Brush fuel pump locked-rotor detection device and method

Abstract

The invention relates to a locked-rotor detection device and method for a brush fuel pump. The device comprises a power module, a control circuit, a driving circuit and a detection circuit. The method comprises the steps that the control circuit calculates the average driving voltage Uout of the motor in real time, calculates a back electromotive force locked-rotor detection threshold Eth = (Uout-Ibus * R) * k, sets a locked-rotor current threshold Ith and calculates a locked-rotor voltage threshold Vth; counter electromotive force locked-rotor detection or current locked-rotor detection is judged and executed in a grading mode by comparing the average driving voltage of the motor with a locked-rotor voltage threshold value, and locked-rotor is accurately recognized according to a comparison result of an operation current Ibus and a locked-rotor current threshold value Ith and a comparison result of a counter electromotive force Vbemf and a counter electromotive force locked-rotor detection threshold value Eth. According to the method, all-condition coverage can be realized only by calibrating one coefficient k, the problems of low-voltage locked-rotor detection blind areas and complex multi-parameter calibration in a traditional scheme are solved, and the method has the advantages of reliable detection and fast response.

Description

Technical Field

[0001] This invention relates to the field of automotive electronics technology, specifically to a brushed fuel pump stall detection device and method. Background Technology

[0002] In automotive fuel supply systems, brushed DC fuel pumps are one of the core components, and their operational stability directly determines the normal operation of the engine. These fuel pumps typically use PWM (Pulse Width Modulation) to adjust the motor voltage, thereby achieving speed regulation. The motor back EMF and motor voltage exhibit a good linear correlation, a characteristic often used in stall detection scenarios.

[0003] However, existing brushed fuel pump stall detection solutions have many shortcomings, making it difficult to simultaneously achieve full operating condition coverage, detection accuracy, and ease of calibration. Specific problems are as follows:

[0004] 1. Fixed current threshold method: Low voltage stall current (e.g., 12-15A) is lower than the conventional stall current threshold (20A). Core operating conditions are prone to forming detection blind spots, making it impossible to identify stall faults in a timely manner;

[0005] 2. Single back EMF stall detection method: This method uses a fixed back EMF threshold for judgment. When the fuel pump is stuck at high speed, the back EMF sampling delay can easily lead to overheating and damage to the motor windings. In addition, this method cannot effectively identify the sub-stall condition where the pump is not completely stuck, which poses a risk of missing fault detection.

[0006] 3. Multi-parameter coupling detection method (refer to patent CN201911071267): It is necessary to calibrate the corresponding current threshold for different motor voltage conditions. The calibration process is complicated, time-consuming, and prone to misjudgment due to temperature drift.

[0007] 4. Speed ​​sensor method: This method requires the addition of a speed detection sensor, which not only increases hardware costs, but also makes the sensor susceptible to corrosion and failure in the fuel environment, reducing the reliability of the detection system.

[0008] In summary, existing testing solutions cannot simultaneously meet the core requirements of "full-condition, blind-spot-free testing" and "simplified calibration process." There is an urgent need for an integrated stall and sub-stall testing solution that dynamically sets the testing threshold based on motor voltage and eliminates the need for complex calibration. Summary of the Invention

[0009] To address the aforementioned problems, this invention provides a brushed fuel pump stall detection device and method that solves the problems of detection blind spots, complex calibration, and response delays in the prior art.

[0010] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a brushed fuel pump stall detection device, comprising a power module, a control circuit, a drive circuit and a detection circuit connected in sequence;

[0011] The power module is used to supply power to the entire system;

[0012] The control circuit integrates an ADC module to calculate the average drive voltage Uout of the motor in real time; and calculates the back EMF stall detection threshold Eth according to the formula Eth=(Uout-Ibus*R)×k, where k is a preset fixed coefficient; the value range of the coefficient k is 0.38~0.42.

[0013] The detection circuit includes a back EMF stall detection circuit for sampling the motor back EMF Vbemf and a current stall detection circuit for sampling the motor operating current Ibus.

[0014] The control circuit is also used for:

[0015] Based on the comparison results of the operating current Ibus and the full stall current threshold Ith, and the comparison results of the back EMF Vbemf and the back EMF stall detection threshold Eth, a graded stall judgment is performed.

[0016] Preferably, the average drive voltage Uout of the motor is calculated according to the formula Uout=Vbus×Duty, where Vbus is the system bus input voltage and Duty is the duty cycle of the PWM signal output from the control circuit to the drive circuit.

[0017] Preferably, the coefficient k is 0.4.

[0018] Preferably, the back EMF stall detection circuit includes a voltage divider circuit composed of voltage divider resistors R1 and R2, and a filter circuit composed of voltage divider resistors R1, R2, and capacitor C3; the current stall detection circuit includes a sampling resistor Rs, an operational amplifier Amp, and a filter circuit composed of resistor R7 and capacitor C5.

[0019] Preferably, the drive circuit consists of MOSFETs Q1 and Q2, which are used to receive the PWM signal from the control circuit and realize the duty cycle adjustment of the average drive voltage Uout of the motor.

[0020] The present invention also provides a method for detecting stall in a brushed fuel pump, which is performed using the above-mentioned device and includes the following steps:

[0021] S1. Start the brushed fuel pump motor, and perform back EMF stall detection and current stall detection simultaneously.

[0022] S2. Real-time acquisition of PWM duty cycle Duty and input voltage Vbus, calculation of motor average drive voltage Uout=Vbus×Duty, and calculation of back EMF stall detection threshold Eth=(Uout-Ibus*R)×k, where k is a preset fixed coefficient;

[0023] S3. Set the stall current threshold Ith, and calculate the stall voltage threshold Vth according to the formula: stall current threshold = stall current threshold / motor resistance;

[0024] S4. Perform a graded judgment based on the comparison between the average motor drive voltage Uout calculated in S2 and the stall voltage threshold Vth calculated in S2.

[0025] A. When Uout < Vth, back EMF stall detection is triggered, the PWM output is periodically turned off, and the back EMF Vbemf of the motor is sampled after the shutdown. If Vbemf = 0, it is determined to be a complete stall; if 0 < Vbemf < Eth, it is determined to be a sub-stall, and a stall fault warning is output in both cases; if Vbemf ≥ Eth, it is determined to be not stalled and is operating normally.

[0026] B. When Uout≥Vth, current stall detection is triggered. The bus current Ibus is collected in real time by ADC and compared with the stall current threshold Ith. If Ibus>Ith, it is determined that the rotor is completely stalled and a stall fault warning is output. If Ibus≤Ith, it is determined that the rotor is not stalled and is operating normally.

[0027] S5. Output the corresponding warning signal based on the judgment result. Under normal operating conditions, restore PWM output to maintain stable motor operation.

[0028] Preferably, in step S4, the back EMF stall detection is performed with a 3-second detection cycle for back EMF sampling: in each cycle, the PWM drive signal is actively turned off for 0.8ms; after turning off the PWM, the freewheeling current is first blocked for 0.5ms, and then the back EMF Vbemf is collected by the ADC within a 0.3ms time window; after the collection is completed, the PWM output is restored.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. Simplified calibration and strong adaptability: Only one fixed coefficient k needs to be determined to make the back EMF stall detection threshold Eth change linearly and adaptively with the average drive voltage U of the motor, which completely avoids the complex calibration work for multiple voltage points and multiple operating conditions, and improves the consistency and anti-drift capability of the system.

[0031] 2. Full operating condition coverage with no detection blind spots: Through the dual judgment mechanism of "current threshold + adaptive back EMF threshold", it can quickly respond to the stall under high driving voltage through the current stall detection method, and accurately identify the complete stall and sub-stall under low driving voltage through the back EMF stall detection method, thus eliminating the detection blind spots of the traditional fixed threshold scheme.

[0032] 3. Fast and reliable response: Current stall detection is real-time, while back EMF stall detection adopts a periodic active shutdown sampling strategy with controllable timing, ensuring that a judgment can be made within an extremely short delay (such as ≤10ms) even when stalling at high speed, effectively avoiding damage to the motor windings due to overheating and improving the safety of fuel pump operation.

[0033] 4. Low cost and easy to implement: No additional speed or position sensors are required. It can be implemented by simply upgrading the software algorithm using the current sampling and motor terminal voltage sampling circuits in the existing drive architecture, resulting in low hardware costs. Attached Figure Description

[0034] Figure 1 This is an overall circuit block diagram of the device of the present invention;

[0035] Figure 2 This is a schematic diagram of the motor drive and detection circuit of the present invention;

[0036] Figure 3 This is a schematic diagram of the back EMF stall detection sampling timing of the present invention;

[0037] Figure 4 This is a flowchart of the stall detection process of the present invention;

[0038] Figure 5 This is a schematic diagram verifying the complete stall effect of the back EMF stall detection method of the present invention;

[0039] Figure 6 This is a schematic diagram illustrating the verification effect of the back EMF stall detection on sub-stall.

[0040] Figure 7 This is a schematic diagram verifying the effectiveness of the stall protection function during normal operation of the present invention;

[0041] in Figure 5-7 The blue curves represent the output of the drive circuit, and the green curves represent the operating current Ibus of the motor bus. Detailed Implementation

[0042] The following will combine Figure 1-7 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.

[0043] According to the motor voltage balance equations: Uout = Ibus*R + Vbemf; Vbemf = Ce*N; Uout = Vbus*Duty, where...

[0044] Uout is the inverter's output voltage, i.e., the average drive voltage of the motor; Ibus is the current flowing through the motor; Ce is the motor's inherent constant; R is the motor's internal resistance; N is the motor's speed; Vbus is the input voltage obtained through voltage sampling; Duty is the inverter's output duty cycle, i.e., the duty cycle of the PWM signal output from the control circuit to the drive circuit.

[0045] Vbemf = Vbus*Duty - Ibus*R = Ce*N;

[0046] When the motor is completely stalled, i.e., speed N = 0, Vbemf = 0; the traditional Eth value is independent of the change in Duty and is set to a fixed value, so it can only detect the complete stall situation. However, our Eth = (Uout - Ibus * R) × k, where k is a fixed coefficient, so Eth is related to the dynamic changes of Vbus and Duty and is a dynamic value. Therefore, our back EMF stall detection can be adapted to both complete stall detection and semi-stall detection. Semi-stall refers to the working condition where the motor is not completely stalled and the speed drops to less than 60% of the normal speed.

[0047] A brushed fuel pump stall detection device includes a power module, a control circuit, a drive circuit, and a detection circuit connected in sequence, such as... Figure 1 As shown;

[0048] The power module is used to supply power to the entire system;

[0049] The control circuit integrates an ADC module to calculate the average motor drive voltage Uout in real time; it calculates the back EMF stall detection threshold Eth according to the formula Eth=(Uout-Ibus*R)×k, where k is a preset fixed coefficient; the value of coefficient k ranges from 0.38 to 0.42, preferably 0.4; where Vbemf is calculated from Uout-Ibus*R. * It is an estimated value; the Vbemf sampled in the detection circuit is a true value.

[0050] The detection circuit includes a back EMF stall detection circuit for sampling the motor back EMF Vbemf and a current stall detection circuit for sampling the motor operating current Ibus.

[0051] like Figure 2As shown, the back EMF stall detection circuit includes a voltage divider circuit composed of voltage divider resistors R1 and R2, and a filter circuit composed of voltage divider resistors R1 and R2 and capacitor C3; the current stall detection circuit includes a sampling resistor Rs, an operational amplifier Amp, and a filter circuit composed of resistor R7 and capacitor C5; the drive circuit consists of MOSFETs Q1 and Q2, which are used to receive the PWM signal from the control circuit, realize the duty cycle adjustment of the average drive voltage Uout of the motor, and thus control the motor speed; through the high-speed switching action of the MOSFETs, the speed control command of the control circuit is accurately responded to.

[0052] The control circuit is also used for:

[0053] Based on the comparison results of the operating current Ibus and the full stall current threshold Ith, and the comparison results of the back EMF Vbemf and the back EMF stall detection threshold Eth, a graded stall judgment is performed.

[0054] Specifically, the average drive voltage Uout of the motor is calculated according to the formula Uout=Vbus×Duty, where Vbus is the system bus input voltage and Duty is the duty cycle of the PWM signal output from the control circuit to the drive circuit.

[0055] A method for detecting stall in a brushed fuel pump, using the aforementioned device, includes the following steps:

[0056] S1. Start the brushed fuel pump motor, and perform back EMF stall detection and current stall detection simultaneously.

[0057] S2. Real-time acquisition of PWM duty cycle Duty and input voltage Vbus, calculation of motor average drive voltage Uout=Vbus×Duty, and calculation of back EMF stall detection threshold Eth=(Uout-Ibus*R)×k, where k is a preset fixed coefficient;

[0058] S3. Set the stall current threshold Ith, and calculate the stall voltage threshold Vth according to the formula: stall current threshold = stall current threshold / motor resistance;

[0059] S4. Based on the comparison between the average motor drive voltage Uout calculated in S2 and the stall voltage threshold Vth calculated in S3, perform a graded judgment, such as... Figure 4 As shown;

[0060] A. When Uout < Vth, back EMF stall detection is triggered, the PWM output is periodically turned off, and the back EMF Vbemf of the motor is sampled after the shutdown. If Vbemf = 0, it is determined to be a complete stall; if 0 < Vbemf < Eth, it is determined to be a semi-stall; and a stall fault warning is output in both complete and semi-stall situations. If Vbemf ≥ Eth, it is determined to be not stalled and operating normally.

[0061] Specifically, the back EMF stall detection performs back EMF sampling according to a 3-second detection cycle: within each cycle, the PWM drive signal is actively turned off for 0.8ms; after turning off the PWM, there is a 0.5ms delay to disable the freewheeling current, and then the back EMF Vbemf is acquired via ADC within a 0.3ms time window; after acquisition, the PWM output is restored. Figure 3 As shown, the back EMF stall detection timing period ΔT1_4 is 3s. When Q1 of the drive circuit is turned on, the ADC cannot detect the back EMF Vbmef, so it is necessary to actively turn off ΔT1_3 time (0.8ms) to detect the back EMF. When Q1 is turned off, the freewheeling time ΔT1_2 (0.5ms) needs to be shielded, and the back EMF Vbmef is detected within the time window interval of ΔT2_3 (0.3ms).

[0062] B. When Uout≥Vth, current stall detection is triggered. The bus current Ibus is collected in real time by ADC and compared with the stall current threshold Ith. If Ibus>Ith, it is determined that the rotor is completely stalled and a stall fault warning is output. If Ibus≤Ith, it is determined that the rotor is not stalled and is operating normally.

[0063] S4. Output the corresponding warning signal based on the judgment result. Under normal operating conditions, restore PWM output to maintain stable motor operation.

[0064] The embodiment of this invention is adapted to a 12V rated voltage fuel pump. After the device is powered on, the power module supplies power to each module, the control circuit is initialized, and the stall current threshold Ith = 20A, the stall voltage threshold Vth = 8V, and k = 0.4 are set. The effect is verified as follows: Figure 5-7 As shown.

[0065] in Figure 5 When Uout is less than 8V, Ibus current = 18.8A, Vbmef = 0; at this time, when the motor is stalled, Uout is less than 8V, Ibus = 18.8A cannot trigger the current stall threshold Ith, the current stall detection method fails, thus triggering the back EMF stall detection. Since Vbmef = 0, it is determined to be completely stalled, and a stall fault warning is output.

[0066] Figure 6 When Uout is less than 8V, Ibus current = 18.8A, Vbmef = 3.04V, and Eth = 3.54V, and the motor stalls, Uout is less than 8V and Ibus = 18.8A, which cannot trigger the current stall threshold Ith. The current detection stall method fails, thus triggering the back EMF stall detection. Since Vbmef is greater than 0 and less than Eth, it is judged as a sub-stall, and a stall fault warning is also output.

[0067] Figure 7 When Uout is less than 8V and Vbemf is greater than Eth, or when Uout is greater than 8V and Ibus is less than Ith, no stall is triggered and the motor operates normally.

[0068] By adjusting the duty cycle of the average drive voltage Uout of the motor using PWM, the motor speed is controlled. Simultaneously, the back EMF stall detection threshold is set using "average drive voltage Uout × fixed coefficient k". Combined with the stall current threshold, a dual judgment mechanism is formed, which solves the problems of detection blind zone and calibration difficulty in traditional solutions. Furthermore, this invention can accurately identify sub-stall by detecting back EMF stall.

[0069] 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 brushed fuel pump stall detection device, characterized in that: It includes a power module, a control circuit, a drive circuit, and a detection circuit connected in sequence; The power module is used to supply power to the entire system; The control circuit integrates an ADC module to calculate the average drive voltage Uout of the motor in real time; and calculates the back EMF stall detection threshold Eth according to the formula Eth=(Uout-Ibus*R)×k, where k is a preset fixed coefficient; the value range of the coefficient k is 0.38~0.

42. The detection circuit includes a back EMF stall detection circuit for sampling the motor back EMF Vbemf and a current stall detection circuit for sampling the motor operating current Ibus. The control circuit is also used for: Based on the comparison results of the operating current Ibus and the full stall current threshold Ith, and the comparison results of the back EMF Vbemf and the back EMF stall detection threshold Eth, a graded stall judgment is performed.

2. The brushed fuel pump stall detection device according to claim 1, characterized in that: The average drive voltage Uout of the motor is calculated according to the formula Uout=Vbus×Duty, where Vbus is the system bus input voltage and Duty is the duty cycle of the PWM signal output from the control circuit to the drive circuit.

3. The brushed fuel pump stall detection device according to claim 1, characterized in that: The coefficient k is set to 0.

4.

4. The brushed fuel pump stall detection device according to claim 1, characterized in that: The back EMF stall detection circuit includes a voltage divider circuit composed of voltage divider resistors R1 and R2, and a filter circuit composed of voltage divider resistors R1, R2, and capacitor C3; the current stall detection circuit includes a sampling resistor Rs, an operational amplifier Amp, and a filter circuit composed of resistor R7 and capacitor C5.

5. The brushed fuel pump stall detection device according to claim 1, characterized in that: The drive circuit consists of MOSFETs Q1 and Q2, which are used to receive the PWM signal from the control circuit and realize the duty cycle adjustment of the average drive voltage Uout of the motor.

6. A method for detecting stall in a brushed fuel pump, using the apparatus described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Start the brushed fuel pump motor, and perform back EMF stall detection and current stall detection simultaneously. S2. Real-time acquisition of PWM duty cycle Duty and input voltage Vbus, calculation of motor average drive voltage Uout=Vbus×Duty, and calculation of back EMF stall detection threshold Eth=(Uout-Ibus*R)×k, where k is a preset fixed coefficient; S3. Set the stall current threshold Ith, and calculate the stall voltage threshold Vth according to the formula: stall current threshold = stall current threshold / motor resistance; S4. Perform a graded judgment based on the comparison between the average motor drive voltage Uout calculated in S2 and the stall voltage threshold Vth calculated in S2. A. When Uout < Vth, back EMF stall detection is triggered, the PWM output is periodically turned off, and the back EMF Vbemf of the motor is sampled after the shutdown. If Vbemf = 0, it is determined to be a complete stall; if 0 < Vbemf < Eth, it is determined to be a sub-stall, and a stall fault warning is output in both cases; if Vbemf ≥ Eth, it is determined to be not stalled and is operating normally. B. When Uout≥Vth, current stall detection is triggered. The bus current Ibus is collected in real time by ADC and compared with the stall current threshold Ith. If Ibus>Ith, it is determined that the rotor is completely stalled and a stall fault warning is output. If Ibus≤Ith, it is determined that the rotor is not stalled and is operating normally. S5. Output the corresponding warning signal based on the judgment result. Under normal operating conditions, restore PWM output to maintain stable motor operation.

7. The method for detecting stall in a brushed fuel pump according to claim 6, characterized in that: In step S4, the back EMF stall detection is performed with a 3-second detection cycle for back EMF sampling: in each cycle, the PWM drive signal is actively turned off for 0.8ms; after turning off the PWM, the freewheeling current is first blocked for 0.5ms, and then the back EMF Vbemf is collected by ADC within a 0.3ms time window; after the collection is completed, the PWM output is restored.

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