Research Of Strapdown Inertial Navigation Algorithm Under Highly Dynamic Environment

For the requirement of improving the attitude and velocity accuracy for strapdown inertial navigation system (SINS), this dissertation analyses the causes of algorithm error under high dynamic environments. The efficient SINS algorithms are designed and the key techniques of SINS algorithms are studied deeply, so that the SINS can deal with the infection of vehicle maneuvers. The main works are as follows:Firstly the causes of attitude algorithm error under highly dynamic environments are analyzed. Those are sample-bandwidth limitation, installation error, synchronous samples, quantization error and scale-factor error. The error of gyro measured angle velocity is given. According to the basic error equation for SINS, the expressions for DC portion of attitude error caused by gyro errors are deduced. The causes of attitude error under high dynamic environment are expatiated completely and systemically.The consistency of different representations for classical coning motion is discussed here. Referred to the classical coning motion, the pseudo coning motion is presented. Setting the example of dithered Laser gyro, the pseudo coning motion induced by dithered machine is studied. The expression of pseudo coning error is obtained, and the causes and influence factors of pseudo coning error are given. The applicability of conventional coning algorithms is studied under pseudo coning motion. In order to minimize the attitude error, the guide line for dithered machine design is provided. The digital filter is designed to demodulate gyro signal. The analysis and simulation show: using coning algorithm will increase the pseudo coning error made by pseudo coning motion. Setting the dithered frequency reasonably, using low-pass digital filter can avoid the effect of pseudo coning motion.The coning algorithms optimized under classical coning motion are applicable under other testing environments. The accuracy rule is provided to evaluate the attitude algorithms. The error expression for quaternion algorithm using Runge-Kutta integration is presented. The improved coning algorithm using angle velocity as input is designed to improve the accuracy for attitude compute. The modified coning algorithm using filter signal as input is designed to avoid the infection of filter-signal aberrance. The modified algorithm can improve the attitude accuracy for dithered laser gyro SINS.The sculling algorithms optimized under classical sculling motion are applicable under other testing environment. Based on the superposition theorem of linear differential equation, the SINS equation is analyzed. The strapdown algorithm is rearranged after predigesting the states equations in two-time scales. A new sculling compensation algorithm is designed to deal with the specific force variation during velocity updating interval. The simulation results show that the new algorithm and the conventional four-sample algorithm have the similar accuracy. The new algorithm expressed in digital discrete format is more suitable for SINS computer than conventional ones.In the end, the screw compensation algorithm based on screw theory is designed. The algorithm uses the cross products of the outputs from inertial sensors to compute the screw compensation term. Set the classical screw environment to optimize the undecided coefficients. The algorithm arrangement and the procedure using the screw vector to compute navigation parameters are listed. The differential equation consistency between screw compensation algorithm and conventional algorithm is verified. The causes of computation error for the two algorithms are analyzed. The analysis and simulations show that the screw compensation algorithm performs better than conventional algorithms with the same samples per update interval.