Human motion simulation for vehicle and workplace design

Digital Human Models (DHMs) are fast becoming an effective tool for performing proactive ergonomics analysis and design. DHM software, such as Jack, SAFEWORK, RAMSIS, SAMMIE, and the UM 3DSSP, are meant to assist a designer early in a product development process, when he or she is attempting to improve the physical design of vehicle interiors and manufacturing workplaces. To become even more effective in meeting such a goal, it is proposed that future DHMs must include valid posture and motion prediction models for various populations. It is argued in this article that existing posture and motion prediction models now used in DHMs must be based on real motion data to assure validity for complex dynamic task simulations. It is further proposed that if valid human posture and motion prediction models are developed, these can be combined with psychophysical and biomechanical models to provide a very powerful tool for predicting dynamic human performance and population specific limitations. © 2007 Wiley Periodicals, Inc. Hum Factors Man 17: 475–484, 2007.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56152/1/20087_ftp.pd

Effects of Pacing When Using Material Handling Manipulators

Common manipulator-assisted materials handling tasks were performed in a laboratory simulation at self-selected and faster (paced) speeds. The effects of pacing on peak hand forces, torso kinematics, spine moments and forces, and muscle antagonism were determined, along with any influences of several task variables on these effects. The faster trials were performed 20% more rapidly than the self-paced trials. It was found that (a) achieving this level of performance required 10% higher hand forces and 5%-10% higher torso moments, (b) consistent torso postures and motions were used for both speed conditions, and (c) the faster trials resulted in 10% higher spine forces and 15% higher levels of lumbar muscle antagonism. On whole, these results suggest a higher risk of musculoskeletal injury associated with performance of object transfers at faster than self-selected speeds with and without a manipulator. Further analysis provided evidence that the use of manipulators involves higher levels of motor coordination than do manual tasks. Several implications regarding the use of material handling manipulators in paced operations are discussed. Results from this investigation can be used in the design, evaluation, and selection of material handling manipulators.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67067/2/10.1518_001872099779591240.pd

Predicting Foot Positions for Manual Materials Handling Tasks

Copyright © 2005 SAE International For many industrial tasks (push, pull, lift, carry, etc.), restrictions on grip locations and visibility constrain the hand and head positions and help to define feasible postures. In contrast, often the foot locations are minimally constrained and an ergonomics analyst can choose several different stances in selecting a posture to analyze. Also, because stance can be a critical determinant of a biomechanical assessment of the work posture, the lack of a valid method for placing the feet of a manikin with respect to the task compromises the accuracy of the analysis. To address this issue, foot locations and orientations were captured in a laboratory study of sagittal plane and asymmetric manual load transfers. A pilot study with four volunteers of varying anthropometry approached a load located on one of three shelves and transferred the load to one of six shelves. The data illustrate foot placements and behaviors that depend on pickup heights, the use of one or two hands to grasp the object, and the participantsʼ body dimensions. Two distinct pickup and delivery strategies were observed. Split stance, with one foot in front of the other, was markedly more frequent than parallel stance with the feet side by side. A statistical model was developed to predict foot placements at load pickup. This study confirms the importance of this topic and provides the basis for the much more comprehensive study that is now underway

Development of computerized human static strength simulation model for job design

This article describes the development of models to predict population static strengths and low back forces resulting from common manual exertions in industry. The resulting biomechanical models are shown to be valid for their intended purposes, but limitations still exist. In particular, they are meant to aid in evaluating very slow or static exertions, such as when carefully lifting, pushing, or pulling on heavy objects, but do not allow dynamic exertions to be simulated. It is shown that use of these models in the early design of workplaces and equipment is dependent on the use of computerized homonoids and behavioral-based inverse kinematic algorithms in conjunction with CAD systems. © 1997 John Wiley & Sons, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/35211/1/3_ftp.pd

Mixed-method study of a conceptual model of evidence-based intervention sustainment across multiple public-sector service settings.

BackgroundThis study examines sustainment of an EBI implemented in 11 United States service systems across two states, and delivered in 87 counties. The aims are to 1) determine the impact of state and county policies and contracting on EBI provision and sustainment; 2) investigate the role of public, private, and academic relationships and collaboration in long-term EBI sustainment; 3) assess organizational and provider factors that affect EBI reach/penetration, fidelity, and organizational sustainment climate; and 4) integrate findings through a collaborative process involving the investigative team, consultants, and system and community-based organization (CBO) stakeholders in order to further develop and refine a conceptual model of sustainment to guide future research and provide a resource for service systems to prepare for sustainment as the ultimate goal of the implementation process.MethodsA mixed-method prospective and retrospective design will be used. Semi-structured individual and group interviews will be used to collect information regarding influences on EBI sustainment including policies, attitudes, and practices; organizational factors and external policies affecting model implementation; involvement of or collaboration with other stakeholders; and outer- and inner-contextual supports that facilitate ongoing EBI sustainment. Document review (e.g., legislation, executive orders, regulations, monitoring data, annual reports, agendas and meeting minutes) will be used to examine the roles of state, county, and local policies in EBI sustainment. Quantitative measures will be collected via administrative data and web surveys to assess EBI reach/penetration, staff turnover, EBI model fidelity, organizational culture and climate, work attitudes, implementation leadership, sustainment climate, attitudes toward EBIs, program sustainment, and level of institutionalization. Hierarchical linear modeling will be used for quantitative analyses. Qualitative analyses will be tailored to each of the qualitative methods (e.g., document review, interviews). Qualitative and quantitative approaches will be integrated through an inclusive process that values stakeholder perspectives.DiscussionThe study of sustainment is critical to capitalizing on and benefiting from the time and fiscal investments in EBI implementation. Sustainment is also critical to realizing broad public health impact of EBI implementation. The present study takes a comprehensive mixed-method approach to understanding sustainment and refining a conceptual model of sustainment

Muscle Fatigue Analysis Using OpenSim

In this research, attempts are made to conduct concrete muscle fatigue analysis of arbitrary motions on OpenSim, a digital human modeling platform. A plug-in is written on the base of a muscle fatigue model, which makes it possible to calculate the decline of force-output capability of each muscle along time. The plug-in is tested on a three-dimensional, 29 degree-of-freedom human model. Motion data is obtained by motion capturing during an arbitrary running at a speed of 3.96 m/s. Ten muscles are selected for concrete analysis. As a result, the force-output capability of these muscles reduced to 60%-70% after 10 minutes' running, on a general basis. Erector spinae, which loses 39.2% of its maximal capability, is found to be more fatigue-exposed than the others. The influence of subject attributes (fatigability) is evaluated and discussed

A biomechanical evaluation of five lifting techniques

Five lifting methods which cover the range of techniques recommended by various back schools have been biomechanically analysed with a static sagittal-plane computer model. The analysis was performed with two load-types (compact and bulky) and three weights in the hands (44 N, 222 N and 400 N). The methods were compared in terms of predicted L5/S1 disc compression, low-back ligament strain and strength requirements at the shoulders, L5/S1, hip and knee joints. In general the method entailing a squat posture, straddle foot stance and flat back (oriented as when standing erect) yielded lower compressions, ligament strains and overall strength requirements than the other methods.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26237/1/0000317.pd

Some biomechanical aspects of the carpal tunnel

Previously presented evidence indicates that carpal tunnel syndrome is related to compression of the median nerve inside the carpal tunnel. Biomechanical arguments in which the extrinsic finger flexor tendons inside the carpal tunnel are characterized as a frictionless pulley-belt mechanism are presented to show quantitatively how wrist size, wrist position and hand position affect forces on the tendons and their adjacent structures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23744/1/0000716.pd

An investigation of the relationship between displacements of the finger and wrist joints and the extrinsic finger flexor tendons

Several investigators have developed biomechanical models of finger flexor tendon displacements during pinching or gripping exertions of hands. Landsmeer has developed the most comprehensive set of models for this purpose. This paper describes experiments in which various sized cadaver hands were used to statistically evaluate the Landsmeer models. In so doing, the effects of hand and wrist anthropometry are included. The results indicate that the tendons displace in relation to joint positions as described by that Landsmeer model in which the tendon is depicted as sliding over the curved articular surface of the proximal bone of the joint. Joint thickness effects were found to modify the parameters in the model as intuitively expected. An empirical prediction model of the anthropometric effects was developed. Further, the tendon displacements for various wrist orientations were expressed empirically for the first time and were shown to be consistent with expected anatomical considerations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22712/1/0000267.pd