CN106394524A - Active braking method based on VANET wireless short-range communication - Google Patents

Abstract

The invention discloses an active braking method based on VANET wireless short-range communication, which comprises the following steps: obtaining the vehicle A₀Vehicle speed signal V₀(ii) a According to the vehicle speed signal V obtained in the step one₀Calculating the acceleration of the vehicle; data G obtained from a road gradient sensor₀And the influence of vehicle acceleration on the data obtained by the road slope sensor G₁Obtaining a reference gradient G of the road surface₂(ii) a Wherein G is₂＝G₀‑G₁(ii) a The slip rate S of the vehicle is calculated by the wheel speed sensor signal, and the longitudinal force F of the wheel is calculated by the vertical load sensor signal_xFurther comprising a vehicle slip ratio S and a wheel longitudinal force F_xCalculating road adhesion coefficient mu according to wheel cylinder pressure sensor signals_max(ii) a Step four: and starting a vehicle networking module, networking with surrounding vehicles, and acquiring surrounding vehicle data. The method can calculate more accurate safe distance in real time under the driving conditions of different road surface gradients, different road surface adhesion coefficients, different vehicle speeds and the like, and greatly improves the reliability, the safety and the stability.

Description

Active braking method based on VANET wireless short-range communication

technical field

The invention relates to an active braking method based on VANET wireless short-range communication.

Background technique

At present, when the car is driving, the brakes are basically controlled by the driver. When the driver is tired and deserted, it is easy to cause a car accident and hit an obstacle in front. The existing electronic equipment basically cannot actively brake. Avoid car accidents.

The Chinese patent with application number 201410677906.7 discloses an intelligent control method and device for emergency braking based on Internet of Vehicles, including a GPS module, a CAN bus module, a wireless communication module and a data processing module. It can remind the driver and apply the brakes when the distance between the vehicle and the vehicle, obstacle or pedestrian in front is less than the safe distance, but this invention has obvious defects, that is, ① the invention does not consider the problem of road gradient, when the vehicle is descending a steep slope When the safety distance calculated by the controller is too small, it will cause a great potential safety hazard, and accidents will easily occur when the driver relies too much on this invention; Therefore, when driving on ice and snow roads, the controller calculates too small a safety distance, causing potential safety hazards and vehicle rear-end collision accidents; If the safety distance is too large, the road resources cannot be fully utilized, which will cause a waste of crowded urban road resources.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide an active braking method based on VANET wireless short-range communication. A more precise safety distance greatly improves reliability, safety and stability.

The technical scheme adopted by the present invention to solve the above-mentioned technical problems is: an active braking method based on VANET wireless short-range communication, the steps of the method include:

Step 1: Obtain the vehicle speed signal V _{0 of the vehicle A 0 ;}

Step 2: Calculate the vehicle acceleration according to the vehicle speed signal V ₀ obtained in Step 1; obtain the reference slope G ₂ of the road surface according to the data G ₀ obtained by the road gradient sensor and the influence G ₁ of the vehicle acceleration on the data obtained by the road gradient sensor; , G ₂ =G ₀ -G ₁ ;

Step 3: Calculate the vehicle slip rate S from the wheel speed sensor signal, calculate the wheel longitudinal force F _x from the wheel vertical load sensor signal, and further calculate the vehicle slip rate S, wheel longitudinal force F _x and wheel wheel cylinder pressure Calculate the road surface adhesion coefficient μ _max from the sensor signal;

Step 4: Start the vehicle networking module, network with surrounding vehicles, and obtain surrounding vehicle data;

Step 5: Judging the movement direction of the vehicle according to the GPS data changes of the vehicle _A0 ; further comparing the GPS data changes of the vehicles around the vehicle, and screening the vehicles with the same movement direction as the vehicle _A0 ; further screening out the front closest to the vehicle A car A ₁ and a car behind;

Step ₆ : Calculate the vehicle distance L _GPS between the vehicle _A0 and the vehicle A1 in front according to the GPS data;

Step 7: Start the radar sensor, collect data from the radar sensor, and calculate the distance L _RA to the nearest obstacle;

Step 8: Determine whether L _GPS is equal to L _RA :

If L _GPS is not equal to L _RA , perform the following steps:

Calculate the relative velocity V ₁ and the absolute velocity V ₂ of the vehicle A ₀ and the vehicle or obstacle in front according to the speed signal V ₀ of the vehicle A ₀ and the rate of change of the data of the radar sensor over time; where, V ₂ =V ₀ +V ₁ , V ₂ , V ₀ and V ₁ are all vectors;

According to V ₀ , V ₁ , V ₂ , G ₂ , μ _max calculate the safety distance L _S1 between the vehicle A ₀ and the vehicle or obstacle in front;

Compare whether the actual distance L _RA is greater than the safety distance L _S1 : if the actual distance L _RA is greater than the safety distance L _S1 , it means that the vehicle A ₀ is relatively safe, then proceed to step 1, otherwise, proceed to step 9;

If L _GPS is equal to L _RA , the following steps are performed:

Obtain the vehicle speed V ₃ , road surface adhesion coefficient, and road surface gradient of the vehicle in front through the network data, and calculate the actual distance L _GPS and the safety distance L _S0 between the vehicle A ₀ and the vehicle A ₁ in front;

Compare whether the actual distance L _GPS is greater than the safety distance L _S0 ; if the actual distance L _GPS is greater than the safety distance L _S0 , it means that the vehicle is relatively safe now, and then proceed to step 1, otherwise, perform step 9;

Step 9: Control the vehicle to slow down the vehicle until the actual distance L _GPS is greater than the safety distance L _S0 or the actual distance L _RA is greater than the safety distance L _S1 ;

Step ten, perform closed-loop control reciprocally from step one to step nine.

Further, in said step nine, send data to the instrument panel control unit through the vehicle internal data CAN bus, control the work indicator light to flash; send data to the engine control unit through the vehicle internal data CAN bus, control the engine to reduce the fuel injection valve Fuel injection duty cycle, reduce fuel supply; send data to the chassis electronic stability program control unit and/or brake anti-lock brake control unit through the vehicle internal data CAN bus, control the vehicle braking system to work, so that the vehicle decelerates until The actual distance L _GPS is greater than the safety distance L _S0 or the actual distance L _RA is greater than the safety distance L _S1 .

Further, in the first step, the setting system ECU obtains the vehicle speed signal V0 from the anti-lock brake system or the vehicle dynamic stability program system through the vehicle internal data CAN bus.

After adopting above-mentioned technical scheme, the present invention has following beneficial effect:

1. This active braking method works completely automatically without human intervention;

2. The method of the present invention utilizes VANET wireless short-range communication to make inter-vehicles communicate with each other, obtain surrounding vehicle information, obtain required vehicle speed, GPS geographic location, utilize road surface gradient sensor and road surface adhesion coefficient module to obtain road surface gradient and calculate the data needed for road surface adhesion coefficient , use the control algorithm to get the road surface adhesion coefficient μmax, so that it can distinguish road surfaces with different slopes, such as uphill roads and downhill roads; road surfaces with different adhesion coefficients, such as ice and snow roads, wet slippery roads, dry cement roads, dry asphalt roads, etc. , so that the controller can calculate a more accurate safety distance in real time, so that the active braking device can work under different road gradients, different road adhesion coefficients, different vehicle speeds and other driving conditions, greatly improving reliability, safety and stability.

2. It can remind the driver when the vehicle is in a dangerous situation, so as to improve the vigilance of the driver and avoid traffic accidents;

3. Be able to actively brake when the vehicle is in an emergency to avoid traffic accidents.

Description of drawings

Fig. 1 is a flow chart of the active braking method based on VANET wireless short-range communication of the present invention.

detailed description

In order to make the content of the present invention more clearly understood, the present invention will be further described in detail below based on specific embodiments and in conjunction with the accompanying drawings.

As shown in Figure 1, a kind of active braking method based on VANET wireless short-range communication, contains in the step of described method:

Step 1: Obtain the vehicle speed signal V _{0 of the vehicle A 0 ;}

Step 2: Calculate the vehicle acceleration according to the vehicle speed signal V ₀ obtained in Step 1; obtain the reference slope G ₂ of the road surface according to the data G ₀ obtained by the road gradient sensor and the influence G ₁ of the vehicle acceleration on the data obtained by the road gradient sensor; , G ₂ =G ₀ -G ₁ ;

Step 3: Calculate the vehicle slip rate S from the wheel speed sensor signal, calculate the wheel longitudinal force F _x from the wheel vertical load sensor signal, and further calculate the vehicle slip rate S, wheel longitudinal force F _x and wheel wheel cylinder pressure Calculate the road surface adhesion coefficient μ _max from the sensor signal;

Step 4: Start the vehicle networking module, network with surrounding vehicles, and obtain surrounding vehicle data;

Step 5: Judging the direction of movement of the vehicle according to the change of GPS data of the vehicle _A0 ; further comparing the changes of GPS data of vehicles around the vehicle, and screening vehicles that are in the same direction as the movement direction of the vehicle _A0 ; A car A ₁ and a car behind;

Step ₆ : Calculate the vehicle distance L _GPS between the vehicle _A0 and the vehicle A1 in front according to the GPS data;

Step 7: Start the radar sensor, collect data from the radar sensor, and calculate the distance L _RA to the nearest obstacle;

Step 8: Determine whether L _GPS is equal to L _RA :

If L _GPS and L _RA are not equal, it means that the vehicle in front is an offline vehicle, a vehicle that cannot be connected to the network, or other types of obstacles. At this time, the data of the radar sensor determines the driving data of the vehicle in front or other types of obstacles. Perform the following steps:

Calculate the relative velocity V ₁ and the absolute velocity V ₂ of the vehicle A ₀ and the vehicle or obstacle in front according to the speed signal V ₀ of the vehicle A ₀ and the rate of change of the data of the radar sensor over time; where, V ₂ =V ₀ +V ₁ , V ₂ , V ₀ and V ₁ are all vectors;

According to V ₀ , V ₁ , V ₂ , G ₂ , μ _max calculate the safety distance L _S1 between the vehicle A ₀ and the vehicle or obstacle in front;

Compare whether the actual distance L _RA is greater than the safety distance L _S1 : if the actual distance L _RA is greater than the safety distance L _S1 , it means that the vehicle A ₀ is relatively safe, then proceed to step 1, otherwise, proceed to step 9;

If L _GPS is equal to L _RA , the vehicle in front is on-line. At this time, the driving data of the vehicle in front is determined by the network data, and the data of the radar sensor is auxiliary data; the network data is more abundant than the data of the radar sensor, including vehicle operating conditions such as vehicle speed, engine operating conditions, and gearbox operating conditions. The data can calculate the safety distance of the vehicle more accurately. The data of the radar sensor is used as auxiliary data, which is always compared with the data calculated by the GPS. Once the two data are not equal, immediately switch to another working mode to increase the safety distance and ensure safety, then perform the following steps:

Obtain the vehicle speed V ₃ , road surface adhesion coefficient, and road surface gradient of the vehicle in front through the network data, and calculate the actual distance L _GPS and the safety distance L _S0 between the vehicle A ₀ and the vehicle A ₁ in front;

Compare whether the actual distance L _GPS is greater than the safety distance L _S0 ; if the actual distance L _GPS is greater than the safety distance L _S0 , it means that the vehicle is relatively safe now, and then proceed to step 1, otherwise, perform step 9;

Step 9: Control the vehicle to slow down the vehicle until the actual distance L _GPS is greater than the safety distance L _S0 or the actual distance L _RA is greater than the safety distance L _S1 ;

Step ten, perform closed-loop control reciprocally from step one to step nine.

In said step nine, (1) send data to the instrument panel control unit through the vehicle internal data CAN bus, and control the work indicator light to flash, indicating that the active braking system is intervening in the work of the vehicle; (2) transmit data to the instrument panel control unit through the vehicle internal data CAN bus. The engine control unit sends data to control the engine to reduce the fuel injection duty cycle of the fuel injection valve and reduce the fuel supply; (3) send the data to the chassis electronic stability program control unit and/or the brake anti-lock brake control unit through the vehicle internal data CAN bus Send data, control the vehicle brake system to work, make the vehicle slow down, until the actual distance L _GPS is greater than the safety distance L _S0 or the actual distance L _RA is greater than the safety distance L _S1 , in (3) of step nine, the PID control algorithm, Fuzzy algorithm, of course, other algorithms can also be used.

In the first step, the setting system ECU obtains the vehicle speed signal V0 from the anti-lock brake system (ABS) or the vehicle dynamic stability program system (ESP) through the vehicle internal data CAN bus.

For example, when the current speed of the vehicle is 80 km/h, the vehicle communicates with the two vehicles in front through the VANET wireless short-range communication module, and obtains the GPS information and network identification codes of the two vehicles in front. The GPS information and the network identification code of the car and the first two cars identify the closest car to the car, and further compare the distance between the two cars L GPS measured by _GPS with the data L _RA measured by the distance sensor. ① If L _GPS and If the L _RA is the same, it means that there are no other vehicles or obstacles that cannot be networked between the vehicle and the preceding vehicle that has been networked. Further, the current speed of the vehicle in front is 75 km/h, and the road gradient is 5° obtained by the road gradient sensor. The road adhesion coefficient μ _max is identified based on the μ-s model. Further, according to the front vehicle speed, the rear vehicle speed, the road gradient, The road surface adhesion coefficient μ _max calculates that the current safety distance L _S0 of the two vehicles is 54m. If L _GPS is greater than L _S0 or 54m, the braking system will not take any action; if L _GPS is less than L _S , the braking system will take action. Slow down or stop the vehicle until L _GPS is greater than or equal to L _S or stop, the valid action indicator light on the vehicle dashboard will flash. ②If L _GPS and L _RA are not the same, it means that there are other vehicles or obstacles that cannot be networked between the vehicle and the networked vehicle in front. The road surface slope is 5° obtained by the road surface slope sensor, and the road surface adhesion coefficient μ _max is identified based on the μ-s model. Further, the safety of the current two vehicles or the vehicle and the obstacle is calculated according to the vehicle speed, road surface slope, and road surface adhesion coefficient μ _max . The distance L _S is 60m, if L _RA is greater than L _S1 ie 60m, the braking system will not take any action; if L _RA is less than L _S1 , the braking system will take action to slow down or stop the vehicle until L _RA is greater than or equal to L _S1 or stop, the active action indicator light on the vehicle dashboard will flash.

The difference between the above two situations is that the safety distance is different. In the first case, there is no obstacle between the two vehicles, and the two vehicles can communicate, so that the theoretical safety distance between the two vehicles becomes smaller and the road is fully utilized. In the second case, there are obstacles or other vehicles that cannot communicate between the two vehicles, so that the theoretical safety distance between the vehicle and the obstacles or other vehicles that cannot communicate becomes larger. The above two situations have improved the safety of the vehicle.

The specific embodiments described above have further described the technical problems, technical solutions and beneficial effects solved by the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (3)

1. An active braking method based on VANET wireless short-range communication, characterized in that the steps of the method contain: Step 1: Obtain the vehicle speed signal V _{0 of the vehicle A 0 ;} Step 2: Calculate the vehicle acceleration according to the vehicle speed signal V ₀ obtained in Step 1; obtain the reference slope G ₂ of the road surface according to the data G ₀ obtained by the road gradient sensor and the influence G ₁ of the vehicle acceleration on the data obtained by the road gradient sensor; , G ₂ =G ₀ -G ₁ ; Step 3: Calculate the vehicle slip rate S from the wheel speed sensor signal, calculate the wheel longitudinal force F _x from the wheel vertical load sensor signal, and further calculate the vehicle slip rate S, wheel longitudinal force F _x and wheel wheel cylinder pressure Calculate the road surface adhesion coefficient μ _max from the sensor signal; Step 4: Start the vehicle networking module, network with surrounding vehicles, and obtain surrounding vehicle data; Step 5: Judging the movement direction of the vehicle according to the GPS data changes of the vehicle _A0 ; further comparing the GPS data changes of the vehicles around the vehicle, and screening the vehicles with the same movement direction as the vehicle _A0 ; further screening out the front closest to the vehicle A car A ₁ and a car behind; Step ₆ : Calculate the vehicle distance L _GPS between the vehicle _A0 and the vehicle A1 in front according to the GPS data; Step 7: Start the radar sensor, collect data from the radar sensor, and calculate the distance L _RA to the nearest obstacle; Step 8: Determine whether L _GPS is equal to L _RA : If L _GPS is not equal to L _RA , perform the following steps: Calculate the relative velocity V ₁ and the absolute velocity V ₂ of the vehicle A ₀ and the vehicle or obstacle in front according to the speed signal V ₀ of the vehicle A ₀ and the rate of change of the data of the radar sensor over time; where, V ₂ =V ₀ +V ₁ , V ₂ , V ₀ and V ₁ are all vectors; According to V ₀ , V ₁ , V ₂ , G ₂ , μ _max calculate the safety distance L _S1 between the vehicle A ₀ and the vehicle or obstacle in front; Compare whether the actual distance L _RA is greater than the safety distance L _S1 : if the actual distance L _RA is greater than the safety distance L _S1 , it means that the vehicle A ₀ is relatively safe, then proceed to step 1, otherwise, proceed to step 9; If L _GPS is equal to L _RA , the following steps are performed: Obtain the vehicle speed V ₃ , road surface adhesion coefficient, and road surface gradient of the vehicle in front through the network data, and calculate the actual distance L _GPS and the safety distance L _S0 between the vehicle A ₀ and the vehicle A ₁ in front; Compare whether the actual distance L _GPS is greater than the safety distance L _S0 ; if the actual distance L _GPS is greater than the safety distance L _S0 , it means that the vehicle is relatively safe now, and then proceed to step 1, otherwise, perform step 9; Step 9: Control the vehicle to slow down the vehicle until the actual distance L _GPS is greater than the safety distance L _S0 or the actual distance L _RA is greater than the safety distance L _S1 ; Step ten, perform closed-loop control reciprocally from step one to step nine. 2. The active braking method based on VANET wireless short-range communication according to claim 1, characterized in that: in said step 9, data is sent to the dashboard control unit through the vehicle internal data CAN bus to control the flashing of the work indicator light ;Send data to the engine control unit through the vehicle internal data CAN bus to control the engine to reduce the fuel injection duty cycle of the fuel injection valve and reduce the fuel supply; through the vehicle internal data CAN bus to the chassis electronic stability program control unit and/or brake The anti-lock braking control unit sends data to control the vehicle braking system to decelerate the vehicle until the actual distance L _GPS is greater than the safety distance L _S0 or the actual distance L _RA is greater than the safety distance L _S1 . 3. The active braking method based on VANET wireless short-range communication according to claim 1, characterized in that: in said step 1, the system ECU is set to send the brake anti-lock braking system or vehicle dynamics information through the vehicle internal data CAN bus. The stability program system acquires the vehicle speed signal V ₀ .