Patent Publication Number: US-11019769-B2

Title: Lateral tilt control for an agricultural harvester

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/404,643, filed Jan. 12, 2017, the disclosure of which is hereby incorporated by reference herein in its entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The present subject matter relates generally to agricultural harvesters and, more particularly, to an improved lateral tilt control system for controlling the lateral orientation of a header or other harvesting implement of as agricultural harvester. 
     BACKGROUND OF THE INVENTION 
     A harvester is an agricultural machine that is used to harvest and process crops. For instance, a forage harvester may be used to cut and comminute silage crops, such as grass and corn. Similarly, a combine harvester may be used to harvest grain crops, such as wheat, oats, rye, barley, corn, soybeans, and flax or linseed. In general, the objective is to complete several processes, which traditionally were distinct, in one pass of the machine over a particular part of the field. In this regard, most harvesters are equipped with a detachable harvesting implement, such as a header, which cuts and collects the crop from the field and feeds it to the base harvester for further processing. 
     Conventionally, the operation of most harvesters requires substantial operational involvement and control by the operator. For example, with reference to a combine, the operator is typically required to control various operating parameters, such as the direction of the combine, the speed of the combine, the height of the combine header, the air flow through the combine cleaning fan, the amount of harvested crop stored on the combine; and/or the like. To address such issues, many current combines utilizes an automatic header height and tilt control system to maintain a constant cutting height above the ground regardless of the ground contour or ground position relative to the base combine. For instance, it is known to utilize electronically controlled tilt cylinders to automatically adjust the lateral orientation or tilt of the header relative to the ground based on sensor measurements. However, such systems often exhibit significant lag and slow response times, particularly when the harvester is operating at high ground speeds. As a result, these systems are not equipped to adjust the lateral orientation of the header sufficiently fast enough to account for quickly changing ground contours and/or ground positions. 
     Accordingly, an improved lateral tilt control system for an agricultural harvester that addresses one or more of the issues identified above would be welcomed in the technology. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one aspect, the present subject matter is directed to a lateral tilt control system for an agricultural harvester including a support structure and an implement pivotally coupled to the support structure. The system may include first and second tilt cylinders coupled between the support structure and the implement. The first tilt cylinder may include a first cap-side chamber and a first rod-side chamber and the second tilt cylinder may include a second cap-side chamber and a second rod-side chamber. The system may also include a first fluid line providing a flow path between the first cap-side chamber of the first tilt cylinder and the second rod-side chamber of the second tilt cylinder and a second fluid line providing a flow path between the first rod-side chamber of the first tilt cylinder and the second cap-side chamber of the second tilt cylinder. Additionally, the system may include a pressure relief valve coupled between the first and second fluid lines. The pressure relief valve may be configured to be opened to allow fluid to be transferred between the first and second fluid lines when a fluid pressure within one of the first fluid line or the second fluid line exceeds a relief pressure setting associated with the pressure relief valve. 
     In another aspect, the present subject matter is directed to a lateral tilt control system for an agricultural harvester including a support structure and an implement pivotally coupled to the support structure. The system may include a tilt cylinder coupled between the support structure and the implement, with the tilt cylinder including a cap-side chamber and a rod-side chamber. Additionally, the system may include a pressurized fluid source in fluid communication with the tilt cylinder, a first fluid line providing a flow path between the cap-side chamber of the tilt cylinder and the pressurized fluid source, and a second fluid line providing a flow path between the rod-side chamber of the tilt cylinder and the pressurized fluid source. The system may also include a pressure relief valve coupled between the first and second fluid lines. The pressure relief valve may be configured to be opened to allow fluid to be transferred between the first and second fluid lines when a fluid pressure within one of the first fluid line or the second fluid line exceeds a relief pressure setting associated with the pressure relief valve. 
     In a further aspect, the present subject matter is directed to an agricultural harvester including a feeder, a header pivotally coupled to the feeder, and a lateral tilt control system configured to allow the header to pivot relative to the feeder to adjust a lateral orientation of the header. The lateral control system may include first and second tilt cylinders coupled between the support structure and the implement. The first tilt cylinder may include a first cap-side chamber and a first rod-side chamber and the second tilt cylinder may include a second cap-side chamber and a second rod-side chamber. The lateral control system may also include a first fluid line providing a flow path between the first cap-side member of the first tilt cylinder and the second rod-side chamber of the second tilt cylinder and a second fluid line providing a flow path between the first rod-side chamber of the first tilt cylinder and the second cap-side chamber of the second tilt cylinder. Additionally, the lateral control system may include a pressure relief valve coupled between the first and second fluid lines. The pressure relief valve may be configured to be opened to allow fluid to be transferred between the first and second fluid lines when a fluid pressure within one of the first fluid line or the second fluid line exceeds a relief pressure setting associated with the pressure relief valve. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  illustrates a simplified, partial sectional side view of one embodiment of an agricultural combine in accordance with aspects of the present subject matter; 
         FIG. 2  illustrates a simplified, schematic view of one embodiment of a lateral tilt control system for an agricultural harvester in accordance with aspects of the present subject matter; 
         FIG. 3  illustrates another schematic view of the lateral tilt control system shown in  FIG. 2 , particularly illustrating the header of the harvester pivoted relative to the feeder of the harvester in a first direction; 
         FIG. 4  illustrates yet another schematic view of the lateral tilt control system shown in  FIG. 2 , particularly illustrating the header pivoted relative to the feeder in a second direction opposite the first direction; 
         FIG. 5  illustrates a more detailed, schematic view of one embodiment of a lateral tilt control system tor an agricultural harvester in accordance with aspects of the present subject matter; 
         FIG. 6  illustrates another schematic view of the lateral tilt control system shown in  FIG. 5 , particularly illustrating the header pivoted relative to the feeder in the first direction during implementation of a passive control mode of the disclosed system; and 
         FIG. 7  illustrates a schematic view of another embodiment of a lateral tilt control system for an agricultural harvester in accordance with aspects of the present subject matter. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as comes within the scope of the appended claims and their equivalents. 
     In general, the present subject matter is directed to an improved lateral tilt control system for an agricultural harvester that provides for improved system responsiveness in allowing a harvesting implement of the harvester (e.g., a header) to pivot relative to its associated support structure (e.g., a feeder of the harvester). Specifically, in several embodiments, the system may include first and second tilt cylinders coupled between the header and the feeder of the harvester, with the tilt cylinders being hydraulically coupled in parallel via a fluid circuit of the system. For instance, in one embodiment, the fluid circuit may include both a first fluid line coupled between a cap-side chamber of the first tilt cylinder and a rod-side chamber of the second tilt cylinder end a second fluid line coupled between a rod-side chamber of the first tilt cylinder and a cap-side chamber of the second tilt cylinder. In addition, the system may, in several embodiments, include an electronically controlled pressure relief valve coupled between the first and second fluid lines. In such an embodiment, when the fluid pressure within one of the fluid lines exceeds the relief pressure setting associated with the pressure relief valve, the valve may be opened to allow fluid to be transferred from the high pressure line to the sow pressure line. 
     As will be described below, the disclosed system may be utilized to implement a free-float or passive control mode in which the header is allowed to “float” relative to the ground and tilt laterally to accommodate changes in the contour or elevation of the ground. As a result, the lateral orientation of the header may be adjusted without any significant lag in the control system, thereby increasing the system&#39;s overall responsiveness to quickly changing ground contours and/or elevations. Moreover, when implementing the passive control mode, the relief pressure setting for the pressure relief valve may be adjusted, as desired by the operator, to vary the “float” sensitivity or spring rate of the system. 
     Referring now to the drawings,  FIG. 1  illustrates a simplified, partial sectional side view of one embodiment of an agricultural harvester  10  in accordance with aspects of the present subject matter. As shown, the harvester  10  is configured as an axial-flow type combine, wherein crop material is threshed and separated while it is advanced by and along a longitudinally arranged rotor  12 . The harvester  10  may include a chassis or main frame  14  having a pair of driven, ground-engaging front wheels  16  and a pair of steerable rear wheels  18 . Additionally, an operator&#39;s platform  20  with an operator&#39;s cab  22 , a threshing and separating assembly  24 , a grain cleaning assembly  26 , a holding tank  28  and an engine  30  may be supported by the frame  14 . Moreover, as shown in  FIG. 1 , a harvesting implement (e.g., a header  32 ) and an associated feeder  34  may extend forward of the main frame  14  and may be pivotally secured thereto for generally vertical movement. In general the feeder  34  may be configured to serve as support structure for the header  32 . As shown in  FIG. 1 , the feeder  34  extend between a forward end  36  coupled to the header  32  and a rear end  38  positioned adjacent to the threshing and separating assembly  24 . As is generally understood, the rear end  38  of the feeder  34  may be pivotally coupled to a portion of the harvester  10  to allow the forward end  36  of the feeder  34  and thus, the header  32  to be moved upwardly and downwardly relative to the ground  70  to set the desired harvesting or cutting height for the header  32 . For instance, as shown in  FIG. 2 , one or more height control cylinders  40  may be coupled to the feeder  34  to allow the header  32  to be raised and lowered relative to the ground. 
     As the harvester  10  is propelled forwardly over a field with standing crop, the latter is severed from the stubble by a sickle bar  42  at the front of the header  32  and delivered by a header auger  44  to the forward end  36  of the feeder  34 , which supplies the cut crop to the threshing and separating assembly  24 . As is generally understood, the threshing and separating assembly  24  may include a cylindrical chamber  46  in which the rotor  12  is rotated to thresh and separate the crop received therein. That is, the crop is rubbed and beaten between the rotor  12  and the inner surfaces of the chamber  46 , whereby the grain, seed or the like, is loosened and separated from the straw. 
     Crop material which has been separated by the threshing and separating assembly falls onto a series of pans  48  and associated sieves  50 , with the separated crop material being spread out via oscillation of the parts  48  and/or sieves  50  and eventually falling through apertures defined in the sieves  50 . Additionally, a cleaning fan  52  may be positioned adjacent to one or more of the sieves  50  to provide an air flow through the sieves  50  that removes chaff and other imparities from the crop material. For instance, the fan  52  may blow the impurities off of the crop material for discharge from the harvester  10  through the outlet of a straw hood  54  positioned at the back end of the harvester  10 . 
     The cleaned crop material passing through the sieves  50  may then fall into a trough of an auger  56 , which may be configured to transfer the crop material to an elevator  58  for delivery to the associated holding tank  28 . Additionally, a pair of tank augers  60  at the bottom of the holding tank  28  may be used to urge the cleaned crop material sideways to an unloading lube  62  for discharge from the harvester  10 . 
     Moreover, in several embodiments, the harvester  10  may also include a lateral tilt control system  100  that is configured to adjust a lateral orientation or tilt of the header  32  relative to the ground  70  so as to maintain the desired cutting height between the header  32  and the ground  70  across the entire width of the header  32 . As will be described below, the lateral tilt control system  100  may include first and second tilt cylinders  102 ,  104  coupled between the header  32  and the feeder  34  to allow the header  32  to be tilted or otherwise pivoted laterally or side-to-side relative to the feeder  34 . As such, the tilt cylinders  102 ,  104  may allow the header  34  to pivot relative to the feeder  34  to accommodate differences in the elevation or contour of the ground  70  across the width of the header  34 . 
     Referring now to  FIGS. 2-4 , simplified, schematic views of one embodiment of the lateral tilt control system  100  described above with reference to  FIG. 1  is illustrated in accordance with aspects of the present subject matter. As shown, the header  32  may generally extend side-to-side or in a lengthwise direction (indicated by arrow  105  in  FIG. 2 ) between a first lateral end  106  and a second lateral end  108 . Additionally, the header  32  may be pivotally coupled to the feeder  32  at a pivot point  110  defined at a central location of the header  34  between its first and second lateral ends  106 ,  108  to allow the header  32  to tilt or pivot laterally relative to the feeder in both a first direction (e.g., as indicated by arrow  112  in  FIG. 3 ) and an opposite section direction (e.g., as indicated by arrow  114  in  FIG. 3 ). 
     As indicated above, the lateral tilt control system  100  may include first and second tilt cylinders  102 ,  104 . For instance, as shown in the illustrated embodiment, a first tilt cylinder  102  may be coupled between the header  32  and the feeder  34  along one lateral side of the pivot point  110  and a second tilt cylinder  104  may be coupled between the header  32  and the feeder  37  along the opposed lateral side of the pivot point  110 . In general when the lateral tilt control system  100  is operating in an active control mode, the operation of the tilt cylinders  102 ,  104  may be configured to be actively controlled (e.g., via an associated controller) to adjust the lateral orientation of the header  32  relative to the ground  70 . For instance, one or more height sensors  116 ,  118  may be provided on the header  32  to monitor a local distance or height  120  defined between the header  32  and the ground  70 . Specifically, as shown in  FIGS. 2-4 , a first height sensor  116  may be provided at or adjacent to the first lateral end  106  of the header  32  and a second height sensor  118  may be provided at or adjacent to the second lateral end  108  of the header  32 . In such an embodiment, when one of the height sensors  116 ,  118  detects that the local height  120  defined between the header  32  and the ground  70  differs from a desired height (or falls outside a desired height range), the tilt cylinders  116 ,  118  may be actively controlled so as to adjust the lateral orientation of the header  33  in a manner that maintains the header  32  located at the desired height (or within the desired height range) relative to the ground  70 . 
     For example, as shown in  FIG. 3 , when a portion of the header  34  adjacent to the first lateral end  106  passes over a raised section  122  of the ground  70 , the reduction in the height  120  defined between the header  32  and the ground  70  may be detected (e.g., via the first height sensor  116 ). The tilt cylinders  102 ,  104  may then be actively controlled to adjust the lateral orientation of the header  32  in a manner that pivots the header  32  relative to the feeder  34  about the pivot point  110  in the first direction  112  such that the first lateral end  106  is raised relative to the ground  70 . Similarly, as shown in  FIG. 4 , when a portion of the header  34  adjacent to the second lateral end  108  passes over a raised section  124  of the ground  70 , the reduction in the height  120  defined between the header  32  and the ground  70  may be detected (e.g., via the second height sensor  118 ). The tilt cylinders  102 ,  104  may then be actively controlled to adjust the lateral orientation of the header  32  in a manner that pivots the header  32  relative to the feeder  34  about the pivot point  110  in the second direction  114  such that the second lateral end  108  is raised relative to the ground  70 . It should be appreciated that, in combination with the active control of the operation of the tilt cylinders  102 ,  104 , the operation of the height control cylinder(s)  40  may also be actively controlled to ensure that the header  33  is maintained at the desired height (and/or within the desired height range) relative to the ground  70 . 
     Additionally, as will be described in greater detail below, the lateral tilt control system  100  may also be configured to be operated in a free-float or passive control mode. In such an operating mode, the active control of the tilt cylinders  102 ,  104  may be stopped and the header  32  may be allowed to freely “float” or tilt relative to the ground  70 , thereby permitting the header  32  to pivot based on changes in the contour or elevation of the ground  70 . For instance, when the header  32  passes over a raised section  122 ,  124  of the ground  70  such that a portion of the header  32  contacts the ground  70  along either side of the pivot point  110  and a sufficient moment force is applied through the header  32 , the header  32  may be allowed to pivot freely about the pivot point  110  to reduce or alleviate the loading on the header  32 . In such instance, the fluid circuit associated with tilt cylinders  102 ,  104  may allow hydraulic fluid to be transferred between opposed chambers of the cylinders  102 ,  104  in a manner to accommodate such pivoting of the header  32 . 
     Referring now to  FIG. 5 , a more detailed, schematic view of one embodiment of the lateral tilt control system  100  described above with reference to  FIGS. 2-4  is illustrated in accordance with aspects of the present subject matter. As shown, the system  100  may include a controller  130  configured to electronically control the operation of one or more other components of the system  100 . Specifically, as will be described below, the controller  130  may be configured to control the operation of one more control valves  132  for regulating the flow of hydraulic fluid supplied from an associated pressurized fluid source (e.g., a suitable pump  134 ) to the tilt cylinders  102 ,  104 . In addition, the controller  130  may be configured to control the operation of a pressure relief valve  136  based on a corresponding relief pressure setting associated with the valve  136 , thereby allowing the “float” sensitivity or spring rate of the system  100  to be adjusted as desired. 
     In general, the controller  130  may correspond to any suitable processor-based device known in the art, such as a computing device or any suitable combination of computing devices. Thus, in several embodiments, the controller  130  may include one or more processor(s)  138  and associated memory device(s)  140  configured to perform a variety of computer-implemented functions. As used herein, the term “processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s)  140  of the controller  130  may generally comprise memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s)  140  may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s)  137 , configure the controller  130  to perform various computer-implemented functions, such as one or more aspects of the control functionality described herein. In addition, the controller  130  may also include various other suitable components, such as a communications circuit or module, one or more input/output channels, a data/control bus and/or the like. 
     It should be appreciated that the controller  130  may correspond to an existing controller of the associated harvester  10  or the controller  130  may correspond to a separate processing device. For instance, in one embodiment, the controller  130  may form all or part of a separate plug-in module that may be installed within the harvester  10  to allow the present subject matter to be implemented without requiring additional software to be uploaded onto existing control devices of the harvester  10 . 
     As shown in  FIG. 5 , each tilt cylinder  102 ,  104  may include a piston  142  encased within an associated cylinder housing  144  and a piston rod  146  extending outwardly from the housing  144 . In one embodiment, to couple the tilt cylinders  102 ,  104  between the header  32  and the feeder  34 , one of the housing  144  or the piston rod  146  of each tilt cylinder  102 ,  104  may be coupled to the header  32 , with the other of the housing  144  or the piston rod  146  being coupled to the feeder  34 . Additionally, each cylinder  102 ,  104  may define opposed cylinder chambers along either side of its piston  142 . For instance, as shown in  FIG. 5 , the first tilt cylinder  102  may include both a first cap-side chamber  148  and a first rod-side chamber  150 . Similarly, the second tilt cylinder  104  may include a second cap-side chamber  152  and a second rod-side chamber  154 . 
     Moreover, as shown in the illustrated embodiment, the system  100  may also include a fluid circuit  160  providing a fluid coupling or path between the pump  134  and the tilt cylinders  102 ,  104 . For instance, as shown in  FIG. 5 , the pump  134  may be fluidly coupled to the control valve(s)  132  via one or more pump lines  162  to allow pressurized hydraulic fluid to be supplied from the pump  134  to the control valve(s)  132 . Additionally, the control valve(s)  132  may be fluidly coupled to the first and second tilt cylinders  102 ,  104  via first and second fluid lines  164 ,  166 . For instance, as shown in  FIG. 3 , the first fluid line  164  may be configured to provide a fluid path between the control valve(s)  132  and opposite chambers of the first and second tilt cylinders  102 ,  104 . Specifically, the first fluid line  164  may include a first cap-side leg  168  that provides a flow path between the control valve(s)  132  and the cap-side chamber  148  of the first tilt cylinder  102  and a first rod-side leg  170  that provides a flow path between the control valve(s)  132  and the rod-side chamber  154  of the second tilt cylinder  104 , with the first cap-side and rod-side legs  168 ,  170  being fluidly coupled to the control valve(s)  132  via a first valve leg  172  of the first fluid line  164 . Similarly, as shown in  FIG. 3 , the second fluid line  166  may be configured to provide a field path between the control valve(s)  132  and the remaining opposite chambers of the first and second tilt cylinders  102 ,  104 . Specifically, the second fluid line  166  may include a second rod-side leg  174  that provides a flow path between the control valve(s)  132  and the rod-side chamber  150  of the first tilt cylinder  102  and a second cap-side leg  176  that provides a flow path between the control valve(s)  132  and the cap-side chamber  132  of the second tilt cylinder  104 , with the second rod-side and cap-side legs  174 ,  176  being fluidly coupled to the control valve(s)  112  via a second valve leg  178  of the second fluid line  166 . 
     Additionally, as indicated above, the system  100  may also include a pressure relief valve  136  provided is fluid communication with the fluid circuit  160 . Specifically, as shown in  FIG. 5 , the pressure relief valve  136  may be fluidly coupled between the first and second fluid lines  164 ,  166 , such as by coupling the pressure relief valve  136  between the first and second valve legs  172 ,  178  of the fluid lines  164 ,  166 . As such, the pressure relief valve  136  may provide a means for transferring hydraulic fluid between the fluid lines  164 ,  166  when the pressure within either fluid line  164 ,  166  exceeds the relief pressure setting associated with the pressure relief valve  136 . For instance, when the fluid pressure within each fluid line  164 ,  166  is below the relief pressure setting for the pressure relief valve  136 , the valve  136  may remain in a closed position so as to fluidly isolate the first fluid line  164  from the second fluid line  166 . However, when the fluid pressure within the first fluid line  164  exceeds the relief pressure setting, the pressure relief valve  136  may be configured to be opened in a manner that allows hydraulic fluid within the first fluid line  164  to flow through the valve  136  to the second fluid line  166 . Similarly, when the fluid pressure within the second fluid line  166  exceeds the relief pressure setting, the pressure relief valve  136  may be configured to be opened in a manner that allows hydraulic fluid within the second fluid line  166  to flow through the valve  136  to the first fluid line  164 . 
     It should be appreciated that, in several embodiments, the pressure relief valve  136  may correspond to any suitable electronically controllable valve (and/or any suitable combination of electronically controllable valves) that allows the disclosed system  100  to function as described herein, such as an electronically controlled, dual-acting pressure relief valve. In such embodiments, the controller  130  may be configured to electronically control the operation of the pressure relief valve  136  based on the fluid pressure within each fluid line  164 ,  166 . For instance, as shown in  FIG. 5 , the controller  130  may be communicatively coupled to one or more pressure sensors  180  provided in fluid communication with each fluid line  164 ,  166 . Thus, by monitoring the fluid pressure within each fluid line  164 ,  166  and comparing such fluid pressure to the relief pressure setting for the pressure relief valve  136 , the controller  130  may be configured to control the operation of the pressure relieve valve  136  to allow fluid to be transferred between the fluid lines  164 ,  166  when the fluid pressure within one of the fluid lines  164 ,  166  exceeds the pressure relief setting. 
     Additionally, by configuring the pressure relief valve  136  as an electronically controlled valve, the relief pressure setting for the valve  136  may, for example, be automatically adjusted by the controller  130  based on inputs received from the operator. For instance, based on the desired sensitivity or spring rate for the system  100 , the operator may provide a suitable operator input (e.g., via an input device housed within the cab  22 ) instructing the controller  130  to increase or decrease the relief pressure setting for the valve  136 . Upon receipt of the operator input, the controller  130  may then adjust the relief pressure setting stored within its memory to the desired relief pressure. Thereafter, the controller  130  may monitor the fluid pressure within each fluid valve  164 ,  166  (e.g., via the pressure sensors  180 ) relative to the new relief pressure setting. 
     Referring still to  FIG. 5 , by fluidly coupling the pump  34  to the tilt cylinders  102 ,  104  via the fluid circuit  160 , the controller  130  may be configured to implement an active control mode for the disclosed system  100  within which the controller  130  actively controls the actuation/retraction of the tilt cylinders  102 ,  104  via electronic control of the operation of the control valve(s)  132 , thereby allowing the controller  130  to automatically adjust the lateral orientation of the header  32 . Specifically, when it is desired to pivot the header  32  about the pivot point  110  in the first pivot direction (indicated by arrow  112  in  FIG. 5 ), the operation of the control valve(s)  132  may be controlled such that pressurized hydraulic fluid is supplied from the pump  134  through the valve(s)  132  to the first fluid line  164 . In such instance, the pressurized fluid supplied through the first fluid line  164  may be delivered to both the cap-side chamber  148  of the first tilt cylinder  102  and the rod-side chamber  154  of the second tilt cylinder  104 , thereby causing the header  32  to be pivoted in the first direction  112  (e.g., due to retraction of the piston rod  146  of the first tilt cylinder  102  and extension of the piston rod  146  of the second tilt cylinder  104 ). Similarly, when it is desired to pivot the header  32  about the pivot point  110  in the second pivot direction (indicated by arrow  114  in  FIG. 5 ), the operation of the control valve(s)  132  may be controlled such that pressurized hydraulic fluid is supplied from the pump  134  through the valve(s)  132  to the second fluid line  166 . In such instance, the pressurized fluid supplied through the second fluid line  166  may be delivered to both the rod-side chamber  150  of the first tilt cylinder  102  and the cap-side chamber  152  of the second tilt cylinder  104 , thereby causing the header  32  to be pivoted in the second direction  114  (e.g., due to extension of the piston rod  146  of the first tilt cylinder  102  and retraction of the piston rod  146  of the second tilt cylinder  104 ). In one embodiment, the controller  130  may be configured to implement such active control of the retraction/extension of the tilt cylinder  102 ,  104  based on feedback provided by one or more sensors, such as sensor feedback from the height sensors  116 ,  118  shown in  FIG. 204  or sensor feedback from any other suitable sensors (e.g., one or more orientation sensors, load sensors, and/or the like). 
     It should be appreciated that the control valve(s)  132  may generally correspond to any suitable electronically controllable valve (and/or any suitable combination of electronically controllable valves) that allows the disclosed system  100  to function as described herein. For instance, in one embodiment, the control valve(s)  132  may correspond to a spring-centered, pilot-operated directional control valve. In such an embodiment, the control valve(s)  132  may include a valve spool (not shown) configured to be actuated between various different valve positions to allow hydraulic fluid to be supplied from the pump  132  to either fluid line  164 ,  166  when desired and to also allow the supply of hydraulic fluid from the pump  134  to be cut-off (e.g., when the control valve(s)  132  is located at its closed or neutral position). 
     Additionally, as indicated above, the disclosed system  100  may also include a free-float or passive control mode in which the header  32  is allowed to “float” relative to the ground and tilt laterally to accommodate changes in the contour or elevation of the ground. To implement the passive control mode, the controller  130  may be configured to control the operation of the control valve(s)  132  such that the supply of pressurized hydraulic fluid from the pump  134  is cut-off (e.g., by moving the valve(s)  132  to its closed or neutral position), thereby creating a closed-loop circuit between the first and second fluid lines  164 ,  166  across the pressure relief valve  136 . Thereafter, when the “free-floating” header  32  contacts the ground, a moment force may be applied through the header  32  that, in turn, results in an increase in the fluid pressure within either the first fluid line  164  or the second fluid line  100  depending on the rotational direction of the force (e.g., either the first direction  112  or the second direction  114 ). In the event that the increase in pressure in the associated fluid line  164 ,  166  exceeds the relief pressure setting selected for the pressure relief valve  136 , the pressure relief valve  136  may be opened to allow fluid to be transferred from the high pressure line to the low pressure line, thereby permitting the header  32  to pivot relative to the feeder  34  about the pivot point  110  in the corresponding rotational direction of the applied force. Alternatively, if the increase in pressure in the associated fluid line  154 ,  166  does not exceed the relief pressure setting, the pressure relief valve  136  may remain closed, thereby presenting the header  32  from pivoting relative to the feeder  34 . Thus, as indicated above, the specific relief pressure setting selected for the pressure relief valve  136  may serve to define the “float” sensitivity or spring rate tor the system  100 . 
     Referring now to  FIG. 6 , an example implementation of the above-described free-float or passive control mode is illustrated in accordance with aspects of the present subject matter. In the illustrated embodiment, a moment force (e.g., as indicated by arrow  190 ) is being applied through the header  32  that is associated with pivoting the header  32  relative to the feeder  34  in the fast direction  112 , such as when the first lateral end  106  of the header  32  contacts the ground. As a result, the fluid pressure within the first fluid line  164  may be increased as the force is transferred through the lift cylinders  102 ,  104 . Assuming that the force is sufficient to increase the fluid pressure with so the first fluid line  164  to a pressure exceeding the relief pressure setting for the pressure relief valve  136 , the controller  130  may be configured to open the pressure relief valve  136  to allow the high pressure fluid contained within the first fluid line  164  to flow to the second fluid line  166  (e.g., as indicated by arrows  192  in  FIG. 6 . Such fluid exchange between the fluid lines  164 ,  166  may result in the piston rod  146  of the first tilt cylinder  102  retracting and the piston rod  146  of the second tilt cylinder  104  extending to pivot the header  32  relative to the feeder  34  in the first direction  112 . 
     It should be appreciated that system  100  may be configured to operate similarly when the moment force applied through the header  32  that is associated with pivoting the header  32  relative to the feeder  34  in the opposite direction (i.e., the second direction  114 ). In such instance, assuming that the force is sufficient to increase the fluid pressure within the second fluid line  166  to a pressure exceeding the relief pressure setting for the pressure relief valve  136 , the controller  130  may be configured to open the pressure relief valve  136  to allow the high pressure fluid contained within the second fluid line  166  to flow to the first fluid line  166 . Such fluid exchange between the fluid lines  164 ,  166  may result in the piston rod  146  of the first tilt cylinder  102  extending and the piston rod  146  of the second tilt cylinder  104  retracting to pivot the header  32  relative to the feeder  34  in the second direction  114 . 
     It should also be appreciated that, in alternative embodiments, the disclosed system may be operated in both its active control mode and its passive control mode utilizing a single tilt cylinder as opposed to a pair of tilt cylinders. For example,  FIG. 7  illustrates an alternative embodiment of the system  100  described above in which a single tilt cylinder  202  is coupled between the header  32  and the feeder  34 . As shown, the tilt cylinder  202  may be configured similar to the tilt cylinders  102 ,  104  described above. For instance, the tilt cylinder  202  may include a piston  242  encased within an associated cylinder housing  244  and a piston rod  246  extending outwardly from the housing  244 . Additionally, the cylinder  202  may define opposed cylinder chambers along either side of its piston  242 . For instance, as shown in  FIG. 6 , the tilt cylinder  202  may include both a cap-side chamber  248  and a rod-side chamber  250 . 
     Additionally, the system  100  may also include a fluid circuit  260  providing a fluid coupling or path between the pump  134  and the tilt cylinder  202 . For instance, as shown in  FIG. 7 , the pump  134  may be fluidly coupled to the control valve(s)  132  via one or more pump lines  262  to allow pressurized hydraulic fluid to be supplied from the pump  134  to the control valve(s)  132 . Additionally, the control valve(s)  132  may be fluidly coupled to the tilt cylinder  102  via first and second fluid lines  264 ,  166 . For instance, as shown in  FIG. 7 , the first fluid line  264  may be configured to provide a fluid path between the control valve(s)  132  and the rod-side chamber  250  of the tilt cylinder  202 . Similarly, the second fluid line  266  may be configured to provide a fluid path between the control valve(s)  132  and the cap-side chamber  248  of the tilt cylinder  202 . 
     In the embodiment shown in  FIG. 7 , the active and passive control modes may be implemented similar to that described above with reference to  FIGS. 5 and 6 . Specifically, when in the active control mode, the controller  130  may be configured to actively control the actuation/retraction of the tilt cylinder  202  via electronic control of the operation of the control valve(s)  132 , thereby allowing the controller  130  to automatically adjust the lateral orientation of the header  33 . Specifically, when it is desired to pivot the header  32  about the pivot point  110  in the first pivot direction (indicated by arrow  112  in  FIG. 7 ), the operation of the control valve(s)  132  may be controlled such that pressurized hydraulic fluid is supplied from the pump  134  through the valve(s)  132  to the first fluid line  264 . In such instance, the pressurized fluid supplied through the first fluid line  364  may be delivered to the rod-side chamber  250  of the tilt cylinder  202 , thereby causing the header  32  to be pivoted in the first direction  112 . Similarly, when it is desired to pivot the header  32  about the pivot point  110  in the second pivot direction (indicated by arrow  114  in  FIG. 7 ), the operation of the control valve(s)  132  may be controlled such that pressurized hydraulic fluid is supplied from the pump  134  through the valve(s)  132  to the second fluid line  266 . In such instance, the pressurized fluid supplied through the second fluid line  266  may be delivered to the cap-side chamber  248  of the tilt cylinder  202 , thereby causing the header  32  to be pivoted in the second direction  114 . 
     Moreover, when in the passive control mode, the controller  130  may be configured to control the operation of the control valve(s)  132  such that the supply of pressurized hydraulic fluid from the pump  134  is cut-off (e.g., by moving the valve(s)  132  to its closed or neutral position), thereby creating a closed-loop circuit between the first and second fluid lines  264 ,  266  across the pressure relief valve  136 . Thereafter, when the “free-floating” header  32  contacts the ground, a moment force may be applied through the header  32  that, in turn, results in an increase in the fluid pressure within either the first fluid line  264  or the second fluid line  266  depending on the rotational direction of the force (e.g., either the first direction  112  or the second direction  114 ). In the event that the increase in pressure in the associated fluid line  264 ,  266  exceeds the relief pressure setting selected for the pressure relief valve  136 , the pressure relief valve  136  may be opened to allow fluid to be transferred from the high pressure line to the low pressure line, thereby permitting the header  32  to pivot relative to the feeder  34  about the pivot point  110  in the corresponding rotational direction of the applied force. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ front the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.