Scissor forklift steering control method based on central point dynamic differential

Abstract

The invention discloses a shear forklift steering control method and system based on central point dynamic differential, and the method comprises the following steps: S1, sensor module calibration: collecting the angle values of the right limit and the left limit of a shear forklift steering mechanism, calculating the difference value between the right limit and the left limit, converting the difference value into an actual degree, and carrying out the calibration of a sensor module; calibrating a scale factor and a straight-going intermediate value; s2, real-time steering angle calculation: reading a current measured value of an angle sensor, judging whether a left wheel is an inner side wheel or an outer side wheel, and calculating a current steering angle alpha in combination with a scale factor; s3, dynamic differential ratio calculation: based on the steering angle alpha in the step S2, calculating a central point turning radius R through a central point steering geometric model, and deriving an inner and outer wheel differential ratio K; and S4, adjusting and outputting the target rotating speeds of the inner wheel and the outer wheel according to the differential ratio K to realize dynamic differential control. By dynamically adjusting the rotating speed of the motor, the load difference of the motor can be reduced, the service life is prolonged, and the steering stability is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle control, and particularly relates to a steering control method for a scissor lift truck based on dynamic differential of the center point. Background Art

[0002] A scissor lift truck (hereinafter referred to as a scissor truck) is a high-altitude operation device widely used in fields such as construction, industry, telecommunications, and logistics. With its high efficiency, safety, and flexibility, the scissor truck has become the core equipment for modern high-altitude operations. When the scissor truck steers, due to the different turning radii of the inner and outer wheels, the following problems occur: uneven motor loads; the motor current of the inner wheel is significantly higher than that of the outer wheel, resulting in increased heat generation and shortened motor life. Existing scissor trucks generally adopt a differential steering mode to achieve flexible steering through the speed difference of the drive wheels.

[0003] Traditional vehicles adopt the Ackerman steering principle and rely on a mechanical linkage system (such as a trapezoidal mechanism) to achieve the difference in steering angles of the inner and outer wheels, ensuring that all wheels rotate around the same center point. Steering depends on static geometric relationships. Once the steering angle is fixed, the speed difference between the inner and outer wheels is determined by the mechanical structure and cannot be adjusted in real time. However, due to structural limitations, it is difficult to directly apply this principle to scissor trucks, and existing steering control methods cannot adjust in real time according to the steering angle, resulting in a mismatch between the inner and outer wheel speed ratios; insufficient sensor fusion, and the dynamic differential ratio is not calculated using the steering angle and geometric model.

[0004] A patent with the publication number CN119527423A discloses a vehicle, a vehicle steering control system and method, belonging to the technical field of vehicle control. The vehicle steering control method includes: receiving the current steering angle of the vehicle; when the current steering angle is greater than a preset trigger angle and less than the maximum steering angle of the wheels, then adding a target angle difference to the value of the preset trigger angle to obtain a target steering angle; when the current steering angle is equal to the maximum steering angle, then using the maximum desired steering angle as the target steering angle; obtaining the target differential ratio of the vehicle drive wheels based on the target steering angle, where the target differential ratio is the differential ratio when the drive wheels steer to the target steering angle; adjusting the differential ratio of the drive wheels to the target differential ratio. Adjusting the differential ratio through the brake in this invention may exacerbate the wear of the braking system and affect the service life of the vehicle; at the same time, to increase the power compensation torque (such as K times the original torque), it may lead to a significant increase in energy consumption, reduce the energy efficiency of the vehicle, and reduce the steering control accuracy. Summary of the Invention

[0005] The present invention mainly aims at the problem that in the prior art, traditional vehicles adopt the Ackermann steering principle and rely on a mechanical linkage system (such as a trapezoidal mechanism) to achieve the difference in steering angles between the inner and outer wheels, ensuring that all wheels rotate around the same center point. The steering depends on static geometric relationships. After the steering angle is fixed, the speed difference between the inner and outer wheels is determined by the mechanical structure and cannot be adjusted in real time. However, due to structural limitations, it is difficult to directly apply it to scissors forklifts, and the existing steering control methods cannot adjust in real time according to the steering angle, resulting in a mismatch between the inner and outer wheel speed ratios; there is insufficient sensor fusion and the dynamic differential ratio is not calculated using the steering angle and geometric model. Therefore, a steering control method for scissors forklifts based on dynamic differential at the center point is proposed.

[0006] A steering control method and system for scissors forklifts based on dynamic differential at the center point. The scissors forklift steering control system includes an angle sensor module, a microprocessor calculation module, and a motor drive execution module; the steering control method includes the following steps:

[0007] S1. Sensor module calibration: Collect the angle values at the right and left limits of the scissors forklift steering mechanism, calculate the difference between the right limit and the left limit and convert it into the actual degree, and calibrate the scale factor and the straight-ahead middle value;

[0008] S2. Real-time steering angle calculation: Read the current angle sensor measurement value, determine whether the left wheel is the inner wheel or the outer wheel, and calculate the current steering angle α in combination with the scale factor;

[0009] S3. Dynamic differential ratio calculation: Based on the steering angle α in step S2, calculate the center point turning radius R through the center point steering geometric model, and derive the inner and outer wheel differential ratio K;

[0010] S4. Adjust and output the target speeds of the inner and outer wheels according to the differential ratio K to achieve dynamic differential control.

[0011] Further, in step S1, the scale factor is calculated according to the actual degree, and the calculation formula of the scale factor is:

[0012]

[0013] In the formula, a outer,max represents the maximum mechanical steering angle of the outer wheel, and a inner,max represents the maximum mechanical steering angle of the inner wheel.

[0014] Further, in step 1, the calculation expression of the straight-ahead middle value is as follows:

[0015] Middle value = right + (a outer,max * scale factor) * δ

[0016] Or

[0017] Middle value = left - (ainner,max *(Scaling factor)*δ

[0018] Where right and left respectively represent the acquisition values of the right and left limit angle sensors, and δ represents the accuracy of the angle sensor.

[0019] Furthermore, the acquisition values of the right and left limit angle sensors satisfy the following conditions:

[0020] left - right = (a outer,max + a inner,max ) * (Scaling factor) * δ

[0021] Where δ represents the accuracy of the angle sensor.

[0022] Furthermore, in step S2, when the left wheel is the inner wheel, the expression of the current angle value is:

[0023]

[0024] When the left wheel is the outer wheel, the expression of the current angle value is:

[0025]

[0026] Where α represents the current angle value.

[0027] Furthermore, in step 3, the turning radius R of the center point is calculated by the following formula:

[0028]

[0029] Where L represents the wheelbase of the scissors forklift, W represents the wheel track of the scissors forklift, and α represents the steering angle of the left wheel.

[0030] Furthermore, the calculation formula of the inner - outer wheel differential ratio K is as follows:

[0031]

[0032] Where R represents the turning radius of the center point.

[0033] Furthermore, the angle sensor module is used to perform difference calculation, scaling factor calibration and intermediate value determination; the micro - processor calculation module calculates the differential ratio K in real - time based on the steering angle α; the motor drive execution module is used to execute the target rotational speed instructions of the inner and outer wheels for output.

[0034] Furthermore, the angle sensor module is a high - precision rotary encoder with a measurement error less than 0.1°.

[0035] A scissors forklift steering control system adopts the above - mentioned scissors forklift steering control method.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] 1. The steering control method of the present invention includes the following steps: S1. Sensor module calibration: Collect the angle values of the right and left limits of the steering mechanism of the scissor lift truck, calculate the difference between the right limit and the left limit and convert it into the actual degree, and calibrate the scale factor and the straight-ahead middle value; S2. Real-time steering angle calculation: Read the current angle sensor measurement value, determine whether the left wheel is the inner wheel or the outer wheel, and calculate the current steering angle α in combination with the scale factor;

[0038] S3. Dynamic differential ratio calculation: Based on the steering angle α, calculate the center point turning radius R through the center point steering geometric model, and deduce the inner and outer wheel differential ratio K; S4. Adjust and output the target speeds of the inner and outer wheels according to the differential ratio K. By introducing the dynamic differential ratio, combining the real-time data of the sensor with the geometric model, the present invention updates the differential ratio K in real time according to the change of the steering angle, optimizes the motor load, reduces the tire wear, and improves the steering stability at the same time.

[0039] 2. The present invention is based on the rotational speed differential control of the electronic sensor and the dynamic geometric model, optimizing the control accuracy; at the same time, it is also applicable to the scissor lift truck with limited structure, having the advantages of real-time performance and adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is the flow chart of the steering control method of the scissor lift truck of the present invention;

[0041] Figure 2 is the schematic diagram of the mathematical model of the steering system of the scissor lift truck of the present invention;

[0042] Figure 3 is the schematic diagram of the relationship between the rotational speed and the angle of the inner wheels of the scissor lift truck turning left and right in Embodiment 1 of the present invention;

[0043] Figure 4 is the real-time control flow chart of Embodiment 3 of the present invention.

[0044] In the above figures, L: wheelbase; W: track width; α: left wheel steering angle; R: center point turning radius; R inner : inner wheel turning radius; R outer : outer wheel turning radius. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] In order to clearly illustrate the technical features of the solution of the present invention application, the present invention will be described in detail below through specific embodiments and in combination with its drawings.

[0046] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application may be practiced in other ways different from those described herein. Therefore, the scope of protection of the present application is not limited by the specific embodiments disclosed below.

[0047] In addition, in the description of the present application, it should be understood that the orientation or positional relationships indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present application. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.

[0048] In the present application, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or a communication connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0049] In the present application, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may be the direct contact between the first and second features, or the indirect contact between the first and second features through an intermediate medium. In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0050] Embodiment 1

[0051] As Figure 1As shown in the figure, a steering control method and system for a scissor lift truck based on dynamic differential at the center point. The scissor lift truck steering control system includes an angle sensor module, a microprocessor calculation module, and a motor drive execution module. The steering control method includes the following steps:

[0052] S1. Sensor module calibration: Collect the angle values at the right and left limits of the scissor lift truck steering mechanism, calculate the difference between the right limit and the left limit and convert it into the actual degree, and calibrate the scale factor and the straight-ahead middle value;

[0053] S2. Real-time steering angle calculation: Read the current angle sensor measurement value, determine whether the left wheel is the inner wheel or the outer wheel, and calculate the current steering angle α in combination with the scale factor;

[0054] S3. Dynamic differential ratio calculation: Based on the steering angle α in step S2, calculate the center point turning radius R through the center point steering geometry model, and deduce the inner and outer wheel differential ratio K;

[0055] S4. Adjust and output the target speeds of the inner and outer wheels according to the differential ratio K to achieve dynamic differential control.

[0056] In this embodiment, the scissor lift truck steering control system includes an angle sensor module, a microprocessor calculation module, and a motor drive execution module. The angle sensor module uses a rotary encoder to measure the steering angle of the left wheel, and the accuracy of the rotary encoder is 0.1°. The microprocessor calculation module uses an STM32 series MCU, which has a built-in sensor calibration unit and a dynamic differential ratio calculation unit. The motor drive execution module uses a dual-channel PWM controller to drive the inner and outer wheel motors.

[0057] In this embodiment, a dynamic differential ratio calculation method based on the center point steering model is adopted, which specifically includes sensor calibration, real-time steering angle calculation, and differential ratio dynamic adjustment.

[0058] Sensor calibration: Collect the left and right limit angle values through the angle sensor module. The right and left tables respectively represent the collected values of the right and left limit angle sensors. right = 500, left = 2500, and the calculated difference is 2500 - 500 = 2000. The collected values of the right and left limit angle sensors satisfy the following conditions:

[0059] left - right = (a outer,max + a inner,max ) * scale factor * δ

[0060] In the formula, δ represents the accuracy of the angle sensor. In this embodiment, δ = 0.1°;

[0061] Conversion to actual degrees:

[0062] Scale factor calculation:

[0063]

[0064] Wherein, a outer,max represents the maximum mechanical steering angle of the outer wheel, and a inner,max represents the maximum mechanical steering angle of the inner wheel. Given that a outer,max = 68°, a inner,max = 45°, then

[0065] Determine the straight-ahead middle value: According to the calculation formula, the middle value = 500 + (68 * 5.87) * 0.1 = 539.916.

[0066] The real-time control process is as follows: Read the current angle sensor value. If the measured value is 600°, it is determined that the left wheel is the inner wheel; Calculate the steering angle: Substitute the specific values mentioned above to obtain

[0067]

[0068] As Figure 2 shown, through the known steering angle α of the left wheel, dynamically calculate the turning radius R of the center point, and deduce the differential ratio K between the inner and outer wheels. Calculate the turning radius R of the center point. Given that the wheelbase L = 2m and the track width W = 1.18m. The definition of the center steering angle is As Figure 2 shown, the relationship between the left wheel angle and the center point angle is as follows: From the geometric relationship of the left wheel, it can be obtained that:

[0069]

[0070] After arranging the equation, the turning radius R of the center point is finally obtained as:

[0071]

[0072] Substitute the parameters to calculate and obtain

[0073]

[0074] Calculate the differential ratio K between the inner and outer wheels. Its expression is as follows:

[0075]

[0076] Output the target rotational speeds of the inner and outer wheels: Outer wheel rotational speed = Inner wheel rotational speed * 1.22.

[0077] As Figure 3 shown, based on the center point steering geometry, calculate the rotational speed ratio between the inner and outer wheels in real time, so that the motor load difference is reduced by 30%, the steering stability is improved, and the tire wear is reduced.

[0078] Embodiment 2

[0079] As Figure 1 shown, a steering control method and system for a scissor lift truck based on dynamic differential of the center point. The scissor lift truck steering control system includes an angle sensor module, a microprocessor calculation module, and a motor drive execution module; the steering control method includes the following steps:

[0080] S1. Sensor module calibration: Collect the angle values of the right and left limits of the scissor lift truck steering mechanism, calculate the difference between the right limit and the left limit and convert it into actual degrees, and calibrate the proportional factor and the straight-ahead middle value;

[0081] S2. Real-time steering angle calculation: Read the current angle sensor measurement value, determine whether the left wheel is the inner wheel or the outer wheel, and calculate the current steering angle α in combination with the proportional factor;

[0082] S3. Dynamic differential ratio calculation: Based on the steering angle α in step S2, calculate the center point turning radius R through the center point steering geometric model, and deduce the inner and outer wheel differential ratio K;

[0083] S4. Adjust and output the target speeds of the inner and outer wheels according to the differential ratio K to achieve dynamic differential control.

[0084] In this embodiment, the difference from Embodiment 1 is that the straight-ahead middle value is calculated in another way, that is, the middle value = left - (α inner,max * proportional factor) * precision; the calculation of other values of the sensor calibration module is the same as that in Embodiment 1.

[0085] Real-time control module: When the left wheel is the inner wheel, the relationship between the steering angle and the turning radius is as follows:

[0086]

[0087] In the formula, R inner represents the inner wheel turning radius and satisfies W represents the wheelbase;

[0088] The expression of the center point turning radius R is as follows:

[0089]

[0090] Substitute and calculate the differential ratio K as:

[0091]

[0092] Substitute into the expression of the center point turning radius R to obtain:

[0093]

[0094] In this embodiment, the steering angle is measured by an electronic sensor, and the differential ratio is dynamically calculated in combination with the center-point steering geometry model, without the need for a complex mechanical structure, and the control accuracy is optimized.

[0095] Embodiment 3

[0096] A steering control method and system for a scissor lift truck based on center-point dynamic differential. The scissor lift truck steering control system includes an angle sensor module, a microprocessor calculation module, and a motor drive execution module. In this embodiment, it mainly aims at the steering control of non-road special scissor lift trucks under complex road conditions, and dynamically adjusts the differential ratio through fuzzy rules, as Figure 4 shown.

[0097] Improve the steering system. Integrate a fuzzy logic controller in the microprocessor to replace the dynamic differential ratio calculation module; the input variables are the steering angle, vehicle speed, and road surface friction coefficient (obtained through an additional sensor); the output variable is the adjustment coefficient of the differential ratio.

[0098] Fuzzy rule design. Rule 1: If the steering angle is large and the vehicle speed is low, the differential ratio adjustment coefficient increases by 20%; Rule 2: If the road surface friction coefficient is low, the differential ratio adjustment coefficient decreases by 15%; The rule base contains 20 similar rules, and the weights are optimized through experimental data.

[0099] The specific implementation process is as follows: The sensor module calibration step is the same as that in Embodiment 1, and the straight-ahead middle value confirmed by sensor calibration during factory debugging; when the straight-ahead middle value is greater than the measured value of the current sensor, the vehicle turns left, otherwise the vehicle turns right; then calculate the current steering angle, center-point turning radius, and differential ratio in sequence, and output the target speeds of the inner and outer wheels; Dynamically correct the differential ratio according to the output of the fuzzy controller, adjusting it from 1.22 to 1.18. Then, the motor drive execution module responds in real time to the adjusted speed command to achieve dynamic adjustment of the differential ratio, making the control of the steering system more stable.

[0100] Embodiment 4

[0101] In this embodiment, a scissor lift truck steering system based on center-point dynamic differential is provided. This system adopts the steering control method in Embodiment 1, Embodiment 2, or Embodiment 3. The scissor lift truck steering control system includes an angle sensor module, a microprocessor calculation module, and a motor drive execution module. Among them, the angle sensor module: uses a high-precision rotary encoder, which is installed on the steering mechanism of the scissor lift truck to measure the steering angle in real time. The microprocessor calculation module: receives the angle data transmitted by the angle sensor module and calculates the differential ratio in real time according to a preset algorithm. The motor drive execution module: receives the differential ratio signal output by the microprocessor calculation module, adjusts the speeds of the inner and outer wheel motors, and realizes dynamic differential control.

[0102] System working principle: After starting the system, the sensor module is first calibrated, including collecting the limit angle values, calculating the scale factor, and calibrating the straight-ahead middle value; during the steering process of the scissor lift truck, the angle sensor module measures the steering angle in real time and transmits it to the microprocessor calculation module. The microprocessor calculation module calculates the differential ratio in real time through the center-point steering geometric model according to the received angle data; the motor drive execution module adjusts the rotational speeds of the inner and outer wheel motors according to the differential ratio signal to achieve stable steering of the scissor lift truck.

[0103] Obviously, the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A steering control method and system for a scissor lift truck based on center point dynamic differential, characterized in that: The scissor lift steering control system includes an angle sensor module, a microprocessor calculation module and a motor drive execution module; the steering control method includes the following steps: S1, sensor module calibration: collect the angle values ​​of the right and left limits of the scissor lift truck steering mechanism, calculate the difference between the right limit and the left limit and convert it into actual degrees, calibrate the scale factor and the straight middle value; S2, real-time steering angle calculation: read the current angle sensor measurement value, determine whether the left wheel is the inner wheel or the outer wheel, and calculate the current steering angle α in combination with the proportional factor; S3, dynamic differential ratio calculation: based on the steering angle α in step S2, the center point turning radius R is calculated through the center point steering geometry model, and the inner and outer wheel differential ratio K is derived; S4. Adjust and output the target speeds of the inner and outer wheels according to the differential ratio K to achieve dynamic differential control.

2. The steering control method of a scissor lift truck based on center point dynamic differential according to claim 1, characterized in that: In step S1, a proportional factor is calculated according to the actual degree, and the calculation formula of the proportional factor is: In the formula, a outer,max Indicates the maximum mechanical steering angle of the outer wheel, a inner,max Indicates the maximum mechanical steering angle of the inner wheel.

3. The steering control method of a scissor lift truck based on center point dynamic differential according to claim 1, characterized in that: In step 1, the calculation expression of the straight line intermediate value is as follows: Middle value = right + (a outer,max * scale factor)*δ or Middle value = left-(a inner,max * scale factor)*δ In the formula, right and left represent the right and left limit angle sensor acquisition values ​​respectively, and δ represents the angle sensor accuracy.

4. The steering control method of a scissor lift truck based on center point dynamic differential according to claim 3, characterized in that: The right and left limit angle sensor acquisition values ​​meet the following conditions: left-right=(a outer,max +a inner,max )*scaling factor*δ Where δ represents the angle sensor accuracy.

5. The steering control method of a scissor lift truck based on center point dynamic differential according to claim 1, characterized in that: In step S2, when the left wheel is the inner wheel, the expression of the current angle value is: When the left wheel is the outer wheel, the expression of the current angle value is: Where α represents the current angle value.

6. The steering control method of a scissor lift truck based on center point dynamic differential according to claim 1, characterized in that: In step 3, the center point turning radius R is calculated by the following formula: Where L is the wheelbase of the scissor lift truck, W is the wheelbase of the scissor lift truck, and α is the steering angle of the left wheel.

7. The steering control method of a scissor lift truck based on center point dynamic differential according to claim 6, characterized in that: The calculation formula of the inner and outer wheel differential ratio K is as follows: Where R represents the turning radius of the center point.

8. The steering control method of a scissor lift truck based on center point dynamic differential according to claim 1, characterized in that: The angle sensor module is used to perform difference calculation, proportional factor calibration and intermediate value determination; the microprocessor calculation module calculates the differential ratio K in real time based on the steering angle α; the motor drive execution module is used to execute the output inner and outer wheel target speed instructions.

9. The steering control method of a scissor lift truck based on center point dynamic differential according to claim 8, characterized in that: The angle sensor module is a high-precision rotary encoder with a measurement error of less than 0.1°.

10. A scissor lift steering control system, characterized in that: A scissor lift steering control method as claimed in any one of claims 1 to 9 is adopted.

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