No abstract

As one of the most influential factors leading to gear vibrations, transmission errors of the engaging gears must be controlled to achieve a desirable dynamic performance for a power transmission system. It is well known that tooth modification is an effective way to reduce the fluctuations of the transmission error of a gear pair. The challenge is determining how to establish a quantitative relationship between the tooth modification parameters and the transmission error fluctuations of a gear pair. The present study aims to reveal the sensitivity of the tooth modification parameters on the transmission error fluctuations of a helical planetary gear train in a wind turbine gearbox. For this purpose, a sophisticated parametric three-dimensional contact model that included the micro-geometries of the tooth modification is developed in the ROMAX® environment. Based on this model, a loaded tooth contact analysis is carried out to compute the meshing characteristics, such as the contact pressure and transmission error of each gear pair in the planetary gear train. With the obtained meshing characteristics, the tooth modification amounts of the engaging gears were determined using empirical formulas. These modification amounts are designated as the mean values of the samples generated by the central composite method. After repeating the loaded tooth contact analysis process for each generated sample, a quadratic polynomial function is derived using the response surface method to describe the quantitative relationship between the tooth modification parameters and the dynamic transmission error fluctuations. A large number of random samples are generated using a Monte Carlo method, and the corresponding dynamic transmission error fluctuations are determined with the aforementioned quadratic polynomial function. Based on these samples, a reliability sensitivity analysis is carried out to demonstrate the effects of the tooth modification parameters on the dynamic transmission error fluctuations of the helical planetary gear train.

In order to better solve the new problems encountered in the national development, China is gradually establishing a new national territory spatial planning system. It can implement the requirements of whole-area and multi-element control of land and space. Underground space planning is a special planning in the new spatial planning system. We will explore how to scientifically and reasonably prepare underground space planning. Combined with the planning practice of Beijing and Sub-Center, we propose that the underground space planning system should be further improved, especially at the regulatory planning level. It can not only refine the master planning requirements of underground space, but also effectively guide the detailed planning and project construction of underground space. This paper attempts to put forward the main characteristics of underground space regulatory planning, hoping to provide reference for other cities’ underground space planning. The first is ecological priority and limited utilization. Detailed geological survey is the basis of underground space planning. In the Sub-Center, we evaluated the requirements of geological ecological protection and the impact of geological disasters, and delineated the three-dimensional utilization boundary of underground space and the influence scope of geological disasters. The second is the improvement of space management and space vitality. We explore the allocation method of underground space covered area, and divide the covered area into each construction site, giving priority to the key areas such as Universal Studios and metro station areas. The third is multi-dimensional utilization and planning integration. The underground facilities are planned in depth and intensively. The plan puts forward detailed in-depth layout guidance, focusing on the construction of Facility Service Ring, and coordinating the intensive construction of underground tunnels, metro and underground municipal facilities. The fourth is to encourage the application of new technologies. The planning will reserve sufficient space for future development, such as the construction of underground logistics, multistage rainwater collection and underground heat utilization in the Sub-Center.