New energy automobile speed calculation method

Abstract

The invention relates to the technical field of new energy automobile control, in particular to a new energy automobile speed calculation method which specifically comprises the following steps that a VCU receives and analyzes basic information serving as vehicle speed calculation; scale quantities of four tires are arranged in the VCU, actual tire radius information is calibrated off line into VCU software according to different tire configurations of different vehicle types of the whole vehicle, and then online VCU software flashing is performed, so that software and hardware matching of the actual tire radius information is realized; the VCU sends a vehicle speed obtained based on a vehicle speed calculation algorithm of the VCU to the ABS through a bus for receiving so as to carry out ABS control; the specific calculation algorithm is decided according to different operation conditions, the vehicle speed algorithm module is provided with a plurality of algorithm units according to the operation conditions, and the problems that in order to guarantee universality, software management cost and part cost, an ABS at the present stage can use one part to adapt to one vehicle type or even different vehicle types, and the cost is low are solved. Therefore, one set of software cannot meet the requirements of different vehicle types.

Description

Technical Field

[0001] The invention relates to the technical field of new energy vehicle control, and specifically designs a method for calculating the vehicle speed of a new energy vehicle. Background Art

[0002] Vehicle speed is one of the most important operating information of the vehicle. Drivers will often pay attention to the vehicle speed to control the vehicle to ensure vehicle driving safety. For example, when driving on speed-limited sections of urban roads or cruising on highways, they need to pay attention to the vehicle speed and speed limit signs to drive reasonably. The accuracy of speed information is very important for safe driving. If the speed information is inaccurate or has large deviations, it will seriously affect the vehicle's driving safety and road safety.

[0003] For the whole vehicle control, the vehicle speed affects the driving torque, energy recovery, anti-lock braking control and driving anti-skid control, etc. Different tire specifications require ABS to be recalibrated, otherwise the vehicle speed calculation will be inaccurate. In order to ensure versatility and software management costs as well as component costs, the current ABS will use one component to adapt to one model or even different models, resulting in one set of software being unable to meet the needs of different models. Summary of the invention

[0004] The present invention provides a vehicle speed calculation method for a new energy vehicle. The ABS sends wheel speed information to a bus, and a vehicle controller VCU can perform adaptive calibration according to tire data of different vehicle models, and combine the wheel speed information with tire radius information to obtain a true and accurate vehicle speed of the whole vehicle, thereby helping the driver to understand vehicle information more accurately, providing protection for driving safety, and not increasing the cost of the whole vehicle.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a method for calculating the speed of a new energy vehicle, which specifically includes the following steps:

[0006] Step S1, ABS sends the wheel speed information of the four tires of the whole vehicle to the bus, and the VCU receives and analyzes it as the basic information for calculating the vehicle speed;

[0007] Step S2, the calibration values ​​of four tires are set inside the VCU, namely, the left front wheel radius calibration value FrontLeftWheelRadius_C, the right front wheel radius calibration value FrontRightWheelRadius_C, the left rear wheel radius calibration value RearLeftWheelRadius_C, and the right rear wheel radius calibration value RearRightWheelRadius_C;

[0008] Step S3, according to different tire configurations of different vehicle models, or different tire configurations of the same vehicle model, the actual tire radius information is offline calibrated into the VCU software, and then the VCU software is flashed online to achieve the software and hardware matching of the real tire radius information. The VCU sends the vehicle speed obtained based on its own vehicle speed calculation algorithm to the ABS through the bus to perform ABS control;

[0009] Step S4, adopting a strategy of dynamically deciding which calculation algorithm to use according to different operating conditions, and the vehicle speed algorithm module is provided with a number of algorithm units according to the operating conditions.

[0010] It is further defined that the vehicle speed algorithm module is provided with four algorithm units for vehicle speed calculation, which are respectively a straight-line driving algorithm unit, a turning operation algorithm unit, a high slip rate algorithm unit and a high slip rate algorithm unit according to the operating conditions. For vehicle speed calculation, the vehicle operating conditions are divided into five major categories, namely, straight-line driving, turning, drive slip, braking lock (or slip rate is higher than a threshold) and vehicle speed calculation under fault conditions.

[0011] To further define, the specific control architecture steps are as follows:

[0012] When the vehicle is traveling in a straight line or tending to travel in a straight line, that is, when the steering wheel angle sent by the electric power steering EPS is lower than the threshold, and the driving wheel slip rate and slip rate are both lower than the threshold, this working condition is a straight and stable driving condition, and the vehicle speed will be calculated based on the wheel speed of the driven wheel;

[0013] When the vehicle is not in a straight-line driving state, when the steering wheel angle sent by EPS is greater than the threshold, and the driving wheel slip rate and slip rate are both lower than the threshold, according to the Ackerman steering principle, when the car is turning, the inner and outer wheels turn at different angles, the turning radius of the inner tire is smaller than that of the outer tire, and the turning radius of the outer steering wheel is the largest, so the difference between it and the actual running speed of the vehicle is also the largest, and the turning radius of the inner steering wheel is second, while the driving wheel rotates at a speed relatively closer to the vehicle speed, and is more inclined to linear motion than the steering wheel, so at this time the driving wheel speed should be used as the basic speed for calculating the vehicle speed;

[0014] When the driving wheel slip rate of the vehicle is higher than the threshold, it means that the driving wheel is in a slipping state. When the driving wheel slips, the tire rotation speed is higher than the actual running speed of the vehicle. Therefore, the driving wheel speed should not be used as the basic wheel speed for calculating the vehicle speed, but the driven wheel speed should be used as the basic wheel speed for calculating the vehicle speed.

[0015] When the wheels are locked or the slip rate is higher than the threshold, the rotation speed of the wheel with the slip rate higher than the threshold is lower than the actual running speed of the vehicle. Therefore, the vehicle speed calculation at this time should be based on the wheel speed of the two wheels with the lowest slip rate.

[0016] When the wheel speed sensor fails and ABS cannot send out valid wheel speed information, for the first four major operating conditions, the VCU will adopt a fault degradation processing strategy, that is, based on the four major conventional operating conditions, combined with the information of the faulty wheel speed sensor to decide how to calculate the vehicle speed.

[0017] Further limiting, the specific circumstances for determining whether the wheel speed sensor is faulty are as follows:

[0018] If the wheel speed sensor of a wheel fails, the VCU will further determine whether the wheel speed sensor is the wheel speed sensor information to be used in the four major working conditions. If not, the calculation algorithm of the vehicle speed will continue to be executed according to the established calculation algorithms of the four major working conditions;

[0019] If the faulty wheel speed sensor is the wheel speed sensor required for the four types of working conditions, the VCU will use an alternative wheel speed or a single wheel speed to calculate the vehicle speed.

[0020] It is further defined that for straight-line driving conditions, the normal driven wheel speed and the opposite driving wheel speed will be used to calculate the vehicle speed; for turning conditions, that is, a driving wheel speed sensor fails, the VCU will determine whether the vehicle is turning left or right based on the steering wheel angle information, and use the corresponding inner driven wheel and the normal driving wheel speed as the basic wheel speed information for speed calculation; for driving slip conditions, that is, the driving wheel slip rate is higher than the threshold, and a driven wheel speed sensor fails, then the VCU will use the normal driven wheel speed sensor speed information to calculate the vehicle speed, that is, only one normal driven wheel speed is used to calculate the vehicle speed; for braking lock or slip rate higher than the threshold, the VCU continues to use the wheel speed of the two wheels with the lowest slip rate as the calculation basis to calculate the vehicle speed, so as to obtain a relatively more accurate vehicle speed; if two or more wheel speed sensors fail, the VCU will use an alternative speed calculation algorithm based on different transmission system architectures to calculate the alternative speed of the vehicle.

[0021] It is further limited that the switching between different working conditions will cause the vehicle speed calculation to synchronously switch the wheel speed to be used by the established algorithm. Before the wheel speed is switched, a certain debounce filtering process is required to prevent the calculated vehicle speed from fluctuating due to instantaneous working condition switching or data noise. If the working condition identified by the working condition recognition module is updated, a certain debounce time is required before the speed calculation algorithm for different working conditions can be switched.

[0022] It is further defined that the transition between different vehicle speeds adopts different linear gradients when the vehicle speed increases or decreases slightly before and after the calculation, and the vehicle speed increase gradient and the vehicle speed decrease gradient are set separately. The decision on whether to use the vehicle speed increase gradient or the vehicle speed decrease gradient is made according to the size relationship before and after the vehicle speed calculation. In order to ensure the stability of the vehicle speed display, the median filtering algorithm is used to smooth the initial value of the vehicle speed. The calculation of the driving wheel slip rate and slip rate are both based on the calculated vehicle speed and the wheel speed of a certain wheel. If the vehicle speed is updated, the corresponding driving wheel slip rate and slip rate are updated synchronously.

[0023] The beneficial effects of adopting the above technical solution are:

[0024] The present invention collects the four wheel speed information of the whole vehicle sent by ABS, including the wheel speed information of each tire of the driven wheel and the driving wheel, combines different operating conditions, identifies different conditions to dynamically adjust the vehicle speed calculation algorithm, can not only obtain more accurate vehicle speed information, provide the driver with accurate vehicle body movement reference, provide more accurate data reference for driving safety, but also be compatible with different models and different tire specifications, without increasing the cost of the whole vehicle, thus achieving technical cost reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a control architecture diagram of the present invention;

[0026] Figure 2 It is a control strategy flow chart of the present invention. DETAILED DESCRIPTION

[0027] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0028] The present invention is a method for calculating the speed of a new energy vehicle. Specifically, Figure 1-Figure 2 As shown, the specific steps include:

[0029] Step S1, ABS sends the wheel speed information of the four tires of the whole vehicle to the bus, and the VCU receives and analyzes the information as the basic information for calculating the vehicle speed;

[0030] Step S2, the calibration values ​​of four tires are set inside the VCU, namely, the left front wheel radius calibration value FrontLeftWheelRadius_C, the right front wheel radius calibration value FrontRightWheelRadius_C, the left rear wheel radius calibration value RearLeftWheelRadius_C, and the right rear wheel radius calibration value RearRightWheelRadius_C;

[0031] Step S3, according to different tire configurations of different vehicle models, or different tire configurations of the same vehicle model, the actual tire radius information is offline calibrated into the VCU software, and then the VCU software is flashed online, so as to achieve the software and hardware matching of the real tire radius information, and the speed calculation algorithm of the VCU with a certain robustness is combined to obtain the real and accurate vehicle speed that is compatible with different tire specifications, and then the VCU sends the speed obtained based on its own speed calculation algorithm to the ABS through the bus to receive and perform ABS control. Through adaptive calibration, the ABS can achieve one version of software compatible with different tire specifications, avoiding the problem of increased vehicle cost caused by changing the ABS software;

[0032] Step S4, for the vehicle speed calculation strategy, a strategy of dynamically deciding which specific calculation algorithm to adopt according to different operating conditions is adopted. Under different vehicle operating conditions, the difference between the wheel speed reflected by different tires and the actual vehicle speed is different. Therefore, it is necessary to identify the different operating conditions of the vehicle to decide which algorithm to adopt. The operating condition identification module, the vehicle speed calculation algorithm module and the vehicle speed sending module are set to realize the vehicle speed calculation and use. The vehicle speed algorithm module has four algorithm speed calculation algorithm units, which are respectively a straight-line driving algorithm unit, a turning operation algorithm unit, a high slip rate algorithm unit, and a high slip rate algorithm unit according to the operating conditions. For vehicle speed calculation, the vehicle operating conditions are divided into 5 major categories, namely, straight-line driving, turning, drive slip, braking lock (or slip rate is higher than the threshold) and vehicle speed calculation under fault conditions.

[0033] When the vehicle is traveling in a straight line or tending to travel in a straight line, that is, when the steering wheel angle sent by the electric power steering EPS is lower than the threshold, and the driving wheel slip rate and slip rate are both lower than the threshold, this working condition is a straight and stable driving condition, and the vehicle speed will be calculated based on the wheel speed of the driven wheel;

[0034] When the vehicle is not in a straight-line driving state, when the steering wheel angle sent by EPS is greater than the threshold, and the driving wheel slip rate and slip rate are both lower than the threshold, according to the Ackerman steering principle, when the car is turning, the inner and outer wheels turn at different angles, the turning radius of the inner tire is smaller than that of the outer tire, and the turning radius of the outer steering wheel is the largest, so the difference between it and the actual running speed of the vehicle is also the largest, and the turning radius of the inner steering wheel is second, while the driving wheel rotates at a speed relatively closer to the vehicle speed, and is more inclined to linear motion than the steering wheel, so at this time the driving wheel speed should be used as the basic speed for calculating the vehicle speed;

[0035] When the driving wheel slip rate of the vehicle is higher than the threshold, it means that the driving wheel is in a slipping state. When the driving wheel slips, the tire rotation speed is higher than the actual running speed of the vehicle. Therefore, the driving wheel speed should not be used as the basic wheel speed for calculating the vehicle speed, but the driven wheel speed should be used as the basic wheel speed for calculating the vehicle speed.

[0036] When the wheels are locked or the slip rate is higher than the threshold, the rotation speed of the wheel with the slip rate higher than the threshold is lower than the actual running speed of the vehicle. Therefore, the vehicle speed calculation at this time should be based on the wheel speed of the two wheels with the lowest slip rate.

[0037] When the wheel speed sensor fails and ABS cannot send out valid wheel speed information, for the first four major operating conditions, the VCU will adopt a fault degradation processing strategy, that is, based on the four major conventional operating conditions, combined with the information of the faulty wheel speed sensor to decide how to calculate the vehicle speed.

[0038] If the wheel speed sensor of a wheel fails, the VCU will further determine whether the wheel speed sensor is the wheel speed sensor information to be used in the four major working conditions. If not, the calculation algorithm of the vehicle speed will continue to be executed according to the established calculation algorithms of the four major working conditions;

[0039] If the faulty wheel speed sensor is the wheel speed sensor required for the four types of working conditions, the VCU will use an alternative wheel speed or a single wheel speed to calculate the vehicle speed.

[0040] For straight-line driving conditions, the normal driven wheel speed and the opposite driving wheel speed are used to calculate the vehicle speed, because the opposite driving wheel and the diagonal steering wheel can cover or approach the center of mass of the vehicle, and are also closer to the actual operating state of the vehicle body. Therefore, the normal driven wheel and the opposite driving wheel speed are used to calculate the vehicle speed; for turning conditions, that is, a driving wheel speed sensor fails, then the VCU will determine whether the vehicle is turning left or right based on the steering wheel angle information, and use the corresponding inner driven wheel and the normal driving wheel speed as the basic wheel speed information for speed calculation. The inner driven wheel speed is closer to the actual vehicle speed, so the inner driven wheel speed is used as the alternative wheel speed for speed calculation in this case; for drive slip conditions, that is, the driving wheel slip rate is higher than the threshold, a driven wheel speed If the sensor fails, the VCU will use the normal wheel speed information of the driven wheel speed sensor to calculate the vehicle speed. That is, only one wheel speed sensor is used as the basis to calculate the vehicle speed. The purpose is not to bring into the influence of the drive wheel slip on the vehicle speed calculation. Therefore, only one normal driven wheel speed is used to calculate the vehicle speed. For braking lock or slip rate higher than the threshold, the VCU continues to use the wheel speed of the two wheels with the lowest slip rate as the basis for calculating the vehicle speed, so as to obtain a relatively more accurate vehicle speed. Among them, except for the drive slip condition, the speed calculation algorithm for other conditions is to take the average of the two wheel speeds to be based on. If two or more wheel speed sensors fail, the VCU will use an alternative speed calculation algorithm based on a different transmission system architecture to calculate the alternative speed of the vehicle.

[0041] Switching between different working conditions will cause the vehicle speed calculation to synchronously switch the wheel speed to be used by the established algorithm. Before the wheel speed is switched, a certain debounce filtering process must be performed to prevent the calculated vehicle speed from fluctuating due to instantaneous working condition switching or data noise. If the working condition identified by the working condition recognition module is updated, a certain debounce time is required before the speed calculation algorithm for different working conditions can be switched. If the speed calculation working condition completes the debounce and the working condition is switched, the wheel speed information used in different working conditions is different. Before and after the working condition is switched, VC The speed calculated by U may have slight or even large fluctuations. Therefore, in order to ensure that the speed changes linearly and does not change suddenly, and provide the driver with a better speed information experience, it is necessary to gradually transition the current speed to the next calculated speed with a certain gradient. The transition between different speeds uses different linear gradients when the speed increases or decreases slightly before and after the calculation. The speed increase gradient and speed decrease gradient are set separately. The speed increase gradient or speed decrease gradient is decided according to the size relationship before and after the speed calculation. In order to ensure the stability of the speed display, the median filter algorithm is used to smooth the initial value of the speed. The reason why the median filter is used instead of the mean filter is that the median filter is very effective in suppressing data smoothing impulse noise, so the processing effect is good, while the mean filter algorithm cannot remove the noise, but can only slightly weaken it. For the calculation of the driving wheel slip rate and slip rate, they are calculated based on the calculated vehicle speed and the wheel speed of a certain wheel. If the vehicle speed is updated, the corresponding driving wheel slip rate and slip rate are updated synchronously.

[0042] The above vehicle speed calculation methods are all for front-wheel steering and rear-wheel drive vehicles. For the vehicle speed calculation of vehicles with other drive layouts, targeted analysis is required to design the vehicle speed calculation algorithm.

[0043] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above-mentioned concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for calculating the speed of a new energy vehicle, characterized in that: The specific steps include: Step S1, ABS sends the wheel speed information of the four tires of the whole vehicle to the bus, and the VCU receives and analyzes the information as the basic information for calculating the vehicle speed; Step S2, the calibration values ​​of four tires are set inside the VCU, namely, the left front wheel radius calibration value FrontLeftWheelRadius_C, the right front wheel radius calibration value FrontRightWheelRadius_C, the left rear wheel radius calibration value RearLeftWheelRadius_C, and the right rear wheel radius calibration value RearRightWheelRadius_C; Step S3, according to different tire configurations of different vehicle models, or different tire configurations of the same vehicle model, the actual tire radius information is offline calibrated into the VCU software, and then the VCU software is flashed online to achieve the software and hardware matching of the real tire radius information. The VCU sends the vehicle speed obtained based on its own vehicle speed calculation algorithm to the ABS through the bus to perform ABS control; Step S4, adopting a strategy of dynamically deciding which specific calculation algorithm to adopt according to different operating conditions, and the vehicle speed algorithm module is provided with a number of algorithm units according to the operating conditions.

2. A method for calculating the speed of a new energy vehicle according to claim 1, characterized in that: The vehicle speed algorithm module is equipped with four algorithm units for calculating vehicle speed, which are respectively a straight-line driving algorithm unit, a turning operation algorithm unit, a high slip rate algorithm unit and a high slip rate algorithm unit according to the operating conditions. For vehicle speed calculation, the vehicle operating conditions are divided into five categories, namely, straight-line driving, turning, drive slip, braking lock (or slip rate higher than the threshold) and vehicle speed calculation under fault conditions.

3. A method for calculating the speed of a new energy vehicle according to claim 2, characterized in that: The specific control architecture steps are as follows: When the vehicle is traveling in a straight line or tending to travel in a straight line, that is, when the steering wheel angle sent by the electric power steering EPS is lower than the threshold, and the driving wheel slip rate and slip rate are both lower than the threshold, this working condition is a straight and stable driving condition, and the vehicle speed will be calculated based on the wheel speed of the driven wheel; When the vehicle is not in a straight-line driving state, when the steering wheel angle sent by EPS is greater than the threshold, and the driving wheel slip rate and slip rate are both lower than the threshold, according to the Ackerman steering principle, when the car is turning, the inner and outer wheels turn at different angles, the turning radius of the inner tire is smaller than that of the outer tire, and the turning radius of the outer steering wheel is the largest, so the difference between it and the actual running speed of the vehicle is also the largest, and the turning radius of the inner steering wheel is second, while the driving wheel rotates at a speed relatively closer to the vehicle speed, and is more inclined to linear motion than the steering wheel, so at this time the driving wheel speed should be used as the basic speed for calculating the vehicle speed; When the driving wheel slip rate of the vehicle is higher than the threshold, it means that the driving wheel is in a slipping state. When the driving wheel slips, the tire rotation speed is higher than the actual running speed of the vehicle. Therefore, the driving wheel speed should not be used as the basic wheel speed for calculating the vehicle speed, but the driven wheel speed should be used as the basic wheel speed for calculating the vehicle speed. When the wheels are locked or the slip rate is higher than the threshold, the rotation speed of the wheel with the slip rate higher than the threshold is lower than the actual running speed of the vehicle. Therefore, the vehicle speed calculation at this time should be based on the wheel speed of the two wheels with the lowest slip rate. When the wheel speed sensor fails and ABS cannot send out valid wheel speed information, for the first four major operating conditions, the VCU will adopt a fault degradation processing strategy, that is, based on the four major conventional operating conditions, combined with the information of the faulty wheel speed sensor to decide how to calculate the vehicle speed.

4. A method for calculating the speed of a new energy vehicle according to claim 3, characterized in that: The specific situations for judging whether the wheel speed sensor is faulty are as follows: If the wheel speed sensor of a wheel fails, the VCU will further determine whether the wheel speed sensor is the wheel speed sensor information to be used in the four major working conditions. If not, the calculation algorithm of the vehicle speed will continue to be executed according to the established calculation algorithms of the four major working conditions; If the faulty wheel speed sensor is the wheel speed sensor required for the four types of working conditions, the VCU will use an alternative wheel speed or a single wheel speed to calculate the vehicle speed.

5. A method for calculating the speed of a new energy vehicle according to claim 4, characterized in that: For straight-line driving conditions, the normal driven wheel speed and the reverse driving wheel speed will be used to calculate the vehicle speed; For turning conditions, that is, if a driving wheel speed sensor fails, the VCU will determine whether the vehicle is turning left or right based on the steering wheel angle information, and use the corresponding inner driven wheel and the normal driving wheel speed as the basic wheel speed information for vehicle speed calculation; For the driving slip condition, that is, the driving wheel slip rate is higher than the threshold, and a driven wheel speed sensor fails, then the VCU will use the normal driven wheel speed sensor wheel speed information to calculate the vehicle speed, that is, only one normal driven wheel speed is used to calculate the vehicle speed; In the case of brake locking or slip ratio higher than the threshold, VCU continues to use the wheel speed of the two wheels with the lowest slip ratio as the basis for calculating the vehicle speed to obtain a relatively more accurate vehicle speed. If two or more wheel speed sensors fail, the VCU will use an alternative speed calculation algorithm based on a different transmission system architecture to calculate the alternative speed of the vehicle.

6. A method for calculating the speed of a new energy vehicle according to claim 5, characterized in that: Switching between different working conditions will cause the vehicle speed calculation to synchronously switch the wheel speed to be used by the established algorithm. Before the wheel speed is switched, a certain debounce filtering process is required to prevent the calculated vehicle speed from fluctuating due to instantaneous working condition switching or data noise. If the working condition identified by the working condition recognition module is updated, a certain debounce time is required before the speed calculation algorithm for different working conditions can be switched.

7. A method for calculating the speed of a new energy vehicle according to claim 6, characterized in that: The transition between different vehicle speeds adopts different linear gradients when the vehicle speed increases or decreases slightly before and after the calculation. The speed increase gradient and the speed decrease gradient are set separately. The speed increase gradient or the speed decrease gradient is decided according to the size relationship before and after the speed calculation. In order to ensure the stability of the vehicle speed display, the median filtering algorithm is used to smooth the initial speed value. The calculation of the driving wheel slip rate and slip rate are based on the calculated vehicle speed and the wheel speed of a certain wheel. If the vehicle speed is updated, the corresponding driving wheel slip rate and slip rate are updated synchronously.

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