Underactuated spacecraft angular velocity stabilization and three-axis attitude stabilization using two single gimbal control moment gyros

Angular velocity stabilization control and attitude stabilization control for an underactuated spacecraft using only two single gimbal control moment gyros （SGCMGs） as actuators is investigated. First of all, the dynamic model of the underactuated spacecraft is established and the singularity of different configurations with the two SGCMGs is analyzed. Under the assumption that the gimbal axes of the two SGCMGs are installed in any direction, and that the total system angular momentum is not zero, a state feedback control law via Lyapunov method is designed to globally asymptotically stabilize the angular velocity of spacecraft. Under the assumption that the gimbal axes of the two SGCMGs are coaxially installed along anyone of the three principal axes of spacecraft inertia, and that the total system angular momentum is zero, a discontinuous state feedback control law is designed to stabilize three-axis attitude of spacecraft with respect to the inertial frame. Furthermore, the singularity escape of SGCMGs for the above two control problems is also studied. Simulation results demonstrate the validity of the control laws.

IMPROVED QUANTITATIVE FEEDBACK THEORY TECHNIQUE AND APPLICATION TO THREE-AXIS HYDRAULIC SIMULATOR

In order to meet tracking performance index of three-axis hydraulic simulator, based on classical quantitative feedback theory （QFT）, an improved QFT technique is used to synthesize controller of low gain and bandwidth. By choosing a special nominal plant, the improved method assigns relative magnitude and phase tracking error between system uncertainty and nominal control plant. Relative tracking error induced by system uncertainty is transformed into sensitivity problem and relative tracking error induced by nominal plant forms into a region on Nichols chart. The two constraints further form into a combined bound which is fit for magnitude and phase loop shaping. Because of leaving out pre-filter of classical QFT controller structure, tracking performance is enhanced greatly. Furthermore, a cascaded two-loop control strategy is proposed to heighten control effect. The improved technique＇s efficacy is validated by simulation and experiment results.

A Three-Axis Robot Using a Remote Network Control System

For the petroleum industry, to reduce the risk of a gas explosion in dangerous working areas, the use of explosion-proof equipment such as air-driven devices which are free from explosions becomes essential. Moreover, for the purpose of saving manpower, a remote operation using a robot via a visual monitoring system and a network is used. However, to overcome the drawback of costly manpower and to improve safety in explosion-prone zones, a three-axis robot using a remote network control system is proposed. In this paper, the three-axis robot can be monitored online via the USB protocol. Furthermore, it also can be remotely manipulated via the TCP/IP protocol by clicking the command of the VB interface on the client pc. Consequently, the remote-control three-axis robot can not only work for people in severe and dangerous circumstances but also can reduce the cost of manpower.

Misalignment Angle Calculation Accuracy Analysis of Three-Axis Stabilized Geostationary Satellite

The most challenging problem of navigation in three-axis stabilized geostationary satellite is accurate calculation of misalignment angles, deduced by orbit measurement error, attitude measurement error, thermal elastic deformation, time synchronization error, and so on. Before the satellite is launched, the misalignment model must be established and validated. But there were no observation data, which is a non-negligible risk of yielding the greatest returns on investment. On the basis of misalignment modeling using landmarks and stars, which is not available between different organizations and is developed by ourselves, experimental data are constructed to validate the navigation processing flow as well as misalignment calculation accuracy. In the condition of using landmarks, the maximum misalignment calculation errors of roll, pitch, and yaw axis are 2, 2, and 104 micro radians, respectively, without considering the accuracy of image edge detection. While in the condition of using stars, the maximum errors of roll, pitch, and yaw axis are 1, 1, and 3 micro radians, respectively, without considering the accuracy of star center extraction. Results are rather encouraging, which pave the way for high-accuracy image navigation of three-axis stabilized geostationary satellite. The misalignment modeling as well as calculation method has been used in the new generation of geostationary meteorological satellite in China, FY-4 series, the first satellite of which was launched at the end of 2016.

The Impact Study of Three-axis Servo System Interference Torque based on Virtual Prototype

The three-axis servo system with the core of gyro stabilization is the foundation to realize its function, and a key technology of the seeker devolopment. In order to reduce the costs, improve the efficiency of research and devolopment, a new method that instead of physical prototype by virtual prototype was proposed. Adams and MATLAB/simulink are used to establish the mechanical dynamics model and controller model of the three-axis servo system. The simulation data which was processed and analyzed is compared with test data, to determine the control parameters of the virtual prototype and improve the accuracy of the model, and test the multiple condition simulation,which can provide a reference for practical production.The simulation results verify the feasibility of the models.

Three-axis coupled flight control law design forflying wing aircraft using eigenstructure assignment method

Due to elimination of horizontal and vertical tails,flying wing aircraft has poor longitudinal and directional dynamic characteristics.In addition,flying wing aircraft uses drag rudders for yaw control,which tends to generate strong three-axis control coupling.To overcome these problems,a flight control law design method that couples the longitudinal axis with the lateraldirectional axes is proposed.First,the three-axis coupled control augmentation structure is specified.In the structure,a‘‘soft/hard"cross-connection method is developed for three-axis dynamic decoupling and longitudinal control response decoupling from the drag rudders;maneuvering turn angular rate estimation and subtraction are used in the yaw axis to improve the directional damping.Besides,feedforward control is adopted to improve the maneuverability and control decoupling performance.Then,detailed design methods for feedback and feedforward control parameters are established using eigenstructure assignment and model following technique.Finally,the proposed design method is evaluated and compared with conventional method by numeric simulations.The influences of control derivatives variation of drag rudders on the method are also analyzed.It is demonstrated that the method can effectively improve the dynamic characteristics of flying wing aircraft,especially the directional damping characteristics,and decouple the longitudinal responses from the drag rudders.

A study of PID and L1 adaptive control for automatic balancing of a spacecraft three-axis simulator

Purpose–The three-axis simulator relies on the air film between the air bearing and the bearing seat to achieve weightlessness and the frictionless motion condition,which is essential for simulating the micro-disturbance torque of a satellite in outer space.However,at the beginning of the experiment,the disturbance torque caused by the misalignment between the center of gravity of the simulator and the center of rotation of the bearing is the most important factor restricting the use of the space three-axis simulator.In order to solve this problem,it is necessary to set the balance adjustment system on the simulator to compensate the disturbance torque caused by the eccentricity.The paper aims to discuss these issues.Design/methodology/approach–In this paper,a study of L1 adaptive automatic balancing control method for micro satellite with motor without other actuators is proposed.L1 adaptive control algorithm adds the low-pass filter to the control law,which in a certain sense to reduce the high-frequency signal and speed up the response time of the controlled system.At the same time,by estimating the adaptive parameter uncertainty in object,the output error of the state predictor and the controlled object can be stabilized under Lyapunov condition,and the robustness of the system is also improved.The automatic balancing method of PID is also studied in this paper.Findings–Through this automatic balancing mechanism,the gravity disturbance torque can be effectively reduced down to 10−6 Nm,and the automatic balancing time can be controlled within 7 s.Originality/value–This paper introduces an automatic balancing mechanism.The experimental results show that the mechanism can greatly improve the convergence speed while guaranteeing the control accuracy,and ensuring the feasibility of the large angle maneuver of spacecraft three-axis simulator.

RESEARCH AND SIMULATION OF THE INFLUENCE OF THREE-AXIAL COMPACTION ON POWDER METALLURGIC PRODUCT PROPERTIES

The warm powder compaction process is simulated by the finite element analysis software, MSCJMARC. The thermal mechanically coupled analysis method is applied on the basis of the updated Lagrangian Method, to simulate the warm powder compaction process. The warm powder compaction process is simulated, and the influence of friction condition and pressing styles are researched on the density of powder green and the mechanics behavior at certain temperature. The results indicate that for cylindrical compacts, with the improvement of the friction condition, the uniformity of distribution of green relative density is largely improved, the pressing force and stress decrease, and the nonconforming pressing processes influence the distribution of green density to some degree. The status of stress distribution of the process that punches firstly press and die finally press is different from the other three processes, and presents the figure of ＇flume ＇.

Mechanical properties of copper nanocube under three-axial tensile loadings

The mechanical properties of copper nanocubes by molecular dynamics are investigated in this paper. The [100], [110], [111] nanocubes are created, and their energies, yield stresses, hydrostatic stresses, Mises stresses, and the relation- ships between them and strain are analyzed. Some concepts of the microscopic damage mechanics are introduced, which are the basis of studying the damage mechanical properties by molecular dynamics. The [100] nanocube exhibits homo- geneity and isotropy and achieves a balance easily. The [110] nanocube presents transverse isotropy. The [111] nanocube shows the complexity and anisotropy because the orientation sizes in three directions are different. The broken point occurs on a surface, but the other two do not. The [100] orientation model will be an ideal model for studying the microscopic damage theory.

Social–financial approach for analyzing financial transitions

This study proposes a social-financial approach(SFA)to fill the methodological research gap in strategic policy design for managing financial transitions during social changes.The SFA seeks to characterize inclusive transitions in response to innovation and analyze financial management in social changes.Using a multilevel perspective,we combine evolutionary finance and inclusive growth analytics into this framework.We contend that the interaction between the different levels can be summarized as spontaneous adjustments and the alignment of financial elements with the indicators.Actors who attempt to achieve their goals based on past performance evaluations and other forms of bounded rationality strive to cope with adjustments and further trigger a reorientation of the existing regime.We also developed a new configuration tool called the three-axis description to describe the evolution of financial transitions at different stages.These methods allow us to analyze the evolution of financial transition and efficiency,and we argue that market efficiency evolves in stages with the finan-cial transition.Finally,to demonstrate the capability of SFA to identify diverse financial transition pathways,we examined an example case:the establishment of the Bretton Woods System.

一种用系统机和单片机实现的机床数控系统

研制了用系统机和单片机组成的精密电火花加工机床微机数控系统。采用一台系统机为主机、四片单片机为子机组成主从式控制系统，实现四轴三联动数控。

基于机器视觉的智能读书架

根据调查显示,中国小学生视力不良检出率达到45.71%,初中生达到74.36%,高中生达到83.28%,我国青少年近视率远高于其他国家。读写时坐姿不正确及视距过近等是导致近视的罪魁祸首,同时,这些不良习惯也是导致斜视、弱视和颈椎、脊椎发育不良的主要原因之一^([1])。本文研制一款基于机器视觉的用于辅助中小学生矫正坐姿的智能读书架,能够帮助阅读者端正坐姿,挺直腰背,养成良好的读写习惯,提高学习效率,有效防止颈椎、脊椎问题,保护青少年的身心健康。

多功能精密电火花加工机床数控系统的研制

本文论述了我们研制的用系统机和单片机组成的精密电火花加工机床数控系统。该系统采用４８６系统机实现多种加工功能和人机交互功能，可实现４轴３联动；采用４片８０３１单片机同时驱动４轴步进电机，提高了系统的插补速度和进给精度。

基于C8051F020单片机的无人机加速度采集系统

为了满足无人机三轴加速度测量与控制的需要,设计了一种简易、方便的加速度采集系统。本系统采用高集成度单片机C8051F020进行多通道数据的采集和A/D转换,在单片机内部完成数据存储、数据处理,再利用串行通信接口将数据传送至上位机,然后由无线发射模块发送至地面接收设备。在试验条件下,可以将采集到的数据传送至PC机进行分析或者由液晶显示仪显示。

一般三次代数方程求根公式的特殊推导——三元数应用一例

应用三元数运算,推导得到了一般三次代数方程的求根公式,结果证明与卡尔丹公式是一致的。

基于Simulink的三轴变轨迹等厚振动筛动力学仿真

介绍了一种三轴变轨迹等厚振动筛。针对该振动筛建立了三自由度动力学模型,分析了激振力不通过质心时振动筛的工作原理,得到了振动筛质心的振动微分方程及筛箱任意点运动方程。并在Simulink基础上,结合设计实例,对振动筛质心的振动微分方程及筛箱任意点的运动方程进行了仿真计算。结果表明,该振动筛质心和筛面的运动符合等厚振动筛的运动特性,通过适当调整激振器的力心和质心的相对位置,可设计出处理能力更大的变椭圆轨迹等厚振动筛,从而为进一步研究和产品设计提供了理论依据。