Shan Qian

Kalman Filtering for Relative Spacecraft Attitude and Position Estimation: A Revisit

I N [1], an extended Kalman filter (EKF) was formulated to estimate the relative position and attitude between the chief and deputy spacecraft using the vision-based-navigation (VISNAV) system coupled with gyro measurements from each spacecraft. The VISNAV system consists of an optical sensor combined with specific light sources (beacons) to achieve a selective vision. In general, the known beacon locations are defined in the chief’s body frame, whereas the relative position vector is expressed in its local vertical/ local horizontal (LVLH) frame. In [1], it was implicitly assumed (but not clearly stated) that the absolute position and attitude of the chief were known, and only the relative quantities needed to be estimated. Therefore, a simplified assumption that the chief body frame coincides with its LVLH frame was made in [1] to construct the lineof-sight (LOS) observations for convenience. Unfortunately, this assumption is not valid under all situations, or in some rigorous sense, it is only a special case. One approach to solve this problem is to formulate the relative equations ofmotion in the chief body frame [2], and thus, the beacon-location vectors and relative position vector between the chief and deputy spacecraft are described in the same coordinates. However, this approach has two main disadvantages in practice: 1) the angular velocity of the chief body frame generally varies rapidly, and its measured value is contaminated by the gyro measurement error, which may cause large computation errors in the relative equations of motion; and 2) the linear relative dynamics are not obtained, and relative rotational and translational motions are interlaced in highly nonlinear and coupled fashions. The objectives of this Notewere to revisit this relative position and attitude estimation problem, and to design a novel navigation filter without the assumption. Two relative quaternions thatmap the chief’s LVLH frame to the chief body frame and to the deputy body frame are involved. The corresponding attitude matrices are used to construct the LOS observations, and thus, the assumption that both the chief’s body and the LVLH frames are the same can be removed. An EKF is derived to estimate the mentioned relative quaternions, relative position, and velocity of two spacecraft, as well as gyro biases. The relative attitude between two spacecraft is obtained by using these two relative quaternions. This Note extends the previous work [1] to additionally estimate the attitudes of both spacecrafts relative to the LVLH frame, in which the relative orbit equations are written, so that the attitude of the chief need not be known a priori.

Research on angles-only/SINS/CNS relative position and attitude determination algorithm for a tumbling spacecraft

In this paper, the relative navigation technique of final approach phase for a tumbling target spacecraft is studied and exploited. It is assumed that the tumbling target is in failure or out of control and there is no good a priori rotation rate information. The Euler’s rotational dynamics is used to propagate the target angular velocity, and the unknown inertia parameter circumstance is also considered. The chaser spacecraft is equipped with three strapdown gyros and accelerometers and a star sensor that determine the absolute motion parameters, and an optical camera that measures relative azimuth and elevation angles to the target spacecraft. On the basis of the rotational and translational motions of both spacecrafts, an angles-only/ strapdown inertial navigation system/celestial navigation system navigation filter is designed. Simulation results indicate that the proposed algorithm can accurately estimate the relative position, velocity, and attitude between two spacecrafts and compensate the biases of the gyros and accelerometers.

Unscented Kalman Filtering for Relative Spacecraft Attitude and Position Estimation

A novel relative spacecraft attitude and position estimation approach based on an Unscented Kalman Filter (UKF) is derived. The integrated sensor suite comprises the gyro sensors on each spacecraft and a vision-based navigation system on the slave spacecraft. In the traditional algorithm, an assumption that the masters body frame coincides with its Local Vertical Local Horizontal (LVLH) frame is made to construct the line-of-sight observations for convenience. To solve this problem, two relative quaternions that map the masters LVLH frame to the slave and master body frames are involved. The general relative equations of motion for eccentric orbits are used to describe the positional dynamics. The implementation equations for the UKF are derived. A modified version of the UKF is presented based on the averaging-quaternion algorithm. Simulation results indicate that the proposed filters provide more accurate estimates of relative attitude and position than the Extended Kalman Filter (EKF).

Research on Angles-Only/SINS/CNS/GNSS Relative Position and Attitude Determination Algorithm for Uncooperative Target

In this paper, the relative navigation technique of final approach phase for uncooperative target is studied and exploited. The chaser spacecraft is equipped with three strap-down gyros and accelerometers, a star sensor, an optical camera and Global Navigation Satellite System. On the basis of the rotational and translational motion of both spacecrafts, an angles-only/SINS/CNS/GNSS navigation filter is designed. Simulation results indicate that the proposed algorithm can accurately estimate the relative position, velocity and attitude between two spacecrafts and compensate the drifts of the gyros and accelerometers. The relative navigation accuracy meets the requirements for autonomous rendezvous and docking missions.

Optimal Control Techniques for Spacecraft Attitude Maneuvers

The capability of attitude maneuvers and attitude tracking for spacecrafts is required in the current sophisticated space missions. In short, it is to obtain command requirements and attitude orientation after some form of control. With the development of space missions, the ability of rapid and energy-saved large-angle attitude maneuvers is actively expected. And the high requirements for the attitude control design system are increasingly demanded. Consequently, optimal control for attitude maneuvers has become an important research direction in the aerospace control area. From control aspect, spacecraft attitude maneuvers mainly involve trajectory planning (Guidance), attitude determination (Navigation), and attitude control (Control). Further researches about these three key technologies are necessary to achieve optimal control for attitude maneuvers. In this chapter, the necessary background on optimal control for attitude maneuvers of three-axis stabilized spacecraft is provided, and the recent work about guidance and navigation as well as control is summarized, which is presented from three parts as follows: 1. The optimal trajectory planning method for minimal energy maneuvering control problem (MEMCP) of a rigid spacecraft; 2. Attitude determination algorithm based on the improved gyro-drift model; 3. Attitude control of three-axis stabilized spacecraft with momentum wheel system.