Real-time estimation of dynamic lever arm effect of transfer alignment for wing's elastic deformation

Abstract

When the carrier does angular motion, the different installation position between master strapdown inertial navigation system (M-SINS) and the wing-mounted slave strapdown inertial navigation system (S-SINS) will lead to lever arm effect, which seriously affects the accuracy of transfer alignment of S-SINS. In practical flight, wing's elastic deformation will change the length of lever arm and lead to dynamic lever arm effect. This paper presents a real-time dynamic lever arm estimation method. The proposed method estimates the length of the dynamic lever arm in real time by adding the length into state variables of transfer alignment. Firstly, the relationships of the length of lever arm with lever-arm velocity error and lever-arm acceleration error are established, and both of them are added into the error equations of S-SINS system as parameters to establish the complete error equations of S-SINS system with lever arm effect error. Then, the filter model of S-SINS system is designed. On the one hand, the state matrix is derived according to the error equations of S-SINS, which contains the length of lever arm as state variable. On the other hand, the measurement equation is inferred from the relation between the output of M-SINS and S-SINS with velocity plus angular velocity matching method. Finally, the length of dynamic lever arm is estimated by unscented Kalman Filter (UKF) as one of state variables. The estimated length of dynamic lever arm can be used to calculate lever-arm velocity error and lever-arm acceleration error. To validate the proposed method, a simulation experiment is conducted in MATLAB. The simulation experiment uses second-order Markov process to simulate the elastic deformation of wing. The simulation results indicate that the proposed method is able to estimate the change of the dynamic lever arm caused by the elastic deformation of wing in real-time, and achieves the high accuracy estimation of misalignment angle after compensating the lever arm effect error.