Cybernetic manufacturing systems project-ergonomics solutions for flexible production systems

peer-reviewedIntroduction to special issue: cybernetic manufacturing systems project—ergonomics solutions for flexibleACCEPTEDpeer-reviewe

Effects of a passive back exoskeleton on the mechanical loading of the low-back during symmetric lifting

Low-back pain is the number one cause of disability in the world, with mechanical loading as one of the major risk factors. Exoskeletons have been introduced in the workplace to reduce low back loading. During static forward bending, exoskeletons have been shown to reduce back muscle activity by 10% to 40%. However, effects during dynamic lifting are not well documented. Relative support of the exoskeleton might be smaller in lifting compared to static bending due to higher peak loads. In addition, exoskeletons might also result in changes in lifting behavior, which in turn could affect low back loading. The present study investigated the effect of a passive exoskeleton on peak compression forces, moments, muscle activity and kinematics during symmetric lifting. Two types (LOW and HIGH) of the device, which generate peak support moments at large and moderate flexion angles, respectively, were tested during lifts from knee and ankle height from a near and far horizontal position, with a load of 10 kg. Both types of the trunk exoskeleton tested here reduced the peak L5S1 compression force by around 5-10% for lifts from the FAR position from both KNEE and ANKLE height. Subjects did adjust their lifting style when wearing the device with a 17% reduced peak trunk angular velocity and 5 degrees increased lumbar flexion, especially during ANKLE height lifts. In conclusion, the exoskeleton had a minor and varying effect on the peak L5S1 compression force with only significant differences in the FAR lifts

The effect of human autonomy and robot work pace on perceived workload in human-robot collaborative assembly work

Collaborative robots (in short: cobots) have the potential to assist workers with physically or cognitive demanding tasks. However, it is crucial to recognize that such assistance can have both positive and negative effects on job quality. A key aspect of human-robot collaboration is the interdependence between human and robotic tasks. This interdependence influences the autonomy of the operator and can impact the work pace, potentially leading to a situation where the human’s work pace becomes reliant on that of the robot. Given that autonomy and work pace are essential determinants of job quality, design decisions concerning these factors can greatly influence the overall success of a robot implementation. The impact of autonomy and work pace was systematically examined through an experimental study conducted in an industrial assembly task. 20 participants engaged in collaborative work with a robot under three conditions: human lead (HL), fast-paced robot lead (FRL), and slow-paced robot lead (SRL). Perceived workload was used as a proxy for job quality. To assess the perceived workload associated with each condition was assessed with the NASA Task Load Index (TLX). Specifically, the study aimed to evaluate the role of human autonomy by comparing the perceived workload between HL and FRL conditions, as well as the influence of robot pace by comparing SRL and FRL conditions. The findings revealed a significant correlation between a higher level of human autonomy and a lower perceived workload. Furthermore, a decrease in robot pace was observed to result in a reduction of two specific factors measuring perceived workload, namely cognitive and temporal demand. These results suggest that interventions aimed at increasing human autonomy and appropriately adjusting the robot’s work pace can serve as effective measures for optimizing the perceived workload in collaborative scenarios

Sub-movement organisation, pen pressure and muscle activity are modulated to precision demands in 2D tracking

The authors investigated how tracking performance, submovement organization, pen pressure and muscle activity in forearm and shoulder muscles were affected by target size in a 2D tracking task performed with a pen on a digitizer tablet. Twenty-six subjects took part in an experiment, in which either a small dot or a large dot was tracked, while it moved quasirandomly across a computer screen at a constant velocity of 2cm/s. The manipulation of precision level was successful, because mean distance to target and the standard deviation of this distance were significantly smaller with the small target than with the large target. With a small target, subjects trailed more behind the center of target and used submovements with larger amplitudes and of shorter duration, resulting in higher tracking accuracy. This change in submovement organization was accompanied by higher pen pressure, while at the same time muscle activity in the forearm extensors and flexors was increased, indicating higher endpoint stability. In conclusion, increased precision demands were accommodated by both a different organization of submovements and higher endpoint stability in a 2D tracking task performed with a pen on a digitizer tablet. © 2012 Copyright Taylor and Francis Group, LLC

Sitting comfort and discomfort and the relationships with objective measures

The concepts of comfort and discomfort in sitting are under debate. There is no widely accepted definition, although it is beyond dispute that comfort and discomfort are feelings or emotions that are subjective in nature. Yet, beside several subjective methodologies, several objective methods (e.g. posture analysis, pressure measurements, electromyography (EMG)) are in use to assess sitting comfort or discomfort. In the current paper a theoretical framework is presented, in which comfort and discomfort were defined and the hypothetical associations with underlying factors were indicated. Next, the literature was reviewed to determine the relationships between objective measures and subjective ratings of comfort and discomfort. Twenty-one studies were found in which simultaneous measures of an objective parameter and a subjective rating of comfort or discomfort were obtained. Pressure distribution appears to be the objective measure with the most clear association with the subjective ratings. For other variables, regarding spinal profile or muscle activity for instance, the reported associations are less clear and usually not statistically significant

Cybernetic manufacturing systems project-ergonomics solutions for flexible production systems

Introduction to special issue: cybernetic manufacturing systems project—ergonomics solutions for flexibl

The potential and acceptance of exoskeletons in industry

Worldwide, a significant interest in wearable robots or exoskeletons does exist, also from an industrial background. This paper provides an overview of assistive exoskeletons that have specifically been developed for industrial purposes. It discusses their potential in increasing performance and flexibility on one hand and in reducing the mechanical loads on workers involved in manual work on the other. From this it is concluded that exoskeletons have the potential to increase performance under specific conditions and to reduce physical loads significantly. However, several technical issues hinder mainstay practical use of exoskeletons in industry until now. One main issue concerns the human-machine interaction which stands in the way of acceptance. This issue and its linkage to ethics and standardization will be discussed during the conference