Blade tilt system and method for a work vehicle

A work vehicle may comprise a chassis, a ground-engaging blade, a sensor assembly, and a controller. The ground-engaging blade may be movably connected to the chassis via a linkage configured to allow the blade to be tilted relative to the chassis. The sensor assembly may be connected to the work vehicle and configured to provide a tilt signal indicative of an angle of the blade in a roll direction and a roll signal indicative of a rotational velocity of the blade in the roll direction. The controller may be configured to determine a target tilt angle, receive the tilt signal, receive the roll signal, and send a command to tilt the blade toward the target tilt angle, the command based on the tilt signal, the roll signal, and the target tilt angle.

FIELD OF THE DISCLOSURE

The present disclosure relates to machine. An embodiment of the present disclosure relates to a system and method for tilting a ground-engaging blade of a work vehicle.

BACKGROUND

Work vehicles with ground-engaging blades may be used to shape and smooth ground surfaces. Such work vehicles may be supported by wheels or tracks which may encounter raised and lowered features on the ground as the work vehicle moves, which may cause the work vehicle to tilt left or tilt right if the feature is encountered differently by the left and right sides of the work vehicle. This tilting of the work vehicle may be transmitted to the ground-engaging blade, causing it to tilt left and right relative to the ground and create unintended variations on the ground surface. This effect may be amplified for those work vehicles with a ground engaging blade in front of the work vehicles' tires or tracks, as the work vehicle may create new and larger unintended variations as it passes over the unintended variations just created by the ground-engaging blade due to earlier tilting left and right. If this self-reinforcing effect goes uncorrected by an operator, it may create a “washboard” or “wavy” type surface on the ground or other unintended surface pattern.

SUMMARY

According to an aspect of the present disclosure, a work vehicle may include a chassis, a ground-engaging blade, a sensor assembly, and a controller. The ground-engaging blade may be movably connected to the chassis via a linkage configured to allow the blade to be tilted relative to the chassis. The sensor assembly may be connected to the work vehicle, configured to provide a tilt signal indicative of an angle of the blade in a roll direction, and configured to provide a roll signal indicative of a rotational velocity of the blade in the roll direction. The controller may be configured to determine a target tilt angle, receive the tilt signal, receive the roll signal, and send a command to tilt the blade toward the target tilt angle, the command based on the tilt signal, the roll signal, and the target tilt angle.

According to another aspect of the present disclosure, the sensor assembly may be connected to the blade at a fixed relative position to the blade and the tilt signal is indicative of an angle of the blade relative to the direction of gravity.

According to another aspect of the present disclosure, the sensor assembly may be a first sensor assembly and the work vehicle may further include a second sensor assembly. The second sensor assembly may be connected to the chassis at a fixed relative position to the chassis. The second sensor assembly may be configured to provide a chassis roll signal indicative of a rotational velocity of the chassis in the roll direction. The command may be based on the tilt signal, the roll signal, the target tilt angle, and the chassis roll signal.

According to another aspect of the present disclosure, the controller may be further configured to receive a tilt command from an operator input and determine the target tilt angle based on the tilt signal after the most recent tilt command.

According to another aspect of the present disclosure, the controller may be further configured to determine the target tilt angle based on a signal from a satellite-based navigation system or a local positioning system.

According to another aspect of the present disclosure, the controller may be further configured to determine the command signal based on a first gain applied to a difference between the tilt signal and the target tilt angle and a second gain applied to the roll signal.

According to another aspect of the present disclosure, the work vehicle may further include a means for communicating a difference between the tilt signal and the target tilt angle to an operator.

According to another aspect of the present disclosure, a method of controlling a work vehicle with a ground-engaging blade may include determining a target tilt angle, receiving a tilt signal indicative of a tilt angle of the work vehicle in the roll direction, receiving a roll signal indicative of a rotational velocity of the work vehicle in a roll direction, and determining a command signal to tilt the blade toward the target tilt angle based on the tilt signal, the roll signal, and the target tilt angle.

According to another aspect of the present disclosure, the tilt signal may be a blade tilt signal indicative of a tilt angle of the blade relative to the direction of gravity, the roll signal may be a blade roll signal indicative of a rotational velocity of the blade in the roll direction, and the method may further include receiving a chassis roll signal indicative of a rotational velocity of a chassis of the work vehicle in the roll direction, where the command signal is determined based on the blade tilt signal, the blade roll signal, and the chassis roll signal.

According to another aspect of the present disclosure, the method may further include receiving a chassis tilt signal indicative of a tilt angle of the chassis relative to the direction of gravity, where the command signal is determined based on the blade tilt signal, the blade roll signal, the chassis tilt signal, and the chassis roll signal.

According to another aspect of the present disclosure, the target tilt angle may be determined based on the tilt signal after an operator's most recent tilt command.

According to another aspect of the present disclosure, the target tilt angle may be determined based on a signal from a satellite-based navigation system or a local positioning system.

According to another aspect of the present disclosure, the command signal may be determined based on a first gain applied to a difference between the tilt signal and the target tilt angle and a second gain applied to the roll signal.

According to another aspect of the present disclosure, the tilt signal and the roll signal may be provided by a sensor assembly comprising at least one accelerometer and at least one gyroscope, where the tilt signal is based on a signal from the at least one accelerometer and the roll signal is based on a signal from the at least one gyroscope.

According to another aspect of the present disclosure, a crawler-dozer may include a chassis, a ground-engaging blade, a hydraulic cylinder, an electrohydraulic valve assembly, a sensor assembly, and a controller. The ground-engaging blade may be movably connected to the chassis via a linkage configured to allow the blade to be tilted. The hydraulic cylinder may be connected to the linkage and configured to tilt the blade. The electrohydraulic valve assembly may be hydraulically connected to the hydraulic cylinder and configured to actuate the hydraulic cylinder. The sensor assembly may be connected to the blade at a fixed relative position to the blade and configured to provide a blade tilt signal indicative of a tilt angle of the blade relative to the direction of gravity and a blade roll signal indicative of a rotational velocity of the blade in a roll direction. The controller may be in communication with the sensor assembly and the electrohydraulic valve assembly and configured to determine a target tilt angle, receive the blade tilt signal, receive the blade roll signal, determine a command signal to tilt the blade toward the target tilt angle based on the blade tilt signal, the blade roll signal, and the target tilt angle, and send the command signal to the electrohydraulic valve assembly.

According to another aspect of the present disclosure, the sensor assembly may be a first sensor assembly and the crawler-dozer may further include a second sensor assembly. The second sensor assembly may be connected to the chassis at a fixed relative position to the chassis. The second sensor assembly may be configured to provide a chassis roll signal indicative of a rotational velocity of the chassis in the roll direction. The controller may be further configured to determine the command signal based on the blade tilt signal, the blade roll signal, and the chassis roll signal to tilt the blade toward the target tilt angle.

According to another aspect of the present disclosure, the controller may be further configured to receive a tilt command from an operator input and determine the target tilt angle based on the blade tilt signal after the most recent tilt command.

According to another aspect of the present disclosure, the controller may be further configured to determine the target tilt angle based on a signal from a satellite-based navigation system or a local positioning system.

According to another aspect of the present disclosure, the controller may be further configured to determine the command signal based on a first gain applied to a difference between the blade tilt signal and the target tilt angle and a second gain applied to the blade roll signal.

According to another aspect of the present disclosure, the sensor assembly may be comprised of at least one gyroscope and at least one accelerometer.

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 the several figures.

DETAILED DESCRIPTION

FIG. 1is a perspective view of work vehicle100. Work vehicle100is 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 vehicle100may 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 vehicle100may be referred to from the perspective of an operator seated within operator station136: the left of work vehicle100is to the left of such an operator, the right of work vehicle100is to the right of such an operator, the front or fore of work vehicle100is the direction such an operator faces, the rear or aft of work vehicle100is behind such an operator, the top of work vehicle100is above such an operator, and the bottom of work vehicle100is below such an operator. While operating, work vehicle100may experience movement in three directions and rotation in three directions. Direction for work vehicle100may also be referred to with regard to longitude102or the longitudinal direction, latitude106or the lateral direction, and vertical110or the vertical direction. Rotation for work vehicle100may be referred to as roll104or the roll direction, pitch108or the pitch direction, and yaw112or the yaw direction or heading.

Work vehicle100is supported on the ground by undercarriage114. Undercarriage114includes left track116and right track118, which engage the ground and provide tractive force for work vehicle100. Left track116and right track118may 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 idlers120, track rollers122, rear sprockets124and top idlers126. Such interconnecting components may include links, pins, bushings, and guides, to name a few components. Front idlers120, track rollers122, and rear sprockets124, on both the left and right sides of work vehicle100, provide support for work vehicle100on the ground. Front idlers120, track rollers122, rear sprockets124, and top idlers126are all pivotally connected to the remainder of work vehicle100and rotationally coupled to their respective tracks so as to rotate with those tracks. Track frame128provides structural support or strength to these components and the remainder of undercarriage114.

Front idlers120are positioned at the longitudinal front of left track116and right track118and provide a rotating surface for the tracks to rotate about and a support point to transfer force between work vehicle100and the ground. Left track116and right track118rotate about front idlers120as 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 idlers120is engaged with left track116or right track118. This engagement may be through a sprocket and pin arrangement, where pins included in left track116and right track118are engaged by recesses in front idler120so as to transfer force. This engagement also results in the vertical height of left track116and right track118being only slightly larger than the outer diameter of each of front idlers120at the longitudinal front of left track116and right track118. Frontmost engaging point130of left track116and right track118can be approximated as the point on each track vertically below the center of front idlers120, which is the frontmost point of left track116and right track118which engages the ground. When work vehicle100encounters a ground feature when traveling in a forward direction, left track116and right track118may first encounter it at frontmost engaging point130. If the ground feature is at a higher elevation than the surrounding ground surface (i.e., an upward ground feature), work vehicle100may begin pitching backward (which may also be referred to as pitching upward) when frontmost engaging point130reaches the ground feature. If the ground feature is at a lower elevation than the surrounding ground surface (i.e., a downward ground feature), work vehicle100may continue forward without pitching until the center of gravity of work vehicle100is vertically above the edge of the downward ground feature. At that point, work vehicle100may pitch forward (which may also be referred to as pitching downward) until frontmost engaging point130contacts the ground. In this embodiment, front idlers120are not powered and thus are freely driven by left track116and right track118. In alternative embodiments, front idlers120may 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 track116and right track118.

Track rollers122are longitudinally positioned between front idler120and rear sprocket124along the bottom left and bottom right sides of work vehicle100. Each of track rollers122may be rotationally coupled to left track116or right track118through engagement between an upper surface of the tracks and a lower surface of track rollers122. This configuration may allow track rollers122to provide support to work vehicle100, and in particular may allow for the transfer of forces in the vertical direction between work vehicle100and the ground. This configuration also resists the upward deflection of left track116and right track118as they traverse an upward ground feature whose longitudinal length is less than the distance between front idler120and rear sprocket124.

Rear sprockets124may be positioned at the longitudinal rear of left track116and right track118and, similar to front idlers120, provide a rotating surface for the tracks to rotate about and a support point to transfer force between work vehicle100and the ground. Left track116and right track118rotate about rear sprockets124as 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 sprockets124is engaged with left track116or right track118. This engagement may be through a sprocket and pin arrangement, where pins included in left track116and right track118are engaged by recesses in rear sprockets124so as to transfer force. This engagement also results in the vertical height of left track116and right track118being only slightly larger than the outer diameter of each of rear sprockets124at the longitudinal back or rear of left track116and right track118. Rearmost engaging point132of left track116and right track118can be approximated as the point on each track vertically below the center of rear sprockets124, which is the rearmost point of left track116and right track118which engages the ground. When work vehicle100encounters a ground feature when traveling in a reverse or backward direction, left track116and right track118may first encounter it at rearmost engaging point132. If the ground feature is at a higher elevation than the surrounding ground surface, work vehicle100may begin pitching forward when rearmost engaging point132reaches the ground feature. If the ground feature is at a lower elevation than the surrounding ground surface, work vehicle100may continue backward without pitching until the center of gravity of work vehicle100is vertically above the edge of the downward ground feature. At that point, work vehicle100may pitch backward until rearmost engaging point132contacts the ground.

In this embodiment, each of rear sprockets124may be powered by a rotationally coupled hydraulic motor so as drive left track116and right track118and thereby control propulsion and traction for work vehicle100. 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 engine134of work vehicle100, and may be controlled by an operator in operator station136issuing commands which may be received by controller138and communicated to the left and right hydrostatic pumps by controller138. In alternative embodiments, each of rear sprockets124may be driven by a rotationally coupled electric motor or a mechanical system transmitting power from engine134.

Top idlers126are longitudinally positioned between front idlers120and rear sprockets124along the left and right sides of work vehicle100above track rollers122. Similar to track rollers122, each of top idlers126may be rotationally coupled to left track116or right track118through engagement between a lower surface of the tracks and an upper surface of top idlers126. This configuration may allow top idlers126to support left track116and right track118for the longitudinal span between front idler120and rear sprocket124, and prevent downward deflection of the upper portion of left track116and right track118parallel to the ground between front idler120and rear sprocket124.

Undercarriage114is affixed to, and provides support and tractive effort for, chassis140of work vehicle100. Chassis140is the frame which provides structural support and rigidity to work vehicle100, allowing for the transfer of force between blade142and left track116and right track118. In this embodiment, chassis140is 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. Sensor144is affixed to chassis140of work vehicle100and configured to provide a signal indicative of the movement and orientation of chassis140. In alternative embodiments, sensor144may not be affixed directly to chassis140, but may instead be connected to chassis140through intermediate components or structures, such as rubberized mounts. Connecting sensor144to chassis140in a fixed relative position through the use of mounts or brackets may allow sensor144to experience and measure the motion of chassis140, enabling measurements by sensor144to be indicative of the similar measurements taken from a sensor directly affixed to chassis140.

Sensor144is an optional component configured to provide a signal indicative of the angle of chassis140in the direction of roll104and the angular velocity of chassis140in the direction of roll104. These signals may be referred to as a chassis tilt signal and a chassis roll signal, respectively. Sensor144may also be configured to provide a signal or signals indicative of other positions or velocities of chassis140, including its inclination (i.e., an angle of chassis140relative to the direction of gravity) in a direction such as the direction of roll104, pitch108, and yaw112, its angular velocity or angular acceleration in a direction such as the direction of roll104, pitch108, yaw112, or its linear velocity or linear acceleration in a direction such as the direction of longitude102, latitude106, and vertical110. Sensor144may be configured to directly measure angular acceleration, angular velocity, or angular position, or measure one of these and derive or integrate the measurements to arrive at another of these (e.g., integrate angular velocity to arrive at angular position). The placement of sensor144on chassis140instead of on blade142or linkage146may allow sensor144to be better protected from damage, more firmly affixed to work vehicle100, more easily packaged, or more easily integrated into another component of work vehicle100such as controller138. This placement may allow for sensor144to be more cost effective, durable, reliable, or accurate than if sensor144were placed on blade142or linkage146, even though placing sensor144directly on blade142or linkage146(such as sensor149) may allow for a more direct reading of a position, velocity, or acceleration of those components.

Blade142is a work implement which may engage the ground or material to move or shape it. Blade142may 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, blade142of work vehicle100may be referred to as a six-way blade, six-way adjustable blade, or power-angle-tilt (PAT) blade. Blade142may 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 blade with fewer hydraulically controlled degrees of freedom, such as a 4-way blade that may not be angled, or actuated in the direction of yaw112.

Blade142is movably connected to chassis140of work vehicle100through linkage146, which supports and actuates blade142and is configured to allow blade142to be tilted relative to chassis140(i.e., moved in the direction of roll104). Linkage146may include multiple structural members to carry forces between blade142and the remainder of work vehicle100and may provide attachment points for hydraulic cylinders which may actuate blade142in the lift, tilt, and angle directions.

Linkage146includes c-frame148, a structural member with a C-shape positioned rearward of blade142, with the C-shape open toward the rear of work vehicle100. Each rearward end of c-frame148is pivotally connected to chassis140of work vehicle100, such as through a pin-bushing joint, allowing the front of c-frame148to be raised or lowered relative to work vehicle100about the pivotal connections at the rear of c-frame148. The front portion of c-frame148, which is approximately positioned at the lateral center of work vehicle100, connects to blade142through a ball-socket joint. This allows blade142three degrees of freedom in its orientation relative to c-frame148(lift-tilt-angle) while still transferring rearward forces on blade142to the remainder of work vehicle100.

Sensor149is affixed to blade142above the ball-socket joint connecting blade142to c-frame148. Sensor149, like sensor144, may be configured to measure orientation, angular velocity, or acceleration. Sensor149may be connected to blade142through an intermediate component, such as a bracket, mount, or portion of linkage146, at a fixed relative position to blade142so that may experience and measure the motion of blade142, enabling measurements by sensor149to be indicative of similar measurements taken from a sensor directly affixed to blade142. Sensor149may include one more gyroscopes which it may use to sense angular velocities and one or more accelerometers which it may use to measure linear acceleration. Sensor149may sense the tilt angle of blade142by measuring linear acceleration in three substantially perpendicular axes, and using those measurements to determine the direction of gravity and thereby determine the tilt angle of blade142. Controller138may actuate blade142based on the signals it receives from sensor144and sensor149, as further described with regard toFIG. 2,FIG. 3,FIG. 4, andFIG. 5. 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.

Blade142may be raised or lowered relative to work vehicle100by the actuation of lift cylinders150, which may raise and lower c-frame148and thus raise and lower blade142, which may also be referred to as blade lift. For each of lift cylinders150, the rod end is pivotally connected to an upward projecting clevis of c-frame148and the head end is pivotally connected to the remainder of work vehicle100just below and forward of operator station136. The configuration of linkage146and the positioning of the pivotal connections for the head end and rod end of lift cylinders150results in the extension of lift cylinders150lowering blade142and the retraction of lift cylinders150raising blade142. In alternative embodiments, blade142may be raised or lowered by a different mechanism, or lift cylinders150may be configured differently, such as a configuration in which the extension of lift cylinders150raises blade142and the retraction of lift cylinders150lowers blade142.

Blade142may be tilted relative to work vehicle100by the actuation of tilt cylinder152, which may also be referred to as moving blade142in the direction of roll104. For tilt cylinder152, the rod end is pivotally connected to a clevis positioned on the back and left sides of blade142above the ball-socket joint between blade142and c-frame148and the head end is pivotally connected to an upward projecting portion of linkage146. The positioning of the pivotal connections for the head end and the rod end of tilt cylinder152result in the extension of tilt cylinder152tilting blade142to the left or counterclockwise when viewed from operator station136and the retraction of tilt cylinder152tilting blade142to the right or clockwise when viewed from operator station136. In alternative embodiments, blade142may be tilted by a different mechanism (e.g., an electrical or hydraulic motor) or tilt cylinder152may be configured differently, such as a configuration in which it is mounted vertically and positioned on the left or right side of blade142, or a configuration with two tilt cylinders.

Blade142may be angled relative to work vehicle100by the actuation of angle cylinders154, which may also be referred to as moving blade142in the direction of yaw112. For each of angle cylinders154, the rod end is pivotally connected to a clevis of blade142while the head end is pivotally connected to a clevis of c-frame148. One of angle cylinders154is positioned on the left side of work vehicle100, left of the ball-socket joint between blade142and c-frame148, and the other of angle cylinders154is positioned on the right side of work vehicle100, right of the ball-socket joint between blade142and c-frame148. This positioning results in the extension of the left of angle cylinders154and the retraction of the right of angle cylinders154angling blade142rightward, or yawing blade142clockwise when viewed from above, and the retraction of left of angle cylinder150and the extension of the right of angle cylinders154angling blade142leftward, or yawing blade142counterclockwise when viewed from above. In alternative embodiments, blade142may be angled by a different mechanism or angle cylinders154may be configured differently.

Due to the geometry of linkage146and the geometry of the pivotal connections of tilt cylinder152in this embodiment, blade142is not tilted at a rate that is perfectly proportional to the extension or refraction speed of tilt cylinder152. This means that the tilt velocity of blade142is not perfectly proportional to the linear velocity with which tilt cylinder152is extending or retracting, and the tilt velocity of blade142may vary even when the linear velocity of tilt cylinder152is constant. This also means that tilt cylinder152has a mechanical advantage which varies depending on the tilt angle of blade142. Given a kinematic model of blade142, linkage146, and/or tilt cylinder152(e.g., formula(s) or table(s) providing a relationship between the position and/or movement of portions of blade142, linkage146, and tilt cylinder152) and the state of blade142, linkage146, and/or tilt cylinder152(e.g., sensor(s) sensing one or more positions, angles, or orientations of blade142, linkage146, and tilt cylinder152, such as sensor149), at least with respect to blade tilt, controller138may 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) or if only limited compensation accuracy is desired. Controller138may utilize this compensation and a desired velocity, for example a command to tilt blade142at a particular tilt velocity, to issue a command that may achieve a flow rate into tilt cylinder152that results in blade142being tilted at the particular vertical velocity regardless of the current position of blade142. For example, controller138may issue commands which vary the flow rate into tilt cylinder152in order to achieve a substantially constant tilt velocity of blade142.

Similarly, due to the positioning of lift cylinders150and angle cylinders154and the configuration of their connection to blade142, the velocity of blade lift and the angular velocity of blade angle are not perfectly proportional to the linear velocity of lift cylinders150and angle cylinders154, respectively, and the velocity of blade lift and the angular velocity of blade angle may vary even when the linear velocity of lift cylinders150and angle cylinders154, respectively, is constant. This also means that lift cylinders150and angle cylinders154each has a mechanical advantage which varies depending on the position of blade142. Much like with tilt cylinder152, given a kinematic model of blade142and linkage146, and the state of blade142and linkage146, at least with respect to blade lift and angle, controller138may 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 and angle) or if only limited compensation accuracy is required. Controller138may utilize this compensation and a desired velocity, for example a command to lift blade142at a particular velocity or angle blade142at a particular angular velocity, to issue commands that may vary the flow rate into lift cylinders150or angle cylinders154to result in blade142being lifted or angled at the particular velocity or angular velocity regardless of the current position of blade142or linkage146.

In alternative embodiments, blade142may be connected to the remainder of work vehicle100in a manner which tends to make the blade lift velocity (in direction of vertical110), tilt angular velocity (in the direction of roll104), or angle angular velocity (in the direction of yaw112) proportional to the linear velocity of lift cylinders150, tilt cylinder152, or angle cylinders154, respectively. This may be achieved with particular designs of linkage146and positioning of the pivotal connections of lift cylinders150, tilt cylinder152, and angle cylinders154. In such alternative embodiments, controller138may not need to compensate for non-linear responses of blade142to the actuation of lift cylinders150, tilt cylinder152, and angle cylinders154, or the need for compensation may be reduced.

Each of lift cylinders150, tilt cylinder152, and angle cylinders154is 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 toFIG. 2.

FIG. 2is a schematic of a portion of a system for controlling the hydraulic cylinder, the system including hydraulic and electrical components. Each of lift cylinders150, tilt cylinder152, and angle cylinders154is hydraulically connected to hydraulic control valve156, which may be positioned in an interior area of work vehicle100. Hydraulic control valve156may also be referred to as a valve assembly or manifold. Hydraulic control valve156receives pressurized hydraulic fluid from hydraulic pump158, which may be rotationally connected to engine134, and directs such fluid to lift cylinders150, tilt cylinder152, angle cylinders154, and other hydraulic circuits or functions of work vehicle100. Hydraulic control valve156may 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 valve156may 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 valve156may 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 inFIG. 1, the spools of hydraulic control valve156are shifted by pilots whose pressure is controlled, at least in part, by electrohydraulic pilot valve160in communication with controller138. Electrohydraulic pilot valve160is positioned within an interior area of work vehicle100and receives pressurized hydraulic fluid from a hydraulic source and selectively directs such fluid to pilot lines hydraulically connected to hydraulic control valve156. In this embodiment hydraulic control valve156and electrohydraulic pilot valve160are 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 pump158. In alternative embodiments, a pressure reducing valve may be used to reduce the pressure of pressurized hydraulic fluid provided by hydraulic pump158to a set pressure, for example 600 pounds per square inch, for usage by electrohydraulic pilot valve160. In the embodiment illustrated inFIG. 2, individual valves within electrohydraulic pilot valve160reduce the pressure from the received hydraulic fluid via solenoid-actuated spools which may drain hydraulic fluid to a hydraulic reservoir. In this embodiment, controller138actuates these solenoids by sending a specific current to each (e.g., 600 mA). In this way, controller138may actuate blade142by issuing electrical commands signals to electrohydraulic pilot valve160, which in turn provides hydraulic signals (pilots) to hydraulic control valve156, which shift spools to direct hydraulic flow from hydraulic pump158to actuate lift cylinders150, tilt cylinder152, and angle cylinders154. In this embodiment, controller138is in direct communication with electrohydraulic pilot valve160via electrical signals sent through a wire harness and is indirectly in communication with hydraulic control valve156via electrohydraulic pilot valve160.

Controller138, which may be referred to as a vehicle control unit (VCU), is in communication with a number of components on work vehicle100, including hydraulic components such as electrohydraulic pilot valve160, electrical components such as operator inputs within operator station136, sensor144, sensor149, and other components. Controller138is electrically connected to these other components by a wiring harness such that messages, commands, and electrical power may be transmitted between controller138and the remainder of work vehicle100. Controller138may be connected to some of these sensors or other controllers, such as an engine control unit (ECU), through a controller area network (CAN). Controller138may then send and receive messages over the CAN to communicate with other components on the CAN.

In alternative embodiments, controller138may send a command to actuate blade142in a number of different manners. As one example, controller138may 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 controller138and send current to specific solenoids within electrohydraulic pilot valve160based on those messages. As another example, controller138may send a command to actuate blade142by sending a command to actuate an input in operator station136. For example, an operator may use a joystick to issue commands to actuate blade142, and the joystick may generate hydraulic pressure signals, pilots, which are communicated to hydraulic control valve156to cause the actuation of blade142. In such a configuration, controller138may be in communication with electrical devices (e.g., solenoids, motors) which may actuate a joystick in operator station136. In this way, controller138may actuate blade142by sending commands to actuate these electrical devices instead of communicating signals to electrohydraulic pilot valve160.

FIG. 3is a perspective view of work vehicle100as work vehicle100drives over ground feature162, 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 vehicle100drives over ground feature162, left track116engages ground feature162while right track118does not. This causes work chassis140to tilt or roll, as left track116rises over ground feature162and right track118remains at the same height. This tilting or rolling motion for chassis140is transmitted to blade142via linkage146, and may cause blade142to tilt right (i.e., the left side of blade142will rise relative to the right side, or blade142will rotate clockwise when viewed from operator station136). Sensor144will measure and provide a signal indicative of the angular velocity of chassis140in the direction of roll104(i.e., a chassis roll signal), and sensor149will measure and provide a signal indicative of the angular velocity of blade142in the direction of roll104(i.e., a blade roll signal). Sensor144will also measure and provide a signal indicative of the orientation or angular position of chassis140relative to the direction of gravity (i.e., a chassis tilt signal) and sensor149will also measure and provide a signal indicative of the orientation or angular position of blade142relative to the direction of gravity (i.e., a blade tilt signal). Controller138may receive these signals. As one example, before encountering ground feature162, controller138may receive a chassis tilt signal and a blade tilt signal indicative of an angle of 3 degrees and a chassis roll signal and blade roll signal indicative of a roll rate of 0 degrees per second. As work vehicle100begins climbing ground feature162, controller138may receive a chassis tilt signal indicative of an angle of 5 degrees, a blade tilt signal indicative of an angle of 4.5 degrees, a chassis roll signal indicative of a roll rate of 10 degrees per second, and a blade roll signal indicative of a roll rate of 9 degrees per second. When left track116crests ground feature162, controller138may receive a chassis tilt signal and blade tilt signal indicative of an angle of 7 degrees and a chassis roll signal and blade roll signal indicative of a roll rate of 0 degrees per second.

During the process of work vehicle100driving over ground feature162, blade142will tilt relative to the ground surface as it tilts with chassis140. If the operator of work vehicle100fails to correct for ground feature162by commanding blade142to tilt in a manner that counteracts the effect of ground feature162on the tilt of blade142, work vehicle100will create variations on the ground surface instead of a smooth surface, such as a hill and a valley. As work vehicle100drives over these newly created hills and valleys will cause further tilting of chassis140, and blade142will once again be tilted and create further variations on the ground surface. This series of hills and valleys may be referred to as a “washboard” pattern or a “wavy” pattern.

While this is occurring, sensor144and sensor149send tilt and roll signals indicative of the tilt angle and roll rate of chassis140and blade142, respectively. Controller138may also receive signals from controls in operator station138which the operator may use to issue commands, for example a command to tilt blade142. If controller138does not sense a command from the operator to tilt blade142, but receives a tilt and/or roll signal from sensor144or sensor149indicating that chassis140or blade142is tilting, controller138may issue a command to electrohydraulic pilot valve160to tilt blade142to counteract the effect of this tilt. In this manner, controller138may attempt to mitigate or attenuate the effect of unintended tilting of chassis140and thereby create a smoother ground surface, as further described with regard toFIG. 4.

In this embodiment, each of the chassis tilt signal, chassis roll signal, blade tilt signal, and blade roll signal may indicate a value which indicates both the direction and magnitude of its value. For example, for the tilt signals, values in one half of the range may indicate a magnitude of a clockwise tilt while values in the other half of the range indicating a magnitude of counterclockwise tilt. These signals may be encoded as CAN messages, voltages, or currents, to name but three possible examples, which may be received by controller138.

In this embodiment, each of sensor144and sensor149comprise 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, sensor144and sensor149may each directly measure the linear acceleration or angular velocity in any direction, including the directions of longitude102, latitude106, vertical110, roll104, pitch108, and yaw112. 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 sensor144and sensor149. The measurements from the accelerometers and gyroscopes of sensor144and sensor149may 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 gravity very quickly but be subject to drift if these changes are integrated to determine the direction and error is allowed to accumulate.

The ability of sensor144and sensor149to provide both a tilt signal and a roll signal may allow controller138to better determine appropriate commands to actuate blade142. By examining just a tilt signal from sensor149, controller138may be able to maintain blade142near a target tilt angle with a relatively high degree of accuracy when work vehicle100is operating on a smooth surface. However, when work vehicle100is operating on rough terrain and tilting as it encounters ground features that are asymmetric in the direction of latitude106, the addition of a roll signal from sensor149may allow controller138to keep blade142nearer the target tilt angle. The roll signal from sensor149may provide an earlier indication that blade142is moving away from the target tilt angle and thereby allow controller138to more rapidly respond with a command to actuate blade142to keep it near the target tilt angle. Alternative embodiments may determine a derivative of a tilt signal or other signal indicative of the orientation or position of blade142in an effort to gain an earlier indication that blade142is moving away from the target tilt angle, but such methods may introduce or compound error in the signal and thereby reduce the accuracy with which controller138may keep blade142near the target tilt angle.

FIG. 4is a flowchart of control system400for actuating blade142of work vehicle100to create a level ground surface. Control system400is implemented on controller138of work vehicle100, and is initiated at the start of work vehicle100. In alternative embodiments, control system400may be initiated by the actuation of an operator control in operator station136, such as a button or a selection on an interactive display. In step402, controller138receives a signal from a blade control input in operator station136, such as a joystick that the operator may actuate to issue a blade tilt command. In step404, controller138determines whether the blade control input signal is outside of a deadband by determining whether the signal indicates a command (i.e., blade raise, tilt, or angle) above a threshold. This deadband may be used to avoid unintentional movement of the joystick near it neutral position, which may occur with vibration or machine movement, from being interpreted as a command to actuate blade142. The size of the deadband, and the corresponding threshold before a command is interpreted as an actual command, may be adjusted and may differ from work vehicle to work vehicle. If controller138determines that the blade control input signal is outside of the deadband, controller138performs step402. This loop between step402and step404effectively suspends control system400until the blade control input signal indicates that the operator is not issuing a command.

If the blade control input signal is in the deadband, which indicates that the operator is not issuing a command, controller138may perform step406next. In step406, controller138determine the target tilt angle of blade142. In this embodiment, controller138uses the tilt angle of blade142after the most recent tilt command of the operator as the target tilt angle. In this way, control system400may maintain blade142at the tilt angle it was last commanded to by the operator. In alternative embodiments, the target tilt angle may be set by the operator directly, such as through a switch which sends a command to set the target tilt angle to the current tilt angle of the blade when actuated, through increment or decrement buttons which may modify the target tilt angle when actuated, or through an interactive display in which the operator may directly input the target tilt angle. In other alternative embodiments, the target tilt angle may be set based on a signal received from a satellite-based navigation system (e.g., a Global Navigation Satellite System such as GPS, GLONASS, Compass, or Galileo) or a local positioning system, or a combination thereof. For example, a site plan may specify particular grades for different areas of the site and the location of work vehicle100may be determined based on the signal received from the navigation or positioning system and used to determine the appropriate target tilt angle from the site plan.

In step408, controller138receives the blade tilt signal from sensor149. As an example, controller138may receive a CAN message transmitted from sensor149to controller138via a wire harness. Controller138may be programmed to interpret the CAN message to read a value from 1 to 100, where 1 indicates a blade tilt angle of −15 degrees (i.e., 15 degree counterclockwise tilt when viewed from operator station136) and 100 indicates a blade tilt angle of +15 degrees with intermediate blade tilt angles represented by intermediate values 2-99.

In step410, controller138receives the blade roll signal from sensor149. As an example, controller138may receive a CAN message transmitted from sensor149to controller138via a wire harness. Controller138may be programmed to interpret the CAN message to read a value from 1 to 100, where 1 indicates a blade roll rate of −20 degrees per second (i.e., a tilt rate of 20 degrees per second counterclockwise when viewed from operator station136) and 100 indicates a blade roll angle of +20 degrees per second with intermediate blade roll rates represented by intermediate values 2-99.

In step412, controller138determines a command signal based on the target tilt angle determined in step406, the blade tilt signal received in step408, and the blade roll signal received in step410. In the embodiment illustrated inFIG. 4, controller138determines the command signal by applying a first gain to the difference between the target tilt angle and the blade tilt signal, applying a second gain to the blade roll signal, and combining the two results. For example, the first gain may be 5, the second gain may be −4, and the command signal may be indicative of a percent of maximum flow for tilt cylinder152. In this example, if the target tilt angle is −2 degrees, the blade tilt signal indicates a blade tilt of −4 degrees, and the blade roll signal indicates a roll rate of −3 degrees per second, the command signal will be 22, or 22% of the maximum flow of tilt cylinder152in the retraction direction to tilt blade142toward the target tilt angle of −2 degrees. In an alternative embodiment, the command signal may be determined with a two-axis lookup table which utilizes two values (the difference between the target tilt angle and the blade tilt signal; the blade roll signal) to return the command signal. Such a two-axis lookup table may be programmed to achieve the desired behavior for control system400. In other alternative embodiments, controller138may determine the command signal by a different method, including through the use of multiple lookup tables, equations, gains which are dependent on other factors, or PID (proportional-integrative-derivative) controllers, to name just a few possibilities. While the determination of the command signal in step412is based on the target tilt angle, blade tilt signal, and blade roll signal, other factors may also be used in the determination (e.g., speed of work vehicle100, soil type or condition, steering command or actual steering rate for work vehicle100).

In step414, controller138may optionally utilize a means for displaying the command signal and the difference between the target tilt angle and the blade tilt signal for the operator. Such means may include a display which may receive a signal from controller138and display the two values, a speaker which may receive a signal from controller138and audibly describe the two values, or a light or series of lights which may receive a signal from controller138and illuminate to communicate the two values.

In step416, the command signal determined in step412is sent by controller138to electrohydraulic pilot valve160. This command signal may be in the form of a CAN message to another controller which directly controls electrohydraulic pilot valve160or may be a current carried by a wire harness directly to a solenoid in electrohydraulic pilot valve160. This command signal may be used to change the pressure of one or more pilots from electrohydraulic pilot valve160to hydraulic control valve156, and thereby change the metering of hydraulic fluid to a hydraulic function such as tilt cylinder152to tilt blade142.

In alternative embodiments, control system400may be modified so as to suspend its operation while work vehicle100is turning. This modification may involve the addition of a step between step404and step406, in which controller138determines whether work vehicle100is turning (i.e., changing its heading or rotating in the direction of yaw112) greater than a minimum threshold. If it is, controller138may revert to step402. If it does not, controller138may proceed to step406. This modification to control system400may be beneficial if the design of sensor149is such that rotation of work vehicle100in the direction of yaw112interferes with the measurement of blade tilt or blade roll. In such cases, control system400may be suspended until work vehicle100is done turning, or a time period after that if sensor149needs further time to settle and accurately measure blade tilt and blade roll, to prevent control system400from operating based on inaccurate signals.

FIG. 5is a flowchart of control system500for actuating blade142of vehicle100. Control system500, unlike control system400, utilizes signals from sensor144to determine the command signal.

In step502, controller138receives a signal from a blade control input in operator station136. In step504, controller138determines whether the blade control input signal is outside of a deadband. If controller138determines that the blade control input signal is outside of the deadband, controller138performs step502. This loop between step502and step504effectively suspends control system500until the blade control input signal indicates that the operator is not issuing a command. In alternative embodiments, control system500may be adjusted so that it also operates when the operator is issuing a command. In such embodiments, control system500may sum the operator commands and its command signal to provide a summed command signal, or it may weight or adjust the operator commands and its command signal to achieve a modified command signal that is not simply the sum of the operator command and the determined command signal.

If the blade control input signal is in the deadband, which indicates that the operator is not issuing a command, controller138may perform step506next. In step506, controller138determine the target tilt angle of blade142. In this embodiment, controller138uses the tilt angle of blade142specified by a site plan for the current location work vehicle100.

In step508, controller138receives the blade tilt signal and blade roll signal from sensor149. As an example, controller138may receive a CAN message transmitted from sensor149to controller138via a wire harness. Controller138may be programmed to interpret the CAN message to read two values, one of which indicates a blade tilt angle and the other of which indicates the blade roll rate.

In step510, controller138receives the chassis roll signal from sensor144. As an example, controller138may receive a CAN message transmitted from sensor144to controller138via a wire harness. Controller138may be programmed to interpret the CAN message to read a value which indicates a chassis roll rate (i.e., the angular velocity of chassis140in the direction of roll104). In alternative embodiments, controller138may also receive the chassis tilt signal (i.e., the angle of chassis140relative to the direction of gravity) from sensor144.

In step512, controller138determines a command signal based on the target tilt angle determined in step506, the blade tilt signal received in step508, the blade roll signal received in step508, and the chassis roll signal received in step510. In the embodiment illustrated inFIG. 5, controller138determines the command signal by applying a first gain to the difference between the target tilt angle and the blade tilt signal and a second gain to the greater absolute value of the blade roll signal and chassis roll signal. For example, the first gain may be 5, the second gain may be −4, and the command signal may be indicative of a percent of maximum flow for tilt cylinder152. In this example, if the target tilt angle is −2 degrees, the blade tilt signal indicates a blade tilt of −4 degrees, the blade roll signal indicates a roll rate of −2 degrees per second, and the chassis roll signal is −3 degrees per second, the command signal will be 22, or 22% of the maximum flow of tilt cylinder152in the retraction direction to tilt blade142toward the target tilt angle of −2 degrees. In an alternative embodiment, the command signal may be determined with a three-axis lookup table which utilizes three values (the difference between the target tilt angle and the blade tilt signal; the blade roll signal; the chassis roll signal) to return the command signal. Such a three-axis lookup table may be programmed to achieve the desired behavior for control system500. In other alternative embodiments, controller138may determine the command signal by a different method, including through the use of multiple lookup tables, equations, gains which are dependent on other factors, or PID (proportional-integrative-derivative) controllers, to name just a few possibilities. While the determination of the command signal in step512is based on the target tilt angle, blade tilt signal, blade roll signal, and chassis roll signal, other factors may also be used in the determination (e.g., chassis tilt signal, speed of work vehicle100, soil type or condition, steering command or actual steering rate for work vehicle100). For example, controller138may utilize a chassis tilt signal from sensor144to determine the command signal by applying a gain to the signal and summing it with the other factors or by adjusting the magnitude of the chassis roll signal based on the chassis tilt signal, to name but two possibilities.

In step514, controller138may optionally utilize a means for displaying the command signal and the difference between the target tilt angle and the blade tilt signal for the operator. Such means may include a display which may receive a signal from controller138and display the two values, a speaker which may receive a signal from controller138and audibly describe the two values, or a light or series of lights which may receive a signal from controller138and illuminate to communicate the two values.

In step516, the command signal determined in step512is sent by controller138to electrohydraulic pilot valve160. This command signal may be in the form of a CAN message to another controller which directly controls electrohydraulic pilot valve160or may be a current carried by a wire harness directly to a solenoid in electrohydraulic pilot valve160. This command signal may be used to change the pressure of one or more pilots from electrohydraulic pilot valve160to hydraulic control valve156, and thereby change the metering of hydraulic fluid to a hydraulic function such as tilt cylinder152to tilt blade142.

While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is not restrictive in character, it being understood that illustrative embodiment(s) have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. Alternative embodiments of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may devise their own implementations that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the appended claims.