Fault Diagnosis of RV Reducers Used in Industrial Robots Based on Vibration Analysis

RV reducer is a key component used in the joint of an industrial robot due to its high transmission ratio, high load-carrying capacity and smooth transmission. Condition monitoring allows the faults of RV reducer to be detected at an early stage and prevent it develops into a critical fault or complete failure, which cause massive losses of production. To fulfil early diagnostics, this paper built up an RV reducer test rig and investigated the diagnosis of abnormal engagement between sun gear and planet gear using vibration analysis. Firstly, a misalignment fault of input shaft and sun gear bearing clearance fault were carried out on the RV reducer test rig, then the vibration signals of the RV reducer were collected. Besides, through analysis of the vibration spectrum, the characteristic frequencies such as gear meshing frequency and shaft rotating frequency can be clearly identified in the vibration spectrum. A statistical analysis of RMS values was applied on the specific frequency band of gear characteristic frequencies. The results show that the RMS value increased with the increase of the degree of misalignment due to the increased periodical mesh interfere and decreased with the increase of the sun gear bearing clearance due to the optimized meshing interference. This phenomenon becomes obvious in high-speed operations. These results are quite beneficial to study the feature extraction for fault diagnosis of RV reducer used in robot joints.