Relative position and attitude estimation method based on antenna arrays

The accurate knowledge of relative position and attitude is essential to reduce control error and avoid collision in small satellite formation flying. However, the traditional relative navigation systems composed of many sensors have usually large volume and high cost. Considering the miniaturization and highly integrated functional modules of small satellites, cost-effective relative position and attitude estimation method is required. In this paper, we propose a novel approach, called Relative States Estimation based on Double Antenna arrays (RSEDA). The approach utilizes the existing communication systems on flying vehicles. In RSEDA, the chief vehicle is equipped with two planar antenna arrays to receive the probing signal transmitted by the planar antenna array installed on the deputy vehicle. Thus two sets of angle-of-arrival (AoA) and angle-of-departure (AoD) of the line-of-sight (LOS) signal propagation path from transmitting antenna to the two receiving antennas can respectively be estimated using the array signal processing. The distance between the two receiving antenna in the frame of the chief body frame is to be known. Then based on this distance and the measured AoAs and AoDs of the LOS paths from the transmitting antenna to the two receiving antennas, the relative distance between the chief and deputy vehicles can be deduced. Then the observation equation of the EKF can be derived. Based on which, the relative position and attitude between the CV and DVs can be estimated iteratively. RSEDA is theoretically proved and also validated by the simulation results in this paper. The signal transceiver architecture for inter-vehicle communications and the RSEDA method are also presented for implementation in a real vehicle.