Investigation of transient response motion of differential planetary gear train during reverse rotation and starting by using high-speed camera monitoring

Abstract

Planetary gear trains (PGTs) have been used in various applications, including hybrid and electric vehicles, owing to their advantages such as compactness, light weight, and large torque-to-weight ratio; however, recently, their transient response, such as sudden stop in differential usage when applied to cooperative robots (CRs), has emerged as a critical issue. It is difficult to elucidate the motion mechanism of PGTs, due to differing meshing conditions among internal and external meshing, the large number of meshing points, and simultaneous rotation and revolution. Therefore, few experimental investigations concerning PGT transient responses have been performed worldwide. This study aims to elucidate the transient response, in particular in the case of reverse rotation, considering the critical issues pertaining to the use of PGTs in CRs. Transient response has three continuous phases: braking, stopping, and starting. A novel gear train, named 2K-HV PGT, having a clear acrylic carrier, was developed to enable direct observation of the planet gear motion, because it is otherwise impossible to observe the inner mechanisms of the conventional 2K-H PGT. Direct observations of the novel PGT were recorded using a high-speed camera. The observations of the transient responses showed differences in the switching times or stopping phases, due to differences in the moments of inertia and torsional rigidities among the PGT components. The transient response of reverse rotation did not occur instantaneously, but rather gradually within a certain time band.