Control Effects and Material Parameters of Piezoelectric Smart Moment Controllers

The control using piezoelectric smart moment (PSM) controllers for seismically excited structures was studied.The radical principle of PSM controller was introduced firstly and then the different formulae of control shear force for different structures were derived with the stiffness ratio of columns taken into consideration.With the active control algorithm based on the theory of modern optimal control,this study proposes a simulative computation on the frame structure and mill structure respectively,and the results indicate that the installation of this smart controller with proper parameters can significantly reduce seismic responses of different structures. The optimal parameters of the damper can be identified through a parameter study.

Direct Yaw Moment Control for Distributed Drive Electric Vehicle Handling Performance Improvement

For a distributed drive electric vehicle（DDEV） driven by four in-wheel motors, advanced vehicle dynamic control methods can be realized easily because motors can be controlled independently, quickly and precisely. And direct yaw-moment control（DYC） has been widely studied and applied to vehicle stability control. Good vehicle handling performance： quick yaw rate transient response, small overshoot, high steady yaw rate gain, etc, is required by drivers under normal conditions, which is less concerned, however. Based on the hierarchical control methodology, a novel control system using direct yaw moment control for improving handling performance of a distributed drive electric vehicle especially under normal driving conditions has been proposed. The upper-loop control system consists of two parts： a state feedback controller, which aims to realize the ideal transient response of yaw rate, with a vehicle sideslip angle observer; and a steering wheel angle feedforward controller designed to achieve a desired yaw rate steady gain. Under the restriction of the effect of poles and zeros in the closed-loop transfer function on the system response and the capacity of in-wheel motors, the integrated time and absolute error（ITAE） function is utilized as the cost function in the optimal control to calculate the ideal eigen frequency and damper coefficient of the system and obtain optimal feedback matrix and feedforward matrix. Simulations and experiments with a DDEV under multiple maneuvers are carried out and show the effectiveness of the proposed method： yaw rate rising time is reduced, steady yaw rate gain is increased, vehicle steering characteristic is close to neutral steer and drivers burdens are also reduced. The control system improves vehicle handling performance under normal conditions in both transient and steady response. State feedback control instead of model following control is introduced in the control system so that the sense of control intervention to drivers is relieved.

Dual-steering mode based on direct yaw moment control for multi-wheel hub motor driven vehicles:Theoretical design and experimental assessment

One of the main challenges for multi-wheel hub motor driven vehicles is the coordination of individual drivetrains to improve mobility and stability in the steering process.This paper proposes a dual-steering mode based on direct yaw moment control for enhancing vehicle steering ability in complex environ ments.The control system is designed as a hierarchical structure,with a yaw moment decision layer and a driving force distribution layer.In the higher-level layer,the objective optimization function is con-structed to obtain the slip steering ratio,which represents the degree of vehicle slip steering in the dual-steering mode.Ayaw moment controller using active disturbance rejection control theory is designed for continuous yaw rate control.When the actual yaw rate of the vehicle deviates from the reference yaw rate obtained by the vehicle reference model and the slip steering ratio,the yaw moment controller isactuated to determine the yaw moment demand for vehicle steering.In the lower-level layer,there is a torque distribution controller based on distribution rules,which meets the requirement of yaw moment demand without affecting the total longitudinal driving force of the vehicle.For verifying the validity and feasibility of the dual-steering mode,simulations were conducted on the hardware-in-loop real-time simulation platfomm.Additionally,corresponding real vehicle tests were carried out on an eight-wheel prototype vehicle.Test results were generally consistent with the simulation results,thereby demon-strating that the proposed dual-steering mode reduces steering radius and enhances the steering per-formance of the vehicle.

Research on Direct Yaw Moment Control Strategy of Distributed-Drive Electric Vehicle Based on Joint Observer

Combined with the characteristics of the distributed-drive electric vehicle and direct yaw moment control,a double-layer structure direct yaw moment controller is designed.The upper additional yaw moment controller is constructed based on model predictive control.Aiming at minimizing the utilization rate of tire adhesion and constrained by the working characteristics of motor system and brake system,a quadratic programming active set was designed to optimize the distribution of additional yaw moments.The road surface adhesion coefficient has a great impact on the reliability of direct yaw moment control,for which joint observer of vehicle state parameters and road surface parameters is designed by using unscented Kalman filter algorithm,which correlates vehicle state observer and road surface parameter observer to form closed-loop feedback correction.The results show that compared to the“feedforward+feedback”control,the vehicle’s error of yaw rate and sideslip angle by the model predictive control is smaller,which can improve the vehicle stability effectively.In addition,according to the results of the docking road simulation test,the joint observer of vehicle state and road surface parameters can improve the adaptability of the vehicle stability controller to the road conditions with variable adhesion coefficients.

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 flexi- ble 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.

Model predictive control of rigid spacecraft with two variable speed control moment gyroscopes

In this paper, an attitude maneuver control problem is investigated for a rigid spacecraft using an array of two variable speed control moment gyroscopes （VSCMGs） with gimbal axes skewed to each other. A mathematical model is constructed by taking the spacecraft and the gyroscopes together as an integrated system, with the coupling interaction between them considered. To overcome the singular issues of the VSCMGs due to the conventional torque-based method, the first-order derivative of gimbal rates and the second-order derivative of the rotor spinning velocity, instead of the gyroscope torques, are taken as input variables. Moreover, taking external disturbances into account, a feedback control law is designed for the system based on a method of nonlinear model predictive control （NMPC）. The attitude maneuver can be realized fast and smoothly by using the proposed controller in this paper.

Underactuated spacecraft angular velocity stabilization and three-axis attitude stabilization using two single gimbal control moment gyros

Angular velocity stabilization control and attitude stabilization control for an underactuated spacecraft using only two single gimbal control moment gyros （SGCMGs） as actuators is investigated. First of all, the dynamic model of the underactuated spacecraft is established and the singularity of different configurations with the two SGCMGs is analyzed. Under the assumption that the gimbal axes of the two SGCMGs are installed in any direction, and that the total system angular momentum is not zero, a state feedback control law via Lyapunov method is designed to globally asymptotically stabilize the angular velocity of spacecraft. Under the assumption that the gimbal axes of the two SGCMGs are coaxially installed along anyone of the three principal axes of spacecraft inertia, and that the total system angular momentum is zero, a discontinuous state feedback control law is designed to stabilize three-axis attitude of spacecraft with respect to the inertial frame. Furthermore, the singularity escape of SGCMGs for the above two control problems is also studied. Simulation results demonstrate the validity of the control laws.

OPTIMAL CONTROL OF BRAKING MOMENT FOR A WHEEL AND TYRE

in the design of the antiskid braking system (ABS) of an aircraft, the braking moment is one of the most important parameters, because it influences not only the deceleration and the taxiing distance of an aircraft, but also the strength and the fatigue life of the landing gear. Furthermore, the determination of braking moment will be concerned in the reasonableness of the demands proposed for the material design of a brake. For this reason, through setting up the mechanical model of a wheel and tyre under taxiing and braking, dynamic simulations on the optimal closed-loop control of braking moment are carried out by means of the nonlinear control theory. The simulation results show that the difference between the real output of the ABS and the expected one can tend to the minimum under the optimal control. And also, this optimal control can guarantee the braking moment to change smoothly.

Application of Ultrasonic Motor to Control of Moment Gyroscope Gimbal Servo System

Attitude control system is one of the most important subsystems in a spacecraft.As a key actuator,the control moment gyroscope(CMG)mainly determines the performance of attitude control system.Whereas,the control accuracy and output torque smoothness of the CMG depends more on its gimbal servo system.Considering the constraints of size,mass and power consumption for a small satellite,here,a mini-CMG is designed,in which the gimbal servo system is driven by an ultrasonic motor.The good performances of the CMG are obtained by both the ultrasonic motor and the rotary inductosyn.The direct drive of gimbal improves its dynamic performance,with the output bandwidth above 20 Hz.The angular and speed closed-loop control obtains the 0.02°/s gimbal rate,and the output torque resolution better than 2×10^(-3) N·m.The ultrasonic motor provides 1.0N·m self-lock torque during power-off,with 12arc-second position accuracy.

Control of flight forces and moments by flapping wings of model bumblebee

The control of flight forces and moments by flapping wings of a model bumblebee is studied using the method of computational fluid dynamics. Hovering flight is taken as the reference flight： Wing kinematic parameters are varied with respect to their values at hovering flight. Moments about （and forces along） x, y, z axes that pass the center of mass are computed. Changing stroke amplitude （or wingbeat frequency） mainly produces a vertical force. Changing mean stroke angle mainly produces a pitch moment. Changing wing angle of attack, when down- and upstrokes have equal change, mainly produces a vertical force, while when down- and upstrokes have opposite changes, mainly produces a horizontal force and a pitch moment. Changing wing rotation timing, when dorsal and ventral rotations have the same timing, mainly produces a vertical force, while when dorsal and ventral rotations have opposite timings, mainly produces a pitch moment and a horizontal force. Changing rotation duration has very small effect on forces and moments. Anti-symmetrically changing stroke amplitude （or wingbeat frequency） of the contralateral wings mainly produces a roll moment. Anti-symmetrically changing angles of attack of the contralateral wings, when down- and upstrokes have equal change, mainly produces a roll moment, while when down- and upstrokes have opposite changes, mainly produces a yaw moment. Anti-symmetrically changing wing rotation timing of the contralateral wings, when dorsal and ventral rotations have the same timing, mainly produces a roll moment and a side force, while when dorsal and ventral rotations have opposite timings, mainly produces a yaw moment. Vertical force and moments about the three axes can be separately controlled by separate kinematic variables. A very fast rotation can be achieved with moderate changes in wing kinematics.

Attitude control of a rigid spacecraft with one variable-speed control moment gyro

Nonlinear controllability and attitude stabilization are studied for the underactuated nonholonomic dynamics of a rigid spacecraft with one variable-speed control moment gyro （VSCMG）, which supplies only two internal torques. Nonlinear controllability theory is used to show that the dynamics are locally controllable from the equilibrium point and thus can be asymptotically stabilized to the equilibrium point via time-invariant piecewise continuous feedback laws or time-periodic continuous feedback laws. Specifically, when the total angular momentum of the spacecraft-VSCMG system is zero, any orientation can be a controllable equilib- rium attitude. In this case, the attitude stabilization problem is addressed by designing a kinematic stabilizing law, which is implemented through a nonlinear proportional and deriva- tive controller, using the generalized dynamic inverse （GDI） method. The steady-state instability inherent in the GDI con- troller is elegantly avoided by appropriately choosing control gains. In order to obtain the command gimbal rate and wheel acceleration from control torques, a simple steering logic is constructed to accommodate the requirements of attitude sta- bilization and singularity avoidance of the VSCMG. Illustrative numerical examples verify the efficacy of the proposed control strategy.

STUDY ON THE CONTROL SYSTEM OF HYDRAULIC MOMENT-ADJUSTED BRAKE FOR DOWNWARD BELT CONVEYOR

Having analyzed the drawbacks on the design of control system of hydraulic moment-adjusted brake system, the author presents a closed loop control system in the process of start and braking of the conveyer. On the basis of the concept of the critical time and the critical ac-celeration and its deductions, the working mode of the conveyer can be identified and controlled in feedback, furthermore, thus realize the process of soft start. ln the deceleration process, the author points out the problems that exist in the present control system and sets forward the control process that acted by the combined function of brake moment of motor and the drag torque of hy-draulic brake at the beginning of deceleration, it will further improved reliability of conveyor sys-tem.

采用SGCMG的两轮单辙平台自平衡控制技术

针对以自行车、摩托车为代表的两轮单辙平台的自然不稳定问题,采用单框架控制力矩陀螺(SGCMG)为平衡控制机构,研究两轮单辙平台不同工况下自平衡控制算法。分析两轮单辙平台横向力矩,推导横滚转动动力学方程,并根据不同状态误差设计了增益调度PID控制器;建立轮-地接触点模型,修正曲线运动时目标横滚角,减小反馈静差,获得更好的动态响应;以前叉转向趋势预估未来时刻转向角度与目标平衡横滚角度,提前调整姿态以重力矩抵消离心力矩,模拟人骑行时的预判压弯行为。相关算法经仿真验证与实车测试,可在静止与曲线运动等工况下保持动态平衡,效果良好,表明了算法的有效性。

新能源汽车电机节能直接横摆力矩控制研究

为了降低电动汽车在行驶过程中的电机能量消耗,采用直接横摆力矩控制方法,并对车辆的车轮力矩和电机功率变化进行仿真验证。建立了车辆模型简图,根据牛顿第二定律推导出车辆转向运动方程式。针对传统两轮等力矩控制方法进行改进,提出了一种主动直接横摆力矩控制方法,推导出车辆连续行驶和转弯过程中的力矩分配律。利用转弯过程中车辆车轮的力矩变化来调节电机的功率变化,从而降低车辆电机的能量消耗。采用MATLAB软件对车辆横摆角速度、车轮力矩和电机能量消耗进行仿真,与两轮等力矩控制方法进行对比。结果显示:采用两轮等力矩控制方法,车辆横摆角速度跟踪误差较大,车轮力矩变化幅度较小,自适应调节能力较差,导致电机能量消耗较多;采用直接横摆力矩控制方法,车辆横摆角速度跟踪误差较小,车轮力矩变化幅度较大,自适应调节能力较好,使电机能量消耗较少。采用直接横摆力矩控制方法,能够自适应调整车轮力矩的变化,从而达到降低电机能量消耗目的。

机械弹性电动轮驱动车辆横摆稳定性协调控制

针对匹配机械弹性电动轮(MEEW)车辆的横摆稳定性控制问题,提出一种基于主动前轮转向(AFS)与直接横摆力矩控制(DYC)的稳定性协调控制策略。为修正车辆行驶过程中的前轮转角输入,设计了基于微分平坦与RBF神经网络的AFS控制器,从而提高车辆的转向能力。针对AFS控制器在极限工况下易失效的缺陷,引入基于线性二次型调节器(LQR)的直接横摆力矩控制算法,并依照轴荷比分配四轮力矩。最后,依据机械弹性电动轮的质心侧偏角-质心侧偏角速度相平面图划分稳定域,实现AFS与DYC的协调控制。通过Matlab/Simulink和Carsim进行联合仿真,结果表明:所提出的AFS控制算法在高速高附着工况下有良好的稳定控制性能,但在高速、低附着极限工况下控制效果受到影响。而AFS/DYC协调控制策略效果较好,跟踪精度优于单一控制器,质心侧偏角和横摆角速度的最大跟踪误差仅为3.03°和1.82(°)/s,可保证汽车在极限工况下转向时的横摆稳定性。

应用变速控制力矩陀螺的航天器姿态自适应控制

为提高敏捷挠性航天器在轨连续机动的快速性和高稳定性,应用变速控制力矩陀螺(variable speed control moment gyroscopes,VSCMGs)作为姿态控制执行机构,提出了一种将观测器与自适应控制结合的姿态控制律与VSCMGs复合操纵律。考虑到机动过程中挠性模态及精确惯量不可知,采用模态观测器和转动惯量估计器对不可测的状态或参数进行辨识,辨识结果用于精确估计前馈补偿力矩,利用Lyapunov分析方法证明了闭环控制系统的稳定性。鉴于VSCMGs实际使用的力矩分配能力、避奇异能力、轮速平衡能力与末态框架角定位能力,分别设计了加权伪逆操纵律与3种对应的零运动。基于雅可比矩阵条件数提出了末态框架角的优选方法,给出了VSCMGs零运动在机动过程不同阶段的部署方案。结果表明:通过连续姿态机动数值仿真验证了所提算法的有效性;VSCMGs在连续机动过程中平滑切换模式,在不同的机动阶段实现了相应功能。模态观测值和惯量估计值在多次机动后收敛至真值附近,经过参数辨识后的控制器使航天器在机动末端更快更稳地达到指向精度要求。

CMG框架超低速无电流环矢量控制研究

针对控制力矩陀螺框架在超低速工况下存在转速测量精度低、多源扰动力矩及非线性摩擦等问题,提出了基于无电流环矢量控制的超低速驱动控制方法。首先,建立超低速工况下的框架电机的机电模型,设计了无电流环磁场矢量控制器(field-oriented control,简称FOC);其次,针对转速测量精度的问题,设计了转速观测器作为反馈环节。结果表明,与方波驱动法相比,该方法无换相转矩,提高了转速测量精度,且在面对多源扰动、非线性摩擦时具有鲁棒性。仿真和实验结果验证了该方法的可行性和有效性。

基于载荷发散控制的旋翼高原气动设计

直升机高原重载快速飞行时,旋翼处于大总距状态,更易发生旋翼失速,导致操纵载荷显著增加。为解决这一问题,本文提出了基于载荷发散控制的旋翼高原气动设计方法。传统直升机旋翼设计中,性能、噪声、空机重量控制等要求是常规的设计目标,对拉力性能影响不大的旋翼失速问题往往被忽视,但其对高原直升机来说影响重大。文中构建了旋翼动力学模型,并据此计算了桨叶动态气动力矩系数C_(m)随单位实度拉力系数C_(T)/σ的变化曲线。以C_(m)突增作为旋翼失速基本判据,分析不同前进比μ下C_(m)突增点,形成旋翼失速载荷发散单位实度拉力系数C_(T)/σ包线,以此作为旋翼高原气动设计边界之一。运用该方法设计的AC313大型民用直升机的理论分析和试飞结果均表明,该设计可极大地减少旋翼在高原典型飞行剖面发生旋翼失速的风险,有效控制旋翼操纵系统的载荷,增加操纵系统使用寿命,提升飞行舒适性,很大程度上保证了飞行安全,在直升机的全生命周期使用中作用积极。

基于后轮转向与制动协同的车辆操控性可调控制方法研究

为解决后轮转向与制动协同的车辆操控性控制面临的转向不足、控制效果难以标定、控制器设计复杂难于工程应用等问题,提出一种后轮转向和制动的作用强度均可自由调节的控制方法,应用非线性模型设计与前馈/反馈结构,根据设计参数调节控制强度,达到按照期望程度降低车辆质心侧偏角、加快横摆响应速度的效果,并兼顾不足转向度、燃油经济性等指标。此外,该方法提供了基于可调参数进行车辆操控性调校的方法,具有精度高、运算量小、无需质心侧偏角估计及便于标定等优点。

四驱电动汽车变附着路面行驶操稳性控制研究

针对四轮驱动电动汽车行驶时路面峰值附着系数和附着利用率变化的问题,提出利用直接横摆力矩控制提高操纵稳定性的控制策略。该策略采用分层控制,上层控制器负责目标车速的追踪、滑移率调整力矩的计算、以及根据行驶危险程度实现对质心侧偏角和横摆角速度的协调控制,下层控制器包括以轮胎利用率最优为目标的分配算法及集成滑移率控制的分配算法,根据滑移率大小实时切换。Carsim-Simulink联合仿真结果表明,在对开路面行驶时,相比于转矩平均分配控制策略,该控制策略能够使车辆具有良好操稳性的同时保持各车轮处于最佳滑移率区间内,有效改善了车辆性能。