1,720,983 research outputs found
The effect of human-mattress interface's temperature on perceived thermal comfort
No full textAbstract
In recent years, methods that allow for an objective evaluation of perceived comfort, in terms of postural, physiological, cognitive and environmental comfort, have received a great deal of attention from researchers. This paper focuses on one of the factors that influences physiological comfort perception: the temperature difference between users and the objects with which they interact. The first aim is to create a measuring system that does not affect the perceived comfort during the temperatures' acquisition. The main aim is to evaluate how the temperature at the human-mattress interface can affect the level of perceived comfort. A foam mattress has been used for testing in order to take into account the entire back part of the human body. The temperature at the interface was registered by fourteen 100 Ohm Platinum RTDs (Resistance Temperature Detectors) placed on the mattress under the trunk, the shoulders, the buttocks, the legs, the thighs, the arms and the forearms of the test subject. 29 subjects participated in a comfort test in a humidity controlled environment. The test protocol involved: dress-code, anthropometric-based positioning on mattress, environment temperature measuring and an acclimatization time before the test. At the end of each test, each of the test subject's thermal sensations and the level of comfort perception were evaluated using the ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) scale. The data analyses concerned, in the first instance, correlations between the temperature at the interface and comfort levels of the different parts of the body. Then the same analyses were performed independently of the body parts being considered. The results demonstrated that there was no strong correlation among the studied variables and that the total increase of temperature at interface is associated with a reduction in comfort
Shed Light on the Path of Human-Machine Interaction in Autonomous Vehicles: Where Did We Come from, Where We Are Going? Part I, State of the Art
No full textAs vehicles have become more complicated, Human-Machine Interaction (HMI) is becoming crucial. Nowadays, HMI is a substantial element in autonomous vehicles (AVs). Numerous studies are lately being published regarding significant parameters of AVs which can affect HMI. Hence, it is imperative to have a comprehensive prospect, to improve people’s acceptance of AVs. In AVs, the driver’s role will change to a passenger, however, it can be switched in some special situations. This work is divided in two parts: the first study has mapped from 299 papers in this area and found the most impressive concerns of people in using AVs. Regarding the researchers’ expertise and aim(s), each study has investigated the interactions between human and vehicle from a specific facet. In general, it can be claimed that a dramatic shift from physical parameters to psycho-emotional ones can be observed in recent years. The results showed that trust and comfort are ranked first and second in the reviewed articles, respectively. The second part is dedicated to the explanation of methodology, the synthesis of findings and the perspectives about the future scenarios. Finally, a novel model named 3p is proposed which includes personal, psycho-emotional, and physical parameters, and states the current trend of momentous features affecting HMI in AVs
Passenger Seating Behavior and Discomfort in the Middle Rear Seat: A Pilot Study
No full textThis study investigates the perception of postural discomfort experienced by passengers seated in the middle rear seat of a vehicle—an area often overlooked in ergonomic research. A total of 20 participants (12 males and 8 females) were involved in a pilot test using two car models: a City Car (Fiat Panda) and a C-SUV (Renault Arkana). Each participant completed a short on-road ride (~24 min, 11.7 km) in both vehicles. Discomfort was assessed using a 5-point Likert scale, considering both overall and localized body discomfort, as well as other elements/factors, such as those involved in the human–car interaction (e.g., the central tunnel, the headrest, AC vents, and other passengers). The results showed that overall discomfort was significantly higher in the City Car (mean: 3.75 ± 0.72) compared to the SUV (mean: 3.00 ± 1.16). The most affected body regions in the City Car were the arms (mean: 3.95), knees (3.90), and legs/feet (3.55). In the SUV, discomfort was lower across all regions, with the arms (3.15) and knees (3.05) still being notably impacted. Strong correlations were observed between discomfort and several vehicle features: backrest width, headrests, interference with adjacent passengers, and rear air conditioning vents. This study highlights specific ergonomic issues in the middle rear seat and suggests design improvements, including wider backrests and headrests, repositioned air vents, and the inclusion of lateral supports. These findings offer actionable insights for automotive manufacturers to enhance passenger comfort in multi-passenger configurations
Comfort driven redesign methods: An application to mattresses production systems
No full textThe definitions of methods and tools used to evaluate how workers perceive the comfort during their activities remains an “open” problem at this time. Many researchers have dealt with that problem in the last twenty years, focusing their efforts primarily on the automotive sector and on VDT workstation comfort. This paper analyzes how workers position themselves at workstations used in industrial processes that sew together the edges of mattresses. The aim of the analysis is to determine whether workers can position themselves in ways that allow them to carry out activities in simple and economical ways. The Strain Index was used to identify the most critical and risky work phases in order to evaluate workers' risk of biomechanical overload. The OCRA checklist was used to evaluate the overall risk level associated with repeated completions of the total cycle of work and to develop a virtual-postural analysis to evaluate workers' perceived levels of discomfort. For the virtual-postural analysis, DELMIA® software was used to virtually model a workstation, and records of activities and the postures associated with various repetitive actions were gathered in a non-invasive manner with cameras and video cameras. CaMAN® software developed by the researchers from the Department of Industrial Engineering in Salerno (Italy) was used to calculate comfort indexes. An analysis of the comfort indexes was used to make as the basis for suggestions to correct workers' postures and for plans to redesign the workstations in order to improve ergonomics and allow workers to perceive them as more comfortabl
Manual assembly workstation redesign based on a new quantitative method for postural comfort evaluation
No full textMain purpose of this work is to show how easy and economics an ergonomic/comfort based approach, in re-design a manual assembly workplace, can be; authors, using a new comfort/ergonomic evaluation criterion, analyzed a workstation and identified the critical issues under ergonomic/comfort point of view and finally gave several guidelines to re-design the workplace, implementing minor modification, and improve work-safety, work-quality and productivity. The postural analysis was performed by non-invasive and especially inexpensive methods, based on cameras and video-recorder use and by photogrammetric analysis; DELMIA® DHM software has been used to perform all simulations; comfort analysis was performed by the software developed by researchers of Departments of Industrial Engineering of Salerno: CaMAN®. The test case is an automatic assembly machine that has been modeled and used for virtual postural analysis. Main results of this work can be found in a very good numerical/experimental correlation between acquired/simulated postures and real ones, and on the powerful use of an objective comfort evaluation method, based on biomechanics and posture analysis, for giving to designers the guidelines to re-design a workplace and a work-cycle. This kind of approach seemed to be very powerful in re-designing the work-place and in re-scheduling the work time-sheet because it allowed to improve an ergonomic corrective action with minor costs for company. Obtained results demonstrated the validity of re-design hypotheses through the increase of all comfort indexes and the improvement of workstation/operator productivity
The effect of posture, pressure and load distribution on (dis)comfort perceived by students seated on school chairs
No full textThe study of ergonomics and (dis)comfort is a major topic of interest to scientific literature since the introduction of ISO 11228. Over the past 30 years, researchers have attempted to understand the mechanisms underlying perceptions of (dis)comfort for a seated subject. Three main factors are recognized as paramount for the comfort performance of a seat: human body posture, pressure at interface, and load distribution on the contact area; this study investigates the relationships between them and examines their significance for (dis)comfort perception. Physiological factors are known to play a role in (dis)comfort perception, and we consider these as a consequence of the three main parameters above. An explanation is given for this hypothesis. Experimental tests were conducted using a school chair with a rigid seat pan and no armrests for reducing the number of factors of influence. Conclusions show the levels of correlation between acquired information and perceived (dis)comfort
Human-Centered Design and Manufacturing of a Pressure-Profile-Based Pad for Better Car Seat Comfort
No full textA car seat’s function is to support, protect, and make passengers and drivers feel comfortable during a trip. A more uniform pressure distribution and a larger contact area usually provide less discomfort. Consequently, the seat pan’s material and geometry play an essential role in the design process. A shaped pad was opportunely designed and realized, starting from the pressure distributions between the buttocks and the seat pan; pressure data were acquired during an initial experiment involving 41 people, representing a wide range of percentiles. The shaped pad was compared with a standard one by building a special seat with an interchangeable internal pad and testing the standard and the new seat; the second experiment involved 52 people that tested both seats. The tests were conducted to assess comfort (33 subjects were asked to be seated for 1 min each) and discomfort (19 subjects were asked to be seated for 15 min each); during the tests, pressure distribution and contact area data were gathered. The results showed that, for both tests, about 80% of the participants, among which 100% of the female sample, preferred the shaped seat pan pad. Even if the material was exactly the same, the shaped pad seemed to be softer, more comfortable, and more suited to the body’s shape than the standard one. The design methodology was demonstrated to be very useful for granting a more uniform pressure distribution and a wider contact area, i.e., higher comfort and less discomfort
Virtual human centered design: an affordable and accurate tool for motion capture in mixed reality
No full textThe introduction of Digital Human Modeling and Virtual Production in the industrial
field has made possible to bring the user to the center of the project in order to guarantee
the safety of workers and well-being in the performance of any activity. Traditional
methods of motion capture are unable to represent user interaction with the environment.
The user runs a simulation without the realistic objects, so his behavior
and his movements are inaccurate due to the lack of real interaction. Mixed reality,
through a combination of real objects and virtual environment, allows to increase
the human-object interaction, improving the accuracy of the simulation. A real-time
motion capture system produces considerable advantages: the possibility of modifying
the action performed by the simulator in real time, the possibility of modifying
the user’s posture and obtaining feedback on it, and finally, after having suffered
a post - data processing, without first processing the recorded animation. These
developments have introduced Motion Capture (MoCap) technology into industrial
applications, which is used for assessing and occupational safety risks, maintenance
procedures and assembly steps. However, real-time motion capture techniques are
very expensive due to the required equipment. The aim of this work, therefore, is to
create an inexpensive MoCap tool while maintaining high accuracy in the acquisition.
In this work, the potential of the Unreal Engine softwarewas initially analyzed, in terms
of ergonomic simulations. Subsequently, a case study was carried out inside the passenger
compartment of the vehicle, simulating an infotainment reachability test and
acquiring the law of motion. This procedurewas performed through two cheap MoCap
techniques: through an optical system, using ArUco markers and through a markerless
optical system, using the Microsoft Kinect® as a depth sensor. The comparison of
the results showed an average difference, in terms of calculated angles, between the
two methodologies, of about 2,5 degrees. Thanks to this small error, the developed
methods allows to have a simulation in mixed reality with user’s presence and offers
an accurate analysis of performed movements
The Role of Expectation in Comfort Perception: The Mattresses’ Evaluation Experience
No full textWhat are the new trends in research for comfort evaluation and the objective and predictive techniques for quantifying and qualifying comfort perception by humans? This paper has attempted to answer this question in a wide literature review, whereby it is possible to highlight many partial aspects that have been studied successfully. Just a few researchers [1–3] have studied the problem of comfort perception and evaluation under a wider point of view. Nevertheless, some aspects seem not to have yet been taken into account. In a previous paper, the authors extended the Vink–Hallbeck model to build a comfort perception/evaluation matrix in which four kinds of comfort related to different humans’ perception were studied and linked to the whole environment's characteristics. In the resultant perception-scheme and in the proposed “fusion rule” (for different kinds of perceived comfort/discomfort), one aspect that played a fundamental role in the final comfort/discomfort perception/evaluation was expectation. Expectation due to preconceived data (acquired or formed in the users’ minds) and the influence of the working environment, can act in terms of additive or subtractive factor in the comfort experience by altering the final comfort/discomfort perception and changing the subjective comfort/discomfort evaluation. This paper presents the results of expectation influence analysis on comfort evaluation. Using the placebo effect, authors conducted a wide experimental test with a wide sample of users, asking them to use and evaluate two identical mattresses that were dressed and described as two different products (the first one as a very cheap mattress and the second one as a high-level and expensive mattress). Differences between subjective evaluations have been statistically processed and correlated to anthropometric parameters to individuate and understand the role of expectatio
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