Showing papers on "Sliding mode control published in 1997"

Terminal sliding mode control of MIMO linear systems

Abstract: A new terminal sliding mode control of MIMO linear systems is proposed in this paper. It is shown that, by inserting a nonlinear term of the system state in the MIMO linear sliding mode, a new terminal sliding mode is developed for MIMO linear systems. A terminal sliding mode controller can then be designed to drive the system state variables to reach and retain in the terminal sliding mode. By suitably designing the parameter matrices of the terminal sliding mode, the system state variables reach the system origin in finite time and the closed loop system is infinite stable in the terminal sliding mode.

Application of state space averaging method to sliding mode control of PWM DC/DC converters

Abstract: A novel approach for the analysis and design of sliding mode controllers for PWM DC/DC power converters is presented. The main advantage of this nonlinear controller is that there is no restriction on the size of the signal variations around the operating point. Small as well as large signal variations around the operating point are considered. Sliding mode controllers for buck, boost, buck-boost, and Cuk power converters have been designed and discussed. These controllers have been simulated on a digital computer and their dynamic performances have been shown to be satisfactory. Finally, Lyapunov's second theorem has been used to verify the stability of the designed sliding mode controller for the Cuk power converter.

Small-signal analysis of DC-DC converters with sliding mode control

Abstract: This paper deals with small-signal analysis of DC-D converters with sliding mode control. A suitable small signal model is developed which allows selection of control coefficients, analysis of parameter variation effects, characterization of the closed loop behavior in terms of audiosusceptibility, output and input impedances, and reference to output transfer function. Unlike previous analyses, the model includes effects of the filters used to evaluate state variable errors. Simulated and experimental results demonstrate model potentialities.

Sliding Mode Control With Sliding Perturbation Observer

Abstract: This work introduces a new robust motion control algorithm using partial state feedback for a class of nonlinear systems in the presence of modelling uncertainties and external disturbances. The effects of these uncertainties are combined into a single quantity called perturbation. The major contribution of this work comes as the development and design of a robust observer for the state and the perturbation which is integrated into a Variable Structure Controller (VSC) structure. The proposed observer combines the procedures of Sliding Observers (Slotine et al, 1987) with the idea of Perturbation Estimation (Elmali and Olgac, 1992). The result is what is called Sliding Perturbation Observer (SPO). The VSC follows the philosophy of Sliding Mode Control (SMC) (Slotine and Sastry, 1983). This combination of controller/observer gives rise to the new routine called Sliding Mode Control with Sliding Perturbation Observer (SMCSPO). The stability analysis shows how the algorithm parameters are scheduled in order to assure the sliding modes of both controller and observer. A simplified form of the general design procedure is also presented in order to ease the practical applications of SMCSPO. Simulations are presented for a two-link manipulator to verify the proposed approach. Experimental validation of the methodology is also performed on a PUMA 560 robot. A superior control performance is obtained over some full state feedback techniques such as SMC and Computed Torque Method.

Practical results of a longitudinal control concept for truck platooning with vehicle to vehicle communication

Abstract: Practical results of a longitudinal control concept for truck platooning are presented. The approach is based on distance measurement between the vehicles and on vehicle to vehicle communication but does not need road infrastructure. A two layered control structure is proposed. The inner control loop includes a nonlinear acceleration controller linearizing a large part of the nonlinearities. Despite this linearisation, due to the different actuator systems the dynamic behaviour of the vehicle is different during acceleration and braking. Furthermore, each vehicle may have different power trains and loads and additional disturbances might occur. Therefore, a robust platoon controller is introduced for the outer control loop by use of sliding mode control design. Practical results of a platoon consisting of 7 trucks show that by use of the proposed control concept string stability can be achieved.

Designing fuzzy controllers from a variable structures standpoint

Abstract: A procedure is presented for designing fuzzy controllers based upon variable structures techniques. Three such controllers are presented: the fuzzy equivalents of sliding-mode controllers, saturating controllers, and tanh controllers. By using an approach based upon variables structures (VSS) techniques, the stability of each of these controllers is assured. By using a sliding surface, the order of the rule base is reduced to size r/spl times/m, where r is the number of inputs and m is the number of fuzzification levels. This combination makes the proposed design procedure able to generate simple controllers with guaranteed stability properties. To illustrate the proposed design procedure, fuzzy controllers are designed for a ball-and-beam system. It is demonstrated that in spite of this system being a fourth-order unstable system, the proposed design procedure results in simple stable fuzzy controllers.

Output feedback sliding mode design for linear uncertain systems

Abstract: The paper considers the development of output feedback sliding mode controllers for a class of uncertain linear systems. The presence of stable invariant zeros and matched uncertainty is incorporated in the design procedure. The sufficient conditions for developing static output feedback sliding mode controllers are first reviewed. If the so-called ‘Kimura–Davison’ conditions are not satisfied, it is shown that it may not be possible to determine a static output feedback sliding mode controller. In this case, dynamic output feedback sliding mode control is necessary. It is shown that both the switching surface design problem for the static case and the switching surface and compensator design for the dynamic case may be formulated as a static output feedback problem for particular system triples. A robust design procedure is used to solve this static output feedback problem to minimise the effects of any unmatched uncertainty which will affect the reduced order sliding motion in many practical systems. A controller is synthesised to tolerate matched model uncertainty. The measurements of robustness are described. A numerical example demonstrates the procedure.

The use of sliding modes to simplify the backstepping control method

Abstract: We propose a simple sliding mode based controller for nonlinear systems with mismatched uncertainties. The design methodology is similar to backstepping and multiple surface control method but with the inclusion of sliding mode filters for estimating the derivatives of the plant output.

Practical Design of a Sliding Mode Controller for Pneumatic Actuators

Abstract: Pneumatic robot manipulators are characterized by high-order, time-variant actuator dynamics, nonlinearities due to compressibility of air, external disturbances such as static and Coulomb friction, and wide range of payload variations. Conventional PID controllers suffer from problems of gain tuning under these conditions. In this paper, a new control algorithm is proposed for the position and trajectory control of pneumatic actuators based on the sliding mode control approach. The stability of motion is proved for the case of a linear, time-invariant switching surface. A disadvantage of using sliding mode control for third- and higher-order mechanical systems is the need for acceleration feedback. In this paper, to overcome this difficulty we propose the use of differential pressure. The proposed controller is simple, easy to implement, and robust to payload and parametric variations. The effectiveness of the new scheme for position and trajectory control is illustrated by experiments on an industrial piston-driven cylindrical actuator with proportional valves.

Adaptive Terminal Sliding Mode Tracking Control for Rigid Robotic Manipulators with Uncertain Dynamics.

Abstract: A robust adaptive terminal sliding mode tracking control is proposed for rigid robotic manipulators. First, it is shown that, when a rigid robotic manipulator is treated as a partially known system, the system uncertainty is not only related to the model properties but also to the structure of the controllers. It is also proved that, if the control input vector does not contain the acceleration signals, the system uncertainty is upper bounded by a positive function of the position and velocity measurements. The property is very useful for the design of robust and adaptive controllers where only position and velocity measurements are available. Second, an MIMO terminal sliding mode is defined for the error dynamics of the robot control system, and an adaptive mechanism is introduced to estimate the upper bounds of system uncertainty in the Lyapunov sense. The estimates are then used as controller parameters so that the effects of uncertain dynamics can be eliminated and a finite time error convergence can be guaranteed. A simulation is given in support of the proposed control scheme.

Experiments and simulations on the nonlinear control of a hydraulic servosystem

Abstract: Presents the derivation, simulation and implementation of a nonlinear tracking control law for a hydraulic servosystem. An analysis of the nonlinear system equations is used in the derivation of a Lyapunov function that provides for exponentially stable force trajectory tracking. This control law is then extended to provide position tracking. The proposed controller is simulated and then implemented on an experimental hydraulic system to test the limits of its performance and the realistic effects of friction.

Active and semi-active control of structures under seismic excitation

Abstract: Considerable effort has been devoted to develop passive and active methods for reducing structural response under seismic excitations. Passive control approaches have already found application in practice. Active control methods, on the other hand, are being vigorously examined for application to civil structures. This paper investigates the application of active and semi-active control schemes to structures subjected to seismic excitations, and it focuses on the use of the sliding-mode control approach for the development of the control algorithms. The possibility of control redundancy with respect to the number of sliding constraints is taken into account in the controller design. Several sets of numerical results are obtained for a realistic 10-storey shear building, subjected to earthquake-induced ground motions and controlled by active or semi-active control schemes. It is observed that both active and semi-active control schemes can be used to reduce the dynamic response. Active control performs very effectively in reducing the structural response, but the required control force values can be quite large to limit its practical application in the case of large and massive buildings. Active regulation of linear viscous dampers was found unnecessary for this type of structural system, as it did not induce any significantly more reduction in the response than the dampers acting passively. On the other hand, it is shown that active regulation of stiffness can be used with advantage to reduce the response. © 1997 by John Wiley & Sons, Ltd.

Iterative controller optimization for nonlinear systems

Abstract: A data-driven model-free control design method has been proposed in Hjalmarsson et al (1994) It is based on the minimization of a control criterion with respect to the controller parameters using an iterative gradient technique In this paper, we extend this method to the case where both the plant and the controller can be nonlinear It is shown that an estimate of the gradient can be constructed using only signal based information It is also shown that by using open loop identification techniques, one can obtain a good approximation of the gradient of the control criterion while performing fewer experiments on the actual system

Neuro-sliding mode control of robotic manipulators

Abstract: In this paper, a synergistic combination of neural networks with sliding mode control (SMC) is proposed. As a result, the chattering is eliminated and error performance of SMC is improved. In such an approach, two parallel NNs are proposed to realize SMC. The equivalent control and the corrective term of SMC are the outputs of the NNs. The gradient descent method is used for the weight adaptation. This novel approach is applied to control of a SCARA type robot manipulator and simulation results are given.

Discrete-Time Sliding Mode Control: The Linear Case

Abstract: This paper discusses the application of a class of discrete-time sliding mode controllers (DSMC) which was previously shown to be robustly stable. Further insight into design and performance of DSMC is obtained considering the case of linear plants. A simple numerical example is used to illustrate the properties of this technique.

Dynamical adaptive sliding mode output tracking control of a class of nonlinear systems

Abstract: An alternative adaptive scheme to achieve output tracking for a class of minimum-phase dynamically input–output linearizable nonlinear systems with parametric uncertainties is considered. The proposed approach is based upon a combination of the adaptive backstepping design method and a sliding mode control (SMC) scheme to design dynamical adaptive sliding mode controllers and provide robust output tracking even in the presence of unknown disturbances. The validity of the proposed approach, regarding tracking objectives and robustness with respect to bounded stochastic perturbation inputs, is tested through digital computer simulations. © 1997 by John Wiley & Sons, Ltd.

Robust stabilization of a class of uncertain time delay systems in sliding mode

Abstract: This paper addresses the problem of robust stabilization of a class of uncertain systems subject to internal (i.e., in the state) point delays, external (i.e., in the input) point delays and nonlinear disturbances by using sliding mode control. Methods for the design of sliding mode controllers based on state feedback, static output feedback and dynamic output feedback, respectively, are proposed. Sufficient conditions for the asymptotic stability and robustnesss of the closed–loop systems are given under a wide class of admissible nonlinear disturbances. © 1997 by John Wiley & Sons, Ltd.

Experimental evaluation of a chatter free sliding mode control for lateral control in AHS

Abstract: Presents the design and experimental evaluation of a vehicle lateral controller for automated highway systems (AHS) based on sliding mode control (SMC). The primary control objective is to track the lane center line. The dynamic model of the, vehicle is nonlinear and has parametric uncertainties. SMC, a robust control technique is used to take care of the nonlinearities and parametric uncertainties in the model. Importance is given to reduction or elimination of the control chatter inherent in the SMC systems involving switching functions. An SMC based controller is designed such that asymptotic tracking is assured without chatter. A robust observer is designed for lateral velocity estimation. Closed loop experiments done on a passenger car are presented.

Decentralized variable-structure control design for uncertain large-scale systems with series nonlinearities

Abstract: This paper presents a robust decentralized control for large-scale interconnected systems with series nonlinearities through variable-structure control. The proposed variable-structure control ensures the global reaching condition of the sliding mode of the composite system. The uncertain nonlinear system also possesses insensitivity to uncertainties and disturbances like a linear system does. Furthermore, the sliding mode can converge within a specified exponential speed.

Nonlinear performance of a PI controlled missile: an explanation

Abstract: Considers the practical interest of an approach to nonlinear system analysis. Based on the incremental norm, this approach proposes performance and robustness analysis criteria. Using computationally efficient tests involving linear matrix inequality optimization, these criteria enable us to guarantee the performance and the robustness of a realistic PI controlled nonlinear missile.

Sliding mode control with compensator for wind and seismic response control

Abstract: Recently, it has been demonstrated that control techniques based on sliding mode control (SMC) are robust and their performances are quite remarkable for applications to active/hybrid control of seismic-excited linear, non-linear or hysteretic civil engineering structures. In this paper, sliding mode control methods are further extended by introducing a compensator. The incorporation of a compensator provides (i) a convenient way of making trade-offs between control efforts and specific response quantities of the structure through the use of linear quadratic optimal control theory, and (ii) a convenient design procedure for static output feedback controllers to facilitate practical implementations of control systems. Since civil engineering structures generally involve excessive degrees of freedom, a controller design based on a full-order system may be difficult, in particular for wind-excited tall buildings. In this paper, three reduced-order control methods have been used and their performances have been investigated. Applications of sliding mode control with compensators to active control of buildings subject to either earthquakes or strong wind gusts have been demonstrated through numerical simulations. Simulation results show that the performance of the sliding mode controller with compensators for the reduced-order system is quite close to that of the controller based on the full-order system as long as enough vibrational modes are taken into account in the reduced-order system. © 1997 John Wiley & Sons, Ltd.

Active power filter with sliding mode control

Abstract: Indexing terms: Active power filter, Harmonics, Sliding mode controller, Reactive power, Neutral current Abstract: The paper presents an active power filter (APF) to eliminate harmonics and to compensate reactive power and neutral current of three-phase four-wire symmetrical and unbalanced nonlinear loads. A set of three single- phase insulated-gate bipolar transistor (IGBT)- based voltage source inverter (VSI) bridges with a common DC bus capacitor is used as the APF. A sliding mode controller (SMC) over the average DC bus voltage is used for the control. A hysteresis rule based carrierless pulse width modulation (PWM) current control is employed to generate the gating signals to the switching devices. A set of three single-phase diode bridge rectifiers with capacitive-resistive loading is used for nonlinear loading. The simulation results show that the APF is capable of compensating reactive power, neutral current and load unbalance and reducing the harmonic level below the limit specified in IEEE-519 standard.

Force Tracking Control of a Flexible Gripper Driven by Piezoceramic Actuators

Abstract: This paper presents a robust force tracking control of a flexible gripper driven by a piezoceramic actuator characterizing its durability and quick response time. The mathematical governing equation for the proposed system is derived by employing Hamilton’s principle and a state space control model is subsequently obtained through the modal analysis. Uncertain parameters such as frequency variation are included in the control system model. The sliding mode control theory which has inherent robustness to the system uncertainties is adopted to design a force tracking controller for the piezoceramic actuator. Using the output information from a tip force sensor, a full-order observer is constructed to estimate state variables of the system. Force tracking performances for desired trajectories represented by sinusoidal and step functions are evaluated by undertaking both simulation and experimental works. In addition, in order to illustrate practical feasibility of the proposed method, a two-fingered gripper is constructed and its performance is demonstrated by showing a capability of holding an object.