Nonlinear H∞ based underactuated attitude control for small satellites with two reaction wheels

Underactuated attitude control is supposed to be used on spacecraft when failure happens with onboard actuators. One main problem with existing underactuated attitude control designs is their limited capabilities against disturbances. In order to solve this problem, an approach based on the theory of H∞$H\infty$ is proposed in this paper. Two propositions are derived from the H∞$H\infty$ theory to improve the robustness of one popular underactuated attitude control design, which was presented by Tsiotras et al. It is proved mathematically that the controller satisfying these two propositions respectively can stabilize the underactuated attitude system locally or globally. The numerical simulations show that the improved controllers based on the H∞$H\infty$ theory could provide higher pointing accuracy for small satellites against disturbances. This validates the effectiveness of the proposed H∞$H\infty$ based approach to improve existing underactuated attitude control designs.     

Advanced reaction wheel controller for attitude control of spacecraft

A design procedure is presented for an attitude control system consisting of a momentum wheel and a reaction wheel. Control laws are designed for this system using modern control techniques. The observer based method produces a control scheme which achieves a good transient response.     

姿态控制系统安全阀排放研究

恒压挤压式姿态控制系统一般采用压力调节器对气瓶中的高压气体进行调节,并采用安全阀保证系统的安全。设计时一般保证压力调节器节流口在任何情况下均为临界截面,气体通过压力调节器节流口后压力降低,一般远高于大气压力。由于节流口后气流涡流和管路摩擦的作用,气流在到达安全阀排放口后,仍然为临界流动状态。因此,可以采用收缩喷嘴节流公式计算压力调节器节流口和安全阀排放口的压力和流量参数。根据该数学模型,计算了姿态控制系统安全阀前气体压力和流量,试验结果表明所采用的计算方法可行。     

Attitude pointing enhancement for combined energy and attitude control system

This paper extends the previous works that appeared in Acta Astronautica. An approach that incorporates the Active Force Control (AFC) technique into a conventional Proportional-Derivative (PD) controller is proposed for a 50 kg small satellite. Numerical treatments are performed to validate the effectiveness of AFC. The attitude control capability of the combined energy and attitude control system (CEACS) is expected to improve. The result shows an important attitude pointing enhancement for the CEACS attitude control task.     

一种姿轨控发动机地面试验控制系统设计

控制系统在试车过程中发出指令信号,使发动机和试车台各工艺系统按照预定的程序完成规定试车任务。为了适应某型号姿轨控发动机试验对控制精度要求的提高,需要对现有控制系统进行改造,基于现场可编程门阵列和高速固态继电器设计了一种新的控制系统,其控制模块用于操作人员对试验系统上的各路电磁阀进行手动与自动控制,其复记模块可以实时记录系统状态以便于指挥人员了解系统工作状况,并能够进行数据分析判断。该系统建成后可以满足该型号姿轨控发动机试验的要求,控制精度为0.1 ms。     

大机动飞行情况下姿态控制系统的设计

本文针对目前战术导弹广泛使用捷联系统这个现状,以及对大机动飞行器采用姿态角误差反馈进行控制有时出现的奇异问题,提出并研究了基于四元数进行大机动战术导弹姿态控制系统的设计问题.首先,给出了大机动飞行情况下基于四元数描述的弹体动力学模型,然后,基于非线性控制系统综合方法设计了姿态控制系统,并验证了系统的稳定性.研究结果表明,基于四元数进行姿态控制系统的设计,既解决了姿态角表示法存在的奇异性问题,又可减少捷联计算机的计算量,对战术导弹具有重要实际意义.最后,通过数值仿真验证了本文提出方法的有效性.     

末修姿控系统极性检测仪设计

为满足末修姿控动力系统与控制系统一致性和协调性检测而研制的末修姿控系统极性检测仪,能实时检测并显示末修姿控动力系统根据控制系统发出的控制指令按时序动作的情况,从而为控制系统提供可靠的判断数据,确保了末修姿控动力系统的正常工作。末修姿控系统极性检测仪使用方便,操作界面简单,可自动记录、保存检测数据,并可离线浏览、打印,自动化程度高;同时仪器内部嵌入控制信号模拟线路,可自动进行模拟自检测试,从而提高工作效率,减少设备投入,其便携式、小型化设计更适应了机动、灵活的使用需求。     

自增压系统在轨姿控动力系统中的应用

自增压轨姿控动力系统结合了涡轮泵压式火箭发动机的高性能、轻质量和挤压式推进系统的可重复启动能力。降低贮箱压力和减少惰性气体用量的同时,通过采用紧凑的高压推力室减少了其他组件的结构尺寸和重量。介绍了自增压系统在轨姿控动力系统的应用优势、技术特点、工作原理和目前的技术发展情况,分析了相应的关键技术,并基于目前技术基础,展望了发展的必要性和技术策略及途径。     

Adaptive attitude control of spacecraft using neural networks

An adaptive control technique can be applicable to reorient spacecraft with uncertain properties such as mass, inertial and various misalignments. A nonlinear quaternion feedback controller is chosen as a baseline attitude controller. A linearly added adaptive input supported by neural networks to the baseline controller can estimate and eliminate the uncertain spacecraft property adaptively. The normalized input neural networks (NINNs) are examined for reliable computation of the adaptive input. The newly defined learning rules of the neural networks are established appropriately for a spacecraft. To prove the stability of the closed-loop dynamics with the control law, Lyapunov stability theory is considered. As a result, the proposed approach results in the uniform ultimate boundedness in tracking error and robustness of the chattering and the singularity problems.     

采用平行构型变速控制力矩陀螺群的航天器姿态控制

研究了平行构型变速控制力矩陀螺群的控制律及其在航天器姿态控制中的应用。首先建立了以变速控制力矩陀螺为执行机构的航天器姿态动力学模型，并给出了全局渐近稳定的姿态反馈控制律。将每一对框架平行的陀螺作为独立的单元控制，引入了与控制力矩陀螺的框架运动相关的动坐标系，在此基础上给出了控制力矩陀螺的一种控制律。此控制律使陀螺群在奇异状态下仍具有可控性，并且力矩误差在动坐标系的某一方向始终为零，从而利用共轴的构型特点和陀螺转子的可变速性补偿控制力矩陀螺的力矩误差，使变速控制力矩陀螺群的输出力矩与期望的力矩相等。最后以双平行构型为例，对航天器的姿态稳定控制进行了数值仿真，并给出了一种控制力矩的分配方案。仿真结果证明了控制律算法的有效性。     

Experiments and numerical simulations of an electrodynamic tether deployment from a spool-type reel using thrusters

The amount of space debris is ever increasing, and pollution of the space environment has become a serious problem that can no longer be ignored. Consequently, the active removal of large space debris from crowded economically useful orbits should begin as soon as possible. The Japan Aerospace Exploration Agency has been investigating an active debris removal system that employs highly efficient electrodynamic tether (EDT) technology for orbital transfer. This study investigates the tether deployment from a spool-type reel using thrusters by means of numerical simulations of an EDT system. The thrusters are used in order to ensure the deployment of a tether with the length of several kilometers. In the simulations using a multiple mass tether model, the key parameters are estimated from various on-ground experiments. By means of the numerical simulations, the dynamics of tether deployment is studied and requirements of thruster needed for the deployment, such as the thrust forces and the periods of thruster activation, are clarified.     

轨姿控推进系统用电磁阀性能仿真研究

轨姿控推进系统采用电磁阀控制内部流体通路的开启与断流,从而实现其重复启动和脉冲工作.在轨姿控推进系统快速稳定工作问题的研究中,电磁阀的性能对推进系统至关重要.针对轨姿控推进系统用电磁阀,基于电磁学及运动学等基本原理,建立了电磁阀动态数学模型,利用Matlab Simulink软件进行了动态仿真,得到了电磁阀动态响应特性;采用CFD软件对阀门内部流场进行数值模拟仿真,获得了精确的静态流阻特性,直观展现了电磁阀动态流场,为电磁阀的性能优化和轨姿控推进系统的性能提高提供依据.     

固体姿轨控针栓推力器内流场数值仿真

为研究针栓推力器内.流场的特征和规律,采用二维轴对称模型,开展了针栓运动过程的非稳态及稳态流场仿真,分析了不同开度下的流场结构、针栓所受气动力及流场对针栓几何参数的敏感性.结果表明:由于针栓的干扰作用,流场结构呈现出复杂激波系、顶端流动分离等现象;气动力系数与针栓头部锥角大小呈正相关关系,与集气室压强无关;节流面形状对气流参数分布、激波强度及位置、气动力等表征的流动模态影响很大.     

姿控发动机试验阀门电流信号采集系统设计

介绍了液体火箭姿控发动机阀门电流信号采集系统的设计要点、研制方法与主要开发过程。较详细阐述了高速数据采集系统应用软件开发及系统集成后的调试方法。该采集系统实现了多路液体火箭姿控发动机试车阀门电流信号的数字化测量。     

Magnetic dipole moment estimation and compensation for an accurate attitude control in nano-satellite missions

Nano-satellites provide space access to broader range of satellite developers and attract interests as an application of the space developments. These days several new nano-satellite missions are proposed with sophisticated objectives such as remote-sensing and observation of astronomical objects. In these advanced missions, some nano-satellites must meet strict attitude requirements for obtaining scientific data or images. For LEO nano-satellite, a magnetic attitude disturbance dominates over other environmental disturbances as a result of small moment of inertia, and this effect should be cancelled for a precise attitude control. This research focuses on how to cancel the magnetic disturbance in orbit. This paper presents a unique method to estimate and compensate the residual magnetic moment, which interacts with the geomagnetic field and causes the magnetic disturbance. An extended Kalman filter is used to estimate the magnetic disturbance. For more practical considerations of the magnetic disturbance compensation, this method has been examined in the PRISM (Pico-satellite for Remote-sensing and Innovative Space Missions). This method will be also used for a nano-astrometry satellite mission. This paper concludes that use of the magnetic disturbance estimation and compensation are useful for nano-satellites missions which require a high accurate attitude control.     

大推力姿控发动机推进剂控制阀流场分析

采用数值分析与试验研究相结合的方法,对姿控发动机控制阀内部流场进行分析.数值计算与试验数据相吻合,可以认为数值分析能够较真实地反映控制阀的内部流动特性.对流场参数的分析表明：来流撞击阀芯和阀口收缩节流,是控制阀内流动能量损失的两个主要环节,在结构设计中应尽量避免;另外,流道截面的连续性及流动空间的充分性也是控制阀内部结构设计需要考虑的重要环节.     

Self-stabilising attitude control for spinning tethered formations

The paper analyses the dynamics of a spinning tethered formation where the tethered units are modelled as extended rigid bodies. The system, composed by two platforms linked by a flexible tether a few hundreds of meters long, constitutes the building block of more complex tethered architectures utilised in proposed space interferometry missions. The issue investigated herein is the transfer of a collimated beam from one platform to another in the presence of environmental perturbations and structural vibrations affecting the position and attitude of the two tethered units. We propose to damp residual oscillations and limit the effect of environmental torques with the aid of two passive dampers placed at the tether attachment point. When the damping system is properly tuned, this approach has the considerable advantage of rapidly bringing the system to a minimum energy configuration (zero residual vibrations) without any external control force. Numerical results show the effectiveness of the proposed control strategy and provide an important element towards the implementation of future space-based observatories and formation-flying demonstration mission based on tether-connected architectures.     

小卫星的鲁棒自适应姿态控制

对于中低轨道的小卫星而言，设计能克服参数不确定性及非参数不确定性影响的鲁棒自适应控制器具有重要的工程意义和理论价值。考虑存在参数不确定性及非参数不确定性，分析了小卫星的姿态动力学及运动学方程，设计出了一种鲁棒自适应控制器，证明了该控制器可以保证控制系统全局一致最终有界稳定。仿真结果验证了该控制器的有效性。