基于一类含极少运动副四支链两转一移三自由度并联机构的五轴混联机器人

Five-degrees-of-freedom hybrid manipulator based on a class of four-branch parallel mechanisms with two rotational and one translational degrees of freedom containing extremely few kinematic joints

首先提出了一类含较少运动副四支链两转一移三自由度(2R1T)并联机构(PMs)2RPU-UPR-RPR和2UPRRPU-RPR,然后提出了极限约束力螺旋系的概念,分析四支链2R1T并联机构末端的极限约束力螺旋系,对所提出的四支链2R1T并联机构是否同类机构中含运动副最少进行了论证。基于提出的四支链并联机构构造了一种五自由度混联机器人机构,建立了2-RPU-UPR-RPR并联机构的位置反解模型,并将其等效成一个三自由度串联机构RPR,进而对整个混联机器人机构进行了位置正反解分析,建立得到了混联机器人机构位置反解的显式解析表达式,并用加工球面轨迹的算例对所建运动学模型的正确性进行验证。提出的五自由度混联机器人含有极少的运动副,且所有转动自由度均具有连续转轴,能够得到解析的位置模型表达式,很容易实现轨迹规划与运动控制,具有良好的应用前景。

Firstly,this paper proposes a type of'two rotational degrees of freedom'and'one translational degree of freedom(2 R1 T)Parallel Mechanisms(PMs)with relatively few kinematic joints and adopting the four branches 2 RPU-UPR-RPR and 2 UPR-RPU-RPR.Then the concept of the ultimate constraint wrenches is put forward.The ultimate constraint wrenches exerted on the moving platform of 2 R1 TPMs with four branches are analyzed to verify whether the proposed four-branch2 R1 TPMs have extremely fewer kinematic joints compared with the same kinds of mechanisms.Based on the proposed fourbranch parallel mechanisms,a novel mechanism for the five-axis hybrid manipulator is constructed,and the inverse position model for the 2 RPU-UPR-RPR parallel mechanism is established.The model is equivalent to a serial mechanism of RPR with three-degree-of-freedom,and the forward and inverse position models for the whole mechanism of the hybrid manipulator are analyzed.An explicit analytical expression for the inverse position of the hybrid mechanism is established.Finally,an example of machining a spherical locus is given to verify the correctness of the kinematic models.The five-degrees-of-freedom hybrid manipulator proposed in this paper can easily achieve trajectory planning and motion control because it contains extremely few kinematic joints,and all of its rotational degrees of freedom possess continuous axes and capable of obtaining the analytical expression of the position models.These benefits afford good application prospects for the proposed manipulator.