提出分支中含有平面闭回路结构的完全各向同性空间移动并联机器人机构型综合的一种系统方法。首先基于螺旋理论给出移动并联机构的速度表达式,然后根据互易螺旋理论确定出分支的主动螺旋、可动非主动螺旋和惰性螺旋,再依照分支连接度的不同列举出所有可行的基本分支运动链,并通过运动副替换得到分支中含有闭回路结构的运动链,最后利用所综合出的支链按照主动副的配置要求将动平台和静平台连接起来即可实现预期的机构。利用该方法综合出41种分支中含有闭回路的对称完全各向同性空间移动并联机构。
A systemic approach of type synthesis for fully--isotropic spatial translational parallel manipulators containing planar closed--loop structures within limbs was proposed. Firstly, velocity expression of translational parallel manipulator was presented based on the screw theory. Secondly, the actuated screw, the actively unactuated screws and idle screws of each limb were determined according to the reciprocal screw theory. Then, all basic kinematic chains were enumerated by means of the number of limb connectivity and the limbs containing closed--loops were obtained by replacing the passive prismatic joints in the basic kinematic chains with planar closed--loop structures. Finally, the desired mechanisms are synthesized by using the limbs to connect the moving platform with the fixed base and 41 symmetrical fully--isotropic spatial translational parallel manipulators containing planar closed--loops are obtained.