Extruder temperature and pressure integrated self-adaptive control method

Abstract

The present application relates to the field of automatic control system of extruder, in particular to a kind of extruder temperature-pressure integrated self-adaptive control method;The present application calculates the mechanical power variation reflecting the melt load state by collecting the actual torque signal and the actual speed signal of screw driving motor;Combined with screw structure parameters, operating speed interval and the working state of each heating zone of barrel, the allowable limit of power variation is generated;When the mechanical power variation exceeds the allowable limit, the torque given variation rate is limited in the inner ring level of screw driving control loop, while the continuous output of head pressure control loop is maintained;And under the premise that the mechanical power variation is limited, the barrel cooling unit is started to participate in thermal regulation according to the barrel wall temperature change trend;The present application can maintain continuous and stable operation of extrusion process, improve the uniformity of melt radial flow and the consistency of product forming.

Description

Technical Field

[0001] This invention relates to the field of automatic control system technology for extruders, and more specifically to an integrated temperature and pressure adaptive control method for extruders. Background Technology

[0002] Extruders are core equipment in the molding and processing of polymer materials. The uniformity of the melt temperature field and the stability of the die pressure directly determine the physical properties and dimensional accuracy of the final product. Existing extruder temperature and pressure control technologies mainly adopt a strategy combining independent temperature control of the barrel sections with screw speed linkage adjustment. This typically involves installing heating coils and cooling fans in each section of the barrel, using thermocouples to collect barrel wall temperature data and transmitting it to a controller for PID calculations, while simultaneously monitoring die pressure through pressure sensors, forming a closed-loop control system with the pressure signal and screw speed or feed rate. Patent CN120080527A discloses a multi-parameter linkage intelligent control system for extruders. This scheme analyzes changes in process parameters such as extruder speed, melt pump speed, and outlet pressure in real time, automatically adjusting various parameters during system operation. The aim is to smooth pressure fluctuations by dynamically changing the extruder speed and feed rate, thereby maintaining the continuity and stability of the extrusion process. In actual use, when the control system rapidly adjusts the screw speed according to the existing logic in order to maintain stable pressure at the die head, a large amount of shear heat will be generated instantly inside the material due to the conversion of mechanical energy, causing the actual temperature of the melt to fluctuate rapidly.

[0003] However, existing technologies rely on temperature sensors typically installed inside the barrel wall. Limited by the enormous heat capacity and thermal conductivity time constant of the metal barrel, these sensors exhibit a significant lag in sensing temperature changes at the core of the material. This time-domain response discrepancy prevents the control system from performing energy decoupling compensation at the initial moment of shear heat generation. Often, the control algorithm only determines overheating and delays the activation of external air cooling after the heat has been transferred to the wall and captured by the sensor. This delayed forced cooling results in a sharp drop in temperature and a dramatic increase in viscosity in the melt layer close to the barrel wall, while the melt deep in the screw channel remains at a high temperature and low viscosity due to shearing, creating a large viscosity gradient and velocity difference in the radial direction of the material. This radial flow inhomogeneity leaves significant residual thermal stress inside the extruded product, leading to quality defects such as irregular warping, inconsistent shrinkage, and even surface melt cracking after cooling. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention discloses an integrated temperature and pressure adaptive control method for extruders, which aims to reduce the temperature response mismatch between the melt interior and the barrel wall, improve the radial flow uniformity of the melt, and maintain continuous and stable operation of the extrusion process.

[0005] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution: An integrated temperature and pressure adaptive control method for an extruder, applied to an extrusion equipment including a screw drive motor, screw, barrel heating unit, barrel cooling unit, and die head pressure sensor, includes the following steps: S1. Collect the actual torque and speed signals of the screw drive motor during the continuous control cycle, and calculate the instantaneous effective mechanical power acting on the melt load; S2. Perform differential calculation on the instantaneous effective mechanical power within adjacent control cycles to obtain the change in mechanical power per unit time, which serves as a control reference for the screw's rate of injecting melt energy. S3. Determine the allowable limit of mechanical power variation under the current working conditions based on the screw structure parameters, the current speed range, and the working status of each heating zone of the barrel; S4. Compare the mechanical power change with the allowable limit of mechanical power change. When the mechanical power change exceeds the allowable limit of mechanical power change, apply a constraint signal to the torque command channel of the screw drive motor to limit the rate of change of the torque command value. S5. The torque given change rate limit acts on the inner loop level of the screw drive control circuit. Under the condition of the inner loop limitation, the pressure control circuit formed by the die head pressure sensor continuously outputs speed regulation or flow regulation commands to maintain the continuous operation of the extrusion process. S6. During the period when the change in mechanical power is limited, the barrel wall temperature signal is continuously collected. When the barrel wall temperature signal shows a continuous upward trend, the barrel cooling unit is controlled to enter the working state.

[0006] Preferably, the working process of S1 includes: The actual speed signal and actual torque signal of the screw drive motor are acquired within the same control cycle; When the extruder is in a stable extrusion condition, a reference torque value for the corresponding speed range is established based on the actual speed signal and the actual torque signal. The reference torque value is used to characterize the mechanical loss torque of the screw drive system. During the extrusion process, the reference torque value corresponding to the speed range is subtracted from the actual torque signal to obtain the equivalent shear torque acting on the melt load; The screw's angular acceleration is calculated based on the change in the actual rotational speed signal within adjacent control cycles, and the inertial torque caused by the system's inertia is calculated based on the pre-set equivalent rotational inertia parameters of the screw and transmission shaft system. The inertial torque is subtracted from the equivalent shear torque to obtain the corrected melt load torque; The corrected melt load torque is multiplied with the corresponding actual speed signal to obtain the instantaneous effective mechanical power acting on the melt load.

[0007] Preferably, step S3 defines the physical upper bound of mechanical power variation by constructing a power variation benchmark constraint that reflects the screw's mechanical shearing capacity and the barrel's thermal compensation capacity. The construction process includes: Obtain the effective axial length of the screw compression section, the screw diameter, and the average depth of the screw groove; calculate the unfolded area of ​​the screw surface participating in shearing within the screw compression section. Collect the actual torque of the screw drive motor during the current control cycle. Compared with actual speed and according to Calculate the corresponding instantaneous mechanical shear power; Within a continuous control cycle, differential calculation is performed on the instantaneous mechanical shear power to obtain the change in mechanical power per unit time, and the upper limit of the change in mechanical power per unit shear action area is determined using the unfolded area of ​​the screw surface as a constraint. The rated heating power and current actual output power of each heating zone of the barrel are collected to obtain the adjustable power margin of each heating zone under the current operating conditions. Based on the adjustable power margin and the average residence time of the melt in the barrel, the amount of external heat compensation that can be used to offset the heat input caused by changes in mechanical power per unit time is calculated. Based on the quantitative relationship between the upper limit of mechanical power change per unit shear area and the external heat compensation amount, a baseline limit for mechanical power change is determined.

[0008] Preferably, the mechanical power variation reference limit is constructed by spatial correction processing based on the screw axial structural parameters and the axial distribution of barrel heating power to build candidate limits for mechanical power variation. The process includes: Based on the screw structure parameters, the screw is divided into a feeding section, a compression section and a metering section along the axial direction, and the effective cross-sectional area of ​​the screw groove, the change in screw groove depth and the corresponding material compression ratio are determined for each screw section. Within the current screw speed range, the theoretical conveying volume of material per unit time in each screw section is calculated based on the effective cross-sectional area of ​​the screw groove and the screw speed of each screw section. The real-time heating power of each heating zone in the barrel is collected, and the heating power is distributed to the corresponding screw segment according to the coverage length of each heating zone in the screw axis, so as to obtain the external heat input power per unit time of each screw segment. Calculate the external heat input per unit time of each screw section based on the external heat input power per unit time and the corresponding theoretical conveying volume; Using the theoretical conveying volume of each screw section as a weight, the baseline limit for mechanical power variation is weighted and corrected to obtain candidate limits for mechanical power variation.

[0009] Preferably, the candidate limit for mechanical power change is determined by time-domain constraint processing to obtain the final limit for mechanical power change used for torque change rate control. The process includes: Within a continuous control cycle, the average power change of the instantaneous effective mechanical power acting on the melt load within the first time window and the average power deviation within the second time window are calculated respectively, wherein the time length of the first time window is shorter than the time length of the second time window. The average power change within the first time window is represented as the transient change intensity of the screw shear power; the power deviation from the average within the second time window is represented as the continuous accumulation state of the screw shear power. Based on the transient change intensity and the continuous accumulation state, the candidate limit for mechanical power change is corrected in the time domain, and the expression is: in: This is the allowable limit for the final mechanical power change used to constrain the rate of torque change during screw drive; These are candidate limits for mechanical power variation after screw functional segment correction and heat input correction; For the first Instantaneous effective mechanical power within each control cycle; This represents the average instantaneous effective mechanical power within the second time window; These correspond to the number of sampling points within the first and second time windows, respectively. ; These correspond to the weighting coefficients for transient power change and sustained power accumulation, respectively.

[0010] Preferably, in step S4, the rate of change of the torque setpoint of the screw drive motor is limited by power torque mapping constraints, and the process includes: Within a continuous control cycle, calculate the change in mechanical power for each control cycle. Corresponding to the allowable limit of mechanical power variation The super limited edition ; The excess amount is converted into the equivalent torque change in the corresponding control cycle. ,in For the screw in the first The actual rotational speed of the control cycle; and As the upper limit of the incremental limit of the torque setpoint in the current control cycle; Inside the motor controller, a torque setpoint register is used. Using the previous cycle's setpoint, the increment of the torque setpoint for the current control cycle is limited, as expressed by: in, This is the unconstrained torque increment calculated according to process requirements. Indicates will The limit is within the range [ ]Inside, This is the torque setpoint after incremental limiting.

[0011] Preferably, step S4 involves continuously and periodically adaptively adjusting the upper limit of the torque increment limit of the screw drive motor, including: Record the change in mechanical power in each of N consecutive control cycles. Corresponding to the allowable limit of mechanical power variation The super limited edition The cumulative power over-limit integral value ; according to Upper limit of torque increment for the next control cycle To achieve adaptive adjustment, the formula expression is: in, This is the upper limit of the initial torque increment; This is an adjustment coefficient used to control the rate at which constraints are tightened; As the upper limit of the torque setpoint increment limit for the next control cycle; Will The output is sent to the motor controller to constrain the torque increment for the next control cycle, without directly modifying the torque setpoint for the current control cycle.

[0012] Preferably, in S5, when the torque given rate of change limit is applied to the inner loop level of the screw drive control loop, the output signal of the head pressure control loop participates in the screw drive control through a restricted interface processing, specifically including: Within the control cycle where the rate of change of torque is limited, the torque increment request of the pressure control loop is obtained by using the proportional-integral control method based on the difference between the real-time pressure collected by the head pressure sensor and the head set pressure. The torque increment request is compared with the current allowed torque increment limit of the inner loop level, and the part exceeding the torque increment limit is truncated to obtain the restricted torque increment request. The restricted torque increment request is used as the effective torque adjustment input of the screw drive motor, so that the pressure control loop can still participate in the screw drive adjustment process under the inner loop restricted state.

[0013] Preferably, the barrel cooling unit is started and participates in thermal regulation through a conditional control method associated with a limited state of mechanical power variation, the process including: During a continuous control cycle, determine whether the change in mechanical power remains below the corresponding allowable limit for mechanical power change. If so, the barrel wall temperature signal is continuously sampled, and the trend of barrel wall temperature change is determined based on the change in barrel wall temperature over multiple adjacent control cycles. When the barrel wall temperature change trend is in a unidirectional upward state within a preset time window, the initial input level of the barrel cooling unit is determined based on the duration of the mechanical power change being in a limited state. The initial input level is used as the start-up control parameter for the barrel cooling unit, enabling the barrel cooling unit to participate in the thermal conditioning process in a controlled manner during periods of limited mechanical power variation.

[0014] Preferably, the mechanical power variation-limited state satisfies: u1. During the continuous control cycle, the actual change in mechanical power is determined to exceed the corresponding allowable limit for mechanical power change after comparison. u2. During the control cycle in which the determination is made, the rate of change of the torque given of the screw drive motor is constrained based on the allowable limit of the mechanical power change, and is executed by the inner loop level of the screw drive control loop. u3. The torque given rate of change constraint shall remain in effect for no less than a preset number of consecutive control cycles. When all of the above conditions are met, the extruder is determined to be in a state of limited mechanical power variation during operation.

[0015] Based on the above technical solution, the positive and beneficial effects of the present invention are as follows: 1. This invention constructs a mechanical power change that reflects the true energy input of the melt load by collecting the actual torque and speed signals of the screw drive motor. When this power change exceeds the allowable limit for mechanical power change generated based on the screw structure parameters, speed range, and working state of the barrel heating zone, a constraint is imposed on the torque setpoint change rate at the inner loop level of the screw drive control loop. This control method limits the rate of mechanical energy input to thermal energy before shear heat is conducted through the barrel wall and sensed by the temperature sensor. This reduces the time-domain difference in thermal response between the melt core and the near-wall region from the control source, avoiding the passive forced cooling intervention caused by temperature detection lag in existing technologies.

[0016] 2. This invention does not directly initiate cooling after the barrel wall temperature exceeds the limit. Instead, it limits the participation of the barrel cooling unit to the premise that the "mechanical power change is limited" condition is met, and triggers the judgment based on the time change trend of the barrel wall temperature signal. Since the power input rate of the screw drive side is constrained by the inner loop when the limited state is entered, the intervention of barrel cooling no longer corresponds to the peak stage of the energy input inside the melt. This avoids the condition where the temperature of the near-wall melt layer drops sharply while the melt in the deep part of the screw channel remains at a high temperature and low viscosity. This helps to reduce the discontinuous change of the radial viscosity distribution of the melt, reduce the residual thermal stress inside the extruded product and the resulting quality defects such as warping and inconsistent shrinkage.

[0017] 3. This invention explicitly applies a torque setpoint change rate limit to the inner loop level of the screw drive control circuit, enabling the pressure control circuit, composed of the die head pressure sensor, to continuously output control commands at the outer loop level. The executability of these pressure commands is automatically filtered through inner loop constraints. This layered control structure avoids the problem of frequent oscillations or failures in the pressure control circuit caused by forced intervention in screw speed in existing technologies. While maintaining continuous and stable operation of the extrusion process, it achieves refined management of the mechanical power input rate, improving the adaptability of the integrated temperature and pressure control under complex operating conditions. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a schematic diagram of the steps of the present invention; Figure 2 This invention generates a logic diagram for the permissible limit of mechanical power variation. Figure 3 This is a schematic diagram of the time-domain processing of the screw mechanical power variation in this invention; Figure 4 This is a schematic diagram illustrating the principle of determining the limited state of mechanical power variation in this invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] In one possible implementation, taking a single-screw plastic extruder as an example, the implementation of the temperature and pressure integrated adaptive control method of the present invention in engineering applications is illustrated. The extruder includes a screw drive motor, a screw body, a barrel and its segmented heating system, a die head pressure sensor, a barrel wall temperature sensor, a barrel cooling unit, and a PLC controller module. The screw drive motor is a DC servo motor, and its torque and speed signals are acquired in real time through a built-in encoder and a Hall current sensor. A set of Pt100 platinum resistance temperature sensors is arranged every 200 mm along the barrel length. The die head pressure sensor is a high-response piezoelectric sensor, both connected to the PLC high-speed acquisition module interface. The barrel cooling unit includes a water circulation cooling channel, an adjustable flow valve, a cooling pump, and a flow sensor, and cooling start-up and flow gradient adjustment are achieved through PLC control.

[0021] The PLC controller acquires screw motor torque and speed signals in real time with a 10-millisecond data acquisition cycle, and calculates the instantaneous mechanical power acting on the melt load. ,in Let ω(t) be the motor torque and ω(t) be the screw angular velocity. The change in mechanical power is statistically analyzed over several consecutive control cycles and compared with the allowable power change limit. The screw body is divided into a feeding section, a compression section, a metering section, and a mixing section. A parameter structure is established for each section, including section length, screw channel depth, screw diameter, and allowable shear load coefficient per unit speed. The instantaneous allowable power change value for each section is calculated using the formula... Calculation, where The segment shearing coefficient, This is a geometric correction function. The minimum value among the values ​​of each segment is taken to form the allowable limit for the mechanical power variation of the entire screw.

[0022] In the control logic, the PLC inner-loop torque constraint module receives the mechanical power change and allowable limit. If the power change exceeds the limit, the module applies a rate-of-change limitation (e.g., 0.3–0.5 N·m / ms) to the servo drive torque command channel and updates the torque command in real time through a double-buffered register. The outer-loop pressure control loop calculates the PI control command based on the die head pressure signal, and generates the final screw torque command after passing through the inner-loop constraint, ensuring decoupling between continuous die head pressure adjustment and screw power constraint. When the inner-loop constraint remains in effect for several consecutive control cycles, the PLC marks the operating status as power-limited and transmits the status information to the cooling unit control module. The cooling unit starts when the power is limited and the barrel wall temperature shows a continuous upward trend, with the flow rate linearly increasing from 50 L / min to 80 L / min, gradually adjusting the wall temperature to avoid sudden cooling of the near-wall melt and abrupt changes in radial viscosity.

[0023] The PLC internally establishes a cyclic queue management system for data flow: a motor torque and speed queue for power calculation, a screw section parameter queue for generating allowable limits, a power-limited state queue for state determination, and a wall temperature history queue for cooling intervention logic. In each control cycle, the signal sequentially passes through acquisition, power calculation, limit generation, inner loop constraints, outer loop pressure command processing, power-limited state determination, and cooling control, ensuring that each link is continuous, traceable, and responsive in a timely manner.

[0024] In this embodiment, under typical operating conditions, the screw speed in the feeding section is set to 50 rpm, the compression section length is 400 mm, the screw groove depth gradually decreases from 10 mm to 4 mm, the screw diameter is 50 mm, the barrel heating power is 1200–1800 W / m², and the cooling flow rate can be dynamically adjusted according to the constrained conditions. Through mechanical power constraints at the screw end, segmented limit calculations, layered coordinated control of inner and outer rings, and cooling gradient adjustment, the temperature response of the melt core is synchronized with the barrel wall temperature, reducing the accumulation of shear heat peaks, improving the uniformity of radial melt flow, maintaining stable die head pressure, and ensuring continuous extrusion. Compared with the prior art, this invention overcomes the technical biases of relying on wall temperature hysteresis feedback, forced speed adjustment, and asynchronous cooling intervention, achieving coordinated temperature and pressure control and highly consistent molding.

[0025] To facilitate a deeper understanding of the technology in this invention, a detailed description of an integrated temperature and pressure adaptive control method for an extruder disclosed in the embodiments of this application is provided below. Please refer to [link to relevant documentation]. Figure 1 The schematic diagram shown illustrates the steps of the invention, which include: S1. Acquire the actual torque and speed signals of the screw drive motor within a continuous control cycle, and calculate the instantaneous effective mechanical power acting on the melt load. Specifically, the control system operates with a fixed control cycle, preferably 5 to 10 milliseconds. Within each control cycle, the actual speed signal is acquired through the encoder of the screw drive motor, and the corresponding actual torque signal is acquired simultaneously through the current detection unit built into the motor driver. The aforementioned speed and torque signals are acquired and latched within the same control cycle.

[0026] Because mechanical losses such as bearing friction, gear meshing, and coupling damping are unavoidable in screw drive systems, and this energy consumption is unrelated to the melt, directly incorporating it into power calculations would distort the assessment of the melt shear state. Therefore, when the extruder is under stable extrusion conditions and the die pressure fluctuations are within acceptable limits, a reference torque calibration is performed on the screw drive system. Specifically, the actual motor torque values ​​under stable operating conditions are recorded within multiple discrete speed ranges, and the torque data within the same range are averaged over time to form a reference torque value for that speed range. The speed range can be divided according to the screw's designed speed range, for example, every 5 rpm or 10 rpm. This reference torque value characterizes the mechanical loss characteristics of the screw drive system within that speed range and serves as a fixed reference value for subsequent operation.

[0027] During extrusion operation, the control system retrieves the corresponding reference torque value based on the current actual rotational speed range, and subtracts this reference torque value from the acquired actual torque signal to obtain the equivalent shear torque. This equivalent shear torque characterizes the combined torque applied by the screw to the melt, but it still includes an inertial torque component caused by changes in rotational speed.

[0028] To further eliminate system inertial factors, differential calculations are performed on the actual rotational speed signal within adjacent control cycles to calculate the change in screw angular velocity, thereby obtaining the screw's angular acceleration. Combined with pre-set equivalent moment of inertia parameters of the screw body, transmission shaft system, and coupling, the corresponding inertial torque is calculated. These equivalent moment of inertia parameters can be determined once during equipment installation and commissioning through manufacturing parameters or experimental calibration, and stored in the control system, requiring no dynamic adjustment during operation.

[0029] Subsequently, the inertial torque is subtracted from the equivalent shear torque to obtain the corrected melt load torque. This correction process avoids the problem of misinterpreting the system's inertial work as melt shear work during screw acceleration or deceleration, ensuring that the obtained torque data only reflects the true resistance of the melt load to the screw.

[0030] After completing the torque correction, the control system multiplies the corrected melt load torque with the actual speed signal within the corresponding control cycle to obtain the instantaneous effective mechanical power acting on the melt load. This instantaneous effective mechanical power serves as the basis for calculating the mechanical power change, determining the allowable limit of power change, and identifying the power-limited state in subsequent steps, maintaining a consistent data caliber throughout the entire temperature and pressure integrated adaptive control process.

[0031] S2. Perform differential calculation on the instantaneous effective mechanical power within adjacent control cycles to obtain the change in mechanical power per unit time, which serves as a control reference quantity for the screw's energy injection rate into the melt. In the specific implementation of this invention, S2 is used to characterize the change in energy injection into the melt during the screw drive process on a time scale. Its core purpose is to obtain a control reference quantity that can reflect the growth or decay trend of shear energy.

[0032] After calculating the instantaneous effective mechanical power in S1, the control system stores this power value as a time series within a continuous control cycle. Preferably, the control cycle is consistent with the motor drive control cycle, typically 5–10 milliseconds. Within each control cycle, the control system retrieves the instantaneous effective mechanical power value of the current cycle and the instantaneous effective mechanical power value of the previous control cycle, and performs a difference operation on the two. The difference result is then time-normalized to obtain the change in mechanical power per unit time.

[0033] The aforementioned change in mechanical power characterizes the rate of change of mechanical energy applied by the screw to the melt under the current operating conditions. This quantity does not reflect the absolute energy input level of the screw to the melt, but rather whether there is a rapid increase or decrease in energy input over a short timescale. Through this approach, the control system can detect changes in melt shear conditions in the early stages of screw speed or torque adjustments, without waiting for significant changes in hysteretic signals such as barrel wall temperature or die head pressure.

[0034] In engineering implementation, to avoid interference from fluctuations at a single sampling point in the judgment of power change, the control system can perform a simple moving average processing on the instantaneous effective mechanical power before differential calculation. The moving average window length can be set to 2 to 3 control cycles. This processing is only used to suppress high-frequency jitter and does not change the time response characteristics of the power change, ensuring that the quantity can still reflect the true trend of energy injection change.

[0035] S3. Determine the allowable limit of mechanical power variation under the current working conditions based on the screw structure parameters, the current speed range, and the working status of each heating zone of the barrel; In practical implementation, the structural parameters of the screw are pre-entered into the control system. These parameters include at least the effective axial length of the compression section, the screw outer diameter, and the average depth of the screw grooves within the compression section. The effective axial length of the compression section refers to the axial range of the screw actually involved in melt compaction and shearing, excluding the transition and metering sections. The average depth of the screw grooves is an equivalent value obtained by averaging the groove depths along the axial direction of the compression section, reflecting the contact characteristics between the melt and the screw surface in this region.

[0036] It should be noted that the "expanded surface area of ​​the screw" referred to in this application is not simply the area of ​​the outer cylinder of the screw, but rather the equivalent surface area within the compression section that actually participates in the melt shearing action, considering the presence of screw channels. This area is obtained by axially expanding the outer surface of the screw and correcting for the shear contact area by incorporating the screw channel depth. It is used to reflect the physical carrier scale of the shear energy distributed by the melt within this region. The purpose of introducing this parameter is to avoid using only the change in total power as a criterion, while ignoring the influence of different screw structures on the shear energy carrying capacity.

[0037] Please see Figure 2 As shown, during the extrusion process, the control system collects the actual torque and actual speed of the screw drive motor in each control cycle, and calculates the corresponding instantaneous mechanical shear power according to the relationship P = 2π·n·T. The instantaneous mechanical shear power is obtained based on the correction results in steps S1 and S2, and has eliminated the influence of mechanical loss torque and system inertial torque, and is used to characterize the effective shear power applied by the screw to the melt at that moment.

[0038] Subsequently, within a continuous control cycle, the instantaneous mechanical shear power is differentially calculated to obtain the change in mechanical power per unit time. This change reflects the trend of energy injection into the melt by the screw, rather than the steady-state energy level. The control system normalizes this change in mechanical power with the aforementioned screw surface area to obtain the intensity of mechanical power change per unit shear area. This intensity value is used to describe the rate of change of mechanical energy per unit shear area within the compression section.

[0039] Meanwhile, the control system acquires the rated heating power of each heating zone in the barrel and the actual output power within the current control cycle in real time. By comparing the two, it calculates the power margin that each heating zone can still adjust under the current operating conditions. This power margin reflects the heating system's ability to absorb or offset additional heat input without changing the target set temperature.

[0040] It should be noted that the "external heat compensation" referred to in this application does not refer to additional heating power, but rather to the equivalent thermal regulation capacity of the barrel thermal system, which is not yet occupied under the current heating control state and can be used to balance changes in mechanical shear heat. This capacity is related to the power margin of the heating zone and the average residence time of the melt in the barrel. By converting the power margin into the melt residence time, the amount of external heat compensation per unit time that can be used to offset the heat input caused by changes in mechanical power can be obtained.

[0041] Based on this, the control system matches the magnitude of the mechanical power change per unit shear area with the external thermal compensation amount to determine the baseline limit that the mechanical power change should not exceed under the current screw structure conditions and barrel thermal state conditions. This baseline limit is used to define the basic physical upper bound of the mechanical power change, and its essence comes from the shear distribution capacity that the screw structure can withstand and the thermal regulation margin of the barrel thermal system under the current operating conditions, rather than empirical settings or control strategy outputs.

[0042] Based on the aforementioned mechanical power variation baseline limit, the axial structural differences of the screw and the axial distribution of the barrel heating power are introduced to correct the mechanical power variation capability in a spatial dimension, so as to avoid treating the screw as an axially uniform object and causing the limit deviation.

[0043] In practical implementation, the control system, based on the screw design parameters, clearly divides the screw axis into a feeding section, a compression section, and a metering section. For each screw section, the effective cross-sectional area of ​​the screw groove, the change in screw groove depth, and the compression ratio of the material within that section are determined. These parameters are all derived from the screw structure design data. The effective cross-sectional area of ​​the screw groove characterizes the material holding and conveying capacity per unit speed, while the change in screw groove depth and the compression ratio reflect the spatial characteristics of the melt volume change and shear state within that section.

[0044] Within the current screw speed range, the control system calculates the theoretical material conveying volume of each screw segment per unit time based on the effective cross-sectional area of ​​the screw groove and the actual speed. This theoretical conveying volume is used to describe the relative magnitude of material handling capacity at different axial positions under the same speed conditions, and is not used as a measurement value of actual output.

[0045] Simultaneously, the control system collects the actual heating power of each heating zone in the barrel in real time, and, combined with the coverage length relationship of each heating zone in the screw axial direction, distributes the heating power to the corresponding screw segments according to the axial length ratio. This yields the external heat input power corresponding to each screw segment per unit time. It should be noted that the "external heat input power" referred to in this application refers only to the heat applied by the barrel heating system and does not include the mechanical heat generated by screw shearing.

[0046] After obtaining the external heat input power for each screw section, the control system further calculates the external heat input per unit volume of material for each screw section by combining the theoretical conveying volume of the corresponding screw section. This amount is used to reflect the difference in the external heat compensation capability that can be obtained per unit volume of melt at different axial positions.

[0047] Based on this, the control system uses the theoretical conveying volume of each screw segment as a weight to perform a weighted correction on the aforementioned mechanical power variation baseline limit. Screw segments with larger theoretical conveying volumes receive a higher weight during the correction process, thus making the corrected limit closer to the actual energy distribution. After the above spatial correction process, the result is used as a candidate limit for mechanical power variation, reflecting the reasonable upper bound of mechanical power variation in the spatial dimension under the current screw structure, speed range, and axial distribution of barrel heating power.

[0048] After obtaining candidate limits for mechanical power variation after screw functional segment correction and heat input correction, time-domain processing is further introduced to generate the final allowable limit for mechanical power variation used to constrain the rate of torque change during screw drive. The purpose of this time-domain processing is not to perform conventional filtering of the power signal, but to dynamically shrink and adaptively correct the candidate limits based on the engineering fact that the mechanism by which mechanical shear power affects the melt state at different time scales during extrusion.

[0049] Please see Figure 3 The diagram shows the time-domain processing of screw mechanical power variation. The horizontal axis represents the time axis corresponding to a continuous control cycle, and the vertical axis represents the instantaneous effective mechanical power calculated based on the actual torque and speed signals of the screw drive motor. The solid curve in the diagram represents the actual curve of mechanical power variation with the control cycle collected during normal extruder operation. This curve includes non-ideal fluctuations introduced by screw load fluctuations, melt state changes, and drive system characteristics.

[0050] The power curve is marked with a first time window and a second time window. The first time window covers several adjacent control cycles and is used to statistically analyze the changes in instantaneous effective mechanical power within adjacent control cycles. The power difference between adjacent sampling points within this time window is used to characterize the magnitude of mechanical power change over a short time scale. The second time window covers a larger number of control cycles than the first time window and is used to statistically analyze the deviation of mechanical power from its average level over a longer time range. The deviation of each sampling point within this time window from the window's average power is used to reflect the continuous deviation of mechanical power under the current operating condition.

[0051] By simultaneously introducing a first time window and a second time window onto the same power curve, it is possible to distinguish between transient fluctuations in mechanical power caused by screw torque or speed adjustments in a short period of time, and the continuous offset trend caused by shear heat accumulation over a longer period of time. The time window processing results shown in the figure serve as the basis for time-domain correction in the subsequent generation of allowable limits for mechanical power changes, and are used to constrain the rate of change of screw drive torque during actual control.

[0052] In actual extrusion operations, the mechanical power variation of the screw on the melt typically exhibits both rapid fluctuations over short timescales and sustained shifts over longer timescales. The former is primarily caused by rapid adjustments to screw torque or speed commands, manifesting as drastic changes in instantaneous shear power. This change alters the shear stress distribution and localized temperature rise of the melt within a short period. The latter manifests as mechanical power consistently exceeding or falling below stable operating levels over a longer period. Even small variations per unit time can lead to an overall shift in the melt temperature field due to continuous heat accumulation. Evaluating mechanical power variation based solely on a single timescale can easily overlook one of these influence paths, resulting in a mismatch between limit settings and actual thermo-mechanical coupling behavior.

[0053] Based on the above understanding, this embodiment sets a first time window and a second time window in the control system to perform parallel time-domain analysis on the instantaneous effective mechanical power. The first time window has a shorter duration than the second time window and is used to characterize the transient changes in mechanical power; the second time window is used to characterize the continuous accumulation of mechanical power. It should be noted that the "time window" is a logical time interval composed of several consecutive control cycles, and its specific length can be set according to the drive control cycle, screw inertia characteristics, and melt thermal response time.

[0054] Within the first time window, the instantaneous effective mechanical power in the continuous control cycle is differentially calculated between adjacent cycles. The absolute value of the difference results is then averaged to obtain the average change of mechanical power over a short time scale. This quantity characterizes the transient change intensity of the screw shear power, and its physical meaning lies in reflecting the degree of instantaneous disturbance to the melt shear state caused by torque or speed changes. Absolute values ​​are used here to avoid the numerical cancellation of positive and negative changes, ensuring that the evaluation result only reflects the magnitude of the change itself. The average value is used instead of the peak value to reduce the impact of a single abnormal sampling on the control judgment.

[0055] Within the second time window, the average instantaneous effective mechanical power is first calculated, and this average value is used as a reference level. Then, the deviation of the power value from this reference level within each control cycle is calculated, again by taking the absolute value and averaging the results to obtain the average power deviation. This quantity characterizes whether the mechanical power continuously deviates from the steady-state operating condition over a longer time scale. Its engineering meaning lies in reflecting the heat accumulation trend of the melt within the barrel due to long-term high or low mechanical shear heat.

[0056] After obtaining the two time-domain feature quantities mentioned above, this embodiment obtains the final allowable limit for mechanical power change by performing time-domain correction on the candidate limit values ​​for mechanical power change. The calculation method is as follows: in, This represents the final allowable limit for mechanical power change used to constrain the rate of torque change during screw drive. This represents the candidate limit value for mechanical power variation after screw functional segment correction and heat input correction; Indicates the first Instantaneous effective mechanical power calculated within each control cycle; This represents the average instantaneous effective mechanical power within the second time window; This indicates the number of sampling points included in the first time window; This indicates the number of sampling points included within the second time window, and satisfies... ; This is a weighting coefficient for transient power changes, used to adjust the degree of influence of short-term power fluctuations on limit corrections; This is the continuous power accumulation weighting coefficient, used to adjust the degree of influence of long-term power offset on limit correction.

[0057] The above formula introduces transient and cumulative terms as reduction factors into the candidate limit, thereby reducing the allowable range of mechanical power variation when mechanical power fluctuates drastically in a short period or deviates from the steady-state level over a longer period. This allows for earlier constraint on the rate of torque change. This avoids the lag problem of compensation only being made after the power anomaly has already had a significant impact on the melt temperature or pressure.

[0058] As one possible implementation, the length of the first time window can be selected to cover several drive control cycles to ensure that power transitions caused by torque or speed adjustments can be captured; the length of the second time window can be selected to cover the typical thermal response time range of the melt in the barrel to reflect the heat accumulation effect. Weighting coefficients and The value of can be set according to the screw size, drive power level and thermal sensitivity characteristics of the processed material, and its specific value does not affect the realization of the time domain correction idea of ​​this invention.

[0059] S4. Compare the change in mechanical power with the allowable limit of mechanical power change. When the change in mechanical power exceeds the allowable limit of mechanical power change, apply a constraint signal to the torque setting channel of the screw drive motor to limit the rate of change of the torque setting value. Note that this step does not adjust the mechanical power signal itself, but rather applies a constraint to the change process of the torque setting value within the drive controller, so that the change in mechanical power is controlled by the aforementioned energy boundary conditions.

[0060] In practical systems, screw drive motors are typically controlled by independent servo drivers or frequency converters. These drivers have internal torque setpoint registers that receive outputs from the host control system. This register receives a new torque setpoint in each control cycle and adjusts the motor output accordingly. It's important to note that the torque setpoint channel refers to the internal link within the drive controller used to generate current or torque commands, not the mechanical structure itself.

[0061] Within each control cycle, the control system first generates the mechanical power change corresponding to the current control cycle based on the mechanical power change per unit time obtained in step S2. At the same time, based on the final permissible limit for mechanical power variation determined in S3, the permissible value for the current cycle is obtained. The two complete alignment within the same control cycle.

[0062] The control system then compares the two quantities mentioned above, and only generates an over-limit quantity to constrain torque changes when the change in mechanical power exceeds the allowable limit. This over-limit quantity is calculated as follows: in, Indicates the first The portion of mechanical power variation exceeding the allowable range within a control cycle. When the mechanical power variation does not exceed the allowable limit, the excess is zero, and no additional constraints are applied to the torque setpoint variation.

[0063] Since the actual control object that the drive controller can execute is the torque setpoint, rather than the power quantity, it is necessary to convert the power over-limit into the corresponding equivalent torque change. In this embodiment, this conversion is based on the physical relationship between power, torque, and speed. Specifically, in the first... Within each control cycle, based on the actual rotation of the screw... Convert the power over-limit into an equivalent torque change. ,in, For the first The actual angular velocity of the screw is collected within each control cycle. It should be noted that this application uses the real-time collected actual rotational speed, not the set or rated speed. This is to ensure that the change in equivalent torque truly reflects the constraint of power variation on torque variation under the current operating conditions. When the rotational speed is low, the equivalent torque change corresponding to the same power over-limit is larger; when the rotational speed is high, the corresponding equivalent torque change is relatively smaller. This relationship conforms to the actual physical characteristics of screw shear energy injection.

[0064] Inside the drive controller, the torque setpoint from the previous control cycle... It is stored in the torque setpoint register. During the current control cycle, the process control loop (e.g., the control command generated by the headstock pressure control loop) will provide an unconstrained target torque increment. The target torque increment reflects the process requirements themselves, without considering the impact of instantaneous changes in mechanical power on the melt state.

[0065] This invention does not directly modify the calculation logic of the target torque increment, but rather applies a power constraint-based limiting process to its change amplitude before it enters the torque setpoint register. Specifically: in, Indicates the variable The torque increment is limited to the interval [a, b]. When the absolute value of the target torque increment is less than the equivalent torque change, the torque setpoint changes according to the original process requirements; when the torque change that the target torque increment attempts to cause exceeds the allowable equivalent torque change in the current cycle, its change amplitude is limited to the dynamic boundary determined by the mechanical power over-limit.

[0066] It should be noted that the above-mentioned limiting range is not a fixed parameter, but is calculated in real time within each control cycle. Dynamically generated. Therefore, this constraint is not a fixed limit on the rate of torque change in the traditional sense, but an adaptive torque change constraint that is directly related to the actual power state, speed state, and thermal constraint conditions of the screw.

[0067] By adjusting the torque setpoint after incremental limiting The output is sent to the screw drive motor. While maintaining continuous operation of the control loop, the driver avoids sudden changes in mechanical power caused by rapid torque variations, thus controlling the screw's energy injection process into the melt within the aforementioned permissible limit for mechanical power variation. As one possible implementation, the aforementioned torque setpoint constraint can be implemented internally by the driver, or it can be calculated by the upper-level control system and then sent to the driver for execution via a communication interface. The specific implementation method does not affect the validity of the technical concept described in this step.

[0068] In actual extrusion operation, even if the change in mechanical power within a single control cycle is limited, if the power change frequently approaches or exceeds the allowable limit over multiple consecutive cycles, it often means that the screw's energy injection into the melt is already at a high intensity, while the thermal inertia of the melt and barrel has not yet been fully released. In this case, relying solely on instantaneous limiting on a cycle-by-cycle basis may still lead to a continuous accumulation of melt temperature over time, thereby triggering the risk of subsequent thermal instability. Based on this engineering understanding, this invention introduces a cross-cycle cumulative evaluation of power over-limit behavior.

[0069] Specifically, within N consecutive control cycles, the control system calculates the change in mechanical power for each cycle. Corresponding permissible limits for mechanical power variation The power overrun within each cycle is determined according to the following relationship: in, It takes a non-zero value only when the power change exceeds the allowable range, characterizing the actual degree of exceedance within that period. When the power change is within the allowable range, this value is zero and does not participate in subsequent accumulation.

[0070] Based on this, the control system accumulates the aforementioned power over-limit over the NNN consecutive control cycles to form a power over-limit integral value. This power over-limit integral value reflects the overall intensity of mechanical power over-limit behavior over a recent period, rather than abnormal fluctuations in a single cycle. It should be noted that the "integral" is not a mathematical integral in the continuous-time sense, but rather a discrete accumulation based on the control cycle. The accumulation length N can be set according to the screw size, melt thermal inertia, and drive control cycle. As one possible implementation, N can be selected to cover the typical thermal response time range of the melt within the barrel, so that the integral value matches the heat accumulation process on a time scale.

[0071] After obtaining the power over-limit integral value, this embodiment does not further modify the torque setpoint within the current control cycle. Instead, it uses the integral result to adjust the upper limit of the allowable torque increment for the next control cycle. The purpose of this deferred action is to avoid abrupt interference with the torque execution result already formed in the current cycle, while simultaneously establishing a more stringent change boundary in advance for subsequent cycles.

[0072] Specifically, the upper limit of torque increment in the next control cycle. Determined according to the following relationship: in, This represents the upper limit of the initial torque increment used when no power over-limit accumulation has occurred. Its value can be set according to the drive system's capability and torque variation requirements under normal operating conditions; kkk is an adjustment coefficient used to control the rate at which power over-limit accumulation tightens the torque variation capability. Power over-limit integral value. The larger the value, the greater the decay of the exponent, and the smaller the upper limit of the corresponding torque increment.

[0073] It should be noted that the significance of using an exponential rather than a nonlinear reduction method is that when the power over-limit is low, the impact on torque variation capability is relatively mild, avoiding excessive suppression of process adjustments; while when the power over-limit continues to accumulate, the tightening speed of torque variation capability is significantly accelerated, thus suppressing further high-intensity energy injection in advance. This nonlinear tightening method is more in line with the actual characteristic that the risk of melt heat accumulation increases rapidly over time.

[0074] In actual implementation, the upper limit of the adaptive torque increment The incremental limit logic provided to the motor controller is used as the maximum permissible range of torque setpoint change in the next control cycle. This upper limit only applies to the constraint boundary of the torque increment and does not directly modify the torque setpoint or target torque command in the current cycle, thereby maintaining the continuity and stability of the drive control loop.

[0075] S5. The torque given rate of change limit acts on the inner loop level of the screw drive control circuit. Under the condition of the inner loop being limited, the pressure control circuit formed by the die head pressure sensor continuously outputs speed regulation or flow regulation commands to maintain the continuous operation of the extrusion process. The core of this step is to clearly define the hierarchical structure of the screw drive control circuit so that the torque change constraint only acts on the inner loop level of the drive circuit, without directly interrupting or blocking the pressure control circuit formed by the die head pressure sensor.

[0076] In this application, the screw drive control loop is divided into an inner loop level and an outer loop level. The inner loop level refers to the control level that directly acts on the motor torque setpoint or current command, and its controlled object is the drive execution capability itself. The outer loop level refers to the control loop that uses process variables as the control target, such as a pressure control loop composed of a die head pressure sensor, whose output is used to adjust the screw speed or torque to maintain a stable extrusion state. It should be noted that the terms "inner loop" and "outer loop" in this application are not fixed control topology limitations, but rather functional divisions of the controlled object and control level.

[0077] In step S4 above, when the change in mechanical power is constrained, the rate of change of the torque setpoint is already constrained at the inner loop level. In this state, directly stopping or freezing the output of the pressure control loop can easily lead to a continuous accumulation of pressure deviation. Once the inner loop constraint is lifted, the system will experience a large torque jump, which will exacerbate power fluctuations. Therefore, this embodiment chooses to maintain the continuous operation of the pressure control loop under the constrained inner loop condition, only limiting its "amplitude capability" acting on the driving inner loop.

[0078] Specifically, within the control cycle where the rate of change of the torque setpoint is limited, the die head pressure sensor continuously collects the actual pressure signal at the die head and compares it with the preset die head pressure setpoint to obtain the pressure deviation. Based on this pressure deviation, the pressure control loop uses proportional-integral control to calculate the corresponding torque increment request. It should be noted that the proportional-integral control here is a common pressure regulation method in extrusion equipment. Its function is to generate a smooth adjustment request based on the magnitude and duration of the pressure deviation. This application does not consider the control algorithm itself as an innovation.

[0079] In this embodiment, the pressure control loop outputs not a directly executable torque setpoint, but rather a "torque increment request," which characterizes the expected change in screw torque under the current operating conditions. This torque increment request needs to be processed through a restricted interface before entering the screw drive control inner loop.

[0080] The restricted interface processing refers to comparing the torque increment request output by the pressure control loop with the upper limit of the currently allowed torque increment at the inner loop level when the torque setpoint change rate is constrained by the inner loop. When the absolute value of the torque increment request does not exceed the upper limit of the allowed torque increment at the inner loop, the request can be fully transmitted to the inner loop for execution; when the torque increment request attempts to exceed the allowable change capacity of the inner loop, only the portion not exceeding the upper limit is retained, and the excess portion is truncated and does not enter the inner loop for execution.

[0081] In this way, the pressure control loop continues to participate in the screw drive regulation process even under the inner loop constraint, but its effect on the drive system is limited to the range allowed by the current mechanical power constraints. It should be noted that this limitation does not involve limiting or reconfiguring the pressure control loop itself, but rather constraining the interface before its output signal enters the drive execution layer, thus avoiding frequent switching of the control structure.

[0082] In engineering practice, this structure enables the pressure control loop to continuously reflect the changing trend of the die head pressure deviation, and its integral term can gradually accumulate adjustment during the inner loop constraint period. Once the torque change rate constraint is relaxed or removed, the adjustment request previously formed by the pressure control loop can be smoothly released without triggering sudden torque changes. This inner and outer loop coordination method is beneficial for maintaining the continuity and stability of the extrusion process under mechanical power constraints. As one possible implementation, the constrained interface processing can be implemented in the host controller or internally in the drive controller by configuring intermediate variable registers. The specific implementation location does not affect the control concept of inner loop constraint and outer loop continuous participation described in this step.

[0083] S6. During periods when the mechanical power variation is limited, continuously collect the barrel wall temperature signal. When the barrel wall temperature signal shows a continuous upward trend, control the barrel cooling unit to enter the working state. It should be emphasized that this step does not use the barrel wall temperature exceeding a certain fixed threshold as the cooling start condition, but rather associates the operation of the cooling unit with the limited mechanical power variation state, so that the cooling behavior matches the system's adjustability.

[0084] In steps S4 and S5, when the change in mechanical power exceeds the corresponding allowable limit, and the rate of change of the screw drive motor's torque is constrained at the inner loop level and remains effective for multiple consecutive control cycles, the system determines that the extruder operation has entered a state of restricted mechanical power change. This state indicates that, under the current operating conditions, the screw drive system can no longer absorb or balance the energy changes inside the melt by increasing or rapidly changing the mechanical power. If heat continues to accumulate, it will mainly manifest as an increase in the barrel wall temperature and the melt temperature.

[0085] For specific implementation details, please refer to [link / reference]. Figure 4 As shown, the system continuously determines whether the change in mechanical power is below the corresponding allowable limit during consecutive control cycles. "Being below the allowable limit" does not mean there is absolutely no exceedance, but rather that the actual change in mechanical power has been successfully limited by the constraint logic over multiple consecutive control cycles, and the torque setpoint change rate limitation condition of the screw drive motor remains in effect. It should be noted that this determination is not the result of a single cycle, but a comprehensive assessment of the continuous cycle states. Its purpose is to eliminate the impact of transient power disturbances or single-cycle limiting false triggers on the cooling logic.

[0086] Once the system determines that the mechanical power change is limited, it begins continuous sampling of the barrel wall temperature signal. The barrel wall temperature signal described in this application refers to the temperature data collected by a temperature sensor installed on the outer wall of the barrel or near the inner wall, and its trend reflects the overall heat accumulation status of the barrel and the melt. This application does not require the temperature signal to have absolute accuracy, but rather focuses on its direction and magnitude of change within a continuous control cycle.

[0087] Based on the above considerations, this embodiment only performs targeted trend analysis on the barrel wall temperature signal during periods when the mechanical power variation is limited. In specific implementation, the system samples the barrel wall temperature signal within a continuous control cycle and calculates the temperature change between adjacent control cycles. It should be noted that this application focuses on the trend of barrel wall temperature change, rather than the absolute temperature value of a single sampling point, in order to avoid malfunctions of the cooling unit caused by sensor noise or transient disturbances.

[0088] When the barrel wall temperature change remains positive within a preset time window and does not show a significant drop, the system considers the barrel and melt to be in a state of continuous heat accumulation. The length of the time window can be set according to the barrel material, wall thickness, and thermal inertia characteristics. As one possible implementation, this time window corresponds to several continuous control cycles to distinguish between short-term temperature fluctuations and the actual temperature rise trend.

[0089] After confirming a continuous upward trend in temperature, the system does not directly activate the barrel cooling unit at maximum capacity. Instead, it determines the initial activation level of the barrel cooling unit based on the duration of the limited mechanical power variation state. It should be noted that the duration of the limited mechanical power variation state reflects the degree of limitation in the drive system's adjustment capability. When this state lasts for a short time, it indicates that the system may still be in a state of operation switching or transient phase, in which case the cooling unit only participates at a lower activation level. When the limited state lasts for a long time, it indicates that the drive side has been in a limited operating condition for an extended period, and the cooling activation level is correspondingly increased to compensate for the heat that cannot be released through the mechanical path.

[0090] In this application, the barrel cooling unit can be an air-cooled device, a water-cooled device, or other device with adjustable cooling capacity. The "engagement level" is used to characterize the cooling capacity, and its specific implementation is related to the structural form of the cooling unit. As one possible implementation, when using air cooling, the engagement level can correspond to the speed range of the cooling fan; when using water cooling, the engagement level can correspond to the opening range of the cooling water valve or the flow rate of the cooling medium; when using a segmented cooling structure, the engagement level can also be reflected as the step-by-step engagement of different cooling sections.

[0091] It should be noted that the input level is not fixed as a fixed number of discrete levels; it can be either discrete or continuously adjustable, depending on the controllable precision of the cooling actuator. This application does not limit the specific number of input levels, but emphasizes the correlation between the input level and the state of limited mechanical power change, that is, the intensity of cooling capacity input changes with the duration of the limited state.

[0092] After the barrel cooling unit is started at its initial input level, it participates in the extrusion process as a compensatory thermal regulation means, rather than replacing the original heating and pressure control logic. In other words, the role of the cooling unit is to suppress the heat accumulation caused by the limitation of mechanical regulation, rather than to dominate the control of the melt temperature. As the limitation of mechanical power change is lifted, that is, when the rate of change of the screw drive motor torque returns to an unrestricted state, the system can correspondingly reduce or deactivate the input level of the barrel cooling unit, so that the extrusion process returns to an operating state in which mechanical regulation is the main factor and cooling is the secondary factor.

[0093] In this embodiment, the determination of a limited mechanical power variation state requires the simultaneous fulfillment of conditions u1, u2, and u3. u1 confirms the actual existence of the power variation exceeding the limit; u2 confirms that the exceeding limit has actually triggered the inner drive loop constraint; and u3 confirms that the constraint has temporal continuity. It should be noted that a single condition is prone to misjudgment due to instantaneous disturbances, measurement noise, or control boundary effects. Only when all three conditions are met simultaneously is the system considered to have indeed entered an operating state with limited drive adjustment capability.

[0094] In this embodiment, by limiting the start-up and operation intensity of the barrel cooling unit to the period of limited mechanical power change, and introducing temperature trend and limited duration as a joint criterion, the frequent intervention of the cooling unit under unnecessary circumstances is avoided, thereby reducing interference with the melt plasticizing process and temperature field distribution, and improving the operating stability and controllability of the extruder under complex working conditions.

[0095] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these specific embodiments are merely illustrative. Those skilled in the art can omit, substitute, and modify the details of the above methods and systems in various ways without departing from the principles and essence of the present invention. For example, combining the above method steps to perform substantially the same function and achieve substantially the same result according to substantially the same method falls within the scope of the present invention. Therefore, the scope of the present invention is defined only by the appended claims.

Claims

1. An integrated temperature and pressure adaptive control method for an extruder, applied to an extrusion equipment including a screw drive motor, a screw, a barrel heating unit, a barrel cooling unit, and a die head pressure sensor, characterized in that: The method includes the following steps: S1. Collect the actual torque and speed signals of the screw drive motor during the continuous control cycle, and calculate the instantaneous effective mechanical power acting on the melt load; S2. Perform differential calculation on the instantaneous effective mechanical power within adjacent control cycles to obtain the change in mechanical power per unit time, which serves as a control reference for the screw's rate of injecting melt energy. S3. Determine the allowable limit of mechanical power variation under the current working conditions based on the screw structure parameters, the current speed range, and the working status of each heating zone of the barrel; S4. Compare the mechanical power change with the allowable limit of mechanical power change. When the mechanical power change exceeds the allowable limit of mechanical power change, apply a constraint signal to the torque command channel of the screw drive motor to limit the rate of change of the torque command value. S5. The torque given change rate limit acts on the inner loop level of the screw drive control circuit. Under the condition of the inner loop limitation, the pressure control circuit formed by the die head pressure sensor continuously outputs speed regulation or flow regulation commands to maintain the continuous operation of the extrusion process. S6. During the period when the change in mechanical power is limited, the barrel wall temperature signal is continuously collected. When the barrel wall temperature signal shows a continuous upward trend, the barrel cooling unit is controlled to enter the working state.

2. The integrated temperature and pressure adaptive control method for an extruder according to claim 1, characterized in that: The working process of S1 includes: The actual speed signal and actual torque signal of the screw drive motor are acquired within the same control cycle; When the extruder is in a stable extrusion condition, a reference torque value for the corresponding speed range is established based on the actual speed signal and the actual torque signal. The reference torque value is used to characterize the mechanical loss torque of the screw drive system. During the extrusion process, the reference torque value corresponding to the speed range is subtracted from the actual torque signal to obtain the equivalent shear torque acting on the melt load; The screw's angular acceleration is calculated based on the change in the actual rotational speed signal within adjacent control cycles, and the inertial torque caused by the system's inertia is calculated based on the pre-set equivalent rotational inertia parameters of the screw and transmission shaft system. The inertial torque is subtracted from the equivalent shear torque to obtain the corrected melt load torque; The corrected melt load torque is multiplied with the corresponding actual speed signal to obtain the instantaneous effective mechanical power acting on the melt load.

3. The integrated temperature and pressure adaptive control method for an extruder according to claim 1, characterized in that: The S3 defines the physical upper bound of mechanical power variation by constructing a power variation benchmark constraint that reflects the screw's mechanical shearing capacity and the barrel's thermal compensation capacity. The construction process includes: Obtain the effective axial length of the screw compression section, the screw diameter, and the average depth of the screw groove; calculate the unfolded area of ​​the screw surface participating in shearing within the screw compression section. Collect the actual torque of the screw drive motor during the current control cycle. Compared with actual speed and according to Calculate the corresponding instantaneous mechanical shear power; Within a continuous control cycle, differential calculation is performed on the instantaneous mechanical shear power to obtain the change in mechanical power per unit time, and the upper limit of the change in mechanical power per unit shear action area is determined using the unfolded area of ​​the screw surface as a constraint. The rated heating power and current actual output power of each heating zone of the barrel are collected to obtain the adjustable power margin of each heating zone under the current operating conditions. Based on the adjustable power margin and the average residence time of the melt in the barrel, the amount of external heat compensation that can be used to offset the heat input caused by changes in mechanical power per unit time is calculated. Based on the quantitative relationship between the upper limit of mechanical power change per unit shear area and the external heat compensation amount, a baseline limit for mechanical power change is determined.

4. The integrated temperature and pressure adaptive control method for an extruder according to claim 3, characterized in that: The mechanical power variation baseline limit is constructed by spatial correction processing based on the screw axial structural parameters and the axial distribution of barrel heating power to build candidate mechanical power variation limits. The process includes: Based on the screw structure parameters, the screw is divided into a feeding section, a compression section and a metering section along the axial direction, and the effective cross-sectional area of ​​the screw groove, the change in screw groove depth and the corresponding material compression ratio are determined for each screw section. Within the current screw speed range, the theoretical conveying volume of material per unit time in each screw section is calculated based on the effective cross-sectional area of ​​the screw groove and the screw speed of each screw section. The real-time heating power of each heating zone in the barrel is collected, and the heating power is distributed to the corresponding screw segment according to the coverage length of each heating zone in the screw axis, so as to obtain the external heat input power per unit time of each screw segment. Calculate the external heat input per unit time of each screw section based on the external heat input power per unit time and the corresponding theoretical conveying volume; Using the theoretical conveying volume of each screw section as a weight, the baseline limit for mechanical power variation is weighted and corrected to obtain candidate limits for mechanical power variation.

5. The integrated temperature and pressure adaptive control method for an extruder according to claim 4, characterized in that: The candidate limits for mechanical power variation are used to determine the final limit for mechanical power variation for torque change rate control through time-domain constraint processing. The process includes: Within a continuous control cycle, the average power change of the instantaneous effective mechanical power acting on the melt load within the first time window and the average power deviation within the second time window are calculated respectively, wherein the time length of the first time window is shorter than the time length of the second time window. The average power change within the first time window is represented as the transient change intensity of the screw shear power; the power deviation from the average within the second time window is represented as the continuous accumulation state of the screw shear power. Based on the transient change intensity and the continuous accumulation state, the candidate limit for mechanical power change is corrected in the time domain, and the expression is: in: This is the allowable limit for the final mechanical power change used to constrain the rate of torque change during screw drive; These are candidate limits for mechanical power variation after screw functional segment correction and heat input correction; For the first Instantaneous effective mechanical power within each control cycle; This represents the average instantaneous effective mechanical power within the second time window; These correspond to the number of sampling points within the first and second time windows, respectively. ; These correspond to the weighting coefficients for transient power change and sustained power accumulation, respectively.

6. The integrated temperature and pressure adaptive control method for an extruder according to claim 1, characterized in that: In step S4, the rate of change of the torque setpoint of the screw drive motor is limited by power torque mapping constraints. The process includes: Within a continuous control cycle, calculate the change in mechanical power for each control cycle. Corresponding to the allowable limit of mechanical power variation The super limited edition ; The excess amount is converted into the equivalent torque change in the corresponding control cycle. ,in For the screw in the first The actual rotational speed of the control cycle; and As the upper limit of the incremental limit of the torque setpoint in the current control cycle; Inside the motor controller, a torque setpoint register is used. Using the previous cycle's setpoint, the increment of the torque setpoint for the current control cycle is limited, as expressed by: in, This is the unconstrained torque increment calculated according to process requirements. Indicates will The limit is within the range [ ]Inside, This is the torque setpoint after incremental limiting.

7. The integrated temperature and pressure adaptive control method for an extruder according to claim 6, characterized in that: The S4 continuously and periodically adaptively adjusts the upper limit of the torque increment limit of the screw drive motor, including: Record the change in mechanical power in each of N consecutive control cycles. Corresponding to the allowable limit of mechanical power variation The super limited edition The cumulative power over-limit integral value ; according to Upper limit of torque increment for the next control cycle To achieve adaptive adjustment, the formula expression is: in, This is the upper limit of the initial torque increment; This is an adjustment coefficient used to control the rate at which constraints are tightened; As the upper limit of the torque setpoint increment limit for the next control cycle; Will The output is sent to the motor controller to constrain the torque increment for the next control cycle, without directly modifying the torque setpoint for the current control cycle.

8. The integrated temperature and pressure adaptive control method for an extruder according to claim 1, characterized in that: In S5, when the torque given rate of change limit is applied to the inner loop level of the screw drive control loop, the output signal of the head pressure control loop participates in the screw drive control through a restricted interface, specifically including: Within the control cycle where the rate of change of torque is limited, the torque increment request of the pressure control loop is obtained by using the proportional-integral control method based on the difference between the real-time pressure collected by the head pressure sensor and the head set pressure. The torque increment request is compared with the current allowed torque increment limit of the inner loop level, and the part exceeding the torque increment limit is truncated to obtain the restricted torque increment request. The restricted torque increment request is used as the effective torque adjustment input of the screw drive motor, so that the pressure control loop can still participate in the screw drive adjustment process under the inner loop restricted state.

9. The integrated temperature and pressure adaptive control method for an extruder according to claim 1, characterized in that: The barrel cooling unit is started and participates in thermal regulation through a conditional control method associated with the limited state of mechanical power variation. The process includes: During a continuous control cycle, determine whether the change in mechanical power remains below the corresponding allowable limit for mechanical power change. If so, the barrel wall temperature signal is continuously sampled, and the trend of barrel wall temperature change is determined based on the change in barrel wall temperature over multiple adjacent control cycles. When the barrel wall temperature change trend is in a unidirectional upward state within a preset time window, the initial input level of the barrel cooling unit is determined based on the duration of the mechanical power change being in a limited state. The initial input level is used as the start-up control parameter for the barrel cooling unit, enabling the barrel cooling unit to participate in the thermal conditioning process in a controlled manner during periods of limited mechanical power variation.

10. The integrated temperature and pressure adaptive control method for an extruder according to claim 9, characterized in that: The restricted state of mechanical power change satisfies: u1. During the continuous control cycle, the actual change in mechanical power is determined to exceed the corresponding allowable limit for mechanical power change after comparison. u2. During the control cycle in which the determination is made, the rate of change of the torque given of the screw drive motor is constrained based on the allowable limit of the mechanical power change, and is executed by the inner loop level of the screw drive control loop. u3. The torque given rate of change constraint shall remain in effect for no less than a preset number of consecutive control cycles. When all of the above conditions are met, the extruder is determined to be in a state of limited mechanical power variation during operation.

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