Resistance and inductance identification method for servo system

Abstract

The invention relates to the technical field of servo system measurement, in particular to a method for identifying resistance and inductance of a servo system, which aims at solving the nonlinear problems of dead zones and the like during resistance identification and inversion of a servo driver, so that two adjacent groups of voltage differences are divided by two adjacent groups of corresponding current differences, and the resistance and inductance of the servo system are identified. Resistance values can be obtained in a difference solving mode, then the resistance values are averaged again for several times to obtain final resistance Rs, so that identified resistance data are more stable, the average effective current value of the stage is recorded and calculated during inductance identification, then the average amplitude current of the stage is obtained based on the average effective current value, and finally the resistance value Rs is obtained. Therefore, the problem of inaccurate automatic searching of the amplitude of the alternating current feedback signal is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of servo system measurement, and particularly to a method for identifying the resistance and inductance of a servo system. Background Art

[0002] A servo system includes a servo driver and a servo motor. The current loop control parameters in the servo driver are directly related to the resistance and inductance values of the servo motor. For example, model-based predictive control, deadbeat control, etc. all require accurate resistance and inductance values to perform current prediction at the next moment. Even the proportional-integral (PI) control method commonly used in the current loop of servo drivers in the industrial field currently also needs to know the resistance and inductance parameters of the servo motor so as to perform parameter tuning design of the current loop circuit by means of zero-pole cancellation.

[0003] Currently, it is found that the related technology has at least the following problems: When identifying the resistance and inductance values of a servo motor offline, especially in the identification of the inductance value, the servo driver sends out an AC excitation signal and then samples the AC feedback signal to obtain the signal amplitude. This method is theoretically correct, but in actual industrial applications, there are situations where the amplitude of the AC feedback signal cannot be accurately found automatically, which will affect the final identification result and thus lead to inaccurate identification results. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for identifying the resistance and inductance of a servo system, aiming to solve the problem that the amplitude of the AC feedback signal cannot be accurately found automatically.

[0005] To achieve the above purpose, the present invention provides a method for identifying the resistance and inductance of a servo system, including the following steps:

[0006] Determine the d-axis voltage reference value;

[0007] Calculate the average feedback current of the d-axis voltage reference value at different voltage multiples to obtain multiple average current feedback values;

[0008] Calculate based on the d-axis voltage reference value at different voltage multiples and multiple average current feedback values to obtain the final resistance;

[0009] Calculate the amplitude of the d-axis voltage reference value at different multiples to obtain multiple average amplitude currents;

[0010] Calculate based on the d-axis voltage reference value at different voltage multiples, multiple average amplitude currents and the final resistance to obtain the inductance.

[0011] Among them, in the step of "calculating the average feedback current of the d-axis voltage reference value at different voltage multiples to obtain a plurality of average current feedback values", the different voltage multiples are 0.8 times, 0.9 times, 1.0 times, 1.1 times, and 1.2 times respectively.

[0012] Among them, in the step of "calculating the average feedback current of the d-axis voltage reference value at different voltage multiples to obtain a plurality of average current feedback values", the injection duration of the different voltage multiples is 100 ms.

[0013] Among them, in the step of "calculating the amplitudes of the d-axis voltage reference values at different multiples to obtain a plurality of average amplitude currents", the different multiples are 1.0 times and 1.2 times.

[0014] Among them, in the step of "calculating the inductance based on the d-axis voltage reference values at different voltage multiples, a plurality of the average amplitude currents, and the final resistance", it includes:

[0015] Calculating the impedance based on the d-axis voltage reference values at different voltage multiples and a plurality of the average amplitude currents;

[0016] Calculating the inductance based on the impedance and the final resistance.

[0017] A method for identifying the resistance and inductance of a servo system according to the present invention includes the following steps: determining the d-axis voltage reference value; calculating the average feedback current of the d-axis voltage reference value at different voltage multiples to obtain a plurality of average current feedback values; calculating the final resistance based on the d-axis voltage reference values at different voltage multiples and a plurality of the average current feedback values; calculating the amplitudes of the d-axis voltage reference values at different multiples to obtain a plurality of average amplitude currents; calculating the inductance based on the d-axis voltage reference values at different voltage multiples, a plurality of the average amplitude currents, and the final resistance. When identifying the resistance in the present invention, when the servo driver is inverting, there are non-linear problems such as dead zones. Therefore, by using the voltage difference between two adjacent groups and dividing it by the corresponding current difference between two adjacent groups, the resistance value can be obtained through the differential calculation method. Then, the several resistance values are averaged to obtain the final resistance Rs, which makes the identified resistance data more stable. When identifying the inductance, the average effective current value at this stage is recorded and calculated, and then the average amplitude current at this stage is obtained based on the average effective current value, thereby solving the problem of inaccurate automatic search for the amplitude of the AC feedback signal. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 It is a flowchart of a method for identifying the resistance and inductance of a servo system provided by the present invention.

[0020] Figure 2 It is a flowchart for calculating the inductance based on the d-axis voltage reference value, multiple average amplitude currents, and the final resistance under different voltage multiples. Detailed implementation manners

[0021] The following will describe in detail the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention, but should not be construed as a limitation of the present invention.

[0022] Please refer to Figure 1 - Figure 2 , the present invention provides a method for identifying the resistance and inductance of a servo system, including the following steps:

[0023] S1 Determine the d-axis voltage reference value;

[0024] Specifically, the q-axis voltage Uq = 0, the d-axis voltage Ud increases from zero, and then the d-axis feedback current id is detected, so that the value of the feedback current id is between 0.8 times and 1.0 times the rated current of the servo motor. At this time, the value of Ud is recorded as Ud reference. This is to ensure that in the case of current open-loop, the d-axis directly gives voltage, and after passing through the servo motor, the generated current is within the rated current of the servo motor, which is used to protect the servo motor and avoid overcurrent of the servo motor during identification. At the same time, this method can also be applied to different servo motors, and can avoid overcurrent of the servo motor during identification.

[0025] S2 Calculate the average feedback current of the d-axis voltage reference value under different voltage multiples to obtain multiple average current feedback values;

[0026] The different voltage multiples are 0.8 times, 0.9 times, 1.0 times, 1.1 times, and 1.2 times respectively, and the injection duration of the different voltage multiples is 100 ms.

[0027] Specifically, when identifying the resistance, different voltages Ud are injected in sequence and maintained for a period of time, and then the average feedback current iq at the corresponding stage is recorded and calculated. For example:

[0028] Inject 0.8 times U d基准 , denoted as U d08 , injection time is 100 ms, and the average current feedback iq at this stage is obtained R08 ;

[0029] Inject 0.9 times U d基准 , denoted as Ud 09 , injection time is 100 ms, and the average current feedback iq at this stage is obtained R09；

[0030] Inject 1.0 times U d基准 , denoted as Ud 10 , injection time is 100 ms, and the average current feedback iq at this stage is obtained R10 ;

[0031] Inject 1.1 times U d基准 , denoted as Ud 11 , injection time is 100 ms, and the average current feedback iq at this stage is obtained R11 ;

[0032] Inject 1.2 times U d基准 , denoted as Ud 12 , injection time is 100 ms, and the average current feedback iq at this stage is obtained R12 .

[0033] S3 calculates based on the d-axis voltage reference value and multiple average current feedback values under different voltage multiples to obtain the final resistance;

[0034] Specifically, with the injection voltage Ud and the feedback current iq, the resistance can be obtained by dividing the voltage difference between two adjacent groups by the corresponding current difference between two adjacent groups through the differential method. And through the above multiple groups of data, the average value of the resistance can be calculated to obtain the final resistance Rs;

[0035] Using Ohm's law formula: resistance = voltage / current, the resistance value can be obtained. However, due to non-linear problems such as dead zones during the inversion of the servo drive, the resistance value is obtained by dividing the voltage difference between two adjacent groups by the corresponding current difference between two adjacent groups through the differential method, and then the several resistance values are averaged to obtain the final resistance Rs, which makes the identified resistance data more stable. The above injection time is set to 100 ms, which is actually adjustable.

[0036] Rs 0809 =(Ud 09 –Ud 08) / (iq R09 –iq R08 );

[0037] Rs 0910 =(Ud 10 –Ud 09 ) / (iq R10 –iq R09 );

[0038] Rs 1011 =(Ud 11 –Ud 10 ) / (iq R11 –iq R10 );

[0039] Rs 1112 =(Ud 12 –Ud 11 ) / (iq R12 –iq R11 );

[0040] Rs=(Rs 0809 +Rs 0910 +Rs 1011 +Rs 1112 ) / 4。

[0041] Thus, the resistance Rs of the servo motor is obtained.

[0042] S4 calculates the amplitudes of the d-axis voltage reference values at different multiples to obtain multiple average amplitude currents;

[0043] The different multiples are 1.0 times and 1.2 times

[0044] Specifically, the q-axis voltage Uq = 0, and a sine signal with an amplitude of 1.0 times the Ud reference is injected into the d-axis voltage Ud, with a frequency f = 800 Hz, and the amplitude is denoted as Ud Sin10 , and it is maintained for 100 ms.

[0045] The q-axis voltage Uq = 0, and a sine signal with an amplitude of 1.2 times the Ud reference is injected into the d-axis voltage Ud, with a frequency f = 800 Hz, and the amplitude is denoted as Ud Sin12 , and it is maintained for 100 ms. The amplitude of the average amplitude current iq at this stage is obtained as 12.

[0046] S5 calculates the inductance based on the d-axis voltage reference values at different voltage multiples, the multiple average amplitude currents, and the final resistance.

[0047] S51 calculates the impedance based on the d-axis voltage reference values at different voltage multiples and the multiple average amplitude currents;

[0048] Specifically, using the formula: Impedance = Voltage / Current, the impedance (Z) can be obtained. However, due to non-linear problems such as dead zones during the inversion of the servo drive, the impedance (Z) can be obtained by dividing the voltage difference between two adjacent groups by the corresponding current difference between two adjacent groups through differential calculation. The above injection time is set to 100 ms, and the injection frequency of 800 Hz is actually adjustable.

[0049] Impedance (Z) = (Ud Sin12 – Ud Sin10 ) / (iq 幅值12 – iq 幅值10 );

[0050] S52 calculates based on the impedance and the final resistance to obtain the inductance.

[0051] Specifically, to eliminate the influence of the resistance, for an inductive circuit, we can get: Inductive reactance (XL) = Impedance (Z) – Resistance (Rs). From the formula of inductive reactance (XL): XL = 2 * π * f * L, where L represents the inductance and π is a constant 3.1415926…, we can get: Inductance (L) = (Z – Rs) / (2 * π * f).

[0052] A servo system resistance and inductance identification method of the present invention has the following beneficial effects:

[0053] 1. When identifying the resistance, during the inversion of the servo drive, there are non-linear problems such as dead zones. Therefore, by dividing the voltage difference between two adjacent groups by the corresponding current difference between two adjacent groups and obtaining the resistance value through differential calculation, and then averaging several resistance values, the final resistance Rs can be obtained, which makes the identified resistance data more stable.

[0054] 2. When identifying the inductance, the present invention adopts the method of recording and calculating the average effective current value iq_effective10 at this stage, and then multiplying iq_effective10 by the square root of 2 to obtain the average amplitude current iq_amplitude10 at this stage. This method successfully solves the problems such as inaccurate automatic search for the amplitude of the AC feedback signal mentioned above.

[0055] The above-disclosed is only a preferred embodiment of a servo system resistance and inductance identification method of the present invention. Of course, the scope of the rights of the present invention cannot be limited by this. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A method for identifying resistance and inductance of a servo system, characterized in that: The following steps are involved: Determine the d-axis voltage reference value; Calculating the average feedback current of the d-axis voltage reference value at different voltage multiples to obtain a plurality of average current feedback values; Calculating based on the d-axis voltage reference value at different voltage multiples and the plurality of average current feedback values ​​to obtain a final resistance; Calculating the amplitude of the d-axis voltage reference value at different multiples to obtain a plurality of average amplitude currents; The inductance is obtained by performing calculation based on the d-axis voltage reference value at different voltage multiples, a plurality of the average amplitude currents and the final resistance.

2. The servo system resistance and inductance identification method according to claim 1, characterized in that: In “calculating the average feedback current of the d-axis voltage reference value under different voltage multiples to obtain multiple average current feedback values”, the different voltage multiples are 0.8 times, 0.9 times, 1.0 times, 1.1 times and 1.2 times respectively.

3. The servo system resistance and inductance identification method according to claim 2, characterized in that: In “calculating the average feedback current of the d-axis voltage reference value under different voltage multiples to obtain multiple average current feedback values”, the injection duration of the different voltage multiples is 100 ms.

4. The servo system resistance and inductance identification method according to claim 1, characterized in that: In “calculating the amplitude of the d-axis voltage reference value at different multiples to obtain multiple average amplitude currents”, the different multiples are 1.0 times and 1.2 times.

5. The servo system resistance and inductance identification method according to claim 4, characterized in that: In “calculating based on the d-axis voltage reference value at different voltage multiples, a plurality of the average amplitude currents and the final resistance to obtain the inductance”, it includes: calculating impedance based on the d-axis voltage reference value at different voltage multiples and a plurality of the average amplitude currents; The inductance is obtained by calculation based on the impedance and the final resistance.

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