STEERING CONTROL SYSTEMS FOR WORK VEHICLES

Abstract

Steering control systems for a work vehicle can include a control element that provides a steering command indicating the vehicle's path curvature. The system can include a hydraulic steering system with a steering pump, hydraulic cylinders, and a cylinder control valve that responds to the steering command. A control system is designed to detect the rate of change of the steering command from the control element. Based on this detected rate, an expected rate of change of the path curvature is calculated, and based on this expected rate of change, an adjusted steering command is generated to maintain a constant rate of change of path curvature. Based on this adjusted steering command, the control system then activates the cylinder control valve to vary the hydraulic flow or pressure to the hydraulic cylinders, thus steering the work vehicle at the constant rate of change of path curvature.

Description

DESCRIPTION

[0001] This disclosure concerns steering control systems for work vehicles and in particular the automatic steering control in hydraulic steering control systems. BACKGROUND OF THE REVELATION

[0002] The efficiency and precision of work vehicles can be influenced by the technical sophistication and responsiveness of their steering control systems. In environments such as agriculture, construction sites, and industry, the operator's ability to precisely control the vehicle's path can be crucial. This precision not only increases the vehicle's performance but also contributes to the overall safety and efficiency of the tasks performed. Conventional steering control systems may lack the differentiated control required for complex operations, particularly with varying loads and terrain. Advances in hydraulic steering and control technology have led to the development of adaptive and responsive steering systems.These systems, for example, enable real-time adjustment of steering commands through the integration of sensors and intelligent control devices, thus ensuring consistent driving characteristics regardless of external conditions. The development of such advanced steering control mechanisms aligns with the industry's efforts to increase the uptime of work vehicles, reduce maintenance, and leverage the potential for semi- or fully autonomous operations. These not only reduce or eliminate the physical demands on the operator but also enhance the precision and safety of vehicle operations, thereby expanding the operational capabilities of work vehicles in challenging environments. SUMMARY OF THE REVELATION

[0003] Steering control systems for a work vehicle are disclosed. In various embodiments, a steering control system for a work vehicle comprises a control element that provides a steering command indicating a path curvature of the work vehicle; a hydraulic steering system with a steering pump, hydraulic cylinders, and a cylinder control valve that responds to the steering command from the control element to effect the path curvature; and a control system with a processor and memory architecture that is coupled to the control element and the hydraulic steering control system and is designed to: detect the speed of the steering command from the control element; determine an expected rate of change of the path curvature based on the detected speed of the steering command; and determine an adapted steering command corresponding to a constant rate of change of the path curvature based on the expected rate of change of the path curvature.and, based on the adapted steering command, to actuate the cylinder control valve, changing the hydraulic flow or pressure to the hydraulic cylinders in order to steer the work vehicle at the constant rate of change of the track curvature.

[0004] In some cases, the work vehicle includes ground engagement elements, each coupled to an associated hydraulic cylinder, and comprises a first and a second ground engagement element that rotate about a common axis and whose associated hydraulic cylinders are connected to each other in a closed hydraulic circuit that includes the cylinder control valve, so that by extending a piston of the hydraulic cylinder for the first ground engagement element, a piston of the hydraulic cylinder for the second ground engagement element is retracted.

[0005] Under certain circumstances, the control system evaluates a steering angle associated with the first and second ground-contact elements when determining the expected rate of change of the path curvature. The work vehicle may also include a first and a second sensor associated with the first and second ground-contact elements, which output a signal used by the control system to detect the steering angle.

[0006] In one embodiment, the steering control system further comprises a primary pump that is hydraulically connected to the cylinder control valve and the reservoir. Based on the adapted steering command, the control system instructs the cylinder control valve to direct an increased flow of hydraulic fluid from the primary pump into the closed hydraulic circuit to produce a stronger steering response.

[0007] In some cases, the control system is designed to calculate the adapted steering command partly based on operating parameters that include the steering angle of the first and second ground engagement elements and / or a driving speed of the working vehicle and / or a loading state of the working vehicle and / or a position of a working device of the working vehicle.

[0008] In certain embodiments, the control system instructs the cylinder control valve, based on the adapted steering command, to direct an increased flow of hydraulic fluid from a primary pump into the closed hydraulic circuit to produce a stronger steering response. Furthermore, the adapted steering command is resolved such that the control system instructs the cylinder control valve to increase or decrease the flow to the hydraulic cylinders of the first and second ground engagement elements. The control system can instruct the cylinder control valve to increase the flow to the hydraulic cylinders of the first and second ground engagement elements to produce a four-wheel steering response, and to decrease the flow to the hydraulic cylinders of the first and second ground engagement elements to produce a two-wheel steering response.

[0009] According to some embodiments, the present disclosure may relate to a work vehicle comprising ground engagement elements coupled to hydraulic cylinders; a control element that provides a steering command; a hand pump coupled to the control element; a cylinder control valve that responds to the steering command from the control element; a control system with a processor and memory architecture coupled to the control element and the hydraulic steering control system and designed to detect the speed of the steering command from the control element; to determine, based on the detected speed of the steering command, an expected rate of change of the path curvature derived from the steering command; and, based on the expected rate of change of the path curvature, to determine an adapted steering command corresponding to a constant rate of change of the path curvature.and, based on the adapted steering command, to actuate the cylinder control valve, to change the hydraulic flow or pressure to the hydraulic cylinders in order to steer the work vehicle at the constant rate of change of the track curvature.

[0010] In some cases, the ground engagement elements comprise a first and a second ground engagement element that rotate about a common axis and whose associated hydraulic cylinders are connected to each other in a closed hydraulic circuit that includes the cylinder control valve, so that by extending a piston of the hydraulic cylinder for the first ground engagement element, a piston of the hydraulic cylinder for the second ground engagement element is retracted.

[0011] In further embodiments, the control system evaluates a steering angle associated with the first and second ground engagement elements when determining the expected rate of change of the path curvature. The work vehicle can include a first and a second sensor assigned to the first and second ground engagement elements, which output a signal used by the control system to detect the steering angle.

[0012] In one embodiment, the work vehicle further comprises a primary pump that is hydraulically connected to the cylinder control valve and the reservoir. Based on the adapted steering command, the control system instructs the cylinder control valve to direct an increased flow of hydraulic fluid from the primary pump into the closed hydraulic circuit to produce a stronger steering response.

[0013] In some cases, the adapted steering command is resolved such that the control system instructs the cylinder control valve to increase or decrease the flow to the hydraulic cylinders of the first and second ground engagement elements. The control system instructs the cylinder control valve to increase the flow to the hydraulic cylinders of the first and second ground engagement elements to produce a four-wheel steering response, and the control system instructs the cylinder control valve to decrease the flow to the hydraulic cylinders of the first and second ground engagement elements to produce a two-wheel steering response.

[0014] In one embodiment, the control system detects a change in the pivot point of the working vehicle during the transition between the four-wheel steering response and the two-wheel steering response, using the change in the pivot point to determine a rate of change of the path curvature.

[0015] The details of one or more embodiments are set out in the accompanying drawings and in the description below. Further features and advantages will become apparent from the description, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] At least one example of the present revelation is described below in connection with the following figures: Fig. Figure 1 is a perspective view of an exemplary work vehicle that can be used to implement embodiments of the present disclosure; Fig. Figure 2 is a schematic view of an exemplary steering control system thereof; Fig. 3 and Fig. Figure 4 shows process diagrams of an example method of the present disclosure for providing a constant speed input for the steering system of the work vehicle; Fig. Figure 5 shows schematic example views of the work vehicle with two-wheel or four-wheel steering; and Fig. Figure 6 is a process diagram of an example procedure for maintaining a constant path curvature for the work vehicle during the transition between steering modes.

[0017] In the various drawings, the same reference numerals denote the same elements. For the sake of simplicity and clarity, descriptions and details of known features and methods may be omitted in order to clearly highlight the exemplary and non-limiting embodiments of the invention described in the following detailed description. It is further understood that features or elements shown in the accompanying figures are not necessarily drawn to scale unless otherwise indicated. DETAILED DESCRIPTION

[0018] Embodiments of the present disclosure are shown in the accompanying figures of the drawings, which are briefly described above. For the person skilled in the art, various modifications of the exemplary embodiments may be conceivable without deviating from the scope of protection of the present invention as defined in the appended claims. OVERVIEW

[0019] The present disclosure relates to an advanced steering control system with improved maneuverability and steering performance for work vehicles. This innovative system integrates mechanical components, hydraulic mechanisms, and sophisticated control algorithms to enable intuitive and adaptive steering behavior under various operating conditions.

[0020] The disclosed system includes a control interface that captures steering commands specifying the desired curvature of the work vehicle's trajectory. These inputs are processed by a control system incorporating a processor and memory architecture to dynamically adjust the hydraulic steering system. The hydraulic steering system, comprising a steering pump, hydraulic cylinders, and a cylinder control valve, is responsively tuned to produce the trajectory curvature in accordance with the operator's steering command.

[0021] The system detects the speed of the steering command from the control element. Based on this detected speed, the control system determines an expected rate of change of the track curvature and an adjusted steering command corresponding to a constant rate of change of track curvature. In this way, the hydraulic flow or pressure to the hydraulic cylinders can be varied by the command of the cylinder control valve, thereby steering the work vehicle at the desired rate of change of track curvature.

[0022] Ground-penetrating elements (e.g., wheels or tracks), each coupled to an associated hydraulic cylinder, are designed to rotate, with the associated hydraulic cylinders connected to each other in a closed hydraulic circuit via the cylinder control valve. This arrangement allows the extension of a piston in the hydraulic cylinder for one ground-penetrating element to cause the retraction of a piston in the hydraulic cylinder for another.

[0023] The control system instructs the cylinder control valve, by evaluating the steering angles associated with the ground engagement elements and applying adapted steering commands, to either divert hydraulic fluid from the closed hydraulic circuit to a reservoir to achieve a damped steering response, or to increase the flow of hydraulic fluid from a primary pump to the closed hydraulic circuit to achieve a stronger steering response. This adaptive response is further refined by considering the speed of the steering command and various operating parameters of the work vehicle, such as steering angle, travel speed, load status, and the position of any implement.Through adaptive, responsive and precise steering control, the system not only increases the operational efficiency and safety of work vehicles, but also provides a technical solution to the technical challenges associated with automatic vehicle steering control.

[0024] The implementation of advanced steering control systems in agricultural machinery significantly reduces crop damage during operation, particularly when maneuvering through field turns, such as headland turns. Precise steering not only increases operational efficiency but also plays a crucial role in preserving crop integrity and preventing accidental trampling, which can lead to significant yield losses and consequently, reduced income for farmers. The use of semi- or fully automatic steering control systems in agricultural vehicles addresses this problem by ensuring that machines adhere to predetermined paths with high accuracy, thereby minimizing crop damage during these operations.Farmers can achieve greater efficiency and sustainability in their agricultural practices, leading to better crop yields and higher economic returns.

[0025] Exemplary embodiments of steering control systems for work vehicles are now discussed in more detail in connection with the accompanying drawings. While the exemplary steering control systems are described below mainly in the context of a specific type of work machine, embodiments of the steering control systems can be used in conjunction with a wide range of work vehicles employed in construction, agriculture, forestry, mining, and other industrial contexts. Accordingly, the following description should be understood merely as a presentation of a non-restrictive example context in which embodiments of the present disclosure are more readily understood. EXAMPLE OF A STEERING CONTROL SYSTEM FOR WORK VEHICLES

[0026] With reference to Fig. 1 is a spraying system 12 housed in or otherwise supported by an exemplary work vehicle 10 in the form of a self-propelled vehicle (e.g., a field sprayer). The work vehicle 10 can be either manned or autonomous. The spraying system 12 can be primarily implemented for distributing and / or spreading a primary fluid (e.g., fertilizer, insecticide, water, or another fluid) over a geographical area (e.g., a field). The spraying system 12 can comprise a fluid source and a pump coupled to multiple spray nozzles via an arrangement of piping, generally corresponding to the system or group of lines, pipes, valves, tanks, and the like that enable the flow of primary fluid (and other fluids) in the spraying system 12.In general, the work vehicle 10 can comprise a vehicle frame or chassis 14 which lifts off the ground by means of ground engagement elements 16 (e.g. wheels or tracks) and carries a cabin 18.

[0027] Fig. Figure 2 shows a schematic diagram of a part of the work vehicle 10. In general, the work vehicle 10 comprises a control element 20 that issues a steering command specifying a path curvature for the work vehicle's movement. The control element 20 can be a steering wheel mechanically coupled to a hydraulic steering system 22. The control element 20 receives rotational inputs from the operator, which are used by the hydraulic steering system 22 to effect changes in the steering angle (sometimes also referred to as the "road wheel angle") of the ground engagement elements 24 as the operator steers.

[0028] Specifically, the work vehicle comprises four ground engagement elements 24, including a front pair and a rear pair. In an orientation that allows the vehicle to travel straight ahead, the front pair of ground engagement elements 24 rotates about an axis A1, and the rear pair of ground engagement elements 24 rotates about an axis A2.

[0029] Each of the ground engagement elements 24 is hydraulically coupled to a hydraulic cylinder 30. The hydraulic cylinders are part of the hydraulic steering system 22, which also includes a hand pump 40, a primary pump 41, and a cylinder control valve 42. The hydraulic steering system 22 may also include a reservoir 44. In some embodiments, the two front hydraulic cylinders 30 are connected in a closed hydraulic circuit, which also includes the cylinder control valve 42. Generally, the cylinder control valve 42 can be actuated by a control system, which is described in more detail below, to control the flow of hydraulic fluid to the front hydraulic cylinders 30 and thus ensure a constant (or designed) steering ratio for the work vehicle 10.

[0030] In other words, the control element 20 issues a steering command specifying a path curvature for the work vehicle 10. The hydraulic steering system 22 responds to the steering command from the control element 20 to effect the path curvature. The work vehicle 10 incorporates an electronic control system 46, which includes a processor and memory architecture coupled with the control element 20 and the hydraulic steering system 22. In some cases, the control system 46 includes a control element position sensor (BEPS) 48, which receives input from the control element 20 to determine the steering command. In some embodiments, the BEPS 48 provides information indicating the speed of the steering command from the control element 20.

[0031] Furthermore, each of the ground engagement elements 24 is assigned to a steering angle sensor 50 to measure the steering angle of the ground engagement elements 24. These sensors 50 are used by the control system 46 to adjust the direction of the work vehicle based on various inputs, including the steering command, engine speed, vehicle speed, and the actual steering angle of the ground engagement elements 24. By detecting the steering angle of each ground engagement element 24, these sensors 50 enable the control system 46 of the work vehicle to accurately determine the current direction of travel of the work vehicle and to adjust the steering to achieve the desired trajectory.

[0032] After detecting the speed of the steering command from the control element 20, the control system 46 can determine an expected rate of change of the path curvature based on the detected speed of the steering command. The process of determining an expected rate of change of the path curvature based on the detected speed of the steering command involves a prediction (e.g., steering ratio) of how quickly the path or direction (path curvature) of the work vehicle 10 will change over time, considering the current rate at which the steering command is changed by the operator. This prediction is used by the control system 46 to adjust the response of the hydraulic steering system 22 to ensure smooth and precise vehicle handling.The control system 46 uses the speed of the steering command to predict the future steering ratio of the work vehicle 10, which allows for adjustment of the hydraulic steering system 22. This ensures that the movement of the work vehicle corresponds to the operator's inputs, improving control and safety, especially at different speeds or operating conditions.

[0033] The control system 46 can also be configured to determine an adapted steering command based on the expected rate of change of the path curvature, which is associated with a constant rate of change of the path curvature. In general, the control system 46 can determine an adapted steering command that is a scaled version of the actual input, determined from the speed of the steering command. The steering command is adapted to ensure a constant rate of change of the path curvature with respect to the expected rate of change of the path curvature.

[0034] The concept of determining an adapted steering command based on the expected rate of change of the path curvature, as mentioned in connection with the steering control system of the work vehicle, involves predicting how quickly the direction (path curvature) of the work vehicle 10 will change based on the speed of the current steering command. Using this prediction, the control system 46 calculates an adjustment of the steering command that would result in a constant steering ratio for the work vehicle 10, regardless of the initial steering command speed. This approach enables smoother and more predictable vehicle steering by ensuring that changes in direction occur at a consistent rate, thereby improving maneuverability and stability.

[0035] Based on the above, the control system 46 is designed to control the cylinder control valve 42 in such a way as to maintain a constant relationship between the movement of the control element 20 and the corresponding change in the steering angle of the front ground engagement elements 24, regardless of the steering mode or the configuration of the work vehicle 10. This concept ensures that the steering feel and response for the operator remain consistent even when the steering conditions or configurations of the work vehicle change, e.g., when switching between two-wheel steering (2RL) and four-wheel steering (4RL). By dynamically adjusting the proportion of the steering command acting on the front ground engagement elements 24, the cylinder control valve 42 (or a similar system component) can neutralize part of the steering angle. This adjustment means that the overall steering ratio (i.e.,The ratio between the degree of rotation of the control element 20 and the degree of rotation of the ground engagement elements 24 remains constant despite changes in the steering configuration of the work vehicle. This is intended to provide a predictable and consistent steering experience and improve control and operator comfort under varying driving conditions.

[0036] Based on the adjusted steering command, the control system 46 can then instruct the cylinder control valve 42 to change the hydraulic flow or pressure to the hydraulic cylinders 30 in order to steer the work vehicle 10 at the constant rate of change of the track curvature. In other words, during this process, the control system 46 calculates adjustments that ultimately result in changes to the steering angle of the ground engagement elements 24 based on the adjusted steering commands. The control system 46 instructs the cylinder control valve 42 to regulate the flow or pressure of the hydraulic fluid to the hydraulic cylinders 30 for the front ground engagement elements 24. By modulating the hydraulic flow or pressure, the position and / or movement of the ground engagement elements 24 is adjusted to steer the work vehicle 10 according to the planned path, which is defined by a constant rate of change of the track curvature.

[0037] For example, if the adapted steering command prescribes a gradual increase in rightward curvature, the control system 46 instructs the cylinder control valve 42 to adjust the hydraulic flow to the hydraulic cylinders 30 so that the rightward steering is smooth and constant. This could mean increasing the hydraulic pressure to the hydraulic cylinder 30 on one side of the work vehicle 10 and decreasing it on the other side to steer the work vehicle 10 to the right.

[0038] The control system 46 can implement forward control that takes into account disturbances or changes in the steering rate and calculates the necessary action to mitigate course deviations from the constant curvature. Essentially, such forward control is a proactive control system based on predictions generated from the steering command and the desired outcome, namely the maintenance of a constant path curvature.

[0039] In one instance, the forward signals are the commands sent to the cylinder control valve 42 to anticipate the necessary steering adjustments based on inputs such as the desired steering rate and steering command speed. The control system 46 uses these anticipated inputs to maintain a constant steering ratio, even when the work vehicle 10 turns, thus improving the stability and predictability of the work vehicle 10's handling.

[0040] In Fig. Figure 2 shows an example data flow of the control system 46 within the dashed line. In this configuration, it is assumed that the steering ratio would double in most cases when 4RL is activated. The physical relationship between the control element 20 and the front ground engagement elements 24 (i.e., the relationship between the handwheel and the road wheel) is typically determined by the hydraulic architecture. More specifically, the BEPS 48 detects the position of the control element 20 after or during the operator inputs the desired direction and angle of rotation, which serves as the primary input for the control system 46.

[0041] The cylinder control valve 42 acts as a controller or modulator, receiving inputs from the BEPS 48 and modifying the hydraulic flow or pressure to adjust the steering dynamics and thus maintain a constant steering ratio. The forward correction valve commands 52 are anticipatory control commands generated by the control system 46, as described above, to anticipate the necessary steering corrections. By determining the desired front steering rate, the control system 46 can compensate for any necessary changes. The desired front steering ratio 54 specifies the target speed at which the front ground engagement elements 24 should rotate, based on the operator input resolved by the BEPS 48.The control loop 56 for the front axle position is a feedback system that ensures the actual steering angle matches the angle commanded by the operator. The BEPS->curvature defines the relationship between the position of the control element 20 and the curvature of the work vehicle's path, ensuring the steering command results in a suitable driving trajectory. The commands for the rear left target position 58 and the rear right target position 60 are outputs from the control system 46 that determine the target position of the rear ground engagement element 24. These commands ensure that the steering angle of the rear ground engagement elements 24 complements the steering angle of the front ground engagement elements 24 to maintain the stability and maneuverability of the work vehicle.

[0042] In some cases, the control system 46 can be designed to define and enforce threshold values. For example, the control system 46 can be programmed to resolve the adapted steering command such that the control system 46 instructs the cylinder control valve 42 to produce a damped steering response if the speed of the steering command exceeds a speed threshold. The control system 46 is programmed to monitor the rotational speed of the control element 20 (angular velocity in degrees per second) and compare it with a predefined threshold value.

[0043] One function of the control system 46 is to maintain a constant steering ratio, ensuring that the resulting change in the vehicle's path curvature remains the same for any input to the control element 20, regardless of whether the work vehicle 10 is in two-wheel or four-wheel steering mode. This is achieved without limiting the speed at which the operator steers. Instead of limiting the steering rate, the control system 46 dynamically adjusts the hydraulic flow or pressure via the cylinder control valve 42 to the hydraulic cylinders 30 assigned to the front ground engagement elements. This adjustment ensures that the steering command is translated into changes in curvature in a consistent ratio, enabling predictable and smooth vehicle behavior.Through this mechanism, the control system 46 seamlessly ensures that the steering behavior and maneuverability of the vehicle are optimized, thereby improving the operational efficiency and safety of the work vehicle 10 in various steering scenarios.

[0044] The control system 46 can be programmed so that the adapted steering command is partly based on certain operating parameters. Examples of operating parameters include, but are not limited to, the steering angle of the front ground engagement elements 24, the engine speed or driving speed of the work vehicle 10, the load status of the work vehicle 10, the position of a work implement of the work vehicle 10, etc.

[0045] In some embodiments or operating conditions of the work vehicle 10, the control system 46, based on the adapted steering command, instructs the cylinder control valve 42 to direct an increased flow of hydraulic fluid from the primary pump 41 (not shown) into the closed hydraulic circuit to produce an enhanced steering response.

[0046] In certain embodiments, the control system 46 uses the adapted steering command by modulating the hydraulic fluid flow. This is achieved by commands to the cylinder control valve 42, which cause it to allow an increased flow of hydraulic fluid from a reservoir into the hydraulic circuit. The control system 46 calculates the required adjustment of the flow rate or pressure based on the extent and nature of the steering command's deviation from a basic setting or expected behavior, which can be determined, for example, by real-time monitoring of the steering dynamics and the vehicle's operating parameters.

[0047] When the operator of the work vehicle 10 executes a steering command, the control system 46 does not attempt to dampen or smooth this input for reasons of stability or to prevent rollovers. Rather, the control system 46 actively analyzes the steering command in the context of the vehicle's current steering mode, whether two-wheel or four-wheel steering (as well as the operating parameters mentioned above). If a significant deviation in the input is detected that could affect the steering ratio, the control system 46 immediately calculates and applies a precise adjustment of the hydraulic flow or pressure via the cylinder control valve 42 to the hydraulic cylinders 30 assigned to the ground engagement elements. This calculated adjustment is intended to ensure that the input results in a uniform change in curvature, so that the steering ratio remains constant across different steering modes.By focusing on adjusting the transmission ratios, the control system 46 enables the work vehicle 10 to respond predictably to operator inputs and improve maneuverability without compromising operational efficiency or the vehicle's driving characteristics.

[0048] Furthermore, the control system 46 can adjust the threshold and extent of this enhanced response based on various operating parameters of the work vehicle 10. These parameters include, among others, the engine speed or vehicle speed, the steering angle, the load being transported or pulled by the work vehicle 10, and the type or position of any attached implements. This adaptability ensures that the work vehicle's response is tailored to both the operator's expectations and the current operating context (parameters), thereby optimizing the work vehicle's performance and safety.

[0049] In some embodiments, the adapted steering command is resolved such that the control system 46 instructs the cylinder control valve 42 to increase or decrease the flow or pressure to the hydraulic cylinders 30 of the front ground engagement elements 24. For example, in scenarios requiring precision, such as navigating through densely planted crops or avoiding obstacles in confined spaces, the control system 46 could incrementally increase the hydraulic flow or pressure to make subtle directional adjustments, thereby improving maneuverability while maintaining the slow pace required for precise operations.Conversely, in cases where maintaining a straight course with minimal deviation is crucial, such as during linear crossings over a field, the control system 46 can modulate the flow or pressure to the hydraulic cylinders 30 of the front ground engagement elements 24 so that the desired steering ratio is achieved.

[0050] The control system 46 can also command the cylinder control valve 42 to increase the flow to the hydraulic cylinders 30 of the front ground engagement elements 24 to produce a 4RL or 2RL response, resulting in a higher steering ratio. When the operating situation requires increased maneuverability, such as when making tight turns within rows of plants or maneuvering around obstacles, the control system 46 can cause the cylinder control valve 42 to increase the hydraulic fluid flow or pressure to the hydraulic cylinders 30 of the front ground engagement elements 24. This action results in a 4RL response, in which all four wheels rotate, providing a tighter turning radius and improved maneuverability. Conversely, there are scenarios where precision and straight-line stability take precedence over maneuverability, such as when applying chemicals over long, straight stretches.In these cases, the control system 46 can cause the cylinder control valve 42 to reduce the hydraulic flow to the hydraulic cylinders 30 for the front ground engagement elements 24, effectively switching the work vehicle 10 into a 2RL mode in which only the front or rear ground engagement elements 24 rotate to steer the work vehicle 10.

[0051] By increasing or decreasing the hydraulic flow or pressure to the hydraulic cylinders 30 of the front ground engagement elements 24, the control system 46 can influence the driving characteristics of the work vehicle. For example, increasing the hydraulic flow or pressure could simulate the effect of the rear ground engagement elements rotating in the same direction as the front ground engagement elements (common in high-speed 4RL for stability reasons), while decreasing the hydraulic flow or pressure could simulate the rear ground engagement elements rotating in the opposite direction (used in low-speed maneuvers for maneuverability). This method provides flexible steering behavior that adapts to different driving conditions without the mechanical complexity of a physical 4RL system.

[0052] In some cases, the control system 46 can also be designed to monitor a pivot point of the work vehicle 10. The control system 46 can detect a change in the pivot point of the work vehicle 10 during the transition between 4RL mode and 2RL mode. In some cases, the change in the pivot point can be used by the control system 46 to determine a rate of change of the path curvature. An example of the pivot point of the work vehicle 10 is shown in Fig. Figure 5 illustrates this. By detecting a change in the pivot point, the control system 46 can provide an adaptive steering response, which is useful when the work vehicle 10 switches between four-wheel and 2RL modes. In 4RL mode, for example, the work vehicle 10 may make a sharper turn, which can shift the pivot point closer to the center of the work vehicle 10. When transitioning to 2RL, the pivot point may shift, typically toward the rear of the work vehicle 10. By monitoring these changes, the control system 46 can adjust the steering dynamics to ensure optimal maneuverability and stability. Furthermore, understanding the change in the pivot point helps the control system 46 calculate the rate of change of the path curvature.This calculation can influence adjustments to the steering commands to ensure that the desired path is followed smoothly and efficiently, thereby improving the operator's control over the work vehicle 10 and enhancing overall performance in various operational scenarios.

[0053] Fig. Figure 3 is a process diagram of an example method of the present disclosure. The method includes receiving a position signal from a control element and a front axle steering angle signal as input in step 62. The position signal from the control element is referred to as the steering rate, and the front axle steering angle is measured in degrees and expressed as a position. In step 64, a configuration control element position signal can also be input, which is analyzed to determine a current position (measured in degrees) and a ratio between the control element position and the steering angle. The position signal from the control element and the output of the front axle steering angle signal, the current position, and the ratio of control element position to steering angle are processed to determine a normal steering rate in step 66.

[0054] The procedure can also include determining a pivot point value and a wheelbase value, which can be processed to determine half a wheelbase value and finally a reduction in the steering rate value in step 68. This reduced steering rate value and the normal steering rate are processed together to determine a desired steering rate, measured in degrees per second, in step 70. The desired steering rate is then analyzed to determine a correction steering rate in step 72. The positive and negative steering rates are calculated based on the current position of the front axle steering angle and a maximum steering rate in step 74. The positive and negative steering rates are converted into a percentage valve command in step 76 and then into a correction steering rate in step 78.The percentage valve command and the correction steering rate are processed together to calculate a percentage steering ratio command in step 80. This percentage steering ratio command is used in step 82 to determine a final percentage valve command, which is sent by the control system 46 to the cylinder control valve 42. It is understood that the units of measurement described do not represent a limitation.

[0055] Fig. Figure 4 illustrates a related procedure that involves the use of the pivot point of the work vehicle 10, which provides an input for determining the in Fig. The percentage steering ratio command discussed in section 3 is generated. In one embodiment, the method begins in step 84 with the input of a path curvature of the work vehicle 10, measured in degrees per second, along with a pivot point. A corrected pivot point is calculated and combined with a wheelbase value to derive or determine a distance between the front axle and the pivot point in step 86. In step 88, the velocity of the pivot point is calculated.

[0056] This derivative is combined with the pivot point velocity to generate a steering angle steering rate correction. This pivot point correction factor is combined with the maximum steering rate in step 92 to create a front steering correction command based on the pivot point movement and is converted into a percentage correction steering rate in step 94. This percentage pivot point command is combined with the percentage steering ratio command ( Fig. 3 Step 80) processed to generate the final percentage valve command ( Fig. 3 Step 82). TRANSITION BETWEEN 2RL AND 4RL

[0057] The disclosed steering control system 46 can also serve to maintain a constant path curvature during the transition between multi-axle steering (here referred to as 4RL) and single-axle steering (here referred to as 2RL) by using an inline velocity of the pivot / geometry center (DP) to predict and adjust the steering rate at the front axle. The control system 46 aims to ensure that the work vehicle 10 maintains its intended path of movement without abrupt changes in the turning radius that could otherwise occur during such mode transitions. In manual steering systems, switching from 4RL to 2RL or vice versa can unexpectedly change the vehicle's turning radius, either doubling or halving it, which could impair maneuverability and precision.

[0058] In some embodiments, a forward coupling term is integrated at the level of the control system, which can be used to adjust the steering angles of the front ground engagement elements 24 (or a single mean effective steering angle of the front axle) in correlation with the DP inline speed (using commands to the cylinder control valve). This strategy is designed to maintain constant curvature during the transition by ensuring that the front axle rotates at a speed that aligns the vehicle along the same turning radius, thus avoiding sudden changes in direction or radius. Unlike a closed-loop control system, which could restrict manual steering interventions by the operator, the control system operates with an open-loop (forward) control system.This approach allows manual steering commands to influence the vehicle's direction of travel without being affected by automated adjustments, thus ensuring that operators can modify the steering during transition phases.

[0059] An example implementation of this procedure involves calculating a rotation rate for the front ground-engagement elements 24 to maintain the desired path curvature of the work vehicle 10. This calculation may utilize trigonometric functions and derivatives based on the geometry of the work vehicle and the motion (and velocity) of the DP. To account for the constraints imposed by the steering geometry of the work vehicle (which may originally have been based on Ackerman principles for a fixed rear axle alignment), the control system 46 also calculates a mean effective front steering angle. This calculation incorporates potential wheel slip, representing a simplified steering input for the axle that does not allow independent angle settings for each front tire.

[0060] This approach ensures that operators can switch between steering modes while driving, enabling smooth and precise control without compromising the ability to adjust the turning radius during curves. It also addresses the technical challenge of maintaining consistent vehicle behavior and uniform curvature during steering mode transitions. The present disclosure can implement a method for dynamically adjusting the steering rate based on the inline speed of the DP, an aspect not considered in manual steering control systems. This feature improves the maneuverability and operational efficiency of work vehicles requiring versatile steering capabilities.

[0061] In some cases, steering precision and responsiveness can be improved, particularly during transitions between different steering modes. In some cases, the control system 46 can either determine and / or apply a speed limit for the pivot point (DP) speed to a predefined maximum, based on steering rate limits. This ensures that the speed at which the DP moves does not exceed the operating capacities of the hydraulic steering system 22, as specified by the steering input from the control element 20.

[0062] The steering rate limits are predefined parameters in Control System 46 that represent the maximum speed at which the vehicle's steering can be adjusted. To ensure accuracy, the parameters can be predefined based on the expected valve, pressure, and flow of the anticipated system, or calibrated using steering response tests to suit a specific machine. These limits are used in scenarios requiring rapid DP adjustments. By setting a maximum DP change rate, Control System 46 prevents the vehicle from attempting steering changes that exceed the physical or operational capabilities of the steering system, thus ensuring smoother transitions between steering configurations.

[0063] This determination or limitation of the DP's maximum speed is a direct response to the steering input speed received from the control element 20. The control system 46 can continuously monitor the steering input to detect changes in the desired direction of turn or steering mode. If a change is detected that requires an adjustment of the DP's rate of change, the control system 46 calculates the necessary parameters for this adjustment. If the calculated speed exceeds the predefined limits for the steering rate, the control system 46 automatically limits the DP's speed to the maximum permissible value.This function can be achieved by directly limiting the DP position command before input to the control system, as opposed to modulation at the actuator control loop level, thereby adjusting the hydraulic flow or pressure within the hydraulic steering system 22 as controlled by the control system 46 and the cylinder control valve 42 in accordance with the calculated transition steering input.

[0064] Furthermore, this control strategy ensures that the steering system adjustments are both proactive and anticipatory, corresponding to the concept of a forward control mechanism. That is, forward control is maintained in the ability of the control system 46 to predict changes and adapt preventively, thereby ensuring that the steering of the work vehicle remains within the operating parameters defined by the steering rate limits.

[0065] It will now be on Fig. 2, Fig. 5 and Fig. 6. Referenced, whereby Fig. Figure 5 illustrates both a 2RL mode and a 4RL mode for a work vehicle 10. The control system 46 is designed to detect changes in the pivot point DP of the work vehicle 10 based on the steering command from the control element 20. The position of the DP is crucial for the turning radius and maneuverability of the work vehicle. By accurately identifying the steering adjustments made by the operator, the control system 46 can determine corresponding displacements of the DP. This enables precise control of the steering dynamics of the work vehicle and ensures that adjustments to the travel path W or the orientation of the work vehicle are accurately reflected in the response generated by the control system 46.

[0066] As shown, in 2RL mode the DP is located at the rear axle and in 4RL mode more towards the center of the work vehicle 10. However, the DP can vary along a longitudinal centerline between the front and rear ends of the chassis 14 and beyond. Changes in the steering mode from 2RL to 4RL (or any other position not explicitly 4RL, and vice versa) result in a shift of the DP. The speed of this shift is referred to as the rate of change of the DP.

[0067] Following the detection of a change in the DP, the control system 46 determines the rate of this change based on the steering command from the control element 20. The rate at which the DP moves is used to calibrate a response required to maintain a constant path curvature (the turning rate required to keep the vehicle on path W). By quantifying the rate of DP movement, the control system 46 can adjust the subsequent actions of the cylinder control valve 42 and the front axle hydraulic cylinders 30 to the specific dynamics of the transition. This determination of the DP rate ensures that the control system 46 can precisely adapt to changes in the steering command.

[0068] Once the change in the speed of the DP has been detected, the control system 46 determines a transition steering command to maintain a constant path curvature during the transition period. This involves calculating the steering input required to compensate for the change in the DP and ensure that the path of the work vehicle remains constant despite the transition.

[0069] Finally, the control system 46 instructs the cylinder control valve 42 to change the hydraulic flow or pressure to the hydraulic cylinders 30 based on the determined transition steering command. This action causes a physical steering of the work vehicle 10 according to the calculated requirements for maintaining a constant path curvature, as determined by the control system 46.

[0070] The front ground engagement elements 24 are designed to rotate about an upright axis of rotation DA that is approximately orthogonal to the track curvature (vehicle path W). That is, the axis around which these elements rotate is perpendicular to the direction of the vehicle path W. This orthogonal relationship ensures that the work vehicle 10 can steer effectively and maintain its intended path.

[0071] Furthermore, the front engagement elements 24 are capable of rotating about an upright steering axis AA, which runs orthogonally to the axis of rotation DA. The AA can be vertical or inclined at an angle to the vertical in one or more directions. A detailed section in Fig. Figure 5 shows one of the ground engagement elements 24 and its AA and DA. The AA, around which the ground engagement elements rotate to change direction, is positioned vertically and perpendicular to the DA, as shown. The ground engagement elements can therefore be pivoted to directly influence the vehicle's direction of travel without affecting the rotational movement that propels the work vehicle 10 forward or backward.

[0072] In some embodiments, the control system 46 is designed to calculate the steering rate at which the front ground engagement elements 24 rotate about the AUs. In this way, the control system 46 can accurately determine the speed and extent of the steering movements required to achieve the desired path curvature or to navigate through varying terrain and obstacles. By calculating the steering rate, the control system 46 can optimize the rotational movements of the front ground engagement elements 24 and ensure that they are synchronized and aligned with the overall steering objectives. All adjustments to the rotation of the front ground engagement elements 24 are made by commands to the cylinder control valve 42 and ultimately to the hydraulic cylinders 30.

[0073] In some embodiments, the control system 46 is designed to adjust the steering rate of the front ground engagement elements 24 such that the DA of each of the front ground engagement elements 24 intersects a turning radius point WP. That is, the radius of the path curvature of the work vehicle 10 has a projected point in space, which is referred to as WP. The control system 46 is designed to adjust the steering rate of the front ground engagement elements 24 such that the DA of each of the front ground engagement elements 24 points to the turning radius point WP. When the work vehicle changes between steering modes, the change in the speed of the DP affects the ability of the work vehicle 10 to maintain a constant path curvature. Ideally, the DA of each of the front ground engagement elements 24 points to the WP during the steering mode transitions in order to maintain a constant path curvature.

[0074] As previously mentioned, the control system 46 can perform steering by calculating a mean effective angle for the front axle. This angle is the average of the predicted radii generated by each ground-engagement element based on the Ackerman geometry. This calculation of the mean effective angle is an example of an approach to achieving precise steering control. By averaging the steering angles, the control system 46 can generate a single, effective steering command that reflects the combined influence of both ground-engagement elements on the path curvature of the work vehicle, with optimized processing efficiency.

[0075] Furthermore, the control system 46 is designed to adjust this mean effective angle of the front axle. This adjustment is made by actuating the cylinder control valve 42 to change the hydraulic flow or pressure in the hydraulic cylinders 30. These changes directly affect the steering rate of the front ground engagement elements 24. These settings ensure that the DA for each ground engagement element 24 matches the WP.

[0076] In some embodiments, the control system 46 is designed to respond to operator inputs and, in response, control the steering dynamics of the work vehicle. When the operator issues a steering command, the control system 46 is designed to detect any change in the pivot point of the work vehicle, as described above. This capability allows the control system 46 to interpret how the operator's steering actions result in movement adjustments of the work vehicle 10. After detecting a change in the pivot point, the control system 46 uses algorithms to determine the rate of this change. By knowing the rate at which the pivot point is moving, the control system 46 can make adjustments to the steering responses of the work vehicle. Based on the rate of change of the pivot point, the control system 46 calculates a transitional steering command.This input is used to maintain a constant path curvature during the period between 4RL and 4RL.

[0077] To implement the calculated transition steering command, the control system 46 instructs the cylinder control valve 42 to change the hydraulic flow or pressure to the hydraulic cylinders 30 of the front ground engagement elements 24, enabling the work vehicle 10 to steer along the desired constant path curvature. By adapting the hydraulic steering system 22 to the dynamic steering requirements, the control system 46 ensures that the work vehicle 10 can respond to operator inputs and environmental conditions, maintaining a stable and predictable path.

[0078] In various embodiments, the control system 46 is designed to dampen changes in the steering rate associated with the steering command, changes in the differential position (DP) of the work vehicle 10, or both. In other embodiments, the control system 46 is designed to mitigate sudden fluctuations in the steering rate or positional shifts in the DP of the work vehicle 10, potentially addressing both factors simultaneously. This approach provides a smoother and more predictable steering experience, which is particularly advantageous during turning maneuvers or when precise control is required. By damping rapid changes in steering dynamics, the control system 46 contributes to improved vehicle stability and handling, which is a crucial advantage in various work environments where equipment maneuverability is paramount.

[0079] In other embodiments, the control system 46 is designed to receive an operator input for the DP of the work vehicle 10 and to make a DP change based on the operator input in order to avoid exceeding a threshold value for the DP rate. In this case, the control system 46 adjusts the hydraulic flow or pressure during the transition period and ensures that the changes do not exceed a predetermined threshold value for the steering rate. This threshold value serves as a limit to prevent sudden or excessive changes in steering behavior, thereby improving vehicle control and safety.

[0080] Fig.Figure 6 shows an example of a procedure that can be carried out with the work vehicle 10 and, in particular, with the control system 46. The procedure can include a step 96 in which a change in the DP of the work vehicle 10 is detected based on the steering command from the control element 20. By detecting changes in the DP, the control system 46 can dynamically adjust the steering behavior of the work vehicle, thereby improving maneuverability and operational efficiency.

[0081] Consider, for example, a scenario in which the work vehicle 10 is used in a confined field requiring tight turns and precise steering. The operator inputs a steering command to navigate around an obstacle. If, as a result of this input, the control system 46 detects a change in the desired DP (Distance Path), it adjusts the steering mechanism to align itself with the new path. In this setting, the hydraulic flow to the steering cylinders could be altered, thus changing the angle of the wheels and consequently the steering angle. The procedure can then include step 98, in which the rate of change of the DP is determined based on the steering command from the control element.

[0082] In some embodiments, the method includes step 100, which determines a transition steering command based on the rate of change of the DP (displacement parameter) to ensure a constant path curvature during the transition between 4RL (front-to-back) and 2RL (back-to-back) of the work vehicle 10. Essentially, a correction factor (transition steering command) is applied to compensate for the rate change caused by the steering mode transition, thus controlling the steering behavior to maintain a constant path curvature. This function is also important in situations where the work vehicle 10 is traveling in a curve, for example, when turning at the end of a crop row. The method may also include step 102, in which, based on the transition steering command, the cylinder control valve 42 is instructed to change the hydraulic flow or pressure to the hydraulic cylinders 30 to steer the work vehicle 10 with the constant path curvature. CONCLUSION

[0083] Advanced steering control systems for integration into work vehicles have been described. The disclosed embodiments of the steering control system offer precise control, adaptive response, and enhanced control functions aimed at significantly reducing the operational complexity and maintenance requirements of work vehicles while simultaneously improving steering accuracy and vehicle reliability. In certain embodiments, sensor data relating to steering rate and steering angle are processed and stored in memory, enabling in-depth analysis of steering performance. This data allows for the refinement of steering control algorithms and thus the optimization of steering behavior according to varying operating conditions.Furthermore, such sensor data can be transmitted to networked data centers, enabling remote monitoring of the work vehicle's steering system status and allowing for the provision of tailored maintenance recommendations or adjustments to the vehicle's maintenance schedule. The steering system status and any necessary steering command adjustments can also be communicated to the operator via displays in the operator's cab, enhancing operational safety and system transparency. For work vehicles equipped with advanced steering functions, such as variable steering response based on operating parameters, the steering control system's processing subsystem can execute specific algorithms to dynamically adjust steering commands and hydraulic flow, ensuring optimal steering performance.Furthermore, these processing subsystems in the context of semi-autonomous and autonomous work vehicles utilize the described functionalities to refine the operating commands related to vehicle control, thereby maximizing the operating time, efficiency, and lifespan of the vehicle in various working environments.

[0084] As used here, lists of elements separated by conjunctions (e.g., "and") and further preceded by the phrase "one or more of" or "at least one of," unless otherwise limited or modified, indicate configurations or arrangements that may include individual elements of the list or any combination thereof. For example, "at least one of A, B, and C" or "one or more of A, B, and C" indicate the possibilities of only A, only B, only C, or any combination of two or more of A, B, and C (e.g., A and B; B and C; A and C; or A, B, and C). Furthermore, the use of "one or more of" or "at least one of" in the claims for certain elements does not imply that other elements are in the singular form, nor does it have any other effect on the other claim elements.

[0085] The singular forms "ein / e / r" and "der / die / das," as used here, are also intended to include the plural forms, unless the context clearly indicates otherwise. Furthermore, it is understood that any use of the terms "umfasst" and / or "umfassend" in this document indicates the presence of specified features, integers, steps, processes, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, processes, elements, components, and / or groups thereof.

[0086] The description of the present disclosure is provided for illustrative and descriptive purposes only and is not intended to be exhaustive or limiting to the disclosure as disclosed. To the person skilled in the art, many modifications and variations are apparent without deviating from the scope and essence of the disclosure. The embodiments explicitly mentioned herein have been selected and described to best explain the principles of the disclosure and their practical application, and to enable other persons skilled in the art to understand the disclosure and recognize many alternatives, modifications, and variations of one or more of the described examples. Accordingly, various embodiments and implementations other than those explicitly described fall within the scope of protection of the following claims.

Claims

[1] Steering control system (46) for a work vehicle (10), comprising: a control element (20) that provides a steering input specifying a direction of curvature of the work vehicle (10); a hydraulic steering system (22) with a steering pump (40), hydraulic cylinders (30) and a cylinder control valve (42) that responds to the steering input from the control element (20) to achieve the direction of curvature; and a control system (46) with a processor and memory architecture that is coupled to the control element (20) and the hydraulic steering system (22) and is designed to: detect a speed of the steering input from the control element (20); determine an expected rate of change of the direction of curvature based on the detected speed of the steering input; determine an adapted steering input corresponding to a constant rate of change of the path curvature based on the expected rate of change of the direction of curvature;and, based on the adapted steering input, to actuate the cylinder control valve (42), to change the hydraulic flow or pressure to the hydraulic cylinders (30) in order to steer the working vehicle (10) at the constant rate of change of the curvature direction. [2] Steering control system (46) according to claim 1, which further comprises ground engagement elements (24) which are each coupled to an associated hydraulic cylinder (30) and comprise a first and a second ground engagement element (24) which rotate about a common axis and whose associated hydraulic cylinders (30) are connected to each other in a closed hydraulic circuit which includes the cylinder control valve (42), such that by extending a piston of the hydraulic cylinder (30) for the first ground engagement element (24) a piston of the hydraulic cylinder (30) for the second ground engagement element (24) is retracted. [3] Steering control system (46) according to claim 2, wherein the control system (46) evaluates a steering angle connected to the first and the second ground engagement element (24) when determining the expected rate of change of the curvature direction. [4] Steering control system (46) according to claim 3, further comprising a first and a second sensor (50) associated with the first and second ground engagement element (24) which output a signal which is used by the control to detect the steering angle. [5] Steering control system (46) according to claim 3, wherein the control system (46) instructs the cylinder control valve (42) based on the adapted steering input to direct hydraulic fluid from the closed hydraulic circuit to a reservoir (44) in order to achieve a damped steering response. [6] Steering control system (46) according to claim 5, wherein the adapted steering input is resolved such that the control system (46) instructs the cylinder control valve (42) to produce a damped steering response when the speed of the steering command exceeds a speed threshold. [7] Steering control system (46) according to claim 6, wherein the speed threshold is variable depending on one or more operating parameters of the work vehicle (10). [8] Steering control system (46) according to claim 7, wherein the operating parameters include the steering angle of the first and second ground engagement element (24) and / or a driving speed of the work vehicle (10) and / or a loading state of the work vehicle (10) and / or a position of a work device of the work vehicle (10). [9] Steering control system (46) according to claim 3, wherein the control system (46) instructs the cylinder control valve (42) based on the adapted steering input to direct an increased flow of hydraulic fluid from a reservoir (44) into the closed hydraulic circuit to produce an enhanced steering response. [10] Steering control system (46) according to claim 2, wherein the adapted steering input is resolved such that the control system (46) instructs the cylinder control valve (42) to increase the flow to the hydraulic cylinders (30) of the first and second ground engagement element (24) or to decrease the flow to the hydraulic cylinders (30) of the first and second ground engagement element (24); wherein the control system (46) instructs the cylinder control valve (42) to increase the flow to the hydraulic cylinders (30) of the first and second ground engagement element (24) to produce a four-wheel steering response; and wherein the control system (46) instructs the cylinder control valve (42) to decrease the flow to the hydraulic cylinders (30) of the first and second ground engagement element (24) to produce a two-wheel steering response. [11] Working vehicle (10) comprising: ground engagement elements (24) coupled to hydraulic cylinders (30); a control element (20) providing a steering input; a steering pump (40) coupled to the control element (20); a cylinder control valve (42) responding to the steering input from the control element (20); a control system (46) with a processor and memory architecture coupled to the control element (20) and the hydraulic steering control system (22) and designed to: detect a speed of steering input from the control element (20); determine, based on the detected speed of steering input, an expected rate of change of the direction of curvature determined from the steering input; determine, based on the expected rate of change of curvature direction, an adapted steering input corresponding to a constant rate of change of curvature direction;and, based on the adapted steering input, to actuate the cylinder control valve (42), to change the hydraulic flow or pressure to the hydraulic cylinders (30) in order to steer the working vehicle (10) at the constant rate of change of the curvature direction. [12] Working vehicle (10) according to claim 11, wherein the ground engagement elements (24) comprise a first and a second ground engagement element (24) which rotate about a common axis and whose associated hydraulic cylinders (30) are connected to each other in a closed hydraulic circuit which includes the cylinder control valve (42), such that by extending a piston of the hydraulic cylinder (30) for the first ground engagement element (24) a piston of the hydraulic cylinder (30) for the second ground engagement element (24) is retracted. [13] Working vehicle (10) according to claim 12, wherein the control system (46) evaluates a steering angle connected to the first and the second ground engagement element (24) when determining the expected rate of change of the curvature direction. [14] Working vehicle (10) according to claim 13, which further comprises a first and a second sensor (50) associated with the first and second ground engagement element (24) which output a signal which is used by the control to detect the steering angle. [15] Working vehicle (10) according to claim 13, wherein the control system (46) instructs the cylinder control valve (42) based on the adapted steering input to direct hydraulic fluid from the closed hydraulic circuit to a reservoir (44) in order to produce a damped steering response.

Images