Calculation method of downhill braking energy feedback torque of automobile

Abstract

A method for calculating the downhill braking energy feedback torque of an automobile comprises the following steps: S1. a vehicle control unit collects longitudinal acceleration signals, output shaft speed signals and activation conditions for calculating the downhill braking energy feedback torque in real time; S2. the vehicle control unit calculates a slope signal and a downhill slope according to the longitudinal acceleration signals and the output shaft speed signals; S3. the activation conditions are judged, the vehicle control unit judges whether the vehicle state meets the activation conditions and the setting requirements of the slope signal, if so, the downhill braking energy feedback torque calculation is activated, if not, the downhill braking energy feedback torque is 0; S4. the vehicle control unit determines a downhill braking energy feedback torque factor according to a fuzzy control system; S5. the vehicle control unit obtains the downhill braking energy feedback torque by looking up a two-dimensional table according to the downhill braking energy feedback torque factor and the speed of a driving motor, so that the vehicle runs according to the energy feedback torque.

Description

Technical Field

[0001] The invention relates to the technical field of hybrid vehicle control, and in particular to a method for calculating a downhill braking energy feedback torque of a vehicle. Background Art

[0002] In recent years, the world has been facing increasingly prominent problems such as energy shortage and environmental pollution. Traditional fuel vehicles have problems such as low efficiency of internal combustion engines, serious waste emission pollution, and high energy consumption. In order to reduce environmental pollution and energy consumption, major automobile manufacturers around the world are accelerating the development of new energy vehicles. Hybrid vehicles and pure electric vehicles, as new energy vehicles, can effectively reduce energy consumption and environmental pollution, and are increasingly valued by major automobile manufacturers.

[0003] Both hybrid vehicles and pure electric vehicles have motor energy feedback function under braking, which can effectively improve the vehicle's endurance and achieve energy saving and consumption reduction. However, the existing braking energy feedback control method does not take into account the vehicle's driving slope, which is prone to braking safety problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for calculating the downhill braking energy feedback torque of a vehicle in view of the deficiencies in the prior art, which can improve the safety and stability of the vehicle under downhill braking conditions and improve the efficiency of the vehicle's braking energy feedback.

[0005] The technical solution of the present invention is: a method for calculating the downhill braking energy feedback torque of an automobile, the steps are as follows:

[0006] S1. Signal acquisition: the vehicle control unit collects the longitudinal acceleration signal, output shaft speed signal and activation conditions for downhill braking energy feedback torque calculation in real time;

[0007] S2. Calculate the slope. The vehicle control unit calculates the slope signal θ and the downhill slope θ based on the longitudinal acceleration signal and the output shaft speed signal. dwn ;

[0008] S3. Determine the activation conditions. The vehicle control unit determines whether the vehicle state meets the activation conditions and the setting requirements of the slope signal. If so, the downhill braking energy feedback torque calculation is activated. If not, the downhill braking energy feedback torque is 0.

[0009] S4. Calculate the downhill braking energy feedback torque factor, and the vehicle control unit determines the downhill braking energy feedback torque factor according to the fuzzy control system;

[0010] S5. Calculate the downhill braking energy feedback torque. The vehicle control unit looks up a two-dimensional table according to the downhill braking energy feedback torque factor and the speed of the drive motor to obtain the downhill braking energy feedback torque, so that the vehicle runs according to the energy feedback torque. The two-dimensional table is a two-dimensional table of the relationship between the downhill braking energy feedback torque factor and the speed of the drive motor determined by calibration.

[0011] Furthermore, the activation conditions include the key switch state, handle position, vehicle power system state, accelerator pedal position, brake pedal position, brake pedal position signal validity state, slope signal, and request to prohibit braking energy feedback function. If the above activation conditions all meet the set requirements, the downhill braking energy feedback torque calculation is activated. If any one of the conditions is not met, the downhill braking energy feedback torque is 0.

[0012] Furthermore, the activation conditions need to meet the following requirements: the key switch state is "ON", the vehicle power system state is activated, the handle position is "D" or "R", the accelerator position is 0, the brake pedal position is greater than 0, the brake pedal position signal is valid, the slope signal is less than the set threshold, and the request to prohibit the braking energy feedback function is 0.

[0013] Furthermore, in S4, the specific steps of the vehicle control unit determining the downhill braking energy feedback torque factor according to the fuzzy control system are as follows:

[0014] 1) Variable input, the vehicle control unit will downhill slope θ dwn , brake pedal position BP, and the maximum charging power of the high-voltage battery are used as inputs of the fuzzy control system of the downhill braking energy feedback torque factor;

[0015] 2) Fuzzify variables and determine the membership function of input and output:

[0016] The downhill slope is divided into three subsets {S, M, B}, with the domain being [0,1], where S represents a small downhill slope, M represents a medium downhill slope, and B represents a large downhill slope;

[0017] The brake pedal position BP is divided into three subsets {L, M, H}, with the domain being [0,1], where L represents the low brake pedal position, M represents the middle brake pedal position, and H represents the high brake pedal position;

[0018] The maximum charging power P of the high-voltage battery is divided into four subsets {Z, S, M, B}, and the domain is [0,150], where Z represents the maximum charging power of the high-voltage battery is zero, L represents the maximum charging power of the high-voltage battery is small, M represents the maximum charging power of the high-voltage battery is medium, and H represents the maximum charging power of the high-voltage battery is large;

[0019] The downhill braking energy feedback torque factor K is divided into five subsets {Z, VS, S, M, B, VB}, with a domain of [0,1], where Z represents a downhill braking energy feedback torque factor of zero, VS represents a very small downhill braking energy feedback torque factor, S represents a small downhill braking energy feedback torque factor, M represents a moderate downhill braking energy feedback torque factor, B represents a large downhill braking energy feedback torque factor, and VB represents a very large downhill braking energy feedback torque factor;

[0020] 3) Generate a fuzzy control rule base, and the vehicle control unit obtains the corresponding fuzzy control rule base according to the membership function;

[0021] 4) Output fuzzy quantity K. The vehicle control unit can obtain the fuzzy quantity K of the downhill braking energy feedback torque factor according to the input quantity and the fuzzy control rule library;

[0022] 5) Defuzzification: The fuzzy quantity K is defuzzified using the centroid method, and the fuzzy quantity K is converted into an actual value through inverse mapping of the membership function.

[0023] Furthermore, the slope signal θ and the downhill slope θ dwn The calculation of is as follows,

[0024] 1) The vehicle control unit collects longitudinal acceleration signals and output shaft speed signals in real time;

[0025] 2) The vehicle control unit performs differential processing on the output shaft speed to obtain the output shaft speed slope, and the original slope θ is obtained by calculating the difference between the longitudinal acceleration and the output shaft speed slope raw ;

[0026] 3) The vehicle control unit calculates the original slope θ raw Normalization is performed to obtain the slope signal θ. When the slope signal θ is positive or 0, the downhill slope θ dwn Equal to 0, when the slope signal θ is negative, the downhill slope θ dwn Equal to the absolute value of the slope signal θ.

[0027] Furthermore, the fuzzy control rule base is shown in the following table:

[0028]

[0029]

[0030] Furthermore, the membership of the downhill slope, the brake pedal position BP and the high-voltage battery maximum charging power P all adopt a trapezoidal type, and the membership of the downhill braking energy feedback torque factor K adopts a Gaussian type.

[0031] Beneficial effects of adopting the above technical solution:

[0032] The present invention calculates the downhill braking energy feedback torque factor using a fuzzy control system according to the downhill slope, the brake pedal position, and the maximum charging power of the high-voltage battery, and calculates the downhill braking energy feedback torque according to the downhill braking energy feedback torque factor and the driving motor speed. The safety and stability of the vehicle in downhill braking conditions can be improved, and the efficiency of the vehicle's braking energy feedback can be improved, thereby improving the vehicle's endurance and improving the vehicle's driving comfort.

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic structural diagram of a dual-motor hybrid vehicle according to an embodiment of the present invention;

[0035] Figure 2 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0036] See also Figure 1 , is a schematic diagram of the structure of a hybrid vehicle implementing the present invention, comprising an engine 1, a clutch 2, a generator 3, a transmission 4, a drive motor 5, a reducer 6, wheels 8, and a high-voltage battery 9 (exceeding a safety voltage of 60V and lower than 1000V), wherein the engine 1 is connected to the generator 3 through a primary reduction gear, the engine 1 and the generator 3 are connected to the input shaft of the transmission 4 through the clutch 2, the drive motor 5 is coupled to the reducer through a primary reduction gear, the output end of the transmission 4 is connected to the vehicle 8 through the reducer 6, and the high-voltage battery 9 is respectively connected to the generator 3 and the drive motor 5 through high-voltage wires.

[0037] See also Figure 2 The method for calculating the downhill braking energy feedback torque of the hybrid vehicle mentioned above comprises the following steps:

[0038] S1. Signal acquisition: The vehicle control unit obtains the key switch status, accelerator pedal position signal, brake pedal position signal, and the effective status of the brake pedal position signal through the key switch, accelerator pedal position sensor, and brake pedal position sensor; the vehicle control unit obtains the handle position signal from the electronic shifter through the controller area network bus, obtains the longitudinal acceleration signal from the body stability control unit, obtains the output shaft speed signal from the transmission control unit, and obtains the maximum charging power of the high-voltage battery from the high-voltage battery control unit; the vehicle control unit obtains the activation status of the vehicle power system and the request to prohibit the braking energy feedback function from the internal vehicle working mode management module and the fault diagnosis processing module respectively.

[0039] S2. Calculate the slope:

[0040] 1) The vehicle control unit performs differential processing on the output shaft speed to obtain the output shaft speed slope, and the original slope θ is obtained by calculating the difference between the longitudinal acceleration and the output shaft speed slope raw ;

[0041] 2) The vehicle control unit calculates the original slope θ raw Normalization is performed to obtain the slope signal θ. The physical range of the slope signal θ is [-1, 1], where (0, 1] is uphill, 0 is flat road, and [-1, 0) is downhill. When the slope signal θ is positive or 0, the downhill slope θ dwn Equal to 0, when the slope signal θ is negative, the downhill slope θ dwn Equal to the absolute value of the slope signal θ.

[0042] S3. Determine the activation conditions. The vehicle control unit determines whether the vehicle status meets the activation conditions. The requirements for each activation condition are as follows:

[0043] The key switch state is "ON", the vehicle power system state is activated, the handle position is "D" or "R", the accelerator position is 0, the brake pedal position is greater than 0, the brake pedal position signal is valid, the slope signal θ is less than the set threshold (for example: the set threshold is -0.05), and the request to prohibit the braking energy feedback function is 0;

[0044] If all the above activation conditions meet the set requirements, the downhill braking energy feedback torque calculation is activated. If any one of the conditions is not met, the downhill braking energy feedback torque is 0.

[0045] S4. Calculate the downhill braking energy feedback torque factor. The vehicle control unit determines the downhill braking energy feedback torque factor according to the fuzzy control system. The specific steps are as follows:

[0046] 1) Variable input, the vehicle control unit will downhill slope θ dwn , brake pedal position BP, and high-voltage battery maximum charging power P are used as inputs of the downhill braking energy feedback torque factor fuzzy control system;

[0047] 2) Fuzzify variables and determine the membership function of input and output:

[0048] The downhill slope is divided into three subsets {S, M, B}, with the domain of [0,1], and the membership degree adopts a trapezoidal type, where S represents a small downhill slope, M represents a medium downhill slope, and B represents a large downhill slope;

[0049] The brake pedal position BP is divided into three subsets {L, M, H}, with the domain of [0,1], and the membership degree adopts a trapezoidal type, where L represents the low brake pedal position, M represents the middle brake pedal position, and H represents the high brake pedal position;

[0050] The maximum charging power P of the high-voltage battery is divided into four subsets {Z, S, M, B}, with a domain of [0,150], and the membership degree adopts a trapezoidal type, where Z represents the maximum charging power of the high-voltage battery is zero, L represents the maximum charging power of the high-voltage battery is small, M represents the maximum charging power of the high-voltage battery is medium, and H represents the maximum charging power of the high-voltage battery is large;

[0051] The downhill braking energy feedback torque factor K is divided into five subsets {Z, VS, S, M, B, VB}, the domain is [0,1], and the membership degree adopts Gaussian type, among which Z represents the downhill braking energy feedback torque factor is zero, VS represents the downhill braking energy feedback torque factor is very small, S represents the downhill braking energy feedback torque factor is small, M represents the downhill braking energy feedback torque factor is moderate, B represents the downhill braking energy feedback torque factor is large, and VB represents the downhill braking energy feedback torque factor is very large;

[0052] 3) Generate a fuzzy control rule base. The vehicle control unit obtains the corresponding fuzzy control rule base according to the membership function, as shown in Table 1:

[0053] Table 1, Fuzzy control rule base

[0054]

[0055] 4) Output fuzzy quantity K. The vehicle control unit can obtain the fuzzy quantity K of the downhill braking energy feedback torque factor according to the input quantity and the fuzzy control rule library;

[0056] 5) Defuzzification: The fuzzy quantity K is defuzzified using the centroid method, and the fuzzy quantity K is converted into an actual value through inverse mapping of the membership function.

[0057] S5. Calculate the downhill braking energy feedback torque. The vehicle control unit looks up the two-dimensional table according to the downhill braking energy feedback torque factor and the speed of the drive motor to obtain the downhill braking energy feedback torque, so that the vehicle runs according to the energy feedback torque. The two-dimensional table is a two-dimensional table of the relationship between the downhill braking energy feedback torque factor and the speed of the drive motor determined by calibration. The two-dimensional table of the downhill braking energy feedback torque factor K and the speed N of the drive motor in this embodiment is shown in Table 2.

[0058] Table 2. Two-dimensional table of the relationship between downhill braking energy feedback torque factor K and drive motor speed N

[0059]

[0060] The present invention calculates the downhill braking energy feedback torque factor using a fuzzy control system according to the downhill slope, the brake pedal position, and the maximum charging power of the high-voltage battery, and calculates the downhill braking energy feedback torque according to the downhill braking energy feedback torque factor and the driving motor speed. This is beneficial to improving the safety and stability of the vehicle under downhill braking conditions, improving the vehicle's braking energy feedback efficiency, improving the vehicle's endurance, and improving the vehicle's driving comfort.

[0061] The above is a detailed description of the present technical solution. It should be understood that due to the limitations of text and the diversity of technical solutions, technicians in this field can also implement the present technical solution by replacing the text, grammar or other equivalents of the present technical solution. Therefore, such replacements should be deemed to be within the scope of protection of this application.

Claims

1. A method for calculating the downhill braking energy feedback torque of a vehicle, characterized in that Here are the steps: S1. Signal acquisition: the vehicle control unit collects the longitudinal acceleration signal, output shaft speed signal and activation conditions for downhill braking energy feedback torque calculation in real time; S2. Calculate the slope. The vehicle control unit calculates the slope signal θ and the downhill slope θ based on the longitudinal acceleration signal and the output shaft speed signal. dwn ; S3. Determine the activation conditions. The vehicle control unit determines whether the vehicle state meets the activation conditions and the setting requirements of the slope signal. If so, the downhill braking energy feedback torque calculation is activated. If not, the downhill braking energy feedback torque is 0. S4. Calculate the downhill braking energy feedback torque factor. The vehicle control unit determines the downhill braking energy feedback torque factor according to the fuzzy control system. The specific steps are as follows: 1) Variable input, the vehicle control unit will downhill slope θ dwn , brake pedal position BP, and the maximum charging power of the high-voltage battery are used as inputs of the fuzzy control system of the downhill braking energy feedback torque factor; 2) Fuzzify variables and determine the membership function of input and output: The downhill slope is divided into three subsets {S, M, B}, with the domain being [0,1], where S represents a small downhill slope, M represents a medium downhill slope, and B represents a large downhill slope; The brake pedal position BP is divided into three subsets {L, M, H}, with the domain being [0,1], where L represents the low brake pedal position, M represents the middle brake pedal position, and H represents the high brake pedal position; The maximum charging power P of the high-voltage battery is divided into four subsets {Z, S, M, B}, with a domain of [0,150], where Z represents the maximum charging power of the high-voltage battery is zero, S represents the maximum charging power of the high-voltage battery is small, M represents the maximum charging power of the high-voltage battery is medium, and B represents the maximum charging power of the high-voltage battery is large; The downhill braking energy feedback torque factor K is divided into five subsets {Z, VS, S, M, B, VB}, with a domain of [0,1], where Z represents a downhill braking energy feedback torque factor of zero, VS represents a very small downhill braking energy feedback torque factor, S represents a small downhill braking energy feedback torque factor, M represents a moderate downhill braking energy feedback torque factor, B represents a large downhill braking energy feedback torque factor, and VB represents a very large downhill braking energy feedback torque factor; 3) Generate a fuzzy control rule base. The vehicle control unit obtains the corresponding fuzzy control rule base according to the membership function. The fuzzy control rule base is shown in the following table: ; 4) Output fuzzy quantity K. The vehicle control unit can obtain the fuzzy quantity K of the downhill braking energy feedback torque factor according to the input quantity and the fuzzy control rule library; 5) Defuzzification: Defuzzify the fuzzy quantity K using the centroid method, and transform the fuzzy quantity K into the actual value through the inverse mapping of the membership function; S5. Calculate the downhill braking energy feedback torque. The vehicle control unit looks up a two-dimensional table according to the downhill braking energy feedback torque factor and the speed of the drive motor to obtain the downhill braking energy feedback torque, so that the vehicle runs according to the energy feedback torque. The two-dimensional table is a two-dimensional table of the relationship between the downhill braking energy feedback torque factor and the speed of the drive motor determined by calibration.

2. The method for calculating the downhill braking energy feedback torque of an automobile according to claim 1, characterized in that: The activation conditions include the key switch state, handle position, vehicle power system state, accelerator pedal position, brake pedal position, brake pedal position signal validity state, slope signal, and request to prohibit braking energy feedback function. If all of the above activation conditions meet the set requirements, the downhill braking energy feedback torque calculation is activated. If any one of the conditions is not met, the downhill braking energy feedback torque is 0.

3. The method for calculating the downhill braking energy feedback torque of an automobile according to claim 2, characterized in that: The activation conditions must meet the following requirements: the key switch state is "ON", the vehicle power system state is activated, the handle position is "D" or "R", the accelerator position is 0, the brake pedal position is greater than 0, the brake pedal position signal is valid, the slope signal is less than the set threshold, and the request to prohibit the braking energy feedback function is 0.

4. The method for calculating the downhill braking energy feedback torque of an automobile according to claim 1, characterized in that: The slope signal θ and the downhill slope θ dwn The calculation of is as follows, 1) The vehicle control unit collects longitudinal acceleration signals and output shaft speed signals in real time; 2) The vehicle control unit performs differential processing on the output shaft speed to obtain the output shaft speed slope, and the original slope θ is obtained by calculating the difference between the longitudinal acceleration and the output shaft speed slope. raw ; 3) The vehicle control unit calculates the original slope θ raw Normalization is performed to obtain the slope signal θ. When the slope signal θ is positive or 0, the downhill slope θ dwn Equal to 0, when the slope signal θ is negative, the downhill slope θ dwn Equal to the absolute value of the slope signal θ.

5. The method for calculating the downhill braking energy feedback torque of an automobile according to claim 1, characterized in that: The membership of the downhill slope, the brake pedal position BP and the high-voltage battery maximum charging power P all adopt a trapezoidal type, and the membership of the downhill braking energy feedback torque factor K adopts a Gaussian type.

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