A method and device for detecting locked-rotor of a brushless electronic fan of a vehicle

Abstract

This invention relates to a stall detection method for a brushless electric fan in automobiles. Based on the Infineon 9877 chip, it performs stall detection after the brushless motor is driven in open-loop operation. The specific steps are as follows: A fixed driving torque is applied to the three phases. After the fan blades are driven to a certain speed without position estimation, the three-phase MOS bridge arms are turned off. Back EMF sampling is used to obtain the variation pattern of the three-phase zero-crossing points. If the difference between adjacent serial numbers jumps irregularly between positive and negative values ​​or the difference is always 0, it is determined to be stalled; if the difference between adjacent serial numbers is always -1 or 1, it is determined to be normal operation. Based on this pattern, the brushless motor can be quickly stopped to protect it. A detection device for implementing this detection method is also provided. This invention quickly identifies stall during the open-loop operation stage of the brushless motor, interrupting the fault in advance and avoiding overcurrent hardware damage due to the lag of closed-loop protection. Furthermore, it abandons the traditional stall detection mode that relies on speed estimation, significantly improving the reliability and stability of the detection system.

Description

Technical Field

[0001] This invention relates to the technical field of automotive brushless motors, specifically to a method and device for detecting stall in automotive brushless electric fans. Background Technology

[0002] In recent years, brushless motors have become increasingly widely used in automotive electronics due to their advantages such as high efficiency, energy saving, and long lifespan, with their market share in components such as automotive electric fans continuing to rise. During the operation of a brushless motor control system, stalling is a critical abnormal condition that must be monitored closely. Brushless motor stalling refers to the sudden stop of the motor rotor due to excessive load, mechanical blockage, or other reasons, while the stator windings maintain their rated voltage input. At this time, because the back electromotive force, which normally limits current, is almost zero, the motor current increases sharply. This not only significantly reduces motor efficiency but may also damage the brushless motor and drive circuit due to overcurrent. In severe cases, it can cause a short circuit in the motor windings, leading to the complete failure of the motor. Therefore, establishing an effective brushless motor stall detection and handling mechanism to promptly address the instantaneous high current during stalling is crucial to ensuring the safe and reliable operation of the motor and drive circuit.

[0003] With increasing demands for cost control, automotive brushless motor controllers are gradually reducing the use of sensors, instead relying on sensorless control stall detection algorithms to estimate rotor position and speed and determine stall conditions. Automotive electric fans are installed at the front of passenger vehicles near the ground, making them highly susceptible to damage from ground protrusions or obstacles. It is common for foreign objects such as branches and stones to be swept into the front compartment, causing blockages in the electric fan. Prolonged blockage of the electric fan by foreign objects can have serious consequences.

[0004] Most current mainstream sensorless motor stall detection algorithms determine stall based on parameters such as speed, back electromotive force, phase current, and bus current after the brushless motor enters the closed-loop speed control stage. However, this approach has significant drawbacks: during motor positioning or open-loop start-up, a sudden increase in load can lead to incorrect rotor position estimation, preventing the motor from starting normally; similarly, under low-speed operation and heavy load conditions, the algorithm's rotor position estimation error increases significantly, also causing start-up failure. In both of these conditions, the motor enters a stall state, but due to inaccurate rotor position estimation by the software algorithm, the calculated speed is not zero, preventing the controller from promptly detecting the stall. If the stall persists for an extended period, the brushless motor will burn out due to overheating. Therefore, developing a technology that can accurately determine the stall state of a brushless motor and avoid motor damage caused by untimely stall detection has become a crucial problem urgently needing to be solved in the industry. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method and apparatus for detecting stall in automotive brushless electric fans that directly detects stall during the open-loop stage, avoiding overcurrent hardware damage caused by the lag of closed-loop protection, and improving detection reliability.

[0006] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a stall detection method for a brushless electric fan in automobiles, based on the Infineon 9877 chip, which performs stall detection after the brushless motor is driven in open loop. The specific steps are as follows:

[0007] S1. Apply a fixed driving torque to the three phases of the brushless motor to drive the rotor to move, and drag the fan blades to a certain speed through position estimation;

[0008] S2. Turn off the three-phase MOS bridge arm, stop the drive and enter the free-sliding state;

[0009] S3. Real-time sampling of the back EMF zero-crossing signal of the three-phase winding, converting it into a digital sequence through a comparator, and obtaining the variation law of the three-phase zero-crossing;

[0010] S4. Determine the stall status based on the changing pattern of the three-phase zero-crossing points described in step S3:

[0011] If the difference between adjacent serial numbers jumps irregularly between positive and negative values ​​or the difference is always 0, it is determined to be a stalled turn.

[0012] If the difference between adjacent serial numbers is always -1 or 1, it is determined to be normal operation;

[0013] S5. When a stall condition is detected, immediately cut off the power supply to the motor and trigger the protection mechanism.

[0014] Preferably, the variation law of the three-phase zero-crossing points is specifically determined as follows:

[0015] When rotated clockwise, the comparator output changes in a cyclical pattern of 001→011→010→110→100→101→001, and is numbered ①②③④⑤⑥① from left to right according to the sequence number.

[0016] When rotated counterclockwise, the comparator output changes in a cyclical pattern of 001→101→100→110→010→011→001, and is numbered ⑥⑤④③②①⑥ from left to right according to the sequence number.

[0017] Preferably, the difference calculation adopts a modulo-6 compensation mechanism:

[0018] When rotating clockwise, the difference between the previous and next serial numbers is always -1. When ⑥-①=5, compensation of -6 makes the difference always -1. When rotating counterclockwise, the difference between the previous and next serial numbers is always 1. When ①-⑥=-5, compensation of 6 makes the difference always 1.

[0019] When rotating clockwise, the difference between the next serial number and the previous serial number is always 1. When ①-⑥=-5, compensation 6 makes the difference always 1. When rotating counterclockwise, the difference between the next serial number and the previous serial number is always -1. When ⑥-①=5, compensation -6 makes the difference always -1.

[0020] The present invention also provides a stall detection device for a brushless electric fan in automobiles, comprising:

[0021] The drive module is used to apply a fixed driving torque to the three phases of the brushless motor to drive the fan blades to a certain speed.

[0022] The comparator circuit is used to acquire the zero-crossing signal of the back electromotive force and generate a digital sequence;

[0023] A control unit configured to perform logical judgments of the method according to any one of claims 1-3.

[0024] Preferably, the device is implemented based on the Infineon 9877 chip.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Ultra-early fault detection and response: Breaking through the limitations of traditional closed-loop detection, stall detection is intervened in the open-loop drive stage of the brushless motor. By observing the change law of the zero-crossing point of the back electromotive force, stall can be quickly identified, and the fault can be interrupted in advance to avoid damage to the overcurrent hardware due to the lag of the closed-loop protection.

[0027] 2. Avoid the risk of closed-loop dependence: Abandon the traditional stall judgment mode that relies on speed estimation, and directly judge based on the change law of the back EMF zero crossing point. Even if the rotor position estimation is inaccurate in the early stage of motor start-up and under low speed and high load conditions, the stall state can be accurately identified, avoiding false or missed judgments of stall due to algorithm deviation, and significantly improving the reliability and stability of the detection system.

[0028] 3. Enhanced robustness under all operating conditions: It fully covers the entire motor startup process. For extreme conditions such as load jamming at startup, vibration in complex road conditions, and sudden load, the open-loop protection mechanism serves as the first line of defense and responds quickly to stall anomalies. Compared with closed-loop detection, which requires waiting for the startup process to complete and integrating stall judgment and observer algorithms, this solution reduces intermediate links, reduces system complexity, and significantly improves the stability of motor operation in harsh environments.

[0029] 4. Adaptable to complex environments: During vehicle operation, in the face of sudden situations such as road bumps, foreign object impacts, and sudden load changes, the open-loop stall protection can respond immediately, making up for the response delay of closed-loop detection. By intervening in fault handling in advance, it ensures that the motor continues to operate stably in complex dynamic environments, extends the service life of the motor and drive circuit, and reduces vehicle maintenance costs. Attached Figure Description

[0030] Figure 1 This is a schematic diagram showing the correspondence between the back electromotive force and the zero-crossing reversal of the present invention;

[0031] Figure 2 This is a schematic diagram of signal changes in this invention (i.e., a schematic diagram of the correspondence between the comparator output value and the sequence number);

[0032] Figure 3 This is a schematic diagram of the phase current waveform when judging the stall state of a brushless motor after the closed loop of the existing technology (channel 0 is the state of the brushless motor, channel 1 is the stall flag, and channels 2, 3, and 4 are the currents of the three phases UVW respectively).

[0033] Figure 4 This is a schematic diagram of the phase current waveform when the brushless motor is stalled after open-loop drive according to the present invention (channel 0 is the brushless motor state, channel 1 is the stall flag, channel 2 is the back electromotive force, and channels 3, 4, and 5 are the currents of the three phases UVW respectively).

[0034] Figure 5 This is a schematic diagram of the phase current waveform when the fan blades glide without stalling after being dragged by the present invention (channel 0 is the brushless motor state, channel 1 is the stall flag, channel 2 is the back electromotive force, and channels 3, 4, and 5 are the currents of the three phases UVW respectively).

[0035] Figure 6 This is a schematic diagram of the stall detection method of the present invention. Detailed Implementation

[0036] The following will combine Figures 1-6 The present invention will be described in detail below. The illustrative embodiments and descriptions herein are used to explain the invention, but are not intended to limit the invention.

[0037] Fans typically produce noise before stall protection activates. This is because when a brushless motor starts in stall mode, stall detection only begins after the motor's speed enters a closed-loop state. When the brushless motor stalls, the fan blades vibrate, causing inaccurate speed estimation. This leads to the motor mistakenly believing it has entered a closed-loop state, causing it to accelerate and produce a high-frequency, piercing whistling sound. Stall protection is activated when the speed exceeds a threshold.

[0038] To more quickly protect the brushless motor in a stalled state without generating high-frequency noise, this patent, based on the Infineon 9877 chip, performs a stall detection on the brushless motor after it is started in open-loop operation. The specific detection method is as follows: A fixed driving torque is applied to the three phases. After the fan blades are driven to a certain speed without position estimation, the three-phase MOS bridge arms are turned off. The back electromotive force is sampled to obtain the change pattern of the three-phase zero-crossing points. Based on this pattern, the brushless motor can be quickly stopped to protect it.

[0039] Due to the characteristics of the comparator, it can quickly identify changes in the zero-crossing point, thus switching once. When the back electromotive force changes from negative to positive, the comparator outputs 1; when the back electromotive force changes from positive to negative, the comparator outputs 0. Therefore, when rotating clockwise, the change pattern of the comparator output is 001→011→010→110→100→101→001→……; when rotating counterclockwise, the change pattern of the zero-crossing point is 001→101→100→110→010→011→001→……. Converted to decimal, the clockwise value is 1→5→4→6→2→3→1→……, and the counterclockwise value is 1→3→2→6→4→5→1→…….

[0040] If we label the comparator output signals from left to right as ①②③④⑤⑥① when rotating clockwise, then the sequence numbers for counter-clockwise rotation are ⑥⑤④③②①⑥. The relationship between the sequence numbers and the comparator output signals is as follows: Figure 2As shown. If the fan rotates normally, the difference between adjacent serial numbers will always be -1 or 1. Our difference calculation uses a modulo-6 compensation mechanism. That is, when rotating clockwise, the difference between the previous and next serial numbers is always -1. When ⑥ - ① = 5, compensation of -6 makes the difference always -1. Similarly, when rotating counter-clockwise, the difference between the previous and next serial numbers is always 1. When ① - ⑥ = -5, compensation of -6 makes the difference always 1. If the brushless motor is stalled at this time, it may also exhibit vibration. During this vibration, the back EMF zero-crossing point will fluctuate between clockwise and counterclockwise, resulting in a sequence of ①②③②③… The sequence number subtraction will produce an irregular jump of 1, 1, -1, 1… Alternatively, it may be completely stuck, failing to cross the zero point, meaning the sequence number change remains constant at 0. Therefore, when the value after subtracting the sequence number switches between positive and negative numbers or remains constant at 0, we consider the brushless motor to be stalled and wait for the next restart command to attempt a restart. If the value after subtracting the sequence number is constant at -1 or constant at 1, we consider the brushless motor to be operating normally without stalling, and the fan will start normally with tailwind, efficiently entering closed-loop control. This operation not only protects the brushless motor from damage but also accelerates the fan's closed-loop entry time.

[0041] A stall detection method for a brushless electric fan in automobiles, based on the Infineon 9877 chip, performs stall detection after the brushless motor is driven in open loop. The specific steps are as follows:

[0042] S1. Apply a fixed driving torque to the three phases of the brushless motor to drive the rotor to move, and drag the fan blades to a certain speed through position estimation;

[0043] S2. Turn off the three-phase MOS bridge arm, stop the drive and enter the free gliding state. Use the inertia of the fan blades to glide for a period of time, while detecting the back electromotive force generated due to the blocking current change.

[0044] S3. Real-time sampling of the back EMF zero-crossing signal of the three-phase winding, converting it into a digital sequence through a comparator, and obtaining the variation law of the three-phase zero-crossing;

[0045] S4. Determine the stall status based on the changing pattern of the three-phase zero-crossing points described in step S3:

[0046] If the difference between adjacent serial numbers jumps irregularly between positive and negative values ​​or the difference is always 0, it is determined to be a stalled turn.

[0047] If the difference between adjacent serial numbers is always -1 or 1, it is determined that the motor starts with the wind according to the set direction and runs normally.

[0048] S5. When a stall condition is detected, immediately cut off the power supply to the motor and trigger the protection mechanism.

[0049] The stall detection device for automotive brushless electric fans of the present invention is based on the Infineon 9877 chip and specifically includes:

[0050] The drive module is used to apply a fixed driving torque to the three phases of the brushless motor to drive the fan blades to a certain speed.

[0051] The comparator circuit is used to acquire the zero-crossing signal of the back electromotive force and generate a digital sequence;

[0052] The control unit is configured to perform logical judgments for the stall detection method of the automotive brushless electric fan.

[0053] Figure 3 This is a commonly used method for determining stall after a closed-loop circuit. Figure 4 and Figure 5 To determine the stall mode after open-loop dragging, it is obvious Figure 4 After using the detection method of the present invention, the time for determining stall is shorter, and the time for entering the closed loop with the tailwind is also shorter.

[0054] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for detecting stall in a brushless electric fan for automobiles, characterized in that: Based on the Infineon 9877 chip, a stall detection is performed after the brushless motor is driven in open loop. The specific steps are as follows: S1. Apply a fixed driving torque to the three phases of the brushless motor to drive the rotor to move, and drag the fan blades to a certain speed through position estimation; S2. Turn off the three-phase MOS bridge arm, stop the drive and enter the free-sliding state; S3. Real-time sampling of the back EMF zero-crossing signal of the three-phase winding, converting it into a digital sequence through a comparator, and obtaining the variation law of the three-phase zero-crossing; S4. Determine the stall status based on the changing pattern of the three-phase zero-crossing points described in step S3: If the difference between adjacent serial numbers jumps irregularly between positive and negative values ​​or the difference is always 0, it is determined to be a stalled turn. If the difference between adjacent serial numbers is always -1 or 1, it is determined to be normal operation; S5. When stall is detected, immediately cut off the power supply to the motor and trigger the protection mechanism.

2. The method for detecting stall in a brushless electric fan for automobiles according to claim 1, characterized in that, The specific determination of the variation law of the three-phase zero-crossing point is as follows: When rotated clockwise, the comparator output changes in a cyclical pattern of 001→011→010→110→100→101→001, and is numbered ①②③④⑤⑥① from left to right according to the sequence number. When rotated counterclockwise, the comparator output changes in a cyclical pattern of 001→101→100→110→010→011→001, and is numbered ⑥⑤④③②①⑥ from left to right according to the sequence number.

3. The method for detecting stall in a brushless electric fan for automobiles according to claim 2, characterized in that, The difference calculation adopts a modulo-6 compensation mechanism: When rotating clockwise, the difference between the previous and next serial numbers is always -1. When ⑥-①=5, compensation of -6 makes the difference always -1. When rotating counterclockwise, the difference between the previous and next serial numbers is always 1. When ①-⑥=-5, compensation of 6 makes the difference always 1.

4. A stall detection device for a brushless electric fan in automobiles, characterized in that, include: The drive module is used to apply a fixed driving torque to the three phases of the brushless motor to drive the fan blades to a certain speed. The comparator circuit is used to acquire the zero-crossing signal of the back electromotive force and generate a digital sequence; A control unit configured to perform logical judgments of the method according to any one of claims 1-3.

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