Advantages Of Sliding Mode Control Research Articles

Adaptive fractional-order integral fast terminal sliding mode and fault-tolerant control of dual-arm robots

AbstractClosed-loop kinematics of a dual-arm robot (DAR) often induces motion conflict. Control formulation is increasingly difficult in face of actuator failures. This article presents a new approach for fault-tolerant control of DARs based on advanced sliding mode control. A comprehensive fractional-order model is proposed taking nonlinear viscous and viscoelastic friction at the joints into account. Using integral fast terminal sliding mode control and fractional calculus, we develop two robust controllers for robots subject to motor faults, parametric uncertainties, and disturbances. Their merits rest with their strong robustness, speedy finite-time convergence, shortened reaching phase, and flexible selection of derivative orders. To avoid the need for full knowledge of faults, robot parameters, and disturbances, two versions of the proposed approach, namely adaptive integral fractional-order fast terminal sliding mode control, are developed. Here, an adaptation mechanism is equipped for estimating a common representative of individual uncertainties. Simulation and experiment are provided along with an extensive comparison with existing approaches. The results demonstrate the superiority of the proposed control technique. The robot performs well the tasks with better responses (e.g., with settling time reduced by at least 16%).

Improved performance and robustness of synchronous reluctance machine control using an advanced sliding mode and direct vector control

AbstractThis article focuses on improving the control approach for a synchronous reluctance motor (SynRM) drive powered by a two‐level pulse width modulation (PWM) inverter. While classical sliding mode control (SMC) has been extensively used in control system design, it comes with various drawbacks such as pronounced chattering effects, considerable transient state errors, and reduced robustness. These limitations hinder its practical applicability. To enhance the performance of the SynRM, this paper introduces a novel strategy that combines direct vector control (DVC) with advanced sliding mode control (ASMC), here referring to third‐order sliding mode command (TOSMC), for regulating speed and dq‐axis stator currents. The primary objective of this approach is to achieve precise and efficient control while minimizing total harmonic distortion (THD) in current and reducing output torque fluctuations. Notably, this strategy capitalizes on the strengths of TOSMC and DVC. The efficacy of the proposed control scheme is verified through two sets of thorough simulations realized in MATLAB/Simulink environment. The first set of simulations encompasses the load–torque test, where the motor is subjected to two different levels of load torque. The results from these tests showcase the control scheme's performance under varying load conditions. The second set of simulations involves the speed variation test, where intentional changes are applied to the motor's speed. This test assesses the control approach's ability to handle dynamic speed changes effectively. The proposed control strategy is further compared with conventional control methods, including proportional–integral and second‐order sliding mode command (SOSMC) controls. The results consistently demonstrate the superior performance of the novel approach in terms of accurate control, robustness, and overall stability. The combination of DVC and TOSMC offers a promising avenue for achieving enhanced motor control in the presence of load disturbances and speed variations.

A hybrid control combining an advanced sliding mode control law with a proportional-derivative control by applying on vibration suppression

A hybrid controller is proposed to control the vibration of a cantilever structure. The hybrid adaptive controller combines sliding mode controller (SMC) and proportional-derivative (PD) controller. Meanwhile, a type-2 fuzzy neural network (T2FNN) with a zero-order consequent part and certain center is applied to SMC due to the unknown of the controlled object. The initial parameters of T2FNN are obtained through the identification by an SMC-theory based T2FNN. The adaption laws of the controller and T2FNN are given through Lyapunov stability. The state space equation of the beam is established for simulation. The proposed controller is applied to vibration control of a cantilever beam bonded with piezoelectric actuator to verify its effectiveness. The simulation and experiment results show excellent control performance of disturbance rejection and vibration suppression of the proposed controller.

Finite-time robust speed control of synchronous reluctance motor using disturbance rejection sliding mode control with advanced reaching law.

In recent years, there has been a significant focus on synchronous reluctance motors (SynRM) owing to their impressive efficiency and absence of magnetic material. Although the SynRM shows great potential for use in electric vehicles, its widespread adoption is limited by unmodeled dynamics and external disturbances. Moreover, the uncertainty factor significantly restricts SynRM's peak efficiency and superior control performance, leading to an unjustifiable current loop reference command. To address these issues, this work presents various new research contributions which focus on the robust control of SynRM to optimize performance through the novel reaching law-based sliding mode control. Initially, a novel advanced sliding mode control reaching law (ASMCRL) with adaptive gain is proposed, to enhance the acceleration of the system state reaching the sliding surface. After that, an extended state observer (ESO) is designed to estimate and compensate for the overall disturbances of the system. Finally, the ASMCRL and ESO are integrated to design two nonlinear controllers namely, the disturbance-rejection sliding mode controller (DRSMC) and the disturbance-rejection sliding mode speed regulator (DRSMSR) for SynRM. The proposed DRSMSR eliminates the steady-state error and eradicates inherent chattering in DRSMC. Moreover, this yields a system trajectory that converges to a predetermined proximity of the sliding surface, irrespective of any lumped disturbances. The steady-state error of DRSMSR is less as compared to DRSMC. Furthermore, the speed response of this technique is 22.62% faster as compared to the state-of-the-art finite-time adaptive terminal sliding mode control. Additionally, the asymptotic stability of the proposed system is validated using Lyapunov's theorem. Thus the experimental results demonstrate the effectiveness and robustness of the proposed approach.

Sliding Sector-Based Controller for Regulating Voltage/Frequency in Autonomous Microgrid

The application of microgrids (MG) has a vital role in grid modernization. However, a larger number of installations of electronically coupled distributed energy resources (DER) units in MGs have created opportunities and threats for grid operations. Therefore, efficient and reliable control strategies for MG operation are essential. This article introduces the concept of sector design to show the stabilization of voltage source converter-interfaced DER units in MG applications. The sliding sector design is advanced sliding mode control to obtain a region of attraction such that the state space is divided into attractive and nonattractive regions. In addition, a variable structure-based controlling method has been introduced to drive the trajectories of a plant from the exterior to the interior of the sector and strictly inside throughout the process. In autonomous MG operation, the proposed controller focuses on stabilizing the electronically coupled DER unit’s voltage and frequency response. Besides, it confirms the safety of the power conversion system from external disturbances. The system stability is proven using the Lyapunov candidate function. The proposed strategy has been effectively validated through PSCAD/EMTDC. The simulation results have examined the impact of balanced, unbalanced, nonlinear, and dynamic loading patterns in islanded MG.

A Novel Sliding Mode Controller Applied to SPMSM of Material Conveying System

As an important power component of the material conveying system, the motor will inevitably cause the vibration of the mechanical structure when rotating, thus affecting the stable operation of the motor. Most material conveying systems have high requirements for motor vibration level, and usually take vibration performance and electrical performance as the evaluation criteria of the same level. A nonlinear terminal sliding mode controller is proposed to solve the phase delay and vibration problems in the sliding mode control system of surface-mounted permanent magnet synchronous motor (SPMSM) in material transmission system.. The sliding surface is an organic combination of nonlinear sliding mode and fast terminal mode, and its relative stability is verified by Lyapunov function. Through MATLAB simulation and fine comparison analysis with other advanced sliding mode control system methods, it can be seen from the simulation results that the signal of the proposed method can obviously control the noise, and the global root-mean-square error is only 1.9%, so it can be seen that the scheme is feasible..

Robust Intelligent Tracking Control Technique for Single-Phase SPWM Inverters

This paper presents a robust intelligent tracking-control technique which is subsequently applied to single-phase SPWM inverters. The proposed technique mixes advanced sliding mode control (ASMC) with grey-Markov model (GMM). The advanced sliding mode control allows the system state to converge quickly to the origin in a limited amount of time. Unfortunately, a chattering problem frequently occurs when the inverter suffers drastically from highly nonlinear or internal parameters changes. The large power losses and high harmonic distortion emerge in the inverter output. The role that the grey-Markov model plays is to reduce the chattering of the ASMC during system uncertainty overestimation, or to reduce the steady-state error caused by underestimation of system uncertainty. In conjunction with the GMM and the ASMC, fast transient response, low distortion of the sinusoidal output-voltage and reduced chattering can be obtained. Simulation results of the proposed single-phase SPWM inverter are carried out in MATLAB/Simulink. The experimental results have been validated through digital signal processors, enabling the single-phase SPWM inverter output to effectively improve the transient tracking speed and steady-state performance.

Nonsingular fast terminal control for the DFIG-based variable-speed hydro-unit

Pumped storage power plants (PSPPs) with variable-speed hydro-units are credible when tackling the impact caused by the introduction of renewable energy into grids. However, the units suffer from instability when the grid transients occur because the adopted doubly-fed induction generators (DFIG) have a strong coupling and nonlinearity. Conventional controllers failed to handle this situation. Although the sliding mode controller (SMC) is robust enough, it has problems of infinite convergence time and chattering issues. Nonsingular fast terminal sliding mode controller (NFTSMC) - an advanced SMC - is a promising method to solve these problems. This paper took the DFIG-based variable-speed hydro-unit as the studied object and adopted a newly-designed NFTSMC in the rotor side converter to secure the stable operation of the unit. Especially, a feedback control law and a modified coefficient of the sliding mode surface were combined with the adaptive super-twisting algorithm to handle the additional information of the derivatives of the sliding mode surface and guarantee the theoretical stability. Simulations under load rejection, parameter variation, voltage dips were imposed on the unit. Results showed the proposed controller has lower settling times, oscillations, and less over-shooting. The efficiency of the proposed controller is thus proved.

Advanced Sliding Mode Control of Heating and Ventilation Unit in a Light Rail Vehicle

Advanced Sliding Mode Control of Heating and Ventilation Unit in a Light Rail Vehicle

Active Vehicle Suspension with Anti-Roll System Based on Advanced Sliding Mode Controller

In the paper authors consider the active suspension of the wheeled vehicle. The proposed controller consists of a sliding mode controller used to roll reduction and linear regulators with quadratic performance index (LQRs) for struts control was shown. The energy consumption optimization was taken into account at the stage of strut controllers synthesis. The studied system is half of the active vehicle suspension using hydraulic actuators to increase the ride comfort and keeping safety. Instead of installing additional actuators in the form of active anti-roll bars, it has been decided to expand the active suspension control algorithm by adding extra functionality that accounts for the roll. The suggested algorithm synthesis method is based on the object decomposition into two subsystems whose controllers can be synthesized separately. Individual suspension struts are controlled by actuators that use the controllers whose parameters have been calculated with the LQR method. The mathematical model of the actuator applied in the work takes into account its nonlinear nature and the dynamics of the servovalve. The simulation tests of the built active suspension control system have been performed. In the proposed solution, the vertical displacements caused by uneven road surface are reduced by controllers related directly to suspension strut actuators.

Modelling and Simulation of DC-DC Boost Converter using Sliding Mode Control

DC-to-DC converter is an electronic circuit that converts direct current (DC) from a given voltage to another. DC-DC converters have a broad range of applications, starting from electronic gadgets to household equipment, adapters of mobile phone and laptops, aero plane control frameworks and communication hardware. This paper illustrates the practical application of DC-DC boost converter using Sliding Mode Control (SMC). DC-DC converters can be categorized into different categories in terms of mechanical, electrical and electronic features. SMC DC-DC converters show better performance compared to other converters under certain conditions. This nonlinear control system is especially well suited for Variable Structure Systems. The most significant advantage of Sliding Mode Control over conventional control systems is its robustness against load, line and parametric uncertainties.

Robust Pitching Disturbance Force Attenuation for Tractor Considering Functional Constraints

Tractors are attached with function-specific implements with the help of an electro-hydraulic hitch system, to carry out various farm operations. Forces arising during travel with the lifted implement on uneven terrain, generate disturbance forces on the hitch system. In this study, the electro-hydraulic system was controlled such that the disturbance forces are attenuated. A second order transfer function model of the hitch system was obtained using experimental data. In order to account for the nonlinearities in the system, an advanced Sliding Mode Controller with Power Rate Exponential Reaching Law was developed to control the hitch system to attenuate the disturbance forces. Variation in system parameters due to change of implements was taken into account by making the system adaptive using a Recursive Least Squares (RLS) parameter estimator, which was used to estimate and update the system parameters in the controller. Position regulation was incorporated to prevent the implement from reaching its mechanical limits. Valve deadzone and operating input limits were incorporated into this design. Also, considering the presence of two valves to supply fluid to the same cylinder, a trigger logic was developed to suitably choose the valve to be operated. The controller was found to provide an average disturbance force attenuation of 82.9% while being robust to a random variation in each parameter up to ±80%.

An Improved Sliding Mode Control Technique to Mitigate Mismatched Parameter Uncertainties of Three-Phase Voltage Source Inverters

This paper proposes a theoretical and experimental implementation of an advanced sliding mode control (SMC) for a three-phase voltage source inverter (VSI) to achieve robustness against the unknown uncertainties of an LC filter. The significant contributions of the proposed SMC are summarized as considerations for the matched and mismatched uncertainties of the LC filter, more relaxed norm-bounds, dynamic characterization of sliding surface, and unique stability analysis. Unlike the conventional SMC techniques with matched uncertainties, the mismatched uncertainties in the state matrix are taken for the design of the proposed SMC. Also, the relaxed norm-bound designed for matched and mismatched uncertainties allows a wide range of variations in the values of LC filter. The voltage tracking errors are significantly reduced and the total harmonic distortions (THDs) are highly suppressed by characterizing the sliding surface in terms of flexible linear matrix inequalities (LMIs). Next, the stability analysis and reachability conditions are given using the Lyapunov criterion. The authenticity of the proposed SMC method is proved by TMS320LF28335 DSP based experimental results with a prototype 1-kVA test-bed. The comparative experimental results and analysis for the proposed SMC scheme, the conventional SMC scheme, and the conventional PI-PI control scheme are presented under the load step change, unbalanced load, and non-linear load step change with the parameter uncertainties to demonstrate the excellent performance of the proposed controller such as fast transient response, small steady-state error, and low THD.

Robust control of connected vehicles via V2V communication

AbstractThis paper introduces a robust controller for connected vehicles which are communicating through dedicated short‐range communication (DSRC) protocol to avoid collision and improve safety. By a comprehensive analysis on both longitudinal and lateral dynamics of the vehicles, the controller covers a wide range of collision avoidance scenarios, such as: Intersection Movement Assistant (IMA), Automatic Emergency Brake (AEB) and Lane Change Warning (LCW). By implementing an advanced Sliding Mode Controller (SMC), the effect of uncertainties will be mitigated for a variety of path plans. It turns out that the proposed control scheme can robustly improve the safety. Finally, we optimize the performance of vehicles in tracking the paths by an MPC controller.

Fuzzy sliding-mode control with low pass filter to reduce chattering effect: an experimental validation on Quanser SRIP

Stabilization of a single rotary inverted pendulum (SRIP) system is a benchmark nonlinear control problem. Inherent instability of SRIP in upright position and the presence of modelling uncertainty pose a challenge for control engineers. Sliding-mode control (SMC) is the most widely accepted robust control technique. Various versions of SMCs to stabilize SRIP have been reported in literature. Advantages of SMC come at the cost of chattering of input, which inhibits its usage in many practical applications. Several works have been done to reduce the chattering in SMC. Application of fuzzy logic in SMC to reduce chattering has been analysed extensively in the literature. Even though implementation of fuzzy SMC (FSMC) in theory/simulations completely eliminates chattering, practical implementation of FSMC does not reduce chattering to zero. In this paper, a filtered FSMC is proposed, which filters the high frequency component in the system input. Experimental results of SMC, FSMC and a fuzzy sliding-mode controller with filter (FSMCF) are given in this paper. Results indicate that filtering the output of FSMCF reduces the chattering effect in the system without affecting the closed loop dynamics.

Disturbance Observer-Based Fuzzy SMC of WECSs Without Wind Speed Measurement

The main role of control system for wind turbines is tracking the optimal power via regulating the rotor speed of the generator. A high performance controller, which can deal with unmodeled dynamics, uncertainties, and external disturbance, can effectively increase the captured power from the wind. This paper focuses on designing an advanced sliding mode control (SMC) scheme for wind energy conversion systems (WECSs). As the proposed SMC scheme includes a nonlinear disturbance observer (DOB) for estimating aerodynamic torque and wind speed, there is no requirement to measure aerodynamic torque or wind speed. The proposed control scheme considers not only the uncertainties and disturbance but also the random nature of wind speed and intrinsic nonlinear behavior of the WESCs. Via designing sliding surface based on estimated information, the proposed control system can avoid disadvantages associated with the robust control techniques. To totally remove chattering as well as improving other control criteria, a fuzzy-based variable switching gain scheme is introduced. Comparative simulation results are shown to verify the effectiveness and superior performance of the proposed DOB-based fuzzy SMC scheme.

Four-phase interleaved DC/DC boost converter interfaces for super-capacitors in electric vehicle application based onadvanced sliding mode control design

Electric vehicles (EVs) has received an increasing interest from the power community and have become increasingly popular due to their importance in fighting climate change. An advanced power electronic converter remains the main and common topic for research in this area. In this paper, an advanced sliding mode control (ASMC) is designed for Four Phase Interleaved Boost Converter (FP-IBC). The novelty of the proposed controller relies on the use of an adaptive delay-time block with the conventional sliding mode control scheme which is designed based on chattering elimination method. The new scheme succeed to reduce the ripple contents in the converter's output voltage and inputs currents, and achieve fast convergence and transient response. An experimental comparison study has been investigated between the proposed controller and Self-tuning Lead Lag Compensator (SLLC). The comparison study is performed at different loading conditions using Super-Capacitor (SC) module. The experimental results show that the dynamic response of FP-IBC is significantly improved based on the proposed control design.

New Design Approach for Sliding Mode Control of Plants with a Time Delay

Sliding mode control (SMC) has demonstraed good robustness, and thus, it is widely used in many control systems. However, because it is not suitable for a plant with a time delay because it is not considered a time delay control method. In this study, to solve the above problem, we propose an advanced SMC technique for plants having time delays. In our method, we introduce a simple plant predictor to the SMC method. Our method is easy to design. In simulation studies, the results show that the proposed method is applicable to plants having time delays. In an experiment using a pneumatic actuator, we confirm the practicality of the proposed method.

FPGA and dSPACE based Sliding Mode Control of Boost Converter for PEM Fuel Cell Application

This paper presents a non-linear dynamic model of a PEM (Proton Exchange Membrane) fuel cell and its simulation in MATLAB. A single cell and three cells stack is fabricated and simulation results obtained are validated experimentally with the dynamic response of the system for change in values of different system parameters. To meet the varying requirements of the load, boost converter circuit is designed and classical PID as well as advanced sliding mode control strategies are simulated in MATLAB and implemented using FPGA (Field Programmable Gate Array) and d-SPACE for experimental validation.

Dynamic performance enhancement of microgrids by advanced sliding mode controller

Dynamics are the most important problems in the microgrid operation. In the islanded microgrid, the mismatch of parallel operations of inverters during dynamics can result in the instability. This paper considers severe dynamics which can occur in the microgrid. Microgrid can have different configurations with different load and generation dynamics which are facing voltage disturbances. As a result, microgrid has many uncertainties and is placed in the distribution network where is full of voltage disturbances. Moreover, characteristics of the distribution network and distributed energy resources in the islanded mode make microgrid vulnerable and easily lead to instability. The main aim of this paper is to discuss the suitable mathematical modeling based on microgrid characteristics and to design properly inner controllers to enhance the dynamics of microgrid with uncertain and changing parameters. This paper provides a method for inner controllers of inverter-based distributed energy resources to have a suitable response for different dynamics. Parallel inverters in distribution networks were considered to be controlled by nonlinear robust voltage and current controllers. Theoretical prove beyond simulation results, reveal evidently the effectiveness of the proposed controller.