Control Of Space Vehicles Research Articles

A nonlinear optimal control approach for autonomous reentry space vehicles

Nonlinear control for autonomous reentry space vehicles has been a topic of intensive research during the last years in the area of aerospace science and technology. The associated dynamic model is obtained by expressing position variables and orientation angles of the space vehicle in different coordinate frames, namely an earth-fixed, an earth rotating and a body fixed frame. In this article, a nonlinear optimal control approach is proposed for the dynamic model of reentry space vehicles. It is proven that the longitudinal motion dynamic model of reentry space vehicles is differentially flat and a flatness-based controller is designed about it. Next, in the nonlinear optimal control approach, the dynamic model of the reentry space vehicle undergoes approximate linearization around a temporary operating point that is recomputed at each time-step of the control method. The linearization relies on Taylor series expansion and on the associated Jacobian matrices. For the linearized state-space model of the reentry space vehicle a stabilizing optimal (H-infinity) feedback controller is designed. This controller stands for the solution to the nonlinear optimal control problem under model uncertainty and external perturbations. To compute the controller’s feedback gains an algebraic Riccati equation is repetitively solved at each iteration of the control algorithm. The stability properties of the control method are proven through Lyapunov analysis. The proposed nonlinear optimal control approach achieves fast and accurate tracking of reference setpoints under moderate variations of the control inputs and a minimum dispersion of energy.

Demonstration And Analysis of The Guiding Control System for Aerospace Crafts

The development of space vehicle guidance and control systems gradually becomes a focus in recent research as a key to space vehicles’ information processing and control in the space environment. In general, among the popular methods in G&C systems, artificial intelligence-based algorithms contain a wide prospect. This study offers descriptions of the current methods in AI-based algorithms, proposed challenges involved in this field, and described the recent achievements in solving these issues. To be specific, the basic descriptions of the controlling systems as well as the various state-of-art machine learning approaches that are suitable for the G&C system are demonstrated and analyzed including ANN, DNN, RL, SVM, DRL, etc. According to the analysis, the challenges as well as the drawbacks of the advanced scenarios are estimated as well as propose the future prospects to improve the performance of landing. Overall, these results shed light on guiding further exploration of aerospace vehicles.

Numerical Analysis of the Kinematic Accuracy of the Hermetic Harmonic Drive in Space Vehicles

The unfriendly-for-humans environment of space causes automatic or remotely controlled vehicles and devices to be used for its research. In robot and manipulator control systems, and also in mechanisms adjusting antennas and photovoltaic panels, the hermetic harmonic drive can be used. A special advantage of this type of gear is the ability to transfer power to an isolated space separated by physical barriers from external influences. Therefore, the purpose was to design gears that will allow achieving the highest kinematic precision for control systems by simultaneously maintaining their hermetics. The article presented an analysis of the kinematic accuracy of harmonic hermetic drives powered by four different types of wave generators. The generators used differed in construction but also caused other deformations of the flexspline. The calculation of angular displacement was prepared in the computer program Abaqus. The simulations were performed on virtual models of a complete harmonic hermetic drive using the finite element method (FEM). The results from the analysis allow the most favorable solution to be applied to the Mars rover drive or spacecraft control system. It was determined for which of the wave generators the kinematic accuracy is the highest and how high the backlash exists for the reversing rotation. Finally, the proposed design will allow one to increase the accuracy of the working movements and control of space vehicles while ensuring a minimal influence of the external ambient.

Ground control system for distant space vehicles

The demand for research of a promising ground-based long-range spacecraft control complex, which has great capabilities not only in the control of deep space vehicles, but also in carrying out fundamental and applied radio astronomical research. Much attention is paid to the analysis of the requirements to the radio complex, which must be fulfilled to realize the possibility of several directions of scientific research and, first of all: planetary radiolocation: interferometry with ultra-long baselines; radio-reflecting; radioastronomy. Based on the analysis of the state of the ground control system of deep spacecraft, the directions of its development on the basis of modernization of existing facilities are revealed, and the prospects for the use of new technologies for the development of deep space on flight paths to the Moon, Mars, other celestial bodies of the solar system, the objects of alien and interplanetary infrastructure are shown.

New Construction Solutions of Gear Using in Space Vehicle Control Systems

Outer space presents construction challenges that are completely different from the terrestrial environment. They should be characterized by high resilience and indefinite durability because there is no possibility of repair during exploitation. There are drives in spacecraft control systems that are necessary to move solar panels, robotic arms, and manipulators, and also to position antennas. In these devices, they have applications where harmonic drives are characterized by high kinematic accuracy but relatively low mechanical strength. The analysis presented in this study is aimed at modifying the shape of the harmonic drive to increase its durability and reliability. In this study, the most vulnerable damage element of the harmonic drive is the flexspline. The calculation was carried out using the finite element method (FEM) in the computer program ABAQUS. A standardized shape was tested as a basic model, and several other design solutions were proposed. For each of them, the mechanical strength was determined, which allowed the selection of the most preferred shape for the flexspline of the harmonic drive. The specific environmental requirements of the expectations for sand for gear used in spacecraft control systems were included in the analysis. The selected construction solutions of the flexspline allow for longer work and transfer of greater loads by the harmonic driver than the solutions currently used. The choice of harmonic driver design shape allows for failure-free and maintenance-free work in space vehicle control systems.

Adaptive neural fault-tolerant control for output-constrained attitude tracking of unmanned space vehicles

The challenging problem of attitude tracking control for unmanned space vehicles (USVs) subject to actuator faults and output constraints is addressed in this study. A novel adaptive neural fault-tolerant controller is proposed by integrating the neural networks (NNs) and barrier Lyapunov function (BLF) with the backstepping technique. Two NNs are adopted to approximate the uncertain nonlinear terms caused by unknown attitude dynamics and actuator faults, respectively. Moreover, the BLF is introduced to tackle the output constraints. It is strictly proved that all the closed-loop error signals are uniformly ultimately bounded under the proposed controller. Totally, the proposed adaptive neural fault-tolerant controller has the following two distinctive features. (1) The proposed controller is model-free and can still be applicable even when the USV attitude dynamic model is completely unknown in advance. (2) The proposed controller can guarantee the attitude tracking error always within the predefined output constraints even in the presence of actuator faults and thus ensuring safety. Finally, the excellent tracking performance of the proposed controller is verified through numerical simulations and comparisons.

Adaptive Robust Tracking Control for Near Space Vehicles with Multi-Source Disturbances and Input–Output Constraints

In this paper, considering the simultaneous influence of multi-source disturbances, system modeling uncertainties and input–output constraints, an adaptive robust attitude tracking control scheme is proposed for near space vehicles (NSVs) which is expressed as a stochastic nonlinear system. A multi-dimensional Taylor polynomial network (MTPN) is utilized to handle the system uncertainties, and the nonlinear disturbance observer (NDO) based on MTPN is designed to estimate the external disturbances. Furthermore, by constructing the auxiliary system to tackle the input saturation and introducing the Tan-type barrier Lyapunov function (TBLF) to solve the output constraint, the constrained control strategy can be obtained. Combining with backstepping control (BC) technique and stochastic control method, an adaptive robust stochastic control scheme is developed based on NDO, MTPN, and auxiliary system, and the closed-loop system stability in the sense of probability is analyzed based on stochastic Lyapunov stability theory. Finally, numerical simulations further demonstrate the feasibility of the proposed tracking control scheme.

Sensor hybridization using neural networks for rocket terminal guidance

The Guidance, Navigation and Control (GNC) of air and space vehicles, including artillery rockets, has been one of the spearheads of research in the aerospace field in recent times. Increasing the accuracy of these ballistic projectiles is the major goal. Using Global Navigation Satellite Systems (GNSS) and inertial navigation systems, accuracy may be detached from range. However, during the terminal stage of flight, when movement is governed by highly changing nonlinear forces and moments, GNC strategies based on these systems cause enormous errors in determining attitude and position. These effects can be diminished using additional sensors, independent of jamming and cumulative errors, such as the quadrant photo-detector semi-active laser. This paper proposes a novel non-linear hybridization algorithm, which is based on neural networks, to feed GNC systems while complexity and costs are reduced. It fuses the information from multi-sensor signals, such as GNSS, inertial navigation systems, and semi-active lasers, to predict the line of sight vector, which joins the target and the projectile and drives the flight. As compared to traditional approaches, the use of a neural network presents the advantage that once the network is trained, it is no longer necessary to know the physical-mathematical foundations that govern the dynamics of flight. Instead, it is the network that learns the dynamics. Six-degree-of-freedom non-linear simulations, which are based on real flight dynamics, are used to train the neural networks in the hybridization process. Once training is finished, the approach is tested and simulated together with modified proportional navigation techniques and control methods. Monte Carlo analysis is conducted to determine the suitability of the closed-loop performance across a full spectrum of uncertainty conditions regarding launch, sensor performance, atmospheric, and thrust.

Applying Neural Networks in Aerial Vehicle Guidance to Simplify Navigation Systems

The Guidance, Navigation and Control (GNC) of air and space vehicles has been one of the spearheads of research in the aerospace field in recent times. Using Global Navigation Satellite Systems (GNSS) and inertial navigation systems, accuracy may be detached from range. However, these sensor-based GNC systems may cause significant errors in determining attitude and position. These effects can be ameliorated using additional sensors, independent of cumulative errors. The quadrant photodetector semiactive laser is a good candidate for such a purpose. However, GNC systems’ development and construction costs are high. Reducing costs, while maintaining safety and accuracy standards, is key for development in aerospace engineering. Advanced algorithms for getting such standards while eliminating sensors are cornerstone. The development and application of machine learning techniques to GNC poses an innovative path for reducing complexity and costs. Here, a new nonlinear hybridization algorithm, which is based on neural networks, to estimate the gravity vector is presented. Using a neural network means that once it is trained, the physical-mathematical foundations of flight are not relevant; it is the network that returns dynamics to be fed to the GNC algorithm. The gravity vector, which can be accurately predicted, is used to determine vehicle attitude without calling for gyroscopes. Nonlinear simulations based on real flight dynamics are used to train the neural networks. Then, the approach is tested and simulated together with a GNC system. Monte Carlo analysis is conducted to determine performance when uncertainty arises. Simulation results prove that the performance of the presented approach is robust and precise in a six-degree-of-freedom simulation environment.

Study on the Transverse Elastic Vibration Equation and the Generalized Aerodynamic Force of Space Vehicle

In order to avoid divergence of space vehicle attitude, structural elastic movements should be taken into consideration in the control system design. Space vehicle structure generally has a large length-diameter ratio, the corresponding rolling and longitudinal modal with higher natural frequency has a slight impact on the design of the control system, while the transverse elastic modal with lower natural frequency including pitching and yawing should be paid more attention in the design of space vehicle control system. In this paper, the influence of elastic vibration on the design of attitude control system of space vehicle is analyzed firstly. Then the transverse elastic vibration equation of spacecraft and the calculation method of generalized aerodynamic force are studied. Furthermore, the equation of elastic vibration considering the coupling effect of aerodynamic force between pitching and yawing control channels is proposed and the engineering calculation method of generalized aerodynamic force for typical stations in spacecraft is improved. The research results can provide significant reference for the design of the new generation of spacecraft control system.

Switching disturbance rejection attitude control of near space vehicles with variable structure

A switching disturbance rejection attitude control law is proposed for a near space vehicle (NSV) with variable structure. The multiple flight modes, system uncertainties and disturbances of the NSV are taken into account based on switched nonlinear systems. Compared with traditional backstepping design methods, the proposed method utilizes the added integrals of attitude angle and angular rate tracking errors to further decrease the tracking errors. Moreover, to reduce the computation complexity, a rapid convergent differentiator is employed to obtain the derivative of the virtual control command. Finally, for disturbance rejection, based on the idea from the extended state observer (ESO), two disturbance observers are designed by using non-smooth functions to estimate the disturbances in the switched nonlinear systems. All signals of the closed-loop system are proven to be uniformly ultimately bounded under the Lyapunov function framework. Simulation results demonstrate the effectiveness of the proposed control scheme.

АНАЛІЗ ВПЛИВУ ОБСЯГУ ГІДРОАКУМУЛЯТОРУ НА ПРАЦЕЗДАТНІСТЬ ДВОФАЗНОГО КОНТУРУ ТЕПЛОПЕРЕНОСУ СИСТЕМИ ТЕРМОРЕГУЛЮВАННЯ КОСМІЧНОГО АПАРАТУ

The world trend in the development of space vehicles is the expansion of their functionality, which leads to an increase in the power consumption, most of which is allocated in the elements of spacecraft equipment in the form of heat. To remove heat from the equipment elements, transfer it to the heat sink subsystem with subsequent removal to outer space, and also to maintain the required temperature mode of the equipment operation, thermal control systems are used. The increase in the power-to-weight ratio and linear dimensions of new spacecraft in conditions of severe design and weight-and-size limitations leads to a complication and growth of the mass of the system of thermal control of space vehicles. At present, thermal control systems for space vehicles based on single-phase fluid heat transfer loops are used. For space vehicles with an energy consumption of more than 10 kW, thermal control systems based on two-phase heat transfer loops are the most promising. They have a number of advantages in comparison with single-phase thermal control systems: two-phase heat transfer loops can transfer much more heat per unit of flow; the use of heat transfer during boiling allows to maintain the temperature of objects practically on the whole extent of the circuit close to the saturation temperature; the mass of the thermal control system with a two-phase coolant is substantially less than with a single-phase coolant , and the energy consumption of the pump for pumping the coolant is negligible. In this paper, a two-phase heat transfer loop performances are analyzed. The process of increasing the thermal power up to the maximum under conditions of full filling of the accumulator is considered. The study was carried out on an experimental two-phase heat transfer loop with an ammonia. Transient processes associated with an increase in the thermal load from 73 % to 100 % are considered. The obtained data correlate well with the results of the calculation. Based on the results of the analysis, conclusions were made on the operability and stability of the spacecraft thermal control system under these conditions, and recommendations on the choice of the volume of the accumulator are given.

Adaptive sliding mode backstepping control for near space vehicles considering engine faults

A fault tolerant control methodology based adaptive sliding mode (ASM) backstepping is proposed for near space vehicle (NSV) attitude control system under engine faults. The proposed scheme combined adaptive backstepping with the sliding mode control strategy could guarantee the system's stability and track desired signals under external disturbances and engine faults. Firstly, attitude mode description and the engine faulty model are given. Secondly, a nominal control law is designed. Thirdly, a sliding mode observer is given later in order to estimate both the information of engine faults and external disturbances. An adaptive sliding mode technology based on the previous nominal control law is developed via updating faulty parameters. Finally, analyze the system's fault-tolerant performance and reliability through experiment simulation, which verifies the proposed design of fault-tolerant control can tolerate engine faults, as well as the strong robustness for external disturbance.

Active disturbance rejected predictive functional control for space vehicles with RCS

Reaction control system (RCS) is a powerful and efficient actuator for space vehicles attitude control, which is typically characterized as a pulsed unilateral effector only with two states (off/on). Along with inevitable internal uncertainties and external disturbances in practice, this inherent nonlinear character always hinders space vehicles autopilot from pursuing precise tracking performance. Compared to most of pre-existing methodologies that passively suppress the uncertainties and disturbances, a design based on predictive functional control (PFC) and generalized extended state observer (GESO) is firstly proposed for three-axis RCS control system to actively reject that with no requirement for additional fuel consumption. To obtain a high fidelity predictive model on which the performance of PFC greatly depends, the nonlinear coupling multiple-input multiple-output (MIMO) flight dynamics model is parameterized as a state-dependent coefficient form. And based on that, a MIMO PFC algorithm in state space domain for a plant of arbitrary orders is deduced in this paper. The internal uncertainties and external disturbances are lumped as a total disturbance, which is estimated and cancelled timely to further enhance the robustness. The continuous control command synthesised by above controller-rejector tandem is finally modulated by pulse width pulse frequency modulator (PWPF) to on-off signals to meet RCS requirement. The robustness and feasibility of the proposed design are validated by a series of performance comparison simulations with some prominent methods in the presence of significant perturbations and disturbances, as well as measurement noise.

Testing and analysis of a morphing radiator concept for thermal control of crewed space vehicles

Spacecraft designed for future missions must satisfy increasingly difficult thermal requirements. Crewed vehicles, in particular, must maintain a relatively constant temperature irrespective of external conditions; this is the role of the thermal control system (TCS). A TCS may be required to reject a higher heat load to warm environments and a lower heat load to cold environments, necessitating a high turndown ratio, often on the order of 12:1. This work presents a novel radiator concept that employs shape memory alloys (SMAs) to geometrically reconfigure the radiator, enabling a lighter TCS for space exploration vehicles. The thermally driven morphing effect allows passive control of both radiator view of space and primary surface emissivity. Thermal modeling of the morphing radiator predicts a turndown ratio ranging from 12:1 to 35:1 independent of the other aspects of TCS configuration. A system-level mass analysis shows that by enabling a single-loop architecture, this design could reduce the TCS mass by approximately 25%. Two benchtop prototypes provide proof-of-concept demonstrations of the radiator’s principles of operation. Additionally, an analysis framework is developed for the first time that is capable of simulating the unique and highly nonlinear thermomechanical coupling present in the radiator. The framework provides high-fidelity results of both the stress in the radiator as well as its thermal behavior.

Robust tracking control of near space vehicles with input and output saturation

A robust adaptive tracking control scheme is proposed for the attitude model of the near space vehicles (NSVs) with input saturation, output constraint, unknown external disturbances and modeling uncertainties. Firstly, a second-order sliding model disturbance observer is adopted to estimate the compound disturbance including system uncertainties and external disturbances. Then, the constraints of the output are equivalent to that of the tracking errors which are transformed into unconstrained signals by selecting an appropriate transforming function. Moreover,an auxiliary system is designed to solve the input saturation problem, and the robust adaptive controller is developed for the transformed system by using the backstepping technology. Meanwhile, the boundness of the tracking errors and closed-loop system’s internal signals is rigorously proved. Finally, the developed controller is applied to the attitude control of a NSV, and the simulation results are presented to validate the effectiveness of the proposed robust adaptive control scheme.

The automated system for technological process of spacecraft's waveguide paths soldering

The paper solves the problem of automated process control of space vehicles waveguide paths soldering by means of induction heating. The peculiarities of the induction soldering process are analyzed and necessity of information-control system automation is identified. The developed automated system makes the control of the product heating process, by varying the power supplied to the inductor, on the basis of information about the soldering zone temperature, and stabilizing the temperature in a narrow range above the melting point of the solder but below the melting point of the waveguide. This allows the soldering process automating to improve the quality of the waveguides and eliminate burn-troughs. The article shows a block diagram of a software system consisting of five modules, and describes the main algorithm of its work. Also there is a description of the waveguide paths automated soldering system operation, for explaining the basic functions and limitations of the system. The developed software allows setting of the measurement equipment, setting and changing parameters of the soldering process, as well as view graphs of temperatures recorded by the system. There is shown the results of experimental studies that prove high quality of soldering process control and the system applicability to the tasks of automation.

Transient characteristics of flow boiling in large micro-channel heat exchangers

This study investigates both time-averaged and transient characteristics of large area micro-channel evaporators incorporated into an R-134a vapor compression loop that simulates thermal control for future space vehicles. The loop contains two separate micro-channel evaporators, one to simulate heat acquisition from the spacecraft crew and the other from the avionics. Both evaporators feature parallel 1×1-mm2 micro-channels, with the smaller crew evaporator yielding relatively low qualities, and the larger avionics evaporator both low and high qualities. Heat transfer measurement and high speed video are used to investigate variations of heat transfer coefficient with quality for different mass velocities and heat fluxes, as well as transient fluid flow and heat transfer behavior. Relatively low qualities in the crew evaporator are dominated by slug flow and the nucleate boiling mechanism. On the other hand, the avionics evaporator produces different flow regimes and heat transfer mechanisms depending on quality range, with low qualities associated with slug flow and dominated by nucleate boiling, and high qualities by annular flow and convective boiling. Further increases in quality trigger incipient dryout of the annular film and transition to mist flow. An important transient phenomenon that influences both fluid flow and heat transfer is a liquid wave composed of remnants of liquid slugs from the slug flow regime. The liquid wave serves to replenish dry wall patches in the slug flow regime and to a lesser extent the annular regime. Two-phase flow in the two evaporators shows clear signs of parallel-channel instability.

Adaptive neural prescribed performance tracking control for near space vehicles with input nonlinearity

In this paper, an adaptive neural tracking controller with prescribed performance is developed for near space vehicles (NSVs) with unknown parametric uncertainties, external disturbances and input nonlinearities including input saturation and dead-zone. By placing the right inverse of the dead-zone before the input nonlinearity, the serial input nonlinearity consisting of input saturation and dead-zone can be regarded as an equivalent input saturation which is solved by a common constrained control method. To guarantee the prescribed performance of the closed-loop system including the transient and steady-state performance, the constrained prescribed performance is changed into unconstrained transformation error using error transformed technology. Meanwhile, the radial basis function neural networks (RBFNNs) are adopted to tackle the system uncertainties. Then, using the auxiliary system and backstepping technology, an adaptive tracking control scheme is proposed, and all the closed-loop system signals are proved to be bounded. Finally, extensive simulations are given for the attitude motion of the NSV to illustrate the effectiveness of the developed adaptive neural control scheme.

Fault Tolerant Control for Near Space Vehicles with Input Saturation Using Disturbance Observer and Neural Networks

In this paper, a fault tolerant sliding mode control scheme is derived for near space vehicles with actuator faults, unknown external disturbance, system uncertainty and input saturation based on disturbance observer and neural networks (NNs). To deal with actuator faults, the radial basis function NNs are employed. The nonlinear disturbance observer is designed to eliminate the effect of external disturbance and system uncertainty. To tackle input saturation, the known bound of saturation is used to design the control law such that the control input is within the bounded range. Lyapunov stability analysis shows that the closed-loop system is stable and all closed-loop signals are uniformly ultimately bounded. Simulation results demonstrate the effectiveness of the developed fault tolerant control scheme, when actuator faults, unknown external disturbance, system uncertainty and input saturation appear simultaneously.