Effects of user experience,working posture and joint hardness on powered nutrunner torque reactions

Powered hand tools produce reaction forces that may be associated with upper extremity musculoskeletal disorders. The handle displacement, grip force and upper limb muscle activity (electromyography (EMG)) due to the effects of operator experience, working height and distance, type of tool and fastener joint hardness were measured in this study with 15 experienced and 15 novice nutrunner users. The results show that when pistol grip handles were used to work on a horizontal surface, experienced users allowed an average handle displacement of 7.9°, while novice users allowed 11.5°. Average EMG scaled by reference voluntary contraction (RVC) at forearm flexors, forearm extensors and biceps were greater for experienced users (318% RVC, 285% RVC, 143% RVC, respectively) than for novice users (246% RVC, 219% RVC, 113% RVC, respectively). Experienced users exerted more grip force than novice users when using right angle handles, but less force when using pistol grip handles. The results suggest that it is possible to minimize tool handle displacement by adapting the workplace layout to permit different working postures for each user group.     

The effects of joint torque, pace and work:rest ratio on powered hand tool operations

Repetitive use of hand-held power tools is associated with work-related upper extremity musculoskeletal disorders. Using a pneumatic nutrunner, 21 men completed twelve 360 repetitive fastener-driving sessions on three joints (hard, soft and control) at slow and fast pace, and two different work:rest patterns. Handgrip force and perceived exertions were collected throughout each session. For the control joint, the mean grip force exerted was 39.6% of maximum voluntary exertion (MVE) whereas during hard and soft joint sessions it was 48.9% MVE and 56.9% MVE, respectively. Throughout each session, the grip force decreased, more while operating soft and hard joints as compared with the control joint (regression slope: ?0.022 and ?0.023, compared with ?0.007 N/drive, respectively), suggesting considerable upper extremity muscular effort by participants during torque buildup. Fast work pace resulted in higher average grip forces by participants but a greater decrease in the force as the session progressed. Providing rest breaks reduced perceived exertions. The findings gain additional knowledge for assembly task design to possibly reduce the hand/arm injury risks for the operator.

Practitioner Summary: Powered hand tools are widely used in assembly and manufacturing industries. However, the nature of their repetitive use on human operator biomechanical and perceptual responses is not fully understood. This study examined work-related risk factors such as joint torque, pace and work:rest ratios on powered hand tool performance.     

位移式许用扭矩传感器的设计与研究

许用扭矩是拧紧螺纹紧固件时可施加的最大扭矩值,它是保证螺纹连接安全可靠的重要参数;由于现有扭矩扳手需要人工依靠经验或理论计算来设定所需扭矩值,设计了一种通过自动识别螺栓规格并计算许用扭矩的位移式许用扭矩传感器;螺栓夹持装置开口大小的调整与电位器阻值调整通过齿轮相关联用于识别螺栓规格信息,单片机HT66F50采集电位器的模拟信号经模数转换为数字信号运算并处理,计算结果通过液晶显示模块LCD1602进行显示;通过数据拟合及公式推导建立许用扭矩计算理论,硬件采用技术成熟的集成模块,软件设计采用模块化思想,建立了传感器原理样机;测试结果表明,数据计算误差在允许范围内,能够快速准确地计算许用扭矩值,达到了设计要求。     

Autonomous industrial assembly using force,torque, and RGB-D sensing

ABSTRACT

We present algorithms and results for a robotic manipulation system that was designed to be easily programable and adaptable to various tasks common to industrial setting, which is inspired by the Industrial Assembly Challenge at the 2018 World Robotics Summit in Tokyo. This challenge included assembly of standard, commercially available industrial parts into 2D and 3D assemblies. We demonstrate three tasks that can be classified into ‘peg-in-hole’ and ‘hole-on-peg’ tasks and identify two canonical algorithms: spiral-based search and tilting insertion. Both algorithms use hand-coded thresholds in the force and torque domains to detect critical points in the assembly. After briefly summarizing the state of the art in research, we describe the strategy and approach utilized by the tested system, how it's design bears on its performance, statistics on 20 experimental trials for each task, lessons learned during the development of the system, and open research challenges that still remain.     

From industrial safety to corporate health management

Occupational health and safety is one of the most important topics of ergonomics. In many countries the practical issues are addressed in worker protection laws or rules and most companies have some sort of occupational health and safety system. As with many other ergonomics approaches, such activities are often necessary because of legal requirements. Such efforts are often viewed by management as primarily cost intensive. To change this image, it would be helpful to have a more positive, management-oriented approach. Corporate health management as a module of an integrated management system can fulfil this goal.     

A Survey of Hand Anthropometry and Biomechanical Measurements of Dentistry Students in Turkey

The objectives of this study were 1) to determine various hand dimensions and biomechanics measurements for Turkish dentistry students, 2) to evaluate the differences between males and females and between the right and left hand, and 3) to compare these data with similar data for other populations (Thai, Indian, Malaysian, British, Jordanian, Nigerian, Mexican, Bangladesh, and Vietnamese). The present study was undertaken to generate hand anthropometric and biomechanics data of 92 male and 73 female students studying at dentistry faculty. Sixty‐seven anthropometric and 26 biomechanics measurements were taken in both hands. The means, standard deviations, and percentile values were tabulated and compared with other populations. The results suggest that the Turkish female fingers are thinner than those of other females except Indians, and that the Turkish male fingers are wider than those of the other males. Furthermore, the results also suggest that the Turkish female strength in handgripping is greater than that of other females except British females, and the Turkish male handgrip strength is greater than that of other males except Americans. This study provides insights about Turkish hand dimensions and biomechanics; it can be a basis for future studies and the design of dental tools meant for the Turkish market. © 2012 Wiley Periodicals, Inc.     

Assembly torque data regression using sEMG and inertial signals

Assembly torque monitoring is an important aspect of assembly process monitoring. Currently, in manual assembly lines, torque monitoring sensors are usually installed on assembly tools or assembly jigs. This approach is restricted by the working environment and assembly space. To this end, operators can use wearable devices containing sensors without being restricted by the tool and working spaces, with the added advantage of portability. To use wearable electromyography equipment to monitor the assembly torque, this paper proposes an assembly torque monitoring method using surface electromyography (sEMG) and inertial signals. Two torque regression models, one based on a heterogeneous-kernel-based temporal convolutional network (Het-TCN) and the other based on a two-stream convolutional neural network (CNN), are proposed and compared with CNN, long short-term memory (LSTM), and temporal convolutional network (TCN) models. The experimental results show that, compared with using sEMG signals alone, performing an assembly torque data regression using a combination of sEMG and inertial signals can significantly reduce the regression error. The proposed Het-TCN model has the best regression performance, with an average error of 3.31 N m an RMSE of 9.18 %, and a coefficient of determination R² of 0.72. Thus, the proposed Het-TCN along with the application of both sEMG and inertial signals can help effectively perform assembly torque data regression, which can be used for assembly torque or operation monitoring.     

Comparing the biomechanical and perceived exertion imposed on workers when using manual mechanical and powered cargo management systems during ladder loading and unloading tasks

This study aimed to compare the effects of two different cargo management systems (one powered system, i.e., the RazerLift®, and one Traditional system) on the biomechanical and perceived exertion experienced by workers when performing routine ladder loading and unloading tasks. Seven experienced workers performed ladder loading and unloading tasks. Compared to when the Traditional system was being used, the cumulative static low-back compression force was reduced by 57.9% (p < 0.05) and 39.3% (p < 0.05) when the RazerLift® was being used to perform ladder loading and unloading tasks, respectively. Overall, the cumulative shoulder flexor moments were reduced by 34.8% (p < 0.05) and 41.3% (p < 0.05) when the RazerLift® was being used to perform ladder loading and unloading tasks, respectively. Overall, the perceived exertion score was reduced by 250.1% (p < 0.05) when the RazerLift® was being used compared to the Traditional system. In conclusion, our study demonstrated that the RazerLift® reduces the biomechanical and psychophysical exposure associated with the development of musculoskeletal disorders while performing ladder loading and unloading tasks.     

Physiological and biomechanical responses to a prolonged repetitive asymmetric lifting activity

This study investigated the effects of a prolonged repetitive asymmetric lifting task on behavioural adaptations during repetitive lifting activity, measures of tissue oxygenation and spine kinematics. Seventeen volunteers repeatedly lifted a box, normalised to 15% of the participant's maximum lifting strength, at the rate of 10 lifts/min for a period of 60 min. The lifts originated in front of the participants at ankle level and terminated on their left side at waist level. Overall, perceived workload increased during the repetitive lifting task. Erector spinae oxygenation levels, assessed using near-infrared spectroscopy, decreased significantly over time. Behavioural changes observed during the repetitive lifting task included increases in the amount of forward bending, the extension velocity and the lateral bending velocity, and a reduced lateral bending moment on the spine. These changes, with the exception of the reduced lateral bending moment, are associated with increased risk of low back disorder.     

Psychophysical and physiological responses to lifting symmetrical and asymmetrical loads symmetrically and asymmetrically

Eighteen adult males (mean age 22·6 years, weight 78·6kg and height 176·6cm) participated in a study designed to investigate the effects of symmetrical and asymmetrical lifting on the maximum acceptable weight of lift and the resulting physiological cost. Each subject performed sixty different lifting tasks involving two lifting heights, three lifting frequencies and five containers. For each lifting task, the load was lifted either symmetrically (sagittal lifting) or asymmetrically (turning 90^° while continuing to lift). The heart rate and oxygen uptake of the individuals at the maximum acceptable weight of lift were measured. At the end of the experiment, subjects also verbally indicated their preference for symmetrical and asymmetrical lifting. When lifting asymmetrically, subjects accepted approximately 8·5% less weight. There was, however, no difference in the physiological costs when lifting symmetrically or asymmetrically. Lifting asymmetrical loads also resulted in lower maximum acceptable weights. No difference in either oxygen uptake or heart rate was observed when the centre of gravity of the load was offset by 10·16 or 20·32 cm from the mid-sagittal plane in the frontal plane towards the preferred hand. All subjects indicated, verbally, that asymmetrical lifting tasks were physically more difficult to perform.     

Handle height and expectation of cart movement affect the control of trunk motion at movement onset in cart pushing

As unexpected sudden unloading of the trunk may cause low-back injury, the objective of the present study was to investigate whether handle height and the expectation of cart movement in pushing affect trunk control at movement onset. Eleven healthy male participants pushed a 200-kg cart with handles at shoulder and hip heights. The cart would suddenly move when externally released (externally triggered condition) or when static friction was overcome (self-initiated condition). Before self-initiated cart movement, trunk stiffness and muscle activity were significantly higher than before an externally triggered onset at comparable pushing force. Lower muscle activity and trunk stiffness at shoulder height compared with the hip height before the onset resulted in higher trunk inclination after the onset. In conclusion, higher preparatory activation of trunk muscles serves to increase trunk stiffness in anticipation of cart movement and may reduce the impact of the perturbation associated with the onset of cart movement.

Statement of Relevance: Sudden cart movement in pushing causes an unexpected unloading perturbation to the trunk. This perturbation was shown to cause uncontrolled trunk movement, which may explain how pushing tasks can be associated with low-back injury. Effects of handle height and awareness of the subjects of the possible cart movement suggest directions for prevention.     

A quick identification model for assessing human anxiety and thermal comfort based on physiological signals in a hot and humid working environment

We propose a simple and quick method for quantifying workers' anxiety and thermal comfort levels using physiological signals. Nine subjects enrolled in a series of controlled laboratory experiments involving varying temperature, relative humidity, and labor intensities. A total of 40 experiments were conducted, and 1592 groups of anxiety data and 1624 groups of thermal comfort data were obtained, respectively. During 2-h-working trials, Electroencephalogram (EEG), photoplethysmography (PPG), and pupil diameter of each subject were collected synchronously, and the State-Trait Anxiety Inventory (STAI) and thermal comfort vote (TCV) were completed in stages. Random Forest was adopted to screen out the appropriate sensitivity feature indicators of anxiety levels and thermal comfort levels from the 70 features of the 10 EEG channels. Finally, Random Forest, Gradient Boosting Decision Tree, K-nearest Neighbor Algorithm, and Support Vector Machine were used to determine relevant physiological data combinations and modeling algorithms. The Precision of the anxiety level and thermal comfort level quick identification model based on Random Forest Algorithm can reach 81.04% and 84.79%, respectively. This suggests that the proposed quick identification method for assessing workers' anxiety and thermal comfort levels holds promise. Physiological data need to be obtained by monitoring only PPG, pupil diameter, and 5 EEG channels. By processing these data, the workers' anxiety and thermal comfort level could be judged realistically to ensure their safety. It is suggested that PPG, pupil diameter, and EEG should be considered all together in the future study of anxiety and thermal comfort.     

Cardiorespiratory responses of firefighters to a computerized fire strategies and tactics drill during physical activity

Firefighters are subjected to a combination of physical and mental challenges in the course of their occupational responsibilities. However, due to the ecological factors involved with firefighting, it makes it extremely difficult to examine physiological and psychological changes that occur as a result of these combined challenges. The purpose of this study was to examine the efficacy of a computer-based Fire Strategies and Tactics Drill (FSTD) in eliciting psychological and physiological measures of stress in professional firefighters. In one session, participants exercised at 60% VO_2max for 37 min (exercise alone condition, EAC), and in the other session the firefighter exercised for an equal amount of time and responded to the FSTD (dual challenge condition; DCC) while exercising. Cardiorespiratory (heart rate [HR], respiration rate [RR], minute ventilation [V_E], oxygen consumption [VO₂], ventilatory efficiency [V_E/VO₂], and respiratory exchange ratio [RER]) and psychometric measures (State Anxiety Inventory [SAI] and Ratings of Perceived Exertion [RPE]) were obtained throughout the experimental protocols. The NASA Task Load Index was used to assess perceived physical and mental load during each condition. The results demonstrated that the participants perceived overall workload to be higher in the DCC. Repeated measures ANOVAs revealed no differences between the EAC and DCC for VO₂ or RER, but the DCC did elicit significantly greater elevations in HR, RR, V_E, and V_E/VO₂ compared to the EAC. These results suggest that the FSTD utilized in this study provides an effective method for examining the physiological and psychological responses of firefighters in a research laboratory environment.     

Revision and validation of the Connor-Davidson Resilience Scale of coal miners in China

The psychological state of coal miners may have negative changes because of the long-term underground working environment and complex production process and will cause unsafe behaviour. Resilience can enhance the adaptability of individuals to high-risk and high-pressure environments and predict unsafe behaviour. However, currently little research has been done to develop resilience measuring tools for coal miners. Therefore, this paper revised and verified the Connor-Davidson Resilience Scale (CD-RISC) among coal miners in China and developed an individual resilience scale available for the coal industry. Five hundred and twenty subject coal miners have finished the initial test, and the exploratory factor analysis and reliability analysis were used to revise the CD-RISC. Another survey on 639 samples was then conducted to assess a confirmatory factor analysis and test-retest reliability of the resilience scale. The resulting scale has two dimensions, tenacity and strength, including a collection of 6 items. This study assists in further exploring the structural factor of individual resilience level for China coal industry, and provides a new research idea for occupational health, and contributes to the safety management and sustainable development of the coal enterprises.     

The effects of operator position,pallet orientation,and palletizing condition on low back loads in manual bag palletizing operations

Many mining commodities are packaged and shipped using bags. Small bags are typically loaded onto pallets for transport and require a significant amount of manual handling by workers. This specific task of manual bag handling has been associated with the development of musculoskeletal disorders (MSDs), especially low back disorders. This study evaluates the biomechanical demands of different work layouts when performing manual palletizing of small bags, and evaluates the biomechanical stresses associated with different stacking techniques. Results indicate that peak forward bending moments as well as spinal compression and shear forces are higher when the pallet is situated at the side of the conveyor as opposed to the end of the conveyor. At low levels of the pallet, controlled bag placement results in higher peak forward bending moments than stacking at higher levels and when dropping the bag to lower levels. The results of this study will be used to inform the development of an audit tool for bagging operations in the mining industry.Relevance to industryIn many cases for workers loading small bags, compression forces exceed the NIOSH criterion of 3400 N. Orientation of the pallet has a significant impact on spinal compression, and positioning the pallet at the end of the conveyor reduces the estimated compressive loading on the lumbar spine by approximately 800 N.     

Worker productivity, and occupational health and safety issues in selected industries

The main objective of this research was to identify factors that affected worker productivity, occupational health and safety in selected industries in a developing country. Fifty production managers participated in the study. Fifty-four percent of the managers reported hot environmental conditions, 28% a noisy environment, and 26% a lack of resources and facilities. Managers received worker complaints of fatigue, back pain, upper-body pain, hand and wrist pain and headaches. Management (88%) acknowledged not having knowledge or access to ergonomics information. Ninety-four percent of the companies did not carry out ergonomic assessments. A significant correlation (p<0.01) was found among productivity indicators and health and organizational attributes. Lack of skills in ergonomics and training, communication and resources are believed to be some of the factors contributing to the poor ergonomic conditions and consequent loss of worker productivity and reduced health and safety in these industries.     

Immune and inflammatory responses of Australian firefighters after repeated exposures to the heat

When firefighters work in hot conditions, altered immune and inflammatory responses may increase the risk of a cardiac event. The present study aimed to establish the time course of such responses. Forty-two urban firefighters completed a repeat work protocol in a heat chamber (100 ± 5°C). Changes to leukocytes, platelets, TNFα, IL-6, IL-10, LPS and CRP were evaluated immediately post-work and also after 1 and 24 h of rest. Increases in core temperatures were associated with significant increases in leukocytes, platelets and TNFα directly following work. Further, platelets continued to increase at 1 h (+31.2 ± 31.3 × 10⁹ l, p < 0.01) and remained elevated at 24 h (+15.9 ± 19.6 × 10⁹ l, p < 0.01). Sustained increases in leukocytes and platelets may increase the risk of cardiac events in firefighters when performing repeat work tasks in the heat. This is particularly relevant during multi-day deployments following natural disasters.

Practitioner Summary: Firefighters regularly re-enter fire affected buildings or are redeployed to further operational tasks. Should work in the heat lead to sustained immune and inflammatory changes following extended rest periods, incident controllers should plan appropriate work/rest cycles to minimise these changes and any subsequent risks of cardiac events.     

Assembly failures and action cost in relation to complexity level and assembly ergonomics in manual assembly (part 2)

Earlier studies have demonstrated strong relationships between manual assembly at high physical load levels and increased amounts of quality defects compared to assembly at low physical load levels. A recent Swedish interview study of engineers in design and manufacturing engineering indicated that assembly complexity factors are of additional importance for the assembly quality. The objective of this study was therefore to examine the significance of high and low complexity criteria and the relationships between assembly ergonomics and assembly complexity and quality failures by analyzing manual assembly tasks in car manufacturing. In total, 47 000 cars were analyzed and the results showed several significant correlations between assembly ergonomics and assembly complexity, assembly time, failures and action costs. The action costs for high complexity tasks were 22.4 times increased per task per car compared to low complexity tasks.     

Physiological computing for occupational health and safety in construction: Review,challenges and implications for future research

Recent advances in physiological computing have been made due to Artificial Intelligence and Machine Learning, which have profoundly begun to influence occupational health and safety (OHS) in construction. Acknowledging the current and future use of physiological computing, we address the following research question in this paper: What developments in physiological computing can be used to improve OHS in construction? Using a narrative systematic review, we examine studies that have used physiological computing in construction to monitor people OHS. Our review indicates that there is a need for physiological computing systems to be: (1) more accurate; (2) portable and easier to use; (3) generalizable across varying work tasks; and (4) accepted by users and their benefits realized. Considering our observations derived from the prevailing literature and practice, we suggest that future research should aim to mitigate OHS risks by focusing on: (1) development of high-quality database; (2) feature engineering extraction by using an array of machine learning techniques; (3) understanding the context and enacting intervention strategies. The upshot of performing such a review is to provide a signpost for future research in physiological computing of OHS in construction.     

多媒体视频处理基础知识解析

文章通过对多媒体影视制作中所涉及到的技术的探讨，结合实际制作经验，简要阐述了在多媒体视频处理中，所涉及到的基础知识、硬件设备及各种连接方式，为视频的处理提供一个良好的操作平台，确保作品质量，再配备合适的软件加以处理将带给观赏者更完美、更赏心悦目的画面.