Electric wheelchair power and drive cycle 2016-2017

Morgado Ramirez, Dafne Zuleima and Rasha, Lara and Barbareschi, Giulia and Suzuki, Tatsuto and Irving, Caplan and Iain, McKinnon and Brett, Dan and Holloway, Catherine (2019). Electric wheelchair power and drive cycle 2016-2017. [Data Collection]. Colchester, Essex: UK Data Service. 10.5255/UKDA-SN-853486

The aim of Power-Up! is to adapt an existing power add-on used by people who self-propel their wheelchairs so that it provides an optimal level of proportional assistance and incorporates fuel cell technology to drastically reduce the weight of the device. This will have considerable benefits both for those who self-propel and those currently pushed by a carer as it will increase a person's ability to push themselves, reducing the burden on carers and increasing the independence of wheelchairs users. The research idea has derived both from end-user demand and also technological advances in three areas: 1) The development of a light-weight force-sensing handrim for manual wheelchair users (the SenseWheel); 2) a model of proportional power assistance; 3) hybrid power source development incorporating a new low-cost, high-performance fuel cell technology. A key part of the project will be in determining requirements of the system from a technology (using a drive cycle method) and user-needs perspectives. The average wheelchair user is an overweight/obese 57 years old with a long-term health condition and dependent in some way on a carer [5]. There are seven million carers in the UK. Of those, 1.2 million carers have suffered a physical injury due to caring and over half have had to stop giving care due to mental and/or physical health complaints. Over 50% of carers are the spouse/partner of the person being cared for and 65% are themselves overweight or obese. It is clear that carers are struggling physically to care for wheelchair users [5]. At the other end of the spectrum are the 240,000 active wheelchair users who are busy getting on with their daily activities [2]; going to work, collecting their children from school, etc. With each push they further wear their shoulder and eventually, nearly all will have upper limb injuries, some so severe they will be unable to independently push themselves. Injuries are thought to arise in part to the cyclical nature of the wheelchair push cycle [6], [7] and are exasperated by the low gross mechanical efficiency of wheelchair pushing - only 10% of effort goes directly into making a person move forwards [8]and this is when pushing along flat, smooth surfaces such as hospital lino. On more challenging surfaces such as slopes, cross-slopes and rough or loose surfaces (e.g. gravel) the push forces will be much higher .To give an indication of scale of the problem: the incidence of shoulder pain is reported to range from 42% [9] to 66% [10], with the most commonly reported injury damage to the rotator cuff muscles [11]. The overall workflow is given in Figure 1. The initial work package will use the tools developed in current ARCCS project (EP/L023849/11 Dr. Holloway is Co-I) and further improve these to automatically produce probes to help understand user needs. The results from WP1 will help inform the specific tasks to be conducted at the PAMELA facility as well as the outdoor route. The recently invented SenseWheel will be used to measure the biomechanics of pushing during WP3. These will inform the shoulder forces which are occurring as people push their wheelchair with a power-assist device.In tandem we will collect the power consumption of the commercially available SmartDrive wheel, using a bespoke set of sensors. WP3 will be used to construct drive cycles of everyday journeys, which have been undertaken in WP1. Furthermore, the process of using micro-trips will be validated by comparing the actual power consumption during an outside route and the one predicted by the PAMELA micro-trips. The results of WP2 will be used to inform the specification of the new hybrid fuel cell system (WP3) and the proportional control system (WP4). The final design will be trialled at the Queen Elizabeth Olympic Park. The project is supported by the London Legacy Development Corporation as well as being closely linked to a PhD studentship,which is already awarded and will overlap with this grant.

Data description (abstract)

Improvements in electric wheelchair designs have left aside the power source. Electric wheelchair designs continue to use deep-cycle lead acid batteries which are heavy and large. The implementation of new lighter and smaller power sources for portable assistive technology, such as electric wheelchairs, requires the estimation of power demand under different driving conditions. These estimations are not available for electric wheelchairs. The estimation of power demand in the form of power cycles from driving cycles is a common methodology in the automotive industry and critical for sizing the power sources used in propulsion systems. The purpose of this data collection was to to determine electric wheelchair power and driving cycles in simulated standard outdoor conditions adapting a methodology derived from the microtrip approach, which is widely used in the automotive industry. The microtrip method allowed the testing of driving conditions to be examined separately and then combined to form a “typical” wheelchair journey which is presented here as a suggested representative electric wheelchair drive cycle.

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