| dc.description.abstract | The two-stage planetary gear drives have various types of structure according to the different given coupling and boundary conditions. The characteristics of each variant can only be known through calculations, so it is necessary to establish specific formulaes. In general, it is not easy for designers to determine the appropriate mechanism variants and gearing design parameters while designing a two-stage planetary gear drive. Meanwhile the process of creating drawings for gear boxes often requires operations across different software, e.g., the parameters of designed parts need to be given into the drawing software to generate the CAD solid models. However, the planetary gear mechanism involves various types of parts, which can lead to parameter input errors. Therefore, with aid of computer programs, designers can quickly analyz and design a two-stage planetary gear drive, and if the design parameters for complex parts can be given through an integrated interface, allowing the program to control the drawing software and create the drawing automatically, it would greatly reduce the design time and enhance the development efficiency of two-stage planetary gear drives.
The aim of this study is to develop a computer-aided design (CAD) system that can be used to design and analyz a two-stage planetary gear drive and is capable of generating drawings automatically. The system can guide the designer to decide the structure of the variant and set the corresponding parameters of the mechanism through the program interface, and then quickly complete the calculation of torque distribution and the speed ratio of the mechanism. The designers can then confirm if the gearing parameters meet the requirements through the load capacity analysis and loaded tooth contact analysis; at last, designers can obtain the drawings of the connected components generated by the system.
In order to design the variant of two-stage planetary gear drive, this study classifies the variants by the properties of the external componet and establishes a coding principle. The properties of the external components can be used to classify the variants into three types of mechanisms: parallel mechanism, serial mechanism, and differnetial mechanism. The power flow characteristics of these three types of mechanisms are different, and the design of the basic speed ratios for each stage is related to tehm. So, this classification allows the system to provide the information to designers, and assit them to adopt the appropriate design method for the basic speed ratios.
In order to carry out the analysis of the gearing parameters, a standardized calculation module of the gear load capacity according to ISO 6336 is created and the developed model of the loaded tooth contact analysis is incorporated into the system, so that the basic parameters of the gearing can be analysed quickly with the help of this system to confirm that it meets the requirements.
Finally, for the automatic generation of CAD models, the system is designed on the basis of CAD template files. A parameter substitution program module and an open database of parameters are set up to substitute and record the parameters of the CAD sample files. According to the set variables, the system reads the corresponding variable names from the parameter database, and sets the values of the variables by calculation results and user′s own decisions, and then uses the parameter substitution program to read in the model variables and update the parameters of the CAD template file. The designer can also add the corresponding parameters of the customized template file into the open parameter database according to the parameter record format of the database, and the parameters of the template file can be read and replaced by the same parameter replacement program. | en_US |