PLC-controlled oil pump pressure flow linear output method and system

Abstract

The invention discloses a PLC control oil pump pressure flow linear output method, which belongs to the technical field of hydraulic control, and comprises the following steps: S10, establishing a plane coordinate relation to obtain a linear curve relation between voltage and a preset pressure / flow value; step S20, performing linear calibration to obtain linear calibration data; and S30, outputting a control signal for controlling the oil pump on the basis of the linear calibration data under the condition of executing the control operation. The linear relation between the output voltage and the preset pressure / flow value is set through the plane coordinate relation, linear calibration is carried out according to the feedback pressure / flow value obtained through feedback detection, linear calibration data are obtained, linear output data association preparation is completed, and a control signal for controlling an oil pump is output under the condition that control operation is executed. The purpose of controlling oil pump pressure flow linear output is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic control, and particularly to a method for linearly outputting the pressure and flow rate of an oil pump controlled by a PLC. Background Art

[0002] A PLC is a general-purpose industrial control computer. The biggest problem in its application in a one-step injection blow hollow molding machine is how to control the hydraulic system. The response speed and operation control accuracy of the hydraulic system need to be realized by the designer through programming. The stable and fast performance of the machine is greatly related to the programming. At present, most injection molding machines use professional industrial control computers with built-in programs. The hydraulic action algorithms are modular, and the hydraulic control system is quite mature. Its disadvantage is that modifying the program requires more professional technicians than a PLC. For adding or subtracting actions, a PLC is more flexible. Since the one-step injection blow hollow molding machine often needs to modify actions to adapt to different mold process requirements, therefore, a PLC control system is selected for the one-step injection blow hollow molding machine.

[0003] Since the one-step injection blow hollow molding machine uses a variable pump to provide hydraulic power, there is an acceleration and deceleration process for the output of the action pressure and flow rate. In order to make the action fast and stable, there are higher requirements for the linear output of the variable pump.

[0004] On the one hand, the relationship between the pressure and flow rate output of the variable pump and the given analog output is non-linear. The PLC controls the variable pump with a straight line with a slope of K for the analog output. However, the pressure and flow rate output by the variable pump do not have a one-to-one linear relationship with the PLC given analog signal. On the other hand, in the 0%-10% section of the pressure and flow rate output, due to the existence of dead zones, the linear distortion is serious, the linearity is poor, and the control accuracy is low; the 10%-95% section is an ideal section, but due to the inductance of the analog signal control coil output, there is a signal delay, and the pressure and flow rate output deviate above and below the standard straight line; when the output is 95%-100%, saturation and overshoot are likely to occur. Summary of the Invention

[0005] The invention purpose of the present invention is to provide a method for linearly outputting the pressure and flow rate of an oil pump controlled by a PLC to solve the above problems, which can realize the linear output of the oil pump, make the given value equal to the output value, and improve the moving repetition accuracy.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A method for controlling the linear output of the pressure and flow rate of an oil pump includes the following content:

[0008] Step S10: Establish a planar coordinate relationship to obtain a linear curve relationship between voltage and preset pressure / flow rate values. Specifically, it includes the following: Taking the output voltage value range of the control signal output by the main controller as the Y-axis and the preset pressure / flow rate value range input through the input device as the X-axis to form a linear curve relationship between the output voltage and the preset pressure / flow rate values.

[0009] Step S20: Perform linear calibration to obtain linear calibration data. Specifically, it includes the following processing flow:

[0010] Step 21: According to the linear curve relationship between the output voltage and the preset pressure / flow rate values, configure several groups of preset pressure / flow rate values and output voltage values according to the measurement accuracy.

[0011] Step 22: Take a group of preset pressure / flow rate values and output voltage values, output a control signal to control the oil pump, and obtain the feedback pressure / flow rate value obtained from the output of the oil pump through detection.

[0012] Step 23: Compare and judge the feedback pressure / flow rate value with the corresponding preset pressure / flow rate value. If they are equal or within the error range, store the preset pressure / flow rate value and the output voltage value as linear calibration data. If they are not equal or exceed the error range, adjust a new output voltage value until they are equal or within the error range, and then store the group of preset pressure / flow rate values and the new output voltage value as linear calibration data.

[0013] Step 24: Repeat the above Steps 22 - 23 to perform the acquisition and storage operations on each group of data, complete the acquisition and storage of all groups of data, form linear calibration data, and complete the complete linear calibration operation.

[0014] Step S30: Based on the linear calibration data, output a control signal to control the oil pump in the case of performing a control operation.

[0015] Among them, the preset pressure / flow rate value refers to the preset pressure value or the preset flow rate value. The linear curve relationship between the output voltage and the preset pressure / flow rate value refers to the linear curve relationship between the output voltage and the preset pressure value or the linear curve relationship between the output voltage and the preset flow rate value. Similarly, other pressure / flow rate values are correspondingly selected. The main controller is a PLC, PAC, microcontroller (single-board computer), etc. Here, the PLC is taken as an example for illustration.

[0016] As described above, set the linear relationship between the output voltage and the preset pressure / flow rate values through the planar coordinate relationship, perform linear calibration based on the feedback pressure / flow rate value obtained by combining the feedback detection, obtain the linear calibration data, complete the preparation for the linear output data association, and output a control signal to control the oil pump in the case of performing a control operation to achieve the purpose of linearly outputting the pressure and flow rate of the oil pump.

[0017] Based on the foregoing solution, in an improved solution, the method for linearly outputting the pressure and flow rate of the control oil pump further includes the following: Step S5: Based on the master controller, output the control signal to the oil pump through the dual proportional op-amp board. According to the zero-current value range of the dual proportional op-amp board, increase the output voltage value range of the control signal output by the master controller so that the current value output by the dual proportional op-amp board is greater than or equal to the termination value of the zero-current value range in the case of its starting value (the starting value of the output voltage value range). In this way, the dead zone of the output pressure / flow rate value of the oil pump can be shielded.

[0018] Based on the foregoing solution, in an improved solution, in order to monitor whether there is a deviation phenomenon after the device has been running for a period of time, the method for linearly outputting the pressure and flow rate of the control oil pump further includes the following: Step S40: Perform linear calibration; specifically, it includes the following processing flow: Step 41: In the current control operation situation, obtain the current feedback pressure / flow rate value obtained by detecting the output of the oil pump; Step 42: Compare and judge the current feedback pressure / flow rate value with the corresponding preset pressure / flow rate value; if they are equal or within the error range (for example, ±0.01), it is determined to be qualified, and a qualified calibration result is output, and then the next calibration operation is performed; if they are not equal or exceed the error range, it is determined to be unqualified, and an unqualified calibration result is output, and then the next calibration operation is performed. Among them, when comparing the feedback pressure / flow rate value, the result of subtracting the minuend from the subtrahend corresponds to the equal situation, and vice versa; corresponding to the situation within the error range (for example, greater than or equal to -0.01 and less than or equal to 0.01), and vice versa for exceeding the error range (for example, less than -0.01 or greater than 0.01). In this way, real-time calibration can be performed to promptly detect whether there is a deviation after running for a period of time.

[0019] Based on the foregoing solution, in an improved solution, in order to correct the deviation phenomenon during the operation of the device, the method for linearly outputting the pressure and flow rate of the control oil pump further includes the following: Step S50: Update the linear calibration data according to the linear calibration result; specifically including the following: Based on the linear calibration result being unqualified, if the number of consecutive unqualified calibration results reaches the update threshold (for example, the update threshold is 5 times), then a new output voltage value is adjusted in real time until the current feedback pressure / flow rate value is equal to or within the error range of the corresponding preset pressure / flow rate value, and then this set of preset pressure / flow rate values and the new output voltage value are stored as linear calibration data to complete the operation of updating the linear calibration data; or, based on the linear calibration result being unqualified, if the number of consecutive unqualified calibration results reaches the alarm range (for example, greater than or equal to 5 times), then corresponding alarms are issued according to different alarm levels (for example, a combination of on-screen display, turning on red and yellow alarm lights, and sounding an alarm, etc. to distinguish), where there are at least 2 alarm levels (for example, 5 - 10 times is the first-level alarm and 11 - 15 times is the second-level alarm), and in the case of stopping the current control operation, step S20 is executed to complete the operation of updating the linear calibration data. In this way, the update scheme specifically has a real-time update and a shutdown (stopping the current control operation) update scheme. It is possible to directly execute the real-time update operation when determining an unqualified result (the number of consecutive unqualified calibration results reaches the update threshold), or execute the shutdown update operation after confirming the alarm for the determined unqualified result, or in the initial stage (for example, the number of consecutive unqualified calibration results is less than or equal to 20 times), execute the shutdown update after confirming the alarm for the determined unqualified result, and in the later stage (for example, the number of consecutive unqualified calibration results is greater than 20 times), execute the real-time update operation, so as to update the linear calibration data, timely correct the deviation phenomenon, and ensure linear output.

[0020] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0021] 1. The present invention sets the linear relationship between the output voltage and the preset pressure / flow rate value through the plane coordinate relationship, and accordingly combines the feedback pressure / flow rate value obtained by feedback detection for linear calibration to obtain the linear calibration data, completing the preparation for associating the linear output data. Based on this, when executing the control operation, a control signal for controlling the oil pump is output to achieve the purpose of linearly outputting the pressure and flow rate of the control oil pump.

[0022] 2. The present invention can perform real-time calibration to timely detect whether there is a deviation after running for a period of time; it can update the linear calibration data to timely correct the deviation phenomenon and ensure linear output. Description of the Drawings

[0023] Figure 1 It is a flowchart of the method for controlling the pressure and flow rate of the oil pump by PLC of the present invention.

[0024] Figure 2 It is the circuit schematic diagram of the PLC controlling the oil pump pressure and flow rate of the present invention.

[0025] Figure 3 It is the schematic diagram of the pressure and voltage data storage of the present invention.

[0026] Figure 4 It is the flow chart of the pressure parameter setting, linear calibration, acquisition and storage of the present invention.

[0027] Figure 5 It is the characteristic curve of pressure and current of the present invention.

[0028] Figure 6 It is the schematic diagram of the flow rate and voltage data storage of the present invention.

[0029] Figure 7 It is the flow chart of the flow rate parameter setting, linear calibration, acquisition and storage of the present invention.

[0030] Figure 8 It is the characteristic curve of flow rate and current of the present invention.

[0031] Figure 9 It is the characteristic curve of flow rate and current in the test example of the hollow molding machine of the present invention.

[0032] Figure 10 It is the characteristic curve of pressure and current in the test example of the hollow molding machine of the present invention.

[0033] In the attached drawings, 1. Logic controller PLC; 2. Digital-to-analog converter; 3. Analog-to-digital converter; 4. Dual proportional operational amplifier board; 5. Variable pump; 6. AC motor; 7. Pressure sensor; 8. Flowmeter; 9. Electromagnetic directional valve; 10. Touch screen; 11. Proportional pressure ammeter; 12. Proportional flow ammeter; i1. Variable pump pressure control signal; i2. Variable pump flow control signal; A. Output curve of the variable pump flow rate after calibration; B. Decreasing output curve of the variable pump flow rate before calibration; C. Rising output curve of the variable pump flow rate before calibration; D. Output curve of the variable pump pressure after calibration; E. Output curve of the variable pump pressure before calibration. Specific embodiments

[0034] The following further describes the specific implementation of the invention with reference to the attached drawings.

[0035] Embodiment 1

[0036] See Figure 1, as described above, a method for linearly outputting the pressure and flow rate of an oil pump according to the present invention has a basic solution including steps S10 - S30, and there is also an improved solution, the improved solution including steps S5 - S40. Further, for example, it includes steps S10 - S40, or includes steps S5 - S50, etc. Refer to the foregoing to form several specific application solutions according to the actual situation. The following will further elaborate by taking the solution that uses a PLC and includes steps S5 - S30 as an example, specifically, a specific solution for a method of linearly outputting the pressure and flow rate of an oil pump controlled by a PLC.

[0037] As Figure 2 shown, a schematic diagram of the motor electro - hydraulic principle is given. Taking the variable pump as an example for the oil pump, the PLC 1 is connected to the variable pump 5 through a dual - proportional amplifier board 4, and a pressure sensor 7 or a flowmeter 8 is used to detect the output result of the variable pump 5 and feedback it to the PLC.

[0038] Control output mode: After the logic controller PLC 1 receives a hydraulic action instruction, it converts the data corresponding to the action (such as pressure 0 - 2000 and flow rate 0 - 1600, with an accuracy of 0.1) on the touch screen (such as Figure 2 the touch - screen HMI shown) 10 into a control signal (0 - 10VDC) through a digital - to - analog converter DA 2 and outputs it to the dual - proportional amplifier board 4. When the dual - proportional amplifier board 4 receives a pressure control signal (0 - 10VDC voltage signal), it outputs a corresponding current (80 - 720mA) to the pressure valve of the variable pump 5, and the pressure valve controls the variable pump 5 to output a corresponding pressure (0 - 200bar). When the dual - proportional amplifier board 4 receives a flow - rate control signal (0 - 10VDC), it outputs a corresponding current (300 - 900mA) to the proportional speed - control valve of the variable pump 5, and the proportional speed - control valve controls the variable pump 5 to output a corresponding flow rate (0 - 160l / min).

[0039] Feedback input mode: When the pressure sensor 7 (full - scale range 250bar) receives a pressure signal, it sends out a corresponding pressure - data electrical signal (0 - 8VDC) to the analog - to - digital converter AD 3. The analog - to - digital converter AD 3 converts the electrical signal (0 - 8VDC) generated by the pressure sensor 7 into pressure data (0 - 2000) and transmits it to the PLC 1. When the flowmeter 8 (full - scale range 200l / min) receives a flow - rate signal, it sends out a corresponding flow - rate - data electrical signal (0 - 8VDC) to the analog - to - digital converter AD 3. The analog - to - digital converter AD 3 converts the electrical signal (0 - 8VDC) generated by the flowmeter 8 into flow - rate data (0 - 1600) and transmits it to the PLC 1.

[0040] The specific content of the PLC - controlled linear output of the oil - pump pressure is as follows.

[0041] 1. The pressure output of the variable pump, the PLC pressure parameter setting, and the linear calibration acquisition and storage, and the relationship between the touch screen setting parameters and the PLC stored pressure parameters S1 / S2

[0042] 1.1 The rated pressure or the set maximum pressure of the variable pump 5 is 200 bar. Converted according to the measurement accuracy of 0.1%, it becomes 2000 pressure data. The PLC 1 will input the pressure data (preset pressure value) S1 (0 - 2000) in ascending order and output 1000 data (increasing by 2 each time it runs) one by one to the dual proportional op-amp board 4 through the DA module 2. The oil pressure output by the variable pump 5 is detected by the pressure sensor 7 and converted into an electrical signal and input to the AD module 3. The PLC 1 receives it and converts the input value of the AD module 3 into a feedback pressure value, and then compares this feedback pressure value with the preset pressure value (pressure input value) S1; when the values are the same (within the allowable error range), the preset pressure value S1 and the control pressure voltage data (output voltage value) S2 given by the PLC to the DA module are stored in the PLC power-off retention data area; when the values are different (exceeding the allowable error range), the PLC 1 adjusts the output voltage data size given to the DA module 2 through self-tuning to make the feedback pressure value input by the signal of the pressure sensor 7 to the PLC consistent with the preset pressure value S1, and then stores the preset pressure value S1 and the output voltage value S2 self-tuned by the PLC to the DA module in the PLC power-off retention data area. The schematic diagram of the PLC pressure and voltage data storage is as Figure 3 shown.

[0043] 1.2 The pressure output of the variable pump, the PLC pressure parameter setting, and the linear calibration acquisition and storage (set pressure 200 bar)

[0044] As Figure 4 and Figure 5 shown, the following will explain the process of pressure parameter setting, linear calibration acquisition and storage.

[0045] Step S101: Calibrate the pressure zero point of the dual proportional op-amp board

[0046] When the current of the proportional overflow valve is 0 - 80 mA, the output pressure of the variable pump is 0 bar. Therefore, the starting value of the pressure control current signal of the dual proportional op-amp board 4 is set to 80 mA, aiming to shield the dead zone of the variable pump output pressure.

[0047] Step S102: Input a DC 10V voltage signal to the input end of the dual proportional op-amp board, and adjust the output current of the dual proportional op-amp board 4 to make the oil pump output pressure 200 bar, and calibrate the maximum pressure of the oil pump.

[0048] Step S103: Establish a plane coordinate relationship in the PLC

[0049] As in the above steps S101 and S102, accordingly adjust the output voltage value range of the control signal output by the PLC. Input the preset pressure data S1 (0 - 2000) on the X-axis, which actually represents the set oil pressure of 0 - 200 bar. When the PLC receives the preset pressure data S1 (0 - 2000) input from the touch screen (input device), it converts it proportionally and outputs a DC 0 - 10V control signal to the dual proportional op-amp board 4 through the DA module. The dual proportional op-amp board 4 converts the DC 0 - 10V voltage signal into an 80 - 720 mA current signal and outputs it to control the pressure valve, controlling the variable pump 5 to output a corresponding pressure of 0 - 200 bar.

[0050] Step S104, start the PLC self-tuning function

[0051] Based on the plane coordinate reference established in step S103, with the X-axis as the input signal (i.e., inputting a pressure of 0 - 2000 from the touch screen 10), and the Y-axis as the output (i.e., the DA module outputs a DC 0 - 10V signal), perform the first tuning with X = 2.

[0052] Step S105, determine X = the feedback value of the pressure sensor (error ±1)

[0053] Judge whether the X value (preset pressure value) in the current round is equal to the feedback value of the pressure sensor (feedback pressure value). When X = the feedback value of the pressure sensor, execute step S106; otherwise, return to step S104 to adjust the output voltage data size given to the DA module and repeat the above operations. The pressure sensor detects the feedback pressure signal, and the PLC receives this pressure signal and converts it into a feedback pressure value.

[0054] Step S106, store the X data S1 of the current round and the output voltage data S2 input by the PLC to the DA module in their respective corresponding addresses. This output voltage data S2 is obtained from self-tuning.

[0055] Step S107, N + 1 = N / X + 2 = X

[0056] Transfer to the next set of data to perform the next set of data acquisition and storage.

[0057] Step S108, determine that the current round N < 1000

[0058] When the current round N < 1000, return to step S104 and repeat the above operations to perform the next set of data acquisition and storage. When N >= 1000, execute the end program and the linear calibration ends.

[0059] 1.3 Relationship between the touch screen set parameters and the PLC stored pressure parameters S1 / S2

[0060] When the PLC 1 receives a hydraulic operation instruction, it finds the corresponding operation pressure parameter P1 set on the touch screen 10, and compares the parameter P1 set on the touch screen with the stored pressure parameter S1 in the PLC. When P1 = S1, it is determined that the pressure parameter P1 belongs to a certain set of data ranges configured in advance (for example, the required pressure value for the operation is 10.5 bar, and when configuring a certain set of data in advance, it is configured according to 0.1% of the pressure value of 10.5 bar). The pressure control signal parameter (output voltage value) S2 stored in the PLC is output through the digital-to-analog converter DA to output a corresponding control signal (DC0 - 10V) to the dual proportional amplifier board; when the dual proportional amplifier board 4 receives the corresponding control signal (DC0 - 10V), it outputs a corresponding current (80 - 720 mA) to control the variable pump 5 to output a corresponding pressure value (0 - 200 bar). Note that during the movement of the hydraulic actuator (cylinder), the preset pressure value set on the touch screen is often greater than the actual pressure output by the variable pump. The reason is that the output pressure of the variable pump is equal to the resistance of the hydraulic actuator.

[0061] The specific content of the PLC control of the linear output of the oil pump flow is as follows.

[0062] 2. Relationship between the flow output of the variable pump, the PLC flow parameter setting, and the linear calibration acquisition and storage, and the relationship between the touch screen setting parameter and the PLC stored flow parameters L1 / L2

[0063] 2.1 The maximum flow output of the variable pump 5 is 160 l / min. Converted according to the measurement accuracy of 0.1%, it becomes 1600 data. The PLC 1 outputs 1600 data (increasing by 1 each time it runs) one by one from small to large to the dual proportional amplifier board 4 through the DA module 2 according to the flow input data (preset flow value) L1 (0 - 1600). The output flow is converted into an electrical signal by the flowmeter 8 and input into the AD module 3. The PLC 1 converts the input value of the AD module 3 into feedback flow data and compares it with the preset flow value L1; when the values are the same (within the allowable error range), the preset flow value L1 and the control flow voltage data (output voltage value) L2 given by the PLC to the DA module are stored in the PLC power-off retention data area; when the values are different (exceeding the allowable error range), the PLC adjusts the output voltage value L2 given to the DA module through self-tuning so that the feedback flow value converted from the flowmeter signal input to the PLC is the same as the preset flow value, and the preset flow value L1 and the output voltage value L2 self-tuned by the PLC to the DA module are stored in the PLC power-off retention data area. The schematic diagram of the PLC flow and voltage data storage is as Figure 6 shown.

[0064] 2.2 Flow output of the variable pump, PLC flow parameter setting, and linear calibration acquisition and storage process (set flow 160 l / min)

[0065] As Figure 7 andFigure 8 As shown below, the following will explain the flow parameter setting and the linear calibration acquisition and storage process.

[0066] Step L101: Calibrate the flow zero of the dual proportional op-amp board

[0067] When the proportional overflow valve passes a current of 0 - 300 mA, the variable pump output flow is 0 l / min. Thus, the starting value of the flow control current of the dual proportional op-amp board 4 is set to 300 mA, aiming to shield the dead zone of the variable pump output flow.

[0068] Step L102: Input DC10V to the input terminal of the dual proportional op-amp board, and adjust the output current of the dual proportional op-amp board 4 to make the oil pump output flow 160 l / min, and set the maximum flow of the oil pump.

[0069] Step L103: Establish a plane coordinate relationship in the PLC

[0070] As in the above steps L101 and L102, accordingly adjust the output voltage value range of the control signal output by the PLC. Input the preset flow value L1 (0 - 1600) on the X-axis, which actually represents the set flow of 0 - 160 l / min. When the PLC 1 receives the preset flow value L1 (0 - 1600) input from the touch screen, it is proportionally converted and outputs a DC0 - 10V control signal to the dual proportional op-amp board 4 through the digital-to-analog DA. The dual proportional op-amp board 4 converts the DC0 - 10V voltage signal into a 300 - 900 mA current signal, outputs to control the proportional speed control valve, and controls the variable pump 5 to output a corresponding flow of 0 - 160 l / min.

[0071] Step L104: Start the PLC self-tuning function

[0072] The PLC 1 uses the plane coordinate reference established in step L103, with the X-axis as the input signal (i.e., input the preset flow value 0 - 1600 from the touch screen), and the Y-axis as the output signal (i.e., the digital-to-analog DA outputs DC0 - 10V), and executes the first tuning with X = 1.

[0073] Step L105: Determine X = the feedback value of the flowmeter (error ±1)

[0074] Judge whether the X value (preset flow value) in the current round is equal to the feedback value of the flowmeter (feedback flow value). When X = the flowmeter feedback value, execute step L106; otherwise, return to step L104 to adjust the output voltage data size to the DA module and repeat the above operations. The flowmeter detects the feedback flow signal, and the PLC receives this flow signal and converts it into a feedback flow value.

[0075] Step L106: Store the current X value L1 and the output voltage data L2 given by the PLC to the DA module at their respective corresponding addresses. The output voltage data L2 is obtained through self-tuning.

[0076] Step L107: M + 1 = M / X + 1 = X

[0077] Transfer to the next set of data to perform the acquisition and storage of the next set of data.

[0078] Step L108: Determine whether the current round M < 1600

[0079] When the current round M < 1600, return to Step L104, repeat the above operations, and perform the acquisition and storage of the next set of data. When M >= 1600, execute the end program and the linear calibration ends.

[0080] 2.3 Relationship between the touch screen set parameters and the PLC stored flow parameters L1 / L2

[0081] When the PLC receives a hydraulic action instruction, it finds the corresponding action flow parameter F1 set on the touch screen, compares the touch screen set parameter F1 with the PLC stored preset flow value L1. When F1 = L1, it is determined that the flow parameter F1 belongs to a certain set of data ranges configured in advance (for example, when the required flow value for the action is 50.5 l / min, a certain set of data is configured according to 0.1% of this flow value of 50.5 l / min). The PLC stores the preset flow parameter L2 and outputs a (DC0 - 10V) signal to the double proportional op-amp board through a digital-to-analog converter DA; when the double proportional op-amp board receives the control flow voltage signal (DC0 - 10V), it outputs a corresponding current (300 - 900 mA) to control the variable pump to output a corresponding flow (0 - 160 l / min).

[0082] 3. Application test of this pressure-flow linear output in a one-step injection blow molding machine

[0083] 3.1 The linear output of the flow improves the stability of the injection system and solves the problem of air entrapment at the tail of the product

[0084] Such as Figure 9As shown, the flow rate and current characteristic curve of the test example is given. Curve A is the calibrated output curve (linear output curve), and curves B and C are the original output curves (actual output fitting curves). Before tuning, when the preset flow rate value of 100 (10 l / min) is input to the PLC through the touch screen, the DA module controls the dual proportional op-amp board to output a current of 337 mA at point a (the PLC outputs a voltage signal corresponding to the current at point a based on the core principle of linear output). The flow rate corresponding to the current at point a on the original output curve C is at point D, and the value of the Y-axis coordinate d corresponding to point D is approximately 7.5 l / min. It can be seen that actually the required preset flow rate value of 10 l / min is input, while the output of the variable pump is 7.5 l / min, with an error of 25%. After tuning, when a flow rate of 100 (10 l / min) is input to the PLC, the DA module controls the dual proportional op-amp board to output a current of 355 mA at point b (the PLC outputs a tuned voltage signal corresponding to the current at point b). The flow rate corresponding to the current at point b on the original output curve C is at point B, and the value of the Y-axis coordinate corresponding to point B is approximately 10 l / min. In fact, the voltage signal output from the PLC to the DA module is non-linear, and through self-tuning correlation, the linear output of the variable pump flow rate is achieved.

[0085] The first-stage injection is used to adjust the air entrapment problem at the bottom of the injection plastic product. The injection speed is relatively slow, and the flow rate is generally controlled at 8 - 16 l / min. As mentioned above, after tuning, the variable pump improves the sensitivity of the first-stage injection speed, making it more controllable and improving the product stability.

[0086] 3.2 Pressure linear output improves the stability of the injection system and makes it easier to solve the shrinkage problem at the mouth of the product

[0087] As Figure 10 shown, the pressure and current characteristic curve of the test example is given. Curve D is the calibrated output curve (linear output curve), and curve E is the original output curve (actual output fitting curve). Before tuning, when the required preset pressure value of 1000 (100 bar) is input to the PLC through the touch screen, the DA-2 module controls the dual proportional op-amp board to output a current of 400 mA at point J. The pressure corresponding to the current at point J on the original output curve E is at point G, and the value of the Y-axis coordinate g corresponding to point G is approximately 88 bar. It can be seen that actually the required preset pressure value of 100 bar is input, while the output of the variable pump is 88 bar, with an error of 12%. After tuning, when a pressure of 1000 (100 bar) is input to the PLC, the DA module controls the dual proportional op-amp board to output a current of 440 mA at point f. The pressure corresponding to the current at point f on the original output curve E is at point F, and the value of the Y-axis coordinate corresponding to point F is approximately 100 bar. In fact, the voltage signal output from the PLC to the DA module is non-linear, and through self-tuning correlation, the linear output of the variable pump pressure is achieved.

[0088] Injection holding pressure is used to adjust the fullness of the bottle mouth of injection-molded plastic products. If the injection holding pressure is too high, the product will have mold swelling and be difficult to demold; if the injection holding pressure is too low, the bottle mouth of the product will shrink. The pressure is generally controlled between 80 - 120 bar. As mentioned above, the set holding pressure of the variable pump can quickly react on the product after tuning. According to the changes in the product, it can find a suitable pressure point faster, with stronger controllability and improved product stability.

[0089] As mentioned above, the present invention provides a method for linearly outputting the control of a variable pump by a PLC. By setting the linear relationship between the output voltage and the preset pressure / flow rate value through the plane coordinate relationship, and then linearly calibrating according to the feedback pressure / flow rate value obtained from the feedback detection, the linear calibration data is obtained, completing the preparation for the linear output data association. Based on this, when performing the control operation, the control signal for controlling the oil pump is output to achieve the purpose of linearly outputting the pressure and flow rate of the oil pump. As a specific application test, it is applied to an injection-blow molding machine to solve the problem of poor stability of the injection system of the existing injection-blow molding machine and improve the moving repeat accuracy. It has the following advantages: 1. The self-tuning pressure and flow rate given values are equal to the output values; 2. Improve the controllability of the hydraulic actuator (oil pump), reduce hydraulic shock, and achieve precise displacement control; 3. Reduce energy consumption; 4. Can shorten the molding cycle.

[0090] Embodiment 2

[0091] Based on the aforementioned method for linearly outputting the control of the oil pump pressure and flow rate, a system for linearly outputting the control of the oil pump pressure and flow rate can be formed. For its application examples and feature combinations, please refer to the aforementioned Embodiment 1. Taking the PLC as an example, specifically, it is a PLC control system for linearly outputting the oil pump pressure and flow rate. The following will briefly describe it.

[0092] A system for linearly outputting the control of the oil pump pressure and flow rate according to the present invention includes the following:

[0093] Setting module: Used to establish a plane coordinate relationship to obtain the linear curve relationship between the voltage and the preset pressure / flow rate value; specifically includes the following: Taking the output voltage value range of the control signal output by the main controller as the Y-axis and the preset pressure / flow rate value range input through the input device as the X-axis to form the linear curve relationship between the output voltage and the preset pressure / flow rate value;

[0094] Calibration module: Used to perform linear calibration to obtain linear calibration data; specifically includes the following processing flow:

[0095] Step 21: According to the linear curve relationship between the output voltage and the preset pressure / flow rate value, configure several groups of preset pressure / flow rate values and output voltage values according to the measurement accuracy;

[0096] Step 22: Obtain a set of preset pressure / flow values and output voltage values, output a control signal for controlling the oil pump, and obtain the feedback pressure / flow values obtained from the output of the oil pump through detection;

[0097] Step 23: Compare and determine the feedback pressure / flow values with the corresponding preset pressure / flow values; if they are equal or within the error range, store the preset pressure / flow values and the output voltage values as linear calibration data; if they are not equal or exceed the error range, adjust a new output voltage value until they are equal or within the error range, and then store the set of preset pressure / flow values and the new output voltage value as linear calibration data;

[0098] Step 24: Repeat the above Steps 22 - 23 to perform the acquisition and storage operations on each set of data, complete the acquisition and storage of all sets of data, form linear calibration data, and complete the linear calibration operation;

[0099] Output module: Used to output a control signal for controlling the oil pump based on the linear calibration data in the case of performing a control operation.

[0100] As described above, the linear relationship between the output voltage and the preset pressure / flow values is set through the plane coordinate relationship. Based on this, linear calibration is performed in combination with the feedback pressure / flow values obtained from the feedback detection to obtain linear calibration data, complete the preparation for linear output data association, and accordingly output a control signal for controlling the oil pump in the case of performing a control operation, so as to achieve the purpose of linearly outputting the pressure and flow of the oil pump.

[0101] Based on the foregoing solution, in an improved solution, the system for linearly outputting the pressure and flow of the oil pump further includes the following: Zero adjustment module: Used to output the control signal to the oil pump through the dual proportional op-amp board based on the main controller, and increase the output voltage value range of the control signal output by the main controller according to the zero-current value range of the dual proportional op-amp board, so that the current value output by the dual proportional op-amp board is greater than or equal to the termination value of the zero-current value range in its starting value case. The main controller is a PLC. In this way, the dead zone of the output pressure / flow values of the oil pump can be shielded.

[0102] Based on the foregoing solution, in an improved solution, the control oil pump pressure and flow linear output system further includes the following: a calibration module: used for performing linear calibration; specifically including the following processing flow: Step 41, in the current control operation scenario, obtain the current feedback pressure / flow value obtained by detecting the output of the oil pump; Step 42, compare and judge the current feedback pressure / flow value with the corresponding preset pressure / flow value; if they are equal or within the error range, it is determined to be qualified, and a qualified calibration result is output, and then the next calibration operation is performed; if they are not equal or exceed the error range, it is determined to be unqualified, and an unqualified calibration result is output, and then the next calibration operation is performed. In this way, real-time calibration can be carried out to timely detect whether there is a deviation after running for a period of time.

[0103] Based on the foregoing solution, in an improved solution, the control oil pump pressure and flow linear output system further includes the following: an update module: used for updating the linear calibration data according to the linear calibration result; specifically including the following: Based on the linear calibration result being unqualified, if the continuous number of unqualified calibration results reaches the update threshold, a new output voltage value is adjusted in real time until the current feedback pressure / flow value is equal to or within the error range of the corresponding preset pressure / flow value, and then the set of preset pressure / flow values and the new output voltage value are stored as linear calibration data to complete the operation of updating the linear calibration data; or, based on the linear calibration result being unqualified, if the continuous number of unqualified calibration results reaches the alarm range, corresponding alarms are issued according to different alarm levels, where there are at least 2 alarm levels, and step S20 is executed in the case of stopping the current control operation to complete the operation of updating the linear calibration data. In this way, the linear calibration data can be updated to timely correct the deviation phenomenon and ensure linear output.

[0104] It should be noted that the examples of the above embodiments can be preferably selected one or more in combination according to actual needs, and the accompanying drawings of a set of combined technical features are used for multiple examples, which will not be elaborated one by one here.

[0105] The above description is a detailed description and illustration of the preferred feasible embodiments of the present invention, but these descriptions are not intended to limit the scope of protection required by the present invention. Any equivalent changes or modifications completed under the technical teachings disclosed by the present invention shall fall within the scope of patent protection covered by the present invention.

Claims

1. A method for controlling the linear output of the pressure and flow rate of an oil pump, characterized in that, It includes the following: Step S10: Establish a plane coordinate relationship to obtain a linear curve relationship between voltage and preset pressure / flow rate values. Specifically, it includes the following: Taking the output voltage value range of the control signal output by the main controller as the Y-axis and the preset pressure / flow rate value range input through the input device as the X-axis to form a linear curve relationship between the output voltage and the preset pressure / flow rate values. Step S20: Perform linear calibration to obtain linear calibration data. Specifically, it includes the following processing flow: Step 21: According to the linear curve relationship between the output voltage and the preset pressure / flow rate values, configure several groups of preset pressure / flow rate values and output voltage values according to the measurement accuracy. Step 22: Take a group of preset pressure / flow rate values and output voltage values, output a control signal to control the oil pump, and obtain the feedback pressure / flow rate value obtained by detecting the output of the oil pump. Step 23: Compare and judge the feedback pressure / flow rate value with the corresponding preset pressure / flow rate value. If they are equal or within the error range, store the preset pressure / flow rate value and the output voltage value as linear calibration data. If they are not equal or exceed the error range, adjust a new output voltage value until they are equal or within the error range, and then store the group of preset pressure / flow rate values and the new output voltage value as linear calibration data. Step 24: Repeat the above steps 22 - 23 to perform the acquisition and storage operations on each group of data, complete the acquisition and storage of all groups of data, form linear calibration data, and complete the complete linear calibration operation. Step S30: Based on the linear calibration data, output a control signal to control the oil pump in the case of performing a control operation.

2. A method for controlling the linear output of the pressure and flow rate of an oil pump according to claim 1, characterized in that It also includes the following: Step S5: Based on the main controller outputting the control signal to the oil pump through the dual proportional op-amp board, according to the zero-current value range of the dual proportional op-amp board, increase the output voltage value range of the control signal output by the main controller so that the output current value of the dual proportional op-amp board is greater than or equal to the termination value of the zero-current value range in its starting value case, where the main controller is a PLC.

3. A method for linearly outputting the pressure and flow rate of an oil pump according to claim 1, characterized in that, It also includes the following: Step S40: Perform linear verification. Specifically, it includes the following processing flow: Step 41: In the current control operation case, obtain the current feedback pressure / flow rate value obtained by detecting the output of the oil pump. Step 42: Compare and judge the current feedback pressure / flow rate value with the corresponding preset pressure / flow rate value. If they are equal or within the error range, it is determined to be qualified, output a qualified verification result, and then perform the next verification operation. If they are not equal or exceed the error range, it is determined to be unqualified, output an unqualified verification result, and then perform the next verification operation.

4. A method for linearly outputting the pressure and flow rate of an oil pump according to claim 3, characterized in that, It also includes the following: Step S50: Update the linear calibration data according to the linear calibration result; specifically, it includes the following: Based on the fact that the linear calibration result is unqualified, if the continuous number of unqualified calibration results reaches the update threshold, then a new output voltage value is adjusted in real time until the current feedback pressure / flow value is equal to or within the error range of the corresponding preset pressure / flow value, and then this set of preset pressure / flow values and the new output voltage value are stored as linear calibration data to complete the operation of updating the linear calibration data; or, based on the fact that the linear calibration result is unqualified, if the continuous number of unqualified calibration results reaches the alarm range, corresponding alarms are issued according to different alarm levels, where there are at least 2 alarm levels, so as to execute Step S20 in the case of stopping the current control operation to complete the operation of updating the linear calibration data.

5. A linear output system for controlling the pressure and flow rate of an oil pump, characterized in that, Including the following: Setting module: Used to establish a plane coordinate relationship to obtain the linear curve relationship between voltage and preset pressure / flow values; specifically, it includes the following: Taking the output voltage value range of the control signal output by the main controller as the Y-axis and the preset pressure / flow value range input through the input device as the X-axis to form the linear curve relationship between the output voltage and the preset pressure / flow values. Calibration module: Used to perform linear calibration to obtain linear calibration data; specifically, it includes the following processing flow: Step 21: According to the linear curve relationship between the output voltage and the preset pressure / flow values, configure several groups of preset pressure / flow values and output voltage values according to the measurement accuracy. Step 22: Take a set of preset pressure / flow values and output voltage values, output the control signal for controlling the oil pump, and obtain the feedback pressure / flow value obtained from the output of the oil pump after detection. Step 23: Compare and judge the feedback pressure / flow value with the corresponding preset pressure / flow value; if they are equal or within the error range, then store this set of preset pressure / flow values and the output voltage value as linear calibration data; if they are not equal or exceed the error range, then adjust a new output voltage value until they are equal or within the error range, and then store this set of preset pressure / flow values and the new output voltage value as linear calibration data. Step 24: Repeat the above Steps 22 - 23 to perform the acquisition and storage operations on each group of data, complete the acquisition and storage of all groups of data, form the linear calibration data, and complete the complete linear calibration operation. Output module: Used to output the control signal for controlling the oil pump based on the linear calibration data in the case of performing the control operation.

6. A linear output system for controlling the pressure and flow rate of an oil pump according to claim 1, characterized in that, It also includes the following: Zero adjustment module: Used to increase the output voltage value range of the control signal output by the main controller based on the main controller outputting the control signal to the oil pump through the dual proportional operation amplifier board, according to the zero current value range of this dual proportional operation amplifier board, so that the output current value of this dual proportional operation amplifier board is greater than or equal to the termination value of this zero current value range in its starting value case, where the main controller is a PLC.

7. A linear output system for controlling the pressure and flow rate of an oil pump according to claim 1, characterized in that, It also includes the following: a calibration module for performing linear calibration, which specifically includes the following processing flow: Step 41: Under the current control operation scenario, obtain the current feedback pressure / flow value obtained by detecting the output of the oil pump; Step 42: Compare and determine the current feedback pressure / flow value with the corresponding preset pressure / flow value. If they are equal or within the error range, it is determined to be qualified, and a qualified calibration result is output, and then the next calibration operation is performed; If they are not equal or exceed the error range, it is determined to be unqualified, an unqualified calibration result is output, and then the next calibration operation is performed.

8. A linear output system for controlling the pressure and flow rate of an oil pump according to claim 7, characterized in that, It also includes the following: an update module for updating the linear calibration data according to the linear calibration result, which specifically includes the following: Based on the linear calibration result being unqualified, if the number of consecutive unqualified calibration results reaches the update threshold, a new output voltage value is adjusted in real time until the current feedback pressure / flow value is equal to or within the error range of the corresponding preset pressure / flow value, and then this set of preset pressure / flow values and the new output voltage value are stored as linear calibration data to complete the operation of updating the linear calibration data; or, based on the linear calibration result being unqualified, if the number of consecutive unqualified calibration results reaches the alarm range, corresponding alarms are issued according to different alarm levels, where there are at least 2 alarm levels, and step S20 is performed under the condition of stopping the current control operation to complete the operation of updating the linear calibration data.

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