Showing papers on "Sliding mode control published in 2001"

Robust Adaptive Variable Structure Control of Spacecraft Under Control Input Saturation

Abstract: In this paper we propose two globally stable control algorithms for robust stabilization of spacecraft in the presence of control input saturation, parametric uncertainty, and external disturbances. The control algorithms are based on variable structure control design and have the following properties: 1 ) fast and accurate response in thepresenceofbounded external disturbancesand parametricuncertainty;2 )explicit accounting forcontrol input saturation; 3 ) computational simplicity and straightforward tuning. We include a detailed stability analysis for the resulting closed-loop system. The stability proof is based on a Lyapunov-like analysis and the properties of the quaternion representation of spacecraft dynamics. It is also shown that an adaptive version of the proposed controller results in substantially simpler stability analysis and improved overall response. We also include numerical simulations to illustrate the spacecraft performance obtained using the proposed controllers.

Modeling and nonlinear control of magnetic levitation systems

Abstract: In this paper, the authors propose a nonlinear model for magnetic levitation systems which is validated with experimental measurements. Using this model, a nonlinear control law based on differential geometry is firstly synthesized. Then, its real-time implementation is developed. In order to highlight the performance of the proposed control law, experimental results are given.

Sliding mode observer for nonlinear uncertain systems

Abstract: A new sliding mode observer for a class of nonlinear uncertain systems is proposed in this article. The proposed sliding mode observer works under much less conservative conditions than previous nonlinear unknown input observers. Also, a functional version of the observer is proposed in certain cases where it may not be possible to design an observer capable of estimating the entire state of the system.

Observer-based control of systems with slope-restricted nonlinearities

Abstract: An observer design is presented which makes use of bounds on the slope of system nonlinearities. Necessary and sufficient conditions are derived for the feasibility of the design. A class of state feedback control laws are characterized which, when implemented with the observer states, ensure global asymptotic stability. One such certainty-equivalence design is illustrated on an active magnetic bearing example.

Analysis and design of impulsive control systems

Abstract: Some sufficient conditions for asymptotic stability of impulsive control systems with impulses at fixed times have recently been presented. In this paper, we derive some less conservative conditions for asymptotic stability of such impulsive control systems and the results are used to design impulsive control for a class of nonlinear systems. The class of nonlinear systems considered is also extended.

An averaging approach to chattering

Abstract: The singularly perturbed relay control systems (SPRCS) as mathematical models of chattering in the small neighborhood of the switching surface in sliding mode systems are examined. Sufficient conditions for existence and stability of fast periodic solutions to the SPRCS are found. It is shown that the slow motions in such SPRCS are approximately described by equations derived from equations for the slow variables of SPRCS by averaging along fast periodic motions. It is shown that In the general case, when the equations of a plant contain relay control nonlinearly, the averaged equations do not coincide with the equivalent control equations or with the Filippov's definition (1988) for the sliding motions in the reduced system; however, in the linear case, they coincide.

Fuzzy sliding-mode controllers with applications

Abstract: This paper concerns the design of robust control systems using sliding-mode control that incorporates a fuzzy tuning technique. The control law superposes equivalent control, switching control, and fuzzy control. An equivalent control law is first designed using pole placement. Switching control is then added to guarantee that the state reaches the sliding mode in the presence of parameter and disturbance uncertainties. Fuzzy tuning schemes are employed to improve control performance and to reduce chattering in the sliding mode. The practical application of fuzzy logic is proposed here as a computational-intelligence approach to engineering problems associated with sliding-mode controllers. The proposed method can have a number of industrial applications including the joint control of a hydraulically actuated mini-excavator as presented in this paper. The control hardware is described together with simulated and experimental results. High performance and attenuated chatter are achieved. The results obtained verify the validity of the proposed control approach to dynamic systems characterized by severe uncertainties.

Output feedback sampled-data control of nonlinear systems using high-gain observers

Abstract: This paper studies sampled-data control of nonlinear systems using high-gain observers. The observer is designed in continuous time, then discretized using three different discretization methods. Closed-loop analysis shows that the sampled-data controller recovers the performance of the continuous time controller as the sampling frequency and observer gain become sufficiently large. The theory is illustrated by experimental results.

Naive control of the double integrator

Abstract: We deal with a form of controller evaluation that may be called naive control In naive control, a control algorithm derived under nominal (or ideal) conditions is evaluated by analytical or numerical means under off-nominal (or nonideal) conditions that were not assumed in the formal synthesis procedure Under such nonideal conditions, the controller may or may not perform well This approach is distinct from robust control, which seeks to accommodate off-nominal perturbations in the synthesis procedure We consider the double integrator plant, which is one of the most fundamental systems in control applications, representing single degree-of-freedom translational and rotational motion Applications of the double integrator include low-friction, free rigid-body motion, such as single-axis spacecraft rotation and rotary crane motion The double integrator plant considered includes a saturation nonlinearity on the control input

Nonlinear maneuvering and control of ships

Abstract: We address the problem of maneuvering ships onto curves or paths in the plane. To do this, we introduce the Serret-Frenet equations and show how these fit the scope for control design with 3 degrees-of-freedom (DOF) hydrodynamic ship models in the loop. The Davidson and Schiff (1946) linear parametrically varying ship model is used in the design, and we show how we can manipulate this by introducing acceleration feedback and by moving the body-frame freely. This simplifies the control design in such a way that we do not have to deal with zero-dynamics. Instead we use a 3-step backstepping design and theory for interconnecting subsystems. Real data from a 175 m container ship is used in a computer simulation to validate the design.

Adaptive nonlinear output-feedback control with unknown high-frequency gain sign

Abstract: A global adaptive output-feedback control scheme, which does not require a priori knowledge of high-frequency gain sign, is proposed for general nonlinear systems in output-feedback form. Unlike in Ding (1998), the removal of a priori knowledge of the high-frequency gain sign is not at the price of making growth restrictions on system nonlinearities, and furthermore, only the minimal number of parameters needs to be updated.

A model following sliding mode controller for semi-active suspension systems with MR dampers

Abstract: This paper presents a new sliding mode controller for semi-active suspension systems with Magnetorheological (MR) dampers which have undesirable nonlinear properties. In the proposed controller, a desired semi-active suspension system is chosen as the reference model to be followed, and the control low is determined so that an asymptotically stable sliding mode will occur in the error dynamics between the plant and the reference model states. The advantages of the proposed controller are: (1) measurement of the-damper force is not required, (2) the reference model specifies the desired performance considering the passivity constraint of the damper, (3) it is highly possible to maintain the sliding mode and achieve high robustness against model uncertainties and disturbances. Numerical simulations illustrate the effectiveness of the controller.

Side-slip control to stabilize vehicle lateral motion by direct yaw moment

Abstract: Following to the experimental validation of the side-slip estimation by model observer, the experimental study on the effects of the side-slip control by direct yaw moment on stabilizing vehicle motion which is impaired due to nonlinear tire characteristics is carried out. A double lane change test as well as a single lane change test with braking is conducted in order to prove the effect of the control on stabilizing the vehicle motion during severe maneuvering. It is proved that the side-slip control by DYC has a higher ability to stabilize the vehicle motion compared with 4WS because the vehicle losses its stability due to deterioration of rear tire characteristics, however, 4WS has to use the deteriorated rear tire to control the vehicle motion. The side-slip control is also proved to be superior to the yaw rate control to compensate for loss of stability due to nonlinear tire characteristics.

Robust nonlinear motion control of a helicopter

Abstract: We consider the problem of controlling the vertical motion of a nonlinear model of a helicopter to a reference signal, while stabilizing the lateral and horizontal position and maintaining a constant attitude. The reference to be tracked is given by a sum of a constant and a fixed number of sinusoidal signals, and it is assumed not to be available to the controller. This represents a possible situation in which the helicopter is required to synchronize its vertical motion with that of an oscillating platform, as the one given by a sea carrier subject to wave-induced oscillations. We design a nonlinear controller which combines results on nonlinear adaptive output regulations and robust stabilization of systems in feedforward form by means of saturated controls. Simulation results show the effectiveness of the method and its ability to cope with large uncertainties on the plant, the actuator model and the exogenous reference signal.

Global sliding-mode control. Improved design for a brushless DC motor

Abstract: An improved global sliding-mode control (GSMC) was proposed for controlling second-order time-varying systems with bounded uncertain parameters and disturbances. The proposed controller drives the system states along the minimum time trajectory within the input torque limit. If the reference input and the bounds of the uncertain parameters and disturbances are specified, the minimum arrival time and the acceleration are expressed in closed-form equations. The proposed controller was applied to the brushless DC motor with uncertain loads. Experimental results of the proposed controller are quite similar to simulation and closed-form equation results and showed the best performance compared with other SMC. The closed-form equation can be used for designing motor-based actuators for mechanical systems without simulation and experiments.

Nonlinear control of a pneumatic muscle actuator: backstepping vs. sliding-mode

Abstract: This paper weighs up the pros and cons of three different tracking controllers for a pneumatic muscle actuator: robust backstepping, adaptive backstepping and sliding-mode. Robustness is assured for three controllers in the presence of model uncertainties and external perturbations. Ultimate boundedness is proved for the robust and adaptive backstepping tracking controller. Exponential stability is proved for the sliding-mode tracking controller. The tracking is well achieved by the sliding-mode and the adaptive controller. On the contrary, the robust backstepping shows a noticeable tracking error. The sliding-mode leads to a high-frequency switching control law.

Hybrid control using recurrent fuzzy neural network for linear induction motor servo drive

Abstract: A hybrid control system using a recurrent fuzzy neural network (RFNN) is proposed to control a linear induction motor (LIM) servo drive. First, feedback linearization theory is used to decouple the thrust force and the flux amplitude of the LIM. Then, a hybrid control system is proposed to control the mover of the LIM for periodic motion. In the hybrid control system, the RFNN controller is the main tracking controller, which is used to mimic a perfect control law, and the compensated controller is proposed to compensate the difference between the perfect control law and the RFNN controller. Moreover, an online parameter training methodology, which is derived using the Lyapunov stability theorem and the gradient descent method is proposed to increase the learning capability of the RFNN. The effectiveness of the proposed control scheme is verified by both the simulated and experimental results. Furthermore, the advantages of the proposed control system are indicated in comparison with the sliding mode control system.

An adaptive fuzzy sliding-mode controller

Abstract: This paper deals with a new adaptive fuzzy sliding-mode controller and its application to a robot manipulator arm. The theory for this approach and for the heuristics-based linguistic adaptation is presented, and a mathematical description is derived. Furthermore, an application of this adaptive controller for a two-link robot arm is shown. The obtained results show the high efficiency of the new controller type.

Sliding control of an electropneumatic actuator using an integral switching surface

Abstract: This paper presents a synthesis of a nonlinear switching control of a rotational electropneumatic servo drive using a sliding mode approach. A nonlinear sliding mode control law is applied to the system under consideration. First, the model of the electropneumatic servo drive is developed. This model is nonlinear with respect to both the state variables and the control input. It is transformed to be linear with respect to a new control variable and a coordinate transformation is then related to make possible the implementation of the nonlinear discontinuous controller. Two sliding mode controllers are synthesized with and without an integral term in the switching surface. The sliding regimes are particularly pointed out and their stability analyzed to show that the integral discontinuous control provides best results especially for a steady-state error cancellation. Practical considerations are proposed for choosing the control parameters. Finally, the experimental results are presented and discussed.

Power control of a photovoltaic array in a hybrid electric generation system using sliding mode techniques

Abstract: A variable structure controller to regulate the output power of a standalone hybrid generation system is presented. The system comprises photovoltaic and wind generation, a storage battery bank and a variable monophasic load. The control law admits two modes of operation. The first takes place when the insolation regime is sufficient to satisfy the power demand. The second mode of operation takes place under insufficient insolation regimes. The latter leads the system operation at the maximum power operation point to save as much stored energy as possible. A new method based on the IncCond algorithm is developed. Sliding mode control techniques are used to design the control law. These techniques provide a simple control law design framework and contribute with their well known robustness properties. Finally, guidelines based on chattering considerations are given for the design of the practical system.

Adaptive-predictive control of a class of SISO nonlinear systems

Abstract: In this paper, an adaptive-predictive control algorithm is developed for a class of SISO nonlinear discrete-time systems based on a generalized predictive control (GPC) approach. The design is model-free, based directly on pseudo-partial-derivatives derived on-line from the input and output information of the system using a recursive least squares type of identification algorithm. The proposed control is especially useful for nonlinear systems with vaguely known dynamics. Robust stability of the closed-loop system is analyzed and proven in the paper. Simulation and real-time application examples are provided for real nonlinear systems which are known to be difficult to model and control.

Design of adaptive variable structure controllers for perturbed time-varying state delay systems

Abstract: The problem of stabilizing a class of perturbed linear dynamic systems with time-varying state delay is investigated in this paper. By applying the Lyapunov stability theorem, we develop a delay-independent adaptive variable structure controller to drive the states of system to zero. Based on the variable structure control (VSC) technique, the proposed controller can drive the system into a pre-specified sliding hyperplane to obtain the desired dynamic performance. Once the dynamics of system reach the sliding plane, the proposed controlled system is insensitive to perturbations. The use of adaptive technique is to overcome the unknown upper bound of perturbations so that the reaching condition (or sliding condition) can be satisfied. Furthermore, the globally asymptotic stability is guaranteed for the proposed control scheme under certain conditions. Finally, an example is given to illustrate the feasibility of the proposed control methodology.

A fuzzy adaptive variable structure controller with applications to robot manipulators

Abstract: A new adaptive fuzzy control algorithm is developed in this paper, which has a regular fuzzy controller and a supervisory control term. This control algorithm does not require the system model, but has stability assurance for the closed-loop controlled system. The design is simple, in the sense that both the membership functions and the rule base are simple, yet generic. It can be applied to a large class of robotic and other mechanical systems.