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