Unscented Kalman Filter Applied to the Spacecraft Attitude Estimation with Euler Angles

Abstract

The aim of this work is to test an algorithm to estimate, in real time, the attitude of an artificial satellite using real data supplied by attitude sensors that are on board of the CBERS-2 satellite (China Brazil Earth Resources Satellite). The real-time estimator used in this work for attitude determination is the Unscented Kalman Filter. This filter is a new alternative to the extended Kalman filter usually applied to the estimation and control problems of attitude and orbit. This algorithm is capable of carrying out estimation of the states of nonlinear systems, without the necessity of linearization of the nonlinear functions present in the model. This estimation is possible due to a transformation that generates a set of vectors that, suffering a nonlinear transformation, preserves the same mean and covariance of the random variables before the transformation. The performance will be evaluated and analyzed through the comparison between the Unscented Kalman filter and the extended Kalman filter results, by using real onboard data.

O Filtro H estendido de segunda ordem para estimação de atitude e bias de giros

“…O sistema não linear que representa as equações de processo e de medida para o satélite CBERS-2 e dada por [3,7]:…”

“…Ver Figura 1. A matriz de tranformação R apresentada nas Referências [2,3,7] na sequência 3-2-1, relaciona o sistema de coordenadas no corpo de satélite (x, y, z) com o sistema orbital local (x o , y o , z o ).…”

“…Os giros são alinhados aos três eixos dos satélites e fornecem a medidas da velocidades angulares com bias no sitema de referência do corpo. A medidas utilizadas nessa pesquisa, foram registradas pelo Centro de Controle de Satélites do INPE (Instituto Nacional de Pesquisas Espaciais) [3,7].…”

Line-of-Sight Rate Estimation Based on UKF for Strapdown Seeker

“…However, we should still assume the posterior probability distributed as Gaussian. Here the UKF algorithm [23] is introduced. The nonlinear system model can be given by…”

Unscented Kalman filter for spacecraft attitude estimation using modified Rodrigues parameters and real data

“…Finally, the update of the state vector and the covariance is given, respectively, by the following formulation (Garcia et al 2012):…”