A unified theoretical framework for the synthesis of cam mechanisms.

摘要

In this thesis, a unified formulation for the synthesis of cam mechanisms is presented, which allows the design of spatial, spherical and planar mechanisms within a single theoretical framework. This formulation has led to the design of novel cam mechanisms, as yet unknown.;The theory is then extended to the study of four-link cam mechanisms, where an intermediate element, namely, a roller, is placed between the cam and the follower. In general, the surface of the roller is shown to be a hyperboloid, which, for the planar case, becomes a regular cylinder, and, for the spherical case, a regular cone. The two theorems stated for three-link cam mechanisms are then extended to four-link mechanisms. A general formulation is presented for the study of the pressure angle in both three- and four-link cam mechanisms. With this formulation, the general expression for the pressure angle of spherical mechanisms is derived as a particular case of the general expression for spatial cam mechanisms. Moreover, the pressure-angle expression corresponding to planar cam mechanisms is derived as a particular case of spherical cam mechanisms.;The unified formulation is then applied to the synthesis of planar cam mechanisms via graphical methods. Here, an innovative technique is introduced, which consists of finding contact points of the cam profile, in contrast to traditional graphical techniques that employ cam envelopes, and, hence, are prone to inaccuracies.;Special attention is given to the synthesis of indexing cam mechanisms. In this context, a theorem is established for the determination of one of the design parameters that is used to avoid undercutting on the cam profile. A novel design of an indexing cam mechanism, called PRICAM, in which pure rolling and positive motion are achieved for planar and spherical mechanisms, is obtained using a combination of three- and four-link cam mechanisms.;The unified formulation is implemented in the software package USYCAMS, in which, with visualization aids, the user can design cam mechanisms of the three types and animate their motion, by providing the design parameters on-line. USYCAMS allowed the design of two versions of PRICAM, one planar and one spherical, and produced a database describing the contact surfaces, which served as input to the CNC machine tool used to cut actual prototypes of these mechanisms. (Abstract shortened by UMI.)