George Blankenship, Rick Heilshorn, Michael Cunningham, Scott Thieman
Cerebral palsy is a central motor dysfunction that affects muscle tone, posture and movement. Spastic cerebral palsy is the most common type of cerebral palsy. The patient is hypertonic and has mobility impairment. Treatment for this type of cerebral palsy include medications such as baclofen which cause the muscles in the body to relax. Since the muscles are relaxed, physical therapy can help develop the muscles well enough that the patient will be able to move on their own with the assistance of devices such as forearm walkers. The objective of this project is to develop a scooter that will help with the muscle development of a seven year old boy with cerebral palsy. In order for the scooter to work various muscle groups the scooter needed to be adjustable in many ways. Such ways include height adjustable and different types of workouts. The scooter will be able to adjust in height so that the client can work different muscle groups in his arms. The main function of the scooter will be for the client to lie down on the scooter and push himself around with his arms. The scooter can also be used in a rowing function allowing him to work muscles in his arms, back, shoulders, and legs. Through continued use our client will be able to develop all the main muscle groups required to walk all while having fun.
Will is a seven year old boy with Spastic Cerebral Palsy. Like most people with Cerebral Palsy he has limited use of his arms and legs and he has very little core strength. He also has a Baclofen pump just under the skin on his stomach that releases a muscle relaxer into his spinal column to keep the muscles from spasming. This means that Will can no longer rely on his muscle spasms for strength and he will need to develop his muscles and motor skills in hopes that he can someday walk with crutches.
The goal of this project was to develop a scooter board that would allow Will to lay on his stomach and pull himself around using his arms. This scooter board would be adjustable in height so he could work different muscle groups as well as be adjustable in length so it could grow with him as he gets older. As Will progresses in his development, he would then be able to use the scooter board as a rowing machine which would then allow him to work not only his arms but his legs and core as well.
Will needs to develop his muscles in hopes that he can someday walk. He needs a scooter board that can accommodate his Baclofen pump and target several muscle groups. The goal was to design a scooter board that would adjust to different heights off the ground allowing him to start targeting different muscle groups from day one. As his development progresses he can transition to rowing feature of this board to develop even more muscle groups.
Design and Development
The frame of the scooter board is made from thin gauge steel tubing which was chosen over aluminum tubing primarily for added strength and ease of welding. The drawback is the that the steel does make the design weigh about seven pounds more but the benefits of the steel outweigh the the drawback. We were able to recoup some of the weight by using smaller light weight plastic wheels instead of metal wheels and high strength polyethylene board to cover the frame.
The Rowing Linkage And Ratcheting Mechanism
The rowing linkage is made from thin wall steel tubing because it would not bend or flex when a load was applied to it. The linkage connects to the ratcheting mechanism which is essentially a 30mm rachet that is twelve inches long and connected to each rear wheel which propels this scooter board forward. The ratchet allows the linkage to connect to it at different heights which allows us to vary the resistance of the rowing motion. Figure 1 shows the scooter in its lowest position.
As stated above we used light weight plastic 16” wheels with a low rolling resistance tire. The tire features a smooth tread design which will make it easier and quieter than a typical bike tire allowing for smooth operation in and outside the house.
The final device was evaluated to assess durability, ease of use to the client, device effectiveness at targeting the various muscle groups, and overall safety. Durability was assessed during the design phase so that the scooter board would withstand the weight of the client as well as the forces applied to the rowing mechanism. Ease of use to the client was assessed by observation and actual testing of the client. Figure 2 depicts the client using the developed unit. Device effectiveness at targeting various muscle groups was assessed during the design phase by implementing different workout motions to stimulate muscle growth as well as during client testing and evaluation. Hazard analysis and risk considerations were conducted and and risks identified were addressed through redesign.
Three dimensional designs were presented to a panel made of professors and mechanical engineering students. Feedback and suggestions were provided during these presentations. Modifications were made based on information gathered from these presentations as well as from client testing of our prototype.
Discussions and Conclusion
In conclusion, the scooter board met the requirements of the client successfully. It successfully implements all of the goals of the project including:
Ability to lie on stomach and move around.
Adjust to different heights.
Adjust in length to grow with the client.
Accomodate Baclofen Pump.
Increase in difficulty as muscles develop.
Currently, our client, is very unfamiliar with the board and therefore has trouble using it properly. It is also difficult for him due to his low muscle strength, which was expected since the main purpose of the project was to help build his strength. The parents are sure that given enough time, our client, will become more comfortable with the device and strong enough to use it more effectively.
During the design process, two items accounted for the majority of the challenges. These two items were the height adjustment of the tires, and implementing the rowing system and a second source of movement.
For the adjustment of the tires, many different ideas were looked at, however it was determined that for the front tires a simple four bar mechanism would be appropriate and provide the necessary stability to the front wheel assembly. In the rear it was even more difficult due to the fact that the drive mechanism was also included in the rear axle. It was decided that, for simplicity, the tires would adjust in height on a sliding post and the angle of the drive mechanism would change to accommodate this movement. This is a benefit because depending on the angle of the drive mechanism, force needed to move the system changes and allows for continued growth as the clients development progresses. Both front and rear tire assemblies can adjust by a simple three step process.
Remove the pins holding the assembly in place.
Raise or lower the wheel.
Re-Insert pins into the desired location to lock the wheels in place.
For the design of the rowing system many different types of linkages were looked at. The final decision was made to go with a three bar linkage that could accommodate the change in height in the system. The two sides of the system were also made independent from one another in order for the client to focus on both sides of his body as well as to make sharp turns.
It was also determined that the rowing mechanism should be adjustable to allow for more adjustability in the force required to move forward. This was accomplished by pinning the three bar mechanism in different locations. When the linkage is set in the top location, the system will require less input force from the user to provide motion. On the other hand, when the linkage is set in the lowest location closest to the axle as shown in figure 1, the force to move the system is greater but it will provide more speed and farther movement.
When it comes to safety of the mechanism, the board was designed to reduce the number of pinch points and to shield those that were remaining. All sharp edges on the board were removed or rounded off to reduce the chances of any cuts or scrapes. The design was also modified so as to not allow the client to roll off the side while using the board.
These factors allowed the project to be completed while meeting all of the design requirements, project goals, and safety concerns.
We would like to like to thank all those who have helped us along during this project. We give thanks to our client and his parents for being such great inspiration and giving us a great experience working with them. We’d also like to thank the Ability Clinic for their support. In addition, John Jaegly laboratory supervisor, for assisting us and allowing us to make our parts in the College of Engineering machine shop. This would not have been possible without the guidance and support from our advisors Dr. Mohamed Samir Hefzy and Dr. Mehdi Pourazady. This work was supported by grant BCS-0931643 from the General & Age Related Disabilities Engineering (GARDE) program from the Biomedical Engineering and Engineering Healthcare cluster of the Chemical, Bioengineering, Environmental, and Transport Systems (CBET) division of the National Science Foundation.”