A work vehicle MRF joystick system operable in a modified stiffness mode

Abstract

The present invention relates to a work vehicle magnetorheological fluid joystick system operable in a modified joystick stiffness mode. Embodiments of a work vehicle magnetorheological fluid (MRF) joystick system include a joystick device having a base housing, a joystick movably mounted to the base housing, and a joystick position sensor configured to monitor joystick movement. The MRF joystick resistance mechanism can be controlled to vary the joystick stiffness resisting movement of the joystick relative to the base housing while a controller architecture is coupled to the joystick position sensor and the MRF joystick resistance mechanism. The controller architecture is configured to: (i) selectively place the work vehicle MRF joystick system in a modified joystick stiffness mode during operation of the work vehicle; and (ii) when the work vehicle MRF joystick system is placed in the modified joystick stiffness mode, command the MRF joystick resistance mechanism to vary the joystick stiffness at least in part based on movement of the joystick relative to the base housing.

Description

Technical Field

[0001] The present disclosure relates to a work vehicle magnetorheological fluid (MRF) joystick system operable in a modified joystick stiffness mode. Background Art

[0002] Joystick devices are commonly used to control various operational aspects of work vehicles employed in the construction, agricultural, forestry, and mining industries. For example, in the case of a work vehicle equipped with a boom assembly, an operator can use one or more joystick devices to control the movement of the boom assembly, and thus control the movement of a tool or implement mounted to the outer terminal end of the boom assembly. Common examples of work vehicles having a boom assembly controlled by a joystick include excavators, feller bunchers, skidders, tractors (on which modular front loaders and backhoe attachments can be mounted), tractor loaders, wheel loaders, and various compact loaders. Similarly, in the case of bulldozers, graders, and other work vehicles equipped with a dozer blade, an operator can use one or more joysticks to control the movement and positioning of the blade. In the case of graders, bulldozers, and certain loaders (such as skid steer loaders), joystick devices are also commonly used to maneuver or otherwise control the directional movement of the work vehicle chassis. Given the widespread use of joystick devices within work vehicles (combined with the relatively challenging dynamic environments in which work vehicles often operate), there is a continuing need for improvements in the design and functionality of work vehicle joystick systems, particularly to the extent that such improvements can enhance the safety and efficiency of work vehicle operation. Summary of the Invention

[0003] Disclosed is a work vehicle magnetorheological fluid (MRF) joystick system for use on a work vehicle. In an embodiment, the work vehicle MRF joystick system includes a joystick device having a base housing, a joystick movably mounted to the base housing, and a joystick position sensor configured to monitor movement of the joystick relative to the base housing. While a controller architecture is coupled to the joystick position sensor and an MRF joystick resistance mechanism, the MRF joystick resistance mechanism is controllable to vary a joystick stiffness that resists movement of the joystick relative to the base housing in at least one degree of freedom. The controller architecture is configured to: (i) selectively place the work vehicle MRF joystick system in a modified joystick stiffness mode during operation of the work vehicle; and (ii) when the work vehicle MRF joystick system is placed in the modified joystick stiffness mode, command the MRF joystick resistance mechanism to vary the joystick stiffness based at least in part on movement of the joystick relative to the base housing.

[0004] In other embodiments, the work vehicle MRF includes a joystick device, an MRF resistance mechanism, and a controller architecture. The joystick device further includes: a base housing; a joystick movably mounted to the base housing; at least one elastic element within the base housing and applying a biasing force on the joystick to urge the joystick to return to the central position when moved away from the central position; and a joystick position sensor configured to monitor the movement of the joystick relative to the base housing. The MRF joystick resistance mechanism is controllable to vary the joystick stiffness resisting movement of the joystick relative to the base housing in at least one degree of freedom. The controller architecture (coupled to the joystick position sensor and the MRF joystick resistance mechanism) is configured to control the MRF joystick stiffness mechanism: (i) to permit the joystick to return to the central position only under the influence of the biasing force when the work vehicle MRF joystick system is operating in a first joystick stiffness mode; and (ii) to prevent the joystick from returning to the central position only under the influence of the biasing force when the work vehicle MRF joystick system is operating in a second joystick stiffness mode.

[0005] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Hereinafter, at least one example of the present disclosure will be described with reference to the following drawings:

[0007] Figure 1 is a schematic view of an example magnetorheological fluid (MRF) joystick system operable on a work vehicle (here an excavator) and in at least one modified joystick stiffness mode;

[0008] Figure 2 is illustrative of Figure 1 a perspective view of two joystick devices that can be included in an example MRF joystick system and used by an operator to control the movement of an excavator boom assembly as seen from within the excavator cab shown in

[0009] Figure 3 and Figure 4 is a cross-sectional schematic view of an example MRF joystick system partially shown and taken along a vertical cross-sectional plane through the joystick included in the joystick device, illustrative of a possible configuration of the MRF joystick system.

[0010] Figure 5 is a process appropriately performed by the controller architecture of the work vehicle MRF joystick system to selectively place the MRF joystick system in at least one modified joystick stiffness mode;

[0011] Figure 6 is a schematic diagram illustrating an example of the joystick movement range and possible positions of an MRF stop that can be selectively generated or modified when the MRF joystick system is operating in a modified joystick stiffness mode in an example implementation of the modified joystick stiffness mode; and

[0012] Figure 7 is a diagram exemplifying, in a non-exhaustive manner, additional example work vehicles into which an implementation of the MRF joystick system can be beneficially integrated.

[0013] In the respective figures, like reference symbols indicate like elements. For simplicity and clarity of illustration, descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the examples and non-limiting implementations of the present invention described in the subsequent detailed description. It should be further understood that features or elements shown in the figures need not be drawn to scale unless otherwise stated. Detailed Description

[0014] Embodiments of the present disclosure are shown in the figures of the plurality of diagrams briefly described above. Those skilled in the art can conceive of various modifications to the example embodiments without departing from the scope of the invention as set forth in the appended claims.

[0015] Overview

[0016] A work vehicle magnetorheological fluid (MRF) joystick system operable in a modified joystick stiffness mode is described below. As used herein, the term "modified joystick stiffness mode" refers to an operating mode in which the MRF joystick system changes the behavior of the joystick device (relative to a default operating mode) by controllably generating an MRF that resists joystick movement in at least one degree of freedom (DOF). For this purpose, embodiments of the work vehicle MRF joystick system described below include a processing subsystem or "controller architecture" operably coupled to an MRF joystick resistance mechanism; that is, a mechanism, device, or damper that contains a magnetorheological fluid and is capable of modifying the rheology (viscosity) of the fluid by changing the intensity of an electromagnetic (EM) field to provide a controlled adjustment of the resistance that resists joystick movement. The resistance that resists the joystick is generally referred to herein as "MRF resistance", and the degree to which the MRF resistance resists joystick movement in a particular direction or combination of directions is referred to herein as "joystick stiffness". Depending on the implementation, the MRF joystick resistance mechanism can be controlled by the controller architecture to apply various different resistance effects within any given range of motion (ROM) of the joystick and by applying a continuously varying magnitude of the resisting force, thereby selectively hindering or inhibiting joystick movement in any given direction.

[0017] Embodiments of the MRF joystick system include at least one MRF joystick device that includes a joystick that is movable relative to a base housing in at least one DOF. In embodiments where the joystick is movable relative to the base housing in multiple DOFs, the MRF joystick system can increase the joystick stiffness in a single DOF or, alternatively, can independently increase the joystick stiffness in multiple DOFs of the joystick. For example, in an implementation where a given joystick is rotatable about two perpendicular axes relative to its base housing, the MRF joystick resistance mechanism can independently increase the MRF resistance, thereby suppressing rotation of the joystick about either or both of the rotational axes of the joystick (and thus suppressing joystick stiffness). Thus, in such a case, the controller architecture can command the MRF joystick system to independently vary a first joystick stiffness and a second joystick stiffness that respectively resist rotation of the joystick about the first axis and the second axis to provide a desired resistance effect or joystick behavior. In this manner, the controller architecture of the MRF joystick system can monitor the joystick position and, in certain cases or operating modes, selectively command the MRF joystick resistance mechanism in a predetermined manner to limit the ROM of the joystick; for example, temporarily limiting the ROM of the joystick to movement along a particular axis or in a particular direction to selectively confine the movement of the joystick to a predefined trajectory or movement pattern (e.g., an H-shaped or plus-shaped trajectory), or otherwise alter the behavior of the joystick when the MRF joystick system is operating in a default joystick stiffness mode or a modified joystick stiffness mode.

[0018] In at least some implementations, the controller architecture can command the MRF joystick resistance mechanism to create local regions of increased resistance (referred to herein as "MRF stops") that the joystick encounters as it moves to specific positions. When the joystick is self-centering (i.e., when the operator moves it away from its neutral or mid-position, it is biased to return to the neutral or mid-position), MRF stops can be created to apply MRF resistance sufficient to overcome the biasing or "centering" force applied to the joystick, thereby preventing the joystick from returning to its centered position without additional force being applied to the joystick by the operator. This type of MRF stop is referred to more specifically herein as a "holding stop". In other instances, MRF stops can be created with a lower MRF resistance (which is perceptible to an operator of a work vehicle operating a self-centering joystick), while also being insufficient to prevent the self-centering joystick from returning to its centered position solely under the influence of the joystick centering force. This latter type of MRF stop is referred to herein as a "sensing stop". When the work vehicle MRF joystick system is placed in a particular joystick stiffness mode, the controller architecture can command the MRF joystick resistance mechanism to create such MRF stops (whether holding stops, sensing stops, or a combination thereof) at any number of predefined joystick positions, with varying intensities, and for various purposes, as discussed further below. In other implementations, the controller architecture does not cause MRF stops to be created in the joystick stiffness modes described below; or the controller architecture can permit the work vehicle operator to selectively enable and disable MRF stops as desired (and potentially assign various functions to the MRF stops).

[0019] The above-described MRF application change in joystick behavior can be implemented by a controller architecture in accordance with one or more joystick stiffness modification algorithms or control schemes stored in a local memory on the work vehicle. In an implementation where the MRF joystick system is operable in multiple modified stiffness modes, a corresponding number of joystick stiffness modification algorithms can be stored in a memory accessible by the controller architecture. During operation, the work vehicle MRF joystick system can typically operate in a default or unmodified joystick stiffness mode and, for example, transition to operate at a particular modified joystick stiffness when appropriate in response to the occurrence of a predefined trigger event. The trigger event can be, for example, a request from an operator to enter a particular modified joystick stiffness mode, the execution of a particular type of work task using the work vehicle (inferred from operator input or sensor data), the work vehicle entering a drive mode that utilizes joystick movement to maneuver or otherwise control the work vehicle propulsion, and other such predefined events, additional examples of which are described below. When operating in a modified joystick stiffness mode, the controller architecture then commands the MRF joystick resistance mechanism to selectively change the joystick stiffness in accordance with the joystick stiffness modification algorithm based at least in part on movement of the joystick relative to the base housing. The manner in which the joystick resistance behavior is adjusted when the MRF joystick system is operating in a modified joystick stiffness mode will vary based on a wide range of factors, which specifically include the particular type of work vehicle (herein, the "host work vehicle") into which the MRF joystick system is integrated and the joystick control functions of the host work vehicle.

[0020] As briefly noted above, implementations of the controller architecture can selectively place the work vehicle MRF joystick system in a modified joystick stiffness mode when using one or more MRF joystick devices to maneuver and / or control the propulsion of a host work vehicle. For example, in an implementation where a self-centering joystick is used to maneuver a work vehicle such as an excavator or other work vehicle placed in a travel mode, the controller architecture can command the MRF joystick resistance mechanism to selectively increase the joystick stiffness to a level sufficient to prevent the joystick from returning to its centered position under the action of only the joystick's inherent biasing force. This is useful in implementations that permit an operator to select between a speed-based joystick steering scheme and a position-based joystick steering scheme, where, when the speed-based joystick steering scheme is selected, the controller architecture enables the joystick to return to the self-centered position. Similarly, in the case of bulldozers and other work vehicles capable of operating in a creep mode (i.e., a mode that permits fine-tuning of the work vehicle speed within a limited speed range), when the work vehicle is placed in the creep mode, the work vehicle MRF joystick system can transition to operation in a modified joystick stiffness mode. In this latter case, the controller architecture can command the MRF joystick system to enable push-pull joystick operation for work vehicle travel while generating one or more MRF stops to assist the operator in driving the work vehicle when in the creep mode; for example, one or more holding stops can be generated to hold the joystick in the position commanded by the operator when the work vehicle is creeping in the forward or reverse direction.

[0021] In another implementation of the MRF joystick system of a work vehicle, in response to attaching a particular type of replaceable implement or tool to the work vehicle, the controller architecture can place the MRF joystick system in a modified joystick stiffness mode. The particular type of implement currently attached to the work vehicle can be automatically determined by sensors on the work vehicle, or the operator can input information specifying the type of implement currently attached. Then, when the controller architecture places the MRF joystick system in a particular joystick stiffness mode in response to the attachment (or use) of a particular type of work implement, the controller architecture can selectively change the joystick stiffness by transmitting appropriate commands to the MRF joystick resistance mechanism to best suit the joystick behavior to the newly attached work implement. As a particular non-limiting example, the controller architecture can modify the joystick ROM based on characteristics of the work implement, such as the number of joystick control functions of the implement. In this regard, in the case of an implement that is movable in a single DOF or otherwise capable of performing a single function (such as, in the case of a simple bucket), the MRF joystick rotation can be restricted to a single axis. In contrast, for an implement capable of multi-DOF movement or otherwise capable of performing multiple functions (e.g., as in the case of a multi-purpose or 4-in-1 bucket), the MRF joystick system can enable the joystick to rotate about two substantially perpendicular axes or tracks, where the joystick movement along each track controls or "maps to" different functions of the work vehicle.

[0022] In other embodiments, the controller architecture can place the MRF joystick system in a modified joystick stiffness mode in response to the occurrence of various other events or control modalities of the work vehicle. Consider, for example, a work vehicle equipped with an electrohydraulic (EH) actuation system that drives the movement of a boom assembly such as an articulated boom assembly of an excavator, a front end loader (FEL) assembly of a loader, or an FEL attachment mounted to a tractor. Typically, such an EH actuation system can be operable in a variety of different control modes such as a lift mode and a boost mode. In such a scenario, when the lift mode or boost mode of the EH actuation system is enabled to, for example, reduce the overall joystick stiffness to provide a tactile cue to the operator that additional hydraulic power is temporarily available for controlling the boom assembly, the controller architecture can place the MRF joystick system in a modified joystick stiffness mode. Other examples of such trigger events or conditions for placing the work vehicle MRF joystick system in a particular modified joystick stiffness mode are discussed below, which are the various ways in which joystick behavior can be altered when the MRF joystick system is operating in a given modified joystick stiffness mode. A non-exhaustive list of other trigger events or work vehicle conditions that can trigger the MRF joystick system to enter an associated modified joystick stiffness mode includes performing grading tasks with certain work vehicles (e.g., graders and bulldozers), operator personalization or customization of joystick behavior (e.g., joystick stiffness, joystick ROM, presence of MRF stops, etc.), placing certain work vehicles (e.g., loaders) in a particular performance mode, calibration of certain work vehicle functions, and entering an optimal speed mode that encourages the operator (through tactile cues applied by the MRF) to hold the joystick in a position that maintains the work vehicle speed at a level that optimizes a particular work vehicle parameter such as fuel efficiency.

[0023] Now in connection with Figures 1 to 6Describe an example implementation of an MRF joystick system for a work vehicle. In the following example implementation, the MRF joystick system is mainly discussed in the context of a specific type of work vehicle, namely, an excavator. Additionally, in the following examples, the MRF joystick system includes two joystick devices, each of which has a joystick rotatable about two perpendicular axes and is used to control the movement of the excavator boom assembly and the implement (e.g., bucket, grapple, or hydraulic hammer) attached thereto. Despite the following examples, in other implementations, the MRF joystick system may include a greater or lesser number of joysticks, where each joystick device can move in any number of DOFs and along any suitable motion pattern; for example, in an alternative implementation, a given joystick device is rotatable about a single axis, or it is possible to move along a restricted (e.g., H-shaped or plus-shaped) track or motion pattern. Further, the MRF joystick system described below can be deployed on a wide range of work vehicles having joystick control functionality, and additional examples thereof are discussed below in conjunction with Figure 7 Discuss additional examples thereof.

[0024] An example MRF joystick system operable in a modified joystick stiffness mode

[0025] Initially referring to Figure 1 , an example work vehicle (here, an excavator 20) equipped with an MRF joystick system 22 for a work vehicle is presented. In addition to the MRF joystick system 22, the excavator 20 also includes a boom assembly 24 that terminates in a tool or implement such as a bucket 26. A variety of other implements can be interchanged with the bucket 26 and attached to the terminal end of the boom assembly 24, including, for example, other buckets, grapples, and hydraulic hammers. The excavator 20 is characterized by a body or chassis 28, a crawler undercarriage 30 that supports the chassis 28, and a cab 32 located at the front of the chassis 28 and surrounding the operator's station. The excavator boom assembly 24 extends from the chassis 28 and includes an internal or proximal boom 34 (hereinafter referred to as the "hoist boom 34"), an external or distal boom 36 (hereinafter referred to as the "bucket stick 36"), and a plurality of hydraulic cylinders 38, 40, 42 as major structural components. The hydraulic cylinders 38, 40, 42 in turn include two hoist cylinders 38, a stick cylinder 40, and a bucket cylinder 42. The extension and retraction of the hoist cylinder 38 causes the hoist boom 34 to rotate about a first pivot joint where the hoist boom 34 engages the excavator chassis 28, here, at a position adjacent to the right side of the cab 32. The extension and retraction of the stick cylinder 40 causes the bucket stick 36 to rotate about a second pivot joint where the bucket stick 36 engages the hoist boom 34. Finally, the extension and retraction of the bucket cylinder 42 causes the excavator bucket 26 to rotate or "curl" about a third pivot joint where the bucket 26 engages the bucket stick 36.

[0026] Hydraulic cylinders 38, 40, 42 are included in an electrohydraulic (EH) actuation system 44, which is enclosed by Figure 1 box 46 titled "Actuator for Joystick Control Function" in

[0027] As Figure 1 schematically illustrated in the upper left, the work vehicle MRF joystick system 22 includes one or more MRF joystick devices 52, 54. As used herein, the term "MRF joystick device" refers to an operator input device that includes at least one joystick or control lever, the movement of which is impeded by a variable resistance or "stiffness force" applied by an MRF resistance mechanism of the type described herein. For clarity, although one such MRF joystick device 52 is schematically shown in Figure 1 the MRF joystick system 22 can include any actual number of joystick devices, as indicated by the reference numeral 58. In the case of the exemplary excavator 20, the MRF joystick system 22 will typically include two joystick devices; for example, the joystick devices 52, 54 described below in connection with Figure 2 The manner in which the movement of the excavator boom assembly 24 can be controlled using two such joystick devices 52, 54 is discussed further below. However, first, a general discussion of the joystick device 52, schematically illustrated in Figure 1 is provided to establish a general framework that can better understand the embodiments of the present disclosure.

[0028] As Figure 1Illustrated schematically in the figure, the MRF joystick device 52 includes a joystick 60 mounted to a lower support structure or base housing 62. The joystick 60 is movable relative to the base housing 62 in at least one DOF and is rotatable relative to the base housing 62 about one or more axes. In the depicted embodiment, and as indicated by arrow 64, the joystick 60 of the MRF joystick device 52 is rotatable relative to the base housing 62 about two perpendicular axes and will be described as such below. The MRF joystick device 52 includes one or more joystick position sensors 66 for monitoring the current position and movement of the joystick 60 relative to the base housing 62. The MRF joystick device 52 may also include a variety of other components 68, including buttons, dials, switches, or other manual input features that may be located on the joystick 60 itself, on the base housing 62, or a combination thereof. A spring element (gas or mechanical), a magnet, or a fluid damper may be incorporated into the joystick device 52 to provide a desired speed for returning the joystick to its original position while fine-tuning the desired feel of the joystick 60 perceived by the operator when interacting with the MRF joystick device 52. Such a mechanism is referred to herein as a "joystick biasing mechanism" and may be included within the MRF joystick device 52 when having a self-centering design. In more complex components, a variety of other components (e.g., possibly including one or more artificial force feedback (AFF) motors) may also be incorporated into the MRF joystick device 52. In other implementations, such components may be omitted from the MRF joystick device 52.

[0029] The MRF joystick resistance mechanism 56 is at least partially integrated into the base housing 62 of the MRF joystick device 52. The MRF joystick resistance mechanism 56 can be controlled to adjust the MRF resistance and thus the joystick stiffness to resist joystick movement in at least one DOF relative to the base housing 62. During operation of the MRF joystick system 22, the controller architecture 50 can selectively command the MRF joystick resistance mechanism 56 to increase the joystick stiffness to prevent the joystick from rotating about a particular axis or combination of axes. As discussed more fully below, when adapted to perform any of a variety of enhanced joystick functions, the controller architecture 50 can command the MRF joystick resistance mechanism 56 to increase the joystick stiffness by increasing the strength of the EM field in which the magnetorheological fluid contained within the mechanism 56 is at least partially immersed. Below, a common example of one way in which the MRF joystick resistance mechanism 56 can be implemented is described in conjunction with Figure 3 and Figure 4 describing a common example of one way in which the MRF joystick resistance mechanism 56 can be implemented.

[0030] The excavator 20 is also equipped with any number of on-board sensors 70. In an embodiment, such sensors 70 can include sensors included in an obstacle detection system, which can be integrated into the excavator 20. The non-joystick input sensors 70 can also include any number and type of boom assembly tracking sensors 72 adapted to track the position and movement of the excavator boom assembly 24. In an embodiment, such sensors can include rotary or linear variable displacement sensors integrated into the excavator boom assembly 24. For example, in one possible implementation, a rotary position sensor can be integrated into the pivot joint of the boom assembly 24; and the angular displacement readings captured by the rotary position sensor can be used in combination with the known dimensions of the boom assembly 24 (retrieved from memory) to track the posture and position of the boom assembly 24 (including the bucket 26) in three-dimensional space. In other cases, the extension and reaction of the hydraulic cylinders 38, 40, 42 can be measured (e.g., using linear variable displacement sensors), and used to calculate the current posture and positioning of the excavator boom assembly 24. As a supplement or alternative to the above sensor readings (such as inertial sensor readings) captured by inertial sensors (such as MEMS gyroscopes, accelerometers, and magnetometers that may be packaged as an IMU) attached at various locations on the excavator 20, other sensor inputs can also be considered. For example, the IMU can be attached to one or more locations (different links) of the excavator chassis 28 and the excavator boom assembly 24. When used to perform the functions described below, a vision system capable of tracking the excavator implement or performing other functions related to the operation of the excavator 20 can also be included in the on-board sensors 70.

[0031] In at least some implementations of the work vehicle MRF joystick system 22, one or more load measurement sensors (such as weight- or strain-based sensors) can be further included in the non-joystick sensor input 70. In an embodiment, such load measurement sensors can be used to directly measure the load carried by the bucket 26 (commonly referred to as the "load moving implement") at any given time during excavator operation. In an embodiment, the load measurement sensors can also measure other parameters indicating the load carried by the boom assembly 24 (e.g., one or more hydraulics within the EH actuation system 44). In other implementations, the MRF joystick system 22 can be integrated into a work vehicle having a load bed or storage tank for transporting materials (such as the load bed of an articulated dump truck). In the latter case, the load measurement sensor 76 can take the form of a payload weighing sensor capable of weighing or approximating the weight of the materials carried within the load bed or storage tank of the work vehicle at any particular moment.

[0032] In an embodiment, the interference force sensor 70 further includes a plurality of vehicle motion data sources 74. The vehicle motion data sources 74 can include any sensors or data sources that provide information related to changes in the position, speed, heading, or orientation of the excavator 20. Again, an IMU incorporating MEMS gyroscopes, accelerometers, and possibly magnetometers can be utilized to detect and measure such changes. In an embodiment, an inclinometer or a similar sensor can be employed to monitor the orientation of some parts of the excavator chassis 28 or the boom assembly 24 relative to gravity. The vehicle motion data sources 74 can also include a global navigation satellite system (GNSS) module (such as a global positioning system (GPS) module) for monitoring the position and motion state of the excavator. In an embodiment, the vehicle motion data sources 74 can further include sensors from which the rotational speed of the undercarriage track can be calculated, an electronic compass for monitoring the heading, and other such sensors. In some cases, GPS or other GNSS data (possibly together with map data stored in the memory 48) can also be utilized to determine when the excavator 20 (or other work vehicles) is operating in an environment where significant interference forces are likely to be encountered. Finally, the vehicle motion data sources 74 can include various sensors for monitoring the motion and position of the boom assembly 24 and the bucket 26, including MEMS devices integrated into the boom assembly 24 (as previously described), sensors for measuring the angular displacement at the pin joints of the boom assembly, sensors for measuring the strokes of the hydraulic cylinders 38, 40, 42, and the like.

[0033] In addition to the previously described embodiments, embodiments of the MRF joystick system 22 can also include any number of other non-joystick components 76. Such additional non-joystick components 76 can include an operator interface 78 (different from the MRF joystick device 52), a display device 80 located in the excavator cab 32, and various other types of non-joystick sensors 82. Specifically, the operator interface 78 can include any number and type of non-joystick input devices for receiving operator input, such as buttons, switches, knobs, and similar manual inputs external to the MRF joystick device 52. Such input devices included in the operator input interface 78 can also include cursor-type input devices for interacting with a graphical user interface (GUI) generated on the display device 80, such as a trackball or a joystick. The display device 80 can be located within the cab 32 and can take the form of any image generation device capable of visually presenting visual alerts and other information. The display device 80 can also generate a GUI for receiving operator input, or can include other input elements (e.g., buttons or switches) for receiving operator input, which can be related to the controller architecture 50 when performing the processes described below. In some cases, the display device 80 can also have touch input capabilities.

[0034] Finally, the MRF joystick system 22 can include a variety of other non-joystick sensors 82 that provide data inputs to the controller architecture 50 for performing the processes described below. For example, when this information is considered by the controller architecture 50 to determine when to increase joystick stiffness to perform certain enhanced joystick functions described herein, the non-joystick sensors 82 can include, in some implementations, sensors that automatically determine the type of implement currently attached to the excavator 20 (or other work vehicle); for example, such sensors 82 can sense a label (e.g., a radio frequency identification tag) or read other identification information present on the implement by performing a visual analysis of a camera feed capturing the implement or using any other technique to determine the specific implement type currently attached to the excavator 20. In other cases, the operator can simply enter information selecting the type of implement currently attached to the boom assembly 24 by, for example, interacting with a GUI generated on the display device 80. In still other cases, such other non-joystick sensors 82 can include sensors or cameras capable of determining when the operator is grasping the joystick 60 or otherwise in contact with the joystick 60. In other embodiments, such sensors may not be included in the MRF joystick system 22.

[0035] As further schematically depicted in Figure 1 the controller architecture 50 is associated with the memory 48 and can communicate with the various illustrated components via any number of wired data connections, wireless data connections, or any combination thereof; for example, as generally illustrated, the controller architecture 50 can receive data from the various components via a centralized vehicle or controller area network (CAN) bus 84. As used herein, the term "controller architecture" is used in a non-limiting sense to generally denote the processing subsystem of a work vehicle MRF joystick system (such as the example MRF joystick system 22). Thus, the controller architecture 50 can include any actual number of processors, individual controllers, computer-readable memories, power supplies, storage devices, interface cards, and other standard components or can be associated therewith. In many cases, the controller architecture 50 can include a local controller directly associated with the joystick interface and other controllers located within the operator station surrounded by the cab 32, where the local controller communicates with other controllers on the excavator 20 as needed. The controller architecture 50 can also include any number of firmware programs, software programs, or computer-readable instructions designed to perform the various processing tasks, calculations, and control functions described herein or to cooperate therewith. Such computer-readable instructions can be stored in a non-volatile sector of the memory 48 associated with (accessible to) the controller architecture 50. Although in Figure 1The memory is generally illustrated as a single block, but the memory 48 can include any number and type of storage media suitable for storing computer-readable code or instructions and other data to support the operation of the MRF joystick system 22. In an embodiment, the memory 48 can be integrated into the controller architecture 50 as, for example, a system-in-package, a system-on-chip, or another type of microelectronic package or module.

[0036] Turning to the joystick configuration or layout of the excavator 20 in more detail, the number of joystick devices included in the MRF joystick system 22 and the structural and functional aspects of such joysticks will vary from embodiment to embodiment. As previously mentioned, although only a single joystick device 52 is schematically shown in Figure 1 , the MRF joystick system 22 will typically have two joystick devices 52, 54 that support control of the excavator boom assembly. To further illustrate this, Figure 2 a perspective view of the interior of the excavator cab 32 is provided, showing two MRF joystick devices 52, 54 suitably included in an embodiment of the MRF joystick system 22. It can be seen that the MRF joystick devices 52, 54 are on opposite sides of the operator's seat 86 such that the operator can relatively easily manipulate the left MRF joystick device 52 and the right joystick device 54 simultaneously with both hands. Continuing with the reference numerals introduced above in conjunction with Figure 1 , each joystick device 52, 54 includes a joystick 60 mounted to a lower support structure or base housing 62 for rotation about two vertical axes relative to the base housing 62. The joystick devices 52, 54 also each include a flexible cover or protective shroud 88 that engages between the lower portion of the joystick 60 and their respective base housings 62. Additionally, joystick input elements are provided in the form of thumb-accessible buttons on each joystick 60, and it is possible to provide other non-illustrated manual input elements (e.g., buttons, dials, and / or switches) provided on the base housing 62. Figure 2 Other notable features of the excavator 20 shown in

[0037] The movement of the joystick 60 included in the joystick devices 52, 54 can be translated into corresponding movement of the excavator boom assembly 24 using different control schemes. In many instances, the excavator 20 will support boom assembly control in either “backhoe control” and “SAE control” modes and “International Organization for Standardization” or “ISO” control mode (and will typically allow switching between them). In the case of backhoe control mode, movement of the left joystick 60 to the left of the operator (arrow 94) causes the excavator boom assembly 24 to swing in the left direction (corresponding to counterclockwise rotation of the chassis 28 relative to the crawler undercarriage 30), movement of the left joystick 60 to the right of the operator (arrow 96) causes the boom assembly 24 to swing in the right direction (corresponding to clockwise rotation of the chassis 28 relative to the crawler undercarriage 30), movement of the left joystick 60 in the forward direction (arrow 98) causes the hoist boom 34 to lower, and movement of the left joystick 60 in the rear or backward direction (arrow 100) causes the hoist boom 34 to raise. Additionally, in the case of backhoe control mode, movement of the right joystick 60 to the left (arrow 102) causes the bucket 26 to curl inward, movement of the right joystick 60 to the right (arrow 104) causes the bucket to release or “open,” movement of the right joystick 60 in the forward direction (arrow 106) causes the bucket stick 26 to rotate outward, and movement of the right joystick 60 in the rear or backward direction (arrow 108) causes the bucket stick 26 to rotate inward. In contrast, in the case of ISO control mode, the joystick movements for swing commands and bucket curl commands remain the same, while the joystick mappings for the hoist boom and bucket stick are reversed. Thus, in ISO control mode, forward and backward movement of the left joystick 60 controls bucket stick rotation in the manner previously described, while forward and rearward movement of the right joystick 60 controls the hoist boom 34 to move (raise and lower) in the manner described above.

[0038] Now turning to Figure 3 and Figure 4, an example configuration of the MRF joystick device 52 and the MRF joystick resistance mechanism 56 is represented by two simplified cross-sectional schematic diagrams. Although these illustrations show a single MRF joystick device (i.e., the MRF joystick device 52), the following description equally applies to the other MRF joystick devices 54 included in the example MRF joystick system 22. The following description is provided only by way of non-limiting example, noting that numerous different joystick designs that incorporate or cooperate functionally with the MRF joystick resistance mechanism are possible. The specific composition of the magnetorheological fluid is also largely immaterial to the embodiments of the present disclosure, so long as there is a meaningful change in the rheological properties (viscosity) of the magnetorheological fluid in conjunction with a controlled change in the EM field strength, as described below. However, for completeness, note that one magnetorheological fluid composition that is well-suited for use in the embodiments of the present disclosure includes magnetically permeable (e.g., carbonyl iron) particles dispersed in a carrier fluid that consists primarily by weight of oil or alcohol (e.g., ethylene glycol). Such magnetically permeable particles may have an average diameter in the micron range (or other maximum cross-sectional dimension if the particles possess a non-spherical (e.g., rectangular) shape); for example, in one embodiment, spherical magnetically permeable particles having an average diameter between 1 micron and 10 microns are used. Various other additives (such as dispersants or diluents) may also be included in the magnetorheological fluid to fine-tune its properties.

[0039] Now referring to Figure 3 and Figure 4 the example joystick configuration shown in Figure 3 and Figure 4The X and Y axes of the coordinate legend 118 as shown; and at the same time, translation movement of the joystick 60 along the X, Y, and Z axes of the coordinate legend 118 is generally prevented. In other embodiments, various other mechanical arrangements (such as gimbal arrangements) can be employed to mount the joystick to the base housing while enabling the joystick to rotate about two perpendicular axes. In less complex embodiments, a pivot or pin joint can be provided to permit the joystick 60 to rotate relative to the base housing 62 about a single axis.

[0040] The joystick 60 of the MRF joystick device 52 also includes a magnetic needle or lower joystick extension 120 that extends from the generally spherical base 112 in a direction opposite to the joystick handle 110. In the illustrated schematic diagram, the lower joystick extension 120 is coupled to a static attachment point of the base housing 62 by a single return spring 124; it should be noted here that this arrangement is simplified for illustrative purposes, and in an actual embodiment of the MRF joystick device 52, a more complex spring return arrangement (or other joystick biasing mechanism, if any) will generally be employed. When the joystick 60 is displaced from Figure 3 the neutral position or original position shown in Figure 4 , the return spring 124 deflects as shown in Figure 3 to urge the joystick 60 back to the original position ( Figure 3 ). Thus, as an example, after rotating to the position shown in Figure 4 , if the work vehicle operator subsequently releases the joystick handle 110, the joystick 60 will return to the neutral position or original position shown in Figure 3 under the action of the return spring 124. In other embodiments, the MRF joystick device 52 may not be self-centering and may alternatively take the form of a friction-holding joystick that remains in a specific position without the operator applying a force to move the joystick away from that position.

[0041] The exemplary MRF joystick resistance mechanism 56 includes a first MRF cylinder 126 and a second MRF cylinder 128 as shown in Figure 3 and Figure 4 respectively. The first MRF cylinder 126 ( Figure 3 ) is mechanically engaged between the lower joystick extension 120 and a static attachment point or infrastructure feature 130 of the base housing 62 as shown. Similarly, the second MRF cylinder 128 ( Figure 4 ) is mechanically engaged between the lower joystick extension 120 and a static attachment point 132 of the base housing 62, where the MRF cylinder 128 is rotated approximately 90 degrees about the Z axis of the coordinate legend 118 relative to the MRF cylinder 126. Due to this structural configuration, the MRF cylinder 126 ( Figure 3 ) can be controlled to selectively resist rotation of the joystick 60 about the X axis of the coordinate legend 118, while the MRF cylinder 128 (Figure 4 ) can be controlled to selectively resist rotation of the joystick 60 about the Y-axis of the coordinate legend 118. Additionally, both of the MRF cylinders 126, 128 can be jointly controlled to selectively resist rotation of the joystick 60 about any axis that lies between the X-axis and the Y-axis and extends within the X-Y plane. In other embodiments, different MRF cylinder configurations can be utilized, which include a greater or lesser number of MRF cylinders; for example, in implementations where it is desired to selectively resist rotation of the joystick 60 about only the X-axis or only the Y-axis, or in implementations where the joystick 60 rotates about only a single axis, a single MRF cylinder or a pair of opposing cylinders can be employed. Finally, although not shown in the simplified schematic, in other implementations, any number of additional components can be included in or associated with the MRF cylinders 126, 128. Such additional components can include sensors for monitoring the stroke of the cylinders 126, 128 (if it is desired to know, for example, to track the position of the joystick) in place of the joystick sensors 182, 184 described below.

[0042] Each of the MRF cylinders 126, 128 includes a cylinder body 134 into which pistons 138, 140 are slidably mounted. Each cylinder body 134 contains a cylindrical cavity or bore 136, and a head 138 of one of the pistons 138, 140 is mounted within the cavity or bore 136 to translate along the longitudinal axis or centerline of the cylinder body 134. Each piston head 138 is fitted with one or more dynamic seals (e.g., O-rings) around its outer periphery to sealingly engage the inner surface of the cylinder body 134, thereby dividing the bore 136 into two opposing variable-volume hydraulic chambers. The pistons 138, 140 also each include an elongate piston rod 140 that extends from the piston head 138 toward the lower joystick extension 120 of the joystick 60. The piston rod 140 extends through an end cap 142 attached above the open end of the cylinder body 134 (also engaging any number of seals) to be attached to the lower joystick extension 120 at a joystick attachment point 144. In the illustrated example, the joystick attachment point 144 takes the form of a pin or pivot joint; however, in other embodiments, a more complex joint (e.g., a ball joint) can be employed to form this mechanical connection. Opposite the joystick attachment point 144, the opposite ends of the MRF cylinders 126, 128 are mounted to corresponding static attachment points 130, 132 via ball joints 145. Finally, hydraulic ports 146, 148 are also provided in the opposite end portions of each of the MRF cylinders 126, 128 to allow the inflow and outflow of the magnetorheological fluid in conjunction with the translation movement or stroke of the pistons 138, 140 along the respective longitudinal axes of the MRF cylinders 126, 128.

[0043] The MRF cylinders 126, 128 are fluidly interconnected with the corresponding MRF valves 150, 152 via flow line connectors 178, 180, respectively. As with the MRF cylinders 126, 128, the MRF valves 150, 152 are shown as being the same in the illustrated example, but may be different in other implementations. Although commonly referred to as "valves" (especially considering the function of the MRF valves 150, 152 is to control the flow of magnetorheological fluid), it will be observed that in the present example the MRF valves 150, 152 lack valve elements and other moving mechanical parts. As a beneficial corollary, the MRF valves 150, 152 provide fail-safe operation because in the unlikely event of an MRF valve failure, magnetorheological fluid is still permitted to pass through the MRF valves 150, 152 with relatively little resistance. Thus, if either or both of the MRF valves 150, 152 fail for any reason, the ability of the MRF joystick resistance mechanism 56 to apply a resistance that restricts or inhibits joystick movement will be impaired; however, the joystick 60 will remain free to rotate about the X and Y axes in a manner similar to a conventional non-MRF joystick system, and typically, the MRF joystick device 52 will remain capable of controlling the excavator boom assembly 24.

[0044] In the depicted embodiment, each of the MRF valves 150, 152 includes a valve housing 154 that contains end caps 156 attached above opposite ends of an elongate cylinder core 158. A generally annular or tubular flow channel 160 extends around the cylinder core 158 between two fluid ports 162, 164 that are disposed through the opposite end caps 156. The annular flow channel 160 is surrounded (extends through it) by a plurality of EM inductor coils 166 (hereinafter, "EM coils 166") that are wound around a paramagnetic retainer 168 and interspersed with a plurality of axially or longitudinally spaced ferrite rings 170. A tubular shroud 172 surrounds the assembly, while a plurality of leads are provided through the shroud 172 to facilitate electrical interconnection with the contained EM coils 166. Two such wires and the corresponding electrical connections to a power and control source 177 are in Figure 3 and Figure 4is schematically represented by lines 174, 176. As indicated by arrow 179, the controller architecture 50 is operatively coupled to the power source and control source 177 in a manner that enables the controller architecture 50 to control the source 177 to vary the current supplied to the EM coil 166 or the voltage applied across the EM coil 166 during operation of the MRF joystick system 22. Accordingly, this structural arrangement allows the controller architecture 50 to command or control the MRF joystick resistance mechanism 56 to vary the intensity of the EM field generated by the EM coil 166. The annular flow channel 160 extends through the EM coil 166 (and may be substantially coaxial therewith) such that when the magnetorheological fluid is directed through the MRF valves 150, 152, the magnetorheological fluid passes through the center of the EM field.

[0045] The fluid ports 162, 164 of the MRF valves 150, 152 are fluidly connected, respectively, via the above-mentioned conduits 178, 180 to the ports 146, 148 of the corresponding MRF cylinders 126, 128. The conduits 178, 180 may be, for example, lengths of flexible tubing having sufficient slack to accommodate any movement of the MRF cylinders 126, 128 that occurs in conjunction with rotation of the joystick 60. In this regard, consider Figure 4 an example scenario. In this example, the operator moves the joystick handle 110 in the operator input direction (indicated by arrow 185) such that the joystick 60 rotates about the Y-axis of the coordinate legend 118 in a clockwise direction. In conjunction with this joystick movement, the MRF cylinder 128 rotates about the spherical joint 145 to tilt slightly upward as shown. Additionally, along with this operator-controlled joystick movement, the pistons 138, 140 contained within the MRF cylinder 128 retract such that the piston head 138 moves Figure 4 toward the left side in (toward the attachment point 132). The translational movement of the pistons 138, 140 forces the magnetorheological fluid to flow through the MRF valve 152 to accommodate the reduction in volume of the chamber to the left of the piston head 138 and the corresponding increase in volume of the chamber to the right of the piston head 138. Accordingly, at any moment during such operator-controlled joystick rotation, the controller architecture 50 can vary the current supplied to the EM coil 166 or the voltage applied across the EM coil 166 to vary the force resisting the flow of the magnetorheological fluid through the MRF valve 152, thereby achieving the desired MRF resistance to further stroke of the pistons 138, 140.

[0046] Given the responsiveness of the MRF joystick resistance mechanism 56, the controller architecture 50 can control the resistance mechanism 56 to apply such MRF resistance only briefly, so as to increase the intensity of the MRF resistance in a predetermined manner (e.g., in a progressive or stepwise manner) as the piston displacement increases, or provide various other resistance effects (e.g., a haptic stop or a pulsation effect), as discussed in detail below. The controller architecture 50 can similarly control the MRF joystick resistance mechanism 56 to selectively provide such a resistance effect when the pistons 138, 140 included in the MRF valves 150 are stroked in combination with the rotation of the joystick 60 about the X-axis of the coordinate legend 118. In addition, the MRF joystick resistance mechanism 56 can independently change the EM field intensity generated by the EM coils 166 in the MRF valves 150, 152 to allow independent control of the MRF resistance, thereby suppressing the rotation of the joystick about the X-axis and Y-axis of the coordinate legend 118.

[0047] The MRF joystick device 52 can also include one or more joystick position sensors 182, 184 (e.g., optical or non-optical sensors or transformers) to monitor the position or movement of the joystick 60 relative to the base housing 62. In the illustrated example, specifically, the MRF joystick device 52 includes a first joystick position sensor 182 ( Figure 3 ) for monitoring the rotation of the joystick 60 about the X-axis of the coordinate legend 118 and a second joystick position sensor 184 ( Figure 4 ) for monitoring the rotation of the joystick 60 about the Y-axis of the coordinate legend 118. The data connections between the joystick position sensors 182, 184 and the controller architecture 50 are represented by lines 186, 188, respectively. In other implementations, the MRF joystick device 52 can include various other unillustrated components, and so can the MRF joystick resistance mechanism 56. Such components can include, when appropriate, operator inputs and corresponding electrical connections provided on the joystick 60 or the base housing 62, an AFF motor, and pressure and / or flow sensors included in the flow circuit of the MRF joystick resistance mechanism 56 to best suit a particular application or use.

[0048] As previously emphasized, the above-described embodiments of the MRF joystick device 52 are provided only by way of non-limiting examples. In alternative implementations, the construction of the joystick 60 can vary in various aspects. Relative to Figure 3 and Figure 4In the example shown, the MRF joystick resistance mechanism 56 may also be different in other embodiments, as long as the MRF joystick resistance mechanism 56 can be controlled by the controller architecture 50 to selectively apply resistance (by changing the rheological properties of the magnetorheological fluid) to inhibit movement of the joystick relative to the base in at least one DOF. In other implementations, an EM inductor coil similar or identical to the EM coil 166 may be directly integrated into the MRF cylinders 126, 128 to provide the desired controllable MRF resistance effect. In such an implementation, flow of the magnetorheological fluid between variable volume chambers within a given MRF cylinder 126, 128 may be permitted by providing one or more apertures through which the piston head 138 passes, by providing an annular or slightly annular gap around the inner surface of the piston head 138 and the cylinder body 134, or by providing a flow channel through the cylinder body 134 or the sleeve itself. Advantageously, such a configuration can impart a relatively compact integrated design to the MRF joystick resistance mechanism. In contrast, using one or more external MRF valves (such as the MRF valves 150, 152( Figure 3 and Figure 4 )) can facilitate cost-effective manufacturing and allow the use of commercially available modular components in at least some cases.

[0049] In other implementations, the design of the MRF joystick device may permit the magnetorheological fluid to encapsulate and act directly on the lower portion of the joystick 60 itself (such as the peripheral base 112 in the case of the joystick 60), with the EM coil disposed around the lower portion of the joystick and surrounding the magnetorheological fluid body. In such an embodiment, the spherical base 112 may be provided with ribs, grooves, or similar topological features to facilitate displacement of the magnetorheological fluid in conjunction with joystick rotation, where energizing the EM coil increases the viscosity of the magnetorheological fluid, thereby impeding flow of the fluid through restricted flow channels disposed around the spherical base 112, or perhaps due to diversion of the magnetorheological fluid in conjunction with joystick rotation. In other embodiments of the MRF joystick system 22, various other designs are possible.

[0050] Regardless of the specific design of the MRF joystick resistance mechanism 56, the joystick stiffness that selectively generates variable MRF resistance or inhibits (resists or blocks) the movement of a target joystick using MRF technology provides several advantages. As a primary advantage, the MRF joystick resistance mechanism 56 (and generally, MRF joystick resistance mechanisms) is highly responsive and can achieve a desired change in the EM field strength, the rheology of the magnetorheological fluid, and ultimately the MRF-applied joystick stiffness to inhibit joystick movement during a highly abbreviated time period (e.g., in some cases, a time period of about 1 millisecond). Correspondingly, the MRF joystick resistance mechanism 56 can enable the removal (or at least a substantial reduction) of MRF resistance at an equal speed by rapidly reducing the current flowing through the EM coil and restoring the rheology (e.g., fluid viscosity) of the magnetorheological fluid to its normal unstimulated state. The controller architecture 50 can also control the MRF joystick resistance mechanism 56 to generate MRF resistance having a continuous series of resistance forces or intensities within certain limits by taking advantage of a corresponding change in the strength of the EM field generated by the EM coil 166. Advantageously, the MRF joystick resistance mechanism 56 can provide reliable and substantially noiseless operation over an extended time period. Additionally, the magnetorheological fluid can be formulated to be essentially non-toxic (such as when the magnetorheological fluid includes carbonyl iron-based particles dispersed in an alcohol-based or oil-based carrier fluid), as previously described. Finally, as another advantage, the above-described configuration of the MRF joystick resistance mechanism 56 allows the MRF joystick system 22 to selectively generate a first resistance or joystick stiffness that prevents the joystick from rotating about a first axis (e.g., Figure 3 and Figure 4 the X-axis of the coordinate legend 118 in

[0051] Now referring to Figure 5 , an example process 190 is shown that is appropriately executed by the controller architecture 50 to selectively place the MRF joystick system 22 in one or more modified joystick stiffness modes. The process 190 (hereinafter referred to as the "joystick stiffness modification process 190") includes a plurality of process steps 192, 194, 196, 198, 200, 202, 204, 206, each of which is described in turn below. Additionally, as indicated during step 204, the controller architecture 50 can apply any number of different modified joystick stiffness modes 208, 210, 212, 214, 216 in accordance with a pre-established joystick stiffness control scheme or algorithm stored in the memory 48 of the MRF joystick system 22. Depending on the specific manner in which the joystick stiffness modification process 190 is implemented,Figure 5 Each of the steps generally illustrated herein may require a single process or multiple sub - processes. Additionally, the steps illustrated herein and described below are provided by way of non - limiting example only. Figure 5 In an alternative embodiment of the joystick stiffness modification process 190, additional process steps may be performed, some steps may be omitted, and / or the illustrated process steps may be performed in an alternative order.

[0052] In response to the occurrence of a predetermined trigger event, the joystick stiffness modification process 190 begins at step 192. The initiation of the joystick stiffness modification process 190 places the work vehicle MRF joystick system 22 in a selected modified joystick stiffness mode, such as any one of the exemplary joystick stiffness modes 208, 210, 212, 214, 216 shown on the right. The trigger event can be any event, condition, or occurrence that is desired to cause the MRF joystick system 22 to transition from its operation in the current joystick stiffness mode (e.g., the default or unaltered joystick stiffness mode) to operation in a particular modified joystick stiffness mode. In this regard, the joystick stiffness modification process 190 can respond to, for example, Figure 5 the start of the work vehicle as shown in Figure 1 and Figure 2 to start at step 192 (e.g., the start of the exemplary excavator 20). Alternatively, the trigger event can be an operator input that requests the initiation or execution of the joystick stiffness modification process 190; for example, in one embodiment, the operator can interact with a GUI generated on the display device 80 to initiate the joystick stiffness modification process 190, thereby placing the MRF joystick system 22 in a selected joystick stiffness change mode. In other cases, when it is determined that the work vehicle is engaged in a particular type of work task, when the work vehicle or a system on the work vehicle (e.g., the EH actuation system 44 of the excavator 20) is placed in a particular operating mode, or when a particular type of work implement is attached to the work vehicle, the controller architecture 50 can automatically (i.e., without operator input) begin the joystick stiffness modification process 190.

[0053] After beginning the joystick stiffness modification process 190, the controller architecture 50 proceeds to step 194 to collect relevant non - joystick data inputs and uses these data inputs to perform the remainder of the process 190. Such data inputs will vary depending on the nature or implementation details of the newly activated modified joystick stiffness mode, as described below in connection with Figure 5The example joystick stiffness modes 208, 210, 212, 214, 216 shown on the right are further discussed. Generally, the data inputs collected during step 194 can include information received from sensors on the work vehicle when utilizing such sensor inputs in determining the appropriate MRF application adjustment for joystick stiffness. For example, in the case of the speed optimization mode described below, sensor data for calculating the optimal speed of the work vehicle (e.g., to maximize fuel efficiency) can be collected during step 194. In some embodiments, during step 194, any relevant data can also be retrieved from on-board memory (e.g., the memory 48 of the excavator 20). In this regard, and as other examples, data can be retrieved from the memory 48 that defines the primary parameters of the modified joystick stiffness mode and forms part of the joystick stiffness modification algorithm or control scheme. Any operator-customized configuration file specifying operator-customized settings regarding joystick behavior affected by the MRF (e.g., overall joystick stiffness, the presence or strength of MRF stops, any changes to the joystick ROM, etc.) can also be retrieved from the memory 48 during step 194 and then utilized during step 204 of process 190 in determining the MRF joystick stiffness adjustment, as further described below.

[0054] Next, proceeding to step S196 of the joystick stiffness modification process 190, the controller architecture 50 receives data indicative of the current joystick movement and position of one (or more) MRF joystick devices under consideration. In the case of the example excavator 20, the controller architecture 50 receives data from the joystick position sensors 182, 184 that describes the movement of the respective joysticks 60 included in the devices 52, 54. In step 198, the controller architecture 50 then utilizes this data to determine whether one or more operationally significant movements of the joystick(s) have occurred during the current iteration of the joystick stiffness modification process 190. If an operationally significant joystick movement is detected, the controller architecture 50 proceeds to step 204 of the joystick stiffness modification process 190, as discussed in detail below. Otherwise, the controller architecture 50 proceeds to step 200 and determines whether the current iteration of the joystick stiffness modification process 190 should terminate, e.g., due to the work vehicle being shut down, due to the joystick control function being continuously inactive for a predetermined period of time, or due to the elimination of a condition or triggering event in response to initially starting process 190 in step 192. If it is determined in step 200 that the joystick stiffness modification process 190 should terminate, the controller architecture 50 proceeds to step 202 and process 190 terminates accordingly. The termination of process 190 can cause the MRF joystick system 22 to return to its default operating mode. If alternatively it is determined that the joystick stiffness modification process 190 should continue, the controller architecture 50 returns to step 194 and the above process steps are repeated or looped.

[0055] In response to detecting an operationally significant joystick rotation (or other joystick movement) in step 202, the controller architecture 50 proceeds to step 204 of the joystick stiffness modification process 190. During step 204 of process 190, the controller architecture 50 determines, at least in part, an appropriate way to vary the MRF resistance (and thus vary the joystick stiffness) to inhibit a given joystick movement based on the current joystick position and the particular modified joystick stiffness at which the work vehicle MRF joystick system 22 is operating at this time. Below, several examples of ways in which the controller architecture 50 can command the MRF joystick resistance mechanism 56 to modify joystick behavior when the MRF joystick system 22 is placed in a particular modified joystick stiffness mode are discussed in detail. After determining the appropriate MRF stiffness adjustment in step 204, the controller architecture 50 then proceeds to step 206 and applies the newly determined MRF resistance or joystick stiffness by transmitting an appropriate command to the MRF joystick resistance mechanism 56 to vary the rheology (viscosity) of one (or more) MRF fluid bodies in a manner that achieves the desired MRF applied resistance effect. Thereafter, the controller architecture 50 then proceeds to step 200 and determines whether the current iteration of the joystick stiffness modification process 190 should terminate or whether an additional iteration of process 190 should be performed, as previously described. In this way, the controller architecture 50 can appropriately repeat successive iterations of process 190 to selectively transition the MRF joystick system 22 between the default joystick stiffness mode and one or more modified joystick stiffness modes.

[0056] As described above, in Figure 5Several examples of modified joystick stiffness modes 208, 210, 212, 214, 216 are shown. The illustrated modified joystick stiffness modes 208, 210, 212, 214, 216 are provided by way of non-limiting examples and are discussed individually below. Initially with respect to the joystick steering mode 208, the controller architecture 50 may use the MRF joystick device 52 in combination to implement different joystick stiffness modification modes to control the steering and / or propulsion of the work vehicle in various contexts. In some embodiments where the work vehicle may operate in different steering modes, the controller architecture 50 may transition the MRF joystick system 22 between a default joystick stiffness mode and a modified joystick stiffness mode in conjunction with the user's selection of different steering modes of the work vehicle 20. For example, an embodiment of the work vehicle may be operable according to a position-based joystick steering scheme (or mode) or a speed-based steering scheme (also referred to as "speed-based steering"). When speed-based joystick steering is activated, the movement of the joystick may control the speed at which the wheels of the work vehicle rotate about the steering axis. In contrast, when position-based joystick steering is activated, the positioning of the joystick may be utilized to set the desired centered angle of the wheels of the work vehicle.

[0057] Continuing with the above description where the work vehicle operator may switch between a speed-based joystick steering mode or scheme and a position-based joystick steering mode or scheme, the controller architecture 50 may operate in a first (e.g., default or unaltered) joystick stiffness mode when applying a speed-based joystick steering scheme. When operative in the first (e.g., default) joystick stiffness mode, the controller architecture 50 may command the MRF joystick resistance mechanism 56 to act on the joystick biasing mechanism within the joystick device that permits the work vehicle to self-center the joystick, such as Figure 3 and Figure 4When returning to its central position under the influence of the spring 124 shown in [description], less (down to no) MRF resistance is applied. Thus, when using a velocity-based joystick steering scheme to control the rotation of a work vehicle about a steering axis, joystick self-centering can be permitted when the MRF joystick is operating appropriately in a first (e.g., default) joystick stiffness mode. Conversely, when applying a position-based joystick steering scheme, the controller architecture 50 transitions the MRF joystick system 22 to operate in a second (e.g., modified) joystick stiffness mode. In this case, the controller architecture 50 commands the MRF joystick resistance mechanism 56 to apply an increased MRF resistance as appropriate to prevent the joystick from returning to its central position under the influence of only the joystick's inherent biasing or centering force. Thus, appropriately when the position-based joystick steering mode is activated, when the operator releases or otherwise stops applying force to the joystick in a manner similar to a non-self-centering (friction-holding) joystick, the joystick will remain in the position commanded by the operator. In this way, the operator is permitted to actively switch between a velocity-based steering scheme and a position-based joystick steering scheme without the need to change hardware, while maintaining a common joystick axis to perform steering between different control schemes.

[0058] In additional embodiments, when controlling the steering and / or propulsion of a work vehicle using one or more MRF joystick devices, a variety of other modified joystick stiffness modes may be employed. As other examples, in the case of a work vehicle capable of operating in a creep mode (such as a bulldozer, a trenching or cold planning mode), the controller architecture 50 may incorporate placing the work vehicle MRF joystick system 22 in a modified joystick stiffness mode in conjunction with placing the work vehicle in a particular creep mode. In one possible approach, the controller architecture 50 may transition the MRF joystick system 22 to operate in a modified joystick stiffness mode when the work vehicle is placed in a creep mode, while enabling push / pull joystick operation for the work vehicle to travel. Specifically, when operating in a modified joystick stiffness mode, the controller architecture 50 may command the MRF joystick resistance mechanism 56 to selectively generate (based on joystick position) one or more stops to assist the operator in driving the work vehicle when in a creep mode; for example, when the work vehicle is creeping in a forward or backward direction, one or more MRF hold stops may be generated to hold the joystick in the position commanded by the operator. In other scenarios, when controlling the steering and / or propulsion of a work vehicle using one or more MRF joystick devices, other types of modified joystick stiffness modes may be employed. For example, in some implementations, the controller architecture 50 may be configured to establish a target speed for the work vehicle based on at least one performance parameter (such as fuel efficiency) when the work vehicle MRF joystick system 22 is operating in a modified joystick stiffness mode. The controller architecture 50 may then command the MRF joystick resistance mechanism 56 to vary the MRF joystick stiffness to provide haptic feedback via the joystick device indicating when the current speed of the work vehicle matches the target speed of the work vehicle to assist the operator in better managing the work vehicle speed to achieve a desired performance parameter, such as minimizing fuel consumption and emissions.

[0059] The next modified joystick stiffness mode changes the ROM of the joystick ( Figure 5In pattern 210), when the MRF joystick system of the work vehicle is placed in a modified joystick stiffness mode, the controller architecture 50 can command the MRF joystick resistance mechanism 56 to limit, expand, or otherwise change the ROM of the joystick. For example, in an embodiment, the controller architecture 50 can limit the ROM of a given MRF joystick device based on the type of work implement attached to the work vehicle. For example, an embodiment of the MRF joystick system 22 can transition to operation in a modified joystick stiffness mode in which the ROM of the joystick is changed (relative to the default joystick stiffness mode) in response to a particular type of replaceable tool or implement being attached to the work vehicle. In such an embodiment, sensors on the work vehicle can automatically determine the type of implement currently attached to the work vehicle; for example, some of the sensors 82 in the excavator 20. For example, such sensors can identify the particular implement type currently attached to the work vehicle by visual analysis of a camera feed capturing the implement or by sensing a tag (e.g., a radio frequency identification tag) or reading other identification information present on the implement using other techniques. In other cases, the operator can input information specifying the type of implement currently attached to the boom assembly of the work vehicle by, for example, interacting with a GUI generated on a display device 80 located at the operator station of the work vehicle.

[0060] When appropriate, the controller architecture 50 then places the MRF joystick system 22 in a modified joystick stiffness mode suitable for optimally controlling the currently attached work implement or tool. For example, in a method, in the case of an implement that is movable in a single DOF or otherwise capable of performing a single function (such as in the case of a simple bucket), MRF joystick rotation can be limited to a single axis. In contrast, for an implement capable of multi-DOF movement or otherwise capable of performing multiple functions, the MRF joystick system can enable the joystick to rotate about two substantially perpendicular axes or tracks, where joystick movement along each track controls or "maps to" different functions of the currently attached work vehicle. Examples of implements with multiple functions include multi-purpose buckets (4-in-1 buckets with movable panels or grapples), certain agricultural implements (e.g., swather headers), and other implements with additional hydraulic control functions. The controller architecture 50 can determine when to place the MRF joystick system 22 in a modified joystick stiffness mode in response to the attachment or use of a particular implement type by identifying the implement type and then using a multi-dimensional look-up table or similar data structure stored in the memory 48 to determine the specific joystick stiffness mode corresponding to the newly attached implement.

[0061] In an embodiment, the controller architecture 50 may also selectively limit the ROM of the MRF joystick to prevent, for example, crosstalk between different control axes. For example, in some cases, when the MRF joystick system 22 is placed in a first mode, the controller architecture may command the MRF joystick resistance mechanism 56 to limit the joystick movement to a predetermined trajectory mode, while permitting joystick movement outside the predetermined trajectory mode when the MRF joystick system 22 is placed in a second mode. To provide a useful but non-limiting example, when the work vehicle is equipped with a forward boom-mounted work implement or tool (e.g., a front-end loader (FEL) bucket), the controller architecture 50 may place the work vehicle MRF joystick system 22 in a modified joystick mode in which joystick movement is limited to a fixed trajectory mode when the MRF joystick is used for functions related to the work vehicle transmission; and place the MRF joystick system 22 in a default joystick stiffness mode that permits the joystick to move throughout the ROM when the joystick is used to control the movement of the FEL bucket. This is further illustrated in Figure 6 which is Figure 6 a schematic diagram 217 including a circular graphic 218 that represents the entire ROM of an example joystick (e.g., corresponding to any of the joysticks 60 shown in Figure 2 ) when rotatable about two orthogonal axes relative to a base housing (also note key point 220).

[0062] Continuing with the above example, when the MRF joystick system 22 is placed in the modified joystick stiffness mode, the controller architecture 50 may control the MRF joystick resistance mechanism 56 to selectively increase the joystick stiffness to limit the joystick movement to a restricted ROM mode that includes at least a first linear track (or straight path) extending from or passing through the center position 230 of the joystick. For example, in some implementations, as indicated in Figure 6 , the joystick travel may be limited to a first linear track 232, 236 and a second linear track 234, 238 that extend substantially perpendicular to each other and intersect at the center position 230 of the joystick. It is noted that given the versatility of the MRF joystick technology described herein, the controller architecture 50 may limit the joystick movement to substantially any desired movement mode, including a mode in which the joystick movement is limited to a path having a more complex (e.g., curved) geometry that is optimized to best suit a particular joystick control application or function when the MRF joystick system 22 is placed in a particular stiffness mode,

[0063] As previously indicated, the controller architecture 50 can command the MRF joystick resistance mechanism 22 to create local regions of increased MRF resistance or "MRF stops" that the joystick encounters when moved to or through specific positions in the various different joystick stiffness modes. In this regard, when the work vehicle MRF joystick system 22 is placed in a particular joystick stiffness mode, the controller architecture 50 can command the MRF joystick resistance mechanism 56 to create such MRF stops (whether hold stops, feel stops, or a combination thereof) at any number of predetermined joystick positions to provide a haptic cue to the operator such that the operator can temporarily set the joystick in a particular position (in the case of a hold stop), such that the operator can selectively perform certain stop-triggered functions, or for other reasons. Additionally, in at least some embodiments, the MRF joystick system 22 can permit the operator to assign different work vehicle functions to the stop positions, or otherwise vary aspects of the MRF stops; e.g., stop holding force, stop position, stop positioning, or stop activation. In Figure 6 Examples of joystick positions where such MRF stops 222, 224, 226, 228 can be created are shown. By way of example, the MRF stop positions 222, 224, 226, 228 are illustrated, noting that in the various embodiments of the MRF joystick system 22, only a single stop position, a subset of stop positions, or stop positions having different positions within the joystick ROM can be created. Additionally, in certain instances, the joystick can be rotated to or through a particular stop position 222, 224, 226, 228 as indicated by arrows 240, 242, 244, 246 respectively to activate or trigger a particular work vehicle function, such as a recoil function that (when executed) causes a bucket or other implement to be raised or lowered to a preset position (e.g., a default position or another position previously specified by the work vehicle operator).

[0064] Next, referring to Figure 5 the EH system control mode 212 shown in, in the case where the work vehicle is equipped with an EH actuation system that includes cylinders that control the movement of a boom assembly (such as cylinders 38, 40, 42 included in the boom assembly of the exemplary excavator 20), e.g., Figure 1In the illustrated embodiment of the EH actuation system 44, the controller architecture 50 can place the MRF joystick system 22 in a modified joystick stiffness mode when the EH actuation system 44 is temporarily placed in a dedicated or non-default hydraulic control mode. Examples of such hydraulic control modes include: (i) a lift mode in which the pressure limit of the EH actuation system is increased while the maximum pump flow of the EH braking system is decreased; and (ii) a boost mode in which the circuit pressure within the EH actuation system is temporarily increased. When operating in the lift mode, the controller architecture 50 can appropriately transition the MRF joystick system 22 to an operation in a corresponding modified joystick stiffness mode that increases or decreases the joystick stiffness to provide the operator with tactile feedback regarding the controllability of the machine and potentially indicating a pressure change within the hydraulic system. Similarly, when operating in the boost mode, the controller architecture 50 can place the MRF joystick in a modified joystick stiffness mode that decreases the joystick stiffness to provide the operator with an intuitive tactile cue that additional hydraulic power is now available to perform the current task using the boom assembly of the work vehicle. In other embodiments, the controller architecture 50 can selectively place the MRF joystick system 22 in a modified joystick mode in conjunction with the EH actuation system being placed in another dedicated control mode, such as a non-default hydraulic flow priority mode.

[0065] Next, proceed to the operator-customizable joystick stiffness mode 214, further illustrated within step 204 of process 1900 ( Figure 5 ), which can permit the operator to adjust various aspects of the joystick behavior to preferentially utilize the MRF joystick system 22 in an embodiment. Such aspects can include the stiffness and travel range of a given joystick device included within the MRF joystick system 22, such as either of the joysticks 52, 54 of the exemplary excavator 20 described above in connection with Figures 1 to 4 . Similarly, in an embodiment, the operator can be permitted to adjust the position, force, and / or position span of any MRF stops generated in a particular modified joystick stiffness mode; and at least in some cases, selectively turn the stops on and off. In the latter case, as briefly indicated above, the MRF joystick system 22 can also enable the operator to program the MRF stops in some implementations; that is, assign different work vehicle functions to the MRF stops and then trigger the work vehicle functions as the operator moves the corresponding joystick into or through a given MRF stop during subsequent work vehicle operation.

[0066] The operator personalization settings can be stored in a memory (e.g., memory 48) accessible to the controller architecture 50 and then retrieved and applied when the MRF joystick system 22 is placed in a particular joystick stiffness mode (here, the operator-customized stiffness mode). For this purpose, an implementation of the controller architecture 50 can first identify a particular operator (e.g., via a wireless key or fob carried by the operator and input into the work vehicle being operated, by analyzing a camera feed capturing the operator's face, or in another way obtaining operator-specific data such as a unique pin), and then apply the corresponding MRF-related personalization settings corresponding to the identified operator when placing the work vehicle MRF joystick system 22 in the operator-customized or personalized stiffness mode. Thus, in at least some implementations, the controller architecture 50 can (i) place the work vehicle MRF joystick system 22 in the operator-customized stiffness mode in response to identifying an operator associated with an operator-customized profile of the work vehicle; and (ii) when the work vehicle MRF joystick system 22 is placed in the operator-customized stiffness mode, command the MRF joystick resistance mechanism 56 to change the joystick stiffness according to the operator-customized profile to, for example, impart a particular stiffness, ROM, or stop configuration previously adjusted for the operator's preference to the joystick device.

[0067] In another implementation of the joystick stiffness modification process 190( Figure 5 ), the controller architecture 50 can place the work vehicle MRF joystick system 22 in various other modified joystick stiffness modes 216. For example, in some implementations where the work vehicle is operable in multiple performance modes, the controller architecture 50 can selectively place the work vehicle MRF joystick system 22 in a modified joystick stiffness mode based at least in part on operator input data that places the work vehicle 20 in a selected one of the multiple performance modes. As a specific example, in a compact loader, a skid-steer loader (e.g., as described below in connection with Figure 7In the case of the described exemplary skid steer loader 250) or another loader that can operate in two or more performance modes (e.g., precision, utility, or production modes), the controller architecture 50 can control the MRF joystick resistance mechanism 56 to achieve a corresponding joystick stiffness mode when the loader is placed in the precision performance mode, such as an increased stiffness joystick stiffness mode. In somewhat similar aspects, when using a grader, bulldozer, or similar work vehicle to perform grading tasks, an implementation of the controller architecture 50 can selectively place the MRF joystick system 22 in a modified joystick stiffness mode. Specifically, in an implementation where the work vehicle includes a grading control system and a blade positioned using a joystick device, when the operator controls the blade during a grading task using the grading control system, the controller architecture 50 can place the work vehicle MRF joystick system 22 in a modified joystick stiffness mode. Additionally, in certain cases, the controller architecture 50 commands the MRF joystick resistance mechanism to change one or more of the following joystick stiffness characteristics relative to operation in the default joystick stiffness mode: (i) changing the ROM of the joystick, (ii) suppressing the generation of one or more MRF stops, and / or (iii) eliminating the float function of the blade. This modified joystick stiffness mode can be beneficially implemented in conjunction with a grader (such as the exemplary grader 252 described below Figure 7 ).

[0068] The MRF joystick system 22 can apply various other modified joystick stiffness modes in response to the work vehicle entering a specific operation mode, using the MRF joystick device to control a specific work vehicle function, or in response to various other specified conditions. To provide yet another example, the controller architecture 50 can selectively place the MRF joystick system 22 in a modified joystick stiffness mode in conjunction with the execution of a work vehicle calibration process, using such a calibration process to establish EH settings in the case of an excavator (e.g., excavator 20) or another work vehicle equipped with a hydraulically controlled boom assembly. In this case, as an example, the controller architecture 50 can command the MRF joystick resistance mechanism 56 to generate at least one MRF stop at the calibration position, thereby providing the operator with a tactile cue to hold the joystick in the calibration position until the calibration process is complete. In other words, the MRF stops can be temporarily generated to encourage the operator to hold the joystick command at the desired position until the calibration process is completed, after which the controller architecture 50 can return the MRF joystick system 22 to operation in the default joystick stiffness mode. In this way, when commanding a function until that function reaches a pressure threshold and holding that command for a period of time, the likelihood of calibration error can be reduced. This function can dynamically form MRF stops to prevent the operator from reducing the command below the threshold before calibration is complete.

[0069] Additional examples of work vehicles beneficially equipped with an MRF joystick system

[0070] Turning now Figure 7 , additional examples of work vehicles in which embodiments of an MRF joystick system can be beneficially incorporated are illustrated. Specifically, initially referring to the upper portion of the figure, three such work vehicles are shown: wheel loader 248, SSL 250, and grader 252. First with respect to the wheel loader 248, the wheel loader 248 can be equipped with an exemplary MRF joystick device 254 located within the cab 256 of the wheel loader 248. When so provided, the MRF joystick device 254 can be used to control the movement of the FEL 258 terminating in the bucket 260; the FEL 258 and front end loader are generally regarded as being of the "boom assembly" type in the background of this document. In contrast, two MRF joystick devices 262 can be located in the cab 264 of the exemplary SSL 250 and are used not only to control the movement of the FEL 266 and its bucket 268, but also to control the movement of the chassis 270 of the SSL 250 in a well-known manner. Finally, the grader 252 likewise includes two MRF joystick devices 272 located within the cab 274 of the grader 252. The MRF joystick devices 272 can be used to control the movement of the grader chassis 276 (by controlling a first transmission driving the rear wheels of the grader and possibly a second (e.g., hydrostatic) transmission driving the front wheels), and also, for example, to control the movement of the grader blade 278 by rotation and angular adjustment of the blade carousel assembly 280 and adjustment of the side offset angle of the blade 278.

[0071] In each of the above-mentioned examples, the primary work vehicle is beneficially equipped with an MRF joystick system operable in one or more modified joystick stiffness modes adapted to assist an operator in controlling the work vehicle in question. Examples of such modified joystick stiffness modes and associated joystick controller work vehicle functions have been described above, including modified joystick stiffness modes well-suited for implementation in conjunction with wheel loaders, skid-steer (and compact loaders), and graders (noting, for example, the above-mentioned joystick stiffness modes adapted to improve controllability or joystick behavior during grading operations). Thus, any one or all of the exemplary wheel loader 248, SSL 250, and grader 252 can be equipped with a work vehicle MRF joystick system including at least one joystick device, an MRF joystick resistance mechanism, and a controller architecture. Finally, in Figure 7 the bottom portion, other examples of work vehicles usefully equipped with embodiments of the MRF joystick system described herein are illustrated and include a tractor 282 equipped with an FEL, a log grapple harvester 284, a skidder 286, a combine harvester 288, and a bulldozer 290.

[0072] Enumeration Examples of the MRF Joystick System of a Work Vehicle

[0073] For ease of reference, the following examples of the MRF joystick system of a work vehicle are provided and numbered.

[0074] 1. In an embodiment, the MRF joystick system of a work vehicle includes a joystick device having a base housing, a joystick movably mounted to the base housing, and a joystick position sensor configured to monitor the movement of the joystick relative to the base housing. The MRF joystick resistance mechanism can be controlled to change the joystick stiffness resisting the movement of the joystick relative to the base housing with at least one degree of freedom while a controller architecture is coupled to the joystick position sensor and the MRF joystick resistance mechanism. The controller architecture is configured to: (i) selectively place the MRF joystick system of the work vehicle in a modified joystick stiffness mode during operation of the work vehicle; and (ii) when the MRF joystick system of the work vehicle is placed in the modified joystick stiffness mode, command the MRF joystick resistance mechanism to change the joystick stiffness at least partially based on the movement of the joystick relative to the base housing.

[0075] 2. The MRF joystick system of a work vehicle according to Example 1, wherein the controller architecture is configured to selectively set the MRF joystick system of the work vehicle at least partially based on the type of work implement attached to the work vehicle.

[0076] 3. The MRF joystick system of a work vehicle according to Example 2, wherein the type of work implement takes the form of a multi-functional implement having a first function and a second function. Additionally, the controller architecture is configured to command the MRF joystick resistance mechanism to limit the movement of the joystick to a first basic linear track and a second basic linear track when the MRF joystick system of the work vehicle is placed in the modified joystick stiffness mode, wherein the movement of the joystick along the first basic linear track and the second basic linear track controls the first function and the second function of the multi-functional implement, respectively.

[0077] 4. The MRF joystick system of a work vehicle according to Example 1, wherein the joystick device includes at least one elastic element that biases the joystick to return to a center position when the joystick is moved away from the center position. The modified joystick stiffness mode is a joystick position holding mode in which the controller architecture commands the MRF joystick resistance mechanism to selectively increase the joystick stiffness in a manner that prevents the joystick from returning to the center position when the joystick is moved away from the center position.

[0078] 5. The work vehicle MRF joystick system according to Example 4, wherein the controller architecture is configured to place the work vehicle MRF joystick system in a modified joystick stiffness mode in response to an operator input that transitions the work vehicle from a speed-based joystick steering scheme to a position-based joystick steering scheme.

[0079] 6. The work vehicle MRF joystick system according to Example 1, wherein the work vehicle is operable in a plurality of performance modes; and the controller architecture is configured to selectively place the work vehicle MRF joystick system in a modified joystick stiffness mode based at least in part on operator input data that places the work vehicle in a selected one of the plurality of performance modes.

[0080] 7. The work vehicle MRF joystick system according to Example 1, wherein the work vehicle is operable in a creep mode, and in the creep mode, the joystick device can be used to control the movement of the work vehicle at least in the forward and reverse directions. Additionally, the controller architecture is configured to selectively place the work vehicle MRF joystick system in a modified joystick stiffness mode when the work vehicle is placed in the creep mode.

[0081] 8. The work vehicle MRF joystick system according to Example 7, wherein when the work vehicle MRF joystick system is placed in the modified joystick mode, the controller architecture: (i) commands the MRF joystick resistance mechanism to generate one or more MRF stops at one or more predetermined joystick positions; and (ii) selectively causes the work vehicle to continue creeping in the forward or reverse direction based on the movement of the joystick relative to the one or more MRF stops.

[0082] 9. The work vehicle MRF joystick system according to Example 1, wherein when the work vehicle MRF joystick system is operating in the default joystick stiffness mode, the controller architecture commands the MRF joystick resistance mechanism to generate one or more MRF stops at one or more predetermined joystick positions.

[0083] 10. The work vehicle MRF joystick system according to Example 9, wherein the controller architecture is further configured to: (i) command the MRF joystick resistance mechanism to generate one or more MRF stops at a first force level when the work vehicle MRF joystick system is operating in the default joystick stiffness mode; and (ii) command the MRF joystick resistance mechanism to generate one or more MRF stops at a second force level different from the first force level when the work vehicle MRF joystick system is operating in the default joystick stiffness mode.

[0084] 11. The work vehicle MRF joystick system according to Example 9, wherein the controller architecture is configured to control the MRF joystick resistance mechanism to suppress the generation of one or more MRF stops when the work vehicle MRF joystick system operates in the default joystick stiffness mode.

[0085] 12. The work vehicle MRF joystick system according to Example 1, wherein the modified joystick stiffness mode takes the form of a calibration mode during which a calibration process is performed. The controller architecture is configured to command the MRF joystick resistance mechanism to generate an MRF stop at the calibration position, thereby providing the operator with a tactile cue to hold the joystick at the calibration position until the calibration process is complete.

[0086] 13. The work vehicle MRF joystick system according to Example 1, the system further includes a memory accessible to the controller architecture and storing an operator-customized profile. The modified joystick stiffness mode takes the form of an operator-customized stiffness mode, and the controller architecture is further configured to: (i) place the work vehicle MRF joystick system in the operator-customized stiffness mode in response to identifying an operator associated with the operator-customized profile of the work vehicle; and (ii) command the MRF joystick resistance mechanism to change the joystick stiffness according to the operator-customized profile when the work vehicle MRF joystick system is placed in the operator-customized stiffness mode.

[0087] 14. The work vehicle MRF joystick system according to Example 1, wherein the work vehicle includes an EH actuation system operable in a modified EH control mode such as a lift mode or a boost mode. The controller architecture is configured to place the work vehicle MRF joystick system in the modified joystick stiffness mode in response to an operator input activating the modified EH control mode.

[0088] 15. The work vehicle MRF joystick system according to Example 1, wherein the joystick is rotatable relative to the base housing about a first axis and a second axis substantially perpendicular to the first axis. Additionally, the controller architecture commands the MRF joystick resistance mechanism to permit joystick movement throughout the ROM when operating in the default joystick stiffness mode. Finally, when the work vehicle MRF joystick system is placed in the modified joystick stiffness mode, the controller architecture controls the MRF joystick resistance mechanism to selectively increase the joystick stiffness to limit joystick movement to a restricted ROM mode including at least a first linear track.

[0089] Conclusion

[0090] Accordingly, a work vehicle MRF joystick system operable in a modified joystick stiffness mode is provided below. By selectively applying this modified joystick stiffness mode, the MRF joystick system can provide additional functionality or otherwise adapt joystick behavior by strategically applying the resistance imposed by the MRF to enhance the way an operator interacts with the MRF joystick device to control various work vehicle functions. As described above, in response to a wide range of conditions or trigger events, an implementation of the MRF joystick system can be selectively placed in a changing joystick stiffness mode; and when operating in a particular joystick stiffness mode, various different aspects of joystick behavior can be altered by such a change in the joystick stiffness determined by the MRF. Such alterations in joystick behavior can include changes to the joystick ROM (e.g., selectively restricting the joystick to move along a restricted ROM such as a track pattern), changes in joystick stiffness when the joystick rotates about one or more specific axes or axes, and the presence (and strength) of MRF stops. As a result, operator convenience and overall work vehicle efficiency can be improved.

[0091] As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that when used in this specification, the terms "comprises" and / or "comprising" specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0092] The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the present disclosure. The embodiments and implementations described herein are chosen and described in order to best explain the principles of the present disclosure and its practical application and to enable others of ordinary skill in the art to understand the present disclosure and identify alternative, modifications, and variations of the described examples. Accordingly, various embodiments and implementations other than those expressly described are within the scope of the following claims.

[0093] Cross - Reference to Related Applications

[0094] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 63 / 019,083, filed May 1, 2020, with the United States Patent and Trademark Office.

Claims

1. An operating vehicle magnetorheological fluid joystick system (22), i.e., an operating vehicle MRF joystick system (22), for use on an operating vehicle (20), the operating vehicle MRF joystick system (22) comprising: A joystick device (52, 54), the joystick device comprising: A base housing (62); A joystick (60) movably mounted to the base housing (62); and A joystick position sensor (66) configured to monitor movement of the joystick (60) relative to the base housing (62); An MRF joystick resistance mechanism (56) controlled to vary joystick stiffness that resists movement of the joystick (60) relative to the base housing (62) in at least one degree of freedom; and A controller architecture (50) coupled to the joystick position sensor (66) and the MRF joystick resistance mechanism (56), the controller architecture (50) being configured to: During operation of the operating vehicle (20), selectively place the operating vehicle MRF joystick system (22) in a modified joystick stiffness mode; and When the operating vehicle MRF joystick system (22) is placed in the modified joystick stiffness mode, command the MRF joystick resistance mechanism (56) to vary the joystick stiffness based at least in part on movement of the joystick (60) relative to the base housing (62), Wherein, when the operating vehicle MRF joystick system (22) is operating in a default joystick stiffness mode, the controller architecture (50) commands the MRF joystick resistance mechanism (56) to generate one or more MRF stops (222, 224, 226, 228) at one or more predetermined joystick positions.

2. The work vehicle MRF joystick system (22) according to claim 1, wherein, The controller architecture (50) is configured to selectively place the operating vehicle MRF joystick system (22) in the modified joystick stiffness mode based at least in part on the type of work implement (26) attached to the operating vehicle (20).

3. The work vehicle MRF joystick system (22) according to claim 2, wherein, The type of the work implement (26) includes a multi-functional implement having a first function and a second function; And Wherein, when the operating vehicle MRF joystick system (22) is placed in the modified joystick stiffness mode, the controller architecture (50) commands the MRF joystick resistance mechanism (56) to limit joystick movement to a first linear track and a second linear track, and the joystick movement along the first linear track and the second linear track controls the first function and the second function of the multi-functional implement, respectively.

4. The work vehicle MRF joystick system (22) according to claim 1, wherein, The joystick device (52, 54) includes at least one elastic element (124) that biases the joystick to return to the central position when the joystick (60) is moved away from the central position; and Among them, the modified joystick stiffness mode includes a joystick position holding mode. In the joystick position holding mode, the controller architecture (50) commands the MRF joystick resistance mechanism (56) to selectively increase the joystick stiffness in such a way as to prevent the joystick (60) from returning to the central position when the joystick (60) is moved away from the central position.

5. The work vehicle MRF joystick system (22) according to claim 4, wherein, The controller architecture (50) is further configured to place the work vehicle MRF joystick system (22) in the modified joystick stiffness mode in response to an operator input that transitions the work vehicle (20) from a speed-based joystick steering scheme to a position-based joystick steering scheme.

6. The work vehicle MRF joystick system (22) according to claim 1, wherein, The work vehicle (20) is capable of operating in a variety of performance modes; And Among them, the controller architecture (50) is configured to selectively place the work vehicle MRF joystick system (22) in the modified joystick stiffness mode at least partially based on operator input data that places the work vehicle (20) in a selected one of the variety of performance modes.

7. The work vehicle MRF joystick system (22) according to claim 1, wherein, The work vehicle (20) is capable of operating in a creep mode. In the creep mode, the joystick devices (52, 54) can be used to control the movement of the work vehicle (20) in at least the forward and reverse directions; And Among them, the controller architecture (50) is configured to selectively place the work vehicle MRF joystick system (22) in the modified joystick stiffness mode when the work vehicle (20) is placed in the creep mode.

8. The work vehicle MRF joystick system (22) according to claim 1, wherein, The controller architecture (50) is further configured to: When the work vehicle MRF joystick system (22) operates in the default joystick stiffness mode, command the MRF joystick resistance mechanism (56) to generate the one or more MRF stops (222, 224, 226, 228) at a first force level; and When the work vehicle MRF joystick system (22) operates in the default joystick stiffness mode, command the MRF joystick resistance mechanism (56) to generate the one or more MRF stops (222, 224, 226, 228) at a second force level different from the first force level.

9. The work vehicle MRF joystick system (22) according to claim 1, wherein, The controller architecture (50) is configured to control the MRF joystick resistance mechanism (56) to inhibit the generation of the one or more MRF stops (222, 224, 226, 228) when the work vehicle MRF joystick system (22) operates in the default joystick stiffness mode.

10. A work vehicle magnetorheological fluid joystick system (22) for use on a work vehicle (20), i.e., a work vehicle MRF joystick system (22), the work vehicle MRF joystick system (22) comprising: Joystick devices (52, 54), the joystick devices comprising: A base housing (62); A joystick (60) movably mounted to the base housing (62); and A joystick position sensor (66) configured to monitor movement of the joystick (60) relative to the base housing (62); An MRF joystick resistance mechanism (56) controlled to vary a joystick stiffness that resists movement of the joystick (60) relative to the base housing (62) in at least one degree of freedom; and A controller architecture (50) coupled to the joystick position sensor (66) and the MRF joystick resistance mechanism (56), the controller architecture (50) being configured to: During operation of the work vehicle (20), selectively place the work vehicle MRF joystick system (22) in a modified joystick stiffness mode; and When the work vehicle MRF joystick system (22) is placed in the modified joystick stiffness mode, command the MRF joystick resistance mechanism (56) to vary the joystick stiffness at least in part based on movement of the joystick (60) relative to the base housing (62), Wherein the work vehicle (20) is capable of operating in a creep mode in which the joystick devices (52, 54) can be used to control movement of the work vehicle (20) in at least a forward direction and a reverse direction; Wherein the controller architecture (50) is configured to selectively place the work vehicle MRF joystick system (22) in the modified joystick stiffness mode when the work vehicle (20) is placed in the creep mode, and Wherein when the work vehicle MRF joystick system (22) is placed in the modified joystick mode, the controller architecture (50): Commands the MRF joystick resistance mechanism (56) to create one or more MRF stops (222, 224, 226, 228) at one or more predetermined joystick positions; and Selectively causes the work vehicle (20) to continue creeping in a forward or reverse direction based on joystick movement relative to the one or more MRF stops (222, 224, 226, 228).

11. A work vehicle magnetorheological fluid joystick system (22) for use on a work vehicle (20), the work vehicle MRF joystick system (22) comprising: A joystick device (52, 54) including: A base housing (62); A joystick (60) movably mounted to the base housing (62); and A joystick position sensor (66) configured to monitor movement of the joystick (60) relative to the base housing (62); An MRF joystick resistance mechanism (56) controlled to vary a joystick stiffness that resists movement of the joystick (60) relative to the base housing (62) in at least one degree of freedom; and A controller architecture (50) coupled to the joystick position sensor (66) and the MRF joystick resistance mechanism (56), the controller architecture (50) being configured to: During operation of the work vehicle (20), selectively place the work vehicle MRF joystick system (22) in a modified joystick stiffness mode; and When the work vehicle MRF joystick system (22) is placed in the modified joystick stiffness mode, command the MRF joystick resistance mechanism (56) to change the joystick stiffness at least partially based on movement of the joystick (60) relative to the base housing (62), Wherein the modified joystick stiffness mode includes a calibration mode that performs a calibration process; and Wherein the controller architecture (50) is configured to command the MRF joystick resistance mechanism (56) to generate MRF stops (222, 224, 226, 228) at calibration positions to provide a tactile cue for an operator to hold the joystick at the calibration positions until the calibration process is complete.

12. A work vehicle magnetorheological fluid joystick system (22), i.e., a work vehicle MRF joystick system (22), for use on a work vehicle (20), the work vehicle MRF joystick system (22) comprising: A joystick device (52, 54), the joystick device comprising: A base housing (62); A joystick (60) movably mounted to the base housing (62); and A joystick position sensor (66) configured to monitor movement of the joystick (60) relative to the base housing (62); An MRF joystick resistance mechanism (56) controlled to change a joystick stiffness that resists movement of the joystick (60) relative to the base housing (62) in at least one degree of freedom; and A controller architecture (50) coupled to the joystick position sensor (66) and the MRF joystick resistance mechanism (56), the controller architecture (50) being configured to: During operation of the work vehicle (20), selectively place the work vehicle MRF joystick system (22) in a modified joystick stiffness mode; and When the work vehicle MRF joystick system (22) is placed in the modified joystick stiffness mode, command the MRF joystick resistance mechanism (56) to change the joystick stiffness at least partially based on movement of the joystick (60) relative to the base housing (62); and A memory (48) accessible to the controller architecture (50) and storing an operator customization profile; Wherein the modified joystick stiffness mode includes an operator-customized stiffness mode; and Wherein the controller architecture (50) is further configured to: In response to identifying an operator of the work vehicle (20) associated with the operator customization profile, placing the work vehicle MRF joystick system (22) in the operator-customized stiffness mode; and When the work vehicle MRF joystick system (22) is placed in the operator-customized stiffness mode, commanding the MRF joystick resistance mechanism (56) to change the joystick stiffness according to the operator customization profile.

13. A work vehicle magnetorheological fluid joystick system (22), i.e., a work vehicle MRF joystick system (22), used on a work vehicle (20), the work vehicle MRF joystick system (22) comprising: A joystick device (52, 54), the joystick device comprising: A base housing (62); A joystick (60) movably mounted to the base housing (62); and A joystick position sensor (66) configured to monitor the movement of the joystick (60) relative to the base housing (62); An MRF joystick resistance mechanism (56) controlled to change the joystick stiffness that resists the movement of the joystick (60) relative to the base housing (62) in at least one degree of freedom; and A controller architecture (50) coupled to the joystick position sensor (66) and the MRF joystick resistance mechanism (56), the controller architecture (50) being configured to: During operation of the work vehicle (20), selectively place the work vehicle MRF joystick system (22) in a modified joystick stiffness mode; and When the work vehicle MRF joystick system (22) is placed in the modified joystick stiffness mode, commanding the MRF joystick resistance mechanism (56) to change the joystick stiffness at least partially based on the movement of the joystick (60) relative to the base housing (62), Wherein the work vehicle (20) includes an EH actuation system (44) operable in a modified electrohydraulic (EH) control mode, i.e., a modified EH control mode, the modified EH control mode including a lift mode or a boost mode; and Wherein the controller architecture (50) is configured to place the work vehicle MRF joystick system (22) in the modified joystick stiffness mode in response to an operator input activating the modified EH control mode.

14. A work vehicle magnetorheological fluid joystick system (22), i.e., a work vehicle MRF joystick system (22), used on a work vehicle (20), the work vehicle MRF joystick system (22) comprising: A joystick device (52, 54), the joystick device comprising: A base housing (62); A joystick (60) movably mounted to the base housing (62); and A joystick position sensor (66) configured to monitor movement of the joystick (60) relative to the base housing (62); An MRF joystick resistance mechanism (56) controlled to vary joystick stiffness that resists movement of the joystick (60) relative to the base housing (62) in at least one degree of freedom; and A controller architecture (50) coupled to the joystick position sensor (66) and the MRF joystick resistance mechanism (56), the controller architecture (50) being configured to: During operation of the work vehicle (20), selectively place the work vehicle MRF joystick system (22) in a modified joystick stiffness mode; and When the work vehicle MRF joystick system (22) is placed in the modified joystick stiffness mode, command the MRF joystick resistance mechanism (56) to vary the joystick stiffness based at least in part on movement of the joystick (60) relative to the base housing (62), wherein the joystick (60) is rotatable relative to the base housing (62) about a first axis and a second axis substantially perpendicular to the first axis; wherein the controller architecture (50) commands the MRF joystick resistance mechanism (56) to permit joystick movement throughout a range of motion ROM when operating in a default joystick stiffness mode; and wherein when the work vehicle MRF joystick system (22) is placed in the modified joystick stiffness mode, the controller architecture (50) controls the MRF joystick resistance mechanism (56) to selectively increase the joystick stiffness to limit joystick movement to a restricted ROM mode including at least first linear tracks (232, 234, 236, 238).

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