Sliding Mode Control Strategy for Buck Converters based on Linear Extended State Observer

To eliminate the effect of the uncertain disturbances and improve the control accuracy of spacecraft Attitude Control System, a nonlinear control algorithm named nonsingular terminal sliding-mode feedback controller is proposed in this work, which is mainly made up of nonsingular terminal sliding-mode controller and sliding-mode feedback controller. In the first place, nonsingular terminal sliding-mode controller is designed, which guarantees global asymptotic convergence of the attitude in the presence of the uncertain perturbations from the space. Despite that, it is the influence of the uncertain disturbances that hinder the control accuracy. Then, in order to promote the control accuracy, the sliding-mode feedback controller based on the principle of minimum sliding-mode error is proposed, which is used to compensate the control errors of the nonsingular terminal sliding-mode controller caused by the uncertainties. Hence, the determination principle of the weighting matrix in sliding-mode feedback controller is discussed, and the algorithm structure of the sliding-mode feedback controller is also analyzed, which provides the theoretical basis for the sliding-mode feedback controller. By contrast, an adaptive fuzzy algorithm is designed and introduced into the nonsingular terminal sliding-mode controller to improve the control accuracy, which named the nonsingular terminal fuzzy sliding-mode controller. Last but not the least, several numerical examples are presented to demonstrate the efficacy of the proposed nonsingular terminal sliding-mode feedback controller. Simulation results confirm that the control accuracy of the nonsingular terminal sliding-mode feedback controller is higher than the nonsingular terminal sliding-mode controller and the same as nonsingular terminal fuzzy sliding-mode controller. Not only is the calculation of the nonsingular terminal fuzzy sliding-mode feedback controller smaller than nonsingular terminal fuzzy sliding-mode controller, the adjusted parameters are also fewer than nonsingular terminal fuzzy sliding-mode controller obviously. The numerical results clearly indicate that the proposed nonsingular terminal sliding-mode feedback controller based on the principle of minimum sliding-mode error can compensate control errors accurately and quickly; therefore, it can reduce the effect of the uncertainties from the space indirectly.

Three-phase voltage PWM rectifier is a multivariable, strong coupling, nonlinear multi-input and multi-output system. In the design of rectifier control systems, with PI control it is difficult to achieve the ideal control effect, the dynamic performance is poor, and the parameter computation is complex. Moreover, the traditional sliding mode control voltage outer loop suffers from the problem of chattering, which is difficult to solve. Responding to the above issues, a new type of variable speed reaching law is proposed, which is applied to the voltage outer loop sliding mode control, while the feedback linearization principle is introduced to the current inner loop, and a new type of double closed-loop sliding mode control system is obtained by applying the two theories to the design of the sliding mode controller. A simulation model is established in MATLAB/Simulink to compare the PI control, the SMC control and the V-SMC control strategy proposed in this paper (voltage outer loop V-SMC current inner loop FLC-SMC control), and the simulation results show that the rectifier under the new dual-closed-loop sliding mode control strategy has the advantages of good dynamic performance, strong robustness and strong anti-interference ability. At the same time, compared with the traditional sliding mode control strategy, the vibration suppression effect under the proposed control strategy is obvious. Finally, a 10 kW rectifier control system is built on a semi-physical hardware-in-the-loop experimental platform to further verify the correctness and superiority of the proposed control strategy.

This paper proposes full-order terminal sliding-mode control strategies for wind energy conversion systems. Nonsingular terminal sliding-mode manifolds and related second-order sliding-mode control strategies are designed respectively for the d- and q-axis currents respectively. The control signals in the proposed sliding-mode controllers are continuous and have no chattering phenomenon. So the proposed controllers are suitable for practical applications.

This paper mainly introduces the output voltage control of the three‐phase inverter without current sensor. Aiming at internal parameter perturbation and external unknown disturbance, a generalized proportional integral observer (GPIO) is designed to observe the lumped interference and feedforward compensation. Then, a finite‐time control strategy based on nonsingular terminal sliding mode control (NTSMC) is designed to improve control accuracy and fault tolerance under various interference. Compared with traditional PI control and sliding mode control (SMC), this strategy has the finite‐time convergence of voltage tracking error and active anti‐interference ability. The stability of the proposed control strategy is proved strictly. Finally, the simulation results show that in the presence of interference, the proposed control strategy has better robustness and smaller chattering. The feasibility and effectiveness of the controller are fully illustrated by exploring the experimental results. This controller eliminates the current sensor and has active anti‐interference capability. The output voltage chattering and overshoot under interference conditions are both significantly attenuated.

In this chapter an adaptive sliding mode controller for the Furuta pendulum is proposed. The Furuta pendulum is a class of underactuated mechanical systems commonly used in many control systems laboratories due to its complex stabilization which allows the analysis and design of different nonlinear and multivariable controllers that are useful in some fields such as aerospace and robotics. Sliding mode control has been extensively used in the control of mechanical systems as an alternative to other nonlinear control strategies such as backstepping, passivity based control etc. The design and implementation of an adaptive sliding mode controller for this kind of system is explained in this chapter, along with other sliding mode controller variations such as second order sliding mode (SOSMC) and PD plus sliding mode control (PD \(+\) SMC) in order to compare their performance under different system conditions. These control techniques are developed using the Lyapunov stability theorem and the variable structure design procedure to obtain asymptotically stable system trajectories. In this chapter the adaptive sliding mode consist of a sliding mode control law with an adaptive gain that makes the controller more flexible and reliable than other sliding mode control (SMC) algorithms and nonlinear control strategies. The adaptive sliding mode control (ASMC) of the Furuta pendulum, and the other SMC strategies shown in this chapter, are derived according to the Furuta’s pendulum dynamic equations making the sliding variables, position errors and velocity errors reach the zero value in a specified reaching time. The main reason of deriving two well known sliding mode control strategy apart from the proposed control strategy of this chapter (adaptive sliding mode control) is for comparison purposes and to evince the advantages and disadvantages of adaptive sliding mode control over other sliding mode control strategies for the stabilization of the Furuta pendulum. A chattering analysis of the three SMC variations is done, to examine the response of the system, and to test the performance of the ASMC in comparison with the other control strategies explained in this chapter.

This paper develops a nonsingular terminal sliding mode controller (NTSMC) based on extended state observer (ESO) for a buck converter subject to load disturbances and input voltage variations. First, a novel modeling method is developed to transform the matched and mismatched disturbances caused by load resistance and input voltage variations into a uniform matched total disturbance. Second, an ESO is established to estimate the differential of the output voltage and the total disturbance. Third, a NTSMC based on ESO is designed to achieve faster tracking speed and better tracking accuracy around the expected voltage. In addition, the theoretical stability of the proposed controller is analyzed by a Lyapunov stability criterion. Finally, both simulation and experimental results show that the proposed NTSMC-ESO controller with the novel modeling method can attenuate the input voltage variation effectively and has a better load disturbance rejection ability than the reduced-order ESO based sliding mode controller. Abbreviations: ADRC: active disturbance rejection control; ESO: extended state observer; NTSMC: nonsingular terminal sliding mode control; RESO: reduced-order extended state observer; SMC: sliding mode control;

Vehicle platoon is one of the innovations in the automated highway systems, which has the potential to reduce fuel consumption, alleviate traffic congestion and lighten the driver’s burden. How to control the vehicle effectively to ensure the stability of the queue is a challenge. Aiming to overcome the shortcomings of the platoon control method based on traditional sliding mode control, a non-singular terminal sliding mode control method optimized by the extreme learning machine is proposed in this paper. Firstly, the vehicle longitudinal dynamics are derived from the analysis of the forces acting on the vehicle in the longitudinal direction. A constant time headway policy is taken as the spacing policy. The modified non-singular terminal sliding mode control method has outstanding performance, simulation results demonstrate that the following vehicles can rapidly track the trajectory of the leading vehicle in the platoon with less spacing error and guarantee string stability. In this study, several experiments are set up to consider the disturbance and other uncertain practical factors. The performance of the proposed method is superior to the traditional sliding mode control method. Experimental results show that the proposed method can significantly reduce chattering and has good robustness under the circumstances of the disturbance.

The DC distribution network has more advantages in power transmission, grid connection of distributed energy, and reliability of power supply when compared with AC distribution network, but there are still many problems in the development of DC distribution network. DC bus voltage control is one of the hot issues in the research of DC distribution network. To solve this problem, in this paper, a new type of sliding mode active disturbance rejection control (SMADRC) controller for AC/DC converters is designed and applied to the voltage outer loop. The linear extended state observer (LESO) can observe the state variables and the total disturbance of the system. The SMADRC is composed of a sliding mode controller, LESO, and disturbance compensator, which can compensate the total disturbance observed by LESO properly. Therefore, it improves the dynamic. At the same time, it can also reduce the system jitter that is caused by sliding mode controller. The state variables that are observed by the LESO are used in the design of sliding mode controller, which greatly simplifies the design of sliding mode controller. Finally, the simulation results of Matlab/Simulink show that the controller has good start-up performance and strong robustness.

When a permanent magnet synchronous motor runs at low speed, the inverter will output discontinuous current and generate torque ripple; when the motor is runs at high speed, a large amount of stator harmonic current generates, which affects its speed following ability and torque stability. To ensure the fast and smooth switching of a permanent magnet synchronous motor in the full speed domain, this paper proposes the nonsingular terminal sliding mode control of PMSM speed control based on the improved exponential reaching law. Firstly, the improved exponential reaching law is composed of the state variables and power terms of the sliding mode surface functions. The reaching law function is designed in sections to balance the fast dynamic response of the system and chattering control. Secondly, an improved exponential reaching law based on the sliding mode control strategy of the PMSM speed loop is proposed. By designing the initial value of the integral term in the nonsingular terminal sliding mode surface function, the initial state of the system is located on the sliding mode surface. The integral sliding mode surface is used to reduce the system steady-state error, while the proposed sliding mode reaching law is used to increase the arrival speed and suppress system chattering, ultimately affecting modeling error problems, complex working conditions, and uncertainty factors. This paper proposes a sliding mode observer based on an improved exponential reaching law to compensate for the disturbances. Lyapunov stability theory can prove that this system can make the speed tracking error converge to zero in finite time. Hardware-in-the-loop experiments were used to validate the effectiveness of the proposed method.

This paper presents a non-linear Sliding Mode Control (SMC) strategy based on continuous switching law for large-power (10MW) Permanent Magnet Synchronous Generator (PMSG) based Wind-Energy Conversion System (WECS). The WECS model consists of a wind turbine, PMSG, rectifier fed boost converter, PWM inverter and the filter. The controller is used to maintain the DC-link voltage constant and to generate controlled active and reactive power for grid. For verification of validity of proposed control scheme and model, the proposed system's dynamic model is simulated in MATLAB/Simulink. SMC has the promising features of: fast switching, insensitivity to parameter uncertainty, disturbance rejection quality, and more robustness than the conventional linear controllers. The proposed continuous control compelled the states trajectories of the system onto the surface in error space (sliding surface) for the system behavior to obtain design specifications. Simulation results demonstrate that the proposed SMC is effective and gives superior performance than conventionally tuned PI controller.

This paper presents a decoupled nonsingular terminal sliding mode controller (DNTSMC) for a novel 3-DOF parallel manipulator with actuation redundancy. According to kinematic analysis, the inverse dynamic model for a novel 3-DOF redundantly actuated parallel manipulator is formulated in the task space using Lagrangian formalism and decoupled into three entirely independent subsystems under generalized coordinates to significantly reduce system complexity. Based on the dynamic model, a decoupled sliding mode control strategy is proposed for the parallel manipulator; the idea behind this strategy is to design a nonsingular terminal sliding mode controller for each subsystem, which can drive states of three subsystems to the original equilibrium points simultaneously by two intermediate variables. Additionally, a RBF neural network is used to compensate the cross-coupling force and gravity to enhance the control precision. Simulation and experimental results show that the proposed DNTSMC can achieve better control performances compared with the conventional sliding mode controller (SMC) and the DNTSMC without compensator.

The single robot joint, which contains a DC torque motor and a harmonic reducer, was designed. And sliding mode control strategy by the self-adaptive adjustment of the sliding parameter e was proposed in this paper. This control strategy can adaptively adjust e by switching variables and their derivatives according to the system. It is applied in the control of robot joint to solve the contradiction between the exponential reaching law response speed and chattering. Simulation results show that the open-loop control response time of the parameter adaptive adjustment sliding mode control is 0.3s. The experiment results show that under the control of adaptive sliding mode with joint angle 45 and rise-time 0.23s, the maximum overshoot is 0.4%, with no chattering and a good dynamic quality.

Fractional-order nonsingular terminal sliding mode controller for a quadrotor with disturbances

To address the challenges of strong electromechanical coupling, nonlinear friction, and poor disturbance rejection in semi-direct-drive scraper conveyor systems under complex coal mining conditions, this paper aims to propose a high-performance drive control strategy that balances dynamic response speed with steady-state operational smoothness. First, an integrated electromechanical coupling dynamic model incorporating Permanent Magnet Synchronous Motor (PMSM) vector control and the time-varying meshing stiffness of a two-stage planetary gear train is established. Subsequently, a Sliding Mode Control (SMC) strategy optimized with a saturation boundary layer is designed and compared with traditional Proportional-Integral (PI) control under multiple operating conditions. Time-frequency domain analysis indicates that SMC significantly enhances the dynamic stiffness of the drive system. Under sudden load change conditions, the speed recovery time is shortened by approximately 76%, and the steady-state error is reduced by 37% compared to PI control. Microscopic characteristic evaluation based on FFT and Total Variation (TV) metrics reveals that SMC achieves active disturbance rejection through spectral broadening of the electromagnetic torque. Crucially, the steady-state cumulative control effort of SMC is equivalent to that of PI, implying no additional mechanical stress burden, while the equivalent dynamic transmission force fluctuation in the mechanical chain is reduced by about 3%. The study confirms that the proposed strategy successfully achieves a synergistic optimization of “macroscopic rapid response” and “microscopic smooth operation,” providing a theoretical basis for the high-precision control of heavy-duty underground transmission equipment.

This paper suggests a new hybrid control strategy, called Optimal Type II Fuzzy Sliding Mode (OT2FSM) control scheme, to realize the control of general uncertain chaotic systems. The proposed controller not only guaranties the stability and robustness against the lumped uncertainties caused by unmodeled dynamics and external disturbances, but also can significantly reduce the control chattering inherent in conventional sliding mode control. In the proposed controller, a novel heuristic algorithm namely particle swarm optimization with random inertia weight (RNW–PSO) is employed. To achieve an optimal performance, the parameters of the proposed controller as well as the input and output membership functions are optimized simultaneously by RNW–PSO. The globally asymptotic stability of the closed-loop system is mathematically proved. To evaluate the performance of the proposed controller, the results are compared with those obtained by Optimal H-infinity Adaptive PID (OHAPID) controller and an optimal Type-2 fuzzy proportional integral derivative (OT2FPID), which are the latest researches in the problem in hand. Simulation results show the effectiveness of the OT2FSM controller.