Closed-loop feedback drive systems for motor graders

Abstract

A closed-loop feedback drive system (12) used on board a motor grader (10), wherein the closed-loop feedback drive system (12) comprises the following: an operator input device (76); a share (38) which is rotatable about a share rotation axis (58); a multi-speed hydraulic motor (60; 100; 132) with a motor output shaft (108) which is mechanically connected to the share (38), wherein a rotation of the motor output shaft (108) causes a rotation of the share (38) about the share rotation axis (58); and a control unit (14) that is operationally coupled to the operator input device (76) and to the multi-speed hydraulic motor (60; 100; 132) and is configured to: a target blade rotation speed (v Schar_Ziel ) depending on share rotation commands received via the operator input device (76); and to control the multi-speed hydraulic motor (60; 100; 132) to implement the share rotation commands, while a speed of the motor output shaft (108) is modified to compensate for discrepancies between the target share rotation speed (v Schar_Ziel ) and a current share rotation speed (v Schar_aktuell ) due to fluctuations in the load forces that resist the blade rotation during operation of the motor grader (10).

Description

AREA OF REVELATION

[0001] This disclosure relates to closed-loop feedback circular drive systems for controlling a multi-speed circular rotary motor (e.g., a variable displacement or two-speed hydraulic motor) used to adjust the rotary position of a blade on a motor grader. BACKGROUND OF THE REVELATION

[0002] A motor grader is often equipped with a rotary drive system for adjusting the rotational position of a circular blade assembly, that is, an assembly comprising a relatively large, generally circular structure or "circle" under which a blade is suspended. Conventionally, a rotary drive system includes either a hydraulic cylinder assembly or a fixed-displacement hydraulic motor to rotate the circular blade assembly, and thus the blade, around a blade axis of rotation perpendicular to the motor grader's direction of travel. As a specific example, in one common embodiment, the circle is provided with a toothed inner circumference forming a large ring gear into which a smaller gear or pinion engages. The pinion is mechanically connected, directly or indirectly via an intermediate gearbox, such as a reduction gear, to the output shaft of a fixed-displacement hydraulic motor.During operation of the motor grader, operator commands received via a joystick (or similar input device) are relayed to a valve actuator mechanically linked to a spool contained within a directional control valve. The valve actuator adjusts the translational position of the spool within the directional control valve according to the operator commands. This regulates the direction and rate of hydraulic fluid flow through the fixed-displacement hydraulic motor, which in turn drives the rotation of the pinion to rotate the circular blade assembly around its axis of rotation in the commanded manner.

[0003] However, there is a need for a motor grader with reduced fluctuations in the share speed that arise due to changes in share loading conditions. SUMMARY OF THE REVELATION

[0004] Closed-loop feedback drive systems for use on board motor graders are disclosed, satisfying the aforementioned need. In embodiments, the closed-loop feedback drive system includes an operator input device, a blade rotatable about a blade axis, and a multi-speed hydraulic motor with a motor output shaft. The motor output shaft is mechanically connected to the blade such that rotation of the motor output shaft causes rotation of the blade about the blade axis. A control unit is operationally coupled to the operator input device and the multi-speed hydraulic motor.The control system is configured to: (i) receive share rotation commands via the operator input device to rotate the share around the axis of rotation as commanded; and (ii) control the multi-speed hydraulic motor to implement the share rotation commands, while repeatedly adjusting the speed of the motor output shaft to reduce variations in share speed due to changes in share loading conditions that occur during motor operation.

[0005] In further embodiments, the closed-loop feedback drive system includes an operator input device, a share rotatable about a rotary axis, a multi-speed hydraulic motor with a motor output shaft mechanically connected to the share, and a first sensor configured to monitor a parameter indicating a rotational speed of the share. A controller is operationally coupled to the operator input device, the multi-speed hydraulic motor, and the first sensor. The controller is configured to: (i) maintain a target share rotational speed (v Schar_Ziel ) as a function of operator command signals received via the operator input device; (ii) a discrepancy (v Schar_Δ ) between the target blade rotation speed (v Schar_Ziel ) and a current share rotation speed (v Schar_aktuell) to determine; and (iii) to modify a rotational speed of the motor output shaft to reduce the discrepancy (v Schar_Δ ) between the target blade rotation speed (v Schar_Ziel ) and the current share rotation speed (v Schar_aktuell ) to reduce if the discrepancy (VSchar-") exceeds a predetermined threshold.

[0006] In further embodiments, the closed-loop feedback drive system includes a two-speed hydraulic motor with a single motor output shaft. The two-speed hydraulic motor can operate in a low-torque, high-speed (LP / HP) mode and a high-torque, low-speed (HP / LP) mode. The two-speed hydraulic motor is mechanically connected to a blade of the motor grader and configured to selectively rotate the blade around a pivot axis. The closed-loop feedback drive system also includes a controller that is operationally coupled to the two-speed hydraulic motor.The control system is configured to: (i) selectively switch the dual-speed hydraulic motor between ND / HD mode and HD / ND mode during operation of the motor grader; and (ii) furthermore, to control a motor output shaft speed to minimize variations in share rotation speed when switching the dual-speed hydraulic motor between ND / HD mode and HD / ND mode.

[0007] The details of one or more embodiments are specified in the accompanying drawings and in the description below. Other features and advantages will become apparent from the description, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] At least one example of the present revelation is described below in conjunction with the following figures: Fig. Figure 1 is a side view of a motor grader equipped with an embodiment of the closed-loop feedback circular drive system (partially shown schematically) as represented in accordance with an exemplary embodiment of the present disclosure; Fig. 2 is a top view or floor plan of the space in Fig. 1 Motor grader shown, illustrating exemplary displacements of the circular blade assembly and thus of the motor grader share around a share rotation axis; The Fig. 3 and Fig. 4 are schematic representations of a first exemplary implementation of a closed-loop feedback drive system (suitable for use as the circular drive system as generally in Fig. 1 shown), including a two-speed hydraulic motor that operates in a low-torque, high-speed mode ( Fig. 3) and a high torque, low rotational speed mode ( Fig. 4) can be operated; and Fig. Figure 5 is a schematic representation of a second exemplary implementation of the closed-loop feedback drive system, which is further suitable for use as the drive system generally found in Fig. Figure 1 shows a hydraulic motor with variable displacement.

[0009] Identical reference symbols in the different drawings denote the same elements. For the sake of simplicity and clarity, descriptions and details of known features and techniques may be omitted to avoid unnecessarily obscuring the exemplary and non-limiting embodiments of the invention described in the detailed description below. It is further understood that features or elements appearing in the accompanying figures are not necessarily drawn to scale unless otherwise indicated. DETAILED DESCRIPTION

[0010] The embodiments of the present disclosure are illustrated in the accompanying figures of the drawings briefly described above. Various modifications of the exemplary embodiments may be considered by those skilled in the art without departing from the scope of the present invention, as specified in the accompanying claims. OVERVIEW

[0011] As briefly discussed above, conventional rotary drive systems typically rely on fixed-displacement hydraulic motors to drive the rotation of rotary blade assemblies, and thus motor grader blades, around a blade axis of rotation according to operator commands. While reliable, such conventional rotary drive systems are associated with several shortcomings. One such shortcoming arises when reversing the motor grader, that is, when a motor grader is controlled to reverse its direction of travel while the blade position is reset to prepare the blade for a new earthmoving pass. During reversing, several blade position adjustments are typically made in rapid succession.Such blade position adjustments involve initially raising the motor grader blade to a surface position, rotating the blade to a new angular position (typically mirrored from the previous blade position), and then lowering the blade again to a ground-penetrating position (referred to here as a "position in the ground"). These and other hydraulically driven functions of the motor grader can be slowed down due to the substantial hydraulic demands of the fixed-displacement engine, which is traditionally oversized by design to meet the peak torque requirements that occur during blade rotation in the ground. This can negatively impact motor grader performance and operator experience.

[0012] In light of these and other limitations, improved circular drive systems with multi-speed hydraulic motors have been developed and implemented. The term "multi-speed hydraulic motor," as it appears in this document, is defined to include all types of hydraulic motors except fixed-displacement hydraulic motors. Thus, the term "multi-speed hydraulic motor" includes, among others, two-speed hydraulic motors and variable-displacement hydraulic motors, as detailed below. Examples of motor grader circular drive systems with multi-speed hydraulic motors are presented in the following document, the contents of which are incorporated by reference: U.S. Patent No. 7,874,377 B1 entitled "CIRCULAR DRIVE ARRANGEMENT FOR MOTOR GRADERS," issued by the U.S. Patent and Trademark Office (USPTO) on January 25, 2011, and assigned to the assignee of this document (Deere & Company).By using multi-speed hydraulic motors and other related components, these improved rotary drive systems are better able to handle both high-speed, low-torque blade rotation when the blade is positioned above ground (or otherwise lightly loaded), and low-speed, high-torque blade rotation when it is in the ground (or otherwise heavily loaded). The integration of multi-speed hydraulic motors into rotary drive systems thus allows for both operating extremes, avoiding motor oversizing and minimizing the hydraulic demands placed on the motor. This, in turn, enables the rapid operation of the various hydraulically driven functions of the motor grader during turning.

[0013] For the reasons stated above, the development and implementation of rotary drive systems with multi-speed hydraulic motors represents a significant advancement in motor grader design. Nevertheless, current rotary drive systems with multi-speed hydraulic motors remain limited in some respects. The primary limitation of such systems is that using a multi-speed hydraulic motor to drive blade rotation can lead to undesirable fluctuations in blade rotation speed in conjunction with fluctuations in blade load. Such fluctuations in blade rotation speed can be significant and perceptible to motor grader operators. This can negatively impact operator satisfaction and efficiency, especially when non-trivial disparities occur between shifts in control input (e.g.,Joysticks) and blade rotation speed evolve over various iterations of motor grader operation. Consequently, there is a continuing industry demand for circular drive systems that increase consistency, where operator blade rotation commands result in an expected blade rotation speed output, while largely, if not completely, breaking the correlation between blade rotation speed and blade load. At the same time, it is desirable that such a circular drive system retains the advantages described above associated with using a multi-speed hydraulic motor to drive blade rotation and preserves the rapid execution of hydraulically driven functions during motor grader turning.

[0014] To meet this ongoing industrial demand, circular drive systems with integrated motor graders and multi-speed hydraulic motors, operated by unique closed-loop feedback control schemes, have been employed in the following designs. The closed-loop feedback control schemes are implemented by a controller operationally coupled to the multi-speed hydraulic motor and to at least one operator input device (e.g., a joystick) used to control the angular position of the motor grader blade. As appears in this document, the term "controller" is used in a non-restrictive sense to refer generally to the processing architecture of a closed-loop feedback circular drive system.The controller can include or be connected to any number of processors, control computers, computer-readable memories, power supplies, storage devices, interface cards, and other standardized components. The controller can also include or interact with any number of firmware and software programs or computer-readable instructions used to perform the various process tasks, calculations, and control functions described herein. Such computer-readable instructions can be stored in a non-volatile sector of memory that the controller can access, as further described below.

[0015] The controller can implement various control schemes to regulate the speed and direction of the output shaft of the multi-speed hydraulic motor during operation of the closed-loop feedback drive system. In some embodiments, the controller can first set a commanded or "target" share rotation speed (V). Schar_Ziel ) depending on share rotation commands received via the operator input device. The controller can then control the multi-speed hydraulic motor to implement the share rotation commands, while selectively adjusting the motor output shaft speed to compensate for discrepancies between the target share rotation speed (v) and the actual speed. Schar_Ziel ) and a current share rotation speed (v Schar_aktuell ) due to fluctuations in the load forces resisting share rotation. For example, in certain embodiments, the control system may initially detect a discrepancy (v Schar_Δ) between the target blade rotation speed (v Schar_Ziel ) and the current share rotation speed (v Schar_aktuell ) calculate. The controller can then modify the speed of the motor output shaft to compensate for such a discrepancy (v Schar_Δ The control system reduces the rotational speed when a predetermined threshold is exceeded. In certain embodiments, the predetermined threshold may be zero; however, a non-zero value (fixed or variable) is more advantageous to avoid small, redundant blade angle adjustments or "fluttering" of the motor grader blade. The control system preferably repeats this process on a relatively fast (e.g., real-time) iterative basis to provide a closed-loop feedback control scheme that maintains the rotational speed of the motor grader blade at target levels, independent of (or with reduced dependence on) fluctuations in blade load conditions.

[0016] The control system can adjust the current share rotation speed (v) Schar_aktuell ) using data received from one or more sensors, which are further included in the closed-loop feedback drive system. For example, in certain embodiments, the controller can receive data from a sensor (e.g., a rotatable variable differential transformer) that monitors the angular position of the motor grader blade or possibly another component that rotates in a fixed relationship with the blade. The controller can then use this sensor input to detect changes in the blade angle over time and thus the current blade rotation speed (v). Schar_aktuell). In other implementations, the controller can receive data input from a speed sensor, such as an accelerometer and / or gyroscope for microelectromechanical systems (MEMS), configured to monitor the rotational speed of an output shaft of the multi-speed hydraulic motor, the rotational speed of the motor grader blade or circular blade assembly itself, or the rotational speed of any other component in the rotary transmission path extending from the hydraulic motor to the circular blade assembly. The controller then uses this sensor input to determine the current blade rotational speed (v). Schar_aktuell ) for comparison with the target blade rotation speed (v Schar_Ziel ), as previously described.

[0017] The specific way in which the controller controls (i.e., influences) the operation of the multi-speed hydraulic motor varies depending on the embodiment. If the multi-speed hydraulic motor is designed as a variable displacement hydraulic motor, the controller can use the variable displacement control to repeatedly change the displacement setting of the hydraulic motor while adjusting the speed of the motor output shaft. Furthermore, in addition to selectively modifying the displacement setting of the hydraulic motor, the controller can also repeatedly adjust the position of a sizing element (e.g., a slide valve) contained within a directional control valve to vary the rate and direction of hydraulic fluid flow through the variable displacement hydraulic motor, thereby further controlling the speed and direction of rotation of the motor output shaft.In other cases, the control system can modify the speed and / or direction of rotation of the motor output shaft in a different way, for example, by controlling the flow rate of a pump downstream of the multi-speed hydraulic motor. Conversely, in embodiments where the multi-speed hydraulic motor takes the form of a two-speed hydraulic motor, the control system can also control the motor output speed (and direction of rotation) by adjusting the rate and direction of the hydraulic fluid flow through the hydraulic motor; for example, by adjusting the translational position of a spool in a directional control valve downstream of the two-speed hydraulic motor.In this latter case, however, the ability of the dual-speed hydraulic motor to operate in at least two modes, referred to here in a relative sense as "low torque, high rotational speed (ND / HD) mode" and "high torque, low rotational speed (HD / ND) mode," introduces an additional layer of control complexity. Accordingly, the control system can determine when to switch the dual-speed hydraulic motor between these operating modes, while further controlling the hydraulic motor to minimize the variation in motor speed during the switch. This can make the switching of the dual-speed hydraulic motor less noticeable to a motor grader operator, thus improving the operator experience.

[0018] In implementations where the rotary drive system includes a two-speed hydraulic motor with a first and a second power element, the controller can switch or toggle between motor operating modes by varying whether the power elements are fluidically coupled in parallel or in series. For example, in one possible implementation, the controller can be coupled to a selector valve containing a bistable valve element, such as a spool. The spool can be movable between two stable positions to determine whether the power elements are fluidically coupled in parallel (moving the two-speed hydraulic motor into high / low pressure mode) or in series (moving the hydraulic motor into low / high pressure mode).During operation of the closed-loop feedback drive system, the controller can determine when to switch the two-speed hydraulic motor between its operating modes, at least partially, based on receiving at least one sensor input indicating a share load. Such a sensor input can be received from a sensor configured to measure the share load directly; for example, a force sensor mechanically coupled between the motor output and the share. In other cases, the sensor input can be provided by a sensor configured to monitor a parameter that is indirectly indicative of the share load, such as by monitoring hydraulic pressures within the flow circuit of the drive system using one or more pressure sensors, as described in more detail below.Additionally or alternatively, in such embodiments, the control system of the rotary drive can also be configured to selectively shift the dual-speed hydraulic motor between operating modes in response to a predicted or expected change in the blade loading conditions. For example, in certain implementations, the control system can switch the dual-speed hydraulic motor to HD / ND mode when it is determined that the motor grader blade has been lowered from a position above ground to a position in the ground (or to a certain penetration depth); and then return the hydraulic motor to ND / HD mode when the blade is raised back to the above-ground position.

[0019] Now, with reference to the accompanying drawings, an exemplary embodiment of a closed-loop feedback drive system, which includes a two-speed hydraulic motor, is described below in conjunction with the Fig. 3 and Fig. 4 is discussed, while an exemplary embodiment of a closed-loop feedback drive system incorporating a variable-speed hydraulic motor is further described below in conjunction with Fig. 5 discussed. First, however, an exemplary motor grader, which is expediently equipped with an embodiment of the closed-loop feedback drive system, will be described below in conjunction with the Fig. 1 and Fig. 2 described. While the following discussion relates to a specific type of motor grader with certain features, embodiments of the closed-loop feedback drive system can be used without restriction on board various types of motor graders. EXAMPLE OF A MOTORGRADER EQUIPPED WITH A GENERALIZED CLOSED-LIVE RECIRCULATION DRIVE SYSTEM

[0020] With reference to the Fig. 1 and Fig. Figure 2 shows an exemplary motor grader 10 equipped with a closed-loop feedback drive system 12. For illustrative purposes, only selected components of the closed-loop feedback drive system 12 are shown schematically. Fig. Figure 1, which includes, for example, a controller 14 and a computer-readable memory 16. As noted above, the term "controller" is defined herein to generally encompass the processing architecture of the closed-loop feedback drive system 12, which executes certain control schemes (examples of which are described below) in accordance with computer-readable instructions or code stored in the memory 16. Furthermore, although generally illustrated as a single block, the memory 16 may comprise any number and type of storage media suitable for storing computer-readable code or instructions, as well as other data used to support the operation of the closed-loop feedback drive system 12.Additional components that may be included in specific implementations of the exemplary closed-loop feedback drive system 12 are discussed further below in connection with the . Fig. 3-5 discussed; however, first the design and operation of the motor grader 10 is discussed in order to provide a non-restrictive context in which the closed-loop feedback drive system 12 can be better understood.

[0021] In the exemplary embodiment of the Fig. 1 and Fig. Figure 2. The motor grader 10 comprises a front frame 18 and a rear frame 20, which is articulated to a rear section of the front frame 18. The front frame 18 is supported by a pair of front ground-engaging wheels 22, while the rear frame 20 is also supported by left and right tandem rear wheels 24. An operator's cab 28 is located immediately behind an inclined front section 26 of the rear frame 20. An engine (not shown) is contained in an engine compartment housing 30, which is further mounted to the rear frame 20 at a location immediately behind the operator's cab 28. During operation of the motor grader 10, the engine (e.g., an internal combustion engine) within the engine compartment housing 30 delivers drive power to the rear wheels 24 via a transmission (not shown).The front ground engagement wheels 22 of the motor grader 10 can also be driven by a hydrostatic support transmission not shown.

[0022] With particular reference to the front frame 18 of the motor grader 10, the front frame 18 comprises an upper, longitudinally elongated section (hereinafter referred to as the “raised section 32”) and a front, vertically elongated nose section (hereinafter referred to as the “front end section 34”). Together, sections 32 and 34 give the front frame 18 a generally L-shaped geometry when viewed from one side of the motor grader 10. Due to the L-shaped geometry of the front frame 18, a spatial volume or shell 36 is created beneath the front frame 18 for accommodating a motor grader attachment. As shown in the Fig. 1 and Fig. As shown in Figure 2, the motor grader attachment often takes the form of an earthmoving blade (or other material moving blade) and is therefore referred to below as the “motor grader blade 38”. Notwithstanding this example, the motor grader blade 38 may in other cases be interchangeable with other motor grader attachments, such as a snowplow attachment. The motor grader blade 38 is suspended beneath a relatively large structure or “circle” 40, which has a generally circular form factor when viewed from top to bottom ( Fig. 2) Together, the motor grader blade 38 and the circle 40 form a rotatable circular blade assembly 42, as discussed below. While in Fig. 1 shown in full, are sections of the front frame 18 in Fig. 2 hidden to better see the circular knife assembly 42.

[0023] A drawbar 44 with angled legs 46, 48 extends from the front end section 34 of the front frame 18 to the circle 40 of the circular knife assembly 42. Due to the angled orientation of the legs 46, 48, the drawbar 44 has a substantially V-shaped form factor in plan view ( Fig. 2) At its front (narrow) end, the drawbar 44 is connected to the front end section 34 by a joint 50 with several degrees of freedom, such as a ball joint. Two linear actuators (here hydraulic cylinders 52) are pivotally mounted between the front frame 18 and the arms 46, 48 of the drawbar 44. The cylinders 52 (of which only one is visible) enable angular adjustments of the circular blade assembly 42 about a longitudinal or yaw axis of the front frame 18, as shown by a dashed line 54 in Fig. 2 shown. Similarly, a hydraulic cylinder 56 is mounted between the front frame 18 and the circular blade assembly 42 to further adjust the angular alignment of the motor grader blade 38 (in particular the lateral displacement angle of the motor grader blade 38) according to operator commands received via input control devices located inside the operator cabin 28, as described in more detail below.

[0024] With further reference to the Fig. 1 and Fig. 2, the exemplary motor grader 10 is further equipped with a multi-speed hydraulic motor 60, which is included in the closed-loop feedback drive system 12. The multi-speed hydraulic motor 60 is configured to control the angular alignment of the circular blade assembly 42 and thus of the motor grader blade 38 about a blade rotation axis 58 (in Fig. 2) to adjust. The multi-speed hydraulic motor 60 includes a motor output shaft (examples of which are given in the Fig. 3-5), which is mechanically connected to a gear or pinion 64. The output shaft of the multi-speed hydraulic motor 60 can be directly connected to the pinion 64 (e.g., via a splined coupling); or alternatively, the motor shaft can be mechanically connected to the pinion 64 via any number of interposed components, such as a gear reduction. In either case, the pinion 64 has a toothed outer circumference that is positioned in meshing engagement with a toothed inner circumference 66 of the circle 40 of the circular blade assembly 42. The circle 40 thus acts as a relatively large ring gear, with its rotation being driven by the rotation of the pinion 64.

[0025] The control unit 14 of the closed-loop feedback drive system 12 is coupled to the multi-speed hydraulic motor 60 in a manner that allows the control unit 14 to modify certain operating aspects of the hydraulic rotary motor 60, including the speed and direction of the motor output shaft. The operating relationship between the control unit 14 and the multi-speed hydraulic motor 60 is described in Fig. 1 represented by a control line 68. In various embodiments, the controller 14 can modify the output speed and direction of the output shaft of the multi-speed hydraulic motor 60, at least partially, based on data received from one or more sensors 70 included in the closed-loop feedback drive system 12. The data link 72 between the sensor(s) 70 and the controller 14 can be a wired connection, a wireless connection, or a combination thereof. The sensor or sensors 70 can monitor various operating parameters used in implementing the share rotation control schemes described below.Such parameters may include, among others: data indicative of the rotational speed (speed and direction of rotation) of the motor grader blade 38; data indicative of the rotational speed of the motor output shaft; data indicative of the angular position of the motor grader blade 38 about the blade rotation axis 58; and / or data indicative of load forces resisting blade rotation about the axis 58. In certain embodiments, the sensor(s) 70 of the controller 14 may also provide data indicative of an anticipated or expected load exerted on the motor grader blade 38; for example, as can be deduced from data indicating whether the motor grader blade 38 is currently in a position above or in the ground.A further description of possible implementations of the sensor(s) 70 and the multi-speed hydraulic motor 60 and exemplary control schemes that are appropriately executed by the control unit 14 during the operation of the motor grader 10 are described below in conjunction with the . Fig. 3-5 discussed.

[0026] A steering wheel 74 and other operator input devices 76 are located inside the operator's cab 28 of the exemplary motor grader 10. While seated or standing in the operator's cab 28, an operator manipulates the steering wheel 74 and the other operator input devices 76 to control various aspects of the operation of the motor grader 10, including the rotation of the circular blade assembly 42 about the blade axis of rotation 58. The operator input devices 76 often include at least one joystick or lever, which is operated by an operator to control the rotation of the circular blade assembly 42 and thus the motor grader blade 38. Notwithstanding the above, the operator input devices 76 can take any form suitable for receiving operator input commands (including blade rotation commands) specifying the operator's desired settings for the positioning of the circular blade assembly 42.Accordingly, the operator input devices 76 can take the form of various other physical input devices (e.g., buttons, rotary knobs, switches, and the like) and devices (e.g., a trackball or touchscreen interface) for interacting with elements of the graphical user interface (GUI) generated on a display screen located within the operator cabin 28. The controller 14 receives such operator input commands from the operator input devices 76 via a wired or wireless data connection 78 and then converts these operator input commands accordingly into position settings or movement of the circular knife assembly 42.

[0027] The angle of the motor grader blade 38, as taken about the blade rotation axis 58, can be expressed in terms of the rotational displacement of the motor grader blade 38 relative to a virtual reference plane 82 ( Fig. 2) will be described. The reference plane 82 can bisect the circle 40 and is essentially orthogonal to the direction of the motor grader movement. In this respect, an example scenario can be considered in which the motor grader blade 38 is rotated from a neutral position (i.e., a position aligned with the reference plane 82) to the position corresponding to the dashed line 84, where line 84 indicates the angular orientation of the front of the motor grader blade 38. To reach this position, the motor grader blade 38 is rotated by a first angular displacement (α1) in a first direction of rotation (clockwise in the illustrated example) due to the action of the multi-speed hydraulic motor 60 under the command of the control 14.This brings the motor grader blade 38 into an operator-commanded position, for example, to prepare the motor grader 10 to perform an initial earthmoving pass over a given work area. After the motor grader 10 has completed this pass, the operator can then command the motor grader 10 to reverse for a subsequent pass over the work area. During the reversal, the operator further controls the motor sorting blade 38 to reset the blade angle (i.e., return the motor grader blade 38 to the neutral position aligned with the reference plane 82) and then rotates the motor grader blade 38 by an equivalent angular displacement (α2) in a second, opposite direction of rotation (clockwise in the orientation illustrated in Figure 1). Fig. 2) This brings the motor grader blade 38 into an angular position corresponding to a dashed line 86, which is opposite the blade position corresponding to line 84, relative to the reference plane 82. Positioned in this way, the motor grader blade 38 continues to move earth (or other material) to the same side of the motor grader 10 as the motor grader 10 reverses its direction of travel and performs a subsequent earthmoving pass over the work area.

[0028] As previously stated, the hydraulically driven functions of the motor grader 10 can be significantly slowed down during turning if one relies on a circular drive system that includes a fixed-displacement hydraulic motor to rotate the circular blade assembly 42 and the motor grader blade 38. Due to its ability to vary the relationship between the volume of hydraulic fluid passed through the multi-speed hydraulic motor 60 per revolution of the motor output shaft, the multi-speed hydraulic motor 60 can be controlled by the controller 14 ( Fig. 1) are controlled to better accommodate both high-speed, low-torque rotation of the motor grader blade 38 and low-speed, high-torque rotation of the motor grader blade 38. Furthermore, since the hydraulic requirements of the multi-speed hydraulic motor 60 are reduced compared to a fixed-displacement motor used for the same application, the rapid operation of the various hydraulically driven functions of the motor grader 10 (including raising, rotating, and lowering the motor grader blade 38) can be maintained while the motor grader is turning.

[0029] The use of a multi-speed hydraulic motor for blade rotation can lead to undesirable fluctuations in blade rotation speed in conjunction with fluctuations in blade load conditions if sufficient countermeasures are not provided. Therefore, the motor grader 10 is further equipped with the closed-loop feedback drive system 12, which serves to minimize or eliminate fluctuations in blade rotation speed in response to fluctuations in blade load that occur during operation of the motor grader. The specific manner in which the closed-loop feedback drive system 12 is implemented will necessarily vary between embodiments that are at least partially based on the form assumed by the multi-speed hydraulic motor 60; e.g.,whether the multi-speed hydraulic motor 60 takes the form of, for example, a two-speed hydraulic motor or instead a variable displacement hydraulic motor. To further emphasize this point, a first exemplary implementation of the closed-loop feedback drive system 12, which includes a two-speed hydraulic motor, is now presented in conjunction with the . Fig. 3 and Fig. 4. Following this, a second exemplary implementation of the closed-loop feedback drive system 12, which includes a variable displacement hydraulic motor, will be described below in conjunction with Fig. 5 shown. EXEMPLOYMENT OF THE CLOSED-LIVE REACTION SYSTEM, INCLUDING A TWO-SPEED HYDRAULIC MOTOR

[0030] The Fig. 3 and Fig. Figure 4 shows a schematic representation of a first exemplary implementation of a closed-loop feedback drive system 12-1; the addition of “-1” indicates that the illustrated closed-loop feedback drive system 12-1 is only one possible implementation of the generalized closed-loop feedback drive system 12, which was described above in conjunction with Fig. 1 describes. Where applicable, other reference numerals from the preceding drawing figures are also adopted; with reference, for example, to the labeling of the control unit 14, the memory 16 and the operator input device 76 in the Fig. 3 and Fig. 4. In addition to the above components, the closed-loop feedback drive system 12-1 also includes a plurality of sensors 70 which are connected to the sensor(s) 70 from Fig. 2 correspond. The sensors 70 include two pressure sensors 70-1, 70-2, a speed sensor 70-3, and any number of additional sensors 70-4, such as a rotary angle sensor. The sensors 70 and the ways in which the controller 14 can take into account the data provided by the sensors 70 when controlling the various components of the closed-loop feedback drive system 12-1 are discussed below. First, however, the hydraulic components of the closed-loop feedback drive system 12-1 are described.

[0031] A flow network 90, consisting of a number of flow lines 90-1 to 90-8, connects the hydraulic components of the closed-loop feedback drive system 12-1. These hydraulic components include: (i) a drip tray 92, (ii) a pump 94, (iii) a directional control valve 96, (iv) a mode selection valve 98, and (v) a two-speed hydraulic motor 100 (corresponding to the multi-speed hydraulic motor 60 from the Fig. 1 and Fig. 2) The two-speed hydraulic motor 100, in turn, includes a first power element 102 and a second power element 104, which are fluidically connected to each other via the flow network 90. ​​The power elements 102 and 104 are mounted on a common shaft 106 of the two-speed hydraulic motor 100, which rotates with (and may be integral to) an output shaft 108, which is also contained within the two-speed hydraulic motor 100. During operation of the closed-loop feedback drive system 12-1, hydraulic fluid is passed through the power elements 102 and 103 to drive the rotation of the motor output shaft 108. In practice, the closed-loop feedback drive system 12-1 may also include various other hydraulic components, such as additional (e.g.,Amplifiers, pumps, filters, check valves and the like; however, such components are tangential to the core functions of the closed-loop feedback drive system 12-1 and are therefore not shown to avoid obscuring the drawings.

[0032] In the exemplary implementation in the Fig. 3 and Fig. 4 The directional control valve 96 is designed as a four-way, three-position spool valve. Accordingly, the directional control valve 96 includes a spool (generally a "valve element") which is arranged in a valve body or sleeve for translational movement therein. The spool is shown in an intermediate or neutral position in the illustrated schematic representation and can move from this position in both directions along its translational axis, as indicated by arrows 110 and 112. The positioning of the spool within the directional control valve 96 is set by the control unit 14 using one or more valve actuators 114, which are further contained in or associated with the directional control valve 96.Upon excitation or other actuation, the valve actuator(s) 114 act in conjunction with or against preload forces exerted on the spool by one or more spring elements 116, such as helical compression springs, contained in the sleeve of the directional control valve 96. In embodiments, the valve actuator(s) 114 can be a solenoid or a pair of solenoids that is selectively excited by the control unit 14 to determine the translational position of the spool within the directional control valve 96. In further embodiments, the valve actuator 114 can take various other forms, such as a hydraulic actuator, another type of electrical actuator, or a combination thereof.

[0033] During operation of the closed-loop feedback drive system 12-1, the controller 14 commands the valve actuator(s) 114 to selectively adjust the translational position of the spool within the sleeve of the directional control valve 96. Controlling the spool position in this way influences the rate and direction of the fluid flow through the directional control valve 96 and thus through the two-speed hydraulic motor 100. For example, consider a scenario in which the controller 14 commands the valve actuator 114 to move the spool from the neutral position (downward in the illustrated diagram) in the direction indicated by arrow 112. In this case, the directional control valve 96 directs the fluid flow through the primary flow circuit (i.e.,the flow circuit downstream of the directional control valve 96 (consisting of flow lines 90-2 to 90-7) in a first flow direction, as indicated by the upper pair of arrows within the corresponding valve symbol. This generally results in a clockwise flow, as illustrated schematically, to drive the rotation of the motor output shaft 108 in a first direction of rotation. As the spool slides further towards the position extremum, as indicated by arrow 112, the flow rate through the directional control valve 96 increases (provided that the other flow conditions remain constant) along with the rotational speed of the motor output shaft 108. Conversely, from the neutral position ( Fig. 3 and Fig. 4) A movement of the spool in the opposite direction, corresponding to arrow 110, prepares the port-to-port connections indicated by the lower pair of arrow symbols in the schematic representation of the directional control valve 96. Accordingly, the direction of the hydraulic fluid flow through the primary flow circuit is reversed (providing an essentially counterclockwise flow in the illustrated schematic), which drives the rotation of the motor output shaft 108 in a second, opposite direction. Again, the flow rate through the directional control valve 96 increases as the spool moves further in the direction of the corresponding extreme position arrow 112, which further accelerates the rotation of the motor output shaft 108 in the second direction of rotation.

[0034] By adjusting the translation position of the slide within the directional control valve 96 in the manner just described, the control 14 can selectively control the speed and direction of the motor output shaft 108 and thus the speed and direction of the motor grader blade 38 about the blade rotation axis 58 ( Fig. 2) modify. In certain implementations, the controller 14 can further control the speed and direction of the motor output shaft 108 in other ways, such as by controlling the pump 94 to regulate the pump outlet, if the pump 94 is capable of being controlled in this manner; although such a control mechanism cannot be used in embodiments such as when the pump 94 is gear-driven. In other cases, the controller 14 can control the speed and direction of the motor output shaft 108 both by modulating the directional control valve 96 and by selectively switching or toggling the two-speed hydraulic motor 100 between several operating modes.In the illustrated example, the control unit 14 further controls in particular the speed and direction of the motor output shaft 108 by selectively switching the two-speed hydraulic motor 100 between two operating modes using the mode selection valve 98, as now described.

[0035] Like the directional control valve 96, the mode selection valve 98 in the illustrated implementation takes the form of a four-way, three-position spool valve. The movement of the spool contained in the mode selection valve 98 is controlled by a valve actuator 118, such as a solenoid. As commanded by the control 14, the valve actuator 118 forces the piston movement in a specific translational direction (downward in the illustrated orientation) when the output force of the actuator is sufficient to overcome a preload force further exerted on the piston by at least one spring element 120, such as a coil spring, within the sleeve of the mode selection valve 98. In contrast to the directional control valve 96, the mode selection valve 98 in the illustrated example is given a bistable design. Accordingly, the spool of the mode selection valve 98 is positioned between a first stable position (shown in Fig. 3) and a second stable position (shown in Fig. 4) movable. The movement of the slide within the mode selection valve 98 into the first stable position ( Fig. 3) fluidically places the power elements 102, 104 into flow series, thereby switching the two-speed hydraulic motor 100 into LP / HP operating mode. Conversely, by moving the mode selection valve 98 into the second stable position ( Fig. 4) the power elements 102, 104 arranged in a parallel flow arrangement which puts the hydraulic motor with two speeds 100 into the HD / ND operating mode.

[0036] As just mentioned, the movement of the mode selection valve 98 couples into the first stable position ( Fig. 3) The power elements 102, 104 flow fluidically in a flow series. To further clarify this point, it is assumed that the slide of the directional control valve 96 is in the position extremum corresponding to arrow 112 in Fig. 3 is shifted. In this case, the mode selection valve 98 initially receives a hydraulic fluid flow from the directional control valve 96 via flow line 90-2, which is then directed by the valve 98 into flow line 90-3. The hydraulic fluid flows through flow line 90-3, through the power element 104, through flow line 90-4, and finally returns to the mode selection valve 98. Subsequently, the mode selection valve 98 redirects the hydraulic fluid flow into flow line 90-5, which directs the fluid flow through the power element 102. From the power element 102, the hydraulic fluid then flows back through the flow line 90-6 to the mode selection valve 98. The returning hydraulic fluid passes through the mode selection valve 98 into the flow line 90-7, flows through the directional control valve 96 and is finally returned to the collection tray 92 via the flow line 90-8.This results in a rotation of the motor output shaft 108 in a first direction of rotation; and accordingly in the rotation of the motor grader share 38 in a first direction of rotation about the share rotation axis 58 (. Fig. 2) In general, in the example scenario, the following will then occur: Fig. 3. The hydraulic fluid delivered by pump 94 is passed through the power elements 102, 104 of the dual-speed hydraulic motor 100 in series flow to provide low-torque, high-speed operation of the dual-speed hydraulic motor 100. This operating mode of the dual-speed hydraulic motor 100 is optimal for driving the blade rotation when the motor grader blade 38 is under a light load or no load, such as when the motor grader blade 38 is in a position above the ground. The flow pattern described above is reversed when the controller 14 commands movement of the spool of the directional control valve 96 beyond the neutral position in the opposite direction (according to arrow 110).Thus, by modulating the directional control valve 96 in this latter manner, the control unit 14 can cause the motor output shaft 108 and the motor grader blade 38 to rotate in the opposite direction when commanded by blade rotation commands received via the operator input device 76.

[0037] If the control 14 instead causes a movement of the slide of the mode selection valve 98 into the second stable position ( Fig. 4) The power elements 102 and 104 are arranged in a parallel flow configuration to switch the two-speed hydraulic motor 100 into high-pressure / low-pressure mode. An example scenario is again considered in which the spool of the directional control valve 96 is located at the positional extremum corresponding to arrow 112. In this case, the hydraulic fluid flow received at an inlet port of the mode selection valve 98 is split between the flow lines 90-3 and 90-5 and thus passed in parallel through the power elements 102 and 104. After passing through the power elements 102 and 104, the hydraulic fluid is directed via the flow lines 90-4 and 90-6 to the inlet ports of the mode selection valve 98. The hydraulic fluid flow is then consolidated within the mode selection valve 98, discharged through an outlet of the valve 98 and returned to the collection tray 92 via the flow line 90-8.This results in a rotation of the motor output shaft 108 and thus of the motor grader blade 38 in the first direction of rotation. Conversely, the flow pattern described above is reversed if the spool of the directional control valve 96 is instead moved beyond the neutral position in the direction indicated by arrow 110 to drive the rotation of the motor output shaft 108 and the motor grader blade 38 in the second, opposite direction. The control unit 14 can move the hydraulic motor at two speeds 100 in high-pressure / low-pressure operating mode when the motor grader blade 38 is in a position in the ground or is otherwise under heavy load, as discussed below.

[0038] In embodiments, the controller 14 determines when the two-speed hydraulic motor 100 should be switched, at least partially, based on one or more sensor inputs indicating the load forces resisting blade rotation about the blade rotation axis 58 (also referred to here as the "anti-rotation load forces"). Such a sensor input can directly measure the blade load, for example, using a force sensor contained in the additional sensors 70-4, which is mechanically coupled between the motor output shaft 108 and the motor grader blade 38.In such embodiments, the controller 14 can be configured to switch the two-speed hydraulic motor 100 from ND / HD mode to HD / ND mode when the antirotation load forces exerted on the motor grader blade 38 exceed a predetermined threshold, and to return the two-speed hydraulic motor 100 to ND / HD mode when the antirotation load forces exerted on the motor grader blade 38 fall below the predetermined threshold again. In other cases, the controller 14 can receive sensor inputs that indirectly correspond to the antirotation load forces occurring during the rotation of the motor grader blade 38.For example, embodiments of the closed-loop feedback drive system 12-1 may include at least one pressure sensor configured to monitor the pressure in a flow line fluidically coupled between an outlet of the pump 94 and a port of the two-speed hydraulic motor 100. In this latter case, the controller 14 may monitor this hydraulic pressure using the pressure sensor(s), such as the pressure sensor 70-1 or 70-2 (discussed below), and then issue the appropriate commands to switch the two-speed hydraulic motor 100 from LP / HP mode to HP / LP mode when the monitored pressure in a flow line exceeds a predetermined value.

[0039] In accordance with the preceding discussion, it is shown that the closed-loop feedback drive system 12-1 includes two pressure sensors 70-1 and 70-2. The controller 14 can receive data indicating the hydraulic pressure in the flow line 90-3 from pressure sensor 70-1, and thus downstream of the two-speed hydraulic motor 100, when the fluid flow through the circuit occurs in a first direction (generally clockwise in the illustrated scheme). The controller 14 can then use this pressure data to determine when the two-speed hydraulic motor 100 needs to be switched between its operating modes or states. For example, if the pressure in the flow line 90-3 exceeds a predetermined threshold, the controller 14 can command the mode selection valve 98 to switch the two-speed hydraulic motor 100 to the high-pressure / low-pressure operating mode ( Fig. 4) to move. If the pressure in the flow line 90-3 falls below the threshold again, the controller 14 can then command the mode selection valve 98 to switch the hydraulic motor to the LP / HD operating mode ( Fig. 3) to displace. Conversely, the controller 14 can use the pressure sensor 70-2 to monitor the hydraulic pressure in the flow line 90-4 downstream of the two-speed hydraulic motor 100 when the spool of the directional control valve 96 is moved such that hydraulic fluid flow occurs in the opposite direction (generally counterclockwise in the illustrated example). Again, the controller 14 can instruct the mode selection valve 98 to move the two-speed hydraulic motor 100 into the high-pressure / low-pressure mode ( Fig. 4) to be displaced when the pressure in the flow line 90-4 exceeds a predetermined threshold, indicating a high torque requirement to be applied to the motor grader blade 38. In other embodiments, a different number of pressure sensors and / or a different control scheme may be used. For example, a single pressure sensor may be used to monitor the higher pressure in one of the flow lines 90-3, 90-4 by, for example, using a diverter valve (or a similar device) to direct the higher pressure from one of the flow lines 90-3, 90-4 to the pressure sensor in a manner that is described below in conjunction with Fig. It is similar to the one described in section 5.

[0040] In addition to or instead of considering a sensor input indicative of the actual load resisting rotation of the motor grader blade 38, the controller 14 can also consider sensor inputs predicting a current blade load or an expected blade load when determining when to engage the two-speed hydraulic motor 100 in a specific operating mode. For example, in one embodiment, the controller 14 can monitor whether the motor grader blade 38 is currently in a position above or below ground, e.g., via a blade height or depth sensor contained in one or more additional sensors 70-4 included in the closed-loop feedback drive system 12-1. The controller 14 can then modulate the operating state of the two-speed hydraulic motor 100 accordingly.In particular, in such embodiments the control 14 can instruct the mode selection valve 98 to put the two-speed hydraulic motor 100 into the ND / HD operating mode (. Fig. 3) when it is determined that the motor grader blade 38 is in a position above the ground. Conversely, the controller 14 can instruct the two-speed hydraulic motor 100 and switch further into HD / ND mode when it is determined that the motor grader blade 38 is in a position in the ground. In other implementations, a similar approach can be used with a different prediction factor or event, such as a predetermined blade penetration depth; e.g., the controller 14 can instruct the two-speed hydraulic motor 100 to switch to HD / ND operating mode ( Fig. 4) reposition when the motor grader blade 38 penetrates the soil (or other material) to a specified depth. In further embodiments, a more complex control scheme can be used, taking into account both the blade penetration depth and the blade load.

[0041] In at least some implementations, the controller 14 of the closed-loop feedback drive system 12-1 also advantageously adjusts the speed of the motor output shaft 108 to minimize variations in the rotational speed of the motor grader blade 38 when the two-speed hydraulic motor 100 is switched between the low-pressure / high-pressure mode and the high-pressure / low-pressure mode. To some extent, this may occur inherently due to the implementation of a closed-loop feedback control scheme by the controller 14, examples of which are given below. Additionally or alternatively, the controller 14 may adjust the position of the spool of the directional control valve 96 by a predetermined amount or a set linear displacement when the two-speed hydraulic motor 100 is switched between the high-pressure / low-pressure mode and the low-pressure / high-pressure mode.For example, in this case, the controller 14 can command the valve actuator 114 to move, or "jump," the spool of the directional control valve 96 by a predetermined translational displacement. This movement of the spool is generally intended to maintain the motor output speed by transitioning between the two-speed operating modes of the hydraulic motor 100. Subsequently, the controller 14 can then adjust the position of the spool within the directional control valve 96 according to a closed-loop control scheme, as described in more detail below.

[0042] In addition to determining when the two-speed hydraulic motor 100 should be switched between operating modes, the controller 14 also regulates the rate and direction of the hydraulic fluid flow through the two-speed hydraulic motor 100 to generally maintain the rotational speed of the motor output shaft 134 at commanded levels despite variations in the blade load conditions. The controller 14 can execute various closed-loop feedback control schemes according to computer-readable instructions or code stored in memory 16 to perform this function. In an exemplary approach, the controller 14 initially sets a current rotational speed of the motor grader blade 38 (v Schar_aktuell ) fixed. The control unit 14 can set the current share rotation speed (v). Schar_aktuell) using various sensor inputs provided by the sensors 70 contained in the closed-loop feedback drive system 12-1. For example, the controller 14 can monitor the angular or rotational position of the motor grader blade 38 using a circular rotation angle sensor contained in the additional sensor 70-4. In other cases, the controller 14 can monitor the angular position of another component in the rotary transmission chain that rotates with the motor grader blade 38 in a fixed (1:1 or other proportional) relationship. The controller 14 can then convert changes in the blade angle over time into a corresponding current blade rotation speed (v). Schar_aktuell ) convert. In further embodiments, the control unit 14 can convert the current share rotation speed (v). Schar_aktuell) monitor in a more direct way; e.g., using a sensor configured to monitor the rotational speed of the motor output shaft 108 or any other component that rotates with it. As, for example, in Fig. As shown in Figure 4, a sensor 70-3, such as a rotary differential transformer or a MEMS device (e.g. a MEMS accelerometer and / or gyroscope), can monitor the rotational speed of the motor output shaft 108 and provide this information to the controller 14.

[0043] After, before or simultaneously with setting the current share rotation speed (v Schar_aktuell ) the control 14 further determines a target rotational speed of the motor grader blade 38 (v Schar_Ziel Generally, the controller determines the voltage at 14 V. Schar_Ziel depending on operator command signals received via the operator input device 76. In embodiments, the target share rotation speed (v) can be set. Schar_Ziel) the displacement of the operator input device 76 is assigned in a substantially proportional relationship. In embodiments in which the operator input device 76 takes the form of a joystick or lever, the control 14 can determine the magnitude and direction from a neutral or starting position and then convert this value into a corresponding target shaft rotation speed (v). Schar_Ziel) convert. For example, the controller 14 can determine that an operator has moved the joystick a certain percentage (e.g., 25%) of the joystick's maximum range of motion (BB) away from the neutral position in a first direction, and then convert this joystick displacement into a corresponding percentage (e.g., 25%) of the maximum rotational speed of the motor grader blade 38 in a first direction of rotation. Similarly, a 25% displacement of the joystick from the neutral joystick position (i.e., 25% of the joystick's maximum range of motion) in a second, opposite direction can also be converted into a value of 25% of a maximum rotational speed of the motor grader blade 38 in a second, opposite direction of rotation.In other embodiments, movements of the operator input device 76 can be converted into the target share rotation speed (v. ) using a different approach, such as a position-based approach, in which the movement of a joystick from a first position to a second position in a given period of time is converted into a corresponding share rotation speed. Schar_Ziel ) are mapped or converted.

[0044] Next, control unit 14 calculates the difference or disparity (here “v”). Schar_Δ ) between the target blade rotation speed (v Schar_Ziel ) and the current share rotation speed (v Schar_aktuell In certain cases, the disparity can be v Δ between v Schar_Ziel and v Schar_aktuell be zero, even in cases where the motor grader pack is desirablely stationary (in which case v Schar_Ziel and v Schar_aktuell(also values ​​of zero). In other cases, such as when an operator input is received via the operator input device 76 commanding a blade rotation, and the rotation of the motor grader blade is opposed by a load, a non-zero inequality may arise between v Schar_Ziel and v Schar_aktuell develop. If the value of v” exceeds a predetermined threshold, the controller 14 adjusts the speed of the two-speed hydraulic motor 100 in the manner described above to compensate for the discrepancy (v). Schar_Δ ) between the current share rotation speed (v Schar_aktuell ) and the target blade rotation speed (v Schar_Zielto reduce. The predetermined threshold may have a value of zero in embodiments, but more often it has a non-zero value to prevent repeated minor adjustments to the rotational speed of the motor grader pack 38. The value of the predetermined threshold may be stored as a fixed parameter in memory 16 or, alternatively, be adjustable as a "sensitivity" setting of the closed-loop feedback drive system 12-1 according to operator or customer preferences.

[0045] The controller 14 then repeats the process steps described above on a relatively fast (e.g., near real-time) iterative basis to provide a closed-loop feedback control that regulates the rotational speed of the motor grader blade 38. In this way, the controller 14 effectively ensures that the motor grader blade 38 achieves a desired rotational speed regardless of the load-resistant blade rotation. Thus, a more consistent relationship between shifts in the control input (e.g., joystick) and the rotational speed of the motor grader blade 38 can be maintained across different iterations of the motor grader operation, improving operator satisfaction and productivity levels. At the same time, the closed-loop feedback drive system 12-1 retains the use of a multi-speed hydraulic motor (i.e.,a two-speed hydraulic motor (100) to enable a reduction in the size and hydraulic requirements of the motor relative to fixed displacement motors, thus maintaining rapid execution of hydraulically driven functions during the turning of the motor grader. EXEMPLOYMENT OF THE CLOSED-LIVE REACTION SYSTEM, INCLUDING A VARIABLE DISPENSITY HYDRAULIC MOTOR

[0046] Finally, it will be noted that Fig. 5 Referenced, in which a schematic representation of a second exemplary implementation of the closed-loop feedback drive system 12-2 is shown, which is further suitable for use as the closed-loop feedback drive system 12, which is generally in Fig. Figure 1 is shown. In many respects, the closed-loop feedback drive 12-2 is similar to the closed-loop feedback drive 12-1, which is shown above in conjunction with the Fig. 3 and Fig. 4 is described. For example, the closed-loop feedback drive system 12-2 includes the controller 14 described above, the memory 16, the operator input device 76, the speed sensor 70-3, the additional sensors 70-4, the drip tray 92, and the pump 94. These components have been described previously and are not described in detail here to avoid redundancy. Components from the above list may be modified to some extent with respect to the preceding description, however, as required to support the operation of the closed-loop feedback drive 12-2; e.g., the computer-readable code located in the memory 16 differs to allow the controller 14 to implement a different control scheme suitable for controlling a variable displacement hydraulic motor (e.g.,of the variable displacement hydraulic motor 132), instead of a two-speed hydraulic motor, as explained below.

[0047] The in Fig. The exemplary closed-loop feedback drive system 12-2 shown in Figure 5 further includes a flow network 122 comprising flow lines 122-1 to 122-7. The flow network 122 fluidically connects a pressure-operated changeover valve 124, a solenoid-operated selector valve 126, and a hydraulic actuator 128, including a spring-loaded piston 130. As with the closed-loop feedback drive system 12-1 shown above, the closed-loop feedback drive system 12-2 also includes a hydraulic motor having a motor output shaft 134, suitable for use as the multi-speed hydraulic motor 60 described above in conjunction with the Fig. 1 and Fig. 2 described. In contrast to the Fig. 3 and Fig. 4, however, the hydraulic motor is designed as a variable displacement hydraulic motor 132 and is therefore referred to below as the “variable displacement hydraulic motor 132”. The variable displacement hydraulic motor 132 includes a power element 136, which is fluidically arranged in the flow network 122, and a displacement adjustment mechanism 138, which is mechanically coupled to the rod end of the spring-loaded piston 130.

[0048] In addition to the spring-loaded piston 130, the hydraulic actuator 128 also includes a spring 140 (e.g., a helical compression spring) and a hydraulic control chamber 142. The pressurization of the control chamber 142 is regulated by the control unit 14 using the solenoid-operated selector valve 126, which includes a spring 144 and a solenoid 146 that is operatively coupled to the control unit 14. When energized by the control unit 14, the solenoid 146 exerts a force on the spool of the selector valve 126 sufficient to overcome the spring preload of the spring 144 and thereby move the spool to the position indicated in the lower half of the symbol representing the valve 126. This practically couples the flow line 122-3 fluidically to the flow line 122-4, which directs pressurized hydraulic fluid flow into the control chamber 142 of the hydraulic actuator 128.When the cumulative force acting on the surface of the piston 130 is sufficient to overcome the preload force of the spring 140, the piston 130 extends to adjust the displacement adjustment mechanism 138 as commanded. Conversely, when it is desired to retract the piston 130, the control 14 commands the electromagnet 146 to move the slide of the selector valve 126 to the opposite position (indicated by the upper half of the symbol of the valve 126); for example, more precisely, the control 14 can switch off the electromagnet to move the slide of the selector valve 126 when the spring 144 relaxes. This fluidically couples the flow line 122-4 to the flow line 122-5, allowing hydraulic fluid to flow from the control chamber 142 through the selection valve 126 and into the collection basin 92 when the piston 130 retracts to adjust the displacement adjustment mechanism 138 as desired.In further embodiments, the hydraulic actuator 128 can be replaced by another type of actuator, such as an electric linear actuator, which is used by the control 14 to vary the displacement setting of the variable displacement hydraulic motor 132 in the same way.

[0049] During operation of the closed-loop feedback drive system 12-2, the controller 14 can control the operation of the variable displacement hydraulic motor 132 using a closed-loop feedback control scheme similar to the one previously used in conjunction with the Fig. 3 and Fig. 4 is similar, if not essentially identical. Accordingly, the control unit 14 can initially set a target rotational speed (v). Ziel) of the motor grader blade 38 as a function of operator command signals received via the operator input device 76, as previously described. Next, the controller 14 then determines a discrepancy (v Schar_Δ ) between the share rotation speed (v Schar_Ziel ) and a current share rotation speed (v Schar_aktuell ), as determined using one or more sensor inputs received by the sensors 70 (again as described previously). Also during this step and as in Fig.As indicated by 5, a single pressure sensor 70-5 can be used to monitor the pressure in flow line 122-3, which is fluidically connected to the pressure in flow line 122-2 or flow line 122-6 (whichever is greater) through the action of the changeover valve 124. The controller 14 can then adjust the displacement setting of the variable displacement hydraulic motor 132 as a function of the hydraulic pressure detected by the pressure sensor 70-5. Finally, the controller 14 modifies the speed of the motor output shaft 134 (and, if necessary, a direction of rotation) to compensate for the discrepancy (v Schar_Δ ) between the share rotation speed (v Schar_Ziel ) and the current share rotation speed (v Schar_aktuell ) to reduce if the discrepancy (v Schar_Δ) exceeds a predetermined threshold stored in memory 16. In further embodiments, a different control scheme can be suitably employed by the controller 14 to provide closed-loop feedback control of the blade rotation using the variable displacement hydraulic motor 132. In this scenario, the controller 14 commands the variable displacement hydraulic motor 132 in a manner that better maintains the rotational speed of the motor output shaft 134 at desired levels despite fluctuations in blade load conditions. This improves the consistency with which operator inputs result in an expected blade rotation speed output, while maintaining the rapid execution of hydraulically driven functions during the turning of the motor grader. LISTING OF EXAMPLES OF THE CLOSED-Loop Feedback Drive System

[0050] The following examples of the closed-loop feedback drive system are numbered for better reference.

[0051] 1. In a first embodiment, the closed-loop feedback drive system comprises an operator input device, a blade rotatable about a blade axis, and a multi-speed hydraulic motor with a motor output shaft. The motor output shaft is mechanically connected to the motor grader blade, such that rotation of the motor output shaft causes rotation of the motor grader blade about the blade axis. A control unit is operationally coupled to the operator input device and the multi-speed hydraulic motor.The control system is configured to: (i) receive blade rotation commands via the operator input device to rotate the motor grader blade about the axis of rotation as commanded; and (ii) control the multi-speed hydraulic motor to execute the blade rotation commands while repeatedly adjusting the speed of the motor output shaft to reduce variations in the speed of the motor grader blade due to changes in blade loading conditions that occur during operation of the motor grader.

[0052] 2. The closed-loop feedback drive system according to Example 1 further includes a first sensor configured to monitor a parameter indicating the rotational speed of the motor grader blade. The controller is operationally coupled to the first sensor and configured to provide a current blade rotational speed (v). Schar_aktuell) to monitor using data provided by the first sensor.

[0053] 3. The closed-loop feedback drive system according to Example 2, wherein the control is further configured to: (i) maintain a target rotational speed (v Ziel ) to determine the motor grader group as a function of the operator command signals received via the operator input device; (ii) a discrepancy (v Schar_Δ ) between the share rotation speed (v Schar_Ziel ) and the current share rotation speed (v Schar_aktuell ) to determine; and (iii) if the discrepancy (v Schar_Δ ) exceeds a predetermined threshold, adjust the speed of the motor output shaft to compensate for the discrepancy (v Schar_Δ ) between the share rotation speed (v Schar_Ziel ) and the current share rotation speed (v Schar_aktuell to reduce.

[0054] 4. The closed-loop feedback drive system according to Example 3, wherein the control is configured to: (i) determine a displacement direction and size of the operator input device relative to a neutral position thereof; and (ii) input the displacement direction and size of the operator input device into the share rotational speed (v Schar_Ziel to convert.

[0055] 5. The closed-loop feedback drive system according to Example 2, wherein the first sensor takes the form of a rotary angle sensor configured to monitor a rotary angle of the motor grader pack.

[0056] 6. The closed-loop feedback drive system according to Example 2, wherein the first sensor takes the form of a speed sensor configured to monitor the speed of the motor output shaft.

[0057] 7. The closed-loop feedback drive system according to Example 1 further includes a pump and a directional control valve fluidically coupled between the pump and the multi-speed hydraulic motor. The control system is configured to adjust the speed of the motor output shaft, at least partially, by controlling the directional control valve to vary the rate of hydraulic fluid flow through the multi-speed hydraulic motor.

[0058] 8. The closed-loop feedback drive system according to Example 1, wherein the multi-speed hydraulic motor includes a variable displacement hydraulic motor which incorporates a displacement adjustment mechanism. The control is configured to adjust the speed of the motor output shaft, at least partially, by setting a displacement setting of the variable displacement hydraulic motor using the displacement adjustment mechanism.

[0059] 9. The closed-loop feedback drive system according to Example 1, wherein the multi-speed hydraulic motor includes a two-speed hydraulic motor with a first and a second power element. The closed-loop feedback drive system further includes a selection valve that is fluidically coupled to the first and the second power element.

[0060] 10. The closed-loop feedback drive system according to Example 9, wherein the control is operationally coupled to the selection valve and is configured to at least partially adjust the speed of the motor output shaft by selectively switching the selection valve between: (i) a first position in which the first and second power elements are fluidically coupled in series; and (ii) a second position in which the first and second power elements are fluidically coupled in parallel.

[0061] 11. The closed-loop feedback drive system of Example 1, wherein the multi-speed hydraulic motor includes a dual-speed hydraulic motor that can be operated in a low-torque, high-speed (ND / HD) mode and a high-torque, low-speed (HD / ND) mode. The control system is further configured to: (i) selectively switch the dual-speed hydraulic motor between the ND / HD range mode and the HD / ND mode during operation of the motor grader; and (ii) further control the dual-speed hydraulic motor to minimize variations in the rotational speed of the motor grader blade when the dual-speed hydraulic motor switches between the ND / HD mode and the HD / ND mode.

[0062] 12. The closed-loop feedback drive system according to Example 11, further comprising a sensor configured to monitor a parameter indicating the share loading conditions. The controller is operationally coupled to the second sensor and further configured to determine when to switch the two-speed hydraulic motor between ND / HD mode and HD / ND mode, at least partially, based on data received from the sensor.

[0063] 13. The closed-loop feedback drive system according to Example 12, further comprising a flow line and a directional control valve fluidically coupled to the multi-speed hydraulic motor through the flow line. The sensor takes the form of a pressure sensor configured to monitor hydraulic pressure in the flow line. The controller is configured to determine, at least partially based on whether the hydraulic pressure exceeds a predetermined threshold, when to switch the two-speed hydraulic motor from LP / HP mode to HP / LP mode.

[0064] 14. The closed-loop feedback drive system according to Example 11, wherein the control is configured to determine, at least partially, on the basis of whether the motor grader share is currently in a position above the ground or in a position in the ground, when to switch the two-speed hydraulic motor from the ND / HD mode to the HD / ND mode.

[0065] 15. In further embodiments, the closed-loop feedback drive system includes an operator input device, a blade rotatable about a rotary axis, a multi-speed hydraulic motor with a motor output shaft mechanically connected to the motor grader blade, and a first sensor configured to monitor a parameter indicating a rotational speed of the motor grader blade. A controller is operationally coupled to the operator input device, the multi-speed hydraulic motor, and the first sensor. The controller is configured to: (i) a blade rotational speed (v Schar_Ziel ) as a function of operator command signals received via the operator input device; (ii) a discrepancy (v Schar_Δ ) between the share rotation speed (v Schar_Ziel ) and a current share rotation speed (v Schar_aktuell) to determine; and (iii) to modify a rotational speed of the motor output shaft to reduce the discrepancy (v Schar_Δ ) between the share rotation speed (v Schar_Ziel ) and the current share rotation speed (v Schar_aktuell ) to reduce if the discrepancy (VSchar-") exceeds a predetermined threshold. CONCLUSION

[0066] For this reason, embodiments of a closed-loop feedback circular drive system have been provided for controlling a multi-speed circular rotary motor (e.g., a variable displacement or dual-speed hydraulic motor) used to adjust the rotational position of a motor grader blade. The closed-loop feedback circular drive systems described above increase the consistency with which operator command inputs result in an expected blade rotation speed output by reducing or eliminating fluctuations in blade rotation speed under changing load conditions. Simultaneously, the circular drive systems utilize a multi-speed hydraulic motor to drive the blade rotation, thus better maintaining rapid execution of hydraulically driven functions during motor grader turning.Furthermore, in embodiments where the rotary drive system includes a dual-speed hydraulic motor, the controller can selectively switch the dual-speed hydraulic motor between a first (e.g., low torque, high speed) operating mode and a second (e.g., high torque, low speed) operating mode while controlling the dual-speed hydraulic motor to minimize fluctuations in motor speed when switching between operating modes. In the manner described above, the way in which operator control commands are translated into blade rotation speed settings can be made more consistent and predictable throughout the use of the motor grader, thereby improving the operator experience and efficiency.

Claims

[1] Closed-loop feedback drive system (12) used on board a motor grader (10), wherein the closed-loop feedback drive system (12) comprises: an operator input device (76); a share (38) which is rotatable about a share rotation axis (58); a multi-speed hydraulic motor (60; 100; 132) with a motor output shaft (108) which is mechanically connected to the share (38), wherein a rotation of the motor output shaft (108) causes a rotation of the share (38) about the share rotation axis (58); and a control unit (14) that is operationally coupled to the operator input device (76) and to the multi-speed hydraulic motor (60; 100; 132) and is configured to: a target blade rotation speed (v Schar_Ziel ) depending on share rotation commands received via the operator input device (76); and to control the multi-speed hydraulic motor (60; 100; 132) to implement the share rotation commands, while a speed of the motor output shaft (108) is modified to compensate for discrepancies between the target share rotation speed (v Schar_Ziel ) and a current share rotation speed (v Schar_aktuell ) due to fluctuations in the load forces that resist the blade rotation during operation of the motor grader (10). [2] Closed-loop feedback drive system (12) according to claim 1, further comprising a first sensor (70) configured to monitor a parameter indicating a share rotation speed; wherein the controller (14) is operationally coupled to the first sensor (70) and configured to monitor the current share rotation speed (v Schar_aktuell ) to monitor using data provided by the first sensor (70). [3] Closed-loop feedback drive system (12) according to claim 2, wherein the controller (14) is further configured to: a discrepancy (v Schar_Δ ) between the target blade rotation speed (v Schar_Ziel ) and the current share rotation speed (v Schar_aktuell ) to determine; and to modify the speed of the motor output shaft (108) to reduce the discrepancy (v Schar_Δ ) to reduce it if a predetermined threshold is exceeded. [4] Closed-loop feedback drive system (12) according to claim 2 or 3, wherein the first sensor (70) comprises a rotation angle sensor (70-4) configured to monitor a rotation angle of the share (38). [5] Closed-loop feedback drive system (12) according to one of claims 2 to 4, wherein the first sensor (70) comprises a speed sensor (70-3) configured to monitor the speed of the motor output shaft (108). [6] Closed-loop feedback drive system (12) according to any one of claims 1 to 5, wherein the controller (14) is configured to: to determine a direction of displacement and size of the operator input device (76) relative to a neutral position thereof; and the displacement direction and size of the operator input device (76) into a target share rotation speed (v Schar_Ziel to convert. [7] Closed-loop feedback drive system (12) according to any one of claims 1 to 6, further comprising: a pump (94); and a directional control valve (96) which is fluidically coupled between the pump (94) and the multi-speed hydraulic motor (60; 100; 132); wherein the control (14) is configured to adjust the speed of the motor output shaft (108) at least partially by controlling the directional control valve (96) in order to vary a rate of hydraulic fluid flow through the multi-speed hydraulic motor (60; 100; 132). [8] Closed-loop feedback drive system (12) according to any one of claims 1 to 7, wherein the multi-speed hydraulic motor (60; 132) comprises a variable displacement hydraulic motor (132) which includes a displacement adjustment mechanism (138); and wherein the control (14) is configured to adjust the speed of the motor output shaft (108) at least partially by adjusting a displacement setting of the variable displacement hydraulic motor (132) using the displacement adjustment mechanism (138). [9] Closed-loop feedback drive system (12) according to any one of claims 1 to 8, wherein the multi-speed hydraulic motor (60; 100) comprises a two-speed hydraulic motor (100) with a first and a second power element (102, 104); and wherein the closed-loop feedback drive system (12) further comprises a selection valve (98) which is fluidically coupled to the first and the second power element (102, 104). [10] Closed-loop feedback drive system (12) according to claim 9, wherein the controller (14) is operationally coupled to the selection valve (98) and is configured to at least partially adjust the speed of the motor output shaft (108) by selectively switching the selection valve (98) between: a first position in which the first and second power elements (102, 104) are fluidically coupled in series; and a second position in which the first and second power elements (102, 104) are fluidically coupled in parallel. [11] Closed-loop feedback drive system (12) according to any one of claims 1 to 10, wherein the multi-speed hydraulic motor (60; 100) includes a two-speed hydraulic motor (100) that can be operated in a low-torque, high-speed (ND / HD) mode and a high-torque, low-speed (HD / ND) mode; and wherein the controller (14) is further configured to: to switch the hydraulic motor with two speeds (100) between the ND / HD range mode and the HD / ND mode during operation of the motor grader (10); and to further control the two-speed hydraulic motor (100) to minimize variations in the rotational speed of the share (38) when the two-speed hydraulic motor (100) is switched between ND / HD mode and HD / ND mode. [12] Closed-loop feedback drive system (12) according to claim 11, further comprising a sensor (70) configured to monitor a parameter indicative of share load conditions; wherein the controller (14) is operationally coupled to the second sensor (70) and further configured to determine when to switch the two-speed hydraulic motor (100) between the ND / HD mode and the HD / ND mode, at least partially, based on data received via the sensor (70). [13] Closed-loop feedback drive system (12) according to claim 12, further comprising: a flow line (90-3, 90-4); and a directional control valve (96) which is fluidically coupled to the multi-speed hydraulic motor (60; 100) via the flow line (90-3, 90-4); wherein the sensor (70) comprises a pressure sensor (70-1, 70-2) configured to monitor hydraulic pressure in the flow line (90-3, 90-4); and wherein the control (14) is configured to determine, at least partially based on whether the hydraulic pressure exceeds a predetermined threshold, when the two-speed hydraulic motor (100) should be switched from ND / HD mode to HD / ND mode. [14] Closed-loop feedback drive system (12) according to one of claims 11 to 13, wherein the control (14) is configured to determine, at least partially, on the basis of whether the share (38) is currently in a position above the ground or in a position in the ground, when the two-speed hydraulic motor (100) should be switched from the ND / HD mode to the HD / ND mode. [15] Closed-loop feedback drive system (12) used on board a motor grader (10), wherein the closed-loop feedback drive system (12) comprises: an operator input device (76); a share (38) which is rotatable about a share rotation axis (58); a multi-speed hydraulic motor (60; 100; 132) with a motor output shaft (108) which is mechanically connected to the share (38); a first sensor (70) configured to monitor a parameter indicating a rotational speed of the share (38); and a control unit (14) that is operationally coupled with the operator input device (76), the multi-speed hydraulic motor (60; 100; 132) and the first sensor (70) and is configured to: a target blade rotation speed (v Schar_Ziel ) as a function of operator command signals received via the operator input device (76); a discrepancy (v Schar_Δ ) between the target blade rotation speed (v Schar_Ziel ) and a current share rotation speed (v aktuell ) to determine; and to modify the rotational speed of the motor output shaft (108) to reduce the discrepancy (v Schar_Δ ) between the target blade rotation speed (v Schar_Ziel ) and the current share rotation speed (v aktuell ) to reduce if the discrepancy (v Schar_Δ) exceeds a predetermined threshold. [16] Closed-loop feedback drive system (12) according to claim 15, further comprising: a pump (94); and a directional control valve (96) which is fluidically coupled between the pump (94) and the multi-speed hydraulic motor (60; 100; 132); wherein the control (14) is configured to modify the speed of the motor output shaft (108) by varying the hydraulic fluid flow through the multi-speed hydraulic motor (60; 100; 132) using the directional control valve (96). [17] Closed-loop feedback drive system (12) according to claim 16, wherein the multi-speed hydraulic motor (60; 100; 132) comprises one from the group consisting of a variable displacement hydraulic motor (132) and a two-speed hydraulic motor (100). [18] Closed-loop feedback drive system (12) used on board a motor grader (10), wherein the closed-loop feedback drive system (12) comprises: a two-speed hydraulic motor (100) with a motor output shaft (108), wherein the two-speed hydraulic motor (100) can be operated in a low torque and high rotational speed (ND / HD) mode and a high torque and low rotational speed (HD / ND) mode; a share (38) which is mechanically connected to the hydraulic motor with two speeds (100) and is selectively rotated about a share rotation axis (58); a control unit (14) that is operationally coupled to the two-speed hydraulic motor (100) and configured to: to selectively switch the hydraulic motor with two speeds (100) between the ND / HD mode and the HD / ND mode during operation of the closed-loop feedback drive system (14); and furthermore, to control the speed of the motor output shaft (108) in order to minimize deviations in a share rotation speed when the two-speed hydraulic motor (100) is switched between the ND / HD mode and the HD / ND mode. [19] Closed-loop feedback drive system (12) according to claim 18, further comprising: a pump (94); and a directional control valve (96) which is fluidically coupled between the pump (94) and the two-speed hydraulic motor (100); wherein the control (14) is further operatively coupled and configured with the directional control valve (96) to control an output speed of the dual-speed hydraulic motor (100) by selectively switching the dual-speed hydraulic motor (100) between the ND / HD mode and the HD / ND mode, while the directional control valve (96) is modulated to regulate a rate and direction of the hydraulic fluid flow through the dual-speed hydraulic motor (100). [20] Closed-loop feedback drive system (12) according to claim 18 or 19, further comprising: an operator input device (76); and a sensor configured to monitor a parameter of the closed-loop feedback drive system (12) that specifies a rotational speed of the share (38); wherein the controller (14) is operationally coupled to the operator input device (76) and to the sensor (70) and is further configured to: a target blade rotation speed (v Schar_Ziel ) as a function of operator command signals received via the operator input device (76); a discrepancy (v Δ ) between the target blade rotation speed (v Schar_Ziel ) and a current share rotation speed (v aktuell to appreciate; and if v Δ exceeds a threshold value, setting an output speed of the multi-speed hydraulic motor (60; 100; 132) to v Δ to reduce.

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