Active Fault Tolerant Nonsingular Terminal Sliding Mode Control for Electromechanical System Based on Support Vector Machine

Effective fault diagnosis and fault-tolerant control method for aeronautics electromechanical actuator is concerned in this paper.By borrowing the advantages of model-driven and data-driven methods,a fault tolerant nonsingular terminal sliding mode control method based on support vector machine(SVM)is proposed.A SVM is designed to estimate the fault by off-line learning from small sample data with solving convex quadratic programming method and is introduced into a high-gain observer,so as to improve the state estimation and fault detection accuracy when the fault occurs.The state estimation value of the observer is used for state reconfiguration.A novel nonsingular terminal sliding mode surface is designed,and Lyapunov theorem is used to derive a parameter adaptation law and a control law.It is guaranteed that the proposed controller can achieve asymptotical stability which is superior to many advanced fault-tolerant controllers.In addition,the parameter estimation also can help to diagnose the system faults because the faults can be reflected by the parameters variation.Extensive comparative simulation and experimental results illustrate the effectiveness and advancement of the proposed controller compared with several other main-stream controllers.

Improved Hybrid Robust Control Method for the Electromechanical Actuator in Aircrafts

In the flight process of aircrafts, their electromechanical actuators（EMA） must have the ability of enduring uncertainties caused by factors such as load disturbance, the variation of work temperature and the EMA＇s nonlinearity. At present, in order to increase the EMA＇s robustness on the uncertainties, the H, control method has been applied in aircrafts. The major problems with standard H∞ control lie in the large overshoot of step response and the high orders of the controller. For the purpose of addressing the two problems, this paper investigates several kinds of robust control strategies of the EMA. A mathematical model of the EMA is first built, and then with MATLAB software a H∞ controller and an improved hybrid robust controller composed of a reduced order H∞controller and a lead compensator are designed. In order to make a scientific comparison of the control effects of H∞ controller, hybrid controller and classic proportion-integral-differential（PID） controller, a simulation research is made in respect of the open loop frequency response and the closed loop step response of the three controllers. For comparing the robustness of the three controllers, the load torque is entered as a disturbance and the disturbance response of error and control input are thus obtained. The experiments with the three controllers are also conducted. Through giving the EMA a command and a disturbance torque successively, the transient response and disturbing process of EMA are recorded. The simulation and experiment results show that with the help of the hybrid controller, the EMA not only guarantees good dynamic characteristics, but also has strong robustness of disturbance rejection. Therefore, the excogitated H∞ hybrid control method effectively solves the problem of large overshoot in dynamic response, and moderately meets the requirement of overcoming the uncertainties in the EMA of aircrafts.

Experimental study and electromechanical model analysis of the nonlinear deformation behavior of IPMC actuators

This paper develops analytical electromechanical formulas to predict the mechanical deformation of ionic polymer-metal composite (IPMC) cantilever actuators under DC excitation voltages. In this research, IPMC samples with Pt and Ag electrodes were manufactured, and the large nonlinear deformation and the effect of curvature on surface electrode resistance of the IPMC samples were investigated experimentally and theoretically. A distributed electrical model was modified for calculating the distribution of voltage along the bending actuator. Then an irreversible thermodynamic model that could predict the curvature of a unit part of an IPMC actuator is combined with the electrical model so that an analytical electromechanical model is developed. The electromechanical model is then validated against the experimental results obtained from Pt- and Ag-IPMC actuators under various excitation voltages. The good agreement between the electromechanical model and the actuators shows that the analytical electromechanical model can accurately describe the large nonlinear quasi-static deflection behavior of IPMC actuators.

Large nonlinear deflection behavior of IPMC actuators analyzed with an electromechanical model

This study presents an electromechanical engineering model for the analysis of the large deflection curves of ionic polymer-metal composite(IPMC)cantilever actuators under direct current(DC)voltages.In this paper,the longitudinal normal strain performance of the material was investigated using digital image correlation on a micro-scale.The deflection of the actuator is analytically obtained with the application of an elliptic integration method based on the relationship between strain gradient and excitation voltage,and the minimum excitation voltage is derived based on the assumption that the actuators have small deformations.The validity of the electromechanical model is then justified with the experimental results obtained from Pt-and Ag-IPMC actuators at various excitation voltages.The findings of this study confirm that the introduced electromechanical model can accurately describe the large nonlinear deflection behavior of IPMC actuators.

Research and Design of Coordinated Control Strategy for Smart Electromechanical Actuator System

In order to improve the frequency response and anti-interference characteristics of the smart electromechanical actuator(EMA)system,and aiming at the force fighting problem when multiple actuators work synchronously,a multi input multi output(MIMO)position difference cross coupling control coordinated strategy based on double‑closed-loop load feedforward control is proposed and designed.In this strategy,the singular value method of return difference matrix is used to design the parameter range that meets the requirements of system stability margin,and the sensitivity function and the H_(∞)norm theory are used to design and determine the optimal solution in the obtained parameter stability region,so that the multi actuator system has excellent synchronization,stability and anti-interference.At the same time,the mathematical model of the integrated smart EMA system is established.According to the requirements of point-to-point control,the controller of double-loop control and load feedforward compensation is determined and designed to improve the frequency response and anti-interference ability of single actuator.Finally,the 270 V high-voltage smart EMA system experimental platform is built,and the frequency response,load feedforward compensation and coordinated control experiments are carried out to verify the correctness of the position difference cross coupling control strategy and the rationality of the parameter design,so that the system can reach the servo control indexes of bandwidth 6 Hz,the maximum output force 20000 N and the synchronization error≤0.1 mm,which effectively solves the problem of force fighting.

Design and fabrication of a bistable electromagnetic microactuator

An electromagnetic microactuator with two stable positions is presented. The actuator consists of a cantilever beam with two free ends, a torsional beam with two fixed ends, planar coils and permanent magnets. The cantilever beam has two stable positions due to the use of permanent magnets. With electromagnetic actuation arising from the planar coils, the cantilever beam will switch from one stable position to the other. Mechanical and magnetic analysis are carried out on the actuator, and the device with a size of 2.2 mm × 2.5 mm is fabricated with the UV-LIGA technology. The test results show that a current pulse with an amplitude of 70 mA is needed for actuator＇ s switching between the two stable states, and the switching time is no more than 6 ms. Displacement of the end of cantilever is about 15 μm.

基于分数阶自适应神经网络的电动舵机伺服系统摩擦干扰补偿控制

摩擦干扰力矩影响电动舵机伺服系统的跟踪性能,造成位置和速度跟踪偏差,甚至可能导致伺服系统不稳定。针对摩擦力矩干扰下的电动舵机伺服系统跟踪性能差的问题,本文提出了一种分数阶自适应神经网络摩擦补偿算法(FOANN),估计并补偿摩擦干扰力矩。首先,建立基于LuGre模型的电动舵机伺服系统模型,利用径向基神经网络估计模型中的不可测状态变量。其次,设计FOANN摩擦补偿控制器,利用李雅普诺夫稳定性理论证明电动舵机闭环系统的稳定性。最后,利用仿真和实验平台,对比分析了FOANN、传统PD控制和模型自适应控制的性能。结果表明,基于本文所提出的FOANN摩擦力矩补偿控制算法,电动舵机伺服系统的位置跟踪误差和速度跟踪误差均大幅减小,FOANN算法能够有效估计并补偿摩擦力矩,降低摩擦干扰对电机舵机伺服系统的影响,提高伺服系统的动态性能。

含实时电流补偿的开关磁阻式机电作动器自适应PI控制

针对传统控制算法难以克服开关磁阻电机的非线性并有效抑制转向叶片的负载扰动,因而无法对开关磁阻式机电作动器进行快速高精度位置跟踪控制的问题,提出了一种含实时电流补偿的自适应PI控制器。首先,通过负载观测器对作用于转向叶片上的空气动力负载进行实时估算,进而转化为电流环的实时补偿电流来抑制负载扰动的影响;然后,基于开关磁阻电机的转矩电流特性拟合曲线与实时电流反馈值对转速环PI参数进行自适应最优调节,从而削弱了开关磁阻电机的非线性,增强了机电作动器的转速调节性能;最后,通过引入位置前馈环节,有效提高了机电作动器的响应速度和位置跟踪精度。仿真和实验结果表明:相较于传统PI控制器、自适应PI控制器和含前馈环节的自适应PI控制器,所提控制器将开关磁阻式机电作动器的响应速度分别提高了49.3%、44.4%和30%,位置跟踪精度分别提高了54.8%、49.2%和2.9%,从而使得机电作动器具备更强的位置跟踪性能。

基于天牛须BP神经网络的船舶电动舵机自抗扰控制

将自抗扰控制器(ADRC)引入到智能船舵机控制优化问题中,同时将神经网络嵌入到自抗扰控制,针对电动舵机快响应、非线性的特点提出一种神经网络自抗扰控制。将天牛须搜索(BAS)寻优能力强的特性与BP神经网络中的权值与阈值寻优过程相结合,建天牛须BP神经网络自抗扰控制器,弥补了BP神经网络训练时间较长、收敛速度较慢的问题。以船舶电动舵机系统作为被控对象在该控制器下的舵机系统的控制性能得到了提升,控制精度高无超调同时具有良好的鲁棒性,同时建立的BAS-BP神经网络自抗扰控制器对于实际应用具有指导意义。

电动舵机内部扰动分析及建模

电动舵机中的减速机构通常会引入齿隙和摩擦等非线性内部扰动,此类非线性扰动会对电动舵机的动、静态性能造成一定影响。针对电动舵机减速器造成的内部扰动进行了分析,为了解除两级减速器内部的耦合关系,将其分为2个部分分别进行建模,再进行串联仿真。基于蜗轮蜗杆减速器建立了随外部负载变化的非线性摩擦模型,基于圆柱齿轮减速器建立了包含非线性力矩传递特性的齿隙模型。通过将模型仿真结果与舵机实测结果进行对比,确认了模型与舵机具有相同的非线性特性,验证了电动舵机内部扰动的来源,并为舵机控制算法的研究提供了良好的平台。

基于预设性能的飞机全电刹车系统滑模控制

针对飞机全电防滑刹车系统具有较强的非线性特征,以及机电作动器(EMA)中存在的干扰不利于系统稳定性,提出一种有限时间预设性能反演滑模控制方法。在合理简化的基础上,建立含滑移率子系统和EMA子系统的飞机全电防滑刹车系统的数学模型,并引入有限时间预设性能函数;利用预设性能反演控制方法设计滑移率控制器,获得参考刹车压力控制率,保证滑移率跟踪误差在有限时间内收敛到预设范围内;为跟踪参考刹车压力,利用非奇异终端滑模控制方法设计EMA控制器,针对EMA中存在的干扰,设计扩张状态观测器估计,并在控制器中进行补偿,提高控制器的鲁棒性和控制精度;通过干跑道和冰跑道2种情况下的数值仿真验证所提方法控制效果。

基于符号键合图的电静压伺服机构多故障诊断研究

针对电静压伺服机构(EHA)服役时存在多种故障且难以诊断的问题,提出了一种考虑参数贡献度的符号键合图(SBG)故障诊断方法。首先,根据EHA工作原理与键合图理论构建了键合图模型,设定了系统参数数值及分布标准差,再利用键合图模型推导了其解析冗余式(ARR),并构建了故障特征矩阵,将键合图模型转换为符号键合图模型,根据符号键合图元件之间的因果关系和一致性路径,推理出了EHA可能故障集;然后,定义并计算了EHA系统参数贡献度,筛选出了高贡献度系统参数,对可能故障集中难以引起解析冗余式残差数据变化的低贡献度系统参数进行了剔除,缩小了可能的故障参数范围;最后,利用键合图仿真软件20-sim,通过改变EHA中Q轴电阻与电机磁通链的数值,进行了多故障仿真实验,对所提多故障诊断方法进行了验证。研究结果表明:当EHA发生多故障时,将剔除低贡献度系统参数的可能故障集同传感器数据、解析冗余式残差数据进行结合,能准确诊断出预置的两个高贡献度故障参数,相比于常规SBG故障诊断的可能故障集,能更准确地锁定EHA系统故障参数。

低成本高性能EMA相关技术最新研究进展

ACTUATION 2015是欧盟为推动EMA技术发展而进行的一个国际合作项目,主要从EMA模型构建技术、关键模块设计技术、健康监测技术以及标准化等方面来提升EMA的设计水平和安全可靠性、降低EMA综合成本。文中依照ACTUATION 2015 4个研究方向,从4个方面介绍了ACTUATION 2015项目中低成本高性能EMA相关技术研究的典型成果,以期为国内相关工作者的研究开发和应用提供一定启发。

余度机电作动器(EMA)系统BIT设计分析

讨论了一种由稀土永磁无刷电机构成的具有余度结构的机电作动器（EMA）系统的BYF设计问题。首先分析了该系统的测试性，然后根据BIT功能要求提出了故障检测方法。

锥形电活性聚合物薄膜作动器的力电响应研究

以一款锥形电活性聚合物薄膜作动器为研究对象,选用Ogden材料模型对作动器进行数值计算。控制外力变化,对薄膜在变形状态下的应变量、厚度及临界电场强度进行分析,研究了预拉伸对薄膜力电稳定性的影响。结果表明:外力增加会显著提高薄膜内各点的径向应变,减小膜厚,并使得临界电场强度的分布发生改变;薄膜预拉伸程度的增加,也会提高薄膜临界电场强度,使得薄膜的力电稳定性得到增强。

Modelling and simulation of flight control electromechanical actuators with special focus on model architecting, multidisciplinary effects and power flows

In the aerospace field, electromechanical actuators are increasingly being implemented in place of conventional hydraulic actuators. For safety-critical embedded actuation applications like flight controls, the use of electromechanical actuators introduces specific issues related to thermal balance, reflected inertia, parasitic motion due to compliance and response to failure. Unfortunately, the physical effects governing the actuator behaviour are multidisciplinary, coupled and nonlinear. Although numerous multi-domain and system-level simulation packages are now available on the market, these effects are rarely addressed as a whole because of a lack of scientific approaches for model architecting, multi-purpose incremental modelling and judicious model implementation. In this publication, virtual prototyping of electromechanical actuators is addressed using the Bond-Graph formalism. New approaches are proposed to enable incremental modelling,thermal balance analysis, response to free-run or jamming faults, impact of compliance on parasitic motion, and influence of temperature. A special focus is placed on friction and compliance of the mechanical transmission with fault injection and temperature dependence. Aileron actuation is used to highlight the proposals for control design, energy consumption and thermal analysis, power network pollution analysis and fault response.

Output constrained IMC controllers in control systems of electromechanical actuators

Electromechanical actuators are widely used in many industrial applications. There are usually some constraints existing in a designed system. This paper proposes a simple method to design constrained controllers for electromechanical actuators. The controllers merge the ideas exploited in internal model control and model predictive control. They are designed using the standard control system structure with unity negative feedback. The structure of the controllers is relatively simple as well as the design process. The output constraint handling mechanism is based on prediction of the control plant behavior many time steps ahead. The mechanism increases control performance and safety of the control plant. The benefits offered by the proposed controllers have been demonstrated in real-life experiments carried out in control systems of two electromechanical actuators： a DC motor and an electrohydraulic actuator.

EMA、EHA和IAP三种作动器比较

介绍了EMA、EHA和IAP三种作动器,并对其进行了比较,介绍了国外的比较研究,最后对战术导弹上对三种作动器的选择进行了分析。

Low-and high-field electromechanical responses of relaxor-based multicomponent ceramics for application in multiregime actuators

The electromechanical responses of multicomponent solid solutions Pb_(0.95)Ba_(0.05)(Mg_(1/3)Nb_(2/3))_(0.471)(Zn_(1/3)Nb_(2/3))_(0.102)(Ni_(1/3)Nb_(2/3))_(0.152)Ti_(0.275)O_(3)in low and high electric fields were studied.In both cases,significant electromechanical responses are observed.In particular,the maximum values of the large-signal piezoelectric coefficient d_(33)reach 1600 m/V at very low values of the electric field(≈5 kV/cm).The observed features of the electromechanical responses of the studied ceramics are advantages in terms of their possible application in actuators.

飞机EMA过载保护装置摩擦片的优化设计研究

为提高飞机大功率EMA摩擦盘的稳定性和实用性,对摩擦盘内的摩擦片进行了优化设计与研究。首先根据加权因子法分析,选定最适合飞机上使用的摩擦片材料为铁铜基粉末冶金摩擦材料;其次采用粉末冶金材料激光表面增强技术,提高了金属粉末冶金材料的表面质量,从而提高了在大功率负载作用下材料的稳定性;再次通过电控摩擦试验,采用改变外加电场的方法来改变金属材料表面摩擦因数;最后通过摩擦片有限元分析来判断摩擦片各处的受力情况,分析检验摩擦片强度,最终设计出合理的摩擦片。结果表明,设计出的摩擦片具有高稳定性、高耐热性和高强度等特性,增强了摩擦盘的稳定性和实用性。