Amphibious three-axle vehicle oil-gas suspension hydraulic system, control method and vehicle

Abstract

The application discloses an amphibious three-axle vehicle oil-gas suspension hydraulic system, a control method and a vehicle, relates to the field of automobile suspension systems, and the oil-gas cylinder of each single wheel is a single-rod piston cylinder, an electric control damping valve is arranged between the oil-gas cylinder and the corresponding accumulator, the oil-gas cylinders on the same side of the second axle and the third axle are communicated through electromagnetic reversing valves, so that the rodless chambers on the same side of the second axle and the third axle are communicated with each other, and the rod chambers are communicated with each other; the oil-gas cylinders on the left side and the right side of the second axle and the third axle are communicated through electromagnetic reversing valves, so that the rodless chamber on the left side is communicated with the rod chamber on the right side, and the rodless chamber on the right side is communicated with the rod chamber on the left side; the hydraulic pump is connected with the rod chambers and the rodless chambers of the oil-gas cylinders through electromagnetic reversing valves, and when the electromagnetic reversing valves are switched at different working positions, the output oil liquid of the hydraulic pump can be introduced into the rod chambers or the rodless chambers of the corresponding oil-gas cylinders. The application forms a hydraulic balance axle, is fast in response, and is high in reliability; meanwhile, a fault wheel is isolated by using a hydraulic isolation method, and the safety margin of the suspension system is improved.

Description

Technical Field

[0001] This invention relates to the field of automotive suspension systems, and more particularly to an amphibious three-axle vehicle's hydropneumatic suspension hydraulic system, control method, and vehicle. Background Technology

[0002] In the suspension system of a three-axle amphibious three-axle vehicle, the second and third axles usually adopt solid axle balanced suspension or independent suspension. When solid axle balanced suspension is used, its unsprung mass is large and it occupies a lot of longitudinal space. When traditional independent suspension is used, there is a large difference in axle load between the two rear axles, which can easily lead to single axle overload and wheel suspension.

[0003] Existing hydraulic interconnected suspension systems connect the cylinders of different wheels via hydraulic lines. However, when a hydraulic circuit in one wheel fails, the physical connection of the hydraulic lines allows the faulty pressure or leakage to be transmitted to other suspensions, causing adjacent suspensions to simultaneously lose function. Furthermore, when an amphibious tri-axle vehicle is navigating in water, the wheels of a traditional independent suspension are in a normally extended state, with large areas of the wheels and suspension guide rods exposed to the water, resulting in high drag and affecting navigation performance. When the tri-axle vehicle turns at low speeds, both the second and third axles are non-steering axles, leading to uncoordinated wheel trajectories and a larger turning radius. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide an amphibious three-axle vehicle with an oil-gas suspension hydraulic system, control method, and vehicle, forming a hydraulic balance bridge with rapid response and high reliability; at the same time, a hydraulic isolation method is used to isolate the faulty wheel, improving the safety margin of the suspension system.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, embodiments of the present invention provide an amphibious tri-axle vehicle hydraulic suspension system, including a hydraulic cylinder, an accumulator, and a hydraulic pump. Each single wheel's hydraulic cylinder is a single-rod piston cylinder, with its rodless chamber used to connect to the vehicle body and its rod chamber used to connect to the suspension guide rod. Each single wheel's hydraulic cylinder is equipped with an electrically controlled damping valve between it and its corresponding accumulator. The hydraulic cylinders on the same side of the second and third axles are connected by an electromagnetic reversing valve, so that the rodless chambers and rod chambers on the same side of the second and third axles are connected to each other. The left and right sides of the second and third axles are connected by an electromagnetic reversing valve, so that the left rodless chamber is connected to the right rod chamber, and the right rodless chamber is connected to the left rod chamber. The second axle is equipped with a left hydraulic cylinder and a right hydraulic cylinder, and the third axle is equipped with a left hydraulic cylinder and a right hydraulic cylinder. The left hydraulic cylinder, right hydraulic cylinder, left hydraulic cylinder, and right hydraulic cylinder of the second and third axles are all connected to a three-position six-way valve between the wheels of the second and third axles. The rodless chamber and the rod chamber of the right hydraulic cylinder of the second axle are connected to a right solenoid valve of the second and third axles, and the rodless chamber and the rod chamber of the right hydraulic cylinder of the third axle are also connected to a right solenoid valve of the second and third axles. The rodless chamber and rod chamber of the left hydraulic cylinder of the second bridge are connected to the left solenoid directional valve of the second and third bridges, and the rodless chamber and rod chamber of the left hydraulic cylinder of the third bridge are connected to the left solenoid directional valve of the second and third bridges. The hydraulic pump is connected to the rod chamber and rodless chamber of each oil cylinder through an electromagnetic directional valve. When the electromagnetic directional valve switches between different working positions, the output oil of the hydraulic pump can be introduced into the rod chamber or rodless chamber of the corresponding oil cylinder.

[0006] As a further implementation, one bridge is provided with a left oil-gas cylinder and a right oil-gas cylinder, and a three-position six-way valve between the left oil-gas cylinder and the right oil-gas cylinder is connected. Solenoid valves and accumulators are provided between the rodless chambers of the right and left oil cylinders of the first axle and the three-position six-way valve between the wheels of the first axle. The accumulators are connected to damping valves.

[0007] As a further implementation, an inter-axle three-position six-way valve is connected between the first axle wheel-to-wheel three-position six-way valve and the second and third axle wheel-to-wheel three-position six-way valves, and a speed regulating valve is installed between the inter-axle three-position six-way valve and the hydraulic pump. The hydraulic pump is connected to the mounting valve.

[0008] As a further implementation, the rodless chambers of the left hydraulic cylinder of the second bridge, the right hydraulic cylinder of the second bridge, the left hydraulic cylinder of the third bridge, and the right hydraulic cylinder of the third bridge are all connected to a solenoid valve and an accumulator, and the accumulator is connected to a damping valve.

[0009] As a further implementation, a controller is also included, which is electrically connected to each electromagnetic directional valve and each damping valve, and is connected to the position sensor of each single wheel.

[0010] Secondly, embodiments of the present invention also provide a control method for a hydraulic system of an amphibious three-axle vehicle's pneumatic suspension, comprising: During normal driving, the control of each electromagnetic reversing valve enables the rodless chambers on the same side of the second and third axles to be interconnected, and the rod chambers to be interconnected, and also enables the rodless chambers on the left and right sides to be connected with the rod chambers on the opposite side. The damping valves of each accumulator remain open, and the pressure difference between the rodless and rod chambers of each oil cylinder provides the vehicle support force. When lifting the wheels during navigation, the damping valves of each accumulator are closed, and the hydraulic pump is controlled to supply oil to the rod chamber of each hydraulic cylinder, pushing the hydraulic cylinder to compress and lift each wheel; when each wheel is detected to have reached the set position, the rodless chamber circuit of the corresponding hydraulic cylinder is cut off, the hydraulic pump stops working, and each wheel is kept in the lifting position. When turning at low speed, the rodless chamber circuit of the third axle hydraulic cylinder is cut off, and the accumulators of the second and third axles are also cut off. The hydraulic pump is controlled to supply oil to the rodless chamber of the second axle hydraulic cylinder, causing the second axle hydraulic cylinder to extend and lift under differential action until the third axle tires are off the ground. Then the second axle hydraulic cylinder is locked, and the hydraulic pump stops working.

[0011] As a further implementation, after the voyage is completed, the hydraulic pump is controlled to supply oil to the rodless chamber of each oil cylinder, pushing the oil cylinder to extend and return each wheel to its normal position; when it is detected that each wheel has reached the set position, the hydraulic pump stops working, and then each solenoid directional valve is returned to its initial state. After low-speed steering is completed, restore all solenoid directional valves to their initial state, and the hydraulic system returns to normal driving conditions.

[0012] As a further implementation, the control method also includes a fault isolation step: When a fault is detected in any wheel suspension, the faulty wheel is lifted or rigidly locked, and then the rodless chamber hydraulic circuit of the faulty wheel is cut off, isolating the faulty wheel from the other suspension hydraulic circuits.

[0013] As a further implementation, in the fault isolation step, when the faulty wheel is located on a bridge, a rigid locking operation is performed on the faulty wheel; When one or two wheels on opposite sides of the second or third axle fail, a wheel-lifting isolation operation is performed on the failed wheel. When two or more wheels on the same side of the second or third axle fail, a rigid locking operation is performed on the failed wheels.

[0014] As a further implementation, the rigid locking method is as follows: The control solenoid directional valve connects the rodless chamber and the rod chamber of the target wheel, and then the rodless chamber damping valve of the target wheel is shut off, using the incompressibility of hydraulic oil to keep the target wheel locked.

[0015] Thirdly, embodiments of the present invention also provide an amphibious three-axle vehicle equipped with the aforementioned oil-gas suspension hydraulic system.

[0016] The beneficial effects of this invention are as follows: This invention connects the rodless chambers and rod chambers of the hydraulic cylinders on the same side of the second and third axles, and cross-connects the rodless chambers on the left and right sides with the rod chambers on the opposite side. According to Pascal's law, the hydraulic oil pressure in each connected chamber automatically tends to be equal. Under the same area difference between the rodless and rod chambers, each hydraulic cylinder of the second and third axles generates the same lifting force, achieving passive and balanced distribution of axle load on the four wheels of the second and third axles. No active control intervention is required. It has a rapid response and high reliability, fundamentally eliminating the uneven axle load distribution, single axle overload, and wheel suspension caused by the deformation coordination problem of the elastic elements of each wheel in traditional independent suspension. This invention utilizes independently shut-off solenoid valves installed on the rodless chamber side of each hydraulic cylinder. When a wheel suspension malfunctions, the faulty wheel can be lifted or rigidly locked, cutting off its rodless chamber hydraulic circuit. This physically isolates the faulty wheel from the hydraulic circuits of the rest of the suspension, improving the safety margin of the suspension system and the vehicle's fault tolerance. By controlling the hydraulic pump to actively fill the rod chamber of each hydraulic cylinder with oil, the hydraulic pressure pushes the hydraulic cylinder to compress and lift each wheel, while cutting off the rodless chamber circuit to maintain the lifted wheel position. This effectively reduces the water-facing area of ​​the wheels and suspension guide rods when the amphibious vehicle is navigating in water, reducing navigation resistance. Furthermore, the active hydraulic wheel lifting method is more efficient than the gravity-dependent passive wheel lifting method. This invention uses a rigid shut-off circuit of the rodless chamber of the three-axle hydraulic cylinder and shuts off the accumulators of the second and third axles. By utilizing the incompressibility of hydraulic oil, the second axle hydraulic cylinder is rapidly lifted under differential hydraulic pressure until the third axle tires are off the ground. When turning at low speeds, only the second axle follows the steering, reducing the equivalent wheelbase. This effectively solves the problems of large turning radius and tire drag and wear caused by the uncoordinated movement trajectories of the second and third axles when the three-axle vehicle turns at low speeds. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 This is a schematic diagram of the hydraulic system of the air suspension according to one or more embodiments of the present invention; in the figure, RU represents the right rodless chamber, RD represents the right rod chamber, LU represents the left rodless chamber, LD represents the left rod chamber, and S represents the solenoid valve. Among them, 1-Right hydraulic cylinder of the first axle, 2-Solenoid valve of the right hydraulic cylinder of the first axle, 3-Right accumulator of the first axle, 4-Damping valve of the right accumulator of the first axle, 5-Three-position six-way valve between the axles, 6-Right hydraulic cylinder of the second axle, 7-Solenoid valve of the right hydraulic cylinder of the second axle, 8-Right accumulator of the second axle, 9-Damping valve of the right accumulator of the second axle, 10-Right solenoid directional valve of the second and third axles, 11-Right accumulator of the third axle, 12-Damping valve of the right accumulator of the third axle, 13-Solenoid valve of the right hydraulic cylinder of the third axle, 14-Right hydraulic cylinder of the third axle, 15-Three-position six-way valve between the wheels of the second and third axles, 16-Left accumulator of the third axle. Energy accumulator, 17-Third bridge left accumulator damping valve, 18-Third bridge left hydraulic cylinder solenoid valve, 19-Third bridge left hydraulic cylinder, 20-Second and third bridge left solenoid directional valve, 21-Second bridge left accumulator damping valve, 22-Second bridge left accumulator, 23-Second bridge left hydraulic cylinder solenoid valve, 24-Second bridge left hydraulic cylinder, 25-Hydraulic pump, 26-Safety valve, 27-Speed ​​control valve, 28-First bridge left hydraulic cylinder, 29-First bridge left hydraulic cylinder solenoid valve, 30-First bridge left accumulator damping valve, 31-First bridge left accumulator, 32-First bridge wheel-to-wheel three-position six-way valve. Detailed Implementation

[0019] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0020] For ease of description, the words "up," "down," "left," and "right" appearing in this invention only indicate that they are consistent with the up, down, left, and right directions of the accompanying drawings themselves. They do not limit the structure and are merely for the purpose of facilitating the description of this invention and simplifying the description. They do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] Definitions: First axle: the axle at the very front of the vehicle; Second axle: the axle in the middle of the vehicle; Third axle: the axle at the very rear of the vehicle.

[0022] Example 1: In existing technologies, for three-axle vehicles, when the rear two axles are unbalanced axles, the axle load is statically indeterminate, requiring deformation coordination equations, which leads to certain differences in axle load. Using traditional balanced axles presents problems such as large unsprung mass and large space occupation. Furthermore, in traditional hydraulic interconnected suspension systems, when a single wheel hydraulic system fails, the interconnected suspension will also lose function, resulting in insufficient safety margin. Traditional three-axle vehicles cannot solve the problems of large turning radius and tire wear caused by the uncoordinated motion trajectories of the second and third axles during low-speed turns. Additionally, when amphibious three-axle vehicles are navigating in water, the existing suspension structure has a large water-facing area, resulting in high drag and affecting navigation performance.

[0023] Based on this, this embodiment provides a hydraulic system for the pneumatic suspension of an amphibious three-axle vehicle, referring to... Figure 1 Each single-wheel suspension guide structure adopts an independent suspension structure. The elastic element is composed of a hydraulic spring consisting of a hydraulic cylinder and an accumulator, and the damping element is a damping valve between the hydraulic cylinder and the accumulator.

[0024] The vehicle has six hydraulic cylinders corresponding to its six wheels: cylinder 1 (right axle), cylinder 28 (left axle), cylinder 6 (right axle), cylinder 24 (left axle), cylinder 14 (right axle), and cylinder 19 (left axle). Each cylinder uses a single-rod piston structure. One end of the rodless chamber is fixedly connected to the vehicle body, while the other end of the rod chamber is connected to the suspension guide rod via a piston rod. The hydraulic action area of ​​the rodless chamber is larger than that of the rod chamber. Under the condition that the pressures in both chambers are equal, the hydraulic pressure generated in the rodless chamber is greater than that generated in the rod chamber. The difference in hydraulic pressure between the two chambers is the supporting force exerted by the cylinder on the vehicle body.

[0025] Each single-wheel hydraulic cylinder is equipped with a damping valve (electronically controlled damping switch valve) between itself and its corresponding accumulator to provide the suspension with elastic cushioning and damping energy dissipation functions. A damping valve 4 is connected between the right hydraulic cylinder 1 of the first axle and the right accumulator 3 of the first axle; a damping valve 30 is connected between the left hydraulic cylinder 28 of the first axle and the left accumulator 31 of the first axle; a damping valve 9 is connected between the right hydraulic cylinder 6 of the second axle and the right accumulator 8 of the second axle; a damping valve 21 is connected between the left hydraulic cylinder 24 of the second axle and the left accumulator 22 of the second axle; a damping valve 12 is connected between the right hydraulic cylinder 14 of the third axle and the right accumulator 11 of the third axle; and a damping valve 17 is connected between the left hydraulic cylinder 19 of the third axle and the left accumulator 16 of the third axle. Each damping valve remains open under normal driving conditions, allowing the compressed gas in the accumulator and the hydraulic oil in the oil cylinder to form an oil-air spring, providing elastic support and damping buffer for wheel bounce.

[0026] The hydraulic connection between the left and right wheels of the axle is achieved by the three-position six-way valve 32 between the wheels. Under normal driving conditions, the three-position six-way valve 32 between the wheels is in its initial working position. The rodless chamber of the right hydraulic cylinder 1 of the axle is connected to the rod chamber of the left hydraulic cylinder 28 of the axle, and both are connected to the right accumulator 3 of the axle; the rodless chamber of the left hydraulic cylinder 28 of the axle is connected to the rod chamber of the right hydraulic cylinder 1 of the axle, and both are connected to the left accumulator 31 of the axle. The above cross-connection method enables the rodless chambers of the hydraulic cylinders on both sides of the axle to form a pressure balance relationship with the rod chambers on the opposite side. Under the condition that the accumulator pressure is equal, the difference in the hydraulic action area between the rodless chamber and the rod chamber provides support force for the wheels of the axle.

[0027] The hydraulic connection between the second and third axles enables the hydraulic balance bridge function, as shown in the reference. Figure 1The rodless chamber of the right hydraulic cylinder 6 of the second bridge is connected to the rodless chamber of the right hydraulic cylinder 14 of the third bridge via the right hydraulic cylinder solenoid valve 7 (solenoid switch valve) of the second bridge and the right solenoid directional valve 10 of the second and third bridges; the rodless chamber of the right hydraulic cylinder 14 of the third bridge is also connected to the above-mentioned circuit via the right hydraulic cylinder solenoid valve 13 of the third bridge; the rod chamber of the right hydraulic cylinder 6 of the second bridge and the rod chamber of the right hydraulic cylinder 14 of the third bridge are connected to each other via the right solenoid directional valve 10 of the second and third bridges. Symmetrically arranged on the left side: the rodless chamber of the left hydraulic cylinder 24 of the second bridge is connected to the rodless chamber of the left hydraulic cylinder 19 of the third bridge via the left hydraulic cylinder solenoid valve 23 of the second bridge and the left solenoid directional valve 20 of the second and third bridges; the rodless chamber of the left hydraulic cylinder 19 of the third bridge is also connected to the above-mentioned circuit via the left hydraulic cylinder solenoid valve 18 of the third bridge; the rod chamber of the left hydraulic cylinder 24 of the second bridge and the rod chamber of the left hydraulic cylinder 19 of the third bridge are connected to each other via the left solenoid directional valve 20 of the second and third bridges.

[0028] Based on the aforementioned same-side connectivity, the three-position six-way valve 15 (three-position six-way directional valve) between the second and third axles further enables cross-connection between the left and right sides. The right rodless chamber circuit, composed of the rodless chambers of the right hydraulic cylinder 6 of the second axle and the right hydraulic cylinder 14 of the third axle, is connected to the left rod chamber circuit, composed of the rod chambers of the left hydraulic cylinder 24 of the second axle and the left hydraulic cylinder 19 of the third axle, through the three-position six-way valve 15 between the second and third axles, and is jointly connected to the right accumulator 8 of the second axle and the right accumulator 11 of the third axle; the left rodless chamber circuit is connected to the right rod chamber circuit through the three-position six-way valve 15 between the second and third axles, and is jointly connected to the left accumulator 16 of the third axle and the left accumulator 22 of the second axle. Thus, the four hydraulic cylinders of the second and third axles form a closed hydraulic balance network through the above-mentioned connectivity topology.

[0029] Hydraulic pump 25 is the active hydraulic power source of the system. A safety valve 26 and a speed control valve 27 are installed on its outlet line. The safety valve 26 provides overflow protection for the outlet pressure of hydraulic pump 25 to prevent system overpressure. The speed control valve 27 is connected between the inter-axle three-position six-way valve 5 and hydraulic pump 25, limiting the output flow of hydraulic pump 25. The output oil from hydraulic pump 25 enters the inter-axle three-position six-way valve 5 after passing through the speed control valve 27. The inter-axle three-position six-way valve 5 connects the first axle wheel three-position six-way valve 32 and the second and third axle wheel three-position six-way valves 15. Depending on the working position switching of different control modes, the output oil from hydraulic pump 25 is directed to the rod-side or rodless-side chambers of each hydraulic cylinder, providing hydraulic power for active control functions such as navigation wheel lifting, low-speed auxiliary steering, and single-wheel lifting.

[0030] Each hydraulic cylinder has an independent solenoid valve on its rodless chamber side, used to cut off the corresponding rodless chamber hydraulic circuit in fault isolation mode, thereby physically isolating the faulty wheel from the other suspension hydraulic circuits. Specifically, the rodless chamber side of the first axle right hydraulic cylinder 1 is connected to the first axle right hydraulic cylinder solenoid valve 2; the rodless chamber side of the first axle left hydraulic cylinder 28 is connected to the first axle left hydraulic cylinder solenoid valve 29; the rodless chamber side of the second axle right hydraulic cylinder 6 is connected to the second axle right hydraulic cylinder solenoid valve 7; the rodless chamber side of the second axle left hydraulic cylinder 24 is connected to the second axle left hydraulic cylinder solenoid valve 23; the rodless chamber side of the third axle right hydraulic cylinder 14 is connected to the third axle right hydraulic cylinder solenoid valve 13; and the rodless chamber side of the third axle left hydraulic cylinder 19 is connected to the third axle left hydraulic cylinder solenoid valve 18.

[0031] The hydraulic system of the air suspension in this embodiment also includes a controller, which is electrically connected to each solenoid directional valve, each damping valve, and each single-wheel position sensor. The controller determines the position status of each wheel based on the feedback signals from each single-wheel position sensor, and issues power-on / off commands to each valve according to the current control mode, thereby realizing the switching control of various working conditions such as normal driving, wheel lifting during navigation, low-speed steering, and fault isolation.

[0032] Under normal driving conditions, all solenoid valves are de-energized and in their initial positions, and all damping valves are in the conducting state. The pre-charge pressure of the right accumulator 3 and the left accumulator 31 of the first axle is set according to the axle load and target frequency deviation of the first axle. The pre-charge pressure of the right accumulator 8 of the second axle, the right accumulator 11 of the third axle, the left accumulator 16 of the third axle, and the left accumulator 22 of the second axle is set according to the axle load and target frequency deviation of the second and third axles, and the pre-charge pressure of the above four accumulators is equal to that of each other.

[0033] In the initial state described above, the rodless chamber of the right hydraulic cylinder 1 of the first axle is connected to the rod chamber of the left hydraulic cylinder 28 of the first axle via a three-position six-way valve 32 and connected to the right accumulator 3 of the first axle. Similarly, the rodless chamber of the left hydraulic cylinder 28 and the rod chamber of the right hydraulic cylinder 1 of the first axle are connected to the left accumulator 31 of the first axle via the three-position six-way valve 32. The pressures in both accumulators are equal, and the difference in hydraulic action area between the rodless and rod chambers provides support force to the wheels of the first axle, allowing the first axle suspension to perform normal elastic buffering and damping functions.

[0034] For the second and third axles, in the initial position under normal driving conditions, the rodless chamber of the right hydraulic cylinder 6 of the second axle and the rodless chamber of the right hydraulic cylinder 14 of the third axle are interconnected through the right hydraulic cylinder solenoid valve 7 of the second axle, the right solenoid directional valve 10 of the second and third axles, and the right hydraulic cylinder solenoid valve 13 of the third axle. The rod chamber of the right hydraulic cylinder 6 of the second axle and the rod chamber of the right hydraulic cylinder 14 of the third axle are interconnected through the right solenoid directional valve 10 of the second and third axles. The rodless chamber of the left hydraulic cylinder 24 of the second axle and the rodless chamber of the left hydraulic cylinder 19 of the third axle are interconnected through the left hydraulic cylinder solenoid valve 23 of the second axle, the left solenoid directional valve 20 of the second and third axles, and the left hydraulic cylinder solenoid valve 18 of the third axle. The rod chamber of the left hydraulic cylinder 24 of the second axle and the rod chamber of the left hydraulic cylinder 19 of the third axle are interconnected through the left solenoid directional valve 20 of the second and third axles.

[0035] Meanwhile, the right rodless cavity circuit and the left rod cavity circuit are cross-connected through the three-position six-way valve 15 between the second and third bridge wheels, and connected to the right accumulator 8 of the second bridge and the right accumulator 11 of the third bridge; the left rodless cavity circuit and the right rod cavity circuit are cross-connected through the three-position six-way valve 15 between the second and third bridge wheels, and connected to the left accumulator 16 of the third bridge and the left accumulator 22 of the second bridge.

[0036] The four accumulators have equal pre-charge pressure. According to Pascal's law, in a closed hydraulic balance network, the hydraulic oil pressure in each connected chamber tends to be equal. That is, the rodless chamber pressures of the right hydraulic cylinder 6 of the second axle and the right hydraulic cylinder 14 of the third axle are equal, the rodless chamber pressures of the left hydraulic cylinder 24 of the second axle and the left hydraulic cylinder 19 of the third axle are equal, and the right rodless chamber pressure is equal to the left rod chamber pressure, and the left rodless chamber pressure is equal to the right rod chamber pressure. Under the condition that the area difference between the rodless and rod chambers of each hydraulic cylinder is the same, the lifting force generated by the four hydraulic cylinders is the same, and the axle load of each wheel of the second and third axles is passively balanced, eliminating the uneven axle load distribution phenomenon caused by the deformation coordination problem of the elastic elements of each wheel in traditional independent suspensions. The hydraulic balance bridge function is based on the principle of hydrostatics, with rapid response and high reliability.

[0037] In this embodiment, the rodless chamber and the rod chamber on the opposite side are cross-connected via a three-position six-way valve 32 between the left and right sides of the axle, and are respectively connected to the corresponding accumulators. A solenoid valve 2 for the right axle cylinder 1 is provided between the right axle cylinder 1 and the right axle accumulator 3, and a solenoid valve 29 for the left axle cylinder 28 and the left axle accumulator 31 is provided between the left axle cylinder 28 and the left axle accumulator 31. Both can independently cut off the hydraulic circuit of the corresponding rodless chamber according to the control mode, providing a valve control basis for the single wheel lifting, locking or fault isolation operation of the axle.

[0038] A three-position six-way valve 5 between the axle and the first axle is connected between the first axle and the second and third axle are connected between the second and third axle are connected between the two axle and the third axle hydraulic circuits, depending on the control mode. Under normal driving conditions, the three-position six-way valve 5 between the axle and the second and third axle circuits isolates the first axle circuit from the second and third axle circuits, allowing them to work independently. When unified active control of the entire axle is required, the three-position six-way valve 5 between the axle and the second and third axle switches to the connected position, allowing the output oil from the hydraulic pump 25 to simultaneously enter the cylinder chambers of the first axle and the second and third axles. A speed control valve 27 is connected in series between the three-position six-way valve 5 between the axle and the hydraulic pump 25. A safety valve 26 is also connected to the outlet of the hydraulic pump 25. The speed control valve 27 ensures that the operating speed of each cylinder is controllable, and the safety valve 26 prevents system overpressure.

[0039] Each hydraulic cylinder is equipped with a solenoid valve on its rodless chamber side. In fault isolation mode, the solenoid valve cuts off the hydraulic circuit of the rodless chamber of the faulty wheel, physically isolating the faulty wheel from the hydraulic circuits of the rest of the suspension. Each rodless chamber solenoid valve can be independently energized and de-energized. When a fault occurs in the suspension of a certain wheel, the rodless chamber circuit of that faulty wheel can be cut off individually after lifting or rigidly locking the faulty wheel, without affecting the normal operation of the suspensions of the rest of the wheels. This overcomes the defect of traditional hydraulic interconnection systems where a single-wheel fault propagates along the pipeline, causing simultaneous failure of adjacent suspensions, and improves the safety margin of the suspension system and the fault tolerance of the entire vehicle.

[0040] Furthermore, the two ends of the right solenoid directional valve 10 of the second and third axles are respectively connected to the rodless chamber and the rod chamber of the right hydraulic cylinder 6 of the second axle, while the rodless chamber and the rod chamber of the right hydraulic cylinder 14 of the third axle are also connected to the right solenoid directional valve 10 of the second and third axles; the two ends of the left solenoid directional valve 20 of the second and third axles are respectively connected to the rodless chamber and the rod chamber of the left hydraulic cylinder 24 of the second axle, while the rodless chamber and the rod chamber of the left hydraulic cylinder 19 of the third axle are also connected to the left solenoid directional valve 20 of the second and third axles. Under the hydraulic balance axle condition, the right solenoid directional valve 10 and the left solenoid directional valve 20 of the second and third axles maintain the interconnection of chambers on the same side to balance the axle load; under the rigid locking condition, by switching the working position of the above-mentioned directional valves, the rodless chamber and the rod chamber of the target wheel are connected, and then the corresponding rodless chamber solenoid valve is closed, using the incompressibility of hydraulic oil to achieve rigid locking of the wheel, forming a double locking.

[0041] Example 2: This embodiment provides a control method for the hydraulic system of the hydropneumatic suspension of an amphibious three-axle vehicle. The control method is based on the hydraulic system of the hydropneumatic suspension described in Embodiment 1 and includes multiple working modes such as normal driving mode, single wheel lifting and raising control, single wheel rigid locking control, single wheel fault hydraulic isolation control, navigation wheel lifting control, and low-speed steering control.

[0042] Specifically, in normal driving mode, all solenoid valves are de-energized and in their initial positions, while all damping valves remain open. The rodless chambers on the same side of the second and third axles are interconnected, as are the rod-side chambers. The rodless chambers on the left and right sides are cross-connected with the opposite rod-side chambers. Each accumulator is connected to the hydraulic cylinder via its corresponding damping valve. The pressure difference between the rodless and rod-side chambers of each hydraulic cylinder provides support for the vehicle. According to Pascal's law, the hydraulic oil pressure in each connected chamber tends to be equal, resulting in the same lifting force on each wheel of the second and third axles. This achieves a passively balanced distribution of axle load, passively realizing the function of the hydraulic balance bridge.

[0043] The single-wheel lifting and hoisting control strategy has the same logic for each wheel. Taking the right wheel of the first axle as an example, the controller issues a lifting or hoisting command for the right wheel of the first axle according to the chassis control logic. When lifting the wheel, the relevant solenoid valves of the right accumulator damping valve 4, the inter-axle three-position six-way valve 5, and the inter-wheel three-position six-way valve 32 of the first axle are energized. The high-pressure oil of the hydraulic pump 25 enters the rod chamber of the right hydraulic cylinder 1 of the first axle through the speed regulating valve 27, the inter-axle three-position six-way valve 5, and the inter-wheel three-position six-way valve 32. The high-pressure oil pushes the piston rod to move towards the rodless chamber, and the hydraulic cylinder performs compression motion, thus lifting the right wheel of the first axle upward.

[0044] During lifting, high-pressure oil enters the rodless chamber of the right hydraulic cylinder 1 of the first axle. The high-pressure oil pushes the piston rod to extend towards the rod chamber, causing the hydraulic cylinder to extend and lifting the right wheel of the first axle downwards. Once in position, the hydraulic pump 25 is de-energized and stops working, and the damping valve 4 of the right accumulator of the first axle is energized and shut off. The rodless chamber and the rod chamber of the right hydraulic cylinder 1 of the first axle are connected through the three-position six-way valve 32 between the wheels of the first axle. The areas of the rodless chamber and the rod chamber are unequal, and the connection between the two chambers generates a net lifting force, keeping the wheel in the lifted or raised position, thus forming a locked state.

[0045] Furthermore, the solenoid valve 2 of the right hydraulic cylinder of the first axle can be de-energized to seal the oil in the rodless chamber of the right hydraulic cylinder 1 of the first axle, further improving the locking reliability by utilizing the incompressibility of hydraulic oil. At this time, the rodless chamber and rod chamber of the left hydraulic cylinder 28 of the first axle are connected through the three-position six-way valve 32 between the wheels of the first axle and connected to the left accumulator 31 of the first axle, and the left wheel of the first axle maintains normal suspension function; the hydraulic pipeline connection method of the second and third axle suspensions is the same as under normal driving conditions, and they have normal suspension function. When it is necessary to restore the lifting state to the normal position, the operation is reversed according to the above oil supply direction. After the position sensor detects that the wheel has reached the set position, the hydraulic pump 25 is de-energized, all solenoid valves are de-energized, and the hydraulic system returns to the initial state.

[0046] The single-wheel rigid locking control strategy is illustrated using the right wheel of a single axle and the right wheel of a triple axle as examples: When the right wheel of a single axle is rigidly locked, the solenoid valve corresponding to the damping valve 4 of the right accumulator of the single axle is energized and cut off. The rodless chamber and the rod chamber of the right hydraulic cylinder 1 of the single axle are connected through the three-position six-way valve 32 between the wheels of the single axle. The right accumulator 3 of the single axle is cut off. The unequal area of ​​the rodless chamber and the rod chamber and the incompressibility of the hydraulic oil together keep the wheel in a rigid locking state. Furthermore, the solenoid valve 2 of the right hydraulic cylinder of the single axle can be energized and cut off to seal the oil in the rodless chamber to improve the locking safety margin.

[0047] The left hydraulic cylinder 28 of the first axle maintains normal suspension function, and the hydraulic pipeline connection method of the second and third axles is the same as that under normal driving conditions. When the right wheel of the third axle is rigidly locked, the solenoid valve corresponding to the damping valve 12 of the right accumulator of the third axle and the relevant solenoid valves of the right solenoid directional valves 10 of the second and third axles are energized. The rodless chamber of the right hydraulic cylinder 14 of the third axle is connected to the rod chamber through the right solenoid directional valves 10 of the second and third axles, and the right accumulator 11 of the third axle is cut off. The incompressibility of hydraulic oil makes the right wheel of the third axle in a rigid locked state. Furthermore, the solenoid valve 13 of the right hydraulic cylinder of the third axle can be energized and cut off to seal the oil in the rodless chamber to improve the locking safety margin.

[0048] At this time, the rodless and rod-driven chambers of the right hydraulic cylinder 6 of the second axle are connected to the right accumulator 8 of the second axle via the right solenoid directional valve 10 of the second and third axles, and the right wheel of the second axle has normal suspension function; the rodless and rod-driven chambers of the two hydraulic cylinders on the left side of the second and third axles are interconnected and connected to the left accumulator 16 of the third axle and the left accumulator 22 of the second axle, and have normal suspension function. When the lock is released, all solenoid valves are de-energized, and the hydraulic system returns to its initial state.

[0049] The rigid locking mechanism works as follows: The solenoid directional valve connects the rodless chamber and the rod chamber of the target wheel, and then the rodless chamber damping valve is closed. The incompressibility of the hydraulic oil keeps the target wheel locked. After the rodless and rod chambers are connected, the pressure in the two chambers tends to balance, and the area of ​​the rodless chamber is larger than that of the rod chamber. The hydraulic cylinder still has a net lifting force to keep the wheel in position. After the rodless chamber damping valve is closed, the oil in the rodless chamber is sealed, and the incompressibility of the hydraulic oil further ensures the reliability of the locking mechanism, forming a dual locking mechanism.

[0050] The single-wheel failure hydraulic isolation control strategy implements tiered processing based on the location of the faulty wheel. When a wheel suspension fails, the controller first lifts or rigidly locks the faulty wheel, then cuts off the rodless chamber hydraulic circuit of the faulty wheel, physically isolating the faulty wheel from the other suspension hydraulic circuits, ensuring that the vehicle still has a certain degree of driving capability when a single or multiple wheel failure occurs.

[0051] When the faulty wheel is located on the first axle, a rigid locking operation is performed on the faulty wheel. This closes the corresponding rodless chamber damping valve, connecting the rodless chamber to the rod chamber, and using the incompressibility of hydraulic oil to lock the faulty wheel. The other wheel on the same side and all wheels on the second and third axles maintain normal suspension function. When one wheel or two wheels on opposite sides of the second or third axle fail, a wheel-lifting isolation operation is performed on the faulty wheel. Set the rodless chamber solenoid valves of all wheels except the faulty wheel to the off state, set all accumulator damping valves to the off state, and connect the high-pressure oil of hydraulic pump 25 to the rod chamber of the target faulty wheel through the solenoid directional valve. Connect the rodless chamber to the hydraulic oil tank. Hydraulic pump 25 fills the rod chamber of the oil cylinder with oil to increase the pressure, thereby lifting the faulty wheel. After reaching the position, shut off the corresponding rodless chamber solenoid valve to isolate the faulty wheel from the other suspension hydraulic circuits, and restore the normal suspension function of the other wheels.

[0052] When two or more wheels on the same side of the second or third axle fail, a rigid locking operation is performed on the failed wheels, cutting off the corresponding rodless chamber solenoid valve to isolate the failed wheel from the hydraulic circuit, ensuring the vehicle retains a certain degree of drivability. This tiered isolation strategy takes into account the connectivity characteristics of the hydraulic circuit under different fault scenarios, ensuring reliable isolation of the failed wheels while maximizing the maintenance of normal operation of the remaining suspension components.

[0053] The wheel-lifting control strategy is executed when the vehicle enters the water navigation mode: The controller issues a wheel-lifting command based on the chassis control logic. First, it closes the damping valves of each accumulator, disconnecting each accumulator from its corresponding hydraulic cylinder. Subsequently, high-pressure oil from the hydraulic pump 25 passes through the speed control valve 27, the inter-axle three-position six-way valve 5, the first axle inter-wheel three-position six-way valve 32, and the second and third axle inter-wheel three-position six-way valve 15, respectively, and enters the rod chambers of the hydraulic cylinders of the first, second, and third axles. The high-pressure oil pushes each hydraulic cylinder to perform compression motion, lifting each wheel. When the position sensor detects that a wheel has been lifted to the set position, it energizes and cuts off the solenoid valve connected to the rodless chamber of that wheel's hydraulic cylinder, putting that wheel's hydraulic cylinder in a cut-off state and stopping the wheel-lifting operation; the remaining wheels continue to be lifted until all wheels have reached the set position.

[0054] Once all wheels are in position, hydraulic pump 25 is de-energized and stops working. The rodless chamber solenoid valves of each hydraulic cylinder and the damping valves of each accumulator are all in the off state. Each wheel remains in the lifted position, and the wheels and suspension guide rods are off the water surface, reducing the vehicle's surface area facing the water and lowering drag. Compared to gravity-dependent passive wheel lifting methods, active hydraulic wheel lifting is more efficient and responds more quickly.

[0055] After navigation ends, the controller issues a recovery command. High-pressure oil from hydraulic pump 25 flows through speed control valve 27, inter-axle three-position six-way valve 5, first axle inter-wheel three-position six-way valve 32, and second and third axle inter-wheel three-position six-way valve 15, entering the rodless chamber of each hydraulic cylinder. The high-pressure oil pushes each hydraulic cylinder to extend, restoring each wheel to its normal position. When the position sensor detects that a wheel has returned to the set position, it energizes and de-energizes the solenoid valve connected to the rodless chamber of that wheel, putting the hydraulic cylinder of that wheel in the off state. After all wheels have returned to the set position, hydraulic pump 25 is de-energized and stops working. Subsequently, all solenoid valves are de-energized, the hydraulic system returns to its initial state, each accumulator damping valve is re-energized, and the suspension resumes its normal elastic cushioning function.

[0056] The low-speed steering control strategy is executed when the vehicle is turning at low speed: The controller issues a low-speed steering command according to the chassis control logic. The three-position six-way valve 5 between the axles switches to the neutral position, disconnecting the hydraulic circuit between the first axle and the hydraulic circuits of the second and third axles. The hydraulic connection of the first axle is the same as under normal driving conditions, and the hydraulic cylinders on both sides of the first axle maintain normal suspension function. The solenoid valves 13 and 18 of the right hydraulic cylinder of the third axle are energized, cutting off the rodless chamber hydraulic circuit of the third axle hydraulic cylinder. The solenoid valves corresponding to the right accumulator damping valve 9, the left accumulator damping valve 21, the right accumulator damping valve 12, and the left accumulator damping valve 17 of the third axle are energized and cut off, and all accumulators of the second and third axles are in the cut-off state.

[0057] In the aforementioned valve state, the high-pressure oil from the hydraulic pump 25 passes through the speed control valve 27, the inter-axle three-position six-way valve 5, the second and third axle wheel three-position six-way valve 15, the second and third axle right solenoid directional valve 10, and the second and third axle left solenoid directional valve 20, entering the rodless chamber of the second axle right cylinder 6 and the second axle left cylinder 24. The rodless chamber of the third axle cylinder is cut off, and the third axle cylinder is in a rigidly locked state. The support force of the third axle tire on the ground is borne by the locking force of the third axle cylinder. The hydraulic pump 25 continuously fills the rodless chamber of the second axle cylinder with oil, and the second axle cylinder performs an extension movement under the action of high-pressure oil differential action, increasing the second axle axle load until the third axle tire leaves the ground.

[0058] When the position sensor detects that the third axle tires have lifted off the ground, the solenoid valves corresponding to the right accumulator damping valve 9 and the left accumulator damping valve 21 of the second axle are energized and cut off, locking the second axle hydraulic cylinders and stopping the hydraulic pump 25. At this time, when the vehicle turns, the third axle tires do not contact the ground; only the second axle steers accordingly. This reduces the equivalent wheelbase and the turning radius, eliminating the tire drag and wear problem caused by the incoordination of the second and third axle movement trajectories.

[0059] This embodiment employs a rigid shut-off three-axle design and a shut-off accumulator, utilizing the incompressibility of hydraulic oil to rapidly increase the load on the second axle, resulting in high efficiency and rapid response. After low-speed steering is completed, all solenoid valves are de-energized, the hydraulic system returns to its initial state, the third axle tires are brought back to the ground, and the vehicle resumes three-axle drive.

[0060] Example 3: This embodiment provides an amphibious tri-axle vehicle with an overall 6×6 structure, including a vehicle body, three axles and wheels on each axle, and is equipped with the oil-gas suspension hydraulic system described in Embodiment 1.

[0061] Each single-wheel suspension guide structure adopts an independent suspension structure. The rodless chamber of each hydraulic cylinder is fixedly connected to the vehicle body, and the rod chamber is connected to the suspension guide rod of the corresponding axle through the piston rod. The hydraulic spring composed of the hydraulic cylinder and the accumulator provides elastic support for each wheel, and the damping valve provides damping buffer for each wheel.

[0062] Under off-road driving conditions, the amphibious three-axle vehicle utilizes the hydraulic balance axle function of its hydropneumatic suspension system to passively and evenly distribute the axle load across the second and third axles. This ensures good tire contact with the ground, allowing the vehicle to adapt to uneven road surfaces and effectively preventing single-axle overload or wheel suspension. This enhances off-road capability, climbing ability, and driving safety. The hydraulic balance axle function is passively implemented based on hydrostatic principles, requiring no active control intervention, resulting in a rapid system response and high reliability.

[0063] During water navigation, the controller issues a wheel-lifting command. The hydraulic system of the hydropneumatic suspension actively fills the rod-side chambers of each cylinder with oil, lifting all six wheels to their designated positions. The wheels and suspension guide rods retract, reducing the vehicle's surface area facing the water and lowering drag. This active hydraulic wheel-lifting method is more efficient than gravity-dependent passive wheel-lifting, allowing for a faster transition between water and land modes. After navigation, the controller issues a recovery command. The hydraulic system actively fills the rodless chambers of each cylinder with oil, returning the wheels to their normal positions. The suspension system then resumes its elastic cushioning function, ensuring smooth landing and driving.

[0064] During low-speed steering, the controller issues a low-speed steering command. The hydraulic system of the hydropneumatic suspension disconnects the rodless chamber circuit of the third axle's hydropneumatic cylinder and the accumulators of the second and third axles. Hydraulic pump 25 actively fills the rodless chamber of the second axle's hydropneumatic cylinder with oil, using differential hydraulic pressure to lift the second axle, causing the third axle tires to lift off the ground. Subsequently, the second axle's hydropneumatic cylinder is locked. When the vehicle turns at low speed, only the second axle follows the steering, reducing the equivalent wheelbase and turning radius. This eliminates tire drag wear caused by the incoordination of the second and third axle's motion trajectories, improving low-speed maneuverability. After steering is completed, the hydraulic system returns to its initial state, the third axle tires touch the ground again, and the vehicle returns to three-axle drive mode.

[0065] When a single or multiple wheel suspension failure occurs, the controller implements a graded hydraulic isolation strategy based on the location of the faulty wheel. After lifting or rigidly locking the faulty wheel, the corresponding rodless chamber hydraulic circuit is cut off, so that the faulty wheel is physically isolated from the other suspension hydraulic circuits. This ensures that the vehicle still has a certain driving capability in the fault state, and the vehicle's fault tolerance and driving safety are improved.

[0066] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A hydraulic system for an amphibious three-axle vehicle's pneumatic suspension, characterized in that, It includes hydraulic cylinders, accumulators, and hydraulic pumps. Each single wheel's hydraulic cylinder is a single-rod piston cylinder, with its rodless chamber used to connect to the vehicle body and its rod chamber used to connect to the suspension guide rod. Each single wheel's hydraulic cylinder is equipped with an electrically controlled damping valve between it and its corresponding accumulator. The hydraulic cylinders on the same side of the second and third axles are connected by an electromagnetic reversing valve, so that the rodless chambers and rod chambers on the same side of the second and third axles are connected to each other. The left and right sides of the second and third axles are connected by an electromagnetic reversing valve, so that the left rodless chamber is connected to the right rod chamber, and the right rodless chamber is connected to the left rod chamber. The second axle is equipped with a left hydraulic cylinder and a right hydraulic cylinder, and the third axle is equipped with a left hydraulic cylinder and a right hydraulic cylinder. The left hydraulic cylinder, right hydraulic cylinder, left hydraulic cylinder, and right hydraulic cylinder of the second and third axles are all connected to a three-position six-way valve between the wheels of the second and third axles. The rodless chamber and the rod chamber of the right hydraulic cylinder of the second axle are connected to a right solenoid valve of the second and third axles, and the rodless chamber and the rod chamber of the right hydraulic cylinder of the third axle are also connected to a right solenoid valve of the second and third axles. The rodless chamber and rod chamber of the left hydraulic cylinder of the second bridge are connected to the left solenoid directional valve of the second and third bridges, and the rodless chamber and rod chamber of the left hydraulic cylinder of the third bridge are connected to the left solenoid directional valve of the second and third bridges. The hydraulic pump is connected to the rod chamber and rodless chamber of each oil cylinder through an electromagnetic directional valve. When the electromagnetic directional valve switches between different working positions, the output oil of the hydraulic pump can be introduced into the rod chamber or rodless chamber of the corresponding oil cylinder.

2. The hydraulic system for the hydropneumatic suspension of an amphibious three-axle vehicle according to claim 1, characterized in that, One bridge is equipped with a left oil-gas cylinder and a right oil-gas cylinder, and a three-position six-way valve between the left oil-gas cylinder and the right oil-gas cylinder is connected between the bridge wheels. Solenoid valves and accumulators are provided between the rodless chambers of the right and left oil cylinders of the first axle and the three-position six-way valve between the wheels of the first axle. The accumulators are connected to damping valves.

3. The hydraulic system for the hydropneumatic suspension of an amphibious three-axle vehicle according to claim 1, characterized in that, An inter-axle three-position six-way valve is connected between the first axle wheel-to-wheel three-position six-way valve and the second and third axle wheel-to-wheel three-position six-way valves. A speed regulating valve is installed between the inter-axle three-position six-way valve and the hydraulic pump. The hydraulic pump is connected to the valve.

4. The hydraulic system for the hydropneumatic suspension of an amphibious three-axle vehicle according to claim 1, characterized in that, The rodless chambers of the left and right hydraulic cylinders of the second bridge, the left and right hydraulic cylinders of the third bridge, and the right hydraulic cylinder of the third bridge are all connected to solenoid valves and accumulators, and the accumulators are connected to damping valves.

5. The hydraulic system for the pneumatic suspension of an amphibious three-axle vehicle according to claim 1, characterized in that, It also includes a controller, which is electrically connected to each electromagnetic directional valve and each damping valve, and is connected to the position sensor of each single wheel.

6. A control method for a hydraulic system of an amphibious three-axle vehicle's pneumatic suspension according to any one of claims 1-5, characterized in that, include: During normal driving, the control of each electromagnetic reversing valve enables the rodless chambers on the same side of the second and third axles to be interconnected, and the rod chambers to be interconnected, and also enables the rodless chambers on the left and right sides to be connected with the rod chambers on the opposite side. The damping valves of each accumulator remain open, and the pressure difference between the rodless and rod chambers of each oil cylinder provides the vehicle support force. When lifting the wheels during navigation, the damping valves of each accumulator are closed, and the hydraulic pump is controlled to supply oil to the rod chamber of each hydraulic cylinder, pushing the hydraulic cylinder to compress and lift each wheel; when each wheel is detected to have reached the set position, the rodless chamber circuit of the corresponding hydraulic cylinder is cut off, the hydraulic pump stops working, and each wheel is kept in the lifting position. When turning at low speed, the rodless chamber circuit of the third axle hydraulic cylinder is cut off, and the accumulators of the second and third axles are also cut off. The hydraulic pump is controlled to supply oil to the rodless chamber of the second axle hydraulic cylinder, causing the second axle hydraulic cylinder to extend and lift under differential action until the third axle tires are off the ground. Then the second axle hydraulic cylinder is locked, and the hydraulic pump stops working.

7. The control method for the hydraulic system of the hydropneumatic suspension of an amphibious three-axle vehicle according to claim 6, characterized in that, After the voyage is completed, the hydraulic pump supplies oil to the rodless chamber of each hydraulic cylinder, pushing the hydraulic cylinder to extend and return each wheel to its normal position; when the set position is detected, the hydraulic pump stops working, and then each solenoid directional valve is returned to its initial state. After the low-speed steering is completed, restore all solenoid directional valves to their initial state, and the hydraulic system returns to normal driving conditions.

8. The control method for the hydraulic system of the hydropneumatic suspension of an amphibious three-axle vehicle according to claim 6, characterized in that, The control method further includes a fault isolation step: When a fault is detected in any wheel suspension, the faulty wheel is lifted or rigidly locked, and then the rodless chamber hydraulic circuit of the faulty wheel is cut off, isolating the faulty wheel from the other suspension hydraulic circuits.

9. The control method for the hydraulic system of the hydropneumatic suspension of an amphibious three-axle vehicle according to claim 8, characterized in that, In the fault isolation step, when the faulty wheel is located on a bridge, a rigid locking operation is performed on the faulty wheel; When one or two wheels on opposite sides of the second or third axle fail, a wheel-lifting isolation operation is performed on the failed wheel. When two or more wheels on the same side of the second or third axle fail, a rigid locking operation is performed on the failed wheels.

10. The control method for the hydraulic system of the hydropneumatic suspension of an amphibious three-axle vehicle according to claim 9, characterized in that, The rigid locking method is as follows: The control solenoid directional valve connects the rodless chamber and the rod chamber of the target wheel, and then the rodless chamber damping valve of the target wheel is shut off, using the incompressibility of hydraulic oil to keep the target wheel locked.

11. An amphibious three-axle vehicle, characterized in that, It is equipped with the hydropneumatic suspension hydraulic system as described in any one of claims 1-5.

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