A lightweight stacked residual low-light image en-hancement network was proposed to overcome the difficulty in accurately sensing the environment under low-light conditions for unmanned surface vessels(USV).Firstly,a pyramid multi-scale pooling was introduced into feature fusion to better preserve image details.Secondly,depthwise separable convo-lution was introduced to reduce network burden and improve the image processing speed.Thirdly,a new composite loss function with color loss was designed to reduce color distor-tion.Finally,LeakyReLU activation function was used to pre-vent neuronal death.Results show that compared to the low il-lumination image enhancement network of stacked attention residual network(SARN),the proposed method improves im-age quality while accelerating image processing speed.The structural similarity and peak signal-to-noise ratio are im-proved by 3.31％and 2.08％,respectively.The model com-putation,parameter count,and single image processing time are reduced by 81.88％,75％,and 43.02％,respectively.
This paper proposes a real-time trajectory planning method for automatic berthing of an underactuated ship. This method considers the overall constraints of the ship’s dynamics model and obstacles, introduces a global planning algorithm to avoid falling into local optimum. First, the global optimal path is planned based on the A* algorithm and redundant points are deleted to obtain the reference waypoints for trajectory planning. Second, based on Extended Dynamic Window Algorithm (EDWA), the berthing trajectory of the ship, including the constant force phase and the deceleration phase, is predicted in real-time, and the desired heading is achieved through PID control. After performing the feasibility test on the predicted trajectories, the optimal trajectory is obtained by using the evaluation function that considers the constraints of the goal point, reference waypoints, and obstacles. This optimal trajectory is then used to guide the ship at the next sampling time. Finally, taking Rizhao Port as an example, this paper uses the proposed method to plan a smooth and reliable trajectory, successfully guiding the ship to the designated berth while meeting the requirements of speed and heading, and avoiding obstacles.
针对海上舷梯末端点位置镇定控制问题,通过运动学反解,计算出补偿海浪引起的船舶摇荡运动对舷梯末端点位置的扰动,保证舷梯末端点位置在惯性坐标系下保持不变的舷梯关节期望位置;综合考虑舷梯动力学模型参数不确定及海浪引起的船舶摇荡运动对舷梯的扰动力,构造扩张状态观测器(ESO),估计由参数不确定及海浪引起的船舶摇荡运动对舷梯的扰动力组成的总扰动;进一步,设计基于ESO的终端滑模关节位置跟踪控制律,保证舷梯的关节位置跟踪其期望位置.理论分析证明了所构造的ESO的状态估计误差有界和所设计的基于ESO的终端滑模控制律使舷梯的关节位置跟踪误差在有限时间内收敛至零,从而保证舷梯末端点位置在惯性坐标系下保持不变.仿真结果验证了设计控制律的有效性.
为研究非平衡等离子体对氨气/空气在常温常压下燃烧的影响,利用CHEMKIN软件模拟实验条件下氨气/空气点火延迟时间,使用ZDPlaskin程序包研究常温常压下氨气/空气放电情况.将得到的O、H、OH自由基作为CHEMKIN初始条件,研究其对氨气/空气点火延迟时间的影响,分析点火时刻温度及活性自由基的敏感性.ZD-Plaskin的研究结果表明,不同当量比混合气放电所产生的自由基粒子数密度相差不大.CHEMKIN的仿真结果表明,未加自由基时,当量比为0.8-1.2时,点火延迟时间受当量比的变化影响较小,加入自由基后,点火延迟时间随当量比的减小而降低;O、H、OH自由基可明显降低氨气/空气点火延迟时间,降低程度随初始温度的升高而减小;相同初始温度下,反应方程式与温度敏感性最大的反应方程式相同,随着温度升高,敏感性最大的反应式将发生变化,并且敏感性大幅度降低;不同初始温度下,多个反应式在温度与自由基敏感性最大反应式中重复出现,这是机理简化的重要依据.
为研究船舶横摇对行人疏散速度的影响,通过计算行人在横摇运动空间中不同维度的受力,依据实时更新的横摇角度和角速度,建立一种考虑船舶横摇运动的三维动态社会力模型.以横摇幅度和横摇周期为变量,设置多场景的仿真实验,计算行人平均运动速度和疏散时间,分析不同横摇状态下的行人运动规律.仿真结果表明:相较静态倾斜,船舶横摇进一步导致行人移动速度衰减及疏散进程延缓,随着横摇幅度增大,行人速度不断降低,横摇幅度超过15.后,疏散时间迅速增加;增大船舶横摇周期对疏散过程有一定的积极影响,可以有效提升人员行走速度,减少疏散时间,但其影响程度仍与横摇幅度有关;在相同横摇幅度情况下,当横摇周期达到10 s及以上时,疏散效率可以显著提高.研究结果可为设计人员提升船舶安全性和管理者制定人员疏散决策提供理论依据和技术支撑.
