Drive wheel low load condition under the forward-moving forklift starting traction control method and equipment

Abstract

The application discloses a front-moving forklift starting traction control method and equipment under low load working condition of driving wheels, comprising: a controller acquires an acceleration instruction, and when the acceleration instruction exceeds a preset starting threshold, it is determined that the driver has a starting intention; data acquisition and slip tendency discrimination: the controller acquires the actual linear speed of the driven wheel and the actual linear speed of the driving wheel in real time, and calculates the speed difference; at the same time, the controller acquires the portal displacement signal and the load weight signal, and calculates the actual load of the driving wheel under the current working condition according to the signals; when it is determined that the starting intention exists, the controller determines the current starting traction control mode according to the relationship between the actual load of the driving wheel and the preset load threshold, and outputs the traction force according to the acceleration rate corresponding to the current starting traction control mode; during the starting process, the controller dynamically adjusts the change rate of the traction force output according to the real-time calculated speed difference; the method controls the traction force by limiting the current rise rate, forms closed-loop regulation, and smoothly transitions to normal driving after the slip is eliminated.

Description

Technical Field

[0001] This invention relates to the field of forklift technology, and in particular to a method and device for starting and controlling the traction of a reach truck under low load conditions on the drive wheels. Background Technology

[0002] Reach trucks are widely used in short-to-medium distance material handling scenarios such as warehouses and factories due to their compact structure and maneuverability. Currently, most reach trucks adopt a rear-mounted single-drive wheel design, meaning the drive wheel is located at the rear of the truck for propulsion, while the load-bearing wheels (driven wheels) on the front outriggers are responsible for carrying goods. This structure results in a significant variation in the vehicle's center of gravity distribution depending on the mast position and the weight of the goods. In existing technologies, the starting control of reach trucks typically relies on the driver's operation of the accelerator pedal / handle. The controller directly outputs the corresponding torque or speed to the traction motor based on the opening of the accelerator pedal / handle. To prevent excessively abrupt starts, some control strategies employ fixed soft-start algorithms, i.e., pre-setting an acceleration rise curve to mitigate the impact of starting the vehicle.

[0003] The aforementioned conventional control strategies have significant limitations. First, traditional control systems often only equip the drive motor with a speed sensor, indirectly reflecting vehicle speed by monitoring the motor's rotation speed. This method struggles to directly and accurately determine whether the drive wheels are slipping relative to the ground. Second, under conditions such as full load (mast forward movement), the normal force on the drive wheels decreases, resulting in severely insufficient traction with the ground. In this situation, if traction is still output at the conventional acceleration rate, even with a soft start, the drive wheels are highly susceptible to overcoming static friction and momentarily slipping. Once the drive wheels slip, it not only causes abnormal tire wear and energy waste but also leads to vehicle swaying during start-up and loss of steering control, posing a significant safety hazard, especially on slippery surfaces.

[0004] To address the issue of slippage during startup, existing solutions, such as the patent with publication number CN111056497A, propose an anti-slip control method for rear-wheel-drive forklifts. This method detects slippage by monitoring the front-to-rear wheel speed ratio and reduces motor output power accordingly. However, these solutions are mostly intervention controls implemented after slippage occurs, representing passive remedial measures. Furthermore, the control parameters are relatively simple, failing to fully consider the proactive prevention needs of reach trucks during startup, particularly under conditions where the preload on the drive wheels is extremely low due to changes in mast position. Therefore, how to proactively identify slippage risks and optimize traction output in advance during the startup phase of reach trucks, especially under low-load conditions, to achieve a smooth start, has become a pressing technical problem for those skilled in the art. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a method and device for starting traction control of reach trucks under low load conditions of drive wheels. The traction force is controlled by limiting the rate of increase of current, forming a closed-loop regulation until slippage is eliminated and the truck smoothly transitions to normal driving.

[0006] The present invention proposes a method for starting and controlling the traction of a reach truck under low load conditions on the drive wheels, comprising: The controller receives an acceleration command, and when the acceleration command exceeds the preset starting threshold, it determines that the driver intends to start. Data acquisition and slippage tendency detection: The controller acquires the actual linear velocity of the driven wheel in real time. and the actual linear velocity of the drive wheels And calculate the speed difference Simultaneously, the controller acquires the gantry displacement signal and load weight signal, and calculates the actual load on the drive wheels under the current operating conditions. When a starting intention is detected, the controller determines the current start traction control mode based on the relationship between the actual load of the drive wheels and the preset load threshold, and outputs traction force according to the acceleration rate corresponding to the current start traction control mode. During the start-up process, the controller dynamically adjusts the rate of change of traction output based on the real-time calculated speed difference.

[0007] Furthermore, the real-time acquisition of the actual linear velocity of the driven wheel and the actual linear velocity of the drive wheels Specifically: The actual linear velocity The speed is obtained by the right front wheel speed sensor and the left front wheel speed sensor installed on the right front wheel and the upper left front wheel of the reach truck. The actual linear velocity of the drive wheel The speed is obtained by a drive wheel speed sensor installed on the drive wheel of the traction motor.

[0008] Furthermore, the actual load on the drive wheel The calculation formula is derived from the torque balance equation and is as follows:

[0009] If the rear wheel is a single wheel, then ; If the rear wheels are dual wheels, then , This is a correction factor for the load on the drive wheels; in, For rear wheel load, The weight of the vehicle under standard unloaded conditions. The distance between the center of gravity and the front wheel. This is the load weight signal, which is the weight value of the cargo measured by the load weight sensor. The distance between the load center and the front wheel. This refers to the wheelbase of the entire vehicle.

[0010] Furthermore, the statement based on the actual load of the drive wheel The relationship with the preset load threshold determines the current start-up traction control mode, specifically including: Preset multiple load thresholds ,and Multiple acceleration rates can be set accordingly. ,and ; when Maintain acceleration rate ; when Maintain acceleration rate ; when Maintain acceleration rate ; when Maintain acceleration rate .

[0011] Furthermore, the aforementioned Differentiate according to the preset force level.

[0012] Furthermore, the step of outputting traction force according to the acceleration rate corresponding to the current traction control mode is specifically as follows: The controller switches to traction control mode, limiting the rate of increase of the traction motor current. To achieve control of traction force, the actual output torque of the traction motor. :

[0013] in, Based on the base torque.

[0014] Furthermore, the controller dynamically adjusts the rate of change of the traction force output based on the real-time calculated speed difference, specifically as follows: speed difference The difference between the preset base slip speed threshold Compare; like If the first preset time is maintained, the current acceleration rate will remain unchanged; like If it continues for the second preset time, it will automatically reduce to the next acceleration level.

[0015] Furthermore, it also includes an exit step: When speed difference While maintaining the preset time, the controller gradually relaxes the restriction on the rate of change of traction output according to the preset release curve until it returns to the normal acceleration characteristic curve that matches the current acceleration command. This is the preset exit threshold.

[0016] A reach truck, characterized by employing the method described above.

[0017] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described above.

[0018] The advantages of the reach truck starting traction control method and equipment under low load conditions of the drive wheels provided by this invention are as follows: After detecting the driver's intention to start, the judgment threshold is dynamically corrected by comparing the speed difference between the driven wheel (actual vehicle speed) and the drive wheel (which may slip), and combining the mast position (load state). Once slippage is detected, the traction force is immediately controlled by limiting the rate of current rise, forming a closed-loop regulation until the slippage is eliminated and the vehicle smoothly transitions to normal driving. Attached Figure Description

[0019] Fig. 1 This is a schematic diagram of the process of the present invention; Fig. 2 This is a simplified electrical schematic diagram of this embodiment; Fig. 3 A simplified diagram of the mechanical properties of the entire wheel load; Among them, 1-power battery, 2-vehicle key switch, 3-controller, 4-accelerator pedal, 5-traction motor, 6-drive wheel speed sensor, 7-right front wheel speed sensor, 8-left front wheel speed sensor, 9-mast displacement sensor, 10-load weight encoder. Detailed Implementation

[0020] The technical solution of the present invention will now be described in detail through specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0021] like Figs. 1-3 As shown, the present invention proposes a method for starting and controlling the traction of a reach truck under low-load conditions of the drive wheels, comprising: Step 1: Determining the Starting Intent: The controller receives the acceleration command. When the acceleration command exceeds the preset starting threshold, it determines that the driver has a starting intent. Step 2: Data Acquisition and Slippage Tendency Determination: The controller acquires the actual linear velocity of the driven wheel in real time. and the actual linear velocity of the drive wheels And calculate the speed difference Simultaneously, the controller acquires the gantry displacement signal and load weight signal, and calculates the actual load on the drive wheels under the current operating conditions. Step 3: When a starting intention is detected, the controller determines the current start-up traction control mode based on the relationship between the actual load of the drive wheels and the preset load threshold, and outputs traction force according to the acceleration rate corresponding to the current start-up traction control mode. Step 4: During the start-up process, the controller dynamically adjusts the rate of change of traction output based on the real-time calculated speed difference.

[0022] Through steps one through four, after detecting the driver's intention to start, the judgment threshold is dynamically adjusted by comparing the speed difference between the driven wheel (actual vehicle speed) and the drive wheel (which may slip), and combining this with the mast position (load status). Once slippage is detected, the traction force is immediately controlled by limiting the rate of current rise, forming a closed-loop regulation until the slippage is eliminated and the vehicle smoothly transitions to normal driving.

[0023] The above control method can be implemented through a set control system, specifically including a power battery 1, a vehicle key switch 2, a controller 3, an accelerator pedal 4, a traction motor 5, drive wheel speed sensors 6, a right front wheel speed sensor 7, a left front wheel speed sensor 8, a mast displacement sensor 9, and a load weight encoder 10. The controller 3 communicates with the accelerator pedal 4, drive wheel speed sensors 6, right front wheel speed sensors 7, left front wheel speed sensors 8, mast displacement sensor 9, and load weight sensor 10 via CAN signals. The accelerator pedal 4 outputs a voltage signal U, with a preset dead zone voltage of 0.5V (configurable). When in the dead zone, the controller 3 does not issue a start command to the traction motor 5. The mast displacement sensor 9 uses a wire encoder with millimeter-level accuracy. The drive wheel speed sensors 6, right front wheel speed sensors 7, and left front wheel speed sensors 8 are all pulse sensors, and the collected pulse signals are input to the controller for speed calculation.

[0024] 1. Driver intent analysis and starting condition determination; The controller 3 monitors the voltage signal U of the accelerator pedal 4 in real time. When it detects an increase in the opening of the accelerator pedal 4, and the opening value exceeds the preset starting threshold (i.e., the starting dead zone threshold), it determines that the driver intends to start. At the same time, it detects the current gear signal (forward / reverse) and the brake pedal status to confirm that the vehicle is in a safe state of no braking and permissible driving, and then triggers subsequent control logic.

[0025] The actual linear velocity of the driven wheel The speed is collected by the speed sensor 7 installed on the right front wheel and the speed sensor 8 installed on the left front wheel respectively. The speed collected by the speed sensor 8 on the left front wheel is defined as follows: The speed collected by the right front wheel speed sensor 7 is defined as follows: ,but Since the front wheels are driven wheels, their linear velocity accurately reflects the vehicle's actual speed relative to the ground.

[0026] Actual linear velocity of the drive wheel The data is collected by the drive wheel speed sensor 6, which is installed on the traction motor 5 on the drive wheel.

[0027] The controller 3 filters the raw pulse signals collected by the right front wheel speed sensor 7, the left front wheel speed sensor 8, and the drive wheel speed sensor 6, removes abnormal abrupt values, and calculates the real-time linear velocity values ​​for each.

[0028] 2. Dynamic slippage tendency judgment; Controller 3 calculates the speed difference between the drive wheel and the driven wheel in real time. To adapt to different load conditions, dynamic thresholds are set.

[0029] This embodiment monitors the speed difference between the driven wheel and the driving wheel in real time, enabling intervention control at the critical point (micro-slip stage) when the tire is about to experience macro-slippage with the ground, thus achieving a leap from post-slippage remediation to pre-slippage prevention.

[0030] Preset baseline slip speed difference threshold: The baseline slip speed difference threshold is set through calibration tests. (Can be preset to 0.1m / s).

[0031] Operating condition correction: Controller 3 reads signals from gantry displacement sensor 9 (gantry displacement) and load weight sensor 10 (load weight). Based on... Fig. 2 The load F3 on the drive wheel is calculated according to the torque balance equation: ; If the rear wheel is a single wheel, then ; If the rear wheels are dual wheels, then , This is a correction factor for the drive wheel load, determined and provided by the manufacturer. in, For rear wheel load, The distance between the load center and the front wheel. The load weight signal is the weight value of the cargo measured by the load weight sensor. The standard unloaded vehicle weight is a known quantity, preset by the manufacturer and input into controller 3; The distance between the center of gravity and the front wheel is a known quantity, measured by the manufacturer and pre-valued into the controller; The wheelbase of the vehicle is a known value, preset by the manufacturer and entered into the controller.

[0032] in, , This refers to the center distance of the cargo load, and its specific value can be determined based on the working conditions. The displacement of the gantry is measured by the gantry displacement sensor.

[0033] At start-up, if the calculated drive wheel load Below the preset load threshold (positive pressure on the drive wheel) indicates that it is under low load and has a tendency to slip dynamically.

[0034] This embodiment combines data collection and calculation with devices such as gantry displacement sensors and load weight sensors. The strategy can intelligently identify the positive pressure state of the drive wheels (low load condition) and dynamically adjust the control sensitivity, solving the technical pain point that the gantry is prone to slippage when starting after moving forward.

[0035] 3. Control strategy execution; Once slippage is detected, the controller immediately switches from "target torque / speed control mode" to "traction control activation mode". The specific control logic is as follows: Limiting the rate of acceleration: Instead of directly reducing the current torque, the rate of current rise of the traction motor 5 is strictly limited. ), Actual output torque of traction motor 5 , The base torque, which typically corresponds to the initial output torque of the motor at the current moment when entering the start-up traction control mode, serves as the starting point for integral calculation, ensuring that the torque can transition continuously when switching control modes and avoiding abrupt changes.

[0036] Integrating the rate of current rise yields the change in current. This integral term reflects the cumulative increase in current over time since entering control mode. This term is then compared with the base torque. Superposition yields the actual output torque that varies over time. .

[0037] This integral method ensures a smooth transition of traction and avoids sudden torque changes. It replaces the rapid ascent slope originally mapped from accelerator pedal 4 with a slope based on drive wheel load. The smooth slope when the velocity difference When the current decreases, controller 3 appropriately relaxes the current rise rate limit to adjust the motor acceleration. Specifically: Preset multiple load thresholds ,and Multiple acceleration rates can be set accordingly. ,and ; when Maintain acceleration rate ; when Maintain acceleration rate ; when Maintain acceleration rate ; when Maintain acceleration rate .

[0038] in They are differentiated according to preset force (e.g., 5000N).

[0039] Closed-loop regulation during start-up: establishing a speed difference To control the target, using the current rise rate A closed-loop control system for controlling the output.

[0040] speed difference The difference between the preset base slip speed threshold If a comparison is made, And if it continues for the first preset time (which can be 0.2s), the current acceleration rate will remain unchanged; if If it continues for the second preset time (which can be 0.2s), it will automatically reduce to the next acceleration level.

[0041] This embodiment uses the current rise rate to smoothly output traction, eliminating vehicle jerking and abnormal noise caused by slippage in traditional control, resulting in a smooth and stable start-up process, while reducing tire wear and improving starting safety on slippery roads.

[0042] 4. Activate traction control mode and exit; The controller continuously monitors the speed difference. .when (That is, when the speed drops below the threshold with a certain margin, which can be taken as 0.05m / s) and remains there for a certain preset time (which can be taken as 0.2s), the slippage state is determined to be eliminated. This is the preset exit threshold.

[0043] At this time, controller 3 does not immediately switch back to the original mode, but gradually relaxes the restriction on the rate of change of traction output according to the preset slow release curve, until it returns to the normal acceleration characteristic curve that matches the current opening of accelerator pedal 4.

[0044] Once the recovery is complete, the vehicle enters normal driving control mode, and the starting process ends.

[0045] Based on the above description of the embodiments, those skilled in the art will understand that the reach truck starting traction control method and device under low-load conditions of the drive wheels described in this embodiment can be implemented in pure software or deployed and run on a general-purpose or dedicated computing hardware platform. Based on this essence, the technical solution of this embodiment can be specifically implemented in the form of a software product containing program instructions. This software product can be stored on various non-volatile storage media or directly deployed as a local or cloud service. The program instructions are used to cause computer devices with processing capabilities—including but not limited to personal computers, server clusters, mobile terminals, or other network devices—to execute the steps described in this embodiment.

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for starting and controlling the traction of a reach truck under low load conditions on the drive wheels, characterized in that, include: The controller receives an acceleration command, and when the acceleration command exceeds the preset starting threshold, it determines that the driver intends to start. Data acquisition and slippage tendency detection: The controller acquires the actual linear velocity of the driven wheel in real time. and the actual linear velocity of the drive wheels And calculate the speed difference Simultaneously, the controller acquires the gantry displacement signal and load weight signal, and calculates the actual load on the drive wheels under the current operating conditions. When a starting intention is detected, the controller determines the current start traction control mode based on the relationship between the actual load of the drive wheels and the preset load threshold, and outputs traction force according to the acceleration rate corresponding to the current start traction control mode. During the start-up process, the controller dynamically adjusts the rate of change of traction output based on the real-time calculated speed difference.

2. The method according to claim 1, characterized in that, The real-time acquisition of the actual linear velocity of the driven wheel and the actual linear velocity of the drive wheels Specifically: The actual linear velocity The speed is obtained by the right front wheel speed sensor and the left front wheel speed sensor installed on the right front wheel and the upper left front wheel of the reach truck. The actual linear velocity of the drive wheel The speed is obtained by a drive wheel speed sensor installed on the drive wheel of the traction motor.

3. The method according to claim 1, characterized in that, Actual load on the drive wheel The calculation formula is derived from the torque balance equation and is as follows: If the rear wheel is a single wheel, then ; If the rear wheels are dual wheels, then , This is a correction factor for the load on the drive wheels; in, For rear wheel load, The weight of the vehicle under standard unloaded conditions. The distance between the center of gravity and the front wheel. This is the load weight signal, which is the weight value of the cargo measured by the load weight sensor. The distance between the load center and the front wheel. This refers to the wheelbase of the entire vehicle.

4. The method according to claim 1, characterized in that, The actual load on the drive wheel The relationship with the preset load threshold determines the current start-up traction control mode, specifically including: Preset multiple load thresholds ,and Multiple acceleration rates can be set accordingly. ,and ; when Maintain acceleration rate ; when Maintain acceleration rate ; when Maintain acceleration rate ; when Maintain acceleration rate .

5. The method according to claim 1, characterized in that, The Differentiate according to the preset force level.

6. The method according to claim 1, characterized in that, The output of traction force according to the acceleration rate corresponding to the current traction control mode is specifically as follows: The controller switches to traction control mode, limiting the rate of increase of the traction motor current. To achieve control of traction force, the actual output torque of the traction motor : in, Based on the base torque.

7. The method according to claim 1, characterized in that, The controller dynamically adjusts the rate of change of traction force output based on the real-time calculated speed difference, specifically: speed difference Difference threshold between the preset base slip speed and the threshold Compare; like If the first preset time is maintained, the current acceleration rate will remain unchanged; like If it continues for the second preset time, it will automatically reduce to the next acceleration level.

8. The method according to claim 1, characterized in that, It also includes an exit step: When speed difference While maintaining the preset time, the controller gradually relaxes the restriction on the rate of change of traction output according to the preset release curve until it returns to the normal acceleration characteristic curve that matches the current acceleration command. This is the preset exit threshold.

9. A reach truck, characterized in that, The method as described in any one of claims 1 to 8 shall be used.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1-8.

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