Method for automatic depth control for earth moving and grading

• US 4,918,608 A
• Filed: 06/09/1988
• Issued: 04/17/1990
• Est. Priority Date: 06/09/1988
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Christopher O. Middleton, Colin L. Robson
• Inventors: Middleton, Christopher O., Robson, Colin L.
• Primary Examiner(s): Chin, Gary
• Application Number:
  US07/204,508
• Time in Patent Office: 677 Days
• Field of Search: 364/424.07, 364/571.03, 364/571.04, 364/571.07, 364/474.35, 364/562, 364/561, 56/10.2, 56/DIG. 15, 172/4, 172/4.5, 73/624, 73/629
• US Class Current: 701/50
• CPC Class Codes: E02F 3/847 using electromagnetic, optical or acoustic beams to determine the blade position, e.g. laser beams
• CPC Class Codes: E02F 5/14 Component parts for trench excavators, e.g. indicating devices travelling gear chassis, supports, skids
• CPC Class Codes: G01S 15/88 Sonar systems specially adapted for specific applications seismic or acoustic prospecting or detecting G01V1/00
• CPC Class Codes: G01S 2007/52012 involving a reference ground return
• CPC Class Codes: G01S 7/52006 with provision for compensating the effects of temperature

Abstract

A method and apparatus for automatically controlling the depth of earth grading for utilization with a grader or paver is disclosed. The method includes determination of time taken for an acoustic pulse to travel from a transducer to a reference surface and back, with this value being used to calibrate a microprocessor-controlled distance-measuring device. As the grader moves over a surface to be graded, the distance to the reference surface is constantly detected by a repeated emission and detection of such acoustic pulses. The timing of the echoed pulses is converted to addresses in a look-up table which contains control words symbolizing commands to be given to hydraulic rams carried by the grader. By implementing these commands, the depth of the blade relative to the reference surface is constantly updated, compensating for variations with the height of the reference surface. A thermistor is provided to automatically compensate for temperature variations as the grading takes place. Displays are provided for the operator of the vehicle to show what type of adjustments are being made to the blade, and whether the height of the reference surface is outside the range of sensitivity of the follower. The follower is automatically calibrated for a given blade depth by repeated incrementation of a delay time variable until a zero adjustment command is generated for the blade control.

Claims

1. A method of controlling a hydraulic system for grading a first surface at a chosen depth relative to a reference surface by means of an earth grader carrying a vertically adjustable blade at the chosen depth relative to the reference surface by action of the hydraulic system on the blade, including the steps of:

implementing a calibration procedure, including determining a reference time interval relating to a travel time of an acoustic pulse from a transducer to the reference surface and back to the transducer, so that the reference time interval corresponds to the chosen depth of the blade as determined by an operator of the earth grader;

emitting a ranging pulse from the transducer toward the reference surface and starting a counter at a first time, the transducer being mounted in a fixed position relative to the blade, such that the ranging pulse reflects from the reference surface back toward the transducer;

stopping the counter when the reflected ranging pulse reaches the transducer, thereby generating a count corresponding to the length of time taken by the ranging pulse to reflect from the reference surface back to the transducer and further corresponding to an actual blade depth;

vertically adjusting the blade by a distance relating to the count such that the actual blade depth corresponds to the chosen blade depth;

repeating the steps of emitting the ranging pulse, starting and stopping the counter, and vertically adjusting the blade, whereby variations in the height of the reference surface are automatically compensated by the adjustments of the blade as the grader moves along the reference surface; and

compensating the adjustments of the blade for temperature variations after the reference time interval has been determined, and before each time the ranging pulse is emitted.

2. A method of controlling a hydraulic system for grading a first surface at a chosen depth relative to a reference surface by means of an earth grader carrying a vertically adjustable blade at the chosen depth relative to the reference surface by action of the hydraulic system on the blade, including the steps of:

implementing a calibration procedure, including determining a reference time interval relating to a travel time of an acoustic pulse from a transducer to the reference surface and back to the transducer, so that the reference time interval corresponds to the chosen depth of the blade as determined by an operator of the earth grader;

emitting a ranging pulse from the transducer toward the reference surface and starting a counter at a first time, the transducer being mounted in a fixed position relative to the blade, such that the ranging pulse reflects from the reference surface back toward the transducer;

stopping the counter when the reflected ranging pulses reaches the transducer, thereby generating a count corresponding to the length of time taken by the ranging pulse to reflect from the reference surface back to the transducer and further corresponding to an actual blade depth;

vertically adjusting the blade by a distance relating to the counter such that the actual blade depth corresponds to the chosen blade depth;

repeating the steps of emitting the ranging pulse, starting and stopping the counter, and vertically adjusting the blade, whereby variations in the height of the reference surface are automatically compensated by the adjustments of the blade as the grader moves along the reference surface; and

determining the distance of the vertical adjustment of the blade by locating an instruction in a preset control table at a control table address corresponding to the count, where the control table includes instructions to raise and lower the blade, and further includes at least one instruction for refraining from adjusting the blade, such that each address of the control table corresponds to a level of the reference surface.

3. The method of claim 2, further including the steps of:

before the step of starting the counter, determining whether the reflected pulse has already reached the transducer, and if so, bypassing the steps of starting and stopping the counter, and providing a zero adjustment to the blade and a lower limit error display signal on a display to the operator;

after the step of starting the counter, stopping the counter at a predetermined value if the reflected ranging pulse does not reach the transducer before the predetermined value is reached, and providing a zero adjustment to the blade and an upper limit error display signal on the display to the operator;

after the step of stopping the counter, providing a downward adjustment to the blade and a downward adjustment display signal to the operator when the control table address corresponding to the counter is at an upper portion of the control table;

after the step of stopping the counter, providing zero adjustment to the blade and a zero adjustment display signal to the operator when the control table address corresponding to the counter is at a central portion of the control table; and

after the step of stopping the counter, providing an upward adjustment to the blade and an upward adjustment display signal to the operator when the control table address corresponding to the count is at a lower portion of the control table.

4. A method for automatic depth control for providing a surface by a grader at a chosen height relative to a reference surface having a variable height, where the grader includes a follower for acoustically following the height of the reference surface and for controlling the height of a blade carried by the grader, including the steps of:

setting the blade at a desired height relative to the height of the reference surface;

sending a first acoustic pulse form the follower to the reference surface for reflection thereby;

detecting the first pulse at the follower after reflection by the reference surface;

determining a first time interval between the sending of the first pulse and the detecting of the reflected first pulse;

setting an error margin for the earth grading;

commencing the grading by operating the grader at an area adjacent the reference surface;

emitting a second acoustic pulse from the follower for reflection by the reference surface;

enabling the follower to detect the reflected second pulse;

determining a second time interval between the emitting of the second pulse and the detecting of the reflected second pulse;

comparing the second time interval with the first time interval;

if the second time interval is greater than the first time interval by an amount no greater than the error margin, lowering the height of the blade by a distance corresponding to the amount by which the second time interval exceeds the first time interval; and

if the second time interval is less than the first time interval by an amount no greater than the error margin, raising the height of the blade by a distance corresponding to the amount by which the first time interval exceeds the second time interval;

such that a change in the height of the reference surface is accommodated by a substantially equal change in the height of the blade, for grading areas adjacent the reference surface at a constant depth relative thereto; and

further including, after the step of determining the first time interval and before setting the error margin, the steps of;

subtracting a predetermined number from the first time interval to generate a calibration constant, where the predetermined number comprises a predetermined pointer address for an instruction in a memory relating to zero adjustment to the blade height; and

storing the calibration constant in the memory;

and wherein the step of comparing the second time interval with the first time interval includes the steps of subtracting the calibration constant from the second time interval to generate a variable pointer address for locating instructions in the memory relating to the adjustment of the height of the blade.

5. The method of claim 4, further including, after the step of determining the first time interval, the steps of:

detecting a first time interval adjustment value input by the operator of the grader;

adjusting the first time interval by adding the first time interval adjustment value thereto; and

utilizing the adjusted first time interval in subsequent comparisons with the second time interval.

6. A method for automatic depth control for producing a surface by a grader at a chosen height relative to a reference surface having a variable height, where the grader includes a follower for acoustically following the height of the reference surface and for controlling the height of a blade carrier by the grader, including the steps of:

setting the blade at a desired height relative to the height of the reference surface;

sending a first acoustic pulse from the follower to the reference surface for reflection thereby;

detecting the first pulse at the follower after reflection by the reference surface;

determining a first time interval between the sending of the first pulse and the detecting of the reflected first pulse;

setting an error margin for the earth grading;

commencing the grading by operating the grader at an area adjacent the reference surface;

emitting a second acoustic pulse from the follower for reflection by the reference surface;

enabling the follower to detect the reflected second pulse;

determining a second time interval between the emitting of the second pulse and the detecting of the reflected second pulse;

comparing the second time interval with the first time interval;

if the second time interval is greater than the first time interval by an amount no greater than the error margin, lowering the height of the blade by a distance corresponding to the amount by which the second time interval exceeds the first time interval; and

if the second time interval is less than the first time interval by an amount not greater than the error margin, raising the height of the blade by a distance corresponding to the amount by which the first time interval exceeds the second time interval;

such that a change in the height of the reference surface is accommodated by a substantially equal change in the height of the blade, for grading areas adjacent the reference surface at a constant depth relative thereto; and

compensating for effect for effects on the second time interval due to changes in the speed of propagation of the acoustic pulse as a result of changes in ambient temperature, with the compensating step comprising the steps of generating a compensation factor corresponding to a change in temperature, and adjusting the first time interval based upon the compensation factor, after the step of commencing the grading and before the step of comparing the second time interval with the first time interval.

7. A method for automatic control of a depth of a blade carried by a surface grader relative to a reference surface, where the grader includes a vertically adjustable blade to which a frame is affixed, with the frame carrying an acoustic follower positioned above the reference surface, with the follower including a microprocessor having a program stored therein for governing a height of the blade, the follower and the frame relative to the reference surface by means of hydraulic controls, including the steps of:

positioning the blade at a chosen depth;

initializing a delay variable to a predetermined minimum value;

incrementing the delay variable;

determining a first temperature compensation variable;

emitting a first acoustic chirp from the follower toward the reference surface for reflection thereby back to the follower;

detecting whether the reflected first chirp has reached the follower;

after a first period of time after the emission of the first acoustic chirp, with the first period of time being determined by the value of the delay variable as adjusted for temperature by the temperature compensation variable, starting a first decrementation of an accumulator of the microprocessor from a predetermined maximum value at a fixed rate;

stopping the first decrementation of the accumulator upon reception of the reflected first chirp at the follower or upon decrementing the accumulator to a predetermined minimum value, whichever happens first;

setting a first point address equal to the value of the accumulator after stopping the first decrementation thereof;

comparing the first pointer address with addresses of a preset control table in the memory, with the control table including control words for governing the depth of the blade by providing signals to the hydraulic controls, for determining whether the first pointer address addresses a control word including a zero adjustment signal for the hydraulic controls;

if the control word addressed by the first pointer address does not include a zero adjustment signal for the hydraulic controls, repeating the steps of incrementing the delay variable, determining the first temperature compensation variable, emitting the first acoustic chirp, detecting whether the reflected first chirp has reached the follower, starting and stopping the first decrementation of the accumulator, setting the first pointer address, and comparing the first pointer address with the addresses of the control table until the control word addressed by the first pointer address includes a zero adjustment value for the hydraulic controls;

storing the delay variable;

determining a second temperature compensation variable;

emitting a second acoustic chirp from the follower toward the reference surface for reflection thereby back to the follower;

detecting whether the reflected second chirp has reached the follower, and if so, providing a zero adjustment command to the hydraulic controls and further providing a first display pattern on an output display to an operator of the grader indicating the detection of the reflected second chirp before the passing of a second period of time after the emission of the second acoustic chirp, with the second period of time being determined by the value of the delay variable as adjusted for temperature by the second temperature compensation variable, and returning to and proceeding from the step of determining the second temperature compensation variable;

after the second period of time after the emission of the second acoustic chirp, starting a second decrementation of the accumulator from the predetermined maximum at the predetermined rate;

stopping the second decrementation of the accumulator upon reception of the reflected second chirp at the follower or upon decrementing the accumulator to the predetermined minimum value, whichever happens first;

setting a second pointer address equal to the value of the accumulator after stopping the second decrementation thereof;

providing a control word in the control table as instructions to the hydraulic controls, where the control word is addressed by the second pointer address and relates to upward adjustments to the depth of the blade for values of the second pointer address which are less than the first pointer address, to downward adjustments to the depth of the blade for values of the second pointer address which are greater than the first pointer address, and to zero adjustments to the depth of the blade for values of the second pointer address which are substantially equal to the first pointer address and for values of the second pointer address which exceed either an upper or a lower predetermined sensitivity range for the follower;

providing an output display to the operator with a second display pattern for signalling the upward adjustments, a third display pattern for signalling the downward adjustments, a fourth pattern for signalling the zero adjustments where the second pointer address is equal to the first pointer address, a fifth pattern for signalling the zero adjustments where the second pointer address exceeds the upper predetermined sensitivity range, and a sixth pattern for signalling the zero adjustments where the second pointer address exceeds the lower predetermined sensitivity range for the follower; and

repeating the steps of determining the second temperature compensation variable, emitting the second acoustic chirp, detecting whether the reflected second chirp has reached the follower, starting an stopping the second decrementation of the accumulator, setting the second pointer address, providing the control word as instructions to the hydraulic controls, and providing the output display to the operator, with the repetition being carried out at a predetermined rate.

8. A method of controlling a hydraulic system for grading a first surface at a chosen depth relative to a reference surface by means of an earth grader carrying a vertically adjustable blade at the chosen depth relative to the reference surface by action of the hydraulic system on the blade, including the steps of:

implementing a calibration procedure, including determining a reference time interval relating to a travel time of an acoustic pulse from a first transducer to the reference surface and back to the first transducer, so that the reference time interval corresponds to the chosen depth of the blade as determined by an operator of the earth grader;

emitting a ranging pulse from a second transducer toward the reference surface and starting a counter at a first time, the transducer being mounted in a fixed position relative to the blade, such that the ranging pulse reflects from the reference surface back toward the second transducer;

stopping the counter when the reflected ranging pulse reaches the second transducer, thereby generating a counter corresponding to the length of time taken by the ranging pulse to reflect from the reference surface back to the second transducer and further corresponding to an actual blade depth;

vertically adjusting the blade by a distance relating to the count such that the actual blade depth corresponds to the chosen blade depth;

repeating the steps of emitting the ranging pulse, starting and stopping the counter, and vertically adjusting the blade, whereby variations in the height of the reference surface are automatically compensated by the adjustments of the blade as the grader moves along the reference surface; and

compensating the adjustments of the blade for temperature variations after the reference time interval has been determined, and before each time the ranging pulse is emitted.

9. A method of controlling a hydraulic system for grading a first surface at a chosen depth relative to a reference surface by means of an earth grader carrying a vertically adjustable blade at the chosen depth relative to the reference surface by action of the hydraulic system on the blade, including the steps of:

implementing a calibration procedure, including determining a reference time interval relating to a travel time of an acoustic pulse from a first transducer to the reference surface and back to the first transducer, so that the the reference time interval corresponds to the chosen depth of the blade as determined by an operator of the earth grader;

emitting a ranging pulse from a second transducer toward the reference surface an starting a counter at a first time, the second transducer being mounted in a fixed position relative to the blade, such that the ranging pulse reflects from the reference surface back toward the second transducer;

stopping the counter when the reflected ranging pulse reaches the second transducer, thereby generating a count corresponding to the length of time taken by the ranging pulse to reflect from the reference surface back to the second transducer and further corresponding to an actual blade depth;

vertically adjusting the blade by a distance relating to the count such that the actual blade depth corresponds to the chosen blade depth; and

repeating the steps of emitting the ranging pulse, starting and stopping the counter, and vertically adjusting the blade, whereby variations in the height of the reference surface are automatically compensated by the ajustments of the blade as the grader moves along the reference surface;

and determining the distance of the vertical adjustment of the blade by locating an instruction in a preset control table at a control table address corresponding to the count, where the control table includes instructions to raise and lower the blade, and further includes at least one instruction for refraining from adjusting the blade, such that each address of the control table corresponds to a level of the reference surface.

10. A method of controlling a hydraulic system for grading a first surface at a chosen depth relative to a reference surface by means of an earth grader carrying a vertically adjustable blade at the chosen depth relative to the reference surface by action of the hydraulic system on the blade, including the steps of:

implementing a calibration procedure, including determining a reference time interval relating to a travel time of an acoustic pulse from a transducer to the reference surface and back to the transducer, so that the reference time interval corresponds to the chosen depth of the blade as determined by an operator of the earth grader;

emitting a ranging pulse from the transducer toward the reference surface at a first time, the transducer being mounted in a fixed position relative to the blade, such that the ranging pulse reflects from the reference surface back toward the transducer;

starting a counter at a second time which is a delay time after the first time;

stopping the counter when the reflected ranging pulse reaches the transducer, thereby generating a count corresponding to the length of time taken by the ranging pulse to reflect from the reference surface back to the transducer and further corresponding to an actual blade depth;

vertically adjusting the blade by a distance relating to the count such that the actual blade depth corresponds to the chosen blade depth;

repeating the steps of emitting the ranging pulse, starting and stopping the counter, and vertically adjusting the blade, whereby variations in the height of the reference surface are automatically compensated by the adjustments of the blade as the grader moves along the reference surface; and

compensating the adjustments of the blade for temperature variations after the reference time interval has been determined, and before each time the ranging pulse is emitted.

11. A method of controlling a hydraulic system for grading a first surface at a chosen depth relative to a reference surface by a means of an earth grader carrying a vertically adjustable blade at the chosen depth relative to the reference surface by action of the hydraulic system on the blade, including the steps of:

implementing a calibration procedure, including determining a reference time interval relating to a travel time of an acoustic pulse from a transducer to the reference surface and back to the transducer, so that the reference time interval corresponds to the chosen depth of the blade as determined by an operator of the earth grader;

emitting a ranging pulse from the transducer toward the reference surface at a first time, the transducer being mounted in a fixed position relative to the blade, such that the ranging pulse reflects from the reference surface back toward the transducer;

starting a counter at a second time which is a delay time after the first time;

stopping the counter when the reflected ranging pulse reaches the transducer, thereby generating a count corresponding to the length of time taken by the ranging pulse to reflect from the reference surface back to the transducer and further corresponding to an actual blade depth;

vertically adjusting the blade by a distance relating to the count such that the actual blade depth corresponds to the chosen blade depth;

repeating the steps of emitting the ranging pulse, starting and stopping the counter, and vertically adjusting the blade, whereby variations in the height of the reference surface are automatically compensated by the adjustments of the blade as the grader moves along the reference surface; and

determining the distance of the vertical adjustment of the blade by locating an instruction in a preset control table at a control table address corresponding to the count, where the control table includes instructions to raise and lower the blade, and further includes at least one instruction for refraining from adjusting the blade, such that each address of the control table corresponds to a level of the reference surface.

12. A method of controlling a hydraulic system for grading a first surface at a chosen depth relative to a reference surface by means of an earth grader carrying a vertically adjustable blade at the chosen depth relative to the reference surface by action of the hydraulic system on the blade, including the steps of:

implementing a calibration procedure, including determining a reference time interval relating to a travel time of an acoustic pulse from a first transducer to the reference surface and back to the first transducer, so that the the reference time interval corresponds to the chosen depth of the blade as determined by an operator of the earth grader;

emitting a ranging pulse from a second transducer toward the reference surface at a first time, the transducer being mounted in a fixed position relative to the blade, such that the ranging pulse reflects from the reference surface back toward the second transducer;

starting a counter at a second time which is a delay time after the first time;

a stopping the counter when the reflected ranging pulse reaches the second transducer, thereby generating a count corresponding to the length of time taken by the ranging pulse to reflect from the reference surface back to the second transducer and further corresponding to an actual blade depth;

vertically adjusting the blade by a distance relating to the count such that the actual blade depth corresponds to the chosen blade depth;

repeating the steps of emitting the ranging pulse, starting and stopping the counter, and vertically adjusting the blade, whereby variations in the height of the reference surface are automatically compensated by the adjustable of the blade as the grader moves along the reference surface; and

compensating the adjustments of the blade for temperature variations after the reference time interval has been determined, and before each time the ranging pulse is emitted.