Research on Line-of-Sight rate extraction of strapdown seeker

The strapdown guidance technology, which can improve the system reliability and reduce cost efficiently, has been paid great attention and developed quickly. However, the detecting information of strapdown seeker can't be used to proportional navigation directly because it is coupled with missile attitude, so the method of Line-of-Sight (LOS) rate extraction for strapdown seeker is investigated. Background noise and any inaccurate metrical information would be reflected to the extraction result, thus a LOS rate extraction method based on nonlinear Tracking-Differentiator(TD) and unscented Kalman filter (UKF) was proposed to obtain more precise guidance information. At the last, Monte Carlo simulations are performed; the results verify the performance and effectiveness of the designed method.

1 Introduction

Strapdown guidance system has become one of development trends of missile guidance system for its many potential advantages, such as eliminating the tracking rate and structure limitations of gimbals, reducing the mechanical complexity of implementation, improving the reliability and decreasing the weapon cost. However, the detector of strapdown seeker is fixed rigidly to the missile body, compared with the traditional seeker using inertial platform; there are two fatal disadvantages in strapdown guidance system. First, only LOS angles relative to body coordinates can be measured by the strapdown seeker. The measurement is coupled with the body attitude motion, which introduces high nonlinearity to the strapdown guidance system. Second, there is more serious measurement noise induced compared with the conventional guidance system. Owing to the high nonlinearity and more serious measurement noise, it is difficult to extract inertial LOS rate, which is essential to the design of the guidance law [1].