Boom lowering speed control method and apparatus

Abstract

This application provides a method and apparatus for controlling the boom descent speed, which can be applied to the field of hydraulic control technology. The method includes: acquiring the rodless chamber pressure and rod chamber pressure of the boom cylinder in each control cycle; determining the equivalent support force characterizing the boom cylinder's effect on the boom and load based on the rodless chamber pressure and rod chamber pressure; calculating the deviation between the actual value and the target value of the current equivalent support force; determining a correction amount for the opening area of ​​the speed control main valve core based on the deviation, wherein the correction amount is used to adjust the opening area of ​​the speed control main valve core in the current control cycle; and re-acquiring the equivalent support force and calculating the deviation in the next control cycle until the equivalent support force approaches and remains at the target value.

Description

Technical Field

[0001] This application relates to the field of hydraulic control technology, and more specifically, to a method and device for controlling the boom descent speed. Background Technology

[0002] Hydraulic excavators are among the most energy-intensive pieces of construction machinery. Their booms are frequently raised and lowered, especially during loading and unloading operations, where boom descent accounts for 30% to 50% of the machine's work cycle. When the boom descends, the gravitational potential energy of the boom and the material in the bucket is converted into hydraulic energy through the hydraulic cylinder. If this energy is not recovered, it will be largely converted into heat energy, resulting in energy waste and excessive temperature rise in the hydraulic system, which shortens the life of components.

[0003] To address this issue, relevant technicians proposed an energy-saving hydraulic excavator boom potential energy recovery configuration: a speed control main valve core is installed in the boom descent circuit, with its inlet connected to the rodless chamber of the boom cylinder and its outlet connected to an accumulator to recover gravitational potential energy. However, in practical applications, situations such as drastic changes in bucket load, continuous time-varying accumulator back pressure, and coupling interference from complex actions may occur, leading to difficulties in maintaining a constant boom descent speed with this configuration. Summary of the Invention

[0004] In view of this, this application provides a method and apparatus for controlling the boom descent speed to overcome at least some of the technical problems of the aforementioned related technologies.

[0005] The first aspect of this application provides a boom descent speed control method, comprising: acquiring the rodless chamber pressure and the rod chamber pressure of the boom cylinder in each control cycle; determining, based on the rodless chamber pressure and the rod chamber pressure, an equivalent support force characterizing the boom cylinder's support for the boom and load; calculating the deviation between the actual value and the target value of the current equivalent support force; determining a correction amount for the opening area of ​​the speed control main valve core based on the deviation, wherein the correction amount is used to adjust the opening area of ​​the speed control main valve core in the current control cycle; and re-acquiring the equivalent support force and calculating the deviation in the next control cycle until the equivalent support force approaches and remains at the target value.

[0006] According to an embodiment of this application, determining the equivalent supporting force of the boom cylinder on the boom and load based on the rodless chamber pressure and the rod chamber pressure includes: obtaining the effective working area of ​​the rodless chamber and the effective working area of ​​the rod chamber of the boom cylinder; weighting the rod chamber pressure according to the ratio of the effective working area of ​​the rod chamber to the effective working area of ​​the rodless chamber; and using the difference between the rodless chamber pressure and the converted rod chamber pressure as the controlled variable.

[0007] According to an embodiment of this application, determining the opening area correction amount of the speed control main valve core based on the deviation includes: obtaining the handle opening degree of the current control cycle; generating a first area correction amount based on the handle opening degree; generating a second area correction amount based on the deviation between the actual value and the target value of the equivalent support force; and superimposing the first area correction amount and the second area correction amount as the opening area correction amount of the speed control main valve core for the current control cycle.

[0008] According to an embodiment of this application, generating a second area correction amount based on the deviation between the actual value and the target value of the equivalent support force further includes: determining a positive maximum adjustable area limit value and a negative maximum adjustable area limit value based on the first area correction amount; when the second area correction amount is positive, limiting the second area correction amount to an upper limit using the positive maximum adjustable area limit value; when the second area correction amount is negative, limiting the absolute value of the second area correction amount to an upper limit using the negative maximum adjustable area limit value.

[0009] According to an embodiment of this application, a second area correction amount is generated based on the deviation between the actual value and the target value of the equivalent support force, including: determining a first gain coefficient, a second gain coefficient, and a third gain coefficient based on the handle opening degree of the current control cycle; multiplying the deviation by the first gain coefficient to obtain a first component for responding to the current deviation; accumulating the deviation cycle by cycle and multiplying it by the second gain coefficient to obtain a second component for eliminating the accumulated deviation; multiplying the change in deviation relative to the previous cycle by the third gain coefficient to obtain a third component for responding to the trend of deviation change; and superimposing the first component, the second component, and the third component as the second area correction amount.

[0010] According to an embodiment of this application, the first gain coefficient, the second gain coefficient, and the third gain coefficient are determined based on the handle opening degree of the current control cycle, including: determining the opening degree interval to which the current handle opening degree belongs based on a preset correspondence between the handle opening degree interval and the gain coefficient, and obtaining the first gain coefficient, the second gain coefficient, and the third gain coefficient corresponding to the opening degree interval; wherein, the range of change of the handle opening degree is divided into multiple consecutive opening degree intervals, and different opening degree intervals correspond to different combinations of gain coefficients.

[0011] According to an embodiment of this application, generating a first area correction amount based on the handle opening includes: obtaining a preset mapping function, the mapping function being the correspondence between the handle opening and the normalized area coefficient; substituting the handle opening of the current control cycle into the mapping function to obtain the corresponding normalized area coefficient; and multiplying the normalized area coefficient by the maximum opening area of ​​the speed control main valve core to obtain the first area correction amount.

[0012] According to an embodiment of this application, the method further includes: in each control cycle, obtaining the rodless chamber pressure of the boom cylinder in the current control cycle, and calculating the difference between the rodless chamber pressure in the current control cycle and the rodless chamber pressure in the previous control cycle; comparing the difference with a preset descent rate threshold, and when the difference is less than the descent rate threshold, determining it as a sudden unloading condition and performing an emergency protection operation.

[0013] According to an embodiment of this application, the emergency protection operation includes: replacing the original first gain coefficient with a first gain coefficient multiplied by a preset attenuation coefficient, and using this multiplier to generate the correction amount for the current control cycle; pausing the accumulation of the deviation of the current control cycle into the accumulated deviation value, and determining the correction amount for the current control cycle based on the accumulated deviation value before the pause; resuming the normal control process after the correction amount for the current control cycle is generated; continuously calculating the difference in rodless chamber pressure in subsequent control cycles, and deactivating the emergency protection state when the number of times the difference is continuously less than the drop rate threshold reaches a preset number, and gradually restoring the accumulated deviation value to the normal accumulation state at a preset recovery rate.

[0014] A second aspect of this application provides a boom descent speed control device, comprising: an acquisition module for acquiring the rodless chamber pressure and the rod chamber pressure of the boom cylinder in each control cycle; a first calculation module for determining, based on the rodless chamber pressure and the rod chamber pressure, an equivalent support force characterizing the boom cylinder's support for the boom and load; a second calculation module for calculating the deviation between the actual value and the target value of the current equivalent support force; and a determination module for determining, based on the deviation, an opening area correction amount for the speed control main valve core, the opening area correction amount being used to adjust the opening area of ​​the speed control main valve core in the current control cycle. Attached Figure Description

[0015] The above and other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0016] Figure 1 A schematic diagram of hydraulic hardware according to an embodiment of this application is shown;

[0017] Figure 2 A flowchart illustrating a boom descent speed control method according to an embodiment of this application is shown schematically.

[0018] Figure 3 A schematic diagram illustrating the principle of a boom descent speed control method according to an embodiment of this application is shown.

[0019] Figure 4 The diagram illustrates the physical meaning of the equivalent support force and a force analysis diagram;

[0020] Figure 5A schematic diagram illustrating the comparison of the handle opening degree-valve core area mapping function is shown.

[0021] Figure 6 The diagram illustrates the variation of the gain coefficient with the handle opening degree in an embodiment of this application.

[0022] Figure 7 A schematic diagram illustrating load drop detection and emergency protection according to an embodiment of this application is shown.

[0023] Figure 8 A schematic block diagram of a boom descent speed control device according to an embodiment of this application is shown.

[0024] Figure label:

[0025] 1-Boom cylinder; 2-Anti-settlement valve; 3-Handle pressure reducing valve; 4-Speed ​​control main valve; 5-Accumulator; 6-Boom cylinder rod chamber pressure sensor; 7-Boom cylinder rodless chamber pressure sensor; 8-Accumulator pressure sensor; 9-Controller. Detailed Implementation

[0026] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0028] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0029] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0030] This application provides a method for controlling the boom descent speed. Before introducing the technical solution provided in this application, the relevant technologies involved in this application will be explained.

[0031] Taking an energy-saving hydraulic excavator as an example, its typical configuration is as follows: a speed control main valve core is installed in the boom descent circuit, with its inlet connected to the rodless chamber (high-pressure chamber) of the boom cylinder and its outlet connected to the accumulator; at the same time, a regeneration valve core and an unloading valve core are configured to form a multi-valve core coordinated control system. This configuration can recover gravitational potential energy during boom descent and realize oil regeneration circulation through the regeneration valve core, reducing the output power of the main pump.

[0032] However, in practical applications, the control of the excavator boom descent faces the following technical problems.

[0033] First, the speed disturbance caused by drastic load changes. During excavator operation, the weight of the material in the bucket changes dramatically—fluctuating drastically from an empty bucket (approximately several hundred kilograms) to a full bucket (several tons). These load changes directly affect the pressure P in the rodless chamber of the boom cylinder. u The pressure difference at the valve orifice fluctuates drastically. With the valve core opening constant, fluctuations in the valve core pressure result in changes in the flow rate, causing the boom's descent speed to fluctuate wildly. Especially during a heavy-load, full-bucket descent, excessively slow speeds affect operational efficiency; conversely, during the empty-bucket recovery after unloading, if the valve core opening is not adjusted promptly, the boom will suddenly accelerate its descent, posing a serious safety hazard.

[0034] Second, the time-varying back pressure of the accumulator leads to a continuous decrease in speed. During continuous boom descent operations, the accumulator is continuously filled with oil, and its internal pressure P... acc The pressure gradually increases with the increase of oil filling volume. This pressure serves as the back pressure on the outlet side of the speed control main valve core, and is related to the high pressure P in the rodless chamber. u The net pressure difference across the valve core is determined by both of these factors. As the accumulator pressure rises, the net pressure difference gradually decreases, resulting in a slower and slower boom descent. If the controller continuously increases the main valve core opening to maintain speed, a sudden increase in speed, boom impact, or even structural damage can easily occur when the accumulator pressure reaches its upper limit or the load is suddenly reduced.

[0035] Third, the coupling interference of excavator's compound actions. During excavator operation, boom lowering is often combined with stick digging and swinging actions. The movement of the stick valve or swing valve will cause a readjustment of the main pump flow distribution, resulting in fluctuations in the flow supplied to the boom cylinder, further exacerbating the problem. u The disturbance caused by multi-actuator coupling interference is a control challenge unique to excavators and does not exist in single lifting equipment (such as cranes and mine hoists).

[0036] Existing control methods, whether open-loop valve spool control or closed-loop control based on handle mapping, struggle to simultaneously decouple and adaptively adjust for load disturbances, time-varying accumulator back pressure, and coupled disturbances from combined actions. This problem is amplified, especially in multi-valve spool collaborative potential energy recovery configurations, where the coupling between valve spools further exacerbates the issue.

[0037] Therefore, there is an urgent need for a constant speed control method that can resist load disturbances, adapt to changes in accumulator back pressure, and suppress compound motion disturbances during the boom descent of an excavator.

[0038] Based on the above problems, this application proposes a boom descent speed control method to at least solve the problems of boom descent speed fluctuation caused by drastic changes in bucket load, continuous speed decay and self-adaptation difficulties caused by time-varying accumulator back pressure, and coupling interference problems of excavator compound actions.

[0039] The method includes: acquiring the rodless chamber pressure and rod chamber pressure of the boom cylinder in each control cycle; determining the equivalent support force of the boom cylinder on the boom and load based on the rodless chamber pressure and rod chamber pressure; calculating the deviation between the actual value and the target value of the current equivalent support force; determining the opening area correction amount of the speed control main valve core based on the deviation; adjusting the opening area of ​​the speed control main valve core in the current control cycle with the opening area correction amount; and re-acquiring the equivalent support force and calculating the deviation in the next control cycle until the equivalent support force approaches and remains at a constant target value.

[0040] In common technologies, boom speed control usually uses speed or position as the directly controlled variable. However, the embodiments of this application propose to determine the opening area correction amount by equivalent support force, rather than speed itself.

[0041] This application's embodiments depart from the conventional technical route of speed measurement and control, and instead use force balance as the core of control. The control objective of this method is to maintain the equivalent support force at a constant and reasonable value that can provide sufficient support to prevent stalling without excessively inhibiting descent, thereby indirectly achieving a smooth and constant descent speed.

[0042] The equivalent support force, as a controlled variable, differs fundamentally from the control of speed or position in existing technologies. Existing speed closed-loop control can only respond to speed deviations, failing to distinguish whether the deviation originates from load changes or back pressure drift, often resulting in oscillations or slow responses. In contrast, the equivalent support force in this application directly stems from the mechanical equilibrium equations, quantifying load torque and back pressure changes into a single equivalent support force value. The closed-loop control directly addresses the physical root cause of the disturbance. When the support force deviates from the target, pressure is released or built up by adjusting the valve opening, causing the support force to return to the target. This shift in control paradigm from speed measurement to force measurement gives the system a natural physical consistency in suppressing various disturbances, avoiding the complex architecture of designing compensators separately for different disturbance sources in traditional methods. The method provided in this application does not rely on boom angle or cylinder displacement information; it only requires conventionally installed boom cylinder large and small chamber pressure sensors.

[0043] Figure 1 A schematic diagram of hydraulic hardware according to an embodiment of this application is shown.

[0044] See Figure 1 The hydraulic hardware includes a boom cylinder 1, an anti-settlement valve 2, a handle pressure reducing valve 3, a speed control main valve 4, an accumulator 5, a rod-side pressure sensor 6, a rodless-side pressure sensor 7, an accumulator pressure sensor 8, and a controller 9. This hydraulic hardware can be applied to, for example, excavators, cranes, or port machinery.

[0045] The boom cylinder is a differential hydraulic cylinder, with pressure sensors installed in both its rodless and rod-side chambers. The rodless chamber pressure sensor 7 is installed on the oil line on the rodless side of the boom cylinder, measuring the hydraulic oil pressure in that chamber in real time. The rod-side pressure sensor 6 is installed on the oil line on the rod-side side of the boom cylinder, also measuring the hydraulic oil pressure in that chamber in real time. The inlet of the speed control main valve 4 is connected to the rodless chamber of the boom cylinder, and the outlet is connected to the accumulator 5. Taking the boom lowering operation as an example, the hydraulic oil in the rodless chamber of the boom cylinder is discharged under gravity, passes through the anti-settlement valve 2, and reaches the inlet of the speed control main valve 4. After passing through the valve port of the speed control main valve, it flows into the accumulator 5. By adjusting the opening of the speed control main valve, the flow capacity of the rodless chamber to the accumulator 5 can be controlled, thereby controlling the boom lowering speed. The accumulator 5 is used to absorb return oil pressure shocks and recover energy.

[0046] The handle opening signal is collected by the operator operating the handle (not shown in the figure). When the operator pushes or pulls the handle, the handle outputs a pressure signal proportional to the deflection angle through the handle pressure reducing valve 3. This signal is transmitted to the controller 9 in real time to reflect the operator's demand for the boom descent speed.

[0047] The boom descent speed control method provided in this embodiment is executed by controller 9. The input signals to controller 9 include: the rodless chamber pressure P of the boom cylinder. u (Pressure sensor in the rodless chamber of the boom cylinder), pressure P in the rod chamber of the boom cylinder r (Pressure sensor from the rod chamber of the boom cylinder), accumulator pressure P acc (From the accumulator pressure sensor), handle opening signal α (from the operator operating the handle, reflected by the pressure output through the handle pressure reducing valve).

[0048] Within each control cycle, controller 9 acquires the rodless chamber pressure of the boom cylinder via rodless chamber pressure sensor 7 and the rod chamber pressure via rod chamber pressure sensor 6. Based on the acquired rodless and rod chamber pressures, controller 9 comprehensively considers the proportional relationship between the effective working areas of the two chambers to determine the equivalent support force of the boom cylinder on the boom and load. This equivalent support force is not the actual pressure value of a single chamber, but rather a quantitative representation of the actual upward net support force of the cylinder (i.e., the upward thrust generated by the rodless chamber pressure and the downward pull generated by the rod chamber pressure). The difference between the two, weighted according to their respective effective working areas, is the equivalent support force output by the cylinder.

[0049] The controller 9 also pre-stores a target value for the equivalent support force, which is a constant independent of the boom posture. In each control cycle, the controller 9 calculates the deviation between the current equivalent support force and this constant target value, and determines the opening area correction of the speed control main valve 4 according to a preset control algorithm based on this deviation. Subsequently, the controller 9 converts this opening area correction into a corresponding pilot valve drive current or PWM signal, outputting it to the pilot control port (i.e., the electromagnet drive end) of the speed control main valve 4, driving the valve core of the speed control main valve 4 to produce a corresponding displacement, thereby changing the actual opening area of ​​the main valve core.

[0050] The speed control main valve 4 can be an electro-proportional valve, whose spool position is controlled by the input current. When the opening area correction is applied to the electromagnet of the speed control main valve, the electromagnet generates a thrust proportional to the command, pushing the spool to the corresponding position, thus creating a corresponding flow area at the valve orifice. The change in the opening area of ​​the main valve spool directly alters the flow capacity of the rodless chamber to the accumulator via the speed control main valve. When the opening degree increases, the pressure relief accelerates, the pressure in the rodless chamber decreases, the equivalent support force decreases, and the boom descent speed increases; when the opening degree decreases, the pressure relief slows down, the pressure in the rodless chamber increases, the equivalent support force increases, and the boom descent speed decreases.

[0051] After the current control cycle is completed, controller 9 repeats the above steps at the beginning of the next control cycle, namely, reacquiring the rodless chamber pressure and rod chamber pressure, re-determining the equivalent support force, recalculating the deviation, re-determining the opening area correction, and readjusting the opening area of ​​the speed control main valve. This cycle continues in a fixed control cycle, causing the equivalent support force to continuously approach a constant target value in each cycle, eventually being locked within the allowable error range near the target value, thereby indirectly maintaining the boom's smooth descent at a constant speed.

[0052] It should be noted that, Figure 1 The hydraulic hardware shown is merely an exemplary application scenario and does not constitute any limitation on the scope of protection of this application. Those skilled in the art should understand that in other embodiments, the outlet of the speed control main valve can also be connected to other forms of energy recovery devices. All hydraulic systems employing the boom descent speed control method provided in this application fall within the scope of protection of this application. The control method provided in the embodiments of this application can be used in conjunction with the specific hardware architecture described above, but the method itself is not limited to... Figure 1 The specific hydraulic hardware architecture shown can also be applied to other hydraulic control systems with two-chamber pressure sensors for the boom cylinder and a speed control main valve.

[0053] Figure 2 A flowchart illustrating a boom descent speed control method according to an embodiment of this application is shown schematically. Figure 3 A schematic diagram of a boom descent speed control method according to an embodiment of this application is shown.

[0054] See Figure 2 and Figure 3 The boom descent speed control method of this embodiment includes operations S110 to S150.

[0055] During operation S110, the rodless chamber pressure and rod chamber pressure of the boom cylinder are acquired in each control cycle.

[0056] Taking the boom lowering operation of an excavator as an example, when the excavator is in normal working condition and the operator commands the boom to lower via the control handle, the controller initiates the control method of this application embodiment. For example, the method is executed sequentially within each control cycle at a fixed time interval (e.g., 10 milliseconds).

[0057] In some embodiments, at the beginning of each control cycle, the pressure P in the rodless chamber (high-pressure chamber) of the boom cylinder can be read by a pressure sensor located at the rodless chamber of the boom cylinder. u The pressure P in the rod chamber (low-pressure chamber) of the boom cylinder is read by a pressure sensor installed in the rod chamber of the boom cylinder. r .

[0058] In operation S120, the equivalent supporting force of the boom cylinder on the boom and load is determined based on the rodless chamber pressure and the rod chamber pressure.

[0059] In some embodiments, the read rodless chamber pressure P u and rod chamber pressure P r Substituting into the equivalent support force expression, calculate the equivalent support force P of the boom cylinder on the boom and load under the current state. eq This equivalent support force is not the actual pressure of a single chamber, but rather a quantitative representation of the actual upward support effect of the hydraulic cylinder after comprehensively considering the area difference between the two chambers of the differential cylinder.

[0060] In operation S130, the deviation between the actual value and the target value of the current equivalent support force is calculated.

[0061] In some embodiments, the target value may be the target equivalent pressure difference P determined during the factory calibration phase. eq,target The target value is set as a constant.

[0062] For example, the calibration method for the target value can be as follows: under typical load (such as the rated load of a standard bucket capacity), when running at the desired intermediate falling speed, record the P value at this time. eq Value; a small safety margin can be added on top of this. This is to ensure that the system does not enter the stall zone during load fluctuations. Once set, this target value is a constant and does not change with variations in operating parameters such as boom posture, load size, and accumulator pressure.

[0063] A constant target value ensures that the hydraulic cylinder maintains a sufficient and appropriate equivalent support force on the boom and material under any load and back pressure conditions. This target value prevents the boom from falling uncontrollably without affecting descent efficiency. This support force target corresponds to a stable desired speed, and the closed-loop control is fine-tuned around this target.

[0064] The deviation signal is obtained by subtracting the current equivalent support force from the constant target value. When the deviation signal is positive, it indicates that the current equivalent support force is higher than the target value, the boom is receiving excessive upward support, and the descent speed is too slow. When the deviation signal is negative, it indicates that the current equivalent support force is lower than the target value, the boom support force is insufficient, and there is a risk of accelerated descent.

[0065] In operation S140, the opening area correction amount of the speed control main valve core is determined based on the deviation, wherein the opening area correction amount is used to adjust the opening area of ​​the speed control main valve core in the current control cycle.

[0066] In some embodiments, the deviation is used as input to calculate the opening area correction of the current cycle speed control main valve core according to a preset control algorithm. This correction is an area value, which can be positive or negative. A positive value indicates that the opening needs to be increased based on the current opening area, while a negative value indicates that the opening needs to be decreased based on the current opening area.

[0067] For example, a proportional-integral-derivative (PID) controller can be used to calculate the opening area correction. The PID controller is a feedback control algorithm that can calculate the deviation between the actual value of the controlled variable and the desired target value, and apply corresponding correction actions according to the mathematical characteristics of the deviation, and finally generate the control variable (i.e. the correction).

[0068] The pressure relief level of the rodless chamber can be changed by adjusting the opening area of ​​the main valve core, thereby controlling the boom descent speed. The calculated correction is applied to the current control signal of the speed control main valve core, adjusting the opening area of ​​the speed control main valve core in the current control cycle.

[0069] For example, the correction amount can be converted into a corresponding pilot valve drive current or PWM signal and output to the pilot stage of the main valve core. This drives the valve core to produce a corresponding displacement, thereby changing the actual opening area of ​​the main valve core. The change in the opening area of ​​the main valve core directly alters the flow capacity of the rodless chamber to the accumulator through the main valve core. When the opening increases, the pressure relief accelerates, the pressure in the rodless chamber decreases, the equivalent support force decreases, and the boom descent speed increases. When the opening decreases, the pressure relief slows down, the pressure in the rodless chamber increases, the equivalent support force increases, and the boom descent speed decreases. After the correction amount is output, the current control cycle ends.

[0070] In operation S150, the actual value of the equivalent support force is reacquired and the deviation is calculated in the next control cycle until the equivalent support force approaches and remains at the constant target value.

[0071] After the current control cycle is completed, the controller waits for the start time of the next control cycle and repeats steps S110~S140 in the next control cycle. This cycle continues with a fixed control period, in which the pressure in both chambers is reacquired, the equivalent support force is recalculated, the deviation is recalculated, the correction amount is re-determined, and the opening area is readjusted. After repeated corrections over multiple cycles, the equivalent support force gradually approaches a constant target value and is maintained within the allowable error range near that target value, without significant deviations.

[0072] Since the equivalent support force is constant, the upward support resistance of the boom is constant, and the gravity of the boom and the load is approximately constant on a macroscopic scale. The difference between the two is constant, and the descent acceleration of the boom is constant, ultimately achieving a smooth descent of the boom at a constant speed.

[0073] This embodiment of the application indirectly ensures that the boom descent speed is unaffected by load changes, time-varying accumulator back pressure, and interference from coupled compound movements by locking the equivalent support force to a constant target value, thus solving the problem of inconsistent boom descent speed in the prior art. The constant target value is independent of the boom posture. Differences in gravitational torque at different positions of the boom throughout its full stroke are automatically adapted by closed-loop control. When the boom approaches horizontal, the equivalent support force tends to increase, and the controller automatically increases the opening to release pressure and cause it to fall back down; when the boom approaches vertical, the equivalent support force tends to decrease, and the controller automatically decreases the opening to build up pressure and cause it to rise again. No posture information input is required throughout the entire process; it can be completed solely by pressure sensors.

[0074] This application's embodiments start from the mechanical equilibrium equation, uniformly quantify various disturbances into deviations of equivalent support forces, and the closed-loop control directly acts on the physical root cause of the disturbances, thus exhibiting natural physical consistency in suppressing various disturbances.

[0075] According to an embodiment of this application, determining the equivalent supporting force of the boom cylinder on the boom and load based on the rodless chamber pressure and the rod chamber pressure includes: obtaining the effective working area of ​​the rodless chamber and the effective working area of ​​the rod chamber of the boom cylinder; weighting the rod chamber pressure according to the ratio of the effective working area of ​​the rod chamber to the effective working area of ​​the rodless chamber; and using the difference between the rodless chamber pressure and the converted rod chamber pressure as the controlled variable.

[0076] In some embodiments, the pressure in the rod chamber generates a downward pulling force in the cylinder, but its effective area is smaller than that in the rodless chamber. Its contribution to the net output force of the cylinder cannot be directly measured by the pressure value. Instead, it must be calculated based on the actual effective area before it can be compared and combined with the pressure in the rodless chamber under the same benchmark.

[0077] Based on the effective working area A of the rodless cavity u and the effective working area A of the rod cavity r Calculate the ratio A of the effective working area of ​​the rod-shaped cavity to the effective working area of ​​the rodless cavity. r / A u This ratio is less than 1 (because the area of ​​the rodless chamber in the differential cylinder is larger than the area of ​​the rod chamber), and is used as a fixed weighting factor. This ratio is then multiplied by the rod chamber pressure P. r The weighted rod chamber pressure value is obtained.

[0078] The rodless chamber pressure P u Subtracting the weighted rod-side pressure value from the weighted value yields the difference, which is the equivalent support force P. eq The expression is:

[0079]

[0080] Figure 4 The diagram illustrates the physical meaning of the equivalent support force and the force analysis diagram.

[0081] See Figure 4 Equivalent support force P eq This value characterizes the upward equivalent support force (converted to equivalent pressure value) exerted by the rodless chamber of the boom cylinder on the piston, affecting the boom and bucket load. It comprehensively considers the pressure difference between the two chambers of the boom cylinder and the area difference between them, representing the net upward support force (expressed in pressure units) generated by the cylinder piston on the boom and load. It is not the actual pressure of any single chamber, but rather an equivalent, comprehensive indicator representing the actual output force of the cylinder. The imbalance between the upward support force and the downward force of gravity determines the boom's descent acceleration. When the downward force of gravity is greater than the upward support force, the boom accelerates its descent; when the downward force of gravity is less than the upward support force, the boom decelerates or stops descent.

[0082] The boom cylinder is a differential cylinder, with unequal effective working areas in the rodless and rod chambers, resulting in different contributions of the pressure in each chamber to the piston output. Directly using the pressure in the rodless chamber as the control basis, or simply taking the pressure difference between the two chambers (without weighting by area ratio), will lead to misjudgment of the actual output of the cylinder.

[0083] This embodiment uses area ratio weighting to convert the rod chamber pressure to the same benchmark as the rodless chamber pressure, ensuring that the equivalent support force accurately reflects the actual net output force of the cylinder, providing an accurate physical quantity for subsequent control. The equivalent support force is expressed in pressure units (MPa or bar), and its value is on the same order of magnitude as the rodless chamber pressure. Controller parameters such as target values, deviations, and corrections can all be calibrated and tuned using this unit, eliminating the need for repeated conversions between different physical quantities (force, pressure, area). The entire determination process involves only multiplication and subtraction operations, requiring no complex iterations or table lookups, resulting in minimal computational load. This allows for rapid completion within each control cycle, meeting real-time control requirements. Furthermore, the required parameters are only two pressure sensor signals and two cylinder structural constants, simplifying sensor configuration and ensuring high system reliability.

[0084] According to one embodiment of this application, determining the opening area correction amount of the speed control main valve core based on the deviation includes: obtaining the handle opening degree of the current control cycle; generating a first area correction amount based on the handle opening degree; generating a second area correction amount based on the deviation between the actual value of the equivalent support force and the constant target value; and superimposing the first area correction amount and the second area correction amount as the opening area correction amount of the speed control main valve core for the current control cycle.

[0085] In some embodiments, the first area correction amount is a valve core opening area adjustment component corresponding to the handle opening degree, used to characterize the operator's active control command on the boom descent speed. The amount the operator pushes the handle corresponds to a basic adjustment amount of the valve core opening. This correction amount changes monotonically with the handle opening degree; when the handle opening degree increases, the correction amount increases, the valve core leakage capacity is enhanced, and the boom descent speed increases; when the handle opening degree decreases, the correction amount decreases, the valve core leakage capacity is weakened, and the boom descent speed decreases.

[0086] The second area correction refers to the additional adjustment required to correct the deviation when the current equivalent support force deviates from the target value (i.e., the actual boom descent speed is inconsistent with the expected speed). This adjustment reflects the objective compensation requirement for disturbances. The first area correction determines the basic level of the valve core opening; that is, the valve core roughly opens to where the handle is pushed. The second area correction makes further adjustments based on this basic level to ensure that external disturbances do not disrupt speed stability.

[0087] According to one embodiment of this application, generating a first area correction amount based on the handle opening includes: obtaining a preset mapping function, the mapping function being the correspondence between the handle opening and the normalized area coefficient; substituting the handle opening of the current control cycle into the mapping function to obtain the corresponding normalized area coefficient; and multiplying the normalized area coefficient by the maximum opening area of ​​the speed control main valve core to obtain the first area correction amount.

[0088] In some embodiments, the current handle opening can be adjusted. Substitute into the mapping function Determine the corresponding normalized area coefficient. And based on the normalized area coefficient and the maximum opening area A of the main valve core. max Determine the first area correction amount A base (k):

[0089]

[0090] Wherein, mapping function A max The unit is mm 2 k is the sequence number of the current control cycle.

[0091] Figure 5 A schematic diagram illustrating the comparison of the handle opening degree-valve core area mapping function is shown.

[0092] See Figure 5 The mapping function can be determined by any one of three methods: linear mapping, piecewise linear mapping, and exponential mapping.

[0093] Taking linear mapping as an example, the mapping function This method is suitable for routine operations.

[0094] Taking a piecewise polyline as an example, this method is suitable for both fine-grained and rapid tasks. In this method, the mapping function consists of multiple linear segments connected together, and the slope and threshold of each segment's inflection point can be calibrated. A typical configuration is a three-segment structure (micro-motion segment, linear segment, and rapid segment). For example, the micro-motion segment is... This segment has a low slope K1, used to improve micro-manipulation precision. The linear segment is... This section has a medium slope of K2 and is used for routine adjustments. The fast section is... This segment has a high slope K3, which meets the requirements for fast response under heavy load. The slope and threshold of each segment's inflection point are specified. Each can be calibrated independently. It should be noted that the low slope, medium slope and high slope in this embodiment are relative to each linear segment, that is, K1 < K2 < K3.

[0095] Taking exponential mapping as an example, this method is suitable for scenarios where operational smoothness is desired. Mapping function Among them, the aperture resolution is higher when 0 < c < 1, and the aperture region control is more refined when c > 1. The typical value c ∈ [0.7, 1.5].

[0096] In some embodiments, the actual value P of the equivalent support force in the current control cycle is... eq With the target value P eq,target Using the deviation as input, the second area correction A is calculated based on a preset control algorithm. adj The second area correction is an additional area adjustment amount used to compensate for the effects of external disturbances and bring the equivalent support force back to the target value. It can be positive or negative. When the deviation is positive (i.e., the equivalent support force is higher than the target value and the decline is slower), the second area correction is positive, indicating that the opening area needs to be further increased to release pressure and reduce the equivalent support force. When the deviation is negative (i.e., the equivalent support force is lower than the target value and the decline is faster), the second area correction is negative, indicating that the opening area needs to be reduced to establish back pressure and increase the equivalent support force.

[0097] The first area correction A base With the second area correction A adj The values ​​are superimposed to generate the opening area correction A of the speed control main valve core in the current control cycle. The lower limit of this opening area correction is 0, and the upper limit is the maximum opening area A of the speed control main valve core. max .

[0098] In this embodiment, the opening area correction is determined by a first area correction and a second area correction. The first area correction is determined by the handle opening degree, representing the operator's macroscopic control intention and constituting the main body of the valve core opening area. The second area correction is determined by the closed-loop deviation, representing the compensation requirement for external disturbances and correcting the main body area. When the two are combined, the total opening area correction changes monotonically with the operator's handle opening degree and automatically adjusts with the equivalent support force deviation, achieving coordination between control commands and disturbance rejection compensation. During this process, the operator's actions are fully preserved, eliminating the nonlinearity of a mismatch between the handle position and the descent speed.

[0099] Simultaneously, the second area correction, driven by the closed-loop deviation, can automatically generate reverse compensation when the equivalent support force deviates from the target value. This allows the total opening area correction to be fine-tuned at the operator's desired level, achieving adaptive suppression against disturbances. In this process, the two area corrections have clear divisions of labor and do not interfere with each other: the first area correction only responds to the handle opening, and the second area correction only responds to the equivalent support force deviation. Both are independently sourced and calculated, and only act together on the valve core after being superimposed. This effectively avoids the potential interference problems that may occur when control commands and disturbance compensation are coupled into the same algorithm.

[0100] According to one embodiment of this application, generating a second area correction amount based on the deviation between the actual value and the target value of the equivalent support force further includes: determining a positive maximum adjustable area limit value and a negative maximum adjustable area limit value based on the first area correction amount; when the second area correction amount is positive, limiting the second area correction amount to an upper limit using the positive maximum adjustable area limit value; when the second area correction amount is negative, limiting the absolute value of the second area correction amount to an upper limit using the negative maximum adjustable area limit value.

[0101] In some embodiments, the positive maximum adjustable area limit value and the reverse maximum adjustable area limit value can be determined based on the first area correction value before determining the second area correction value. For example, after determining the first area correction value based on the handle opening and the mapping function, the first area correction value and a preset calibrable coefficient (…) can be used to determine the second area correction value. , Calculate the maximum adjustable area limit value in the positive direction respectively. and reverse maximum adjustable area limit value .

[0102] The maximum adjustable area in the positive direction is used to increase the opening degree, and its expression is:

[0103]

[0104] The reverse maximum adjustable area is used to reduce the opening, and its expression is:

[0105]

[0106] in, This characterizes the proportion of the base area that allows the PID to increase its opening beyond the base area, given the current handle opening. This characterizes the proportion of the base area that the system allows the PID to reduce by an additional amount of opening below the base area, given the current handle opening.

[0107] The initial second area correction amount u(k) is calculated based on the deviation between the equivalent support force and the target value in the current control cycle. This correction amount is not limited and is the expected value directly calculated by the controller based on the deviation. Its value may exceed the reasonable range allowed by the project.

[0108] When the initial second area correction is positive, it indicates a desire to increase the opening based on the current opening area. In this case, the initial second area correction u(k) can be compared with the positive maximum adjustable area limit value. The two values ​​are compared, and the smaller value is taken as the second area correction A. adj (k) to ensure that the opening increment does not exceed the lower limit.

[0109] When the initial second area correction is negative, it indicates a desire to increase the opening based on the current opening area. In this case, the initial second area correction u(k) can be compared with the reverse maximum adjustable area limit value. The larger of the two values ​​is taken as the second area correction A. adj (k) to ensure that the reduction in valve opening does not exceed the lower limit and to avoid excessive valve closure.

[0110] For example, the second area correction A adj The expression for (k) can be:

[0111]

[0112] In some embodiments, the second area correction A after limiting is... adj (k) and the first area correction A base By superimposing these values, we obtain the opening area correction A(k). The expression for the opening area correction A(k) is:

[0113]

[0114] Where A(k) is the correction amount for the total opening area of ​​the main valve core in the current cycle. This area value can be converted into pilot valve control current or PWM signal through the calibrated valve core flow-area characteristic curve and output to the pilot stage of the main valve core.

[0115] Because of A base (k) , All three are proportional to f map (α(k)), therefore, the total opening area A(k) naturally maintains a monotonically positive correlation with the handle opening, that is, the larger the handle opening, the larger the base area, and the larger the absolute value of the adjustable range. The overall level of the total opening area rises or falls synchronously with the handle opening.

[0116] By limiting the amplitude, the operator's control intention (expressed through the handle opening) always takes precedence under any operating condition, while closed-loop regulation only makes fine-tuning within its allowable range. This retains the intuitiveness of traditional handle operation while achieving adaptive suppression of disturbances. Without amplitude, the PID controller may over-adjust during micro-movements, compromising the control feel; if the constant target value does not match the dynamic amplitude limit, opening saturation or under-adjustment may occur.

[0117] According to one embodiment of this application, a second area correction amount is generated based on the deviation between the actual value and the target value of the equivalent support force, including: determining a first gain coefficient, a second gain coefficient, and a third gain coefficient based on the handle opening degree of the current control cycle; multiplying the deviation by the first gain coefficient to obtain a first component for responding to the current deviation; accumulating the deviation cycle by cycle and multiplying it by the second gain coefficient to obtain a second component for eliminating the accumulated deviation; multiplying the change in deviation relative to the previous cycle by the third gain coefficient to obtain a third component for responding to the trend of deviation change; and superimposing the first component, the second component, and the third component as the second area correction amount.

[0118] In some embodiments, the initial second area correction u(k) (i.e., the unlimited second area correction) can be calculated using a PID control algorithm. The expression for the initial second area correction u(k) can be:

[0119]

[0120] Among them, T s To control the cycle, K p K is the first integral gain coefficient (i.e., the proportional gain coefficient). i K is the second gain coefficient (i.e., the integral gain coefficient). d This is the third gain coefficient (i.e., the differential gain coefficient).

[0121] Multiply the deviation of the current control cycle by the first gain coefficient to obtain the first component. The sign of the first component is consistent with the deviation, and its magnitude changes linearly with the magnitude of the absolute value of the current deviation, which can realize an instantaneous response for correction based on the change of deviation.

[0122] The deviations of each control cycle are accumulated cycle by cycle to obtain the accumulated deviation value. Multiply it by the second gain coefficient K i The second component of the current control cycle is obtained. T s To control the cycle.

[0123] The second component also varies with the direction of the deviation; a long-term positive deviation produces a positive correction, and a long-term negative deviation produces a negative correction. Even if the deviation in the current control cycle is very small or even zero, as long as the accumulated deviation value from the previous period has not been completely offset, the second component still exists and continues to apply correction. Therefore, the second component can eliminate steady-state errors in the system caused by factors such as friction and leakage that are difficult to completely eliminate by the first component. In practical implementation, to prevent the accumulated value from becoming too large and causing system saturation, anti-integral saturation logic can be set, stopping the accumulation when the accumulated value reaches preset upper and lower limits.

[0124] Calculate the difference between the deviation e(k) of the current control cycle and the deviation e(k-1) of the previous control cycle. This value represents the change in deviation relative to the previous period, and is multiplied by the third gain coefficient K. d Then divide by the control period T s The third component is obtained. .

[0125] The direction of the third component depends on the trend of the deviation. When the deviation is increasing (e.g., the equivalent support force is accelerating its deviation from the target), the third component strengthens the deviation in either the positive or negative direction, applying an additional "push" to the correction and accelerating the correction process. When the deviation is decreasing (e.g., the equivalent support force is returning to the target value), the third component acts in the opposite direction, preventing over-correction from causing oscillations. The third component is used to predict the trend of deviation changes and to apply a correction at the beginning of the trend formation.

[0126] This application's embodiments address different control problems through three components, each responsible for a specific aspect. The first component responds to the instantaneous magnitude of the current deviation, providing rapid, immediate correction, enabling the controller to react quickly to sudden disturbances. The second component eliminates long-term accumulated residual deviations, ensuring the system ultimately achieves zero steady-state error control, meaning the equivalent support force converges precisely to a constant target value without leaving any fixed deviation. The third component responds to the trend of deviation changes, applying correction before the deviation becomes too large, while simultaneously providing damping to the control process, preventing over-correction that could lead to oscillations. The combination of these three components enables the system to simultaneously possess rapid response capability, high steady-state accuracy, and good dynamic stability.

[0127] The first gain coefficient, second gain coefficient, and third gain coefficient in this embodiment can adaptively change with the current handle opening. Under the condition of small handle opening and micro-motion, the controller is conservative and robust to prevent oscillation and impact and ensure micro-control accuracy; under the condition of large handle opening and heavy load, the controller is aggressive and powerful to provide sufficient adjustment force to overcome large-range disturbances and ensure speed stability under heavy load.

[0128] According to one embodiment of this application, the deviation is accumulated periodically and then multiplied by a second gain coefficient to obtain a second component for eliminating the accumulated deviation. This includes: calculating the accumulated value of the deviation in each control cycle, and setting an upper limit and a lower limit of the accumulated value based on the limit value of the second area correction amount in the current cycle; stopping further accumulation of the accumulated value when the accumulated value reaches the upper limit and the actual value of the deviation indication equivalent support force in the current cycle is higher than the constant target value; and stopping further accumulation of the accumulated value when the accumulated value reaches the lower limit and the actual value of the deviation indication equivalent support force in the current cycle is lower than the constant target value.

[0129] In some embodiments, in each control cycle, an anti-integral saturation process can be used to determine whether to accumulate the current deviation. Taking the k-th control cycle as an example, the deviation e(k) of the effective support force in the current control cycle is calculated, and the accumulated deviation value up to the previous median cycle is read. The accumulated deviation value is the result of accumulating the deviations periodically, and is used to generate the integral component (i.e. the second component) in the second area correction.

[0130] Obtain the positive maximum adjustable area limit value for the current control cycle. and reverse maximum adjustable area limit value .

[0131] Based on the maximum adjustable area limit, the current deviation e(k), the previous cycle deviation e(k-1), and the proportional gain coefficient K p and differential gain coefficient K d， The upper limit I for calculating the cumulative integral value max (k). Upper limit value I max (k) represents the maximum value allowed for the integral term in the current control cycle, after the proportional and derivative terms have contributed a portion of the correction. The remaining space after subtracting these two terms from the positive limit value is the maximum value allowed for the integral term in the current cycle. Its expression is:

[0132]

[0133] The cumulative integral value cannot exceed this upper limit; otherwise, the total PID output will exceed the positive limit.

[0134] Based on the maximum adjustable area limit value in the reverse direction Current deviation e(k), previous cycle deviation e(k-1), proportional gain coefficient K p and differential gain coefficient K d Calculate the lower limit I of the accumulated integral. min (k). Lower limit value I min (k) is used to characterize the minimum (negative) value allowed for the integral term in the current period after deducting the proportional and differential terms from the reverse limit value. Its expression is:

[0135]

[0136] The cumulative integral value cannot be lower than this lower limit; otherwise, the total PID output will exceed the reverse limit value.

[0137] When accumulating, the system determines whether to accumulate based on the current state of the accumulated integral value.

[0138] When the accumulated value has reached the upper limit, and the current deviation indicates that the correction amount needs to be increased, the deviation e(k) of the current control cycle is > 0 (the equivalent support force is higher than the target value, and the opening needs to be increased to reduce the equivalent support force), while the accumulated value has reached the upper limit I. max (k). If the current positive deviation continues to be added, the integral accumulation value will exceed the upper limit, causing the final calculated correction to exceed the positive limit. The excess portion will be truncated by the limit and cannot be actually output. However, the excess portion in the accumulation value does not disappear and will cause excessive reverse correction when the deviation reverses. Therefore, in this case, the current deviation is not added to the accumulator, and the accumulation value remains unchanged. That is:

[0139] like If e(k) > 0, then it is not accumulated.

[0140] When the accumulated value has reached the lower limit, and the current deviation indicates that the correction amount needs to be further reduced, the deviation e(k) of the current control cycle is < 0 (the equivalent support force is lower than the target value, and the opening needs to be reduced to increase the equivalent support force), while the accumulated value has reached the lower limit I. min (k). If the current negative deviation continues to be accumulated, the integral accumulation value will fall below the lower limit, causing the final calculated correction to exceed the reverse limit value. Therefore, in this case, the controller does not accumulate the current deviation into the accumulator, and the accumulation value remains unchanged. That is:

[0141] like If e(k) < 0, then it is not accumulated.

[0142] If the accumulated value has not reached the upper or lower limit, the deviation e(k) of the current control cycle continues to be accumulated, and the accumulated value is updated.

[0143] This application's embodiment uses anti-integral saturation processing to preemptively identify and prevent unnecessary accumulation during the accumulation process, eliminating the need to wait until the correction is calculated and limited before passive processing. This avoids the problem of the integral term continuously accumulating and growing larger in the limiting storage device. By stopping accumulation early, anti-integral saturation processing prevents overshoot during reverse operation after the correction is ineffectively truncated. By using anti-integral saturation and dynamic limiting to impose dual constraints on the correction at both the accumulation and output ends, it prevents excessive accumulation of the integral term during the limiting period and prevents the final output from exceeding the safety boundary, ensuring that the output always remains within a reasonable range and avoiding system oscillation and overshoot caused by integral saturation.

[0144] According to one embodiment of this application, the first gain coefficient, the second gain coefficient, and the third gain coefficient are determined based on the handle opening degree of the current control cycle, including: determining the opening degree interval to which the current handle opening degree belongs based on a preset correspondence between the handle opening degree interval and the gain coefficient, and obtaining the first gain coefficient, the second gain coefficient, and the third gain coefficient corresponding to the opening degree interval; wherein, the range of change of the handle opening degree is divided into multiple consecutive opening degree intervals, and different opening degree intervals correspond to different combinations of gain coefficients.

[0145] In some embodiments, the range of change of the handle opening can be pre-divided into multiple consecutive opening intervals, with each interval separated by a preset threshold.

[0146] Taking a typical three-segment division as an example, the first threshold α1 separates the micro-motion range from the normal operation range, and the second threshold α2 separates the normal operation range from the heavy-load operation range. The handle opening range [0,1] can be divided into a first opening range, a second opening range, and a third opening range. Among them, the first opening range [0,α1) corresponds to the micro-motion condition, the second opening range [α1, α2) corresponds to the normal operation condition, and the third opening range [α2, 1] corresponds to the heavy-load rapid descent condition. Each threshold and the number of ranges are calibrable parameters, set at the factory according to the specific machine model's operating characteristics.

[0147] The handle opening α read in the current control cycle is compared sequentially with each threshold to determine the opening interval to which the current handle opening belongs, and the corresponding gain coefficient combination is obtained according to the interval. For example, the first gain coefficient K corresponding to the current interval can be read from a preset gain coefficient mapping table. p Second gain coefficient K i Third gain coefficient K d Different opening intervals correspond to different combinations of gain coefficients, and the three gain coefficients within the same interval are fixed values.

[0148] Figure 6The diagram illustrates the change in gain coefficient with handle opening degree in an embodiment of this application.

[0149] See Figure 6 Continuing with the three-segment division as an example, the principles for setting the gain coefficient of each interval are as follows:

[0150] The first opening interval (i.e., the micro-motion interval, α < α1) corresponds to the small opening micro-motion condition of the handle. At this time, the valve core opening is small, the flow gain is low, and the system is more sensitive to parameter changes. Therefore, within this interval, the first gain coefficient K... p Choose a smaller value to prevent valve core oscillation due to excessive gain; the second gain coefficient K i Choose a larger value to ensure that steady-state error can be eliminated and speed can be accurately followed during micro-motion control; the third gain coefficient K d An appropriate value is selected to suppress jitter caused by high-frequency pressure pulsations. The design of this range controller is conservative and robust, with the core objective being smooth micro-motion.

[0151] The second opening range (normal operating range, α1 ≤ α < α2) corresponds to the most common normal operating conditions, i.e., the valve core opening is moderate and the system operates in a region with good linearity. Therefore, within this range, all three gain coefficients are taken as the nominal optimal values ​​obtained through factory step response tests, balancing response speed and stability. The design orientation of the controller in this range is balanced, with the core objective of obtaining the most versatile control performance across the entire operating range.

[0152] The third opening range (heavy-load operation range, α≥α2). This range corresponds to the heavy-load rapid descent condition with the handle at a large opening. At this point, the effects of load disturbances and accumulator back pressure changes are most severe, requiring stronger adjustment capabilities. Therefore, within this range, the first gain coefficient K... p Choose a larger value to quickly suppress large-range deviations; the second gain coefficient K i Choose an appropriate value to avoid overshoot caused by excessively rapid integral saturation; the third gain coefficient K d A smaller value is chosen to prevent high-frequency noise amplification from causing valve core chatter. This range controller is designed with an aggressive and forceful approach, with the core objective of ensuring sufficient regulation power to overcome large-scale disturbances even under heavy loads.

[0153] For example, linear interpolation or piecewise constant mapping can be used to determine each gain coefficient. The first gain coefficient K... p The expression is:

[0154]

[0155] Second gain coefficient K i The expression is:

[0156]

[0157] Third gain coefficient k d The expression is:

[0158]

[0159] In practical implementation, if the number of opening intervals exceeds three segments, the setting of each threshold and the value of the gain coefficient for each interval are extended according to the above principle: small opening intervals are more robust, large opening intervals are more powerful, and the intermediate intervals are a gradual transition. Each segment threshold and its corresponding gain value must be tuned before leaving the factory according to the specific model through a step response test, ensuring optimal dynamic response and steady-state accuracy for each opening interval while maintaining system stability. This tuning can be assisted by an automatic parameter optimization algorithm.

[0160] The following uses specific numerical examples to illustrate the process of segment determination.

[0161] Assume the first threshold α1 = 0.2 and the second threshold α2 = 0.7. If the currently read handle opening α = 0.15, which is less than the first threshold 0.2, the controller determines that it is currently in the first opening interval and reads the corresponding gain coefficient combination for that interval, for example, K. p =0.5, K i =0.8, K d =0.3, used for calculating the correction amount for the current cycle.

[0162] If the current handle opening α = 0.5, which is between 0.2 and 0.7, the controller determines that it is currently in the second opening interval and reads the corresponding gain coefficient combination for that interval, such as K. p =1.0, K i =0.5, K d =0.2.

[0163] If the current handle opening α = 0.85, which is greater than the second threshold of 0.7, the controller determines that it is currently in the third opening interval and reads the corresponding gain coefficient combination for that interval, such as K. p =2.0, K i =0.3, K d =0.1. The above values ​​are only examples to illustrate the segmentation determination process. In actual applications, each parameter should be adjusted experimentally according to the specific model.

[0164] The handle opening directly reflects the operator's judgment of the current working condition and speed requirements. This embodiment automatically determines the gain coefficient based on the handle opening, enabling the controller's response characteristics to automatically match and adjust to the current working condition, improving the accuracy and flexibility of the response characteristics. By setting different gain combinations in segments, each opening interval can obtain specially adapted control parameters, effectively expanding the controller's working condition adaptability range. The implementation method of dividing intervals by thresholds and using a fixed gain coefficient for each interval has low computational load, clear logic, and requires no complex online parameter identification or adaptive algorithms. It can be directly deployed on existing excavator controller hardware, possessing high engineering practical value.

[0165] Figure 7 A schematic diagram illustrating load drop detection and emergency protection according to an embodiment of this application is shown.

[0166] See Figure 7 According to an embodiment of this application, the method further includes: in each control cycle, obtaining the rodless chamber pressure of the boom cylinder in the current control cycle, and calculating the difference between the rodless chamber pressure in the current control cycle and the rodless chamber pressure in the previous control cycle; comparing the difference with a preset descent rate threshold, and when the difference is less than the descent rate threshold, determining it as a sudden unloading condition and performing an emergency protection operation.

[0167] In some embodiments, the rodless chamber pressure P of the boom cylinder in the current control cycle is obtained. u (k) Simultaneously, the rodless chamber pressure P stored in the previous control cycle is retrieved from the memory. u (k-1).

[0168] Calculate the difference between the rodless chamber pressure in the current control cycle and the rodless chamber pressure in the previous control cycle. ,in, This difference is used to represent the change in rodless chamber pressure over a control cycle interval.

[0169] Rate of change of difference Compared with the preset decline rate threshold -Th load If a comparison is made, Less than the rate of decline threshold -Th load (Right now If the boom experiences a sudden unloading condition, then it is determined that a sudden unloading operation has occurred. The descent rate threshold -Th load The unit is consistent with the pressure difference (MPa), representing the maximum allowable decrease in rodless chamber pressure within one control cycle. A typical value can be Th. load =2MPa / s. The drop rate threshold can be calibrated according to the specific model. For example, the drop rate threshold can be reduced as much as possible while ensuring that it is not triggered falsely under normal operating conditions, so that sudden unloading can be identified as early as possible.

[0170] For example, in the specific implementation process, in order to eliminate false triggering that may be caused by single-point noise, the difference between multiple consecutive control cycles can be averaged or a first-order low-pass filter can be used to ensure the reliability of the detection results and avoid frequent false triggering caused by sensor noise or electromagnetic interference.

[0171] During normal descent, the pressure in the rodless chamber fluctuates slowly with load changes, and the pressure difference between two adjacent control cycles is usually small (e.g., -0.2MPa to -0.5MPa), with its rate of change not triggering the descent rate threshold. When material suddenly falls or is unloaded from the bucket, the total weight of the boom and load decreases sharply. Under the original equivalent support force, the boom suddenly loses balance, resulting in an accelerated descent. This trend is initially manifested as a sharp drop in the pressure in the rodless chamber due to the sudden decrease in pressure relief demand. Therefore, by monitoring the sharp drop in the pressure in the rodless chamber, sudden unloading conditions can be quickly identified, and an early warning can be issued before the speed changes significantly.

[0172] Upon detecting a sudden unloading, the emergency protection operation is immediately triggered to prevent the boom from accelerating uncontrollably or causing impact after the sudden unloading. The pressure difference is continuously monitored until the working conditions are confirmed to have returned to normal, at which point the protection status is released.

[0173] This application directly utilizes the pressure change rate of the rodless chamber as the detection basis, eliminating the need to wait for the speed sensor to detect the speed change before responding. The pressure change occurs before the speed change, thus enabling detection and protective measures to be implemented before the boom experiences significant acceleration, preventing runaway acceleration at its source. This effectively improves the speed of identifying sudden operating conditions and achieves rapid response. This application utilizes only existing pressure sensor signals, achieving detection through differential calculation of pressure values ​​from adjacent control cycles, without requiring additional sensors or hardware, resulting in low system complexity and high reliability.

[0174] According to one embodiment of this application, the emergency protection operation includes: replacing the original first gain coefficient with a first gain coefficient multiplied by a preset attenuation coefficient, and using this multiplier to generate the correction amount for the current control cycle; pausing the accumulation of the deviation of the current control cycle into the accumulated deviation value, and determining the correction amount for the current control cycle based on the accumulated deviation value before the pause; resuming the normal control process after the correction amount for the current control cycle is generated; continuously calculating the difference in pressure of the rodless chamber in subsequent control cycles, and deactivating the emergency protection state when the number of times the difference is continuously less than the drop rate threshold reaches a preset number, and gradually restoring the accumulated deviation value to the normal accumulation state at a preset recovery rate.

[0175] In some embodiments, at the trigger moment of the current control cycle, based on the pressure difference in the rodless chamber, it is determined that the current condition is a sudden unloading operation, and an emergency protection operation is executed. At this time, the opening area correction amount for the current control cycle has not yet been calculated, and the correction amount for the current control cycle can be generated in the following manner.

[0176] The first gain coefficient K of the current control cycle p Multiply by the preset attenuation coefficient The temporary first gain coefficient K is obtained. p_temp Using this temporary coefficient K p_temp Replace the original first gain coefficient K p Generate the correction amount for the current control cycle.

[0177] Among them, attenuation coefficient It is a positive number less than 1, and its specific value can be set according to the model. This attenuation coefficient is used to reduce the impact of deviation on the correction amount while ensuring system stability.

[0178] Because the equivalent support force decreases sharply during sudden unloading and the deviation instantly becomes a large negative value, if the original first gain coefficient K is still used... p If the correction amount is involved in generation, the absolute value of the generated negative correction amount will be too large (i.e., the valve core will be significantly closed), causing the boom to be subjected to severe impact or even stop. K p By multiplying by the attenuation coefficient to temporarily reduce the proportional gain, the controller is prevented from responding too aggressively to the current large deviation, thus preventing the valve core from being closed too drastically in an instant.

[0179] Furthermore, during emergency protection operations, the second gain coefficient K is frozen. i That is, stop accumulating points and freeze the points for a period of time T. freeze This is to prevent the integral term from overshooting during sudden load changes.

[0180] It should be noted that the second gain coefficient K in the current control cycle i and the third gain coefficient K d Keeping it unchanged, only the first gain coefficient K p The reason for the attenuation is that during a sudden unloading, the main risk is that the drastic change in the deviation will cause the proportional response to be excessive. Maintaining the derivative term helps to suppress the sudden change trend, and keeping the cumulative value of the integral term unchanged can avoid the impact of integral saturation. Therefore, there is no need to treat these three coefficients in the same way.

[0181] In some embodiments, during the current control cycle when a sudden unloading occurs, the equivalent support force will generate a large negative deviation due to the sharp drop in pressure. If this deviation is added to the accumulated deviation value, the accumulated value will decrease dramatically or even change sign instantly, causing a drastic jump in the correction amount. To avoid this, the addition of the deviation of the current control cycle to the accumulated deviation value is paused, and the accumulated deviation value before the pause is used to participate in the determination of the correction amount for the current control cycle. This keeps the accumulated deviation value unchanged at the level before the sudden unloading, preventing the second component of the correction amount (driven by the accumulated deviation) from jumping instantaneously due to the sudden unloading, thereby maintaining the relative smoothness of the correction amount.

[0182] Based on the attenuated first gain coefficient K p_temp The second gain coefficient K remains unchanged after pausing accumulation. i and the third gain coefficient K d Together, they generate a second area correction value for the current control cycle. This second area correction value is then superimposed on the first area correction value and output to the main valve core to drive the valve core to move.

[0183] In subsequent control cycles, the controller continuously calculates the pressure difference ΔP in the rodless chamber at the beginning of each control cycle. u and the decline rate threshold -Th load Compare. When ΔP u consecutively less than -Th load If the number of attempts has not yet reached the preset number, continue to maintain the emergency protection status.

[0184] After a sudden unloading occurs, the difference is continuously monitored. When the number of consecutive values ​​less than the threshold reaches a preset number (e.g., 5 consecutive cycles), it is determined that the sudden unloading condition has ended, the boom has returned to a stable descent state, and the emergency protection state is released.

[0185] After the emergency protection state is lifted, the deviation values ​​that were not accumulated during the freeze period will be restored at a preset recovery rate. The accumulated deviation is added back gradually to avoid sudden spikes in the correction amount and secondary shocks caused by a one-time addition. The recovery rate can be determined through calibration, for example, by restoring 10% of the total deviation during the freeze period each control cycle or by a fixed step size, until the entire deviation is recovered.

[0186] During sudden unloading, the deviation increases sharply, easily leading to overcorrection. This embodiment of the application temporarily reduces the proportional response strength by multiplying the first gain coefficient by the attenuation coefficient, ensuring the correction remains within a reasonable range under sudden operating conditions and preventing severe boom impact or stoppage due to excessive valve closure. Pausing deviation accumulation keeps the accumulated deviation value at the level before sudden unloading, preventing the huge negative deviation generated by sudden unloading from instantly changing the sign or value of the accumulated value, thereby preventing jumps in the correction due to abrupt changes in the integral term.

[0187] After the freeze period expires, the accumulated deviation value is gradually restored at a preset rate, rather than being added all at once. This avoids sudden changes in the correction amount caused by a sudden increase in the accumulated deviation value and ensures the smoothness of the emergency protection exit process.

[0188] During emergency protection operations, only the first gain coefficient and deviation accumulation behavior are temporarily modified without changing the way the correction is generated. After the emergency ends, normal closed-loop control can be automatically restored without mode switching or parameter reloading, thus avoiding control interruption when protection exits.

[0189] The boom descent speed control method provided in this application maintains a constant target value for the equivalent support force of the hydraulic cylinder on the boom and bucket under any load, any accumulator back pressure, and any boom posture. This constant support force corresponds to the desired descent speed. By locking the equivalent support force to a constant target through closed-loop control, constant-speed descent can be indirectly achieved.

[0190] In existing technologies, boom speed control typically uses speed or position as the directly controlled variable. However, this application uses equivalent support force as the core of speed control, which departs from the conventional speed measurement-control approach and instead uses force balance as the control core. Under macroscopic working conditions (the boom's own weight is much greater than the load fluctuation), the gravitational active force can be considered constant. The actual acceleration of the boom is determined by the difference between the active force and the equivalent support resistance.

[0191] When the equivalent support force is higher than the target value, it indicates that the current support resistance is too high, meaning the driving force is insufficient to overcome the resistance, resulting in a slower boom descent speed. In this case, the controller needs to increase the main valve opening to release the pressure in the rodless chamber, reducing the support resistance to the target value, and the speed will return to normal. When the equivalent support force is lower than the target value, it indicates that the current support resistance is too low, meaning the driving force is much greater than the resistance, and the boom is at risk of uncontrolled acceleration during descent. In this case, the controller needs to decrease the main valve opening to establish back pressure, increasing the support resistance to the target value to suppress acceleration.

[0192] The time-varying accumulator back pressure, as provided in this application embodiment, can also be automatically compensated for through this closed-loop mechanism. The interference of the accumulator back pressure's time-varying speed is uniformly incorporated into the feedback regulation of the equivalent support force within the closed-loop framework. As the accumulator pressure gradually increases with the increase in oil filling volume, the back pressure on the main valve core outlet side increases, leading to an increase in the equivalent support force and creating additional resistance that causes the boom descent speed to continuously slow down. At this point, after the controller detects that the equivalent support force is higher than the target value, it increases the main valve core opening, reduces the rodless chamber pressure, and causes the equivalent support force to fall back to the target value, restoring the desired speed.

[0193] Conversely, when the accumulator pressure drops due to unloading or cessation of oil filling, the back pressure decreases, the equivalent support force decreases, and the support force is insufficient, causing the boom to tend to accelerate. At this time, the controller detects that the equivalent support force is lower than the target value, reduces the opening of the main valve core, establishes sufficient back pressure, and raises the equivalent support force to the target value, thereby suppressing acceleration.

[0194] The control objective of this application embodiment is to maintain the equivalent support force at a constant and reasonable value that provides sufficient support to prevent stalling without excessively inhibiting descent, thereby indirectly achieving a smooth and constant descent speed.

[0195] The embodiments of this application employ a constant target equivalent pressure difference, and closed-loop control automatically adapts to changes in gravitational torque throughout the entire stroke range of the boom. No attitude information is required, which can effectively reduce system complexity and hardware costs.

[0196] Load disturbances, time-varying accumulator back pressure, and coupled disturbances from combined actions all ultimately manifest as fluctuations in the equivalent support force. Load changes alter the gravitational torque, accumulator back pressure changes the valve operating point, and combined actions change the oil supply pressure. This embodiment achieves synchronous suppression of all the aforementioned disturbances through a closed-loop equivalent support force mechanism, realizing a unified adaptive suppression capability for different disturbances. It eliminates the need to design independent observers or feedforward compensators for each disturbance, resulting in a simple and efficient control architecture.

[0197] Dynamic limiting allows the closed-loop adjustment force to scale proportionally with the handle opening, providing delicate adjustment at fine movements and powerful adjustment at large openings. Segmented PID parameter tuning makes the controller more robust in the small opening range and more forceful in the large opening range. These two aspects work together to retain the intuitiveness of traditional handle operation while achieving high-precision speed stability across all operating conditions. Furthermore, by detecting the rate of pressure drop in the rodless chamber to identify sudden unloading, and by immediately attenuating the proportional gain and freezing the integral term, uncontrolled boom acceleration or impact can be effectively prevented, ensuring operational safety.

[0198] Figure 8 A schematic block diagram of a boom descent speed control device according to an embodiment of this application is shown.

[0199] like Figure 8As shown, the boom descent speed control device 800 of this embodiment includes an acquisition module 810, a first calculation module 820, a second calculation module 830, and a determination module 840.

[0200] The acquisition module 810 is used to acquire the rodless chamber pressure and the rod chamber pressure of the boom cylinder in each control cycle. In one embodiment, the acquisition module 810 can be used to perform the operation S110 described above, which will not be repeated here.

[0201] The first calculation module 820 is used to determine the equivalent supporting force characterizing the boom cylinder on the boom and load based on the rodless chamber pressure and the rod chamber pressure. In one embodiment, the first calculation module 820 can be used to perform the operation S120 described above, which will not be repeated here.

[0202] The second calculation module 830 is used to calculate the deviation between the actual value and the target value of the current equivalent support force. In one embodiment, the second calculation module 830 can be used to perform the operation S130 described above, which will not be repeated here.

[0203] The determining module 840 is used to determine the opening area correction amount of the speed control main valve core based on the deviation, wherein the opening area correction amount is used to adjust the opening area of ​​the speed control main valve core in the current control cycle. In one embodiment, the determining module 840 can be used to perform the operation S140 described above, which will not be repeated here.

[0204] In some embodiments, the equivalent support force is re-acquired and the deviation is calculated in the next control cycle until the equivalent support force approaches and remains at the target value.

[0205] According to embodiments of this application, any multiple modules among the acquisition module 810, the first calculation module 820, the second calculation module 830, and the determination module 840 can be combined into one module, or any one of these modules can be split into multiple modules. Alternatively, at least some of the functions of one or more of these modules can be combined with at least some of the functions of other modules and implemented in one module. According to embodiments of this application, at least one of the acquisition module 810, the first calculation module 820, the second calculation module 830, and the determination module 840 can be at least partially implemented as hardware circuitry, such as a field-programmable gate array (FPGA), a programmable logic array (PLA), a system-on-a-chip, a system-on-a-substrate, a system-on-package, an application-specific integrated circuit (ASIC), or implemented in hardware or firmware by any other reasonable means of integrating or packaging the circuitry, or implemented in any one of the three implementation methods of software, hardware, and firmware, or in a suitable combination of any of these. Alternatively, at least one of the acquisition module 810, the first calculation module 820, the second calculation module 830, and the determination module 840 may be implemented at least partially as a computer program module, which can perform corresponding functions when the computer program module is run.

[0206] The embodiments of this application have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of this application. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this application is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this application, and all such substitutions and modifications should fall within the scope of this application.

Claims

1. A method for controlling the descent speed of a boom, characterized in that, include: Within each control cycle, the rodless chamber pressure and rod chamber pressure of the boom cylinder are obtained; The equivalent supporting force of the boom cylinder on the boom and load is determined based on the rodless chamber pressure and the rod chamber pressure. Calculate the deviation between the actual value and the target value of the current equivalent support force; The opening area correction amount of the speed control main valve core is determined based on the deviation, wherein the opening area correction amount is used to adjust the opening area of ​​the speed control main valve core in the current control cycle. In the next control cycle, the equivalent support force is re-acquired and the deviation is calculated until the equivalent support force approaches and is maintained at the target value.

2. The method according to claim 1, characterized in that, The step of determining the equivalent supporting force of the boom cylinder on the boom and load based on the rodless chamber pressure and the rod chamber pressure includes: Obtain the effective working area of ​​the rodless chamber and the effective working area of ​​the rod chamber of the boom cylinder; The pressure in the rod cavity is weighted according to the ratio of the effective working area of ​​the rod cavity to the effective working area of ​​the rodless cavity; The difference between the rodless chamber pressure and the converted rod chamber pressure is used as the controlled variable.

3. The method according to claim 1, characterized in that, The step of determining the opening area correction amount of the speed control main valve core based on the deviation includes: Obtain the handle opening degree of the current control cycle, and generate a first area correction amount based on the handle opening degree; A second area correction amount is generated based on the deviation between the actual value of the equivalent support force and the target value. The first area correction amount and the second area correction amount are superimposed to obtain the opening area correction amount of the speed control main valve core in the current control cycle.

4. The method according to claim 3, characterized in that, The step of generating a second area correction amount based on the deviation between the actual value of the equivalent support force and the target value further includes: The positive maximum adjustable area limit and the reverse maximum adjustable area limit are determined based on the first area correction amount; When the second area correction amount is positive, the second area correction amount is limited to the upper limit of the positive maximum adjustable area limit value. When the second area correction amount is negative, the absolute value of the second area correction amount is limited by the reverse maximum adjustable area limit value.

5. The method according to claim 3, characterized in that, The step of generating a second area correction amount based on the deviation between the actual value of the equivalent support force and the target value includes: The first gain coefficient, the second gain coefficient, and the third gain coefficient are determined based on the handle opening degree of the current control cycle. Multiply the deviation by the first gain coefficient to obtain the first component used to respond to the current deviation; The deviation is accumulated periodically and then multiplied by the second gain coefficient to obtain the second component used to eliminate the accumulated deviation. Multiplying the change in the deviation relative to the previous period by the third gain coefficient yields the third component used to respond to the trend of deviation change. The first component, the second component, and the third component are superimposed to form the second area correction amount.

6. The method according to claim 5, characterized in that, The process of determining the first gain coefficient, the second gain coefficient, and the third gain coefficient based on the handle opening degree of the current control cycle includes: Based on the preset correspondence between the handle opening range and the gain coefficient, determine the opening range to which the current handle opening belongs, and obtain the first gain coefficient, the second gain coefficient and the third gain coefficient corresponding to the opening range. The range of the handle opening is divided into multiple consecutive opening intervals, and different opening intervals correspond to different combinations of gain coefficients.

7. The method according to claim 3, characterized in that, The step of generating the first area correction amount based on the handle opening includes: Obtain a preset mapping function, wherein the mapping function is the correspondence between the handle opening degree and the normalized area coefficient; Substitute the handle opening degree of the current control cycle into the mapping function to obtain the corresponding normalized area coefficient; The first area correction amount is obtained by multiplying the normalized area coefficient by the maximum opening area of ​​the speed control main valve core.

8. The method according to claim 1, characterized in that, Also includes: Within each control cycle, the rodless chamber pressure of the boom cylinder in the current control cycle is obtained, and the difference between the rodless chamber pressure in the current control cycle and the rodless chamber pressure in the previous control cycle is calculated. The difference is compared with a preset drop rate threshold. When the difference is less than the drop rate threshold, it is determined to be a sudden unloading condition, and an emergency protection operation is performed.

9. The method according to claim 8, characterized in that, The emergency protection operations include: The original first gain coefficient is replaced by multiplying the current first gain coefficient by the preset attenuation coefficient, and used to generate the correction amount for the current control cycle; The pause function adds the deviation of the current control cycle to the accumulated deviation value, and uses the accumulated deviation value before the pause to determine the correction amount for the current control cycle. After the correction amount for the current control cycle is generated, the normal control process resumes. In subsequent control cycles, the difference in pressure in the rodless chamber is continuously calculated. When the number of times the difference is continuously less than the drop rate threshold reaches a preset number, the emergency protection state is released, and the accumulated deviation value is gradually restored to the normal accumulation state at a preset recovery rate.

10. A boom descent speed control device, characterized in that, include: The acquisition module is used to acquire the rodless chamber pressure and rod chamber pressure of the boom cylinder in each control cycle. The first calculation module is used to determine the equivalent supporting force characterizing the boom cylinder on the boom and load based on the rodless chamber pressure and the rod chamber pressure. The second calculation module is used to calculate the deviation between the actual value and the target value of the current equivalent support force. The determination module is used to determine the opening area correction amount of the speed control main valve core based on the deviation, and the opening area correction amount is used to adjust the opening area of ​​the speed control main valve core in the current control cycle.

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