Track speed compensation for engine speed droop

A system and method for compensating reduced track speed because of engine droop for a work machine is disclosed. The system may comprise a frame, an attachment coupled to the frame, a ground-engaging mechanism adapted to support the frame, an engine, a motor, a track speed sensor, an engine speed sensor, and a controller. The engine may drive the ground-engaging mechanism and attachment. The engine may be coupled through a variable speed transmission to the ground-engaging mechanism and the attachment. They variable speed transmission may include a hydrostatic circuit. The controller may be adapted to send an increased transmission command signal based on a drop in the engine speed signal when the work machine engages an increased load. The increased transmission command signal may increase a motor speed to cause an increase in track speed to compensate at least a portion of the reduced track speed from the engine speed droop.

CROSS-REFERENCE TO RELATED APPLICATIONS

FIELD OF THE DISCLOSURE

The present disclosure relates to a work machine and method for track speed compensation for engine speed droop.

BACKGROUND

In the construction industry (and others), various work machines are operated to perform various tasks at a work site. For example, crawler dozers (hereafter “dozers”), motor graders, and other bladed vehicles are well-suited for spreading, shearing, carrying, and otherwise moving relatively large volumes of earth. Typically, on the work machine, the transmission ratio is held constant during initial engagement with a load. Thereby an increase in load may cause a droop in engine speed. This droop in engine speed may generate a relatively jerky experience for the operator as the engine speed “catches up” to meet load demand. Therein lies a need for a smoother transition during changes in load.

SUMMARY

This summary is provided to introduce a selection of concepts that are further described below in the detailed description and accompanying drawings. This summary is not intended to identify key or essential features of the appended claims, nor is it intended to be used as an aid in determining the scope of the appended claims.

The present disclosure includes an apparatus and system which allows for a work machine to meet increases in load for work machine to compensate for a loss in speed for the ground-engaging mechanism.

According to an aspect of the present disclosure, a system for compensating reduced track speed because of an engine speed droop for work machine is disclosed. The system may comprise of a frame, an attachment coupled to the frame, a ground-engaging mechanism adapted to support the frame, an engine, a motor, a track speed sensor, an engine speed sensor, and a controller. The engine may drive the ground-engaging mechanism and the attachment. The engine may be coupled through a variable speed transmission to the ground-engaging mechanism and the attachment. The variable speed transmission may include a hydrostatic circuit. The hydrostatic circuit may include a pump. The motor may be adapted to further drive the ground-engaging mechanism. The track speed sensor may be adapted to detect a track speed of the ground-engaging mechanism and generate a track speed signal. The engine speed sensor may be adapted to detect an engine speed and generate an engine speed signal. A controller may be adapted to send an increased transmission command signal based on a drop in the engine speed signal when the work machine engages an increased load. The increased transmission command signal may increase a motor speed to cause an increase in track speed to compensate at least a portion of the reduced track speed from the engine speed droop.

The increased transmission command signal may cause one or more of an increase in pump flow and a decrease in motor displacement.

The system may further comprise an operator interface control adapted to receive an operator input. The operator input may include a multiplicative factor for one or more of the increased transmission command signal and a target track speed based on the drop in the engine speed signal. The multiplicative factor may comprise a first setting, a second setting, and third setting. The first setting may include an off position. The second setting may include a multiplicative factor of 1:1. The third setting may include a multiplicative factor of X:1. The multiplicative factor of X may be predefined.

The drop in the engine speed signal may be identified by an inflection point in a torque-engine speed curve.

The increased transmission command signal may be based on the engine speed signal and a target track speed.

The drop in the engine speed signal may be anticipated through a sensory device coupled to the work machine.

The drop in the engine speed signal may be anticipated by a rate of change in the engine speed droop.

The increased load may result from one or more of the attachments engaging a payload, a ground conditions profile, and the steering of the work machine.

The increased transmission signal may only apply when the engine speed signal is above an anti-stall threshold.

According to an aspect of the present disclosure, a method of compensating reduced track speed because of an engine speed droop for a work machine may include one or more of the following steps: determining, by an engine speed sensor of the work machine, an engine speed associated with the work machine; determining, by a controller of the work machine, if the engine speed is above an anti-stall threshold; determining, by a track speed sensor of the work machine, a track speed of a ground-engaging mechanism of the work machine;

receiving by the controller an operator input from an operator interface control, the operator input including a multiplicative factor for one or more of an increased transmission command signal and a target track speed when a drop in the engine speed occurs; detecting a drop in the engine speed signal; calculating an increase in the transmission command signal by the controller based on one or more of the engine speed, the operator input, and a target track speed; and generating an increase in the transmission command signal for increasing a motor speed to cause an increase in track speed to compensate at least a portion of the reduced track speed from the engine speed droop.

These and other features will become apparent from the following detailed description and accompanying drawings, wherein various features are shown and described by way of illustration. The present disclosure is capable of other and different configurations and its several details are capable of modification in various other respects, all without departing from the scope of the present disclosure. Accordingly, the detailed description and accompanying drawings are to be regarded as illustrative in nature and not as restrictive or limiting.

DETAILED DESCRIPTION

The following describes one or more example embodiments of the disclosed system and method, as shown in the accompanying figures of the drawings described briefly above.

Various modifications to the example embodiments may be contemplated by one of skill in the art.

As used herein, the term controller refers to any hardware, software, firmware, electronic control component, processing logic, and/or processor device, individually or in any combination, including without limitation: application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.

For the sake of brevity, conventional techniques related to signal processing, data transmission, signaling, control, and other functional aspects of the system (and the individual operating components of the systems) may not be described in detail herein. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and/or physical coupling between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the present disclosure.

Discussion herein may focus on the exemplary embodiment and method of a crawler dozer. In other applications of the disclosed system and method, other configurations are also possible. For example, work machines in some embodiments may be configured as various work machines with attachments such as motor graders, skid-steer loaders or similar machines. Further, work machines may be configured as machines other than construction vehicles, including machines from agriculture, forestry and mining industries, such as tractors.

FIG.1illustrates the work machine10(hereinafter also referred to as a “crawler dozer”) including a frame12, an attachment13coupled to the frame12, and a cab14supported by the frame12. A ground-engaging mechanism26may be adapted to support the frame12. The ground-engaging mechanism26may contain top rollers20, bottom rollers22, sprockets and/or idlers24, and twin tracks25. In further embodiments, the ground-engaging mechanism26can be replaced by a different type of mechanism including wheels, friction or positively-driven belts, or another mechanism suitable for moving the crawler dozer10across a tract of land, such as off-road terrain. The attachment13may comprise of a blade including a lower cutting edge. The attachment13may be mounted to a forward portion of the frame by an outer control linkage18, which is constructed of various links, joints, and other structural elements. The linkage18may include, for example, a push frame joined to the frame12at pivot points.

Advancing now toFIG.2with continued to reference toFIG.1, a schematic of the exemplary crawler dozer10is shown. Here it can be seen that the crawler dozer10includes a number of additional components beyond those previously described inFIG.1. Such additional components, for example, can include an engine64for driving the ground-engaging mechanism26and positioning of the attachment13relative to the frame12. The engine64may be coupled through a variable speed transmission66to the ground-engaging mechanism26(i.e. in this embodiment, a left final drive68, and a right final drive70with tracks25) and the attachment13. The variable speed transmission66may include a variable speed circuit76. The hydrostatic circuit76may include a pump (i.e. a left hydrostatic pump72, a right hydrostatic pump74). During operation of the crawler dozer10, the engine64drives rotation of the track25through the variable speed transmission66and the final drives (68,70). In one example, the rotating mechanical output of the engine64drive left and right hydrostatic pumps (72,74) that may be included within the variable speed transmission66. The hydrostatic pumps (72,74) are fluidly interconnected through other fluid-conducting components in the hydrostatic circuit76, such as filters, reservoirs, heat exchangers, and the like.

A motor (in this embodiment, a left hydrostatic motor78, a right hydrostatic motor80) may be adapted further drive the ground-engaging mechanism26. The hydrostatic pumps72,74are further fluidly coupled to and drive the motor (78,80) contained with the variable speed transmission66. The mechanical output shafts (79,81) of the motors (78,80) then drive rotation of the tracks25through the final drives (68,70). The engine64and the power train of the crawler dozer10may vary in other embodiments. One or more motor sensors82may be further included in the motor (78,80). The motor sensors82each include a sensor for monitoring the speed of the respective shaft (79,81) of the motors (78,80). During operation of the crawler dozer10, the motor sensors82may observe the output shafts79,81associated with the motor78,80and generate motor sensor signals27or sensor data based thereon, which is communicated to the controller84onboard the crawler dozer10.

A track speed sensor30may be adapted to detect a track speed32of the ground-engaging mechanism26and generate a track speed signal34. A track speed sensor30observes a track speed of the work machine10, such as rotation of the ground-engaging mechanism26(or tracks25, or components thereof) associated with the work machine10. The track speed sensor may further be coupled to a global positioning system, a sensor associated with the ground speed or velocity of the work machine10and generate track speed signal34based thereon, which may be received and processed by the controller84to determine a track speed32of the work machine10. The work machine track speed32may differ from a ground speed of the work machine due to slip in the tracks.

At least one engine speed sensor65is associated with the engine64. An engine speed sensor65observes an operational speed of the engine64, such as a rotation speed of an output shaft67associated with the engine64and generates engine sensor signals based thereon, which may be received and processed by the controller84to determine a speed of the engine64. That is, the engine speed sensor65may be adapted to detect an engine speed85and generate an engine speed signal52.

The one or more controllers84are schematically represented inFIG.2by a single block84although the controller84can include any number of processing devices, which can be distributed throughout the crawler dozer10and interconnected utilizing different communication protocols and memory architectures. The controller84(or others) may be configured as a computing device with associated processor devices and memory architectures85, as a hard-wired computing circuit (or circuits), as a programmable circuit, as a hydraulic, electrical or electro-hydraulic controller, or otherwise. As such, the work vehicle controller84may be configured to execute various computational and control functionality with respect to the crawler dozer10(or other machinery). In some embodiments, the controller84may be configured to receive input signals in various formats (e.g., as hydraulic signals, voltage signals, current signals, and so on), and to output command signals in various formats (e.g., as hydraulic signals, voltage signals, current signals, mechanical movements, and so on). In some embodiments, the controller84(or a portion thereof) may be configured as an assembly of hydraulic components (e.g., valves, flow lines, pistons and cylinders, and so on), such that control of various devices (e.g., pumps or motors) may be effected with, and based upon, hydraulic, mechanical, or other signals and movements.

Referring toFIG.3with continued reference toFIG.2, in the system200, the controller84may be adapted to send an increased transmission command signal54based on a drop in the engine speed signal52when the work machine10engages an increased load. The increased transmission command signal54increases a motor speed29to cause an increase in track speed32to compensate at least a portion of the reduced track speed32from the engine speed droop. The increased transmission command signal54may cause one or more of an increase in pump flow87and a decrease in motor displacement89. The increased transmission command signal54may occur at, immediately before, or immediately after the drop in the engine speed signal52. Note the drop in the engine speed signal52may sudden, gradual, anticipated, or detected, to name a few. The controller84, advantageously uses the increased transmission command signal54to soften the transition to accommodate the increased load on the work machine10without increasing the engine speed signal52, thereby improving the comfort to the operator. Furthermore, the target track speed32may advantageously differ from a first track to a second track thereby addressing any increased load observed during track slippage, and turning of the work machine10.

An operator interface control90may be adapted to receive an operator input92. The operator input92including a multiplicative factor94for one or more of the increased transmission command signal54and a target track speed98based on the drop in the engine speed signal52. In one embodiment, the target track speed98may comprise of a target motor speed (i.e. the speeds of the left hydrostatic motor78and the right hydrostatic motor80). Generally, the operator interface control90may include one or more joysticks, such as the joystick16a(shown inFIG.1), various switches or levers, one or more buttons, a touchscreen interface16b(shown inFIG.1) that may be overlaid on a display, a keyboard, a speaker, a microphone associated with a speech recognition system, control pedals, or various other human-machine interface devices. The operator may actuate one or more devices of operator interface control90for purposes of operating the crawler dozer10, and for providing operator input92to the system200for compensating reduced track speed because of engine speed droop120and the method400outlined in the disclosure. In this example, the multiplicative factor94may be selected from a form of the embodiments of the above-mentioned operator interface controls90. In a first embodiment, the operator interface control90may comprise of a touchscreen16b. In another embodiment, the operator control may comprise of a series of buttons, or alternatively, a dial.

The multiplicative factor94may comprise a first setting104, a second setting106, and a third setting108. The first setting104may include an off position. The second setting106may include a multiplicative factor94of 1:1. The third setting108may include a multiplicative factor94of X:1 wherein the multiplicative factor94of X may be one or more of pre-defined or user selected. In one exemplary embodiment, third setting108in a pre-defined scenario may include a multiplicative factor of 1.1:1; or 1.3:1; or 2:1; but preferably 1.5:1; for example. The multiplicative factor94may represent the ratio of a target track speed98from pre-load engagement and post-load engagement. The target track speed98may be derived from a target track speed, or alternatively a sensor adapted to determine a target track velocity of the work machine100.

Now further referring toFIG.4, an exemplary torque-engine speed curve is shown. The drop in the engine speed signal52may be identified by an inflection point132in a torque-engine speed curve134.

The increased transmission command signal54may be based on the engine speed signal52and a target track speed98.

The drop in the engine speed signal52may be anticipated by a rate of change in speed droop120. The rate of change of engine speed droop120may be derived from the slope136of the torque-engine speed curve134.

Now returning toFIGS.1and2, the drop in the engine speed signal52may additionally or alternatively be anticipated through data inputs122from a sensory device96coupled to the work machine10which, are further coupled to one or more inputs of the controller84and which can be distributed across the infrastructure of the work machine10. The sensory device96may include any number of sensors generating data that may be utilized by the work vehicle controller84in performing embodiments of the above-mentioned system200for compensating reduced track speed32because of engine speed droop120. In one example, one or more of these sensory devices96associated system may include one or more of a forward facing camera, lidar, radar, sonar, piezoelectric feedback, load sensor coupled to the attachment, GPS to determine track speed, to name a few. The sensory device96may also be adapted to detect the degree to which the work machine10is steered when turning. Detection of the degree to which the work machine10is turned when steering may include identifying a differential in track speed32from a first track to a second track.

The increased load may result from one or more of the attachment13engaging a payload125, ground conditions profile126and the steering127of the work machine, for example.

The increased transmission command signal54may only apply when the engine speed signal52is above an anti-stall threshold129, the anti-stall threshold129referring to the minimum engine speed85required to keep the engine64on the work machine10from stalling. Upon reaching an engine speed signal52below the anti-stall threshold129, the transmission command signal54may cease to increase.

Now turning toFIG.5, a method400of compensating reduced track speed32because of engine speed droop120for a work machine10is shown. In one example, the method400begins at step402. At step404, the method400determines, by an engine speed sensor65of the work machine10, an engine speed85associated with the work machine10.

At step406, the method400determines by a controller84of the work machine, if the engine speed85is above an anti-stall threshold129. If the engine speed85is above an anti-stall threshold129, the method proceeds to step408. Otherwise, the method ends at410, or alternatively upon reaching an engine speed signal52below the anti-stall threshold129, the transmission command signal54may cease to increase. At step412, receiving by the controller84an operator input92from an operator interface controller90wherein the operator92input includes a multiplicative factor94for one or more of an increased transmission command signal54and a target track speed98when a drop in the engine speed signal52occurs.

At step414, the method comprises detecting a drop in the engine speed85. The detection in the drop of the engine speed85may be derived from a drop or change in the engine speed signal52.

At step416, the controller84may calculate an increase in the transmission command signal54based on one or more of the engine speed85, the operator input92, and a target track speed98.

At step418, the controller84may generate an increase in the transmission command signal54for increasing a motor speed29to cause an increase in track speed32to compensate at least a portion of the reduced track speed32from the engine speed droop120.

At step420, the controller84may end the increased transmission command signal54when one or more of the increased load subsides, the engine speed85is modified to reflect sustained longer periods of increased load, or the engine speed85drops below the anti-stall threshold129, to name a few.

As will be appreciated by one skilled in the art, certain aspects of the disclosed subject matter may be embodied as a method, system (e.g., a work vehicle control system included in a work vehicle), or computer program product. Accordingly, certain embodiments may be implemented entirely as hardware, entirely as software (including firmware, resident software, micro-code, etc.) or as a combination of software and hardware (and other) aspects. Further-more, certain embodiments may take the form of a computer program product on a computer-usable storage medium having computer-usable program code embodied in the medium.

Any suitable computer usable or computer readable medium may be utilized. The computer usable medium may be a computer readable signal medium or a computer readable storage medium. A computer-usable, or computer-readable, storage medium (including a storage device associated with a computing device or client electronic device) may be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device. In the context of this document, a computer-usable, or computer-readable, storage medium may be any tangible medium that may contain or store a program for use by or in connection with the instruction execution system, apparatus, or device.

Aspects of certain embodiments are described herein may be described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of any such flowchart illustrations and/or block diagrams, and combinations of blocks in such flowchart illustrations and/or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

Any flowchart and block diagrams in the figures, or similar discussion above, may illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block (or otherwise described herein) may occur out of the order noted in the figures. For example, two blocks shown in succession (or two operations described in succession) may, in fact, be executed substantially concurrently, or the blocks (or operations) may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of any block diagram and/or flowchart illustration, and combinations of blocks in any block diagrams and/or flowchart illustrations, may be implemented by special purpose hardware based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

The terminology used herein is for the purpose of describing particular embodiments or implementations and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the any use of the terms “has,” “have,” “having,” “include,” “includes,” “including,” “comprise,” “comprises,” “comprising,” or the like, in this specification, identifies the presence of stated features, integers, steps, operations, elements, and/or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

One or more of the steps or operations in any of the methods, processes, or systems discussed herein may be omitted, repeated, or re-ordered and are within the scope of the present disclosure.