Pressure testing method, medium and pressure testing system based on closed-loop control

Abstract

The application provides a pressure test method, medium and pressure test system based on closed-loop control, and belongs to the technical field of automatic test. The method comprises the following steps: step 1, obtaining a target force trajectory signal; step 2, obtaining an actual pressure acting on a measured object, and calculating a force error according to the actual pressure and the target force at a corresponding moment k; step 3, calculating a feedforward voltage based on an electrical dynamic model according to the target force trajectory signal and an electrical parameter set of a voice coil motor; step 4, calculating a feedback voltage according to the force error and a gain coefficient; step 5, calculating a driving voltage according to the feedforward voltage and the feedback voltage; step 6, driving the voice coil motor to generate a force acting on the measured object according to the driving voltage; and repeatedly executing steps 2 to 6, so that the actual pressure trajectory signal converges to the target force trajectory signal in the time domain. The application can improve the force response speed and accuracy.

Description

Technical Field

[0001] This application relates to the field of automated testing technology, and in particular to a pressure testing method, medium, and pressure testing system based on closed-loop control. Background Technology

[0002] In fields such as materials mechanical property testing, precision micro-assembly, and biomedical engineering, the accuracy and dynamic response capability of pressure testing directly impact product development and quality evaluation. Currently, mainstream precision pressure testing systems primarily employ two technical approaches: indirect force control systems based on displacement or velocity closed-loop systems and high-end force control systems based on hydraulic servos. However, these two approaches are increasingly unable to simultaneously meet the application requirements of high precision, high dynamics, and low cost.

[0003] In recent years, some researchers have proposed using voice coil motors in conjunction with force sensors to form direct force closed-loop control systems. For example, patent CN116470726A discloses a closed-loop force-controlled voice coil motor and pressure control method, which improves force control accuracy by forming a complete closed loop with the driver, force sensor, and voice coil motor module. However, these solutions often employ single PID feedback control or feedforward control that relies on the identification of complex mechanical systems, without considering the electrical dynamic characteristics (resistance, inductance, and back EMF) of the voice coil motor itself. This results in significant phase lag when tracking rapidly changing force trajectories, limiting system bandwidth and thus still exhibiting technical defects such as control lag and insufficient dynamic response.

[0004] Therefore, how to provide a direct force closed-loop pressure testing method that does not require complex mechanical model identification, can directly compensate for electrical dynamics, and has high bandwidth response characteristics has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a pressure testing method, medium, and pressure testing system based on closed-loop control, thereby solving at least one of the above-mentioned technical problems.

[0006] In a first aspect, this application provides a pressure testing method based on closed-loop control, applied to a direct-drive pressure testing system comprising a voice coil motor, a force sensor, and a controller, the method comprising: Step 1: Acquire the target force trajectory signal; Step 2: Obtain the actual pressure acting on the object being measured detected by the force sensor at time k according to the preset sampling period, and calculate the force error based on the actual pressure and the target force at time k in the target force trajectory signal. Step 3: Calculate the feedforward voltage based on the target force trajectory signal and the electrical parameter set of the voice coil motor, using an electrical dynamic model. The electrical parameter set includes winding resistance, winding inductance, and back electromotive force constant. Step 4: Obtain the gain coefficient, input the force error and the gain coefficient into the preset feedback control model, and output the feedback voltage; Step 5: Calculate the driving voltage based on the feedback voltage and the feedforward voltage; Step 6: Drive the voice coil motor according to the driving voltage to generate a force acting on the object being tested; Repeat steps 2 to 6 to make the actual pressure trajectory signal converge to the target force trajectory signal in the time domain.

[0007] Optionally, the step of calculating the feedforward voltage based on the target force trajectory signal and the electrical parameter set of the voice coil motor using an electrical dynamic model includes: The corresponding desired current is calculated based on the target force trajectory signal; Based on the desired current and the electrical parameter set, the resistance voltage drop compensation component and the inductance voltage drop compensation component are calculated. The feedforward voltage is calculated based on the resistor voltage drop compensation component and the inductor voltage drop compensation component.

[0008] Optionally, the desired current I at time k d (k)=F t (k) / Kt, where Kt is the thrust constant; The voltage drop compensation component U R (k) = R×I d (k); The inductor voltage drop compensation component I d (k-1) represents the desired current at time k-1; The feedforward voltage U ff (k)= U R (k)+U L (k).

[0009] Optionally, before calculating the feedforward voltage based on the resistor voltage drop compensation component and the inductor voltage drop compensation component, the method further includes: The back electromotive force is calculated based on the desired current and the set of electrical parameters. The step of calculating the feedforward voltage based on the resistor voltage drop compensation component and the inductor voltage drop compensation component includes: The feedforward voltage is calculated based on the resistor voltage drop compensation component, the inductor voltage drop compensation component, and the back electromotive force.

[0010] Optionally, the feedback control model is a PID control model, and the gain coefficient includes proportional gain, integral gain, and derivative gain; the step of inputting the force error and the gain coefficient into the preset feedback control model and outputting a feedback voltage includes: The PID control model is invoked, and the corresponding proportional term voltage is calculated based on the proportional gain and the force error at time k. The integral term voltage is calculated based on the integral gain and the force error at each time point; The corresponding error change rate is calculated based on the force error and the sampling period, and the differential term voltage is calculated based on the differential gain and the error change rate at time k. The feedback voltage is calculated based on the proportional term voltage, integral term voltage, and derivative term voltage.

[0011] Optionally, obtaining the gain coefficient includes: determining the gain coefficient based on the target force trajectory signal and / or force error.

[0012] Optionally, determining the gain coefficient based on the target force trajectory signal and / or force error includes: The working condition matching time k is identified based on the target force trajectory signal and the force error; Obtain the gain coefficient corresponding to the matched operating condition.

[0013] Optionally, the driving voltage U c (k)=w(k)×U ff (k)+U fb w(k) is the feedforward voltage U at time k. ff (k) weight in the driving voltage, U fb w(k) is the feedback voltage at time k, and the value of w(k) is positively correlated with the rate of change of the force of the target force trajectory signal at time k.

[0014] In a second aspect, this application provides a computer-readable storage medium storing executable instructions that, when executed by a processor, cause the processor to perform the method described in any embodiment of this application.

[0015] A third aspect of this application provides a direct-drive pressure testing system, comprising: Voice coil motors are used to directly generate test pressure. An item placement platform is used to place the items to be tested. A force sensor for measuring the pressure applied to the object being tested; A power driver is used to drive a voice coil motor to generate the corresponding force. A controller for performing the methods described in any embodiment of this application.

[0016] The pressure testing method, medium, and direct-drive pressure testing system based on closed-loop control in this application employ a voice coil motor as a direct-drive actuator. There are no intermediate transmission mechanisms such as reducers, couplings, or ball screws between the actuator and the load, eliminating backlash, friction, and inertia in the mechanical transmission chain. Furthermore, it eliminates the need for complex mechanical transmission mechanisms, resulting in a compact system structure, simple maintenance, and long service life. By constructing a feedforward + feedback composite control architecture, the actual pressure detected in real-time by a force sensor is used as the feedback term to directly control the force in a closed loop, avoiding the accuracy loss caused by indirectly calculating the force through a stiffness model in the displacement closed-loop mode. A feedforward voltage Uff(k) based on an electrical dynamic model is used to pre-compensate for the resistance and inductance voltage drops of the voice coil motor. When the target force changes rapidly (such as with ramp loading or sinusoidal tracking), the feedforward term can output the required drive voltage in advance, ensuring that the actual force value closely follows the target force trajectory. This eliminates the hysteresis of the current loop, significantly improves the force response speed, and reduces dynamic tracking errors. Furthermore, the electrical parameters (resistance R, inductance L, thrust constant Kt) upon which the feedforward calculation relies can be obtained using a multimeter, LCR bridge, or simple static calibration experiments. This eliminates the need to identify complex models of the mechanical system's damping, stiffness, and resonance modes, reducing both the difficulty and cost of system deployment and improving computational efficiency. The direct-drive characteristics of the voice coil motor, combined with the closed-loop control algorithm, simultaneously achieve high-precision control in the μN to several kN range and dynamic force response up to several hundred Hz. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0018] Figure 1 This is a schematic diagram of the structure of a direct-drive pressure testing system in one embodiment; Figure 2 This is a schematic diagram of the direct-drive pressure testing system in another embodiment; Figure 3 This is a flowchart illustrating a pressure testing method based on closed-loop control in one embodiment. Figure 4 This is a schematic diagram of the process for calculating the feedforward voltage based on an electrical dynamic model in one embodiment. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0020] All terms used in this application (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0021] For example, the terms "first" and "second" used in this application are only used to distinguish similar objects and differentiate the first object from another object, rather than to describe a specific order or sequence, nor should they be interpreted as indicating or implying relative importance.

[0022] This application proposes a pressure testing method based on closed-loop control, which is applied to a direct-drive pressure testing system that includes a voice coil motor, a force sensor, and a controller.

[0023] A direct-drive pressure testing system refers to a testing system in which there are no intermediate transmission mechanisms such as reducers, couplings, or ball screws between the actuator (voice coil motor) and the load (test object). In traditional pressure testing systems, servo motors typically need to convert rotary motion into linear motion via ball screws, which involves gear backlash, friction loss, and transmission inertia, all of which reduce the accuracy and response speed of force control. The direct-drive structure adopted in this application rigidly connects the mover of the voice coil motor directly to the force sensor and the test object via a connector, eliminating backlash and elastic deformation in the transmission chain, allowing the electromagnetic thrust of the motor to act on the test object with minimal delay. Figure 1 and Figure 2 As shown, the direct-drive pressure testing system includes: a voice coil motor 10, an item placement platform 20, a force sensor 30, a power driver (not shown), and a controller (not shown).

[0024] The voice coil motor 10 directly generates the test pressure and includes a stator (magnet assembly) and a mover (coil assembly), the mover being capable of linear motion along the axial direction. The object placement platform 20 is used to place the object to be tested. The force sensor 30 measures the pressure applied to the object and converts it into an electrical signal for feedback. The power driver receives command signals from the controller (such as the drive voltage U). c The controller is used to drive the voice coil motor to generate the corresponding force; the controller is used to execute the pressure test method based on closed-loop control in any embodiment of this application.

[0025] The force sensor can be a high-precision pressure gauge, such as a strain gauge miniature force sensor, and can be directly integrated into a suitable location such as the pressure probe, the object placement platform 20, or the testing fixture. The controller is the core processing unit of the system, which receives feedback signals from the force sensor (actual pressure F). aThe system receives a preset force command (target force trajectory signal) from the host computer and executes the corresponding control algorithm (such as PID, feedforward compensation, adaptive control, etc.) to calculate the drive signal (drive voltage U). c The sample placement platform 20 is used to fix the sample to be tested and can have multi-dimensional fine-tuning functions to ensure centering, such as rigid connection or integrated design with the force sensor.

[0026] Specifically, the output end of the voice coil motor 10 is fixedly connected to one end of the force sensor 30 via a rigid connector (such as the central motion plate 40); the other end of the force sensor 30 is fixedly / movably connected to the object being tested or the testing fixture, for real-time and direct measurement of the actual pressure exerted by the voice coil motor on the object being tested. The measurement axis of the force sensor 30 is collinear with the motion axis of the voice coil motor 10 to avoid measurement errors introduced by lateral forces. This application uses a direct series force sensor without flexible hinges for pressure measurement, eliminating the influence of additional stiffness and hysteresis nonlinearity introduced by flexible hinges on force measurement. The thrust of the voice coil motor is approximately linearly proportional to the driving current (the proportionality constant is the thrust constant Kt), and this linear characteristic makes it possible to precisely control the force by controlling the voltage.

[0027] Furthermore, the direct-drive pressure testing system also includes a central motion plate 40, a tension spring 50, an angle bracket 60, a guide rod 70, a testing fixture 80, and a base 90. Multiple guide rods 70 may be provided, each standing upright on the inner edge of the testing fixture 80; the central motion plate 40 is a plate-like structure, on which multiple sliding bearings 41 (e.g., ...) are provided. Figure 2 (Two are shown in the image). Each sliding bearing is fitted onto a guide rod 70, allowing the central motion plate 40 to move linearly along the guide rod 70, thereby adjusting the force sensor 30, fixed to the lower surface of the central motion plate 40, to a suitable height position. Angle brackets 60 are used to fix the voice coil motor 10 to the test fixture 80. The test fixture 80 can be made of aluminum profile and has a cuboid outer frame. The voice coil motor is fixed to the lower end of the upper surface of the test fixture 80. The two ends of the tension spring 50 are connected to the voice coil motor 10 and the test fixture 80, respectively, to provide preload or reset force to the voice coil motor 10. The item placement platform 20 is located directly below the voice coil motor 10 and the force sensor 30.

[0028] In one embodiment, such as Figure 3 As shown, the stress testing method based on closed-loop control includes: Step 310: Obtain the target force trajectory signal.

[0029] Target force trajectory signal F tThis refers to the function of the force applied to the test object as a function of its change over time. This signal is preset by the operator using host computer software and can have various waveform forms to meet different testing needs. For example, target force trajectory types include: constant value (e.g., maintaining a constant pressure of 100N for creep testing), ramp waveform (e.g., linearly increasing at a rate of 10N / s for stiffness testing), sine waveform (e.g., a sinusoidal alternating force with a peak-to-peak value of 50N and a frequency of 10Hz for fatigue testing), trapezoidal impact waveform (e.g., rapidly rising to 200N, holding for 2 seconds, and then rapidly unloading to simulate impact loads), and user-defined arbitrary force spectrum functions (e.g., force-time curves recorded based on actual working conditions). For example, when testing the fatigue life of an automotive shock absorber rubber bushing, the target force trajectory can be set to a sine wave with a frequency of 5Hz and a peak-to-peak value of 500N, continuously for 1 million cycles.

[0030] Specifically, relevant testing personnel can set the corresponding target force trajectory signal and sampling period and other related parameters on the host computer to generate the corresponding target force trajectory signal. The host computer then sends this signal to the corresponding pressure testing system through communication with the system. The controller in the pressure testing system can load the acquired target force trajectory signal into its memory, and can directly read the target force trajectory signal from the memory when the test starts.

[0031] Step 320: Obtain the actual pressure acting on the object being measured detected by the force sensor at time k according to the preset sampling period, and calculate the force error based on the actual pressure and the target force at time k in the target force trajectory signal.

[0032] The force error *e* represents the difference between the target force and the actual feedback force. The sampling period *Ts* refers to the time interval between two consecutive data readings from the force sensor by the controller. The sampling period can be set according to the actual situation; for example, it can be set to a fixed value or a dynamically changing value. For instance, for test scenarios with higher dynamic requirements (such as impact testing), the sampling period can be shortened.

[0033] Based on the target force trajectory signal, the target force at each corresponding moment can be identified, and the target force F at the same moment k can be determined. t (k) and the actual pressure F measured at the corresponding time. a By comparing (k), the force error e(k) can be obtained. For example, e(k) = F t (k)- F a (k).

[0034] For example, taking a fixed sampling period Ts=0.1ms as an example, the current sampling time k=1000 (corresponding to a time of 100ms), if the target force value at the corresponding time is F t(1000) = 150N, actual pressure F a (1000) = 144 N, then the force error e(1000) = F t (1000)-F a (1000) = 150N - 144N = 6N. This means that at 100ms, the actual force applied to the tested object was 6N less than the expected value.

[0035] Step 330: Calculate the feedforward voltage based on the target force trajectory signal and the electrical parameter set {R,L,Ke} of the voice coil motor using an electrical dynamic model.

[0036] Where R is the winding resistance, L is the winding inductance, and Ke is the back electromotive force constant. The electrical dynamic model is a mathematical equation describing the electrical characteristics of the voice coil motor. The feedforward voltage is the voltage component directly calculated from the desired force trajectory to compensate for the known dynamic characteristics of the system. The feedforward voltage is calculated based on the electrical dynamic model of the voice coil motor.

[0037] The winding resistance R can be obtained by directly measuring the DC resistance of the motor winding with a multimeter; the winding inductance L can be obtained by measuring with an LCR bridge or by applying a step voltage and recording the current response for fitting; the back electromotive force constant Ke is numerically equal to the thrust constant Kt, which can be obtained through static calibration experiments, such as applying a constant current and measuring the steady-state force. Furthermore, the electrical parameter set can also include the damping coefficient B. est Damping coefficient B est It is used to calculate back electromotive force, which can be obtained by setting up a constant speed drag experiment and recording the relationship between steady-state force and velocity.

[0038] Specifically, the electrical dynamic model can be a calculation model based on the voltage balance equation, which can simultaneously compensate for one, two, or all three of the following three terms: resistance voltage drop, inductance voltage drop, and back electromotive force (EMF). For example, it can simultaneously compensate for resistance voltage drop, inductance voltage drop, and back EMF; or when the back EMF term is small, it can be ignored, making it suitable for medium- and low-speed testing scenarios and reducing the system's requirements for sensor configuration; or when the inductance is small (e.g., L < 0.1 mH) or the rate of force change is low, the influence of the inductance voltage drop can be ignored, and only the resistance voltage drop needs to be compensated.

[0039] Furthermore, considering the voice coil motor and its driver as an equivalent current closed-loop system, the feedforward voltage U ff (k) This is obtained through proportional-integral-derivative (PID) feedforward calculation of the desired current. Alternatively, a mapping table between the target force and the feedforward voltage can be established by pre-calibrating the voice coil motor offline and stored in the controller's memory. Based on the target force F at the current moment... t (k) Look up the corresponding feedforward voltage U in the table.ff (k), and linear interpolation can be used to improve resolution.

[0040] Calibration process: A series of different voltage commands are applied to the voice coil motor, and the corresponding steady-state output force is recorded to form a voltage-force mapping table. For reverse application, the required voltage is found based on the target force.

[0041] Step 340: Obtain the gain coefficient, input the force error and the gain coefficient into the preset feedback control model, and output the feedback voltage.

[0042] Gain coefficients are parameters used in feedback control models to adjust the strength of the control action. They typically include the first two or three of the proportional gain Kp, integral gain Ki, and derivative gain Kd. In this embodiment, the gain coefficients can be a set of fixed values ​​or dynamically scheduled variables based on the system's operating state (referred to as gain scheduling) to adapt to control requirements under different operating conditions.

[0043] Feedback control models are algorithmic models that generate control quantities based on error signals. For example, a feedback control model can be a standard proportional-integral-derivative (PID) control model, or any suitable model such as a PI control model, integral-separated PID control model, variable-speed integral PID control model, fuzzy PID control model, active disturbance rejection control model, etc.

[0044] The proportional element provides a rapid response proportional to the error, correcting the current deviation; the integral element reflects the accumulated historical error, used to eliminate steady-state error and ensure long-term accuracy. Furthermore, a differential element or a feedforward element can be added. The differential element predicts the error change trend and suppresses overshoot; the feedforward element directly provides a compensation signal based on the rate of change of the target force, improving dynamic tracking performance.

[0045] Step 350: Calculate the driving voltage based on the feedback voltage and the feedforward voltage.

[0046] In this embodiment, the feedforward voltage U ff (k) and feedback voltage U fb (k) Combined, forming the final drive command. Drive voltage U c The synthesis method of (k) can include any suitable superposition method such as linear superposition of feedforward voltage and feedback voltage, superposition with weighted coefficients, or saturation limiting superposition.

[0047] For example, U c (k)= U fb (k)+ U ff (k).

[0048] Or U c (k)= U fb(k)+ w(k)×U ff w(k) represents the weight of the feedforward voltage in the driving voltage at time k. The value of w(k) can be a preset fixed value or an adaptively adjusted value based on the characteristics of the target force trajectory signal.

[0049] Step 360: Drive the voice coil motor according to the driving voltage to generate a thrust acting on the object being tested.

[0050] Drive voltage U c (k) After calculation, the signal can be converted into an analog signal (such as an analog voltage signal) and output to the power driver. The power driver may include modules such as an input conditioning circuit (for filtering and buffering the input signal), a pulse width modulation (PWM) generator, power switching transistors (usually an H-bridge or three-phase bridge composed of MOSFETs or IGBTs), and current detection and protection circuits. The power driver converts the input analog signal into a PWM signal with a certain duty cycle, and uses this PWM signal to control the on and off of the power switching transistors, modulating the DC bus power supply into a high-frequency pulse voltage applied to the voice coil motor windings. Since the motor inductance smooths the high-frequency pulses, the actual current flowing through the windings is an average current proportional to the PWM duty cycle, thereby achieving current control.

[0051] The power driver can specifically use either voltage control mode or current control mode to drive the voice coil motor to generate a thrust acting on the object being measured, so that the thrust acting on the object is close to the target force.

[0052] After receiving a drive signal from a power driver, the voice coil motor converts electrical energy into mechanical energy based on the principle of electromagnetic induction. Depending on the magnitude and direction of the drive signal, the voice coil motor directly generates a corresponding thrust or pull force. This thrust is transmitted to the object being measured through the motor mover, rigid connectors, and / or force sensor, causing the object to be compressed or stretched.

[0053] By using the output voltage as the control command for the voice coil motor, it can be applied to most voltage-type voice coil motor drivers without modifying the internal structure of the driver, thus having strong compatibility.

[0054] Repeat steps 2 to 6 to make the actual pressure trajectory signal F a The target force trajectory signal F in the time domain t Convergence. Steps 2 through 6 constitute a complete control cycle, which will be repeatedly executed at sampling intervals Ts during the test. Each cycle updates the drive voltage based on the latest feedback information, forming a closed-loop negative feedback process of "measurement-calculation-drive".

[0055] The pressure testing method based on closed-loop control in this application uses a voice coil motor as a direct-drive actuator. There are no intermediate transmission mechanisms such as reducers, couplings, or ball screws between the actuator and the load, eliminating backlash, friction, and inertia in the mechanical transmission chain. Furthermore, it eliminates the need for complex mechanical transmission mechanisms, resulting in a compact system structure, simple maintenance, and long service life. By constructing a feedforward + feedback composite control architecture, the actual pressure detected in real time by the force sensor is used as the feedback term to directly control the force in a closed loop, avoiding the accuracy loss caused by indirectly calculating the force through a stiffness model in the displacement closed-loop mode. A feedforward voltage U based on an electrical dynamic model is employed. ff (k) By pre-compensating for the resistance and inductance voltage drops of the voice coil motor, the feedforward term can output the required drive voltage in advance when the target force changes rapidly (such as ramp loading or sinusoidal tracking), ensuring that the actual force value closely follows the target force trajectory. This eliminates the hysteresis of the current loop, significantly improves the force response speed, and reduces dynamic tracking errors. Furthermore, the electrical parameters (resistance R, inductance L, thrust constant Kt) upon which the feedforward calculation relies can be obtained through a multimeter, LCR bridge, or simple static calibration experiments. This eliminates the need to identify complex models of the mechanical system's damping, stiffness, and resonance modes, reducing system deployment difficulty and cost while improving computational efficiency. The direct-drive characteristics of the voice coil motor, combined with the closed-loop control algorithm, simultaneously achieve high-precision control in the μN to several kN range and dynamic force response up to several hundred Hz.

[0056] In one embodiment, such as Figure 4 As shown, the feedforward voltage is calculated based on the electrical dynamic model, including: Step 410: Calculate the corresponding desired current based on the target force trajectory signal.

[0057] In this embodiment, the desired current is expressed as the theoretical value of the voice coil motor winding current required to generate the target force. Wherein, the electromagnetic thrust F of the voice coil motor... em The relationship between F(t) and the current I(t) is F em (t) = Kt × I(t), that is, the desired current I at time k. d (k) = F t (k) / Kt.

[0058] Step 420: Calculate the resistance voltage drop compensation component and the inductance voltage drop compensation component based on the desired current and electrical parameter set.

[0059] Resistance voltage drop compensation component U R Its function is to offset the voltage consumed by the winding resistance, ensuring that the voltage applied to the motor can generate the required current. The voltage drop compensation component U at time k... R (k), U R (k) = R×I d (k).

[0060] Inductor voltage drop compensation component U L The function of the inductor is to overcome its inertia, allowing the current to quickly follow changes in the desired value. The voltage across the inductor is proportional to the rate of change of the current, therefore U L = ,in, The differential term representing the current can be approximated in the discrete time domain using a first-order backward difference, which yields the following result. I d (k-1) represents the expected current at time k-1.

[0061] Furthermore, high-frequency noise that may be present in the current differential term can be filtered to obtain the filtered current differential term I. d (k)', where I d (k)'=y× I d (k) + (1- y) ×I d (k-1)', where y is the filter coefficient, which can take values ​​from 0.1 to 0.3, then:

[0062] In addition, another Among them, U L max and U L min is the preset limit value for the inductance compensation component.

[0063] Step 430: Calculate the feedforward voltage based on the resistor voltage drop compensation component and the inductor voltage drop compensation component.

[0064] Feedforward voltage U ff (k) can be the sum of the above compensation terms, i.e., U ff (k)= U R (k)+ U L (k).

[0065] Furthermore, prior to step 430, the method further includes: calculating the back electromotive force based on the desired current and the set of electrical parameters.

[0066] In a voice coil motor, the movement of the mover induces a back electromotive force U in the winding. emf = Ke × v, where Ke is the back electromotive force constant and v is the mover velocity. The existence of back electromotive force means that even if the current has reached the desired value, if the mover is moving, an additional voltage is needed across the motor to overcome the back electromotive force. For a voice coil motor, the back electromotive force constant Ke is numerically equal to the thrust constant Kt. By measuring the mover velocity in real time, the mover velocity v(k) at time k can be obtained, and thus the back electromotive force U at the corresponding time k can be obtained.emf (k) = Ke×v(k) = Kt×v(k).

[0067] The feedforward voltage U is calculated based on the resistor voltage drop compensation component, the inductor voltage drop compensation component, and the back electromotive force. ff (k). That is, U ff (k)= U R (k)+ U L (k)+ U emf (k).

[0068] In one embodiment, the feedback control model is a PID control model, and the gain coefficients include proportional gain Kp, integral gain Ki, and derivative gain Kd. The step of inputting the force error and the gain coefficients into a preset feedback control model and outputting a feedback voltage includes: calling the PID control model to calculate the corresponding proportional term voltage based on the proportional gain and the force error at time k; calculating the integral term voltage based on the integral gain and the force error at each time; calculating the corresponding error change rate based on the force error and the sampling period; calculating the derivative term voltage based on the derivative gain and the error change rate at time k; and calculating the feedback voltage based on the proportional term voltage, integral term voltage, and derivative term voltage.

[0069] Specifically, the voltage of this proportional term Integral term voltage Differential term voltage , This represents the rate of change of error at time k.

[0070] Feedback voltage The feedback voltage can be the sum of the proportional, integral, and differential voltages mentioned above, or a weighted sum of the three. The weights can be set according to specific circumstances. Taking a weight of 1 for each term as an example, the feedback voltage... .

[0071] In this embodiment, K p K i K d The coefficient can be a fixed value or an adaptively adjusted value based on the target force trajectory signal and / or force error.

[0072] In one embodiment, obtaining the gain coefficient includes: determining the gain coefficient based on the target force trajectory signal and / or force error.

[0073] For example, when time k is in the dynamic change phase (i.e., the target force changes rapidly) of the target force trajectory signal, one set of gain coefficients is used; while when time k is in the force maintenance phase (i.e., the target force is constant), another set of gain coefficients can be used. K in the two sets of gain coefficients...p K i K d At least one parameter has a different value.

[0074] For example, the proportional gain K p and differential gain K d Both are positively correlated with the absolute value of the force error, and both increase as the absolute value of the force error increases. The integral gain K... i It is negatively correlated with the absolute value of the force error, and decreases as the absolute value of the rate of change of the force error increases.

[0075] Specifically, based on the target force trajectory signal and the force error, the working condition matching the current time k is identified; and the gain coefficient corresponding to the matched working condition is obtained.

[0076] For example, this working condition includes a dynamic change phase / working condition and a force holding phase / working condition. When the rate of change of the target force... ,or If the force is in a dynamic change phase, it is determined to be in the force-maintaining phase; otherwise, it is in the force-holding phase. The preset force change threshold, This is the force error threshold.

[0077] For K i In the dynamic tracking phase, the corresponding K i For a relatively small value, during the force holding phase, K i It is a relatively large value, that is, K used during the force holding phase. i The value is greater than K used in the dynamic tracking phase. i Value. K i K d The two phases can remain unchanged, or they can be switched simultaneously.

[0078] In one embodiment, it can also be set when hour, ;when hour Among them, K i0 K is the maximum integral gain for force error. i1 To maintain the target value of the integral gain during the phase, This is the initial threshold for integration (e.g., 10% of full scale). The function has the following property: when... When the value is large (during the dynamic tracking phase), the integral action is suppressed to prevent saturation; when When the force approaches zero (during the force maintenance phase), Ki≈K i0 The integral action is fully activated, eliminating steady-state error; when When the value is small (during the force holding phase), the integral gain is large; when When the value is large (during the dynamic tracking phase), the rate of change of integral gain with force. Increases while decreasing.

[0079] Similarly, ; .

[0080] and The sensitivity coefficient for proportional gain. For and e is the sensitivity coefficient of the differential gain. max The maximum force error threshold, This is the threshold for the rate of change of the maximum force error.

[0081] By adaptively adjusting the integral gain, the system uses a small integral gain (or even turns off integration) during the dynamic tracking phase to avoid saturation and overshoot; and uses a large integral gain during the force holding phase to effectively eliminate steady-state errors caused by sample creep, temperature drift, etc., thus achieving a balance between dynamic performance and steady-state accuracy.

[0082] In one embodiment, U c (k)=w(k)×U ff (k)+U fb w(k) represents the weight of the feedforward voltage in the driving voltage at time k, and the value of w(k) is positively correlated with the rate of change of the target force trajectory signal at time k.

[0083] Rate of change of force at time k When the target force changes rapidly, the feedforward weight increases, and the system relies more on feedforward control to achieve rapid tracking; when the target force is constant or changes slowly, the feedforward weight decreases, and the system relies more on feedback control to ensure steady-state accuracy and disturbance rejection capability.

[0084] For example, Where w0 is the minimum weight in the maintenance phase, w1 is the maximum weight in the dynamic tracking phase, and w3 is the adjustment constant.

[0085] or, Among them, w0 is the basic weight, and w5 and w6 are the contribution factors of the force change rate term and the force error term, respectively. The specific values ​​can be set according to the actual situation.

[0086] In this embodiment, by making w(k) positively correlated with the rate of change of force, the system automatically increases the feedforward weight when the target force changes rapidly (such as during loading startup or when the sine wave crosses zero), utilizing the speed of feedforward to achieve high-speed tracking. When the target force is constant or changes slowly (such as during the force holding phase), the system automatically decreases the feedforward weight, strengthening feedback control to eliminate disturbances and steady-state errors. Furthermore, when there are errors in the identification of electrical parameters R, L, or Kt, or when changes in motor temperature cause parameter drift, pure feedforward control (w(k)=1) will generate continuous tracking errors. By introducing confidence correction based on historical errors into the feedforward weight, the system can automatically reduce the feedforward weight and increase the feedback weight when the model mismatch occurs, thereby maintaining the stability and robustness of the system.

[0087] In one embodiment, a computer-readable storage medium is provided having executable instructions stored thereon, which, when executed by a processor, cause the processor to perform the steps in the above method embodiments.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0089] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are meant to be within the scope of this application and form different embodiments. For example, all the embodiments above can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A pressure testing method based on closed-loop control, characterized in that, The method, applied to a direct-drive pressure testing system comprising a voice coil motor, a force sensor, and a controller, includes: Step 1: Acquire the target force trajectory signal; Step 2: Obtain the actual pressure acting on the object being measured detected by the force sensor at time k according to the preset sampling period, and calculate the force error based on the actual pressure and the target force at time k in the target force trajectory signal. Step 3: Calculate the feedforward voltage based on the target force trajectory signal and the electrical parameter set of the voice coil motor, using an electrical dynamic model. This includes: calculating the corresponding desired current based on the target force trajectory signal; calculating the resistance voltage drop compensation component and the inductance voltage drop compensation component based on the desired current and the electrical parameter set; and calculating the feedforward voltage based on the resistance voltage drop compensation component and the inductance voltage drop compensation component. The electrical parameter set includes winding resistance, winding inductance, and back electromotive force constant. Step 4: Obtain the gain coefficient, input the force error and the gain coefficient into the preset feedback control model, and output the feedback voltage; Step 5: Calculate the driving voltage based on the feedback voltage and the feedforward voltage; Step 6: Drive the voice coil motor according to the driving voltage to generate a force acting on the object being tested; Repeat steps 2 to 6 to make the actual pressure trajectory signal converge to the target force trajectory signal in the time domain.

2. The method according to claim 1, characterized in that, The expected current I at time k d (k)=F t (k) / Kt, where Kt is the thrust constant, F t (k) represents the target force at time k in the target force trajectory signal; The voltage drop compensation component U R (k) = R×I d (k), where R is the winding resistance; The inductor voltage drop compensation component L is the winding inductance, I d (k-1) represents the desired current at time k-1; The feedforward voltage U ff (k)= U R (k)+U L (k).

3. The method according to claim 1, characterized in that, Before calculating the feedforward voltage based on the resistor voltage drop compensation component and the inductor voltage drop compensation component, the method further includes: The back electromotive force is calculated based on the desired current and the set of electrical parameters. The step of calculating the feedforward voltage based on the resistor voltage drop compensation component and the inductor voltage drop compensation component includes: The feedforward voltage is calculated based on the resistor voltage drop compensation component, the inductor voltage drop compensation component, and the back electromotive force.

4. The method according to claim 1, characterized in that, The feedback control model is a PID control model, and the gain coefficient includes proportional gain, integral gain, and derivative gain; the step of inputting the force error and the gain coefficient into the preset feedback control model and outputting a feedback voltage includes: The PID control model is invoked, and the corresponding proportional term voltage is calculated based on the proportional gain and the force error at time k. The integral term voltage is calculated based on the integral gain and the force error at each time point; The corresponding error change rate is calculated based on the force error and the sampling period, and the differential term voltage is calculated based on the differential gain and the error change rate at time k. The feedback voltage is calculated based on the proportional term voltage, integral term voltage, and derivative term voltage.

5. The method according to claim 4, characterized in that, The acquisition of the gain coefficient includes: determining the gain coefficient based on the target force trajectory signal and / or force error.

6. The method according to claim 5, characterized in that, Determining the gain coefficient based on the target force trajectory signal and / or force error includes: The working condition matching time k is identified based on the target force trajectory signal and the force error; Obtain the gain coefficient corresponding to the matched operating condition.

7. The method according to any one of claims 1 to 6, characterized in that, The driving voltage U c (k)=w(k)×U ff (k)+U fb w(k) is the feedforward voltage U at time k. ff (k) weight in the driving voltage, U fb w(k) is the feedback voltage at time k, and the value of w(k) is positively correlated with the rate of change of the force of the target force trajectory signal at time k.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores executable instructions that, when executed by a processor, cause the processor to perform the method as described in any one of claims 1 to 7.

9. A direct-drive pressure testing system, characterized in that, include: Voice coil motors are used to directly generate test pressure. An item placement platform is used to place the items to be tested. A force sensor for measuring the pressure applied to the object being tested; A power driver is used to drive a voice coil motor to generate the corresponding force. A controller for performing the method as described in any one of claims 1 to 7.

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