声学黑洞(Acoustic Black Hole,ABH)效应是弯曲波在楔形结构中传播时波速逐渐减小至零从而不发生反射的现象。由于弯曲波在理想黑洞结构中不发生反射,这就意味着能量被集中在楔形结构的尖端部分,这一现象使得黑洞结构在减振降噪,能量回...声学黑洞(Acoustic Black Hole,ABH)效应是弯曲波在楔形结构中传播时波速逐渐减小至零从而不发生反射的现象。由于弯曲波在理想黑洞结构中不发生反射,这就意味着能量被集中在楔形结构的尖端部分,这一现象使得黑洞结构在减振降噪,能量回收等领域中具有极大的应用潜力。为了对截面呈幂率变化的杆结构进行动力学分析,首先建立相应的物理模型,然后利用小波函数拟合杆振动时的挠度曲线并结合拉格朗日方程建立系统的动力学方程;通过对其进行求解得到系统的振动响应。分析计算结果可知,相较于均匀杆结构,截面呈幂律变化的杆结构能够有效的抑制其振动;进一步比较楔形梁和圆杆的振动响应表明,黑洞结构对两者振动响应的抑制效果相似,但锥形杆的尖端聚能效果要优于楔形梁结构。展开更多
声学黑洞(Acoustic Black Hole,ABH)效应通过幂指数律剪裁厚度或者材料参数梯度变化等方式,来减小弯曲波速度并在末端实现能量聚集和吸收,一直是近年来的研究热点。本文从能量角度出发,基于半解析建模方法,建立一维声学黑洞梁的解析模型...声学黑洞(Acoustic Black Hole,ABH)效应通过幂指数律剪裁厚度或者材料参数梯度变化等方式,来减小弯曲波速度并在末端实现能量聚集和吸收,一直是近年来的研究热点。本文从能量角度出发,基于半解析建模方法,建立一维声学黑洞梁的解析模型,选取Morlet小波为振型函数,对解析模型进行数值求解,分析能量密度的分布情况。研究表明:黑洞段的能量密度远大于均匀段能量密度,尖端部分对声学黑洞效应起到关键作用。理论分析结果对梁结构的振动控制和能量回收具有重要的参考价值。展开更多
This paper proposes a novel motion planning and tracking framework based on improved artificial potential fields(APFs) and a lane change strategy to enhance the performance of the active collision avoidance systems of...This paper proposes a novel motion planning and tracking framework based on improved artificial potential fields(APFs) and a lane change strategy to enhance the performance of the active collision avoidance systems of autonomous vehicles on structured roads. First, an improved APF-based hazard evaluation module, which is inspired by discrete optimization, is established to describe driving hazards in the Frenet-Serret coordinate. Next, a strategy for changing lane is developed in accordance with the characteristics of the gradient descent method(GDM). On the basis of the potential energy distribution of the target obstacle and road boundaries, GDM is utilized to generate the path for changing lane. In consideration of the safety threats of traffic participants, the effects of other obstacles on safety are taken as additional safety constraints when the lane-changing speed profile for ego vehicles is designed. Then, after being mapped into the Cartesian coordinate, the feasible trajectory is sent to the tracking layer, where a proportional-integral control and model predictive control(PI-MPC) based coordinated controller is applied. Lastly, several cases composed of different road geometrics and obstacles are tested to validate the effectiveness of the proposed algorithm. Results illustrate that the proposed algorithm can achieve active collision avoidance in complex traffic scenarios.展开更多
文摘声学黑洞(Acoustic Black Hole,ABH)效应是弯曲波在楔形结构中传播时波速逐渐减小至零从而不发生反射的现象。由于弯曲波在理想黑洞结构中不发生反射,这就意味着能量被集中在楔形结构的尖端部分,这一现象使得黑洞结构在减振降噪,能量回收等领域中具有极大的应用潜力。为了对截面呈幂率变化的杆结构进行动力学分析,首先建立相应的物理模型,然后利用小波函数拟合杆振动时的挠度曲线并结合拉格朗日方程建立系统的动力学方程;通过对其进行求解得到系统的振动响应。分析计算结果可知,相较于均匀杆结构,截面呈幂律变化的杆结构能够有效的抑制其振动;进一步比较楔形梁和圆杆的振动响应表明,黑洞结构对两者振动响应的抑制效果相似,但锥形杆的尖端聚能效果要优于楔形梁结构。
文摘声学黑洞(Acoustic Black Hole,ABH)效应通过幂指数律剪裁厚度或者材料参数梯度变化等方式,来减小弯曲波速度并在末端实现能量聚集和吸收,一直是近年来的研究热点。本文从能量角度出发,基于半解析建模方法,建立一维声学黑洞梁的解析模型,选取Morlet小波为振型函数,对解析模型进行数值求解,分析能量密度的分布情况。研究表明:黑洞段的能量密度远大于均匀段能量密度,尖端部分对声学黑洞效应起到关键作用。理论分析结果对梁结构的振动控制和能量回收具有重要的参考价值。
基金supported by the National Natural Science Foundation of China(Grant No.51875061)the Technological Innovation and Application Development of Chongqing(Grant No.cstc2019jscx-zdztzxX0032)the Graduate Scientific Research and Innovation Foundation of Chongqing,China(Grant No.CYB19063)。
文摘This paper proposes a novel motion planning and tracking framework based on improved artificial potential fields(APFs) and a lane change strategy to enhance the performance of the active collision avoidance systems of autonomous vehicles on structured roads. First, an improved APF-based hazard evaluation module, which is inspired by discrete optimization, is established to describe driving hazards in the Frenet-Serret coordinate. Next, a strategy for changing lane is developed in accordance with the characteristics of the gradient descent method(GDM). On the basis of the potential energy distribution of the target obstacle and road boundaries, GDM is utilized to generate the path for changing lane. In consideration of the safety threats of traffic participants, the effects of other obstacles on safety are taken as additional safety constraints when the lane-changing speed profile for ego vehicles is designed. Then, after being mapped into the Cartesian coordinate, the feasible trajectory is sent to the tracking layer, where a proportional-integral control and model predictive control(PI-MPC) based coordinated controller is applied. Lastly, several cases composed of different road geometrics and obstacles are tested to validate the effectiveness of the proposed algorithm. Results illustrate that the proposed algorithm can achieve active collision avoidance in complex traffic scenarios.
