Limitations of Ultrasonic Obstacle Sensors for Industrial Lift Truck Applications

Accidents involving pedestrians and moving industrial lift trucks are a concern to both lift truck manufacturers and end-users. Many of these accidents occurred even though some type of additional pedestrian warning system was previously installed on the lift truck. The recurring problems involving a failed warning system are the result of ineffective activation methods available.

Advances in technology continue to bring to market new and innovative ways of activating pedestrian warning systems, each designed to eliminate the problematic symptoms of habituation and false signal. These symptoms are especially prevalent in industrial lift truck applications because of three characteristics unlike any other industrial vehicle. An industrial lift truck is capable of lifting heavy loads to elevated heights, can turn within its respective wheel base dimension, and is utilized in confined work spaces. When pedestrian warning systems are employed, in addition to the standard service horn, proper activation of the warning system is critical in producing positive results.

This paper highlights the limitations of ultransonic obstacle sensors as a method of activating pedestrian warning systems installed on industrial lift trucks. Review of literature and actual reverse travel test data will be described and discussed in detail, including the impact ultrasonic sensors have on creating false signals. Successive analyses will be discussed concerning the application of ultrasonic sensors for forward travel and lateral obstacle detection.