Research On Airborne SAR Transfer Alignment Technology Using Inertial Sensor

With the development of war in modern society,the capacities to remotely detection,monitor,combat ground and air targets of the enemy has become one of the symbols of a country’s military strength.Airborne SAR can work in all sorts of complicated weather and carry out all-weather monitoring to land targets.These exclusive advantages make it have an extensive use in the military field.As the key technology realizing high-resolution airborne SAR imaging,motion compensation decides whether the fighter plane is able to finish the task of effectively monitoring and combating ground and air targets.Motion compensation technology of airborne SAR,which is based on inertial sensor,has the ability to provide short and long-term posture and position information of antenna phase center in the circumstance of complex electromagnetism.But its prerequisite lies in resolving the systematic error of inertial sensor and measurement errors of the sensor arising out of structure deformation in antenna phase center.It is concluded that the paper focuses on researching airborne SAR transfer alignment technology applied the inertial sensor.The main study work of the thesis includes the following aspects:1.We introduce the basic working principle of inertial navigation.Based on this,the attitude matching and velocity matching and "velocity+position" matching methods in traditional transfer alignment methods are analyzed theoretically.Under four different deflections,the gesture accuracy of the sub-inertial navigation system achieved by "velocity+position" matching is simulated and analyzed.The simulation results show that "velocity+position" transfer alignment has strong limitations in dealing with deflection deformation and the position accuracy of aligned sub-inertial navigation system can not meet the needs of airborne SAR motion compensation.2.Proposing the relative inertial navigation algorithm to solve the problems that the bending deformation of the airframe ant the antenna phase center cannot be accurately modeled,and the attitude and position accuracy of the sub-inertial navigation cannot meet the motion compensation requirements of the airborne SAR.The basic principle of the relative inertial navigation algorithm is elaborated,and the relative motion relationship between main inertial navigation system and sub-inertial navigation system and its solution method are deduced in details.Simulating and analyzing the relative inertial navigation algorithm without device error and initial relative gesture error.the simulation results show that the relative inertial navigation algorithm can track the deflection at the phase center of the carrier SAR antenna in real time gesture and position information at the sub-inertial navigation.But when there are device error and inertial relative gesture angle error in the sub-inertial navigation algorithm,the navigation accuracy of the sub-inertial navigation algorithm can not meet the needs of airborne SAR motion compensation,and it also shows the limitation of the algorithm.3.Giving the derivation process of the transfer alignment error equation of relative inertial navigation,and establishing the state space model of the system.Aiming at the problems of device errors and initial relative gesture errors in sub-inertial navigation,a transfer alignment method of relative inertial navigation is proposed to solve those errors.The simulation results show that attitude and position accuracy of the sub-inertial navigation obtained by the transfer alignment method can meet the needs of airborne SAR motion compensation.In order to solve the problem that the sub-inertial inertial navigation attitude error is larger than that of the inertial navigation transfer alignment due to the direct flat motion of the carrier aircraft,a solution of the sub-inertial inertial navigation attitude error is proposed,and the simulation results show that the higher accuracy of the sub-inertial inertial navigation attitude information can be obtained by using this scheme.By setting three groups of different initial relative gesture error angles,the applicability of relative initial navigation transfer alignment is simulated and analyzed and the comparison between relative inertial navigation transfer alignment is made.The simulation results show that the alignment time of "speed+position" transfer alignment is shorter,but its alignment accuracy is lower.In view of the above-said research,the thesis has a great significance of theory and application in the enhancement of the accuracy of APC inertial navigation.