Singularity avoidance of CMGs by virtual actuators

An implementable and practical steering law of control moment gyros (CMGs) to avoid singularity is addressed in this paper. The singularity strategy of CMGs revised in this paper is based on a simple but practical virtual actuator methodology. It is known that in a special case of singularity and torque requirement, the virtual CMGs can provide perfect command torque without torque error, which can be proven analytically. In this paper, much extensive analysis is accomplished to provide the performance of the virtual actuator concept, which can avoid the singular configuration of CMGs with possibly smaller control torque error than the conventional singularity robustness method. Finally, the steering law based on the virtual actuator concept is demonstrated by numerical simulations.     

Controllability of Spacecraft Attitude Using Control Moment Gyroscopes

This technical note describes an application of nonlinear controllability theory to the problem of spacecraft attitude control using control moment gyroscopes (CMGs). Nonlinear controllability theory is used to show that a spacecraft carrying one or more CMGs is controllable on every angular momentum level set in spite of the presence of singular CMG configurations, that is, given any two states having the same angular momentum, any one of them can be reached from the other using suitably chosen motions of the CMG gimbals. This result is used to obtain sufficient conditions on the momentum volume of the CMG array that guarantee the existence of gimbal motions which steer the spacecraft to a desired spin state or rest attitude.      

参数不确定SGCMG系统的自适应操纵律设计

在单框架控制力矩陀螺(SGCMG)系统操纵律的设计中,如果考虑框架伺服特性,往往假设系统的物理参数是确切已知的.为消除参数的不确定性对操纵性能的影响,设计了一种自适应操纵律.该操纵律可对系统物理参数进行在线估计,并能根据航天器姿态控制给出的角动量(或力矩)指令,直接计算出每个框架驱动系统所需的控制力矩.由于操纵律没有算法奇异,在SGCMG系统不出现运动奇异的情况下,可使操纵误差渐近收敛至零.同时,该操纵律对系统参数变化具有良好的适应性,且形式简单,易于实现.对应用在航天器上的某SGCMG系统的仿真结果表明,上述操纵律是可行的.     

The parameters optimisation design for variable speed control momentum gyroscopes

Control momentum gyroscopes (CMGs) have many advantages over other actuators for the attitude control of a spacecraft. Compared with the single-gimbal control moment gyroscopes (SGCMGs), the mass and power of the flywheel of variable-speed control moment gyroscopes (VSCMGs) are greatly increased. In this paper, a new solving strategy of singularity problem is proposed, which concludes the exchangeable momentum and steering law, and the parameters of VSCMGs are designed based on the constraint of singular problem. The configuration characteristics of VSCMGs with the constraint of upper and lower bounds of the flywheel regulation speed are revealed. The steering characteristics of weighted pseudo-inverse with null motion (WPINM) are analysed, then the flywheel torque requirement of WPINM is evaluated based on the geometry theory. At last, the parameter design problem of VSCMGs is cast as multi-objectives and bi-level programming problem. The bi-level programming is transformed into a single-level programming problem by using of the Karush–Kuhn–Tucker condition. Finally, the intelligent algorithm of particle swarm optimisation is presented to solve the nonlinear multi-objective problem.     

大输出微控制力矩陀螺的设计

为了提高微控制力矩陀螺的输出力矩,提出了一种微型控制力矩陀螺的设计方案.所设计的微型控制力矩陀螺用角振动代替了传统控制力矩陀螺的转动,由转子角振动系统及框架角振动系统组成,实现了基于科氏效应的控制力矩输出.通过框架角振动系统的电极位置居中设置及在玻璃上挖槽的设计,避免了静电吸合现象.四个完全相同的微型控制力矩陀螺构成一...     

An Adaptive Control Technique for Motion Synchronization by On-line Estimation of a Recursive Least Square Method

This article presents an adaptive technique to tune controller gains for the motion synchronization of two gimbal systems by using a recursive least square method in the real-time fashion. In the master-slave configuration, the slave gimbal system follows the master’s motion while the master tracks the reference. In order for the slave gimbal system to synchronize with the motion of the master gimbal system, the dynamic difference between two systems is compensated by the controller gains. The controller gains of the slave are adaptively adjusted by the recursive least square method to cope with the deviation. The performances of three control schemes such as an independent PD control, a dependent torque control, and an RLS torque control scheme are evaluated by the experimental studies for the low cost gimbal systems. Experimental studies confirm that the RLS-based adaptive scheme actually outperforms by adjusting controller gains for the motion synchronization of the master and slave configuration.     

SGCMG系统非奇异路径规划

单框架控制力矩陀螺 (SGCMG)是应用在航天器上的一类惯性执行机构 .在航天器的姿态控制中 ,通常采用三个或以上的SGCMG ,以满足三轴控制的要求 .但是 ,当多个SGCMG协调工作时 ,系统会出现奇异现象 ,并极大地降低了SGCMG系统的操纵性能 .为回避SGCMG系统的奇异 ,本文提出了一种新的奇异回避条件 ,并通过对非线性规划中当前Kuhn Tucker乘子值的估计 ,得到了冗余SGCMG系统闭合形式的非奇异路径 ,而不需繁杂的数值求解 .正是由于这些新的手段 ,使得本文提出的算法不仅具有良好的奇异回避性能 ,而且形式简单 ,易于实现 .对金字塔构形的 4 SGCMG系统的仿真结果表明 ,上述算法是可行的 .     

欠驱动刚体航天器姿态运动规划的遗传算法

研究欠驱动刚体航天器姿态的非完整运动规划问题．航天器利用3个动量飞轮可以控制其姿态和任意定位,当其中一轮失效,航天器姿态通常表现为不可控．在系统角动量为零的情况下,系统的姿态控制问题可转化为无漂移系统的运动规划问题．基于优化控制理论,提出了求解欠驱动刚体航天器的姿态运动控制遗传算法,并且数值仿真表明：该方法对欠驱动航天器姿态运动的控制是有效的．     

新型动态控制力矩陀螺操纵律设计

首先提出一类新型控制力矩陀螺(CMG)操纵律,改变使用静态数据求逆构造力矩分配矩阵的设计思路,利用近似的动态微分特性构造力矩分配矩阵,进而对新型操纵律奇异性进行分析.基于奇异分析结果,设计一种切换型CMG奇异回避策略,使CMG能在首选力矩分配矩阵接近奇异时,使用非奇异的备选分配矩阵将之替换.仿真结果表明,所设计的CMG操纵律具有较高的计算精度,同时具有一定的奇异适应性.     

Nonsingular predefined-time dynamic surface control of a flexible-joint space robot with actuator constraints

To achieve predefined-time trajectory tracking control of a flexible-joint space robot(FJSR) with actuator constraints, a nonsingular predefined-time dynamic surface control scheme is developed. The input saturation caused by actuator constraints is addressed via the designed predefined-time anti-saturation compensator. On this basis, two different control laws are designed for such high-order nonlinear systems by utilizing the backstepping technique, and a novel nonlinear filter is constructed to filter the virtual control signals, thus avoiding the “differential expansion” phenomenon. Moreover, a singularity-free auxiliary function is designed to solve the singularity issue generated by the derivative of fractional power terms in the predefined-time control algorithm framework. The closed-loop system is proven to be semi-globally predefined-timely uniformly ultimately bounded (SGPTUUB) via constructing the suitable Lyapunov function. The difference and effectiveness of the two designed control laws are illustrated by the conducted simulations. Both of them allow the FJSR system to track the desired trajectory in a reasonably predefined time.     

Research on nonlinear friction compensation of harmonic drive in gimbal servo-system of DGCMG

The purpose of this paper is to present our results in overcoming the influence of the nonlinear friction afforded by harmonic drive to the gimbal servo-system of double-gimbal control momentum gyro (DGCMG). The existence of compliance and oscillation inherent in harmonic drive systems, and the lack of any technical information on the internal dynamics of the transmission, make the development of friction compensation in harmonic drive system extremely challenging. In this paper, the modeling of nonlinear friction in harmonic drive gear transmission in gimbal servo-system of the DGCMG is proposed. The relationship among the nonlinear friction, the angular velocity and the angular position with an improved Coulomb-Viscous model is derived, and the experiments to identify the various parameters of the improved model are given. At last a feed-forward compensation controller based on the improved model is designed to carry out the friction compensation study.     

电动汽车方向盘绝对角位置传感器的研究

方向盘±720°绝对角位置的测量是轮式驱动电动汽车转矩协调控制解决方案的关键之一.通过16位处理器dsPIC30F6010A与两片TLES012通信,设计了一种基于iGMR的+720°绝对角位置非接触式传感器,并可通过外部中断设置方向盘的回正零点.给出了该传感器的具体实现方案,包括2个从动齿轮的齿数设计,绝对角位置的计...     

基于气动力矩和模型预测的LEO卫星角动量管理算法

为抑制气动力矩对近地轨道(LEO)卫星姿态控制系统的影响,改善卫星电磁环境,设计一种基于气动力矩和模型预测的LEO卫星角动量管理算法,利用气动力矩管理卫星角动量并通过磁力矩器辅助提高角动量管理效率和可靠性.利用所设计的角动量管理算法构建卫星姿态动力学的线性化模型和姿态控制律,预测角动量变化趋势;通过在卫星太阳阵常规运动上附加额外的小角度偏转,将LEO卫星主导摄动力矩的气动力矩转化为管理卫星角动量的控制力矩.仿真实验表明,与传统的角动量管理策略相比,所设计的角动量管理算法通过将气动力矩转化为角动量管理控制力矩,能够有效节省卫星角动量管理的消耗.此外,该算法在不增加物理机构的前提下可以作为卫星的备用角动量管理策略,能够显著增强卫星姿态系统的可靠性和鲁棒性.     

Attitude tracking control of a flexible spacecraft under angular velocity constraints

In this paper, a new technique is proposed for trajectory tracking of a flexible spacecraft subject to angular velocity constraints. The problem is addressed using an output to input saturation transformation (OIST) which converts the prescribed bounds into state-dependent saturations on the control input signals. It is shown that an interval observer can be used in combination with the OIST technique to ensure that the constraints remain satisfied despite unmeasured flexible modes and torque disturbances. Some realistic simulations conclude the paper and validate our approach.     

Synthesis of linear antenna array using flower pollination algorithm

Linear antenna array (LAA) design is a classical electromagnetic problem. It has been extensively dealt by number of researchers in the past, and different optimization algorithms have been applied for the synthesis of LAA. This paper presents a relatively new optimization technique, namely flower pollination algorithm (FPA) for the design of LAA for reducing the maximum side lobe level (SLL) and null control. The desired antenna is achieved by controlling only amplitudes or positions of the array elements. FPA is a novel meta-heuristic optimization method based on the process of pollination of flowers. The effectiveness and capability of FPA have been proved by taking difficult instances of antenna array design with single and multiple objectives. It is found that FPA is able to provide SLL reduction and steering the nulls in the undesired interference directions. Numerical results of FPA are also compared with the available results in the literature of state-of-the-art algorithms like genetic algorithm, particle swarm optimization, cuckoo search, tabu search, biogeography based optimization (BBO) and others which also proves the better performance of the proposed method. Moreover, FPA is more consistent in giving optimum results as compared to BBO method reported recently in the literature.

     

基于驾驶状态预测的人机力矩协同转向控制器设计

针对人机协同转向控制中对于驾驶员参与和驾驶员状态考虑较少这一问题,提出一种基于驾驶员状态预测的人机力矩协同(human-vehicle torque collaborative based on driver state prediction,HVTC-DSP)转向控制方法.该方法以力矩为人机交互接口,提高了驾驶员的参与程度;同时,在控制器设计过程中采用模型预测控制方法,将驾驶员状态考虑在内,对驾驶员状态进行预测.采用高精度车辆仿真软件veDYNA进行仿真验证,结果表明,与不考虑驾驶员状态的人机协同力矩(human-vehicle torque collaborative based on no driver state prediction,HVTC-NDSP)转向控制方法相比,所提方法可以使辅助力矩更好地跟随驾驶员动作,提高车辆转向性能,减小侧向位移偏差,同时对不同驾驶员也有较好的适应性.进而,以驾驶员下一步动作为参考,使驾驶员当前力矩尽可能接近下一步期望的力矩,在转向性能几乎不受影响的情况下,适当减轻驾驶员操作负担.     

基于力矩信息的拖拉机转向动态PID控制方法

针对拖拉机驾驶机器人自主转向系统在转向过程中的阻尼具有非线性和时变性的特点,同时为了提高转向系统的控制性能,设计了基于力矩信号检测的拖拉机转向控制系统,其由力矩传感器、STM32处理器、工控机、驱动器及直流电机等组成.首先通过仿真研究不同力矩时的最优PID控制参数,给出不同力矩时的最优PID参数规律,再通过力矩传感器检测的力矩信号动态调整PID参数来控制电机的转向.仿真及实验结果均表明,基于力矩信号反馈的拖拉机动态PID转向控制方法能够有效控制拖拉机的方向,响应快、超调小、适应性强.     

线控转向系统的转向盘力反馈控制策略研究

线控转向系统取消了转向盘和转向轮之间的机械连接,因而可以根据车况主动提供路感,提高车辆的操纵稳定性.首先研究了转向刚度力矩、由侧向加速度确定的转向盘回正力矩、由轮胎回正力矩确定的转向盘回正力矩、转向阻尼力矩等进行转向盘力反馈的四种力矩.然后,研究了四种组合的转向盘力反馈控制策略及其进行双纽线试验、蛇行试验的性能.结果表明,调整各种力反馈方案的相应参数可以获得低速时的转向轻便性和高速时的良好路感.     

Quasi-optimal deceleration of rotations of a rigid body with a moving mass in a resistive medium

The problem of time quasi-optimal deceleration of the rotations of a dynamically symmetric rigid body is studied. It is assumed that the body contains a point mass connected to it with a strong viscoelastic element (damper). The body is acted on by a small linear resistance torque of the medium that is proportional to the angular momentum and a small control torque bounded by an ellipsoidal domain. An approximate synthesis of control is proposed, and an asymptotic solution based on a procedure of averaging the precession motion over the phase is obtained; numerical integration is performed. The main properties of the quasi-optimal motion are determined.     

基于终端滑模控制的电动汽车转向稳定性研究

针对电动汽车转向时的稳定性问题,以双轮毂电机电动汽车为研究对象,利用线性二自由度车辆模型得到理想参数,提出了基于横摆角速度的终端滑模横摆力矩控制。同时利用Simulink搭建了整车七自由度的车辆模型,通过低速和高速两种情况来进行算法验证。仿真结果表明,上述算法相对于垂直载荷力矩控制和传统滑模控制而言,能够有效的减少目标参数趋于稳定的时间,抗干扰能力强。力矩分配之后输出力矩作用于轮毂电机,便可以有效的保证车辆运行转向时的安全性和稳定性。