Structural-kinematic synthesis method for (planar) link

Abstract

While mechanism design engineer deals with two tasks: first, to choose a mechanism scheme (structural synthesis); secondly, to determine its main dimensions (parametric synthesis). In the article, it is proposed to set requirements for mechanism properties after completing the second task. For this purpose, the system for setting the requirements is developed. The system for representing planar link mechanisms using minimum required set of initial structural units with lower kinematic pairs (five types with 0-2 links and 0-3 kinematic pairs in each) is also developed. Moreover, one secondary multiple-link type – Mech-group – is considered. Mechanisms description system is oriented on automatic generation of algorithms and programs for kinematic and force analysis and geometric synthesis. These two systems (mechanism description system and requirements setting system) allow developing the bases for mechanisms structural-kinematic synthesis method and for motion simulation kineto-dynamic method appropriate for any planar link mechanisms (including mechanisms for which equations degenerate, i.e., system of equations determinant and design equation denominator are equal to zero). The article describes structural-kinematic synthesis method that can reduce the complexity of structural units linking configuration determination, especially for multiple-link groups. Consideration of kineto-dynamic simulation method is within the framework of the article. Two types of kinematic chains mobility are introduced: structural depending on the chain topology (determined, for example, according to the Chebyshev formula) and kinematic depending on geometric dimensions and kinematic pairs relative position. Two types of kinematic mobility are considered: local (“momentary”) and global. Types of planar and driven kinematic pairs and a set of initial structural units (basic, structural and graphic) are described in the article. Initial one- and two-link structural groups with rotating pairs installation method and a brief description of the basics of a language for describing planar mechanisms and its schemes synthesis methods are presented in the article. The examples of description of mechanisms with its structural-kinematic schemes synthesis conditions and kinematic analyses sequence are given. In conclusion, the following is considered: main features and advantages of the developed method; unresolved issues and challenges; development directions and method disadvantages; areas of application of the method and its relevant programs.