Off-road vehicle dwell pressure self-adaptive calculation method and electronic parking system

Abstract

The invention relates to the technical field of vehicle control, in particular to an off-road vehicle dwell pressure self-adaptive calculation method and an electronic parking system. The self-adaptive calculation method provided by the invention can accurately calculate and adapt to different loads, gradients and vehicle conditions according to different road gradients and vehicle driving modes, ensures that the electronic parking system always provides proper dwell pressure under complex working conditions, effectively avoids the vehicle sliding risk caused by insufficient pressure or brake loss caused by overlarge pressure, and improves the safety and reliability of the electronic parking system. And the parking stability and reliability are obviously improved. According to the self-adaptive calculation method provided by the invention, by constructing a parameter adjustment function, depending on the whole vehicle mass and the temperature sensor real-time sensing technology, the change of parameters such as the vehicle load, the transmission system state, the brake temperature and the accumulative mileage is dynamically responded, the material characteristic attenuation coefficient of the brake friction plate is comprehensively considered, and the pressure maintaining pressure is automatically adjusted; and the parking safety of the vehicle is improved while the parking potential safety hazard is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the field of vehicle control technology, and in particular to an adaptive calculation method for pressure maintaining pressure of an off-road vehicle and an electronic parking system. Background Art

[0002] In today's booming automotive industry, the performance and convenience of vehicle parking systems have become a focus of attention. This is why the Auto Hold system (AUTO HOLD) has emerged. By precisely controlling the brake fluid pressure at all four wheels, the friction pads and brake discs are tightly clamped together, smoothly completing the parking maneuver. This process eliminates the need for the driver to continuously apply the brake pedal, significantly improving driving convenience and safety. The Auto Hold system operates based on advanced sensor technology and electronic control systems. This function activates when the vehicle is temporarily parked and is expected to be restarted within a short period of time. At this point, a series of sensors, including the vehicle leveling sensor and wheel torque sensors, are activated, collecting real-time vehicle data and transmitting this data to the vehicle's electronic control unit (ECU). Based on this data, the ECU accurately determines the vehicle's tendency to roll and then issues commands to the braking system, applying the appropriate braking force to stop the vehicle. This braking force is carefully designed to effectively prevent the vehicle from moving, but not so strong that it would cause the vehicle to lurch forward if the driver presses the accelerator again, thus ensuring a smooth and comfortable ride.

[0003] Taking a four-wheel drive off-road vehicle as an example, its transfer case drive system typically features multiple modes, including 2H (low-speed 2WD), 4H (high-speed 4WD), and 4L (low-speed 4WD). The vehicle's idle torque varies depending on the mode. 2H mode has lower idle torque, while 4H high-speed 4WD systems have slightly higher idle torque. In contrast, 4L low-speed 4WD systems, due to the increased transfer case ratio, significantly increase the torque delivered to the wheels at the same engine idle torque, resulting in significantly higher idle torque. This means that when the automatic parking system is parked, a uniform holding pressure setting cannot be used to prevent the vehicle from rolling away. Specifically, the holding pressure of the automatic parking system needs to be adjusted based on the different modes, with separate holding pressure settings for each mode.

[0004] Currently, existing technologies for setting the holding pressure of automatic parking systems are often relatively simple, failing to flexibly and accurately adjust the system to the vehicle's different drive modes and actual operating conditions. When faced with vehicles like four-wheel drive off-road vehicles, which have multiple drive modes and significantly different idle torques, traditional methods for setting the holding pressure of automatic parking systems are insufficient, which can easily lead to safety hazards such as vehicle rollaway and power supply problems when restarting the vehicle, seriously affecting the driving experience and safety.

[0005] Chinese patent document CN114954396A discloses a "redundant parking control method and controller for new energy vehicles." This method, which measures vehicle speed and brake fluid pressure in real time, determines the current slope when the driver intends to park. If the current slope is less than a first threshold, the system enters normal parking mode, using the automatic parking system to achieve parking. If the current slope is greater than or equal to the first threshold and less than a second threshold, the system enters redundant parking mode, using the automatic parking system and controlling the drive motor speed to achieve parking. If the current slope is greater than or equal to the second threshold and less than a third threshold, the system enters forced parking mode, using the automatic parking system and the electronic parking brake to achieve parking. The main shortcomings of this technology include: first, the inability to adaptively calculate the holding pressure based on road slope and vehicle driving mode, resulting in significant brake wear; second, the system fails to consider vehicle mass, slope, idle torque, drivetrain efficiency, and brake temperature decay, resulting in an unreasonable holding pressure setting. Summary of the Invention

[0006] Technical purpose: In order to overcome the deficiencies in the prior art, the present invention provides an adaptive calculation method for holding pressure of an off-road vehicle and an electronic parking system to solve the problems raised in the background technology.

[0007] Technical solution: To achieve the above purpose, the present invention discloses an adaptive calculation method for off-road vehicle pressure maintaining pressure, which is used to calculate the pressure of the off-road vehicle. α The pressure maintaining system of the electronic parking system for a car with slope parking is characterized by including: [S1] Establish the formula for calculating the relevant parameters of the holding pressure: [S1.1] Calculate the sliding force generated by the vehicle mass , as shown in Formula 1: Formula 1; in, G is the vehicle mass, unit Kg, α is the slope angle, unit: °; [S1.2] Calculate the vehicle traction caused by idle torque , as shown in Formula 2: Formula 2; in, is the idling torque, unit N, is the gearbox ratio, is the main reduction ratio, is the transfer case speed ratio, R is the wheel radius, unit m , η is the real-time efficiency of the transmission system, and the calculation method is shown in Formula 3; Formula 3; Wherein, is the transmission reference efficiency, taking the calibration value under the normal temperature and no-load condition; is the torque correction coefficient, the calculation formula is , is the rated idle torque, unit N; is the temperature correction coefficient, the calculation formula is , is the real-time temperature of the transmission system obtained through the oil temperature sensor, unit ℃; is the wear compensation coefficient, the calculation formula is , S is the cumulative mileage of the vehicle, unit km; [S1.3] Calculate the front axle braking force As shown in formula 4: Formula 4; Wherein, p is the holding pressure, unit MPa, is the front wheel brake cylinder diameter, unit m , is the number of front wheel brake cylinders, is the front brake efficiency factor, and is the effective radius of the front brake, unit m ; [S1.4] Calculate the rear axle braking force As shown in formula 5: Formula 5; Wherein, is the rear wheel brake cylinder diameter, unit m , is the number of rear wheel brake cylinders, is the rear brake efficiency factor, is the effective radius of the rear brake, unit m ; [S2] Parking scene analysis and holding pressure calculation, the parking dynamics formula is shown in formula 6: Downward force generated by the vehicle mass + Car traction force caused by idle torque = (Front axle braking force + Rear axle braking force ) × Temperature attenuation coefficient Formula 6; The temperature attenuation coefficient calculation method is: Formula 7; Wherein, TThe brake real-time temperature is in ℃, which is obtained by the brake temperature sensor; T 0 The reference temperature is 25 ℃, which is the calibration value under normal temperature conditions; The brake friction plate temperature attenuation coefficient is determined by the brake friction plate material characteristics; The formula 1, formula 2, formula 4, formula 5, formula 7 are substituted into formula 6, and after conversion, it is shown in formula 8: Formula 8; [S3] The pressure maintaining pressure calculation with a safety factor, the Theoretical minimum value of the automobile electronic parking system pressure maintaining pressure; in order to ensure the safety of the automobile parking, a safety factor greater than 1 is multiplied on the basis of The pressure maintaining pressure calculation formula with a safety factor is shown in formula 9: Formula 9.

[0008] Further, the whole vehicle mass in step [S1.1] G is collected in real time by the strain gauge sensor array distributed in the vehicle body suspension, and the sampling frequency is not less than 12 Hz.

[0009] Further, the transmission system reference efficiency in step [S1.2] The value range is .

[0010] Further, the brake friction plate temperature attenuation coefficient in step [S2] When the brake friction plate material is ceramic-based, the value range is 0.52-0.78; when the brake friction plate material is semi-metal-based, the value range is 0.93-1.17.

[0011] Further, the value range of the safety factor in formula 9 is: .

[0012] Further, the value function of the floating safety factor is established with the change of the slope inclination angle α When α is large, the value tends to 1.2 infinitely; when α is small, the value tends to 1 infinitely; as shown in formula 10: Formula 10; Wherein, the value range of the slope inclination angle α is: .​

[0013] An off-road vehicle electronic parking system characterized in that the adaptive calculation method of any one of claims 1-6 is applied to calculate the parking pressure.

[0014] The beneficial effects of the present application are: 1. The off-road vehicle parking pressure adaptive calculation method provided by the present application can accurately calculate the adaptation to different loads, slopes and vehicle conditions according to the road slope and the different vehicle driving modes, ensure that the electronic parking system always provides appropriate parking pressure under complex working conditions, effectively avoids the risk of vehicle sliding caused by insufficient pressure or brake wear caused by excessive pressure, and significantly improves the parking stability and reliability.

[0015] 2. The off-road vehicle parking pressure adaptive calculation method provided by the present application constructs a parameter adjustment function, which approaches 1 in a small angle scene and approaches 1.2 in a large angle scene, ensuring that in a large angle and low friction limit state, both energy waste and component wear caused by pressure redundancy on a small slope are avoided, and sufficient safety reserves are provided in high-risk scenes such as large slopes.

[0016] 3. The off-road vehicle parking pressure adaptive calculation method provided by the present application relies on real-time sensing technology of vehicle mass and temperature sensor, dynamically responds to changes in vehicle load, transmission system state, brake temperature, cumulative mileage and other parameters, comprehensively considers the friction material characteristic attenuation coefficient of the brake, and automatically adjusts the parking pressure, thereby significantly reducing parking safety hazards while improving vehicle parking safety. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0018] Figure 1 It is an off-road vehicle parking pressure adaptive calculation method flowchart; Figure 2 It is an off-road vehicle parking pressure adaptive calculation force analysis diagram. DETAILED DESCRIPTION

[0019] The following will be described in conjunction with the accompanying Figure 1 to the accompanying Figure 2 The principles and characteristics of the present application are described, and the examples are only used to explain the present application, and not to limit the scope of the present application.

[0020] Embodiment 1 is an off-road vehicle parking pressure adaptive calculation method for calculating the parking pressure of an off-road vehicle inα The holding pressure of the electronic hill hold system of the car is shown as Figure 1 [S1] Establish the formula of the holding pressure calculation related parameters: [S1.1] Calculate the downhill force generated by the vehicle mass As shown in formula 1: Formula 1; Wherein, G M is the vehicle mass, unit Kg, α is the slope angle, unit °; [S1.2] Calculate the car traction force caused by idle torque As shown in formula 2: Formula 2; Wherein, T is the idle torque, unit N, is the transmission speed ratio, is the main reduction ratio, is the transfer case speed ratio, R is the wheel radius, unit m , η is the real-time efficiency of the transmission system, and the calculation method is shown in formula 3; Formula 3; Wherein, is the reference efficiency of the transmission system, and the value is the calibration value under the normal temperature and empty load condition; is the torque correction coefficient, and the calculation formula is , is the rated idle torque, unit N; is the temperature correction coefficient, and the calculation formula is , is the real-time temperature of the transmission system obtained through the oil temperature sensor, unit ℃; is the wear compensation coefficient, and the calculation formula is , S is the cumulative mileage of the vehicle, unit km; In this step, η The real-time efficiency formula of the transmission system realizes the real-time correction of the transmission system efficiency by introducing three types of dynamic parameters of torque, temperature and wear. Among them, the reference efficiency ensure the rationality of the theoretical basis, the torque correction coefficient reflects the influence of load change on efficiency, the temperature correction coefficient compensates the influence of lubricating oil performance degradation at high temperature, and the wear compensation coefficient adapts to the change of mechanical loss after long-term use, which is consistent with the dynamic change law of the efficiency of the automobile transmission system with working condition.

[0021] [S1.3] Calculate the front axle braking force​ , as shown in Formula 4: Formula 4; in, p is the holding pressure, unit is MPa, is the front wheel brake cylinder diameter, unit m , is the number of front wheel brake cylinders, is the front brake efficiency factor, is the effective radius of the front brake, unit m ; [S1.4] Calculate the rear axle braking force , as shown in Formula 5: Formula 5; in, is the rear wheel brake cylinder diameter, unit m , is the number of rear wheel brake cylinders, is the rear brake efficiency factor, is the effective radius of the rear brake, unit m ; [S2] Parking scenario analysis and pressure holding pressure calculation, such as Figure 2 As shown, the parking dynamics formula is shown in Formula 6: Sliding force generated by the vehicle's mass + Car pulling force due to idle torque =(front axle braking force +Rear axle braking force )×temperature attenuation coefficient Formula 6; The temperature attenuation coefficient is calculated as: Formula 7; in, T The real-time temperature of the brake, in °C, is obtained through the brake temperature sensor; T 0 The reference temperature is 25℃, which is the calibration value under normal temperature conditions; is the brake friction pad temperature attenuation coefficient, which is determined by the brake friction pad material properties; In Formula 6, the front and rear axle braking forces are multiplied by the temperature attenuation coefficient. This is because the front wheel brakes will heat up due to friction during operation, especially during frequent braking or long downhill parking. The friction pad material of the brake has a thermal decay characteristic - rising temperature will reduce the friction coefficient, thereby reducing the braking force efficiency. The temperature attenuation coefficient (λ tIt is just for quantifying the degree of brake force attenuation caused by temperature change, by real-time correction of the calculated value of front axle brake force, to ensure that the actual braking capacity can still be accurately evaluated under high temperature working condition, to avoid the risk of parking failure caused by thermal decay.

[0022] Substitute formula 1, formula 2, formula 4, formula 5, formula 7 into formula 6, and the conversion is shown in formula 8: Formula 8; The actual vehicle parameters shown in Table 1 are introduced below and applied to formula 8 to calculate the actual pressure holding pressure value: Table 1: Vehicle actual parameters and calculation results , It should be emphasized here that due to the difference in the differential case speed ratio i AWD of the 2H / 4H and 4L driving modes, there is a significant difference in the calculated pressure holding pressure value under the two driving modes, that is, different pressure holding parameters are used according to the differential case speed ratio i AWD . Substitute the parameters in Table 1 into formula 1- formula 8, and the calculation results are shown in Table 2: Table 2: Pressure holding pressure calculation results; , PSI (Pounds per square Inch) is a pressure unit commonly used in Europe and the United States, 1 psi ≈6.895 KPa (KiloPascal) ≈6894.757 Pa (Pascal), and the calculation results after unit conversion are shown in Table 3: Table 3: Pressure holding pressure calculation results after unit conversion; , [S3] Pressure holding pressure calculation with safety factor, the calculated by formula 8 is the minimum value of the theoretical pressure holding pressure of the automobile electronic parking system; to ensure the safety of the automobile parking, a safety factor greater than 1 is multiplied on the basis of when the vehicle is stationary; The pressure holding pressure calculation formula with safety factor is shown in formula 9: Formula 9; The value range of the safety factor in formula 9 is: To ensure the safety rate of slope parking, a floating safety factor value function is established with the change of slope inclination angle α , when α is large, the value tends to 1.2; when α is small, The value approaches 1 infinitely; as shown in formula 10: The value range of the slope inclination angle α is: .

[0023] In formula 10, the sine trigonometric function is used to control the initial growth rate, the tan function monotonically increases from 0 to 1 in the interval of 0 to 45, and the growth is slow in the early stage and fast in the later stage, which meets the “slow start” characteristics at low angles. The exponential function controls the medium growth rate, and the effect is to make the curve show a more obvious upward trend in the middle stage (15°~30°). The natural logarithm limits the growth amplitude in the later stage, and the effect is to constrain the growth rate of the function in the later stage, and ensure that it finally converges to 1.2 stably. The product of the three eventually forms a continuous, monotonic, and reasonable curve that changes from (0, 1) to (45, 1.2), which adapts to the influence law of the slope change on the result.

[0024] The slope angle α=20° in table 1 is substituted into formula 10, and the calculation result is shown in table 4: Table 4: Calculation results of pressure maintaining pressure with safety factor , Embodiment 2 is an off-road vehicle electronic parking system, which applies the adaptive calculation method of any one of claims 1-6 to calculate the parking pressure maintaining pressure; the whole calculation process has been described in detail in embodiment 1, and will not be repeated here.

[0025] The above only describes the preferred embodiments of the present application, and does not limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.​

Claims

1. An adaptive calculation method for off-road vehicle pressure maintenance pressure, used to calculate α The maintaining pressure of the electronic parking system of the car for slope parking is characterized by: include: [S1] Establish the formula for calculating the relevant parameters of the holding pressure: [S1.1] Calculate the sliding force generated by the vehicle mass , as shown in Formula 1: Formula 1: in, G is the vehicle mass, unit Kg, α is the slope angle, unit: °; [S1.2] Calculate the vehicle traction caused by idle torque , as shown in Formula 2: Formula 2: in, is the idling torque, unit N, is the gearbox ratio, is the main reduction ratio, is the transfer case speed ratio, R is the wheel radius, unit m , η is the real-time efficiency of the transmission system, and the calculation method is shown in Formula 3; Formula 3: in, is the base efficiency of the transmission system, which is the calibrated value at room temperature and no-load condition; is the torque correction coefficient, and the calculation formula is , is the rated idle torque, unit N; is the temperature correction coefficient, and the calculation formula is , The real-time temperature of the transmission system obtained by the oil temperature sensor, unit: °C; is the wear compensation coefficient, and the calculation formula is , S The cumulative mileage of the vehicle, in km; [S1.3] Calculate the front axle braking force , as shown in Formula 4: Formula 4: in, p is the holding pressure, unit is MPa, is the front wheel brake cylinder diameter, unit m , is the number of front wheel brake cylinders, is the front brake efficiency factor, is the effective radius of the front brake, unit m ; [S1.4] Calculate the rear axle braking force , as shown in Formula 5: Formula 5: in, is the rear wheel brake cylinder diameter, unit m , is the number of rear wheel brake cylinders, is the rear brake efficiency factor, is the effective radius of the rear brake, unit m ; [S2] Parking scenario analysis and holding pressure calculation. The parking dynamics formula is shown in Formula 6: Sliding force generated by the vehicle's mass + Car pulling force due to idle torque =(front axle braking force +Rear axle braking force )×temperature attenuation coefficient Formula 6; The temperature attenuation coefficient is calculated as: Formula 7; in, T The real-time temperature of the brake, in °C, is obtained through the brake temperature sensor; T 0 The reference temperature is 25℃, which is the calibration value under normal temperature conditions; is the brake friction pad temperature attenuation coefficient, which is determined by the brake friction pad material properties; Substituting Formula 1, Formula 2, Formula 4, Formula 5, and Formula 7 into Formula 6, the conversion is as shown in Formula 8: Formula 8: [S3] Calculation of holding pressure with safety factor, calculated by formula 8 Theoretically, the minimum pressure of the electronic parking system is maintained. To ensure the parking safety of the vehicle, the vehicle is kept stationary. Multiply the basis by a safety factor greater than 1 The calculation formula for holding pressure with a safety factor is shown in Formula 9: Formula 9.

2. The adaptive calculation method for holding pressure of an off-road vehicle according to claim 1, characterized in that: The vehicle mass described in step [S1.1] G The data is collected in real time through the strain gauge sensor array distributed on the vehicle body suspension, with a sampling frequency of no less than 12Hz.

3. The adaptive calculation method for holding pressure of an off-road vehicle according to claim 1, characterized in that: The transmission system baseline efficiency described in step [S1.2] The value range is .

4. The adaptive calculation method for holding pressure of an off-road vehicle according to claim 1, characterized in that: Step [S2] The brake friction plate temperature attenuation coefficient When the brake friction pad material is ceramic-based, the value range is 0.52~0.78; when the brake friction pad material is semi-metal-based, the value range is 0.93~1.

17.

5. The adaptive calculation method for holding pressure of an off-road vehicle according to claim 1, characterized in that: Safety factor described in formula 9 The value range is: .

6. The adaptive calculation method for holding pressure of an off-road vehicle according to claim 5, characterized in that: Establishing the accompanying slope angle α The value function of the variable floating safety factor is α When it is larger, The value approaches 1.2 infinitely; when α When smaller, The value approaches 1 infinitely; as shown in formula 10: Formula 10; Among them, the slope angle α The value range is: .

7. An off-road vehicle electronic parking system, characterized by: The parking pressure maintaining pressure is calculated by applying the adaptive calculation method described in any one of claims 1 to 6.

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