A method for obtaining the external characteristics of a permanent magnet synchronous motor online using acceleration and power

Abstract

The present invention relates to the field of electric power steering systems for automobiles. Specifically, it is a method for obtaining the external characteristics of a permanent magnet synchronous motor online using acceleration and power. The method calibrates the motor's DC bus current drop value under different accelerations; calibrates the motor's motor speed drop value under different accelerations; when the motor speed exceeds a threshold, a table is consulted to obtain the current bus current drop value and the motor speed drop value after considering acceleration; the actual maximum available bus current value and the current motor speed are calculated; the current theoretical maximum input power, actual maximum input power, maximum power loss, and actual power loss are calculated; the relationship between the current speed and base speed is determined, and the maximum output torque is calculated. Compared with the prior art, the external characteristics are obtained based on real-time online calculation of power and acceleration, so that the accuracy and dynamic performance of the obtained maximum output torque of the motor can meet current industry requirements.

Description

Technical Field

[0001] The present invention relates to the field of electric power steering systems for automobiles, and in particular to a method for obtaining external characteristics of a permanent magnet synchronous motor online using acceleration and power. Background Art

[0002] The automotive industry is rapidly developing, with increasing levels of vehicle electrification and consumers demanding a more refined driving experience. Electric Power Steering (EPS), a power steering system that relies directly on an electric motor to provide assist torque, is more capable of meeting the higher standards and requirements for steering feel required by vehicle manufacturers than traditional hydraulic systems (HPS).

[0003] EPS generally uses a small-sized, high-power-density permanent magnet synchronous motor as its power source. Figure 1 The characteristic curve represents the maximum output capacity of the motor at rated voltage, ensuring stable operation, limiting bus current, and extending motor life. Therefore, obtaining an accurate characteristic curve is an important prerequisite for motor control.

[0004] Traditional methods for obtaining the external characteristic curves of permanent magnet synchronous motors (PMSMs) rely on calibrating the motor's maximum output torque at different voltages and speeds. This requires calibrating the curves at several voltages, a labor-intensive process and requiring numerous tables to be stored. EPS systems frequently experience rapid steering wheel rotation. These sudden, high-frequency conditions can cause sudden drops in battery voltage, current, and motor speed, limiting the motor's maximum output capacity. In these situations, the interpolation lookup table method for obtaining the motor's maximum output torque no longer meets the required accuracy and dynamic performance.

[0005] Therefore, it is necessary to design a method to obtain the external characteristics of permanent magnet synchronous motors online using acceleration and power. Summary of the Invention

[0006] The present invention overcomes the difficulties of the prior art and designs a method for obtaining the external characteristics of a permanent magnet synchronous motor online using acceleration and power.

[0007] To achieve the above objectives, the present invention designs a method for online acquisition of the external characteristics of a permanent magnet synchronous motor using acceleration and power, the steps of which are as follows:

[0008] Step 1: Use the motor performance test bench to calibrate the DC bus current drop value of the motor under different accelerations;

[0009] Step 2: Use the motor performance test bench to calibrate the motor speed drop value under different accelerations;

[0010] Step 3: Store the DC bus current drop value and motor speed drop value calibrated in step 1 and step 2 into the chip;

[0011] Step 4: When the motor speed exceeds the threshold, the current bus current drop value and the motor speed drop value after considering the acceleration are obtained by looking up the table based on the current acceleration value. The threshold is 5% above the base speed.

[0012] Step 5: Calculate the maximum available bus current value and the current motor speed;

[0013] Step 6: Calculate the current theoretical maximum input power, actual maximum input power, maximum power loss, and actual power loss;

[0014] Step 7: Determine the relationship between the current speed and the base speed, and calculate the maximum output torque.

[0015] The method for calibrating the DC bus current drop value in step 1 is as follows: the servo motor of the motor performance test bench is made to complete the acceleration process from 0 to 4000 rpm in 1s, 5s, and 10s and maintain a stable speed of 4000 rpm for 1s, and the speed signal of the motor acceleration process is differentiated. Get acceleration signal , then use the current sensor to collect the bus current, and use Vector's CANape to record the acceleration The bus current value under and bus current value at stable speed , and record the bus current drop value at the same time .

[0016] The method for calibrating the motor speed drop value under different acceleration in step 2 is as follows: the servo motor of the motor performance test bench is accelerated from 0 to 4000 rpm in 1s, 5s, and 10s and maintained at a stable speed of 4000 rpm for 1s, and the acceleration is recorded using Vector's CANape Motor speed drop value under .

[0017] Maximum bus current value in step 3 and current speed The calculation formula is as follows:

[0018] ;

[0019] ;

[0020] in is the maximum rated bus current, is the current speed of the motor, is the threshold set in step 4.

[0021] The calculation formulas for the current theoretical maximum input power, actual maximum input power, maximum power loss, and actual power loss in step 6 are as follows:

[0022] Theoretical maximum input power: ;

[0023] Maximum power loss: ;

[0024] Actual power loss: ;

[0025] Actual maximum input power: ;

[0026] in: is the bus voltage value, is the stator resistance, is the rated phase current peak value, is the actual phase current peak value, factor is the error coefficient, the error coefficient factor It is obtained by comparing the measured actual power with the calculated power. is the rated maximum torque value;

[0027] The judgment method in step 7 is as follows: if the current speed is greater than the base speed, the maximum output torque is calculated based on the maximum input power, actual power loss, and the current speed; if the current speed is less than the base speed, the maximum output torque is calculated based on the maximum input power and maximum power loss. The calculation formula for the maximum output torque is as follows:

[0028] .

[0029] Compared with the prior art, the present invention obtains external characteristics based on real-time online calculation of power and acceleration, so that the accuracy and dynamic performance of the obtained maximum output torque of the motor can meet current industry needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the external characteristic curve of the permanent magnet synchronous motor at rated voltage.

[0031] Figure 2 It is a flowchart of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described with reference to the accompanying drawings.

[0033] Combine Figure 2 The present invention designs a method for obtaining the external characteristics of a permanent magnet synchronous motor online using acceleration and power, and the steps are as follows:

[0034] Step 1: Use the motor performance test bench to calibrate the DC bus current drop value of the motor under different accelerations. The method for calibrating the DC bus current drop value is as follows: The servo motor of the motor performance test bench completes the acceleration process from 0 to 4000 rpm in 1s, 5s, and 10s and maintains a stable speed of 4000 rpm for 1s, and then differentiates the speed signal of the motor acceleration process. Get acceleration signal , then use the current sensor to collect the bus current, and use Vector's CANape to record the acceleration The bus current value under and bus current value at stable speed , and record the bus current drop value at the same time .

[0035] Step 2: Use the motor performance test bench to calibrate the motor speed drop value under different accelerations. The method for calibrating the motor speed drop value under different accelerations is as follows: The servo motor of the motor performance test bench completes the acceleration process from 0 to 4000 rpm in 1s, 5s, and 10s and maintains a stable speed of 4000 rpm for 1s. Use Vector's CANape to record the acceleration. Motor speed drop value under .

[0036] Step 3: Store the DC bus current drop value and motor speed drop value calibrated in step 1 and step 2 into the chip;

[0037] Step 4: When the motor speed exceeds the threshold, the current bus current drop value and the motor speed drop value after considering the acceleration are obtained by looking up the table based on the current acceleration value. The threshold is 5% above the base speed.

[0038] Step 5: Calculate the maximum available bus current value and the current motor speed; the maximum bus current value and current speed The calculation formula is as follows:

[0039] ;

[0040] ;

[0041] in is the maximum rated bus current, Current motor speed , is the threshold set in step 4.

[0042] Step 6: Calculate the current theoretical maximum input power, actual maximum input power, maximum power loss, and actual power loss using the following formula:

[0043] Theoretical maximum input power: ;

[0044] Maximum power loss: ;

[0045] Actual power loss: ;

[0046] Actual maximum input power: ;

[0047] in: is the bus voltage value, is the stator resistance, is the rated phase current peak value, is the actual phase current peak value, factor is the error coefficient, the error coefficient factor It is obtained by comparing the measured actual power with the calculated power. is the rated maximum torque value.

[0048] Step 7: Determine the relationship between the current speed and the base speed and calculate the maximum output torque. The determination method is as follows: If the current speed is greater than the base speed, the maximum output torque is calculated based on the maximum input power, actual power loss, and the current speed; if the current speed is less than the base speed, the maximum output torque is calculated based on the maximum input power and maximum power loss. The calculation formula for the maximum output torque is as follows:

[0049] .

Claims

1. A method for obtaining the external characteristics of a permanent magnet synchronous motor online using acceleration and power, characterized by: Here are the steps: Step 1: Use the motor performance test bench to calibrate the DC bus current drop value of the motor under different accelerations; Step 2: Use the motor performance test bench to calibrate the motor speed drop value under different accelerations; Step 3: Store the DC bus current drop value and motor speed drop value calibrated in step 1 and step 2 into the chip; Step 4: When the motor speed exceeds a threshold, the current bus current drop value and the motor speed drop value after considering the acceleration are obtained by looking up the table based on the current acceleration value. The threshold is 5% of the base speed. Step 5: Calculate the maximum available bus current value and the current motor speed; Step 6: Calculate the current theoretical maximum input power, actual maximum input power, maximum power loss, and actual power loss; Step 7: Determine the relationship between the current speed and the base speed and calculate the maximum output torque; The calculation formulas for the current theoretical maximum input power, actual maximum input power, maximum power loss, and actual power loss in step 6 are as follows: Theoretical maximum input power: Pow max =U dc *I dcMax ; Maximum power loss: Actual power loss: Actual maximum input power: Pow maxAct =PLoss Max +T Max *ω b ; Among them: U dc is the bus voltage value, R s is the stator resistance, Is Max Is the rated phase current peak value, fbk is the actual phase current peak value, ω b is the base speed, factor is the error coefficient, and the error coefficient factor is obtained by comparing the measured actual power with the calculated power, T Max is the rated maximum torque value; The judgment method in step 7 is as follows: if the current speed is greater than the base speed, the maximum output torque is calculated based on the maximum input power, the actual power loss, and the current speed; if the current speed is less than the base speed, the maximum output torque is calculated based on the maximum input power and the maximum power loss. The calculation formula for the maximum output torque is as follows:

2. The method for online obtaining the external characteristics of a permanent magnet synchronous motor using acceleration and power according to claim 1, characterized in that: The method for calibrating the DC bus current drop value in step 1 is as follows: by making the servo motor of the motor performance test bench complete the acceleration process from 0 to 4000 rpm at 1s, 5s, and 10s and maintain a stable speed of 4000 rpm for 1s, the speed signal of the motor acceleration process is differentiated a=dv / dt to obtain acceleration signals a1, a2, and a3, and then the bus current is collected using a current sensor, and the bus current value I under acceleration a1, a2, and a3 is recorded through Vector's CANape. dc_a and bus current value I at stable speed dc_s , and record the bus current drop value I dc_d =I dc_s -I dc_a .

3. The method for online obtaining the external characteristics of a permanent magnet synchronous motor using acceleration and power according to claim 1, characterized in that: The method for calibrating the motor speed drop value under different accelerations in step 2 is as follows: the servo motor of the motor performance test bench is made to complete the acceleration process from 0 to 4000 rpm in 1s, 5s, and 10s and maintain a stable speed of 4000 rpm for 1s, and the motor speed drop value Spd under acceleration a1, a2, and a3 is recorded using Vector's CANape d .

4. The method for online acquiring the external characteristics of a permanent magnet synchronous motor using acceleration and power according to claim 1, characterized in that: The maximum bus current value I in step 5 dcMax The calculation formula of the current speed SpdAct is as follows: in is the maximum rated bus current, Spd is the current motor speed, and threhold is the threshold set in step 4.

Images