Sensorless control method of brushless DC motor

Abstract

The invention provides a sensorless control method for a direct current brushless motor, and the method comprises the following specific steps: 1, judging whether a Hall sensor on the motor fails or not: executing a second step if the Hall sensor is normal; if yes, executing the third step; 2, judging whether the angle sensor fails or not: if so, returning to the first step; if the absolute value of the error is greater than 0.2 degree, determining that the angle sensor fails, and executing the third step; 3, sectors are divided, a control time sequence is determined, each electrical angle period of a motor rotor is divided into six sectors, and a motor winding waits for 3 ms after passing through the six sectors; and 4, carrying out sensorless control: electrifying a winding in the motor by adopting a stepping control mode according to the time sequence of the step 3 until the control system stops working. According to the invention, the technical problem of failure of the position sensor for driving the servo mechanism in severe environments of high speed, high temperature and high vibration is solved, and the reliability of servo control of the direct current brushless motor is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electricity and control, and particularly relates to a sensorless control method for a direct current brushless motor. Background Art

[0002] The engine drive regulation technology and its control method have become the key technologies restricting the development of power. When operating at high speeds, the harsh environment of high temperature and high vibration is very likely to cause the position sensor of the drive servo mechanism used in the power system to fail, resulting in abnormal commutation and rotation of the motor, and further leading to the failure of the flight mission. Summary of the Invention

[0003] The object of the present invention is to provide a sensorless control method for a direct current brushless motor, which solves the technical problem of the failure of the position sensor of the drive servo mechanism in the harsh environment of high speed, high temperature and high vibration, and improves the reliability of the servo control of the direct current brushless motor.

[0004] The technical solution of the present invention is that the specific steps of a sensorless control method for a direct current brushless motor are as follows: Taking the forward rotation of the direct current brushless motor as an example,

[0005] First step, determine whether the Hall sensor on the motor fails:

[0006] The controller in the control system collects the output data of the Hall sensor every 0.1 ms, filters and saves it. The controller compares the currently collected data with the data collected last time. If it meets the output signal sequence of a normal Hall sensor, the Hall sensor is normal, and the second step is executed; otherwise, the Hall sensor is abnormal, and the third step is executed.

[0007] Second step, determine whether the angle sensor in the control system fails:

[0008] The controller in the control system collects the output data of the angle sensor every 0.1 ms. The controller compares the currently collected data with the data collected last time. If the absolute value of the error is greater than 0.2°, the angle sensor fails, and the third step is executed; otherwise, return to the first step until the motor operation ends.

[0009] Third step, divide the sectors and determine the control timing:

[0010] Each electrical angle period of the motor rotor is divided into 6 sectors, and each sector interval is set to 0.8 ms; after the motor windings complete 6 sectors, wait for 3 ms, and then perform the next motor rotor cycle;

[0011] Among them, the first sector is powered on for 0.6 ms; the second sector is powered on for 0.6 ms; the third sector is powered on for 0.5 ms; the fourth sector is powered on for 0.5 ms; the fifth sector is powered on for 0.5 ms; the sixth sector is powered on for 0.4 ms; Step 4, implement sensorless control:

[0012] According to the timing sequence of the third step, the windings in the motor are powered on in a step-by-step control manner until the control system ends its operation.

[0013] The output signal sequence of the normal Hall sensor is as shown in the table,

[0014] Table 1 Output signal sequence of the normal Hall sensor

[0015] Electrical angle <![CDATA[Hall signal (H A 、H B 、H C )]]> Conducting winding 0～π / 3 100 A→C π / 3～2π / 3 110 B→C 2π / 3～π 010 B→A π～4π / 3 011 C→A 4π / 3～5π / 3 001 C→B 5π / 3～2π 101 A→B

[0016] The beneficial effects of the present invention are that the present invention provides an effective method for improving the reliability of the sensorless control method. When the motor operates at a high speed, in the harsh environment of high temperature and high vibration, the position sensor of the drive servo mechanism used in the power system fails, and the present invention ensures the normal operation state of the motor. By using the step-by-step control method of the present invention to control the sensorless DC brushless motor used in the engine drive adjustment system, through the analysis of the simulation results, the present invention can relatively accurately obtain the position of the motor rotor, providing a theoretical basis for improving the reliability of the sensorless control method. Brief Description of the Drawings

[0017] The included drawings are used to provide a further understanding of the embodiments of the present invention, which form a part of the specification, are used to illustrate the embodiments of the present invention, and are used together with the written description to explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0018] Figure 1 It is a schematic diagram of the composition of the control system using the control method of the present invention;

[0019] Figure 2 It is the working principle of the brushless DC motor in the present invention;

[0020] Figure 3 It is the commutation timing sequence of the stator windings in the present invention;

[0021] Figure 4 It is a schematic diagram of the angle sensor fault flag in the present invention;

[0022] Figure 5 It is a schematic diagram of the control timing of the brushless DC motor in the present invention;

[0023] Figure 6It is a comparison diagram of the servo mechanism rotation angle command value and the actual value in the embodiment of the present invention;

[0024] Figure 7 It is a comparison diagram of the actual angle and the estimated angle of the output shaft of the servo mechanism in the embodiment of the present invention;

[0025] Figure 8 It is a partial enlarged view of the actual angle and the estimated angle of the output shaft of the servo mechanism in the embodiment of the present invention. Detailed implementation manners

[0026] The technical solution of the present invention will be further described in detail below with reference to the specification drawings and embodiments.

[0027] As Figure 1 shown, the main architecture of a sensorless control system for a DC brushless motor of the present invention is in the architecture form of DSP + peripheral drive circuit. A sensorless control system for a DC brushless motor of the present invention includes a calculation module, an isolation module, a signal acquisition module, a power drive module, a motor, and a reduction mechanism.

[0028] The specific steps of a sensorless control method for a DC brushless motor of the present invention are as follows: Taking the forward rotation of the DC brushless motor as an example, its control and working timing are:

[0029] The first step is to determine whether the Hall sensor on the motor fails:

[0030] The controller in the control system collects the output data (level signal) of the Hall sensor every 0.1 ms, filters and saves it. The controller compares the currently collected data with the data collected last time (the sampling period is 0.1 ms). If the output signal sequence of the normal Hall sensor is satisfied, the current Hall signal and the signal 0.1 ms ago are adjacent, the Hall sensor is normal, and the second step is executed; otherwise, it is considered that the Hall sensor is abnormal, the Hall sensor fault flag bit is set, and this flag bit cannot be changed thereafter. The motor control mode is switched to sensorless control, that is, the third step is executed.

[0031] Table 1 shows the output signal sequences of the normal Hall sensor when the rotor is in different sectors. For example, when the Hall signal data collected at the previous stage is "010", and the data collected at the current moment is "110", "011", or "010", the Hall sensor is considered normal; otherwise, the Hall sensor is considered abnormal. After detecting the Hall sensor fault, the Hall sensor fault flag bit is set in the control algorithm, and this flag bit cannot be changed thereafter. The motor control mode is switched from sensor control to sensorless control mode.

[0032] Table 1 Output signal sequences of the normal Hall sensor

[0033] Electrical angle <![CDATA[Hall signal (H A 、H B 、H C )]]> Conducting winding 0～π / 3 100 A→C π / 3～2π / 3 110 B→C 2π / 3～π 010 B→A π～4π / 3 011 C→A 4π / 3～5π / 3 001 C→B 5π / 3～2π 101 A→B

[0034] Step 2: Determine whether the angle sensor in the control system fails:

[0035] The controller in the control system collects the output data of the angle sensor (the angle of the output shaft of the actuator reducer) every 0.1 ms, and the controller compares the currently collected data with the previously collected data (the sampling period is 0.1 ms). If the absolute value of the error is greater than 0.2°, it is considered that the angle sensor is faulty, and the angle displacement sensor fault flag bit is set in the control algorithm. After that, this flag bit cannot be changed, and the motor control switches to sensorless control, that is, execute Step 3. Otherwise, return to Step 1 until the control system stops working.

[0036] Step 3: Divide the sectors and determine the control timing:

[0037] Each electrical angle period of the motor rotor is divided into 6 sectors. To ensure smooth and reliable commutation of the motor without oscillation, the motor windings complete 6 commutations through 6 sectors, wait for 3 ms, and then proceed to the next motor rotor period, cycling until the motor stops working.

[0038] Among the 6 sectors, the conduction time of the sectors gradually decreases, causing the motor rotor to gradually decelerate and preventing the rotor from continuously swinging after reaching the specified position.

[0039] (1) Set the interval between each sector to 0.8 ms;

[0040] (2) The first sector is powered on for 0.6 ms;

[0041] (3) The second sector is powered on for 0.6 ms;

[0042] (4) The third sector is powered on for 0.5 ms;

[0043] (5) The fourth sector is powered on for 0.5 ms;

[0044] (6) The fifth sector is powered on for 0.5 ms;

[0045] (7) The sixth sector is powered on for 0.4 ms;

[0046] (8) Wait for 3 ms,

[0047] Step 4: Implement sensorless control:

[0048] Power on the windings in the motor in a step-by-step control manner according to the timing sequence in Step 3 until the control system stops working.

[0049] If Figure 2As shown in the figure, the basic working principle of the motor is shown. Taking the forward rotation of the motor as an example, when the motor is working normally, the motor changes phase six times within one electrical angle cycle. Each change of phase is related to the position of the sector where the rotor is located and is determined by the output signal of the Hall sensor. The position information of the sector where the rotor is located can be obtained through the Hall sensor. The three position information output by the Hall sensor are respectively represented by three level signals. The three level signals are level signal Ha, level signal Hb, and level signal Hc. The phase difference between the three level signals is 120°, and the pulse width is 180°. There are six combinations of the three level signals in one cycle, as shown in Table 1. The rising edge and falling edge of each level signal are the commutation points of the rotor. For example, the rising edge of the level signal Ha turns on the power devices VT1 and VT6 in the control system, and the falling edge of the level signal Ha turns on the power devices VT3 and VT4 in the control system. The conduction states caused by the rising and falling edges of the other two level signals are similar, such as Figure 3 shown.

[0050] According to the control method of the present invention, based on the commutation principle of the brushless DC motor, the stator magnetic vector of the motor always leads the rotor magnetic vector by 60° to 120°. If a stator magnetic vector of appropriate size is applied to the rotor at a fixed time interval, the rotor will also rotate with the stator magnetic vector without the need for a Hall sensor to guide the stator commutation.

[0051] Example:

[0052] The method of the present invention needs to detect Hall sensor failure. The specific implementation method is to collect Hall sensor data every 0.1ms and compare the data 0.1ms ago with the current data. When the current Hall signal is adjacent to the signal 0.1ms ago, the Hall sensor is normal. Table 1 shows the output signal of the Hall sensor under different rotor electrical angles. For example, when the Hall signal data saved 0.1ms ago is "010" and the current data is "110", "011" or "010", the Hall sensor is considered normal; otherwise, the sensor data is considered abnormal. After the Hall sensor failure is detected, the Hall sensor failure flag is set in the control algorithm, and the flag cannot be changed thereafter. The motor control mode is switched from position sensor control to position sensorless control.

[0053] Similarly, the present invention needs to detect the output shaft sensor fault. The specific implementation method is to collect the angular displacement sensor data every 0.1ms, filter and save it, and compare the data 0.1ms ago with the current data. If the absolute value of the error is greater than 0.2°, it is considered that the angular displacement sensor is faulty. When the output shaft sensor fault is detected, the angular displacement sensor fault flag is set in the control algorithm, and the flag cannot be changed thereafter. The motor control mode is switched from position sensor control to position sensorless control.

[0054] To verify the reliability of the algorithm, at 0.15 s, a fault of the angular displacement sensor was set, that is, a 0.3° disturbance was added to the actual feedback rotation angle of the sliding disk. Figure 4 The curve showing the change of the angular sensor fault flag over time is shown. The simulation results show that the angular sensor fault was detected in time at 0.15 s.

[0055] Among them, when the motor runs at the rated speed, the motor rotor rotates 8000 / 60 revolutions per second, that is, the time required for the motor rotor to rotate 2π mechanical angles per revolution is 7.5 ms, and the time required for the motor rotor to rotate 2π electrical angles per revolution is 2.5 ms. The time for the motor rotor to pass through each sector (π / 6 electrical angle) is approximately 0.4 ms.

[0056] The motor rotor position control imitates the first-stage forced commutation process in the three-stage starting process of the DC brushless motor. The interval between each sector is set to 0.8 ms, that is, the first sector is energized for 0.6 ms → the second sector is energized for 0.6 ms → the third sector is energized for 0.5 ms → the fourth sector is energized for 0.5 ms → the fifth sector is energized for 0.5 ms → the sixth sector is energized for 0.4 ms. Through the above energization timing of the rotor winding, the rotor can be forced to rotate a 2π electrical angle. The specific energization timing is as Figure 5 shown.

[0057] Among them, to ensure smooth, reliable and oscillation-free commutation of the motor, after the motor winding completes 6 commutations, it waits for 3 ms and then performs the next rotor positioning. The energization timing is as Figure 5 shown. Among the 6 sectors, the conduction time of each sector gradually decreases, so that the motor rotor gradually decelerates to prevent the rotor from continuously swinging after reaching the specified position.

[0058] Figure 6 The figure shown is the comparison diagram of the rotation angle command value and the actual value of the control system with the sensorless backup algorithm under heavy load conditions at 0.15 s when the angular sensor fails. It can be seen from the simulation curve that after 0.15 ms, the motor control mode switches from Hall sensor control to sensorless control.

[0059] Figure 7 and Figure 8 The figure shown is the comparison diagram of the actual angle and the estimated angle of the output shaft of the servo mechanism. It can be seen from the simulation curve that the estimated angle deviation of the sliding disk output shaft is within 0.05°. The simulation shows that the angular displacement sensor fault criterion is effective and the proposed sensorless motor control algorithm is effective.

[0060] After switching to the Hall sensorless control mode, in order to improve the accuracy of rotor position estimation, the speed of the output shaft of the slip disk, that is, the commutation frequency of the stator magnetic vector, is reduced to about 40% of that in the Hall sensor control mode. Since the servo command angle required during normal engine operation is a slow non-periodic change command with non-step changes, the speed reduction of the output shaft of the slip disk caused by the Hall sensorless control mode basically has no impact on the engine response time.

[0061] A sensorless control system and method for a DC brushless motor proposed by the present invention can accurately estimate the rotor position of the motor, providing an effective method for improving the reliability of the sensorless control mode.

[0062] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A sensorless control method for a DC brushless motor, characterized in that: The specific steps of this control method are as follows: Taking the forward rotation of the DC brushless motor as an example, The first step is to determine whether the Hall sensor on the motor is faulty: The controller in the control system collects the output data of the Hall sensor every 0.1 ms, filters and saves it. The controller compares the currently collected data with the data collected last time. If it meets the output signal sequence of a normal Hall sensor, the Hall sensor is normal, and the second step is executed; otherwise, the Hall sensor is abnormal, and the third step is executed; The second step is to determine whether the angle sensor in the control system is faulty: The controller in the control system collects the output data of the angle sensor every 0.1 ms. The controller compares the currently collected data with the data collected last time. If the absolute value of the error is greater than 0.2°, the angle sensor is faulty, and the third step is executed; otherwise, return to the first step until the motor stops working. The third step is to divide the sectors and determine the control timing: Each electrical angle cycle of the motor rotor is divided into 6 sectors, and each sector interval is set to 0.8 ms; after the motor windings complete 6 sectors, wait for 3 ms, and then perform the next motor rotor cycle; Among them, the first sector is energized for 0.6 ms; the second sector is energized for 0.6 ms; the third sector is energized for 0.5 ms; the fourth sector is energized for 0.5 ms; the fifth sector is energized for 0.5 ms; the sixth sector is energized for 0.4 ms; The fourth step is to implement sensorless control: Energize the windings in the motor in a step-by-step control manner according to the timing in the third step until the motor stops working.

2. The sensorless control method for a DC brushless motor according to claim 1, characterized in that: The output signal sequence of the normal Hall sensor is shown in Table 1. Table 1 Output signal sequence of normal Hall sensor

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