Synthesis Algorithm for Control System with Saturated Actuator

SummaryThis article investigates the devise issue of a practical finite‐time output‐tracking control for uncertain nonlinear nonstrict‐feedback systems subject simultaneously to time‐varying output constraints (TVOC), actuator saturation, and bounded unmatched disturbances. An adaptive fuzzy approximator‐based control system is devised using the dynamic surface control (DSC) concept. System output constraints are addressed by employing an appropriate barrier Lyapunov function. Adaptive fuzzy disturbance observers are constructed to practically deal with time‐varying unmatched but bounded disturbances. It is verified via Lyapunov stability analysis and simulation experiments that all closed‐loop signals remain bounded, the output tracking error practically converges in finite time to a tiny but adjustable neighborhood around the origin, and the system output stays within its required time‐varying bounds.

Every physical system in our real life has nonlinearities and very little can be done to overcome them. Many practical systems are sufficiently nonlinear so that important features of their performance may be completely overlooked if they are analysed and designed through linear techniques. In HDD servo systems, major nonlinearities are frictions, high-frequency mechanical resonances and actuator saturation nonlinearities. Among all these, the actuator saturation could be the most significant nonlinearity in designing an HDD servo system. When the actuator saturates, the performance of the control system designed will seriously deteriorate. Interested readers are referred to a recent monograph by Hu and Lin [97] for a fairly complete coverage of many newly developed results on control systems with actuator nonlinearities.

Control allocation based fault tolerant control of descriptor system with actuator saturation

In this paper, an adaptive fuzzy state feedback control method is proposed for the single-link robotic manipulator system. The considered system contains unknown nonlinear function and actuator saturation. Fuzzy logic systems (FLSs) and a smooth function are used to approximate the unknown nonlinearities and the actuator saturation, respectively. By combining the command-filter technique with the backstepping design algorithm, a novel adaptive fuzzy tracking backstepping control method is developed. It is proved that the adaptive fuzzy control scheme can guarantee that all the variables in the closed-loop system are bounded, and the system output can track the given reference signal as close as possible. Simulation results are provided to illustrate the effectiveness of the proposed approach.

With the development of science and industry the rapid increase in time-delay systems has prompted more and more researchers to use intermittent control theory to analyze and synthesize the stability of the time-delay systems subject to actuator saturation and random perturbation. This note investigates the development status and research significance of time-delay systems, Intermittent control and actuator saturation, and that by method of Intermittent control analysis and discussion of the stability of time-delay systems with actuator saturation is of great theoretical significance and practical application value.

Many control methods are used in attitude control of reentry vehicle, such as optimal control and classical control methods. However, those control laws may not work effectively if the attitude system is confronted with actuator faults and saturation. This paper proposes an adaptive fault tolerant attitude control method for the reentry vehicle's attitude control system, by combining the radial basis function network technology with adaptive fault tolerant control method. We simultaneously considered actuator fault, actuator saturation, time varying unknown disturbances and uncertainties when designing the control method. First, we set up the reentry attitude dynamic model concerning actuator fault; second, a finite-time H∞ adaptive fault-tolerant attitude controller is introduced to deal with the actuator fault, saturation, unknown disturbances and uncertainties of the reentry vehicle system; we proved the stability of our proposed adaptive attitude fault-tolerant controller through the Lyapunov function and the linear matrix inequality method. Finally, the effectiveness of such adaptive fault-tolerant control method has been identified by numerous simulation results. The simulation results show that our proposed method can not only effectively deal with actuator fault in the attitude control system, but also has very good robustness for actuator saturation, time varying unknown disturbances and uncertainties.

This article addresses the finite-time tracking control for multi-input and multi-output (MIMO) nonlinear nonstrict feedback systems with actuator faults and saturations. First, a fuzzy state observer is constructed to approximate the unmeasured system states, where the restrictions of the known actuator faults are removed from the observer design. Based on the state observer, a novel adaptive output feedback control is then proposed to achieve favorable tracking performance even if actuator saturations and faults occur. Also, the nonlinear functions in the MIMO nonlinear systems are not required to follow the linearly parameterization or growth conditions making the control design more generally available. Furthermore, the dynamic surface control technique is adopted to avoid tedious analytic computations inherent in the backstepping procedure. It can be proved that the proposed control can not only guarantee the closed-loop system states bounded, but also regulate the tracking errors to a small neighborhood around the equilibrium in finite time despite the existence of the actuator saturations and faults. Finally, comparative simulations are carried out to demonstrate the feasibility and effectiveness of the theoretical results.

Event-based dynamic output-feedback controller design for networked control systems with sensor and actuator saturations

SummaryA robust adaptive tracking control scheme is presented for a class of multiple‐input and multiple‐output mechanical systems with unknown disturbances under actuator saturation. The unknown disturbances are expressed as the outputs of a linear exogenous system with unknown coefficient matrices. An adaptive disturbance observer is constructed for the online disturbance estimation. An actuator saturation compensator is introduced to attenuate the adverse effects of actuator saturation. The adaptive backstepping method is then applied to design the robust adaptive tracking control law. It is proved that the designed control law makes the system outputs track the desired trajectories and guarantees the global uniform ultimate stability of the closed‐loop control system. Simulations on a two‐link robotic manipulator verify the effectiveness of the proposed control scheme.

Parallel manipulators with less than six degrees of freedom (DOF) have been increasingly used in high-speed hybrid machine tools. The structural features of parallel manipulators are dynamic, a characteristic that is particularly significant when these manipulators are used in high-speed machine tools. However, normal kinematic control method cannot satisfy the requirements of the control system. Many researchers use model-based dynamic control methods, such as the dynamic feedforward control method. However, these methods are rarely used in hybrid machine tools because of the complex dynamic model of the parallel manipulator. In order to study the dynamic control method of parallel manipulators, the dynamic feedforward control method is used in the dynamic control system of a 3-PSP (prismatic-spherical-prismatic) 3-DOF spatial parallel manipulator used as a spindle head in a high-speed hybrid machine tool. Using kinematic analysis as basis and the Newton-Euler method, we derive the dynamic model of the parallel manipulator. Furthermore, a model-based dynamic feedforward control system consisting of both kinematic control and dynamic control subsystems is established. The dynamic control subsystem consists of two modules. One is used to eliminate the influence of the dynamic characteristics of high-speed movement, and the other is used to eliminate the dynamic disturbances in the milling process. Finally, the simulation model of the dynamic feedforward control system of the 3-PSP parallel manipulator is constructed in Matlab/Simulink. The simulations of the control system eliminating the influence of the dynamic characteristics and dynamic disturbances are conducted. A comparative study between the simulations and the normal kinematic control method is also presented.The simulations prove that the dynamic feedforward control method effectively eliminates the influence of the dynamic disturbances and dynamic characteristics of the parallel manipulator on high-speed machine tools, and significantly improves the trajectory accuracy. This is the first attempt to introduce the dynamic feedfordward control method into the 3-PSP spatial parallel manipulator whose dynamic model is complex and provides a study basis for the real-time dynamic control of the high-speed hybrid machine tools.

In this paper, the problem of fault-tolerant control for simultaneous stabilization r uncertain singular systems subject to both time-varying nonlinear perturbation and actuator saturation is investigated. A sufficient condition for the existence of simultaneous stabilization controller is proposed which guarantees the regularity, impulse-free and stability of the r uncertain closed-loop singular systems with time-varying nonlinear perturbation and actuator saturation. Meanwhile a design approach to the simultaneous stabilization controller is designed via using linear matrix inequalities (LMIs).

In this paper, the simple adaptive control (SAC) with the anti-windup compensator (SAC-AW) is proposed for the attitude tracking of aircraft when actuator fault and saturation happen. First, the aircraft attitude model with actuator saturation is established. Then the SAC-AW is designed to handle the actuator fault and saturation in aircraft attitude control system. Meanwhile, the closed loop system stability is proved by utilizing Lyapunov's direct method. Simulation results verify the effectiveness of the presented method for aircraft attitude control in the presence of the actuator fault and saturation.

Dynamical analysis and robust control for dive plane of supercavitating vehicles

The papers in this special section focus on modeling, analysis, and advanced control in motion-control systems. Precision, agility, robustness, efficiency, and intelligence are now becoming the design indexes for modern motion control systems. High control performance, intelligent functions, or efficiency improvements advance the level of motion control products or systems and bring a lot of benefits for companies. The difficulties for the control research academics and practicing engineers lie in various factors, such as nonlinearities, friction, complex internal dynamics, time-varying parameters in the system dynamics, external disturbances in the working environment, and complex work tasks. These make the control design a very challenging work. To employ advanced control algorithms and schemes, time-/frequency-domain modeling, system identification, observation for unmeasured states, estimation for pivotal parameters, and the corresponding analyses are often necessary.

In the application of the linear quadratic (LQ) optimal regulator theory to the control system design, it is difficult to find suitable weighting matrices Q, R in the performance function. That is, the designer must resort to trial and error iteration to find them. And so it is rather difficult to design the optimal control systems.On the other hand, the inverse linear quadratic (ILQ) optimal servo theory was recentry proposed. This design theory is developed from the practical view point by applying some results on the inverse problem of LQ regulator. In this method there is a close relationship between the characteristic of the transient response of the control system and the design parameters. And when the design condition is fullfilled, it is able to construct a control system which has no interaction between the controlled variables, and it is also able to express the optimal feedback gain in terms of the system matrices and the design parameters.In this paper, we tried to apply ILQ optimal servo theory to the design of a control system for manoeuvring motion of a ship. It is shown that by ILQ design method the control system for manoeuvring motion of a ship can be designed very easily compared with usual LQ design method. Response characteristics can be selected with design parameters. A control system can be constructed not to interact between the control variables. And as the gain is expressed in terms of the system matrices and the design parameters, it is able to construct a control system which is adaptable to the change of the characteristic of the controlled object.