Non-contacting range sensing and control device

• US 4,733,355 A
• Filed: 02/10/1986
• Issued: 03/22/1988
• Est. Priority Date: 02/10/1986
• Status: Expired due to Term

• Current Assignee: Topcon Laser Systems, Inc.
• Original Assignee: AGTEK Development Co., Inc. (Hexagon AB)
• Inventors: Davidson, Richard W., Fletcher, John W.
• Primary Examiner(s): Chin, Gary
• Application Number:
  US06/828,155
• Time in Patent Office: 771 Days
• Field of Search: 364/424, 364/561, 364/562, 56/10.2, 56/DIG. 15, 377/16, 377/17, 73/624, 73/629, 73/640, 172/4, 172/4.5, 172/26
• US Class Current: 701/50
• CPC Class Codes: B60G 2300/09 Construction vehicles, e.g. graders, excavators
• CPC Class Codes: B60G 2401/176 Radio or audio sensitive means, e.g. Ultrasonic
• CPC Class Codes: E02F 3/842 using electromagnetic, optical or photoelectric beams, e.g. laser beams
• CPC Class Codes: E02F 3/847 using electromagnetic, optical or acoustic beams to determine the blade position, e.g. laser beams
• CPC Class Codes: G01S 15/18 wherein range gates are used

Abstract

A non-contacting range sensing and control device for controlling the position of a grading implement relative to a datum is disclosed. The device includes a non-contacting distance measuring device that periodically measures the separation distance between the distance measuring device and the datum. Also included is a reference circuit that defines consecutive first, second, and third intervals for comparison to the separation distance, and a comparison circuit that periodically compares the intervals to the separation distance, and generates a positive error signal if the separation distance is within the limits of the first interval, generates no error signal if the separation distance is within the limits of the second interval, and generates a negative error signal if the separation distance is within the limits of the third interval.

Claims

1. An apparatus for controlling the position of a grading implement of an earth-moving vehicle relative to a datum that extends along the direction of travel of the vehicle and that is elevated above ground level, said apparatus comprising:

position adjustment means coupled to the implement for moving the implement in one direction relative to the datum in response to a positive error signal and for moving the implement in an opposite direction relative to the datum in response to a negative error signal;

sonic means coupled for movement with the implement 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 positive 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 negative 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 positive error signal if said measurement time period ends during said first coparison time interval, for generating said negative error signal if 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.

2. An apparatus as recited in claim 1 wherein said sonic means includes means for transmitting the sonic signal toward the datum in response to a first time reference signal, and includes means for generating a second time reference signal upon the receipt of the reflected sonic signal, wherein said first and second time reference signals respectively define the beginning and end of said measurement time period.

3. An apparatus as recited in claim 2 wherein said first comparison time interval begins a delay time period after the receipt of said first time reference signal, and wherein said delay time period is selected so that, when the grading implement is positioned at its nominal position relative to the datum, said measurement time period 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.

4. An apparatus as recited in claim 3 wherein said apparatus further includes means for periodically generating said first time reference signal to periodically initiate a correction of the position of the grading implement.

5. An apparatus as recited in claim 2 wherein said first comparison time interval is defined by an output signal of a first monostable multivibrator triggered by said first time reference signal, wherein said second comparison time interval is defined by an output signal of a second monostable multivibrator triggered by the end of said first comparison time interval, and wherein said third comparison time interval is defined by an output signal of a third monostable multivibrator triggered by the end of said second comparison time interval.

6. An apparatus as recited in claim 5 wherein the durations of said first, and second, and third comparison time intervals are respectively determined by timing components coupled to said first, second, and third monostable multivibrators.

7. An apparatus as recited in claim 5 wherein said comparison means includes first and second gate means, wherein said first gate means receives said second time reference signal and the output signal of said first monostable multivibrator and generates said positive error signal when both inputs thereto are simultaneously present, and wherein said second gate means receives said second time reference signal and the output signal of said third monostable multivibrator and generates said negative error signal when both inputs thereto are simultaneously present.

8. An apparatus as recited in claim 1 wherein said first gate means includes a first AND gate that receives said second time reference signal and the output signal of said first monostable multivibrator, and a fourth monostable multivibrator that receives the output signal of said first AND gate and generates said positive error signal having a duration defined by timing components coupled to said fourth monostable multivibrator.

9. An apparatus as recited in claim 7 wherein said second gate means includes a second AND gate that receives said second time reference signal and the output signal of said third monostable multivibrator, and a fifth monostable multivibrator that receives the output signal of said second AND gate and generates said negative error signal having a duration defined by timing components coupled to said fifth monostable multivibrator.

10. An apparatus as recited in claim 1 wherein said first comparison time interval includes a first subinterval and a second subinterval with said second subinterval extending between the end of said first subinterval and the beginning of said second comparison time interval, said first subinterval defining a large positive error region and said second subinterval defining a small positive error region, and wherein said comparison means is further operable for generating said positive error signal for a longer duration when said measurement time period ends during said first subinterval than when said measurement time period ends during said second subinterval.

11. An apparatus as recited in claim 1 wherein said third comparison time interval includes a first subinterval and a second subinterval with said first subinterval extending between the end of said second comparison time interval and the beginning of said second subinterval, said first subinterval defining a small negative error region and said second subinterval defining a large negative error region, and wherein said comparison means is further operable for generating said negative error signal for a longer duration when said measurement time period ends during said second subinterval than when said measurement time period ends during said first subinterval.

12. 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.

13. An apparatus as reoited in claim 12 Wherein said first comparison time interval consists of a first subinterval that defines a large positive error region and a second subinterval that defines a small positive error region, wherein said third comparison time interval consists of a third subinterval that defines a small negative error region and a fourth subintnerval that defines a large negative erorr region, wherein said first subinterval, said second subinterval, said second comparison time interval, said third subinterval, and said fourth subinterval occur in succession, wherein said positive error signal has a shorter duration if said echo signal is received during said second subinterval than if said echo signal is recieved during said first subinterval, and wherein said negative error signal has a shorter duration if said echo signal is received during said third subinterval than if said echo signal is received during said fourth subinterval.

14. 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.