CN110673032B - Overload detection method and system for servo system - Google Patents

Overload detection method and system for servo system Download PDF

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CN110673032B
CN110673032B CN201910909012.9A CN201910909012A CN110673032B CN 110673032 B CN110673032 B CN 110673032B CN 201910909012 A CN201910909012 A CN 201910909012A CN 110673032 B CN110673032 B CN 110673032B
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value
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overload detection
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sum
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赵雪峰
任强
黄武
席小鹭
田炜
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Beijing Changfeng Tiantong Technology Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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Abstract

The invention relates toAnd the motor overload detection field. The invention discloses an overload detection method and system of a servo system, which are used for detecting the running current of a servo motor in real time, precisely rectifying a converted voltage signal after resistance sampling and filtering, and calculating a voltage effective value V after analog-to-digital conversionRMS(ii) a If VRMS＞Vn，VnIf the voltage value is a voltage value corresponding to the rated current of the motor, performing integral accumulation operation to obtain an accumulated value SUM; if SUM is greater than MAX and MAX is a set threshold value, an alarm signal is sent out to control the servo motor to stop; if VRMS≤VnWhen SUM is greater than 0, integral desaturation operation is carried out, when SUM is less than or equal to 0, SUM is made to be 0, and operation of the next period is continued.

Description

Overload detection method and overload detection system of servo system
Technical Field
The invention relates to the technical field of motor overload detection, in particular to an overload detection method and an overload detection system of a servo system.
Background
With the continuous development of power electronic technology and intelligent control technology, servo systems are increasingly applied to the fields of automation and the like. Because the automatic production line has the characteristics of long continuous working time and large equipment load, the overload running state often occurs to the servo system, the high-performance servo motor has certain overload capacity, short-time overload is allowed, but when the servo motor or the servo driver has a long-time continuous overload condition, the servo driver or the servo motor is easily burnt, even serious safety accidents can be caused, and the overload running state of the servo system needs to be effectively monitored.
Common overload detection methods in the prior art include a temperature detection method, a thermal overload relay method and a current segmentation detection protection method, but the temperature detection method has hysteresis due to a temperature curve, and when a large load current suddenly appears and a short-circuit protection current threshold is not reached, the overload detection method is often damaged because the overload detection method is not in time to protect; the thermal overload relay method needs to set relay parameters, but is limited by site construction conditions, the parameter setting is easy to be inaccurate, and the thermal overload relay is easily influenced by environmental temperature, the reliability of a contact is poor, and the protection failure is often caused; the subsection detection protection method usually uses integral multiple of rated current to continue for a specific time to carry out protection, but because the subsection interval is larger, if the servo system runs between a low-section current and a high-section current and is close to the high-section current, the system can still be protected by the low-section current protection time, and the heat accumulation exceeds a set value under the running state, so that the protection is invalid. Therefore, the prior art has the problem that the overload protection is not reliable enough.
Disclosure of Invention
Technical problem to be solved
Based on the above problems, the present invention provides an overload detection method and system for a servo system, which can improve the reliability of overload protection for the servo system.
(II) technical scheme
Based on the above technical problem, the present invention provides an overload detection method for a servo system, where the detection method includes:
s1, detecting the running current of the servo motor in real time, and obtaining a voltage signal V through resistance sampling and filteringinFor the converted voltage signal VinCarrying out precision rectification;
s2, sampling, AD converting and storing the precisely rectified voltage waveform, and calculating the voltage effective value VRMS；
S3, judging whether V is presentRMS＞Vn，VnIf the voltage value is the voltage value corresponding to the rated current of the motor, the step is carried out in S4, and if the voltage value is not the voltage value, the step is carried out in S5;
s4, carrying out integral accumulation operation to obtain an accumulated value SUM, and continuing to the step S6;
s5, determining whether the SUM is greater than 0, if not, making SUM equal to 0, and returning to step S1; if yes, the integration desaturation operation is carried out, and then the step returns to the step S1;
s6, judging whether the accumulated value SUM is larger than MAX or not, wherein MAX is a set threshold value, if yes, the servo system is in overload operation, sending an alarm signal, entering the step S7, and if not, returning to the step S1;
and S7, the servo driving module receives the alarm signal and controls the servo motor to stop.
Further, the precision rectified full-wave rectification circuit described in step S1 includes two operational amplifiers U1A, U1B, four diodes D1, D2, D3, D4, and three resistors R1, R2, R3; vinThe input end of the R1, the equidirectional input end of the U1B, the other end of the R1, the reverse input end of the U1A, the positive electrode of the D1 and one end of the R2, the equidirectional input end of the U1A is grounded, the negative electrode of the D1 is connected with the output end of the U1A and the positive electrode of the D2, the reverse input end of the U1B is connected with the positive electrode of the D3 and one end of the R3, the negative electrode of the D3 is connected with the output end of the U1B and the positive electrode of the D4, the other end of the R2, the negative electrode of the D2, the other end of the R3 and the negative electrode of the D4 are connected with the VoutAnd R is1＝R2。
Further, the minimum input voltage required by the precision rectified full-wave rectifier circuit described in step S1 is:
Figure GDA0003577428600000031
wherein, VDFAnd the forward conduction voltage drop exists for the diode, and K is the open-loop differential mode amplification factor of the integrated operational amplifier.
Further, the effective voltage value V in step S2RMSThe calculation formula of (c) is:
Figure GDA0003577428600000032
wherein, t1To measure time, V (t) is a function of voltage versus time.
Further, the effective voltage value V in step S2RMSThe calculation formula of (2) is as follows:
Figure GDA0003577428600000033
wherein, the count value Cout is determined by the rotation speed of the servo motor, and V is a voltage value.
Further, the calculation formula of the accumulated value SUM obtained by the integral and accumulation operation in step S4 is as follows:
Figure GDA0003577428600000041
wherein, N ═ t2T, representing the actual overload time in numerical value, T2T is the calculation period for the overload time.
Further, the calculation formula of the integral desaturation operation in step S5 is as follows:
Figure GDA0003577428600000042
wherein T is the calculation period.
The overload detection system of the servo system comprises a sampling filtering module, a precise rectifying module, an MCU module and a servo driving module which are sequentially connected, and can execute the overload detection method of the servo system.
Further, the MCU module includes an effective value calculating module, an integral accumulation and integral desaturation calculating module, and an alarm module, wherein the effective value calculating module performs step S2, the integral accumulation and integral desaturation calculating module performs steps S3 to S5, and the alarm module performs step S6.
(III) advantageous effects
The technical scheme of the invention has the following advantages:
(1) according to the invention, smooth sampling is adopted, the current effective value is obtained in real time, the converted voltage waveform is smoother through the filter and the full-wave rectification circuit, and the variable can be obtained in time even if the current of the motor jumps faster, so that the phenomenon of untimely protection or failure protection possibly occurring under a segmented detection protection method is avoided;
(2) the integral accumulation operation adopted by the invention is a smooth accumulation mode, rather than directly carrying out segmented timing protection, the smooth accumulation mode reduces errors, and the overload judgment method by using heat leads to higher reliability of overload protection;
(3) the precision rectification module skillfully utilizes the characteristics of virtual short, virtual disconnection and amplification gain of the integrated operational amplifier, full-wave rectification is realized by adjusting the size of the resistor, the precision is higher, and the full-wave rectification circuit can accurately capture and further process even if the current of the motor slightly changes;
(4) the invention is provided with the integral desaturation module, considers the actual situation that the accumulated heat can be slowly dissipated when the current of the servo motor is reduced to the rated current for running after exceeding the rated current for a short time, so that the accumulated value SUM is more accordant with the actual situation of heat accumulation, and the judgment of overload detection is more effective;
(5) the integral accumulation operation of the invention considers the relation between the heat generated by the servo system and the current and the time, and the calculation is simple but effective;
(6) the invention improves the reliability of overload detection, thereby improving the safety, reducing the loss and saving the cost.
Drawings
The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:
FIG. 1 is a schematic diagram of an overload detection system of a servo system according to an embodiment of the present invention;
FIG. 2 is a flowchart of an overload detection method for a servo system according to an embodiment of the present invention;
FIG. 3 is a schematic circuit diagram of a precision rectifier module according to an embodiment of the invention;
fig. 4 is a flowchart of voltage effective value calculation according to an embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.
The invention discloses an overload detection system of a servo system, which comprises a sampling filtering module, a precise rectifying module, an MCU module and a servo driving module which are sequentially connected as shown in figure 1, wherein the MCU module comprises an effective value calculating module, an integral accumulation and integral desaturation operation module and an alarm module.
The overload detection system can realize an overload detection method of a servo system, and a flow chart of the detection method is shown in fig. 2, and comprises the following steps:
s1, the sampling and filtering module detects the running current of the servo motor in real time, and voltage signals V are obtained through resistance sampling and filteringinThen, full-wave precision rectification is carried out through a precision rectification module;
the rectifying circuit is shown in fig. 3 and comprises two operational amplifiers U1A and U1B, four diodes D1, D2, D3 and D4, and three resistors R1, R2 and R3; vinThe input end of the R1, the equidirectional input end of the U1B, the other end of the R1, the reverse input end of the U1A, the positive electrode of the D1 and one end of the R2, the equidirectional input end of the U1A is grounded, the negative electrode of the D1 is connected with the output end of the U1A and the positive electrode of the D2, the reverse input end of the U1B is connected with the positive electrode of the D3 and one end of the R3, the negative electrode of the D3 is connected with the output end of the U1B and the positive electrode of the D4, the other end of the R2, the negative electrode of the D2, the other end of the R3 and the negative electrode of the D4 are connected with the Vout。
The principle of the rectification circuit is as Vin>At 0, diodes D1, D2, D3 and D4 are all turned on, and there is Vout＝Vin(ii) a When V isin<At 0, diodes D1, D2, D3 and D4 are all cut off, so that
Figure GDA0003577428600000061
Let R1＝R2Then V isout＝-VinThereby achieving the purpose of full-wave rectification.
The rectifying circuit uses a diode for rectification, and the diode has forward conduction voltage drop VDFHowever, since the open-loop differential-mode amplification factor K of the integrated operational amplifier can be very large, in the order of hundreds of thousands of times, in order to make the diodeOn, the minimum required input voltage is:
Figure GDA0003577428600000062
for example, when the forward conduction voltage drop V of the diodeDF0.7V, 5X 10 open-loop differential mode amplification factor K of integrated operational amplifier5In order to turn on the diode, the required input voltages are:
Figure GDA0003577428600000071
it follows that the input voltage V can be obtained even if the open-loop differential-mode amplification of the integrated operational amplifier is chosen to be sufficiently largeinVery small changes are generated, and the diode can be conducted to realize precise rectification.
S2, sampling, AD/A converting and storing the precisely rectified voltage waveform by the effective value calculating module, and calculating the effective value V of the voltageRMS：
Figure GDA0003577428600000072
Wherein VRMSIs an effective value of voltage, t1For measuring time, v (t) is a function of voltage versus time, but v (t) does not necessarily have a fixed periodicity, and is generally represented digitally in an actual procedure, that is, the effective value of voltage shown in fig. 4 is obtained by the following calculation method in an actual procedure:
s2.1, performing AD conversion on the voltage signal subjected to precise rectification;
s2.2, performing square sum operation on the voltage signals, and enabling Cout to be equal to Cout-1;
and S2.3, judging whether the count value Cout is equal to 0, if so, averaging the square sum, and then starting a root, otherwise, returning to the step S2.1.
I.e. effective value of voltage VRMSThe calculation formula of (a) is as follows:
Figure GDA0003577428600000073
wherein, the count value Cout is determined by the rotation speed of the servo motor, and V is a voltage value.
Then, the integral accumulation and integral desaturation operation module executes the steps S3 to S5:
s3, judging whether V is presentRMS＞Vn，VnIf the voltage value is the voltage value corresponding to the rated current of the motor, the step is carried out in S4, and if the voltage value is not the voltage value, the step is carried out in S5;
s4, performing integral accumulation operation to obtain an accumulated value SUM:
Figure GDA0003577428600000081
wherein, N ═ t2T, representing the actual overload time in numerical value, T2If the overload time is the overload time and T is the calculation period, continuing to step S6;
the formula is based on a heat accumulation curve, which is proportional to the square of the current times time.
S5, determining whether SUM is greater than 0, if not, making SUM equal to 0, and returning to step S1; if yes, integral desaturation operation is carried out, and order is carried out
Figure GDA0003577428600000082
Then returns to step S1;
after the current of the servo motor is operated for a short time exceeding the rated current and is reduced to the operation below the rated current, the accumulated heat is slowly dissipated, namely the value of the SUM is reduced, and the integral desaturation operation is performed at the moment.
S6, the alarm module judges whether SUM is larger than MAX, MAX is a set threshold value, if yes, the servo system is overloaded, an alarm signal is sent, the step S7 is entered, and if not, the step S1 is returned;
and S7, the servo driving module receives the alarm signal and controls the servo motor to stop.
In summary, the overload detection method and the overload detection system for the servo system have the following advantages:
(1) according to the invention, smooth sampling is adopted, the current effective value is obtained in real time, the converted voltage waveform is smoother through the filter and the full-wave rectification circuit, and the variable can be obtained in time even if the current of the motor jumps faster, so that the phenomenon of untimely protection or failure protection possibly occurring under a segmented detection protection method is avoided;
(2) the integral accumulation operation adopted by the invention is a smooth accumulation mode, rather than directly carrying out segmented timing protection, the smooth accumulation mode reduces errors, and the overload judgment method by using heat leads to higher reliability of overload protection;
(3) the precision rectification module skillfully utilizes the characteristics of virtual short, virtual disconnection and amplification gain of the integrated operational amplifier, full-wave rectification is realized by adjusting the size of the resistor, the precision is higher, and the full-wave rectification circuit can accurately capture and further process even if the current of the motor slightly changes;
(4) the invention has the integral desaturation module, consider the actual situation that the accumulated heat will be slowly dissipated after the servo motor current is operated for a short time in excess of the rated current and is reduced to the operation below the rated current, so that the accumulated value SUM is more in line with the actual situation of heat accumulation, and the judgment of overload detection is more effective;
(5) the integral accumulation operation of the invention considers the relation between the heat generated by the servo system and the current and the time, and the calculation is simple but effective;
(6) the invention improves the reliability of overload detection, thereby improving the safety, reducing the loss and saving the cost.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims (7)

1. An overload detection method for a servo system, the detection method comprising:
s1, detecting the running current of the servo motor in real time, and obtaining a voltage signal V through resistance sampling and filteringinPerforming precise rectification;
s2, sampling, AD converting and storing the precisely rectified voltage waveform, and calculating the voltage effective value VRMS；
S3, judging whether V is presentRMS＞Vn，VnIf the voltage value is the voltage value corresponding to the rated current of the motor, the step is carried out in S4, and if the voltage value is not the voltage value, the step is carried out in S5;
s4, performing integral and accumulation operation to obtain an accumulated value SUM, and continuing to step S6, wherein the calculation formula of the accumulated value SUM obtained by the integral and accumulation operation in step S4 is as follows:
Figure FDA0003577428590000011
wherein, N ═ t2T, representing the actual overload time in numerical value, T2The overload time is T, and the calculation period is T;
s5, determining whether the SUM is greater than 0, if not, making SUM equal to 0, and returning to step S1; if yes, the integration desaturation operation is carried out, and then the step returns to the step S1; in step S5, the calculation formula of the integral desaturation operation is:
Figure FDA0003577428590000012
wherein T is a calculation period;
s6, judging whether the accumulated value SUM is larger than MAX or not, wherein MAX is a set threshold value, if yes, the servo system is in overload operation, sending an alarm signal, entering the step S7, and if not, returning to the step S1;
and S7, the servo driving module receives the alarm signal and controls the servo motor to stop.
2. The overload detection method for the servo system according to claim 1, wherein the precision rectified full-wave rectifier circuit in step S1 includes two operational amplifiers U1A, U1B, four diodes D1, D2, D3, D4, three resistors R1, R2, R3; vinThe input end of the R1, the equidirectional input end of the U1B, the other end of the R1, the reverse input end of the U1A, the positive electrode of the D1 and one end of the R2, the equidirectional input end of the U1A is grounded, the negative electrode of the D1 is connected with the output end of the U1A and the positive electrode of the D2, the reverse input end of the U1B is connected with the positive electrode of the D3 and one end of the R3, the negative electrode of the D3 is connected with the output end of the U1B and the positive electrode of the D4, the other end of the R2, the negative electrode of the D2, the other end of the R3 and the negative electrode of the D4 are connected with the VoutAnd R is1＝R2。
3. The overload detection method for a servo system according to claim 1 or 2, wherein the minimum input voltage required by the precision rectified full-wave rectifier circuit in step S1 is:
Figure FDA0003577428590000021
wherein, VDFAnd the forward conduction voltage drop exists for the diode, and K is the open-loop differential mode amplification factor of the integrated operational amplifier.
4. The overload detection method for a servo system according to claim 1, wherein the effective voltage value V in step S2RMSThe calculation formula of (2) is as follows:
Figure FDA0003577428590000022
wherein, t1For measuring time, V (t) is electricityPressure as a function of time.
5. The overload detection method for a servo system according to claim 1, wherein the effective voltage value V in step S2RMSThe calculation formula of (2) is as follows:
Figure FDA0003577428590000031
wherein, the count value Cout is determined by the rotation speed of the servo motor, and V is a voltage value.
6. An overload detection system of a servo system, which is characterized by comprising a sampling filter module, a precision rectifying module, an MCU module and a servo driving module which are connected in sequence, and being capable of executing the overload detection method of the servo system according to any one of claims 1 to 5.
7. The overload detection system of claim 6, wherein the MCU module comprises an effective value calculating module, an integral accumulation and integral desaturation calculating module and an alarm module, the effective value calculating module performs step S2, the integral accumulation and integral desaturation calculating module performs steps S3 to S5, and the alarm module performs step S6.
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