Posture and Movement Estimation Based on Reduced Information. Application to the Context of FES-based Control of Lower-Limbs

International audienc

Biomechanical Modelling of Manual Material Handling Tasks: A Comprehensive Review

AbstractIn a developing country like India where industrial tasks are labour-intensive, involving Manual Material Handling (MMH) in many situations; workload measurement in terms of Newtonian anthropometry and physiological parameters is important to identify unduly heavy tasks, to evaluate traditional work methods, and to arrive at more efficient methods of work. In jobs which require prolonged manual labour like construction jobs, assessment of cardiovascular capacity may be used to determine a worker's level of fitness for work. To tackle the issues as mentioned, various approaches, such as biomechanical, physiological and physical evaluations may be used for proper quantification and minimization of risks of Musculoskeletal Disorders (MSDs) associated with different types of material handling tasks in order to reduce fatigue and physical stress. Among all evaluations, biomechanical evaluation deals with the study of the physical interaction of workers with their tools, machines, and materials so as to enhance the worker's performance while minimizing the risk of MSDs. In this context, studies of various biomechanical models (static and dynamic) are required to be studied. In this paper, a comprehensive review of the concepts of static and dynamic models as applicable for MMH task is presented. Starting with various types of static and dynamic models, the issues on occupational risk assessment related to various manual handling tasks are discussed progressively. The distinctiveness of the models are highlighted. Finally, based on the critical appraisal of the existing approaches, future research directions on various models of biomechanical evaluation are delineated

Hazards and Risks at Rotary Screen Printing (Part 5/6): Pushing and Pulling

Pushing and pulling-tasks were initially-intended to-replace manual-materials-handling, including lifting, and to-help to-reduce-stress on musculoskeletal-system. Pushing, pulling, and maneuvering materials- handling (MH)-equipment, however, still involve some of the-old-hazards (overexertion), while creating new-ones. This-study was focused on hazards and risks, associated with pushing and pulling-tasks, at finishing-department, of a-textile-mill. Document-analysis, questionnaire, and numerous-observations (via site-visits) were utilized, as main-instruments for the-study. In-compliance with the-ISO 20252:2006 (E), the-questionnaire was pre-tested, for validity and reliability; SPPS-17, version 22 was applied, to-compute the-Cronbach’s coefficient. Descriptive-statistics was employed, to-analyze both; qualitative and quantitative-data. The-research targeted 12 printing-machine-operators; response-rate obtained (RR=92%). Majority of the-respondents (91%), indicated, that: repetitive-pushing and pulling-tasks were-conducted, daily; the-loads were heavy; moreover operators were not aware about the-actual-weigh, of a-particular load, so they just approximated; they also-pointed-out, that high-initial-forces were-required, to-get the-load moving; the-loads lacked good-handholds; and pushing and pulling-tasks were-conducted, in-confined spaces and/or narrow-doorways. 73% stated, that they performed more of pushing, than pulling-tasks. 64% indicated, that pushing and pulling involved: manoeuvring of the-load, into-position, or around-obstacles; some of the-MH-equipment was without brakes, making it difficult to-stop; and floors were, largely, uneven, damaged, and/or slippery. 45% claimed, that: occasionally, push or pull-movements involved high-speed and/or long-distances; MH-equipment (trolleys, carts), and floor-surfaces, were poorly maintained, cleaned and/or repaired; the-majority of MH-equipment was heavy, old, and hard to-steer; and that there was an-absence of the-suitable personal-protective-equipment, provided, and, hence, worn. In-addition to the-questionnaire, observation of different-pushing and pulling-practices, was conducted; one-illustrative-example of which, is presented, in-detail. Moreover, to-bring broader-perspective, the-following-aspects were covered: Pushing vs. pulling ongoing-debate; Pushing and Pulling Capability-Standards, Guidelines, and tools; Pushing and pulling-task phases and forces, involved; as-well-as relevant-factors/characteristics of: load; individual; equipment; and work-practice-environment. Finally, the-study offered general, as-well-as specific-recommendations, to-improve current-practices of pulling and pushing, at the-department. These should-be useful, to-employers and practitioners, who design and analyze, pushing and pulling-tasks, at the-department, and in-the-textile-printing-industry, at-large. Keywords: forces, friction, MSDs, MSIs, human-machine-interface

Estimating hand-grip forces causing Cumulative Trauma Disorder

Wearable sensors have garnered considerable interest because of their potential for various applications. However, much less has been studied about the Stretchsense pressure sensor characteristics and its workability for industrial application to prevent potential risk situations such as accidents and injuries. The proposed study helps investigate Stretchsense pressure sensors\u27 applicability for measuring hand-handle interface forces under static and dynamic conditions. The BendLabs sensors - a multi-axis, soft, flexible sensing system was attached to the wrist to evaluate the wrist angle deviations. In addition, the StretchSense stretch sensors were attached to the elbow joint to help estimate the elbow flexion/extension. The research tests and evaluates the real-time pressure distribution across the hand while performing given tasks and investigates the relationship between the wrist and elbow position and grip strength. The research provides objective means to assess the magnitudes of high pressures that may cause pressure-induced discomfort and pain, thereby increasing the hand\u27s stress. The experiment\u27s most significant benefit lies in its applicability to the actual tool handles outside the laboratory settings

Characteristic Of Elderly People Hand And Its Effect To Walking Stick Handle:A Case Study In Malacca

Hand is best known as an ultimate operative instrument, the hand helps in assisting human to grip,pinch,hold and others.According to the statistic in year 2015,the population of elderly people in Malaysia aged 60 years old and above was 2.8 million and by year 2035,the population projection of elderly people will up to 5.6 million.The projection figures give a preliminary picture on the demand for the usage of walking aids among elderly people.This study is to investigate the hand characteristics and biomechanics of elderly people and its effect to different design of handle of walking stick and propose handle of walking stick considering ergonomics aspects of elderly Malaysian.The sample of elderly people was taken from Rumah Seri Kenangan,Cheng, Malacca.They comprises of female and male of Malay, Chinese and Indian races,their age were sixty and above. Physical characteristics of hand such as:contact area, hand length,hand width,hand size,inside grip diameter and grip strength,grip force,was taken.Other than measuring physical dimension of hand,survey was also captures their opinion regarding the comfortability of using three types of handles walking stick design which were mostly used. Three types of walking stick handle were chosen based on market demand.There were positive correlations on hand length and hand size,hand size and inside grip diameter, hand size and grip strength.It has negative correlation for both genders for grip strength and age.Among the three handle of walking stick,the one that contribute to distributed force was handle Swan neck type followed by T-type handle and Crook type handle.On distribution of force among 5 location identified,the location on ulnar nerve area was the highest force.This was also confirmed by results of questionnaires and interview.For recommendation,the design of handle stick that give better comfort those that provide equally distributed force to hand.The size of handle should follow the hand size of elderly people.According to the result,the handle should have three different sizes.Padded handle stick would provide not only better grip but also comfort ability

Design Assessment of Two-Wheeled Luggage Based on Mechanical Models and a Usability Test

The purpose of this study is to ergonomically assess two-wheeled luggage design based on mechanical models and a usability test. Three mechanical models were developed for the pulling force estimation and important luggage design factor finding. Three pulling conditions with three motion stages were considered in the model. In addition, a set of pre-questionnaires and a set of post-questionnaires were prepared for the investigation of users’ preferences for each design factor. From the mechanical models, the minimum pulling force was found at the tilted angle of 65.56° in static staus, at the tilted angle of 30° in the initial phase, and at the tilted angle of 65.56° in the sustained phase. Based on the optimal tilted angle, several pole lengths were suggested (41.5” for 5%ile female, 45.5” for 5%ile male and 50%ile female groups, 49.5” for 50%ile male, 95%ile female groups, and 52.5” for 95%ile male group). In addition, some important design factors contributory to the minimum pulling force were found through the mechanical models. According to the results of mechanical models, tilted angles of luggage(), the distance between center of mass and the bottom of luggage (b), and weight of luggage (W) significantly affected the pulling force. Two luggage prototypes were developed by considering the important design factors resulted from the mechanical models and a usability test was conducted. For the usability test, two load weights (33 lbs and 50 lbs), six pole lengths (38.5”, 41.5”, 44.5”, 45.5”, 49.5”, and 52.5”), four subject groups (5%ile female, 50%ile female, 50%ile male, and 95%ile male groups), and two luggage size (22”×14”×10” and 30”×21”×11.5”) were considered in experimental design. Subjects answered pre- and post-questionnaires as soon as they conducted the experiment. Test results demonstrated that most upper body parts were affected by load weights, pole length, and subjects’ knuckle heights. In addition, pole lengths between 38.5” and 49.5” were selected from all subject groups. A pole should be adjustable within the range from 38.5” to 49.5” although the mechanical models suggested the pole lengths between 38.5” and 52.5”. Tilted angle should be maintained from 30º to 50º in this range. This result indicated that there is a gap between the theoretical and practical results. In conclusion, load weights, pole lengths, and subjects’ knuckle heights should primarily be considered when luggage is designed. However, additional studies need to get deeper understanding of the gap between mechanical models and usability. In addition, more systematical survey questionnaires should be developed to provide any possible solutions to reduce the gap

Finger Flexor Tendon Orientation and Location as a Function of Postural Changes of the Wrist and Forearm: The Quantification of Musculoskeletal Loading in Jobs with Deviated Forearms

Forearm pronation/supination is common during manual activities, and has been linked to upper limb disorders in the workplace (Hughes et al. 1997). Forearm deviations from neutral (palm of the hand facing medially) can increase discomfort and forearm musculature activity (EMG) (Khan 2009a; Domizio & Keir, 2010), particularly when combined with wrist postures deviated from neutral. Yet ergonomic tools commonly used to assess the risk of developing distal upper limb disorders (e.g., Strain Index and RULA), often disregard or only minimally account for forearm pronation/supination posture. As a result, the risk of injury may be underestimated. This dissertation first examined methods of measuring pronation in the workplace by testing instantaneous agreement of forearm posture measurements between Inertial Motion Units (Xsens, Netherlands) and a laboratory-based motion capture system (Vicon, UK). Participants turned metallic and non-metallic handles in front of them, in order to quantify the effect of magnetic disturbance and sensor orientation on the Xsens. On average, RMSE errors of 12.6 deg around metal, and 8.6 deg around plastic were observed on instantaneous measures. Higher rotational velocities appeared associated with larger errors. Summarized data revealed smaller discrepancies. Second, this dissertation examined the effect of forearm pronation/supination coupled with wrist flexion/extension on the orientation and location of finger flexor tendons with respect to a radial coordinate system, using MRI of 4 healthy wrists. Pronation/supination caused movement almost exclusively in the frontal plane. Radial tendons exhibited larger angular deviations in pronation, whereas ulnar tendons were nearly straight, and the opposite was observed in supination. Larger angular deviations were thought to increase contact forces within the tunnel in the direction of the bend, which combined with finger movement could increase the risk of tenosynovitis. Finally the results of these studies were combined to measure tendon movement during a repetitive task. The three tendons with the greatest angular movement in the tunnel were: FDP2 (0.16 deg/pronation/supination degree), FDS3 (0.15 deg/ pronation/supination degree), and FDS4 (0.17 deg/ pronation/supination degree)

Verbal estimation of peak dynamic hand forces in experienced and novice manual material handlers

This study examined participants\u27 verbally estimated peak dynamic hand forces compared to actual hand forces during various pushing and pulling tasks. Effects of manual material handling (MMH) experience and feedback training on hand force self-reporting were studied. Verbally estimated hand forces were similar across all four groups, despite different amounts of feedback training received and MMH experience. Participants were more accurate verbally estimating pushes than pulls for two-handed tasks, and at low force level for one and two-handed tasks (mean errors =10.2 % MVC and 9.4 % MVC). Verbal estimation differences existed between high and medium forces for two-handed tasks, and medium and low forces for one and two-handed tasks. No differences were found between genders. Values generated by prediction equations demonstrated a strong relationship between actual and verbally estimated hand forces indicated by high R2. Results indicate that a similar methodology could be performed in workplaces to attain force magnitudes