| The platform inertial navigation system(PINS),which has been widely used in longendurance and high-precision systems especially in the strategic missiles,has the advantages of high precision,good stability,and being insusceptible to external factors such as nuclear radiation.In order to improve the hit precision of the strategic missile,it is necessary to improve the precision of PINS.At present,relevant researchers mainly improve the precision of the inertial navigation system from two aspects: one is to adopt advanced materials and heat treatment technology,and to improve the processing,manufacturing of the components and overall assembly process;the other is to improve the calibration precision of the inertial navigation system and take necessary compensation measures.In the research of the manufacturing process of inertial instruments,environmental factors such as temperature and humidity and many other unknown factors need to be considered,which often requires a lot of time and effort.Therefore,to improve the precision of the inertial instrument by improving the manufacturing process of the instrument has reached the bottleneck,and the effect is limited.Recently,using high-precision inertial navigation test equipment and the advanced measurement method to calibrate the errors of inertial instrument and PINS with some compensation approaches is testified to be a more effective method.This paper takes the PINS and the inertial instruments used in the PINS—quartz accelerometer and liquid floated gyroscope as the research objects.The error sources of the inertial navigation test equipment are analyzed.Combined with the error models of the inertial instruments,the accurate and complete calibration models of the inertial instruments and the PINS on the test equipment are established.And test and calibration methods of effectively eliminating or suppressing equipment errors are designed.Firstly,the error compensation and suppression technology of high-order error model coefficient calibration of quartz accelerometer tested on the precision centrifuge is studied.In order to eliminate the influence of dynamic and static error sources of precision centrifuge on calibration precision,9 coordinate systems are established considering centrifuge errors,the motion parameters and errors are propagated by homogeneous transformation method,and the accurate specific forces acting on three axes of the tested accelerometer are obtained.A test plan of 12-position under three mounting modes is designed.Based on the error model and the accurately computed input specific forces of the accelerometer,the indicated outputs of the tested accelerometer are derived,a calibration model of the accelerometer is established.Finally,all the high order error model coefficients of the tested accelerometer are calibrated accurately by the leastsquares method.In the calibration method,the dynamic errors of precision centrifuge are introduced into the observation vectors,and the static errors are introduced into the vectors to be identified.Therfore,the influence of centrifuge static errors is automatically eliminated and the influence of centrifuge dynamic errors is suppressed.Error analysis implies that the calibration precision is improved greatly.Secondly,the test and calibration method of liquid floated gyroscope on the two-axis turntable is studied.The calibration model of the gyroscope on the two-axis turntable is established by introducing the two-axis turntable errors,gyroscope installation errors and gyroscope static error model.The gyroscope's input and output models are established by16-position method and 20-position method in the gravity field.Then the error model coefficients are calibrated by the error separation method and the least square method.Comparing with the 8-position method,floated gyroscope's calibration precision can be improved by suppressing the turntable errors automatically and eliminating the influence of the gyroscope installation errors which are difficult to measure.Moreover,error analysis of the two multiple-position calibration methods implies that the error model coefficients of the floated gyroscope have a high calibration precision,which verifies the effectiveness of the proposed method.The test and calibration method of the second-order term error coefficients in the static error model coefficients of the floated gyroscope is studied,and a method of vibrating within the integer number of periods on linear vibration table is proposed to calibrate the floated gyroscope.On the basis of fully considering the parasitic rotation,perpendicularity of the linear vibrating table,the angular vibration error generated during the test and the installation error of the gyroscope,a six-position calibration scheme is designed to calibrate the gyroscope's second-order error coefficients.Influences of the parasitic rotation of the linear vibration table,the angular vibration,and the installation error of the gyroscope on the calibration precision are effectively suppressed in the process of calibrating,which can improve the calibration precision of the floated gyroscope tested on the vibration table.Finally,the corresponding error analysis proves that this method can accurately calibrate the second-order error model coefficients of the gyroscope,and is of engineering practical value.Finally,the method of testing and calibrating PINS error model coefficient on precision centrifuge with counter-rotating platform is studied.The error sources of the precision centrifuge are analyzed firstly.Combined with the error models of the inertial instruments(liquid floated gyroscope and quartz accelerometer)in the PINS,the calibration model of the PINS tested on the centrifuge,i.e.,the state equation and observation equation,is deduced.The Euler angles of the platform,the error model coefficients of the inertial instruments,the installation errors of the instruments,and especially the centrifuge errors are taken as the state variables of the system,and the outputs of the accelerometers and the Euler angles of the platform are taken as the observation variables.Then in order to reduce the complexity of identifying all the coefficients at one time,a multi-position combined calibration scheme of the PINS tested on the centrifuge is designed,and the corresponding simulation analysis is carried out.The error model coefficients of the instruments are estimated by the nonlinear Kalman filter.The influence of centrifuge errors on the calibration results is analyzed,which is verified that the proposed method can effectively eliminate the influence.Thereby the calibration precision of the inertial navigation platform system is improved,especially high-order error coefficients.At the same time,the influence of the radius error and the rotation speed error between the spindle and the counter-rotating platform of the precision centrifuge on the calibration results are analyzed,and the necessity of compensating for the radius error and controlling the rotation speed error in a certain precision range is verified. |
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