Open-loop and feedback-controlled mouse cursor movements in linear paths

Path length (A), path width (W) and movement direction (θ) are identified as the main factors affecting visually-controlled movement times in linear paths. Effects of A and W are well described by Drury's ( 1971 . Movements with lateral constraint. Ergonomics, l4 (2), 293-305.) model in which movement time is linearly related to the ratio of A/W. At low A/W values, departure from linearity has been identified but not investigated in detail. Data are presented for both open-loop and feedback-controlled movements in linear paths at 0, 60 and 150° movement directions. Movement amplitude and path width were varied over a wide range to determine the effects of A and (A/W) on movement time. Movements were found to be made ballistically or in open-loop mode when the ratio (A/W) was less than about 8 to 10 and the movement times were linearly related to √A for all angles of movement. Feedback-controlled movements followed Drury's law; ballistic movements had movement speed linear with √A. PRACTITIONER SUMMARY: Many tasks require manoeuvring equipment or devices through a path of limited width. These movements can be made with or without feedback control, depending on the path constraints. The conditions for the two forms of movement are determined in this research.     

(Abstracts)Changing Industrial Demands

Abstract

The frequency dependence of discomfort caused by vertical mechanical shocks has been investigated with 20 seated males exposed to upward and downward shocks at 13 fundamental frequencies (1–16 Hz) and 18 magnitudes (±0.12 to ±8.3 ms^?2). The rate of growth of discomfort with increasing shock magnitude depended on the fundamental frequency of the shocks, so the frequency dependence of equivalent comfort contours (for both vertical acceleration and vertical force measured at the seat) varied with shock magnitude. The rate of growth of discomfort was similar for acceleration and force, upward and downward shocks, and lower and higher magnitude shocks. The frequency dependence of discomfort from shocks differs from that of sinusoidal vibrations having the same fundamental frequencies. This arises in part from the frequency content of the shock. Frequency weighting W_b in BS 6841:1987 and ISO 2631-1:1997 provided reasonable estimates of the discomfort caused by the shocks investigated in this study.

Practitioner Summary: No single frequency weighting can accurately predict the discomfort caused by mechanical shocks over wide ranges of shock magnitude, but vibration dose values with frequency weighting W_b provide reasonable estimates of discomfort caused by shocks similar to those investigated in this study with peak accelerations well below 1 g.     

Ergonomics modelling and evaluation of automobile seat comfort

Automobile seats are developed in an iterative manner because subjective feedback, which is usually of questionable quality, drives the design. The time and cost associated with iteration could be justified if the process was guaranteed to produce a comfortable seat. Unfortunately, this is not the case. Current practices are based on the premise that seat system design teams need objective, measurable laboratory standards, which can be linked to subjective perceptions of comfort. Only in this way can predictions be made regarding whether or not a particular design will be viewed by the consumer as comfortable. This type of forecasting ability would effectively improve the efficiency with which automobile seats are designed. In this context, the research reported, developed, and validated a stepwise, multiple linear regression model relating seat interface pressure characteristics, occupant anthropometry, occupant demographics, and perceptions of seat appearance to an overall, subjective comfort index derived from a survey with proven levels of reliability and validity. The model performance statistics were: adjusted r ²?=?0.668, standard error of estimate?=?2.308, F (6, 38)?=?15.728, p?=?0.000, and cross-validated r (15)?=?0.952, p?=?0.000. From the model, human criteria for seat interface pressure measures were established. These findings could not have been attained without first demonstrating that (1) the data collection protocol for seat interface pressure measurement was repeatable and (2) seat interface pressure measurements can be used to distinguish between seats.     

Comparison of two suspension control strategies for multi-axle heavy truck

Two simple and effective control strategies for a multi-axle heavy truck, modified skyhook damping (MSD) control and proportional-integration-derivative (PID) control, were implemented into functional virtual prototype (FVP) model and compared in terms of road friendliness and ride comfort. A four-axle heavy truck-road coupling system model was established using FVP technology and validated through a ride comfort test. Then appropriate passive air suspensions were chosen to replace the rear tandem suspensions of the original truck model for preliminary optimization. The mechanical properties and time lag of dampers were taken into account in simulations of MSD and PID semi-active dampers implemented using MATLAB/Simulink. Through co-simulations with Adams and MATLAB, the effects of semi-active MSD and PID control were analyzed and compared, and control parameters which afforded the best comprehensive performance for each control strategy were chosen. Simulation results indicate that compared with the passive air suspension truck, semi-active MSD control improves both ride comfort and road-friendliness markedly, with optimization ratios of RMS vertical acceleration and RMS tyre force ranging from 10.1% to 44.8%. However, semi-active PID control only reduces vertical vibration of the driver’s seat by 11.1%, 11.1% and 10.9% on A, B and C level roads respectively. Both strategies are robust to the variation of road level.     

Thermal-environment characteristics and comfort of combined radiant-floor （Korean heating system ondol） and convective cooling system

The thermal-environment characteristics of the existing forced-convection cooling system were compared with those of the convective cooling system, which combined the radiant-floor cooling system using floor-heating panel typically applied to apartments in South Korea with the forced-convection cooling system using improved fan coil unit. The subjective warm/cool-feeling responses to the combined radiant-floor and convective cooling system in the questionnaire survey conducted among the test subjects were analyzed to establish the basic data for the combined cooling system. The results show that in the thermal-equilibrium condition, the vertical air temperature difference in the model living room is larger in the forced-convection-cooling condition. Most of the subjects feel a proper warm/cool feeling on their entire body, but they feel colder on the foot and lower body in the combined-cooling condition.     

地板辐射供冷系统的实验与分析

对人体舒适性的评价方法进行了简要介绍,阐述了采用地板辐射供冷时室内温度和围护结构壁面温度的确定方法.以上海电力学院浦东校区艺术厅为研究对象进行实验,结果表明:地板表面温度在21.56℃以下、空气湿度为55%~65%时,室内的人体舒适性较好,同时也验证了采用地板供冷系统来提高舒适度是可行的.     

基于平顺性某型汽车悬架的优化选择

研究了汽车悬架参数与平顺性的关系,并在此基础上探讨了悬架参数的优化设计．将某一区间的悬架刚度与阻尼比等分为若干份并进行排列组合,然后将每一组参数代入汽车三自由度振动模型并进行平顺性分析计算,从中优选出汽车振动系统“输出”较好的悬架参数组合．     

基于乘客感受的沥青路面平整度评价方法

从道路使用者的角度对乘车舒适性与路面平整度之间的关系进行研究.以乘客的心电指标RMSSD(rootmean square of the squared differences of successive n-n intervals)为主要评价依据,选取平整度范围为1.06～5.53 m/km的12条沥青路面进行室外乘车试验.实验数据表明:不同速度下RMSSD随平整度的变化有明显的变化规律,同时结合主观打分法和振动加速度评价法,提出基于乘客舒适性的平整度临界值.     

西安火车站过渡季节热环境调查分析

通过对客流量的统计以及室内外温湿度等环境参数的现场测试,分析了西安火车站候车厅的热环境现状．用ASHRAE七级热指标尺度进行了热舒适现场问卷,调查了候车厅内人们对环境的满意度．讨论适应性问题,推导出室内舒适温度与室外平均温度之间的关系式,并将所得结果与其他研究成果进行对比．     

应用人机工学的平蹬摆式自行车开发研究

骑乘舒适、操控科学、使用便捷、运动可持续,一直是困扰人们骑乘自行车之一大难题。基于人机工学原理解读这一难题反映的诸多因素,从人的因素影响、骑行时的疲劳等问题切入,剖析问题根源与症结。以人机工学理论为依据,对其进行全方位综合研究,另辟蹊径,开发研制出独具特色之专利产品:从传动原理到结构形式都与众不同之新型自行车——PB-A型低座平蹬摆式自行车。陈述了该自行车的设计思路、结构组成与特点等。