Fuzzy Feedback Control for Electro-Hydraulic Actuators

Electro-hydraulic actuators(EHA)have recently played a significant role in modern industrial applications,especially in systems requiring extremely high precision.This can be explained by EHA’s ability to precisely control the position and force through advanced sensors and innovative control algorithms.One of the promising approaches to improve control accuracy for EHA systems is applying classical to modern control algorithms,in which the proportional–inte-gral–derivative(PID)algorithm,fuzzy logic controller,and a hybrid of these methods are popular options.In this paper,we developed a novel version of the fuzzy control algorithm and linear feedback control method,namely fuzzy lin-ear feedback control,to improve the control performance.To achieve the highest performance,wefirst designed a mathematical EHA model based on the Matlab/Simulink software packages thanks to the selected parameters,which are similar to a real EHA system.Then,we respectively applied PID,fuzzy PID(FPID),and fuzzy linear feedback control(FLFC)before comparing them to have a full view of the outstanding advantages of the proposed algorithm.The simulation results showed that the proposed FLFC algorithm is approximately 99%and 77%super-ior in performance to the PID and feedback control algorithms,respectively.

A New Type of Automotive Braking Actuator for Decentralized Electro-hydraulic Braking System

This paper presents a new type of automotive braking actuator for a kind of brake-by-wire system called decentralized electro-hydraulic braking system( DEHB) to replace the traditional automobile braking system. The actuator of this system is driven by an electrical motor instead of the conventional vacuum booster to make the brake pressure be linearity controlled quickly. Therefore,the system has the advantages of quick response speed,good control performance and simple structure. Firstly,an overview of the actuator and the whole DEHB system is shown. Secondly,the possibility of this new kind of actuator working for the system is ensured based on some braking theories. Thirdly,the appropriate dynamic simulations are done to get some results to show the relations of different parameters and the effect of braking. Eventually,the proper parameters are determined to build a test bench which shows that DEHB system can achieve the maximum pressure of 13 MPa within 100 ms after parametric optimization,and meanwhile,the actuator is able to reduce pressure quickly after maintaining high pressure. All of the bench test results can meet with the design requirements and real demand of vehicle and this actuator may improve vehicle braking effect in the future. Besides,this actuator can be widely applied to the regenerative braking system because of its linear braking performance.

FLUTTER SUPPRESSION USING DISTRIBUTED PIEZOELECTRIC ACTUATORS

The Flutter suppression using distributed piezoelectric actuators has been analyzed and tested. In constructing the finite element equation, effects of piezoelectric matrices are investigated. LQG method is used in designing the control law. In reducing the order of the control law, both balance realization and LK methods are used. For the rational approximation of the unsteady aerodynamic forces LS method is improved. In determining the piezoelectric constants d31 a new dynamic response method is developed. Laser vibrameter is used to pick up the model response and in ground resonance test the model is excited by piezoelectric actuators. Reasonable agreement of the wind tunnel flutter suppression test with calculated results is obtained.

New Method to Improve Dynamic Stiffness of Electro-hydraulic Servo Systems

Most current researches working on improving stiffness focus on the application of control theories.But controller in closed-loop hydraulic control system takes effect only after the controlled position is deviated,so the control action is lagged.Thus dynamic performance against force disturbance and dynamic load stiffness can’t be improved evidently by advanced control algorithms.In this paper,the elementary principle of maintaining piston position unchanged under sudden external force load change by charging additional oil is analyzed.On this basis,the conception of raising dynamic stiffness of electro hydraulic position servo system by flow feedforward compensation is put forward.And a scheme using double servo valves to realize flow feedforward compensation is presented,in which another fast response servo valve is added to the regular electro hydraulic servo system and specially utilized to compensate the compressed oil volume caused by load impact in time.The two valves are arranged in parallel to control the cylinder jointly.Furthermore,the model of flow compensation is derived,by which the product of the amplitude and width of the valve’s pulse command signal can be calculated.And determination rules of the amplitude and width of pulse signal are concluded by analysis and simulations.Using the proposed scheme,simulations and experiments at different positions with different force changes are conducted.The simulation and experimental results show that the system dynamic performance against load force impact is largely improved with decreased maximal dynamic position deviation and shortened settling time.That is,system dynamic load stiffness is evidently raised.This paper proposes a new method which can effectively improve the dynamic stiffness of electro-hydraulic servo systems.

Position Control of Electro-hydraulic Actuator System Using Fuzzy Logic Controller Optimized by Particle Swarm Optimization

The position control system of an electro-hydraulic actuator system （EHAS） is investigated in this paper. The EHAS is developed by taking into consideration the nonlinearities of the system： the friction and the internal leakage. A variable load that simulates a realistic load in robotic excavator is taken as the trajectory reference. A method of control strategy that is implemented by employing a fuzzy logic controller （FLC） whose parameters are optimized using particle swarm optimization （PSO） is proposed. The scaling factors of the fuzzy inference system are tuned to obtain the optimal values which yield the best system performance. The simulation results show that the FLC is able to track the trajectory reference accurately for a range of values of orifice opening. Beyond that range, the orifice opening may introduce chattering, which the FLC alone is not sufficient to overcome. The PSO optimized FLC can reduce the chattering significantly. This result justifies the implementation of the proposed method in position control of EHAS.

Fuzzy impedance control of an electro-hydraulic actuator with an extended disturbance observer

In this paper,we deal with both velocity control and force control of a single-rod electro-hydraulic actuator subject to external disturbances and parameter uncertainties.In some implementations,both velocity control and force control are required.Impedance control and an extended disturbance observer are combined to solve this issue.Impedance control is applied to regulate the dynamic relationship between the velocity and output force of the actuator,which can help avoid impact and keep a proper contact force on the environment or workpieces.Parameters of impedance rules are regulated by a fuzzy algorithm.An extended disturbance observer is employed to account for external disturbances and parameter uncertainties to achieve an accurate velocity tracking.A detailed model of load force dynamics is presented for the development of the extended disturbance observer.The stability of the whole system is analyzed.Experimental results demonstrate that the proposed control strategy has not only a high velocity tracking performance,but also a good force adjustment performance,and that it should be widely applied in construction and assembly.

Structural Nonlinear Flutter Characteristics Analysis for an Actuator-fin System with Dynamic Stiffness

The flutter characteristics of an actuator-fin system are investigated with structural nonlinearity and dynamic stiffness of the electric motor. The component mode substitution method is used to establish the nonlinear governing equations in time domain and frequency domain based on the fundamental dynamic equations of the electric motor and decelerator. The existing describing function method and a proposed iterative method are used to obtain the flutter characteristics containing preload freeplay nonlinearity when the control command is zero. A comparison between the results of frequency domain and those of time domain is studied. Simulations are carried out when the control command is not zero and further analysis is conducted when the freeplay angle is changed. The results show that structural nonlinearity and dynamic stiffness have a significant influence on the flutter characteristics. Limit cycle oscillations （LCOs） are observed within linear flutter boundary. The response of the actuator-fin system is related to the initial disturbance. In the nonlinear condition, the amplitude of the control command has an influence on the flutter characteristics.

Robust fault-tolerant control for wing flutter under actuator failure

Many control laws, such as optimal controller and classical controller, have seen their applications to suppressing the aeroelastic vibrations of the aeroelastic system. However, those control laws may not work effectively if the aeroelastic system involves actuator faults. In the current study for wing flutter of reentry vehicle, the effect of actuator faults on wing flutter system is rarely considered and few of the fault-tolerant control problems are taken into account. In this paper, we use the radial basis function neural network and the finite-time H-infinity adaptive fault-tolerant control technique to deal with the flutter problem of wings, which is affected by actuator faults, actuator saturation, parameter uncertainties and external disturbances. The theory of this article includes the modeling of wing flutter and fault-tolerant controller design. The stability of the finite-time adaptive fault-tolerant controller is theoretically proved. Simulation results indicate that the designed fault-tolerant flutter controller can effectively deal with the faults in the flutter system and can promptly suppress the wing flutter as well. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.

Dynamic stiffness testing-based flutter analysis of a fin with an actuator

Engineering-oriented modeling and synthesized modeling of the fin-actuator system of a missile fin are introduced, including mathematical modeling of the fin, motor and multi-stage gear reducer. The fin-actuator model is verified using dynamic stiffness testing. Good agreement is achieved between the test and theoretical results. The parameter-variable analysis indicates that the inertia of the motor rotor, reduction ratio of the reducer, connection stiffness and damping between the actuator and fin shaft have significant impacts on the dynamic stiffness characteristics. In flutter analysis, test data are directly used in the frequency domain method and indirectly used in the time domain method through the updated fin-actuator model. The two methods play different roles in engineering applications but are of equal importance. The results indicate that dynamic stiffness and constant stiffness treatments may lead to completely different flutter characteristics. Attention should be paid to the design of the fin-actuator system of a missile.

考虑舵机动力学的舵系统颤振特性分析

飞行器舵面的颤振特性与舵机动态特性有很大关系.提出了2种考虑舵机复刚度颤振分析的工程分析方法,第1种方法思想是对舵面和舵机的耦合系统(下文称舵系统)模型在各种来流速度下进行状态矩阵的稳定性判断,称为时域方法;第2种方法是将舵机复刚度特性包含在频域颤振方程中,使用改进的V-g法求解该方程得到舵系统颤振特性,称为频域方法.通过对舵系统模型算例的数值计算验证了方法的可行性;发现传统的按扭转频率进行舵机刚度等效的舵面颤振工程计算方法的结果相对于该方法有较大差别.说明当舵机动力学特性较差时,在舵面颤振分析中考虑舵机复刚度特性是很有必要的.

采用分布式压电驱动器升力面的颤振主动抑制

对采用分布式压电驱动器升力面的颤振主动抑制进行了理论与试验研究.应用 LQG最优控制法设计了主动控制律,在控制律降阶时提出了平衡实现与LK法结合使用的新途径,在对不定常气动力进行有理函数拟合时对LS法进行了改进.试验中利用激光测速仪非接触测量模型的速度响应并在地面共振试验中用压电驱动器激振模型.颤振风洞试验结果表明,理论计算合理并与试验结果吻合良好.

折叠翼飞行器机翼折叠过程的颤振仿真分析

折叠翼是一种很有前景的变体飞行器设计方案。在折叠过程中,相当于飞机具有多个不同的机翼构型,所以其颤振特性将会发生剧烈的变化。为了提高求解效率,提出用准静态方法代替实时模拟方法来模拟折叠过程,并对折叠翼飞机进行了颤振特性的变参分析。得出了以下两个结论:1)当折叠角进入变体折叠的中间阶段时,机翼的颤振速压降低较大。2)折叠作动器的刚度会明显影响机翼的颤振速压。

采用分布式压电驱动器的翼面热颤振主动抑制

高超声速气动加热会严重影响飞行器结构的颤振特性,本文开展了采用分布式压电驱动器的热颤振主动抑制方法研究。以某飞行器小展弦比翼面为研究对象,进行了常温和热载荷边界条件下的结构振动和颤振分析。在此基础上,对频域非定常气动力进行有理函数拟合,建立包含压电驱动器的翼面耦合结构系统状态空间形式的运动方程;对典型热载荷边界条件下的被控对象设计颤振主动抑制控制律,分别设计出LQG及PID控制器;对比分析了系统开、闭环颤振特性。结果表明,通过主动控制律的实施,达到了热颤振主动抑制的目的,验证了这种颤振主动抑制方法的有效性。

智能复合材料机翼的气动弹性剪裁

通过含有位移和电自由度的四节点板元,利用哈密尔顿原理,推导了含有压电传感器和作动器的智能复合材料机翼的机电耦合动力学方程。采用西奥道生非定常气动理论结合片条理论构建气动力模型,获得机翼的颤振方程,并利用v-g法分析了复合材料的铺层方式和反馈增益对颤振速度的影响。结果表明:复合材料的铺设方式和反馈增益系数是在相互影响下改变机翼颤振速度的。

基于LMI方法的电液舵机动刚度H_∞控制器分析与设计

舵机刚度特性决定着航行器对舵面位置的"把控"能力,航行器运动时随着舵面负载扰动频率的变化,刚度特性也是不断变化的,如果某一频率点上刚度达到最小值,引起了舵面剧烈抖动,整个航行器的运行安全将无法保证。所以舵机控制器设计过程中需要大量的仿真计算,从开始设计阶段找到提高舵机刚度特性的方法;建立电液舵机的系统模型,仿真得到系统刚度特性,基于LMI方法设计了H_∞控制器,通过求解含约束条件的LMI优化问题使设计的控制器能够较大程度上的提高系统动刚度。仿真结果表明:控制器能提高了系统抗扰动能力,系统的刚度在一定扰动频率范围内不变,扰动通道增益减小;在系统参数发生波动的情况下依然能保持较好的抗扰动能力,鲁棒性较强,结合实际项目验证了设计控制器的有效性。

民用液压舵机动刚度仿真与分析

动刚度是舵机的一项重要性能指标,必须满足飞机操纵面颤振抑制要求,对飞机安全有着重大意义。舵面颤振总是发生在特定的频率,提高舵机在该频率下的动刚度特性,以保证民机的抗舵面颤振飞行安全。通过对民用液压舵机系统建模,给其施加不同频率的正弦外干扰力,仿真得到不同频率下的舵机系统输出位移,计算得出舵机动刚度特性,分析不同频率下民用液压舵机动刚度变化规律。仿真分析结果表明,民用舵机动刚度特性满足舵面颤振抑制要求,保证民机飞行安全。研究民用液压舵机动刚度特性,掌握舵机动刚度变化规律,填补国内民用液压舵机动刚度研究领域空白,对民机工程有重要指导意义。

民用液压舵机动刚度研究浅析

液压伺服舵机广泛应用于民机电传飞行控制系统,舵机的众多特性引起了设计者的重视。动刚度作为液压舵机的一项重要性能指标,对飞机飞行安全有重大意义,其设计必须满足飞机操纵面颤振抑制要求。介绍了液压舵机动刚度的定义、动刚度特性研究的重要性、操纵面防颤振抑制设计原则以及舵机防颤振抑制设计方法。建立了液压舵机系统数学模型,提出了舵机动刚度特性的分析和测试验证方法。随着电液伺服技术和民用舵机设计的发展,舵机动刚度特性的研究将引起更多工程设计人员的重视。

基于压电作动与鲁棒控制的弯-剪耦合叶片挥舞失速颤振抑制

针对风力机叶片的挥舞断裂失效,阐述压电作动与鲁棒控制下的挥舞/横向剪切(弯-剪)耦合叶片失速颤振及主动控制过程;结构模型是在复合材料基体中嵌入压电材料的薄壁单闭室叶型截面,气动力是适合于纯变桨运动的失速气动力模型。基于Galerkin方法进行解耦处理,气动力沿叶片展长计算采用片条理论;基于压电反馈作动理论和三权值混合灵敏度H_∞鲁棒控制,研究基于时域响应的稳定性分析和失速颤振抑制方法;压电反馈基于结构裁剪技术,反馈为叶尖挥舞弯曲运动。三权值鲁棒控制通过第三权值在噪声衰减中,制约输出信号大小,迫使其稳定;通过大范围变化的变桨角和铺层角条件下的特征值分析及相平面分析,验证了三权值混合灵敏度H_∞鲁棒控制不失一般性。

高超声速飞行器空气舵系统耦合特性分析及颤振抑制研究

为了预防高超声速飞行器空气舵系统流、固、热、电、磁等多物理场的耦合作用所引发颤振失稳开展颤振抑制研究,建立了将热环境下舵面结构动力特性、高超声速非定常气动力、舵机环节非线性动力学特性耦合起来的舵机-舵面耦合系统数学模型和颤振特性分析方法;对某舵系统进行了数值分析,研究了热环境、电动舵机设计参数以及指令信号幅值对颤振速度的影响,提出在舵机电流环加入超前滞后环节的颤振抑制措施。仿真结果表明,该方法能有效地提高舵系统的颤振速度。

电动伺服舵系统动力学建模及颤振分析

舵机动力学对舵系统颤振有最直接影响,其动力学模型的准确建立是颤振分析的关键。以某电动伺服舵系统为对象,分别建立了电机、减速器及控制回路模型。基于其地面振动试验(GVT)数据特征,考虑了减速器中零部件间隙及滚珠丝杠间接触刚度2类非线性因素。动力学仿真结果复现了试验现象,证明了接触刚度和间隙对该伺服舵系统动力学特征的主导作用。在颤振分析中,对比了接触刚度和常数刚度2种假设下,舵机在不同阶跃角指令下的舵偏角响应。发现常数刚度下舵系统仅存在极限环(LCO)和失稳2个域,临界速度不会随间隙大小而变化;而接触刚度下存在稳定、LCO和失稳3个域,且相同风速下,其临界指令角较常数刚度假设更高,但其临界速度却会随间隙增大而减小,甚至小于常数刚度假设,应引起足够重视。