Control Chattering Research Articles

Sliding mode control strategy based on intermediate variable observer for cyber-physical systems under false data injection attack

A sliding mode control problem based on intermediate variable observer for non-linear cyber-physical systems in the existence of false data injection attack on actuator is investigated in this article. By constructing an intermediate variable observer to obtain accurate system states and reconstruct attack signals, based on which a non-singular terminal sliding mode control strategy is proposed to eliminate the effects of false data injection attack on the system. This strategy increases the convergence speed and transient response of the system in comparison with existing results. Furthermore, a continuous switching term is designed to suppress controller chattering. Parameters of the intermediate variable observer are determined by solving linear matrix inequality. The proposed method is applied to an electric amplidyne system for verifying its superiority.

Milling stability considering multiple effects and variable rotational speed milling chatter control

One of the most frequent barriers to decreasing the surface quality of workpieces during milling machining is chatter, and the accuracy of chatter prediction is directly impacted by the number of effects that are considered during the modeling of the milling process. Previous researchers have studied the impact of chatter suppression on the spindle variable rotational speed method in the milling model while considering various effects. The variable rotational speed waveforms primarily focus on the fundamental waveform or a composite of sine waveforms. The study presents a novel method for variable speed control, utilizing a waveform that combines sine and triangular waveforms. The effect of this method on chatter suppression is investigated in a milling dynamics model that considers regenerative, modal coupling, and process damping effects. This novel method overall improves milling stability significantly. The accuracy of the novel method is verified by simulation and experiment. Next, the analysis focuses on the influence of immersion rate, spindle modulation coefficients, and phase difference on stability, based on stability prediction. The choice of these parameters has a direct influence on the ability to suppress chatter.

Collision avoidance control of an automated guided vehicle based on hierarchical trajectory planning and fixed-time prescribed adaptive sliding mode

In this paper, a hybrid collision avoidance control (CAC) approach including trajectory planner and controller is proposed for an automated guided vehicle (AGV). Firstly, by combing the improved A* and timed-elastic-band method, a hierarchical trajectory planner is developed to realize the flexible collision avoidance trajectory planning of AGV. Subsequently, the trajectory controller is constructed to achieve the accurate tracking of the planned trajectory. Since the controller is developed based on a faster fixed-time stable system and a prescribed performance function, both the fixed-time and prescribed bounded convergences of the trajectory tracking system can be realized. In addition, a newly designed sliding mode filter-based nested adaptive law is adopted in the controller to update the control gain, thereby releasing the prior bound information of AGV unknown disturbance and minimizing control chattering. The global stability and prescribed convergence of the system are proved by Lyapunov theory. Finally, the effectiveness and merits of the presented CAC approach in flexible trajectory planning and accurate tracking are demonstrated by experimental validations on an AGV.

A fractional adaptive type-2 fuzzy structural control system: Theoretical/experimental study

A fractional adaptive type-2 fuzzy structural control system: Theoretical/experimental study

Adaptive arbitrary time synchronisation control for fractional order chaotic systems with external disturbances

In this paper, adaptive synchronisation of fractional order chaotic systems with external disturbances is studied. For this purpose, first, a new integer order system is introduced and its convergence to zero exponentially within an arbitrary time is proven. Using this system, a novel adaptive exponential arbitrary time sliding mode controller is established to synchronise the fractional order chaotic systems. Then, to estimate the disturbance terms of the fractional systems an exponential arbitrary time disturbance observer is developed. The use of the disturbance observer can lead to simple controller design, low chattering control input, and more accurate response. Finally, a disturbance observer based sliding mode control is presented, that by incorporating the disturbance estimation in controller design ensures synchronisation of chaotic systems. The exponential arbitrary time synchronisation and the stability of the closed loop control system are confirmed using the Lyapunov theory. Simulation results on synchronisation of different fractional order systems, validate the proposed control schemes. It is noteworthy that the introduced adaptive sliding mode controllers can be used for controlling a wide variety of fractional order systems.

Fixed-time adaptive sliding mode-based active rollover prevention control of automated guided vehicles via improved super-twisting observer

As an important component of automated guided vehicle (AGV) active safety systems, the active rollover prevention (ARP) control has been widely studied. In this paper, a fixed-time adaptive sliding mode (FTASM) control strategy based on nested adaptive law (NAL) and improved super-twisting observer (ISTO) is developed for the AGV. Firstly, the lateral and roll motion dynamics of AGV are established, and the ARP problem is transformed into the yaw stability control with constraints. Subsequently, a faster fixed-time stable system-based FTASM composite controller is proposed to guarantee a fixed and faster convergence time of the yaw rate tracking error, such that the rollover stability will reach a region of permissible risk. The adoption of NAL enables the adaptive controller to automatically search the minimum switching gain satisfying the reaching condition of sliding mode, thus the conservative assumption constraint of the disturbance upper bound is released. In addition, an ISTO is developed to estimate the unknown disturbance to further improve the control robustness and attenuate the control chattering. The closed-loop stability analysis is rigorously given by Lyapunov theory. Finally, the performance of the proposed control strategy is validated by hardware-in-loop simulations with Adams and Matlab software and an actual steer-by-wire plant.

Enhanced chatter control in milling with electromagnetic actuator embedded in the tool holder

Enhanced chatter control in milling with electromagnetic actuator embedded in the tool holder

Process-integrated computerized numerical control: an analysis on process-machine coupling and feed scheduling

Computerized numerical controls (CNCs) have been invented for the automation of industrial processes. They are used, when the process to be automated is required to be exact and fast with repeatable quality. Originally, the use of CNCs was primarily focused on milling and drilling processes. Today, CNCs are utilized in a wide range of industrial processes due to the growing importance of automation. However, the integration of process information or adaptation to the needs of these processes to achieve advanced manufacturing with CNCs is difficult: Industrial CNCs are rather closed real-time machining systems. Today, process integration is possible, when the interaction between the process and the machine is decoupled in view of the bandwidth of machine dynamics and process dynamics. There are interfaces that allow for process-motivated control loops that are realized on top of the machine control loop (e.g. chatter control). Then, machine-integrated real-time control is not the focus. Besides, it is often possible to change desired values inside the control loop (position, velocity, acceleration) on an axes basis. In this case, adaptation to the process can be realized in each computation cycle. However, process dynamics and machine axes dynamics are generally treated separately. The same holds for extra actuators (e.g., in the spindle) for position control. This paper has two goals. First, it wants to create an understanding for different levels of process-machine coupling. Second, the problem of direct coupling of process dynamics and machine dynamics is focused. Machining systems design propositions as well as some examples for the coupling of process and machine dynamics in the CNC are given.

Adaptive trajectory tracking control of robotic manipulators based on integral sliding mode

AbstractThis paper proposes an adaptive control scheme with finite‐time convergent property based on integral sliding mode to achieve trajectory tracking control of rigid robotic manipulators. The novel adaptive gain can be adjusted automatically with the system disturbance, as long as the disturbance and its derivative are bounded without requiring more information. Therefore, the control chattering effect can be mitigated obviously. The global robustness of system is guaranteed by Lyapunov stability analysis. Finally, the simulation of a two‐link manipulator is given to show that the desired trajectory tracking performance is obtained with the proposed adaptive sliding mode approach.

An Advanced Control Method for Aircraft Carrier Landing of UAV Based on CAPF–NMPC

This paper investigates a carrier landing controller for unmanned aerial vehicles (UAVs), and a nonlinear model predictive control (NMPC) approach is proposed considering a precise motion control required under dynamic landing platform and environment disturbances. The NMPC controller adopts constraint aware particle filtering (CAPF) to predict deck positions for disturbance compensation and to solve the nonlinear optimization problem, based on a model establishment of carrier motion and wind field. CAPF leverages Monte Carlo sampling to optimally estimate control variables for improved optimization, while utilizing constraint barrier functions to keep particles within a feasible domain. The controller considers constraints such as fuel optimization, control saturation, and flight safety to achieve trajectory control. The advanced control method enhances the solution, estimating optimal control sequences of UAV and forecasting deck positions within a moving visual field, with effective trajectory tracing and higher control accuracy than traditional methods, while significantly reducing single-step computation time. The simulation is carried out using UAV “Silver Fox”, considering several scenarios of different wind scales compared with traditional CAPF–NMPC and the nlmpc method. The results show that the proposed NMPC approach can effectively reduce control chattering, with a landing error in rough marine environments of around 0.08 m, and demonstrate improvements in trajectory tracking capability, constraint performance and computational efficiency.

Robust adaptive decoupled-like sliding mode controller design based on iterative learning for overhead cranes

This paper proposes a novel model-free controller, considering the overhead crane systems cannot be accurately modeled and affected by external disturbances. The suggested scheme contains a variable exponential decoupled-like sliding mode control (VEDSMC), an adaptive power-reaching law (APRL), and a dynamic learning law-based iterative learning controller (DLLILC); they are combined in a parallel structure to form VEDSMC–APRL–DLLILC. The VEDSMC can effectively enhance the convergence speed of the displacement variables and improve the transient performance of the crane system. The APRL consists of an adaptive switching gain; it can estimate the optimal switching gain according to the unknown dynamics of the crane system and the disturbance, reduce the controller chattering, and guarantee the robustness. The DLLILC term can further improve anti-swing and positioning performance of the overhead crane without accurate information of the crane dynamics model in advance. Moreover, a nonlinear dynamic learning law (DLL) is developed to guarantee both convergence speed and steady-state accuracy in the learning process. Finally, the stability analysis of the designed controller is performed using Lyapunov theory and Barbalat’s lemma, and the simulation results illustrate the effectiveness of the suggested control scheme.

A novel fractional-order boundary layer fast terminal sliding mode controller for permanent magnet linear synchronous motor

This paper presents a novel fractional-order boundary layer fast terminal sliding mode (FBLFTSM) control method for high-precision tracking tasks of the permanent magnet linear synchronous motor (PMLSM). Specifically, a dynamic model of PMLSM with lumped uncertainty is established by considering the tracking task involving parameter variations, disturbance load, etc. Then, based on the dynamic model, a FBLFTSM control law is designed to guarantee higher tracking accuracy of the surface motion than the classical terminal sliding mode control even if the system suffers from unknown disturbance. Meanwhile, the fractional-order boundary layer control has the feature of “large error turns into large gain, small error turns into small gain,” which solves the contradiction between weak chattering and fast convergence in the integer-order boundary layer control and improves the dynamic performance of the system. Finally, the effectiveness of the control approach is verified by conducting tracking experiments on the cSPACE-based motor platform.

Dynamics analysis and chatter control of a polishing and milling nonideal flexible manipulator

Some robots are designed to be lightweight and flexible, enabling them to access small and challenging paths in various applications. These features enable robots to collaborate with humans in performing specific production tasks. However,the movement of the flexible manipulator can become self-excited when handling a cutting tool on a workpiece, which can lead to a control problem. This article presents a control solution for lightweight robotic manipulators with rotating tools, such as polishing and milling, using smart actuators. The control discretization method is also introduced to facilitate integration into digital controllers. The paper starts by describing the governing equations of the non-ideal flexible manipulator for polishing and milling and analysing its dynamic behavior. Subsequently, models for the controllers of the DC motor-only actuators and the hybrid (shape memory alloy and DC motors) actuators were formulated using shape memory alloy and a suboptimal control scheme known as the discrete state-dependent Riccati equation. The coupled system was analysed dynamically, and it was observed that it exhibits chaotic behavior. The results suggest that incorporating smart actuators into the motor group of the system could decrease the positioning error of the manipulator and significantly reduce the oscillation of the robot’s end-effector.

New Adaptive Super-Twisting Extended-State Observer-Based Sliding Mode Scheme with Application to FOWT Pitch Control

This paper details the transformation of the velocity or position-tracking problem of a class of uncertain systems using finite time stability control for first-order uncertain systems. A new composite extended-state observer sliding mode (ESOSM) scheme is proposed, which includes an adaptive super-twisting-like ESO and an adaptive super-twisting controller. The adaptive super-twisting controller is implemented through a barrier function-based second-order sliding mode algorithm. To further reduce control chattering and improve control performance, the adaptive super-twisting-like ESO, which employs high-order terms in the super-twisting algorithm to accelerate convergence, is designed to observe the lumped uncertainty in real time. The advantages of the proposed scheme are verified by a numerical example and application with regard to floating offshore wind turbine (FOWT) pitch control. Compared with proportional integral (PI) and adaptive super-twisting sliding mode (ASTSM) schemes, better results are obtained in velocity tracking and fatigue load suppression. For the FOWT pitch control application, the platform roll, pitch, and yaw are decreased by 3%, 2%, and 4%, respectively, compared to the PI scheme at an average turbulent wind speed of 17 m/s and turbulence intensity of 17.27%.

Design of event-based sliding mode controller for high-order systems via a reduced-order method

This paper investigates the event-triggered sliding mode control (SMC) problem using the reduced-order method for high-order systems subject to perturbation. To reduce the complexity of control design, a reduced-order approach is introduced by retaining the dominant mode of the system state. In addition, by injecting a power term, a new controller is constructed that aims to decrease the partial system control chattering. An event-triggered mechanism is designed by utilizing a time-varying trigger threshold; it is obvious that the proposed event-triggered strategy has fewer triggering times, larger triggering intervals between two neighboring events, and conserves system communication resources. Then, the existence of a positive lower bound on inter-event time is ensured to avoid the Zeno phenomenon. The effectiveness of the proposed approach is verified by magnetic control systems.

Chattering analysis of an electro-hydraulic backstepping velocity controller

This paper focuses on the chattering analysis in a backstepping controller used to drive an electro-hydraulic servo system. The chattering phenomenon, well known in sliding mode control, strongly reduces operating performance while causing premature wear of the system. Four cases are studied to highlight the factors influencing the chattering in the backstepping control. In the first case, the effect of the unmodeled fast servo valve dynamics is analysed by comparing a reduced-order backstepping controller with a full-order controller. The second case analyses the sensitivity to the tuning gains of the backstepping controller. The third case emphasises the influence of the parameter of sign function approximation. The last case analyses the sensitivity of the parameter of the time derivative of the virtual controls. The simulation results in the Matlab/Simulink show that the chattering is mitigated by an appropriate gains tuning but above all an appropriate calculation of the derivatives of the virtual controls, particularly for high-order systems.

Satellite Attitude Control Using Faulty Double Gimbal Variable Speed Control Moment Gyroscope

A rigid satellite attitude control requires stable finite-time attitude convergence in the presence of rotation unwinding, external disturbances, and actuator faults. To achieve this, a new nonsingular fast fixed-time sliding mode controller is proposed to ensure finite-time convergence independent of the initial conditions of the system. Rotation unwinding is addressed using the body and shadow pair of the Modified Rodrigues Parameters (MRPs). Convergence behavior of the states errors in the neighborhood of the MRPs switching surface is also addressed. Attitude control is achieved using a double-gimbal variable-speed control moment gyro (DGVSCMG). For the first time, a DGVSCMG having all possible electrical and mechanical faults is considered for control design. A novel nonsingular fast fixed-time anti-unwinding fault-tolerant sliding control using a new sliding surface is proposed. This eliminates switching of the sliding surfaces and minimizes control chattering. Four new propositions are proposed and proved to establish fast fixed-time global stability of the system for tracking maneuver in fault and fault-free conditions with anti-unwinding. Simulation results are presented and compared with existing fixed-time sliding control approaches. The results show superiority of the proposed anti-unwinding fault-tolerant fast fixed-time control for the tracking maneuver in terms of convergence time, energy efficiency, and fault tolerance.

Analysis of virtual inerter-based passive absorber for active chatter control

Analysis of virtual inerter-based passive absorber for active chatter control

The Non-Singular Terminal Sliding Mode Control of Underactuated Unmanned Surface Vessels Using Biologically Inspired Neural Network

Underactuated Unmanned Surface Vessels (USVs) are widely used in civil and military fields due to their small size and high flexibility, and trajectory tracking control is a critical research area for underactuated USVs. This paper proposes a trajectory tracking control strategy using the Biologically Inspired Neural Network (BINN) for USVs to improve tracking speed and accuracy. A virtual control law is designed to obtain the required virtual velocity for trajectory tracking control, in which the velocity error is calibrated to ensure that the position error converges to zero. To observe and compensate for unknown and complex environmental disturbances such as wind, waves, and currents, a nonlinear extended state observer (NESO) is designed. Then, a controller based on Non-singular Terminal Sliding Mode (NTSM) is designed to resolve the problems of singular value and controller chattering and to improve the controller response speed. A BINN is introduced to simplify the process of differentiation, reduce the input values of the initial state, and solve the problem of thruster input saturation. Finally, the Lyapunov stability theory is utilized to analyze the stability of the proposed algorithm. The simulation results show that the proposed algorithm has a higher trajectory tracking accuracy and speed than traditional methods.

Adaptive continuous twisting control for speed regulation in PMSM

ABSTRACT Traditional vector control strategies cannot eliminate the disturbances existing in permanent magnet synchronous motor (PMSM) systems while maintaining their dynamic performances. To address this issue, this paper proposes an adaptive continuous twisting (ACT) control method to further improve the control accuracy and anti-interference ability of the PMSM system. Firstly, a continuous twisting controller is designed to generate a continuous signal, which is utilised in the speed loop. It can guarantee that the tracking error of the speed regulation system finite-time converges to zero. This not only enhances the robustness of PMSM system but also effectively weakens the control chattering. Secondly, on this basis, an ACT controller is constructed to handle the disturbances with unknown bounds in PMSM systems. Finally, simulation and experimental results show that the proposed control method can improve the performances of PMSM system.