2002 Annual Report
Research
Human Presence Sensors and Control Systems to Prevent Machinery Entanglement
Injuries
Michael Venem, Graduate Student
John Shutske, Associate Professor
William Gilbert, Electromechanical Systems Specialist, Physics and Astronomy
Funding Source
National Institute for Occupational Safety and Health; Marshfield Medical
Research Foundation; Minnesota Agricultural Experiment Station
Objective
To develop an effective prototype sensor-based human presence detection
system that prevents people from being entangled in dangerous agricultural
and industrial equipment.
Project Description
Over the past 10 years, almost 300 Minnesota farmers, farm employees,
and children have died because of hazards in the farm workplace. A significant
percentage of these fatalities result from entanglement with rotating
power take-offs, drive shafts, gears, belt drives, and other dangerous
components that are rotating at high speed and transmitting large amounts
of power. This project examines the application of existing electronic
sensor technologies to detect and protect people who are working near
dangerous, rotating agricultural and industrial machinery.
Results
During 2002, a detailed literature review was completed to examine the
application of a variety of sensor technologies in the mining, automotive,
aerospace, and military equipment industries. We also conducted laboratory
and field evaluations of various types of sensors using a tractor and
self-unloading forage wagon to evaluate sensor performance characteristics
and limitations using a randomized 3 X 3-factorial design for each category
of sensors with 8 repetitions per test condition in both lab and outdoor
field conditions. A total of 288 tests with four different sensor technologies
explored the reliability of current security sensors for human detection.
Test data were statistically analyzed to determine how the sensor technology,
approach angle, and mounting height affect the distance from the hazard
at the time of detection. Upon completion of testing, a working prototype
safety system was created that turned off the PTO of a tractor if a person
entered into the PTO hazard area, causing the PTO to stop rotating before
the person could come in contact with it. The system also caused an alarm
to sound and strobe light to flash after detection, signaling that a person
has entered into the PTO hazard area and tripped the alarm.
These and previous sensor tests indicate that radar-based sensing technologies perform well in a wide range of conditions, providing there is adequate time to detect a person and provide for either an automatic warning or machine shut down. The next step in this research is to develop an industry partnership or obtain other sources of private support to create a low-cost, field-ready sensing and shut-down or warning device with the coverage pattern needed to reduce false alarms.