CN105257629A - Non-linear correction system and method for pressure proportional valve of injection molding hydraulic system - Google Patents

Abstract

The invention relates to a correction method for an injection molding machine hydraulic system, in particular to a non-linear correction system and method for a pressure proportional valve of the injection molding hydraulic system. The non-linear correction system comprises the injection molding machine hydraulic system, the pressure proportional valve, a starting correction module, a pressure non-linear correction module and an analog output module, wherein the pressure non-linear correction module corrects a pressure output value according to the actual pressure value displayed by a pressure gage and sends the corrected value to the analog output module for pressure control; the analog output module amplifies and outputs an analog signal to the pressure proportional valve and controls the opening degree of the pressure proportional valve; the starting correction module is connected with the pressure non-linear correction module; the pressure non-linear correction module, the analog output module and the pressure proportional valve are sequentially connected through a signal line. The non-linear correction system and method for the pressure proportional valve of the injection molding hydraulic system can replace the functions of a pressure feedback sensor. People do not need to take part in calculation in the whole correction process, and compensation calculation is automatically achieved completely through the pressure non-linear correction module. Therefore the correction operation difficulty is greatly lowered, and a common operator can implement correction easily.

Description

Nonlinear Correction System and Method for Pressure Proportional Valve of Injection Molding Hydraulic System

technical field

The invention relates to a correction method for a hydraulic system of an injection molding machine. More specifically, the invention relates to a nonlinear correction method for a pressure proportional valve in the hydraulic system of an injection molding machine.

Background technique

Injection molding is one of the main molding methods of plastic products. The injection molding machine heats and melts polymer raw materials and injects them into a designed closed mold cavity for cooling and molding to form various plastic products with high dimensional accuracy and complex shapes, which are suitable for mass production and high-precision production. There are three types of driving methods for injection molding machines: hydraulic, all-electric and electro-hydraulic hybrid. Among them, hydraulic injection molding machines have become the mainstream of injection molding machines due to their high load capacity, low cost, and simple design. Usually, the hydraulic system of hydraulic injection molding accurately controls the pressure and speed of the hydraulic system through a pressure proportional valve and flow proportional valve, and then combines various solenoid valves and flow valves to realize the motion control of each module of the injection molding machine, in which the pressure proportional valve and flow rate Proportional valve is the core of hydraulic system control and guarantees the precise control of injection molding process. In the hydraulic system, the hydraulic oil drives the oil pump through the motor to enter the hydraulic system pipeline. First, it is controlled by a flow proportional valve to meet the flow requirements set by the injection molding process, and then the hydraulic pressure is controlled by controlling the opening of the pressure proportional valve to achieve the injection molding process. The setting value of the machine can finally realize the precise control of each part of the injection molding machine.

The pressure proportional valve and flow proportional valve in the hydraulic system of the injection molding machine are generally current input type, and the opening of the proportional valve is controlled by inputting a current of 0-1 ampere, thereby accurately controlling the pressure and flow of the hydraulic system. However, due to the nonlinear nature of the pressure proportional valve and the coupling effect of hydraulic system pressure and flow, the input current and output pressure of the pressure proportional valve are not linearly corresponding, and there is a large nonlinear phenomenon, especially at the initial low pressure. stage. Therefore, in order to accurately control the pressure of the hydraulic system, the nonlinear correction of the pressure proportional valve must be performed to achieve the effect of linear output. Generally, the internal control circuit of the pressure proportional valve itself has a certain nonlinear compensation function, but it still cannot overcome the nonlinear characteristics of the injection molding process. The control system of the injection molding machine must have nonlinear correction capabilities to achieve linear control of the pressure of the injection molding hydraulic system. ability.

At present, most ordinary hydraulic injection molding machines do not have the nonlinear correction function of the pressure proportional valve, so the pressure control accuracy of the hydraulic system is very poor, and only some plastic products with low precision requirements can be produced. The more advanced injection molding machine control system has the function of nonlinear correction with pressure proportional valve, but the correction method is to set several nonlinear characteristic points for the output range of pressure proportional valve, and then manually correct these characteristic points by trial and error. The pressure output reference value, and the control system performs linear interpolation correction through the output reference value obtained by these manual trials. The key to the correction method is the setting of the reference value of the result feature point, and the setting of the reference value is set by the operator or professional debugger by trial and error, manual calculation, etc., which is a waste of time, and it is generally difficult for non-professionals to set it properly. The correction value of , resulting in poor nonlinear correction effect.

Usually, a pressure indicator is installed on the injection molding machine to display the current pressure of the hydraulic system, but this gauge is an analog pressure gauge, which is mainly used for observation by the injection molding machine operator, and cannot be directly input to the injection molding machine controller for use by the control system. The present invention adopts the method of manual simple participation, utilizes the existing pressure display instrument of the injection molding machine, realizes the non-linear automatic correction of the pressure proportional valve of the hydraulic system of the injection molding machine, does not need manual calculation, and greatly reduces the difficulty of non-correction methods.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a non-linear correction system and method for the hydraulic system of the injection molding machine. Specifically, the operator is used to read the pressure gauge value of the injection molding machine and give feedback to realize the automatic nonlinear correction of the pressure proportional valve of the hydraulic system of the injection molding machine. The present invention is based on simple feedback from the operator, reducing computational requirements for the operator.

For solving technical problems, the technical scheme that the present invention adopts is as follows:

Provide a non-linear correction system for the pressure proportional valve of the injection molding hydraulic system, including the hydraulic system of the injection molding machine installed on the injection molding machine; the hydraulic system of the injection molding machine is equipped with a pressure proportional valve, and the outlet of the pressure proportional valve is connected to the pressure gauge through a pipeline ; The nonlinear correction system also includes:

Start a correction module, which is used to start the nonlinear correction process of the pressure proportional valve;

The pressure nonlinear correction module corrects the pressure output value according to the actual pressure value displayed by the pressure gauge, and sends the corrected value to the analog output module for pressure control;

Analog output module, which amplifies and outputs the analog signal to the pressure proportional valve to control its opening;

The starting correction module is connected with the pressure non-linear correction module, and the pressure non-linear correction module, the analog output module and the pressure proportional valve are sequentially connected through signal lines.

In the present invention, the analog output module has a built-in signal amplifier.

The present invention further provides a method for nonlinear correction of the pressure proportional valve of the injection molding hydraulic system, including correction of the characteristic points within the output range of the pressure proportional valve and the maximum output value of the pressure. The process specifically includes:

(1) First correct the maximum output range point of the pressure proportional valve:

Make the pressure correction output module directly output the theoretical pressure value P _max of the maximum output range point, and then directly adjust the amplifier set in the analog output module until the actual output pressure displayed by the pressure gauge is equal to P _max ; indicating that the calibration is completed;

(2) Select k feature points at intervals within the pressure output range of the hydraulic system of the injection molding machine, and divide the entire pressure output process into k+1 segments, where k is a positive integer ranging from 1 to 15;

(3) The theoretical pressure output value P _k ^' and the maximum value P _max of the pressure output range corresponding to the k feature points are respectively used as the pressure output set value by the pressure nonlinear correction module, and sent to the analog output module for pressure control; The analog output module outputs the analog signal to the pressure proportional valve to control its opening to increase the pressure of the hydraulic system of the injection molding machine; read the current actual pressure value displayed by the pressure gauge, and input the value into the pressure non-linear correction module. The nonlinear correction module uses the formula (a) to calculate the correction value P _kt of the pressure output set value, and sends it to the analog output module as the second corrected set value;

P _kt =P _k0 +P _k -P _ks (Formula a)

In formula a, P _kt is the corrected pressure output setting value; P _k is the uncorrected pressure output setting value of the kth feature point, and its value is equal to P _k ' or P _max ; P _ks is The current actual pressure value of the hydraulic system displayed by the pressure gauge;

(4) Repeat step (3), when the current actual pressure value displayed by the pressure gauge is the same as the pressure output set value, it is considered that the nonlinear compensation of the pressure proportional valve at the characteristic point or the maximum value has been fully realized;

For the first calibration, set P _k0 =P _k in formula a. If multiple calibrations are repeated, P _k0 is the P _kt obtained after the last calibration.

(5) Repeat the above steps (3) and (4) until all the selected k feature points are corrected, then the correction process of the entire injection molding hydraulic system ends.

In the present invention, in the actual operation after the calibration of the injection molding machine is completed, the pressure nonlinear correction module performs nonlinear correction in the following manner according to the previously obtained correction data of the characteristic points and the maximum output value, and uses the correction value as the actual The output value is sent to the analog output module, so that the actual output pressure of the hydraulic system of the injection molding machine is consistent with the pressure output set value:

(1) When the pressure output value P _x set by the injection molding system satisfies the condition P _{k ≤} P _x < P _k+1 (when P _k is the last feature point, P _k+1 = P _max ), according to the formula b Make nonlinear corrections:

P＝P _kt +(P _x -P _k )×(P _(k+1)t -P _kt )/(P _k+1 -P _k ) (formula b)

(2) When P _x < P ₁ , that is, when P _x is in the first section of the entire pressure output process, perform nonlinear correction as follows:

P=P _x ×P _1t /P _k (formula c);

In the above formulas, P _x is the pressure value of the injection hydraulic system required by the injection molding process, that is, the pressure output setting value; P is the corrected pressure output setting value, that is, the actual output value of the pressure nonlinear correction module; P _kt is the corrected pressure output setting value of the kth feature point; P _k is the uncorrected pressure output setting value of the kth feature point; P _(k+1)t is the corrected k+th The pressure output setting value of 1 characteristic point; P _k+1 is the uncorrected pressure output setting value of the k+1th characteristic point.

In the present invention, for the hydraulic system of the injection molding machine with a pressure output range of 0-145 bar, the value of k is 5-8.

The present invention further provides a pressure control method for an injection molding hydraulic system based on the foregoing method, comprising the following steps:

(1) After the nonlinear correction of the pressure proportional valve is completed each time, an instruction is sent to the controller through the man-machine dialogue interface, and the pressure nonlinearity correction module sends the data corresponding to the pressure value to the storage module of the controller for storage;

The pressure value correspondence data refers to the correspondence relationship data between the actual output value of the pressure nonlinear correction module that has been corrected multiple times and meets the nonlinear compensation requirements and the pressure value required by the injection molding process, that is, the pressure output set value;

(2) For the new injection molding process:

When the input injection molding process requires that the pressure value matches the data stored in the storage unit, the controller directly calls the actual output value of the corresponding pressure nonlinearity correction module and sends it to the analog output module to control the opening of the pressure proportional valve ;

When the input injection molding process requires that the pressure value does not match the data stored in the storage unit, the pressure nonlinear correction module calculates the actual pressure output value according to formula (b) and formula (c), and then transmits it to the analog output Module, the latter outputs an analog signal to the pressure proportional valve to control its opening, and finally realizes the pressure control of the injection hydraulic system.

Compared with prior art, the beneficial effect of the present invention is:

The present invention only needs to manually read the pressure gauge of the injection molding machine to realize the function of replacing the pressure feedback sensor. The whole calibration process does not require manual calculation, and the compensation calculation is completely automatically realized by the pressure nonlinear correction module. Therefore, the operation difficulty of calibration is greatly reduced, and ordinary operators can simply implement it.

Instructions attached

Attached Figure 1: Block diagram of the nonlinear correction system for the pressure proportional valve of the injection hydraulic system;

Attached Figure 2: Schematic diagram of the calibration process;

Attached Figure 3: The 7-stage calibration curve with the maximum output pressure of the hydraulic system being 140bar.

detailed description

First of all, it needs to be explained that the present invention relates to database technology, which is an application of computer technology in the field of industrial control. During the implementation of the present invention, the application of multiple software function modules will be involved. The applicant believes that, after carefully reading the application documents and accurately understanding the realization principle and purpose of the present invention, combined with existing known technologies, those skilled in the art can fully implement the present invention by using their software programming skills. The aforementioned software function modules include but are not limited to: start-up correction module, pressure nonlinear correction module, analog output module, etc. All mentioned in the application documents of the present invention belong to this category, and the applicant will not list them one by one.

The present invention proposes a non-linear correction system (as shown in FIG. 1 ) for the pressure proportional valve of the injection molding hydraulic system. The system includes a startup correction module 101 , a pressure nonlinearity correction module 102 , an analog output module 103 , an injection molding machine hydraulic system 104 and an injection molding machine 105 . The startup correction module 101 is connected to the pressure nonlinearity correction module 102, and is used to start the whole pressure nonlinearity correction process. The pressure nonlinear correction module 102 is connected to the analog output module 103 through a signal line, and outputs the calculated pressure output control to the analog output module 103 . The analog output module 103 is connected to the pressure proportional valve of the hydraulic system 104 of the injection molding machine through a signal line to control its opening. The injection molding machine hydraulic system 104 is installed at the corresponding position of the injection molding machine 105 . During the correction process, the operator or technician of the injection molding machine needs to read the value of the pressure gauge installed on the injection molding machine, and then input the value into the pressure nonlinear correction module 102, which calculates the correction value of the pressure output characteristic point through the correction process, and then The corrected pressure control data is output to the hydraulic system 104 of the injection molding machine through the analog output module 103 , and the hydraulic system 104 of the injection molding machine controls the action of the injection molding machine 105 .

The pressure nonlinear correction method is divided into the following steps:

1. Make the pressure correction output module directly output the theoretical pressure value P _max of the maximum output range point, and then directly adjust the amplifier set in the analog output module until the actual output pressure displayed by the pressure gauge is equal to P _max ; indicating that the calibration is completed;

2. According to the output range of the hydraulic system of the injection molding machine [0, P _max ], set several characteristic points, and divide the entire pressure output process into corresponding sections [0, P ₁ , P ₂ ,...P _k ... P _max ]. For an injection molding machine with an output range of 145bar, 7 feature points are generally set. The selection of feature points generally chooses densely selected areas with strong nonlinearity, and the selection range can be enlarged for weaker nonlinear areas. In practice, [0,10,20 is usually selected. ,30,60,90,120,130,145]. If you don’t know the nonlinear situation of the system at all, you can use the average segmentation method. If it is set to n segments, the interval of each range is P _max /n, and the entire output range becomes [0, P _max /n, 2× P _max /n, . . . , (n-1)×P _max /n, P _max ].

3. After selecting the characteristic points and dividing the system into several sections, the calibration is performed from the first section.

The pressure non-linear correction module first outputs the characteristic point pressure value P ₁ of the first segment according to the linear condition to control the hydraulic system of the injection molding machine. The injection molding machine is controlled by the hydraulic system. The pressure gauge displays the current actual hydraulic system value P _1s . Method The operator reads the value of the pressure gauge and inputs it to the pressure nonlinear correction module, and the pressure nonlinear correction module uses the formula (a1) to calculate the correction value of this point:

P _1t =P ₁₀ +P ₁ -P _1s (a1)

Among them, P ₁₀ is the original linear output value or the value after the last correction, and P ₁ is the theoretical pressure value corresponding to the first feature point. If it is the first calibration, then P ₁₀ =P ₁ , otherwise P ₁₀ is the P _1t obtained after the last calibration.

By analogy, if it is other feature point correction, use the formula (a2) to calculate:

P _kt =P _k0 +P _k -P _ks (a2)

Among them, P _k0 is the original linear output value or the value after the last correction, and P _k is the theoretical pressure value corresponding to the kth point when dividing the feature points. If it is the first calibration, then P _k0 =P _k , then P _k0 is the P _kt obtained after the last calibration.

The pressure non-linear correction module 102 corrects the pressure values of other characteristic points and the maximum value according to the method in step 2. Repeat step 3. When the current actual pressure value displayed by the pressure gauge is the same as the pressure output set value, it is considered that the nonlinear compensation of the pressure proportional valve at the characteristic point or the maximum value has been fully realized.

4. After obtaining all the characteristic points and the correction values of the maximum value, the pressure nonlinearity correction module 102 can perform the actual operation of the injection molding machine in the following manner according to the correction data of the previously obtained characteristic points and the maximum output value: Non-linear correction, and the correction value is sent to the analog output module as the actual output value, so that the actual output pressure of the hydraulic system of the injection molding machine is consistent with the pressure output set value:

(1) When the pressure output value P _x set by the injection molding system satisfies the condition P _{k ≤} P _x < P _k+1 (when P _k is the last feature point, P _k+1 = P _max ), according to the formula b Make nonlinear corrections:

P＝P _kt +(P _x -P _k )×(P _(k+1)t -P _kt )/(P _k+1 -P _k ) (formula b)

(2) When P _x < P ₁ , that is, when P _x is in the first section of the entire pressure output process, perform nonlinear correction as follows:

P=P _x ×P _1t /P _k (formula c);

In the above formulas, P _x is the pressure value of the injection hydraulic system required by the injection molding process, that is, the pressure output setting value; P is the corrected pressure output setting value, that is, the actual output value of the pressure nonlinear correction module; P _kt is the corrected pressure output setting value of the kth feature point; P _k is the uncorrected pressure output setting value of the kth feature point; P _(k+1)t is the corrected k+th The pressure output setting value of 1 characteristic point; P _k+1 is the uncorrected pressure output setting value of the k+1th characteristic point.

Based on the above correction method, the present invention can also realize the automatic control of the pressure of the injection molding hydraulic system, including the following steps:

When the input injection molding process requires that the pressure value matches the data stored in the storage unit, the controller directly calls the actual output value of the corresponding pressure nonlinearity correction module and sends it to the analog output module to control the opening of the pressure proportional valve ;

When the input injection molding process requires that the pressure value does not match the data stored in the storage unit, the pressure nonlinear correction module calculates the actual pressure output value according to formula (b) and formula (c), and then transmits it to the analog output Module, the latter outputs an analog signal to the pressure proportional valve to control its opening, and finally realizes the pressure control of the injection hydraulic system.

Below, the implementation process of the present invention is described in detail in conjunction with specific implementation examples:

This embodiment takes the nonlinear correction of the pressure proportional valve of the hydraulic system of the injection molding machine as an example to illustrate the realization of the nonlinear correction method of the pressure proportional valve of the hydraulic system of the injection molding machine in the present invention, other types and pressure output ranges. The nonlinear correction of the pressure proportional valve of the hydraulic system of the injection molding machine is considered to be within the scope of the present invention.

The non-linear correction section of the pressure proportional valve in the hydraulic system of the injection molding machine in this embodiment is shown in FIG. 3 . Set 7 pressure correction feature points in the pressure output range, respectively P ₁ (10bar), P ₂ (20bar), P ₃ (30bar), P ₄ (60bar), P ₅ (90bar), P ₆ (120bar) and P ₇ (130bar), where the pressure value in brackets is the theoretical value of the corresponding feature point. The maximum output of 145bar has been calibrated through the maximum range. The main task of this calibration system is to obtain the pressure correction value of the above 7 points.

The calibration process of the pressure proportional valve’s maximum output range point of 145bar is as follows: the pressure calibration output module directly outputs the theoretical pressure value P _max of the maximum output point = 145bar, and the user directly adjusts the amplifier of the pressure analog output module until the actual output pressure is equal to 145bar. Calibration complete.

The correction process of the seven feature points is introduced in detail below.

Firstly, the first characteristic point P ₁ (10 bar) is corrected.

According to the steps introduced in the summary of the invention, the pressure non-linear correction module first outputs the pressure value of 10 bar linearly to the hydraulic system of the injection molding machine. After the hydraulic system of the injection molding machine operates, an actual hydraulic pressure value P will be displayed on the pressure gauge on the injection molding machine. _1s , at this time, it is necessary to read the value of the pressure gauge and input P _1s into the pressure nonlinear correction module through the operation panel screen of the man-machine dialogue device, assuming that P _1s is 8bar.

Next, the pressure nonlinear correction module calculates the pressure correction value of point P ₁ through P _1s .

Formula (a1) is used to obtain P _1t =P ₁₀ +P ₁ -P _1s =10+10-8=12 bar.

At this time, the pressure nonlinear correction module saves the correction value P _1t for use in the pressure output of the injection molding machine control system, or the second correction needs to use P _1t after the first correction does not meet the requirements. Here, due to the first calibration, P ₁₀ is the theoretical value of the default feature point P ₁ , which is 10bar.

Next, the calibration of point _P2 is performed.

_The pressure nonlinearity correction module outputs the pressure 20bar at point P2 to the hydraulic system of the injection molding machine, and the pressure gauge of the injection molding machine will display the current actual pressure value _P2s . Then input P2s into the pressure nonlinearity correction module through manual feedback, assuming it is 19bar. The pressure nonlinearity correction module calculates the correction value of point P2 through the formula (a2), and k=2 at this time.

P _kt =P _2t =P _k0 +P _k -P _ks =P ₂₀ +P ₂ -P _2s =20+20-19=21 bar. Due to the first calibration, P ₂₀ =P ₂ =20 bar.

Calculate and correct P ₃ (30bar), P ₄ (60bar), P ₅ (90bar), P ₆ (120bar) and P ₇ (130bar) points by the same method as above to obtain the correction values of 7 characteristic points.

After the correction value of each point is obtained, the pressure nonlinearity correction module 102 can calculate the actual output pressure value through the correction value of the feature point. Assume that a pressure of 40 bar needs to be output at this time. 40bar is located in the pressure range of characteristic points P ₃ (30bar) and P ₄ (60bar). The pressure nonlinearity correction module firstly calculates the output value after pressure correction through the formula (b). Assume that P _3t = 35bar, P _4t = 70bar after the above correction.

Use the formula (b) to calculate the correction value required for the actual output of 40bar as follows

$\begin{array}{c}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 35</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 40</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 30</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 70</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 35</span>}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 60</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 30</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 46.67</span>}\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; .</span>\end{array}$

After the pressure nonlinearity correction module 102 obtains the correction value P of 40 bar, the actual output of the fifth step can be performed. Assuming that the DA output chip in the analog output module 103 is an output with 12-bit precision, the digital value corresponding to the output value of the actual 40 bar pressure is P/145×2 ¹² =659. The pressure nonlinear correction module 102 outputs 659 to the analog output module 103 to control the DA chip, and the hydraulic system can obtain a pressure of 40 bar.

After the complete calibration is completed, you can test the actual effect after calibration. Set a pressure value to control the output corresponding pressure of the injection molding machine control system and observe whether the actual pressure gauge of the injection molding machine shows whether it is the same as the set value. If the multi-point test in the entire pressure output range is satisfied Non-linear correction is done if required.

If the actual injection molding machine pressure gauge display is different from the set value after the first calibration is completed, the second calibration can be continued. Instead of correcting the points that meet the requirements, directly correct those feature points that do not meet the requirements. Assuming that the first point P ₁ (10bar) does not meet the requirements after calibration, the second calibration can be performed. Same as the above process, firstly the pressure non-linearity correction module outputs the pressure of P ₁ (10bar) point 10bar according to the value after the first correction, manually read the pressure P ₁ (10bar) point pressure P _1s of the pressure gauge of the injection molding machine, and the pressure Input the pressure nonlinear correction module, assuming 9bar.

The pressure nonlinearity correction module 102 calculates the correction value for the second time by formula (a1).

P _1t =P ₁₀ +P ₁ -P _1s =12+10-9=13 bar. Because it is not the first calibration, P ₁₀ is the value after the previous calibration, and P _1t after the first calibration is 12bar.

If there are other segments that do not meet the requirements, the second correction can also be performed.

This correction method corrects the theoretical output value, rather than the digital value before the DA output of the conventional method. Conventional calibration methods usually require manual calculation and continuous trial and error to figure out the digital value or voltage value before the DA output. This method greatly reduces the requirements on the operator. Moreover, since the present invention adopts the method of manually reading the value feedback of the pressure gauge, it does not require manual intervention in selection or calculation, so it can be used as a generally applicable technical solution.

It should be understood that the present invention is not limited to the exact structure and method as shown and described above, and various changes and modifications can be made to the invention without departing from the spirit and scope of the present invention defined by the claims. It is considered to be the protection scope of the present invention.

Claims (6)

1. The non-linear correction system of the pressure proportional valve of the injection molding hydraulic system, including the hydraulic system of the injection molding machine installed on the injection molding machine; the hydraulic system of the injection molding machine is equipped with a pressure proportional valve, and the outlet of the pressure proportional valve is connected to the pressure gauge through the pipeline; It is characterized in that the nonlinear correction system also includes: Start a correction module, which is used to start the nonlinear correction process of the pressure proportional valve; The pressure nonlinear correction module corrects the pressure output value according to the actual pressure value displayed by the pressure gauge, and sends the corrected value to the analog output module for pressure control; Analog output module, which amplifies and outputs the analog signal to the pressure proportional valve to control its opening; The starting correction module is connected with the pressure non-linear correction module, and the pressure non-linear correction module, the analog output module and the pressure proportional valve are sequentially connected through signal lines. 2. The system according to claim 1, wherein the analog output module has a built-in signal amplifier. 3. The method of nonlinear correction of the pressure proportional valve of the injection molding hydraulic system, which is characterized in that it includes the correction of the characteristic points in the output range of the pressure proportional valve and the maximum output value of the pressure. The process specifically includes: (1) First correct the maximum output range point of the pressure proportional valve: Make the pressure correction output module directly output the theoretical pressure value P _max of the maximum output range point, and then directly adjust the amplifier set in the analog output module until the actual output pressure displayed by the pressure gauge is equal to P _max ; indicating that the calibration is completed; (2) Select k feature points at intervals within the pressure output range of the hydraulic system of the injection molding machine, and divide the entire pressure output process into k+1 segments, where k is a positive integer ranging from 1 to 15; (3) The theoretical pressure output value P _k ^' corresponding to the k characteristic points and the maximum value P _max of the pressure output range are respectively used as the pressure output set value by the pressure nonlinear correction module, and sent to the analog output module for pressure control; The analog output module outputs the analog signal to the pressure proportional valve to control its opening to increase the pressure of the hydraulic system of the injection molding machine; read the current actual pressure value displayed by the pressure gauge, and input the value into the pressure non-linear correction module. The nonlinear correction module uses the formula (a) to calculate the correction value P _kt of the pressure output set value, and sends it to the analog output module as the second corrected set value; P _kt =P _k0 +P _k -P _ks (Formula a) In formula a, P _kt is the corrected pressure output setting value; P _k is the uncorrected pressure output setting value of the kth feature point, and its value is equal to P _k ^' or P _max ; P _ks is The current actual pressure value of the hydraulic system displayed by the pressure gauge; (4) Repeat step (3), when the current actual pressure value displayed by the pressure gauge is the same as the pressure output set value, it is considered that the nonlinear compensation of the pressure proportional valve at the characteristic point or the maximum value has been fully realized; For the first calibration, set P _k0 = P _k in formula a. If multiple calibrations are repeated, P _k0 is the P _kt obtained after the last calibration; (5) The above steps (3) and (4) are repeated until all the selected k feature points are corrected, and the calibration process of the entire injection molding hydraulic system ends. 4. The method according to claim 3, characterized in that, during the actual operation of the injection molding machine after the correction is completed, the pressure nonlinearity correction module performs the following steps according to the previously obtained correction data of the characteristic points and the maximum output value Non-linear correction is carried out by means of non-linear correction, and the correction value is sent to the analog output module as the actual output value, so that the actual output pressure of the hydraulic system of the injection molding machine is consistent with the pressure output set value: (1) When the pressure output value P _x set by the injection molding system satisfies the condition P _{k ≤} P _x <P _k+1 , perform nonlinear correction according to formula b; when P _k is the last feature point, P _k+1 = P _max ; P＝P _kt +(P _x -P _k )×(P _(k+1)t -P _kt )/(P _k+1 -P _k ) (formula b) (2) When P _x < P ₁ , that is, when P _x is in the first section of the entire pressure output process, perform nonlinear correction as follows: P=P _x ×P _1t /P _k (formula c); In the above formulas, P _x is the pressure value of the injection hydraulic system required by the injection molding process, that is, the pressure output setting value; P is the corrected pressure output setting value, that is, the actual output value of the pressure nonlinear correction module; P _kt is the corrected pressure output setting value of the kth feature point; P _k is the uncorrected pressure output setting value of the kth feature point; P _(k+1)t is the corrected k+th The pressure output setting value of 1 characteristic point; P _k+1 is the uncorrected pressure output setting value of the k+1th characteristic point. 5. The method according to claim 3 or 4, characterized in that, for a hydraulic system of an injection molding machine with a pressure output range of 0-145 bar, the value of k is 5-8. 6. The injection molding hydraulic system pressure control method based on any one of claims 2 to 5, characterized in that it comprises the following steps: (1) After the nonlinear correction of the pressure proportional valve is completed each time, an instruction is sent to the controller through the man-machine dialogue interface, and the pressure nonlinearity correction module sends the data corresponding to the pressure value to the storage module of the controller for storage; The pressure value correspondence data refers to the correspondence relationship data between the actual output value of the pressure nonlinear correction module that has been corrected multiple times and meets the nonlinear compensation requirements and the pressure value required by the injection molding process, that is, the pressure output set value; (2) For the new injection molding process: When the input injection molding process requires that the pressure value matches the data stored in the storage unit, the controller directly calls the actual output value of the corresponding pressure nonlinearity correction module and sends it to the analog output module to control the opening of the pressure proportional valve ; When the input injection molding process requires that the pressure value does not match the data stored in the storage unit, the pressure nonlinear correction module calculates the actual pressure output value according to formula (b) and formula (c), and then transmits it to the analog output Module, the latter outputs an analog signal to the pressure proportional valve to control its opening, and finally realizes the pressure control of the injection hydraulic system.