Dominant Types of Errors at Parallel Kinematics Machine Tools

Theoretically, parallel kinematics machine tools should be very accurate and rigid due to their closed loop structure and no error accumulation characteristics. Unfortunately, these theoretical presumptions have not been confirmed in practice, due to manufacturing and assembly errors, kinematic errors in the actuators and joints, elastic deformations due to the gravity, thermal deformations, limited sensor accuracy, control errors, etc. This paper gives a survey of the types of errors which significantly decrease the expected accuracy of the parallel kinematics machine tools.