Resonance Suppression Strategy for Humanoid Robot Arm

To address the problem of resonance in the control of a robot arm, a resonance suppression strategy is proposed for a single-joint humanoid robot arm based on the proportional-resonant(PR) controller. First, an arm joint model of the humanoid robot is established. Then the influence of resonance frequency on the performance of the control system with the robot arm is analyzed. The voltage fluctuation of the drive motor caused by the changes in arm motion is recognized as the disturbance of the current loop. The PR controller has the characteristic of disturbance rejection at a specific frequency. The output fluctuation of the driving system caused by the change of arm motion state at the resonance frequency is suppressed. Therefore the output current of the inverter will not be affected by the vibration of the arm at the resonance frequency. Finally, the control system is verified by MATLAB/Simulink simulation. The simulation results demonstrate that the control strategy for the humanoid robot arm based on the PR controller can suppress the resonance of the arm effectively, improving the dynamic performance and system stability.     

基于CFD方法的无限大平板热扩散数值模拟

传统CFD方法在求解不可压缩流动Navier⁃Stokes方程时,压力方程具有椭圆形,无法推进求解,收敛性较差,因此传统CFD方法具有一定的局限性。对此研究格子玻尔兹曼方法与传统CFD方法的计算效率与准确性,以恒温边界的平板热扩散问题为例,分别运用有限元体积法、有限差分法及格子玻尔兹曼方法对平板间的温度场进行求解,通过对比求解结果及归一化迭代步数,明确格子玻尔兹曼方法计算的可行性、准确性与高效性。结果表明,相同物理模型条件下,格子玻尔兹曼方法和有限差分法的求解准确性要略优于有限元体积法;格子玻尔兹曼方法的求解速度最快,迭代步数最少,有限差分法、有限元体积法求解速度最慢。     

Ag3PO4/GO光催化剂的制备及性能研究

以氧化石墨烯(GO)为基底,利用离子交换法制备了球形和立方体表面结构的Ag₃PO₄/GO复合光催化剂。通过X射线衍射(XRD)、扫描电子显微镜(SEM)和紫外-可见光谱(UV-Vis DRS)对样品进行了表征。罗丹明B的光催化降解实验结果表明：Ag₃PO₄/GO催化剂在100 min内对20 mg/L罗丹明B的去除率可达98.5%,明显高于球形Ag₃PO₄ (83.8%)及立方形Ag₃PO₄ (88.1%)。另外,Ag₃PO₄/GO复合材料在光催化降解重复性实验中表现出良好的稳定性,循环五次后对罗丹明B的去除率仍可达95%以上。     

多转子离心抛雪机的机械结构设计

针对小区校园等小范围区域大型除雪机器无法进入作业等问题,设计了一种小型、智能化的多转子离心抛雪机,抛雪机包括集雪系统、抛雪系统、动力系统和智能控制系统四部分,抛雪机设有多组离心转子能够减少盲区、提高除雪效率;设有智能控制系统能够减少地面障碍物对铲雪浆的损耗、增加机械使用寿命,该抛雪机体积小巧,使用更加灵活,可满足家庭、公园等小范围区域的使用需求。     

微生物降解含蜡原油机理研究进展

微生物清防蜡具有成本低、操作安全、对地层无任何损伤等优点。介绍了复杂环境对微生物降解的影响,分析了微生物降解酶的作用,阐述了微生物产生的有机溶剂和生物表面活性剂降解含蜡原油的情况。基于此,指出应加强研究微生物降解酶的产生机理、有机溶剂的产生机理和表面活性剂的产生机理,使微生物对含蜡原油的降解技术有更为广阔的应用前景     

A new method of developing elastic-plastic-viscous constitutive model for clays

A new method is presented to develop the existing elastic-plastic constitutive model into an elastic-plastic-viscous one for clays. The actual loading process is divided into an instant process and a delayed process denoting the elastic-plastic strain and viscous strain, respectively. The elastic-plastic strain is determined by either an elastic-plastic model for overconsolidated clays or an improved model based on the elastic-plastic model for normally consolidated clays. In order to calculate viscous strain, a reference state line is defined based on the actual loading path. Combining the reference state line, an existing elastic-plastic model can be conveniently developed into an elastic-plastic-viscous model. Furthermore, using the proposed method, the modified cam clay model is extended into an elastic-plastic-viscous model. Comparisons with test results demonstrate that the extended model can capture the main time-dependent behaviours of clays, including creep, stress relaxation and strain rate effects.     

金属氧化物掺杂对ZnO气敏特性的影响

掺杂金属氧化物可大大提高ZnO的气敏特性,目前对这种性质的研究成为了研究热点.本文综述了掺杂金属氧化物对ZnO气敏特性的主要影响及机理;总结了目前研究中所掺杂的多种金属氧化物,并就各种掺杂物对ZnO气敏特性的作用进行了具体分析.     

桥式起重机定位和防摆的粒子群算法优化PID 控制

为使桥式起重机精确定位和快速消摆,设计了利用PSO算法优化PID参数的定位防摆控制器。通过在Matlab中编写PSO算法程序和连接Matlab与Simulink的调用函数程序,结合在Simulink中建立的起重机吊重系统模型,完成了PSO-PID控制器控制的吊重系统的仿真。通过仿真,起重机小车实现了无超调无静差的快速定位,吊重摆动也得到快速有效的抑制。仿真结果证明了该控制器的可行性和有效性。     

关于大角度范围内四元数与欧拉角转换的思考

在存在大角度姿态机动的场景中,航天飞行器通常采用基于姿态四元数的姿态运动模型,同时又多以欧拉角形式给定其期望姿态,因此研究四元数到欧拉角的转换关系十分必要.但是,姿态四元数与欧拉角之间并不存在一一对应的关系.以飞行器姿态为纽带,依据姿态四元数和欧拉角与飞行器姿态之间的内在关系,对各种可能出现的情形进行分析,在控制所对应的期望姿态的牵引下,确定出符合姿态控制利益的姿态四元数到欧拉角的转换关系.鉴于姿态四元数到欧拉角转换关系的复杂性,在飞行器进行大角度姿态机动控制时,建议采用基于四元数的姿态运动模型.     

Light scattering of ideal random copolymers in bulk

Copolymerization is a useful way of modifying the physical properties of a material to meet specific needs, but it can result in a significant light scattering loss due to dielectric fluctuations in the material. Ideal random copolymers are known to be more transparent; however, the light-scattering properties of such copolymers in bulk have not been fully studied. In this paper, two representative ideal random copolymers were synthesized: methyl methacrylate (MMA)/benzyl methacrylate (BzMA) and MMA/2,2,2-trifluoroethyl methacrylate (TFEMA). The effects of copolymer composition and polymerization temperature on the light-scattering properties were investigated. Polarized light scattering (V_V) in copolymers was more sensitive to the polymerization temperature. Higher temperatures were necessary to homogenize the dielectric fluctuations and minimize excess light scattering. However, once the heterogeneous structures vanished, the copolymer bulk exhibited low scattering losses, which are comparable with homopolymers, over the entire range of copolymer compositions.