Elderly individuals with limited mobility and/or cognitive deterioration often rely on wheelchairs as a means of transportation. However, many elderly individuals are not confident with operating the wheelchairs themselves, and are often accompanied by caregivers who are responsible for steering manual wheelchairs. Through research and numerous meetings with the stakeholders at Lingnan University, it was determined that there is a need for a solution that reduces the load of the caregiver pushing the wheelchair, since it is common for this person to also be an elderly individual who may have a higher physical and/or cognitive capacity than the passenger.  A study on the burdens faced by carers demonstrated that a large portion of them experience physical and psychological stress associated with assisting wheelchair users, and the large amount of effort and time required can often limit their day-to-day activities.  

Components of Design

The team’s design is centered around an intuitive control system that will interpret the driver's intention and assist with moving the wheelchair. 

The user input component of the design focuses on accurately receiving data from the caregiver driving the wheelchair, which can subsequently be translated into movement. With elderly individuals in Hong Kong as the primary target user, it is important that the input actions required for the control system mirror the natural motions used to control a manual wheelchair. This prevents a steep learning curve for the users during the adoption of the proposed solution, and also helps the design remain less conspicuous and more socially acceptable. Other design objectives including ergonomic considerations are described in detail in the Design Requirements section.

The motion control component of the design focuses on mapping the received user input data into desired output motions. It involves accurately interpreting driving intention from input data and controlling the wheelchair movement in a way that is intuitive to the caregiver and comfortable for the passenger. 

Modifications to Design Intent

Before the candidate designs are discussed, it is important to note some changes that have been made to the project since prior design milestones due to feedback provided during the Design Review.

The problem statement proposed in this document is modified from the earlier statement provided in the project requirements. The change in direction was deemed necessary after an in-person meeting with Professor Albert Ko, a representative from Lingnan University who had worked closely on the first design iteration for this project. Namely, the previous approach of designing an input control system (with the wheelchair passenger as the primary user) to reduce muscular deterioration was misaligned with the original intent of the project. From the meeting, the team gained more insight into the target users for the design (the caregivers) and their preferences regarding a discrete design that does not draw unwanted attention in public, resulting in a shift in project direction. Additionally, the scope was reduced such that secondary design targets such as hill hold and curb assist mechanisms were no longer included. The preliminary candidate designs for these targets from early stages of the project are available in Appendices A and B.

Due to the change in design objectives, the team focused their efforts on the following three tasks: 

1. An intuitive control system implemented in software

2. A motor drive system for validation of software control system implementation

3. Ergonomic design for caregiver input  

The main stakeholders for this project are listed below: 

1. Lingnan University

2. Caregivers of wheelchair users

3. Elderly manual wheelchair users in Hong Kong  

4. Professor Roger Carrick 

The client for this project is the Office of Service-Learning at Lingnan University. The main contacts at the client’s institution are Nicole Lee and Edward Lam, who have presented the team with the task of reducing the burden on caregivers of elderly wheelchair users by reducing the effort needed to manually drive transport wheelchairs.

One of the target users for the adapted electric wheelchair control system is the caregiver. The control system will receive input from the caregiver and translate it to the desired output motion behavior. In doing so, the control system will aid the caregiver by reducing the amount of effort required to drive the wheelchair. The goal is to reduce the caregiver’s physical burden from traveling with and operating the wheelchair when assisting the passenger, and allow the caregiver to make further and/or longer trips or reduce the amount of time required to reach a destination. This will help address burdens associated with participation limitations as well. 

The wheelchair user is another stakeholder who is also subject to the control system design, since the different motions they experience as the passenger are directly related to the design of the control system (e.g. accelerations, smoothness of directional transitions, etc.). Similarly, the power-assisted wheelchair design will allow the wheelchair user to carry out their daily activities with more ease and efficiency, as they may no longer be imposing as large of a burden on their caregiver for transportation.

Lastly, the project supervisor is Professor Roger Carrick, who is providing support and direction in obtaining an engineering solution for the presented problem statement.

Adjustable Frame Assembly

In the following section, each part designed as part of the adjustability mechanism will be described. The design objectives for the adjustability mechanism that will be described in this section are mentioned in Section 4.2, and the BOM details the quantity of each part needed in the assembly. As mentioned previously, there is a heavy emphasis on an understated and minimalistic design as to not draw attention to the passenger and caregiver. More iteration needs to be done to make the design more discrete for real world application, but this design objective played a heavy role in the prototype.

The structure of the design is based upon the usage of telescoping pipes which allow for height and rotational adjustment. The following image contains the full adjustable frame assembly that can easily be mounted onto standard transport wheelchairs.