Attitude Maneuver Research Articles

Advances in Variable Stiffness Vibration Isolator and its Application in Spacecraft

Variable stiffness vibration isolator (VSVI) can be switched between the low stiffness state and high stiffness state, respectively suitable for spacecraft requirement in cutting off the jitter transmitted from the bus to high accuracy payload and for avoiding long term adjustment during the process of attitude maneuver. For the advantage stated, the mechanism of VSVI is investigated for several types, considering the following factors: parallel manipulator with positive and negative stiffness components, structure with nonlinearity stiffness characteristics, smart materials or mechanisms, and maglev configuration. The design objectives of variable mechanisms are summarized into three indexes: adjustment range of stiffness, a lower limit of resonant frequency, and region with quasi-zero stiffness. Experimental studies for related isolators were presented, and the typical configuration or schematic diagram was shown under each index. As for the application of VSVI in spacecraft, research on the two significant problems, i.e. dynamic modeling and non-collocated control problem, is investigated for the design of control law of VSVI’s stiffness. Besides the complete description of spacecraft flexibility, variable stiffness characteristic that leads to a time-varying system and is easily coupled with the maneuvering process is worthy of more attention. Finally, challenges and future research are suggested for improving the performance in spacecraft application.

A Steering Method With Multiobjective Optimizing for Nonredundant Single-Gimbal Control Moment Gyro Systems

The steering problems are investigated for nonredundant three single-gimbal control moment gyros (SGCMGs), in which no null-motion can be utilized to avoid the singular gimbal configurations. A gimbal configuration far away from the singularity is selected as a candidate nominal configuration, and a comprehensive multiobjective optimal cost function is constructed with respect to the actual gimbal angular vector error, the gimbal command variation, and the torque output error. By minimizing the cost function, an optimal gimbal angle command formula is derived consequently, and a corresponding equivalent gimbal angular rate command formula is also presented. Moreover, according to the pattern of the rest-to-rest attitude maneuver, dynamically weight-adjusting strategies for the cost function are designed, and a complete steering scheme for the nonredundant SGCMG system is built up based on the derived algorithms of the gimbal command. The proposed steering method can guarantee successful singularity-avoiding during the attitude maneuver and gimbal-returning back to the vicinity of the nominal angles at the end of the maneuver, and its effectiveness is verified by both numerical simulations and experimental tests.

Deep learning-based nonlinear model predictive control of the attitude manoeuvre of a barbell electric sail through voltage regulation

An electric solar wind sail (electric sail or E-sail) is a new type of propulsion system that does not require propellant. This paper proposes a nonlinear model predictive control law based on deep learning to control the attitude of a barbell electric sail. A barbell E-sail is composed of two tip satellites connected via long conductive tethers to a central insulated confluence point. The two tethers are insulated from each other at the confluence point such that the voltages of the two tethers can be independently controlled. The attitude dynamics of the system is modelled using a nonsingular description of tether orientation. To reduce online computation loads, the proposed control scheme has a two-stage design, namely, an offline stage and an online stage. In the offline stage, a large amount of data is generated using the nonlinear model predictive control law and then taken as a dataset to train a deep neural network. In the online stage, feedback control of the system attitude is achieved with extremely low computational cost by performing real-time mapping from the system state to the control output using the trained deep neural network. Finally, the efficacy and performance of the proposed deep learning-based control law are demonstrated via numerical case studies.

Event-triggered attitude maneuver control of spacecraft under angular velocity constraints

Considering the spacecraft attitude system subject to angular velocity constraints, limited communication resources, the inaccurate moment of inertia, and external interference, a neural network-based adaptive event-triggered attitude maneuver control scheme is proposed. Specifically, the angular velocity constraint is first transformed into the performance boundary constraint based on the prescribed performance method, and then the equivalent error model of the attitude system is established using error transformation, which tactfully transforms the attitude maneuver control problem with angular velocity constraints into the state-bounded stability control problem of the unconstrained error system. Subsequently, by applying the radial basis function neural network, an adaptive online updating law is designed to approximate the uncertainty term caused by the unknown moment of inertia online. Meanwhile, considering the limited communication resources, a unified time-varying event-triggered mechanism is developed by establishing the explicit relationship between the trigger control signal and the real-time control one. The control command and the adaptive law are synchronously updated once the trigger condition is satisfied. By doing so, the frequent network signal transmissions between the controller and the actuator are reduced significantly. In addition, the time-varying term in the event-triggered mechanism strictly guarantees that no Zeno phenomenon occurs. The simulation results show that the proposed attitude control algorithm can achieve the specified attitude maneuver task with higher accuracy, stability, and robustness and reduce frequent control signal updates by about 97.50%, significantly reducing the on-board communication burden.

Attitude control of spin-type space membrane structures using electromagnetic force in earth orbit

This research proposes a novel attitude control method for a membrane structure that uses electromagnetic torque while in Earth orbit. A spin-type membrane structure with a satellite’s body at its center is lightweight and highly compactible, enabling the realization of systems that require a large surface area. The attitude control of such a structure poses an issue because of a relatively large angular momentum of the membrane, requiring a large torque to shorten attitude control duration. Moreover, application of this torque to both the body and membrane is desired to prevent vibration on the membrane. A typical method using reaction wheels and thrusters applies a relatively large torque only to the body, which requires propellant consumption. Another method using solar radiation pressure applies torque only to the membrane, resulting in a weak torque. Thus, conventional methods cannot achieve a sufficiently large torque applied to both the body and membrane without extraneous propellant consumption. In the proposed magnetic attitude control method, the electric current flowing along the edge of the membrane and the magnetic torquers in the body interact with the Earth’s geomagnetic field and generate a large, controllable electromagnetic torque applied to both the body and membrane, which enables a large torque without consuming propellant. This research evaluates the performance of the proposed method in terms of the attitude maneuverability and vibration of the membrane using numerical simulations. Specifically, this research investigates the effects of the electric current, spin rate, and orbit inclination, which are related to the strength and direction of the electromagnetic torque. A dynamics model of the numerical simulations is derived from the multi-particle method. The numerical simulations reveal that the proposed method induces a larger torque compared with that by solar radiation pressure, improving maneuverability. This maneuverability is related to the electric current intensity and the orbit inclination. The vibration caused on the membrane during the attitude control is small; the maximum amplitude is only 3.1% of the membrane size. This amplitude decreases as spin rate increases because of geometric stiffness. Based on the results, this research concludes that the proposed method is technically feasible and contributes to the actualization of a large membrane structure.

Active attitude control for microspacecraft; A survey and new embedded designs

Novel technologies and design techniques of the active attitude control systems (ACS) for microspacecraft are briefly covered in this survey. Electric propulsion (EP) thrusters for satellites orbit correction and interplanetary vehicles acceleration have recently emerged as the focal point and front subject in propulsion fields due to their low mass, low cost and high specific impulse. Therefore, micro propulsion thrusters are explored for small satellites in terms of its performance, lifetime and future prospects. The focus of the review is at the center of research published in the last few years and state-of-the-art design concepts in terms of control, reliability, fault analysis and response to failure has been discussed for reaction wheels and magnetorquers. Finally, novel embedded planar magnetorquers which are integrated inside the internal layers of PCB for providing attitude maneuverability to various small satellites are discussed and simulated for critical tasks such as damping the initial angular velocities after vehicle launch. As the proposed magnetorquers are integrated in the form of copper traces, thermal analyses are done to maintain the temperature gradients.

A versatile method for target area coverage analysis with arbitrary satellite attitude maneuver paths

The agile Earth observation satellite (AEOS) is rapidly becoming the leading platform in Earth observation missions, as it implements attitude maneuvers and remote sensing simultaneously. However, present methods limit not only its remote sensing coverage to a small area during attitude maneuvering but also its operation to only certain orbit shapes. This paper proposes a new method, namely envelope curves hierarchical overlapping (ECHO), for the target area coverage analysis of an AEOS that implements attitude maneuvers during its mission. This method involves two stages. In the preparation stage, the satellite's instantaneous access area (IAA) is defined and analytically determined by solving the spatial equations of an oblate Earth and the sensor's view field. Then, the coverage belt of an AEOS is delineated by the envelope curves of a set of IAAs. In the manipulation stage, the coverage problem of a target area is solved by iteratively using the polygon clipping technique and hierarchically taking the intersection parts between the coverage belt and the target area. Numerical simulations demonstrate the practicability and high accuracy of the proposed method.

Rigid-flexible coupling identification and attitude control based on deep neural networks

Rigid-flexible coupling significantly affects the attitude control accuracy during attitude maneuvering of spacecraft with large flexible appendages. On-orbit identification of flexible parameters such as modal frequency is very important for attitude control. However, large errors could exist in current identification methods, especially for extreme scenarios such as large deformation or configuration transformation of spacecraft. Unlike previous studies that identified natural frequencies or modal shapes, this paper proposes a method of directly estimating the rigid-flexible coupling term based on deep neural networks (DNNs). By using the neural network (NN), the proposed identification method is independent of the specific dynamic model and has better adaptability. We establish a rigid-flexible dynamic model considering uncertainties and analyze the possibility of identifying the rigid-flexible coupling term in the attitude dynamic equation through selected system states. To verify the feasibility of training the neural networks mapping from system states to the coupling term, we design a numerical experiment. Five attitude maneuvers with different target attitude angles are conducted with the data collected for training. The experimental results show that all estimation errors of neural networks are relatively small. Based on this, we further propose an improved PD controller. We assume that the DNNs can be well trained offline, followed by online prediction of the rigid-flexible coupling term to improve attitude control accuracy. Five random attitude maneuvers are performed for offline training, and a large angle attitude maneuver under the proposed improved PD controller is simulated. The experiment proves that the improved PD controller is effective and can improve system performance. The Elman neural network appears the best choice for rigid-flexible estimation and the improved PD controller.

Integrated Control of Attitude Maneuver and Vibration Suppression Using Pyramid-Type SGCMGs

In this paper, a pyramid-type single-gimbal control moment gyro (SGCMG) system mounted on space structure is employed to realize the integrated control of singularityavoidance attitude maneuver and vibration suppression. The rest-to-rest attitude maneuver is divided into three sections, in which null motion is applied to achieve the above two objects leading to a better control performance. The effectiveness of the proposed control strategy is verified using numerical simulation examples.

Compound Attitude Maneuver and Collision Avoiding Control for a Novel Noncontact Close-Proximity Formation Satellite Architecture

In order to achieve the attitude maneuver performance of the noncontact close-proximity formation satellite architecture, this paper presents a compound control strategy with variable-parameter sliding mode control and disturbance observer-based feedforward compensation. Firstly, the variable-parameter sliding mode control is proposed to guarantee the attitude maneuver performance of the payload module. Secondly, the collision avoiding control with disturbance observer-based feedforward compensation is proposed to guarantee the synchronization of the two separated modules within the small air clearance constraint of the noncontact Lorentz actuator. Finally, a physical air-floating platform is established to verify the effectiveness of the proposed approach.

Satellite attitude PDE-based controller design considering fluid fuel sloshing in planar maneuver

Due to significance of high-accuracy attitude control, the fuel sloshing effects on the satellite attitude should be considered, more precisely. This work deals with the attitude control of a liquid propellant-filled satellite considering the incompressible fuel sloshing in the planar maneuver. The satellite consists of a rigid body, a partially-filled tank and a flexible diaphragm. Hamilton's principle is employed to derive nonlinear coupled PDEs-ODEs governing the coupled satellite-diaphragm propellant tank system. Afterwards, to dispense with the spillover instability, a PDE-based controller is designed to realize the satellite attitude control while tracking a desired pitch angle and suppressing the sloshing of the fuel. One of the main benefits of the introduced controller is stabilization of the infinite-degree-of-freedom system without any simplification which is fulfilled using only one control torque applied to the rigid satellite. In addition, the closed-loop system stability is proven using Lyapunov stability approach, even if the viscosity of the fuel and any environmental damping are disregarded. Assessing of the proposed controller capability and its effectiveness indicates that the present study can pave the way toward more accurate satellite attitude maneuvers.

Application of the Improved Grey Wolf Algorithm in Spacecraft Maneuvering Path Planning

In many space missions, spacecraft are required to have the ability to avoid various obstacles and finally reach the target point. In this paper, the path planning of spacecraft attitude maneuver under boundary constraints and pointing constraints is studied. The boundary constraints and orientation constraints are constructed as finite functions of path evaluation. From the point of view of optimal time and shortest path, the constrained attitude maneuver problem is reduced to optimal time and path solving problem. To address this problem, a metaheuristic maneuver path planning method is proposed (cross-mutation grey wolf algorithm (CMGWO)). In the CMGWO method, we use angular velocity and control torque coding to model attitude maneuver, which increases the difficulty of solving the problem. In order to deal with this problem, the grey wolf algorithm is used for mutation and evolution, so as to reduce the difficulty of solving the problem and shorten the convergence time. Finally, simulation analysis is carried out under different conditions, and the feasibility and effectiveness of the method are verified by numerical simulation.

Propellant-free attitude control of solar sails with variable-shape mechanisms

Solar sails can realize propellant-free attitude control if they have the ability to change their shape by moving reflective surfaces to harness the force of incident solar radiation pressure (SRP). In this paper, we formulate a stability analysis of the attitude motion of a sail spacecraft with large deformation under SRP, and propose stable attitude control methods using variable-shape mechanisms. The basic principle is that the attitude is maintained at a stable equilibrium point that suppresses the disturbance torque due to SRP and prevents disturbance angular momentum from accumulating in the reaction wheels. The equilibrium point can be shifted by moving reflective surfaces, and the attitude follows the new equilibrium point by reaction wheel control. The stability of the equilibrium points can be quickly evaluated by a stability analysis based on linearized equations of motion, and one can choose any equilibrium point by setting the reflective surfaces to a corresponding configuration. This control scheme enables the spacecraft body to be pointed towards desired directions, and even if the attitude maneuver and maintenance accumulate angular momentum in the reaction wheels, this momentum can also be unloaded without propellant by using SRP and shape variation. The dynamics formulation aims at a zero-momentum system that is generally applicable to arbitrarily shaped spacecraft, and the formulation of the stability analysis and control methods were verified by numerical simulations.

Quantum-inspired diffusion Monte Carlo optimization algorithm applied to space trajectories and attitude maneuvers

In this work, an algorithm for solving optimization problems is proposed, inspired by a computational method employed in Quantum Mechanics: the Diffusion Monte Carlo method, commonly used for the computation of ground states of many-particle systems. The optimization problem is re-formulated as the problem of sampling the ground state wave function of a particle subject to a potential based on the function to be minimized. The algorithm is applied to problems in space trajectory and spacecraft attitude maneuvers optimization, the first application is to the problem of transfer between circular orbits, the results obtained are compared to the results from the literature, then it is applied to the problem of rendezvous with the asteroid Pallas, and finally to the optimization of an attitude maneuver in the presence of several constraints, and the obtained results are compared to two widely used methods: Particle Swarm Optimization and Differential Evolution algorithms. The algorithm is of simple implementation, and the numerical results show better performance than the comparison methods in the considered problems.

Reaction Wheel Torque Distribution Algorithm for Enhancing the Agility of the Spacecraft using Null motion

Earth observation satellites require rapid attitude maneuvering and stringent pointing accuracy for imaging payloads. Four numbers of Reaction Wheel (RW) are usually configured in standard tetrahedral configuration for attitude manoeuvring as well as for fine pointing. The Reaction wheel maximum torque is one of the critical parameters that determine the agility of the spacecraft. Three axis attitude control torque signal is distributed to 4 Reaction wheels using standard pseudo inverse solution which minimizes the sum of the square of the individual wheel torque rather than the maximum of the individual wheel torque. The pseudo inverse solution leads to wheel saturation even when the total momentum does not reach the envelope and there by limiting the agility of the spacecraft. In this paper, new approach is adopted to optimally utilize the full capacities of RWs and thereby enhancing the agility of the spacecraft. The new algorithm is based on the null motion of the reaction wheel torque alignment matrix. The proper choice of the null vector results in equal wheel torque demand when combining with the pseudo inverse solution. The maneuver & control algorithms are integrated together with new distribution method and have been demonstrated for typical rest to rest and rate to rate maneuver.

Disturbance observer-based constrained attitude control for flexible spacecraft

This paper investigates the difficult issue of fixed-time constrained attitude control for a flexible spacecraft under the influence of the system uncertainties, environmental disturbance and abrupt actuator faults. The contributions of the proposed control framework are twofold. Firstly, an observer is presented to precisely reconstruct the uncertain dynamics within a fixed time regardless of the initial estimation error while the settling time is given as a specific parameter. Secondly, using a combination of prescribed performance control (PPC) and barrier Lyapunov function (BLF) approaches, a simple structure constrained attitude control for flexible spacecraft is proposed while desired performance specifications for both quaternion and rotation velocity are indirectly achieved by constraining the sliding manifold. A distinctive feature of the suggested control framework is that the settling time of the closed-loop system is finite and explicitly expressed as two tunable gains even when abrupt actuators faults happen. Numerical simulations substantiate the ability of the offered control to effectively accomplish favorable attitude maneuver under the negative effect of the inertia matrix uncertainty, external disturbances, flexible structures vibration and actuators faults.

Multi-objective Optimization of Observation Scheduling Avoiding Attitude Maneuvering Conflict

Multi-objective Optimization of Observation Scheduling Avoiding Attitude Maneuvering Conflict

Attitude dynamics and control of solar sail with multibody structure

In the history of solar sail research, numerous methods have been proposed to control the spacecraft attitude. Different in detailed operations, almost all of them rely on solar radiation pressure torques generated by manipulating the offset between the center of mass and the center of pressure. In this paper, a solar sail attitude control method that does not rely on solar radiation pressure is proposed. The method is demonstrated for the case of a quad sail that consists of 4 separate triangular wings. Each wing is able to pitch along its own longitudinal axis. During the pitch, according to the conservation of angular momentum, an internal torque exerted on the remaining part of the sail would be generated. Analysis is conducted regarding the kinematic behavior of the solar sail attitude during wings pitching, based on which two different attitude maneuver strategies are proposed. On one hand, the proposed attitude control method is a new one that no longer relies on the solar radiation pressure. On the other hand, this research also serves as a supplement to some of the existing research, in which relative motion between parts of the sail are involved but the internal torque effect is either neglected or treated as disturbance.

Refined Disturbance Rejection-Based Composite Control of Flexible Spacecrafts for Tracking a Tumbling Non-Cooperative Target

When tracking a tumbling non-cooperative target, the position and attitude maneuver control with high-precision as well as fast-response performances is required for flexible spacecrafts. However, the unknown rigid-flexible coupling and model uncertainties will degrade the control performances significantly. Therefore, this paper proposes a refined disturbance rejection-based composite control method for spacecraft position and attitude tracking. First of all, the disturbances including the rigid-flexible coupling and model uncertainties are described by an exogenous model by fully using the partially known disturbance information (e.g., modal frequency and damping). Then, a novel exogenous model-based sliding mode disturbance observer (SMDO) is proposed to achieve the refined disturbance estimation. Next, by combining the SMDO in the feedforward loop and an adaptive terminal sliding mode control (ATSMC) in the feedback loop, a finite-time composite control law is proposed to ensure the fast disturbance rejection and position/attitude tracking simultaneously. In the composite controller, a novel nonsingular terminal sliding mode surface with arctangent function is proposed. Moreover, a time-varying boundary Lyapunov function (BLF) is designed to preassign the transient and steady-state performances of sliding mode surface. Finally, the effectiveness of proposed method is verified via numerical simulation.

Selecting Initial Gimbal Angles of Roof-type CMG System for Avoiding Singularities in Spacecraft Attitude Maneuver

Selecting Initial Gimbal Angles of Roof-type CMG System for Avoiding Singularities in Spacecraft Attitude Maneuver