CN111222024B - A data processing method for vehicle permanent magnet synchronous motor bench deceleration calibration - Google Patents

Abstract

The invention relates to the technical field of motor testing, in particular to a method for processing speed-reducing calibration data of a rack of a permanent magnet synchronous motor for a vehicle, which comprises the following steps of S1, starting a calibration test in a high-speed weak magnetic area according to a preset rotating speed and a preset voltage, presetting a plurality of weak magnetic points in the weak magnetic area according to a preset rule, collecting first calibration data of the plurality of weak magnetic points, and S2, establishing a three-dimensional curved surface according to the first calibration data of the plurality of weak magnetic points; s3, performing surface interpolation on the three-dimensional surface by a surface interpolation method to obtain second calibration data of conventional test voltage and conventional test rotating speed, wherein the second calibration data comprises conventional q-axis current and conventional d-axis current. The invention solves the problems of slower calibration process and low efficiency caused by the fact that the temperature of the motor rises too fast when the peak power of the permanent magnet synchronous motor for the vehicle is calibrated in the prior art.

Description

A data processing method for speed reduction calibration of a permanent magnet synchronous motor for vehicles

Technical Field

The present invention relates to the technical field of motor testing, and in particular to a method for processing speed reduction calibration data of a vehicle permanent magnet synchronous motor bench.

Background Art

Permanent Magnet Synchronous Motor (PMSM) has been widely used in drive systems with high requirements on efficiency and stability, such as electric vehicles, due to its high power density, high reliability and high efficiency.

At present, since the controller can only detect current but not torque, in order to give full play to the performance of permanent magnet synchronous motor, it is necessary to calibrate the motor. Motor calibration is to test the correspondence between the output current of the controller and the output torque of the motor on the test bench. Generally, the relationship between output torque and current is tested under different voltage platforms and different speeds.

Normally, the vehicle drive motor is mounted and fixed on the test bench for calibration to determine the torque to current lookup table. In the test bench calibration, when the speed of the drive motor increases to the weak magnetic field area, the power of the drive motor is already the peak power when the torque reaches the peak. Generally, the peak power test only requires 1 minute of testing. At this time, the temperature of the drive motor rises very quickly and it is easy to reach the motor temperature protection limit. Then it is necessary to wait for the drive motor to cool down until the drive motor returns to normal temperature before continuing the calibration test of the next point. The cooling process of the drive motor generally takes several minutes to more than ten minutes. The repeated loading of temperature increase and temperature reduction waiting results in a very low calibration efficiency of the drive motor. Therefore, the temperature during calibration in the weak magnetic field area is the biggest factor affecting the calibration progress.

Therefore, it is necessary to propose a method that can avoid excessive temperature rise of the motor and thus improve the calibration efficiency.

Summary of the invention

The purpose of the present invention is to provide a method for processing data of speed reduction calibration of a vehicle permanent magnet synchronous motor test bench, which solves the problem of slow calibration process and low efficiency due to excessive increase of motor temperature when calibrating the peak power of the vehicle permanent magnet synchronous motor in the prior art.

To achieve the above object, the present invention provides a method for processing speed reduction calibration data of a vehicle permanent magnet synchronous motor test bench, comprising the following steps:

S1. Start a calibration test in the high-speed weak magnetic region according to a preset speed and a preset voltage. Preset a number of weak magnetic points in the weak magnetic region according to a preset rule and collect first calibration data of the number of weak magnetic points. The first calibration data includes a preset speed, an output current, and a torque corresponding to the output current; the output current includes a q-axis current and a d-axis current; the preset voltage is less than a conventional test voltage, and the preset speed is less than a conventional test speed;

S2. establishing a three-dimensional surface according to first calibration data of a plurality of weak magnetic points;

S3. Performing surface interpolation on a three-dimensional surface by using a surface interpolation method to obtain second calibration data under a conventional test voltage and a conventional test speed, wherein the second calibration data includes a conventional q-axis current and a conventional d-axis current.

The working principle and advantages of the present invention are:

First, the voltage and speed are reduced in the constant power weak magnetic area to prepare for the calibration test. Several weak magnetic points are set in the weak magnetic area according to the preset rules. The data collected at the weak magnetic points are the first calibration data obtained under the conditions of voltage reduction and speed reduction. Since the first calibration data is obtained by reducing the voltage and speed in the constant power weak magnetic area, it will not work under the rated voltage condition. Therefore, when the torque, one of the parameters of the permanent magnet synchronous motor, reaches the peak value, the power of the drive motor will not reach the peak power. Even if the temperature of the drive motor rises, it will not easily reach the motor temperature protection limit, so there is no need to wait for the drive motor to cool down, so the calibration test of the next point can be continued. After the first calibration data is obtained, a three-dimensional surface is established, and then the second calibration data corresponding to the conventional test method is obtained by surface interpolation. The second calibration data is a calculated value based on the first calibration data, and there is no need to perform actual measurement, which avoids the problems that conventional tests may encounter in actual measurements. Moreover, it corresponds to the calibration value under conventional test conditions, which can be used as the calibration data of the permanent magnet synchronous motor. This method reduces the power dissipation and temperature rise of the motor during calibration, can reduce the maximum temperature of the motor during operation and slow down the rate of temperature rise, and can measure more calibration data before the motor overheat protection, thereby improving the calibration efficiency, saving calibration time, and thus saving the cost of using the test bench.

Furthermore, the collection of the first calibration data specifically includes the following steps:

S101, during the calibration test, under the conditions of preset voltage and preset speed, preset the q-axis current, and control the d-axis current on the voltage limit circle through automatic magnetic weakening, and then obtain the d-axis current;

S102, obtaining corresponding torque according to current q-axis current and d-axis current;

S103, adjusting the preset q-axis current, repeating the above steps, and collecting several groups of q-axis currents, d-axis currents and corresponding torques;

S104, increasing the preset speed according to the preset step length, and repeating the above steps until the preset speed reaches the maximum preset speed;

S105. Under the same preset speed and preset voltage conditions, count the corresponding d-axis current and torque under several groups of different preset q-axis current conditions, and record them as a group of calibration data. Count the calibration data under several groups of different preset speeds as the first calibration data.

During the calibration test, the preset voltage is kept unchanged, and only the preset speed value is changed. After the preset speed value is determined, the q-axis current is preset. After the q-axis current command is input into the motor controller of the permanent magnet synchronous motor, the weak magnetic algorithm in the controller will guide the d-axis current command to the voltage limit circle, and the permanent magnet synchronous motor will output the torque corresponding to the q-axis current and the d-axis current. Therefore, the torque value can be controlled near the specified value by reasonably presetting the size of the q-axis current command. By changing the preset q-axis current, multiple sets of q-axis current, d-axis current and corresponding torque are collected; then, by continuously increasing the preset speed, the above steps are repeated to increase the data volume to obtain several sets of calibration data, so that the first calibration data covers all working speeds.

Further, the establishment of the curved surface includes the following steps:

S201, establishing a first three-dimensional surface with the speed radius as the x-axis, the torque as the y-axis, and the q-axis current as the z-axis;

S202 , establishing a second three-dimensional surface with the speed radius as the x-axis, the torque as the y-axis, and the d-axis current as the z-axis.

By establishing the first three-dimensional surface and the second three-dimensional surface, it is convenient to obtain the conventional q-axis current and the conventional d-axis current under the conditions of conventional test voltage and conventional test speed, which are the calibration values required for the controller torque lookup table.

Further, the rotation speed radius value includes a first rotation speed radius value and a second rotation speed radius value, the first rotation speed radius value is applied to the first three-dimensional surface and the second three-dimensional surface, and the second rotation speed radius value is applied to surface interpolation.

The setting of the first speed radius and the second speed radius facilitates obtaining the second calibration data through surface interpolation under the preset voltage and preset speed conditions, so that there is no need to conduct conventional speed high power consumption tests to collect data, thus saving test costs.

Further, the calculation formula of the first speed radius ρ _ω/2 value corresponding to the preset voltage and the preset speed is:

其中U_LIM为相电压最大值，i_s为相电流幅值，R_s为相电阻，T_e为扭矩，ω_e为电气角速度，p为转子极对数。

Where U _LIM is the maximum phase voltage, i _s is the phase current amplitude, R _s is the phase resistance, T _e is the torque, ω _e is the electrical angular velocity, and p is the number of rotor pole pairs.

The first rotational speed radius ρ _ω/2 value is obtained by calculation after recording the torque, and thus serves as the x-axis of the first three-dimensional curved surface and the second three-dimensional curved surface.

Further, the calculation formula of the second speed radius _ρω value corresponding to the conventional test voltage and the conventional test speed is:

其中U_LIM为相电压最大值，i_s为相电流幅值，R_s为相电阻，T_e为扭矩，ω_e为电气角速度，p为转子极对数。

Where U _LIM is the maximum phase voltage, i _s is the phase current amplitude, R _s is the phase resistance, T _e is the torque, ω _e is the electrical angular velocity, and p is the number of rotor pole pairs.

The establishment of the first three-dimensional surface is obtained by marking the first speed radius ρ _ω/2 value, torque and d-axis current in the three-dimensional coordinate system. Since the motor characteristics are fixed and can be described by the surface equation, the second speed radius ρ _ω value is obtained by reverse interpolation from the required calibrated torque and speed. Finally, the conventional q-axis current and the conventional d-axis current can be conveniently obtained by interpolating the first three-dimensional surface and the second three-dimensional surface.

Furthermore, the preset rotation speed is 1/2 of the conventional test rotation speed, and the preset voltage is 1/2 of the conventional test voltage.

The selection of preset speed and preset voltage can reduce the maximum temperature of the motor during calibration and slow down the temperature rise. More calibration data points can be added before motor temperature protection, which improves calibration efficiency and saves calibration time and bench usage costs.

Furthermore, in step S103, 10 or more q-axis currents are preset at the same preset speed.

Collect multiple sets of test data to make the first calibration data collection as comprehensive as possible while meeting the standards.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flowchart of a method for processing speed reduction calibration data of a vehicle permanent magnet synchronous motor bench according to an embodiment of the present invention;

2 is a schematic diagram showing a comparison between a voltage limit circle of a vehicle permanent magnet synchronous motor bench speed reduction calibration data processing method according to an embodiment of the present invention and a conventional calibration method;

FIG3 is a schematic diagram showing a comparison between first data of voltage reduction and speed reduction and second calibration data of conventional test calibration obtained by surface interpolation;

FIG4 is a schematic diagram of a curve interpolation method.

DETAILED DESCRIPTION

The following is further described in detail through specific implementation methods:

Example

A method for processing speed reduction calibration data of a vehicle permanent magnet synchronous motor bench, the main steps of which are shown in FIG1 , specifically comprising the following steps:

S1. Start a calibration test in the high-speed weak magnetic region according to a preset speed and a preset voltage, preset a number of weak magnetic points in the weak magnetic region according to a preset rule and collect first calibration data of the number of weak magnetic points;

The preset rule and the collection of the first calibration data according to the preset rule specifically include the following steps:

S101. During the calibration test, under the conditions of preset voltage and preset speed, the q-axis current is preset, and the d-axis current is controlled on the voltage limit circle through automatic magnetic weakening; automatic magnetic weakening is an existing program in the controller of the permanent magnet synchronous motor, and this embodiment will not be elaborated on this.

S102, inputting the current q-axis current and d-axis current into the controller of the permanent magnet synchronous motor, and then obtaining the torque corresponding to the output shaft of the permanent magnet synchronous motor through a torque sensor;

S103, adjusting the preset q-axis current, repeating the above steps S101 and S102, and collecting several groups of q-axis currents, d-axis currents and corresponding torques; wherein, the adjustment of the q-axis current requires the preset of 10 or more q-axis currents.

S104, increasing the preset speed according to the preset step length, and repeatedly performing steps S101, S102, and S103 until the preset speed reaches the maximum preset speed;

S105. Under the same preset speed and preset voltage conditions, 10 or more groups of corresponding d-axis currents and torques under different preset q-axis current conditions are counted and recorded as a group of calibration data, and several groups of calibration data under different preset speeds are counted as first calibration data. When the preset speed, preset voltage, preset q-axis current, d-axis current, and torque are all determined (stable) singly, the point is defined as a weak magnetic point (calibration point).

The first calibration data includes a preset speed, an output current and a torque corresponding to the output current; the output current includes a q-axis current and a d-axis current; the preset voltage is less than the conventional test voltage, and the preset speed is less than the conventional test speed; the preset speed is 1/2 of the conventional test speed, and the preset voltage is 1/2 of the conventional test voltage.

S2. establishing a three-dimensional surface according to first calibration data of a plurality of weak magnetic points;

The creation of the surface includes the following steps:

S201, establishing a first three-dimensional surface with the speed radius as the x-axis, the torque as the y-axis, and the q-axis current as the z-axis;

S202 , establishing a second three-dimensional surface with the speed radius as the x-axis, the torque as the y-axis, and the d-axis current as the z-axis.

The rotation speed radius value includes a first rotation speed radius value and a second rotation speed radius value. The first rotation speed radius value is applied to the first three-dimensional surface and the second three-dimensional surface, and the second rotation speed radius value is applied to surface interpolation.

The derivation process of the first speed radius value and the second speed radius value is as follows:

The voltage limit circle equation under the preset speed and preset voltage conditions is as follows:

The voltage limit circle is established by the above formula. The specific process is: establish a two-dimensional coordinate system, use the q-axis current in the first calibration data as the Y-axis, and the d-axis current as the X-axis. The coordinate points (I _d , I _q ) formed by several d-axis currents and q-axis currents are all on the voltage limit circle, as shown in FIG2 .

Equation (1) is simplified as follows:

It can be seen that the equivalent equation of this speed reduction and voltage reduction method is that of the conventional speed and voltage method after the resistance is doubled.

The conventional test method considers the voltage limit circle equation of the resistor to be expanded as follows:

简化上式(3)后得到：by

After simplifying the above formula (3), we can get:

Adjust the torque formula as follows:

Substituting formula (5) into formula (4) yields the following formula:

The right side of the formula (6) corresponding to the conventional test voltage and the conventional test speed is defined as the speed radius ρ _ω value, as follows:

Since the equivalent resistance of the motor becomes twice that of the conventional test after the preset voltage and preset speed, the following formula can be obtained:

The calculation formula for defining the speed radius ρ _ω/2 corresponding to the preset voltage and the preset speed is:

Where U _LIM is the maximum phase voltage, _is is the phase current amplitude, _Rs is the phase resistance, _Te is the torque, _ωe is the electrical angular velocity, p is the number of rotor pole pairs, and the electrical angular velocity _ωe is a constant when the speed is determined.

S3. Performing surface interpolation on a three-dimensional surface by using a surface interpolation method to obtain second calibration data under a conventional test voltage and a conventional test speed, wherein the second calibration data includes a conventional q-axis current and a conventional d-axis current.

Step S3 specifically includes the following steps:

S301, obtaining the torque in the first calibration data, and interpolating in the first three-dimensional surface according to the second speed radius to obtain a conventional q-axis current;

S302 , obtaining the torque in the first calibration data, and interpolating in the second three-dimensional surface according to the second rotation speed radius to obtain a conventional d-axis current.

The three-dimensional surface interpolation can refer to the two-dimensional curve interpolation. The schematic diagram of the two-dimensional curve interpolation is shown in Figure 4. The coordinates of two known points are obtained, and the average value of the horizontal coordinates of the two points is taken as the horizontal coordinate of the interpolation, and the average value of the vertical coordinates of the two points is taken as the vertical coordinate of the interpolation. The same principle is adopted in this embodiment. The surface interpolation calls the matlab function griddata, and the function call format is: zq = griddata (x, y, z, xq, yq).

Specific implementation method:

The conventional test voltage is set to 380V in this embodiment, and the conventional test speed is 5000rpm. Therefore, in the initial state, the preset speed is 2500rpm and the preset voltage is 190V. The increment step of the preset speed is 250rpm/time. In the weak magnetic region, after the q-axis current is obtained, the d-axis current can be obtained through the voltage limit circle, and after the q-axis current and the d-axis current are input into the motor controller of the permanent magnet synchronous motor, the permanent magnet synchronous motor will output the torque corresponding to the q-axis current and the d-axis current. Therefore, the specified value of the torque can be obtained or the value of the torque can be controlled to be around the specified value by reasonably presetting the size of the q-axis current. In this embodiment, there are 10 set values for controlling the torque in this embodiment, that is, there are also 10 q-axis currents that need to be preset, and the 10 torques are -125, -100, -75, -50, -25, 0, 25, 50, 75, 100 respectively. A set of data in the first calibration data is specifically recorded in the following Table 1.

Table 1

The calibration data of the speed range (2500-5000 rpm) were collected respectively by the method in Table 1, with a total of 11 groups.

After the first calibration data is collected, a second three-dimensional surface is established corresponding to each point with the first speed radius ρ _ω/2 as the x-axis, the torque as the y-axis, and the q-axis current as the z-axis. A first three-dimensional surface is established corresponding to each point with the first speed radius ρ _ω/2 as the x-axis, the torque as the y-axis, and the d-axis current as the z-axis.

The torque of the first calibration data is obtained, and the torque and related known parameters are substituted into formula (7) to calculate the second speed radius ρ _ω value. Since the torque is known and the calculated second speed radius ρ _ω value is obtained, the conventional q-axis current and conventional d-axis current under the corresponding torque condition are obtained through the interpolation method. The conventional q-axis current and conventional d-axis current obtained correspond to the q-axis current and d-axis current under the conventional test voltage and conventional test speed, and the calibration data of the permanent magnet synchronous motor under the rated working environment is obtained. By performing coordinate interpolation on the conventional q-axis current and the conventional d-axis current, the interpolated voltage limit circle will be obtained, as shown in Figure 3. Moreover, by comparing Figure 2, it can be seen that the conventional current data obtained by interpolation (the line segment shown by the dotted line) is equivalent to rotating the speed reduction data in Figure 2 counterclockwise. The interpolation result of Figure 3 also rotates the data counterclockwise, which is consistent with Figure 2, ensuring the correctness of the interpolation result.

The above is only an embodiment of the present invention. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field of the invention before the application date or priority date, can know all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims (7)

1. A method for processing the speed-reducing calibration data of a rack of a permanent magnet synchronous motor for a vehicle is characterized by comprising the following steps of: comprises the steps of,

s1, starting a calibration test in a high-speed weak magnetic area according to a preset rotating speed and a preset voltage, presetting a plurality of weak magnetic points in the weak magnetic area according to a preset rule, and collecting first calibration data of the plurality of weak magnetic points, wherein the first calibration data comprises the preset rotating speed, an output current and a torque corresponding to the output current; the output current includes q-axis current and d-axis current; the preset voltage is smaller than the conventional test voltage, and the preset rotating speed is smaller than the conventional test rotating speed; the acquisition of the first calibration data specifically comprises the following steps:

s101, during calibration test, presetting q-axis current under the preset rotating speed condition of preset voltage, controlling d-axis current on a voltage limit circle through automatic field weakening, and obtaining d-axis current;

s102, acquiring corresponding torque according to the current q-axis current and d-axis current;

s103, adjusting preset q-axis currents, repeatedly executing the steps, and collecting a plurality of groups of q-axis currents, d-axis currents and corresponding torques;

s104, increasing the preset rotating speed according to a preset step length, and repeatedly executing the steps until the preset rotating speed reaches the highest preset rotating speed;

s105, under the same preset rotating speed and preset voltage conditions, counting a plurality of groups of d-axis currents and torques corresponding to different preset q-axis current conditions, recording the d-axis currents and torques as a group of calibration data, and counting the calibration data of the plurality of groups of different preset rotating speeds as first calibration data;

s2, establishing a three-dimensional curved surface according to first calibration data of a plurality of weak magnetic points; the creation of the curved surface comprises the steps of,

s201, establishing a first three-dimensional curved surface with a rotating speed radius value as an x axis, torque as a y axis and q-axis current as a z axis;

s202, establishing a second three-dimensional curved surface with a rotating speed radius value as an x axis, torque as a y axis and d-axis current as a z axis;

s3, performing surface interpolation on the three-dimensional surface by a surface interpolation method to obtain second calibration data of conventional test voltage and conventional test rotating speed, wherein the second calibration data comprises conventional q-axis current and conventional d-axis current.

2. The method for processing the speed-reducing calibration data of the rack of the permanent magnet synchronous motor for the vehicle according to claim 1, wherein the method comprises the following steps of: the rotational speed radius values include a first rotational speed radius value applied to the first three-dimensional curved surface and a second rotational speed radius value applied to the curved surface interpolation.

3. The method for processing the speed-reducing calibration data of the rack of the permanent magnet synchronous motor for the vehicle according to claim 2, wherein the method comprises the following steps of: a first rotating speed radius rho corresponding to different points under the preset voltage and the preset rotating speed _ω/2 The calculation formula of the value is that,

wherein U is _LIM At the maximum value of phase voltage, i _s For the phase current amplitude, R _s Is of phase resistance, T _e Is torque, omega _e For electrical angular velocity, p is the rotor pole pair number.

4. The method for processing the speed-reducing calibration data of the rack of the permanent magnet synchronous motor for the vehicle according to claim 2, wherein the method comprises the following steps of: the second rotating speed radius rho corresponding to the conventional test voltage and the conventional test rotating speed _ω The calculation formula of the value is that,

wherein U is _LIM At the maximum value of phase voltage, i _s For the phase current amplitude, R _s Is of phase resistance, T _e Is torque, omega _e For electrical angular velocity, p is the rotor pole pair number.

5. The method for processing the speed-reducing calibration data of the rack of the permanent magnet synchronous motor for the vehicle according to claim 2, wherein the method comprises the following steps of: the step S3 specifically includes the following steps,

s301, acquiring torque in first calibration data, and interpolating in a first three-dimensional curved surface according to a second rotating speed radius to obtain a conventional q-axis current corresponding to each point;

s302, acquiring torque in the first calibration data, and interpolating in the second three-dimensional curved surface according to the second rotating speed radius to obtain the conventional d-axis current.

6. The method for processing the speed-reducing calibration data of the rack of the permanent magnet synchronous motor for the vehicle according to claim 2, wherein the method comprises the following steps of: the preset rotating speed corresponding to the rotating speed radius formula is 1/2 of the conventional test rotating speed, and the preset voltage is 1/2 of the conventional test voltage.

7. The method for processing the speed-reducing calibration data of the rack of the permanent magnet synchronous motor for the vehicle according to claim 1, wherein the method comprises the following steps of: in step S103, 10 or more q-axis currents are preset at the same preset rotational speed.

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