Patent Publication Number: US-8977441-B2

Title: Method and system for calculating and displaying work tool orientation and machine using same

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to calculating a current work tool orientation, and more particularly to displaying a deviation of the current work tool orientation from an operator selected orientation of the work tool. 
     BACKGROUND 
     Machines may be equipped with a variety of work tools, such as, for example, buckets, blades, forks, and the like, for performing work operations, such as material handling operations. Typically, the work tool is attached to the machine using an implement assembly. For example, the implement assembly may include a lift arm assembly for raising and lowering the work tool, and a tilt linkage for pivoting the work tool relative to the machine. In some instances, the implement assembly may include a coupler, or similar mechanism, for facilitating attachment of the implement assembly to a variety of interchangeable work tools. Thus, the machine may be more readily attached to the appropriate work tool as dictated by the current operation. 
     Typical work operations require the positioning and repositioning of the work tool using one or more controllers, such as a lift adjustment controller and a tilt adjustment controller, positioned within an operator control station of the machine. Such work operations may require precise positioning of the work tool, which may require a relatively high degree of operator skill. Further, according to some implement assemblies, one or more components of the lift arm assembly and/or the tilt linkage may interfere with the line of sight of the operator. Thus, manipulation of the controllers to move the work tool, particularly according to repeated work cycles, may prove difficult and tedious, contributing to operator fatigue and diminished work efficiency. 
     U.S. Pat. No. 6,766,600 to Ogura et al. teaches a display for a construction machine that allows an operator to set a target plane for a work operation to be performed under automatic control. More specifically, the operator may select a gradient of the target plane and the plane may be displayed at an angle corresponding to the selected gradient. A bucket symbol corresponding to a bucket angle, which is calculated by a control unit using a bucket angle sensor, is also displayed. The bucket symbol is rotatable depending on the current angle of the bucket. By displaying both the target gradient and the bucket angle, an operator may view the relative difference between the two angles. 
     The present disclosure is directed to one or more of the problems set forth above. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect, a machine includes a plurality of ground engaging elements and an operator control station supported on a frame. A work tool is pivotably attached to the frame using a lift arm assembly and a tilt linkage. At least one device measures a quantity associated with at least one of the lift arm assembly, the tilt linkage, and the work tool. An electronic controller, in communication with an operator display and the at least one device, is configured to store an operator selected orientation of the work tool, calculate a current orientation of the work tool based at least in part on the quantity, and calculate a deviation of the current orientation from the operator selected orientation. A visual representation of the deviation is displayed on the operator display. 
     In another aspect, a method of operating a machine includes a step of storing an operator selected orientation of a work tool on an electronic controller. A current orientation of the work tool is calculated based at least in part on a measured quantity associated with at least one of a lift arm assembly, a tilt linkage, and the work tool using the electronic controller. A deviation of the current orientation from the operator selected orientation is calculated using the electronic controller, and a visual representation of the deviation is displayed on an operator display. 
     In yet another aspect, a control system for a machine includes an electronic controller including a memory having a work tool positioning display algorithm and an operator selected orientation stored thereon. The electronic controller includes a processor configured to execute the work tool positioning display algorithm. The work tool positioning display algorithm is configured to receive a device signal corresponding to a measured quantity associated with at least one of a lift arm assembly, a tilt linkage, and the work tool. The work tool positioning display algorithm is further configured to calculate a current orientation of the work tool based at least in part on the measured quantity, calculate a deviation of the current orientation from the operator selected orientation, and send a first display signal corresponding to the deviation to an operator display. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side diagrammatic view of a machine having a system for calculating and displaying work tool orientation, according to the present disclosure; 
         FIG. 2  is a side diagrammatic view of the implement assembly of  FIG. 1 , and an exemplary control system for calculating and displaying work tool orientation, according to one aspect of the present disclosure; 
         FIG. 3  is an illustration of an exemplary display screen of an operator display of the machine of  FIG. 1 , according to another aspect of the present disclosure; and 
         FIG. 4  is an illustration of another exemplary display screen of an operator display of the machine of  FIG. 1 , according to another aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     An exemplary embodiment of a machine  10  is shown generally in  FIG. 1 . The machine  10  may be an off-highway machine, such as, for example, a wheel loader, or any other machine having a plurality of ground engaging elements, such as wheels  12 , supported on a frame  14 . Although wheels are shown, the present disclosure is equally applicable to machines having other ground engaging means, such as, for example, a tracked undercarriage. The machine  10  also includes an operator control station  16  supported on the frame  14  and may house an operator display  18  for displaying various operational information relating to the machine  10 . A lift adjustment controller  20  and a tilt adjustment controller  22  may also be positioned within the operator control station  16  for controlling an implement assembly  24  of the machine  10 . 
     The implement assembly  24  generally comprises a lift arm assembly  26 , a tilt linkage  28 , and a work tool  30 . Although a pair of forks  32  is shown, it should be appreciated that the machine  10  may support any of a variety of different work tools, including, for example, a bucket or blade. According to some embodiments, the machine  10  may include a coupler  34 , or other similar mechanism, which provides a means for coupling a variety of interchangeable work tools, such as work tool  30 , to the machine  10 . The lift arm assembly  26  may be pivotably attached to the frame  14 , while the tilt linkage  28  may be pivotably attached to the lift arm assembly  26 . Although alternative configurations are applicable to the present disclosure, a specific embodiment of an implement assembly  24  is provided herein for exemplary purposes. 
     Turning now to  FIG. 2 , but referring also to  FIG. 1 , the lift arm assembly  26  includes a pair of hydraulic lift cylinders  40  (only one of which is shown) having first ends  42  pivotably attached to the frame  14  at first lift cylinder pivot points  44  and second ends  46  pivotably attached to lift arms  48  at second lift cylinder pivot points  50 . The lift arms  48  have first ends  52  pivotably attached to the frame  14  at first lift arm pivot points  54  and second ends  56  to which the work tool  30  is pivotably attached at first work tool pivot points  58 . According to the exemplary embodiment of  FIG. 2 , the work tool  30  is exemplified as a bucket  60 . However, it should be appreciated that alternative work tools, such as the forks  32  of  FIG. 1 , may be substituted for the bucket  60 . 
     The work tool  30  is pivotably mounted to the lift arms  48  at the first work tool pivot points  58  and is pivotably connected to a hydraulic tilt cylinder  62  via the tilt linkage  28 . The tilt linkage  28  includes a first link member  64  and a second link member  66 . Although not shown, it should be appreciated that the tilt linkage  28  may include a pair of first link members  64  and a pair of second link members  66 , according to alternative configurations. A first end  68  of the first link member  64  is pivotably attached to the hydraulic tilt cylinder  62  at first link member pivot points  70 , and a second end  72  is pivotably attached to the lift arms  48  at second link member pivot points  74 . The second link member  66  has a first end  76  pivotably attached to the lift arms  48  at the pivot points  74  and a second end  78  pivotably attached to the work tool  30  at second work tool pivot points  80 . As the hydraulic tilt cylinder  62  is actuated, the first link members pivot about frame supported pivot points  82 . 
     The hydraulic lift and tilt cylinders  40  and  62  are extendable and retractable in response to movement of the lift adjustment controller  20  and tilt adjustment controller  22 , introduced above, using a control system  83 . Generally speaking, for example, the hydraulic lift cylinders  40  are positioned to adjust the angular orientation of the lift arm assembly  26  responsive to movement of the lift adjustment controller  20 . More specifically, as the hydraulic lift cylinders  40  extend and retract, the lift arms  48  may be pivoted relative to the frame  14  at the first lift arm pivot points  54 , thus raising and lowering the work tool  30 . The hydraulic tilt cylinder  62  is positioned to adjust the angular orientation of the tilt linkage  28  in response to movement of the tilt adjustment controller  22 . More specifically, as the hydraulic tilt cylinder  62  extends and retracts, the work tool  30  is pivoted toward the machine  10  and pivoted away from the machine  10  using the tilt linkage  28 . 
     The movements of the implement assembly  24 , as described above, may be carried out using an electro-hydraulic system, as is known in the art. For example, according to the exemplary embodiment, the actuation of the lift arm assembly  26  may be carried out using a first electro-hydraulic circuit, shown generally at  84 , hydraulically coupled to the hydraulic lift cylinders  40 . Electro-hydraulic circuits are known and generally include a fluid reservoir, pump, electronically actuated valve, filters, and the like for controlling a hydraulic fluid along the hydraulic circuit. Specifically, an electronic controller  86  may communicate with the electro-hydraulic circuit  84 , or an electronically actuated valve thereof, to control the flow of hydraulic fluid to and from the hydraulic lift cylinders  40  via the electro-hydraulic circuit  84 . 
     The operator may control the movement of the lift arm assembly  26  by manipulating the lift adjustment controller  20 . Specifically, for example, the lift adjustment controller  20  may be configured to generate a first lift control signal in proportion to a degree of manipulation in a particular direction of the lift adjustment controller  20  by the operator, the first lift control signal being proportional to a desired lift arm assembly movement. The electronic controller  86 , in communication with the lift adjustment controller  20  and hydraulic lift cylinders  40 , receives the first lift control signal and responds by generating a second lift control signal proportional to the first lift control signal, which is received by the electro-hydraulic circuit  84 . The electro-hydraulic circuit  84  responds to the second lift control signal by directing hydraulic fluid to and from the hydraulic lift cylinders  40  at a rate proportional to the second lift control signal, causing the hydraulic lift cylinders  40  to move the lift arms  48  about the pivot points  54  accordingly. 
     Actuation of the tilt linkage  28  may also be carried out using an electro-hydraulic circuit, such as a second electro-hydraulic circuit  88 , hydraulically coupled to the hydraulic tilt cylinder  62 . Specifically, for example, the tilt adjustment controller  22  may be configured to generate a first tilt control signal in proportion to a degree of manipulation by the operator and proportional to a desired movement of the work tool  30 . The electronic controller  86 , in communication with the tilt adjustment controller  22  and hydraulic tilt cylinder  62 , receives the first tilt control signal and responds by generating a second tilt control signal proportional to the first tilt control signal, which is received by the electro-hydraulic circuit  88 . The electro-hydraulic circuit  88  responds to the second tilt control signal by directing hydraulic fluid to and from the hydraulic tilt cylinder  62 , causing the hydraulic tilt cylinder  62  to extend and retract and, thus, pivot the work tool  30 . 
     The electronic controller  86  may be of standard design and may include a processor  90 , such as, for example, a central processing unit, a memory  92 , and an input/output circuit  94  that facilitates communication internal and external to the electronic controller  86 . The processor  90 , for example, may control operation of the electronic controller  86  by executing operating instructions, such as, for example, computer readable program code stored in the memory  92 , wherein operations may be initiated internally or externally to the electronic controller  86 . Control schemes may be utilized that monitor outputs of systems or devices, such as, for example, sensors, actuators, or control units, via the input/output circuit  94  to control inputs to various other systems or devices. The memory  92 , as used herein, may comprise temporary storage areas, such as, for example, cache, virtual memory, or random access memory, or permanent storage areas, such as, for example, read-only memory, removable drives, network/internet storage, hard drives, flash memory, memory sticks, or any other known volatile or non-volatile data storage devices. One skilled in the art will appreciate that any computer based system or device utilizing similar components for controlling the machine systems or components described herein, is suitable for use with the present disclosure. 
     The electronic controller  86  may communicate with various systems and components of the machine  10  via one or more wired and/or wireless communications lines  96 , or other similar communication circuits. For example, regarding the control system  83 , the electronic controller  86  may communicate with the lift and tilt adjustment controllers  20  and  22 , the electro-hydraulic circuits  84  and  88 , and various additional components of the machine  10  via communications lines  96  to affect a control scheme described herein. More specifically, for example, the electronic controller  86  may also communicate with first and second sensors  98  and  100  via communications lines  96 . According to the exemplary embodiment, the first and second sensors  98  and  100  may be rotary sensors for monitoring the angular displacement of particular linkage points, or pivot points, of the implement assembly  24 . 
     Rotary sensors, such as first and second sensors  98  and  100 , are known and may function by having a first portion attached to a linkage pin, such as a linkage pin defining one of the pivot points described above, and a second portion attached to a housing surrounding the linkage pin. As the linkage pin rotates relative to the housing, the rotary sensor senses the amount of rotation and provides an electrical signal indicative of this rotation. According to a specific example, the first sensor  98  may be positioned at first lift arm pivot points  54  and may be configured to detect an angular displacement of the lift arms  48  relative to a reference plane P 1 , such as, for example, the frame  14  or the ground. More specifically, the first sensor  98  may detect the angular displacement of a second plane P 2  intersecting pivot points  54  and  58  of the lift arms  48  relative to the reference plane P 1 . The second sensor  100  may be positioned and configured to detect an angular displacement of the work tool  30  relative to the lift arms  48 . More specifically, the second sensor  100  may detect the angular displacement of a third plane P 3  intersecting pivot points  70  and  82  of the first link member  64  relative to the second plane P 2 . 
     The rotational values detected by the first and second sensors  98  and  100  may be used by the electronic controller  86  to calculate, or otherwise determine, various information pertaining to the implement assembly  24 , including lengths of the hydraulic cylinders  40  and  62 . For example, the angular displacement of the lift arms  48 , or second plane P 2 , relative to the reference plane P 1  may provide a lift arm angle. The lift arm angle may be correlated to a length of the hydraulic lift cylinders  40  in an informational table stored in memory  92 . The length of the hydraulic lift cylinders  40  may, in turn, be correlated to a height of a specific reference point of the work tool  30 . For example, the cylinder length may be correlated to a height of one of pivot points  58  and  80  relative to the frame  14  or the ground. As such, the angular displacement detected by the first sensor  98 , along with informational data stored in memory  92 , may be used to determine a current height associated with the work tool  30 . 
     The angular displacement of the first link member  64  or, more specifically, the third plane P 3  relative to the second plane P 2  may provide a first link member angle. The first link member angle may be correlated to an angle of the work tool  30  relative to the lift arms  48 , or the second plane P 2 , in another informational table stored in memory  92 . The work tool angle may represent the angle of a fourth plane P 4  intersecting pivot points  58  and  80  relative to the lift arms  48 , or the second plane P 2 . The work tool angle may be used in additional calculations, as will be described below, and may be correlated to a length of the hydraulic tilt cylinder  62  in another informational table stored in the memory  92 . As should be appreciated, alternative sensors may be used and, further, the sensors may be positioned in alternative locations. Such changes, as should be appreciated, may affect the correlation data stored in memory  92 . Such correlation data may be provided by the manufacturer and/or may be determined using various measurements and/or equations, as should be appreciated by those skilled in the art. 
     The control system  83  may also allow an operator to select and store one or more operator selected positions. Specifically, for example, the electronic controller  86  may store an operator selected orientation corresponding to an operator selected angular displacement of the work tool  30  relative to the reference plane P 1 . The operator selected orientation, which may also be referred to as a kickout, return-to-dig, or automatic bucket leveler feature by those skilled in the art, may be based on operator selected positions of the lift adjustment controller  20  and tilt adjustment controller  22 , and may be selected using an orientation selector  102 . For example, the orientation selector  102  may be a push-button switch or other appropriate device, which may or may not be integrated with the tilt adjustment controller  22 , for producing an orientation signal corresponding to the operator selected orientation. In response to receiving the orientation signal, the electronic controller  86  may store the operator selected orientation in memory  92 . 
     According to a specific example, the electronic controller  86 , in response to receiving the orientation signal, may determine the current orientation of the work tool  30  using the first and second sensors  98  and  100 , as described above. The electronic controller  86  may then store in memory  92  information indicative of the operator selected orientation. For example, the electronic controller  86  may store angular displacements as detected by the first and second sensors  98  and  100  or, alternatively, may store cylinder lengths corresponding to the hydraulic lift cylinder  40  and the hydraulic tilt cylinder  62 . The electronic controller  86  may be further configured to store a default orientation, which may correspond to a manufacturer selected default value, of the work tool  30  in memory  92 . 
     The electronic controller  86  may also store first and second operator selected heights corresponding to an operator selected angular displacement of the lift arms  48 , or second plane P 2 , relative to the reference plane P 1 . As described above, this angular displacement may be correlated to a height of the work tool  30 . The operator selected heights may be based on operator selected positions of the lift adjustment controller  20  and may be selected using a height selector  104 . The height selector  104 , similar to the orientation selector  102 , may be a push-button switch or other appropriate device, which may or may not be integrated with the lift adjustment controller  20 , for producing one or more height selection signal(s) corresponding to the operator selected height(s). In response to receiving the height selection signal(s), the electronic controller  86  may store the operator selected height(s) in memory  92 . The electronic controller  86  may be further configured to store one or more default heights, which may correspond to manufacturer selected default values, of the work tool  30 . 
     The memory  92  may also store a work tool positioning display algorithm, along with the operator selected orientation and the one or more operator selected heights. The processor  90  may be configured to execute the work tool positioning display algorithm, which includes receiving a first angular orientation signal from the first sensor  98 , which corresponds to an angular orientation of the lift arm assembly  26 , and a second angular orientation signal from the second sensor  100 , which corresponds to an angular orientation of the tilt linkage  28 . Specifically, as described above, the first sensor  98  may be configured to detect an angular displacement of the lift arm  48  relative to the reference plane P 1 , and the second sensor  100  may be configured to detect an angular displacement of the work tool  30  relative to the lift arm  48 . 
     A current orientation of the work tool  30  may then be calculated based on the angular orientations determined above. Specifically, the current orientation may be calculated by adding the lift arm angle, which is the angular displacement of the lift arms  48 , or second plane P 2 , relative to the reference plane P 1  as detected by the sensor  98 , and the work tool angle, which is the angle of a fourth plane P 4  intersecting pivot points  58  and  80  relative to the lift arms  48 , or the second plane P 2 . As stated above, the work tool angle is selected from memory  92  and is correlated to the first link member angle, which is the angular displacement of the first link member  64  or, more specifically, the third plane P 3  relative to the second plane P 2  as detected by second sensor  100 . The lift arm angle and the work tool angle may be added together to arrive at the current orientation of the work tool  30  relative to the reference plane P 1 . 
     According to the work tool positioning display algorithm, the electronic controller  86  may also calculate a deviation of the current orientation of the work tool  30  from the operator selected orientation. Specifically, the electronic controller  86  may subtract the operator selected orientation from the current orientation to arrive at the deviation. The deviation may represent a difference, in degrees of angular displacement, of the current orientation relative to the operator selected orientation. Alternatively, if an operator selected orientation is not stored in memory  92 , the deviation may represent a difference of the current orientation relative to the default orientation. The electronic controller  86 , after performing the steps of the work tool positioning display algorithm described above, may then send a first display signal corresponding to the deviation to an operator display  106 . As will be discussed below, a visual representation of the deviation may be displayed on the operator display  106  or, more particularly, a display screen  108  of the operator display  106 . 
     The work tool positioning display algorithm may also include a calculation of a current height of the work tool  30  based on the angular orientation of the lift arm assembly  26 . As described above, for example, the angular displacement of the lift arms  48 , or second plane P 2 , relative to the reference plane P 1 , as detected by the first sensor  98 , may provide a lift arm angle. The lift arm angle may be correlated to a length of the hydraulic lift cylinders  40  in an informational table stored in memory  92 . The length of the hydraulic lift cylinders  40  may, in turn, be correlated to a height of a specific reference point of the work tool  30 . As such, the angular displacement detected by the first sensor, along with informational data stored in memory  92 , may be used to determine the current height of the work tool  30 . 
     The electronic controller  86 , in accordance with the work tool positioning display algorithm, may also be configured to calculate a deviation of the current height of the work tool  30  from an operator selected height, or default height, stored in memory  92 . Specifically, the electronic controller  86  may subtract the operator selected height, or default height, from the current height to arrive at the deviation. The electronic controller  86  may send a second display signal corresponding to the deviation to the operator display  106 . As described above, a visual representation of the deviation may be displayed on the operator display  106  in response to the second display signal. Alternatively, for example, it may be desirable to display a visual representation of the current height relative to one or more operator selected heights. 
     Although the exemplary embodiment teaches the use of rotary sensors  98  and  100  for determining the current orientation of the work tool  30 , it should be appreciated that the present disclosure has wider applicability. Specifically, the machine  10  may include any of a number of devices for measuring a quantity associated with at least one of the lift arm assembly  26 , the tilt linkage  28 , and the work tool  30 , and transmitting a device signal corresponding to the quantity to the electronic controller  86 . The current orientation of the work tool  30  is then calculated based at least in part on the quantity. For example, the machine  10  may include sensors for detecting the length of one or more of the hydraulic lift cylinders  40  and the hydraulic tilt cylinder  62 . The cylinder lengths may then be used, in a known fashion, to calculate the current work tool orientation. According to another example, the machine  10  may include one or more inclinometers for detecting an angular rotation of the work tool  30 . These one or more quantities may then be used by the electronic controller  86  to calculate the work tool orientation. 
     Turning now to  FIG. 3 , an exemplary embodiment of the operator display  106  is illustrated. The operator display  106  may correspond to the operator display  18  of  FIG. 1 , positioned within the operator control station  16 , or may be an additional, or alternative, operator display positioned within the operator control station  16  or elsewhere, such as at a location remote from the machine  10 . According to one example, the operator display  106  may be a secondary operator display, while the operator display  18  of  FIG. 1  may be a primary operator display. As should be appreciated, a primary operator display may display information that is more frequently observed by the operator, such as machine speed, engine speed, fuel level, temperatures, etc., while the secondary operator display may display information that is not referenced as often as the information of the primary operator display. Further, it may be desirable to configure the operator display  106  such that the operator may select which one or more screens, or pieces of information, are displayed. For example, the operator may only wish to display the work tool orientation information described herein when performing a particular work operation. 
     According to the exemplary operator display  106  of  FIG. 3 , the display screen  108  may depict a digital readout  120  corresponding to a deviation of the current work tool orientation from the operator selected orientation. For example, the operator selected orientation may correspond to 0 degrees, which may represent an orientation of the work tool  30  that is substantially level, or parallel, with respect to the frame  14  or the ground. According to this example, the deviation may represent a number of degrees of deviation of the current orientation relative to 0 degrees. So, if the current orientation is −5 degrees, the deviation is −5 degrees minus 0 degrees, which is −5 degrees. It should be appreciated that “rack” may represent an orientation pivoted toward the machine, while “dump” may represent an orientation pivoted away from the machine. The display screen  108  may also depict a description  122 , such as “Tool Pitch,” which provides the operator with an indication of the particular information being displayed. Thus, for example, when the operator views the operator display  108  of  FIG. 3 , the operator can easily be advised that the current pitch, also referred to as angular orientation, of the work tool  30  relative to the operator selected orientation is −5 degrees, or pivoted 5 degrees toward the machine  10 . 
     Turning now to  FIG. 4 , an alternative illustration is depicted on the display screen  108  of the operator display  106 . Specifically, the −5 degrees deviation of the work tool orientation relative to the operator selected orientation may be illustrated using a digital readout  130 , which may be similar to the digital readout  120  of  FIG. 3 , and may be further illustrated by depicting a work tool symbol  132  having an arrow indicating the information being conveyed. For example, the arrow of work tool symbol  132  may visually reference the angular movement of the work tool  30 . The operator display  106  may also depict a relational symbol  134  illustrating the deviation of the current orientation, depicted using an arrow, relative to the operator selected orientation, depicted using a bar having a line corresponding to the set point. Thus, the operator can look to the operator display  106  of  FIG. 4  to ascertain that the current angular orientation of the work tool is −5 degrees, which is below, or less than, the operator selected setting, by 5 degrees. 
     The operator display  106  may also depict a digital readout  136  corresponding to the current height of the work tool  30 , such as in inches. The current height may be further illustrated by depicting a work tool symbol  138  having an arrow indicating the information being conveyed. For example, the arrow of work tool symbol  138  may visually reference the vertical movement, or height, of the work tool  30 . The operator display  106  may also depict a relational symbol  140  illustrating the current height, depicted using an arrow, relative to first and second operator selected heights, depicted using a bar having lines corresponding to the two operator selected heights. Thus, the operator can look to the operator display  106  of  FIG. 4  to also ascertain that the current height of the work tool is 40.1 inches, which is closer to a lower operator selected height than an upper operator selected height. 
     As should be appreciated, the specific illustrations of  FIGS. 3 and 4  are provided for exemplary purposes only. The information discussed above may be conveyed in any useful manner, which may include the depiction of any one or more letters, numbers, symbols, as well as graphics, animations, sounds, colors, and the like. According to a specific example, the illustration provided for the operator may be color coded, such that a deviation less than a predetermined deviation is displayed in green, while a deviation greater than the predetermined deviation is represented in red. A deviation range corresponding to the predetermined deviation may be displayed to the operator in yellow. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure may be applicable to machines having work tools attached to the machine through an implement assembly, which may include a lift arm assembly and a tilt linkage. Further, the present disclosure may be applicable to such machines having an electronic control system, such as, for example, an electro-hydraulic system, for controlling movement of the implement assembly. Yet further, the present disclosure may be applicable to machines having electronically controlled implement assemblies and electronically stored operator selected orientations. 
     Referring to  FIG. 1-4 , a machine  10 , such as a wheel loader, may include a plurality of ground engaging elements  12  supported on a frame  14 . The machine  10  may also include an operator control station  16  supported on the frame  14  and housing one or more operator displays, such as operator display  18  and operator display  106 . An implement assembly  24 , supported on the frame  14 , generally comprises a lift arm assembly  26 , a tilt linkage  28 , and a work tool  30 . A lift adjustment controller  20  may be positioned within the operator control station  16  and used to control an angular orientation of the lift arm assembly  26  via an electro-hydraulic circuit  84 , while a tilt adjustment controller  22 , also positioned within the operator control station  16 , may be used to control an angular orientation of the tilt linkage  28  using another electro-hydraulic circuit  88 . First and second sensors  98  and  100 , which may be rotary sensors as described above, may be positioned to detect angular orientations of the lift arm assembly  26  and the tilt linkage  28 , respectively. 
     To operate the machine  10 , an operator may move the lift adjustment controller  20  to raise or lower the work tool  30 , and may move the tilt adjustment controller  22  to adjust the angular orientation, or pitch, of the work tool  30 , as described above. If desired, the operator may use a control system  83  to select and store an operator selected orientation and one or more operator selected heights of the work tool. The operator selected orientation and operator selected heights, which may be selected and stored as described above, may correspond to particular work tool positions to which the operator may wish to return. For example, for a repeated work cycle, the operator may wish to store an operator selected height and operator selected orientation corresponding to ground and level. Thus, during the repeated work cycle, the operator can request the control system  83  return the implement assembly  24  to the ground and level position, such as by actuating a button, lever, or device, without having to manually manipulate the lift and tilt adjustment controllers  20  and  22  to return the implement assembly  24  to the repeated position of the work cycle. 
     The method and system described herein for calculating and displaying work tool orientation and work tool height may be used to further assist the operator in performing certain work operations. According to a specific example, when utilizing forks  32 , an operator may perform a work cycle consisting of loading a material, such as a palletized material, from a truck bed and unloading the material to the ground. As such, the operator may have stored an operator selected orientation and height corresponding to level and ground for loading the palletized material. Thus, the operator may use these stored settings when manipulating the implement assembly  24  to perform the work operation. 
     However, according to a specific example, the operator may have difficulty maintaining a level orientation of the forks  32  when positioning the forks  32  to lift and unload the palletized material from the truck bed. The control system  83  described herein, including the work tool positioning display algorithm stored on and executed by the electronic controller  86 , may display work tool positioning information on the operator display  106  that may assist the operator in performing the work operation. In particular, the work tool positioning information this is displayed may supplement the line of sight of the operator to assist the operator in more precisely positioning the work tool  30  during the work operation. For example, it may be challenging for an operator to position the forks  32  at a relatively level orientation, or pitch, with respect to the truck bed. 
     The work tool positioning display algorithm, which may run continuously or at predetermined intervals, stores the operator selected orientation, calculates a current orientation of the work tool  30 , as described herein, calculates a deviation of the current orientation of the work tool  30  from the operator selected orientation, and displays a visual representation of the deviation, such as the visual representations of  FIGS. 3 and 4 , on the operator display  106 . The operator may then use the visual representation of the deviation to adjust the position of the work tool  30 , using lift and tilt adjustment controllers  20  and  22 , to correspond to the operator selected orientation. 
     The method and system for calculating and displaying work tool orientation, as described herein, provides a visual representation of the deviation of the current work tool orientation from the operator selected orientation on an operator display, which may be located on the machine or at a location remote from the machine. This information may assist operators in more efficiently and accurately performing work operations, including, for example, manual, remote control, autonomous, and semi-autonomous operations. For machines already configured to electronically identify and store operator selected orientations, the work tool positioning display algorithm may provide an efficient means for conveying useful information to the operator, without requiring additional hardware. Specifically, for machines, such as hydraulic or electro-hydraulic machines, equipped to utilize operator selected orientations, the algorithm described herein may be provided as a retrofit by modifying software on one or more electronic controllers. 
     It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.