Solar power is becoming an increasingly popular source of energy, and researchers have found a way to use it to power such things as seafaring robots and wireless sensors. Now, a team of engineering students at the University of Virginia has found a use for it with a more altruistic angle -- to power a wheelchair that can be used for people with ailments such as cerebral palsy.
The solar-powered wheelchair designed by students in UVA's School of Engineering and Applied Science won first place and a prize of $20,000 in a contest called "Change My World in One Minute" held in conjunction with last year's World Cerebral Palsy Day in September. The prize was announced in late April. The suggestion to build a solar-powered wheelchair came from Alper Sirvan, a Turkish resident who submitted the idea for the contest.
Inspired by the retractable roofs on convertibles, students attached solar panels that can move in a similar way to the top of a wheelchair that is also powered by standard batteries. In addition to harvesting solar energy, the panels can provide shade on sunny days. The team did its best to ensure the addition of the panels did not take away from the mobility of the chair, UVA computer engineering graduate student and team member Dennis Waldron told Design News in an interview:
- From our perspective, the most pressing requirement was to increase the mobility of the user. There are solar-power wheelchair designs that increase battery life, but they all increase the size of the chair, preventing its use indoors, on public transportation, etc. Our design incorporated retractable panels so that the user would have both extended range and the ability to take the chair where they please.
The team used a stock motorized chair to which they attached a frame and an assembly of panels with actuators that deploy and retract the panels with the flip of a switch. The frame was mainly 3/4-inch low-carbon machinable steel with 14-gauge (0.083 inch) wall thickness. The team also used some 1-inch aluminum T-slot bar and hand-fabricated brackets to construct it, Waldron said.
To operate the chair, a user only needs to be able to use a joystick, since a single switch controls the chair. Students also included a seatbelt, armrests, a footrest, and adjustable seating as comfort and safety options on the chair. Additionally, there are USB power outlets for the tech-savvy user that can charge items such as mobile phones, GPS navigation devices, table computers, or reading lights. The wheelchair can operate for more than 4 1/2 hours at a speed of 5 mph on a fully solar-charged battery. It can run indefinitely at a speed of 1 mph on solar power alone without use of the battery, Waldron told us.
He described how the battery-solar design of the wheelchair works in this way:
- Our panels simply feed into a charge controller that charges the batteries. Electrically speaking, everything attaches to the same place -- the battery terminals -- so when the chair is running and receiving current from the panels, the motors draw from the panels and the batteries simultaneously. If the motors draw less current than the panels provide, the excess is fed to the batteries; conversely, if the motors draw more, the motors feed from the batteries and panels.
In addition to Waldron, the team -- advised by UVA and National Institute of Aerospace electrical and computer engineering professor Mool Gupta -- included electrical and computer engineering graduate students Duncan McGillivray, Craig Ungaro, and Ankit Shah, who work at the National Institute of Aerospace and NASA, Langley Research Center. Also on the team were undergraduate mechanical and aerospace engineering students Maria Michael and Kyung Kim. The students built the wheelchair primarily at the National Institute of Aerospace's Research and Innovation Laboratories Facility in Hampton, Va. Support for the project came from the Engineering School's Experiential Program through funding from an alumnus. Gupta also provided financial support.
The team intends to use its prize money to refine the chair to its final design and then ship it to Sirvan, the person who suggested it be built. Any remaining prize money will be returned to United Cerebral Palsy in support of future World Cerebral Palsy Day competitions, according to Waldron.
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