Proposed Solar-Powered Wheelchair

Introduction

In Africa, most elderly undergo myriad physical challenges like impaired mobility, muscular and nerve degeneration, and reduced balance and motor function. As a result, the wheelchair is considered a vital tool to enhance living quality, mobility, and dignity for the elderly (Chien, 2014). The current wheelchairs are either under the electric-powered category, manual, or power-assisted (Gurrama et al. 2012). The old manual wheelchairs usually bring about a higher respiratory exchange ratio and massive oxygen consumption, hence advantageous when used effectively for the users health (Yang et al. 2007). Nonetheless, such wheelchairs gross mechanical efficiency is only about 2-13.8 percent (the metabolic and external power ratio) based on the technology of propulsion, injury level, the intensity of undertaken exercise, and the adjustments made to the wheelchair interface (Wang & Chiang, 2012). The low mechanical efficiency and a more physical strain induced on the users movement can lead to fatigue or strain-triggered injuries in some instances (Pasion, 2019). Therefore, designing and developing electric-powered Wheelchairs has been of great value and need in the recent decade.

Electric-powered wheelchairs essentially have a lot of merits over manual wheelchairs. For instance, electric-powered wheelchairs have minimal risks of strain-triggered injuries and reduced user effort (Chien, 2014). Consequently, they have become more prevalent in recent decades, prompting users to shift from the manual wheelchairs propelled manually to electric-powered wheelchairs that use motor propulsion (Pasion, 2019). Nevertheless, the current wheelchairs that are electrically enabled also still have a lot of demerits (de Groot et al., 2013). For example, they are heavyweight, expensive, substantial physical size, and have a long charging time (Bhatnagar et al.2022). In addition, due to their electrical and mechanical components, most electrically powered wheelchairs are not easy to maintain (Chien, 2014). Furthermore, they cannot be disassembled and folded easily; hence, they are hectic to transport and store. Due to this, they have a significant market share compared to the old manual wheelchairs.

Consequently, wheelchairs that use electric (push rim-activated power-assist wheelchairs) and human power have been developed recently (Wang & Chiang, 2012). The human-powered uses the action of arms on push rims, and the electric-powered uses electric motors torque from the battery (Gurrama et al. 2012). Any typical push rim-activated power-assist wheelchair can detect the torque on the push rim to produce effective assist torques by engines (De Groot et al. 2008). Also, push rim-activated power-assist wheelchairs can assist the user in maintaining physical condition due to reduced risk of injuries and pain in the upper limbs (Bhatnagar et al., 2022). Nonetheless, due to its strong dependence on user interaction, push-rim-activated power-assist wheelchairs can still be a challenge to some individual users.

Besides, the motors use batteries to run the electric wheelchairs. Therefore, they cannot travel long distances as they require frequent recharge (Wang & Chiang, 2012). Many research studies have tried to find out possible means of overcoming the limitations of electric wheelchair by developing a wheelchair fitted with solar power to ensure a constant power supply (De Groot et al. 2008). However, there are a limited number of solar power-assisted Electric Wheelchairs to date. Besides, in their design, the wheelchairs have a solar panel rigidly fixed at the back using a metal frame that cannot easily be disassembled (Chien, 2014). Also, such wheelchairs operate in electric mode only, thus, losing the benefit of being used as an exercise device. In addition, Messenger and Melanson also developed a proposal to merge electric-powered Wheelchairs with solar panels (de Groot et al., 2013). Unfortunately, both the designs still exhibit most of the old challenges with the electric-powered wheelchair, like the heavyweight, unable to fold, and substantial physical size (Wang & Chiang, 2012). Subsequently, Curran et al. made some improvements to the solar-powered wheelchair by introducing modifications to the mainframe to reduce weight (Bhatnagar et al., 2022). However, the wheelchairs power module and frame could not fold; simultaneously, they could not be propelled manually.

To solve the challenges of the current wheelchairs, this study intends to design and develop an electric wheelchair that is solar-powered; and will enable the user to either use electric propulsion or manual by introducing a switch (Chien, 2014). Also is a mechanism to easily remove solar panels and batteries to allow quick disassembling and folding for easy transportation and storage.

Methods

Quality Function Deployment

The quality function deployment perspective is used to design this proposed wheelchair. The quality function deployment perspective includes taking a customers needs into engineering characteristics or design requirements that are then transformed into product requirements and process plans (Yang et al. 2007). The initial step is to know who the users are, their needs, and how to achieve such conditions. For this study, users are elderly persons from Africa, specifically Kenya (Chien, 2014). After identifying customer needs, this study will apply a statistical approach to the questionnaire data to assign a degree of importance to every customer requirement through a weighting factor with a value from 5 to 1, where 5- is very important, and 1- is not essential (De Groot et al. 2008). The connection between design and customer requirements can be shown in a house quality matrix.

Subsequently, the design requirements will consider the users preferences and needs for the solar-powered electric wheelchair from the quality function deployment perspective. It will also show various design specifications to be addressed to achieve market success and customer satisfaction (Wang & Chiang, 2012). In this study, a cross-functional team that includes industrial designers, clinicians, therapists, and wheelchair engineers will identify the designer requirements (Gurrama et al., 2012). Moreover, the design team will assign the strength weightings as per the relationship between the designer and customer requirements (Chien, 2014). Lastly, the relative and absolute weighting values will be accorded to every designers needs (Liu et al. 2010). The total weighting value will then be computed for every designer requirement as shown by the equation below:

AI j = Wi Rij ,1 m,

where Wiis the eighting value allocated to CRi,i= 1, m; Rijis the weighing value illustrating the strength of the relationship between DRj[31] and CRi; and AIjis the conclusive weighting rating of DRj,j= 1,,n (Gurrama et al. 2012).

Solar Power System Evaluation

The proposed wheelchairs solar power systems performance will be gauged based on statistical results received for a 5-kW solar power system considering that with daily sunshine exposure of 3.44 h in Tainan.

Travel Range

The prototype wheelchairs highest travel range will be calculated through consumed energy over the experimental tract backed by depletion measurements of a fully charged battery of...

Quick Release Mechanisms

This studys prototype wheelchair will be made around the main commercial foldable MW frame. Various modules and Compartments of the Wheelchair will be attached to the mainframe by use of quick-release fasteners, hence, allowing easy collapse and dissemblance for quick transportation and storage (Wang & Chiang, 2012). The batter set and solar panel must be taken out of the frame before the wheelchair is collapsed and folded (Yang et al. 2007). Compared with old manual wheelchairs, disassembly is considered longer and has to be facilitated by an energetic person (Chien, 2014). Nevertheless, compared with the current electric-powered wheelchairs, the proposed wheelchairs offer more convenience and can be transported by a regular car, not a special van as in the case of current electric-powered wheelchairs. Thus, a significant improvement and benefit.

Battery Monitor and LED Taillights

Usually, the rechargeable batteries life is shortened due to excessive overcharging and discharging. Nonetheless, due to the habit effect, most operators charge their wheelchair batteries at night to charge by morning hours fully (Chien, 2014). However, in front of the hand-activated Joystick is a voltmeter that reads the amount of battery remaining. Moreover, light-emitting diodes are fitted at the rear seat to act as taillights.

Tests

Travel Range

The prototype wheelchairs maximum travel range will be evaluated without and with a solar power module connected to the power supply system. The wheelchair will have a lead-acid battery set of 25V/12Ah, while the weight of the wheelchair and the user combined is 112kg. During the test procedure, the user will need to complete at least 25 laps of a 200 m track at an average speed of 3 kmh?1 (Yang et al. 2007). The rate is chosen according to an individual driving a conventional electric-powered wheelchairs average travel speed (Gurrama et al. 2012). The test will involve using a battery set alone and a solar power supply separately. Battery capacity must be at least 80 percent to act as the benchmark (De Groot et al. 2008). After that, the maximum theoretical travel range will be computed with and without solar power supply accordingly (Chien, 2014). The difference in distance covered will be the wheelchairs full travel range increased by the solar power panel.

Static Stability

Static Stability test will be carried out as indicated in the below photos. If all the angles exceed the value (7) marked by the ISO 71761 standard, then the static stability of the wheelchair shall be confirmed as appropriate. Usually, the larger the tip-over angle is, the more stable the wheelchair is to determine the stability.

(Chien, 2014)

Static stability test of solar power-assisted manual/electric wheelchair: (a) rearward and (b) lateral (Chien, 2014).

Below are the anticipated results to confirm the stability of the wheelchair.

Table 2.

Anticipated Static tip-over angles (in degrees) of proposed wheelchairs, EPWs, and MWs [3940].

Wheelchair

Forward

Rearward

Lateral

Proposed Wheelchair

23

20

20

EP

E&J Lanser

28

20

18

Quickie P200

22

23

19

Invacare Storm

20

24

16

Pride Jazzy

21

15

16

Permobil Chairman

30

18

20

Mean Value

24.2

20

17.8

MW

TiLite AeroZ

23

29

21

Invacare Crossfire

24

10

24

Quickie GT

21

26

18

Kuschall AirPro

24

8

19

Mean Value

EPW = electric-powered wheels

23

hair, MW = ma

18.3

nual Wheelchair.

20.5

(Wang & Chiang, 2012)

Conclusions

This study will adopt a quality function deployment perspective in designing and developing a solar power-assisted electric/manual wheelchair (Chien, 2014). The proposed wheelchair will have various enhanced compartments like solar power, an auxiliary power supply, a direct motor for every wheel, a modular design for easier folding and disassembling,…