The future (and the present) of motor vehicle propulsion systems

Limited reserves of oil and the increasing environmental effect of its usage as a motor fuel represent global issue related to the constantly increasing number of motor vehicles. Therefore, the reduction of the fossil fuel consumed and the emission produced in internal combustion engines is the primary goal of the development of motor vehicle propulsion systems. In that sense, the present and the future of motor vehicles relies on hybrid drive systems, electric drive systems and drive systems which use hydrogen as a fuel (either by its combustion or by production of electric energy with the help of fuel cells). In this paper, the authors have presented the aforementioned motor vehicle propulsion systems by explaining their function and design, their basic elements and their functions. Authors have also analysed advantages and disadvantages of the mentioned propulsion systems in comparison to conventional internal combustion engine based systems, both technically and environmentally speaking, but also in relation to available infrastructure and energy resources

The future (and the present) of motor vehicle propulsion systems

Limited reserves of oil and the increasing environmental effect of its usage as a motor fuel represent global issue related to the constantly increasing number of motor vehicles. Therefore, the reduction of the fossil fuel consumed and the emission produced in internal combustion engines is the primary goal of the development of motor vehicle propulsion systems. In that sense, the present and the future of motor vehicles relies on hybrid drive systems, electric drive systems and drive systems which use hydrogen as a fuel (either by its combustion or by production of electric energy with the help of fuel cells). In this paper, the authors have presented the aforementioned motor vehicle propulsion systems by explaining their function and design, their basic elements and their functions. Authors have also analysed advantages and disadvantages of the mentioned propulsion systems in comparison to conventional internal combustion engine based systems, both technically and environmentally speaking, but also in relation to available infrastructure and energy resources

Design, control, and pilot study of a lightweight and modular robotic exoskeleton for walking assistance after spinal cord injury

Walking rehabilitation using exoskeletons is of high importance to maximize independence and improve the general well-being of spinal cord injured subjects. We present the design and control of a lightweight and modular robotic exoskeleton to assist walking in spinal cord injured subjects who can control hip flexion, but lack control of knee and ankle muscles. The developed prototype consists of two robotic orthoses, which are powered by a motor-harmonic drive actuation system that controls knee flexion–extension. This actuation module is assembled on standard passive orthoses. Regarding the control, the stance-to-swing transition is detected using two inertial measurement units mounted on the tibial supports, and then the corresponding motor performs a predefined flexion–extension cycle that is personalized to the specific patient’s motor function. The system is portable by means of a backpack that contains an embedded computer board, the motor drivers, and the battery. A preliminary biomechanical evaluation of the gait-assistive device used by a female patient with incomplete spinal cord injury at T11 is presented. Results show an increase of gait speed (+24.11%), stride length (+7.41%), and cadence (+15.56%) when wearing the robotic orthoses compared with the case with passive orthoses. Conversely, a decrease of lateral displacement of the center of mass (-19.31%) and step width (-13.37% right step, -8.81% left step) are also observed, indicating gain of balance. The biomechanical assessment also reports an overall increase of gait symmetry when wearing the developed assistive device.Peer ReviewedPostprint (published version

Development of a biomechanical energy harvester

© 2009 Li et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

The plot thickens: the emerging role of matrix viscosity in cell mechanotransduction

Cell mechanotransduction is an area of intense research focus. Until now, very limited tools have existed to study how cells respond to changes in the extracellular matrix beyond, for example, mechanical deformation studies and twisting cytometry. However, emerging are a range of elastic, viscoelastic and even purely viscous materials that deform and dissipate on cellular length and timescales. This article reviews developments in these materials, typically translating from 2D model surfaces to 3D microenvironments and explores how cells interact with them. Specifically, it focuses on emerging concepts such as the molecular clutch model, how different extracellular matrix proteins engage the clutch under viscoelastic‐stress relaxation conditions, and how mechanotransduction can drive transcriptional control through regulators such as YAP/TAZ

A Study on the Integration of a High-Speed Flywheel as an Energy Storage Device in Hybrid Vehicles

The last couple of decades have seen the rise of the hybrid electric vehicle as a compromise between the outstanding specific energy of petrol fuels and its low-cost technology, and the zero tail-gate emissions of the electric vehicle. Despite this, considerable reductions in cost and further increases in fuel economy are needed for their widespread adoption. An alternative low-cost energy storage technology for vehicles is the high-speed flywheel. The flywheel has important limitations that exclude it from being used as a primary energy source for vehicles, but its power characteristics and low-cost materials make it a powerful complement to a vehicle's primary propulsion system. This thesis presents an analysis on the integration of a high-speed flywheel for use as a secondary energy storage device in hybrid vehicles. Unlike other energy storage technologies, the energy content of the flywheel has a direct impact on the velocity of transmission. This presents an important challenge, as it means that the flywheel must be able to rotate at a speed independent of the vehicle's velocity and therefore it must be coupled via a variable speed transmission. This thesis presents some practical ways in which to accomplish this in conventional road vehicles, namely with the use of a variator, a planetary gear set or with the use of a power-split continuously variable transmission. Fundamental analyses on the kinematic behaviour of these transmissions particularly as they pertain to flywheel powertrains are presented. Computer simulations were carried out to compare the performance of various transmissions, and the models developed are presented as well. Finally the thesis also contains an investigation on the driving and road conditions that have the most beneficial effect on hybrid vehicle performance, with a particular emphasis on the effect that the road topography has on fuel economy and the significance of this

Biomimetic agonist-antagonist active knee prosthesis

Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 92-96).The loss of a limb is extremely debilitating. Unfortunately, today's assistive technologies are still far from providing fully functional artificial limb replacements. Although lower extremity prostheses are currently better able to give assistance than their upper-extremity counterparts, important locomotion problems still remain for leg amputees. Instability, gait asymmetry, decreased walking speeds and high metabolic energy costs are some of the main challenges requiring the development of a new kind of prosthetic device. These challenges point to the need for highly versatile, fully integrated lower-extremity powered prostheses that can replicate the biological behavior of the intact human leg. This thesis presents the design and evaluation of a novel biomimetic active knee prosthesis capable of emulating intact knee biomechanics during level-ground walking. The knee design is motivated by a mono-articular prosthetic knee model comprised of a variable damper and two series elastic clutch units spanning the knee joint. The powered knee system is comprised of two series-elastic actuators positioned in parallel in an agonist-antagonist configuration. This investigation hypothesizes that the biomimetic active-knee prosthesis, with a variable impedance control, can improve unilateral transfemoral amputee locomotion in level-ground walking, reducing the metabolic cost of walking at selfselected speeds. To evaluate this hypothesis, a preliminary study investigated the clinical impact of the active knee prosthesis on the metabolic cost of walking of four unilateral above-knee amputees. This preliminary study compared the antagonistic active knee prosthesis with subjects' prescribed knee prostheses. The subjects' prescribed prostheses encompass four of the leading prosthetic knee technologies commercially available, including passive and electronically controlled variable-damping prosthetic systems. Use of the novel biomimetic active knee prosthesis resulted in a metabolic cost reduction for all four subjects by an average of 5.8%. Kinematic and kinetic analyses indicate that the active knee can increase self-selected walking speed in addition to reducing upper body vertical displacement during walking by an average of 16%. The results of this investigation report for the first time a metabolic cost reduction when walking with a prosthetic system comprised of an electrically powered active knee and passive foot-ankle prostheses, as compared to walking with a conventional transfemoral prosthesis. With this work I aim to advance the field of biomechatronics, contributing to the development of integral assistive technologies that adapt to the needs of the physically challenged.by Ernesto Carlos Martinez-Villalpando.Ph.D

Technical and economic feasibility of a regenerative braking system with on-board energy storage for freight trains

This dissertation presents the technical and economic feasibility of a novel regenerative braking system (RBS) for the freight rail industry. A concept for a distributed RBS, integrated into the bogies of freight rail wagons, is proposed in a patent by Transnet SOC Ltd. The system allows for numerous RBSs to be installed on a single freight train, in a distributed manner, which collectively functions together to perform regenerative braking on the train with the goal of reducing the energy consumption of the train. The proposed system would, if implemented successfully, alleviate challenges and limitations with current RBS on diesel-powered freight trains. The patent also proposes that the RBS utilise mechanical energy storage by means of a high-speed flywheel which is connected to the train axles by a continuously variable transmission (CVT). The proposed RBS is conceptualised in this study by first establishing the requirements of the system from in-service train data, followed by the development of the subsystems to deliver workable concepts that would meet the requirements identified. A multi-domain, physical system simulation model is subsequently developed to establish the energy savings performance of each of the system concepts for typical freight train routes. The simulation results show that energy savings of between 10% and 24% can be realised by the feasible system concepts, depending on the configuration of the RBS concept and the duty-cycle of the specific train route. This proves the technical feasibility of the proposed system. Next, the proposed system and the candidate concepts are evaluated in economic terms. A cost-benefit analysis (CBA) is performed in which the cost and benefits over the life cycle of the RBS were combined into a single distribution and analysed. The decision criteria calculated in the CBA provide unanimous results as to which of the candidate concepts are economically feasible. It is shown that four of the candidate concepts, all utilising the same transmission topology incorporating a CVT with different flywheel configurations, are economically feasible. The RBS concepts show good return on investment and provide an internal rate of return (IRR) of 17% and a benefit-cost ratio (BCR) of 2.13. These results therefore indicate that the proposed distributed RBS for freight trains is economically feasible and would deliver favourable financial returns if pursued.Dissertation (MEng)--University of Pretoria, 2018.Mechanical and Aeronautical EngineeringMEngUnrestricte

Hybrid-electric vehicle design and applications

This paper discusses the considerations involved in hybrid-electric vehicle design. The tradeoffs between issues such as drive scheme/arrangement, motor choice, batteries, and temperature control are investigated. The technologies and components which are currently available, and those which are likely in the near future, are described. A sport utility vehicle is taken as a specific case study because they are very popular and relatively inefficient. Calculations indicate that a hybrid sport utility vehicle with all wheel drive is feasible using existing components. The next generation vehicle using new technologies is also predicted