Nonlinear Sampled-data Attitude Stabilization of Underactuated Spacecraft

2026-07-22

Space stakeholders manifest an increasing interest in small satellites dictated by reduced, global costs and “time to market”. Since redundancy is kept to a minimum, achieving attitude stabilization in actuator failure mode with the remaining control torques can offer a fail-safe operation mode, improving the reliability of the attitude control system. The, still open, underlying control problem is challenging, since the nonlinear underactuated system is nonholonomic, admitting only non-smooth stabilizing feedback. Depending on actuator type and additional restrictions on the symmetricity of the spacecraft or its angular momenta, non standard, discontinuous or time-varying solutions have been proposed. Though any continuous-time controller is inevitably implemented digitally on the on-board computer, leading to loss of performance or even destabilization, the effect of sampling is never considered in the state-of-the-art. The aim of the present proposal is to develop novel control algorithms for three-axis attitude stabilization of an underactuated spacecraft in actuator failure mode without significant performance degradation with the remaining control torques. To this purpose, we follow a sampled-data methodology that considers the sampling issues from the beginning in the design process. Theoretical investigations will be conducted for ad-hoc digital solutions based on equivalent discrete models, finite computability and multirate control laws, permitting to impose digital performance objectives that cannot be set in continuous-time. The quality of the innovative algorithms developed is assured by extensive software simulations and application on an experimental attitude control platform. In-orbit technology demonstration and testing, and exploitation of the research outcomes are the focus of the industrial secondment foreseen. The applicability of the results to general classes of underactuated mechanical systems and other related control problems is expected.

Italy

2026-01-01