The Equiliberator: A Balance Therapy Entertainment System [Rice University]

Figure 1: The Equiliberator

Figure 1: The Equiliberator

Drew Berger, Matt Jones, and Michelle Pyle
Abstract
Balance disorders rob millions of children every year of their right to stand up and walk through life. The condition can arise from many nervous or muscular maladies such as cerebral palsy, but fortunately can be improved by therapeutic exercises that challenge the patient to maintain appropriate balance. Existing balance therapy devices are expensive, ineffective at engaging the patient, and do not account for the patient’s reliance on balance aids. Our sponsor, Shriner’s Hospital for Children has asked us to create an inexpensive device that could challenge, entertain, and reward a patient while improving autonomous balance. The device must also collect useful data on the patient’s performance and progress. Our final device accomplishes these goals by using Nintendo® Wii Boards in conjunction with innovative force-measuring handrails. This device is used to control an interactive video game that is attractive to and fun for the patient while providing the appropriate incentives for practicing good balance and collecting performance data. The system has the potential to greatly improve the balance of millions of children as well as to assess the effectiveness of physical therapies or surgeries.
Introduction
Our target patient audience is children with balance disorders. These patients may range from having trouble simply standing alone to lacking the muscle control needed to walk and turn in place. Many of these patients will rely on crutches, walkers, or other aids for balance, and our goal is quantify, disincentivize, and eventually reduce their reliance on these aids. In order to make the therapy attractive to patients, we have integrated the measuring device into a video game experience. The game encourages successful completion of simple balance tasks while discouraging the use of handrails for balance. In this way, balance practice becomes informative for therapists and fun for young patients.
Problem Statement
Balance disorders can be improved by therapeutic exercises that challenge the patient to perform certain tasks requiring concerted efforts to maintain appropriate balance. Existing devices for applying this therapy do not combine balance practice with balance testing and are expensive and ineffective at promoting continued use by the patient, and they do not account for the reliance of the patient on balance aids. An inexpensive device that could challenge, entertain, and reward a patient for decreased reliance on balance aids and increased balance while also collecting useful data on the patient’s performance and progress would aid in assessing the effectiveness of physical therapies or surgeries.
Design and Development
The Equiliberator device is combination of commercial gaming products and innovative force transducers combined to measure both the patients center of balance and use of handrails to remain upright.
Base
In order to measure a patient’s center of balance over a 0.848 square meter area, the device uses five Balance Board joystick controllers designed by Nintendo® to be used with the Wii game system. Each of these boards gathers force information from its four force transducers and sends that numeric information via Bluetooth. Each Bluetooth signal can be uniquely determined by a receiver and data from multiple boards can be collected. The Bluetooth signals are collected for diagnostic purposes by a commercial USB Bluetooth receiver and then processed as a joystick signal in the PC environment. The balance boards are housed in a plywood box in order to simplify the set-up of the device. This box allows for easy access to the Bluetooth sync function for each balance board, as well as providing a Plexiglas cover on the top of the boards to eliminate gaps between them while preventing applied forces from distributing inappropriately over the boards. The covers meet each other and the bounding edges of the box, and the clear material allows children to see that they are playing with video game controllers. Surrounding the edges of the plywood housing are low angle ramps which will allow for patients to easily walk onto the device and prevent falls.
Handrails
 

Handrail Force Sensor CAD

Figure 2: Handrail Force Sensor

Figure 2 – Handrail Sensor Box
The main structure for the handrails of the device is composed of standard size aluminum railing commonly used in pediatric hospitals. Bars and uprights are arranged as shown in figure 1. At the top of each upright, an innovative transducer housing attaches the horizontal bars along the length of the pathway. This transducer box contains four aluminum deflection beams instrumented with three strain gauges each, for a total of 12 gauges. These gauges are grouped into a full bridge measurement for each of the x, y, and z directions. Signals from these gauges are collected by a National Instruments 9219 DAQ, designed specifically for bridge circuit measurements. This DAQ device is USB capable and can be driven by a National Instruments LabVIEW stand-alone VI or using a C-directory. For diagnostic purposes, the device uses a stand-alone VI, or Virtual Instrument, to collect, store, and display the patient’s center of balance and applications of force to the handrails.
Software
This device has also been designed to allow for integration into a video game therapy program. The C-directory for the handrail sensors allows use-of-aid data to be collected and used within a PC game without the use of a diagnostic interface, allowing for faster and more entertaining gameplay. While the Wii board is not immediately usable with a PC, there are several versions of open-source software which can allow the signal to be processed as a PC joystick rather than a Nintendo device, allowing for them to be used in PC gameplay. Examples of these open-source programs are GlovePIE, which collects joystick or other human interface device signals, and PPJoy, which emulates PC joystick signals.
Evaluation
The final device has been evaluated to assess accuracy of measurements, ease of setup, software robustness, and safety. Accuracy was tested to assure that the center of balance data collected about the sponsor was reliable. Ease of setup was assessed by asking a third-party individual to assemble and launch the system using only the user’s manual as guidance. The robustness of the software was tested simply in using the device and running the software for many hours. Detailed hazard analysis and risk assessment were conducted and risks identified were addressed through redesign, such as adding ramps, cushioning areas, and grounding electrical components. Prototypes made from PVC pipes and wood were presented to professors, biomedical engineering students, computer science students, and physical therapists. Feedback and suggestions were taken from these and other groups during these and other more formal presentations.  Modifications were made based on suggestions gathered from prototype testing using engineering students.
Discussion and Conclusions
In conclusion, The Equiliberator meets all of the design criteria specified by the sponsor:
  • Measures reliance on rails for balance
  • Measures center of balance
  • Create gaming space large enough to walk and turn around
  • Provides interactive gaming experience
  • Ensure patient safety
As a result, the system will be able to meet all of the overall project goals:
  • Encourage patient use of therapy
  • Discourage reliance on balance aids
  • Quantify patient performance
When first given our task, we brainstormed many methods of achieving the objectives, and put forth many options before choosing one that fit within the scope of our available knowledge, abilities, time frame and budget. To compare all of the alternatives, we created decision matrices comparing the necessary components of the system: force measurements from feet, force measurements from hands, and the video game element.
Balance Measurements
Five possible methods of obtaining measurements of forces applied by the patient’s feet were considered: Wii Boards, commercial force plates, commercial pressure mats, sensors embedded in the patients’ shoes, and a design for a force plate made from grip force instruments, referred to as the DIY Grip Board. To narrow our choices we analyzed seven parameters of the design: size, cost, weight/portability, sampling rate, measurement range, measurement accuracy, and breadth of eligible users
It was determined that the Wii boards resulted in the highest weighted score, giving us a direction to start in our development of a physical product. The other four options were largely affected by their cost in relation to the Wii board. We intended on our final product being low enough in cost that it could potentially be implemented in the home, so our budget does not allow for more expensive options. The DIY Grip Board would have been a great candidate for us to customize our floor sensor, but the cost was far out of our budget constraint. The second ranked option, sensors placed inside the shoes, is not easily adapted to a wide range of users and would be difficult for us to account for different foot shapes and other extraneous factors in multiple patients.
The major problem with the Wii boards was the inability of the boards to fit flush with one another when placed in line. Our current solution is to adhere a rectangular piece of plexiglass atop each Wii board that exceeds the dimensions of the board the minimum amount necessary to cover the gaps between the boards.
Aid Reliance Measurements
Using the same method in determining the source of measurement for forces applied by the feet, we analyzed four options for measurements of the forces applied by the patient’s hands including an instrumented handrail with sensors on the rail (figure 2), an instrumented handrail with sensors on the floor, special instrumented gloves, and sensors that could attach to any individuals’ personal balance aids. The only change in parameters compared to the balance measurement components is the exchange of ‘Ease of Use’ for ‘Size’. All of the options were of negligible size, and ‘Ease of Use’ was a factor we considered important to include.
The highest scoring option was the handrail with sensors placed directly on the railing. Cost was not as much of a factor in this decision since the options were all fairly evenly priced, but measurement range and the breadth of users were critical elements in the ultimate decision.
Glove sensors were easily discarded as an option after a closer look into the needs of that design. The complications associated with the measurements being taken were far too great for us to handle. The option of having sensors attached to the patient’s walking aid was not a bad idea in terms of receiving the correct data, but the implementation of these sensors onto the patient’s supports and the central idea of their ability to perform these exercises without the supports were factors worth discounting the concept. Additionally, transmitting the information could have proven difficult, bulky, and restrictive.
Ultimately the handrail with sensors mounted on the railing was the best option. Having sensors on the floor would result in a greater window for error in calculation due to the mechanical forces applied to the handrail at different distances. It also increases the total floor coverage of the device, and space should be minimized for the product’s ease of use. Having the sensors mounted on the handrails will give us more accurate readings of the forces applied by the user. Signals are transmitted into a LabVIEW program through a National Instruments 9219 Data Acquisition unit. A drawing of our handrail sensor can be seen in figure 2.
Video Game Component
Designing the video game presented its own challenges. Since many but not all of the target patient audience suffers impaired cognitive ability as well as disordered balance, the game needed to be simple enough not to frustrate some patients, but able to provide the entertainment of a challenge to all.
The creative potential for the video game component is staggering. When the perspective is taken that the device we have made is essentially just a giant video game controller, uses for this controller begin to flower and evolve. The five boards measure center of balance, giving the input not only direction and magnitude, but also location if the boards are identified individually. Turret defense games become far more interesting when each board controls a different turret, the direction of lean controls aim, and the magnitude of lean controls the power of the shot. Of course, not every aspect of the input need be incorporated; simpler rhythm games can rise out of simply detecting on what board the player stands.
The only common threads between acceptable games are age and ability appropriateness and the convention of punishing the player’s performance when the handrails were relied on when balance was required. The handrails can also be incorporated as positive input devices for menu selections or game controls as long as sufficient portions of the game ban reliance upon them.
The game that was eventually developed for the launch of The Equiliberator is a game that requires intercepting incoming enemies by moving to the appropriate board (representing one of five alleys down which the enemies approach). The difficulty is scaled by the speed of the enemies as well as requiring advanced players to move certain defenses between alleys to successfully avoid failure. Graphics and sounds are designed to appeal to children of all ages, and players are encouraged to compete with themselves and each other, but most of all to have fun.
Regarding safety, the final device was modified to minimize safety hazards. Ramps were attached all around the device, and any protrusions were cut off and sanded down to keep the device free of tripping, scraping, and cutting hazards. All electrical components were appropriately grounded to avoid electrical issues. Moreover, the base was kept close to the floor to minimize the step up required to mount the device.
Thus, The Equiliberator meets all design specifications, project goals, sponsor needs, and safety targets.
Acknowledgements
We’d like to thank our sponsor, the Shriner’s Hospital for Children, particularly Mr. Steven Irby of the Gait Analysis lab for the impetus for this project as well as essential critiques during the design process. We’d also like to thank Dr. Maria Oden and Dr. Marcia O’Malley, our professors, for being at all our weekly meetings, contributing their expertise, and giving constructive feedback and advice for our device. Special thanks are in order for Mr. Carlos Amaro, Joe, and the rest of the staff of the Oshman Engineering Design Kitchen of Rice University for providing parts, guidance, and milling.

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