Copy of Prelimary report edit.docx

Wheelchair, Walker, Cane System

Preliminary Report

Group 14

David Dwight

Gayathri Srinivasan

Joseph Tejan

September 19, 2014

NEED AND PROJECT SCOPE

I. PROJECT PURPOSE

To devise a wheelchair, walker, and cane system that is easily transported, intuitive, and functional in the majority of environments the user will travel through. The users of the transport system will be children; therefore the system solution will be catered to that market. The wheelchair, walker, and cane should all be adjustable as the child grows.

II. PROJECT GOALS

1. To develop a theoretical model of a system comprised a wheelchair, a walker, and cane.

2. To delineate which parts of the system are adjustable, and how to customize those parts for each child.

3. To create physical prototypes of key elements in the system.

III. PROJECT EXCLUSIONS

1. Due to time and funding restraints, a fully functional model will not be developed.

Based on insufficient funds, and inability to fully build the final product, a full model will not be included in this project's scope. As further discussed in the Project Tasks section, even though the fully functional model will not be part of the project, a physical mock-up of the final design’s key parts will be created.

IV. PROJECT TASKS

1. Research current models of wheelchairs, walkers, and canes

To better understand the problem and what is currently available on the market, a thorough investigation of existing models and designs will be conducted. A document will be compiled with notes and critiques on the relevancy of these models to the this project’s solution.

2. Determine range of sizes of wheelchair parts, walkers, and canes for children

This information will help to determine the range of of ages and sizes of children who can safely use the final products. Also determines if multiple sizes are necessary.

3. Based on information gathered during research, brainstorm innovative ways to solve the problem.

Once the range of existing products has been understood, new ideas will be brainstormed to solve our specific problem.

4. Design a website for our project and design process.

The website will serve as a central location for the project and ideas that form as it develops. This will allow for a clear mapping of the projects timeline and a home base for viewing the development process.

5. Use modeling software to create theoretical designs for our intended product.

The computer model will be of the system in it’s entirety, making sure to fully demonstrate any features the final design has incorporated.

6. Create a physical mockup of key elements of the system.

Any integral elements of the design will be prototyped in physical form to show the functionality of the transport system. Key elements include any parts that directly contribute to the original problems associated with the project. Therefore the entire transport system (wheelchair, etc.) need not be physically created.

BACKGROUND

Cerebral Palsy or CP is a general term for a number of neurological conditions that affect movement and coordination. It is caused by problems in the brain and nervous system, specifically the parts responsible for controlling muscles. The conditions are likely caused due to the brain developing abnormally or is damaged, potentially due to a lack of oxygen, before, during, or shortly after birth. The main symptoms of the conditions are muscle stiffness or floppiness, muscle weakness, random or uncontrolled body movements, and balance and coordination problems (nhs.uk). There is no cure for CP, but treatment usually includes removal of pain and allowing the person with the condition to be as independent as possible through physical therapy and also occupational therapy. It is a non-progressive disease meaning that as the person ages the problem does not directly get worse. For this condition this means there is no further damage to the brain.

People with CP the current treatment focuses on independent movement. This is in the form of using three different types of devices to help overcome the motor control and muscle problems. They include a wheelchair, a walker, and canes. A wheelchair is a chair fitted with wheels for use as a means of transport by a person who is unable to walk. There are several different types of wheelchairs used by people with CP, but this is the primary mode of transportation, particularly for longer distances. A walker is a frame used by disabled or infirm people for support while walking typically made of metal and possessing wheels or rubber tipped feet. There are two types of walkers, posterior walkers and anterior walkers. Anterior walkers are the standard walker with the frame on the sides and the front of the user, while the posterior walker is around the sides and the rear of the user (Benefits of Gait Training). A cane is a stick or short staff used by many people to assist one in walking.

The cane and walker are most beneficial to help the person be more independent, but they lead to huge amounts of energy used for movement, when compared with an average person. The current treatment for CP patients uses a posterior walker as opposed to an anterior walker due to the fact that a posterior walker facilitates a more upright position and increases the walking speed (Park). Most importantly the posterior walker decreases energy consumption for the person using it, thereby making it more favorable for use by people who rely on it heavily (Park).

SPECIFIC DESIGN REQUIREMENTS

The wheelchair-walker-cane system will be designed for a 12 year old child. The average 12-year-old female weighs 91.5 lbs and is 59.0 inches tall. An average 12-year-old male weighs 88.0 lbs and is 58.7 inches tall (disabled-world.com). Thus the product will fit a child who weighs around 90 lbs and is about 5 feet tall.

Measurements averaged from three existing wheelchair brands (Wallaby Pediatric Folding Wheelchair, Kanga TS Pediatric Folding Tilt-in-Space Wheelchair, Krypto Ultra Light Children’s Wheelchair (1800wheelchair.com)) are shown in Table 1 below.

Table 1. Average measurements for pediatric wheelchair systems.

Weight Capacity

150 lbs

Product Width

20-35 lbs

Seat Width

12-14 inches

Seat Depth

13-15 inches

Seat-to-Floor Height

19-20 inches

Backrest Height

19-20 inches

Overall Length

37-40 inches

Push Handle Height

35-39 inches

Armrest Height

7 inches

Back Angle

90 degrees

Rear Wheels radius

22-24 inches

Front wheels radius

6-8 inches

As explained in the Background section, posterior walkers are superior to anterior walkers for people with CP. Measurements averaged from three existing posterior walking systems (Nimbo Lightweight Posterior Pediatric Safety Walker, Star Posterior Gait Trainer, Luminator Posterior Gait Trainer (1800wheelchair.com) are shown in Table 2 below.

Table 2. Average measurements for pediatric walker systems.

Weight Capacity

100 lbs

Product Weight

10 lbs

Height

17-20 inches

Width within handles

13.5-14 inches

Overall width

22-24 inches

Depth at base

22-27 inches

Measurements averaged from three existing walking cane systems (Walk Easy Youth Tripod Straight Neck Cane, Offset Handle Adjustable Cane, Quad Cane (medicaleshop.com)) are shown in Table 3 below.

Table 3. Average measurements for pediatric cane systems.

Weight Capacity

300 lbs

Product Weight

0.7-2 lbs

Patient Height

52-70 inches

Product Height

22.75-36 inches

Overall Width

8.25 inches

Depth

6 inches

Patient Height Range

52-70 inches

Product Base

can have 1, 3, or 4 legs for stability

EXPLORATION OF EXISTING SOLUTIONS AND PATENT SEARCH

Looking at the project scope, it is possible to see that this problem has been ongoing for many years. It is therefore important to see different ideas that have been tried in the past. There are several reasons for this, including the fact that the problem might have been solved very well by another person, thereby eliminating the problem altogether and the need for time spent on the problem. However, more than likely the problem either has been solved using an ineffective or outdated solution, or there may be no solution altogether.

Based on the project scope and background given earlier, it is necessary to see what has been done to create a wheelchair, walker, and cane system that is easily transported, intuitive, and functional in the majority of environments the user will travel through.

Looking through the patents, there have been numerous patents that combine a system that uses a wheelchair. One of the earlier patents is a combination wheelchair and walker apparatus by Thomas Houston and Raymond Metzger . Their apparatus as shown in figure 1 shown on the next page is motorized and appears to function more as a chair than walker. The main purpose according to the patents is to help a person go from a sitting position to a standing position and then back again. This motion is automated. According to the patent, the walker will function as an anterior walker. Based on the patent and the figures shown below, this system appears to function primarily as a motorized wheelchair. It is good that the wheelchair is motorized as this would help a person be more independent as it is not necessary to exert energy to move and it is not necessary to have someone push the wheelchair. However, this is a very complex and possibly expensive system due to numerous motors and electricals, and would be very complex to fix if it broke down. It also does not appear to be very child friendly either and this would be a key component to any system designed as it would be used from an early age.

Figure 1. Houston Wheelchair, Walker Apparatus

Another patent for a combination wheelchair and walker was patented in 1995 and was invented by Raleigh Pickard. This design is shown in figure 2 on the next page and is a wheelchair with a foldable seat, allowing the wheelchair to be converted into an anterior walker. The design is very simple and easy for a person to use, but the fact that is is an anterior walker means it would be harder for a person to use due to the extra energy used when compared to a posterior walker. There is a hand brake on the chair for stopping when seated or in the standing position.

Figure 2. Pickard Combination Wheelchair and Walker

It should be noted that neither of the two patents just discussed are found in today’s market, but it is unknown why this is the case. The next patent that is a potential solution is the combination walker/cane/quad cane. It was patented in 1991 and the inventors are Doris Hirn, Joyce Boin, and Susan Breakwell. The device is a walker that breaks apart into a cane. There is a separate leg attachment that would allow the cane to become a quad cane by adding the quad attachment to the bottom as figure 3 below shows.

Figure 3. Boin Combination Walker/Cane/Quad Cane

Two of the current systems on the market are on The Wright Stuff website. There is the Walker Holder for Scooter and the Wheelchair or Scooter Cane Carrier. The Walker Holder for Scooter is essentially a bag made of a water resistant fabric that has straps to attach to the back of a scooter. The bag is made to hold a standard size anterior walker and can be seen in figure 4 below. The Wheelchair or Scooter Cane Carrier is very similar to the Walker Holder. It is a bag made of a water resistant fabric with straps to attach to the back of a Wheelchair or Scooter. The bag is built for a slender cane and would not be able to hold a quad cane. This bag can also be seen in the figure 4 below. One of the good things about this system is how simple the designs are. The bags would be cheap and easy to manufacture, and they attach simply to the backs of the chairs. However, the cane design would not be compatible with a quad base cane or tri base cane. The walker design also has some problems as most people with CP use a posterior walker as opposed to an anterior walker and so this walker would not be able to fit into the bag like the anterior walker does. Also, these systems are specific to mobility scooters and are not currently available for the wheelchairs that CP patients use.

Figure 4. Left: Scooter or Wheelchair Cane Carrier. Right: Walker Holder for Scooter

Another system on the market is the Walker Holder accessory for the Invacare 3-Wheel Compact scooter. The holder is a metal bar attachment with two hooks on it for a standard walker to be attached to it. The bar appears to attach below the seat of the scooter. The figure below shows the bar attachment with a walker hanging from it. This system would be relatively easy to manufacture as well, and due to the metal components it would be pretty durable. However, like the other system for walkers above, it is designed for an anterior walker as opposed to a posterior walker which is a potential problem. It also is designed for a mobility scooter and not a wheelchair and so would have to be converted to be wheelchair specific for CP patients.

Figure 5. Walker Holder Accessory for Invacare Scooter

PRELIMINARY ANALYSIS

An essential aspect of this project, and to ultimately create a successful, integrative system for the transport of persons with Cerebral Palsy (CP), is to first fully investigate and understand the biomechanics and kinetics of movement when the user utilizes a mobility assisting device. This will allow the project solutions to focus on incorporating the technologies best suited for the particular needs of people, particularly children, with CP. There is a wealth of research examining how differing designs of assist devices can significantly affect the patients physical health and mobility, especially when focusing on the three most common devices: the wheelchair, walker, and cane. A large portion of this research has been conducted in the past 10 years, and the conclusions of the work have not yet been fully incorporated into the design of new mobility aids. Therefore this information is an important consideration and point of preliminary analysis for the project to determine the designs with the best outcomes for children with CP when they use the transport system.

Looking first at walkers reveals, as previously mentioned in the background section, that there are two overarching designs of walkers. They are the anterior and posterior walker, the first word of the name referring to the position of the hands and arms as the device is used. Examples of each kind can be seen in Fig 6 below. The major way to analyze these two designs is to record the forces, and moments on various parts of the body to find patterns and therefore a clear indication of which walker is the preferred one. The forces were scaled based on the subject’s weight in Newtons, while the moments were scaled by the height of the subject.

Figure 6, the two types of walkers mostly commonly used

As an example of the necessary equations for the Joint Rotating Moment, the rate of change of angular momentum of the distal segments center of mass (H), the moment applied to the distal joint (M), and the moment contributions from forces at the proximal and distal joints (F), with the moment arms between the center of mass and the joints (R). [Konop]

JRM = -[H_distalsegment - M_distaljoint - [R x F]_proximaljoint + [R x F] distal joint

This equation is applied to each of the joints and the values can then be compared to determine which walker is better for the user’s Upper Extremities (UE). Figure 7 displays all the joints that are important to examine for determining how the UE are loaded during use of each walker type.

Figure 7, showing the joints that will be examined in the UE for gait comparison

While smaller trends were found in the data analysis, there was no statistically significant difference observed in the forces applied to the UE during use of the posterior and anterior walkers. [Konop] This suggests that there are more similarities than differences between the two types of walkers, at least statistically. The sample sizes of both were fairly small, making it harder to make statistically significant conclusions from the data. On the other hand, clinical studies have shown that the posterior walker encourages far better postural behaviour in the user including decreased anterior torso tilt, decreased torso rotation, increased shoulder extension, and a host of other positive actions.

Despite a lack of statistically significant differences between walkers when examining UE forces and moments as well as in Lower Extremity kinematics [Klos], it has been shown through clinical examinations that the posterior walker necessitates a better posture from the user which can translate for most into a more comfortable experience and increased stability. This understanding is essential for which type of walker is used in the preliminary designs of the projects solution.

Also due to the possible implementation of a new design of walkers and canes, it will be necessary to understand how the stress, strain, and shear stress will affect different components of the possible designs. Some basic important formulas and constants that will be needed are the equations for stress, strain, and shear stress, as well as the constants for the elastic moduli for various metals.

Normal stress- σ = Fn / A, Strain- ε = dl / lo=σ / E, Shear Stress- τ = Fp / A

Fn-Normal Force, A- Area, lo-original length, dl-change in length, E- Young’s Modulus, Fp-shear force

Table 4: Constants of Elastic Moduli

Material

Young's Modulus

Shear Modulus

Bulk Modulus

1010 N/m2

106 lb/in2

1010 N/m2

106 lb/in2

1010 N/m2

106 lb/in2

Aluminum

7.0

10

2.4

3.4

7.0

10

Brass

9.1

13

3.6

5.1

6.1

8.5

Copper

11

16

4.2

6.0

14

20

Iron

9.1

13

7.0

10

10

14

Steel

20

29

8.4

12

16

23

PRELIMINARY DESIGN SCHEDULE

Table 5. Table of tasks and their start and end dates.

Table 6. Gantt chart for project tasks and dates.

CURRENT ORGANIZATION OF TEAM RESPONSIBILITIES

In addition to a detailed and well thought-out design schedule, it is essential that the team have an organizational structure that will allow for a maximization of efficiency in working towards an end solution or product with the maximum efficacy. The responsibilities fall mainly under two categories. First are responsibilities that the team together must fulfil which keep members on track, and second are individual responsibilities which are essential for the support and furthering of the overall group goals.

As a team, there is a responsibility to the client to realize an end solution that will address all the problems originally presented in the project description. This includes maintaining steady communication throughout the duration of the semester, and being sure to clearly convey the current status of the design and any questions the team or a team member may have.

Individually, each member must be sure to complete any tasks they have been assigned and to actively seek to take on new tasks. Through this active system of support and consistent check-ins, equity in the workloads of each team member will be maintained. Each member will also be expected to communicate any particularly busy times in their schedule or days when they will be away from campus, so that work can be distributed in advance.

To facilitate these team expectations and responsibilities, several lines of communication and organization have been created to ensure project success. A GroupMe chat message forum has been made which will allow for quick, easy conversations between all group members. In terms of organization, a google drive account and folder has been created. This will serve as a central location for all files, documents, designs, etc., located on Google’s servers and easily accessible to all users, eliminating the need for long emails, and countless attachments.

By following the responsibilities outlined in this section, the team will stay on track with the design schedule and reach a successful solution to the project.

REFERENCES

“Benefits of Gait Training” Especianeeds

Boin, Joyce R., Susan L. Breakwell, and Doris D. Hirn. "Combination walker/cane/quad cane." U.S. Patent No. 4,995,412. 26 Feb. 1991.

Houston, Thomas T., and Raymond H. Metzger. "Combination wheelchair and walker apparatus." U.S. Patent No. 4,809,804. 7 Mar. 1989.

“Kids Wheelchairs.” 1-800 Wheelchair. .

Klos, Stephen S. "Presentation 2: Lower-Extremity Characterization of Walker-Assisted Gait in Children With Spastic Diplegic Cerebral Palsy." Archives of Physical Medicine and Rehabilitation 86.10 (2005): e6.

Konop, Katherine A., et al. "A biomechanical analysis of upper extremity kinetics in children with cerebral palsy using anterior and posterior walkers."Gait & posture 30.3 (2009): 364-369.

“Lynx 3-Wheel Compact Scooter by Invacare” My special World

Park, Eun Sook, Chang Il Park, and Jong Youn Kim. "Comparison of anterior and posterior walkers with respect to gait parameters and energy expenditure of children with spastic diplegic cerebral palsy." Yonsei medical journal 42.2 (2001): 180-184.

Pickard, Raleigh H. "Combined wheelchair and walker." U.S. Patent No. 5,451,193. 19 Sep. 1995.

“Pediatric Canes and Crutches.” Medical eShop. .

“Pediatric Walkers.” 1-800 Wheelchair. .

“Wheelchair or scooter cane carrier” The Wright Stuff

“Walker Holder for Scooter” The Wright Stuff