An on-line microcomputer-based respiratory monitor for manual materials handling

The main objective of the present study is to develop a low cost microcomputer-based respiratory system that is capable of computing the oxygen consumption and minute ventilation of individuals engaged in manual materials handling on an on-line basis. The design, specifications, and merits of the system are given. The software package developed was written in assembly language for the IBM AT personal computer.     

Multiple criteria decision-making for the resolution of conflicting ergonomic knowledge in manual materials handling

The ergonomic design of manual materials handling tasks typically utilizes one or more of three approaches; biomechanical, physiological, and psychophysical. Unfortunately, a comprehensive design is rarely obtained because of the difficulty of resolving the conflicting guidelines and criteria for each of the three approaches. This paper describes a methodology utilizing the multiple criteria decision-making (MCDM) process for resolving this conflict. This approach calculates the ratio of the contribution from each type of stress to an overall stress level as determined by the unacceptability of this stress to the user. An example is presented to demonstrate this technique.     

Applied anthropometry for common industrial settings design: Working and ideal manual handling heights

Anthropometry has been used extensively for designing safe and sustainable products and workplaces. However, it is common that designers need straightforward guidelines and dimensions, which they often lack, for specific design situations. Anthropometric data are usually presented in tables that summarize percentile values, separated by gender, of a specific population, which makes it difficult for designers to generate applications for mixed populations, such as industrial settings. Using a recently collected anthropometric database of Chilean workers (male and female), international standards of dimensions for working height, depth, and ideal manual handling height are tested with univariate and bivariate methods. Alternative dimensions are presented for both adjustable and non-adjustable designs. Additionally, procedures to combine samples, and for knowing how many users match with a particular design are explained using the sample data. As expected, adjustable designs proved to match with higher numbers of users, while non-adjustable dimensions recommended by ISO presented low levels of matching. Furthermore, the non-adjustable design achieved 83% of matching, which increased to the desired levels (90%) with the inclusion of a 50 mm increase platform. Finally, the Z-Score equation proved to be a useful tool to know the percentages of the population that are matched with a particular design dimension.Relevance for the industryDimensions for working height, depth, and ideal manual handling heights, which are currently not available, are provided for Chilean workers. A method to determine the matching percentage in a population is explained, in order to assess matching probabilities when having only summarized anthropometric tables and the dimensions for the design itself.     

A survey of the optimal handle position for boxes with different sizes and manual handling positions

Handles on objects are very important for enhancing the safety and efficiency of manual handling for people who use them. In this study, four different prototype boxes with auxiliary handles were designed to determine the optimal handle position of a box based on the evaluated user preferences and body part discomfort (BPD). Twenty male students participated in the experiment. Likert-5 point summated rating was applied to evaluate user preferences for the provided boxes with handles in upper, middle, and lower positions, in four different sizes and manual handling positions. Ten additional subjects were asked to indicate their BPD on a body chart after performing a similar experiment. The results show that the subjects preferred the upper part of the handle on a small box regardless of handling position; while the mid to upper parts of the handle on a big box were preferred for handling above the waist height. BPD also indicated that an upper handle was less stressful for a relatively smaller box than a big one; and mid to upper handles were less comfortable for a big box. The optimal handle positions depending on box size and handling position were suggested based on the results of the evaluation. It is thus recommended that a box provides a handle according to its relevant position, depending on size and manual handling condition, to reduce the musculoskeletal stress and in turn to increase user satisfaction.     

A national cross-sectional study in the Danish wood and furniture industry on working postures and manual materials handling

Musculoskeletal disorders constitute a major problem in the wood and furniture industry and identification of risk factors is needed urgently. Therefore, exposures to different work tasks and variation in the job were recorded based on an observation survey in combination with an interview among 281 employees working in wood working and painting departments. A questionnaire survey confirmed high frequencies of symptoms from the musculoskeletal system: The one-year prevalence of symptoms from the low back was 42% and symptoms from the neck/shoulder was 40%. The exposure was evaluated based on: (1) classification of work tasks, (2) work cycle time, (3) manual materials handling, (4) working postures, and (5) variation in die job. Among the employees 47% performed feeding or clearing of machines, 35% performed wood working or painting materials, and 18% performed various other operations. Among the employees 20% had no variation in their job while 44% had little variation. Manual materials handling of 375 different burdens was observed, which most often occurred during feeding or clearing of machines. The weight of burdens lifted was 0·5-87·0 kg, where 2% had a weight of more than 50 kg. Among the lifting conditions 30% were evaluated as implying a risk of injury. An additional risk factor was the high total tonnage lifted per day, which was estimated to range from 132 kg to 58 800 kg. Working postures implied a risk of injury due to prolonged forward and lateral flexions of the neck, which was seen most frequently during wood working or painting materials. These data substantiate the finding that work tasks mainly during feeding or clearing of machines imply a risk of injury to the low back and a risk of injury to the neck and shoulder area mainly during wood working or painting materials. Optimal strategies for job redesign may be worked out by using these data in order to prevent occupational musculoskeletal disorders.     

Manual materials handling in mining: the effect of rod heights and foot positions when lifting "in-the-hole" drill rods

There is a paucity of studies focusing on the lifting of rods or long awkward heavy objects. In-the-hole (ITH) drilling is a heavy repetitive mining task, which has been identified as having a relatively high incidence and severity rate of musculoskeletal injuries. The purpose of this study was to examine how the load experienced by ITH drill operators changed when lifting a vertical drilling rod (1.61 m, 35 kg) using two rod heights and four different foot positions. In addition, a symmetrical lift with a lifting index (LI) of 1.4 also served as a comparison to determine possible risk of low back injury. Eleven experienced ITH drill operators participated in the study. Each subject was required to lift a vertical drilling rod until the upper body was in an erect posture using four different foot positions (0°=subject facing the rod, 45°=subject oblique to the rod, 90°=subject right side to the rod and freestyle). In addition, two rod height conditions were studied where the base of the vertical rod was supported either (1) at ground level (height of rod CG=0.83 m) or (2) on a 20 cm rack (height of rod CG=1.03 m). Finally, each subject lifted a 21.5 kg box in the sagittal plane, which corresponded to an LI of 1.4 in the NIOSH lifting equation. Reflective markers were placed on the subjects, and three video cameras and one force plate were used to record the forces and the motion of the subjects’ segments. Two surface electrodes were applied on the right and the left erector spinae (ES) at the level of L3. Back loading was defined by the level of the peak moments, the mechanical work and erector spinae muscle activity (EMG). It was found that the vertical height of the rod had the most significant impact on back loading, while the effect of the initial foot positioning relative to the rod was limited by the technique adopted by the drillers. Moreover, it was found that some of the subjects used techniques less strenuous for the back than others. Finally, the asymmetrical lifting component was found to be the most negative aspect of lifting an ITH drill rod compared to a standard symmetrical lift (NIOSH).     

Evaluation and assessment of lumbar load during total shifts for occupational manual materials handling jobs within the Dortmund Lumbar Load Study – DOLLY

The load on the lumbar spine during occupational manual materials handling was previously investigated with respect to short activity sections or to specified load-handling types such as lifting or carrying. Within the so-called Dortmund Lumbar Load Study, analysis of the occupationally induced load on the lumbar spine during total working shifts in the field of surface construction, drop forge, industrial meat processing, and refuse collection was performed on the shop-floor. The body postures adopted, the action forces applied at the hands, and the resultant lumbar load for all load-handling tasks were analysed for 2 shifts in each field on the basis of video evaluations. Via a newly developed detailed classification procedure, the spatial position of the body segments as well as amplitude and direction of the action forces were described in a detailed manner. Consecutive biomechanical model calculations lead, for total shifts, to time courses of various measures for the load on the lumbar spine, such as flexion or torsional moments of force as well as compression and shear forces at the lumbosacral disc. In relation to recommended limits for the maximal disc compression provided in the literature, lumbar load is exceeded in numerous situations during a shift, in particular, with regard to persons of higher age. In a “dose model” applied in this study, the cumulative effect of single-task exposures was considered by superproportional weighting of the compressive force with respect to the corresponding duration of a working task.

Relevance to industry

A comprehensive evaluation of lumbar load for complete shifts is presented considering the real shop-floor conditions. Analyses for dustbin removal, surface construction and industrial meat processing have discovered numerous exceedings of lumbar-load limits. Such tasks should not be performed by older persons from the preventive point of view.     

A knowledge-based system for the design of manual materials handling

The purpose of this paper is to develop and test an expert system for the design of new and existing repetitive manual materials handling (RMMH) tasks. For new jobs, the expert system provides recommendations on the maximum acceptable weight to be handled under a variety of worker and task variables. For existing jobs, the expert system provides possible solutions to the design of RMMH tasks if the weight handled on the job is greater than the recommended one. The expert system was implemented on an IBM PCXT personal computer. Two examples on how to utilise the expert system in designing new and existing jobs are given.     

An evaluation of classification algorithms for manual material handling tasks based on data obtained using wearable technologies

With recent progress in wearable measurement systems, physical exposures can be feasibly assessed at high precision in the workplace. Such systems, however, generally lack contextual information for a given job (e.g. task type, duration). To extract such information, we explored three classification algorithms to classify manual material handling (MMH) tasks during a simulated job in a laboratory, using several combinations of outputs from commercially available inertial motion capture and in-shoe pressure measurement systems. A total of 10 participants completed three replications of four cycles of a simulated job. Precision and recall values of ≥ ～90% and 80%, respectively, and errors in estimated task duration of < ～14%, could be achieved across the MMH task examined. Classification performance, however, varied between classification algorithms, input data sets and task types. Overall, combining wearable technology with task classification could be an effective approach for field-based exposure assessment, though field-testing is needed to demonstrate the applicability of this method.

Practitioner Summary: Combining wearable technologies with task classification was explored to extract exposure context, specifically task type and duration. Results supported that task classification can facilitate the use of wearable technologies in field-based exposure assessment, specifically by aiding in task identification from within the rather large data sets obtained from these technologies.     

A cross-validation of the NIOSH limits for manual lifting

The psychophysical, biomechanical, and physiological criteria used in establishing the NIOSH limits for manual lifting were cross-validated against the data published by different researchers in the subject literature. Assessment of the 1991 NIOSH lifting equation indicated that: (1) NIOSH-based limits are significantly different from the psychophysical limits in the (i) low and high frequencies of lift, and (ii) small and large horizontal distances; (2) NIOSH limits are highly correlated with the data of Snook and Ciriello (1991) in the low frequency range, with the Recommended Weight Limit (RWL) protecting about 85% of the female population and 95% of the male population; (3) the 3·4 kN limit for compression on the lumbosacral joint cannot protect the majority of the worker population on the basis of damage load concept; and (4) energy expenditure limits used in development of the RWL index can be sustained by 57 to 99% of worker population when compared to the physiological limits based on previous fatigue studies. Results of the cross-validation for psychophysical criterion confirmed the validity of assumptions made in the 1991 NIOSH revised lifting equation. However, the results of cross-validation for the biomechanical and physiological criteria were not in total agreement with the 1991 NIOSH model     

Logical data base design: A management-oriented approach

A logical data base consists of data definitions and data relationships. It is typically very large and complex even for a small organization, but it is generally designed in an ad hoc manner. However, several approaches have recently been proposed that allow for a systematic logical data base design.To make a data base more useful to the managers, it is imperative to encourage and obtain their involvement in the initial phase of the logical data base design. “Surface semantic models” are used in the logical data base design process to increase this involvement. A special type of this, called a “hierarchical external view model”, is proposed. It has been successfully used to develop a logical data base for the Department of Aging in Pennsylvania.     

A history of low back pain affects pelvis and trunk mechanics during a sustained lift/lower task

This study compared three-dimensional trunk and pelvis range of motion (ROM) during a sustained asymmetric box lift/lower task between a group with a history of low back pain (HBP, n = 9) and a group with no history of low back pain (NBP, n = 9). Participants lifted an 11-kg box for 10 min at 12 cycles/min from ankle height in front to shelves 45 deg off-centre at waist height. Kinematic data were collected at the beginning (min1), middle (min5) and end of the bout (min9). Two-way analyses of variance were performed for all variables. Pelvis and trunk transverse ROM were similar at min1. By min9, HBP group did not change (31.9 ± 9 deg); however, ROM decreased in NBP group (21.6 ± 6 deg, p < 0.05). Therefore, despite no current pain, the HBP group demonstrated protective lifting mechanics compared to controls. Also discussed are implications for studying lifting paradigms at sub-maximal effort over longer periods of time.

Practitioner summary: Differences between groups over time demonstrate residual consequences of low back pain (LBP) in a manual materials handling scenario. Individuals with a history of LBP (pain free for 6 months) demonstrated more conservative lifting mechanics towards the end of the bout compared to controls with no history of LBP.     

A psychophysical approach to determine the frequency and duration of work-rest schedules for manual handling operations

Abstract

The primary objectives of this study were: (1) to test whether rest allowances could be ascertained using a psychophysical methodology; and (2) to examine the effects of gender and frequency of handling on work-rest schedules. Two experiments were conducted, each experimental session at 4 h. A psychophysical methodology was used where the subject was given control of the working and resting durations. The results of the study indicated that: (1) the total working time decreased and the total resting time decreased with an increase in the frequency of handling; (2) high frequency tasks required more frequent rest allowances; (3) for the same manual handling tasks, women needed more frequent and longer allowances than men; (4) experience with the manual handling of material reduced the variability collected from the psychophysical methodology. The application of the psychophysical methodology in industry is discussed.     

The architecture of the PLAIN data base handler

The programming language PLAIN has been designed to support conversational access to a data base, and incorporates relations as a built-in data type. This paper describes the architecture of the data base handler for PLAIN, emphasizing the separation of the data base handler from other aspects of the language processor, and the modularization of the data base architecture to support modifications to the language and its implementation with minimal difficulty. The data base architecture is layered in order to provide the greatest possible degree of information hiding and separation of functionality. The paper shows the structure of the data base handler and the functions of the various modules of the system.     

Computer-aided design method for the components made of heterogeneous materials

With rapid developments of high-tech in various fields, there appear more critical requirements for special functions of components/products, which can be satisfied only by using heterogeneous materials: composite materials, functionally graded materials, or heterogeneous materials with a periodic microstructure. However, currently there exists no systematic and effective method for designing components made of these heterogeneous materials. This paper develops such a computer-aided design method, under the guide of Axiomatic Design, which can apply the functions of current CAD/CAE software. With the design method, all the information about both configuration and materials of a heterogeneous component, needed for creating its CAD model, can be obtained.     

A target-based population approach for determining the risk of injury associated with manual pushing and pulling

A new procedure for determining the risk of injury associated with manual pushing and pulling was developed based upon characteristics of the user population (i.e. age, gender and stature) and task requirements (i.e. working height, task frequency and travel distance). The procedure has been integrated into international (ISO, 2004) and European (CEN, 2004) standards for determining recommended force limits for pushing and pulling that can be adapted to suit the user population. These limits consider the muscular strength of the intended target population, as well as the compressive loads on the lumbar spine. Examples are provided to demonstrate variability of the proposed ‘safety’ limits for different task scenarios.

Relevance to industry

The manual handling of physical loads are known risk factors associated with work-related musculoskeletal disorders (WMSD). These disorders are common throughout the industry and may incur considerable costs to both the employer and the employee. The new risk rating procedure enables pushing and pulling tasks to be more closely aligned to the capabilities of the user population and, therefore, has an important role to play in helping to reduce the suffering and costs associated with these disorders.     

Research to reality: a critical review of the validity of various criteria for the prevention of occupationally induced low back pain disability

Criteria have been suggested to reduce the incidence, or severity of low back pain disability. Five underlying theories for such criteria have been identified in the literature, and a critical review of the validity of these criteria has been carried out. Despite attributions elsewhere, peer-reviewed validation of the various criteria range from modest to nil. The need for a validation criterion for use in workplace design in order to reduce low back pain disability, or severity, is identified and the need for an international protocol to allow cross-study validation of present and future criteria is suggested.     

切削刀具综合管理系统的数据采集和存储设计研究*

为建立满足汽车发动机制造企业需求的切削刀具综合管理系统,本文研究了该系统数据库的基础数据采集和存储问题。针对生产现场数据采集困难的问题,设计基于射频识别技术的数据采集方法,提高采集的效率和数据的可靠度。提出刀具与工步对应的存储方法,将刀具信息与生产线相应信息有效衔接。建立系统E-R模型,应用关系规范化理论进行数据存储分析,设计数据表及其相互关系,解决数据库存储的冗余问题。以上述研究成果为基础建立切削刀具数据库,并验证数据库企业实施的可行性。研究成果为建立具有高可靠性和操作性的刀具综合管理系统提供了理论和实践保障。