Prescribed Control Performance Research Articles

Online Active Fault Detection for Over-Actuated Systems With Prescribed Control Performance

In the field of fault detection, active fault detection for dynamic systems is an emerging research topic. By redesigning the control input, active fault detection can enhance fault detection performance. In this study, the online active fault detection problem is investigated for over-actuated systems, where the control input is designed by considering both the prescribed control performance and the fault detection performance. A two-stage input design architecture is constructed, where the first stage is a virtual controller design and the second stage is a control allocation design. In the first stage, the virtual control input is designed by utilizing a prescribed performance function to fulfill the control requirement. In the second stage, a differential evolution method is adopted to obtain an optimal control allocation algorithm for improving the fault detection performance. The designed control input can both improve fault detection performance and achieve the prescribed control performance. Two cases, including a numerical example and a manned submersible propulsion system, are studied to support theoretical results. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —In this study, the aim is to design a control input for over-actuated systems to obtain better fault detection performance while achieving prescribed control performance. To achieve it, a two-stage control input design architecture is constructed, where the first stage is a virtual controller design and the second stage is a control allocation design. In the first stage, choose a proper prescribed performance function and a sliding mode function to accomplish the transient and steady behavioral bounds on the tracking errors. In the second stage, design a special observer to generate the system residual signal, which is used for indicating system faults. Based on the residual signal, construct an index for the control allocation algorithm. Differential evolution algorithm is applied to obtain the optimal control allocation algorithm by maximizing the index. Thus the control allocation algorithm which can improve fault detection performance is designed. In this way, the input can improve fault detection performance without affecting system behavior. The proposed technique of this study can be applied to dynamic systems with input redundancy.

An Intelligent Controller Based on Extension Theory for Batteries Charging and Discharging Control

The main purpose of this paper is to develop an intelligent controller for the DC-link voltage of bidirectional soft-switching converters used in the batteries with equalizing charge and discharge control. To accelerate the equalizing charge and discharge speed of batteries, the DC-link voltage controller of the bidirectional converters is designed based on extension theory. Firstly, the photovoltaic module arrays (PVMAs) are used with the intelligent maximum power point tracker (MPPT) for supplying the power to the load side. Through the bidirectional soft-switching converters, the PVMAs will be allowed to carry out the uniform charging and discharging for the storage battery in order to achieve the intended energy storage and auxiliary power supply functions. In terms of the controller design, the quantitative design techniques are utilized, by which the P-I controller parameters will be designed for the converter when attempting to achieve the same control performance at different working points. As a next step, the aforesaid parameters are used together with the extenics theory. Based on the variation in the output power of the bidirectional converter and that in the voltage of the storage battery, it allows the system to find out the intended P-I controller parameters that will be approximate to the prescribed control performance when operating under different working conditions. As a result, the P-I controller will be provided with more efficient control flexibility and control performances. Finally, actual test results demonstrated that the response time of the proposed intelligent extension controller is shortened by 3% compared to the quantitative design of the proportional–integral (P-I) controller. Based on the proposed quantitative design of an intelligent controller for uniform charging and discharging management of batteries, the sustainable utilization of renewable sources of energy can be improved. At the same time, the better economic benefit of the energy preservation system is obtained. In addition, it also prolongs the life cycle of batteries, and then enhances the reliability of the batteries.

A Model-Free-Based Control Method for Robot Manipulators: Achieving Prescribed Performance and Ensuring Fixed Time Stability

This paper addresses three significant challenges in controlling robot manipulators: improving response time, minimizing steady-state errors and chattering, and enhancing controller robustness. It also focuses on eliminating the need for computing the robot’s dynamic model and unknown functions, as well as achieving global fixed-time convergence and the prescribed performance for the control system. To achieve these objectives, a fixed-time sliding mode function is designed, which uses transformation errors to achieve prescribed control performance, with adjustments made to the maximum overshoot, convergence time, and tracking errors to keep them within predefined bounds. Additionally, a radial basis function neural network (RBFNN) is used to eliminate the need for knowledge of the robot’s dynamical properties and uncertain terms, which also reduces negative chattering. Finally, a novel fixed-time terminal sliding mode control (TSMC) algorithm is developed for robot manipulators without using their dynamical model. The fixed-time stability of the control system is thoroughly demonstrated by applying Lyapunov criteria and conducting simulations on a robot manipulator to showcase its effectiveness.

Event-triggered fixed-time tracking of state-constrained surface ships under actuation saturation with prescribed control performance

This paper investigates the event-trigger-based fixed-time tracking control of a fully-actuated marine surface vehicle subject to full-state constraints, lumped disturbances, model uncertainties, and input saturation. The definition of the constrainedly practically fixed-time stability (CPFTS) is given first, and a sufficient condition for CPFTS is subsequently provided. To handle the input saturation, an auxiliary system is designed elaborately. Then applying the barrier Lyapunov function technology and blending an error transformation into backstepping scheme, the model-based adaptive controller and neural-network-based (NN-based) adaptive controller are proposed, respectively. Under these two controllers, the resulting closed-loop system signals are CPFTS and the settling time is not only independent of the system initial conditions but also assigned by users previously. Besides, it is proved that the tracking errors can converge to an arbitrarily small preset compact set within the preassigned time at a prescribed decay rate whilst all system states preserve the time-varying constraints.

Active Structural Control of Base-Isolated Building Using Equivalent-Input-Disturbance Approach With Reduced-Order State Observer

Abstract Active base isolation has been studied in the last few decades to improve the control performance of base isolation. As a two-degree-of-freedom active disturbance-rejection method, the equivalent-input-disturbance (EID) approach shows its validity for structural control. It uses a state observer to estimate the effect of disturbances on a control input channel. However, since the model of a base-isolated building has high degrees-of-freedom, the resulting control system has a high order. Thus, the use of a full-order state observer results in the complexity of a control-system implementation. To solve this problem, this paper presents an EID control system that uses a reduced-order state observer (ROSO) to reduce the expense of control-system implementation and ensure system reliability. First, the condition of using an ROSO in an EID control system is derived, and the configuration of an ROSO-based EID control system is presented. Next, the concept of perfect regulation is used to design the gain of the state observer. A stability condition of the system with prescribed control performance is derived in the form of a linear matrix inequality (LMI) that is used to design the gain of the state feedback. Finally, the seismic control of a base-isolated building demonstrates the validity of the method.

Event-triggered observer-based H ∞ control of switched linear systems with time-varying delay

This paper is devoted to study the issue of event-triggered observer-based control of switched linear systems subject to time-varying state delay and exogenous disturbance. Firstly, an observer-based event-triggered controller is provided under the proposed event-triggered mechanism. Then, based on the average dwell time scheme and Jensen's Inequality technique, delay-dependent less conservative sufficient conditions in terms of Linear Matrix Inequalities (LMIs) are obtained to guarantee the resulting augmented switched systems is exponential stabilisation and satisfies a prescribed control performance. Furthermore, observer-based event-triggered controller is designed, and it is shown that there exists a positive lower bound of inter-event intervals. Finally, numerical example and comparison results are provided to illustrate the effectiveness and advantages of the proposed method.

Continuous Finite-Time Torque Control for Flexible Assistance Exoskeleton with Delay Variation Input

SUMMARYAccurate torque control is a critical issue in the compliant human–robot interaction scenario, which is, however, challenging due to the ever-changing human intentions, input delay, and various disturbances. Even worse, the performances of existing control strategies are limited on account of the compromise between precision and stability. To this end, this paper presents a novel high-performance torque control scheme without compromise. In this scheme, a new nonlinear disturbance observer incorporated with equivalent control concept is proposed, where the faster convergence and stronger anti-noise capability can be obtained simultaneously. Meanwhile, a continuous fractional power control law is designed with an iteration method to address the matched/unmatched disturbance rejection and global finite-time convergence. Moreover, the finite-time stability proof and prescribed control performance are guaranteed using constructed Lyapunov function with adding power integrator technique. Both the simulation and experiments demonstrate enhanced control accuracy, faster convergence rate, perfect disturbance rejection capability, and stronger robustness of the proposed control scheme. Furthermore, the evaluated assistance effects present improved gait patterns and reduced muscle efforts during walking and upstair activity.

Fixed-time adaptive event-triggered tracking control of uncertain nonlinear systems

This paper addresses the event-triggered tracking control problem of nonlinear systems with predefined performance in a fixed-time environment. Unlike the existing event-triggered schemes, the developed triggering mechanism only compares the difference between the signal to be transmitted and the holding signal. The proposed control method also considers the response of the triggering mechanism. In order to achieve prescribed control performance under the condition of unmatched uncertainties and uncertain gain functions, a new adaptive fixed-time control strategy is proposed by introducing an error transformation scheme. The proposed control method under the event-triggered framework can reduce the amount of control signals transmitted while ensuring that the system output tracking error converges to a small neighborhood close to zero within a fixed-time frame. The results of two examples, including comparative studies and a practical application, show the effectiveness of the proposed control method.

HGO-based adaptive super-twisting sliding mode power level control with prescribed performance for modular high-temperature gas-cooled reactors

This paper proposes a high-gain observer-based adaptive super-twisting sliding mode control strategy with prescribed performance (HGO-ASTSMCS-PP) for the power level of a modular high-temperature gas-cooled reactor (MHTGR). The dynamic model of the MHTGR is firstly described. By using this established model, a high-gain observer is constructed to recover the unmeasured states including relative density of delayed neutron precursor and reactor core temperature in real time. On the basis of the recovering values from the HGO, an adaptive super-twisting sliding mode control method with prescribed performance is designed. The super-twisting sliding mode control approach is adopted to improve control performance of power level for a MHTGR and suppress high-frequency chattering effects simultaneously. An adaptive mechanism is introduced to tune the control gains online so as to overcome the overestimation of the unknown disturbance boundary. In addition, by error transformation and introduction of performance function, the prescribed control performance of power level is guaranteed, which implies that the desirable convergence rate, steady power error, and maximum overshoot can be prescribed in advance. It is verified through Lyapunov stability theory that the overall closed-loop control system is globally uniformly ultimately bounded (GUUB). Finally, simulation and comparison results are presented to reveal the effectiveness of the proposed control scheme in terms of the steady and dynamic performance.

불확실 일반 선형 시스템의 레규레이션 제어를 위한 사전 제어 성능을 갖는 개선된 연속 변환된 적분 슬라이딩 모드 제어

불확실 일반 선형 시스템의 레규레이션 제어를 위한 사전 제어 성능을 갖는 개선된 연속 변환된 적분 슬라이딩 모드 제어

Adaptive coordinated control of uncertain free-floating space manipulators with prescribed control performance

The paper proposes an adaptive coordinated control scheme on free-floating space manipulators at the dynamic level, with kinematic and dynamic uncertainties. The free-floating space manipulator can be controlled to realize the end-effector trajectory tracking task and the spacecraft attitude regulation task simultaneously, based on the carefully designed prescribed performance error transformations and the reaction null space. In face of nonlinearly parametric feature of the uncertain free-floating space manipulators, a novel attractive manifold control method is proposed by introducing the nonlinear filters on dynamics of the free-floating space manipulators. The parameter estimation error terms can converge to zero, independent of persistent excitation conditions. The proposed adaptive coordinated control scheme can guarantee that both the end-effector tracking error and the spacecraft attitude regulation error possess the prescribed control performances, in the presence of the nonlinearly parametric feature and the nonzero linear and angular momenta of the free-floating space manipulators. The simulation results show the effectiveness of the proposed control scheme.

An Improved Continuous Integral Variable Structure Systems with Prescribed Control Performance for Regulation Controls of Uncertain General Linear Systems

An Improved Continuous Integral Variable Structure Systems with Prescribed Control Performance for Regulation Controls of Uncertain General Linear Systems

Robust control with finite frequency specification for uncertain discrete linear repetitive processes

This paper is dedicated to the study of robust stability and controller synthesis for discrete linear repetitive processes with polytopic uncertainty. In the robust control domain, conditions based on parameter dependent Lyapunov functions are proposed in order to reduce the conservatism related to uncertainty problems. The solution is a class of Lyapunov functions that depends in a polytopic way on the uncertain parameters and that can be derived from linear matrix inequality conditions. Nevertheless, in many cases in practice, the frequency range of reference signals, noises and disturbances are known beforehand. Therefore, performing controller synthesis in the full frequency range is not practically suited and may introduce conservatism to some extent. Based on generalized Kalman–Yakubovich–Popov Lemma, a finite frequency controller is derived for uncertain discrete linear repetitive processes which are the most investigated class of 2D systems. Hence, the designer can specify a frequency range where the prescribed control performance is required, where, for example, this range could be determined by inspection of frequency spectrums of the available signals.

Quantised output feedback control via limited capacity communication networks

This article addresses the output feedback stability problem for single-input single-output (SISO) linear systems with quantised measurements of the plant output, where sensors and controllers are connected via errorless digital channels carrying a finite number of bits per unit time. The main idea here is to present a lower bound of data rates, above which there exists a quantisation, coding and control scheme to guarantee both stability and a prescribed control performance of the unstable plant. A quantisation and coding scheme, which is based on the distribution of measurements and the dynamics of the plant, is proposed. The proof techniques rely on both information-theoretic and control-theoretic tools. An illustrative example is given to demonstrate the effectiveness of the proposed scheme.

Quantized Feedback Control for Networked Control Systems Under Communication Constraints

This paper investigates the feedback stabilization problem for networked control systems (NCSs) with unbound process noise, where sensors and controllers are connected via noiseless digital channels carrying a finite number of bits per unit time. A sufficient condition for stabilization of NCSs, which relies on a variable-rate digital link used to transmit state measurements, is derived. A lower bound of data rates, above which there exists a quantization, coding and control scheme to guarantee both stabilization and a prescribed control performance of the unstable discrete-time plant, is presented. An illustrative example is given to demonstrate the effectiveness of the proposed method.

Modeling and control of soft‐switching mode rectifiers with power factor correction

The small‐signal modeling and quantitative controller design of a soft‐switching mode rectifier (SSMR) is presented in this paper. First, a single‐phase boost‐type SSMR is formed from the traditional boost‐type switching mode rectifier (SMR) with auxiliary resonant branch to achieve zero‐voltage‐transition (ZVT) soft switching for the main and auxiliary switches. For the current‐controlled pulse width modulation (PWM) scheme, the small signal model of the current control loop is obtained using a statespace averaging method and the parameters of the controller are found based on a frequency response approach. As for the voltage control loop design, the dynamic model of the proposed SSMR is first derived using averaging method for two‐time‐scale (AMTTS) and averaged power method. Then, a quantitative procedure is proposed to find the parameters of the voltage controller according to the prescribed control performance. The accuracy of the derived SSMR dynamic model and the effectiveness of the proposed controller are demonstrated by some simulation and experimental results.

Microprocessor-Based Adjustable-Speed DC Motor Drives Using Model Reference Adaptive Control

Model reference adaptive control (MRAC) is applied to microprocessor-based adjustable-speed dc motor drives. The algorithm of the MRAC is based on the linear model following control (LMFC) and is the combination of the adaptive controller with the LMFC. The MRAC-based speed controller allows the indistinctness and/or inaccuracy in the motor and load parameters in the system design stage. It also maintains the prescribed control performance in the presence of the motor parameter perturbations and the load disturbances. The experimental setup is constructed using a microprocessor. The experimental results confirm the useful effects of the MRAC-based speed controller.

パルスＭＩＧ溶接における溶融池の画像処理とデジタル制御

It is important as a basis of research in automatic arc welding to control the weld pool shape against the disturbance and the variation of system parameters. For this purpose it is useful to control the weld pool width. A basic visual robot is proposed for observing and controlling the weld pool shape by using the pulsed current.It has been difficult to observe the weld pool with a TV camera, since the arc light is too strong to watch the molten metal under the arc. The authors tried to make periodically the current low enough to watch clearly the weld pool with CCD (Charge coupled device) camera without after image.The weld pool is recognized by taking advantage of the feature on the brightness of the weld pool and its outskirts. A personal computer calculates the weld pool width and area in real time. The authors study the transient response of the weld pool width and area.The welding current is determined to get a desired response of the weld pool. It is shown how to determine the digital controller characteristic. Small variations of system parameter during operation caused by the change in the base metal thickness, heat conductivity, temperature rise are allowed while the prescribed control performance is maintained.Experiments demonstrate the good controllability of the adjustable weld pool formation with the digital controller.