Study on Friction Torque Loading with an Electro-hydraulic Load Simulator

This article, in order to precisely impose friction on aircraft and weapon actuation systems, presents a new friction loading method characteristic of “torque-zero velocity” switching control with an electro-hydraulic load simulator. As the general Stribeck friction model has little related to static friction, it proposes a “torque-zero velocity” switcher, in which a zero-velocity controller is developed to load the static friction and a torque controller the kinetic friction. With the help of mathematical modeling, this article designs a “torque-zero velocity” switching controller and, correspondingly, provides a “dual-threshold judgment” algorithm. Simulation results indicate that the proposed method can be successfully used to carry out the static and kinetic friction simulation with an electro-hydraulic load simulator.     

QFT force loop design for the aerodynamic load simulator

A dynamic load simulator which can reproduce on-ground the aerodynamic hinge moment of a control surface is an essential rig for conducting performance and stability tests of aircraft actuation systems. The hinge moment varies widely over the flight envelope, depending on the specific flight condition and maneuvering status. To replicate the wide spectrum of this hinge moment variation within some accuracy hounds, a force controller is designed based on the Quantitative Feedback Theory (QFT). A dynamic model of the load actuation system Is derived, and compared with experimental results. Through this comparison, a nominal model of the load actuation system with some uncertainty bounds is developed. The efficacy of the QFT force controller is verified by a numerical simulation, in which combined aircraft dynamics, flight control law and hydraulic actuation system dynamics of the aircraft control surface are considered     

High dynamic output feedback robust control of cascaded extended state observer

High dynamic tracking performance is a key technical index of hydraulic flight motion simulator(HFMS). However, the strong nonlinearities, various model uncertainties and measurement noise in hydraulic actuation systems limit the high dynamic performance improvement. In this paper, the outer axis frame of a HFMS is taken as a case study and its nonlinear dynamic model with consideration of strong nonlinearities, matched and mismatched uncertainties is established.A novel cascaded extended state ...     

重载航空负载模拟器非线性最优前馈补偿控制

重载航空负载模拟器是用来模拟"C919"、"运-20"等重载飞机舵面工作载荷的地面仿真平台。设计了一种重载航空负载模拟器,采用非对称缸作为执行机构以在小体积下完成大载荷加载。为了消除多余力对重载航空负载模拟器加载精度的影响,分析了非对称缸正反向运动和大载荷变化下伺服阀流量增益的非线性变化对前馈补偿函数的影响,并设计了非线性参数估计控制器。同时分析了加速度等动态参数变化和静态参数的误差对多余力消除的影响,设计了参数最优控制器。仿真和试验结果均表明,相比于传统前馈补偿控制器,所设计的非线性最优前馈补偿控制器下的加载精度和多余力抑制能力提高了50%以上。     

Nonlinear Adaptive Robust Force Control of Hydraulic Load Simulator

This paper deals with the high performance force control of hydraulic load simulator. Many previous works for hydraulic force control are based on their linearization equations, but hydraulic inherent nonlinear properties and uncertainties make the conventional feedback proportional-integral-derivative control not yield to high-performance requirements. In this paper, a nonlinear system model is derived and linear parameterization is made for adaptive control. Then a discontinuous projection-based nonlinear adaptive robust force controller is developed for hydraulic load simulator. The proposed controller constructs an asymptotically stable adaptive controller and adaptation laws, which can compensate for the system nonlinearities and uncertain parameters. Meanwhile a well-designed robust controller is also developed to cope with the hydraulic system uncertain nonlinearities. The controller achieves a guaranteed transient performance and final tracking accuracy in the presence of both parametric uncertainties and uncertain nonlinearities; in the absence of uncertain nonlinearities, the scheme also achieves asymptotic tracking performance. Simulation and experiment comparative results are obtained to verify the high-performance nature of the proposed control strategy and the tracking accuracy is greatly improved.     

A practical nonlinear robust control approach of electro-hydraulic load simulator

This paper studies a nonlinear robust control algorithm of the electro-hydraulic load simulator （EHLS）. The tracking performance of the EHLS is mainly limited by the actuator＇s motion disturbance, flow nonlinearity, and friction, etc. The developed controller is developed based on the nonlinear motion loading model. The problems of the actuator＇s disturbance and flow nonlinearity are considered. To address the friction problem, the friction model of the loading motor is identified experimentally. The friction disturbance is compensated using the obtained friction model. Therefore, this paper considers the main three factors comprehensively. The developed algorithm is easy to apply since the controller can be obtained just with one step back-stepping design. The stability of the developed algorithm is proven via Lyapunov analysis. Both co-simulation and experiments are performed to verify the effectiveness of this method.     

Adaptive Fuzzy Torque Control of Passive Torque Servo Systems Based on Small Gain Theorem and Input-to-state Stability

Passive torque servo system (PTSS) simulates aerodynamic load and exerts the load on actuation system, but PTSS endures position coupling disturbance from active motion of actuation system, and this inherent disturbance is called extra torque. The most important issue for PTSS controller design is how to eliminate the influence of extra torque. Using backstepping technique, adaptive fuzzy torque control (AFTC) algorithm is proposed for PTSS in this paper, which reflects the essential characteristics of PTSS and guarantees transient tracking performance as well as final tracking accuracy. Takagi-Sugeno (T-S) fuzzy logic system is utilized to compensate parametric uncertainties and unstructured uncertainties. The output velocity of actuator identified model is introduced into AFTC aiming to eliminate extra torque. The closed-loop stability is studied using small gain theorem and the control system is proved to be semiglobally uniformly ultimately bounded. The proposed AFTC algorithm is applied to an electric load simulator (ELS), and the comparative experimental results indicate that AFTC controller is effective for PTSS.     

Friction compensation for low velocity control of hydraulic flight motion simulator: A simple adaptive robust approach

Low-velocity tracking capability is a key performance of flight motion simulator (FMS), which is mainly affected by the nonlinear friction force. Though many compensation schemes with ad hoc friction models have been proposed, this paper deals with low-velocity control without friction model, since it is easy to be implemented in practice. Firstly, a nonlinear model of the FMS middle frame, which is driven by a hydraulic rotary actuator, is built. Noting that in the low velocity region, the unmodeled friction force is mainly characterized by a changing-slowly part, thus a simple adaptive law can be employed to learn this changing-slowly part and compensate it. To guarantee the boundedness of adaptation process, a discontinuous projection is utilized and then a robust scheme is proposed. The controller achieves a prescribed output tracking transient performance and final tracking accuracy in general while obtaining asymptotic output tracking in the absence of modeling errors. In addition, a saturated projection adaptive scheme is proposed to improve the globally learning capability when the velocity becomes large, which might make the previous proposed projection-based adaptive law be unstable. Theoretical and extensive experimental results are obtained to verify the high-performance nature of the proposed adaptive robust control strategy.     

基于滑模变结构和扩张状态观测器的电动舵机复合控制方法

为提高电动舵机伺服系统的鲁棒性,同时解决实际工作中电动舵机不确定负载引起的跟踪精度低的问题,提出了一种采用指数趋近率的滑模变结构控制率结合扩张状态观测器对负载扰动进行实时估计的电动舵机的伺服控制方法,给出了控制器设计方法和试验验证。仿真和试验结果表明,与常规的滑模控制器相比,采用扩张状态观测器的变结构控制能有效提高电动舵机的跟踪性能。     

一种改进的基于分解控制的非线性力矩补偿策略及其在直流电机系统中的应用

 针对直流电机系统中存在的非线性摩擦力矩和波动力矩，提出一种改进的非线性力矩补偿策略，将重复控制机制引入到基于分解控制的补偿策略中。其中，鲁棒自适应补偿器用来补偿系统中存在的非线性摩擦力矩和波动力矩；而插入的重复控制器用来进一步提高系统运动曲线的跟踪性能。二者的综合构成了系统完整的控制律。Lyapunov方法证明了闭环控制系统的全局稳定性。最后，通过对高精度伺服系统的仿真研究证明了该改进补偿策略的有效性。     

Adaptive Nonlinear Optimal Compensation Control for Electro-hydraulic Load Simulator

 Directing to the strong position coupling problem of electro-hydraulic load simulator (EHLS), this article presents an adap-tive nonlinear optimal compensation control strategy based on two estimated nonlinear parameters, viz. the flow gain coeffi-cient of servo valve and total factors of flow-pressure coefficient. Taking trace error of torque control system to zero as control object, this article designs the adaptive nonlinear optimal compensation control strategy, which regards torque control output of closed-loop controller converging to zero as the control target, to optimize torque tracking performance. Electro-hydraulic load simulator is a typical case of the torque system which is strongly coupled with a hydraulic positioning system. This article firstly builds and analyzes the mathematical models of hydraulic torque and positioning system, then designs an adaptive nonlinear optimal compensation controller, proves the validity of parameters estimation, and shows the comparison data among three control structures with various typical operating conditions, including proportion-integral-derivative (PID) controller only, the velocity synchronizing controller plus PID controller and the proposed adaptive nonlinear optimal compensation controller plus PID controller. Experimental results show that systems’ nonlinear parameters are estimated exactly using the proposed method, and the trace accuracy of the torque system is greatly enhanced by adaptive nonlinear optimal compensation control, and the torque servo system capability against sudden disturbance can be greatly improved.     

A linear ADRC-based robust high-dynamic double-loop servo system for aircraft electro-mechanical actuators

Compared with traditional hydraulic actuators, an Electro-Mechanical Actuator(EMA)is small in size and light in weight, so it has become more widely used. Aerodynamic load on aircraft control surface varies dramatically, and a change of flight environment leads to uncertainties of motor parameters. Therefore, high-dynamic response and strong anti-disturbance capability of an EMA are of great significance for aircraft rudder control and flight attitude adjustment. In order to improve dynamic response and disturbance rejection of an EMA and simplify control parameters tuning, a robust high-dynamic servo system based on Linear Active Disturbance Rejection Control(LADRC) is proposed for an EMA employing a Permanent Magnet Synchronous Motor(PMSM).Firstly, total disturbances of the EMA are analyzed, including parameter uncertainties, load variation, and static friction. A disturbance observer based on a reduced-order Extended State Observer(ESO) is designed to improve the anti-interference ability and dynamic performance. Secondly, the servo control architecture is simplified to a double-loop system, and a composite control of position and speed with acceleration feed-forward is presented to improve the EMA frequency bandwidth.Thirdly, the ideal model of the EMA is transformed into a simple cascade integral form with a disturbance observer, which makes it convenient to analyze and design the controller. Robustness performance comparisons are realized in frequency domain. Finally, simulation and experimental results have verified the effectiveness of the proposed strategy for EMAs.     

基于扩展状态观测器的电动负载模拟器反演滑模控制

针对电动负载模拟器中存在的强位置扰动、摩擦、间隙非线性以及参数时变等不确定干扰,提出了一种基于扩展状态观测器的反演滑模控制策略。基于反演设计的思想,将电动负载模拟器分解为负载力矩子系统和永磁同步电机驱动子系统。对负载力矩子系统,利用带有滤波器的扩展状态观测器,消除量测噪声对系统的影响,同时估计出系统中存在的干扰,而后采用比例趋近滑模控制律,得出负载力矩子系统所对应的虚拟控制量;对永磁同步电机驱动子系统,利用常规扩展状态观测器估计出子系统中的复合扰动,采用非奇异终端滑模控制律,消除观测误差以及干扰对系统的影响,并得出系统所需的最终控制量。最后,利用李雅普诺夫方法证明了电动负载模拟器的稳定性,并通过实验验证了所提方法的有效性。     

微型飞行器过失速降落轨迹跟踪控制设计

采用基于张量积的T-S模糊建模与控制方法,对微型飞行器过失速降落纵向运动的轨迹跟踪控制问题进行了研究。首先,建立了过失速降落中飞行器纵向运动的线性变参数动力学模型;然后,通过张量积模型转化方法,将线性变参数模型转化为张量积胞体模型,基于该模型设计了并行分布补偿控制器,用Lyapunov稳定性理论证明了闭环系统的稳定性,并推导了区域极点配置条件以获得更好的暂态响应性能;最后,对飞行器的过失速降落过程进行了仿真,验证了所设计的跟踪控制器的有效性。     

Application in prestiction friction compensation for angular velocity loop of inertially stabilized platforms

To overcome the influence of the nonlinear friction on the gimbaled servo-system of an inertial stabilized platforms(ISPs) with DC motor direct-drive, the methods of modeling and compensation of the nonlinear friction are proposed. Firstly, the inapplicability of LuGre model when trying to interpret the backward angular displacement in the prestiction regime is observed experimentally and the reason is deduced theoretically. Then, based on the dynamic model of direct-drive ISPs, a modified LuGre model is proposed to describe the characteristic of the friction in the prestiction regime. Furthermore, the state switch condition of the three friction regimes including presliding, gross sliding and prestiction is presented. Finally, a composite compensation controller including a nonlinear friction observer and a feedforward compensator based on the novel LuGre model is designed to restrain the nonlinear friction and to improve the control precision. Experimental results indicate that compared with those of the conventional proportion–integration–differentiation(PID) control method and the PID plus LuGre model-based friction compensation method, the dwell-time has decreased from 0.2 s to almost 0 s, the position error decreased to 86.7%and the peak-to-peak value of position error decreased to 80% after the novel compensation controller is added. It concludes that the composite compensation controller can greatly improve the control precision of the dynamic sealed ISPs.     

基于改进型趋近律与负载观测器的永磁同步电机滑模速度控制器设计

为了提高三相永磁同步电机(PMSM)调速系统的动态品质,改善传统滑模速度控制器的控制性能,抑制系统抖振,提高控制精度,设计了基于新型趋近律与负载观测器的改进型滑模速度控制器。利用MATLAB/Simulink仿真软件,搭建控制系统模型并进行仿真分析。仿真验证了所设计的改进型PMSM速度控制器的有效性。该控制器可获得较好的速度跟踪精度和抗负载扰动能力,提高系统的稳定性和鲁棒性。     

考虑预设性能约束的运输机姿态容错控制

针对运输机舵面故障情况下的姿态容错控制问题,提出了一种考虑预设性能约束的自适应指令滤波增量反步(Adaptive Command-filtered Incremental Backstepping,ACFIBS)容错控制器。首先,构造运输机故障模型,在反步控制设计结构下,通过构造预设性能函数,保证外回路姿态角跟踪误差的动态性能。然后,考虑舵机偏转速率和幅值限制,引入受限指令滤波器和补偿信号,综合考虑气动参数不确定性,采用增量方法设计反步内环控制律。在此基础上,进一步考虑舵面故障情况,引入自适应方法及低通滤波器改进增量反步控制器。最后,通过理论推导和仿真试验验证了控制方法的有效性。仿真结果表明,所设计的控制器具有良好的容错性能,在不同舵面故障条件下均可实现对指令信号的预设性能跟踪,且在参数摄动情况下具有较强的鲁棒性。     

基于极限性能要求的电液负载模拟器多刚度与非线性复合数学模型

 揭示了传统模型的建模精度是影响电液负载模拟器极限性能研究的主要问题。分析并建立了多刚度与非线性复合数学模型,引入了基于舵机安装刚度、负载刚度、力矩传感器刚度、加载马达轴刚度的多刚度模型;合成了伺服阀的流量非线性、系统的饱和与摩擦等非线性环节;并与传统线性模型进行了比对分析与仿真实验,验证了模型的精确性。结果表明复合数学模型更真实而且精确地表征了系统物理情况,为系统结构参数优化设计和控制策略研究提供了理论基础。     

大粘滞摩擦因数的永磁伺服系统自适应反步控制

对于粘滞摩擦系数大的永磁伺服系统,传统的自适应反步控制会导致参数辨识结果波动较大、不易稳定、转速跟踪性能较差。设计了一种实时辨识粘滞摩擦因数的自适应反步控制器,同时对转动惯量、负载转矩和粘滞摩擦因数进行辨识,提高了对粘滞摩擦因数较大系统的转速跟踪性能和转动惯量及负载转矩辨识精度。所提方法结构简单、易于实现,在dSPACE公司的DS1103系统试验平台上对其进行了试验验证,试验结果表明了所提方法的正确性和有效性。