Overload prevention monitoring method for heavy telescopic boom forklift

Abstract

The invention provides an anti-overload monitoring method for a heavy telescopic boom forklift, which comprises the following steps of: calculating the change rates of horizontal and vertical coordinates of the gravity center of goods, when one of the change rates exceeds a set threshold value, judging that the goods have a falling risk, and then executing goods anti-falling avoidance operation by the forklift; when the change rate is smaller than the set threshold value, the dynamic risk parameter grade is calculated by combining the load spectrum data measured by the forklift on the horizontal ground, the ground slope information, the current actual load and the like, and corresponding operation is performed according to the dynamic risk parameter grade, so that the operation safety of the forklift under various terrain conditions is improved, overload of the forklift is avoided, and the working efficiency is improved. The service life of the forklift is effectively prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of forklifts, and particularly relates to an overload prevention monitoring method for a heavy telescopic boom forklift. Background Art

[0002] As a kind of cargo handling equipment widely used in fields such as logistics, warehousing, and manufacturing, the safety of forklifts has always been the focus of industry attention. During actual operation, forklifts need to operate on complex and changeable road conditions, such as long uphill sections, long downhill sections, or sections with uneven ground. The instability of these road conditions easily causes the center of gravity position of the goods on the fork to change.

[0003] In particular, when the goods carried by the forklift are loose boxes, the items inside the box may slide due to going uphill or downhill; for liquid containers, the center of gravity position is different from that in the flat position due to going uphill or downhill; for live animals with cages, the live animals move randomly, and the center of gravity changes irregularly, prone to sudden deviation. The above risks of center of gravity change will be further exacerbated due to the characteristics of the goods themselves.

[0004] Moreover, for the lifting boom of the forklift at different lifting heights, and when the center of gravity of the goods is at different horizontal distances from the root of the fork, its maximum safe load value is different. Once the change in the center of gravity of the goods exceeds the safe range, it is easy to cause the maximum safe load value to be exceeded, that is, the overload phenomenon, thus leading to safety accidents.

[0005] Currently, although some forklifts are equipped with cargo fixing devices or center of gravity monitoring systems, these technologies are usually only applicable to specific types of goods or simple working conditions, and cannot comprehensively address the problem of center of gravity change caused by complex road conditions and diverse goods. In addition, the existing center of gravity monitoring systems often cannot adapt to the changes of forklifts in a dynamic environment in real time and accurately, resulting in limited effects in actual applications.

[0006] Therefore, developing a technology that can monitor and adapt to the change of the center of gravity of goods on forklifts under complex road conditions in real time is of great significance for improving the safety and operation efficiency of forklifts. Summary of the Invention

[0007] Aiming at the deficiencies in the prior art, the purpose of the present invention is to propose an overload prevention monitoring method for a heavy telescopic boom forklift to solve the problems mentioned in the above background art section.

[0008] The present invention is realized through the following technical solutions: An overload prevention monitoring method for a heavy telescopic boom forklift, the heavy telescopic boom forklift includes a vehicle frame, a lifting boom rotatably arranged on the vehicle frame, the front end of the lifting boom forms a fork, a plurality of weighing sensors are arranged on the fork, and an inclination sensor is arranged on the vehicle frame; The overload prevention monitoring method includes: S1. Obtain the load spectrum data measured by the forklift on a horizontal ground. The load spectrum data is the maximum safe load value at different lifting heights of the lifting boom and different horizontal distances from the center of gravity of the goods to the root of the fork; S2. Obtain the horizontal and vertical coordinate change rates of the center of gravity of the goods through the weighing sensor. When one of the change rates exceeds the set threshold, it is determined that there is a risk of the goods falling. Then, the forklift performs an operation to avoid the goods from falling. Otherwise, proceed to step S3; S3. Obtain the angle between the ground on which the forklift travels and the horizontal plane through the tilt angle sensor. This angle is equal to the slope angle; obtain the current actual load on the lifting boom and the horizontal coordinate change rate of the center of gravity of the goods through the weighing sensor. Determine the dynamic risk parameter by combining the current actual load, the horizontal coordinate change rate of the center of gravity of the goods, the slope angle, and the maximum safe load value; S4. If the dynamic risk parameter exceeds the preset threshold, generate a risk classification signal including low and high levels, and perform the corresponding avoidance operation, specifically as follows: When the risk classification signal is a low-level risk signal, the forklift performs a low-risk avoidance operation. The low-risk avoidance operation includes any one or a combination of operations such as cutting off the lifting function of the lifting boom, adjusting the tilt angle of the lifting boom, and reducing the vehicle speed of the forklift; When the risk classification signal is a high-level risk signal, the forklift performs a high-risk avoidance operation. The high-risk avoidance operation includes temporarily increasing the pressure of the relief valve in the hydraulic system used to drive the lifting boom.

[0009] Further, the dynamic risk parameter is calculated by the following formula:

[0010] In the formula, represents the current actual load, obtained through the weighing sensor; represents the maximum safe load value in the load spectrum data corresponding to when the lifting height of the fork is h and the horizontal distance from the center of gravity of the goods to the root of the fork is d; represents the slope angle, obtained through the tilt angle sensor; represents the horizontal coordinate change rate of the center of gravity of the goods; represents the empirical coefficient.

[0011] Further, in step S3, it also includes inputting the ground coefficient into the formula model of the dynamic risk parameter. The dynamic risk parameter is calculated by the following formula:

[0012] In the formula, represents the ground coefficient; represents the current actual load, obtained by the load cell; represents the maximum safe load value in the corresponding load spectrum data when the lifting height of the forklift forks is h and the horizontal distance from the center of gravity of the goods to the root of the forklift forks is d; represents the slope angle, obtained by the tilt angle sensor; represents the change rate of the abscissa of the center of gravity of the goods; represents the empirical coefficient.

[0013] Further, in step S2, the operation for avoiding the falling of the goods includes: When the change rate of the ordinate of the center of gravity of the goods exceeds the set threshold, and the forklift is equipped with an electric leveling mechanism for leveling the lifting and lowering arm, a voice prompt or automatically controlling the electric leveling mechanism to rotate in the opposite direction of the offset of the center of gravity of the goods at a predetermined step length; When the change rate of the abscissa of the center of gravity of the goods exceeds the set threshold, a voice prompt or automatically controlling the forklift forks to tilt backward.

[0014] Further, when 0.8 ≤ DRP < 1, a low-risk classification signal is generated; when 1 < DRP < 1.5, a high-risk classification signal is generated.

[0015] Further, the pressure setting of the overflow valve in the hydraulic system of the lifting and lowering arm is set to at least two levels of maximum rated output pressure; when the dynamic risk parameter is within the safe preset range or the low-level risk range, the maximum output pressure of the overflow valve is set to the first-level maximum rated output pressure; when the dynamic risk parameter is within the high-level risk range, the maximum output pressure of the overflow valve is set to the second-level maximum rated output pressure, and the second-level maximum rated output pressure is greater than the first-level maximum rated output pressure.

[0016] The beneficial effects of the present invention are as follows: By calculating the change rates of the abscissa and ordinate of the center of gravity of the goods, when one of the change rates exceeds the set threshold, it is determined that there is a risk of the goods falling, and then the forklift performs an operation to avoid the falling of the goods; when the change rate is less than the set threshold, the dynamic risk parameter level is calculated by combining the load spectrum data measured by the forklift on the horizontal ground, the ground slope information, the current actual load, etc., and corresponding operations are performed according to the dynamic risk parameter level, which improves the operation safety of the forklift under various terrain conditions, avoids the overload of the forklift, and effectively improves the service life of the forklift. Description of the Drawings

[0017] Figure 1 is a flowchart of the overload prevention monitoring method for the heavy telescopic boom forklift of the present invention.

[0018] Figure 2This is an example of the load spectrum data measured for the heavy telescopic forklift of the present invention on a horizontal ground.

[0019] Figure 3 It is a schematic diagram of the layout of multiple weighing sensors provided on the forklift forks. Specific embodiments

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It should be noted here that the descriptions of these embodiments are used to help understand the present invention, but do not constitute a limitation to the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] Refer to Figures 1 to 3 As shown, a method for overload prevention monitoring of a heavy telescopic forklift, the heavy telescopic forklift includes a vehicle frame, a lifting boom rotatably provided on the vehicle frame, the front end of the lifting boom forms a forklift fork, multiple weighing sensors are provided on the forklift fork, and an inclination sensor is provided on the vehicle frame; The overload prevention monitoring method includes: S1. Obtain the load spectrum data measured for the forklift on a horizontal ground, and the load spectrum data is the maximum safe load value at different lifting heights of the lifting boom and different horizontal distances from the center of gravity of the goods to the root of the forklift fork. Among them, the load spectrum data refers to Figure 2 As shown.

[0022] S2. Obtain the horizontal and vertical coordinate change rates of the center of gravity of the goods through the weighing sensors. When one of the change rates exceeds the set threshold, it is determined that there is a risk of the goods falling, and then the forklift performs an operation to avoid the goods from falling. Otherwise, go to step S3; Refer to Figure 3 As shown, multi-point strain gauge weighing sensors are symmetrically installed on both sides of the forklift fork. A coordinate system is established at the center position of the root of the forklift fork teeth, and the abscissa of the center of gravity of the goods Is calculated by the following formula:

[0023] In the formula, Is the force measured by each weighing sensor, that is, referring to Figure 3 Among them, the readings of the weighing sensors on the left side are respectively: Fa1, Fa2, Fa3,..., Fan, and the readings of the weighing sensors on the right side are respectively: Fb1, Fb2, Fb3,..., Fbn; Is the horizontal distance from each weighing sensor to the root of the forklift fork, that is, referring to Figure 3Among them, the distances between each load cell and the root of the fork are X1, X2, X3, …, Xn respectively; Thus, the abscissa center of gravity change rate of the goods is calculated by the following formula:

[0024] In the formula, represents the sampling interval. To ensure the sampling accuracy, it is recommended that ≤0.1 s.

[0025] Similarly, the ordinate of the center of gravity of the goods is calculated by the following formula:

[0026] In the formula, is the force measured by each load cell, that is, referring to Figure 3 among them, the readings of the left load cells are: Fa1, Fa2, Fa3, ……, Fan, and the readings of the right load cells are: Fb1, Fb2, Fb3, ……, Fbn; is the horizontal distance from each load cell to the central axis of the fork root, that is, referring to Figure 3 among them, the distance between the left load cell and the fork root is -L, and the distance between the right load cell and the fork root is L.

[0027] Therefore, in step S2, the set threshold is set to 0.1 m / s. Therefore, when or , it is determined that there is a risk of the goods falling, and then the forklift performs an anti-falling avoidance operation on the goods. Otherwise, it enters step S3.

[0028] In step S2, the anti-falling avoidance operation of the goods includes: when the ordinate change rate of the center of gravity of the goods exceeds the set threshold, by it is determined whether the center of gravity of the goods deviates to the left or right. And the forklift is equipped with an electric leveling mechanism for leveling the lifting arm. The electric leveling mechanism adjusts the different strokes of the two cylinders, and through voice prompts or automatically controls the electric leveling mechanism to rotate in the opposite direction of the deviation of the center of gravity of the goods at a predetermined step length; for example, it is adjusted at a step length of 0.1° - 0.5° until the center of gravity of the goods stops changing, and the driver is reminded to re-fix the goods. If the forklift is not equipped with an electric leveling mechanism, it can be prompted by voice that there is a risk of lateral slipping of the goods, and the driver is reminded to re-fix the goods.

[0029] When the horizontal coordinate change rate of the center of gravity of the goods exceeds the set threshold, the forklift forks are automatically tilted backward through voice prompts or automatic control. The forklift forks can be automatically tilted backward by 2° to 5°. By using gravity, the goods are pulled towards the root of the forklift forks, that is, the mast direction, and a voice prompt is given that there is a risk of the goods slipping forward or backward, reminding the driver to re-fix the goods.

[0030] S3. Through the tilt angle sensor, obtain the angle between the ground on which the forklift travels and the horizontal plane, and this angle is equal to the slope angle; obtain the current actual load on the lifting boom and the horizontal coordinate change rate of the center of gravity of the goods through the weighing sensor. By combining the current actual load, the horizontal coordinate change rate of the center of gravity of the goods, the slope angle, and the maximum safe load value, determine the dynamic risk parameter. S4. If the dynamic risk parameter exceeds the preset threshold, generate a risk classification signal including low and high levels, and perform corresponding avoidance operations, specifically as follows: When the risk classification signal is a low-level risk signal, the forklift performs a low-risk avoidance operation, and the low-risk avoidance operation includes any one or a combination of operations such as cutting off the lifting function of the lifting boom, adjusting the tilt angle of the lifting boom, and reducing the speed of the forklift.

[0031] Specifically, on an uphill section, when the risk classification signal is within the range of a low-level risk signal, the forklift forks travel at a low speed and uniformly, avoiding accelerating and causing the goods to slide backward; on a downhill section, the forklift forks are lowered to the lowest height, and the forklift forks are automatically tilted backward by 1° to 2° to avoid exceeding the maximum safe load value due to the change in the center of gravity of the goods exceeding the limit.

[0032] When the risk classification signal is a high-level risk signal, the forklift performs a high-risk avoidance operation, and the high-risk avoidance operation includes temporarily increasing the pressure of the relief valve in the hydraulic system used to drive the lifting boom.

[0033] Specifically, the pressure of the relief valve in the hydraulic system of the lifting boom is set to at least two levels of maximum rated output pressure; when the dynamic risk parameter is within the safe pre-set range or the low-level risk range, the maximum output pressure of the relief valve is set to the first-level maximum rated output pressure; when the dynamic risk parameter is within the high-level risk range, the maximum output pressure of the relief valve is set to the second-level maximum rated output pressure, and the second-level maximum rated output pressure is greater than the first-level maximum rated output pressure. Among them, the relief valve with at least two levels of maximum rated output pressure belongs to the prior art. For example, Atos AGAM type pilot-operated relief valve, DB2U type multi-stage electro-hydraulic pilot relief valve, etc. The above relief valves all have the ability of multi-stage output pressure regulation.

[0034] The thrust (F) of the hydraulic cylinder of the lifting boom is determined by the system working pressure (P) and the effective area of the piston (A): F = P × A; Assume that the piston diameter of a forklift hydraulic cylinder is 100 mm (radius 50 mm), then the area A = πr 2 ≈78.5 cm 2 ².

[0035] If the pressure setting of the relief valve is 20 MPa (i.e., the maximum rated output pressure of the first stage), then the theoretical thrust: F = 20 × 78.5 ≈ 16 tons of force. Therefore, when the dynamic risk parameter is in the high-level risk range, the pressure of the relief valve is adjusted to 25 MPa (i.e., the maximum rated output pressure of the second stage), and the thrust increases to 19.6 tons of force. After increasing the maximum rated output pressure of the relief valve, the maximum pressure allowed by the system rises, and the hydraulic cylinder can output a greater thrust, which may barely lift a load slightly exceeding the rated value, but this will sacrifice part of the safety of the forklift. Therefore, preferably, the load spectrum data measured on the horizontal ground of the above forklift is tested with the relief valve adopting the maximum rated output pressure of the first stage. The load-bearing structure of the forklift, as well as the design of structures such as the hydraulic cylinder and piston rod, are designed to meet the load when the relief valve adopts the maximum rated output pressure of the second stage, so as to ensure the safety of the forklift and improve the service life of the forklift.

[0036] Since the uphill section or the downhill section is the most likely direct cause of the change in the center of gravity of the goods, and the direction of the goods sliding caused by the uphill section or the downhill section is usually along the length direction of the fork, that is Figure 3 the horizontal coordinate direction in. Therefore, the present invention determines the dynamic risk parameter by combining the current actual load, the horizontal coordinate change rate of the center of gravity of the goods, the slope angle, and the maximum safe load value. The dynamic risk parameter is calculated by the following formula:

[0037] In the formula, represents the current actual load, obtained by the weighing sensor, ; represents the lifting height of the fork as h ( Figure 2 the longitudinal coordinate value in), and when the horizontal distance from the center of gravity of the goods to the root of the fork is d ( Figure 2 the horizontal coordinate value in), the maximum safe load value in the corresponding load spectrum data; represents the slope angle, obtained by the tilt angle sensor; represents the horizontal coordinate change rate of the center of gravity of the goods; represents the empirical coefficient.

[0038] Further, in step S3, it also includes inputting the ground coefficient into the formula model of the dynamic risk parameter, quantifying the correction factor of the influence of different ground conditions on the forklift's load capacity through the ground coefficient. The core is to adjust the rated load through the friction coefficient ratio and the ground deformation characteristics to prevent the forklift from slipping due to exceeding the rated load. When the ground conditions are worse (such as low friction, soft) the smaller it is, the smaller the denominator, which makes the DRP increase and the risk rise.

[0039] Specifically, the dynamic risk parameter is calculated by the following formula:

[0040] In the formula, represents the ground coefficient; represents the current actual load, obtained through the weighing sensor; represents the maximum safe load value in the load spectrum data when the lifting height of the fork is h and the horizontal distance from the center of gravity of the goods to the root of the fork is d; represents the slope angle, obtained through the tilt angle sensor; represents the horizontal coordinate change rate of the center of gravity of the goods; represents the empirical coefficient.

[0041] The value of

[0042] Specifically, in one embodiment, when the forklift is moving on dry concrete, takes 1.0; when the forklift is moving on wet and slippery concrete, takes 0.7 - 0.9; when the forklift is moving on loose sand, takes 0.3 - 0.5; when the forklift is moving on ice and snow roads, takes 0.1 - 0.2. The driver can judge the road conditions and select the road conditions on the operation interface in the cockpit to adjust the formula, improving the accuracy of formula use. Specifically, through experiments, it is determined that , that is, under different ground conditions, the motion state of the forklift is tested by different actual loads in turn, such as the forklift slipping.

[0043] In the above formula, can be adjusted according to the goods that the forklift often transports. When the goods transported by the forklift are loose containers can take 0.2. When the goods transported by the forklift are liquid containers can take 0.1. When the goods transported by the forklift are live animals can take 0.3. In addition, for example, the comparison between novice drivers and experienced drivers Differentially set the coefficients. Specifically, determine through experiments , that is, artificially induce the goods to slide at different slopes and record the critical DRP value.

[0044] When 0.8 ≤ DRP < 1, generate a low-risk classification signal; when 1 < DRP < 1.5, generate a high-risk classification signal. The maximum range of the high-risk classification signal is set by combining the set threshold for the forklift to perform cargo anti-drop avoidance and the secondary maximum rated output pressure of the overflow valve. Usually, when DRP > 1.5, the forklift cannot lift the goods even on flat ground. When DRP < 0.8, the forklift is in a normal carrying state.

[0045] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention 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 therefore should not be construed as a limitation to the present invention.

[0046] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0047] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for monitoring overload prevention of a heavy telescopic forklift, characterized in that: The heavy-duty telescopic forklift comprises a vehicle frame, a lifting arm rotatably arranged on the vehicle frame, the front end of the lifting arm forms a fork, a plurality of weighing sensors are arranged on the fork, and the vehicle frame is provided with an inclination sensor; The anti-overload monitoring method comprises: S1. Obtain load spectrum data measured by a forklift on a horizontal ground, wherein the load spectrum data is the maximum safe load value of the lifting arm at different lifting heights and at different horizontal distances from the center of gravity of the cargo to the root of the fork; S2, obtaining the change rate of the horizontal and vertical coordinates of the center of gravity of the cargo through the weighing sensor, and when one of the change rates exceeds a set threshold, it is determined that the cargo is at risk of falling, and then the forklift performs an anti-falling evasive operation for the cargo, otherwise it goes to step S3; S3. Obtain the angle between the ground on which the forklift is traveling and the horizontal plane through the tilt angle sensor, which is equal to the slope angle; obtain the current actual load on the lifting arm and the rate of change of the horizontal coordinate of the center of gravity of the cargo through the weighing sensor, and determine the dynamic risk parameter by combining the current actual load, the rate of change of the horizontal coordinate of the center of gravity of the cargo, the slope angle and the maximum safe load value; S4. If the dynamic risk parameter exceeds the preset threshold, a risk classification signal including low and high levels is generated, and corresponding avoidance operations are performed, as follows: When the risk classification signal is a low-level risk signal, the forklift performs a low-risk avoidance operation, which includes any one of cutting off the lifting function of the lifting arm, adjusting the tilt angle of the lifting arm, and reducing the speed of the forklift, or a combination of multiple operations; When the risk classification signal is a high-level risk signal, the forklift performs a high-risk avoidance operation, and the high-risk avoidance operation includes temporarily increasing the pressure of a relief valve in a hydraulic system used to drive the lifting arm.

2. The anti-overload monitoring method for a heavy-duty telescopic forklift according to claim 1, characterized in that: The dynamic risk parameter is calculated by the following formula: In the formula, represents the current actual load, obtained by the weighing sensor; It indicates the maximum safe load value in the load spectrum data when the lifting height of the fork is h and the horizontal distance from the center of gravity of the cargo to the root of the fork is d; represents the slope angle, obtained by the tilt angle sensor; Indicates the rate of change of the abscissa of the cargo's center of gravity; Represents the empirical coefficient.

3. The anti-overload monitoring method for a heavy-duty telescopic forklift according to claim 1, characterized in that: Step S3 also includes inputting the ground coefficient into the formula model of the dynamic risk parameter, and the dynamic risk parameter is calculated by the following formula: In the formula, represents the ground factor; represents the current actual load, obtained by the weighing sensor; It indicates the maximum safe load value in the corresponding load spectrum data when the lifting height of the fork is h and the horizontal distance from the center of gravity of the cargo to the root of the fork is d; represents the slope angle, obtained by the tilt angle sensor; Indicates the rate of change of the abscissa of the cargo's center of gravity; Represents the empirical coefficient.

4. The anti-overload monitoring method for a heavy-duty telescopic forklift according to claim 3, characterized in that: The ground factors include: The values ​​decrease in the order of dry concrete, slippery concrete, loose sand, and ice and snow.

5. The anti-overload monitoring method for a heavy-duty telescopic forklift according to claim 1, characterized in that: In step S2, the cargo anti-falling avoidance operation includes: When the rate of change of the longitudinal coordinate of the cargo gravity center exceeds a set threshold, and the forklift is equipped with an electric leveling mechanism for leveling the lifting arm, the electric leveling mechanism is rotated in the opposite direction of the deviation of the cargo gravity center by a predetermined step length through voice prompts or automatic control; When the rate of change of the horizontal coordinate of the center of gravity of the cargo exceeds a set threshold, the cargo fork automatically tilts back through voice prompts or automatic control.

6. A method for monitoring overload prevention of a heavy telescopic forklift according to claim 2 or 3, characterized in that: When 0.8≤DRP<1, a low-risk classification signal is generated; When 1<DRP<1.5, a high-risk classification signal is generated.

7. The anti-overload monitoring method for a heavy-duty telescopic forklift according to claim 1, characterized in that: The overflow valve pressure in the hydraulic system of the lifting arm is set with at least two levels of maximum rated output pressure; when the dynamic risk parameter is in the safety prefabricated range or the low-level risk range, the maximum output pressure of the overflow valve is set to the first-level maximum rated output pressure; when the dynamic risk parameter is in the high-level risk range, the maximum output pressure of the overflow valve is set to the second-level maximum rated output pressure, and the second-level maximum rated output pressure is greater than the first-level maximum rated output pressure.

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