Hydraulically driven in-place steering control system and aerial platform

Abstract

This invention provides a hydraulically driven stationary steering control system, comprising: a power source; a bidirectional closed-loop piston pump; a flow divider / combiner valve, whose two main ports are respectively connected to the two main ports of the bidirectional closed-loop piston pump; a left-side drive assembly, which is connected to the flow divider port of the flow divider / combiner valve to form a bidirectional drive oil circuit; a right-side drive assembly; and a directional valve assembly connected between the flow divider / combiner valve and the right-side drive assembly. The directional valve assembly has at least a first working state and a second working state. In the first working state, the driving direction of the right-side drive assembly is the same as that of the left-side drive assembly; in the second working state, the driving direction of the right-side drive assembly is opposite to that of the left-side drive assembly. This invention achieves stationary steering using hydraulic components, reducing costs and control complexity while maintaining the high reliability and high torque output capability of hydraulic drive, making it particularly suitable for engineering machinery such as aerial work platforms.

Description

Technical Field

[0001] This invention relates to the field of aerial work platform steering control technology, and particularly to a hydraulically driven stationary steering control system and an aerial work platform. Background Technology

[0002] Aerial work platforms, as core equipment for high-altitude operations, are widely used in construction, power maintenance, municipal engineering and other scenarios. Their turning flexibility directly affects work efficiency and site adaptability.

[0003] Currently, the most widely used drive system for aerial work platforms is four-wheel drive with two-wheel steering. When in-place turning is required, existing technology primarily uses four independent motors to control the wheels, meaning the two left wheels turn forward and the two right wheels turn backward, allowing the vehicle to turn clockwise or counter-clockwise. However, the four-motor independent drive scheme has the following drawbacks: firstly, the system cost is high, as the four independent drive motors and corresponding controllers significantly increase manufacturing costs; secondly, it places extremely high demands on the electronic control system, requiring complex torque vector control algorithms; and thirdly, under heavy-load conditions, motor drive has certain limitations in torque output compared to hydraulic drive. In the field of construction machinery, hydraulic drive technology is widely used due to its advantages such as high torque density, high reliability, and adaptability to harsh working conditions. Therefore, developing a hydraulic drive in-place steering control system that is simple in structure, low in cost, and highly reliable has significant practical implications. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of high cost and complex electronic control in the existing technology of aerial work platform vehicles that rely on four independent motor drive schemes for on-the-spot steering. It provides a hydraulically driven on-the-spot steering control system and aerial work platform vehicle, which adopts pure hydraulic drive, reduces system cost, simplifies control logic, and improves reliability under heavy load conditions.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a hydraulically driven stationary steering control system, characterized in that it comprises: Power source; A bidirectional closed-loop piston pump, driven by the aforementioned power source; The flow divider and manifold valve has two main oil ports that are respectively connected to the two main oil ports of the bidirectional closed plunger pump. The left drive assembly is connected to the split port of the split and combine valve to form a bidirectional drive oil circuit that allows the left drive assembly to rotate forward or in reverse. Right-side drive component; A reversing valve assembly connected between the flow divider / combiner valve and the right-side drive assembly; The reversing valve assembly has at least a first operating state and a second operating state. In the first operating state, the driving direction of the right-side drive assembly is the same as that of the left-side drive assembly. In the second operating state, the driving direction of the right-side drive assembly is opposite to that of the left-side drive assembly.

[0006] The beneficial effects of this invention are as follows: By setting up a reversing valve group to connect the right-side flow circuit of the flow divider and combiner valve to the right-side drive assembly, the reversing valve group switches the hydraulic oil flow direction of the right-side drive assembly, so that the driving direction of the right-side drive assembly can be the same as or opposite to that of the left-side drive assembly. Thus, the switching between straight-line driving and stationary turning modes can be realized through hydraulic components only, without the need for a four-motor independent drive scheme, which significantly reduces system cost and electrical control complexity, while maintaining the advantages of high torque density and high reliability of hydraulic drive under heavy load conditions. Attached Figure Description

[0007] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below.

[0008] Figure 1 This is a schematic diagram of the hydraulic system of the present invention.

[0009] Figure 2 This is a schematic diagram of the reversing valve assembly and the right-side drive assembly of the present invention.

[0010] Explanation of reference numerals in the attached figures: 1. Oil tank; 2. Power source; 3. Two-way closed piston pump; 4. Brake valve; 401. First T-port; 5. Diverter / combiner valve; 501. Second T-port; 6. Directional valve assembly; 7. Hydraulic motor; 8. Brake; 9. Shuttle valve; 10. Pressure reducing valve. Detailed Implementation

[0011] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0012] Example 1: Please refer to Figure 1 , Figure 2 As shown in the figure, this embodiment presents a hydraulically driven stationary steering control system suitable for four-wheel drive aerial work platforms. The system includes: an oil tank 1, a power source 2, a bidirectional closed-loop piston pump 3, a brake valve 4, a flow divider / combiner valve 5, a directional valve group 6, four hydraulic motors 7, four brakes 8, a shuttle valve 9, a pressure reducing valve 10, and a controller (not shown in the figure).

[0013] Power source 2 uses an engine (e.g., a diesel or gasoline engine). The engine's output shaft is directly connected to the input shaft of the bidirectional closed-circuit piston pump 3, driving the pump to rotate. The bidirectional closed-circuit piston pump 3 is a variable swashplate type, internally equipped with a swashplate and a control terminal (not shown in the figure). The swashplate angle is changed by the control terminal. When the control terminal receives an electrical signal from the controller, it drives the swashplate to deflect, thereby switching the hydraulic oil output direction of the two main ports (P1 and P2) of the bidirectional closed-circuit piston pump 3. The swashplate angle determines the pump's displacement, thus achieving stepless speed regulation.

[0014] The two main oil ports (P1 and P2) of the bidirectional closed-loop piston pump 3 are connected one-to-one with the two main oil ports (P3 and P4) of the flow divider / combiner valve 5. Specifically, port P1 of the bidirectional closed-loop piston pump 3 is connected to port P4 of the flow divider / combiner valve, and port P2 of the bidirectional closed-loop piston pump 3 is connected to port P3 of the flow divider / combiner valve.

[0015] The flow divider / combiner valve 5 is a flow control valve that can distribute a single oil flow into multiple oil flows (with multiple flow divider ports) in a proportional ratio (1:1 in this embodiment), or combine multiple oil flows into a single oil flow. It can ensure that even if the loads on both sides are different, the output flow on both sides can be kept equal, thereby ensuring that the speed of the left and right wheels is synchronized.

[0016] In this embodiment, the left drive assembly includes a left front hydraulic motor and a left rear hydraulic motor, and the right drive assembly includes a right front hydraulic motor and a right rear hydraulic motor. All four hydraulic motors 7 are bidirectional hydraulic motors, each with two working ports (A and B), allowing hydraulic oil to enter from either port A or port B to achieve forward or reverse rotation.

[0017] It should be noted that in this embodiment, the right motor is installed in the opposite direction to the left motor. Specifically, the left motor is configured to drive the left wheel forward when hydraulic oil enters from port A and exits from port B. The right motor is configured to drive the right wheel forward when hydraulic oil enters from port B and exits from port A. In other words, with the same oil inlet direction (e.g., both hydraulic motors have oil inlet at port A), the left and right wheels rotate in opposite directions; however, by switching the oil inlet and outlet directions of the right motor using the reversing valve assembly 6, the right wheel can rotate in the same direction or in the opposite direction to the left wheel. This reverse installation method simplifies the hydraulic pipeline connection, allowing both wheels to move forward in the same direction when oil enters from port A of the left motor and port B of the right motor during forward movement. When turning on the spot is required, simply switching the oil inlet and outlet directions of the right motor using the reversing valve assembly 6 can reverse the direction of the right wheel, thereby achieving on-the-spot turning of the entire vehicle.

[0018] Specifically, the flow divider / combiner valve 5 has eight flow divider ports, including a first group of flow divider ports (M1, M3, M5, M7) and a second group of flow divider ports (M2, M4, M6, M8). The first group of flow divider ports is directly connected to the two hydraulic motors of the left drive assembly. Specifically, port M1 of the flow divider / combiner valve is connected to port B of the left rear motor, port M3 is connected to port A of the left rear motor, port M5 is connected to port B of the left front motor, and port M7 is connected to port A of the left front motor. In this way, ports A and B of the two motors on the left are connected to different flow divider ports of the flow divider / combiner valve, forming a bidirectional drive oil circuit. When hydraulic oil enters from port A and exits from port B, the motor rotates forward; otherwise, it rotates in reverse.

[0019] In this embodiment, the directional valve assembly 6 uses a solenoid valve assembly. The solenoid valve assembly consists of eight two-position valves (SV1 to SV8), which are divided into an upper valve-controlled motor unit (hereinafter referred to as the "upper valve assembly") and a lower valve-controlled motor unit (hereinafter referred to as the "lower valve assembly") with identical structures, respectively controlling the two hydraulic motors 7 on the right side (i.e., the right front motor and the right rear motor). The second group of diversion ports (M2, M4, M6, M8) of the diversion and combiner valve 5 supply hydraulic oil to the directional valve assembly 6, which drives the right motor after switching the direction via the directional valve assembly 6.

[0020] The M8 port of the flow divider / combiner valve 5 serves as the main oil inlet line on the A1 side of the upper valve group, and the M6 ​​port serves as the main oil inlet line on the B1 side of the upper valve group. The specific connections are as follows: After M8 port connects to A1 port of the upper valve assembly, the oil circuit splits into two paths: one connects to the inlet of SV1, and the other connects to the inlet of SV2. The outlet of SV1 splits into two paths: one connects to port B of the right front hydraulic motor, and the other connects to the inlet of SV4. The outlet of SV4 connects to M6 port via B1 port of the upper valve assembly. The outlet of SV2 splits into two paths: one connects to port A of the right front hydraulic motor, and the other connects to the inlet of SV3. The outlets of SV3 and SV4 are combined and then connected to M6 port via B1 port of the upper valve assembly.

[0021] The connection relationship of the lower valve group is the same as that of the upper valve group. The M4 port of the flow divider / combiner valve 5 serves as the main oil inlet line on the A1 side of the lower valve group, and the M2 port serves as the main oil inlet line on the B1 side of the lower valve group. After M4 port connects to A1 port of the lower valve assembly, the oil circuit splits into two paths: one connects to the inlet of SV5, and the other connects to the inlet of SV6. The outlet of SV5 splits into two paths: one connects to port B of the right rear hydraulic motor, and the other connects to the inlet of SV8. The outlet of SV8 connects to port M2 via port B1 of the lower valve assembly. The outlet of SV6 splits into two paths: one connects to port A of the right rear hydraulic motor, and the other connects to the inlet of SV7. The outlets of SV7 and SV8 are combined and then connected to port M2 via port B1 of the lower valve assembly.

[0022] The reversing valve assembly 6 has a first operating state and a second operating state. In the first operating state, SV1 to SV8 are de-energized. When SV1 to SV8 are de-energized, the configuration is as follows: SV1 is on, SV2 is off, SV3 is on, SV4 is off, SV5 is on, SV6 is off, SV7 is on, and SV8 is off. At this time, the hydraulic oil flow direction of the right front hydraulic motor and the right rear hydraulic motor is from B to A.

[0023] In the second operating state, SV1 to SV8 are energized. When SV1 to SV8 are energized, they are configured as follows: SV1 is off, SV2 is on, SV3 is off, SV4 is on, SV5 is off, SV6 is on, SV7 is off, and SV8 is on. At this time, the hydraulic oil flow direction of the right front hydraulic motor and the right rear hydraulic motor is from A to B.

[0024] To ensure walking safety, this system is also equipped with a braking circuit.

[0025] The shuttle valve 9 is located inside the flow divider / combiner valve 5 and has two inlets. One inlet of the shuttle valve 9 is connected to the P2 port of the bidirectional closed-circuit piston pump 3 via the P3 port of the flow divider / combiner valve 5. The other inlet of the shuttle valve 9 is connected to the P1 port of the bidirectional closed-circuit piston pump 3 via the P4 port of the flow divider / combiner valve 5. The shuttle valve 9 is a "two-choice" valve, and its outlet automatically selects the higher pressure of the two inlets for output. Since in the closed hydraulic system, the P1 and P2 ports of the bidirectional closed-circuit piston pump 3 alternately become the high-pressure side depending on the direction of the pump's swashplate, the presence of the shuttle valve 9 ensures that pressurized oil can always be drawn from the high-pressure side to release the brake, regardless of whether the vehicle is moving forward or backward.

[0026] The outlet of shuttle valve 9 is connected to the X port of the flow divider / combiner valve 5. The X port of the flow divider / combiner valve 5 is a pilot port or oil take-up port, which leads out the high-pressure oil selected by shuttle valve 9 and connects it to the P port of brake valve 4.

[0027] The brake valve 4 incorporates a pressure reducing valve 10 and a solenoid valve SV0. The pressure reducing valve 10 is a hydraulic component that stably reduces the input high-pressure oil to a predetermined low pressure. In this embodiment, the pressure in the main oil circuit is typically between 300 bar and 400 bar, while the release pressure required by the brake 8 is 35 bar. Therefore, the pressure needs to be reduced to 35 bar via the pressure reducing valve 10. The reduced-pressure hydraulic oil is then connected to the four brakes 8 sequentially through the solenoid valve SV0 and the BRK port of the brake valve 4. The solenoid SV0 acts as the "master switch" or "hydraulic lock" of the brake oil circuit, and its default state is normally closed (i.e., the oil circuit is cut off when power is lost). The control terminal of the solenoid SV0 is electrically connected to the controller, which controls the energization and de-energization of SV0 according to received driving commands (forward, reverse, or stationary turning).

[0028] It should be noted that in this embodiment, SV0 and SV1 to SV8 in the reversing valve group 6 adopt a cooperative control logic: that is, the switching of SV1 to SV8 is only meaningful when SV0 is energized (the brake has been released); if SV0 is de-energized, even if SV1 to SV8 are activated, the vehicle cannot move because the brake 8 is still in the braking state. This logical sequence of "releasing the brake first, then allowing movement" effectively avoids the risk of "driving while dragging the brake" and significantly improves the safety of the system.

[0029] The brake valve 4 is also provided with a first T port 401, and the diverter valve 5 is also provided with a second T port 501. The first T port 401 and the second T port 501 are both return oil ports. After they are connected, they are combined and connected back to the oil tank 1 to guide leaked oil or return oil back to the oil tank.

[0030] The brake 8 preferably adopts a spring braking and hydraulic release form, that is, when the brake oil circuit loses pressure, the brake is in a braking state under the action of spring force; when the hydraulic oil pressure reaches 35 bar, it pushes the piston to overcome the spring force and releases the brake.

[0031] The system also includes a controller (not shown in the figure). The controller can be implemented using a programmable logic controller (PLC), a microcontroller, or a dedicated control circuit. The controller is electrically connected to each solenoid in the reversing valve group 6 and the solenoid valve SV0 in the brake valve 4, and is also electrically connected to the control terminal (e.g., a proportional solenoid) of the bidirectional closed piston pump 3.

[0032] The controller receives commands from the operator, including driving direction commands (forward / reverse) and steering commands (straight / turn on the spot). Driving direction commands typically come from the accelerator pedal or the forward / reverse lever, while steering mode commands come from a separate toggle switch or switch.

[0033] The specific working principle of this embodiment is as follows: Normal straight driving (forward): When the operator gives a forward command, the controller executes the following sequence of control: Step 1: The bidirectional closed-loop piston pump operates, generating high-pressure oil. The controller outputs an electrical signal corresponding to the forward command to the variable control terminal (e.g., proportional electromagnet) of the bidirectional closed-circuit piston pump 3, driving the swashplate to deflect in one direction (e.g., forward). The engine 2 drives the bidirectional closed-circuit piston pump 3 to rotate, and the pump's P2 port outputs high-pressure oil, while the P1 port becomes a low-pressure return port. The high-pressure oil flows out from the pump's P2 port and enters the P3 port of the flow divider / combiner valve 5.

[0034] Step 2: High-pressure oil releases the brake via shuttle valve and brake valve. After the high-pressure oil enters the flow divider valve 5, a portion of the oil flows out through the internal oil passage via the shuttle valve 9 and the X port, entering the P port of the brake valve 4. After entering the brake valve 4, the high-pressure oil passes through the built-in pressure reducing valve 10, which reduces the pressure to 35 bar before outputting from the BRK port, simultaneously opening the four brakes 8 and releasing the brakes.

[0035] It should be noted that the brake valve 4 contains an electromagnet SV0. When the controller receives a forward command, it first energizes SV0, opening the oil circuit inside the brake valve 4, allowing high-pressure oil to flow through the pressure reducing valve 10 to the brake 8. If SV0 is de-energized, the brake oil circuit is cut off, the brake cannot be released, and the vehicle cannot move.

[0036] Step 3: High-pressure oil drives the hydraulic motor, propelling the vehicle forward. After the brake is released, the other part of the high-pressure oil entering the flow divider valve 5 is evenly divided: the oil output from the first set of flow divider ports (M3, M7) enters the A port of the left front hydraulic motor and the left rear hydraulic motor respectively. The oil output from the second set of flow divider ports (M4, M8) passes through the reversing valve group 6 (which is in the first working state at this time, i.e., SV1 to SV8 are de-energized) and then enters the B port of the right front motor and the right rear motor respectively.

[0037] Oil enters through port A and returns through port B of the left motor, causing the left wheel to rotate forward. Similarly, oil enters through port B of the right motor and returns through port A, causing the right wheel to rotate forward as well. The return oil from ports B of the left motor and A of the right motor is collected at the corresponding ports of the flow divider / combiner valve 5 and flows back from port P4 of the flow divider / combiner valve 5 to port P1 of the bidirectional closed-circuit piston pump 3, forming a closed loop. The vehicle's forward speed is determined by the swashplate angle of the bidirectional closed-circuit piston pump 3.

[0038] Normal straight driving (reverse): When the operator gives a reverse command, the controller executes the following sequence of control: Step 1: Reverse operation of the bidirectional closed-loop piston pump The controller outputs a reverse electrical signal to the variable control terminal of the bidirectional closed-circuit piston pump 3, causing the swashplate to deflect in the opposite direction (overtaking the neutral position). At this time, the P1 port of the bidirectional closed-circuit piston pump 3 outputs high-pressure oil, and the P2 port becomes a low-pressure return port. The high-pressure oil flows out from the pump's P1 port and enters the P4 port of the flow divider / combiner valve 5.

[0039] Step 2: High-pressure hydraulic release of the brake Since the two oil inlets of shuttle valve 9 are connected to the pump's P1 and P2 ports respectively, and P1 port is the high-pressure side, shuttle valve 9 automatically selects the pressure oil output from P1 port to X port. After passing through brake valve 4 (SV0 is energized) and pressure reducing valve 10, the braking of the four brakes 8 is released with a pressure of 35 bar.

[0040] Step 3: High-pressure oil drives the hydraulic motor, causing the vehicle to reverse. After the high-pressure oil enters through port P4 of the diversion and manifold valve 5, it is evenly distributed to the first and second group of diversion ports. The oil output from the first group of diversion ports (M1, M5) enters port B (reverse inlet) of the left motor, while the oil output from the second group of diversion ports (M2, M6) enters port A (reverse inlet) of the right motor after passing through the reversing valve group 6, thereby driving the four motors to reverse and the vehicle to move backward.

[0041] Turning in place: When the operator switches the steering wheel to the "Stationary Steering" mode and simultaneously issues a driving command (e.g., a forward command), the controller executes the following sequence of control: Step 1: The bidirectional closed-loop piston pump operates according to the driving command. The controller causes the swashplate of the bidirectional closed piston pump 3 to deflect in the positive direction according to the driving command (forward), and high-pressure oil is output from port P2, the same as when moving forward.

[0042] Step 2: High-pressure hydraulic release of the brake As in the forward motion, the high-pressure oil releases the four brakes 8 after passing through shuttle valve 9, brake valve 4 (SV0 is energized) and pressure reducing valve 10.

[0043] Step 3: The reversing valve assembly switches the right-side oil circuit to achieve in-situ steering. Unlike normal forward movement, the controller now simultaneously energizes all electromagnets (SV1 to SV8) of the reversing valve assembly 6 (second operating state). The switching of the reversing valve assembly 6 reverses the oil inlet and outlet directions of the right motor: previously, when moving forward, the right motor had oil inlet at port B and oil outlet outlet A; now, it has oil inlet at port A and oil outlet outlet B. This is because the right motor is installed in reverse relative to the left (e.g., ...). Figure 1 As shown in the diagram, oil entering through port A causes the right wheel to rotate backward.

[0044] Therefore, the left wheel moves forward and the right wheel moves backward, causing the entire vehicle to turn clockwise around the center.

[0045] If the operator gives a reverse command and simultaneously performs a stationary turn, the swashplate of the bidirectional closed piston pump 3 deflects in the opposite direction, high-pressure oil is output from port P1, the left motor reverses (backwards), while the reversing valve group 6 remains in the second working state, and the oil inlet and outlet directions of the right motor are reversed to become forward (forwards), and the whole vehicle turns counterclockwise in place.

[0046] Example 2: This embodiment provides an aerial work platform vehicle. The aerial work platform vehicle adopts the hydraulic drive stationary steering control system of Embodiment 1, which can realize flexible switching between three modes: stationary steering (clockwise or counterclockwise), forward and backward. It is especially suitable for high-altitude operations in narrow spaces (such as indoor stadiums and dense building complexes), eliminating the need for multiple adjustments to the vehicle's position and greatly improving work efficiency.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hydraulically driven stationary steering control system, characterized in that, include: Power source (2); A two-way closed-loop piston pump (3) is driven by the power source (2); The flow divider valve (5) has two main oil ports that are respectively connected to the two main oil ports of the bidirectional closed plunger pump (3); The left drive assembly is connected to the split oil port of the split and combine valve (5) to form a bidirectional drive oil circuit that allows the left drive assembly to rotate forward or reverse. Right-side drive component; A reversing valve assembly (6) is connected between the flow divider / combiner valve (5) and the right-side drive assembly; The reversing valve assembly (6) has at least a first working state and a second working state. In the first working state, the driving direction of the right driving component is the same as that of the left driving component. In the second working state, the driving direction of the right driving component is opposite to that of the left driving component.

2. The hydraulically driven stationary steering control system according to claim 1, characterized in that, Both the left-side drive assembly and the right-side drive assembly include multiple hydraulic motors (7), and all of the multiple hydraulic motors (7) are bidirectional hydraulic motors.

3. The hydraulically driven stationary steering control system according to claim 1, characterized in that, The diversion and combination valve (5) is provided with a first diversion port and a second diversion port. The first diversion port is connected to the left drive assembly, and the second diversion port is connected to the right drive assembly through the reversing valve group (6).

4. The hydraulically driven stationary steering control system according to claim 1, characterized in that, The reversing valve group (6) is a solenoid valve group. The solenoid valve is used to switch the hydraulic oil flow direction of the right drive component, thereby changing the driving direction of the right drive component.

5. The hydraulically driven stationary steering control system according to claim 1, characterized in that, The bidirectional closed piston pump (3) is a variable swashplate bidirectional closed piston pump. The bidirectional closed piston pump (3) switches the hydraulic oil output direction of its two main oil ports by changing the swashplate angle, thereby changing the rotation direction of the left drive assembly and the right drive assembly.

6. The hydraulically driven stationary steering control system according to claim 1, characterized in that, It also includes a brake valve (4), a brake (8) and an oil tank (1). The brake valve (4) is provided with a P port, a first T port (401) and a BRK port. The diverter valve (5) is also provided with an X port and a second T port (501). The P port is connected to the X port. The first T port (401) is connected to the second T port (501) and then connected back to the oil tank (1). The BRK port is connected to the brake (8). The brake (8) is used to brake the left drive assembly and the right drive assembly.

7. The hydraulically driven stationary steering control system according to claim 6, characterized in that, It also includes a shuttle valve (9), the two inlets of which are respectively connected to the two main oil ports of the bidirectional closed plunger pump (3), and the outlet of the shuttle valve (9) is connected to the X port.

8. The hydraulically driven stationary steering control system according to claim 6, characterized in that, The brake valve (4) has a built-in pressure reducing valve (10), which is used to reduce the pressure of the hydraulic oil introduced from the X port and output it from the BRK port to the brake (8) to release the braking state of the brake (8).

9. The hydraulically driven stationary steering control system according to claim 1, characterized in that, It also includes a controller, the control terminals of the reversing valve group (6) and the bidirectional closed piston pump (3) are electrically connected to the controller, the controller is used to control the reversing valve group (6) to switch between the first working state and the second working state according to the received steering command, and to control the swashplate angle of the bidirectional closed piston pump (3) to switch the hydraulic oil output direction according to the received driving direction command.

10. An aerial work platform, characterized in that, The system includes a hydraulically driven stationary steering control system as described in any one of claims 1 to 9.

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