Bachelor Degree Project

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S EATING COMFORT ANALYSIS FOR VIRTUAL DRIVER RESEARCH

Ba che lor D egre e P roj ec t

Bachelor degree project in Product Design Engineering

Level G2E 22.5 ECTS Spring term 2015

Pamela Ruiz Castro

Supervisor: Lars Hanson

Co-‐supervisor: Chrisitian Bergman Examiner: Peter Thorvald

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Assurance of own work

This project report has, on 23/07/2015, been submitted by Pamela Ruiz Castro to the University of Skövde as a part in obtaining credits on basic level G2E within Product Design Engineering.

I hereby confirm that for all the material included in this report which is not my own, I have reported a source and that I have not – for obtaining credits – included any material that I have earlier obtained credits within my academic studies.

Pamela Ruiz Castro

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Abstract

There has been a rapid growth in the vehicle industry market, companies are expected to provide comfortable and safer products, improving with every new model. Hence, the interest on developing Digital Human Modelling (DHM) tools that are focused on their needs.

The aim of this project is to suggest a standard seating posture that could be used with ergonomic software like IMMA, to address the research an initial literature study was performed to understand existing methods used in the industry and previous posture studies.

In order to visualize the extent of the topic, it was required to acquire information from the vehicle industries and make an investigation on preferred postures by real drivers.

Comparisons are made between the different categories of observed vehicles, and literature found for ideal postures. The results were also used to implement suggestions for the ergonomic IMMA software development.

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1 Introduction

The objective of this chapter is to present an introduction to the report by providing a background, aims and objectives, limitations of the project.

1.1 Background

The market for new products has grown and become stricter with norms, which encourage industries to provide better quality products for the new demanding consumers. Companies, require improvements in the interaction between the users and their designed products, they are expected to provide safer and healthier environments for their clients. It has been demonstrated that the ideal time to evaluate the products, is before the product is manufactured (Chaffin, 2001). This should be done to decrease the costs and time in the development process, and avoid long periods of prototype testing. Therefore, product development industries have become more interested in virtual tools that can predict the interaction of the future users, to ensure their well being.

Hence, the interest of the vehicle industry on developing Digital Human Modelling (DHM) tools that are focused on their needs. Companies are expected to improve the cockpit environment for the driver, having a special focus on providing enough tools to simplify the tasks to be executed and preventing health hazards.

One of the main objectives is to accommodate drivers comfortably and avoid fatigue in the cockpit of the different vehicles. For that, designers should consider:

population sizes, tasks to accomplish, special physical characteristics, and understand that the preferred postures selected by the drivers might vary according to the different factors. Thus, selecting seats and controls inside the cockpit area is a complicated chore for the designers. Understanding these necessities in the vehicle industry, ergonomic evaluations have evolved. Before, postures were defined by 2-‐dimensional evaluations but adjustments were needed later in the design process when full size prototypes were available. Now, 3D human simulations can provide a more complete assessment of the posture that drivers will acquire and make the required modifications early in the design process.

The available software has facilitated the ergonomic assessments, but still has areas of improvement. Most of the existing software require expert skills to make verifications of driver-‐vehicle interaction, tasks require a lot of manual

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manipulation which decreases the accuracy of the evaluations and makes them time consuming. Therefore, assessments are limited, because there is no option to instruct the manikins to repeat tasks and make comparisons; consequently, there is not much time available to reevaluate with other population sizes.

Companies require improvements in software to ensure their vehicles are safer and more comfortable, cost effective and less time consuming, ergonomic evaluations that will ensure them to be more competitive on the market. Knowing the expectations and necessities of the vehicle industries, the Intelligently Moving manikin (IMMA, 2015) software was developed in cooperation with: the University of Skövde, Fraunhofer-‐Chalmers Research Center for Industrial Mathematics (FCC), Chalmers University of Technology, Volvo Group and Scania. Their goal is to reach product development departments by providing a tool that could aid designers in studying the driver-‐vehicle interaction by having ergonomic evaluations early on the design process, in order to achieve this they have initiated the Virtual Driver research project.

1.2 Aims and Objectives

The aim of this project is to suggest a standard seating posture that could be used with ergonomic software like IMMA. This could assist to provide an adequate predicted posture for the vehicle industry during product development. This model or models should be valid for the different seat models, relevant to some of the most important vehicle categories in the industry, which include: busses, trucks, construction vehicles and cars.

Some of the general objectives shared with the Virtual Driver Project are:

-‐ To provide the user with a predicted posture, having in consideration the different anthropometry that drivers could have.

-‐ Having an easy and quick interface for the users to manipulate manikins to perform specific virtual tasks.

-‐ Consider the different types of interactions that a driver could have with a vehicle, not only with the seat but also with other controls inside and outside the cockpit.

Specifically, the aim of this research report, as a contribution to the Virtual Driver project, is to identify a comfort model for driver seating preferences for a wide range of vehicles. And have it demonstrated with the Virtual Driver implementation of the IMMA software.

In order to successfully achieve the research project, some objectives are to be considered:

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3 - Compare predicted postures based on literature information with preferred postures for drivers of trucks, buses, construction vehicles and cars.

- Demonstrate with the IMMA software the comparison of postures.

- Propose a posture prediction editor interface.

- Suggest procedures for software usage.

1.3 Limitations

In reference to the literature study; the majority of the available references, with a similar structure for measuring the body angles, were limited to car postures or working postures which not necessarily include the driving task. There were not many significant studies found, on driver preferred postures for other types of vehicles. Hence, the comparison between literature ideal postures and observed ones is limited.

Ideally the driver study should have a large sample for each type of vehicle and include different models within each category, to provide with a more accurate range for each angle of the preferred postures. However, due to time limitations, for the purpose of this research there was only a sample of drivers from the different categories and most samples were with different models.

1.4 Project overview

The purpose of the research was to identify a seating comfort model that could be used as a default posture in the IMMA software for the different types of vehicles that had to be evaluated in the industry.

To meet the purpose, the first step was to have a clear understanding of the topic and of the problematic related to the driving seated postures. This would help define how software can affect in the development process in the industry.

Secondly, to define the ideal postures for the drivers a comparison was needed between previous posture studies, selected postures by drivers and predicted postures of different software. With this a more accurate posture prediction model could be defined and used for the Virtual Driver project.

To start the literature study, vehicles had to be identified and defined to understand the specific characteristics for each category (trucks, buses, construction vehicles and cars). Also, since the topic of the research was focused on the vehicle industry, knowledge on the standards and specifications were required as well. Furthermore, an understanding of the characteristics of existing

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seated postures models and why were they defined with certain attributes. This, was included in the theory background, along with the study for existing ergonomic evaluations and international standards that the software is expected to include for the ergonomic evaluations. Additionally, existing software had to be analyzed, by observing the procedures of usage by the industry experts, to determine the most important features of the software.

This preview study had the objective to understand the expectations that the research had to achieve and the actual limitations with software, that IMMA could overcome.

Even though the main users of the software are the designers or engineers in the vehicle industry, their work directly affects the end-‐users of the vehicles: drivers and passengers. Hence, for the Virtual Driver Research the aim is to include the interactions of all the passengers with the vehicles. However, the scope of this research will only focus on the driver as an end-‐user.

Accordingly, the input of the end-‐user had to be considered in order to compare and contrast with the literature study and the predicted postures of existing software. To have that input of the user a driver study was done, focusing in the preferred seated postures of the different types of vehicles.

As part of contributing with the development of the Virtual Driver the IMMA software had to be examined in order to understand, from a user point of view, how the software worked. Since IMMA is under development there was access to personalize relevant features of the software, like the seated posture prediction, and be able to test the functionality before the official release was public. From being involved with the software, and having a user point of view along with the insight of the industry experts, gave the opportunity to propose suitable modifications and suggest improvements that could be included in future versions of the software. Therefore, recommendations were made for the specific features that were related to the posture prediction and placement of the manikin.

Initially, the contact with the industry was limited to the usage of existing software, therefore a deeper study was needed to see what the experts needed without the limitations of the actual procedures. Hence, a focus group was organized with the experts in ergonomics of the industry. Taking advantage of this expert focus group some of the proposed suggestions for the software were demonstrated, to obtain feedback from future users of the software and with that refine the suggested modifications before they were considered for the software.

Having in consideration all the input from: the vehicle industry, end users from the driver study, previous posture studies and existing standards; as the result of this research a proposal was presented for the posture prediction toolkit in the software. This, included the suggested default postures for the different types of vehicles and a proposal for software considerations, as the interface and method

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5 of operation, concerning the features used for the posture prediction toolkit.

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2 Design strategy

This chapter will present the methodology used in order to reach the aims and objectives of this project (the execution of the project will be presented in the following chapters), the approach taken was to divide the research in the following sections:

-‐ A literature study or preview study. Containing the process to analyze the theory behind the ergonomic software for driver seating postures.

-‐ Data collection. Includes the methods selected for gathering information from the users that will be potentially benefited from ergonomic software in the vehicle industry.

-‐ Software recommendations. Methodology followed for creating a proposal for improvements in the IMMA software.

-‐ Analysis and evaluations.

2.1 Literature study

For a better understanding of the concepts that will be dealt with throughout this project a literature study was made with information from books, articles, and databases. Focusing the search on: ergonomic concepts, published papers from experts in ergonomic assessments, and suggested driving postures from previous experimental investigations. Also, since some of the objectives of this research are to improve ergonomic software, existing software was reviewed through a literature study on published papers and the available manuals. The software available through the University of Skövde were Ramsis 8.3 and Jack 5.2, which provided an initial comprehension of virtual ergonomic evaluations.

The obtained literature study was processed and presented in the Theory Background in Chapter 3 of this report. Which was divided by sections, starting with a general overview of Digital Human Modelling softwares (section 3.1) and their existing toolkits in Occupant Packaging (section 3.2), followed by a general overview on the Seated Postures (section 3.3) and the Comfort Angles (section 3.4) that define the driver postures.

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7 2.2 Data collection

Since the Literature Study was based in secondary information obtained from books, research papers and software manuals, primary information for the specific research was needed. Therefore, the data collection was focused on the ergonomic experts in the industry (the users) and the different vehicle drivers (the end-‐users), providing primary information for this research.

It was noted that the ergonomic software is used mainly by experts in the field, therefore an observation study of existing software was required. Having as an objective going to the industries and observing the software during the design development stages for all the types of vehicles and in the different industries involved in the Virtual Driver project.

Another important input from the vehicle industry was to define the necessities the experts had when making ergonomic assessments, without being biased by the characteristics of the existing software. Therefore a focus group with the experts in the industry was the selected method, which would allow the participants to express their ideas on improving ergonomic evaluations in their field. Giving a better feedback, which could provide a more complete improvement in ergonomic software, based on the specific needs of ergonomic experts.

The main objective of this research is to define optimal seating postures, consequently the input of vehicle drivers was required. Hence, a driver study was planned, to obtain general information of the drivers and their preferred seating posture for each type of vehicles.

2.2.1 Observation study of existing software.

This section was focused in understanding the procedures used in the vehicle industry to evaluate ergonomic comfort postures and how they apply this knowledge to their designs.

The companies that were part of the collaboration in the Virtual Driver project and had the availability to participate in the observation study were: Volvo Trucks, Volvo Construction Vehicles, and Scania.

The study was planned as an open interview because it was the first contact with the industry experts, since the objective was to understand how the experts interacted with their software it was decided that they needed the freedom to present what they considered a priority. But in

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order to obtain similar data to compare from the companies a questionnaire was sent, allowing them to prepare previous to the presentation and giving some guidance of what was expected in the meeting. This type of interview was casual and gave the opportunity for follow up questions when further explanations were needed.

Each company organized their own type of meeting and presentation, based on the same questions (included in the Appendix A) which were mainly about: the procedures followed by the experts in making an ergonomic assessment, the steps to use a virtual manikin in DHM software, the types of assessments used to verify the obtained ergonomic information. One of the objectives was also to understand where in the process of product development were the ergonomic evaluations needed, how detailed, and how frequently. Some questions were more specific for the type of software and the type of information required to get an adequate evaluation.

The process followed during the interview consisted in the experts explaining their evaluation procedures and having time at the end for follow up questions. The entire meeting was audio recorded for future revision and to prevent important information to be misinterpreted.

2.2.2 Focus group with industry experts.

In order to define the necessities the ergonomic experts had, without being biased their existing software. A focus group was planned to obtain feedback from the experts on the ergonomic evaluation process.

From the observation study in the companies, the contact with the experts of the ergonomic software was already established, but due to time limitations the focus group was only made with one of the involved companies. Therefore the participants on the focus group were: three ergonomic assessment experts (each with different experience time), a software expert, and an ergonomic expert. Being this ones the participants previously involved in the observation study.

There were two main parts for the focus group, one focused on the needs of the ergonomic experts and the other one to obtain feedback for the suggested software modifications (this last one will have a complete explanation in section 2.3 of this report). To understand the real needs of the experts, two activities were planned under specific time: a Best/Worst experience with DHM software and an Ideal Scenario:

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● For the best/worst case scenario, the participants were asked to think of specific situations in their daily work with DHM software that had an extremely positive outcome and one with an extremely negative one, this could be directly related to the software or an external factor could have been the trigger. They were provided with pen and paper to write down their experiences and then asked to describe them step by step of how it happened, it was finalized with the participants sharing their experiences and commenting on the experiences of others.

● As a second activity in this part, the participants were asked to think of an ideal scenario assuming they were their own boss, and describe what would be the best input or set of orders to gain the best ergonomic assessment in their specific areas of expertise. Then they were asked to present their scenarios and comment on the scenarios presented by the rest of the group to understand the inputs and outputs that sometimes are missing for their daily tasks.

To make sure that there will be no information loss, all the activities were audio recorded for a later review.

2.2.3 Driver study.

From the literature study (presented in the Theory Background in Chapter 3 of this report) it was noted that not all vehicles were driven the same way and therefore different drivers had to be observed to get a better understanding of the range of seated postures in the vehicle industry.

A visit was made to 3 different companies that owned a variety of vehicles in the Skövde area, there the professional drivers (for buses, trucks and construction vehicles) volunteered from their companies to participate in the study. The volunteer car drivers were found in Skövde as well. Therefore the small sample of drivers for the study consisted in 20 different drivers from various backgrounds; ranging in age from 22-‐

56, height from 1.60 m to 1.90.

Three car drivers were females, the rest of the drivers were males. The drivers for the study were: 4 for buses, 5 for trucks, 6 for construction vehicles, and 10 non-‐professional car drivers.

First, a basic survey (Appendix B)was applied to the drivers, which asked information about their driver experience, the type of vehicles they normally drove, a description of the tasks they did with the vehicle, the time they were in the cockpit either driving or doing another task. And

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also, general information about the drivers was asked, like age and height.

Some of the drivers changed vehicles everyday, specially for buses and construction vehicles. In those cases they were asked to try different seat heights and inclinations until they found the most comfortable for them.

For drivers that used the same vehicle all the time they were asked to make sure they were in their normal comfort position.

Once the drivers were comfortable in their driving posture (hands on the wheel and feet on pedals) a side picture was taken. The pictures were taken from different sides depending on the vehicle considering where the access was in relation to the seat, so pictures were taken to the right of the driver from the access door for buses and from the left of the seated driver through the driver door for all other vehicles

The obtained pictures were selected for an optimal view of the posture and from the selection, lines and angles were traced to obtain the body angle measurements with software. Measurement tables were obtained from this procedure containing the angles for thigh-‐back, knee, ankle, shoulder, elbow and wrist as seen from the side pictures of the drivers.

2.3 Software recommendations

As part of contributing with the development of the Virtual Driver research, suggestions were made for the IMMA software. This section of the report will focus on the explaining the process of developing software modifications by following a general design methodology of: Exploration, Generation, Evaluation and Communication (Cross, 2000).

2.3.1 Exploration

For this Exploration stage the IMMA software was revised, initially to understand the principles behind ergonomic evaluations and afterwards from a user point of view. Gathering enough information to propose adequate improvements in the software.

From the observation study and the focus group it was noted that the ergonomic experts in the industry have limited results in their assessments because of software limitations, therefore it became of great importance to improve IMMA in those specific areas.

While trying out the IMMA software as a user, it was observed that some modifications needed to be made in order to facilitate the use of the software

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11 and the manipulation of the manikins. Therefore key areas had to be reevaluated, like the way the input had to be entered for a new manikin or a new scene, the interface for the posture prediction toolkit and the feedback the software gives to the user.

2.3.2 Generation

In the Exploration stage the needs and areas of improvement for the software were defined. So, in this Generation stage the acquired knowledge will be taken into consideration for the defining how the improvements of the software should be.

The needs of the users along with the capabilities of the actual IMMA software have to be contemplated for the suggestions, since the idea is that the recommendations are applied in the next version release of the software. This stage will be part of a cycle since constant evaluation will be made to define the most adequate software improvements.

To simplify the creative process the main issues of the software that had to be addressed are: simplify the placement of a manikin in a virtual scenario , facilitate the usage of the posture prediction toolkit, and improve the presentation of results for an ergonomic evaluation.

2.3.3 Evaluation

An initial proposal was created for each of the main areas of development for the software, this suggested interface was presented to the focus group for an evaluation and later on improvements were made to the suggestions, considering the comments from the experts.

The main evaluation done for this software suggestion was the focus group. A sample of the software interface suggestion was exposed to the experts in a step by step presentation, giving an initial objective to achieve with the software and demonstrating how it could be done with IMMA.

For the focus group, a scenario was given with certain tasks to complete. Then, a step by step presentation was given, of how the tasks would be handled, with the specific modifications proposed for the IMMA software. The experts of the focus group made some comments on the software interface and the demonstrated postures, which allowed to re arrange the suggestions and include the expert's input.

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2.3.4 Communication

Since the development process for the software suggestions is considered a cycle, the communication stage had to be constant throughout the process.

Because, not only was the proposal presented to the focus group of experts, but it was also explained and exposed to the software developers which had to understand what were the reasons to modify the IMMA software and apply the changes as suggested in the newer versions of the software. This stage will also include the graphical demonstration, shown in the Results chapter of this report, of the suggested improvements to the software.

2.4 Analysis and evaluation

This section will be for the analysis and evaluation of the obtained information. In this case it will consist in comparisons between the different obtained data and presenting it in the Result section of this report. Starting, with comparing the literature values suggested for ideal seating postures and the obtained values from the drivers study with their preferred postures. Another comparison will be between the industry procedures for ergonomic assessments and the ones found in the literature study.

As part of the evaluation, various options for ergonomic models/strategies will be used and evaluated for their accuracy. Also, a tryout of the strategies will be done with the IMMA software; to demonstrate the differences between postures

strategies for the different types of vehicles.

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3 Theory background

The objective of the Theory background is to understand where the project stands as a research project and in the market. To fully understand the needs of the vehicle industries towards ergonomic software and the possibilities this might bring in a near future.

3.1 Digital Human Modeling (DHM)

Due to the speed and the competitive environment in which products are developed and manufactured, it is required to fulfill safety requirements in the most effective way early in the development process, which leads to testing before productions begins. This has been addressed by digital evaluations of the products previous to their manufacturing. (Chaffin, 2007). Therefore, digital humans are created to virtually simulate interactions with the products and generate assessments that will help the designers improve the features of the product even before physical existence.

Seen from an ergonomic point of view, digital avatars or manikins have been created with specific characteristics representing a certain population and predicting the human interaction with the objects. These digital humans are specified by the designer with some group attributes like: stature, weight, gender or age (Kullberg, 2014). To make an evaluation, the manikin has to be placed in a virtual scenario in which certain tasks should be fulfilled, the designer sets the manikin to do the tasks and an evaluation is presented for the health risks that the specific assignment might provoke to the manikin. Focusing on the forces applied in the joints through the postures acquired.

The development of DHM software has increased in the last 40 years, more than 150 ergonomic evaluations with virtual humans are known according to Duffy (2009), from which they are focused in different industries, having a bigger impact in manufacturing areas and in the vehicle industries, from aircrafts to construction vehicles.

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Figure 3.1: 3D CAD digital male and female with reach envelopes (University of California, 2014).

Figure 3.2: Manikin sample and use of Jack Medical software (Siemens, 2010).

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Figure 3.3: IMMA manikins in assembly analysis (FCC, 2014).

Some existing software in the market is used in the industries to analyze the ergonomic postures of workers, focusing mainly on a series of tasks along the production line and evaluating the risk levels throughout the working process, this helps avoid worker injuries and provides safe interactions that will improve efficiency along the line. In other cases, software is used to test vehicles and the interaction with them, including default posture prediction for drivers; this can be obtained by placing the manikin in the adequate position on the seat and selecting possible tasks or movements; an ergonomic assessment can be obtained from the final postures.

The ergonomic software studied for this theoretical background was: Ramsis, Jack and Delmia Human, for their default seated postures and posture prediction toolkits. For further understanding of the principles behind the software, there will be an observation study of the real usage of the software by experts in ergonomic assessments; during the visits to vehicle companies.

Jack was studied as a reference to ergonomic software, but it was not in use in any of the visited industries. The available version to study had some of the functions for predicting postures from the occupant-‐packaging tool. However, it must be noted that the found default seated postures are not designed for driver seating, they are designed focusing on seated work tasks. One of the interesting features that the software has, is the availability to set tasks to the manikin in order to repeat them with different size manikins, generating a more complete evaluation.

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Ramsis was another reference of ergonomic software, having the opportunity to verify postures and obtain ergonomic evaluations. Also, Ramsis software was found in the industry, so observations were noted from expert users. The software can be used as part of the Catia software, this provides different functions and the feel of the software is different since the interface used is the one from Catia.

There are different versions of Ramsis, according to the needs, in reference to posture prediction the software is specialized in driver seating, therefore the occupant packaging toolkit seems to be complete for static seated postures. Also, it was observed that there are different default postures like: a regular seating posture, a car seated posture and the opportunity of a truck seated posture (which are not available in all the versions of the software).

Another software observed in the industry was Delmia Human, but due to the access limitations, this software could not be studied directly even though, it is used by the companies related to this study. As well as Ramsis, Delmia Human can be used as a tool within the interface of Catia. This software is not specialized in seating postures but seems to be more efficient for other types of assessments between the different vehicle interactions and the manikins.

All the software studied can be used to obtain predicted seated postures for vehicles, but each software has a specific procedure in order to make an evaluation and also provides different type of data even though the safety standards that they will have to fulfill might be the same. Each of the software was created for specific needs in the industry, but have now evolved and include similar toolkits to solve ergonomic evaluations even though the principle behind each software is different. Due to these characteristics the evaluations for a vehicle might not be the same with the different software, but as long as the international standards are covered the evaluations are valid.

3.2 Occupant Packaging

The seated posture prediction feature is usually included in the Occupant Packaging toolkit of the Digital Human Modelling software, therefore this section will be focused in the toolkit and some of the international standards that should be considered for the driver postures.

The automotive industry uses the term “Packaging” for the activities that involve arranging the distribution of space within a vehicle. Having in consideration components, systems and occupants to be placed adequately without compromising their functions and limited to the available space defined by the concept designers (Bhise, 2012).

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Occupant Packaging in DHM software, assist the designers and engineers on how to position the virtual manikins within the occupant compartment of the vehicles, throughout a virtual representation that can include drawings and models of the relevant areas to be assessed. Certain standards, reference points, and key measurements are taken in consideration when developing a vehicle.

According to Bhise (2012) some of the main considerations for occupant packaging can be grouped into:

1. Entry and egress space.

2. Comfortable seated posture.

3. Hand and foot controls.

4. Visibility.

5. Storage space 6. Service.

The vehicle industry needs ergonomic software to include an occupant packaging toolkit for ergonomic evaluations during the development process, to distribute efficiently the space inside the cockpit. This toolkit can include human factor analysis for comfort and performance (Jack manual, 2013) that are based in existing parameters. For example, some of the tools provided by Jack software (Jack manual, 2013) within the Occupant Package Toolkit are:

● SAE packaging guidelines

● Posture prediction

● Comfort assessment

● Pedal behavior

● Vision analysis

These types of tools aid designers to find: comfortable seated postures, ideal location of the hand and foot controls, and evaluate the visibility levels in the vehicles. Therefore, some of the main considerations as defined by Bhise (2012) are covered (2.Comfortable seated posture, 3.Hand and foot controls, and 4.Visibility), leaving further analysis to the engineers, for a complete assessment of space and the interaction with the passengers.

In order to accommodate the manikin in the virtual vehicle environment, it is required to understand certain concepts; like international standards based in anthropometric criteria, from which vehicle measurements are made.

Bhise (2012) and Ghikas (2013), mention that some of the most common reference points (Figure 2.1), based on SAE standards, used in the automotive industry are (Ghikas, 2013):

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Figure 3.4: Interior package reference points and dimensions (Bhise, 2012).

AHP. Accelerator Heel Point. Contact of driver’s lowest heel point with vehicle floor.

A47. Pedal plane angle. Angle of accelerator pedal from the horizontal of the vehicle.

BOF. Ball of foot. Point on a straight line tangent to the bottom of the shoe, located on the middle of the foot width.

H-‐point. Point in a human body acting like center between torso and thigh.

SgRP. Seating reference point. It is a specific H-‐point used in occupant packaging .

Since there are different types of vehicles and each one has specific needs, a target group should be identified; hence a specific range of body sizes can be selected to fulfill the task and be accommodated having in consideration the mentioned reference points. In the industry, depending on the product there are population percentiles used to test a product, to make sure the health and safety requirements apply for most users (Kullberg, 2014).

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3.3 Seating Postures

Since the purpose of the research was to identify a seated comfort model, this section of the report is a summary focusing on analyzing previous research studies on seating postures.

Some of the literature found with detailed explanation on the seating postures were experimental studies made for working postures, which require certain concentration, and the user to be seated according to the characteristics of the task to be accomplished.

It is important for the industries to adequately use simulations to evaluate the seats being developed, because customers often complain about postural discomfort in (Andersson, 1999; Ebe & Griffin, 2001):

● neck

● shoulder

● lower back

Therefore, the design of products that will require seated postures cannot be ergonomically evaluated only on a static reference, other considerations should be done, since external factors will affect the posture and the level of comfort will change according to the task and length of working period. To avoid health risks various simulations should be made previous to defining a seat arrangement.

Similarly, for the vehicle industry, in order to define the driver seating posture all factors related to the driver should be considered, not only the driving difficulty, but also other tasks that will be executed within the cockpit area. Hence, studies have been made specializing on a vehicle type and in relation to specific tasks to avoid discomfort and fatigue with seating postures. Some examples are the investigations for car driving optimum seating postures from Andersson, Örtengren, Nachemson, and Elfström, (1974) and Hanson, Sperling & Akselsson (2006) which also have external factors in consideration to define a suitable posture, and observe that drivers adjust their position throughout the a period of time.

Several studies were found on seated driver postures, however using old references to predict postures might not be appropriate since, some older studies defined postures according to strength required for driving tasks. However, due to the improvements in technology, the human strength does not play such an important role in driving. Hydraulics, computer aided mechanisms, along with

Bachelor Degree Project

S EATING COMFORT ANALYSIS FOR VIRTUAL DRIVER RESEARCH