Error analysis and compensation for lever-arm effect in transfer alignment

Lever-arm effect error is one of the major factors that influence the velocity matching transfer alignment, it must be compensated. Because the compensation result of commonly used digital filter compensation method is not satisfactory, a direct calculation compensation method is proposed in this paper aiming at the nonlinear system under the condition of large azimuth misalignment. The precondition of the calculation compensation method is that the length of the lever-arm is known. If it is unknown, a new algorithm is proposed, which first estimates the lever-arm length with the extending dimension unscented Kalman filter method and then compensates the lever-arm velocity term with the calculation compensation method. Simulation and experiment were carried out to verify the effectiveness of the new method. The azimuth misalignment is converged to 0.381° in 120 seconds under simulation condition and converged to -0.031° in 0.8 hour under experiment condition. The simulation and experiment results both show that the initial alignment speed and accuracy are enhanced greatly compared with the digital filter compensation method.