A kinematic-coupling-based adaptive fixture for high precision positioning applications in flexible manufacturing systems

Abstract

The means to achieve micron level accuracy and repeatability with detachable fixtures will be an enabling technology in future manufacturing processes. Given the many sources of time variable errors in fixture alignment (i.e. thermal, load, vibration), the integration of actuators and sensors within fixtures will be necessary to achieve real-time error compensation. This thesis examines the fundamental issues and design challenges associated with implementing a first prototype of a mechanized fixture. The device utilizes adjustable parallel kinematics (to achieve accuracy) and the interface of a three-groove kinematic coupling (to achieve repeatability). The result is a new fixture technology, dubbed the Accurate and Repeatable Kinematic Coupling (ARKC). The ARKC is equipped to accept six independent actuation inputs that make it possible to obtain decoupled small-motion adjustment in six axes. The kinematic model for the adjustable position control of the coupling is derived. The main contribution of this thesis is the experimental verification of the model. Experiments show less than 13% systematic error between the adjustable kinematic theory and experimental data. Although not a subject of this work, the systematic error can be mapped and removed from the coupling performance via software. The result will be a coupling with accuracy and repeatability of approximately 5 microns. Implementation of the device in flexible manufacturing systems is discussed. A case study that examines the performance of the ARKC in a next generation manufacturing process is included. Theoretical results from the case study show that the ARKC can be used to provide the precision alignment and positioning requirements of next generation semiconductor test equipment.