Magnetorheological (MR) fluids are materials that change their rheological behavior upon applying a magnetic field. They have been promising as functional fluids that can improve the properties of mechanical systems. We have developed an actuator using MR fluid. In the previous paper, a method of designing MR-fluid actuators was proposed on the basis of magnetic circuit theory. The basic experiments were carried out and static properties that agreed well with the design were obtained. However, the transient response, which was not considered in the design phase, was not very fast. In this study, we investigate the dynamics of the MR-fluid actuator and aim to improve the response. The transient magnetic analysis is examined in consideration of the eddy current. Two approaches to improving the response are proposed. Finally, we realize a much faster MR-fluid actuator.

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It is known that a continuous stable high-gain PD control system may become unstable when the controller is implemented digitally. Recent works consider this problem and determine the stability regions of such systems. In most cases the stability regions are obtained numerically. This work introduces a new analytical approach for obtaining the stability criteria for digital systems. The approach is based on the critical constraints of simplified version of Jury test and makes use of the capabilities of MATLAB software. The approach is applied to digital PD control systems. Here, the effect of computation time in addition to that of sampling period are considered. The resulting stability criteria are presented in closed forms that are suitable for design purposes and make it possible to map the stability region for various control design parameters. This versatile capability is illustrated via design examples. To the contrary of previous knowledge, the results show that, in certain cases, the stability is obtained through increasing the proportional gain or computation time rather than by decreasing them. A comparison with the literature shows that this approach is straightforward, versatile and even corrects some of the stability regions that have been reported.

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A piezo-driven inchworm linear motor with a reduction lever mechanism has been designed and characterized. The inchworm motor consists of two clamping devices for gripping a moving shaft and one push-pull device operated by three piezoelectric stacks. To reduce positioning errors caused by control voltage fluctuations and to improve positioning accuracy, a reduction lever mechanism with a monolithic flexure structure is employed to the push-pull device. For the design analysis of the push-pull and clamping devices, their analytical models and equations were developed, by which the static characteristics were evaluated. The positioning performances of the inchworm motor assembled with the push-pull and clamping devices were experimentally characterized. The developed inchworm linear motor proved effective not only in performing a step movement of 1nm up to 82.5nm, with the step size optionally adjusted, but also in providing ultra high positioning accuracy.

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In this paper, a robust model reference adaptive control of a cantilevered flexible structure with unknown spatiotemporally varying coefficients and disturbance is investigated. Any mechanically flexible manipulators/structures are inherently distributed parameter systems whose dynamics are described by partial, rather than ordinary, differential equations. Robust adaptive control laws are derived by the Lyapunov redesign method on an infinite dimensional Hilbert space. Under the assumption that disturbances are uniformly bounded, the proposed robust adaptive scheme guarantees the boundedness of all signals in the closed loop system and the convergence of the state error near to zero. With an additional persistence of excitation condition, the parameter estimation errors are shown to converge near to zero as well.

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This paper proposes a sliding-mode controller design with adaptable pole-clustering capability for linear multiple-input multiple-output systems, in which the influences of parameter uncertainties and external disturbances on the system performance can be arbitrarily lessened to cluster all closed-loop poles within the desired regions in a complex plane. Due to parameter uncertainties or variations in a physical system, the closed-loop poles through linear state feedback might be perturbed away from the required ones and could not be constrained within the specified regions in a complex plane. In established sliding-mode control, system responses during sliding motions are completely invariant to system perturbations satisfying the so-called matching condition. However, this invariance property usually accompanies undesirable chatter phenomenon. In this paper, the proposed sliding-mode controller is designed to decrease the effects of system perturbations to an extent that is acceptable according to performance specifications, instead of being completely insensitive. One advantage of this design over the conventional one is the reduction of chatter level. To be precise, chatter alleviation can be achieved while the sliding mode is guaranteed during an entire response in this design. To verify the scheme, we performed experiments on its implementation in a two-degree-of-freedom magnetic levitation system. The results show that the proposed scheme not only satisfies the requirements for performance robustness but also achieves chatter alleviation.

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A shooting method is a very powerful numerical method to obtain periodic solutions of nonlinear systems. However, as a variational equation of motion is needed in the shooting method and it is very difficult to obtain it in the impact systems, the shooting method for impact systems has not been developed. In this report, a shooting method for impact systems is presented by solving this problem of variational equation. Namely, the variational equation with the delta function and its differentiation is derived. It is shown that the calculation speed of this method is very fast and complicated periodic solutions are easily obtainable in high accuracy. The stabilities of periodic solutions obtained in the shooting method are in good accordance with those obtained by the analytical method. The discontinuities in the stability of the periodic solutions are shown using characteristic multiplier. Lyapunov exponents are also calculated by applying the integral technique of variational equation.

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Centrifugal fans, which are frequently used in our daily lives and various industries, usually make severe noise problems. Generally, the centrifugal fan noise consists of tones at the blade passing frequency and its higher harmonics. These tonal sounds come from the interaction between the flow discharged from the impeller and the cutoff in the casing. Prediction of the noise from a centrifugal fan becomes more necessary to optimize the design to meet both the performance and noise criteria. However, only some limited studies on noise prediction method exist because there are difficulties in obtaining detailed information about the flow field and casing effect on noise radiation. This paper aims to investigate the noise generation mechanism of a centrifugal fan and to develop a prediction method for the unsteady flow and acoustic pressure fields. In order to do this, a numerical analysis method using acoustic similarity law is proposed, and it is verified that the method can predict the noise generation mechanism very well by comparing the predicted results with available experimental results.

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The spectrum of impulse response signal from the impact hammer testing is widely used to obtain the frequency response function (FRF). However the FRFs obtained from the impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed by the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer testing are transient and damped, they are undoubtedly non-periodic. It is inevitable that the signals acquired for limited recording time should cause several errors. This paper makes clear the relation between the errors in the FRF and the length of the recording time. A new method is suggested to reduce the errors in the FRF in this paper. Several numerical examples involving 1-dof models are considered to elucidate the properties of the errors and the validity of the proposed method.

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In teleoperation field robotic system such as hydraulically actuated robotic excavator, the maneuverability and convenience is the most important in the operation of robotic excavator. Particularly the force information is important in dealing with digging and leveling operation in the teleoperated excavator. This paper presents a new force reflecting joystick in a velocity-force type bilateral teleoperation system. The master system is electrical joystick and the slave system is hydraulic cylinder. Particularly pneumatic motor is used newly in the master joystick for force reflection and the information of the pressure of slave cylinder is measured and utilized as force feedback signal. This paper also proposes a novel force-reflection gain selecting algorithm based on artificial neural network. Finally a series of experiments are conducted under various load conditions using a laboratory-made one axis slave cylinder and load simulator.

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In this paper, an analysis of volumetric efficiency of hydrostatic pumps in a variety conditions is investigated by using a proposed neural network. The effects of the parameters, such as the number of revolution, hydraulic oil temperature and exit pressures, which act on performances of hydrostatic pumps like gear pumps, vane pumps, and axial reciprocal pumps with swash plate, on the volumetric efficiency have been examined. The revolution number of the pumps, exit pressure of the system and the hydraulic oil temperatures are greatly affected by the leakage flowrate. The neural network structure is very suitable for this kind of system. The network is capable of predicting the leakage flowrate of the experimental system. The network has a parallel structure and fast learning capacity. As it can be seen from the results for both approaches, neural network could be modeled hydrostatic pump systems in real time applications.

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This paper proposes an optimal design scheme to improve an intake's capacity of noise reduction of the exhaust system by combining the Taguchi and Kriging method. As a measuring tool for the performance of the intake system, the performance prediction software which is developed by Oh, Lee and Lee (1996) is used. In the first stage, the length and radius of each component of the current intake system are selected as control factors. Then, the L₁₈ table of orthogonal arrays is adapted to extract the effective main factors. In the second stage, we use the Kriging method with the robust design to solve the non-linear problem and find the optimal levels of the significant factors in intake system. The L₁₈ table of orthogonal arrays with main effects is proposed and the Kriging method is adapted for more efficient results. We notice that the Kriging method gives noticeable results and another way to analyze the intake system. Therefore, an optimal design of the intake system by reducing the noise of its system is proposed.

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The performance of a common-rail fuel injection system and its effects on diesel engine combustion are strongly influenced by the injector characteristics. The injection timing and the injection rate of the common-rail injection system are important factors for combustion control and pollutant formation mechanism during the engine operation. This paper presents a dynamic model of the common-rail injector for high speed direct injection (HSDI) diesel engines and introduces a methodology for estimating the injection timing and the injection rate of the injector. The numerical simulation and the experimental results show that the proposed sliding mode observer (SMO) can effectively estimate the injection timing and the injection rate of the common-rail injector.

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Simulators have been used to evaluate drivers' reactions to various transportation products. Most research, however, has concentrated on their technical performance. This paper considers driver's motion perception on a vehicle simulator through the analysis of human sensibility ergonomics. A sensibility ergonomic method is proposed in order to improve the reliability of vehicle simulators. A simulator in a passenger vehicle consists of three main modules such as vehicle dynamics, virtual environment, and motion representation modules. To evaluate drivers' feedback, human perceptions are categorized into a set verbal expressions collected and investigated to find the most appropriate ones for translation and angular accelerations of the simulator. The cut-off frequency of the washout filter in the representation module is selected as one sensibility factor. Sensibility experiments were carried out to find a correlation between the expressions and the cut-off frequency of the filter. This study suggests a methodology to obtain an ergonomic database that can be applied to the sensibility evaluation of dynamic simulators.

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Drive-by-Wire (DBW) technologies improve conventional vehicle performance and a Steer-by-Wire (SBW) system is one of the DBW technologies. The control algorithm of the SBW system was designed in this paper. To verify the control algorithm, the SBW system is modeled using the bond graph method. The first aim of the control algorithm is controlling the steering wheel assist motor to make the real vehicle's steering feel and for a vehicle designer to adjust the steering feel as he finds necessary. Therefore, torque map is designed to determine the steering wheel reactive torque. The second aim is controlling the front wheel assist motor to improve vehicle's maneuverability and stability by using understeer and oversteer propensity of a vehicle. Furthermore, high performance control algorithm is proposed in this paper and Active Roll Stability Control (ARSC) method is designed as one of the high performance control algorithm.

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In this paper, a state-of-the-art contact mechanics model of a planetary gear set is employed to study the effect of a number of manufacturing and assembly related carrier and gear errors on the load sharing amongst the planets. Three different groups of errors are considered: (i) time-invariant, assembly-independent errors such as carrier planet pinhole position errors, (ii) time-invariant, assembly-dependent errors such as planet tooth thickness errors, and (iii) time-varying, assembly-dependent errors such as gear run-out errors. With such errors present, planet load sharing characteristics of an n-planet system (n=3 to 6) is investigated for different piloting configurations under quasi-static conditions. Load sharing behavior as a function of key manufacturing errors is quantified and design guidelines are proposed for better planet load sharing behavior.

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The study deals with the manufacture of fly-eye mirrors for EUVL by means of ultraprecision 5-axis control milling. The mirrors consist of many small spherical mirror elements with many steps among them. In the present study, two new methods for manufacturing the mirrors using a single-crystal diamond tool are proposed. One method uses a sphere type tool with a circular arc cutting edge. Though the method is theoretically efficient, it is found that it is not practical due to the difficulty of manufacturing the tool accurately. The other one uses a cylinder type tool with a right-angled cutting edge. The tool enables the manufacturing of spherical surfaces with any radius and supports practical use because the efficiency of this method is independent of tool form accuracy. The fly-eye mirror was machined by the latter method to have an array of four spherical mirror elements with the required steps and without any burrs.

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Powder forging (P/F), which combines powder metallurgy (P/M) and forging technologies, leads to refined poreless microstructure in the material. Therefore, the mechanical property of the P/F material can be greatly improved comparing with that of the sintered material. In this paper, the rolling contact fatigue tests were conducted using a two-cylinder testing machine, and the surface failure and durability of the case-hardened P/F rollers were compared with those of the case-hardened conventional steel rollers. From the experimental and analytical results, it could be concluded that the failure mode of the P/F and the steel rollers was mainly spalling, and the surface durability of the P/F rollers was almost the same as that of the steel rollers. Evaluating the rolling contact fatigue life by the amplitude of the ratio of orthogonal shear stress τ _yz to Vickers hardness Hv, considering the case that every hardness distribution is the same to each other, the fatigue life of the Ni rich P/F roller was rather longer than that of the steel ones. The P/F process effectively improves the microstructure of the P/M material and makes the surface durability of the P/F material with high content of Ni approach to the level of steel. The P/F process was a good method to improve the mechanical properties of the sintered materials.

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The aim of this research is to develop an in-process tool wear monitoring system for CNC turning machine. The exponential decay function is employed to represent the relation between the nominal specific cutting resistance and feed rate. An index value a in the exponential decay function is defined to estimate the flank wear, which is equivalent to the rate of increase in the nominal specific cutting resistance at zero feed rate as compared to that at infinite feed rate. In order to obtain the characteristic value a, the additional cutting cycles is proposed here to alter the feed rate deliberately during the normal cutting cycle to measure the cutting forces and identify the rate of increase in the nominal specific cutting resistance at smaller feed rates. Series of cutting tests were carried out to estimate the flank wear, and it is proved that the index mentioned above can be a good measure of tool wear, even though the depths of cut, the cutting speeds and the cutting tools, as well as the work materials are different.

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The present paper deals with the development of synchronizing controller for dual-drive servo system that is often used for SMD (Surface Mount Device) assembly machine. Instead of coordinating the commands to the individual feed drives and implementing closed position loop control for each axis, this work is achieved by the evaluation of an optimal cross-coupled compensator aimed specifically at improving synchronous accuracy in dual feed drives. The optimal control formulation explicitly includes the synchronous error in the performance index to be minimized. In this paper, surface chip mounter is used for experiment. It demands to synchronize the positions of its two primary driving axes. The system is modeled as the first order approximation and cross-coupled optimal synchronizing controller is designed. The synchronizing control is simulated and experimented with actual system for various velocity profiles. The results show that the proposed controller reduces the synchronous error considerably, compared to the conventional uncoupled control for the dual-drive system.

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