Plastic Flow Modeling of Ti-5 Al-2 Sn-2 Zr-4 Mo-4 Cr Alloy at Elevated Temperatures and High Strain Rates

The true stress-sWain relationships of Ti-5A1-2Sn-2Zr-4Mo-4Cr（TC17） alloy with a wide range of strain rates were investigated by tmiaxial quasi-static and dynamic compression tests, respectively. Quasi- static compression tests were carried out with Instron 8874 test machine, while dynamic compression tests were performed with the split Hopkinson pressure bar （SHPB） which was installed with heating device and synchro- assembly system. The dynamic mechanical behaviors tests of TC17 were carded out from room temperature to 800 ℃ at intervals of 200 ℃ and at high sWain rates （5 500-1 9200 s-l）. The stress-strain curves considering temperature-sWain rate coupling actions were obtained. The Johnson-Cook constitutive model was developed through data fitting of the stress-sWain curves. The material constants in the developed constitutive model can be determined using isothermal and adiabatic stress-strain curves at different strain rates. The Johnson-Cook constitutive model provided satisfied prediction of the plastic flow stress for TC17 alloy.

基于遗传算法的行李码放机械臂轨迹优化

根据行李码放机械臂运动学与动力学约束,提出一种基于遗传算法的机械臂轨迹优化方法。优化方案以关节速度和加速度为约束条件,优化目标为时间最优或者关节加加速度最优,为提高算法收敛效率,用改进的遗传算法得到初始的种群,采用4-5多项式曲线对关节轨迹进行拟合,该方法对提高机械手臂的关节轨迹的平滑性有明显效果,最终实现关节加加速度和机械臂时间的最优的轨迹规划;模拟结果表明,该方法可以有效提高货码放稳定性与效率。

Delta机器人运动轨迹动态规划方法

针对Delta机器人末端的残余振动和抓取效率问题,提出一种基于Bézier曲线的轨迹动态规划方法,并为每段轨迹的运动周期提供设置依据。首先,以机器人路径中障碍物作为控制点的设置原则,利用多阶Bézier曲线动态调整路径中不同数量障碍物所对应的轨迹几何形状。其次,采用3-4-5次多项式对轨迹运动规律进行三维规划,获得轨迹插补点的位置、速度和加速度。最后,优化轨迹几何形状,并基于关节能量近似函数优选机器人运动周期,以满足运动过程中的高效性和稳定性要求。运动轨迹及运动规律仿真结果表明,所提轨迹规划方法能够有效规避障碍物,并且运动速度与加速度连续且光滑。在搭建的Delta机器人样机上采用所提轨迹规划方法进行抓取实验,结果表明,抓取速率可达100次/分钟,且能够有效降低运动停止后机器人末端的残余振动。