Traditional versus improved designs for cycloidal speed reducers with a small tooth difference: The effect on dynamics

• The shortcomings of cycloidal drives with a small tooth difference are shown.
• The improved design with a multitooth difference is proposed.
• A mathematical model of improved design and its undercutting equations are derived.
• The dynamic analysis models are constructed for traditional and improved designs.
• Dynamic effect comparisons between traditional and improved designs are completed.

Whereas traditional cycloid reducers tend to have a one tooth difference design, a two teeth difference design is common when the transmission ratio is low (≦ 17). The dynamic characteristics of these small teeth difference designs, however, remain unclear. Hence, this study constructs an analytic model of system dynamics in a cycloid reducer with a small tooth difference. Specifically, taking a transmission ratio of 17 as an example, it analyzes both free-pin and fixed-pin designs to show the shortcomings of traditional designs. It then proposes a nonpin design that improves on these shortcomings, one in which the pinwheel is replaced by a cycloid internal gear. Next, adopting the theory of gearing, it constructs a mathematical model of the nonpin design with a multitooth difference and derives undercutting equations to check for the persistence of undercutting on the tooth profile. It also determines the parameter design range of nonundercutting. In an analysis of system dynamics, it then investigates twelve nonpin cases with a small tooth difference, showing the effect of the design parameters on the reducer's system dynamics. The results indicate that appropriate design parameters can indeed improve on the shortcomings of the traditional design.