The effects of joint clearance on the kinematic error of the hexapod tables

Clearance in spherical joints of a hexapod table is useful for decreasing the sensitivity of the table to manufacturing inaccuracies. However, such clearance affects the kinematic accuracy of the table and other adverse effects such as noise and vibration. The present paper investigates the influence of clearance in the spherical joints on the kinematics error in positioning and orientating of the table. A mathematical model for the relationship between the clearance in the spherical joints on the motion error of the table is derived. Numerical analysis of the error model is performed and experimental tests validate the proposed model.