Patent Description:
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, barely, 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 utilize 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 height and tilt cylinders to automatically adjust the height and lateral orientation, or tilt, of the header relative to the ground based on sensor measurements. An example of such a header height control system is provided by the <CIT>. However, such systems often exhibit significant lag and slow response times, particularly when the harvester is operating at high ground speeds. The parameters of such systems can be selected to improve performance. Determining optimal parameters of such a control system, however, can be difficult.

Accordingly, an improved method and related system for calibrating a height control system for an implement of an agricultural work vehicle that addresses one or more of the issues identified above would be welcomed in the technology.

In one aspect, the present subject matter is directed to a method for calibrating a height control system as set out in the claims.

In another aspect, the present subject matter is directed to a height control system as set out in the claims.

In general, the present subject matter is directed to a method for calibrating a height control system for an implement of an agricultural work vehicle. The calibration method can be performed between agricultural operations (e.g., harvesting operations), for example, while the work vehicle is stationary. The height control system can be configured to implement a proportional-integral ("PI") or proportional-integral-derivative ("PID") control loop to adjust the height of the implement during an agricultural operation. An input signal (e.g., a step input) can be input to the height control system to adjust a height of the implement relative to the ground surface. The response of the height control system to the input signal can be measured. More specifically, the method can include monitoring the height of the implement relative to the ground surface. An implement height sensor can detect the height of the implement as the vehicle control system adjusts the height of the implement in response to the input signal. One or more gains of the height control system can be automatically set based on a maximum stability gain of the height control system. The maximum stability gain can correspond with a stability point of the height control system at which the height control system transitions from stable to unstable, for example as described below with reference to <FIG> and <FIG>. The gain(s) of the height control system can be selected to provide desirable response characteristics for the particular properties and/or dynamics of the height control system, such as the weight of the header. As an example, the gain(s) of can include one or more of a proportional signal gain, an integral signal gain, and a derivative signal gain.

In one embodiment, one or more gains of the system can be determined by increasing the gain(s) until it is approximately equal to the maximum stability gain. An operational gain(s) of the height control system can then be calculated based on the maximum stability gain, for example, using predetermined relationships, equations, look-up tables, etc. Some or all of the steps can be performed automatically by the height control system. Thus, a desirable and/or optimal gain(s) for the height control system can be quickly and/or automatically determined according to aspects of the present disclosure.

Referring now to the drawings, <FIG> illustrates a simplified, partial sectional side view of one embodiment of a work vehicle, a harvester <NUM>. The harvester <NUM> may be 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 <NUM>. The harvester <NUM> may include a chassis or main frame <NUM> having a pair of driven, ground-engaging front wheels <NUM> and a pair of steerable rear wheels <NUM>. The wheels <NUM>, <NUM> may be configured to support the harvester <NUM> relative to a ground surface <NUM> and move the harvester <NUM> in a forward direction of movement <NUM> relative to the ground surface <NUM>. Additionally, an operator's platform <NUM> with an operator's cab <NUM>, a threshing and separating assembly <NUM>, a grain cleaning assembly <NUM>, and a holding tank <NUM> may be supported by the frame <NUM>. Additionally, as is generally understood, the harvester <NUM> may include an engine and a transmission mounted on the frame <NUM>. The transmission may be operably coupled to the engine and may provide variably adjusted gear ratios for transferring engine power to the wheels <NUM>, <NUM> via a drive axle assembly (or via axles if multiple drive axles are employed).

Moreover, as shown in <FIG>, a harvesting implement (e.g., a header <NUM>) and an associated feeder <NUM> may extend forward of the main frame <NUM> and may be pivotally secured thereto for generally vertical movement. In general, the feeder <NUM> may be configured to serve as support structure for the header <NUM>. As shown in <FIG>, the feeder <NUM> may extend between a front end <NUM> coupled to the header <NUM> and a rear end <NUM> positioned adjacent to the threshing and separating assembly <NUM>. As is generally understood, the rear end <NUM> of the feeder <NUM> may be pivotally coupled to a portion of the harvester <NUM> to allow the front end <NUM> of the feeder <NUM> and, thus, the header <NUM> to be moved upwardly and downwardly relative to the ground <NUM> to set the desired harvesting or cutting height for the header <NUM>.

As the harvester <NUM> is propelled forwardly over a field with standing crop, the crop material is severed from the stubble by a sickle bar <NUM> at the front of the header <NUM> and delivered by a header auger <NUM> to the front end <NUM> of the feeder <NUM>, which supplies the cut crop to the threshing and separating assembly <NUM>. As is generally understood, the threshing and separating assembly <NUM> may include a cylindrical chamber <NUM> in which the rotor <NUM> is rotated to thresh and separate the crop received therein. That is, the crop is rubbed and beaten between the rotor <NUM> and the inner surfaces of the chamber <NUM>, 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 <NUM> falls onto a series of pans <NUM> and associated sieves <NUM>, with the separated crop material being spread out via oscillation of the pans <NUM> and/or sieves <NUM> and eventually falling through apertures defined in the sieves <NUM>. Additionally, a cleaning fan <NUM> may be positioned adjacent to one or more of the sieves <NUM> to provide an air flow through the sieves <NUM> that removes chaff and other impurities from the crop material. For instance, the fan <NUM> may blow the impurities off of the crop material for discharge from the harvester <NUM> through the outlet of a straw hood <NUM> positioned at the back end of the harvester <NUM>.

The cleaned crop material passing through the sieves <NUM> may then fall into a trough of an auger <NUM>, which may be configured to transfer the crop material to an elevator <NUM> for delivery to the associated holding tank <NUM>. Additionally, a pair of tank augers <NUM> at the bottom of the holding tank <NUM> may be used to urge the cleaned crop material sideways to an unloading tube <NUM> for discharge from the harvester <NUM>.

Moreover, in several embodiments, the harvester <NUM> may also include a hydraulic system <NUM> which is configured to adjust a height of the header <NUM> relative to the ground <NUM> so as to maintain the desired cutting height between the header <NUM> and the ground <NUM>. The hydraulic system <NUM> may include a height control cylinder <NUM> configured to adjust the height of the header <NUM> relative to the ground. For example, in some embodiments, the height control cylinder <NUM> may be coupled between the feeder <NUM> and the frame <NUM> such that the height control cylinder <NUM> may pivot the feeder <NUM> to raise the header <NUM> relative to the ground <NUM>. In some embodiments, hydraulic system <NUM> may include first and second tilt cylinders <NUM>, <NUM> coupled between the header <NUM> and the feeder <NUM> to allow the header <NUM> to be tilted relative to the ground <NUM> or pivoted laterally or side-to-side relative to the feeder <NUM>.

Referring now to <FIG>, a simplified, schematic view of one embodiment of the hydraulic system <NUM> described above with reference to <FIG> is illustrated in accordance with aspects of the present subject matter. As shown, the header <NUM> may generally extend side-to-side or in a lengthwise direction (indicated by arrow <NUM> in <FIG>) between a first lateral end <NUM> and a second lateral end <NUM>. Additionally, the header <NUM> may be coupled to the feeder <NUM> at a location between its first and second lateral ends <NUM>, <NUM> to allow the header <NUM> to tilt laterally relative to the feeder <NUM> (e.g., as indicated by arrows <NUM>, <NUM> in <FIG>). For example the header <NUM> may be coupled to the feeder <NUM> roughly at a center <NUM> of the header <NUM>. The height control cylinder <NUM> may be configured to raise and lower the end of the feeder <NUM> relative to the frame <NUM> of the harvester (e.g., as indicated by arrow <NUM>). The lateral tilt cylinders <NUM>, <NUM> may be configured to laterally tilt the header <NUM> relative to the ground <NUM> (e.g., as indicated by arrows <NUM>, <NUM>). In some embodiments, the tilt cylinders <NUM>, <NUM> may also be configured to raise and lower the header <NUM> with respect to the feeder <NUM> (e.g., as indicated by arrow <NUM>).

As indicated above, the hydraulic system <NUM> may include the height control cylinder <NUM> and one or more tilt cylinders <NUM>, <NUM>. For instance, as shown in the illustrated embodiment, a first tilt cylinder <NUM> may be coupled between the header <NUM> and the feeder <NUM> along one lateral side of the connection between the header <NUM> and the feeder <NUM>, and a second tilt cylinder <NUM> may be coupled between the header <NUM> and the feeder <NUM> along the opposed lateral side of the connection between the header <NUM> and the feeder <NUM>. In general, the operation of the height control cylinder <NUM> and tilt cylinders <NUM>, <NUM> may be controlled (e.g., via an associated controller) to adjust the height and angle of the header <NUM> relative to the ground <NUM>. For instance, one or more height sensors <NUM>, <NUM>, <NUM> may be provided on the header <NUM> to monitor one or more respective local distances or heights <NUM> defined between the header <NUM> and the ground <NUM>. Specifically, as shown in <FIG>, a first height sensor <NUM> may be provided at or adjacent to the first lateral end <NUM> of the header <NUM>, and a second height sensor <NUM> may be provided at or adjacent to the second lateral end <NUM> of the header <NUM>. In some embodiments, a third height sensor <NUM> may be provided at or adjacent the center <NUM> of the header <NUM>. In such an embodiment, when one of the height sensors <NUM>, <NUM>, <NUM> detects that the local height <NUM> defined between the header <NUM> and the ground <NUM> differs from a desired height (or falls outside a desired height range), the height control cylinder <NUM> and/or the tilt cylinders <NUM>, <NUM> may be actively controlled so as to adjust the height and/or tilt of the header <NUM> in a manner that maintains the header <NUM> at the desired height (or within the desired height range) relative to the ground <NUM>. In some embodiments, the desired height may be an average, weighted average, or other suitable mathematical combination of the local heights <NUM> measured by one or more of the height sensors <NUM>, <NUM>, <NUM>.

Referring now to <FIG>, a schematic view of one embodiment of a control system <NUM> is provided for automatically controlling the height of an agricultural implement (such as the header <NUM> of the harvester <NUM> described above) relative to the ground <NUM> in accordance with aspects of the present subject matter. In general, the control system <NUM> will be described herein with reference to the harvester <NUM> and header <NUM> illustrated in <FIG>. However, it should be appreciated that the disclosed control system <NUM> may be implemented to control the height of any suitable agricultural implement associated with a work vehicle having any other suitable configuration.

As shown, the control system <NUM> may generally include a controller <NUM> installed on and/or otherwise provided in operative association with the harvester <NUM> and/or the implement (e.g., header <NUM>). In general, the controller <NUM> of the disclosed system <NUM> may correspond to any suitable processor-based device(s), such as a computing device or any combination of computing devices. Thus, in several embodiments, the controller <NUM> may include one or more processor(s) <NUM> and associated memory device(s) <NUM> 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) <NUM> of the controller <NUM> 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) <NUM> may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s) <NUM> configure the controller <NUM> to perform various computer-implemented functions, such as one or more aspects of a method <NUM> for controlling the height of the implement described below with reference to <FIG>.

In addition, the controller <NUM> may also include various other suitable components, such as a communications circuit or module, a network interface, one or more input/output channels, a data/control bus and/or the like, to allow the controller <NUM> to be communicatively coupled with any of the various other system components described herein. In some embodiments, the controller <NUM> may be configured to monitor and/or control the engine <NUM> and transmission <NUM> of the harvester <NUM>.

Referring still to <FIG>, the controller <NUM> may generally be configured to control the operation of one or more components of the harvester <NUM>. For instance, in several embodiments, the controller <NUM> may be configured to control the operation of one or more components that regulate the height of the header <NUM> relative to the ground <NUM>. For example, the controller <NUM> may be communicatively coupled to one or more control valve(s) <NUM> configured to regulate the supply of fluid (e.g., hydraulic fluid or air) to one or more corresponding actuator(s) <NUM>. In some embodiments, the actuators <NUM> may correspond with the height control cylinder <NUM>, first tilt cylinder <NUM>, and/or second tilt cylinder <NUM>. The control valve(s) <NUM> may correspond with one or more valves associated with the cylinder(s) <NUM>, <NUM>, <NUM>.

Moreover, as shown in the illustrated embodiment, the vehicle controller <NUM> may be communicatively coupled to a user interface <NUM> of the harvester <NUM>. In general, the user interface <NUM> may correspond to any suitable input device(s) configured to allow the operator to provide operator inputs to the vehicle controller <NUM>, such as a touch screen display, a keyboard, joystick, buttons, knobs, switches, and/or combinations thereof located within the cab <NUM> of the harvester <NUM>. The operator may provide various inputs into the system <NUM> via the user interface <NUM>. In one embodiment, suitable operator inputs may include, but are not limited to, a target height for the implement, a crop type and/or characteristic indicative of a suitable target header height, and/or any other parameter associated with controlling the height of the implement.

Additionally, controller <NUM> may also be communicatively coupled to the various sensors associated the header <NUM>. For instance, as shown in <FIG>, the controller <NUM> may be coupled to one or more header height sensor(s) <NUM> configured to monitor the height of the header <NUM> relative to the ground <NUM>. In one embodiment, the header height sensor(s) <NUM> may correspond to one or more of the one or more height sensors <NUM>, <NUM>, <NUM> configured to monitor local distance(s) or height(s) <NUM> defined between the header <NUM> and the ground <NUM>.

Referring now to <FIG>, a flow diagram of one embodiment of a method <NUM> for calibrating a height control system for an implement of an agricultural work vehicle is illustrated in accordance with aspects of the present subject matter. Although <FIG> depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the methods disclosed herein can be omitted, rearranged, combined, and/or adapted in various ways without deviating from the scope of the present disclosure. Moreover, the method <NUM> will generally be described herein with reference to the harvester <NUM> and header <NUM> shown in <FIG>, as well as the various system components shown in <FIG>. However, it should be appreciated that the disclosed method <NUM> may be implemented to control the height of any suitable agricultural implement associated with a work vehicle having any other suitable configuration and may be used in connection with any system having any suitable system configuration.

Referring to <FIG>, the method <NUM> may include, at (<NUM>), providing an input signal to the height control system <NUM> (e.g., controller <NUM>) to adjust a height <NUM> of the implement (e.g., header <NUM>) relative to the ground surface <NUM>. The input signal can include a signal commanding the controller <NUM> to increase or decrease the height <NUM> of the header <NUM> by a predetermined distance. For instance, the input signal can include a step input signal, a ramp input signal, or other suitable input signal that causes the header <NUM> to be moved from a first height relative to the ground surface <NUM> to a second, different height relative to the ground surface <NUM>. In some implementations, the input signal can include a repeating pattern, such as a sinusoidal pattern.

The method <NUM> may include, at (<NUM>), monitoring the height of the implement (e.g., header <NUM>) relative to the ground surface <NUM>. For example, the controller <NUM> may receive signals from the header height sensor(s) <NUM> (e.g., height sensors <NUM>, <NUM>, <NUM> configured to monitor local distance(s) or height(s) <NUM> defined between the header <NUM> and the ground <NUM>). The controller <NUM> may be configured to receive signals from the height sensor(<NUM>) <NUM> and convert the signals into a measurement.

In some implementations, the input signal can be provided to the height control system <NUM> and/or the height <NUM> of the implement (e.g., header <NUM>) relative to the ground surface <NUM> can be monitored while the agricultural work vehicle <NUM> is stationary. For instance, the method <NUM> can be performed in a headland or area adjacent a field in which an agricultural operation (e.g., harvesting) is to be performed. The method <NUM> can be performed after changing the implement of the work vehicle or otherwise adjusting the configuration or settings of the work vehicle or height control system <NUM>. Generally, the method <NUM> is performed while the vehicle <NUM> is stationary. However, in alternative embodiments, the method <NUM> can be performed while the vehicle <NUM> is moving.

The method <NUM> may include, at (<NUM>), adjusting (e.g., increasing) at least one gain of the height control system (e.g., controller <NUM>). Example gains that can be adjusted (e.g., increased) include a proportional signal gain associated with a proportional signal, an integral signal gain associated with an integral signal, and a derivative signal gain associated with a derivative signal of the height control system <NUM> (e.g., controller <NUM>). As one example, the proportional signal gain can be increased while the integral and/or derivative signal gains are held constant (e.g., are set to zero). As additional examples, the integral and/or derivative signal gains can be increased, and/or the proportional signal gain can be held constant (e.g., set to zero).

The method <NUM> may include, at (<NUM>), determining a maximum stability gain of the height control system <NUM> based on the adjusted gain and the monitored height. The maximum stability gain may correspond with a stability point of the height control system <NUM> at which the height control system <NUM> transitions from stable to unstable, for example as described below with reference to <FIG> and <FIG>. In some embodiments, the height control system <NUM> can automatically increase the gain(s) of the height control system 200and automatically determine when the maximum stability gain has been reached, for example, by analyzing the time-varying height of the implement (e.g., as described below with reference to <FIG> and <FIG>). In other embodiments, however, the operator can manually control one or more aspects of the calibration procedure. For example, the operator can observe the procedure and can perform an input action when the operator observes that the maximum stability gain has been reached. This approach can allow the operator to adjust the performance of the system.

For instance, the operator can cause the calibration procedure to result in slightly lower gains for a slightly more stable and less responsive response. The operator can indicate that the maximum stability gain has been reached at a slightly lower gain level (e.g., earlier in the process of increasing the gain(s) until the maximum stability gain is reached). This can allow the operator to calibrate the height control system <NUM> to be slightly more stable and less responsive or aggressive (e.g., slower). On the other hand, the operator can indicate that the maximum stability gain has been reached at a gain closer to the actual maximum stability gain, resulting in the height control system <NUM> being more responsive or aggressive (e.g., faster) but less stable.

The method <NUM> may include, at (<NUM>), setting the gain(s) of the height control system <NUM> based on the maximum stability gain. In some implementations, an oscillation period of the height control system <NUM> at the maximum stability gain may be measured and/or stored, for example as described below with reference to <FIG>. The gain(s) of the height control system <NUM> can be calculated based on the maximum stability gain. For example, gain(s) of the height control system <NUM> can be looked up and/or calculated using a look-up table based on the maximum stability gain. For example, a look-up table may show values for proportional signal gain, Kp, integral signal gain, Ki, and derivative signal gain, Kd, based on the maximum stability gain, Kms, and oscillation period, Tu, at the maximum stability gain.

In some implementations, the gain(s) of the height control system <NUM> can be iteratively increased to determine the maximum stability gain. For example, step input signals can be iteratively provided to the height control system <NUM> and the gain(s) of the height control system <NUM> can be iteratively increased concurrently. For example, a first input signal can be provided while the gain(s) (e.g., proportional signal gain) of the height control system <NUM> is set at a first gain value or values. The height <NUM> of the implement (e.g., header <NUM>) can be monitored as the height control system <NUM> adjusts the height <NUM> of the header <NUM> in response to the first input signal. The gain(s) of the height control system <NUM> can be increased to a second gain value or values. A second input signal can be provided while the gain(s) of the height control system <NUM> is at the second gain value(s). The height <NUM> of the implement (e.g., header <NUM>) can again be monitored as the height control system <NUM> adjusts the height <NUM> of the header <NUM> in response to the second input signal. This process can be repeated until the gain(s) of the height control system <NUM> is approximately equal to the maximum stability gain (or gains) of the height control system. For instance the proportional signal gain can be increased until the maximum stability is reached while other gains are set to zero. At that point, the current gain(s) of the height control system <NUM> can be stored in the memory <NUM> of the height control system <NUM> and/or communicated for storage in another non-transitory computer-readable media.

In several embodiments, the height control system <NUM> may be configured as a PID controller in which one or more of the gains of the PID controller is determined based on the maximum stability gain of the height control system <NUM>. An equation may show the output signal, u(t), of a PID controller in accordance with aspects of the present disclosure, where e(t) represents an implement height error as a function of time, t; and Kp, Ki, and Kd represent respective constant gains for each of the proportional, integral, and derivative signal components.

The implement height error is a difference between a monitored implement height and an input signal instructing the PID controller loop to set the implement height at a specific height. In other implementations, the controller can be a proportional (P) or proportional-integral (PI) or proportional-derivative (PD) controller. In other words, one or more of the proportional gain, integral gain, and/or derivative gain can be set equal to zero.

<FIG> provides a simplified example plot <NUM> of an input signal <NUM> and a first monitored implement height <NUM> for a first gain that is less than the maximum stability gain and a second monitored implement height <NUM> for a second gain that is greater than the maximum stability gain. The input signal <NUM> can include a step from a first implement height <NUM> to a second implement height <NUM>. In response to the input signal <NUM>, the first monitored implement height <NUM> overshoots the second implement height <NUM> and oscillates about the second implement height <NUM>. As the first gain is less than the maximum stability gain, the first monitored height <NUM> eventually converges at the second implement height <NUM> (illustrated by dotted lines <NUM>).

In contrast, the second implement height <NUM> corresponds with a second gain that is greater than the maximum stability gain. As such, oscillations of the second implement height <NUM> increase in magnitude over time (illustrated by dotted lines <NUM>), resulting in instability of the height control system <NUM>. In other words, the second implement height <NUM> diverges, illustrating that the height control system <NUM> is unstable. Such instability can cause damage to the height control system <NUM>, for example by damaging the actuators used to control the implement height.

<FIG> provides a simplified example plot <NUM> of an input signal <NUM> and a third monitored implement height <NUM> for a third gain that is approximately equal to the maximum stability gain. The input signal <NUM> can include a step from a first implement height <NUM> to a second implement height <NUM>. As illustrated, the third monitored implement height <NUM> can oscillate about the second implement height <NUM>. The third monitored implement height <NUM>, however, neither converges nor diverges. Rather, as illustrated by the dotted lines <NUM>, the third monitored implement height <NUM> can oscillate in a steady state condition (e.g., as a sinusoidal signal).

An oscillation period <NUM> of the third monitored implement height <NUM> can be determined by timing the oscillations (e.g., from peak to peak). As indicated above, the gain(s) of the control system <NUM> can be increased until approximately equal to the maximum stability gain (e.g., equal to the third gain). The gain and oscillation period <NUM> can be stored. The operational gain(s) of the control system <NUM> can be set based on the third gain.

Aspects of the present disclosure are also directed to the height control system <NUM> that has been calibrated according to aspects of the present disclosure. The height control system <NUM> can be configured to adjust the height of the implement using a PI or PID loop having one or more gains determined based on the maximum stability gain.

Additionally, the height control system <NUM> can be configured to adjust the angle of the implement relative to the ground (e.g., lateral tilt and/or fore/aft tilt) to account for ground unevenness. For example, the height control system <NUM> may be configured to adjust the height of the implement (e.g., header <NUM>) based on the inputs from height sensor(s) <NUM>, <NUM>, <NUM>. As indicated above, in some embodiments, the tilt cylinders <NUM>, <NUM> may be capable of adjusting the angle of the header <NUM> of the harvester <NUM>. For example, the controller <NUM> of the height control system <NUM> may be configured to adjust the local height(s) <NUM> measured at the center <NUM> of the header <NUM>, using the height control cylinder(s) <NUM>. Additionally, in some embodiments, the controller <NUM> may be configured to adjust the local height(s) <NUM> of the header <NUM> at each end <NUM>, <NUM> of the header <NUM> using the tilt cylinders <NUM>, <NUM>. Moreover, in some embodiments, the controller <NUM> may be configured to perform discrete or linked control loops for each of the local heights <NUM> of the header <NUM> using any suitable technique or combination of techniques described herein to adjust the lateral tile and/or fore/aft tilt of the header <NUM>. For instance, distinct respective gains for the discrete control loops can be determined using the techniques described herein.

The maximum stability gain of the height control system <NUM> can vary depending on the properties and dynamics of the system, which can include the weight of the implement (e.g., header <NUM>), center or gravity of the implement, and/or other characteristics of the implement, harvester <NUM>, or height control system <NUM>. Thus, the gain(s) that is determined based on the maximum stability gain can similarly vary based on the characteristics of the implement, among other variables.

In some embodiments, the height control system <NUM> can be configured to extrapolate appropriate gains for a substitute implement, for example, based on the weight, center of gravity, etc. of the original implement and the weight, center of gravity, etc. of the substitute implement. The operator can perform the calibration procedure with the first, original implement connected with the work vehicle. Later, if the operator wishes to swap the original implement for a substitute implement, the operator can avoid performing some or all steps of the calibration procedure again for the substitute implement. Instead, the operator can input properties (e.g., weight, center of gravity, etc.) of the original implement and properties of the substitute implement. Alternatively, the operator can input model information about the one or both of the implements, and the height control system <NUM> can determine the relevant properties of the implement(s), for example from a look-up table, through an Internet interface, etc. The height control system <NUM> can extrapolate appropriate gain(s) for the substitute implements based on their characteristics such that the substitute implement can be used without performing a completely new calibration procedure for the substitute implement.

Claim 1:
A method (<NUM>) for calibrating a height control system (<NUM>) for an implement (<NUM>) of an agricultural work vehicle (<NUM>), the method (<NUM>) comprising:
providing, with one or more computing devices (<NUM>), an input signal to the height control system (<NUM>) to adjust a height (<NUM>) of the implement (<NUM>) relative to the ground surface (<NUM>);
monitoring, with the one or more computing devices (<NUM>), the height (<NUM>) of the implement (<NUM>) relative to the ground surface (<NUM>); and
adjusting, with the one or more computing devices (<NUM>), at least one gain of the height control system (<NUM>);
determining, with the one or more computing devices (<NUM>), a maximum stability gain of the height control system (<NUM>) based on the at least one gain and the monitored height (<NUM>), wherein the maximum stability gain corresponds with a stability point of the height control system (<NUM>) at which the height control system (<NUM>) transitions from stable to unstable; and
setting, with the one or more computing devices (<NUM>), the at least one gain of the height control system (<NUM>) based on the maximum stability gain; wherein
providing the input signal to the height control system (<NUM>) comprises iteratively providing step input signals to the height control system (<NUM>);
adjusting the at least one gain of the height control system (<NUM>) comprises iteratively increasing the at least one gain of the height control system (<NUM>) concurrently with providing the step input signals to the height control system (<NUM>);
iteratively increasing the at least one gain of the height control system (<NUM>) concurrently with providing the step input signals to the height control system (<NUM>) comprises increasing the at least one gain of the height control system (<NUM>) until the at least one gain of the height control system (<NUM>) is approximately equal to the maximum stability gain of the height control system (<NUM>); and
determining the maximum stability gain of the height control system (<NUM>) based on the at least one gain comprises storing, in a non-transitory computer-readable media (<NUM>), the at least one gain when the at least one gain is approximately equal to the maximum stability gain.