PVDF actuator for high‐frequency fatigue test of thin‐film metals

This paper suggests a poly(vinylidene fluoride) (PVDF) piezoelectric diaphragm actuator used in a novel fatigue test method for thin metal films. A thin‐film metal specimen is stamped on top of the actuator using a stamping epoxy. As the actuator vibrates, the stress in the specimen increases until it fails under fatigue. A finite element model of the actuator is built, and its vibration amplitude is confirmed to be in a good agreement with experiment. Then, a model of the specimen is added to this model to simulate the vibration of the specimen for fatigue test. Stress analysis of the specimen at a driving voltage of 200 V_0−p confirms that this actuator can increase the stress in the specimen to near 1 GPa, which is high enough for the fatigue test of metals such as titanium. In the experiment, a thin‐film titanium specimen is stamped on top of the actuator which is then vibrated. The stress in the fatigue gauge on thin‐film specimen increased until the specimen failed under fatigue. This shows that the proposed PVDF actuator is suitable for the fatigue test of thin‐film metals such as titanium. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Pressure sensing by electrical admittance measurement of a comb‐drive actuator

This paper describes a micromachined pressure sensor that senses pressure not by a diaphragm structure but by a resonantly vibrating comb‐drive actuator. The electrical admittance of the comb‐drive actuator was directly measured using a lock‐in amplifier, and its pressure dependence was examined. From the experiment, it was found that the resonant frequency of the comb‐drive actuator gradually drops as the pressure increases. The sensitivity of the comb‐drive actuator as a pressure sensor was 0.34 Hz/MPa at atmospheric pressure and 0.1 Hz/MPa at 0.4 MPa absolute pressure. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Dynamic Characteristics Analysis of Two‐DOF Oscillatory Actuator and Experimental Verification of Prototype

Recently, linear oscillatory actuators have been used in a wide range of applications. In particular, small linear oscillatory actuators are expected to be used in haptic devices by being extended to provide multi‐degree‐of‐freedom motion with arbitrary acceleration. In this paper, we propose a compact two‐DOF oscillatory actuator that can move in various directions on a plane. The static and dynamic characteristics of the actuator are determined by the 3D finite element method. The effectiveness of this method is shown through a comparison of the measured results with the experimental results from a prototype. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(1): 58–65, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22312     

A discrete‐time indirect adaptive multiple‐model actuator failure compensation scheme

A new discrete‐time actuator failure compensation control scheme is developed, using a multiple‐model adaptive control approach which has the capacity to achieve faster and more accurate compensation of failure uncertainties. An individual adaptive system, for each possible failure pattern in a failure pattern set of interest for compensation, is designed using an indirect model reference adaptive control scheme for actuator failure compensation. A multiple‐model control switching mechanism for discrete‐time systems is set up by finding the minimal performance index to select the most appropriate control law. The performance indices are based on the adaptive estimation errors of individual parameterized systems with actuator failures. Simulation results from an aircraft flight control system example are presented to show the desired closed‐loop system stability and tracking performance despite the presence of uncertain actuator failures. Copyright © 2014 John Wiley & Sons, Ltd.     

Robust adaptive output‐feedback control for a class of nonlinear systems with time‐varying actuator faults

A robust adaptive output‐feedback control scheme is proposed for a class of nonlinear systems with unknown time‐varying actuator faults. Additional unmodelled terms in the actuator fault model are considered. A new linearly parameterized model is proposed. The boundedness of all the closed‐loop signals is established. The desired control performance of the closed‐loop system is guaranteed by appropriately choosing the design parameters. The properties of the proposed control algorithm are demonstrated by two simulation examples. Copyright © 2010 John Wiley & Sons, Ltd.     

Adaptive neural dynamic surface control of MIMO nonlinear time delay systems with time‐varying actuator failures

In this paper, an adaptive dynamic surface control approach is developed for a class of multi‐input multi‐output nonlinear systems with unknown nonlinearities, bounded time‐varying state delays, and in the presence of time‐varying actuator failures. The type of the considered actuator failure is that some unknown inputs may be stuck at some time‐varying values where the values, times, and patterns of the failures are unknown. The considered actuator failure can cover most failures that may occur in actuators of the systems. With the help of neural networks to approximate the unknown nonlinear functions and combining the dynamic surface control approach with the backstepping design method, a novel control approach is constructed. The proposed design method does not require a priori knowledge of the bounds of the unknown time delays and actuator failures. The boundedness of all the closed‐loop signals is guaranteed, and the tracking errors are proved to converge to a small neighborhood of the origin. The proposed approach is employed for a double inverted pendulums benchmark as well as a chemical reactor system. The simulation results show the effectiveness of the proposed method. Copyright © 2016 John Wiley & Sons, Ltd.     

Adaptive output feedback actuator failure compensation for a class of non‐linear systems

An adaptive compensation control scheme using output feedback is designed and analysed for a class of non‐linear systems with state‐dependent non‐linearities in the presence of unknown actuator failures. For a linearly parameterized model of actuator failures with unknown failure values, time instants and pattern, a robust backstepping‐based adaptive non‐linear controller is employed to handle the system failure, parameter and dynamics uncertainties. Robust adaptive parameter update laws are derived to ensure closed‐loop signal boundedness and small tracking errors, in general, and asymptotic regulation, in particular. An application to controlling the angle of attack of a non‐linear hypersonic aircraft dynamic model in the presence of elevator segment failures is studied and simulation results show that the developed adaptive control scheme has desired actuator failure compensation performance. Copyright © 2004 John Wiley & Sons, Ltd.     

Active fault‐tolerant control system design with trajectory re‐planning against actuator faults and saturation: Application to a quadrotor unmanned aerial vehicle

During the past 30 years, various fault‐tolerant control (FTC) methods have been developed to address actuator or component faults for various systems with or without tracking control objectives. However, very few FTC strategies establish a relation between the post‐fault reference trajectory to track and the remaining resources in the system after fault occurrence. This is an open problem that is not well considered in the literature. The main contribution of this paper is in the design of a reconfigurable FTC and trajectory planning scheme with emphasis on online decision making using differential flatness. In the fault‐free case and on the basis of the available actuator resources, the reference trajectories are synthesized so as to drive the system as fast as possible to its desired setpoint without violating system constraints. In the fault case, the proposed active FTC system (AFTCS) consists in synthesizing a reconfigurable feedback control along with a modified reference trajectories once an actuator fault has been diagnosed by a fault detection and diagnosis scheme, which uses a parameter‐estimation‐based unscented Kalman filter. Benefited with the integration of trajectory re‐planning using the flatness concept and the compensation‐based reconfigurable controller, both faults and saturation in actuators can be handled effectively with the proposed AFTCS design. Advantages and limitations of the proposed AFTCS are illustrated using an experimental quadrotor unmanned aerial vehicle testbed.Copyright © 2013 John Wiley & Sons, Ltd.     

A series‐connected hybrid triple converter system

This paper proposes a hybrid multiconverter system aiming at a large‐capacity high‐voltage high‐efficiency converter system free from harmonics in its input/output. The system consists of n (n: integer) GTO converters and a single neutral‐point‐clamped IGBT converter connected in series by n + 1 output transformers. The GTO converters operate in a square‐wave switching mode while the IGBT converter operates in a PWM switching mode. The former produces a base part of the resultant output voltage. The latter not only produces an additional part of the resultant output voltage, but offsets the voltage harmonics generated by the GTO converters. A basic voltage control strategy for the hybrid converter system is proposed, and its validity is verified by experimental results. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 64–70, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20210     

Active fault‐tolerant attitude control for flexible spacecraft with loss of actuator effectiveness

A theoretical framework for active fault‐tolerant attitude stabilization control is developed and applied to flexible spacecraft. The proposed scheme solves a difficult problem of fault‐tolerant controller design in the presence of severe partial loss of actuator effectiveness faults and external disturbances. This is accomplished by developing an observer‐based fault detection and diagnosis mechanism to reconstruct the actuator faults. Accordingly, a backstepping‐based fault‐tolerant control law is reconfigured using the reconstructed fault information. It is shown that the proposed design approach guarantees that all of the signals of the closed‐loop system are uniformly ultimately bounded. The closed‐loop performance of the proposed control strategy is evaluated extensively through numerical simulations. Copyright © 2012 John Wiley & Sons, Ltd.     

Two‐stage Kalman filter‐based actuator/surface fault identification and reconfigurable control applied to F‐16 fighter dynamics

In this study, an active fault‐tolerant control technique with reconfiguration against actuator/surface failures is presented. A two‐stage Kalman filter is designed in order to identify the control distribution matrix elements that correspond to the faulty actuator/surface; thus, the control reconfiguration is carried out using this identified control distribution matrix. The actuator/surface fault identification problem is solved through two jointly operating Kalman filters: the first one is for the estimation of the control distribution matrix elements that correspond to the faulty actuator/surface, and the second one is for the estimation of the state variables of the aircraft model. A structure for the active fault‐tolerant aircraft flight control system with reconfiguration against actuator/surface failures is presented. A control reconfiguration action is taken in order to keep the performance of the impaired aircraft the same as that of the unimpaired aircraft. In simulations, the nonlinear flight dynamics of an AFTI/F‐16 fighter model is considered, and the performance of the proposed actuator/surface failure identification and reconfigurable control schemes are examined for this model. Copyright © 2012 John Wiley & Sons, Ltd.     

Fault‐tolerant control using command‐filtered adaptive back‐stepping technique: Application to hypersonic longitudinal flight dynamics

In this paper, the adaptive back‐stepping controller is investigated for a class of strict‐feedback systems using the command filter technique. Adaptive laws are designed for updating the controller parameters when both the plant parameters and actuator‐failure parameters are unknown. Furthermore, the auxiliary dynamics is developed to deal with the input constraints. Closed‐loop stability and asymptotic‐state tracking are ensured. The method is applied to the longitudinal dynamics of a generic hypersonic aircraft in the presence of actuator faults and input constraints. Based on the parameter estimation, the command‐filtered adaptive back‐stepping control is presented. Simulation results on the control‐oriented model show that the proposed approach achieves good tracking performance. Copyright © 2015 John Wiley & Sons, Ltd.     

A new decentralized retrofit adaptive fault‐tolerant flight control design

In this paper, we develop a new decentralized retrofit adaptive fault‐tolerant control design for a class of nonlinear models arising in flight control. The proposed adaptive fault‐tolerant controller is designed to accommodate loss‐of‐effectiveness (LoE) failures in flight control actuators and achieve accurate estimation of failure‐related parameters. The design is based on local estimation of LoE parameters and generation of local retrofit control signals to accommodate the failures. Using state‐dependent closed‐loop estimation errors, we show the overall system to be stable and demonstrate the tracking error to converge to zero asymptotically for any combination of actuator failures. Through computer simulation of F/A‐18 aircraft under actuator LoE failures, the proposed approach is also shown to achieve better parameter estimation performance compared to the fully centralized design and the design employing local observers and a centralized adaptive controller. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparison with film substrates of polyimide and Ni for cantilevered magnetic actuators

This paper describes a cantilevered actuator driven by magnetostriction in a low magnetic field. The dimensions of the two‐layer actuator were 1 mm × 5 mm, and amorphous FeSiB was used as the positive magnetostrictive material. The theoretical formulas for the amount of displacement and force of the actuator were obtained. In the experiment, a nonmagnetic polyimide film material and a negative magnetostrictive Ni film material were used as the substrates. The change in the characteristics of the actuator caused by changing the substrate was examined with theoretical formulas and experiments. It is shown that the actuator with Ni as the substrate was designed to obtain the largest displacement and the largest force. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Artificial muscle using conducting polymers

We have investigated a method of preparing a large‐size anisotropic polypyrrole (PPy) film using a slab vessel consisting of poly(tetrafluoroethylene) (PTFE) walls as well as its actuation abilities. The PPy film can be grown along one side of the PTFE walls and exhibits morphological anisotropy of the PPy packing density along the thickness direction. A piece bends in a regular direction (the surface in contact with the PTFE wall) and reverts during a redox cycle without the use of any additional processes such as lamination. The actuation properties of the anisotropic PPy actuator strongly depend on the size of the cation in the driving electrolyte, and the bending behavior of this actuator at room temperature becomes slower for larger cations. On investigating the temperature dependence of actuation properties, the arrival time of the actuator (the time required for the tip of the actuator to touch the electrolyte surface upon stepwise potential change) was found to become shorter in all electrolyte solutions with different electrolytes. This result can be understood in terms of the thermally activated microscopic movement of the PPy main chains. Such behavior based on electrochemical stimulus not only provides information related to ionic transfer and storage but also suggests that the anisotropic PPy film can be put to practical use as an electrochemical actuator for artificial muscle which directly converts electrical energy into mechanical energy. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(4): 7–13, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20066     

Active fault tolerant control of piecewise affine systems with reference tracking and input constraints

An active fault tolerant control (AFTC) method is proposed for discrete‐time piecewise affine (PWA) systems. Only actuator faults are considered. The AFTC framework contains a supervisory scheme, which selects a suitable controller in a set of controllers such that the stability and an acceptable performance of the faulty system are held. The design of the supervisory scheme is not considered here. The set of controllers is composed of a normal controller for the fault‐free case, an active fault detection and isolation controller for isolation and identification of the faults, and a set of passive fault tolerant controllers (PFTCs) modules designed to be robust against a set of actuator faults. In this research, the piecewise nonlinear model is approximated by a PWA system. The PFTCs are state feedback laws. Each one is robust against a fixed set of actuator faults and is able to track the reference signal while the control inputs are bounded. The PFTC problem is transformed into a feasibility problem of a set of LMIs. The method is applied on a large‐scale live‐stock ventilation model. Copyright © 2013 John Wiley & Sons, Ltd.     

A totally enclosed traction motor using a permanent magnet synchronous motor

Ventilated‐type traction motors are widely used for railway vehicles. However, they require overhauls to clean inside them. In addition, they are a major noise source in railway vehicles. To solve these problems, we propose a totally enclosed‐type traction motor using a permanent magnet synchronous motor that has the same weight power ratio as that of a conventional ventilated‐type traction motor. In this paper, we report the test results of the proposed motor. The test results demonstrate that the temperature rise values are within its limit and the noise level is decreased by 10 dB compared to conventional motors. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(3): 71–80, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20079     

Two‐degree‐of‐freedom model matching control of shift‐by‐wire system with emergency mechanical link

A new shift‐by‐wire system having a standby mechanical link with backlash is proposed. The link directly connects the select lever and the manual lever of the automatic transmission in case of emergency. Thus, it is necessary to keep the backlash free during normal operations without generating a force. The angles of the manual lever driven by an actuator should follow the angles of the select lever exactly and quickly. A two‐degree‐of‐freedom model matching control is developed to meet this requirement. It is shown that the backlash is kept free during the range select operation. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(3): 45–52, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21049     

Image template matching based on edge‐spin correlation

This paper proposes a new method for image template matching that is based on the correlation between edge‐spins. The edge‐spin is defined by the direction of the change of edge directions between neighboring pixels. When an edge direction rotates to the left from an objective pixel to its right neighboring pixel, the edge‐spin has the value 1. When an edge direction rotates to the right, the edge‐spin has the value 0. The edge‐spin is a binary data that represents the rotation of the edge direction. The edge‐spin is supposed to be robust to the change of brightness because the edge direction is not influenced by the linear change of brightness. The experimental results show that the proposed method has the superior reliability for the matching about most inferior experimental conditions in comparison with the conventional image template matching methods. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(2): 45–51, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20184     

Simultaneous time‐varying actuator and sensor fault reconstruction based on PI observer for LPV systems

We consider problems of actuator and sensor fault reconstruction simultaneously for linear parameter varying systems expressed in polytopic forms. By extending the sensor fault as an auxiliary state, a polytopic unknown input proportional‐integral observer in which the actuator fault signals are assumed to be time varying is developed to estimate the system states and the actuator and sensor fault at the same time. The existence conditions of the observer are derived in terms of linear matrix inequalities that can be readily handled via some efficient tools. An example is given to demonstrate the advantages of the proposed method in comparison to the existing results. Copyright © 2014 John Wiley & Sons, Ltd.