Towards intelligent design optimization: Progress and challenge of design optimization theories and technologies for plastic forming

Plastic forming is one of enabling and fundamental technologies in advanced manufacturing chains. Design optimization is a critical way to improve the performance of the forming system, exploit the advantages of high productivity, high product quality, low production cost and short time to market and develop precise, accurate, green, and intelligent (smart) plastic forming technology. However, plastic forming is quite complicated, relating to multi-physics field coupling, multi-factor influence, multi-defect constraint, and triple nonlinear, etc., and the design optimization for plastic forming involves multi-objective, multi-parameter, multi-constraint, nonlinear, high-dimensionality, non-continuity, time-varying, and uncertainty, etc. Therefore, how to achieve accurate and efficient design optimization of products, equipment, tools/dies, and processing as well as materials characterization has always been the research frontier and focus in the field of engineering and manufacturing. In recent years, with the rapid development of computing science, data science and internet of things (IoT), the theories and technologies of design optimization have attracted more and more attention, and developed rapidly in forming process. Accordingly, this paper first introduced the framework of design optimization for plastic forming. Then, focusing on the key problems of design optimization, such as numerical model and optimization algorithm, this paper summarized the research progress on the development and application of the theories and technologies about design optimization in forming process, including deterministic and uncertain optimization. Moreover, the applicability of various modeling methods and optimization algorithms was elaborated in solving the design optimization problems of plastic forming. Finally, considering the development trends of forming technology, this paper discusses some challenges of design optimization that may need to be solved and faced in forming process.     

Imaging of target with complicated motion using ISAR system based on IPHAF-TVA

The technique of imaging a target with a complicated motion using an Inverse Synthetic Aperture Radar (ISAR) system is an effective tool in the field of radar signal processing. After the translational compensation, the received signal reflected from the target can take the form of a multi-component Polynomial Phase Signal (m-PPS), and the high quality ISAR image can be provided via the combination between the estimated parameters of the m-PPS and the Range Instantaneous-Doppler technique (RID). For a target with a high maneuvrability, the occurrence of scatterers Migration Through Resolution Cell (MTRC), caused by the rotational movement could be appearing. That is why the variation in the amplitude of the echo during the time of observation cannot be neglected. The purpose of this study is the parameters estimation of the m-PPS signal with order three in the case of the Time Varying Amplitude (TVA). The Improved-version of the Product High-order Ambiguity Function (IPHAF) with TVA is proposed to improve the quality of the ISAR image compared with traditional techniques based on a constant amplitude; the experimental outcomes confirm that the new IPHAF-TVA method presented in this study is an effective technique to make the ISAR image very clear.     

Effect of scavenge port angles on flow distribution and performance of swirl-loop scavenging in 2-stroke aircraft diesel engine

Swirl-Loop Scavenging (SLS) improves the performance of 2-stroke aircraft diesel engine because the involved swirl may not only benefit the scavenging process, but also facilitate the fuel atomization and combustion. The arrangement of scavenge port angles greatly influences in-cylinder flow distribution and swirl intensity, as well as the performance of the SLS engine. However, the mechanism of the effect and visualization experiment are rarely mentioned in the literature. To further investigate the SLS, Particle Image Velocimetry (PIV) experiment and Computational Fluid Dynamics (CFD) simulation are adopted to obtain its swirl distribution characteristics, and the effect of port angles on scavenging performance is discussed based on engine fired cycle simulation. The results illustrate that Reynolds Stress Turbulence model is accurate enough for in-cylinder flow simulation. Tangential and axial velocity distribution of the flow, as well as the scavenging performance, are mainly determined by geometric scavenge port angles α_geom and β_geom. For reinforcement of scavenging on cross-sections and meridian planes, α_geom value of 27° and β_geom value of 60° are preferred, under which the scavenging efficiency reaches as high as 73.7%. Excessive swirl intensity has a negative effect on SLS performance, which should be controlled to a proper extent.     

伺服机构负载模拟系统设计与动态特性分析

针对火箭发动机喷管伺服机构的负载模拟问题,采用机械的方式,设计了一种可对伺服机构的惯性负载、摩擦力矩负载、弹性力矩负载、安装刚度以及发动机喷管柔性特征进行模拟的负载模拟器,并建立了模拟器和伺服机构数学模型。仿真分析了惯性负载、弹性力矩以及喷管柔性对伺服机构负载多自由度特性的影响。通过对伺服机构扫频实验,负载模拟器中的负载在一定范围内调节,可复现伺服机构实际工作中的动态特性。说明该负载模拟器结构设计合理,从而为具有多自由度特性的火箭伺服机构的负载模拟系统设计提供参考。该系统已经得到实际应用。     

利用定标站对旋转扫描扇形波束散射计的信号频率估计

该文基于中法海洋卫星(Chinese-French Oceanic Satellite,CFOSAT)雷达散射计系统参数,给出了可行的在轨Doppler预补偿方法并利用地面定标站实现对RFSCAT信号频率的估计.对比了3种信号频率估计方法,通过仿真分析表明,可达到优于0.05kHz的频率估计精度.仿真结果表明,通过把估计的频率与Doppler预补偿查找表和Doppler频率进行比较,可实现对RFSCAT在轨Doppler预补偿状态及生命周期内的载频漂移监测.     

采用阵列天线的GPS接收机的多径抑制方法

提出一种新的用于阵列天线GPS接收机的多径抑制方法。考虑到通常GPS视线信号的来波方向与多径的来波方向不同,在每个导航数据符号位内测距（C/A）码重复,通过对阵列接收的信号矢量与它本身的延迟信号矢量互相关,提高接收机前端信噪比,再利用最大特征值法和前后向空间平滑技术准确地估计期望卫星视线信号（LOSS）的来波方向。最后综合多个GSC子阵列有效地降低了相关多径对码跟踪精度的影响。仿真结果显示,该方法能使接收机在与LOSS码同步前准确估计LOSS的角度信息,有效抑制相关多径,且鉴相结果准确。     

弱撞击对接机构捕获系统运动空间研究

以弱撞击对接机构（LIDM）捕获系统的运动空间为研究对象,提出了影响运动空间的主要因素如驱动臂长度、转动副转角、结构框内径等对运动空间的限制。在此基础上,对捕获系统运动空间及其各截面进行了分析,并详细讨论了结构框内径对运动空间的影响,对LIDM的设计和优化具有重要意义。     

航天器自主交会对接的高精度目标定位方法

根据航天器自主式交会对接的实际应用背景和技术需求,针对交会对接过程中所要求的高精度、实时性和强抗扰的技术指标,在合作目标特性分析的基础上,将高斯曲面拟合与双线性插值相结合,提出了一种高精度的合作目标定位方法。首先根据目标图像的灰度分布进行双线性插值和高斯曲面拟合,在此过程中可同时利用目标原有像素和插值点的亚像素信息,使拟合曲面各幅值点的坐标精度达到亚像素级,以确定目标的中心位置。仿真图像和实拍图像的试验结果表明,此定位方法具有亚像素级的定位精度,其总体定位误差可达到1/20个像素左右,并能满足实时性要求,可以在航天器交会对接与空间遥操作等方面的应用中发挥重要作用。     

深空测控通信中GMSK体制非相干解调算法研究

针对深空测控通信中GMSK体制非相干解调损失较大的难点,提出了一种改进的GMSK信号非相干维特比解调算法。通过分析相位状态网格图中相位转移规律,建立理论仿真模型。通过原理样机的研制和测试,实测数据表明：该算法具有解调损失低、实现复杂度适中的优点;相比于理论的最佳相干解调算法,在误码率1×10 -4 量级下,实测仅损失0.6 dB。目前该算法已应用于国内某深空测控通信系统GMSK体制基带设备中,并成功解调出欧空局Herschel–Planck卫星数据。     

某新型改性双基推进剂的热安全性

采用热重分析仪( TG)、差示扫描量热仪( DSC)以及加速量热仪( ARC)研究了一种以高氯酸铵( AP )为氧化剂的新型改性双基推进剂GATo-3的热安全性,并将实验结果与双基发射药SF-3进行了比较。通过TG/DSC实验得到了GA-To-3的热分解过程,并初步分析了AP等组分对其热稳定性的影响。 DSC的测试结果显示,GATo-3的2个分解峰温分别为180.5℃和187.7℃,低于SF-3的分解峰温;ARC的测试结果显示,GATo-3在理想绝热条件下的起始分解温度为129.1℃,绝热温升为1177.8℃,最大温升速率为58053.5℃/min,最大压力上升速率为52.5×105 Pa/min,单位质量生成气体的最大压力为112.4×105 Pa/g,用速率常数法计算活化能E=116.8 kJ/mol和指前因子A=5.1×1011 s-1,最大反应速率达到时间为24 h时,所对应起始温度TD24=74.0℃。研究结果表明,与双基发射药SF-3相比,GATo-3的热安全性较差,爆炸性较强。