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Due to the lightly damped resonance and intrinsic nonlinearities, it is difficult for the piezoactuated nanopositioning stage to realize high-bandwidth and high-accuracy control. To handle these limitations, in this work, a dual-loop control scheme based on state-feedback-based modal method is designed to both actively damp and stiffen the resonant mode and to suppress the effects of nonlinearities of the piezoactuated nanopositioning stage. In this scheme, the state-feedback-based modal controller is first designed in the inner loop to enlarge both the damping ratio and natural frequency of the first resonant mode. Then, a proportional–integral (PI) controller is utilized in the outer loop for eliminating the tracking errors caused by other disturbances and nonlinearities including hysteresis and creep. To maximize the control bandwidth of system under the proposed dual-loop scheme, an optimization method is thus proposed for simultaneously tuning the parameters of the inner and the outer loop controllers. Finally, to validate the proposed dual-loop control scheme, comparative experiments are carried out on a piezoactuated nanopositioning stage. Results demonstrate that the proposed control scheme improves the bandwidth of the system from 497 Hz (with PI control) and 1543 Hz (with a commonly used positive acceleration, velocity, and position damping control and a PI controller) to 6546 Hz, which is 664 Hz larger than the first resonant frequency of the original system, validating the effectiveness of the proposed dual-loop scheme on high-bandwidth control. Note to Practitioners—The demand of high-bandwidth and high-accuracy piezoactuated nanopositioning stages increases rapidly. However, the lightly damped resonance of the mechanism and the intrinsic nonlinearities of the piezoelectric actuator limit the tracking performance of the stage. A dual-loop control structure is adopted in this work to improve the tracking performance of the nanopositioning stage. Different from most of the vibration control methods proposed in the literature which aimed only at improving the damping ratio, a state-feedback-based modal controller is designed in the inner-loop for improving both the damping ratio and the stiffness of the system. This task is realized by re-placing the resonant poles of the system to the optimized location. The outer-loop controller adopts the high-gain PI control for eliminating the tracking errors. More importantly, in order to realize the high-bandwidth and high-accuracy control, a numerical optimization method is proposed for simultaneously tuning the parameters of the controllers in inner and outer loops. The controller design is simple, and it can be applied to other systems with second or higher order in which the first resonant mode dominates the system dynamics. [ABSTRACT FROM AUTHOR]

Odd-harmonic repetitive control (ORC) has been successfully applied to improve the triangular trajectory tracking performance of nanopositioners. However, the conventional ORC tends to amplify the tracking errors at frequencies other than the odd-harmonic components, mainly the even harmonics of the fundamentals of the intended triangular trajectory to be tracked. Due to the influence from the hysteresis nonlinearity of the piezoelectric actuator, this would result in significant tracking errors. To overcome this limitation, this article proposes an enhanced odd-harmonic repetitive control (EORC) using the spectrum-selection filtering scheme to improve the loop-shaping property of the ORC. This effectively eliminates the problem of amplifying the tracking errors while preserving the advantages of the conventional ORC, such as fast convergence speed and low computation cost. The EORC is combined with a proportional–integral tracking controller to improve the tracking performance. The controller design, stability analysis, and performance evaluation are presented. The experimental results demonstrating the effectiveness of the proposed EORC-based control scheme are presented showing the excellent tracking of triangular trajectories with fundamental frequencies up to 1000 Hz. Moreover, a reduction in rms tracking errors by up to 52% is achieved. Note to Practitioners—The high-speed atomic force microscopy (AFM) plays an increasingly vital role in observing and manipulating objects at the nanoscale. In the raster scanning of AFMs, the most challenging issue is the triangular trajectory tracking of nanopositioning stages with high precision. Although the odd-harmonic repetitive control (ORC) has been successfully applied to improve the tracking performance, the conventional ORC would amplify the tracking errors distributed at the frequencies other than the odd harmonics, especially those at the even harmonics, resulting from the inherent complicated hysteresis nonlinearity. This problem of amplifying the tracking errors would lead to larger tracking errors, deteriorating the performance of AFM imaging. To address this issue, this article proposes an enhanced ORC using the spectrum-selection filtering scheme to improve the loop-shaping property of the ORC, so as to eliminate the problem of amplifying the tracking errors while preserving the advantages of the conventional ORC, such as fast convergence speed and low computation cost. The experimental results show that, with this simple modification, the positioning errors are reduced greatly, all-the-while preserving the benefits of the conventional ORC scheme– fast convergence speed and low computation cost. In terms of tracking accuracy and the simple structure, this development can be easily implemented to other systems that challenge from the tracking accuracy under ORC scheme. [ABSTRACT FROM AUTHOR]

This paper is concerned with the analysis and integrated design of a type of observer-based fault detection (FD) system for general nonlinear processes. To this end, the existence and design condition for this type of nonlinear observer-based FD systems is first introduced. In this context, the integrated design scheme is investigated by dealing with the design condition with the aid of Takagi–Sugeno (T–S) fuzzy dynamic modeling technique. To be specific, the universal T–S fuzzy observer-based residual generator is developed via fuzzy Lyapunov functions. Subsequently, an integrated observer-based FD scheme is proposed with an embedded dynamic threshold, which is generated to meet the real-time FD requirements from industrial processes. In the end, a numerical example and case simulation study on a continuous stirred tank heater process are performed to show the application of the proposed method. [ABSTRACT FROM PUBLISHER]

This paper addresses real-time fault-tolerant control (FTC) of nonlinear systems by adopting the internal model control structure with embedded iterative computation. We first study the Runge–Kutta (RK) type methods for solving the nonlinear ordinary differential equations and derive the convergence conditions in the control-theoretic framework. Then, we propose an observer-like iterative solution to improve the convergence rate of the RK method by embedding the sensor signals into the iterative computation. Based on these results, real-time FTC is achieved and enhanced by employing the modified numerical algorithm in the iterative computation and estimation. This paper is mainly motivated by the increasing demands on the reliability of integrating the fast converging iterative solutions of differential equations into the embedded control systems. The effectiveness of the proposed schemes is demonstrated through the experimental and simulation results on three-tank systems. [ABSTRACT FROM PUBLISHER]

In this research, we aimed to design a novel brain-computer interaction (BCI) approach in routing and forwarding mechanisms to realize a networking multi-modal and multi-brain linked control. In recent years, the field programmable gate array (FPGA) has become a popular choice to construct a heterogeneous network for routing and forwarding processes due to its ability to complete a high performance computation in single node. Conventional BCI mode focus on capturing the dynamic EEG signals from multiple electrode channels and this concept neglects the existing complexity and diversity of connecting information between two brain regions. To this moment, we build a heterogeneous multi-agent system (HMAS) architecture to simulate the memristive neuron networks (MNN) with a set of logic units for multi-agent in the Internet. Specifically, we first feed the non-linear features into an intelligent router to adjust their routing and forwarding processes. Subsequently, at one-time step, the output of all testing nodes is written into a heterogeneous logic space, which mainly consists of the sub-agent, forward port, and memory memristive neuron. In the FPGA, each programmable cell selectively integrates and stores a huge number of motion information between multiple interacting channels. We can achieve the networking cooperative functions of forward and route through FPGA large-scale computation. According to the extensive experimental results on several data, we validate the effectiveness of the proposed HMAS-BCI architecture to compare the optimization method of the multiple simulations. [ABSTRACT FROM AUTHOR]

This paper is concerned with a control performance-based fault-tolerant control strategy for singular systems in presence of multiplicative faults. To be specific, the observer-based realization of Youla parameterization is first addressed for singular systems. Then the fault-tolerant margin for closed-loop systems is studied and further modified to bring forth the stability margin degradation, which serves as an indicator for the performance change caused by the faults in the closed-loop. Based on it, a control performance-based fault detection scheme is realized, aiming at detecting those faults that may affect the system stability. Controller reconstruction rule is given afterwards to ensure the system performance when fault occurs. A circuit system model is finally provided to illustrate the validness of the derived control scheme. [ABSTRACT FROM AUTHOR]

This paper presents the rotation control design and experimental performance of a micro-electromechanical systems (MEMS) variable-capacitance motor where a free-spinning rotor is suspended and centered in an evacuated vacuum cavity by a contactless electrostatic bearing. The micromachined device is based on a glass/silicon/glass bonding structure, fabricated by bulk micromachining, driven by a three-phase electrostatic motor, and used as an angular rate gyroscope by spinning-up the rotor rate over \text10^\text4\;\textr/min. A closed-loop phase commutation scheme is proposed in our rotation design where three-phase drives are switched depending on one channel of the rotor’s angular position. The design of the micromotor spin-up and constant-speed operation is described based on the proposed electronic commutation. Experimental results of the motor spin-up process under different vacuum settings, static, and dynamic characteristics of the constant-speed control loop together with scale factor of the spinning-rotor gyroscope are described for the device operated in vacuum. It is indicated that the rotor can be spun up to \text2.5\times\text10^\text4\;\textr/min within 400 s, and up to \text2.96\times\text10^\text4\;\textr/min in steady state under a drive voltage of 11.8 V. Measurement data in constant-speed control mode show that the standard deviation of the spin rate error is 0.07 r/min at a rated speed of \text1.5\times\text10^\text4\;\textr/min. [ABSTRACT FROM PUBLISHER]

This paper addresses fault-tolerant control (FTC) issues for linear systems with model uncertainty and multiplicative faults. The left and right coprime factorization techniques are first adopted for system modeling. Then, the fault detection (FD) approaches are investigated in the coprime factorization context. Based on the information provided by the FD systems, the corresponding FTC architectures and design schemes are presented. Moreover, the gap metric techniques are applied to fault detectability analysis, including the fault detectability indicators to quantify the detection performance in the presence of model uncertainty. The effectiveness of the developed methods for industrial application is illustrated by a case study on a dc motor. [ABSTRACT FROM AUTHOR]

A stabilizing regulator designed by any technique whatsoever can be viewed as the combination of a state estimate feedback controller and additional feedback from a dynamic compensator driven by the residual signal (difference between actual and estimated system outputs). Motivated by such an observation, this paper presents the controller design from the premise that system stability is first guaranteed. Control performance can then be enhanced by the optimal design of a residual-driven dynamic compensator subject to some quadratic performance index. The resulting compensator design methods are carried out using both offline and online iterative algorithms with guaranteed convergence. Moreover, the final iterative realization strategy can be implemented online with observed state variables and input updates in case of unknown system dynamics or parameter changes. Simulation results are presented to illustrate design procedures as well as the feasibility of our proposed scheme. [ABSTRACT FROM PUBLISHER]

In this paper, regarding the observer form of the well-known Youla parameterization, the controller design and optimization are exhibited with an integrated residual access. To better reveal this philosophy, the feedback control loop is interpreted on the basis of the observer-based residual generator. The next main attention is drawn to the generation of residuals, the design of a deadbeat controller for system stabilization both in the data-driven environment, and later the optimal adaptive realization of a dynamic system that translates residuals into compensatory control inputs to meet certain performance specifications. Towards these goals, numerical algorithms are summarized, and for the issues of controller optimization, the reinforcement learning algorithm is introduced using only measured input-output and residual signals. In addition, the effectiveness of developed schemes for industrial applications is also illustrated by experimental studies on a laboratory continuous stirred tank heater (CSTH) process. [ABSTRACT FROM PUBLISHER]