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This paper proposes a prescribed performance control policy for spacecraft attitude tracking control. The designed controller employs a kind of performance envelope function that can configure the convergence rate arbitrarily. Moreover, the controller design is based on the barrier Lyapunov function and indirect adaptive methods, which can suppress the fluctuation of external disturbances to obtain lower steady-state errors. Compared to prior studies on spacecraft attitude tracking, the proposed policy can arbitrarily configure the system convergence performance to achieve performance trade-offs in different scenarios. Moreover, the barrier Lyapunov function design and adaptive methods can achieve low steady-state errors with low computational resource consumption. Simulations that verify its effectiveness and superiority are provided herein. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the relative translational control for multiple spacecraft formation flying. This paper proposes an engineering-friendly, structurally simple, fast and model-free control algorithm. Design/methodology/approach: This paper proposes a tanh-type self-learning control (SLC) approach with variable learning intensity (VLI) to guarantee global convergence of the tracking error. This control algorithm utilizes the controller's previous control information in addition to the current system state information and avoids complicating the control structure. Findings: The proposed approach is model-free and can obtain the control law without accurate modeling of the spacecraft formation dynamics. The tanh function can tune the magnitude of the learning intensity to reduce the control saturation behavior when the tracking error is large. Practical implications: This algorithm is model-free, robust to perturbations such as disturbances and system uncertainties, and has a simple structure that is very conducive to engineering applications. Originality/value: This paper verified the control performance of the proposed algorithm for spacecraft formation in the presence of disturbances by simulation and achieved high steady-state accuracy and response speed over comparisons. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to study the attitude control problem with mutating orbital rate and actuator fading. Design/methodology/approach: To avoid malicious physical attacks and hide itself, the spacecraft may irregularly switch its orbit altitude within a specific range, which will bring about variations in orbital rate, thereby causing mutations in the attitude dynamics model. The actuator faults will also cause changes in system dynamics. Both factors affect the control performance. First, this paper determines the potential switching orbits. Then under different conditions, design controllers that can accommodate actuator faults according to the statistical law of actuator fading. Findings: This paper, to the best of the authors' knowledge, for the first time, introduces the Markovian jump framework to model the possible unexpected mutating of orbital rate and actuator fading of spacecraft and then designs a novel control policy to solve the attitude control problem. Practical implications: This paper also provides the algorithm design processes in detail. A comparative numerical simulation is given to verify the effectiveness of the proposed algorithm. Originality/value: This is an early solution for spacecraft attitude control with dynamics model mutations. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to address the spacecraft attitude regulation problem in the presence of extrinsic disturbances and actuator faults. Design/methodology/approach: Based on adaptive backstepping design technique, a new concise adaptive dual-mode control scheme is proposed, which can either use the fault information detected by fault diagnosis mechanisms or switch to the fault-unknown mode when the fault diagnosis information is non-existent for control signal generation. These two modes share an adaptive mechanism that reduces the complexity of the algorithm. Findings: The new fault-tolerant attitude control algorithm can accommodate both modes with and without fault diagnosis mechanisms. Originality/value: The proposed algorithm in this paper can be applied to both cases when the attitude control system is equipped with or without fault diagnosis capability. This also enhances the robustness of attitude control algorithm. This study performs numerical simulations and verifies that the algorithm could effectively adapt to both modes. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the attitude regulation for spacecraft in the presence of time-varying inertia uncertainty and exogenous disturbances. Design/methodology/approach: The high gain approaches are typically used in existing researches for theoretical advantages, bringing better performance but sensitive to parameter selection, making the controller conservative. A reset-control policy is presented to achieve the spacecraft attitude control with easy control parameter tuning. Findings: The reset-control policy guarantees satisfying control performance despite using performance tuning function and saturation function besides reducing the conservativeness of the controller, thus reducing the effort in tuning control parameters. Originality/value: Notably, the adaptive function owns a reset mechanism, which is reset to a preset condition when the controlled variable crosses zero. The mathematical analysis also shows the system trajectory can converge to a set centered at the origin. [ABSTRACT FROM AUTHOR]

This brief investigates event-triggered control for spacecraft attitude stabilization under the influence of actuator output nonlinearities. Under a designed event-triggered policy, the influences of actuators’ inherent nonlinearity and network quantized transmission are evaluated under a unified framework. Compared with the previous results, the influences of data transmission and actuators’ inherent nonlinearities are uniformly described as the actuator output nonlinearities, and the event-triggered policy reduces the effects of constants commonly introduced into triggering conditions on the final state convergence regions and achieves Zeno-free triggering. Simulations verify theoretical results. [ABSTRACT FROM AUTHOR]

A novel integrated quantized- and event-based control (IQEC) scheme for intra-spacecraft with communication-saving ability is proposed to address the attitude tracking control problem. The IQEC scheme reduces the control updating frequency and the data length per transmission based on the event-based control and quantized communication techniques, thus reducing the system communication occupation. By suitable control system configuration, the purpose of communication-saving is achieved, from sensors to the computing unit and from the computing unit to actuators. The proposed algorithm’s effectiveness is verified via numerical simulation that uses a general actuator model with second-order dynamics. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study the general actuator modeling in spacecraft attitude control systems. Design/methodology/approach: The proposed module in this paper provides various non-ideal factors such as the second-order dynamic time response, time-delay, bias torques, dead-zones and saturation. The actuator module can make the simulation as close to the practical situation as possible. Findings: This paper presents a practical integrated module for the simulation of attitude control algorithms. Based on theoretical modeling, we give simulation modules and numerical examples. The proposed model can be directly used in spacecraft control simulation. Instead of considering only a few of them, it makes the simulation more convincing. Though it may not be perfect, it is better than totally ignoring the actuator dynamics. Originality/value: The authors provide an integrated actuator model for spacecraft attitude control simulation, considering as many nonlinear factors as possible once time. [ABSTRACT FROM AUTHOR]

Purpose: Recent spacecraft attitude control systems tend to use wireless communication for cost-saving and distributed mission purposes while encountering limited communication resources and data exposure issues. This paper aims to study the attitude control problem with low communication frequency under the sampled-data. Design/methodology/approach: The authors propose constructive control system structures based on quantization and event-triggered methods for intra-spacecraft and multi-spacecraft systems, and they also provide potential solutions to shield the control system's data security. The proposed control architectures can effectively save communication resources for both intra-spacecraft and multi-spacecraft systems. Findings: The proposed control architectures no longer require sensors with trigger-ing mechanism and can achieve distributed control schemes. This paper also provides proposals of employing the public key encryption to secure the data in control-loop, which is transmitted by the event-triggered control mechanism. Practical implications: Spacecraft attempts to use wireless communication, yet the attitude control system does not follow up promptly to accommodate these variations. Compared with existing approaches, the proposed control structures can save communication resources of control-loop in multi-sections effectively, and systematically, by rationally configuring the location of quantization and event-triggered mechanisms. Originality/value: This paper presents several new control schemes and a necessary condition for the employment of encryption algorithms for control systems based on event-based communication. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to investigate the attitude cooperation control of multi-spacecraft with in-continuous communication. Design/methodology/approach: A decentralized state-irrelevant event-triggered control policy is proposed to reduce control updating frequency and further achieve in-continuous communication by introducing a self-triggered mechanism. Findings: Each spacecraft transmits data independently, without the requirement for the whole system to communicate simultaneously. The local predictions and self-triggered mechanism avoid continuous monitoring of the triggering condition. Research limitations/implications: This investigation is suitable for small Euler angle conditions. Practical implications: The control policy based on event-triggered communication can provide potential solutions for saving communication resources. Originality/value: This investigation uses event- and self-triggered policy to achieve in-communication for the multi-spacecraft system. [ABSTRACT FROM AUTHOR]

Abstract The attitude cooperative control of multi-spacecraft under undirected information flow is studied in this paper based on a novel state-irrelevant event-triggered control (ETC) strategy. In the proposed algorithm, the control updating and data-transfer among spacecraft need only be executed when certain conditions are triggered. Then, the system model is utilized to predict the future state based on the last transmission and to calculate the time of the next transmission event. Firstly, the proposed algorithm reduces the control updating frequency remarkably and avoids continuous communication; secondly, each spacecraft updates its controller independently, without requiring all members to update simultaneously; thirdly, it is still effective in the presence of input limitation. The consensus can be guaranteed under such control strategy. It has proved that there exists a lower bound for the update interval, avoiding a phenomenon that the infinite number of events may appear in a finite time interval, also called the Zeno phenomenon. The efficacy of the proposed algorithm is verified via simulations. [ABSTRACT FROM AUTHOR]

This paper addresses the attitude synchronization and tracking control (ASTC) for multi-spacecraft formation system (MFS) under undirected and directed graph. First, a new adaptive nonsingular fast terminal sliding mode surface (ANFTSMS) is developed. It has both the merits of the NFTSM avoiding singularity and the adaptive method regulating the relative weighting of parameters. This provides designers a new way to improve the control performance. Second, by applying ANFTSMS, the proposed ANFTSM-controllers (ANFTSMCs) provide high precision finite-time convergence, robust to time-varying disturbances, uncertainties and accommodate to actuator faults, limited inputs. Moreover, the ANFTSMCs also achieve simple structure, inexpensive computations and chattering-free for continuous design. Few studies have addressed these problems simultaneously. Finally, effectiveness of the algorithms are verified via simulations. [ABSTRACT FROM AUTHOR]

This paper investigates the attitude fault-tolerant stabilization problem for a spacecraft subjected to its actuator effectiveness loss, inertia uncertainties and space disturbances. A novel Iterative Learning Sliding Mode Observer (ILSMO) is proposed to reconstruct the actuator effectiveness factors robustly and accurately by combining the P-type iterative learning algorithm with the sliding mode approach. Based on the reconstructed fault signals, an Iterative Learning Sliding Mode Controller (ILSMC) is designed to guarantee the closed-loop spacecraft attitude fault-tolerant stabilization by compensating for its lumped disturbance. The ILSMO and ILSMC stabilities are guaranteed using the Lyapunov direct approach, respectively. Finally, the numerical simulation results show that the proposed ILSMO-ILSMC-based spacecraft attitude fault-tolerant stabilization method is effective and superior. [ABSTRACT FROM AUTHOR]

This paper proposes a neural network and event-based fault-tolerant control scheme for spacecraft attitude stabilization in the presence of lumped disturbances, which consists of space disturbances, inertia uncertainties, and actuator faults. A neuro-adaptive estimator is employed to approximate the lumped disturbances, with the help of its powerful adaptive estimation capability of approximating any unknown smooth nonlinear function with arbitrary accuracy. The estimation is then utilized to formulate an integrated event-based dual-channel control scheme that can both guarantee the system's convergence and ensure the event triggering sequence possessing no-Zeno behavior simultaneously. The proposed control scheme provides a new and straightforward way for spacecraft attitude control to deal with lumped disturbances while requiring a low actuator updating frequency, thus saves on-board communication resources. Numerical simulations show the effectiveness of the algorithms. [ABSTRACT FROM AUTHOR]

This paper studies the spacecraft attitude stabilization problem with external disturbances. A new control scheme entitled online-learning control is proposed to achieve a robust, accurate, and simple-structure control algorithm. Compared with the conventional control design, an obvious distinction of the online-learning control algorithm is that it together utilizes the previous control input information and the system's current state information, as if learning experience from previous control input. In contrast, the conventional control scheme does not fully use the existing information and chooses to discard the previous control input information when generating control instructions. Due to the learning strategy, the utility of adaptive- or observer-based tools can be avoided when designing a robust control law, making a simple, effective algorithm, moreover saving system resources. The proposed control law can stabilize the attitude system by achieving the uniformly ultimately bounded convergence. [ABSTRACT FROM AUTHOR]

This paper investigates the orbit determination problem for fuel station (FS) in multiple Sun-Synchronous Orbit (SSO) spacecrafts refueling mission. A novel K-M-N transportation network to solve this general refueling problem is proposed, which contains several FSs with their reusable servicing spacecraft (SSC) and a large number of targets. The proposed network allows the FS drifting in a cooperative rendezvous to reduce the fuel consumption considering the J 2 perturbation. Furthermore, one-to-one mode is chosen as the refueling strategy between the FS and the target, which makes it feasible to determine the number and orbit of the FS. In order to achieve such an economical refueling strategy, the problem is formulated as a facility location–allocation (FLA) model, subject to the different demands among targets and the limitation of SSC's capacity. Then, a hybrid Density-Based Spatial clustering algorithm (HDBSCAN) is designed to solve the multi-objective optimization model. Finally, two numerical examples are presented to illustrate the effectiveness and validity of the proposed algorithm. [ABSTRACT FROM AUTHOR]

This paper presents a propellantless spacecraft rendezvous method by using the optimal combination of aerodynamic force and Lorentz force. Aerodynamic force is provided by the rotations of the plates attached to the spacecraft, and Lorentz force is achieved by modulating spacecraft's electrostatic charge. Considering the limitation of the charging level of the spacecraft and physical constraints of the plates system, an optimal open-loop rendezvous trajectory is designed, which aims to minimize the energy consumed to actuate the hybrid system. The rotation rates of the plates and the electrostatic charge are constrained in the optimization problem, which is solved via the Gauss pseudospectral method. To track the open-loop trajectory in the presence of external perturbations, a novel adaptive nonsingular terminal sliding mode controller is designed. The stability of the closed-loop system is proved by the Lyapunov-based method. Several numerical examples are conducted to verify the validity of both the open-loop and closed-loop control strategy. [ABSTRACT FROM AUTHOR]

This paper investigates an optimal fuel station (FS) arrangement problem for multiple geosynchronous (GEO) spacecrafts with many-to-many (M2M) refueling, subject to the capacity of the servicing spacecraft (SSC) and the different fuel requirements of the targets. Several FSs with their reusable SSC are arranged on GEO, while the SSC commutes between fuel-deficient targets and FSs to refuel the multiple targets. To avoid building a fuel station at the exact position of the target in traditional M2M refueling, the problem is formulated as a location–allocation problem. Based on that, a novel modified K-means clustering is proposed, in which the difficulty caused by the limitation of the SSC's capacity is solved. With the proposed method, the FS is allowed to be arranged in the exact region without inaccessible targets, where the minimum number of the required FS and the minimized fuel cost are determined in turn. Finally, numerical simulations validate the performance of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a prescribed performance control (PPC) scheme for spacecraft attitude tracking with anti-disturbance and performance-adjustable properties is proposed. The proposed controller is based on the barrier Lyapunov function (BLF) approach, which can arbitrarily adjust the state convergence performance and possess high steady-state performance. Compared with previous works, this strategy is more robust to external disturbances and thus has higher steady-state performance with low computing resource occupancy. What's more, it has the property of freely adjusting performance to meet the control objectives and performance requirements in different scenarios. Simulation results in this paper verify the effectiveness and superiority of the proposed method. [ABSTRACT FROM AUTHOR]

This article presents a finite-time prescribed performance (FTPP) control approach based on a learning Chebyshev neural network (LCNN) for spacecraft attitude tracking with modeling uncertainties, actuator faults, and external disturbances. An FTPP function is designed to specify the desired accuracy boundary and finite-time convergence. Further, an FTPP-based learning sliding mode controller (LSMC) is constructed, where the lumped disturbance is approximated and compensated via a novel LCNN model. Unlike conventional adaptive CNN models, the LCNN model employs an iterative learning mechanism for adjusting the weights of the CNN model, reducing computing costs. The FTPP-based LSMC approach is presented with a detailed stability analysis. The proposed method offers a broad range of applications with the FTPP criteria satisfied. A series of simulations are performed to verify the validity and applicability of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper investigates an adaptive leader-following formation tracking control approach for multiple spacecraft under a directed communication topology with consideration of external disturbances, formation safety and limited sensing ranges. Through developing a novel logarithmic potential function-based approach, the neighboring spacecraft can always move within the region of maintaining connectivity and avoiding collision. Additionally, by establishing a new state-independent performance function, the specified-time stability of the SFF system can be guaranteed, wherein, the convergence time can be arbitrarily appointed in advance. Compared with the existing results, the major advantage of the proposed scheme is that the specified-time stability, connectivity preservation and collision avoidance can be considered simultaneously with superior capacity of rejecting disturbance. Meanwhile, the formation tracking performance of the SFF system can be ensured a priori. By virtue of the Lyapunov theory, the detailed theoretical analysis for the proposed protocol has been derived. Finally, extensive simulations are carried out to validate the effectiveness of the proposed control protocol. [ABSTRACT FROM AUTHOR]