Research On Identification Method Of Dynamic System Of Floated Inertial Platform

Floated inertial platform is a frameless inertial navigation system.Compared to the traditional frame system,it can endure the large overload and high dynamic movement of the carrier.Thus,it is the ideal inertial navigation system of the strategic delivery system.This paper focuses on the measurement of the shell attitude,the identification of the installation positions and misalignment angles of the photoelectric sensors and the identification of the mass properties of the sphere.Specifically,the main research contents are organized as follows:(1)The attitude measurement method of the carrier guided by floated inertial platform is studied.Based on the measurement principle of photoelectric sensor,a photoelectric attitude measurement method is designed.The characteristics of the attitude measurement of the shell are analyzed,and several coordinate systems are established.The rotation process of the spherical shell relative to the sphere is detailedly analyzed,and the attitude calculation model is established using the quaternion.According to the random rotation of spherical shell,the simulation calculation of spherical shell attitude is carried out by MATLAB.If the photoelectric sensors with resolution of 10000 DPI are used,the mean value of the attitude error is-0.00212° and the standard deviation of the attitude error is 0.00201°,which is a high accurate solving results.The feasibility of the designed method is verified.(2)The installation position and misalignment angle of the photoelectric sensor mounted on the sphere are identified.Based on the photoelectric attitude measurement method,the source of the installation error is analyzed and the installation error model is established.The identification method of installation position and misalignment angle is designed based on weighted recursive least square method.In the process of simulation analysis,the measurement data of photoelectric sensor is obtained by setting the rotation sequence of the shell and used to identify the installation position and misalignment angle of the photoelectric sensor.By setting a reasonable rotation sequence,the relative errors of the installation position and the misalignment angle are not more than 0.5%,which is a high accurate identification results.This work is significant for the practical application of the photoelectric attitude measurement method.(3)The mass properties of the sphere are identified.On the one hand,a method of hanging a weight to rotate the sphere is proposed to identify the rotational inertia of the sphere,considering the sphere floating on the liquid and sticking out a little.The rotational dynamics model of the sphere is established.The rotation of the sphere is measured by the gyroscopes.A weighted recursive least squares identification method based on attitude calculation is designed.The influences of gyroscope measurement error,initial alignment error and suspension position error on the identification results are analyzed by simulation.The simulation results show that the rotational inertia of the sphere can be identified by selecting two hanging points reasonably.This method is simple to add moments,and can identify the rotational inertia of the sphere after adjusting the rotational inertia.On the other hand,in consideration of the practical working environment of the sphere,a method of using the torquer to derive the rotation of the sphere is designed to identify the inertia tensor,centroid position and damping moment coefficient of the sphere.The rotational dynamic model of the sphere is established.Similarly,the weighted recursive least squares identification method based on attitude calculation is used to identify the inertia tensor,centroid position and damping moment coefficient of the sphere.This method does not need additional measuring devices and operations.The algorithm is convenient to realize on-line identification.Through the simulation analysis,the parameters are identified with a very high accuracy(the relative error less than 1.5%),which is of great significance to achieve high-accuracy stability control of the sphere.