Opportunities and potential of model predictive control for low-thrust spacecraft station-keeping and momentum-management

Abstract

While electric propulsion generates fuel-efficient thrust for spacecraft control, it can only produce low levels of thrust, necessitating continuous actuation to impart an equivalent impulse to that of chemical thrusters. Thus, many of the standard open-loop propulsion scheduling techniques, developed for impulsive thrust, do not transfer to low-thrust architectures. Continuous actuation, together with tighter anticipated requirements for spacecraft station keeping, e.g., in geostationary Earth orbit (GEO), provides great opportunity for the application of feedback control. We demonstrate that model predictive control (MPC) can provide significant advantages as a control strategy for station keeping of low-thrust spacecraft, provided that its features, such as the capability to enforce output constraints, and the use of a prediction model for the plant and disturbances, are fully exploited. We develop a basic MPC design for station keeping in GEO, and compare its performance with an advanced MPC design that includes output constraints and disturbance prediction. We show that the basic MPC achieves precise regulation, albeit with unsustainable fuel consumption, whereas the advanced MPC satisfies the target mission requirements with fuel consumption in line with that of carefully designed open-loop strategies.

Geostationary Station-Keeping of Electric-Propulsion Satellite Equipped with Robotic Arms

“…Although this result is higher than that in Ref. 28, it is still very competitive because they considered the on-off nature of the thruster. Unlike these three studies, Zou et al considered the geostationary station-keeping problem with the MPC as an optimization problem based on the orbital elements instead of the position and velocity [33].…”

“…Being good at coordinating multiple inputs/outputs and handling constraints [27], the MPC is capable of optimizing the station-keeping performance while considering various constraints in the actual application. Walsh et al studied applying the MPC for station-keeping and momentum management [28][29][30]. In their work, the controller used a prediction model based on the linearization of the orbital and attitude dynamics of GEO satellites to optimize the fuel consumption while enforcing the constraints caused by the thruster configuration.…”

Additive Manufacturing of Large Structures Using Free-Flying Satellites

“…Disturbances to which spacecraft on-orbit are subjected include, aerodynamic forces, solar radiation pressure and dynamic coupling, though these are smaller in magnitude than those experienced on the ELISSA table. For example, a typical 4,000 kg spacecraft in geostationary orbit experiences disturbance forces up to 50 mN along each axis, resulting in an acceleration of approximately 1.25 × 10 −2 mm/s 2 (Weiss and Di Cairano, 2015). Spacecraft therefore also require control systems for station keeping.…”

A three-step decomposition method for solving the minimum-fuel geostationary station keeping of satellites equipped with electric propulsion

“…Conversely, indirect methods rely on the derivation of necessary optimality conditions expressed via the socalled Pontryagin Maximum Principle (PMP) and on the numerical solution of the two-points boundary value problem obtained from these optimality conditions. In order to counteract uncertainties affecting the control law, the use of Model Predictive Control algorithms is proposed in [29,30]. To deal with on-off models of thrusts, the references [31,32] use the Pulse Width Modulation technique to generate rectangular profiles from a continuous one.…”