Sensitivity of planetary gear natural frequencies to system parameters

This paper investigates influence of the system parameters such as output flexibility (carrier rotational stiffness) on the natural frequencies with unequally spaced planets. Sun gear is modeled as input for two states of fixed and floating. Each component such as sun gear, carrier, ring gear and planets considered to three degrees of freedom. Besides, bearing and mesh stiffnesses are modeled in the form of linear springs. The vibration modes are classified in to three generally modes of planet, rotational and translational modes. For systems with three and four unequally spaced planets, the results show that the most important effect of the carrier rotational flexibility is on the first natural frequency; while, for the case of free rotational carrier the first natural frequency for both fixed and floating sun gear is zero, i.e., rigid body motion is appeared. By variation of the output flexibility for both state of the input, the first natural frequency is sensible to the output flexibility variations. Moreover, for system with four unequally spaced planets, the output flexibility for both fixed and floating input (sun gear) isn’t effective on the last natural frequencies. So, by transfer behavior of the output to rigid state, the first, 10th, 13th to 21th natural frequencies for both state of the input are equaled. Furthermore, for the system with three unequally spaced planets, the output flexibility is effective on natural frequencies of rotational modes.

Keywords:

Planetary gear , Natural frequency , Output flexibility , Vibration modes