Abstract

Planetary gears are one part of the whole transmission chain, and the dynamics and vibration characteristics of them are strongly coupled with external rotors. In this paper, to demonstrate the interaction between multistage planetary gears and external rotors as well as investigate the lateral‐torsional coupling characteristics of them, a coupling model of a two‐stage planetary gear rotor system is proposed. In such a model, the two‐stage planetary gear subsystem is established as a lumped‐parameter model and the external rotor subsystem is established as a finite element model. The vibration mode distribution properties and lateral‐torsional coupling characteristics are both analyzed by modal strain energy. Three different conditions are considered: uncoupled, partially coupled, and fully coupled. The results indicate that the coupling among multiple subsystems and the lateral‐torsional coupling mainly exist in the low‐mode region. Natural frequencies dominated by the two‐stage planetary gear subsystem are sensitive to coupled conditions, whereas natural frequencies dominated by the input rotor subsystem are remarkably insensitive to coupled conditions. Furthermore, the natural frequency of the first torsional mode can be obtained only in the fully coupled condition. Experiments are implemented to obtain natural frequencies, and the experiment results validate the numerical results.

Highlights

  • In the fields of helicopter, marine, automotive, and wind power, variable-speed devices with high power density, heavy carrying capacity, high torque-to-weight ratio, and efficiency are in demand

  • Similar to the previous case, the natural frequencies dominated by the input rotor subsystem under uncoupled, partially coupled, and fully coupled condition are selected, respectively

  • The influence of external rotors has been investigated on the vibration characteristics of planetary gears and the lateral-torsional coupling characteristics of the entire system, and a coupled modelling methodology of a two-stage planetary gear rotor system is presented

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Summary

Introduction

In the fields of helicopter, marine, automotive, and wind power, variable-speed devices with high power density, heavy carrying capacity, high torque-to-weight ratio, and efficiency are in demand. Kahraman [2] studied the vibration characteristics with different configurations and speed ratios using a purely rotational model. It is essential to develop a coupling mathematical model when the rigidity of external rotors is so large that input and output units have significant influence on multistage planetary gears Through this way, one can get a more correct and more reliable vibration characteristics of multistage planetary gears. A lateral-torsional coupling mathematical model is proposed to investigate the free vibration characteristics of a two-stage planetary gear rotor system (the simplest form of the multistage planetary gear rotor system); three different coupling conditions between each two adjacent subsystems are considered in such a model. Spinning test and modal test are implemented on a test rig, and Harmonic Response Analysis and Experimental Modal Analysis are performed in order to compare the experimental natural frequencies with the numerical results

Coupled Modelling and Equations of Motion
Natural Frequencies and Vibration Modes
Experimental Validation
Findings
Conclusion
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