Three computation schemes of time-frequency representations have been developed and implemented to identify different components of mechanical noise emitted from the transmission system of electrical vehicles. This study explores the close relationships between three time-frequency representations, i. e. the spectrogram based on windowed Fourier transform, the Wigner-Ville distribution, and the smoothed Wigner-Ville distribution. One main purpose is to pursue the efficiency of computing the smoothed Wigner-Ville distribution of a dynamic signature. The revised scheme can tremendously reduce the computation time to a scale of around 1/90, compared with the original scheme. To assess the validation of these time-frequency representation schemes, firstly, four synthetic signals are designed and processed. Secondly, the developed time-frequency representations are applied to distinguish different spectral components of transmission noise, and identify their sources. This study takes an electrical scooter with a continuous variable transmission system as a test bench. The continuous-variable-transmission-belt noise, helical-gear whine noise, and fan noise can be clearly identified via the processing of the time-frequency representations. These obtained conclusions can be used as references for machine element modification to reduce annoying noise.

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This paper deals with the polygonal deformation phenomena of rolls in a reversible hot plate leveler of the steel making machine experimentally and analytically. The plates leveled by rolls with polygonal deformation become so called defective products because the profile of deformed roll is transferred to the surface of plate. From the measurements of deformed rolls, two kinds of polygonal wear were found. Then, from the vibration measurement of a hot leveler in actual operation, natural frequencies of the hot leveler were determined and the process of the polygonization of rolls was observed. Finally, the authors analyzed a simple model theoretically, regarding the polygonal deformation phenomena as unstable vibration of the hot leveler system caused by time retardation accompanied by wear on the surfaces of rolls. A good agreement between experimental and theoretical results was also confirmed.

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Vibration of a nearly axisymmetric disk is analyzed by using a newly developed finite annular plate element with slight deviation from axisymmetry. Even if the developed annular plate element has four degrees of freedom, the annular element can contain the effects of slight deviation in density, stiffness or thickness. To provide validity of the proposed annular element, the natural frequencies of disks with deviation are computed by the finite element method using the new annular elements and the convergence and accuracy of the natural frequencies are investigated. It is shown that, when a disk has slight deviation, the finite element method using the proposed elements is more efficient to compute the natural frequencies and the mode shapes compared to a commercial code. Furthermore, the effects of deviation on the dynamic characteristics are also analyzed. Finally, it is evaluated how much deviation is acceptable for the proposed method to result in reliable computations.

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This paper investigates the problems of stability analysis and sliding mode control for a class of uncertain neutral delay-differential systems. First, we develop a new delay dependent condition such that uncertain neutral systems are not only asymptotically stable but also with a prescribed stability degree. Then, a proportional-integral switching surface is newly proposed such that the sliding mode motion is robustly stable with a prospective stability degree. This type of switching surface does not allow for a reduction of system order as it is the case with most sliding mode control. This property of switching surface makes it easy to design a sliding mode controller for the considered neutral systems. Based on the switching surface, a sliding mode controller is derived to guarantee the occurrence of sliding mode motion in finite time. Last, two illustrative examples are included to demonstrate the superiority of the obtained results.

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This paper presents a Cartesian to polar conversion technique based on a polynomial interpolation. The method is used for the processing of data from the two-orientation method for measuring spherical surfaces with an interferometer. The interferometer output consists of points on a square-grid coordinate system, which are then converted to a polar-grid coordinate system. The profile height data of the points on the polar-grid are calculated from a polynomial neighborhood analysis of points on the square-grid. Since the converted point on the polar-grid does not need to be at the center of the points in the analysis, profiles along concentric circles near to the edge of the test surface can also be calculated. A simulation of the polynomial and conventional 4-point techniques is carried out to verify the process. The comparison shows that the polynomial technique has produce a higher data conversion accuracy. Experiments on a phase-measuring interferometer were also conducted to verify the approach.

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In order to realize a power assisting suit for assisting a nurse caring a patient in her arm, a hardness sensor of muscle using load cell and a pneumatic rotary actuator utilizing pressure cuffs have been developed. The power assisting suit consists of shoulders, arms, waist and legs made of aluminum, and is fitted on the nurse body. The power assisting suit is originated with the concept of a master and slave system in one body. The arms, waist and legs have the pneumatic rotary actuators. The pneumatic rotary actuators are constructed with pressure cuffs sandwiched between thin plates. The action of the arms, waist and legs of the nurse are sensed with the muscle hardness sensor utilizing load cell with diaphragm mounted on a sensing tip. The dent of the sensing tip corresponds to the hardness of the muscle so that exerting muscle force produces electric signal. This paper gives the design and characteristics of the power assisting suit using the cuff type pneumatic rotary actuators and the muscle hardness sensor verifying its practicability.

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As an electrode quickly moves towards the discharge field, and then starts to discharge, the proposed variable structure system (VSS) with large switched proportional (P) gains can suddenly hold the electrode at the appropriate position. The erosion process can start quickly and stably in order to decrease the idle time of the whole eroding process. The design procedure of the VSS is presented according to a practical gap control system for an EDM. This advantage can provide high performance on the nonlinear and time-varying gap condition during eroding process. The practical experimental results of an EDM with the VSS controller show a decrease of the machining time, compared to the time required by the conventional proportional (P) controlled EDM.

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This paper deals with the analytical modeling, and the experimental verification of the strain rate self-sensing mechanism for a cantilevered piezoelectric beam. The piezoelectric beam consists of two laminated lead zirconium titanates (PZT) on a metal shim. A mathematical model of this beam dynamics is derived by the Hamilton's principle. It turns out that a method using an adaptive filter for the strain rate estimation of a piezoelectric beam works not properly due to the phase delay effect in a piezoelectric material and the structural shortcomings of an adaptive filter. In order to reduce the phase delay effect of the piezoelectric material on the performance of a strain rate self-sensing mechanism, a circuit for the phase delay compensation is devised. A systematic mechanism for the better strain rate estimation of a cantilevered piezoelectric beam compared to that using an adaptive filtering is proposed. The efficacy of this method is investigated through the comparison of experimental results with those from the analytical method.

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This paper investigates the constraint characteristics of parallel manipulators with three and four degrees of freedom. An analytical method of using equivalent screw groups is developed in the study based on the linear independence of screw systems and reciprocal screw systems. A procedure for determining overconstraints in spatial parallel mechanisms with fewer six degrees of freedom is given. With this method, the constraint characteristics of four parallel mechanisms with three or four degrees of freedom, i. e. 3-RRC, 3-CPR, 3-URU/SPS and 4-UPU mechanisms, are revealed. The constraint characteristics of three types of parallelogram linkage unites are then discovered, which gives the corresponding equivalent representations in terms of serial mechanisms. The approach is further applied to the geometric analysis of parallel mechanisms with hybrid limbs including 3-R(4U)_RPP and 3-R(4S)_RRRP mechanisms.

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This paper aims at developing an approach for the motion control and trajectory planning of a lightweighted three-link manipulator possessing two unactuated joints. The system is a case of second-order nonholonomy due to the presence of dynamical constraints. A three-flexible-link arm with a single actuator at the shoulder joint is modeled as a nonlinear Affine system, where the deflection is approximated as static bending. The way to attain the optimal positioning of this nonlinear system subjected to extreme conditions is to express the control input as a general function of a Fourier basis parameter acquired by using the Ritz method. Then this parameter is optimized through the application of the Newton method. To demonstrate the validity of this approach, simulations are carried out.

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This paper presents a cross-coupling (CC) controller for tracking contours to effectively reduce the contouring error of a direct-drive robot. Because contouring performance is a primary target over point-to-point tracking performance in a contour-tracking task, a cross-coupling control (CCC) algorithm design based on Lyapunov stability criteria and the recursive updating technique is proposed to enhance the contouring performance by coordinating the motion of multiple axes in spite of considerable model uncertainties and external disturbances. Furthermore, the proposed CCC design, which is a typical MIMO system with nonlinear time varying characteristic, has been verified as being locally stable. The control algorithm developed in tracking a circular and an elliptic contour is experimentally implemented on a two-axis direct-drive manipulator for various payload configurations. It is seen that the controller exhibits a certain degree of robustness, with the contouring performance being only slightly affected by changes in the payload. A comparison of the experimental results with those obtained by a tracking control law, which has no contouring consideration, and a conventional PID-type CCC tuned with the learning automata technique indicates that the proposed CCC can significantly enhance the contouring performance under different contouring commands and various payload configurations.

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This paper presents a novel distributed navigation strategy of multiple holonomic mobile robots to make group formations adapting to geometrical constraints in their working environment. Each mobile robot in this navigation strategy has its own coordinate system and it senses its relative position to others, so as to make group formations. Each mobile robot especially has a two-dimensional control input referred to as a “formation vector” and the formation is controllable by the vectors. Adjusting the vectors in a distributed fashion, the group makes the formations fitting into the geometrical constraints determined by the arrangements of landmarks that specify the location of the group, and obstacles. The validity of this navigation strategy is supported by computer simulations.

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The quasi-linear H₂/H_∞/LTR control method is presented for the robust control of hardnonlinear multivariable systems. The hard nonlinear elements such as Coulomb friction, dead-zone and backlash are replaced by their random input describing functions (RIDF) to develop a quasi-linear model for designing a quasi-linear H₂/H_∞ controller. However, a nonlinear correction term appears in the coupled Riccati equations when the quasi-linear H₂/H_∞ method is applied for a quasi-linear model. It is shown that a nonlinear correction term can be ignored using the loop transfer recovery (LTR) under the appropriate condition. Thus, the quasi-linear H₂/H_∞ controller can be synthesized by introducing the inverse random input describing function (IRIDF). To show the effectiveness of the proposed control method, it will be applied to a flexible parallel inverted pendulum with Coulomb friction. The results of simulation show that the proposed control method is robust to nonlinear effects and the vibration of end tip.

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The problem of model reference variable structure control for a class of perturbed time-delay systems with input nonlinearities is investigated. In this paper, the variable structure control is incorporated with an adaptive law to drive the state error between the desired model state and the controlled plant state to zero. The adaptive law is utilized for adapting the unknown upper bounds of the perturbations, and variable structure control is used for enhancing the robustness of the controlled systems. Hence, the information of the upper bounds of the perturbations is not required beforehand. It also shows that the proposed method ensures the property of globally asymptotically stable or uniformly ultimate boundness for the overall controlled system. Finally, a practical example is given to illustrate the feasibility of the proposed control methodology.

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A position tracking control schemes on the precise servo system in the presence of nonlinear dynamic friction is proposed. A nonlinear dynamic friction is regarded as the bristle friction model to compensate effects of friction. The conventional VSC method that often has used as a non-model-based friction controller has a poor tracking performance in high-precision position tracking application since it completely cannot compensate the friction effect below a certain precision level. Thus to improve the precise position tracking performance, we propose the VSC method combined with the friction-model-based observer having tunable structure of the transient response. Then this control scheme has a good transient response as well as the high precise tracking performance compared with the conventional VSC system without observer and the control system with similar type of observer. The experiments on the ball-screw drive table with the nonlinear dynamic friction show the feasibility of the proposed control scheme.

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High load capacity of carburized gears originates mainly from the hardened layer and induced residual stress. On the other hand, surface decarburization, which causes a nonmartensitic layer, and inclusions such as oxides and segregation act as latent defects which considerably reduce fatigue strength. In this connection, the authors have proposed a formula of strength evaluation by separately quantifying defect influence. However, the principal defect which limits strength of gears with several different defects remains unclarified. This study presents a method of inferential identification of principal defects based on test results of carburized gears made of SCM420 clean steel, gears with both an artificial notch and nonmartensitic layer at the tooth fillet, and so forth. It clarifies practical uses of presented methods, and strength of carburized gears can be evaluated by focusing on principal defect size.

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The effect of air bubbles evenly distributed in lubricating oil on the bearing performances is analyzed theoretically. The Reynolds equation for the bubbly lubricant in a steady-state and isothermal condition is solved with an iterative numerical method. Surface tension and the radius of bubble are taken into account in the analysis. It is assumed that bubbles move along streamlines and do not split apart or coalesce. The density and the viscosity of air-oil mixture are treated as functions of oil film pressure and the volume fraction of air. Numerical results show that the load carrying capacity of a journal bearing increases as bubbles in the supplied lubricant become smaller or the surface tension is getting larger. The load carrying capacity increases as the volume fraction increases up to a critical volume fraction that gives maximum load carrying capacity. Beyond the critical volume fraction, it decreases as the volume fraction increases.

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This paper describes a general method for reconstruction of a subdivision surface from polygon model or a set of scattered data points. The basic idea is to use the subdivision limit position to adapt the control mesh of the subdivision surface to the data points. This method is not a time consuming process involving global optimization. It does, however, fail to capture local characteristics of input model. Consequently, the proposed method is not suitable for generating a surface that precisely interpolates the input model, but it will be useful for quickly generating one that captures the overall shape constituted by the input model.

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In machine tools industry, new product developments with global competitiveness are urgently required. In particular, a man-machine interface for machine tools plays a dominant role in success or failure in new product developments. Nevertheless, a desirable man-machine interface for CNC controller has not been investigated in the previous academic literatures. Performances of man-machine interface largely influence on usefulness or acceptability of the machine tools. In this study, therefore, a usability measure with multiple attributes was defined based on the results of interview investigations with some mature operators. And also, a structured method for identifying the important design items was proposed. Using the proposed method, mutual relationships among the design items of control panel of CNC controller were identified to improve usability.

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This paper presents the influence of Ca sulfonate on tool life (flank wear), crater wear and finished surface roughness in hobbing. Experiments were carried out using two kinds of fully coated fly tools with TiN and (Al, Ti)N films respectively. As the results, when using the TiN fully coated tool, Ca sulfonate prolongs the tool life, and decreases the crater wear compared with the machine oil 23 as a base oil. With the (Al, Ti)N fully coated tool, an interesting result was obtained that the base oil containing no additives gives a longer tool life and a smaller crater wear than those obtained with Ca sulfonates added. It was suggested that the increase in the flank wear and the crater wear is caused by the chemical and/or the corrosive actions of Ca sulfonate, when Ca sulfonate was used for the (Al, Ti)N coated tool. Ca sulfonates improve the finished surface roughness for both coated tools.

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