The design, kinematics and error modelling of a novel micro-CMM parallel manipulator

[摘要] ENGLISH ABSTRACT: The research presented in this dissertation establishes a micro-CMM parallel manipulator as a viable positioning device for three degree of freedom micro measurement applications. The machine offers the advantages associated with parallel kinematic manipulators, such as light carrying weight, high stiffness and no accumulation of errors, while avoiding some of the traditional disadvantages of parallel manipulators such as the associated effects of angular errors (Abbé error), singularity problems, work space limitation and the extensive use of spherical joints.In this dissertation, the direct position kinematic solution is developed analytically and the solution of the inverse position kinematic is solved numerically. A workspace analysis has been performed. A fully functional prototype demonstrator is fabricated to demonstrate this machine. While the demonstrator was not intended to achieve submicron accuracy, it was intended to validate the error models. Computer controlled measurement is developed and used to position the probe and to record measurements.A reliable kinematic error model based on the theory of error propagation is derived analytically. A numerical method is used to verify the analytical results. Comparison shows that the results of the error model, both analytical and numerical, represent a very good match and follow the same trend.The kinematic position model is validated using a conventional CMM. Results show that an average difference of less than 0.5 mm over a set of 30 points is achieved. This result of the micro-CMM demonstrator measurements falls within the error budget of approximately 0.75 mm estimated by the proposed analytical error model.

[发布机构] Stellenbosch University