Adaptive Fuzzy Sliding Mode Control Research Articles

A reduced-order approach to the adaptive fuzzy sliding mode control of the constrained manipulator

A reduced-order approach to the adaptive fuzzy sliding mode control of the constrained manipulator is proposed. Based on the Udwadia–Kalaba motion constraint equation, the dynamic equation of the constrained manipulator with both ideal and non-ideal constraints is obtained. Considering the uncertainty of the terminal non-ideal constrained force and the chattering phenomenon of sliding mode control, the adaptive fuzzy and the sliding mode control method are combined to control the constrained manipulator. Because the system is constrained, the model order reduction method is innovatively used in the control algorithm. The stability of the system is proved by Lyapunov theorem. For demonstrating the effectiveness of the control algorithm, the 2-degree-of-freedom manipulator is taken as the research object. Finally, the high-precision control of the manipulator is achieved and the chattering phenomenon caused by the sliding mode control is weakened.

Fuzzy-Model-Based Sliding Mode Control of Nonlinear Descriptor Systems.

This paper addresses the problem of sliding mode control (SMC) for a type of uncertain time-delay nonlinear descriptor systems represented by T-S fuzzy models. One crucial contributing factor is to put forward a novel integral fuzzy switching manifold involved with time delay. Compared with previous results, the key benefit of the new manifold is that the input matrices via different subsystems are permitted to be diverse, and thus much more applicability will be achieved. By resorting to Frobenius' theorem and double orthogonal complement, the existence condition of the fuzzy manifold is presented. The admissibility conditions of sliding motion with a strictly dissipative performance are further provided. Then, the desired fuzzy SMC controller is synthesized by analyzing the reachability of the manifold. Moreover, an adaptive fuzzy SMC controller is also proposed to adapt the input saturation and the matched uncertainty with unknown upper bounds. The feasibility and virtue of our theoretical findings are demonstrated by a fuzzy SMC controller implementation for a practical system about the pendulum.

Pneumatic Artificial Muscle-Driven Control Loading System (iFUZZY2017)

A control loading system (CLS) provides a force feel about the state of devices. In this paper, the technique for a pneumatic artificial muscle (PAM)-actuated control loading system is developed. The proposed PAM-based control loading system is made with a steel string fixed at one end and the other end connected to a control column, and a force feedback to an operator can be achieved according to the system state. In order to demonstrate the dynamic force feedback characteristics, a second-order mass-spring-damper model is used for the computed force, and the force control is implemented via the position-loop architecture. Moreover, due to the structure and parametric uncertainties of the designed control loading system, the adaptive fuzzy sliding mode controller are employed to improve the fidelity feeling of the force exerted on the control column. Benchmark tests compare the adaptive fuzzy sliding mode controller with other controllers. Results demonstrate the designed PAM-driven control loading system.

Robust fixed-time synchronization of fractional order chaotic using free chattering nonsingular adaptive fractional sliding mode controller design

In this paper, fixed-time synchronization of two fractional order chaotic systems in the presence of uncertainties and exogenous disturbances using a fuzzy adaptive sliding mode controller has been investigated. In the proposed approach, the upper bound of the synchronization time is completely independent of the difference between the initial conditions of the master and slave systems and just depends on the design parameters of the switching surface and controller. Adaption laws are proposed for selecting controllers and switching surface parameters to have a proper control and reduce control dependence on estimation of disturbances upper bound. Furthermore, to remove chattering phenomenon a fuzzy logic system is used. The fixed-time stability and controller design are driven based on Lyapunov stability theorem and simulations results are provided to show the effectiveness of proposed method.

Hybrid force/position control of robotic arms manipulating in uncertain environments based on adaptive fuzzy sliding mode control

In this study, the hybrid force/position control of robotic manipulators operating in uncertain environments is addressed by integrating the fuzzy logic with conventional sliding mode control (SMC). After decomposition of the manipulator dynamics into position, force, and redundant joint subspaces, the universal approximation capability of fuzzy systems is employed to approximate the equivalent part of the control input constructed based on SMC concept. The robust part of the controller is estimated by an adaptive PI controller to compensate for deviations due to the presence of model uncertainties and perturbations. Furthermore, some adaptation laws are derived for updating the parameters online when some changes in the system dynamics are made. The proposed adaptive fuzzy sliding mode control (AFSMC) requires the minimum information about the manipulator dynamic structure and environment physical properties among the other hybrid force/position control methods presented so far. Indeed, it needs neither estimation of the dynamic model nor bounds of uncertainties in advance. The asymptotic stability of the proposed controller is also proved in the sense of Lyapunov theorem. The simulation results show the good performance of the proposed controller in coping with uncertainties. The proposed scheme is also compared with standard SMC methodology, and its superior robustness is shown in comparison with those methods which require an estimation of the plant mathematical model.

New approach of sliding mode control for nonlinear uncertain pneumatic artificial muscle manipulator enhanced with adaptive fuzzy estimator

A new enhanced adaptive fuzzy sliding mode control approach is proposed in this article with its good availability for application in control of a highly uncertain nonlinear two-link pneumatic artificial muscle manipulator. Stability demonstration of the robust convergence of the closed-loop pneumatic artificial muscle manipulator system based on a novel enhanced adaptive fuzzy sliding mode control is experimentally proved using Lyapunov stability theorem. Obtained result confirms that the new enhanced adaptive fuzzy sliding mode control method, applied to the two-link uncertain nonlinear pneumatic artificial muscle manipulator system, is fully investigated with better robustness and precision than the standard sliding mode control and fuzzy sliding mode control techniques.

New AFSMC Method for Nonlinear System with State-dependent Uncertainty: Application to Hexapod Robot Position Control

Conventional Adaptive Fuzzy Sliding Mode Control (AFSMC) method is extended for nonlinear affine systems with state-dependent upper bound of uncertainties. More general affine model of the system with state-dependent uncertainties is proposed where such a model is more applicable in robotics. Position control of a Stewart Manipulator (SM) is then considered as a challenging case study to experimentally verify the effectiveness of the proposed Extended AFSMC (E-AFSMC) method. The proposed method is encompassed of a fuzzy system for estimation of a nonlinear system, a robust controller for compensation of uncertainties and some appropriate adaptation laws for optimization of performance. The second Lyapunov theorem and Barbalat lemma are used to prove the closed-loop asymptotic stability. Furthermore, numerical simulations depict the robustness of the proposed controller and in particular, under the very critical situation of actuator saturation and unexpected uncertainties. The effectiveness of the proposed control method is validated through experimental results.

Robust position and vibration control of an electrohydraulic series elastic manipulator against disturbance generated by a variable stiffness actuator

This paper presents an electrohydraulic series elastic manipulator (ESEM) system containing a novel variable stiffness actuator (VSA) and a hybrid robust control. The ESEM includes a series elastic manipulator (SEM), an adjustable stiffness mechanism (ASM), and an electrohydraulic servo system (EHS). Thus, the ESEM can benefit from the advantages of the EHS, such as high-power density and a high torque-to-weight ratio. Besides, the ESEM system can use the advantages of the VSA to give the system a suitable dynamic in unknown environments as well as low energy consumption for cyclic tasks. The proposed VSA adjusts the stiffness by changing the position of the springs along the ball screw. This system can provide fast stiffness regulation in a much broader range. However, the variant characteristics of the VSA, and nonlinearities and uncertainties in the EHS, such as friction, leakages, and dependence of bulk modulus on temperature, are major challenges for the control design. The new design of a backstepping adaptive fuzzy sliding mode control (BAFSMC) is addressed in this study. It is developed via sliding mode control, backstepping technique, and an adaptive fuzzy scheme. The controller is separated into two control loops for the mechanical dynamics and the hydraulic dynamics. The SMC is embedded for each loop to reduce the system's order and to ensure that the system's state variables reach and stay on the sliding surface. The adaptive fuzzy scheme is used to replace the robust term in the control effort of the conventional SMC to get rid of the chattering phenomenon and to deal with uncertainties in the mechanical and hydraulic subsystems. The Lyapunov approach and backstepping technique are used to prove the robustness and stability of the controlled system and to derive the adaptive laws. On the other hand, a fuzzy input shaping (FIS) scheme which combines an input shaping technique (IST) and a fuzzy logic system, was proposed to minimize the residual vibration at the end effector robustly over the expected operating range of the VSA system. Numerical experiments and comparisons with some existing algorithms are presented to illustrate the theoretical results and show the efficiency of the proposed controller.

Position control of Stewart manipulator using a new extended adaptive fuzzy sliding mode controller and observer (E-AFSMCO)

Previously proposed adaptive fuzzy sliding mode control (AFSMC) and adaptive fuzzy sliding mode observer (AFSMO) methods are mixed and extended for the case of affine systems in which the input gain matrix is state-dependent, non-diagonal and non-positive definite. The proposed Extended AFSMCO (E-AFSMCO) method is then applied for position control of a Stewart Manipulator (SM), whose parameters are strongly state-dependent and complex and not suitable for practical control purposes. A robust observer-based control method which can work with a simplified model of the plant, and at the same time can preserve the stability and performance of the overall complex system is of great need. In this study, the SM dynamic model is simplified by removing the dynamic effects of the legs and the neglected terms are considered as un-modeled dynamics, for which the upper bound of the uncertainty is progressively estimated using the proposed adaptation rules. The final controller is comprised of a fuzzy controller in parallel with a robust switching controller. The second Lyapunov theorem is used to prove the closed-loop asymptotic stability. The proposed E-AFSMCO method is verified numerically and experimentally, depicting the effectiveness of the method for real-time industrial applications.

Maximum Power Point Tracking and Output Power Control on Pressure Coupling Wind Energy Conversion System

This paper proposed a combined method for wind energy conversion system using pressure coupling (PC) hydrostatic transmission. The operation strategy is the combination of maximizing power point tracking at the input power and stabilizing the output power. The maximum power point tracking method is to control the turbine speed for tracking the optimal tip speed ratio (TSR). For maximizing the input power, a PID controller and a sliding mode controller are applied for speed control to track a predefined speed that is calculated from the optimal TSR. The output power is stabilized by using a high-pressure accumulator for accumulating and compensating the power. The driven speed of the generator is controlled by the PC principle, using a PID controller and an adaptive fuzzy sliding mode controller. Experiments are carried out to verify the proposed method. The overall efficiency in several wind speed profiles is about 40%.

Adaptive Fuzzy Sliding Mode Control of Under-actuated Nonlinear Systems

A new extension of the conventional adaptive fuzzy sliding mode control (AFSMC) scheme, for the case of under-actuated and uncertain affine multiple-input multiple-output (MIMO) systems, is presented. In particular, the assumption for non-zero diagonal entries of the input gain matrix of the plant is relaxed. In other words, the control effect of one actuator can propagate from a subgroup of canonical state equations to the rest of equations in an indirect sense. The asymptotic stability of the proposed AFSM control method is proved using a Lyapunov-based methodology. The effectiveness of the proposed method for the case of under-actuated systems is investigated in the presence of plant uncertainties and disturbances, through simulation studies.

Adaptive Second-Order Sliding Mode Fuzzy Control Based on Linear Feedback Strategy for Three-Phase Active Power Filter

The increasing use of nonlinear loads entails serious electrical energy quality problems in power grids. Active power filter could lead to significant improvement in harmonic compensation performance. In this paper, an adaptive second-order sliding mode fuzzy control based on linear feedback strategy for a three-phase active power filter is proposed to eliminate harmonics. This scheme is constituted by adaptive controller, second-order sliding mode controller, fuzzy controller, and linear feedback controller. The linear feedback controller can compensate the system’s nonlinearities and make the new system have a linear behavior between the input and output. Moreover, the second-order sliding mode controller could transfer the discontinuities in the controller and reduce system chattering. Simulation results illustrate the proposed controller has better performance compared with fuzzy control and adaptive sliding mode fuzzy control.

Adaptive Fuzzy Sliding Mode Control for Translational Oscillator With Rotating Actuator: A Fuzzy Model

This paper is concerned with the issue of adaptive fuzzy sliding mode control for fuzzy underactuated translational oscillator with rotating actuator (TORA). Since the system considered in this paper is accompanied by strong inputs coupling and nonlinear characteristics, the feedback decoupling and fuzzy technique are introduced to establish a linear fuzzy underactuated TORA system. The two-order fuzzy sliding surface with adaptive parameters is designed, where the adaptive control is introduced to adjust the parameters of sliding surface such that the system performance could be improved. The sliding mode control law is synthesized to guarantee the sliding mode dynamics to be asymptotically stable and robust, and the reachability analysis is presented to ensure that the system trajectories can be driven onto the sliding mode surface and remain there for the subsequent time. Simulation results are provided to compare with the existing results and validate the effectiveness and feasibility of the proposed scheme.

Robust fuzzy sliding mode control for air supply on PEM fuel cell system

In this paper, an adaptive fuzzy sliding mode controller is employed for air supply on proton exchange membrane fuel cell (PEMFC) systems. The control objective is to adjust the oxygen excess ratio at a given set point in order to prevent oxygen starvation and damage to the fuel-cell stack. The proposed control scheme consists of two parts: a sliding mode controller (SMC) and fuzzy logic controller (FLC) with an adjustable gain factor. The SMC is used to calculate the equivalent control law and the FLC is used to approximate the control hitting law. The performance of the proposed control strategy is analysed through simulations for different load variations. The results indicated that the adaptive fuzzy sliding mode controller (AFSMC) is excellent in terms of stability and several key performance indices such as the integral squared error (ISE), the integral absolute error (IAE) and the integral time-weighted absolute error (ITAE), as well as the settling and rise times for the closed-loop control system.

A fuzzy adaptive sliding mode controller for uncertain nonlinear multi motor systems

Multi-motor drive systems are nonlinear, multi-input multi-output (MIMO) and strong-coupling complicated system, including the effect of friction and elastic, backlash. They have been widely used in many modern industries. The control law for this dive system much depend on the determining of the tension being hard to obtain this tension in practice based on a load cell or a pressure meter due to the accuracy of sensors or external disturbance. An emerging proposed technique in the control law is the use of adaptive sliding mode control scheme to stabilize closed system. However, the control system would be affected by chattering phenomenon. In order to eliminate this term, fuzzy technique is proposed by adjusting equivalent coefficients. The theory analysis and simulation results point out the good performance of the proposed fuzzy adaptive sliding mode control for the drive system.

ADAPTIVE FUZZY SLIDING MODE CONTROL: APPLICATION TO SATELLITE LAUNCH VEHICLE’S ATTITUDE CONTROL

This paper presents a control design approach for attitude tracking of Satellite Launch Vehicles (SLVs) based on adaptive fuzzy sliding mode control (AFSMC) with integral sliding mode switching surfaces.

Fuzzy adaptive sliding-mode control for hypersonic vehicles

This study focuses on a novel anti-disturbance flight control scheme for the near space hypersonic vehicle (NHV) based on the fuzzy sliding-mode control technique and disturbance observer. First, a fuzzy system is employed to approximate the uncertainty nonlinear dynamics; furthermore, an auxiliary fast dynamic observation system is introduced to tackle the system uncertainty and the time-varying unknown external disturbance of the NHV. Second, the dynamic adaptive terminal sliding-mode control strategy is raised to alleviate the chattering phenomenon. Third, the Lyapunov method is used to prove that the adaptive control system can be guaranteed to be stable and the tracking errors are converged in finite time. Finally, the effectiveness of the proposed method is verified with simulation.

Fault Tolerant Control Based on Adaptive Fuzzy Sliding Mode Controller for Induction-Motors

Fault Tolerant Control Based on Adaptive Fuzzy Sliding Mode Controller for Induction-Motors

Semi-Active Vortex Induced Vibration Control of an Elastic Elliptical Cylinder with Energy Regeneration Capability

The concept of energy-regenerative damping is adopted in semi-active vortex-induced vibration (VIV) suppression of an elastically supported inclined impenetrable elliptical cylinder modeled as a two degree-of-freedom (DOF) system in laminar cross-flow at low Reynolds numbers (Re = 210). It is based on the intelligent (model free) adaptive fuzzy sliding mode control (AFSMC) strategy in conjunction with switch-based energy regenerating circuit of a tunable electromagnetic (EM) damper. The semi-active damper is linked to the plant model in a multi-field co-simulation framework via MATLAB/Simulink coupled with a user defined function in a CFD package. The AFSM controller initially calculates the desired transverse control force for suppression of the cylinder VIV. Consequently, by smart adjustment of the variable circuit load resistance, the current flow through EM damper circuit is adaptively modulated in such a way that the damping force continually tracks its active counterpart in a semi-active manner. Furthermore, when the damper is operating in the regeneration mode, the mechanical vibration energy that is traditionally dissipated as heat in conventional viscous dampers will be stored as electric charge in a capacitor. Numerical simulations demonstrate that the regenerative semi-active EM-based VIV control system can effectively suppress the cylinder motion while recovering a certain portion of mechanical vibration energy through the cooperative action of two distinct operation modes of the EM damper. Unlike conventional active control systems, the proposed system does not require a large external power supply, and at least part of the required power may be provided by the recovered energy.

Adaptive Fuzzy Sliding Mode Diving Control for Autonomous Underwater Vehicle with Input Constraint

This paper develops a novel adaptive fuzzy sliding mode controller for the diving control of autonomous underwater vehicle (AUV). Unlike most previous AUVs’ control approaches, in this paper, the problem of input saturation constraint of rudder angle is considered, and the new auxiliary systems are proposed. Considering the modeling uncertainty of the dynamic model, an adaptive sliding mode controller based on fuzzy logic system is proposed, and the new update laws of control parameters are given. For the adaptive sliding mode controller design, although the input gain of each subsystem is partially known, only one fuzzy logic system is needed for online identification, which is a distinct difference from the previous adaptive sliding mode controllers. The uniformly ultimately boundedness of tracking error is proven by Lyapunov theorem. The effectiveness of the proposed control scheme is illustrated by simulation.