Evaluation of a microwave and infrared human-presence sensing system for agricultural equipment

The potential use of electronic safety sensors to protect operators from agricultural equipment with rotating hazards has been identified and discussed as a possible means to prevent traumatic entanglement injury. A multi-sensor human-presence sensing system to protect persons approaching a rotating PTO shaft powering a stationary implement was developed using commercially available, passive infrared and microwave sensors. A control and data acquisition system was designed and constructed to evaluate sensor performance and response. The sensor system performed well during 822 warm weather test passes in which a person approached the potentially hazardous area near the drawbar and PTO/IID located between an IH 986 test tractor and a self-unloading forage wagon. During the 822 test passes, there were no false alarms and no misses. Operators approached the hazard space walking from 92 to 227 cm/second. During tests, the sensing system yielded warning times generally between 0.5 and 1.0 seconds, providing an estimate of the time available to accomplish machine shutdown or operator warnings. Additional cold weather tests caused the control and data acquisition hardware to function erratically. This work suggests that multi-sensor human detection systems have the potential to reduce false alarms through redundancy when more than one sensor is required to detect a person before the system signals a "detect" condition. However, the use of multiple, redundant sensors also increases the potential for a "miss." Further work is needed to determine whether these types of sensor can yield timely enough information to prevent injury via mechanical shutdown or operator warnings.