as) United States
`a2) Patent Application Publication 0) Pub. No.: US 2002/0154948 Al
`
` Brabecet al. (43) Pub. Date: Oct. 24, 2002
`
`
`US 20020154948A1
`
`(54) AUTOMATIC MODE SELECTION IN A
`CONTROLLER FOR GRADING
`IMPLEMENTS
`
`(75)
`
`Inventors: Vernon J. Brabec, Livermore, CA
`(US); Wai Y. Chan, San Ramon, CA
`(US); Raymond O’Connor, Danville,
`CA (US)
`;
`TomesbondenceAddress
`open Maser Systery ane.
`37 West Century Road
`Paramus, NJ 07652 (US)
`
`(73) Assignee: TOPCON LASER SYSTEMS,INC.
`
`(21) Appl. No.:
`.
`(22)
`Filed:
`
`09/761,941
`Jan. 17, 2001
`Publication Classification
`
`CSL) Tt C0 eecccccceeecccssssssssnnsecceesnnnnnnseecsesnnnees EO1C 7/06
`
`(52) US. C0. eee ecsecssecssesseesnessnsenceasessrenssenssnscenseeses 404/75
`
`(57)
`
`ABSTRACT
`
`A method is disclosed for a controller to automatically
`switch to an alternative control modeto control the height of
`a grading implement whenthe output of a positioning sensor
`is not available. According to the invention, the controller
`recognizes sensor unavailability and automatically switches
`1
`.
`.
`d .
`LI
`to an a. ternative operating mode to maintain contro .
`In one
`alternative operating mode, the controller recognizes sensor
`unavailability and automatically routes the control signal
`from the unaffected side to the control channel for the
`affected side. In another alternative operating mode, the
`controller monitors the current value of an additional sensor
`for an alternative mode of control until one of the primary
`sensors becomes unavailable,
`and then automatically
`switches to the alternative mode for the affected side, using
`the last knownvalueforthe alternative modeas the set point.
`
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`US 2002/0154948 Al
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`Oct. 24, 2002 Sheet 1 of 3
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`Page 2 of 8
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`Patent Application Publication Oct. 24,2002 Sheet 2 of 3
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`US 2002/0154948 Al
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`Patent Application Publication Oct. 24,2002 Sheet 3 of 3
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`US 2002/0154948 Al
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`US 2002/0154948 Al
`
`Oct. 24, 2002
`
`AUTOMATIC MODE SELECTION INA
`CONTROLLER FOR GRADING IMPLEMENTS
`
`BACKGROUND OF THE INVENTION
`
`[0001]
`
`1. Field of the Invention
`
`[0002] This invention relates generally to machine control
`systemsthat control the orientation of a grading implement
`on a construction machine. Specifically, the invention is a
`method to automate the selection of various alternative
`operating modesof the controller to eliminate the need for
`manual operator intervention when a positioning sensor is
`inoperative.
`
`[0003]
`
`2. Description of the Relevant Art
`
`[0004] Current control systems used for controlling grad-
`ing implements for earth moving and the like may have
`several automatic operating modes using different position-
`ing sensors or control methods. In this case, an operator
`needs to select a single operating mode. This selection is
`done manually by the operator who determines when and
`what mode to select for automatic control. If the operator
`selects a mode that does not have a functioning sensor
`currently connected to the system or if a selected sensoris
`currently not providing data for control, the control system
`will switch from automatic mode to manual mode. When
`
`this happens, the operator must either manually switch the
`system to another automatic mode (which uses an active
`sensor) or somehow provide inputs to the controller that
`mimic the inactive sensor.
`
`[0005] For example, if the machine is set up to control
`height relative to a rotating laser reference plane, each end
`of the grading implement would have a laser receiver
`extending vertically on a mast. FIG. 1 shows a laser-
`controlled concrete screed as an example of such a system.
`The screed 10 is a grading implement that is moved by a
`boom 12 that extends outwardly from a base 16. Two masts
`14 havelaser receivers that sense a rotating laser used as a
`height reference. The laser receivers are connected to a
`control system that outputs control signals to hydraulic
`valves at each end of the screed. The receivers sense the
`vertical position of the laser beam and the control system
`uses this sensed position to control the elevation of the
`grading implementwith respect to the laser reference plane.
`
`If during movementof the machinea laser receiver
`[0006]
`moves to a position where the beam from the laser is
`blocked, the normal responseof the control system is to turn
`off the control outputs for the affected side. The laser
`receiver on the opposite side may have an unobstructed path
`to the laser and, if so, continues to operate in a normal
`manner. This may happen, for example, when the concrete
`screed is used inside a building and interior posts block the
`laser beam at certain positions.
`
`[0007] The effect of these periods of sensor blackout or
`unavailability on the final elevation of the grade depends on
`the movementof the implement during the blackout periods
`and the desired tolerance of the finished grade.
`If the
`uncontrolled movementof the implement during the black-
`out periods would result
`in a surface that exceeds the
`required finish tolerance,
`the operator must intervene to
`mitigate the problem. Aside from the present
`invention,
`there are two methods of operator intervention in this
`circumstance—open loop and closed loop.
`
`In an open-loop intervention, the operator must
`[0008]
`provide control signals to the controller for the affected side
`by using the manual controls for that side. The operator may
`accomplish this by manually controlling the elevation of the
`affected side by visually matching a previous pass. Or, the
`operator may attempt to manually input the same control
`signals as the unaffected side. This intervention is practical
`only if the control signals are simple on/off signals and are
`represented on a control display by lights or other easily
`identifiable indicators.
`
`the operator must
`In a closed-loop intervention,
`[0009]
`change the current mode of the control system from laser
`mode to an alternative control mode that uses a different
`
`sensor, such as a sonic elevation sensor or a slope sensor.
`The operator accomplishes this in a typical control system
`by putting the system in manual, switching the system to the
`alternative control mode, entering the current elevation or
`slope to initialize the new mode, and then re-enabling the
`system for automatic control. The operator must make these
`multiple inputs quickly or the implement may moveoutside
`of the required tolerance during the transition period.
`
`Thefinal grading finish depends on prompt opera-
`[0010]
`tor action and therefore may degrade if the operator is
`distracted or otherwise unable to intervene during a blackout
`period.
`
`SUMMARYOF THE INVENTION
`
`In summary, the present invention is a method for
`[0011]
`automatically switching to an alternative control mode when
`the output of a positioning sensor is not available. The
`present invention replaces manualintervention by the opera-
`tor with a new automatic method of intervention by the
`controller. According to the invention, the control system
`recognizes the periods of sensor blackout or unavailability
`and automatically switchesto an alternative operating mode
`to maintain control. The control system can make this
`decision based upon a predeterminedpriority for the avail-
`able sensors and control modes and can switch back to the
`
`most preferable mode available when the sensors are avail-
`able and operating.
`
`invention has two basic modes of
`[0012] The present
`operating, open loop and closed loop. In the open-loop
`mode,
`the controller recognizes the sensor blackout or
`unavailability on the affected side and automatically routes
`the control signal from the unaffected side to the control
`channel for the affected side. The controller continues this
`
`modeof operation until the affected sensor is available and
`valid again and then reinstates the original mode of opera-
`tion. Since the controller is rerouting the control signals, the
`signals can be more complex than simple on/off signals that
`manual intervention could handle. The resulting finish will
`be closer to the desired tolerance and the corrective move-
`
`ment of the implement will be less when the unavailable
`sensor signal is reacquired.
`
`the controller of the
`In the closed-loop mode,
`[0013]
`invention monitors the current value of an additional sensor
`
`for an alternative mode of control until one of the primary
`
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`US 2002/0154948 Al
`
`Oct. 24, 2002
`
`sensors loses its signal. The controller then automatically
`switches the mode for the affected side to the alternative
`
`mode, using the last known valuefor the alternative mode as
`the set point. The controller remains in this alternative mode
`until recovery from the blackout (sensor unavailability) and
`then switches back to the original mode.
`
`[0014] The features and advantages described in the speci-
`fication are not all inclusive, and particularly, many addi-
`tional features and advantages will be apparent to one of
`ordinary skill in the art in view of the drawings, specification
`and claims hereof. Moreover, it should be noted that the
`language used in the specification has been principally
`selected for readability and instructional purposes, and may
`not have been selected to delineate or circumscribe the
`
`inventive subject matter, resort to the claims being necessary
`to determine such inventive subject matter.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0015] FIG. 1 is a perspective view of a prior Somero
`S-160 laser screed, which is one possible platform for the
`present invention.
`
`[0016] FIG. 2 is a diagram of an open-loop mode of
`operation of the present invention under normal operating
`conditions.
`
`[0017] FIG. 3 is a diagram of the open-loop mode of
`operation of the present invention under a sensor-blackout
`condition.
`
`[0018] FIG. 4 is a diagram of a closed-loop mode of
`operation of the present invention under normal operating
`conditions.
`
`[0019] FIG. 5 is a diagram of the closed-loop mode of
`operation of the present invention under a sensor-blackout
`condition.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`[0020] The drawings depict various preferred embodi-
`ments of the present invention for purposes of illustration
`only. One skilled in the art will readily recognize from the
`following discussion that alternative embodiments of the
`structures and methodsillustrated herein may be employed
`without departing from the principles of the invention
`described herein. The description omits basic information
`about grading implement control systems, which a person of
`ordinary skill is presumed to know.
`
`[0021] The present invention is a method for automatically
`switching to an alternative control mode when the output of
`a positioning sensoris not available and switching back to
`a preferred control mode whenthe sensor becomesavailable
`again. According to the invention, the control system rec-
`ognizes periods of sensor unavailability, and then automati-
`cally switches to an alternative operating mode to maintain
`automatic control. The control system can makethis deci-
`sion based upon a predetermined priority for the available
`sensors and can switch back to the most preferable mode
`available when the associated sensors are available and
`
`operating. The present invention reduces the need for inter-
`vention by the operator to produce acceptable grading
`results.
`
`invention has two basic modes of
`[0022] The present
`operation, open loop and closed loop, as explained below.
`
`[0023] Open Loop
`
`In the open-loop mode,the controller of the inven-
`[0024]
`tion recognizes the sensor blackout or unavailability on the
`affected side and automatically routes the control signal
`from the unaffected sensor to the affected side. The control-
`ler continues this mode of operation until the affected sensor
`is available again. When the controller recognizes that both
`sensors are active, it reinstates the original mode of opera-
`tion. Since the controller is outputting the control signals,
`the signals can be more complex than the simple on/off
`controls required for manual open-loop intervention accord-
`ing to prior practice. For example,
`the control signals
`compatible with the invention may be proportional control
`signals instead of simple on/off signals. The resulting grad-
`ing finish will be closer to the desired tolerance and the
`corrective movementof the grading implement will be less
`when the unavailable sensor signal is reacquired.
`
`FIGS.2 and3 illustrate the open-loop mode of the
`[0025]
`invention with two sensors 20 and 22. The sensors 20 and 22
`
`may be laser receivers as described above, although other
`sensors, such as sonic distance sensors or contacting sensors
`or other position-sensing devices, could be used. FIG. 2
`shows the system in normal operation when both sensors 20
`and 22 generate output signals 24 and 26 that are input to a
`controller 28. The controller 28 outputs left and right control
`signals 30 and 32 that cause hydraulic cylinders 34 and 36
`(or other motive devices) to raise or lower the grading
`implement.
`
`In normal operating mode, the controller 28 con-
`[0026]
`trols the height of the left side of the implement according
`to the output of the left sensor 20. The left sensor 20 supplies
`its output signal 24 to the controller 28, which generates the
`control signal 30 and supplies it to the left-side hydraulic
`cylinder 34 to cause the left side of the grading implement
`to be raised or lowered to reduce any deviation from a
`desired set point.
`
`[0027] Similarly, the controller 28 controls the height of
`the right side of the implement according to the output of the
`right sensor 22 in normal operating mode. The right side
`sensor 22 supplies its output signal 26 to the controller 28,
`which generates the control signal 32 and supplies it to the
`right-side hydraulic cylinder 36 to cause the right side ofthe
`grading implement to be raised or lowered to reduce any
`deviation from the set point.
`
`[0028] Arrows 38 and 40 indicate that this is a closed-loop
`controller for each side of the grading implement. The
`hydraulic cylinders 34 and 36 respond to the controller by
`moving the implement up or down. The up and down
`movement of the implement is detected by the sensors 20
`and 22 and fed back to the controller 28.
`
`FIG.3 illustrates the method of the present inven-
`[0029]
`tion when the right sensor 22 is blocked or otherwise
`unavailable and does not output a valid signal. The sensors
`20 and 22 and the controller 28 are in constant communi-
`cation because the controller periodically samples the status
`and outputof the sensors. In the preferred embodiment, each
`sensor has a vertically-disposed linear array of laser detec-
`tors, with the center being the set point. The positioning
`error is determined by which detector in the linear array
`
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`

`US 2002/0154948 Al
`
`Oct. 24, 2002
`
`detects the laser and howfarit is from the centerof the array.
`The laser beam that provides the reference plane is a rotating
`laser that rotates at least five revolutions per second. This
`means that the sensor expects to detect the laser every 200
`milliseconds. If more than 200 milliseconds elapses, then the
`sensor assumesthat the laser light is blocked and signals the
`controller 28 accordingly. This is accomplished by a 250
`millisecond timer, which is reset by each detected laser
`strike.
`
`Ifthe timer in the right sensor 22 times out, then the
`[0030]
`sensor signals the controller 28 that no laser is detected. In
`that case, the output signal 24 of the left sensor 20 is used
`by the controller 28 to control both sides of the implement.
`The controller 28 uses the valid output signal 24 to generate
`both control signals 30 and 32. The left side feedback path
`38 is still intact, but the right side is operating open loop
`because the right sensor is temporarily inoperative.
`
`[0031] When the right sensor 22 reacquires the laser and
`outputs a valid signal 26, the controller 28 switches back to
`the normal mode shown in FIG. 2. The controller 28
`
`continuously monitors the status of the sensors 20 and 22, so
`when the right sensor 22 signals the controller that it has
`detected the laser,
`the controller switches to the normal
`mode.
`
`If the left sensor signal 24 is unavailable or invalid
`[0032]
`but the right sensor signal 26 is available, then the controller
`28 uses the right sensor signal to control the elevation of
`both left and right sides of the grading implement.
`
`[0033] Closed Loop
`
`In the closed loop mode of the present invention,
`[0034]
`there is an additional sensor and associated control circuitry
`providing an alternative control mode that is used as a
`backup when a primary sensor is blocked or otherwise
`unavailable. The controller of the invention monitors the
`
`current value of the alternative control mode until a primary
`sensor is blocked or otherwise unavailable and loses its
`signal. The controller then automatically switches to the
`alternative control modefor the affected side, using the last
`knownoutput of the alternative sensor as the set point. This
`maintains the position of the affected side of the grading
`implement during the period in which the primary sensoris
`unavailable. The controller remains in this alternative mode
`
`until the primary sensor is available again, and then switches
`back to the original mode.
`
`[0035] The operation of the closed-loop mode of the
`invention is illustrated in FIGS. 4 and 5. FIG. 4 showsthe
`
`control system in normal operation, where both primary
`sensors 20, 22 generate output signals 24, 26 and the
`controller 28 and cylinders 34 and 36 control the height of
`the right side of the implement accordingto the right sensor
`and controls the height of the left side of the implement
`according to the left sensor. The output 44 of an alternate
`sensor 42 is also monitored and temporarily stored by the
`controller 28. The primary sensors 20 and 22 maybe, for
`example, two laser receivers and the alternate sensor 42 may
`be a slope sensor or an ultrasonic distance sensor.
`
`[0036] FIG. 5 illustrates what happens in the present
`invention whenthe right sensor 22 is blocked or otherwise
`unavailable and does not output a valid signal. In that case,
`the controller 28 uses the output 44 of the alternate sensor 42
`to control the right side of the implement. The last signal
`
`output by the alternate sensor 42 prior to the right sensor 22
`becoming unavailable is used as a set point for the right
`channel of the controller 28. The controller 28 generates a
`control signal 32 to raise or lower the right side of the
`grading implement to minimize the deviation from that set
`point. In other words,the alternate sensor 42 is used to keep
`the right side in the same position or attitude as it was in
`whenthe primary sensor 22 became blocked. The movement
`of the implement affects the alternate sensor 42, thus pro-
`viding a feedback path 46 and closed-loop control of the
`implement height.
`
`[0037] When the unavailable sensor signal 26 is reac-
`quired, the control system shifts back to its normal mode, as
`shown in FIG. 4. The description above assumes that the
`right sensor is unavailable, but the closed-loop mode of the
`present
`invention also operates when the left sensor is
`unavailable.
`
`[0038] One preferred embodimentof the present invention
`includes laser receivers as the primary sensors 20 and 22,
`and a slope sensor as the alternate sensor 42. When one of
`the laser receivers is blocked, then the controller 28 auto-
`matically switches to a mode where the slope sensoris used
`to generate the control output for the affected side. The
`controller 28 uses the last signal output by the slope sensor
`prior to the blockage as the set point. The control system
`controls the height of the affected side to maintain the same
`slope of the implement as when the blockage occurred.
`Whenthe blocked laser receiver becomes available again,
`operation reverts to both laser receivers and the slope sensor
`reverts to its backup role.
`
`[0039] Both the open- and closed-loop modes of the
`present invention can be available in the controller 28 at the
`same time. The controller 28 selects the appropriate mode
`based upon a predetermined priority set by the operator.
`
`[0040] Furthermore, there may be more than onealternate
`sensor for the closed-loop mode, and a selection priority
`amongthe alternative sensors can be set by the operator.If
`the quality of the signal is available in a form other than
`on/off, e.g., a proportional control signal, then the controller
`28 can select between the alternate sensors based on a user
`entered threshold level.
`
`[0041] The sensors and associated control systemsare not
`intended to be limited to just the examples presented above,
`unless so specified in the claims. The primary sensors could
`be laser receivers as discussed above, but they also could be
`other sensors such as sonic distance sensors or GPS (global
`positioning satellite). Furthermore,
`the alternate sensors
`used in the closed-loop mode can be sonic distance sensors,
`slope sensors, accelerometers or inertial platforms,
`laser
`receivers, GPS, or a variety of contact sensors.
`
`[0042] From the above description, it will be apparentthat
`the invention disclosed herein provides a novel and advan-
`tageous method for grading-implementcontrollers that auto-
`matically switches to an alternative control mode when the
`output of a positioning sensoris not available. The foregoing
`discussion discloses and describes merely exemplary meth-
`ods and embodiments of the present invention. As will be
`understood by those familiar with the art, the invention may
`be embodied in other specific forms without departing from
`the spirit or essential characteristics thereof. Accordingly,
`the disclosure of the present invention is intended to be
`
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`US 2002/0154948 Al
`
`Oct. 24, 2002
`
`illustrative, but not limiting, of the scope of the invention,
`whichis set forth in the following claims.
`Whatis claimedis:
`1. A method for operating a controller for controlling the
`height of a grading implement, comprising the steps of:
`
`providing a left sensor that outputs a left-side output
`signal indicative of the height of the left side of the
`grading implement;
`
`providing a right sensor that outputs a right-side output
`signal indicative of the height of the right side of the
`grading implement;
`
`providing a controller that is responsive to the left-side
`output signal for controlling the heightof a left side of
`the grading implement and is responsive to the right-
`side output signal for controlling the height of a right
`side of the grading implement;
`
`the height of the
`operating the controller to control
`grading implement by responding to the left-side and
`right-side output signals when both are available; and
`
`if the left-side or right-side output signal is unavailable,
`then automatically using an alternative sensor to con-
`trol the height of the grading implementonthe side of
`the unavailable output signal.
`2. A method as recited in claim 1 wherein the step of
`automatically using an alternative sensor includes using the
`right-side output signal to control both sides of the grading
`implementif the left-side output signal is unavailable, and
`using the left-side output signal to control both sides of the
`grading implementif the nght-side output signal is unavail-
`able.
`
`3. A method as recited in claim 1 wherein the step of
`automatically using an alternative sensor includes using an
`output signal of a third sensor to control the side of the
`grading implement having an unavailable output signal.
`4. Amethodasrecited in claim 3 further including a step
`of monitoring the output signal of the third sensor while the
`left-side and right-side output signals are available, and
`using the last monitored value of the output signal of the
`third sensor as a set point when the left-side or right-side
`output signal becomes unavailable.
`5. A methodas recited in claim 3 wherein the third sensor
`
`is a slope sensor.
`6. Amethod asrecited in claim 3 wherein the third sensor
`is a distance sensor.
`
`7. Amethodasrecited in claim 1 further comprising a step
`of ceasing to use the alternative sensor when the unavailable
`output signal becomes available again.
`8. Amethodasrecited in claim 1 whereinthe left and right
`sensors are laser receivers.
`
`9. A method as recited in claim 1 wherein the grading
`implement is a concrete screed.
`10. Amethod for operating a controller for controlling the
`height of a grading implement, comprising the steps of:
`
`providing a left sensor that outputs a left-side output
`signal indicative of the height of the left side of the
`grading implement;
`
`providing a right sensor that outputs a right-side output
`signal indicative of the height of the right side of the
`grading implement;
`
`providing a controller that is responsive to the left-side
`output signal for controlling the heightof a left side of
`the grading implement and is responsive to the right-
`side output signal for controlling the height of a right
`side of the grading implement;
`
`the height of the
`operating the controller to control
`grading implement by responding to the left-side and
`right-side output signals when both are available;
`
`if the left-side output signal is unavailable, then automati-
`cally using the right-side output signal to control both
`sides of the height of the grading implement; and
`
`if the right-side output signal is unavailable, then auto-
`matically using the left-side output signal to control
`both sides of the height of the grading implement.
`11. A methodfor operating a controller for controlling the
`height of a grading implement, comprising the steps of:
`
`providing a left sensor that outputs a left-side output
`signal indicative of the height of the left side of the
`grading implement;
`
`providing a right sensor that outputs a right-side output
`signal indicative of the height of the right side of the
`grading implement;
`
`providing a controller that is responsive to the left-side
`output signal for controlling the heightof a left side of
`the grading implement and is responsive to the right-
`side output signal for controlling the height of a right
`side of the grading implement;
`
`the height of the
`operating the controller to control
`grading implement by responding to the left-side and
`right-side output signals when both are available; and
`
`if the left-side or right-side output signal is unavailable,
`then automatically using an output signal of a third
`sensor to control the side of the grading implement
`having an unavailable output signal.
`*
`*
`*
`*
`*
`
`Page 8 of 8
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