Exoskeletons for industrial application and their potential effects on physical work load

The aim of this review was to provide an overview of assistive exoskeletons that have specifically been developed for industrial purposes and to assess the potential effect of these exoskeletons on reduction of physical loading on the body. The search resulted in 40 papers describing 26 different industrial exoskeletons, of which 19 were active (actuated) and 7 were passive (non-actuated). For 13 exoskeletons, the effect on physical loading has been evaluated, mainly in terms of muscle activity. All passive exoskeletons retrieved were aimed to support the low back. Ten-forty per cent reductions in back muscle activity during dynamic lifting and static holding have been reported. Both lower body, trunk and upper body regions could benefit from active exoskeletons. Muscle activity reductions up to 80% have been reported as an effect of active exoskeletons. Exoskeletons have the potential to considerably reduce the underlying factors associated with work-related musculoskeletal injury.

Practitioner Summary:

Worldwide, a significant interest in industrial exoskeletons does exist, but a lack of specific safety standards and several technical issues hinder mainstay practical use of exoskeletons in industry. Specific issues include discomfort (for passive and active exoskeletons), weight of device, alignment with human anatomy and kinematics, and detection of human intention to enable smooth movement (for active exoskeletons).     

Muscle- and task-dependent responses to concurrent physical and mental workload during intermittent static work

Many workers experience combined physical and mental demands in their jobs, yet the contribution of these demands to the development of musculoskeletal disorders is unclear. The purpose of this study was to investigate muscle- and task-dependent responses to concurrent demands during intermittent static work. Twenty-four participants performed shoulder, wrist, and torso exertions at three levels of physical workload (PWL) in the absence (control) and presence (concurrent) of a mental arithmetic task. Compared to the control, concurrent demand conditions resulted in decreased muscle activity (4–9% decrease), increased cardiovascular load (2–4% increase), and impaired motor co-ordination (9–24% increase in force fluctuation). Furthermore, these outcomes were more prominent at higher PWL levels and within postural (shoulder and torso) muscles. Mental task performance exhibited greater interference with the physical task at low and high PWL levels. Thus, it may be important to consider these muscle- and task-specific interactions of concurrent demands during job design to address worker health and performance issues.

Practitioner Summary: Occupational tasks place both physical and mental demands on workers. These demands can adversely affect physiological responses and performance, and are muscle- and task-dependent. Findings from this research may facilitate the development of ergonomics interventions, such as task redesign and tool/workstation design, that may help reduce risk of workplace injuries.     

The associations between psychosocial workload and mental health complaints in different age groups

The objective of the present study was to explore associations between psychosocial workload and mental health complaints in different age groups. A questionnaire was sent to 2021 employees of a Dutch railway company. Six aspects of psychosocial workload (work pressure, mental workload, emotional workload, autonomy, social support from colleagues and social support from supervisors) and three mental health outcomes (work-related fatigue, stress and burnout) were assessed. Associations between the aspects of psychosocial workload (distributed into tertiles) and health complaints were analysed by logistic regression analysis in four age groups (22–35, 36–45, 46–55 and 56–66 years old). In all age groups, worse work pressure was a significant risk factor for having mental health complaints. Worse emotional load in the younger employees and lack of social support in older employees were associated with a higher risk of having mental health complaints. Age-specific preventive measures should be implemented on both individual and group levels.

Statement of Relevance: With an ageing workforce, understanding relationships between age and work-related health ailments is increasingly important. This study found that emotional workload in younger and lack of social support in older employees were associated with a higher risk of mental health complaints. Work pressure was a risk factor in all age groups.     

The effect of sonification display pulse rate and reliability on operator trust and perceived workload during a simulated patient monitoring task

The present study investigated the effects of sonification pulse rate and sensor reliability on operator trust and mental workload. Processing resources and operator trust were sensitive to both pulse rate and sensor reliability. These findings suggest that setting pulse rates to 60 pulses per min may have considerable benefits in critical task environments.     

Cultural influences on the measurement of subjective mental workload

Cognitive ergonomics is well entrenched in North American and most European work environments, where systems and products are designed with the capabilities and limitations of the user in mind. A prominent technique for analysing task demands is subjective mental workload measurement. Subjective ratings of mental workload have been shown—in North American and European populations—to be reliable and sensitive to changes in mental workload. However, there is reason to think that cultural differences may affect subjective ratings. This study compared the performance and subjective mental workload ratings of Indonesian (n = 87) and Dutch (n = 88) students in the context of a hybrid memory/visual search task. Performance was comparable for the two groups, but the sensitivity of the subjective workload measures was better in the Dutch than in the Indonesian group. The results are interpreted in light of social axioms and cultural values.

Statement of Relevance: Now more than ever ergonomists must think beyond national borders in improving work processes. Globalisation requires that cultural differences be taken into account in developing and applying ergonomic techniques. This paper presents empirical work showing that cultural differences seriously impact the sensitivity of mental workload measures.     

Age-related difference in perceptual responses and interface pressure requirements for driver seat design

Due to typical physiological changes with age, older individuals are likely to have different perceptual responses to and different needs for driver–seat interface design. To assess this, a study was conducted in which a total of 22 younger and older participants completed six short-term driving sessions. Three subjective ratings (comfort, discomfort and overall) were obtained, along with 36 driver–seat interface pressure measures, and were used to assess differences and similarities between the two age groups. For both age groups, localised comfort ratings were more effective at distinguishing between driver seats and workspaces. Older individuals appeared to be less sensitive to discomfort than younger individuals. Across age groups, two distinct processes were used in determining whole-body comfort and discomfort perceptions based on localised comfort/discomfort perceptions. Whole-body discomfort levels were largely affected by lower back discomfort in the younger group versus upper back discomfort in the older group. Four specific pressure measures at several body regions differed between the age groups, suggesting distinct contract pressure requirements and loading patterns among these groups.     

Developing measures for information ergonomics in knowledge work

Information ergonomics is an evolving application domain of ergonomics focusing on the management of workload in the real-world contexts of information-intensive tasks. This study introduces a method for the evaluation of information ergonomics in knowledge work. To this end, five key dimensions of information ergonomics were identified: contextual factors of knowledge work, multitasking, interruptions at work, practices for managing information load, and perceived job control and productivity. In total, 24 measures focusing on the above dimensions were constructed. The measures include, for example, the number of fragmented work tasks per work day. The measures were preliminarily tested in two Finnish organisations, making use of empirical data gathered by interviews, electronic questionnaires and log data applications tracking work processes on personal computers. The measures are applicable to the evaluation of information ergonomics, even though individual measures vary with regard to the amount of work and time needed for data analysis.

Practitioner Summary:

The study introduces a method for the evaluation of information ergonomics in knowledge work. To this end, 24 measures were constructed and tested empirically. The measures focus on contextual factors of knowledge work, multitasking, interruptions at work, practices for managing information load, and perceived job control and productivity.     

Fighter pilots’ heart rate,heart rate variation and performance during instrument approaches

Fighter pilots’ heart rate (HR), heart rate variation (HRV) and performance during instrument approaches were examined. The subjects were required to fly instrument approaches in a high-fidelity simulator under various levels of task demand. The task demand was manipulated by increasing the load on the subjects by reducing the range at which they commenced the approach. HR and the time domain components of HRV were used as measures of pilot mental workload (PMWL). The findings of this study indicate that HR and HRV are sensitive to varying task demands. HR and HRV were able to distinguish the level of PMWL after which the subjects were no longer able to cope with the increasing task demands and their instrument landing system performance fell to a sub-standard level. The major finding was the HR/HRV’s ability to differentiate the sub-standard performance approaches from the high-performance approaches.

Practitioner Summary:

This paper examined if HR and HRV were sensitive to varying task demands in a fighter aviation environment and if these measures were related to variations in pilot’s performance.     

Mental workload measurement for emergency operating procedures in digital nuclear power plants

Mental workload is a major consideration for the design of emergency operation procedures (EOPs) in nuclear power plants. Continuous and objective measures are desired. This paper compares seven mental workload measurement methods (pupil size, blink rate, blink duration, heart rate variability, parasympathetic/sympathetic ratio, total power and (Goals, Operations, Methods, and Section Rules)-(Keystroke Level Model) GOMS-KLM-based workload index) with regard to sensitivity, validity and intrusiveness. Eighteen participants performed two computerised EOPs of different complexity levels, and mental workload measures were collected during the experiment. The results show that the blink rate is sensitive to both the difference in the overall task complexity and changes in peak complexity within EOPs, that the error rate is sensitive to the level of arousal and correlate to the step error rate and that blink duration increases over the task period in both low and high complexity EOPs. Cardiac measures were able to distinguish tasks with different overall complexity. The intrusiveness of the physiological instruments is acceptable. Finally, the six physiological measures were integrated using group method of data handling to predict perceived overall mental workload.

Practitioner Summary: The study compared seven measures for evaluating the mental workload with emergency operation procedure in nuclear power plants. An experiment with simulated procedures was carried out, and the results show that eye response measures are useful for assessing temporal changes of workload whereas cardiac measures are useful for evaluating the overall workload.     

Mental strain and annoyance during cognitive performance in different traffic noise conditions

In built-up areas, an increasing number of persons are affected by road traffic noise while performing mental work. This experimental study focused on annoyance and mental strain due to various noise scenarios. A total of 102 healthy, young persons (51 women, 51 men, aged 18–31 years) were randomly assigned to one of five experimental conditions determined by traffic flow (even, lumped) and traffic composition (20%, 40% heavy vehicles). While exposed to noise they performed a grammatical reasoning and a mathematical processing task. Performance and mental strain were not affected by any of the five noisy conditions. Individuals with high noise sensitivity were partially more annoyed and performed less than persons with low sensitivity.

Statement of Relevance: The present study provides information about mental strain due to tasks with different cognitive demands and the role of noise sensitivity in various traffic noise conditions. The results show that measures aiming at the reduction of the proportion of heavy vehicles should additionally consider particular traffic flow.     

Effects of tactile cueing on concurrent performance of military and robotics tasks in a simulated multitasking environment

This study examined the concurrent performance of military gunnery, robotics control and communication tasks in a simulated environment. More specifically, the study investigated how aided target recognition (AiTR) capabilities (delivered either through tactile or tactile + visual cueing) for the gunnery task might benefit overall performance. Results showed that AiTR benefited not only the gunnery task, but also the concurrent robotics and communication tasks. The participants' spatial ability was found to be a good indicator of their gunnery and robotics task performance. However, when AiTR was available to assist their gunnery task, those participants of lower spatial ability were able to perform their robotics tasks as well as those of higher spatial ability. Finally, participants' workload assessment was significantly higher when they teleoperated (i.e. remotely operated) a robot and when their gunnery task was unassisted. These results will further understanding of multitasking performance in military tasking environments. These results will also facilitate the implementation of robots in military settings and will provide useful data to military system designs.     

Cardiovascular and eye activity measures as indices for momentary changes in mental effort during simulated flight

This study examines effects of momentary changes in mental effort on cardiovascular and eye activity measures. A total of 19 male pilots performed an instrument flight task. Task load was manipulated by having the pilots perform flight manoeuvres of varying complexity. Multilevel analyses demonstrated clear effects of momentary changes in mental effort on both the cardiovascular and the eye activity measures. An increase in task load resulted in an increase of heart rate and a decrease in heart rate variability, mean dwell time and fixation duration. Heart rate differentiated between resting period and task execution. Heart rate variability from short data segments provided more insight in intermediate levels of mental effort. The eye activity measures were sensitive to intermediate levels of mental effort as well. Attitude changes resulted in an increase of mean dwell time and mean fixation duration. Task analysis is required to use eye measures as valid indices of mental effort. Having indications of the effects of changing mental demands during daily work of operators is of great importance nowadays. This paper presents an approach to estimate such effects on the basis of heart rate and eye activity measures. In particular, the use of averaged short-term heart rate variability measures is a relatively new aspect.     

个体经验和行为的IEBTrust信任模型

在分布式网络中,由于节点主观特性和客观特性的非对称性,使得同一节点在不同场景中,可能具有不同的交互经验和行为,节点的信任评价值应该因场景的不同而有所差异,现有信任模型不能客观的反应这个问题.为此,考虑了节点个体行为的差异,通过引入经验因子的方法,提出一种基于个体经验和个体行为的信任模型.算法分析表明,新模型在反馈可信度的算法等方面有较大的改善.