Time-Periodic Spacecraft Attitude Control with the Use of Slewing Permanent Magnets

Introduction. Electromagnetic actuators are widely used in spacecraft (SC) attitude control systems. These actuators can be modified by using slewing permanent magnets (ASPM) as sources of torque instead of electromagnets. These modified devices consume less onboard electricity for SC attitude control than the conventional ones.Problem Statement. An algorithm for attitude stabilization of a SC using ASPM was proposed in previous studies, where the pole placement technique and pulse-width modulation (PWM) were used to design the controller. However, this approach does not allow the designers to find optimal values of the required magnetic torques, which may result in frequent engagement of the stepper motors of the ASPMs and their significant energy consumption. This controller has such a drawback because its gains are selected without taking into account time-periodic properties of the Earth magnetic field.Purpose. The purpose of the study is to design the algorithm for the SC angular stabilization by the ASPMs taking into account time-periodic properties of the Earth magnetic field.Materials and Methods. The solution of the time-periodic Riccati equation was used for the controller design. Mathematical modeling and computer simulation of SC motion was applied to build the model of the plan and validate the results.Results. A time-periodic based SC attitude control algorithm has been designed. Taking into consideration the time-periodic properties of the magnetic field of Earth allow us to optimize the required magnetic control torques. This algorithm minimizes the frequency of the actuation of the ASPM sashes, and thus reduces onboard energy consumption.Conclusions. The designed algorithm increases the control efficiency of SC attitude control by using jointly the ASPMs, time-periodic linear-quadratic regulator and pulse-width modulator.