An anti-windup strategy for active vibration isolation systems

An anti-windup augmentation technique for active vibration isolation systems is considered in this paper and shown to lead to high-performance vibration isolation through simulations and experiments. First, the anti-windup construction is described and desirable properties of the augmented closed-loop system are illustrated. Then, the anti-windup technique is tested on a simulation example and finally shown to perform excellently on a commercial vibration isolation device: Newport Corporation's Elite 3^TM active vibration isolation system which has been patented and is now commercialized with this architecture. Both simulation and experimental results confirm the effectiveness of the anti-windup scheme.     

An analytical method for analysis and design of control systems

A new method for analysis and design of control systems is presented. The method is based upon a set of simultaneous algebraic equations; the roots and the parameters of the compensator are calculated simultaneously. The method is a direct synthesis, no trial and error is needed. Since analytical expressions are derived, the method is well-suited for implementation by digital computer. Several examples of different compensators are presented and the general expressions for some specific cases have been derived.     

An effective analytical criterion for stability testing of fractional-delay systems

This paper investigates the BIBO stability of a class of fractional-delay systems with rational orders, a stability that holds true if all the characteristic roots have negative real parts only. Based on the Argument Principle for complex functions as well as Hassard’s technique for ordinary time-delay systems, an explicit formula is established for calculating the number of characteristic roots lying in the closed right-half complex plane of the first sheet of the Riemann surface, and in turn a sufficient and necessary condition is obtained for testing the BIBO stability of fractional-delay systems. As shown in the illustrative examples, this stability criterion involves easy computation and works effectively.     

An investigation of expert systems for die design

This article introduces fuzzy set theory to process the design details of the uncertain portion in die design, and assist the designer to transform those design items with fuzziness into those with definite and reasonable design attributes. For the design parameters of die block thickness, die clearance angle and die sets choice in die design, which possess intermediate features, fuzzy cluster analysis is used to obtain the design attributes. As for single-sided die clearance, stripper pressure and guide bushing-type die design, whose theory or empirical formulas possess uncertainty coefficients or preference design parameters, the fuzzy weighted average method is adopted to obtain the feature parameters that conform with the die design requirement. This study established an expert system prototype to combine the aforementioned uncertainty problems into two kinds of die design, and help the designer obtain a definite design strategy when faced with uncertain design items.     

Interactive cartography—An analytical tool for management information systems

An interactive time-sharing graphical system has been developed at Princeton University for applications in education, engineering design, and management information systems. Graphical processors have been integrated into a general purpose interactive computer system, providing for easy graphical input and output in a time-sharing mode. The present report discusses the capabilities of the interactive system for applications in which cartographical displays serve as tools for analysis and reporting. The interactiveness of the system permits the analyst and the policy decision maker to quickly explore alternative solutions.     

An investigation of self-powered systems for condition monitoring applications

Over recent years there has been a growing interest in the field of micro-systems and their applications across a wide range of areas, including sensor-based systems able to operate with full galvanic isolation. This paper details the development of a self-powered system, specifically for sensor applications that can be energised on a test rig by an electromagnetic vibration-powered generator. This enables wireless operation without the use of a battery with a finite service life. The results of two systems designed for remote sensing in condition monitoring applications are discussed. The first system uses a liquid crystal display to provide the system output; the second uses an infra-red link to transmit the data output.     

An analytical model for loss estimation in network traffic analysis systems

Simulation models have been developed in order to foresee characteristics of networks, systems or protocols when carrying out tests in laboratories is very expensive or even impossible. This paper presents a simulation model of a multiprocessor network traffic analysis system. The model, which is based on closed networks of queues, evaluates the efficiency of the system depending on the hardware/software platform features. Therefore, this model is able to estimate performance early in the design and development stages simulating a multiprocessor architecture in charge of analysing network traffic. The goodness of the model will be checked by comparing analytical results with practical ones obtained in laboratory using a traffic analysis system that runs on a multiprocessor platform.     

An analytical approach to one-parameter MIMO systems passivity enforcement

Stable linear time-invariant systems can be made passive by a feedforward action. In this article, an analytical approach to obtain the matrix which allows to enforce passivity in the system is proposed. This matrix depends only on one parameter, namely α. The introduced method is based on the calculation of the characteristic polynomial of the Hamiltonian matrix associated to the Positive Real problem. This polynomial is then used to derive a finite set of values of the parameter α, in which the value assuring passivity enforcement with minimum dissipation can be selected. Numerical examples are reported.     

Decentralized fault detection and isolation in wireless structural health monitoring systems using analytical redundancy

One of the most critical issues when deploying wireless sensor networks for long-term structural health monitoring (SHM) is the correct and reliable operation of sensors. Sensor faults may reduce the quality of monitoring and, if remaining undetected, might cause significant economic loss due to inaccurate or missing sensor data required for structural assessment and life-cycle management of the monitored structure. This paper presents a fully decentralized approach towards autonomous sensor fault detection and isolation in wireless SHM systems. Instead of physically installing multiple redundant sensors in the monitored structure (“physical redundancy”), which would involve substantial penalties in cost and maintainability, the information inherent in the SHM system is used for fault detection and isolation (“analytical redundancy”). Unlike traditional centralized approaches, the analytical redundancy approach is implemented distributively: Partial models of the wireless SHM system, implemented in terms of artificial neural networks in an object-oriented fashion, are embedded into the wireless sensor nodes deployed for monitoring. In this paper, the design and the prototype implementation of a wireless SHM system capable of autonomously detecting and isolating various types of sensor faults are shown. In laboratory experiments, the prototype SHM system is validated by injecting faults into the wireless sensor nodes while being deployed on a test structure. The paper concludes with a discussion of the results and an outlook on possible future research directions.     

An analytical investigation of an energy flow divider to attenuate hand-transmitted vibration

A five-degrees-of-freedom (DOF) bio-mechanical model of the hand-arm system is developed to study the vibration transmissibility characteristics of the human hand-arm. The model parameters are identified from the characteristics of vibration transmitted to the hand, forearm and upper arm, measured in the 10–200 Hz frequency range under a constant 25.0 N grip force. A concept of an energy flow divider is proposed to reduce the flow of vibration energy into the hand. The coupled hand-arm-divider is modeled as a six-DOF dynamical system and the response characteristics are evaluated for handle excitations caused by a palm-grip orbital sander. The response characteristics of the coupled hand-arm-divider model are compared to those of the hand-arm model to demonstrate the potential performance benefits of the proposed energy flow divider. The hand-transmitted vibration is further assessed using the overall weighted acceleration response, and it is concluded that the proposed energy flow divider can reduce the magnitude of hand-transmitted vibration considerably.     

An empirical investigation of two electronic mail systems

Two electronic mail systems were studied within an organization: an executive system for upper management and a general system for all employees. The results from 130 interviews indicated that both systems were perceived to contribute to productivity, a reduction in use of memos and a reduction in telephone calls. However, the executive system was perceived to be more satisfactory and more effective than the general system. The ratio of positive comments to negative comments was used as an independent measure of satisfaction with each electronic mail system. The user comments were also classified and discussed in terms of types of perceived advantages and problems with these systems.     

An investigation of neuro-fuzzy systems in psychosomatic disorders

A neuro-fuzzy model for diagnosis of psychosomatic disorders is proposed in this paper. The symptoms and signs are collected from the patients through oral interview. For the linguistic nature of patient's inputs, an artificial domain is created and fuzzy membership values are defined. The fuzzy values are fed as inputs to feedforward multilayer neural network. The network is trained using Backpropagation training algorithm. The trained model is tested with new patient's symptoms and signs. Further, the performance of the diagnosing capability is compared with medical expert. The performance of the model is also compared with probability model based on Bayesian Belief Network and statistical model using Linear Discriminant analysis     

An investigation on technologies to fabricate microcoils for miniaturized actuator systems

Within the framework of the Collaborate Research Center Design and Fabrication of Active Microsystems (Sonderforschungsbereich 516), one aspect is the development of fabrication technology for driving coil systems to be applied to in electromagnetic microactuators. The two key focus areas are the fabrication of high aspect ratio conductors and insulating them by applying planarizing polymer material. The research activities included the development of technologies like for UV depth lithography, electroplating through lithographic masks (galvanoforming), as well as embedding in and planarization by insulation material. Combining these technologies allows to create high aspect ratio integrated multi-layer coils with integrated magnetic flux guiding structures. The materials applied were copper as a conductor, NiFe for magnetic cores and the negative tone resists SU-8 (MicroChem Corp.) as well as BCB (DOW Chemical) for insulation and embedding purposes. For electroplating molds, the DNQ/Novolak type photoresists AZ4562 and AZ9260 (Clariant) were utilized. The established technologies were integrated into process flows for fabricating thick and high aspect ratio planar and helical coils for electromagnetic linear actuators.This work was sponsored in part by the German Research Foundation as part of their support for the Collaborative Research Center Design and Fabrication of Active Microsystems.     

Expert systems adoption. An analytical study of managerial issues and concerns

The experience of introducing expert systems technology into six automotive component manufacturing organizations in the mid-western United States is described. The domain of expert system application as well as the procedural and organizational hurdles that were encountered are also documented. An overview of relevant literature shows the shortage of studies of this kind. A synthesis is provided of the study observations and implications for better management of expert systems adoption in manufacturing.     

An investigation on technologies to fabricate magnetic microcomponents for miniaturized actuator systems

Soft magnetic yokes, cores, and poles, as well as permanent magnets are the potential magnetic components of an electromagnetic microactuator system. Depending on the requirements of the actuator, soft magnetic materials, hard magnetic materials or a combination of both have to be applied. Their design and fabrication as well as their integration into coil systems is one aspect of the Collaborate Research Center Design and Fabrication of Active Microsystems (Sonderforschungsbereich 516). The investigations presented in this paper cover alternative technologies for depositing various magnetic materials as well as their capability of being utilized for fabricating electromagnetic Microsystems. In the area of soft magnetic materials, the application of NiFe (Permalloy) in various compositions was investigated. Technologies utilized for their deposition were electroplating, sputtering, and gas flow sputtering. For fabricating rather thick soft magnetic micro structures with heights of up to 70 m, electroplating is particularly well suited. In the area of hard magnetic materials, sputtering was applied for depositing Samarium-Cobalt (SmCo). Hereby, layers with a thickness of up to 50 m with very good hard magnetic properties were deposited and patterned using wet chemical etching.This work was sponsored in part by the German Research Foundation as part of their support for the collaborative research center Design and Fabrication of Active Microsystems.     

An investigation into the electrostatic force representation for electrically actuated microelectromechanical systems

The ever-increasing demand for microelectromechanical systems (MEMS) in modern electronics has reinforced the need for extremely accurate analytical and reduced-order models to aid in the design of MEMS devices. Many MEMS designs consist of cantilever beams with a tip mass attached at the free end to act as a courter electrode for electrical actuation. One critical modeling aspect of electrically actuated MEMS is the electrostatic force that drives these systems. The two most used representations in the literature approximate the electrostatic force between two electrodes as a point force. In this work, the effects of the representation of the electrostatic force for electrically actuated microelectromechanical systems are investigated. The system under investigation is composed of a beam with an electrode attached to its end. The distributed force, rigid body, and point mass electrostatic force representations are modeled, studied, and their output results are compared qualitatively. Static and frequency analyses are carried out to investigate the influences of the electrostatic force representation on the static pull-in, fundamental natural frequency, and mode shape of the system. A nonlinear distributed-parameter model is then developed in order to determine and characterize the response of electrically actuated systems when considering various representation of the electrostatic forces. The results show that the size of the electrode may strongly affect the natural frequencies and static pull-in when the point mass, rigid body, and plate representations are considered. From nonlinear analysis, it is also proven that the representation may affect the hardening behavior of the system and its dynamic pull-in. This modeling and analysis give guidelines about the usefulness of the electrostatic force representations and possible erroneous assumptions that can be made which may result in inaccurate design and optimal performance detection for electrostatically actuated systems.

     

The value of explanation in expert systems for auditing: An experimental investigation

Providing explanations for recommended actions is one of the most important capabilities of expert systems (ESs). The nature of the auditing domain suggests that ESs designed for audit applications should provide an explanation facility. There is little empirical evidence, however, that explanation facilities are, in fact, useful. This paper investigates the impact of explanations on changes in user beliefs toward ES-generated conclusions. Grounded on a theoretical model of argument, the study utilized a simulated expert system to provide three alternative types of ES explanations: trace; justification; and strategy. Ten expert and ten novice auditors performing an analytical review task evaluated the outputs of the system in a laboratory setting. The results indicate that explanation facilities can make a system's advice more agreeable and hence acceptable to auditors, and that justification is the most effective type of ES explanation to bring about changes in auditor attitudes toward the system. In addition, the results suggest that auditors at different levels of expertise may value each explanation type differently.     

An investigation into the method of energy monitoring and reduction for machining systems

Improving the energy efficiency of machining systems (MSs) is an urgent and challenging issue in sustainable manufacturing. Considering the dynamics and uncertainty of MSs, a five-dimension model is developed to monitor and reduce the energy consumption (EC) of MSs. In this model, the automatic acquisition of EC data from physical MSs is driven by Radio Frequency IDentification (RFID) read events. The EC service model provides monitoring and scheduling services for reducing the EC of physical MSs by connecting with virtual MSs in real time. The procedures of the EC reduction method for the MSs are presented. A case study of MSs for auto parts was conducted to illustrate the proposed method. The results showed that the time and EC of MSs were reduced by 148 s and 49.67 KJ, respectively.     

Bayesian error isolation for models of large-scale systems

A methodology is presented for use in isolating sources of misspecification in system models that are known to be invalid. The methodology relies on a technique based on stochastic approximation in the context of a Bayesian formulation. This approach has significant advantages in computational efficiency, relative to a straightforward Bayesian analysis, for large-scale systems. Moreover, it applies to arbitrary model forms (e.g. state-space, regression, etc.) and applies when the probability distribution for the system output is not necessarily Gaussian