Study On Drift Mechanism And Its Suppressing Techniques Of The Cupped Wave Gyroscope

Gyroscopes utilize sensitive elements to measure the rotation of carriers, thus become the core devices of navigation equipments. Bias drift is one of the most important parameters for a gyroscope, which directly affects the accuracy of the weapons. However, technical data of high performance gyroscopes are scarcely published. Therefore, carrying on an independent research and improving the gyroscope performance is of great importance.Cupped wave gyroscopes are appealing because of their advantages of high accuracy, long life and good impact resistance, etc. The cupped resonator is the core element in the cupped wave gyroscope, thus its quality will determine the performance of the gyroscope. However, the cupped resonator is a typical thin shell structure. Its geometric accuracy is sensitive to the machining process. There is residual stress inner the structure and the material itself is inhomogeneous. These basic imperfections will result in frequency split, inhomogeneous damping and inner stress. Thus the drift is finally generated. Aiming at the problems of drift mechanism and its suppression, this research will provide a novel design theory and method for developing high performance shell gyroscopes. The main contents of this dissertation are as follows:1. Basic theoretical principles for the cupped wave gyroscopes. The basic structure and operating principle of the gyroscope are introduced, and the nature frequency, quality factor and eigenmode are analyzed. The formula for calculating the nature frequency is deduced. The losses of the cupped resonator are analyzed, which include the air damping loss, surface loss, supporting loss, thermoelastic damping loss and internal friction loss. Moreover, the finite element method(FEM) is used to analyze the eigenmodes of the cupped resonator.2. Formation mechanism of quality imperfection for the cupped wave gyroscopes. The manufacturing errors during the machining process are analyzed, and the formation mechanism of the quality imperfection is studied. The model of frequency split caused by inhomogeneous mass and stiffness is built. The inhomogeneous damping generated by uncontinuous structure is analyzed, and the mode deflection caused by stress concentration is studied. In addition, a method for measuring the quality imperfections is given. It utilizes the superposition of the standing wave to obtain the information of the frequency split, mode deflection and quality factor, etc.3. Drift mechanism of the cupped wave gyroscopes. The drift of the gyroscope caused by quality imperfections is disscussed. The parameters which give rise to the drift signal are studied. In theory, the drift under the conditon of free vibration or caused by continus excitation is deduced. The phase error of the nodes is then studied. In additon, the drift caused by inhomogeneous damping and stress is obtained.4. Drift suppression of the cupped wave gyroscopes. From a manufacture, trimming and circuit control point of view, the drift suppression of the gyroscope is studied. Methods for eliminating the manufacture error and material imperfection are analyzed. The trimming of the resonator is studied to suppress the gyroscope drift. In theory, the frequency split can be eliminated by using the mass trimming and stiffness trimming. The mode deflection can be also adjusted by using the mass trimming and the stress control. Moreover, the principle of the force rebalance circuit for eliminating frequency mismatch is studied.5. Performance test of the cupped wave gyroscopes. The tests of the gyroscopes before and after quality trimming were implemented. These experiments included frequency trimming, damping drift adjustment, stress trimming and circuit control. The experimental results showed that the performance of the gyroscopes was significantly improved.