Spacecraft Dynamics Research Articles

The Radiative Gas Dynamics of Spacecraft in the Martian Atmosphere

The Radiative Gas Dynamics of Spacecraft in the Martian Atmosphere

Composite adaptive attitude control for combined spacecraft with inertia uncertainties

This paper examines the attitude control problem of the combined spacecraft subject to inertia uncertainties. A composite adaptive finite-time control scheme with guaranteed parameter convergence is proposed to address this challenging problem, in the absence of persistent excitation. As a stepping stone, the attitude dynamics of the combined spacecraft is first established with explicit consideration of the center-of-mass variation and thruster reconfiguration. Then, a composite adaptive finite-time controller is developed based on a constructive time-varying sliding manifold, and in particular, the concurrent learning technique is used in conjunction with the dynamic regressor extension and mixing procedure to achieve parameter convergence under finite excitation that is strictly weaker than the persistent excitation. Lyapunov stability analysis shows that the derived adaptive controller can simultaneously guarantee finite-time convergence of the attitude tracking and parameter estimation errors; moreover, its robustness against inertia variations and external disturbances is also analyzed. Finally, a set of numerical simulations under ideal and practical scenarios are performed to validate the effectiveness and outperformance of the proposed method.

Prescribed Performance Rotating Formation Control of Multi-Spacecraft Systems with Uncertainties

This paper investigates the problem of rotating formation control for multi-spacecraft systems with prescribed performance in the presence of model uncertainties. Firstly, The spacecraft dynamics containing unmodelled parts is described in a polar coordinate system, which is to solve the problem of the controllable angular velocity of rotating formation. Then, the prescribed performance control method is improved by developing new prescribed performance functions. Based on the improved prescribed performance control method, the distributed controller is designed for multi-spacecraft systems to achieve rotating formations with prescribed performance, i.e., the formations error converges to a predefined arbitrarily small residual set, with convergence time no less than a prespecified value. And an RBF neural network is used to fit the unmodelled components of the spacecraft dynamics. Compared with the existing works of literature, this paper not only solves the robust prescribed performance rotating formation control of multi-spacecraft system, but also acheives rotating formation with adjustable angular velocity. Finally, the Lyapunov approach is employed for convergence analysis, and simulation results are provided to illustrate the effectiveness of the theoretical results.

Rapid capture trajectories from parabolic orbit with modulated radial thrust

The aim of this paper is to analyze the performance of a radially-accelerated spacecraft in a capture mission scenario, in which a space vehicle transfers from a parabolic approaching trajectory of assigned semilatus rectum to a target circular orbit around a generic celestial body. The radial propulsive acceleration provided by the spacecraft propulsion system can be modulated within a suitable given range, and the radial thrust can be either inward- or outward-directed. The transfer mission performance is analyzed in an optimal framework, by minimizing the total flight time with an indirect approach. In this context, the paper proposes a semi-analytical method to reduce the computation time required to solve the optimal control problem. Using a proper description of the spacecraft dynamics in a dimensionless form, the paper reports a set of graphs and tables that allow the designer to obtain a rapid approximation of the optimal mission performance with an accuracy consistent with that of a preliminary trajectory design. Finally, the proposed approach is used to describe the minimum time capture trajectories in a mission scenario towards Ceres.

The generalized method of phase trajectory curvature synthesis in spacecraft attitude dynamics tasks

The attitude dynamics of a variable mass spacecraft is considered. The variability of mass-inertia parameters in time is associated with operation of a jet-engine, which forms an interorbital impulse. The thrust of the jet-engine is directed along the longitudinal spacecraft axis, which fulfills the nutational-precessional motion relative to a planned direction in the inertial space. Therefore, to increase an accuracy of the thrust impulse formation during the jet-rocket engine work, and to reduce dispersion of the thrust due to the precessional rotation, it is needed to synthesize the motion regime with monotonously decreasing nutation angle. Such regimes allow to obtain a spiral twisting of the longitudinal axis to the predefined target direction, when the thrust will be focusing to target direction. To analyze and to synthesize this nutational-precessional motion properties, the curvature of the corresponded phase trajectories is evaluated in an angular phase space. The phase trajectory curvature evaluation gives an opportunity to synthesize the appropriate time-dependencies of inertia-mass parameters of spacecraft, which allows to increase the accuracy of the thrust impulse formation during operation of the jet-rocket engine. The proposed appropriate technique for positive phase trajectory synthesis is based on the previously developed method of curvature evaluation.

Deep Learning and Artificial Neural Networks for Spacecraft Dynamics, Navigation and Control

The growing interest in Artificial Intelligence is pervading several domains of technology and robotics research. Only recently has the space community started to investigate deep learning methods and artificial neural networks for space systems. This paper aims at introducing the most relevant characteristics of these topics for spacecraft dynamics control, guidance and navigation. The most common artificial neural network architectures and the associated training methods are examined, trying to highlight the advantages and disadvantages of their employment for specific problems. In particular, the applications of artificial neural networks to system identification, control synthesis and optical navigation are reviewed and compared using quantitative and qualitative metrics. This overview presents the end-to-end deep learning frameworks for spacecraft guidance, navigation and control together with the hybrid methods in which the neural techniques are coupled with traditional algorithms to enhance their performance levels.

A 6-DOF extended state observer–based adaptive generalized super twisting algorithm of fault-tolerant control for coupled spacecraft with actuator saturation

This paper aims to address an integrated relative attitude and position fault-tolerant control strategy between a follower spacecraft and a leader spacecraft for coupled spacecraft tracking maneuver in the case of inertia parametric uncertainties, external disturbances, actuator failures, and saturation. The coupled rotational and translational kinematics and dynamics of the rigid spacecraft are derived on the Lie group SE(3), where the actuator failures and saturation are taken into account. Then, a 6-DOF extended state observer is proposed by using terminal sliding mode technique to estimate the lumped disturbance in finite time. An adaptive generalized super twisting algorithm of fault-tolerant controller is developed to guarantee the finite-time stability based on the estimated lumped disturbance information. The stability of the closed-loop system is proved in spite of the aforementioned disturbances via the Lyapunov analysis. Finally, the numerical simulation illustrates the effectiveness of the proposed control strategy.

A direct analysis and control of nonlinear time-variant spacecraft dynamics in the vicinity of small irregularly shaped bodies

A direct analysis and control of nonlinear time-variant spacecraft dynamics in the vicinity of small irregularly shaped bodies

Image-Based Meta-Reinforcement Learning for Autonomous Guidance of an Asteroid Impactor

This paper focuses on the use of meta-reinforcement learning for the autonomous guidance of a spacecraft during the terminal phase of an impact mission toward a binary asteroid system. The control policy is replaced by a convolutional-recurrent neural network, which is used to map optical observations collected by the onboard camera to the control thrust and thrusting times. The network is trained by a proximal policy optimization algorithm, a family of reinforcement learning methods. The final phase of NASA’s Double Asteroid Redirection Test (DART) mission is used as a test case. The objective is to maneuver the spacecraft to impact the smaller object, Dimorphos, in the Didymos binary system. The spacecraft dynamics are described using the bi-elliptic restricted four-body problem with solar radiation pressure. The initial conditions are randomly scattered according to the actual specifications of the DART mission. A random error on the orbital position of Dimorphos is also considered to reflect uncertainty on the binary system’s characteristics and dynamics. The control system aims at minimizing the error on the final spacecraft position. Numerical results show that the guidance system can correctly drive the spacecraft toward the final impact point in more than 98% of the 500 test scenarios.

A model predictive control for attitude stabilization and spin control of a spacecraft with a flexible rotating payload

Many Earth Observation missions, implementing space-based microwave sensing techniques for collecting surface information, employ spinning sensors to cover large swaths of terrestrial areas, thus improving the rate at which global maps of those measured data are generated. These spacecraft (as Soil Moisture Active Passive (SMAP) developed by NASA or Copernicus Imaging Microwave Radiometer (CIMR) currently under development by Thales Alenia Space) consist of a main non-spun platform and a rotating part composed of an antenna boom, a deployable reflector and a rotation mechanism. As the reflector is designated to rotate about the nadir axis producing conically scanned antenna beams with precise surface incidence angle, the payload pointing accuracy needs to be addressed at both spin subsystem and platform level. In this work, a representative model of the dynamic behaviour of SMAP satellite is developed as a study case to design the proposed control strategies; in particular, a SMAP-like payload structural model is built using FEM commercial codes. The spacecraft is equipped with a Reaction Wheels Assembly (RWA) to accomplish both momentum compensation for the spun element and three-axis attitude control and a motor for the spin mechanism. The objective of the study is to develop the spacecraft control architecture in the frame of Model Predictive Control (MPC) theory. MPC refers to a class of algorithms in which the control action is obtained by computing an open-loop optimal sequence of control moves over a predefined time horizon; moreover, the ability to set constraints on process inputs and outputs directly in the problem formulation allows to account for actuators’ limits. In the study two operative phases of the satellite are addressed: the Spin-up, in which the 6-meter diameter antenna is spun-up to the operative condition of 14.6 RPM, and the Science Phase, in which precise nadir pointing and stability of the flexible system must be kept for acquiring high-resolution measurements. To this purpose, control–structure interaction between attitude/spin control system and flexible dynamics, as well as system’s imbalances, are carefully addressed by the proposed control architecture. The nonlinear in-orbit dynamics of the flexible spacecraft is then used to evaluate the performance of the MPC controller in terms of pointing accuracy and robustness to uncertainties.

Analysis of the Impact of Orbit-Attitude Coupling at Higher-Degree Potential Models on Spacecraft Dynamics

Analysis of the Impact of Orbit-Attitude Coupling at Higher-Degree Potential Models on Spacecraft Dynamics

Сучасні низькоорбітальні угруповання космічних апаратів дистанційного зондування землі з використанням радарів із синтезованою апертурою

The purpose of this work is to determine the current trends in the development of low-orbit constellations of spacecraft with synthetic aperture radar (SAR), which have a number of significant advantages in Earth remote sensing. It is shown that the demand for Earth remote sensing data and products and services based thereon continues to grow worldwide. The applicability of SAR to Earth remote sensing is considered. The main differences and advantages of image acquisition using SAR spacecraft in comparison with optical spacecraft are shown. The main directions of using low-orbit SAR spacecraft in Earth remote sensing are identified. Land and water surface observation using SAR spacecraft is shown to be one of the most effective remote sensing methods. In particular, it is shown that low-orbit spacecraft constellations can be used to advantage in solving many tasks in the socio-economic sector and tasks aimed at continuous real-time monitoring of various objects. The characteristics of the various Earth remote sensing spacecraft constellations, in particular low-orbit commercial ones, launched into orbit during the past decade are considered. Problems in and prospects for the development of low-orbit SAR spacecraft constellations are elucidated. Existing and planned SAR spacecraft constellations with traditional and mini-satellite platform technologies are overviewed. It is shown that the performance characteristics continue to improve, thus allowing one to get data from any area of the Earth at any time. It is shown that small spacecraft in low and ultralow orbits have significant benefits over traditional spacecraft in power characteristics, but are outperformed by them in the duration of communication sessions and active life. The results obtained make it possible to work out recommendations on the designing of low-orbit constellations of domestic Earth remote sensing spacecraft, in particular on the development of orbit determination models and algorithms and spacecraft dynamics models.

Orbital dynamics of gravity tractor spacecraft employing artificial halo orbit

In this paper, the equations of motion for modeling a spacecraft near an earth-threatening asteroid are proposed and studied for deflecting the asteroid using a gravity tractor that effectively tows the asteroid with mutual gravity attraction. The motion of the spacecraft is expressed by separation distance between the two objects, two Eulerian angles expressing the attitude of the spacecraft–asteroid system, and their derivatives; it is assumed that the spacecraft and asteroid are connected with a variable-length gravity tether. The motion of the spacecraft in an artificial halo orbit (AHO) is investigated using the proposed equations. These equations are suitable for the investigation because the spacecraft in the AHO moves in a circular orbit at a constant angular velocity and distance from the asteroid. The results indicate that the AHO is unstable, and a linear quadratic regulator will be required to control the spacecraft. Numerical simulation results suggest that the AHO–AHO transfer can be realized by employing a control law that linearizes the proposed equations. The achievable deflection distance yielded by 1000 days of a towing mission is calculated for fictional Earth impactors; the results indicate that the proposed system is feasible for conducting long-term simulations.

Shape-based approach to attitude motion planning of reconfigurable spacecraft

Internal torques generated from shape reconfiguration can be helpful in Micro-Satellite attitude control. The configuration-attitude-coupled non-holonomic dynamics of a multi-body spacecraft is investigated. A shape-based motion trajectory in the form of water drop curve is proposed to synchronously reach target attitude and target shape configuration. With the shape-based approach, the motion planning problem is converted into a system of non-linear equations in three unknowns. The advantages of this approach is demonstrated from the views of simplicity, reachability, and efficiency. Simulations are conducted to test the planning function, and the results are compared with those obtained from the optimal control method.

Mathematical Modeling of the Dynamics of a Low-Flying Spacecraft with a Ramjet Electric Propulsion Engine

Mathematical Modeling of the Dynamics of a Low-Flying Spacecraft with a Ramjet Electric Propulsion Engine

Information-Based Guidance and Control Architecture for Multi-Spacecraft On-Orbit Inspection

Inspection or mapping of a target spacecraft in a low Earth orbit using multiple observer spacecraft in stable passive relative orbits (PROs) is a key enabling technology for future space missions. Our guidance and control architecture uses an information gain approach to directly consider the tradeoff between gathered data and fuel/energy cost. The architecture has four components: information estimation, spacecraft’s absolute and relative state estimation, motion planning for relative orbit initialization and reconfiguration, and relative orbit control. The information estimation quantifies the information gain during inspection of a spacecraft, given past and potential future poses of all spacecraft. The estimated information gain is a crucial input to the motion planner, which computes PROs and reconfiguration strategies for each observer to maximize the information gain from distributed observations of the target spacecraft. The resulting motion trajectories jointly consider observational coverage of the target spacecraft and fuel/energy cost. For the PRO trajectories, a fuel-optimal attitude trajectory that minimizes rest-to-rest energy for each observer to inspect the target spacecraft is designed. The validation on a mission simulation to visually inspect the target spacecraft and on a three-degree-of-freedom robotic spacecraft dynamics simulator testbed demonstrates the effectiveness and versatility of our approach.

Characterizing an Air-Bearing Testbed for Simulating Spacecraft Dynamics and Control

Ground-based testbeds play a critical role in developing and testing different methods of spacecraft dynamics and control. To find the dynamic behavior in such an air-bearing testbed, a detailed characterization of the testbed must be provided via systematic testing approaches. This paper describes a planar air-bearing testbed to develop control methods in spacecraft on-orbit operations. This testbed has an almost frictionless surface and can be used to simulate two-dimensional motions in the microgravity environment, with one rotational and two translational degrees of freedom (DOF). The hardware and software architectures of the testbed are presented in detail and key parameters are characterized by a series of systematic test approaches. In addition, a new visual navigation method was designed as an alternative to the external visual system. Finally, two typical case studies are presented to demonstrate the performance of the developed testbed.

Reliable event detection for Taylor methods in astrodynamics

ABSTRACT We present a novel approach for the detection of events in systems of ordinary differential equations. The new method combines the unique features of Taylor integrators with state-of-the-art polynomial root finding techniques to yield a novel algorithm, ensuring strong event detection guarantees at a modest computational overhead. Detailed tests and benchmarks focused on problems in astrodynamics and celestial mechanics (such as collisional N-body systems, spacecraft dynamics around irregular bodies accounting for eclipses, computation of Poincaré sections, etc.) show how our approach is superior in both performance and detection accuracy to strategies commonly employed in modern numerical integration works. The new algorithm is available in our open source Taylor integration package heyoka.

Finite-time active fault-tolerant attitude control for flexible spacecraft with vibration suppression and anti-unwinding

In this paper, a finite-time active fault-tolerant control scheme is designed for a flexible spacecraft’s attitude control experiencing inertial parametric variations, external disturbances, multiple actuator faults, and estimation errors while suppressing the flexible appendages’ vibrations without using smart vibration suppression actuators. First, relative attitude dynamics of a flexible spacecraft with multiple actuator faults are outlined, and a sliding mode observer is designed to estimate flexible appendages-related vibrations. The proposed fault detection and identification (FDI) strategy can efficiently detect actuator faults, avoiding the false alarms caused by uncertainties and disturbances, and accurately estimate the cumulative fault effects on the spacecraft via Chebyshev neural network (CNN) based estimator. Based on a novel fast nonsingular terminal sliding mode surface, a finite-time, unwinding-free, and adaptive fault-tolerant attitude controller is designed to acclimatize the detected faults and uncertainties effectively, also heeding the errors in the estimation of flexible modes and faults. The spacecraft can carry out the coveted control objective in a definable time, and the stability of the proposed controller is corroborated via Lyapunov techniques. Finally, a comparative simulation analysis with the existing results elucidated the proposed scheme’s efficacy.

A new angular velocity observer for attitude tracking of spacecraft

This paper proposes a new angular velocity observer for attitude tracking of spacecraft based on contraction analysis. The observer is designed in the inertial reference frame via estimating the inertial angular momentum to avoid the square term of the angular velocity when the spacecraft dynamics is expressed in the body frame. It employs a continuous angular-velocity dependent innovation term generated by means of a simple first-order linear filter, instead of a discontinuous attitude-dependent innovation term commonly used in angular velocity observer designs, resulting in a smooth behavior. The global exponential convergence is achieved. Moreover, when combined with the exponentially convergent tracking controller devised in this paper, it gives an overall system with exponential stability relying on a separation property. Finally, a switching function with hysteresis is introduced to stabilize the closest equilibrium in the configuration space, achieving the global exponential stability. Numerical simulations are included to illustrate the performance of the proposed observer in the closed loop, comparison with similar results, and robustness verification under inertia parameter uncertainties and noisy measurements.