Research on nano-film composite lubricated triboelectric speed sensor for bearing skidding monitoring

Triboelectric speed sensors (TSS) have the advantage of easy integration to be used to monitor the bearing skidding. However, dry friction between materials can reduce the durability and stability of TSS and interfere with the operation of the cage. In this paper, BaTiO3/polyimide (BTO/PI) nanocomposite films and lubricants are introduced to triboelectric nanogenerator (TENG) and the effects of lubricant species and nanoparticles doping mass fraction on tribological and electrification performance are investigated. The results show that the TENG with squalane and BTO/PI nanocomposite film of 20 wt% has a lower friction coefficient and mass loss while higher output and stability. Then, the nano-film composite lubricated TSS (NFCL-TSS) integrated with bearing is constructed based on the rotary freestanding TENG (RF-TENG) with optimal nanocomposite film and squalene, where the signal processing circuit with wireless transmission is integrated on the back of RF-TENG stator to improve the integration of the sensing system. The results show that the NFCL-TSS has 84.81% lower mass loss, 95.26% and 97.75% higher electrical output and stability than that of the TSS with pure PI under dry conditions, respectively. Moreover, the cage speed before and after installation of NFCL-TSS remains mostly unchanged, and the error between the cage speed measured by NFCL-TSS and commercial sensor is below 0.26%. Finally, based on the bearing test platform, the monitoring of skidding is achieved by NFCL-TSS under different speeds and loads. This study provides a new strategy for the design of TSS with high durability, stability and integration.