Coupled position and attitude control of a servicer spacecraft in rendezvous with an orbiting target

Abstract

Rendezvous is one of the fundamental phases of on-orbit servicing (OOS) missions. Since it requires high accuracy and safety, modeling is an indispensable part. Therefore, this article puts forward an approach for boosting the exactitude of the final proximity phase of a servicer spacecraft using precise modeling. Unlike other similar works that solely use linear models to design controllers, this paper employs a fully nonlinear model and considers most possible uncertainties and disturbances. In this regard, first a complete nonlinear relative pose (i.e., concurrent position attitude) motion dynamic is developed, which includes (1) the role of the reaction wheels and (2) the major environmental force and torque model. Second, taking the thruster's adverse torque into account, two sliding mode-based control techniques with different nonlinear sliding surfaces are designed. Moreover, the Lyapunov stability criterion is used to handle high nonlinearity effects, control input saturation, actuator misalignment, external disturbance torque/force, measurement error, uncertainties of both inertia parameters, and control inputs. Even the PWPF modulator of the thrusters has been considered to make the outcomes more realistic. Finally, three different scenarios are comprehensively simulated to illustrate the feasibility and efficiency of the designed scheme. The results prove that the proposed closed-form controller is more executable to implement than other existing approaches.

Model prediction of spatial non-cooperative target measurement information based on the Koopman operator

“…Non-cooperative space targets typically refer to a category of targets without artificial identification, which cannot actively or cooperatively provide relative information to servicing spacecraft 1 . Their on-orbit maintenance, space debris removal, and other on-orbit services are crucial for ensuring the safe operation of spacecraft [2][3][4] . Relative navigation is a prerequisite for the on-orbit operation of non-cooperative space targets.…”

Modeling, Simulation and Control of a Spacecraft: Automated Rendezvous under Positional Constraints

“…We shall present a multi-objective control strategy to make a spacecraft safely approach an orbital station while avoiding still as well as moving obstacles, until the final guidance phase which guarantees collision-free docking with the correct attitude. In fact, even automated orientation control plays a crucial role during the docking phase, since safe docking may take place only if the docking axis of the spacecraft is precisely oriented parallel to the axis of a station's docking port [20,21]. In this phase, orientation is supposed to happen with extreme precision, facilitated by the alleged absence of directional obstructions.…”

Nonlinear adaptive pose motion control of a servicer spacecraft in approximation with an accelerated tumbling target

“…1 ). It is quite understandable that the risk of collision increases as the distance between vehicles decreases, and for this reason, accuracy and robustness are especially important in close-range rendezvous 6 . Accordingly, unlike the long-range approach, in which only the translational distance reduction is a matter of concern, attitude synchronization is also necessary in addition to reducing the relative distance in the close-range approach 7 .…”