Improved Sliding Mode Control Research Articles

Trajectory Tracking Control of Mobile Manipulator Based on Improved Sliding Mode Control Algorithm

Research on trajectory tracking control for climbing welding robots holds significant importance in the field of automated welding. However, existing trajectory tracking methods suffer from issues such as jitter and slow speed. In this paper, an improved sliding mode control strategy is proposed based on the self-designed wall-climbing welding mobile manipulator. Firstly, a new adaptive sliding mode control strategy is proposed for the mobile platform based on the kinematic model. By introducing a new approach law, the controller is designed when the distance between the center of mass is unknown. Secondly, regarding the manipulator, we analyze simplified dynamic equations, extract uncertain components, and utilize a CNN for compensation. This compensation strategy is integrated into the sliding mode control law, achieving precise control over the manipulator and effectively resolving issues like slow tracking speeds, large errors, and chattering. The stability of the robot control system is proved by the Lyapunov function. Through simulation analysis and experimental validation, the proposed control method is confirmed to be feasible and superior.

Improved Sliding Mode Control for a Robotic Manipulator With Input Deadzone and Deferred Constraint

Improved Sliding Mode Control for a Robotic Manipulator With Input Deadzone and Deferred Constraint

Control Strategy Based on Improved Sliding Mode Control for T-type 3L PV Grid-connected Inverter

This paper analyzes the mathematical model and working principle of a T-type 3 L PV inverter and introduces the control structure of a grid-connected PV inverter. In view of the influence of the sliding mode controller (SMC) rooted on the traditional reaching law (RL) on the control performance for grid-connected PV inverters as the current inner loop, such as large THD, this paper proposes a novel RL in the inner loop SMC to improve the tracking effect and robustness of the controller. The design method of each link of the SMC based on the proposed novel RL is described in the paper. Then, the stability analysis of the improved SMC is carried out. The experiment has been carried out on the experimental operating platform of the T-type 3 L PV grid-connected inverter system. The experimental results allow expressing that the designed control strategy can modify the dynamic performance of the system, reduce the harmonic distortion rate of the incoming current, and maintain the system with strong anti-interference capability under the premise of making the PV power generation system operate stably.

Time-varying disturbance-observer-based tracking control of uncertain flexible-joint manipulator

This paper presents a time-varying disturbance-observer- (TVDO-) based improved sliding-mode control (ISMC) method to achieve tracking control of uncertain flexible-joint manipulator (UFJM). Based on the UFJM dynamic model and its ideal dynamic model regardless of uncertainties, an error system in the form of an integral chain with disturbances is established. The tracking control objective of the UFJM is achieved by designing the TVDO-based ISMC law to guarantee the ultimate boundedness of link angle errors for the error system. Specifically, by employing the TVDO, the disturbances in the error system are estimated. By using the TVDO-based ISMC method, the uncertainties are overcome, and the chattering problem is reduced. The contradiction between high tracking accuracy and suitable torque without peaking phenomenon is alleviated. Finally, the stability analysis of the closed-loop control system is presented, and the validity of the proposed method is illustrated by simulation and experiment.

Trajectory Tracking Control of Autonomous Vehicles Based on an Improved Sliding Mode Control Scheme

This paper addresses the issue of external unknown environmental interference affecting the trajectory tracking performance and driving stability of autonomous vehicles. This seriously impacts the performance and stability of the vehicle while driving. In order to provide precise, reliable, and safe trajectory tracking performance for autonomous vehicles, this paper proposes a recursive integral terminal sliding mode control (RITSMC) method. The proposed RITSMC combines the advantages of recursive integral sliding mode (RISM), terminal sliding mode (TSM), and adaptive algorithms, and can effectively achieve precise trajectory tracking and driving stability of autonomous vehicles. Furthermore, compared with traditional methods, an adaptive algorithm is introduced on the recursive sliding surface to enable real-time adaptation of the control parameters of the recursive controller, further improving the trajectory tracking accuracy and driving stability of autonomous vehicles. The stability of this control system is demonstrated by using a Lyapunov function. Finally, multiple simulation tests were conducted on different lane speeds on both wet and dry asphalt road sections. By comparing the simulation results, it was found that the proposed RITSMC exhibits excellent performance in terms of the precision of tracking trajectories and the stability of driving, in contrast to traditional sliding mode controllers (SMC) and integral terminal sliding mode controllers (ITSMC).

Speed Synchronization Control of Dual-SRM Drive With ISMC-Based Cross-Coupling Control Strategy

To improve the speed synchronization performance of dual switched reluctance motor (SRM) drive with traditional sliding mode control (TSMC), the improved sliding mode control (ISMC) based cross-coupling control strategy is proposed. Firstly, the overall control structure of the dual-SRM drive is represented. Secondly, the state variable is introduced to reduce the torque fluctuation and adjustment time of the dynamic process of each SRM drive in the system based on the traditional sliding surface and sliding mode reaching law. The adaptive law is introduced into the sliding mode controller to avoid the load torque observation. Thirdly, the ISMC-based cross-coupling control method for the speed synchronization of the dual-SRM drive is designed. The novel sliding surface is proposed considering the speed synchronization deviation. The novel sliding mode reaching law is represented by introducing the state variables. Then the ISMC-based cross-coupling control method is realized for speed synchronization. The stability is proved by Lyapunov function. Simulations and experiments are implemented to verify the effectiveness of the proposed method.

An Improved Sliding Mode Controller for MPP Tracking of Photovoltaics

Maximum power point tracking (MPPT) through an effective control strategy increases the efficiency of solar panels under rapidly changing atmospheric conditions. Due to the nonlinearity of the I–V characteristics of the PV module, the Sliding Mode Controller (SMC) is considered one of the commonly used control approaches for MPPT in the literature. This paper proposed a Backstepping SMC (BSMC) method that ensures system stability using Lyapunov criteria. A fuzzy inference system replaces the saturation function, and a modified SMC is used for MPPT to ensure smooth behavior. The proposed Fuzzy BSMC (FBSMC) parameters are optimized using a Particle Swarm Optimization (PSO) approach. The proposed controller is tested through various case studies on account of MPP’s dependence on temperature and solar radiation. The controller performance is assessed in partial shading conditions as well. The simulation results show that less settling time, a small error, and enhanced power extraction capability are achieved by applying the PSO-based FBSMC approach compared to the conventional BSMC- and ABC-based PI control presented in previous research in different scenarios. Moreover, the proposed approach provides faster adaptation to temperature and solar radiation variation, ensuring faster convergence to the MPP. Finally, the robustness of the proposed controller is validated by providing variation within the system components. The result of the proposed controller clearly indicates the lowest value of RMSE measured between PV voltage and the reference voltage, as well as the RMSE between PV power and maximum power. The results also show that the proposed MPPT controller exhibits the highest dynamic efficiency and mean power.

An Improved Sliding Mode Control Method to Increase the Speed Stability of Permanent Magnet Synchronous Motors

A permanent magnet synchronous motor (PMSM) plays an important role in the operation performance of an electric vehicle. In order to increase the speed stability of PMSMs, an improved sliding mode control (SMC) method is proposed in this paper. Firstly, the control process of a PMSM is divided into parts, which are the torque closed-loop control and speed closed-loop control. Secondly, an integrated control method with proportional integral (PI) and inverter switching frequency is adopted in order to increase the torque performance of the PMSM. Lastly, compared with the traditional SMC method, an improved SMC method with saturation function is proposed in order to decrease the speed fluctuation of the PMSM from 7.7% to 5.9%, thereby increasing the speed stability of the PMSM. The results of the experimental test indicate that both the speed stability and starting performance of the PMSM are increased by the improved SMC method.

Improved sliding mode control for permanent magnet synchronous motor servo system

In this study, an improved sliding mode control (ISMC) method combining continuous non-singular terminal sliding mode (CNTSM) and linear active disturbance rejection control (LADRC) for permanent magnet synchronous motor (PMSM) servo system is proposed to improve the performance of PMSM. Based on the mathematical model of PMSM, combined with SMC theory and LADRC theory, CNTSM controller based on continuous function is proposed to solve the singularity of terminal sliding mode (TSM) control. In order to solve the contradiction between the convergence performance of sliding mode control and the ability of chattering suppression, fuzzy control is introduced to adjust the gain of sliding mode controller in real time. LADRC is developed to ensure the current starting conditions of the motor and improve the robustness. Moreover, the asymptotic stability of the system is guaranteed by the Lyapunov theorem and it is verified by the AISim MBD servo motor experimental platform. Experiments show that the algorithm has good tracking performance and robustness.

A Novel MPPT Algorithm for Photovoltaic Systems Based on Improved Sliding Mode Control

Due to the poor tracking performance and significant chattering of traditional sliding mode control in the maximum power point tracking (MPPT) algorithm, a novel MPPT algorithm based on sliding mode control for photovoltaic systems is proposed in this paper. The sliding mode control structure and new sliding mode surface of the multi-power reaching law are designed with the boost converter as the carrier of the photovoltaic system, and the sigmoid function is proposed to replace the symbolic function and saturation function in the power reaching law to improve the reaching rate and control quality of the traditional sliding mode control. Furthermore, the Liapunov function is employed to analyze the accessibility, existence and stability of the improved sliding mode control. Simulation results under dynamic and partial shading conditions show that compared with exponential sliding mode and constant speed sliding mode, the improved sliding mode control strategy can quickly track the maximum power point of photovoltaic systems under various atmospheric conditions. The proposed MPPT algorithm has stronger robustness and universality. Additionally, the efficiency of the proposed algorithm is improved by 2.3% and 5.6% as compared to the exponential sliding model control algorithm and constant velocity sliding model control algorithm. In addition, the experimental platform is constructed to further validate the feasibility and effectiveness of the proposed algorithm.

Parameters uncertainty analysis of posture control of a four-wheel-legged robot with series slow active suspension system

This paper focuses on the posture control performance on uneven terrain for a wheel-legged robot (WLR). Firstly, a novel four-wheel-legged robot (FWLR) with series slow active suspension system (SSASS) is proposed. Secondly, the parameters uncertainty of posture control is studied, and an 11 DOF dynamic model and the corresponding system state equation are presented. Thirdly, to suppress the chattering problem and enhance the robustness of traditional sliding mode controller (TSMC), the second order low-pass filter (SOLPF), equivalent speed control, saturation function, terrain estimation model and the actuator model are introduced into the control system, and an improved sliding mode controller (ISMC) is proposed. Finally, both the co-simulation and experiment on uneven terrain are carried out, the results show that even if the system parameters have 30% variation, the robot posture angle can be improved effectively. That is, the proposed robot and ISMC control strategy have good posture control performance with low parameters sensitivity on uneven terrain. Overall, this paper attempts to provide an effective way for the application of WLR on uneven terrain.

An Improved Sliding Mode Control with Integral Surface for a Modular Multilevel Power Converter

This paper presents a novel method for current control for a modular multilevel converter (MMC). The proposed current control methodology is based on a modified sliding mode control (SMC) with proportional and integral (PI) sliding surface which allows fast transient responses and improves the robustness of the MMC control performance. As the proposed method is derived via Lyapunov direct method, the closed-loop stability is ensured and results in globally asymptotically stable. Furthermore, the reaching time is also guaranteed by the proposed method, leading to fast transient responses. The proposed method is validated by comparing with some existing methods, which are proportional integral controller and conventional SMC, via offline and hardware-in-loop (HIL) simulations where a 10 MW, medium-voltage MMC system is tested. According to these results, the proposed method is able to provide fast transient responses, zero overshoot, and robustness to the weak grid and short-circuit conditions.

Improved Sliding Mode Control of Permanent Magnet Synchronous Linear Motor Based on Model-Assisted Linear Extended State Observer

Aiming at the problem that generalized disturbance such as parameter perturbation, load disturbance and unmodeled dynamics will reduce the performance of the mover speed control of the permanent magnet synchronous linear motor (PMSLM), an improved sliding mode control (ISMC) strategy of PMSLM based on model-assisted linear extended state observer (MALESO) is proposed. Firstly, a speed mathematical model of PMSLM considering generalized disturbance is established, then the speed tracking error signal is introduced into the traditional exponential reaching law (TERL) as the system state variable, and the improved exponential reaching law (IERL) based on the system state variable is designed and applied to the integral sliding mode surface to obtain the control variable with generalized disturbance. Secondly, MALESO is designed to estimate the generalized disturbance and its estimated value is feedforward compensated to the output signal of the improved sliding mode speed controller (ISMSC). Finally, the speed control of PMSLM under the generalized disturbance is realized. The simulation results show that the proposed control strategy can significantly optimize the dynamic and static quality, anti-disturbance ability and robustness of the system, and at the same time effectively weaken the chattering phenomenon of sliding mode control.

Stabilization control for unmanned helicopter-slung load system based on active disturbance rejection control and improved sliding mode control

Unmanned helicopters are widely used in military and civil fields. One of the most important applications is flying with an underslung load, but the pendulum-like behavior of the load can cause damage or even forced landing to the helicopter. To solve this problem, a control strategy to stabilize the helicopter/load system based on active disturbance rejection control (ADRC) and improved sliding mode control (ISMC) algorithms is proposed in this paper. First, the helicopter/load system is modelled using Newton-Euler equations according to the multi-body dynamics theory. Then a manipulation strategy which can reduce the swing angle of the load and an overall control strategy for the helicopter/load system are presented. Specifically, ADRC is applied to attitude control due to its ability to regard the pendulum-like behavior as the internal uncertainties of the system, meanwhile ISMC to position control. Within ISMC, two sliding surfaces with adjustable weights are constructed by employing the position of the helicopter as well as the swing angle of the load. In addition, a real-time beetle antennae search algorithm is designed to online modify the weights by taking the minimum error at current time as the optimization objective. Besides, the radial basis function neural network is introduced to approach the uncertainty coefficients considering the system’s complexity. At last, relevant simulations are carried out and the results indicate that the system is capable of not only controlling the attitude and position of the helicopter precisely but also stabilizing the underslung load rapidly with ADRC and ISMC.

Data Driven Model-Free Adaptive Control Method for Quadrotor Formation Trajectory Tracking Based on RISE and ISMC Algorithm.

In order to solve the problems of complex dynamic modeling and parameters identification of quadrotor formation cooperative trajectory tracking control, this paper proposes a data-driven model-free adaptive control method for quadrotor formation based on robust integral of the signum of the error (RISE) and improved sliding mode control (ISMC). The leader-follower strategy is adopted, and the leader realizes trajectory tracking control. A novel asymptotic tracking data-driven controller of quadrotor is used to control the system using the RISE method. It is divided into two parts: The inner loop is for attitude control and the outer loop for position control. Both use the RISE method in the loop to eliminate interference and this method only uses the input and output data of the unmanned aerial vehicle(UAV) system and does not rely on any dynamics and kinematics model of the UAV. The followers realize formation cooperative control, introducing adaptive update law and saturation function to improve sliding mode control (SMC), and it eliminates the general SMC algorithm controller design dependence on the mathematical model of the UAV and has the chattering problem. Then, the stability of the system is proved by the Lyapunov method, and the effectiveness of the algorithm and the feasibility of the scheme are verified by numerical simulation. The experimental results show that the designed data-driven model-free adaptive control method for the quadrotor formation is effective and can effectively realize the coordinated formation trajectory tracking control of the quadrotor. At the same time, the design of the controller does not depend on the UAV kinematics and dynamics model, and it has high control accuracy, stability, and robustness.

Data Driven Model-Free Adaptive Control Method for Quadrotor Trajectory Tracking Based on Improved Sliding Mode Algorithm

In order to solve the problems of dynamic modeling and complicated parameters identification of trajectory tracking control of the quadrotor, a data driven model-free adaptive control method based on the improved sliding mode control (ISMC) algorithm is designed, which does not depend on the precise dynamic model of the quadrotor. The design of the general sliding mode control (SMC) algorithm depends on the mathematical model of the quadrotor and has chattering problems. In this paper, according to the dynamic characteristics of the quadrotor, an adaptive update law is introduced and a saturation function is used to improve the SMC. The proposed control strategy has an inner and an outer loop control structures. The outer loop position control provides the required reference attitude angle for the inner loop. The inner loop attitude control ensures rapid convergence of the attitude angle. The effectiveness and feasibility of the algorithm are verified by mathematical simulation. The mathematical simulation results show that the designed model-free adaptive control method of the quadrotor is effective, and it can effectively realize the trajectory tracking control of the quadrotor. The design of the controller does not depend on the kinematic and dynamic models of the unmanned aerial vehicle (UAV), and has high control accuracy, stability, and robustness.

Wind energy conversion systems analysis of PMSG on offshore wind turbine using improved SMC and Extended State Observer

In this paper, an improved Sliding Mode Control(SMC) is proposed based on the Wind Energy Conversion System(WECS), which is with offshore wind turbine Permanent Magnet Synchronous Generator(PMSG) connected to the grid. Moreover, an aerodynamic torque observer is presented to improve the performance of Maximum Power Point Tracking(MPPT). Since the wind energy conversion system is a complicated nonlinear system, an enhanced reach law of sliding mode controller is designed to reduce the chattering issue. Compared to traditional control methods, the simulation results show that the control method proposed in this paper significantly improves the stability and robustness of PMSG-Based WECS in the area of MPPT.

An Improved Sliding Mode Control via Discrete Time Optimal Control and its Application to Magnetic Suspension System

Sliding Mode Control (SMC) is a robust control strategy that is insensitive to system uncertainties and external disturbances. It is widely used in designing controllers, observers and differentiators. However, the inevitable chattering problem affects the SMC applications in real-life engineering. This paper presents an improved SMC algorithm based on discrete second-order time optimal control (TOC). The proposed algorithm adopts a simple method to calculate the distance from the state variable to the sliding surface, and it can adjust the linear or nonlinear control law according to the calculated distance. On the other hand, the control law deviation in the two-step reachable region is corrected. The improved control algorithm shortens the convergence time and reduces the chattering problem of the system. It is applied to the design of magnetic suspension controllers. This allows the system to achieve a fast, accurate and stable suspension target when the system has external disturbances and internal parameter perturbations.

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.

Improved Sliding Mode Control for Finite-Time Synchronization of Nonidentical Delayed Recurrent Neural Networks.

This brief further explores the problem of finite-time synchronization of delayed recurrent neural networks with the mismatched parameters and neuron activation functions. An improved sliding mode control approach is presented for addressing the finite-time synchronization problem. First, by employing the drive-response concept and the synchronization error of drive-response systems, a novel integral sliding mode surface is constructed such that the synchronization error can converge to zero in finite time along the constructed integral sliding mode surface. Second, a suitable sliding mode controller is designed by relying on Lyapunov stability theory such that all system state trajectories can be driven onto the predefined sliding mode surface in finite time. Moreover, it is found that the presented control approach can be conveniently verified and does not need to solve any linear matrix inequality (LMI) to guarantee the finite-time synchronization of delayed recurrent neural networks. Finally, three numerical examples are exploited to demonstrate the effectiveness of the presented control approach.