Non-contacting range sensing and control device

An apparatus for determining the positional error of a grading implement of an earth-moving machine with respect to a datum, said apparatus comprising:

• means for periodically generating a trigger signal;
• ultrasonic means coupled for movement with the implement for transmitting an ultrasonic signal toward the datum in response to said trigger signal and for generating an echo signal upon receipt of an ultrasonic signal reflected from the datum;
• timing means for defining a delay time period upon receipt of said trigger signal and for defining consecutive first, second, and third comparison time intervals immediately after said delay time period, wherein said first comparison time interval defines a positive error region, said second comparison time interval defines a nominal error region within which the positional error of the implement is acceptably small, said third comparison time interval defines a negative error region, and wherein said delay time period is selected so that the time period between the generation of said trigger signal and the generation of said echo signal is substantially equal to the sum of said delay time period plus said first comparison time interval plus one half of said second comparison time interval when the grading implement is positioned at its nominal position relative to the datum;
• and
• comparison means for comparing said echo signal to said comparison time intervals, for generating a positive error signal if said echo signal is received during said first comparison time interval, for generating a negative error signal if said echo signal is received during said third comparison time interval, and for generating no error signals if said echo signal is received before said first comparison time interval begins, if received during said second comparison time interval, and if received after said third comparison time interval ends.

An apparatus for controlling the vertical position of a grading implement of an earth-moving vehicle relative to a datum that extends alog the direction of travel of the vehicle, wherein said vehicle includes means coupled to the implement for moving the implement upward in response to a low error signal and for moving the implement downward in response to a high error signal, said apparatus comprising:

• sonic means, coupled for movement with the implement and positioned above the datum, for periodically transmitting a sonic signal downward toward the datum and for receiving a sonic signal reflected upward from the datum, wherein the time period between the transmission and receipt of said sonic signal defines a measurement time period that is proportional to the separation distance between said sonic means and the datum;
• timing means for periodically defining consecutive first, second, and third comparison time intervals of finite duration, wherein said first comparison time interval defines a low error region beginning at a time after the transmission of the sonic signal by said sonic means, said second comparison time interval defines a nominal error region beginning at the end of said first comparison time interval, and said third comparison time interval defines a high error region beginning at the end of said second comparison time interval;
• and
• comparison means for periodically comparing said measurement time period to said comparison time intervals, for generating said low error signal if said measurement time period ends during said first comparison time interval, for generating said high error signal is said measurement time period ends during said third comparison time interval, for generating no error signals if said measurement time period ends during said second comparison time interval, for generating no error signals if said measurement time period ends before said first comparison time interval begins, and for generating no error signals if said measurement time period ends after said third comparison time interval ends.