A new energy management strategy for IPACS of spacecrafts

This paper investigates the design problem of an integrated power and attitude control system (IPACS) for spacecrafts. A Lyapunov-typed IPACS controller is designed firstly for a spacecraft equipped with 4 flywheels (3 orthogonal +1 skew). This controller keeps in the nonlinear properties of original systems, so the control result can be more precise. A control law of the flywheels is also proposed to accomplish the attitude control and energy storage simultaneously. Aiming at the limitations existed in the power conversion characteristic and the wheel's motor, a new strategy of energy management is proposed at the last part of this work. If the power provided by the solar arrays is assumed as a constant, as doing in general research, it may lose the energy more than 5%. In the practice, since the plane of the array is cold when the spacecraft just enters into the sunlight period, the efficiency of power conversion is rising. Then the power conversion effect is decreasing along with the rising of array's temperature. To make use of this part of energy, a new strategy of energy management has been proposed. The strategy can not only make the charged/ discharged energy reaching balance in each orbital period, but also sufficiently utilize the power provided by the solar arrays. Therefore, it can make the size and mass of solar arrays decreased and the cost of spacecraft economized. A simulation example illustrates the validity of the designed IPACS.