Automatic Synthesis Of Planetary Gear Trains And Plane Linkage Kinematic Chains And Creative Design Of Equipment

The innovation of advanced equipment is one of the five key projects presented by “Made in China 2025”.The creative design of advanced mechanical equipment is an important direction of national strategic development,and also is a key technology that needs to be improved in our country.In the field of automobile,our country is a large producer of automobiles,but has not mastered the technology to develop the core part of automobile—automatic transmission.Hence,our country has to spend a large amount of money importing automatic transmissions from abroad.In the field of engineering machinery,foreign countries have developed several kinds of face-shovel hydraulic excavators with excellent performance.Due to the lack of proprietary intellectual property rights,our country can only manufacture one kind of face-shovel hydraulic excavators which have inferior performance.Developing new automatic transmissions and face-shovel hydraulic excavators with Chinese intellectual property rights is a challenging and key technology which needs to be solved urgently.The core mechanism of an automatic transmission is a planetary gear train,and the core mechanism of a face-shovel hydraulic excavator is a plane linkage mechanism with prismatic pairs.The first key problem of developing novel mechanical equipment is the creative design of their core mechanisms.The structural synthesis of mechanisms is an effective method for the creative design of mechanisms,and also a research hotspot in the international field of mechanism science.Since Graph Theory was introduced into the field of mechanism in 1960 s,the structural synthesis of planetary gear trains(PGTs)and plane linkage mechanisms has made a great progress,but still exists the following problems:(1)Due to low efficiency,most synthesis methods for PGTs are limited to those PGTs with no more than eight links.Moreover,due to low reliability,the synthesis results derived from different researchers are not consistent with each other.(2)Only a few methods involve the synthesis of plane linkage kinematic chains with prismatic pairs(plane linkage kinematic chain is abbreviated as kinematic chain),and these methods exist counterexamples.(3)Most existing methods for sketching kinematic chains are only applicable for simple kinematic chains with a small number of links.To resolve the above problems,this paper aims to develop efficient and reliable methods for automatic synthesis of PGTs and kinematic chains,and to study the creative design of mechanisms of automatic transmissions and face-shovel hydraulic excavators based on the synthesis results.The main work and novelty in this paper are as follows.A new kind of topological graph of PGT is established.Based on this graph model,the formula for computing the degree-of-freedom(DOF)of PGT sub-graphs is derived,and a loop addition-based algorithm for automatic detection of degenerate sub-chains in PGTs is presented.Besides,the concept of loop weight string is defined,the way of classifying PGT graphs and the rule for relabeling inner vertices are given,a perimeter loop-based algorithm for automatic detection of isomorphism in PGTs is presented,and the PGT isomorphism detection problem is resolved.The reliability of the algorithms are verified and counterexamples in the existing methods are analyzed.Based on the algorithms for automatic detection of degenerate sub-chains and isomorphism in PGTs,and the concepts of transfer vertex variable equation and revolute edge group,a systematic method for automatic synthesis of PGTs is presented,and the problem of fully automatic synthesis of PGTs is resolved.The complete atlas of 1-DOF PGTs with 3–9 links is established.Besides,the reasons for the contradictory synthesis results in literature are analyzed,and the reliability of our synthesis results is verified.The concepts of vertex weight and vertex weight sequence are defined,and a vertex group-based algorithm for automatic detection of isomorphism in kinematic chains with prismatic pairs is presented.Then,the kinematic chains with prismatic pairs are synthesized automatically,and the atlas of kinematic chains with prismatic pairs and with 6–14 links is established.The reliability of our synthesis method is verified and counterexamples in the existing methods are analyzed.The concepts of moving sign and moving sign string of an inner edge are defined,and a new method to determine the optimal layout of topological graph with the minimum edge crossings is presented.Then,the concept of inner angle is defined,a new correction algorithm for multiple links is presented,and the problem of eliminating link crossings and concave angles in multiple links is resovled.The automatic sketching of various kinds of kinematic chains with 6–19 links is achieved.Based on the established atlas of PGTs,the creative design of mechanisms of 6-speed automatic transmissions is studied.Several new mechanisms of 6-speed automatic transmissions are generated,and the experimental prototypes of some transmissions are developed.Based on the atlas of kinematic chains with prismatic pairs and the automatic sketching of kinematic chains,the creative design of mechanisms of face-shovel hydraulic excavators is studied.Several new mechanisms of face-shovel hydraulic excavators are generated,and the physical prototype of the first new face-shovel hydraulic excavator with Chinese intellectual property rights is developed.The synthesis methods presented in this paper are automated by developing software using computer language C++.The research in this paper can greatly promote the development of the international mechanism science.Besides,the creative design of automatic transmissions and face-shovel hydraulic excavators based on the synthesis of mechanisms is helpful for breaking up foreign technology monopolies,and improving the ability of developing equipment and economic level in our country.