Research On Dynamic Measurement Methods Of Angular Rigidity Of Combined Flexible Joints

Dynamically Tuned Gyro (DTG) is a kind of high precision flexible gyro which isstill widely used in navigation system currently in our country. In the DTG, the flexiblejoints play critical roles in flexible supporting and transmitting driving torque to therotor, which characteristic size is about tens of microns. And the angular rigidity as thekey index is more or less effected by some parameters, such as the machining accuracy,surface roughness, material properties and geometric error. Although quality controlare performed after each important process, the value of the angular rigidity of theprocessed flexible joints still has much difference due to the manufacturing process iscomplicated. Thus, the angular rigidity can’t be accurately depicted by mathematicalmodel. Consequently, as the final testing methods after the machining process, themeasurement of angle rigidity is crucial.The paper does researches on the complex structures, dynamic characteristics anddynamic testing method of angle rigidity based on the inner and outer joints of thecombined flexible joints.First of all, the calculation and analysis of static rigidity of the inner and outerjoints are performed respectively based on the static simulation analysis and theempirical formula of circular flexure hinge stiffness. Through comparing the empiricalformula calculation results with the analysis results, the calculation results areabandoned. The influence on the angular rigidity of the similarities and differences ofthe joints’ structures is studied. The first four modes of natural frequencies andvibration modes are attained by the modal analysis. The moments of inertia of thethree-dimensional model are calculated by software and the dynamic rigidity value iscalculated according to the theoretical calculation formula of dynamic rigidity.Then, based on the theory of vibration testing and modal experiment and in orderto achieve the measurement requirements, the overall system solution is designed indriving signals, actuator apparatus, support structure and vibration picking device. Theactual components are designed and selected according to the overall solution.Finally, basic vibration response test of the device is tested before rigiditymeasurement. The vibration response test of the micro displacement vibration device isperformed in the real environments. The test is to ensure the output displacement andvibration frequency achieving the test requirements and eliminate noise frequencyduring the process of actual test of inherent frequency. After the environmental noisedetection, vibration responses of two orthogonal directions of a pair of inner and outerjoints are tested with methods of resonant excitation method and transient excitation method. After the data processing, environmental noise frequency and excitationfrequency components are eliminated and consequently, the natural frequency of theflexible joints is got. The tested inherent frequencies are compared to the modalanalysis results.The dynamic angular rigidity values calculated with the experimentalfrequencies and static theoretical calculation results are compared and the error sourcesare analyzed which indicate that the measurement method is available.