A method and system for controlling nonlinear load force in a precision forming process of a press charge

Abstract

The application discloses a kind of precision forming process nonlinear load force control method and system of press charging, belong to the related technical field of pyrotechnics press forming.The application is based on the control block diagram of the electro-hydraulic position servo system of press charging forming device, load force signal is introduced into compensator, the transfer function of compensator is solved inversely by non-linear cancellation, and then the output of compensator is applied to the control input end of proportional valve, the influence of system nonlinear load force on system is inhibited by cancellation mechanism, so that the system becomes decoupled linear system, the speed jitter caused by nonlinear load force in the process of granular body pressing is reduced, the pressing force decay oscillation phenomenon caused by granular body creep characteristic in the pressure maintaining stage is inhibited, the stiffness and controllability of the system are improved, and the control precision of the whole system is also improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of the press forming of initiating explosive, and more particularly to a method and system for controlling the nonlinear load force in the precision forming process of the press charge. BACKGROUND

[0002] The forming of the press charge is one of the most critical process steps in the production of initiating explosive, and the quality of the charge directly affects the precision strike and damage capacity on the battlefield. To meet the three major requirements of high damage, penetration use, and high reliability of the initiating explosive, it is important to ensure that the large-size charge column has high density and low anisotropic density difference, which is an important indicator of the control performance of the press charge forming device. Therefore, the precision forming technology of the press charge has become one of the hotspots in the field of granular body pressing. However, the press forming technology is a dynamic process involving the flow, friction, and crushing of granular bodies at the micro-nano scale, and the current control method for the press charge forming has the following problems: (1) When the granular particles undergo elastic-plastic deformation, the load stiffness presents complex nonlinear time-varying characteristics, and the control system is affected by strong nonlinear load force, which easily causes speed jitter and increases the control difficulty. (2) When the conventional PID control algorithm is used, the elastic-plasticity of the granular material disappears completely during the pressure maintaining stage in the pressing forming process, and the load force is very sensitive to the small change in displacement, and the dynamic process of the control system easily induces large fluctuations in the pressing force of the granular body or even unloading, which poses great challenges and safety hazards to the precision forming of the press charge. SUMMARY

[0003] In view of the defects of the prior art, the present application aims to provide a method and system for controlling the nonlinear load force in the precision forming process of the press charge, which solves the problems of speed jitter caused by the strong nonlinear load force and the decay oscillation of the pressing force caused by the creep characteristics of the granular material during the pressure maintaining stage, thereby causing fatal defects such as hammering explosion or structural damage of the sample.

[0004] To achieve the above object, the application provides a kind of nonlinear load force control method in precision forming process of press charge, wherein the electro-hydraulic servo system of press charge forming device includes: electric control unit, motor, hydraulic pump, check valve, pressure gauge, electromagnetic overflow valve, proportional valve, first safety valve, cutoff valve, one-way sequence valve, second safety valve, first pressure sensor, second pressure sensor, hydraulic cylinder, grating ruler, weighing sensor, slider, punch, analog load, mold cavity, cover.The electric control unit includes industrial computer IPC610 and data acquisition card PCI1716, PCI1784, and the industrial computer is responsible for writing, compiling and generating control program, and the data acquisition card is integrated in the PCI slot of industrial computer, responsible for collecting the signals of various sensors and generating the control signals of proportional valve and cutoff valve.The motor drives hydraulic pump to output hydraulic oil with certain pressure and flow rate, which flows to the P port of proportional valve through check valve.The A port of proportional valve is connected with the rod cavity of hydraulic cylinder through one-way sequence valve, and the B port of proportional valve is connected with the rodless cavity of hydraulic cylinder through cutoff valve.The first safety valve and first pressure sensor are bypassed between the T port of proportional valve and rodless cavity, and the second safety valve and second pressure sensor are bypassed between the T port of proportional valve and rod cavity.The first safety valve limits the pressure of rodless cavity of hydraulic cylinder, and opens overflow when the pressure of rodless cavity of hydraulic cylinder exceeds the maximum set value of first safety valve, to protect the safety of system.The second safety valve limits the pressure of rod cavity of hydraulic cylinder, and opens overflow when the pressure of rod cavity of hydraulic cylinder exceeds the maximum set value of second safety valve, to protect the safety of system.The electromagnetic overflow valve and pressure gauge are bypassed between the outlet of check valve and P port of proportional valve.The lower end of piston rod of hydraulic cylinder is connected with weighing sensor, slider and punch in sequence, the weighing sensor detects the load force of granular body pressing forming in real time, and the grating ruler on the outside of slider detects the displacement data of slider in real time.

[0005] The control method comprises the following steps:

[0006] Detecting load pressure And hydraulic cylinder displacement Introducing the two functions into linear network with transfer function G1 (s), G2 (s), and then synthesizing with gravity load to obtain load force observation signal Wherein G1 (s)=A n , G2 (s)=ms 2 +Bs, A n Is the equivalent action area of hydraulic cylinder, m is the equivalent load mass driven by hydraulic cylinder, s is differential operator, and G is equivalent load weight;

[0007] Introducing the load force observation signal into linear network with transfer function G LThe output signal of the link is introduced into the control input of the proportional valve, and the load force is dynamically compensated in real time through the nonlinear cancellation mechanism. The transfer function of the nonlinear load force compensator can be obtained by inverse solving of the cancellation mechanism. L

[0008] G L (s)=L0s+L1

[0009]

[0010]

[0011] Wherein, L0, L1 are constant terms, K v is the spool displacement-control voltage gain of the proportional valve, K q is the flow gain, F L (X p ) is the pressing load force, K c is the flow pressure coefficient, C tp is the total leakage coefficient of the hydraulic cylinder, h is the proportional coefficient, β e is the bulk modulus of the hydraulic oil; V t is the total volume of the hydraulic cylinder.

[0012] The closed-loop deviation control with negative feedback in the electro-hydraulic servo system of the pressing charge forming device plays a major role in regulation, and its control algorithm adopts the PID control algorithm. The electro-hydraulic position servo system of the pressing charge forming device belongs to a typical valve-controlled asymmetric cylinder power element, and the control block diagram of the electro-hydraulic position servo system is drawn based on the three basic equations of the valve-controlled cylinder. When the load force signal of the pressing charge forming device is difficult to measure, the load force can be estimated by a linear network observer constructed by the load pressure and the hydraulic cylinder displacement. The load force signal is introduced into the control block diagram of the electro-hydraulic position servo system, and on the basis of the control block diagram of the electro-hydraulic position servo system of the pressing charge forming device, the load force signal is introduced into the compensator, and then the output of the compensator is applied to the control input of the proportional valve. Through the cancellation mechanism, the adverse effects of the nonlinear load force in the pressing process on the control system are suppressed or approximately cancelled, so that the system becomes a linear decoupling system, the control difficulty is reduced, and the control accuracy of the system is improved.

[0013] Further, the nonlinear load force compensation closed-loop control block diagram of the electro-hydraulic servo system of the pressing charge forming device is constructed, and the control algorithm adopts the PID+LOC (load force compensation) control algorithm. The analog expression of the PID+LOC control algorithm is:

[0014] ​​

[0015] Wherein, u(PID+LOC) is proportional valve control voltage, k p is proportional coefficient, T i is integral time constant, T d is differential time constant.

[0016] Beneficial effects: the PID+LOC control algorithm has good trajectory tracking performance, the disturbance of strong nonlinear load force change in the process of granular body compaction is obviously reduced, the displacement response curve basically presents linear trend change, the stiffness and controllability of the system are significantly improved, and the control difficulty of the system is reduced.Classical PID control algorithm, with the growth of the pressure maintaining time, the actual compaction displacement of the granular sample is greater than the expected instruction, negative control deviation is generated, thereby causing the zero position correction adjustment mechanism of the closed loop system to work, and then causing the compaction force to oscillate, which easily causes sample hammer explosion or structure damage and other fatal defects.After the PID+LOC algorithm is applied, the small position deviation amount and the compensation amount of load force change caused by the creep characteristic in the pressure maintaining stage are mutually cancelled or approximately cancelled, the valve control cylinder adjusted by the controller is equivalent to parameters without change, the proportional valve spool is still in the original zero position state, the compaction force oscillation phenomenon induced by the creep characteristic of the granular body is effectively inhibited, and strong robustness is obtained.

[0017] The application also provides a nonlinear load force control system in the process of precision forming of a pressed charge, which comprises a load force observation signal acquisition module, a load compensator, a PID+LOC controller,

[0018] The load force observation signal acquisition module is used for detecting load pressure and hydraulic cylinder displacement The two functions are introduced into a linear network with transfer functions G1(s) and G2(s), and then the load force observation signal is obtained after comprehensive consideration of the gravity load Wherein G1(s)=A n , G2(s)=ms 2 +Bs, A n is the equivalent action area of the hydraulic cylinder, m is the equivalent load mass driven by the hydraulic cylinder, s is a differential operator, and G is the equivalent load weight.

[0019] The load compensator is used for receiving the load force observation signal and outputting a compensation signal.

[0020] The PID+LOC controller is used for dynamically compensating the load force in real time through a nonlinear cancellation mechanism.

[0021] Further, the transfer function G L (s) of the load compensator is inversely solved through the cancellation mechanism, and the following equation is established Obtained:

[0022] G L (s) = L0s + L1

[0023]

[0024]

[0025] wherein, L0, L1 are constant terms, K v is proportional valve spool displacement-control voltage gain, K q is flow gain, F L (X p ) is the pressing forming load force, K c is flow pressure coefficient, C tp is the total leakage coefficient of hydraulic cylinder, h is proportional coefficient, β e is the bulk modulus of hydraulic oil; V t is the total volume of the hydraulic cylinder.

[0026] Further, the analog expression of the PID+LOC controller is:

[0027]

[0028] Wherein, u(PID+LOC) is proportional valve control voltage, k p is proportional coefficient, T i is integral time constant, T d is the differential time constant.

[0029] Overall, by the above technical solutions conceived by the present application, compared with the prior art, has the following beneficial effects:

[0030] 1、The present application introduces the load force signal into the compensator on the basis of the control block diagram of the electro-hydraulic position servo system of the pressing charge forming device, and then applies the output of the compensator to the control input end of the proportional valve, forming a compound control combining open-loop control and closed-loop control. In the compound control, the closed-loop system with negative feedback controls its main adjustment action according to the deviation, improving the dynamic performance of the system; and the open-loop control with feedforward plays an auxiliary compensation role, suppresses or approximately cancels the adverse effects of the nonlinear load force in the pressing forming process on the control system through the cancellation mechanism, so that the system becomes a linear decoupling system, reducing the control difficulty. Such bidirectional compound control has strong anti-load disturbance ability, can significantly improve the control accuracy of the system, and thus ensures that the large-size charge column has high density and low anisotropy.

[0031] 2, The present application introduces the nonlinear load force into the control system by establishing the mathematical model of the electro-hydraulic servo system of the pressed charge forming device, compensates the transfer function of the nonlinear inverse solver through the nonlinear cancellation, applies the output of the compensator to the control input end of the proportional valve, suppresses the influence of the nonlinear load force of the system on the system through the cancellation mechanism, makes the system a decoupled linear system, reduces the speed jitter caused by the nonlinear load force in the process of the granular body pressing, suppresses the pressing force decay oscillation phenomenon caused by the creep characteristics of the granular body in the pressure maintaining stage, improves the stiffness and controllability of the system, and improves the control accuracy of the whole system. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is the principle diagram of the electro-hydraulic servo system of the pressed charge forming device of the embodiment of the present application;

[0033] Figure 2 It is the control block diagram of the electro-hydraulic position servo system of the embodiment of the present application;

[0034] Figure 3 It is the nonlinear load force compensation control block diagram of the electro-hydraulic position servo system of the embodiment of the present application;

[0035] Figure 4 It is the position error comparison curve of the case of the present application using the classic PID control algorithm and the PID+LOC load force compensation control algorithm;

[0036] Figure 5 It is the load force comparison curve of the case of the present application using the classic PID control algorithm and the PID+LOC load force compensation control algorithm;

[0037] The figure mark: 1-electric motor, 2-hydraulic pump, 3-one-way valve, 4-pressure gauge, 5-electromagnetic overflow valve, 6-proportional valve, 7-first safety valve, 8-isolation valve, 9-one-way sequence valve, 10-second safety valve, 11-first pressure sensor, 12-second pressure sensor, 13-hydraulic cylinder, 14-grating ruler, 15-weighing sensor, 16-sliding block, 17-punch, 18-analog load, 19-mold cavity, 20-muffle cover. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0039] The present application provides a new type of electro-hydraulic servo system nonlinear load force control method for pressed charge forming device, which comprisesFigures 1-3 As shown, the main components include the schematic diagram of the electro-hydraulic servo system of the compression filling device, the control block diagram of the electro-hydraulic position servo system, and the nonlinear load force compensation control block diagram of the electro-hydraulic position servo system, as detailed below.

[0040] like Figure 1 As shown, the electro-hydraulic servo system includes an electronic control unit, an electric motor 1, a hydraulic pump 2, a one-way valve 3, a pressure gauge 4, an electromagnetic relief valve 5, a proportional valve 6, a first safety valve 7, an isolation valve 8, a one-way sequence valve 9, a second safety valve 10, a first pressure sensor 11, a second pressure sensor 12, a hydraulic cylinder 13, a grating ruler 14, a weighing sensor 15, a slider 16, a punch 17, a simulated load 18, a mold cavity 19, and a cap 20.

[0041] The electrical control unit includes an industrial computer IPC610 and data acquisition cards PCI1716 and PCI1784. The industrial computer is responsible for writing and compiling the control program, and the data acquisition card is integrated in the PCI slot of the industrial computer. It is responsible for acquiring the signals of the first pressure sensor 11, the second pressure sensor 12, the grating ruler 14, and the weighing sensor 15, and generating the control signals of the proportional valve 6 and the isolation valve 8.

[0042] The electric motor 1 drives the hydraulic pump 2 to output hydraulic oil with a certain pressure and flow rate. This oil flows through the one-way valve 3 to the P port of the proportional valve 6. The A port of the proportional valve is connected to the rod chamber of the hydraulic cylinder 13 via a one-way valve 9, and the B port of the proportional valve 6 is connected to the rodless chamber of the hydraulic cylinder 13 via an isolation valve 8. A weighing sensor 15, a slider 16, and a punch 17 are sequentially connected to the lower end of the piston rod of the hydraulic cylinder 13. A grating ruler 14 is installed on the outside of the slider 16 to monitor its displacement data in real time and send it to the data acquisition card PCI-1716. The first safety valve 7 limits the pressure in the rodless chamber of the hydraulic cylinder 13. When the pressure in the rodless chamber exceeds the maximum set value of the first safety valve 7, it opens to overflow and protect the system. The second safety valve 10 limits the pressure in the rod chamber of the hydraulic cylinder 13. When the pressure in the rod chamber exceeds the maximum set value of the second safety valve 10, it opens to overflow and protect the system. The one-way sequence valve 9 sets the back pressure of the rod chamber of the hydraulic cylinder 13 to overcome the gravity of the moving parts of the hydraulic cylinder 13, thereby preventing overload. The isolation valve 8 is a two-position, two-way, leak-free seat valve plate structure. When the electromagnet is de-energized, it can achieve the requirement of absolutely leak-free shut-off of the hydraulic cylinder 13, thereby enabling the system to maintain pressure when the output displacement of the control system reaches the desired value, in order to improve the stress distribution at the edges and corners of the sample, making the overall density more uniform and the sealing difference in all directions more consistent. The pressure gauge 4 and the electromagnetic relief valve 5 are arranged in a bypass manner between the P port of the one-way valve 3 and the proportional valve 6.

[0043] The punch 17 is detachably connected with the slide block 16, and the cover 20 is detachably connected with the die cavity 19. Before the granular body is pressed and formed, the cover 20 is installed at the lower end face of the die cavity by means of a screw, and the simulated load 8 is filled from the upper opening of the die cavity. The inner diameter of the die cavity is φ30 mm, and the length of the die cavity is 120 mm. In consideration of good demolding effect and safety, the simulated load 8 in the embodiment is the granular body mixed by laundry powder and salt at a ratio of 1:6.

[0044] Figure 2 The control block diagram is based on three equations of the valve-controlled asymmetric hydraulic cylinder, and a hydraulic cylinder displacement closed-loop control block diagram is obtained from a load flow. The control block diagram adopts a negative feedback closed-loop control system, a controller adopts a classical PID control algorithm, and a deviation control plays a main adjusting role to improve system dynamic performance. An analog expression of the PID controller in a time domain is:

[0045]

[0046] Wherein u(PID) is a differential coefficient, k p is a proportional coefficient, T i is an integral time constant, T d is a differential time constant, and e(t) is a control deviation.

[0047] By using the classical PID control algorithm, on the one hand, when the punch contacts the granular body, the pressing displacement curve appears obvious jitter phenomenon, and with the increase of the pressing displacement, the tracking error further increases, and the lag becomes more and more obvious. On the other hand, with the increase of the pressure maintaining time, the actual pressing displacement of the granular body sample is greater than the expected instruction, a negative control deviation is generated, and thus a zero position correction adjustment mechanism of the closed-loop system is started to work, and then a pressing force decay oscillation phenomenon is caused, which easily causes fatal defects such as sample hammer explosion or structure damage.

[0048] Figure 3 The nonlinear load force compensation control block diagram of the electro-hydraulic position servo system is based on the control block diagram of the electro-hydraulic position servo system. Figure 2 The load force is introduced into the control system, the load pressure and the hydraulic cylinder displacement are detected, the two functions are introduced into a transfer function G1(s), G2(s) linear network, and then the load force observation signal is obtained by synthesizing the two signals and the gravity load. n Wherein the transfer function G1(s)=A 2 , G2(s)=ms L(s) is introduced into the control input of the proportional valve, the load force is dynamically compensated in real time through the nonlinear counteracting nonlinear mechanism, the speed jitter and the decline of system dynamic performance caused by the load force are inhibited, the system becomes a decoupled linear system, and the control difficulty of the system is reduced.

[0049] The transfer function of the compensator G L (s) is solved by reverse solving the counteracting mechanism, and here G

[0050]

[0051] G L (s) = L0s + L1

[0052] After the load force control method (PID + LOC) is applied, the control algorithm is:

[0053]

[0054]

[0055]

[0056] Where, K v is the spool displacement-control voltage gain of the proportional valve, K q is the flow gain, F L (X p ) is the load force of the compression molding, K c is the flow pressure coefficient, A n is the equivalent acting area of the asymmetric hydraulic cylinder defined by the weighted average method, C tp is the total leakage coefficient of the hydraulic cylinder, h is the proportional coefficient, β e is the bulk modulus of the hydraulic oil; V t is the total volume of the hydraulic cylinder, and L0 and L1 are constant terms.

[0057] The PID+LOC nonlinear load force compensation algorithm is a composite controller composed of a traditional PID control algorithm and a nonlinear load force compensator, wherein the PID control algorithm plays a main adjusting role according to an error control to improve the dynamic performance of the system. The load force compensation algorithm is added on the basis of the PID control algorithm. First, the nonlinear load force is constructed by a load force observer, and then the open-loop control of the load force feedforward correction plays an auxiliary compensation role. Through the nonlinear cancellation mechanism, the adverse effects of the nonlinear load force in the process of the granular body compression molding on the system performance are suppressed, so that the system becomes a decoupled linear system. For the controller, the effects of any nonlinear factors and external disturbances presented by the multi-scale mechanical properties such as flow, friction and crushing of the granular body in the compression molding process are mutually or approximately cancelled, and the system adjusted by the controller is equivalent to a system with unchanged parameters, which greatly reduces the control difficulty of the system, improves the static and dynamic stiffness and control accuracy of the whole system, and does not affect the stability of the closed loop of the system.

[0058] After the PID+LOC nonlinear load force compensation algorithm is applied, in the compression molding stage, the compression process of the granular body is stable, the displacement curve has good following performance with respect to the expected command, the disturbance of the load force change on the control system performance is obviously reduced, and the displacement response curve basically presents a linear trend, which shows that the load force compensation algorithm improves the stiffness and controllability of the system. In the pressure maintaining stage, the small position deviation and the compensation amount caused by the load force change are mutually or approximately cancelled due to the creep characteristics, the valve-controlled cylinder adjusted by the controller is equivalent to a system with unchanged parameters, the spool of the proportional valve is still in the original zero position, the compression force decay oscillation phenomenon induced by the creep characteristics of the granular body can be effectively suppressed, and the robustness is strong.

[0059] The specific implementation of the nonlinear load force control method of the electro-hydraulic servo system of the novel compression molding device for propellant is as follows:

[0060] Before the granular body is compressed and molded, the muff cover 20 is installed on the lower end face stop of the mold cavity 19 and is tightened by a screw. To ensure good safety and demolding effect, a mixture of washing powder and salt is used as a simulated load. The washing powder and salt are fully stirred and mixed at a ratio of 1:6 to ensure good fluidity, and 35g of the granular body is loaded into the upper end inlet of the mold cavity as a simulated load.

[0061] The electro-hydraulic servo system control program of the starting press forming device is started, the suitable PID control parameters are inputted in the control program, the motor is started under no load, the system working pressure is set as 10 MPa by loading through the electromagnetic overflow valve 5 when the hydraulic cylinder 13 is at the limit position. Then the displacement instruction is inputted in the control program in the industrial computer, and the running button is clicked. According to the error e(t) of the expected displacement instruction and the actual tracking displacement, the proportional valve 6 is controlled in proportion by the PID controller, and when the PID controller output value is 4-12 mA, the proportional valve 6 is in the P-B, A-T open state. The cutoff valve 8 and the proportional valve 6 are logically interlocked, so the cutoff valve 8 is also in the open state. The high-pressure oil output by the hydraulic pump 2 enters the rodless cavity of the hydraulic cylinder 13 through the one-way valve 3, the P-B channel of the proportional valve 6 and the cutoff valve 8 in turn, and the downward pressing forming action is started. At the same time, the load force signal collected by the weighing sensor is applied to the control input end of the proportional valve through the compensator G L (s) after the feedforward correction, the system becomes a decoupling linear system through the cancellation mechanism to cancel or approximately cancel the adverse effects of the nonlinear load force in the granular body pressing forming process on the system. The compound control is formed by combining the PID closed-loop control and the LOC open-loop control, the PID closed-loop control plays a main adjusting role according to the deviation control, and the LOC open-loop control plays an auxiliary compensation role. For the controller, the effects of the nonlinear load force in the granular body pressing forming process and other external disturbances are mutually compensated through the cancellation mechanism, so that the system adjusted by the controller is equivalent to that the parameters have not changed, the control difficulty is reduced, and the controllability is improved.

[0062] The better control parameters in the case implementation process of the application are: k p =0.04, k i =0.01, k d =0, L0=4.5x10 -7 , L1=1.1x10 -6 .

[0063] Figure 4 , Figure 5 The position error comparison curve and the load force comparison curve of the classical PID control algorithm and the PID+LOC load force compensation control algorithm respectively adopted in the case of the application.

[0064] From Figures 4-5It can be seen that when the pressing displacement reaches the expected instruction, the system enters the pressure maintaining stage. After the PID+LOC load force compensation control algorithm proposed by the present application is applied, the sensitivity of the control system to the small displacement change in the pressure maintaining stage is effectively reduced, and the large-range fluctuation of the granular body pressing force or even unloading caused by the small displacement change due to the overshoot and creep performance of the control system in the pressure maintaining stage is successfully solved. Not only the robustness and anti-interference ability of the controller are improved, but also the control precision of the system is greatly improved, the high density and low anisotropy of the pyrotechnics pressing charge are significantly improved, and the safety hazard of the pressing charge is eliminated.

[0065] When the pressure maintaining time reaches the requirement, the cover 20 at the lower end of the mold cavity 19 is removed, the leg mold instruction is input in the control program, and the running button is clicked. Then, the electro-hydraulic servo system of the pressing charge forming device drives the hydraulic cylinder 13 to drive the punch 17 to push the pressing formed sample out of the mold cavity 19 from top to bottom, and the pressing formed sample 18 is taken out. Finally, the return instruction is input again in the control program, the electro-hydraulic servo system of the pressing charge forming device drives the hydraulic cylinder 13 to drive the punch 17 to return to the initial position, and the next working cycle is entered.

[0066] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A nonlinear load force control method for a precision compression molding process of a drug filling device, wherein the electro-hydraulic servo system of the compression molding device includes an electrical control unit, a motor, a hydraulic pump, a check valve, a pressure gauge, an electromagnetic relief valve, a proportional valve, a first safety valve, an isolation valve, a one-way sequence valve, a second safety valve, a first pressure sensor, a second pressure sensor, a hydraulic cylinder, a linear encoder, a load cell, a slider, a punch, a simulated load, a mold cavity, and a cap; the motor drives the hydraulic pump to output hydraulic oil, which flows through the check valve to the P port of the proportional valve; the A port of the proportional valve is connected to the rod chamber of the hydraulic cylinder through the one-way sequence valve; an electromagnetic relief valve and a... are provided as a bypass between the outlet of the check valve and the P port of the proportional valve. The pressure gauge and the proportional valve's B port are connected to the rodless chamber of the hydraulic cylinder via an isolation valve. A first safety valve and a first pressure sensor are bypassed between the proportional valve's T port and the rodless chamber. A second safety valve and a second pressure sensor are bypassed between the proportional valve's T port and the rod chamber. A load cell, a slider, and a punch are sequentially connected to the lower end of the hydraulic cylinder's piston rod. The load cell performs real-time online detection of the load force during granular material compression molding. A grating ruler is installed on the outside of the slider to perform real-time online detection of the slider's displacement data. The electronic control unit is used to collect signals from various sensors, introduce load force signals, and generate control signals for the proportional valve and the isolation valve. Its features are, The control method includes the following steps: Detect load pressure and hydraulic cylinder displacement These two functions are introduced into a linear network with transfer functions G1(s) and G2(s), and then combined with the gravity load to obtain the load force observation signal. Where G1(s) = A n G2(s) = ms 2 +Bs, A n denoted as the equivalent working area of ​​the hydraulic cylinder, m as the equivalent load mass driven by the hydraulic cylinder, s as the differential operator, and G as the equivalent load weight. The load force observation signal is introduced into the transfer function as G. L The compensator of (s) then introduces the output signal of this link to the control input of the proportional valve, and performs real-time dynamic compensation of the load force through a nonlinear cancellation mechanism.

2. The control method according to claim 1, characterized in that, The compensator G is solved by inverse solution using the cancellation mechanism. L The transfer function of (s) is let get: G L (s)=L0s+L1 Where L0 and L1 are constant terms, K v K represents the valve core displacement-control voltage gain of the proportional valve. q For flow gain, F L (X p K represents the load force during compression molding. c C is the flow-pressure coefficient. tp β is the total leakage coefficient of the hydraulic cylinder, h is the proportional coefficient, and β is the total leakage coefficient of the hydraulic cylinder. e V is the bulk modulus of hydraulic oil. t This refers to the total volume of the hydraulic cylinder.

3. The control method according to claim 2, characterized in that, The simulation expression for real-time dynamic compensation of load force through a nonlinear cancellation mechanism is as follows: Where u(PID+LOC) is the proportional valve control voltage, k p T is the proportionality coefficient. i Let T be the integration time constant. d is the differential time constant.

4. The control method according to claim 1, characterized in that, The electronic control unit includes an industrial computer IPC610 and data acquisition cards PCI1716 and PCI1784. The industrial computer IPC610 is responsible for writing, compiling and generating control programs. The data acquisition cards PCI1716 and PCI1784 are integrated in the PCI slots of the industrial computer IPC610 and are responsible for acquiring signals from various sensors and generating control signals for proportional valves and isolation valves.

5. A nonlinear load force control system for a precision compression molding process of a drug, characterized in that, Includes a load force observation signal acquisition module, a load compensator, and a PID+LOC controller. The load force observation signal acquisition module is used to detect load pressure. and hydraulic cylinder displacement These two functions are introduced into a linear network with transfer functions G1(s) and G2(s), and then combined with the gravity load to obtain the load force observation signal. Where G1(s) = A n G2(s) = ms 2 +Bs, A n Let m be the equivalent working area of ​​the hydraulic cylinder, and m be the equivalent load driven by the hydraulic cylinder. Mass, s is the differential operator, and G is the equivalent load weight; The load compensator is used to receive the load force observation signal and output a compensation signal after internal calculation. The PID+LOC controller is used to perform real-time dynamic compensation of load force through a nonlinear cancellation mechanism.

6. The control system according to claim 5, characterized in that, The transfer function G of the load compensator L (s) Solve in reverse by using the cancellation mechanism, let get: G L (s)=L0s+L1 Where L0 and L1 are constant terms, K v K represents the valve core displacement-control voltage gain of the proportional valve. q For flow gain, F L (X p K represents the load force during compression molding. c C is the flow-pressure coefficient. tp β is the total leakage coefficient of the hydraulic cylinder, h is the proportional coefficient, and β is the total leakage coefficient of the hydraulic cylinder. e V is the bulk modulus of hydraulic oil. t This refers to the total volume of the hydraulic cylinder.

7. The control system according to claim 6, characterized in that, The simulation expression for the PID+LOC controller is: Where u(PID+LOC) is the proportional valve control voltage, k p T is the proportionality coefficient. i Let T be the integration time constant. d is the differential time constant.

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