Elastic Robot Control: Nonlinear Inversion and Linear Stabilization

An approach to the control of elastic robot systems for space applications using inversion, servocompensation, and feedback stabilization is presented. For simplicity, a robot arm (PUMA type) with three rotational joints is considered. The third link is assumed to be elastic. Using an inversion algorithm, a nonlinear decoupling control law Ud is derived such that in the closed-loop system independent control of joint angles by the three joint torquers is accomplished. For the stabilization of elastic oscillations, a linear feedback torquer control law us is obtained applying linear quadratic optimization to the linearized arm model augmented with a servocompensator about the terminal state. Simulation results show that in spite of uncertainties in the payload and vehicle angular velocity, good joint angle control and damping of elastic oscillations are obtained with the torquer control law u = ud + us.     

Control and stabilization of nonlinear uncertain elastic roboticarm

An approach is presented to the control of an uncertain nonlinear flexible robot arm (PUMA-type) with three rotational joints. The third link is assumed to be elastic. A torquer control law, which is a function of the trajectory error, is derived for controlling the joint angles. The knowledge of the system dynamics is not required for the derivation of the controller. This controller includes a reference model to generate command joint angle trajectories, and a dynamic system in the feedback path which requires only joint angle and rate for feedback. The torquer controller asymptotically decouples the elastic dynamics into two subsystems, representing the transverse vibration of the elastic link in two orthogonal planes. For the damping of the elastic vibration, a force control law using modal velocity feedback is synthesized. Simulation results are presented to show that the combination of the torque and force control law accomplishes reference joint angle trajectory tracking and elastic mode stabilization despite the uncertainty in the system     

飞机机身-机翼接头精加工条件评价技术

 在飞机机身部件数字化对接装配过程中,为保证机身-机翼接头配合面与连接孔精加工的安全性,在加工前安排机身-机翼接头的在线三坐标测量工序。具体阐述了基于专用数控机床的机身-机翼接头测量方法,提出了被测孔与平面理想几何要素的稳健最小二乘拟合方法,并给出了基于被测孔、面拟合方位的机身-机翼接头可加工性评价模型。仿真结果表明：接头孔与平面的稳健拟合方法具有较高的精度和较强的抗粗差能力,机身-机翼接头的可加工性检验能揭示不合理的飞机机身、机翼位姿所带来的加工安全隐患,从而避免精加工过程破坏机身-机翼接头。     

基于碰撞检测的自适应阻抗控制机械臂系统(英文)

针对柔性关节机械臂,本文阐述了机械臂能够像人手一样安全操作的方法。3种方法相结合,以便机械臂能够柔顺的接触操作对象并控制接触力在预设定范围内。首先,提出采用虚拟分解法的笛卡尔阻抗控制用来实现机械臂在笛卡尔空间的柔顺控制。其次,引入自适应关节动态补偿器使得机械臂能够实施更为精确的控制。最后,设计了基于笛卡尔力反馈的实时路径规划,从而使机械臂能够检测碰撞并控制接触力。基于碰撞检测的自适应阻抗控制器能够简化其在机械臂上的实施,保持机械臂对环境的友好操作,并且严格满足系统的全局稳定性。实验在4自由度的卫星在轨自维护机械臂平台得以验证。碰撞检测实验和轨迹跟踪实验结果证明了所提出方法的有效性和可行性。     

体视投影图初析

从体视投影的原理出发，论述了体视投影角、体视投影面的建立及空间直角坐标的体视投影等问题，提出了在平面上绘制立体图象的投影体系和投影作图的具体方法。     

带褶皱的等张力体航天服软关节设计与实验

面向未来行星表面探测任务,航天服的活动性能需要进一步提高。为此,应改进航天服软关节的结构形式。根据等张力体形状内部承压时不存在周向应力的理论,在该曲面周向上加入褶片结构,设计出了带褶皱的等张力体关节,使之能够沿周向弯曲或伸展。为验证关节性能,利用柔性单自由度关节测量设备,进行了多次加卸载和不同运动范围的力矩特性研究,分析了关节的几何形态、等容性以及主应力状态,并将该关节与无褶皱的等张力体关节和平褶式关节进行了比较,最后讨论了关节的优化方向。结果表明,在测试的0°~80°范围内,关节力矩较小,最大容积变化为1.6%。关节弯曲时,等张力体曲面上周向应力仍可忽略不计。首次加载与之后的加载有一定的差异,而不同的运动范围对关节活动性能无影响。与其他两种关节形式比较,带褶皱等张力体关节在几何尺寸、运动形态和活动性能上都具有一定的优势。此外,该关节可在结构和材料方面进一步优化。     

构型及二次燃烧对RBCC引射模态推力性能的影响

提出了掺混度模型并数值研究了五种构型和两种燃烧组织模式对RBCC发动机引射模态推力性能的影响,其中改进构型获得了推力增强.得出如下结论:(1)在引射掺混的前段,掺混过程主要由一次流喷管结构决定.而在引射掺混后段,后体构型对掺混过程影响较大.(2)获得较高掺混速率、较优引射比并在掺混过程中产生高于环境压强的流动状态是改进构型获得推力增强的两个重要因素.(3)与SMC燃烧组织模式相比,改进构型的SPI模式有效延迟了二次燃烧,不仅提高了燃烧效率而且没有使引射比过度下降.     

A Hybrid Optimization Approach for SRM FINOCYL Grain Design

This article presents a method to design and optimize 3D FINOCYL grain （FCG） configuration for solid rocket motors （SRMs）. The design process of FCG configuration involves mathematical modeling of the geometry and parametric evaluation of various independent geometric variables that define the complex configuration. Virtually infinite combinations of these variables will satisfy the requirements of mass of propellant, thrust, and burning time in addition to satisfying basic needs for volumetric loading fraction and web fraction. In order to ensure the acquisition of the best possible design to be acquired, a sound approach of design and optimization is essentially demanded. To meet this need, a method is introduced to acquire the finest possible performance. A series of computations are carried out to formulate the grain geometry in terms of various combinations of key shapes inclusive of ellipsoid, cone, cylinder, sphere, torus, and inclined plane. A hybrid optimization （HO） technique is established by associating genetic algorithm （GA） for global solution convergence with sequential quadratic programming （SQP） for further local convergence of the solution, thus achieving the final optimal design. A comparison of the optimal design results derived from SQP, GA, and HO algorithms is presented. By using HO technique, the parameter of propellant mass is optimized to the minimum value with the required level of thrust staying within the constrained burning time, nozzle and propellant parameters, and a fixed length and outer diameter of grain.     

多接头大载荷机翼加载处理方法

由于试验件缺少右外翼部分,对接接头多且复杂,试验考核载荷较大,给机翼载荷的施加带来较大难题。对三组接头设计独立的加载夹具,前中接头通过延伸加载力线间距的方式降低实际加载点载荷,依据上下接头处载荷方向相反的特点,设计不同的加载接头连接形式,保证了飞机实际对接接头的变形自由度。依靠坐标转换将后接头载荷进行调整,方便试验现场实施。该方法能够保证传递至接头上的载荷准确,避免了各接头之间的刚度匹配问题,且方便安装,满足试验要求。采用局部约束装置,有效避免了接头处有害损伤的产生,对接头起到实时保护。     

三维极坐标视线动力学

阐述了极坐标视线动力学方程的研究现状。建立了三维极坐标视线动力学方程，讨论了该动力学方程的简化问题，得到了特殊平面（攻击平面）内的简化形式，该简化形式在特定的条件下与三维极坐标视线动力学方程是等价的。     

固体火箭发动机燃烧室喷管一体化网格生成

给出固体火箭发动机燃烧室喷管一体化网格策略,用二维方法生成平面网格经旋转或堆砌形成空间网格。对网格正交性受几何域形状限制的情况进行了讨论。给出了一种燃烧室－喷管外形的网格结果。     

战斗机气动布局划分

战斗机气动布局的类别,没有统一标准,分类众多。本文在归纳战斗机气动布局划分的基础上,提出目前可将战斗机气动布局划分成5种形式。     

Crippled motion in robots

The feasibility of harnessing redundant degrees of freedom in a robotic arm in order to keep it in service, pending repair, after it has lost mobility in one of its joints, is examined. The concept of critical crippling is introduced, and three familiar robots are investigated as case studies. Guidelines on how one might enhance a manipulator's ability to continue operating productively even with a crippled joint are suggested     

SiO2f/SiO2复合材料自身及其与铜、不锈钢的钎焊

采用AgCuTi活性钎料,在880℃/10min规范下成功实现了SiO2f/SiO2自身、SiO2f/SiO2与Cu和SiO2f/SiO2与1Cr18Ni9Ti三种接头的连接。实验结果表明,三种接头中靠近SiO2f/SiO2母材的界面处均形成了一层薄薄的扩散反应层组织,反应层中出现了Ti和O的富集,根据两者的原子比例推断生成了TiO2相;另外,三种接头中心区都形成了由灰色相和白色相共同组成的Ag-Cu共晶组织,其中灰色相为Cu基固溶体,白色相为Ag基固溶体。接头剪切强度结果显示,SiO2f/SiO2/Cu接头剪切强度为12.4MPa,SiO2f/SiO2/1Cr18Ni9Ti接头剪切强度为18.4MPa,接头中的残余应力是决定接头强度大小的重要因素之一。     

航天器高超声速气动力的数值计算

本文把航天器的外形用数以百计的平面四边形元素来近似。利用高超声速绕流时面积元素之间的干扰可忽略的假设,分别计算出各面积元素的气动力,积分后得出航天器的气动力,算例的结果是令人满意的。本文也描述了航天器表面网格的生成技术和计算机绘制航天器在不同视角下外形图的原理。本文方法可供航天器初步气动设计时用。     

In-Flight Alignment and Calibration of Inertial Measurement Units?Part II: Experimental Results

This is the second part of a two-part paper which summarizes work pursued by the author in 1967 [2]. The paper describes the application of minimum-variance estimation techniques for in-flight alignment and calibration of an inertial measurement unit (IMU) relative to another IMU and/or some other reference. The first paper [1] formulates the problem, and this paper reports numerical results and analyses. The approach taken is to cast the problem into the framework of Kalman-Bucy estimation theory, where velocity and position differences between the two IMU's are used as observations and the IMU parameters of interest become part of the state vector. Instrument quantization and computer roundoff errors are considered as measurement noise, and environmental induced random accelerations are considered as state noise. In this paper, numerical results for three important IMU error parameter configurations are presented and discussed. The main results of the paper determine the effects of state and observation noise levels and the nominal trajectory on the identifications of the errors for these configurations. A discussion of the minimum number of trajectory maneuvers and of the optimal trajectory maneuvering is given.     

OPPORTUNITIES FOR MAGNETOSPHERIC RESEARCH WITH COORDINATED CLUSTER AND GROUND-BASED OBSERVATIONS

ESA's first multi-satellite mission Cluster is unique in its concept of 4 satellites orbiting in controlled formations. This will give an unprecedented opportunity to study structure and dynamics of the magnetosphere. In this paper we discuss ways in which ground-based remote-sensing observations of the ionosphere can be used to support the multipoint in-situ satellite measurements. There are a very large number of potentially useful configurations between the satellites and any one ground-based observatory; however, the number of ideal occurrences for any one configuration is low. Many of the ground-based instruments cannot operate continuously and Cluster will take data only for a part of each orbit, depending on how much high-resolution (burst-mode') data are acquired. In addition, there are a great many instrument modes and the formation, size and shape of the cluster of the four satellites to consider. These circumstances create a clear and pressing need for careful planning to ensure that the scientific return from Cluster is maximised by additional coordinated ground-based observations. For this reason, the European Space Agency (ESA) established a working group to coordinate the observations on the ground with Cluster. We will give a number of examples how the combined spacecraft and ground-based observations can address outstanding questions in magnetospheric physics. An online computer tool has been prepared to allow for the planning of conjunctions and advantageous constellations between the Cluster spacecraft and individual or combined ground-based systems. During the mission a ground-based database containing index and summary data will help to identify interesting datasets and allow to select intervals for coordinated studies. We illustrate the philosophy of our approach, using a few important examples of the many possible configurations between the satellite and the ground-based instruments.     

Design and Optimization of 3D Radial Slot Grain Configuration

Upper stage solid rocket motors (SRMS) for launch vehicles require a highly efficient propulsion system. Grain design proves to be vital in terms of minimizing inert mass by adopting a high volumetric efficiency with minimum possible sliver. In this article, a methodology has been presented for designing three-dimensional (3D) grain configuration of radial slot for upper stage solid rocket motors. The design process involves parametric modeling of the geometry in computer aided design (CAD) software through...     

Through-thickness heterogeneity in creep properties of friction stir welding 7B50-T7451 aluminum alloy thick plate joint: Experiments and modeling

Through-thickness heterogeneity in creep properties of 7B50-T7451 aluminum alloy Friction Stir Welding(FSW) joints was investigated. Creep tests for three slices of the FSW joint were conducted at the temperature of 150–200 °C and applied stress of 60–225 MPa. The theta projection method was used to predict creep curves and minimum creep rate. The results show that the minimum creep rate increases and creep rupture life decreases with the increase of creep temperature and applied stress. Creep p...     

基于广义Kalman估计的机载雷达高精度控制系统

 研究了在某型现役机载雷达系统中, 采用广义Kalman 滤波器方法来预估目标机的俯仰角和方位角,产生跟踪目标用的雷达天线驱动信号, 替代传统的速率陀螺测量元件来补偿本机机动所造成的扰动的方法,同时对探测信号本身所具有的延迟起到了补偿作用。对目标的运动采用直角坐标系中的Singer 模型描述, 而对测量信号则是应用极坐标系中的描述, 采用广义Kalman 滤波器来完成估计, 即在每一步的估计和控制中对计算测量方程进行线性化结果, 实现两种坐标系的转换。通过应用Matlab/ Simulink 软件对整个系统的建模、设计及仿真研究, 得到了满意的结果。