This project has established the technical merit and feasibility of using ultrasonic technology in developing electronic safety devices, to protect construction workers from two of the major construction worksite accidents: (i) 'struck-by', 'struck-against', and 'caught in/under/between' equipment, and (ii) falls from roofs, and open-sided floors/platforms. These accidents account for 18.9% of the construction accidents and cost the nation $981 million annually. The devices will be built into the rear-side of the worker's tool-belt or waist-belt and warn the worker via sound and/or vibration alarm whenever he/she is closer than a safe distance from the approaching equipment or the edge of the roof/open-sided floors. To determine the safety devices design parameters, the safe clear distances were determined in the early phase of this project. For safety against moving equipment, safe clear distance was estimated to be 30 feet; and for safety against falls from roof edges and from floors/platforms, the clear distance was estimated to be 6 feet. These safe clear distances were used in the design and testing of the prototypes. Preliminary studies done prior to this project had examined the potential of all of the available technologies: ultrasonic, RF wave, laser, and infrared; and determined that only ultrasonic, and RF wave (radar) technologies can be used for the proposed safety devices. Prototype devices using each of the two technologies: ultrasonic, and RF wave, were then designed and assembled in this project, and were tested in the laboratory as well as in the field. These tests concluded that the ultrasonic technology is the appropriate technology for the safety devices. The RF wave technology was found to have several limitations: (i) it cannot measure short distances, as required in this project, to any acceptable accuracy, (ii) the RF wave reflection is a function of the material of the reflected surface, it will therefore give inaccurate measurements from construction equipments that have a lot of rubber and glass material and could also be covered with mud, (iii) the RF device would be more expensive, larger and heavier than the ultrasonic device, and (iv) it has been documented in the literature that radar energy can cause blindness, sterility and other serious health problems. Three prototypes using ultrasonic sensors were developed: (i) A Moving Hazard Warning (MHW) device with single ultrasonic sensor, (ii) A Moving Hazard Warning (MHW) device with three ultrasonic sensors, and (iii) An Edge Detector (ED) device with single ultrasonic sensor. These prototype devices were tested for: (i) the directionality of the device; (ii) the effect of the noise: acoustic, electrical, and high winds; (iii) signal attenuation through the worker's jacket or mud; (iv) calibration after being dropped or covered with mud; (v) possibility of system failures; (vi) battery life; (vii) effect of environment (rain and temperature extremes); and (viii) the physical dimensions and weight of the device. The prototypes performed satisfactorily on all of these test-items. At this time, any engineering controls for preventing the accidents of the type listed above do not exist. Assuming a 50% utilization of the developed products, the savings are estimated to be $490 million per year in the construction industry alone, besides saving 98 lives and 21,000 lost time Injuries.
Technological Systems Research, Design and Education, 126 Viscount Drive, Williamsville, NY 14221
Technological Systems Research, Design and Education, Williamsville, New York