Links

Process blog: https://physicalcomputing2014.wordpress.com/

Community outreach: http://www.hcde.washington.edu/news/hcde-students-demo-projects-at-computing-open-house

Description

While the basic white cane has served as a universally effective mobility aid for vision impaired users, it does have its limitations. By extending a cane during travel, users are able to detect objects approaching at the ground level. However, raised obstacles including hanging signs, low hanging branches and elevated railings remain problematic. The Hummingbird Mobility Aid System attempts to fill this void by detecting obstacles and alerting users through haptic feedback. In short, the Hummingbird is a small, three mode sensor attachment that easily clips to any white cane. Press the mode button once and the Hummingbird activates its raised distance sensor. As a user approaches a raised obstacle, haptic feedback increases in frequency. A constant vibration in the handle indicates that the user should immediately correct their course. Press the mode button a second time and the Hummingbird enters line mode. Vibrations will persist until the user is within two meters of the person in front of them. When the line moves forward a vibrating motor will reactivate, indicating that the user should step forward until the vibration stops. The Hummingbird also offers a third experimental retracted mode. This mode allows users to retract their cane indoors or in a crowded setting and continue to receive feedback about elevation changes immediately in front of them. Pressing the mode button a fourth time will turn the device off. In addition to haptic feedback, this change is indicated by a small LED for low vision or sighted users who may also be handling the device.

Implementation
The Hummingbird was built using an Arduino Uno, two Maxbotix Ultrasonic Rangefinders (Model HRLV – EZ1) wired in series , one Vibrating Mini Motor Disc and one adjustable cane clip which was 3D printed to tightly fit the two distance sensors. As a prototype, the Hummingbird does not use wireless technology. Instead, it makes use of a breadboard and generous amounts of hookup wire. The Hummingbird’s source code uses a counter to keep track of how many times the button has been pressed and passes on a mode number from one to four. In mode one, the first distance sensor pulse is triggered on a loop. If distance is recorded at less than a factor of 40, the vibrating motor is switched to the on position. Line mode reverses this function. The motor is instead switched to the on position as long as distance is greater than two meters. The third mode combines this feedback, turning the motor steadily on as long as distance is less than floor length and pulsing the motor when a drop off manifests as exceeding floor length. Additionally, while the device is on, an indicator LED is likewise switched to the on position.