An unmanned vehicle parking brake drive-by-wire system and control method

Abstract

This invention discloses a drive-by-wire parking brake system for an unmanned vehicle, comprising a brake oil circuit consisting of an oil pump, an accumulator, and a negative brake pair. A charging solenoid valve is connected between the oil pump and the accumulator, and a negative brake release solenoid valve is connected between the accumulator and the negative brake pair. An accumulator pressure detection switch one and an accumulator pressure detection switch two are sequentially connected between the charging solenoid valve and the accumulator. A brake valve pressure detection switch is connected between the accumulator and the negative brake release solenoid valve. A control method for the parking brake of an unmanned vehicle is also provided. This application employs a drive-by-wire parking brake control method with negative braking and pressure switch detection, enabling closed-loop detection of the braking status when the drive-by-wire braking device malfunctions. This avoids a series of safety problems caused by the vehicle driving with the brakes on due to braking failure, resulting in damage to the friction pads, or by a lack of feedback due to brake failure.

Description

Technical Field

[0001] This invention relates to the field of forklift technology, specifically to a parking brake control system and control method for unmanned vehicles. Background Technology

[0002] The parking brake system of motor vehicles mainly consists of a mechanical parking brake handle, which uses a lever and cable to connect the parking brake to lock the drive shaft or rear wheels to apply the brakes. Currently, more and more vehicles are adopting electronically controlled drive-by-wire braking systems, which integrate temporary braking during driving and long-term braking after parking, and implement parking braking electronically.

[0003] Braking-by-wire (EWBS) is an electronic braking system, primarily divided into mechanical and hydraulic types. Its main functions include assisting with braking, active braking, energy recovery, ABS, ESP, AVH, AEB, and brake failure protection. Furthermore, EWBS integrates traditional braking functions such as TCS (Traction Control System), ESC, ABS, and EPB, simplifying installation. It can also integrate third-party control software, such as tire pressure monitoring, EBD (Electronic Brakeforce Distribution), AEB (Automatic Brake Assist), and AVH (Automatic Parking Assist), fully realizing intelligent requirements. In the field of electric vehicles, it can effectively recover kinetic energy and extend the driving range of electric vehicles.

[0004] Existing driverless vehicle parking brake drive-by-wire systems use an electric push rod connected to the parking brake lever to replace manual pushing and pulling of the brake lever, achieving parking braking by controlling the stroke of the electric push rod; however, the following problems still exist:

[0005] 1. The existing drive-by-wire parking brake system achieves the parking brake function by pushing and pulling the brake lever with an electric device. This will cause the parking brake to fail when the vehicle is powered off, because the electric push lever cannot work when the power is off.

[0006] 2. The existing drive-by-wire parking brake system achieves the parking brake function by pushing and pulling the brake lever with an electric device. It does not detect the pressure of the brake valve and cannot perform closed-loop detection of its braking status when the drive-by-wire parking brake fails. Summary of the Invention

[0007] The purpose of this invention is to provide a parking brake control system and control method for unmanned vehicles.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] The first objective of this invention is to provide a parking brake drive-by-wire system for an unmanned vehicle, comprising a brake oil circuit consisting of an oil pump, an accumulator, and a negative brake pair. A charging solenoid valve is connected between the oil pump and the accumulator, and a negative brake release solenoid valve is connected between the accumulator and the negative brake pair. An accumulator pressure detection switch one and an accumulator pressure detection switch two are sequentially connected between the charging solenoid valve and the accumulator. A brake valve pressure detection switch is connected between the accumulator and the negative brake release solenoid valve.

[0010] In a further embodiment, the first accumulator pressure detection switch is a normally open switch with a rated pressure of 85 bar; the second accumulator pressure detection switch is a normally closed switch with a rated pressure of 85-160 bar; and the brake valve pressure detection switch is a normally open switch with a rated pressure of 75 bar.

[0011] A further embodiment also includes a vehicle VCU, wherein the signal output terminals of the accumulator pressure detection switch one, the accumulator pressure detection switch two, and the brake valve pressure detection switch are all connected to the vehicle VCU, and the vehicle VCU is interactively connected to the travel motor controller and the motor controller respectively; the travel motor controller drives the travel motor to work, and the pump motor controller drives the oil pump motor to work.

[0012] A further solution also includes a lithium battery pack, which powers the drive motor controller, drive motor, pump motor controller, and oil pump motor, while the vehicle's VCU collects battery information from the lithium battery pack.

[0013] The second objective of this invention is to provide a control method for the parking brake of an unmanned vehicle, which includes the following steps:

[0014] Step S1. Connect accumulator pressure detection switch one and accumulator pressure detection switch two in sequence between the filling solenoid valve and the accumulator; and collect relevant information affecting parking brake control.

[0015] Step S2. Initialize the oil pump motor speed setting to 0 rpm, close the filling solenoid valve, and reset the fault signal;

[0016] Step S3. Determine the pressure state of the accumulator based on the information related to the parking brake control obtained in step S1:

[0017] When both accumulator pressure detection switch one and accumulator pressure detection switch two show a signal, it indicates that the pressure is normal.

[0018] When there is no signal from accumulator pressure detection switch one, but a signal from accumulator pressure detection switch two, it indicates that the pressure of the accumulator is too low.

[0019] When there is a signal from accumulator pressure detection switch one, but no signal from accumulator pressure detection switch two, it indicates that the accumulator pressure is sufficient and filling will stop.

[0020] When neither accumulator pressure detection switch one nor accumulator pressure detection switch two has a signal, it indicates that the pressure detection switch is faulty, outputs a filling fault signal, and displays it on the instrument display.

[0021] Step S4. After receiving the liquid filling fault signal, the travel motor speed setting value is limited and the output is zero; the travel motor speed setting value will be output normally only after the liquid filling fault signal disappears.

[0022] Step S5. When the travel motor speed setting value is not less than 10 rpm, open the negative brake release solenoid valve, and high-pressure hydraulic oil is input into the negative brake pair through the hydraulic oil pipe to realize the parking function; at the same time, the brake valve pressure detection switch determines whether the brake pressure meets the braking requirements; when the brake valve pressure detection switch has no signal output or the travel motor speed setting value is less than 10 rpm, close the negative brake release solenoid valve.

[0023] In a further embodiment, the information related to the parking brake control mentioned in step S1 includes the brake valve pressure detection switch signal SW3, the accumulator pressure detection switch one signal SW1, the accumulator pressure detection switch two signal SW2, the set value and feedback value of the travel motor speed, and the set value and feedback value of the oil pump motor speed.

[0024] In a further proposed solution, the step of determining the pressure state of the accumulator in step S3 is as follows:

[0025] S311. When both accumulator pressure detection switch one and accumulator pressure detection switch two have signals, execute step S314;

[0026] When there is no signal from accumulator pressure detection switch one, but a signal from accumulator pressure detection switch two, proceed to step S312.

[0027] When there is a signal from accumulator pressure detection switch one, but no signal from accumulator pressure detection switch two, proceed to step S314.

[0028] When neither accumulator pressure detection switch one nor accumulator pressure detection switch two has a signal, it indicates that the pressure detection switch is faulty and outputs a filling fault signal.

[0029] S312. Open the filling solenoid valve and set the speed of the oil pump motor to 1000 rpm to quickly fill the accumulator; at the same time, determine whether the pressure state of the accumulator has changed. If it has changed, proceed to step S311; if it has not changed, determine whether the speed feedback value of the oil pump motor is not less than 500 rpm. If it is, proceed to step S313.

[0030] S313. Determine if the pressure state of the accumulator has changed. If it has changed, return to step S3. If it has not changed, determine if there is a falling edge signal from the accumulator pressure detection switch. If there is, proceed to step S311.

[0031] S314. Set the oil pump motor speed to 0 rpm, close the accumulator charging solenoid valve, and repeat step S311 after the fault signal is reset.

[0032] In a further step, after outputting the liquid filling fault signal in step S3, the speed setting value of the walking motor is set to 0.

[0033] In a further step, if either accumulator pressure detection switch one or accumulator pressure detection switch two sends a signal in step S3, the following steps are used to control the opening and closing of the negative brake release solenoid valve:

[0034] S321. The travel motor speed setting value is based on the pre-set acceleration and deceleration rates, so that the travel motor speed is output according to a certain acceleration and deceleration curve;

[0035] S322. When the speed setting value of the walking motor is greater than or equal to 10 rpm, the negative brake release solenoid valve is opened.

[0036] S323. At this time, determine whether there is a signal from the brake valve pressure detection switch. If there is, proceed to step S324; if not, close the negative brake release solenoid valve.

[0037] S324. Determine whether the speed feedback value of the walking motor is not less than 10 rpm. If yes, proceed to step S325. At the same time, determine whether the speed setting value of the walking motor is less than 10 rpm. If yes, proceed to step S326.

[0038] S325. Determine whether the set value of the walking motor speed is less than 10 rpm. If so, proceed to step S326.

[0039] S326. Control the walking motor to perform braking operation;

[0040] S327. Determine if the feedback value of the travel motor speed is less than 10 rpm. If so, close the negative brake release solenoid valve and set the travel motor speed to 0.

[0041] This application discloses a control method for a parking brake drive-by-wire system for unmanned vehicles, which solves the problems of detecting the braking status when the drive-by-wire device malfunctions and the inability to perform parking brake when the vehicle is powered off.

[0042] In addition, this application adopts a drive-by-wire parking brake control method with negative braking (power failure braking) and pressure detection switch detection, so as to realize closed-loop detection of braking status when the drive-by-wire braking device fails, thereby avoiding a series of safety problems caused by the vehicle driving with the brakes on due to braking failure, resulting in damage to the friction pads or no feedback due to brake failure.

[0043] This application uses a pressure detection switch to detect the hydraulic oil level in the accumulator, and simultaneously uses the same switch to detect the oil pressure of the negative brake release solenoid valve, thereby determining whether to open the negative brake release solenoid valve. Once opened, high-pressure hydraulic oil flows through the hydraulic oil pipe to the negative brake pair, realizing the parking function. In other words, parking braking is achieved without interrupting power. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the control system of this application;

[0045] Figure 2 For the control process of this application Figure 1 ;

[0046] Figure 3 For the control process of this application Figure 2 ;

[0047] In the diagram: 1-Accumulator, 2-Accumulator pressure detection switch 2, 3-Accumulator pressure detection switch 1, 4-Filling solenoid valve, 5-Walking motor controller, 6-Walking motor, 7-Lithium battery pack, 8-Oil pump motor, 9-Oil pump, 10-Pump motor controller, 11-Instrument display, 12-Vehicle VCU, 13-Negative brake release solenoid valve, 14-Brake valve pressure detection switch. Detailed Implementation

[0048] 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.

[0049] Example 1:

[0050] See Figure 1An unmanned vehicle parking brake drive-by-wire system includes a brake oil circuit consisting of an oil pump 9, an accumulator 1, and a negative brake pair. A filling solenoid valve 4 is connected between the oil pump 9 and the accumulator 1, and a negative brake release solenoid valve 13 is connected between the accumulator 1 and the negative brake pair. An accumulator pressure detection switch 3 and an accumulator pressure detection switch 2 are connected in sequence between the filling solenoid valve 4 and the accumulator 1. A brake valve pressure detection switch 14 is connected between the accumulator 1 and the negative brake release solenoid valve 13.

[0051] The accumulator pressure detection switch 3 is a normally open switch with a rated pressure of 85 bar. When the oil pressure in the hydraulic pipe reaches 75 bar, the switch contacts actuate, opening the oil circuit and allowing the hydraulic oil pumped from the pump to pass through the charging solenoid valve 4, accumulator pressure detection switch 3, and accumulator pressure detection switch 2, before entering the accumulator 1. Accumulator pressure detection switch 2 is a normally closed switch with a rated pressure of 85-160 bar. When the oil pressure in the hydraulic pipe is between 85-160 bar, its oil circuit is open; however, when the oil pressure is below 85 bar, its contacts open, preventing the accumulator from being charged. The brake valve pressure detection switch 14 is a normally open switch with a rated pressure of 75 bar, the same as accumulator pressure detection switch 3.

[0052] A further embodiment also includes a vehicle VCU, wherein the signal output terminals of the accumulator pressure detection switch 13, the accumulator pressure detection switch 2, and the brake valve pressure detection switch 14 are all connected to the vehicle VCU 12. The vehicle VCU 12 is interactively connected to the travel motor controller 5 and the pump motor controller 10, respectively. The travel motor controller 4 drives the travel motor 6 to work, and the pump motor controller 10 drives the oil pump motor 8 to work. The oil pump motor 8 drives the oil pump 9 to guide hydraulic oil from the oil tank into the accumulator 1.

[0053] In this application, the vehicle VCU, drive motor controller 5, pump motor controller 10, drive motor 6, and oil pump motor 8 are all conventional devices already present in existing autonomous vehicles. This application does not involve any improvement to their performance, but only some changes to the connection methods. The accumulator pressure detection switch 1 (3), accumulator pressure detection switch 2 (2), and brake valve pressure detection switch 14 are commercially available products. This application is not limited to specific models; any product that can achieve the relevant functions described in this application is acceptable, as all products come with instruction manuals that can be used for reference when purchasing.

[0054] In this application, the vehicle VCU receives pressure signals from accumulator pressure detection switch 3, accumulator pressure detection switch 2, and brake valve pressure detection switch 14. It also receives the speed feedback values ​​of the travel motor and the oil pump motor. On the other hand, the vehicle VCU transmits the travel motor speed setting value to the travel motor controller and the oil pump motor speed setting value to the pump motor controller, which are used to control the speed of the travel motor and the oil pump motor, respectively.

[0055] A further solution also includes a lithium battery pack 7, which supplies power to the drive motor controller 5, drive motor 6, pump motor controller 10, and oil pump motor 8, while the vehicle's VCU collects battery information from the lithium battery pack.

[0056] This system uses the pressure signals from accumulator pressure detection switches 1 (3) and 2 (2) to determine the amount of hydraulic oil in the accumulator and replenishes it as needed. Specifically, when both switches 1 and 2 show a signal, the pressure is normal. When switch 1 shows no signal but switch 2 shows a signal, the accumulator pressure is too low; in this case, the filling solenoid valve needs to be opened, and the oil pump motor speed is set to 1000 rpm for rapid filling. When switch 1 shows a signal but switch 2 shows no signal, the accumulator pressure is sufficient; the oil pump motor speed is set to 0 rpm, and the filling solenoid valve closes to stop filling. When both switches 1 and 2 show no signal, a filling fault signal is output and displayed on the instrument panel for easy identification; after outputting the filling fault signal, the travel motor speed setting is set to 0.

[0057] Meanwhile, the pressure of the negative brake release solenoid valve is detected by the brake valve pressure detection switch 14. When the speed setting value of the travel motor is greater than or equal to 10 rpm, the negative brake release solenoid valve is opened; the high-pressure hydraulic oil is delivered to the negative brake pair through the hydraulic oil pipe to realize the parking function.

[0058] Example 2:

[0059] like Figure 2 , 3 As shown, a control method for parking brake of an unmanned vehicle includes the following steps:

[0060] Step S1. Connect accumulator pressure detection switch one and accumulator pressure detection switch two in sequence between the charging solenoid valve and the accumulator; collect information related to the parking brake control; wherein the information related to the parking brake control includes brake valve pressure detection switch signal SW3, accumulator pressure detection switch one signal SW1, accumulator pressure detection switch two signal SW2, the set value and feedback value of the travel motor speed, and the set value and feedback value of the oil pump motor speed;

[0061] Step S2. Initialize the oil pump motor speed setting to 0 rpm, close the filling solenoid valve, and reset the fault signal;

[0062] Step S3. Determine the pressure state of the accumulator based on the information related to the parking brake control obtained in step S1:

[0063] When both accumulator pressure detection switch one and accumulator pressure detection switch two show a signal, it indicates that the pressure is normal.

[0064] When there is no signal from accumulator pressure detection switch one, but a signal from accumulator pressure detection switch two, it indicates that the pressure of the accumulator is too low.

[0065] When there is a signal from accumulator pressure detection switch one, but no signal from accumulator pressure detection switch two, it indicates that the accumulator pressure is sufficient and filling will stop.

[0066] When neither accumulator pressure detection switch one nor accumulator pressure detection switch two sends a signal, it indicates a fault in the pressure detection switch. A filling fault signal is output and displayed on the instrument display for easy visual identification. After outputting the filling fault signal, the travel motor speed setting is set to 0.

[0067] Step S4. After receiving the fluid filling fault signal, the travel motor speed setpoint is limited and the output is zero. That is, the travel motor controller no longer responds to the travel motor speed command value issued by the throttle accelerator or the intelligent driving system, and the travel motor speed setpoint is limited to zero. The travel motor speed setpoint will be output normally until the fluid filling fault signal disappears.

[0068] Step S5. When the travel motor speed setting value is not less than 10 rpm, open the negative brake release solenoid valve, and high-pressure hydraulic oil is input into the negative brake pair through the hydraulic oil pipe to realize the parking function; at the same time, the brake valve pressure detection switch determines whether the brake pressure meets the braking requirements; when the brake valve pressure detection switch has no signal output or the travel motor speed setting value is less than 10 rpm, close the negative brake release solenoid valve.

[0069] See Figure 2 The steps for determining the pressure state of the accumulator in step S3 are as follows:

[0070] S311. When both accumulator pressure detection switch one and accumulator pressure detection switch two have signals, execute step S314;

[0071] When there is no signal from accumulator pressure detection switch one, but a signal from accumulator pressure detection switch two, proceed to step S312.

[0072] When there is a signal from accumulator pressure detection switch one, but no signal from accumulator pressure detection switch two, proceed to step S314.

[0073] When neither accumulator pressure detection switch one nor accumulator pressure detection switch two has a signal, it indicates that the pressure detection switch is faulty and outputs a filling fault signal.

[0074] S312. Open the filling solenoid valve and set the speed of the oil pump motor to 1000 rpm to quickly fill the accumulator; at the same time, determine whether the pressure state of the accumulator has changed. If it has changed, proceed to step S311; if it has not changed, determine whether the speed feedback value of the oil pump motor is not less than 500 rpm. If it is, proceed to step S313.

[0075] S313. Determine if the pressure state of the accumulator has changed. If it has changed, return to step S3. If it has not changed, determine if there is a falling edge signal from the accumulator pressure detection switch. If there is, proceed to step S311.

[0076] S314. Set the oil pump motor speed to 0 rpm, close the accumulator charging solenoid valve, and repeat step S311 after the fault signal is reset.

[0077] See Figure 3 If either accumulator pressure detection switch one or accumulator pressure detection switch two sends a signal in step S3, the following steps are used to control the opening and closing of the negative brake release solenoid valve:

[0078] S321. The travel motor speed setting value is based on the pre-set acceleration and deceleration rates, so that the travel motor speed is output according to a certain acceleration and deceleration curve;

[0079] S322. When the speed setting value of the walking motor is greater than or equal to 10 rpm, the negative brake release solenoid valve is opened.

[0080] S323. At this time, determine whether there is a signal from the brake valve pressure detection switch. If there is, proceed to step S324; if not, close the negative brake release solenoid valve.

[0081] S324. Determine whether the speed feedback value of the walking motor is not less than 10 rpm. If yes, proceed to step S325. At the same time, determine whether the speed setting value of the walking motor is less than 10 rpm. If yes, proceed to step S326.

[0082] S325. Determine whether the set value of the walking motor speed is less than 10 rpm. If so, proceed to step S326.

[0083] S326. Control the walking motor to perform braking operation;

[0084] S327. Determine if the feedback value of the travel motor speed is less than 10 rpm. If so, close the negative brake release solenoid valve and set the travel motor speed to 0.

[0085] In this application, the speed of the travel motor is sent to the travel controller via the CAN bus, the speed of the oil pump motor is sent to the oil pump controller via the CAN bus, and the control signal outputs of the filling solenoid valve and the negative brake release solenoid valve are output through the PWM port of the VCU. After the negative brake release solenoid valve is opened, the high-pressure hydraulic oil goes through the hydraulic oil pipe to the negative brake pair to realize the parking function.

[0086] This application adopts a drive-by-wire parking brake control method with negative braking and pressure switch detection, so as to realize closed-loop detection of braking status when the drive-by-wire braking device fails, thereby avoiding a series of safety problems caused by the vehicle driving with the brakes on due to braking failure, resulting in damage to the friction pads, or by the lack of feedback due to brake failure.

[0087] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0088] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A parking brake drive-by-wire system for an unmanned vehicle, comprising a brake oil circuit consisting of an oil pump, an accumulator, and a negative brake pair, characterized in that: A charging solenoid valve is connected between the oil pump and the accumulator, and a negative brake release solenoid valve is connected between the accumulator and the negative brake pair; an accumulator pressure detection switch one and an accumulator pressure detection switch two are connected in sequence between the charging solenoid valve and the accumulator; a brake valve pressure detection switch is connected between the accumulator and the negative brake release solenoid valve. The first accumulator pressure detection switch is a normally open switch with a rated pressure of 85 bar; the second accumulator pressure detection switch is a normally closed switch with a rated pressure of 85-160 bar; and the brake valve pressure detection switch is a normally open switch with a rated pressure of 75 bar.

2. The parking brake drive-by-wire system for an unmanned vehicle according to claim 1, characterized in that: It also includes a vehicle VCU, and the signal output terminals of the accumulator pressure detection switch one, the accumulator pressure detection switch two and the brake valve pressure detection switch are all connected to the vehicle VCU. The vehicle VCU is interactively connected to the travel motor controller and the pump motor controller respectively. The travel motor controller drives the travel motor to work, and the pump motor controller drives the oil pump motor to work.

3. The parking brake drive-by-wire system for an unmanned vehicle according to claim 2, characterized in that: It also includes a lithium battery pack, which is used to power the drive motor controller, drive motor, pump motor controller, and oil pump motor. At the same time, the vehicle's VCU collects battery information from the lithium battery pack.

4. A control method for parking brake of an unmanned vehicle, employing the parking brake drive-by-wire system for an unmanned vehicle as described in claim 1, characterized in that: Includes the following steps: Step S1. Connect accumulator pressure detection switch one and accumulator pressure detection switch two in sequence between the filling solenoid valve and the accumulator; and collect relevant information affecting parking brake control. Step S2. Initialize the oil pump motor speed setting to 0 rpm, close the filling solenoid valve, and reset the fault signal; Step S3. Determine the pressure state of the accumulator based on the information related to the parking brake control obtained in step S1: When both accumulator pressure detection switch one and accumulator pressure detection switch two show a signal, it indicates that the pressure is normal. When there is no signal from accumulator pressure detection switch one, but a signal from accumulator pressure detection switch two, it indicates that the pressure of the accumulator is too low. When there is a signal from accumulator pressure detection switch one, but no signal from accumulator pressure detection switch two, it indicates that the accumulator pressure is sufficient and filling will stop. When neither accumulator pressure detection switch one nor accumulator pressure detection switch two has a signal, it indicates that the pressure detection switch is faulty, outputs a filling fault signal, and displays it on the instrument display. Step S4. After receiving the liquid filling fault signal, the travel motor speed setting value is limited and the output is zero; the travel motor speed setting value will be output normally only after the liquid filling fault signal disappears. Step S5. When the travel motor speed setting value is not less than 10 rpm, open the negative brake release solenoid valve, and high-pressure hydraulic oil is input into the negative brake pair through the hydraulic oil pipe to realize the parking function; at the same time, the brake valve pressure detection switch determines whether the brake pressure meets the braking requirements; when the brake valve pressure detection switch has no signal output or the travel motor speed setting value is less than 10 rpm, close the negative brake release solenoid valve.

5. The control method according to claim 4, characterized in that: The information related to the parking brake control mentioned in step S1 includes the brake valve pressure detection switch signal SW3, the accumulator pressure detection switch one signal SW1, the accumulator pressure detection switch two signal SW2, the set value and feedback value of the travel motor speed, and the set value and feedback value of the oil pump motor speed.

6. The control method according to claim 4, characterized in that: The steps for determining the pressure state of the accumulator in step S3 are as follows: S311. When both accumulator pressure detection switch one and accumulator pressure detection switch two have signals, execute step S314; When there is no signal from accumulator pressure detection switch one, but a signal from accumulator pressure detection switch two, proceed to step S312. When there is a signal from accumulator pressure detection switch one, but no signal from accumulator pressure detection switch two, proceed to step S314. When neither accumulator pressure detection switch one nor accumulator pressure detection switch two has a signal, it indicates that the pressure detection switch is faulty and outputs a filling fault signal. S312. Open the filling solenoid valve and set the speed of the oil pump motor to 1000 rpm to quickly fill the accumulator; at the same time, determine whether the pressure state of the accumulator has changed. If it has changed, proceed to step S311; if it has not changed, determine whether the speed feedback value of the oil pump motor is not less than 500 rpm. If it is, proceed to step S313. S313. Determine if the pressure state of the accumulator has changed. If it has changed, return to step S3. If it has not changed, determine if there is a falling edge signal from the accumulator pressure detection switch. If there is, proceed to step S311. S314. Set the oil pump motor speed to 0 rpm, close the accumulator charging solenoid valve, and repeat step S311 after the fault signal is reset.

7. The control method according to claim 4, characterized in that: After outputting the liquid filling fault signal in step S3, the walking motor speed setting value is set to 0.

8. The control method according to claim 4, characterized in that: If either accumulator pressure detection switch one or accumulator pressure detection switch two sends a signal in step S3, the following steps are used to control the opening and closing of the negative brake release solenoid valve: S321. The travel motor speed setting value is based on the pre-set acceleration and deceleration rates, so that the travel motor speed is output according to a certain acceleration and deceleration curve; S322. When the speed setting value of the walking motor is greater than or equal to 10 rpm, the negative brake release solenoid valve is opened. S323. At this time, determine whether there is a signal from the brake valve pressure detection switch. If there is, proceed to step S324. If not, then close the negative brake release solenoid valve; S324. Determine whether the speed feedback value of the walking motor is not less than 10 rpm. If yes, proceed to step S325. At the same time, determine whether the speed setting value of the walking motor is less than 10 rpm. If yes, proceed to step S326. S325. Determine whether the set value of the walking motor speed is less than 10 rpm. If so, proceed to step S326. S326. Control the walking motor to perform braking operation; S327. Determine if the feedback value of the travel motor speed is less than 10 rpm. If so, close the negative brake release solenoid valve and set the travel motor speed to 0.

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