基于焊缝路点局部点云的焊枪空间姿态确定

针对目前基于三维视觉传感面向几何与位置信息不确定工件的机器人焊接研究中,焊缝路点的焊枪空间姿态确定方法针对性强、局限性高等问题,提出了一种基于焊缝路点局部点云的焊枪空间姿态确定方法.首先描述了焊枪的空间姿态参数模型,然后通过考虑传感器的前置安装距离确定kd-tree的最小搜索半径,获取焊缝路点处的局部点云,并逐步确定该路点处焊枪的偏摆平面与倾斜平面,从而确定焊枪在该焊缝路点处与工件的无碰空间姿态.结果表明,该方法适应性强、有效性好.由于点云表面质量的原因,姿态确定结果与真实姿态存在一定波动,后续经过平滑处理可以满足机器人焊接需求,有望提升基于三维视觉传感面向几何与位置信息不确定工件的机器人自主焊接作业水平.

基于多模态时间序列建模的机器人安全监控

针对多模态时间序列建模的机器人安全监控问题,基于多模态粘性层级狄利克雷过程隐马尔可夫模型(MD-sHDPHMM)提出了一种能准确、可靠、快速、通用地实现机器人执行过程识别与异常事件监测的方法.该方法首先把机器人的执行任务分割成序列化的执行过程,然后通过对比执行过程中累积观察数据的对数似然函数值的大小实现执行过程的识别.在此基础上,根据正常执行过程训练得到的对数似然函数值的梯度阈值,实现了机器人执行过程中的实时异常监测.实验结果表明,该方法能有效地实现基于多模态时间序列建模的机器人安全监控.

包含多重嵌套封闭环的平面切割建模与优化

为解决在平面图形切割领域中采用不同的切割顺序以及切割起止点导致切割路径空行程相差甚远的问题,提出一种包含多重嵌套封闭环的平面切割路径优化算法.首先提出一种多重嵌套封闭环识别子算法,并以四向链表节点为基础构建包含多重嵌套封闭环的平面切割路径模型;然后考虑各封闭环的几何特征以及彼此之间的关系,将切割路径优化问题转化为多个关联的动态旅行商问题组合;最后通过逐层多次调用禁忌贪婪算法对切割路径进行优化求解,在优化中同时考虑封闭环之间的切割顺序及各封闭环切割起止点的选择.仿真实验结果表明,该算法对包含多重嵌套封闭环的平面切割路径建模和优化是可行和有效的.

Multi-objective Topology Optimization of Thermo-mechanical Compliant Mechanisms

The material characteristics of a structure will change with temperature variation,and will induce stress within the structure.Currently,the optimal design for the topology of compliant mechanisms is mainly performed in single physical field.However,when compliant mechanisms work in high temperature environments,their displacement outputs are generated not only by mechanical load,but also by the temperature variation which may become the prominent factor.Therefore,the influence of temperature must be considered in the design.In this paper,a novel optimization method for multi-objective topology of thermo-mechanical compliant mechanisms is presented.First,the thermal field is analyzed with finite-element method,where the thermal strain is taken into account in the constitutive relation,and the equivalent nodal thermal load is derived with the principle of virtual work.Then the thermal load is converted into physical loads in elastic field,and the control equation of the thermo-mechanical compliant mechanism is obtained.Second,the mathematical model of the multi-objective topology optimization is built by incorporating both the flexibility and stiffness.Meanwhile,the coupling sensitivity function and the sensitivity analysis equations of thermal steady-state response are derived.Finally,optimality criteria algorithm is employed to obtain numerical solution of the multi-objective topology optimization.Numerical examples show that the compliant mechanisms have better performance and are more applicable if the temperature effect is taken into account in the design process.The presented modeling and analysis methods provide a new idea and an effective approach to topology optimization of compliant mechanisms in electrothermic coupling field and multiphysics fields.

三维气动软体驱动器弯曲建模与分析

为设计弯曲性能优越的三维气动软体驱动器,针对单腔通气时驱动器的弯曲变形机理,展开了弯曲特性的研究。首先基于Yeoh模型的能量密度分布函数,结合驱动器弯曲时的静力平衡方程,建立驱动气压与驱动器弯曲角度变形的非线性数学模型;其次,通过数学模型分析气腔半径、中心圆半径以及壁厚对弯曲的影响,并通过建立单目标多约束优化模型寻找最优尺寸组合;然后通过有限元仿真,进一步研究两腔通气时驱动器弯曲角、偏转角与末端点坐标的变化规律。最后通过对比理论模型、有限元仿真、样机试验的数据。结果表明:在60kPa气压的范围内,理论结果、仿真结果与试验结果的表明上述分析参数对弯曲影响的趋势保持一致,从而验证了理论模型的正确性。上述研究为设计气动软体弯曲驱动器提供了可靠的理论基础。