- Top of Page
The present disclosure relates to a load estimator and, more particularly, to a load estimator for a scraper.
A scraper is a mobile construction machine used for transporting material over short distances. The scraper generally consists of a tractor that tows a vertically movable hopper known as a bowl over a ground surface. A horizontal blade is connected to a leading lower edge of the bowl such that, when the tractor tows the bowl forward and the bowl is lowered, the horizontal blade cuts into the ground surface and fills the bowl with excavated material. After the bowl is loaded to capacity, the bowl is raised away from the ground surface and closed at the leading edge by a vertical blade known as an apron. The scraper then transports its load to a dump area where the apron is raised and an ejector located at a back end of the bowl pushes the load forward out of the bowl. The cycle is then repeated until a desired amount of material has been moved.
During operation of the scraper, it can be important to keep track of the amount of material moved by the scraper. For example, the amount of material moved by the scraper (i.e., the weight of the material, also known as the payload weight or the load) during each excavation cycle may be used in determining productivity of the scraper or of a particular scraper operator. In another example, the payload of the scraper may aid in determining completion of a project, billing of a particular customer, and/or scheduling of the scraper. Historically, the amount of material moved by a scraper was determined based directly on measured pressures of hydraulic rams or cylinders associated with the scraper's bowl. Unfortunately, this method of estimating loading of the scraper was prone to error, as the pressures can fluctuate significantly during different operations of the scraper. For example, during loading when the horizontal blade is engaged with the ground surface, fluid pressures within the hydraulic cylinders can be much higher than when the blade is away from the ground surface, even though the payload of the scraper may not have changed.
One attempt to improve payload estimation of a scraper is disclosed in U.S. Pat. No. 3,154,160 of Rockwell et al. that issued on Oct. 27, 1962 (“the '160 patent”). Specifically, the '160 patent discloses a device for indicating to an operator the weight of a load carried by a wheeled scraper. The load indicating device is responsive to hydraulic pressure in a load carrying ram of the scraper. The load indicating device is operative only when front and rear units of the scraper are pivoted to their raised travel positions and a valve for controlling the ram is in a neutral or hold position. With this configuration, false readings may be prevented by inhibiting load measuring during engagement of the scraper with a ground surface.
While the load indicating device of the '160 patent may help to improve payload estimating in some situations, the device may still be less than optimal. Specifically, there may be situations where the front and rear units are not fully raised before travel of the scraper and, in these situations, the load indicating device may be inhibited from estimating the load. Further, the '160 patent describes no way to calibrate the load indicating device, without which measurement accuracy may degrade over time. In addition, the load indicating device is a purely mechanical device and provides no display flexibility, recording functionality, accumulation tabulation functionality, or communication ability.
The present disclosure is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.
- Top of Page
In one aspect, the present disclosure is directed to a load estimator for a scraper. The load estimator may include a first sensor configured to generate a first signal indicative of a performance parameter of the scraper, a second sensor configured to generate a second signal indicative of a hydraulic pressure associated with a bowl of the scraper, and a controller in communication with the first and second sensors. The controller may be configured to classify a current segment of an ongoing work cycle based on the first signal. The controller may also be configured to selectively estimate a load of material contained with the bowl of the scraper based on the second signal only when the current segment is a segment wherein the load can be reliably estimated.
In another aspect, the present disclosure is directed to a method of estimating a load for a scraper. The method may include sensing a performance parameter of the scraper and sensing a hydraulic pressure associated with a bowl of the scraper. The method may also include classifying a current segment of an ongoing work cycle based on the performance parameter, and selectively estimating a load of material contained within the bowl of the scraper based on the hydraulic pressure only when the current segment is classified as a segment where the load can be reliably estimated.
BRIEF DESCRIPTION OF THE DRAWINGS
- Top of Page
FIG. 1 is a pictorial illustration of an exemplary disclosed machine;
FIG. 2 is a diagrammatic illustration of an exemplary disclosed load estimator that may be used with the machine of FIG. 1; and
FIG. 3 is a flowchart depicting an exemplary disclosed method of estimating payload for the machine of FIG. 1.
- Top of Page
FIG. 1 illustrates an exemplary earth-moving machine 10. Machine 10 may be a wheeled tractor scraper configured to load material at a first location, transport the material from the first location to a second location, and unload the material at the second location. Although commonly referred to as a “wheeled” tractor scraper, it is contemplated that machine 10 may be propelled by way of wheels, continuous tracks, and/or belts, as desired. Machine 10 may include a tractor 12 operatively connected to a bowl portion 14 and configured to tow bowl portion 14 across a ground surface 16.
Tractor 12 may include multiple components that interact to power and control operations of bowl portion 14. Specifically, tractor 12 may include a frame 18, a front axle assembly 20, a power source 22, an articulated hitch assembly 24, and an operator station 26. Frame 18 may be connected to front axle assembly 20 and configured to support power source 22. Power source 22 may include, for example, a combustion engine 28 that drives front axle assembly 20 via a transmission 30 and/or provides electrical and hydraulic power to bowl portion 14. Transmission 30 may embody an electric transmission, a hydraulic transmission, a mechanical transmission, or a hybrid transmission having a reverse gear ratio and one or more selectable forward gear ratios. Articulated hitch assembly 24 may connect tractor 12 to bowl portion 14, while allowing some relative movement between tractor 12 and bowl portion 14 in both vertical and horizontal directions. Operator station 26 may facilitate control of tractor 12 and bowl portion 14.
Articulated hitch assembly 24 may include a curved main beam 32 having a front end 34 and a back end 36. Front end 34 of beam 32 may be connected through a vertical hinge joint 38 and a horizontal hinge joint 40 to frame 18 such that beam 32 may pivot both in the horizontal direction and in the vertical direction relative to frame 18. A cushion actuator 42, for example a hydraulic cylinder, may be associated with horizontal hinge joint 40 to provide for selective isolation of operator station 26 from vertical movements of bowl portion 14. Cushion actuator 42, together with horizontal hinge joint 40, may form what is known as a cushion hitch 45. Cushion hitch 45 may be hydraulically locked during some modes of operations such that beam 32 is inhibited from moving in the vertical direction relative to frame 18, and unlocked during other modes of operations to allow beam 32 and bowl portion 14 to float in the vertical direction relative to frame 18.
Back end 36 of beam 32 may be connected to bowl portion 14 via a pair of arms 46 located at opposing sides of beam 32 (only one side shown in FIG. 1). Each arm 46 may include a first end 48 and a second end 50. First end 48 may be pivotally connected to back end 36 of beam 32 via a first pin 52, while second end 50 may be connected to bowl portion 14 via a second pin 54. A pair of bowl actuators 56, for example hydraulic cylinders, may be connected between beam 32 at back end 36 and bowl portion 14, and configured to selectively raise bowl portion 14 away from ground surface 16 and lower bowl portion 14 toward ground surface 16 by retractions and extensions thereof, respectively.
Operator station 26 may include one or more interface devices 58 located proximal an operator seat and configured to generate control signals and/or present displays associated with operation of machine 10. In one example, interface device 58 may be used to display information regarding operation of machine 10, for example payload information, as will be described in more detail below.
Bowl portion 14 may include a bowl 60 connected to and supported by a rear axle assembly 62. During extension and retraction of bowl actuators 56, bowl 60 may be caused to pivot in the vertical direction about rear axle assembly 62 such that a leading or front end 64 of bowl 60 may be raised and lowered relative to ground surface 16. In some embodiments, an additional power source 66 may be contained within bowl portion 14 and supported by rear axle assembly 62. In these embodiments, power source 66 may be operated to drive rear axle assembly 62 and thereby push machine 10 across ground surface 16.
Bowl 60 may be a tool embodied as a generally hollow enclosure having an opening 68 at front end 64. A horizontal blade 70 may be located at front end 64 and positioned to selectively engage ground surface 16 as front end 64 is lowered by the extension of bowl actuators 56. In this configuration, an extension length of bowl actuators 56 may affect a depth of blade 70 into ground surface 16 and, in conjunction with a travel speed of machine 10, a rate of material removal from ground surface 16. Similarly, a pressure of fluid within bowl actuators 56 may reflect a force generated by a load contained within bowl 60.
In one embodiment, bowl portion 14 may also include an apron 72 configured to close off opening 68 of bowl 60. Apron 72 may embody a tool member that is pivotally connected to bowl 60 at a first end 74 and free to move at a second end 76 in a fore/aft machine direction relative to bowl 60. An apron actuator 78 may be connected to a front side of apron 72 (i.e., to an outside of apron 72 relative to bowl 60) and configured to selectively pull apron 72 forward to pivot from a closed position to an open position, and push apron 72 backward to pivot from the open position to the closed position. In one embodiment, apron actuator 78 may include an arm 80 pivotally connected at a first end 82 to beam 32, a rod 84 pivotally connected between a second end 86 of arm 80 and the front side of apron 72, and a hydraulic cylinder 88 connected between beam 32 and arm 80. An extension of hydraulic cylinder 88 may function to push second end 86 of arm 80 up away from beam 32, while a retraction of hydraulic cylinder 88 may function to pull second end 86 down toward beam 32. The upward movement of second end 86 of arm 80 may pull rod 84 up and cause apron 72 to pivot forward away from bowl 60 and expose opening 68. The downward movement of second end 86 may push rod 84 down and cause apron 72 to pivot backward toward bowl 60 and close off opening 68. It should be noted that, in other embodiments, machine 10 may be equipped with an elevator (not shown) instead of apron 72. In these embodiments, the elevator may function to move material entering opening 68 of bowl 60 rearward and upward away from opening 68.
Bowl portion 14 may be provided with an ejector 90 configured to selectively push material accumulated within bowl 60 out through opening 68 when apron 72 has been pulled up by hydraulic cylinder 88. Ejector 90 may include an ejector plate 92, and an ejector cylinder 94 connected between ejector plate 92 and a frame member (not shown) of bowl portion 14. Ejector plate 92 may be moved by ejector cylinder 94 from a full retract position at a back end 95 of bowl 60 (shown in FIG. 1) toward a full dump position at front end 64 of bowl 60. When ejector plate 92 is away from the full dump position, material may be loaded into bowl 60 via opening 68 and/or transported within bowl 60. When ejector plate 92 is moved toward the full dump position, material accumulated within bowl 60 may be pushed out of opening 68. Ejector cylinder 94 may be selectively provided with and drained of pressurized fluid to cause ejector cylinder 94 to retract and extend, thereby moving ejector plate 92.
As shown in FIG. 2, bowl actuators 56 may be equipped with one or more pressure sensors 96 configured to sense hydraulic pressures of fluid within one or more different chambers of bowl actuators 56 (e.g., a pressure sensor 96 disposed within or otherwise fluidly connected to each pressure chamber of bowl actuators 56) and to generate corresponding signals. The signals generated by pressure sensors 96 may be indicative of forces acting on bowl 60. When bowl 60 is engaged with ground surface 16, the forces may be generated by bowl actuators 56 pushing blade 70 into ground surface 16 and ground surface 16 resisting the motion. When bowl 60 is away from ground surface 16 (i.e., not engaged with ground surface 16), the forces may be generated by a weight of material captured within bowl 60 (i.e., the payload of machine 10). Values of the signals generated by pressure sensors 96 may be directed to a controller 98.
Controller 98, together with pressure sensor 96 and other components of machine 10, may form a load estimator 102 configured to detect performance parameters of machine 10 and the forces acting on bowl 60, and responsively estimate the weight of material loaded into bowl 60 of machine 10 (i.e., the payload of machine 10). The performance parameters detected by load estimator 102 can include any type of parameter associated with any one or more components of machine 10 that are described above. In the disclosed embodiment, these components include transmission 30, cushion hitch 45, apron 72, and ejector 90. It is contemplated, however, that other components may additionally or alternatively be used in determining the payload of machine 10, if desired, for example the elevator described above (not shown). Controller 98 may communicate directly with some or all of these components and/or indirectly with these components, for example via one or more sensors 100, to detect the performance parameters. The performance parameters may include, among other things, a travel speed and/or location (e.g., GPS location or location relative to designated dig and dump locations) of machine 10, a selected gear ratio of transmission 30, a condition of cushion hitch 45 (e.g., locked or unlocked status, position, pressure, etc.), a condition of apron 72 (e.g., opened, closed, position, pressure, etc.), a condition of ejector 90 (e.g., retracted, extended, position, pressure, etc.), a condition of the elevator (e.g., position and/or pressure), and/or a condition of bowl actuators 56 (e.g., position and/or pressure). As will be described in more detail below, controller 98, based on the signal(s) from sensor(s) 100, may classify a current segment of an ongoing excavation cycle being performed by machine 10 as one of a plurality of known segments. In the disclosed embodiment, the known segments include a dig segment (e.g., a segment during which bowl 60 is being loaded with material), a carry segment (e.g., a segment during which bowl 60 is full of material, bowl 60 is not engaged with ground surface 16, and machine 10 is traveling), a dump segment (e.g., a segment during which bowl 60 is actively being emptied of material), and a return segment (e.g., a segment during which bowl 60 is empty of material, bowl 60 is not engaged with ground surface 16, and machine 10 is traveling). It is contemplated that other classifications may also or alternatively be utilized, if desired. And based on the classification and the signal from sensor(s) 96, controller 98 may be configured to selectively estimate the load carried by bowl 60.
Controller 98 may include any components or combination of components for monitoring, recording, storing, indexing, processing, conditioning, and/or communicating operational aspects of machine 10 described above. These components may include, for example, a memory, one or more data storage devices, a central processing unit, or any other components that may be used to run an application. Furthermore, although aspects of the present disclosure may be described generally as being stored in memory, one skilled in the art will appreciate that these aspects can be stored on or read from types of computer program products or computer-readable media, such as computer chips and secondary storage devices, including hard disks, floppy disks, optical media, CD-ROM, or other forms of RAM or ROM. Controller 98 may execute sequences of computer program instructions stored on the computer readable media to perform a method of load estimating that will be explained below.
In some embodiments, controller 98 may communicate information relating to performance of machine 10 and/or an operator of machine 10 to an offboard entity. Communication between controller 98 and the offboard entity may be facilitated via a communication device 104 located onboard each machine 10 (e.g., within operator station 26). This information may include, for example, the load estimated to be carried by machine 10, a linked identity of machine 10, a linked identity of the operator of machine 10, a machine location, a cycle count for machine 10, and other similar pieces of information. Data messages associated with load estimator 102 may be sent and received via a direct data link and/or a wireless communication link, as desired. The direct data link may include an Ethernet connection, a connected area network (CAN), or another data link known in the art. The wireless communications may include satellite, cellular, infrared, and any other type of wireless communications that enable communication device 104 to exchange information between controller 98 and the offboard entity.
FIG. 3 illustrates an exemplary method stored as instructions on the computer readable medium that are executable by controller 98 to perform load estimating for machine 10. FIG. 3 will be discussed in more detail in the following section to further illustrate the disclosed concepts.
The disclosed load estimator may be applicable to any type of scraper that is configured to dig, transport, and dump material in a known repeatable excavation cycle. The disclosed load estimator may provide for accurate and reliable estimating of payloads in an autonomous manner. Operation of load estimator 102 will now be explained with respect to FIG. 3.
As shown in FIG. 3, the method may begin by controller 98 measuring one or more pressures of hydraulic fluid associated with bowl 60 (e.g., the pressures within opposing chambers of bowl actuators 56 and/or cushion actuator 42—Step 300). The pressures may be measured by way of pressure sensors 96. These pressures may then be used by controller 98 to selectively calculate a force acting on the corresponding actuator(s) and the payload of machine 10 (Step 305). Calculation of this force may be accomplished utilizing well-known equations based on the sensed pressures and known effective hydraulic areas within the corresponding actuator(s). In the disclosed embodiment, the payload may be determined utilizing a lookup chart, algorithm, and/or equation stored in the memory of controller 98 that directly relates the force (or alternatively the pressure) to a weight value of the load.
Controller 98 may then receive and/or detect any number of different performance parameters of machine 10 (Step 310). As described above, these performance parameters may include, among other things, a travel speed and/or location, a selected gear ratio, a cushion hitch condition, an apron condition, an ejector condition, an elevator condition, a bowl actuator condition, or another condition known in the art. The parameter(s) may be received directly from the corresponding component or detected via one or more sensors 100 associated with the component. Although shown as the third step in the flowchart of FIG. 3, it is contemplated that step 310 may be completed before steps 300 and/or 305, simultaneous with steps 300 and/or 305, and/or continuously throughout operation of machine 10, as desired.
Controller 98 may be configured to classify a current operation of machine 10 as one of a plurality of known segments of a repeatable and ongoing excavation cycle (Step 315). As described above, exemplary known segments generally include the dig segment, the carry segment, the dump segment, and the return segment. Controller 98 may classify the current operation based on any one or more of the performance parameters received/detected in step 310 described above.
For example, when ejector 90 is at a full dump position (all the way forward in bowl 60), bowl 60 of machine 10 may most likely be empty and dumping may have already occurred. Accordingly, when ejector 90 is detected as being at the full dump position, controller 98 may classify the current operation as the return segment of the excavation cycle, during which machine 10 is traveling back to a dig location after having dumped its load. In contrast, when ejector 90 is away from the full dump position (i.e., at the full retract position all the way rearward in bowl 60), machine 10 could be loaded and controller 98 may classify the current operation as the carry segment of the excavation cycle, during which machine 10 is traveling away from the dig location after having acquired its load.
In another example, when cushion hitch 45 is detected as being in the locked mode of operation, machine 10 could still be digging. In this situation, controller 98 may classify the current operation as the dig segment. However, when cushion hitch 45 is in the float mode of operation, machine 10 is likely to have completed or be in the process of completing the carry segment of the excavation cycle and controller 98 may classify the current operation accordingly.
In yet another example, when transmission 30 is in a high-speed gear, machine 10 may be traveling or has traveled above a minimum speed to move from a dig location to a dump location. In this situation, controller 98 may be configured to classify the current operation as one of the carry or return segments. In some embodiments, controller 98 may classify the current operation based on any combination of these and/or other performance parameters.
After classifying the current operation, controller 98 may determine if the classified operation is a particular segment of the excavation cycle (e.g., the carry segment, where the load can be reliably estimated) and respond accordingly (Step 320). For example, when controller 98 determines that the current operation is not classified as the carry segment (Step 320: NO), control may return to step 300. However, when the current operation is classified as the carry segment (Step 320:YES), control may proceed to step 325, where the payload signal (i.e., the calculation of the instantaneous payload of machine 10) may be processed (e.g., filtered and averaged relative to other calculations performed during the same segment of the same excavation cycle). This processing may help to improve accuracy in the payload value.
Controller 98 may then determine if the carry segment has been completed (Step 330). This determination may be made in many different ways. In the disclosed embodiment, controller 98 may determine that the carry segment has been completed by determining that the dump segment has been initiated. In other embodiments, however, controller 98 may conclude that the carry segment has been completed based on a travel speed, a bowl actuator position, an apron condition, an elevator condition, or in another manner known in the art. Control may cycle through steps 300-330 until controller 98 determines that the carry segment has been completed.
When controller 98 determines that the carry segment has been completed (Step 330:YES), the filtered and averaged payload signal may then be reported (Step 335). This reporting may include, among other things, display of a representation of the payload signal within operator station 26 via interface device 58. This representation may take any form known in the art (e.g., a numerical value, a percent of a desired load, a picture, a bar graph, etc.), and may provide information to the operator regarding a current load being transported by machine 10, a highest load transported within a particular time period (e.g., during a shift or a lifetime of machine 10), and/or a running total of material weight transported within the particular period of time. Controller 98 may tabulate the running total by tracking completion of cycles during the time period and adding the load estimation for each cycle. The operator of machine 10 may then use the information displayed on interface device 58 to improve operation throughout the time period, to diagnose problems with machine 10, to bill a particular customer, to track progress in completion of an assigned task, and/or for other purposes.
In some embodiments, controller 98 may also be configured to transmit the payload signal to an offboard entity for further processing. For example, the information may be transmitted via communication device 104 to a worksite manager located remotely from machine 10. The worksite manager may then use the information for similar purposes described above.
After reporting of the machine payload value, controller 98 may continue to monitor machine operation and determine when the ensuing dump segment has been completed (Step 340). Control may cycle through step 340 until the dump segment has been completed. Once controller 98 determines that the dump segment has been completed, controller 98 may then selectively implement calibration of load estimator 102 (Step 345). It is contemplated that the calibration procedure may be implemented after completion of every dump segment, after a certain amount of time has elapsed, after a particular amount of material has been moved, after completion of a desired number of excavation cycles, or according to another strategy known in the art.
The calibration procedure may be implemented after completion of the dump segment (e.g., during the return segment) because bowl 60 should be relatively empty at that point in time and because the motion of bowl actuators 56 should be relatively stable. For example, bowl 60 should not engage ground surface 16 during the return segment and bowl actuators 56 should be stationary. Thus, the pressures of hydraulic fluid within bowl actuators 56 should accurately reflect a known empty weight of bowl 60 (and other components normally supported by bowl actuators 56). Accordingly, the pressures measured during the return segment of the excavation cycle should be relatively consistent throughout time, and controller 98 may be configured to determine adjustment factors based on any changes in the pressures detected between different return segments. These adjustment factors may then be applied to future payload estimations to help ensure accuracy of the process.
Because load estimator 102 may implement payload estimations during only a particular segment of the excavation cycle of machine 10, accuracy in the estimations may be high. Further, because load estimator 102 may use many different criteria for classifying the current segment, there may be more opportunity to estimate the payload of machine 10 without incurring error in the process. Further, because load estimator 102 may be capable of calibration during every excavation cycle, accuracy may be ensured throughout the useful life of machine 10. Finally, the ability to display different aspects of machine payload within operator station 26 and or at a remote offboard location may improve use of the information and productivity of machine 10.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed load estimator. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed load estimator. For example, it is contemplated that fluid pressures associated with cushion hitch 45 could additionally or alternatively be used to determine the payload of machine 10, if desired. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.