Friction stir welding(FSW)has been widely applied in many fields as an alternative to traditional fusion welding.Although serial robots can provide the orientation capability required to weld along curved surfaces,the...Friction stir welding(FSW)has been widely applied in many fields as an alternative to traditional fusion welding.Although serial robots can provide the orientation capability required to weld along curved surfaces,they cannot adequately support the huge axial downward forces that FSW generates.Available parallel mechanism architectures,particularly redundantly actuated architectures for FSW,are still very limited.In this paper,a redundantly actuated 2 UPR-2 RPU parallel robot for FSW is proposed,where U denotes a universal joint,R denotes a revolute joint and P denotes a prismatic pair.First,its semi-symmetric structure is described.Next,inverse kinematics analysis involving an analytical representation of rotational axes is implemented.Velocity analysis is also conducted,which leads to the formation of a Jacobian matrix.Sensitivity performance is evaluated utilizing level set and convex optimization methods,where the local sensitivity indices are unit consistent,coordinate free,and of definite physical significance.Furthermore,global and hierarchical sensitivity indices are proposed for the design process.Finally,dimension synthesis is conducted based on the sensitivity indices and the optimal link parameters of the parallel robot are obtained.In summary,this paper proposes a dimensional synthesis method for a redundantly actuated parallel robot for FSW based on sensitivity indices.展开更多
针对6061-T6铝合金机器人搅拌摩擦焊(RFSW)展开研究,首先在库卡机器人的末端和搅拌摩擦焊电主轴之间安装六维力传感器,搭建六维力传感器数据采集系统。其次采用不同的工艺参数对5 mm 6061-T6铝合金进行焊接,在焊接过程中实时监测搅拌头...针对6061-T6铝合金机器人搅拌摩擦焊(RFSW)展开研究,首先在库卡机器人的末端和搅拌摩擦焊电主轴之间安装六维力传感器,搭建六维力传感器数据采集系统。其次采用不同的工艺参数对5 mm 6061-T6铝合金进行焊接,在焊接过程中实时监测搅拌头受到的轴向力和前进抗力,焊后对焊缝横截面进行观察与分析,对焊缝横截面进行拉伸测试和硬度测量,分析轴向力和前进抗力对焊缝微观组织及力学性能的影响。结果表明:搅拌头转速在800~3400 r/min之间,搅拌头转速对焊缝力学性能影响较小;焊接速度在60~360 mm/min之间,焊缝力学性能良好。焊接过程中搅拌针下压阶段轴向力最大,达到约5000 N,焊接阶段稳定时,轴向力约为3600 N,焊接阶段前进抗力最大,达到约−550 N。在焊接过程中,轴向力/前进抗力的比值为−6.5左右时焊缝性能良好。展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.U1713202,51525504).
文摘Friction stir welding(FSW)has been widely applied in many fields as an alternative to traditional fusion welding.Although serial robots can provide the orientation capability required to weld along curved surfaces,they cannot adequately support the huge axial downward forces that FSW generates.Available parallel mechanism architectures,particularly redundantly actuated architectures for FSW,are still very limited.In this paper,a redundantly actuated 2 UPR-2 RPU parallel robot for FSW is proposed,where U denotes a universal joint,R denotes a revolute joint and P denotes a prismatic pair.First,its semi-symmetric structure is described.Next,inverse kinematics analysis involving an analytical representation of rotational axes is implemented.Velocity analysis is also conducted,which leads to the formation of a Jacobian matrix.Sensitivity performance is evaluated utilizing level set and convex optimization methods,where the local sensitivity indices are unit consistent,coordinate free,and of definite physical significance.Furthermore,global and hierarchical sensitivity indices are proposed for the design process.Finally,dimension synthesis is conducted based on the sensitivity indices and the optimal link parameters of the parallel robot are obtained.In summary,this paper proposes a dimensional synthesis method for a redundantly actuated parallel robot for FSW based on sensitivity indices.
文摘采用基于焊接机器人的新型搅拌摩擦焊机,进行了35 mm厚的5083铝合金板材的单道次对接焊试验,并与普通搅拌摩擦焊机所得接头进行了显微组织、力学性能和耐腐蚀性能的对比与分析。结果表明,与普通搅拌摩擦焊机相比,基于焊接机器人的新型搅拌摩擦焊机获得接头的接头效率从66%提高至94%,屈服强度提高39 MPa;断后伸长率提高6.6%,腐蚀电位正移315 m V。