Disturbance Observer-based Sliding Mode Control Research Articles

Disturbance observer-based sliding mode control of active vertical suspension for high-speed rail vehicles

Disturbance observer-based sliding mode control (SMC) on the active vertical suspension (AVS) is developed to suppress the car body’s rigid and flexible vibration to improve ride comfort for a high-speed rail vehicle. A vertical-dynamics-intended vehicle model is foremost built with the bounce, pitch, and bending mode of the car body involved. Two sliding surfaces and disturbance observers are then designed for SMC, which only require the car body states, obviating the bogies’ states. The observer is successful in estimating the effect of unknown track irregularities perturbation as well as externally straightforwardly excitations on the car body with good accuracy. Control efficacy is verified through comparison with passive cases and sky-hook controls. With modal damping below 2% in passive cases, the mode shape function, especially with large displacement at the suspension support, would enlarge the car body acceleration. Moreover, the longitudinal traction rod can significantly multiply the flexible vibration at certain speeds. Comparative studies indicate that SMC provides satisfactory outcomes in the rigid and bending vibration suppression when all the car body’s three modes are considered in the sliding surface. However, it requires a high-frequency response actuator and allows a tighter tolerance of the control time delay than the sky-hook control.

Disturbance Observer-Based Sliding Mode Control Using Barrier Function for Output Speed Fluctuation Constraints of PMSM

Disturbance Observer-Based Sliding Mode Control Using Barrier Function for Output Speed Fluctuation Constraints of PMSM

Modified Three-Element Modeling and Robust Tracking Control for a Planar Pneumatic Soft Actuator

In pneumatic soft robotics systems, pneumatic soft actuators (PSAs) are the most important components, so it is necessary to study the precise modeling and control over PSAs for application. This paper focuses on a self-designed planar PSA, named pneumatic bellow actuator (PBA), and proposes a modified three-element model (MTEM) and a nonlinear disturbance observer-based sliding mode control (NDO-based SMC) method to achieve the robust tracking control objective of the PBA with multiple uncertainties. Firstly, the dynamic characteristics of the PBA are analyzed based on experimental data obtained from open-loop experiments of the PBA. Then, based on these dynamic characteristics, a semi-phenomenological MTEM is established considering coupling between the dynamics of the PBA and load as well as friction, which can describe the dynamics of the PBA with changing loads in the rough horizontal plane precisely. Model parameters are then identified by Levenberg-Marquardt (LM) algorithm. Next, identification errors, device disturbances and external disturbances are regarded as the multiple uncertainties of the PBA, and the NDO-based SMC method is proposed based on the MTEM to realize the robust tracking control objective of the PBA. The stability of the control system is proved. The effectiveness of the proposed method is verified by experiments.

Sliding-Mode Control for PMLSM Position Control—A Review

Owing to the competitive advantages of fast response speed, large pushing force, high reliability, and high precision, the permanent magnet linear synchronous motor (PMLSM) has played an increasingly vital role in various high-speed and high-precision control systems. However, PMLSM exhibits nonlinear behavior in actual operation, and position tracking precision is negatively affected by friction, load changes, and other external disturbances. To meet the growing demand and solve the position tracking control problem for the PMLSM, the control system is critical. Sliding-mode control (SMC) has been used extensively in nonlinear control systems due to its superior performance characterized by simplicity, good dynamic response and insensitivity to parameter perturbation and external disturbances, and has been implemented in PMLSMs to track practical position. The objective of this article is to classify, scrutinize and review the major sliding-mode control approaches for position control of PMLSM. The three different conventional SMC methods, namely the boundary layer approach, the reaching law approach and the disturbance observer-based SMC, are discussed in detail. The four advanced forms of SMC, namely terminal SMC, super-twisting SMC, adaptive SMC and intelligent SMC, are also presented. A comparison of these approaches is given, in which the advantages and disadvantages of each approach are presented; additionally, they are presented in table form in order to facilitate reading. It is anticipated that this work will serve as a reference and provide important insight into position control of PMLSM systems.

Disturbance observer-based sliding mode control of series elastic actuators with unmatched disturbances

This paper is concerned with tracking control of series elastic actuators with unmatched disturbances based on sliding mode control. The state- and disturbance-observers are constructed to estimate the states and mismatched disturbances of series elastic actuators, respectively. Using the argument of differential flatness, the desired states are generated and modified by the estimation of disturbances. Then, a linear sliding surface in terms of tracking errors is designed, and the sliding mode dynamics is transformed into a full-order descriptor system. Furthermore, the asymptotic stability of the sliding mode closed-loop system is analyzed. Finally, a case study is given to show the effectiveness of the proposed control scheme.

Disturbance Observer-Based Sliding Mode Control for MEMS with Prescribed Performance

In this study, we study the performance guaranteed tracking problem for the uncertain MEMS gyroscope dynamics. A fixed-time nonlinear function and the transformed error are introduced to establish the preset time control property for the closed-loop system. Then, a funnel sliding mode controller is presented to stabilize the system. To compensate for the uncertainty and external disturbance, a novel lumped disturbance observer is proposed. Different from most existing compensation control results for the MEMS gyroscope with antidisturbance that can only achieve uniformly ultimately bounded, the proposed control scheme is able to ensure that the system errors converge to the preassigned compact sets within a given time rather than infinite time and the system outputs track the desired command asymptotically. Simulation verification also confirms the effectiveness of the proposed approach.

Fixed-time Disturbance Observer-based Sliding Mode Control for Mismatched Uncertain Systems

Fixed-time Disturbance Observer-based Sliding Mode Control for Mismatched Uncertain Systems

Nonlinear Disturbance Observer-based sliding mode control of interleaved boost converter for fuel cell used in microgrids

In microgrids, the use of fuel cells (FCs) supplied with hydrogen as a type of clean energy is continuously rising. Integrating FCs into microgrids has shown interesting advantages in improving the performance of microgrids and promoting the use of hydrogen energy. They are usually associated with other sources of energy, mostly intermittent, to feed a DC bus. However, FCs are current intensive sources that produce electricity at low voltage. DC-DC converters are used to adapt the FC voltage to the DC bus level. The suitable converter topology and the selected controller are also requested in most applications with stable output voltage and power quality. In this paper, nonlinear disturbance observer (NDOB)-based sliding mode control is proposed to the interleaved boost converter (IBC) to enhance the output robustness and weaken the influences brought by uncertainties in the input voltage and the load resistance. Rigorous stable analysis of NDOBs and global systems are presented and proved by Lyapunov functions. Last, the simulations were performed to verify the effectiveness of the proposed controller in light of the varying load resistance and input voltage.

Disturbance observer-based sliding mode control for consensus tracking of chaotic nonlinear multi-agent systems

This paper deals with the finite-time consensus of chaotic MIMO nonlinear heterogeneous multi-agent systems subjected to matched uncertainties and disturbances. This study proposes a consensus protocol utilizing a novel dynamic sliding mode control, ensuring robust performance and chattering attenuation. For this purpose, firstly, a new time-varying nonlinear sliding manifold is introduced that guarantees exponential finite-time stability. Secondly, a novel reaching law is established that ensures fixed reaching time independent of initial conditions. The fixed reaching time enables the specification of the reaching time by considering the problem constraints. Then, a novel terminal disturbance observer is proposed to efficiently estimate the overall effect of uncertainties and disturbances in the finite-time. Finally, an adaptive form of the proposed controller is presented by incorporating the disturbance observer into the proposed sliding mode control. The proposed consensus protocols are applied to a multi-agent system consisting of two well-known chaotic power systems (PMSM and BLDCM). Computer simulations and comparative studies confirm the results of this study in terms of tracking errors and fast convergence.

A non-linear disturbance observer-based cooperative adaptive cruise control for real traffic scenarios

Cooperative adaptive cruise control (CACC) has a strong potential to improvise highway traffic capacity and ease traffic disturbances. Extensive exploration is not carried out in the area of CACC for a cut-in maneuver. Contemporary control strategies proposed for CACC cannot regulate the peaking of control input and thus the acceleration/deceleration of following vehicles when applied for various real traffic scenarios. This paper aims to develop a non-linear disturbance observer-based sliding mode control to control a CACC system for various traffic scenarios. The proposed observer estimates the uncertainty present in the actuator dynamics and the preceding vehicle’s acceleration as the lumped disturbance at the same time, it adjusts the observer gain to alleviate the peaking of control input. The stability of individual vehicles and the string stability of vehicle platoon are derived The performance of the proposed scheme is validated with various traffic scenarios, that is, cut-in maneuver, cut-out maneuver, and non-zero initial conditions. The effectiveness of the proposed scheme is demonstrated by comparing it with a linear disturbance observer-based control.

Disturbance Observer-Based Feedback Linearization Control for a Quadruple-Tank Liquid Level System

A novel input/output feedback linearization control method by utilizing nonlinear disturbance observer (NDOB) is proposed for a quadruple-tank liquid level (QTLL) system in this paper. Firstly, the mathematical model of QTLL system is established by using Bernoulli’s law and mass conservation. Secondly, in view of the nonlinear and coupling characteristics of the QTLL system, a input/output feedback linearization controller is designed. Then, a NDOB is proposed to estimate disturbances and applied to compensation control. Finally, simulation and experimental results show that the proposed strategy has better control performances than PID control and the disturbance observer-based sliding mode control (DOBSMC).

Adaptive sliding mode disturbance observer-based control for rendezvous with non-cooperative spacecraft

This paper investigates the tracking and control problem of a spacecraft rendezvous with a non-cooperative and tumbling space target subject to parametric uncertainty and unknown external disturbances. The kinematics and dynamics of spacecraft position and attitude are described by dual quaternions. A novel adaptive sliding mode disturbance observer is proposed to track the pose of non-cooperative tumbling target without need for upper bounds of first and second derivatives of lumped disturbance. Based on the proposed observer, a finite time sliding mode control is developed in term of dual quaternion. Different from existing sliding mode control schemes, the conditions on the controller parameters bounds are relaxed. The stability and robustness of the overall closed-loop control is proved by the Lyapunov framework. The robustness and effectiveness of the proposed control scheme are validated by numerical simulations in comparison with existing approaches.

Harmonic disturbance observer-based sliding mode control of MEMS gyroscopes

Harmonic disturbance observer-based sliding mode control of MEMS gyroscopes

A Disturbance-Observer-Based Sliding Mode Control for the Robust Synchronization of Uncertain Delayed Chaotic Systems: Application to Data Security

This article proposes a disturbance observer-based Sliding Mode Control (SMC) approach for the robust synchronization of uncertain delayed chaotic systems. This is done by, first, examining and analyzing the electronic behavior of the master and slave Sprott chaotic systems. Then, synthesizing a robust sliding mode control technique using a newly proposed sliding surface that encompasses the synchronization error between the master and slave. The external disturbances affecting the system were estimated using a disturbance observer. The proof of the semi-globally bounded synchronization between the master and slave was established using the Lyapunov stability theory. The efficiency of the proposed approach was first assessed using a simulation study, then, experimentally validated on a data security system. The obtained results confirmed the robust synchronization properties of the proposed approach in the presence of time-delays and external disturbances. The experimental validation also confirmed its ability to ensure the secure transfer of data.

Nonlinear Disturbance Observer-Based Sliding Mode Control for the PMSM with Matched and Mismatched Disturbances

High-efficiency permanent-magnet synchronous motor (PMSM) is a key technology to improve the driving range of batteries in electric vehicles, while the mismatched disturbance that is caused by external disturbances and parameter perturbation may easily result in speed fluctuations and overshoot of the PMSM, which further deteriorate the performance and efficiency of batteries. To solve the problem, a novel nonlinear disturbance observer-based sliding mode control (NDO-SMC) is proposed. Compared with the traditional SMC method, the NDO-SMC scheme has better disturbance rejection ability in the presence of matched and mismatched uncertainties and disturbances by introducing the estimation value of the nonlinear disturbance observer in the sliding surface. Furthermore, owing to the compensation of the disturbance observer, the switching gain is only required to be greater than the bound of the disturbance estimation error rather than that of the disturbance; thus, the chattering problem is substantially alleviated. A rigorous stability proof of the whole closed-loop system is given in detail using Lyapunov theory by designing an appropriate Lyapunov function. The simulation results demonstrate the feasibility and superiority of the proposed NDO-SMC strategy.

Maximum Power Point Tracking Using Disturbance Observer-Based Sliding Mode Control for Estimation of Solar Array Voltage

The output power of solar panel in photovoltaic systems is affected by changes in environmental and load conditions. Most currently developed MPPT control algorithms require measurements of panel output voltage, output current, and converter output voltage. In this paper, a new scheme that can cater to uncertainties in the environmental and load condition, is developed using a disturbance observer-based sliding mode control (DOSMC). The proposed DOSMC scheme obviates the need of using a panel output voltage sensor. The proposed scheme does not use a discontinuous control, thereby overcoming the problems of chatter normally associated with the conventional sliding mode control (SMC). The stability is proven in the sense of ultimate boundedness. The proposed scheme is validated by extensive simulation and laboratory experimentation under various scenarios of irradiation, temperature, and load conditions and compared with two existing popular schemes.

Disturbance Observer-Based Integral Backstepping Control for a Two-Tank Liquid Level System Subject to External Disturbances

A novel method of disturbance observer-based integral backstepping control is proposed for the two-tank liquid level system with external disturbances. The problem of external disturbances can be settled in this paper. Firstly, the mathematical model of the two-tank liquid level system is established based on fluid mechanics and principle of mass conservation. Secondly, an integral backstepping control strategy is designed in order to ensure liquid level tracking performance by making the tracking errors converge to zero in finite time. Thirdly, a disturbance observer is designed for the two-tank liquid level system with external disturbances. Finally, the validity of the proposed method is verified by simulation and experiment. By doing so, the simulation and experimental results prove that the scheme of disturbance observer-based integral backstepping control strategy can suppress external disturbances more effective than the disturbance observer-based sliding mode control method and has better dynamic and steady performance of the two-tank liquid level system.

Underactuated Microsatellite Electromagnetic Docking Control Using Disturbance Observer-Based Sliding Mode Controller

This paper presents a novel control method that combines sliding mode controllers, disturbance observers and an exact robust differentiator to solve the underactuated microsatellite electromagnetic docking control problem, in which each docking satellite is equipped with only one single electromagnetic coil. The far-field model of electromagnetic force/torque is given and its model error is analyzed; and a six-degree-of-freedom (6-DOF) docking dynamics model using the far-field model is established. The generation method of the desired trajectory and desired attitude in the docking process is presented; and then an improved exact robust differentiator based on the 3rd-order sliding mode is proposed to produce the desired angular velocity and angular acceleration. In the presence of model uncertainties, external disturbances and input constraints, a disturbance observer-based sliding mode control scheme for underactuated microsatellite electromagnetic docking is developed. The whole closed-loop control system contains an inner-loop attitude controller and an outer-loop position controller. Numerical simulation results are presented to validate the effectiveness and the superior properties of the proposed control scheme.

Antlion Optimized Robust Control Approach for Micropositioning Trajectory Tracking Tasks

Planar 3-Degree of Freedom (3-DOF) micropositioning stages are widely adopted in many precision applications for their ability to provide in-plane rotation. However, their motion accuracy is adversely affected by cross-couplings, model uncertainty, and external disturbances. This work proposes an optimized robust control methodology based on disturbance estimation to address these issues. Systematic modeling of a 3-DOF precision micropositioning stage was utilized to develop a nonlinear disturbance observer-based sliding mode control methodology. This methodology can estimate and compensate the unavoidable cross-couplings between the major axes of motion. A stability analysis is conducted to prove the stability of the feedback system when the control approach is combined with the disturbance observer. A maximum bound on the tracking error is derived through finite-time analysis, and the parameters that affect this bound are identified. The antlion optimizer algorithm is used to optimize the control parameter based on the mean square error cost function to eliminate the requirement for manual tuning and to achieve the best attainable performance. The proposed control method is experimentally demonstrated to track complex trajectory with less tracking error than the classical sliding mode approach. The main contribution of this study is the improvement of the trajectory tracking accuracy in multi-DOF micropositioners using an optimized disturbance observer-based robust control technique.

Disturbance Attenuation for Surface-Mounted PMSM Drives Using Nonlinear Disturbance Observer-Based Sliding Mode Control

This paper proposes a nonlinear disturbance observer (NDO)-based sliding mode speed controller (SMSC) to guarantee the superior control performance in terms of robustness, fast transient response, and small steady-state error for a surface-mounted permanent magnet synchronous motor (SPMSM) drive. Generally, the control performance of the SPMSM drives can be degraded by disturbances, so an NDO with a proper disturbance rejection capability is proposed to appropriately improve the tracking performance of the SMSC designed for the SPMSM drives. Unlike the linear disturbance observers (LDOs), the proposed NDO can efficiently estimate the lumped disturbance such as uncertainties parameters and unmodeled dynamics by using the nonlinear design function. The proposed NDO rejects the complex disturbances as well as self-regulates the observer gains to increase the convergence rate. The feasibility of the proposed NDO-based SMSC is verified by using a MATLAB/Simulink software program and a prototype SPMSM drive system with a TI TMS320F28335 digital signal processor (DSP). The comparative results with a conventional LDO-based SMSC are analyzed under load torque disturbances and model uncertainties to prove the excellent performance of the proposed NDO-based SMSC.