A fork arm lifting stability control method and system applied to a forklift AGV

Abstract

The application relates to the technical field of forklift AGV control, and particularly discloses a lifting stability control method and system applied to a forklift AGV. The method comprises the following steps: obtaining acceleration data output by an inertial measurement unit and pressure data output by a pressure sensor, determining a compensated lifting control instruction based on a target speed and the acceleration data, and determining a pressure change representation result, a maximum lifting speed and a preset constraint condition according to the pressure data; when the preset constraint condition is a speed limit condition, the proportional valve opening is determined under the constraint of the maximum lifting speed to control the lifting of the fork arm; and when the preset constraint condition is a stop condition, a deceleration stop control is output and deceleration stopping is performed. The method and system can form continuous and stable control on the lifting process of the fork arm when the dynamic fluctuation caused by the working condition change of the forklift AGV, and improve the stability, continuity and controllability of the lifting process of the fork arm of the forklift AGV.

Description

Technical Field

[0001] This invention relates to the field of AGV forklift control technology, and in particular to a method and system for stabilizing the lifting of fork arms in forklift AGVs. Background Technology

[0002] In warehousing and logistics scenarios, forklift AGVs undertake tasks such as high-level racking, loading, transfer, and shelving. The lifting and lowering process of the forklift directly affects the operational status of goods during lifting, alignment, and placement. In high-level racking operations, the forklift typically needs to operate continuously within a large lifting range, and the load state, operating rhythm, and on-site conditions may change at different stages of the operation. With changes in operating height and continuous operation, the operational status of the forklift during lifting and lowering will exhibit dynamic fluctuations, and these fluctuations may present inconsistent patterns throughout the lifting range. In this situation, if the system cannot maintain stable control over the forklift's operational status throughout the entire lifting range, the consistency of control and the continuity of execution during the lifting and lowering process will be affected, leading to instability in the lifting control under different operating conditions. These issues limit the continuous operation, operational reliability, and stable operation during high-level racking and lowering, making it difficult for the system to maintain a stable and controlled state during the lifting and lowering process when faced with changing operating conditions. Summary of the Invention

[0003] This invention proposes a method and system for stable control of forklift lifting in forklift AGVs, in order to solve the dynamic fluctuation problem caused by changes in working height, load and operating conditions during high-position loading and unloading operations of forklift AGVs.

[0004] Therefore, this invention introduces both acceleration data and pressure data during the lifting and lowering process of the forklift. On the one hand, a compensated lifting and lowering control command is formed based on the target speed and acceleration data. On the other hand, pressure change characterization results, maximum lifting and lowering speed, and preset constraint conditions are formed based on the pressure data. Thus, the lifting and lowering control of the forklift is constructed as a control method that combines the control output formation process and the constraint output formation process.

[0005] Based on this, when the preset constraint is a speed limit condition, the proportional valve opening is determined according to the compensated lifting control command under the maximum lifting speed constraint to control the fork arm to continue lifting and lowering; when the preset constraint is a stop condition, a deceleration stop control is output to make the fork arm enter a deceleration stop state. Thus, the fork arm lifting process can form an appropriate execution control relationship for different operating conditions.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for stabilizing the lifting of a forklift arm applied to a forklift AGV, comprising the following steps: Acquire acceleration data output by the inertial measurement unit; Acquire the target speed, and determine the compensated lifting control command based on the target speed and the acceleration data; Acquire pressure data output by a pressure sensor, and determine a pressure change characterization result based on the pressure data. The pressure change characterization result is used to characterize the degree of dynamic change of the pressure data within a predetermined time window. Also, determine the maximum acceleration / deceleration speed and preset constraints based on the pressure change characterization result. The preset constraints include at least a speed limit condition and a stopping condition. When the preset constraint is a speed limit condition, under the constraint of the maximum lifting speed, the opening of the proportional valve is determined according to the compensated lifting control command, and the lifting of the fork arm is controlled according to the opening of the proportional valve. When the preset constraint condition is a stop condition, a deceleration stop control is output, and the lifting and lowering of the fork arm is decelerated and stopped according to the deceleration stop control.

[0007] A second aspect of the present invention provides a forklift lifting and stabilization control system for forklift AGVs, comprising: an inertial measurement unit, a pressure sensor, a proportional valve, and a control module, wherein... The inertial measurement unit is connected to the control module and is used to output acceleration data to the control module; The pressure sensor is connected to the control module and is used to output pressure data to the control module; The proportional valve is connected to the control module and is used to receive the control signal output by the control module to adjust the lifting of the fork arm; The control module includes an inner control section and an outer constraint section. The inner control section is used to acquire the target speed and determine a compensated lifting control command based on the target speed and the acceleration data; The outer constraint portion is used to determine the pressure change characterization result based on the pressure data, and to determine the maximum lifting speed and preset constraint conditions based on the pressure change characterization result. The control module is further configured to, when the preset constraint condition is a speed limit condition, determine the opening degree of the proportional valve according to the compensated lifting control command under the constraint of the maximum lifting speed, and control the lifting and lowering of the fork arm through the proportional valve; and when the preset constraint condition is a stop condition, output a deceleration stop control, and perform deceleration stop on the lifting and lowering of the fork arm through the proportional valve according to the deceleration stop control.

[0008] Compared with the prior art, the present invention provides a method and system for stabilizing the lifting of forklift arms in forklift AGVs, which has the following technical advantages: This forklift lifting stability control method combines acceleration and pressure data to generate corresponding control and constraint outputs during the lifting process of the forklift AGV. Firstly, it generates compensated lifting control commands based on target speed and acceleration data, allowing the control output to be dynamically adjusted according to the current operating state of the forklift. Secondly, it generates pressure change representations, maximum lifting speeds, and preset constraints based on pressure data, enabling the system to establish corresponding execution boundaries and branch control bases according to the degree of pressure change.

[0009] Therefore, under speed-limited conditions, the system can control the fork arm to continue lifting and lowering within the maximum lifting speed constraint, ensuring continuous operation of the fork arm within the limited speed range. Under stopping conditions, the system can output deceleration and stop control, causing the fork arm to transition from the current operating state to a deceleration and stop state. Thus, this invention can adjust the control output according to changes in operating conditions throughout the entire fork arm lifting process, and generate speed-limiting or stop control when dynamic fluctuations increase, thereby improving the stability, continuity, and controllability of the fork arm lifting process. Attached Figure Description

[0010] Figure 1 A flowchart illustrating a method for stabilizing the lifting of a forklift arm in a forklift AGV, provided by an embodiment of the present invention; Figure 2 This is a combined flowchart of a forklift lifting and stabilization control method for forklift AGVs provided in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the relationship between outer constraint formation and branch execution, provided in an embodiment of the present invention. Figure 4 This invention provides a schematic diagram of a forklift lifting and stabilization control system for forklift AGVs. Figure label: 100-Forklift AGV, 110-Fork arm, 120-Inertial measurement unit, 130-Pressure sensor, 140-Proportional valve, 150-Control module, 151-Inner control part, 152-Outer constraint part, 160-Lifting actuator. Detailed Implementation

[0011] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0012] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0013] Example 1 like Figure 1 As shown, this embodiment relates to a method for stabilizing the lifting of a forklift arm applied to a forklift AGV. Figure 1 This embodiment provides a schematic flowchart of a forklift boom lifting stability control method applied to forklift AGVs. This embodiment applies to the forklift boom lifting process of forklift AGVs in high-level rack operations. During the lifting process from the starting position to the target position, the dynamic characteristics of the lifting execution system, composed of the mast, forks, and load, change with the working height, current load status, and on-site operating conditions. Simultaneously, the hydraulic execution circuit may experience pressure fluctuations, response lag, or instantaneous disturbances during the lifting process. Therefore, if the control output is based solely on the target speed to form a single path, inconsistencies between the actual operating state of the forklift and the control requirements can easily occur, affecting the stability control effect throughout the lifting range. This manifests as speed following deviation, local overshoot, amplified vibration, or insufficient smoothness in the stopping process.

[0014] To ensure continuous and controlled operation of the forklift throughout its lifting range, this embodiment incorporates both acceleration and pressure data during the lifting process. The forklift lifting control process is organized into two categories: a lifting control command formation process and a lifting constraint formation process. One type of process generates control outputs for the actuator, while the other generates constraint outputs for the actuator. This allows the control and constraint outputs to work together in subsequent execution phases of the forklift lifting process. In other words, this embodiment does not organize the forklift lifting control as a single-path process that generates control commands solely based on the target speed. Instead, through the synergistic effect of the control chain and constraint chain, the forklift lifting process can establish corresponding execution control relationships for different operating conditions.

[0015] In this embodiment, the method flow includes the following steps: S100: Acquire acceleration data output by the inertial measurement unit; S200: Obtain the target speed and generate a compensated lifting control command based on the target speed and acceleration data; S300: Acquire pressure data output by the pressure sensor, and generate pressure change characterization results, maximum lifting and lowering speeds, and preset constraint conditions based on the pressure data; S400: When the preset constraint is a speed limit condition, under the maximum lifting speed constraint, the opening degree of the proportional valve is determined according to the compensated lifting control command, and the lifting of the fork arm is controlled according to the opening degree of the proportional valve. S500: When the preset constraint condition is a stop condition, output deceleration stop control, and perform deceleration stop on the lifting and lowering of the fork arm according to the deceleration stop control.

[0016] Therefore, during the same forklift lifting process, the lifting control command formation process is used to generate control outputs that respond to the forklift lifting target and the current operating state of the forklift, while the lifting constraint formation process is used to generate boundary information and branch conditions that constrain subsequent execution behaviors. Both of them jointly participate in the control of the forklift lifting process in the subsequent execution stage.

[0017] In this embodiment, the inertial measurement unit (IMU) is positioned to reflect the lifting and lowering state of the forklift and continuously outputs acceleration data during the lifting and lowering process. To more accurately reflect the vertical dynamic response of the forklift, in one specific arrangement, the IMU can be installed on the fork carriage, fork backplate, lifting carriage, or other structural components rigidly related to the forklift movement, and synchronously sense changes in the forklift's operating state during the lifting and lowering process. Preferably, the vertical axis of the IMU's sensing axis is consistent with or approximately consistent with the lifting and lowering direction of the forklift. In some embodiments, the data output by the IMU can be zero-biased, installation attitude compensated, or coordinate transformed before subsequent control processing to improve the accuracy of the acceleration data in representing the actual vertical dynamic changes of the forklift. After the acceleration data output by the IMU enters the control processing, it is first used as one of the input information for forming the lifting and lowering control command. The acceleration data is not only used to display the current state, but also participates in the formation of subsequent lifting and lowering control commands together with the target velocity, thereby directly affecting the lifting and lowering control process.

[0018] To enable the acceleration data to characterize the current operating state of the forklift, in this embodiment, acceleration information corresponding to the vertical motion of the forklift is first extracted from the acceleration data. This acceleration information is then processed to form an acceleration metric characterizing the current operating state of the forklift. In one specific implementation, the acceleration information corresponding to the vertical motion of the forklift can be obtained from the vertical acceleration information output by the inertial measurement unit. This vertical acceleration information is then high-pass filtered to extract the dynamic components related to the lifting and lowering process of the forklift. The purpose of the high-pass filtering is to weaken the influence of gravity components, low-frequency attitude change components, or slowly changing terms on the dynamic state characterization, thereby highlighting the changing components related to vibration, impact, or dynamic deviation during the lifting and lowering process of the forklift. The processed result is determined as the acceleration metric characterizing the current operating state of the forklift. Therefore, the subsequent control processing uses not the original acceleration data, but an acceleration metric that better reflects the changes in the current operating state of the forklift. In some embodiments, the high-pass filtering can also be implemented using digital high-pass filtering, differential filtering, discrete filtering, or other processing methods that can highlight dynamic components, without being limited to a specific filtering structure.

[0019] While acquiring acceleration data, the target speed corresponding to the current lifting and lowering process of the forklift is also acquired. The target speed characterizes the desired operating speed for the current lifting and lowering phase. In this embodiment, an uncompensated lifting and lowering control command is first generated based on the target speed, and then a control compensation quantity is generated based on the aforementioned acceleration measurement. The uncompensated lifting and lowering control command and the control compensation quantity are then combined to form a compensated lifting and lowering control command. The uncompensated lifting and lowering control command reflects the target control requirements during the lifting and lowering process, while the control compensation quantity reflects the correction result of the current operating state of the forklift to the target control requirements. Therefore, the resulting compensated lifting and lowering control command simultaneously embodies both the target control requirements and the current operating state of the forklift. Thus, the compensated lifting and lowering control command is not an abstract concept but an actual control output that can be incorporated into the subsequent execution control process.

[0020] Furthermore, in one specific implementation, the uncompensated lifting control command and the control compensation amount can be formed as follows: First, the uncompensated lifting control command is generated based on the target speed. Second, target change information is formed based on the changes in the target speed. In one example, the target change information can be represented as target acceleration information corresponding to the target speed, which can be obtained by differentiating the target speed or derived from a pre-planned speed change curve. Third, the current operating state of the forklift is characterized by the aforementioned acceleration metric, and the difference between the target change information and the acceleration metric is used as the basis for forming the control compensation amount. In some embodiments, the control compensation amount can be formed based on the difference, deviation trend, absolute value of deviation, or weighted deviation between the target acceleration information and the acceleration metric; correspondingly, the control compensation amount can be generated using proportional compensation, weighted compensation, segmented compensation, lookup table compensation, or other equivalent methods. Finally, the control compensation amount is superimposed on the uncompensated lifting control command to form the compensated lifting control command. In this embodiment, the superposition can manifest as amplitude correction of the uncompensated lifting control command, or boundary correction or control quantity correction of the uncompensated lifting control command; the resulting compensated lifting control command can be updated with each control cycle. Therefore, the compensated lifting control command can be dynamically adjusted according to the current operating state of the forklift in each control cycle, thereby reducing the inconsistency between the target control requirements and the actual dynamic response of the forklift.

[0021] In this embodiment, a pressure sensor is positioned at a pressure measurement location corresponding to the hydraulic control circuit of the forklift lifting mechanism, and continuously outputs pressure data during the lifting process. To more accurately characterize the dynamic changes in the hydraulic circuit during the lifting process, in a preferred arrangement, the pressure sensor can be located near the output end of the proportional valve, on the hydraulic line corresponding to the lifting cylinder, or at a hydraulic node on the inlet and / or return side of the lifting circuit. Preferably, it should be as close as possible to the hydraulic position that can characterize the changes in the lifting state of the forklift, so as to reduce the influence of intermediate hydraulic line transmission on the pressure change characterization. After the pressure data enters the control processing, it is not directly used as the final control result, but is first used to form the pressure change characterization result.

[0022] In one specific implementation, pressure data output from a pressure sensor is continuously acquired, and the pressure data is filtered during control processing to extract pressure change information corresponding to the dynamic changes in the lifting and lowering of the forklift. As an example, the pressure data can be high-pass filtered, and changes in the processed continuous pressure data can be extracted within a predetermined time window to form characterization information reflecting the degree of pressure change, which is then determined as the pressure change characterization result. The purpose of the high-pass filtering is to highlight the pressure fluctuations, pulsations, or transient changes in the hydraulic circuit during the lifting and lowering of the forklift, rather than simply reflecting the static pressure value. In one example, the predetermined time window can be set to 0.1s to 0.3s, preferably 0.2s, to balance the timeliness of the change response and the stability of the continuous data characterization. In some embodiments, the pressure change characterization result can be formed by the peak value, peak-to-peak value, mean square value, cumulative absolute change value, or other statistical quantities that can reflect the degree of pressure change within the predetermined time window; preferably, the peak value within the predetermined time window can be determined as the pressure change characterization result. Therefore, the pressure change characterization results reflect the degree of pressure change during the lifting and lowering of the forklift, rather than a simple static pressure value.

[0023] After forming the pressure change characterization result, this embodiment further forms the maximum lifting speed and preset constraint conditions based on the pressure change characterization result. Specifically, in one implementation, the control module corresponds the pressure change characterization result to multiple preset change intervals to determine the change level to which the current pressure change degree belongs; then, it forms the corresponding maximum lifting speed based on the change level, and further forms the current preset constraint conditions based on the change level. For change levels that still allow the forklift to continue lifting but require a speed limit, a speed limit condition is formed; for higher change levels that are no longer suitable to continue operating in the current lifting mode, a stop condition is formed. As an example, the change level may include at least three or four levels, such as a normal level, a light constraint level, a moderate constraint level, and a stop level; different change levels correspond to different maximum lifting speed limits, and as the pressure change level increases, the maximum lifting speed is tightened by gradually decreasing, proportionally decreasing, segmented decreasing, or by table lookup mapping. In at least two preset pressure change level intervals, the lower pressure change level may correspond to a speed limit condition, and the higher pressure change level may correspond to a stop condition. In this way, the pressure change characterization results are first used to characterize the degree of pressure change during the lifting and lowering of the forklift, and then further derived into two outputs: maximum lifting speed and preset constraint conditions. The maximum lifting speed serves as the outer constraint quantity, used to form boundary constraints for the lifting and lowering control of the forklift in the subsequent execution stage, while the preset constraint conditions serve as the basis for entering subsequent branch executions. Compared with the method of directly stopping the machine using only a single threshold, this embodiment forms a hierarchical control relationship between continued operation and safety constraints by hierarchically generating the maximum lifting speed and preset constraint conditions.

[0024] When the preset constraint is a speed limit condition, this embodiment does not terminate the forklift lifting control, but continues to execute the forklift lifting control under the constraint of the maximum lifting speed. Specifically, the execution requirement corresponding to the compensated lifting control command is first compared with the allowable execution limit corresponding to the maximum lifting speed; when the execution requirement corresponding to the compensated lifting control command does not exceed the allowable execution limit, the proportional valve opening is determined according to the compensated lifting control command; when the execution requirement exceeds the allowable execution limit, the allowable execution limit is used as the boundary basis for determining the proportional valve opening, and the execution range corresponding to the compensated lifting control command is limited before determining the proportional valve opening. In other words, the maximum lifting speed is not a separately displayed result, but an outer constraint directly applied to the proportional valve opening determination process. In this way, the forklift lifting speed corresponding to the finally determined proportional valve opening will not exceed the maximum lifting speed.

[0025] Furthermore, in some implementations, the maximum lifting speed can be directly used as a speed boundary in the execution requirement comparison, or it can be first converted into an allowable execution upper limit based on the speed-valve opening correspondence, lookup table relationship, or function relationship before being used in the proportional valve opening determination. In other words, the outer constraint is not only reflected in the judgment of whether the forklift should continue lifting or lowering, but also in the boundary restrictions of the proportional valve opening determination process. As an example, under speed-limited conditions, the forklift can continue to operate within a range lower than the current normal lifting speed upper limit, thereby maintaining a controlled state of the forklift lifting process while maintaining continuous operation, and reducing the possibility of further amplification of dynamic fluctuations caused by continuous high-speed execution.

[0026] When the preset constraint condition is a stop condition, this embodiment no longer executes the continued control method under the speed limit condition, but instead outputs deceleration stop control. In one specific implementation, after the control module identifies the stop condition, it no longer determines the proportional valve opening to maintain the continuous lifting and lowering of the fork arm according to the continued lifting and lowering path, but instead outputs a deceleration stop control signal and controls the proportional valve to enter the execution state corresponding to the deceleration stop, so that the fork arm changes from the current running state to the deceleration stop state. Further, in some embodiments, the deceleration stop control may include gradually reducing the current proportional valve opening, segmented reduction control, or attenuation control according to a predetermined deceleration trajectory; when the fork arm running speed decreases below a preset threshold, the proportional valve can enter a closed state, a holding state, or a neutral state to achieve a smooth stop. Thus, when a corresponding stop condition occurs during the lifting and lowering of the fork arm, the control result switches from the continued running branch to the deceleration stop branch, forming a clear distinction from the execution method under the speed limit condition. Preferably, the deceleration stop control avoids a direct switch from the continued lifting and lowering state to the abrupt stop state, thereby reducing secondary vibrations or hydraulic shocks caused by control abrupt changes.

[0027] In this embodiment, there is a clear priority relationship between the continue control branch under speed-limited conditions and the deceleration and stop branch under stop conditions. Specifically, under speed-limited conditions, the compensated lifting control command still participates in the control as the basic execution input, but is constrained by the outer boundary corresponding to the maximum lifting speed; under stop conditions, the deceleration and stop control overrides the continue lifting control in priority, and the execution process no longer unfolds according to the continue lifting path, but is taken over by the deceleration and stop control. When the preset constraint condition changes from speed-limited conditions to stop conditions, the execution control changes accordingly from the continue running branch to the deceleration and stop branch. Thus, in this embodiment, the control output and constraint output do not simply exist side by side, but form different execution priority relationships under different preset constraint conditions.

[0028] In this embodiment, the formation of the compensated lifting control command, maximum lifting speed, and preset constraints can be organized in different ways, but all maintain the same technical concept. For example, in one organization method, an uncompensated lifting control command is first formed based on the target speed, and then a control compensation amount is formed based on the acceleration measurement. The two are then combined to form the compensated lifting control command. In another organization method, the target speed and acceleration data can be processed synchronously within the same control cycle to form the compensated lifting control command. Correspondingly, in the pressure chain processing, the pressure change characterization result can be formed first, and then the maximum lifting speed and preset constraints can be formed based on the pressure change characterization result. Alternatively, in the same constraint processing process, the pressure change characterization result can be formed first, and then the maximum lifting speed and preset constraints can be derived immediately. Furthermore, in some embodiments, acceleration data and pressure data can be updated separately and participate in corresponding processing within the same control cycle. The compensated lifting control command, pressure change characterization result, maximum lifting speed, and preset constraints can also be updated cyclically according to the preset control cycle to adapt to the dynamic response characteristics of the forklift AGV hydraulic actuator system. The different organizational methods described above do not change the basic control relationship of this embodiment, that is, the control output and constraint output jointly participate in the execution control of the forklift lifting process.

[0029] In some optional implementations, to improve the control integrity of the system under abnormal operating conditions, an anomaly or degradation handling mechanism can also be set. For example, when the inertial measurement unit output is abnormal, the pressure sensor output is abnormal, or the continuity and validity of the corresponding data do not meet the preset conditions, the control module can enter a degradation control mode. In the degradation control mode, a conservative speed limit can be adopted, high-speed lifting and lowering can be prohibited, or deceleration and stop control can be directly triggered. This degradation control mode does not change the basic technical concept of control execution by both control output and constraint output in this embodiment, but is used to maintain the safety and controllability of the forklift lifting process under abnormal operating conditions.

[0030] From an implementation perspective, this embodiment does not organize the forklift lifting control process as a single-path control output process. Instead, it organizes it into two different processing processes: lifting control command formation and lifting constraint formation. Lifting control command formation generates compensated lifting control commands in response to the forklift lifting target and the current operating state of the forklift. Lifting constraint formation generates the maximum lifting speed and preset constraint conditions to provide boundary constraints and branching conditions for subsequent execution. Under speed-limited conditions, the control output given in the lifting control command formation process continues to participate in execution, but is constrained by the maximum lifting speed. Under stopping conditions, the execution process no longer continues along the lifting path, but is taken over by deceleration and stopping control. Therefore, throughout the entire lifting range, the forklift lifting process does not rely on a single control output to maintain operation, but rather the control output and constraint output work together at the execution end, thus forming a continuous control relationship oriented towards different operating conditions.

[0031] In summary, in this embodiment, acceleration data enters the lifting control command formation process, and pressure data enters the lifting constraint formation process. The former forms a compensated lifting control command, while the latter forms the pressure change characterization result, maximum lifting speed, and preset constraint conditions. When the preset constraint condition is a speed limit condition, the maximum lifting speed constrains the execution range corresponding to the compensated lifting control command, and based on this, the proportional valve opening is determined to control the fork arm to continue lifting. When the preset constraint condition is a stop condition, deceleration and stop control takes over the fork arm lifting execution process, causing the fork arm to enter a deceleration and stop state. Thus, this embodiment forms a complete control closed loop from input acquisition, control output formation, constraint output formation to execution branch switching. Specifically, by compensating for uncompensated lifting control commands through an acceleration chain, the inconsistency between the target control requirements and the actual dynamic response of the forklift can be reduced; by forming the maximum lifting speed and preset constraints through a pressure chain, a graded balance can be achieved between continued operation and safety constraints; by implementing outer boundary constraints under speed-limited conditions and implementing deceleration and stop control under stopping conditions, speed mutations and pressure disturbance accumulation during the lifting process can be reduced, thereby enabling the forklift to maintain a continuous and controlled operating state according to the corresponding working conditions throughout the entire lifting range.

[0032] Example 2 Based on the basic method described in Embodiment 1 above, this embodiment further explains the combined implementation of the forklift lifting stability control method. This embodiment mainly combines... Figure 2 and Figure 3 To explain, among other things, Figure 2 This is a combined flowchart of a forklift lifting and stabilization control method for forklift AGVs provided in an embodiment of the present invention, used to illustrate the combined relationship between the inner control processing flow, the outer constraint processing flow, and the branch execution flow; Figure 3This is a schematic diagram illustrating the relationship between outer constraint formation and branch execution, provided as an embodiment of the present invention. It is used to explain the hierarchical, conditional, and result relationships between outer constraint formation and branch execution. It should be noted that... Figure 2 The step numbers in the code are used to characterize the processing nodes in the method combination process. Figure 3 The numbers in the diagram are used to represent the corresponding nodes or results in the relationship between the formation of outer constraints and the execution of branches. Both refer to the same technical concept in this embodiment under different diagram levels, rather than being independent and separate from each other.

[0033] This embodiment does not repeat the basic process described in Embodiment 1 item by item. Instead, it further explains the acceleration measurement formation process, the target speed derivation process, the control compensation amount and the compensated lifting control command formation process, the pressure change characterization result formation process, the pressure change level and preset constraint condition formation process, the execution path under speed limit conditions and stopping conditions, and example parameters and optional processing paths in several further embodiments. The method processing can be executed by the corresponding control system.

[0034] See Figure 2 The method combination process in this embodiment includes an inner control processing flow, an outer constraint processing flow, and a branch execution flow. Figure 2 The left-hand flow is used to generate compensated lift control commands, including step 201 of acquiring acceleration data, step 202 of generating acceleration measurement, step 203 of acquiring target velocity, step 204 of generating uncompensated lift control commands, step 205 of generating control compensation amount, and step 206 of generating compensated lift control commands. Figure 2 The right-hand flow is used to generate pressure change characterization results, maximum acceleration and deceleration rates, and preset constraints, including step 207 of acquiring pressure data, step 208 of generating pressure change characterization results, step 209 of generating maximum acceleration and deceleration rates, and step 210 of generating preset constraints. Figure 2 The lower process is used to form different execution paths under different preset constraint conditions. In the execution path corresponding to the speed limit condition, it includes step 213 of determining the proportional valve opening and step 214 of controlling the fork arm to continue lifting and lowering. In the execution path corresponding to the stop condition, it includes step 215 of outputting deceleration and stop control and step 216 of controlling the fork arm to enter the deceleration and stop state. In this embodiment, the compensated lifting control command 206 serves as the main control input for the execution stage, the maximum lifting speed 209 serves as the outer constraint input for the execution stage, and the preset constraint condition 210 serves as the basis for entering branch execution. Therefore, during the same fork arm lifting and lowering process, the control output, constraint output, and execution branch are not independent of each other, but rather jointly participate in determining the proportional valve opening and subsequent fork arm lifting and lowering control.

[0035] Furthermore, in this embodiment, Figure 2 The illustrated combined process can be repeatedly executed according to the control cycle. That is, within each control cycle, the acceleration data output by the inertial measurement unit and the pressure data output by the pressure sensor are first updated. Then, an acceleration measurement 202 is generated from the acceleration data, and a pressure change characterization result 208 is generated from the pressure data. Subsequently, the target acceleration corresponding to the target velocity 203, the uncompensated lifting control command 204, the control compensation amount 205, the compensated lifting control command 206, the maximum lifting speed 209, and the preset constraint condition 210 are updated. Finally, based on the updated compensated lifting control command 206, the maximum lifting speed 209, and the preset constraint condition 210, the proportional valve opening determination 213 or the deceleration stop control output 215 is executed. Thus, Figure 2 The process shown is not a one-time static processing relationship, but a dynamic control process that can be continuously and cyclically executed throughout the entire lifting and lowering process of the forklift.

[0036] exist Figure 2 In the process on the left, the acceleration data output by the inertial measurement unit is first acquired through step 201, and the acceleration data is used to form an acceleration metric 202 to characterize the current operating state of the forklift. To more accurately reflect the vertical dynamic changes during the lifting and lowering of the forklift, in this embodiment, Z-axis acceleration information related to the vertical motion of the forklift can be extracted from the acceleration data, and the Z-axis acceleration information is subjected to high-pass filtering to obtain the acceleration components corresponding to the dynamic changes in the lifting and lowering of the forklift. The processed result can be determined as the acceleration metric 202. Therefore, the acceleration metric 202 is not a direct copy of the original acceleration data, but a processed dynamic quantity used to characterize the current operating state of the forklift.

[0037] In some implementations, the inertial measurement unit (IMU) can be positioned to accurately reflect the dynamic response of the forklift's lifting action. For example, the IMU can be located inside the forklift backplate, or on the fork carriage, lifting carriage, or other structural components rigidly related to the forklift's movement. Optionally, to facilitate establishing the correspondence between the forklift's movement direction and the IMU's output coordinate axes, the IMU's installation direction can be pre-defined to align with the vehicle coordinate system or ground reference direction; for example, the positive Z-axis can point upwards, the positive X-axis towards the fork tip, and the positive Y-axis towards the left of the fork tip. Preferably, before subsequent control processing, the data output by the IMU can undergo zero-bias correction, attitude compensation, or coordinate transformation to improve the accuracy of the acceleration data in representing the actual vertical dynamic changes of the forklift. Thus, the acceleration data output by the IMU can establish a stable correspondence with the forklift's vertical, forward / backward, and lateral movements, providing a basis for the formation of the acceleration measurement 202.

[0038] To make the acceleration metric 202 more suitable for participation in the subsequent control compensation process, in one example, the acceleration information reported by the inertial measurement unit exhibits normal fluctuations, which may be within the range of ±0.15 m / s². Therefore, when forming the acceleration metric 202, these normal fluctuations can be filtered out, weakened, or smoothed as background fluctuations to reduce their impact on the subsequent control compensation process. Furthermore, in one embodiment, the acceleration metric 202 can be updated on a rolling basis within each control cycle. That is, after a new batch of acceleration data arrives in the current control cycle, the corresponding Z-axis acceleration information can be re-extracted, and the acceleration metric 202 can be re-formed, thus keeping the acceleration metric 202 synchronized with the current operating state of the forklift. Since the dynamic response of the forklift may differ under different lifting stages, different load states, and different field conditions, continuously updating the acceleration metric 202 helps to ensure that the subsequent compensation processing remains consistent with the current operating state of the forklift. Therefore, the acceleration metric 202 is not merely a static result after a single measurement, but a dynamic update quantity throughout the entire lifting process of the forklift.

[0039] While forming the acceleration metric 202, the target speed corresponding to the current lifting process of the forklift is obtained through step 203. The target speed is used to characterize the operating speed that is expected to be achieved in the current lifting phase. In this embodiment, the target speed can be given by the current task, the current lifting phase, or the current control scheduling logic, and can be updated with the control cycle. For example, the target speed can correspond to different speed targets in the lifting phase, the approaching target height phase, and the descent phase; the target speed can also be adjusted according to the current task requirements under different load conditions. Based on the target speed, speed tracking control can be executed to obtain the uncompensated lifting control command 204; at the same time, the target acceleration can also be formed based on the target speed. Thus, in this embodiment, the target speed 203 forms two types of intermediate results: one is the uncompensated lifting control command 204, and the other is the target acceleration, both of which participate in the subsequent formation process of the compensated lifting control command.

[0040] Furthermore, in one embodiment, the target acceleration can be obtained by differentiating the target velocity; in another embodiment, the target acceleration can also be obtained by velocity planning from the target velocity, wherein the velocity planning can adopt a smooth velocity planning method, such as an S-curve planning method. The uncompensated lift control command 204 can also be referred to as the uncompensated lift control command, which is used to reflect the basic control requirements corresponding to the current target velocity. For the sake of consistent terminology throughout the text, in the following descriptions of this embodiment, it is preferred to use "uncompensated lift control command 204" for explanation.

[0041] Building upon the above, this embodiment further generates a control compensation quantity 205 based on the target acceleration and acceleration metric 202. Specifically, the target acceleration characterizes the change in target speed during the lifting and lowering of the forklift, while the acceleration metric 202 characterizes the actual dynamic information corresponding to the current operating state of the forklift. Based on the difference between the target acceleration and the acceleration metric 202, the control compensation quantity 205 is generated, establishing a correspondence between the control output and the target change information and the current operating state. Therefore, the control compensation quantity 205 is not an independent final control result, but rather an intermediate quantity used to correct the uncompensated lifting and lowering control command 204.

[0042] In a further embodiment of this example, the control compensation amount 205 can be characterized by a feedforward compensation amount, which can be a preferred implementation of the control compensation amount 205 and can be formed according to the following formula: Feedforward compensation = K × (target acceleration − actual acceleration) The actual acceleration can be characterized by the aforementioned acceleration metric 202, and K is the feedforward gain weight. Thus, the feedforward compensation amount can reflect the difference between the target acceleration and the actual acceleration, and participate in subsequent processing as a correction amount for the basic control output. Further, in an optional embodiment, K can be adjusted according to different operating conditions. For example, different feedforward gain weights can be used under load and no-load conditions to better match the feedforward compensation amount with the current operating condition; or, for example, different feedforward gain weights can be used in the initial stage of forklift lifting, the uniform lifting stage, and the stage approaching the target height to further improve the responsiveness of the compensated lifting control command 206 to changes in operating conditions. It should be noted that the specific value of K, as the feedforward gain weight, can be tuned according to the vehicle's response characteristics, load state, and hydraulic actuation characteristics; this embodiment does not impose a unique limitation on this.

[0043] After forming the control compensation amount 205, this embodiment further forms a compensated lifting control command 206 based on the uncompensated lifting control command 204 and the control compensation amount 205. In one main implementation of this embodiment, a superposition method can be used to superimpose the control compensation amount 205 onto the uncompensated lifting control command 204 to obtain the compensated lifting control command 206. Thus, the compensated lifting control command 206 simultaneously includes basic control output and operating state compensation output. In an optional implementation, in addition to the superposition method, other combination methods can also be used to correct the uncompensated lifting control command 204, but this embodiment preferably uses the superposition method. During the continuous control cycle, the target speed 203, target acceleration, acceleration measurement 202, and control compensation amount 205 can all be updated synchronously, so that the compensated lifting control command 206 is continuously updated with the current operating state of the forklift. After the compensated lifting control command 206 is formed, it serves as the direct control input for the subsequent proportional valve opening determination 213 process.

[0044] To further explain Figure 2 The combination and implementation relationship of the processes on the left can be understood as a clear control-output chain, namely: Target speed 203 → Uncompensated lift control command 204 / Target acceleration → Control compensation amount 205 → Compensated lift control command 206.

[0045] Specifically, the target speed 203 generates both an uncompensated lift control command 204 and a target acceleration; the target acceleration and the acceleration measurement 202 together form a control compensation quantity 205; the control compensation quantity 205 then combines with the uncompensated lift control command 204 to form a compensated lift control command 206. Thus, Figure 2 The processing nodes in the left-hand flow logically form a control chain that is passed down and corrected step by step, rather than being multiple isolated processing actions.

[0046] exist Figure 2In the right-hand flow, pressure data output by the pressure sensor is acquired in step 207, and pressure change characterization result 208 is formed from the pressure data. In one specific embodiment, the pressure sensor is set at the pressure measurement position corresponding to the hydraulic control circuit of the forklift lifting to continuously collect hydraulic pressure change information. To more accurately obtain the dynamic pressure changes related to the lifting execution state of the forklift, in some embodiments, the pressure sensor can be set near the outlet of the proportional valve, preferably at a position close to the proportional valve, for example, less than 50cm away from the proportional valve, to reduce the attenuation of the pressure pulsation signal by the pipeline. In an optional connection method, the original high-pressure pipe can be disconnected at the outlet of the proportional valve, and the original pipeline and the pressure sensor can be connected through a pressure-testing tee connector. The pressure sensor can be, for example, a pressure sensor with a 4-20mA output. Correspondingly, the connection relationship can be, for example, as follows: proportional valve outlet → pressure-testing tee connector → original pipe to lifting cylinder, and the pressure sensor is connected at the pressure measurement port of the pressure-testing tee connector. The above positional relationship, connection relationship and signal form are all optional implementation methods, used to illustrate the specific implementation path of pressure data acquisition, and do not constitute the only limitation of this embodiment. Therefore, the pressure data can be stably fed into the subsequent processing flow, and provide the basis for the collection of pressure change characterization results 208.

[0047] When forming the pressure change characterization result 208, the pressure data can be high-pass filtered, and the processed pressure change peak value can be statistically analyzed within a predetermined time window. The pressure change peak value is then determined as the pressure change characterization result 208. The high-pass filtering is used to extract the dynamic change components in the pressure data, making the pressure change characterization result 208 more suitable for characterizing the fluctuation of hydraulic pressure during the lifting and lowering of the forklift. In one example, the predetermined time window can be 0.1s to 0.3s, preferably 0.2s. Within the above time window, the processed continuous pressure data is statistically analyzed, and the pressure change peak value is obtained. Therefore, the pressure change characterization result 208 is not simply a static pressure value, but a characterization result of the dynamic change of pressure during the lifting and lowering of the forklift. Furthermore, in the continuous control cycle, the pressure change peak value can be continuously updated using a rolling window method, so that the pressure change characterization result 208 is continuously updated throughout the entire lifting and lowering process of the forklift.

[0048] See Figure 3After forming the pressure change characterization result 302, this embodiment further forms a pressure change level 303 based on the pressure change characterization result 302. Specifically, the pressure change characterization result 302 can be compared with at least two preset pressure change level intervals to determine the pressure change level 303 corresponding to the current forklift lifting process. In an optional embodiment, when the pressure change peak value is greater than 0.8 MPa and not greater than 1.5 MPa, it can correspond to a slight vibration level; when the pressure change peak value is greater than 1.5 MPa and not greater than 3.0 MPa, it can correspond to a moderate vibration level; and when the pressure change peak value is greater than 3.0 MPa, it can correspond to a severe vibration level. The above thresholds are only examples used to illustrate how to map the pressure change characterization result to different pressure change levels and do not constitute a unique limitation. Thus, the pressure change characterization result 302 can be mapped to different pressure change levels 303 for use in the subsequent maximum lifting speed 304 and preset constraint condition 305 formation process.

[0049] After establishing a pressure change level 303, this embodiment further establishes a maximum lifting / lowering speed 304 and a preset constraint condition 305 based on the pressure change level 303. Specifically, different pressure change levels correspond to different maximum lifting / lowering speeds 304, and the maximum lifting / lowering speed 304 decreases progressively as the pressure change level increases. In an optional embodiment, slight vibration levels and moderate vibration levels may correspond to a speed limit condition 306, and severe vibration levels may correspond to a stop condition 307; simultaneously, under the speed limit condition 306, different levels may also correspond to different maximum lifting / lowering speed limits. For example, in one example, when the current pressure change level corresponds to a slight vibration level, the maximum lifting / lowering speed 304 can be limited to 80% of the normal lifting / lowering speed limit; when the current pressure change level corresponds to a moderate vibration level, the maximum lifting / lowering speed 304 can be limited to 50% of the normal lifting / lowering speed limit; when the current pressure change level corresponds to a severe vibration level, a stop condition 307 can be established and deceleration and stop control can be initiated. The aforementioned proportional relationships are merely examples, used to illustrate the formation of the maximum acceleration / deceleration rate 304 and the preset constraint condition 305 under different pressure change levels, and do not constitute the sole limitation of this embodiment. Thus, the pressure change characterization results form a clear constraint output chain, namely: Pressure data 301 → Pressure change characterization result 302 → Pressure change level 303 → Maximum lifting and lowering speed 304 / Preset constraint conditions 305.

[0050] The maximum lifting speed 304 serves as an outer constraint for subsequent boundary control; the preset constraint 305 serves as the basis for entering subsequent branch execution.

[0051] In this embodiment, the maximum lifting speed 304 is used as an outer constraint quantity, directly affecting the proportional valve opening determination process, rather than existing only as an independently displayed result. Figure 2 and Figure 3 As shown, under speed-limited conditions, the compensated lifting control command 206 and the maximum lifting speed 209 / 304 jointly participate in determining the proportional valve opening 213 / 308. Specifically, a speed boundary constraint corresponding to the maximum lifting speed 209 / 304 can be applied to the compensated lifting control command 206 first. The compensated lifting control command 206 after the speed boundary constraint is applied is then used to determine the proportional valve opening 213 / 308. Thus, the maximum lifting speed 209 / 304 forms boundary control during the execution phase, causing the inner control output to be transformed into a restricted execution output under the action of the outer constraint.

[0052] Furthermore, in a preferred implementation, the speed boundary constraint can be implemented by comparing the execution requirement with the allowable execution limit. Specifically, the execution requirement corresponding to the compensated lifting control command 206 can be compared with the allowable execution limit corresponding to the maximum lifting speed 209 / 304. When the execution requirement does not exceed the allowable execution limit, the proportional valve opening 213 / 308 can be determined according to the execution range corresponding to the compensated lifting control command 206; when the execution requirement exceeds the allowable execution limit, the allowable execution limit is used as the boundary basis to restrict the execution range corresponding to the compensated lifting control command 206, and the proportional valve opening 213 / 308 is determined within the restricted execution range. Thus, the speed boundary constraint is not an abstract constraint relationship, but rather a concrete action on the proportional valve opening determination process through the comparison between the execution requirement and the allowable execution limit, and the boundary restriction after exceeding the limit.

[0053] Furthermore, the compensated lifting control command 206, after being constrained by the speed boundary, can be determined as the proportional valve opening 213 / 308 through unit conversion or a preset mapping relationship. The unit conversion or preset mapping relationship is used to establish the correspondence between the control command and the proportional valve opening, so that the compensated lifting control command 206, after being constrained by the maximum lifting speed 209 / 304, can be converted into the corresponding execution opening. In a further embodiment, the execution speed calculated by pure PID can be superimposed with the PID feedforward compensation speed, and then the final proportional valve opening can be obtained through unit conversion; in this embodiment, the unit conversion or preset mapping relationship can be regarded as the execution link that maps the compensated lifting control command 206 to the proportional valve opening 213 / 308. The above-mentioned PID calculation, feedforward superposition, and mapping relationship are all optional implementation methods used to illustrate the specific implementation of the proportional valve opening determination process and do not constitute a unique limitation. Therefore, the proportional valve opening 213 / 308 is not determined solely by the target speed or the pressure change characterization result, but rather by the combined effect of the compensated lifting control command 206 and the constraint of the maximum lifting speed 209 / 304. Ultimately, the lifting speed of the forklift corresponding to the proportional valve opening 213 / 308 does not exceed the maximum lifting speed 209 / 304.

[0054] When the preset constraint is a speed-limited condition, this embodiment enters a branch execution path for continued lifting and lowering. At this time, the proportional valve opening 213 / 308 is determined within the range of the maximum lifting and lowering speed 209 / 304, thereby allowing the fork arm to continue operating within the limited speed range. In the aforementioned example, when the current pressure change level corresponds to a slight jitter level, the lifting and lowering speed of the fork arm can be limited to 80% of the upper limit of the normal lifting and lowering speed; when the current pressure change level corresponds to a moderate jitter level, the lifting and lowering speed of the fork arm can be limited to 50% of the upper limit of the normal lifting and lowering speed. The above proportions are only examples used to illustrate the graded execution effect under speed-limited conditions. In the continuous control cycle, the compensated lifting and lowering control command 206 after speed boundary constraints is continuously updated, and the proportional valve opening 213 / 308 is also updated accordingly, thereby allowing the fork arm to maintain an execution state of continued lifting and lowering but with limited speed under speed-limited conditions. Therefore, the execution path under speed-limited conditions is not a stopping path, but a limited running path under the action of the outer constraint quantity, corresponding to Figure 2 The continued rise and fall steps 214 and Figure 3 The result of continuing the process is 309.

[0055] When the preset constraint condition is a stop condition, this embodiment enters the deceleration stop branch execution path. At this time, the proportional valve opening for maintaining the continuous lifting and lowering of the fork arm is no longer determined according to the continued lifting and lowering path. Instead, a deceleration stop control 215 is output, causing the proportional valve to enter the execution state corresponding to the deceleration stop, and the deceleration stop control takes over the subsequent execution process. In one specific embodiment, when the current pressure change level corresponds to a severe vibration level, a stop condition 307 is formed, and a deceleration stop control signal is output after the stop condition is detected. Subsequently, the proportional valve enters the execution state corresponding to the deceleration stop, causing the fork arm to transition from the current operating state to the deceleration stop state. Figure 2 Step 216 and Figure 3 The deceleration and stopping result is 310.

[0056] Furthermore, in some optional embodiments, the deceleration stop control is not simply a matter of cutting off the continued lifting and lowering control, but can employ a smoother takeover method. For example, the current proportional valve opening can be gradually reduced, segmented, or attenuated according to a predetermined deceleration trajectory; when the forklift's operating speed decreases below a preset threshold, the proportional valve can enter a closed state, a holding state, or a neutral state to achieve a smooth stop. Thus, the control results under stopping conditions are clearly distinguished from those under speed-limiting conditions: under speed-limiting conditions, the forklift continues to lift and lower, but its speed is limited; under stopping conditions, the proportional valve opening used to maintain the forklift's continued lifting and lowering is no longer determined according to the continued lifting and lowering path, but rather the deceleration stop control causes the proportional valve to enter an execution state corresponding to deceleration stop, and the forklift enters a deceleration stop state. Preferably, the deceleration stop control can avoid a direct switch from the continued lifting and lowering state to the abrupt stop state, thereby reducing secondary vibrations or hydraulic shocks caused by control abrupt changes.

[0057] In addition to the above-described combined implementation, this embodiment also introduces anomaly detection and protection control based on an inertial measurement unit (IMU) as a further implementation and protective supplement to the aforementioned method. In this further implementation, anomaly detection related quantities can be constructed based on triaxial acceleration data. Specifically, the X-axis acceleration can be denoted as ax, the Y-axis acceleration as ay, and the Z-axis acceleration as az, and the magnitudes of the three accelerations can be calculated. ; Simultaneously, calculate the horizontal acceleration modulus: .

[0058] Furthermore, considering the existence of a basically stable gravitational acceleration along the Z-axis, the gravitational acceleration can be, for example, taken as g = 9.81. In one example, it can be determined whether mod − g is greater than 0.7, or whether the change in az is greater than 0.4; if either of these conditions is met, it can be considered that there is an abnormality corresponding to the loosening, tilting, or severe impact of the inertial measurement unit. In another example, it can be determined whether mod1 is greater than 0.8 to detect abnormal horizontal vibration; mod can also be high-pass filtered, and it can be determined whether the mod after high-pass filtering is greater than 0.6 to detect abnormal high-frequency jitter; a sliding window method can also be used to record the peak value of the difference between the maximum and minimum acceleration within 0.2s, and when the peak value is greater than 6, it is determined that there is a severe jitter abnormality. The above-mentioned abnormality detection related quantities, thresholds, and their corresponding relationships are all examples in further implementation methods, used to form a protective supplement to the aforementioned control scheme, and do not change the basic technical concept of the aforementioned method.

[0059] Therefore, anomaly detection based on the inertial measurement unit further forms a protection and control related quantity chain, namely: Three-axis acceleration data → mod / mod1 / az change / mod after high-pass filtering / sliding window peak value → anomaly detection result.

[0060] Upon detecting the aforementioned severe anomalies, deceleration and stop control can be further triggered. Specifically, when the detection results indicate the presence of a loose inertial measurement unit, tilting, severe impact, significant horizontal vibration, high-frequency jitter, or short-term severe anomaly, the continuous lifting path can be discontinued, and deceleration and stop control can be output, causing the proportional valve to switch to the execution state corresponding to deceleration and stop, thereby providing a safety supplement to the aforementioned combined control scheme. In other words, in a further embodiment of this example, in addition to the stop condition formed by the pressure change level, the deceleration and stop triggering basis can also be formed by the anomaly detection result of the inertial measurement unit, so that the fork arm can enter the protection control state under abnormal conditions from different sources.

[0061] In summary, this embodiment further explains the combined implementation of the forklift lifting stability control method. Among other things, Figure 2 The process on the left corresponds to the inner control processing chain, forming a clear control output chain, namely the processing chain between target speed 203, target acceleration, acceleration measurement 202, control compensation amount 205 and compensated lifting control command 206. Figure 2 The process on the right and Figure 3Corresponding to the outer constraint processing chain, a clear constraint output chain is formed, namely the processing chain between pressure data 301, pressure change characterization result 302, pressure change level 303, maximum lifting speed 304, and preset constraint condition 305. Under speed-limited conditions, the maximum lifting speed 209 / 304 applies speed boundary constraints to the compensated lifting control command 206, and determines the proportional valve opening 213 / 308 based on comparing the execution requirements with the allowable execution upper limit, so that the fork arm continues to lift and lower. Under stopping conditions, the proportional valve opening used to maintain the continuous lifting and lowering of the fork arm is no longer determined according to the continued lifting and lowering path. The deceleration stop control 215 causes the proportional valve to enter the execution state corresponding to the deceleration stop, and causes the fork arm to enter the deceleration stop state 216 / 310. In addition, this embodiment also incorporates examples of inertial measurement unit installation direction, pressure sensor installation method, predetermined time window, pressure change peak threshold, speed limit ratio, feedforward compensation amount formation method, and abnormal detection and protection control in the form of further implementation methods and optional implementation methods, thereby forming a deepening, expansion, and combination description of the aforementioned method scheme. The above-described processing procedure can be executed by a corresponding system architecture, which will be further described in subsequent implementations.

[0062] Example 3 Based on the above method embodiments, this embodiment provides a forklift lifting stability control system applied to forklift AGVs, such as... Figure 4 The diagram shown is a schematic of a forklift lifting stability control system for a forklift AGV, provided by an embodiment of the present invention. The system is applied to the forklift AGV 100 and is used to stably control the lifting process of the forklift 110. This embodiment mainly describes the system's structure, connection relationships, and cooperation methods. The system is used to execute the aforementioned forklift lifting stability control method, thereby enabling the system to generate control outputs, constraint outputs, and corresponding execution signals during the forklift lifting process, thus achieving stable control during the forklift lifting process. This embodiment does not elaborate on the aforementioned processing flow step by step, but focuses on explaining the connection relationships between the components in the system, the division of functions, and the execution methods under different preset constraint conditions.

[0063] like Figure 4As shown, the system includes an inertial measurement unit 120, a pressure sensor 130, a proportional valve 140, and a control module 150. The control module 150 serves as the central control unit of the system. The inertial measurement unit 120 and the pressure sensor 130 are connected to the control module 150 as input acquisition terminals. The proportional valve 140 is connected to the control module 150 as the execution terminal, and it adjusts the lifting and lowering of the fork arm 110 via a lifting actuator 160. Furthermore, the control module 150 internally includes an inner control section 151 and an outer constraint section 152. The processing results of the inner control section 151 and the outer constraint section 152 are integrated by the control module 150 to form a control signal for the proportional valve 140. The inner control section 151 generates a control output for the execution terminal, and the outer constraint section 152 generates a constraint output for the execution terminal. Thus, the system structurally forms an overall closed loop of input terminal—control terminal—execution terminal.

[0064] In this embodiment, the inertial measurement unit 120 is connected to the control module 150 and is used to output acceleration data to the control module 150. In a further embodiment, the inertial measurement unit 120 can be disposed inside the fork arm back plate to more directly sense the dynamic changes of the fork arm during the lifting and lowering process of the fork arm 110; in other optional embodiments, it can also be disposed on the fork carriage, lifting carriage, or related structural components that are rigidly related to the movement of the fork arm. In order to establish a stable correspondence between the data output by the inertial measurement unit 120 and the lifting and lowering direction of the fork arm, in a further embodiment, the installation direction of the inertial measurement unit 120 is kept horizontal with respect to the ground, wherein the positive Z-axis points upward, the positive X-axis points towards the fork tip, and the Y-axis points to the left of the fork tip. Thus, the three-axis acceleration data output by the inertial measurement unit 120 can respectively correspond to the dynamic changes in the vertical, forward and backward, and lateral directions of the fork arm.

[0065] Furthermore, in this embodiment, the acceleration data output by the inertial measurement unit 120 enters the control module 150 and is received and processed by the inner control section 151. That is, the control module 150 does not simply store or forward the output data of the inertial measurement unit 120, but uses the acceleration data as one of the basic inputs for forming compensated lifting control commands. Thus, during the lifting and lowering process of the forklift 110, the inertial measurement unit 120 continuously senses the current operating state of the forklift, and the control module 150 further utilizes and controls this state information.

[0066] In this embodiment, pressure sensor 130 is connected to control module 150 and is used to output pressure data to control module 150. In a further embodiment, pressure sensor 130 can be set at a pressure measuring position near the outlet of proportional valve 140 to acquire pressure data that reflects the hydraulic execution state of the forklift lifting mechanism. Further, in a preferred embodiment, pressure sensor 130 can be set at a position close to proportional valve 140, for example, less than 50cm, to reduce the attenuation effect of pipeline on pressure pulsation signal. In a specific connection method, the original high-pressure pipeline can be disconnected at the outlet of proportional valve 140, and the original pipeline and pressure sensor 130 can be connected through a pressure measuring tee connector. At this time, the connection relationship can be: proportional valve 140 outlet → pressure measuring tee connector → original pipeline to lifting cylinder, and pressure sensor 130 is connected at the pressure measuring port of the pressure measuring tee connector. In a further embodiment, pressure sensor 130 can be a pressure sensor with 4-20mA output to output the collected pressure change information to control module 150. The installation location, distance, connection method, and signal form mentioned above are all optional or preferred implementation methods, and do not constitute the only limitation.

[0067] The pressure data output by the pressure sensor 130 enters the control module 150 and is received and processed by the outer constraint section 152. Specifically, the outer constraint section 152 generates a pressure change characterization result based on the pressure data, and further determines the maximum lifting speed and preset constraint conditions based on the pressure change characterization result. Thus, the role of the pressure sensor 130 in the system is not simply to measure static pressure, but to provide the input data basis for the outer constraint formation process. Through the connection between the pressure sensor 130 and the control module 150, the system can continuously acquire hydraulic pressure change information during the lifting of the fork arm 110, and form the boundary constraints and condition judgment results required for subsequent control execution based on this information.

[0068] In this embodiment, the proportional valve 140 is connected to the control module 150 and is used to receive the control signal output by the control module 150 and adjust the lifting and lowering of the fork arm 110 according to the control signal. Specifically, the proportional valve 140 is located in the hydraulic control circuit for fork arm lifting and acts on the lifting and lowering of the fork arm 110 through the lifting actuator 160. The lifting actuator 160 may include, for example, a lifting cylinder or a hydraulic actuator corresponding to the lifting and lowering of the fork arm 110. When the control module 150 outputs a control signal corresponding to the opening degree of the proportional valve, the proportional valve 140 adjusts its own opening degree according to the control signal, thereby changing the hydraulic flow or execution state entering the lifting actuator 160, thus regulating the lifting and lowering process of the fork arm 110. Therefore, the proportional valve 140 constitutes the execution interface between the control module 150 and the lifting and lowering execution of the fork arm 110.

[0069] Furthermore, in this embodiment, the control signal received by the proportional valve 140 is not limited to a single type of opening adjustment signal, but can correspond to different control forms according to the current operating conditions. Under speed-limiting conditions, the control signal can be an execution signal used to determine the opening of the proportional valve, so that the fork arm 110 continues to rise and fall under the maximum lifting speed constraint; under stopping conditions, the control signal can be an execution signal corresponding to deceleration and stop control, so that the proportional valve 140 enters the execution state corresponding to deceleration and stop, thereby causing the fork arm 110 to enter the deceleration and stop state. Thus, the role of the proportional valve 140 in the system is not only to adjust the lifting speed, but also to accept different control results under different preset constraint conditions.

[0070] The control module 150 is the central control unit in the system. It receives acceleration data from the inertial measurement unit 120 and pressure data from the pressure sensor 130, and outputs control signals to the proportional valve 140 based on the input data. In one optional embodiment, the control module 150 can be implemented by an independent control unit; in another optional embodiment, the control module 150 can also be implemented by a functional area in the vehicle controller; in a further embodiment, the control module 150 can also be implemented by a processor, a memory, and a program that executes the corresponding control logic. Regardless of the hardware implementation method of the control module 150, it can logically include an inner control part 151 and an outer constraint part 152. The acceleration data output by the inertial measurement unit 120 is input to the inner control part 151, and the pressure data output by the pressure sensor 130 is input to the outer constraint part 152. The processing results of the inner control part 151 and the outer constraint part 152 are integrated by the control module 150 to form a control signal for the proportional valve 140. Therefore, the control module 150 not only serves to aggregate input data, but also to synthesize internal processing results and output execution signals.

[0071] In this embodiment, the inner control unit 151 is used to acquire the target speed and determine a compensated lifting control command based on the target speed and the acceleration data. Specifically, the inner control unit 151 receives the target speed given by an external task, the current lifting stage, or control scheduling logic, and receives acceleration data from the inertial measurement unit 120. Based on the target speed and the acceleration data, the inner control unit 151 performs target speed-related control processing and acceleration-related state processing to form a compensated lifting control command. Thus, the role of the inner control unit 151 in the system is to combine the target control requirements with the current operating state of the forklift to form a control output suitable for subsequent control execution.

[0072] Further, in an optional embodiment, the inner control unit 151 can execute the inner control processing procedure in the aforementioned method embodiment. For example, the inner control unit 151 can generate an uncompensated lifting control command based on the target speed, and further generate a target acceleration based on the target speed; it can also generate a control compensation quantity based on the difference between the target acceleration and the operating state representation quantity formed by the acceleration data, and combine the control compensation quantity with the uncompensated lifting control command to form a compensated lifting control command. In a further embodiment, the control compensation quantity can be represented by a feedforward compensation quantity, which can be generated based on the difference between the target acceleration and the actual acceleration. It should be noted that the above processing procedure is used to illustrate the scope of responsibility of the inner control unit 151; the specific formulas, parameters, and example thresholds have been described in the aforementioned method embodiment and will not be repeated here.

[0073] In this embodiment, the outer constraint portion 152 is used to determine the pressure change characterization result based on the pressure data, and to determine the maximum acceleration / deceleration rate and preset constraint conditions based on the pressure change characterization result. Specifically, the outer constraint portion 152 receives pressure data from the pressure sensor 130 and performs pressure change-related constraint processing on the pressure data to form a pressure change characterization result. Subsequently, the outer constraint portion 152 determines the maximum acceleration / deceleration rate based on the pressure change characterization result and determines the current preset constraint conditions. Thus, the responsibility of the outer constraint portion 152 is not only to detect pressure data, but also to transform the detection result into the basis for execution boundaries and branch control.

[0074] Further, in an optional embodiment, the outer constraint portion 152 can execute the outer constraint processing procedure described in the aforementioned method embodiment. For example, the outer constraint portion 152 can perform high-pass filtering on the pressure data and statistically analyze the processed pressure change peak value within a predetermined time window, determining the pressure change peak value as the pressure change characterization result; it can also form a pressure change level based on the pressure change characterization result, and further form a corresponding maximum acceleration / deceleration speed and preset constraint conditions based on the pressure change level. In a further embodiment, the preset constraint conditions may include speed limit conditions and stop conditions, wherein, in at least two preset pressure change level intervals, the lower pressure change level may correspond to the speed limit condition, and the higher pressure change level may correspond to the stop condition. It should be noted that the examples of the above-mentioned level intervals, thresholds, and proportions have been described in the aforementioned method embodiment and will not be repeated here. Through the above processing relationships, the outer constraint portion 152 can form constraint outputs for subsequent execution control.

[0075] In this embodiment, the control module 150 does not simply transmit the outputs of the inner control section 151 and the outer constraint section 152 to the execution end separately, but rather integrates the two types of outputs. When the preset constraint condition is a speed limit condition, the control module 150 receives the compensated lifting control command generated by the inner control section 151 and the maximum lifting speed generated by the outer constraint section 152, and applies a speed boundary constraint to the compensated lifting control command based on the maximum lifting speed to form an execution control signal for the proportional valve 140. Under the speed limit condition, the control module 150 determines the opening degree of the proportional valve 140 according to the compensated lifting control command after the speed boundary constraint, and controls the fork arm 110 to continue lifting and lowering through the proportional valve 140. Further, in an optional embodiment, the control module 150 can compare the execution requirement corresponding to the compensated lifting control command with the allowable execution limit corresponding to the maximum lifting speed; when the execution requirement does not exceed the allowable execution limit, the opening degree of the proportional valve 140 is determined according to the compensated lifting control command; when the execution requirement exceeds the allowable execution limit, the execution range corresponding to the compensated lifting control command is limited by using the allowable execution limit as a boundary basis, and then the opening degree of the proportional valve 140 is determined, and a proportional valve opening control signal is output to the proportional valve 140. Thus, under speed-limited conditions, the control module 150 does not simply forward the processing result of the inner control part 151, but rather comprehensively determines the final execution opening degree under the maximum lifting speed constraint formed by the outer constraint part 152.

[0076] After the control module 150 outputs a proportional valve opening control signal, the proportional valve 140 adjusts its opening according to the control signal, and the lifting actuator 160 adjusts the fork arm 110 to continue lifting and lowering. Since the control module 150 applies a maximum lifting and lowering speed constraint to the corresponding opening of the proportional valve 140 under speed-limited conditions, the lifting and lowering speed of the fork arm 110 does not exceed the maximum lifting and lowering speed. Furthermore, under speed-limited conditions, the control module 150 does not change the execution direction of the fork arm 110's continued lifting and lowering, but instead controls the opening of the proportional valve 140 to allow the fork arm 110 to continue lifting and lowering within the allowable speed range. Thus, the system can allow the fork arm 110 to continue operating under speed-limited conditions while remaining within the allowable speed range, thereby forming a restricted lifting and lowering execution path.

[0077] In this embodiment, when the preset constraint condition formed by the outer constraint portion 152 is a stop condition, the control module 150 outputs a deceleration stop control, and performs deceleration stop on the lifting and lowering of the fork arm 110 through the proportional valve 140 according to the deceleration stop control. Specifically, under the stop condition, the control module 150 no longer determines the opening of the proportional valve 140 to maintain the continuous lifting and lowering of the fork arm 110 according to the continued lifting and lowering path, but instead outputs a control signal corresponding to the deceleration stop, causing the proportional valve 140 to enter the execution state corresponding to the deceleration stop. Subsequently, the lifting actuator 160, under the control of the proportional valve 140, causes the fork arm 110 to switch from the current operating state to the deceleration stop state. Thus, the system forms an execution path different from the speed limit condition under the stop condition.

[0078] Furthermore, under stopping conditions, the deceleration stop control replaces or takes over the aforementioned continuous lifting and lowering execution path. That is, under speed-limited conditions, the control module 150 outputs a proportional valve opening control signal to maintain the continuous lifting and lowering of the fork arm 110; however, under stopping conditions, the control module 150 no longer determines the proportional valve opening to maintain the continuous lifting and lowering of the fork arm 110 according to the continuous lifting and lowering path, but instead outputs a deceleration stop control signal, causing the proportional valve 140 to enter an execution state corresponding to deceleration stop. Thus, the system can generate two types of execution results—limited continued operation and deceleration stop—based on different current preset constraints, thereby completing branch control at the system level; and when the stopping condition is met, the deceleration stop control has priority over the continuous lifting and lowering control.

[0079] In a further embodiment, the control module 150 may further include anomaly detection and protection control logic. Specifically, anomaly judgment results can be formed based on the triaxial acceleration data output by the inertial measurement unit 120; when anomalies such as loosening, tilting, abnormal impact, or severe vibration of the inertial measurement unit are detected, the control module 150 may output a deceleration and stop control signal, or enter a conservative control mode, to provide a protective supplement to the aforementioned control process. It should be noted that the anomaly detection and protection control logic is a further embodiment used to improve the safety and controllability of the system under abnormal operating conditions, without changing the basic technical concept of the aforementioned system structure and control cooperation.

[0080] In summary, this embodiment forms an input-control-execution closed loop through the inertial measurement unit 120, pressure sensor 130, control module 150, and proportional valve 140. Specifically, the inertial measurement unit 120 outputs acceleration data to the control module 150, and the pressure sensor 130 outputs pressure data to the control module 150. The inner control section 151 and the outer constraint section 152 within the control module 150 work together to generate control output and constraint output, respectively. Under speed-limited conditions, the control module 150 combines speed boundary constraints to generate a proportional valve opening control signal. Under stopping conditions, it no longer determines the proportional valve opening to maintain the continuous lifting and lowering of the fork arm 110 according to the continuing lifting and lowering path, causing the proportional valve to enter an execution state corresponding to deceleration and stopping, thereby generating a deceleration and stopping control signal. The proportional valve 140 adjusts the lifting and lowering of the fork arm 110 through the lifting actuator 160. Therefore, the system can execute the aforementioned fork arm lifting and lowering stability control method, and achieve continuous lifting and lowering control and deceleration and stopping control under speed-limited and stopping conditions, respectively. The above system implementation method is consistent with the above method implementation method in terms of technical concept, and is used to further explain the above technical solution from the perspective of system composition and system cooperation.

[0081] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for stabilizing the lifting of a forklift arm applied to a forklift AGV, characterized in that, include: Acquire acceleration data output by an inertial measurement unit; wherein the inertial measurement unit is installed on the fork carriage, fork back plate or lifting carriage, and the inertial measurement unit synchronously senses the changes in the operating state of the fork arm during the lifting and lowering process, and the vertical axis of the sensing axis of the measurement unit is consistent with the lifting and lowering direction of the fork arm; Acquire the target speed and determine the compensated lifting control command based on the target speed and the acceleration data; acquire the pressure data output by the pressure sensor and determine the pressure change characterization result, maximum lifting speed and constraint conditions based on the pressure data; When the constraint condition is a speed limit condition, under the constraint of the maximum lifting speed, the opening degree of the proportional valve is determined according to the compensated lifting control command, and the lifting of the fork arm is controlled according to the opening degree of the proportional valve. When the constraint condition is a stop condition, a deceleration stop control is output, and the lifting and lowering of the fork arm is decelerated and stopped according to the deceleration stop control; The step of determining the compensated lifting control command based on the target speed and the acceleration data includes: determining an acceleration metric based on the acceleration data to characterize the current operating state of the fork arm; The step of determining the acceleration metric used to characterize the current operating state of the fork arm based on the acceleration data includes: extracting Z-axis acceleration information related to the vertical motion of the fork arm from the acceleration data; performing high-pass filtering on the Z-axis acceleration information; and determining the high-pass filtered Z-axis acceleration information as the acceleration metric used to characterize the current operating state of the fork arm. in, Determining the pressure change characterization result based on the pressure data includes: performing high-pass filtering on the pressure data; statistically analyzing the peak value of the pressure data after high-pass filtering within a predetermined time window; and determining the peak value as the pressure change characterization result. The step of determining the pressure change characterization result, maximum acceleration / deceleration rate, and constraint conditions based on the pressure data further includes: The pressure change characterization result is compared with multiple preset pressure change level ranges to determine the pressure change level corresponding to the pressure change characterization result; the corresponding maximum lifting speed is determined according to the pressure change level; and the constraint condition is determined to be a speed limit condition or a stop condition according to the pressure change level; wherein, as the pressure change level increases, the maximum lifting speed decreases step by step, and higher pressure change levels correspond to the stop condition, and the maximum lifting speed is used as the outer constraint quantity for constraining the lifting control of the fork arm.

2. The forklift lifting stability control method according to claim 1, characterized in that, The step of determining the compensated lifting control command based on the target speed and the acceleration data further includes: Determine the target acceleration based on the target velocity; The uncompensated lift control command is determined based on the target speed; The step of determining the target acceleration based on the target velocity and determining the uncompensated lift control command based on the target velocity includes: The target acceleration is determined by differentiating the target velocity or by performing velocity planning on the target velocity. Speed ​​tracking control is performed based on the target speed to obtain the uncompensated lifting control command.

3. The forklift lifting stability control method according to claim 2, characterized in that, The step of determining the compensated lifting control command based on the target speed and the acceleration data further includes: The control compensation amount is determined based on the target acceleration and the acceleration metric used to characterize the current operating state of the fork arm; The compensated lifting control command is determined based on the uncompensated lifting control command and the control compensation amount; The step of determining the control compensation amount based on the target acceleration and the acceleration metric used to characterize the current operating state of the forklift, and determining the compensated lifting control command based on the uncompensated lifting control command and the control compensation amount, includes: The feedforward compensation amount is determined based on the difference between the target acceleration and the acceleration metric, and the feedforward compensation amount is determined as the control compensation amount; The uncompensated lifting control command is combined with the control compensation amount to obtain the compensated lifting control command.

4. The forklift lifting stability control method according to claim 1, characterized in that, When the constraint condition is a speed limit condition, under the constraint of the maximum lifting speed, determining the proportional valve opening according to the compensated lifting control command, and controlling the lifting of the fork arm according to the proportional valve opening, includes: Apply a speed boundary constraint corresponding to the maximum lifting speed to the compensated lifting control command; The proportional valve opening is determined based on the compensated lifting control command after the speed boundary constraint. So that the lifting speed of the fork arm corresponding to the opening degree of the proportional valve does not exceed the maximum lifting speed.

5. The forklift lifting stability control method according to claim 1, characterized in that, When the constraint condition is a stop condition, the proportional valve opening for maintaining the continuous lifting and lowering of the fork arm is no longer determined according to the continuous lifting and lowering path. Instead, the deceleration stop control is output, so that the proportional valve enters the execution state corresponding to the deceleration stop, and the fork arm is controlled to enter the deceleration stop state.

6. The forklift lifting stability control method according to claim 5, characterized in that, Determining the proportional valve opening based on the compensated lifting control command after the speed boundary constraint includes: The execution requirements corresponding to the compensated lifting control command are compared with the allowable execution limit corresponding to the maximum lifting speed; When the execution demand does not exceed the allowed execution limit, the proportional valve opening is determined according to the compensated lifting control command; When the execution demand exceeds the allowed execution limit, the execution range corresponding to the compensated lifting control command is limited based on the allowed execution limit, and the proportional valve opening is determined based on the limited execution range.

7. A forklift lifting and stabilization control system for implementing the method of any one of claims 1 to 6, characterized in that, include: The system includes an inertial measurement unit, a pressure sensor, a proportional valve, and a control module. The inertial measurement unit is connected to the control module and is used to output acceleration data to the control module; The pressure sensor is connected to the control module and is used to output pressure data to the control module; The proportional valve is connected to the control module and is used to receive the control signal output by the control module to adjust the lifting of the fork arm; The control module includes an inner control section and an outer constraint section; The inner control section is used to acquire the target speed and determine the compensated lifting control command based on the target speed and the acceleration data; The outer constraint portion is used to determine the pressure change characterization result based on the pressure data, and to determine the maximum lifting speed and constraint conditions based on the pressure change characterization result; The control module is also used to: when the constraint condition is a speed limit condition, under the constraint of the maximum lifting speed, determine the opening degree of the proportional valve according to the compensated lifting control command, and control the lifting of the fork arm through the proportional valve; and when the constraint condition is a stop condition, output a deceleration stop control, and perform deceleration stop on the lifting of the fork arm through the proportional valve according to the deceleration stop control. The step of determining the compensated lifting control command based on the target speed and the acceleration data includes: determining an acceleration metric based on the acceleration data to characterize the current operating state of the fork arm; The step of determining the acceleration metric used to characterize the current operating state of the fork arm based on the acceleration data includes: extracting Z-axis acceleration information related to the vertical motion of the fork arm from the acceleration data; performing high-pass filtering on the Z-axis acceleration information; and determining the high-pass filtered Z-axis acceleration information as the acceleration metric used to characterize the current operating state of the fork arm. in, Determining the pressure change characterization result based on the pressure data includes: performing high-pass filtering on the pressure data; statistically analyzing the peak value of the pressure data after high-pass filtering within a predetermined time window; and determining the peak value as the pressure change characterization result. The step of determining the pressure change characterization result, maximum acceleration / deceleration rate, and constraint conditions based on the pressure data further includes: The pressure change characterization result is compared with multiple preset pressure change level ranges to determine the pressure change level corresponding to the pressure change characterization result; the corresponding maximum lifting speed is determined according to the pressure change level; and the constraint condition is determined to be a speed limit condition or a stop condition according to the pressure change level; wherein, as the pressure change level increases, the maximum lifting speed decreases step by step, and higher pressure change levels correspond to the stop condition, and the maximum lifting speed is used as the outer constraint quantity for constraining the lifting control of the fork arm.

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