Frequency weighting for the evaluation of steering wheel rotational vibration

The human perception of rotational hand–arm vibration has been investigated by means of a test rig consisting of a rigid frame, an electrodynamic shaker unit, a rigid steering wheel, a shaft assembly, bearings and an automobile seat. Fifteen subjects were tested while seated in a driving posture. Four equal sensation tests and one annoyance threshold test were performed using sinusoidal excitation at 18 frequencies in the range from 3 to 315 Hz. In order to guarantee the generality of the equal sensation data, the four tests were defined to permit checks of the possible influence of three factors: reference signal amplitude, psychophysical test procedure and temporary threshold shift caused by the test exposure. All equal sensation tests used a reference sinusoid of 63 Hz at either 1.0 or 1.5 m/s² r.m.s. in amplitude. The four equal sensation curves were similar in shape and suggested a decrease in human sensitivity to hand–arm rotational vibration with increasing frequency. The slopes of the equal sensation curves changed at transition points of approximately 6.3 and 63 Hz. A frequency weighting, called W_s, was developed for the purpose of evaluating steering wheel rotational vibration. The proposed W_s has a slope of 0 dB per octave over the frequency range from 3 to 6.3 Hz, a slope of −6 dB per octave from 6.3 to 50 Hz, a slope of 0 dB per octave from 50 to 160 Hz and a slope of −10 dB per octave from 160 to 315 Hz. W_s provides a possible alternative to the existing W_h frequency weighting defined in International Standards Organisation 5349-1 (2001) and British Standards Institution BS 6842 (1987).

Relevance to industry

For the manufacturers of tyres, steering systems and other vehicular components the proposed W_s frequency weighting provides a more accurate representation of human perception of steering wheel rotational vibration than the W_h weighting of ISO 5349-1 and BS6842.     

A multivariate investigation of gender differences in the number of online tests received-checking for perceived self-regulation

The purpose of the study was to investigate whether the number of formative e-tests taken differed by gender, using students' perceived self-regulation levels as a covariate. The sample was 340 teacher candidates reached through purposeful sampling. The study lasted a semester; students were involved in a blended learning environment where classroom lessons supported by self-regulatory e-tests as a part of an online course management system, called MOODLE. It was possible for students to take 10-item online quizzes and 20-item practice tests as many as they wanted. In the analysis, a factorial ANOVA design was applied. Findings indicated a moderate correlation between the number of formative e-tests taken and the perceived self-regulation levels, indicating higher perceived self-regulation levels as the number of formative e-tests increased. By using perceived self-regulation levels as a covariate, the gender differences in the number of e-tests taken were also investigated. According to finding, gender variable did not explain the differences in the compound variable “the number of formative e-tests”. However, after controlling for the effect of perceived self-regulation, the findings were significant. Hence, we can conclude that self-regulated behavior is independent of students' gender; therefore, e-assessments is a self-regulated, technology-based instructional aid in higher education.     

Effects of power tool vibration on peripheral nerve endings

Exposure to high frequency (kHz) vibration from impact power tools is overlooked in the ISO 5349-1 risk prediction for acquiring Hand Arm Vibration Syndrome. The biological effects of high frequency, power tool vibration have not been adequately studied. We characterized the magnitude and transmissibility of riveting hammer vibration in a rat tail model using a light weight piezoelectric sensor. The performance of the newly-introduced piezoelectric sensor was validated by showing its similarities to the previously published laser vibrometer. ISO 5349-1 frequency weighting revealed major risk from the 35 Hz component of the riveting hammer vibration, whereas the weighted values of the kHz components were not calculated to reach exposure action value in 24 h– However, the unweighted acceleration magnitudes at 12.4 and 16.3 kHz were about 10 and 50 times larger than the unweighted acceleration peak observed at 35 Hz. A transmissibility of <1 was calculated for 12.4 and 16.3 kHz, indicating tissue absorbance, while 35 Hz exhibited a transmissibility of 9.05, suggesting tissue resonance. The largest absolute change in acceleration was at 12.4 and 16.3 kHz, implicating that a considerable amount of high frequency vibration energy was absorbed by the tissue. A progressive reduction in intact sensory nerve endings was observed in the tissue when increasing vibration exposure from 1 min to 12 min.     

Hand-transmitted vibration from the steering wheel to drivers of a small four-wheel drive tractor

The paper presents research results of the vibration transmitted from the steering wheel of the small tractor with a 4-wheel drive to the driver's hands. The vibration measurements were carried out on the tractor randomly chosen from the producer's store-house. Before testing the tractor was examined and adjusted following the producer's recommendations. The vibration levels were measured at idling and at full load. The vibration level on the steering wheel was measured and analyzed and the frequency spectra for the chosen working conditions were obtained. The frequency-weighted acceleration, given in m/s(-2), was calculated. The vibration total value was defined as the root-mean-square of the three component values. The obtained values are graphically represented in accordance with ISO/DIS 5349-1979 and ISO5349-1-2001. The vibration exposure for the predicted 10% prevalance of vibration-induced white finger in accordance with Annex C of the same standard was also tested.     

Effects of gender differences and spatial abilities within a digital pentominoes game

Spatial ability is a critical skill in geometric learning. Several studies investigate how to use digital games to improve spatial abilities. However, not every learner favors this kind of support. To this end, there is a need to examine how human factors affect learners’ reactions to the use of a digital game to support geometric learning. In this vein, this paper addresses this issue by developing a digital pentominoes game and examining the effects of two essential human factors, especially gender differences and spatial abilities, on students’ performance. The results demonstrate that students’ spatial abilities were significantly improved after they took the digital pentominoes game. The results also demonstrate that the digital game can reasonably reduce the differences between boys and girls. Moreover, the major gender differences lie within mental rotation among the three types of spatial ability and also mainly exist in the low spatial ability group. Finally, the findings are applied to develop a framework that can be used to enhance the understanding of gender differences and spatial abilities within the digital pentominoes game.     

基于SAW原理汽车转向扭矩测量的研究

针对市场上已有的电动助力转向EPS(Electric Steering System)扭矩测量装置存在的易受噪声干扰、寿命较短、构造复杂且供电困难等缺点[1],提出基于声表面波SAW(Surface Acoustic Wave)原理对转向扭矩进行测量的方案,能够进一步实现EPS系统扭矩测量装置的轻型化和数字化.基于COMSOL软件强大的物理分析功能,对测量方案中关键的主轴和压电基片进行理论和仿真研究,并且基于Matlab软件对仿真结果进行统计和分析,验证了该方案的可实施性.     

Gender differences and the effects of perceived internet privacy on self-reports of sexual behavior and sociosexuality

The use of the Internet for conducting research has found that the level of anonymity intrinsic to web-based surveys is useful in deterring various participant biases. Though, concerns about Internet privacy could interfere with the effects of perceived anonymity and influence how a person responds. In this study, participants were asked to take an Internet survey and then were randomly assigned to conditions with varying degrees of implied privacy in which they answered questions about their desire for casual sex (sociosexuality) and their lifetime sexual partners. Only in the condition without any threat to the participant’s anonymity was there no difference between men and women’s reports of their sexual behavior. However, in every condition men reported having a significantly higher sociosexuality than women. Findings are consistent with both the biologic and gender-biased explanations in differences of self-report for sexual information. Implications for social constraints and Internet based research are discussed.     

基于虚拟仪器的旋转设备振动监测与分析系统设计

针对旋转设备振动监测的改造升级项目的用户需求,采用虚拟仪器技术,设计开发了一种分布式的振动监测与分析系统,可对多个设备进行监测并提供多种振动分析图形。系统保留了原有监视仪表的使用,从其BUFFER口或串口采集振动信号,降低了改造费用,实现了平稳升级。LabWindows/CVI软件开发平台的使用,使显示界面和仪表相类似,便于操作人员使用,还大大缩短了开发周期。本文论述了该系统的总体结构和软件功能开发,系统已在工业现场进行了初步测试,效果良好,具有实用价值。     

Shared control for lane departure prevention based on the safe envelope of steering wheel angle

The ability to prevent lane departure has become an important feature for commercialized vehicles. This paper proposes a shared steering assistance strategy based on a safe envelope of steering wheel angle (SWA). This solves the human-machine conflict issue in lane departure prevention (LDP) system which uses steering control to help the driver keep the vehicle within the correct lane. The system combines a driver steering control model, current vehicle states and vehicle-road deviation. The desired SWAs are calculated when the driver intends to drive along the left or right side of the lane, and then the two angles are used to generate the safe envelope. Next, a driver intention estimator is designed to predict driver’s intended SWA and the assistance control is activated by judging whether the driver intended SWA is go beyond the safe envelope. Finally, a H∞ controller and a disturbance observer are developed to determine the assistance torque. In this way, the SWA is limited to safe values to mitigate lane departure and the controller intervention is minimized. The effectiveness of the proposed method is evaluated via numerical simulation with different driving scenarios and human-in-the-loop experiment on a driving simulator. The obtained results show that this method not only can avoid lane departures effectively, but also ensures a good human-machine cooperative performance.     

Effects of surface characteristics on the plantar shape of feet and subjects' perceived sensations

Orthotics and other types of shoe inserts are primarily designed to reduce injury and improve comfort. The interaction between the plantar surface of the foot and the load-bearing surface contributes to foot and surface deformations and hence to perceived comfort, discomfort or pain. The plantar shapes of 16 participants’ feet were captured when standing on three support surfaces that had different cushioning properties in the mid-foot region. Foot shape deformations were quantified using 3D laser scans. A questionnaire was used to evaluate the participant's perceptions of perceived shape and perceived feeling. The results showed that the structure in the mid-foot could change shape, independent of the rear-foot and forefoot regions. Participants were capable of identifying the shape changes with distinct preferences towards certain shapes. The cushioning properties of the mid-foot materials also have a direct influence on perceived feelings. This research has strong implications for the design and material selection of orthotics, insoles and footwear.     

Biomechanical response of the musculoskeletal system to whole body vibration using a seated driver model

ObjectiveThis study aimed to assess the effects of backrest inclination and vibration frequency on muscle activity in a dynamic environment using a musculoskeletal model.MethodThe muscle activity modeling method was used to analyze a full body musculoskeletal system of a seated person with a public domain rigid body model in an adjustable car seat. This model was established using AnyBody Modeling System, based on the inverse dynamic approach. And the min/max criterion in dealing with the muscle redundancy problem. Ten healthy subjects were exposed to whole body vibration (WBV) with five frequencies (3, 4.5, 6, 7, and 8 Hz) in the vertical direction in a randomized order on three separate days. The displacement of the seat-pan and head was measured using a hybrid Polaris spectra system to obtain the seat-to-head (STH) transmissibility. Muscle oxygenation was measured using near-infrared spectroscopy. The validity of the model was tested using STH transmissibility and muscle oxygenation.ResultsIncreased vibration frequency caused high muscle activities of the abdomen and the right leg with a backrest forward inclination angle. The muscle activities of the left leg decreased at a backrest backward inclination except at inclination angles of 15° and 30°. Muscle activity of the lumbar suddenly increased at a backrest inclination angle of 5° and vibration frequency of 5 Hz. Muscle activities were higher under vibration than that without vibration.ConclusionVibration frequency significantly affected the muscle activity of the lumbar area. Likewise, the inclination degree of the backrest significantly affected the muscle activities of the right leg and the abdomen. The combination of vibration and forward inclination of the backrest can be used to maximize the muscle activity of the leg, similar to the abdomen and lumbar muscles.Relevance to the industryThe musculoskeletal model established in the present study provides a method that can be used to investigate the biomechanical response of seated drivers to WBV. This model helps protect drivers from occupational injury.     

一种调节阀减振降噪方法的探索

流体诱发问振动是常见的现象。根据流体诱发阀振动及频率的随机性,用概率论指导研制的“异径多束流调节阀”,在几种工况下,经多年的运行表明,新阀有效地解决了原使用传统调节阀时未能避免的振动,并且其工作特性优良,而所需成本仅为进口低噪音阀的1／8左右。这对解决流体诱发调节间的振动与噪音具有理论和实际价值。     

Effect of coating over the handle of a drill machine on vibration transmissibility

This study was to see the effect of different coatings on the handle of hand-held drilling machines. Out of five different handles chosen for this study, including one handle uncoated. Root mean square (rms) values of the vibration levels (acceleration) were recorded at the surface of handle and wrist of the operators. Results showed that maximum vibrations were reduced by coating of handle coated with rubber sheet and Rexene (H4) followed by handle coated with cotton sandwiched between jeans cloth (H5). Equivalent vibrations transmitted through coating of handles coated with sponge and velvet (H2) and jute and cotton (H3) were of almost same magnitude and these two coated handles were able to reduce least vibration transmitted. Transmissibility of vibrations along dominant (Z) direction was analyzed using ANOVA. Results showed that coating on handles significantly affected vibration transmitted in Z direction. Vibration transmissibility ratios were found to be 0.354, 0.571, 0.408, 0.4326, and 0.3555 for handles H1, H2, H3, H4 and H5 respectively.     

Properties of the posterior distribution of a regression model based on Gaussian random fields

We consider the regression problem based on Gaussian processes. We assume that the prior distribution on the vector of parameters in the corresponding model of the covariance function is non-informative. Under this assumption, we prove the Bernstein-von Mises theorem that states that the posterior distribution on the parameters vector is close to the corresponding normal distribution. We show results of numerical experiments that indicate that our results apply in practically important cases.     

基于特征模型的挠性结构自适应振动控制

航天器是一种由中心刚体和挠性附件组成的刚柔耦合复杂系统，由于系统调姿或外部扰动作用时将引起振动，尤其是在平衡位置的小幅度振动对姿态稳定度和指向控制精度严重影响，并且难以控制．为了解决该问题，采用基于特征模型的黄金分割自适应控制方法，并引入逻辑微分阻尼项进行振动主动控制．建立了刚柔耦合结构实验平台，进行了包括位置设定点及转动振动主动控制的算法实验比较，结果表明，采用的基于特征模型的方法得到了比较理想的振动抑制效果，尤其是对低频小幅值振动的抑制，在相同条件下，与传统控制方法相比，大大减少了振动抑制的时间．实验研究表明采用的算法快速抑制振动的有效性．     

动力吸振器对转子系统气流激振稳定性影响分析

针对气流激振引起离心压缩机转子振动失稳的问题,提出了采用动力吸振方法提高转子系统的稳定性.首先建立流体激励作用下转子 吸振系统动力学模型;其次采用Lyapunov理论研究附加吸振器后流体激励作用下转子系统的稳定性;分析了吸振器参数变化对转子系统稳定性的影响;最后采用数值方法进行验证.结果表明,动力吸振方法能够有效地提高转子系统失稳转速,吸振器固有频率和阻尼比对转子稳定性有较大的影响.     

SAS macros for estimation of the cumulative incidence functions based on a Cox regression model for competing risks survival data

When considering competing risks survival data, the cause specific hazard functions are often modelled by the proportional hazards Cox regression model. First, we present how to estimate the parameters in this model when some of the covariates are allowed to have exactly the same effect on several causes of failure. In many cases, the focus is not on the parameter estimates, but rather on the probability of observing a failure from a specific cause for individuals with specified covariate values. These probabilities, the cumulative incidences, are not simple functions of the parameters and they are, so far, not provided by the standard statistical software packages. We present two SAS macros: a SAS macro named CumInc for estimation of the cumulative incidences and a SAS macro named CumIncV for estimation of the cumulative incidences and the variances of the estimated cumulative incidences. The use of the macros is demonstrated through an example.     

基于时域有限差分和非参数核回归的室内移动通信干扰信号预测模型研究

针对网络优化和干扰实施中电磁辐射预测准确率不高的问题,本文利用多制式移动通信干扰器对室内的复杂场景进行了干扰防护的信号强度预测,对实际场景建立几何模型后采用时域有限差分算法获得信号强度预测值,并结合实际测量改进非参数核回归预测算法获得统计分析预测值,最后提出混合加权预测模型,对电磁辐射进行定量预测分析。预测结果表明,本文提出的基于时域有限差分算法和非参数核回归算法的混合加权预测模型能对复杂室内场景下信号强度进行预测,准确率较高。     

Adaptive model predictive control for a class of constrained linear systems based on the comparison model

This paper proposes an adaptive model predictive control (MPC) algorithm for a class of constrained linear systems, which estimates system parameters on-line and produces the control input satisfying input/state constraints for possible parameter estimation errors. The key idea is to combine the robust MPC method based on the comparison model with an adaptive parameter estimation method suitable for MPC. To this end, first, a new parameter update method based on the moving horizon estimation is proposed, which allows to predict an estimation error bound over the prediction horizon. Second, an adaptive MPC algorithm is developed by combining the on-line parameter estimation with an MPC method based on the comparison model, suitably modified to cope with the time-varying case. This method guarantees feasibility and stability of the closed-loop system in the presence of state/input constraints. A numerical example is given to demonstrate its effectiveness.     

Effects of strap support in a hand-held device on the muscular activity in female workers assessed by electromyography and subjective rating

The present study evaluates the potential mitigation of physical workload when using strap support for a portable device. The experiments were designed as consecutive sessions over a 2-h period. Electromyogram signals were recorded from four muscles of six subjects. The perceived level of fatigue on the whole body as well as in the shoulder, arm, lower back and legs was assessed using Borg's CR-10 scale. All subjects were tested under eight experimental conditions. Results indicated that the biceps brachii muscle displayed significantly lower activity with strap support than without a strap. In the experiments with and without a strap, different levels of force were imposed on the various muscles, which caused changes in the distribution of the physical load. Although the role of the strap might seem evident, using strap support did not always decrease the sensation of fatigue. However, for short-term tasks, using a strap may be recommended.