SAT STABILIS · Nonlinear Sampled-data Attitude Stabilization of Underactuated Spacecraft
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2015-10-01 → 2017-09-30
- EU contribution
- €180,277
- Participants
- 1
- Scheme
- MSCA-IF-EF-CAR
Lines connect the coordinator with its partners.
Results in brief
Nonlinear Sampled-data Attitude Stabilization of Underactuated Spacecraft
The Attitude Determination and Control System (ADCS) has a major impact on the efficiency of space missions. Its task is to control the orientation (attitude) of a satellite in space to a high pointing accuracy and maintain stability, in order to meet key mission requirements imposed by the payload and the electrical power and communication subsystems. However, several space missions suffered disastrous consequences due to failures in ADCS actuators that remained uncooperative. In actuator failure mode, the number of controlled inputs is reduced, from three necessary independent actuators, to two, converting a fully-actuated system to an underactuated one, leading to destabilization. The impact of underactuation on performance degradation is more catalytic in small satellites, since here reaction wheel redundancy is not a feasible option, due to mass, power and financial resources. A viable alternative, to ensure high mission reliability, is to stabilize the spacecraft with the remaining actuators. The underlying underactuated control problem to be addressed is challenging, since the underactuated system is non-holonomic, admitting only non-standard, non-smooth stabilizing feedback. State-of-the-art controllers, though continuous in nature, are inevitably implemented digitally on the on-board computer, leading to loss of performance and instabilities. Under this framework, the overall objectives set for the SAT STABILIS project were to: • Conduct theoretical investigations in order to derive ad-hoc digital control solutions based on nonlinear sampled-data control methodologies for active, high precision, three-Axis Attitude Stabilization (3-AAS) of underactuated satellites subject to reaction wheel failures. • Verify and validate the robustness and applicability of the innovative attitude control algorithms developed, by performing extensive software simulations and implementing them on the embedded processor of an attitude control experimentation platform. • Deploy a plan for in-orbit technology demonstration and testing of the project outcomes on a CubeSat like nano-satellite. The control algorithms conceived offer a fail-safe operation mode without significant performance degradation, improving the reliability of the attitude control system, a catalytic factor for the nowadays emerging small satellite technology. The project stays in line with the EU’s space policy, which considers the small satellite market crucial for human activities and the Space Horizon 2020 objectives to enable advances in space technologies.
Data: CORDIS, © European Union
Project objective
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.
Original text from CORDIS.
Participants
- UNIVERSITA DEGLI STUDI DI ROMA LA SAPIENZA · RomaCoordinatorItaly
Links
Data: CORDIS, © European Union