Ride control using pressure regulated cylinders

Abstract

A work vehicle includes a work implement movable relative to a frame. A hydraulic control circuit includes a pump, a reservoir and a hydraulic actuator. A hydraulic control valve controls supply of hydraulic fluid between the pump, the actuator and the reservoir. A proportional pressure regulating valve selectively communicates the rod end of the hydraulic actuator with the pump and the reservoir. At least one position sensor is configured to detect a position of the work implement relative to the vehicle frame. A controller includes a ride control mode configured such that the controller controls the proportional pressure regulating valve to actively regulate the fluid pressure at the rod end of the hydraulic actuator as a function of the at least one position signal.

Description

BACKGROUND

[0001] The present disclosure relates to a system for reducing resonant porpoising motion in a motor grader or similar work vehicle when in a transport mode with a working implement raised above the ground surface.DESCRIPTION OF THE PRIOR ART

[0002] Offroad machines tend to lope or porpoise when transporting at higher speeds. The transport motion excites vertical or pitch resonant motion modes involving the vehicle frame and tires of the machine. Lope is a natural phenomenon in motor graders occurring at resonant speeds that correspond to the natural frequency of the vehicle and its tires as a spring mass system. The lope phenomenon is also affected by the distribution of weight on the motor grader, tire inflation pressures, tire size, road conditions, and whether the rims or tires are out of round. Each of these factors can contribute to the natural resonant frequency of the system and thereby change the speed and intensity at which the lope occurs.

[0003] Lope is a particular problem for motor graders because they support a heavy vehicle frame from a plurality of large pneumatic tires without any suspension and damping system between the vehicle frame and the tires. This essentially presents an undamped spring mass system, the resonant frequency of which will be dependent primarily on the mass of the vehicle, the distribution of that mass, and the spring rate provided by the pneumatic tires. Historically lope has been dealt with in motor graders simply by avoiding transport operation at the most problematic speeds for a given road grader. Other adjustments which can be made include checking of rims and tires for roundness and replacement of faulty components, changing inflation pressure of tires, changing size or type of tires with radial tires being preferred, and adjusting weight distribution on the machine.

[0004] One solution that has previously been proposed for reducing lope in a motor grader is the addition of hydraulic accumulators and hydraulic damping in the hydraulic circuits to the rod ends of the lift cylinders which support the grader blade and attached structures from the main vehicle frame of the motor grader. Such systems are seen for example in U.S. Pat. No. 7,793,740 to Thomson et al and U.S. Patent Publication No. 2021 / 0102358 to Fulcher et al.

[0005] This can turn the hydraulically suspended grader blade into a tuned mass damper that is allowed to passively oscillate relative to the vehicle frame and thereby dampen the resonant lope motion of the motor grader.SUMMARY OF THE DISCLOSURE

[0006] The present disclosure provides a system using pressure regulated hydraulic lifting cylinders for the work implement of a motor grader, along with a controller configured to provide a ride control mode which monitors movement of the grader implement relative to the vehicle frame and actively regulates fluid pressure at the rod ends of the hydraulic lifting cylinders as a function of position data representative of the movement of the grader implement relative to the vehicle frame. The disclosed system provides a virtual tuned mass damper without the need for any hydraulic accumulators connected to the rod ends of the hydraulic lifting cylinders.

[0007] In one embodiment, the present disclosure provides a work vehicle including a frame, a work implement movable relative to the frame, and a hydraulic control circuit operable to control movement of the work implement. The hydraulic control circuit includes a pump and a reservoir. A hydraulic actuator is configured to raise and lower the work implement relative to the vehicle frame. The hydraulic actuator includes a head end and a rod end. An operating control valve is configured to control supply of hydraulic fluid from the pump to the actuator and to control return of hydraulic fluid from the actuator to the reservoir. A proportional pressure regulating valve selectively communicates the rod end of the hydraulic actuator with the pump and the reservoir, the proportional pressure regulating valve being configured to regulate fluid pressure at the rod end of the hydraulic actuator. At least one position sensor is configured to detect a position of the work implement relative to the vehicle frame and to generate at least one position signal representative of the position of the work implement relative to the vehicle frame. A controller is configured to receive the at least one position signal, and to control the proportional pressure regulating valve to regulate fluid pressure at rod end of the hydraulic actuator. The controller includes a ride control mode configured such that when the work vehicle is traveling with the work implement raised out of engagement with a ground surface and with the ride control mode enabled, the controller controls the proportional pressure regulating valve to actively regulate the fluid pressure at the rod end of the hydraulic actuator as a function of the at least one position signal.

[0008] In another embodiment a method is provided of reducing a porpoising motion of a work vehicle when the work vehicle is in a traveling mode, the work vehicle including a vehicle frame, a work implement movable relative to the vehicle frame, and a hydraulic control circuit including: a pump; a reservoir; a hydraulic actuator configured to raise and lower the work implement relative to the vehicle frame, the hydraulic actuator including a head end and a rod end; an operating control valve configured to control supply of hydraulic fluid from the pump to the rod end of the hydraulic actuator to raise the work implement relative to the vehicle frame, and to control return of hydraulic fluid from rod end of the hydraulic actuator to the reservoir to lower the work implement relative to the vehicle frame; and a proportional pressure regulating valve selectively communicating the rod end of the hydraulic actuator with the pump and the reservoir, the proportional pressure regulating valve being configured to regulate fluid pressure at the rod end of the hydraulic actuator, the method comprising: detecting a position of the work implement relative to the vehicle frame with at least one position sensor; generating with the at least one position sensor at least one position signal representative of the position of the work implement relative to the vehicle frame; receiving the at least one position signal with a controller, the controller including a ride control mode; and when the work vehicle is traveling with the work implement raised out of engagement with a ground surface and the ride control mode is enabled, controlling the proportional pressure regulating valve to regulate the fluid pressure at the rod end of the hydraulic actuator as a function of the at least one position signal.

[0009] Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a perspective view of a work vehicle in which the disclosed hydraulic control circuit may be implemented.

[0011] FIG. 2 is another perspective view of the work vehicle of FIG. 1.

[0012] FIG. 3 is a schematic diagram of a hydraulic control circuit for one hydraulic actuator according to some embodiments of the disclosure.

[0013] FIG. 4 is a schematic diagram of an electronic control system associated with the hydraulic control circuit of FIG. 3.

[0014] FIG. 5 is a flow diagram showing one possible mode of operation of the variable blade impact system when grading in a float control mode.

[0015] FIG. 6 is a flow diagram showing another possible mode of operation of the variable blade impact system when grading in a float control mode.

[0016] FIG. 7 is a schematic diagram of the hydraulic control circuit for a motor grader incorporating a control circuit like that of FIG. 3 for each of its grader blade lifting actuators.

[0017] FIG. 8 is a schematic depiction of a touch screen control panel for operator inputs describing a current configuration of the motor grader.

[0018] FIG. 9 is schematic diagram of the suspended work implement modeled as a spring, mass, damper system.DETAILED DESCRIPTION

[0019] Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways.

[0020] FIG. 1 illustrates a work vehicle, which is a motor grader (or simply “grader”) 110 in the illustrated embodiment. The grader 110 includes a chassis 114 with a front frame 118 and a rear frame 122. The front frame 118 supports an operator cab 126 that may include an operator seat, controls for operating the grader 110, and the like. A prime mover 130 (e.g., a diesel engine) is supported on the rear frame 122 and is enclosed within a compartment 134. The chassis 114 is supported by front wheels 138 at the front of the grader 110 and by tandem rear wheels 142 at the rear of the grader 110. The front and rear wheels 138 and 142 may be pneumatic tires 138 and 142.

[0021] The grader 110 includes a circle 146 disposed in front of the operator cab 126 and suspended below the front frame 118 by a lifter bracket 150 and a drawbar 154. A work implement, which is a blade 158 or moldboard in the illustrated embodiment, extends laterally across the circle 146. The work implement 158 may be considered to include the circle 146 and drawbar 154 as parts thereof, and in the discussion below of the mass of the work implement 158 that mass will be understood as including all the structures assembled with the work implement 158 that move up and down together when the implement 158 is raised or lowered relative to the front frame 118. The grader 110 includes a blade positioning assembly 162 that allows the position and orientation of the blade 158 to be adjusted. In the illustrated embodiment, a left lift actuator 166 and a right lift actuator 168 extend between the lifter bracket 150 and the circle 146 to tilt, raise, and lower the circle 146 and the blade 158. A shift actuator 170 is provided to shift the blade 158 laterally relative to the front frame 118, and a pitch actuator 174 (FIG. 2) is provided to vary a pitch angle of the blade 158. The blade positioning assembly 162 also includes a rotary actuator 178 to rotate the blade 158 about a vertical axis. In the illustrated embodiment, the various actuators 166, 168, 170, 174, 178 of the blade positioning assembly 162 are hydraulic actuators (e.g., single or double acting cylinders, hydraulic motors, etc.); however, in some embodiments the blade positioning assembly 162 may alternatively include one or more electric motors, pneumatic actuators, or the like in place of any of the hydraulic actuators 166, 168, 170, 174, 178.

[0022] The prime mover 130 is coupled to the rear wheels 142 via a suitable transmission (not shown) to drive the rear wheels 142 (FIG. 1). Alternatively, or additionally, the prime mover 130 may be coupled to the front wheels 138 to drive the front wheels 138. The front frame 118 supports a steering assembly 182 for steering the front wheels 138 (FIG. 2). The steering assembly 182 includes steering actuators 186, which are hydraulic actuators in the illustrated embodiment. In other embodiments, other types of actuators can be used. In addition, in some embodiments, additional steering actuators may be provided such that both the front wheels 138 and the rear wheels 142 may be steerable.

[0023] The front frame 118 of the grader 110 defines a first or front longitudinal axis 190, and the rear frame 122 of the grader 110 defines a second or rear longitudinal axis 194. An articulation joint 198 pivotally couples the front frame 118 and the rear frame 122 and defines a vertical pivot or articulation axis 196 (FIG. 2). The front frame 118 is pivotable relative to the rear frame 122 about the articulation axis 196 to vary an orientation of the front longitudinal axis 190 relative to the rear longitudinal axis 194. The illustrated articulation joint 198 is part of an active articulation assembly 192 that includes first and second articulation actuators 184, 188 extending between the front frame 118 and the rear frame 122 on opposite lateral sides of the articulation axis 196. Each of the illustrated articulation actuators 184, 188 is a double-acting hydraulic cylinder having a head 176 pivotally coupled to the rear frame 122 and a rod 180 pivotally coupled to the front frame 118. In other embodiments, the number and / or arrangement of articulation actuators 184, 188 may vary.

[0024] As shown in FIG. 1, a user interface 172 is positioned in the in the operator cab 126 to permit the user to operate the grader 110. In some embodiments, a user could operate the grader 110 from a location outside of the cab (i.e., by remote control). The illustrated grader 110 includes a controller 402 further described below with reference to FIG. 4. The controller 402 is configured to control operation of various components of the grader 110 in response to input from the user interface 172 and / or one or more controls remote from the grader 110.

[0025] FIG. 3 illustrates a schematic hydraulic control circuit 300 according to some embodiments. The hydraulic control circuit 300 is operable to control movement of the work implement 158, particularly by controlling one or both of the lifting actuators 166 and / or 168. As is further explained below with regard to FIG. 7, some or all of the components of the hydraulic control circuit 300 may be duplicated, with one hydraulic control circuit 300 controlling the first lifting actuator 166 and a second hydraulic control circuit 300 controlling the second lifting actuator 168. The hydraulic control circuit 300 includes a pump 302, which in one embodiment may be a variable output pump 302 including a pump inlet 304 and a pump outlet 306. The pump inlet 304 draws hydraulic fluid from a reservoir or tank 308. The pump 302 will provide hydraulic fluid under pressure to the hydraulic actuator 166 and / or 168 which is in fluid communication with the pump 302 and the reservoir 308 through the hydraulic control circuit 300. The actuator 166 and / or 168 may include a piston 311 attached to a rod 315, with the piston 311 received within a cylinder 313.

[0026] The hydraulic actuator 166 and / or 168 includes a first side 312 and a second side 314. The first side 312 may also be referred to as a head side or head end 312, and the second side 314 may also be referred to as a rod side or rod end 314. An operating control valve 316 is fluidly positioned between the pump 302 and the hydraulic actuator 166 and / or 168 to control the flow of hydraulic fluid between the hydraulic actuator 166 and / or 168 and the pump 302 and the reservoir 308 to lower or raise the grader blade 158. Flow of hydraulic fluid to the head end 312 will push the piston of hydraulic cylinder 166 and / or 168 and the attached implement 158 down. Flow of hydraulic fluid to the rod end 314 will push the piston of hydraulic cylinder 166 and / or 168 up to lift the implement 158. A hydraulic fluid supply line 318 connects the pump outlet 306 with the control valve 316. A hydraulic fluid return line 320 connects the reservoir 308 with the control valve 316.

[0027] The control valve 316 may be a four port, three position electrohydraulic control valve as shown. In a middle position 316.1 flow through the supply and return lines 318 and 320 is blocked. In the left position 316.2 hydraulic fluid from pump 302 flows through supply line 318 to the head end 312 of actuator 166 and / or 168 to lower the implement 158, and hydraulic fluid from rod end 314 returns to reservoir 308 through return line 320. In the right position 316.3 hydraulic fluid hydraulic fluid from pump 302 flows through supply line 318 to the rod end 314 of actuator 166 and / or 168 to raise the implement 158, and hydraulic fluid from head end 312 returns to reservoir 308 through return line 320. The control valve 316 may operate in response to a command signal 316C from the controller 402.

[0028] The hydraulic circuit 300 also includes a variable float control system 322 generally indicated within the dashed box shown in FIG. 3. The variable float control system 322 may also be referred to as a hydraulic actuator pressure regulation system 322. As is further explained below, the hydraulic actuator pressure regulation system 322 allows the operator of the work vehicle 110 to selectively actuate the hydraulic actuator pressure regulation system 322 to add or subtract from the gravitational downward force acting on the implement 158 when the implement 158 is operating in a floating mode. As is also further explained below the hydraulic actuator pressure regulation system 322 also may be utilized to provide a ride control mode of operation during transport operation of the work vehicle 110.

[0029] The pump 302 also provides hydraulic fluid under pressure to a pressure supply line 324. The pressure supply line 324 is communicated with the head end 312 of actuator 166 and / or 168 through a first proportional pressure regulating and / or relief valve (PPRV) 326 and a first electrohydraulic on / off valve 328. The pressure supply line 324 is communicated with the rod end 314 of actuator 166 and / or 168 through a second proportional pressure regulating and / or relief valve (PPRV) 330 and a second electrohydraulic on / off valve 332. The first and second PPRV's 326 and 330 are also communicated through a pressure return line 338 with the reservoir 308.

[0030] The pressure supply line 324 directly communicates the outlet 306 of pump 302 with each of the first and second PPRV's 326 and 330 without any intervening control valve between the pump 302 and the PPRV 326 or 330. This is contrasted to a system like that shown in U.S. Pat. No. 11,408,144 wherein a control valve is located between the pump and the PPRV's.

[0031] A first pressure sensor 334 is configured to sense a pressure at the first side 312 of the hydraulic actuator 166 and / or 168, the first pressure sensor 334 configured to generate a first pressure signal 334S. A second pressure sensor 336 is configured to sense a pressure at the second side 314 of the hydraulic actuator 166 and / or 168, the second pressure sensor 336 configured to generate a second pressure signal 336S.

[0032] As noted, each of the first and second PPRV's 326 and 330 may be a proportional pressure regulating and / or relief valve. As used herein, the term “proportional pressure regulating and / or relief valve” refers to a valve that has the capability to both regulate the fluid pressure provided from the pump 302 to the actuator 166 and / or 168 through the valve, and to relieve excess fluid pressure occurring at the actuator 166 and / or 168 and acting on the valve. The valve does not have to perform both functions at the same time, but it is capable of performing either function when needed. The present disclosure also refers to each of the valves 326 and 330 in the context of the “ride control mode” discussed below as a “proportional pressure regulating valve.” It will be understood that a “proportional pressure regulating valve” may also include a pressure relief valve function, but it is not required to include such a pressure relief valve function.

[0033] As noted, an operator of the working vehicle 110 may selectively enable the hydraulic actuator pressure regulation system 322 by entering an appropriate command to the controller 402 which is further described below with regard to FIG. 4. The operator may also enter a set value for the pressure to be maintained by the PPRV's 326 and 330 on the head end 312 and rod end 314, respectively, of actuator 166 and / or 168. The pressures in the head end 312 and rod end 314 may be independently adjusted. The operator may input such commands via a user interface located in the operator cab 126 as further described below with regard to the controller 402.

[0034] The first PPRV 326 may operate as follows. The first PPRV 326 may be an inversely proportional PPRV, meaning that as the magnitude of an electric command signal 326C to the first PPRV 326 increases, the pressure provided from the first PPRV 326 to the head end 312 of actuator 166 and / or 168 decreases, and vice versa. The command signal 326C may be provided by controller 402 as further described below. The first PPRV 326 may be a spool type valve that is moved by a solenoid 326A between the two positions pictorially depicted in FIG. 3. Excess hydraulic fluid bleeds back to the reservoir 308 via pressure return line 338. Second PPRV 330 may operate in a substantially identical manner to control pressure in rod end 314.

[0035] When the operator enables the hydraulic actuator pressure regulation system 322 the electrohydraulic on / off valves 328 and 332 receive command signals 328C and 332C directing them to move to their open positions. When the operator disables the hydraulic actuator pressure regulation system 322 the command signals 328C and 332C direct the electrohydraulic on / off valves 328 and 332 to move to their closed positions. As pictorially depicted when in the closed positions flow in either direction through the electrohydraulic on / off valves 328 and 332 is blocked by a pair of internal check valves. The first and second electrohydraulic on / off valves 328 and 332 may be configured to directly receive the electrical command signals 328C and 332C from the controller 402, as contrasted to a system like that shown in U.S. Pat. No. 11,408,144 wherein the on / off valves are pilot operated and the electrical command signal goes to a separate control valve which controls flow of pilot hydraulic fluid to the on / off valves.

[0036] In some embodiments the hydraulic actuator pressure regulation system 322 may also include a hydraulic accumulator 340 connected to a pressure conduit 342 between the first PPRV 326 and the first side 312 of the actuator 166 and / or 168. An electrohydraulic on / off valve 344 may be placed between the pressure conduit 342 and the hydraulic accumulator 340 so as to enable or disable the hydraulic accumulator 340 in response to a command signal 344C from the controller 402. In other embodiments the hydraulic accumulator 340 may not be present. The hydraulic accumulator 340 may serve two purposes. First, accumulator 340 may function as a hydraulic spring to cushion the effect of physical impacts on the grader blade 158 and to cushion the corresponding spikes in hydraulic pressure in the hydraulic control circuit 300. Second, in an event where the grader blade 158 is initially held above the ground surface and then released to drop to the ground surface, the accumulator 340 can provide an immediate source of hydraulic fluid to prevent or reduce cavitation in the head end 312 of the actuator 310.

[0037] In some embodiments the hydraulic actuator pressure regulation system 322 may also include an electrohydraulic recirculation valve 346 which allows hydraulic fluid from the pressure supply line 324 to recirculate to a second pump inlet 348 through recirculation line 350. The electrohydraulic recirculation valve 346 and recirculation line 350 allow the variable flow pump 302 to operate at maximum flow rate when the hydraulic control circuit 300 is initially turned on, so as to provide increased hydraulic pressure to the hydraulic control circuit 300. The electrohydraulic recirculation valve 346 may be operated in response to a command signal 346C from the controller 402. In some embodiments the electrohydraulic recirculation valve 346 and recirculation line 350 may not be present.

[0038] The electrohydraulic recirculation valve 346 allows hydraulic fluid from the pressure supply line 324 to recirculate to the second pump inlet 348 through recirculation line 350. The electrohydraulic recirculation valve 346 and recirculation line 350 allow the variable flow pump 302 to operate at maximum flow rate when the hydraulic control circuit 300 is initially turned on, so as to provide increased hydraulic pressure to the hydraulic control circuit 300. The electrohydraulic recirculation valve 346 may be operated in response to a command signal 346C from the controller 402. The use of the electrohydraulic recirculation valve 346 to increase available system operating pressures on start-up is a further means of avoiding or reducing cavitation in the actuator 310 in situations where the hydraulic control circuit 300 would otherwise be unable to initially keep up with the gravitational forces acting on the work implement 158.

[0039] More generally, the controller 402 may be configured to direct the electrohydraulic recirculation valve 346 to open and the variable output pump 302 to increase its output in response to a detected need for increased hydraulic pressure in the hydraulic control circuit.

[0040] As schematically shown in FIG. 7, when implemented in the motor grader 110, the details of the hydraulic control circuit 300 may be duplicated, with a separate control circuit provided for each of the hydraulic lifting actuators 166 and 168 of the motor grader 110. As shown in FIG. 7 a common pump 302 and reservoir 308 may be used for both lifting actuators 166 and 168. Separate pumps and reservoirs could also be used.The Control System:

[0041] As schematically illustrated in FIG. 4, the work vehicle 110 may include a control system 400 including a controller 402. The controller 402 is configured to receive input signals from the various sensors. The signals transmitted from the various sensors to the controller 402 are schematically indicated in FIG. 4 by lines connecting the sensors to the controller with an arrowhead indicating the flow of the signal from the sensor to the controller 402.

[0042] The controller 402 may receive position signals 404S from position sensors 404 associated with the actuator 166 and / or 168. The position sensors 404 may be configured to generate the position signals 404S representative of a position of the piston 311 relative to the cylinder 313 of the hydraulic actuator 166 and / or 168. In some embodiments hydraulic actuator 166 and / or 168 may be in the form of a hydraulic “smart cylinder” in which the position sensor 404 is integrated within the hydraulic actuator 166 and / or 168. In other embodiments the position sensor 404 may be external to the hydraulic actuator 166 and / or 168, for example in the form of a wire rope sensor having one end connected to the cylinder 313 and another end connected to the rod 315 attached to the piston 311.

[0043] The controller 402 may also receive one or more vehicle position signals such as 406S and 408S from position sensors 406 and 408 mounted on the work vehicle 110 (See FIG. 1). The position sensors 406 and 408 may for example be Inertial Measurement Units (IMU's) mounted on the front frame 118 and the drawbar 154.

[0044] The position sensors 404, 406 and 408 may collectively be referred to as at least one position sensor configured to detect a position of the work implement 158 relative to the vehicle frame 118 and to generate at least one position signal 404S, 406S, and 408S representative of the position of the work implement 158 relative to the vehicle frame 118. Depending on the specific types of position sensors selected the controller 402 may determine displacement, velocity and / or acceleration of the work implement 158 relative to the vehicle frame 118.

[0045] Similarly, the controller 402 will generate control signals for controlling the operation of the various valves of the hydraulic control system 300 discussed above.

[0046] Controller 402 includes or may be associated with a processor 410, a computer readable medium 412, a data base 414 and an input / output module or control panel 416 having a display 418. An input / output device 420, such as a keyboard, joystick or other user interface, is provided so that the human operator may input instructions to the controller. It is understood that the controller 402 described herein may be a single controller having all of the described functionality, or it may include multiple controllers wherein the described functionality is distributed among the multiple controllers.

[0047] Various operations, steps or algorithms as described in connection with the controller 402 can be embodied directly in hardware, in a computer program product 422 such as a software module executed by the processor 410, or in a combination of the two. The computer program product 422 can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, or any other form of computer-readable medium 412 known in the art. An exemplary computer-readable medium 412 can be coupled to the processor 410 such that the processor can read information from, and write information to, the memory / storage medium. In the alternative, the medium can be integral to the processor. The processor and the medium can reside in an application specific integrated circuit (ASIC). The ASIC can reside in a user terminal. In the alternative, the processor and the medium can reside as discrete components in a user terminal.

[0048] The term “processor” as used herein may refer to at least general-purpose or specific-purpose processing devices and / or logic as may be understood by one of skill in the art, including but not limited to a microprocessor, a microcontroller, a state machine, and the like. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0049] The control panel 416 may for example be physically located on the work vehicle 110, for example in the cab 126, such that the control panel 416 is supported directly or indirectly from the frame 118. Optionally, or additionally, the control panel 416 or some portion thereof may be remotely located, such as on a handheld device carried by a human operator. Further, in the event of an autonomous machine 110 the control panel 416 or some portion thereof may be located at a remote-control station and may be communicated with the controller 402 wirelessly. The input / output device 420 may include the user interface 172, or may be in addition to the user interface 172.

[0050] As is further described below with regard to various modes of operation the controller 402 is operably connected to the various control valves discussed above and with the variable pump 302, and sends command signals to each of those components. Each command signal is indicated in FIGS. 3 and 4 by the number of the component followed by the suffix “C”. For example, the pump 302 receives a command signal 302C.Open Loop Floating Control Mode-FIG. 5:

[0051] FIG. 5 provides a flow chart of the operating logic for the controller 402 when the controller 402 is configured to perform a grading operation using float control in an open loop control mode 500. In the open loop control mode the controller 402 does not utilize feedback from the pressure sensors 334 and 336, but instead merely sets the selected set points for the PPRV's 326 and 330 and allows the PPRV's to operate. In the open loop control mode 500 the operator first decides whether to enable the open loop control mode as indicated at block 502.

[0052] If the operator chooses to disable the float control as indicated at block 504, the controller 402 will turn off the hydraulic actuator pressure regulation system 322 as indicated at block 506 by moving the on / off valves 328 and 332 to their closed positions. The operator input may be made via the input / output device 420. Then the operator may operate the work implement 158 by controlling the operation of the actuator 166 and / or 168 through the control valve 316.

[0053] If the operator chooses to enable the float control as indicated at block 508 the controller 402 checks at block 510 for other operator inputs determinative of a desired set point for the relief pressures of the PPRV's 326 and 330. For example, the operator may have selected between several available performance settings for the work vehicle 110, and the selected performance setting may have associated therewith a preferred set point for the force to be applied by the actuator 166 and / or 168 to the work implement 158. For example, the actuator 166 and / or 168 may be representative of the left and right lift actuators 166 and 168 which raise and lower the grader blade / work implement 158 on the motor grader 110. There will be a hydraulic control system 300 such as depicted in FIG. 3 associated with each of the left and right lift actuators 166 and 168.

[0054] Simultaneously with the setting of the set points for the PPRV's 326 and 330, the controller 402 will command the on / off valves 328 and 332 to their open positions, as indicated at block 514. Then as indicated at block 516 the grader blade 158 will be in an open loop control floating mode. If for example, the grader blade 158 encounters a large rock or other obstacle creating a sudden pressure increase in the head end 312 of the left and / or right lift actuators 166 and 168, the respective PPRV 326 associated with that head end 312 will relieve that excess pressure to the reservoir 308 via the return line 324.

[0055] In the context of the operation just described the first PPRV 326 may be described as a first proportional pressure regulating and / or relief valve (PPRV) 326 fluidly positioned between the reservoir 308 and the first side 312 of the hydraulic actuator 166 and / or 168, the first PPRV 326 being configured to permit flow of fluid from the first side 312 of actuator 166 and / or 168 to the reservoir 308 in response to a pressure at the first side 312 of the hydraulic actuator 166 and / or 168 being greater than a first predetermined pressure value. In this context, the first predetermined pressure value would be the value achieved by the set point of the first PPRV 326, regardless of whether that value was exactly equal to the desired value which the operator was attempting to achieve, or which the controller 402 selected based on the operator's selected performance setting.

[0056] Similarly, the second PPRV 330 may be described as being configured to permit flow of fluid from the second side 314 of the actuator 166 and / or 168 to the reservoir 308 in response to the pressure at the second side 314 of the hydraulic actuator 166 and / or 168 being greater than a second predetermined pressure value associated with the set point for the second PPRV 330.

[0057] It will be appreciated that in the open loop control mode, the setting of the set points for the PPRV's 326 and 330 is done by a single command signal from the controller 402 based on the operator input, such as the selected performance setting. The controller 402 will be configured to provide an appropriate command signal to the PPRV's which is determined to be correct for the desired downward force to be maintained on the grader blade 158. The command signal for a given set point may be determined from historical data, but there is no feedback or confirmation that the desired down force has been achieved. The selected set point may add force to the gravitational weight of the grader blade 158 by increasing the pressure in the head end 312 of the actuators, or it may reduce the effective gravitational weight of the grader blade 158 by increasing the pressure in the rod end 314. The set points for the PPRV's will be associated with a desired pressure value to be maintained at the head end 312 and / or rod end 314, but there is no feedback or confirmation that the exact desired pressure value has been achieved.Closed Loop Floating Control Mode-FIG. 6:

[0058] FIG. 6 provides a flow chart of the operating logic for the controller 402 when the controller 402 is configured to perform a grading operation in a closed loop control mode 600. In the closed loop control mode 600 the controller 402 uses feedback from the pressure sensors 334 and 336 to continuously adjust the set points of the PPRV's 326 and 330 if and as needed to achieve a desired pressure in the head ends 312 and rod ends 314 and corresponding down force on the grader blade 158.

[0059] In the closed loop control mode 600 the operator first decides whether to enable the closed loop control mode as indicated at block 602. If the operator chooses to disable the float control as indicated at block 604, the controller 402 will turn off the hydraulic actuator pressure regulation system 322 as indicated at block 606 by moving the on / off valves 328 and 332 to their closed positions. The operator input may be made via the input / output device 420. Then the operator may operate the work implement 158 by controlling the operation of the actuator 166 and / or 168 through the control valve 316.

[0060] If the operator chooses to enable the float control as indicated at block 608 the controller 402 checks at block 610 for other operator inputs determinative of a desired set point for the relief pressures of the PPRV's 326 and 330. For example, the operator may have selected between several available performance settings for the work vehicle 110, and the selected performance setting may have associated therewith a preferred set point for the force to be applied by the left and right lift actuators 166 and 168 which raise and lower the grader blade / work implement 158 on the motor grader 110. There will be a hydraulic control system 300 such as depicted in FIG. 3 associated with each of the left and right lift actuators 166 and 168.

[0061] Simultaneously with the setting of the set points for the PPRV's 326 and 330, the controller 402 will command the on / off valves 328 and 332 to their open positions, as indicated at block 614.

[0062] After receiving the base setting of the set point or set value for the PPRV's at block 610, the controller 402 checks at block 612 for input signals 334S and / or 336S from the pressure sensors 334 and 336 associated with the head end 312 and rod end 314, respectively, of the associated hydraulic actuator 166 and / or 168. Then as indicated at block 616 the controller 402 calculates an adjusted command signal 326C and / or 330C to the PPRV's to achieve the desired pressure value at the actuator 166 and / or 168. For example, if the desired floating pressure in the head end 312 of the hydraulic actuator 166 and / or 168 is 1000 psi the controller 402 may determine an appropriate command signal 326C and / or 330C based on preprogrammed information as it does in block 510 of the open loop control mode, but now in block 616 the controller 402 can determine whether it needs to adjust that command signal up or down to achieve the desired downward force at head end 312. At block 618 the controller 402 sends the adjusted command signal 326C and / or 330C to the PPRV's based on the sensor feedback from the pressure sensors 334 and 336. At block 620 the PPRV's 326 and / or 330 make the commanded adjustment in setting. As a result of the feedback from the pressure sensors 334 and 336 the controller directs adjustment of the PPRV's such that the actual pressure achieved at the head end 312 and rod end 314 is closer to the set value that it was before the adjustment.

[0063] Then as indicated at block 622 the PPRV's 326 and 330 control the pressure applied to the actuator 166 and / or 168 so that the grader blade 158“floats” with the desired down force. If the grader blade 158 encounters a large rock or other obstacle creating a sudden pressure increase in the head end 312 of the left and / or right lift actuators 166 and 168, the respective PPRV 326 associated with that head end 312 will relieve that excess pressure to the reservoir 308 via the return line 324. As indicated at block 624, the pressure sensors 334 and 336 continuously monitor the actual pressure in head end 312 and rod end 314 and feed that information back to controller 402 as signals 334S and 336S.

[0064] In the context of the closed loop control mode 600, the controller 402 may be described as being in electrical communication with the control valve 316, the first and second PPRV's 326 and 330, and the first and second pressure sensors 334 and 336, the controller 402 being configured to receive a set value for the first predetermined pressure value (such as through the operator's performance setting), and to receive the first pressure signal 334S from the first pressure sensor 334, the controller 402 being configured to send a command signal 326C to the first PPRV 326 to adjust the first predetermined pressure value based at least in part on the set value for the first predetermined pressure value and based at least in part on the first pressure signal 334S.Ride Control Mode:

[0065] The hydraulic control circuit 300, and particularly the hydraulic actuator pressure regulation system 322 thereof including its first and second PPRV's provides multiple functionalities. In addition to providing the various float control modes of grading operation explained above, it may be controlled in a manner to provide a “ride control” mode of operation to reduce resonant loping or porpoising motion of the work vehicle 110 during transport of the vehicle at relatively high speeds with the work implement 158 raised above the ground surface.

[0066] As previously noted, some prior offroad machines have mitigated such porpoising by adding hydraulic accumulators to the rod end of the hydraulic cylinders supporting work implements or other attachments from the vehicle frame, thus turning the attachments into tuned mass dampers. In the context of a motor grader like the motor grader 110 this would include adding a hydraulic accumulator connected to the rod end 314 of each of the lifting actuators 166 and 168 so that the suspended weight of the work implement 158, circle 146 and drawbar 154 would be supported in a damped resilient manner. The operating principle of a tuned mass damper is that some of the kinetic energy of the larger structure (the porpoising motor grader) bouncing at its resonant frequency, is dissipated in the motion of the tuned mass damper so that the motion of the larger structure is reduced.

[0067] The ride control mode of the present disclosure does not include any hydraulic accumulator connected to the rod end of its cylinders, but instead actively regulates fluid pressure at the hydraulic actuators 166 and 168 using the hydraulic actuator pressure regulation system 322. This is accomplished without the expense of, or commitment of space on the vehicle 110 to, any hydraulic accumulators connected to the rod ends of the hydraulic actuators 166 and 168. The controller 402 monitors motion of the work implement158 relative to the vehicle frame 118 by receiving the position signals from the position sensors 404, 406 and 408, and controls the PPRV's connected to the rod ends of the hydraulic actuators 166 and 168 as a function of those position signals. The controller 402 may also control the PPRV's connected to the head ends of the hydraulic actuators 166 and 168 as a function of those position signals. The function applied by the ride control mode controls movement of the work implement 158, including the circle 146 and draw bar 154 attached to the work implement 158, relative to the vehicle frame 118 so that such movement mimics the relative motion of the work implement 158 that the use of a hydraulic accumulator and hydraulic damper would achieve, and the resulting configuration provides a “virtual” tuned mass damper without the cost or mechanical complexity of adding hydraulic accumulators to the rod ends of the hydraulic actuators 166 and 168 of the hydraulic circuit 300.

[0068] The application of this disclosure to any given work vehicle is highly dependent on the physical characteristics of the particular work vehicle and its attached work implement(s). One important factor in such analysis and design is to determine the resonant frequency of the problematic porpoising motion of the work vehicle. This is a function of the mass of the work vehicle and all attachments carried by the work vehicle, the distribution of that mass, the location of the pneumatic tires, the spring rates of the pneumatic tires, and the inherent structural damping present in all of the above. For a given work vehicle this resonant frequency will be affected by certain variables which may change from day to day in the operating life of the work vehicle.

[0069] The controller 402 may be configured to take these variables into account by providing the operator with the input / output device 420 configured in a way that the operator may make operator inputs representative of a configuration of the work vehicle. Such operator inputs may include the identification of selectable attachments carried by the vehicle 110. For example, FIG. 8 schematically illustrates the input / output device 420 in the form of a touch screen display 420 in which the operator may indicate the type of work implement 158 currently mounted on the work vehicle 110 by virtual buttons 428 and 430, whether a ripper is mounted on the work vehicle 110 by virtual button 432, the type of tires on the work vehicle 110 by virtual buttons 434 and 436, and the current inflation pressure of the work vehicle 110 at input space 438. The controller 402 may be configured for a given work vehicle 110 to calculate or estimate the resonant frequency of any expected porpoising motion of the work vehicle 110 with the current configuration. This may be described as calculating or estimating a vehicle frame porpoising resonance frequency based in part on a mass of the selected attachments carried by the work vehicle 110 and / or based in part on a spring rate of the selected pneumatic tires.

[0070] The controller 402 may also estimate the resonant frequency of the work vehicle 110 by observing the chassis motion, especially using the signals from the IMU's 406 and 408 attached to the vehicle frame 118 and the drawbar 154.

[0071] The touch screen 420 may also provide options whereby the operator of the work vehicle 110 may selectively engage and disengage the ride control mode of the controller 400, such as by virtual ON and OFF buttons 424 and 426.

[0072] The controller 400 may be further configured, when in ride control mode, to adjust the control function of the ride control mode based on the expected resonant frequency of the porpoising motion. The determination of the desired control function may then be determined by the controller 400 based on a modeling of the mechanical system supporting the work implement 158.

[0073] FIG. 9 schematically illustrates the work implement 158, circle 146 and draw bar 154 as a suspended mass, suspended by a linear spring of spring constant “k” and a linear damper of damping constant “b”. The forces acting on such an actual spring, mass, damper system may be described by the following equation:F=m⁢a+ks⁢x+bvwhere:m=mas⁢ (of⁢ the⁢ work⁢ implement⁢ 158,circle⁢ 146⁢ and⁢ draw⁢ bar⁢ 154);a=acceleration⁢ of⁢ the⁢ mass;k=spring⁢ constant⁢ of⁢ the⁢ spring;x=displacement⁢ of⁢ the⁢ mass⁢ and⁢ spring;b=damping⁢ constant⁢ of⁢ the⁢ damper;andv=velocity⁢ of⁢ the⁢ mass;

[0074] The displacement “x”, the velocity “v” and / or the acceleration “a” of the work implement 158 relative to the vehicle frame 118 may be detected by the one or more position sensors 404, 406, 408 discussed above. The force “F” supporting the mass of the work implement 158, circle 146 and draw bar 154 is equal to the pressure in the rod ends of the lifting actuators 166, 168 times the cross-sectional area across the pistons of the actuators.

[0075] Thus, if the pressure in the rod ends is controlled as a linear function of the displacement “x”, the force applied to the work implement 158 by the lifting actuators 166, 168 will be similar to that which would have resulted from the use of hydraulic accumulators connected to the rod ends of the lifting actuators 166, 168, with those accumulators providing a spring constant “k” equal to the linear function of the displacement “x” applied by the control function of the ride control mode. Such a control function component may be described as a virtual spring component.

[0076] And if the pressure in the rod ends is controlled as a linear function of the velocity “v”, the force applied to the work implement 158 by the lifting actuators 166, 168 will be similar to that which would have resulted from the use of hydraulic dampers between the work implement 158 and the vehicle frame 118, with those hydraulic dampers providing a damping constant “b” equal to the linear function of the velocity “v” applied by the control function of the ride control mode. Such a control function component may be described as a virtual damper component.

[0077] And if the pressure in the rod ends is controlled as a linear function of the acceleration “a”, the force applied to the work implement 158 by the lifting actuators 166, 168 will be similar to that which would have resulted from a change in the mass of the work implement 158 and attached structures. Such a control function component may be described as a virtual mass component.

[0078] The actual control function applied may be complex and may combine or estimate any combination of the above described virtual features.

[0079] Also, the control function may be determined through experimental trial and error analysis instead of or in addition to computational techniques.

[0080] Although the discussion above is primarily in the context of regulating the pressure in the rod ends of the lifting actuators 166 and 168, it will be understood that during a porpoising motion of the vehicle there will also be pressure surges in the head ends of the lifting actuators 166 and 168 and the controller 402 may regulate the pressures in both the rod ends and the head ends of the lifting actuators to control the porpoising motion.

[0081] In one example, the work implement 158 has been lifted out of engagement with the ground surface by the action of the operating control valve 316 in its position 316.3 directing hydraulic fluid into the rod end 314 of the lift cylinder 166 or 168 to raise the work implement 158 to the desired elevation relative to the front frame 118. Then the operating control valve 316 is moved to its closed position 316.1 and the hydraulic actuator pressure regulation system 322 is enabled. When the controller 402 enables the ride control mode the proportional pressure regulating valve 330 is configured to regulate fluid pressure at the rod end 314 of the lift cylinder 166 or 168. If there is no loping motion of the work vehicle occurring as the vehicle 110 travels across the ground, the required pressure in the rod ends 314 to hold the work implement in the selected raised position is simply the pressure required to offset the static weight of the work implement 158 and attached structures. If the work vehicle 110 begins to lope, the inertia of the work implement 158 and attached structures will cause the pressure in the rod end 314 to surge as the work vehicle 110 plunges downward compressing its tires, and will cause the pressure in the head ends 312 to surge when the work vehicle bounces upward towards the apex of its porpoising motion. The position sensors 404, 406, 408 will detect downward and / or upward movement of the work implement 158 relative to the work vehicle frame 118. If the control function of the control mode is constructed to mimic the use of a hydraulic accumulator and hydraulic damper connected to the rod end 314, then the controller 402 may regulate the pressure in the rod end 314 to have a virtual spring component and a virtual damping component. The virtual spring component may be dependent on a detected vertical displacement of the work implement 158 relative to the vehicle frame 118. The virtual damping component may be dependent on a detected velocity of the work implement 158 relative to the vehicle frame 118.

[0082] It will be understood that when using two lifting cylinders 166 and 168, as is typically done in a motor grader 110, there will be a proportional pressure regulating valve 330 associated with each lifting cylinder 166 and 168. The two lifting cylinders 166 and 168 may be controlled to move in the same direction to lift or lower the work implement. And the two lifting cylinders 166 and 168 may be moved in opposite directions to tilt the work implement.

[0083] It will also be understood that there may be active regulation of the pressure in the rod ends 312 of each of the lifting cylinders 166 and 168. When the controller 402 enables the ride control mode the proportional pressure regulating valve 326 is configured to regulate fluid pressure at the head end 312 of the lift cylinder 166 or 168. A similar control function to that described above may be applied so that both the rod end pressure and the head end pressure are controlled to emulate a tuned mass damper.

[0084] Thus, it is seen that the apparatus and methods of the embodiments disclosed herein readily achieve the ends and advantages mentioned as well as those inherent therein. While certain preferred embodiments have been illustrated and described for purposes of the present disclosure, numerous changes in the arrangement and construction of parts and steps may be made by those skilled in the art, which changes are encompassed within the scope and spirit of the present invention as defined by the appended claims.

Examples

Embodiment Construction

[0019]Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways.

[0020]FIG. 1 illustrates a work vehicle, which is a motor grader (or simply “grader”) 110 in the illustrated embodiment. The grader 110 includes a chassis 114 with a front frame 118 and a rear frame 122. The front frame 118 supports an operator cab 126 that may include an operator seat, controls for operating the grader 110, and the like. A prime mover 130 (e.g., a diesel engine) is supported on the rear frame 122 and is enclosed within a compartment 134. The chassis 114 is supported by front wheels 138 at the front of the grader 110 and by tandem rear wheels 142 at the rear of the gra...

BACKGROUND

[0001] The present disclosure relates to a system for reducing resonant porpoising motion in a motor grader or similar work vehicle when in a transport mode with a working implement raised above the ground surface.DESCRIPTION OF THE PRIOR ART

[0002] Offroad machines tend to lope or porpoise when transporting at higher speeds. The transport motion excites vertical or pitch resonant motion modes involving the vehicle frame and tires of the machine. Lope is a natural phenomenon in motor graders occurring at resonant speeds that correspond to the natural frequency of the vehicle and its tires as a spring mass system. The lope phenomenon is also affected by the distribution of weight on the motor grader, tire inflation pressures, tire size, road conditions, and whether the rims or tires are out of round. Each of these factors can contribute to the natural resonant frequency of the system and thereby change the speed and intensity at which the lope occurs.

[0003] Lope is a particular problem for motor graders because they support a heavy vehicle frame from a plurality of large pneumatic tires without any suspension and damping system between the vehicle frame and the tires. This essentially presents an undamped spring mass system, the resonant frequency of which will be dependent primarily on the mass of the vehicle, the distribution of that mass, and the spring rate provided by the pneumatic tires. Historically lope has been dealt with in motor graders simply by avoiding transport operation at the most problematic speeds for a given road grader. Other adjustments which can be made include checking of rims and tires for roundness and replacement of faulty components, changing inflation pressure of tires, changing size or type of tires with radial tires being preferred, and adjusting weight distribution on the machine.

[0004] One solution that has previously been proposed for reducing lope in a motor grader is the addition of hydraulic accumulators and hydraulic damping in the hydraulic circuits to the rod ends of the lift cylinders which support the grader blade and attached structures from the main vehicle frame of the motor grader. Such systems are seen for example in U.S. Pat. No. 7,793,740 to Thomson et al and U.S. Patent Publication No. 2021 / 0102358 to Fulcher et al.

[0005] This can turn the hydraulically suspended grader blade into a tuned mass damper that is allowed to passively oscillate relative to the vehicle frame and thereby dampen the resonant lope motion of the motor grader.SUMMARY OF THE DISCLOSURE

[0006] The present disclosure provides a system using pressure regulated hydraulic lifting cylinders for the work implement of a motor grader, along with a controller configured to provide a ride control mode which monitors movement of the grader implement relative to the vehicle frame and actively regulates fluid pressure at the rod ends of the hydraulic lifting cylinders as a function of position data representative of the movement of the grader implement relative to the vehicle frame. The disclosed system provides a virtual tuned mass damper without the need for any hydraulic accumulators connected to the rod ends of the hydraulic lifting cylinders.

[0007] In one embodiment, the present disclosure provides a work vehicle including a frame, a work implement movable relative to the frame, and a hydraulic control circuit operable to control movement of the work implement. The hydraulic control circuit includes a pump and a reservoir. A hydraulic actuator is configured to raise and lower the work implement relative to the vehicle frame. The hydraulic actuator includes a head end and a rod end. An operating control valve is configured to control supply of hydraulic fluid from the pump to the actuator and to control return of hydraulic fluid from the actuator to the reservoir. A proportional pressure regulating valve selectively communicates the rod end of the hydraulic actuator with the pump and the reservoir, the proportional pressure regulating valve being configured to regulate fluid pressure at the rod end of the hydraulic actuator. At least one position sensor is configured to detect a position of the work implement relative to the vehicle frame and to generate at least one position signal representative of the position of the work implement relative to the vehicle frame. A controller is configured to receive the at least one position signal, and to control the proportional pressure regulating valve to regulate fluid pressure at rod end of the hydraulic actuator. The controller includes a ride control mode configured such that when the work vehicle is traveling with the work implement raised out of engagement with a ground surface and with the ride control mode enabled, the controller controls the proportional pressure regulating valve to actively regulate the fluid pressure at the rod end of the hydraulic actuator as a function of the at least one position signal.

[0008] In another embodiment a method is provided of reducing a porpoising motion of a work vehicle when the work vehicle is in a traveling mode, the work vehicle including a vehicle frame, a work implement movable relative to the vehicle frame, and a hydraulic control circuit including: a pump; a reservoir; a hydraulic actuator configured to raise and lower the work implement relative to the vehicle frame, the hydraulic actuator including a head end and a rod end; an operating control valve configured to control supply of hydraulic fluid from the pump to the rod end of the hydraulic actuator to raise the work implement relative to the vehicle frame, and to control return of hydraulic fluid from rod end of the hydraulic actuator to the reservoir to lower the work implement relative to the vehicle frame; and a proportional pressure regulating valve selectively communicating the rod end of the hydraulic actuator with the pump and the reservoir, the proportional pressure regulating valve being configured to regulate fluid pressure at the rod end of the hydraulic actuator, the method comprising: detecting a position of the work implement relative to the vehicle frame with at least one position sensor; generating with the at least one position sensor at least one position signal representative of the position of the work implement relative to the vehicle frame; receiving the at least one position signal with a controller, the controller including a ride control mode; and when the work vehicle is traveling with the work implement raised out of engagement with a ground surface and the ride control mode is enabled, controlling the proportional pressure regulating valve to regulate the fluid pressure at the rod end of the hydraulic actuator as a function of the at least one position signal.

[0009] Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a perspective view of a work vehicle in which the disclosed hydraulic control circuit may be implemented.

[0011] FIG. 2 is another perspective view of the work vehicle of FIG. 1.

[0012] FIG. 3 is a schematic diagram of a hydraulic control circuit for one hydraulic actuator according to some embodiments of the disclosure.

[0013] FIG. 4 is a schematic diagram of an electronic control system associated with the hydraulic control circuit of FIG. 3.

[0014] FIG. 5 is a flow diagram showing one possible mode of operation of the variable blade impact system when grading in a float control mode.

[0015] FIG. 6 is a flow diagram showing another possible mode of operation of the variable blade impact system when grading in a float control mode.

[0016] FIG. 7 is a schematic diagram of the hydraulic control circuit for a motor grader incorporating a control circuit like that of FIG. 3 for each of its grader blade lifting actuators.

[0017] FIG. 8 is a schematic depiction of a touch screen control panel for operator inputs describing a current configuration of the motor grader.

[0018] FIG. 9 is schematic diagram of the suspended work implement modeled as a spring, mass, damper system.DETAILED DESCRIPTION

[0019] Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways.

[0020] FIG. 1 illustrates a work vehicle, which is a motor grader (or simply “grader”) 110 in the illustrated embodiment. The grader 110 includes a chassis 114 with a front frame 118 and a rear frame 122. The front frame 118 supports an operator cab 126 that may include an operator seat, controls for operating the grader 110, and the like. A prime mover 130 (e.g., a diesel engine) is supported on the rear frame 122 and is enclosed within a compartment 134. The chassis 114 is supported by front wheels 138 at the front of the grader 110 and by tandem rear wheels 142 at the rear of the grader 110. The front and rear wheels 138 and 142 may be pneumatic tires 138 and 142.

[0021] The grader 110 includes a circle 146 disposed in front of the operator cab 126 and suspended below the front frame 118 by a lifter bracket 150 and a drawbar 154. A work implement, which is a blade 158 or moldboard in the illustrated embodiment, extends laterally across the circle 146. The work implement 158 may be considered to include the circle 146 and drawbar 154 as parts thereof, and in the discussion below of the mass of the work implement 158 that mass will be understood as including all the structures assembled with the work implement 158 that move up and down together when the implement 158 is raised or lowered relative to the front frame 118. The grader 110 includes a blade positioning assembly 162 that allows the position and orientation of the blade 158 to be adjusted. In the illustrated embodiment, a left lift actuator 166 and a right lift actuator 168 extend between the lifter bracket 150 and the circle 146 to tilt, raise, and lower the circle 146 and the blade 158. A shift actuator 170 is provided to shift the blade 158 laterally relative to the front frame 118, and a pitch actuator 174 (FIG. 2) is provided to vary a pitch angle of the blade 158. The blade positioning assembly 162 also includes a rotary actuator 178 to rotate the blade 158 about a vertical axis. In the illustrated embodiment, the various actuators 166, 168, 170, 174, 178 of the blade positioning assembly 162 are hydraulic actuators (e.g., single or double acting cylinders, hydraulic motors, etc.); however, in some embodiments the blade positioning assembly 162 may alternatively include one or more electric motors, pneumatic actuators, or the like in place of any of the hydraulic actuators 166, 168, 170, 174, 178.

[0022] The prime mover 130 is coupled to the rear wheels 142 via a suitable transmission (not shown) to drive the rear wheels 142 (FIG. 1). Alternatively, or additionally, the prime mover 130 may be coupled to the front wheels 138 to drive the front wheels 138. The front frame 118 supports a steering assembly 182 for steering the front wheels 138 (FIG. 2). The steering assembly 182 includes steering actuators 186, which are hydraulic actuators in the illustrated embodiment. In other embodiments, other types of actuators can be used. In addition, in some embodiments, additional steering actuators may be provided such that both the front wheels 138 and the rear wheels 142 may be steerable.

[0023] The front frame 118 of the grader 110 defines a first or front longitudinal axis 190, and the rear frame 122 of the grader 110 defines a second or rear longitudinal axis 194. An articulation joint 198 pivotally couples the front frame 118 and the rear frame 122 and defines a vertical pivot or articulation axis 196 (FIG. 2). The front frame 118 is pivotable relative to the rear frame 122 about the articulation axis 196 to vary an orientation of the front longitudinal axis 190 relative to the rear longitudinal axis 194. The illustrated articulation joint 198 is part of an active articulation assembly 192 that includes first and second articulation actuators 184, 188 extending between the front frame 118 and the rear frame 122 on opposite lateral sides of the articulation axis 196. Each of the illustrated articulation actuators 184, 188 is a double-acting hydraulic cylinder having a head 176 pivotally coupled to the rear frame 122 and a rod 180 pivotally coupled to the front frame 118. In other embodiments, the number and / or arrangement of articulation actuators 184, 188 may vary.

[0024] As shown in FIG. 1, a user interface 172 is positioned in the in the operator cab 126 to permit the user to operate the grader 110. In some embodiments, a user could operate the grader 110 from a location outside of the cab (i.e., by remote control). The illustrated grader 110 includes a controller 402 further described below with reference to FIG. 4. The controller 402 is configured to control operation of various components of the grader 110 in response to input from the user interface 172 and / or one or more controls remote from the grader 110.

[0025] FIG. 3 illustrates a schematic hydraulic control circuit 300 according to some embodiments. The hydraulic control circuit 300 is operable to control movement of the work implement 158, particularly by controlling one or both of the lifting actuators 166 and / or 168. As is further explained below with regard to FIG. 7, some or all of the components of the hydraulic control circuit 300 may be duplicated, with one hydraulic control circuit 300 controlling the first lifting actuator 166 and a second hydraulic control circuit 300 controlling the second lifting actuator 168. The hydraulic control circuit 300 includes a pump 302, which in one embodiment may be a variable output pump 302 including a pump inlet 304 and a pump outlet 306. The pump inlet 304 draws hydraulic fluid from a reservoir or tank 308. The pump 302 will provide hydraulic fluid under pressure to the hydraulic actuator 166 and / or 168 which is in fluid communication with the pump 302 and the reservoir 308 through the hydraulic control circuit 300. The actuator 166 and / or 168 may include a piston 311 attached to a rod 315, with the piston 311 received within a cylinder 313.

[0026] The hydraulic actuator 166 and / or 168 includes a first side 312 and a second side 314. The first side 312 may also be referred to as a head side or head end 312, and the second side 314 may also be referred to as a rod side or rod end 314. An operating control valve 316 is fluidly positioned between the pump 302 and the hydraulic actuator 166 and / or 168 to control the flow of hydraulic fluid between the hydraulic actuator 166 and / or 168 and the pump 302 and the reservoir 308 to lower or raise the grader blade 158. Flow of hydraulic fluid to the head end 312 will push the piston of hydraulic cylinder 166 and / or 168 and the attached implement 158 down. Flow of hydraulic fluid to the rod end 314 will push the piston of hydraulic cylinder 166 and / or 168 up to lift the implement 158. A hydraulic fluid supply line 318 connects the pump outlet 306 with the control valve 316. A hydraulic fluid return line 320 connects the reservoir 308 with the control valve 316.

[0027] The control valve 316 may be a four port, three position electrohydraulic control valve as shown. In a middle position 316.1 flow through the supply and return lines 318 and 320 is blocked. In the left position 316.2 hydraulic fluid from pump 302 flows through supply line 318 to the head end 312 of actuator 166 and / or 168 to lower the implement 158, and hydraulic fluid from rod end 314 returns to reservoir 308 through return line 320. In the right position 316.3 hydraulic fluid hydraulic fluid from pump 302 flows through supply line 318 to the rod end 314 of actuator 166 and / or 168 to raise the implement 158, and hydraulic fluid from head end 312 returns to reservoir 308 through return line 320. The control valve 316 may operate in response to a command signal 316C from the controller 402.

[0028] The hydraulic circuit 300 also includes a variable float control system 322 generally indicated within the dashed box shown in FIG. 3. The variable float control system 322 may also be referred to as a hydraulic actuator pressure regulation system 322. As is further explained below, the hydraulic actuator pressure regulation system 322 allows the operator of the work vehicle 110 to selectively actuate the hydraulic actuator pressure regulation system 322 to add or subtract from the gravitational downward force acting on the implement 158 when the implement 158 is operating in a floating mode. As is also further explained below the hydraulic actuator pressure regulation system 322 also may be utilized to provide a ride control mode of operation during transport operation of the work vehicle 110.

[0029] The pump 302 also provides hydraulic fluid under pressure to a pressure supply line 324. The pressure supply line 324 is communicated with the head end 312 of actuator 166 and / or 168 through a first proportional pressure regulating and / or relief valve (PPRV) 326 and a first electrohydraulic on / off valve 328. The pressure supply line 324 is communicated with the rod end 314 of actuator 166 and / or 168 through a second proportional pressure regulating and / or relief valve (PPRV) 330 and a second electrohydraulic on / off valve 332. The first and second PPRV's 326 and 330 are also communicated through a pressure return line 338 with the reservoir 308.

[0030] The pressure supply line 324 directly communicates the outlet 306 of pump 302 with each of the first and second PPRV's 326 and 330 without any intervening control valve between the pump 302 and the PPRV 326 or 330. This is contrasted to a system like that shown in U.S. Pat. No. 11,408,144 wherein a control valve is located between the pump and the PPRV's.

[0031] A first pressure sensor 334 is configured to sense a pressure at the first side 312 of the hydraulic actuator 166 and / or 168, the first pressure sensor 334 configured to generate a first pressure signal 334S. A second pressure sensor 336 is configured to sense a pressure at the second side 314 of the hydraulic actuator 166 and / or 168, the second pressure sensor 336 configured to generate a second pressure signal 336S.

[0032] As noted, each of the first and second PPRV's 326 and 330 may be a proportional pressure regulating and / or relief valve. As used herein, the term “proportional pressure regulating and / or relief valve” refers to a valve that has the capability to both regulate the fluid pressure provided from the pump 302 to the actuator 166 and / or 168 through the valve, and to relieve excess fluid pressure occurring at the actuator 166 and / or 168 and acting on the valve. The valve does not have to perform both functions at the same time, but it is capable of performing either function when needed. The present disclosure also refers to each of the valves 326 and 330 in the context of the “ride control mode” discussed below as a “proportional pressure regulating valve.” It will be understood that a “proportional pressure regulating valve” may also include a pressure relief valve function, but it is not required to include such a pressure relief valve function.

[0033] As noted, an operator of the working vehicle 110 may selectively enable the hydraulic actuator pressure regulation system 322 by entering an appropriate command to the controller 402 which is further described below with regard to FIG. 4. The operator may also enter a set value for the pressure to be maintained by the PPRV's 326 and 330 on the head end 312 and rod end 314, respectively, of actuator 166 and / or 168. The pressures in the head end 312 and rod end 314 may be independently adjusted. The operator may input such commands via a user interface located in the operator cab 126 as further described below with regard to the controller 402.

[0034] The first PPRV 326 may operate as follows. The first PPRV 326 may be an inversely proportional PPRV, meaning that as the magnitude of an electric command signal 326C to the first PPRV 326 increases, the pressure provided from the first PPRV 326 to the head end 312 of actuator 166 and / or 168 decreases, and vice versa. The command signal 326C may be provided by controller 402 as further described below. The first PPRV 326 may be a spool type valve that is moved by a solenoid 326A between the two positions pictorially depicted in FIG. 3. Excess hydraulic fluid bleeds back to the reservoir 308 via pressure return line 338. Second PPRV 330 may operate in a substantially identical manner to control pressure in rod end 314.

[0035] When the operator enables the hydraulic actuator pressure regulation system 322 the electrohydraulic on / off valves 328 and 332 receive command signals 328C and 332C directing them to move to their open positions. When the operator disables the hydraulic actuator pressure regulation system 322 the command signals 328C and 332C direct the electrohydraulic on / off valves 328 and 332 to move to their closed positions. As pictorially depicted when in the closed positions flow in either direction through the electrohydraulic on / off valves 328 and 332 is blocked by a pair of internal check valves. The first and second electrohydraulic on / off valves 328 and 332 may be configured to directly receive the electrical command signals 328C and 332C from the controller 402, as contrasted to a system like that shown in U.S. Pat. No. 11,408,144 wherein the on / off valves are pilot operated and the electrical command signal goes to a separate control valve which controls flow of pilot hydraulic fluid to the on / off valves.

[0036] In some embodiments the hydraulic actuator pressure regulation system 322 may also include a hydraulic accumulator 340 connected to a pressure conduit 342 between the first PPRV 326 and the first side 312 of the actuator 166 and / or 168. An electrohydraulic on / off valve 344 may be placed between the pressure conduit 342 and the hydraulic accumulator 340 so as to enable or disable the hydraulic accumulator 340 in response to a command signal 344C from the controller 402. In other embodiments the hydraulic accumulator 340 may not be present. The hydraulic accumulator 340 may serve two purposes. First, accumulator 340 may function as a hydraulic spring to cushion the effect of physical impacts on the grader blade 158 and to cushion the corresponding spikes in hydraulic pressure in the hydraulic control circuit 300. Second, in an event where the grader blade 158 is initially held above the ground surface and then released to drop to the ground surface, the accumulator 340 can provide an immediate source of hydraulic fluid to prevent or reduce cavitation in the head end 312 of the actuator 310.

[0037] In some embodiments the hydraulic actuator pressure regulation system 322 may also include an electrohydraulic recirculation valve 346 which allows hydraulic fluid from the pressure supply line 324 to recirculate to a second pump inlet 348 through recirculation line 350. The electrohydraulic recirculation valve 346 and recirculation line 350 allow the variable flow pump 302 to operate at maximum flow rate when the hydraulic control circuit 300 is initially turned on, so as to provide increased hydraulic pressure to the hydraulic control circuit 300. The electrohydraulic recirculation valve 346 may be operated in response to a command signal 346C from the controller 402. In some embodiments the electrohydraulic recirculation valve 346 and recirculation line 350 may not be present.

[0038] The electrohydraulic recirculation valve 346 allows hydraulic fluid from the pressure supply line 324 to recirculate to the second pump inlet 348 through recirculation line 350. The electrohydraulic recirculation valve 346 and recirculation line 350 allow the variable flow pump 302 to operate at maximum flow rate when the hydraulic control circuit 300 is initially turned on, so as to provide increased hydraulic pressure to the hydraulic control circuit 300. The electrohydraulic recirculation valve 346 may be operated in response to a command signal 346C from the controller 402. The use of the electrohydraulic recirculation valve 346 to increase available system operating pressures on start-up is a further means of avoiding or reducing cavitation in the actuator 310 in situations where the hydraulic control circuit 300 would otherwise be unable to initially keep up with the gravitational forces acting on the work implement 158.

[0039] More generally, the controller 402 may be configured to direct the electrohydraulic recirculation valve 346 to open and the variable output pump 302 to increase its output in response to a detected need for increased hydraulic pressure in the hydraulic control circuit.

[0040] As schematically shown in FIG. 7, when implemented in the motor grader 110, the details of the hydraulic control circuit 300 may be duplicated, with a separate control circuit provided for each of the hydraulic lifting actuators 166 and 168 of the motor grader 110. As shown in FIG. 7 a common pump 302 and reservoir 308 may be used for both lifting actuators 166 and 168. Separate pumps and reservoirs could also be used.The Control System:

[0041] As schematically illustrated in FIG. 4, the work vehicle 110 may include a control system 400 including a controller 402. The controller 402 is configured to receive input signals from the various sensors. The signals transmitted from the various sensors to the controller 402 are schematically indicated in FIG. 4 by lines connecting the sensors to the controller with an arrowhead indicating the flow of the signal from the sensor to the controller 402.

[0042] The controller 402 may receive position signals 404S from position sensors 404 associated with the actuator 166 and / or 168. The position sensors 404 may be configured to generate the position signals 404S representative of a position of the piston 311 relative to the cylinder 313 of the hydraulic actuator 166 and / or 168. In some embodiments hydraulic actuator 166 and / or 168 may be in the form of a hydraulic “smart cylinder” in which the position sensor 404 is integrated within the hydraulic actuator 166 and / or 168. In other embodiments the position sensor 404 may be external to the hydraulic actuator 166 and / or 168, for example in the form of a wire rope sensor having one end connected to the cylinder 313 and another end connected to the rod 315 attached to the piston 311.

[0043] The controller 402 may also receive one or more vehicle position signals such as 406S and 408S from position sensors 406 and 408 mounted on the work vehicle 110 (See FIG. 1). The position sensors 406 and 408 may for example be Inertial Measurement Units (IMU's) mounted on the front frame 118 and the drawbar 154.

[0044] The position sensors 404, 406 and 408 may collectively be referred to as at least one position sensor configured to detect a position of the work implement 158 relative to the vehicle frame 118 and to generate at least one position signal 404S, 406S, and 408S representative of the position of the work implement 158 relative to the vehicle frame 118. Depending on the specific types of position sensors selected the controller 402 may determine displacement, velocity and / or acceleration of the work implement 158 relative to the vehicle frame 118.

[0045] Similarly, the controller 402 will generate control signals for controlling the operation of the various valves of the hydraulic control system 300 discussed above.

[0046] Controller 402 includes or may be associated with a processor 410, a computer readable medium 412, a data base 414 and an input / output module or control panel 416 having a display 418. An input / output device 420, such as a keyboard, joystick or other user interface, is provided so that the human operator may input instructions to the controller. It is understood that the controller 402 described herein may be a single controller having all of the described functionality, or it may include multiple controllers wherein the described functionality is distributed among the multiple controllers.

[0047] Various operations, steps or algorithms as described in connection with the controller 402 can be embodied directly in hardware, in a computer program product 422 such as a software module executed by the processor 410, or in a combination of the two. The computer program product 422 can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, or any other form of computer-readable medium 412 known in the art. An exemplary computer-readable medium 412 can be coupled to the processor 410 such that the processor can read information from, and write information to, the memory / storage medium. In the alternative, the medium can be integral to the processor. The processor and the medium can reside in an application specific integrated circuit (ASIC). The ASIC can reside in a user terminal. In the alternative, the processor and the medium can reside as discrete components in a user terminal.

[0048] The term “processor” as used herein may refer to at least general-purpose or specific-purpose processing devices and / or logic as may be understood by one of skill in the art, including but not limited to a microprocessor, a microcontroller, a state machine, and the like. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0049] The control panel 416 may for example be physically located on the work vehicle 110, for example in the cab 126, such that the control panel 416 is supported directly or indirectly from the frame 118. Optionally, or additionally, the control panel 416 or some portion thereof may be remotely located, such as on a handheld device carried by a human operator. Further, in the event of an autonomous machine 110 the control panel 416 or some portion thereof may be located at a remote-control station and may be communicated with the controller 402 wirelessly. The input / output device 420 may include the user interface 172, or may be in addition to the user interface 172.

[0050] As is further described below with regard to various modes of operation the controller 402 is operably connected to the various control valves discussed above and with the variable pump 302, and sends command signals to each of those components. Each command signal is indicated in FIGS. 3 and 4 by the number of the component followed by the suffix “C”. For example, the pump 302 receives a command signal 302C.Open Loop Floating Control Mode-FIG. 5:

[0051] FIG. 5 provides a flow chart of the operating logic for the controller 402 when the controller 402 is configured to perform a grading operation using float control in an open loop control mode 500. In the open loop control mode the controller 402 does not utilize feedback from the pressure sensors 334 and 336, but instead merely sets the selected set points for the PPRV's 326 and 330 and allows the PPRV's to operate. In the open loop control mode 500 the operator first decides whether to enable the open loop control mode as indicated at block 502.

[0052] If the operator chooses to disable the float control as indicated at block 504, the controller 402 will turn off the hydraulic actuator pressure regulation system 322 as indicated at block 506 by moving the on / off valves 328 and 332 to their closed positions. The operator input may be made via the input / output device 420. Then the operator may operate the work implement 158 by controlling the operation of the actuator 166 and / or 168 through the control valve 316.

[0053] If the operator chooses to enable the float control as indicated at block 508 the controller 402 checks at block 510 for other operator inputs determinative of a desired set point for the relief pressures of the PPRV's 326 and 330. For example, the operator may have selected between several available performance settings for the work vehicle 110, and the selected performance setting may have associated therewith a preferred set point for the force to be applied by the actuator 166 and / or 168 to the work implement 158. For example, the actuator 166 and / or 168 may be representative of the left and right lift actuators 166 and 168 which raise and lower the grader blade / work implement 158 on the motor grader 110. There will be a hydraulic control system 300 such as depicted in FIG. 3 associated with each of the left and right lift actuators 166 and 168.

[0054] Simultaneously with the setting of the set points for the PPRV's 326 and 330, the controller 402 will command the on / off valves 328 and 332 to their open positions, as indicated at block 514. Then as indicated at block 516 the grader blade 158 will be in an open loop control floating mode. If for example, the grader blade 158 encounters a large rock or other obstacle creating a sudden pressure increase in the head end 312 of the left and / or right lift actuators 166 and 168, the respective PPRV 326 associated with that head end 312 will relieve that excess pressure to the reservoir 308 via the return line 324.

[0055] In the context of the operation just described the first PPRV 326 may be described as a first proportional pressure regulating and / or relief valve (PPRV) 326 fluidly positioned between the reservoir 308 and the first side 312 of the hydraulic actuator 166 and / or 168, the first PPRV 326 being configured to permit flow of fluid from the first side 312 of actuator 166 and / or 168 to the reservoir 308 in response to a pressure at the first side 312 of the hydraulic actuator 166 and / or 168 being greater than a first predetermined pressure value. In this context, the first predetermined pressure value would be the value achieved by the set point of the first PPRV 326, regardless of whether that value was exactly equal to the desired value which the operator was attempting to achieve, or which the controller 402 selected based on the operator's selected performance setting.

[0056] Similarly, the second PPRV 330 may be described as being configured to permit flow of fluid from the second side 314 of the actuator 166 and / or 168 to the reservoir 308 in response to the pressure at the second side 314 of the hydraulic actuator 166 and / or 168 being greater than a second predetermined pressure value associated with the set point for the second PPRV 330.

[0057] It will be appreciated that in the open loop control mode, the setting of the set points for the PPRV's 326 and 330 is done by a single command signal from the controller 402 based on the operator input, such as the selected performance setting. The controller 402 will be configured to provide an appropriate command signal to the PPRV's which is determined to be correct for the desired downward force to be maintained on the grader blade 158. The command signal for a given set point may be determined from historical data, but there is no feedback or confirmation that the desired down force has been achieved. The selected set point may add force to the gravitational weight of the grader blade 158 by increasing the pressure in the head end 312 of the actuators, or it may reduce the effective gravitational weight of the grader blade 158 by increasing the pressure in the rod end 314. The set points for the PPRV's will be associated with a desired pressure value to be maintained at the head end 312 and / or rod end 314, but there is no feedback or confirmation that the exact desired pressure value has been achieved.Closed Loop Floating Control Mode-FIG. 6:

[0058] FIG. 6 provides a flow chart of the operating logic for the controller 402 when the controller 402 is configured to perform a grading operation in a closed loop control mode 600. In the closed loop control mode 600 the controller 402 uses feedback from the pressure sensors 334 and 336 to continuously adjust the set points of the PPRV's 326 and 330 if and as needed to achieve a desired pressure in the head ends 312 and rod ends 314 and corresponding down force on the grader blade 158.

[0059] In the closed loop control mode 600 the operator first decides whether to enable the closed loop control mode as indicated at block 602. If the operator chooses to disable the float control as indicated at block 604, the controller 402 will turn off the hydraulic actuator pressure regulation system 322 as indicated at block 606 by moving the on / off valves 328 and 332 to their closed positions. The operator input may be made via the input / output device 420. Then the operator may operate the work implement 158 by controlling the operation of the actuator 166 and / or 168 through the control valve 316.

[0060] If the operator chooses to enable the float control as indicated at block 608 the controller 402 checks at block 610 for other operator inputs determinative of a desired set point for the relief pressures of the PPRV's 326 and 330. For example, the operator may have selected between several available performance settings for the work vehicle 110, and the selected performance setting may have associated therewith a preferred set point for the force to be applied by the left and right lift actuators 166 and 168 which raise and lower the grader blade / work implement 158 on the motor grader 110. There will be a hydraulic control system 300 such as depicted in FIG. 3 associated with each of the left and right lift actuators 166 and 168.

[0061] Simultaneously with the setting of the set points for the PPRV's 326 and 330, the controller 402 will command the on / off valves 328 and 332 to their open positions, as indicated at block 614.

[0062] After receiving the base setting of the set point or set value for the PPRV's at block 610, the controller 402 checks at block 612 for input signals 334S and / or 336S from the pressure sensors 334 and 336 associated with the head end 312 and rod end 314, respectively, of the associated hydraulic actuator 166 and / or 168. Then as indicated at block 616 the controller 402 calculates an adjusted command signal 326C and / or 330C to the PPRV's to achieve the desired pressure value at the actuator 166 and / or 168. For example, if the desired floating pressure in the head end 312 of the hydraulic actuator 166 and / or 168 is 1000 psi the controller 402 may determine an appropriate command signal 326C and / or 330C based on preprogrammed information as it does in block 510 of the open loop control mode, but now in block 616 the controller 402 can determine whether it needs to adjust that command signal up or down to achieve the desired downward force at head end 312. At block 618 the controller 402 sends the adjusted command signal 326C and / or 330C to the PPRV's based on the sensor feedback from the pressure sensors 334 and 336. At block 620 the PPRV's 326 and / or 330 make the commanded adjustment in setting. As a result of the feedback from the pressure sensors 334 and 336 the controller directs adjustment of the PPRV's such that the actual pressure achieved at the head end 312 and rod end 314 is closer to the set value that it was before the adjustment.

[0063] Then as indicated at block 622 the PPRV's 326 and 330 control the pressure applied to the actuator 166 and / or 168 so that the grader blade 158“floats” with the desired down force. If the grader blade 158 encounters a large rock or other obstacle creating a sudden pressure increase in the head end 312 of the left and / or right lift actuators 166 and 168, the respective PPRV 326 associated with that head end 312 will relieve that excess pressure to the reservoir 308 via the return line 324. As indicated at block 624, the pressure sensors 334 and 336 continuously monitor the actual pressure in head end 312 and rod end 314 and feed that information back to controller 402 as signals 334S and 336S.

[0064] In the context of the closed loop control mode 600, the controller 402 may be described as being in electrical communication with the control valve 316, the first and second PPRV's 326 and 330, and the first and second pressure sensors 334 and 336, the controller 402 being configured to receive a set value for the first predetermined pressure value (such as through the operator's performance setting), and to receive the first pressure signal 334S from the first pressure sensor 334, the controller 402 being configured to send a command signal 326C to the first PPRV 326 to adjust the first predetermined pressure value based at least in part on the set value for the first predetermined pressure value and based at least in part on the first pressure signal 334S.Ride Control Mode:

[0065] The hydraulic control circuit 300, and particularly the hydraulic actuator pressure regulation system 322 thereof including its first and second PPRV's provides multiple functionalities. In addition to providing the various float control modes of grading operation explained above, it may be controlled in a manner to provide a “ride control” mode of operation to reduce resonant loping or porpoising motion of the work vehicle 110 during transport of the vehicle at relatively high speeds with the work implement 158 raised above the ground surface.

[0066] As previously noted, some prior offroad machines have mitigated such porpoising by adding hydraulic accumulators to the rod end of the hydraulic cylinders supporting work implements or other attachments from the vehicle frame, thus turning the attachments into tuned mass dampers. In the context of a motor grader like the motor grader 110 this would include adding a hydraulic accumulator connected to the rod end 314 of each of the lifting actuators 166 and 168 so that the suspended weight of the work implement 158, circle 146 and drawbar 154 would be supported in a damped resilient manner. The operating principle of a tuned mass damper is that some of the kinetic energy of the larger structure (the porpoising motor grader) bouncing at its resonant frequency, is dissipated in the motion of the tuned mass damper so that the motion of the larger structure is reduced.

[0067] The ride control mode of the present disclosure does not include any hydraulic accumulator connected to the rod end of its cylinders, but instead actively regulates fluid pressure at the hydraulic actuators 166 and 168 using the hydraulic actuator pressure regulation system 322. This is accomplished without the expense of, or commitment of space on the vehicle 110 to, any hydraulic accumulators connected to the rod ends of the hydraulic actuators 166 and 168. The controller 402 monitors motion of the work implement158 relative to the vehicle frame 118 by receiving the position signals from the position sensors 404, 406 and 408, and controls the PPRV's connected to the rod ends of the hydraulic actuators 166 and 168 as a function of those position signals. The controller 402 may also control the PPRV's connected to the head ends of the hydraulic actuators 166 and 168 as a function of those position signals. The function applied by the ride control mode controls movement of the work implement 158, including the circle 146 and draw bar 154 attached to the work implement 158, relative to the vehicle frame 118 so that such movement mimics the relative motion of the work implement 158 that the use of a hydraulic accumulator and hydraulic damper would achieve, and the resulting configuration provides a “virtual” tuned mass damper without the cost or mechanical complexity of adding hydraulic accumulators to the rod ends of the hydraulic actuators 166 and 168 of the hydraulic circuit 300.

[0068] The application of this disclosure to any given work vehicle is highly dependent on the physical characteristics of the particular work vehicle and its attached work implement(s). One important factor in such analysis and design is to determine the resonant frequency of the problematic porpoising motion of the work vehicle. This is a function of the mass of the work vehicle and all attachments carried by the work vehicle, the distribution of that mass, the location of the pneumatic tires, the spring rates of the pneumatic tires, and the inherent structural damping present in all of the above. For a given work vehicle this resonant frequency will be affected by certain variables which may change from day to day in the operating life of the work vehicle.

[0069] The controller 402 may be configured to take these variables into account by providing the operator with the input / output device 420 configured in a way that the operator may make operator inputs representative of a configuration of the work vehicle. Such operator inputs may include the identification of selectable attachments carried by the vehicle 110. For example, FIG. 8 schematically illustrates the input / output device 420 in the form of a touch screen display 420 in which the operator may indicate the type of work implement 158 currently mounted on the work vehicle 110 by virtual buttons 428 and 430, whether a ripper is mounted on the work vehicle 110 by virtual button 432, the type of tires on the work vehicle 110 by virtual buttons 434 and 436, and the current inflation pressure of the work vehicle 110 at input space 438. The controller 402 may be configured for a given work vehicle 110 to calculate or estimate the resonant frequency of any expected porpoising motion of the work vehicle 110 with the current configuration. This may be described as calculating or estimating a vehicle frame porpoising resonance frequency based in part on a mass of the selected attachments carried by the work vehicle 110 and / or based in part on a spring rate of the selected pneumatic tires.

[0070] The controller 402 may also estimate the resonant frequency of the work vehicle 110 by observing the chassis motion, especially using the signals from the IMU's 406 and 408 attached to the vehicle frame 118 and the drawbar 154.

[0071] The touch screen 420 may also provide options whereby the operator of the work vehicle 110 may selectively engage and disengage the ride control mode of the controller 400, such as by virtual ON and OFF buttons 424 and 426.

[0072] The controller 400 may be further configured, when in ride control mode, to adjust the control function of the ride control mode based on the expected resonant frequency of the porpoising motion. The determination of the desired control function may then be determined by the controller 400 based on a modeling of the mechanical system supporting the work implement 158.

[0073] FIG. 9 schematically illustrates the work implement 158, circle 146 and draw bar 154 as a suspended mass, suspended by a linear spring of spring constant “k” and a linear damper of damping constant “b”. The forces acting on such an actual spring, mass, damper system may be described by the following equation:F=m⁢a+ks⁢x+bvwhere:m=mas⁢ (of⁢ the⁢ work⁢ implement⁢ 158,circle⁢ 146⁢ and⁢ draw⁢ bar⁢ 154);a=acceleration⁢ of⁢ the⁢ mass;k=spring⁢ constant⁢ of⁢ the⁢ spring;x=displacement⁢ of⁢ the⁢ mass⁢ and⁢ spring;b=damping⁢ constant⁢ of⁢ the⁢ damper;andv=velocity⁢ of⁢ the⁢ mass;

[0074] The displacement “x”, the velocity “v” and / or the acceleration “a” of the work implement 158 relative to the vehicle frame 118 may be detected by the one or more position sensors 404, 406, 408 discussed above. The force “F” supporting the mass of the work implement 158, circle 146 and draw bar 154 is equal to the pressure in the rod ends of the lifting actuators 166, 168 times the cross-sectional area across the pistons of the actuators.

[0075] Thus, if the pressure in the rod ends is controlled as a linear function of the displacement “x”, the force applied to the work implement 158 by the lifting actuators 166, 168 will be similar to that which would have resulted from the use of hydraulic accumulators connected to the rod ends of the lifting actuators 166, 168, with those accumulators providing a spring constant “k” equal to the linear function of the displacement “x” applied by the control function of the ride control mode. Such a control function component may be described as a virtual spring component.

[0076] And if the pressure in the rod ends is controlled as a linear function of the velocity “v”, the force applied to the work implement 158 by the lifting actuators 166, 168 will be similar to that which would have resulted from the use of hydraulic dampers between the work implement 158 and the vehicle frame 118, with those hydraulic dampers providing a damping constant “b” equal to the linear function of the velocity “v” applied by the control function of the ride control mode. Such a control function component may be described as a virtual damper component.

[0077] And if the pressure in the rod ends is controlled as a linear function of the acceleration “a”, the force applied to the work implement 158 by the lifting actuators 166, 168 will be similar to that which would have resulted from a change in the mass of the work implement 158 and attached structures. Such a control function component may be described as a virtual mass component.

[0078] The actual control function applied may be complex and may combine or estimate any combination of the above described virtual features.

[0079] Also, the control function may be determined through experimental trial and error analysis instead of or in addition to computational techniques.

[0080] Although the discussion above is primarily in the context of regulating the pressure in the rod ends of the lifting actuators 166 and 168, it will be understood that during a porpoising motion of the vehicle there will also be pressure surges in the head ends of the lifting actuators 166 and 168 and the controller 402 may regulate the pressures in both the rod ends and the head ends of the lifting actuators to control the porpoising motion.

[0081] In one example, the work implement 158 has been lifted out of engagement with the ground surface by the action of the operating control valve 316 in its position 316.3 directing hydraulic fluid into the rod end 314 of the lift cylinder 166 or 168 to raise the work implement 158 to the desired elevation relative to the front frame 118. Then the operating control valve 316 is moved to its closed position 316.1 and the hydraulic actuator pressure regulation system 322 is enabled. When the controller 402 enables the ride control mode the proportional pressure regulating valve 330 is configured to regulate fluid pressure at the rod end 314 of the lift cylinder 166 or 168. If there is no loping motion of the work vehicle occurring as the vehicle 110 travels across the ground, the required pressure in the rod ends 314 to hold the work implement in the selected raised position is simply the pressure required to offset the static weight of the work implement 158 and attached structures. If the work vehicle 110 begins to lope, the inertia of the work implement 158 and attached structures will cause the pressure in the rod end 314 to surge as the work vehicle 110 plunges downward compressing its tires, and will cause the pressure in the head ends 312 to surge when the work vehicle bounces upward towards the apex of its porpoising motion. The position sensors 404, 406, 408 will detect downward and / or upward movement of the work implement 158 relative to the work vehicle frame 118. If the control function of the control mode is constructed to mimic the use of a hydraulic accumulator and hydraulic damper connected to the rod end 314, then the controller 402 may regulate the pressure in the rod end 314 to have a virtual spring component and a virtual damping component. The virtual spring component may be dependent on a detected vertical displacement of the work implement 158 relative to the vehicle frame 118. The virtual damping component may be dependent on a detected velocity of the work implement 158 relative to the vehicle frame 118.

[0082] It will be understood that when using two lifting cylinders 166 and 168, as is typically done in a motor grader 110, there will be a proportional pressure regulating valve 330 associated with each lifting cylinder 166 and 168. The two lifting cylinders 166 and 168 may be controlled to move in the same direction to lift or lower the work implement. And the two lifting cylinders 166 and 168 may be moved in opposite directions to tilt the work implement.

[0083] It will also be understood that there may be active regulation of the pressure in the rod ends 312 of each of the lifting cylinders 166 and 168. When the controller 402 enables the ride control mode the proportional pressure regulating valve 326 is configured to regulate fluid pressure at the head end 312 of the lift cylinder 166 or 168. A similar control function to that described above may be applied so that both the rod end pressure and the head end pressure are controlled to emulate a tuned mass damper.

[0084] Thus, it is seen that the apparatus and methods of the embodiments disclosed herein readily achieve the ends and advantages mentioned as well as those inherent therein. While certain preferred embodiments have been illustrated and described for purposes of the present disclosure, numerous changes in the arrangement and construction of parts and steps may be made by those skilled in the art, which changes are encompassed within the scope and spirit of the present invention as defined by the appended claims.

Examples

Embodiment Construction

[0019]Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways.

[0020]FIG. 1 illustrates a work vehicle, which is a motor grader (or simply “grader”) 110 in the illustrated embodiment. The grader 110 includes a chassis 114 with a front frame 118 and a rear frame 122. The front frame 118 supports an operator cab 126 that may include an operator seat, controls for operating the grader 110, and the like. A prime mover 130 (e.g., a diesel engine) is supported on the rear frame 122 and is enclosed within a compartment 134. The chassis 114 is supported by front wheels 138 at the front of the grader 110 and by tandem rear wheels 142 at the rear of the gra...

Claims

1. A work vehicle, comprising:a vehicle frame;a work implement movable relative to the vehicle frame; anda hydraulic control circuit including:a pump;a reservoir;a hydraulic actuator configured to raise and lower the work implement relative to the vehicle frame, the hydraulic actuator including a head end and a rod end;an operating control valve configured to control supply of hydraulic fluid from the pump to the rod end of the hydraulic actuator to raise the work implement relative to the vehicle frame, and to control return of hydraulic fluid from rod end of the hydraulic actuator to the reservoir to lower the work implement relative to the vehicle frame;a proportional pressure regulating valve selectively communicating the rod end of the hydraulic actuator with the pump and the reservoir, the proportional pressure regulating valve being configured to regulate fluid pressure at the rod end of the hydraulic actuator;at least one position sensor configured to detect a position of the work implement relative to the vehicle frame and to generate at least one position signal representative of the position of the work implement relative to the vehicle frame; anda controller configured to receive the at least one position signal, and to control the proportional pressure regulating valve to regulate the fluid pressure at the rod end of the hydraulic actuator, the controller including a ride control mode configured such that when the work vehicle is traveling with the work implement raised out of engagement with a ground surface and the ride control mode is enabled, the controller controls the proportional pressure regulating valve to actively regulate the fluid pressure at the rod end of the hydraulic actuator as a function of the at least one position signal.

2. The work vehicle of claim 1, wherein:the controller is configured such that the ride control mode simulates a tuned mass damper action of the work implement relative to the frame, without the use of any hydraulic accumulator communicated with the rod end of the hydraulic actuator.

3. The work vehicle of claim 1, wherein:the controller is configured to receive operator inputs representative of a configuration of the work vehicle, the operator inputs including identification of selectable attachments carried by the vehicle; andthe ride control mode is configured to adjust the function controlling the regulation of the fluid pressure at the rod end of the hydraulic actuator based on the operator inputs representative of the configuration of the work vehicle.

4. The work vehicle of claim 3, wherein:the ride control mode is configured to calculate a vehicle frame porpoising resonance frequency based in part on a mass of the selected attachments carried by the vehicle; andthe ride control mode is configured to adjust the function controlling the regulation of the fluid pressure at the rod end of the hydraulic actuator based on the calculated vehicle frame porpoising resonance frequency.

5. The work vehicle of claim 4, wherein:the operator inputs further include a tire selection for a plurality of pneumatic tires supporting the vehicle frame;the ride control mode is configured to calculate the vehicle frame porpoising resonance frequency based in part on a spring rate of the selected pneumatic tires; andthe ride control mode is configured to adjust the function controlling the regulation of the fluid pressure at the rod end of the hydraulic actuator based on the calculated vehicle frame porpoising resonance frequency.

6. The work vehicle of claim 3, wherein:the operator inputs further include a tire selection for a plurality of pneumatic tires supporting the vehicle frame;the ride control mode is configured to calculate a vehicle frame porpoising resonance frequency based in part on a spring rate of the selected pneumatic tires; andthe ride control mode is configured to adjust the function controlling the regulation of the fluid pressure at the rod end of the hydraulic actuator based on the calculated vehicle frame porpoising resonance frequency.

7. The work vehicle of claim 1, wherein:the at least one position sensor includes a first Inertial Measurement Unit (IMU) attached to the vehicle frame and a second IMU attached to the work implement so that the second IMU moves relative to the first IMU when the work implement moves relative to the vehicle frame.

8. The work vehicle of claim 7, wherein:the at least one position sensor includes an extension sensor associated with the hydraulic actuator and configured to detect an extension of a rod of the hydraulic actuator relative to a cylinder of the hydraulic actuator.

9. The work vehicle of claim 1, wherein:the work vehicle is a motor grader;the work implement includes a draw bar pivotally supported from the vehicle frame, a circle mounted on the draw bar, and a grader blade supported on the circle; andthe hydraulic actuator is a first hydraulic lift actuator and the work vehicle further includes a second hydraulic lift actuator.

10. The work vehicle of claim 1, further comprising:an operator input device configured such that a human operator of the work vehicle may selectively engage and disengage the ride control mode of the controller.

11. The work vehicle of claim 1, wherein:the ride control mode is configured such that the function includes a virtual damping component dependent on a detected velocity of the work implement relative to the vehicle frame.

12. The work vehicle of claim 11, wherein:the ride control mode is configured such that the function includes a virtual spring component dependent on a detected vertical displacement of the work implement relative to the vehicle frame.

13. The work vehicle of claim 1, wherein:the ride control mode is configured such that the function includes a virtual spring component dependent on a detected vertical displacement of the work implement relative to the vehicle frame.

14. The work vehicle of claim 1, wherein:the ride control mode is configured such that the function includes a virtual mass component dependent on a detected acceleration of the work implement relative to the vehicle frame.

15. The work vehicle of claim 1, wherein:the hydraulic control circuit includes a further proportional pressure regulating valve selectively communicating the head end of the hydraulic actuator with the pump and the reservoir, the further proportional pressure regulating valve being configured to regulate fluid pressure at the head end of the hydraulic actuator; andthe controller is configured such that when the ride control mode is enabled the controller controls the further proportional pressure regulating valve to actively regulate the fluid pressure at the head end of the hydraulic actuator as a function of the at least one position signal.

16. The work vehicle of claim 1, wherein:the at least one position sensor includes an Inertial Measurement Unit (IMU) attached to the vehicle frame; andthe ride control mode is configured to determine a vehicle frame porpoising resonance frequency based at least in part on analysis of a signal from the IMU.

17. A method of reducing a porpoising motion of a work vehicle when the work vehicle is in a traveling mode, the work vehicle including a vehicle frame, a work implement movable relative to the vehicle frame, and a hydraulic control circuit including: a pump; a reservoir; a hydraulic actuator configured to raise and lower the work implement relative to the vehicle frame, the hydraulic actuator including a head end and a rod end; an operating control valve configured to control supply of hydraulic fluid from the pump to the rod end of the hydraulic actuator to raise the work implement relative to the vehicle frame, and to control return of hydraulic fluid from rod end of the hydraulic actuator to the reservoir to lower the work implement relative to the vehicle frame; and a proportional pressure regulating valve selectively communicating the rod end of the hydraulic actuator with the pump and the reservoir, the proportional pressure regulating valve being configured to regulate fluid pressure at the rod end of the hydraulic actuator, the method comprising:detecting a position of the work implement relative to the vehicle frame with at least one position sensor;generating with the at least one position sensor at least one position signal representative of the position of the work implement relative to the vehicle frame;receiving the at least one position signal with a controller, the controller including a ride control mode; andwhen the work vehicle is traveling with the work implement raised out of engagement with a ground surface and the ride control mode is enabled, controlling the proportional pressure regulating valve to regulate the fluid pressure at the rod end of the hydraulic actuator as a function of the at least one position signal.

18. The method of claim 17, wherein:the controller ride control mode simulates a tuned mass damper action of the work implement relative to the frame, without the use of any hydraulic accumulator communicated with the rod end of the hydraulic actuator.

19. The method of claim 17, wherein:the ride control mode is configured such that the function includes a virtual damping component dependent on a detected velocity of the work implement relative to the vehicle frame.

20. The work vehicle of claim 17, wherein:the ride control mode is configured such that the function includes a virtual spring component dependent on a detected vertical displacement of the work implement relative to the vehicle frame.

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