CN111120434A

CN111120434A - Hydraulic system for automatic leveling test bed

Info

Publication number: CN111120434A
Application number: CN201911393642.1A
Authority: CN
Inventors: 扈凯; 张文毅; 陈昆仑; 任成钰; 贺广迎
Original assignee: Nanjing Research Institute for Agricultural Mechanization Ministry of Agriculture
Current assignee: Nanjing Research Institute for Agricultural Mechanization Ministry of Agriculture
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2020-05-08

Abstract

A hydraulic system for an automatic leveling test bed is characterized in that four supporting hydraulic cylinders are connected to a lower supporting frame; a piston rod of the supporting hydraulic cylinder is fixedly connected with the bearing disc; the lower part of the upper supporting frame is hinged with four connecting steel pipes, each two connecting steel pipes are fixedly connected with two ends of an upper cross beam, and the end part of the upper cross beam is fixedly connected with a sliding shoe arranged on the bearing disc through a supporting bolt; the horizontal tilt angle sensor is arranged in the middle of the upper frame; the controller is respectively connected with the four supporting hydraulic cylinders through the four electromagnetic proportional reversing valves and is also respectively connected with the leveling hydraulic cylinder through the four electromagnetic proportional reversing valves; a displacement sensor is arranged on the supporting hydraulic cylinder, and a hydraulic control reversing valve and a variable throttle valve are arranged on an oil path where a rodless cavity of the supporting hydraulic cylinder is located; and a displacement sensor and a speed sensor are arranged on the leveling hydraulic cylinder. The system can realize the simulation of various road surface unevenness, can simulate different traveling speeds of vehicles, and can verify the leveling effect in real time in the test process.

Description

Hydraulic system for automatic leveling test bed

Technical Field

The invention belongs to the technical field of agricultural machinery test equipment, and particularly relates to a hydraulic system for an automatic leveling test bed.

Background

In recent years, with the development of an automatic leveling technology, the automatic leveling technology is widely applied to the fields of engineering machinery and agricultural machinery, and the trafficability and driving comfort of the machine are effectively improved. The automatic leveling function is usually realized by installing a hydraulic suspension in the agricultural machine, so that the agricultural machine can automatically level the frame on an uneven road surface, and the automatic leveling device is better suitable for ground type operation on hilly and mountainous regions.

Because the hydraulic suspension needs to be adjusted in real time, a series of problems such as large heat productivity, slow response and the like of a hydraulic system are easily caused, even the whole machine possibly breaks down, a test bench is urgently needed to perform test analysis on the leveling system, the research and development efficiency is improved, and the research and development cost is reduced. But at the same time, the automatic leveling system lacks an effective test means because the road surface spectrum is difficult to simulate and the test cost is high.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a hydraulic system for an automatic leveling test bed, which can realize the simulation of various road surface unevenness, can simulate different traveling speeds of vehicles and can verify the action effect of leveling a hydraulic suspension in real time in the test process.

In order to achieve the aim, the invention provides a hydraulic system for an automatic leveling test bed, which comprises the automatic leveling test bed, a hydraulic control system and a controller;

the automatic leveling test bed comprises a lower support frame, four upper support plates, four support hydraulic cylinders, four bearing discs, an upper leveling mechanism, a top support beam a and a horizontal tilt angle sensor; the lower supporting frame consists of a lower frame and four supporting legs with equal length, the lower frame consists of two lower cross beams a which are correspondingly distributed at the front and the back and two lower cross beams b which are correspondingly distributed at the left and the right, which are sequentially and fixedly connected, and the upper ends of the four supporting legs are respectively and fixedly connected with the four corners of the lower end of the lower frame; the four upper supporting plates are respectively and fixedly connected to four corners of the upper end of the lower frame, and through holes A are formed in the centers of the four upper supporting plates; the four supporting hydraulic cylinders are respectively marked as a supporting hydraulic cylinder A, a supporting hydraulic cylinder B, a supporting hydraulic cylinder C and a supporting hydraulic cylinder D; the four supporting hydraulic cylinders are respectively arranged at the lower parts of the four upper supporting plates, and the lower ends of the cylinder barrels of the supporting hydraulic cylinders are all positioned above the lower ends of the supporting legs; the upper ends of the cylinders of the four supporting hydraulic cylinders are respectively fixedly connected with the lower end faces of the four upper supporting plates, and piston rods of the four supporting hydraulic cylinders respectively penetrate through the through holes A in the four upper supporting plates in a sliding manner and are respectively fixedly connected with four connecting plates a arranged above the four upper supporting plates; the four bearing disks are respectively arranged above the four connecting plates a, and the upper ends of the four bearing disks are fixedly connected with annular coamings; the centers of the lower ends of the four bearing disks are fixedly connected with the centers of the upper ends of the four connecting plates a through four support columns; the upper leveling mechanism comprises an upper supporting frame, a connecting shaft, two upper cross beams, four connecting steel pipes, four connecting lugs d, four leveling hydraulic cylinders and four connecting lugs a; the four leveling hydraulic cylinders are respectively marked as a leveling hydraulic cylinder A, a leveling hydraulic cylinder B, a leveling hydraulic cylinder C and a leveling hydraulic cylinder D; the upper support frame consists of an upper frame, a middle connecting plate and four middle supports with equal length, the upper frame consists of two upper main beams b which are correspondingly distributed at the front and the back and two upper main beams a which are correspondingly distributed at the left and the right and are sequentially and fixedly connected, and the size of the upper frame is smaller than that of the lower frame; the size of the middle connecting plate is smaller than that of the upper frame, and the middle connecting plate is arranged in the center below the upper frame; the upper ends of the four middle supports are respectively fixedly connected with the end parts of the two upper main beams b, and the lower ends of the four middle supports are respectively fixedly connected with four corners at the upper end of the middle connecting plate; the left part and the right part of the lower end of the middle connecting plate are oppositely and fixedly connected with a pair of connecting lug plates a, and the lower parts of the connecting lug plates a are correspondingly provided with a pair of through holes B; the connecting shaft is rotatably arranged in the pair of through holes B in a penetrating way, and the left end and the right end of the connecting shaft are correspondingly and fixedly connected with two side end plates; the front end and the rear end of the left side end plate and the front end and the rear end of the right side end plate are respectively fixedly connected with two connecting lug plates b; the two upper cross beams are respectively arranged on the left side and the right side above the lower supporting frame, and the end parts of the two upper cross beams respectively correspond to the upper parts of the four bearing discs; the lower end parts of the two upper cross beams are respectively and fixedly connected with four sliding shoes through four supporting bolts, the four sliding shoes are respectively and slidably arranged on the upper parts of the four bearing disks, and the limit of the sliding range is carried out through annular enclosing plates on the four bearing disks; the inner ends of the four connecting steel pipes are respectively and fixedly connected with the outer ends of the four connecting plates e, and the inner ends of the four connecting plates e are respectively connected with the four connecting lug plates b through four connecting pin shafts e; the outer ends of the four connecting steel pipes are respectively fixedly connected with the end parts of the two upper cross beams; the upper ends of the four connecting lugs d are respectively and fixedly connected with four corners of the lower end of the upper frame; the lower ends of the four connecting lugs d are respectively and rotatably connected with the upper ends of the four connecting lugs c through four connecting pin shafts d; the piston rod ends of the four leveling hydraulic cylinders are respectively and rotatably connected with the lower ends of the four connecting lugs c through four connecting pin shafts c; the cylinder ends of the four leveling hydraulic cylinders are respectively and rotatably connected with the upper ends of the four connecting lugs b through four connecting pin shafts b; the lower ends of the four connecting lugs b are respectively and rotatably connected with the upper ends of the four connecting lugs a through four connecting pin shafts a, and the lower ends of the four connecting lugs a are respectively and fixedly connected with the upper parts of the outer ends of the four connecting steel pipes; the top support beam a is fixedly connected between the two upper main beams a; the horizontal inclination angle sensor is arranged in the middle of the top support beam a;

the hydraulic control system comprises a motor, a variable pump, a gear pump, a hydraulic suspension leveling control unit and a road surface simulation control unit;

the hydraulic suspension leveling control unit comprises a leveling hydraulic cylinder A, a leveling hydraulic cylinder B, a leveling hydraulic cylinder C, a leveling hydraulic cylinder D, an electromagnetic proportional reversing valve A, an electromagnetic proportional reversing valve B, an electromagnetic proportional reversing valve C and an electromagnetic proportional reversing valve D; the road surface simulation control unit comprises a supporting hydraulic cylinder A, a supporting hydraulic cylinder B, a supporting hydraulic cylinder C, a supporting hydraulic cylinder D, an electromagnetic proportional reversing valve E, an electromagnetic proportional reversing valve F, an electromagnetic proportional reversing valve G and an electromagnetic proportional reversing valve H;

the electric motor is respectively connected with the variable pump and the gear pump through the transfer case, oil suction ports of the variable pump and the gear pump are respectively connected with the oil tank, and oil discharge ports of the variable pump and the gear pump are respectively connected with the oil tank through a safety valve I and a safety valve II; the oil discharge port of the variable displacement pump is also connected with the ports P of the electromagnetic proportional reversing valve A, the electromagnetic proportional reversing valve B, the electromagnetic proportional reversing valve C and the electromagnetic proportional reversing valve D through a fixed-differential pressure reducing valve A, a fixed-differential pressure reducing valve B, a fixed-differential pressure reducing valve C and a fixed-differential pressure reducing valve D respectively; the T ports of the electromagnetic proportional reversing valve A, the electromagnetic proportional reversing valve B, the electromagnetic proportional reversing valve C and the electromagnetic proportional reversing valve D are all connected with an oil tank; the port A and the port B of the electromagnetic proportional directional valve A are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder A and are also respectively connected with two comparison oil ports of the shuttle valve A, and the oil outlet of the shuttle valve A is connected with a control port of the fixed-differential pressure reducing valve A; the port A and the port B of the electromagnetic proportional directional valve B are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder B and are also respectively connected with two comparison oil ports of the shuttle valve B, and the oil outlet of the shuttle valve B is connected with a control port of the fixed-differential pressure reducing valve B; the port A and the port B of the electromagnetic proportional directional valve C are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder C and are also respectively connected with two comparison oil ports of the shuttle valve C, and the oil outlet of the shuttle valve C is connected with a control port of the fixed-differential pressure reducing valve C; the port A and the port B of the electromagnetic proportional directional valve D are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder D and are also respectively connected with two comparison oil ports of the shuttle valve D, and an oil outlet of the shuttle valve D is connected with a control port of the fixed-differential pressure reducing valve D; the leveling hydraulic cylinder A, the leveling hydraulic cylinder B, the leveling hydraulic cylinder C and the leveling hydraulic cylinder D are respectively connected with a displacement sensor E, a displacement sensor F, a displacement sensor G and a displacement sensor H which are used for measuring displacement, and are also respectively connected with an acceleration sensor A, an acceleration sensor B, an acceleration sensor C and an acceleration sensor D which are used for measuring acceleration;

the oil discharge port of the gear pump is also respectively connected with the ports P of the electromagnetic proportional reversing valve E, the electromagnetic proportional reversing valve F, the electromagnetic proportional reversing valve G and the electromagnetic proportional reversing valve H, and the ports T of the electromagnetic proportional reversing valve E, the electromagnetic proportional reversing valve F, the electromagnetic proportional reversing valve G and the electromagnetic proportional reversing valve H are all connected with the oil tank; the port A of the electromagnetic proportional directional valve E is connected with the rodless cavity of the supporting hydraulic cylinder A sequentially through the hydraulic control one-way valve A and the variable throttle valve A, and the port B of the electromagnetic proportional directional valve E is connected with the rod cavity of the supporting hydraulic cylinder A and the hydraulic control port of the hydraulic control one-way valve A respectively; the port A of the electromagnetic proportional reversing valve F is connected with a rodless cavity of the supporting hydraulic cylinder B sequentially through the hydraulic control one-way valve B and the variable throttle valve B, and the port B of the electromagnetic proportional reversing valve F is connected with a rod cavity of the supporting hydraulic cylinder B and a hydraulic control port of the hydraulic control one-way valve B respectively; the port A of the electromagnetic proportional directional valve G is connected with the rodless cavity of the supporting hydraulic cylinder C sequentially through the hydraulic control one-way valve C and the variable throttle valve C, and the port B of the electromagnetic proportional directional valve G is connected with the rod cavity of the supporting hydraulic cylinder C and the hydraulic control port of the hydraulic control one-way valve C; the port A of the electromagnetic proportional directional valve H is connected with a rodless cavity of the supporting hydraulic cylinder D sequentially through a hydraulic control one-way valve D and a variable throttle valve D, and the port B of the electromagnetic proportional directional valve H is connected with a rod cavity of the supporting hydraulic cylinder D and a hydraulic control port of the hydraulic control one-way valve D respectively; the supporting hydraulic cylinder A, the supporting hydraulic cylinder B, the supporting hydraulic cylinder C and the supporting hydraulic cylinder D are respectively connected with a displacement sensor A, a displacement sensor B, a displacement sensor C and a displacement sensor D which are used for measuring displacement;

the controller is respectively connected with the horizontal tilt sensor, the displacement sensor A, the displacement sensor B, the displacement sensor C, the displacement sensor D, the displacement sensor E, the displacement sensor F, the displacement sensor G, the displacement sensor H, the acceleration sensor A, the acceleration sensor B, the acceleration sensor C and the acceleration sensor D.

Further, in order to increase area of contact, reduce the pressure to ground to prevent that the test bench from causing destruction to ground, still include four supporting baseplate, four supporting baseplate fixed connection are at the lower extreme of four supporting legs, and supporting baseplate is the square.

Further, in order to increase the connection strength, the end part of the lower cross beam a and the upper end of the supporting leg are fixedly connected, and the end part of the lower cross beam b and the upper end of the supporting leg are fixedly connected through a triangular reinforcing plate; the middle part of the lower cross beam a and the lower part of the supporting leg, and the middle part of the lower cross beam b and the lower part of the supporting leg are fixedly connected through lower reinforcing ribs.

Furthermore, in order to increase the bearing capacity of the upper frame, two sides of the middle part of the top support beam a are fixedly connected with two upper main beams b through two top support beams b.

Furthermore, for convenient installation and dismantlement, still include four connecting plates d and four connecting plates c, four connecting plates d are fixed connection respectively in the four corners department of upper portion frame lower extreme, and four connecting plates c are fixed connection respectively in the upper end of connecting lug d, through a plurality of connecting bolt fixed connection between four connecting plates d and four connecting plates c.

Further, for convenience of installation and disassembly, a through hole C for a supporting bolt to pass through is formed in the end portion of the upper cross beam, the upper end of the supporting bolt passes through the through hole C, and a nut b and a nut a are connected to the upper side and the lower side of the upper cross beam in a threaded fit mode respectively.

Further, in order to avoid impurities from blocking the valve body in the system, an oil suction port of the variable pump is connected with the oil tank through a filter A, and an oil suction port of the gear pump is connected with the oil tank through a filter B; in order to cool the hydraulic oil, the T ports of the electromagnetic proportional reversing valve E, the electromagnetic proportional reversing valve F, the electromagnetic proportional reversing valve G and the electromagnetic proportional reversing valve H are connected with an oil tank through coolers.

Furthermore, in order to simulate the actual load condition, the device also comprises a balancing weight fixedly connected to the center of the upper end of the bracket frame.

According to the invention, the lower support frame can effectively support the whole test bed, piston rods of four support hydraulic cylinders connected with the lower parts of the four upper support plates can penetrate through the through holes A in the upper support plates so as to control the bearing disc supporting the upper support to lift in the longitudinal direction, so that the outer ends of the corresponding connecting steel pipes lift in the longitudinal direction, and the fluctuation state of a road surface can be effectively simulated through stroke control of the four support hydraulic cylinders. The hydraulic control one-way valve can realize locking various positions of the hydraulic cylinder, and the variable throttle valve can control the oil supply flow, so that the dual functions of flow regulation and hydraulic cylinder locking can be considered, and the fluctuation state of the road surface can be better simulated. The supporting hydraulic cylinder is controlled by the electromagnetic proportional directional valve, so that the road surface simulation process can be conveniently realized by switching value control, and the cost can be saved. The end part of the connecting steel pipe is fixedly connected with the sliding shoe arranged on the bearing disc in a sliding mode through the supporting bolt, so that the sliding shoe has a certain sliding space in the process that the connecting steel pipe rotates around the connecting pin shaft a, and the process of ascending or descending can be simulated effectively. The upper supporting frame can have a certain range of rotational freedom around the connecting shaft through the through hole B on the connecting lug plate a, the connecting steel pipe can have a certain range of rotational freedom around the connecting pin e relative to the upper supporting frame, the upper end of the leveling hydraulic cylinder has a certain range of rotational freedom relative to the upper end of the upper supporting frame, and the lower end of the leveling hydraulic cylinder has a certain range of rotational freedom relative to the outer end of the connecting steel pipe, so that a hydraulic suspension can be effectively simulated. The pressure compensation is carried out on the electromagnetic proportional reversing valve connected with the leveling hydraulic cylinder through the fixed-differential pressure reducing valve, so that the oil supply flow of the leveling hydraulic cylinder is only related to the opening size of the electromagnetic proportional reversing valve and is not related to the working load, the system impact is reduced, the control precision is effectively improved, and the leveling operation can be more accurately realized. When the two supporting hydraulic cylinders at the front part of the lower supporting frame extend out to simulate an ascending slope, the piston rods of the two leveling hydraulic cylinders at the rear side of the upper supporting frame can be controlled to extend out to compensate, so that the upper supporting frame is kept in a horizontal state, and when the two supporting hydraulic cylinders at the middle and rear parts of the lower supporting frame extend out to simulate a descending slope, the piston rods of the two leveling hydraulic cylinders at the front side of the upper supporting frame can be controlled to extend out to compensate, so that the upper supporting frame is kept in a horizontal state continuously. The test bed has multiple degrees of freedom, can effectively simulate the actual road spectrum, and can effectively perform corresponding compensation on an uphill state and a downhill state at the same time, so that the upper support frame is always kept in a horizontal state. The extending or retracting speed of the piston rod of the hydraulic cylinder can be changed by controlling the oil feeding flow of the hydraulic cylinder, so as to indirectly simulate different traveling speeds of the vehicle. Compared with the traditional test bed, the test bed has the advantages that the system structure is simplified, the hydraulic system is easier to realize, the manufacturing cost of the test bed is effectively reduced, the hydraulic system is easier to realize, the simulation of various road surface unevenness can be effectively carried out, meanwhile, the levelness can be fed back through the horizontal inclination angle sensor, and then the effect of the leveling hydraulic suspension is verified in real time. The system adopts the variable pump as a power element, the output flow of the variable pump only maintains the leakage of the system when the system does not work, and the output flow of the variable pump is rapidly increased when the leveling operation is started, so that the rapid response of the system is ensured. The hydraulic cylinder can be cooled through the cooler, so that the economical efficiency of the system is effectively improved, and the heating condition of the system is reduced. The road surface unevenness can be conveniently acquired through the horizontal inclination angle sensor. The invention can conveniently acquire a plurality of parameters such as road surface unevenness, hydraulic suspension response speed, frame adjustment levelness and the like, and can better complete the test process of automatically leveling the hydraulic suspension.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a right side view of FIG. 1;

FIG. 3 is a top view of FIG. 1;

fig. 4 is a hydraulic schematic of the present invention.

In the figure: 1. supporting bottom plate, 2, supporting legs, 3, triangular reinforcing plates, 4, supporting hydraulic cylinders 5, lower beams a, 6, lower reinforcing ribs, 7, lower beams b, 8, connecting plates a, 9, supporting columns, 10, bearing disks, 11, supporting bolts, 12, upper beams, 13, connecting pins a, 14, connecting pins b, 15, leveling hydraulic cylinders, 16, connecting lugs a, 17, connecting lugs b, 18, intermediate connecting plates, 19, intermediate supports, 20, connecting pins c, 21, connecting lugs c, 22, connecting lugs d, 23, connecting plates c, 24, connecting plates d, 25, connecting bolts, 26, upper girders a, 27, upper girders b, 28, connecting steel pipes, 29, connecting plates e, 30, connecting pins e, 31, connecting shafts, 32, top supporting beams a, 33, top supporting beams b, 34, upper supporting plates, 35, Annular enclosing plates 36, sliding shoes 37, nuts a, 38, nuts B, 39, connecting pin shafts D, 40, horizontal inclination angle sensors 41, connecting lug plates a, 42, side end plates 43, connecting lug plates B, 44, lower frames 45, upper frames 46, motors 47, variable pumps 48, gear pumps 49, safety valves I, 50, safety valves II, 51, oil tanks 52, constant differential pressure reducing valves A, 53, constant differential pressure reducing valves B, 54, constant differential pressure reducing valves C, 55, constant differential pressure reducing valves D, 56, electromagnetic proportional reversing valves A, 57, electromagnetic proportional reversing valves B, 58, electromagnetic proportional reversing valves C, 59, electromagnetic proportional reversing valves D, 60, leveling hydraulic cylinders A, 61, leveling hydraulic cylinders B, 62, leveling hydraulic cylinders C, 63, leveling hydraulic cylinders D, 64, supporting hydraulic cylinders A, 65, supporting hydraulic cylinders B, 66, supporting hydraulic cylinders C, 67, 60, leveling hydraulic cylinders A, 61, leveling hydraulic cylinders B, 62, leveling hydraulic cylinders C, 63, leveling hydraulic cylinders D, 64, supporting hydraulic cylinders A, 65, supporting hydraulic cylinders B, A support hydraulic cylinder D, 68, an electromagnetic proportional directional valve E, 69, an electromagnetic proportional directional valve F, 70, an electromagnetic proportional directional valve G, 71, an electromagnetic proportional directional valve H, 72, a shuttle valve A, 73, a shuttle valve B, 74, a shuttle valve C, 75, a shuttle valve D, 76, a pilot operated check valve A, 77, a variable throttle valve A, 78, a pilot operated check valve B, 79, a variable throttle valve B, 80, a pilot operated check valve C, 81, a variable throttle valve C, 82, a pilot operated check valve D, 83, a variable throttle valve D, 84, a displacement sensor A, 85, a displacement sensor B, 86, a displacement sensor C, 87, a displacement sensor D, 88, a displacement sensor E, 89, a displacement sensor F, 90, a displacement sensor G, 91, a displacement sensor H, 92, an acceleration sensor A, 93, an acceleration sensor B, 94, an acceleration sensor C, 95, an acceleration sensor D, 96. balancing weight 97, filter A, 98, filter B, 99 and cooler.

Detailed Description

The invention will be further explained with reference to the drawings.

As shown in fig. 1 to 4, a hydraulic system for an automatic leveling test bed comprises an automatic leveling test bed, a hydraulic control system and a controller;

the automatic leveling test bed comprises a lower support frame, four upper support plates 34, four support hydraulic cylinders 4, four bearing discs 10, an upper leveling mechanism, a top support beam a32 and a horizontal inclination angle sensor 40; the lower supporting frame consists of a lower frame 44 and four supporting legs 2 with equal length, the lower frame 44 consists of two lower beams a5 which are correspondingly distributed at the front and the back and two lower beams b7 which are correspondingly distributed at the left and the right and are fixedly connected in sequence, and the upper ends of the four supporting legs 2 are respectively and fixedly connected with four corners at the lower end of the lower frame 44; the supporting leg 2 can be made of a square tube, the size of the square tube can be designed according to actual conditions, for example, the cross section size of the square tube can be 80mmx80mm, and the thickness of the square tube can be 5 mm. The four upper supporting plates 34 are respectively and fixedly connected to four corners at the upper end of the lower frame 44, and through holes A are formed in the centers of the four upper supporting plates 34; the four supporting hydraulic cylinders 4 are respectively marked as a supporting hydraulic cylinder A64, a supporting hydraulic cylinder B65, a supporting hydraulic cylinder C66 and a supporting hydraulic cylinder D67; preferably, the upper support plate 34 has a thickness of 10 mm. The four supporting hydraulic cylinders 4 are respectively arranged at the lower parts of the four upper supporting plates 34, and the lower ends of the cylinder barrels of the supporting hydraulic cylinders 4 are all positioned above the lower ends of the supporting legs 2; the upper ends of the cylinder barrels of the four supporting hydraulic cylinders 4 are respectively fixedly connected with the lower end faces of the four upper supporting plates 34, and the piston rods of the four supporting hydraulic cylinders 4 respectively penetrate through the through holes A in the four upper supporting plates 34 in a sliding mode and are respectively fixedly connected with four connecting plates a8 arranged above the four upper supporting plates 34; preferably, web a8 has a thickness of 10 mm;

as a preference, the support cylinder 4 is selected as a double-acting cylinder, the maximum stroke of which is 200 mm.

The lower cross beam a5 and the lower cross beam b7 can be made of square tubes, and the size of the square tubes can be designed according to actual conditions, for example, the cross section size can be 60mmx60mm, and the thickness can be 5 mm.

The four bearing disks 10 are respectively arranged above the four connecting plates a8, and the upper ends of the four bearing disks 10 are fixedly connected with annular coamings 35; the centers of the lower ends of the four bearing disks 10 are fixedly connected with the centers of the upper ends of the four connecting plates a8 through four supporting columns 9; preferably, the supporting column 9 is a cylinder with a diameter of 20mm, and the height thereof can be 30 mm. Preferably, the carrier disc 10 has a diameter of 20mm and a thickness of 10 mm. The annular shroud 35 is preferably 20mm in height and 3mm thick.

The upper leveling mechanism comprises an upper supporting frame, a connecting shaft 31, two upper cross beams 12, four connecting steel pipes 28, four connecting lugs d22, four leveling hydraulic cylinders 15 and four connecting lugs a 16; the four leveling hydraulic cylinders 15 are respectively marked as a leveling hydraulic cylinder A60, a leveling hydraulic cylinder B61, a leveling hydraulic cylinder C62 and a leveling hydraulic cylinder D63; the upper support frame is composed of an upper frame 45, a middle connecting plate 18 and four middle supports 19 with equal length, the upper frame 45 is composed of two upper main beams b27 which are correspondingly distributed front and back and two upper main beams a26 which are correspondingly distributed left and right, and the upper main beams a26 and the upper main beams b27 can be made of square tubes, the size of each square tube can be designed according to actual conditions, for example, the size of the cross section of each square tube can be 40mmx40 mm. Preferably, the intermediate connecting plate 18 is made of a steel plate having a size of 150mmx150 mm. The intermediate bracket 19 may be made of a square tube, and the size of the square tube may be designed according to actual conditions, for example, the cross-sectional size may be 40mmx40 mm.

The size of the upper frame 45 is smaller than that of the lower frame 44; the intermediate connection plate 18 has a size smaller than that of the upper frame 45 and is disposed at the center below the upper frame 45; the upper ends of the four middle brackets 19 are respectively fixedly connected with the end parts of the two upper main beams b27, and the lower ends of the four middle brackets are respectively fixedly connected with four corners at the upper end of the middle connecting plate 18; a pair of connecting lug plates a41 are oppositely and fixedly connected to the left part and the right part of the lower end of the middle connecting plate 18, and a pair of through holes B are correspondingly formed in the lower parts of the connecting lug plates a 41; the connecting shaft 31 is rotatably arranged in the pair of through holes B in a penetrating way, and the left end and the right end of the connecting shaft 31 are correspondingly and fixedly connected with two side end plates 42; two connecting ear plates b43 are fixedly connected to the left side of the left side end plate 42 and the right side of the right side end plate 42 respectively; the two upper cross beams 12 are respectively arranged on the left side and the right side above the lower support frame, and the end parts of the two upper cross beams 12 are respectively corresponding to the upper parts of the four bearing discs 10; the lower end parts of the two upper cross beams 12 are respectively fixedly connected with four sliding shoes 36 through four supporting bolts 11, the four sliding shoes 36 are respectively arranged on the upper parts of the four bearing disks 10 in a sliding manner, and the limit of the sliding range is carried out through the annular enclosing plates 35 on the four bearing disks 10; preferably, the bottom of the shoe 36 is coated with a lubricating oil to reduce resistance during sliding. Preferably, the support bolt 11 has a specification of M20x150 mm. The upper beam 12 may be made of a square pipe, and the size of the square pipe may be designed according to actual conditions, for example, the cross-sectional size may be 40mmx40mm, and the thickness is 5 mm.

Preferably, the vertical distance between the two upper cross members 12 is equal to the actual track width of the vehicle being simulated; the length of the upper cross beam 12 is equal to the actual wheelbase of the simulated vehicle, so that the simulation effect is effectively improved.

The inner ends of the four connecting steel tubes 28 are respectively fixedly connected with the outer ends of the four connecting plates e29, and the inner ends of the four connecting plates e29 are respectively connected with the four connecting ear plates b43 through four connecting pin shafts e 30; the outer ends of the four connecting steel pipes 28 are respectively fixedly connected with the end parts of the two upper cross beams 12; preferably, the connecting steel pipe 28 may be made of a square pipe, and the size of the square pipe may be designed according to practical situations, for example, the cross-sectional size of the square pipe may be 50mmx50 mm. The connecting plate e29 may be made of a steel plate having a thickness of 4 mm.

The upper ends of the four connecting lugs d22 are respectively fixedly connected at the four corners of the lower end of the upper frame 45; the lower ends of the four connecting lugs d22 are respectively and rotatably connected with the upper ends of the four connecting lugs c21 through four connecting pin shafts d 39; the piston rod ends of the four leveling hydraulic cylinders 15 are respectively and rotatably connected with the lower ends of the four connecting lugs c21 through four connecting pin shafts c 20; preferably, the leveling cylinder 15 is a double-acting cylinder. The parameters such as stroke, cylinder diameter, rod diameter ratio and the like can be selected according to actual requirements.

The four leveling hydraulic cylinders 15 correspond to the four wheel suspensions respectively, and the frame can be adjusted within a certain range to be in a horizontal state.

The cylinder ends of the four leveling hydraulic cylinders 15 are respectively and rotatably connected with the upper ends of the four connecting lugs b17 through four connecting pin shafts b 14; the lower ends of the four connecting lugs b17 are respectively and rotatably connected with the upper ends of the four connecting lugs a16 through four connecting pin shafts a13, and the lower ends of the four connecting lugs a16 are respectively and fixedly connected with the upper parts of the outer ends of the four connecting steel pipes 28; the top support beam a32 is fixedly connected between two upper main beams a 26; the horizontal tilt angle sensor 40 is installed at the middle of the top support beam a 32;

the hydraulic control system comprises a motor 46, a variable pump 47, a gear pump 48, a hydraulic suspension leveling control unit and a road surface simulation control unit;

the hydraulic suspension leveling control unit comprises a leveling hydraulic cylinder A60, a leveling hydraulic cylinder B61, a leveling hydraulic cylinder C62, a leveling hydraulic cylinder D63, an electromagnetic proportional directional valve A56, an electromagnetic proportional directional valve B57, an electromagnetic proportional directional valve C58 and an electromagnetic proportional directional valve D59; the road surface simulation control unit comprises a supporting hydraulic cylinder A64, a supporting hydraulic cylinder B65, a supporting hydraulic cylinder C66, a supporting hydraulic cylinder D67, an electromagnetic proportional directional valve E68, an electromagnetic proportional directional valve F69, an electromagnetic proportional directional valve G70 and an electromagnetic proportional directional valve H71;

the electromagnetic proportional directional valve A56, the electromagnetic proportional directional valve B57, the electromagnetic proportional directional valve C58 and the electromagnetic proportional directional valve D59 all have O-shaped neutral functions, and the flow direction of hydraulic oil of the system can be controlled by changing the positions of the left, middle and right valve cores. When the left position of the three-position four-way electromagnetic proportional reversing valve is electrified, the port P is communicated with an oil path between the port A, the port T is communicated with an oil path between the port B, when the right position of the three-position four-way electromagnetic proportional reversing valve is electrified, the port P is communicated with an oil path between the port B, the port T is communicated with an oil path between the port A, when the left position and the right position of the three-position four-way electromagnetic proportional reversing valve are not electrified, the three-position four-way electromagnetic proportional reversing valve works in a middle position, and the port P, the port T;

the electromagnetic proportional directional valve E68, the electromagnetic proportional directional valve F69, the electromagnetic proportional directional valve G70 and the electromagnetic proportional directional valve H71 are three-position four-way electromagnetic proportional directional valves which have Y-shaped neutral functions, and the flow direction of hydraulic oil of the system can be controlled by changing the positions of the left, middle and right valve cores. When the left position of the three-position four-way electromagnetic proportional reversing valve is electrified, the port P is communicated with an oil way between the port A, the port T is communicated with an oil way between the port B, when the right position of the three-position four-way electromagnetic proportional reversing valve is electrified, the port P is communicated with an oil way between the port B, the port T is communicated with an oil way between the port A, when the left position and the right position are not electrified, the three-position four-way electromagnetic proportional reversing valve works in a middle position, the port P is stopped, and the port T is simultaneously communicated with the port A and the port B;

preferably, the electric motor 46 is rated at 1500 rpm, and the electric motor 46 is connected to the variable pump 47 and the gear pump 48 via a transfer case, wherein one shaft of the transfer case is connected to the power element gear pump 3 via a transmission gear, and the other shaft is connected to the variable pump 2 via a coupling. Preferably, the variable displacement pump 2 is a constant pressure variable displacement pump. The constant-pressure variable pump is a power element of the system, can adjust the displacement of the constant-pressure variable pump to maintain the pressure of the system stable, and has a quick response speed.

The transmission gear has the function of increasing speed, the transmission ratio is 2, and preferably, the gear pump is an external gear pump 3, and the displacement can be selected according to the size and the stroke of an actuating element.

The oil suction ports of the variable pump 47 and the gear pump 48 are both connected with an oil tank 51, and the oil discharge ports of the variable pump 47 and the gear pump 48 are respectively connected with the oil tank 51 through a safety valve I49 and a safety valve II 50; the safety valve is used for ensuring the safety of the system when the actuating element does not work unloading or the system pressure is too high, and preferably, the set pressure of the safety valve is 120%. The oil outlet of the variable displacement pump 47 is also connected with the P ports of an electromagnetic proportional directional valve A56, an electromagnetic proportional directional valve B57, an electromagnetic proportional directional valve C58 and an electromagnetic proportional directional valve D59 through a constant-differential directional valve A52, a constant-differential directional valve B53, a constant-differential directional valve C54 and a constant-differential directional valve D55 respectively; the T ports of the electromagnetic proportional directional valve A56, the electromagnetic proportional directional valve B57, the electromagnetic proportional directional valve C58 and the electromagnetic proportional directional valve D59 are all connected with the oil tank 51; the port A and the port B of the electromagnetic proportional directional valve A56 are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder A60 and are also respectively connected with two comparison oil ports of a shuttle valve A72, and the oil outlet of the shuttle valve A72 is connected with a control port of a fixed-differential pressure-reducing valve A52; the port A and the port B of the electromagnetic proportional directional valve B57 are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder B61 and are also respectively connected with two comparison oil ports of a shuttle valve B73, and the oil outlet of the shuttle valve B73 is connected with a control port of a fixed-differential pressure-reducing valve B53; the port A and the port B of the electromagnetic proportional directional valve C58 are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder C62 and are also respectively connected with two comparison oil ports of a shuttle valve C74, and the oil outlet of the shuttle valve C74 is connected with a control port of a fixed-differential pressure-reducing valve C54; the port A and the port B of the electromagnetic proportional directional valve D59 are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder D63 and are also respectively connected with two comparison oil ports of a shuttle valve D75, and the oil outlet of the shuttle valve D75 is connected with a control port of a fixed-differential pressure-reducing valve D55; the leveling hydraulic cylinder A60, the leveling hydraulic cylinder B61, the leveling hydraulic cylinder C62 and the leveling hydraulic cylinder D63 are respectively connected with a displacement sensor E88, a displacement sensor F89, a displacement sensor G90 and a displacement sensor H91 which are used for measuring displacement, and are also respectively connected with an acceleration sensor A92, an acceleration sensor B93, an acceleration sensor C94 and an acceleration sensor D95 which are used for measuring acceleration; the displacement sensor and the acceleration sensor are connected with a piston rod of the leveling hydraulic cylinder and are respectively used for measuring the displacement and the acceleration of the piston rod, the horizontal inclination angle sensor is installed on the upper frame and is used for measuring the horizontal degree of the upper frame, data collected by all the test elements are transmitted to the controller, and the controller can be connected with an upper computer so as to carry out data processing through the upper computer. Preferably, the controller is of the type TTC 60.

The constant-differential pressure reducing valve and the shuttle valve are matched with each other to form a pressure compensation system for ensuring the constant pressure difference between two sides of the electromagnetic proportional directional valve.

An oil discharge port of the gear pump 48 is also respectively connected with P ports of an electromagnetic proportional directional valve E68, an electromagnetic proportional directional valve F69, an electromagnetic proportional directional valve G70 and an electromagnetic proportional directional valve H71, and T ports of the electromagnetic proportional directional valve E68, the electromagnetic proportional directional valve F69, the electromagnetic proportional directional valve G70 and the electromagnetic proportional directional valve H71 are all connected with an oil tank; the port A of the electromagnetic proportional directional valve E68 is connected with the rodless cavity of the supporting hydraulic cylinder A64 through a hydraulic control one-way valve A76 and a variable throttle valve A77 in sequence, and the port B of the electromagnetic proportional directional valve E68 is connected with the rod cavity of the supporting hydraulic cylinder A64 and the hydraulic control port of the hydraulic control one-way valve A76 respectively; the port A of the electromagnetic proportional directional valve F69 is connected with a rodless cavity of a supporting hydraulic cylinder B65 through a hydraulic control one-way valve B78 and a variable throttle valve B79 in sequence, and the port B of the electromagnetic proportional directional valve is connected with a rod cavity of the supporting hydraulic cylinder B65 and a hydraulic control port of a hydraulic control one-way valve B78 respectively; the port A of the electromagnetic proportional directional valve G70 is connected with a rodless cavity of a supporting hydraulic cylinder C66 through a pilot-controlled check valve C80 and a variable throttle valve C81 in sequence, and the port B of the electromagnetic proportional directional valve G70 is connected with a rod cavity of the supporting hydraulic cylinder C66 and a pilot-controlled port of a pilot-controlled check valve C80; the port A of the electromagnetic proportional directional valve H71 is connected with the rodless cavity of the supporting hydraulic cylinder D67 through a hydraulic control one-way valve D82 and a variable throttle valve D83 in sequence, and the port B of the electromagnetic proportional directional valve H71 is connected with the rod cavity of the supporting hydraulic cylinder D67 and the hydraulic control port of the hydraulic control one-way valve D82 respectively; a displacement sensor A84, a displacement sensor B85, a displacement sensor C86 and a displacement sensor D87 which are used for measuring displacement are respectively connected to the supporting hydraulic cylinder A64, the supporting hydraulic cylinder B65, the supporting hydraulic cylinder C66 and the supporting hydraulic cylinder D67; preferably, the displacement sensor is a pull-wire type displacement sensor, and is used for monitoring the displacement of the supporting hydraulic cylinder in real time and transmitting data to the controller.

The hydraulic control one-way valve mainly has the function of locking the position of the hydraulic cylinder. The variable throttle valve can change the diameter of the throttle opening to control the flow of the system.

The controller is respectively connected with a horizontal tilt angle sensor 40, a displacement sensor A84, a displacement sensor B85, a displacement sensor C86, a displacement sensor D87, a displacement sensor E88, a displacement sensor F89, a displacement sensor G90, a displacement sensor H91, an acceleration sensor A92, an acceleration sensor B93, an acceleration sensor C94 and an acceleration sensor D95.

In order to increase the contact area and reduce the pressure on the ground to prevent the test bench from damaging the ground, the test bench further comprises four supporting base plates 1, the four supporting base plates 1 are fixedly connected to the lower ends of the four supporting legs 2, and the supporting base plates 1 are square. The size of the support base plate 1 can be designed according to practical situations, for example, the area can be 100mmx100mm, and the thickness is 5 mm.

In order to increase the connection strength and prevent the occurrence of impact damage, the end part of the lower beam a5 and the upper end of the supporting leg 2, and the end part of the lower beam b7 and the upper end of the supporting leg 2 are fixedly connected through a triangular reinforcing plate 3; the middle part of the lower cross beam a5 and the lower part of the supporting leg 2, and the middle part of the lower cross beam b7 and the lower part of the supporting leg 2 are fixedly connected through lower reinforcing ribs 6. Preferably, the triangular reinforcing plate 3 is an isosceles right triangle, and the size of the triangular reinforcing plate is preferably 100mmx100mm, and the thickness of the triangular reinforcing plate is 5 mm. Preferably, the lower reinforcing rib 6 is made of a square pipe, and the size of the square pipe can be designed according to actual conditions, for example, the cross section size of the square pipe can be 40mmx40 mm.

Because the upper frame 45 is also required to be loaded with a certain mass during actual operation, in order to increase the bearing capacity of the upper frame 45, the two sides of the middle of the top supporting beam a32 are fixedly connected with the two upper main beams b27 through the two top supporting beams b 33.

In order to facilitate mounting and dismounting, the connecting device further comprises four connecting plates d24 and four connecting plates c23, wherein the four connecting plates d24 are fixedly connected to four corners of the lower end of the upper frame 45 respectively, the four connecting plates c23 are fixedly connected to the upper ends of the connecting lugs d22 respectively, and the four connecting plates d24 and the four connecting plates c23 are fixedly connected through a plurality of connecting bolts 25.

For the convenience of installation and disassembly, the end of the upper cross beam 12 is provided with a through hole C for the support bolt 11 to pass through, the upper end of the support bolt 11 passes through the through hole C, and nuts b38 and a37 are respectively connected to the upper side and the lower side of the upper cross beam 12 through threaded fit.

In order to avoid the impurities from blocking the valve body in the system, the oil suction port of the variable pump 47 is connected with the oil tank 51 through a filter A97, and the oil suction port of the gear pump 48 is connected with the oil tank 51 through a filter B98; in order to cool the hydraulic oil, the T ports of the electromagnetic proportional directional valve E68, the electromagnetic proportional directional valve F69, the electromagnetic proportional directional valve G70 and the electromagnetic proportional directional valve H71 are all connected with the oil tank 51 through a cooler 99. The filter is used for filtering impurities in the oil filter box 51, and the filter filtering precision is 100 um.

In order to simulate the actual load situation, a counterweight 96 fixedly connected to the center of the upper end of the bracket frame 45 is also included.

In the actual working process, the controller controls the expansion and contraction of the piston rods of the support hydraulic cylinder A64, the support hydraulic cylinder B65, the support hydraulic cylinder C66 and the support hydraulic cylinder D67 to simulate a ground road spectrum by controlling the electromagnetic proportional directional valve E68, the electromagnetic proportional directional valve F69, the electromagnetic proportional directional valve G70 and the electromagnetic proportional directional valve H71 respectively, the controller can adjust the expansion and contraction speed of the support hydraulic cylinders by controlling the change of oil supply amount of the electromagnetic proportional directional valve, when the uphill process is simulated, the electromagnetic proportional directional valves corresponding to the front two support hydraulic cylinders can be controlled to extend the piston rods of the front two support hydraulic cylinders, the rear two support hydraulic cylinders are kept in the maximum contraction state and the wheel base and the axle base of an actual vehicle are combined to simulate a certain degree gradient. In the process of simulating an ascending slope, if the simulation of different slopes is realized, the extension lengths of the piston rods of the two front supporting hydraulic cylinders can be different, and the extension speeds can be different according to the required conditions; similarly, in the process of simulating the downhill, the two front supporting hydraulic cylinders are controlled to keep the maximum retraction state unchanged, so that the piston rods of the two rear supporting hydraulic cylinders extend out. The upper supporting frame is mainly used for simulating an actual hydraulic suspension, when the lower supporting hydraulic cylinder simulates a road spectrum, the controller controls the actions of the electromagnetic proportional directional valve A56, the electromagnetic proportional directional valve B57, the electromagnetic proportional directional valve C58 and the electromagnetic proportional directional valve D59 through signals fed back by the horizontal tilt angle sensor, further controls the actions of piston rods of the leveling hydraulic cylinder A60, the leveling hydraulic cylinder B61, the leveling hydraulic cylinder C62 and the leveling hydraulic cylinder D63, enables the horizontal tilt sensor 40 to keep a horizontal state, and enables the frame to keep a horizontal state all the time.

Claims

1. A hydraulic system for an automatic leveling test bed comprises the automatic leveling test bed, and is characterized by further comprising a hydraulic control system and a controller;

the automatic leveling test bed comprises a lower support frame, four upper support plates (34), four support hydraulic cylinders (4), four bearing discs (10), an upper leveling mechanism, a top support beam a (32) and a horizontal tilt angle sensor (40); the lower supporting frame consists of a lower frame (44) and four supporting legs (2) with equal length, the lower frame (44) consists of two lower cross beams a (5) which are correspondingly distributed at the front and the back and two lower cross beams b (7) which are correspondingly distributed at the left and the right and are sequentially and fixedly connected, and the upper ends of the four supporting legs (2) are respectively and fixedly connected with the four corners of the lower end of the lower frame (44); the four upper supporting plates (34) are respectively and fixedly connected to four corners of the upper end of the lower frame (44), and through holes A are formed in the centers of the four upper supporting plates (34); the four supporting hydraulic cylinders (4) are respectively marked as a supporting hydraulic cylinder A (64), a supporting hydraulic cylinder B (65), a supporting hydraulic cylinder C (66) and a supporting hydraulic cylinder D (67); the four supporting hydraulic cylinders (4) are respectively arranged at the lower parts of the four upper supporting plates (34), and the lower ends of the cylinder barrels of the supporting hydraulic cylinders (4) are all positioned above the lower ends of the supporting legs (2); the upper ends of the cylinder barrels of the four supporting hydraulic cylinders (4) are respectively fixedly connected with the lower end faces of the four upper supporting plates (34), and piston rods of the four supporting hydraulic cylinders (4) respectively penetrate through the through holes A in the four upper supporting plates (34) in a sliding mode and are respectively fixedly connected with four connecting plates a (8) arranged above the four upper supporting plates (34); the four bearing disks (10) are respectively arranged above the four connecting plates a (8), and the upper ends of the four bearing disks (10) are fixedly connected with annular enclosing plates (35); the centers of the lower ends of the four bearing disks (10) are fixedly connected with the centers of the upper ends of the four connecting plates a (8) through four supporting columns (9); the upper leveling mechanism comprises an upper supporting frame, a connecting shaft (31), two upper cross beams (12), four connecting steel pipes (28), four connecting lugs d (22), four leveling hydraulic cylinders (15) and four connecting lugs a (16); the four leveling hydraulic cylinders (15) are respectively marked as a leveling hydraulic cylinder A (60), a leveling hydraulic cylinder B (61), a leveling hydraulic cylinder C (62) and a leveling hydraulic cylinder D (63); the upper supporting frame consists of an upper frame (45), a middle connecting plate (18) and four middle supports (19) with equal length, the upper frame (45) consists of two upper main beams b (27) which are correspondingly distributed front and back and two upper main beams a (26) which are correspondingly distributed left and right, which are sequentially and fixedly connected, and the size of the upper frame (45) is smaller than that of the lower frame (44); the size of the middle connecting plate (18) is smaller than that of the upper frame (45), and the middle connecting plate is arranged in the center below the upper frame (45); the upper ends of the four middle brackets (19) are respectively fixedly connected with the end parts of the two upper main beams b (27), and the lower ends of the four middle brackets are respectively fixedly connected with four corners at the upper end of the middle connecting plate (18); the left part and the right part of the lower end of the middle connecting plate (18) are oppositely and fixedly connected with a pair of connecting lug plates a (41), and the lower parts of the connecting lug plates a (41) are correspondingly provided with a pair of through holes B; the connecting shaft (31) is rotatably arranged in the pair of through holes B in a penetrating way, and the left end and the right end of the connecting shaft (31) are correspondingly and fixedly connected with two side end plates (42); the front end and the rear end of the left side end plate (42) and the front end and the rear end of the right side end plate (42) are respectively fixedly connected with two connecting lug plates b (43); the two upper cross beams (12) are respectively arranged on the left side and the right side above the lower support frame, and the end parts of the two upper cross beams (12) respectively correspond to the upper parts of the four bearing discs (10); the lower end parts of the two upper cross beams (12) are respectively and fixedly connected with four sliding shoes (36) through four supporting bolts (11), the four sliding shoes (36) are respectively and slidably arranged on the upper parts of the four bearing disks (10), and the limiting of the sliding range is carried out through annular enclosing plates (35) on the four bearing disks (10); the inner ends of the four connecting steel pipes (28) are respectively fixedly connected with the outer ends of the four connecting plates e (29), and the inner ends of the four connecting plates e (29) are respectively connected with the four connecting ear plates b (43) through four connecting pin shafts e (30); the outer ends of the four connecting steel pipes (28) are respectively fixedly connected with the end parts of the two upper cross beams (12); the upper ends of the four connecting lugs d (22) are respectively and fixedly connected with four corners of the lower end of the upper frame (45); the lower ends of the four connecting lugs d (22) are respectively and rotatably connected with the upper ends of the four connecting lugs c (21) through four connecting pin shafts d (39); the piston rod ends of the four leveling hydraulic cylinders (15) are respectively and rotatably connected with the lower ends of the four connecting lugs c (21) through four connecting pin shafts c (20); the cylinder ends of the four leveling hydraulic cylinders (15) are respectively and rotatably connected with the upper ends of the four connecting lugs b (17) through four connecting pin shafts b (14); the lower ends of the four connecting lugs b (17) are respectively and rotatably connected with the upper ends of the four connecting lugs a (16) through four connecting pin shafts a (13), and the lower ends of the four connecting lugs a (16) are respectively and fixedly connected with the upper parts of the outer ends of the four connecting steel pipes (28); the top support beam a (32) is fixedly connected between the two upper main beams a (26); the horizontal inclination angle sensor (40) is arranged in the middle of the top supporting beam a (32);

the hydraulic control system comprises a motor (46), a variable pump (47), a gear pump (48), a hydraulic suspension leveling control unit and a road surface simulation control unit;

the hydraulic suspension leveling control unit comprises a leveling hydraulic cylinder A (60), a leveling hydraulic cylinder B (61), a leveling hydraulic cylinder C (62), a leveling hydraulic cylinder D (63), an electromagnetic proportional directional valve A (56), an electromagnetic proportional directional valve B (57), an electromagnetic proportional directional valve C (58) and an electromagnetic proportional directional valve D (59); the road surface simulation control unit comprises a supporting hydraulic cylinder A (64), a supporting hydraulic cylinder B (65), a supporting hydraulic cylinder C (66), a supporting hydraulic cylinder D (67), an electromagnetic proportional directional valve E (68), an electromagnetic proportional directional valve F (69), an electromagnetic proportional directional valve G (70) and an electromagnetic proportional directional valve H (71);

the electric motor (46) is respectively connected with the variable pump (47) and the gear pump (48) through the transfer case, oil suction ports of the variable pump (47) and the gear pump (48) are respectively connected with the oil tank (51), and oil discharge ports of the variable pump (47) and the gear pump (48) are respectively connected with the oil tank (51) through a safety valve I (49) and a safety valve II (50); the oil discharge port of the variable pump (47) is also connected with the P ports of the electromagnetic proportional reversing valve A (56), the electromagnetic proportional reversing valve B (57), the electromagnetic proportional reversing valve C (58) and the electromagnetic proportional reversing valve D (59) through a fixed-differential pressure reducing valve A (52), a fixed-differential pressure reducing valve B (53), a fixed-differential pressure reducing valve C (54) and a fixed-differential pressure reducing valve D (55); the T ports of the electromagnetic proportional reversing valve A (56), the electromagnetic proportional reversing valve B (57), the electromagnetic proportional reversing valve C (58) and the electromagnetic proportional reversing valve D (59) are all connected with the oil tank (51); the port A and the port B of the electromagnetic proportional directional valve A (56) are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder A (60) and are also respectively connected with two comparison oil ports of a shuttle valve A (72), and an oil outlet of the shuttle valve A (72) is connected with a control port of the constant-differential pressure reducing valve A (52); an A port and a B port of the electromagnetic proportional directional valve B (57) are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder B (61), and are also respectively connected with two comparison oil ports of the shuttle valve B (73), and an oil outlet of the shuttle valve B (73) is connected with a control port of the constant-differential pressure reducing valve B (53); the port A and the port B of the electromagnetic proportional directional valve C (58) are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder C (62) and are also respectively connected with two comparison oil ports of the shuttle valve C (74), and the oil outlet of the shuttle valve C (74) is connected with a control port of the constant-differential pressure reducing valve C (54); an A port and a B port of the electromagnetic proportional directional valve D (59) are respectively connected with a rodless cavity and a rod cavity of the leveling hydraulic cylinder D (63), and are also respectively connected with two comparison oil ports of the shuttle valve D (75), and an oil outlet of the shuttle valve D (75) is connected with a control port of the constant-differential pressure reducing valve D (55); a leveling hydraulic cylinder A (60), a leveling hydraulic cylinder B (61), a leveling hydraulic cylinder C (62) and a leveling hydraulic cylinder D (63) are respectively connected with a displacement sensor E (88), a displacement sensor F (89), a displacement sensor G (90) and a displacement sensor H (91) which are used for measuring displacement, and are also respectively connected with an acceleration sensor A (92), an acceleration sensor B (93), an acceleration sensor C (94) and an acceleration sensor D (95) which are used for measuring acceleration;

an oil discharge port of the gear pump (48) is also respectively connected with P ports of an electromagnetic proportional reversing valve E (68), an electromagnetic proportional reversing valve F (69), an electromagnetic proportional reversing valve G (70) and an electromagnetic proportional reversing valve H (71), and T ports of the electromagnetic proportional reversing valve E (68), the electromagnetic proportional reversing valve F (69), the electromagnetic proportional reversing valve G (70) and the electromagnetic proportional reversing valve H (71) are all connected with an oil tank; the port A of the electromagnetic proportional directional valve E (68) is connected with the rodless cavity of the supporting hydraulic cylinder A (64) sequentially through the hydraulic control one-way valve A (76) and the variable throttle valve A (77), and the port B of the electromagnetic proportional directional valve E is connected with the rod cavity of the supporting hydraulic cylinder A (64) and the hydraulic control port of the hydraulic control one-way valve A (76) respectively; the port A of the electromagnetic proportional directional valve F (69) is connected with the rodless cavity of the supporting hydraulic cylinder B (65) sequentially through the hydraulic control one-way valve B (78) and the variable throttle valve B (79), and the port B of the electromagnetic proportional directional valve F (69) is connected with the rod cavity of the supporting hydraulic cylinder B (65) and the hydraulic control port of the hydraulic control one-way valve B (78) respectively; the port A of the electromagnetic proportional directional valve G (70) is connected with a rodless cavity of the supporting hydraulic cylinder C (66) through a hydraulic control one-way valve C (80) and a variable throttle valve C (81) in sequence, and the port B of the electromagnetic proportional directional valve G is connected with a rod cavity of the supporting hydraulic cylinder C (66) and a hydraulic control port of the hydraulic control one-way valve C (80); the port A of the electromagnetic proportional directional valve H (71) is connected with a rodless cavity of the supporting hydraulic cylinder D (67) sequentially through a hydraulic control one-way valve D (82) and a variable throttle valve D (83), and the port B of the electromagnetic proportional directional valve H is connected with a rod cavity of the supporting hydraulic cylinder D (67) and a hydraulic control port of the hydraulic control one-way valve D (82) respectively; a displacement sensor A (84), a displacement sensor B (85), a displacement sensor C (86) and a displacement sensor D (87) for measuring displacement are respectively connected to the supporting hydraulic cylinder A (64), the supporting hydraulic cylinder B (65), the supporting hydraulic cylinder C (66) and the supporting hydraulic cylinder D (67);

the controller is respectively connected with the horizontal tilt sensor (40), the displacement sensor A (84), the displacement sensor B (85), the displacement sensor C (86), the displacement sensor D (87), the displacement sensor E (88), the displacement sensor F (89), the displacement sensor G (90), the displacement sensor H (91), the acceleration sensor A (92), the acceleration sensor B (93), the acceleration sensor C (94) and the acceleration sensor D (95).

2. The hydraulic system for the automatic leveling test bed is characterized by further comprising four supporting base plates (1), wherein the four supporting base plates (1) are fixedly connected to the lower ends of the four supporting legs (2), and the supporting base plates (1) are square.

3. The hydraulic system for the automatic leveling test bed according to the claim 2 is characterized in that the end part of the lower cross beam a (5) and the upper end of the supporting leg (2) and the end part of the lower cross beam b (7) and the upper end of the supporting leg (2) are fixedly connected through a triangular reinforcing plate (3); the middle part of the lower cross beam a (5) and the lower part of the supporting leg (2) and the middle part of the lower cross beam b (7) and the lower part of the supporting leg (2) are fixedly connected through a lower reinforcing rib (6).

4. A hydraulic system for an automatic leveling test bed according to claim 2 or 3, characterized in that the two sides of the middle of the top support beam a (32) are fixedly connected with the two upper main beams b (27) through the two top support beams b (33).

5. The hydraulic system for the automatic leveling test bed according to claim 4, further comprising four connecting plates d (24) and four connecting plates c (23), wherein the four connecting plates d (24) are respectively and fixedly connected at four corners of the lower end of the upper frame (45), the four connecting plates c (23) are respectively and fixedly connected at the upper ends of the connecting lugs d (22), and the four connecting plates d (24) and the four connecting plates c (23) are fixedly connected through a plurality of connecting bolts (25).

6. The hydraulic system for the automatic leveling test bed according to claim 5, wherein the end of the upper cross beam (12) is provided with a through hole C for the support bolt (11) to pass through, the upper end of the support bolt (11) passes through the through hole C, and a nut b (38) and a nut a (37) are respectively connected to the upper side and the lower side of the upper cross beam (12) through threaded fit.

7. The hydraulic system for the automatic leveling test stand according to claim 6, wherein the oil suction port of the variable displacement pump (47) is connected to the oil tank (51) through a filter A (97), and the oil suction port of the gear pump (48) is connected to the oil tank (51) through a filter B (98); the T ports of the electromagnetic proportional directional valve E (68), the electromagnetic proportional directional valve F (69), the electromagnetic proportional directional valve G (70) and the electromagnetic proportional directional valve H (71) are connected with the oil tank (51) through a cooler (99).

8. The hydraulic system for automatically leveling a test stand according to claim 7, further comprising a counterweight (96) fixedly attached to the center of the upper end of the support frame (45).