Model Reference Sliding Mode Control Research Articles

Model reference sliding mode control for two-degree-of-freedom electro-hydraulic shaking table

The multi-axis electro-hydraulic shaking table (EHST) is capable of simulating complex vibration environments to assess product reliability under vibrational excitation. The random vibration control method plays a crucial role in simulating these environments. However, the unmolded disturbances and the nonlinearity of the system have a significant impact on the control accuracy of the EHST. Sliding mode control (SMC) can be used in single-input single-output electro-hydraulic servo systems (EHSS) to attenuate the influence of disturbance forces. The conventional SMC is not suitable for acceleration random vibration control of the multi-axis EHST because the coupling between the axes and the actuators and the null bias of the servo valve are not taken into account. A model reference sliding mode control (MRSMC) is presented in this paper based on the nonlinear dynamic model of the EHST. The MRSMC designed based on the backstepping method and Lyapunov theory is used to compensate for the disturbance forces and the null bias of the servo valve. Experimental acceleration random vibration responses show that the MRSMC enhances the accuracy of tracking the acceleration random signal.

Study on Dynamic Pressure Control of Air-Breathing Hypersonic Vehicle

To satisfy the strict requirements of dynamic pressure for air-breathing hypersonic vehicle during the initiation, a dynamic pressure control method based on the model reference sliding mode theory is designed. Firstly, the motion equation of the air-breathing hypersonic vehicle is built, and the dynamic pressure linearization model is established by the small perturbation method. Secondly, the control system, designed by the model reference sliding mode control theory, can quickly track the reference model. Finally, the six degrees of freedom simulation model is built and used for digital simulation. The simulation results show that the designed control system can accurately track the dynamic pressure command with great robustness.

Random Vibration Model Reference Sliding Mode Control of Electro-hydraulic Shaking Table with Valve Null Bias Compensation

Random Vibration Model Reference Sliding Mode Control of Electro-hydraulic Shaking Table with Valve Null Bias Compensation

Adaptive neural network sliding mode control for active suspension systems with electrohydraulic actuator dynamics

The object of this article is to design an observer-based adaptive neural network sliding mode controller for active suspension systems. A general nonlinear suspension model is established, and the electrohydraulic actuator dynamics are considered. The proposed controller is decomposed into two loops. Since the dynamics of the actuator is assumed highly nonlinear with uncertainties, the adaptive neural network is presented in the inner loop to ensure the control system robustness against uncertainties, and the self-tuning weighting vector is adjusted online according to the updated law obtained by Lyapunov stability theory. In the outer loop, a model reference sliding mode controller is developed to track the desired states of the hybrid reference model that combines skyhook and groundhook control methods. Besides, to obtain the unmeasured states of the system, an unscented Kalman filter is utilized to provide necessary information for the controller. Simulation results show that the exerted force can be tracked precisely even in the existence of uncertainties. Moreover, the proposed controller can improve the suspension’s performance effectively.

Robust Adaptive Control for an Aircraft Landing Gear Equipped with a Magnetorheological Damper

A landing gear of an aircraft is required to function at touchdown in different landing scenarios with parametric uncertainties. A typical passive damper in a landing gear has limited performance in differing landing scenarios, which can be overcome with magnetorheological (MR) dampers. An MR damper is a semi-active system that can adjust damping force by changing the amount of electric current applied to it. This paper proposes a new robust controller based on model reference sliding mode control and adaptive hybrid control to improve the efficiency of absorbing landing impact energy, not only considering the variables of aircraft weight and sink speed but also managing uncertainties, such as ambient temperature and passive damping coefficient. To verify the effectiveness of the proposed controller, comparative numerical simulations were performed with a passive damper, a skyhook controller, and the proposed controller under various landing scenarios. The simulation results show that the proposed controller improves the total energy absorber efficiency by up to 10% higher than that of the skyhook controller. In addition, the proposed controller is demonstrated to have better adaptability and robustness than the other control algorithms in the differing landing scenarios and parametric uncertainties.

Feedback Linearization Kalman Observer Based Sliding Mode Control for Semi-Active Suspension Systems

In this paper, a new approach for an observer based controller for semi-active suspension systems is presented. The observer part is a feedback linearization Kalman filter which is based on differential geometry. The original nonlinear system is transferred to a linear system by certain coordinate transfer after the verification of observability and solvability of the system observer design problem under certain sensor placement configurations. Then, a linear Kalman filter algorithm can be applied to the linearized system. The state information can be obtained through an inverse coordinate transfer of the estimation results of the linear Kalman filter. The observer is verified by a simulation test under different road profiles, and a comparison between the designed observer and extended Kalman filter shows that the feedback linearization Kalman filter has better performance. A model reference sliding mode controller based on the estimation results of the observer is also proposed. A rig test system for the semi-active suspension system is implemented, and, both the designed observer and controller are verified through the rig test. Experimental results show that the proposed new approach for semi-active suspension control can significantly improve vehicle ride comfort with common and low-cost sensors.

State estimation and damping control for unmanned ground vehicles with semi-active suspension system

The new type of transportation based on intelligent driverless vehicles will bring great changes to people’s travel modes and put forward higher requirements for the ride comfortability of vehicles. This paper presents a new observing algorithm to estimate the suspension states in real time and cooperate with sliding mode controller to improve the ride comfortability. First, the nonlinear model of an air suspension system equipped with a continuously controllable damper is described in detail. Then, this nonlinear suspension model is linearized precisely based on the differential geometry theory; a linear Kalman filter observer is implemented for this linearized model; through the coordinate reverse transformation, the designed linear observer is transformed into a nonlinear one, which will be suitable for the original nonlinear system, so that, the proposed state observer can estimate all the states of the nonlinear quarter car suspension system. Then, in this nonlinear suspension system, a model reference sliding mode controller is designed to continuously control the damping force to improve the ride comfortability. Finally, the effectiveness and advantage of the proposed feedback linearization Kalman observer is illustrated by comparing with a traditional extended Kalman filter observer. The simulation research shows that the proposed feedback linearization observer enjoys a better estimation accuracy, higher operation efficiency, and greater control performance while cooperating with the sliding mode controller in ride comfortability control.

Integrated Control With DYC and DSS for 4WID Electric Vehicles

This paper investigates the front-wheel differential steering system (DSS) for a four-wheel independent-drive (4WID) electric vehicle (EV) with a steer-by-wire (SBW) system in case of the steering failure. The nonlinear dynamic model of differential steering vehicle (DSV) is established and the stability regions at different adhesion coefficients are determined based on the theory of phase plane. The traditional front-wheel steering vehicle is selected as the reference model. The direct yaw moment control (DYC) aiming to restore the vehicle to the stability region, and the DSS control aiming to achieve the normal steering function based on the theory of model reference sliding mode control, are researched and applied to the nonlinear dynamic model successively. The direct yaw moment and differential driving torque of the front-wheel needed for the vehicle stability and DSS are obtained respectively. The simulation results show that the proposed integrated control can simultaneously ensure the differential steering and vehicle stability of the nonlinear vehicle on different adhesion coefficient roads.

Fixed-time adaptive model reference sliding mode control for an air-to-ground missile

This paper addresses the fixed-time adaptive model reference sliding mode control for an air-to-ground missile associated with large speed ranges, mismatched disturbances and un-modeled dynamics. Firstly, a sliding mode surface is developed by the tracking error of the state equation and the model reference state equation with respect to the air-to-ground missile. More specifically, a novel fixed-time adaptive reaching law is presented. Subsequently, the mismatched disturbances and the un-modeled dynamics are treated as the model errors of the state equation. These model errors are estimated by means of a fixed-time disturbance observer, and they are also utilized to compensate the proposed controller. Therefore, the fixed-time controller is obtained by an adaptive reaching law and a fixed-time disturbance observer. Closed-loop stability of the proposed controller is established. Finally, simulation results including Monte Carlo simulations, nonlinear six-Degree-Of-Freedom (6-DOF) simulations and different ranges are presented to demonstrate the efficacy of the proposed control scheme.

Model reference sliding mode control of underwater vehicle-manipulator systems

UVMS consisting of the underwater vehicle and underwater manipulator is a dynamically coupled system. The movement of the underwater manipulator has a great impact on the stability of the underwater vehicle. A control scheme combining robust feedback control of the vehicle and feed forward compensation of the manipulator is proposed. First, the dynamic modelling of UVMS by Newton-Euler method is presented and used to obtain compensation. And then, we designed a sliding mode controller with the compensation. Finally, computer physics simulations are performed to investigate the effectiveness of this scheme in stability.

Evaluation of an advanced model reference sliding mode control method for cardiac assist device using a numerical model.

In this study, the physiological control algorithm using sliding mode control method is implemented to track the reference input signal. The controller is developed using feed‐forward part, reference model, and steady‐state flow estimator. The proposed control method is evaluated using a dynamic heart‐pump interaction model incorporating descriptions of the cardiovascular system – rotary blood pump. The immediate response of the controller to preload as well as afterload was studied. Stability and feasibility of the control system were demonstrated through the tests. The results showed that the present controller, which allows the left ventricular to automatically adjust to the right ventricular output, reduces the risk of suction.

Comprehensive Analysis for Influence of Controllable Damper Time Delay on Semi-Active Suspension Control Strategies

This paper presents a comprehensive comparison and analysis for the effect of time delay on the five most representative semi-active suspension control strategies, and refers to four unsolved problems related to semi-active suspension performance and delay mechanism that existed. Dynamic characteristics of a commercially available continuous damping control (CDC) damper were first studied, and a material test system (MTS) load frame was used to depict the velocity-force map for a CDC damper. Both inverse and boundary models were developed to determine dynamic characteristics of the damper. In addition, in order for an improper damper delay of the form t+τ to be corrected, a delay mechanism of controllable damper was discussed in detail. Numerical simulation for five control strategies, i.e., modified skyhook control SC, hybrid control (HC), COC, model reference sliding mode control (MRSMC), and integrated error neuro control (IENC), with three different time delays: 5 ms, 10 ms, and 15 ms was performed. Simulation results displayed that by changing control weights/variables, performance of all five control strategies varied from being ride comfort oriented to being road handling oriented. Furthermore, increase in delay time resulted in deterioration of both ride comfort and road handling. Specifically, ride comfort was affected more than road handling. The answers to all four questions were finally provided according to simulation results.

Sliding Mode Control for Hexacopter Stabilization with Motor Failure

[abstFig src='/00280006/18.jpg' width='300' text='Hovering with 5 rotors' ] This study presents a fault-tolerance approach for hexacopters with failed propulsion systems (i.e., motors and propellers) using sliding mode control theory. In this study, we use an explicit control allocation method with linear constraints for allocating the control input to redundancy actuators, as well as a new sliding model controller designed to stabilize the attitude and maintain the basic flight performance of a vehicle with a single failed motor during an outdoor autonomous flight mission. An asymmetrical motor rotation arrangement is applied in order to ensure controllability for all degrees of freedom. We verify the developed system on a real hexacopter suffering propulsion-system failure. Finally, the comparative results between the linear-quadratic-integral controller and model reference sliding mode controller are presented to evaluate the robustness of each controller against the failure of redundancy actuators.

Design a Methodology to Model-Reference Control of First Order Delays System

Design a nonlinear controller for second order nonlinear uncertain dynamical systems is one of the most important challenging works. This research focuses on the design, and analysis of a model-reference sliding mode controller for first order delay system, in presence of uncertainties. In order to provide high performance nonlinear methodology, model-reference sliding mode controller is selected. Pure sliding mode controller can be used to control of partly known nonlinear dynamic parameters. Conversely, pure sliding mode controller is used in many applications; it has an important drawback namely; chattering phenomenon. To attenuation the chattering, new filter based high speed control technique is introduced. In this technique, two type derivative techniques are used to improve the rate of delay as well stability, robustness and chattering attenuation. This technique cased to improve the rate of delay compare with conventional PID controller and conventional sliding mode controller.

Design and control of a cascaded piezoelectric actuated two-degrees-of-freedom positioning compliant stage

A novel piezoelectric driven compliant stage and its associated PC-based X–Y axes control schemes have been developed as a potential carrier of automatic optical inspection (AOI) systems and other possible applications in precision positioning. The design is based on compliant structure with a mechanical amplifier mechanism. Two orthogonal stages are integrated into a final 2-DoF design. This approach offers the advantages of directly using a well-development design with minor modifications and the performance can be more precisely controlled. However, this also brings concerns in coupling between two motion axes due to manufacturing and alignment errors and this issue is examined experimentally. By integrating feedback control with the stage, it is possible to perform precision positioning and vibration suppression for improving the dynamic performance. This cascaded structure design can effectively reduce the system complexity and can be further extended for additional degrees of freedom. Based on the test results, the designed stage can achieve a closed loop bandwidth up to 100Hz and a steady state resolution less than 50nm using a model reference sliding mode controller. In addition, a shaping-control integration approach is also demonstrated for providing faster positioning while maintaining the robustness against possible external disturbances. Meanwhile, the experimental results indicate that the coupling due to manufacturing and assembly errors exists but this can be effectively reduced by proper trajectory planning with incorporating of dual-axis control. In summary, this study has realized a structurally-simple and low-cost positioning system and is able to achieve high-precise motion. It is hope that this study can be further expanded to longer stroke and higher precise positioning system, and integrates with cutting edge technologies for developing more superior precise instrument in the future.

Model-reference sliding mode control of a three-phase four-leg voltage source inverter for stand-alone distributed generation systems

This paper proposes a discrete-time model-reference sliding mode control of three-phase four-leg voltage source inverters for stand-alone distributed generation systems. Three-phase four-leg voltage source inverters (VSIs) are used in a broad area. A discrete-time model-reference sliding mode controller, having superior advantages such as insensitivity to external disturbances, system parameter variations, and modeling errors, is applied to control the output voltage of three-phase four-leg VSIs. As a new study, the discrete-time model-reference sliding mode control with a supplemented output feedback integral controller is proposed so that the controlled output voltages of the VSI tracks the input reference signal. The controller is designed using the augmented discrete-time error dynamics presented in this paper and is applied to control the output voltage control of a three-phase four-leg based uninterruptable power supply. It is shown that the output voltage of the VSI controlled by the proposed method is accurately regulated for various load conditions such as linear balanced/unbalanced, nonlinear balanced/unbalanced, and instantaneous load changes. The robustness of the proposed method against variations by 20{\%}--50{\%} in R, L, and C filter parameters and 5 different cases are showed. \vs{1mm}

Attitude and Altitude Controller Design for Quad-Rotor Type MAVs

Micro air vehicles (MAVs) have a wide application such as the military reconnaissance, meteorological survey, environmental monitoring, and other aspects. In this paper, attitude and altitude control for Quad-Rotor type MAVs is discussed and analyzed. For the attitude control, a new method by using three gyroscopes and one triaxial accelerometer is proposed to estimate the attitude angle information. Then with the approximate linear model obtained by system identification, Model Reference Sliding Mode Control (MRSMC) technique is applied to enhance the robustness. In consideration of the relatively constant altitude model, a Linear Quadratic Gaussian (LQG) controller is adopted. The outdoor experimental results demonstrate the superior stability and robustness of the controllers.

Development of a sliding mode controller for semi-active vehicle suspensions

Sliding mode control of semi-active suspensions possesses excellent performance as well as high robustness. However, it is difficult to obtain sufficient data concerning the various states of the suspension. A model reference sliding mode controller that is easy to implement has been designed. The proposed controller needs only two acceleration sensors and eliminates the necessity of measuring road signals in real-time. The controller uses an approximate ideal skyhook system as a reference model, and the control law is determined so that an asymptotically stable sliding mode will occur in the error dynamics between the plant and the reference model states. The effectiveness of this controller has been verified via experimental studies. A real-time control system has been constructed with a virtual instrument system. Experimental rapid control prototyping for the proposed controller has been conducted on a quarter-car suspension system. The experimental results indicate that, compared with a practical skyhook controller and a passive suspension, the sliding mode controller can effectively improve ride comfort and safety performance. The designed controller should be directly transferable to commercial implementations of semi-active vehicle suspensions.

Vibration suppression control of a flexible arm using a nonlinear observer with simultaneous perturbation stochastic approximation

The main objective in this study is the vibrational control of a one-link flexible arm system. A variable structure system (VSS) nonlinear observer has been proposed in order to reduce the oscillation when controlling the angle-of the flexible arm. The parameters of the nonlinear observer are optimized using a modified version of the simultaneous perturbation stochastic approximation (SPSA) algorithm. The SPSA algorithm is especially useful when the number of parameters to be adjusted is large, and makes it possible to estimate them simultaneously. For the vibration and position control, a model reference sliding-mode control (MR-SMC) has been proposed. The MR-SMC parameters are also optimized using a modified version of the SPSA algorithm. The simulations show that vibrational control of a one-link flexible arm system can be achieved more efficiently using our method. Therefore, by applying the MR-SMC method to a nonlinear observer, we can improve the performance in this kind of model using our proposed SPSA algorithm, and we can determine the control parameters very easy and efficiently.

Hybrid sliding mode control of semi-active suspension systems

In order to design a controller which can take both ride comfort and road holding intoconsideration, a hybrid model reference sliding mode controller (HMRSMC) is proposed.The controller includes two separate model reference sliding mode controllers (MRSMC).One of the controllers is designed so as to force the plant to follow the ideal Sky-hookmodel and the other is to force the plant to follow the ideal Ground-hook model; then theoutputs of these two controllers are linearly combined and applied to the plant asthe input. Also, since the designed controller requires a knowledge of the terraininput, this input is approximated by the unsprung mass displacement. Finally,in the simulation section of this study, the effect of the relative ratio betweenthe two MRSMCs and the knowledge of the terrain on the performance of thecontroller is numerically investigated for both steady-state and transient cases.