Vehicle collision avoidance system

In an automatic guidance system having first and second self-propelled vehicles adapted to follow a predetermined guidepath having an intersecting portion on the floor surface, each of said vehicles having energizing means for driving said vehicles along said guidepath, the improvement which comprises:

• means for applying activating signals to said first vehicle energizing means when said first vehicle is stopped on said guidepath;
• transmitter means on said first vehicle responsive to said activating signals for transmitting a polling signal;
• receiver means on said second vehicle for detecting said polling signal;
• transmitter means on said second vehicle for transmitting a blocking signal in response to said receiving means on said second vehicle receiving said polling signal when said second vehicle is within a predetermined area on said guidepath;
• receiver means on said first vehicle for detecting said blocking signal and for generating a stop signal corresponding thereto;
• and
• control means on said first vehicle coupled to said receiver means on said first vehicle and responsive to said stop signal for prohibiting application of said activating signals to said first vehicle energizing means until such time as said blocking signal is no longer received by said receiver means on said first vehicle, whereby said first vehicle will remain stopped on said guidepath as long as said second vehicle is passing through said predetermined area.

A method for prohibiting collisions between first and second vehicles adapted to follow a predetermined guidepath having an intersecting portion defining a potential congestion zone on a floor surface, said method comprising the steps of:

• (a) sensing the approach of said first vehicle into said intersecting portion;
• (b) transmitting from said first vehicle a polling signal in response to the sensed approach of said first vehicle into said intersecting portion;
• (c) receiving said polling signal at said second vehicle and transmitting a blocking signal in response thereto only when said second vehicle is within said collision zone;
• (d) receiving said blocking signal at said first vehicle;
• and
• (e) stopping said first vehicle in response to said blocking signal and prohibiting said first vehicle from entering said intersecting portion until such time as said blocking signal is no longer received at said first vehicle.

A method for prohibiting collisions between first and second vehicles automatically guided along a guidepath having intersecting guide lines, said method comprising the steps of:

• (a) sensing the approach of said first vehicle to a guidepath intersection and generating polling signals from said first vehicle indicative thereof;
• (b) receiving said polling signals from said first vehicle at said second vehicle;
• (c) transmitting blocking signals from said second vehicle in response to said polling signals only when said second vehicle is within a predetermined zone surrounding said guidepath intersection;
• and
• (d) ceasing movement of said first vehicle in response to reception by said first vehicle of said transmitted blocking signals.