Motor Grader Cross Slope Control With Articulation Compensation

Abstract

A motor grader is provided having cross slope cut angle control for providing accurate cuts generally, and particularly while the machine is travelling in other than a straight and level fashion. A controller is configured to adjust the cross slope angle of the blade, so that the cross slope cut angle corresponds to a desired cross slope cut angle. The controller receives a signal indicative of the desired cross slope cut angle and executing a pure pursuit procedure to identify a blade cross slope angle to yield the desired cross slope cut angle. The pure pursuit procedure includes identifying a blade travel direction, and identifying a horizontal component thereof. The blade edge is projected onto a plane perpendicular to the horizontal component of the blade travel direction, generating a slope function specifying the cross slope cut angle as a function of blade cross slope angle.

What is claimed is: 
     
         1 . A method for controlling a blade of a motor grader to provide a desired cross slope cut angle, the motor grader including a frame having a front frame portion and a rear frame portion, the blade, wherein the blade has an edge and a center point, one or more blade slope actuators, and a plurality of machine sensors, the method comprising:
 receiving a signal indicative of the desired cross slope cut angle;   receiving one or more sensor signals from the plurality of sensors;   executing a pure pursuit procedure to identify a blade slope to yield the desired cross slope cut angle based on the one or more sensor signals, the pure pursuit procedure comprising:
 identifying a direction of travel of the blade based on at least one of the sensor signals, the direction of travel of the blade having a horizontal component, and 
   identifying an angle between the horizontal component and the front frame portion;
 identifying a machine travel direction at the blade center point; 
 generating a projection of the blade edge onto a plane perpendicular to the horizontal component of the direction of travel of the blade; and 
 based on the projection of the blade edge onto the perpendicular plane, generating a slope function specifying the cross slope cut angle as a function of blade cross slope angle. 
   
     
     
         2 . The method for controlling a blade of a motor grader in accordance with  claim 1 , further comprising outputting a blade slope command to the one or more blade slope actuators, the blade slope command representing a blade slope angle that will yield the desired cross slope cut angle in keeping with the slope function. 
     
     
         3 . The method for controlling a blade of a motor grader in accordance with  claim 1 , wherein the plurality of sensors include a blade slope sensor for sensing the slope of the blade relative to the front frame portion and a blade rotation sensor for sensing a rotation of the blade relative to the front frame portion. 
     
     
         4 . The method for controlling a blade of a motor grader in accordance with  claim 3 , wherein the plurality of sensors include a mainfall sensor for sensing a pitch angle of the motor grader and a roll angle of the motor grader. 
     
     
         5 . The method for controlling a blade of a motor grader in accordance with  claim 4 , wherein the plurality of sensors further include a steering sensor for sensing a steering angle of the motor grader and an articulation sensor for sensing an articulation angle between the front frame portion and the rear frame portion. 
     
     
         6 . The method for controlling a blade of a motor grader in accordance with  claim 5 , wherein the articulation angle is non-zero. 
     
     
         7 . The method for controlling a blade of a motor grader in accordance with  claim 1 , wherein the signal indicative of the desired cross slope cut angle is generated based on an operator command. 
     
     
         8 . A motor grader having improved cross slope cut angle control, the motor grader comprising:
 a frame having a front frame portion and a rear frame portion,   a blade movably attached to the front frame portion, wherein the blade has an edge and a center point;   one or more blade slope actuators to adjust the cross slope angle of the blade;   a plurality of machine sensors; and   a controller configured to adjust the cross slope angle of the blade, so that the cross slope cut angle corresponds to a desired cross slope cut angle, by receiving a signal indicative of the desired cross slope cut angle, receiving one or more sensor signals from the plurality of sensors, and executing a pure pursuit procedure to identify a blade cross slope angle to yield the desired cross slope cut angle based on the one or more sensor signals, the pure pursuit procedure comprising:
 identifying a direction of the blade cutting edge based on at least one of the sensor signals; 
 identifying a machine travel direction at the blade center point; 
 generating a normal direction of the plane formed by the blade cutting edge and the travel direction; and 
 based on the normal direction of the plane formed by the blade cutting edge and the travel direction, generating a slope function specifying the cross slope cut angle as a function of blade cross slope angle. 
   
     
     
         9 . The motor grader in accordance with  claim 8 , wherein the controller is further configured to output a blade slope command to the one or more blade slope actuators, the blade slope command representing a blade slope angle that will yield the desired cross slope cut angle in keeping with the slope function. 
     
     
         10 . The motor grader in accordance with  claim 8 , wherein the plurality of sensors include a blade slope sensor for sensing the slope of the blade relative to the front frame portion and a blade rotation sensor for sensing a rotation of the blade relative to the front frame portion. 
     
     
         11 . The motor grader in accordance with  claim 10 , wherein the plurality of sensors include a mainfall sensor for sensing a pitch angle of the motor grader and a roll angle of the motor grader. 
     
     
         12 . The motor grader in accordance with  claim 11 , wherein the plurality of sensors further include a steering sensor for sensing a steering angle of the motor grader and an articulation sensor for sensing an articulation angle between the front frame portion and the rear frame portion. 
     
     
         13 . The motor grader in accordance with  claim 8 , wherein the controller is further configured to generate the signal indicative of the desired cross slope cut angle based on receipt of an operator command. 
     
     
         14 . A method for controlling a blade of a motor grader to provide a desired cross slope cut angle via one or more blade slope actuators the method comprising:
 measuring a blade cross slope angle;   generating a blade travel vector representing a direction of travel of the blade;   projecting the blade travel vector onto a horizontal surface to define a blade travel projection, and generating a plane perpendicular to the blade travel projection;   projecting a cutting edge of the blade onto the plane perpendicular to the projection to generate a cut projection as a function of blade cross slope angle; and   adjusting a cross slope angle of the blade such that an angle of the cut projection matches the desired cross slope cut angle.   
     
     
         15 . The method for controlling a blade of a motor grader in accordance with  claim 14 , wherein measuring the blade cross slope angle includes receiving a slope signal from a blade slope sensor. 
     
     
         16 . The method for controlling a blade of a motor grader in accordance with  claim 14 , wherein generating a blade travel vector representing a direction of travel of the blade includes sensing a pitch angle and roll angle of the motor grader and sensing a steering angle and articulation angle of the motor grader. 
     
     
         17 . The method for controlling a blade of a motor grader in accordance with  claim 16 , wherein sensing a pitch angle and roll angle of the motor grader includes receiving a signal from a mainfall sensor. 
     
     
         18 . The method for controlling a blade of a motor grader in accordance with  claim 17 , wherein the mainfall sensor is a gravitational sensor. 
     
     
         19 . The method for controlling a blade of a motor grader in accordance with  claim 17 , wherein the mainfall sensor is a gyroscopic sensor. 
     
     
         20 . The method for controlling a blade of a motor grader in accordance with  claim 14 , wherein adjusting a cross slope angle of the blade such that an angle of the cut projection matches the desired cross slope cut angle includes sending a slope command to one or more blade slope actuators.