Driving ergonomics for an elevated seat position in a light commercial vehicle

With more legislation being enforced to achieve a reduction in road transport CO2 emissions, automotive companies are having to research and develop technologies that deliver greener driving . Whilst emissions from passenger vehicles have dropped over recent years, there has been an increase in emissions from light commercial vehicles (LCVs). The nature of LCV delivery work is a routine of ingress/egress of the vehicle, changing from a standing to a seated posture repetitively throughout the day. One research focus is packaging occupants in to a smaller vehicle space, in order to reduce the amount of vehicle emissions over its lifecycle. For LCVs, benefits from space saving technology could be an increase in overall loading space (with the same vehicle length) or a reduction in the overall length/weight of the vehicle. Furthermore, an elevated seat posture could reduce the strain on drivers during ingress/egress, as it is closer than that of a conventional seat to a standing posture. Whilst space saving technology has obvious benefits, current driving conventions and standards are not inclusive of new and novel seated postures when packaging a driver in to a vehicle. The fundamental purpose of a vehicle driver s seat is to be comfortable and safe for the occupant and to facilitate driving. It has been shown that a seat needs both good static and dynamic factors to contribute to overall seat comfort. Additionally, comfortable body angles have been identified and ratified by studies investigating comfortable driving postures; however, this knowledge only applies to conventional driving postures. For an elevated posture , defined as having the driver s knee point below the hip point, there is little research or guidance. The overall aim of this thesis is to identify the ergonomic requirements of a wide anthropometric range of drivers in an elevated driving posture for LCVs, which was investigated using a series of laboratory based experiments. An iterative fitting trial was designed to identify key seat parameters for static comfort in an elevated posture seat. The results showed that in comparison with a conventional seat: Seat base length was preferred to be shorter (380mm compared with 460mm); Seat base width was preferred to be wider (560mm compared with 480mm); Backrest height was preferred to be longer (690mm compared with 650mm). These findings provided a basis for a seat design specification for an elevated posture concept seat, which was tested in two subsequent laboratory studies. A long-term discomfort evaluation was conducted, using a driving simulator and a motion platform replicating real road vibration. Discomfort scores were collected at 10-minute intervals (50-minutes overall) using a body map and rating scale combination. The results indicated that in comparison with the conventional posture, the elevated posture performed as well, or better (significantly lower discomfort for right shoulder and lower back; p<0.05, two-tailed), in terms of long-term discomfort. Furthermore, the onset of discomfort (i.e. the time taken for localised discomfort ratings to be significantly higher than the baseline ratings reported before the trial) occurred after as little as 10 minutes (conventional posture) and 20 minutes (elevated posture) respectively. A lateral stability evaluation was conducted using low-frequency lateral motion on a motion platform (platform left and right rolls of 14.5°). Stability scores were reported after each sequence of rolls, comparing scores on a newly developed lateral stability scale between three seats: Conventional posture seat; Elevated posture concept seat (EPS1); Elevated posture concept seat with modifications aimed at improving stability (EPS2). Participants reported being more unstable in EPS1, compared with the conventional posture seat (p<0.05, Wilcoxon). However, the EPS2 seat performed equally to the conventional posture seat. These findings suggest that the elevated posture seat developed in this research is a feasible and comfortable alternative to a conventional posture seat. Furthermore, the final elevated seating positions showed that real space saving can be achieved in this posture thus allowing for more compact and lighter vehicles and potentially reducing strain on drivers during ingress/egress

How power tilt is used in daily life to manage sitting pressure: Perspectives of adults who use power tilt and therapists who prescribe this technology

Recent research studies have identified that use of large amplitudes of power tilt as a pressure management strategy used by adults who use wheelchairs and are at risk of developing pressure ulcers, was low. While the reason for low use was not identified, a lack of fit between using large amplitudes of tilt and daily life function was speculated as a main reason across studies. Using a post-positivist grounded theory approach, this study explored how power tilt was used in daily life particularly for managing sitting pressures, from the perspectives of five people experienced with using power tilt and six therapists who prescribe power tilt. Data were collected from two in-depth semi-structured interviews and a journal that tracked the context of tilt occurrences throughout each of three days. Theoretical saturation was reached at five and six participants respectively. Data were analyzed in separate groups and then combined using a constant comparative approach. The analysis resulted in the generation of a substantive theory from which the process of using power tilt in the context of daily life can be understood. The abstract, cognitive nature of the process specific to using power tilt for pressure management differed from the tacit and tangible nature of the process for all other daily life uses of power tilt. Contextual elements were identified which affected the use of large amplitudes of tilt such as fear of tipping over, social image and lack of functionality. The critical influence of knowledge related to using tilt for pressure management is highlighted including potential implications for clinical practice. The theory scheme offers a preliminary avenue for examining the transactive relationships of person, environment, technology and occupation that comprise daily life, influencing how power tilt is used. The substantive theory and its associated concepts contribute to the wheelchair technology field, addressing the identified knowledge gap specific to advancing the understanding of how power tilts, and potentially other wheelchair technologies, are integrated in daily life occupations. The substantive theory is preliminary, requiring further research however; potential is demonstrated to also inform the understanding of the person-environment-occupation relationship in the discipline of occupational science

A Systematic Approach to Human Powered Vehicle Design with an Emphasis on Providing Guidelines for Mentoring Students

The objective of this research is to provide guidebook that approaches the design of a human powered vehicle (HPV) from a systematic view for an ASME competition. The guidebook introduces students to design and enhances their current understanding related to design, general engineering principals, and engineering principals specific to HPVs. In terms of the design process a combination between the traditional design process and the systems engineering design process is discussed. From here the design process in broken into six main sections for the guidebook, and an evaluation section used to emphasis the usefulness of the guidebook. First an overall view of the traditional and system engineering design processes are given, along with an overview of the human powered vehicle competition (HPVC). This is followed by details of project planning and problem development. Next the conceptual stage is introduced where concept generation and evaluation methods and examples are discussed. Embodiment design is given in the following section, where solution variants are modeled in a preliminary layout. Next, methods of how to create a more defined preliminary layout are given in the detail design section were a definitive layout is established. Finally prototyping, testing, redesigns, and final design recommendations are outlined in the last section. In addition, the guidebook provided is meant to serve as a method that can be used to mentor students in the design process of an HPV. As such, the guidebook has been developed through a literature review of design theories, managerial, organizational, and engineering practices that have had beneficial impacts, and past experiences with designing HPVs. In terms of past experiences, the interactions with students involved in a creative inquiry at Clemson University have used as a subjective means to outline some of the important design considerations needed to be discussed. Additionally, Clemson\u27s HPVs have primarily consisted of tadpole tricycles and as such, a more in depth analysis is included for this particular HPV style

Aeronautical Engineering: A special bibliography with indexes, supplement 62

This bibliography lists 306 reports, articles, and other documents introduced into the NASA scientific and technical information system in September 1975

Tribology and Rotordynamics of Small High-Speed Cryogenic Turboexpander

Turboexpander is considered as the heart of present-day cryogenic process plants such as helium, hydrogen and nitrogen liquefiers, low-temperature refrigerators and air separation units, . The operational objective of a turboexpander is to refrigerate a gas stream, by removing work from the gas, and expanding the gas nearly isentropically. The turbine based cryogenic process plants in recent years are low-pressure system and have the advantage of high thermodynamic efficiency and high reliability. The high efficiency is possible at highspeed of the turboexpander, and these turboexpanders in a typical cryogenic refrigerator or liquefier run at high-speed greater than 50,000 rpm without contaminating the process gas. Such operating condition imposes rigorous constraints on tribo-pair design. Oil-free gas bearings have advanced as the most acceptable solution for supporting small and high-speed cryogenic turboexpander rotors. An inherent issue with classic gas bearing is its lower dynamic properties such as stiffness and damping because of its low viscosity. Low stiffness and damping are prone to instability at high rotational speed. So gas foil bearings (GFBs) have received much attention for research, development, and experiment over past three decades for its ability to tailor the stiffness and damping with the use of compliant foils. Bump type compliant foil gas being is quite popular among researchers for various turbomachines for its high load carrying capacity, simplified numerical analysis, and easy fabrication methodology compared to other types. In the present work, a modest attempt is made to understand, standardize and document the numerical analysis, design methodology and fabrication methodology. It evaluates the rotor bearing performance to determine the feasibility of bump type gas foil bearings for axial and radial support of cryogenic turboexpanders. The work presented in current dissertation classified into five parts. The first part includes the status of research and development in the field of gas bearings in turboexpanders and a broad literature review of gas foil bearings. The outcome of the literature review directs that extensive research is essential for designing and development of gas bearing for a more advanced cryogenic system which is technically and economically better than present gas bearings. The second part deals with the design and numerical analysis of gas foil journal and thrust bearings and its feasibility to apply in a small and high-speed cryogenic turboexpander. The numerical analysis helps to fix the dimensions of foils such as its thickness, bump length, and pitch. for a previously designed rotor and its load carrying capacity. The dynamic properties of the bearings are determined to be used in the rotordynamics analysis. Finally, a step by step detailed design procedure itemized for both the gas foil bearings. Transverse vibration being a major issue for high speed rotating machinery such as a cryogenic turboexpander, a detailed vibration analysis completed in part three. The vibration analysis includes determination of critical speeds, mode shapes and unbalanced response for the desired configuration of the rotor-bearing system with determined stiffness and damping from previous part. A small clearance between the gas bearings and the rotor is maintained in order of 10 to 40 m; This makes a cryogenic turboexpander with gas foil bearing a precision equipment. All precision equipment demands micron scale manufacturing tolerance, so fourth part of the dissertation explains the details design methodology for gas foil bearings, the rotor and other associated parts of turboexpander. A broad analysis is done on bump forming methodology for fabrication of bump foil of the desired dimension. A Finite Element Method (FEM) simulation of forming process carried to simplifies the die design process. Special attention is given to the material selection of bearing components, balancing of the rotor, tolerance analysis, fabrication, coating of solid lubricant and assembly of the turboexpander. The last part includes performance study of the fabricated turboexpander with gas foil journal and thrust bearing. Several issues are encountered during this phase, and most of them are rectified either by modification of design process or rectification in fabrication methodology. A vibration study is done using accelerometers on the bearing housing close to the journal bearings. The vibration analysis reveals gas foil bearings can be an alternative rotor bearing system for a high-speed small sized cryogenic turboexpander. A satisfactory operation is carried out for the duration of 30 hrs with an achievable speed of 81,000 rpm with multiple starts and stops

Aeronautical engineering: A continuing bibliography with indexes, supplement 98

This bibliography lists 399 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 197