Method for controlling an electric motor of an electric vehicle

Abstract

The invention relates to a method for controlling an electric motor of an electric vehicle. The method includes monitoring the current strength and temperature of a motor control unit in real time and making a decision to adjust the operating mode according to the values of the monitored parameters. The method includes three levels of torque monitoring. On a first level, the state of the electric motor is determined to be safe if the torque meets a predetermined lower torque threshold value. On a second level, the current actual torque value of the electric motor is compared with a required torque value of the electric motor. On a third level, the voltage, current strength and temperature of the motor control unit are monitored. If the state of the electric motor is not determined to be safe, the torque of the electric motor is controlled to achieve a safe state. If a safe state of the electric motor is not achieved within a predetermined time, the motor control unit sends an error message to a vehicle control unit with a command to stop the electric motor. The result is an increase in the safety of an electric vehicle.

Description

[0001] Description of the invention

[0002] Method of controlling the electric motor of an electric vehicle

[0003] Field of technology

[0004] The invention relates to methods for controlling traction motors of vehicles and can be used in electric vehicles.

[0005] Prior art

[0006] A method for controlling the power system of an all-wheel drive vehicle is known, which includes receiving by the engine control unit (hereinafter referred to as ECU) a command to control the torque of the electric motor from the vehicle control unit (hereinafter referred to as VCU) and controlling the torque of the electric motor based on the received signal with feedback from the current-measuring sensor of the electric motor (patent WO 2023082854, published on 19.05.2023).

[0007] The disadvantages of the known solution include unsatisfactory safety of the electric motor and ECU operation due to the lack of torque and temperature monitoring.

[0008] The closest in terms of the set of essential features - the prototype of the claimed invention - is a method for controlling an electric motor, including real-time monitoring of the current strength and temperature of the ECU and making a decision to change the operating mode depending on the value of the monitored parameters (Patent No. RU 2657868, published on 18.06.2018. Bulletin No. 17). According to the known solution, the criteria may be events of excessive increase in phase currents and / or rotation speed of the electric motor, and / or equality or excess of the actual temperature threshold value.

[0009] The disadvantages of the known solution include its limited ability to control the torque of the electric motor.

[0010] 1

[0011] SUBSTITUTE SHEET (RULE 26) Disclosure of the invention

[0012] In the context of this application, the following terms will be used as synonyms:

[0013] - "electric motor of an electric vehicle", "traction motor of an electric vehicle";

[0014] - "torque", "torque of an electric motor".

[0015] The technical problem that the creation of the present invention was aimed at solving is to provide additional control of the torque of the traction motor of an electric vehicle.

[0016] The technical result of implementing the proposed invention consists in increasing the safety of an electric vehicle.

[0017] The solution to the technical problem is achieved by implementing a three-level control of the electric motor torque as follows: at the first level, the state of the electric motor is determined as safe when the torque reaches a preset lower threshold value of torque; at the second level, the current actual value of the electric motor torque is compared with the required value of the electric motor torque and the state of the electric motor is determined as safe if the difference between the actual and required values ​​does not exceed the preset value;at the third level, the voltage, current and temperature of the ECU are monitored in real time and the state of the electric motor is determined to be safe if the said parameters are within the preset safe limit values, and if the state of the electric motor is not determined to be safe, the torque of the electric motor is controlled so as to ensure a safe state, and if the safe state of the electric motor is not;

[0018] 2

[0019] SUBSTITUTE SHEET (RULE 26) is reached within a preset time, the ECU sends an error message and a command to stop the electric motor to the BCU.

[0020] The novelty of the proposed technical solution is the introduction of two additional levels of torque control into the method for controlling the electric motor of an electric vehicle, namely, determining at the first level the state of the electric motor as safe when the torque reaches a predetermined lower threshold value of torque, comparing at the second level the current actual value of torque with the required value of torque of the electric motor and determining the state as safe in the event that the difference between the actual and specified values ​​of torque does not exceed a predetermined value, and introducing real-time monitoring of the voltage of the current on the electric motor.

[0021] Torque is determined by the current strength of the electric motor in the motor mode of operation, whereas in the energy generation mode, i.e., in the generator mode, the current strength of the electric motor depends on the resistance of the circuit to which the electric motor is connected, the internal resistance of the electric motor windings and the speed of rotation of the electric motor rotor. Thus, torque directly affects the current strength in the high-voltage circuit and the temperature of the electric motor and the ECU. As a result, the three-level torque control system in the claimed method ensures the temperature, electrical and mechanical safety of the electric motor and the ECU.

[0022] In normal operation, the ECU receives signals from the accelerator pedal of the electric vehicle, converts them into torque control commands and speed control commands, and sends them to the ECU.

[0023] SUBSTITUTE SHEET (RULE 26) When the ECU receives a torque control command, the ECU converts it into a current control command on the electric motor and controls the torque of the electric motor with feedback from the electric motor current sensor, i.e., in a closed loop with the current sensor. Control of torque and rotation speed with feedback from the electric motor current sensor allows creating a closed automatic control system that continuously and in real time controls the rotation speed and / or torque.

[0024] In addition, the ECU receives signals from temperature sensors in the system, including the electric motor temperature sensors and temperature sensors, and if any of the temperatures exceeds a preset threshold, it reduces the electric motor torque until a safe state is reached in which the temperature is below the specified threshold.

[0025] In addition, the ECU monitors the current in the high-voltage circuit and the voltage at the DC high-voltage bus terminals, and if any of the specified preset threshold values ​​are exceeded, it performs protection to protect the ECU from damage, such as opening the ECU circuit and / or connecting a shunt resistor and sending an error message to the ACU. In addition, if any of the specified preset threshold values ​​are exceeded, the ECU can reduce the torque down to zero.

[0026] In addition, the ECU monitors the rotation speed of the electric motor and, if it detects that the current rotation speed has exceeded a preset threshold value, reduces the torque.

[0027] 4

[0028] SUBSTITUTE SHEET (RULE 26) The said preset safe lower threshold value, the difference between the actual and required torque value, the limiting values ​​of voltage, current and temperature of the ECU are determined so that the said values ​​ensure safe, trouble-free operation of the electric motor and the ECU in accordance with the tests performed or in accordance with the recommendations of the manufacturer of the electric motor and the ECU. Specific values ​​of the said quantities are not the subject of protection under this application.

[0029] The specified feature is new, significant, from the point of view of achieving the declared technical result, and industrially applicable, since it is based on known technologies.

[0030] Brief description of the drawings

[0031] Fig. 1 shows a block diagram of the proposed method for controlling the electric motor of an electric vehicle.

[0032] Implementation of the invention

[0033] The implementation of the proposed method for controlling the electric motor of an electric vehicle is illustrated by a block diagram, which shows the main stages of the method (Fig. 1). The beginning of the implementation is shown as a conditional - zero - stage (designated "O"),

[0034] Positions 1, 2, 3 indicate torque control levels.

[0035] At torque monitoring level 1, the actual torque value is determined. If the actual value has reached the safe preset lower torque threshold, the electric motor state is determined as safe, and when the torque reaches this value, the ECU is switched on with low voltage (the event of accepting such an assessment is designated by position 11 in the block diagram).

[0036] At level 2, the current actual torque value is compared with the required value. If the difference between these 5

[0037] SUBSTITUTE SHEET (RULE 26) values ​​do not exceed the specified value, the state of the electric motor is determined as safe (the event of acceptance of such an assessment on the block diagram is designated by position 21).

[0038] At torque control level 3, the voltage, current and temperature of the ECU are monitored in real time. The state of the electric motor is determined as safe if the mentioned parameters are within the preset safe limit values ​​(the event of acceptance of such an assessment in the block diagram is designated by position 21).

[0039] At each control level, it is possible that the assessment of the electric motor state is not accepted as safe. In these cases, the torque of the electric motor is controlled by the ECU so as to ensure a safe state (steps 41 in the block diagram). In this case, the state of the electric motor is monitored to check whether the electric motor has reached the state that will be assessed as safe within a predetermined time (steps 42 in the block diagram). In the event that the safe state of the electric motor is not reached, regardless of the reasons for this event, the ECU sends an error message to the ACU and a command to stop the electric motor (step 5 in the block diagram). At this point, the control of the motor torque is terminated (step 6 in the block diagram).

[0040] As noted above, due to the proposed additional control stages, the ECU provides protection for the electric motor and ECU from overheating, current and / or voltage overload, maintains torque within safe limits, and also protects the electric motor from overspeeding.

[0041] Thus, the proposed method of controlling the electric motor of an electric vehicle ensures the achievement of the declared technical 6

[0042] SUBSTITUTE SHEET (RULE 26) of the result, namely, increasing the safety of operation of the electric vehicle.

[0043] The proposed method of controlling an electric motor of an electric vehicle is focused on the use of existing serial technologies for the production of electric motors, electric vehicles and control devices. This allows us to speak about the industrial applicability of the proposed invention.

[0044] 7

[0045] SUBSTITUTE SHEET (RULE 26)

Claims

Invention formula Method of controlling the electric motor of an electric vehicle 1. A method for controlling an electric motor of an electric vehicle, including real-time monitoring of the current strength and temperature of the engine control unit and making a decision to change the operating mode depending on the value of the monitored parameters, characterized in that it includes additional levels of torque monitoring, at the first of which the state of the electric motor is determined as safe when the torque reaches a predetermined lower threshold torque value, at the second level of monitoring the current actual value of the electric motor torque is compared with the required value of the electric motor torque and the state of the electric motor is determined as safe if the difference between the actual and required values does not exceed a predetermined value, at the third level, real-time monitoring of the voltage is carried out,the current strength and temperature of the engine control unit and the state of the electric motor are determined as safe if the said parameters are within the predetermined safe limit values, and if the state of the electric motor is not determined to be safe, the torque of the electric motor is controlled by the engine control unit so as to ensure a safe state, and if the safe state of the electric motor is not achieved within a predetermined time, the engine control unit sends an error message and a command to stop the electric motor to the electric vehicle control unit. 8 SUBSTITUTE SHEET (RULE 26)

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