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71.
Manipulation of friction at the nanoscale has been traditionally approached by chemical means (lubrication). Recent friction force microscopy (FFM) experiments demonstrated that it can be done mechanically by applying vibration to accessible elements of the system. This paper provides analytic understanding on why vibration can reduce friction based on a 1D model imitating the FFM tip moving on a substrate. Open-loop stability is first studied, and a feedback vibration control is then designed using the accessible variable. Comparing to the open-loop system, friction force is significantly reduced in the closed-loop system. Numerical simulations show satisfactory performances. 相似文献
72.
73.
Byung-Ho Jeon Marco Ajovalasit Joseph Giacomin 《International Journal of Industrial Ergonomics》2009,39(5):736-743
The aims of this study were to determine equal sensation curves for hand–arm steering wheel rotational vibration and to investigate the effect of gender on the subjective perceived intensity of steering wheel hand–arm vibration. Psychophysical response tests of 40 participants (20 males and 20 females) were performed using a steering wheel rotational vibration simulator using the category-ratio Borg CR10 scale procedure for direct estimation of perceived intensity. The test stimuli were sinusoidal vibrations at 22 third octave band centre frequencies in the range from 3 to 400 Hz, with acceleration amplitudes in the range from 0.04 to 27 m/s2 r.m.s. Multivariate regression procedures were applied to the experimentally acquired data in order to establish a regression model expressing the Borg CR10 perceived intensity values as a function of the two independent parameters of the frequency and amplitude of vibration. The equal sensation curves suggested a non-linear dependency of the subjective perceived intensity on both frequency and amplitude. Females were found to provide higher Borg CR10 perceived intensity values than males (p < 0.05), particularly at the higher intensity levels above approximately 1.0 m/s2 r.m.s and at the higher frequencies above approximately 20 Hz.
Relevance to industry
For the manufacturers of steering systems and of other automobile components this study provides vibration perception curves and identifies the possible importance of gender towards the perception of vibration which arrives at the steering wheel. 相似文献74.
Hsieh-Ching Chen Wei-Chyuan Chen Yung-Ping Liu Chih-Yong Chen Yi-Tsong Pan 《International Journal of Industrial Ergonomics》2009,39(5):708-718
Riders of twelve motorcycles, comprising 6 full-scale motorbikes and 6 motor-scooters, and 5 sedan vehicles, performed test runs on a 20.6 km paved road composed of 5 km, 5 km, and 10.6 km of rural, provincial and urban routes, respectively. Each test run of motorcycle was separately performed under speed limits of 55 km/h and 40 km/h. Tri-axial accelerations of whole-body vibration (WBV) were obtained by using a seat pad and a portable data logger, and the driver's view was videotaped with a portable media recorder. Root mean square (RMS) acceleration, 8-h estimated vibration dose value (VDV(8)) and 8-h estimated daily dose of static compression dose (Sed) were determined from the collected data in accordance with ISO 2631-1 and ISO 2631-5 standards. Experimental results indicate that the WBV values of the sedan vehicle drivers have low RMS, VDV(8) and Sed values (RMS 0.27–0.32 m/s2; VDV(8) 6.3–8.3 m/s1.75; Sed 0.21–0.26 MPa). However, over 90% of the motorcycle riders had VDV(8) (mean 23.5 m/s1.75) exceeding the upper boundary of health guidance caution zone (17 m/s1.75) recommended by ISO 2631-1, or had Sed (mean 1.17 MPa) exceeding the value associated with a high probability of adverse health effects (0.8 MPa) recommended by ISO 2631-5. Over 50% of the motorcycle riders reached these boundary values for VDV and Se in less than 2 h. The WBV exposure levels of the full-scale motorbikes riders and motor-scooter riders were not significantly different. However, the RMS and VDV(8) values of motorcycle riders indicate significant roadway effect (p < 0.001), while their Sed values indicate significant speed limit effect (p < 0.05). This study concludes that the WBV exposure levels of common motorcycle riders are distinctively higher than those of sedans, even on a regular paved road. The impact on health of WBV exposure in motorcycle riders should be carefully addressed with reference to ISO 2631-1 and ISO 2631-5.
Relevance to industry
This study compares the predicted health risks of motorcycle riders according to ISO 2631-1 and ISO 2631-5 standards. Experimental data suggest that the vibration dose value of ISO 2631-1 and daily dose of equivalent static compression stress of ISO 2631-5 have roughly equivalent boundaries for probable health effects. 相似文献75.
Chunling Du Author Vitae Lihua Xie Author Vitae Author Vitae Youyi Wang Author Vitae 《Automatica》2009,45(10):2244-2249
This paper is concerned with the rejection of multiple narrowband disturbances in hard disk drives (HDDs). Inspired by a control blending idea, the multi-frequency disturbance rejection is formulated as a blending control problem. Each disturbance rejection is accomplished by using the H2 optimal control method. Based on all H2 optimal controllers, the blending technique is applied to yield a single controller which is capable of achieving rejection of all disturbances. Rejections of two and three disturbances for a 1.8-inch HDD VCM actuator are taken as application examples in the paper. Simulation and experimental results show that the ultimate controller results in a simultaneous attenuation of disturbances with frequencies higher or lower than the closed-loop system bandwidth. Moreover, the method turns out to be able to lift phase and thus prevent phase margin loss when it is used to deal with disturbances near bandwidth. 相似文献
76.
Vibration control of load for rotary crane system using neural network with GA-based training 总被引:4,自引:0,他引:4
Kunihiko Nakazono Kouhei Ohnishi Hiroshi Kinjo Tetsuhiko Yamamoto 《Artificial Life and Robotics》2008,13(1):98-101
A neuro-controller for vibration control of load in a rotary crane system is proposed involving the rotation about the vertical
axis only. As in a nonholonomic system, the vibration control method using a static continuous state feedback cannot stabilize
the load swing. It is necessary to design a time-varying feedback controller or a discontinuous feedback controller. We propose
a simple three-layered neural network as a controller (NC) with genetic algorithm-based (GA-based) training in order to control
load swing suppression for the rotary crane system. The NC is trained by a real-coded GA, which substantially simplifies the
design of the controller. It appeared that a control scheme with performance comparable to conventional methods can be obtained
by a relatively simple approach.
This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January
31–February 2, 2008 相似文献
77.
Ping Yang Fuyun Liu Yong Liu Ningbo Liao Binghao Bao 《Structural and Multidisciplinary Optimization》2008,35(5):489-498
Electronic equipment’s system is always manufactured as a superprecision system. However, it will be used in harsh environment.
For example, the computer in moving vehicles will be acted by vibrations. The objective of this paper is to provide a systematic
investigation to test and computer-aided design of the vibration isolator for protection of electronic equipment’s system
in harsh vibration environment. A micro-oil damping vibration isolator is designed and manufactured through coupling the oil
and spring by ingenious tactics. The structure of the oil damping vibration isolator can achieve circulating oil damping function
with an inner tube and an outer tube (some orifices are manufactured on upside and underside of the inner tube). The dynamics
of the key model machine is systematically investigated. Based on the test, a nonlinear dynamic model for the vibration isolator
is presented by analyzing the internal fluid dynamic phenomenon with respect to the vibration isolator. The model considers
all the physical parameters of the structure. Comparisons with experimental data confirm the validity of the model. In the
other, the model is integrated by introducing normalization measure. The normalization model shows the actual physical characteristics
of the oil damping vibration isolator by considering quadratic damping, viscous damping, Coulomb damping, and nonlinear spring
forces. An approximate solution is deduced by introducing harmonic transform method and Fourier transform method. Therefore,
a parameter-matching optimal model for computer-aided design of the vibration isolator is build based on approximate solution.
An example confirms the validity of the computer-aided design integration.
相似文献
Ping YangEmail: |
78.
Considering the characteristics of two component forces on component synthesis vibration suppression(CSVS) method, two theorems on two component forces suppressing fractional multiple design frequency are given respectively. Meanwhile, the control force, which is composed by two arbitrary component forces with different initial time, can suppress certain frequencies for secondorder undamped vibration system. Using the above theorems, control moment of jet attitude maneuver on flexible spacecraft is designed on the basis principle of CSVS method. The simulations validate the correctness and effectiveness of the proposed method. 相似文献
79.
《Ergonomics》2012,55(8):911-926
The vibration from chain saws can cause vibration-induced white finger disease (VWFD). Measurements of vibration levels on the front and rear handles of different chain saw-types, and on the operator's middle finger were collected at three logging camps on Vancouver Island. Factors effecting the vibration levels on the finger and handles were investigated. The acceleration at the firing frequency was found to be the dominant factor effecting handle and finger vibration. Other factors which were investigated were: grip force; the presence of handle covers; and chain sharpening procedure. Weighted acceleration levels are calculated and this information is used to assess the latency period for fallers to develop VWF disease. 相似文献
80.
Jafar Zarei 《Expert systems with applications》2012,39(1):68-73
This paper proposes a systematic procedure based on a pattern recognition technique for fault diagnosis of induction motors bearings through the artificial neural networks (ANNs). In this method, the use of time domain features as a proper alternative to frequency features is proposed to improve diagnosis ability. The features are obtained from direct processing of the signal segments using very simple calculation. Three different cases including, healthy, inner race defect and outer race defect are investigated using the proposed algorithm. The ANNs are trained with a subset of the experimental data for known machine conditions. Once the network is trained, efficiency of the proposed method is evaluated using the remaining set of data. The obtained results indicate that using time domain features can be effective in accurate diagnosis of various motor bearing faults with high precision and low computational burden. 相似文献