Rigid body attitude tracking without angular velocity feedback

In this paper, we revisit the classical problem of attitude tracking for a rigid body. The interesting difference in the formulation is the assumption that only attitude measurements are available. We proceed to construct globally stabilizing control laws in terms of a minimal set of three-dimensional kinematic parameters that enable the rigid body to track any specified trajectory without requiring angular velocity measurements. The results presented here complement and extend some recent developments available for the nonminimal case of Euler parameters (quaternions).     

基于旋转矩阵描述的航天器无角速度测量姿态跟踪无源控制

利用系统无源性和旋转矩阵性质研究无角速度测量下的姿态跟踪控制问题. 为了避免姿态参数的奇异性和模糊性, 提出基于三维特殊正交群(SO(3)) 的控制策略. 首先利用旋转矩阵建立姿态跟踪误差方程, 然后分析了系统的内在无源性, 从而揭示了闭环系统的稳定性. 当角速度无法获得时, 利用新的无源滤波提出一种无角速度测量控制律, 并给出了严格的Lyapunov 稳定性分析. 最后, 通过数值仿真验证了所提出的控制方法的有效性.

     

Attitude control of spacecraft simulator without angular velocity measurement

In this paper the attitude control of a spacecraft simulator using Reaction Wheels (RW) as the actuators is investigated. The main goal of the current study is to bring the RWs to the rest at the end of the maneuver without angular velocity measurement. A modified feedback linearization controller is applied by considering the Euler angles of the simulator as the output and the RWs angular momentums as the internal state variables. The stability of the proposed controller and the internal dynamics is analyzed using Lyapunov theory. Two modified sliding mode observers are designed to estimate the angular velocities of the spacecraft attitude control subsystem simulator. The proposed observers do not use the control input and the detailed knowledge of the model and thus it can be implemented easily. The global stability of the system is proved. The proposed controller and observers are finally evaluated numerically and experimentally on an attitude spacecraft simulator.     

Marginalized particle filter for spacecraft attitude estimation from vector measurements

An algorithm based on the marginalized particle filters （MPF） is given in details in this paper to solve the spacecraft attitude estimation problem： attitude and gyro bias estimation using the biased gyro and vector observations. In this algorithm, by marginalizing out the state appearing linearly in the spacecraft model, the Kalman filter is associated with each particle in order to reduce the size of the state space and computational burden. The distribution of attitude vector is approximated by a set of particles and estimated using particle filter, while the estimation of gyro bias is obtained for each one of the attitude particles by applying the Kalman filter. The efficiency of this modified MPF estimator is verified through numerical simulation of a fully actuated rigid body. For comparison, unscented Kalman filter （UKF） is also used to gauge the performance of MPE The results presented in this paper clearly derfionstrate that the MPF is superior to UKF in coping with the nonlinear model.     

Marginalized particle filter for spacecraft attitude estimation from vector measurements

An algorithm based on the marginalized particle filters (MPF) is given in details in this paper to solve the spacecraft attitude estimation problem: attitude and gyro bias estimation using the biased gyro and vector observations. In this algorithm, by marginalizing out the state appearing linearly in the spacecraft model, the Kalman filter is associated with each particle in order to reduce the size of the state space and computational burden. The distribution of attitude vector is approximated by a set of particles and estimated using particle filter, while the estimation of gyro bias is obtained for each one of the attitude particles by applying the Kalman filter. The efficiency of this modified MPF estimator is verified through numerical simulation of a fully actuated rigid body. For comparison, unscented Kalman filter (UKF) is also used to gauge the performance of MPF. The results presented in this paper clearly demonstrate that the MPF is superior to UKF in coping with the nonlinear model.     

Spacecraft attitude control using magnetic actuators

The problem of inertial pointing for a spacecraft with magnetic actuators is addressed and an almost global solution to the problem is obtained by means of static attitude and rate feedback. A local solution based on dynamic attitude feedback is also presented. Simulation results demonstrate the practical applicability of the proposed approach.     

基于DDFC的航天器姿态控制器设计方法

对高精度在轨航天器姿态控制问题进行了研究,提出了一个基于直接动态反馈补偿(direct dynamics feedback compen-sation,DDFC)的航天器姿态控制方法.方法使得系统的输入量为执行机构的转速,也就是使得执行机构工作在速率模式,可以避免高频噪声对控制系统的影响,提高系统的可靠性.仿真结果表明,方法可以有效地克服模型参数不确定等非理想因素,航天器的姿态角以较高的精度快速跟踪目标值,最终偏差满足要求,系统性能良好.这种方法物理概念清晰、数学过程简明,便于工程实现.     

Disturbance observer-based quadrotor attitude tracking control for aggressive maneuvers

In this paper, a disturbance observer-based quadrotor attitude controller for aggressive maneuvering is presented. The controller is made up of the cascade connection between two control-loops: an outer quaternion-based attitude control-loop and an inner disturbance observer-based angular velocity tracking control-loop. The disturbance observer is designed to estimate and compensate for the Coriolis term and the external disturbances. It is shown that, for fast maneuvers, the disturbance observer needs to take into account the motor dynamics. This allows to notably increase the observer bandwidth, leading to significant improvements in the disturbance rejection capabilities. The stability of the resulting closed-loop is analyzed. Also, different simulations and flight tests are carried out to validate the main results, showing an outstanding tracking performance when aggressive attitude maneuvers are being executed, even in the presence of strong disturbances such as suspended payloads.     

空间飞行器姿态控制器设计与仿真

该文对空间飞行器姿态系统设计了一种变结构控制器。首先,应用误差四元数法描述空间飞行器姿态运动。同时,在考虑结构摄动和外界扰动的界未知情况下,其基本方法是采用模糊规则优化滑模变结构控制的设计,并且能够在线对结构摄动和外界扰动的界进行估计,使得系统轨迹既能快速趋近滑动面又能降低抖振,从而提高了变结构控制系统的品质。仿真结果表明,该系统对模型：不确定性和外来干扰具有较强的鲁棒性,同时避免了变结构系统固有的抖振问题,性能令人满意。     

Position tracking in delayed bilateral teleoperators without velocity measurements

This work considers the control of nonlinear bilateral teleoperators with variable time delays without the need of velocity measurements. The recently proposed Immersion and Invariance observer is used to obtain an exponentially convergent estimate of the unmeasured velocities. Under the classical assumption that the human operator and the environment define passive, velocity to force, maps, it is proved that with this observer and a Proportional plus damping controller, velocities and position error are globally bounded. Finally, in the case that the human operator and the environment do not exert forces on the local and remote manipulators, respectively, global asymptotic convergence of velocities and of position error to zero is achieved. The theoretical results are sustained with simulations using a couple of two degrees‐of‐freedom nonlinear manipulators. Copyright © 2015 John Wiley & Sons, Ltd.     

Synchronization of multiple autonomous underwater vehicles without velocity measurements

In this paper,we investigate the synchronization control of multiple autonomous underwater vehicles (AUVs),considering both state feedback and output feedback cases.Treating multiple AUVs as a graph,we define the tracking error of each AUV with both its own tracking error and the relative position errors with respect to its neighbors taken into account.Lyapunov analysis is used to derive the control law for each AUV.For the output feedback case,a passive filter is used to compensate for the unknown relative velocity errors among AUVs,and an observer is employed to estimate the velocity of the AUV itself.Rigid mathematical proof is provided for the proposed algorithms for both state feedback and output feedback cases.Simulations are provided to demonstrate the effectiveness of the proposed approach.It is shown that,the synchronization error is smaller in the case of considering the relative errors between AUVs than in the case of considering the tracking error of the single AUV only.     

基于MATLAB模糊控制器的预测跟踪控制仿真分析

该文主要针对空间飞行器大角度机动调整的姿态控制方面的问题,从空间飞行器的动力学模型出发,讨论了利用强跟踪滤波进行无控预报的预测技术,以及以此预报信息对空间飞行器大角度机动调整进行姿态解耦的控制技术。同时,在预测控制中发现：姿态角跟踪路径的指数衰减因子随着其偏差不同及时调整时,控制系统收敛较快。因此,进一步讨论了利用NATLMB模糊控制器来调整预测控制的指数衰减因子的模糊预测控制方法。通过仿真计算,该方法具有收敛快,稳定性高等特点。     

微小型航天器无角速度测量姿态控制

研究微小型航天器姿态跟踪在角速度不可测量以及控制力矩受限情况下的的控制方法。首先基于无源性原理,仪依赖姿态测量,建立一个类似PD控制的方法。为了让初始状态和角度误差始终在合理的控制范围内,对误差函数加入跳变规则,从而获得一种混合控制方法;然后利用Lyapunov原理证明了闭环系统的全局渐进稳定性;最后通过仿真与已有方法进行比较研究,验证了控制方法的有效性,即使初始速度估计误差和初始角度误差很大,依然可以控制。     

Spacecraft formation reconfiguration with collision avoidance

In this paper we present a behavioral control solution for reconfiguration of a spacecraft formation using the Null-Space Based (NSB) concept. The solution is task based, and aims to reconfigure and maintain a rigid formation while avoiding collisions between spacecraft. A model of relative translation is derived, together with a passivity-based sliding surface controller which globally stabilizes the equilibrium point of the closed-loop system. The NSB control method is implemented by giving each task different priorities and then calculating desired velocity and a Jacobian matrix for each spacecraft and each task. The velocity vector for each task is then projected into the null-space for higher prioritized tasks to remove conflicting velocity components. Simulation results are presented, showing that each spacecraft moves into the predefined formation without breaking any rules for the higher priority tasks, and all collisions are avoided.     

Nonlinear formation control strategies for agents without relative measurements under heterogeneous networks

This paper proposes cooperative control protocols for a group of unmanned vehicles to make a stable formation around a maneuvering target. The control protocols are proposed on the basis of heterogeneous communication networks, which represents more challenging and generalized situations. Two different scenarios are considered. Separate control protocols are developed for each case. In both scenarios, agents do not have relative position, velocity, and acceleration measurements as feedback. In the first scenario, each agent uses its own position and velocity measurement in a consensus algorithm. In the second scenario, each agent needs only its own position information for the consensus algorithm. For both protocols, agents compute virtual estimates of a target's position and velocity and exchange these among the neighbors. Three different communication networks are used for exchanging two virtual estimates calculated by each agent and a time derivative of one virtual estimate. Each interagent communication network is represented by a fixed, undirected, and connected graph. Furthermore, it is considered that at least one agent receives the position, velocity, and acceleration information of the maneuvering target. It is not necessary that the agent receiving the target's position and the agent receiving the velocity and/or the acceleration information of the target be the same. However, the target does not receive any information about any agent. Stability of the formation is analyzed by using Barbalat's lemma. It is also shown that, despite the large difference in received information, the acceleration of the agents remains bounded for all time. The performance of the proposed formation control protocols is illustrated through numerical simulations.     

飞行仿真技术新的发展及其在航天领域中应用

本文综述和分析近十年来飞行仿真技术新的发展及其在航天器中的应用。这些新技术包括：仿真机，多自由度运动模拟器，全轨道目标模拟器，人工智能和虚拟现实技术等。在航天器具体应用方面包括：高精度长寿命卫星姿态控制仿真、挠性和多体的大型结构仿真、 交会对接仿直人、飞行器再入和实时故障分析和对策仿真等。     

Asymptotic stabilization of the position of a rigid body with fixed point without velocity measurements

The problem of stabilization of a rigid body with a fixed point in reference to its velocity and position is considered. It is assumed that the rigid body is controlled by three external torques. The proposed controlling torques need neither the measurements of the velocity nor the information about the inertial parameters. Such a control may be realized by the on-line solution of the auxiliary differential equations.The stability of the closed loop nonlinear system is established by means of the Lyapunov function and Barbashin's theorem. The proposed control may be applied to stabilize the satellites controlled by the reactive jets.     

Task-space fully distributed tracking control of networked uncertain robotic manipulators without velocity measurements

This paper investigates the task-space synchronised tracking problem of uncertain networked manipulators interconnected on directed graphs, where the dynamic leader is available to only a subset of followers and followers have only local interaction. A fully distributed tracking controller is proposed, which is composed of a distributed desired trajectory estimator, a joint-space velocity observer and an adaptive cooperative control algorithm. Specifically, the proposed controller allows each manipulator to track the dynamic leader solely using local task-space position measurements. Besides, in the presence of both dynamic and kinematic uncertainties, the adaptive cooperative control algorithm indeed improves the system's robustness. Furthermore, it is strictly proved that the proposed control scheme ensures that both task-space position and velocity tracking errors converge to zero as time tends to infinity. In the end, simulation results are provided to demonstrate the effectiveness of the proposed controller.     

Global partial-state feedback and output-feedback tracking controllers for underactuated ships

New global partial-state feedback and output-feedback control schemes for tracking control of an underactuated surface ship without sway force available are presented. For the case of partial-state feedback, we do not require measurements of the ship sway and surge velocities, while, for the case of output-feedback, none of the ship velocities are required for feedback. The reference trajectory to be tracked can be a curve including a straight-line. Global nonlinear coordinate changes are introduced to transform the ship dynamics to a system affine in the ship velocities to design observers to globally exponentially estimate unmeasured velocities. The controllers’ development is based on Lyapunov's direct method and backstepping technique, and utilizes the passive property of ship dynamics and their interconnected structure. Numerical simulations are provided to illustrate the effectiveness of the proposed controllers.