Speed self-adaptive control system of liquid die forging forming process

Abstract

The application relates to the technical field of liquid die forging equipment control, and particularly discloses a speed self-adaptive regulation and control system for a liquid die forging forming process, which comprises: an equipment operation controller used for generating a control signal according to process information and transmitting the control signal to a hydraulic transmission hybrid servo system; the equipment operation controller is used for calculating a PLC analog output voltage by using a target speed curve in process parameters according to a hydraulic transmission principle, generating a control signal, or generating a control signal according to a speed deviation of a sliding block and a change rate of the speed deviation, or generating a control signal according to a multi-dimensional prediction and fuzzy logic fusion control strategy; and the hydraulic transmission hybrid servo system is used for driving the sliding block to move according to the control signal. The application realizes accurate speed control of the hydraulic transmission hybrid servo system and effectively reduces the requirement for the accuracy of hydraulic components.

Description

Technical Field

[0001] This invention relates to the field of liquid forging equipment control technology, and in particular to a speed adaptive control system for liquid forging forming process. Background Technology

[0002] Liquid forging (also known as extrusion casting) is an advanced near-net-shape forming process in which liquid metal is poured directly into a metal mold cavity and formed in one step under high pressure, undergoing a liquid-semi-solid-solid process. This process combines the advantages of casting filling and forging densification, enabling the production of high-quality parts with dense microstructure and excellent mechanical properties.

[0003] In liquid forging, the movement speed of the equipment slide is one of the core process parameters affecting the quality of the casting. The forming process requires the equipment to meet the functional requirements of low-speed filling, micro-speed extrusion, and high-pressure solidification. In the liquid-semi-solid-solid one-step forming process, the equipment needs to perform forging extrusion at a slow speed to ensure the uniformity of the workpiece's grain structure and mechanical properties. The precision of speed control directly determines the final quality of the casting.

[0004] In the existing technology, the speed control of liquid forging equipment has the following shortcomings: (1) When facing the strong nonlinear and time-varying characteristics of liquid metal gradually turning into solid during liquid forging, the traditional PID controller has difficulty in balancing control accuracy and response speed. Especially in the micro-speed extrusion stage, the load gradually turns from liquid to solid, and the system parameters change drastically. The traditional control method has difficulty in ensuring the stability of the speed; (2) There is a lack of an adaptive adjustment mechanism based on load mode changes. It is impossible to dynamically adjust the control parameters according to the real-time changes in the load state during the forming process, which makes the inherent chattering problem of sliding mold control particularly prominent in practical applications; (3) High-precision speed control heavily relies on high-performance hydraulic servo components. Summary of the Invention

[0005] This invention aims to solve the aforementioned problems. To this end, this invention provides a speed adaptive control system for a liquid forging process. By integrating modal prediction and adaptive sliding mode control theories, a hydraulic-electric transmission control model is established. Combining multidimensional prediction and fuzzy logic fusion control strategies, precise speed control of the hydraulic transmission hybrid servo system is achieved, effectively reducing the precision requirements on the hydraulic components themselves.

[0006] This invention also provides a speed adaptive control system for a liquid forging process, the technical solution of which includes: The human-machine interaction monitoring module is used for setting process parameters and displaying process information in real time. A multi-source sensor detection module is used to acquire process information in real time and feed it back to the equipment operation controller and the human-machine interaction monitoring module; the process information includes the displacement and speed of the slider, as well as the pressure changes and load status of the hydraulic transmission hybrid servo system; The equipment operation controller is used to generate control signals based on process information and transmit them to the hydraulic transmission hybrid servo system; the equipment operation controller includes a approach control module, a sliding mode control module, a control strategy fusion module, and a position control module; The approach control module is used to calculate the PLC analog output voltage based on the hydraulic transmission principle and the target speed curve in the process parameters, and then generate a control signal. The sliding mode control module is used to generate control signals based on the speed deviation of the slider and the rate of change of the speed deviation; The control strategy fusion module is used to select either the approach control module or the sliding mode control module to generate control signals based on the speed deviation of the slider. The position control module is used to calculate the predicted deceleration displacement and current remaining displacement of the slider based on the process information, and to determine whether to start the position control mode. When the position control mode is started, a control signal is generated based on the multi-dimensional prediction and fuzzy logic fusion control strategy. A hydraulic transmission hybrid servo system is used to drive the slider to move according to control signals.

[0007] Furthermore, at the same time, a control signal is generated by one of the approach control module, sliding mode control module, and position control module and output to the hydraulic transmission hybrid servo system.

[0008] Furthermore, in the sliding mode control module, the speed following error is selected as the sliding surface, which is defined as follows: in, Let e ​​be the sliding surface and 'e' be the velocity deviation. Let λ be the rate of change of the velocity deviation, and λ be the sliding surface parameter. Sliding surface satisfies , for The first derivative; The sliding mode control law is: in, The system speed gain coefficient; The desired speed of the slider; ε is the PLC analog output voltage output by the sliding mode control module; k is the exponential approach coefficient; and sign(s) is the sign function.

[0009] Furthermore, the sliding surface parameters are adaptively adjusted according to the load rate and load change rate. When the load changes drastically, the sliding surface parameters are reduced to reduce chattering caused by sliding control. When the load changes gently, the sliding surface parameters are increased to improve the convergence speed and make the slider speed run smoothly.

[0010] Furthermore, the formula for calculating the sliding surface parameters is as follows: Where η is the current load rate; This represents the load change rate. These are the lower limits of the sliding surface parameters; This represents the upper limit value of the sliding surface parameters; This is the load weighting coefficient; This is the weighting coefficient for the load change rate.

[0011] Furthermore, the control strategy fusion module selects either the approach control module or the sliding mode control module to generate a control signal based on the speed deviation of the slider. Specifically, when the speed deviation is outside the preset switching threshold range, the approach control module generates a control signal; when the speed deviation is within the preset switching threshold range, the sliding mode control module generates a control signal.

[0012] Furthermore, the position control module determines whether to activate the position control mode, specifically as follows: When the predicted deceleration displacement is greater than the current remaining distance, the position control module generates a control signal; The formula for predicting deceleration displacement is: in, The predicted deceleration displacement of the slider. denoted as 'a', where 'a' is the actual velocity of the slider and 'a' is the acceleration of the slider.

[0013] Furthermore, the multidimensional prediction and fuzzy logic fusion control strategy is a triple control strategy that combines linear fitting predictive control of the proportional relief valve, pressure-flow-pressure compensation, and load PID dynamic optimization. Based on the slider's speed, acceleration, and position deviation, the servo motor speed and the proportional relief valve opening are calculated.

[0014] Furthermore, the hydraulic transmission hybrid servo system includes a hydraulic pump set, which adopts a combination configuration of hydraulic pumps with different displacements. In view of the requirements of the hydraulic transmission hybrid servo system for small flow rate and flow rate switching accuracy, the variable range is broadened by speed-flow rate analysis fitting.

[0015] Furthermore, the hydraulic transmission hybrid servo system includes a high-frequency response proportional valve, which adopts a multi-stage joint control method, cascading proportional valves of different specifications to achieve a combination of coarse and fine adjustment.

[0016] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: (1) This invention integrates approach control and sliding mode control. When the speed deviation is large, approach control is used to quickly approach the target speed. When the speed deviation enters the set threshold range, sliding mode control is switched to perform precise tracking, realizing the seamless switching between the two control strategies and taking into account both the fast response characteristics and steady-state tracking accuracy of the system.

[0017] (2) The present invention uses a sliding mold control module to adaptively adjust the sliding mold surface parameters according to the modal change law of the load gradually changing from liquid to solid during the liquid forging process. When the load changes drastically, the sliding mold surface parameters are reduced to reduce the chattering caused by the sliding mold control. When the load changes gently, the sliding mold surface parameters are increased to improve the convergence speed, so that the slider speed runs more smoothly and effectively meets the slider speed control requirements of the low-speed filling stage, micro-speed extrusion stage and high-pressure solidification stage of the liquid forging process.

[0018] (3) The present invention adopts a multidimensional prediction and fuzzy logic fusion control strategy, combined with proportional overflow valve linear fitting prediction control, pressing speed-flow pressure compensation and load PID dynamic optimization, to achieve high-precision flexible adjustment of pressure during the pressing process, with pressure control accuracy reaching ±0.2MPa and slider positioning accuracy ±0.2mm.

[0019] (4) The hydraulic pump group of the present invention adopts a combination configuration of hydraulic pumps with different displacements. By expanding the variable range through speed and flow analysis fitting, it realizes the performance substitution of imported proportional variable pumps. At the same time, the abnormal detection and protection module monitors abnormal states such as abnormal pressure rise, speed runaway, and temperature over-limit in real time, realizes oil temperature graded control and emergency deceleration shutdown protection, and ensures the safety and reliability of the molding process.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a structural block diagram provided by the present invention.

[0023] Figure 2This is a schematic diagram of the load / sliding surface parameters of the liquid forging process provided by the present invention.

[0024] Figure label: 1. Human-machine interaction monitoring module; 2. Multi-source sensor detection module; 3. Equipment operation controller; 4. Hydraulic transmission hybrid servo system; 5. Anomaly detection and protection module. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention but should not be used to limit the scope of this invention.

[0026] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0027] The following is combined Figure 1 and Figure 2 The present invention will be further described in detail below, including a speed adaptive control system for a liquid forging process: In this embodiment, as Figure 1 As shown, a speed adaptive control system for liquid forging forming process is provided, which is applied to liquid forging equipment. The liquid forging equipment is mainly used for liquid forging forming processes of materials such as aluminum alloys. The system includes a human-machine interaction monitoring module 1, a multi-source sensor detection module 2, an equipment operation controller 3, a hydraulic transmission hybrid servo system 4, and an anomaly detection and protection module 5.

[0028] The human-machine interaction monitoring module is used for setting process parameters and displaying process information in real time.

[0029] The human-machine interface monitoring module includes an industrial touchscreen, a data storage unit, and a remote communication unit. The industrial touchscreen displays real-time process information such as the slider's running speed curve, displacement curve, pressure curve, and load status, and provides settings and modifications for process parameters such as the target speed curve, initial parameters of the sliding surface, and approach control calibration table. The data storage unit stores complete process data for each molding process in an industrial database for process optimization and quality traceability. The remote communication unit supports the Ethernet communication protocol, enabling data interaction with the host computer management system.

[0030] The multi-source sensor detection module is used to acquire process information in real time and feed it back to the equipment operation controller and the human-machine interaction monitoring module; the process information includes the displacement and speed of the slider, as well as the pressure changes and load status of the hydraulic transmission hybrid servo system.

[0031] The multi-source sensor detection module includes a displacement sensor, a pressure sensor, and a speed detection unit. The displacement sensor is an absolute linear displacement sensor, mounted on the piston rod of the hydraulic cylinder, used to detect the displacement of the slider in real time, enabling digital position setting. The speed detection unit obtains the real-time movement speed of the slider by performing differential calculations on the displacement signal. The pressure sensor is installed in key components of the hydraulic transmission hybrid servo system to detect pressure changes and load status of the system in real time.

[0032] The equipment operation controller is used to generate control signals based on process information and transmit them to the hydraulic transmission hybrid servo system.

[0033] The equipment operation controller is the core control component of this system. It integrates approach control algorithm, sliding mode control algorithm, and multi-dimensional prediction and fuzzy logic fusion control strategy to meet the slider speed control requirements of the low-speed filling stage (alloy is in liquid stage), micro-speed extrusion stage (alloy is in semi-solid stage) and high-pressure solidification stage (alloy is in solid stage) of the liquid forging process. It can effectively control the hydraulic transmission hybrid servo system and achieve precise regulation of the equipment movement speed.

[0034] The equipment operation controller includes a approach control module, a sliding mode control module, a control strategy fusion module, and a position control module.

[0035] The approach control module is used to calculate the PLC analog output voltage based on the hydraulic transmission principle and the target speed curve in the process parameters, and then generate a control signal.

[0036] The approach control module establishes a linear relationship model between the slider's running speed and the servo motor's rotational speed based on the hydraulic transmission principle. By directly outputting the linear calibration value of the servo motor's rotational speed, it achieves control over the approach speed to the sliding surface and the target speed. The linear relationship model is as follows: in, The desired velocity of the slider is determined based on the target velocity curve. For the pump's displacement, The PLC analog output voltage. This is the voltage setpoint when the servo motor reaches its maximum speed. Let R be the maximum speed of the servo motor and R be the radius of the hydraulic cylinder. From this, the desired speed of the slider can be obtained. With servo motor control voltage They are directly proportional.

[0037] The sliding mode control module is used to generate control signals based on the speed deviation of the slider and the rate of change of the speed deviation.

[0038] The core principle of sliding mode control is as follows: By designing discontinuous control laws, the system state is forced to move along a preset sliding surface, achieving robustness against disturbances and parameter changes. In the system's state space, the switching surface s=0 divides the state space into two parts: s>0 and s<0. When all points in a certain region on the switching surface are termination points, that is, when a moving point reaches the vicinity of the switching surface, it tends towards that point from both sides, this region is called the sliding dynamic region, and the system's motion in the sliding region is called sliding motion. According to the requirement that all moving points in the sliding mode region must be termination points, when a moving point reaches the vicinity of the switching surface s(x)=0, it must satisfy... This inequality corresponds to the Lyapunov function. Stability conditions.

[0039] The sliding surface enables the slider to quickly track the desired speed and suppresses parameter uncertainties and external disturbances; the speed following error is selected as the sliding surface, which is defined as follows: in, denoted as the sliding surface, and e as the speed deviation, which is the difference between the desired speed and the actual speed of the slider; it is calculated based on the target speed curve in the process parameters and the real-time movement speed of the slider measured by the multi-source sensor detection module. λ is the rate of change of velocity deviation, i.e., the first derivative of velocity deviation; λ is the sliding surface parameter, λ>0, which determines the error convergence rate.

[0040] The stability condition of sliding mode control satisfies the necessary condition of the Lyapunov function, that is, when the moving point reaches the vicinity of the switching surface s(x)=0, the following condition is met: in, for The first derivative.

[0041] This inequality corresponds to the Lyapunov function of the system. derivative This ensures that the system is stable on the switching surface s=0, so that all moving points in the sliding mode area are termination points, and the system is attracted to move on the sliding mode surface once the system state reaches the sliding mode surface. for The first derivative.

[0042] The sliding mode control law is designed using an exponential reaching law. The reaching law is as follows: Where ε is the switching gain, ε>0; k is the exponential approach coefficient, k>0; sign(s) is the sign function.

[0043] Based on the linear relationship between the slider speed and the PLC analog output voltage, the sliding mode control law can be obtained from the reaching law condition as follows: in, The system velocity gain coefficient, ; s is the desired velocity of the slider; s is the sliding surface; These are the parameters of the sliding surface; The PLC analog output voltage is the output voltage of the sliding mode control module.

[0044] In this control law, / For the feedforward control component based on the linear model of hydraulic transmission, The sliding mode feedback correction component ensures the speed tracking of the system under nominal operating conditions, while the feedback component ensures the robustness of the system under disturbances and parameter changes.

[0045] The input to the sliding mode control module is: the desired speed of the slider. (Determined by the target speed curve), load status (acquired by a pressure sensor, used for adaptive adjustment of sliding surface parameters). The output of the sliding mode control module is: the PLC analog output voltage, which is transmitted as a control signal to the servo driver of the hydraulic transmission hybrid servo system.

[0046] The sliding mold control module includes a load mode prediction unit. This unit is used to predict the sliding mold surface parameters based on the modal change pattern of the load as it gradually changes from a liquid to a solid state during liquid forging. Perform adaptive adjustment. Reduce [load] when there are drastic load changes. To reduce chattering caused by sliding mode control, increase the load when the load changes gradually. This improves the convergence speed and makes the slider move more smoothly. For example... Figure 2As shown, during the liquid stage, the load is low, and the values ​​of the sliding surface parameters are relatively large (e.g., (Taking values ​​from 5.0 to 8.0), the system reacts aggressively and is highly sensitive to speed deviations, requiring rapid attainment of the target speed, with minimal chattering impact; in the semi-solid stage, load changes drastically, and sliding surface parameters continuously decrease (e.g., (Reduced to 2.0~5.0), the system response is moderate and balanced, which can correct deviations quickly without excessive chattering; in the solid state stage, the load is high and stable, and the changes are gradual. The values ​​of the sliding surface parameters are small and increase gradually and slightly (e.g. (Take a value of 0.5~2.0). The system responds conservatively and gently to speed deviations, prioritizing stable operation and avoiding vibration that could damage the workpiece structure.

[0047] The adaptive adjustment method for sliding surface parameters is as follows: based on the modal change law of the load gradually changing from liquid to solid, a system is established... With load rate and load change rate The linear calibration relationship between them is calculated using the following formula: Where η is the current load rate, , The current load force is determined based on the load status measured by the multi-source sensor detection module. This is the system's maximum rated load capacity; Let t be the load change rate, and t be time. This represents the lower limit value of the sliding surface parameters, with a range of 0.5 to 1.0. This represents the upper limit value of the sliding surface parameters, with a range of 5.0 to 8.0. This is the load weighting coefficient, with a value ranging from 0.4 to 0.6; The load change rate weighting coefficient has a value range of 0.3 to 0.5 and satisfies α + β ≤ 1.

[0048] In the initial stage of load change (low-speed charging phase), the load rate Smaller and When it is large, decrease The value is used to reduce chattering caused by sliding mode control; when the load changes and tends to reach a steady state in the later stage (micro-speed extrusion stage). Increase Approaching zero, increasing This value is used to improve the convergence speed and make the slider speed run more smoothly.

[0049] The control strategy fusion module is used to select either the approach control module or the sliding mode control module to generate control signals based on the speed deviation of the slider.

[0050] Specifically, when the speed deviation is outside the preset switching threshold range, the approach control mode is adopted, and the approach control module generates the control signal; when the speed deviation is within the preset switching threshold range, the sliding mode control mode is adopted, and the sliding mode control module generates the control signal.

[0051] The control strategy fusion module integrates approach control and sliding mode control. When the speed deviation is large, approach control is used to quickly approach the target speed. When the speed deviation enters the set threshold range, it switches to sliding mode control for precise tracking, realizing a seamless switching between the two control strategies.

[0052] For liquid forging of aluminum alloys (such as A356 and 6061), the switching threshold range is set to ±0.5 mm / s; that is, -0.5 mm / s ≤ When the speed is ≤0.5mm / s, the sliding mode control mode is used; <-0.5mm / s or 0.5mm / s< When this occurs, a approach control mode is adopted.

[0053] The position control module is used to calculate the predicted deceleration displacement and current remaining displacement of the slider based on the process information, and to determine whether to start the position control mode. When the position control mode is started, a control signal is generated based on the multi-dimensional prediction and fuzzy logic fusion control strategy.

[0054] The position control module calculates the current remaining distance based on the process information; and calculates the predicted deceleration displacement of the slider based on the uniformly decelerated linear motion model. The calculation formula is as follows: in, The predicted deceleration displacement of the slider. Let be the actual velocity of the slider, 'a' be the acceleration of the slider, 'a=(Fs-Fk) / m', where Fs is the pressure provided by the slider, Fk is the load resistance, and m is the mass of the slider.

[0055] When the predicted deceleration displacement is greater than the current remaining distance, it indicates that deceleration will be carried out according to the current speed and acceleration, and the slider will exceed the target position. At this time, the position control mode is immediately activated, switching from the sliding mode control mode to the position control mode. That is, the module that generates the control signal is changed from the sliding mode control module to the position control module.

[0056] The multi-dimensional prediction and fuzzy logic fusion control strategy is a triple control strategy combining proportional relief valve linear fitting predictive control, pressing speed-flow-pressure compensation, and load PID dynamic optimization. Based on the slider's speed, acceleration, and position deviation, the servo motor speed and proportional relief valve opening are calculated, achieving high-precision flexible adjustment of pressure during the pressing process, with a pressure control accuracy of ±0.2MPa. Specifically, the proportional relief valve linear fitting predictive control predicts the pressure output of the controlled object by linearly fitting the proportional relief valve's command value-pressure characteristic curve; the pressing speed-flow-pressure compensation linearly compensates for the proportional relief valve's output command value based on different slider operating speeds, compensating for the different effects on pressure caused by different flow rates passing through the proportional pressure control valve; and the load PID dynamic optimization dynamically adjusts the output command value within a small range of ±10 from the command value using a PID control algorithm.

[0057] The multidimensional prediction and fuzzy logic fusion control strategy is as follows: The fuzzy controller uses slider speed, acceleration, and position deviation as input variables, and servo motor speed and proportional relief valve opening as output variables. The fuzzy subsets of the input variables are all {negative (N), zero (Z), positive (P)}. The fuzzy subsets of the output variable servo motor speed are {negative large (NB), negative small (NS), zero (ZO), positive small (PS), positive large (PB)}. The fuzzy subsets of the output variable proportional relief valve opening are {very small (VS), small (S), medium (M), large (L), very large (VL)}. The fuzzy rule base contains 3×3×3=27 rules. The Mamdani inference method is used for fuzzy inference, and the centroid method is used for defuzzification to output precise control quantities, achieving a slider positioning accuracy of ±0.2mm.

[0058] The fuzzy rule base is built based on the following control strategies: When the position deviation is positive (the slider has not reached the target position), the motor speed is adjusted according to the velocity and acceleration to approach the target. When the position deviation is close to zero and the speed is positive, increase the opening of the relief valve to achieve deceleration and precise positioning. When both velocity and acceleration are negative, reduce the opening of the relief valve to apply braking pressure.

[0059] The specific rules are shown in Table 1.

[0060] Table 1

[0061] Fuzzy reasoning employs the Mamdani reasoning method, specifically: The input variables are fuzzified, and the membership degree of each input variable to each fuzzy subset is calculated. Based on the fuzzy rule base and the input membership degree, the minimum value method is used to perform fuzzy inference to obtain the fuzzy set of the output variables; The output fuzzy set is defuzzified using the centroid method to calculate the precise control quantity.

[0062] The system operates in three modes: approach control, sliding mode, and position control. The control strategy fusion module controls the switching between approach control and sliding mode; the position control module controls the switching between sliding mode and position control. The system operates in only one mode at a time. A control signal is generated by one of the approach control, sliding mode, or position control modules and output to the hydraulic transmission hybrid servo system.

[0063] The hydraulic-driven hybrid servo system is used to drive the slider movement according to control signals. The system receives control signals from the equipment's operating controller and uses its hydraulic cylinders to move the slider.

[0064] The hydraulic transmission hybrid servo system includes a servo driver, a servo motor, a hydraulic pump unit, a high-frequency response proportional valve, a proportional relief valve, and a hydraulic cylinder.

[0065] Specifically, when the hydraulic transmission hybrid servo system receives control signals from the approach control module or the sliding mode control module, the servo driver receives the control signals output by the equipment operation controller and drives the servo motor to precisely adjust its speed. The servo motor drives the hydraulic pump unit to output high-pressure oil, which is then regulated by a high-frequency response proportional valve and input into the hydraulic cylinder. The hydraulic cylinder drives the slider to move. When the hydraulic transmission hybrid servo system receives control signals from the position control module, the servo driver receives the control signals output by the equipment operation controller and drives the servo motor to precisely adjust its speed. The servo motor drives the hydraulic pump unit to input high-pressure oil into the hydraulic cylinder, and some of the high-pressure oil flows back to the oil tank through a proportional relief valve. The hydraulic cylinder drives the slider to move.

[0066] The hydraulic pump unit employs a combination of hydraulic pumps with different displacements. Addressing the requirements of the hydraulic transmission hybrid servo system for low flow rates and precise flow switching, speed-flow analysis and fitting are used to broaden the variable range, achieving performance replacement for imported proportional variable pumps. The high-frequency response proportional valves utilize a multi-stage combined control method, cascading proportional valves of different specifications to achieve a combination of coarse and fine adjustment.

[0067] The velocity-flow analysis of the hydraulic pump unit uses the least squares method for linear fitting to establish a precise mapping relationship between the servo motor speed and the slider speed. The fitted straight line equation is as follows: Among them, slope The calculation formula is: The formula for calculating the intercept b is: in, Let i be the value of the independent variable for the i-th data point. Let i be the value of the dependent variable for the i-th data point. For all The mean, For all The mean value of x; a precise mapping relationship between the servo motor speed and the slider speed is established through linear fitting. x is the servo motor speed, and y is the slider speed.

[0068] The hydraulic transmission hybrid servo system adopts a pump-controlled load-sensitive system architecture. The pressure of the variable pump is always higher than the maximum working pressure by a pressure difference. When the pressure difference decreases, the displacement of the variable pump increases, and when the pressure difference increases, the displacement of the variable pump decreases until the pressure difference reaches equilibrium again. The system is equipped with a constant differential pressure reducing type pressure compensation valve, so that the pressure difference at the valve port of the high-frequency response proportional valve remains basically unchanged after compensation. The system flow rate is only related to the valve opening of the directional valve and is not related to the load size.

[0069] The anomaly detection and protection module is used to monitor and protect against abnormal conditions during the liquid forging process in real time. Abnormal conditions include abnormal pressure increases, speed runaway, and temperature exceeding limits. When the oil temperature is below 15°C, only the auxiliary pump is allowed to circulate and preheat the oil. When the oil temperature reaches 45°C, the cooling system is activated. When the oil temperature reaches 60°C, all oil pumps except the lubrication pump and low-pressure control pump stop operating. Emergency deceleration and shutdown protection are immediately triggered when an abnormal speed or pressure is detected.

[0070] The specific process of this system is as follows: During system initialization, the human-machine interaction monitoring module loads process parameters, including the target speed curve, initial parameters of the sliding surface, and the approach control calibration table.

[0071] The multi-source sensor detection module collects process information (multi-source sensor data) and sends it to the equipment operation controller. Among them, the absolute linear displacement sensor detects the slider displacement in real time and obtains the real-time speed through differential calculation; the pressure sensor detects the pressure and load status of the hydraulic transmission hybrid servo system.

[0072] The equipment operation controller calculates the speed deviation of the slider based on process parameters and process information. If the speed deviation is greater than a set threshold, it enters the approach control mode; if the speed deviation is within the threshold range, it enters the sliding mode.

[0073] Approach Control Mode: Based on the hydraulic transmission principle and utilizing the target speed curve in the process parameters, the approach control module calculates the PLC analog output voltage and generates a control signal. This control signal is transmitted to the hydraulic transmission hybrid servo system, where the hydraulic cylinders drive the slider movement.

[0074] When the control strategy fusion module of the device's operating controller detects that the speed deviation is within the threshold range, it switches from the approach control mode to the sliding mode control mode. The approach control module stops working, and the sliding mode control module starts working.

[0075] Sliding mode control mode: The load mode prediction unit of the sliding mode control module calculates the load rate and load change rate based on the load state, and then calculates the sliding surface parameters. The sliding mode control module is based on the sliding surface. The calculation of the control law makes The system generates control signals and outputs them to the servo motor of the hydraulic transmission hybrid servo system. Finally, the hydraulic cylinder of the hydraulic transmission hybrid servo system drives the slider to move.

[0076] In sliding mode, the position control module calculates the predicted deceleration displacement and current remaining displacement of the slider in real time based on the process information.

[0077] The current remaining displacement is calculated as follows: Current remaining displacement = target position - current slider position The target position is determined based on the slider stroke set in the process parameters, and the current position of the slider is acquired in real time by the displacement sensor of the multi-source sensor detection module.

[0078] Specifically, during the liquid forging process, the slider moves from the starting position (top dead center) to the target position (set pressing depth), and the current remaining displacement represents the distance of the slider from the target position.

[0079] When the predicted deceleration displacement is greater than the current remaining distance, the system switches from sliding mode control to position control mode. The sliding mode control module stops working, and the position control module generates the control signal instead.

[0080] Position control mode: The position control module is based on a multi-dimensional prediction and fuzzy logic fusion control strategy. It uses the slider speed, acceleration and position deviation as input variables of the fuzzy controller to calculate the servo motor speed and proportional relief valve opening, generate control signals and output them to the hydraulic transmission hybrid servo system; control the servo motor and proportional relief valve of the hydraulic transmission hybrid servo system, and finally drive the slider movement by the hydraulic cylinder of the hydraulic transmission hybrid servo system.

[0081] This system operates in position control mode until liquid forging is completed.

[0082] Taking the forming of aluminum alloy parts as an example, the usage process of this embodiment is explained. The forming process is divided into three stages: (1) Low-speed filling stage: The slider descends slowly at a speed of 0.5~2mm / s, and the liquid aluminum alloy smoothly enters the mold cavity. The load is small during this stage, and the system adopts the approach control mode to make the slider speed quickly reach the desired speed; when the speed deviation is within the switching threshold range (±0.5mm / s), the approach control mode is switched to the sliding control mode. At this time, λ takes a larger value (such as λ=5), and the speed control accuracy reaches ±0.1mm / s.

[0083] (2) Micro-speed extrusion stage: Under the control of the sliding mold control mode, the slider performs die forging extrusion at a micro speed of 0.02~0.5mm / s, and the aluminum alloy gradually changes from liquid to semi-solid. During this stage, the load increases sharply. The load mode prediction unit detects the increase in the load change rate and automatically reduces the λ value (e.g., λ=1~2), effectively suppressing chattering. The speed control accuracy reaches ±0.01mm / s, ensuring the uniformity of the workpiece grain structure.

[0084] (3) High pressure solidification stage: When the predicted deceleration displacement is greater than the current remaining distance, the sliding mode is switched to the position control mode, and the control strategy fusion module takes over and generates control signals. Through the multi-dimensional prediction and fuzzy logic fusion control strategy, the slider positioning accuracy reaches ±0.2mm and the holding pressure is maintained. The pressure control accuracy reaches ±0.2MPa, and the holding time is set according to the workpiece wall thickness.

[0085] In addition, the hydraulic transmission hybrid servo system is equipped with an independent circulating cooling unit, using 46# anti-wear hydraulic oil, with a specified allowable normal operating oil temperature greater than 15℃ and less than 60℃. The circulating cooling unit is controlled by an abnormality detection and protection module. When the oil temperature is below 15℃, only the auxiliary pump is allowed to start for preheating; when the oil temperature reaches 45℃, the cooling water and hydraulic oil automatically exchange heat in the plate heat exchanger; when the oil temperature reaches 60℃, all oil pumps except the lubrication pump and the low-pressure control pump stop working.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A speed adaptive control system for a liquid forging process, characterized in that, include: The human-machine interaction monitoring module is used for setting process parameters and displaying process information in real time. A multi-source sensor detection module is used to acquire process information in real time and feed it back to the equipment operation controller and the human-machine interaction monitoring module; the process information includes the displacement and speed of the slider, as well as the pressure changes and load status of the hydraulic transmission hybrid servo system; The equipment operation controller is used to generate control signals based on process information and transmit them to the hydraulic transmission hybrid servo system; the equipment operation controller includes a approach control module, a sliding mode control module, a control strategy fusion module, and a position control module; The approach control module is used to calculate the PLC analog output voltage based on the hydraulic transmission principle and the target speed curve in the process parameters, and then generate a control signal. The sliding mode control module is used to generate control signals based on the speed deviation of the slider and the rate of change of the speed deviation; The control strategy fusion module is used to select either the approach control module or the sliding mode control module to generate control signals based on the speed deviation of the slider. The position control module is used to calculate the predicted deceleration displacement and current remaining displacement of the slider based on the process information, and to determine whether to start the position control mode. When the position control mode is started, a control signal is generated based on the multi-dimensional prediction and fuzzy logic fusion control strategy. A hydraulic transmission hybrid servo system is used to drive the slider to move according to control signals.

2. The speed adaptive control system for a liquid forging process as described in claim 1, characterized in that, At the same time, a control signal is generated by one of the approach control module, sliding mode control module and position control module and output to the hydraulic transmission hybrid servo system.

3. The speed adaptive control system for a liquid forging process as described in claim 1, characterized in that, In the sliding mode control module, the speed following error is selected as the sliding surface, and the sliding surface is defined as follows: in, Let e ​​be the sliding surface, and 'e' be the velocity deviation. Let λ be the rate of change of the velocity deviation, and λ be the sliding surface parameter. Sliding surface satisfies , for The first derivative; The sliding mode control law is: in, The system speed gain coefficient; The desired speed of the slider; ε is the PLC analog output voltage output by the sliding mode control module; k is the exponential approach coefficient; and sign(s) is the sign function.

4. The speed adaptive control system for a liquid forging process as described in claim 3, characterized in that, The sliding surface parameters are adaptively adjusted according to the load rate and load change rate. When the load changes drastically, the sliding surface parameters are reduced to reduce chattering caused by sliding control. When the load changes gently, the sliding surface parameters are increased to improve the convergence speed and make the slider speed run smoothly.

5. The speed adaptive control system for a liquid forging process as described in claim 4, characterized in that, The formula for calculating the parameters of the sliding surface is: Where η is the current load rate; This represents the load change rate. These are the lower limits of the sliding surface parameters; This represents the upper limit value of the sliding surface parameters; This is the load weighting coefficient; This is the weighting coefficient for the load change rate.

6. The speed adaptive control system for a liquid forging process as described in claim 1, characterized in that, The control strategy fusion module selects either the approach control module or the sliding mode control module to generate a control signal based on the speed deviation of the slider. Specifically, when the speed deviation is outside the preset switching threshold range, the approach control module generates the control signal; when the speed deviation is within the preset switching threshold range, the sliding mode control module generates the control signal.

7. The speed adaptive control system for a liquid forging process as described in claim 1, characterized in that, The position control module determines whether to activate the position control mode, specifically as follows: When the predicted deceleration displacement is greater than the current remaining distance, the position control module generates a control signal; The formula for predicting deceleration displacement is: in, The predicted deceleration displacement of the slider. denoted as 'a', where 'a' is the actual velocity of the slider and 'a' is the acceleration of the slider.

8. The speed adaptive control system for a liquid forging process as described in claim 1, characterized in that, The multidimensional prediction and fuzzy logic fusion control strategy is a triple control strategy that combines linear fitting predictive control of proportional relief valve, pressure-flow-pressure compensation, and load PID dynamic optimization. Based on the speed, acceleration, and position deviation of the slider, the servo motor speed and the opening degree of the proportional relief valve are calculated.

9. The speed adaptive control system for a liquid forging process as described in claim 1, characterized in that, The hydraulic transmission hybrid servo system includes a hydraulic pump group, which adopts a combination configuration of hydraulic pumps with different displacements. In view of the requirements of the hydraulic transmission hybrid servo system for small flow rate and flow rate switching accuracy, the variable range is broadened by speed-flow rate analysis and fitting.

10. The speed adaptive control system for a liquid forging process as described in claim 1 or 9, characterized in that, The hydraulic transmission hybrid servo system includes a high-frequency response proportional valve, which adopts a multi-stage joint control method, cascading proportional valves of different specifications to achieve a combination of coarse and fine adjustment.

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