Mechanics of a Two Axes Passive Precision Level Monitor for Machine Tools. Volume 2

摘要

A mechanism is proposed as a means of passively leveling an optical assembly about two horizontal axes within a tolerance of one arc-second. The mechanism is designed so that it will stimulate a spherical pendulum for input motions up to 100 arc-seconds. In order to insure the operation of the mechanism and establish the proper geometry, three analytical models were developed. Planar and spatial models which assumed rigid links with pin joints and a planar model assuming deformable links with pin and clamped joints were studied. These results are compared with experimental data gathered for three geometry combinations. It is shown that the results from the planar and spatial analytics agree to within 10%, with the spatial model predicting less error. Hence, the less complicated planar analysis may be performed with little loss in accuracy. Neither rigid link models compare well with the experimental data, with as much as an 80% discrepancy in some cases. When deformable links are included in the planar model, the results are within 16% of the experimental results. This indicates that the resistance to bending at the points can not be neglected in modeling and mechanism to act like a spherical pendulum, and guidelines are established for the design. This report represents, with minor changes, the thesis submitted by Mr. James York to the Faculty of Purdue University for the award of the Degree of Master of Science in Mechanical Engineering.