Research On Planar Mechanism Type Synthesis And Innovative Scheme Designs

It is the main task of mechanisms to innovatively complete mechanism designs. An innovative mechanism design aims to achieve expected mechanism functions by creating and inventing new mechanism. One of the most difficult tasks in innovative mechanism design is to bring forward creative mechanism types, which are of good operating quality and industrial value, and meet the function requirements as expected. Therefore innovative designs of mechanism scheme become the most important ground stone for transmission scheme designs for mechanical system. The mechanism type synthesis is an effective approach to researching mechanism structure composition, by which various comparable schemes are offered for innovative mechanism designs. And so it is the basis for creative conceptions, inventions and innovative designs of new mechanism.In this paper, planar mechanism is taken as object and innovative scheme designs as main target for a study. A deep and systematic research was made in kinematic chain type synthesis, automatic sketching of mechanism and automatic generating of scheme designs. It provides a theoretical basis for innovative mechanical designs. The main research achievements covered in this paper are summarized as follows:In accordance with the structural features of planar mechanism closed kinematic chains, the concepts of classification code and isomorphism code were presented. The adoption of classification code in classifying kinematic chains not only brings clear and definite significance to the doctrine of mechanism composition of various kinematic chains, but also makes finer classification of kinematic chain types. The application of spectrum code method, which combines classification code with isomorphism code, to identifying isomorphic kinematic chains makes a possible great reduction in operation. Moreover, the problems of isomorphism identification of kinematic chain were researched, and the distance summation sequence method of isomorphism identification of kinematic chain was presented after some new structural invariant sequences were defined.With regard to the planar closed kinematic chains with simple joints, multiple links and multiple degrees of freedom, the basic links structure-tree method was put forward to complete chain type synthesis on the basis of synthesizing link sequence, contracted link sequence, link degree sequence and basic links connective sequence. The method has strong regular pattern and its results are advantageous to eliminating follow-up rigid sub-chains as well as identifying isomorphic chains. Besides, the methods to eliminate rigid sub-chains in kinematic chains were thoroughly studied.On the basis of the topology graph, the independent loops of kinematic chain can be derived by means of broadness-first spanning tree. And based on loops add-subtract operation and loop crossing detector, a maximal loop approach to automatic sketching for planar mechanism closed kinematic chain was presented. It is expected that the using of this approach in mechanism design will greatly enhance its efficiency.Based on defined design rules and selected graph carrier, the design requirements were firstly symbolized by rules, and then the function symbols were used to describe the function links so that the innovated scheme can be expressed by symbol. So, the computer could make logic reasoning from the design rules and get symbolization design scheme to achieve innovative scheme designs generated automatically. Furthermore, the similarity code method in determining the similarities of links on the kinematic chains was presented, which can effectively inhibit isomorphic design schemes from coming into being in the mechanism scheme innovation. At last, a principle was brought forward to achieving a new type of puls variable-speeded transmission mechanism. By means of which the scheme design and the structural design of the puls variable-speeded mechanism were accomplished by using an innovative design method based on the design rules, and the kinematic characteristics of this puls variable-speeded transmission were also studied.