Aerial work platform chassis control system and control method thereof

Abstract

The invention discloses an aerial work platform chassis control system and a control method thereof.The aerial work platform chassis control system comprises a power assembly, a walking hydraulic system, a steering bridge expansion hydraulic system, a controller assembly and a chassis assembly, and the power assembly provides high-pressure oil for the walking hydraulic system and the steering bridge expansion hydraulic system; the controller assembly is in signal connection with the walking hydraulic system and the steering bridge expanding hydraulic system, and the walking hydraulic system and the steering bridge expanding hydraulic system are installed on the chassis assembly and drive execution components of the chassis assembly to work. The device has the beneficial effects that a set of power device is adopted to simultaneously drive the walking pump and the steering bridge expansion pump, and two sets of mutually independent hydraulic control systems are adopted, so that bridge expansion can be assisted to be driven on the premise of ensuring the running performance of the whole machine; by means of the control method of in-situ bridge expansion, tire abrasion can be reduced, the service life of tires can be prolonged, by means of the control method of additionally arranging the walking system, the pressure loss of the closed system is reduced, and therefore the running performance of the whole machine is improved.

Description

Technical Field

[0001] This invention relates to a chassis control system and its control method, and particularly to a chassis control system and its control method for an aerial work platform, belonging to the field of engineering vehicle technology. Background Technology

[0002] The axle expansion function of an aerial work platform refers to the technology that allows the chassis axles to expand and contract in width via a hydraulic system. During transport and travel, the chassis is in a narrower configuration to ensure maneuverability; during aerial work, the axle expansion increases the chassis width, thereby improving the overall operational stability of the machine. The axle expansion system typically consists of a frame, outriggers, and axle expansion cylinders. The four outriggers are hinged to the frame via pins, and one end of the axle expansion cylinder is connected to the frame, while the other end is connected to the outriggers. When the cylinder extends, it pushes the outriggers outward, increasing the outrigger span; when retracting, it closes the outriggers, reducing the overall width of the platform.

[0003] For aerial work platforms designed for high-speed applications, the chassis are typically equipped with outriggers to accommodate various operating conditions. Generally, the outriggers retract during transport or short-distance travel, and extend to provide greater support arm for stability during operation. Currently, the most common outrigger extension solutions are the "X-type" and "H-type" outriggers. However, these require continuous movement of the machine to extend, resulting in significant tire wear and potential issues with the outriggers failing to extend due to malfunctions in the travel system.

[0004] While in-situ axle widening techniques have emerged in the industry for "X-shaped axles," such as the in-situ axle widening chassis and aerial work platform disclosed in Chinese Patent CN115257233 A, this technique widens the axle by pushing the wheel assembly and rotating it so that its rolling direction aligns with the swing tangent of the half-axle structure. During the swing, the wheel assembly rolls synchronously, thus widening the axle on the spot. However, this technique relies on a bypass valve to block high-pressure oil from entering the travel motor, allowing communication between the high and low pressure oil ports of the motor, and releasing the brakes, allowing it to rotate under external force. When widening the axle on uneven ground, relying solely on the axle widening cylinder can lead to insufficient power, making widening difficult or even impossible. Furthermore, asynchronous widening can cause the vehicle body to twist and tilt, resulting in poor widening performance.

[0005] Chinese patent CN 119348341 A discloses a method and system for extending a vehicle chassis axle. The method includes a normal extension mode, an obstacle-encounter extension mode, a limit extension mode, and a free extension mode. In the normal extension mode, if an obstacle is encountered and the pressure of the extension cylinder increases beyond the system's set pressure, the system switches to the obstacle-encounter extension mode. After the wheels are swung, the pressure decreases, and the axle continues to extend. If the pressure does not decrease, the system switches to the limit extension mode. The free extension mode involves manual control of at least one wheel or axle via an operating panel. Automatic obstacle avoidance and successful axle extension within a limited area are achieved through individually controlled valve groups and coordinated control logic. This technical solution uses individual control of the four wheels or increases the pressure of the extension cylinders to achieve obstacle-encounter extension. However, this solution fails to fundamentally improve the obstacle-crossing and axle extension capability and requires higher pressure values ​​and larger extension cylinders, which reduces the overall reliability of the machine while increasing its cost and energy consumption. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to address the technical problems existing in the prior art by providing a chassis control system and method for aerial work platforms. This system enables the travel motor to rotate under the drive of the travel pump and assists in driving the bridge expansion, thereby reducing the force of the bridge expansion cylinder and lowering the overall cost of the machine. At the same time, it adds a stationary bridge expansion function selection module, which reduces the pressure loss of the closed hydraulic system and improves the overall driving performance of the machine.

[0007] Technical solution: A chassis control system for an aerial work platform includes a powertrain, a travel hydraulic system, a steering and axle expansion hydraulic system, a controller assembly, and a chassis assembly. The powertrain provides high-pressure hydraulic fluid to the travel hydraulic system and the steering and axle expansion hydraulic system. The controller assembly is connected to the travel hydraulic system and the steering and axle expansion hydraulic system via signals. The travel hydraulic system and the steering and axle expansion hydraulic system are mounted on the chassis assembly and drive the actuators of the chassis assembly. The powertrain includes a power unit, a travel pump, and a steering expansion pump. The power output terminal of the power unit is simultaneously connected to the travel pump and the steering expansion pump. The walking hydraulic system includes a walking control valve, a left front walking motor, a left rear walking motor, a right front walking motor, and a right rear walking motor. The walking pump drives the left front walking motor and the left rear walking motor on the left side and the right front walking motor and the right rear walking motor on the right side simultaneously through the walking control valve. The steering bridge expansion hydraulic system includes a steering bridge expansion control valve, a left front steering cylinder, a left front expansion cylinder, a left rear steering cylinder, a left rear expansion cylinder, a right front steering cylinder, a right front expansion cylinder, a right rear steering cylinder, and a right rear expansion cylinder; the steering bridge expansion pump controls the extension and retraction of the left front steering cylinder, the left front expansion cylinder, the left rear steering cylinder, the left rear expansion cylinder, the right front steering cylinder, the right front expansion cylinder, the right rear steering cylinder, and the right rear expansion cylinder respectively through the steering bridge expansion control valve; The controller assembly is connected to the travel control valve and the steering bridge control valve via signals, respectively. The drive chassis assembly includes a frame assembly, a left front support leg, a left front steering link, a left rear support leg, a left rear steering link, a right front support leg, a right front steering link, a right rear support leg, and a right rear steering link; the left front support leg, left rear support leg, right front support leg, and right rear support leg are respectively hinged to the frame assembly; A left front travel motor is swayably mounted at the end of the left front outrigger. The left front steering cylinder drives the left front travel motor to sway relative to the left front outrigger through the left front steering linkage. The left front expansion cylinder is installed between the left front outrigger and the frame assembly to drive the left front outrigger to rotate relative to the frame assembly. A left rear travel motor is swayably mounted at the end of the left rear outrigger. The left rear steering cylinder drives the left rear travel motor to sway relative to the left rear outrigger through the left rear steering linkage. The left rear expansion axle cylinder is installed between the left rear outrigger and the frame assembly to drive the left rear outrigger to rotate relative to the frame assembly. The right front outrigger is equipped with a swingable right front travel motor at its end. The right front steering cylinder drives the right front travel motor to swing relative to the right front outrigger via the right front steering linkage. The right front expansion cylinder is installed between the right front outrigger and the frame assembly to drive the right front outrigger to rotate relative to the frame assembly. The right rear outrigger is equipped with a swing-mounted right rear travel motor at its end. The right rear steering cylinder drives the right rear travel motor to swing relative to the right rear outrigger via the right rear steering linkage. The right rear expansion axle cylinder is installed between the right rear outrigger and the frame assembly to drive the right rear outrigger to rotate relative to the frame assembly.

[0008] This invention employs a single power unit to simultaneously drive the travel pump and the steering bridge expansion pump. The entire machine utilizes two independent hydraulic control systems for travel and steering bridge expansion. This allows for assistance in driving the bridge expansion while ensuring the overall machine's driving performance; that is, the travel motor drives the wheels to rotate during obstacle crossing and bridge expansion, thereby improving obstacle-crossing capability.

[0009] The travel hydraulic system adopts a hydrostatic transmission system that is lighter, smaller, more compact, and has a higher average working efficiency for the same power. The steering axle expansion hydraulic system adopts a mature and common open hydraulic system. It can realize the rotation of the travel motor under the drive of the travel pump and assist in driving the axle expansion, reducing the pressure value of the axle expansion cylinder and reducing the cost of the whole machine. At the same time, the addition of a stationary axle expansion function selection module reduces the pressure loss of the closed hydraulic system, thereby improving the overall driving performance of the machine.

[0010] In a preferred embodiment, to further reduce energy consumption and facilitate overall machine control, the travel pump includes a left travel pump and a right travel pump, and the power output terminal of the power unit is simultaneously connected to both the left and right travel pumps; the left travel pump drives the left front travel motor and the left rear travel motor respectively through a travel control valve; the right travel pump drives the right front travel motor and the right rear travel motor respectively through a travel control valve.

[0011] The travel pump uses two pumps, a left-side travel pump and a right-side travel pump, to form two relatively independent hydrostatic transmission systems. This avoids pressure loss at the travel control valve due to high flow rates, further saving energy and facilitating precise control of the motors on both sides.

[0012] In a preferred embodiment, for precise control of the two hydrostatic travel systems, the left travel pump includes a left travel pump solenoid control valve, which is a three-position four-way solenoid valve. Electromagnets Y10 and Y11, connected to the controller assembly, are respectively located on both sides of the left travel pump solenoid control valve. When neither electromagnet Y10 nor Y11 is energized, the left travel pump solenoid control valve is in the neutral position, and the left travel pump flow is zero. When either electromagnet Y10 or Y11 is energized, the left travel pump begins to supply oil, and when either electromagnet Y10 or Y11 is energized, the direction of oil supply by the left travel pump is opposite. The right-side travel pump includes a right-side travel pump solenoid control valve, which is a three-position four-way solenoid valve. Electromagnets Y12 and Y13, which are signal-connected to the controller assembly, are respectively located on both sides of the right-side travel pump solenoid control valve. When neither electromagnet Y12 nor Y13 is energized, the right-side travel pump solenoid control valve is in the neutral position, and the right-side travel pump flow is zero. When either electromagnet Y12 or Y13 is energized, the right-side travel pump begins to supply oil, and when either electromagnet Y12 or Y13 is energized, the direction of oil supply by the right-side travel pump is opposite.

[0013] The controller assembly controls the oil flow direction of the left travel pump and thus the steering of the left wheels via electromagnets Y10 and Y11 of the left travel pump solenoid control valve; simultaneously, it controls the oil flow direction of the right travel pump and thus the steering of the right wheels via electromagnets Y12 and Y13 of the right travel pump solenoid control valve. When the flow direction and flow rate are the same on both sides, the wheels on both sides turn and rotate at the same speed, achieving straight forward and backward movement of the vehicle; when the flow rates are different, the wheels on both sides rotate at different speeds, allowing the vehicle to drift and turn towards the slower-rotating side; when the flow directions are opposite on both sides but the flow rates are the same, the wheels on both sides turn in opposite directions but rotate at the same speed, achieving in-place turning of the vehicle.

[0014] In a preferred embodiment, in order to improve the overall walking efficiency and climbing ability of the machine, the walking control valve includes a left rear two-position two-way bidirectional shut-off solenoid valve, a left front two-position two-way bidirectional shut-off solenoid valve, a right rear two-position two-way bidirectional shut-off solenoid valve, a right front two-position two-way bidirectional shut-off solenoid valve, a left diverter valve, and a right diverter valve. The left rear two-position two-way bidirectional shut-off solenoid valve is located in the oil line between the left travel pump and the left rear travel motor. The electromagnet Y1 of the left rear two-position two-way bidirectional shut-off solenoid valve is connected to the controller assembly signal. The left front two-position two-way bidirectional shut-off solenoid valve is located in the oil line between the left travel pump and the left front travel motor. The electromagnet Y2 of the left front two-position two-way bidirectional shut-off solenoid valve is connected to the controller assembly signal. The right rear two-position two-way bidirectional shut-off solenoid valve is located in the oil line between the left travel pump and the right rear travel motor. The electromagnet Y3 of the right rear two-position two-way bidirectional shut-off solenoid valve is connected to the controller assembly signal. The right front two-position two-way bidirectional shut-off solenoid valve is located in the oil line between the left travel pump and the right front travel motor. The electromagnet Y4 of the right front two-position two-way bidirectional shut-off solenoid valve is connected to the controller assembly signal. The left-side diverting and combining valve is connected in parallel to the oil ports at both ends of the left rear two-way bidirectional shut-off solenoid valve and the left front two-way bidirectional shut-off solenoid valve. The right-side diverter valve is connected in parallel to the two oil ports of the right rear two-way bidirectional shut-off solenoid valve and the right front two-way bidirectional shut-off solenoid valve.

[0015] The machine has two travel modes: "flat ground mode" and "climbing mode". When the machine is in "climbing mode", electromagnets Y1, Y2, Y3 and Y4 are de-energized. At this time, the oil is evenly distributed to the travel motors on both sides through the left and right diversion and diversion valves, thereby achieving uniform flow distribution and improving the driving force of the machine.

[0016] When the machine is in "flat ground" mode, electromagnets Y1, Y2, Y3 and Y4 are all energized. The oil bypasses the left and right diversion valves and enters the travel motor directly through the solenoid valve, reducing pressure loss and improving energy efficiency.

[0017] Preferably, to further improve the working efficiency of the travel motors, the left front travel motor, left rear travel motor, right front travel motor, and right rear travel motor are all variable displacement motors. The aforementioned travel motor control oil circuit is equipped with an electromagnetic reversing valve, which is equipped with an electromagnet Y9 that is signal-connected to the controller assembly; the travel pump provides control oil that is connected to the travel motor control oil circuit and oil tank through the electromagnetic reversing valve, and controls the travel motor displacement through the electromagnetic reversing valve.

[0018] When high torque and low speed are required, the controller assembly controls the electromagnetic reversing valve through electromagnet Y9 to control the displacement of the travel motor; at the same time, it can also achieve the switching of low torque and high speed.

[0019] In a preferred embodiment, in order to achieve separate control of the front and rear travel motors, hydraulic brakes are respectively provided on the left front travel motor, left rear travel motor, right front travel motor and right rear travel motor; The control oil circuit of the hydraulic brake on the left and right rear travel motors is equipped with a rear brake solenoid control valve, and the rear brake solenoid control valve is equipped with an electromagnet Y7 that is signal-connected to the controller assembly. The control oil circuit of the hydraulic brake on the left front travel motor and the right front travel motor is equipped with a front brake solenoid control valve, and the front brake solenoid control valve is equipped with an electromagnet Y8 that is signal-connected to the controller assembly. The travel pump provides control oil that is connected to the hydraulic brake of the travel motor via the rear brake solenoid control valve and the front brake solenoid control valve. The controller assembly controls the hydraulic brake of the rear travel motor and the hydraulic brake of the front travel motor respectively via electromagnets Y7 and Y8.

[0020] When it is necessary to control the front travel motor or the rear travel motor separately, the controller assembly controls the rear brake solenoid control valve or the front brake solenoid control valve through electromagnet Y7 or electromagnet Y8, thereby releasing the brake of the corresponding front travel motor or the rear travel motor, and thus realizing the separate control of the front and rear travel motors.

[0021] In a preferred embodiment, in order to enable the free rotation of the four wheels and facilitate the expansion cylinder to expand the bridge in place, the travel control valve is provided with a left-side bidirectional shut-off solenoid valve that connects to the inlet and outlet of the left travel pump and a right-side bidirectional shut-off solenoid valve that connects to the inlet and outlet of the right travel pump. The left-side oil circuit bidirectional shut-off solenoid valve is equipped with an electromagnet Y5 that is signal-connected to the controller assembly. The right-side oil circuit bidirectional shut-off solenoid valve is equipped with an electromagnet Y6 that is connected to the controller assembly for signal transmission.

[0022] When the controller assembly energizes solenoid Y5, the left-side bidirectional shut-off solenoid valve connects the oil passage between the inlet and outlet of the left travel pump, and simultaneously connects the oil passage between the inlet and outlet of the left motor. High-pressure oil no longer enters the left motor, and the left motor can rotate freely. Similarly, when the controller assembly energizes solenoid Y6, the right-side bidirectional shut-off solenoid valve connects the oil passage between the inlet and outlet of the right travel pump and the right motor. High-pressure oil no longer enters the right motor, and the right motor can rotate freely.

[0023] Preferably, to reduce travel pressure shock, an inlet throttle valve is installed between the oil inlets of the left and right travel pumps within the travel control valve; a return throttle valve is installed between the oil return inlets of the left and right travel pumps within the travel control valve. These inlet and return throttle valves connect two independent closed hydraulic systems, thereby achieving pressure exchange and reducing travel pressure shock.

[0024] A control method for a chassis control system of an aerial work platform includes a travel mode control method and a bridge-expanding mode control method. The travel mode control method includes a flat ground travel mode, a hill climbing travel mode, and a steering travel mode. In walking mode, electromagnets Y5 and Y6 are de-energized, while electromagnets Y7 and Y8 are energized. Flat ground driving mode: The controller assembly controls electromagnets Y1, Y2, Y3 and Y4 to be energized, and electromagnet Y9 to be energized. The oil does not pass through the left and right diverter valves and directly passes through the left rear two-way two-way bidirectional cut-off solenoid valve, the left front two-way two-way two-way cut-off solenoid valve, the right rear two-way two-way two-way cut-off solenoid valve and the right front two-way two-way two-way two-way cut-off solenoid valve to enter the four travel motors. Hill Climbing Mode: The controller assembly controls electromagnets Y1, Y2, Y3 and Y4 to lose power, and electromagnet Y9 to lose power. The oil is then distributed to the travel motors on both sides through the left and right diversion and diversion valves. Steering driving mode: First, determine the steering angle by designating one of the four wheels as the active steering angle detection wheel and the other three tires as steering angle following wheels. Set a threshold for determining the steering angle and monitor the steering angle of the active steering angle detection wheel. If the steering angle of the active steering angle detection wheel is within the set judgment steering threshold range, the displacement of the left and right travel pumps is the same, the flow rate of the two motors is the same, the controller assembly controls the whole machine to move forward or backward, and the travel flow rate of the two travel systems is the same. If the steering angle of the active steering angle detection wheel exceeds the set steering threshold range, the steering direction is determined based on the sign of the steering angle value of the active steering angle detection wheel. When turning left, the displacement of the left travel pump is reduced while the displacement of the right travel pump remains unchanged. The differential speed of the whole machine when turning left is achieved through the mutual flow coupling of the two pumps. When turning right, the displacement of the left travel pump remains unchanged, while the displacement of the right travel pump decreases. The differential speed of the machine when turning right is achieved through the mutual flow coupling of the two pumps.

[0025] Preferably, to adapt to bridge expansion under different road conditions, the bridge expansion mode control method includes an obstacle-crossing bridge expansion mode and a flat-ground bridge expansion mode. In the obstacle crossing and bridge expansion mode, neither the solenoid Y5 of the left oil circuit bidirectional shut-off solenoid valve nor the solenoid Y6 of the right oil circuit bidirectional shut-off solenoid valve should be energized. The specific method is as follows: Step 1: Front axle expansion. The controller assembly controls the solenoid Y8 of the front brake solenoid control valve to be energized, while the solenoid Y7 of the rear brake solenoid control valve is de-energized, releasing the brakes of the left and right front travel motors, while keeping the left and right rear travel motors braked. The steering expansion pump supplies oil to the rod chambers of the left and right front steering cylinders, and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly. When the tire reaches the set angle of the controller assembly, the steering cylinder stops supplying oil, the solenoid Y9 of the solenoid reversing valve is energized, and at the same time the solenoid Y11 of the left travel pump and the solenoid Y12 of the right travel pump are energized. The left travel pump supplies oil to the left front travel motor, the right travel pump supplies oil to the right front travel motor, and the steering expansion pump supplies oil to the rodless chamber of the left front expansion cylinder and the right front expansion cylinder. The aforementioned expansion cylinders begin to extend, and the expansion angle sensor monitors the angle of the left front outrigger and the right front outrigger in real time until the set value of the controller assembly is reached. When the axle expansion angle reaches the set value angle of the controller assembly, the solenoid Y9 of the electromagnetic reversing valve is de-energized, and at the same time, the solenoids Y11 of the left travel pump and Y12 of the right travel pump are de-energized, and the travel pump stops supplying oil to the travel motor; the steering expansion pump stops supplying oil to the rodless chamber of the left front expansion cylinder and the right front expansion cylinder, and the steering expansion pump supplies oil to the rodless chamber of the left front steering cylinder and the right front steering cylinder until the tire angle reaches the initial value. Finally, the solenoid Y8 of the front brake electromagnetic control valve is de-energized, and the front axle expansion is completed. Step 2: Rear axle expansion. The controller assembly controls the rear brake solenoid control valve solenoid Y7 to be energized, while the front brake solenoid control valve solenoid Y8 is de-energized, releasing the brakes of the left and right rear travel motors, while keeping the left and right front travel motors braked. The steering expansion pump supplies oil to the rod chambers of the left and right rear steering cylinders, and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly. When the tire reaches the set angle of the controller assembly, the steering cylinder stops supplying oil, the solenoid Y9 of the solenoid reversing valve is energized, and at the same time the solenoid Y10 of the left travel pump and the solenoid Y13 of the right travel pump are energized. The left travel pump supplies oil to the left rear travel motor, the right travel pump supplies oil to the right rear travel motor, and the steering expansion pump supplies oil to the rodless chamber of the left and right rear expansion cylinders. The aforementioned expansion cylinders begin to extend, and the expansion angle sensor monitors the angle of the left and right rear outriggers in real time until the set value of the controller assembly is reached. When the bridge expansion angle reaches the set angle of the controller assembly, the solenoid Y9 of the electromagnetic reversing valve is de-energized, and at the same time, the solenoids Y10 and Y13 of the left travel pump and the right travel pump are de-energized, and the travel pump stops supplying oil to the travel motor; the steering bridge expansion pump stops supplying oil to the rodless chamber of the left and right rear bridge expansion cylinders, and the steering bridge expansion pump supplies oil to the rodless chamber of the left and right rear steering cylinders until the tire angle reaches the initial value. Finally, the solenoid Y7 of the rear brake electromagnetic control valve is de-energized, and the bridge expansion is completed. Step 3: Rear axle retraction. The controller assembly controls the rear brake solenoid control valve solenoid Y7 to be energized, while the front brake solenoid control valve solenoid Y8 is de-energized, releasing the brakes of the left and right rear travel motors, while keeping the left and right front travel motors braked. The steering expansion pump supplies oil to the rod chambers of the left and right rear steering cylinders, and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly. When the tire reaches the set angle of the controller assembly, the steering cylinder stops supplying oil, the solenoid Y9 of the solenoid reversing valve is energized, and at the same time the solenoid Y11 of the left travel pump and the solenoid Y12 of the right travel pump are energized. The left travel pump supplies oil to the left rear travel motor, the right travel pump supplies oil to the right rear travel motor, and the steering expansion pump supplies oil to the rod chamber of the left and right rear expansion cylinders. The aforementioned expansion cylinders begin to retract, and the expansion angle sensor monitors the angle of the left and right rear outriggers in real time until the set value of the controller assembly is reached. When the bridge extension angle reaches the set angle of the controller assembly, the solenoid Y9 of the electromagnetic reversing valve is de-energized, and at the same time, the solenoids Y11 of the left travel pump and Y12 of the right travel pump are de-energized, and the travel pump stops supplying oil to the travel motor; the steering bridge extension pump stops supplying oil to the rod chamber of the left and right rear bridge extension cylinders, and the steering bridge extension pump supplies oil to the rodless chamber of the left and right rear steering cylinders until the tire angle reaches the initial value. Finally, the solenoid Y7 of the rear brake electromagnetic control valve is de-energized, and the rear axle retracts. Step 4: The front axle retracts, and the controller assembly energizes the solenoid Y8 of the front brake solenoid control valve while de-energizing the solenoid Y7 of the rear brake solenoid control valve, releasing the brakes of the left and right front travel motors, while keeping the left and right rear travel motors braked. The steering expansion pump supplies oil to the rod chambers of the left and right front steering cylinders, and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly. When the tire reaches the set angle of the controller assembly, the steering cylinder stops supplying oil, the solenoid Y9 of the solenoid reversing valve is energized, and at the same time the solenoid Y10 of the left travel pump and the solenoid Y13 of the right travel pump are energized. The left travel pump supplies oil to the left front travel motor, the right travel pump supplies oil to the right front travel motor, and the steering expansion pump supplies oil to the rod chamber of the left front expansion cylinder and the right front expansion cylinder. The aforementioned expansion cylinders begin to retract, and the expansion angle sensor monitors the angle of the left front outrigger and the right front outrigger in real time until the set value of the controller assembly is reached. When the bridge expansion angle reaches the set angle of the controller assembly, the solenoid Y9 of the electromagnetic reversing valve is de-energized, and at the same time, the solenoids Y10 and Y13 of the left travel pump and the right travel pump are de-energized, and the travel pump stops supplying oil to the travel motor; the steering bridge expansion pump stops supplying oil to the rod chamber of the left front bridge expansion cylinder and the right front bridge expansion cylinder, and the steering bridge expansion pump supplies oil to the rodless chamber of the left front steering cylinder and the right front steering cylinder until the tire angle reaches the initial value. Finally, the solenoid Y8 of the front brake electromagnetic control valve is de-energized, and the front axle retraction is completed. In the flat ground bridge expansion mode, during the bridge expansion and retraction process, the solenoid Y5 of the left oil circuit bidirectional shut-off solenoid valve and the solenoid Y6 of the right oil circuit bidirectional shut-off solenoid valve are energized, and at the same time, the solenoid Y9 of the solenoid reversing valve is energized. The travel motor has a small displacement and is easy to rotate. The specific method is as follows: Step 1: Front axle expansion. The controller assembly controls the solenoid Y8 of the front brake solenoid control valve to be energized, while the solenoid Y7 of the rear brake solenoid control valve is de-energized, releasing the brakes of the left and right front travel motors, while keeping the left and right rear travel motors braked. The steering expansion pump supplies oil to the rod chambers of the left and right front steering cylinders, and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly. When the tire reaches the set angle of the controller assembly, the steering cylinder stops supplying oil, the solenoid Y2 of the left front two-position two-way bidirectional cut-off solenoid valve and the solenoid Y4 of the right front two-position two-way bidirectional cut-off solenoid valve are energized, the solenoid of the travel pump is not energized, the front travel motor achieves two oil port connection in the travel control valve, and the front travel motor can rotate freely. The steering expansion pump supplies oil to the rodless chambers of the left and right front expansion cylinders, and the aforementioned expansion cylinders begin to extend. The expansion angle sensor monitors the angles of the left and right front outriggers in real time until they reach the set value of the controller assembly. When the axle expansion angle reaches the set value of the controller assembly, the steering axle expansion pump stops supplying oil to the rodless chambers of the left and right front axle expansion cylinders, and the steering axle expansion pump supplies oil to the rodless chambers of the left and right front steering cylinders until the tire angle reaches the initial value. Then, the solenoid Y2 of the left front two-position two-way bidirectional cut-off solenoid valve and the solenoid Y4 of the right front two-position two-way bidirectional cut-off solenoid valve are de-energized, and the solenoid Y8 of the front brake solenoid control valve is de-energized, thus completing the front axle expansion. Step 2: Rear axle expansion. The controller assembly controls the rear brake solenoid control valve solenoid Y7 to be energized, while the front brake solenoid control valve solenoid Y8 is de-energized, releasing the brakes of the left and right rear travel motors, while keeping the left and right front travel motors braked. The steering expansion pump supplies oil to the rod chambers of the left and right rear steering cylinders, and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly. When the tire reaches the set angle of the controller assembly, the steering cylinder stops supplying oil, the solenoid Y1 of the left rear two-position two-way bidirectional shut-off solenoid valve and the solenoid Y3 of the right rear two-position two-way bidirectional shut-off solenoid valve are energized, the solenoid of the travel pump is not energized, the rear travel motor achieves two oil port connection in the travel control valve, and the rear travel motor can rotate freely. The steering expansion pump supplies oil to the rodless chambers of the left and right rear expansion cylinders, and the aforementioned expansion cylinders begin to extend. The expansion angle sensor monitors the angles of the left and right rear outriggers in real time until they reach the set value of the controller assembly. When the bridge expansion angle reaches the set value angle of the controller assembly, the steering bridge expansion pump stops supplying oil to the rodless chamber of the left and right rear bridge expansion cylinders, and the steering bridge expansion pump supplies oil to the rodless chamber of the left and right rear steering cylinders until the tire angle reaches the initial value. Electromagnets Y1, Y3, Y5, Y6 and Y7 are de-energized, and the bridge expansion is completed. Step 3: Rear axle retraction. The controller assembly controls the magnet Y7 of the rear brake solenoid control valve to be energized, while the electromagnet Y8 of the front brake solenoid control valve is de-energized, releasing the brakes of the left and right rear travel motors, while keeping the left and right front travel motors braked. The steering expansion pump supplies oil to the rod chambers of the left and right rear steering cylinders, and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly. When the tire reaches the set angle of the controller assembly, the steering cylinder stops supplying oil, electromagnets Y1 and Y3 are energized, the electromagnet of the travel pump is de-energized, and the two oil ports of the rear travel motor are connected in the travel control valve, allowing the rear travel motor to rotate freely. The steering expansion pump supplies oil to the rod chambers of the left and right rear expansion cylinders, and the aforementioned expansion cylinders begin to retract. The expansion angle sensor monitors the angles of the left and right rear outriggers in real time until they reach the set value of the controller assembly. When the bridge extension angle reaches the set value of the controller assembly, the steering bridge extension pump stops supplying oil to the rod chambers of the left and right rear bridge extension cylinders, and the steering bridge extension pump supplies oil to the rodless chambers of the left and right rear steering cylinders until the tire angle reaches the initial value. Then, electromagnets Y1, Y3, Y5, Y6 and Y7 are de-energized, and the rear axle retracts. Step 4: The front axle retracts, and the controller assembly energizes the electromagnet Y8 of the front brake solenoid control valve while de-energizing the electromagnet Y7 of the rear brake solenoid control valve, releasing the brakes of the left and right front travel motors, while the left and right rear travel motors remain braked. The steering expansion pump supplies oil to the rod chambers of the left and right front steering cylinders, and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly. When the tire reaches the set angle of the controller assembly, the steering cylinder stops supplying oil, electromagnets Y2 and Y4 are energized, the electromagnet of the travel pump is de-energized, and the two oil ports of the front travel motor are connected in the travel control valve, allowing the front travel motor to rotate freely. The steering expansion pump supplies oil to the rod chambers of the left and right front expansion cylinders, and the aforementioned expansion cylinders begin to retract. The expansion angle sensor monitors the angles of the left and right front outriggers in real time until they reach the set value of the controller assembly. When the axle extension angle reaches the set value of the controller assembly, the steering axle extension pump stops supplying oil to the rod chambers of the left and right front axle extension cylinders, and supplies oil to the rodless chambers of the left and right front steering cylinders until the tire angle reaches the initial value. Then, electromagnets Y2, Y4, Y5, Y6, Y8, and Y9 are de-energized, completing the front axle retraction.

[0026] Beneficial Effects: This invention employs a single power unit to simultaneously drive the travel pump and the steering bridge-expanding pump. The entire machine's travel and steering bridge-expanding operations utilize two independent hydraulic control systems. This allows for bridge-expanding operations while ensuring overall machine performance; specifically, the travel motor drives the wheels to rotate during obstacle-crossing bridge-expanding, enhancing obstacle-crossing capability. It solves the problem of enabling bridge-expanding operations on large-scale aerial work platforms in confined spaces. The on-site bridge-expanding control method reduces tire wear and extends tire lifespan, while also reducing stress on the bridge-expanding outriggers, allowing for smaller cylinder sizes and lower operating costs. Furthermore, the improved control method for the travel system reduces pressure loss in the closed system, thereby enhancing the overall machine's performance. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 This is a hydraulic schematic diagram of the present invention; Figure 2 This is a schematic diagram of the structure of the present invention; Figure 3 This is a hydraulic schematic diagram of the traveling pump of the present invention; Figure 4 This is a hydraulic schematic diagram of the walking hydraulic system of the present invention; Figure 5 This is the electrical control schematic diagram of the present invention; Figure 6 This is a schematic diagram of the front axle structure in the steering state of the present invention; Figure 7 This is a schematic diagram of the rear axle structure in the steering state of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0031] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0032] like Figure 1 , 2 As shown in Figure 5, a chassis control system for an aerial work platform includes a powertrain 1, a travel hydraulic system 2, a steering and bridge expansion hydraulic system 3, a controller assembly 4, and a chassis assembly 5. The powertrain 1 provides high-pressure hydraulic fluid to the travel hydraulic system 2 and the steering and bridge expansion hydraulic system 3, respectively. The controller assembly 4 is connected to the travel hydraulic system 2 and the steering and bridge expansion hydraulic system 3 by signals. The travel hydraulic system 2 and the steering and bridge expansion hydraulic system 3 are mounted on the chassis assembly 5 and drive the actuators of the chassis assembly 5 to work. The powertrain 1 includes a power unit 11, a travel pump and a steering expansion pump 12, and the power output end of the power unit 11 is simultaneously connected to the travel pump and the steering expansion pump 12. The walking hydraulic system 2 includes a walking control valve 21, a left front walking motor 22, a left rear walking motor 23, a right front walking motor 24, and a right rear walking motor 25. The walking pump drives the left front walking motor 22 and the left rear walking motor 23 on the left side and the right front walking motor 24 and the right rear walking motor 25 on the right side simultaneously through the walking control valve 21. The steering bridge expansion hydraulic system 3 includes a steering bridge expansion control valve 31, a left front steering cylinder 32, a left front expansion cylinder 33, a left rear steering cylinder 34, a left rear expansion cylinder 35, a right front steering cylinder 36, a right front expansion cylinder 37, a right rear steering cylinder 38, and a right rear expansion cylinder 39; the steering bridge expansion pump 12 controls the extension and retraction of the left front steering cylinder 32, the left front expansion cylinder 33, the left rear steering cylinder 34, the left rear expansion cylinder 35, the right front steering cylinder 36, the right front expansion cylinder 37, the right rear steering cylinder 38, and the right rear expansion cylinder 39 respectively through the steering bridge expansion control valve 31; The controller assembly 4 is connected to the travel control valve 21 and the steering bridge control valve 31 via signals, respectively. The drive chassis assembly 5 includes a frame assembly 51, a left front support leg 52, a left front steering link 53, a left rear support leg 54, a left rear steering link 55, a right front support leg 56, a right front steering link 57, a right rear support leg 58, and a right rear steering link 59; the left front support leg 52, the left rear support leg 54, the right front support leg 56, and the right rear support leg 58 are respectively hinged to the frame assembly 51; A left front travel motor 22 is oscillatingly mounted at the end of the left front outrigger 52. The left front steering cylinder 32 drives the left front travel motor 22 to oscillate relative to the left front outrigger 52 through the left front steering linkage 53. The left front axle expansion cylinder 33 is installed between the left front outrigger 52 and the frame assembly 51 to drive the left front outrigger 52 to rotate relative to the frame assembly 51. The left rear support leg 54 is equipped with a left rear travel motor 23 that can swing at the end. The left rear steering cylinder 34 drives the left rear travel motor 23 to swing relative to the left rear support leg 54 through the left rear steering linkage 55. The left rear expansion cylinder 35 is installed between the left rear support leg 54 and the frame assembly 51 to drive the left rear support leg 54 to rotate relative to the frame assembly 51. The right front support leg 56 is equipped with a right front travel motor 24 that can be oscillating at its end. The right front steering cylinder 36 drives the right front travel motor 24 to oscillate relative to the right front support leg 56 through the right front steering linkage 57. The right front expansion cylinder 37 is installed between the right front support leg 56 and the frame assembly 51 to drive the right front support leg 56 to rotate relative to the frame assembly 51. The right rear support leg 58 is equipped with a right rear travel motor 25 that can swing at its end. The right rear steering cylinder 38 drives the right rear travel motor 25 to swing relative to the right rear support leg 58 through the right rear steering linkage 59. The right rear expansion cylinder 39 is installed between the right rear support leg 58 and the frame assembly 51 to drive the right rear support leg 58 to rotate relative to the frame assembly 51.

[0033] This invention employs a single power unit 11 to simultaneously drive the travel pump and the steering bridge widening pump 12. The entire machine's travel and steering bridge widening utilize two independent hydraulic control systems. This allows for assisting in bridge widening while ensuring overall machine performance; specifically, when encountering obstacles and widening the bridge, the travel motor drives the wheels to rotate, improving obstacle-crossing capability.

[0034] The walking hydraulic system 2 adopts a hydrostatic transmission system that is lighter, smaller, more compact, and has a higher average working efficiency for the same power. The steering bridge expansion hydraulic system 3 adopts a mature and common open hydraulic system. It can realize the rotation of the walking motor under the drive of the walking pump and assist in driving the bridge expansion, reducing the pressure value of the bridge expansion cylinder and reducing the cost of the whole machine. At the same time, it adds a stationary bridge expansion function selection module, which reduces the pressure loss of the closed hydraulic system, thereby improving the driving performance of the whole machine.

[0035] like Figure 1 As shown, in order to further reduce energy consumption and facilitate the control of the whole machine, the walking pump includes a left walking pump 13 and a right walking pump 14, and the power output end of the power unit 11 is connected to both the left walking pump 13 and the right walking pump 14. The left-side travel pump 13 drives the left front travel motor 22 and the left rear travel motor 23 respectively through the travel control valve 21; the right-side travel pump 14 drives the right front travel motor 24 and the right rear travel motor 25 respectively through the travel control valve 21.

[0036] The travel pump uses two pumps, left travel pump 13 and right travel pump 14, to form two relatively independent hydrostatic transmission systems. This can avoid pressure loss caused by large flow at the travel control valve 21, further saving energy consumption, and also facilitating precise control of the motors on both sides.

[0037] like Figure 3 As shown, in order to precisely control the two hydrostatic walking systems, the left walking pump 13 includes a left walking pump solenoid control valve 131, which is a three-position four-way solenoid valve. Electromagnets Y10 and Y11, which are signal-connected to the controller assembly 4, are respectively provided on both sides of the left walking pump solenoid control valve 131. When neither electromagnet Y10 nor electromagnet Y11 is energized, the left walking pump solenoid control valve 131 is in the neutral position and the flow rate of the left walking pump 13 is zero. When either electromagnet Y10 or electromagnet Y11 is energized, the left walking pump 13 begins to supply oil, and when either electromagnet Y10 or electromagnet Y11 is energized, the direction of oil supply by the left walking pump 13 is opposite. The right-side travel pump 14 includes a right-side travel pump solenoid control valve 141, which is a three-position four-way solenoid valve. Electromagnets Y12 and Y13, which are signal-connected to the controller assembly 4, are respectively located on both sides of the right-side travel pump solenoid control valve 141. When neither electromagnet Y12 nor electromagnet Y13 is energized, the right-side travel pump solenoid control valve 141 is in the neutral position, and the flow rate of the right-side travel pump 14 is zero. When either electromagnet Y12 or electromagnet Y13 is energized, the right-side travel pump 14 begins to supply oil, and when either electromagnet Y12 or electromagnet Y13 is energized, the direction of oil supply by the right-side travel pump 14 is opposite.

[0038] The controller assembly 4 controls the oil flow direction of the left travel pump 13 via electromagnets Y10 and Y11 of the left travel pump solenoid control valve 131, thereby controlling the steering of the left wheels; simultaneously, it controls the oil flow direction of the right travel pump 14 via electromagnets Y12 and Y13 of the right travel pump solenoid control valve 141, thereby controlling the steering of the right wheels. When the flow direction and flow rate are the same on both sides, the wheels on both sides turn and rotate at the same speed, achieving straight forward and backward movement of the vehicle; when the two flow rates are different, the wheels on both sides rotate at different speeds, achieving the vehicle to slide and turn towards the side with the slower speed; when the flow directions are opposite on both sides but the flow rates are the same, the wheels on both sides turn in opposite directions but rotate at the same speed, achieving the vehicle to turn in place.

[0039] like Figure 4 As shown, in order to improve the overall walking efficiency and climbing ability of the machine, the walking control valve 21 includes a left rear two-position two-way bidirectional shut-off solenoid valve 211, a left front two-position two-way bidirectional shut-off solenoid valve 212, a right rear two-position two-way bidirectional shut-off solenoid valve 213, a right front two-position two-way bidirectional shut-off solenoid valve 214, a left diversion and combination valve 215, and a right diversion and combination valve 216. The left rear two-position two-way bidirectional shut-off solenoid valve 211 is located in the oil line between the left travel pump 13 and the left rear travel motor 23. The electromagnet Y1 of the left rear two-position two-way bidirectional shut-off solenoid valve 211 is connected to the controller assembly 4 via signal. The left front two-way bidirectional shut-off solenoid valve 212 is located in the oil line between the left travel pump 13 and the left front travel motor 22. The electromagnet Y2 of the left front two-way bidirectional shut-off solenoid valve 212 is connected to the controller assembly 4 via signal. The right rear two-way two-position bidirectional shut-off solenoid valve 213 is located in the oil line between the left travel pump 13 and the right rear travel motor 25. The electromagnet Y3 of the right rear two-way two-position bidirectional shut-off solenoid valve 213 is connected to the controller assembly 4 via signal. The right front two-way bidirectional shut-off solenoid valve 214 is located in the oil line between the left travel pump 13 and the right front travel motor 24. The electromagnet Y4 of the right front two-way bidirectional shut-off solenoid valve 214 is connected to the controller assembly 4. The left-side diversion and combination valve 215 is connected in parallel to the oil ports at both ends of the left rear two-way bidirectional shut-off solenoid valve 211 and the left front two-way bidirectional shut-off solenoid valve 212. The right-side diverter valve 216 is connected in parallel to the two oil ports of the right rear two-way bidirectional shut-off solenoid valve 213 and the right front two-way bidirectional shut-off solenoid valve 214.

[0040] The machine has two travel modes: "flat ground mode" and "climbing mode". When the machine is in "climbing mode", electromagnets Y1, Y2, Y3 and Y4 are de-energized. At this time, the oil is evenly distributed to the travel motors on both sides through the left diversion and collection valve 215 and the right diversion and collection valve 216, thereby achieving uniform flow distribution and improving the driving force of the machine.

[0041] When the machine is in "flat ground" mode, electromagnets Y1, Y2, Y3 and Y4 are all energized. The oil bypasses the left diversion valve 215 and the right diversion valve 216 and enters the travel motor directly through the solenoid valve, reducing pressure loss and improving energy efficiency.

[0042] like Figure 1 and 4 As shown, in order to further improve the working efficiency of the travel motors, the left front travel motor 22, left rear travel motor 23, right front travel motor 24, and right rear travel motor 25 are all variable displacement motors. The aforementioned travel motor control oil circuit is equipped with an electromagnetic reversing valve 217, which is equipped with an electromagnet Y9 that is signal-connected to the controller assembly 4; the travel pump provides control oil that is connected to the travel motor control oil circuit and oil tank through the electromagnetic reversing valve 217, and controls the displacement of the travel motor through the electromagnetic reversing valve 217.

[0043] When high torque and low speed are required, the controller assembly 4 controls the electromagnetic reversing valve 217 through the electromagnet Y9 to control the displacement of the travel motor; at the same time, it can also achieve the switching of low torque and high speed.

[0044] In order to achieve separate control of the front and rear travel motors, hydraulic brakes are respectively provided on the left front travel motor 22, the left rear travel motor 23, the right front travel motor 24 and the right rear travel motor 25; The control oil circuit of the hydraulic brake on the left rear travel motor 23 and the right rear travel motor 25 is provided with a rear brake solenoid control valve 218, and the rear brake solenoid control valve 218 is provided with an electromagnet Y7 that is signal-connected to the controller assembly 4. The control oil circuit of the hydraulic brake on the left front travel motor 22 and the right front travel motor 24 is provided with a front brake solenoid control valve 219, and the front brake solenoid control valve 219 is provided with an electromagnet Y8 that is signal-connected to the controller assembly 4. The travel pump provides control oil that is connected to the hydraulic brake of the travel motor via the rear brake solenoid control valve 218 and the front brake solenoid control valve 219. The controller assembly 4 controls the hydraulic brake of the rear travel motor and the hydraulic brake of the front travel motor respectively via electromagnets Y7 and Y8.

[0045] When it is necessary to control the front travel motor or the rear travel motor separately, the controller assembly 4 controls the rear brake solenoid control valve 218 or the front brake solenoid control valve 219 through electromagnet Y7 or electromagnet Y8 to release the brake of the corresponding front travel motor or the rear travel motor, thereby realizing the separate control of the front and rear travel motors.

[0046] In order to enable the free rotation of the four wheels and facilitate the expansion cylinder to expand the bridge in place, the travel control valve 21 is equipped with a left oil circuit bidirectional shut-off solenoid valve 132 that connects to the oil inlet and outlet of the left travel pump 13 and a right oil circuit bidirectional shut-off solenoid valve 142 that connects to the oil inlet and outlet of the right travel pump 14. The left-side oil circuit bidirectional shut-off solenoid valve 132 is equipped with an electromagnet Y5 that is signal-connected to the controller assembly 4. The right-side oil circuit bidirectional shut-off solenoid valve 142 is equipped with an electromagnet Y6 that is signal-connected to the controller assembly 4.

[0047] When controller assembly 4 energizes electromagnet Y5, the left-side bidirectional shut-off solenoid valve 132 connects the oil passage between the inlet and outlet of the left travel pump 13, and simultaneously connects the oil passage between the inlet and outlet of the left motor. High-pressure oil no longer enters the left motor, and the left motor can rotate freely. Similarly, when controller assembly 4 energizes electromagnet Y6, the right-side bidirectional shut-off solenoid valve 142 connects the oil passage between the inlet and outlet of the right travel pump 14 and the right motor. High-pressure oil no longer enters the right motor, and the right motor can rotate freely.

[0048] To reduce travel pressure shock, an inlet throttle valve 133 is installed between the pipes connecting the inlets of the left travel pump 13 and the right travel pump 14 within the travel control valve 21; a return throttle valve 143 is installed between the pipes connecting the return ports of the left travel pump 13 and the right travel pump 14 within the travel control valve 21. The inlet throttle valve 133 and the return throttle valve 143 can connect two independent closed hydraulic systems, thereby achieving pressure exchange and reducing travel pressure shock.

[0049] like Figure 1-7 As shown, a control method for a chassis control system of an aerial work platform is described. The overall walking hydraulic system 2 adopts hydrostatic drive and is mainly configured with two walking pumps controlling four walking motors. Specifically, the left walking pump 13 drives the two motors on the left side, and the right walking pump 14 drives the two walking motors on the right side.

[0050] The control methods include driving mode control method and bridge expansion mode control method. The driving mode control method includes flat ground driving mode, hill climbing driving mode and turning driving mode. In walking mode, electromagnets Y5 and Y6 are de-energized, while electromagnets Y7 and Y8 are energized. Flat ground driving mode: The controller assembly 4 controls electromagnets Y1, Y2, Y3 and Y4 to be energized, and electromagnet Y9 to be energized. The oil bypasses the left diversion and combination valve 215 and the right diversion and combination valve 216 and directly enters the four travel motors through the left rear two-position two-way bidirectional cut-off solenoid valve 211, the left front two-position two-way bidirectional cut-off solenoid valve 212, the right rear two-position two-way bidirectional cut-off solenoid valve 213 and the right front two-position two-way bidirectional cut-off solenoid valve 214; reducing pressure loss and improving energy utilization efficiency.

[0051] Hill Climbing Mode: The controller assembly 4 controls electromagnets Y1, Y2, Y3 and Y4 to be de-energized, and electromagnet Y9 to be de-energized. The oil is then evenly distributed to the travel motors on both sides through the left diversion and combination valve 215 and the right diversion and combination valve 216, thereby achieving uniform flow distribution and improving the overall driving force of the machine.

[0052] Steering driving mode: The machine has four steering modes. When the steering mode is switched to "front wheel steering" or "all wheel steering", the left front wheel is the active steering angle detection wheel, and the other three tires are the steering angle following wheels. When the tire angle sensor detects that the tire angle is within the range... , Within the range, the displacement of the two walking pumps is the same, ensuring that the flow of the motors on the left and right sides is the same. The control controller assembly 4 controls the machine to move forward or backward, and the walking flow of the walking systems on both sides is the same.

[0053] When the tire angle sensor detects the tire angle at < Range, if active steering tire angle is defined When the machine is in the left-turn zone, if it is in the driving zone, the displacement of the left driving pump 13 is reduced while the displacement of the right driving pump 14 remains unchanged. The differential speed of the machine's left-turn driving is achieved through the mutual flow coupling of the two pumps.

[0054] When the tire angle sensor detects the tire angle at < Range, if active steering tire angle is defined < When the machine is in the right turn zone, if it is in the driving zone, the displacement of the left driving pump 13 is kept constant, while the displacement of the right driving pump 14 is reduced. The differential speed of the whole machine is achieved by coupling the flow of the two pumps to make a right turn.

[0055] When the steering mode is switched to "rear wheel steering" or "crab steering," the left rear wheel becomes the active steering angle detection wheel, while the other three tires act as steering angle following wheels. When the tire angle sensor detects that the tire angle is within a certain range... , Within this range, the displacement control of the two walking pumps is the same, ensuring that the flow of the motors on the left and right sides is the same. The operation controller assembly 4 controls the machine to move forward or backward, and the walking flow of the walking systems on both sides is roughly the same.

[0056] When the tire angle sensor detects the tire angle at The range, if the active steering tire angle is defined as < When the machine is in the left-turn zone, if it is in the driving zone, the displacement of the left driving pump 13 is reduced while the displacement of the right driving pump 14 remains unchanged. The differential speed of the machine's left-turn driving is achieved through the mutual flow coupling of the two pumps.

[0057] When the tire angle sensor detects that the tire angle is < Range, if active steering tire angle is defined When the machine is in the right turn zone, if it is in the driving zone, the displacement of the left driving pump 13 is kept constant, while the displacement of the right driving pump 14 is reduced. The differential speed of the whole machine is achieved by coupling the flow of the two pumps to make a right turn.

[0058] To adapt to different road conditions, the bridge expansion mode control method includes an obstacle-crossing bridge expansion mode and a flat-ground bridge expansion mode. In the obstacle crossing and bridge expansion mode, neither the electromagnet Y5 of the left-side oil circuit bidirectional shut-off solenoid valve 132 nor the electromagnet Y6 of the right-side oil circuit bidirectional shut-off solenoid valve 142 should be energized. The specific method is as follows: Step 1: Front axle expansion. The controller assembly 4 controls the front brake solenoid control valve 219 solenoid Y8 to be energized, while the rear brake solenoid control valve 218 solenoid Y7 is de-energized, releasing the brakes of the left front travel motor 22 and the right front travel motor 24, while the left rear travel motor 23 and the right rear travel motor 25 remain braked. The steering expansion pump 12 supplies oil to the rod chambers of the left front steering cylinder 32 and the right front steering cylinder 36. The aforementioned steering cylinders begin to retract, and the steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly 4. When the tire reaches the set angle of the controller assembly 4, the steering cylinder stops supplying oil, the solenoid Y9 of the solenoid reversing valve 217 is energized, and at the same time the solenoid Y11 of the left travel pump 13 and the solenoid Y12 of the right travel pump 14 are energized. The left travel pump 13 supplies oil to the left front travel motor 22, the right travel pump 14 supplies oil to the right front travel motor 24, and the steering expansion pump 12 supplies oil to the rodless chamber of the left front expansion cylinder 33 and the right front expansion cylinder 37. The aforementioned expansion cylinders begin to extend, and the expansion angle sensor monitors the angle of the left front outrigger 52 and the right front outrigger 56 in real time until the set value of the controller assembly 4 is reached. When the bridge expansion angle reaches the set value angle of the controller assembly 4, the electromagnet Y9 of the electromagnetic reversing valve 217 is de-energized, and at the same time, the electromagnet Y11 of the left travel pump 13 and the electromagnet Y12 of the right travel pump 14 are de-energized, and the travel pump stops supplying oil to the travel motor; the steering bridge expansion pump 12 stops supplying oil to the rodless chamber of the left front bridge expansion cylinder 33 and the right front bridge expansion cylinder 37, and the steering bridge expansion pump 12 supplies oil to the rodless chamber of the left front steering cylinder 32 and the right front steering cylinder 36 until the tire angle reaches the initial value. Finally, the electromagnet Y8 of the front brake electromagnetic control valve 219 is de-energized, and the front axle expansion is completed. Step 2: Rear axle expansion. The controller assembly 4 controls the rear brake solenoid control valve 218 solenoid Y7 to be energized, while the front brake solenoid control valve 219 solenoid Y8 is de-energized, releasing the brakes of the left rear travel motor 23 and the right rear travel motor 25, while keeping the left front travel motor 22 and the right front travel motor 24 braked. The steering expansion pump 12 supplies oil to the rod chambers of the left rear steering cylinder 34 and the right rear steering cylinder 38. The aforementioned steering cylinders begin to retract, and the steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly 4. When the tire reaches the set angle of the controller assembly 4, the steering cylinder stops supplying oil, the solenoid Y9 of the solenoid reversing valve 217 is energized, and at the same time the solenoid Y10 of the left travel pump 13 and the solenoid Y13 of the right travel pump 14 are energized. The left travel pump 13 supplies oil to the left rear travel motor 23, the right travel pump 14 supplies oil to the right rear travel motor 25, and the steering expansion pump 12 supplies oil to the rodless chamber of the left rear expansion cylinder 35 and the right rear expansion cylinder 39. The aforementioned expansion cylinders begin to extend, and the expansion angle sensor monitors the angle of the left rear outrigger 54 and the right rear outrigger 58 in real time until the set value of the controller assembly 4 is reached. When the bridge expansion angle reaches the set value angle of the controller assembly 4, the solenoid Y9 of the solenoid reversing valve 217 is de-energized. At the same time, the solenoid Y10 of the left travel pump 13 and the solenoid Y13 of the right travel pump 14 are de-energized, and the travel pumps stop supplying oil to the travel motors. The steering bridge expansion pump 12 stops supplying oil to the rodless chambers of the left rear bridge expansion cylinder 35 and the right rear bridge expansion cylinder 39, and the steering bridge expansion pump 12 supplies oil to the rodless chambers of the left rear steering cylinder 34 and the right rear steering cylinder 38 until the tire angle reaches the initial value. Finally, the solenoid Y7 of the rear brake solenoid control valve 218 is de-energized, and the bridge expansion is completed. Step 3: Rear axle retraction. The controller assembly 4 controls the rear brake solenoid control valve 218 solenoid Y7 to be energized, while the front brake solenoid control valve 219 solenoid Y8 is de-energized, releasing the brakes of the left rear travel motor 23 and the right rear travel motor 25, while keeping the left front travel motor 22 and the right front travel motor 24 braked. The steering expansion pump 12 supplies oil to the rod chambers of the left rear steering cylinder 34 and the right rear steering cylinder 38. The aforementioned steering cylinders begin to retract, and the steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly 4. When the tire reaches the set angle of the controller assembly 4, the steering cylinder stops supplying oil, the solenoid Y9 of the solenoid reversing valve 217 is energized, and at the same time the solenoid Y11 of the left travel pump 13 and the solenoid Y12 of the right travel pump 14 are energized. The left travel pump 13 supplies oil to the left rear travel motor 23, the right travel pump 14 supplies oil to the right rear travel motor 25, and the steering expansion pump 12 supplies oil to the rod chamber of the left rear expansion cylinder 35 and the right rear expansion cylinder 39. The above expansion cylinders begin to retract, and the expansion angle sensor monitors the angle of the left rear outrigger 54 and the right rear outrigger 58 in real time until the set value of the controller assembly 4 is reached. When the bridge expansion angle reaches the set value angle of the controller assembly 4, the electromagnet Y9 of the electromagnetic reversing valve 217 is de-energized, and at the same time, the electromagnet Y11 of the left travel pump 13 and the electromagnet Y12 of the right travel pump 14 are de-energized, and the travel pumps stop supplying oil to the travel motors; the steering bridge expansion pump 12 stops supplying oil to the rod chambers of the left rear bridge expansion cylinder 35 and the right rear bridge expansion cylinder 39, and the steering bridge expansion pump 12 supplies oil to the rodless chambers of the left rear steering cylinder 34 and the right rear steering cylinder 38 until the tire angle reaches the initial value. Finally, the electromagnet Y7 of the rear brake electromagnetic control valve 218 is de-energized, and the rear axle retracts. Step 4: The front axle retracts, and the controller assembly 4 controls the electromagnet Y8 of the front brake solenoid control valve 219 to be energized, while the electromagnet Y7 of the rear brake solenoid control valve 218 is de-energized, releasing the brakes of the left front travel motor 22 and the right front travel motor 24, while the left rear travel motor 23 and the right rear travel motor 25 remain braked. The steering expansion pump 12 supplies oil to the rod chambers of the left front steering cylinder 32 and the right front steering cylinder 36. The aforementioned steering cylinders begin to retract, and the steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly 4. When the tire reaches the set angle of the controller assembly 4, the steering cylinder stops supplying oil, the solenoid Y9 of the solenoid reversing valve 217 is energized, and at the same time the solenoid Y10 of the left travel pump 13 and the solenoid Y13 of the right travel pump 14 are energized. The left travel pump 13 supplies oil to the left front travel motor 22, the right travel pump 14 supplies oil to the right front travel motor 24, and the steering expansion pump 12 supplies oil to the rod chamber of the left front expansion cylinder 33 and the right front expansion cylinder 37. The above expansion cylinders begin to retract, and the expansion angle sensor monitors the angle of the left front outrigger 52 and the right front outrigger 56 in real time until the set value of the controller assembly 4 is reached. When the bridge expansion angle reaches the set value angle of the controller assembly 4, the electromagnet Y9 of the electromagnetic reversing valve 217 is de-energized, and at the same time, the electromagnet Y10 of the left travel pump 13 and the electromagnet Y13 of the right travel pump 14 are de-energized, and the travel pump stops supplying oil to the travel motor; the steering bridge expansion pump 12 stops supplying oil to the rod chamber of the left front bridge expansion cylinder 33 and the right front bridge expansion cylinder 37, and the steering bridge expansion pump 12 supplies oil to the rodless chamber of the left front steering cylinder 32 and the right front steering cylinder 36 until the tire angle reaches the initial value. Finally, the electromagnet Y8 of the front brake electromagnetic control valve 219 is de-energized, and the front axle retraction is completed. In the flat ground bridge expansion mode, during the bridge expansion and retraction process, the electromagnet Y5 of the left oil circuit bidirectional shut-off solenoid valve 132 and the electromagnet Y6 of the right oil circuit bidirectional shut-off solenoid valve 142 are energized, and at the same time, the electromagnet Y9 of the solenoid reversing valve 217 is energized. The travel motor has a small displacement and is easy to rotate. The specific method is as follows: Step 1: Front axle expansion. The controller assembly 4 controls the front brake solenoid control valve 219 solenoid Y8 to be energized, while the rear brake solenoid control valve 218 solenoid Y7 is de-energized, releasing the brakes of the left front travel motor 22 and the right front travel motor 24, while the left rear travel motor 23 and the right rear travel motor 25 remain braked. The steering expansion pump 12 supplies oil to the rod chambers of the left front steering cylinder 32 and the right front steering cylinder 36. The aforementioned steering cylinders begin to retract, and the steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly 4. When the tire reaches the set angle of the controller assembly 4, the steering cylinder stops supplying oil, the solenoid Y2 of the left front two-position two-way bidirectional shut-off solenoid valve 212 and the solenoid Y4 of the right front two-position two-way bidirectional shut-off solenoid valve 214 are energized, the solenoid of the travel pump is not energized, the front travel motor achieves two oil port connection in the travel control valve 21, and the front travel motor can rotate freely. Steering expansion pump 12 supplies oil to the rodless chambers of left front expansion cylinder 33 and right front expansion cylinder 37. The aforementioned expansion cylinders begin to extend. Expansion angle sensor monitors the angles of left front outrigger 52 and right front outrigger 56 in real time until they reach the set value of controller assembly 4. When the bridge expansion angle reaches the set value angle of the controller assembly 4, the steering bridge expansion pump 12 stops supplying oil to the rodless chamber of the left front bridge expansion cylinder 33 and the right front bridge expansion cylinder 37, and the steering bridge expansion pump 12 supplies oil to the rodless chamber of the left front steering cylinder 32 and the right front steering cylinder 36 until the tire angle reaches the initial value. The electromagnet Y2 of the left front two-position two-way bidirectional shut-off solenoid valve 212 and the electromagnet Y4 of the right front two-position two-way bidirectional shut-off solenoid valve 214 are de-energized, and the electromagnet Y8 of the front brake solenoid control valve 219 is de-energized, thus completing the front axle expansion. Step 2: Rear axle expansion. The controller assembly 4 controls the rear brake solenoid control valve 218 solenoid Y7 to be energized, while the front brake solenoid control valve 219 solenoid Y8 is de-energized, releasing the brakes of the left rear travel motor 23 and the right rear travel motor 25, while keeping the left front travel motor 22 and the right front travel motor 24 braked. The steering expansion pump 12 supplies oil to the rod chambers of the left rear steering cylinder 34 and the right rear steering cylinder 38. The aforementioned steering cylinders begin to retract, and the steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly 4. When the tire reaches the set angle of the controller assembly 4, the steering cylinder stops supplying oil, the solenoid Y1 of the left rear two-position two-way bidirectional shut-off solenoid valve 211 and the solenoid Y3 of the right rear two-position two-way bidirectional shut-off solenoid valve 213 are energized, the solenoid of the travel pump is not energized, the rear travel motor achieves two oil port connection in the travel control valve 21, and the rear travel motor can rotate freely. Steering expansion pump 12 supplies oil to the rodless chambers of left rear expansion cylinder 35 and right rear expansion cylinder 39. The aforementioned expansion cylinders begin to extend. Expansion angle sensor monitors the angles of left rear outrigger 54 and right rear outrigger 58 in real time until they reach the set value of controller assembly 4. When the bridge expansion angle reaches the set value angle of the controller assembly 4, the steering bridge expansion pump 12 stops supplying oil to the rodless chambers of the left rear bridge expansion cylinder 35 and the right rear bridge expansion cylinder 39, and the steering bridge expansion pump 12 supplies oil to the rodless chambers of the left rear steering cylinder 34 and the right rear steering cylinder 38 until the tire angle reaches the initial value. Then, electromagnets Y1, Y3, Y5, Y6 and Y7 are de-energized, and the bridge expansion is completed. Step 3: Rear axle retraction. The controller assembly 4 controls the rear brake solenoid control valve 218 solenoid Y7 to be energized, while the front brake solenoid control valve 219 solenoid Y8 is de-energized, releasing the brakes of the left rear travel motor 23 and the right rear travel motor 25, while keeping the left front travel motor 22 and the right front travel motor 24 braked. The steering expansion pump 12 supplies oil to the rod chambers of the left rear steering cylinder 34 and the right rear steering cylinder 38. The aforementioned steering cylinders begin to retract, and the steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly 4. When the tire reaches the set angle of the controller assembly 4, the steering cylinder stops supplying oil, electromagnets Y1 and Y3 are energized, the electromagnet of the travel pump is de-energized, and the two oil ports of the rear travel motor are connected in the travel control valve 21, allowing the rear travel motor to rotate freely. Steering expansion pump 12 supplies oil to the rod chambers of left rear expansion cylinder 35 and right rear expansion cylinder 39. The aforementioned expansion cylinders begin to retract. Expansion angle sensor monitors the angles of left rear outrigger 54 and right rear outrigger 58 in real time until they reach the set value of controller assembly 4. When the bridge expansion angle reaches the set value angle of the controller assembly 4, the steering bridge expansion pump 12 stops supplying oil to the rod chambers of the left rear bridge expansion cylinder 35 and the right rear bridge expansion cylinder 39, and the steering bridge expansion pump 12 supplies oil to the rodless chambers of the left rear steering cylinder 34 and the right rear steering cylinder 38 until the tire angle reaches the initial value. Electromagnets Y1, Y3, Y5, Y6 and Y7 are de-energized, and the rear axle is retracted. Step 4: The front axle retracts, and the controller assembly 4 controls the electromagnet Y8 of the front brake solenoid control valve 219 to be energized, while the electromagnet Y7 of the rear brake solenoid control valve 218 is de-energized, releasing the brakes of the left front travel motor 22 and the right front travel motor 24, while the left rear travel motor 23 and the right rear travel motor 25 remain braked. The steering expansion pump 12 supplies oil to the rod chambers of the left front steering cylinder 32 and the right front steering cylinder 36. The aforementioned steering cylinders begin to retract, and the steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly 4. When the tire reaches the set angle of the controller assembly 4, the steering cylinder stops supplying oil, electromagnets Y2 and Y4 are energized, the electromagnet of the travel pump is de-energized, the front travel motor achieves two oil port connection in the travel control valve 21, and the front travel motor can rotate freely. Steering expansion pump 12 supplies oil to the rod chambers of left front expansion cylinder 33 and right front expansion cylinder 37. The aforementioned expansion cylinders begin to retract. Expansion angle sensor monitors the angles of left front outrigger 52 and right front outrigger 56 in real time until they reach the set value of controller assembly 4. When the bridge expansion angle reaches the set value angle of the controller assembly 4, the steering bridge expansion pump 12 stops supplying oil to the rod chambers of the left front bridge expansion cylinder 33 and the right front bridge expansion cylinder 37, and the steering bridge expansion pump 12 supplies oil to the rodless chambers of the left front steering cylinder 32 and the right front steering cylinder 36 until the tire angle reaches the initial value. Then, electromagnets Y2, Y4, Y5, Y6, Y8 and Y9 are de-energized, and the front axle retraction is completed.

[0059] The controller assembly 4 can be equipped with a human or AI recognition module. When the chassis is uneven, the obstacle crossing and bridge expansion mode can be selected, and when the ground is flat, the flat ground and bridge expansion mode can be selected.

[0060] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0061] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A chassis control system for an aerial work platform, comprising a powertrain (1), a travel hydraulic system (2), a steering and axle expansion hydraulic system (3), a controller assembly (4), and a chassis assembly (5), wherein the powertrain (1) provides high-pressure hydraulic fluid to the travel hydraulic system (2) and the steering and axle expansion hydraulic system (3), and the controller assembly (4) is signal-connected to the travel hydraulic system (2) and the steering and axle expansion hydraulic system (3), respectively; the travel hydraulic system (2) and the steering and axle expansion hydraulic system (3) are mounted on the chassis assembly (5) and drive the actuators of the chassis assembly (5); characterized in that: The powertrain (1) includes a power unit (11), a travel pump and a steering expansion pump (12), and the power output end of the power unit (11) is simultaneously connected to the travel pump and the steering expansion pump (12). The walking hydraulic system (2) includes a walking control valve (21), a left front walking motor (22), a left rear walking motor (23), a right front walking motor (24), and a right rear walking motor (25). The walking pump drives the left front walking motor (22) and the left rear walking motor (23) on the left side and the right front walking motor (24) and the right rear walking motor (25) on the right side simultaneously through the walking control valve (21). The steering bridge expansion hydraulic system (3) includes a steering bridge expansion control valve (31), a left front steering cylinder (32), a left front expansion cylinder (33), a left rear steering cylinder (34), a left rear expansion cylinder (35), a right front steering cylinder (36), a right front expansion cylinder (37), a right rear steering cylinder (38), and a right rear expansion cylinder (39); the steering bridge expansion pump (12) controls the extension and retraction of the left front steering cylinder (32), the left front expansion cylinder (33), the left rear steering cylinder (34), the left rear expansion cylinder (35), the right front steering cylinder (36), the right front expansion cylinder (37), the right rear steering cylinder (38), and the right rear expansion cylinder (39) respectively through the steering bridge expansion control valve (31); The controller assembly (4) is connected to the travel control valve (21) and the steering bridge control valve (31) respectively; The drive chassis assembly (5) includes a frame assembly (51), a left front support leg (52), a left front steering link (53), a left rear support leg (54), a left rear steering link (55), a right front support leg (56), a right front steering link (57), a right rear support leg (58), and a right rear steering link (59); the left front support leg (52), the left rear support leg (54), the right front support leg (56), and the right rear support leg (58) are respectively hinged to the frame assembly (51); A left front travel motor (22) is swayably mounted at the end of the left front outrigger (52). The left front steering cylinder (32) drives the left front travel motor (22) to sway relative to the left front outrigger (52) through the left front steering linkage (53). The left front expansion cylinder (33) is installed between the left front outrigger (52) and the frame assembly (51) to drive the left front outrigger (52) to rotate relative to the frame assembly (51). A left rear travel motor (23) is swayably mounted at the end of the left rear support leg (54). The left rear steering cylinder (34) drives the left rear travel motor (23) to sway relative to the left rear support leg (54) through the left rear steering linkage (55). The left rear expansion cylinder (35) is installed between the left rear support leg (54) and the frame assembly (51) to drive the left rear support leg (54) to rotate relative to the frame assembly (51). The right front support leg (56) is equipped with a right front travel motor (24) that can swing at the end. The right front steering cylinder (36) drives the right front travel motor (24) to swing relative to the right front support leg (56) through the right front steering linkage (57). The right front expansion cylinder (37) is installed between the right front support leg (56) and the frame assembly (51) to drive the right front support leg (56) to rotate relative to the frame assembly (51). The right rear outrigger (58) is equipped with a right rear travel motor (25) that can swing at the end. The right rear steering cylinder (38) drives the right rear travel motor (25) to swing relative to the right rear outrigger (58) through the right rear steering linkage (59). The right rear expansion cylinder (39) is installed between the right rear outrigger (58) and the frame assembly (51) to drive the right rear outrigger (58) to rotate relative to the frame assembly (51).

2. The aerial work platform chassis control system according to claim 1, characterized in that: The walking pump includes a left walking pump (13) and a right walking pump (14), and the power output end of the power unit (11) is simultaneously connected to the left walking pump (13) and the right walking pump (14). The left-side travel pump (13) drives the left front travel motor (22) and the left rear travel motor (23) respectively through the travel control valve (21); the right-side travel pump (14) drives the right front travel motor (24) and the right rear travel motor (25) respectively through the travel control valve (21).

3. The aerial work platform chassis control system according to claim 2, characterized in that: The left-side travel pump (13) includes a left-side travel pump solenoid control valve (131), which is a three-position four-way solenoid valve. The left-side travel pump solenoid control valve (131) is provided with electromagnets Y10 and Y11 on both sides, which are connected to the controller assembly (4) via signals. When neither electromagnet Y10 nor electromagnet Y11 is energized, the left-side travel pump solenoid control valve (131) is in the middle position and the flow rate of the left-side travel pump (13) is zero. When one of the electromagnets Y10 and Y11 is energized, the left-side travel pump (13) starts to supply oil, and when either electromagnet Y10 or electromagnet Y11 is energized, the direction of oil supply of the left-side travel pump (13) is opposite. The right-side travel pump (14) includes a right-side travel pump solenoid control valve (141), which is a three-position four-way solenoid valve. The right-side travel pump solenoid control valve (141) is provided with electromagnets Y12 and Y13 on both sides, which are connected to the controller assembly (4) via signals. When neither electromagnet Y12 nor electromagnet Y13 is energized, the right-side travel pump solenoid control valve (141) is in the middle position and the flow rate of the right-side travel pump (14) is zero. When one of the electromagnets Y12 and Y13 is energized, the right-side travel pump (14) starts to supply oil, and when either electromagnet Y12 or electromagnet Y13 is energized, the oil supply direction of the right-side travel pump (14) is opposite.

4. The aerial work platform chassis control system according to claim 2 or 3, characterized in that: The walking control valve (21) includes a left rear two-way two-position bidirectional shut-off solenoid valve (211), a left front two-way two-position bidirectional shut-off solenoid valve (212), a right rear two-way two-position bidirectional shut-off solenoid valve (213), a right front two-way two-position bidirectional shut-off solenoid valve (214), a left diversion and combination valve (215), and a right diversion and combination valve (216). The left rear two-way two-position bidirectional shut-off solenoid valve (211) is located on the oil line between the left walking pump (13) and the left rear walking motor (23). The electromagnet Y1 of the left rear two-way two-position bidirectional shut-off solenoid valve (211) is connected to the controller assembly (4) via signal. The left front two-way two-way bidirectional shut-off solenoid valve (212) is located on the oil line between the left travel pump (13) and the left front travel motor (22). The electromagnet Y2 of the left front two-way two-way bidirectional shut-off solenoid valve (212) is connected to the controller assembly (4) by signal. The right rear two-way two-position bidirectional shut-off solenoid valve (213) is located on the oil line between the left walking pump (13) and the right rear walking motor (25). The electromagnet Y3 of the right rear two-way two-position bidirectional shut-off solenoid valve (213) is connected to the controller assembly (4) via signal. The right front two-way two-way bidirectional shut-off solenoid valve (214) is located on the oil line between the left travel pump (13) and the right front travel motor (24). The electromagnet Y4 of the right front two-way two-way bidirectional shut-off solenoid valve (214) is connected to the controller assembly (4) via signal. The left-side diverter valve (215) is connected in parallel to the oil ports at both ends of the left rear two-way two-position bidirectional shut-off solenoid valve (211) and the left front two-way two-position bidirectional shut-off solenoid valve (212). The right-side diverter valve (216) is connected in parallel to the oil ports at both ends of the right rear two-way two-way bidirectional shut-off solenoid valve (213) and the right front two-way two-way bidirectional shut-off solenoid valve (214).

5. The aerial work platform chassis control system according to claim 4, characterized in that: The left front travel motor (22), left rear travel motor (23), right front travel motor (24), and right rear travel motor (25) are all variable displacement motors. The control oil circuit of the aforementioned walking motor is equipped with an electromagnetic reversing valve (217), and the electromagnetic reversing valve (217) is equipped with an electromagnet Y9 that is signal-connected to the controller assembly (4); the walking pump provides control oil that is connected to the control oil circuit and oil tank of the walking motor through the electromagnetic reversing valve (217), and controls the displacement of the walking motor through the electromagnetic reversing valve (217).

6. The aerial work platform chassis control system according to claim 5, characterized in that: Hydraulic brakes are provided on the left front travel motor (22), left rear travel motor (23), right front travel motor (24) and right rear travel motor (25); The control oil circuit of the hydraulic brake on the left rear travel motor (23) and the right rear travel motor (25) is provided with a rear brake solenoid control valve (218), and the rear brake solenoid control valve (218) is provided with an electromagnet Y7 that is signal-connected to the controller assembly (4). The control oil circuit of the hydraulic brake on the left front travel motor (22) and the right front travel motor (24) is provided with a front brake solenoid control valve (219), and the front brake solenoid control valve (219) is provided with an electromagnet Y8 that is signal-connected to the controller assembly (4); The travel pump provides control oil that is connected to the control oil circuit of the hydraulic brake of the travel motor through the rear brake solenoid control valve (218) and the front brake solenoid control valve (219). The controller assembly (4) controls the hydraulic brake of the rear travel motor and the hydraulic brake of the front travel motor respectively through electromagnets Y7 and Y8.

7. The aerial work platform chassis control system according to claim 2 or 6, characterized in that: The walking control valve (21) is equipped with a left oil circuit bidirectional shut-off solenoid valve (132) that connects to the inlet and outlet of the left walking pump (13) and a right oil circuit bidirectional shut-off solenoid valve (142) that connects to the inlet and outlet of the right walking pump (14). The left-side oil circuit bidirectional shut-off solenoid valve (132) is equipped with an electromagnet Y5 that is signal-connected to the controller assembly (4); The right-side oil circuit bidirectional shut-off solenoid valve (142) is equipped with an electromagnet Y6 that is signal-connected to the controller assembly (4).

8. The aerial work platform chassis control system according to claim 2, characterized in that: An oil inlet throttle valve (133) is provided between the pipes connecting the oil inlets of the left travel pump (13) and the right travel pump (14) inside the travel control valve (21). The travel control valve (21) is equipped with a return oil throttle valve (143) between the pipes connecting the return oil ports of the left travel pump (13) and the right travel pump (14).

9. A control method for the chassis control system of an aerial work platform according to any one of claims 1-8, characterized in that: It includes a driving mode control method and a bridge expansion mode control method. The driving mode control method includes a flat ground driving mode, an uphill driving mode, and a turning driving mode. In walking mode, electromagnets Y5 and Y6 are de-energized, while electromagnets Y7 and Y8 are energized. Flat ground driving mode: The controller assembly (4) controls electromagnets Y1, Y2, Y3 and Y4 to be energized, and electromagnet Y9 to be energized. The oil does not pass through the left diversion and collection valve (215) and the right diversion and collection valve (216) but directly passes through the left rear two-way two-way bidirectional cut-off solenoid valve (211), the left front two-way two-way two-way cut-off solenoid valve (212), the right rear two-way two-way two-way cut-off solenoid valve (213) and the right front two-way two-way two-way cut-off solenoid valve (214) to enter the four travel motors; Climbing driving mode: The controller assembly (4) controls electromagnets Y1, Y2, Y3 and Y4 to lose power, and electromagnet Y9 to lose power. The oil is distributed to the walking motors on both sides through the left diversion and collection valve (215) and the right diversion and collection valve (216). Steering driving mode: First, determine the steering angle by designating one of the four wheels as the active steering angle detection wheel and the other three tires as steering angle following wheels. Set a threshold for determining the steering angle and monitor the steering angle of the active steering angle detection wheel. If the steering angle of the active steering angle detection wheel is within the set judgment steering threshold range, the displacement of the left walking pump (13) and the right walking pump (14) is the same, the flow rate of the two motors is the same, the controller assembly (4) controls the whole machine to move forward or backward, and the walking flow rate of the two walking systems is the same. If the steering angle of the active steering angle detection wheel exceeds the set steering threshold range, the steering direction is determined based on the sign of the steering angle value of the active steering angle detection wheel. When turning left, the displacement of the left-side travel pump (13) is reduced, while the displacement of the right-side travel pump (14) remains unchanged. The differential speed of the whole machine when turning left is achieved through the mutual flow coupling of the two pumps. When turning right, the displacement of the left-side travel pump (13) remains unchanged, while the displacement of the right-side travel pump (14) decreases. The differential speed of the whole machine when turning right is achieved through the mutual flow coupling of the two pumps.

10. The control method of the aerial work platform chassis control system according to claim 9, characterized in that: The bridge expansion mode control method includes obstacle-crossing bridge expansion mode and flat-ground bridge expansion mode. In the obstacle crossing and bridge expansion mode, neither the electromagnet Y5 of the left oil circuit bidirectional shut-off solenoid valve (132) nor the electromagnet Y6 of the right oil circuit bidirectional shut-off solenoid valve (142) should be energized. The specific method is as follows: Step 1: Front axle expansion, controller assembly (4) controls the electromagnet Y8 of the front brake solenoid control valve (219) to be energized, while the electromagnet Y7 of the rear brake solenoid control valve (218) is de-energized, releasing the brakes of the left front travel motor (22) and the right front travel motor (24), while the left rear travel motor (23) and the right rear travel motor (25) remain braked. The steering expansion pump (12) supplies oil to the rod chambers of the left front steering cylinder (32) and the right front steering cylinder (36), and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly (4). When the tire reaches the set angle of the controller assembly (4), the steering cylinder stops supplying oil, the electromagnet Y9 of the electromagnetic reversing valve (217) is energized, and at the same time the electromagnet Y11 of the left travel pump (13) and the electromagnet Y12 of the right travel pump (14) are energized. The left travel pump (13) supplies oil to the left front travel motor (22), the right travel pump (14) supplies oil to the right front travel motor (24), and the steering expansion pump (12) supplies oil to the rodless chamber of the left front expansion cylinder (33) and the right front expansion cylinder (37). The above expansion cylinders begin to extend, and the expansion angle sensor monitors the angle of the left front outrigger (52) and the right front outrigger (56) in real time until the set value of the controller assembly (4) is reached. When the bridge expansion angle reaches the set value angle of the controller assembly (4), the electromagnet Y9 of the electromagnetic reversing valve (217) is de-energized, and at the same time the electromagnet Y11 of the left travel pump (13) and the electromagnet Y12 of the right travel pump (14) are de-energized, and the travel pump stops supplying oil to the travel motor; the steering bridge expansion pump (12) stops supplying oil to the rodless chamber of the left front bridge expansion cylinder (33) and the right front bridge expansion cylinder (37), and the steering bridge expansion pump (12) supplies oil to the rodless chamber of the left front steering cylinder (32) and the right front steering cylinder (36) until the tire angle reaches the initial value, and finally the electromagnet Y8 of the front brake electromagnetic control valve (219) is de-energized, completing the front axle expansion; Step 2: Rear axle expansion, controller assembly (4) controls the rear brake solenoid control valve (218) solenoid Y7 to be energized, while the front brake solenoid control valve (219) solenoid Y8 is not energized, releasing the braking of the left rear travel motor (23) and the right rear travel motor (25), and keeping the left front travel motor (22) and the right front travel motor (24) braking. The steering expansion pump (12) supplies oil to the rod chambers of the left rear steering cylinder (34) and the right rear steering cylinder (38), and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly (4). When the tire reaches the set angle of the controller assembly (4), the steering cylinder stops supplying oil, the electromagnet Y9 of the electromagnetic reversing valve (217) is energized, and at the same time the electromagnet Y10 of the left travel pump (13) and the electromagnet Y13 of the right travel pump (14) are energized. The left travel pump (13) supplies oil to the left rear travel motor (23), the right travel pump (14) supplies oil to the right rear travel motor (25), and the steering expansion pump (12) supplies oil to the rodless chamber of the left rear expansion cylinder (35) and the right rear expansion cylinder (39). The above expansion cylinders begin to extend, and the expansion angle sensor monitors the angle of the left rear outrigger (54) and the right rear outrigger (58) in real time until the set value of the controller assembly (4) is reached. When the bridge expansion angle reaches the set value angle of the controller assembly (4), the electromagnet Y9 of the electromagnetic reversing valve (217) is de-energized, and at the same time the electromagnet Y10 of the left travel pump (13) and the electromagnet Y13 of the right travel pump (14) are de-energized, and the travel pump stops supplying oil to the travel motor; the steering bridge expansion pump (12) stops supplying oil to the rodless chamber of the left rear bridge expansion cylinder (35) and the right rear bridge expansion cylinder (39), and the steering bridge expansion pump (12) supplies oil to the rodless chamber of the left rear steering cylinder (34) and the right rear steering cylinder (38) until the tire angle reaches the initial value, and finally the rear brake electromagnetic control valve (218) electromagnet Y7 is de-energized, and the bridge expansion is completed; Step 3: Rear axle retraction, controller assembly (4) controls the rear brake solenoid control valve (218) solenoid Y7 to be energized, while the front brake solenoid control valve (219) solenoid Y8 is not energized, releasing the braking of the left rear travel motor (23) and the right rear travel motor (25), while keeping the left front travel motor (22) and the right front travel motor (24) braking. The steering expansion pump (12) supplies oil to the rod chambers of the left rear steering cylinder (34) and the right rear steering cylinder (38), and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly (4). When the tire reaches the set angle of the controller assembly (4), the steering cylinder stops supplying oil, the electromagnet Y9 of the electromagnetic reversing valve (217) is energized, and at the same time the electromagnet Y11 of the left travel pump (13) and the electromagnet Y12 of the right travel pump (14) are energized. The left travel pump (13) supplies oil to the left rear travel motor (23), the right travel pump (14) supplies oil to the right rear travel motor (25), and the steering expansion pump (12) supplies oil to the rod chamber of the left rear expansion cylinder (35) and the right rear expansion cylinder (39). The above expansion cylinders begin to retract, and the expansion angle sensor monitors the angle of the left rear outrigger (54) and the right rear outrigger (58) in real time until the set value of the controller assembly (4) is reached. When the bridge expansion angle reaches the set value angle of the controller assembly (4), the electromagnet Y9 of the electromagnetic reversing valve (217) is de-energized, and at the same time the electromagnet Y11 of the left travel pump (13) and the electromagnet Y12 of the right travel pump (14) are de-energized, and the travel pump stops supplying oil to the travel motor; the steering bridge expansion pump (12) stops supplying oil to the rod chamber of the left rear bridge expansion cylinder (35) and the right rear bridge expansion cylinder (39), and the steering bridge expansion pump (12) supplies oil to the rodless chamber of the left rear steering cylinder (34) and the right rear steering cylinder (38) until the tire angle reaches the initial value, and finally the rear brake electromagnetic control valve (218) electromagnet Y7 is de-energized, and the rear axle retracts; Step 4: The front axle retracts, and the controller assembly (4) controls the electromagnet Y8 of the front brake solenoid control valve (219) to be energized, while the electromagnet Y7 of the rear brake solenoid control valve (218) is de-energized, releasing the brakes of the left front travel motor (22) and the right front travel motor (24), while the left rear travel motor (23) and the right rear travel motor (25) remain braked. The steering expansion pump (12) supplies oil to the rod chambers of the left front steering cylinder (32) and the right front steering cylinder (36), and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly (4). When the tire reaches the set angle of the controller assembly (4), the steering cylinder stops supplying oil, the electromagnet Y9 of the electromagnetic reversing valve (217) is energized, and at the same time the electromagnet Y10 of the left travel pump (13) and the electromagnet Y13 of the right travel pump (14) are energized. The left travel pump (13) supplies oil to the left front travel motor (22), the right travel pump (14) supplies oil to the right front travel motor (24), and the steering expansion pump (12) supplies oil to the rod chamber of the left front expansion cylinder (33) and the right front expansion cylinder (37). The above expansion cylinders begin to retract, and the expansion angle sensor monitors the angle of the left front outrigger (52) and the right front outrigger (56) in real time until the set value of the controller assembly (4) is reached. When the bridge expansion angle reaches the set value angle of the controller assembly (4), the electromagnet Y9 of the electromagnetic reversing valve (217) is de-energized, and at the same time the electromagnet Y10 of the left travel pump (13) and the electromagnet Y13 of the right travel pump (14) are de-energized, and the travel pump stops supplying oil to the travel motor; the steering bridge expansion pump (12) stops supplying oil to the rod chamber of the left front bridge expansion cylinder (33) and the right front bridge expansion cylinder (37), and the steering bridge expansion pump (12) supplies oil to the rodless chamber of the left front steering cylinder (32) and the right front steering cylinder (36) until the tire angle reaches the initial value, and finally the electromagnet Y8 of the front brake electromagnetic control valve (219) is de-energized, completing the front axle retraction; In the flat-ground bridge expansion mode, during the bridge expansion and retraction process, the electromagnet Y5 of the left oil circuit bidirectional shut-off solenoid valve (132) and the electromagnet Y6 of the right oil circuit bidirectional shut-off solenoid valve (142) are energized, and at the same time, the electromagnet Y9 of the electromagnetic reversing valve (217) is energized. The specific method is as follows: Step 1: Front axle expansion, controller assembly (4) controls the electromagnet Y8 of the front brake solenoid control valve (219) to be energized, while the electromagnet Y7 of the rear brake solenoid control valve (218) is de-energized, releasing the brakes of the left front travel motor (22) and the right front travel motor (24), while the left rear travel motor (23) and the right rear travel motor (25) remain braked. The steering expansion pump (12) supplies oil to the rod chambers of the left front steering cylinder (32) and the right front steering cylinder (36), and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly (4). When the tire reaches the set angle of the controller assembly (4), the steering cylinder stops supplying oil, the electromagnet Y2 of the left front two-way two-way two-way shut-off solenoid valve (212) and the electromagnet Y4 of the right front two-way two-way two-way shut-off solenoid valve (214) are energized, the electromagnet of the travel pump is not energized, the front travel motor achieves two oil port connection in the travel control valve (21), and the front travel motor can rotate freely. The steering expansion pump (12) supplies oil to the rodless chambers of the left front expansion cylinder (33) and the right front expansion cylinder (37), and the above expansion cylinders begin to extend. The expansion angle sensor monitors the angles of the left front outrigger (52) and the right front outrigger (56) in real time until they reach the set value of the controller assembly (4). When the bridge expansion angle reaches the set value angle of the controller assembly (4), the steering bridge expansion pump (12) stops supplying oil to the rodless chamber of the left front bridge expansion cylinder (33) and the right front bridge expansion cylinder (37), and the steering bridge expansion pump (12) supplies oil to the rodless chamber of the left front steering cylinder (32) and the right front steering cylinder (36) until the tire angle reaches the initial value. The electromagnet Y2 of the left front two-position two-way bidirectional shut-off solenoid valve (212) and the electromagnet Y4 of the right front two-position two-way bidirectional shut-off solenoid valve (214) are de-energized, and the electromagnet Y8 of the front brake solenoid control valve (219) is de-energized, thus completing the front axle expansion. Step 2: Rear axle expansion, controller assembly (4) controls the rear brake solenoid control valve (218) solenoid Y7 to be energized, while the front brake solenoid control valve (219) solenoid Y8 is not energized, releasing the braking of the left rear travel motor (23) and the right rear travel motor (25), and keeping the left front travel motor (22) and the right front travel motor (24) braking. The steering expansion pump (12) supplies oil to the rod chambers of the left rear steering cylinder (34) and the right rear steering cylinder (38), and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly (4). When the tire reaches the set angle of the controller assembly (4), the steering cylinder stops supplying oil, the electromagnet Y1 of the left rear two-position two-way bidirectional shut-off solenoid valve (211) and the electromagnet Y3 of the right rear two-position two-way bidirectional shut-off solenoid valve (213) are energized, the electromagnet of the travel pump is not energized, the rear travel motor achieves two oil port connection in the travel control valve (21), and the rear travel motor can rotate freely. The steering expansion pump (12) supplies oil to the rodless chambers of the left rear expansion cylinder (35) and the right rear expansion cylinder (39). The aforementioned expansion cylinders begin to extend. The expansion angle sensor monitors the angles of the left rear outrigger (54) and the right rear outrigger (58) in real time until they reach the set value of the controller assembly (4). When the bridge expansion angle reaches the set value angle of the controller assembly (4), the steering bridge expansion pump (12) stops supplying oil to the rodless chamber of the left rear bridge expansion cylinder (35) and the right rear bridge expansion cylinder (39), and the steering bridge expansion pump (12) supplies oil to the rodless chamber of the left rear steering cylinder (34) and the right rear steering cylinder (38) until the tire angle reaches the initial value. Electromagnets Y1, Y3, Y5, Y6 and Y7 are de-energized, and the bridge expansion is completed. Step 3: Rear axle retraction, controller assembly (4) controls the rear brake solenoid control valve (218) solenoid Y7 to be energized, while the front brake solenoid control valve (219) solenoid Y8 is not energized, releasing the braking of the left rear travel motor (23) and the right rear travel motor (25), while keeping the left front travel motor (22) and the right front travel motor (24) braking. The steering expansion pump (12) supplies oil to the rod chambers of the left rear steering cylinder (34) and the right rear steering cylinder (38), and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly (4). When the tire reaches the set angle of the controller assembly (4), the steering cylinder stops supplying oil, the electromagnets Y1 and Y3 are energized, the electromagnet of the travel pump is de-energized, the rear travel motor achieves two oil port connection in the travel control valve (21), and the rear travel motor can rotate freely. The steering expansion pump (12) supplies oil to the rod chambers of the left rear expansion cylinder (35) and the right rear expansion cylinder (39). The expansion cylinders begin to retract. The expansion angle sensor monitors the angles of the left rear outrigger (54) and the right rear outrigger (58) in real time until they reach the set value of the controller assembly (4). When the bridge expansion angle reaches the set value angle of the controller assembly (4), the steering bridge expansion pump (12) stops supplying oil to the rod chambers of the left rear bridge expansion cylinder (35) and the right rear bridge expansion cylinder (39), and the steering bridge expansion pump (12) supplies oil to the rodless chambers of the left rear steering cylinder (34) and the right rear steering cylinder (38) until the tire angle reaches the initial value. Electromagnets Y1, Y3, Y5, Y6 and Y7 are de-energized, and the bridge is retracted. Step 4: The front axle retracts, and the controller assembly (4) controls the electromagnet Y8 of the front brake solenoid control valve (219) to be energized, while the electromagnet Y7 of the rear brake solenoid control valve (218) is de-energized, releasing the brakes of the left front travel motor (22) and the right front travel motor (24), while the left rear travel motor (23) and the right rear travel motor (25) remain braked. The steering expansion pump (12) supplies oil to the rod chambers of the left front steering cylinder (32) and the right front steering cylinder (36), and the aforementioned steering cylinders begin to retract. The steering tire angle sensor monitors the tire angle in real time until it reaches the set value of the controller assembly (4). When the tire reaches the set angle of the controller assembly (4), the steering cylinder stops supplying oil, the electromagnets Y2 and Y4 are energized, the electromagnet of the travel pump is de-energized, the front travel motor achieves two oil port connection in the travel control valve (21), and the front travel motor can rotate freely. The steering expansion pump (12) supplies oil to the rod chambers of the left front expansion cylinder (33) and the right front expansion cylinder (37). The expansion cylinders begin to retract. The expansion angle sensor monitors the angles of the left front outrigger (52) and the right front outrigger (56) in real time until they reach the set value of the controller assembly (4). When the bridge expansion angle reaches the set value angle of the controller assembly (4), the steering bridge expansion pump (12) stops supplying oil to the rod chambers of the left front bridge expansion cylinder (33) and the right front bridge expansion cylinder (37), and the steering bridge expansion pump (12) supplies oil to the rodless chambers of the left front steering cylinder (32) and the right front steering cylinder (36) until the tire angle reaches the initial value. Electromagnets Y2, Y4, Y5, Y6, Y8 and Y9 are de-energized, and the front axle retraction is completed.

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