Control method based on crane jib luffing

Abstract

The invention provides a control method based on crane jib luffing, which comprises the following steps of: firstly, carrying out no-load ascending and no-load descending debugging on a jib, and then carrying out load ascending and load descending control on the jib, so that the jib and a load weight can stably ascend and descend; by means of the technical scheme, the situation that in the rising process, oil pressure is instantly increased, and consequently a suspension arm is instantly stuck together can be prevented, damage to the variable-amplitude oil cylinder is avoided, meanwhile, it is guaranteed that the opening degree of the balance valve is adjusted by controlling the change of pressure in an oil way in the variable-amplitude descending process, therefore, the descending shaking phenomenon is avoided, and the rising and descending processes of the suspension arm can be accurately controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of cranes, and in particular to a control method based on the luffing of a crane boom. Background Art

[0002] In the actual operation of engineering cranes, the actuator is usually a luffing cylinder. In the process of boom luffing, hydraulic closed-loop control is generally adopted. However, in actual applications, due to different loads, the boom often shakes violently and has poor micro-mobility during the process of closing and lowering. In order to solve this technical problem, a patent document with Chinese patent application number 201510391773.1 and announcement date 2017.06.30 discloses a boom luffing hydraulic system, including a main pump, a main valve, a luffing cylinder, a first An oil circuit and a second oil circuit, the first oil circuit is connected to the first chamber oil port of the variable-length oil cylinder, the second oil circuit is connected to the second chamber oil port of the variable-length oil cylinder, the first oil circuit is connected to the first working oil port of the main valve, the second oil circuit is connected to the second working oil port of the main valve, the main pump is connected to the oil inlet of the main valve, and a pressure control valve is arranged in the first oil circuit; it also includes a servo pump and a servo oil circuit, the servo pump supplies oil to the servo oil circuit, the servo oil circuit is connected to the pilot oil port of the pressure control valve, and a hydraulic valve is arranged in the servo oil circuit, and the hydraulic valve controls the opening of the pressure control valve.

[0003] In the above-mentioned document, the pressure of the small chamber oil port of the boom cylinder is detected by a pressure sensor, and the controller obtains the pressure sensor signal. When the boom is lowered too fast, the displacement of the main pump and the opening of the pressure control valve are controlled by the controller to control the amplitude of the boom descent. Since the main pump is connected to the boom cylinder through the main valve, and the pressure control valve is connected to the other end of the boom cylinder, it cannot ensure a balancing valve between the two oil circuits connected to the boom cylinder. In addition, it does not clearly define the control method during the rising process, and there are rising jams and falling jitters during the rising and falling of the boom during the boom luffing process. Summary of the invention

[0004] The purpose of the present invention is to provide a control method based on the boom luffing of a crane. During the luffing process, it is possible to prevent the oil pressure from increasing instantaneously during the ascent, which may cause the boom to become stuck after it is instantly raised, thereby avoiding damage to the luffing cylinder. At the same time, during the luffing descent process, it is possible to adjust the opening of the balancing valve by controlling the change in pressure in the oil circuit, thereby avoiding the descent jitter phenomenon and accurately controlling the ascent and descent process of the boom.

[0005] In order to achieve the above object, a control method based on the boom luffing of a crane is provided, which is implemented by a boom luffing system. The boom luffing system includes a main pump oil circuit, a reversing valve, a pressure relief oil circuit, a first oil circuit, a second oil circuit and a luffing cylinder, and a balancing valve is provided between the first oil circuit and the second oil circuit; the method includes the following steps: S1 performs no-load luffing commissioning on the boom, including no-load raising and no-load lowering. S1.1 During the no-load lifting process, open the first pressure valve connected to the main pump oil circuit, and then make the hydraulic oil in the main pump oil circuit flow into the first oil circuit through the reversing valve, and the second oil circuit enters the pressure relief oil circuit for pressure relief after passing through the reversing valve, and at the same time adjust the pressure value of the first pressure valve, so that the luffing cylinder drives the boom to rise at a uniform speed; S1.2 After the boom rises to the preset height, stop rising; S1.3 During the no-load descent process, adjust the reversing valve so that the hydraulic oil in the main pump oil circuit flows into the second oil circuit. The oil pressure in the first oil circuit passes through the reversing valve and enters the pressure relief oil circuit for pressure relief, thereby opening the balance valve through the branch oil circuit, thereby driving the boom to descend at a uniform speed.

[0006] In the above method, during the no-load debugging process, the hydraulic oil pressure of the main pump oil circuit is adjusted by the first pressure valve, and the reversing valve is used to switch the main pump oil circuit to supply oil to the first oil circuit, and then the second oil circuit is relieved of pressure, thereby preventing the boom from swaying and shaking due to excessive pressure at the beginning of the ascent. The opening of the balance valve is controlled by adjusting the pressure of the first pressure valve, thereby achieving stable descent of the boom and avoiding momentary pauses during the descent; and the opening of the balance valve is controlled by adjusting the pressure of the first pressure valve, so that the pressure difference between the first oil circuit and the second oil circuit is fixed, thereby achieving stability of the boom and the load, effectively avoiding pauses or jitters, and the control method is simple and reliable.

[0007] Furthermore, after step S1, step S2 is also included to perform boom load amplitude control, including load increase and load decrease. S2.1 During the load raising process, the pressure value of the first pressure valve is adjusted to keep the pressure difference between the first oil circuit and the second oil circuit unchanged, thereby causing the boom to rise at a constant speed driven by the luffing cylinder; S2.2 After the boom and the load are raised to a preset height, the main pump of the main pump oil circuit stops working, and then drives the boom and the load to rotate to a preset angle through the slewing mechanism, and enters step S2.3; S2.3 During the load lowering process, the opening of the balance valve is controlled by adjusting the pressure of the first pressure valve to ensure that the pressure difference between the first oil circuit and the second oil circuit is a fixed value, thereby driving the boom and the load to descend at a uniform speed; S3 After the load is unloaded, the boom is now in an unloaded state, and step S1 is repeated to reset the boom.

[0008] With the above arrangement, during the process of lifting and luffing of the boom under load, by adjusting the pressure value of the first pressure valve, it is possible to prevent the luffing cylinder from extending momentarily when too much pressure is initially supplied to the luffing cylinder, causing the boom and the load to become stuck or jittery momentarily, and the boom and the load can only rise normally and at a uniform speed after the normal pressure supply is restored; and controlling the opening of the balancing valve by controlling the flow of hydraulic oil can easily make the opening of the balancing valve too small, and the hydraulic oil of the luffing cylinder cannot flow back to the oil tank through the balancing valve, causing the boom and the load to accelerate their descent under the action of their own gravity, until the opening of the balancing valve can allow the part of the hydraulic oil of the luffing cylinder in the retraction process to flow back to the oil tank through the balancing valve and the first oil circuit, so that the descent speed of the boom and the load can be actively controlled, and pauses or jitters may occur in this process.

[0009] Furthermore, the step S1.1 also includes S1.1 to S1.3, S1.1.1 Open the first pressure valve connected to the main pump oil circuit, then adjust the reversing valve, and at the same time open the pressure valve group connected to the reversing valve; S1.1.2 The starter motor drives the oil pump to work, so that the hydraulic oil in the main pump oil circuit flows into the first oil circuit through the reversing valve, and then flows through the balance valve into the luffing cylinder; S1.1.3 adjusts the pressure value of the first pressure valve so that the pressure difference between the first oil circuit and the second oil circuit is a fixed value T1, thereby driving the boom cylinder to extend and drive the boom to rise at a uniform speed.

[0010] The above arrangement, by adjusting the pressure value of the first pressure valve, prevents the boom from rising sharply and instantly due to excessive pressure at the beginning of its rise.

[0011] Furthermore, the step S1.3 also includes S1.3.1 to S1.3.3, S1.3.1 Adjust the reversing valve so that the hydraulic oil in the main pump oil circuit flows into the second oil circuit after passing through the reversing valve. Then the second oil circuit opens the balance valve through the branch oil circuit and drives the luffing cylinder to retract at the same time. S1.3.2 controls the pressure of the main pump oil circuit to the second oil circuit after passing through the reversing valve by adjusting the pressure value of the first pressure valve, and then controls the opening of the balance valve to ensure that after the first oil circuit is connected to the luffing cylinder through the balance valve, the pressure difference between the first oil circuit and the second oil circuit is a fixed value T2, thereby driving the boom to descend at a uniform speed; S1.3.3 After the boom is lowered and reset, stop descending.

[0012] The above arrangement controls the opening of the balance valve by adjusting the pressure of the first pressure valve, thereby achieving stable descent of the boom and avoiding momentary pauses during the descent.

[0013] Furthermore, the step S2.1 also includes S2.1.1 to S2.1.3, S2.1.1 Open the first pressure valve connected to the main pump oil circuit, then adjust the reversing valve, and at the same time open the pressure valve group connected to the reversing valve; S2.1.2 The starter motor drives the oil pump to work, so that the hydraulic oil in the main pump oil circuit flows into the first oil circuit after passing through the reversing valve, and then flows through the balancing valve into the luffing cylinder; S2.1.3 adjusts the pressure value of the first pressure valve so that the pressure difference between the first oil circuit and the second oil circuit is a fixed value T3, thereby driving the boom cylinder to extend and driving the boom and the load to rise at a uniform speed.

[0014] The above setting, by adjusting the pressure value of the first pressure valve, can prevent the boom and load from being stuck or jittered momentarily only after the pressure supply to the boom cylinder is restored to normal, causing the boom and load to extend momentarily when too much pressure is supplied to the boom cylinder at the beginning.

[0015] Furthermore, the step S2.3 also includes S2.3.1 to S2.3.3, S2.3.1 Adjust the reversing valve so that the hydraulic oil in the main pump oil circuit flows into the second oil circuit after passing through the reversing valve. Then the second oil circuit opens the balance valve through the branch oil circuit and drives the luffing cylinder to retract at the same time. S2.3.2 controls the pressure of the main pump oil circuit distributed to the second oil circuit after passing through the reversing valve by adjusting the pressure value of the first pressure valve, and then controls the opening of the balance valve to ensure that after the first oil circuit is connected to the luffing cylinder through the balance valve, the pressure difference between the first oil circuit and the second oil circuit is a fixed value T4, thereby driving the boom and the load to descend at a uniform speed; S2.3.3 After the boom and the load are lowered to the preset position, the main pump in the main pump oil circuit is stopped and the load is unloaded.

[0016] The above arrangement controls the opening of the balancing valve by adjusting the pressure of the first pressure valve, so that the pressure difference between the first oil circuit and the second oil circuit remains constant, thereby achieving stable descent of the boom and the load, and effectively avoiding the situation where the opening of the balancing valve cannot achieve a fixed pressure difference between the first oil circuit and the second oil circuit due to inaccurate control of the hydraulic oil flow, thereby causing pauses or jitters during the descent of the boom and the load. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the work flow chart of the present invention.

[0018] Figure 2 It is a connection diagram of the hydraulic system in the present invention.

[0019] Figure 3for Figure 2 Enlarged view of point E in the middle.

[0020] Figure 4 for Figure 2 Enlarged view of point F in the middle. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1-4 As shown, a control method based on the boom luffing of a crane includes a boom luffing hydraulic system, the boom luffing hydraulic system includes a main pump oil circuit 1, a reversing valve 2, a pressure relief oil circuit 3, a first oil circuit 4, a second oil circuit 5 and a luffing cylinder 60, the main pump oil circuit 1 is connected to the pressure relief oil circuit 3 and the reversing valve 2 respectively, the main pump oil circuit 1 and the pressure relief oil circuit 4 are both connected to the oil tank 6, the main pump oil circuit 1 includes an oil pump 11 and a third oil circuit 13 connected to the oil pump 11, one end of the third oil circuit 13 is connected to the oil outlet C of the oil pump 11, the oil inlet D of the oil pump 11 is connected to the oil tank 6, the oil pump 11 is connected to the output end of the motor 12 arranged on the outside of the oil pump 11, so that the oil pump 11 can be controlled to work through the motor 12, and the hydraulic oil of the oil tank 6 is drawn into the third oil circuit 13.

[0023] The pressure relief oil circuit 3 includes a first pressure valve 31 and a return oil filter. One end of the first pressure valve 31 is connected to the other end of the third oil circuit 13. The other end of the first pressure valve 31 is respectively connected to the valve port A of the reversing valve 2, the valve port B of the reversing valve 2 and the return oil filter. The return oil filter is connected to the oil tank 6. A pressure valve group is provided at the valve port A of the reversing valve 2 and the valve port B of the reversing valve 2. In this embodiment, the stroke of the valve core of the reversing valve 2 can be adjusted by moving the handle arranged outside the reversing valve 2 to adjust the pressure flowing through the reversing valve 2. When the pressure of the hydraulic oil passing through the reversing valve 2 reaches a fixed value, the pressure is relieved through the pressure relief oil circuit 3, so that the first pressure valve 31 can be opened and connected to the return oil filter. The oil filter is connected, so that the local hydraulic oil in the main pump oil circuit 1 flows back to the oil tank 6 through the first pressure valve 31 and the return oil filter; the pressure valve group includes a second pressure valve 42 and a third pressure valve 43, one end of the second pressure valve 42 is connected to the A valve port of the reversing valve 2, one end of the third pressure valve 43 is connected to the B valve port of the reversing valve 2, and the other end of the second pressure valve 42 and the other end of the third pressure valve 43 are both connected to the return oil filter. In this way, when the hydraulic oil in the first oil circuit 4 flows back to the reversing valve 2, the local pressure of the reversing valve 2 can be unloaded through the pressure valve group, so that the local hydraulic oil flows to the return oil filter through the pressure valve group, and finally flows back to the oil tank 6, so as to prevent the reversing valve 2 from being damaged by excessive pressure.

[0024] The return oil filter includes a pressure gauge 7, a filter 8 and a one-way valve 9. The one-way valve 9 is connected in parallel at both ends of the filter 8. The rear end of the filter 8 is connected to the oil tank 6, and the pressure gauge 7 is connected to the front end of the filter 8, so that the oil pressure entering the filter 8 can be monitored by the pressure gauge 7. At the same time, the local hydraulic oil can be diverted through the one-way valve 9 to avoid damage to the filter 8 due to excessive oil pressure.

[0025] The P1 valve port of the reversing valve 2 is connected to one end of the first oil circuit 4, and the P2 valve port of the reversing valve 2 is connected to one end of the second oil circuit 5. A balancing valve 10 is provided between the first oil circuit 4 and the luffing cylinder 60, and a branch oil circuit 20 is provided between the second oil circuit 4 and the balancing valve 10. The balancing valve 10 is connected through the branch oil circuit 20. The balancing valve 10 is respectively connected to the other end of the first oil circuit 4 and one end of the luffing cylinder 60, and the other end of the second oil circuit 5 is connected to the other end of the luffing cylinder 60. In this embodiment, the luffing cylinder 60 is a single-piston rod luffing cylinder. A single piston rod 603 is provided, and the single piston rod 603 divides the interior of the variable-length oil cylinder 60 into a first chamber 601 and a second chamber 602. The first chamber 601 is connected to the balancing valve 10, and the second chamber 602 is connected to the other end of the second oil circuit 5, so that the first oil circuit 4 can be connected to the first chamber 601 through the balancing valve 10, and the second oil circuit 5 is connected to the second chamber 602, thereby pushing the single piston rod 603 to move in the variable-length oil cylinder 60, thereby realizing variable-length lifting and lowering. In this embodiment, the first chamber 601 and the second chamber 602 are filled with hydraulic oil.

[0026] In this embodiment, the boom luffing hydraulic system is used to control the luffing cylinder 60, and both ends of the luffing cylinder 60 are respectively connected to the slewing mechanism and the boom, so that the boom can be raised or lowered under the drive of the luffing cylinder 60.

[0027] In this embodiment, a first pressure sensor 604 and a second pressure sensor 605 are respectively provided on the first chamber 601 and the second chamber 602. The hydraulic oil pressures in the first chamber 601 and the second chamber 602 are respectively tested by the first pressure sensor 604 and the second pressure sensor 605, so that the pressure value of the first pressure valve 31 can be adjusted according to the pressure difference between the first pressure sensor 604 and the second pressure sensor 605.

[0028] The following specific steps are also included: S1 performs no-load luffing commissioning on the boom, including S1.1~ S1.3. S1.1 is in the process of no-load rising, including S1.1.1~ S1.1.3, S1.1.1 Open the first pressure valve connected to the main pump oil circuit, then adjust the reversing valve, and at the same time open the pressure valve group connected to the reversing valve, so that the reversing valve moves to the first cavity A1 position, the first oil circuit 4 is connected to the main pump oil circuit, and the second oil circuit 5 is connected to the third pressure valve through the reversing valve B port; S1.1.2 The motor is started to drive the oil pump to work, so that the hydraulic oil in the main pump oil circuit flows into the first oil circuit after passing through the reversing valve, and then flows through the balancing valve into the first chamber 601 of the luffing cylinder; S1.1.3 In this embodiment, the hydraulic oil pressure values ​​of the first oil circuit and the second oil circuit are obtained respectively through the first pressure sensor 604 and the second pressure sensor 605, and then the pressure of the first pressure valve 31 is adjusted so that the pressure difference between the first oil circuit 4 and the second oil circuit 5 is a fixed value T1. At this time, the pressure of the first oil circuit 4 is greater than the pressure of the second oil circuit 5, and the pressure of the second oil circuit 5 is less than the pressure required to open the balance valve 10. Therefore, the hydraulic oil in the second oil circuit 5 cannot conduct the balance valve 10 and directly flows back to the reversing valve 2, thereby driving the variable-length oil cylinder to extend and drive the boom to rise at a uniform speed; S1.2 After the boom rises to the preset height, turn off the motor and stop the boom from rising; S1.3 During the no-load descent process, including S1.3.1 to S1.3.3, S1.3.1 Adjust the reversing valve 2 to reversing, so that the reversing valve 2 moves to the third chamber B1 position, the second oil circuit 5 is connected to the main pump oil circuit 1, and the first oil circuit 4 is connected to the second pressure valve 42 through the A port to achieve pressure relief, so that the hydraulic oil of the main pump oil circuit flows into the second oil circuit 5 after passing through the reversing valve 2, and at the same time, the second pressure valve 42 is connected to the first oil circuit 4 at the A valve port of the reversing valve, and then the second oil circuit 5 opens the balance valve 10 through the branch oil circuit, and at the same time, the second oil circuit 5 is connected to the second chamber 602 of the variable amplitude cylinder, driving the variable amplitude cylinder to retract; S1.3.2 controls the pressure of the main pump oil circuit to the second oil circuit 5 after passing through the reversing valve 2 by adjusting the pressure value of the first pressure valve 31, and then controls the opening of the balance valve 10, ensuring that after the first oil circuit 4 is connected with the first chamber 601 of the variable-length oil cylinder through the balance valve 10, the pressure difference between the first oil circuit and the second oil circuit is a fixed value T2 through the pressure values ​​of the first pressure sensor 604 and the second pressure sensor 605, thereby driving the boom to descend at a uniform speed. In this embodiment, the fixed value T2 is equal to the fixed value T1; S1.3.3 After the boom is lowered and reset to rest on the boom support frame, stop descending.

[0029] S2 is used to control the boom load amplitude, including S2.1~S2.3. S2.1, during the load increase process, includes S2.1.1 to S2.1.3. S2.1.1 Open the first pressure valve 31 connected to the main pump oil circuit, then adjust the reversing valve 2, and at the same time open the pressure valve group connected to the reversing valve 2, so that the third pressure valve 43 is connected to the second oil circuit 5 at the valve port B of the reversing valve. In this way, when the hydraulic oil pressure in the second oil circuit 5 is greater than the preset pressure of the third pressure valve 43, the third pressure valve 43 is turned on, so that the local hydraulic oil in the second oil circuit flows to the return oil through the third pressure valve 43 to relieve the pressure, thereby avoiding damage to the reversing valve 2; S2.1.2 The motor is started to drive the oil pump to work, so that the hydraulic oil in the main pump oil circuit passes through the reversing valve 2 to the first chamber A1, and then the reversing valve P1 port is connected with the main pump oil circuit 1 and flows into the first oil circuit 4. The first oil circuit 4 is connected to the third pressure valve 43 through the reversing valve P1 port and the A port to relieve pressure, and then flows through the balance valve 10 into the first chamber 601 of the variable amplitude oil cylinder; S2.1.3 The pressure of the first pressure valve is adjusted by the pressure values ​​of the first pressure sensor 604 and the second pressure sensor 605, so that the pressure difference between the first oil circuit 4 and the second oil circuit 5 is a fixed value T3. At this time, the pressure of the first oil circuit 4 is greater than the pressure of the second oil circuit 5, and the pressure of the second oil circuit 5 is less than the pressure required to open the balance valve 10. Therefore, the hydraulic oil in the second oil circuit 5 cannot conduct the balance valve 10 and directly flows back to the reversing valve 5, thereby driving the luffing cylinder to extend, driving the boom and the load to rise at a uniform speed; S2.2 After the boom and the load are raised to a preset height, the motor is turned off, the main pump of the main pump oil circuit stops working, and then the boom and the load are driven to rotate to a preset angle through the slewing mechanism, and the process goes to step S2.3; S2.3, during the load reduction process, includes S2.3.1 to S2.3.3. S2.3.1 Adjust the reversing valve 2 to reverse, so that the reversing valve 2 is switched to the third chamber B1, so that the second oil circuit 5 is connected with the main pump oil circuit 1 through the reversing valve, and the first oil circuit 4 is connected to the second pressure valve 42 through the P1 port and the A port of the reversing valve to achieve pressure relief, so that the hydraulic oil of the main pump oil circuit flows into the second oil circuit 5 after passing through the reversing valve 2, and at the same time, the second pressure valve 42 is connected to the first oil circuit 4 at the A valve port of the reversing valve, and then the second oil circuit 5 opens the balance valve through the branch oil circuit, and at the same time, the second oil circuit 5 is connected with the second chamber 602 of the boom cylinder, driving the boom cylinder to retract, so that after the first oil circuit 4 is connected with the boom cylinder through the balance valve 10, when the hydraulic oil pressure in the first oil circuit 4 is greater than the preset pressure of the second pressure valve 42, the second pressure valve 42 is turned on, so that the local hydraulic oil in the first oil circuit 4 flows to the return oil filter through the second pressure valve 42 to prevent damage to the reversing valve 2; S2.3.2 controls the pressure of the main pump oil circuit to the second oil circuit 5 after passing through the reversing valve 2 by adjusting the pressure value of the first pressure valve 31, and then controls the opening of the balance valve 10, ensuring that after the first oil circuit 4 is connected with the first chamber 601 of the variable-length oil cylinder through the balance valve 10, the pressure difference between the first oil circuit and the second oil circuit is a fixed value T4 through the pressure values ​​of the first pressure sensor 604 and the second pressure sensor 605, thereby driving the boom and the load to descend at a uniform speed; S2.3.3 After the boom and the load are lowered to the preset position, the main pump of the main pump oil circuit is stopped and the load is unloaded; S3 After the load is unloaded, the boom is now in an unloaded state, and steps S1.1 to S1.2 are repeated, and then the slewing mechanism is reversely rotated to the preset angle in step S2.2, and step S1.3 is repeated.

[0030] The working principle of the present invention is as follows: during the no-load debugging process, the hydraulic oil pressure of the main pump oil circuit 1 is adjusted by the first pressure valve 31, and the reversing valve 2 is used to switch the main pump oil circuit 1 to supply oil to the first oil circuit 4, and then the second oil circuit 5 is depressurized, thereby preventing the boom from swaying and shaking due to excessive pressure at the beginning of the ascent. The opening of the balance valve is controlled by adjusting the pressure of the first pressure valve 31, so that the boom can be steadily lowered and momentary pauses can be avoided during the descent. The opening of the balance valve is controlled by adjusting the pressure of the first pressure valve 31, so that the pressure difference between the first oil circuit 4 and the second oil circuit 5 is fixed, thereby achieving stability of the boom and the load, effectively avoiding pauses or jitters, and the control method is simple and reliable.

Claims

1. A control method based on the boom luffing of a crane is implemented by a boom luffing system, wherein the boom luffing system includes a main pump oil circuit, a reversing valve, a pressure relief oil circuit, a first oil circuit, a second oil circuit and a luffing cylinder, and is characterized in that: A balancing valve is arranged between the first oil circuit and the second oil circuit; the process comprises the following steps: S1 performs no-load luffing commissioning on the boom, including no-load raising and no-load lowering. S1.1 During the no-load lifting process, open the first pressure valve connected to the main pump oil circuit, and then make the hydraulic oil in the main pump oil circuit flow into the first oil circuit through the reversing valve, and the second oil circuit enters the pressure relief oil circuit for pressure relief after passing through the reversing valve, and at the same time adjust the pressure value of the first pressure valve, so that the luffing cylinder drives the boom to rise at a uniform speed; S1.2 After the boom rises to the preset height, stop rising; S1.3 During the no-load descent process, adjust the reversing valve so that the hydraulic oil in the main pump oil circuit flows into the second oil circuit. The oil pressure in the first oil circuit passes through the reversing valve and enters the pressure relief oil circuit for pressure relief, thereby opening the balance valve through the branch oil circuit, thereby driving the boom to descend at a uniform speed.

2. A control method based on crane boom luffing according to claim 1, characterized in that: After step S1, step S2 is also included to perform boom load amplitude control, including load increase and load decrease. S2.1 During the load raising process, the pressure value of the first pressure valve is adjusted to keep the pressure difference between the first oil circuit and the second oil circuit unchanged, thereby causing the boom to rise at a constant speed driven by the luffing cylinder; S2.2 After the boom and the load are raised to a preset height, the main pump of the main pump oil circuit stops working, and then the boom and the load are driven to rotate to a preset angle through the slewing mechanism, and then the process goes to step S2.3; S2.3 During the load lowering process, the opening of the balance valve is controlled by adjusting the pressure of the first pressure valve to ensure that the pressure difference between the first oil circuit and the second oil circuit is a fixed value, thereby driving the boom and the load to descend at a uniform speed; S3 After the load is unloaded, the boom is now in an unloaded state, and step S1 is repeated to reset the boom.

3. The control method based on crane boom luffing according to claim 1 is characterized in that: The step S1.1 also includes S1.1 to S1.3, S1.1.1 Open the first pressure valve connected to the main pump oil circuit, then adjust the reversing valve, and at the same time open the pressure valve group connected to the reversing valve; S1.1.2 The starter motor drives the oil pump to work, so that the hydraulic oil in the main pump oil circuit flows into the first oil circuit through the reversing valve, and then flows through the balance valve into the luffing cylinder; S1.1.3 adjusts the pressure value of the first pressure valve so that the pressure difference between the first oil circuit and the second oil circuit is a fixed value T1, thereby driving the boom cylinder to extend and drive the boom to rise at a uniform speed.

4. The control method based on crane boom luffing according to claim 1 is characterized in that: The step S1.3 also includes S1.3.1 to S1.3.3, S1.3.1 Adjust the reversing valve so that the hydraulic oil in the main pump oil circuit flows into the second oil circuit after passing through the reversing valve. Then the second oil circuit opens the balance valve through the branch oil circuit and drives the luffing cylinder to retract at the same time. S1.3.2 controls the pressure of the main pump oil circuit to the second oil circuit after passing through the reversing valve by adjusting the pressure value of the first pressure valve, and then controls the opening of the balance valve to ensure that after the first oil circuit is connected to the luffing cylinder through the balance valve, the pressure difference between the first oil circuit and the second oil circuit is a fixed value T2, thereby driving the boom to descend at a uniform speed; S1.3.3 After the boom is lowered and reset, stop descending.

5. The control method based on crane boom luffing according to claim 2 is characterized in that: The step S2.1 also includes S2.1.1 to S2.1.3, S2.1.1 Open the first pressure valve connected to the main pump oil circuit, then adjust the reversing valve, and at the same time open the pressure valve group connected to the reversing valve; S2.1.2 The starter motor drives the oil pump to work, so that the hydraulic oil in the main pump oil circuit flows into the first oil circuit after passing through the reversing valve, and then flows through the balancing valve into the luffing cylinder; S2.1.3 adjusts the pressure value of the first pressure valve so that the pressure difference between the first oil circuit and the second oil circuit is a fixed value T3, thereby driving the boom cylinder to extend and driving the boom and the load to rise at a uniform speed.

6. The control method based on crane boom luffing according to claim 3 is characterized in that: The step S2.3 also includes S2.3.1 to S2.3.3, S2.3.1 Adjust the reversing valve so that the hydraulic oil in the main pump oil circuit flows into the second oil circuit after passing through the reversing valve. Then the second oil circuit opens the balance valve through the branch oil circuit and drives the luffing cylinder to retract at the same time. S2.3.2 controls the pressure of the main pump oil circuit distributed to the second oil circuit after passing through the reversing valve by adjusting the pressure value of the first pressure valve, and then controls the opening of the balance valve to ensure that after the first oil circuit is connected to the luffing cylinder through the balance valve, the pressure difference between the first oil circuit and the second oil circuit is a fixed value T4, thereby driving the boom and the load to descend at a uniform speed; S2.3.3 After the boom and the load are lowered to the preset position, the main pump in the main pump oil circuit is stopped and the load is unloaded.

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