Dynamic model of underwater snake-like robot using Kane’s method

In this paper, a dynamic model for an underwater snake-like robot is developed based on Kane＇s dynamic equations. This methodology allows construction of the dynamic model simply and incrementally. The partial velocity is deduced. The forces which contribute to dynamics are determined by Kane＇s approach. The generalized active forces and the generalized inertia forces are deduced. The model developed in this paper includes inertia force, inertia moment, gravity, control torques, and three major hydrodynamic forces： added mass, profile drag and buoyancy. The equations of hydrodynamic forces are deduced. Kane＇s method provides a direct approach for incorporating external environmental forces into the model. The dynamic model developed in this paper is obtained in a closed form which is well suited for control purposes. It is also computationally efficient and has physical insight into what forces really influence the system dynamics. The simulation result shows that the proposed method is feasible.     

基于Kane动力学和通路矩阵的水下自重构机器人建模

文章推导出基于通路矩阵和Kane方法的水下自重构机器人的运动学和动力学方程。引入图论的知识解决水下自重构机器人的统一构形描述问题,提出采用通路矩阵描述水下自重构机器人的不同构形,结合Kane方法,建立了水下自重构机器人的运动学和动力学模型。以水下自重构机器人的典型构形(水下四足行走构形)为例,验证了该方法的有效性和可用性。     

基于钻杆力学推算的水下定向钻进艏向校正算法

针对水下导向攻泥器钻头安装空间有限,钻进导航所用的紧凑型MEMS惯性器件精度较低且长时间工作艏向角容易发散等问题,提出了一种基于柔性钻杆力学模型的位姿推算和辅助校准方法,在不增加传感器的条件下可有效提高原有导航精度。根据柔性杆理论建立钻头艏向角与坐标之间的数学模型,利用钻杆近端刚性大和变形量小的特点,在惯导数据误差偏大时采用卡尔曼滤波算法对MEMS惯导数据与钻杆变形量进行数据融合,从而实现艏向角纠偏和校准的目的。最后在不同工况下通过Abaqus有限元软件进行仿真试验,得出柔性钻杆变形量的对比数据,验证钻杆力学推算算法的有效性。试验表明：基于钻杆力学推算的艏向校正算法满足艏向角辅助校正的基本要求。     

刑事推定及其在司法实践中的运用

刑事推定是一种证明方法,即在刑事诉讼之中,裁判者以法律的规定为依据,在反驳不成立的情况下,由基础事实认定推定事实的一种事实认定方式.目前我国解决刑事司法实践中的一些问题时,在使用刑事推定的过程中往往存在标准不一,容易出现错误认定,造成错案,不利于准确打击犯罪和保护社会法益,给社会带来诸多负面影响.因此,刑事推定的立法规范极其必要,并且应该尽快研究确立刑事推定所遵循的原则和适用规则.