Experimental Investigation On Friction Characteristics Of Inertial Navigation Bearings

High-precision inertial navigation systems(short for INS) are mainly used in key areas such as modern aircrafts, ships and precision-guided weapons. The gyro-motor rotor of INS adopts rolling element bearings as supporters. The rolling element bearings’ friction characteristics influence the carrier’s attitude stabilization and the associated instruments’ indicating accuracy, therefore it needs to be strictly controlled. INS bearings belong to ultra precision miniature ball bearing category. It is different from ordinary bearings in size, application environment, operational requirements and lubrication conditions. The majority of the existing research findings are based on EHL theory. They are not suitable for INS bearings. Currently, there is no clear understanding of INS bearings’ friction characteristics. The calculation formula which can be used in the relevant engineering practice is still deficient. Carrying out experimental research in this area is to provide data support for the relevant engineering practice and reference for further study.Since the problem of lacking corresponding test equipments is serious, a newly test rig was developed. The development process of the test rig was divided into three parts: firstly,on the basis of studying existing bearing’s friction torque measuring apparatus and test methods, the overall scheme was determined; secondly, the test rig’s designation of main mechanical structure, control system and data acquisition system was completed independently; finally, the installation and adjustment of each component were conducted to complete the establishment of the test platform.Taking a certain type gyro-spin bearing as researching subject, the friction torque test was conducted under conditions of different speeds, axial loads and ambient temperatures. The results show regulations as follows: 1 The rotating speed has the largest impact on the gyro-spin bearing’s friction torque. The friction torque fluctuates along with speed variation. 2 The friction torque of the gyro-spin bearing increases with the increasing axial load, but they are not in linear relationship. Besides, the friction torque’s fluctuation along with speed variation is not significant on condition of a smaller axial load. 3 Ambient temperature has an obvious effect on the gyro-spin bearing’s friction torque. In the test range, when the bearing’s dn value is relatively low, the friction torque decreases steadily with the increasing ambient temperature; when the dn value is in middle range, the friction torque reaches a steady state after a rapidly decrease with the increasing ambient temperature; when the dn value is higher in the test range, the bearing’s friction torque experiences the changing process from dropping to stabilizing to rising. 4 Aging has an effect on gyro-spin bearings’ friction torque. The bearing needs some running-time to achieve stable operating state. The friction torque has a short fall in the initial phase, after that it keeps essentially unchanged.Last of all, an equation was built up based on the regression of the measured values, which is applied for calculating the gyro-spin bearing’s friction torque. The regression equation’s calculated values were compared with the measured values. The results show that the regression equation’s fitting curves are consistent well with the test results. The regression equation has a great practical value.