Because of the disturbance of random error, the rotative error motion will not have strict periodicity, which will lead to the least square centers not appearing repeatedly in the same position.

• 由于随机误差的千扰以及截面最小二乘圆心的回转误差运动不具严格的周期性，导致了截面最小二乘圆心并不在某一确定位置上周期性复现。