Showing papers on "Sliding mode control published in 2003"

Continuous finite-time control for robotic manipulators with terminal sliding modes

Abstract: A continuous finite-time control scheme for rigid robotic manipulators is proposed using a new form of terminal sliding modes. The robustness of the controller is established using the Lyapunov stability theory. Theoretical analysis and simulation results show that faster and high-precision tracking performance is obtained compared with the conventional continuous sliding mode control method.

A survey of applications of second-order sliding mode control to mechanical systems

Abstract: The effective application of sliding mode control to mechanical systems is not straightforward because of the sensitivity of these systems to chattering. Higher-order sliding modes can counteract this phenomenon by confining the switching control to the higher derivatives of the mechanical control variable, so that the latter results are continuous. Generally, this approach requires the availability of a number of time derivatives of the sliding variable, and, in the presence of noise, this requirement could be a practical limitation. A class of second-order sliding mode controllers, guaranteeing finite-time convergence for systems with relative degree two between the sliding variable and the switching control, could be helpful both in reducing the number of differentiator stages in the controller and in dealing with unmodelled actuator dynamics. In this paper different second-order sliding mode controllers, previously presented in the literature, are shown to belong to the above cited class, and some cha...

Fuzzy adaptive sliding-mode control for MIMO nonlinear systems

Abstract: A stable adaptive fuzzy sliding-mode controller is developed for nonlinear multivariable systems with unavailable states. When the system states are not available, the estimated states from a semi-high gain observer are used to construct the output feedback fuzzy controller by incorporating the dynamic sliding mode. It is proved that uniformly asymptotic output feedback stabilization can be achieved with the tracking error approaching to zero. A nonlinear system simulation example is presented to verify the effectiveness of the proposed controller.

Backstepping and control allocation with applications to flight control

Abstract: In this thesis we study a number of nonlinear control problems motivated by their appearance in flight control. The results are presented in a general framework and can also be applied to other areas. The two main topics are backstepping and control allocation.Backstepping is a nonlinear control design method that provides an alternative to feedback linearization. Here, backstepping is used to derive robust linear control laws for two nonlinear systems, related to angle of attack control and flight path angle control, respectively. The resulting control laws require less modeling information than corresponding designs based on feedback linearization, and achieve global stability in cases where feedback linearization can only be performed locally. Further, a method for backstepping control of a rigid body is developed, based on a vector description of the dynamics. We also discuss how to augment an existing nonlinear controller to suppress constant input disturbances. Two methods, based on adaptive backstepping and nonlinear observer design, are proposed.Control allocation deals with actuator utilization for overactuated systems. In this thesis we pose the control allocation problem as a constrained least squares problem to account for actuator position and rate constraints. Efficient solvers based on active set methods are developed with similar complexity to existing, approximate, pseudoinverse methods. A method for dynamic control allocation is also proposed which enables a frequency dependent control distribution among the actuators to be designed. Further, the relationship between control allocation and linear quadratic control is investigated. It is shown that under certain circumstances, the two techniques give the same freedom in distributing the control effort among the actuators. An advantage of control allocation, however, is that since the actuator constraints are considered, the control capabilities of the actuator suite can be fully exploited.

Robust sliding-mode control for uncertain time-delay systems: an LMI approach

Abstract: This note is devoted to robust sliding-mode control for time-delay systems with mismatched parametric uncertainties. A delay-independent sufficient condition for the existence of linear sliding surfaces is given in terms of linear matrix inequalities, based on which the corresponding reaching motion controller is also developed. The results are illustrated by an example.

A hybrid adaptive fuzzy control for a class of nonlinear MIMO systems

Abstract: A hybrid indirect and direct adaptive fuzzy output tracking control schemes are developed for a class of nonlinear multiple-input-multiple-output (MIMO) systems. This hybrid control system consists of observer and other different control components. Using the state observer, it does not require the system states to be available for measurement. Assisted by observer-based state feedback control component, the adaptive fuzzy system plays a dominant role to maintain the closed-loop stability. Being the auxiliary compensation, H/sup /spl infin// control and sliding mode control are designed to suppress the influence of external disturbance and remove fuzzy approximation error, respectively. Thus, the system performance can be greatly improved. The simulation results demonstrate that the proposed hybrid fuzzy control system can guarantee the system stability and also maintain a good tracking performance.

An adaptive fuzzy sliding mode controller for robotic manipulators

Abstract: This paper proposes an adaptive fuzzy sliding mode controller for robotic manipulators. An adaptive single-input single-output (SISO) fuzzy system is applied to calculate each element of the control gain vector in a sliding mode controller. The adaptive law is designed based on the Lyapunov method. Mathematical proof for the stability and the convergence of the system is presented. Various operation situations such as the set point control and the trajectory control are simulated. The simulation results demonstrate that the chattering and the steady state errors, which usually occur in the classical sliding mode control, are eliminated and satisfactory trajectory tracking is achieved.

Adaptive fuzzy terminal sliding mode controller for linear systems with mismatched time-varying uncertainties

Abstract: A new design approach of an adaptive fuzzy terminal sliding mode controller for linear systems with mismatched time-varying uncertainties is presented in this paper. A fuzzy terminal sliding mode controller is designed to retain the advantages of the terminal sliding mode controller and to reduce the chattering occurred with the terminal sliding mode controller. The sufficient condition is provided for the uncertain system to be invariant on the sliding surface. The parameters of the output fuzzy sets in the fuzzy mechanism are adapted on-line to improve the performance of the fuzzy sliding mode control system. The bounds of the uncertainties are not required to be known in advance for the presented adaptive fuzzy sliding mode controller. The stability of the fuzzy control system is also guaranteed. Moreover, the chattering around the sliding surface in the sliding mode control can be reduced by the proposed design approach. Simulation results are included to illustrate the effectiveness of the proposed adaptive fuzzy terminal sliding mode controller.

An analysis and design of bilateral control based on disturbance observer

Abstract: In this paper, an analysis and design of bilateral control based on disturbance observer are discussed Poles of bilateral control go to the poles of position control and poles of force control respectively when disturbance observer gain is infinite Four-channel controller which is hybrid of position and force in the acceleration dimension based on disturbance observer can be divided into two modes: common and differential modes Position is controlled in differential mode space, force is controlled in common mode space Relationship between these spaces is revealed, design of bilateral control in the virtual space is proposed According to this method, design of bilateral control can be treated as position control and force control about one robot separately These theories are applied to the 6-degree-of-freedom industrial manipulator The numerical and experimental results show viability of the proposed method

A fixed-frequency quasi-sliding control algorithm: application to power inverters design by means of FPGA implementation

Abstract: In this paper, a fixed-frequency quasi-sliding control algorithm based on switching surface zero averaged dynamics (ZAD) is reported. This algorithm is applied to the design of a buck-based inverter, and implemented in a laboratory prototype by means of a field programmable gate array (FPGA), taking into account processing speed versus computational complexity trade-off. Three control laws, namely sliding control (SC), fixed-frequency quasi-sliding ZAD and PWM-based control have been experimentally tested to highlight the features of the proposed algorithm. According to the experimental results presented in the paper, the ZAD algorithm fulfills the requirement of fixed switching frequency and exhibits similar robustness properties in the presence of perturbations to those of sliding control mode.

A decentralized model reference adaptive variable structure controller for large-scale time-varying delay systems

Abstract: In this note, the problem of decentralized model reference adaptive variable structure control for a class of perturbed large-scale systems with varying time-delay interconnections is investigated. Based on the Lyapunov stability theorem, an adaptive variable structure control strategy for solving the robust tracking problem without the knowledge of upper bound of perturbations is developed. The use of adaptive technique is to adapt the unknown upper bound of perturbations so that the objective of globally asymptotical stability is achieved. Once the system enters the sliding manifold, the dynamics of controlled systems are insensitive to matching perturbations. Finally, an example is given to demonstrate the feasibility of the proposed control scheme.

Neural-network hybrid control for antilock braking systems

Abstract: The antilock braking systems are designed to maximize wheel traction by preventing the wheels from locking during braking, while also maintaining adequate vehicle steerability; however, the performance is often degraded under harsh road conditions. In this paper, a hybrid control system with a recurrent neural network (RNN) observer is developed for antilock braking systems. This hybrid control system is comprised of an ideal controller and a compensation controller. The ideal controller, containing an RNN uncertainty observer, is the principal controller; and the compensation controller is a compensator for the difference between the system uncertainty and the estimated uncertainty. Since for dynamic response the RNN has capabilities superior to the feedforward NN, it is utilized for the uncertainty observer. The Taylor linearization technique is employed to increase the learning ability of the RNN. In addition, the on-line parameter adaptation laws are derived based on a Lyapunov function, so the stability of the system can be guaranteed. Simulations are performed to demonstrate the effectiveness of the proposed NN hybrid control system for antilock braking control under various road conditions.

Adaptive fuzzy controller with sliding surface for vehicle suspension control

Abstract: Since the hydraulic actuating suspension system has nonlinear and time-varying behavior, it is difficult to establish an accurate model for designing a model-based controller. Here, an adaptive fuzzy sliding mode controller is proposed to suppress the sprung mass position oscillation due to road surface variation. This intelligent control strategy combines an adaptive rule with fuzzy and sliding mode control algorithms. It has online learning ability to deal with the system time-varying and nonlinear uncertainty behaviors, and adjust the control rules parameters. Only eleven fuzzy rules are required for this active suspension system and these fuzzy control rules can be established and modified continuously by online learning. The experimental results show that this intelligent control algorithm effectively suppresses the oscillation amplitude of the sprung mass with respect to various road surface disturbances.

A comparison study of advanced state observer design techniques

Abstract: This paper presents a comparison study of performances and characteristics of three advanced state observers, including the high-gain observers, the sliding-mode observers and the extended state observers. These observers were originally proposed to address the dependence of the classical observers, such as the Kalman filter and the Luenberger observer, on the accurate mathematical representation of the plant. The results show that, over all, the extended state observer is much superior in dealing with dynamic uncertainties, disturbances and sensor noise. Several novel nonlinear gain functions are proposed to address the difficulty in dealing with unknown initial conditions. Simulation and experimental results are provided.

Robust backstepping control for slew maneuver using nonlinear tracking function

Abstract: The backstepping control method provides useful control logic, especially for a cascaded system. Because spacecraft dynamics and kinematics form a cascaded system, the spacecraft slew maneuver problem can be solved using the backstepping control method. However, the simple linear backstepping controller may result in poor design: sluggish motion, trivial nonlinear term cancellation, and excessive control input. To overcome these defects, an effective backstepping control method using a nonlinear tracking function is proposed. The proposed backstepping control method is based on the redesign of the Lyapunov function and careful gain selections. To evaluate the effectiveness of the proposed method, numerical simulations including parameter uncertainties are performed. Simulation results demonstrate that the proposed backstepping controller can achieve the slew maneuver with shorter settling time and smaller peak control torque than existing methods.

Self-learning fuzzy sliding-mode control for antilock braking systems

Abstract: The antilock braking system (ABS) is designed to optimize braking effectiveness and maintain steerability; however, the ABS performance will be degraded in the case of severe road conditions. In this study, a self-learning fuzzy sliding-mode control (SLFSMC) design method is proposed for ABS. The SLFSMC ABS will modulate the brake torque for optimum braking. The SLFSMC system is comprised of a fuzzy controller and a robust controller. The fuzzy controller is designed to mimic an ideal controller and the robust controller is designed to compensate for the approximation error between the ideal controller and the fuzzy controller. The tuning algorithms of the controller are derived in the Lyapunov sense; thus, the stability of the system can be guaranteed. Also, the derivation of the proposed SLFSMC ABS does not need to use a vehicle-braking model. Simulations are performed to demonstrate the effectiveness of the proposed SLFSMC ABS in adapting to changes for various road conditions.

A new perspective on the tracking control of nonlinear structural and mechanical systems

Abstract: Based on recent results from analytical dynamics, this paper develops a class of tracking controllers for controlling general, nonlinear, structural and mechanical systems. Unlike most control methods that perform some kind of linearization and/or nonlinear cancellation, the methodology developed herein views the nonlinear control problem from a different perspective. This leads to a simple and new control methodology that is capable of ‘exactly’ maintaining the nonlinear system along a certain trajectory, which, in general, may be described by a set of differential equations in the observations/measurements. The approach requires very little computation compared with standard approaches. It is therefore useful for online real–time control of nonlinear systems. The methodology is illustrated with two examples.

Observer-based control of piecewise-affine systems

Abstract: This paper presents a new synthesis method for both state and dynamic output feedback control of a class of hybrid systems called piecewise-affine (PWA) systems. The synthesis procedure delivers stabilizing controllers that can be proven to give either asymptotic or exponential convergence rates. The synthesis method builds on existing PWA stability analysis tools by transforming the design into a closed-loop analysis problem wherein the controller parameters are unknown. More specifically, the proposed technique formulates the search for a piecewise-quadratic control Lyapunov function and a piecewise-affine control law as an optimization problem subject to linear constraints and a bilinear matrix inequality. The linear constraints in the synthesis guarantee that sliding modes are not generated at the switching. The resulting optimization problem is known to be hard, but suboptimal solutions can be obtained using the three iterative algorithms presented in the paper. The new synthesis technique allows con...

Chattering analysis in sliding mode systems with inertial sensors

Abstract: Singularly perturbed relay control systems with second order sliding modes (SP2SM) are considered for modeling of sliding mode control systems with inertial sensors. It is shown that the asymptotically stable slow-motion integral manifold of a smooth singularly perturbed system, describing the motion of an original SP2SM in the second order sliding domain, is the asymptotically stable slow-motions integral manifold of the original SP2SM. For sliding mode control systems with inertial sensors sufficient conditions for the exponential decreasing of the amplitude of chattering and unlimited growth of frequency are found. A formula for asymptotic representation of 'ideal' switching surface oscillations is suggested for sliding mode systems with inertial sensors.

Semi-active control of automotive suspension systems with magneto-rheological dampers

Abstract: This paper is aimed to develop semi-active control for automotive suspension systems with magneto-rheological (MR) fluid dampers. A two degree-of-freedom quarter car model is considered. A mathematical model of MR fluid damper is adopted. In this study, there are two nested controllers including system controller and damper controller. For the system controller, a model-reference sliding mode controller is developed for considering loading uncertainty to result in a robust control system. In order to choose a good reference model, the single-degree-of-freedom skyhook system is analysed. For the damper controller, the continuous-state control is used to track the actual damping force to the desired damping force. The transmissibilities of the MR suspension system are investigated. The performances of the MR suspension systems are evaluated by computer simulation with bump and random excitations. The effectiveness of the MR suspension system is also demonstrated via hardware-in-the-loop simulation (HILS) with sinusoidal excitation.

On the generalized PI sliding mode control of DC-to-DC power converters: a tutorial

Abstract: A tutorial revisiting of the traditional sliding mode control of DC-to-DC power supplies, or power converters, of the 'buck','boost' and 'buck-boost' types is presented. The limitations of the traditional indirect sliding mode controller schemes are critically evaluated. These refer to the availability of the converter inductor current variable and a lack of robustness with respect to unmodelled load resistance variations. These limitations are overcome thanks to recent developments addressed as 'Generalized PI controllers' which are based on integral reconstructors of the unmeasured observable state variables and utilize only available input and output signals.

Adaptive nonlinear guidance law considering control loop dynamics

Abstract: A new adaptive nonlinear guidance law is proposed here. The fourth order state equation for integrated guidance and control loop is formulated taking into consideration the target uncertainties and control loop dynamics. The state equation is further changed into the normal form by nonlinear coordinate transformation. Using the normal form of state equation, an adaptive nonlinear guidance law is proposed to compensate for the uncertainties in both target acceleration and control loop dynamics. The proposed law adopts the sliding mode control approach with adaptation for unknown bound of uncertainties. The present approach can effectively solve the existing guidance problem against target maneuver and the limited performance of control loop. We have provided the stability analyses and performed simulations comparing favorably our approach to the state of the art.

Hybrid control of period-doubling bifurcation and chaos in discrete nonlinear dynamical systems

Abstract: It is a typical route to generate chaos via period-doubling bifurcations in some nonlinear systems In this paper, we propose a new hybrid control strategy in which state feedback and parameter perturbation are used to control the period-doubling bifurcations and to stabilize unstable periodic orbits embedded in the chaotic attractor of a discrete chaotic dynamical system Simulation shows that the higher stable 2n-periodic orbit of the system can be controlled to lower stable 2m-periodic orbits (m

Adaptive vehicle traction force control for intelligent vehicle highway systems (IVHSs)

Abstract: This paper is concerned with robust longitudinal control of vehicles in intelligent vehicle highway systems by adaptive vehicle traction force control. Two different traction force controllers, adaptive fuzzy logic control and adaptive sliding-mode control, are proposed and applied to the fastest stable acceleration/deceleration and robust vehicle platooning problems. The motivation for investigating adaptive techniques arises from the unknown time-varying nature of the tire/road surface interaction that governs vehicle traction. Synchronous application of the engine or brake torques is also proposed for more stable vehicle maneuvers. The lack of controllability during braking (only one net input torque for the two control objectives, i.e., front and rear wheel slips) is partly overcome by applying auxiliary engine torque. Simulations of the two control methods are conducted using a complex nonlinear vehicle model which fully describes the dynamic behavior of the vehicle. Both controllers result in good performance under time-varying operating conditions.

Output-feedback model-reference sliding mode control of uncertain multivariable systems

Abstract: This note considers the robust output tracking problem using a model-reference sliding mode controller for linear multivariable systems of relative degree one. It is shown that the closed loop system is globally exponentially stable and the performance is insensitive to bounded input disturbances and parameter uncertainties. The strategy is based on output-feedback unit vector control to generate sliding mode. The only required a priori information about the plant high frequency gain matrix K/sub p/ is the knowledge of a matrix S/sub p/ such that -K/sub p/S/sub p/ is Hurwitz which relaxes the positive definiteness requirement usually needed by other methods.