PRECISION CONTROL SYSTEM FOR INNER-FORMATION GRAVITY FIELD MEASUREMENT SATELLITE SYSTEM

The inner-formation gravity field measurement satellite system is a novel concept and can finish the high precision gravity field measurement. The inner-formation system is composed of the outer satellite and the inner satellite which shielded in the cavity center of the outer satellite and without connection with the outer satellite. And the control of the inner-formation system can treat as a formation of zero size using the inner satellite as reference. In order to finish the in-orbit, real time control of the inner-formation system and satisfy the performance requirements of gravity field measurement in low orbit, the control system of the inner-formation system need provide precision control. Through compensating most of air drag, the precision control system can reduce the disturbance of the feedback controller. The paper proposed a hybrid control scheme includes feed forward and feedback control, then the nonlinear model predictive control method with disturbance compensation is also proposed which the disturbance estimation method is unscented Kalman filter. The precision control system can finish the integrate control of attitude and orbit for the inner-formation gravity field measurement satellite system with limited inputs, and the maintenance accuracy of the relative position is not surpass 0.05cm, the attitude stabilization control accuracy is better than 0.03 degrees, which meet the strong constraints of the relatively position and high attitude stabilization required by the gravity field measurement mission. The precision control system designed for inner-formation system can ensure that the influence caused by different disturbances is controlled in 10(-11)g level.