Modelling of grinding mechanics: A review

Grinding is one of the most widely used material removal methods at the end of many process chains. Grinding force is related to almost all grinding parameters, which has a great influence on material removal rate, dimensional and shape accuracy, surface and subsurface integrity, thermodynamics, dynamics, wheel durability, and machining system deformation. Considering that grinding force is related to almost all grinding parameters, grinding force can be used to detect grinding wheel wear, energy calculation, chatter suppression, force control and grinding process simulation. Accurate prediction of grinding forces is important for optimizing grinding parameters and the structure of grinding machines and fixtures. Although there are substantial research papers on grinding mechanics, a comprehensive review on the modeling of grinding mechanics is still absent from the literature. To fill this gap, this work reviews and introduces theoretical methods and applications of mechanics in grinding from the aspects of modeling principles, limitations and possible future trendencies.     

Efficient multi-objective CMA-ES algorithm assisted by knowledge-extraction-based variable-fidelity surrogate model

To accelerate the multi-objective optimization for expensive engineering cases, a Knowledge-Extraction-based Variable-Fidelity Surrogate-assisted Covariance Matrix Adaptation Evolution Strategy(KE-VFS-CMA-ES) is presented. In the first part, the KE-VFS model is established. Firstly, the optimization is performed using the low-fidelity surrogate model to obtain the Low-Fidelity Non-Dominated Solutions(LF-NDS). Secondly, aiming to obtain the High-Fidelity(HF) sample points located in promising are...     

安全约束下的空间翻滚目标涡流消旋稳定控制

针对空间翻滚目标涡流消旋任务执行效率低和抵近安全无保证的问题，首先基于椭球包络法给出了服务星机动轨迹的直接线性凸化安全约束，以确保机动过程的安全性和最优轨迹跟踪问题的有限时间可解性；设计了垂直构型下空间消旋任务的抵近期望轨迹以增强服务星消旋力矩的作用强度，缩短任务周期。在此基础上，提出了一种反馈线性化的收缩模型预测控制(FLC MPC)算法，有效跟踪所提出的期望轨迹，并严格保证安全约束及控制输入约束下受控系统的稳定性。最后，利用所提出的控制方法对阿丽亚娜 4火箭上面级进行消旋仿真，结果表明该方法能有效提高消旋效率，并保证服务星的安全稳定。     

在轨高效目标检测加速技术

针对深度卷积网络目标检测算法参数量大、计算量大以及受星上计算资源、存储资源及功耗的限制，难以实现在轨部署的问题，提出了一种在轨高效目标检测算法加速框架与实现方法。首先，设计了一种可以同时兼容三种卷积算子的计算引擎，有效提高了资源利用率;其次，从通道和卷积核两个维度将目标检测算法模型展开，实现了加速器的高度并行化和可扩展性;最后，在多种FPGA平台上实现了该加速器并对其性能进行了评估。实验结果表明：所提出的加速器计算性能可以达到1843.2 GFLOPs(每秒千兆次浮点运算)，推理时间为0.22 ms。与同类加速器方案相比，所提出的加速器框架在性能、功耗、能效比及推理时间方面具有很大优势，适合部署在资源受限环境中，具有良好的星上应用前景和价值。     

槽道式侧推器水动力性能研究进展和展望

侧推器在从事港口作业、科考、救援和海洋资源开发等具有较高操纵性要求的船舶和海洋平台上具有广泛的应用。本文分别对槽道式侧推器的水动力性能预报方法、螺旋桨设计、槽道口减阻降噪设计、做功能力影响因素、空化噪声和脉动压力、减摇作用以及操纵效能等方面的研究进展进行了回顾；重点对影响侧推器做功能力的因素进行了梳理，将其分为槽道口形状、槽道内流场情况、船舶航速与康达效应、槽道及船体形状、侧推器同其他推进器的相互干扰、自由液面和限制水域等几个方面，并对现有相关研究工作进行了阐述。最后对侧推器水动力性能研究方面需要进一步深化以及可以拓展的方向进行了展望。     

利用姿态机动的绳系卫星编队系统轨道协同控制

为克服绳系卫星编队系统在轨道机动过程中的系绳摆动现象，提出一种通过调整领航星推力方向进而实现编队系统轨道跟踪的控制算法。由于推力方向角与状态量互相耦合且少于系统自由度个数，轨道协同控制属于典型的非仿射欠驱动控制问题。针对此问题，首先采用升阶法将角速度作为虚拟控制输入；然后为各子系统设计子滑模面后加权得到高层滑模面和等效控制输入律，并设计观测器估计系统非线性项；其次基于模型预测控制算法优化得到最高层滑模面的趋近控制律；最后采用MATLAB/Simulink验证了所提控制算法的有效性。     

Model predictive control for close-proximity maneuvering of spacecraft with adaptive convexification of collision avoidance constraints

This study investigated model predictive control (MPC) for close-proximity maneuvering of spacecraft. It is essential for a designed MPC to effectively handle collision avoidance between the servicer spacecraft and the client spacecraft, especially while the client is rotating. The rotating motion of the client leads to dynamic changes in the collision avoidance constraints, which increases the difficulty of optimizing the control input in the MPC framework. Therefore, this study presents a method to improve the performance and computational efficiency of MPC for rendezvous and docking with a nonrotating or rotating client. An ellipsoid is adopted to model the client’s keep-out zone (KOZ). Given the spherical KOZ of the servicer, an expanded ellipsoid is introduced to describe the KOZ for the center of mass of the servicer and modeled as a nonlinear constraint. The linearization method for reference points located at the expanded ellipsoid is adopted to convexify the nonlinear constraints. The reference points are adaptively determined according to the positions of the servicer, client, and expanded ellipsoidal KOZ. The resulting hyperplanes are then used to describe the collision avoidance constraints. By utilizing the aforementioned strategies, combined with the calculated reference points, an adaptive convex programming algorithm suitable for real-time implementation of MPC is derived. The performance of the proposed method is demonstrated through numerical simulations.     

Installation error calibration for MEMS angular measurement system in hypersonic wind tunnel

The accuracy of model attitude measurement has an important impact on wind tunnel test results. Microelectromechanical System Inertial Measurement Unit (MEMS IMU) provides a feasible way to measure model attitudes with high accuracy. However, the installation error between MEMS IMU coordinate system and the body coordinate system of test models can make the accuracy of the model attitude measurement decrease. In wind tunnel tests, the installation error depends on the relationship between the IMU and the model mechanism before tests. Therefore, in-field calibration in wind tunnel tests is necessary to reduce installation errors. To improve attitude measurement accuracy, the least squares quaternion calibration method based on MEMS IMU and six-position calibration procedure are proposed. High-precision three-axis turntable tests are performed. The pitch accuracy after calibration is higher than that before calibration in the angle of attack sweeping tests. The Root-Mean-Square Errors (RMSE) in the roll and yaw are within 0.01°, which are smaller than those before calibration. In the roll sweeping tests, RMSE of three attitude angles decrease significantly. In hypersonic wind tunnel tests, the pitch errors before and after calibration are within 0.05° and 0.02° in the angle of attack sweeping tests without wind. In five angle of attack sweeping tests with wind, the deviation between the mean of the pitch and the pitch after the elastic angle correction is within 0.03° and the standard deviation of five tests is within 0.01°. The proposed method is confirmed to enhance the accuracy of attitude measurement effectively, which is convenient for engineering applications.     

一种基于模型预测的火星返回推力器容错控制再分配方法

针对火星返回上升器由于环境等因素造成的推力器故障导致的姿态控制系统失稳而难以安全返回的严重问题，提出基于模型预测的动态容错控制再分配方法。根据推力器动态特性建立上升器推力分配模型，对模型参数误差进行实时估计从而修正分配模型，根据模型预测自适应推力再分配方法实施容错控制。同时，将推力器输出限制作为优化求解器的约束，并将推力器故障模型作为优化求解的约束域，实现最小化分配误差和最小化燃料消耗意义下的最优推力再分配。计算机仿真表明了该方法的可行性和实用性，获得了满意的结果，它能使推力器输出推力误差降低60%以上，姿态控制系统能在故障状态下3～5 s快速镇定。     

Wide-range model predictive control for aero-engine transient state

To perform transient state control of an aero-engine, a structure that combines linear controller and min–max selector is widely adopted, which is inherently conservative and therefore limits the fulfillment of the engine potential. Model predictive control is a new control method that has vast application prospects in the field of aero-engine control. Therefore, this paper proposes a wide-range model predictive controller that can control the engine over a wide range within the flight envelope....