Showing papers on "Sliding mode control published in 1993"

Sliding order and sliding accuracy in sliding mode control

Abstract: The synthesis of a control algorithm that stirs a nonlinear system to a given manifold and keeps it within this constraint is considered. Usually, what is called sliding mode is employed in such synthesis. This sliding mode is characterized, in practice, by a high-frequency switching of the control. It turns out that the deviation of the system from its prescribed constraints (sliding accuracy) is proportional to the switching time delay. A new class of sliding modes and algorithms is presented and the concept of sliding mode order is introduced. These algorithms feature a bounded control continuously depending on time, with discontinuities only in the control derivative. It is also shown that the sliding accuracy is proportional to the square of the switching time delay.

Sliding mode control design principles and applications to electric drives

Abstract: The basic concepts, mathematics, and design aspects of variable-structure systems as well as those with sliding modes as a principle operation mode are treated. The main arguments in favor of sliding-mode control are order reduction, decoupling design procedure, disturbance rejection, insensitivity to parameter variations, and simple implementation by means of power converters. The control algorithms and data processing used in variable structure systems are analyzed. The potential of sliding mode control methodology is demonstrated for versatility of electric drives and functional goals of control. >

Stable adaptive fuzzy control of nonlinear systems

Abstract: A direct adaptive fuzzy controller that does not require an accurate mathematical model of the system under control, is capable of incorporating fuzzy if-then control rules directly into the controllers, and guarantees the global stability of the resulting closed-loop system in the sense that all signals involved are uniformly bounded is developed. The specific formula for the bounds is provided, so that controller designers can determine the bounds based on their requirements. The direct adaptive fuzzy controller is used to regulate an unstable system to the origin and to control the Duffing chaotic system to track a trajectory. The simulation results show that the controller worked without using any fuzzy control rules, and that after fuzzy control rules were incorporated the adaptation speed became much faster. It is shown explicitly how the supervisory control forces the state to remain within the constraint set and how the adaptive fuzzy controller learns to regain control. >

Multivariable sliding mode control for autonomous diving and steering of unmanned underwater vehicles

Abstract: A six-degree-of-freedom model for the maneuvering of an underwater vehicle is used and a sliding-mode autopilot is designed for the combined steering, diving, and speed control functions. In flight control applications of this kind, difficulties arise because the system to be controlled is highly nonlinear and coupled, and there is a good deal of parameter uncertainty and variation with operational conditions. The development of variable-structure control in the form of sliding modes has been shown to provide robustness that is expected to be quite remarkable for AUV autopilot design. It is shown that a multivariable sliding-mode autopilot based on state feedback, designed assuming decoupled modeling, is quite satisfactory for the combined speed, steering, and diving response of a slow AUV. The influence of speed, modeling nonlinearity, uncertainty, and disturbances, can be effectively compensated, even for complex maneuvering. Waypoint acquisition based on line-of-sight guidance is used to achieve path tracking. >

General-purpose sliding-mode controller for DC/DC converter applications

Abstract: A general-purpose sliding-mode controller is described, which can be applied to most DC-DC power converter topologies. It has the same circuit complexity as standard current-mode controllers, but provides extreme robustness and speed of response against supply, load, and parameter variations. Moreover, contrary to other sliding-mode techniques, the proposed solution features constant switching frequency in the steady state, synchronization to external triggers, and absence of steady-state errors in the output voltage. >

On the dynamical sliding mode control of nonlinear systems

Abstract: The consequences of the differential algebraic approach in the sliding mode control of nonlinear single-input single-output systems are reviewed in tutorial fashion. Input-dependent sliding surfaces, possibly including time derivatives of the input signal, are shown to arise naturally from elementary differential algebraic results pertaining to the Fliess's Generalized Controller Canonical Forms of nonlinear systems. This class of switching surfaces generally leads to chattering-free dynamically synthesized sliding regimes, in which the highest time derivative of the input signal undergoes all the bang-bang type discontinuities. Examples illustrating the obtained results are also included.

Sliding mode and classical controllers in magnetic levitation systems

Abstract: An experimental comparison is made between a sliding-mode controller and a classical controller for stabilizing and commanding a magnetic levitation system. The sliding-mode method can be applied to a nonlinear system in the global sense, and the issues of performance and robustness to modeling uncertainties and disturbances can be directly incorporated in the design as tradeoff parameters. >

Sliding-mode controller design for spacecraft attitude tracking maneuvers

Abstract: A robust sliding-mode control law that deals with spacecraft attitude tracking problems is presented. Two important natural properties related to the spacecraft model of motion are discussed. It is shown that by using these properties and the second method of Lyapunov theory, the system stability in the sliding mode can be easily achieved. The success of the sliding-mode controller and its robustness relating to uncertainties are illustrated by an example of multiaxial attitude tracking maneuvers. >

A sliding mode controller with bound estimation for robot manipulators

Abstract: A sliding-mode control algorithm combined with an adaptive scheme, which is used to estimate the unknown parameter bounds, is developed for the trajectory control of robot manipulators. The major contribution of this methodology lies in the use of a special matrix, called the regressor, which makes it possible to isolate the unknown parameters from the robotic dynamics. Based on the upper bounds of those unknown parameters, which are estimated by a simple adaptive law, the proposed VSS (variable-structure-system) controller guarantees the stability of the closed-loop system. The robustness analysis shows that in the presence of the uncertainties, which are assumed to be unbounded and rapidly varying, the closed-loop system can still be stabilized. Chattering is reduced by using the boundary layer technique. Simulation results show the validity of the proposed algorithm. >

Sliding mode control in dynamic systems

Abstract: This paper deals with the generalization of the concept of "sliding mode control" for arbitrary dynamic systems governed by a shift operator This class embraces continuous- and discrete-time, finite- and infinite-dimensional systems, and systems described by difference-differential equations The new concept rests upon the singularity property of a shift operator in systems with sliding modes The design procedures are presented for different classes of dynamic systems >

Fuzzy logic control of a switched reluctance motor drive

Abstract: A FLC (fuzzy logic controller) is applied to the speed control of an SRM (switched reluctance motor) drive. The FLC has been designed in terms of state evaluation control rules derived from a rough formulation of a sliding mode control of the drive. The control rules have been selected to force the drive in the sliding regime when the speed error is high and to decrease the reaching of the steady state when the speed error becomes low. In this way the drive dynamics takes advantage of the intrinsic robustness of the sliding mode control, avoiding the problem of both the switching control and the chattering phenomenon in the steady state. The resulting drive has been simulated and significant tests have been carried out. The traces are in line with the expectations, confirming that the FLC represents a powerful tool to give the drive superior performance. >

A nonlinear control strategy for robust sliding mode performance in the presence of unmatched uncertainty

Abstract: It is well known that sliding mode control schemes provide robustness to the class of uncertainty acting within channels implicit in the control inputs: the so-called matched uncertainty. However, the unmatched uncertainty will affect the ideal dynamics prescribed by the chosen switching surfaces. This paper develops a control strategy to minimize the effects of the unmatched uncertainty upon the dynamic performance prescribed by the switching surfaces. This is achieved for a subclass of the uncertainty class considered by previous authors. The practical application of the control strategy to the design of a stability augmentation system for a light aircraft is presented. For this problem an ideal performance is well known and it is desirable that these ideal dynamics are exhibited across a wide range of flight conditions without degradation.

Discrete-time sliding mode control in the presence of system uncertainty

Abstract: A discrete-time sliding-mode controller is presented in this paper, based on the theory of variable structure systems. It is assumed that the parameters of the system are uncertain and external disturbances are present. A measure of these effects is obtained through the deviations from the desired sliding surface, and this information is incorporated in the control law. A predictive corrective scheme is utilized in the calculation of the control inputs and, as a result, no a priori knowledge of the uncertainty bounds is required. This approach leads to a non-switching type of control, thereby eliminating the fundamental cause of chatter. The convergence and disturbance rejection properties of the approach are verified, and its performance is tested for the tracking control of an industrial robot.

A dynamical variable structure control strategy in asymptotic output tracking problems

Abstract: A dynamical discontinuous feedback strategy of the sliding mode type is presented for asymptotic output tracking problems in nonlinear dynamical systems. N. Fliess' (1989, 1990) generalized observability canonical form (GOCF) is used in the derivation of the dynamical variable structure feedback controller. For a large class of nonlinear systems, a truly effective smoothing of the sliding mode controlled responses is possible, while substantially reducing the chattering for the control output. For this reason, the technique is especially suitable for the control of some mechanical and electromechanical systems. An example, including simulations, is provided. >

Variable Structure Control for Robotics and Aerospace Applications

Abstract: Introduction, K-K.D. Young variable structure systems and sliding mode - state-of-the-art assessment, V.I. Utkin nonlinear pulse width modulation controller design, H. Sira-Ramirez variable structure control and observation of nonlinear/uncertain systems, S.H. Zak et al decentralized systems, U. Oezguener and H. Chan variable structure control of AC electric drives, H.G. Kwatny adaptive sliding mode control of a magnetic suspension system, J.K. Hedrick and W.H. Yao sliding mode for constrained robot motion control, K-K.D. Young variable structure control of redundant mechanisms, K-K.D. Young et al robust control of robot arm with sliding mode - engineering design considerations, H. Hashimoto variable structure control and learning controls for robotic manipulators, R. Shoureshi variable structure control of flexible manipulators, K-K.D. Young et al bandwidth-limited robust sliding control of multi axial spacecraft pointing and tracking manoeuvres, T.A.W. Dsyers III and J. Kim.

Stabilization of multiple input chained form control systems

Abstract: This paper gives a control law for stabilizing multiple input chained form control systems. This extends an earlier result of Teel, Murray, and Walsh (1992) on stabilizing the above class of systems which have two inputs. In addition, the authors generalize this law to control dynamical control systems and construct a transformation from general chained form systems with multiple generators to a power form. A control law which stabilizes the origin of a three-input control system that models the kinematics of a fire truck is simulated, confirming the theoretical results. >

Fixed frequency sliding mode modulator for current mode PWM inverters

Abstract: A fixed frequency current mode PWM modulator that provides output current limiting in sliding mode voltage controlled DC-AC power converters is presented. The modulator is considerably simpler than previous solutions and well adapted for sliding mode control, which is advantageous when the inverter feeds nonlinear or wide ranging loads and performs as a switching power operational amplifier or power operational transconductance amplifier. >

Sliding mode control of a closed-loop regulated PWM inverter under large load variations

Abstract: A discrete sliding mode control scheme is presented for the closed-loop regulation of a pulse-width-modulated (PWM) inverter in application of high-performance uninterruptible power supply (UPS) systems. Based on the dynamic model of the PWM inverter, the sliding condition of the concerned system can be obtained and the PWM pattern is determined at every sampling instant by the proposed sliding mode control algorithm. Time response behavior of the digitally controlled PWM inverter by using a sliding mode control scheme under large load variations has been analyzed and a systematic design procedure is also suggested. A digital signal processor (DSP)-based (TMS 320C25) PWM inverter controller with a sampling rate of 10 kHz is implemented to verify the proposed control scheme. The constructed DSP-based digitally controlled PWM inverter system has fast dynamic response and low total harmonic distortion (THD) for AC phase-controlled nonlinear load. >

Sliding mode controller design based on fuzzy inference for nonlinear systems (power systems)

Abstract: Sliding-mode control can deal with nonlinearities of control systems and is robust. However, it has drawbacks, such as high control gain effect and control chattering. A method of nonlinear feedback control that introduces fuzzy interference into sliding-mode control, to treat nonlinearities and reduce chattering is proposed. The stability of the system is discussed using fuzzy stability theory based on Lyapunov's direct method. The method is applied numerically to the stabilizing control of an electric power system, and is shown to give good results. >

State feedback sliding mode control of a class of uncertain time delay systems

Abstract: The robust stability of a class of uncertain systems involving internal delays while being regulated by a sliding mode controller (SMC) is studied. The method for designing a SMC is proposed for the generation of a sliding motion in the system. The robustness property and asymptotic stability of the system are discussed and conditions for the design of the switching hyperplane are given. Further generalisation results, which lead to a simple design and implementation, are made for the case when the system is in companion form. A method is proposed for the elimination of limit cycles in systems being regulated by a relay SMC while allowing the generation of sliding motion and thus ensuring the closed-loop asymptotic stability.

Adaptive sliding mode control method for object of control including spring system

Abstract: The present invention provides an adaptive sliding mode control method capable of not only improving the convergence of estimated parameters but also providing outstanding vibration-damping properties. In this method, a position deviation e between a command position and a motor position, a speed deviation e, and a position command acceleration θr are determined. The difference et between the motor position and the position of machine's moving part and a differential et based thereon are obtained by observer processing and filtering processing. A phase plane Suf of the motor is obtained by feeding back the deviation et between the motor position and the position of the machine's moving part. Estimated values Jhat, Ahat and Grhat, representing an inertia term, coefficient of dynamic friction, and gravity term respectively, are obtained. A switching input τ1 is set to the maximum Dis or minimum Dis of a disturbance depending on the plus/minus sign of the phase plane Suf. A torque command τ for the motor is obtained and delivered to a current loop. With this method, the vibration of the machines moving part after positioning can be reduced.

Sliding mode with chattering reduction in sampled data systems

Abstract: This paper deals with discrete time sliding mode control with chattering reduction for sampled data systems. The pre-filtering and post-filtering settings are implemented to eliminate chattering with robustness. The proposed method weakens some of the constraints due to the high frequency switching and full state accessibility requirements in continuous time variable structure control. >

Real-time implementation of regressor-based sliding mode control algorithm for robotic manipulators

Abstract: A regressor-based variable-structure control scheme has been developed for the trajectory control of robot manipulators in the presence of disturbances, parameter variations, and unmodeled dynamics. The method is based on the regressor structure given by J.J.E. Slotine and W. Li, without parameter adaptation. This avoids the requirement of persistency of excitation, and the convergence of the overall transient exponential. The method is robust against a class of state-dependent uncertainties, which may result, for example, from unmodeled dynamics. The problem of chattering is solved by the smoothing control law. It is with respect to a set around the origin, which can be made arbitrarily small. To illustrate the feasibility of this controller, it was implemented using a Motorola M68000 microprocessor on a two-link revolute joint manipulator subjected to a variable payload. Experimental results confirm the validity of accurate tracking capability and the robust performance. >

Comparative simulation study of three control techniques applied to a biped robot

Abstract: This paper provides a comparative study, through simulation, of the effectiveness of the local (decoupled) PD control, the computed torque control, and the sliding mode robust control applied to a 5-link biped robot model. The superiority of the sliding mode control in case of existence of large parametric uncertainty is verified. It is argued that sliding mode control appropriately smoothed can be used successfully in actual (experimental or not) bipeds to increase their performance capabilities. >

Sliding mode control for an obstacle avoidance strategy based on an harmonic potential field

Abstract: This paper introduces a new integrated path control strategy (combined path planning and motion control) for autonomous systems of arbitrary dimension. A harmonic artificial potential field is used to specify admissible trajectories leading around obstacles. Using a sliding mode controller, motion is generated along the gradient lines of the potential field, avoiding collisions with the obstacles. The extremely low computational complexity of the proposed method makes it very suitable for online applications. The strategy is applied to mobile robots moving amidst known obstacles. Only the obstacle closest to the robot is considered at each time instance. The switching of the two respective gradient fields along the equi-distance line between two obstacles leads to the interesting phenomenon of an additional "spatial" sliding surface, which is examined in detail. The algorithm guarantees approaching the goal point continuously, following a reasonably short path. Numerical examples are presented to demonstrate the utility of this new strategy. >

Adaptive dynamical sliding mode control via backstepping

Abstract: An advantageous combination of chattering-free dynamical sliding mode control and the adaptive backstepping technique is proposed for the regulation of exactly linearizable systems, placeable in parametric-pure feedback form and in parametric-strict feedback form. >

Quaternion-based rate/attitude tracking system with application to gimbal attitude control

Abstract: The paper deals with rate and attitude control of a rigid body. The discussed control system contains an inner velocity loop which tracks the desired rate command and an outer attitude loop which tracks the desired attitude command. The control algorithm uses quaternions as a measure of attitude errors to achieve instantaneous eigenaxis rotation. The paper discusses the stability of the new algorithm and presents its application to multi-axis gimbal attitude control.

VSS controller design for discrete-time systems

Abstract: This paper presents an optimal and robust VSS controller for discrete-time systems. Firstly, a VSS control law is designed, which enables the system state to move into a sliding sector where the closed-loop system is stable. Then optimal control theory is used to design an optimal sliding sector. Finally, the bounded parameter uncertainty is taken into consideration, the robustness of the VSS control system is shown. The simulation of the pendulum control system shows that the VSS controller proposed in this paper is stable and robust to bounded parameter uncertainty. >

Trajectory control for a low-lift re-entry vehicle

Abstract: This paper presents re-entry trajectory control for a small re-entry vehicle by path following. A tracking controller restricts the vehicle to a multivariable reference trajectory defined by altitude, velocity, and flightpath angle. The controller design is based on several linear system models along a desired reference trajectory. A linear control law is designed to minimize a quadratic performance index at discrete points on the reference. Simulation results of spatial flights over a rotating Earth show that the designed controller effectively responds to entry condition offsets on several reference trajectories. Also, the controller is capable of tolerating changing vehicle parameters as well as atmospheric disturbances. The same controller gain functions are successfully applied to different reference trajectories.

Sliding mode observers for nonlinear models with unbounded noise and measurement uncertainties

Abstract: This work extends the applicability of variable structure observers designed for nonlinear systems in two ways. First, it is proved that these observers using a boundary-layer scheme can be applied to system models described by Ito differential equations, resulting in almost sure and mean square exponential estimation error. Second, the use of variable structure observers is extended to nonlinear measurement models containing disturbance effects. Also, a novel approach for obtaining the required parameters in the observer design is provided. Finally, two examples are given to illustrate the application and favorable convergence properties of these generalizations.