Showing papers on "Sliding mode control published in 2002"

Sliding Mode Control in Engineering

Abstract: 1. Introduction: An Overview of Classical Sliding Mode Control 2. Differential Inclusions and Sliding Mode Control 3. Higher-Order Sliding Modes 4. Sliding Mode Observers 5. Dynamic Sliding Mode Control and Output Feedback 6. Sliding Modes, Passivity, and Flatness 7. Stability and Stabilization 8. Discretization Issues 9. Adaptive and Sliding Mode Control 10. Steady Modes in Relay Systems with Delay 11. Sliding Mode Control for Systems with Time Delay 12. Sliding Mode Control of Infinite-Dimensional Systems 13. Application of Sliding Mode Control to Robotic Systems 14. Sliding Modes Control of the Induction Motor: A Benchmark Experimental Test

Sliding mode control on electro-mechanical systems

Abstract: The first sliding mode control application may be found in the papers back in the 1930s in Russia. With its versatile yet simple design procedure the methodology is proven to be one of the most powerful solutions for many practical control designs. For the sake of demonstration this paper is oriented towards application aspects of sliding mode control methodology. First the design approach based on the regularization is generalized for mechanical systems. It is shown that stability of zero dynamics should be taken into account when the regular form consists of blocks of second-order equations. Majority of applications in the paper are related to control and estimation methods of automotive industry. New theoretical methods are developed in the context of these studies: sliding made nonlinear observers, observers with binary measurements, parameter estimation in systems with sliding mode control.

Fast terminal sliding-mode control design for nonlinear dynamical systems

Abstract: A fast terminal dynamics is proposed and used in the design of the sliding-mode control for single-input single-output nonlinear dynamical systems. The inherent dynamic properties of the fast terminal sliding modes are explored and conditions to ensure its applicability for control designs are obtained.

Direct adaptive NN control of a class of nonlinear systems

Abstract: In this paper, direct adaptive neural-network (NN) control is presented for a class of affine nonlinear systems in the strict-feedback form with unknown nonlinearities. By utilizing a special property of the affine term, the developed scheme,avoids the controller singularity problem completely. All the signals in the closed loop are guaranteed to be semiglobally uniformly ultimately bounded and the output of the system is proven to converge to a small neighborhood of the desired trajectory. The control performance of the closed-loop system is guaranteed by suitably choosing the design parameters. Simulation results are presented to show the effectiveness of the approach.

Adaptive output feedback control of uncertain nonlinear systems using single-hidden-layer neural networks

Abstract: We consider adaptive output feedback control of uncertain nonlinear systems, in which both the dynamics and the dimension of the regulated system may be unknown. However, the relative degree of the regulated output is assumed to be known. Given a smooth reference trajectory, the problem is to design a controller that forces the system measurement to track it with bounded errors. The classical approach requires a state observer. Finding a good observer for an uncertain nonlinear system is not an obvious task. We argue that it is sufficient to build an observer for the output tracking error. Ultimate boundedness of the error signals is shown through Lyapunov's direct method. The theoretical results are illustrated in the design of a controller for a fourth-order nonlinear system of relative degree two and a high-bandwidth attitude command system for a model R-50 helicopter.

A continuous-time observer which converges in finite time

Abstract: It is shown that a continuous-time observer, which comprises two standard nth order observers and a delay D, can observe the state of an nth order linear system in finite time D exactly. In particular, (almost) any convergence time D can be assigned, independent of the observer eigenvalues.

Discrete-time sliding mode control

Abstract: s: Monsees, G. and J. M. A. Scherpen (2001), “Discrete-time output-based sliding mode control”, Proceedings of the 20th Benelux Meeting on Systems and Control, Houfalize, Belgium. Monsees, G., K. George, J. M. A. Scherpen and M. Verhaegen (1999), “A feedforward-feedback interpretation of a sliding mode control law”, Proceedings of the 18th Benelux Meeting on Systems and Control, Houthalen, Belgium.

Tailless aircraft flight control using multiple time scale reconfigurable sliding modes

Abstract: A triple time scale tailless aircraft flight control problem is addressed via continuous sliding mode control. A reconfigurable sliding mode flight controller is designed that achieves robust, high accuracy command angle tracking both before and after damage to an aircraft. Command angles and angular rate commands are robustly tracked in outer and inner loops correspondingly via finite reaching time continuous sliding mode controllers. An optimal control allocation algorithm is employed using nominal mathematical model of an aircraft. Sliding surface boundary layer reconfiguration (direct adaptation) is used in the "very" inner loop to account for actuator dynamics, deflection limits, and rate limits. Online damage identification is not required by this design. The reconfigurable sliding mode flight control technique is applied to a flight dynamics model of a tailless jet fighter that was developed under is the innovative control effectors program. Simulations demonstrate stability and high accuracy tracking performance without violation of actuator limits.

Adaptive backstepping sliding mode control for linear induction motor drive

Abstract: An adaptive backstepping sliding mode controller, which combines both the merits of adaptive backstepping control and sliding mode control, is proposed to control the mover position of a linear induction motor (LIM) drive to compensate for the uncertainties including the friction force. First, the dynamic model of an indirect field-oriented LIM drive is derived. Then, a backstepping sliding mode approach is proposed to compensate the uncertainties which occur in the motion control system. The uncertainties are lumped, and the bound of the lumped uncertainty is necessary in the design of the backstepping sliding mode controller. However, the bound of the lumped uncertainty is difficult to obtain in advance in practical applications. Therefore, an adaptive law is derived to adapt the value of the lumped uncertainty in real-time, and an adaptive backstepping sliding mode control law is proposed. With the adaptive backstepping sliding mode controller, the mover position of the LIM drive possesses the advantages of good transient control performance and robustness to uncertainties for the tracking of periodic reference trajectories. The effectiveness of the proposed control scheme is verified by both the simulated and experimental results.

Control of an optical fiber scanner

Abstract: Controls for an optical scanner, such as a single fiber scanning endoscope (SFSE) that includes a resonating optical fiber and a single photodetector to produce large field of view, high-resolution images. A nonlinear control scheme with feedback linearization is employed in one type of control to accurately produce a desired scan. Open loop and closed loops controllers are applied to the nonlinear optical scanner of the SFSE. A closed loop control (no model) uses either phase locked loop and PID controllers, or a dual-phase lock-in amplifier and two PIDs for each axis controlled. Other forms of the control that employ a model use a frequency space tracking control, an error space tracking control, feedback linearizing controls, an adaptive control, and a sliding mode control.

H/sub /spl infin// tracking-based sliding mode control for uncertain nonlinear systems via an adaptive fuzzy-neural approach

Abstract: A novel adaptive fuzzy-neural sliding-mode controller with H/sub /spl infin// tracking performance for uncertain nonlinear systems is proposed to attenuate the effects caused by unmodeled dynamics, disturbances and approximate errors. Because of the advantages of fuzzy-neural systems, which can uniformly approximate nonlinear continuous functions to arbitrary accuracy, adaptive fuzzy-neural control theory is then employed to derive the update laws for approximating the uncertain nonlinear functions of the dynamical system. Furthermore, the H/sub /spl infin// tracking design technique and the sliding-mode control method are incorporated into the adaptive fuzzy-neural control scheme so that the derived controller is robust with respect to unmodeled dynamics, disturbances and approximate errors. Compared with conventional methods, the proposed approach not only assures closed-loop stability, but also guarantees an H/sub /spl infin// tracking performance for the overall system based on a much relaxed assumption without prior knowledge on the upper bound of the lumped uncertainties. Simulation results have demonstrated that the effect of the lumped uncertainties on tracking error is efficiently attenuated, and chattering of the control input is significantly reduced by using the proposed approach.

Singularly perturbed analysis of chattering in relay control systems

Abstract: For sliding-mode control systems with fast actuators, sufficient conditions for the exponential decreasing of the amplitude of chattering and unlimited growth of frequency are found. The connection between the stability of actuators and the stability of the plant on the one hand and the stability of the sliding-mode system as the whole on the other hand is investigated. The algorithm for correction of sliding-mode equations is suggested for taking into account the presence of fast actuators.

UPS inverter design using discrete-time sliding-mode control scheme

Abstract: This paper presents a novel discrete-time sliding-mode control algorithm for an uninterruptible power supply (UPS) inverter design. The approach offers a dual-loop design, in which a current predictor utilizes the tracking error of output voltage to estimate the desired inductor current, while a current controller is adopted to regulate the inductor current and, thus, produces a control command to the pulsewidth modulation inverter. An explicit condition for stable controller design is derived. The efficacy of this scheme is validated via a successful implementation on a digital-signal-processor-based UPS inverter. The proposed scheme has shown its robustness on low output voltage distortion, excellent voltage regulation, and it is insensitive to load variation, even under nonlinear loads. Experimental studies were performed to further validate the effectiveness of this scheme.

Speed control of induction motors using a novel fuzzy sliding-mode structure

Abstract: This paper presents a new approach to indirect vector control of induction motors. Two nonlinear controllers, one of sliding mode type and the other PI-fuzzy logic-based, define a new control structure. Both controllers are combined by means of an expert system based on Takagi-Sugeno fuzzy reasoning. The sliding-mode controller acts mainly in a transient state while the PI-like fuzzy controller acts in the steady state. The new structure embodies the advantages that both nonlinear controllers offer: sliding-mode controllers increasing system stability limits, and PI-like fuzzy logic based controllers reducing the chattering in permanent state. The scheme has been implemented and experimentally validated.

Dynamic second-order sliding mode control of the hovercraft vessel

Abstract: A suitable combination of the differential flatness property and the second-order sliding mode controller design technique is proposed for the specification of a robust dynamic feedback multivariable controller accomplishing prescribed trajectory tracking tasks for the earth coordinate position variables of a hovercraft vessel model.

A state-dependent boundary layer design for sliding mode control

Abstract: The use of a boundary layer in sliding-mode control has been a common technique to reduce chattering of the control signal. However, different choices of the boundary layer width lead to conflicting effects: a large/small boundary layer width can more/less effectively alleviate the chattering phenomenon, but leads to less/more accurate control results. This note proposes online adjusting the width of the boundary layer based on the state norm for an uncertain linear system. The proposed state-dependent boundary layer design can effectively eliminate chattering while at the same time ensuring almost perfect control accuracy.

Teaching nonlinear modeling, simulation, and control of electronic power converters using MATLAB/SIMULINK

Abstract: This paper describes an efficient method to teach analysis and simulation of power electronic converters to undergraduate students, using system level nonlinear state-space models. System-level modeling of power electronic converters reproduces only the ideal switching behavior of the semiconductors and is a useful concept for the numerical simulation of power converters, since simulations present no convergence problems and require little computational time. Switched state-space models, programmed in the MATLAB/SIMULINK software package, can be advantageously used to simulate power converters at the system level and also to design and study their controllers. Switched state-space nonlinear models should be obtained using a theoretical framework suitable for the enhanced control of variable structure power systems. Since the method is inherently nonlinear, no approximated linear models are needed; and since state-space models are used, modern control techniques (sliding mode, neural networks, fuzzy logic) for power converters can easily be used. This paper summarizes the proposed methodology and gives some examples.

Sliding Mode Control Applied to Reconfigurable Flight Control Design

Abstract: Sliding mode control is applied to the design of a flight control system capable of operating with limited bandwidth actuators and in the presence of significant damage to the airframe and/or control effector actuators. Although inherently robust, sliding mode control algorithms have been hampered by their sensitivity to the effects of parasitic unmodeled dynamics, such as those associated with actuators and structural modes. It is known that asymptotic observers can alleviate this sensitivity while still allowing the system to exhibit significant robustness. This approach is demonstrated. The selection of the sliding manifold as well as the interpretation of the linear design that results after introduction of a boundary layer is accomplished in the frequency domain. The design technique is exercised on a pitch-axis controller for a simple short-period model of the High Angle of Attack F-18 vehicle via computer simulation. Stability and performance is compared to that of a system incorporating a controller designed by classical loop-shaping techniques.

A new state observer for perspective systems

Abstract: In this note, we consider the problem of estimating the state of a class of perspective systems. The problem can be converted into the observation of a dynamical system with nonlinearities. A new discontinuous state observer, which is motivated by the sliding mode control method and adaptive techniques, is proposed for the obtained dynamical system. The assumptions are reasonable, and the convergence conditions are intuitive and have apparently physical interpretations. The attraction of the new method is that the algorithm is very simple and easy to be implemented, and it is robust to measurement noises. Further, minor a priori knowledge of the system is required in the new formulation. Simulation results show the superiority of the new method to the traditional ones.

Designing a genetic neural fuzzy antilock-brake-system controller

Abstract: A typical antilock brake system (ABS) senses when the wheel lockup is to occur, releases the brakes momentarily, and then reapplies the brakes when the wheel spins up again. In this paper, a genetic neural fuzzy ABS controller is proposed that consists of a nonderivative neural optimizer and fuzzy-logic components (FLCs). The nonderivative optimizer finds the optimal wheel slips that maximize the road adhesion coefficient. The optimal wheel slips are for the front and rear wheels. The inputs to the FLC are the optimal wheel slips obtained by the nonderivative optimizer. The fuzzy components then compute brake torques that force the actual wheel slips to track the optimal wheel slips; these torques minimize the vehicle stopping distance. The FLCs are tuned using a genetic algorithm. The performance of the proposed controller is compared with the case when maximal brake torques are applied causing a wheel lockup, and with the case when wheel slips are kept constant while the road surface changes.

On the trajectory tracking control of industrial SCARA robot manipulators

Abstract: In this paper, the authors discuss, from an experimental point of view, the use of different control strategies for the trajectory tracking control of an industrial selective compliance assembly robot arm robot, which is one of the most employed manipulators in industrial environments, especially for assembly tasks. Specifically, they consider decentralized controllers such as proportional-integral-derivative-based and sliding-mode ones and model-based controllers such as the classical computed-torque one and a neural-network-based controller. A simple procedure for the estimation of the dynamic model of the manipulator is given. Experimental results provide a detailed framework about the cost/benefit ratio regarding the use of the different controllers, showing that the performance obtained with decentralized controllers may suffice in a large number of industrial applications, but in order to achieve low tracking errors also for high-speed trajectories, it might be convenient to adopt a neural-network-based control scheme, whose implementation is not particularly demanding.