Exploring 2D projection and 3D spatial information for aircraft 6D pose

The 6D pose estimation is important for the safe take-off and landing of the aircraft using a single RGB image. Due to the large scene and large depth, the exiting pose estimation methods have unstratified performance on the accuracy. To achieve precise 6D pose estimation of the aircraft, an end-to-end method using an RGB image is proposed. In the proposed method, the 2D and 3D information of the keypoints of the aircraft is used as the intermediate supervision, and 6D pose information of the aircraft in this intermediate information will be explored. Specifically, an off-the-shelf object detector is utilized to detect the Region of the Interest (RoI) of the aircraft to eliminate background distractions. The 2D projection and 3D spatial information of the pre-designed keypoints of the aircraft is predicted by the keypoint coordinate estimator (KpNet). The proposed method is trained in an end-to-end fashion. In addition, to deal with the lack of the related datasets, this paper builds the Aircraft 6D Pose dataset to train and test, which captures the take-off and landing process of three types of aircraft from 11 views. Compared with the latest Wide-Depth-Range method on this dataset, our proposed method improves the average 3D distance of model points metric (ADD) and 5° and 5 m metric by 86.8% and 30.1%, respectively. Furthermore, the proposed method gets 9.30 ms, 61.0% faster than YOLO6D with 23.86 ms.     

Design and experimental research of a sub-Newton N2O monopropellant thruster with inner-heater

Nitrous oxide（N₂O） is a green propellant with excellent application prospects. A subNewton N₂O monopropellant thruster with inner-heater and a N₂O self-pressurization stable supply system with regenerative heat compensation are designed in this paper. The experimental research of the thruster is described, including measurements of preheating power, activation temperature, vacuum thrust, specific impulse, life-span and pulsed operation performance. By inserting t...     

星载平面相控阵天线相位中心位姿标定方法

星载平面相控阵天线的相位中心是影响卫星成像质量的一个重要参数，针对平面相控阵天线的相位中心在卫星上的位姿标定问题，本文提出了一种标定平面相控阵天线相位中心位姿的方法。首先，建立了平面相控阵天线相位中心相对卫星主基准位姿传递的数学模型;其次，采用暗室测量系统对平面相控阵天线相位中心进行了标定，测得天线本体坐标系下的天线相位中心位置;最后，利用激光跟踪仪和经纬仪精测系统测出了天线相对卫星基准的位姿矩阵。基于本文提出的数学模型，获取了平面相控阵天线相位中心在卫星基准坐标系下的位置与姿态数据;同时，通过试验验证了平面相控阵天线紧固件的拧紧力矩，其对平面相控阵天线相位中心的影响可忽略。该方法对后续确定搭载平面相控阵天线的卫星相位中心工程验证，提供了参考。     

航空面齿轮磨削碟形砂轮修整方法及误差分析

根据面齿轮专用磨齿机的机械结构,提出了偏置曲线修整方法,设计了砂轮修整装置,并运用VERICUT软件进行修整加工仿真.推导了含各类修整误差情况下面齿轮的齿面方程表达式,并运用MATLAB软件生成了齿面误差云图,为修整过程的误差补偿提供了理论参考.最后进行了磨削及检测试验,将检测结果与误差云图对比,分析可能产生这种误差的原因,并在修整过程中进行误差补偿,使齿面最大法向误差值减少了31.14%,面齿轮齿形精度得到了提高.      

基于智能差分算法的摩擦力补偿方法研究

针对光电平台低速转动时，受摩擦力影响较大，使得速度跟随曲线出现“死区”现象，导致跟踪性能明显下降这一问题，提出了一种基于智能差分进化算法和Lurge摩擦模型的摩擦力补偿控制方法。通过采集记录光电转台正、反向匀速运动时的摩擦力大小，建立转台不同速度和摩擦力之间的对应关系。通过最小二乘法对摩擦模型静态参数进行分段拟合，采用智能差分进化算法辨识摩擦模型动态参数，并基于反馈的速度信息和获得的摩擦模型等效为摩擦补偿力矩输入到电流环控制输入端，实现平台平稳低速运行。实验结果表明：摩擦力补偿后速度响应误差由补偿前的±0.1°/s减小到±0.04 °/s，提出方法效果显著。