Aawaz Shrestha, Andrew Macaluso, Sierra Irwin, and John Dighton
Popular among all age groups, baseball surely is America’s favorite pastime. However, people who are visually impaired do not have the opportunity to indulge in this exciting game. Accordingly, to solve this problem, a design of a better baseball is imminent, in order to help visually impaired people to play baseball and improve their overall quality of life. The AudiBall consists of three main parts: an electronic component, a skeleton made out of ABS plastic, and a layer of viscoelastic material as the outermost shell. It is designed to emit a constant tone and withstand high impact forces. As a result of this project, everyone can enjoy a good game of baseball irrespective of their visual imparity.
The Louisiana Center for the Blind (LCB) is a facility to help visually impaired people to fully participate in the economic, social and spiritual lives of their communities by providing intensive training in the skills of blindness and encouraging the development of a positive attitude about blindness (1). There is an increasing interest in baseball as a sport among the members in the Louisiana Center for the Blind. Currently, there is a baseball team using a beep baseball (the existing product) for the game. The beep baseball, however, does not last very long during the game. Also, the existing product makes beeping sound instead of making a constant tone, which is very difficult to track while playing. Moreover, the ball’s center of gravity does not lie on the center of the sphere; therefore it does not perform like an actual baseball. Unhappy with the current beep baseball, Louisiana Center for the Blind approached us as a senior design group to design a baseball that would overcome all the existing flaws of the beep baseball without compromising the safety of the players.
The project inclines toward creating a safe and durable baseball that emits a constant tone for the visually impaired people to enjoy a better game of baseball and to further enhance the quality of their lives.
The AudiBall consists of three main components. The inner core electronic component produces a constant tone, which helps visually impaired people to keep track of the ball. Spherical shaped ABS plastic skeleton is a protective housing for inner core electronic component. In addition, it provides original spherical shape for the AudiBall. The outermost layer is made out of viscoelastic material for soft feel, and high impact resistance.
Inner Core Electronic Component
The AudiBall electronics are simple, lightweight, and is design to withstand the high impacts. The tone circuit (Figure 1) is designed with the fewest number of components possible: a piezoelectric speaker unit for constant tone, a switch for activation of the circuit, a supercapacitor for powering the circuit, and a small plug for charging the power source. The ideal power source for the ball is a supercapacitor, due to its low weight and maintenance, long life, lack of harsh chemicals, and resistance to shock, heat, and moisture . On the downside, a supercapacitor does not store as much energy as a battery, but it stores enough energy for a reasonable operating time and can be recharged quickly compared to a battery. To achieve quick recharge cycle, it is necessary to use a charging circuit consisting of an adjustable voltage regulator and a current limiting resistor. Therefore, a custom charging circuit (Figure 2) is designed consisting of four pairs of standard AA batteries, a microcontroller to monitor the charge.
ABS Plastic Skeleton
It is important to protect the inner core electronic component, while simultaneously retaining the original spherical shape of the baseball. A baseball, when hit by a bat, goes under a very high amount of force (up to 12000 g) during the collision . Although the baseball for the visually impaired do not undergo such immense force, it is important to have a strong ball to ensure durability of the ball. After researching different materials, Acrylonitrile Butadiene Styrene (ABS) is the best fit for this purpose, not only because of its high impact and thermal resistance, but also because of its manufacturability, economic viability, and product availability .
ABS plastic skeleton is spherical in shape and consists of several acoustic holes (Figure 3). These holes help in transferring the sound to the outside of the ball. For the purpose of prototyping, eight pieces of the AudiBall are printed using rapid prototyping machine. These pieces are glued together using adhesives that perform well under high impact. However, for manufacturing purposes, the skeleton should be injection molded for better strength and performance.
Viscoelastic Outermost Layer
The outermost layer of the AudiBall is exposed to the environment. Considering the safety of the players and the softness of the ball, viscoelastic material is chosen to be the best fit for the outermost layer of the ball. Like ABS plastic, viscoelastic material has high impact resistance and can dissipate a high amount of energy during the collision of the bat and the ball. Moreover, it has ability to recover soon after it is deformed when hit by the bat . Initially, viscoelastic material named techno gel was considered for this purpose. However, because of its rarity, we considered using another viscoelastic material commercially named Dragon Skin® 20. The outermost layer is made such that the holes are not covered, further maintaining the acoustics of the AudiBall. This material provides softness to the AudiBall and helps to dissipate energy during the collision of the bat and the ball, thus increasing the life cycle of the ball.
Different tests are run after manufacturing the first prototype to validate the strength and weaknesses of the AudiBall. Different test results are presented in this section of the report.
Table 1 below shows the result of the audibility test of the AudiBall. This test determines the loudness of the AudiBall at different indoor and outdoor locations.
Table 1 Audibility Test Result
Figure 4 below shows the performance of the AudiBall at elevated temperature of 120 F.
Figure 4 Heat Test
Charge Time Test
Considering 96% to be fully charged condition, the AudiBall is charged at 5.5 minutes. Figure 5 below shows the AudiBall charging time.
Figure 5 Charging Time
Operation Time Test
The AudiBall operates for 85 minutes per charge cycle. Figure 6 below shows the AudiBall discharge cycle.
Figure 6 Operation Time
This test is done to check whether the AudiBall is water-resistant or not. The AudiBall is submerged in water, and then the water is drained out. The AudiBall still emits a constant tone after draining and drying all the water out.
The weight of the AudiBall is 1.39 lb.
Coefficient of Restitution
The AudiBall is dropped from different heights to measure its coefficient of restitution (Table 2).
Table 2 Coefficient of Restitution
The impact testing is done by the video analysis of the high speed camera footage of the collision (Table 3).
Table 3 Impact Test Results
This project is sponsored by the Center for Rehabilitation, Engineering, Science and Technology (CREST) by providing $500.00 for the project. The budget is used for printing ABS plastic skeleton using rapid prototyping machine at a student discount rate. The outer layer of viscoelastic material is ordered from a company named Smooth-On. The electronics are from Texas Instruments (TI) and Sparkfun Electronics; as we also entered TI Analog Design Contest, we received some electronics as a promotion saving us some money.
DISCUSSIONS AND CONCLUSION
After manufacturing our first prototype we ran several tests. Surprisingly, the ball met most of the design specifications and passed most of the tests. However, the AudiBall failed during impact test with its switch failing first, then the adhesive. We have already started working on second prototype focusing on weaknesses of the AudiBall.
The AudiBall is an amazing idea for visually impaired people. This idea can be adapted to different sports globally. All the visually impaired people can get together within their communities to cherish their favorite sports. Moreover, it can also be a solution to increase playability with blind pets. Overall, this project opens a wide area of creativity for younger generations like us to be involved in making people’s life better. It is a good experience for us, and we hope it will inspire others.
We cannot thank CREST enough, for giving us this opportunity, especially to Mr. Michael K. Shipp and Mr. Joel Fernandes for having faith in us. Also, to Dr. Kelly Crittenden, Dr. Hisham Hegab for guiding and helping us to proceed further in our project. Special thanks to Dr. Henry Cardenas for his important advice and Dr. Heath Tims as well as Dr. Lee Sawyer for providing the testing equipment.
 “Louisiana Center for the Blind” Web. Apr. 2012 <http://www.lcb-ruston.com/>
|||D. A. Russell, “Physics and Acoustics of Baseball & Softball Bats,” Web. Apr. 2012, <http://www.acs.psu.edu/drussell/bats/impulse.htm.>|
 “Electric Double-layer Capacitor.” Wikipedia, the Free Encyclopedia. Web. Apr. 2012. <http://en.wikipedia.org/wiki/Supercapacitor>
 “Acrylonitrile Butadiene Styrene.” Wikipedia, the Free Encyclopedia. Web. Apr. 2012.
 R. Lakes, “Viscoelastic Materials,” Web. Apr. 2012 <http://silver.neep.wisc.edu/~lakes/VE.html>