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Design and Development of an Ergonomic Hybrid Forklift Seat
Abstract
Ergonomic designs have positive impact on the end-user experience of any product. One of the main challenges is to accommodate a range of end-users, for which the concept of adjustability has been found to be very effective. The backrest in a forklift, for example, is provided for comfortable driving in the form of leaning/sitting postures. An ergonomic backrest has to consider the anthropometric variation in the human population to ensure optimum levels of comfort for everyone. This study provides a comprehensive methodology for developing an ergonomic backrest by combining the features of two different backrests and incorporating the adjustability concept into the design. Our study comprised of both, field and laboratory evaluations of the original and new designs for a variety of anthropometric characteristics (5th, 50th and 95th percentiles of both males and females). Using the phenomenon of restlessness, discomfort of the user was associated with the amount of body movement, where we have used the motion-capture system and the force platform to quantify the individuals’ movements. The results of the field evaluation indicated that the new backrest improved comfort during both static and driving tasks by ~10% and 23%, respectively. The results of objective metrics showed a reduction in the mean torso and the maximum center of pressure change of locations by 300 and 6 mm, respectively, for the new design. Further, the change in movement during the trials as assessed by the deviation in center of pressure measure was decreased (12%, p-value=0.32) for the new design, compared to the increase of 47% (p-value=0.0078) for the original design, suggesting that new backrest performed better over time. Based on these findings, the new design was further improved. Outcomes of this study may facilitate higher comfort levels to a wide range of forklift operators using a new adjustability concept.
... By implementing adjustability, a new backrest (Reach3) was developed for stand-up reach forklifts by combining features (pocket, side-hook, curvature) from both the backrest that would be comfortable for drivers with a broader range of anthropometric measurements. The Reach3 was developed in our laboratory and the design procedure has been described in our previous published studies (Kuber andRashedi, 2021, 2020a). Adjustability was incorporated in the new design by identifying an oblique plane through an iterative process to enable access to the range of forms from both Reach1 and Reach2 backrests on the backrest surface. ...
... Source: Adapted from Kuber (2020) During the next ten minutes, the participants were instructed to perform a counting task for two reasons: ...
This study assessed the effectiveness of an adjustable backrest towards facilitating comfort to a range of users' body sizes. Twelve participants were recruited in a comparative study to detect the effect of body size (5, 5-95, 95 percentile), sex, backrest type (adjustable, original), and leaning duration on comfort and stability. Body movements related to the perceived discomfort were used to quantify the convenience of individuals while leaning on the backrest. Results showed a decrease in the centre of pressure deviation by 12% for the adjustable backrest, compared to a 47% increase for the original design. Moreover, upper-body movement reduction (~20%, p-value = 0.04) denoted that adjustable backrest was more effective over longer durations. The identified improvement regions on the new backrest included backrest curvature, hook feature, and symmetric material placement. This article presents a comprehensive method for evaluating backrests, which could also be implemented for assessing similar seating products with adjustability features.
... In a survey, it was found that shorter operators with a slimmer waist width found the Reach1 backrest more comfortable; in contrast, larger operators with a larger torso found the Reach2 backrest more comfortable. A new concept design (Reach3) was developed that consisted of improved features for both the backrest would be comfortable for operators with a wider range of anthropometric measurements (Kuber, 2020). Figure 1 shows the adjustability in the Reach3 backrest along an oblique plane to achieve the back-resting surface areas for shorter as well as larger forklift operators. ...
A new forklift backrest has been developed by incorporating adjustability concepts into the design to facilitate comfort to a wide range of users. We have conducted a comparative study between the new and original backrests to assess the effectiveness of design features. Using the phenomenon of restlessness, discomfort of the user was associated with the amount of body movement, where we have used a motion-capture system and a force platform to quantify the individuals' movement for a wide range of body sizes. Meanwhile, subjective comfort and design feedback were collected using a questionnaire. Our results showed a reduction in the mean torso movement and the maximum center of pressure change of location by 300 and 6 mm, respectively, for the new design. Taking advantage of adjustability feature, the new backrest design exhibited enhanced comfort for longer durations and reduced magnitude of discomfort for a wide range of participants' body sizes.
Selection of a single design to delight customers may not be always possible due to the anthropometric differences in humans, wherein a hybrid design can benefit. Using adjustability, we demonstrate our approach for developing a novel forklift backrest to accommodate drivers with a wide range of body sizes. Field and laboratory evaluations were conducted to assess and improve the design. Our results indicated that the new design could provide improved comfort for longer durations. This study reveals the possibilities for human factors professionals to consider adjustability in vehicle operator compartment interiors, especially backrests and seating, of similar industrial vehicles.
Implementation of exoskeletons could be one of the solutions to augment human capacity towards reducing the large number of work-related musculoskeletal disorders (WMSDs) in the industry. While many studies highlight the benefits offered by these devices, some show mixed results, which could be due to lack of standardised processes in both development and testing. Further, our observations show that current exoskeletons could be further improved with a goal towards increasing the end-user experience. We have identified the key factors in the design of exoskeletons that could be one of the reasons for the discomfort, misfit and low acceptance of the devices among the workers. Considering the ergonomics principles, we have determined elements of exoskeletons that can be associated with the identified limitations, then provided an overview of some of the modern technologies that are being/could be used, and opportunities for using smart materials to facilitate their design enhancement. Finally, relevant human–machine interaction aspects and the feasibility of applying these technologies in exoskeletons to the industrial environments are discussed.
A study was carried out with 135 surgeons to obtain a surgical laparoscopic grasper handle design that adapts to the size of each surgeon’s hand, in a functionally appropriate way, and has the sufficient ergonomics to avoid generating the problems detected nowadays. The main conclusion of the work is the practical 3D parametric design obtained for a laparoscopic surgical graspers handle that is scalable to fit each particular surgeon's hand size. In addition, it has been possible to determine that the anthropometric measure of the surgeon's hand defined as Palm Length Measured (PLM) allows the design of the 3D parametric model of the surgical handle to be conveniently scaled.
The results show that both additive manufacturing and the application of ergonomics criterion
provide an efficient method for the custom design and manufacture of this type of specialised tool,
with potential application in other sectors.
Hand-operated tool handles transmit a large magnitude of vibration to the hand-arm system during low-frequency operations. Therefore, the precise design of a hand tool is very important to overcome musculoskeletal disorders, hand-arm vibration, etc. This study was aimed at developing optimal tool handles with an increased contact area and to overcome the contact pressure, which causes discomfort and pain. Six different human hand-based optimal handles (handles B to G) and one optimal cylindrical handle (handle A) were designed and fabricated using 3D printing technology, in order to assess the effect of low-frequency vibrations. The effect of handle shapes was evaluated with objective and subjective measurements using 15 subjects. Objective measurements were performed to assess the vibration transmissibility by experimental study at the frequency range of 0–100 Hz, and subjective measurements were performed to rate the handles based on comfort descriptors and overall comfort of the handles. Root mean square vibration accelerations were recorded at the wrist, elbow, and shoulder of each subject and at the base of the handle fixture to evaluate the vibration transmissibility for each handle. The mean vibration transmissibility was found to be minimum for handle B and was rated to be more comfortable by the subjects. The results indicated that all the human hand-based handles transmit less vibration and were rated to be more comfortable than the optimal cylindrical handle.
A revised pilot oxygen mask design was developed for better fit to the Korean Air Force pilots’ faces. The present study compared an existing pilot oxygen mask and a prototype of the revised mask design with 88 Korean Air Force pilots in terms of subjective discomfort, facial contact pressure, and slip distance on the face in high gravity. The average discomfort levels, facial contact pressures, and slip distance of the revised mask were reduced by 33%–56%, 11%–33%, and 24%, respectively, compared to those of the existing oxygen mask. The mask evaluation method employed in the study can be applied to ergonomic evaluation of full- or half-face mask designs.
Abstract : Traditional vehicle package engineering assumes that driver anthropometry and the location of vehicle controls determine driver posture, and thus seat parameters. Due failure of this approach to provide comfortable seating con-ditions, ERL combines a systems anthropometry model with a force deflec-tion model of the seat and soft tissue Digital Human Model (DHM) to design seat specifications for the driving package. With the systems anthropometry model, we optimize seat design for calculated driver positions and postures. We derive comfort scores from measurements of the interface between the DHM, seat and controls. Analysis of 13 passenger cars and 10 utility vehicles shows that drivers adapt to vehicle interiors with different postures that are inconsistently associated with vehicle type. In conclusion, the seat affects how and where we sit. Thus, DHMs are needed for both seat and package design at the very begin-ning of vehicle development.
A typical manufacturing environment is characterized by
a multitude of interactions between pedestrian workers,
equipment and materials. This dynamic work environment
often fosters nonvisible areas that impede a person’s lineof-
sight. The lack of visibility for equipment operators in
manufacturing environments can contribute to struck-by
events that results in injuries and potentially fatalities. The
objective of this research is to create a framework to evaluate
the visibility of an equipment operator in a manufacturing
environment. Experiments were conducted to simulate
typical movements and actions of a forklift in a manufacturing
plant. The test bed was assessed through laser scanning
to identify areas not visible to the forklift operator.
Point clouds of the test bed were generated and analyzed to
identify nonvisibility areas for forklift operators. The primary
contribution of this research is scientific evaluation
data of operator visibility in a manufacturing environment
as well as a framework for measuring operator visibility in
manufacturing work environments. Results of the research
can be implemented to better understand causes of struck-by
incidents as well as to potentially mitigate visibility
concerns in the manufacturing industry.
Previous studies suggested that the use of inward torque direction in hand-related manual activities not only increases the total normal force and torque capacity but also reduces grip force. This means lesser effort is required to perform the task, which prevents overexertion and hand injuries. Manual screwdrivers are the most common hand tools used in the industry and daily life. However, due to the difficulty users face when unfastening screws, it can also be a hand tool that potentially leads to the development of cumulative trauma disorders. In this study, 50 subjects participated in a psychophysical testing of an ergonomic inward directional screwdriver and a normal manual screwdriver. The comparative study involved the perceptions of grip, comfort and ease-of-twist for both normal and ergonomic manual screwdrivers. The data was analysed using the analysis of variance via Minitab 16. The results showed that grip, comfort and ease-of-twist are significantly affected by torque direction and ergonomics features. Further observations on participant justifications also suggested that participants rated the inward screwdriver as a better tool to be used compared to the normal screwdriver.
One of the most common hand tool wrench used today does not come equipped with a handle facilitating a comfortable grip for its extended use. The purpose of this study was to create an ergonomic design for a hand tool (a wrench) that is commonly used in a wide range of industries all around the Globe. The overall goal of the project involved first designing ergonomic profiles for the wrench handles with grip diameter suitable for ninety-five percentile user population. These handle profiles were created using CAD to prototype subsequently using a 3D printing system. A conventional wrench was then assembled with each of the three handle profiles for ergonomic testing & evaluation. By choosing random male subjects, we compared a standard wrench (with regular handle) with (identical) wrench assembled with the three different profiles of the handle. The maximum amount of torque that the test subjects could apply on each handle was measured using a torque tester; we also measured the muscle activity with each of the handles for each subject with the help of EMG (Electromyography). The experimental data obtained from this process then were analyzed to infer about the performance of the three wrench handle with a standard handle in order to determine one most efficient ergonomic design for the wrench handle profile.
Background. Inappropriate design of sitting furniture and working equipment causes the serious musculoskeletal injuries and various pains as well as reducing working efficiency. Uncomfortable sitting posture in prolonged driving in Bangladesh is an issue to be solved immediately. Therefore, anthropometric databank of user population is significantly essential for the suitable dimensional design for avoiding these remarkable problems. Methods. This study analyses the anthropometric data of the Bangladeshi male vehicle driver aged between 30 and 60 years. A total of 210 Bangladeshi healthy drivers are considered for 15 anthropometric measurements and compared with the similar anthropometrics of other nationalities. Results. The mean stature and sitting height erect of Bangladeshi driver are 1645 mm and 843 mm, respectively. The mean of body mass index (BMI) of the drivers is 26.09 kg/m2, which indicates that the drivers are overweight. The mean stature of Bangladeshi driver is 17 mm shorter than the driver of Korea and 115 mm shorter than the driver of Iran. Conclusion. There are substantial differences between the body dimensions of Bangladeshi driver and similar dimensions of other countries. In comparison, Bangladeshi driver is found to be the shortest compared with the sample of other nationalities.
Nowadays, working in an office environment is ubiquitous. At the same time, progressively more people suffer from occupational musculoskeletal disorders. Therefore, the aim of this pilot study was to analyse the influence of back pain on sitting behaviour in the office environment. A textile pressure mat (64-sensor-matrix) placed on the seat pan was used to identify the adopted sitting positions of 20 office workers by means of random forest classification. Additionally, two standardised questionnaires (Korff, BPI) were used to assess short and long-term back pain in order to divide the subjects into two groups (with and without back pain). Independent t-test indicated that subjects who registered back pain within the last 24 h showed a clear trend towards a more static sitting behaviour. Therefore, the developed sensor system has successfully been introduced to characterise and compare sitting behaviour of subjects with and without back pain.
http://www.la-press.com/force-plate-assessment-of-quiet-standing-balance-control-perspectives--article-a5026
Assessment of balance control is essential to guide physical rehabilitation poststroke. However, current observational assessment tools available to physiotherapists provide limited information about underlying dyscontrol. This paper describes a force plate-based assessment of quiet standing balance control that we have implemented for individuals attending inpatient stroke rehabilitation. The assessment uses two force plates to measure location of ground reaction forces to maintain stability in quiet standing in five conditions (eyes open, eyes closed, standing symmetrically, and maximal loading on the less-affected and more-affected limbs). Measures of interest are variability of the centers of pressure under each foot and both feet combined, weight-bearing asymmetry, and correlation of center of pressure fluctuations between limbs. We present representative values for the above-mentioned measures and case examples to illustrate how the assessment can reveal patient-specific balance control problems and direct treatment. We identify limitations to our current assessment and recommendations for future research.
Farm mechanization has played a key role in increasing production and productivity of farm and farmers in the country with suitable farm equipment/ machineries for most of the unit farm operations. The developed farm equipment/ machinery are being used by the farmers, particularly men while women farmer are still in passive role in agriculture. This might be due to lack of addressing the gender issues in it. Attempt is being done at various research organizations but same could be more effective, if at source, the gender issues are being taken up. Use of human manikins is started in developed country on the basis of anthropometric data and interfacing with product/ work place during the design process. Scope of this technology can be effectively incorporated in developing farm equipment and thereafter its lab testing to produce gender-friendly farm equipment/ machines. Anthropometric data, physiological data, strength data, biomechanics, working
environment and soil conditions may be integrated in developing comprehensive software attached with human manikin for development of ergonomic products and their fabrication. After that it may be linked with product manufacturing software for refining the product in gender perspective. This would have advantage of developing/ producing ergonomic farm equipment which will help in reducing the cost of cultivation by encouraging passive farm workers (women) to active mode.
Today's global competition has prompted many automotive manufacturers to design their products based on consumer's preference and satisfaction. A car driver controls the vehicle and his/her comfort and safety is important to avoid any road injury or unfortunate accident. There are three main objectives for this paper. This paper is to investigate the relationships between car drivers' anthropometric characteristics, comfortable postural angles and seat adjustment, to analyze the force distribution on the car seat and to design a driver car seat that gives comfort and safety ergonomically to the driver. In this case, the measurements need to be taken for both car and the driver and also to propose a design a driver car seat that provides comfort and safety to the driver. This design should be based on ergonomic factors including design, materials used and safety. These findings enhance our understandings of car drivers' perceptions of posture comfort and safety. The data findings and relationship discussed will assist the manufacturers in designing a drivers' car seat with ergonomics value.
Tool-handle design research has been previously limited to determination of diameters of cylindrical handles to increase performance, comfort and avoid acute and cumulative traumatic disorders. However, there is still lack of correct shape determination and systemization of the ergonomic design knowledge. To overcome these limitations, methodology to develop optimal sized and shaped tool-handles for a target population previously developed has been integrated into an existing ergonomics and aesthetics decision support system. The system allows a correct determination of tool-handle size and shape according to the target population and provides general ergonomics knowledge. Resulting handles consider optimal diameters for each finger to maximize maximum voluntary contraction, comfort and contact area, which can lower the risk of acute and cumulative trauma disorders. The system allows development of ergonomic tool-handles with almost no prior ergonomics knowledge and without iterative design process, which decreases the designing time.
Most authors have provided diameter recommendations for cylindrical handle design in order to increase performance, avoid discomfort, and reduce the risk of cumulative trauma disorders. None of the studies has investigated the importance of determining the correct handle shape on the subjective comfort ratings, which could further improve the handles' ergonomics. Therefore, new methods based on a virtual hand model in its optimal power grasp posture have been developed in order to obtain customised handles with best fits for targeted subjects. Cylindrical and anatomically shaped handles were evaluated covering ten subjects by means of an extensive subjective comfort questionnaire. The results suggest large impact of the handle shape on the perceived subjective comfort ratings. Anatomically shaped handles were rated as being considerably more comfortable than cylindrical handles for almost all the subjective comfort predictors. They showed that handle shapes based on optimal power grasp postures can improve subjective comfort ratings, thus maximising performance. Future research should consider real conditions, since the comfort ratings can vary based on the specific task and by the tool selected for the task.
Computer aided visualisation and simulation enables early evaluation of important design parameters of future products and production systems. Typically, humans affect the system performance, and in order to achieve the expected system efficiency ergonomics needs to be considered in the design process in addition to the more technical or logistical matters. Hence, there is a call for ergonomics to be a natural part of the product and production development process, also at virtual stages. Three examples of the development of Digital Human Modelling-(DHM)-based company-specific ergonomics evaluation methods and work processes are portrayed, argued and discussed. These illustrate the use of DHM tools for performing static work and occupant packaging analyses, as well as customising activities made for the implementation of the tools in companies' work processes. This is followed by a discussion of future needs of DHM tools including the call for ergonomics methods for evaluating full work cycles.
Consideration of products' ergonomic qualities is one important component for successful product development. Product designers engaged in the core activity of product development need methods that support the consideration of ergonomics along with other product requirements. This thesis aims to address these needs. The first part of the thesis investigates how people working within product development organisations communicate with and about users of their products. The general need for methods to support communication of user aspects in product development is identified through formal interviews with product developers and a review of the management, ergonomics and design literature. The second part of the thesis studies the factors which affect the integration of ergonomics in product design. Supportive methods, including User Characters, for evoking user consideration among designers together with Overlapping methods for scheduling ergonomics evaluation in product design processes are introduced and argued. The third part of the thesis reviews and discusses computer aided ergonomics as a means for integration of ergonomics in product design. A web-based support system for effective employment of human simulation tools is developed using a participative approach and evaluated based on the system's usability. The objective of the fourth part of the thesis is to study how human simulation tools can aid designers' consideration of human diversity to accommodate users of diverse anthropometric characteristics in multivariate design problems such as automobile cockpits. The work involves the evaluation of different approaches for the generation of specific manikin families which can be used as test groups for fitting trials in the virtual design process. The research demonstrates enhancements in design methodology knowledge to support integration of ergonomics in product design processes with a focus on anthropometric diversity in vehicle design.
Several methods exist for the assessment of balance. In the clinical setting, they are often assessed through qualitative tests. In the laboratory, instrumentation can quantitatively and more accurately measure balance. To date, force platforms remain one of the most commonly used tools in balance assessment. They are, however, costly and cumbersome, making them impractical in clinical settings and field studies. Utilization of accelerometers in balance assessment has been studied but has not yet become a laboratory standard due to the unknown accuracy of this method. If proven accurate, the use of accelerometers in laboratory and clinical environments would be ideal because they are inexpensive, noninvasive, and easy to transport. The purpose of this study was to compare the use of accelerometers as an inclinometer to the use of a force platform in the assessment of postural stability. A triaxial accelerometer was placed on the trunk of five subjects. The subjects stood barefoot on a force platform under various conditions which affect balance: all sensory systems intact; impaired visual feedback; impaired proprioceptive feedback; and impaired visual and proprioceptive feedback. During each trial, trunk acceleration and ground reaction forces and moments were collected. Force plate data was used to plot the path of the center of pressure and acceleration data was used to plot a projected path of the trunk acceleration. Behavioral similarities were seen in both methods of balance assessment. Therefore, balance assessment via accelerometers is feasible. This method does, however, require further investigation.
The economic success of manufacturing firms depends on their ability to identify the customer needs and to quickly create products that meet the need with reasonable price. New product failure rate is still high that mainly caused by inadequate market analysis. Some mistakes of customer need identification and misinterpretation of the customer needs to the product features are identified as sources of the problem. This article tries to solve the problem by analyzing some aspects of cognitive ergonomics that influence customer decision in buying a product. Multi Purpose Vehicle (MPV) is selected as an object of the research. This research applies customer preference analysis and conjoint analysis. The preference analysis result shows that some aspects of quality, easy to use, price and maintenance aspects are emphasized by respondents. Though image and shape is not significantly emphasized, it significantly correlates to shape, price, maintenance, and acceleration, whereas shape is significantly correlated to all other variables. Based on conjoint analysis, some product part shapes are analyzed to identify their contribution to the whole product images. Five images analyzed are luxury, masculinity, formality, modernity, and attractiveness.
One important source of variability in the performance and success of products designed for use by people is the people themselves. In many cases, the acceptability of the design is affected more by the variability in the human users than by the variability attributable to the hardware from which the product is constructed. Designing for human variability as an inherent part of the product optimization process can improve the overall perfor-mance of the product. This paper presents a new approach to artifact design that applies population sampling and stochastic posture prediction in an optimization environment to achieve optimal designs that are robust to variability among users, including differences in age, physical size, strength, and cognitive capability. A case study involving the layout of the interior of a heavy truck cab is presented, focusing on simultaneous placement of the seat and steering-wheel adjustment ranges. Trade-offs between adjustability (an in-dicator of cost), driver accommodation, and safety are explored under this paradigm.
Tractor driving imposes a lot of physical and mental stress upon the operator.
Operator’s seat and noise are two of the detrimental factors that lead to
unhealthy working conditions for the tractor operator. The optimal design of
tractor seat and presence of cabin may be achieved by integrating
anthropometric data with other technical features of the design. This paper
describes the common Egyptian farm tractor controls layout such as foot brake,
foot clutch, foot accelerator (throttle lever), steering wheel, PTO controller,
hand brake, hydraulic lever, gear lever and light control buttons. Comparison
of noise exposed on the operators of the farm tractors with and without a cabin
is investigated. The sound levels (dB) were measured at ear level of the
operators. Measurements of anthropometric data were also conducted to match
and evaluate the existing main controls layout with driver body dimensions. A
two-dimensional measuring device was constructed to measure the tractor
controls layout. The measurements were taken as forward horizontal distance
and vertical distance from seat reference point (SRP). Observed data indicated
that there are large variations in the controls layout on horizontal and vertical
axes for different tractor models. Also, large variation was obtained from
anthropometric data and responses of drivers. The design of an operator
workplace on mobile equipment is frequently a compromise because of
conflicting requirements for the limited space available. The use of a cabin was
useful in the insulation of the noise, particularly at higher frequencies (under
load). The noise levels reached 90 dB when using tractors without cabins
compared to 81 dB only incase of tractors mounted cabins. The measured noise
levels varied also with increasing tractor forward speed as well as load
conditions. In addition; cabins protects the operator from the factors having
detrimental effects on the working efficiency such as high temperature and
dusty environment. Therefore, mounting of cabins on the tractors currently
being used without a cab in rental system in Egyptian farms is highly recommended to provide healthy working conditions for their operators.
In the present study, bent-handled needle-nose pliers, designed from an ergonomic perspective as an improvement over the conventional plier were investigated.
A convenience sample of fourteen volunteer male university students aged between (20 and 24 years old) participated in the study.
Three angles to the jaws of plier (0°, 10° and 20°) were provided in the redesigned pliers to reduce ulnar deviation of wrist. Other two angles (0° and 5°) of jaws with respect to the vertical plane. From this, (3 × 2) six redesigned pliers were investigated. Dependent variables were discomfort--scored on 10~cm Visual Analogue Scale (VAS) and difference in systolic and dysystolic blood pressure (BP).
The results of ANOVA showed that the main and interaction effects of the angle to prevent ulnar deviation of wrist and angle to prevent extension of wrist were highly significant (i.e., p< 0.001) on discomfort score. Effect of angle to prevent ulnar deviation of wrist was only found significant on difference in systolic blood pressure. Of the redesigned pliers, the pliers with 10° angle of handle from jaw to prevent ulnar deviation, and 5° angle of handle to prevent extension of wrist was found to give the minimum level of discomfort score.
Hence it is concluded that bent handle pliers up to certain angles may reduce discomfort, and after that discomfort will increases drastically. These finding will be very significant for the designers to use one more angle as per the requirement of the comfortable use of pliers. Many ergonomically redesigned pliers are available. However none was found be considering angle to give extension of the wrist based on scientific findings.
A quantitative field study measured end-user availability, knowledge and use levels of adjustable office chair functions in Korea-based office workers, together with their perceived barriers towards making adjustments. Fifty-one English-speaking workers were interviewed and surveyed in a related design. Results showed that of the number of adjustable functions available on their office chair (M=5.39, SD=2.3), participants knew fewer than half of them (M=2.51, SD=1.52) and used even less (M=1.86, SD=1.21). Fifty-three percent of participants knew two or less and 73% had used only two or less. Ten percent had used none. Results suggested physical needs (such as increased comfort or postural change) were a strong driver for previous chair adjustment behaviour. Perceived cognitive barriers played a more significant role in limiting chair adjustment knowledge and use than physical or organizational barriers. Highly adjustable office chairs have the possibility of satisfying the adjustment needs of most end-users. However, adjustable chair functions need to be both available and known in order to be used.
The aim of this work is to define a new method that helps researchers to analyze perceptions of (dis)comfort in dynamic conditions. Recent studies pay considerable attention to body movements, mobility, and stability to measure comfort or discomfort when seated. Most of these discuss the relations between subjective comfort/discomfort and objective measurements (e.g. body pressure distribution, body movement and EMG) for short- and medium-term sitting. The present analysis took place in a classroom of the Industrial Engineering Department at the University of Salerno. The participants included 25 students (12 females and 13 males), who were observed during classroom hours. The students were invited to sit at a combo-desk and were free to perform different combinations of movements while writing and listening. These activities required that they adapt their body movements, as the combo-desk was fixed to the floor. A pressure pad was used to detect pressure at interface and center of pressure's changes, allowing for the bodies' motion data to be recorded. The aim was to identify the correct threshold to be used for movement detection and to investigate correlations between the number of movements and the perceived (dis)comfort. The study also identifies those body parts that have the greatest effect on (dis)comfort perception.
Intensive use of the thumbs for text entry on smartphones may contribute to discomfort, pain, or musculoskeletal disorders. This study investigated the effect of twenty-five button positions (5 rows × 5 columns) on a soft keyboard for two-thumb entry. Two experiments measured muscle activity, touch time, and discomfort as a function of the button positions. In Phase I, the muscle activities of two intrinsic (abductor pollicis brevis and first dorsal interossei) and two extrinsic (abductor pollicis longus and extensor digitorum communis) muscles associated with thumb motions were observed for ten college students (age: 24.2). In Phase II, touch time and discomfort were measured for 40 college students (age: 23.6). The results demonstrated that the %MVCs of the intrinsic muscles significantly increased when the thumbs flexed and abducted. Also, the button positions near the rest positions of the thumbs resulted in significantly shorter touch times (0.66 s) and lower discomfort ratings (0.70 pt) than their peripheral buttons (0.76 s; 2.29 pt).
The objective of this study was to evaluate how different workstations may influence physical behavior in office work through motion and how that may affect spinal loads and discomfort. Twenty subjects performed a typing task in three different workstations (seated, standing, and perching) for one hour each. Measures of postural transitions, spinal loads, discomfort, and task performance were assessed in order to understand the effects of workstation interaction over time. Results indicated that standing had the most amount of motion (6–8 shifts/min), followed by perching (3–7 shifts/min), and then seating (<1 shift/min). Standing had the highest reports of discomfort and seating the least. However, spinal loads were highest in A/P shear during standing (190N posterior shear, 407N anterior shear) compared to perching (65N posterior shear, 288N anterior shear) and seating (106N posterior shear, 287 anterior shear). These loads are below the risk threshold for shear, but may still elicit a cumulative response. Perching may induce motion through supported mobility in the perching stool, whereas standing motion may be due to postural discomfort. Office workstation designs incorporating supported movement may represent a reasonable trade-off in the costs-benefits between seating and standing.
Highlights
• Perching was associated with lower spinal loads compared to standing.
• Supported movement resulted in lower discomfort relative to prolonged standing.
• Heart rate variability may provide an objective understanding of discomfort.
This paper presents a new design of computer workstation that is aimed at increasing the comfort of a user working for long periods at a computer. As we have become a society that spends a lot of time working on computers, the computer workstation needs to provide comfort to users. Discomfort and an improper position can negatively affect overall health and productivity. A new type of ergonomic computer workstation, which allows users to sit in multiple working positions, is proposed in order to provide better comfort to people who spend a long time sitting at their workstations. We have designed and developed a new multi-position ergonomic computer workstation which has 19 degrees of freedom and which can accommodate from 5th to 95th percentile human size. Four types of working position (upright, lean-back, zero-gravity and lean-forward) are preset by choosing different angular positions of the workstation parts. Positions of the workstation parts can be changed by controlling the actuators. These four positions were used to evaluate the comfort of the workstation. Subjective and objective evaluations, including comparison of the prototype and standard computer setup, were carried out using human subjects and ergonomic principles. Results showed that the new workstation is much more comfortable, supporting the body in a balanced way. Users have the freedom to stretch and relax in different working positions before they feel any noticeable discomfort; as a result, it lets users work for a longer period without strain, thus resulting in higher productivity.
Hand operation accompanied with any combination of large forces, awkward positions and repetition may lead to upper limb injury or illness and may be exacerbated by vibration. Commercial lawn mowers expose operators to these factors during actuation of hand controls and therefore may be a health concern. A nontraditional lawn mower control system may decrease upper limb illnesses and injuries through more neutral hand and body positioning. This study compared maximum grip strength in twelve different orientations (3 grip spans and 4 positions) and evaluated self-described comfortable handle positions. The results displayed force differences between nontraditional (X) and both vertical (V) and pistol (P) positions (p < 0.0001) and among the different grip spans (p < 0.0001). Based on these results, recommended designs should incorporate a tilt between 45 and 70°, handle rotations between 48 and 78°, and reduced force requirements or decreased grip spans to improve user health and comfort.
Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.
Non-neutral wrist positions and external pressure leading to increased carpal tunnel pressure during computer use have been associated with a heightened risk of carpal tunnel syndrome (CTS). This study investigated whether commonly used ergonomic devices reduce carpal tunnel pressure in patients with CTS. Carpal tunnel pressure was measured in twenty-one patients with CTS before, during and after a computer mouse task using a standard mouse, a vertical mouse, a gel mouse pad and a gliding palm support. Carpal tunnel pressure increased while operating a computer mouse. Although the vertical mouse significantly reduced ulnar deviation and the gel mouse pad and gliding palm support decreased wrist extension, none of the ergonomic devices reduced carpal tunnel pressure. The findings of this study do therefore not endorse a strong recommendation for or against any of the ergonomic devices commonly recommended for patients with CTS. Selection of ergonomic devices remains dependent on personal preference.
Kansei Engineering is a Japanese originated technique that is often used to provide information on a sensual level in the application of products to markets. This paper explores a method of applying Kansei as part of a product design creative process. It explores the use of face-value testing through web-based pictorial questionnaires, firstly applied to a range of existing products, and then to two new product proposals created from information gained in the first questionnaire. The paper then considers if this technique demonstrates a development in the design process that can reasonably be considered to increase product success.
The biomechanical benefits (e.g., muscular activity) of slanted ergonomic mice have been comprehensively identified; however, their effects on task performance and subjective responses have not been fully investigated. The present study examined the effects of two slanted mice (slant angle = 30° and 50°) in comparison with a conventional mouse (slant angle = 0°) in terms of task performance (task completion time and error rate) and subjective responses (perceived discomfort score and overall satisfaction score). Experimental results showed that all of the task and subjective measures worsened as the slant angle of the target mice increases. For example, the task completion time (unit: ms) and overall satisfaction score (unit: point) of the 30° slanted mouse (time = 0.71, satisfaction = -0.09) and 50° slanted mouse (time = 0.73, satisfaction = -0.79) significantly deteriorated than the conventional mouse (time = 0.65, satisfaction = 1.21). The slanted mice seem to compromise biomechanical benefits with task performance and subjective responses.
A significant part of manual work is still done using hand-tools. Therefore, a correct design is crucial for preventing upper-extremity musculoskeletal disorders, such as carpal tunnel syndrome, hand-arm vibration syndrome, tendonitis, etc. When considering the ergonomics of a hand-tool, in addition to its main functionality, the most important part is the tool's handle. Most of the authors have considered cylindrical handles and provided guidelines and mathematical models for determining optimal diameters in order to maximise finger-force exertion, comfort, contact area, thus minimising the chances of cumulative trauma disorders (CTD). However, they have not taken into account the shape of the hand during optimal power-grasp posture when determining the tool-handles' shapes, which could additionally improve the handles' ergonomics. In order to overcome this limitation, we have developed an anatomically accurate static digital human-hand model (DHHM). The developed DHHM allows direct tool-handle modelling and does not require an iterative design process when designing a tool-handle with improved ergonomics. In order to develop DHHM, anthropometric measurements on ten subjects were performed for the manufacturing of corresponding optimal cylindrical pre-handles with variable diameters for each finger. Outer hand moulds were manufactured based on the pre-handles for obtaining the shape of the hand with skin and subcutaneous tissue undeformed. Magnetic resonance imaging was conducted with the outer hand moulds attached, and segmentation and 3D reconstruction were performed on the images to obtain the DHHMs for each subject. Tool-handles based on DHHM were then obtained within common Computer-Aided Design software. Measurements on the handles based on the DHHM have shown that they provide; on average; an over 25% higher contact area compared to the corresponding cylindrical handle. With higher contact area and anatomical shape of the handle, extensive deformation of the soft tissue can be avoided, thus preventing excessive load on the hand. Subjects also compared these DHHM handles with cylindrical handles regarding perceived subjective comfort-rating. It was shown that those tool handles based on the DHHM provided a higher overall comfort-rating compared to cylindrical handles. It has also been demonstrated that anatomically shaped tool-handles based on the developed DHHM can improve user performance and lower the risk of CTD.
The aim of this paper is to give a number of methodological and theoretical indicators concerning the contribution of ergonomists to the execution of design projects of new products. Within the context of a design project, the present work therefore describes the studies and ergonomic analyses that can be undertaken during each phase of the design process from a design model based on concurrent engineering. Encompassing the design of the driving cabin of the new generation of high-speed trains (TGV-NG), this paper, through the ergonomic study of a number of technical sub-systems of this product, illustrates the advisory role of the ergonomist who, within the collective design process, ensures that the specific nature of the “human factor” is fully integrated into the design approach. Thus, throughout the design process, the ergonomist is called upon both to advise the designer on the characteristics of the target users and, on the basis of a “desirable future activities” approach, to help him or her assess the consequences of the design choices made. Ergonomics is described consequently, as an innovation and safety factor.
Owing to the strong dependence of the health risks associated with vibration exposure of the human hand and arm on hand force, a laboratory study was conducted to develop a methodology for measurement of the contact force at the tool handle-hand interface, and to identify the relationship between the contact force and the hand grip and push forces. A simulated tool handle fixture was realized in the laboratory to measure the grip and push forces using compression/extension force sensors integrated within the handle and a force plate, respectively. The contact force was derived through integration of the interface pressure over the contact area. These were measured using a capacitive pressure-sensing grid. The measurements were performed with 10 male subjects and three circular cross-section handles of different sizes under different combinations of grip and push forces. The hand-handle interface pressure data were analyzed to derive the contact force, as functions of the constant magnitudes of the grip and push forces, and the handle size. The results suggest that the hand-handle contact force is strongly dependent upon not only the grip and push forces but also the handle diameter. The contact force for a given handle size can be expressed as a linear combination of grip and push forces, where the contribution of the grip force is considerably larger than that of the push force. The results further suggest that a linear relation can characterize the dependence of the contact force on the handle diameter. The validity of the proposed relationship is demonstrated by evaluating the magnitudes of errors between the estimated contact forces with the measured data for the range of handle diameters, and grip and push forces considered in the study.
Although industrial and product designers are keenly aware of the importance of design aesthetics, they make aesthetic design decisions largely on the basis of their intuitive judgments and "educated guesses". Whilst ergonomics and human factors researchers have made great contributions to the safety, productivity, ease-of-use, and comfort of human-machine-environment systems, aesthetics is largely ignored as a topic of systematic scientific research in human factors and ergonomics. This article discusses the need for incorporating the aesthetics dimension in ergonomics and proposes the establishment of a new scientific and engineering discipline that we can call "engineering aesthetics". This discipline addresses two major questions: How do we use engineering and scientific methods to study aesthetics concepts in general and design aesthetics in particular? How do we incorporate engineering and scientific methods in the aesthetic design and evaluation process? This article identifies two special features that distinguish aesthetic appraisal of products and system designs from aesthetic appreciation of art, and lays out a theoretical foundation as well as a dual-process research methodology for "engineering aesthetics". Sample applications of this methodology are also described.
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