以一种可用于航天航空高速铣削加工和自动装配的面对称3-SPR并联机构为对象，利用矩阵求逆提出一种具有解耦格式的全雅可比矩阵建模方法，并据此构造出一组取值介于[0， 1]之间、量纲一且与坐标系无关的运动学性能评价指标，用于揭示机构尺度参数对这组指标的影响规律。在此基础上，构造出满足给定运动学性能、支链极限杆长比和球副转角等几何与运动学约束的尺度参数可行域，既可满足运动学性能要求，又可为后续设计修改尺度留有余地。

A method for developing the decoupled overall Jacobian of a planar symmetric 3-SPR parallel mechanism is presented by using matrix inversion technique,the 3-SPR parallel mechanism can be used to form the main body of a 5-DOF hybrid manipulator especially designed for high-speed machining and automatic assembling in the aircraft industry. Then a set of novel kinematic performance indices dimensionless,invariant with respect to the coordinate frame,and having a value ranged within [0,1] are developed by using the decoupled overall Jacobian. By investigating the influences of the homogeneous dimensionless parameters on these indices,the feasible domains of dimensionless design variables are obtained subject to the specified kinematic and geometric constraints,which not only meet the requirement of kinematic performance but also leave room for further modification.