运动学反解;然后,基于迭代搜索算法,得到其救援作业空间与姿态空间,并基于单一变量法分析救援机器人机构尺寸参数对救援作业空间的影响;然后,以救援作业空间最大、姿态能力最强为优化目标函数,基于差分进化算法对机构尺寸参数进行优化;最后,研制原理样机并进行调姿能力试验,试验结果证明了方案的可行性与理论分析的正确性,为灾难救援提供一种可行的解决方案。

可重构性和解耦性轮腿式机械腿构型综合方法

基于螺旋理论和可重构机构运动分岔原理,综合出一组完全解耦的可重构轮腿式混联机械腿构型。根据机械腿轮、腿模式自由度需求,分析了机械腿轮腿变换机理,进而综合和筛选出5种主运动支链。基于轮腿变换机理,提出约束支链布局原理和方案,基于螺旋理论构造约束支链,根据主运动支链及约束支链几何条件,进行运动副轴线变换及运动副分解、组合,最终得到134种约束支链。基于并联机构运动解耦概念,导出驱动副选取条件,确定各约束支链上的驱动副位置。通过实例验证机械腿的可重构性和解耦性。研究结果表明:综合出的机械腿基于约束奇异实现轮腿模式切换,减少了构态变换所需的时间消耗,使模式切换更加高效;由于结构约束的存在,轮式运动时,无需锁死与腿模式运动相关的关节,减少了能量消耗及驱动控制难度。

四足机器人单自由度腿部优化设计及仿真

基于仿生原理的四足机器人是当今国内外众多学者研究的热点。针对四足机器人运动平稳性的要求,提出了一种竖直方向改进型等速运动规律和前进方向仿生运动规律相结合的无冲击足端轨迹形式,推导出分段函数表达式;针对四足机器人存在的驱动多、腿部刚度弱的情况,构思了一种由两个曲柄摇杆机构、同步带传动和一对外啮合圆柱齿轮传动组成的单自由度的新型腿部机构,并建立该机构的运动学模型,推导了其足端的坐标;综合利用遗传算法和非线性优化一般方法,以无冲击的足端轨迹的逼近度为目标,优化计算了机构各构件的最佳运动尺寸和初始位置;使用三维建模软件搭建简化的虚拟样机模型,并导入到Adams软件中进行了Trot步态仿真试验,运动效果达到了预期设计。所提出的无冲击轨迹可以为其他足式机器人的足端轨迹规划提供参考,由两个曲柄摇杆机构组成的多连杆腿部机构优化设计方法为足式机器人腿部设计提供了基础和创新思路。

基于R&(2-RPR)+UPS并联机械腿结构参数优化

针对绝大多数并联机械腿工作空间小的问题,提出了一种新型带有放大机构的R&(2-RPR)+UPS并联机械腿,并对其主要结构参数进行了优化。首先,使用SolidWorks软件建立了并联机械腿及四足机器人整机三维模型,推导了单腿机构的位置反解,并通过Adams软件及Matlab软件对其正确性进行了仿真验证;其次,采用蒙特卡洛法求解了单腿工作空间体积,并将其作为优化指标,分别探究了该优化指标与各结构参数之间的规律,确定了优化变量;最后,采用粒子群算法对机械腿主要结构参数进行了优化。结果表明,优化后的机械腿工作空间体积增大了69.83%,在X、Y方向上的工作空间范围分别增大了35.26%、19.51%,提高了四足机器人的快速行走及越障能力。

基于传递矩阵法的足式机器人四连杆腿部机构正向与逆向动力学分析

为了保证足式机器人腿部机构的控制准确性与实时性,利用向量代数方法,对足式机器人四连杆腿部机构进行几何运动学分析;根据有限元形函数理论,建立足式机器人四连杆腿部机构典型构件的质量离散方法;在几何运动学分析的基础上,基于力矩平衡原理,分别进行正向与逆向动力学分析;利用线性变换原理并结合传递矩阵法,建立足式机器人四连杆腿部机构正-逆向动力学统一模型,并利用Adams软件建立足式机器人四连杆腿部机构虚拟样机模型,进行正向与逆向动力学仿真实例分析。结果表明,所建立的足式机器人四连杆腿部机构正-逆向动力学统一模型与虚拟样机模型3个油缸力与3个方向足底力的误差分别小于1%与3%,验证了所建立的足式机器人四连杆腿部机构正-逆向动力学统一模型能够精确地求解油缸力与足底力。

管桁架焊缝质检机器人夹紧机构轻量化设计

为减轻管桁架焊缝质量检测机器人结构重量,文章在分析夹紧机构运动约束及其关键零部件强度约束的基础上,建立夹紧机构各主要零部件力学和运动学模型,运用惩罚函数法对夹紧机构尺寸进行优化。支腿在夹紧机构的零部件中质量较大,经静力学分析发现支腿材料冗余较大,采用拓扑优化进一步减轻支腿重量。结果表明:夹紧架、支腿和底板尺寸分别为60mm、88mm、111mm时,结构最为紧凑;拓扑优化重构后,支腿的质量减轻了121.2g,总质量减少了16.16%。

轮腿式爬楼轮椅前腿机构的控制策略研究

针对爬楼轮椅前腿的位姿调节机构在工作时不能同时触地及受力失衡等问题,文中提出基于模糊比例-积分-微分(Proportional Integral Derivative, PID)的前腿同步位姿调节控制策略。首先,建立了前腿位姿调节机构驱动装置的数学模型。其次,根据爬楼轮椅工作要求设定合适的阈值,通过偏差大小来选用最优的控制算法,建立了基于模糊控制策略与模糊自适应PID控制策略。最后,结合模糊PID复合控制模型,实现前腿机构在复杂工况下的有效控制。实验结果表明:采用模糊PID的前腿同步控制系统超调量较小,达到稳态的时间更少,具有较高的稳定性。

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。

北京2022年冬奥会六足冰壶机器人机构设计与运动规划

When a curling rock slides on an ice sheet with an initial rotation,a lateral movement occurs,which is known as the curling phenomenon.The force of friction between the curling rock and the ice sheet changes continually with changes in the environment;thus,the sport of curling requires great skill and experience.The throwing of the curling rock is a great challenge in robot design and control,and existing curling robots usually adopt a combination scheme of a wheel chassis and gripper that differs significantly from human throwing movements.A hexapod curling robot that imitates human kicking,sliding,pushing,and curling rock rotating was designed and manufactured by our group,and completed a perfect show during the Beijing 2022 Winter Olympics Games.Smooth switching between the walking and throwing tasks is realized by the robot’s morphology transformation based on leg configuration switching.The robot’s controlling parameters,which include the kicking velocity v_(k),pushing velocity v_(p),orientation angle θc,and rotation velocityω,are determined by aiming and sliding models according to the estimated equivalent friction coefficientμ_(equ)and ratio e of the front and back frictions.The stable errors between the target and actual stopping points converge to 0.2 and 1.105 m in the simulations and experiments,respectively,and the error shown in the experiments is close to that of a well-trained wheelchair curling athlete.This robot holds promise for helping ice-makers rectify ice sheet friction or assisting in athlete training.