Gnss Supplemented Slope Control System and Method for a Work Vehicle

The present patent application is a continuation-in-part of U.S. patent application Ser. No. 18/174,750, “GNSS Supplemented Slope Control System and Method for a Work Vehicle”, filed at the United States Patent and Trademark Office on Feb. 27, 2023; the contents of which is incorporated herein by reference.

The present disclosure relates to a work vehicle. An embodiment of the present disclosure relates to a system and method for supplementing the grade control of the work vehicle with a global navigation satellite system (“GNSS”).

Work vehicles with ground-engaging implements may be used to shape and smooth ground surfaces. One such application is the creation of simple slopes or dual slope pads where iterative passes create an even and steady slope across a large area. However, challenges may exist in some environmental conditions where the work vehicle may not be moving in a way that directly correlates with the target heading input. Different soil conditions can have a large impact on grade control performance. For example, in sandy conditions a work vehicle may slide sideways on a steep slope as it travels forward resulting in movement not necessarily anticipated by an antenna. The same system can perform well in hard clay but perform poorly in sand. In another example, damp sand can be one of the most unforgiving soil types for grading since it cuts easily, and clumps together, while supporting the weight of the machine, which when combined can change the trajectory. Heading accuracy is vital in creating simple slopes. If this effect goes uncorrected, additional passes over the area may be required to create the simple slope and thereby impacting productivity and ultimately predicting the time required to complete the job. The impact of the effect is amplified if the work vehicle is run automatically and without a trained operator to intervene to correct the work vehicle path.

According to an aspect of the present disclosure, a work vehicle may include a chassis and a ground-engaging blade movably connected to the chassis via a linkage assembly configured to allow the blade to be raised and lowered relative to the chassis and moved in a roll direction relative to the chassis. A left ground-engaging mechanism and a right ground-engaging mechanism is coupled to the chassis and configured to move the chassis over a ground surface. An input device is included for providing at least a bench surface. A global positioning system is communicatively coupled to the work vehicle. The global positioning system is configured for generating a chassis heading signal indicative of a location of the work vehicle, a chassis inclination signal indicative of a main fall angle of the chassis relative to the bench surface, and a chassis roll signal indicative of a cross slope angle of the chassis relative to the bench surface. A controller is configured to receive the bench surface, the desired cross slope, the desired mainfall slope, and the desired depth. The controller is further configured to receive the bench surface, the chassis heading signal, the chassis inclination signal, and the chassis roll signal. The controller is configured to record the chassis heading signal from a first location to a second location to create a recorded chassis heading and use the recorded chassis heading as a reference chassis heading. The controller is then configured to receive a current chassis heading signal, determine an orientation error based on the reference chassis heading and the current chassis heading signal. The orientation error is indicative of the angular difference between the reference chassis heading and a current chassis heading. The controller is configured to send a command to actuate the right ground-engaging mechanism and the left ground-engaging mechanism to shift the current chassis heading to align with the reference chassis heading based on the orientation error.

According to another aspect of the present disclosure, the work vehicle may further include an implement sensor configured to provide an implement inclination signal indicative of an angle of the implement relative to one of the chassis and the direction of gravity and an implement roll signal indicative of an angle of the implement in the roll direction relative to one of the chassis and the direction of gravity. The input device may further provide a desired cross slope relative to the bench surface, a desired mainfall slope relative to the bench surface, and a desired depth relative to the bench surface. The controller may be further configured to receive the desired cross slope, the desired mainfall slope, and the desired depth. The controller may be further configured to receive the implement inclination signal and the implement roll signal. The controller may then be configured to determine an inclination distance error based on the chassis inclination signal and the implement inclination signal wherein the inclination distance error is indicative of a distance between the implement and the desired mainfall slope. The controller may then determine a roll distance error based on the chassis roll signal and implement roll signal, wherein the roll distance error is indicative of the distance between the implement and the desire cross slope. The controller may then be configured to send a command to move the implement toward the desired mainfall slope and the desired cross slope, based on the inclination distance error and the roll distance error, and towards the desired depth.

The controller may further be configured to abort controlling the left ground-engaging mechanism and the right ground-engaging mechanism based on an orientation error frequency reaching an orientation error frequency threshold. Alternatively, the controller may then be configured to abort controlling the ground-engaging mechanisms based on an orientation error threshold reaching an orientation error angle threshold. The implement sensor may comprise of at least on accelerometer and at least one gyroscope. The implement sensor may comprise of an IMU. The linkage assembly may be configured to allow the implement to be moved in a yaw direction.

According to another aspect of the disclosure, the controller may be configured to update the target grade based on the orientation error wherein the updated target grade include one or more of updating the target cross slope relative to the bench surface, updating the target mainfall slope relative to the bench surface, and updating the target depth relative to the bench surface. The controller may then be configured to send a command to move the implement toward the updated target mainfall slope and the updated target cross slope based on the orientation error threshold and towards the desired depth.

The updated target cross slope and the updated target mainfall slope may interchange upon reaching an orientation error threshold indicative of approximately ninety degrees. According to another aspect, the updated target cross slope and the updated target mainfall slope may change proportionately to the orientation error.

A method of controlling a ground-engaging implement of a work vehicle is disclosed. The method includes receiving a bench surface, a desired cross slope relative to the bench surface, a desired mainfall slope relative to the bench surface, and a desired depth relative to the bench surface. The method further includes receiving a chassis inclination signal indicative of a main fall angle of a chassis of the work vehicle relative to the bench surface and an implement inclination signal indicative of an angle of the implement relative to one of the chassis and the direction of gravity. The method includes receiving a chassis roll signal indicative of a cross slope angle of the chassis relative to the bench surface and an implement roll signal indicative of an angle of the implement in the roll direction relative to one of the chassis and the direction of gravity. The method further includes receiving a chassis heading signal from a first location to a second location during a first pass to create a recorded chassis heading signal. The method includes using the recorded chassis heading signal as a reference chassis heading and receiving a current chassis heading signal. The method then includes determining an orientation error based on the reference chassis heading and the current chassis heading signal. The orientation error is indicative of an angular difference between the reference chassis heading signal and the current chassis heading signal. The method further includes determining an inclination distance error based on the chassis inclination signal and the implement inclination signal wherein the inclination distance error indicative of a distance between the implement and the desired mainfall slope. Then method further includes determining a roll distance error based on the chassis roll signal and the implement roll signal wherein the roll distance error indicative of a distance between the implement and the desired cross slope yet includes receiving an implement inclination signal indicative of an angle of the implement relative to one of the chassis and the direction of gravity. The method then includes controlling the work vehicle to move in an auto heading mode or an auto slope target update mode.

The auto heading mode comprises sending a command to actuate the right ground-engaging mechanism and the left ground-engaging mechanism to shift the current chassis heading to align with the reference chassis heading based on the orientation error.

The auto slope target update mode comprises updating the target grade based on the orientation error wherein the updated target grade includes one or more of an updated target cross slope relative to the bench surface, and an updated target depth relative to the bench surface. The auto slope target update mode then comprises sending a command to move the implement toward the updated target mainfall slope and the updated target cross slope, based on the orientation and towards the desired depth.

The above and other features will become apparent from the following description and accompanying drawings.

Like reference numerals are used to indicate like elements throughout several figures.

is a perspective view of work vehicle. Work vehicleis illustrated as a crawler dozer, which may also be referred to as a crawler, but may be any work vehicle with a ground-engaging blade or work implement such as a compact track loader, motor grader(), scraper, skid steer, and tractor, to name a few examples. Work vehiclemay be operated to engage the ground and cut and move material to achieve simple or complex features on the ground. As used herein, directions with regard to work vehiclemay be referred to from the perspective of an operator seated within an operator station: the left of work vehicleis to the left of such an operator, the right of work vehicleis to the right of such an operator, the front or fore of work vehicleis the direction such an operator faces, the rear or aft of work vehicleis behind such an operator, the top of work vehicleis above such an operator, and the bottom of work vehicleis below such an operator. While operating, work vehiclemay experience movement in three directions and rotation in three directions. Direction for work vehiclemay also be referred to with regard to longitudeor the longitudinal direction, latitudeor the lateral direction, and verticalor the vertical direction. Rotation for work vehiclemay be referred to as rollor the roll direction, pitchor the pitch direction, and yawor the yaw direction or heading.

Work vehicleis supported on the ground by undercarriage. Undercarriageincludes left trackand right track, which engage the ground and provide tractive force for work vehicle. Left trackand right trackmay be comprised of shoes with grousers that sink into the ground to increase traction, and interconnecting components that allow the tracks to rotate about front idlers, track rollers, rear sprocketsand top idlers. Such interconnecting components may include links, pins, bushings, and guides, to name a few components. Front idlers, track rollers, and rear sprockets, on both the left and right sides of work vehicle, provide support for work vehicleon the ground. Front idlers, track rollers, rear sprockets, and top idlersare all pivotally connected to the remainder of work vehicleand rotationally coupled to their respective tracks so as to rotate with those tracks. Track frameprovides structural support or strength to these components and the remainder of undercarriage.

Front idlersare positioned at the longitudinal front of left trackand right trackand provide a rotating surface for the tracks to rotate about and a support point to transfer force between work vehicleand the ground. Left trackand right trackrotate about front idlersas they transition between their vertically lower and vertically upper portions parallel to the ground, so approximately half of the outer diameter of each of front idlersis engaged with left trackor right track. This engagement may be through a sprocket and pin arrangement, where pins included in left trackand right trackare engaged by recesses in front idlerso as to transfer force. This engagement also results in the vertical height of left trackand right trackbeing only slightly larger than the outer diameter of each of front idlersat the longitudinal front of left trackand right track. Frontmost engaging pointof left trackand right trackcan be approximated as the point on each track vertically below the center of front idlers, which is the frontmost point of left trackand right trackwhich engages the ground. When work vehicleencounters a ground feature when traveling in a forward direction, left trackand right trackmay first encounter it at frontmost engaging point. If the ground feature is at a higher elevation than the surrounding ground surface (i.e., an upward ground feature), work vehiclemay begin pitching backward (which may also be referred to as pitching upward) when frontmost engaging pointreaches the ground feature. If the ground feature is at a lower elevation than the surrounding ground surface (i.e., a downward ground feature), work vehiclemay continue forward without pitching until the center of gravity of work vehicleis vertically above the edge of the downward ground feature. At that point, work vehiclemay pitch forward (which may also be referred to as pitching downward) until frontmost engaging pointcontacts the ground. In this embodiment, front idlersare not powered and thus are freely driven by left trackand right track. In alternative embodiments, front idlersmay be powered, such as by an electric or hydraulic motor, or may have an included braking mechanism configured to resist rotation and thereby slow left trackand right track.

Track rollersare longitudinally positioned between front idlerand rear sprocketalong the bottom left and bottom right sides of work vehicle. Each of track rollersmay be rotationally coupled to left trackor right trackthrough engagement between an upper surface of the tracks and a lower surface of track rollers. This configuration may allow track rollersto provide support to work vehicle, and in particular may allow for the transfer of forces in the vertical direction between work vehicleand the ground. This configuration also resists the upward deflection of left trackand right trackas they traverse an upward ground feature whose longitudinal length is less than the distance between front idlerand rear sprocket.

Rear sprocketsmay be positioned at the longitudinal rear of left trackand right trackand, similar to front idlers, provide a rotating surface for the tracks to rotate about and a support point to transfer force between work vehicleand the ground. Left trackand right trackrotate about rear sprocketsas they transition between their vertically lower and vertically upper portions parallel to the ground, so approximately half of the outer diameter of each of rear sprocketsis engaged with left trackor right track. This engagement may be through a sprocket and pin arrangement, where pins included in left trackand right trackare engaged by recesses in rear sprocketsso as to transfer force. This engagement also results in the vertical height of left trackand right trackbeing only slightly larger than the outer diameter of each of rear sprocketsat the longitudinal back or rear of left trackand right track. Rearmost engaging pointof left trackand right trackcan be approximated as the point on each track vertically below the center of rear sprockets, which is the rearmost point of left trackand right trackwhich engages the ground. When work vehicleencounters a ground feature when traveling in a reverse or backward direction, left trackand right trackmay first encounter it at rearmost engaging point. If the ground feature is at a higher elevation than the surrounding ground surface, work vehiclemay begin pitching forward when rearmost engaging pointreaches the ground feature. If the ground feature is at a lower elevation than the surrounding ground surface, work vehiclemay continue backward without pitching until the center of gravity of work vehicleis vertically above the edge of the downward ground feature. At that point, work vehiclemay pitch backward until rearmost engaging pointcontacts the ground.

In this embodiment, each of rear sprocketsmay be powered by a rotationally coupled hydraulic motor so as drive left trackand right trackand thereby control propulsion and traction for work vehicle. Each of the left and right hydraulic motors may receive pressurized hydraulic fluid from a hydrostatic pump whose direction of flow and displacement controls the direction of rotation and speed of rotation for the left and right hydraulic motors. Each hydrostatic pump may be driven by engineof work vehicle, and may be controlled by an operator in operator stationissuing commands which may be received by controllerand communicated to the left and right hydrostatic pumps by controller. In alternative embodiments, each of rear sprocketsmay be driven by a rotationally coupled electric motor or a mechanical system transmitting power from engine.

Top idlersare longitudinally positioned between front idlersand rear sprocketsalong the left and right sides of work vehicleabove track rollers. Similar to track rollers, each of top idlersmay be rotationally coupled to left trackor right trackthrough engagement between a lower surface of the tracks and an upper surface of top idlers. This configuration may allow top idlersto support left trackand right trackfor the longitudinal span between front idlerand rear sprocket, and prevent downward deflection of the upper portion of left trackand right trackparallel to the ground between front idlerand rear sprocket.

Undercarriageis affixed to, and provides support and tractive effort for, chassisof work vehicle. Chassisis the frame which provides structural support and rigidity to work vehicle, allowing for the transfer of force between implement, depicted as blade, and left trackand right track. In this embodiment, chassisis a weldment comprised of multiple formed and joined steel members, but in alternative embodiments it may be comprised of any number of different materials or configurations. A chassis sensormay be affixed to chassisof work vehicleand configured to provide a signal indicative of the movement and orientation of chassis. In alternative embodiments, chassis sensormay not be affixed directly to chassis, but may instead be connected to chassisthrough intermediate components or structures, such as rubberized mounts. In these alternative embodiments, chassis sensoris not directly affixed to chassisbut is still connected to chassisat a fixed relative position so as to experience the same motion as chassis.

The chassis sensormay comprise at least one accelerometer and at least one gyroscope. Alternatively, the chassis sensormay comprise an inertial measurement unit or IMU. The chassis sensormay comprise a global positioning system (“GPS”). GPSmay comprise a Global Navigation Satellite System (GNSS), a terrestrial radio triangulation system, or any other system which is able to provide the locationof the work vehiclein global or local coordinates.illustratively shows that the work vehicle, the chassis sensor, the GPS, and the controllermay be connected over a network. Thus, computing architecture operates in a networked environment, where the networkincludes any of a wide variety of different logical connections such as a local area network (LAN), wide area network (WAN), controller area network (CAN) near field communication network, satellite communication network, cellular networks, or a wide variety of other networks or combination of networks. It is also noted that the controllercan be deployed on the work vehiclesuch that the controllerperforms the operations described herein without a networked connection.

With continued reference to, chassis sensoror GPSis configured to generate a chassis heading signalindicative of a locationof the work vehicle. The chassis heading signalis an angular measurement in the direction of yaw. The chassis heading signalis indicative of a heading angle of a change from an initial heading to an updated heading.

Chassis sensoror GPSis configured to generate a chassis inclination signalindicative of a main fall angle, or inclination, of the chassisrelative to gravity or a bench surface(). The bench surfacemay be provided via an input deviceby an operator. The bench surfacemay be a surface or plane that is defined by a rolland pitchrelative to gravity and a vertical, above sea level for example, that defines a depth. The bench surfacemay be a surface that the work vehicleis currently positioned on. The input devicemay be a joystick. The chassis inclination signalis an angular measurement in the direction of pitch. Controllermay actuate bladebased on this chassis inclination signal. As used herein, “based on” means “based at least in part on” and does not mean “based solely on,” such that it neither excludes nor requires additional factors. Chassis sensormay also be configured to provide a signal or signals indicative of other positions or velocities of chassis, including, its angular position, velocity, or acceleration in a direction such as the direction of roll, pitch, yaw, or its linear acceleration in a direction such as the direction of longitude, latitude, and vertical. Chassis sensormay be configured to directly measure inclination, measure angular velocity and integrate to arrive at inclination, or measure inclination and derive to arrive at angular velocity. Input devicemay also be configured to provide a desired cross sloperelative to the bench surface, a desired mainfall sloperelative to the bench surface, and a desired depthrelative to the bench surface. The cross slope referenceshown in the figures is the exemplary cross-sectional view of a simple slope.

Chassis sensoror GPSis also configured to generate a chassis roll signalindicative of a cross slope angle of the chassisrelative to the bench surfaceor relative to the direction of gravity. The chassis roll signalis an angular measurement in the direction of roll.

Implementdepicted as blademay engage the ground or material to move or shape it. Blademay be used to move material from one location to another and to create features on the ground, including flat areas, grades, hills, roads, or more complexly shaped features. In this embodiment, bladeof work vehiclemay be referred to as a six-way blade, six-way adjustable blade, or power-angle-tilt (PAT) blade. Blademay be hydraulically actuated to move vertically up or vertically down (which may also be referred to as blade lift, or raise and lower), roll left or roll right (which may be referred to as blade tilt, or tilt left and tilt right), and yaw left or yaw right (which may be referred to as blade angle, or angle left and angle right). Alternative embodiments may utilize a different implementor a bladewith fewer hydraulically controlled degrees of freedom, such as a 4-way blade that may not be angled, or actuated in the direction of yaw.

Bladeis movably connected to chassisof work vehiclethrough linkage assembly, which supports and actuates bladeand is configured to allow bladeto be raised or lowered relative to chassis(i.e., moved in the direction of vertical). Linkage assemblymay include multiple structural members to carry forces between bladeand the remainder of work vehicleand may provide attachment points for hydraulic cylinders which may actuate bladein the lift, tilt, and angle directions.

Linkage assemblyincludes c-frame, a structural member with a C-shape positioned rearward of blade, with the C-shape open toward the rear of work vehicle. Each rearward end of c-frameis pivotally connected to chassisof work vehicle, such as through a pin-bushing joint, allowing the front of c-frameto be raised or lowered relative to work vehicleabout the pivotal connections at the rear of c-frame. The front portion of c-frame, which is approximately positioned at the lateral center of work vehicle, connects to bladethrough a ball-socket joint. This allows bladethree degrees of freedom in its orientation relative to c-frame(lift-tilt-angle) while still transferring rearward forces on bladeto the remainder of work vehicle.

An implement sensormay comprise at least one accelerometer and at least one gyroscope. Alternatively, the implement sensormay comprise an inertial measurement unit or IMU. The implement sensormay be affixed to implementorabove the ball-socket joint connecting bladeto c-frame. Implement sensor, like chassis sensor, may be configured to measure angular position (inclination or orientation), velocity, or acceleration, or linear acceleration. Implement sensormay provide an implement inclination signal, which indicates the angle of bladerelative to one of the chassisand the direction of gravity. The implement sensormay be configured to provide an implement roll signalindicative of an angle of the implementin the rolldirection relative to one of the chassisand the direction of gravity. The implement sensormay be configured to provide an implement yaw signalindicative of an angle of the implementin the direction of yawrelative to the chassis.

In alternative embodiments, an implement sensormay be configured to instead measure an angle of linkage assembly, such as an angle between linkage assemblyand chassis, in order to determine a position of blade. In other alternative embodiments, implement sensormay be configured to measure a position of bladeby measuring a different angle, such as one between linkage assemblyand blade, or the linear displacement of a cylinder attached to linkage assemblyor blade. In alternative embodiments, implement sensormay not be affixed directly to blade, but may instead be connected to bladethrough intermediate components or structures, such as rubberized mounts. In these alternative embodiments, implement sensoris not directly affixed to bladebut is still connected to bladeat a fixed relative position so as to experience the same motion as blade.

Controlleris configured to receive the bench surface, the desired cross slope, the desired mainfall slope, and the desired depth, receive the chassis heading signal, the chassis inclination signal, and the chassis roll signal, receive the implement inclination signaland the implement roll signal, determine an inclination distance errorbased on the chassis inclination signaland the implement inclination signal, the inclination distance errorindicative of a distance between the implementand the desired mainfall slope, determine a roll distance errorbased on the chassis roll signaland the implement roll signal, the roll distance errorindicative of a distance between the implementand the desired cross slope, and send a command to move the implementtoward the desired mainfall slopeand the desired cross slope, based on the inclination distance errorand the roll distance error, and towards the desired depth.

Blademay be raised or lowered relative to work vehicleby the actuation of lift cylinders, which may raise and lower c-frameand thus raise and lower blade, which may also be referred to as blade lift. For each of lift cylinders, the rod end is pivotally connected to an upward projecting clevis of c-frameand the head end is pivotally connected to the remainder of work vehiclejust below and forward of operator station. The configuration of linkage assemblyand the positioning of the pivotal connections for the head end and rod end of lift cylindersresults in the extension of lift cylinderslowering bladeand the retraction of lift cylindersraising blade. In alternative embodiments, blademay be raised or lowered by a different mechanism, or lift cylindersmay be configured differently, such as a configuration in which the extension of lift cylindersraises bladeand the retraction of lift cylinderslowers blade.

Blademay be tilted relative to work vehicleby the actuation of tilt cylinder, which may also be referred to as moving bladein the direction of roll. For tilt cylinder, the rod end is pivotally connected to a clevis positioned on the back and left sides of bladeabove the ball-socket joint between bladeand c-frameand the head end is pivotally connected to an upward projecting portion of linkage assembly. The positioning of the pivotal connections for the head end and the rod end of tilt cylinderresult in the extension of tilt cylindertilting bladeto the left or counterclockwise when viewed from operator stationand the retraction of tilt cylindertilting bladeto the right or clockwise when viewed from operator station. In alternative embodiments, blademay be tilted by a different mechanism (e.g., an electrical or hydraulic motor) or tilt cylindermay be configured differently, such as a configuration in which it is mounted vertically and positioned on the left or right side of blade, or a configuration with two tilt cylinders.

Blademay be angled relative to work vehicleby the actuation of angle cylinders, which may also be referred to as moving bladein the direction of yaw. For each of angle cylinders, the rod end is pivotally connected to a clevis of bladewhile the head end is pivotally connected to a clevis of c-frame. One of angle cylindersis positioned on the left side of work vehicle, left of the ball-socket joint between bladeand c-frame, and the other of angle cylindersis positioned on the right side of work vehicle, right of the ball-socket joint between bladeand c-frame. This positioning results in the extension of the left of angle cylindersand the retraction of the right of angle cylindersangling bladerightward, or yawing bladeclockwise when viewed from above, and the retraction of left of angle cylinderand the extension of the right of angle cylindersangling bladeleftward, or yawing bladecounterclockwise when viewed from above. In alternative embodiments, blademay be angled by a different mechanism or angle cylindersmay be configured differently.

Due to the geometry of linkage assemblyin this embodiment, bladeis not raised or lowered in a perfectly vertical line with respect to work vehicle. Instead, a point on bladewould trace a curve as bladeis raised and lowered. This means that the vertical component of the velocity of bladeis not perfectly proportional to the linear velocity with which lift cylindersare extending or retracting, and the vertical component of blade's velocity may vary even when the linear velocity of lift cylindersis constant. This also means that lift cylindershave a mechanical advantage which varies depending on the position of linkage assembly. Given a kinematic model of bladeand linkage assembly(e.g., formula(s) or table(s) providing a relationship between the position and/or movement of portions of bladeand linkage assembly) and the state of bladeand linkage assembly(e.g., sensor(s) sensing one or more positions, angles, or orientations of bladeor linkage assembly, such as implement sensor), at least with respect to blade lift, controllermay compensate for such non-linearity. Incomplete or simplified kinematic models may be used if there is a need to only focus on particular motion relationships (e.g., only those affecting blade lift) or if only limited compensation accuracy is desired. Controllermay utilize this compensation and a desired velocity, for example a command to raise bladeat a particular vertical velocity, to issue a command that may achieve a flow rate into lift cylindersthat results in bladebeing raised at the particular vertical velocity regardless of the current position of linkage assembly. For example, controllermay issue commands which vary the flow rate into lift cylindersin order to achieve a substantially constant vertical velocity of blade.

Similarly, due to the positioning of tilt cylinderand angle cylindersand the configuration of their connection to blade, the angular velocity of blade tilt and angle is not perfectly proportional to the linear velocity of tilt cylinderand angle cylinders, respectively, and the angular velocity of tilt and angle may vary even when the linear velocity of tilt cylinderand angle cylinders, respectively, is constant. This also means that tilt cylinderand angle cylinderseach has a mechanical advantage which varies depending on the position of blade. Much like with lift cylinders, given a kinematic model of bladeand linkage assembly, and the state of bladeand linkage assembly, at least with respect to blade tilt and angle, controllermay compensate for such non-linearity. Incomplete or simplified kinematic models may be used if there is a need to only focus on particular motion relationships (e.g., only those affecting blade tilt and angle) or if only limited compensation accuracy is required. Controllermay utilize this compensation and a desired angular velocity, for example a command to tilt or angle bladeat a particular angular velocity, to issue commands that may vary the flow rate into tilt cylinderor angle cylindersto result in bladebeing tilted or angled at the particular angular velocity regardless of the current position of bladeor linkage assembly.

In alternative embodiments, blademay be connected to the remainder of work vehiclein a manner which tends to make the blade lift velocity (in direction of vertical), tilt angular velocity (in the direction of roll), or angle angular velocity (in the direction of yaw) proportional to the linear velocity of lift cylinders, tilt cylinder, or angle cylinders, respectively. This may be achieved with particular designs of linkage assemblyand positioning of the pivotal connections of lift cylinders, tilt cylinder, and angle cylinders. In such alternative embodiments, controllermay not need to compensate for non-linear responses of bladeto the actuation of lift cylinders, tilt cylinder, and angle cylinders, or the need for compensation may be reduced.

Each of lift cylinders, tilt cylinder, and angle cylindersis a double acting hydraulic cylinder. One end of each cylinder may be referred to as a head end, and the end of each cylinder opposite the head end may be referred to as a rod end. Each of the head end and the rod end may be fixedly connected to another component or, as in this embodiment, pivotally connected to another component, such as a through a pin-bushing or pin-bearing coupling, to name but two examples of pivotal connections. As a double acting hydraulic cylinder, each may exert a force in the extending or retracting direction. Directing pressurized hydraulic fluid into a head chamber of the cylinders will tend to exert a force in the extending direction, while directing pressurized hydraulic fluid into a rod chamber of the cylinders will tend to exert a force in the retracting direction. The head chamber and the rod chamber may both be located within a barrel of the hydraulic cylinder, and may both be part of a larger cavity which is separated by a movable piston connected to a rod of the hydraulic cylinder. The volumes of each of the head chamber and the rod chamber change with movement of the piston, while movement of the piston results in extension or retraction of the hydraulic cylinder. The control of these cylinders will be described in further detail with regard to.

is a schematic of a portion of a system for controlling the hydraulic cylinder, the system including hydraulic and electrical components. Each of lift cylinders, tilt cylinder, and angle cylindersis hydraulically connected to hydraulic control valve, which may be positioned in an interior area of work vehicle. Hydraulic control valvemay also be referred to as a valve assembly or manifold. Hydraulic control valvereceives pressurized hydraulic fluid from hydraulic pump, which may be rotationally connected to engine, and directs such fluid to lift cylinders, tilt cylinder, angle cylinders, and other hydraulic circuits or functions of work vehicle. Hydraulic control valvemay meter such fluid out, or control the flow rate of hydraulic fluid to each hydraulic circuit to which it is connected. In alternative embodiments, hydraulic control valvemay not meter such fluid out but may instead only selectively provide flow paths to these functions while metering is performed by another component (e.g., a variable displacement hydraulic pump) or not performed at all. Hydraulic control valvemay meter such fluid out through a plurality of spools, whose positions control the flow of hydraulic fluid, and other hydraulic logic. The spools may be actuated by solenoids, pilots (e.g., pressurized hydraulic fluid acting on the spool), the pressure upstream or downstream of the spool, or some combination of these and other elements.

In the embodiment illustrated in, the spools of hydraulic control valveare shifted by pilots whose pressure is controlled, at least in part, by electrohydraulic pilot valvein communication with controller. Electrohydraulic pilot valveis positioned within an interior area of work vehicleand receives pressurized hydraulic fluid from a hydraulic source and selectively directs such fluid to pilot lines hydraulically connected to hydraulic control valve. In this embodiment hydraulic control valveand electrohydraulic pilot valveare separate components, but in alternative embodiments the two valves may be integrated into a single valve assembly or manifold. In this embodiment, the hydraulic source is hydraulic pump. In alternative embodiments, a pressure reducing valve may be used to reduce the pressure of pressurized hydraulic fluid provided by hydraulic pumpto a set pressure, for example 600 pounds per square inch, for usage by electrohydraulic pilot valve. In the embodiment illustrated in, individual valves within electrohydraulic pilot valvereduce the pressure from the received hydraulic fluid via solenoid-actuated spools which may drain hydraulic fluid to a hydraulic reservoir. In this embodiment, controlleractuates these solenoids by sending a specific current to each (e.g., 600 mA). In this way, controllermay actuate bladeby issuing electrical commands signals to electrohydraulic pilot valve, which in turn provides hydraulic signals (pilots) to hydraulic control valve, which shift spools to direct hydraulic flow from hydraulic pumpto actuate lift cylinders, tilt cylinder, and angle cylinders. In this embodiment, controlleris in direct communication with electrohydraulic pilot valvevia electrical signals sent through a wire harness and is indirectly in communication with hydraulic control valvevia electrohydraulic pilot valve.

Controller, which may be referred to as a vehicle control unit (VCU), is in communication with a number of components on work vehicle, including hydraulic components such as electrohydraulic pilot valve, electrical components such as operator inputs within operator station, chassis sensor, implement sensor, and other components. Controlleris electrically connected to these other components by a wiring harness such that messages, commands, and electrical power may be transmitted between controllerand the remainder of work vehicle. Controllermay be connected to some of these sensors or other controllers, such as an engine control unit (ECU), through a controller area network (CAN). Controllermay then send and receive messages over the CAN to communicate with other components on the CAN.

In alternative embodiments, controllermay send a command to actuate bladein a number of different manners. As one example, controllermay be in communication with a valve controller via a CAN and may send command signals to the valve controller in the form of CAN messages. The valve controller may receive these messages from controllerand send current to specific solenoids within electrohydraulic pilot valvebased on those messages. As another example, controllermay actuate bladeby actuating an input in operator station. For example, an operator may use input device(e.g., joystick) to issue commands to actuate blade, and the joystick may generate hydraulic pressure signals, pilots, which are communicated to hydraulic control valveto cause the actuation of blade. In such a configuration, controllermay be in communication with electrical devices (e.g., solenoids, motors) which may actuate a joystick in operator station. In this way, controllermay actuate bladeby actuating these electrical devices instead of communicating signals to electrohydraulic pilot valve.

is a left side view of work vehicleas work vehicledrives over ground feature, which in this example is a ground feature at a higher elevation than the surrounding ground surface (e.g., an upward ground feature). As work vehicledrives over ground feature, frontmost engaging pointis the first point on left trackand right trackwhich substantially engages ground feature. As work vehicleengages ground featureat frontmost engaging point, work vehiclebegins to pitch upward or pitch backward as the front of work vehiclerises on ground featurerelative to the rear of work vehicle. When pitching upwards or backwards, work vehiclewill tend to pitch about rearmost engaging point.

During this pitching, chassis sensormay send a chassis inclination signalindicative of the angle of chassisrelative to the direction of gravity (i.e., orientation in the direction of pitch) as well as a chassis pitch signal indicative of an angular velocity of chassisin the direction of pitch. The chassis inclination signaland chassis pitch signal will indicate an inclination and velocity in a first direction, angled and pitching upwards, as opposed to the chassis inclination signaland chassis pitch signal indicating an inclination and velocity in a second direction, angled and pitching downwards. In this embodiment, chassis inclination signaland chassis pitch signal from chassis sensorto controllermay indicate values within a range for which values in one half of the range indicate angles and angular velocities in the first direction and values in the other half of the range indicate angles and angular velocities in the second direction. During the pitching, chassis sensormay also send the chassis roll signaland the chassis heading signal. The signals from chassis sensormay be received by the controller.

Similarly, implement sensormay send an implement inclination signalindicative of the angle of bladerelative to the direction of gravity (i.e., orientation in the direction of pitch) as well as an implement pitch signal indicative of an angular velocity of bladein the direction of pitch. The implement inclination signaland implement pitch signal will indicate an inclination and velocity in a first direction, angled and pitching upwards, as opposed to the implement inclination signaland implement pitch signal indicating an inclination and velocity in a second direction, angled and pitching downwards. In this embodiment, implement inclination signaland implement pitch signal from implement sensorto controllermay indicate values within a range for which values in one half of the range indicate angles and angular velocities in the first direction and values in the other half of the range indicate angles and angular velocities in the second direction. During the pitching, implement sensormay also send the implement roll signaland the implement yaw signal. The signals from the implement sensormay be received by the controller.

As work vehiclecontinues to drive over ground feature, frontmost engaging pointwould cease to engage the ground and instead would remain suspended above the ground by a distance determined in part by the height of ground featurerelative to the surrounding ground surface and the position of work vehicleon ground feature. At this point, although ground featureis an upward ground feature, it has the effect of a downward ground feature at a lower elevation than the surrounding ground surface. Specifically, the area just past ground featureis lower than ground feature. As the center of gravity for work vehiclepasses over the top of ground feature, work vehiclewill pitch forwards and rearmost engaging pointwill leave the ground surface while frontmost engaging pointwill fall until it contacts the ground surface.

During the process of work vehicledriving over ground feature, bladewill rise and fall relative to the ground surface due to the pitching of work vehicle. As work vehiclepitches backward, bladewill rise as c-framepitches backward with work vehicle, and as work vehiclepitches forward, bladewill fall as c-framepitches forward with work vehicle. If the operator of work vehiclefails to correct for ground featureby commanding bladeto rise or fall in a manner that counteracts the effect of ground featureon the height of blade, work vehiclewill create vertical variations on the ground surface instead of a smooth surface, such as a hill and a valley. As work vehicledrives over this newly created hill and valley on the ground surface, bladewill once again be raised and lowered as work vehiclepitches backward and forward, creating further vertical variations. This series of hills and valleys may be referred to as a “washboard” pattern. In addition to creating this pattern, the pitching of work vehiclewill also interrupt efforts to maintain a uniform grade. An operator of work vehiclemay target a particular grade (e.g., 2%) and if traveling up or down the grade, the pitching of work vehiclewill create segments where the actual grade is steeper or shallower than the target grade.

While this is occurring, chassis sensorand implement sensorsend the chassis inclination signal, chassis pitch signal, chassis roll signal, chassis heading signal, implement inclination signal, implement roll signal, implement yaw signal, and implement pitch signal to controller. Controllermay also receive signals from controls in operator stationwhich the operator may use to issue commands, for example a command to raise or lower blade. If controllerdoes not sense a command from the operator to raise or lower blade, but receives a signal from chassis sensoror implement sensorindicating that chassisor bladeis pitching, controllermay issue a command to electrohydraulic pilot valveto raise or lower bladeto counteract the effect from the pitch. In this manner, controllermay attempt to mitigate or attenuate the effect of pitching and ground features and thereby create a smoother ground surface, as further described with regard to.

In this embodiment, each of chassis sensorand implement sensorcomprise three accelerometers, each measuring linear acceleration in one of three perpendicular directions, and three gyroscopes, each measuring angular velocity in one of three perpendicular directions. In this way, chassis sensorand implement sensormay each directly measure linear acceleration or angular velocity in any direction, including the directions of longitude, latitude, vertical, roll, pitch, and yaw. The linear acceleration of each accelerometer may be filtered to remove short term accelerations or otherwise analyzed to determine the direction of gravity, which exerts a constant acceleration of approximately 9.81 meters per square second on chassis sensorand implement sensor. The measurements from the accelerometers and gyroscopes of chassis sensorand implement sensormay be combined or analyzed together to improve the accuracy and/or reduce the latency with which the direction of gravity may be determined. For example, the accelerometers may measure the direction of gravity with high accuracy over a period of time sufficient to remove the effects of short-term accelerations, while the gyroscopes may measure changes to the direction of the sensor relative to the direction of gravity very quickly but be subject to drift if these changes are integrated to determine the direction and error is allowed to accumulate. Chassis sensorand implement sensormay each be an IMU “inertial measurement unit”.

illustrates how controllermay issue commands to move bladeso as to counteract pitching, such as may happen when the tracks of work vehicleengage ground features. As work vehicletravels in a forward direction, it creates profile, which illustrates a cross-section of the ground which work vehicleis working. Controllermay determine a target grade, including based on an operator directly entering a desired cross slope, a desired mainfall slope, a desired depth, and a bench surfaceor a grade (e.g., 2%) via the input deviceor by recording the current grade after an operator is done issuing blade commands. This target grade, which may also be referred to as a target angle or target plane, is illustrated by linein. While lineillustrates the target grade while work vehicleis on slope, it does not represent the target grade while work vehicleis on different portions of profile.