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BACKGROUND 
     The present invention relates to systems and methods of mitigating movement of a vehicle body. More specifically, the present invention relates to mitigating pitch and heave in earth-moving vehicles and similar machines. 
     Construction and earth-moving vehicles (e.g., front loaders, excavators, bull dozers, cranes, etc.) operate on unimproved surfaces and off-road conditions. In addition, such vehicles generally have minimal or no suspension. Thus, traveling over the unimproved surfaces or lifting a load can result in pitching and/or heaving. This pitching and/or heaving can result in the contents of a bucket spilling, discomfort and fatigue for a driver/operator of the machine, and increased chassis loading potentially leading to premature malfunctions. 
     SUMMARY 
     A variety of names are used to refer to vehicles such as the ones described above. The terms “heavy equipment” and heavy-duty vehicles are often used to refer to vehicles designed for executing construction tasks and earth moving. The term “heavy-duty vehicle” will be used herein to refer generically to such machines. 
     In one embodiment, the invention provides a heavy-duty vehicle. The heavy-duty vehicle includes a movable arm, an operator control, an inertial measurement device, and a controller. The operator control directs movement of the movable arm. The inertial measurement device measures a pitch motion and a heave motion of the heavy-duty vehicle. The controller is coupled to the operator control unit and the inertial measurement device, and mitigates pitch motions and heave motions by adjusting a movement of the movable arm. The inertial measurement device detects a motion in one of a first direction and a second direction and determines a direction of movement of the arm (e.g., in one of a third direction and a fourth direction). The controller increases the speed of motion of the arm when the motion is in the first direction and the movement is in the third direction or when the motion is in the second direction and the movement is in the fourth direction. 
     In another embodiment the invention provides a method of mitigating pitch and heave motions in a heavy-duty vehicle by detecting at least one of a pitch motion and a heave motion of the heavy-duty vehicle, determining a direction of a movement of a moveable arm of the heavy-duty vehicle, and altering the movement of the moveable arm to mitigate the detected motion. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a front loader. 
         FIG. 2  is a block diagram of a control system for implementing the invention. 
         FIGS. 3A-3C  illustrate an operation for mitigating pitch and heave in a heavy-duty vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIG. 1  shows a heavy-duty vehicle (e.g., a front loader  100 ). The front loader  100  includes a two axles (at least one of which is driven)  105 , an articulating arm (or boom)  110  with a shovel (or bucket)  115 , a driver&#39;s seat  120 , and various controls  125 . During operation, the front loader  100  is subjected to pitch motions (i.e., roll around a horizontal axis) depicted by arrow  130  and to heave motions (i.e., accelerations in a vertical direction, i.e., up and down) depicted by arrow  135 . These motions can be caused by a number of factors including the raising and/or lowering of the articulated arm  110 , and movement of the front loader  100 , especially over uneven ground. These motions can result in contents of the bucket spilling, wear and tear on the front loader  100 , and discomfort/fatigue for the operator. 
       FIG. 2  shows a schematic diagram of a control system  200  for a heavy-duty vehicle incorporating closed-loop control for mitigating pitch and heave in a heavy-duty vehicle. Electrical connections are shown with dashed lines. Hydraulic connections are shown with solid lines. In the embodiment shown, the control system  200  controls the articulating arm  110  using hydraulics. Other embodiments include different systems such as pneumatic, electric, etc. for controlling the articulating arm  110 . The system  200  includes an operator control unit  205 , an electronic control unit (ECU)  210 , an inertial measurement unit  215 , and a hydraulic system  217  including a pump regulator  220 , a valve driver  225 , a pump  235 , a spool valve  240  having a first end  245  and a second end  250 , a fluid reservoir  255 , and a hydraulic cylinder  260 . The inertial measurement unit  215  incorporates one or more accelerometers, gyroscopes, or other devices capable of detecting motion. 
     The ECU  210  receives a signal from the operator control unit  205  indicating whether the operator wants to raise or lower the articulating arm  110 . The ECU  210  also receives a signal from the inertial measurement unit  215  indicative of movement of the heavy-duty vehicle (e.g., pitch and heave). Based on the various signals the ECU  210  receives, the ECU  210  generates signals or commands to move the spool valve  240  in a first direction or a second direction (via the valve driver  225 ) and controls the pump  235  (via the pump regulator  220 ). By moving the spool valve  240  in a first direction, and running the pump  235 , the ECU  210  causes hydraulic fluid to flow into the first end  245  of the hydraulic cylinder  260  raising the articulating arm  110 . Hydraulic fluid flows out of the second end  250  of the hydraulic cylinder  260 , through the spool valve  240  and into the fluid reservoir  255 . Based on the input from the operator control unit  205 , the ECU  210  controls the speed of the pump  235  to control how quickly the arm  110  is raised. 
     Similarly, the ECU  210 , based on an input from the operator control unit  205 , can move the spool valve  240  in a second direction and run the pump  235 , resulting in hydraulic fluid flowing into the second end  250  of the hydraulic cylinder  260  lowering the articulating arm  110 . Hydraulic fluid flows out of the first end  245  of the hydraulic cylinder  260 , through the spool valve  240  and into the fluid reservoir  255 . Based on the input from the operator control unit  205 , the ECU  210  controls the speed of the pump  235  to control how quickly the arm  110  is lowered. 
     The ECU  210  receives feedback from the inertial measurement unit  215  indicative of the impact of the ECU&#39;s  210  control of the spool valve  240  and the pump  235 , resulting in the control system  200  operating as a closed loop control. 
       FIGS. 3A to 3C  show an embodiment of the operation of the system  200  to mitigate pitch and heave motions in a heavy-duty vehicle. The ECU  210  determines if the inertial measurement unit  215  has detected a pitch motion (e.g., movement in a first pitch direction, i.e., forward, around a horizontal axis or movement in a second pitch direction, i.e., backward, around a horizontal axis) (step  305 ). If there is a pitch motion, the ECU  210  checks if the operator is attempting to raise the articulating arm  110  (i.e., move the articulating arm  110  in a third direction) (step  310 ). That is, the ECU  210  determines if the operator input unit  205  is indicating that the operator is controlling an input indicating the operator wishes to raise the arm  110 . If the operator is attempting to raise the arm  110 , the ECU  210  checks if the pitch motion is in a forward direction (step  315 ). If the pitch motion is in the forward direction, the ECU  210  increases the speed of the arm in the up direction (step  320 ) to attempt to mitigate the forward pitch motion. If the motion is mitigated (step  325 ), the ECU  210  exits operation until the next cycle (e.g., time period) (step  330 ). If the motion was not mitigated at step  325 , the ECU  210  continues operation at step  310 . 
     If the pitch motion was backwards (step  315 ), the ECU  210  decreases the speed at which the arm is being raised (step  335 ) to attempt to mitigate the backward pitch motion. If the motion is mitigated (step  325 ), the ECU  210  exits operation until the next cycle (e.g., time period) (step  330 ). If the motion was not mitigated at step  325 , the ECU  210  continues operation at step  310 . 
     If the operator is not raising the arm  110  (step  310 ), the ECU  210  checks if the operator is attempting to lower the arm  110  (i.e., move the articulating arm  110  in a fourth direction) (step  340 ). If the operator is attempting to lower the arm  110 , the ECU  210  checks if the pitch motion is in a forward direction (step  345 ). If the pitch motion is in the forward direction, the ECU  210  decreases the speed of the arm in the downward direction (step  350 ) to attempt to mitigate the forward pitch motion. If the motion is mitigated (step  325 ), the ECU  210  exits operation until the next cycle (e.g., time period) (step  330 ). If the motion was not mitigated at step  325 , the ECU  210  continues operation at step  310 . 
     If the pitch motion was backwards (step  345 ), the ECU  210  increases the speed at which the arm is being lowered (step  355 ) to attempt to mitigate the backward pitch motion. If the motion is mitigated (step  325 ), the ECU  210  exits operation until the next cycle (e.g., time period) (step  330 ). If the motion was not mitigated at step  325 , the ECU  210  continues operation at step  310 . 
     If the arm is not being raised (step  310 ) nor lowered (step  340 ), the ECU  210  determines whether the pitch motion is forward (step  360 ,  FIG. 3B ). If the motion is forward, the ECU  210  raises the arm  110  up in an attempt to mitigate the motion (step  365 ) even though the operator is not attempting to raise the arm  110 . The ECU  210  then continues operation at step  325  with determining if the motion has been mitigated. If the motion at step  360  was not forward (i.e., was backward), the ECU  210  lowers the arm  110  in an attempt to mitigate the motion (step  370 ) even though the operator is not attempting to lower the arm  110 . The ECU  210  then continues operation at step  325  with determining if the motion has been mitigated. 
     If, the ECU  210  determines the inertial measurement unit  215  has not detected a pitch motion (e.g., movement around a horizontal axis) (step  305 ), the ECU  210  determines if the inertial measurement unit  215  has detected a heave motion (e.g., movement in a first heave direction, i.e., downward, or movement in a second heave direction, i.e., upward) (step  375 ,  FIG. 3C ). If there is not a heave motion, the ECU  210  exits the operation until the next cycle (e.g., time period) (step  380 ). 
     If there is a heave motion, the ECU  210  checks if the operator is attempting to raise the articulating arm  110  (step  385 ). If the operator is attempting to raise the arm  110 , the ECU  210  checks if the heave motion is in an up direction (step  390 ). If the heave motion is in the up direction, the ECU  210  decreases the speed of the arm in the up direction (step  395 ) to attempt to mitigate the upward heave motion. If the motion is mitigated (step  400 ), the ECU  210  continues checking for pitch motion (step  305 ). If the motion was not mitigated at step  400 , the ECU  210  continues operation at step  385 , checking if the arm  110  is being raised. 
     If the heave motion was downward (step  390 ), the ECU  210  increases the speed at which the arm is being raised (step  405 ) in an attempt to mitigate the downward heave motion. If the motion is mitigated (step  400 ), the ECU  210  continues checking for pitch motion (step  305 ). If the motion was not mitigated at step  400 , the ECU  210  continues operation at step  385 , checking if the arm  110  is being raised. 
     If the operator is not attempting to raise the arm  110  (step  385 ), the ECU  210  checks if the operator is attempting to lower the arm  110  (step  410 ). If the operator is attempting to lower the arm  110 , the ECU  210  checks if the heave motion is in an upward direction (step  415 ). If the heave motion is upward, the ECU  210  increases the downward speed of the arm (step  420 ) to attempt to mitigate the upward heave motion. If the motion is mitigated (step  400 ), the ECU  210  continues to check for pitch motion (step  305 ). If the motion was not mitigated at step  400 , the ECU  210  continues operation at step  385 , checking if the arm  110  is being raised. 
     If the heave motion was downward (step  415 ), the ECU  210  decreases the speed at which the arm is being lowered (step  425 ) to attempt to mitigate the downward heave motion. If the motion is mitigated (step  400 ), the ECU  210  continues to check for pitch motion (step  305 ). If the motion was not mitigated at step  400 , the ECU  210  continues operation at step  385 , checking if the arm  110  is being raised. 
     If the arm is not being raised (step  385 ) nor lowered (step  410 ), the ECU  210  lowers the arm  110  with a step input (step  430 ) to induce a pitch motion, and continues with checking if the heave motion has been mitigated (step  400 ). 
     In some embodiments, the system  200  attempts to mitigate pitch and heave motions by controlling a position of the bucket  115 , instead of or in addition to controlling the articulating arm  110 . In some embodiments, the system  200  provides an indication to the operator (e.g., lighting a tell-tale lamp) that a pitch and/or heave motion has been detected, and that the system  200  is taking corrective action. In some embodiments, the system  200  takes into account the magnitude of the pitch and/or heave motion, accelerating countermeasures when the magnitude exceeds one or more thresholds and/or adjusting a speed of movement of the articulating arm  110  based on the magnitude of the pitch and/or heave motion. 
     Various features and advantages of the invention are set forth in the following claims.

Summary:
A heavy-duty vehicle including a movable arm, an operator control unit, an inertial measurement device, and a controller. The operator control unit directs movement of the movable arm. The inertial measurement device measures a pitch motion and a heave motion of the heavy-duty vehicle. The controller mitigates pitch motion and heave motion by adjusting a movement of the movable arm. The inertial measurement device detects a motion in one of a first direction and a second direction. The controller determines a direction of movement of the arm in one of a third direction and a fourth direction. The controller increases the speed of motion of the arm when the motion is in the first direction and the movement is in the third direction or when the motion is in the second direction and the movement is in the fourth direction.