Research On Influencing Factors Of Interference Torque Of Gas-Floated Gyroscope

With development of inertial navigation technology and expansion of application domain, required precision of gyroscope in inertial system becomes very high. At the same time, more and more new type of gyroscope appeared, such as electrostatic gyroscope, laser gyroscope, optical fiber gyroscope, vibratory gyroscope and micro mechanical gyroscope. Depending mature technology and low cost, air-floated gyroscope still plays an irreplaceable role in inertial navigation field. However, by the restriction of machining technology, qualified rate and stability of air-floated gyroscope are unsatisfactory. This problem reduces production efficiency, and increases the cost. There are many factors influencing drift precision of air-floated gyroscope, such as vortex torque caused by manufacturing error and disturbing interference torque caused by thermal instability of center of mass of float module. So, how to control the factors influencing drift precision effectively is the key problem.This paper introduced the drift error model of air-floated gyroscope and the factors making K0 and K1 drift coefficient increase. Manufacturing error causing inhomogeneous flow in gas film of air-floated gyroscope influences K0 drift coefficient, while, thermal instability of center of mass of float module influences K1 drift coefficient. So, in this paper, the factors influencing the interference torque have been studied.Different parts of gas film studied in this paper are usually expressed in cylindrical coordinate and Cartesian coordinate respectively. The thrust part and slot part are usually expressed in cylindrical coordinate, while, radial loading part can be expressed in Cartesian coordinate after expanded into plane. By consistency transformation, the uniform expression of cylindrical coordinate and Cartesian coordinate is obtained. In order to achieve the pressure distribution in gas film, finite element equation is deduced based on aerostatic Reynolds Equation. Then, Reynolds Equation including longitudinal and transverse surface roughness is deduced based on Christensen's roughness model. The formulas solving the vortex torque and bearing capacity are presented at last. Finite element program used to solve Reynolds Equation is composed by using MATLAB, which is commercial mathematic software. Then research of these factors influencing vortex torque can be achieved expediently, and visual output of gas film pressure distribution can be obtained.The shape error generated during manufacturing and assembling process is important factor influencing K0 drift coefficient. In this paper, mathematic models of float oval error, float three-lobing error, slot disalignment error and radial eccentricity ratio are established. Then put these models into finite element equation, and effect of these factors on pressure distribution in gas film is obtained. After that, effect of these factors on vortex torque is analyzed and method controlling vortex torque is put forward. Further, effect of gas film thickness and air supply pressure on vortex torque is also studied, and reasonable matching value of slot width and gas film thickness is obtained. By using vortex torque test instrument, vortex torque of several gyroscopes is measured, and the rationality of emulation is verified.The gas film thickness is very small and vortex torque is quite sensitive, so pressure distribution variation caused by surface roughness will influence vortex torque at a certain extent. In this paper, relation between average arithmetic deviation of surface roughness and parameter of surface roughness in Reynolds Equation is established. Effect of magnitude and direction of surface roughness on vortex torque is studied by using Reynolds Equation including surface roughness.Thermal stability of center of mass of float module is important factor influencing K1 drift coefficient. Finite element model of air-floated gyroscope is established, and screw pretightening force model is established by using nodal restraint equation. By using screw stiffness and pretightenting force equation, relation between screw pretightenting force in finite model and screw tighten torque is obtained. Then, effect of different pretightening force on the stability of center of mass in variable temperature field is studied, and reasonable screw pretightening force is obtained. At last, the deformation nephogram and stress distribution at the key time points is analyzed, and proper suggestion is put forward.