Event-triggered adaptive fuzzy attitude takeover control of spacecraft

The problem of attitude takeover control of spacecraft by using cellular satellites with limited communication, actuator faults and input saturation is investigated. In order to lighten the communication burden of cellular satellites, an event-triggered control strategy is adopted. The filtered attitude information needs to be transmitted only when the defined measurement error reaches the event-triggered threshold in this strategy. Then, to deal with the unknown inertia matrix, actuator faults, external disturbances and the errors caused by event-triggered scheme, fuzzy logic systems is introduced to estimate the uncertainties directly. Combining fuzzy logic control strategy and the event-triggered method, the first event-triggered adaptive fuzzy control law is developed. Then, torque saturation of cellular satellites is further considered in the second control law, where the upper bound of the uncertainties is estimated by fuzzy logic systems. The resulting closed-loop systems under the two control laws are guaranteed to be bounded. Finally, the effectiveness of two proposed control laws is verified by the numerical simulations.     

26 m射电望远镜副面调整机构误差分析

新疆乌鲁木齐南山26 m射电望远镜（NSRT）采用 Stewart 并联机构实现副反射面（简称副面）五自由度运动调整。为确保并联机构的运动精度能满足射电望远镜高精度的指向要求，对影响副面调整机构运动精度的各项误差进行了分析。几何误差模拟结果显示，为使并联机构达到要求的精度，应保证杆长误差小于0.08 mm，铰链误差小于0.04 mm。通过对实测结果与仿真结果分析比较，得出回零误差是造成并联机构误差的主要原因。由于并联机构的回零检测装置主要由增量式编码器与限位开关组成，其中限位开关反馈信号的异常，会引起并联机构的回零误差，分析得到该因素是造成NSRT副面并联机构工作偏差的主要原因，这对并联机构的误差补偿具有指导意义。     

Inertial aided BDS triple-frequency integer ambiguity rounding method

The integer ambiguity resolution (AR) of carrier phase is significant for Global Navigation Satellite System (GNSS) precise positioning. However, in kinematic case, single-epoch AR methods based on alone GNSS are usually not reliable due to the instable pseudorange accuracy. Moreover, the computation of classical AR method Least Squares Ambiguity Decorrelation Adjustment (LAMBDA) is large. Thus, the inertial measurement unit (IMU) is introduced, a new inertial-aided AR method that directly rounds the float ambiguity of BeiDou triple-frequency combined observations, which is characterized by long wavelength, low carrier-phase noise and ionospheric delay, is proposed. The mathematical model of the new method is derived first. Then the impacts of the carrier-phase noise, ionospheric delay and inertial navigation system (INS) position error on the AR success ratio of combined observation are analyzed through probabilistic approach. Based on above investigation, the combinations (0, ?1, 1), (1, 4, ?5) and (4, ?2, ?3) are selected to resolve the original ambiguity. A vehicular integrated navigation test is performed to demonstrate the proposed method. The results show that the average AR success ratios of the three selected combinations, whose float ambiguity errors are 0.041, 0.146, 0.279 cycle respectively, are above 97.25% without regard to low-elevation C05. With respect to positioning accuracy based on our AR method when compared with IE software, the east, north, up error RMS of position are 0.042, 0.024, 0.069 m, respectively. In terms of the AR recover after the BeiDou signals outage, as long as 62 s BeiDou signal complete outage, all the ambiguities of all satellites could be re-fixed immediately. Besides, during the 90 s signals partial outage, the AR is not influenced by the position error, since the float ambiguity errors are all below half-cycle. The research of this contribution demonstrates the effectiveness of the proposed new method, which indicates it is applicable to kinematic positioning, even in BDS degraded and denied environments.     

Guidance laws for attacking defended target

In this paper, two new guidance laws based on differential game theory are proposed and investigated for the attacker in an attacker-defender-target scenario.The conditions for the attacker winning the game are analyzed when the target and defender using the differential game guidance law based on the linear model.The core ideas underlying the two guidance laws are the attacker evading to a critical safe boundary from the defender, and then maintaining a critical miss distance.The guidance law more appropriate for the attacker to win the game differs according to the initial parameters.Unlike other guidance laws, when using the derived guidance laws there is no need to know the target and the defender's control efforts.The results of numerical simulations show that the attacker can evade the defender and hit the target successfully by using the proposed derived guidance laws.     

基于碳纤维复合材料的电容式燃油油位测量传感器

利用解析法和Ansys软件对基于碳纤维复合管材的电容式燃油油位测量传感器设计进行了计算和分析，给出了传感器的结构设计和中和电流法测量电路，实现了碳纤维复合材料在电容式油位测量中的应用。对传感器和测量系统的标定和稳定性、可靠性、高低温等试验，结果表明碳纤维复合管材电容式油位测量传感器在飞机燃油测量中的应用是可行的。     

轴向流中悬臂圆柱体稳定性的实验研究

用实验方法研究了悬臂圆柱体在轴向流作用下的屈曲问题.对实验管道在几种不同的平均流速下做了多次重复实验,获得了第一振型屈曲参数相关实验数据.实验结果表明:当平均流速达到一定值时,悬臂圆柱体会发生第一阶屈曲；流速越大,发生屈曲变形也越大；继续增大流速时,发生颤振失稳；当流速小于一定值时,不发生屈曲.实验结果与理论分析结果基本一致.对可能引起定量误差的原因进行了较详细的分析.