Fixed-time rendezvous control of spacecraft with a tumbling target under loss of actuator effectiveness

This paper investigates the fixed-time fault-tolerant control problem of spacecraft rendezvous and docking with a freely tumbling target in the presence of external disturbance and thruster faults. More specifically, based on the attitude of the target spacecraft, a line-of-sight coordinate frame is defined first, and the dynamical equations relative to the tumbling target are derived to describe the relative position (not six degrees of freedom). Then two fixed-time position controllers are proposed to guarantee that the closed-loop system is stable in finite time in the sense of a fixed-time concept, even in the presence of simultaneous external disturbance and thruster faults. Numerical simulations illustrate that the chaser spacecraft can successfully perform the rendezvous using the proposed controllers

On finite-time anti-saturated proximity control with a tumbling non-cooperative space target

For the challenging problem that a spacecraft approaching a tumbling target with non-cooperative maneuver, an anti-saturated proximity control method is proposed in this paper. First, a brand-new appointed-time convergent performance function is developed via exploring Bezier curve to quantitatively characterize the transient and steady-state behaviors of the pose tracking error system. The major advantage of the proposed function is that the actuator saturation phenomenon at the beginning can be effectively reduced. Then, an anti-saturated pose tracking controller is devised along with an adaptive saturation compensator. Wherein, the finite-time stability of both the pose and its velocity error signals are guaranteed simultaneously in the presence of actuator saturation. Finally, two groups of illustrative examples are organized and verify that the close-range proximity is effectively realized even with unknown target maneuver

Integrated Optimal and Robust Control of Spacecraft in Proximity Operations

With the rapid growth of space activities and advancement of aerospace science and technology, many autonomous space missions have been proliferating in recent decades. Control of spacecraft in proximity operations is of great importance to accomplish these missions. The research in this dissertation aims to provide a precise, efficient, optimal, and robust controller to ensure successful spacecraft proximity operations. This is a challenging control task since the problem involves highly nonlinear dynamics including translational motion, rotational motion, and flexible structure deformation and vibration. In addition, uncertainties in the system modeling parameters and disturbances make the precise control more difficult. Four control design approaches are integrated to solve this challenging problem. The first approach is to consider the spacecraft rigid body translational and rotational dynamics together with the flexible motion in one unified optimal control framework so that the overall system performance and constraints can be addressed in one optimization process. The second approach is to formulate the robust control objectives into the optimal control cost function and prove the equivalency between the robust stabilization problem and the transformed optimal control problem. The third approach is to employ the è-D technique, a novel optimal control method that is based on a perturbation solution to the Hamilton-Jacobi-Bellman equation, to solve the nonlinear optimal control problem obtained from the indirect robust control formulation. The resultant optimal control law can be obtained in closedorm, and thus facilitates the onboard implementation. The integration of these three approaches is called the integrated indirect robust control scheme. The fourth approach is to use the inverse optimal adaptive control method combined with the indirect robust control scheme to alleviate the conservativeness of the indirect robust control scheme by using online parameter estimation such that adaptive, robust, and optimal properties can all be achieved. To show the effectiveness of the proposed control approaches, six degree-offreedom spacecraft proximity operation simulation is conducted and demonstrates satisfying performance under various uncertainties and disturbances

Space Rescue

Space Rescue has been a topic of speculation for a wide community of people for decades. Astronauts, aerospace engineers, diplomats, medical and rescue professionals, inventors and science fiction writers have all speculated on this problem. Martin Caidin's 1964 novel Marooned dealt with the problems of rescuing a crew stranded in low earth orbit. Legend at the Johnson Space Center says that Caidin's portrayal of a Russian attempt to save the American crew played a pivotal role in convincing the Russians to join the real joint Apollo-Soyuz mission. Space Rescue has been a staple in science fiction television and movies portrayed in programs such as Star Trek, Stargate-SG1 and Space 1999 and movies such as Mission To Mars and Red Planet. As dramatic and as difficult as rescue appears in fictional accounts, in the real world it has even greater drama and greater difficulty. Space rescue is still in its infancy as a discipline and the purpose of this chapter is to describe the issues associated with space rescue and the work done so far in this field. For the purposes of this chapter, the term space rescue will refer to any system which allows for rescue or escape of personnel from situations which endanger human life in a spaceflight operation. This will span the period from crew ingress prior to flight through crew egress postlanding. For the purposes of this chapter, the term primary system will refer to the spacecraft system that a crew is either attempting to escape from or from which an attempt is being made to rescue the crew

Present Challenges, Critical Needs, and Future Technological Directions for NASA's GN and C Engineering Discipline

The National Aeronautics and Space Administration (NASA) is currently undergoing a substantial redirection. Notable among the changes occurring within NASA is the stated emphasis on technology development, integration, and demonstration. These new changes within the Agency should have a positive impact on the GN&C discipline given the potential for sizeable investments for technology development and in-space demonstrations of both Autonomous Rendezvous & Docking (AR&D) systems and Autonomous Precision Landing (APL) systems. In this paper the NASA Technical Fellow for Guidance, Navigation and Control (GN&C) provides a summary of the present technical challenges, critical needs, and future technological directions for NASA s GN&C engineering discipline. A brief overview of the changes occurring within NASA that are driving a renewed emphasis on technology development will be presented as background. The potential benefits of the planned GN&C technology developments will be highlighted. This paper will provide a GN&C State-of-the-Discipline assessment. The discipline s readiness to support the goals & objectives of each of the four NASA Mission Directorates is evaluated and the technical challenges and barriers currently faced by the discipline are summarized. This paper will also discuss the need for sustained investments to sufficiently mature the several classes of GN&C technologies required to implement NASA crewed exploration and robotic science missions

Robust output-feedback predictive control for proximity eddy current de-tumbling with constraints and uncertainty

Proximity operation can significantly improve the efficiency of eddy current de-tumbling. However, the tumbling motion and non-cooperation of space debris make the chaser execute collision avoidance maneuvers and be influenced by model uncertainty. In this paper, an inertial-oriented safety corridor is proposed by taking the debris' angular momentum as the central axis, which can avoid the frequent collision maneuvers of the chaser. Meanwhile, a desired de-tumbling trajectory under this safety corridor is designed to de-tumble the angular velocity of space debris. Then, a robust output-feedback controller considering safety corridor and model uncertainty is proposed by combining moving horizon estimation and model predictive control. The moving horizon estimation is employed to estimate the system state and model uncertainty which is compensated by a feedforward control law. Furthermore, the model predictive control without terminal ingredients is designed to realize the optimal performance of fuel consumption and the robust tracking stability of the system. Finally, taking the Chinese Sinosat-2 satellite as the simulation case, the effectiveness of the proposed scheme is verified

Development and characterization of a standardized docking system for small spacecraft

Since the first mating manoeuvre in space, performed in 1966, many different docking mechanisms were developed, mainly for large manned spacecraft. The few systems recently conceived for small satellites have never been verified in space nor scaled to CubeSat size. In the near future, small spacecraft docking procedures could acquire great importance due to the need to share resources between clusters of low-weight and low-cost vehicles: in fact, small spacecraft market is rapidly growing, focusing on commercial low risk application, low budget scientific and educational missions. In this context, this document presents a novel docking mechanism to provide small spacecraft with the ability to join and separate in space, to realize multi-body platforms able to rearrange, be repaired or updated, thus overcoming the actual on board limitations of single small-scale satellites. As for now, the few proposed docking ports present (1) simple probe-drogue interfaces, unable to dock with same-gender ports, or (2) androgynous geometries, that can overcome that problem, but usually employing complex and non-axis-symmetric latches to perform the docking manoeuvre, that would demand robust and stringent navigation and control systems. The proposed solution overcomes the aforementioned drawbacks, using a semi-androgynous shape-shifting mechanism that actuating one interface changes the port into a “drogue" configuration, letting the other port penetrate it and closing around to create a solid joint. The mechanism design through the requirement definition and a trade-off between different concepts is presented, followed by the analysis of the dynamic behaviour of the selected solution, with particular attention to two aspects, i.e. the loads transmitted between the mating ports and the alignment tolerances requested to perform successful docking manoeuvres. Such analysis led to the definition of an instrumented prototype to verify the solution through simple validation tests, which demonstrated the mechanism operations and defined the alignment ranges, that lie in the range of +- 15 mm and up to 6 degrees. Last, a comparison with SPHERES UDP is presented, as part of the activities performed during a visit period at MIT Space Systems Laboratory

Project Gemini - A technical summary

Spacecraft system design, mission planning, and qualification testing for Gemini projec

Application of advanced technology to space automation

Automated operations in space provide the key to optimized mission design and data acquisition at minimum cost for the future. The results of this study strongly accentuate this statement and should provide further incentive for immediate development of specific automtion technology as defined herein. Essential automation technology requirements were identified for future programs. The study was undertaken to address the future role of automation in the space program, the potential benefits to be derived, and the technology efforts that should be directed toward obtaining these benefits

NASA Automated Rendezvous and Capture Review. A compilation of the abstracts

This document presents a compilation of abstracts of papers solicited for presentation at the NASA Automated Rendezvous and Capture Review held in Williamsburg, VA on November 19-21, 1991. Due to limitations on time and other considerations, not all abstracts could be presented during the review. The organizing committee determined however, that all abstracts merited availability to all participants and represented data and information reflecting state-of-the-art of this technology which should be captured in one document for future use and reference. The organizing committee appreciates the interest shown in the review and the response by the authors in submitting these abstracts