Electric fork truck ramp automatic parking control method and system

Abstract

This application discloses an automatic parking control method and system for electric forklifts on ramps, relating to the field of electric forklift parking. The method involves acquiring the total mass of the forklift on a ramp and the ramp angle measured by a longitudinal angle sensor; determining the gravity acting on the forklift based on the total mass; determining the ramp resistance based on the gravity and ramp angle; and determining the rolling resistance based on the gravity, ramp angle, and coefficient of friction. When automatic parking conditions are met, a target ramp parking braking force is determined based on the ramp resistance and rolling resistance. A target current value corresponding to the target ramp parking braking force is determined based on the relationship between the current value and the ramp parking braking force. The current value of the automatic parking brake proportional pressure reducing valve is adjusted to the target current value to achieve automatic parking. Using hydraulic braking as the power source, it does not rely on a motor, avoiding excessively rapid temperature rise due to prolonged motor stalling and eliminating the inability to park properly on ramps due to the driver leaving the vehicle and shifting to neutral, thus ensuring safe and reliable ramp parking.

Description

Technical Field

[0001] This application relates to the field of electric forklift parking, and in particular to an automatic parking control method and system for electric forklifts on ramps. Background Technology

[0002] Electric forklifts, as important material handling equipment, are widely used in logistics, manufacturing, and other industries. In recent years, with the increasing demand for intelligentization, the requirements for the functions and performance of electric forklifts have also gradually increased. Therefore, forklift manufacturers are constantly improving the intelligence level of forklifts to enhance product competitiveness. The automatic parking function, as an important indicator of the intelligence and automation of electric forklifts, primarily replaces the traditional handbrake, improving operational efficiency and safety during use, and is therefore widely adopted.

[0003] Currently, commercially available forklifts rely primarily on manual parking by the driver when they tend to roll backward on slopes. Small-tonnage electric forklifts often use handbrake-type parking brakes, requiring manual application of the handbrake. Large-tonnage forklifts, due to their higher operating force, commonly use electronic parking brakes. When the parking brake switch is open, the brake valve opens, allowing the vehicle to move normally; when the parking brake switch is closed, the parking brake valve closes, achieving parking. For electric vehicles, automatic parking is often achieved by controlling the motor's output torque. While this allows for automatic parking by controlling the motor's output torque, it also presents the following problems: If the motor operates under stall conditions for an extended period, its temperature will rapidly rise to its limit. Excessive temperature will cause the motor to reduce its power output, leading to rolling backward and posing a safety hazard. Furthermore, prolonged operation under high-temperature conditions will affect the motor's lifespan. The forklift has a seat sensing system. When the driver is not in the normal operating position (leaving the seat for 1.5 seconds), the vehicle will cut off the power. The power will only be output normally when the driver returns to the normal operating position. When the vehicle is traveling heavily on a slope, if the driver leaves the seat for 1.5 seconds, the whole vehicle will suddenly shift to neutral and the motor parking torque will fail. This poses a great safety hazard, especially when traveling heavily on a slope.

[0004] How to avoid the problem of rapid temperature rise due to prolonged motor stall, and how to prevent the vehicle from suddenly shifting to neutral when the driver leaves the seat, causing the motor's parking torque to fail and making it unable to properly hold the slope, are problems that need to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide an automatic parking control method and system for electric forklifts on ramps, which solves the problems of rapid temperature rise of the motor due to prolonged stalling when controlling the output torque of the motor for automatic parking, and the problem that the motor's parking torque fails and the vehicle cannot be parked properly when the driver leaves the seat and the vehicle is suddenly put into neutral.

[0006] To address the aforementioned technical problems, this application provides an automatic parking control method for electric forklifts on ramps, comprising: Obtain the total mass of the forklift when it is on a slope, as well as the slope angle measured by the longitudinal angle sensor of the vehicle body; The gravity acting on the forklift is determined based on the total mass; the ramp resistance is determined based on the gravity and the ramp angle; and the rolling resistance is determined based on the gravity, the ramp angle, and the coefficient of friction. When the automatic parking conditions are met, the target slope parking braking force is determined based on the slope resistance and the rolling resistance. The target current value corresponding to the target ramp parking braking force is determined based on the relationship between the current value and the ramp parking braking force. Adjust the current value of the automatic parking brake proportional pressure reducing valve to the target current value to achieve automatic parking.

[0007] In one optional embodiment, determining the ramp resistance based on the gravity and the ramp angle, and determining the rolling resistance based on the gravity, the ramp angle, and the coefficient of friction, includes: The ramp resistance is calculated according to the first preset formula; The first preset formula is: Fi=G sin(θ); Wherein, Fi is the ramp resistance, G is the gravity, and θ is the ramp angle; The rolling resistance is calculated according to the second preset formula; The second preset formula is: Fj=µG cos(θ); Wherein, Fj is the rolling resistance, µ is the coefficient of friction, G is the gravity, and θ is the ramp angle.

[0008] In one optional embodiment, determining the target ramp parking braking force based on the ramp resistance and the rolling resistance includes: The target ramp parking braking force is calculated according to the third preset formula; The third preset formula is: Fb = Fi - Fj; Wherein, Fb is the parking braking force of the target ramp, Fi is the ramp resistance, and Fj is the rolling resistance.

[0009] In an optional embodiment, before determining the target ramp parking braking force based on the ramp resistance and the rolling resistance, the method further includes: The system acquires the accelerator pedal angle from the accelerator pedal angle sensor, the brake pedal angle from the brake pedal angle sensor, the on / off status of the parking brake switch, the current gear position of the gear switch, and the motor speed. If the switch is closed, the manual parking brake solenoid valve is closed, and the current of the automatic parking brake proportional pressure reducing valve is set to zero. If the switch is in the open state, determine whether the forklift's current state meets the automatic parking conditions based on the accelerator pedal angle, the brake pedal angle, the current gear, and the motor speed.

[0010] In one optional embodiment, determining whether the forklift's current state meets the automatic parking conditions based on the accelerator pedal angle, the brake pedal angle, the current gear, and the motor speed includes: The accelerator pedal angle determines whether to release the accelerator, and the brake pedal angle determines whether to apply the brake. If the forklift is currently in a state where the accelerator is released and the brake is not applied and the vehicle is in forward gear, and the forklift decelerates and the motor speed is zero, then the current state of the forklift is determined to meet the conditions for automatic parking uphill. If the forklift is currently in a state where the accelerator is released and the brake is not applied, and the vehicle is in reverse gear, and the forklift decelerates and the motor speed reaches zero, then the current state of the forklift is determined to meet the conditions for automatic parking while reversing uphill.

[0011] This application also provides an automatic parking control system for an electric forklift on a ramp, including: a vehicle controller, a vehicle longitudinal angle sensor, an automatic parking brake proportional pressure reducing valve, a hydraulic oil source, a parking hydraulic brake, and a differential. The longitudinal angle sensor of the vehicle body is connected to the signal input terminal of the vehicle controller. The longitudinal angle sensor of the vehicle body is installed on the bottom of the forklift body and is used to measure the slope angle. The output port of the vehicle controller is connected to the automatic parking brake proportional pressure reducing valve. The hydraulic oil source is connected to the input terminal of the automatic parking brake proportional pressure reducing valve. The output terminal of the automatic parking brake proportional pressure reducing valve is connected to the parking hydraulic brake. The parking hydraulic brake is connected to the left and right drive wheels respectively through the differential. The vehicle controller is used to execute the steps of the electric forklift slope automatic parking control method.

[0012] In one optional embodiment, the system further includes a manual parking brake solenoid valve and a shuttle valve. The output port of the vehicle controller is connected to the manual parking brake solenoid valve and the automatic parking brake proportional pressure reducing valve, respectively. The hydraulic oil source is connected to the input terminals of the automatic parking brake proportional pressure reducing valve and the manual parking brake solenoid valve, respectively. The output terminals of the automatic parking brake proportional pressure reducing valve and the manual parking brake solenoid valve are connected to the input terminal of the shuttle valve, respectively. The output terminal of the shuttle valve is connected to the parking hydraulic brake.

[0013] In one optional embodiment, the system further includes a parking brake switch, a gear position switch, an accelerator pedal angle sensor, a brake pedal angle sensor, a microcontroller, and a motor. The parking brake switch, the gear position switch, the accelerator pedal angle sensor, and the brake pedal angle sensor are connected to the signal input terminal of the vehicle controller. The microcontroller is connected to both the vehicle controller and the motor. The motor is connected to the parking hydraulic brake.

[0014] In one alternative embodiment, the system further includes an on-board instrument cluster connected to the vehicle controller, the on-board instrument cluster being used to display the parking brake status.

[0015] In one optional embodiment, the vehicle controller is connected to the microcontroller and the vehicle instrument cluster via a CAN bus.

[0016] This application provides a method for automatic parking control of an electric forklift on a ramp, comprising: acquiring the total mass of the forklift when it is on a ramp, and the ramp angle measured by a longitudinal angle sensor of the forklift body; determining the gravity acting on the forklift based on the total mass, determining the ramp resistance based on the gravity and the ramp angle, and determining the rolling resistance based on the gravity, the ramp angle, and the coefficient of friction; determining a target ramp parking braking force based on the ramp resistance and the rolling resistance when the automatic parking conditions are met; determining a target current value corresponding to the target ramp parking braking force based on the relationship between the current value and the ramp parking braking force; and adjusting the current value of the automatic parking brake proportional pressure reducing valve to the target current value to achieve automatic parking. The slope angle is detected by a longitudinal angle sensor on the vehicle body. When the automatic parking conditions are met, the current of the automatic parking brake proportional pressure reducing valve is adjusted according to the slope angle and the gravity of the forklift to output a matching slope parking braking force. This application uses hydraulic braking as the parking power source. The parking function does not rely on the motor. This can avoid the problem of the motor overheating due to prolonged stalling, and also avoid the problem of the motor failing to park properly when the vehicle is put in neutral after the driver leaves the seat, thus ensuring safe and reliable slope parking.

[0017] In addition, the hydraulic circuit controlled by the manual parking brake solenoid valve and the hydraulic circuit controlled by the automatic parking brake proportional pressure reducing valve are connected in parallel to the parking hydraulic brake via a shuttle valve. This ensures vehicle parking brake safety even if the automatic parking brake proportional pressure reducing valve automatic parking circuit fails. Therefore, this system solves the problem of excessive temperature rise of the motor parking brake while taking into account vehicle safety and smoothness.

[0018] The beneficial effects and methods of the electric forklift ramp automatic parking control system provided in this application are as described above. Attached Figure Description

[0019] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A flowchart illustrating an automatic parking control method for an electric forklift on a ramp, provided as an embodiment of this application; Figure 2 A structural diagram of an automatic parking control system for an electric forklift ramp provided in an embodiment of this application; Figure 3 A force analysis diagram of a forklift moving forward uphill when stationary, provided as an embodiment of this application; Figure 4 A schematic diagram illustrating the relationship between current value and parking braking force on a ramp, provided as an embodiment of this application; Figure 5 A flowchart illustrating another automatic parking control method for electric forklifts on ramps provided in this application embodiment; Figure 6 A structural diagram of an automatic parking control device for an electric forklift ramp provided in an embodiment of this application; Figure 7 A structural diagram of another electric forklift ramp automatic parking control device provided in an embodiment of this application.

[0021] The attached diagram is labeled as follows: 1-Vehicle controller, 2-Longitudinal angle sensor of vehicle body, 3-Automatic parking brake proportional pressure reducing valve, 4-Manual parking brake solenoid valve, 5-Hydraulic oil source, 6-Shuttle valve, 7-Parking hydraulic brake, 8-Differential, 9-Parking brake switch, 10-Gear switch, 11-Accelerator pedal angle sensor, 12-Brake pedal angle sensor, 13-Microcontroller, 14-Motor, 15-On-board instrument. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0023] The core of this application is to provide an automatic parking control method and system for electric forklifts on ramps, which avoids the problem of rapid temperature rise due to prolonged motor stalling, and also prevents the motor from suddenly shifting to neutral when the driver leaves the seat, causing the parking torque of the motor to fail and preventing normal parking on ramps.

[0024] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Figure 1 A flowchart of an automatic parking control method for an electric forklift on a ramp, as provided in this application embodiment, is shown below. Figure 1 As shown, the automatic parking control method for electric forklifts on ramps includes: S10: Obtain the total mass of the forklift when it is on a slope, as well as the slope angle measured by the longitudinal angle sensor of the vehicle body.

[0026] S11: Determine the gravity acting on the forklift based on the total mass, determine the ramp resistance based on the gravity and ramp angle, and determine the rolling resistance based on the gravity, ramp angle, and coefficient of friction.

[0027] S12: When the automatic parking conditions are met, determine the target slope parking braking force based on the slope resistance and rolling resistance.

[0028] S13: Determine the target current value corresponding to the target slope parking braking force based on the relationship between the current value and the slope parking braking force.

[0029] S14: Adjust the current value of the automatic parking brake proportional pressure reducing valve to the target current value to achieve automatic parking.

[0030] To facilitate understanding, the following describes an automatic parking control system for electric forklifts on ramps that implements the above method. Figure 2 A structural diagram of an automatic parking control system for an electric forklift ramp provided in this application embodiment is shown below. Figure 2 As shown, an automatic parking control system for an electric forklift on a ramp includes: a vehicle controller 1, a vehicle body longitudinal angle sensor 2, an automatic parking brake proportional pressure reducing valve 3, a hydraulic oil source 5, a parking hydraulic brake 7, and a differential 8. The vehicle body longitudinal angle sensor 2 is connected to the signal input terminal of the vehicle controller 1 and is installed on the bottom of the forklift body to measure the ramp angle. The output port of the vehicle controller 1 is connected to the automatic parking brake proportional pressure reducing valve 3. The hydraulic oil source 5 is connected to the input terminal of the automatic parking brake proportional pressure reducing valve 3. The output terminal of the automatic parking brake proportional pressure reducing valve 3 is connected to the parking hydraulic brake 7. The parking hydraulic brake 7 is connected to the left and right drive wheels respectively through the differential 8. The vehicle controller 1 is used to execute the steps of the above-mentioned automatic parking control method for an electric forklift on a ramp.

[0031] It also includes a manual parking brake solenoid valve 4 and a shuttle valve 6. The output ports of the vehicle controller 1 are respectively connected to the manual parking brake solenoid valve 4 and the automatic parking brake proportional pressure reducing valve 3. The hydraulic oil source 5 is respectively connected to the input terminals of the automatic parking brake proportional pressure reducing valve 3 and the manual parking brake solenoid valve 4. The output terminals of the automatic parking brake proportional pressure reducing valve 3 and the manual parking brake solenoid valve 4 are respectively connected to the input terminal of the shuttle valve 6. The output terminal of the shuttle valve 6 is connected to the parking hydraulic brake 7.

[0032] Furthermore, the system also includes a parking brake switch 9, a gear position switch 10, an accelerator pedal angle sensor 11, a brake pedal angle sensor 12, a microcontroller 13 (MCU), and a motor 14. The parking brake switch 9, gear position switch 10, accelerator pedal angle sensor 11, and brake pedal angle sensor 12 are connected to the signal input terminals of the vehicle controller 1. The microcontroller 13 is connected to both the vehicle controller 1 and the motor 14, and the motor 14 is connected to the parking hydraulic brake 7. The system also includes an on-board instrument cluster 15, which is connected to the vehicle controller 1 and is used to display the parking brake status.

[0033] The longitudinal angle sensor 2 is installed at the bottom of the forklift body to collect the slope angle signal in real time and transmit it to the vehicle controller 1, providing slope parameters for calculating the parking braking force on the slope.

[0034] The vehicle controller 1 is the core of the entire control system. It receives input signals from the vehicle longitudinal angle sensor 2, parking brake switch 9, gear switch 10, accelerator pedal angle sensor 11, and brake pedal angle sensor 12. Based on the forklift's weight and the slope angle, it calculates the required parking braking force and outputs control signals to adjust the on / off state of the manual parking brake solenoid valve 4 and the current magnitude of the automatic parking brake proportional pressure reducing valve 3, thereby realizing the control and switching between automatic parking and manual parking.

[0035] The automatic parking brake proportional pressure reducing valve 3 receives the current control signal from the vehicle controller 1 and continuously adjusts the output hydraulic pressure according to the current magnitude to precisely control the parking braking force and achieve a smooth and stable automatic parking function.

[0036] The manual parking brake solenoid valve 4 is used to control the on / off state of the manual parking hydraulic circuit, execute the manual parking command, and serve as a backup braking scheme for the automatic parking system.

[0037] Hydraulic oil source 5 provides stable pressure oil for both automatic and manual parking hydraulic circuits, and is the power supply component of the hydraulic braking system.

[0038] As a component of the hydraulic circuit, the shuttle valve 6 is connected to the output hydraulic oil of both the automatic parking brake proportional pressure reducing valve 3 and the manual parking brake solenoid valve 4. It automatically selects the higher pressure path to deliver the hydraulic oil to the parking brake 7, ensuring that braking can be achieved as long as any parking circuit is effective, thus improving system safety.

[0039] The parking hydraulic brake 7 receives the hydraulic pressure delivered by the shuttle valve 6, converts the hydraulic energy into mechanical braking force, and acts on the transmission mechanism to realize the parking brake of the forklift.

[0040] The differential 8 connects the parking hydraulic brake 7 to the left and right drive wheels of the forklift, and evenly transmits the braking force to the drive wheels on both sides to ensure that the vehicle remains stable and stationary when parked.

[0041] The parking brake switch 9 inputs a manual parking start or stop command to the vehicle controller 1 to switch the manual parking working state.

[0042] The gear switch 10 collects the forward and reverse gear signals of the forklift and transmits them to the vehicle controller 1, which serves as one of the bases for judging the automatic parking conditions.

[0043] The accelerator pedal angle sensor 11 detects the accelerator pedal angle in real time and feeds it back to the vehicle controller 1 to determine whether the driver has released the accelerator pedal and trigger the automatic parking control. The accelerator pedal is used for acceleration.

[0044] Brake pedal angle sensor 12 collects the brake pedal angle and transmits it to vehicle controller 1, which is used to determine the automatic parking conditions. The brake pedal is used for braking.

[0045] The microcontroller 13 is connected to the vehicle controller via the CAN bus. The microcontroller 13 receives instructions from the vehicle controller 1 and controls the motor 14 to operate, and collects the motor speed and transmits it to the vehicle controller 1.

[0046] The motor 14 operates under the control of the microcontroller 13 and can provide auxiliary power to the parking hydraulic brake 7 to ensure braking performance.

[0047] The on-board instrument cluster 15 is connected to the vehicle controller 1 via a CAN bus, displaying the real-time operating status of the parking brake for easy viewing by the driver. CAN stands for Controller Area Network, a dedicated serial communication bus for industrial / vehicle applications.

[0048] When the automatic parking conditions are met, the vehicle controller 1 controls the automatic parking of the electric forklift by continuously adjusting the current of the automatic parking brake proportional pressure reducing valve 3. This ensures normal parking even when the driver leaves the seat during automatic parking on a slope, avoiding the problem of rapid temperature rise due to prolonged stalling of the motor 14, and guaranteeing the smoothness and safety of automatic parking on slopes. The specific steps for adjusting the current of the automatic parking brake proportional pressure reducing valve 3 according to the forklift's weight and the slope angle to achieve automatic parking will be further explained in the embodiments of the method.

[0049] This application provides an automatic parking control system for an electric forklift on a ramp, comprising: a vehicle controller, a vehicle body longitudinal angle sensor, an automatic parking brake proportional pressure reducing valve, a manual parking brake solenoid valve, a hydraulic oil source, a shuttle valve, a parking hydraulic brake, and a differential. The vehicle body longitudinal angle sensor is connected to the signal input terminal of the vehicle controller and is installed at the bottom of the forklift body to measure the ramp angle. The output ports of the vehicle controller are respectively connected to the manual parking brake solenoid valve and the automatic parking brake proportional pressure reducing valve. The hydraulic oil source is respectively connected to the input terminals of the automatic parking brake proportional pressure reducing valve and the manual parking brake solenoid valve. The output terminals of the automatic parking brake proportional pressure reducing valve and the manual parking brake solenoid valve are respectively connected to the input terminals of the shuttle valve. The output terminal of the shuttle valve is connected to the parking hydraulic brake. The parking hydraulic brake is connected to the left and right drive wheels respectively through the differential. The vehicle controller is used to adjust the current of the automatic parking brake proportional pressure reducing valve according to the gravity of the forklift and the ramp angle when the forklift meets the automatic parking conditions, so as to realize automatic parking. This application employs a dual-circuit parking brake structure. While retaining the original manual parking brake hydraulic circuit, an additional automatic parking hydraulic circuit controlled by a proportional pressure reducing valve is added. The system detects the slope angle using a longitudinal angle sensor on the vehicle body. When the automatic parking conditions are met, the current of the automatic parking brake proportional pressure reducing valve is adjusted according to the slope angle and the weight of the forklift to output a matching parking braking force. This application uses hydraulic braking as the parking power source, eliminating the need for a motor. This avoids the problem of excessively rapid temperature rise due to prolonged motor stalling and also prevents the motor from failing to maintain parking torque when the driver leaves the seat and the vehicle is in neutral, thus ensuring safe and reliable parking on slopes.

[0050] In addition, the hydraulic circuit controlled by the manual parking brake solenoid valve and the hydraulic circuit controlled by the automatic parking brake proportional pressure reducing valve are connected in parallel to the parking hydraulic brake via a shuttle valve. This ensures vehicle parking brake safety even if the automatic parking brake proportional pressure reducing valve automatic parking circuit fails. Therefore, this system solves the problem of excessive temperature rise of the motor parking brake while taking into account vehicle safety and smoothness.

[0051] In step S10, the total mass of the forklift when it is on a slope is obtained. The total mass includes the vehicle's own weight and the load, and the unit is kilograms.

[0052] In step S11, Figure 3 A force analysis diagram of a forklift moving forward uphill from a stationary position is provided in an embodiment of this application, as shown below. Figure 3 As shown, a longitudinal angle sensor is installed at the bottom of the forklift body to measure the slope angle θ (θ is positive for forward uphill; θ is negative for reverse uphill). When the forklift is stationary on the slope, it is subjected to the combined forces of gravity G, slope resistance Fi, rolling resistance Fj, and slope parking braking force Fb, where G=mg and Fi=mg. sin(θ), Fj=µmg cos(θ), to ensure the forklift remains stationary on the slope, the rolling resistance and parking braking force should be balanced with the slope resistance, Fi=Fb+Fj; where m is the total mass of the vehicle, g is the acceleration due to gravity (usually taken as 9.8m / s²), G is the gravity acting on the forklift, Fi is the slope resistance, Fj is the rolling resistance, Fb is the parking braking force on the slope, and µ is the coefficient of friction.

[0053] The ramp resistance is determined based on gravity and ramp angle, and the rolling resistance is determined based on gravity, ramp angle, and coefficient of friction, including: calculating the ramp resistance according to a first preset formula; the first preset formula is: Fi=G sin(θ); where Fi is the ramp resistance, G is gravity, and θ is the ramp angle; the rolling resistance is calculated according to the second preset formula; the second preset formula is: Fj=µG cos(θ); where Fj is the rolling resistance, µ is the coefficient of friction, G is gravity, and θ is the ramp angle.

[0054] In step S12, the target slope parking braking force is determined based on the slope resistance and rolling resistance, including: calculating the target slope parking braking force according to the third preset formula; the third preset formula is: Fb=Fi-Fj; where Fb is the target slope parking braking force, Fi is the slope resistance, and Fj is the rolling resistance.

[0055] In step S13, the target current value corresponding to the target ramp parking braking force is determined based on the relationship between the current value and the ramp parking braking force. Figure 4 A schematic diagram illustrating the relationship between current value and parking braking force on a ramp, provided as an embodiment of this application, is shown below. Figure 4 As shown, the target current value corresponding to the target parking braking force can be obtained by linear interpolation based on the curve showing the correspondence between current value and parking braking force on a slope. Alternatively, the target current value corresponding to the target parking braking force can be obtained by looking up a mapping table containing the correspondence between current value and parking braking force on a slope.

[0056] In step S14, regarding how to adjust the current value of the automatic parking brake proportional pressure reducing valve to the target current value, it can be done by continuously outputting a drive signal to the automatic parking brake proportional pressure reducing valve in the form of pulse width modulation (PWM) output or analog output. The vehicle controller collects the actual operating current of the automatic parking brake proportional pressure reducing valve in real time, compares it with the target current value, and dynamically adjusts the duty cycle or voltage amplitude of the output signal according to the deviation, so that the actual current quickly and stably approaches and maintains the target current value, thereby allowing the automatic parking brake proportional pressure reducing valve to output hydraulic pressure that matches the target parking braking force, achieving smooth and precise automatic parking control.

[0057] Based on the above embodiments, before determining the target ramp parking braking force based on ramp resistance and rolling resistance, the method further includes: acquiring the accelerator pedal angle collected by the accelerator pedal angle sensor, the brake pedal angle collected by the brake pedal angle sensor, the on / off state of the parking brake switch, the current gear of the gear switch, and the motor speed; if the switch is closed, the manual parking brake solenoid valve is closed, and the current of the automatic parking brake proportional pressure reducing valve is set to zero. If the switch is open, the forklift's current state is determined to meet the automatic parking conditions based on the accelerator pedal angle, brake pedal angle, current gear, and motor speed.

[0058] The system determines whether the automatic parking conditions are met based on the accelerator pedal angle, brake pedal angle, current gear, and motor speed. This includes: determining whether the accelerator is released based on the accelerator pedal angle, and determining whether the brake is applied based on the brake pedal angle. If the forklift is currently in a forward gear with the accelerator released and the brake not applied, and the forklift decelerates until the motor speed reaches zero, then the forklift is deemed to meet the automatic parking conditions for forward uphill driving. If the forklift is currently in reverse gear with the accelerator released and the brake not applied, and the forklift decelerates until the motor speed reaches zero, then the forklift is deemed to meet the automatic parking conditions for reverse uphill driving. After meeting either the forward or reverse uphill automatic parking conditions, the following steps are performed: determining the target slope parking braking force based on slope resistance and rolling resistance; determining the target current value corresponding to the target slope parking braking force based on the relationship between the current value and the slope parking braking force; and adjusting the current value of the automatic parking brake proportional pressure reducing valve to the target current value to achieve automatic parking. The accelerator pedal angle indicates whether the accelerator is released, and the brake pedal angle indicates whether the brake is applied. For example, if the accelerator pedal angle is greater than the set value, the accelerator is released; if the accelerator pedal angle is less than or equal to the set value, the accelerator is released. If the brake pedal angle is greater than the set value, the brake is not applied; if the accelerator pedal angle is less than or equal to the set value, the brake is applied.

[0059] To make it easier to understand, the following will be combined with Figure 5This paper further introduces the automatic parking control method for electric forklifts on ramps. Figure 5 A flowchart of another electric forklift ramp automatic parking control method provided in the embodiments of this application is shown below. Figure 5 As shown, S20: Acquire the accelerator pedal angle collected by the accelerator pedal angle sensor, the brake pedal angle collected by the brake pedal angle sensor, the on / off state of the parking brake switch, the current gear of the gear switch, and the motor speed; S21: Determine the on / off state of the parking brake switch; if the switch state is closed, proceed to step S22; if the switch state is open, proceed to step S23; Step S22: Close the manual parking brake solenoid valve (use manual parking for braking) and set the current of the automatic parking brake proportional pressure reducing valve to zero; Step S23: Based on the accelerator pedal angle... The forklift's current state is determined by the brake pedal angle, brake pedal angle, current gear, and motor speed to see if the automatic parking condition is met. If the automatic parking condition is met, proceed to step S24; otherwise, proceed to step S27. Step S24: Determine the target ramp parking braking force based on ramp resistance and rolling resistance. Step S25: Determine the target current value corresponding to the target ramp parking braking force based on the relationship between the current value and the ramp parking braking force. Step S26: Adjust the current value of the automatic parking brake proportional pressure reducing valve to the target current value to achieve automatic parking. Step S27: Set the current of the automatic parking brake proportional pressure reducing valve to zero and proceed to step S20.

[0060] This application provides an automatic parking control method for electric forklifts on ramps, applied to the aforementioned automatic parking control system for electric forklifts on ramps. The method includes: acquiring the total mass of the forklift on a ramp and the ramp angle measured by a longitudinal angle sensor; determining the gravity acting on the forklift based on the total mass; determining the ramp resistance based on the gravity and ramp angle; determining the rolling resistance based on the gravity, ramp angle, and coefficient of friction; determining a target ramp parking braking force based on the ramp resistance and rolling resistance when automatic parking conditions are met; determining a target current value corresponding to the target ramp parking braking force based on the relationship between the current value and the ramp parking braking force; and adjusting the current value of the automatic parking brake proportional pressure reducing valve to the target current value to achieve automatic parking. This application utilizes a proportional pressure reducing valve in a vehicle's automatic parking brake system. The required parking braking force is calculated based on the vehicle's total mass and the slope angle. Combining the relationship between current and parking braking force, the vehicle controller calculates the current value of the proportional valve needed to meet the current parking braking conditions. When the forklift meets the automatic parking conditions, the vehicle controller continuously adjusts the current value of the proportional pressure reducing valve and outputs it to the proportional valve's actuator via the output port to complete the automatic parking control. The continuous adjustment of the required parking braking force by the proportional pressure reducing valve improves the smoothness of the parking brake. This application uses hydraulic braking as the parking power source, eliminating the need for a motor. This avoids the problem of excessively rapid temperature rise due to prolonged motor stalling and also prevents the motor from failing to maintain parking torque when the driver leaves the seat and the vehicle is in neutral, thus ensuring safe and reliable parking on slopes. In addition, the hydraulic circuit controlled by the manual parking brake solenoid valve and the hydraulic circuit controlled by the automatic parking brake proportional pressure reducing valve are connected in parallel to the parking hydraulic brake via a shuttle valve. This ensures vehicle parking brake safety even if the automatic parking brake proportional pressure reducing valve automatic parking circuit fails. Therefore, this system solves the problem of excessive temperature rise of the motor parking brake while taking into account vehicle safety and smoothness.

[0061] The above embodiments have described the automatic parking control method for electric forklifts on ramps in detail. This application also provides embodiments corresponding to the automatic parking control device for electric forklifts on ramps. It should be noted that this application describes the embodiments of the device from two perspectives: one is based on the functional modules, and the other is based on the hardware.

[0062] Figure 6 A structural diagram of an automatic parking control device for an electric forklift ramp provided in this application embodiment is shown below. Figure 6 As shown, an automatic parking control device for an electric forklift on a ramp includes: The first acquisition module 20 is used to acquire the total mass of the forklift when it is on a slope, as well as the slope angle measured by the longitudinal angle sensor of the vehicle body. The first determining module 21 is used to determine the gravity acting on the forklift based on the total mass, determine the ramp resistance based on the gravity and ramp angle, and determine the rolling resistance based on the gravity, ramp angle, and coefficient of friction. The second determining module 22 is used to determine the target slope parking braking force based on slope resistance and rolling resistance when the automatic parking conditions are met. The third determining module 23 is used to determine the target current value corresponding to the target slope parking braking force based on the relationship between the current value and the slope parking braking force. The adjustment module 24 is used to adjust the current value of the automatic parking brake proportional pressure reducing valve to the target current value in order to achieve automatic parking.

[0063] Based on the above embodiments, in an optional embodiment, the first determining module includes: The first calculation unit is used to calculate the ramp resistance according to a first preset formula; the first preset formula is: Fi=G sin(θ); where Fi is the ramp resistance, G is gravity, and θ is the ramp angle; The second calculation unit is used to calculate the rolling resistance according to a second preset formula; the second preset formula is: Fj=µG cos(θ); where Fj is the rolling resistance, µ is the coefficient of friction, G is gravity, and θ is the ramp angle.

[0064] Based on the above embodiments, in one optional embodiment, the second determining module includes: The third calculation unit is used to calculate the target slope parking braking force according to the third preset formula; the third preset formula is: Fb=Fi-Fj; where Fb is the target slope parking braking force, Fi is the slope resistance, and Fj is the rolling resistance.

[0065] Based on the above embodiments, in an optional embodiment, it further includes: The second acquisition module is used to acquire the accelerator pedal angle collected by the accelerator pedal angle sensor, the brake pedal angle collected by the brake pedal angle sensor, the on / off status of the parking brake switch, the current gear of the gear switch, and the motor speed. The control module is used to close the manual parking brake solenoid valve and set the current of the automatic parking brake proportional pressure reducing valve to zero if the switch state is closed. The judgment module is used to determine whether the forklift's current state meets the automatic parking conditions if the switch is on, based on the accelerator pedal angle, brake pedal angle, current gear, and motor speed.

[0066] Based on the above embodiments, in an optional embodiment, the determination module includes: The judgment unit is used to determine whether to release the accelerator pedal based on the accelerator pedal angle and whether to apply the brake pedal based on the brake pedal angle. The first determination unit is used to determine that if the current state of the forklift is that the accelerator is released and the brake is not applied and the vehicle is in forward gear, the forklift decelerates and the motor speed is zero, then the current state of the forklift meets the conditions for automatic parking uphill. The second determination unit is used to determine that if the current state of the forklift is that the accelerator is released and the brake is not applied, and the vehicle is in reverse gear, the forklift decelerates and the motor speed is zero, then the current state of the forklift meets the automatic parking condition for reversing uphill.

[0067] Since the embodiments of the apparatus and the embodiments of the method correspond to each other, please refer to the description of the embodiments of the method for the embodiments of the apparatus, which will not be repeated here.

[0068] Figure 7 A structural diagram of another electric forklift ramp automatic parking control device provided in this application embodiment is shown below. Figure 7 As shown, the electric forklift ramp automatic parking control device includes: a memory 30 for storing computer programs; The processor 31 is used to execute a computer program to implement the steps of the electric forklift ramp automatic parking control method as described in the above embodiment.

[0069] The electric forklift ramp automatic parking control device provided in this embodiment can include, but is not limited to, smartphones, tablets, laptops, or desktop computers.

[0070] The processor 31 may include one or more processing cores, such as a quad-core processor or an octa-core processor. The processor 31 may be implemented using at least one of the following hardware forms: Digital Signal Processor (DSP), Field-Programmable Gate Array (FPGA), or Programmable Logic Array (PLA). The processor 31 may also include a main processor and a coprocessor. The main processor, also known as the Central Processing Unit (CPU), is used to process data in the wake-up state; the coprocessor is a low-power processor used to process data in the standby state. In some embodiments, the processor 31 may integrate a Graphics Processing Unit (GPU), which is responsible for rendering and drawing the content to be displayed on the screen. In some embodiments, the processor 31 may also include an Artificial Intelligence (AI) processor, which is used to handle computational operations related to machine learning.

[0071] The memory 30 may include one or more computer-readable storage media, which may be non-transitory. The memory 30 may also include high-speed random access memory and non-volatile memory, such as one or more disk storage devices or flash memory devices. In this embodiment, the memory 30 is used to store at least the following computer program 301, which, after being loaded and executed by the processor 31, is capable of implementing the relevant steps of the electric forklift ramp automatic parking control method disclosed in any of the foregoing embodiments. In addition, the resources stored in the memory 30 may also include an operating system 302 and data 303, and the storage method may be temporary or permanent storage. The operating system 302 may include Windows, Unix, Linux, etc. The data 303 may include, but is not limited to, ramp angles.

[0072] In some embodiments, the electric forklift ramp automatic parking control device may further include a display screen 32, an input / output interface 33, a communication interface 34, a power supply 35, and a communication bus 36.

[0073] Those skilled in the art will understand that Figure 7 The structure shown does not constitute a limitation on the automatic parking control device for electric forklift ramps and may include more or fewer components than shown.

[0074] The electric forklift ramp automatic parking control device provided in this application includes a memory and a processor. When the processor executes the program stored in the memory, it can perform the following methods: obtain the total mass of the forklift when it is on a ramp, and the ramp angle measured by the longitudinal angle sensor of the vehicle body; determine the gravity acting on the forklift based on the total mass, determine the ramp resistance based on the gravity and the ramp angle, and determine the rolling resistance based on the gravity, the ramp angle, and the coefficient of friction; when the automatic parking conditions are met, determine the target ramp parking braking force based on the ramp resistance and the rolling resistance; determine the target current value corresponding to the target ramp parking braking force based on the relationship between the current value and the ramp parking braking force; and adjust the current value of the automatic parking brake proportional pressure reducing valve to the target current value to achieve automatic parking.

[0075] Finally, this application also provides an embodiment corresponding to a computer-readable storage medium. The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps described in the above-described method embodiment for the automatic parking control method of an electric forklift ramp.

[0076] It is understood that if the methods in the above embodiments are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and executes all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0077] The above provides a detailed description of an automatic parking control method and system for electric forklifts on ramps, as provided in this application. The various embodiments in the 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 it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0078] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A method for automatic parking control of an electric forklift on a ramp, characterized in that, include: Obtain the total mass of the forklift when it is on a slope, as well as the slope angle measured by the longitudinal angle sensor of the vehicle body; The gravity acting on the forklift is determined based on the total mass; the ramp resistance is determined based on the gravity and the ramp angle; and the rolling resistance is determined based on the gravity, the ramp angle, and the coefficient of friction. When the automatic parking conditions are met, the target slope parking braking force is determined based on the slope resistance and the rolling resistance. The target current value corresponding to the target ramp parking braking force is determined based on the relationship between the current value and the ramp parking braking force. Adjust the current value of the automatic parking brake proportional pressure reducing valve to the target current value to achieve automatic parking.

2. The automatic parking control method for electric forklifts on ramps according to claim 1, characterized in that, Determining ramp resistance based on gravity and ramp angle, and determining rolling resistance based on gravity, ramp angle, and coefficient of friction, including: The ramp resistance is calculated according to the first preset formula; The first preset formula is: Fi=G sin(θ); Wherein, Fi is the ramp resistance, G is the gravity, and θ is the ramp angle; The rolling resistance is calculated according to the second preset formula; The second preset formula is: Fj=µG cos(θ); Wherein, Fj is the rolling resistance, µ is the coefficient of friction, G is the gravity, and θ is the ramp angle.

3. The automatic parking control method for electric forklifts on ramps according to claim 1, characterized in that, Determining the target slope parking braking force based on the slope resistance and the rolling resistance includes: The target ramp parking braking force is calculated according to the third preset formula; The third preset formula is: Fb = Fi - Fj; Wherein, Fb is the parking braking force of the target ramp, Fi is the ramp resistance, and Fj is the rolling resistance.

4. The automatic parking control method for electric forklifts on ramps according to claim 1, characterized in that, Before determining the target slope parking braking force based on the slope resistance and the rolling resistance, the method further includes: The system acquires the accelerator pedal angle from the accelerator pedal angle sensor, the brake pedal angle from the brake pedal angle sensor, the on / off status of the parking brake switch, the current gear position of the gear switch, and the motor speed. If the switch is closed, the manual parking brake solenoid valve is closed, and the current of the automatic parking brake proportional pressure reducing valve is set to zero. If the switch is in the open state, determine whether the forklift's current state meets the automatic parking conditions based on the accelerator pedal angle, the brake pedal angle, the current gear, and the motor speed.

5. The automatic parking control method for electric forklifts on ramps according to claim 4, characterized in that, Determining whether the forklift's current state meets the automatic parking conditions based on the accelerator pedal angle, the brake pedal angle, the current gear, and the motor speed includes: The accelerator pedal angle determines whether to release the accelerator, and the brake pedal angle determines whether to apply the brake. If the forklift is currently in a state where the accelerator is released and the brake is not applied and the vehicle is in forward gear, and the forklift decelerates and the motor speed is zero, then the current state of the forklift is determined to meet the conditions for automatic parking uphill. If the forklift is currently in a state where the accelerator is released and the brake is not applied, and the vehicle is in reverse gear, and the forklift decelerates and the motor speed reaches zero, then the current state of the forklift is determined to meet the conditions for automatic parking while reversing uphill.

6. An automatic parking control system for electric forklifts on ramps, characterized in that, include: Vehicle controller, vehicle body longitudinal angle sensor, automatic parking brake proportional pressure reducing valve, hydraulic oil source, parking hydraulic brake, differential; The longitudinal angle sensor of the vehicle body is connected to the signal input terminal of the vehicle controller. The longitudinal angle sensor of the vehicle body is installed on the bottom of the forklift body and is used to measure the slope angle. The output port of the vehicle controller is connected to the automatic parking brake proportional pressure reducing valve. The hydraulic oil source is connected to the input terminal of the automatic parking brake proportional pressure reducing valve. The output terminal of the automatic parking brake proportional pressure reducing valve is connected to the parking hydraulic brake. The parking hydraulic brake is connected to the left and right drive wheels respectively through the differential. The vehicle controller is used to execute the steps of the electric forklift slope automatic parking control method according to any one of claims 1 to 5.

7. The electric forklift ramp automatic parking control system according to claim 6, characterized in that, It also includes a manual parking brake solenoid valve and a shuttle valve. The output port of the vehicle controller is connected to the manual parking brake solenoid valve and the automatic parking brake proportional pressure reducing valve, respectively. The hydraulic oil source is connected to the input terminals of the automatic parking brake proportional pressure reducing valve and the manual parking brake solenoid valve, respectively. The output terminals of the automatic parking brake proportional pressure reducing valve and the manual parking brake solenoid valve are connected to the input terminal of the shuttle valve, respectively. The output terminal of the shuttle valve is connected to the parking hydraulic brake.

8. The electric forklift ramp automatic parking control system according to claim 6, characterized in that, It also includes a parking brake switch, a gear position switch, an accelerator pedal angle sensor, a brake pedal angle sensor, a microcontroller, and a motor. The parking brake switch, the gear position switch, the accelerator pedal angle sensor, and the brake pedal angle sensor are connected to the signal input terminal of the vehicle controller. The microcontroller is connected to the vehicle controller and the motor, respectively. The motor is connected to the parking hydraulic brake.

9. The electric forklift ramp automatic parking control system according to claim 8, characterized in that, It also includes an on-board instrument panel, which is connected to the vehicle controller and is used to display the parking brake status.

10. The electric forklift ramp automatic parking control system according to claim 9, characterized in that, The vehicle controller is connected to the microcontroller and the vehicle instrument cluster via a CAN bus.

Images