Foot motions in manual material handling transfer tasks: A taxonomy and data from an automotive assembly plant

Ergonomic job analysis commonly applies static postural and biomechanical analysis tools to particular postures observed during manual material handling (MMH) tasks, usually focusing on the most extreme postures or those involving the highest loads. When these analyses are conducted prospectively using digital human models, accurate prediction of the foot placements is critical to realistic postural analyses. In automotive assembly jobs, workers frequently take several steps between task elements, for example, picking up a part at one location and moving to another location to place it on the vehicle. A detailed understanding of the influence of task type and task sequence on the stepping pattern is necessary to accurately predict the foot placements associated with MMH tasks. The current study examined the patterns of foot motions observed during automotive assembly tasks. Video data for 529 pickup and delivery tasks from 32 automotive assembly jobs were analysed. A minimum of five cycles was analysed for each task. The approach angle, departure angle, hand(s) used, manipulation height and patterns of footsteps were coded from the video. Object mass was identified from the job information sheet provided by the assembly plant. Three independent raters coded each video and demonstrated an intraclass correlation coefficient of 0.54 for identification of the configuration of the lower extremities during terminal stance. Based on an analysis of the distribution of stepping behaviours during object transitions (pickups or deliveries), a transition classification system (TRACS) was developed. TRACS uses a compact notation to quantify the sequence of steps associated with a MMH transition. Five TRACS behaviour groups accounted for over 90% of the transition stepping behaviours observed in the assembly plant. Approximately two-thirds (68.4%) of the object transfers observed were performed with only one foot in contact with the ground during the terminal posture. The results from this paper suggest that a predictive model for choosing a transition stepping behaviour, coupled with a model to scale the selected foot behaviours, is needed to facilitate accurate prospective ergonomic analyses. This study proposes a method for categorising the stepping patterns associated with MMH tasks. The influence of task type and task sequence on the stepping patterns observed during several automotive assembly tasks is discussed. For prospective postural analyses conducted using digital human models, accurate prediction of the foot placements is critical to realistic postural analyses.     

Balance control during lateral load transfers over a slippery surface

Few studies have measured balance control during manual material handling, and even fewer with environmental cofactors. This study examined the effect of different surface frictions during a stationary manual material handling task. Thirty-six healthy participants completed 180° lateral transfer tasks of a load over high- and low-friction surfaces (μ = 0.86 and μ = 0.16, respectively). Balance measures, stance kinematics and lower extremity muscle activities were measured. Success during the novel slippery surface dichotomised our population, allowing us to investigate beneficial techniques to lateral load transfers over the slippery surface. Stance width reduction by 8 cm and 15° of additional external foot rotation towards the load were used to counter the imbalance created by the slippery surface. There was no clear alteration to lower extremity muscular control to adapt to a slippery surface. Changes in stance seemed to be used successfully to counter a slippery surface during lateral load transfers.

Statement of Relevance: Industries requiring manual material handling where slippery conditions are potentially present have a noticeable increase in injuries. This study suggests stance configuration, more so than any other measure of balance control, differentiates vulnerability to imbalance during material handling over a slippery surface.     

Development of the residual sodium quantification method for a fuel assembly of SFRs

ABSTRACT

In a fuel handling system of sodium-cooled fast reactors (SFRs), it is necessary to remove the sodium remaining on spent fuel assemblies (FAs) before storing them in a spent fuel water pool (SFP). A next-generation SFR in Japan has adopted an advanced dry cleaning process which consists of argon gas blowing to remove the metallic residual sodium on the FA, which increases economic competitiveness and reduces waste products thanks to a waterless process. In this R&D work, performance of the dry cleaning process has been investigated. This paper describes experimental and analytical work focusing on the amount of residual sodium remaining on FA components, for instance the handling head, the wrapper tube, the upper shielding, and the entrance nozzle. The tests, using water and sodium, investigated the amount of residual liquid remaining on laboratory scale specimens representing three fundamental shapes: narrow gaps, horizontal holes, and corners. On the basis of the experimental results, the residual sodium quantification method for FA was constructed. The constructed method enables quantitative estimation of the amount of residual sodium on the entire FA before and after the argon gas blowing with 95% reliability.     

Carrying and spine loading

The advantages and disadvantages of different methods of carrying objects on spine loading are still not fully understood. Previous studies have either examined the effects of carrying using physiological measures or examined isolated spine segments using biomechanical models. Additionally, most studies have been restricted to only a small number of carrying conditions. Very few studies have attempted to examine the various factors influencing spine loading together. To improve understanding of interacting factors on carrying, this study assessed the lumbar spine loads of 16 subjects as they assumed six styles of carrying at two weight levels and two activity levels (walking vs. standing). Concurrent with each trial, a subject-specific biomechanical model was used to assess spine forces over the full lumbar spine. Most carrying methods in the trials resulted in relatively low levels of spine loading. Anterior/posterior (A/P) shear loading was the only spine-loading dimension that reached biomechanically meaningful levels. Two carrying conditions, with bins carried in front of the body, significantly increased A/P shear compared with other carrying styles. This increase appeared to be due to the greater moment arms occurring in these conditions. Many of the other carrying styles produced A/P shears that were similar to those observed when carrying nothing at all. Of all the tasks, the backpack carry characteristically produced especially low spine loads. The findings of the study suggest that to achieve optimal carrying in terms of spine loading, loads should be positioned close to the body, even when carrying relatively light loads.     

Foot-ground forces on sloping ground when lifting∗

Slipping risk associated with manual material handling on inclined surfaces was investigated using a 2⁴ factorial experimental design under controlled laboratory conditions. The reaction force data at the shoe sole-sloping surface interface, the box trajectories, and the subjects’ assessment of the risk involved in carrying out the prescribed tasks were obtained and analysed both analytically and statistically. The results of these analyses are presented in this paper.     

仪用压缩空气SAR001MD涡轮流量计故障分析及处理

反应堆厂房入口仪用压缩空气流量计SAR001MD作为核电站重要监测仪表之一,流量数据的准确性关系到机组的安全运行。一旦出现故障必须予以高度重视,及时解决。某核电站CPR1000机组,在1号机组状态首次即将进入临界阶段时,出现SAR001MD流量计大幅度波动现象,导致安全壳泄漏率监测系统不可用,机组状态停滞。     

市政道路软基处理措施分析

本文主要研究了市政道路软基的处理措施，对软基的特点进行了讨论，并总结了几种常见软基处理方案，最后介绍了一种两种方案混合的软基处理方案。这种方案在保证了沉降量满足管道要求的同时也有着更高的经济性，值得研究和推广。     

Biomechanical risk assessment during field loading of hydraulic stretchers into ambulances

The process of loading a stretcher into an ambulance is known to cause a high incidence of back injuries among paramedics. This study aimed to assess the forces at L5/S1 during real-life stretcher loading activities and to determine the variables that contribute significantly to these forces. Analyses involved 58 paramedics (111 shifts) and 175 stretcher loading activities. Estimates of compression and shear forces at L5/S1 were calculated using the 3DSSPP program. Seventy-one percent of loading activities exceeded the safe loading level of 3.4 kN compression force at L5/S1 (mean: 3.9 kN, min–max: 2.1–7.0 kN). About 92% of the variance can be predicted from a combination of several variables, notably hand load (mean: 0.72 kN/number of paramedics) and back sagittal flexion (mean: 32°). Recommendations to reduce the risk of back injuries are proposed with regard to stretcher and ambulance loading design as well as training in stretcher lifting for paramedics.Relevance to the industryThe results of this study suggest that ambulance stretcher manufacturers should make ergonomic design changes to reduce the physical strain on paramedics’ backs during the process of loading a stretcher into an ambulance. Other preventive measures (e.g., training) must be formulated and applied to reduce the risk of back musculoskeletal disorders during the loading of stretcher patients. For instance, training should focus on back posture, teamwork and equipment/patient positioning on stretchers.     

煤炭装卸系统增设筛分设备的改造方法

在简单介绍煤炭专业化连续输送系统和煤炭筛分设备知识的基础上,结合天津港煤码头公司卸车系统筛分设备改造的相关内容,阐述了在传统煤炭连续输送系统中进行煤炭筛分设备改造的方法。     

A comparison between optimization algorithms applied to synchronization of bilateral teleoperation systems against time delay and modeling uncertainties

The goal of this paper is to achieve optimal performance for synchronization of bilateral teleoperation systems against time delay and modeling uncertainties, in both free and contact motions. Time delay in bilateral teleoperation systems imposes a delicate tradeoff between the conflicting requirements of stability and transparency. To this reason, in this paper, population-based optimization algorithms are employed to tuning the proposed controller parameters. The performance of tuned controllers is compared with the gains obtained by Cuckoo Optimization Algorithm (COA), Biogeography-Based Optimization (BBO), Imperialist Competitive Algorithm (ICA), Artificial Bee Colony (ABC), Particle Swarm Optimization (PSO), Genetic Algorithm (GA), Ant Colony Optimization with continuous domain (ACOR), Self-adaptive Differential Evolution with Neighborhood Search (SaNSDE), Adaptive Differential Evolution with Optional External Archive (JADE), Differential Evolution with Ensemble of Parameters and mutation strategies (EPSDE) and Cuckoo Search (CS). Through numerical simulations, the validity of the proposed method is illustrated. It is also shown that the COA algorithm is able to solve synchronization problem with high performance in stable transparent bilateral teleoperation systems.