Adaptive dynamic surface control of NSVs with input saturation using a disturbance observer

An adaptive dynamic surface control(DSC)scheme is proposed for the multi-input and multi-output(MIMO)attitude motion of near-space vehicles(NSVs)in the presence of external disturbance,system uncertainty and input saturation.The external disturbance and the system uncertainty are efficiently tackled using a Nussbaum disturbance observer(NDO),and the adaptive controller is constructed by combining the dynamic surface control technique to handle the problem of‘‘explosion of complexity’’inherent in the conventional backstepping method.For handling the input saturation,an auxiliary system is designed with the same order as that of the studied MIMO attitude system.Using the error between the saturation input and the desired control input as the input of the designed auxiliary system,a series of signals are generated to compensate for the effect of the saturation in the dynamic surface control design.It is proved that the developed control scheme can guarantee that all signals of the closed-loop control system are semi-globally uniformly bounded.Finally,simulation results illustrate that the proposed control scheme can achieve satisfactory tracking performance under the composite effects of the input saturation and the external disturbance.     

Preparing for space: Increasing technical readiness of low-cost high-performance remote sensing using high-altitude ballooning

Two widely available, small size, weight and power camera systems were flown above 97 % of Earth’s atmosphere and showed utility in single filter vegetation and soil analysis in a space analogue environment. The experiment was conducted as a low-cost verification and test analogue to flying on vastly more expensive low Earth orbit missions. Normalised Difference Vegetation Index (NDVI) was used as the metric by which performance was analysed for ground calibration testing, low and near-space altitude remote sensing. Ground calibration testing with a laboratory-grade spectrometer revealed that both cameras were able to return consistent NDVI results, and high-altitude balloon flight allowed similar data capture from an environment similar to space. Although compressed captured imagery had been processed using gamma correction and pre-image processing, these were able to be corrected provided that access to radiometrically-calibrated data was available. The two hobbyist cameras were shown to return scientifically useful results, demonstrating performance, and additionally their utility for citizen science applications in the near-space environment.     

临近空间飞行器的滑模变结构解耦控制

建立了临近空间滑翔飞行器六自由度运动模型,针对模型具有的快时变、强耦合、强非线性和不确定性特点,应用动态逆方法和滑模变结构控制方法分别设计了内环解耦控制器和外环鲁棒控制器,实现了解耦性与鲁棒性的有机结合,显著提高了控制系统性能.内环采用反馈线性化方法实现了姿态运动模型的伪线性化;外环滑模变结构控制器采用等速趋近律,采用饱和函数法抑制抖振现象,有效抑制外界干扰和参数偏差.仿真结果表明:基于动态逆的滑模变结构控制系统可以准确跟踪攻角、侧滑角和倾侧角指令,对外界干扰和参数偏差具有较强的鲁棒性.     

一种用于临近空间飞行器的吸气式电推进技术

针对低速临近空间飞行器提出了一种新型吸气式电推进方案,该方案采用单介质阻挡放电（SDBD）作为等离子体源,因此能在较大气压范围（数Pa~1atm）内电离大气产生等离子体并产生推力。为探究该吸气式电推进方案的推力性能,测量了实验样机在多个气压和电压条件下产生的推力。推力测量结果显示在10~90kPa气压范围内,实验样机产生的推力在10 2~10 3μN量级;气压一定时,产生的推力与驱动电压呈幂次相关;而电压一定时,随着气压自1atm逐渐降低,产生的推力先增大后减小,且达到最大推力的气压与所加驱动电压相关。     

廊坊中频雷达风场FCA算法的研究及应用

中频雷达是获得临近空间60～100 km范围内大气风场的重要探测设备之一. 全相关分析方法是空分天线模式中频雷达的一种重要风场反演方法. 通过介绍全相关分析方法算法的一般理论, 根据廊坊中频雷达的天线配置, 分别研究了利用三副天线数据与四副天线数据的风场反演算法FCA-3A和FCA-4A, 讨论给出了全相关 分析方法的剔除标准. 用廊坊中频雷达实测的回波相位和振幅, 得到由该算法反演 的大气风场. 为验证算法的可靠性, 将其结果与ATRAD公司的反演结果进行比较. 结果显示大气纬向风和经向风随时间和高度的变化特性基本一致. FCA-3A与FCA-4A的风场反演结果基本一致, FCA-4A略好于FCA-3A.      

临近空间高超声速助推-滑翔式轨迹目标跟踪

针对临近空间高超声速、助推-滑翔式轨迹目标跟踪的问题,提出一种经度-纬度-高度坐标系（Longitude-Latitude-Altitude, LLA）下基于目标轨迹特性分析的三维投影跟踪算法。首先,针对临近空间目标在经纬方向上的线性高超声速运动和高度方向上高机动频率运动的不同,将目标量测分别投影到经纬平面和高度方向上,并通过分段跟踪处理,以减小耦合误差对目标跟踪精度的影响;接着,在对目标高超声速特性充分分析的基础上,利用经纬方向上的点迹归并和凝聚处理,以有效解决目标高超声速运动所引起的分裂问题;然后,在对目标高度IMM跟踪的基础上,通过对加速度突变的合理检测和补偿,以进一步实现目标在高度方向上高机动频率运动的可靠跟踪;最后,结合统计学原理,将目标在同一时刻不同跟踪段中的状态估计相关联,以有效实现临近空间高超声速、助推-滑翔式轨迹目标的精确跟踪。仿真结果表明,与现有的临近空间目标跟踪算法相比,该算法具有较高的定位跟踪精度。     

临近空间再生燃料电池储能系统散热风扇性能

针对平流层飞艇再生燃料电池储能系统的风冷散热组件,采用Fluent计算散热风扇在设计飞行高度不同转速条件下的风压、流量、静压效率等性能参数。进而针对海拔0~20km高度的环境温度和压力变化,计算20kW散热能力条件下散热组件风量需求及其对应风扇转速、功耗等变化趋势。在此基础上,进行散热组件不同海拔高度环境下的性能试验,风扇模型计算结果和试验数据吻合较好。结果表明风冷散热组件能够满足再生燃料电池储能系统在包括起飞、高空驻留和降落在内的整个任务周期的散热要求。     

Conceptual design of near-space synthetic aperture radar for high-resolution and wide-swath imaging

Airborne synthetic aperture radar (SAR) has the capability of high-resolution, and spaceborne SAR has the capability of wide-swath. Inspired by recent advances in near-space defined as the region between 20 km and 100 km, this paper conceptually designed near-space vehicle-borne SAR. The near-space vehicle-borne SAR has the synthetical advantages of the satellite and airplane platforms. By placing SAR transmitter or receiver in near-space vehicles, many functions that are currently performed with satellites or airplanes could be performed in low cost way. These advantages make simultaneous high-resolution and wide-swath SAR imaging possible. As such, this paper focuses on the role of near-space vehicle for high-resolution and wide-swath SAR imaging, and deals with conceptual performance, as opposed to technological implementation. The concepts, models and processing algorithms are provided. To further suppress the azimuth ambiguities and extend swath width, multiple beams in azimuth is applied. Furthermore, an example near-space vehicle-borne SAR is designed. It is shown that the use of cost effective near-space vehicles can provide the solutions that were previously thought to be out of reach for remote sensing scientists and customers.     

Optimal predictive sliding-mode guidance law for intercepting near-space hypersonic maneuvering target

The design of optimal guidance law for intercepting a near-space hypersonic maneuvering target with bounded inputs is considered. Firstly, a maneuvering model for near-space hypersonic aircraft is given. Then, the aircraft acceleration prediction can be obtained using this model with two neural networks. By using the target acceleration prediction, which is taken into account when calculating the Zero Effort Miss(ZEM), an optimal sliding-mode guidance law is proposed to fulfill the guidance task...     

基于FLNDO的近空间飞行器鲁棒最优预测控制

针对有强烈干扰和不确定因素影响的近空间高超声速飞行器,提出了一种鲁棒最优广义预测控制律.控制律由最优广义预测控制律(OGPC)和一种新的泛函连接网络干扰观测器(FLNDO)构成.输出的有限时域预测由泰勒级数的展开实现.飞行中的未建模动态以及未知干扰由FLNDO来估计,并且文中也给出了FLNDO和闭环系统的稳定性分析.仿真结果表明对于姿态角和角速率的跟踪问题,设计的控制器达到了满意的控制效果,并且也成功实现了对干扰的抑制以及参数变化的鲁棒性要求.