Stable and optimal controls of a proton exchange membrane fuel cell

In this paper, the trajectory tracking problem of a proton exchange membrane (PEM) fuel cell is considered. To solve this problem, stable and optimal controllers are proposed. The stable and optimal techniques have the objective that the system states should reach the desired trajectories while in the first, the tracking error is minimised, and in the second, the tracking error and inputs are minimised. The effectiveness of the proposed techniques is verified by simulations.     

Robust analysis of flatness based control using interval methods

In this paper a new approach to the robustness analysis of flatness based tracking controllers using interval methods is proposed. This methodology allows us to explicitely determine admissible intervals for the uncertain parameters such that specified error bounds for the state space trajectories are not violated. In contrast to earlier approaches no additional controllers have to be considered to take robustness properties into account. The presented approach also poses no a priori restrictions on the velocity of the reference trajectory. The application of the robustness analysis is demonstrated for a feedforward as well as a feedback tracking controller for the Van de Vusse type continuous stirred tank reactor (CSTR).     

Precise piston trajectory control for a free piston engine

A free piston engine removes the mechanical constraint on the piston motion by eliminating the crankshaft. The extra degree of freedom offers many advantages for reducing fuel consumption and emissions. Nevertheless, stability and robustness of the engine operation has been affected in the meantime. To ensure smooth engine operation, an active motion controller, which utilizes robust repetitive control, was developed previously to regulate the piston motion of a hydraulic free piston engine to track pre-defined trajectories. However, the long piston stroke length, high operating frequency and system nonlinearity impose challenges to precise piston motion control. Therefore, feedforward controllers are investigated in this paper to complement the repetitive control to further improve the tracking performance. The first feedforward design involves the inversion of a linear plant model that describes the dynamics of the engine operation, and the second design is based on the flatness approach, which involves the inversion of a nonlinear model of the system. The two feedforward controllers are designed and implemented on the free piston engine. The experimental and simulation results demonstrate the effectiveness of the proposed control under various operating conditions and reference piston trajectories.     

Nonsmooth finite-time control of uncertain second-order nonlinear systems

Nonsmooth finite-time stabilizing control laws have been developed for the double integrator system. The objective of this paper is to further explore the finite-time tracking control problem of a general form of uncertain second-order affine nonlinear system with the new forms of terminal sliding mode (TSM). Discontinuous and continuous finite-time controllers are also developed respectively without the singularity problem. Complete robustness can be acquired with the former, and enhanced robustness compared with the conventional boundary layer method can be expressed as explicit bounded function with the latter. Simulation results on the stabilizing and tracking problems are presented to demonstrate the effectiveness of the control algorithms.     

Nonsmooth finite-time control of uncertain second-order nonlinear systems

Nonsmooth finite-time stabilizing control laws have been developed for the double integrator system. The objective of this paper is to further explore the finite-time tracking control problem of a general form of uncertain second-order affine nonlinear system with the new forms of terminal sliding mode (TSM). Discontinuous and continuous finite-time controllers are also developed respectively without the singularity problem. Complete robustness can be acquired with the former, and enhanced robustness compared with the conventional boundary layer method can be expressed as explicit bounded function with the latter. Simulation results on the stabilizing and tracking problems are presented to demonstrate the effectiveness of the control algorithms.     

大型空间飞行器的高阶滑模姿态控制律设计

针对大型空间飞行器的大角度姿态控制问题,考虑航天器惯量矩阵中的不确定性和外部扰动力矩,应用高阶滑模控制方法设计了姿态跟踪控制律.采用的二阶滑模控制方法改善了系统针对不确定性及外部扰动的鲁棒性,并减弱了振颤现象.针对所设计的控制器进行了仿真验证,并与一阶滑模控制进行了对比,仿真结果表明了所提出方法的有效性.     

Fuzzy control of robot manipulator with a flexible tool

In some tasks, a rigid robot manipulator handles a long, slender, and flexible tool, which usually has not been equipped with vibration measuring devices. This situation makes a different tool tip position control problem. In this paper, a new method will be presented for simultaneous tip position and vibration suppression control of a flexible tool on a rigid‐link 3‐DOF robot. This approach uses fuzzy logic rule‐based controllers without using any sensors and actuators on the tool or a priori knowledge about the tool. Numerical simulation of robot and tool set has been accomplished and results support the fact that designed fuzzy controllers perform remarkably well in reducing vibrations and precision guidance of robot tool tip for tracking various trajectories. © 2005 Wiley Periodicals, Inc.     

Flatness-based control by quasi-static feedback illustrated on a cascade of two chemical reactors

Flat non-linear systems are linearizable by quasi-static feedback of generalized states. As a consequence, stable tracking of reference trajectories can be achieved with controllers which do not introduce extra dynamics into the loop. If, moreover, the system has a series structure, this may be exploited for simplifying the flatness-based analysis and design. The resulting method is illustrated on a series connection of two chemical reactors. Flatness-based analysis of the stationary solution and using these results the design of reference trajectories which account for constraints are discussed in detail. Quasi-static feedback controllers are designed and some simulations are reported.     

Model-reference robust tuning of 2DoF PI controllers for first- and second-order plus dead-time controlled processes

The aim of this paper is to present a robust tuning method for two-degree-of-freedom (2DoF) proportional integral (PI) controllers. This is based on the use of a model reference optimization procedure with servo and regulatory target closed-loop transfer functions for first- and second-order plus dead-time (FOPDT, SOPDT) controlled process models. The designer is allowed to deal with the performance/robustness trade-off of the closed-loop control system by specifying the desired robustness level by selecting a maximum sensitivity in the range from 1.4 to 2.0. In addition, a smooth servo/regulatory performance combination is obtained by forcing both closed-loop transfer functions to perform as closely as possible to non-oscillatory dynamic targets. A unified set of controller tuning equations is provided for FOPDT and SOPDT models with normalized dead-times from 0.1 to 2.0 that guarantees the achievement of the design robustness level. The robustness of the control system is analyzed as well as the robustness–fragility and performance–fragility of the optimized controllers. Comparative examples show the effectiveness of the proposed tuning method. The exact achievement of the control system robustness target for all the controlled process models considered (first- and second-order) is one of the distinctive characteristics of the proposed model reference robust tuning (MoReRT) method.     

A novel trajectory planning-based adaptive control method for 3-D overhead cranes

A three-dimensional (3-D) overhead crane is a complicated nonlinear underactuated mechanical system, for which high-speed positioning and anti-sway control are the kernel objective. Existing trajectory-based methods for 3-D overhead cranes focus on combining efficient and smooth trajectories with anti-sway tracking controllers without regard for payload motion; moreover, the exact value of plant parameters is required for accurate compensation during the control process. Motivated by these facts, we present a two-step design tracking strategy which consists of a trajectory planning stage and an adaptive tracking control design stage for 3-D overhead cranes. As shown by Lyapunov techniques and Barbalat's Lemma, the proposed controller guarantees asymptotic swing elimination and trolley positioning result in the presence of system uncertainties including unknown parameters and external disturbances. Simulation results also showed the applicability of the proposed method with good robustness against parameter uncertainties and external disturbances.     

ROBUST TRACKING FOR NONLINEAR SYSTEMS VIA HYBRID CONTROL

In this paper, the problem of output tracking for single-input/single-output nonlinear systems in the presence of mismatched uncertainty is studied. In our problem, the so-called matching condition in the literature is further relaxed, and a more general condition on the uncertainty is given. To attenuate the effects of uncertainties on the tracking error, a design method which is referred to as the Stable Combined Variable Perturbation Method (SCVPM) is presented. Based on this design method, a new robust tracking controller is derived using hyb rid control strategy. This controller, taken as a root-controller, is then used to generate two other controllers. All these controllers guarantee robustness of the closed-loop system, only with different tracking accuracies. The design method as well as the robust controllers is characterized by a small robust design parameter, ϵ. The tracking error converges to an ϵ-neighbourhood of the origin, and, by letting ϵ go to zero, the accuracy of tracking can be improved to any desired degree. Finally, an example is given and the simulation results confirm the theoretical analyses, thus show the effectiveness of the new design method and controllers.     

Robust visual tracking control system of a mobile robot based on a dual-Jacobian visual interaction model

This paper presents a novel design of a robust visual tracking control system, which consists of a visual tracking controller and a visual state estimator. This system facilitates human–robot interaction of a unicycle-modeled mobile robot equipped with a tilt camera. Based on a novel dual-Jacobian visual interaction model, a robust visual tracking controller is proposed to track a dynamic moving target. The proposed controller not only possesses some degree of robustness against the system model uncertainties, but also tracks the target without its 3D velocity information. The visual state estimator aims to estimate the optimal system state and target image velocity, which is used by the visual tracking controller. To achieve this, a self-tuning Kalman filter is proposed to estimate interesting parameters and to overcome the temporary occlusion problem. Furthermore, because the proposed method is fully working in the image space, the computational complexity and the sensor/camera modeling errors can be reduced. Experimental results validate the effectiveness of the proposed method, in terms of tracking performance, system convergence, and robustness.     

Singularity-conquering ZG controllers of z2g1 type for tracking control of the IPC system

With wider investigations and applications of autonomous robotics and intelligent vehicles, the inverted pendulum on a cart (IPC) system has become more attractive for numerous researchers due to its concise and representative structure. In this article, the tracking-control problem of the IPC system is considered and investigated. Based on Zhang dynamics (ZD) and gradient dynamics (GD), a novel kind of ZG controllers are developed and investigated for achieving the tracking-control purpose, which contains controllers of z2g0 and z2g1 types according to the number of times of using the ZD and GD methods. Besides, theoretical analyses are presented to guarantee the global and exponential convergence performance of both z2g0 and z2g1 controllers. Computer simulations are further performed to substantiate the feasibility and effectiveness of ZG controllers. More importantly, comparative simulation results demonstrate that controllers of z2g1 type can conquer the singularity problem (i.e. the division-by-zero problem).     

基于领导跟随的欠驱动船舶编队跟踪控制

针对具有三自由度欠驱动水面船舶编队控制问题,提出一种基于领导跟随 ( Leader /Follower) 结构的欠驱动水面船舶队形跟踪控制方法。当系统接收到队形控制指令, 每个欠驱动水面船舶按照自己在编队中的角色进行控制,其中Leader 根据任务中的队形指令 完成航迹跟踪控制,而Followers 则依据Leader 的信息和航行中任务中的队形指令完成航迹跟 踪控制。在航迹跟踪控制中,根据期望队形任务指令为每个船舶设计需要跟踪的参考路径和 速度指令; 基于Lyapunov 理论和重定义输出方法设计非线性速度控制器和路径跟踪控制器跟 踪设计路径和速度指令; 稳定性分析证明了队形跟踪误差是一致最终稳定的。仿真结果表明 船舶可以跟踪任意期望曲线队形,从而验证了方法的有效性。     

基于非线性控制方法的倒立摆系统控制

应用非线性系统跟踪控制方法对倒立摆系统的控制进行研究.基于非线性系统控制方法对倒立摆系统摆的镇定问题、台车位置调节问题和鲁棒控制问题设计出了具体的控制器.最后给出了在所设计的各种控制器作用下系统的仿真结果,结果表明所设计的控制器对倒立摆系统的稳定控制具有良好的效果.     

Linear,parameter-varying control of a supercavitating vehicle

A systematic approach to parameter-dependent control synthesis of a high-speed supercavitation vehicle (HSSV) is presented. The aim of the control design is to provide robust reference tracking across a large flight envelope, while directly accounting for the interaction of liquid and gas phases with the vehicle. A nonlinear dynamic HSSV model is presented and discussed relative to the actual vehicle. A linear, parameter-varying (LPV) controller is synthesized for angle rate tracking in the presence of model uncertainty. The control design takes advantage of coupling in the governing equations to achieve improved performance. Multiple LPV controllers synthesized for smaller overlapping regions of the parameter space are blended together, providing a single controller for the full flight envelope. Time-domain simulations implemented on high-fidelity simulations, provide insight into the performance and robustness of the proposed scheme.     

Fractional robust control of main irrigation canals with variable dynamic parameters

A new method is proposed for controlling main irrigation canals with variable dynamical parameters based on robust fractional order controllers. A methodology for designing PID controllers robust to changes in the time delay and the gain is presented first. Then this method is generalized to design fractional controllers that exhibit the same robustness as the previous PID to time delay and gain changes, but are noticeably more robust to variations in the dominant time constant of the process. This method is applied to control main irrigation canals. Extensive numerical simulations using the dynamic model of a real canal were carried out. Then experimental results were obtained in a prototype canal that proved the effectiveness of the proposed control method in terms of performance and robustness.     

Novel fuzzy fractional order PID controller for non linear interacting coupled spherical tank system for level process

In this paper, a novel Fuzzy Fractional Order Proportional Integral Derivative (FFOPID) controller is proposed to control the liquid level of Two Tank Spherical Interacting System (TTSIS). Spherical tanks are widely used in process industries due to its high storage capacity. These are non-linear due to its varying surface area with respect to its height and hence the level control of a spherical tank system is a challenging task. Fractional Order Proportional Integral Derivative (FOPID) controller is designed for a liquid level control of a spherical tank which is modelled as a fractional Order System. The performance indices such as rise time, settling time, peak time and peak overshoot are analysed for the proposed control scheme and compared to conventional controllers such as PI, PID, PID-SMC, FOPID. Moreover the time integral performance measures such as ITAE, IAE and ISE are analysed. Experimental results are shown to validate the obtained results with those of simulations. It has been proven that FFOPID outperforms all other existing techniques in terms of various time domain specifications and time integral performance measures.     

Intelligent Robust Tracking Controls for Holonomic and Nonholonomic Mechanical Systems Using Only Position Measurements

Intelligent robust tracking control designs are proposed in this paper for both uncertain holonomic and nonholonomic mechanical systems. A unified and systematic procedure, that is based on an adaptive fuzzy (or neural network) system and a linear observer, is employed to derive the controllers for these two constrained mechanical systems. Adaptive fuzzy-based (or neural network-based) position feedback tracking controllers can be constructed such that all the states and signals of the closed-loop systems are bounded and the tracking error locally converges to a small region around zero. Only position measurements are required for feedback. The implementation of the fuzzy (or neural network) basis functions depends only on the desired reference information and so once a set of desired trajectories is given, the required basis functions can be explicitly preassigned. Consequently, the intelligent robust position feedback tracking controllers developed here possess the properties of computational simplicity and easy implementation. Finally, simulation examples are presented to demonstrate the effectiveness of the proposed control algorithms.     

Supervisory control of DC‐DC bidirectional converter for advanced aeronautic applications

In this paper, a sliding manifold‐based control strategy is used for controlling a bidirectional DC‐DC converter for aeronautic applications. The proposed design follows a 2‐level strategy, where low‐level controllers are designed first, then a high‐level supervisor is used for scheduling the low‐level controllers. Different from previous approaches, each of the low‐level controlled system is a globally exponentially stable closed‐loop system, thus resulting into simpler conditions for the stability of the overall system. Moreover, stability of the supervisory strategy is rigorously proved by using a suitable Lyapunov function. Finally, a switching implementation is also considered. The effectiveness and robustness of the proposed strategy is shown by detailed simulations in Matlab/Stateflow/SymPowerSystem.