A method for detecting abnormality of injection molding machine drive unit

Abstract

The present invention discloses a method for detecting an abnormality of a drive unit of an injection molding machine. By setting a current sampling circuit and a drive unit abnormality detection submodule, in the initial stage when the injection molding machine control system controls a certain drive unit to perform an action, the current between the output end of the power supply of the injection molding machine and the common power supply input end of each drive unit of the injection molding machine is collected by the current sampling circuit. The drive unit abnormality detection submodule uses the current collected by the current sampling circuit to form a current action response current data curve of the current drive unit. Based on the current action response current data curve of the current drive unit and pre-stored data, calculation and judgment are performed to finally determine whether the drive unit is abnormal. When the drive unit has an abnormality, the injection molding machine control system is notified to control the alarm of the injection molding machine to alarm, and the abnormal situation can be further judged. The advantage is that the overcurrent abnormality of the drive unit can be detected and warned, and other abnormal drive response failures can be detected and warned.

Description

Technical Field

[0001] The present invention relates to an abnormality detection method, and in particular to an abnormality detection method for a drive unit of an injection molding machine. Background Art

[0002] With the rapid development of electronic products, injection molding machines are moving towards automation and intelligence. The maintenance and repair work after an abnormality occurs in the injection molding machine has become increasingly complicated, and the demand for the abnormality detection function of the injection molding machine control system has also become higher and higher.

[0003] The drive circuit of the injection molding machine control system directly drives the three drive units in the injection molding machine: the solenoid valve, relay, and AC contactor, to control the injection molding machine's movements. The current method for detecting abnormalities in injection molding machines is that multiple drive units share an overcurrent detection and alarm circuit. When an overcurrent abnormality occurs in one of the drive units, the injection molding machine control system stops control and issues an overcurrent abnormality warning through its human-machine interface, reminding the user that the injection molding machine has an overcurrent abnormality. When a drive unit has other drive response abnormalities besides overcurrent, the injection molding machine control system will not take action or issue an alarm. Other drive response abnormalities include damage to the drive circuit of the injection molding machine control system, open circuit failures in the wiring between the injection molding machine control system and the drive unit, non-overcurrent failures in the drive unit, abnormal performance degradation due to aging of the drive unit, abnormal operating power exceeding the rated value of the drive unit, and abnormal foreign matter stuck in the solenoid valve.

[0004] Among them, abnormal performance degradation of the drive unit due to aging, abnormal operating power of the drive unit exceeding the rated value, and abnormal foreign matter stuck in the solenoid valve are not easy to detect in the daily operation of the injection molding machine. However, being in these abnormal working conditions for a long time will affect the quality of the injection molded products, causing product deformation, reduced precision and other problems. More seriously, it may cause damage to the injection molding machine. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for detecting abnormal response of a drive unit of an injection molding machine, which can not only detect and warn of abnormal overcurrent of the drive unit, but also detect and warn of other abnormal drive response failures.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a method for detecting abnormality of a drive unit of an injection molding machine, comprising the following steps:

[0007] Step S1, constructing a current sampling circuit, wherein the current sampling circuit has a power input terminal, a power output terminal, and a digital signal output terminal, and the current sampling circuit is used to convert a power supply current signal between the power input terminal and the power output terminal into a digital signal and output it at the digital signal output terminal;

[0008] Step S2, connecting the power input terminal of the current sampling circuit to the output terminal of the power supply of the injection molding machine, and connecting the power output terminal to the common power input terminal of each drive unit of the injection molding machine;

[0009] Step S3: In the injection molding machine control system, each drive unit of the injection molding machine is numbered respectively so that each drive unit has a unique number. At the same time, a readable data storage area is defined for each drive unit, and the standard action response current data curve and action abnormality judgment standard of the drive unit are pre-stored in the readable data storage area of ​​each drive unit. The standard action response current data curve of each drive unit includes the normal working current values ​​I0', I1 at the time t0 when the drive unit starts the action and the subsequent continuous sampling times t1, t2, t3, ..., t(n-1). ', I2', I3', ..., I(n-1)', time interval △t and current sampling number n, the time interval between any two adjacent moments t0, t1, t2, t3, ..., t(n-1) is equal to the time interval △t, the value range of △t is 1ms-100ms, the value range of n is 2-100, the action abnormality judgment standard includes the similarity calculation result of the current action response current data curve of each drive unit and the standard action response current data curve, the abnormality judgment threshold Q', the maximum allowable working current Imax' and the minimum working current Imin';

[0010] Step S4: constructing a drive unit abnormality detection submodule in the injection molding machine control system, wherein the drive unit abnormality detection submodule is connected to the injection molding machine control system and the digital signal output terminal of the current sampling circuit, respectively. The triggering condition of the drive unit abnormality detection submodule is that the injection molding machine control system issues a certain drive unit command, and the drive unit command corresponds to the number of a certain drive unit;

[0011] Step S5: When the injection molding machine control system sends a control instruction to a certain drive unit to control the certain drive unit to perform an action, it also sends the number of the certain drive unit to the drive unit abnormality detection submodule. At this time, the drive unit abnormality detection submodule is triggered to enter the working state. When the drive unit abnormality detection submodule enters the working state, the timing starts, and the initial timing is recorded as time t0;

[0012] Step S6: At time t0, the drive unit abnormality detection submodule reads the current value currently output by the digital signal output terminal of the current sampling circuit, recorded as I0, and simultaneously reads the time interval Δt and the current sampling number n of the current drive unit in the injection molding machine control system, where the current drive unit refers to the drive unit currently executing an action under the control of the injection molding machine control system;

[0013] Step S7: With time t0 as the initial time, the drive unit abnormality detection submodule continuously reads n-1 current values ​​outputted from the digital signal output terminal of the current sampling circuit at intervals of Δt, and records the n-1 current values ​​as I1, I2, I3, ..., I(n-1) in order of the reading time. A current action response current data curve of the current drive unit is constructed using I0, I1, I2, I3, ..., I(n-1);

[0014] Step S8, the drive unit abnormality detection submodule reads the standard action response current data curve of the current drive unit in the injection molding machine control system, the abnormality judgment threshold Q' of the similarity calculation result, the maximum operating current Imax' and the minimum operating current Imin';

[0015] Step S9: The drive unit abnormality detection submodule obtains the maximum value among I0, I1, I2, I3, ..., In-1 through a pre-stored sorting algorithm, records the maximum value as Imax, compares Imax-I0 with Imax' and Imin' respectively, and if Imin'≤Imax-I0≤Imax', executes step S10; if Imax-I0>Imax', executes step S11; if Imax-I0<Imin', executes step S12;

[0016] In step S10, the drive unit abnormality detection submodule calculates the similarity Q between the current action response current data curve of the current drive unit and its standard action response current data curve, and compares Q with Q'. If Q ≤ Q', it indicates that the current drive unit is normal. The drive unit abnormality detection submodule ends its work and returns to step S5 to wait for the next trigger condition. If Q > Q', step S13 is executed.

[0017] Step S11: The drive unit abnormality detection submodule notifies the injection molding machine control system of the current drive unit abnormality. The injection molding machine control system stops the control of all drive units and controls the injection molding machine alarm to sound an alarm and prompts the human-machine interface that the current drive unit is abnormal. At this time, the abnormality of the current drive unit is that the working power exceeds the rated value and waits for inspection and maintenance.

[0018] Step S12: The drive unit abnormality detection submodule notifies the injection molding machine control system of the current drive unit abnormality. The injection molding machine control system stops controlling all drive units and controls the injection molding machine alarm to sound an alarm and displays a prompt on its human-machine interface that the current drive unit is abnormal. The abnormality at this time may be a damage fault of the drive circuit, an open circuit fault of the wiring, or a drive unit fault, and the fault is waiting for inspection and repair.

[0019] In step S13, the drive unit abnormality detection submodule notifies the injection molding machine control system that the current drive unit is abnormal. The injection molding machine control system stops the control of all drive units and controls the alarm of the injection molding machine and prompts the human-computer interaction interface that the current drive unit is abnormal. The abnormality at this time may be due to aging of the drive unit or abnormality of foreign matter stuck in the solenoid valve, and it is waiting for inspection and maintenance.

[0020] The current sampling circuit includes an operational amplifier, a V / F conversion chip model LM331, an optocoupler isolation chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a first capacitor, a second capacitor and a transistor. The operational amplifier has a power supply terminal, a positive input terminal, a reverse input terminal, an output terminal and a ground terminal. One end of the first resistor, one end of the fifth resistor, the power supply terminal of the operational amplifier and the 8th pin of the V / F conversion chip are connected and the connection end thereof is connected to a first voltage. The first voltage is used to supply the operational amplifier with a power supply terminal. The amplifier and the V / F conversion chip provide a working voltage, the other end of the first resistor is connected to the anode of the optical coupler isolation chip, the cathode of the optical coupler isolation chip is connected to the collector of the transistor, the emitter of the optical coupler isolation chip is grounded, the collector of the optical coupler isolation chip is connected to one end of the second resistor and the connection end is the digital signal output end of the current sampling circuit, the other end of the second resistor is connected to the second voltage, and the second voltage is used to provide a working voltage for the optical coupler isolation chip, the emitter of the transistor, one end of the twelfth resistor, the 4th pin of the V / F conversion chip, and one end of the eleventh resistor are connected. The first end, one end of the first capacitor and the grounding terminal of the operational amplifier are all grounded, the other end of the first capacitor and the other end of the fifth resistor are connected to the 5th pin of the V / F conversion chip, the base of the transistor and one end of the tenth resistor are connected, the other end of the tenth resistor is connected to the 3rd pin of the V / F conversion chip, the 2nd pin of the V / F conversion chip and the other end of the twelfth resistor are connected, the 1st and 6th pins of the V / F conversion chip, one end of the second capacitor and one end of the seventh resistor are connected, the other end of the seventh resistor, the other end of the second capacitor and the other end of the eleventh resistor are connected. The 7th pin of the V / F conversion chip is connected to one end of the fourth resistor, the other end of the fourth resistor and one end of the ninth resistor are connected to the output end of the operational amplifier, the other end of the ninth resistor and one end of the eighth resistor are connected to the inverting input end of the operational amplifier, the non-inverting input end of the operational amplifier is connected to one end of the third resistor, the other end of the third resistor is connected to one end of the sixth resistor and the connection end thereof is the power input end of the current sampling circuit, and the other end of the eighth resistor is connected to the other end of the sixth resistor and the connection end thereof is the power output end of the current sampling circuit.

[0021] Compared with the prior art, the advantage of the present invention is that by setting a current sampling circuit and a drive unit abnormality detection submodule, in the initial stage of the injection molding machine control system controlling a certain drive unit to perform an action, the current between the output end of the injection molding machine power supply and the common power supply input end of each drive unit of the injection molding machine is collected by the current sampling circuit, and the drive unit abnormality detection submodule uses the current collected by the current sampling circuit to form a current action response current data curve of the current drive unit, based on the current action response current data curve of the current drive unit and the pre-stored standard action response current data curve, the similarity calculation result abnormality judgment threshold Q', the maximum allowable working current Imax' and the minimum working current I min' is calculated and judged, and finally it is determined whether the drive unit is abnormal. When the drive unit has an abnormality and notifies the injection molding machine control system to control the alarm of the injection molding machine, it can further determine that the abnormality is one of the following three situations: 1. The working power of the drive unit exceeds the rated value; 2. The drive circuit is damaged, the wiring is open, and the drive unit is faulty; 3. The drive unit is aged and the electromagnetic valve is stuck with foreign objects. The current sampling circuit added by the present invention has a low cost, and the drive unit abnormality detection submodule can be implemented through a software program. Therefore, the present invention adopts a low cost, not only can it detect and warn of the overcurrent abnormality of the drive unit, but also can detect and warn of other drive response abnormalities. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A circuit diagram of a current sampling circuit of a method for detecting abnormality in a drive unit of an injection molding machine according to the present invention;

[0023] Figure 2 is a scatter plot corresponding to a current flow valve opening current data curve obtained by the injection molding machine drive unit abnormality detection method of the present invention when the current drive unit is a flow valve;

[0024] Figure 3 It is a scatter plot corresponding to the current action response current data curve and the standard action response current data curve obtained by the injection molding machine drive unit abnormality detection method of the present invention when the current drive unit is a flow valve. DETAILED DESCRIPTION

[0025] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0026] Example 1: A method for detecting abnormality of a drive unit of an injection molding machine, comprising the following steps:

[0027] Step S1, constructing a current sampling circuit, the current sampling circuit having a power input terminal, a power output terminal, and a digital signal output terminal, the current sampling circuit being used to convert a supply current signal between the power input terminal and the power output terminal into a digital signal and output it at its digital signal output terminal;

[0028] Step S2, connecting the power input terminal of the current sampling circuit to the output terminal of the power supply of the injection molding machine, and connecting the power output terminal to the common power input terminal of each drive unit of the injection molding machine;

[0029] Step S3: In the injection molding machine control system, each drive unit of the injection molding machine is numbered respectively so that each drive unit has a unique number. At the same time, a readable data storage area is defined for each drive unit, and the standard action response current data curve and action abnormality judgment standard of the drive unit are pre-stored in the readable data storage area of ​​each drive unit. The standard action response current data curve of each drive unit includes the normal working current values ​​I0', I1 at the time t0 when the drive unit starts the action and the subsequent continuous sampling times t1, t2, t3, ..., t(n-1). ', I2', I3', ..., I(n-1)', time interval △t and current sampling number n, the time interval between any two adjacent moments t0, t1, t2, t3, ..., t(n-1) is equal to the time interval △t, the value range of △t is 1ms-100ms, the value range of n is 2-100, the action abnormality judgment standard includes the similarity calculation result of the current action response current data curve of each drive unit and the standard action response current data curve, the abnormality judgment threshold Q', the maximum allowable working current Imax' and the minimum working current Imin';

[0030] Step S4: constructing a drive unit abnormality detection submodule in the injection molding machine control system. The drive unit abnormality detection submodule is connected to the injection molding machine control system and the digital signal output terminal of the current sampling circuit, respectively. The triggering condition of the drive unit abnormality detection submodule is that the injection molding machine control system issues a certain drive unit command, and the drive unit command corresponds to the number of a certain drive unit.

[0031] Step S5: When the injection molding machine control system sends a control instruction to a certain drive unit to control the certain drive unit to perform an action, it also sends the number of the certain drive unit to the drive unit abnormality detection submodule. At this time, the drive unit abnormality detection submodule is triggered to enter the working state. When the drive unit abnormality detection submodule enters the working state, the timing starts, and the initial timing is recorded as time t0;

[0032] Step S6: At time t0, the drive unit abnormality detection submodule reads the current value currently output by the digital signal output terminal of the current sampling circuit, recorded as I0, and simultaneously reads the time interval Δt and the current sampling number n of the current drive unit in the injection molding machine control system, where the current drive unit refers to the drive unit currently executing an action under the control of the injection molding machine control system;

[0033] Step S7: With time t0 as the initial time, the drive unit abnormality detection submodule continuously reads n-1 current values ​​outputted from the digital signal output terminal of the current sampling circuit at intervals of Δt, and records the n-1 current values ​​as I1, I2, I3, ..., I(n-1) in order of the reading time. A current action response current data curve of the current drive unit is constructed using I0, I1, I2, I3, ..., I(n-1);

[0034] Step S8, the drive unit abnormality detection submodule reads the standard action response current data curve of the current drive unit in the injection molding machine control system, the abnormality judgment threshold Q' of the similarity calculation result, the maximum operating current Imax' and the minimum operating current Imin';

[0035] Step S9: The drive unit abnormality detection submodule obtains the maximum value among I0, I1, I2, I3, ..., In-1 through a pre-stored sorting algorithm, records the maximum value as Imax, compares Imax-I0 with Imax' and Imin' respectively, and if Imin'≤Imax-I0≤Imax', executes step S10; if Imax-I0>Imax', executes step S11; if Imax-I0<Imin', executes step S12;

[0036] In step S10, the drive unit abnormality detection submodule calculates the similarity Q between the current action response current data curve of the current drive unit and its standard action response current data curve, and compares Q with Q'. If Q ≤ Q', it indicates that the current drive unit is normal. The drive unit abnormality detection submodule ends its work and returns to step S5 to wait for the next trigger condition. If Q > Q', step S13 is executed.

[0037] Step S11: The drive unit abnormality detection submodule notifies the injection molding machine control system of the current drive unit abnormality. The injection molding machine control system stops the control of all drive units and controls the injection molding machine alarm to sound an alarm and prompts the human-machine interface that the current drive unit is abnormal. At this time, the abnormality of the current drive unit is that the working power exceeds the rated value and waits for inspection and maintenance.

[0038] Step S12: The drive unit abnormality detection submodule notifies the injection molding machine control system of the current drive unit abnormality. The injection molding machine control system stops controlling all drive units and controls the injection molding machine alarm to sound an alarm and displays a prompt on its human-machine interface that the current drive unit is abnormal. The abnormality at this time may be a damage fault of the drive circuit, an open circuit fault of the wiring, or a drive unit fault, and the fault is waiting for inspection and repair.

[0039] In step S13, the drive unit abnormality detection submodule notifies the injection molding machine control system that the current drive unit is abnormal. The injection molding machine control system stops the control of all drive units and controls the alarm of the injection molding machine and prompts the human-computer interaction interface that the current drive unit is abnormal. The abnormality at this time may be due to aging of the drive unit or abnormality of foreign matter stuck in the solenoid valve, and it is waiting for inspection and maintenance.

[0040] The design principle of the present invention's method for detecting abnormalities in injection molding machine drive units is as follows: all drive units in the injection molding machine are powered by a single power supply. A current sampling circuit monitors the total current supplied to the drive units by this power supply. When the injection molding machine is not operating, this current remains stable and unchanged, namely, the current I0 at time t0. When a drive unit performs an action, such as opening a flow valve, the flow valve consumes current. The current sampling circuit then collects a current data curve consisting of I0, I1, I2, I3, ..., and I(n-1). This is the current data curve for the current flow valve opening. The response current data curve differs between normal and abnormal operation. The present invention's method for detecting abnormalities in injection molding machine drive units extracts information from the drive unit response current data curve to determine whether a drive unit is abnormal. When a drive unit's operating power exceeds its rated value, it can be detected that the maximum value of the sampled current exceeds the maximum operating current of the drive unit, i.e., Imax - I0 > Imax' in step S9. When the drive circuit is damaged, the wiring is open, or the drive unit is not overcurrent faulted, the injection molding machine control system issues an action command to the drive unit, and the drive unit executes the action. At this time, the sampled current value of the current sampling circuit does not change, that is, there is no current change from time t0 onwards, thus triggering the Imax-I0<Imin' condition in step S9. Abnormal performance degradation of the drive unit due to aging or foreign matter stuck in the solenoid valve will cause the operating current of the drive unit to change. The calculated similarity Q between the current action response current data curve and the standard action current data curve will also increase significantly, exceeding the pre-set threshold Q', thus determining an abnormality.

[0041] Example 2: This example is basically the same as Example 1, except that: Figure 2As shown, in this embodiment, the current sampling circuit includes an operational amplifier U1, a V / F conversion chip U2 of model LM331, an optocoupler isolation chip U3, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a first capacitor C1, a second capacitor C2 and a transistor Q1. The operational amplifier U1 has a power supply terminal, a positive input terminal, a reverse input terminal, an output terminal and a ground terminal. One end of the first resistor R1, one end of the fifth resistor R5, the power supply terminal of the operational amplifier U1 and the V / F conversion chip U2 are connected to the output terminal of the transistor Q1. The 8th pin of the V / F conversion chip U2 is connected and its connection end is connected to the first voltage Vin, the first voltage Vin is used to provide a working voltage for the operational amplifier U1 and the V / F conversion chip U2, the other end of the first resistor R1 is connected to the anode of the optocoupler isolation chip U3, the cathode of the optocoupler isolation chip U3 is connected to the collector of the transistor Q1, the emitter of the optocoupler isolation chip U3 is grounded, the collector of the optocoupler isolation chip U3 is connected to one end of the second resistor R2 and the connection end is the digital signal output end of the current sampling circuit, the other end of the second resistor R2 is connected to the second voltage VCC, the second voltage VCC is used to provide a working voltage for the optocoupler isolation chip U3, the emitter of the transistor Q1, the twelfth resistor R2 and the collector of the optocoupler isolation chip U3 are connected to the digital signal output end of the current sampling circuit, One end of the resistor R12, the 4th pin of the V / F conversion chip U2, one end of the eleventh resistor R11, one end of the first capacitor C1 and the ground terminal of the operational amplifier U1 are all grounded, the other end of the first capacitor C1, the other end of the fifth resistor R5 and the 5th pin of the V / F conversion chip U2, the base of the transistor Q1 and one end of the tenth resistor R10 are connected, the other end of the tenth resistor R10 is connected to the 3rd pin of the V / F conversion chip U2, the 2nd pin of the V / F conversion chip U2 and the other end of the twelfth resistor R12 are connected, the 1st pin and the 6th pin of the V / F conversion chip U2, one end of the second capacitor C2 and one end of the seventh resistor R7 are connected, the other end of the seventh resistor R7 and the second capacitor C1 are connected. The other end of the capacitor C2 is connected to the other end of the eleventh resistor R11, the seventh pin of the V / F conversion chip U2 is connected to one end of the fourth resistor R4, the other end of the fourth resistor R4 and one end of the ninth resistor R9 are connected to the output end of the operational amplifier U1, the other end of the ninth resistor R9 and one end of the eighth resistor R8 are connected to the inverting input end of the operational amplifier U1, the non-inverting input end of the operational amplifier U1 is connected to one end of the third resistor R3, the other end of the third resistor R3 is connected to one end of the sixth resistor R6, and the connection end thereof is the power input end of the current sampling circuit, and the other end of the eighth resistor R8 is connected to the other end of the sixth resistor R6, and the connection end thereof is the power output end of the current sampling circuit.

[0042] The working process of the current sampling circuit of this embodiment is as follows: when the power input terminal of the current sampling circuit is connected to the output terminal of the power supply of the injection molding machine, and the power output terminal is connected to the common power supply input terminal (i.e., the load) of each drive unit of the injection molding machine, the power supply provides power to the load through the sixth resistor R6. The current provided to the load flows through the sixth resistor R6 to generate a small voltage signal (0-10mV). The small voltage signal is input to the proportional amplifier circuit composed of the third resistor R3, the eighth resistor R8, the ninth resistor R9 and the operational amplifier U1 to be amplified 100 times. The amplified signal is input to the 7th pin of the V / F conversion chip U2 through the fourth resistor R4. The V / F conversion chip U2 receives the signal through the 7th pin of the V / F conversion chip U2. The seventh resistor R7, the second capacitor C2 and the eleventh resistor R11 external to pins 1 and 6 configure the voltage / frequency conversion rate. The second pin of the V / F conversion chip U2 is grounded through the twelfth resistor R12 to configure its bias current to zero. The fifth pin of the V / F conversion chip U2 is connected to the RC filter circuit composed of the fifth resistor R5 and the first capacitor C1 to configure the filtering bandwidth of the input signal. The V / F conversion chip U2 converts the voltage signal input at its seventh pin into a PWM square wave 1 of a certain frequency at a fixed ratio according to the configuration parameters of its first, second, fifth and sixth pins, and outputs it from the third pin. The PWM square wave 1 controls the conduction of the transistor Q1 through the tenth resistor R10. When the PWM square wave 1 output by the V / F conversion chip U2 is at a high level, the transistor Q1 is turned on, the cathode of the optocoupler isolation chip U3 is grounded, and the first voltage Vin is input to the anode of the optocoupler isolation chip U3 through the first resistor R1. A voltage difference is generated between the anode and cathode of the optocoupler isolation chip U3, driving the light-emitting diode inside the optocoupler isolation chip U3 to emit light. The light triggers the phototransistor inside the optocoupler isolation chip U3 to turn on, so that the digital signal output end of the current sampling circuit is grounded and outputs a low level; conversely, when the PWM square wave 1 output by the V / F conversion chip U2 is at a low level, the transistor Q1 is turned off, the cathode of the optocoupler isolation chip U3 is suspended, there is no voltage difference between the anode and cathode of the optocoupler isolation chip U3, the light-emitting diode inside the optocoupler isolation chip U3 does not work, the phototransistor inside the optocoupler isolation chip U3 is turned off, and the digital signal output end of the current sampling circuit is pulled up to the second voltage VCC through the second resistor R2 to output a high level. That is, the PWM square wave 1 output by the V / F conversion chip U2 is converted by the tenth resistor R10, the transistor Q1, the first resistor R1, the optocoupler isolation chip U3, and the second resistor R2 into a PWM square wave 2 with a second voltage VCC and a constant frequency. The PWM square wave 1 and the PWM square wave 2 belong to two isolated circuit systems.In summary, the current sampling circuit realizes the function of converting the current value flowing from the power input end to the power output end into a square wave at a fixed frequency, and the output signal is isolated from the first voltage Vin to avoid interference from the first voltage Vin, and the sampling accuracy is high. At the same time, the current sampling circuit has few components, simple design, low cost, and little impact on the existing injection molding machine system. It only needs to occupy one IO input resource of the injection molding machine system and is easy to integrate into the injection molding machine system.

[0043] The process of the drive unit abnormality detection submodule of this embodiment obtaining the current action response current curve is as follows: assuming that the injection molding machine control system issues a command to open the flow valve in step S5, that is, a command for the flow valve to execute the action, and the sampling number n=101 and △t=1ms saved by the flow valve in step S3, the drive unit abnormality detection submodule starts to read the current value currently output by the digital signal output end of the current sampling circuit at time t0, and the reading at time t0 is recorded as I0, and then the timing waits from △t=1ms to time t1=t0+1ms, and the current value of the digital signal output end of the current sampling circuit is read, recorded as I1, and the timing waits from △t=1ms to time t2=t0+2ms, and the current value of the digital signal output end of the current sampling circuit is read, recorded as I2, and so on, until at time t100=t0+100ms, the current value of the digital signal output end of the current sampling circuit is read, recorded as I100. At this point, the drive unit abnormality detection submodule obtains the current flow valve opening response current data curve within 100ms from time t0 to time t100 with a sampling interval of 1ms. By plotting the points (t0, I0), (t1, I1), ..., (t100, I100) in a coordinate system with the horizontal axis as the time axis and the vertical axis as the current value, we can get the following: Figure 2 The scatter curve shown is the current flow valve opening current data curve.

[0044] The process of the drive unit abnormality detection submodule of this embodiment calculating the similarity Q between the current action response current data curve of the current drive unit and its standard action response current data curve is as follows: Assume that the injection molding machine control system issues a flow valve opening command in step S5, the sampling number n of the flow valve saved in step S3 is n=101, △t=1ms, the current flow valve opening current data obtained are I0, I1, I2, I3, ..., I100, and the standard flow valve opening current data saved in step S3 are I0', I1', I2', ..., I100'. These data are plotted in a coordinate system with the horizontal axis as the time axis and the vertical axis as the current value, all starting at time t0 and the interval of △t=1ms, and the following can be obtained: Figure 3The scatter plot is shown. Calculate the current offset △I0= I0- I0', △I1= I1- I1', △I2= I2- I2', ..., △I100= I100- I100' at each moment t0, t1, t2, ..., t100. Then calculate the current offset △I1'=△I1-△I0, △I2'=△I2-△I0, ..., △I100'=△I100-△I0 at each moment t1, t2, ..., t100 relative to △I0. Then calculate the sum of the squares of △I1', △I2', ..., △I100'. The result is the similarity Q between the current action response current data curve of the current drive unit and its standard action response current data curve, which can be expressed by the following formula: .

[0045] In the injection molding machine drive unit abnormality detection method of the present invention, the judgment threshold Q' is obtained based on the parameter evaluation of the corresponding drive unit in advance. The specific evaluation steps are: first, the current waveform of the corresponding drive unit when it is started is tested multiple times, the number of measurements is not less than 10 times, and each time a measured current waveform is obtained as the current action response current data curve, and then the average current value of all the measured current waveforms at each time t0, t1, t2,..., t(n-1) is calculated. Based on the obtained average current value, a standard current curve, i.e., a standard action response current data curve, is obtained. Then, the similarity between each measured current waveform and the standard current curve is obtained using the same calculation method as the similarity Q, and the maximum value is selected from the calculated similarities, and the maximum value is multiplied by 1.2 as the final judgment threshold Q'.

Claims

1. A method for detecting abnormality of an injection molding machine drive unit, characterized in that The following steps are involved: Step S1, constructing a current sampling circuit, wherein the current sampling circuit has a power input terminal, a power output terminal, and a digital signal output terminal, and the current sampling circuit is used to convert a power supply current signal between the power input terminal and the power output terminal into a digital signal and output it at the digital signal output terminal; Step S2, connecting the power input terminal of the current sampling circuit to the output terminal of the power supply of the injection molding machine, and connecting the power output terminal to the common power input terminal of each drive unit of the injection molding machine; Step S3: In the injection molding machine control system, each drive unit of the injection molding machine is numbered respectively so that each drive unit has a unique number. At the same time, a readable data storage area is defined for each drive unit, and the standard action response current data curve and action abnormality judgment standard of the drive unit are pre-stored in the readable data storage area of ​​each drive unit. The standard action response current data curve of each drive unit includes the normal working current values ​​I0', I1 at the time t0 when the drive unit starts the action and the subsequent continuous sampling times t1, t2, t3, ..., t(n-1). ', I2', I3', ..., I(n-1)', time interval △t and current sampling number n, the time interval between any two adjacent moments t0, t1, t2, t3, ..., t(n-1) is equal to the time interval △t, the value range of △t is 1ms-100ms, the value range of n is 2-100, the action abnormality judgment standard includes the similarity calculation result of the current action response current data curve of each drive unit and the standard action response current data curve, the abnormality judgment threshold Q', the maximum allowable working current Imax' and the minimum working current Imin'; Step S4: constructing a drive unit abnormality detection submodule in the injection molding machine control system, wherein the drive unit abnormality detection submodule is connected to the injection molding machine control system and the digital signal output terminal of the current sampling circuit, respectively. The triggering condition of the drive unit abnormality detection submodule is that the injection molding machine control system issues a certain drive unit command, and the drive unit command corresponds to the number of a certain drive unit; Step S5: When the injection molding machine control system sends a control instruction to a certain drive unit to control the certain drive unit to perform an action, it also sends the number of the certain drive unit to the drive unit abnormality detection submodule. At this time, the drive unit abnormality detection submodule is triggered to enter the working state. When the drive unit abnormality detection submodule enters the working state, the timing starts, and the initial timing is recorded as time t0; Step S6: At time t0, the drive unit abnormality detection submodule reads the current value currently output by the digital signal output terminal of the current sampling circuit, recorded as I0, and simultaneously reads the time interval Δt and the current sampling number n of the current drive unit in the injection molding machine control system, where the current drive unit refers to the drive unit currently executing an action under the control of the injection molding machine control system; Step S7: With time t0 as the initial time, the drive unit abnormality detection submodule continuously reads n-1 current values ​​outputted from the digital signal output terminal of the current sampling circuit at intervals of Δt, and records the n-1 current values ​​as I1, I2, I3, ..., I(n-1) in order of the reading time. A current action response current data curve of the current drive unit is constructed using I0, I1, I2, I3, ..., I(n-1); Step S8, the drive unit abnormality detection submodule reads the standard action response current data curve of the current drive unit in the injection molding machine control system, the abnormality judgment threshold Q' of the similarity calculation result, the maximum operating current Imax' and the minimum operating current Imin'; In step S9, the drive unit abnormality detection submodule obtains the maximum value among I0, I1, I2, I3, ..., I(n-1) through a pre-stored sorting algorithm, records the maximum value as Imax, and compares Imax-I0 with Imax' and Imin' respectively. If Imin'≤Imax-I0≤Imax', then execute step S10; if Imax-I0>Imax', then execute step S11; if Imax-I0<Imin', then execute step S12; In step S10, the drive unit abnormality detection submodule calculates the similarity Q between the current action response current data curve of the current drive unit and its standard action response current data curve, and compares Q with Q'. If Q ≤ Q', it indicates that the current drive unit is normal. The drive unit abnormality detection submodule ends its work and returns to step S5 to wait for the next trigger condition. If Q > Q', step S13 is executed. Step S11: The drive unit abnormality detection submodule notifies the injection molding machine control system of the current drive unit abnormality. The injection molding machine control system stops the control of all drive units and controls the injection molding machine alarm to sound an alarm and prompts the human-machine interface that the current drive unit is abnormal. At this time, the abnormality of the current drive unit is that the working power exceeds the rated value and waits for inspection and maintenance. Step S12: The drive unit abnormality detection submodule notifies the injection molding machine control system of the current drive unit abnormality. The injection molding machine control system stops controlling all drive units and controls the injection molding machine alarm to sound an alarm and displays a prompt on its human-machine interface that the current drive unit is abnormal. The abnormality at this time may be a damage fault of the drive circuit, an open circuit fault of the wiring, or a drive unit fault, and the fault is waiting for inspection and repair. In step S13, the drive unit abnormality detection submodule notifies the injection molding machine control system that the current drive unit is abnormal. The injection molding machine control system stops the control of all drive units and controls the alarm of the injection molding machine and prompts the human-computer interaction interface that the current drive unit is abnormal. The abnormality at this time may be due to aging of the drive unit or abnormality of foreign matter stuck in the solenoid valve, and it is waiting for inspection and maintenance.

2. The method for detecting abnormality of an injection molding machine drive unit according to claim 1, characterized in that The current sampling circuit includes an operational amplifier, a V / F conversion chip model LM331, an optocoupler isolation chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a first capacitor, a second capacitor and a transistor. The operational amplifier has a power supply terminal, a positive input terminal, a reverse input terminal, an output terminal and a ground terminal. One end of the first resistor, one end of the fifth resistor, the power supply terminal of the operational amplifier and the 8th pin of the V / F conversion chip are connected and the connection end thereof is connected to a first voltage. The first voltage is used to supply the operational amplifier with a power supply terminal. The amplifier and the V / F conversion chip provide a working voltage, the other end of the first resistor is connected to the anode of the optical coupler isolation chip, the cathode of the optical coupler isolation chip is connected to the collector of the transistor, the emitter of the optical coupler isolation chip is grounded, the collector of the optical coupler isolation chip is connected to one end of the second resistor and the connection end is the digital signal output end of the current sampling circuit, the other end of the second resistor is connected to the second voltage, and the second voltage is used to provide a working voltage for the optical coupler isolation chip, the emitter of the transistor, one end of the twelfth resistor, the 4th pin of the V / F conversion chip, and one end of the eleventh resistor are connected. The first end, one end of the first capacitor and the grounding terminal of the operational amplifier are all grounded, the other end of the first capacitor and the other end of the fifth resistor are connected to the 5th pin of the V / F conversion chip, the base of the transistor and one end of the tenth resistor are connected, the other end of the tenth resistor is connected to the 3rd pin of the V / F conversion chip, the 2nd pin of the V / F conversion chip and the other end of the twelfth resistor are connected, the 1st and 6th pins of the V / F conversion chip, one end of the second capacitor and one end of the seventh resistor are connected, the other end of the seventh resistor, the other end of the second capacitor and the other end of the eleventh resistor are connected. The 7th pin of the V / F conversion chip is connected to one end of the fourth resistor, the other end of the fourth resistor and one end of the ninth resistor are connected to the output end of the operational amplifier, the other end of the ninth resistor and one end of the eighth resistor are connected to the inverting input end of the operational amplifier, the non-inverting input end of the operational amplifier is connected to one end of the third resistor, the other end of the third resistor is connected to one end of the sixth resistor and the connection end thereof is the power input end of the current sampling circuit, and the other end of the eighth resistor is connected to the other end of the sixth resistor and the connection end thereof is the power output end of the current sampling circuit.

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