The Comparison of Methods of Computer-Based Design of Planetary Reduction Gears

Planetary gears have been widely used due to their advantages compared to other types of gears with regards to compact structure, relatively small dimensions and efficient metal consumption. These advantages can be realized only when the optimal scheme and number of teeth of the planetary gears are chosen. However, designing planetary gears is a more complex task than designing gears with stationary axes, hence the abundance of computer programs recommended for designing planetary gears in the literature. To compare computer-based methods of designing planetary gears, a scheme of double-row planetary reduction gear is chosen. It is considered as one of the most time consuming schemes to calculate due to the significantly higher number of unknowns over the pre-set design conditions.   Usually, the transmission ratio and the number of satellites whose quantity provides the increase in the transferred power and static balance of the construction, are taken as the design assignment for the reduction gear. When the transmission ratios of the double-row planetary reduction gears are the same, their dimensions may be different depending on the distribution of the transmission ratios in the two rows of meshing and the arrested planet carrier.  Designing planetary gears is a multi-criteria task; it is associated with a considerable number of kinematic constraints with regards to the number of teeth. A particularly frustrating thing for computer-based calculations is rounding the quotient of whole numbers of teeth, which may happen to be a fractional number, to a whole number. A discrepancy between the actual transmission ratio and the pre-set one occurs. This error is insignificant for power transmissions but can lead to incorrect calculations when performing the assemblability test for reduction gears. That is why computer-based design of planetary gears specifically requires obtaining the solution in whole numbers. The dimensions and the discrepancy between the actual and the pre-set transmission ratios are chosen as the criterion of optimality when designing planetary gears, even though the latter may be insignificant when designing power transmissions.  Despite the fact that planetary gears have been used for more than two thousand years, a universal designing method that would allow minimizing design time and optimizing performance characteristics and manufacturing qualities, still does not exist. In this article the author compares several fundamentally different computer-based programs for designing planetary gears with the aim of determining their usability, possibility of obtaining optimal solutions with regards to dimensions, and assessing their consistency and accuracy.

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