**3. Materials and methods**

The researchers conducted interviews with wheelchair users from local communities as well as visiting some patients at local health facilities such as Baines Physiotherapy & Rehabilitation Centre. The researchers managed to interpret the raw data in terms of customer needs and expectations into technical aspects thus helping in narrowing down the areas that needed improvement as per user needs as given in **Table 1**.

A network of contacts was developed to provide insight and guidance to refine the design output. These included members of the medical rehabilitation field, medical equipment suppliers as well as ergonomics and human motion experts in the field of physiotherapy.

In order to come up with the design mechanism for lifting the user from Sit to Stand (STS) and vice versa, it was crucial for the researchers to undertake a study in to the kinematics of standing up and sitting down from a chair. The next step was to analyse the joint movements (of the angles, knees and hips) for an individual as they stood up from a chair. It was important to follow this procedure (biomimicking human movements) so that the design would offer smooth operation as a physically unchallenged person.

Measurements of the individual formed the basis for determining wheelchair frame size, the need for adjustable ranges in component parts, and the need for customization to meet special needs. This was key in sizing the wheelchair for an


**Table 1.** *Interpretation of user need.* *Development of an Intelligent Standing Wheelchair with Reclining Characteristics DOI: http://dx.doi.org/10.5772/intechopen.96110*

average adult person. Appropriate size determinations of the wheelchair frame, seat, back, leg rests, and armrests based on measurements with an average bodied adult in an optimally seated position were taken and these built the foundation of the wheelchair design.

Three possible design concepts were generated, and the best option was selected using the Binary Dominance Matrix as the ideas were evaluated against the research objectives. Detailed engineering drawing designs were done using Solid Works and AutoCAD software. Special attention was also given to the actuation and sensory systems that were assembled in synergy to give the wheelchair autonomous and intelligent abilities.

The simulation process was carried out for both seated and standing postures. Calculations were done on the design to analyse it on the bending and torsional stresses acting on the components of the wheelchair under load in operation including deformation of stressed parts. The safety factor was obtained from these calculations and was compared against the standard safety factor. The researchers carried out the economic analysis to determine the costs of the parts and this was drafted in the Bill of Quantities to get the total cost of the components and their quantities.

## **4. Detailed design development**

**Table 2** gives the technical specifications of the intended wheel chair design.

#### **4.1 Linear actuator and recliner concept**

From the data gathered, the researchers came up with three possible solutions that were mainly different in the lift actuation mechanisms. Most of the attention of the drawings was paid to the working principle behind the lifting mechanism with the pros and cons for each concept discussed.

From the Binary Dominance Matrix (BDM), the concept on the Hydraulic Linear Actuator Lift and Recliner Mechanism (**Figure 4**) proved to be the optimal solution for the research design and was the most aligned with the requirements.

Eight selection criteria were considered and weighted for each of the design concepts; and each conceptual design was evaluated and scaled against a factor. The concept with the highest rating was considered the optimal solution for the design. The criterion factors considered included:


**Figure 5** shows how the components that make up the mechanism are linked.

#### **4.2 Linear actuator lift and recliner concept working principle**

The mechanism consists of hydraulic linear actuators as the main source of power for the lifting and reclining mechanisms. When the command to lift the user is input, the battery powers the main hydraulic linear actuator to extend, pushing the wheelchair seat at an angle to the vertical. During this action, the


#### **Table 2.**

*Technical specifications.*

#### **Figure 4.** *Wheelchair in seated and standing posture showing max change in height* ∆ = *H . m. max* 0 5

other actuators extend outwards and apply an upward force on the seat through the sliding assembly. The action of these actuators results in a resultant upward lift force that elevates and sustains the weight of the user as illustrated by **Figure 6** below.

*Development of an Intelligent Standing Wheelchair with Reclining Characteristics DOI: http://dx.doi.org/10.5772/intechopen.96110*

**Figure 5.** *Chosen concept exploded view.*

**Figure 6.** *Sliding joint mechanism providing lift for wheelchair.*

The linear actuators used in this concept provide a smooth and stable movement of the wheelchair without delay, during height adjustment. The mechanism provides the possibility to design a better user control method for the convenience of most wheelchair users. However, application of this mechanism results in a relatively higher costs as costs of the linear actuators is higher as well as the other features that accompany it including power sources (batteries) (**Table 3**).

## **4.3 Autonomous drive control systems**

The optimal design will consist of sensors and controls that to help in making it intelligent and providing autonomy. The wheelchair is driven by electronic speed differential motors that are directly coupled to the rear wheels of the chair. These motors provide the required torque for each wheel they are coupled to, and allow for different wheel speeds. This allows the motors to steer the wheelchair sideways when it is turning. The motors are powered by a 12 V lead acid battery connected to an Arduino microcontroller that receives input from the sensors and the joystick.


**Table 3.**

*Wheelchair controls.*

The microcontroller is the central processing unit of the wheelchair. It receives input and gives commands according to the code embedded in it. The coding was done using MatLab and Python tools. According to the International Organisation for Standardisation (ISO), electrically powered wheelchairs intended to carry one person must have a maximum nominal speed not exceeding 15 km/h (4.2 m/s).
