Optimal attitude motion planner for large slew manoeuvers using a shape-based method

Small satellites, in particular Cubesats, have limited torque and power available, thus optimization of slew maneuvers may be required. However, their on-board computational resources are usually low. In this paper a computationally light optimal path planning algorithm is presented, based on a shape-based method. This technique will enable 3-axis stabilized satellites to perform torque-optimal slew maneuvers with low computational overhead, thus especially suited to small satellites. The shape-based method presented relies on a quaternion representation of the trajectory, whose components are assumed to be polynomial functions. A rationale to select the degree of the polynomials is presented. The function’s coefficients are then adjusted according to the maneuver boundary conditions, and by parametric optimization of the free coefficients, the torque is minimized. Once the trajectory is planned, a simple PD controller can track it. The results are validated using a pseudo-spectral optimal control solver, and a two-stage approach is discussed. This work also demonstrates the capacity of the shape-based method to deal with pointing constraints and multi-objective torque-time optimization.