Molecular Electronic Structures of Transition Metal Complexes II
T. Ziegler: A Chronicle About the Development of Electronic Structure Theories for Transition Metal Complexes.- J. Linderberg: Orbital Models and Electronic Structure Theory.- J.S. and J.E. Avery: Sturmians and Generalized Sturmians in Quantum Theory.- B.
- PDF / 5,281,554 Bytes
- 37 Pages / 439.37 x 666.14 pts Page_size
- 55 Downloads / 208 Views
Chapter 4
WITH FLAT-FACE FOLLOWERS
4.1
Introduction
The problem of cam-profile determination, as pertaining to cam mechanisms with translating and oscillating flat-face followers, is han~led in this chapter. The problem addressed here has been solved traditionally using graphical methods-see, e.g., (Rothbart, 1956; Wunderlich, 1971). With the introduction of the computer as an engineering design tool, computer-oriented methods have been proposed-see, e.g., (Chen, 1977) and the references contained therein. However, these methods usually assume that mechanism parameters such as the radius of the base circle have been previously determined, thereby producing a cam profile whose performance is as yet uncertain to a great extent. If, upon a thorough evaluation of the design at hand, this performance turns out to be unacceptable, then the relevant design parameters are changed using rules devised during years of design experience. Within the scope of this book, the design is evaluated through kinematic analysis, as discussed in Chapter 7. As a result of this analysis, the behavior of variables relevant to the mechanism operation can be studied. Variables that need to be monitored for flatface followers are the contact-point eccentricity and the cam-profile curvature. The process of systematically choosing the mechanism parameters in order to produce a given displacement program of the follower, while minimizing the cam size and observing the pertinent constraints on mechanism variables, constitutes what is called cam design optimization. This subject has been given some attention (Chicurel, 1963; Mischke, 1970; Berzak, 1982; Buchsbaum and Freudenstein, 1983; Guoxun et al., 1988). Optimization methods based on spline functions were introduced in Angeles and Lopez-Cajun (1983, 1984a and b, 1988), and were meant for flat-face 75
J. Angeles et al., Optimization of Cam Mechanisms © Kluwer Academic Publishers 1991
4 OPTIMIZATION OF PLANAR CAM MECHANISMS WITH FLAT-FACE FOLLOWERS
and roller-followers of the translating and oscillating types while considering constraints on the pressure angle and contact-point eccentricity. Curvature constraints for flat-face followers were included in (Angeles et al., 1989a and b). Here and in Chapter 5, we expand upon the methods introduced in the aforementioned references and illustrate them with simple examples. While cam-size minimization can be achieved using a straightforward procedure for the case of translating followers, oscillating followers are elusive to the same treatment. In fact, for the latter type of followers, a direct approach is introduced that aims at the minimization of the area of the cam profile by properly choosing the eccentricity of the follower face and the minimum value of the follower angle of rotation. This approach is direct in that it is based on the first-order necessary conditions that the mechanism parameters must satisfy in order to produce a stationary value of the cam area. However, the stationary values thus obtained do not always yield minima, an
Data Loading...
