Ramps is a wheelchair to computer interface that uses existing chair mobility skills with interactive software that encourages creativity and play. The physical product of Ramps is a pair of rollers on top of slight ramps, the direction and speed of each wheel on a manual chair can be detected and transmitted to the computer. The first application made for Ramps was a Wheelchair DJ system that let the user be the MC and listen, sample and share music. The left wheel fades between tracks while the right wheel scratches the current track. Another applications include simple video games were that created to promote wheelchair skills and give the experience to those who do not use them. The design was not inspired by rehabilitation but for promoting the lifestyle of wheelchairs users, while rehabilitation is still a valid application, self expression and creativity is the driving force of Ramps.

BACKGROUND: Wheelchairs are used by over two million people in the United States and many users are bound to these devices for much of their local transportation needs. Like any activity, proficiency is acquired during use: steering manipulation, changing speed and "tricks" ("wheelies" to go over curbs, etc) are part of the skills learned using a wheelchair over time. Ramps gives people with these skills a novel Interface to technology. Encouraging positive and enjoyable experiences with wheelchairs creates a better awareness of their use and role for millions of people in the world.
Current therapy for people who use wheelchairs can involve testing and learning motor skills, endurance and general manipulation skills. These activities, while beneficial, can be dull and time consuming activities for both the patient and the occupational therapist. There is general interest in making the process more fun, which will ultimately lead to better interaction between the therapist and patient, along with increased benefits for all concerned.
Ramps is a project designed as a physical interface between wheelchairs and computer software. One of the main objectives of the project is to allow wheelchair users to be in control. We have designed applications for therapy, entertainment and creativity where the experience is user centered.

METHODOLOGY: Ramps is a project from the collaboration of the Interactive Telecommunications Program and the Department of Occupational Therapy at New York University with funding from the Nathan Cummings Foundation. The Developing Assistive Technology class places designers with occupational therapists in a supportive environment to explore what is possible for the assisted community. The occupational therapists came from the New York City area and were registered students with NYU, the designers (also students) consisted of industrial designers, computer programmers and artists interested in interactive design.
While at the Rusk Institute of Rehabilitation Medicine of the New York University Medical Center our design team observed a dozen young children with cerebral palsy riding in wheelchairs through the hallways in packs, navigating and traveling through tight spaces just having a good time. Their freedom and control in their wheelchairs was the inspiration for Ramps, the project.
Outside of therapy these patients at Rusk enjoy different hobbies. Several boys enjoyed being MC's and performing for the hospital staff. Influenced by the hip hop culture of their peers they were musicians to each other and took turns trying material out. Performing in wheelchairs, they made the hallway their stage to move, stop, turn and reposition for dramatic effect; their wheels were a major part of the performance.
Ramps started with the idea, "What if we could scratch a record with a wheelchair?” Scratching is the popular musical technique in hip hop where a DJ holds and manipulates the speed of a record to create a scratching sound; the process usually involves fading between multiple turntables as well. The system evolved to thinking about creating an interface that would allow the wheelchair user to manipulate other interactive software aimed at therapy and entertainment.
The first objective of our design was to allow a person to use their own wheelchair on the system. We wanted a system where nothing would connect to the person's chair and no special features would be needed - just a manual wheelchair. A second design requirement was to allow a person to use Ramps alone - if they were able to. It was important that the design be inviting to ride up on and easy to start. Finally, we decided to make the design rugged enough so it could be used at a busy children's hospital. Although there are many different styles and sizes of wheelchairs available, we focused on manual wheelchairs. Our target population, children and young adults aged 5- 18 at the Rusk Medical Center, predominantly use manual chairs. However, there are design considerations for electric chairs in the future.

FIRST PROTOTYPE: The first prototype of Ramps [prototype1] was a two track system, each track a ramp with two rollers affixed in the rear. Each track is 36 inches long and slopes to 4.5 inches tall. The tracks are made of 2 x 6 feet pieces of wood and cabinet grade plywood and the rollers are industrial plastic rollers with flange bearings. The ramps are covered with non-slip grip tape that provides traction for the wheels when loading and leaving the system. To use the first prototype, a user must ride backwards up the ramp. This proved to be difficult for an individual; they usually needed assistance from someone to guide and pull the wheelchair onto the rollers. This problem was fixed in the second version.
The wheelchair rests in the rollers when positioned on the system. As the wheels are spun, the rollers spin freely and capture the motion through an optical rotary encoder. The encoder is connected to a micro-controller which sends motion data from each wheel to a computer via a serial connection. Once the micro-controller sends the data to the computer, software programs freely capture the data and use it for various applications.
The first prototype was tested with a 5 year old boy and an 18 year old man, both with cerebral palsy, at the Rusk Medical Institute. We explained the project to them and they agreed to volunteer their wheels and thoughts. We tested several pieces of software (described later) and found that the physical interface was working to our satisfaction. The difference between weight and wheelchair size did not affect the system’s motion capturing. The system responded to each user equally well: Ramps operates silently so all of the user’s attention is focused on the interactive software.

SECOND PROTOTYPE: Overall the first prototype was a great success. However, many problems such as overall size and accessibility needed to be addressed. At three feet long and weighing over 45 pounds, the first prototype was a giant machine; transporting, storing and setting up the system was a process we needed to better resolve. The next system needed to be compact, both for cramped apartments and hospitals, where space is at a premium. Ramps should be able to fit in a closet when not in use. The first system was 4.5 inches tall and some therapists seemed nervous to roll patients up such a tall ramp. The new system needed to be low to the ground with a minimal incline: the front casters of the wheelchair would need to ride over the rollers safely. Using the system ought to be simple; a user should be able to ride onto the system from either side.
The second prototype [prototype2] was started in January and is now nearly complete. It is more functional than its predecessor with an elegant and simple design. Its overall height is now only 1 ¾ inches. The system includes a smaller, lighter roller system made of PVC piping and new optical encoders that make the new Ramps a fraction of the originals dimensions. There are two separate platforms for each wheelchair wheel, consisting of a pair of rollers and sensors. These platforms are connected with sliding rails, allowing Ramps to adjust to different size wheelchairs and still be compact for storage. On the back side of the platforms are two hinged wooden ramps which allow users to ride forward onto the system. On the front are two longer detachable ramps for the front wheelchair casters to rest on while using the system. The second prototype of Ramps weighs about 15 pounds and can fit into a standard gym bag when compacted.
The new system has a USB 2.0 interface for both data communication to the computer and for powering the device. USB is an industry standard communication protocol with cable ports on almost every modern PC and Mac. The second prototype also includes two force sensors (one on each roller platform) that can determine the weight on each side of the wheelchair. This information can be useful to help determine when someone is shifting their weight in the chair and can be used as a command to the computer (such as a mouse click).

SOFTWARE & EXPERIENCE: The ability to detect each wheel's rotation and direction individually, as well as the relative position of the user in the chair, provides a lot of data to create different software applications. We had originally focused on two test applications: one for entertainment, the other for creativity and expression. Now, with the plug-and-play aspect of the wheelchair-as-mouse, any mouse controlled video game can be played. These games can be taken from the internet, store bought or custom designed. In future iterations we are also planning to map the wheelchair to control game consoles such as the X-Box.
One aspect of using a wheelchair to control a video game is that users are physically involved; some use their entire upper body as they spin their wheels and get the cardiovascular benefit that goes along with exercise.
One of the original proprietary games developed was called “Bunny Rescue”. In this game a person controls a Mommy Rabbit on screen by propelling their wheels. The motion of moving the wheels mimics real life motion; moving just the left wheel forward would turn the rabbit to the right, both wheels forward would go straight, etc. The user navigates the Mommy Rabbit through a wooden area and moves over the bunnies to collect them. The game was a successful software application demonstrating the ability to capture wheel motion and have the user engage in hand-eye coordination and cognitive spatial skills.
Wheelchair DJ was the software developed for creativity for the boys who enjoyed hip hop. Depending on which direction the left wheel is spun it fades between two songs. When the right wheel is spun the current song is “scratched”. This was quite a hit with the teenagers who tried it and encouraged us in our goal to develop a physical interface for wheelchairs and creativity.
The project continues to be developed and tested with wheelchair users. The system is designed for a wide spectrum of people. Occupational therapists can use it as an exercise or work session, combining wheelchair usage with game play for an unbeatable motivation factor. Wheelchair users can roll on to it on their own for therapy, entertainment, and creativity.