基于遗传算法的边坡稳定有限元分析

提出了一种边坡稳定计算的新方法,该方法采用Marc有限元软件计算边坡的应力,考虑了几何和材料非线性.采用一条折线模拟边坡滑动面.根据遗传算法原理编制程序,搜索对应最小安全系数折线上的节点,从而确定最危险的滑动面.与通常的边坡稳定计算方法相比,该方法摈弃了圆弧滑动面的假定并考虑了边坡的应力分布,可以更好地反映实际情况.算例比较表明,该方法计算结果更为合理.     

基于卡尔曼滤波的车辆侧偏角软测量

针对车辆稳定性控制过程中难以在线测得车辆侧偏角的问题,该文基于参数软测量理论和离散信号滤波理论,并结合卡尔曼滤波和驾驶员—车辆闭环系统模型建立车辆侧偏角软测量模型。该方法通过易测变量横摆角速度和侧向加速度估算车辆侧偏角,以实现车辆侧偏角的状态估计。基于预瞄最优曲率控制理论和预测—跟随理论所建立的二自由度驾驶员—车辆闭环系统建立了软测量模型,并建立其状态方程和观测方程。为进行状态估计,对模型的状态方程和观测方程进行连续系统离散化,得到以横摆角速度和侧向加速度为观测量的系统离散观测方程。通过双移线试验与蛇形试验进行场地试验获取纵向速度、侧向速度、横摆角速度、侧向加速度及车辆侧偏角等试验数据。估计值和试验值比较显示,两者变化趋势一致,误差均值在试验值幅值的10%以内,试验表明,软测量算法能准确估算出车辆侧偏角是可行的。研究结果可为软测量技术在车辆稳定性控制系统上的应用提供参考。     

Slip Line Field of Plane Strain Problem Obeying the GeneralizedHoek Brown Failure Criterion

According to the characteristics of plane strain problem of elastic and plastic mechanics, the bi parametric expressions were derived for stress components satisfying the generalized Hoek Brown failure criterion. Being substituted into the static equilibrium partial differential equations, a group of first order hyperbolic pseudo linear differential equation partial differential equations was obtained. Utilizing the determinant method and proper variable transformation, the characteristic direction and the differential relation equation for the stress partial differential equations were acquired. The characteristic direction indicted that in plastic zone obliquely intersecting conjugate shear slip surfaces formed two families of non orthogonal slip lines, in which conjugate angle varied with the limit stress state and the material physical properties of Hoek Brown rock mass. Since the principal direction of the maximum principal stress was circumferential in perfectly elasto plastic surrounding rock of the plastic zone around a circular opening suffering the symmetric initial stress field, the angle between the tangential direction of slip line with the principal direction of the maximum principal stress was the function of the minimum principal stress(i.e. the radial stress). Combined with the analytical solution, the polar coordinate differential equation was derived and furthermore, the polar coordinate curve equation for the slip line was obtained.     

Vehicle stability control system design using optimal allocation of yaw moment

In order to improve vehicle handling stability,a control system using optimal allocation of yaw moment was designed.The first layer is a linear quadratic regulator (LQR) controller,which optimizes a desired yaw moment to work on the vehicle and calculates reference wheel slip for the target wheel.The second layer of the control system is a PID controller which can track the reference wheel slip rate,and then apply braking torque on the target wheel to make the vehicle stable.Simulations are carried out by using an 8-dof nonlinear vehicle model under different conditions.The simulation results indicate that the designed control system can effectively improve vehicle handling stability.     

Experimental Study on Working Performance of Rice Rope Direct Seeding Machine

Structure and sowing principles of rice rope direct seeding machine are introduced. In order to test the machine＇ s working performance, such as compacting effect, sowing depth, influence of sowing device to rice rope, etc., field experiments were conducted. It is concluded that mean slip ratio of compacting wheel 1 is 4.44%, wheel 2 is 5.58%, wheel 3 is 7.81%, and wheel 4 is 6.96%; mean depth of planting is 29.72 mm, and mean variability coefficient of planting depth is 6.39%. Maximum variability coefficient of planting depth is 8.40%. Rice rope＇s snapping is closely related with the machine＇s speed and guide thread wheel by sowing device orthogonal experiments. Test results show that the machine has a rational design, safe work and meets to the requirements of planting. This study has laid the foundation for further studying the project.     

自动变速器典型故障分析

文章主要介绍汽车自动变速器故障检测一般程序,分析自动变速器打滑故障的现象、原因及排除方法,以标致307具体故障进行案例分析。     

亚微米级海带粉制备技术研究及物理特性分析

为获得物理特性良好、粒度分布均匀的海带粉体,采用Na OH前处理及湿法粉碎技术制备亚微米级海带粉,并通过单因素和响应面分析法优化工艺条件。结果表明:在Na OH质量分数0.19%、浸泡时间11 min、液固比20 m L·g~(-1)的条件下,海带粉平均粒度D50为328.7 nm,D95为825.5 nm,最大粒径为1 106.2 nm。亚微米级海带粉的物理特性为:休止角为62.5°、滑角为70.6°、水溶性为20.1%、润湿时间为35.3 s、膨胀力为1 266%、持水力为3 197%。与市售超微海带粉相比,亚微米级海带粉休止角增加20.9°,滑角增加27.9°,水溶性增加50.0%,物理特性得到显著改善。本研究可为海带的精深加工提供理论依据。     

株距无级调节器试验及输出函数模型研究

株距无级调节器要进行株距的无级调节,必须要建立株距无级调节器转入转速、输出转速、调节架位移和株距之间的函数模型。滑移率是指播种机工作时地轮滑动成分所占的比例,滑移率是影响播种质量的重要因素。为此,利用齿轮转速传感器测得播种机的滑移率,然后反馈给株距无级调节器的控制系统,通过调节株距无级调节器的调节架位移来改变理论播种株距,从而减小滑移率对播种质量的影响,提高播种的均匀性。     

气力输送中蔗叶滑移率的研究

颗粒在运动流场内的滑移率是判断颗粒气力输送稳定性的重要依据,对输送气流速度的选取有很好的借鉴作用。分析蔗叶在流场内的滑移率,对切段式甘蔗联合收割机除杂系统工作参数的设计与优化有很好的指导作用。为此,通过高速摄像对垂直管流中运行的蔗叶滑移率进行了测量,结果表明:蔗叶在流场内的最终稳定速度与理论计算不符,实际滑移率与蔗叶在流场中的迎风面积密切相关,气流速度的变化对实际滑移率并不产生明显影响。     

NF-X02轻型履带式拖拉机带农具作业稳定性分析

分析了NF轻型履带式拖拉机带农具在纵、横向坡度上的静态稳定性,推导出纵、横向的极限翻倾角和滑移角,以及相关的影响因素,以此为基础,讨论该机跨田埂、在横向坡道上急转弯行驶、或越障碍物时动态稳定性和注意的事项,为拖拉机的优化结构以及安全操作提供帮助.