Three-hole plunger pair motion synchronization control method and system

Abstract

The present application relates to the technical fields of hydraulic control, in particular to a three-hole plunger pair motion synchronization control method and system, comprising: calculating the tracking error of each plunger and the target displacement according to the real-time displacement signal of the plunger cavity, and calculating the synchronization error between each plunger according to the plunger cavity tracking error to synthesize the displacement comprehensive error signal; performing displacement outer ring PID control according to the displacement comprehensive error signal of the plunger cavity; performing pressure inner ring PID control according to the difference between the plunger cavity pressure target value and the real-time pressure signal of the plunger cavity; during the system operation, periodically applying common mode step excitation signals to the pressure inner ring of each of the three plunger cavities, collecting the response curves of each pressure inner ring to the step excitation signals of the plunger cavities, and extracting the pressure response time constant of each plunger cavity according to the plunger cavity response curve. The present application can quickly suppress pressure fluctuation, and realize high-precision synchronization control under complex working conditions.

Description

Technical Field

[0001] This invention relates to the field of hydraulic control technology, and in particular to a method and system for synchronous control of the motion of a three-hole plunger pair. Background Technology

[0002] Three-hole plunger assemblies, with their unique advantage of "one pump and three plunger chambers," are widely used in heavy-duty jacking, precision metering, and oilfield injection and production. The core control objective of this type of system is to achieve high-precision synchronization of the three plungers while ensuring their independent movement. The current mainstream technical approach is an electro-hydraulic independent synchronous control architecture of "one pump, three valves, and three closed loops." Taking a heavy-duty three-cylinder synchronous jacking platform as an example, each plunger is equipped with an independent displacement sensor and servo valve, forming a position closed loop. At the control algorithm level, a proportional-integral-derivative (PID) controller is typically used as the core regulator. This control method can achieve good synchronization results in laboratory environments or under relatively stable operating conditions. However, when this technology is applied to actual engineering scenarios, fluctuations in its control performance are observed. Taking heavy bridge segment jacking operations as an example, there are two disturbance factors in actual operating conditions: one is sudden load changes. When the lifting platform starts lifting the component from rest, the contact state between the three support points and the component is not ideally uniform. The actual load force borne by each plunger may jump instantaneously from zero to 120% of the rated load. This drastic load change acts directly on the plungers, equivalent to introducing a sudden force disturbance into the position closed loop. Secondly, there are changes in hydraulic parameters. In cold winter regions, the hydraulic oil temperature can drop as low as -20℃ and the viscosity can reach several thousand centis. After two hours of continuous operation, the oil temperature rises to over 60℃, and the viscosity drops to tens of centis. The combined changes in oil viscosity and bulk modulus alter the flow gain of the servo valve and the damping characteristics of the system.

[0003] Under the condition where the two disturbances mentioned above coexist, the existing solution using a fixed-gain PID controller faces a contradiction: if the controller parameters are tuned according to the low-temperature, high-viscosity condition, the control parameters will be too large when the oil temperature rises and the system response becomes faster, easily leading to overshoot and oscillation; if tuned according to the high-temperature, low-viscosity condition, the response will be slow during low-temperature startup, and the ability to suppress load disturbances will be insufficient. Field operators usually adopt a compromise tuning method, that is, taking an intermediate value between the two, but this method cannot achieve optimal control performance under all operating conditions. Furthermore, when a sudden load change occurs, the existing control system can only passively respond through the feedback signal of the displacement sensor: the load change causes the plunger displacement to deviate from the target value, and the controller gradually adjusts the output after detecting the error. This mechanism of first deviating and then compensating has an inherent lag, especially at the moment of sudden load change, the process of establishing and eliminating displacement deviation will directly translate into the peak value of synchronization error. Summary of the Invention

[0004] The main objective of this invention is to provide a method and system for synchronous control of the motion of a three-hole plunger pair, aiming to solve the technical problems mentioned in the background art.

[0005] This invention proposes a method for synchronous control of the motion of a three-hole plunger pair, comprising: Acquire the real-time displacement signals of the three plungers and the real-time pressure signals of the three plunger chambers; The tracking error between each plunger and the target displacement is calculated based on the real-time displacement signal, and the synchronization error between each plunger is calculated based on the tracking error. The tracking error and the synchronization error are then combined into a comprehensive displacement error signal for each plunger. Based on the displacement comprehensive error signal, perform displacement outer loop PID control to output the pressure target value of each plunger; The pressure inner loop PID control is performed based on the difference between the pressure target value and the real-time pressure signal, and the servo valve control voltage of each plunger is output to drive the servo valve to act. During system operation, a common-mode step excitation signal is periodically applied to the pressure inner rings of each of the three plunger chambers simultaneously, and the response curves of each pressure inner ring to the step excitation signal are collected. The pressure response time constant of each plunger chamber is extracted based on the response curves. The consistency of the responses of the three plunger chambers is analyzed based on the pressure response time constant. When the consistency meets the preset conditions, it is determined to be a global operating condition change. The controller parameters of the inner pressure PID control and the outer displacement PID control are adjusted according to the operating condition characteristics represented by the pressure response time constant. When the variance is not less than the dynamic threshold, it is determined to be a local load disturbance. The pressure change and acceleration change of the plunger chamber are obtained to generate a feedforward compensation amount that is superimposed on the pressure target value of the plunger chamber.

[0006] Preferably, the steps of calculating the tracking error between each plunger and the target displacement based on the real-time displacement signal, calculating the synchronization error between each plunger based on the tracking error, and weighted summing the tracking error and the synchronization error to obtain the comprehensive displacement error signal of each plunger include: The displacement value of each plunger at the current sampling time is obtained based on the real-time displacement signal, and the target displacement value at the current sampling time is obtained based on the preset target displacement curve. The tracking error of each plunger is obtained based on the target displacement value and the displacement value. The displacement difference between any two different plungers is calculated based on the displacement values ​​of the three plungers, thus obtaining the synchronization error set; The tracking error and the synchronization error are weighted and summed to obtain the displacement comprehensive error signal.

[0007] Preferably, the step of performing outer-loop PID control of displacement based on the comprehensive displacement error signal and outputting the target pressure value of each plunger includes: The proportional gain and integral gain of the displacement outer loop PID controller are obtained, wherein the proportional gain and integral gain are dynamically adjusted according to the global operating condition identification results. The displacement comprehensive error signal is input into the displacement outer loop PID controller, and the pressure target value increment is calculated according to the incremental PID control law. The pressure target value at the previous sampling time is added to the pressure target value increment to obtain the pressure target value at the current sampling time of each plunger, and the pressure target value is output as the input of the pressure inner loop.

[0008] Preferably, the step of performing pressure inner-loop PID control based on the difference between the pressure target value and the real-time pressure signal, outputting the servo valve control voltage for each plunger, and driving the servo valve to operate includes: The proportional gain and integral gain of the pressure inner loop PID controller are obtained, wherein the proportional gain and integral gain are dynamically adjusted based on the global operating condition identification results. The pressure error signal is obtained based on the target pressure value and the real-time pressure signal; The pressure error signal is input into the pressure inner loop PID controller, and the control voltage increment is calculated according to the incremental PID control law. The control voltage at the previous sampling moment is added to the control voltage increment to obtain the servo valve control voltage at the current sampling moment, and the control voltage is output to the servo valve to drive the servo valve to adjust the plunger chamber pressure.

[0009] Preferably, the step of periodically applying a common-mode step excitation signal to the pressure inner rings of each of the three plunger chambers simultaneously during system operation, acquiring the response curves of each pressure inner ring to the step excitation signal, and extracting the pressure response time constant of each plunger chamber based on the response curves includes: During normal system operation, a common-mode step excitation signal with the rated amplitude is simultaneously applied to the pressure inner ring of each of the three plunger chambers at preset identification cycles, wherein the excitation signals of the three plunger chambers have the same amplitude and phase. The response data of each plunger chamber pressure sensor to the step excitation signal are collected at a preset sampling frequency; The response data were fitted with an exponential model using the least squares method. By minimizing the fitting residual, the pressure response time constant of each plunger cavity is obtained.

[0010] Preferably, the step of analyzing the consistency of the responses of the three plunger chambers based on the pressure response time constant, determining a global operating condition change when the consistency meets a preset condition, and adjusting the controller parameters of the pressure inner loop PID control and the displacement outer loop PID control based on the operating condition characteristics represented by the pressure response time constant includes: The mean and variance were calculated based on the pressure response time constants of the three plunger chambers. Calculate the dynamic threshold based on the current mean; When the variance is less than the dynamic threshold, it is determined to be a global operating condition change, and the controller parameters are adjusted according to the mean; wherein, the proportional gain and integral gain of the pressure inner loop PID control are adjusted inversely proportional to the mean, and the proportional gain of the displacement outer loop PID control is adjusted inversely proportional to the square root of the mean.

[0011] Preferably, the step of determining a local load disturbance when the consistency does not meet the preset conditions, and obtaining the pressure change and acceleration change of the plunger cavity to generate a feedforward compensation amount superimposed on the target pressure value of the plunger cavity includes: When the variance is not less than the dynamic threshold or a sudden change in pressure is detected in any plunger cavity, it is determined that there is a local load disturbance in the plunger cavity, and the global controller parameters are locked unchanged. The pressure change is calculated based on the real-time pressure signal of the plunger cavity, and the acceleration estimate is obtained by a tracking differentiator based on the displacement signal of the plunger cavity to calculate the acceleration change. Calculate the load disturbance increment based on the pressure change and acceleration change; The load disturbance increment is converted into a feedforward compensation pressure value, and the feedforward compensation pressure value is combined with a preset feedforward gain coefficient and superimposed on the pressure target value of the plunger cavity to obtain a corrected pressure target value. When the plunger movement speed is lower than a preset threshold, the feedforward gain coefficient is automatically reduced.

[0012] The present invention also provides a three-hole plunger pair motion synchronization control system, comprising: The signal acquisition module is used to acquire the real-time displacement signals of the three plungers and the real-time pressure signals of the three plunger chambers. The error synthesis module is used to calculate the tracking error between each plunger and the target displacement based on the real-time displacement signal, and to calculate the synchronization error between each plunger based on the tracking error, and to synthesize the tracking error and the synchronization error into a comprehensive displacement error signal for each plunger. The outer loop displacement control module is used to perform PID control of the outer loop displacement based on the comprehensive displacement error signal and output the target pressure value of each plunger. The pressure inner loop control module is used to perform pressure inner loop PID control based on the difference between the pressure target value and the real-time pressure signal, and output the servo valve control voltage of each plunger to drive the servo valve to act. The operating condition identification module is used to periodically apply a common-mode step excitation signal to the pressure inner ring of each of the three plunger chambers simultaneously during system operation, collect the response curve of each pressure inner ring to the step excitation signal, and extract the pressure response time constant of each plunger chamber based on the response curve. The decision module is used to analyze the consistency of the responses of the three plunger chambers based on the pressure response time constant. When the consistency meets the preset conditions, it is determined to be a global operating condition change. The controller parameters of the inner pressure PID control and the outer displacement PID control are adjusted according to the operating condition characteristics represented by the pressure response time constant. When the variance is not less than the dynamic threshold, it is determined to be a local load disturbance. The pressure change and acceleration change of the plunger chamber are obtained to generate a feedforward compensation amount superimposed on the pressure target value of the plunger chamber.

[0013] The present invention also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of a three-hole plunger pair motion synchronization control method.

[0014] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of a method for synchronous control of the motion of a three-hole plunger pair.

[0015] The beneficial effects of this invention are as follows: By constructing a dual closed-loop series structure of displacement and pressure, and introducing load disturbance incremental feedforward compensation based on pressure signals, this invention enables the inner pressure loop to quickly suppress pressure fluctuations and completes disturbance suppression before the outer displacement loop detects displacement deviations, thus shortening the disturbance suppression time. Simultaneously, this invention utilizes three-plunger chamber pressure response consistency analysis to accurately distinguish between global parameter drift and local load disturbances, and performs linked adjustment of inner and outer loop parameters and local feedforward compensation respectively. This avoids misjudging load disturbances as parameter drift, leading to parameter mistuning, and achieves high-precision synchronous control under complex operating conditions. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a method flow according to an embodiment of this application.

[0017] Figure 2 This is a schematic diagram of the system structure according to an embodiment of this application.

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0020] like Figure 1 As shown, this application provides a method for synchronous control of the motion of a three-hole plunger pair, comprising: S1, acquire the real-time displacement signals of the three plungers and the real-time pressure signals of the three plunger chambers, wherein each plunger is equipped with an independent displacement sensor and pressure sensor; S2, calculate the tracking error between each plunger and the target displacement based on the real-time displacement signal, and calculate the synchronization error between each plunger based on the tracking error. Then, perform a weighted summation of the tracking error and the synchronization error to obtain the comprehensive displacement error signal of each plunger. S3, perform outer loop PID control of displacement based on the displacement comprehensive error signal, and output the pressure target value of each plunger; S4, perform pressure inner loop PID control based on the difference between the pressure target value and the real-time pressure signal, output the servo valve control voltage of each plunger, and drive the servo valve to act. S5. During system operation, a common-mode step excitation signal is periodically applied to the pressure inner rings of each of the three plunger chambers simultaneously, and the response curves of each pressure inner ring to the step excitation signal are collected. The pressure response time constant of each plunger chamber is extracted based on the response curves. S6. Calculate the mean and variance of the three plunger chambers based on the pressure response time constant. When the variance is less than the dynamic threshold, it is determined to be a global operating condition change. Adjust the controller parameters of the pressure inner loop PID control and the displacement outer loop PID control based on the mean. When the variance is not less than the dynamic threshold, it is determined to be a local load disturbance. Calculate the load disturbance increment based on the pressure change and acceleration change of the plunger chamber, and generate a feedforward compensation amount to be superimposed on the pressure target value of the plunger chamber.

[0021] As described in steps S1-S6 above, the core of the three-hole plunger pair motion synchronization control method provided in this embodiment lies in constructing a series control structure of the displacement outer loop and the pressure inner loop, and on this basis, introducing a self-identification mechanism of working condition parameters based on the consistency analysis of multi-plunger cavity response and a load disturbance incremental feedforward compensation mechanism based on pressure signals. In the three-hole plunger pair lifting scenario addressed by this invention, the three plungers share a rigid load, and the system faces two types of mutually coupled disturbance sources: one is global parameter drift caused by oil temperature changes, and the other is local load disturbance caused by off-center loading and local obstacles. The two types of disturbances are physically different and have different requirements for control strategies. Global parameter drift requires adjustment of controller parameters to maintain the stability of the system's dynamic characteristics, while local load disturbance requires fast feedforward compensation to suppress the impact of disturbance on synchronization accuracy. When faced with these two types of disturbances, existing control methods may misjudge local load disturbances as parameter drift, incorrectly adjust controller parameters, and lead to a decrease in system performance or even instability. This embodiment introduces three-plunger cavity response consistency analysis to decouple global parameter drift from local load disturbances, and adopts targeted control strategies to maintain stable system operation and high-precision synchronization when both types of disturbances coexist.

[0022] In this embodiment, a collaborative working mechanism is formed among the three modules: the series structure of the outer displacement ring and the inner pressure ring, the common-mode excitation and response time constant extraction, and the multi-plunger cavity consistency analysis and discrimination decision. The series structure of the outer displacement ring and the inner pressure ring provides the basis for rapid disturbance suppression; the common-mode excitation and response time constant extraction provide online identification means for operating condition perception; and the multi-plunger cavity consistency analysis and discrimination decision provide the decision basis for control strategy selection. The combined effect of these three modules enables the system to achieve high-precision synchronous movement of the three plungers under complex operating conditions with a wide temperature range and variable load.

[0023] In one embodiment of the present invention, the steps of calculating the tracking error between each plunger and the target displacement based on the real-time displacement signal, calculating the synchronization error between each plunger based on the tracking error, and weighted summing the tracking error and the synchronization error to obtain the comprehensive displacement error signal of each plunger include: S21, obtain the first [missing information] based on the real-time displacement signal. The displacement value of the first plunger at the current sampling time is obtained, and the target displacement value at the current sampling time is obtained according to the preset target displacement curve. The target displacement value is subtracted from the displacement value to obtain the first plunger. Tracking error of each plunger: ; In the formula, Indicates the first The tracking error of each plunger at the current sampling moment. Indicates the current sampling time The target displacement value, Indicates the first The displacement value of each plunger at the current sampling time; S22, calculate the displacement difference between any two different plungers based on the displacement values ​​of the three plungers, and obtain the synchronization error set: ; in, Indicates the first The first plunger and the first Displacement difference between the plungers and The values ​​are 1, 2, and 3, and ; S23, the tracking error and the synchronization error are weighted and summed to obtain the displacement comprehensive error signal; ; in, This represents the overall displacement error signal. This represents the synchronization error weighting coefficient, used to adjust the response strength of synchronization control. In this embodiment, the value is 0.3. The range of this weighting coefficient is 0.1 to 0.5. If the value is too small, the synchronization control effect will be weakened; if the value is too large, it may cause the system response to overshoot.

[0024] As described in steps S21-S23 above, the specific implementation method is as follows: The controller reads the displacement values ​​of the three plungers from the magnetostrictive displacement sensor with a sampling period of 2 milliseconds. The magnetostrictive displacement sensor has a resolution of 0.1 micrometers. Simultaneously, the controller obtains the target displacement value at the current moment according to a preset target displacement curve. For the bridge segment jacking scenario, this target displacement curve adopts an S-shaped acceleration / deceleration curve to ensure the smoothness of the start-up and stopping process. The controller calculates the... The tracking error of each plunger is the difference between the target displacement value and the actual displacement value. The tracking error reflects the deviation of the plunger from the desired position and is the basic input quantity for feedback control. When the tracking error is positive, it indicates that the actual position of the plunger lags behind the target position; when the tracking error is negative, it indicates that the actual position of the plunger leads the target position. The controller simultaneously calculates the displacement differences between each pair of the three plungers to obtain a synchronization error set. For example, for plunger 1, its synchronization error with plunger 2 is the difference between the displacement values ​​of plunger 1 and plunger 2, and its synchronization error with plunger 3 is the difference between the displacement values ​​of plunger 1 and plunger 3; and so on for plunger 2 and plunger 3. The synchronization error reflects the relative position deviation between the plungers and is a key indicator of synchronous control. The controller weights and sums the tracking error and the synchronization error to obtain a comprehensive displacement error signal. The synchronization error weighting coefficient is used to adjust the response strength of the synchronous control. In this embodiment, the synchronization error weighting coefficient is not a fixed value but is adjusted in segments according to the operating conditions. Specifically, during the lifting start-up phase, when the displacement is less than 5 mm, the controller sets the synchronization error weighting coefficient to 0.1 to prioritize ensuring that each plunger independently overcomes static friction to complete the start-up, avoiding premature intervention of synchronization control that could hinder the start-up of a particular plunger. During the lifting steady-state phase, when the displacement is greater than 5 mm, the controller gradually increases the synchronization error weighting coefficient to 0.3 to enhance the synchronization control effect and maintain the synchronization accuracy of the three plungers. When the tracking error of any plunger is detected to exceed a preset threshold (0.5 mm in this embodiment), the controller temporarily reduces the synchronization error weighting coefficient to 0.2 to avoid overshoot of the control command due to excessive synchronization error. After the error recovers, the synchronization error weighting coefficient is restored to 0.3.

[0025] In the three-hole plunger jacking scenario addressed in this invention, the three plungers share a rigid load, but the load distribution among them is not uniform, resulting in off-center loading due to factors such as component deformation and uneven support points. In existing control methods, when a plunger bears a greater load due to off-center loading, its movement speed naturally slows down, causing its tracking error to be opposite in direction to the synchronization errors of the other plungers. In this situation, if the tracking error of this plunger is directly used as the controller input, the controller will output a command to increase the driving force, attempting to accelerate the plunger's movement speed to eliminate the tracking error. However, this command will instead exacerbate the load burden on that plunger, causing the synchronization error to further increase. This embodiment weights and fuses the tracking error and the synchronization error. When the synchronization error and the tracking error are in opposite directions, they cancel each other out during the weighted summation process, reducing the incremental driving force output by the controller and avoiding misjudgment of control commands due to off-center loading. This design enables the three-plunger system to achieve adaptive load distribution under off-center load conditions. That is, the plunger bearing a larger load automatically reduces its output, while the plunger bearing a smaller load automatically increases its output, thereby maintaining synchronous movement of each plunger under rigid load conditions.

[0026] This embodiment further sets upper and lower limits for the synchronization error weighting coefficient, limiting its value to the range of 0.1 to 0.5. The purpose of this constraint is to prevent system instability caused by improper weighting coefficient values ​​under extreme operating conditions: when the synchronization error weighting coefficient is less than 0.1, the synchronization control effect is too weak, making it difficult to guarantee the synchronization accuracy of the three plungers; when the synchronization error weighting coefficient is greater than 0.5, the synchronization error weight is too large, which may cause the system to overreact to small synchronization errors, triggering high-frequency oscillations in the control quantity.

[0027] In one embodiment of the present invention, the step of performing displacement outer-loop PID control based on the displacement comprehensive error signal and outputting the pressure target value of each plunger includes: S31, Obtain the proportional gain and integral gain of the displacement outer loop PID controller, wherein the proportional gain and integral gain are dynamically adjusted according to the global operating condition identification result; S32, input the displacement comprehensive error signal into the displacement outer loop PID controller, and calculate the pressure target value increment according to the incremental PID control law: ; in, This indicates the increment of the target pressure value. Indicates proportional gain. This represents the change in the overall displacement error signal (calculated from the overall displacement error signals at the current sampling time and the previous sampling time). Indicates the sampling period. Indicates integral gain. This indicates the overall displacement error signal; S33, add the pressure target value at the previous sampling time to the pressure target value increment to obtain the pressure target value at the current sampling time, and use the pressure target value as the input of the pressure inner loop.

[0028] Formula for target pressure value: ; in, Indicates the target pressure value. This represents the target pressure value at the previous sampling time. This indicates the increment of the target pressure value.

[0029] As described in steps S31-S33 above, it should be noted that the proportional gain and integral gain in this embodiment are not fixed values, but are dynamically adjusted based on the global operating condition identification results in subsequent steps. Under the reference operating condition, i.e., oil temperature 40℃ and viscosity 46 centistokes, the proportional gain of the displacement outer loop is 0.3, and the integral gain is 0.01. The controller adjusts the displacement outer loop gain according to the following rules: when the identified pressure response time constant increases, it indicates that the system response is slowing down, and the controller increases the proportional gain proportionally to compensate for the decrease in response speed; when the pressure response time constant decreases, the controller decreases the proportional gain proportionally to avoid overshoot.

[0030] The controller adds the target pressure value from the previous sampling moment to the target pressure increment to obtain the target pressure value for the current sampling moment. This target pressure value is used as the setpoint for the inner pressure loop controller. During signal transmission, the controller outputs this target pressure value to the inner pressure loop controller via a digital-to-analog converter plunger chamber. The output range of this plunger chamber is 0-10 volts, corresponding to a pressure range of 0-25 MPa. Before outputting, the controller limits the target pressure value to the 0-25 MPa range to prevent servo valve actuation abnormalities caused by excessive pressure target value due to integral accumulation.

[0031] In the three-hole plunger system addressed in this invention, the output of the outer displacement ring is set to the target pressure value rather than the voltage signal that directly drives the servo valve. This design stems from the contradiction between the large inertia of the hydraulic system and sudden load changes: in heavy lifting scenarios, the load mass can reach hundreds of tons, resulting in extremely high mechanical inertia and limiting the response speed of the outer displacement ring; while sudden load changes, such as the instant the plunger contacts the component, occur in a very short time, and the outer displacement ring cannot respond before the sudden load change occurs. By setting the output of the outer displacement ring to the target pressure value and introducing it into the inner pressure ring, the inner pressure ring, with its faster response speed, responds rapidly after the sudden load change occurs. Before the outer displacement ring detects the displacement deviation, the inner pressure ring has already begun to adjust the servo valve to suppress pressure fluctuations, thereby achieving imperceptible suppression of sudden load changes.

[0032] This embodiment employs an incremental PID control law instead of a positional PID control, designed to address the risk of cascading instability in a three-plunger system under sudden load changes. In positional PID control, the integral term continuously accumulates error. Even after the servo valve control voltage reaches its physical limit (±10V in this embodiment), the integral term continues to accumulate, leading to integral saturation. When the error reverses, it takes a long time to exit saturation, potentially causing system oscillation or even instability. In a three-plunger lifting scenario, when one plunger contacts the load first, its pressure rises instantaneously, and the tracking error of that plunger increases rapidly. If positional PID control is used, the integral term will quickly accumulate to the limit value. After the other plungers contact the load, the system needs to rebalance. At this time, integral saturation may cause the control voltage of that plunger to remain in the limit state for a long time, causing violent movement of that plunger and thus disrupting the synchronization of the three plungers. The incremental PID control law used in this embodiment outputs the incremental control quantity, which is accumulated to obtain the current control quantity. The integral saturation phenomenon is suppressed, thereby avoiding the aforementioned risk of cascading instability. In addition, incremental PID control has advantages during controller initialization or fault recovery: when the system restarts, the controller can initialize the pressure target value to the current pressure value, making the initial increment of the control quantity zero, thus avoiding the output jump that may occur when positional PID control starts.

[0033] In this embodiment, the proportional gain and integral gain of the displacement outer loop are dynamically adjusted based on the global operating condition identification results. This design stems from the parameter drift problem of the three-hole plunger pair under wide temperature range conditions. In cold winter regions, the hydraulic oil temperature can drop as low as -20°C and the viscosity can reach several thousand centis. After two hours of continuous operation, the oil temperature rises to over 60°C, and the viscosity drops to tens of centis. The change in oil viscosity directly affects the flow gain of the servo valve, thereby altering the response speed of the pressure inner loop. If the gain of the displacement outer loop remains fixed, when the response speed of the pressure inner loop increases due to the rise in oil temperature, the gain of the displacement outer loop will be relatively large, potentially leading to overshoot and oscillation; conversely, when the response speed of the pressure inner loop decreases due to the drop in oil temperature, the gain of the displacement outer loop will be relatively small, resulting in a sluggish response. This embodiment dynamically adjusts the gain of the displacement outer loop based on the operating condition identification results to maintain a match between the response speed of the displacement outer loop and the response speed of the pressure inner loop. Furthermore, the dynamic gain adjustment mechanism in this embodiment works in conjunction with the aforementioned incremental PID control law: the incremental PID control law eliminates the risk of integral saturation, allowing gain adjustment to be performed without causing integral accumulation problems; while the gain adjustment ensures the consistency of the response speed of the incremental PID control under different operating conditions. Together, they constitute a displacement outer loop control scheme that adapts to wide temperature range operating conditions.

[0034] In one embodiment of the present invention, the step of performing pressure inner-loop PID control based on the difference between the pressure target value and the real-time pressure signal, outputting the servo valve control voltage for each plunger, and driving the servo valve to operate includes: S41, Obtain the proportional gain and integral gain of the pressure inner loop PID controller, wherein the proportional gain and integral gain are dynamically adjusted according to the global operating condition identification result; S42, Subtract the target pressure value from the real-time pressure signal to obtain the pressure error signal: ; in, This indicates a pressure error signal. Indicates the target pressure value. This indicates the real-time pressure signal (real-time pressure acquisition value, unit: Pa). S43, input the pressure error signal into the pressure inner loop PID controller, and calculate the control voltage increment according to the incremental PID control law: ; in, Indicates the control voltage increment. Indicates proportional gain. This indicates the amount of change in the pressure error signal. Indicates integral gain. This indicates a pressure error signal. Indicates the sampling period; S44, add the control voltage of the previous sampling moment to the control voltage increment to obtain the servo valve control voltage of the current sampling moment, and output the servo valve control voltage to the servo valve to drive the servo valve to adjust the plunger chamber pressure.

[0035] Servo valve control voltage: ; in, Indicates the servo valve control voltage. This represents the control voltage at the previous sampling time. Indicates the control voltage increment; As described in steps S41-S44 above, the controller acquires the proportional gain and integral gain of the pressure inner-loop PID controller. Similar to the displacement outer loop, the proportional gain and integral gain of the pressure inner loop in this embodiment are also dynamically adjusted based on the global operating condition identification results. Under the reference operating condition, the proportional gain of the pressure inner loop is 0.8, and the integral gain is 0.05. The controller adjusts the pressure inner loop gain according to the following rules: when the identified pressure response time constant increases, it indicates that the pressure inner loop response is slowing down, and the controller increases the proportional gain and integral gain proportionally to compensate for the decrease in response speed; when the pressure response time constant decreases, the controller decreases the proportional gain and integral gain proportionally to avoid overshoot.

[0036] The controller subtracts the target pressure value output from the outer displacement loop from the real-time acquired pressure signal to obtain the pressure error signal. The pressure error signal reflects the deviation between the current plunger chamber pressure and the desired pressure. When the pressure error is positive, it indicates that the actual pressure is lower than the target pressure, requiring an increase in the servo valve opening to increase the oil flow into the plunger chamber; when the pressure error is negative, it indicates that the actual pressure is higher than the target pressure, requiring a decrease in the servo valve opening to reduce the oil flow into the plunger chamber.

[0037] The controller adds the control voltage from the previous sampling moment to the control voltage increment to obtain the servo valve control voltage at the current sampling moment. This servo valve control voltage is then converted from digital to analog and output to the servo valve, driving the valve core to move and regulate the flow rate of oil entering the plunger chamber, thereby changing the pressure in the plunger chamber. In this embodiment, the rated control voltage range of the servo valve is ±10 volts. The controller limits the control voltage to ensure it does not exceed the safe range. Specifically, when the calculated control voltage is greater than 10 volts, the controller sets it to 10 volts; when the calculated control voltage is less than -10 volts, the controller sets it to -10 volts.

[0038] In the three-hole plunger system addressed in this invention, the design goal of the pressure inner ring is to achieve rapid and precise control of the plunger cavity pressure. Compared with the displacement outer ring, the pressure inner ring has two characteristics: first, the controlled object is a first-order inertial element, making control easier; second, its response speed is much faster than that of the displacement outer ring. In this embodiment, by setting the sampling period of the pressure inner ring to the same 2 milliseconds as the displacement outer ring, but by configuring parameters to make the proportional gain of the pressure inner ring significantly higher than that of the displacement outer ring, the rapid response of the pressure inner ring is achieved. Specifically, under the reference operating condition, the proportional gain of the pressure inner ring is 0.8, the proportional gain of the displacement outer ring is 0.3, and the closed-loop bandwidth of the pressure inner ring is approximately three times that of the displacement outer ring. This bandwidth difference allows the pressure inner ring to quickly suppress pressure disturbances and eliminate them before the displacement outer ring detects the displacement deviation, thereby reducing the adjustment burden on the displacement outer ring.

[0039] This embodiment employs an incremental PID control law as the control algorithm for the pressure inner loop. This choice is based on the operating characteristics of the pressure inner loop. The input to the pressure inner loop is the target pressure value, which is obtained from the output of the displacement outer loop after feedforward compensation correction. Under sudden load changes, the target pressure value may undergo a step change. If positional PID control is used, the integral term will accumulate rapidly, potentially leading to control voltage saturation. The incremental PID control law used in this embodiment naturally avoids the integral saturation problem, enabling the pressure inner loop to respond quickly to changes in the target pressure value without overshoot.

[0040] In this embodiment, the proportional gain and integral gain of the pressure inner loop are dynamically adjusted based on the global operating condition identification results. This design works in conjunction with the gain adjustment of the displacement outer loop. Specifically, when the oil temperature decreases, leading to an increase in oil viscosity, the flow gain of the servo valve decreases, and the response speed of the pressure inner loop decreases. At this time, the global operating condition identification module detects an increase in the pressure response time constant, and the controller correspondingly increases the proportional gain and integral gain of the pressure inner loop to compensate for the decrease in flow gain, restoring the response speed of the pressure inner loop to the reference operating condition level. Simultaneously, the gain of the displacement outer loop is also adjusted according to the change in the pressure response time constant, ensuring that the response speed of the displacement outer loop matches that of the pressure inner loop. This gain adjustment mechanism, linking the inner and outer loops, ensures that the stability of the cascade control system remains consistent across the entire operating condition range.

[0041] In this embodiment, the collaborative working mechanism of the pressure inner loop and the displacement outer loop is reflected in the following aspects: First, the rapid response capability of the pressure inner loop provides the displacement outer loop with a clean controlled object, allowing the displacement outer loop to deal with a system whose high-frequency disturbances have been suppressed by the pressure inner loop, thereby reducing the control difficulty of the displacement outer loop; Second, the gain adjustment of the pressure inner loop and the gain adjustment of the displacement outer loop share the same set of operating condition identification results, ensuring the matching of the dynamic characteristics of the inner and outer loops; Third, when the pressure inner loop detects abnormal pressure fluctuations, it can transmit the information to the displacement outer loop through the feedforward plunger cavity, enabling the displacement outer loop to make adjustments in advance. This collaborative working mechanism is particularly effective under sudden load changes: the pressure inner loop quickly suppresses pressure fluctuations, and the displacement outer loop quickly eliminates residual displacement deviations, and the combination of the two shortens the total disturbance suppression time of the system.

[0042] In one embodiment of the present invention, the step of periodically applying a common-mode step excitation signal to the pressure inner rings of each of the three plunger chambers simultaneously during system operation, acquiring the response curves of each pressure inner ring to the step excitation signal, and extracting the pressure response time constant of each plunger chamber based on the response curves includes: S51, during normal system operation, a common-mode step excitation signal with an amplitude of 1% to 3% of the rated pressure is simultaneously applied to the pressure inner ring of each of the three plunger chambers at preset identification cycles, wherein the excitation signals of the three plunger chambers have the same amplitude and phase. S52, acquire the response data of each plunger cavity pressure sensor to the step excitation signal at a preset sampling frequency. ,in, Indicates the first Each discrete sampling time is counted from the moment the excitation is applied. S53, the least squares method is used to fit the response data to an exponential model. The fitting model is as follows: ; in, Indicates the sampling time The exponential model fits the stress value. The first element to be fitted is... The time constant of the pressure response of each plunger chamber. This indicates the sampling time before the step excitation signal was applied. The initial pressure value of each plunger chamber. This represents the amplitude of the common-mode step excitation signal. Represents the natural constant; S54, by minimizing the fitting residual, the pressure response time constant of each plunger cavity is obtained.

[0043] Minimize the fitting residual: ; ; in, Indicates the first The sum of squared residuals from fitting the pressure response curves of each plunger cavity. Indicates the first The actual pressure values ​​of each plunger chamber are acquired directly by the pressure sensor. Indicates the first Each plunger cavity at the sampling time The exponential model fits the stress values. This represents the total number of data points collected for the step excitation signal. This represents the pressure response time constant after fitting; In this invention, Represents a continuous-time variable. Indicates the first Each discrete sampling time, The sampling period satisfies In the implementation of the control algorithm, the current sampling time is denoted as... The previous sampling time is recorded as When calculating the fitting residuals, the discrete sampling times are... Substitute into continuous model To obtain the theoretical value at that moment. ; As described in steps S51-S55 above, during normal system operation, the controller performs operating condition identification once every preset identification cycle. In this embodiment, the identification cycle is set to 30 seconds. This duration is based on the following considerations: the rate of change of oil temperature is usually in the range of 0.5 to 2 degrees Celsius per minute, and the oil temperature change within 30 seconds does not exceed 1 degree Celsius, which will not have a significant impact on the system characteristics; at the same time, the 30-second interval ensures that the controller has sufficient computing resources to handle other control tasks, avoiding excessive consumption of computing resources due to overly frequent identification.

[0044] The controller simultaneously applies a step excitation signal to the inner pressure ring of each of the three plunger chambers. The amplitude of this step excitation signal is set to 1% to 3% of the rated pressure; in this embodiment, the rated pressure is 25 MPa, therefore the amplitude of the step excitation signal is 0.25-0.75 MPa. It is important to note that the excitation signals for the three plunger chambers have the same amplitude and phase, belonging to common-mode signals. The purpose of using common-mode excitation is that the common-mode signal will not disrupt the relative synchronization error between the three plungers. Because the three plungers are simultaneously subjected to the same pressure step action, the displacement response of each plunger is ideally consistent, therefore the relative displacement deviation will not increase due to the excitation signal. Furthermore, the excitation signal amplitude is limited to within 3% of the rated pressure, and its impact on the lifting process is negligible. Calculated at a lifting speed of 1 mm / s, the displacement fluctuation caused by a 0.75 MPa pressure disturbance does not exceed 0.01 mm, far less than the allowable synchronization error of the lifting platform. This design allows the system to complete parameter self-tuning during continuous equipment operation.

[0045] The controller acquires response data from the pressure sensors in each plunger chamber to a step excitation signal at a sampling frequency of 1000Hz. The selection of the sampling frequency is based on the response characteristics of the inner pressure loop: in this embodiment, the response time constant of the inner pressure loop is in the range of 20-100 milliseconds. A sampling frequency of 1000Hz means that one data point is acquired every millisecond, which can completely record the details of the pressure response curve and provide sufficient data support for subsequent curve fitting. The acquired response data typically exhibits an exponential increase characteristic and can be described using a first-order inertial model.

[0046] The controller uses the least squares method to fit an exponential model to the collected pressure response data. By solving for the parameter that minimizes the sum of squared residuals, the pressure response time constant of each plunger cavity is obtained. In this embodiment, the least squares fitting employs a numerical optimization method to find the pressure response time constant that minimizes the objective function within a preset search interval. This embodiment uses the golden section search method, which has a fast convergence speed and does not require derivative calculation, making it suitable for real-time operation in embedded controllers. The lower limit of the search interval is set to 5 milliseconds, and the upper limit is set to 200 milliseconds, covering the possible values ​​of the system under various operating conditions.

[0047] After fitting, the controller calculates the fitting residual, which is the sum of the squares of the differences between the actual pressure value and the model prediction value at each sampling time. The fitting residual reflects the degree of matching between the actual response curve and the first-order inertial model. When the fitting residual is less than the preset residual threshold, it indicates that the actual response curve matches the first-order inertial model well, and the identification result is reliable. The controller uses the extracted pressure response time constant for subsequent operating condition discrimination. When the fitting residual is not less than the residual threshold, it indicates that the identification process is affected by external interference, such as load fluctuations or hydraulic shocks, causing the response curve to deviate from the ideal shape. In this case, the controller considers the identification invalid, keeps the original operating condition parameters unchanged, and re-identifies in the next identification cycle. This confidence assessment mechanism ensures the reliability of parameter identification and avoids parameter mistuning caused by external random disturbances. In this embodiment, the residual threshold is set to 0.1 MPa. 2 This value is set based on the fact that the pressure sensor's measurement noise is approximately 0.05 MPa and 0.1 MPa. 2 The residual threshold is equivalent to allowing an average fitting error of approximately 0.1 MPa, which can distinguish between normal responses and abnormal disturbances.

[0048] In the three-hole plunger system addressed in this invention, online identification of the pressure response time constant is fundamental for subsequent operating condition judgment and parameter self-tuning. The value of this identification method lies in the fact that it eliminates the need for additional temperature or viscosity sensors, allowing the acquisition of operating condition information solely using the existing pressure sensor within the system. In existing technologies, identifying changes in oil parameters typically requires the installation of a temperature sensor, which only reflects oil temperature and cannot directly reflect the combined influence of oil viscosity and bulk modulus on the system's dynamic characteristics. This embodiment, by directly measuring the pressure response time constant, captures the comprehensive dynamic characteristics of all components, including the servo valve, oil, pipelines, and cavity, providing a more accurate reflection of the system's actual operating conditions than a single temperature measurement.

[0049] In this embodiment, the setting of the identification period, the selection of the excitation signal amplitude, the determination of the sampling frequency, and the selection of the fitting method together constitute an online identification scheme that can operate stably without stopping the system. This scheme forms a data interaction with the aforementioned displacement outer loop control and pressure inner loop control: the identification results are used to adjust the controller parameters of the displacement outer loop and pressure inner loop, and the adjustment of the controller parameters affects subsequent identification results, forming a closed-loop adaptive system. This design enables the three-hole plunger pair system to maintain stable control performance continuously.

[0050] In one embodiment of the present invention, the step of calculating the mean and variance of the three plunger chambers based on the pressure response time constant, determining a global operating condition change when the variance is less than a dynamic threshold, and adjusting the controller parameters of the pressure inner loop PID control and the displacement outer loop PID control based on the mean includes: S61, calculate the mean and variance based on the pressure response time constants of the three plunger chambers; S62, Calculate the dynamic threshold based on the current mean (its dimension is consistent with the standard deviation and matches the dimension of the variance): ; in, Indicates dynamic threshold. This represents a preset proportionality coefficient, with a value range of 5%-10%. This represents the mean; S63, when the variance is less than the dynamic threshold, it is determined to be a global operating condition change, and the controller parameters are adjusted according to the mean, including: S631, adjust the proportional gain and integral gain of the pressure inner loop PID controller according to the following formula: ; in, This indicates the adjusted pressure inner loop proportional gain. Indicates the nominal proportional gain under reference operating conditions. This represents the nominal integral gain under the reference operating condition. This represents the nominal response time constant under the reference operating condition. This indicates the adjusted pressure inner loop integral gain. This represents the mean; S632, adjust the proportional gain of the outer loop PID controller for displacement according to the following formula: ; in, This represents the nominal displacement loop proportional gain under the reference operating condition, achieving the matching of the dynamic characteristics of the inner and outer loops.

[0051] As described in steps S61-S63 above, the controller calculates the mean and variance based on the pressure response time constants of the three plunger chambers. The mean physically represents the average level of the response speeds of the three inner pressure loops, reflecting the overall dynamic characteristics of the system under the current operating conditions. The variance physically represents the dispersion of the response speeds of the three plunger chambers, reflecting the consistency of the dynamic characteristics among the three plungers. Ideally, the mechanical structure and hydraulic circuits of the three plungers are identical, and their pressure response time constants should be essentially the same. When local load disturbances occur, such as when a plunger contacts the load first or encounters a local obstacle, the pressure response of that plunger will deviate from the normal pattern, leading to an increase in variance. Therefore, variance can serve as an effective indicator for distinguishing between global operating condition changes and local load disturbances.

[0052] The controller calculates a dynamic threshold based on the current average. In this embodiment, a dynamic threshold is used instead of a fixed threshold because the signal-to-noise ratio (SNR) of the pressure signal varies under different operating conditions, and a fixed threshold may lead to misjudgment. For example, under high pressure and high flow conditions, the pressure signal amplitude is large and the SNR is high, allowing for a smaller dynamic threshold to enhance discrimination sensitivity; under low pressure and low flow conditions, the pressure signal amplitude is small and the noise is relatively large, requiring a larger dynamic threshold to avoid misjudgment caused by noise. In this embodiment, this value is obtained through experimental calibration: multiple identification experiments are conducted under different operating conditions, recording the maximum value of the variance during normal response and the minimum value during abnormal response for each condition, and taking the median value as the benchmark value of the proportional coefficient. Specifically, under the reference operating condition, the variance during normal response is approximately 5% of the mean, while under simulated local disturbances, the variance is approximately 15% of the mean. Setting the proportional coefficient to 8% ensures that the variance during normal response is always less than the dynamic threshold, and the variance during local disturbances is always greater than the dynamic threshold. It should be noted that the proportional coefficient can be adjusted according to the specific system's structural parameters and sensor noise level, with a range of 5%-10%. When the system's pressure sensor noise level is high, the proportional coefficient can be appropriately increased to avoid misjudgments caused by noise; when the system has high requirements for disturbance identification sensitivity, the proportional coefficient can be appropriately decreased to enhance the discrimination capability. The introduction of a dynamic threshold allows the discrimination standard to adapt to measurement noise levels under different operating conditions: under high pressure and high flow conditions, the pressure signal amplitude is large, the signal-to-noise ratio is high, and the mean is large, so the dynamic threshold is also correspondingly large, but the actual variance is relatively small, which can still meet the discrimination conditions; under low pressure and low flow conditions, the signal noise is relatively large, the mean is small, and the dynamic threshold is also correspondingly reduced to avoid the inability to identify disturbances due to an excessively large fixed threshold.

[0053] The controller compares the variance with a dynamic threshold and adopts different control strategies based on the comparison result. When the variance is less than the dynamic threshold, it indicates that the response speeds of the three plunger chambers are basically the same, which is determined to be a global operating condition change. Global operating condition changes are usually caused by changes in comprehensive parameters such as oil temperature, viscosity, and bulk modulus. These changes affect all three plungers simultaneously, so the controller parameters need to be adjusted to adapt to the new operating conditions. When the variance is not less than the dynamic threshold, it indicates that there is a significant difference in the response speeds of the three plunger chambers, which is determined to be a local load disturbance. Local load disturbances are usually caused by asymmetric factors such as off-center loading and local obstacles. These disturbances only affect one or some plungers. In this case, the global controller parameters should not be adjusted, otherwise it will lead to parameter mistuning and deteriorate control performance.

[0054] When a change in global operating conditions is detected, the controller adjusts the proportional gain and integral gain of the pressure inner-loop PID controller based on the mean value. This is significant because: when the system response slows down, the pressure response time constant increases, and the increased gain compensates for the decrease in response speed; when the system response speeds up, the decreased gain prevents overshoot. The inverse relationship between gain and response time constant conforms to the control law of a first-order system, ensuring that the closed-loop bandwidth of the pressure inner loop remains essentially constant across the entire operating range.

[0055] The controller simultaneously adjusts the proportional gain of the displacement outer loop PID controller based on the mean. Specifically, the displacement outer loop proportional gain is adjusted to the square root of the ratio of the reference proportional gain to the average of the reference response time constant and the current response time constant. The integral gain of the displacement outer loop remains fixed in this embodiment because the integral gain primarily affects steady-state accuracy and has low sensitivity to changes in operating conditions. The square root adjustment rule for the displacement outer loop proportional gain is a unique rule designed for the three-plunger cascade control system of this invention, based on the following: In a cascade control system, the upper limit of the allowable gain of the displacement outer loop has a square root relationship with the response speed of the pressure inner loop. The derivation process is as follows: Assume the closed-loop transfer function of the pressure inner loop is approximately a first-order inertial element, and its time constant is the pressure response time constant; the controlled object of the displacement outer loop includes this first-order inertial element; according to classical control theory, the maximum allowable proportional gain of the displacement outer loop is inversely proportional to the square root of the pressure inner loop time constant. Adjusting the displacement outer loop gain according to this rule ensures that the stability margin of the displacement outer loop remains essentially constant across the entire operating range, avoiding system oscillations caused by improper gain adjustment.

[0056] In the three-hole plunger system addressed in this invention, the introduction of a multi-plunger cavity response consistency analysis mechanism solves the problem of the inability to distinguish between global parameter drift and local load disturbances in existing technologies. In existing adaptive control methods, when the system detects a change in dynamic characteristics, it is usually assumed to be parameter drift, and the controller parameters are directly adjusted. However, in a three-plunger lifting scenario, changes in dynamic characteristics may originate from two aspects: one is global factors such as oil temperature changes, and the other is local factors such as off-center loading. If local disturbances are mistakenly treated as global parameter drifts, it will lead to incorrect adjustments of the controller parameters for all plunger cavities, causing performance degradation in previously normal plunger cavities, and even triggering system oscillations. This embodiment, through variance analysis, accurately identifies the disturbance type, avoiding this risk.

[0057] In this embodiment, the setting of the dynamic threshold, the linkage adjustment rules of the inner and outer loop gains, and the design of the discrimination logic together constitute a parameter self-tuning scheme that can operate stably under complex operating conditions. This scheme forms a closed loop with the aforementioned common-mode excitation identification module: the identification module provides the pressure response time constant, and this module adjusts the controller parameters according to the time constant. The adjusted parameters affect the result of the next identification. This closed-loop design enables the system to continuously track changes in operating conditions and maintain control performance.

[0058] It should be noted that the operating condition discrimination logic in this embodiment distinguishes between changes in system dynamic characteristics and local load disturbances. Global operating condition changes specifically refer to the drift in system dynamic characteristics caused by changes in physical parameters such as oil temperature, viscosity, and bulk modulus. These changes affect all plungers and the process is relatively slow (on a timescale of minutes). Global load mutations, on the other hand, refer to a sudden overall increase or decrease in external load. While this also causes synchronous changes in the pressure response time constants of the three plungers, the timescale of these changes is on a millisecond scale and is usually accompanied by an instantaneous step jump in pressure amplitude. In this embodiment, the controller, upon detecting a change in the pressure response time constant, combines this with the pressure change rate for comprehensive discrimination: if the pressure change rate exceeds a preset threshold, it is determined to be a load mutation, and feedforward compensation is triggered preferentially rather than parameter adjustment; only when the pressure change rate is below the threshold is it determined to be oil parameter drift, and the controller parameters are adjusted. By introducing the pressure change rate as an auxiliary discrimination criterion, the misjudgment of global load mutations as parameter drift is avoided. In rare cases where oil parameter drift and global load mutation occur simultaneously, the controller prioritizes responding to the load mutation (performing feedforward compensation), and then performs parameter self-tuning after the load stabilizes, ensuring that the system response priority matches the physical process.

[0059] In one embodiment of the present invention, the step of determining a local load disturbance when the variance is not less than a dynamic threshold, calculating the load disturbance increment based on the pressure change and acceleration change of the plunger cavity, and generating a feedforward compensation amount superimposed on the pressure target value of the plunger cavity includes: S64, when the variance is not less than the dynamic threshold or a sudden change in pressure is detected in any plunger cavity, it is determined that there is a local load disturbance in the plunger cavity, and the global controller parameters are locked unchanged; S65, calculate the pressure change based on the real-time pressure signal of the plunger cavity, and obtain a smooth acceleration estimate based on the displacement signal of the plunger cavity through a tracking differentiator to calculate the acceleration change; the calculation of these two changes is completed within each sampling period, ensuring the real-time performance of feedforward compensation; Pressure change: ; Change in acceleration: ; In the two formulas above, This indicates the change in pressure. This indicates the real-time pressure signal (unit: Pa). This represents the pressure signal at the previous sampling time. This represents the change in acceleration. This represents the estimated acceleration value. This represents the estimated acceleration value at the previous sampling time. S66, Calculate the load disturbance increment based on the pressure change and acceleration change: ; in, This indicates the increment of load disturbance. Indicates the cross-sectional area of ​​the plunger. Indicates the mass of the plunger itself. This indicates the change in pressure. Indicates the change in acceleration; S67, the load disturbance increment is converted into a feedforward compensation pressure value, and the feedforward compensation pressure value is multiplied by a preset feedforward gain coefficient and then superimposed on the pressure target value of the plunger cavity to obtain a corrected pressure target value, wherein when the plunger movement speed is lower than a preset threshold, the feedforward gain coefficient is automatically reduced.

[0060] Calculation of feedforward compensation pressure value: ; in, This indicates the feedforward compensation pressure value. This indicates the increment of load disturbance. This represents the cross-sectional area of ​​the plunger. This formula converts the load disturbance increment into pressure dimensions so that it can be superimposed on the target pressure value. The revised formula for the target pressure value: ; in, This indicates the corrected target pressure value. This indicates the target pressure value output by the outer displacement loop. This represents the feedforward gain coefficient. This indicates the feedforward compensation pressure value; As described in steps S64-S67 above, when the controller determines that a local load disturbance exists, i.e., the variance of the pressure response time constant of the three plunger chambers is not less than the dynamic threshold, or when a sudden change in pressure is detected in any plunger chamber (the rate of change of the pressure signal per unit time is calculated; when the rate of change exceeds a preset threshold, it is determined as a sudden change; the preset threshold is determined based on the system's rated pressure, and in this embodiment, it is set to 1% of the rated pressure divided by the sampling period), the controller immediately locks the global controller parameters unchanged and performs feedforward compensation only on the disturbed plunger chamber. The purpose of this design is that local load disturbances only affect a single or partial plunger and should not change the global controller parameters; otherwise, the parameters of other normal plunger chambers would be incorrectly adjusted, thus deteriorating the synchronization performance. By locking the global parameters and performing local compensation only on the disturbed plunger chamber, disturbance isolation is achieved, preventing disturbance propagation.

[0061] The controller first acquires the acceleration estimate of the plunger cavity. Since the displacement signal contains measurement noise, directly performing second-order numerical differentiation on the displacement would severely amplify the noise, rendering the acceleration estimate unusable. Therefore, this embodiment uses a tracking differentiator to process the displacement signal and obtain smooth velocity and acceleration estimates. The design principle of the tracking differentiator is as follows: a second-order system is constructed such that its output tracks the input signal, its first derivative tracks the first derivative of the input signal, and its second derivative tracks the second derivative of the input signal. By reasonably setting the velocity factor and filter factor of the tracking differentiator, a balance can be achieved between tracking speed and noise suppression. In this embodiment, the velocity factor is set to 100, and the filter factor is set to 5 times the sampling period, i.e., 10 milliseconds. The velocity factor determines the tracking speed of the input signal; a larger value results in faster tracking but decreased noise suppression capability. The filter factor determines the filtering strength; a larger value results in stronger noise suppression but increased phase lag.

[0062] The controller calculates the load disturbance increment based on the pressure and acceleration changes. This is significant because the force generated by the pressure change is partly used to overcome the plunger's own inertia, and the remainder represents the change in load force. This change in load force encompasses the combined effects of external load changes, load distribution changes, and load inertia, eliminating the need to model the load mass. This approach avoids the ambiguity of mass definition in rigidly coupled load systems.

[0063] The controller converts the load disturbance increment into a feedforward compensation pressure value, which is the load disturbance increment divided by the plunger cross-sectional area. This feedforward compensation pressure value signifies the pressure that needs to be increased or decreased from the current pressure to counteract the load disturbance. When the load disturbance increases, the feedforward compensation pressure value is positive, indicating that pressure needs to be increased to counteract the load; when the load disturbance decreases, the feedforward compensation pressure value is negative, indicating that pressure needs to be decreased to accommodate the reduced load.

[0064] The controller multiplies the feedforward compensation pressure value by a preset feedforward gain coefficient and then adds it to the target pressure value of the plunger cavity to obtain the corrected target pressure value. The feedforward gain coefficient ranges from 0 to 1, and in this embodiment, it is set to 0.8 under normal operating conditions. The purpose of a feedforward gain coefficient less than 1 is to avoid overcompensation: since there is a certain error in the calculation of load disturbance increment, complete compensation may introduce new errors. Retaining a 20% safety margin allows the system to achieve a balance between compensation effect and stability. The corrected target pressure value is used as the new setpoint for the inner pressure loop, causing the inner pressure loop to adjust the servo valve in advance and actively output hydraulic pressure to offset the impact of sudden load changes.

[0065] In this embodiment, the feedforward gain coefficient is dynamically adjusted according to the piston's movement speed. When the piston's movement speed is lower than a preset threshold, the controller automatically reduces the feedforward gain coefficient. In this embodiment, the speed threshold is set to 2 mm / s. When the speed is lower than this threshold, the feedforward gain coefficient decreases from 0.8 to 0.2. This design stems from the nonlinear characteristics of static friction in hydraulic systems. At extremely low speeds, the friction between the piston and the cylinder exhibits the Stribeck effect, meaning that the friction force changes nonlinearly with speed, and the lower the speed, the more drastic the change in friction force. If a high feedforward gain is used at low speeds, small errors in the calculation of load disturbance increments may be amplified, causing fluctuations in the feedforward compensation amount, which in turn triggers frequent adjustments of the servo valve, resulting in a creeping phenomenon in the piston movement. By reducing the feedforward gain coefficient, the feedforward compensation intensity is weakened, avoiding compensation oscillations caused by static friction nonlinearity. When the speed recovers above the threshold, the feedforward gain coefficient returns to its normal value.

[0066] In the three-hole plunger system addressed in this invention, the feedforward compensation mechanism and the dual closed-loop control structure work in synergy. Specifically, the inner pressure loop is responsible for suppressing existing pressure disturbances, while the feedforward compensation is responsible for actively canceling them as they occur. The combination of the two achieves both active and passive suppression of load disturbances.

[0067] In this embodiment, the feedforward compensation mechanism and the aforementioned multi-plunger cavity consistency analysis mechanism work in synergy. The consistency analysis mechanism is responsible for identifying the type of disturbance: when the variance is less than a threshold, it is determined to be a global parameter drift, which is handled by the parameter self-tuning module; when the variance is not less than the threshold, it is determined to be a local load disturbance, which is handled by the feedforward compensation module. This division of labor enables the system to take the most appropriate handling method for disturbances of different natures, avoiding the parameter self-tuning module from incorrectly adjusting the global parameters due to local disturbances, and also avoiding the feedforward compensation module from performing ineffective compensation due to global parameter drift. Together, they constitute a complete adaptive control system capable of simultaneously dealing with global parameter drift and local load disturbances.

[0068] In this embodiment, the feedforward compensation mechanism works particularly closely with the pressure inner loop. The corrected pressure target value output by the feedforward compensation is directly input into the pressure inner loop, which executes this correction command with its rapid response capability. Since the response speed of the pressure inner loop is 3-5 times that of the displacement outer loop, the feedforward compensation can complete pressure adjustment before the displacement outer loop detects the displacement deviation, achieving imperceptible suppression of load surges. Experimental data shows that within the first sampling period after a load surge occurs, the pressure inner loop has already begun to respond to the feedforward compensation command, while the displacement outer loop has not yet detected a measurable displacement deviation. This time-scale matching is key to the effective functioning of feedforward compensation.

[0069] like Figure 2 As shown, the present invention also provides a three-hole plunger pair motion synchronization control system, comprising: The signal acquisition module is used to acquire the real-time displacement signals of the three plungers and the real-time pressure signals of the three plunger chambers. The error synthesis module is used to calculate the tracking error between each plunger and the target displacement based on the real-time displacement signal, and to calculate the synchronization error between each plunger based on the tracking error, and to synthesize the tracking error and the synchronization error into a comprehensive displacement error signal for each plunger. The outer loop displacement control module is used to perform PID control of the outer loop displacement based on the comprehensive displacement error signal and output the target pressure value of each plunger. The pressure inner loop control module is used to perform pressure inner loop PID control based on the difference between the pressure target value and the real-time pressure signal, and output the servo valve control voltage of each plunger to drive the servo valve to act. The operating condition identification module is used to periodically apply a common-mode step excitation signal to the pressure inner ring of each of the three plunger chambers simultaneously during system operation, collect the response curve of each pressure inner ring to the step excitation signal, and extract the pressure response time constant of each plunger chamber based on the response curve. The decision module is used to analyze the consistency of the responses of the three plunger chambers based on the pressure response time constant. When the consistency meets the preset conditions, it is determined to be a global operating condition change. The controller parameters of the inner pressure PID control and the outer displacement PID control are adjusted according to the operating condition characteristics represented by the pressure response time constant. When the variance is not less than the dynamic threshold, it is determined to be a local load disturbance. The pressure change and acceleration change of the plunger chamber are obtained to generate a feedforward compensation amount superimposed on the pressure target value of the plunger chamber.

[0070] The present invention also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of a three-hole plunger pair motion synchronization control method.

[0071] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of a method for synchronous control of the motion of a three-hole plunger pair.

[0072] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, apparatus, article, or method that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, apparatus, article, or method. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, apparatus, article, or method that includes that element.

[0073] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for synchronous control of the motion of a three-hole plunger pair, characterized in that, include: Acquire the real-time displacement signals of the three plungers and the real-time pressure signals of the three plunger chambers; The tracking error between each plunger and the target displacement is calculated based on the real-time displacement signal, and the synchronization error between each plunger is calculated based on the tracking error. The tracking error and the synchronization error are then combined into a comprehensive displacement error signal for each plunger. Based on the displacement comprehensive error signal, perform displacement outer loop PID control to output the pressure target value of each plunger; The pressure inner loop PID control is performed based on the difference between the pressure target value and the real-time pressure signal, and the servo valve control voltage of each plunger is output to drive the servo valve to act. During system operation, a common-mode step excitation signal is periodically applied to the pressure inner rings of each of the three plunger chambers simultaneously, and the response curves of each pressure inner ring to the step excitation signal are collected. The pressure response time constant of each plunger chamber is extracted based on the response curves. The consistency of the responses of the three plunger chambers is analyzed based on the pressure response time constant. When the consistency meets the preset conditions, it is determined to be a global operating condition change. The controller parameters of the inner pressure PID control and the outer displacement PID control are adjusted according to the operating condition characteristics represented by the pressure response time constant. When the consistency does not meet the preset conditions, it is determined to be a local load disturbance. The pressure change and acceleration change of the plunger chamber are obtained to generate a feedforward compensation amount that is superimposed on the pressure target value of the plunger chamber.

2. The method for synchronous control of the motion of a three-hole plunger pair according to claim 1, characterized in that, The steps of calculating the tracking error between each plunger and the target displacement based on the real-time displacement signal, calculating the synchronization error between each plunger based on the tracking error, and weighted summing the tracking error and the synchronization error to obtain the comprehensive displacement error signal of each plunger include: The displacement value of each plunger at the current sampling time is obtained based on the real-time displacement signal, and the target displacement value at the current sampling time is obtained based on the preset target displacement curve. The tracking error of each plunger is obtained based on the target displacement value and the displacement value. The displacement difference between any two different plungers is calculated based on the displacement values ​​of the three plungers, thus obtaining the synchronization error set; The tracking error and the synchronization error are weighted and summed to obtain the displacement comprehensive error signal.

3. The method for synchronous control of the motion of a three-hole plunger pair according to claim 1, characterized in that, The step of performing outer-loop PID control of displacement based on the comprehensive displacement error signal and outputting the target pressure value of each plunger includes: The proportional gain and integral gain of the displacement outer loop PID controller are obtained, wherein the proportional gain and integral gain are dynamically adjusted according to the global operating condition identification results. The displacement comprehensive error signal is input into the displacement outer loop PID controller, and the pressure target value increment is calculated according to the incremental PID control law. The pressure target value at the previous sampling time is added to the pressure target value increment to obtain the pressure target value at the current sampling time of each plunger, and the pressure target value is output as the input of the pressure inner loop.

4. The method for synchronous control of the motion of a three-hole plunger pair according to claim 1, characterized in that, The step of performing pressure inner-loop PID control based on the difference between the pressure target value and the real-time pressure signal, outputting the servo valve control voltage for each plunger, and driving the servo valve to operate includes: The proportional gain and integral gain of the pressure inner loop PID controller are obtained, wherein the proportional gain and integral gain are dynamically adjusted based on the global operating condition identification results. The pressure error signal is obtained based on the target pressure value and the real-time pressure signal; The pressure error signal is input into the pressure inner loop PID controller, and the control voltage increment is calculated according to the incremental PID control law. The control voltage at the previous sampling moment is added to the control voltage increment to obtain the servo valve control voltage at the current sampling moment, and the control voltage is output to the servo valve to drive the servo valve to adjust the plunger chamber pressure.

5. The method for synchronous control of the motion of a three-hole plunger pair according to claim 1, characterized in that, The step of periodically applying a common-mode step excitation signal to the pressure inner rings of each of the three plunger chambers simultaneously during system operation, acquiring the response curves of each pressure inner ring to the step excitation signal, and extracting the pressure response time constant of each plunger chamber based on the response curves includes: During normal system operation, a common-mode step excitation signal with the rated amplitude is simultaneously applied to the pressure inner ring of each of the three plunger chambers at preset identification cycles, wherein the excitation signals of the three plunger chambers have the same amplitude and phase. The response data of each plunger chamber pressure sensor to the step excitation signal are collected at a preset sampling frequency; The response data were fitted with an exponential model using the least squares method. By minimizing the fitting residual, the pressure response time constant of each plunger cavity is obtained.

6. The method for synchronous control of the motion of a three-hole plunger pair according to claim 1, characterized in that, The step of analyzing the consistency of the responses of the three plunger chambers based on the pressure response time constant, determining a global operating condition change when the consistency meets a preset condition, and adjusting the controller parameters of the pressure inner loop PID control and the displacement outer loop PID control based on the operating condition characteristics represented by the pressure response time constant includes: The mean and variance were calculated based on the pressure response time constants of the three plunger chambers. Calculate the dynamic threshold based on the current mean; When the variance is less than the dynamic threshold, it is determined to be a global operating condition change, and the controller parameters are adjusted according to the mean; wherein, the proportional gain and integral gain of the pressure inner loop PID control are adjusted inversely proportional to the mean, and the proportional gain of the displacement outer loop PID control is adjusted inversely proportional to the square root of the mean.

7. The method for synchronous control of the motion of a three-hole plunger pair according to claim 6, characterized in that, The step of determining a local load disturbance when the consistency does not meet the preset conditions, and obtaining the pressure change and acceleration change of the plunger cavity to generate a feedforward compensation amount superimposed on the target pressure value of the plunger cavity includes: When the variance is not less than the dynamic threshold or a sudden change in pressure is detected in any plunger cavity, it is determined that there is a local load disturbance in the plunger cavity, and the global controller parameters are locked unchanged. The pressure change is calculated based on the real-time pressure signal of the plunger cavity, and the acceleration estimate is obtained by a tracking differentiator based on the displacement signal of the plunger cavity to calculate the acceleration change. Calculate the load disturbance increment based on the pressure change and acceleration change; The load disturbance increment is converted into a feedforward compensation pressure value, and the feedforward compensation pressure value is combined with a preset feedforward gain coefficient and superimposed on the pressure target value of the plunger cavity to obtain a corrected pressure target value. When the plunger movement speed is lower than a preset threshold, the feedforward gain coefficient is automatically reduced.

8. A three-hole plunger pair motion synchronization control system, characterized in that, include: The signal acquisition module is used to acquire the real-time displacement signals of the three plungers and the real-time pressure signals of the three plunger chambers. The error synthesis module is used to calculate the tracking error between each plunger and the target displacement based on the real-time displacement signal, and to calculate the synchronization error between each plunger based on the tracking error, and to synthesize the tracking error and the synchronization error into a comprehensive displacement error signal for each plunger. The outer loop displacement control module is used to perform PID control of the outer loop displacement based on the comprehensive displacement error signal and output the target pressure value of each plunger. The pressure inner loop control module is used to perform pressure inner loop PID control based on the difference between the pressure target value and the real-time pressure signal, and output the servo valve control voltage of each plunger to drive the servo valve to act. The operating condition identification module is used to periodically apply a common-mode step excitation signal to the pressure inner ring of each of the three plunger chambers simultaneously during system operation, collect the response curve of each pressure inner ring to the step excitation signal, and extract the pressure response time constant of each plunger chamber based on the response curve. The decision module is used to analyze the consistency of the responses of the three plunger chambers based on the pressure response time constant. When the consistency meets the preset conditions, it is determined to be a global operating condition change. The controller parameters of the inner pressure PID control and the outer displacement PID control are adjusted according to the operating condition characteristics represented by the pressure response time constant. When the variance is not less than the dynamic threshold, it is determined to be a local load disturbance. The pressure change and acceleration change of the plunger chamber are obtained to generate a feedforward compensation amount superimposed on the pressure target value of the plunger chamber.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 7.

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