Motion Primitives on a Spherical Surface with Application to Tethered Aircraft Guidance

This paper proposes and studies motion primitives and its application to control vehicles operating on a spherical surface. Motion primitives are fundamental motion patterns that enable structured control in robotics and motion planning. Here, they are adapted to movement on a spherical surface and utilized in the context of tethered aircraft guidance. The research defines circular motion on the sphere simply by selecting the center of rotation of a circular path. This work also explores the combination of motion primitives with two path-following guidance methods: we develop an adaptation of the L1 and L0 guidance logics to spherical motion using the proposed primitives. Smooth trajectories, preserving curvature continuity, can be guaranteed by imposing an orthogonality condition at the primitive switching points. Simulation results demonstrate the efficacy of the proposed approach, showcasing successful path adherence manoeuvres that can be applied in the take-off of tethered fixed-wing aircraft.