Composite Sliding Mode Control Research Articles

Barrier Function-Based Adaptive Composite Sliding Mode Control for a Class of MIMO Underactuated Systems Subject to Disturbances

Barrier Function-Based Adaptive Composite Sliding Mode Control for a Class of MIMO Underactuated Systems Subject to Disturbances

Composite sliding mode control for cyber‐physical systems with multi‐source disturbances and false data injection attack

AbstractThis paper investigates the sliding mode control problem for cyber‐physical systems subject to multi‐source disturbances and actuator false data injection attacks simultaneously. Firstly, a series of extended state observers are designed to estimate the unknown multi‐source disturbances. For the actuator false data injection attacks, a sliding mode observer is designed to online estimate the values of attacks. Then, by introducing the disturbance and attack estimations, a dynamic sliding manifold and a composite sliding mode controller are constructed. Under the proposed approach, the unknown disturbances and false data injection attacks can be timely estimated and compensated, which can improve the disturbance rejection ability and guarantee security of the cyber‐physical system. Lyapunov theory is utilized to prove the stability of the closed‐loop system. Finally, simulations of both the numerical example and application to a power converter system demonstrate the effectiveness and superiority of the proposed composite sliding mode control approach.

Robust design of a two-stage composite sliding mode controller for enhanced performance in large-scale systems

This paper introduces an innovative composite sliding mode control strategy tailored for large-scale system, specifically tackling the intricate task of formulating a sliding mode control law for singularly perturbed systems. This paper delineates the development of a composite controller by dissecting it into subsystem controllers for both ‘slow’ and ‘fast’ subsystems, exploring its effectiveness in managing matched bounded external disturbances within the context of large-scale system. While sliding mode control proves to be a robust solution for handling uncertainty and disturbances, its inherent complexity and discontinuous characteristics pose significant challenges in crafting designs suitable for singularly perturbed systems.

Composite Sliding Mode Control of Phase Circulating Current for the Parallel Three-Phase Inverter Systems

The phase circulating current (PCC) of the parallel three-phase inverter systems dramatically affects the power quality and conversion efficiency of the power grid. In this paper, a composite suppression strategy is proposed to solve the PCC issue by using the sliding mode control (SMC) approach and improved virtual impedance droop control. Taking the commonly used 2-group parallel three-phase inverter as an example, an inter- and intra-classification model is established by analyzing the sources of PCC. In order to suppress the inter-PCC, the traditional virtual impedance droop control is given, following the improved substitute by combining SMC. And the variables of the bus voltage, Q-U loop, P-f loop, and the virtual-induced reactance are also introduced for the robust control of the impedance droop. On the other side, a SMC-based suppression approach is designed to solve the issue of the intra-PCC. Its idea is to introduce a regulation factor for the space vector pulse width modulation (SVPWM) so that the zero-sequence voltage can be eliminated and the influence of the intra-PCC can be relieved. Comparative simulations and experiments validate the effectiveness of the methods proposed in this paper.

A composite sliding mode control with the first-order differentiator and sliding mode observer for permanent magnet synchronous machine

This paper proposes a composite sliding mode control (SMC) to optimize the tracking performance and the anti-disturbance performance of permanent magnet synchronous machine (PMSM) speed regulation systems. The differential term in the control law can magnify the measurement noise, resulting in more discontinuity. To filter out the high frequency noise and make the control law smoother, the first-order differentiator (FOD) is employed to estimate the speed error and its derivative. Since the feedforward compensation can improve the robustness of the system, a disturbance observer (DOB) based on the sliding mode observer (SMO) is designed to reinforce the dynamic performance under disturbance variation. Under the effect of the feedforward compensation, chattering can be further weakened by decreasing the switching gain appropriately. Finally, the effectiveness of the proposed methods is confirmed by various experimental results.

Tillage depth regulation system via depth measurement feedback and composite sliding mode control: A field comparison validation study

The existing methodologies employed for the quantification and regulation of tractor’s tillage depth present considerable shortcomings, primarily characterized by their low accuracy and poor disturbance rejection proficiency in complex agricultural terrains. In this study, we present a sophisticated feedback control strategy designed to mitigate these challenges. Our innovative approach hinges on calculating tillage depth from the alignment of the tractor’s hydraulic lifting arm, achieved by employing a mechanical angle sensor. This sensor adeptly gages the angle of the lifting arm, aligning it with the tillage angle of the pull rod and the implement’s angle, resulting in a robust relational model correlating the lifting arm angle with the tillage depth. This pioneering method amalgamates the accuracy inherent in the static model, derived from the tillage angle-based depth measurement, with the dynamic stability afforded by the mechanical ascertainment of the lifting arm angle. In conjunction, we introduce a Hybrid Extended State Observer-Based Backstepping Sliding Mode Controller (HESO-BacksteppingSMC). The HESO is instrumental in estimating unmeasured state variables and lumped disturbances, utilizing the system’s output feedback signal. Our control frame component capitalizes on the fast power-reaching law to yield a continuously smooth control signal, effectively eradicating the conventional chattering phenomenon inherent in controllers and amplifying its functional applicability. Theoretical evaluations affirm the uniformly and ultimately bounded stability of the errors associated with our proposed observer and controller, underscoring their robustness. The superior performance of our proposed tillage depth measurement and control methodology has been corroborated through a series of comprehensive simulation and field plowing trials, attesting to its precision and reliability in complex agricultural settings.

A novel composite fixed‐time sliding mode control scheme for second‐order systems with mismatched disturbances: application to Buck converter

AbstractIn this paper, a composite fixed‐time sliding mode controller is proposed to address the problems of finite‐time escape and large initial error inherent in disturbance observer (DOB) based controllers. The proposed hybrid control strategy utilizes a fixed‐time DOB and is designed to stabilize a class of second‐order systems in the presence of both matched and mismatched disturbances, while ensuring fixed‐time convergence. First, a fixed‐time DOB is developed to estimate both types of disturbances. Second, a robust sliding mode variable with variable exponent coefficient and a former finite‐time sliding mode controller are proposed to guarantee state convergence without using DOB estimation, thereby preventing the state from diverging due to the unknown large initial error caused by DOB and ensuring convergence prior to switching. Third, a latter robust fixed‐time DOB‐based controller is designed after exact estimation of disturbances is achieved and an estimation of the overall convergence time is provided. Furthermore, strict Lyapunov analysis is employed to prove that the disturbed system under the fixed‐time DOB and composite sliding mode controller is fixed‐time stable. Simulation results for a standard planar uncertain system and Buck converter with mismatched disturbance demonstrate the effectiveness of the proposed controller.

Finite-Time Sliding Mode Control Based on Unknown System Dynamics Estimator for Nonlinear Robotic Systems

This article proposes an unknown system dynamics estimator (USDE) based finite-time sliding mode control for nonlinear robotic systems with unknown dynamics. First, an USDE with only one tuned parameter is designed by using filter operations and invariant manifold to estimate the unknown system dynamics. Second, a novel sliding mode surface with faster response time is designed. By incorporating the USDE into the sliding mode surface, a composite sliding mode control (CSMC) is proposed to achieve better dynamic performance. With simple parameter turning, the CSMC can realize the high precision trajectory tracking control of robotic systems. Finally, simulation results illustrate the superiority of the proposed control strategy.

Compound robust control of permanent magnet synchronous motor based on quasi‐Z source inverter

AbstractIn this study, a compound control strategy for motor side and quasi‐Z source side is proposed to improve the robustness of the quasi‐Z source permanent magnet synchronous motor drive system subjected to external disturbance. In this method, the complementary sliding mode control and sliding mode control as feedback controllers are combined with the disturbance observer technology as a feed‐forward compensator to achieve fast tracking and disturbance suppression for the PMSM drive system. Firstly, the signal models of quasi‐Z source inverters and motors are established. Secondly, by introducing state variables, the composite sliding mode controller is designed with strong robustness based on matched disturbances. Then, in order to further improve the disturbance suppression performance, a disturbance observer based on a feed‐forward compensator is designed to estimate the mismatched external disturbances in the motor drive system. Finally, the global asymptotic stability based on Lyapunov criterion is proved. The simulation and experimental results show that the proposed compound control strategy has the advantages of fast convergence, small motor speed pulsation and strong robustness to external disturbances.

Design of Composite Disturbance Observer and Continuous Terminal Sliding Mode Control for Piezoelectric Nanopositioning Stage

The nonlinearities of piezoelectric actuators and external disturbances of the piezoelectric nanopositioning stage impose great, undesirable influences on the positioning accuracy of nanopositioning stage systems. This paper considers nonlinearities and external disturbances as a lumped disturbance and designs a composite control strategy for the piezoelectric nanopositioning stage to realize ultra-high precision motion control. The proposed strategy contains a composite disturbance observer and a continuous terminal sliding mode controller. The composite disturbance observer can estimate both periodic and aperiodic disturbances so that the composite control strategy can deal with the disturbances with high accuracy. Meanwhile, the continuous terminal sliding mode control is employed to eliminate the chattering phenomenon and speed up the convergence rate. The simulation and experiment results show that the composite control strategy achieves accurate estimation of different forms of disturbances and excellent tracking performance.

Composite Error-Based Intelligent Adaptive Sliding Mode Control for Uncertain Bilaterally Symmetrical Hybrid Robot with Variational Desired Trajectories

Some challenging issues exist in trajectory tracking control of an uncertain bilaterally symmetrical hybrid robot (UBSHR) with variational desired trajectories, mainly the uncertainty problem of UBSHR, the synchronization problem of UBSHR’s active joints and bilateral symmetrical hybrid mechanisms, and the flexible control problem of active adaption to different technological requirements without artificially adjusting the control parameters or switching the hardware system. To solve these problems, an adaptive fuzzy neural network in conjunction with subtractive clustering algorithm (SC-AFNN) for UBSHR is proposed. More specifically, a novel composite error is incorporated into the second-order sliding mode control method to generate ideal training data samples and to improve the uncertain system robustness and synchronization performance simultaneously. Furthermore, the SC-AFNN is introduced to realize self-learning and self-adjusting of control rules and control parameters and to enhance the flexible control performance of UBSHR with variational desired trajectories. Strict theoretical proof of the defined errors’ relationship and the stability of the poposed control method is given. Ultimately, simulations and experiments for the prototype system of an UBSHR are conducted to verify the effectiveness of the proposed control method.

A Composite Sliding Mode Control for SPMSM Drives Based on a New Hybrid Reaching Law With Disturbance Compensation

This article presents a composite sliding mode control (CSMC) method for speed control of surface-mounted permanent magnet synchronous motors (SPMSMs). The proposed CSMC consists of a new sliding mode control (SMC) based on a novel hybrid reaching law (HRL) and an extended sliding mode disturbance observer (ESMDO). The new HRL is composed of two parts: a terminal reaching part and an exponential plus proportional reaching part. It can effectively suppress the chattering and reduce the reaching time compared with the conventional constant plus proportional rate reaching law (CPRL). The ESMDO is designed based on CPRL. It can estimate the extra chattering produced by the drive system's lumped disturbance and compensate for the controller's output. Based on the proposed new SMC and ESMDO, an antidisturbance sliding mode speed controller is designed to improve the performance of SPMSM drive systems. The performance of the proposed method has been validated experimentally and compared with the CPRL-based SMC methods under different conditions.

A robust composite wide area control of a DFIG wind energy system for damping inter-area oscillations

This paper presents a novel composite wide area control of a DFIG wind energy system which combines the Robust Exact Differentiator (RED) and Discontinuous Integral (DI) control to damp out inter-area oscillations. RED generates the real-time differentiation of a relative speed signal in a noisy environment while DI control, an extension to a twisting algorithm and PID control, develops a continuous control signal and hence reduces chattering. The proposed control is robust to disturbances and can enhance the overall stability of the system. The proposed composite sliding mode control is evaluated using a modified benchmark two-area power system model with wind energy integration. Simulation results under various operating scenarios show the efficacy of the proposed approach.

Sensorless fractional order composite sliding mode control design for wind generation system

A high-performance control system is essential to transfer maximum power from wind power generation system (WPGS) to the utility grid. In this paper, a fuzzy fractional-order terminal sliding mode control (Fuzzy-FOSMC) is presented based on the boundary layer approach. This boundary layer approach leads to the trade-off between chattering elimination and control performances. Initially a fractional order terminal sliding mode control (FOTSMC) is designed in this paper. Then, the reaching control part of the FOTSMC is replaced by a fuzzy system that eliminates the chattering even in the presence of lumped parametric uncertainties. The fuzzy control part is designed such that:(a) it maintains the stability of the system by introducing a non-linear slope inside the thin boundary layer near the sliding surface, and (b) it eliminates the chattering by acting like a saturation function. A novel wind speed estimation technique is also proposed in this paper based on Gaussian process regression (GPR). The inputs to the GPR framework are selected as the wind turbine power and its rotational speed. The superior performance of the proposed wind speed estimation technique is verified using error comparison with pre-existing techniques. The stability of the proposed GPR-based Fuzzy-FOSMC control paradigm is ensured by using the Lyapunov stability theorem. The proposed paradigm is compared with benchmark sliding mode control (SMC) and FOTSMC strategies. The proposed Fuzzy-FOSMC performance in terms of chattering elimination and stability is validated under normal conditions and lumped parametric uncertainties using extensive simulations in Matlab/SIMULINK and processor in the loop based experimental workbench.

Design and experimental implementation of a new robust observer-based nonlinear controller for DC-DC buck converters

DC-DC buck converters are extensively used in many industrial and end-user applications where significant attention highlights their power-conversion efficiency and robustness to load and source disturbances. This paper considers the problem of DC-DC buck converter control for Maximum Power Point (MPP) and voltage trajectory tracking applications in renewable energy systems. A new nonlinear robust controller is proposed for fast and robust output voltage tracking in the DC bus of the power source. New states are augmented in the design of a novel composite sliding mode controller. Furthermore, a nonlinear state observer is incorporated in the design for current estimation. Parameters of the overall approach are tuned using Particle Swarm Optimization (PSO) algorithm with an objective to ensure a good balance between fast transients, robustness, and dynamic performance in practical implementations. This novel strategy is cost-efficient and accounts for the switched and nonlinear aspects of the problem in addition to disturbances. The stability of the closed-loop system is analyzed and guaranteed through Lyapunov stability theory. The low complexity of the presented controller grants it a remarkable advantage for higher reliability in physical realization. Moreover, comparative simulation tests and experimental results from multiple scenarios show significant trajectory-tracking improvements in terms of faster convergence rate with short transients and effective disturbance rejection performance compared to the optimally tuned Proportional Integral (PI) controller that is widely adopted in industrial applications.

Composite Super-Twisting Sliding Mode Control Design for PMSM Speed Regulation Problem Based on a Novel Disturbance Observer

This paper aims to improve the performance of the permanent magnet synchronous motor (PMSM) speed regulation system by combining a novel disturbance observer (DOB) with the super-twisting sliding mode (STSM) technique. First, a STSM controller is constructed to eliminate the adverse effects of the lumped disturbance in the PMSM speed regulation system. A novel DOB is introduced to estimate and compensate the lumped unknown disturbance, which constitutes a composite controller with a feedforward compensation term and a state-feedback control. As a result, the gain of the composite sliding mode controller can be significantly reduced, which will improve the performance of the closed-loop PMSM speed regulation system. The validity and robustness of the proposed composite control scheme are fully verified by simulation and experimental results.

Composite model reference adaptive sliding mode controller for automatic train operation

With the ever-increasing speed of trains, the passenger comfort, and the desired trajectory tracking play an important role in the design of automatic train operation. As the speed increases, the train experiences uncertainties, non-linearities, unknown disturbances and so on, due to the interaction among track-environment-disturbance-longitudinal train dynamics. Much attention has been drawn to design a suitable control scheme which can improve both longitudinal dynamic performance and operational robustness in view of automatic train operation. In this context, the authors propose a novel composite sliding mode control scheme with model reference adaptation scheme. The sliding surface of the composite control scheme is considered as a two-layer sliding surface to emulate the coupled vehicle dynamics. To derive the adaptive controller gains mathematically, the model reference adaptation framework is chosen that also helps to demonstrate the stability and the convergence using Lyapunov criterion. The effectiveness of the proposed composite algorithm is being tested by tracking a linear time-invariant stable reference model in the simulation under different environmental disturbances such as side wind, wet rail and model parameter uncertainties. The proposed scheme is found to improve passenger comfort with a least tracking error.

A Composite Sliding Mode Controller for Wind Power Extraction in Remotely Located Solar PV–Wind Hybrid System

Ensuring electrification of remote locations continues to be a major challenge for power engineers. To deal with the effect of intermittent nature of wind, this paper presents the design and implementation of a composite sliding mode controller (CSMC) for a battery energy storage (BES) supported solar photovoltaic (PV)–wind hybrid system in a remote location. This control technique comprises of a soft-switching sliding-mode observer (SS-SMO) and a nonsingular terminal sliding mode controller (NTSMC). The SS-SMO is used to observe the disturbances, whereas the NTSMC is used as a speed controller. The chattering problem caused by the conventional sliding mode controller is alleviated by replacing the conventional signum switching function with the smooth hyperbolic tangent function in disturbance observer loop. The fast and finite time convergence NTSMC based speed controller along with the SS-SMO based disturbance rejection unit, serves the benefits of CSMC. This technique exhibits robustness against model uncertainties and external disturbances. Moreover, the complexity of the system is reduced by replacing the mechanical speed and position sensors with parameter estimation. A double-stage configuration using a dc/dc boost converter is adopted for a PV system. A comparative analysis is presented between the proposed and conventional techniques. A prototype of the hybrid system is developed in the laboratory with permanent magnet synchronous generator. The CSMC-based controller with disturbance rejection ability is implemented to harvest peak wind power. A perturb and observe maximum power point tracking technique is adopted to harvest peak solar power. A voltage control technique is adopted to maintain the voltage at the point of common coupling.

Speed regulation of dual-PMSM system under disturbances by composite sliding mode control

In industrial manufacturing system, there exists an urgent demand for dual-motor drive system running at the same speed. This paper adopts a parallel structure to design dual-permanent magnet synchronous motor (PMSM) system with a global fast terminal sliding mode control (GFTSMC) technique optimizing speed tracking performance of dual-PMSM servo system. For each PMSM system, a GFTSMC strategy is introduced. Compared with common sliding mode control strategy, this strategy avoids chattering phenomenon in that it does not contain switching terms. Also, it can make the output speed reach the reference value in finite time, along with a shorter convergence time and a better tracking precision. Since external disturbances may cause the speed difference between two motors, a speed synchronization controller is designed to enhance their synchronization by compensating error between speeds of two motors. Considering the complexity of control laws, S-function in MATLAB is adopted to design the GFTSMC. The validity and robustness of the hybrid scheme are verified by MATLAB simulations.

Composite Sliding Mode Control of a Permanent Magnet Direct-Driven System For a Mining Scraper Conveyor

A composite sliding mode control based on the load characteristic of the permanent magnet direct-driven system is presented for a mining scraper conveyor. First, the mathematical model of a permanent magnet synchronous motor is established based on the coordinate transformation theory. Subsequently, the soft switching sliding mode observer (SS-SMO) is designed to observe the change of load torque in real time. The composite sliding mode speed controller of PMSM is designed on the basis of non-singular terminal sliding mode control, in which the observed load torque is used for feed-forward compensation. The chain characteristics of a scraper conveyor are described by the Kelvin-Vogit model, and the dynamic model of the overall scraper conveyor system is established with the distinct element method. Next, according to the coupling relationship between the permanent magnet direct-driven system and the scraper conveyor, the electromechanical coupling simulation model is established using the MATLAB/Simulink module. The simulation results demonstrate that the composite sliding mode controller of the permanent magnet direct-driven system can achieve smooth starting of the scraper conveyor, and the effectiveness of the designed controller is illustrated by comparing the controller with the related reference. In addition, the designed SS-SMO can estimate the load torque precisely, enhance system robustness and suppress the chattering of the control system caused by the load change.