Back to results
US 5,512,891 AGranted
Drive-up station vehicle detection system and method of using same
AssigneeH. M. Electronics, Inc.
InventorChao M. Kang
Life of this patent
Estimating the term…
Abstract
A method and apparatus for detecting objects disposed in close proximity to a conductive loop, includes the use of a sensitivity selection circuit to compensate for loop sensitivity to metal and other conditions, and a microprocessor circuit for helping to prevent false detections or undesired interruptions of valid detection due to changes in environmental conditions.
Claims26
A detection system for use with a conductive wire loop having a given inductance, said given inductance being subject to change by the effect of at least one external element, comprising:
- loop oscillation means coupled to the conductive wire loop for generating an output frequency rate, said output frequency rate including an idle frequency rate during a non-detection time period interval and an active frequency rate during a detection time period interval;
- said idle frequency rate and said active frequency rate being subject to small incremental frequency rate changes caused by external condition changes;
- drift detection means responsive to said loop oscillation means for generating an idle drift correction signal whenever the output frequency rate of said loop oscillation means drifts by less than a predetermined percentage of a threshold value, said threshold value being equal to a reference frequency rate, said reference frequency rate being dependent upon external changes in temperature or humidity;
- frequency rate referencing means responsive to said idle drift correction signal for adjusting said reference frequency rate during said non-detection time period interval to help prevent false detections during said non-detection time period interval;
- detection determination means for generating an active detection signal whenever the output frequency rate of said loop oscillation means changes by more than a predetermined percentage of said threshold value;
- and
- drift compensation means responsive to said active detection signal for changing said reference frequency rate by a small incremental value to help prevent interruption of a valid detection resulting from external changes in temperature or humidity during said detection time period interval.
4 more elements
A method for helping to prevent false detections in a detection system used with an inductive wire loop disposed in an environment subject to temperature and humidity changes comprising:
- using loop oscillation means coupled to the wire loop;
- generating an output frequency rate, said output frequency rate including an idle frequency rate during a non-detection time period interval and an active frequency rate during a detection time period interval;
- said idle frequency rate and said active frequency rate being subject to small incremental frequency rate changes caused by external changes in temperature or humidity;
- generating and idle drift correction signal whenever the output frequency rate of said loop oscillation means drifts by less than a predetermined percentage of a threshold value, said threshold value being equal to a reference frequency rate, said reference frequency rate being dependent upon external changes in temperature or humidity;
- adjusting said reference frequency rate during said non-detection time period interval to help prevent false detections during said non-detection time period interval;
- generating an active detection signal whenever the output frequency rate of said loop oscillation means changes by more than a predetermined percentage of said threshold value;
- and
- changing said reference frequency rate by a small incremental value to help prevent false interruption of a valid detection resulting from external changes in temperature or humidity during said detection time period interval.
5 more elements
A detection system, comprising:
- a conductive wire loop having a given inductance, said given inductance being subject to change by the effect of at least one external element;
- loop oscillation means coupled to said conductive wire loop for generating an output frequency rate, said output frequency rate including an idle frequency rate during a non-detection time period interval and an active frequency rate during a detection time period interval;
- said idle frequency rate and said active frequency rate being subject to small incremental frequency rate changes caused by external condition changes;
- drift detection means responsive to said loop oscillation means for generating an idle drift correction signal whenever the output frequency rate of said loop oscillation means drifts by less than a predetermined percentage of a threshold value, said threshold value being equal to a reference frequency rate, said reference frequency rate being dependent upon external changes in temperature or humidity;
- frequency rate referencing means responsive to said idle drift correction signal for adjusting said reference frequency rate during said non-detection time period interval to help prevent false detections during said non-detection time period interval;
- detection determination means for generating an active detection signal whenever the output frequency rate of said loop oscillation means changes by more than a predetermined percentage of said threshold value;
- and
- drift compensation means responsive to said active detection signal for changing said reference frequency rate by a small incremental value to help prevent interruption of a valid detection resulting from external changes in temperature or humidity during said detection time period interval.
5 more elements
Dependencies are inferred from the claim text.