Higher Steady-state Precision Research Articles

A fast fixed-time backstepping control method for systems with mismatched disturbances

In this paper, a fast fixed-time backstepping control approach is developed for systems with mismatched disturbances. A novel fast fixed-time disturbance observer (FFTDO), which is convergent within fixed time regardless of initial conditions, is designed to efficiently estimate and compensate the disturbances. On the basis of FFTDO, a novel fast fixed-time backstepping control scheme is proposed, which can guarantee fast fixed-time convergence and high steady-state precision. In addition, a novel fixed-time filter is used to circumvent the problem of “explosion and complexity,” and to ensure overall fixed-time convergence. The fixed-time stability of the closed-loop system under the proposed controller is proved by the Lyapunov stability theory. The simulation results are carried out to confirm the feasibility and superiority of the proposed control strategy.

Backstepping Control Design in Conjunction with an EKF-based Sensorless Field-Oriented Control of an IPMSM

The collector and brushless electronic commutation machines have gained widespread utilization in industrial applications. Among these machines, internal permanent magnet synchronous motors (IPMSMs) have become increasingly popular due to their numerous advantages, including high torque/current and torque/inertia ratios, robust construction, high efficiency, and reliability. However, the incorporation of position sensors in IPMSMs has introduced challenges concerning their application, performance, mass production, and cost. Consequently, the implementation of sensorless control techniques has become essential in drive systems and various applications. This paper proposes a backstepping control approach for achieving speed sensorless control of IPMSMs, employing an extended Kalman filter (EKF). The first step involves developing a comprehensive nonlinear dynamical model of the IPMSM in the direct and quadrature (d-q) rotor frame and obtaining its corresponding state-space representation. Subsequently, backstepping controllers for rotor speed and current tracking are designed to ensure precise tracking and anti-disturbance performance. These controllers are integrated into the field-oriented control (FOC) scheme. The Lyapunov stability theorem is employed to guarantee the asymptotic stability condition of the backstepping controller. To address the challenge of estimating immeasurable mechanical parameters of the IPMSM and accurately tracking the system states, an EKF is designed. This filter enables the estimation of mechanical parameters and achieves high steady-state precision within a finite time. The effectiveness of the proposed methodology is demonstrated through simulations conducted under various dynamic operating conditions, including sudden torque load changes, command speed changes, and parameter variations.

Fixed-time terminal sliding mode control for uncertain robot manipulators

This paper proposes a fixed-time tracking control for robot manipulators in the presence of parametric uncertainties and disturbances. An auxiliary function is first proposed for constructing a fixed-time sliding manifold. Benefited from this fixed-time sliding manifold, a singularity-free robust control is proposed to evade the effects of algebraic loop problem of the commonly-used sliding mode controls (SMC). The key advantages of the proposed approach are: (i) exact fixed-time stability featuring the convergence time does not relate to the initial conditions and is acquired in advance; (ii) the singularity and algebraic loop problems are eliminated completely; (iii) a simple and intuitive control structure is used for easy implementation of trajectory tracking control for uncertain robot manipulators with faster transient and higher steady-state precision. Simulations and experimental comparisons validate the improved tracking performance of the proposed approach.

Proximate fixed-time fault-tolerant tracking control for robot manipulators with prescribed performance

This paper presents a proximate fixed-time fault-tolerant prescribed performance tracking control for robot manipulators with actuator faults, parametric uncertainties, and bounded disturbances. An exact convergent fixed-time prescribed performance function is first introduced. A proximate fixed-time fault-tolerant prescribed performance control (FTPPC) is proposed within the framework of terminal sliding mode control. Lyapunov stability is employed to prove the position tracking error can be ensured proximate fixed-time stability and prescribed performance with an exact convergence time. Advantages of the proposed FTPPC include proximate fixed-time prescribed performance guarantees featuring faster transient and higher steady-state precision and strong robustness to actuator faults, parametric uncertainties, and bounded disturbances. Simulations and experiments utilizing artificial faults demonstrate the improved performances of the proposed approach.

Global Finite-Time Stabilization of Spacecraft Attitude With Disturbances via Continuous Nonlinear Controller

In this paper, a robust continuous controller is investigated to solve the global finite-time attitude stabilization problem of rigid spacecraft system subject to multiple disturbances. The system order is firstly increased by derivation and the derivative of the actual torque is regarded as the virtual control law to be designed. Then, a super-twisting differentiator is constructed to provide finite-time angular acceleration estimations. Finally, based on the estimated angular accelerations, a discontinuous set stabilization control law is designed as the virtual controller. The actual continuous controller is obtained by integrating the discontinuous one. Rigorous proof and stability analysis are presented based on Lyapunov analysis. Compared with most of the existing finite-time control approaches in spacecraft systems, the proposed continuous control scheme guarantees the finite-time set stability of the closed-loop system. Moreover, the system states can converge to the equilibria even in the presence of derivative-bounded disturbances. Simulation studies of the proposed controller are illustrated to demonstrate the strong disturbance rejection ability, fast convergence rate, and high steady-state precision.

Distributed fixed-time sliding mode control of time-delayed quadrotors aircraft for cooperative aerial payload transportation: Theory and practice

This paper investigates a cooperative fixed-time control for networked-delayed and disturbed quadrotors in payload transportation missions. First, the input time-delayed tracking error system is adequately transformed into a delay-free system via Artstein’s reducing transformation. Second, a novel Distributed Cooperative Fixed-Time Stable Control Protocol (DCFTSCP) is proposed for the multi-quadrotor system to stabilize the geometrical spatial formation while carrying the payload. Furthermore, a disturbance observer is incorporated into the control framework to counteract the lumped disturbances and achieve the transportation task with a minimal swing. Overall, the designed DCFTSCP is able to stabilize the delayed tracking states at the origin in fixed-time uniformly to the Initial Conditions (ICs). It is worth mentioning that the proposed controller belongs to the homogeneous sliding mode control class. The reported related works rely on the bi-limit approximation method to prove the fixed-time convergence of the states. Nevertheless, this method suffers from a crucial shortcoming where it is unable mathematically to provide an explicit expression on the settling (convergence) time. In contrast, in the present study, the stability analysis is thoroughly investigated based on the algebraic Lyapunov tools, namely, Algebraic Lyapunov Equation (ALE) and Lyapunov Quadratic Function (LQF). Consequently, the upper-bound on the convergence-time is explicitly derived for the first time for time-delayed quadrotors aircraft used in cooperative payload transportation. MATLAB® simulations and real flight experiments are conducted to corroborate the theoretical studies of the paper. Overall, the results show that the proposed control protocol yields performance improvement regarding fixed-time tracking stability featuring fast transient, strong robustness, and high steady-state precision. In addition, the undesirable chattering problem of regular linear sliding mode control is noticeably attenuated. Furthermore, unlike conventional terminal sliding mode control techniques, the control input is singularity-free. Finally, several challenging issues in cooperative fixed-time control for networked-delayed quadrotors are highlighted for future research.

A novel ship path following method in inland waterways based on adaptive feedforward PID control

Given the complex and time-varying external disturbances of inland waterways, designing an accurate path following controller is challenging. Based on the traditional PID controller, combined with the servo system model and the lead compensator, an adaptive feedforward PID controller for path following of ships in inland waterways is designed considering ship maneuverability and external disturbances. Simulations of a ship in a curved channel in different scenarios are carried out to illustrate the effectiveness of the proposed path following method. Compared with the traditional path following controller, the proposed one based on adaptive feedforward PID control has favorable relative stability, anti-interference ability and high steady-state precision in inland waterways.

Observer-based fixed-time continuous nonsingular terminal sliding mode control of quadrotor aircraft under uncertainties and disturbances for robust trajectory tracking: Theory and experiment

This paper solves an accurate fixed-time attitude and position control problems of a quadrotor UAV system. The aircraft system is subject to nonlinearities, parameter uncertainties, unmodeled dynamics, and external time-varying disturbances. To deal with the under-actuation problem of the quadrotor’s dynamics, a hierarchical control structure with an inner–outer loop framework is adopted for the flight control system design. Robust nonlinear control strategies for attitude and position control are innovatively proposed based on a new continuous nonsingular terminal sliding mode control (CNTSMC) scheme. A full-order homogeneous terminal sliding surface is designed for the attitude and position states in such a way that the sliding motion is fixed-time stable independently of the system’s initial condition. Hence, this contributes to enhancing the control system robustness. A disturbance observer-based control (DOBC) approach is developed to stabilize the inner rotational subsystem (attitude-loop). This compounded control structure integrates a finite-time observer (FTO) and the CNTSMC scheme. The FTO observer is incorporated into the control framework to cope with the strong perturbations. An output-feedback control approach is adopted for the outer translational subsystem (position-loop) to ensure a velocity-free control. In this context, the CNTSMC scheme is combined with a fixed-time extended state observer (FXESO) to achieve an active disturbance rejection control (ADRC) by estimating and canceling the lumped disturbances. Therefore, within the developed control approach including the robust CNTSMC scheme, DOBC, and ADRC strategies, robust and accurate trajectory tracking control can be achieved despite uncertainties and disturbances. Stability analysis of the closed-loop system is rigorously investigated by using the Lyapunov theorem, bi-limit homogeneous theory, and the notion of input-to-state stability (ISS). Extensive experimental tests under the influence of various disturbances are conducted to corroborate the theoretical findings. To this end, an effective model-based design (MBD) framework is established to implement the developed control algorithms in real autopilot hardware. Furthermore, processor-in-the-loop (PIL) experiments are also carried out within the MBD framework. A comparative study is made involving our control algorithms and other control strategies. Overall, the obtained results show that the synthesized control system yields performance improvement regarding fixed-time tracking stability featuring fast transient, strong robustness, and high steady-state precision. Besides, the chattering effect of regular linear sliding mode control (LSMC) is significantly alleviated. Moreover, unlike conventional TSMC, the control input shows no singularity.

Development of Optimized Cooperative Control Based on Feedback Linearization and Error Port-Controlled Hamiltonian for Permanent Magnet Synchronous Motor

The conflict between dynamic rapidity and steady-state accuracy is a crucial factor hindering the performance improvement of motor control system. To overcome the issue, this article proposes an optimized cooperative control combining feedback linearization (FBL) and error port-controlled Hamiltonian (EPCH) for permanent magnet synchronous motor (PMSM). First, FBL and EPCH are separately designed to obtain good dynamic and steady-state performances. Then, considering the individual advantages of FBL and EPCH, a cooperative strategy based on the real-time position error is applied to realize the smooth switching between the two methods, so that each method is utilized efficiently within the corresponding operating range. In addition, the particle swarm optimization (PSO) algorithm is introduced to properly select the controller parameters. Thus, an optimized cooperative control method, which takes into account both fast dynamic response and high steady-state precision, is developed for PMSM drives. The experimental results are finally given to illustrate the effectiveness and superiority of the proposed method.

Design of high precision and high power bidirectional adjustable power supply

Abstract ITER (International Thermonuclear Experimental Reactor) sensor steady-state test platform needs high power supply with high steady-state precision output voltage. In the field of high voltage power supply applications, there is often a contradiction between the power supply capability and the switching frequency of high power switching devices. Limited by switching loss, the switching frequency of high power switching devices is low, which will generate a lot of harmonic in the output voltage. In order to meet the requirement of power supply for high-precision output voltage, the design of high power supply adopts the method of combining H-bridge cascaded topology with carrier phase shift PWM control scheme, which can effectively improve output voltage waveform in the design of high power supply. The harmonic analysis and simulation are carried out, and the experimental results verify the validity of the experimental scheme.

Adaptive Interval Type-2 Fuzzy Fixed-time Control for Underwater Walking Robot with Error Constraints and Actuator Faults Using Prescribed Performance Terminal Sliding-mode Surfaces

Underwater walking robot (UWR) is a kind of autonomous underwater vehicles which can walk underwater. In this work, the fixed-time tracking control problem of UWR with external disturbances, error constraints, and actuator faults is investigated. An interval type-2 fuzzy neural network approximator is designed to tackle nonlinear uncertainties, and a novel prescribed performance terminal sliding-mode surface is proposed to handle error constraints. Furthermore, two fault-tolerant controllers are given, where one is nonsingular and the other has higher steady-state precision. According to Lyapunov theory, the proposed controllers can guarantee that system states will converge to the expected values in a fixed time. Simulation results demonstrate the effectiveness of the proposed control strategies.

Research on Multi-Channel Semantic Fusion Classification Model

In this work, we propose a multi-channel semantic fusion convolutional neural network (SFCNN) to solve the problem of emotional ambiguity caused by the change of contextual order in sentiment classification task. Firstly, the emotional tendency weights are evaluated on the text word vector through the improved emotional tendency attention mechanism. Secondly, the multi-channel semantic fusion layer is leveraged to combine deep semantic fusion of sentences with contextual order to generate deep semantic vectors, which are learned by CNN to extract high-level semantic features. Finally, the improved adaptive learning rate gradient descent algorithm is employed to optimize the model parameters, and completes the sentiment classification task. Three datasets are used to evaluate the effectiveness of the proposed algorithm. The experimental results show that the SFCNN model has the high steady-state precision and generalization performance.

Fixed-Time Inverse Dynamics Control for Robot Manipulators

This paper concerns with global fixed-time trajectory tracking of robot manipulators. A simple nonlinear inverse dynamics control (IDC) is proposed by using bi-limit homogeneity technique. Lyapunov stability theory and geometric bi-limit homogeneity technique are employed to prove global fixed-time tracking stability. It is proved that there exists a convergence time that is uniformly bounded a priori and such a bound is independent of the initial states such that the tracking errors converge to zero globally. The appealing advantages of the proposed control are that it is fairly easy to construct and has the global fixed-time tracking stability featuring faster transient and higher steady-state precision. Numerical simulation comparisons are provided to demonstrate the improved performance of the proposed approach.

Design of Charging Module for DC Charging Pile Based on Two Level Power Conversion

In order to to solve the demand of electric vehicle for high power and high performance DC charging pile, this paper presents a design scheme for charging module of DC charging pile based on two stage power transformation. The pre stage part of the scheme is the VIENNA rectifier controlled by hysteresis current and the phase shift full bridge converter controlled by the average current. The parameters of the main circuit and the control circuit are calculated. At last, the simulation research on the three conditions of the rated load, two times overload and load fluctuation is carried out. The results show that the charging module can achieve high power factor, low harmonic distortion rate, zero voltage switch, low loss operation, strong carrying capacity, good dynamic performance, high steady state precision and simple and easy operation.

Simple relay non‐linear PD control for faster and high‐precision motion systems with friction

This study addresses the problem of robust faster and high-precision positioning of uncertain one-degree-of-freedom mechanical systems with friction. A very simple relay non-linear proportional-derivative (PD) controller is proposed. Global asymptotic positioning stability is proven by Lyapunov's direct method invoking Barbalat's lemma. The appealing features of the proposed control are that it is fairly easy to construct with simple intuitive structure and without reference to modelling parameter and the ability to ensure global asymptotic positioning stability featuring faster transient and higher steady-state precision. Simulations and experiments demonstrate the effectiveness and improved performance of the proposed approach.

Fuzzy Adaptive Repetitive Control for Periodic Disturbance with Its Application to High Performance Permanent Magnet Synchronous Motor Speed Servo Systems

For reducing the steady state speed ripple, especially in high performance speed servo system applications, the steady state precision is more and more important for real servo systems. This paper investigates the steady state speed ripple periodic disturbance problem for a permanent magnet synchronous motor (PMSM) servo system; a fuzzy adaptive repetitive controller is designed in the speed loop based on repetitive control and fuzzy information theory for reducing periodic disturbance. Firstly, the various sources of the PMSM speed ripple problem are described and analyzed. Then, the mathematical model of PMSM is given. Subsequently, a fuzzy adaptive repetitive controller based on repetitive control and fuzzy logic control is designed for the PMSM speed servo system. In addition, the system stability analysis is also deduced. Finally, the simulation and experiment implementation are respectively based on the MATLAB/Simulink and TMS320F2808 of Texas instrument company, DSP (digital signal processor) hardware platform. Comparing to the proportional integral (PI) controller, simulation and experimental results show that the proposed fuzzy adaptive repetitive controller has better periodic disturbance rejection ability and higher steady state precision.

Novel nonsingular fast terminal sliding mode control for a PMSM chaotic system with extended state observer and tracking differentiator

A novel nonsingular fast terminal sliding mode (NNFTSM) control strategy based on the extended state observer (ESO) and the tracking differentiator (TD) is developed for the stabilization and tracking of the uncertain perturbed permanent magnet synchronous motor (PMSM) chaotic system. The proposed NNFTSM surface not only makes the system state rapidly converge to the equilibrium point in finite time with high steady-state precision, but also avoids the singular phenomenon. Furthermore, the ESO which does not rely on the mathematical model of the system is used for estimating uncertainties and disturbances to decrease the chattering caused by the big switching gain through compensating controller. Meanwhile, the TD is introduced to arrange the transition process for the reference input signal to realize the coordinated control between the rapidity and overshoot, and to decrease the initial impulse of the manipulative variable. The simulation results demonstrate that the proposed control scheme can flexibly restrain chaos which provides good dynamic and static performances, and has strong robustness to parameter variations and external load disturbances with low chattering.

High-Order Terminal Sliding-Mode Observer for Parameter Estimation of a Permanent-Magnet Synchronous Motor

This paper proposes a terminal sliding-mode (TSM) observer for estimating the immeasurable mechanical parameters of permanent-magnet synchronous motors (PMSMs) used for complex mechanical systems. The observer can track the system states in finite time with high steady-state precision. A TSM control strategy is designed to guarantee the global finite-time stability of the observer and, meanwhile, to estimate the mechanical parameters of the PMSM. A novel second-order sliding-mode algorithm is designed to soften the switching control signal of the observer. The effect of the equivalent low-pass filter can be properly controlled in the algorithm based on requirements. The smooth signal of the TSM observer is directly used for the parameter estimation. The experimental results in a practical CNC machine tool are provided to demonstrate the effectiveness of the proposed method.

Research of Double Internal Model Control for High Speed Spindle

Based on the internal model control theory and combined the structural characteristics of high speed spindle, the control method of high speed spindle is discussed. And the view of applying the double internal model control to high speed spindle is put forward. Then controllers of current, flux linkage and speed are designed. According to the double internal model control plan, its simulation model is set up. Simulation results indicate that the double internal model control has better dynamic response curve, shorter response time, higher steady state precision by comparing with the vector controller.

Research on CNC Machine Tool Fuzzy Immune PID Position Controller

CNC machine tool position controller connects control system with actuating mechanism and often adopts traditional PID control technology. But the traditional PID technology is hard to achieve rapid adjustment and lesser overshoot at the same time. Consequently, the CNC machine tool fuzzy immune PID position controller based on immunity feedback control theory is developed in the study. The experiment results show that the developed controller can achieve shorter adjust time, better rapidity and higher steady-state precision in contrast to traditional PID position controller.