Robust H∞ control with multiple constraints forthe track-following system of an optical disk drive

In this paper, the authors design a tracking controller which satisfies transient response specifications and maintains tracking error within a tolerable limit for the uncertain track-following system of an optical disk drive. To this end, a robust H_∞ control problem, with regional stability constraints and sinusoidal disturbance rejection is considered. The internal model principle is used for rejecting the sinusoidal disturbance caused by eccentric rotation of the disk. The authors show that a condition satisfying the regional stability constraints can be expressed in terms of a linear matrix inequality (LMI) using the Lyapunov theory and S-procedure. Finally, a tracking controller is obtained by solving an LMI optimization problem involving two LMIs. The proposed controller design method is evaluated through an experiment     

Continuous variable structure controller for BLDDSM positioncontrol with prescribed tracking performance

The continuous, accurate, and robust sliding mode tracking controller based on a disturbance observer for a brushless direct drive servo motor (BLDDSM) is presented. Although the conventional sliding mode control (SMC) or variable structure control (VSC) can give the desired tracking performance, there exists an inevitable chattering problem in control which is undesirable for a direct drive system. With the proposed algorithm, not only are the chattering problems removed, but also the prescribed tracking performance can be obtained by using the efficient compensation of the disturbance observer. The design of the sliding mode tracking controller for the prescribed, accurate, and robust tracking performance without the chattering problem is given based on the results of the detailed stability analysis. The usefulness of the proposed algorithm is demonstrated through the computer simulations for a BLDDSM under load variations     

移动机器人全局轨迹跟踪的自适应滑模控制

讨论了两驱动后轮角速度为控制输入的移动机器人轨迹跟踪问题，针对含有未知参数的非完整移动机器人运动学模型．基于反演（backstepping）控制算法的思想设计了变结构控制的切换函数，并由此构造了具有全局渐近稳定的白适应滑模轨迹跟踪控制器。该方法设计过程简单并具有直观的稳定性分析，适用于移动机器人的全局轨迹跟踪控制。仿真结果表明了该方法的有效性和正确性。     

Robust tracking servo system considering force disturbance for the optical disk recording system

This paper proposes a new robust tracking servo system for the optical disk recording system with feedforward controller based on the prediction of the tracking error. In optical recording systems, the feedback servo system must suppress the influence of force disturbance and parameter variation. To overcome this problem, this paper designs the robust feedback control system by using coprime factorization and disturbance observer. The detecting signal of the optical disk recording system is only a tracking error. Hence, the feedforward controller of the proposed tracking control system is constructed based on both the "zero-phase-error tracking" control theory and the prediction of the tracking error. The experimental results point out that the proposed tracking servo system has a quick and precise tracking response and keeps the residual tracking error below its tolerance.     

一类基于自适应反馈控制的车辆编队研究

文中研究了基于生物刺激神经动力学方法的车辆编队控制问题。以编队车辆的运动学模型为基础,在跟随领航者体系下建立车辆编队系统动态模型。根据李雅普诺夫稳定性理论,设计出新的自适应反馈跟踪控制器,将车辆跟随问题转化为系统误差的控制问题,并运用仿真实验验证控制器的有效性。与现有的反馈跟踪控制器进行对比后可以看到,文中所设计的控制器在稳定性和收敛速度上有了进一步的提高。     

跨音速飞行状态下的一种智能控制方法

讨论了跨音速段飞行状态下复杂的气动特性及其影响,为解决飞机飞行过程中纵向按速度静不稳定这一主要矛盾,设计了一种模糊神经网络控制器,控制器以角度跟踪误差及其微分信号为输入来控制相应的控制舵面,实现对姿态的跟踪控制;以速度跟踪误差及其微分信号为输入来控制油门的偏转,实现对速度的跟踪控制.在此基础上,进一步利用遗传算法对模糊神经网络控制器进行了优化设计,并给出了遗传算法各个参数的选取原则.仿真结果也验证了所设计的控制系统具有良好的性能.     

Self-tuning in integral sliding mode control with a Levenberg–Marquardt algorithm

In high-precision motion systems, tracking often comes with the problem of overshoot or poor settling behavior. To deal with this problem, a sliding mode controller with saturated integrator is studied. For large servo signals, sufficiently removed from the sliding surface, the controller will operate in PD mode. This limits the integrator buffer, and thus the overshoot. At the sliding surface (for small servo signals) the controller operates in PID mode with the aim to avoid steady-state error. Tuning of the controller parameters: the switching gain and the saturation length, strongly affects the tracking performance. For this reason, a self-tuning method is proposed. In the method, the required gradients are partly computed using models of the system and the controller. For the remaining part, sampled data is used to deal with disturbances and model uncertainties. With a Levenberg–Marquardt algorithm numerical problems associated with the gradient computations are avoided. The sliding mode controller with optimized parameters is implemented on an industrial wafer scanner to improve throughput during the wafer stage (chuck) exchange.     

光电跟踪自抗扰控制技术研究

为了实现对快速运动目标高精度跟踪,对光电跟踪系统中的自抗扰控制技术进行了研究。根据速度闭环传递函数,利用三阶非线性扩张观测器估计系统状态变量,实现对不确定性因素的补偿,通过改变位置环被控对象传递函数提高系统的跟踪精度。对系统进行仿真与实验研究,分析自抗扰控制对光电跟踪系统动态和稳态性能的影响,与PI控制相对比,结果表明:对于高速运动目标,利用自抗扰控制技术可以将系统的跟踪精度提高7倍左右;对于低速运动目标,由于摩擦和系统噪声的影响,系统的跟踪精度仅提高了4倍左右。若在控制回路中引入相位超前环节,可以将系统的超调量降低40%,进一步改善了系统的动态性能,该技术的实现对于高精度跟踪控制的研究具有重要的应用价值。     

Sensorless speed tracking of induction motor with unknown torque based on maximum power transfer

In this paper, the authors first derive the maximum power transfer theorem for an induction motor. Then, a nonlinear indirect adaptive sensorless speed tracking controller for the motor with the maximum power transfer is proposed. In this controller, only the stator currents are assumed to be measurable. The rotor flux and speed observers are designed to relax the need of flux and speed measurement. In addition, the rotor resistance estimator is also designed to cope with the problem of the fluctuation of rotor resistance with temperature. Stability analysis based on Lyapunov theory is also performed to guarantee that the controller design here is stable. Finally, the computer simulations and experiments are conducted to demonstrate the satisfactory tracking performance of the authors' design subject to maximum power transfer.     

位置和艏向角约束的非对角欠驱动USV轨迹跟踪

仅配备有纵向推进力和转船力矩装置的无人水面艇是典型的欠驱动系统,不能通过定常光滑反馈控制律镇定到平衡状态。本文针对一类惯性矩阵和阻尼矩阵非对角的欠驱动无人水面艇,设计了基于附加控制器和反步法的光滑时变跟踪控制律,在保证跟踪误差暂态性能的前提下,实现了曲线和直线情形下的轨迹跟踪。首先,通过状态变换将非对角模型转化为对角形式,并运用反馈线性化理论简化控制输入。其次,通过设计虚拟控制函数来镇定误差运动学方程,并通过引入障碍Lyapunov函数(BLF)来保证跟踪误差满足规定的性能。然后,通过在误差镇定函数中引入虚拟控制量解决了系统的欠驱动问题,稳定性分析表明本文控制策略能够保证闭环系统中的所有状态是一致最终有界的。最后,Matlab/Simulink仿真结果表明了该控制器的有效性。     

Robust$H_infty$Power Control for CDMA Cellular Communication Systems

Power control is an important factor for direct-sequence code division multiple access (DS-CDMA) cellular radio systems to achieve higher communication link quality and better system capacity. In order to track the desired signal-to-interference-plus-noise ratio (SINR) under round-trip delay, multiple access interference (MAI), channel fading, and noise, a time delay-based state-space model is developed for representing the tracking error dynamics and a state feedback controller is introduced for SINR tracking control. Then the power tracking problem can be regarded as a control problem. In this paper, a robust$H_infty$power tracking control design is proposed to achieve a robust optimal SINR tracking from the minimization of the worst-case effect point of view. This robust optimal power tracking design problem can be transformed to solving the eigenvalue problem (EVP) under some linear matrix inequality (LMI) constraints. The LMI Matlab toolbox can be used to efficiently solve the EVP via convex optimization to achieve a robust optimal SINR tracking design. Under the proposed distributed framework, the information of channel gain is not needed.     

Vision-based nonlinear tracking controllers with uncertainrobot-camera parameters

This paper considers the problem of position tracking control of planar robot manipulators via visual servoing in the presence of parametric uncertainty associated with the robot mechanical dynamics and/or the camera system. Specifically, by assuming exact knowledge of the mechanical parameters, we design an adaptive camera calibration controller that compensates for uncertain camera parameters and ensures global asymptotic position tracking. We then develop an adaptive robot controller that accounts for parametric uncertainty throughout the entire robot-camera system while producing global asymptotic position tracking. Experimental results illustrating the viability of the adaptive controllers and extensions regarding robust control and redundant robot manipulators are also included     

Sliding-mode control of a nonlinear-input system: application to amagnetically levitated fast-tool servo

Magnetic servo levitation (MSL) is currently being investigated as an alternative to drive fast-tool servo systems that could overcome the range limitations inherent to piezoelectric driven devices while operating over a wide bandwidth. To control such systems, a feedback-linearized controller coupled with a Kalman filter has been previously described. Performance limitations that degrade tracking accuracy suggest the use of a more robust controller design approach, such as sliding-mode control. Current literature on sliding mode deals almost exclusively with systems that are affine on the input, while the magnetic fast-tool servo is nonlinear on it when the control action is current command. This paper discusses a sliding mode-based controller that overcomes the aforementioned problem by defining a modified sliding condition to calculate control action. Experimental results demonstrate the feasibility of achieving long-range fast tracking with magnetically levitated devices by using sliding-mode control     

Motion control of rigid robots driven by current-fed induction motors

The problem of controlling a rigid manipulator driven by induction motors operating in the current-command mode to follow a desired trajectory is considered in this paper. Based on a fourth-order reduced model of an induction motor, a current controller is proposed using only measurements of link positions and velocities as well as stator currents of induction motors. The rotor flux is estimated through a closed-loop observer. Provided that the flux observer is properly initialized, this controller is singularity-free and ensures the global exponential tracking to the desired trajectory. Simulations are presented to illustrate the performance of this controller.     

Perfect tracking control based on multirate feedforward controlwith generalized sampling periods

In this paper, a novel perfect tracking control method based on multirate feedforward control is proposed. The advantages of the proposed method are that: (1) the proposed multirate feedforward controller eliminates the notorious unstable zero problem in designing the discrete-time inverse system; (2) the states of the plant match the desired trajectories at every sampling point of reference input; and (3) the proposed controller is completely independent of the feedback characteristics. Thus, highly robust performance is assured by the robust feedback controller. Moreover, by generalizing the relationship between the sampling period of plant output and the control period of plant input, the proposed method can be applied to various systems with hardware restrictions of these periods, which leads to higher performance. Next, it is shown that the structure of the proposed perfect tracking controller is very simple and clear. Illustrative examples of position control using a DC servomotor are presented, and simulations and experiments demonstrate the advantages of this approach     

Nichtlineare Trajektorienfolgeregelung für einen Laborhelikopter

This contribution is devoted to the nonlinear tracking control problem of the laboratory experiment helicopter 3DOF distributed by Quanser. The laboratory experiment belongs to the class of mechanical systems with three degrees-of-freedom and two control inputs. It is well known that the systematic design of nonlinear controllers for underactuated mechanical systems is a challenge compared to fully actuated systems. On certain simplifying assumptions, which very well apply to the operating range of practical interest, we can show that the mathematical model is configuration flat. Thereby, a mechanical system is said to be configuration flat if it is differential flat and the flat outputs solely depend on the generalized coordinates of the mechanical system. The controller design is based on a formulation of the mechanical system on a Riemannian manifold where the kinetic energy serves as a natural Riemannian metric. In a first step a nonlinear tracking controller including an integral part in the linear error system is designed by means of a quasi-static state feedback. In a second step the design of the tracking controller is based on the theory of exact linearization utilizing the so-called dynamic extension algorithm. The experimental results of both controllers are compared and discussed in detail. In particular, the quasi-static state feedback controller shows an excellent tracking behavior. The performance as being obtained by the nonlinear controlled cannot be achieved by conventional linear control strategies.     

Development of a nonlinear PI controller for accurate positioning of an industrial hydraulic manipulator

Designing a quick, very accurate and robust position controller for industrial hydraulic manipulators is a challenging problem. The controller must contend with many nonidealities that exist in such systems—nonlinear dynamics, hydraulic flow deadband, and stiction are all present. This paper documents step-by-step development and implementation of a novel nonlinear proportional-integral (NPI) controller in an attempt to deal with these issues. A number of modifications are performed on the integral portion of a conventional proportional-integral (PI) controller, each displaying improved performance over the last. The final NPI controller is shown to improve position tracking accuracy by a factor of five, relative to a conventional PI controller, without sacrificing regulation accuracy or robustness. The experiments are performed on the up-down revolute axis of an instrumented Unimate MK-II hydraulic manipulator.     

Finite-time control of DC–DC buck converters via integral terminal sliding modes

This article presents novel terminal sliding modes for finite-time output tracking control of DC–DC buck converters. Instead of using traditional singular terminal sliding mode, two integral terminal sliding modes are introduced for robust output voltage tracking of uncertain buck converters. Different from traditional sliding mode control (SMC), the proposed controller assures finite convergence time for the tracking error and integral tracking error. Furthermore, the singular problem in traditional terminal SMC is removed from this article. When considering worse modelling, adaptive integral terminal SMC is derived to guarantee finite-time convergence under more relaxed stability conditions. In addition, several experiments show better start-up performance and robustness.     

基于模糊逻辑控制的自适应锁相环设计

针对某型雷达在航天器频率的跟踪测量过程中,由于目标动态变化影响较大,存在跟踪稳定性较差、测量精度偏低的问题,提出了对雷达锁相跟踪环路采用模糊逻辑控制的自适应变带宽设计。该方法主要是通过引入模糊逻辑控制器,利用输入值适配控制规则,为每个控制规则确定其适配程度,并且采过加权计算合并规则的输出,控制环路滤波器的系数,从而自动调整环路带宽,达到增强雷达设备频率跟踪稳定性和提高测量精度的目的。仿真结果表明,模糊逻辑控制自适应变带宽锁相环跟踪目标的稳定性和测量精度都优于传统锁相环。     

基于Backstepping的带推力矢量飞艇姿态控制系统设计

推力矢量控制技术可以有效地解决飞艇低速飞行时舵效不足的问题,但其具有很强的非线性特性,加之飞艇体积庞大,易受风干扰,所以经典的控制器难以满足要求。Backstepping是一种基于递推反演的非线性控制方法,特别适用于强非线性及存在不确定性的系统。针对飞艇的六自由度非线性模型,引入Backstepping方法对带推力矢量飞艇设计了姿态控制器并进行了仿真验证,结果表明所设计的非线性控制器具有良好的动态性,实现了对受扰系统的全局镇定和对给定偏航角的渐进跟踪。