回顾和论述了机械传动科学技术的发展历史和研究进展。认为：机械传动作为机械系统的重要组成部份，其科学技术的发展和机械系统一样，是与人类生产力水平的发展而相伴的。生产力水平的发展对机械系统的性能提出了新的要求，而机械系统的原动机、工作机为满足生产力水平而产生的突破性进展对传动机提出的要求推动了机械传动科学技术的进步。21世纪信息与控制技术、能源与环境保护技术、新材料技术、先进制造技术等成为科学技术发展的重要领域，这些领域的科技进步对机械传动科学技术的发展将产生重要的推动作用。

The top-down assembly design process is to define a detailed product's physical description satisfying its functional requirements identified in the functional modeling stage. To effectively realize the top-down process, a product's functional representation and the general assembly model must be considered. Service functions are used to describe the customer's needs, and technical functions/sub-functions form input to the assembly modeling system. The extended assembly features have been proposed to be function carriers, which combine the entities into an assembly to realize the product's functions. Based on the data abstraction of the assembly features and the entities, the general assembly model is used to support the evolution process of the assemblymodeling entities. The inherent relation of assembly features at the different levels is feasible to propagate any design modifications and preserve the product's functions. The formal design process model to describe the top-down design is composed of assembly feature operations, the assembly model and the evaluation process. A design case is used to validate this design process.

By the bond graph theory, a bond graph analysis model of continuously variable transmission is established. On the basis of improving the ratio change response and reducing the engine torque response lag in normal control, a new synthetic control algorithm is developed. By analyzing the engine driving torque characteristics and the transmission inertia torque while ratio is changed under transient condition, the compensation value for engine driving torque is presented. The simulation result shows that by this compensation control algorithm the engine torque response lag can be reduced and the driving torque response can be improved effectively.

An approach of localizing the contact zone of the double-envelope hourglass worm gearing has been proposed to reduce the sensitivity to the errors and the load. The influence of the errors on the contact zone is systematically investigated. The contact deformation, the shift of contact zone and load share among the meshing tooth-pairs has been analyzed using 3D contact FEM. After synthetically considering the influence of the errors and the load, the worm surface is modified into the crowning in height direction in comparison with the hob. The results from the loaded contact analysis demonstrate that this modification drive can absorb the influence of the errors and the load on meshing performance

The automotive industry is seeking new concepts for a continuously variable transmission (CVT) in the driveline. One possible solution for a CVT design is half toroidal traction drive, providing a high torque capacity with quick ratio change. An analytical study on the contact points of the half toroidal CVT has been detailed. The shapes of the contact areas among the input disk, power roller and output disk are considered ellipses. Mathematical equations for estimating the torque capacity, power loss due to spin action, and contact efficiency of the elliptical contacts of the half toroidal CVT are formulated and expressed in the form of integrals which can be readily evaluated by numerical scheme. The contact efficiency calculations of the half toroidal CVT have been developed for the proper spin point locations under the effect of system parameters. Numerical results are presented in graphical forms for considered parameters, which can help the designer to select the proper system parameters to minimize the undesirable spin effects.