不同重力条件下含铰间间隙空间机械臂PD~μ-SMC轨迹跟踪控制

研究了重力对含铰间间隙空间机械臂的轨迹跟踪控制的影响。针对空间机械臂在安装、调试阶段处于地面重力环境,在应用过程中处于空间微重力环境,重力环境的改变会使得在地面设计、装配、调试好的控制器在空间应用时达不到良好的控制精度和效果的问题,设计了不需被控对象模型的分数阶PD滑模控制器(PDμ-SMC)对含铰间间隙空间机械臂进行控制,并基于李亚普诺夫理论证明了渐近稳定性。仿真结果表明该控制策略能有效地抑制外部干扰,实现含铰间间隙空间机械臂在不同重力环境及存在外部扰动情况下仍然能对期望轨迹进行准确快速跟踪。     

考虑铰间间隙和重力效应的空间机械臂建模与控制

分析了不同重力环境下铰间间隙对空间机械臂动力学性能带来的影响,研究了地面装调和空间应用两个阶段的含铰间间隙机构动力学模型,在此基础上设计了不依赖控制对象模型的空间机械臂自抗扰控制(ADRC)算法,以解决重力环境和铰间间隙的改变导致地面调试好的控制系统在空间应用时无法达到控制精度的问题。该算法将机构中重力和铰间间隙的变化作为系统中的干扰,通过利用扩张状态观测器(ESO)对其进行估计,经过非线性反馈控制进行补偿,提高系统控制精度。仿真结果表明,不同重力环境下该控制算法均能达到较高精度控制要求,使系统具有较强的抗干扰性能。     

不同重力环境下含铰间间隙空间机械臂FOTSMC轨迹跟踪控制

空间机械臂需要在空间微重力环境下服役,但是装配、调试与控制器设计、验证都需要在地面进行,设计好的控制器即使在地面调试结果理想,在空间微重力环境下应用时仍达不到良好的精度和效果。由于关节铰间间隙的存在不可避免导致空间机械臂精度和可靠性降低。针对这一问题,本文构造了分数阶终端滑模控制器(FOTSMC),使得含铰间间隙空间机械臂在不改变控制器参数的前提下,可以适应不同重力环境。同时利用李亚普诺夫稳定性定理可以保证系统的稳定性,并通过仿真实验验证了该控制策略可以有效地抑制外部扰动和间隙带来的非线性内部扰动,使得系统可以对期望轨迹进行准确快速跟踪。     

不同重力环境下含间隙旋转铰位置特性仿真研究

为研究不同重力环境下空间机构运动过程中含间隙铰的运动特性,以含间隙曲柄摇杆机构为研究对象,进行了不同重力环境下含间隙旋转铰质心运动行为分析。采用连续接触等效模型建立地面和空间微重力环境下的含间隙曲柄摇杆机构模型;继而在ADAMS软件中搭建模型,分别进行不同重力环境、间隙大小和曲柄转速条件下的含间隙曲柄摇杆机构仿真实验,并完成含间隙旋转铰质心运动特性分析。仿真结果表明:重力场加速度为0时,含间隙旋转铰质心运动行为基本不受转速影响;重力场加速度为1g时,含间隙旋转铰质心运动范围随转速的增大而增大。且两种重力环境下的仿真结果均显示出,间隙越大,含间隙旋转铰质心运动行为越容易发生突变。     

柔性关节空间机械臂奇异摄动自抗扰控制仿真研究

针对不同重力环境条件下考虑摩擦、关节刚度非线性与外扰影响的柔性关节空间机械臂的控制问题,提出了一种基于奇异摄动理论的自抗扰控制方法。首先建立了柔性关节空间机械臂在地面重力和空间微重力环境下的动力学模型;然后采用奇异摄动法将系统模型分为快变子系统和慢变子系统,针对快变子系统设计速度反馈控制律来抑制柔性关节的振动,针对慢变子系统设计加入前馈补偿的自抗扰控制器(ADRC)来抵抗系统的内外扰动,并对系统进行了稳定性分析;最后对设计的控制器进行了仿真验证与对比研究。仿真结果表明,采用该方法,在不同重力环境下柔性关节空间机械臂均能实现很好的轨迹跟踪和抖振抑制,且能有效抵抗内外扰动,系统具有鲁棒性。     

不同重力环境下的柔性关节空间机械臂自适应鲁棒控制

研究了柔性关节空间机器人在不同重力环境下的轨迹跟踪控制。首先建立了地面重力环境下和空间微重力环境下的柔性关节机器人模型,这两个模型均考虑了摩擦带来的影响,然后提出一种基于奇异摄动理论的自适应鲁棒控制柔性关节空间机械臂的方法。该方法为被控对象中的重力项设计了自适应律来实时估计补偿,并加入鲁棒项对逼近误差和其它干扰项进行补偿。用该方法设计了控制器系统,并对其进行了稳定性分析和仿真研究。仿真结果表明,该控制器可以有效消除重力环境变化带来的影响,也可以有效抑制柔性关节引起的系统高频谐振等问题,具有很好的跟踪效果,对柔性关节空间机器人的轨迹跟踪控制具有重要的工程应用价值。     

不同重力环境下空间机械臂轨迹跟踪的自适应反演滑模控制

针对空间机械臂由地面装调到空间应用过程中重力的变化会对机械臂运动所需的驱动力矩及轨迹跟踪精度产生影响的问题,提出了用自适应反演滑模控制器对空间机械臂的末端进行跟踪控制的方法。该控制器根据反演原理设计,通过将重力项视为扰动并采用自适应律对扰动进行在线估计,从而使空间机械臂在地面重力及空间微重力两种环境下均能取得很好的轨迹跟踪效果。基于李雅普诺夫理论证明了这种控制的稳定性,仿真结果验证了这一控制方法的有效性。将轨迹跟踪的仿真结果与PD控制进行了比较,比较结果显示了该控制方法的优越性。     

含间隙铰的机械多体系统动力学模型

对四类间隙铰模型(连续接触模型、有限元模型、经典碰撞模型和接触变形模型)进行分析比较，给出了经典碰撞和接触变形模式的含间隙多体系统动力学模型。经典碰撞模式的动力学模型着重考察系统动力学的整体行为，不能预测碰撞过程中铰关节局部接触力的变化历程。接触变形模式的多体系统动力学模型考虑了碰撞体间的法向和切向接触力，以及阻力矩，能够求解系统运动过程中间隙铰轴销与孔体的碰撞力。采用间隙铰的非线性弹簧阻尼模型，研究了重力场及其方向性对空间可展机构动力学性能的影响。计算结果表明，无重力与有重力环境时含间隙可展机构动力学行为有较大地差别，重力作用使间隙铰内碰撞减弱。为了保证在地面试验中可靠地预测在太空展开性能，可展机构在地面试验时应采取重力补偿措施。     

柔性关节空间机械臂奇异摄动模糊PID控制仿真研究

建立了空间微重力和地面重力两种工况下的柔性关节空间机械臂模型,为空间机械臂末端轨迹跟踪控制设计了基于奇异摄动的模糊PID控制器。奇异摄动法将空间机械臂系统降阶为快子系统和慢子系统,再分别对子系统进行控制。快子系统采用力矩反馈的形式,慢子系统则采用模糊PID控制的形式。模糊部分主要实现对PID的3个参数的实时调整。仿真结果表明基于奇异摄动模糊PID控制器可以在以上两种工况下均可实现较好跟踪。     

考虑重力效应的挠性航天器姿态控制及振动抑制

以单轴转动的挠性航天器为研究对象,建立了考虑重力效应的挠性航天器动力学模型,并对该航天器在地面调试阶段和空间应用阶段的振动特性和姿态控制精度进行了仿真研究。仿真结果表明,重力项对挠性航天器的振动特性和姿态控制精度均有影响。为了使挠性航天器在不同重力环境下均达到较高的姿态控制精度和理想的振动抑制效果,设计了自抗扰控制器(ADRC),ADRC不依赖于被控对象精确的数学模型,能够应用于不同的重力环境。仿真结果表明,该控制器能实现挠性航天器在地面调试与空间应用阶段的姿态控制及振动抑制。     

Effect of Permeable Crystalline Material on Steel Reinforcement Corrosion of Concrete

Permeable crystalline materialcan permeate into pores and cracks of concrete and catalyze the reaction between Ca(OH) 2and unhydrated cement to generate a great quantity needle non-soluble crystals, which can stop up the pores and cracks of concrete, and increase the impermeability of concrete. This paper reported the results of a study conducted to evaluate steel reinforcement corrosion of concrete specimens uncoated and coated with permeable crystalline material as well as mixed with the permeable crystalline material. The properties evaluated for corrosion test were water impermeability, water absorption, compressive strength and potential. The results of water impermeability, water absorption, compressive strength clearly showed that the permeable crystalline material could prohibit water, any soluble salts and moisture from penetrating the concrete to cause corrosion, leaking, and other problems, and it did increase the compressive strength, which was favorable for protection of corrosion of reinforcing steel. Moreover, it was concluded from the potential-time curve that the steel reinforcement of uncoated specimen was in the state of activation whereas that of other specimens coated and mixed with the permeable crystalline material was in the state of inactivation. Above all, it was indicated that the permeable crystalline materialis very effective to protect the steel reinforcement of concrete from corrosion.     

The Research and Application About "Dry Peeling Off" Technology for Airplane Surface Paint Layer

In this paper, the principle of spurting take off lacquer were introduced; and with orthogonal method the unsaturate polyester was prepared ;it was easy to peel airplane paint layer off with this material and equipment.     

Quality Study of Honeycomb Core Shaping Without Wax Stabilization

Sandwich panels utilizing honeycomb cores result in lightweight, high-strength units that are very rigid. Indeed, they give honeycomb panels the best strength-to-weight ratio of any construction type available. Conventionally, the wax is poured into the cell of the core to strengthen the structure and prevent the core from being crushed during milling. Much time and labor is required to wax, mill, and clean the cores. In this study, the process of pouring wax into the core was skipped. In other words, the cutter directly milled the core. Experiments showed that the compressive strength of the core produced without wax stabilization was only 3% lower than that of cores produced using the traditional method. In addition, the drum peel strengths of cores produced without wax stabilization were 38.4% higher than cores produced using the traditional method, in which residual wax seriously polluted the adhesive. It was also found that eliminating the wax process can reduce costs.     

In-process thermal treatment of polylactic acid in fused deposition modelling

Polylactic acid (PLA) is one of the most widely used open source fused filament fabrication materials due to its ease of extrusion, biodegradability, and mechanical strength. The mechanical strength of PLA largely depends on the proper growth of its semi-crystalline structure, which can be severely impaired by a low rate of crystallization, particularly in open source printers. This can be further aggravated by the non-uniform thermal distribution of heat that causes improper curing among the extruded beads of the printing material. As a result, PLA printed on open source printers does not achieve the best mechanical properties. This research, for the first time, proposes an additive-free solution implemented through a detailed set of experimentation to improve the curing rate through in-process temperature variations to cure the joints among the beads. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy is used to confirm the improvements in the bead joints. This work is conducted in two phases of experiments. In the first phase, a full factorial ANOVA is used to investigate various process parameters and the important variables are used in the second phase to print test specimens in four different sets.     

Investigation of the Corrosion Behaviors of HVOF-Sprayed Carbide Cernet Coatings in Molten Al-Zn-Si Alloy Bath

In continuous hot-dip galvanization process the corrosion and chemical stability of the sink roll in the galvanizing bath are important problem which effects on the quality and productivity. In order to protect the sink roll the carbide cermet and/or ceramic coatings were deposited on the surface of the sink roll. The WC-, Cr3 C2-cermet coatings were deposited by high velocity oxygen fuel (HVOF) spray, respectively. The coating samples were immersed in molten Zn-alloy containing 50 wt % aluminum at 833 K for 24 hr and 144 hr, respectively. The inter-diffusion and inter-reaction of Zn, Al and elements in coating and corrosion behaviors of these coatings were investigated by XRD, SEM and EPMA etc. The corrosion mechanisms of the carbide cermet coatings and ceramic coatings in molten High Al-Zn-alloy were approached.     

Fundamental study of adhesion of ice to cooling solid surface (Discussion on influence of copper oxide layer on ice adhesion force)

In many situations, ice often adheres to a cooling solid surface, frequently causing serious accidents. It is critical to clarify the mechanism of ice adhesion to the cooling surface in order to prevent ice adhesion. In a past study, the shearing stresses of two kinds of test plates with a copper surface having the higher thermal conductivity were measured. The shearing stress corresponds to ice adhesion force. Both shearing stresses were significantly different; however, the cause remains unclear.Therefore, the present study focuses on an oxide layer as the main factor causing the difference of both shearing stresses; the influence of the oxide layer formed on shearing stress was discussed. And in the removal and reformation processes of the oxide layer, the time variation of the shearing stress was clarified. Moreover, the relationship between the state of the copper surface and the shearing stress was also clarified by surface analysis.     

＂Three Transformations＂ and Standardization

During his inspection in Henan Province in May, Chinese President Xi Jinping stressed to ＂push forward the transformation from China Speed to China Quality, from Made in China to Created in China, and from Chinese Products to Chinese Brand＂. The ＂Three Transformations＂ are the specific requirements and goal of China＇s national development in the context that market should play a decisive role in the allocation of resources.     

重塑标准推行格局 推动LED照明的普及（英文）

正When you are enjoying the green,energy-saving and healthy lighting of IKEA LED luminaire,you may not realize that most of IKEA’s LED bulbs are produced by the LED luminaire smart manufacturing system of Hangzhou Zhongwei Photoelectricity CO.,LTD(ZVISION).No longer enclosed in the laboratory,the product standards are brought into the factory workshop and even to the entire production process.Thus,the standards are promoted and applied in a favorable way by enterprises,benefitting consumers with high quality products.     

Chinese Experts Contribute to ISO＇s New Toy Standards

正The international standard,ISO 8124-6,Safety of toys–Part 6:Certain phthalate esters in toys and children’s products,was officially issued by ISO worldwide on August 15.It was the first time for Chinese experts to lead the ISO standard development in toys industry.The standard was drafted by a group of Chinese experts from SAC/TC for toys and relevant Chinese departments and finally completed by a dedicated international group of experts.ISO 8124-6 makes a substantive breakthrough in the aspects of the scope of toys,limitation of plasticizer types,control of test cost,accuracy of test,operation convenience,etc.,offering the operational guidance for toy manufactures and testing laboratories.     

SAC Delegation Visits AENOR and Signs Cooperation Agreements

正SAC Administrator Tian Shihong led the Chinese delegation to visit the Spanish Association for Standardization and Certification(AENOR)on September 15,2014.Mrs.Begona Cristeto,the Vice-Minister of Industry,Energy and Tourism of Spain,and Mr.Avelino Brito,the President and CEO of AENOR greeted the delegation.The two sides had a deep and friendly discussion on strengthening the cooperation between China and Spain in the standardization field and promoting the standardization work to support the development of economy and trade in the two countries.