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Research on the biomechanics of manual wheelchair drive for innovative manual and hybrid drives

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Abstract

The wheelchair is a basic device that provides mobility to disabled people. As indicated in "The Polish Population’s Health Status" survey by the Central Statistical Office, 16% of the population is affected by some form of disability of which 46% are people who suffer from motor disabilities (according to the National Census of 2002). The data only concerns the Republic of Poland. However, the number of people with motor disabilities is much higher and, as evidenced by the WHO reports, it continues to rise globally. Therefore, it should be acknowledged that the issue of the development of rehabilitation devices and those that support the functioning of disabled people in society is still relevant and requires increased efforts aimed at improving the quality of life for many members of our society. In the case of motor system disorders, the most common technical solution which compensates for disability is the wheelchair. The first designs of devices that meet the functional requirements of a wheelchair can be traced back to 500 BC. They evolved with time taking on various shapes until the one we know today. The year 1885 can be regarded as significant, as that is when the construction of a manual wheelchair equipped with rims attached to drive the wheels, which is still in use today, was presented. The rims were used to propel the wheelchair using upper limb muscles strength. The first design of an electric wheelchair was presented as early as 1984. In the case of the former, the only things that changed over the years were the materials used for construction and some geometrical features of the structure, while electric wheelchairs, along with the development of technology, were being equipped with new functions, including verticalization, seat lifting, functions for overcoming stairs and architectural obstacles. Despite the broad range of electric wheelchair functions, it has a significant disadvantage. The person using the electric drive is not physically active, being only a passive element of the human-wheelchair anthropotechnical system that does not take an active part in carrying out motor functions, and whose role is limited only to deciding on the direction and speed of movement. Choosing this type of wheelchair results in significant impairment of the rehabilitation process, which is meant to stimulate physical activity. The choice of a wheelchair type for a disabled person must, first of all, be based on the degree of physical disability. The manual wheelchair requires its operator to have upper limb mobility that allows its unrestrained and independent use. It has to be pointed out that a relatively high fitness level of the upper body is required to propel this type of wheelchair, and therefore it is basically designed for paraplegics. The physical fitness of the manual wheelchair operator affects the distance and the type of terrain architectural obstacles that it can overcome. In the case of an electric wheelchair, the electric drive replaces entirely the muscular system of the operator for propulsion, so that the range of the wheelchair and its ability to overcome obstacles depends only on its design and the technical solutions adopted. Electric wheelchairs are designed for all types of disabilities, both for paraplegics and tetraplegics. In many cases, the operator is unable to use the manual wheelchair in a satisfactory and effective manner, so he chooses a wheelchair with an electric drive. As a result, this reduces his physical activity which is vital since physical activity has a positive effect on maintaining the proper functioning of the body. Dilemmas associated with choosing the type of wheelchair resulting from the degree of physical disability point to the fact that there is a need for new innovative designs of wheelchair drives. Innovation should result from functional development or from combining two types of devices, for example, manual and electrical ones. "Research on the development of wheelchair motor functions" ("Studia nad rozwojem funkcji lokomocji wózków inwalidzkich") presents an outline of works implemented as part of the Leader VII project: "Research on the biomechanics of manual wheelchair drive for innovative manual and hybrid drives" ("Badania biomechaniki napędzania ręcznych wózków inwalidzkich dla innowacyjnych napędów ręcznych i hybrydowych") (LIDER/7/0025/L- 7/15/2016), financed by the Polish National Center for Research and Development. One of the objectives of the project was to develop an innovative prototype of a manual hand rim propulsion and a prototype of a hybrid of manual and electric wheelchair equipped with an adaptive control algorithm. The research focused on the experiments on the biomechanics of the wheelchair propulsion system in relation to the entire human-wheelchair anthropotechnical system. It enabled to determine the correlation between given biomechanical, kinematic and dynamic parameters of the entire system, which then allowed us to evaluate the influence of operating conditions on the functionality of the applied structural solutions in relation to the propulsion system. Creating measurement and data processing methods obtained in bench tests was also crucial. As part of the project, methods were developed to illustrate parameters such as: muscular effort, speed, acceleration, wheelchair trajectory, phase duration and the position of the center of gravity of the human body for the tested structures. This lays a foundation for building and analyzing propulsion systems of conventional wheelchairs, but also those with an innovative design.
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Overcoming terrain obstacles presents a major problem for people with disabilities or with limited mobility who are dependent on wheelchairs. An engineering solution designed to facilitate the use of wheelchairs are assisted propulsion systems. The objective of the research described in this article is to analyse the impact of the hybrid manual-electric wheelchair propulsion system on the kinematics of the anthropotechnical system when climbing hills. The tests were carried out on a wheelchair ramp with an incline degree of 4°, using a prototype wheelchair with a hybrid manual-electric propulsion system in accordance with the patent application P.427855. The test subjects were three people whose task was to propel the wheelchair in two assistance modes supporting manual propulsion. The first mode is hill climbing assistance, while the second one is assistance with propulsion torque in the propulsive phase. During the tests, a number of kinematic parameters of the wheelchair were monitored. An in-depth analysis was performed for the amplitude of speed during a hill climb and the number of propulsive cycles performed on a hill. The tests performed showed that when propelling the wheelchair only using the hand rims, the subject needed an average of 13 pushes on the uphill slope, and their speed amplitude was 1.8 km/h with an average speed of 1.73 km/h. The climbing assistance mode reduced the speed amplitude to 0.76 km/h, while the torque assisted mode in the propulsive phase reduced the number of cycles required to climb the hill from 13 to 6. The tests were carried out at various values of assistance and assistance amplification coefficient, and the most optimally selected parameters of this coefficient were presented in the results. The tests proved that electric propulsion assistance has a beneficial and significant impact on the kinematics of manual wheelchair propulsion when compared to a classic manual propulsion system when overcoming hills. In addition, assistance and assistance amplification coefficient were proved to be correlated to operating conditions and the user's individual characteristics.
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Book
Engineering design must be carefully planned and systematically executed. In particular, engineering design methods must integrate the many different aspects of designing and the priorities of the end-user. Engineering Design (3rd edition) describes a systematic approach to engineering design. The authors argue that such an approach, applied flexibly and adapted to a particular task, is essential for successful product development. The design process is first broken down into phases and then into distinct steps, each with its own working methods. The third edition of this internationally-recognised text is enhanced with new perspectives and the latest thinking. These include extended treatment of product planning; new sections on organisation structures, simultaneous engineering, leadership and team behaviour; and updated chapters on quality methods and estimating costs. New examples have been added and existing ones extended, with additions on design to minimise wear, design for recycling, mechanical connections, mechatronics, and adaptronics. Engineering Design (3rd edition) is translated and edited from the sixth German edition by Ken Wallace, Professor of Engineering Design at the University of Cambridge, and Luciënne Blessing, Professor of Engineering Design and Methodology at the Technical University of Berlin. Topics covered include: Fundamentals; product planning and product development; task clarification and conceptual design; embodiment design rules, principles and guidelines; mechanical connections, mechatronics and adaptronics; size ranges and modular products; quality methods; and cost estimation methods. The book provides a comprehensive guide to successful product development for practising designers, students, and design educators. Fundamentals are emphasised throughout and short-term trends avoided; so the approach described provides a sound basis for design courses that help students move quickly and effectively into design practice. Engineering Design is widely acknowledged to be the most complete available treatise on systematic design methods. In it, each step of the engineering design process and associated best practices are documented. The book has particularly strong sections on design from the functional perspective and on the phase of the process between conceptual and detail design in which most key design decisions are made. The 3rd edition includes new material on project planning and scheduling. Anyone committed to understanding the design process should be familiar with the contents of this book. Warren Seering, Weber-Shaughness Professor of Mechanical Engineering, Massachusetts Institute of Technology.
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