Long cane-integrated ultrasonic sensing for spatial obstacle localization.

摘要

Among various forms of disability, blindness has been regarded as one of the most devastating that can strike people of all ages and significantly affects the victim's life. In spite of the significant efforts made by the research community and industry over the past decades on developing electrical travel aids (ETAs) for the blind, their acceptance rate by the blind community has remained surprisingly low, due to a variety of reasons such as bulky size, heavy weight, high cost, lack of user-friendliness and incompatibility with daily walking situations. The majority of blind people nowadays are still using the conventional long cane as the primary travel aid, which is a simple walking stick that does not provide any protection against overhanging obstacles, such as tree branches, signposts, or improperly slung wires. As a result, head injuries of blind cane users often occur in daily walking situations.; This research was motivated by the critical need for a new type of spatial obstacle localization technique that is particularly suited for integration into the long cane structure subject to both swing and tapping motion during its operation and that provides an orientation and travel aid for the blind. The research objective were three-fold: (1) to establish a theoretical framework for ultrasound-based ranging and spatial obstacle localization from a moving reference frame, represented by the long cane, using the time-of-flight (TOF) approach, (2) to design, analyze, implement, and prototype a miniaturized and self-contained ultrasonic transceiver module with wireless data transmission capability, integrate it into the shaft of a modified long cane, and develop a wireless data receiver with voice output display, and (3) to experimentally evaluate the sensor-integrated long cane with respect to sensor directionality, placement, measurement accuracy, repeatability, electromechanical coupling, and effect of mechanical vibration.; A mechatronic approach was taken for the system-level design of the long cane based ultrasound measurement system. Sensor module coordination and ultrasound echo signal processing were controlled in real-time by a microcontroller, which was an integral part of the cane-embedded electronics. A dual-frequency technique has been proposed that introduced information redundancy to improve measurement quality. Quantitative analysis on the systematic and random errors of the embedded system was provided. In addition to providing information on the distance and height of the obstacles in front of the user, the system further incorporated self-test ability.