Application of CAE modeling to establish the interior seating dynamics of autonomous driving passenger vehicles
Creators: name: Parida, Sibashis
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400203
subject: Automotive mechatronics and autonomous systems
classificationCode: 401706
subject: Numerical modelling and mechanical characterisation

description: Autonomous Driving (AD) Technology represent a major innovation for the automotive industry. It is no longer a question of “if” but “when” Autonomous Vehicles (AVs) be available for private use. There are several advantages which AD offer. One of the most important advantages of AD is the value-added-time, which the drivers/users would enjoy, when the tedious task of driving a vehicle becomes obsolete. The users can use this value-added-time to participate in activities other than driving.

The primary aim of this research project is to understand the different non-driving secondary activities associated with AD and to derive comfortable seating postures for these activities in the confined space of a passenger vehicle.

A survey of scientific literature is conducted using recent sources published until 2019 in the fields of public opinion, user acceptance, challenges and future opportunities associated with AD passenger vehicles across the globe. According to the critical literature review, some of the most popular activities that people spend their travel time include taking a nap, relaxing, and doing nothing, talking to fellow passengers, watching outside the window, working on a laptop, mobile phone, or a tablet. Depending on the nature and duration of travel, the same user could choose to participate in a range of activities. Because of the lack of knowledge in the body of literature, an initial experiment was conducted in static conditions to understand the user-acceptance of the seating conditions in a passenger vehicle. The seating postures selected for the experiment were derived from their original environments, i.e., an upright position for working and a rather flat posture for sleeping. These seating postures were negatively rated.

With the knowledge gained from this experiment, a second experiment was conducted, and this time when the vehicle was being driven in city conditions and with a speed ranging from 30km/h to 50km/h. For this study, the participants could select the seating postures themselves and after they confirmed the posture offered the best comfort for the given activity, the body angles (knee, hip, upper back, and neck flexion angle) were measured using preinstalled sensors attached to the body of the subjects. The derived results were clustered under the percentile groups (95, 50 and 5 percentile female and male). The comfort body angles derived from the experiment are validated using an objective comfort questionnaire. This project is the first of its kind to investigate comfortable seating postures and the associated human body angles associated with the most popular AD non-driving secondary activities.

These validated comfort seating postures and body angles are used in the quick space analysis (QSA) model, which is the novum of the thesis. Using the concept of QSA, Digital human modelling (DHM) and kinematic principles of computer aided design (CAD), a model is developed in the engineering design software CATIA V5. This CAD model acts as a three-dimensional virtual representation of the QSA principle and has direct implementation in the interior development of AD vehicles.

The QSA predicts a comfort position for the given use-case, personalized to the user percentile, anthropometry, and sex. The model aims to achieve the comfort seating posture in the shortest timeframe possible, using the lowest power consumption, with optimum use of the space available in the vehicle and without compromising the comfort of the rear-seat and/or front passengers.

One of the common engineering and design problems in the automotive field is the fact that the human element and the human machine interfaces are not considered early and thorough enough in the product development process. This leads to increased time to market, loss of market share and increased last minute product release costs. The developed model is a step forward to close this gap and offers a wide range of industrial applications.

The biggest value-added benefit of the model lies in occupant packaging. Occupant packaging focuses on the system integration of the occupants, that is, the vehicle driver and the passengers, with the emphasis on human anthropometry, biomechanics, psychology, statistics and so forth. Occupant packaging aims to ensure that there is a best possible fit between the vehicle, the driver, and the passengers. Occupant packaging also ensures that a large range of occupants are comfortably accommodated in a vehicle and can participate in a range of non-driving activities in a level-4 &amp; level-5 AD passenger vehicle.

Secondly, in the strategy and concept development phase, the model could be used to do a preliminary analysis and understand if certain use-cases and non-driving activities, are feasible for the given vehicle platform. Currently there are no off-the-self-model which allows to perform an investigation of this nature in a short frame of time. Understanding the geometrical constraints early in the development phase, allows the project team to take informed decisions, saving valuable time and eventually cost.

Thirdly, the model can also generate bounding geometries of the seat kinematics including the different percentile (95, 50 and 5 percentiles including male and female) manikins. These bounding geometries are important for total vehicle integration and component packaging. The bounding geometries for seat kinematics are state-of-the-art, however bounding geometries of the seat, plus the occupant/manikin in new knowledge for industrial application in occupant and component packaging.