Research on measurement for bending stress of gear with Fiber Bragg Grating (FBG) and optimization of FBG probe installation

With the rapid development of robot technology, more and more intelligent robots serve for people in many fields. The gear is important for many robots, teeth root bending stress is one of the gear strength indexes, so measuring teeth root bending stress is very important. Photo elastic method and electrical method have been generally applied. However, there are some disadvantages of those methods. The production and the installation technology of the photo elastic are complex. About electrical method, the sensor is too big to be pasted on the teeth root. In this paper, a new method measuring the bending stress of gear with Fiber Bragg Grating in robot is proposed. The feasibility of this method and the installation of the FBG probe are necessary to be considered. In reality, the probe is installed in a secure area of gear due to the structure of gear. Optimization of FBG probe installation is discussed in details and the best pasting angle is obtained in this work. Cantilever beam was used to instead of gear teeth because the overall stress distribution characteristics of gear are similar to cantilever beam. According to mechanics of materials theory, the relationship between quality/pasting angle and relative offset of FBG reflection wavelength is obtained. The experiment results are consistent with the simulation results. The proposed method with its superior ability was proved to be feasible.