Attitude control of a modular NPU-phonesat based on shape actuation

This paper investigates the attitude control of a modular NPU-PhoneSat based on shape actuation. The PhoneSat is composed of multiple blocks connected by active joints. Much like a falling cat can reorient itself in mid-air, this modular PhoneSat could reorient itself without changes in net angular momentum by altering the shape and instantaneous mass distribution during attitude maneuvers. Given size and cost constraints, the number of actuators should be limited. Thus, this paper focuses on the under-actuated case. Optimal attitude control method to steer the PhoneSat to the desired posture is proposed, with the objective to minimize the input energy. The inequality constraints are established based on the capacity of the actuator. Particle Swarm Optimization algorithm is employed to search the optimal control input to achieve the reorientation while satisfying the imposed constraints. The input torques is parametrized by the spline to guarantee that initial and final values of control input are zero. Simulation results of zero-angular-momentum reorientations of the PhoneSat are presented and confirm the effectiveness of the proposed method.