The X-drive is an elegantly simple device designed to improve the quality of life of wheel chair users. Its design was developed using interviews from wheel chair users and industry retailers/manufacturers. The X-drive fills the need for an inexpensive and convenient method to convert conventional wheel chairs into powered wheel chairs on a permanent or temporary basis. Though reliable and durable, conventional power wheel chairs are too expensive for many consumers and transporting them requires special arrangements such as wheelchair accessible vehicles. The X-Drive allows wheel chair users to be more independent through the use of conventional vehicles like a taxi or their own car.
Innovations from the X-drive include a downloadable app for controlling direction and speed currently available on Android. This means no wiring harness for controls. The X-drive app allows for easy system installation, lowers the cost to produce and update controls and facilitates use by either an independent caregiver or the wheel chair occupant. A proprietary communications protocol restricts interference with the controls by unauthorized sources. The hub-mounted direct drive DC motor used on a gnarly all terrain tire provides sensitive forward and reverse traction along with 140 foot pounds of torque for payloads up to 350 pounds. The universal adapter bar meets the “one size fits all” need of the wheelchair market as there are many different sizes of wheel chairs which all can remain portable through the use of the X-drive. A production version would use a new battery technology developed by Dr Robert-Murray Smith that is low cost, has a higher electrical density than lithium ion batteries and charges in short periods like a capacitor. The battery will power the chair for approx. 1,000 km per charge.
Manufacturability was a primary design criterion. Though several key parts were printed using a 3-D printer, the majority of the parts, such as the motor drivers, are off-the-shelve parts. Custom components such as the fork and frame were made from slightly modified stock parts. The heart of the X-Drive is an Arduino microcontroller. This is an open source board that is available around the world with a vast amount of online support making repair of the drive easier.
Having designed the X-drive to be as simple as possible, it ensures manufacturing remains easy and low cost. This prototype was manufactured for $1,200 USD in parts. Manufacturing the X-drive is straight forward, requiring minimal machining (3 machined and 1 milled component) and a single PCB. The total cost of manufacturing is forecasted to be maximum $500 USD at minimum volume, decreasing as volume increases.
The base market size for this product is large with 3.3 million wheel chair users in the United States alone (USACensus, 2011). The market is growing with the aging population and the market can be further expanded in North America by obtaining a “Medical Device” classification. The combined flexibility and portability of the X-Drive makes the device more accessible around the world than any current powered wheel chair.