Three-axis unmanned vehicle hydraulic drive system and comprehensive energy-saving control strategy thereof

Abstract

This invention belongs to the field of three-axis unmanned vehicle technology and discloses a hydraulic drive system for a three-axis unmanned vehicle and its comprehensive energy-saving control strategy, aiming to solve the problems of complex hydraulic circuit structure and poor attitude stability in existing three-axis unmanned vehicles. The invention includes a six-wheel drive hydraulic system; a steering hydraulic system for providing independent steering for the front and rear wheels of the three-axis unmanned vehicle; a suspension system for adjusting the suspension height of at least each wheel, so that the suspension system's operating modes include, but are not limited to, the following modes: passive suspension mode, semi-active suspension mode, active suspension mode, rigid locking mode, and vehicle height adjustment mode; and a power system for providing hydraulic power for the operation of the six-wheel drive hydraulic system, steering hydraulic system, and suspension system. This invention facilitates the integration of various hydraulic valves into valve blocks, reducing the hydraulic circuit structure and meeting the needs of unmanned vehicles performing specific tasks in the field.

Description

Technical Field

[0001] This invention belongs to the field of three-axis unmanned vehicle technology, specifically relating to a three-axis unmanned vehicle hydraulic drive system and its comprehensive energy-saving control strategy. Background Technology

[0002] Autonomous vehicles, also known as wheeled mobile robots, are a type of intelligent vehicle that achieves driverless operation through onboard computer systems. Currently, most autonomous vehicles are two-axle vehicles, which are generally more suitable for areas with good road conditions. For field operations (such as material transport, terrain surveying, search and rescue, and road obstacle removal), three-axle autonomous vehicles have advantages over two-axle vehicles due to their structural characteristics.

[0003] Currently, there is considerable research on two-axle unmanned vehicles (UAVs). However, due to the more complex hydraulic circuit structure and control methods of three-axle UAVs, research on them is relatively limited. For example, the three-axle UAV and its integrated control system and off-road method disclosed in application number 202110863176X have a structural layout design for their suspension control system, steering control system, and driving power system. This design prevents the centralization of the hydraulic valves in these systems, resulting in a particularly complex hydraulic circuit structure and high manufacturing and maintenance costs. Furthermore, existing three-axle UAV suspensions adjust their operating state solely based on the size of proportional valve openings. The various sub-suspension systems operate independently, leading to extremely poor attitude stability, especially during field operations, and failing to meet the requirements for performing specific tasks in the field. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a three-axis unmanned vehicle hydraulic drive system and its integrated energy-saving control strategy. The technical solution adopted by this invention to solve the technical problems is as follows:

[0005] A three-axis unmanned vehicle hydraulic drive system, characterized in that it comprises:

[0006] The six-wheel drive hydraulic system is used to provide hydraulic power to the wheels of the three-axle unmanned vehicle to drive the wheels to work or to achieve differential steering;

[0007] A steering hydraulic system is used to provide independent steering for the front and rear wheels of the three-axle unmanned vehicle, and the steering hydraulic system, together with the six-wheel drive hydraulic system, recovers energy during wheel braking;

[0008] The suspension system is used to adjust the suspension height of each wheel of the three-axle unmanned vehicle so that the operating modes of the suspension system include, but are not limited to, the following modes: passive suspension mode, semi-active suspension mode, active suspension mode, rigid locking mode and vehicle height adjustment mode.

[0009] A power system with at least a hydraulic pump is used to provide hydraulic power for the operation of the six-wheel drive hydraulic system, steering hydraulic system and suspension system;

[0010] The energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can be used to provide auxiliary acceleration power, auxiliary steering power and auxiliary force for the wheels of the three-axle unmanned vehicle in different working modes.

[0011] In some embodiments, the suspension system can achieve, at least in different operating modes, independent movement of each wheel, unidirectional interconnection between two suspension drive systems of two wheels on the same axle via an oil circuit, cross-interconnection between suspension drive systems of two wheels on the same axle via an oil circuit, and synchronous movement of suspension drive systems of three wheels on the same side.

[0012] In some embodiments, the steering hydraulic system includes a front wheel steering hydraulic system and a rear wheel steering hydraulic system. The front wheel steering hydraulic system includes two second two-position two-way solenoid valves, two first check valves, two first three-position four-way solenoid proportional valves, two first steering hydraulic cylinders, a second check valve, a second three-position four-way solenoid proportional valve, a third three-position four-way solenoid proportional valve, a first hydraulic booster, a first high-pressure accumulator, a first pressure reducing valve, a second pressure reducing valve, a third two-position two-way solenoid valve, and a fourth two-position two-way solenoid valve. The oil inlets of the two second two-position two-way solenoid valves are respectively... The oil circuit connects to the outlet of the hydraulic pump. The outlet of the second 2-position 2-way solenoid valve is connected to the inlet of a first check valve. The outlet of the first check valve is connected to the inlet of a first 3-position 4-way solenoid proportional valve. The return port of the first 3-position 4-way solenoid proportional valve is connected to the inlet of the hydraulic pump and the low-pressure accumulator via an oil circuit. The two working ports of the first 3-position 4-way solenoid proportional valve are connected to a first steering hydraulic cylinder that controls independent steering of the front wheels. The outlet of the first 2-position 2-way solenoid valve in the six-wheel drive hydraulic system is also connected to the first 3-position 4-way solenoid valve via an oil circuit. The inlet of the proportional valve is connected; the inlet of the second three-position four-way solenoid proportional valve is connected to the outlet of the hydraulic pump via an oil circuit; the inlet of the third three-position four-way solenoid proportional valve is connected to the outlet of one of the first check valves via a first pressure reducing valve; one working port of the second three-position four-way solenoid proportional valve and the third three-position four-way solenoid proportional valve is connected to a first high-pressure accumulator; the other working port of the second three-position four-way solenoid proportional valve and the third three-position four-way solenoid proportional valve is closed; the return ports of the second three-position four-way solenoid proportional valve and the third three-position four-way solenoid proportional valve are connected via an oil circuit. The oil circuit is connected to the inlet of the hydraulic pump and the low-pressure accumulator. The outlet of the first check valve is also connected to the third two-position two-way solenoid valve. The other port of the third two-position two-way solenoid valve is connected to the first hydraulic booster. The other port of the first hydraulic booster is connected to the first high-pressure accumulator. The inlet of the fourth two-position two-way solenoid valve is connected to the outlet of the hydraulic pump via an oil circuit. The outlet of the fourth two-position two-way solenoid valve is connected to the second check valve. The outlet of the second check valve is connected to the second pressure reducing valve. The outlet of the second pressure reducing valve is connected to the first high-pressure accumulator.

[0013] In some embodiments, the rear wheel steering hydraulic system includes two fifth two-position two-way solenoid valves, two third check valves, two fourth three-position four-way proportional solenoid valves, a fifth three-position four-way proportional solenoid valve, a sixth three-position four-way proportional solenoid valve, a sixth two-position two-way solenoid valve, a seventh two-position two-way solenoid valve, a third pressure reducing valve, a fourth pressure reducing valve, a second steering hydraulic cylinder, a second high-pressure accumulator, and a second hydraulic booster. The inlets of the two fifth two-position two-way solenoid valves are respectively connected to the outlet of the hydraulic pump via oil circuits. The outlet of the fifth two-position two-way solenoid valve is connected to the inlet of a third check valve. The outlet of the third check valve is connected to the inlet of one of the fourth three-position four-way proportional solenoid valves. The return port of the fourth three-position four-way proportional solenoid valve is connected to the inlet of the hydraulic pump and the low-pressure accumulator via oil circuits. The two working ports of the fourth three-position four-way proportional solenoid valve are connected to a second steering hydraulic cylinder that controls independent steering of the rear wheels. The outlet of the first two-position two-way solenoid valve of the six-wheel drive hydraulic system is also connected to the fourth three-position four-way proportional solenoid valve via oil circuits. The inlet of the first valve is connected; the inlet of the fifth three-position four-way electromagnetic proportional valve is connected to the outlet of the hydraulic pump via an oil circuit; the inlet of the sixth three-position four-way electromagnetic proportional valve is connected to the outlet of one of the third check valves via a third pressure reducing valve; one working port of the fifth three-position four-way electromagnetic proportional valve and the sixth three-position four-way electromagnetic proportional valve is connected to a second high-pressure accumulator; the other working port of the fifth three-position four-way electromagnetic proportional valve and the sixth three-position four-way electromagnetic proportional valve is closed; the return ports of the fifth three-position four-way electromagnetic proportional valve and the sixth three-position four-way electromagnetic proportional valve are connected to the inlet of the hydraulic pump and the low-pressure accumulator via an oil circuit; the outlet of the third check valve is also connected to a sixth two-position two-way electromagnetic valve; the other port of the sixth two-position two-way electromagnetic valve is connected to a second hydraulic booster and a seventh two-position two-way electromagnetic valve; the outlet of the second hydraulic booster is connected to the second high-pressure accumulator; the outlet of the seventh two-position two-way electromagnetic valve is connected to a fourth pressure reducing valve; the other port of the fourth pressure reducing valve is connected to the second high-pressure accumulator.

[0014] In some embodiments, the suspension system includes a suspension stiffness and damping circuit, a suspension energy feeding system, a left front wheel suspension drive system and a right front wheel suspension drive system with identical structures and arranged symmetrically, a left middle wheel suspension drive system and a right middle wheel suspension drive system with identical structures and arranged symmetrically, and a left rear wheel suspension drive system and a right rear wheel suspension drive system with identical structures and arranged symmetrically. The left front wheel suspension drive system, the left middle wheel suspension drive system, and the left rear wheel suspension drive system have identical structures. The left front wheel suspension drive system includes a laterally arranged seventh three-position four-way electromagnetic proportional valve, a laterally arranged first three-position three-way electromagnetic directional valve, a longitudinally arranged second three-position three-way electromagnetic directional valve, and a suspension hydraulic cylinder. The oil inlet of the seventh three-position four-way electromagnetic proportional valve is connected to the oil outlet of the second pressure reducing valve of the front wheel steering hydraulic system via an oil circuit. The seventh three-position four-way electromagnetic proportional valve is connected to the first high-pressure accumulator. The return port of the seventh three-position four-way electromagnetic proportional valve is connected via an oil circuit between the first hydraulic booster and the third two-position two-way electromagnetic valve of the front wheel steering hydraulic system. The two working ports of the seventh three-position four-way electromagnetic proportional valve are respectively connected to the oil port of the lower chamber of the suspension hydraulic cylinder and the suspension stiffness and damping circuit. The inlet port of the first three-position three-way electromagnetic directional valve is connected to the suspension energy supply system. The return port of the first three-position three-way electromagnetic directional valve is connected to the inlet port of the second three-position three-way electromagnetic directional valve. The working port of the first three-position three-way electromagnetic directional valve is connected to the oil port of the upper chamber of the suspension hydraulic cylinder and the suspension stiffness and damping circuit. The return port of the second three-position three-way electromagnetic directional valve is connected to the suspension energy supply system. The working port of the second three-position three-way electromagnetic directional valve is connected to the oil port of the lower chamber of the suspension hydraulic cylinder.

[0015] In some embodiments, the suspension stiffness and damping circuit includes an eighth 2-position two-way solenoid valve, a fifth check valve, and a diaphragm accumulator. The oil inlet of the eighth 2-position two-way solenoid valve is connected via an oil circuit to one working port of a seventh 3-position four-way solenoid proportional valve, the oil port of the upper chamber of the suspension hydraulic cylinder, and the working port of a first 3-position three-way solenoid directional valve. The oil outlet of the eighth 2-position two-way solenoid valve is connected to the fifth check valve. The oil outlet of the fifth check valve is connected to the diaphragm accumulator and an adjustable flow valve. One oil port of the adjustable flow valve is connected to the oil outlet of the fifth check valve and the diaphragm accumulator. The other oil port of the adjustable flow valve is connected to the oil outlet of the eighth 2-position two-way solenoid valve.

[0016] In some embodiments, the suspension energy feeding system includes a sixth check valve, a seventh check valve, an eighth check valve, a ninth check valve, a first accumulator, a second accumulator, a second hydraulic motor, and an energy feeding mechanism. The sixth check valve, the seventh check valve, the eighth check valve, and the ninth check valve form a closed-loop oil circuit. The sixth check valve and the seventh check valve are installed in opposite directions, the sixth check valve and the eighth check valve are installed in the same direction, and the eighth check valve and the ninth check valve are installed in opposite directions. The oil circuit between the eighth check valve and the ninth check valve is connected to the first accumulator and the second hydraulic motor. The second hydraulic motor is connected to the energy feeding mechanism. The oil outlet of the second hydraulic motor is connected to the second accumulator via a pipeline. The oil port of the second accumulator is also connected to the oil circuit between the sixth check valve and the seventh check valve via an oil circuit.

[0017] In some embodiments, the left front wheel suspension drive system and the right front wheel suspension drive system, the left middle wheel suspension drive system and the right middle wheel suspension drive system, and the left rear wheel suspension drive system and the right rear wheel suspension drive system are connected via an oil circuit and a third three-position four-way solenoid valve; the first three-position three-way solenoid valve and the second three-position three-way solenoid valve of the left middle wheel suspension drive system and the right middle wheel suspension drive system are connected to a fourth three-position four-way solenoid valve, and the oil inlet of the first three-position three-way solenoid valve and the oil return of the second three-position three-way solenoid valve are respectively connected to the two working oil ports of the fourth three-position four-way solenoid valve; the oil inlet and the oil return of the fourth three-position four-way solenoid valve are respectively connected to the two working oil ports of the third three-position four-way solenoid valve, or the oil inlet and the oil return of the fourth three-position four-way solenoid valve are connected to the oil inlet and the oil return of the third three-position four-way solenoid valve.

[0018] In some embodiments, the suspension energy feeding system further includes a fifth three-position three-way solenoid directional valve and a sixth three-position three-way solenoid directional valve. The inlet of the fifth three-position three-way solenoid directional valve is connected to the oil passage between the sixth and seventh check valves via an oil circuit. The return port of the fifth three-position three-way solenoid directional valve is connected to the oil passage between the seventh and eighth check valves via an oil circuit. The working port of the fifth three-position three-way solenoid directional valve is connected to the inlet oil passage of the seventh three-position four-way solenoid proportional valve. The return port of the sixth three-position three-way solenoid directional valve is connected to the oil passage between the seventh and eighth check valves via an oil circuit. The inlet of the sixth three-position three-way solenoid directional valve is connected to the oil passage of the front wheel steering hydraulic system.

[0019] Based on the aforementioned three-axis unmanned vehicle hydraulic drive system, this invention also provides a comprehensive energy-saving control strategy for the three-axis unmanned vehicle hydraulic drive system, characterized in that it includes one or more of the following: traction and steering coordination control strategy, braking and steering coordination control strategy, and suspension system working mode control strategy. Attached Figure Description

[0020] Figure 1 This is a structural block diagram of the three-axis unmanned vehicle hydraulic drive system of the present invention;

[0021] Figure 2 The diagram shows the structure of the power system, six-wheel drive hydraulic system, and steering hydraulic system of the present invention. In this diagram, 01, 02, 03, and 04 at the top represent four oil circuits, which correspond one-to-one with and are connected to the four oil circuits (01, 02, 03, and 04) at the bottom of the structure diagram of the suspension system.

[0022] Figure 3 This is a structural block diagram of the suspension system of the present invention, wherein 01, 02, 03 and 04 below the structural block diagram represent four oil circuits for use with... Figure 2 The four oil lines (01, 02, 03 and 04) correspond one-to-one and are connected;

[0023] Figure 4 This is a structural block diagram of the suspension stiffness and damping circuit of the present invention;

[0024] Figure 5 This is a partial structural block diagram of the suspension energy supply system of the present invention. Specifically, the fifth and sixth three-position three-way solenoid directional valves are not shown in this block diagram. The fifth and sixth three-position three-way solenoid directional valves are... Figure 3 This is expressed in the text, while the sixth and third position three-way solenoid directional valve is... Figure 2 This is expressed in the diagram; in this structural block diagram, 03 and 04 at the bottom represent two oil lines, with oil line 03 used to connect with... Figure 2 and Figure 3 Oil line 03 is connected accordingly, and oil line 04 is used to connect with... Figure 2 and Figure 3 The No. 04 oil line in the middle is connected;

[0025] Figure 6 This is a structural block diagram of the suspension system's operating mode according to the present invention;

[0026] The diagram shows the following markings: 1. Power system; 11. Engine; 12. Generator; 13. Battery; 14. Electric motor; 15. Hydraulic pump; 16. Fourth check valve; 17. Pilot-operated solenoid relief valve; 18. Oil tank; 19. Low-pressure accumulator; 2. Six-wheel drive hydraulic system; 21. First three-position four-way solenoid directional valve; 22. First two-position two-way solenoid valve; 23. Hydraulic motor / pump; 24. Second three-position four-way solenoid directional valve; 3. Front wheel steering hydraulic system; 31. Second two-position two-way solenoid valve; 32. First check valve; 33. First three-position four-way solenoid proportional valve; 34. First steering hydraulic cylinder; 35. ... 36. Two- or three-position four-way solenoid proportional valve; 37. First pressure reducing valve; 38. First high-pressure accumulator; 39. Third two-position two-way solenoid valve; 310. First hydraulic booster; 311. Fourth two-position two-way solenoid valve; 312. Second check valve; 313. Second pressure reducer; 314. Adjustable flow valve; 4. Rear wheel steering hydraulic system; 41. Fifth two-position two-way solenoid valve; 42. Third check valve; 43. Fourth three-position four-way solenoid proportional valve; 44. Second steering hydraulic cylinder; 45. Fifth three-position four-way solenoid proportional valve; 46. Sixth three-position four-way solenoid proportional valve; 47. Third pressure reducing valve; 48. Pressure valve; 49. Second high-pressure accumulator; 40. Sixth two-position two-way solenoid valve; 410. Second hydraulic booster; 411. Seventh two-position two-way solenoid valve; 412. Fourth pressure reducing valve; 5. Suspension system; 51. Suspension stiffness and damping circuit; 5101. Eighth two-position two-way solenoid valve; 5102. Fifth check valve; 5103. Diaphragm accumulator; 52. Suspension energy feeding system; 5201. Sixth check valve; 5202. Seventh check valve; 5203. Eighth check valve; 5204. Ninth check valve; 5205. First accumulator; 5206. Second hydraulic motor; 5207. Energy feeding mechanism; 52 08. Second accumulator; 5209. Fifth three-position three-way solenoid directional valve; 5210. Sixth three-position three-way solenoid directional valve; 53. Left front wheel suspension drive system; 54. Right front wheel suspension drive system; 55. Left middle wheel suspension drive system; 56. Right middle wheel suspension drive system; 57. Left rear wheel suspension drive system; 58. Right rear wheel suspension drive system; 59. Seventh three-position four-way solenoid proportional valve; 510. First three-position three-way solenoid directional valve; 511. Second three-position three-way solenoid directional valve; 512. Suspension hydraulic cylinder; 513. Third three-position four-way solenoid directional valve; 514. Fourth three-position four-way solenoid directional valve. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments. These embodiments are merely some, not all, of the embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the protection scope of the present invention.

[0028] Referring to the accompanying drawings, the three-axis unmanned vehicle hydraulic drive system of the present invention includes:

[0029] The six-wheel drive hydraulic system 2 is used to provide hydraulic power to the wheels of the three-axle unmanned vehicle to drive the wheels to work or perform differential steering; referring to the attached figure, the wheels of the three-axle unmanned vehicle include the left front wheel, right front wheel, left middle wheel, right middle wheel, left rear wheel and right rear wheel.

[0030] The steering hydraulic system provides independent steering for the front and rear wheels of the three-axle unmanned vehicle, and together with the six-wheel drive hydraulic system, it recovers energy during wheel braking. The energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can be used to provide auxiliary acceleration power, auxiliary steering power, and auxiliary force for the suspension system in different operating modes for the wheels of the three-axle unmanned vehicle.

[0031] The suspension system 5 is used to adjust the suspension height of at least each wheel of the three-axle unmanned vehicle, such that the suspension system includes, but is not limited to, the following modes: passive suspension mode, semi-active suspension mode, active suspension mode, rigid locking mode, and vehicle height adjustment mode; wherein the passive suspension mode, semi-active suspension mode, and active suspension mode are modes selected based on road surface fluctuations, and the rigid locking mode and vehicle height adjustment mode are modes selected by the operator based on the requirements of the task.

[0032] Among them, the suspension system 5 can achieve independent movement of each wheel, unidirectional interconnection between two suspension drive systems of two wheels on the same axle via oil circuit, cross interconnection between suspension drive systems of two wheels on the same axle via oil circuit, and synchronous movement of suspension drive systems of three wheels on the same side in different working modes.

[0033] A power system 1, having at least a hydraulic pump, is used to provide hydraulic power for the operation of the six-wheel drive hydraulic system, steering hydraulic system, and suspension system. (In conjunction with the attached...) Figure 1 The power system includes at least an engine 11, a generator 12, an electric motor 14, and a hydraulic pump 15. When working, the engine 11 drives the generator 12 to generate electricity, the generator 12 drives the electric motor 14 to work, and the electric motor 14 drives the hydraulic pump 15 to work, thereby outputting high-pressure hydraulic oil through the hydraulic pump 15 to provide power for the operation of the six-wheel drive hydraulic system 2 and the steering hydraulic system (including the front wheel steering hydraulic system 3 and the rear wheel steering hydraulic system 4).

[0034] The power system 1, the six-wheel drive hydraulic system 2, the front-wheel steering hydraulic system 3, the rear-wheel steering hydraulic system 4, and the suspension system 5 are all mounted on the suspension of the three-axle unmanned vehicle. This is readily understood by those skilled in the art and will not be elaborated upon further.

[0035] Preferably, the suspension of the three-axis unmanned vehicle is also equipped with a battery 13, which is electrically connected to the generator 12 and the motor 14. The battery 13 is used to store and release electrical energy to drive the motor 14 and the electronic equipment on the three-axis unmanned vehicle.

[0036] Combined with appendix Figure 2 The six-wheel drive hydraulic system includes four identical front and rear wheel drive subsystems for driving the front and rear wheels, and two identical mid-wheel drive subsystems for driving the middle two wheels. Each front and rear wheel drive subsystem includes a first three-position four-way solenoid valve 21, a first two-position two-way solenoid valve 22, and a hydraulic motor / pump 23. The inlet of the first two-position two-way solenoid valve 22 is connected to the outlet of the hydraulic pump 15 via an oil circuit. The outlet of the first two-position two-way solenoid valve 22 is connected to the inlet of the first three-position four-way solenoid valve 21 via an oil circuit. The return port of the first three-position four-way solenoid valve 21 is connected to the inlet of the hydraulic pump 15 via an oil circuit. The first three-position four-way solenoid valve 21 is connected to the low-pressure accumulator 19. The two working ports of the first three-position four-way solenoid valve 21 are connected to the hydraulic motor / pump 23 used to drive the front and rear wheels. The middle wheel drive subsystem includes a second three-position four-way solenoid valve 24 and a hydraulic motor / pump 23. The oil inlet of the second three-position four-way solenoid valve 24 is connected to the oil outlet of the first two-position two-way solenoid valve 22. The oil return port of the second three-position four-way solenoid valve 24 is connected to the oil inlet of the hydraulic pump 15 and the low-pressure accumulator 19 via an oil circuit. The two working ports of the second three-position four-way solenoid valve 24 are connected to the hydraulic motor / pump 23 used to drive the middle wheel.

[0037] Among them, as attached Figure 2 As shown, in the front and rear wheel drive subsystems, the first three-position four-way solenoid valve 21 for controlling the left front wheel and the first three-position four-way solenoid valve 21 for controlling the right front wheel are symmetrically arranged. Similarly, the first two-position two-way solenoid valve 22 for controlling the left front wheel and the first two-position two-way solenoid valve 22 for controlling the right front wheel are symmetrically arranged. Likewise, the first three-position four-way solenoid valve 24 for controlling the left rear wheel and the first three-position four-way solenoid valve 24 for controlling the right rear wheel are symmetrically arranged. In the center wheel drive subsystem, the second three-position four-way solenoid valve for controlling the left center wheel and the second three-position four-way solenoid valve for controlling the right center wheel are symmetrically arranged.

[0038] Combined with appendix Figure 2 The first three-position four-way solenoid directional valve 21 in the front and rear wheel drive subsystems and the second three-position four-way solenoid directional valve 24 in the middle wheel drive subsystem are arranged longitudinally. The structural layout of the first three-position four-way solenoid directional valve, the second three-position four-way solenoid directional valve, and the first two-position two-way solenoid directional valves facilitates the integration of hydraulic valves into valve blocks, reduces the oil circuit structure, and saves installation space.

[0039] The steering hydraulic system includes a front wheel steering hydraulic system 3 and a rear wheel steering hydraulic system 4. The front wheel steering hydraulic system 3 includes two second two-position two-way solenoid valves 31, two first one-way valves 32, two first three-position four-way solenoid proportional valves 33, two first steering hydraulic cylinders 34, a second one-way valve 312, a second three-position four-way solenoid proportional valve 35, a third three-position four-way solenoid proportional valve 36, a first hydraulic booster 310, a first high-pressure accumulator 38, a first pressure reducing valve 37, a second pressure reducing valve 313, a third two-position two-way solenoid valve 39, and a fourth two-position two-way solenoid valve 311. The oil inlets of the two second two-position two-way solenoid valves 31 are respectively connected via... The oil circuit is connected to the outlet of the hydraulic pump 15. The outlet of the second two-position two-way solenoid valve 31 is connected to the inlet of a first check valve 32. The outlet of the first check valve 32 is connected to the inlet of a first three-position four-way solenoid proportional valve 33. The return port of the first three-position four-way solenoid proportional valve 33 is connected to the inlet of the hydraulic pump 15 and the low-pressure accumulator 19 via the oil circuit. The two working ports of the first three-position four-way solenoid proportional valve 33 are connected to a first steering hydraulic cylinder 34 that controls the independent steering of the front wheels. The outlet of the first two-position two-way solenoid valve 22 of the front and rear wheel drive subsystem is also connected to the inlet of the first three-position four-way solenoid proportional valve 33 via the oil circuit. The oil inlet of the second three-position four-way electromagnetic proportional valve 35 is connected to the oil outlet of the hydraulic pump 15 via an oil circuit. The oil inlet of the third three-position four-way electromagnetic proportional valve 36 is connected to the oil outlet of one of the first check valves 32 via a first pressure reducing valve 37. One working oil port of the second three-position four-way electromagnetic proportional valve 35 and the third three-position four-way electromagnetic proportional valve 36 is connected to a first high-pressure accumulator 38. The other working oil port of the second three-position four-way electromagnetic proportional valve 35 and the third three-position four-way electromagnetic proportional valve 36 is closed. The oil return ports of the second three-position four-way electromagnetic proportional valve 35 and the third three-position four-way electromagnetic proportional valve 36 are connected to the oil inlet of the hydraulic pump 15 via an oil circuit. The low-pressure accumulator 19 is connected, and the oil outlet of the first check valve 32 is also connected to the third two-position two-way solenoid valve 39. The other oil port of the third two-position two-way solenoid valve 39 is connected to the first hydraulic booster 310, and the other oil port of the first hydraulic booster 310 is connected to the first high-pressure accumulator 38. The oil inlet of the fourth two-position two-way solenoid valve 311 is connected to the oil outlet of the hydraulic pump 15 via an oil circuit. The oil outlet of the fourth two-position two-way solenoid valve 311 is connected to the second check valve 312. The oil outlet of the second check valve 312 is connected to the second pressure reducing valve 313. The oil outlet of the second pressure reducing valve 313 is connected to the first high-pressure accumulator 38.

[0040] The outlets of the two first check valves are interconnected via oil circuits. Referring to the attached diagram, two first three-position four-way solenoid proportional valves each control a first steering hydraulic cylinder to perform corresponding actions. The first three-position four-way solenoid proportional valve 33 controlling the left front wheel and the first three-position four-way solenoid proportional valve 33 controlling the right front wheel are symmetrically arranged. Referring to the attached diagram, the two first three-position four-way solenoid proportional valves 33 and one third three-position four-way solenoid proportional valve 35 in the front wheel steering hydraulic system are arranged longitudinally, while the second three-position four-way solenoid proportional valve 36 in the front wheel steering hydraulic system is arranged laterally. Furthermore, the two second two-position two-way solenoid valves 31 and the two first check valves 32 are also symmetrically arranged. This facilitates the integration of the various hydraulic valves in the front wheel steering hydraulic system into a valve block, reducing the oil circuit structure and saving installation space.

[0041] The rear wheel steering hydraulic system includes two fifth two-position two-way solenoid valves 41, two third check valves 42, two fourth three-position four-way solenoid proportional valves 43, a fifth three-position four-way solenoid proportional valve 45, a sixth three-position four-way solenoid proportional valve 46, a sixth two-position two-way solenoid valve 49, a seventh two-position two-way solenoid valve 411, a third pressure reducing valve 47, a fourth pressure reducing valve 412, a second steering hydraulic cylinder 44, a second high-pressure accumulator 48, and a second hydraulic booster 410. The oil inlets of the two fifth two-position two-way solenoid valves 41 are connected to the oil outlets of the hydraulic pump 15 via oil circuits. The outlet of solenoid valve 41 is connected to the inlet of a third check valve 42. The outlet of the third check valve 42 is connected to the inlet of a fourth three-position four-way solenoid proportional valve 43. The return port of the fourth three-position four-way solenoid proportional valve 43 is connected to the inlet of hydraulic pump 15 and low-pressure accumulator 19 via an oil circuit. The two working ports of the fourth three-position four-way solenoid proportional valve 43 are connected to a second steering hydraulic cylinder 44 that controls independent steering of the rear wheels. The outlet of the first two-position two-way solenoid valve 22 of the front and rear wheel drive subsystem is also connected to the inlet of the fourth three-position four-way solenoid proportional valve 43 via an oil circuit. The oil inlet of the fifth three-position four-way electromagnetic proportional valve 45 is connected to the oil outlet of the hydraulic pump 15 via an oil circuit. The oil inlet of the sixth three-position four-way electromagnetic proportional valve 46 is connected to the oil outlet of one of the third check valves 42 via a third pressure reducing valve 47. One working oil port of the fifth three-position four-way electromagnetic proportional valve 45 and the sixth three-position four-way electromagnetic proportional valve 46 is connected to a second high-pressure accumulator 48. The other working oil port of the fifth three-position four-way electromagnetic proportional valve 45 and the sixth three-position four-way electromagnetic proportional valve 46 is closed. For example, the return port of valve 16 is connected to the inlet of hydraulic pump 15 and low-pressure accumulator 19 via an oil circuit. The outlet of one of the third check valves 42 is also connected to a sixth two-position two-way solenoid valve 49. The other port of the sixth two-position two-way solenoid valve 49 is connected to a second hydraulic booster 410 and a seventh two-position two-way solenoid valve 411. The outlet of the second hydraulic booster 410 is connected to a second high-pressure accumulator 48. The outlet of the seventh two-position two-way solenoid valve 411 is connected to a fourth pressure reducing valve 412. The other port of the fourth pressure reducing valve 412 is connected to the second high-pressure accumulator 48.

[0042] The oil outlets of the two third check valves are interconnected via oil passages. (See attached...) Figure 2Two fourth-position four-way proportional solenoid valves 43 each control a second steering hydraulic cylinder 44 to perform corresponding actions. The fourth-position four-way proportional solenoid valve 43 controlling the left rear wheel and the fourth-position four-way proportional solenoid valve 43 controlling the right rear wheel are symmetrically arranged. The fifth two-position two-way solenoid valve 41 and the third check valve 42 controlling the left rear wheel are symmetrically arranged with the fifth two-position two-way solenoid valve 41 and the two third check valves 42 controlling the right rear wheel, respectively. Referring to the attached diagram, the two fourth-position four-way proportional solenoid valves 43 and the one sixth three-position four-way proportional solenoid valve 46 in the rear wheel steering hydraulic system are arranged longitudinally, and the one fifth three-position four-way proportional solenoid valve 45 in the rear wheel steering hydraulic system is arranged laterally.

[0043] Combined with appendix Figure 2 The second two-position two-way solenoid valve 31 and the two first check valves 32 in the front wheel steering hydraulic system 3 are arranged symmetrically with the fifth two-position two-way solenoid valve 41 and the two third check valves 42 in the rear wheel steering hydraulic system 4. The second three-position four-way solenoid proportional valve 35 in the front wheel steering hydraulic system 3 is arranged symmetrically with the fifth three-position four-way solenoid proportional valve 45 in the rear wheel steering hydraulic system 4. This facilitates the integration of various hydraulic valves into valve blocks, further reducing the oil circuit structure and installation space.

[0044] Combined with appendix Figure 2 The return lines of the front and rear wheel drive subsystems of the left front wheel, the front and rear wheel drive subsystems of the left rear wheel, the center wheel drive subsystem of the left center wheel, the first three-position four-way solenoid proportional valve 33 controlling the left front wheel in the front wheel steering hydraulic system, and the fourth three-position four-way solenoid proportional valve 43 controlling the left rear wheel in the rear wheel steering hydraulic system are connected to one return line. The return lines of the front and rear wheel drive subsystems of the right front wheel, the front and rear wheel drive subsystems of the right rear wheel, the center wheel drive subsystem of the left center wheel, the first three-position four-way solenoid proportional valve 33 controlling the right front wheel in the front wheel steering hydraulic system, and the fourth three-position four-way solenoid proportional valve 43 controlling the right rear wheel in the rear wheel steering hydraulic system are connected to one return line. Finally, all of them are connected to the oil inlet of the hydraulic pump 15 and the low-pressure accumulator 19 through a single oil pipe, thereby further reducing the oil circuit structure.

[0045] Preferably, the outlet of the hydraulic pump 15 is connected to a fourth check valve 16. After passing through the fourth check valve 16, the outlet of the hydraulic pump 15 is connected to the oil inlet circuit of the steering hydraulic system and the six-wheel drive hydraulic system. That is, the fourth check valve 16 controls whether oil enters the oil inlet of the first two-position two-way solenoid valve 22 (controlling the first three-position four-way solenoid directional valve 21), the second three-position four-way solenoid directional valve 24, the second two-position two-way solenoid valve 31 (controlling the first three-position four-way solenoid proportional valve 33), the second three-position four-way solenoid proportional valve 35, the fourth two-position two-way solenoid valve 311, the fifth two-position two-way solenoid valve 41 (controlling the fourth three-position four-way solenoid proportional valve 43), and the fifth three-position four-way solenoid proportional valve 45.

[0046] Preferably, a pilot-operated electromagnetic relief valve 17 is also connected to the oil outlet pipe of the fourth one-way valve 16, and the oil outlet of the pilot-operated electromagnetic relief valve 17 is connected to the oil tank 18.

[0047] Preferably, an adjustable flow valve 314 is provided between the first three-position four-way electromagnetic proportional valve 33 and the first steering hydraulic cylinder 34, and between the fourth three-position four-way electromagnetic proportional valve 43 and the second steering hydraulic cylinder 44. The adjustable flow valve 314 is used to further regulate the flow of the first steering hydraulic cylinder 34 and the second steering hydraulic cylinder 44, thereby regulating the steering angle and steering speed of the wheel.

[0048] The steering hydraulic system and the six-wheel drive hydraulic system share a low-pressure accumulator via oil circuits.

[0049] The front wheel steering hydraulic system has two first steering hydraulic cylinders corresponding to the left front wheel and the right front wheel, respectively, which are used to drive the left front wheel and the right front wheel to steer; the rear wheel steering hydraulic system has two second steering hydraulic cylinders corresponding to the left rear wheel and the right rear wheel, respectively, which are used to drive the left rear wheel and the right rear wheel to steer.

[0050] Combined with appendix Figure 3The suspension system includes a suspension stiffness and damping circuit 51, a suspension energy feeding system 52, a left front wheel suspension drive system 53 and a right front wheel suspension drive system 54 with identical structures and symmetrically arranged, a left middle wheel suspension drive system 55 and a right middle wheel suspension drive system 56 with identical structures and symmetrically arranged, and a left rear wheel suspension drive system 57 and a right rear wheel suspension drive system 58 with identical structures and symmetrically arranged. The left front wheel suspension drive system 53, the left middle wheel suspension drive system 55, and the left rear wheel suspension drive system 57 have identical structures. The left front wheel suspension drive system 53 includes a laterally arranged seventh three-position four-way electromagnetic proportional valve 59, a laterally arranged first three-position three-way electromagnetic directional valve 510, a longitudinally arranged second three-position three-way electromagnetic directional valve 511, and a suspension hydraulic cylinder 512. The oil inlet of the seventh three-position four-way electromagnetic proportional valve 59 is connected via an oil circuit to the oil outlet of the second pressure reducing valve 313 of the front wheel steering hydraulic system 3 and the first high-pressure accumulator. The energy generator 38 is connected, and the return port of the seventh three-position four-way electromagnetic proportional valve 59 is connected via an oil circuit between the first hydraulic booster 310 and the third two-position two-way electromagnetic valve 39 in the front wheel steering hydraulic system 3. The two working ports of the seventh three-position four-way electromagnetic proportional valve 59 are respectively connected to the oil port of the lower chamber of the suspension hydraulic cylinder 512 and the suspension stiffness and damping circuit 51; the inlet port of the first three-position three-way electromagnetic reversing valve 510 is connected to the suspension energy supply system 52. The return port of the three-position three-way solenoid directional valve 510 is connected to the inlet port of the second three-position three-way solenoid directional valve 511. The working port of the first three-position three-way solenoid directional valve 510 is connected to the port of the upper chamber of the suspension hydraulic cylinder 512 and the suspension stiffness and damping circuit 51. The return port of the second three-position three-way solenoid directional valve 511 is connected to the suspension energy supply system 52. The working port of the second three-position three-way solenoid directional valve 52 is connected to the port of the lower chamber of the suspension hydraulic cylinder 512.

[0051] Preferably, an adjustable flow valve 314 is provided on the oil line between the second three-position three-way solenoid directional valve 52 of the left front wheel suspension drive system 53, right front wheel suspension drive system 54, left middle wheel suspension drive system 55, right middle wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58 and the lower chamber oil port of the suspension hydraulic cylinder 512. An adjustable flow valve 314 is provided on the oil line between the working oil port of the first three-position three-way solenoid directional valve 510 of the left front wheel suspension drive system 53, right front wheel suspension drive system 54, left middle wheel suspension drive system 55, right middle wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58 and the upper chamber oil port of the suspension hydraulic cylinder 512.

[0052] The left front wheel suspension drive system 53, right front wheel suspension drive system 54, left middle wheel suspension drive system 55, right middle wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58 of the present invention have the same structure. Furthermore, the left front wheel suspension drive system 53 and right front wheel suspension drive system 54, the left middle wheel suspension drive system 55 and right middle wheel suspension drive system 56, and the left rear wheel suspension drive system 57 and right rear wheel suspension drive system 58 are all symmetrically arranged, which allows each hydraulic valve to be integrated into a valve block, further reducing the oil circuit structure.

[0053] Combined with appendix Figure 3 and attached Figure 4 The suspension stiffness and damping circuit 51 includes an eighth two-position two-way solenoid valve 5101, a fifth one-way valve 5102, and a diaphragm accumulator 5103. The oil inlet of the eighth two-position two-way solenoid valve 5101 is connected via an oil circuit to one working port of the seventh three-position four-way solenoid proportional valve 59, the oil port of the upper chamber of the suspension hydraulic cylinder 512, and the working port of the first three-position three-way solenoid directional valve 510. The oil outlet of the eighth two-position two-way solenoid valve 5101 is connected to the fifth one-way valve. Valve 5102, the oil outlet of the fifth check valve 5102 is connected to the diaphragm accumulator 5103 and the adjustable flow valve 314. One oil port of the adjustable flow valve 314 is connected to the oil outlet of the fifth check valve 5102 and the diaphragm accumulator 5103. The other oil port of the adjustable flow valve 314 is connected to the eighth two-position two-way solenoid valve 5101. That is to say, one oil port of the eighth two-position two-way solenoid valve is connected to both the fifth check valve 5102 and the adjustable flow valve 314.

[0054] Combined with appendix Figure 2 Appendix Figure 3 and attached Figure 5The suspension energy feeding system includes a sixth check valve 5201, a seventh check valve 5202, an eighth check valve 5203, a ninth check valve 5204, a first accumulator 5205, a second accumulator 5208, a second hydraulic motor 5206, and an energy feeding mechanism 5207. The sixth check valve 5201, the seventh check valve 5202, the eighth check valve 5203, and the ninth check valve 5204 form a closed-loop oil circuit. The sixth check valve 5201 and the seventh check valve 5202 are installed in opposite directions. The sixth check valve 5201 and the eighth check valve 5204 are installed in opposite directions. The installation directions of valves 5203 and 5204 are the same. The installation directions of the eighth check valve 5203 and the ninth check valve 5204 are opposite. The oil circuit between the eighth check valve 5203 and the ninth check valve 5204 connects to the first accumulator 5205 and the second hydraulic motor 5206. The hydraulic motor 5206 is connected to a power supply mechanism 5207. The oil outlet of the second hydraulic motor 5206 is connected to the second accumulator 5208 via a pipeline. The oil port of the second accumulator 5208 is also connected to the oil circuit between the sixth check valve 5201 and the seventh check valve 5202 via an oil circuit. The power supply mechanism 5207 is an existing technology product, mainly used to store the mechanical energy output by the second hydraulic motor. Simultaneously, the power supply mechanism 5207 can convert the mechanical energy into hydraulic energy for the second hydraulic motor. Figure 5 In the diagram, 03 and 04 represent two oil circuits. Oil circuit 03 is used to connect with the oil inlet of the first three-position three-way solenoid valve 510 in the left front wheel suspension drive system 53, right front wheel suspension drive system 54, left middle wheel suspension drive system 55, right middle wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58. Oil circuit 04 is used to connect with the oil return port of the second three-position three-way solenoid valve 511 in the left front wheel suspension drive system 53, right front wheel suspension drive system 54, left middle wheel suspension drive system 55, right middle wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58.

[0055] The oil inlet of the first three-position three-way solenoid directional valve 510 in the left front wheel suspension drive system 53 is connected via an oil passage to the oil passage between the sixth one-way valve 5201 and the eighth one-way valve 5203. The oil return port of the second three-position three-way solenoid directional valve 511 in the left front wheel suspension drive system is connected via an oil passage to the oil passage between the seventh one-way valve 5202 and the ninth one-way valve 5204, thereby achieving the connection between the left front wheel suspension drive system 53 and the suspension energy supply system 52; or the oil inlet of the first three-position three-way solenoid directional valve 510 in the left front wheel suspension drive system 52 is connected via an oil passage to the oil passage between the seventh one-way valve 5202 and the ninth one-way valve 5204. The return port of the second three-position three-way solenoid directional valve 511 is connected to the third three-position four-way solenoid directional valve 513 and is respectively connected to the two working ports of the third three-position four-way solenoid directional valve 513. The inlet port of the third three-position four-way solenoid directional valve 513 is connected to the oil circuit between the sixth one-way valve 5201 and the eighth one-way valve 5203 via an oil circuit. The return port of the third three-position four-way solenoid directional valve 513 is connected to the oil circuit between the seventh one-way valve 5201 and the ninth one-way valve 5204 via an oil circuit, thereby realizing the connection between the left front wheel suspension drive system and the suspension energy supply system.

[0056] Referring to the accompanying drawings, in some embodiments, the suspension energy supply system 52 is directly connected to the right front wheel suspension drive system 54, the right middle wheel suspension drive system 56, and the right rear wheel suspension drive system 58, while the left front wheel suspension drive system 53, the left middle wheel suspension drive system 55, and the left rear wheel suspension drive system 57 are connected to the suspension energy supply system 52 via a third three-position four-way solenoid directional valve 513. Specifically, the oil inlet of the first three-position three-way solenoid directional valve 510 in the right front wheel suspension drive system 54 is connected to the oil circuit between the sixth one-way valve 5201 and the eighth one-way valve 5203 via an oil circuit. Similarly, the oil return port of the second three-position three-way solenoid directional valve 511 in the right front wheel suspension drive system 54 is connected to the oil circuit between the seventh one-way valve 5202 and the ninth one-way valve 5204 via an oil circuit, thereby achieving the connection between the right front wheel suspension drive system 54 and the suspension energy supply system 52. Likewise, the oil inlet of the first three-position three-way solenoid directional valve 510 in the right middle wheel suspension drive system 56 is connected to the oil circuit between the sixth one-way valve 5201 and the eighth one-way valve 5203 via an oil circuit. The middle front wheel suspension drive system 54... The return port of the second three-position three-way solenoid directional valve 511 in the right rear wheel suspension drive system 58 is connected to the oil circuit between the seventh one-way valve 5202 and the ninth one-way valve 5204 via an oil circuit, thereby realizing the connection between the right middle wheel suspension drive system 56 and the suspension energy supply system 52; the inlet port of the first three-position three-way solenoid directional valve 510 in the right rear wheel suspension drive system 58 is connected to the oil circuit between the sixth one-way valve 5201 and the eighth one-way valve 5203 via an oil circuit, and the return port of the second three-position three-way solenoid directional valve 511 in the right rear wheel suspension drive system 58 is connected to the oil circuit between the seventh one-way valve 5202 and the ninth one-way valve 5204 via an oil circuit, thereby realizing the connection between the right rear wheel suspension drive system 58 and the suspension energy supply system 52.

[0057] Referring to the attached diagram, the left front wheel suspension drive system 53 is connected to the right front wheel suspension drive system 54 and the suspension energy supply system 52 through the third three-position four-way solenoid valve 513 (also known as the anti-roll three-position four-way solenoid valve). The left middle wheel suspension drive system 55 is connected to the right middle wheel suspension drive system 56 and the suspension energy supply system 52 through the third three-position four-way solenoid valve 513. The left rear wheel suspension drive system 57 is connected to the right rear wheel suspension drive system 58 and the suspension energy supply system 52 through the third three-position four-way solenoid valve 513. Specifically, the oil inlet of the first three-position three-way solenoid directional valve 510 and the oil return port of the second three-position three-way solenoid directional valve 511 in the left front wheel suspension drive system 53 are respectively connected to the two working ports of the third three-position four-way solenoid directional valve 513. The oil inlet of the third three-position four-way solenoid directional valve 513 is connected to the oil inlet of the first three-position three-way solenoid directional valve 510 in the right front wheel suspension drive system 54, and the oil return port of the third three-position four-way solenoid directional valve 511 is connected to the oil return port of the second three-position three-way solenoid directional valve 511 in the right front wheel suspension drive system 54. In other words, the third three-position four-way solenoid directional valve 513 is used as a connecting bridge between the left front wheel suspension drive system 53, the right front wheel suspension drive system 54, and the suspension energy dissipation system 52. Similarly, the connection method between the left and right center wheel suspension drive systems 55 is the same as that between the left front wheel suspension drive system 53 and the right front wheel suspension drive system 54, and the connection method between the left and right rear wheel suspension drive systems 57 and 58 is the same as that between the left and right front wheel suspension drive systems 53 and 54. That is, the third-position four-way solenoid valve 513 is used as the connecting bridge between the left and right center wheel suspension drive systems 53 and 54, and between the suspension energy supply system 52 and the left and right rear wheel suspension drive systems 57 and 58, and between the suspension energy supply system 52.

[0058] In specific implementation, the left front wheel suspension drive system 53, the left middle wheel suspension drive system 55, and the left rear wheel suspension drive system 57 can also be directly connected to the suspension energy supply system 52. Then, the right front wheel suspension drive system 54 can be connected to the left front wheel suspension drive system 53 and the suspension energy supply system 52, the right middle wheel suspension drive system 56 can be connected to the left middle wheel suspension drive system 55 and the suspension energy supply system 52, and the right rear wheel suspension drive system 58 can be connected to the left rear wheel suspension drive system 57 and the suspension energy supply system 52 through the third three-position four-way electromagnetic reversing valve 513.

[0059] In the specific implementation process, the left front wheel suspension drive system 53, the left middle wheel suspension drive system 54, the left rear wheel suspension drive system 55, the right front wheel suspension drive system 56, the right middle wheel suspension drive system 57, and the right rear wheel suspension drive system 58 are all connected to a suspension energy supply system 52. That is, the suspension energy supply system 52 is used to assist the operation of the left front wheel suspension drive system 53, the left middle wheel suspension drive system 54, the left rear wheel suspension drive system 55, the right front wheel suspension drive system 56, the right middle wheel suspension drive system 57, and the right rear wheel suspension drive system 58.

[0060] In some embodiments, the first three-position three-way solenoid directional valve 510 and the second three-position three-way solenoid directional valve 511 of the left middle wheel suspension drive system 55 and the right middle wheel suspension drive system 56 are connected to a fourth three-position four-way solenoid directional valve 514. The oil inlet of the first three-position three-way solenoid directional valve 510 and the oil return of the second three-position three-way solenoid directional valve 511 are respectively connected to the two working oil ports of the fourth three-position four-way solenoid directional valve 514. The oil inlet and oil return of the fourth three-position four-way solenoid directional valve 514 are respectively connected to the two working oil ports of the third three-position four-way solenoid directional valve 513. Alternatively, the oil inlet and oil return of the fourth three-position four-way solenoid directional valve 514 are connected to the oil inlet and oil return of the third three-position four-way solenoid directional valve 513. As mentioned earlier, since the third three-position four-way solenoid directional valve 513 serves as a connecting bridge between the left and right center wheel suspension drive systems and the suspension energy supply system, the fourth three-position four-way solenoid directional valve 514, which is connected to the first three-position three-way solenoid directional valve 510 and the second three-position three-way solenoid directional valve 511 in the left center wheel suspension drive system 55, is connected to the two working ports of the third three-position four-way solenoid valve 513. Therefore, the fourth three-position four-way solenoid directional valve, which is connected to the first three-position three-way solenoid directional valve 510 and the second three-position three-way solenoid directional valve 511 in the right center wheel suspension drive system 56, is also connected to the third three-position four-way solenoid directional valve 514. 514 is connected to the inlet and outlet of the third three-position four-way solenoid valve 513; if the fourth three-position four-way solenoid valve 514, which is connected to the first three-position three-way solenoid valve 510 and the second three-position three-way solenoid valve 511 in the left middle wheel suspension drive system 55, is connected to the inlet and outlet of the third three-position four-way solenoid valve 513, then the two working ports of the fourth three-position four-way solenoid valve 514, which is connected to the first three-position three-way solenoid valve 510 and the second three-position three-way solenoid valve 511 in the right middle wheel suspension drive system 56, are connected to the third three-position four-way solenoid valve 513.

[0061] In some embodiments, the suspension energy supply system 52 further includes a fifth three-position three-way solenoid directional valve 5209 and a sixth three-position three-way solenoid directional valve 5210. The oil inlet of the fifth three-position three-way solenoid directional valve 5209 is connected via an oil passage to the oil passage between the sixth one-way valve 5201 and the eighth one-way valve 5203. The oil return port of the fifth three-position three-way solenoid directional valve 5209 is connected via an oil passage to the oil passage between the seventh one-way valve 5202 and the ninth one-way valve 5204. The fifth three-position three-way solenoid directional valve 5209... The working port of valve 9 is connected to the inlet oil circuit of the seventh three-position four-way solenoid proportional valve 59; the return oil port of the sixth three-position three-way solenoid directional valve 5210 is connected to the oil circuit between the sixth one-way valve 5201 and the eighth one-way valve 5203 via an oil circuit; the inlet oil port of the sixth three-position three-way solenoid directional valve 5210 is connected to the oil circuit between the seventh one-way valve 5202 and the ninth one-way valve 5204 via an oil circuit; and the working oil port of the sixth three-position three-way solenoid directional valve 5210 is connected to the oil circuit of the front wheel steering hydraulic system 3.

[0062] Combined with appendix Figure 2 and attached Figure 3 The inlet of the seventh three-position four-way electromagnetic proportional valve 59 is connected via an oil circuit to the outlet of the second pressure reducing valve 313 of the front wheel steering hydraulic system 3 and the first high-pressure accumulator 38. In other words, the oil inlet of the seventh three-position four-way electromagnetic proportional valve 59 is the outlet of the second pressure reducing valve 313 and the first high-pressure accumulator 38. Therefore, the working port of the fifth three-position three-way electromagnetic directional valve 5209 is connected via an oil circuit to the outlet of the second pressure reducing valve 313 of the front wheel steering hydraulic system and the first high-pressure accumulator 38. The working port of the sixth three-position three-way electromagnetic directional valve 5210 is connected to the oil circuit between the first hydraulic booster 310 and the third two-position two-way electromagnetic valve 39. That is, the oil circuit of the front wheel steering hydraulic system described above is the oil circuit between the first hydraulic booster 310 and the third two-position two-way electromagnetic valve 39.

[0063] The braking energy recovery process of this invention is as follows:

[0064] For the left front wheel: When the vehicle is driving normally, the first three-position four-way solenoid valve 21 of the left front wheel is in the lower connected state, and the first two-position two-way solenoid valve 22 of the left front wheel is in the lower connected state. The oil flowing out of the hydraulic pump 15 passes through the check valve 16, the first two-position two-way solenoid valve 22 of the left front wheel, and the first three-position four-way solenoid valve 21 of the left front wheel to the hydraulic motor / pump 23 of the left front wheel, driving the left front wheel to drive normally. When braking, the first three-position four-way solenoid valve 21 of the left front wheel is in the upper connected state, the first two-position two-way solenoid valve 22 of the left front wheel is in the upper closed state, and the third two-position two-way solenoid valve 39 of the front wheel steering hydraulic system 3 is in the lower connected state. The hydraulic motor / pump 23 of the left front wheel draws oil from the low-pressure accumulator 19, and the hydraulic oil flows out from the first three-position four-way solenoid valve 21 of the left front wheel, passes through the third two-position two-way solenoid valve 39, and is recovered to the first high-pressure accumulator 38. The hydraulic pump / motor 21 of the left front wheel creates a pressure differential, applying reverse pressure to the left front wheel to complete the braking action. The braking principle and braking energy principle of the right front wheel are the same as those of the left front wheel, and will not be described again.

[0065] For the left and middle wheels: During normal vehicle operation, the second and third position four-way solenoid valve 24 of the left and middle wheels is in the lower open position. Oil flowing from the hydraulic pump 15 passes through the check valve 16 and the second and third position four-way solenoid valve 24 of the left and middle wheels to the hydraulic pump / motor 23 of the left and middle wheels, driving the left and middle wheels to move normally. During braking, the second and third position four-way solenoid valve 24 of the left and middle wheels is in the upper open position, the first and second position two-way solenoid valve 22 of the left front wheel is in the upper closed position, the first and second position two-way solenoid valve 22 of the left rear wheel is in the lower closed position, the fourth and fifth two-way solenoid valves 31 and 41 are in the right open position, the sixth two-way solenoid valve 49 is in the upper open position, and the third two-way solenoid valve 39 is in the lower open position. The hydraulic pump / motor 23 of the left and middle wheels... The low-pressure accumulator 19 draws in hydraulic oil, which flows out through the second three-position four-way solenoid directional valve 24 of the left middle wheel. The oil is then returned to the first high-pressure accumulator 38 via the upward oil path through the fourth two-position two-way solenoid valve 39, the first check valve 32, the third two-position two-way solenoid valve 39, and the first hydraulic booster 310. Simultaneously, the oil can also be returned to the second high-pressure accumulator 48 via the downward oil path through the fifth two-position two-way solenoid valve 41, the third check valve 42, the sixth two-position two-way solenoid valve 49, and the second hydraulic booster 410. The hydraulic pump / motor 23 of the left middle wheel creates a pressure differential, applying reverse pressure to the left middle wheel to complete the braking action. The braking principle and braking energy principle of the right middle wheel are the same as those of the left middle wheel and will not be described further.

[0066] For the left rear wheel: When the vehicle is driving normally, the first three-position four-way solenoid valve 21 of the left rear wheel is in the lower connected state, and the first two-position two-way solenoid valve 22 of the left rear wheel is in the upper connected state. The oil flowing out of the hydraulic pump 15 passes through the check valve 16, the first two-position two-way solenoid valve 22 of the left rear wheel, and the first three-position four-way solenoid valve 21 of the left rear wheel to the hydraulic pump / motor 23 of the left rear wheel, driving the left rear wheel to drive normally. During braking, the first three-position four-way solenoid valve 21 of the left rear wheel is in the upper open state, the first two-position two-way solenoid valve 22 of the left rear wheel is in the lower closed state, the fifth two-position two-way solenoid valve 41 is in the right open state, and the sixth two-position two-way solenoid valve 49 of the left rear wheel is in the upper open state. The hydraulic pump / motor 23 of the left rear wheel draws oil from the low-pressure accumulator 19, and the hydraulic oil flows out from the first three-position four-way solenoid valve 21 of the left rear wheel, passing through the first two-position two-way solenoid valve 22, the fifth two-position two-way solenoid valve 41, the third check valve 42, the sixth two-position two-way solenoid valve 49, and the second hydraulic booster 410, before being returned to the second high-pressure accumulator 48. The hydraulic pump / motor 23 of the left rear wheel creates a pressure difference, applying reverse pressure to the left rear wheel to complete the braking action. The braking principle and braking energy principle of the right rear wheel are the same as those of the left rear wheel and will not be described again.

[0067] The auxiliary acceleration principle of the first and second high-voltage accumulators of this invention is as follows:

[0068] When the vehicle is in normal driving, the first three-position four-way solenoid valve 21 of the left front wheel, the second three-position four-way solenoid valve 24 of the left middle wheel, the first three-position four-way solenoid valve 21 of the left rear wheel, the first three-position four-way solenoid valve 21 of the right rear wheel, the second three-position four-way solenoid valve 24 of the right middle wheel, and the first three-position four-way solenoid valve 21 of the right front wheel are all in the lower connected state. The first two-position two-way solenoid valve 22 of the left front wheel is in the lower connected state. The first two-position two-way solenoid valve 22 of the left rear wheel, the first two-position two-way solenoid valve 22 of the right rear wheel, and the first two-position two-way solenoid valve 21 of the right front wheel are all in the upper connected state. During assisted acceleration, the sixth and third position four-way solenoid proportional valve 46 and the second and third position four-way solenoid proportional valve 36 are in the lower and upper positions respectively. The first high-pressure accumulator 38 and the second high-pressure accumulator 48 release energy simultaneously. The oil flows through the sixth and third position four-way solenoid proportional valve 46 and the second and third position four-way solenoid proportional valve 36, the fourth pressure reducing valve 47 and the first pressure reducing valve 37, and then through the first and second position two-way solenoid valve 21 to provide flow to the system. By adjusting the valve opening of the first and third position four-way solenoid directional valve 21 of the left front wheel, the second and third position four-way solenoid directional valve 24 of the left middle wheel, the third and fourth position four-way solenoid directional valve 21 of the left rear wheel, the first and third position four-way solenoid directional valve 21 of the right rear wheel, the second and third position four-way solenoid directional valve 24 of the right middle wheel, and the first and third position four-way solenoid directional valve 21 of the right front wheel, the vehicle speed is controlled to achieve the function of assisted acceleration.

[0069] Based on the aforementioned comprehensive energy-saving control strategy for the hydraulic drive system of the three-axis unmanned vehicle, the comprehensive energy-saving control strategy includes one or more of the following: traction and steering coordination control strategy, braking and steering coordination control strategy, and suspension system working mode control strategy.

[0070] The braking and steering coordination control strategy includes the following:

[0071] (1): Select the steering mode according to the working conditions: independent steering or differential steering;

[0072] (2): If differential steering is selected, the two first three-position four-way electromagnetic proportional valves 33 in the front wheel steering hydraulic system 3 and the two fourth three-position four-way electromagnetic proportional valves 43 in the rear wheel steering hydraulic system 4 are in the neutral position (i.e., closed state). The wheel speed and torque of each wheel are controlled by the six-wheel drive hydraulic system, thereby realizing differential steering of the wheels.

[0073] The specific process of differential steering is as follows: the two first-position four-way solenoid proportional valves 33 in the front wheel steering hydraulic system 3 and the two fourth-position four-way solenoid proportional valves 43 in the rear wheel steering hydraulic system 4 are in the neutral position. At this time, differential steering can be achieved using the six-wheel drive hydraulic system. The states of the three-position four-way solenoid directional valves in the six-wheel drive hydraulic system are as follows: the first-position four-way solenoid directional valve 21 of the left front wheel, the second-position four-way solenoid directional valve 24 of the left middle wheel, and the first-position four-way solenoid directional valve 21 of the left rear wheel are in the upper position (or lower position), while the first-position four-way solenoid directional valve 21 of the right rear wheel, the second-position four-way solenoid directional valve 24 of the right middle wheel, and the first-position four-way solenoid directional valve 21 of the right front wheel are all in the lower position (or upper position). Wheel speed and torque control can be achieved by adjusting the opening size (left and right valves) of the first three-position four-way solenoid valve 21 of the left front wheel, the second three-position four-way solenoid valve 24 of the left middle wheel, the first three-position four-way solenoid valve 21 of the left rear wheel, the first three-position four-way solenoid valve 21 of the right rear wheel, the second three-position four-way solenoid valve 24 of the right middle wheel, and the first three-position four-way solenoid valve 21 of the right front wheel, thus realizing differential steering by utilizing the difference in wheel speed.

[0074] (3): If independent steering is selected, the steering hydraulic system also includes an angle sensor for monitoring wheel angle, a pressure sensor and a flow sensor for monitoring steering hydraulic system pressure and flow; the two first three-position four-way electromagnetic proportional valves 33 in the front wheel steering hydraulic system and the two fourth three-position four-way electromagnetic proportional valves 43 in the rear wheel steering hydraulic system are in the non-neutral position, and the first three-position four-way electromagnetic proportional valves 33 and the fourth three-position four-way electromagnetic proportional valves 43 are selected to be connected in the upper or lower position according to the steering direction of the three-axle unmanned vehicle; the selection of independent steering also includes the following:

[0075] (3.1) Determine the braking force required for the three-axle unmanned vehicle and the yaw moment required for the steering of the three-axle unmanned vehicle;

[0076] (3.2) Determine whether the actual steering angle meets the expected value required by the working conditions based on the steering angle sensor, and select different control strategies considering the braking intensity; wherein, the braking intensity is divided into light braking and high-intensity braking, and the braking acceleration a < 0.3 m / s². 2 The braking was light, with a braking acceleration a ≥ 0.3 m / s². 2 The control strategy includes the following:

[0077] (3.21) If the steering angle meets the expected value required by the operating conditions, then the following two different control strategies shall be implemented based on the braking intensity:

[0078] The first control strategy: When the braking intensity is light braking, the steering hydraulic system and the six-wheel drive hydraulic system work together to recover the energy during wheel braking (that is, to recover the energy during wheel braking using the first high-pressure accumulator 38 and the second high-pressure accumulator 48). The recovery of braking energy has been described above and will not be repeated here.

[0079] The second control strategy: When the braking intensity is high-intensity braking, it is determined whether the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system (i.e., the energy stored in the first high-pressure accumulator 38 and the second high-pressure accumulator 48) can provide the braking force and yaw torque required for braking and steering. If the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can provide the braking force and yaw torque required for braking and steering, then the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system is used to provide the braking force and yaw torque required for braking and steering of the wheels. If the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system cannot provide the braking force and yaw torque required for braking and steering, then auxiliary braking is performed through the friction braking system configured on the wheels.

[0080] (3.22) If the steering angle does not meet the expected value required by the operating conditions, the following two different control strategies shall be adopted based on the braking intensity:

[0081] The first control strategy: When the braking intensity is light braking, it is determined whether the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can provide the braking force and yaw torque required for braking and steering. If the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can provide the braking force and yaw torque required for braking and steering, then the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system is used to provide the braking force and yaw torque required for braking and steering. If the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system cannot provide the braking force and yaw torque required for braking and steering, then the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system, as well as the hydraulic pump of the power system, jointly provide the braking force and yaw torque required for braking and steering. That is, the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system is used as auxiliary braking and auxiliary steering for wheel braking and steering.

[0082] When the energy released by the first high-pressure accumulator 38 and the second high-pressure accumulator 48 meets the required braking force and yaw torque (i.e., the energy can supplement the pressure and flow required for steering and braking), the hydraulic circuit operation process is as follows: the hydraulic fluid is released from the first high-pressure accumulator 38 and the second high-pressure accumulator 48, flows through the lower channel of the sixth three-position four-way solenoid proportional valve 46 and the upper channel of the second three-position four-way solenoid proportional valve 36, the fourth pressure reducing valve 47 and the first pressure reducing valve 37, and finally the hydraulic fluid reaches the first three-position four-way solenoid proportional valve 33 of the left front wheel. The first three-position four-way solenoid proportional valve 33 of the right front wheel, the first three-position four-way solenoid proportional valve 33 of the left rear wheel, the first three-position four-way solenoid proportional valve 33 of the right rear wheel, the first three-position four-way solenoid directional valve 21 of the left front wheel, the second three-position four-way solenoid directional valve 24 of the left middle wheel, the first three-position four-way solenoid directional valve 21 of the left rear wheel, the first three-position four-way solenoid directional valve 21 of the right front wheel, the second three-position four-way solenoid directional valve 24 of the right middle wheel, and the three-position four-way solenoid directional valve 21 of the right rear wheel provide power (pressure and flow) for wheel braking and steering.

[0083] When the energy released by the first high-voltage accumulator 38 and the second high-voltage accumulator 48 meets the required braking force and yaw torque (i.e., the energy can supplement the pressure and flow required for steering and braking), the oil circuit process of the first high-voltage accumulator 38 and the second high-voltage accumulator 48 is the same as when powered independently, and will not be described again. While the first and second high-pressure accumulators supply power, the hydraulic pump 15 begins to supply power. The oil circuit operation process of the hydraulic pump 15 is as follows: the oil pumped by the hydraulic pump 15 passes through the third check valve 16 and the first two-position two-way solenoid valve 22, and finally to the first three-position four-way solenoid proportional valve 33 of the left front wheel, the first three-position four-way solenoid proportional valve 33 of the right front wheel, the first three-position four-way solenoid proportional valve 33 of the left rear wheel, the first three-position four-way solenoid proportional valve 33 of the right rear wheel, the first three-position four-way solenoid directional valve 21 of the left front wheel, the second three-position four-way solenoid directional valve 24 of the left middle wheel, the first three-position four-way solenoid directional valve 21 of the left rear wheel, the first three-position four-way solenoid directional valve 21 of the right front wheel, the second three-position four-way solenoid directional valve 24 of the right middle wheel, and the third three-position four-way solenoid directional valve 21 of the right rear wheel, providing power (pressure and flow) for wheel braking and steering. This achieves the joint power supply of the first high-pressure accumulator, the second high-pressure accumulator, and the hydraulic pump.

[0084] The second control strategy: When the braking intensity is high-intensity braking, the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system, together with the hydraulic pump of the power system, provides the braking force required for the wheels. After the hydraulic pump of the power system, the steering hydraulic system and the six-wheel drive hydraulic system recover the energy to provide the braking force required for braking, the pressure and flow (i.e. the energy after braking) are used as the yaw torque required for the steering of the three-axle unmanned vehicle.

[0085] The four scenarios in steps (3.2) (3.21) and (3.22) can be performed alternately within a set time period. The sensors used to collect data (including but not limited to angle sensors, acceleration sensors, pressure sensors, and flow sensors) periodically collect and transmit data according to the data collection cycle. Therefore, the state of the unmanned vehicle will change constantly during operation. Thus, the four strategies in (3.21) and (3.22) can alternately execute different control strategies according to the collected data.

[0086] The determination of the braking force required for the three-axis unmanned vehicle and the yaw moment required for steering the three-axis unmanned vehicle includes the following:

[0087]

[0088]

[0089] Where Fx represents the sum of the longitudinal forces of all wheels of the three-axis unmanned vehicle (i.e., the braking force required by the three-axis unmanned vehicle), (, Af and Cd represent the air density, the vehicle's frontal area (i.e., the frontal area of ​​the three-axis unmanned vehicle) and the air drag coefficient, respectively, Vx is the longitudinal velocity of the vehicle, m, g and ( represent the vehicle's mass, gravitational acceleration and slope, respectively, Ff is the sum of the rolling resistance of all wheels, Fxi represents the longitudinal force of each wheel, i=[fl,fr,ml,mr,rl,rr], where t represents time.

[0090] In independent steering mode, considering the limitations of ground adhesion conditions, the yaw moment required for vehicle steering can be calculated using existing control algorithms:

[0091] First: Using the existing control algorithm, the external yaw moment M generated by the longitudinal force is calculated using the following formula. z :

[0092]

[0093] In the formula, M z K is the external yaw moment generated by the longitudinal force. P K i K d Here, 'e' represents the yaw rate tracking error, and 'e' represents the control parameter. Integral for yaw rate tracking error, The derivative of the yaw rate tracking error;

[0094] Then, using an average distribution approach, the braking force of the six wheels on both sides of the three-axis autonomous vehicle is:

[0095] ,

[0096] Among them, F xfl This refers to the braking force of the left front wheel, F. xml This refers to the braking force of the left and middle wheels, F. xyl This refers to the braking force of the left rear wheel, F. xfr This refers to the braking force of the right front wheel, F. xml This refers to the braking force of the right center wheel, F. xyl This represents the braking force of the right rear wheel, and d is the length of the wheel swing arm of the three-axle unmanned vehicle.

[0097] The energy recovered or released by the steering hydraulic system and the six-wheel drive hydraulic system can be calculated using the following formula:

[0098] ,

[0099] In the formula, p is the pressure of the accumulator. , , These are the pre-charge pressure, working pressure, and final pressure of the accumulators (i.e., the first and second high-pressure accumulators in the steering hydraulic system and the six-wheel drive hydraulic system). , , These are the initial volume, the volume during operation, and the final volume of the accumulator, respectively. It is the gas polyvariance index.

[0100] According to Boyle's law, the thermodynamic equation for the accumulator (i.e., the first and second high-pressure accumulators in the steering hydraulic system and the six-wheel drive hydraulic system) can be expressed as:

[0101] .

[0102] In the specific implementation process, based on the law of conservation of energy, the energy E stored or released by the steering hydraulic system and the six-wheel drive hydraulic system is converted into the pressure of the hydraulic oil, and then into force or torque. Those skilled in the art can understand this, so it will not be elaborated here.

[0103] The traction and steering coordination control strategy described in this invention includes the following:

[0104] (1): Steering mode selected according to working conditions: independent steering or differential steering;

[0105] (2): If differential steering is selected, the two first three-position four-way solenoid proportional valves in the front wheel steering hydraulic system and the two fourth three-position four-way solenoid proportional valves in the rear wheel steering hydraulic system are in the neutral position (i.e., closed state). The wheel speed and torque of each wheel are controlled by the six-wheel drive hydraulic system, thereby realizing differential steering of the wheels.

[0106] (3): If independent steering is selected, the steering hydraulic system also includes an angle sensor for monitoring wheel angle, a pressure sensor and a flow sensor for monitoring steering hydraulic system pressure and flow; the two first three-position four-way electromagnetic proportional valves in the front wheel steering hydraulic system and the two fourth three-position four-way electromagnetic proportional valves in the rear wheel steering hydraulic system are in the non-neutral position, and the first three-position four-way electromagnetic proportional valves and the fourth three-position four-way electromagnetic proportional valves are selected to be connected in the upper or lower position according to the steering direction of the three-axle unmanned vehicle; the specific use of independent steering includes the following:

[0107] (3.1) Determine the desired traction force of the three-axle unmanned vehicle and the yaw moment required for steering. The calculation methods for traction force and yaw moment are the same as those for braking and steering, and will not be repeated here.

[0108] (3.2) Based on the steering angle sensor, determine whether the actual steering angle meets the expected value required by the working condition, and comprehensively consider the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system (i.e. the first high-pressure accumulator and the second high-pressure accumulator), as well as the magnitude of the traction force to select different control strategies.

[0109] (3.21) If the steering angle does not meet the expected value required by the operating conditions, the following two different control strategies shall be adopted based on whether the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system (i.e., the first high-pressure accumulator and the second high-pressure accumulator) can provide the yaw torque required for steering:

[0110] The first strategy: If the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can provide the yaw torque required for steering, then the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system provides the power for wheel steering;

[0111] The second strategy: If the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system is insufficient to provide the yaw torque required for steering, then the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system, as well as the hydraulic pump, will jointly provide the yaw torque required for wheel steering (i.e., the first high-pressure accumulator 38, the second high-pressure accumulator 48 and the hydraulic pump 15 will jointly provide the power required for steering).

[0112] (3.22) If the steering angle meets the expected value required by the operating conditions, then the following two different control strategies will be implemented based on whether the vehicle's traction force meets the expected value:

[0113] The first strategy: When the traction force is less than the desired value, first determine whether the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can compensate for the traction force to reach the desired value. If the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can compensate for the traction force, then the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system supplements the power required to tow the vehicle. If the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system is insufficient to compensate for the traction force to reach the desired value, then the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system, as well as the hydraulic pump, jointly compensate for the power required to tow the vehicle. The oil circuit process released by the steering hydraulic system and the six-wheel drive hydraulic system (i.e., the first high-pressure accumulator and the second high-pressure accumulator) has been described previously and will not be repeated here.

[0114] The second strategy: When the traction force is greater than or equal to the desired value, the excess pressure and flow are recovered to the first and second high-voltage accumulators. The recovery process of the first and second high-voltage accumulators has been described previously and will not be repeated here.

[0115] The traction and steering coordination control strategy and braking and steering coordination control strategy of this invention, compared with the existing technology that directly determines whether the accumulator provides auxiliary power based on the pressure and flow of the accumulator (i.e., the accumulator does not participate in auxiliary power when the pressure is insufficient), fully utilize the power of the accumulator by formulating control strategies for traction and braking, thereby reducing energy consumption. Furthermore, through the formulation of the strategies of this invention, different steering strategies can be adopted for different operating conditions of the three-axle unmanned vehicle, thereby improving the driving stability of the three-axle unmanned vehicle and meeting the special operational requirements of the three-axle unmanned vehicle.

[0116] Referring to the accompanying drawings, the suspension system operating mode control strategy described in this invention is characterized in that the operating modes of the suspension system include, but are not limited to, the following modes: passive suspension mode, semi-active suspension mode, active suspension mode, rigid locking mode, and vehicle height adjustment mode. The three-axle unmanned vehicle selects the corresponding operating mode based on road surface fluctuations and task requirements during operation. The task requirements are operating modes pre-set by the operator based on specific working conditions. Road surface fluctuations are operating modes based on the response feedback made by the three-axle unmanned vehicle during operation according to road conditions. The passive suspension mode, semi-active suspension mode, and active suspension mode are operating modes under road surface fluctuation conditions, while the rigid locking mode and vehicle height adjustment mode are operating modes under task requirements.

[0117] The passive suspension mode described in this invention is as follows: the left front wheel suspension drive system 53, the right front wheel suspension drive system 54, the left middle wheel suspension drive system 55, the right middle wheel suspension drive system 56, the left rear wheel suspension drive system 57, and the right rear wheel suspension drive system 58 passively adjust the suspension (i.e., the left front suspension, right front suspension, left middle suspension, right middle suspension, left rear suspension, and right rear suspension) based on their respective suspension stiffness and damping circuits 52. The diaphragm accumulator 5103 in the suspension stiffness and damping circuit 51 provides nonlinear stiffness to each suspension, and the adjustable flow valve 314 in the suspension stiffness and damping circuit 51 provides nonlinear damping to each suspension.

[0118] In passive suspension mode: the first three-position three-way solenoid valve 510 in the left front wheel suspension drive system 53, right front wheel suspension drive system 54, left middle wheel suspension drive system 55, right middle wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58 is in the left position; the second three-position three-way solenoid valve 511 is in the upper position; the adjustable flow valve 314 in the suspension stiffness and damping circuit 51 is in the open state; and the seventh three-position four-way solenoid proportional valve 59, the third three-position four-way solenoid valve 513, and the fourth three-position four-way solenoid valve 514 are in the middle position. The suspension hydraulic cylinder 512 itself has a certain passive compression stroke to adapt to the up-and-down swinging motion of the control arm when the wheel bounces with the ground.

[0119] If the suspension system is in passive suspension mode and the vehicle needs to temporarily increase stiffness to perform a special task, the switching valve (i.e., the eighth two-position two-way solenoid valve 5101) in the suspension stiffness and damping circuit 51 can be closed. At this time, the upper and lower chambers of the suspension hydraulic cylinder of each wheel are connected, but the suspension stiffness and damping circuit 51 is not connected.

[0120] The semi-active suspension mode described in this invention involves adjusting the damping of each suspension component by regulating the adjustable flow valve 314 in the suspension stiffness and damping circuit 51. In this mode, the opening control of each hydraulic valve remains consistent with the passive suspension mode, and will not be elaborated further here.

[0121] The active suspension mode described in this invention is as follows: active control enables the suspension hydraulic cylinders corresponding to each wheel to actively avoid or compensate for road surface unevenness, thereby obtaining the vertical stability of the entire vehicle under the current road surface.

[0122] When the suspension system is in active suspension mode: the seventh-position four-way electromagnetic proportional valves 59 in the left front wheel suspension drive system 53, right front wheel suspension drive system 54, left middle wheel suspension drive system 55, right middle wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58 calculate the required input pressure based on the active control force output by the controller to determine the corresponding working position. Both the hydraulic pump 15 and the first high-pressure accumulator 38 can output high-pressure oil, but they have completely different operating characteristics. The hydraulic pump can continuously output high-pressure oil at a specified pressure but consumes more energy, while the first high-pressure accumulator 38, due to physical limitations, can only output high-pressure oil at certain times, and the pressure of the output oil can be adjusted within a small range by the first hydraulic booster 310. When a wheel needs active adjustment, the seventh-position four-way electromagnetic proportional valve 59 corresponding to that wheel operates in the left or right position according to the pressure requirement. The switching is based on whether the pressure in the first high-pressure accumulator 38 can meet the pressure requirements of the active control of the suspension hydraulic cylinder 512 of the wheel. If the pressure requirement is met, high-pressure oil is supplied through the first high-pressure accumulator 38. In this case, the energy consumption caused by the hydraulic pump 15 during operation can be reduced, achieving the purpose of energy saving. If the pressure in the first high-pressure accumulator 38 does not meet the requirements, the high-pressure oil required for active control is supplied through the hydraulic pump 15.

[0123] When the suspension system is in active suspension mode: the position and opening of the corresponding seventh-position four-way electromagnetic proportional directional valve 59 are adjusted according to the pressure required by the suspension hydraulic cylinder 512 of each wheel. This adjustment satisfies the pressure required for active control of the suspension system of that wheel (i.e., the left front wheel suspension drive system 53, right front wheel suspension drive system 54, left center wheel suspension drive system 55, right center wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58 mentioned earlier), without affecting the normal operation of other wheel suspension drive systems. In this mode, the seventh-position four-way electromagnetic proportional directional valves 59 in the aforementioned left front wheel suspension drive system 53, right front wheel suspension drive system 54, left center wheel suspension drive system 55, right center wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58 are controlled independently and do not interfere with each other.

[0124] When the suspension system is in rigid lock-up mode: When performing certain special tasks, the vehicle needs to maintain absolute vertical displacement under the current road conditions. Therefore, the suspension system needs to be adjusted to rigid lock-up mode. At this time, the vertical extension / retraction of each wheel suspension subsystem (i.e., the left front wheel suspension drive system 53, right front wheel suspension drive system 54, left center wheel suspension drive system 55, right center wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58 described above) is strictly controlled to 0. In this mode, the eighth two-position two-way solenoid valve 5101 in the suspension stiffness and damping circuit 51 corresponding to the left front wheel suspension drive system 53, right front wheel suspension drive system 54, left middle wheel suspension drive system 55, right middle wheel suspension drive system 56, left rear wheel suspension drive system 57 and right rear wheel suspension drive system 58 is in the closed state, so that the oil in the upper and lower chambers of each suspension hydraulic cylinder 512 does not flow.

[0125] The vehicle height adjustment mode described in this invention is as follows: when certain special environments require the vehicle to adjust its height, the wheels of the three-axle unmanned vehicle are adjusted sequentially in the order of right rear wheel - left rear wheel - left middle wheel - right middle wheel - right front wheel - left front wheel; and when adjusting the height of each wheel, the range of adjustment of each wheel in a single cycle is the same, and the range of adjustment of each wheel in a single cycle is between 4-8mm, and so on until the height is raised or lowered to the expected height.

[0126] If the vehicle needs to adjust its attitude when driving on inclined surfaces for special operational tasks, adjustments can be made to the suspension subsystems on the same axle (e.g., simultaneous adjustment of the left and right front wheels, left and right center wheels, and left and right rear wheels), or to the suspension subsystems on the same side of the vehicle (e.g., simultaneous adjustment of the left front, left center, and left rear wheels, and the right front, right center, and right rear wheels). This allows for active adjustment of the platform's pitch and roll attitude. This mode ensures the vehicle remains level even on inclined surfaces, providing a normal working environment for special operational tasks.

[0127] When the suspension system is in vehicle height adjustment mode, the original vertical operating mode of each wheel remains unchanged (i.e., passive mode, semi-active mode, and active mode). By switching the seventh three-position four-way electromagnetic proportional valve 59 on and off, the corresponding suspension hydraulic cylinder 512 extends or compresses by the corresponding length, thereby achieving vehicle height adjustment. When adjusting the height of one wheel or a wheel on the same axle, the input signal of the corresponding seventh three-position four-way electromagnetic proportional valve 59 of that group of wheels can be kept consistent, so that the extension and retraction of the hydraulic cylinders in that group are equal.

[0128] When the suspension system needs to lift the wheels (e.g., to overcome obstacles), it essentially involves wheel height adjustment. The difference between wheel lifting and vehicle height adjustment is that only the 7th / 3rd position four-way electromagnetic proportional valve 59 corresponding to that wheel is open during wheel lifting; the 7th / 3rd position four-way electromagnetic proportional valves 59 in other suspension subsystems that do not require wheel lifting remain closed. For example, when the left front wheel needs to be lifted, the 7th / 3rd position four-way electromagnetic proportional valve 59 in the left front wheel suspension drive system 53 is open, while the 7th / 3rd position four-way electromagnetic proportional valves 59 in the right front wheel suspension drive system 54, left center wheel suspension drive system 55, right center wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58 are closed.

[0129] In some embodiments, the active suspension modes of the present invention also include an anti-roll mode based on steering requirements and an anti-pitch mode based on acceleration and deceleration requirements. When the vehicle needs to turn or change lanes, the sprung weight of the vehicle body will be transferred due to the influence of inertial forces, causing the vehicle body to roll and thus resulting in a change in the vehicle body attitude. Roll will exacerbate the lateral load transfer phenomenon when the vehicle is turning, thereby changing the tire adhesion.

[0130] After a steering or lane change request is issued, the seventh three-position four-way electromagnetic proportional valve 59 in the left front wheel suspension drive system 53 is in the open state. Meanwhile, the seventh three-position four-way electromagnetic proportional valves 59 in the right front wheel suspension drive system 54, left middle wheel suspension drive system 55, right middle wheel suspension drive system 56, left rear wheel suspension drive system 57, and right rear wheel suspension drive system 58 can still switch to the corresponding working position and opening degree according to the pressure requirements of each wheel, achieving active vertical stability control. Simultaneously, the fourth three-position four-way electromagnetic directional valve 514 equipped with the left middle wheel operates in the left position, and the fourth three-position four-way electromagnetic directional valve 514 equipped with the right middle wheel operates in the right position. At this time, the first three-position three-way solenoid valves 510 of the left front wheel suspension drive system 53, the left middle wheel suspension drive system 55, and the left rear wheel suspension drive system 57 are in the right position, the first three-position three-way solenoid valves of the right front wheel suspension drive system 54, the right middle wheel suspension drive system 56, and the right rear wheel suspension drive system 58 are in the left position, and each of the second three-position three-way solenoid valves 511 is in the lower position. The third three-position four-way solenoid valve 513 is in the lower position to achieve cross-interconnection of the left and right suspension drive systems (wherein, the left front wheel suspension drive system, the left middle wheel suspension drive system, and the left rear wheel suspension drive system belong to the left side suspension drive system, while the right front wheel suspension drive system, the right middle wheel suspension drive system, and the right rear wheel suspension drive system belong to the right side suspension drive system). Taking a left turn as an example, when a vehicle turns left, it tends to tilt to the right, causing the left-side suspension hydraulic cylinders (i.e., the suspension hydraulic cylinders 512 of the left front wheel suspension drive system, left middle wheel suspension drive system, and left rear wheel suspension drive system) to extend while the right-side suspension hydraulic cylinders (i.e., the suspension hydraulic cylinders 512 of the right front wheel suspension drive system, right middle wheel suspension drive system, and right rear wheel suspension drive system) to contract. At this time, the lower chamber of the left-side hydraulic cylinder contracts, and the high-pressure oil flowing out enters the left-side circuit B (i.e., the oil circuit in the left-side suspension drive system), and after passing through the third-position four-way solenoid directional valve 513, enters the circuit A (i.e., the oil circuit in the right-side suspension drive system). Meanwhile, the upper chamber of the right-side suspension hydraulic cylinder 512 is also being compressed, causing the pressure in circuit A to increase. Similarly, the upper chamber of the left-side suspension hydraulic cylinder 512 and the lower chamber of the right-side suspension hydraulic cylinder will also cause changes in the pressure in circuit B, thereby forming an anti-roll moment and significantly improving the anti-roll performance of the suspension system. Furthermore, the oil flow in circuits A and B is stored or compensated through the first accumulator 5205 and the second accumulator 5208.

[0131] Furthermore, by switching the working positions of the fifth and sixth three-position three-way solenoid directional valves 5209 and 5210, the pressure difference between the left circuit B and the right circuit A can be adjusted to achieve active control against roll moment, thereby further improving anti-roll performance. In fact, considering oil leakage and insufficient flow, passive anti-roll methods cannot fully meet the requirements and can only reduce energy consumption caused by active control to a certain extent. Therefore, the anti-roll mode based on steering requirements of this invention, through active anti-roll control, compared with the passive anti-roll method used in the prior art, has the characteristics of large roll stiffness, nonlinear roll stiffness curve, and optimized roll load transfer distribution, which can significantly improve the vehicle's anti-roll performance. When performing actual active adjustment of the suspension system's anti-pitch moment, high-pressure oil is supplied through the first high-pressure accumulator 38 or the hydraulic pump 15 according to the required pressure. If the first high-pressure accumulator can meet the current pressure requirements (the first booster 210 can also provide some assistance), then the high-pressure oil required for the active anti-roll moment is provided only through the first high-pressure accumulator 38; otherwise, the hydraulic pump 15, or the hydraulic pump 15 and the first high-pressure accumulator 38, are used to provide the oil. Since the activation of the hydraulic pump 15 requires additional energy, the use of the high-pressure accumulator 22-2 can improve the energy-saving characteristics of the suspension system.

[0132] In some embodiments, the anti-pitch mode based on acceleration / deceleration demand described in this invention is similar in principle to the anti-roll mode based on steering demand. During the operation of the three-axle unmanned vehicle, the anti-pitch mode based on acceleration / deceleration demand and the anti-roll mode based on steering demand are independent of each other and do not affect each other. After the acceleration / deceleration demand is issued, the six 7th-3rd-position four-way electromagnetic proportional valves 59 in the suspension system can still switch to the corresponding working position and opening degree according to the pressure demand of each wheel to achieve active vertical stability control. When the vehicle generates acceleration / deceleration demand, taking deceleration as an example, the suspension hydraulic cylinders 512 of the front wheels (i.e., the suspension hydraulic cylinders of the left and right front wheels) are compressed, and the suspension hydraulic cylinders 512 of the rear wheels (i.e., the suspension hydraulic cylinders of the left and right rear wheels) are stretched. When the middle axle approaches the front axle, the fourth-position four-way solenoid valve 514 of the left middle wheel suspension drive system operates in the left position, and the fourth-position four-way solenoid valve 514 of the right middle wheel suspension drive system operates in the right position. When the middle axle approaches the rear axle, the fourth-position four-way solenoid valve 514 of the left middle wheel suspension drive system operates in the left position, and the fourth-position four-way solenoid valve 514 of the right middle wheel suspension drive system operates in the right position. At this time, the three first-position three-way solenoid valves 510 in the left suspension drive system operate in the right position, the three first-position three-way solenoid valves 510 in the right suspension system operate in the left position, and the six second-position three-way solenoid valves 511 in the suspension system operate in the lower position. The three third-position four-way solenoid valves 513 (also known as anti-roll three-way solenoid valves) in the suspension system operate in the upper position, realizing the same-direction interconnection between the left and right suspension drive systems. The volume of the upper (lower) chamber of the suspension hydraulic cylinder of the front (rear) wheel is reduced, while the volume of the lower (upper) chamber of all front (rear) wheel hydraulic cylinders is increased, forming an anti-pitch moment. The oil flow in circuit A (oil circuit of the right suspension drive system) and B (oil circuit of the left suspension drive system) in the suspension system is stored or compensated through the first accumulator 5205 and the second accumulator 5208.

[0133] Furthermore, by switching the working positions of the fifth and sixth three-position three-way solenoid directional valves 5209 and 5210, the pressure difference in the anti-pitch circuit can be further adjusted to achieve active control of the anti-pitch moment, thereby further improving anti-pitch performance. In fact, considering oil leakage and insufficient flow, passive anti-pitch is difficult to fully meet the requirements. Therefore, the anti-pitch mode of this invention, based on acceleration and deceleration requirements, can maximize vehicle pitch stability control through active anti-pitch control, suppressing the "nose-up" effect during acceleration and the "nodding" effect during deceleration. When actively adjusting the actual anti-pitch moment, the high-pressure oil is supplied through either the first high-pressure accumulator 38 or the hydraulic pump 15, depending on the required pressure. If the first high-pressure accumulator can meet the current pressure requirement (the first booster 210 can also provide some assistance), then only the first high-pressure accumulator 38 provides the high-pressure oil required for the active anti-roll moment; otherwise, the hydraulic pump 15, or both the hydraulic pump 15 and the first high-pressure accumulator 38, are used. Since the activation of the hydraulic pump 15 requires additional energy, the use of the high-pressure accumulator 22-2 can improve the energy-saving characteristics of the suspension system.

[0134] The suspension system of this invention can achieve energy feeding through the suspension energy feeding system 52. When the vehicle is driving on a rough road, the first accumulator 5205 and the second accumulator 5208 can store and compensate for the flow of oil during pitch, roll, and vertical control. Because when roll or pitch occurs, one of the oil circuits in circuits A and B is compressed, and oil enters the accumulator for storage. Simultaneously, the other circuit requires additional oil due to the extension of the hydraulic cylinder, requiring compensation from the accumulator. Therefore, when the suspension state changes due to vertical fluctuations, steering, and acceleration / deceleration, there is always oil flowing between the first and second accumulators. During this process, the energy feeding circuit (the annular circuit formed by the sixth one-way valve 5201, the seventh one-way valve 5202, the eighth one-way valve 5203, and the ninth one-way valve 5204) ensures that the oil flow direction always passes through the second hydraulic motor 27, thereby driving the second hydraulic motor 27 to rotate and transferring energy to the energy feeding device 28. This process not only recharges energy but also provides some damping to the suspension, further improving the vehicle's stability during the energy recharge process.

[0135] In summary, the structural layout of the six-wheel drive hydraulic system, steering hydraulic system, and suspension system of the three-axle unmanned vehicle of the present invention facilitates the integration of various hydraulic valves into valve blocks, thereby reducing the oil circuit structure and installation space, and solving the problems of complex oil circuits, difficult installation and maintenance of existing three-axle unmanned vehicles.

[0136] Meanwhile, the steering hydraulic system and steering strategy of this invention organically integrate acceleration magnitude and steering angle, enabling the autonomous vehicle to execute corresponding strategies based on different working states, thereby improving the stability of the autonomous vehicle during steering and meeting the specific working tasks of a three-axle autonomous vehicle. Furthermore, when executing different strategies, it can fully utilize recovered energy for assisted braking, accelerated acceleration, and assisted steering. Compared to existing technologies that rely solely on accumulator pressure and flow rate to determine whether to utilize recovered energy (i.e., when accumulator pressure and flow rate are insufficient, the vehicle does not participate in braking, acceleration, or steering until the accumulator pressure and flow rate reach a set value), this invention executes different strategies based on different working states, combining acceleration magnitude and steering angle to fully utilize the recovered energy and achieve energy saving.

[0137] When the suspension system of the present invention is in operation, on the one hand, it improves the adaptability of the unmanned vehicle by selecting multiple modes, and on the other hand, it improves the anti-pitch and anti-roll performance of the unmanned vehicle and enhances the stability during operation through the design and control of the suspension system structure, so as to meet special working requirements.

Claims

1. A three-axis unmanned vehicle hydraulic drive system, characterized in that, include: The six-wheel drive hydraulic system is used to provide hydraulic power to the wheels of the three-axle unmanned vehicle to drive the wheels to work or to achieve differential steering; A steering hydraulic system is used to provide independent steering for the front and rear wheels of the three-axle unmanned vehicle, and the steering hydraulic system, together with the six-wheel drive hydraulic system, recovers energy during wheel braking; The suspension system is used to adjust the suspension height of each wheel of the three-axle unmanned vehicle so that the suspension system can operate in the following modes: passive suspension mode, semi-active suspension mode, active suspension mode, rigid locking mode, and vehicle height adjustment mode. A power system with at least a hydraulic pump is used to provide hydraulic power for the operation of the six-wheel drive hydraulic system, steering hydraulic system and suspension system; Among them, the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can be used to provide auxiliary acceleration power, auxiliary steering power and auxiliary force for the wheels of the three-axle unmanned vehicle in different working modes; The steering hydraulic system includes a front wheel steering hydraulic system and a rear wheel steering hydraulic system. The front wheel steering hydraulic system includes two second two-position two-way solenoid valves, two first check valves, two first three-position four-way solenoid proportional valves, two first steering hydraulic cylinders, a second check valve, a second three-position four-way solenoid proportional valve, a third three-position four-way solenoid proportional valve, a first hydraulic booster, a first high-pressure accumulator, a first pressure reducing valve, a second pressure reducing valve, a third two-position two-way solenoid valve, and a fourth two-position two-way solenoid valve. The oil inlets of the two second two-position two-way solenoid valves are respectively connected to oil circuits. The hydraulic system is connected to the outlet of the hydraulic pump. The outlet of the second two-position two-way solenoid valve is connected to the inlet of a first check valve. The return port of the first check valve is connected to the inlet of a first three-position four-way solenoid proportional valve. The outlet of the first three-position four-way solenoid proportional valve is connected to the inlet of the hydraulic pump and the low-pressure accumulator via an oil circuit. The two working ports of the first three-position four-way solenoid proportional valve are connected to a first steering hydraulic cylinder that controls independent steering of the front wheels. The outlet of the first two-position two-way solenoid valve of the six-wheel drive hydraulic system is also connected to the first three-position four-way solenoid proportional valve via an oil circuit. The oil inlet of the first three-position four-way electromagnetic proportional valve is connected to the oil outlet of the hydraulic pump via an oil circuit; the oil inlet of the third three-position four-way electromagnetic proportional valve is connected to the oil outlet of one of the first check valves via a first pressure reducing valve; one working port of the second three-position four-way electromagnetic proportional valve and the third three-position four-way electromagnetic proportional valve is connected to a first high-pressure accumulator; the other working port of the second three-position four-way electromagnetic proportional valve and the third three-position four-way electromagnetic proportional valve is closed; the oil return ports of the second three-position four-way electromagnetic proportional valve and the third three-position four-way electromagnetic proportional valve are connected to the first high-pressure accumulator via an oil circuit. The inlet of the hydraulic pump is connected to the low-pressure accumulator. The outlet of a first check valve is also connected to a third two-position two-way solenoid valve. The other port of the third two-position two-way solenoid valve is connected to a first hydraulic booster. The other port of the first hydraulic booster is connected to a first high-pressure accumulator. The inlet of a fourth two-position two-way solenoid valve is connected to the outlet of the hydraulic pump via an oil circuit. The outlet of the fourth two-position two-way solenoid valve is connected to a second check valve. The outlet of the second check valve is connected to a second pressure reducing valve. The outlet of the second pressure reducing valve is connected to the first high-pressure accumulator.

2. The three-axis unmanned vehicle hydraulic drive system according to claim 1, characterized in that, The suspension system, in different operating modes, can at least achieve independent movement of each wheel, interconnection between two suspension drive systems of two wheels on the same axle via an oil circuit, cross interconnection between suspension drive systems of two wheels on the same axle via an oil circuit, and synchronous movement of suspension drive systems of three wheels on the same side.

3. The three-axis unmanned vehicle hydraulic drive system according to claim 1, characterized in that, The rear wheel steering hydraulic system includes two fifth 2-position 2-way solenoid valves, two third check valves, two fourth 3-position 4-way proportional solenoid valves, a fifth 3-position 4-way proportional solenoid valve, a sixth 3-position 4-way proportional solenoid valve, a sixth 2-position 2-way solenoid valve, a seventh 2-position 2-way solenoid valve, a third pressure reducing valve, a fourth pressure reducing valve, a second steering hydraulic cylinder, a second high-pressure accumulator, and a second hydraulic booster. The inlets of the two fifth 2-position 2-way solenoid valves are connected to the outlets of the hydraulic pump via oil circuits. The outlet of the fifth 2-position 2-way solenoid valve is connected to the inlet of a third check valve. The outlet of the third check valve is connected to the inlet of one of the fourth 3-position 4-way proportional solenoid valves. The return port of the fourth 3-position 4-way proportional solenoid valve is connected to the inlet of the hydraulic pump and the low-pressure accumulator via oil circuits. The two working ports of the fourth 3-position 4-way proportional solenoid valve are connected to a second steering hydraulic cylinder that controls independent rear wheel steering. The outlet of the first 2-position 2-way solenoid valve of the six-wheel drive hydraulic system is also connected to the fourth 3-position 4-way proportional solenoid valve via an oil circuit. The oil inlet is connected; the oil inlet of the fifth three-position four-way electromagnetic proportional valve is connected to the oil outlet of the hydraulic pump via an oil circuit; the oil inlet of the sixth three-position four-way electromagnetic proportional valve is connected to the oil outlet of one of the third check valves via a third pressure reducing valve; one working oil port of the fifth three-position four-way electromagnetic proportional valve and the sixth three-position four-way electromagnetic proportional valve is connected to a second high-pressure accumulator; the other working oil port of the fifth three-position four-way electromagnetic proportional valve and the sixth three-position four-way electromagnetic proportional valve is closed; the oil return ports of the fifth three-position four-way electromagnetic proportional valve and the sixth three-position four-way electromagnetic proportional valve are connected to the oil inlet of the hydraulic pump and the low-pressure accumulator via an oil circuit; the oil outlet of the third check valve is also connected to a sixth two-position two-way electromagnetic valve; the other oil port of the sixth two-position two-way electromagnetic valve is connected to a second hydraulic booster and a seventh two-position two-way electromagnetic valve; the oil outlet of the second hydraulic booster is connected to the second high-pressure accumulator; the oil outlet of the seventh two-position two-way electromagnetic valve is connected to a fourth pressure reducing valve; the other oil port of the fourth pressure reducing valve is connected to the second high-pressure accumulator.

4. The three-axis unmanned vehicle hydraulic drive system according to claim 1, characterized in that, The suspension system includes a suspension stiffness and damping circuit, a suspension energy feeding system, a left front wheel suspension drive system and a right front wheel suspension drive system with identical structures and symmetrically arranged, a left middle wheel suspension drive system and a right middle wheel suspension drive system with identical structures and symmetrically arranged, and a left rear wheel suspension drive system and a right rear wheel suspension drive system with identical structures and symmetrically arranged. The left front wheel suspension drive system, the left middle wheel suspension drive system, and the left rear wheel suspension drive system have identical structures. The left front wheel suspension drive system includes a laterally arranged seventh three-position four-way electromagnetic proportional valve, a laterally arranged first three-position three-way electromagnetic directional valve, a longitudinally arranged second three-position three-way electromagnetic directional valve, and a suspension hydraulic cylinder. The oil inlet of the seventh three-position four-way electromagnetic proportional valve is connected via an oil circuit to the oil outlet of the second pressure reducing valve and the first high-pressure valve of the front wheel steering hydraulic system. The accumulator is connected, and the return port of the seventh three-position four-way electromagnetic proportional valve is connected via an oil circuit between the first hydraulic booster and the third two-position two-way electromagnetic valve of the front wheel steering hydraulic system. The two working ports of the seventh three-position four-way electromagnetic proportional valve are respectively connected to the oil port of the lower chamber of the suspension hydraulic cylinder and the suspension stiffness and damping circuit. The inlet port of the first three-position three-way electromagnetic directional valve is connected to the suspension energy supply system, the return port of the first three-position three-way electromagnetic directional valve is connected to the inlet port of the second three-position three-way electromagnetic directional valve, the working port of the first three-position three-way electromagnetic directional valve is connected to the oil port of the upper chamber of the suspension hydraulic cylinder and the suspension stiffness and damping circuit, the return port of the second three-position three-way electromagnetic directional valve is connected to the suspension energy supply system, and the working port of the second three-position three-way electromagnetic directional valve is connected to the oil port of the lower chamber of the suspension hydraulic cylinder.

5. The three-axis unmanned vehicle hydraulic drive system according to claim 4, characterized in that, The suspension stiffness and damping circuit includes an eighth 2-position two-way solenoid valve, a fifth check valve, and a diaphragm accumulator. The oil inlet of the eighth 2-position two-way solenoid valve is connected via an oil circuit to one working oil port of a seventh 3-position four-way solenoid proportional valve, the oil port of the upper chamber of the suspension hydraulic cylinder, and the working oil port of a first 3-position three-way solenoid directional valve. The oil outlet of the eighth 2-position two-way solenoid valve is connected to the fifth check valve. The oil outlet of the fifth check valve is connected to the diaphragm accumulator and an adjustable flow valve. One oil port of the adjustable flow valve is connected to the oil outlet of the fifth check valve and the diaphragm accumulator. The other oil port of the adjustable flow valve is connected to the oil outlet of the eighth 2-position two-way solenoid valve.

6. The three-axis unmanned vehicle hydraulic drive system according to claim 4, characterized in that, The suspension energy feeding system includes a sixth check valve, a seventh check valve, an eighth check valve, a ninth check valve, a first accumulator, a second accumulator, a second hydraulic motor, and an energy feeding mechanism. The sixth, seventh, eighth, and ninth check valves form a closed-loop oil circuit. The sixth and seventh check valves are installed in opposite directions, the sixth and eighth check valves are installed in the same direction, and the eighth and ninth check valves are installed in opposite directions. The oil circuit between the eighth and ninth check valves is connected to the first accumulator and the second hydraulic motor. The second hydraulic motor is connected to the energy feeding mechanism. The oil outlet of the second hydraulic motor is connected to the second accumulator via a pipeline. The oil port of the second accumulator is also connected to the oil circuit between the sixth and seventh check valves via an oil circuit.

7. The three-axis unmanned vehicle hydraulic drive system according to any one of claims 4-6, characterized in that, The left front wheel suspension drive system and the right front wheel suspension drive system, the left middle wheel suspension drive system and the right middle wheel suspension drive system, and the left rear wheel suspension drive system and the right rear wheel suspension drive system are connected via an oil circuit and a third three-position four-way solenoid valve. The first three-position three-way solenoid valve and the second three-position three-way solenoid valve of the left middle wheel suspension drive system and the right middle wheel suspension drive system are connected to a fourth three-position four-way solenoid valve. The oil inlet of the first three-position three-way solenoid valve and the oil return of the second three-position three-way solenoid valve are respectively connected to the two working oil ports of the fourth three-position four-way solenoid valve. The oil inlet and oil return of the fourth three-position four-way solenoid valve are respectively connected to the two working oil ports of the third three-position four-way solenoid valve, or the oil inlet and oil return of the fourth three-position four-way solenoid valve are connected to the oil inlet and oil return of the third three-position four-way solenoid valve.

8. The three-axis unmanned vehicle hydraulic drive system according to claim 7, characterized in that, The suspension energy feeding system also includes a fifth three-position three-way solenoid directional valve and a sixth three-position three-way solenoid directional valve. The inlet of the fifth three-position three-way solenoid directional valve is connected to the oil circuit between the sixth and seventh check valves via an oil circuit. The return port of the fifth three-position three-way solenoid directional valve is connected to the oil circuit between the seventh and eighth check valves via an oil circuit. The working port of the fifth three-position three-way solenoid directional valve is connected to the inlet oil circuit of the seventh three-position four-way solenoid proportional valve. The return port of the sixth three-position three-way solenoid directional valve is connected to the oil circuit between the seventh and eighth check valves via an oil circuit. The inlet of the sixth three-position three-way solenoid directional valve is connected to the oil circuit of the front wheel steering hydraulic system.

9. A comprehensive energy-saving control strategy for a three-axis unmanned vehicle hydraulic drive system, characterized in that, The comprehensive energy-saving control strategy for the hydraulic drive system of the three-axis unmanned vehicle based on any one of claims 1-8 includes one or more of the following: traction and steering coordination control strategy, braking and steering coordination control strategy, and suspension system working mode control strategy. The braking and steering coordination control strategy includes the following: (1): Select the steering mode according to the working conditions: independent steering or differential steering; (2): If differential steering is selected, the two first three-position four-way solenoid proportional valves in the front wheel steering hydraulic system and the two fourth three-position four-way solenoid proportional valves in the rear wheel steering hydraulic system are in the middle position. The wheel speed and torque of each wheel are controlled by the six-wheel drive hydraulic system, thereby realizing differential steering of the wheels. (3): If independent steering is selected, the steering hydraulic system also includes an angle sensor for monitoring wheel angle, a pressure sensor and a flow sensor for monitoring steering hydraulic system pressure and flow; the first three-position four-way solenoid proportional valve and the fourth three-position four-way solenoid proportional valve are connected at the upper or lower position according to the steering direction of the three-axis unmanned vehicle; the specific use of independent steering includes the following: (3.1) Determine the braking force required for the three-axle unmanned vehicle and the yaw moment required for steering the three-axle unmanned vehicle. The determination of the braking force required for the three-axle unmanned vehicle and the yaw moment required for steering the three-axle unmanned vehicle includes the following: ； （2）； Where Fx represents the sum of the longitudinal forces on all wheels of the three-axis autonomous vehicle. Af and Cd represent air density, vehicle frontal area, and drag coefficient, respectively; Vx is the vehicle's longitudinal velocity; and m, g, and Let Ff represent the vehicle mass, gravitational acceleration, and gradient, respectively; Fxi represent the sum of the rolling resistance of all wheels; i = [fl, fr, ml, mr, rl, rr]; where t represents time. In independent steering mode, considering the limitations of ground adhesion conditions, the yaw moment required for vehicle steering can be calculated using existing control algorithms: First: Using the existing control algorithm, the external yaw moment M generated by the longitudinal force is calculated using the following formula. z : ； In the formula, M z K is the external yaw moment generated by the longitudinal force. P K i K d Here, 'e' represents the yaw rate tracking error, and 'e' represents the control parameter. Integral for yaw rate tracking error, The derivative of the yaw rate tracking error; Then, using an average distribution approach, the braking force of the six wheels on both sides of the three-axis autonomous vehicle is: ； Among them, F xfl This refers to the braking force of the left front wheel, F. xml This refers to the braking force of the left and middle wheels, F. xyl This refers to the braking force of the left rear wheel, F. xfr This refers to the braking force of the right front wheel, F. xml This refers to the braking force of the right center wheel, F. xyl This expresses the braking force of the right rear wheel, and d is the length of the wheel swing arm of the three-axle unmanned vehicle; The energy recovered or released by the steering hydraulic system and the six-wheel drive hydraulic system can be calculated using the following formula: ； In the formula, P is the pressure of the accumulator. Pre-charge pressure for the accumulator; , These are the initial and final volumes of the accumulator, respectively. It is the gas polyvariance index; (3.2) Determine whether the actual steering angle meets the expected value required by the working conditions based on the steering angle sensor, and select different control strategies considering the braking intensity; wherein, the braking intensity is divided into light braking and heavy braking, and the braking acceleration a < 0.3 m / s². 2 The braking was light, with a braking acceleration a ≥ 0.3 m / s². 2 ; (3.21) If the steering angle meets the expected value required by the operating conditions, then the following two different control strategies shall be implemented based on the braking intensity: The first control strategy: when the braking intensity is light braking, the steering hydraulic system and the six-wheel drive hydraulic system work together to recover the energy during wheel braking; The second control strategy: For high-intensity braking, determine whether the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can provide the braking force and yaw torque required for braking and steering; if the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can provide the braking force and yaw torque required for braking and steering, then utilize the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system to provide the braking force and yaw torque required for braking and steering of the wheels; if the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system cannot provide the braking force and yaw torque required for braking and steering, then assist braking is provided through the friction braking system configured on the wheels. (3.22) If the steering angle does not meet the expected value required by the operating conditions, the following two different control strategies shall be adopted based on the braking intensity: The first control strategy: For light braking, determine whether the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system can provide the braking force and yaw torque required for braking and steering. If the energy recovered by these systems can provide the necessary braking force and yaw torque, then utilize this energy to provide the required braking force and yaw torque for the wheels. If the energy recovered by these systems cannot provide the necessary braking force and yaw torque, then the energy recovered by these systems, along with the hydraulic pump in the power system, will jointly provide the required braking force and yaw torque for the wheels. The second control strategy: When the braking intensity is high-intensity braking, the energy recovered by the steering hydraulic system and the six-wheel drive hydraulic system, together with the hydraulic pump of the power system, provides the braking force required for the wheels. After the hydraulic pump of the power system, the steering hydraulic system and the six-wheel drive hydraulic system recover the energy to provide the braking force required for braking, the pressure and flow rate are used as the yaw torque required for the steering of the three-axle unmanned vehicle.

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