Sliding Mode Algorithm Research Articles

Vibration Reduction System with a Linear Motor: Operation Modes, Dynamic Performance, Energy Consumption

The study aimed to present the features of a 2-DOF vibration reduction system (VRS) equipped with a linear electrodynamic motor in passive, semi-active and active mode. At first, the VRS model was formulated. Then, simulation tests of the VRS were conducted to distinguish its most advantageous features in each mode and to analyze dynamic performance and energy consumption. Next, the VRS was experimentally tested to evaluate its effectiveness in each mode for the assumed excitations and to compare tests results against simulation data. In active mode, a sliding mode algorithm was employed for motor control, while in semi-active mode, the equivalent damping coefficient analysis was used.

Comparison of First- and Second-Order Sliding-Mode Controllers for a DC-DC Dual Active Bridge

This paper compares four sliding-mode control strategies for a dual active bridge. The proposed control algorithms define different switching functions resulting in first-and second-order controllers, and using both discontinuous and continuous sliding-mode algorithms. The paper details the design stage and includes simulation and experimental tests to better compare the performance for each control scheme.

Control allocation based fault tolerant control of descriptor system with actuator saturation

This paper deals with the design of active fault-tolerant control (FTC) system based on control allocation (CA) technique for the uncertain descriptor system (DS) with actuator saturation. This work assumes that a fault detection unit is available to estimate the actuator fault. The proposed CA technique is responsible to redistribute the control effort to the healthy actuators taking the advantage of actuator redundancy of the DS. The so-called virtual control law is designed based on a variable gain super twisting sliding mode algorithm (VGSTSMA) to meet the admissibility criteria of continuous control input for the DS. This VGSTSMA based control strategy is designed based on the generalized regular form (GRF) of DS ensuring the robustness against the actuator faults, error in the fault estimation, and the external uncertainties. The CA scheme developed here is applicable to the DS even with a full rank input matrix which is different from the traditional design where it generally deals with the system with rank deficient input matrix. Furthermore, a static control redistribution mechanism is introduced to handle the actuator saturation which is responsible to re-allocate the excess control efforts to the available healthy actuators in the face of actuator saturation. Finally, a dual-pipe heat exchanger unit, modeled as DS, is simulated with proposed CA-based FTC such that the system can follow the time varying and constant reference trajectories in a situation of actuator faults and saturation. The simulation results are compared with the CA-based FTC where virtual control is designed based on super-twisting algorithm (STA) and with the traditional pseudo inverse-CA-based FTC to establish the superiority of the proposed scheme.

Actively steering a wheeled tractor against potential rollover using a sliding-mode control algorithm: Scaled physical test

Tractor rollover is a severe safety problem in crop production. Active steering (AS) is an effective active control technology that can be used to enhance the lateral stability of the tractor. The purpose of this study is to implement AS system that converts tractor roll and pitch motion to restore the tractor attitude in a potential rollover. Based on the Lagrange method, a nonlinear time-varying attitude dynamic model is established according to different rollover statuses. A sliding mode control (SMC) algorithm for the tractor is constructed based on variable structure theory. A lateral stability indicator depending on tractor dynamic attitude is further proposed. The effectiveness of this SMC-AS control strategy was validated in simulation and scale-model experiments under various test conditions. The results showed that by adopting SMC-AS control, the roll-stable time of tractor was reduced by 46.07%, which demonstrates that the proposed SMC-AS control strategy was robust and effective. The developed approach is expected to supply technical support to help drivers to prevent tractor rollover accidents. • A 7-DOFs nonlinear dynamic tractor model is established. • The sliding mode algorithm is applied to active steering control strategy. • Simulations and scale-model experiments are conducted for verification.

Smooth sliding control to overcome chattering arising in classical SMC and super-twisting algorithm in the presence of unmodeled dynamics

The earlier smooth sliding control (SSC) is revisited. New global stability and chattering alleviation analysis is presented under the more general situation of simultaneous presence of plant uncertainty, unmodeled dynamics and external disturbance. Based on an appropriate prediction error loop, it delivers a smooth filtered control signal to the plant. New explicit conditions are presented for SSC to eliminate chattering. Considering numerical examples recently used in a lively debate between continuous and discontinuous sliding mode control options, the SSC is shown to overcome chattering arising in both classical first-order sliding mode (FOSM) control and the super-twisting algorithm (STA) in the presence of unmodeled dynamics. Besides the original theoretical contribution, one main purpose here is to stir new research about chattering avoidance in both classical and higher-order sliding mode algorithms for uncertain systems.

Positionable Rotor Quadrotor: Dynamic Modeling and Adaptive Finite-Time Sliding-Mode Controller Design

This paper introduces a positionable rotor structure for a quadcopter allowing each of its rotors to be positioned independently in a finite course and in forward and backward movement to increase robustness against disturbances such as wind. At first, the quadrotor motion dynamics are analyzed, and its dynamic model is derived by calculating translational and angular momenta. A hybrid controller with dual interconnected units is designed to achieve acceptable performance. The primary unit determines the common quadruplet control inputs of the quadrotor by an adaptive finite-time sliding-mode algorithm for all the translational and rotational degrees of freedom. The secondary unit uses primary controller outputs to specify each rotor’s suitable position to enhance the drone performance and robustness. Some correction steps are used to calculate more feasible rotor positions. Besides showing the proposed control system’s performance, simulations verify the effectiveness of rotor positioning on the quadrotor stability in harsh conditions. For the case study, up to 70% increase in the capacity of disturbance rejection and an over 30% reduction in power consumption compared to conventional drones are observed.

Variable-Gain Higher-Order Sliding Mode Pitch Control of Floating Offshore Wind Turbine

A variable-gain higher-order sliding mode pitch control strategy is proposed for a strongly nonlinear and coupled floating offshore wind power system. The main goal of the proposed strategy is to suppress platform motion caused by random disturbances such as waves and wind speed and to reduce fatigue loads and power fluctuations. Feedback control and super-twisting second-order sliding mode algorithm were adopted to carry out collective pitch control and track the rated rotor speed, which involves the factor of platform pitch. To adaptively adjust the collective pitch control parameters according to random wave and wind speed disturbances, the barrier function method was used to conceive adaptive sliding mode control gains. For comparison purposes, the proposed control strategy and PI control were executed under different wind and wave conditions on a FAST and MATLAB/Simulink platform. Furthermore, the fatigue load was calculated by Mlife. The results demonstrate that the proposed scheme is effective and robust. Moreover, it has advantages in resisting external disturbances, especially in suppressing the platform pitch and roll, as well as reducing the power fluctuations and the fatigue load on the blade root.

Fuzzy impedance-based control with fast terminal sliding mode force control loop for a series elastic actuator system

This paper proposes a robust control scheme to accomplish the interaction control problem between a series elastic actuator (SEA) and a flexible environment. The adaptability of the controller to unknown variations and robustness of the controller during interaction of the system with environment are the main aims. The control scheme is based on a fuzzy impedance control approach and consists of an inner fast terminal sliding mode force control loop. An experimental setup is designed to prove the efficiency of the developed controller. The experimental results confirm that the proposed fuzzy logic controller guarantees the sensitivity of the controlled system to unpredictable variations. Moreover, by applying the fast terminal sliding mode algorithm for the inner force control loop, the system has faster convergence to the reference path compared with similar control methods found in the literature.

Model free adaptive control design for a tilt trirotor unmanned aerial vehicle with quaternion feedback: Theory and implementation

SummaryThis article focuses on the attitude and altitude tracking control of the tilt trirotor unmanned aerial vehicle (UAV) which is subject to modeling uncertainties and unknown external disturbances. A novel model free adaptive controller is designed to achieve asymptotic tracking control of the UAV attitude and altitude channels. The control scheme is based on the data driven strategy, and relies on the input/output data to estimate the system dynamics online. Furthermore, the discrete sliding mode algorithm is combined to enhance the system robustness, and the quaternion feedback is employed to avoid the singularity associated with the attitude control design. The stability of closed‐loop system and the convergence of the tracking errors are proved. And real time flight experiments are preformed on a tilt trirotor UAV control testbed. The experimental results verify the effectiveness of the proposed control scheme and achieve a strong robustness with respect to the modeling uncertainties and unknown external disturbances.

Fuzzy super twisting algorithm dual direct torque control of doubly fed induction machine

<span>This paper proposes the fundamental aspects of hybrid nonlinear control which is composed of the super twisting algorithm (STA) based second order sliding mode control applying fuzzy logic method (FSOSMC), with pertinent simulation results for a doubly fed induction machine (DFIM) drive. To minimize chattering effect phenomenon due to Signum function employed in sliding mode algorithm, a new method is proposed. This technique consists in replacing the signum function by fuzzy switching function in the SOSMC to minimize flux and torque ripples. This FSOSMC is associated to the double direct torque control DDTC of the doubly fed induction machine (DFIM) by combining the advantages of fuzzy logic (FL) and the advantages of super-twisting sliding mode. The FSOSMC-DDTC strategy is compared with a PI-DDTC and SOSMC-DDTC. Simulation results demonstrate good efficiency and excellent robustness of the hybrid nonlinear controller.</span>

Hierarchical control for cornering stability of dual-motor RWD vehicles with electronic differential system using PSO optimized SOSMC method

This paper proposes a novel control scheme with a three-layer hierarchical structure to improve the cornering stability of the dual-motor rear-wheel drive (RWD) vehicles with the electronic differential system (EDS). The proposed hierarchical structure for the control system includes the observing layer, control layer, and actuation layer. In the observing layer, the driver model is designed to obtain the nominal steering angle, and the state observer is designed to obtain the yaw angle which cannot be easily measured. Then, particle swarm optimization (PSO) and second order sliding mode control (SOSMC) are employed in the control layer. The SOSMC part is used to design the control law to eliminate the chattering problem in the sliding mode algorithm, and the PSO part is used to obtain the optimal weights in the sliding mode surface to meet the minimum sideslip angle error and yaw rate error. The actuation layer allocates the corrected yaw moment by distributing the driving force to each independent driving wheel. Finally, the numerical tests are carried out under the double line change (DLC) maneuver. The results show that the proposed control system can effectively improve the cornering stability of the dual-motor RWD vehicles and reduce their motor power consumption.

Three-Phase Phase-Locked Loop Algorithms Based on Sliding Modes

This article proposes a family of phase-locked loop schemes based on sliding modes. The use of sliding mode algorithms ensures fast response and global stability. In particular, two new algorithms are presented, both based on a complex framework for representing three-phase signals. This article compares the obtained algorithms with the traditional schemes, and a faster response is obtained when sliding modes are used. Additionally, as an application example, the algorithm is combined with a complex-coefficient filter that allows an easy identification of both positive and negative sequence harmonics. The proposed algorithms are illustrated by numerical simulations and experimentally validated using a digital signal processor.

Stability control based on three-dimensional portraits for four-wheel-independent-drive EV

In this paper, a two-stage expectation stability controller was proposed for driving stability of four wheel independent drive electric vehicles. The proposed controller has three levels. There were three steps to the stability control of the vehicle. First, the three-dimensional state portraits were drawn based on the 14DOFs vehicle model and used the s tem equation to find two-stage expectation. The surface was derived from the analysis of the tire-road adhesion divides the portraits into safe areas and unsafe areas. Second, the stability controller with sliding mode algorithm was designed. When the state parameter is in the unsafe areas, the safe boundary surface is taken as the first-stage expectation; after the system enters the safe areas, the stem is taken as the second-stage expectation. Then the fuzzy algorithm is applied to distribute the control demand of yaw moment to generate the torques of each in-wheel motor. Finally, simulation verification is performed in Simulink-CarSim co-simulation environment. The simulation results show that the designed control strategy can improve the lateral stability while the loss of longitudinal speed is within 3.25%.

Fractional-order control with second-order sliding mode algorithm and disturbance estimation for vibration suppression of marine riser

Suppression of the vibration caused by environmental loads in marine risers is critical to prevent irreparable damages. This paper addresses this issue by proposing a novel boundary control for a flexible riser connected to a vessel at its top. In this regard, initially, a sliding mode observer (SMO)-based disturbance estimator is constructed to estimate the uncertainty of the vessel's dynamics. Next, using backstepping, a suitable virtual control along with the respective error dynamics are derived. A fractional-order error surface is defined to achieve Mittag-Leffler convergence for the control error variable. A second-order sliding mode (SOSM) control law is used to stabilize this error surface. The boundedness and ultimate boundedness of the riser's deflection under the proposed boundary control is shown by Lyapunov analysis. Comparative simulations demonstrate the robust vibration suppression performance of the proposed controller.

An Experimental Investigation of Discretized Homogeneous Differentiators: Pneumatic Actuator Case

It is well known that the homogeneous differentiator strategies reduce the chattering in the implementation of sliding-mode algorithms and the recent implicit framework based projector provides very interesting properties when associated with homogeneous design. In this article, it is proposed to evaluate different strategies of homogeneous differentiators based on Euler explicit and promising Euler semi-implicit strategies, for which discrete implementations have been realized on a pneumatic actuator. Experimental results highlight the benefit of a Euler semi-implicit-based structure using a projector.

Study on six‐phase PMSM control strategy based on improved position sensorless detection technology

The six-phase motor control system has low torque ripple, low harmonic content, and high reliability; therefore, it is suitable for electric vehicles, aerospace and other applications requiring high power output and reliability. This study presents a superior sensorless control system for a six-phase permanent magnet synchronous motor (PMSM). The mathematical model of PMSM in stationary coordinate system is presented; its sliding mode observer (SMO) of back electromotive force (BEMF) acquires the motor speed and position information. As torque ripple and harmonic components affect the BEMF estimated value through the traditional SMO, the function of the frequency-variable tracker of the stator current (FVTSC) is used instead of the traditional switching function. By improving the SMO method, the BEMF is estimated independently, and its precision is maintained under startup or variable-speed states. To improve performance of the system, the auto disturbance rejection controller (ADRC) is used to suppress load disturbance and speed overshoot. To reduce model parameters, an ADRC with sliding mode algorithm is proposed, simplifying the structure and simultaneously solving the parameter tuning problem. Finally, comparing the ADRC with FVTSC SMO and the traditional PI controller shows that the new ADRC effectively improves the dynamic and static performance of the PMSM.

Modeling and control of a novel facade cleaning robot with four-ducted fan drive

With the development of modern cities, the demand for cleaning glass curtain walls in urban skyscrapers is increasing, and therefore, many researches on facade cleaning robots have been carried out in the past few decades. In this article, a novel type of facade cleaning robot based on four-ducted fan is proposed. To improve the load capacity of the robot, the lifting and horizontal movement are, respectively, supported by an independent lifting mechanism and a lateral movement mechanism. Unlike the previous passive and active suction, the powerful suction power of the robot is provided by the four-ducted fan. Meanwhile, the obstacle-climbing force is caused by the forward of the four-ducted fan that improves the crossing obstacle ability. In addition, an incremental sliding mode algorithm is applied for controlling the posture when the robot crosses obstacles, which can ensure the stable performance of the cleaning robot under disturbance. Some simulations and experiments are conducted and the results demonstrate the effectiveness and robustness of the designed facade cleaning robot.

Fault tolerant control of wind turbines with simultaneous actuator and sensor faults using adaptive time delay control

In this paper, a new Active Fault Tolerant Control (AFTC) is proposed using adaptive fractional-based Terminal Back-stepping Sliding Mode (TBSM) control strategy for pitch angle control of a variable speed wind turbine in the presence of actuator and sensor faults. In order to detect, isolate and accommodate the faults, Time Delay Estimation (TDE) is used as an online fault estimation algorithm. To eliminate the chattering of conventional sliding mode, supper twisting sliding mode algorithm is applied, which also ensures finite time convergence and high precision. Moreover, wind speed profiles are generated using TurbSim, and the controller is implemented on a simplified two-mass wind turbine model. To verify the validity of the proposed scheme, the simulations are also performed in FAST environment, and finally, the simulation results are presented which reveal the effectiveness of the proposed controller in the presence of faults, uncertainties and turbulent wind fields.

Terminal sliding mode speed control method of permanent magnet synchronous linear motor based on adaptive parameter identification

In order to make the speed adjustment system of the permanent magnet synchronous linear motor more stable and make the convergence performance of the speed control system better, a speed regulator based on the terminal sliding mode algorithm is proposed. In addition, the permanent magnet synchronous linear motor will also be affected by temperature changes during its operation. Aiming to enhance the adaptability of linear motors to parameter changes, a terminal sliding mode speed control idea based on adaptive parameter identification is proposed. The Popov stability theory and the mathematical model of linear motor are used to construct a parameter identification system. The identification flux parameters are used as the control algorithm of the terminal sliding mode speed regulator and the update matching of speed regulator flux parameters and motor system parameters are realized. Through the above algorithm, the performance of the entire speed control system is improved. The results of simulation experiments can illustrate the effectiveness of this control method and its effect on improving the control performance.

Numerical design of Lyapunov functions for a class of homogeneous discontinuous systems

AbstractThis paper deals with the analytical and numerical design of a Lyapunov function for homogeneous and discontinuous systems. First, the presented converse theorems provide two analytic expressions of homogeneous and locally Lipschitz continuous Lyapunov functions for homogeneous discontinuous systems of negative homogeneity degree, generalizing classical results. Second, a methodology for the numerical construction of those Lyapunov functions is extended to the class of systems under consideration. Finally, the developed theory is applied to the numerical design of a Lyapunov function for some higher‐order sliding mode algorithms.