Research On Sun Vector Determination Using Solar Panels Data

Attitude Determination System is the foundation and precondition of satellitecontrol, sun vector is the most commonly used information in the process of attitudedetermination. Sun sensor is usually equipped to measure sun vector. Sincemicro-satellite has very strict requirements on the mass, the volume, the powerconsumption and the cost of the equipments, the measurement program of utilizingthe current information of the multiple non-coplanar solar panels that reused as sunsensor is designed which includes attaining sun vector through processing theinformation of the solar panels on the micro-satellite, the determination of the sunvector according to the information of the current on different solar panels, attitudedetermination through the combination of sun vector and other measurement,etc.The following achievements have been made:To confirm the sun vector by the stimulation of the current on the solar panels,unit vector is employed to describe sun vector. Considering the influence ofmeasurement error of the current on solar panel on the determination of sun vect or，Fuzzycones algorithm is introduced. This method is able to reduce the influencebrought by the measurement of the current on a certain solar panel on thedetermination of the sun vector. By calculating the probability of all the vectorsbeing sun vectors in the unit ball, define the vector with maximum probability inthe unit ball as sun vector. Through mathematical simulation，the feasibility offuzzycones algorithm can be testified.To simplify the determination of sun vector when multiple solar panels areinvolved, a method of sun vector based on spherical projection is introduced. Inspherical projection, sun vector information is projected onto a plane. Thepositioning of the injection points of the sun vectors is completed bytrilateral-incenter localization algorithm based on the simulation the current.Three-dimensional vector calculation can be simplified into two-dimensionalcalculation, which effectively reduced the complexity of the determination of sunvector.The change of sunlight intensity, the deteriorated performance of solar paneland earth-albedo-light will produce inaccurate measurement of sun vector thatdependent on cosine mathematical model. Taking the above factors intoconsideration, the current on solar panels are converted into0-1format. A sunvector determination method that based on stereographic projection and Monte Carlo Localization（MCL）is employed. MCL takes all the possible positions of thesun vector projective points at the moment as posterior probability distribution toestimate the position of the sun vector projective points on a plane through motionprediction, position selection, filter calculation. Thus through inversetransformation, sun vector determination can be finished without given model.Mathematical simulation has proved the feasibility of this algorithm.The influenceof geometry configuration of solar panels and the selection of current threshold onthe accuracy of measurement of sun vector has been confirmed.