Nonlinear Sliding Mode Control Research Articles

Robust fractional-order control of PMSG-based WECS

This paper presents some novel fractional-order nonlinear sliding mode controllers for maximum power extraction of a grid-connected wind energy conversion system. Two similar fractional-order controllers with nonlinear sliding manifolds are proposed for generator-side and grid-side converters. The main role of the generator-side controller is regulating the mechanical speed of wind turbine to follow an optimum speed. On the other hand, the grid-side controller main goal is governing the active and reactive power by tuning DC-link voltage. Practical stability of both controllers is achieved by fractional-order nonlinear stability theorems. Comparative simulations are presented to show the effectiveness of the proposed controllers.

Robust adaptive global nonlinear sliding mode controller for a quadrotor under external disturbances and uncertainties

The present paper proposes an adaptive global nonlinear sliding mode controller (AGNSMC) for the tracking problem of a quadrotor subjected to external disturbances. In order to eliminate the reaching phase and to guarantee the sliding mode of the quadrotor states in the initial time, a novel control law is developed. The upper bounds of disturbances affected the quadrotor dynamics are rejected based on adaptive laws for the both attitude and position subsystem. The tracking performance is enhanced by using the suggested controller. The stability of quadrotor is guaranteed and the global sliding mode surfaces converge to origin values in a finite time. To show the robustness of the proposed control approach against the external disturbances, simulation results are presented and compared with the results of the super-twisting-integral sliding mode controller.

Fractional integral sliding mode nonlinear controller of electrical-hydraulic flight simulator

Fractional integral sliding mode nonlinear controller of electrical-hydraulic flight simulator

Design Intelligent Robust Partly Linear Term SMC for Robot Manipulator Systems

In this paper the development, modeling and high precision robust control of an electro-mechanical continuum robot manipulator is presented. In this paper main controller is a Sliding Mode Controller which modified by modified PD methodology based on the boundary derivative methodology. Parallel fuzzy logic theory is used to compensate the system dynamic uncertainty controller based on sliding mode theory. Sliding mode controller (SMC) is a significant nonlinear controller under condition of partly uncertain dynamic parameters of system. This controller is used to control of highly nonlinear systems especially for continuum robot manipulator, because this controller is robust and stable in presence of partly uncertainties. PD partly switching nonlinear SMC by modified PD boundary derivative method is used to achieve a stable tracking, while the parallel fuzzy-logic optimization added intelligence to the control system through an automatic tuning of the PD modified partly switching sliding mode methodology uncertainties. Adaptive methodology is used to on-line tuning the sliding surface slope and gain updating factor of this methodology. Simulation results demonstrated the validity of the Mamdani parallel fuzzy-optimization control with asymptotic and stable tracking at different position inputs. This compensation demonstrated a well synchronized control signal at different excitation conditions.

Integral sliding mode nonlinear controller of electrical-hydraulic flight simulator based on neural network

Integral sliding mode nonlinear controller of electrical-hydraulic flight simulator based on neural network

Digital modular control of high frequency DC–DC converters

This paper presents a solution for controlling integrated DC–DC converters with high switching frequency (>20MHz). The increase of the switching frequency is a trend biased by output filter volume restrictions and integration demand. The control of DC–DC converters operating at high frequency presents an opportunity to speed up the converter response time but also a challenge specially for the control solution, quiescent current and to limit the sensitivity to process and operating conditions for the mixed signal circuits involved. The solution presented in this work relies on separating the duty-cycle into three parts: a load-free value that depends only on the input and output voltages, a transient fast correction contribution, and an accurate compensation for the IR drop that depends on the load current. The load-free portion of the duty-cycle has a compensation of PVT variations and the fast transient part of the duty-cycle uses a non-linear sliding mode control solution. All the analog blocks required for the implementation of the proposed solution are detailed.

Sliding mode control of a pneumatic muscle actuator system with a PWM strategy

In this paper, a sliding mode control (SMC) strategy is applied to a pulse width modulation (PWM)-driven pneumatic muscle actuator system using high speed on/off solenoid valves. Servo-pneumatic systems with PWM-driven on/off valves can be used instead of expensive servo valves to decrease complexity, weight, and cost of servo-pneumatic systems. Due to the highly nonlinear nature of pneumatics, the system is difficult to model accurately which leads to un-modelled dynamics and uncertainties. In this paper, a robust and nonlinear SMC approach is implemented in order to control the system with sufficient accuracy. A nonlinear model is developed in a single-input single-output form by studying the flow, pressure, and force dynamics of the system. The SMC strategy is applied to three different system configurations: single on/off valve, two on/off valves, and a servo valve. The performance and effectiveness of these configurations are investigated under sinusoidal tracking at different frequencies. The robust...

Force-position control of a robotic exoskeleton to provide upper extremity movement assistance

This paper presents an upper extremity (UE) wearable robot, ETS-MARSE and its control strategy to provide movement assistance and active rehabilitation exercises to physically disabled individuals having impaired UE function. The ETS-MARSE was designed to be worn on the lateral side of UE and is able to assist arm movements at the level of shoulder, elbow, forearm and wrist joint movements. Considering the dynamic modelling of the robot system and the UE motion which are non-linear in nature, a non-linear sliding mode control with exponential reaching law was used to manoeuvre the ETS-MARSE and to provide both passive and assisted arm movement therapy. To provide passive arm movement therapy, pre-programmed trajectories corresponding to recommended passive rehabilitation exercises were used to manoeuvre the ETS-MARSE, whereas in case of assisted rehabilitation therapy user interaction wrist force sensor signals were used to steer the ETS-MARSE in assisting the UE movements. Experiments involving healthy human subjects were performed with the developed ETS-MARSE to evaluate the controller’s performance and that of the ETS-MARSE in regards to providing the therapeutic exercises. Experimental results indicate that with the proposed control strategy, ETS-MARSE can effectively deliver rehabilitation exercises.

Adaptive Sliding Mode Control for Quadrotor Aerial Robot with Ι Type Configuration

This paper presents an adaptive sliding mode control for trajectory tracking of quad rotor aerial robot with I type configuration. A continuous adaptive dynamic vector is used to eliminate the chattering phenomenon in the sliding mode control and the asymptotic stability is achieved. On the base of a nonlinear dynamic model of the quad rotor with I configuration, adaptive sliding mode nonlinear controller is synthesized for the purpose of stabilization and trajectory tracking of quad rotor. In order to validate the robustness of the proposed control method, the model deviations are modeled. It behaves perfectly at the reference altitude and trajectory track in simulation.

Recursive Backstepping Nonlinear Control and Sliding Mode Control of a Novel Hyperchaotic Finance System

In this paper, the recursive backstepping nonlinear control method is proposed. Based on the Lyapunov theory, the controllers are designed to achieve the new hyperchaotic system globally, asymptotically stabilized at the equilibrium point. Furthermore, a robust control method combining backstepping and sliding mode control techniques is used to control the system to another equilibrium point. Numerical simulation results show that the proposed control schemes are effective.

Design Robust Fuzzy Sliding Mode Control Technique for Robot Manipulator Systems with Modeling Uncertainties

This paper describes the design and implementation of robust nonlinear sliding mode control strategies for robot manipulators whose dynamic or kinematic models are uncertain. Therefore a fuzzy sliding mode tracking controller for robot manipulators with uncertainty in the kinematic and dynamic models is design and analyzes. The controller is developed based on the unit quaternion representation so that singularities associated with the otherwise commonly used three parameter representations are avoided. Simulation results for a planar application of the continuum or hyper-redundant robot manipulator (CRM) are provided to illustrate the performance of the developed adaptive controller. These manipulators do not have rigid joints, hence, they are difficult to model and this leads to significant challenges in developing high-performance control algorithms. In this research, a joint level controller for continuum robots is described which utilizes a fuzzy methodology component to compensate for dynamic uncertainties.

Nonlinear sliding mode control of an unmanned agricultural tractor in the presence of sliding and control saturation

The paper considers the problem of automatic path tracking by autonomous farming vehicles subject to wheel slips, which are characteristic for agricultural applications. Two guidance laws are proposed to solve this problem, and both explicitly take into account the constraints on the steering angle and ensure tracking an arbitrarily curved path. The first law is implemented by the pure sliding-mode controller, whereas the second one combines the sliding mode approach with a smooth nonlinear control law and requests control chattering at the reduced amplitude as compared with the first law. Mathematically rigorous proofs of global convergence and robust stability of the proposed guidance laws are presented. In doing so, the slipping effects are treated as bounded uncertainties. Simulation results and real world experiments confirm the applicability and performance of the proposed guidance approach.

Modeling and Adaptive Sliding Mode Control of the Catastrophic Course of a High-speed Underwater Vehicle

The mathematical model of a high-speed underwater vehicle getting catastrophe in the out-of-water course and a nonlinear sliding mode control with the adaptive backstepping approach for the catastrophic course are proposed. The speed change is large at the moment that the high-speed underwater vehicle launches out of the water to attack an air target. It causes motion parameter uncertainties and affects the precision attack ability. The trajectory angle dynamic characteristic is based on the description of the transformed state-coordinates, the nonlinear sliding mode control is designed to track a linear reference model. Furthermore, the adaptive backstepping control approach is utilized to improve the robustness against the unknown parameter uncertainties. With the proposed control of attitude tracking, the controlled navigational control system possesses the advantages of good transient performance and robustness to parametric uncertainties. These can be predicted and regulated through the design of a linear reference model that has the desired dynamic behavior for the trajectory of the high-speed underwater vehicle to attack its target. Finally, some digital simulation results show that the control system can be applied to a catastrophic course, and that it illustrates great robustness against system parameter uncertainties and external disturbances.

Sliding Mode Control of Crowd Dynamics

In this paper, the design of nonlinear sliding mode controllers for models representing crowd dynamics in one dimension is presented. The main contribution of this paper is the stability analysis and robust control synthesis of hyperbolic partial differential equation (PDE) system models using the sliding mode method. The application of this research is in crowd control and in dynamically controlling the evacuation of pedestrians in the presence of disturbances. Crowd densities can change due to blocked exits or due to a varying influx of people. Recent advances in sensor technology have made the measurement of pedestrian densities and velocities possible. As such, the development and implementation of efficient control algorithms to control crowd movements that can avoid jams is realizable. The crowd model presented here is a system of nonlinear hyperbolic PDEs based on the laws of conservation of mass and momentum. The sliding mode control is designed in the presence of both matched and unmatched uncertainties due to external disturbance and parametric variations. The controllers designed are shown to be robust to disturbances.

Direct control of doubly fed induction generator fed by PWM converter with a variable structure control based on a sliding mode control

This paper presents a direct control of doubly fed induction generator (DFIG) with a variable structure control based on a sliding mode controller (SMC). Our aim is to make the stator active and reactive power control track its reference variations. The use of the nonlinear sliding mode control gives very good active and reactive power performance when it applies to DFIG. Simulation results and improvement of the behaviour of the DFIG are presented, using Matlab/Simulink software, and discussed to validate the proposed control strategy.

Nonlinear sliding mode control of switched systems on continuously variable transmission shifting

The control of speed ratio on Continuously Variable Transmission (CVT) is one of the key problems for CVT development. In this paper, a nonlinear Sliding Mode Control (SMC) law of switched systems is designed and employed to control the CVT shifting. Because the CVT shifting control system contains discontinuous characteristics, the way of Filippov solution with discontinuous righthand side is used to design the sliding mode controller. Through the validation of simulation and on-board experiments, it can be concluded that the nonlinear SMC law is a better candidate to control the CVT shifting.

Observer-Based Robust Tracking Control for a Class of Switched Nonlinear Cascade Systems

This paper is devoted to robust output feedback tracking control design for a class of switched nonlinear cascade systems. The main goal is to ensure the global input-to-state stable (ISS) property of the tracking error nonlinear dynamics with respect to the unknown structural system uncertainties and external disturbances. First, a nonlinear observer is constructed through state transformation to reconstruct the unavailable states, where only one parameter should be determined. Then, by virtue of the nonlinear sliding mode control (SMC), a discontinuous nonlinear output feedback controller is designed using a backstepping like design procedure to ensure the ISS property. Finally, an example is provided to show the effectiveness of the proposed approach.

Nonlinear tire-road friction control based on tire model parameter identification

A hierarchical control structure is a more suitable structural scheme for integrated chassis control. Generally, this type of structure has two main functions. The upper layer manages global control and force allocation, while the bottom layer allocates realized forces with 4 independent local tire controllers. The way to properly allocate these target forces poses a difficult task for the bottom layer. There are two key problems that require attention: obtaining the nonlinear time-varying coefficient of friction between the tire and different road surfaces and accurately tracking the desired forces from the upper layer. This paper mainly focuses on longitudinal tire-road friction allocation and control strategies that are based on the antilock braking system (ABS). Although it is difficult to precisely measure longitudinal tire-road friction forces for frequently changing road surface conditions, they can be estimated with a real-time measurement of brake force and angular acceleration at the wheels. The Magic Formula model is proposed as the reference model, and its key parameters are identified online using a constrained hybrid genetic algorithm to describe the evolution of tire-road friction with respect to the wheel slip. The desired wheel slip, with respect to the reference tire-road friction force from the top layer, is estimated with the inverse quadratic interpolation method. The tire-road friction controller of the extended anti-lock braking system (Ext-ABS) is designed through use of the nonlinear sliding mode control method. Simulation results indicate that acceptable modifications to changes in road surface conditions and adequate stability can be expected from the proposed control strategy.

Design Gradient Descent Optimal Sliding Mode Control of Continuum Robots

In this research, a new approach for gradient descent optimal sliding mode controller for continuum robots is proposed. Based on the new dynamic models developed, a novel technique for nonlinear control of continuum manipulators to be employed in various situations has also been proposed and developed. A section of a continuum arm is modeled using lumped model elements (masses, springs and dampers) and control by nonlinear methodology (sliding mode method) and optimization the sliding surface slope by gradient descent method. It is shown that this type of control methodology, although used to a certain model, can be used to conveniently control the dynamics of the arm with suitable tradeoff in accuracy of modeling. This relatively controller is more plausible to implement in an actual real-time when compared to other techniques of nonlinear controller methodology of continuum arms. Principles of sliding mode methodology is based on derive the sliding surface slope and nonlinear dynamic model and applied in the system. Based on the gradient descent optimization method, the sliding surface slope and gain updating factor has been developed in certain and partly uncertain continuum robots. This methodology is represented in certain and uncertain area whose only optimization for certain area and test this optimization for uncertainty. The new techniques proposed and methodologies adopted in this paper supported by MATLAB/SIMULINK results represent a significant contribution to the field of design an optimized nonlinear sliding mode controller for continuum robots. DOI: http://dx.doi.org/10.11591/ijra.v1i4.883

A sliding mode controller for aircraft simulated entry into spin

In this paper, two controllers are presented for commanded departure of an aircraft into spin. The first controller is designed based on the information obtained from the bifurcation analysis results of the aircraft model and trial and error simulation experiments. The second controller is a nonlinear sliding mode controller also designed using bifurcation analysis results of the aircraft as reference maps. The sliding mode controller design problem is formulated as a trajectory tracking problem, where, the reference trajectory to be tracked is defined by spin simulation. Initial conditions are level-flight trim states, computed using extended bifurcation analysis and final states are stable, steady and flat oscillatory spin states.