A three-in-one bridge rotor temperature estimation and torque correction method and system

Abstract

The present application relates to a kind of three-in-one bridge rotor temperature estimation and torque correction method and system, method includes: the modeling of each part of bridge, in combination with the correlation data between rotor temperature, stator winding temperature and reducer oil temperature under multiple operating conditions, obtain rotor temperature estimation model;Change the temperature of cooling water, measure the no-load back emf under different rotor temperatures, and calculate flux linkage, fitting to obtain rotor temperature-flux linkage model;Rotor temperature is determined based on rotor temperature estimation model, the size of flux linkage is determined based on rotor temperature-flux linkage model, the size of torque compensation is determined according to the size of flux linkage, and the smooth output torque is obtained.Compared with prior art, the present application combines theory with practice, considers the influence of stator winding temperature and reducer oil temperature and shell cooling water temperature on rotor temperature under different rotational speeds, torque request, efficiently and high-precision rotor temperature estimation model is established, and can be used on batch production new energy vehicle.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle technology, and in particular to a three-in-one electric bridge rotor temperature estimation and torque correction method and system. Background Technology

[0002] With the rapid growth of the electric vehicle market, thermal analysis related to electric drive performance has received considerable attention. Short-term overload of the IPMSM in an electric drive can output peak power and peak torque, significantly improving vehicle acceleration. However, on the one hand, the excessive temperature rise caused by overload can lead to irreversible demagnetization of the permanent magnets, resulting in a decrease in the actual performance of the motor and impacting the insulation system, reducing its lifespan; on the other hand, excessive temperature rise can reduce magnetic flux linkage, affecting torque output accuracy. Therefore, studying the temperature of electric drives, especially rotor temperature, is of great significance in providing safety protection for components such as magnets and windings, and improving torque accuracy. When the stator winding temperature of the motor is too high, the controller needs to perform torque derating to achieve self-protection of the electric bridge.

[0003] Current techniques for studying rotor temperature generally include Finite Element Analysis (FEA), Lumped Parameter Thermal Network (LPTN) modeling, and direct measurement. FEA analysis requires detailed motor parameters, and parameter discrepancies can lead to significant temperature estimation errors, making it difficult to simulate complex dynamic load changes. While LPTN is simpler and requires fewer parameters, the temperature estimated by LPTN is highly uncertain during overload conditions, resulting in relatively low model accuracy. Direct measurement of rotor temperature under all operating conditions is not only time-consuming but also involves processing large amounts of data, limiting its practicality.

[0004] Furthermore, in the field of new energy vehicle technology, most existing electric axles do not perform torque correction based on rotor temperature estimation, or the rotor temperature estimation model is too simple (such as simply estimating the rotor temperature based on the measured stator winding temperature), resulting in poor accuracy. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology by providing a three-in-one electric bridge rotor temperature estimation and torque correction method and system. Combining theory with practice, it considers the influence of stator winding temperature, reducer oil temperature, and housing cooling water temperature on rotor temperature under different speeds and torque requests. It establishes a highly efficient and accurate rotor temperature estimation model, which can be applied to mass-produced new energy vehicles. Based on the online rotor temperature estimation model, torque correction can effectively compensate for deviations caused by changes in magnetic flux due to rotor temperature variations, improving the control accuracy of the three-in-one electric bridge's torque output, enhancing the acceleration response sensitivity of the driver's license, and improving the customer's driving experience.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] According to a first aspect of the present invention, a method for estimating rotor temperature and correcting torque using a three-in-one electric bridge is provided, the electric bridge comprising a motor, a reducer, and an inverter, comprising the following steps:

[0008] Determine the rotor temperature estimation model: Model each part of the bridge and combine the correlation data between rotor temperature, stator winding temperature and reducer oil temperature under various operating conditions to obtain the rotor temperature estimation model;

[0009] Determine the rotor temperature-flux flux model: Change the temperature of the cooling water, measure the no-load back electromotive force at different rotor temperatures, calculate the flux, and fit the rotor temperature-flux flux model.

[0010] The rotor temperature is determined based on the rotor temperature estimation model, the flux linkage size is determined based on the rotor temperature-flux linkage model, and the torque compensation size is determined based on the flux linkage size to obtain a smooth output torque.

[0011] Furthermore, determining the rotor temperature estimation model includes the following steps:

[0012] Using LPTN simulation, the thermal influence path related to rotor temperature is modeled, resulting in a thermal model including thermal resistance R, heat capacity C, and heat source P. The thermal models of each part of the bridge are then connected according to the direction of heat flow to form a 3-node thermal network model, where the three nodes represent the stator winding temperature T. W Rotor temperature T R and reducer oil temperature T O ;

[0013] A rotor temperature estimation model is established based on a 3-node thermal network model:

[0014]

[0015] Among them, T R T0 is the rotor temperature, and C is the initial rotor temperature.R P is the heat capacity of the rotor, t is time, and P is the heat capacity of the rotor. R It is the thermal power of the rotor, P PM The heat power, P, is caused by the eddy current losses of the rotor magnets. W-R It is the heat power conducted by the stator windings and rotor, P O-R It is the heat power conducted by the reducer oil and the rotor, P C-R It is the heat power transferred by the cooling water and the rotor, P E-R It is the thermal power conducted by the environment and the rotor, K W-R K O-R K C-R K E-R It is the efficiency coefficient of heat transfer, which is inversely proportional to the thermal resistance R, T W It is the stator winding temperature, T O It is the reducer oil temperature, T C and T E These are the cooling water inlet temperature and the ambient temperature, respectively.

[0016] The correlation data between rotor temperature, stator winding temperature and reducer oil temperature under various operating conditions are obtained, substituted into the rotor temperature estimation model, and the parameter values ​​in the rotor temperature estimation model are determined to obtain the rotor temperature estimation model.

[0017] Furthermore, the correlation data between rotor temperature, stator winding temperature, and reducer oil temperature under various operating conditions are obtained as follows:

[0018] A test bench is set up, and the reducer output end of the electric bridge is connected to the test bench. The test bench is used to test the wheel end speed and output torque of the electric bridge. Measuring points are set on the electric bridge, and temperature measurement units are arranged at the measuring points to measure and record the rotor temperature, stator winding temperature and reducer oil temperature under different operating conditions.

[0019] Furthermore, the measuring points include the position of the magnet in the middle of the rotor, the end winding of the stator, and the oil position of the reducer. The temperature measuring unit includes a thermocouple sensor and a signal transmission device, and the signal line of the thermocouple sensor is connected to the signal transmission device.

[0020] Furthermore, the formula for calculating the magnetic flux linkage is as follows:

[0021]

[0022] Where Ψ is the magnetic flux linkage value, U l-peak It is the amplitude of the no-load back EMF, ω e ω is the electrical angular frequency, n is the rotor speed, and p is the number of pole pairs.

[0023] Furthermore, the rotor temperature-flux flux model is obtained by fitting the flux values ​​at different rotor temperatures using a linear equation in two variables, as follows:

[0024] y = -ax 2 -bx+c

[0025] Where y represents magnetic flux linkage, x represents rotor temperature, and a, b, and c represent undetermined constants.

[0026] According to a second aspect of the present invention, a three-in-one bridge rotor temperature estimation and torque correction system is provided, comprising:

[0027] The temperature estimation module is used to determine the rotor temperature estimation model: it models each part of the bridge and combines the correlation data between rotor temperature, stator winding temperature and reducer oil temperature under various operating conditions to obtain the rotor temperature estimation model.

[0028] The flux linkage-temperature module is used to determine the rotor temperature-flux linkage model: by changing the temperature of the cooling water, measuring the no-load back EMF at different rotor temperatures, calculating the flux linkage, and fitting the rotor temperature-flux linkage model.

[0029] The correction module determines the rotor temperature based on the rotor temperature estimation model, determines the flux linkage size based on the rotor temperature-flux linkage model, and determines the torque compensation size based on the flux linkage size to obtain a smooth output torque.

[0030] Furthermore, determining the rotor temperature estimation model includes the following steps:

[0031] Using LPTN simulation, the thermal influence path related to rotor temperature is modeled, resulting in a thermal model including thermal resistance R, heat capacity C, and heat source P. The thermal models of each part of the bridge are then connected according to the direction of heat flow to form a 3-node thermal network model, where the three nodes represent the stator winding temperature T. W Rotor temperature T R and reducer oil temperature T O ;

[0032] A rotor temperature estimation model is established based on a 3-node thermal network model:

[0033]

[0034]

[0035] Among them, T R T0 is the rotor temperature, and C is the initial rotor temperature. R P is the heat capacity of the rotor, t is time, and P is the heat capacity of the rotor. R It is the thermal power of the rotor, P PM The heat power, P, is caused by the eddy current losses of the rotor magnets. W-R It is the heat power conducted by the stator windings and rotor, P O-R It is the heat power conducted by the reducer oil and the rotor, PC-R It is the heat power transferred by the cooling water and the rotor, P E-T It is the thermal power conducted by the environment and the rotor, K W-R K O-R K C-R K E-R It is the efficiency coefficient of heat transfer, which is inversely proportional to the thermal resistance R, T W It is the stator winding temperature, T O It is the reducer oil temperature, T C and T E These are the cooling water inlet temperature and the ambient temperature, respectively.

[0036] The correlation data between rotor temperature, stator winding temperature and reducer oil temperature under various operating conditions are obtained, substituted into the rotor temperature estimation model, and the parameter values ​​in the rotor temperature estimation model are determined to obtain the rotor temperature estimation model.

[0037] Furthermore, the formula for calculating the magnetic flux linkage is as follows:

[0038]

[0039] Where Ψ is the magnetic flux linkage value, U L-PEAk It is the amplitude of the no-load back EMF, ω e ω is the electrical angular frequency, n is the rotor speed, and p is the number of pole pairs.

[0040] Furthermore, the rotor temperature-flux flux model is obtained by fitting the flux values ​​at different rotor temperatures using a linear equation in two variables, as follows:

[0041] y = -ax 2 -bx+c

[0042] Where y represents magnetic flux linkage, x represents rotor temperature, and a, b, and c represent undetermined constants.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The rotor temperature estimation model is established by combining the lumped parameter thermal model LPTN with measurement. This can balance the relationship between the complexity of the model and the accuracy of rotor temperature estimation, and solve the defects of using a single analysis method.

[0045] (2) Compared with the finite element analysis (FEA) method for the temperature of the three-in-one rotor, the lumped parameter thermal model related to rotor temperature proposed in this invention only focuses on important nodes, which is easier to implement in engineering applications, has a small amount of calculation, is closer to the real temperature level, and can be used for rotor temperature estimation under complex and variable working conditions.

[0046] (3) Compared with non-contact measurement, the present invention proposes to measure by direct contact with thermocouples and to transmit temperature signals by wireless transmitters and receivers, and to conduct tests at different temperatures on a test bench. The data obtained is more accurate and the rotor temperature estimation model obtained is more precise. Attached Figure Description

[0047] Figure 1 A flowchart for a three-in-one electric bridge rotor temperature estimation and torque correction method;

[0048] Figure 2 This is a schematic diagram of the cross-section of a three-in-one bridge motor;

[0049] Figure 3 A multi-node lumped parameter thermal network model for rotor temperature estimation in a three-in-one electric bridge;

[0050] Figure 4 A schematic diagram of a three-in-one bridge rotor temperature estimation model;

[0051] Figure 5 A schematic diagram of a test prototype for the rotor temperature of a three-in-one electric bridge.

[0052] Figure 6 A schematic diagram of a test bench for the rotor temperature of a three-in-one electric bridge;

[0053] Figure 7 This is a schematic diagram of the rotor temperature-magnetic flux linkage curve in the embodiment;

[0054] Figure 8 This is a schematic diagram of torque correction control;

[0055] Figure reference numerals: a1, stator; a2, rotor; a3, magnet; a4, stator winding; a5, inverter; a6, wireless transmitter; a7, rear end cover; a8, housing; a9, bearing; a10, reducer; i1~i3: thermocouples.

[0056] a11, Host computer; a12, Canoe box; a13, Three-in-one bridge; a14, Battery simulator; a15, Receiver; a16, Motor; a17, Controller; a18, Dynamometer; a19, Torque and speed sensor; a20, Power supply; a21, Test bench. Detailed Implementation

[0057] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0058] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, some components are appropriately exaggerated in the drawings.

[0059] Example 1:

[0060] This invention provides a method for rotor temperature estimation and torque correction using a three-in-one electric bridge, which includes a motor, a reducer, and an inverter. Figure 1 As shown, the method specifically includes the following steps:

[0061] S1. Determine the rotor temperature estimation model: Model each part of the bridge and combine the correlation data between rotor temperature, stator winding temperature and reducer oil temperature under various operating conditions to obtain the rotor temperature estimation model.

[0062] (1) Establish a multi-node lumped parameter thermal model. For example... Figure 2 As shown, the motor mainly consists of a stator a1, a rotor a2, and magnets a3. The rotor a2 is fitted with magnets a3 made of rare-earth materials with strong magnetic properties. A low-order thermal model (LPTN) is used to simulate the main thermal influence paths related to rotor temperature. Based on heat transfer principles, each part of the motor is modeled. A thermal model including thermal resistance R, heat capacity C, and heat source P is obtained. The thermal models of each part of the bridge are connected according to the direction of heat flow to form a 3-node thermal network model. The three nodes represent the stator winding temperature T. w Rotor temperature T R and reducer oil temperature T O ,like Figure 3 As shown.

[0063] Figure 3 In the middle, T C (°C) is the cooling water inlet temperature, t e (°C) is the ambient temperature, t r (°C) is the rotor temperature, t W (°C) is the stator winding temperature, T O (°C) is the gearbox oil temperature. W (J / ℃) is the heat capacity of the stator winding, C R (J / ℃) is the heat capacity of the rotor, C O (J / ℃) is the heat capacity of the gearbox oil, R W-C (℃ / W), R W-R (℃ / W), R O-R (℃ / W), R O-E(°C / W) represent the thermal resistance between the stator winding and cooling water, the thermal resistance between the stator winding and rotor, the thermal resistance between the stator winding and rotor, and the thermal resistance between the reducer oil and the environment, respectively. W (J / ℃), C R (J / ℃), C O (J / ℃) represent the stator winding heat capacity, rotor heat capacity, and reducer oil heat capacity, respectively. P PM (W) is the heat power caused by the eddy current losses of the rotor magnet, P W (W) represents the stator winding thermal power, P O (W) represents the heat power of the reducer oil, that is, the heat power of gear friction and oil churning in the reducer.

[0064] The lumped parameter thermal network (LPTN) model consists of three nodes, each representing a stator winding temperature T. W Rotor temperature T R and reducer oil temperature T O Each node is connected to thermal ground via thermal capacity C. Coolant inlet temperature T C and ambient temperature T E It is constant. Thermal resistance R i-j This represents the heat flow from node i to node j. Rotor temperature node T R Through R W-R With stator winding temperature T W Connection, rotor temperature node T R Through R O-R With reducer oil temperature node T O connect.

[0065] (2) Establish a rotor temperature estimation model. According to Fourier's law of heat conduction, heat conduction occurs between objects in contact at different temperatures, and the direction of heat transfer is opposite to the direction of the temperature gradient. The total thermal power of the rotor is the sum of the rotor's own eddy current loss power and the thermal conduction power of each node and the rotor, as shown below:

[0066]

[0067] Among them, P R (W) is the thermal power of the rotor, P PM (W) is the heat power caused by the eddy current losses of the rotor magnet, P W-R (W) is the heat power conducted by the stator windings and rotor, P O-R (W) is the heat power conducted by the reducer oil and rotor, P C-R (W) is the heat power transferred by the cooling water and the rotor, P E-R (W) is the thermal power conducted by the environment and rotor, K W-R K O-R K C-R KE-R It is the efficiency coefficient of heat transfer, which is inversely proportional to the thermal resistance R (°C / W), T W It is the stator winding temperature, T O It is the reducer oil temperature, T C and T E These are the cooling water inlet temperature and the ambient temperature, respectively.

[0068] A rotor temperature estimation model is established based on a 3-node thermal network model:

[0069]

[0070] Among them, T R (°C) is the rotor temperature, T0(°C) is the initial rotor temperature, C R (J / ℃) is the heat capacity of the rotor, and t(s) is time, thus establishing an online estimation model for the rotor temperature, such as... Figure 4 As shown;

[0071] Figure 4 This is a schematic diagram of the rotor temperature estimation model of the three-in-one bridge; according to formula (1), the rotor temperature estimation model is as follows. Figure 4 As shown, the rotor temperature T is obtained through the calculation relationship of each parameter. R Among them, P PM (W) represents the thermal power of the rotor magnet, and the current I and rotor speed n. R Positive correlation; K W-R K O-R K C-R K E-R The efficiency coefficient for heat transfer is inversely proportional to the thermal resistance R (°C / W) and also related to the rotor speed n. R and coolant flow rate n cool Related.

[0072] (3) Parameter determination of the rotor temperature estimation model. Compared with FEA, the lumped parameter thermal network (LPTN) model is simpler and requires fewer parameters to be determined. However, the temperature information estimated by LPTN is highly uncertain during the overload stage. Due to the uncertainty of the parameters, the accuracy of the model is not high. Therefore, this application introduces actual measurement data and adopts a method combining the lumped parameter thermal model LPTN and measurement to establish the rotor temperature estimation model. This can balance the relationship between the complexity of the model and the accuracy of rotor temperature estimation, and solve the shortcomings of using a single analysis method. As follows:

[0073] ① Obtain correlation data between rotor temperature, stator winding temperature, and reducer oil temperature under various operating conditions. The process is as follows: A test bench is constructed, with the reducer output end of the bridge connected to it. The test bench is used to test the wheel end speed and output torque of the bridge. Measuring points are set on the bridge, and temperature measurement units are arranged at these points. The rotor temperature, stator winding temperature, and reducer oil temperature under different operating conditions are measured and recorded. Measuring points include the position of the magnet in the middle of the rotor, the stator end winding, and the reducer oil position. The temperature measurement unit includes a thermocouple sensor and a signal transmission device, with the signal line of the thermocouple sensor connected to the signal transmission device.

[0074] In this embodiment, in order to identify the parameters of the rotor temperature estimation model, tests were conducted on a bridge assembly test bench, such as... Figure 5 As shown, the system includes stator winding a4, inverter a5, wireless transmitter a6, rear cover a7, housing a8, bearing a9, and reducer a10. I1 to i3 are thermocouples. K-type thermocouple sensors are placed at key locations on the bridge (the magnet position in the middle of the rotor, the stator end winding, and the reducer oil position). The K-type thermocouples have a single wire diameter of 0.6 mm and a test head diameter of 1.5 mm. A wireless transmitter is used for signal transmission. The thermocouple sensors at the rotor magnet positions are tightly attached to the magnets using thermally conductive adhesive. The signal lines of the thermocouple sensors are led out through slots on the rotor shaft axis and connected to the wireless transmitter. Considering the high-speed rotation of the rotor during testing, a slip ring structure is introduced. The slip ring is fitted onto the shaft and rotates with it, serving as part of the rotating wireless transmitter, which transmits temperature data to the host computer.

[0075] Test bench such as Figure 6 As shown, the reducer output of the three-in-one electric bridge is connected to the test bench via two half-shafts. The test bench provides the necessary cooling water and power supply for testing, and measures the wheel end speed and output torque of the three-in-one electric bridge. Specifically, it includes a host computer (a11), a Canoe box (a12), a three-in-one electric bridge (a13), a battery simulator (a14), a receiver (a15), a motor (a16), a controller (a17), a dynamometer (a18), a torque and speed sensor (a19), a power supply (a20), and a test bench (a21).

[0076] ② Identify the parameters in the rotor temperature estimation model. Obtain the correlation data between rotor temperature, stator winding temperature and reducer oil temperature under various operating conditions, analyze them, substitute them into the rotor temperature estimation model, determine the parameter values ​​in the rotor temperature estimation model, and thus obtain a rotor temperature estimation model with determined parameters.

[0077] S2. Determine the rotor temperature-magnetic flux linkage model: Change the temperature of the cooling water, measure the no-load back electromotive force at different rotor temperatures, calculate the magnetic flux linkage, and fit the rotor temperature-magnetic flux linkage model.

[0078] The formula for calculating magnetic flux linkage is as follows:

[0079]

[0080] Where Ψ is the magnetic flux linkage value, U l-peak (V) is the amplitude of the no-load back EMF, ω e (rad / s) is the electrical angular frequency, n (rpm) is the rotor speed, and p is the number of pole pairs.

[0081] The rotor temperature-magnetic flux linkage model obtained by fitting is as follows: the magnetic flux linkage values ​​at different rotor temperatures are fitted with a linear equation in two variables, as shown below:

[0082] y = -ax 2 -bx+c

[0083] Where y(Wb) represents the flux linkage, x(°C) represents the rotor temperature, and a, b, and c represent undetermined constants.

[0084] The method for measuring back electromotive force (EMF) involves maintaining the rotor temperature at a specific level by varying the cooling water temperature, and then measuring the amplitude of the motor line no-load back EMF at different rotor temperatures in flywheel mode. The flux linkage value is then calculated using the formulas for flux linkage and back EMF. Finally, based on the data from the measurement points, a linear equation in two variables relating rotor temperature and flux linkage can be fitted, such as... Figure 7 As shown.

[0085] S3. Determine the rotor temperature based on the rotor temperature estimation model, determine the flux size based on the rotor temperature-flux model, determine the torque compensation size based on the flux size, and obtain a smooth output torque.

[0086] Once the rotor temperature estimation model is determined, the corresponding flux linkage and the corresponding torque compensation magnitude are identified, thus determining the torque compensation corresponding to the rotor temperature. Using torque compensation control, the inverter adjusts the torque correction coefficient according to different rotor temperatures to perform real-time motor control, achieving a smooth output torque.

[0087] The block diagram of the three-in-one electric drive torque field-oriented control is as follows: Figure 8 As shown. Currently, field-oriented control (FOC) technology is widely used in permanent magnet synchronous motors. It controls the motor torque by controlling the magnitude of the stator current torque component. Based on FOC vector control, a torque correction loop based on rotor temperature estimation is added. The real-time cooling water inlet temperature T is obtained through online measurement. cool Stator temperature T stator Gearbox oil temperature T oil Given the rotational speed n, the rotor temperature can be estimated. The controller will adjust the torque correction coefficient according to different rotor temperatures to control the motor in real time and obtain a stable output torque.

[0088] This application also provides a three-in-one electric bridge rotor temperature estimation and torque correction system, including:

[0089] The temperature estimation module is used to determine the rotor temperature estimation model: it models each part of the bridge and combines the correlation data between rotor temperature, stator winding temperature and reducer oil temperature under various operating conditions to obtain the rotor temperature estimation model.

[0090] The flux linkage-temperature module is used to determine the rotor temperature-flux linkage model: by changing the temperature of the cooling water, measuring the no-load back EMF at different rotor temperatures, calculating the flux linkage, and fitting the rotor temperature-flux linkage model.

[0091] The correction module determines the rotor temperature based on the rotor temperature estimation model, determines the flux linkage size based on the rotor temperature-flux linkage model, and determines the torque compensation size based on the flux linkage size to obtain a smooth output torque.

[0092] The main control and calculation methods of the temperature estimation module, flux linkage-temperature module, and correction module in the system are described above and will not be repeated here.

[0093] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A three-in-one bridge rotor temperature estimation and torque correction method, characterized in that, The electric bridge comprises a motor, a reducer and an inverter, and comprises the following steps: determining a rotor temperature estimation model: modeling each part of the electric bridge, combining the correlation data between the rotor temperature, the stator winding temperature and the reducer oil temperature under various working conditions to obtain the rotor temperature estimation model; determining a rotor temperature-flux linkage model: changing the temperature of the cooling water, measuring the no-load back electromotive force under different rotor temperatures, and calculating the flux linkage to fit the rotor temperature-flux linkage model; determining the rotor temperature based on the rotor temperature estimation model, determining the size of the flux linkage based on the rotor temperature-flux linkage model, determining the size of the torque compensation according to the size of the flux linkage, and obtaining the smooth output torque; determining the rotor temperature estimation model comprises the following steps: The thermal influence path related to the rotor temperature is simulated by using LPTN, each part of the electric bridge is modeled, a thermal model including thermal resistance R, thermal capacity C and heat source P is obtained, the thermal models of each part of the electric bridge are connected according to the direction of heat flow, and a 3-node thermal network model is formed, the three nodes represent the stator winding temperature , the rotor temperature and the reducer oil temperature , respectively. establishing a rotor temperature estimation model based on a 3-node thermal network model: wherein, is the rotor temperature, is the rotor initial temperature, is the thermal capacity of the rotor, is the time, is the thermal power of the rotor, is the thermal power caused by the rotor magnetic steel eddy current loss, is the thermal power conducted by the stator winding and the rotor, is the thermal power conducted by the reducer oil and the rotor, is the thermal power conducted by the cooling water and the rotor, is the thermal power conducted by the environment and the rotor, , , , is the efficiency coefficient of heat transfer, and is inversely proportional to the thermal resistance R, is the stator winding temperature, is the reducer oil temperature, and are the cooling water inlet temperature and the ambient temperature, respectively; obtaining the correlation data between the rotor temperature, the stator winding temperature and the reducer oil temperature under various working conditions, substituting the rotor temperature estimation model, determining the parameter value in the rotor temperature estimation model, and obtaining the rotor temperature estimation model, obtaining the correlation data between the rotor temperature, the stator winding temperature and the reducer oil temperature under various working conditions is specifically: building a test bench, the output end of the reducer of the electric bridge is connected to the test bench, the test bench is used to test the wheel end speed and output torque of the electric bridge, measuring points are arranged on the electric bridge, temperature measuring units are arranged at the measuring points, and the rotor temperature, the stator winding temperature and the reducer oil temperature under different working conditions are measured and recorded.

2. A three-in-one bridge rotor temperature estimation and torque correction method as claimed in claim 1, wherein, The measuring points include the magnetic steel position of the middle part of the rotor, the stator end winding and the reducer oil position, and the temperature measuring unit comprises a thermocouple sensor and a signal transmission device, and the signal line of the thermocouple sensor is connected to the signal transmission device.

3. A three-in-one bridge rotor temperature estimation and torque correction method as claimed in claim 1, wherein, The calculation formula of the flux linkage is as follows: wherein is a flux linkage value, is a no-load back-emf amplitude, is an electrical angular frequency, is a rotational speed of the rotor, is a number of pole pairs.

4. A three-in-one bridge rotor temperature estimation and torque correction method as claimed in claim 1, wherein, The rotor temperature-flux linkage model is fitted as follows: the flux linkage values under different rotor temperatures are fitted by a binary linear equation as follows: y = -ax 2 - bx + c Wherein, y represents the flux linkage, x represents the rotor temperature, and a, b and c represent to-be-determined constants.

5. A three-in-one bridge rotor temperature estimation and torque correction system characterized by, The three-in-one electric bridge rotor temperature estimation and torque correction method based on any one of claims 1-4 comprises: a temperature estimation module for determining a rotor temperature estimation model: modeling each part of the electric bridge, combining the correlation data between the rotor temperature, the stator winding temperature and the reducer oil temperature under various working conditions to obtain the rotor temperature estimation model; a flux linkage-temperature module for determining a rotor temperature-flux linkage model: changing the temperature of the cooling water, measuring the no-load back electromotive force under different rotor temperatures, and calculating the flux linkage to fit the rotor temperature-flux linkage model; a correction module for determining the rotor temperature based on the rotor temperature estimation model, determining the size of the flux linkage based on the rotor temperature-flux linkage model, determining the size of the torque compensation according to the size of the flux linkage, and obtaining the smooth output torque.

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