Spacecraft Control System Research Articles

Star Image Prediction and Restoration under Dynamic Conditions.

The star sensor is widely used in attitude control systems of spacecraft for attitude measurement. However, under high dynamic conditions, frame loss and smearing of the star image may appear and result in decreased accuracy or even failure of the star centroid extraction and attitude determination. To improve the performance of the star sensor under dynamic conditions, a gyroscope-assisted star image prediction method and an improved Richardson-Lucy (RL) algorithm based on the ensemble back-propagation neural network (EBPNN) are proposed. First, for the frame loss problem of the star sensor, considering the distortion of the star sensor lens, a prediction model of the star spot position is obtained by the angular rates of the gyroscope. Second, to restore the smearing star image, the point spread function (PSF) is calculated by the angular velocity of the gyroscope. Then, we use the EBPNN to predict the number of iterations required by the RL algorithm to complete the star image deblurring. Finally, simulation experiments are performed to verify the effectiveness and real-time of the proposed algorithm.

Quaternion-based Finite-time Sliding Mode Controller Design for Attitude Tracking of a Rigid Spacecraft during High-thrust Orbital Maneuver in the Presence of Disturbance Torques

In this paper, a quaternion-based finite-time sliding mode attitude controller is designed for a spacecraft performing high-thrust orbital maneuvers, with cold gas thrusters as its actuators. The proposed controller results are compared with those of a quaternion feedback controller developed for the linearized spacecraft dynamics, in terms of settling time, steady-state error, number of thruster firings and their fuel usage. It is then proved that the sliding mode control has enough robustness against disturbances as well as a high accuracy in attitude tracking and also a low number of thruster firings. A 6 degree of freedom (DOF) total simulation, including spacecraft dynamics, guidance, navigation and control systems is also designed and the sliding mode controller performance in a sample transfer from an ecliptic orbit to a circular one is investigated. In order to solve the chattering problem caused mainly because of the discontinuity of sliding mode control algorithm and multiple switching on sliding surfaces, the sign function in the control input is replaced with a hyperbolic tangent function. Being aware of the advantages of sliding mode control method, using this algorithm in orbital transfers seems to be innovative and efficient.

Fault-Tolerant Architecture of Storage Device for On-board Spacecraft Control Systems

For on-board microelectronic control systems of spacecraft with a long service life, the problem of increasing the fault tolerance of storage devices and ensuring ease of maintenance is solved. The architecture of a fault-tolerant storage device with built-in self-testing and automatic recovery from multiple failures is proposed.

An enhanced anti-disturbance attitude control law for flexible spacecrafts subject to multiple disturbances

As well-known disturbance rejection methods, active disturbance rejection control and disturbance observer-based control can effectively improve the control performances of complex systems in the presence of disturbances. However, the accurate rejection of multiple disturbances for control systems of practical engineering, for example, the attitude control system of flexible spacecraft, is still a bottleneck problem. In order to further improve the anti-disturbance capability and reduce the conservativeness, this paper proposes a novel enhanced anti-disturbance control law for the attitude control system of flexible spacecraft by combining active disturbance rejection control and disturbance observer-based control in a unified framework. More specifically, the disturbance from flexible vibration is described by an uncertain exogenous system based on the partially known information including elastic damping ratios and modal frequencies. The disturbance observer-based control is utilized to estimate and thereby reject this disturbance. On the other hand, the other disturbances such as external environmental disturbance and complex model nonlinearity are merged into a equivalent disturbance with bounded derivative, which is compensated by using the active disturbance rejection control law. Stability and robustness analysis are carried out for the disturbance observer and extended state observer. Finally, simulation results of low-earth-orbit flexible satellite are presented to verify the effectiveness of proposed methods.

ON THE INFLUENCE OF THE LEVEL OF AN EXTERNAL MAGNETIC FIELD AND THE LENGTH ON THE MAGNETIC MOMENT OF CYLINDRICAL CORES

Purpose. Analysis of inhomogeneous magnetization of long cylindrical permalloy 50N cores by a uniform constant magnetic field and the influence of length and field level on their magnetic moment. Methodology. The magnetostatic field of a non-uniformly magnetized in a uniform magnetic field long cylindrical core of an electromagnet of a spacecraft control system is considered. To calculate this field, a transformation of the integral equation with respect to the density of fictitious magnetic charges, as well as an iterative algorithm for its numerical solution, are proposed. Results. The convergence of the algorithm and the fact that the magnetic moment of the core depends heavily on its length and the level of the external magnetic field is shown. We have made an analysis of the influence of the length of a permalloy 50N core in the entire range of the magnetization curve and the level of a uniform external magnetic field on the axial projection of the magnetic moment of the core. Originality. The use of an almost equal distribution of the axial projection of the resulting magnetic field in the cross sections of the greater part of the cylindrical core and its division into cylindrical elements can significantly reduce the order of the system of algebraic equations approximating the integral equation for the surface density of fictitious magnetic charges for its numerical solution. Practical value. Recommendations regarding the level of the external field created by the electromagnet coil, the increase of the magnetic moment in cases of long cores and the choice of the number of cylindrical elements depending on the length of the core are given.

The Study on Reconfigurability Condition of Spacecraft Control System

Reconfigurability refers to the ability of the system to overcome all faults or restore some of its performance by changing the structure or control algorithm under the condition of resource constraints and operating conditions within a certain period of time to ensure the security when the control system fails. The establishment of reconfigurability evaluation and design theoretical system is of great significance for improving the operational reliability and service life of the whole spacecraft. Research projects are being conducted worldwide regarding reconfiguration control technology. We summarize the performance factors that affect system reconfigurability based on several typical reconfiguration methods by analyzing the constraints that the system can satisfy through fault-tolerant approaches. Since the reconfigurability evaluation index reveals the limitations and potentials of reconfigurable ability of the system, we refine the quantitative reconfigurability evaluation method based on various influencing factors. We anticipate that this work will play a guiding role in the reconfiguration strategy and design of spacecraft in-orbit to achieve the fault forward.

A novel sth‐order observer for linear system: Application to state and fault estimation of spacecraft control system

SummaryIn this paper, a fault estimation problem for linear system is considered. A novel sth‐order observer is proposed to cope with this problem. The advantages of the proposed observer are that (i) the observer matching condition is not required to be satisfied in practical systems, (ii) if the sth derivative of fault is unknown and/or unbounded and the (s + 1)th derivative of fault f (t) is naught or bounded, it can simultaneously estimate the state and fault. The sufficient existence condition of the proposed observer is given by a linear matrix inequality. In addition, a feasible method to obtain the design parameters is discussed. Finally, two numerical examples are presented to illustrate the effectiveness of the proposed method.

Dependent failure in multifunctional automatic control systems

The paper considers the components interference of the automated control system. The safety and survivability are investigated. The failure gradation is given. The failure consequences of components and modules of the system that cause failures of other components and modules, the capabilities to prevent these failures are considered. Some probable variants of the dependent failures are provided. It is shown that a possible source of danger can be both module failure and failure of redundant components in these modules. It is assumed that at least the potential danger is not reduced to zero due to the increase in the number of redundant components. The various logical structures of the compound components in the automated control systems (ACS) for spacecraft are discussed. A typical structure of reliability of the automated control system that performs several functions, i.e. a tree structure is presented. The process of failures development in multifunction systems, the mutual influence of components in case of simple linear and branching redundant structures are illustrated. The negative effects of redundancy are considered. An example of the reliability calculation of the system with a parallel connection of the components and their dependent failures caused by these components are given. The conclusion about the necessity of non-redundant methods for improving the reliability and dangerous impact prevention is made.

Resistive Method to Measure Residual Stresses in Parts from Heat-Resistant Alloys

The resistive electrical contact method of measuring residual stresses in the surface layer of various metals and alloys is considered. Studies are carried out to determine technological residual stresses in the process of manufacturing parts from heat-resistant alloys applied in thermal control systems for spacecraft, as well as aerospace, mining and power engineering.

Construction of Highfailurestable Spacecraft Control System with Apply to Adaptive Logic in Diagnostic and Testing Algorithms

Different approaches to problem of improving onboard spacecraft control system failurestable on base principles of analytical excess, optimization and reconfiguration with using probability index and adaptive logic in diagnostic and testing algorithms are considered. One of problem is synthesis of spacecraft control system algorithms with incomplete apriory and distorted current information, action of uncontrolled and random factors, equipment failures and signal loss in information channel. Ways of failure diagnostic are examinated, in particular, problem excluding of failures sensors and power drives. Onboard attitude control system is synthesized and control algorithms are chosen, which guarantee robust stability and failure stability in presence indignant factors. Questions of onboard spacecraft control system failurestable improving are discussed on base reconfiguration with apply to adaptive logic in diagnostic and testing algorithms. The features of simulation are described on instrumental structure and operational modes of the attitude control system, the methods of dynamic research and computer simulation utilized during designing are indicated. Onboard complex control algorithms, diagnostic and reconfiguration are proposed for navigation, communication, geodesy satellites and earth inspectoral vehicles with prolonged utilization (more 10 years) in space flight conditions. Testing system have to decide two problem: discovering and eliminating faults. The mathematical system model is researching with implementation of analytic reserving. Difference signals are formed, which arise at fault appearance. The failure character is established by deciding rules on base difference signals and measures to it eliminating are took. The adaptive approach to development testing and diagnostic systems provide for realization of flexible logic of control system function to take into account factual onboard equipment state. The effectiveness of prepositional approaches and algorithms is confirmed by mathematical modeling results for several actual technical systems. Recommendations to their practical applications are gave.

CFD modeling of thermal contact resistance between solid contacting surfaces

ABSTRACTHeat transfer has considerable applications in different industries such as designing of heat exchanger, nuclear reactor cooling, control system for spacecraft, and designing of microelectronics cooling. As the surfaces of two metals contact each other, this issue becomes so crucial. Thermal contact resistance (TCR) is one of the key physical parameters in heat transfer of mentioned surfaces. Measuring the experimental value of TCR in laboratory is highly expensive and difficult. As an alternative, numerical modeling methods could be engaged. In this study, inverse problem method solution is utilized as a proper method for estimation of TCR value. In this order, three different configurations (flat-flat, flat-cylinder, and cylinder-cylinder) were utilized in two steady and unsteady state conditions to predict the value of TCR. A comparison between the measured values and obtained values from the simulation show the errors for flat-flat, flat-cylinder, and cylinder-cylinder configuration after 10 min from starting the experiment are 4.6074%, 0.1662%, and 0.5622%, respectively. And in steady-state condition, the corresponding errors are 6.06e-3%, 1.506%, and 0.846%, respectively. In conclusion, the final results establish the fact that the inverse problem method solution can predict TCR values between contacting surfaces.

Relative Motion Control System of Spacecraft for Contactless Space Debris Removal

Relative Motion Control System of Spacecraft for Contactless Space Debris Removal

Mathematical modeling of thermal contact resistance for different curvature contacting geometry using robust approach

Nowadays having deep knowledge on thermal contact conductance (TCC) and thermal conduct resistance (TCR) existed between various type metals is interesting during heat transfer occurrence in the nuclear reactor, thermal control system of spacecraft, and heat exchangers. In this present contribution, artificial neural network (ANN) coupled with multi-layer perceptron (MLP) modeling was utilized for the prediction of transient temperature contour in various contacting surface such as flat-flat, flat-cylinder, cylinder-cylinder. In order to develop accurate transient model, position, time, and roughness parameter of metal was used as input parameter and temperature of solid bodies decided as target parameter of model. Modeling results indicates that ANN base modeling show great accuracy in comparison with other numerical methods. Also, values of average absolute relative deviation (AARD), coefficient of determination (R2) for the overall data is 0.056 and 0.996 respectively which clarifies the accuracy and robustness of the proposed model.

Singularity-Free Model Predictive Spacecraft Attitude Regulation Using a Variable-Speed Control Moment Gyroscope Model

This paper discusses spacecraft control using variable-speed CMGs. A new operational concept for VSCMGs is proposed. This new concept makes it possible to approximate the complex nonlinear system by a linear time-varying system (LTV). As a result, an effective control system design method, Model Predictive Control (MPC) using robust pole assignment, can be used to design the spacecraft control system using VSCMGs. A nice feature of this design is that the control system does not have any singular point. A design example is provided. The simulation result shows the effectiveness of the proposed method.

VO2 Thermochromic Metamaterial-Based Smart Optical Solar Reflector

Optical solar reflector smart radiators are able to control the temperature of spacecraft. This work demonstrates a novel smart optical solar reflector using a patterned thermo-chromic VO2 plasmonic meta-surface design. The VO2 meta-surface combines the temperature induced phase transition of VO2 with plasmonic resonances resulting in a significant enhancement of the infrared absorption. The enhanced absorption obtained at a reduced VO2 coverage results in superior emittance tunability Δe and lower solar absorptance α compared to a corresponding thin-film reflector. An emittance tunability of 0.48 is obtained for the meta-reflector design, representing a 30% improvement compared to the unstructured film. Meta-surface based smart optical solar reflectors offer a new route toward energy-efficient and cost-effective passive thermal control systems of spacecraft and other surfaces.

Robust adaptive attitude control for flexible spacecraft in the presence of SGCMG friction nonlinearity

SummaryThis paper investigates attitude maneuver control issues of a flexible spacecraft with pyramid‐type single gimbaled control moment gyroscopes (SGCMGs) as the actuator. The LuGre friction model is adopted to precisely describe the nonlinearity of the SGCMG gimbal friction. Aiming at restraining the adverse effects of the friction existed in SGCMG on the attitude control performance, a robust adaptive attitude controller is proposed, and projection‐based adaptive laws are presented to estimate the friction parametric uncertainties and the bound of friction nonlinearity. By treating the flexible mode coupling effect and external disturbances as lump disturbances, the inertia uncertainties and the bound of the lump disturbances are also estimated and compensated simultaneously to reduce their adverse effect on the system. With the Lyapunov technique, the states of flexible spacecraft control system are proved to be uniformly ultimately bounded. Numerical simulations demonstrate the effectiveness of the proposed scheme.

Multiple Model Adaptive Attitude Control of LEO Satellite with Angular Velocity Constraints

In this paper, the multiple model adaptive control is utilized to improve the transient response of attitude control system for a rigid spacecraft. An adaptive output feedback control law is proposed for attitude control under angular velocity constraints and its almost global asymptotic stability is proved. The multiple model adaptive control approach is employed to counteract large uncertainty in parameter space of the inertia matrix. The nonlinear dynamics of a low earth orbit satellite is simulated and the proposed control algorithm is implemented. The reported results show the effectiveness of the suggested scheme.

Real-Time Optimal Control via Deep Neural Networks: Study on Landing Problems

Recent research has shown the benefits of deep learning, a set of machine learning techniques able to learn deep architectures, for modelling robotic perception and action. In terms of a spacecraft navigation and control system, this suggests that deep architectures may be considered now to drive all or part of the onboard decision-making system. In this paper, this claim is investigated in more detail, training deep artificial neural networks to represent the optimal control action during a pinpoint landing and assuming perfect state information. It is found possible to train deep networks for this purpose, and the resulting landings, driven by the trained networks, are close to simulated optimal ones. These results allow for the design of an onboard real-time optimal control system able to cope with large sets of possible initial states while still producing an optimal response.

Novel approach to improve the attitude update rate of a star tracker

The star tracker is widely used in attitude control systems of spacecraft for attitude measurement. The attitude update rate of a star tracker is important to guarantee the attitude control performance. In this paper, we propose a novel approach to improve the attitude update rate of a star tracker. The electronic Rolling Shutter (RS) imaging mode of the complementary metal-oxide semiconductor (CMOS) image sensor in the star tracker is applied to acquire star images in which the star spots are exposed with row-to-row time offsets, thereby reflecting the rotation of star tracker at different times. The attitude estimation method with a single star spot is developed to realize the multiple attitude updates by a star image, so as to reach a high update rate. The simulation and experiment are performed to verify the proposed approaches. The test results demonstrate that the proposed approach is effective and the attitude update rate of a star tracker is increased significantly.

Numerical investigation of thermal contact conductance between linear and curvilinear contacts

Heat transfer has considerable applications in different industries such as designing of heat exchanger, nuclear reactor cooling, control system for spacecraft and designing of microelectronics cooling. As the surfaces of two metals contact each other, this issue becomes so crucial. Thermal contact resistance is one of the key physical parameters in heat transfer of mentioned surfaces. Measuring the experimental value of thermal contact resistance in laboratory is highly expensive and difficult. As an alternative, numerical modeling methods could be engaged. In this study, Inverse problem method solution is utilized as a proper method for estimation of thermal contact resistance value. In this order, three different configurations (flat-flat, flat-cylinder, and cylinder-cylinder) were utilized in two steady and unsteady state conditions to predict the value of thermal contact resistance. In conclusion, the final results establish the fact that the inverse problem method solution can predict thermal contact resistance values between contacting surfaces.