**3.4 Mechanisms to negotiate uneven terrain**

The system should allow for significantly more maneuverability on uneven (offcamber) terrain than the standard wheelchair. The suspension would manage the off-camber surfaces through autonomous adjustments (**Figure 3**), when the user

**161**

**Figure 4.**

*Independent pass over obstacle [18].*

*Development of a Rough Terrain Wheelchair Design DOI: http://dx.doi.org/10.5772/intechopen.91267*

safely done in a conventional wheelchair [18].

the system work even in a stationary situation as well [17].

is on an incline of around 10 degrees. As the right shock compresses and the left relaxes, consequently enabling the seat to level itself, offering greater stability to the wheelchair structure seat. The determination of shocks ought to take into consideration autonomous control of spring rate and damping ratio, consequently enabling

Different obstacles may require the suspension to work autonomously, for instance, a block of wood or a crack in the walkway can be effectively explored with the same suspension framework. As given in **Figure 4**, the right side of the wheelchair must articulate upwards so as to keep up all the four wheels in contact with the ground surface, as the wheelchair moves over the obstructions. The right rear shock compresses, while the others adjust to equilibrium, allowing for all four wheels to

The operators explore obstructions in their everyday life. A number of these snags require autonomous wheel articulation, while others may require the shocks to work in unison. A typical impediment that wheelchair clients face everyday (or avoid) is the street curb. Assuming the user is moving on a path perpendicular to the curb, the wheels will act in unison as the back end of the chair rolls off of the curb, with the suspension absorbing the force. This is not a navigation that could be

In some cases, there can be need to attach a set of wide auxiliary wheels or wheel extensions to the standard wheelchair for it to be stable when used off road on sandy, loose or unstable terrain. Of late, a couple of expansive tire-like plastic or elastomeric treads are connected and fitted onto the back wheels of the wheelchair to give a substitute handhold grip to the user in a way similar to mounted standard wheels arrangement above [19]. The treads are additionally marginally recessed inward from the original tire, being of a smaller diameter than the back wheel, to allow the wheelchair to ride exclusively on the tire on hard surfaces and make drive on such surfaces equivalent to one would typically anticipate. The treads act together with a second pair of lightweight plastic wheels which are adjusted to fit on either side of every one of the two stanchion mounted front wheels, the combination acting to give an broad bearing surface to better steadiness, load bearing capacity and simpler controlling of said vehicle when utilized on said sandy, loose or shaky landscapes. The wheelchair may likewise be fitted with an anti-tip over mechanical assembly to prevent flipping in reverse when navigating difficult landscape and to allow the wheelchair to be moved in an upward angled position which puts the most substantial portion of the

have some type of contact, and a resulting good stability is achieved [18].

weight on the back wheel, increasing grip on the shaky terrain [19].

**Figure 3.** *Independent suspension travel [18].*

#### *Development of a Rough Terrain Wheelchair Design DOI: http://dx.doi.org/10.5772/intechopen.91267*

*Public Health in Developing Countries - Challenges and Opportunities*

**3.4 Mechanisms to negotiate uneven terrain**

The system should allow for significantly more maneuverability on uneven (offcamber) terrain than the standard wheelchair. The suspension would manage the off-camber surfaces through autonomous adjustments (**Figure 3**), when the user

**160**

**Figure 3.**

**Figure 2.**

*Rock obstructions [7].*

*Independent suspension travel [18].*

is on an incline of around 10 degrees. As the right shock compresses and the left relaxes, consequently enabling the seat to level itself, offering greater stability to the wheelchair structure seat. The determination of shocks ought to take into consideration autonomous control of spring rate and damping ratio, consequently enabling the system work even in a stationary situation as well [17].

Different obstacles may require the suspension to work autonomously, for instance, a block of wood or a crack in the walkway can be effectively explored with the same suspension framework. As given in **Figure 4**, the right side of the wheelchair must articulate upwards so as to keep up all the four wheels in contact with the ground surface, as the wheelchair moves over the obstructions. The right rear shock compresses, while the others adjust to equilibrium, allowing for all four wheels to have some type of contact, and a resulting good stability is achieved [18].

The operators explore obstructions in their everyday life. A number of these snags require autonomous wheel articulation, while others may require the shocks to work in unison. A typical impediment that wheelchair clients face everyday (or avoid) is the street curb. Assuming the user is moving on a path perpendicular to the curb, the wheels will act in unison as the back end of the chair rolls off of the curb, with the suspension absorbing the force. This is not a navigation that could be safely done in a conventional wheelchair [18].

In some cases, there can be need to attach a set of wide auxiliary wheels or wheel extensions to the standard wheelchair for it to be stable when used off road on sandy, loose or unstable terrain. Of late, a couple of expansive tire-like plastic or elastomeric treads are connected and fitted onto the back wheels of the wheelchair to give a substitute handhold grip to the user in a way similar to mounted standard wheels arrangement above [19]. The treads are additionally marginally recessed inward from the original tire, being of a smaller diameter than the back wheel, to allow the wheelchair to ride exclusively on the tire on hard surfaces and make drive on such surfaces equivalent to one would typically anticipate. The treads act together with a second pair of lightweight plastic wheels which are adjusted to fit on either side of every one of the two stanchion mounted front wheels, the combination acting to give an broad bearing surface to better steadiness, load bearing capacity and simpler controlling of said vehicle when utilized on said sandy, loose or shaky landscapes. The wheelchair may likewise be fitted with an anti-tip over mechanical assembly to prevent flipping in reverse when navigating difficult landscape and to allow the wheelchair to be moved in an upward angled position which puts the most substantial portion of the weight on the back wheel, increasing grip on the shaky terrain [19].

**Figure 4.** *Independent pass over obstacle [18].*

Push-bar outfitted gadget permits structures that allow people of varying physical strength to move the wheelchair along a wide scope of landscapes, including delicately tricky terrain. The push-bar enable the users to initiate mobility without hand to wheel system. The unique design drives the chair forward with a forward movement of the drive bars while pulling back on the push-bars effects the braking mechanism. Turning is accomplished with a forward movement on one push-bar and a backward movement on the other push-bar. The off-road seat of this design offers the operator a multi-speed equipped favorable advantage over traditional wheelchairs. Changing into lower gears for very adverse terrain such as sandy environment, gives the operators the opportunity to go where they have not had the option to go with conventional wheelchairs. Just changing into higher gears considers allows for movement on pavement and other hard surfaces. The push-bars are removable and may consequently be put away with so that the wheelchair might be moved utilizing traditional hand-to-wheel pushing [20]. This component enables the user to deal with a wide range of landscapes and conditions that are normally restrictive to operators of ordinary wheelchairs and power wheelchairs to be used particularly in open air situations and elements for example forest floors, uneven and harsh terrain. Further, it very well may be utilized to conquer numerous every day snags, for example, curbs and high thresholds [21]. It is advantageous for people with less upper body and arm strength. Accordingly, it accommodates more independent participation in open air exercises, such as hunting, chasing, and so forth.

The review above points toward one thing that current rough terrain wheelchairs do not provide total stability ("not ideal"). Thus, there is still a need to come up with a wheelchair that will prevent the user either toppling backward, forward or sideways.

### **4. Materials and methods**

The design development process entailed coming up with a design that improves the wheelchair stability mechanism, safety precautions as well as reduce powering requirements. Some investigations were done on existing all-terrain stability mechanisms, including the possibility of redesigning the wheels and adjusting the center of gravity for improved stability. The safety of the operator, the machine and influence to the nearby environment were considered among other key parameters. Some effort was made to ensure that the final framework of the wheelchair would address the issues of user safety.

The researchers carried out a study on current wheelchair powering methods as well as noting their efficiencies. Power transmission mechanism was fundamental in achieving speed and power. Some engagement with different disability organizations was done to acquire first hand expectations of users.

The generated design concepts were evaluated and analyzed for suitability for adoption. The chosen concept was further developed to come up with dimensions of the wheelchair, sizing of the wheelchair parts, material selection and detailed drawing of the final design. The detailed drawings were drawn using AutoCAD (2007) and Autodesk Inventor (2017) was used to simulate the strength of the wheelchair frame. The bill of materials was drawn up and the cost estimate and the feasibility of fabricating the prototype unit in the local workshop were done.

#### **5. Design concept generation**

The concepts were formulated based on the ability of the design to meet the objective criteria which were: reliability, maintainability, efficiency, robustness,

**163**

**Figure 5.**

*Cambered rear wheels.*

*Development of a Rough Terrain Wheelchair Design DOI: http://dx.doi.org/10.5772/intechopen.91267*

**5.1 Cambered rear wheels concept**

**5.2 Extended front caster wheels concept**

following sections.

machinability, stability, safety, cost, ease of operation, and weight. Three possible design solutions were generated for the off road wheelchair as explained in the

The wheelchair is operated like a normal conventional wheelchair, by pushing the wheels forward. Sideways stability is affected by wheelchair width (**Figure 5**). The rear wheels are tilted inwards to increase the base width thus stabilizing the chair. A back-caster wheel is fitted to prevent the wheelchair from falling backwards.

The further out to the side of the wheelchair base, the more the chair l resists tipping over sideways. The camber pushes the wheels nearer to the wheelchair user and more in accordance with the operator's forward push stroke, therefore making it simpler to push. This can be particularly useful for ladies, who normally have smaller shoulders yet more extensive hips than men. Additionally, with cambering, traction is improved when navigating slopes. The wheelchair provides more stability, comfortable seating and it is better for overweight people. On the other hand, a wide wheelchair is more difficult to get through narrow pathways as camber increases the width of the wheelchair. Most anti-tip designs restrict the wheelchair's ability to travel over uneven surfaces (such as kerbs or dips). It is also hard to push.

The user propels the wheelchair forward by pushing the rear wheels to the front. A back-caster wheel is fitted to prevent the wheelchair from tipping backwards.

machinability, stability, safety, cost, ease of operation, and weight. Three possible design solutions were generated for the off road wheelchair as explained in the following sections.
