Conventional Variable Structure Control Research Articles

Trajectory tracking system of wheeled robot based on immune algorithm and sliding mode variable structure

An immune algorithm and a technique of sliding mode variable structure control (VSC) are proposed to achieve real-time and accurate control of wheeled robot in view of uncertainties for time-varying, strong coupling and nonlinear characteristics of wheeled robots, coupled with change of load and influence of external disturbance in traditional control algorithm based on classical control theory. First, the VSC parameters are adjusted online by the immune algorithm, which overcomes limitation that the parameters of reaching law need to be set in advance in conventional VSC. Secondly, the algorithm not only retains advantages of the traditional reaching law, but also effectively improves control quality and eliminates chattering of the system. The experimental results show that the control technique makes the wheeled robot move on sliding surface in an ideal way, for main concern of this paper is to provide an effective systemic for control of wheeled robot.

Multi-phase robust position control scheme for synchronous reluctance motor

In the recent years the synchronous reluctance motor (SynRM) has received much attention due to its desirable controllability and simple structure. In this paper, in order to improve the position control performance of a three phase SynRM, a control scheme is proposed. In the proposed controller design, the smooth operation of the traditional linear controllers and the robustness of variable structure controllers have been considered. The proposed controller eliminates the drawbacks of traditional linear control schemes and conventional variable structure control scheme, such as high frequency chattering at the same time. Yet, their advantages such as smooth operation and robustness are preserved as a big merit. The experimental results clearly demonstrate the superiority of the proposed controller over conventional control schemes.

Multiphase Robust Position Control Scheme for Synchronous Reluctance Motor

In the recent years the synchronous reluctance motor (SynRM) has received much attention due to its desirable controllability and simple structure. In this paper, in order to improve the position control performance of a three phase SynRM, a control scheme is proposed. In the proposed controller design, the smooth operation of the traditional linear controllers and the robustness of variable structure controllers have been considered. The proposed controller eliminates the drawbacks of traditional linear control schemes and conventional variable structure control scheme, such as high frequency chattering at the same time. Yet, their advantages such as smooth operation and robustness are preserved as a big merit. The experimental results clearly demonstrate the superiority of the proposed controller over conventional control schemes.

The Research Based on Fuzzy Sliding Mode Control for Linear Double Inverted Pendulum

This paper involves a linear double inverted pendulum system whose the state space model is established by Lagrange function. In order to solve the chattering problem of the conventional quasi-sliding mode variable structure control, this linear double inverted pendulum system applies the fuzzy control theory to adjust the parameterwhich is in the sliding mode variable structure control law. Then the fuzzy theory is utilized to design the sliding mode and deduce the fuzzy sliding mode reaching law. The significance of this method is that it diffuses the control signal, reduces or avoids the chattering phenomenon of sliding mode control. For the most, the simulation results show that the linear double inverted pendulum system based on fuzzy sliding mode variable structure control not only retains the strong robustness of sliding mode variable structure control, but also improves the dynamic quality of the system and weakens the buffeting of the system. Thus the method is proved to have certain research.

Research of Sliding Mode Control with Integral Compensator for Permanent Magnet Linear Synchronous Machine

In order to solve the high-frequency chattering and low anti-disturbance in conventional variable structure control (VSC) method with sliding mode, a compensator scheme of introducing integral structure before control object is proposed. Firstly, the position loop VSC state equations and equivalent control model are established based on the analyses of the mathematical model of permanent magnet linear synchronous machine (PMLSM). Then it presents a more accurate and comprehensive method to determine the control parameters and the equivalent model parameters. Computer simulation with the motor parameters of a flat type PMLSM verifies the feasibility and effectiveness of the compensator structure. Compared with the conventional VSC, the proposed structure can solve the vibration caused by external disturbance and load variations, and attenuate the chattering effectively. It is concluded through further analyses that the proposed structure can overcome the system oscillations generated by mover mass and permanent magnet flux linkage, and improve the robustness and control precision of the system.

A novel variable structure theory applied in design for wheeled mobile robots

This article is concerned with the control of wheeled mobile robots (WMRs) using a modified variable structure theory. First, we introduce the dynamic characteristics of a WMR. Second, conventional variable structure control is reviewed. In order to considerably improve the transient response during the reaching phase, a modified variable structure control is proposed. The validity of the proposed variable structure theory is verified by means of a simulation test on a home-made wheeled mobile vehicle. The simulation results validate the superiority and practicality of the modified variable structure for WMRs.

Improved fuzzy sliding mode control for a class of MIMO nonlinear uncertain and perturbed systems

In this paper, a stable adaptive fuzzy sliding mode based tracking control is developed for a class of nonlinear MIMO systems that are represented by input output models involving system uncertainties and external disturbances. The main contribution of the proposed method is that the structure of the controller system is partially unknown and does not require the bounds of uncertainties and disturbance to be known. First, a fuzzy logic system is designed to estimate the unknown function. Secondly, in order to eliminate the chattering phenomenon brought by the conventional variable structure control, the signum function is replaced by an adaptive Proportional Derivative (PD) term in the proposed approach. All parameter adaptive laws and robustifying control terms are derived based on Lyapunov stability analysis, so that convergence to zero of tracking errors and boudedness of all signals in the closed-loop system can be guaranteed. Finally, a mass-spring-damper system is simulated to demonstrate the validity and the effectiveness of the proposed controller.

동적신경망을 이용한 비선형 다변수 시스템의 제어기 설계

The variable structure control(VSC) with sliding mode is an important and interesting topic in modern control of nonlinear systems. However, the discontinuous control law in VSC leads to undesirable chattering in practice. As a method solving this problem, in this paper, we propose a scheme of the VSC with neural network sliding surface. A neural network sliding surface with boundary layer is employed to solve discontinuous control law. The proposed controller can eliminate the chattering problem of the conventional VSC. The effectiveness of the proposed control scheme is verified by simulation results.

Position control of synchronous motor drive by modified adaptive two-phase sliding mode controller

A modified adaptive two-phase sliding mode controller for the synchronous motor drive that is highly robust to uncertainties and external disturbances is proposed in this paper. The proposed controller uses two-phase sliding mode control (SMC) where the 1st phase mainly controls the system in steady states and disturbed states — it is a smoothing phase. The 2nd phase is used mainly in the case of disturbed states. Also, it is an autotuning phase and uses a simple adaptive algorithm to tune the gain of conventional variable structure control (VSC). The modified controller is useful in position control of a permanent magnet synchronous drive.

Predictive variable structure control of nonholonomic chained systems

A novel variable structure control strategy for a class of second-order nonlinear systems is presented based on the phase-plane analysis and computing prediction. In this strategy control is switched by online prediction of the trajectory behaviour of the closed-loop system; control switching does not occur continuously, so the chattering that occurs in conventional variable structure control methods can be avoided completely. It is proved that the states of the closed-loop system can be stabilized to the origin exponentially and the trajectory of the closed-loop system does not overshoot in general. As an application, the proposed predictive variable structure control strategy is used to stabilize nonholonomic systems in chained form. An example of a wheeled mobile robot is studied and associated simulation results demonstrate the effectiveness of the proposed control strategy.

Repetitive Learning Control of Nonlinear Continuous-Time Systems Using Quasi-Sliding Mode

In this brief, a quasi-sliding mode (QSM)-based repetitive learning control (RLC) method is proposed for tackling multi-input multi-output nonlinear continuous-time systems with matching perturbations. The proposed RLC method is able to perform rejection of periodic exogenous disturbances as well as tracking of periodic reference trajectories. It ensures a robust system stability when it is subject to nonperiodic uncertainties and disturbances. In this brief, an application to a robotic manipulator is used to illustrate the performance of the proposed QSM-based RLC method. A comparative study with the conventional variable structure control (VSC) technique is also included

Decoupled variable structure control design for trajectory tracking on mechatronic arms

This brief presents a variable structure control (VSC) algorithm to achieve the prespecified trajectory tracking on mechatronic arms. The tracking trajectory is composed of a set of sequentially-operated piecewise continuous sliding surfaces which the system's state can follow to the equilibrium in phase plane. Some sliding mode controllers corresponding to the piecewise continuous sliding surfaces are designed to achieve the hitting motion and ensure the system's state traveling on the trajectory. The algorithm using the boundary layer technique is capable of handling the reaching phase (RP) of the trajectory and chattering effects inherent to the VSC easily and effectively. The advantages of the proposed algorithm are that 1) the state would follow the sliding surfaces in turn so that the tracking control purpose is achieved, 2) the total tracking time by adding up the traveling time for each sliding surface can be evaluated explicitly, and 3) the robustness is as excellent as that of the conventional VSC scheme. A rotational inverted pendulum system subject to external disturbances is illustrated to show the validity of the proposed algorithm.

An adaptive chattering-free variable structure control method for uncertain time-variant chaotic systems

The conventional variable structure control(VSC) methods for controlling chaos have some drawbacks, such as high_frequency chattering and the need of a prior knowledge about the upper bound of the uncertainty. Trying to solve the drawbacks, we proposed an adaptive chatteringfree variable structure control(ACFVSC) method for controlling a class of uncertain timevariable chaotic systems towards arbitrarily desired trajectory. The ACFVSC method not only eliminates the chattering phenomenon and tracks arbitrarily desired trajectory asymptotically, but also removes the prior knowledge about the upper bound of uncertainty. Both the asymptotic tracking analysis of ACFVSC and simulation results show that the arbitrarily desired tracking accuracy can be achieved within a finite time if the parameter of ACFVSC controller is appropriately set.

Design and experimental validation of a multiphase VRM controller

By combining the concepts of multiple-sliding-surface and integral-variable-structure controls, one can develop a robust controller for a multiphase 9 V VRM, which comprises four parallel DC-DC synchronous buck convertors operating at 300 kHz. The advantages of the control scheme are its simplicity in design, good dynamic response, robustness, ability to nullify the bus-voltage error and the error between the load currents of the convertor modules, and ability to reduce the impact of high-frequency dynamics due to parasitics on the closed-loop control system. Unlike a conventional variable-structure controller (VSC), which achieves superior transient performance by optimising (and hence, by varying) the switching frequency, the novel controller is able to retain the excellent dynamic performance of a conventional VSC and yet maintain a constant-frequency operation of a PWM controller under 'steady-state' condition. The latter is achieved by obtaining a duty-ratio signal; however, unlike a PWM controller, the new controller calculates the duty ratio based on Lyapunov's stability crietrion. Thus, the new controller also permits interleaved operation of the VRM modules.

H∞ controlling hyperchaos of the Rössler system with input nonlinearity

Based on the concept of variable structure control, this paper investigates the controller design for suppressing hyperchaos of the Rössler system with H ∞ norm constraint. A proportional-integral (PI) switching surface is newly adopted so that it becomes easy to solve the H ∞ control problem for such chaotic systems in the sliding mode. Based on this PI switching surface, a variable structure controller (VSC) is derived to guarantee the occurrence of sliding mode motion in finite time, even when the system is undergoing both input nonlinearity and external disturbance. Furthermore, a modified continuous controller is proposed to reduce the chattering phenomenon due to the conventional switching type VSC. An illustrative example is given to show the applicability of the proposed VSC design approach.

Variable structure controller with neural compensator

This paper proposes a new variable structure controller combined with a multilayer neural network using an error back-propagation learning algorithm. The neural network acts as a compensator for a conventional variable structure controller in order to improve the control performance when the initial assumptions of the uncertainty bounds of the system parameters are violated. Also, the proposed controller can reduce the steady-state error of a conventional variable structure controller using the boundary layer technique. Computer simulation results show that the proposed method is effective in controlling dynamic systems with unexpected large uncertainties.

Variable-structure control using the idea of a fictitious set point temperature tracking control of a batch reactor process

This paper shows how a control strategy using a ‘fictitious’ set point can be applied to the tracking control problem of a batch reactor process, and demonstrates that excellent control results have been obtained. In this process, the reactor temperature is required to be raised at a fixed rate from the start-up to the desired temperature, and to be kept at that temperature. PID control was previously used to achieve this objective, but the reactor temperature showed frequent variations near the desired temperature, and heating steam and cooling water were wasted in this type of control. Conventional variable-structure control is then considered to avoid such variations. However, a computer simulation shows that the tracking control response cannot be improved by this means. To reduce the frequent temperature variations and the waste of energy, a new control strategy is applied to this process, following computer simulations. The experimental results are that this method is quite effective as compared with PID control and conventional VSC laws, and that the temperature variation and the consumption of both steam and cooling water were decreased by 50 and 45%, respectively.

An Explicit Formula of Linear Sliding Surfaces for a Class of Uncertain Dynamic Systems with Mismatched Uncertainties

In this note, the problem of designing a variable structure control (VSC) law for uncertain systems where the uncertainty in the state model does not satisfy the matching condition is considered. Based on the LMI approach we develop a new design method of linear sliding surfaces which are linear to the state. We give a sufficient condition for the existence of linear sliding surfaces in terms of LMIs and we give an explicit formula of linear sliding surfaces guaranteeing the quadratic stability of the reduced-order equivalent system dynamics restricted to the sliding surfaces. We also give sufficient conditions for the existence of linear sliding surfaces insuring some pole clustering constraints. Thus, one can easily design VSC laws for a class of uncertain systems with mismatched uncertainties which are difficult to deal with by using conventional VSC design methods. Finally, we give a design example.

Design of reduced-order observer-based variable structure power system stabiliser for unmeasurable state variables

In the paper, to design a simpler and more economical observer-based controller, and to solve the problem associated with the unmeasurable state variables in the conventional VSC, a reduced-order (n – m) observer-based variable structure controller (ROOVSC) is proposed and applied to a power system stabiliser (PSS). This ROOVSPSS is obtained by combining the variable structure control (VSC) with a reduced-order observer (ROO): the state estimator by the ROO and the controller by the VSC, which eliminates the need to measure all the state variables in the conventional VSC-PSS. The simulation results are shown by comparison of the ROOPSS with the proposed ROOVSPSS under normal and heavy load operations.

Design of variable structure controllers with continuous switching control

A modified variable structure controller is proposed to deal with the conirol chattering problem which is one of the major difficulties for implementing the variable structure control (VSC). The new control strategy is effective for a class of uncertain nonlinear dynamical systems. Based on a suitably designed sliding sector, a continuous switching controller whose control structure is switched, whereas the control signal at switching remains continuous, is constructed. The complete attractiveness and the stability properties of the sliding sector, in the sense of Lyapunov stability, ensure the retention of benefits achieved with the conventional VSC. Some typical examples are also investigated which show the improvement of system performance.