Optimal control of stretching process of solar arrays on spacecraft using wavelet expansion method

The optimal attitude control problem of spacecraft during its solar arrays stretching process is discussed in the present paper. By using the theory of wavelet analysis in control algorithm, the discrete orthonormal wavelet function is introduced into the optimal control problem, the method of wavelet expansion is substituted for the classical Fourier basic function. An optimal control algorithm based on wavelet analysis is proposed. The effectiveness of the wavelet expansion approach is shown by numerical simulation. This work is supported by the National Natural Science Foundation of China.     

Optimal control of a spacecraft with a solar sail

Analysis of the results indicates that:

Optimal limited-rate slewing of a flexible spacecraft

The paper presents an efficient method of finding the optimal program control for the reorientation of a spacecraft with flexible appendages at a limited slewing rate. The appendages are incorporated into the mathematical model based on the quasistatic approximation. The problem is solved analytically by parametrizing the functional of a multipoint boundary-value problem. The optimal solution is illustrated graphically for different parts of the attainability domains     

基于输入成型的挠性航天器自适应姿态控制（英文）

针对快速调姿挠性航天器的姿态控制问题,提出一种基于输入成型的自适应姿态控制方法,解决俯仰、偏航、滚转三通道的控制耦合问题,抑制航天器挠性振动、提高姿态控制精度。首先,建立了考虑弹性振动、执行器故障及惯量不确定性的挠性航天器姿态动力学模型。基于欧拉轴角提出一种姿态机动参考轨迹设计方法,避免了俯仰、偏航、滚转三通道的耦合问题。通过多模输入成型方法对姿态机动参考轨迹进行修正,以抑制航天器弹性振动。采用自适应容错控制方法对修正后的参考轨迹进行跟踪,以实现挠性航天器快速姿态机动任务。数值仿真结果表明,与传统PD姿态控制方法相比,所提出的基于输入成型的挠性航天器自适应姿态控制方法可将残余弹性振动幅值和姿态控制偏差降低两个数量级,验证了该方法的有效性。     

Influence of flexible solar arrays on vibration isolation platform of control moment gyroscopes

A high-performance vibration isolation platform (VIP) has been developed for a cluster of control moment gyroscopes (CMGs). CMGs have long been used for satellite attitude control. In this paper, the influence of flexible solar arrays on a passive multi-strut VIP of CMGs for a satellite is analyzed. The reasonable parameters design of flexible solar arrays is discussed. Firstly, the dynamic model of the integrated satellite with flexible solar arrays, the VIP and CMGs is conducted by Newton-Euler method. Then based on reasonable assumptions, the transmissibility matrix of the VIP is derived. Secondly, the influences of the flexible solar arrays on both the performance of the VIP and the stability of closed-loop control systems are analyzed in detail. The parameter design limitation of these solar arrays is discussed. At last, by selecting reasonable parameters for both the VIP and flexible solar arrays, the attitude stabilization performance with vibration isolation system is predicted via simulation.     

工程结构优化的进化策略-高斯过程协同优化方法

针对采用仿生全局优化方法进行复杂工程结构优化时数值计算量浩大导致的计算代价过高的公开问题,将自适应协方差矩阵进化策略(CMAES)全局优化算法、高斯过程(GP)机器学习技术与有限元方法相结合,提出了基于自适应协方差矩阵进化策略-高斯过程协同优化算法(CMAES-GP)的结构优化方法。该方法利用全局寻优性好且寻优效率高的CMAES算法进行全局最优搜索,当搜索进入局部寻优阶段时,采用回归性能优秀的GP模型对适应度函数进行动态拟合,进而利用GP模型替代有限元分析进行个体适应度评价,以减小局部寻优阶段的有限元重分析次数,从而实现有效降低工程结构优化计算代价的目的。算例研究表明,与传统结构优化方法相比较,本文方法具有全局性好、计算效率高的优点。     

Passivity-based control for a flexible spacecraft in the presence of disturbances

The attitude regulation control problem for flexible spacecraft is investigated in this paper. Two extended PD+variable structure controllers are proposed using passivity-based control technique instead of sliding mode control approach. The first controller is a basic one, while the second one is an extension of the first one which relaxes the bound requirement for the external disturbances. In the presence of model uncertainties and external disturbances, both controllers presented in this research can make the flexible spacecraft UGAS (uniformly globally asymptotically stable). By virtue of related analysis tools, stability of the proposed controllers is proven theoretically. Numerical simulations are also included to demonstrate the performance of the developed controllers.     

A fast stable control strategy based on system energy for a planar single-link flexible manipulator

Nonlinear Dynamics - This paper presents a stable control strategy based on system energy for a Planar Single-Link Flexible Manipulator (PSLFM) to quickly realize its control objective, which is to...     

Attitude tracking control of flexible spacecraft with large amplitude slosh

This paper is focused on attitude tracking control of a spacecraft that is equipped with flexible appendage and partially filled liquid propellant tank. The large amplitude liquid slosh is included by using a moving pulsating ball model that is further improved to estimate the settling location of liquid in microgravity or a zero-g environment. The flexible appendage is modelled as a three-dimensional Bernoulli–Euler beam, and the assumed modal method is employed.A hybrid controller that combines sliding mode control with an adaptive algorithm is designed for spacecraft to perform attitude tracking. The proposed controller has proved to be asymptotically stable. A nonlinear model for the overall coupled system including spacecraft attitude dynamics,liquid slosh, structural vibration and control action is established. Numerical simulation results are presented to show the dynamic behaviors of the coupled system and to verify the effectiveness of the control approach when the spacecraft undergoes the disturbance produced by large amplitude slosh and appendage vibration. Lastly, the designed adaptive algorithm is found to be effective to improve the precision of attitude tracking.     

Optimal control of a rigid spacecraft programmed motion without angular velocity measurements

This paper considers the problem of optimal controlling a spacecraft programmed motion without its angular velocity measurements. An optimal control law that stabilizes this programmed motion and minimizes the cost that transfers the spacecraft from arbitrary initial state to the programmed state is obtained as a function of the kinematics attitude parameters and their estimates as well as the angle of programmed rotation. The stabilizing properties of the proposed controllers are proved using Liapunov techniques. Numerical simulation study is presented.     

Robust fixed-time attitude stabilization control of flexible spacecraft with actuator uncertainty

Nonlinear Dynamics - A robust fixed-time control framework is presented to stabilize flexible spacecraft’s attitude system with external disturbance, uncertain parameters of inertia, and...     

Torque control strategy for a parallel hydraulic hybrid vehicle

Hydraulic hybrid system is an important branch of hybrid technology, which has the advantage of high power density and the ability to accept the high rates/high frequencies of charging and discharging, therefore hydraulic hybrid technology is well suited for off-road vehicles and heavy-duty trucks. Relatively lower energy density and complicated coordinating operation between two power sources require a special energy control strategy to maximize the fuel saving potential. This paper presents a new configuration of parallel hydraulic hybrid vehicle (PHHV) to improve the braking energy regenerated potential and engine work efficiency. Based on the analysis of optimal energy distribution for the proposed PHHV over a representative urban driving cycle, a fuzzy torque control strategy based on the vehicle load changes is developed to real-time control the energy distribution for the proposed PHHV. Simulation results demonstrate that the proposed PHHV with torque control strategy takes advantage of the high power density and efficiency characteristics of the hydraulic hybrid system, minimizes the disadvantages of low energy density and effectively improves the fuel economy of PHHV.     

Optimal control of attitude for coupled-rigid-body spacecraft via Chebyshev-Gauss pseudospectral method

The attitude optimal control problem(OCP) of a two-rigid-body spacecraft with two rigid bodies coupled by a ball-in-socket joint is considered. Based on conservation of angular momentum of the system without the external torque, a dynamic equation of three-dimensional attitude motion of the system is formulated. The attitude motion planning problem of the coupled-rigid-body spacecraft can be converted to a discrete nonlinear programming(NLP) problem using the Chebyshev-Gauss pseudospectral method(CGPM). Solutions of the NLP problem can be obtained using the sequential quadratic programming(SQP) algorithm. Since the collocation points of the CGPM are Chebyshev-Gauss(CG) points, the integration of cost function can be approximated by the Clenshaw-Curtis quadrature, and the corresponding quadrature weights can be calculated efficiently using the fast Fourier transform(FFT). To improve computational efficiency and numerical stability, the barycentric Lagrange interpolation is presented to substitute for the classic Lagrange interpolation in the approximation of state and control variables. Furthermore, numerical float errors of the state differential matrix and barycentric weights can be alleviated using trigonometric identity especially when the number of CG points is large. A simple yet efficient method is used to avoid sensitivity to the initial values for the SQP algorithm using a layered optimization strategy from a feasible solution to an optimal solution. Effectiveness of the proposed algorithm is perfect for attitude motion planning of a two-rigid-body spacecraft coupled by a ball-in-socket joint through numerical simulation.     

Control strategy of optimal deployment for spacecraft solar array system with initial state uncertainty

A control strategy combining feedforward control and feedback control is presented for the optimal deployment of a spacecraft solar array system with the initial state uncertainty. A dynamic equation of the spacecraft solar array system is established under the assumption that the initial linear momentum and angular momentum of the system are zero. In the design of feedforward control, the dissipation energy of each revolute joint is selected as the performance index of the system. A Legendre pseudospectral method (LPM) is used to transform the optimal control problem into a nonlinear programming problem. Then, a sequential quadratic programming algorithm is used to solve the nonlinear programming problem and offline generate the optimal reference trajectory of the system. In the design of feedback control, the dynamic equation is linearized along the reference trajectory in the presence of initial state errors. A trajectory tracking problem is converted to a two-point boundary value problem based on Pontryagin’s minimum principle. The LPM is used to discretize the two-point boundary value problem and transform it into a set of linear algebraic equations which can be easily calculated. Then, the closed-loop state feedback control law is designed based on the resulting optimal feedback control and achieves good performance in real time. Numerical simulations demonstrate the feasibility and effectiveness of the proposed control strategy.     

Fault-tolerant sliding mode attitude control for flexible spacecraft under loss of actuator effectiveness

In this paper, a novel fault-tolerant attitude control synthesis is carried out for a flexible spacecraft subject to actuator faults and uncertain inertia parameters. Based on the sliding mode control, a fault-tolerant control law for the attitude stabilization is first derived to protect against the partial loss of actuator effectiveness. Then the result is extended to address the problem that the actual output of the actuators is constrained. It is shown that the presented controller can accommodate the actuator faults, even while rejecting external disturbances. Moreover, the developed control law can rigorously enforce actuator-magnitude constraints. An additional advantage of the proposed fault-tolerant control strategy is that the control design does not require a fault detection and isolation mechanism to detect, separate, and identify the actuator faults on-line; the knowledge of certain bounds on the effectiveness factors of the actuator is not used via the adaptive estimate method. The associated stability proof is constructive and accomplished by the development of the Lyapunov function candidate, which shows that the attitude orientation and angular velocity will globally asymptotically converge to zero. Numerical simulation results are also presented which not only highlight the ensured closed-loop performance benefits from the control law derived here, but also illustrate its superior fault tolerance and robustness in the face of external disturbances when compared with the conventional approaches for spacecraft attitude stabilization control.     

Distributed adaptive tracking control of multiple flexible spacecraft under various actuator and measurement limitations

This paper investigates the distributed leader–follower tracking problem for a team of flexible spacecraft over an undirected communication network with uncertain parameters subject to various actuator and measurement limitations. Assuming that at least one team member can receive information from the virtual leader, three scenarios are considered: (i) all the states of the flexible spacecraft can be completely measured and driven, (ii) only the rigid part of the flexible spacecraft can be driven with full state feedback and (iii) only the rigid part of the flexible spacecraft can be measured and driven. In the first case, a continuous adaptive control law is designed by building a unified architecture based on the linear-in-parameter property. In the second case, a distributed adaptive control algorithm is developed with a discontinuous parameter update law by treating the team of flexible spacecraft as two cascading subsystems. In the third case, a distributed adaptive control law is established with feedback from the generalized coordinates, generalized velocities and generalized accelerations of the rigid part of the spacecraft. It is theoretically proved that the closed-loop systems under the three designed adaptive control laws are all convergent to the target states. Finally, three numerical examples are presented to illustrate the effectiveness of the three proposed control laws.     

Dynamic stability of a flexible spacecraft in the presence of nonlinear resonances

Dnepropetrovsk (Ukraine). Translated from Prikladnaya Mekhanika, Vol. 28, No. 11, pp. 69–75, November, 1992.