Modelling of ultrasonic motor with dead-zone based on Hammerstein model structure

The ultrasonic motor (USM) possesses heavy nonlinearities which vary with driving conditions and load-dependent characteristics such as the dead-zone. In this paper, an identification method for the rotary travelling-wave type ultrasonic motor (RTWUSM) with dead-zone is proposed based on a modified Hammerstein model structure. The driving voltage contributing effect on the nonlinearities of the RTWUSM was transformed to the change of dynamic parameters against the driving voltage. The dead-zone of the RTWUSM is identified based upon the above transformation. Experiment results showed good agreement be- tween the output of the proposed model and actual measured output.

Adaptive Variable Structure Control of MIMO Nonlinear Systems with Time-varying Delays and Unknown Dead-zones

In this paper, adaptive variable structure neural control is presented for a class of uncertain multi-input multi-output （MIMO） nonlinear systems with state time-varying delays and unknown nonlinear dead-zones. The unknown time-varying delay uncer- tainties are compensated for using appropriate Lyapunov-Krasovskii functionals in the design. The approach removes the assumption of linear function outside the deadband without necessarily constructing a dead-zone inverse as an added contribution. By utilizing the integral-type Lyapunov function and introducing an adaptive compensation term for the upper bound of the residual and optimal approximation error as well as the dead-zone disturbance, the closed-loop control system is proved to be semi-globally uniformly ultimately bounded. In addition, a modified adaptive control algorithm is given in order to avoid the high-frequency chattering phenomenon. Simulation results demonstrate the effectiveness of the approach.

ADAPTIVE CONTROL OF FLEXIBLE BEAM WITH UNKNOWN DEAD-ZONE IN THE DRIVING MOTOR

Adaptive control of a flexible beam system preceded by an unknown dead-zonein the driving motor is investigated in state space form. By introducing an important lemma forsimplifying error equation between the flexible beam model and the matching reference model, arobust adaptive control scheme is developed by involving the dead-zone inverse terms. The newadaptive control law ensures global stability of the entire system and achieves desired trackingprecision even when the slopes of the dead-zone are not equal. Simulations performed on a typicalflexible beam system illustrate and clarify the validity of this approach.

Anti-Dead-Zone Integral Sliding Control and Active Vibration Suppression of a Free-floating Space Robot with Elastic Base and Flexible Links

Under the conditions of joint torque output dead-zone and external disturbance,the trajectory tracking and vibration suppression for a free-floating space robot(FFSR)system with elastic base and flexible links were discussed.First,using the Lagrange equation of the second kind,the dynamic model of the system was derived.Second,utilizing singular perturbation theory,a slow subsystem describing the rigid motion and a fast subsystem corresponding to flexible vibration were obtained.For the slow subsystem,when the width of deadzone is uncertain,a dead-zone pre-compensator was designed to eliminate the impact of joint torque output dead-zone,and an integral sliding mode neural network control was proposed.The integral sliding mode term can reduce the steady state error.For the fast subsystem,an optimal linear quadratic regulator(LQR)controller was adopted to damp out the vibration of the flexible links and elastic base simultaneously.Finally,computer simulations show the effectiveness of the compound control method.

Adaptive Attitude Control for Multi-MUAV Systems With Output Dead-Zone and Actuator Fault

Many mechanical parts of multi-rotor unmanned aerial vehicle(MUAV)can easily produce non-smooth phenomenon and the external disturbance that affects the stability of MUAV.For multi-MUAV attitude systems that experience output dead-zone,external disturbance and actuator fault,a leader-following consensus anti-disturbance and fault-tolerant control(FTC)scheme is proposed in this paper.In the design process,the effect of unknown nonlinearity in multi-MUAV systems is addressed using neural networks(NNs).In order to balance out the effects of external disturbance and actuator fault,a disturbance observer is designed to compensate for the aforementioned negative impacts.The Nussbaum function is used to address the problem of output dead-zone.The designed fault-tolerant controller guarantees that the output signals of all followers and leader are synchronized by the backstepping technique.Finally,the effectiveness of the control scheme is verified by simulation experiments.

Design of Observer-based Adaptive Controller for Nonlinear Systems with Unmodeled Dynamics and Actuator Dead-zone

This paper presents an up-to-date study on the observer-based control problem for nonlinear systems in the presence of unmodeled dynamics and actuator dead-zone.By introducing a dynamic signal to dominate the unmodeled dynamics and using an adaptive nonlinear damping to counter the effects of the nonlinearities and dead-zone input,the proposed observer and controller can ensure that the closed-loop system is asymptotically stable in the sense of uniform ultimate boundedness.Only one adaptive parameter is needed no matter how many unknown parameters there are.The system investigated is more general and there is no need to solve Linear matrix inequality （LMI）.Moreover,with our method,some assumptions imposed on nonlinear terms and dead-zone input are relaxed.Finally,simulations illustrate the effectiveness of the proposed adaptive control scheme.

Adaptive variable structure control for large-scale time-delayed systems with unknown nonlinear dead-zone

The problem of adaptive fuzzy control for a class of large-scale, time-delayed systems with unknown nonlinear dead-zone is discussed here. Based on the principle of variable structure control, a design scheme of adaptive, decentralized, variable structure control is proposed. The approach removes the conditions that the dead-zone slopes and boundaries are equal and symmetric, respectively. In addition, it does not require that the assumptions that all parameters of the nonlinear dead-zone model and the lumped uncertainty are known constants. The adaptive compensation terms of the approximation errors axe adopted to minimize the influence of modeling errors and parameter estimation errors. By theoretical analysis, the closed-loop control system is proved to be semiglobally uniformly ultimately bounded, with tracking errors converging to zero. Simulation results demonstrate the effectiveness of the approach.

Parameter estimation for dual-rate sampled Hammerstein systems with dead-zone nonlinearity

The identification of nonlinear systems with multiple sampled rates is a difficult task.The motivation of our paper is to study the parameter estimation problem of Hammerstein systems with dead-zone characteristics by using the dual-rate sampled data.Firstly,the auxiliary model identification principle is used to estimate the unmeasurable variables,and the recursive estimation algorithm is proposed to identify the parameters of the static nonlinear model with the dead-zone function and the parameters of the dynamic linear system model.Then,the convergence of the proposed identification algorithm is analyzed by using the martingale convergence theorem.It is proved theoretically that the estimated parameters can converge to the real values under the condition of continuous excitation.Finally,the validity of the proposed algorithm is proved by the identification of the dual-rate sampled nonlinear systems.

Terminal Angular Constraint Integrated Guidance and Control for Flexible Hypersonic Vehicle with Dead-Zone Input Nonlinearity

This paper presents an integrated guidance and control model for a flexible hypersonic vehicle with terminal angular constraints.The integrated guidance and control model is bounded and the dead-zone input nonlinearity is considered in the system dynamics.The line of sight angle,line of sight angle rate,attack angle and pitch rate are involved in the integrated guidance and control system.The controller is designed with a backstepping method,in which a first order filter is employed to avoid the differential explosion.The full tuned radial basis function(RBF)neural network(NN)is used to approximate the system dynamics with robust item coping with the reconstruction errors,the exactitude model requirement is reduced in the controller design.In the last step of backstepping method design,the adaptive control with Nussbaum function is used for the unknown dynamics with a time-varying control gain function.The uniform ultimate boundedness stability of the control system is proved.The simulation results validate the effectiveness of the controller design.

Adaptive feedback control for nonlinear triangular systems subject to uncertain asymmetric dead-zone input

In this paper,an adaptive control strategy is proposed to investigate the issue of uncertain dead-zone input for nonlinear triangular systems with unknown nonlinearities.The considered system has no precise priori knowledge about the dead-zone feature and growth rate of nonlinearity.Firstly,a dynamic gain is introduced to deal with the unknown growth rate,and the dead-zone characteristic is processed by the adaptive estimation approach without constructing the dead-zone inverse.Then,by virtue of hyperbolic functions and sign functions,a new adaptive state feedback controller is proposed to guarantee the global boundedness of all signals in the closed-loop system.Moreover,the uncertain dead-zone input problem for nonlinear upper-triangular systems is solved by the similar control strategy.Finally,two simulation examples are given to verify the effectiveness of the control scheme.

高能激光器波前预补偿技术研究

随着高功率激光技术的发展,目前的以高功率反射式变形镜为核心的波前校正装置只能通过增大口径来避免反射面损伤,还难以解决连续工作加热时的镜面形变问题。本文拟采用低功率变形镜在信号光阶段进行预补偿,达到高功率激光光束质量校正的效果。首先介绍了高能信号光预补偿技术的补偿原理、方法,然后在板条固体激光器输出功率分别为30W和3000W时进行了波前补偿实验,通过预补偿方法激光远场光束质量得到明显的改善和提高:在激光器输出功率为30W时,光束质量从β=10提高到β=15;在激光器输出功率为3000W时,光束质量从β=10提高到β=3,此外,本文还对非平面波前的信号光传输技术以及信号光预补偿技术的校正策略开展了相应的研究与试验。与传统的自适应光学校正方法相比,信号光预补偿技术可以从根本上摆脱强激光对变形镜的加热和损伤问题,无限的扩展了光束净化系统的功率限制。

多线切割机线锯系统张力预补偿控制与试验

针对多线切割机线锯缠绕换向和往复走丝加工硬脆材料,导致线锯张力变化影响加工精度的问题,提出一种新的张力预补偿控制策略。首先通过自主研发的多线切割机和张紧轮系统,研究线锯在导轮两侧的张力变化规律。然后根据线锯张力波动对张紧轮角位移的影响得出张紧控制系统的预补偿模型,结合伺服系统三环架构,设计基于可编程运动控制器的多线切割张力预补偿控制器,进行张力预补偿控制与伺服系统自带的传统PID控制下的张力波动与速度跟随性能测试和试验验证,试验结果表明张力预补偿控制下线锯张力波动差值更小,线锯系统稳定性更好。

数控机床热误差的建模与预补偿

研究了数控机床热误差的预补偿方法。建立了基于主轴转速的热误差自回归模型，从而不需要测量机床的温度场就可以预测热误差。在加工前通过修改工作的数控加工程度即可进行补偿，大大简化了误差补偿过程。可应用于中等精度的数控机床。

预啁啾10GHz、38km色散管理孤子的传输实验

本文利用 5GHz增益开关分布反馈 (DFB)激光器结合 1× 2× 1时分复用耦合器获得了 1 0 GHz带有预啁啾的孤子脉冲串 ,利用此脉冲串进行了 1 0 GHz、3 8km的色散管理孤子的传输实验 .实验结果表明 ,对于小功率的色散管理 (DM)孤子 ,尽管有较大的初始啁啾 ,仍然可以实现孤子的传输 ,这反映了 DM孤子比经典孤子的优越性 .对具有负初始啁啾 DM孤子传输 。

功率放大器非线性对Chirp信号的影响及预补偿方法研究

本文研究功率放大器非线性失真对Chirp信号幅频和相频特性的影响及预补偿方法.在雷达系统中,为了获得足够的作用距离,需要增加发射机的发射功率.对输出功率的要求越高,功率放大器(HPA)的工作点就越接近饱和区.这就使得功率放大器的输出信号产生了非线性失真.功率放大器的非线性失真直接影响了发射线性调频(Chirp)信号的质量,对后续的信号处理带来一定程度的影响.以脉冲压缩为例,分析了非线性失真对主瓣宽度和第一旁瓣抑制的恶化.提出了两种建立在直接数字合成(DDS)技术基础上的预补偿方法.通过理论分析和计算机仿真,证明了两种预补偿方法都可以有效地减小非线性失真.最后对影响两种预补偿方法性能的因素和收敛性进行了分析,对两种预补偿方法的结果进行了比较.

光纤时间频率传输数字相位补偿方法

为提高光纤时间频率传输的精度,提出了数字移相补偿方法。该方法采用单片机量化发送端和接收端射频信号的相位差,然后再控制数字移相器调整发送端射频信号相位,使二者相位趋于一致,实现传输光纤引起相位变化的前置补偿,从而提高时间频率传输精度。实验表明,该系统可将发射端信号和接收端信号的相位差减少到5°以内。

电液比例系统变论域自适应模糊滑模控制

针对具有未知死区的电液比例系统,提出了一种带有死区补偿的变论域自适应模糊滑模控制方法。根据比例换向阀的死区特性,采用模糊逻辑系统设计死区预补偿器;将变论域的思想引入到自适应模糊滑模控制中,在线调节输入输出变量论域和隶属度函数,从而提高传统模糊滑模控制的精度;依据Lyapunov稳定性理论,构造变论域伸缩因子的自适应律,并对模糊逼近误差的上界进行实时估算,无需假设逼近误差上界已知。实验结果表明:采用变论域方法能有效地提高自适应模糊控制器的性能,在电液比例系统的位置跟踪控制中能克服系统固有的非线性特性、参数不确定性及外界干扰的影响,并且死区预补偿器消除了未知死区对跟踪精确度的影响,该方法具有响应快、精确度高、自适应鲁棒性强的特点。

20mm铜铝管焊接电流的预补偿研究

设计了带有焊接电流预补偿的PLC控制系统。建立了晶闸管导通角和电源电压的数据库。每次焊接前,控制系统要测量电源电压,并在数据库中查询得出合适的导通角,传给晶闸管触发板。对20mm铜铝管焊接试验中的电源电压与焊接电流数据进行了区间估计,结果表明焊接电流的总体均值和总体方差的置信区间分别为(51.1,52.7)和(0.06,0.6),说明焊接电流较稳定,从而可保证了铜铝管焊接质量。

TOPSwitch简介及其在功率因数校正中的应用

简单介绍了三端单片开关电源TOPSwitch这一新型开关电源芯片 ,重点阐述了TOPSwitch在PFC电路中的应用 ,建立了占空比预补偿模型 ,给出了设计技术和电路。实验结果表明 ,基于TOPSwitch的PFC ,采用对占空比的预补偿 ,能使功率因数达到 0 .99以上 ,总谐波失真低于 5 % ,效率可达 93%。

一种新型纳米通道单分子检测探头的设计

针对纳米通道单分子检测的探头测量系统,在详细分析探头结构以及测量带宽等属性的基础上,采用前置带宽补偿的原理,提出了一种改进的检测探头的设计方法。该方法不仅能够扩大原有测量系统的测量带宽,而且能够灵活配置系统的零点和极点,加快系统的动态响应过程。通过仿真实验验证了本文方法的可行性和有效性,并且通过实际测量探头电路给出了测量实验结果。