Patent Application
20170284067
The present disclosure is directed to a machine such as a motor grader having a blade positioning system, and more particularly, to apparatus and methods for determining a position of a drawbar of the machine relative to a frame using signals from rotational sensors.
Motor graders are used primarily as finishing tools to sculpt a surface of a construction site to a final shape and contour. Typically, motor graders include many hand-operated controls to steer the wheels of the grader, position a blade, and articulate a front frame of the motor grader. The blade is adjustably mounted to the front frame to move relatively small quantities of earth from side to side. In addition, the articulation of the front frame is adjusted by rotating the front frame of the grader relative to the rear frame of the grader.
One example of a motor grader and a mechanism for positioning a blade of the motor grader is provided in U.S. Pat. No. 8,103,417 issued to Gharsalli et al. (the '417 patent) on Jan. 24, 2012 entitled Machine with Automated Blade Positioning System. The '417 patent discloses a motor grader having a frame to which a drawbar-circle-moldboard (DCM) assembly is mounted. A drawbar is connected to the frame by a ball and socket joint. A pair of double acting hydraulic rams connected between the frame and the drawbar affect vertical movement of the DCM assembly, and a side shift cylinder connected between the drawbar and a link bar adjustable between a plurality of predefined positions affects horizontal movement of the DCM assembly. A circle assembly may be connected to the drawbar by a motor to drivingly support a moldboard assembly having the blade and blade positioning cylinders. The DCM assembly may be controlled to rotate the circle assembly and the moldboard assembly relative to the drawbar, and the blade may be movable horizontally and vertically and oriented relative to the circle assembly via blade positioning cylinders.
To produce a final surface contour, the blade and the frame may be adjusted to many different positions. As may be apparent from the '417 patent, positioning the drawbar and the blade of a motor grader is a complex task that may require information regarding the status and position of many components of the DCM assembly. The information may be used by the operator and/or a controller to ensure that the drawbar and the blade are correctly positioned to produce the desired contour, and to adjust the drawbar and the blade if they are not in the correct position.
In one aspect of the present disclosure, a motor grader is disclosed. The motor grader may include a frame, a drawbar that is multi-dimensional rotationally connected to the frame, a left lift arm pivotally connected to the frame, a right lift arm pivotally connected to the frame, a link bar pivotally connected to the left lift arm and the right lift arm, a left yoke pivotally connected to the left lift arm for rotation relative to the left lift arm about a left yoke primary axis, a left lift cylinder pivotally connected to the left yoke for rotation relative to the left yoke about a left yoke secondary axis, and multi-dimensional rotationally connected to the drawbar, a right yoke pivotally connected to the right lift arm for rotation relative to the right lift arm about a right yoke primary axis, a right lift cylinder pivotally connected to the right yoke for rotation relative to the right yoke about a right yoke secondary axis, and multi-dimensional rotationally connected to the drawbar, and a side shift cylinder multi-dimensional rotationally connected to the link bar by a first side shift cylinder connection and multi-dimensional rotationally connected to the drawbar by a second side shift cylinder connection. The motor grader may further include a left lift arm angle sensor operatively associated with the left lift arm to sense a left lift arm angle relative to the frame and output a left lift arm angle sensor signal that corresponds to the left lift arm angle, a left yoke primary angle sensor operatively associated with the left yoke to sense a left yoke primary angle relative to the left lift arm and output a left yoke primary angle sensor signal that corresponds to the left yoke primary angle, a left lift cylinder length sensor operatively associated with the left lift cylinder to sense a left lift cylinder length of the left lift cylinder and output a left lift cylinder length sensor signal that corresponds to the left lift cylinder length, and a right lift cylinder length sensor operatively associated with the right lift cylinder to sense a right lift cylinder length of the right lift cylinder and output a right lift cylinder length sensor signal that corresponds to the right lift cylinder length. The motor grader may also include a controller operatively connected to the left lift arm angle sensor, the left yoke primary angle sensor, the left lift cylinder length sensor and the right lift cylinder length sensor, with the controller being configured to calculate drawbar orientation angles of the drawbar relative to the frame based on the left lift arm angle sensor signal, the left yoke primary angle sensor signal, the left lift cylinder length sensor signal and the right lift cylinder length sensor signal.
In another aspect of the present disclosure, a method for determining drawbar orientation angles of a drawbar of a motor grader is disclosed. The drawbar of the motor grader is multi-dimensional rotationally connected to a frame of the motor grader, a link bar of the motor grader is connected to the frame by a left lift arm pivotally connected to the frame and to the link bar and a right lift arm pivotally connected to the frame and to the link bar, and the drawbar is suspended from the frame by a left lift cylinder and a right lift cylinder. The left lift cylinder is multi-dimensional rotationally connected to the drawbar and pivotally connected to a left yoke that is pivotally connected to the left lift arm, and the right lift cylinder is multi-dimensional rotationally connected to the drawbar and pivotally connected to a right yoke that is pivotally connected to the right lift arm. A side shift cylinder has a first side shift cylinder multi-dimensional rotation connection to the link bar and a second side shift cylinder multi-dimensional rotation connection to the drawbar. The method for determining the drawbar orientation angles includes calculating a left lift cylinder multi-dimensional rotation connection location relative to the frame, calculating a right lift cylinder multi-dimensional rotation connection location relative to the frame, and calculating the drawbar orientation angles of the drawbar relative to the frame based on the left lift cylinder multi-dimensional rotation connection location and the right lift cylinder multi-dimensional rotation connection location.
In a further aspect of the present disclosure, a motor grader is disclosed. The motor grader includes a frame, a drawbar mounted on the frame by a drawbar ball joint, a left lift arm pivotally connected to the frame, a right lift arm pivotally connected to the frame, a link bar pivotally connected to the left lift arm and the right lift arm, a left yoke pivotally connected to the left lift arm for rotation relative to the left lift arm about a left yoke primary axis, a left lift cylinder pivotally connected to the left yoke for rotation relative to the left yoke about a left yoke secondary axis, and connected to the drawbar by a left lift cylinder ball joint, a right yoke pivotally connected to the right lift arm for rotation relative to the right lift arm about a right yoke primary axis, a right lift cylinder pivotally connected to the right yoke for rotation relative to the right yoke about a right yoke secondary axis, and connected to the drawbar by a right lift cylinder ball joint, and a side shift cylinder connected to the link bar by a first side shift cylinder ball joint and connected to the drawbar by a second side shift cylinder ball joint. The motor grader further includes a left lift arm angle sensor operatively connected to the left lift arm to sense a left lift arm angle relative to the frame and output a left lift arm angle sensor signal that corresponds to the left lift arm angle, a right lift arm angle sensor operatively connected to the right lift arm to sense a right lift arm angle relative to the frame and output a right lift arm angle sensor signal that corresponds to the right lift arm angle, a left yoke primary angle sensor operatively connected to the left yoke to sense a left yoke primary angle relative to the left lift arm and output a left yoke primary angle sensor signal that corresponds to the left yoke primary angle, a right yoke primary angle sensor operatively connected to the right yoke to sense a right yoke primary angle relative to the right lift arm and output a right yoke primary angle sensor signal that corresponds to the right yoke primary angle, a left lift cylinder length sensor operatively connected to the left lift cylinder to sense a left lift cylinder length of the left lift cylinder and output a left lift cylinder length sensor signal that corresponds to the left lift cylinder length, and a right lift cylinder length sensor operatively connected to the right lift cylinder to sense a right lift cylinder length of the right lift cylinder and output a right lift cylinder length sensor signal that corresponds to the right lift cylinder length. The motor grader also includes a controller operatively connected to the left lift arm angle sensor, the right lift arm angle sensor, the left yoke primary angle sensor, the right yoke primary angle sensor, the left lift cylinder length sensor and the right lift cylinder length sensor. The controller is configured to calculate a left lift cylinder ball joint location relative to the frame based on the left lift arm angle of the left lift arm angle sensor signal, the left yoke primary angle of the left yoke primary angle sensor signal and the left lift cylinder length of the left lift cylinder length sensor signal, calculate a right lift cylinder ball joint location relative to the frame based on the right lift arm angle of the right lift arm angle sensor signal, the right yoke primary angle of the right yoke primary angle sensor signal and the right lift cylinder length of the right lift cylinder length sensor signal, and calculate a drawbar roll angle, a drawbar yaw angle and a drawbar pitch angle relative to the frame based on the left lift cylinder ball joint location and the right lift cylinder ball joint location.
Additional aspects are defined by the claims of this patent.
An exemplary embodiment of a machine 10 is illustrated in
Both the steerable traction device 12 and the driven traction device 14 may include one or more wheels located on each side of the motor grader 10 (only one side shown). The wheels may be rotatable and/or tiltable for use during steering and leveling of a work surface (not shown). Alternatively, the steerable traction device 12 and/or the driven traction device 14 may include tracks, belts, or other traction devices known in the art. The steerable traction device 12 may or may not also be driven, while the driven traction device 14 may or may not also be steerable. The frame 18 may connect the steerable traction device 12 to the driven traction device 14 by way of, for example, an articulation joint 26. Furthermore, the motor grader 10 may be caused to articulate the steerable traction device 12 relative to the driven traction device 14 via the articulation joint 26. The motor grader 10 may also include a neutral articulation feature that, when activated, may cause automatic realignment of the steerable traction device 12 relative to the driven traction device 14 to cause the articulation joint 26 to return to a neutral articulation position.
The power source 16 may include an engine (not shown) connected to a transmission (not shown). The engine may be, for example, a diesel engine, a gasoline engine, a natural gas engine, or any other engine known in the art. The power source 16 may also be a non-combustion source of power such as a fuel cell, a power storage device, or another source of power known in the art. The transmission may be an electric transmission, a hydraulic transmission, a mechanical transmission, or any other transmission known in the art. The transmission may be operable to produce multiple output speed ratios and may be configured to transfer power from the power source 16 to the driven traction device 14 at a range of output speeds.
The frame 18 may support a fixedly connected side shift mounting bracket 30. The frame 18 may be, for example, a single formed or assembled beam having a substantially hollow square cross-section. The substantially hollow square cross-section may provide the frame 18 with a substantially high moment of inertia required to adequately support the DCM assembly 20 and the side shift mounting bracket 30. The cross-section of frame 18 may alternatively be rectangular, round, triangular, or any other appropriate shape.
The side shift mounting bracket 30 may support a left lift cylinder 32 and a right lift cylinder 34 (
The left lift arm 40 and the right lift arm 42 may further be pivotally connected to the link bar 38. The link bar 38 may be pivotally connected to the left lift arm 40 by a left link bar pivot pin 72, and pivotally connected to the right lift arm 42 by a right link bar pivot pin 76 along a horizontal right link bar axis 78, with the left link bar axis 74 and the right link bar axis 78 being parallel to the left lift arm axis 50 and the right lift arm axis 62. Connected in this way, the side shift mounting bracket 30, the link bar, the left lift arm 40 and the right lift arm 42 may define a four-bar linkage with the lengths of the links between the axes 50, 62, 74, 78 being known, and the positions of the elements being determinable when an angle between two adjacent links is known. The side shift cylinder 36 may have a first side shift cylinder connection 80 attaching the side shift cylinder 36 to the link bar 38. The first side shift cylinder connection 80 may be proximate the left link bar axis 74 as shown herein, and may provide a multi-dimensional rotational connection to the link bar 38 with an appropriate connection mechanism such as a ball joint so that the side shift cylinder 36 may move relative to the link bar 38 about multiple rotational axes as necessary for the blade control system 24 to position the DCM assembly 20.
The DCM assembly 20 may include a drawbar 82 supported by the frame 18 and multi-dimensional rotational connector such as a ball and socket joint 84 (
The link bar 38 may be configured to be positioned and locked in place relative to the frame 18 and the side shift mounting bracket 30 at any one of a plurality of discrete positions. Referring to
As the lift cylinders 32, 34 and/or the side shift cylinder 36 are actuated, the DCM assembly 20 may pivot about the drawbar ball joint 84. Referring back to
Referring now to
The operator station 22 (
The blade control system 24 may move the blade 116 to commanded positions in response to the command signals received from dashboard 130 and/or the instrument panel 132. To properly position the blade 116, it may be necessary to know the positions, orientations and other parameters of the various components of the DCM assembly 20. Some of the necessary information may be measured directly by sensors or other appropriate means, while other information may be calculated based on the measured information. In the illustrated embodiment, the blade control system 24 may directly measure parameters via a left lift arm angle sensor 142, a right lift arm angle sensor 144, a left yoke primary angle sensor 146 a right yoke primary angle sensor 148, a left lift cylinder length sensor 150 and a right lift cylinder length sensor 152 that may each transmit corresponding sensor signals to the controller 120. It is contemplated that blade control system 24 may include other sensors depending on the particular implementation in the motor grader 10.
The left lift arm angle sensor 142 and the right lift arm angle sensor 144 may sense rotational angles of the left lift arm 40 and the right lift arm 42 about the left lift arm axis 50 and the right lift arm axis 62, respectively. For example, lift arm angle sensors 142, 144 may embody magnetic pickup type sensors associated with a magnet (not shown) embedded within protruding portions of the side shift mounting bracket 30. As the left lift arm 40 rotates about the left lift arm axis 50, the left lift arm angle sensor 142 may sense a left lift arm angle θLLA relative to the frame 18 and output a left lift arm angle sensor signal that corresponds to the left lift arm angle θLLA to the controller 120. As illustrated in
The left yoke primary angle sensor 146 and the right yoke primary angle sensor 148 may be rotational sensors of the types described above, and may sense rotational angles of the left yoke 44 and the right yoke 46 relative to the left lift arm 40 and the right lift arm 42 about the left yoke primary axis 54 and the right yoke primary axis 66, respectively. As the left yoke 44 rotates about the left yoke primary axis 54, the left yoke primary angle sensor 146 may sense a left yoke primary angle θLYP relative to the left lift arm 40 and output a left yoke primary angle sensor signal that corresponds to the left yoke primary angle θLYP to the controller 120. Referring again to
The left lift cylinder length sensor 150 and the right lift cylinder length sensor 152 may sense the extension and retraction of the left lift cylinder 32 and the right lift cylinder 34, respectively. In particular, the lift cylinder length sensors 150, 152 may embody magnetic pickup type sensors associated with magnets (not shown) embedded within the piston assemblies of the lift cylinder length sensors 150, 152. As the left lift cylinder 32 extends and retracts, the left lift cylinder length sensor 150 may sense an amount of extension of the left lift cylinder 32 and output a left lift cylinder length sensor signal that corresponds to the amount of extension so that the controller 120 can convert the amount of extension into a left lift cylinder length LLLC from the left yoke primary axis 54 to a center of the left lift cylinder connection 86 that is connected to the drawbar 82. The right lift cylinder length sensor 152 may similarly sense an amount of extension of the right lift cylinder 34 and output a right lift cylinder length sensor signal that corresponds to the amount of extension so that the controller 120 can convert the extension into a right lift cylinder length LRLC from the right yoke primary axis 66 to a center of the right lift cylinder connection 88 that is connected to the drawbar 82. In alternative embodiments, the lift cylinder length sensors 150, 152 may embody other types of linear or position sensors such as, for example, magnetostrictive-type sensors associated with a wave guide internal to the lift cylinders 32, 34, cable type sensors associated with cables externally mounted to the lift cylinders 32, 34, internally or externally mounted optical type sensors, or any other type of linear or distance sensor known in the art.
The controller 120 may also be electrically connected to output devices to which control signals are transmitted to control the position of the DCM assembly 20 and the blade 116. For purposes of the present disclosure in particular, the controller 120 may be connected to and communicate with a left lift cylinder actuator 162, a right lift cylinder actuator 164, a side shift cylinder actuator 166 and a center pin actuator 168. The actuators 162, 164, 166, 168 may be operatively coupled to the corresponding cylinders 32, 34, 36 and the center pin 106 to cause pressurized fluid flow and cause the cylinders 32, 34, 36 and the center pin 106 to extend and retract to position the drawbar 82 and, correspondingly, the blade 116. The actuators 162, 164, 166, 168 may be a solenoid or other type of actuator to which the controller 120 may output control signals or solenoid current to move a corresponding valve element (not shown) to positions to create fluid flow to the cylinders 32, 34, 36 and the center pin 106 corresponding to commands from an operator at the dashboard 130 and/or the instrument panel 132. In alternative embodiments, the actuators 162, 164, 166, 168 may be any other appropriate actuation device capable of converting the control signals from the controller 120 into extension and retraction of the cylinders 32, 34, 36 and the center pin 106.
While many of important parameters of the DCM assembly 20 may be determined via sensors, such as the parameters sensed by the lift arm angle sensors 142, 144, the yoke primary angle sensors 146, 148 and the lift cylinder length sensors 150, 152 discussed above, it may be impractical to directly determine values for some parameters that are necessary for understanding the total blade position for of the blade 116 and accurately positioning the blade 116 during operation of the motor grader 10. For example, the side shift cylinder 36 as illustrated herein may be located in a confined area of the DCM assembly 20 that may limit the space available to implement a linear sensor that can measure a side shift cylinder length LSSC of the side shift cylinder 36. In the present disclosure, additional parameters may be calculated from known and measured parameters according to a drawbar position and side shift cylinder length calculation routine 180 as shown in
The routine 180 may begin at a block 182 where the controller 120 may determine the left lift arm angle θLLA from the left lift arm angle sensor signals transmitted by the left lift arm angle sensor 142. With the left lift arm angle θLLA known, control may pass to a block 184 where the controller 120 may calculate the location of the first side shift cylinder connection 80 to the link bar 38. In one embodiment, a global coordinate system may be used having its origin on the frame 18 at a center of rotation of the drawbar ball joint 84 with the X-axis aligned parallel to a longitudinal axis of the frame 18, the Y-axis extending vertically and the Z-axis being horizontal and transverse to the longitudinal axis of the frame 18. The X-axis may be positive in the forward direct and negative in the aft direction, the Y-axis may be positive as it extends upward, and the Z-axis may be positive to the right. Also, the lift arm axes 50, 62, the yoke primary axes 54, 66 and the link bar axes 74, 78 may be parallel to the X-axis so that the link bar 38, the lift arms 40, 42 and the yokes 44, 46 move within YZ planes and maintain constant coordinates along the X-axis.
As mentioned previously, the side shift mounting bracket 30, the link bar 38 and the lift arms 40, 42 form a four-bar linkage with known link lengths. In the present embodiment, the first side shift cylinder connection 80 may be centered approximately on the left link bar axis 74 so that the distance to the left lift arm axis 50 is constant. Consequently, the Y- and Z-coordinates of the first side shift cylinder connection 80 may be calculated by the controller 120 based on the known Y- and Z-coordinates of the left lift arm axis 50, the sensed left lift arm angle θLLA and the known distance between the axes 50, 74 in the YZ plane, with the X-coordinate is known and constant as discussed above. The calculation may also be performed using the left lift arm angle θRLA that will also make the other angles and the positions of the link bar axes 74, 78 determinate. Alternatively, because the link bar 38 and the four-bar linkage have a finite number of discrete positions due to the link bar holes 92-104 and the center pin 106, the possible values of the left lift arm angle θLLA and corresponding coordinates of the first side shift cylinder connection 80 may be stored in the memory 124 in a look-up table that may be accessed by the controller 120 using the sensed left lift arm angle θLLA to reduce processing time and computing resources.
With the location of the first side shift cylinder connection 80 calculated at the block 184, control may pass to a block 186 where the controller 120 determines the left yoke primary angle θLYP and the right yoke primary angle θRYP based on the yoke primary angle sensor signals. Control may then pass to a block 188 where the controller 120 may determine the left lift cylinder length LLLC and the right lift cylinder length RLLC from the lift cylinder length sensor signals.
Knowing the lift arm angles θLLA, θRLA, the yoke primary angles θLYP, θRYP and the lift cylinder lengths LLLC, LRLA may allow the controller 120 to calculate the locations of the left lift cylinder connection 86 and the right lift cylinder connection 88 at a block 190. In one embodiment of calculation logic, a left yoke primary global point 192 (
The left yoke primary global point 192 may be located at an intersection of the left yoke primary axis 54 and a perpendicular line 194 between the left yoke primary axis 54 and the left yoke secondary axis 58. The left yoke primary global point 192 and a left yoke secondary global point 196 at the intersection of the perpendicular line 194 and the left yoke secondary axis 58 may be separated by a left yoke axis offset distance dL. The coordinates xL, yL, zL can be found by finding the Y- and Z-coordinates of the left yoke primary axis 54 and the X-coordinate of the left yoke secondary axis. The Y- and Z-coordinates will change based on the discrete positions of the link bar 38 and the left lift arm angle θLLA. The coordinates may be calculated, or may be resolved simply by having a look-up table for the coordinates of the left yoke primary global point 192 and the right yoke global point for each position of the link bar 38 based on either the left lift arm angle θLLA or the right lift arm angle θRLA. An example of such a global point coordinate look-up table 198 is shown in
Once the coordinates xL, yL, zL are determined, coordinates xLH, yLH, zLH of the left yoke secondary global point 196 can be calculated. The left yoke secondary pivot pin 56 may also be known as the left lift cylinder head pin 56, and the left yoke secondary global point 196 provides a global location for the left lift cylinder head pin 56. The coordinates xLH, yLH, zLH may be determined based on the left yoke axis offset distance dL and a left yoke absolute primary angle θLYAP (
The coordinates xLH, yLH, zLH and the left yoke absolute primary angle θLYAP may be used to determine a local coordinate system (
After the locations of the lift cylinder connections 86, 88 are calculated at the block 190, control may pass to a block 200 where the controller 120 may calculate drawbar orientation angles θDBX, θDBY, θDBZ for the rotation of the drawbar 82 about the x-axis, the y-axis and the z-axis, respectively, that will define the total drawbar position. The drawbar orientation angles θDBX, θDBY, θDBZ may be calculated from the global locations of the lift cylinder connections 86, 88 and the constraint of the drawbar 82 being to the frame 18 at the drawbar ball joint 84 at a point having coordinates (0, 0, 0) in the coordinate systems of both the frame 18 and the drawbar 82. Vectors drawn from that point to the locations of the lift cylinder connections 86, 88 define the total drawbar position in the coordinate systems so that the drawbar orientation angles θDBX, θDBY, θDBZ are determinable by the controller 120. The x-axis orientation angle θDBX may correspond to a drawbar roll angle of the drawbar 82 relative to the frame 18, the y-axis orientation angle θDBY may correspond to a drawbar yaw angle of the drawbar 82, and the z-axis orientation angle θDBZ may correspond to a drawbar pitch angle of the drawbar 82.
Calculation of the locations of the lift cylinder connections 86, 88 may also facilitate determination of the side shift cylinder length LSSC of the side shift cylinder 36 that may have been measured directly in previous machines by a length sensor operatively connected to the side shift cylinder 36. After the locations of the lift cylinder connections 86, 88 are calculated at the block 190, control may also pass to a block 202 where the controller 120 may calculate the location of the second side shift cylinder connection 90 to the drawbar 82. A relative location of the second side shift cylinder connection 90 on the drawbar 82 with respect to one or both of the lift cylinder connections 86, 88 will be fixed and known. With the location of the drawbar 82 fixed and the relationships between the connections 86, 88, 90 known, the location of the second side shift cylinder connection 90 may be calculated using equations that will be apparent to those skilled in the art.
With the location of the first side shift cylinder connection 80 calculated at the block 184 and the location of the second side shift cylinder connection 90 calculated at the block 202, control may pass to a block 204 where the controller 120 may calculate the side shift cylinder length LSSC of the side shift cylinder 36. Knowing the coordinates of the two end points of the side shift cylinder length LSSC (i.e., the locations of the side shift cylinder connections 80, 90), the controller 120 may solve the three-dimensional Pythagorean Theorem to calculate the side shift cylinder length LSSC.
With the configuration of the sensors 142-152 and the calculations of the drawbar position and side shift cylinder length calculation routine 180, it is possible to derive the total drawbar position as part of the total blade position without the necessity of directly measuring many relevant parameters of the DCM assembly 20. Utilizing the rotation sensors 142-148 for the lift arms 40, 42 and the yokes 44, 46, it is possible to omit a sensor for directly measuring the side shift cylinder length LSSC where the side shift cylinder 36 is located within a confined space. Moreover, linear sensors can be significantly more expensive than rotary sensors so the arrangement in accordance with the present disclosure may reduce the overall cost of the motor grader 10.
Those skilled in the art will understand that the configuration of the motor grader 10 and the electrical components of the blade control system 24 is exemplary. Variations in the electrical components of the motor grader 10 are contemplated allowing with corresponding modifications to the routine 180. For example, the two lift arm angle sensors 142, 144 and the two yoke primary angle sensors 146, 148 may be provided as illustrated and described herein for redundancy and robustness in the blade control system 24, and the second sensors may reduce the number of calculations and processing resources required of the controller 120 by directly measuring the corresponding angles. However, in alternative embodiments, one of the lift arm angle sensors 142, 144 may be omitted. If the left lift arm angle sensor 142 is provided and the left lift arm angle θLLA is directly measured, the right lift arm angle sensor 144 may be omitted, and the right lift arm angle θRLA may be calculated based on the known parameters of the four-bar linkage formed by the frame 18, the link bar 38 and the lift arms 40, 42, or obtained from the look-up table 198. Similar calculations may be performed for the left lift arm angle θLLA if only the right lift arm angle sensor 144 is provided and measure the right lift arm angle θRLA.
In other alternative embodiments, only one of the yoke primary angle sensors 146, 148 may be needed for the theoretical solution of the total drawbar position outlined above. Where only the left yoke primary angle sensor 146 is incorporated into the design, the left yoke primary angle θLYP may be measured, and the location of the left lift cylinder connection 86 may be calculated as illustrated and described above. With the location of the left lift cylinder connection 86 established, the right yoke primary angle θRYP and the location of the right lift cylinder connection 88 may be calculated based on the location of the left lift cylinder connection 86, the right lift arm angle θRLA (directly measured or derived), the right lift cylinder length LRLC derived from the right lift cylinder length sensor 152, and the known geometries of the right yoke 46 and the drawbar 82. Similar calculations may be performed to determine the left yoke primary angle θLYP and the location of the left lift cylinder connection 86 where only the right yoke primary angle sensor 148 is provided. As will be apparent to those skilled in the art, the total drawbar position may be obtained using up to six sensors or by as few as four sensors as discussed herein, and such variations in the blade control system 24 are contemplated by the inventors as having use in motor graders 10 in accordance with the present disclosure.
While the preceding text sets forth a detailed description of numerous different embodiments, it should be understood that the legal scope of protection is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the scope of protection.
It should also be understood that, unless a term was expressly defined herein, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to herein in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning.
