Design and analysis of a new AUV’s sliding control system based on dynamic boundary layer

The new AUV driven by multi-vectored thrusters not only has unique kinematic characteristics during the actual cruise but also exists uncertain factors such as hydrodynamic coefficients perturbation and unknown interference of tail fluid,which bring difficult to the stability of the AUV’s control system.In order to solve the nonlinear term and unmodeled dynamics existing in the new AUV’s attitude control and the disturbances caused by the external marine environment,a second-order sliding mode controller with double-loop structure that considering the dynamic characteristics of the rudder actuators is designed,which improves the robustness of the system and avoids the control failure caused by the problem that the design theory of the sliding mode controller does not match with the actual application conditions.In order to avoid the loss of the sliding mode caused by the amplitude and rate constraints of the rudder actuator in the new AUV’s attitude control,the dynamic boundary layer method is used to adjust the sliding boundary layer thickness so as to obtain the best anti-chattering effects.Then the impacts of system parameters,rudder actuator’s constraints and boundary layer on the sliding mode controller are computed and analyzed to verify the effectiveness and robustness of the sliding mode controller based on dynamic boundary layer.The computational results show that the original divergent second-order sliding mode controller can still effectively implement the AUV’s attitude control through dynamically adjusting the sliding boundary layer thickness.The dynamic boundary layer method ensures the stability of the system and does not exceed the amplitude constraint of the rudder actuator,which provides a theoretical guidance and technical support for the control system design of the new AUV in real complex sea conditions.     

四轮独立驱动EV侧向稳定性H∞鲁棒容错控制

为解决参数不确定性四轮独立驱动电动汽车发生执行器及传感器故障时车辆侧向稳定性控制问题,提出一种H_∞鲁棒容错控制方法。运用故障矩阵函数引入车辆连续性故障,建立了考虑执行器及传感器故障的二自由度车辆参数不确定性动力学模型。运用线性矩阵不等式求解方法设计车辆侧向稳定性H_∞鲁棒容错控制器,保证车辆动力学系统渐近稳定性及抗干扰能力,实现控制系统H_∞鲁棒性能满足给定的干扰衰减指标。搭建CarSim与MATLAB/Simulink联合仿真实验平台,验证控制器的有效性。仿真实验表明,所设计H_∞鲁棒容错控制器能有效提升了车辆的侧向稳定性及安全性,对车辆故障具有良好的容错控制能力。     

Recurrent-neural-network-based identification of a cascade hydraulic actuator for closed-loop automotive power transmission control

By virtue of its ease of operation compared with its conventional manual counterpart, automatic transmissions are commonly used as automotive power transmission control system in today’s passenger cars. In accordance with this trend, research efforts on closed-loop automatic transmission controls have been extensively carried out to improve ride quality and fuel economy. State-of-the-art power transmission control algorithms may have limitations in performance because they rely on the steady-state characteristics of the hydraulic actuator rather than fully exploit its dynamic characteristics. Since the ultimate viability of closed-loop power transmission control is dominated by precise pressure control at the level of hydraulic actuator, closed-loop control can potentially attain superior efficacy in case the hydraulic actuator can be easily incorporated into model-based observer/controller design. In this paper, we propose to use a recurrent neural network (RNN) to establish a nonlinear empirical model of a cascade hydraulic actuator in a passenger car automatic transmission, which has potential to be easily incorporated in designing observers and controllers. Experimental analysis is performed to grasp key system characteristics, based on which a nonlinear system identification procedure is carried out. Extensive experimental validation of the established model suggests that it has superb one-step-ahead prediction capability over appropriate frequency range, making it an attractive approach for model-based observer/controller design applications in automotive systems.     

Active fault tolerant control based on interval type-2 fuzzy sliding mode controller and non linear adaptive observer for 3-DOF laboratory helicopter

In this paper, a robust controller for a three degree of freedom (3 DOF) helicopter control is proposed in presence of actuator and sensor faults. For this purpose, Interval type-2 fuzzy logic control approach (IT2FLC) and sliding mode control (SMC) technique are used to design a controller, named active fault tolerant interval type-2 Fuzzy Sliding mode controller (AFTIT2FSMC) based on non-linear adaptive observer to estimate and detect the system faults for each subsystem of the 3-DOF helicopter.The proposed control scheme allows avoiding difficult modeling, attenuating the chattering effect of the SMC, reducing the rules number of the fuzzy controller.Exponential stability of the closed loop is guaranteed by using the Lyapunov method. The simulation results show that the AFTIT2FSMC can greatly alleviate the chattering effect, providing good tracking performance, even in presence of actuator and sensor faults.     

A single sensor and single actuator approach to performance tailoring over a prescribed frequency band

Restricted sensing and actuation control represents an important area of research that has been overlooked in most of the design methodologies. In many practical control engineering problems, it is necessitated to implement the design through a single sensor and single actuator for multivariate performance variables. In this paper, a novel approach is proposed for the solution to the single sensor and single actuator control problem where performance over any prescribed frequency band can also be tailored. The results are obtained for the broad band control design based on the formulation for discrete frequency control. It is shown that the single sensor and single actuator control problem over a frequency band can be cast into a Nevanlinna–Pick interpolation problem. An optimal controller can then be obtained via the convex optimization over LMIs. Even remarkable is that robustness issues can also be tackled in this framework. A numerical example is provided for the broad band attenuation of rotor blade vibration to illustrate the proposed design procedures.     

Reduced-order observer based fault estimation and fault-tolerant control for switched stochastic systems with actuator and sensor faults

This paper addresses the problems of fault estimation and fault-tolerant control for a class of switched stochastic systems with sensor and actuator faults. A reduced-order fault estimation observer is designed to estimate the system states, actuator and sensor faults, simultaneously. In the observer design process, intermediate variables are introduced such that the differential information of the measurement output is not included in the designed observer. Compared with the existing results, the dimension of the proposed observer is reduced, and the sensor fault can be completely unknown and unbounded. An observer based fault-tolerant controller is designed to stabilize the switched stochastic systems. Under arbitrary switching signal, the designed observer and controller can ensure that both the estimation error system and the closed-loop system are mean-square exponentially stable with disturbance attenuation performance. At last, both a numerical example and a switched electrical circuit example verify the proposed method.     

Precision tracking of a piezo-driven stage by charge feedback control

This paper presents a novel approach for precisely controlling the motion of a piezo actuator embedded in a mechanical stage without using a displacement sensor. A piezo actuator has a high displacement resolution, but the positioning performance is degraded by hysteresis between the applied voltage and resultant displacement. However, an electromechanical model of a piezo actuator suggests that the charge flowing in the actuator is directly related to the dynamic response of the piezo displacement. Therefore, this study directly measured the charge stored in a piezo actuator, and achieved dynamic reference tracking of the actuator's displacement by regulating the charge flowing through the actuator to follow a predefined trajectory.This novel approach requires neither specially designed charge amplifier circuits nor implementation of an inverse hysteresis model. The complete model identification and the digital controller design procedure for a piezo-driven mechanical stage are presented. The charge feedback controller is designed according to the dynamic characteristics of both the actuator and the stage, so that instability is minimized relative to using a charge amplifier. The experimental results confirm satisfactory tracking performance, and reveal the influence of model uncertainties on the system performance.     

超磁致伸缩执行器的系统建模与控制技术

回顾了超磁致伸缩执行器的系统建模与控制技术的发展历程.归纳出超磁致伸缩执行器的基本设计思想.总结了近年来在传感器、执行器集成、磁滞非线性建模以及控制技术方面的主要研究成果,讨论了该领域尚待解决的问题.     

Active vibration control of clamped beams using positive position feedback controllers with moment pair

This paper investigates the active vibration control of clamp beams using positive position feedback (PPF) controllers with a sensor/moment pair actuator. The sensor/moment pair actuator which is the non-collocated configuration leads to instability of the control system when using the direct velocity feedback (DVFB) control. To alleviate the instability problem, a PPF controller is considered in this paper. A parametric study of the control system with PPF controller is first conducted to characterize the effects of the design parameters (gain and damping ratio in this paper) on the stability and performance. The gain of the controller is found to affect only the relative stability. Increasing the damping ratio of the controller slightly improves the stability condition while the performance gets worse. In addition, the higher mode tuned PPF controller affects the system response at the lower modes significantly. Based on the characteristics of PPF controllers, a multi-mode controllable SISO PPF controller is then considered and tuned to different modes (in this case, three lowest modes) numerically and experimentally. The multi-mode PPF controller can be achieved to have a high gain margin. Moreover, it reduces the vibration of the beam significantly. The vibration levels at the tuned modes are reduced by about 11 dB.     

Finite-time consensus of Markov jumping multi-agent systems with time-varying actuator faults and input saturation

This paper gives attention to the issue of finite-time leader-following consensus of nonlinear discrete-time multi-agent systems with Markov jump parameters. A robust fault-tolerant control protocol that takes the effect of time-varying actuator faults and actuator saturation into account is considered for the addressed system. The main purpose of the paper is to design a fault-tolerant controller such that the leader-following consensus of the addressed system is achieved over a prescribed finite-time interval. By using the Lyapunov functional approach, Abel’s lemma and some properties of Kronecker product, a sufficient condition for the existence of fault-tolerant state feedback controller for the addressed system is presented and an explicit parameterization of such a controller is obtained. Eventually, a numerical example along with its simulation results is exploited to reflect the applicability of the proposed design method, wherein the robust performance of controller is exhibited despite the presence of actuator saturation and time-varying actuator faults.     

基于机器视觉的机器人仿生机械手避障轨迹控制系统

以提高机械手末端关节避障控制精准度为目的,提出一种基于机器视觉的机器人仿生机械手避障轨迹控制系统。以具有高灵敏性和主动性的控制器、伺服驱动器、无线通信器以及高网络带宽的传感监测器为硬件基础,采用机器视觉技术捕捉机械手关节动作。然后根据动力学原理建立避障位姿坐标系,代入关节动作数据计算其在坐标系中的位置。在定义控制范围的基础上,根据隶属度函数计算机械手在轨迹方向上夹角,并随机输出一个动态夹角变量。通过对变量值目标求导得出适配性最高的调节阈值,结合实际情况通过阈值调节实现精准控制。实验表明,该系统能够有效控制机械手末端关节避开障碍物达到指定目标位置,应用效果较好。     

基于μ综合的压电柔性结构振动主动控制

利用模态理论和μ综合方法,对智能柔性悬臂梁进行振动主动控制研究。以压电陶瓷为作动器,电阻应变计为传感器,采用有限元方法和实验模态测试方法建立结构动力学模型,对两种方法所得结果进行比较分析可知有限元模型与实际系统存在误差。考虑外部扰动和量测噪声的不确定性,同时考虑系统固有频率、阻尼比和作动器参数的不确定性,选择模态位移信号为评价量,根据信号的频率特性选择合适的加权函数,利用μ综合方法设计振动控制器。从频域角度分析控制器的有效性,结果表明该控制器能抑制不确定干扰对输出应变的影响,能在系统不确定性情况下满足控制要求,说明控制器具有鲁棒性。进行了振动主动控制实验研究,结果表明,所设计的控制器能有效抑制结构的振动响应。     

中型无人直升机电动舵机控制器设计与实现

针对某中型无人直升机对电动舵机控制回路的特殊需求,设计了一种以“ DSP ＋ FPGA＋ 功率驱动”为主控单元的舵机控制器.其软件设计遵循模块化和层次化的原则;其硬件由主控模块、驱动模块、信号采集模块和电源模块协同合作,能够同时对 ５ 路电动舵机进行控制.针对舵机控制过程中存在的“快、准、稳”问题,提出一种外环采用线性自抗扰控制、内环采用常规控制的复合控制策略;同时搭建相应的测试验证环境.测试和实际试飞结果表明,该舵机控制器解决了负载动态变化的不确定性和小信号指令跟踪差的突出问题,取得了较好的工程应用效果.     

行波管螺旋线缠绕机张力控制系统的设计

介绍了张力控制系统的硬件设计和控制算法的研究。首先进行了张力执行元件的选择,设计了张力检测装置,然后确立数学模型,采用增量式数字PID控制器,设计了张力控制器。通过仿真证明能较好地满足预期的控制要求。     

Design and testing of a hybrid polymeric electrostrictive/piezoelectric beam with bang–bang control

Electrostrictive materials, hard ceramics and soft polymers, have been used as precision actuators in many engineering applications. This study is to examine bang–bang control performance of a hybrid Plexiglas beam laminated with polymeric electrostrictive (RTV 270) actuator and piezoelectric polyvinylidene fluoride (PVDF) sensor layers using both analytical and experimental techniques. Material characteristics are calibrated via static testing first; a hybrid beam model is then fabricated and an experiment set-up, consisting of a bang–bang controller, high-voltage amplifier, data acquisition system and the hybrid beam system, is designed to evaluate vibration control characteristics (i.e., damping ratio estimation) of the hybrid beam subjected to various control conditions. Due to the quadratic behaviour of electrostrictive materials, the controller activates the electrostrictive actuator only in upward motion of the beam, with reference to signals generated from the piezoelectric sensor. Base on constitutive equations and dynamic/control characteristics, a mathematic hybrid beam model is also derived from the electrostrictive thin shell theory and its dynamic responses, based on the finite difference discretization, are simulated to predict damping ratios resulting from control forces induced by the electrostrictive actuators. Dynamic responses (with and without control) of the physical beam model are measured and compared with simulation results. Favourable comparison suggests that the mathematical model describes the experimental model very well and its application to other advanced structures can be proceeded.     

压电主动元件设计与实验研究

为自适应调节和改善空间结构动力学性能 ,利用压电材料的正逆压电效应 ,研制了一种具有传感和驱动双重功能的压电主动元件。该主动元件由压电驱动器、微位移传感器、压力传感器等组成 ,具有输出和实时检测微位移和力的功能。提出了压电主动元件的设计理论 ,并给出其工作机理及组成结构。针对其关键部件——压电驱动器进行了静态实验研究 ,包括位移输出情况、重复精度和稳定性实验。实验结果表明该驱动器输出位移可达 63 .2 μm、重复精度± 0 .0 5μm、稳定性 <0 .1μm,能够用于空间可展结构的精密微位移控制     

Controller design for high-frequency cutting using a piezo-driven microstage

Controller design consists of a feedforward and a feedback controller to support a microstage with flexure hinge structure driven by piezoelectric ceramic actuator for high-frequency nanoscale cutting is developed in this article. The feedforward controller is designed based on a hysteresis dynamic model in order to reduce the nonlinear hysteresis effect of piezoelectric actuator. The position feedback controller is designed based upon an exponentially weighted moving average (EWMA) method embedded in an internal model control (IMC) structure constructing a run-to-run IMC (RtR-IMC) control scheme in order to deal with system bias or modeling inaccuracy. Also, disturbance due to temperature rise will influence actuator's performance, hence an additional compensator is included in the IMC structure. Surfaces dimple micro-machining utilizes piezoelectric-driven microstage for high-speed cutting is selected as an example to investigate system performance. The developed control algorithm is implemented on a DSP-based system to provide 1 kHz operating speed. In experiment, the proposed feedforward and feedback controller is verified to be able to overcome those negative factors efficiently and preserve good positioning accuracy.     

微扑翼飞行器静电驱动机构的机电耦合特性研究

静电微驱动机构在微机械传感器、激励器中有着广泛的应用。对一种用于微型扑翼飞行器的扭转式静电微驱动机构,在建立其非线性动力学模型的基础上,采用数值方法在相空间中分析了系统的非线性动态特性,研究了初始条件和阻尼对临界拉入电压的影响,分析了在不同激励电压信号下系统的响应并得出方波信号较优的结论。最后针对静电扭转梁的有限元模型,采用顺序耦合场分析方法研究了系统的机电耦合特性。所得研究结论对扭转式静电微驱动机构的设计与应用提供了一定的理论依据。     

Practical and intuitive controller design method for precision positioning of a pneumatic cylinder actuator stage

The present paper describes a practical and intuitive controller design method for precision positioning of pneumatic cylinder actuator stages. Pneumatic actuators are easy to use and have numerous advantages, which has led to these actuators having a wide variety of applications. However, pneumatic actuators have notable nonlinear characteristics, which make precision positioning difficult to achieve. The purpose of the present study is to clarify a practical and intuitive controller design procedure for precision positioning of a pneumatic cylinder actuator. In addition to positioning performance, the present study focuses on the realization of easy controller design without the need for the exact model parameters or knowledge in control theory for general-industrial-use pneumatic cylinder actuators with friction characteristics. These considerations are important in order to fully exploit the advantages of pneumatic cylinder actuators in a wide variety of applications. As such, three elements are added to the conventional continuous-motion nominal characteristic trajectory following (CM NCTF) controller. A new design procedure of the improved CM NCTF controller for pneumatic cylinder actuator stages is introduced, and the positioning performance of the designed control system is examined experimentally under several conditions. The positioning results generally indicate a positioning error of 50 nm, which is equal to the sensor resolution.