Motor fault diagnosis method for distributed propulsion system

Abstract

Disclosed in the present invention is a motor fault diagnosis method for a distributed propulsion system (DPS), comprising: first detecting whether an abnormality is present in the voltage, speed and power of each set of dual (multi-) motor drive structures to obtain DPS system-level motor fault diagnosis, then reading bottom motor fault diagnosis, and combining the system-level motor fault diagnosis with the bottom motor fault diagnosis and outputting a final motor fault diagnosis result. According to the present invention, a redundant structure of the DPS is used to further optimize motor fault diagnosis, and the diagnosis of these faults (including a voltage fault, a speed fault, and a power fault) provides more information that cannot be determined by a conventional electric drive system. In the present invention, conventional motor fault diagnosis is combined with the described new fault diagnosis, and some methods (voltage fault integration, speed fault integration, power fault integration, and power, speed and voltage combined fault integration) are provided to refine and determine fault sources, thereby providing faults that cannot be detected by the conventional electric drive system.

Description

Motor Fault Diagnosis Method for Distributed Electric Drive System

Technical field

[0001] The present invention relates to the technical field of motors and electric controls, and in particular to the technical field of motor fault diagnosis methods for distributed electric drive systems. [Background Technology]

[0002] Electric motors are the power source for vehicles such as electric aircraft, new energy vehicles, electric ships, and rail vehicles, and their reliability directly affects transportation safety. These vehicles often adapt to different power levels in different operating modes. High-power mode is usually related to system performance and generally occurs during takeoff or landing (acceleration or overtaking) and is a short-term operation. During most operating times, the system's power demand will be significantly lower than in high-power mode. Instead, it is hoped that under the same cost, space, and weight conditions, the drive system can provide more energy to support a longer driving range (that is, the low-power mode design of the electric drive system is closely related to the mileage of the vehicle).

[0003] Existing centralized single-voltage platform electric drive systems usually have a simple overall design and are easy to implement, but they cannot achieve different power operating modes. In addition, they have relatively low system reliability, and their efficiency and cost cannot be optimized.

[0004] A distributed electric drive system (DPS) includes multiple electric motors and multiple batteries as power sources to drive each drive shaft, which serves as an output terminal. Examples include the control architecture of a distributed electric drive system disclosed in Patent Publication No. CN115431794A and the multi-voltage platform distributed electric drive system disclosed in Patent Publication No. CN114374354B. Referring to FIG1 , a distributed electric drive system is typically based on multiple dual-motor drive structures or multiple multi-motor drive structures. For distributed electric drive systems employing multiple dual-motor drive structures, each drive shaft is simultaneously driven by two motors (e.g., drive shaft 1 in FIG1 is simultaneously driven by motor 1 and motor 2), each battery simultaneously powers both motors (e.g., motor 2 and motor 3 in FIG1 are simultaneously powered by battery 1), and each motor can be powered by two batteries simultaneously. Furthermore, for distributed electric drive systems employing multiple multi-motor drive structures, each drive shaft is simultaneously driven by at least three motors, each battery simultaneously powers at least three motors, and each motor can be powered by at least three batteries simultaneously. Distributed electric drive systems not only enable different power modes but also offer high system reliability, making them ideal for vehicles with high safety requirements, such as electric vertical lift aircraft. However, conventional fault diagnosis methods applied to single-voltage platforms fail to fully exploit the redundant structure of distributed electric drive systems for further fault diagnosis, thus failing to provide more fault information for these new electric drive systems. This urgently requires a solution.

[0005] [Summary of the invention]

[0006] The purpose of the present invention is to solve the problems in the prior art and to propose a motor fault diagnosis method for a distributed electric drive system, which can utilize the redundant structure of the distributed electric drive system for further fault diagnosis.

[0007] To achieve the above objectives, the present invention proposes a motor fault diagnosis method for a distributed electric drive system. The method first detects whether there are any abnormalities in the voltage, speed, and power of each group of dual-motor drive structures or multi-motor drive structures to obtain DPS system-level motor fault diagnosis, then reads the underlying motor fault diagnosis, combines the DPS system-level motor fault diagnosis with the underlying motor fault diagnosis, and outputs the final motor fault diagnosis result.

[0008] Preferably, when detecting whether there is a voltage fault in each set of dual-motor drive structures, first detect whether there is a voltage fault in battery 1 and motors 2 and 3 powered by battery 1, and then detect whether there is a voltage fault in the remaining batteries and motors in sequence;

[0009] When testing the speed of each dual-motor drive structure for any faults, first test the drive shaft 1 and motors 1 and 2 that drive the drive shaft 1 for any speed faults, then test the remaining drive shafts and motors for any speed faults in sequence.

[0010] When detecting whether there is a power failure in each set of dual-motor drive structures, first detect whether there is a power failure in battery 1, and then detect whether there is a power failure in the remaining batteries in sequence.

[0011] Furthermore, the specific process of detecting whether there is a voltage fault in battery 1, motor 2, and motor 3 is as follows:

[0012] S101. Start the process and calculate the voltage difference between battery 1, motor 2, and motor 3 using formulas (1), (2), and (3), and then proceed to step S102; Vbm2 = |Vmtr2-Vbattery1| (1); Vbm3 = |Vmtr3-Vbattery1| (2); Vm23 = |Vmtr2-Vmtr3| (3);

[0013] Where Vmtr2 is the input voltage of motor 2, Vmtr3 is the input voltage of motor 3, Vbattery1 is the output voltage of battery 1, Vbm2 is the absolute value of the voltage difference between motor 2 and battery 1, Vbm3 is the absolute value of the voltage difference between motor 3 and battery 1, and Vm23 is the absolute value of the voltage difference between motor 2 and motor 3 input terminals.

[0014] S102. Determine whether at least two voltage differences are less than a threshold value. If so, proceed to step S103; otherwise, proceed to step S104.

[0015] S103. Output no DPS voltage fault, end the process;

[0016] S104. Determine whether only one voltage difference is less than the threshold value. If so, proceed to step S106; otherwise, proceed to step S105.

[0017] S105. Output: Unable to determine which component is faulty, ending the process;

[0018] S106. Determine whether Vbm3 is less than the threshold. If so, proceed to step S107; otherwise, proceed to step S108.

[0019] S107. Output motor 2DPS voltage failure, end the process;

[0020] S108. Determine whether Vbm2 is less than the threshold. If so, proceed to step S109; otherwise, proceed to step S110.

[0021] S109. Output motor 3DPS voltage failure, end the process;

[0022] S110. Determine whether Vm23 is less than the threshold, if so, proceed to step S111, if not, proceed to step S105;

[0023] S111. Output battery 1DPS voltage failure, end the process.

[0024] Furthermore, the specific method of detecting whether there is a speed fault in the transmission shaft 1, motor 1 and motor 2 is as follows:

[0025] Calculate whether the ratio of the speed difference between motor 1 and motor 2 to the maximum speed is greater than the threshold value by formula (4). If so, a DPS speed fault exists; otherwise, no DPS speed fault exists.

[0026] Where, Mtr1 spd is the speed of motor 1, Mtr2 spd is the speed of motor 2, and Threshold is the speed threshold.

[0027] Furthermore, the specific process of detecting whether battery 1 has a power failure is as follows:

[0028] S201. Start the process, first calculate the useful power output by battery 1 using formula (5), then calculate the output power of battery 1 using formula (6), and continue to step S202; Power_battery1useful=Mtr2_trq*Mtr2_omega+Mtr3_trq*Mtr3_omega (5); battery1 power=Vbattery1*Ibattery1 (6);

[0029] Where Mtr2_trq is the output torque of motor 2, Mtr3_trq is the output torque of motor 3, Mtr2_omega is the angular velocity of motor 2, Mtr3_omega is the angular velocity of motor 3, Vbattery1 is the voltage of battery 1, Ibattery1 is the current of battery 1, battery1power is the output power of battery 1, and Power_battery1useful is the useful power output of battery 1.

[0030] S202 determines whether the speed of motor 2 and motor 3 are greater than the low-efficiency zone speed and the battery relay of battery 1 is closed, if so, proceed to step S203, if not, proceed to step S205;

[0031] S203 determines whether the ratio of the useful power output by battery 1 to the output power of battery 1 is less than the threshold value, if so, proceed to step S204, if not, proceed to step S205;

[0032] S204. Output DPS power failure, end the process;

[0033] S205: Output no DPS power failure, end the process.

[0034] Furthermore, in step S202, when min(Mtr2_spd, Mtr3_spd)>low efficiency zone speed, for example 750 rpm, the speeds of motor 2 and motor 3 are both greater than the low efficiency zone speed, and Mtr2_spd is the speed of motor 2, and Mtr3_spd is the speed of motor 3.

[0035] Preferably, the underlying motor fault is obtained through the motor fault code transmitted via CAN.

[0036] As a preferred method, when combining the DPS system-level motor fault diagnosis with the underlying motor fault diagnosis, the specific method of determining the combined voltage fault is as follows:

[0037] S301 reads the bottom motor battery voltage sensor fault and reads the DPS voltage fault, and then proceeds to step S302;

[0038] S302. Determine whether both the bottom motor battery voltage sensor fault and the DPS voltage fault exist. If so, proceed to step S303; otherwise, proceed to step S304.

[0039] S303 outputs the bottom motor voltage sensor failure and ends the process;

[0040] S304 determines whether there is only a DPS voltage fault, if so, proceed to step S305, if not, proceed to step S306;

[0041] S305 outputs the bottom motor battery voltage sensor reading inaccurate fault, ending the process;

[0042] S306. Determine whether only the bottom motor battery voltage sensor is faulty. If so, proceed to step S308; otherwise, proceed to step S307.

[0043] S307. Output no voltage fault, end the process;

[0044] S308. Output cannot be determined, more information is required.

[0045] As a preferred method, when combining the DPS system-level motor fault diagnosis with the underlying motor fault diagnosis, the specific method of determining the combined speed fault is as follows:

[0046] S401 reads the underlying motor speed or position sensor fault and reads the DPS speed fault, and proceeds to step S402;

[0047] S402 determines whether the bottom motor position sensor fault and DPS speed fault are present, if so, proceed to step S403, if not, proceed to step S404;

[0048] S403. Output the bottom motor position sensor fault and end the process;

[0049] S404 determines whether the bottom motor speed sensor fault and DPS speed fault are present, if so, proceed to step S405, if not, proceed to step S406;

[0050] S405. Output the bottom motor speed sensor failure and end the process;

[0051] S406 determines whether there is only a DPS speed fault, if so, proceed to step S407, if not, proceed to step S408;

[0052] S407. Output the bottom motor speed or position sensor reading inaccurate fault, end the process;

[0053] S408. Determine whether there is only a bottom-level motor speed or position sensor fault. If so, proceed to step S410; otherwise, proceed to step S409.

[0054] S409. Output no speed fault, end the process;

[0055] S410. The output cannot be determined, more information is required, and the process ends.

[0056] As a preferred method, when combining the DPS system-level motor fault diagnosis with the underlying motor fault diagnosis, the specific method of determining the combined power fault is as follows:

[0057] S501 reads the underlying motor fault and reads the DPS speed, voltage and power fault, and proceeds to step S502;

[0058] S502 determines whether there is only a DPS power failure, if so, proceed to step S503, if not, proceed to step S504;

[0059] S503. The output DPS power failure is due to a battery current failure, ending the process;

[0060] S504. Determine whether there is no underlying motor fault, only DPS speed and power faults, if so, proceed to step S505, if not, proceed to step S507;

[0061] S505 determines whether the DPS speed failure is due to being less than the specified speed, if so, proceed to step S506, if not, proceed to step S503;

[0062] S506. The output DPS power failure is due to a DPS speed failure, ending the process;

[0063] S507. Determine whether there is no underlying motor fault and only DPS voltage and power faults. If so, proceed to step S508; otherwise, proceed to step S513.

[0064] S508. Determine whether the DPS voltage fault is due to a DPS motor voltage fault. If so, proceed to step S509; otherwise, proceed to step S510.

[0065] S509. The output DPS power failure is due to a battery current failure, and the process ends;

[0066] S510 determines whether the DPS voltage failure is due to the battery voltage being lower than the normal voltage. If so, proceed to step S511; otherwise, proceed to step S512.

[0067] S511. The output DPS power failure is due to battery voltage and current failure, ending the process;

[0068] S512. The output DPS power failure is due to a DPS voltage failure, and the process ends;

[0069] S513 determines whether there is only a bottom motor fault and a DPS power fault, if so, proceed to step S514, if not, proceed to step S515;

[0070] S514. The output DPS power failure is due to a fault in the underlying motor. End the process.

[0071] S515 determines whether there is no underlying motor fault, DPS speed, voltage and power faults are present, if so, proceed to step S517, if not, proceed to step S516;

[0072] S516. Output cannot be determined, more information is required, and the process ends;

[0073] S517. Determine whether the DPS voltage fault is due to a DPS motor voltage fault. If so, proceed to step S518; otherwise, proceed to step S520.

[0074] S518. Determine whether the DPS motor speed failure is due to being less than the specified speed. If so, proceed to step S519; otherwise, proceed to step S522.

[0075] S519. The output DPS power failure is due to a DPS motor speed failure, ending the process;

[0076] S520 determines whether the DPS voltage failure is due to the battery voltage being less than a specified voltage. If so, proceed to step S521; otherwise, proceed to step S524.

[0077] S521 determines whether the DPS motor speed failure is due to a speed greater than the specified speed, if so, proceed to step S522, if not, proceed to step S523;

[0078] S522. The output DPS power failure is due to a battery current failure, and the process ends;

[0079] S523. Output cannot be determined, more information is required, and the process ends;

[0080] S524. Determine whether the DPS motor speed failure is due to a speed greater than a specified speed. If so, proceed to step S525; otherwise, proceed to step S526.

[0081] S525. The output DPS power failure is due to DPS motor speed and voltage failure, ending the process;

[0082] S526. The output cannot be determined, more information is required, and the process ends.

[0083] Beneficial effects of the present invention:

[0084] The present invention discloses a motor fault diagnosis method for a distributed electric drive system (DPS), comprising first detecting whether there are abnormalities in the voltage, speed and power of each group of dual (multi) motor drive structures to obtain a DPS system-level motor fault diagnosis, then reading the underlying motor fault diagnosis, combining the system-level motor fault diagnosis with the underlying motor fault diagnosis and outputting the final motor fault diagnosis result. The present invention utilizes the redundant structure of the DPS electric drive system to further optimize the motor fault diagnosis, and the diagnosis of these faults (including voltage faults, speed faults and power faults) will provide more information that traditional electric drive systems cannot determine. The present invention also combines traditional motor fault diagnosis with the above new fault diagnosis, and proposes some methods (voltage fault integration, speed fault integration, power fault integration and power, speed and voltage comprehensive fault integration) to refine and determine the source of the fault, thereby providing faults that traditional electric drive systems cannot detect.

[0085] The features and advantages of the present invention will be described in detail through embodiments with reference to the accompanying drawings.

Brief Description of the Drawings

[0086] Figure 1 is a schematic structural diagram of a dual-motor drive system;

[0087] FIG2 is a diagram showing a management structure of a motor fault diagnosis system according to the present invention;

[0088] FIG3 is a specific flow chart of the present invention for detecting whether there is a voltage fault in the battery 1, the motor 2, and the motor 3;

[0089] FIG4 is a schematic diagram showing the principle of detecting whether a speed fault occurs in the transmission shaft 1, the motor 1, and the motor 2 according to the present invention;

[0090] FIG5 is a specific flow chart of the present invention for detecting whether battery 1 has a power failure;

[0091] FIG6 is a specific flow chart of the present invention for determining a combined voltage fault;

[0092] 7 is a specific flow chart of the present invention for determining a merging speed failure;

[0093] FIG8 is a portion of a specific flow chart of the present invention for determining a combined power failure;

[0094] FIG9 is another part of a specific flow chart of the present invention for determining a combined power failure;

[0095] Figure 10 is the first voltage fault implementation;

[0096] Figure 11 is a second voltage fault implementation;

[0097] Figure 12 is a third voltage fault implementation;

[0098] Figure 13 is a fourth voltage fault implementation;

[0099] Figure 14 is the first speed fault implementation;

[0100] Figure 15 is the second speed fault implementation;

[0101] Figure 16 is the first power failure implementation;

[0102] Figure 17 is a second power failure implementation;

[0103] Figure 18 is a third power failure implementation; [Specific implementation method]

[0104] Referring to Figure 2, the motor fault diagnosis method for a distributed electric drive system of the present invention comprises three components: DPS motor fault diagnosis, low-level motor fault reading, and motor fault integration. The first component, DPS motor fault diagnosis, is based on the dual-motor drive structure. The second component reads motor fault codes transmitted by the low-level motor via CAN and converts them into specific faults. The third component combines the DPS motor fault with the low-level motor fault and outputs the final motor fault.

[0105] In a dual-motor drive system, each motor has a battery voltage sensor, and each battery has a voltage sensor. Since these three sensors measure the same voltage, the three measured voltages should be basically the same. Faults can be detected by the voltage difference of these three voltages. If two voltage differences are within the error range, there is no voltage fault; if only one voltage difference is within the error range, the other two voltage differences can be used to determine which sensor has an error. Referring to Figure 3, when detecting whether there is a fault in the voltage of each group of dual-motor drive structures, first detect whether there is a voltage fault in battery 1 and motors 2 and 3 powered by battery 1, and then detect whether there is a voltage fault in the remaining batteries and motors in sequence. The specific process for detecting whether there is a voltage fault in battery 1, motor 2, and motor 3 is as follows:

[0106] S101. Start the process and calculate the voltage difference between battery 1, motor 2, and motor 3 using formulas (1), (2), and (3), and then proceed to step S102; Vbm2 = |Vmtr2-Vbattery1| (1); Vbm3 = |Vmtr3-Vbattery1| (2); Vm23 = |Vmtr2-Vmtr3| (3);

[0107] Where Vmtr2 is the input voltage of motor 2, Vmtr3 is the input voltage of motor 3, Vbattery1 is the output voltage of battery 1, Vbm2 is the absolute value of the voltage difference between motor 2 and battery 1, Vbm3 is the absolute value of the voltage difference between motor 3 and battery 1, and Vm23 is the absolute value of the voltage difference between motor 2 and motor 3 input terminals.

[0108] S102. Determine whether at least two voltage differences are less than a threshold value. If so, proceed to step S103; otherwise, proceed to step S104.

[0109] S103. Output no DPS voltage fault, end the process;

[0110] S104. Determine whether only one voltage difference is less than the threshold value. If so, proceed to step S106; otherwise, proceed to step S105.

[0111] S105. Output: Unable to determine which component is faulty, ending the process;

[0112] S106. Determine whether Vbm3 is less than the threshold. If so, proceed to step S107; otherwise, proceed to step S108.

[0113] S107. Output motor 2DPS voltage failure, end the process;

[0114] S108. Determine whether Vbm2 is less than the threshold. If so, proceed to step S109; otherwise, proceed to step S110.

[0115] S109. Output motor 3DPS voltage failure, end the process;

[0116] S110. Determine whether Vm23 is less than the threshold, if so, proceed to step S111, if not, proceed to step S105;

[0117] S111. Output battery 1DPS voltage failure, end the process.

[0118] For example, consider a voltage difference threshold of 40 volts. Referring to Figure 10, if the three voltage difference thresholds are greater than 40 volts, a fault cannot be determined. Referring to Figure 11, if the difference between the battery 1 voltage and the other voltage readings is greater than the threshold, a battery 1 voltage fault is determined. Referring to Figure 12, if the difference between the motor 2 voltage and the other voltage readings is greater than the threshold, a motor 2 voltage fault is determined. Referring to Figure 13, if the difference between the three voltages and the other voltage readings is less than the threshold, no voltage fault exists. Furthermore, V_Mtr2_fault, V_Mtr3_fault, and V_Battery1_fault represent faults in motor 2, motor 3, and battery 1, respectively. A value of 0 indicates no fault, 1 indicates a fault, and 2 indicates an inability to determine. The horizontal axes of Figures 10 and 11 are normalized time (in seconds).

[0119] In a dual-motor drive system, the two motors are coaxial and should have the same speed. Therefore, if the speed difference and the maximum speed ratio are greater than a threshold, an error has occurred. When testing for speed faults in each dual-motor drive structure, first test drive shaft 1 and motors 1 and 2, which drive drive shaft 1, for speed faults. Then, test the remaining drive shafts and motors in sequence for speed faults. The specific method for testing drive shaft 1, motor 1, and motor 2 for speed faults is as follows:

[0120] Calculate whether the ratio of the speed difference between motor 1 and motor 2 to the maximum speed is greater than the threshold value by formula (4). If so, a DPS speed fault exists; otherwise, no DPS speed fault exists.

[0121] Where, Mtr1 spd is the speed of motor 1, Mtr2 spdis the speed of motor 2, and Threshold is the speed threshold.

[0122] For example, consider a speed threshold of 100 rpm. As shown in Figure 14, if the speed difference between the two motors is greater than 100 rpm, a speed fault has occurred. As shown in Figure 15, if the speed difference between the two motors is less than 100 rpm, there is no speed fault. Furthermore, axle1_spd_fault and axle2_spd_fault represent the fault conditions of motor 1 and motor 2, respectively. A value of 0 indicates no fault, 1 indicates a fault, and 2 indicates an indeterminate fault. The horizontal axes of Figures 14 and 15 represent normalized time (in seconds).

[0123] In a dual-motor drive system, since one battery supplies two motors, the ratio of the output power of the two motors to the output power of the battery should be greater than a threshold. When the motor speed is greater than the low-efficiency zone (speed greater than 750 rpm), this method can be used to determine a power failure (less than the threshold, i.e., an error). Referring to Figures 4 and 5, when detecting whether there is a power failure in each group of dual-motor drive structures, first detect whether there is a power failure in battery 1, and then sequentially detect whether there is a power failure in the remaining batteries. The specific process for detecting whether there is a power failure in battery 1 is as follows:

[0124] S201. Start the process, first calculate the useful power output by battery 1 using formula (5), then calculate the output power of battery 1 using formula (6), and continue to step S202; Power_battery1useful=Mtr2_trq*Mtr2_omega+Mtr3_trq*Mtr3_omega (5); battery1 power=Vbattery1*Ibattery1 (6);

[0125] Where Mtr2_trq is the output torque of motor 2, Mtr3_trq is the output torque of motor 3, Mtr2_omega is the angular velocity of motor 2, Mtr3_omega is the angular velocity of motor 3, Vbattery1 is the voltage of battery 1, Ibattery1 is the current of battery 1, battery1power is the output power of battery 1, and Power_battery1useful is the useful power output of battery 1.

[0126] S202. Determine whether the speeds of Motor 2 and Motor 3 are both greater than the low-efficiency speed (e.g., 750 rpm). If min(Mtr2_spd, Mtr3_spd) > 750 rpm, then the speeds of Motor 2 and Motor 3 are both greater than the low-efficiency speed, Mtr2_spd is the speed of Motor 2, Mtr3_spd is the speed of Motor 3, and the battery relay of Battery 1 is closed. If so, proceed to step S203; otherwise, proceed to step S205.

[0127] S203 determines whether the ratio of the useful power output of battery 1 to the output power of battery 1 is less than the threshold, if so, proceed to step S204, if not, proceed to step S205;

[0128] S204. Output DPS power failure, end the process;

[0129] S205: Output no DPS power failure, end the process.

[0130] For example, a power ratio threshold of 0.7 and a low-efficiency speed of 750 rpm are used. See Figure 16 for a power-free state with a power ratio threshold greater than 0.7; Figure 17 for a power-free state with a power ratio threshold less than 0.7; and Figure 18 for a power-free state with a power ratio threshold less than 0.7 but a speed less than 750 rpm. Furthermore, for battery 1, battery 2, and battery 3, a value of 0 indicates no fault, 1 indicates a fault, and 2 indicates an indeterminate state. The horizontal axes of Figures 16, 17, and 18 are all normalized time (in seconds).

[0131] For the same motor, if both the DPS motor fault and the underlying motor voltage fault occur simultaneously, the voltage fault is assumed to be due to a fault in the underlying motor battery voltage sensor, and the underlying motor voltage sensor fault is ultimately output. If the DPS motor fault occurs but the underlying motor does not, the underlying motor battery voltage sensor reading is assumed to be inaccurate, and the motor battery voltage sensor reading inaccurate fault is ultimately output. If the DPS motor is not faulty but the underlying motor has a voltage fault, the output is "Cannot determine, need more information." Referring to Figure 6, when combining a DPS motor fault with an underlying motor fault, the specific method for determining the combined voltage fault is as follows:

[0132] S301 reads the bottom motor battery voltage sensor fault and reads the DPS voltage fault, and then proceeds to step S302;

[0133] S302. Determine whether both the bottom motor battery voltage sensor fault and the DPS voltage fault exist. If so, proceed to step S303; otherwise, proceed to step S304.

[0134] S303 outputs the bottom motor voltage sensor failure and ends the process;

[0135] S304 determines whether there is only a DPS voltage fault, if so, proceed to step S305, if not, proceed to step S306;

[0136] S305 outputs the bottom motor battery voltage sensor reading inaccurate fault, ending the process;

[0137] S306. Determine whether only the bottom motor battery voltage sensor is faulty. If so, proceed to step S308; otherwise, proceed to step S307.

[0138] S307. Output no voltage fault, end the process;

[0139] S308. Output cannot be determined, more information is required.

[0140] For the same motor, if the DPS motor has a speed fault and the underlying motor has a speed or position fault at the same time, the speed fault is considered to be caused by a fault in the underlying motor speed or position sensor, and the underlying motor speed or position sensor fault is ultimately output. If the DPS motor fails but the underlying motor has no speed or position fault, the underlying motor battery speed or position sensor reading is considered to be inaccurate, and the motor battery speed or position sensor inaccurate fault is ultimately output. If the DPS motor has no fault and the underlying motor has a voltage fault, the output is "Cannot determine, need more information." Referring to Figure 7, when combining a DPS motor fault with a underlying motor fault, the specific method for determining the combined speed fault is as follows:

[0141] S401 reads the underlying motor speed or position sensor fault and reads the DPS speed fault, and proceeds to step S402;

[0142] S402 determines whether the bottom motor position sensor fault and DPS speed fault are present, if so, proceed to step S403, if not, proceed to step S404;

[0143] S403. Output the bottom motor position sensor fault and end the process;

[0144] S404 determines whether the bottom motor speed sensor fault and DPS speed fault are present, if so, proceed to step S405, if not, proceed to step S406;

[0145] S405. Output the bottom motor speed sensor failure and end the process;

[0146] S406 determines whether there is only a DPS speed fault, if so, proceed to step S407, if not, proceed to step S408;

[0147] S407. Output the bottom motor speed or position sensor reading inaccurate fault, end the process;

[0148] S408. Determine whether there is only a bottom-level motor speed or position sensor fault. If so, proceed to step S410; otherwise, proceed to step S409.

[0149] S409. Output no speed fault, end the process;

[0150] S410. The output cannot be determined, more information is required, and the process ends.

[0151] The power fault is related to the battery voltage, current, motor speed and motor fault. First, if the battery voltage, motor speed and motor have no faults, the power fault is due to the battery current. Second, if only the motor speed and power are faulty, the power fault is due to the motor speed. If the motor speed fault is caused by being far less than the specified speed, otherwise the power fault is due to the battery current fault. Third, if only the DPS voltage and power are faulty, the power fault is due to the DPS voltage fault. If the DPS voltage fault is caused by being far less than the normal voltage, otherwise the power fault is due to the battery current and voltage fault. Fourth, if only the motor and power are faulty, the power fault is due to the motor fault. Fifth, if the underlying motor has no faults, the DPS speed, voltage and power are faulty. Sixth, the DPS speed or voltage fault is due to the motor speed or voltage being far less than the specified speed or normal voltage, the power fault is due to the motor speed and voltage fault, otherwise it cannot be determined. Referring to Figures 8 and 9, when combining the DPS motor fault with the underlying motor fault, the specific method of judging the combined power fault is as follows:

[0152] S501 reads the underlying motor fault and reads the DPS speed, voltage and power fault, and proceeds to step S502;

[0153] S502 determines whether there is only a DPS power failure, if so, proceed to step S503, if not, proceed to step S504;

[0154] S503. The output DPS power failure is due to a battery current failure, ending the process;

[0155] S504. Determine whether there is no underlying motor fault, only DPS speed and power faults, if so, proceed to step S505, if not, proceed to step S507;

[0156] S505 determines whether the DPS speed failure is due to being less than the specified speed, if so, proceed to step S506, if not, proceed to step S503;

[0157] S506. The output DPS power failure is due to a DPS speed failure, and the process ends;

[0158] S507. Determine whether there is no underlying motor fault and only DPS voltage and power faults. If so, proceed to step S508; otherwise, proceed to step S513.

[0159] S508. Determine whether the DPS voltage fault is due to a DPS motor voltage fault. If so, proceed to step S509; otherwise, proceed to step S510.

[0160] S509. The output DPS power failure is due to a battery current failure, and the process ends;

[0161] S510 determines whether the DPS voltage failure is due to the battery voltage being lower than the normal voltage. If so, proceed to step S511; otherwise, proceed to step S512.

[0162] S511. The output DPS power failure is due to battery voltage and current failure, ending the process;

[0163] S512. The output DPS power failure is due to a DPS voltage failure, and the process ends;

[0164] S513 determines whether there is only a bottom motor fault and a DPS power fault, if so, proceed to step S514, if not, proceed to step S515;

[0165] S514. The output DPS power failure is due to a fault in the underlying motor. End the process.

[0166] S515 determines whether there is no underlying motor fault, DPS speed, voltage and power faults are present, if so, proceed to step S517, if not, proceed to step S516;

[0167] S516. Output cannot be determined, more information is required, and the process ends;

[0168] S517. Determine whether the DPS voltage fault is due to a DPS motor voltage fault. If so, proceed to step S518; otherwise, proceed to step S520.

[0169] S518. Determine whether the DPS motor speed failure is due to being less than the specified speed. If so, proceed to step S519; otherwise, proceed to step S522.

[0170] S519. The output DPS power failure is due to a DPS motor speed failure, ending the process;

[0171] S520. Determine whether the DPS voltage failure is due to the battery voltage being less than a specified voltage. If so, proceed to step S521; otherwise, proceed to step S524.

[0172] S521 determines whether the DPS motor speed failure is due to being greater than the specified speed, if so, proceed to step S522, if not, proceed to step S523;

[0173] S522. The output DPS power failure is due to a battery current failure, and the process ends;

[0174] S523. Output cannot be determined, more information is required, and the process ends;

[0175] S524. Determine whether the DPS motor speed failure is due to a speed greater than a specified speed. If so, proceed to step S525; otherwise, proceed to step S526.

[0176] S525. The output DPS power failure is due to DPS motor speed and voltage failure, ending the process;

[0177] S526. The output cannot be determined, more information is required, and the process ends.

[0178] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention falls within the protection scope of the present invention.

Claims

1. A motor fault diagnosis method for a distributed electric drive system, characterized in that: First, detect whether there are abnormalities in the voltage, speed and power of each group of dual-motor drive structures or multi-motor drive structures to obtain the DPS system-level motor fault diagnosis, then read the underlying motor fault diagnosis, combine the DPS system-level motor fault diagnosis with the underlying motor fault diagnosis and output the final motor fault diagnosis result.

2. The motor fault diagnosis method of the distributed electric drive system according to claim 1, characterized in that: When detecting whether the voltage of each set of dual-motor drive structures has a fault, first detect whether battery 1 and motors 2 and 3 powered by battery 1 have a voltage fault, and then detect whether the remaining batteries and motors have a voltage fault in sequence; When detecting whether the speed of each set of dual-motor drive structures has a fault, first detect whether the transmission shaft 1 and the motors 1 and 2 driving the transmission shaft 1 have a speed fault, and then detect the remaining transmission shafts and motors in sequence whether they have a speed fault; When detecting whether the power of each set of dual-motor drive structures has a fault, first detect whether battery 1 has a power fault, and then detect whether the remaining batteries have a power fault in sequence.

3. The motor fault diagnosis method of the distributed electric drive system according to claim 2, characterized in that: The specific process of detecting whether there is a voltage fault in battery 1, motor 2 and motor 3 is as follows: S101. Start the process, calculate the voltage difference between battery 1, motor 2 and motor 3 by formulas (1), (2) and (3), and continue to step S102; Vbm2=|Vmtr2-Vbattery1| (1); Vbm3=|Vmtr3-Vbattery1| (2); Vm23=|Vmtr2-Vmtr3| (3); Where Vmtr2 is the input voltage of motor 2, Vmtr3 is the input voltage of motor 3, Vbattery1 is the output voltage of battery 1, Vbm2 is the absolute value of the voltage difference between motor 2 and battery 1, and Vbm3 is the absolute value of the voltage difference between motor 3 and battery 1. Vm23 is the absolute value of the voltage difference between the input terminals of motor 2 and motor 3; S102. Determine whether at least two voltage differences are less than a threshold value, if so, proceed to step S103, if not, proceed to step S104; S103. Output has no DPS voltage fault, and the process ends; S104. Determine whether only one voltage difference is less than the threshold value, if so, proceed to step S106, if not, proceed to step S105; S105. Output cannot determine which component is faulty, and the process ends; S106. Determine whether Vbm3 is less than the threshold value, if so, proceed to step S107, if not, proceed to step S108; S107. Output motor 2DPS voltage failure, end the process; S108. Determine whether Vbm2 is less than the threshold value, if so, proceed to step S109, if not, proceed to step S110; S109. Output motor 3DPS voltage failure, end the process; S110. Determine whether Vm23 is less than the threshold value, if so, proceed to step S111, if not, proceed to step S105; S111. Output battery 1DPS voltage failure, end the process.

4. The motor fault diagnosis method of the distributed electric drive system according to claim 2, characterized in that: The specific method of detecting whether there is a speed fault in the transmission shaft 1, motor 1 and motor 2 is as follows: Calculate whether the ratio of the speed difference between motor 1 and motor 2 to the maximum speed is greater than a threshold value by using formula (4). If so, a DPS speed fault exists. Otherwise, no DPS speed fault exists. Where Mtr1 spd is the speed of motor 1, Mtr2 spd is the speed of motor 2, Threshold is the speed Threshold.

5. The motor fault diagnosis method of the distributed electric drive system according to claim 2, characterized in that: The specific process of detecting whether battery 1 has a power failure is as follows: S201. Start the process, first calculate the useful power output by battery 1 by formula (5), then calculate the output power of battery 1 by formula (6), and continue to step S202; Power_battery1useful=Mtr2_trq*Mtr2_omega+Mtr3_trq*Mtr3_omega (5); battery1 power=Vbattery1*Ibattery1 (6); Wherein, Mtr2_trq is the output torque of motor 2, Mtr3_trq is the output torque of motor 3, Mtr2_omega is the angular velocity of motor 2, Mtr3_omega is the angular velocity of motor 3, Vbattery1 is the voltage of battery 1, Ibattery1 is the current of battery 1, battery1 power is the output power of battery 1, and Power_battery1useful is the useful power output of battery 1; S202. Determine whether the speeds of motor 2 and motor 3 are both greater than the speed in the low efficiency zone and the battery relay of battery 1 is closed. If so, proceed to step S203; otherwise, proceed to step S205; S203. Determine whether the ratio of the useful power output by battery 1 to the output power of battery 1 is less than the threshold value, if so, proceed to step S204, if not, proceed to step S205; S204. Output DPS power failure, end the process; S205. Output has no DPS power failure, and the process ends.

6. The motor fault diagnosis method of the distributed electric drive system according to claim 5, characterized in that: In step S202 , when min(Mtr2_spd, Mtr3_spd)>low efficiency zone speed, the speeds of motor 2 and motor 3 are both greater than the low efficiency zone speed, and Mtr2_spd is the speed of motor 2 , and Mtr3_spd is the speed of motor 3 .

7. The motor fault diagnosis method of the distributed electric drive system according to claim 1, characterized in that: The motor fault code transmitted through CAN is used to obtain the underlying motor fault.

8. The motor fault diagnosis method of a distributed electric drive system according to claim 1, characterized in that: When combining the DPS system-level motor fault diagnosis with the underlying motor fault diagnosis, the specific method for determining the combined voltage fault is as follows: S301. Read the bottom motor battery voltage sensor fault and read the DPS voltage fault, and continue to step S302; S302. Determine whether both the bottom motor battery voltage sensor fault and the DPS voltage fault exist. If so, proceed to step S303; if not, proceed to step S304; S303. Output the bottom motor voltage sensor failure and end the process; S304. Determine whether there is only a DPS voltage fault, if so, proceed to step S305, if not, proceed to step S306; S305. Output the bottom motor battery voltage sensor reading inaccurate fault, and end the process; S306. Determine whether only the bottom motor battery voltage sensor is faulty, if so, proceed to step S308, if not, proceed to step S307; S307. Output no voltage fault, end the process; S308. The output cannot be determined and more information is required.

9. The motor fault diagnosis method of a distributed electric drive system according to claim 1, characterized in that: When combining the DPS system-level motor fault diagnosis with the underlying motor fault diagnosis, the specific method for determining the combined speed fault is as follows: S401. Read the bottom motor speed or position sensor fault and read the DPS speed fault, and continue to step S402; S402. Determine whether both the bottom motor position sensor fault and the DPS speed fault exist. If so, proceed to step S403; if not, proceed to step S404; S403. Output the bottom motor position sensor failure and end the process; S404. Determine whether both the bottom motor speed sensor fault and the DPS speed fault exist. If so, proceed to step S405. If not, proceed to step S406. S405. Output the bottom motor speed sensor failure and end the process; S406. Determine whether there is only a DPS speed fault, if so, proceed to step S407, if not, proceed to step S408; S407. Output the bottom motor speed or position sensor reading inaccurate fault, and end the process; S408. Determine whether there is only a bottom-level motor speed or position sensor fault, if so, proceed to step S410, if not, proceed to step S409; S409. Output no speed fault, end the process; S410. The output cannot be determined, more information is required, and the process ends.

10. The motor fault diagnosis method of a distributed electric drive system according to claim 1, characterized in that: When combining the DPS system-level motor fault diagnosis with the underlying motor fault diagnosis, the specific method for determining the combined power fault is as follows: S501. Read the underlying motor fault and read the DPS speed, voltage and power fault, and continue to step S502; S502. Determine whether there is only a DPS power failure, if so, proceed to step S503, if not, proceed to step S504; S503. The output DPS power failure is due to a battery current failure, and the process ends; S504. Determine whether there is no underlying motor fault, only DPS speed and power faults, if yes, proceed to step S505, if not, proceed to step S507; S505. Determine whether the DPS speed failure is due to being less than the specified speed, if so, proceed to step S506, if not, proceed to step S503; S506. The output DPS power failure is due to a DPS speed failure, and the process ends; S507. Determine whether there is no underlying motor fault, only DPS voltage and power faults, if yes, proceed to step S508, if not, proceed to step S513; S508. Determine whether the DPS voltage failure is due to a DPS motor voltage failure, if so, proceed to step S509, if not, proceed to step S510; S509. The output DPS power failure is due to a battery current failure, and the process ends; S510. Determine whether the DPS voltage failure is due to the battery voltage being lower than the normal voltage. If so, proceed to step S511; otherwise, proceed to step S512; S511. The output DPS power failure is due to battery voltage and current failure, and the process ends; S512. The output DPS power failure is due to a DPS voltage failure, and the process ends; S513. Determine whether only the bottom motor fault and the DPS power fault exist, if so, proceed to step S514, if not, proceed to step S515; S514. The output DPS power failure is due to the underlying motor failure, and the process ends; S515. Determine whether there is no underlying motor fault, DPS speed, voltage and power faults, if yes, proceed to step S517, if not, proceed to step S516; S516. The output cannot be determined, more information is needed, and the process ends; S517. Determine whether the DPS voltage failure is due to a DPS motor voltage failure, if so, proceed to step S518, if not, proceed to step S520; S518. Determine whether the DPS motor speed failure is due to being less than a specified speed, if so, proceed to step S519, if not, proceed to step S522; S519. The output DPS power failure is due to a DPS motor speed failure, and the process ends; S520. Determine whether the DPS voltage failure is due to the battery voltage being less than a specified voltage, if so, proceed to step S521, if not, proceed to step S524; S521. Determine whether the DPS motor speed fault is due to being greater than the specified speed. If so, continue to execute step Step S522, if not, continue to step S523; S522. The output DPS power failure is due to a battery current failure, and the process ends; S523. The output cannot be determined, more information is needed, and the process ends; S524. Determine whether the DPS motor speed failure is due to being greater than a specified speed, if so, proceed to step S525, if not, proceed to step S526; S525. The output DPS power failure is due to the DPS motor speed and voltage failure, and the process ends; S526. The output cannot be determined, more information is required, and the process ends.

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