基于步态规划的四足机器人运动学分析与研究

对四足机器人进行运动学建模和分析,推导运动学的正解和逆解;然后基于五次多项式对机器人足端轨迹进行了步态规划,计算了四足机器人对角步态和三角步态的驱动函数。在仿真软件ADAMS中对三角步态和对角步态进行仿真。最后制作了样机,并对样机进行了测试。通过研究三角步态和对角步态的仿真结果和样机测试结果,验证了理论推导计算的正确性。     

基于步态规划的六足机器人运动学分析与计算

分析六足机器人的侧倾、俯仰、偏航变化情况,验证步态规划的正确性。对设计的六足机器人进行运动学分析,计算机器人运动学的正解和逆解,分析六足机器人运动的时序图,利用五次多项式对机器人足端轨迹进行步态规划。在ADAMS中对机器人进行了运动仿真,得到了运动过程中的RPY角。最后制作了六足机器人样机,测试运行过程中的RPY角。仿真和样机测试结果表明：机器人在步态运动过程中,RPY角度在前进方向上误差最大不超过1°,验证了运动学计算和步态规划的正确性。     

四足机器人运动分析及控制算法研究

为实现一种液压驱动的四足机器人稳定行走,针对JQRI00四足机器人进行了步态规划,并推导出其运动控制算法。根据前期对四足机器人的结构设计,建立其运动学模型,得到各关节运动的逆运动学分析。根据JQRI00的驱动特点,对其运动控制算法进行研究。并利用ADAMS对机器人进行仿真。仿真及控制系统实验的结果准确合理,表明所研究的步态规划正确可行,控制算法实时有效,为机器人后期的复杂动作控制提供参考。     

四足机器人跳跃步态主动柔顺控制研究

为减弱四足机器人跳跃步态起跳与落地时所受到的地面冲击力影响,研究四足机器人跳跃步态主动柔顺控制方法。采用三次多项式拟合五连杆同轴四足机器人跳跃步态机体质心轨迹曲线,通过不同轨迹曲线函数描述跳跃过程中起跳、腾空、缓冲、恢复4个阶段;引入PD控制器修正机体质心落地相轨迹曲线,优化四足机器人落地时收腿缓冲、恢复站立等位移响应曲线;利用Webots仿真平台与试验样机开展大量重复跳跃试验。结果表明：所设计的方法对四足机器人的平稳跳跃有较好的改善效果,能有效提高机器人的运动稳定性。     

基于步态规划的四足机器人运动学分析和仿真

利用三维设计软件设计四足机器人的整机结构。对四足机器人进行了数学建模和数学计算,利用公式计算了运动学的正解和逆解,用MATLAB进行了仿真验证对比。对机器人基于对角步态和三角步态进行步态规划,推导和计算了四足机器人四条腿各个关节的转动角度。利用ADAMS进行了步态的仿真,仿真结果符合预期设计。计算和仿真结果为物理样机的制作提供了数据支撑,有助于缩短研发周期,提升研发效率。     

基于MATLAB Robotics Toolbox的UR5机器人轨迹规划与仿真

为了解UR5机器人实时轨迹变化情况,根据Denavit-Hartenberg参数法在MATLAB Robotics Toolbox中利用Link函数建立了UR机器人的三维数学模型,对UR5机器人进行了正、逆运动学求解与理论分析,推导出各个关节角之间的变化关系;利用三次多项式插值法对任意PTP (点到点)之间的空间轨迹规划进行理论分析,并结合MATLAB Robotics工具箱对UR5机器人数学模型进行了空间轨迹规划和仿真,得到了连续变化的轨迹曲线。仿真结果验证了机器人运动学模型的正确性和合理性,为UR系列机器人的进一步研究和应用提供了理论依据。     

仿生六足机器人机构设计与运动分析

基于蜜蜂腿部结构及运动步态特点和仿生设计基本原理,设计了一种新型六足机器人机构,可实现不同运动步态下的前进、后退和转向,具有较高的步态稳定性和环境适应性。运用空间分解法构建了机器人单腿的运动学模型,利用消元法对模型进行求解,得到逆运动学的唯一解。通过数值求解获得了六足机器人足部末端的运动轨迹,验证了运动学模型的正确性。借鉴蜜蜂的运动步态特征,规划了六足机器人直行和转弯时的运动步态。该研究为六足机器人机构设计与步态规划提供了新的思路和理论参考。     

仿生四足机器人运动学与动力学仿真分析

为了提高四足机器人的设计效率和设计的可靠性,缩短四足机器人研发周期,文章采用虚拟仿真技术对四足机器人进行仿真研究。文章对虚拟样机进行机构运动学与动力学分析,建立仿生四足机器人的运动学方程及拉格朗日动力学方程,利用三维建模软件pro/E建立实体模型导入到ADAMS中进行系统仿真,采用对角小跑步态,通过仿真结果验证了运动学和动力学数学建模的正确性,分析了影响机器人动态稳定性因素,为物理样机的设计提供了理论依据。     

四足机器人容错性步态规划方法研究

四足机器人的运动具有较强的耦合性,任何一个关节出现故障都可能使机器人运动紊乱,从而导致严重的后果。为解决此问题,提出一种适用于关节锁定故障的容错性步态规划方法。通过四足机器人的浮动机体运动学模型,在锁定关节处建立冗余度方程;利用增广雅可比矩阵完成含有优化函数的冗余度方程求解,从而实现容错性步态规划。通过仿真分析和样机试验对所提方法的可行性和有效性进行了验证。结果表明,与现有方法相比,容错性步态规划方法能够有效地提高容错性步态的效率。     

足履机器人的步行建模和运动仿真

足履机器人设计成履带和腿式相结合的运动方式,兼具了履带和腿式机器人的共同优点。利用ADAMS建立每足三自由度的双足履带简化模型机器人,根据行走步态的特点,建立了合理的步行运动方程,使足端在运动起始点和终止点避免冲击,运动平稳,根据运动方程,可逆获得关节处的运动轨迹方程。利用ADAMS对双足履带机器人进行仿真,验证机构设计运动方案的可行性。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.