CN109774709B - Vehicle linear control braking auxiliary safety system under emergency lane change working condition and control method thereof - Google Patents
Vehicle linear control braking auxiliary safety system under emergency lane change working condition and control method thereof Download PDFInfo
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Abstract
The invention discloses a vehicle line control braking auxiliary safety system under an emergency lane change working condition and a control method thereof, wherein the system consists of an environment sensing module, a driver input module, a vehicle ECU module, a state sensing module and an execution module; the system mainly aims at dangerous situations in the process of controlling the vehicle to suddenly change lanes by a driver, assists the driver to brake and control the vehicle, and ensures running safety.
Description
Technical Field
The invention relates to a vehicle linear control braking auxiliary safety system under an emergency lane change working condition and a control method thereof, and belongs to the field of vehicle active safety control.
Background
With the popularization of automobiles, active safety of the automobiles is increasingly receiving attention. The active safety technology intervenes the vehicle before the reaction of the driver by judging the danger in advance so as to avoid the occurrence of vehicle accidents and ensure the life safety. At present, active safety of a vehicle is mainly controlled according to stability of the vehicle, and the existing mature technology comprises a braking anti-lock system, a driving anti-skid system and an electronic stability control system. These systems all control the vehicle by analyzing its own state parameters; in addition, the active steering control technology proposed at present for the steering system of the vehicle is also active braking control technology which controls only the stability of the vehicle itself.
The probability of traffic accidents occurring in the process of changing lanes of a vehicle under investigation, especially under the condition of high speed is obviously higher than that of a common working condition, and the reason is that the emergency lane changing working condition is that a driver is forced to change lanes of the vehicle under a passive condition, in this case, the driver is difficult to accurately analyze the lane changing safety in real time, and meanwhile, the vehicle is difficult to accurately operate for most drivers, and the two factors cause that the vehicle possibly collides with surrounding vehicles in the process, or sideslip occurs due to the fact that the vehicle is out of stability and the steering capability is lost.
In recent years, advanced auxiliary driving systems combining a vehicle itself and a driver have become a hot spot for technical research, which proposes a control scheme to improve the running safety of the vehicle in consideration of the characteristics of the driver and the characteristics of the vehicle itself. At present, a drive-by-wire auxiliary safety system integrating three factors of driving behavior, surrounding vehicle motion state and vehicle stability has not been reported.
Disclosure of Invention
In order to solve the defects of the prior art, the invention aims to provide a vehicle linear control braking auxiliary safety system under an emergency lane change working condition and a control method thereof, which are used for accurately and immediately judging the risk of the lane change working condition under the emergency lane change working condition of a driver, ensuring stable vehicle operation while leading to intervention of the driver, and integrating three factors of the driving behavior of the driver, the motion state of surrounding vehicles and the stability of the vehicles to provide assistance for lane change safety of the driver.
In order to achieve the above object, the present invention adopts the following technical scheme:
a vehicle brake-by-wire auxiliary safety system comprising: the system comprises an environment sensing module, a driver input module, a vehicle ECU module, a state sensing module and an execution module;
the environment sensing module comprises four millimeter wave radars 1, a laser radar 2 and a camera 3, wherein the four millimeter wave radars 1 are arranged on the periphery (front side, rear side, left side and right side) of a vehicle body, the laser radar 2 is arranged on the top of the vehicle body, the camera 3 is arranged on the top of the vehicle body, and the environment sensing module respectively transmits acquired data to the collision risk analysis module 11 through a CAN bus;
the driver input module comprises a steering wheel 6, a steering column 5 connected with the steering wheel, a steering wheel angle and rotating speed sensor 4, a brake pedal 8 and a pedal braking stroke sensor 7 connected with the brake pedal, wherein the steering wheel angle and rotating speed sensor and the brake pedal stroke sensor respectively transmit the obtained data to the collision risk analysis module 11 through a CAN bus; the above terms are all conventional in the art, for example the term "steering column" is referred to in GB/T5179-85 automotive steering system terminology and definition number 2.1.3; the term "brake pedal" is referred to in the literature: chen Gurui automobile Structure lower book [ M ]. 2001;
the state sensing module comprises a GPS inertial navigator 10 and a GPS antenna 9, wherein the GPS inertial navigator 10 transmits the obtained data to the line control power distribution control module 12, the GPS inertial navigator 10 is arranged in the vehicle body, and the GPS antenna 9 is arranged at the top of the vehicle body;
the vehicle ECU module includes a collision risk analysis module 11 and a line control power distribution control module 12 connected to each other;
the execution module comprises a brake sub-valve 13, an accumulator 14 for providing hydraulic pressure for the sub-valve, a hydraulic pump 15 for providing pressure for the accumulator, and four wheels 18; the brake sub valve 13, the energy accumulator 14 and the hydraulic pump 15 are connected in sequence; each wheel 18 is provided with a brake 16 and a brake disc 17; the four brakes 16 and the four brake discs 17 are respectively connected with the output ends of the brake sub-valves 13; the brake valve 13 receives a control signal sent by the line control power distribution control module 12 to work.
In this application, the above-mentioned execution module is a conventional brake-by-wire execution module or a brake-by-wire hydraulic brake system in the art, such as the brake-by-wire system disclosed in document "Zhang Chengli," the brake-by-wire system of an automobile and its control algorithm and simulation research [ D ]. University northeast, 2008.
The invention is suitable for common medium and small-sized passenger cars.
The invention also provides a control method of the brake-by-wire auxiliary safety system based on the vehicle, which comprises the following specific steps:
step 1:
the method comprises the steps that three different sensors, namely a laser radar, a millimeter wave radar and a camera of the environment sensing module, transmit object position information and motion state information around a vehicle to a collision risk analysis module; the collision risk analysis module firstly processes information of different sensors through a sensor fusion algorithm to distinguish the relative position relationship and the relative motion relationship between different moving objects around the vehicle and the vehicle;
the term "fusion algorithm" is a conventional algorithm in the art, as described in documents Wang Junna, lei Jing. Multisensor information fusion and application review [ J ]. Information recording material, 2016,17 (5): 78-79 ";
step 2:
the steering wheel angle and rotating speed sensor acquires steering wheel angle information and brake pedal displacement information and transmits the steering wheel angle information and the brake pedal displacement information to the collision risk analysis module;
step 3:
the collision risk analysis module obtains the lane changing intention of the driver according to the driver input obtained in the step 2, so as to calculate the motion trail of the vehicle at the future moment, and meanwhile, the lane changing operation of the driver is calculated according to the relative position relation and the relative motion relation between different moving objects around the vehicle and the vehicle obtained in the step 1;
if no danger is judged, the driver operation is directly transmitted to the on-line control power distribution control module, and the module is informed that no additional braking operation is performed;
if the risk of collision is judged, calculating proper braking force by comprehensively considering the collision distance time between the vehicle and surrounding objects, and sending the calculation result to a linear control power distribution control module;
specifically:
step 3.1:
firstly, taking a geometric center of a vehicle as an origin, taking a vehicle advancing direction as an X axis, and taking a direction which is perpendicular to the X axis and points to the left side of the vehicle advancing direction through the origin as a Y axis; the relative position information and the relative motion information of the surrounding vehicles and the vehicles are obtained by the environment sensing module at the current moment are described as [ X i (t),Y i (t),V xi (t),V yi (t)]Wherein X is i (t) and Y i (t) is the abscissa value, V, of the object in the vehicle coordinate system xi (t) and V yi (t) the movement speeds of the object in the vehicle coordinate system along the X-axis direction and the Y-axis direction respectively, and the subscript i represents different object numbers;
step 3.2:
obtaining the steering angle theta of the driver at the current moment by a steering angle sensor sw (t) steering wheel speed sensor obtaining driver steering wheel speedThe current longitudinal speed V of the vehicle is obtained by a GPS and an inertial navigator X (t) transverse vehicle speed V Y (t) heading angle θ with respect to lane line Lh (t) judging that the driver is performing emergency lane change operation when the situation that the rotating speed or the rotating angle of the steering wheel is overlarge occurs when the vehicle speed is high on a straight road;
step 3.3:
based on the relative velocity V between vehicles measured by the environment sensing module xi (t) obtaining the relative acceleration value a between vehicles by filtering estimation xi (t)，
Calculating estimated collision time TC of the vehicles and the own vehicle i ：
Wherein i is { OF, CF, CR }, wherein OF is represented as the front vehicle OF the original lane, CF is the front vehicle OF the lane change side, and CR is the rear vehicle OF the lane change side;
step 3.4:
bringing the driver steering wheel angle into the vehicle dynamics equation:
wherein gamma (t) is yaw rate, beta (t) is centroid slip angle, a is distance from vehicle centroid to front axle, b is distance from vehicle centroid to rear axle, k f And k r Respectively the rigidity of the side plates of the front wheel and the rear wheel, n is the transmission ratio of a steering system, m is the mass of the whole vehicle, I z The moment of inertia of the z-axis perpendicular to the ground is bypassed for the whole vehicle.
The state increment of the current moment of the vehicle is obtained by the formula (2), so that the state quantity of the next moment is calculated:
at the same time using the measured steering wheel speedCalculating the predicted steering wheel angle at the next moment>And the predicted state value at time t+1 is substituted into the above-described dynamics equation, whereby the vehicle state values after both times can be predicted +.>And->Substituting the predicted two sets of state values into a vehicle kinematic equation:
Δt in the formula (4) is a time interval;
respectively obtaining the predicted transverse speed of the vehicle relative to the lane lineAnd->Predicting longitudinal velocityAnd->Obtaining the current position X of the vehicle relative to the lane line by the environment sensing module L (t) and Y L (t) and calculating the predicted position from the predicted speed>And->And->And->
Step 3.5:
setting the lane change distance as Y L The lane change process trajectory approximates the following function:
in the formula, the coordinate system takes the straight line of the lane line as the X axis.
The current relative lane line position and the predicted position of the vehicle are carried into the above mode to obtain the total longitudinal distance of the lane change track, and the time estimated value t required by the vehicle to leave the original lane is calculated according to the current speed of the vehicle 1 And a total time t required for the vehicle to leave the original lane and merge into the lane on the lane change side 2 When t 1 ＞TC OF -t s1 When the system judges that braking intervention is needed, the minimum braking strength z min1 The following conditions need to be satisfied:
t is in s1 Representing a safe time threshold;
step 3.6:
taking the collision risk of the vehicle and the original lane vehicle into consideration, and simultaneously taking the collision risk of the vehicle and the lane change side vehicle into consideration, and obtaining the vehicle according to the step 3.4Lateral speed V of vehicle relative to lane line LY Thereby estimating the total time t required for the vehicle to leave the original lane and merge into the lane on the lane change side 2 At this time, it is necessary to classify the states of other vehicles on the lane change side as shown in table 1:
TABLE 1 vehicle State Classification
T in Table 1 s2 And t s3 Is a safe time threshold.
Step 3.7:
different control methods are adopted for different situations
a) Under the condition of prohibiting the lane change, adopting prohibition brake control on the vehicle so as to minimize damage caused by collision;
b) The predicted time for collision with the rear vehicle is recalculated according to the braking intensity in the step 3.5 for the case that the vehicle behind the lane-changing side front vehicle has no danger:
when TC CR ＞t 2 +t s3 Judging no danger, changing the road according to the braking strength in the step 3.5, and when TC CR ＜t 2 +t s3 When the channel changing process is forbidden, the channel changing process is performed;
c) For the case of a low speed of the vehicle in front of the lane change side, it is necessary to first calculate the braking strength z required for collision avoidance min2 Which satisfies the following conditions:
the required brake strength is then found to be z=max (z min1 ,z min2 ) The method comprises the steps of carrying out a first treatment on the surface of the Bringing this brake strength into the formula:
when TC CR ＞t 2 +t s3 Judging no danger, changing the braking strength according to the formula (9), and when TC CR ＜t 2 +t s3 When the channel changing process is forbidden, the channel changing process is performed;
step 3.8, the collision risk analysis module transmits the obtained control result to the line control power distribution control module;
step 4:
the GPS inertial navigator of the state sensing module acquires the motion state information of the vehicle and transmits the motion state information to the line control power distribution control module;
step 5:
the linear control power distribution control module calculates and obtains the braking force control distribution strategy of each wheel by receiving the braking force target in the step 3 and the vehicle motion state obtained in the step 4 and combining the safety requirement of the lateral stability of the vehicle, and transmits the obtained braking force control target of each wheel to the linear control power distribution execution module;
the specific steps of the control and distribution strategy for the braking force of each wheel obtained by combining the safety requirements of the lateral stability of the vehicle are as follows:
1) Obtaining an ideal yaw rate value according to the steering angle of the steering wheel of the driver:
wherein L is the front-rear wheelbase;
2) Calculated yaw rate deviation e=γ d - γ, calculating an active yaw moment control amount by means of a sliding mode control algorithm:
in the middle ofEpsilon and k are slip-form control parameters.
3) And (3) comparing the braking strength control value obtained in the step (3) with the value obtained by the pedal stroke sensor, and taking the larger value of the braking strength control value and the value obtained by the pedal stroke sensor. Meanwhile, the braking force of each wheel is obtained through optimization distribution by combining the active yaw moment control value, and the aim of the optimization distribution is as follows:
in which i= [ FL, FR, RL, RR ]]Four wheels of front left, front right, back left and back right are represented by F xi Representing the longitudinal force of the wheel, F yi Represents the lateral force of the wheel, mu represents the road adhesion coefficient, F zi Representing the vertical load of the wheel. Wherein F is xi The following limits are met for optimizing variables
Wherein c represents the wheel track; f in the formula yi The tire magic formula is used for solving the following steps:
F yi ＝Dsin{Carctan[Bα i -E(Bα i -arctanBα i )]}(14)
wherein B, C, D and E are tire model parameters, alpha i Is the wheel slip angle, wherein the front wheel slip angleRear wheel slip angle->
4) And outputting and converting the obtained braking force distribution result of each wheel into a valve body control signal and transmitting the valve body control signal to an execution module.
Step 6:
the execution module adjusts each component of the brake-by-wire system to work according to the obtained brake force control target, provides accurate brake force for each wheel, and provides a safety auxiliary function for dangerous situations encountered by the vehicle in the lane changing process.
Compared with the prior art, the brake-by-wire technology provided by the invention releases the coupling relation between the driver pedal and the active braking mechanism, integrates three important parts of driver input, environment sensing input and vehicle state value, acquires the input of the driver input and the active braking controller, transmits braking signals to the lower braking actuating mechanism, classifies different working conditions in the process of the driver emergency lane change, gives out a control scheme, carries out braking intervention on the vehicle in advance based on a brake-by-wire mode, solves the interference between the driver input and the active braking input, eliminates or reduces damage to the minimum, and greatly improves the safety of the vehicle.
Drawings
FIG. 1 is a schematic diagram of the connection of the modules of the system of the present application;
FIG. 2 is a flow chart of a lane change risk judging and controlling method;
fig. 3 is a schematic diagram of a vehicle stability control flow.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical solution of the present invention, and are not intended to limit the scope of the present invention.
The vehicle used in the example was curiosity Ai Ruize 5.
Example 1
As shown in fig. 1, a vehicle brake-by-wire auxiliary safety system under an emergency lane change condition comprises; the system comprises an environment sensing module, a driver input module, a vehicle ECU module, a state sensing module and an execution module; in fig. 1, A, B, C, D, E is an environment sensing module, a driver input module, a vehicle ECU module, a state sensing module, and an execution module in this order;
the state sensing module comprises a GPS inertial navigator 10 and a GPS antenna 9 (the Oxts company, the RT2000-GPS/INS inertial navigation combination system) matched with the GPS inertial navigator; the GPS inertial navigator 10 is fixed in the vehicle body, the GPS antenna 9 connected with the GPS inertial navigator is arranged at the top of the vehicle body to accurately acquire the position information and the state parameters of the vehicle, and the acquired data are transmitted to the vehicle ECU module through a can bus;
the environment sensing module comprises a laser radar 2, four millimeter wave radars 1 and a camera 3; the laser radar 2 and the camera 3 are fixedly arranged at the top of the vehicle body, so that a wide visual field is ensured to acquire information of surrounding environment; four millimeter wave radars 1 are respectively installed at the front part, two sides and the rear part of the vehicle body to acquire surrounding environment information in the corresponding direction of the vehicle; the environmental awareness module transmits the obtained data to a vehicle ECU module (purchased from BISCH, model: EDC 17CP14/5/p 680) through can bus;
the driver input module comprises a brake pedal stroke sensor 7 and a steering wheel rotation angle and rotation speed sensor 5; a brake pedal travel sensor 7 is mounted to a vehicle brake pedal position to measure a brake pedal travel; the steering wheel angle and rotation speed sensor 5 is arranged on a steering column of a steering wheel of the vehicle; the driver input module transmits the obtained data to the vehicle ECU module through a can bus;
the vehicle ECU module includes a collision risk analysis module 11 and a line control power distribution control module 12;
the execution module comprises a brake sub-valve (13) which is operated by receiving a control signal sent by the line control power distribution control module (12), an accumulator (14) for providing hydraulic pressure for the sub-valve, a hydraulic pump (15) for providing pressure for the accumulator, a brake (16) and a brake disc (17) which are connected with the output end of the sub-valve and are arranged on wheels (18)
The state sensing module transmits the obtained data to the line control power distribution control module 12 through the GPS inertial navigator 10; the environment sensing module transmits the obtained data to the collision risk analysis module 11 through the laser radar 2, the four millimeter wave radars 1 and the camera 3; the driver input module transmits the obtained data to the collision risk analysis module 11 through the brake pedal travel sensor 7 and the steering wheel angle sensor 5; the collision risk analysis module 11 processes the obtained data and transmits the calculation result to the line control power distribution control module 12; the linear control power distribution control module 12 processes the obtained data and outputs a control signal to brake the valve 13. The split valve distributes the pressure of the accumulator 14 to the brake 16 mounted to each wheel according to the control signal obtained, which applies a braking force to the brake disc 17 so that the wheels are braked.
The embodiment also provides a control method of the vehicle brake-by-wire auxiliary safety system, which comprises the following specific steps:
step 1:
the method comprises the steps that three different sensors, namely a laser radar, a millimeter wave radar and a camera of the environment sensing module, transmit object position information and motion state information around a vehicle to a collision risk analysis module; the collision risk analysis module firstly processes information of different sensors through a sensor fusion algorithm to distinguish the relative position relationship and the relative motion relationship between different moving objects around the vehicle and the vehicle;
step 2:
the steering wheel angle and rotating speed sensor acquires steering wheel angle information and brake pedal displacement information and transmits the steering wheel angle information and the brake pedal displacement information to the collision risk analysis module;
step 3:
the collision risk analysis module obtains the lane changing intention of the driver according to the driver input obtained in the step 2, so as to calculate the motion trail of the vehicle at the future moment, and meanwhile, the lane changing operation of the driver is calculated according to the relative position relation and the relative motion relation between different moving objects around the vehicle and the vehicle obtained in the step 1;
if no danger is judged, the driver operation is directly transmitted to the on-line control power distribution control module, and the module is informed that no additional braking operation is performed;
if the risk of collision is judged, calculating proper braking force by comprehensively considering the collision distance time between the vehicle and surrounding objects, and sending the calculation result to a linear control power distribution control module; the flow chart of the judgment and control of the risk of the sudden change channel is shown in fig. 2, specifically:
step 3.1:
firstly, taking a geometric center of a vehicle as an origin, taking a vehicle advancing direction as an X axis, and taking a direction which is perpendicular to the X axis and points to the left side of the vehicle advancing direction through the origin as a Y axis; the relative position information and the relative motion information of the surrounding vehicles and the vehicles are obtained by the environment sensing module at the current moment are described as [ X i (t),Y i (t),V xi (t),V yi (t)]Wherein X is i (t) and Y i (t) is the abscissa value, V, of the object in the vehicle coordinate system xi (t) and V yi (t) the movement speeds of the object in the vehicle coordinate system along the X-axis direction and the Y-axis direction respectively, and the subscript i represents different object numbers;
step 3.2:
obtaining the steering angle theta of the driver at the current moment by a steering angle sensor sw (t) steering wheel speed sensor obtaining driver steering wheel speedThe current longitudinal speed V of the vehicle is obtained by a GPS and an inertial navigator X (t) transverse vehicle speed V Y (t) heading angle θ with respect to lane line Lh (t) judging that the driver is performing emergency lane change operation when the situation that the rotating speed or the rotating angle of the steering wheel is overlarge occurs when the vehicle speed is high on a straight road;
the content of specific control in this embodiment includes the following two main parts, one is lane change risk degree discrimination and control, and the specific implementation steps are as follows:
step 3.3:
based on the relative velocity V between vehicles measured by the environment sensing module xi (t) obtaining the relative acceleration value a between vehicles by filtering estimation xi (t)，
In the embodiment, 1) firstly, according to the current vehicle speed 60km/h acquired by a state sensing module and a driver input module, a course angle of 0 degree, a steering wheel angle of 10 degrees and a steering wheel rotating speed of 45 degrees/s, judging that a driver performs emergency lane change operation; 2) Secondly, the environment sensing module is real-timeAcquiring motion information OF objects around the vehicle, classifying the measured surrounding vehicles into a front vehicle OF the same lane, a front vehicle CF OF the lane change side and a rear vehicle CR OF the lane change, and acquiring a relative positional relationship and a relative motion relationship [ X ] between the vehicles i (t),Y i (t),V xi (t),V yi (t)]Wherein X is i (t) and Y i (t) is the abscissa value, V, of the object in the vehicle coordinate system xi (t) and V yi (t) is the movement speed OF the object in the vehicle coordinate system along the X-axis direction and the Y-axis direction, i ε { OF, CF, CR }, respectively. Based on the measured relative velocity V between vehicles xi (t) obtaining the relative acceleration value a between vehicles by filtering estimation xi (t). The collision predicted time TC is calculated using the following formula i ：
Wherein i is { OF, CF, CR }, wherein OF is represented as the front vehicle OF the original lane, CF is the front vehicle OF the lane change side, and CR is the rear vehicle OF the lane change side;
calculating to obtain TC OF 2s, TC CF 8s, TC RF 20s.
Step 3.4:
substituting the driver steering wheel input and the vehicle motion state information into a vehicle dynamics formula:
wherein gamma (t) is yaw rate, beta (t) is centroid slip angle, a is distance from vehicle centroid to front axle, b is distance from vehicle centroid to rear axle, k f And k r Respectively the rigidity of the side plates of the front wheel and the rear wheel, n is the transmission ratio of a steering system, m is the mass of the whole vehicle, I z The moment of inertia of the z-axis perpendicular to the ground is bypassed for the whole vehicle.
The state increment of the current moment of the vehicle is obtained from the above, so that the state quantity of the next moment is calculated:
at the same time using the measured steering wheel speedCalculating the predicted steering wheel angle at the next moment>And the predicted state value at time t+1 is substituted into the above-described dynamics equation, whereby the vehicle state values after both times can be predicted +.>And->Substituting the predicted two sets of state values into a vehicle kinematic equation:
wherein Δt is a time interval;
respectively obtaining the predicted transverse speed of the vehicle relative to the lane lineAnd->Predicting longitudinal velocityAnd->Obtaining the current position X of the vehicle relative to the lane line by the environment sensing module L (t) and Y L (t) and calculating from the predicted speedMeasured position->And->And->And->
4) Setting the lane change distance as Y L At 4m, the lane change process trajectory approximates the following function:
in the formula, the coordinate system takes the straight line of the lane line as the X axis.
The current relative lane line position and the predicted position of the vehicle are carried into the above mode to obtain the total longitudinal distance of the lane change track, and the time estimated value t required by the vehicle to leave the original lane is calculated according to the current speed of the vehicle 1 Total time t required for 1s vehicle to leave the original lane and merge into lane change side 2 2s.
Step 3.5:
setting the lane change distance as Y L The lane change process trajectory approximates the following function:
the coordinate system takes the straight line of the lane line as the X axis;
the current relative lane line position and the predicted position of the vehicle are carried into the above mode to obtain the total longitudinal distance of the lane change track, and the time estimated value t required by the vehicle to leave the original lane is calculated according to the current speed of the vehicle 1 And a total time t required for the vehicle to leave the original lane and merge into the lane on the lane change side 2 The method comprises the steps of carrying out a first treatment on the surface of the Setting a safe time threshold t s1 2s because of t 1 ＞TC OF -t s1 So the system judges that the collision danger needs braking intervention, and the minimum braking strength z min1 The following conditions need to be satisfied:
a suitable braking strength of 0.5 was calculated.
Step 3.6:
the collision risk of the vehicle and the original lane vehicle is considered, the collision risk of the vehicle and the lane change side vehicle is considered, and the transverse speed V of the vehicle relative to the lane line is obtained according to the step 3.4 LY Thereby estimating the total time t required for the vehicle to leave the original lane and merge into the lane on the lane change side 2 At this time, it is necessary to classify the states of other vehicles on the lane change side as shown in table 1:
TABLE 1 vehicle State Classification
T in Table 1 s2 And t s3 Is a safe time threshold.
In the present embodiment, due to TC CF ＞t 2 +t s3 There is thus no risk of collision with the lane-change vehicle.
Step 3.8
The collision risk analysis module transmits the obtained control result to the line control power distribution control module; in the embodiment, the calculated braking strength is about to be 0.5, and the TC is obtained by substituting the collision predicted time formula CR ＞t 2 +t s3 Therefore, the vehicles coming from the side of the lane change have no collision threat, the lane change is allowed, and the lane change risk degree judgment and the braking intervention control value are completed.
Step 4:
the GPS inertial navigator of the state sensing module acquires the motion state information of the vehicle and transmits the motion state information to the line control power distribution control module;
step 5:
the linear control power distribution control module calculates and obtains the braking force control distribution strategy of each wheel by receiving the braking force target in the step 3 and the vehicle motion state obtained in the step 4 and combining the safety requirement of the lateral stability of the vehicle, and transmits the obtained braking force control target of each wheel to the linear control power distribution execution module; the stability control flow is shown in FIG. 3 and consists of the following steps
1) Obtaining an ideal yaw rate value according to the steering angle of the steering wheel of the driver:
wherein L is the front-rear wheelbase;
2) Calculated yaw rate deviation e=γ d - γ, calculating an active yaw moment control amount by means of a sliding mode control algorithm:
in the middle ofEpsilon and k are slip-form control parameters.
3) And (3) comparing the braking strength control value obtained in the step (3) with the value obtained by the pedal stroke sensor, and taking the larger value of the braking strength control value and the value obtained by the pedal stroke sensor. Meanwhile, the braking force of each wheel is obtained through optimization distribution by combining the active yaw moment control value, and the aim of the optimization distribution is as follows:
in which i= [ FL, FR, RL, RR ]]Four wheels of front left, front right, back left and back right are represented by F xi Representing the longitudinal force of the wheel, F yi Represents the lateral force of the wheel, mu represents the road adhesion coefficient, F zi Representing the vertical load of the wheel. Wherein F is xi The following limits are met for optimizing variables
Wherein c represents the wheel track; f in the formula yi The tire magic formula is used for solving the following steps:
F yi ＝Dsin{Carctan[Bα i -E(Bα i -arctanBα i )]}(14)
wherein B, C, D and E are tire model parameters, alpha i Is the wheel slip angle, wherein the front wheel slip angleRear wheel slip angle->
In this embodiment, the calculated braking force of the left front wheel is 25% of the total braking force, the left rear wheel is 40%, the right front wheel is 10%, and the right rear wheel is 25%.
4) And converting the obtained braking force distribution result of each wheel into a valve body control signal and outputting the valve body control signal to the execution module. The operation to complete one control cycle thus far starts the next control cycle.
Step 6:
the execution module adjusts each component of the brake-by-wire system to work according to the obtained brake force control target, provides accurate brake force for each wheel, and provides a safety auxiliary function for dangerous situations encountered by the vehicle in the lane changing process.
The execution module comprises a brake sub-valve (13) which receives a control signal sent by the line control power distribution control module (12) to work, an energy accumulator (14) which provides hydraulic pressure for the sub-valve, a hydraulic pump (15) which provides pressure for the energy accumulator, a brake (16) which is connected with the output end of the sub-valve and is arranged on wheels (18), and a brake disc (17) sub-valve which distributes the pressure of the acquired energy accumulator 14 to the brake 16 which is arranged on each wheel according to the acquired control signal, and the brake force is exerted on the brake disc 17 by the brake to brake the wheels.
Claims (5)
1. The control method based on the vehicle line control dynamic auxiliary safety system is characterized by comprising the following specific steps:
step 1:
the environment sensing module transmits the position information and the motion state information of objects around the vehicle to the collision risk analysis module; the collision risk analysis module distinguishes the relative position relation and the relative motion relation between different moving objects around the vehicle and the vehicle through a sensor fusion algorithm;
step 2:
the driver input module collects steering wheel rotation angle information and brake pedal displacement information and transmits the steering wheel rotation angle information and brake pedal displacement information to the collision risk analysis module;
step 3.1:
the collision risk analysis module firstly takes the geometric center of the vehicle as an origin, the advancing direction of the vehicle is an X axis, and the direction which is perpendicular to the X axis and points to the left side of the advancing direction of the vehicle through the origin is a Y axis; the relative position information and the relative motion information of the surrounding vehicles and the vehicles are obtained by the environment sensing module at the current moment are described as [ X i (t),Y i (t),V xi (t),V yi (t)]Wherein X is i (t) and Y i (t) is the abscissa value, V, of the object in the vehicle coordinate system xi (t) and V yi (t) the movement speeds of the object along the X-axis direction and the Y-axis direction in the vehicle coordinate system respectively, wherein i represents different object numbers;
step 3.2:
the collision risk analysis module obtains the steering wheel angle theta of the driver at the current moment by a steering wheel angle sensor sw (t) steering wheel speed sensor obtaining driver steering wheel speedThe current longitudinal speed V of the vehicle is obtained by a GPS and an inertial navigator X (t) transverse vehicle speed V Y (t) heading angle θ with respect to lane line Lh (t) judging that the driver is performing emergency lane change operation when the situation that the rotating speed or the rotating angle of the steering wheel is overlarge occurs when the vehicle speed is high on a straight road;
step 3.3:
based on the relative velocity V between vehicles measured by the environment sensing module xi (t) obtaining the relative acceleration value a between vehicles by filtering estimation xi (t)，
Calculating estimated collision time TC of the vehicles and the own vehicle i ：
Wherein i is { OF, CF, CR }, wherein OF is represented as the front vehicle OF the original lane, CF is the front vehicle OF the lane change side, and CR is the rear vehicle OF the lane change side;
step 3.4:
bringing the driver steering wheel angle into the vehicle dynamics equation:
wherein gamma (t) is yaw rate, beta (t) is centroid slip angle, a is distance from vehicle centroid to front axle, b is distance from vehicle centroid to rear axle, k f And k r Respectively the rigidity of the side plates of the front wheel and the rear wheel, n is the transmission ratio of a steering system, m is the mass of the whole vehicle, I z The moment of inertia of the z-axis perpendicular to the ground and bypassing the mass center for the whole vehicle;
the state increment of the current moment of the vehicle is obtained by the formula (2), so that the state quantity of the next moment is calculated:
at the same time using the measured steering wheel speedCalculating the predicted steering wheel angle at the next moment>And substituting the predicted state value at time t+1 into the dynamics equation, thereby predicting the vehicle state value +.>Andsubstituting the predicted two sets of state values into a vehicle kinematic equation:
Δt in the formula (4) is a time interval;
respectively obtaining the predicted transverse speed of the vehicle relative to the lane lineAnd->Predicting longitudinal velocityAnd->Obtaining the current position X of the vehicle relative to the lane line by the environment sensing module L (t) and Y L (t) and calculating the predicted position from the predicted speed>And->And->And->Step 3.5:
setting the lane change distance as Y L The lane change process trajectory approximates the following function:
the coordinate system takes the straight line of the lane line as the X axis;
the current relative lane line position and the predicted position of the vehicle are carried into the above mode to obtain the total longitudinal distance of the lane change track, and the time estimated value t required by the vehicle to leave the original lane is calculated according to the current speed of the vehicle 1 And a total time t required for the vehicle to leave the original lane and merge into the lane on the lane change side 2 When t 1 ＞TC OF -t s1 When the system judges that braking intervention is needed, the minimum braking strength z min1 The following conditions need to be satisfied:
t is in s1 Representing a safe time threshold;
step 3.6:
deriving lateral speed V of vehicle relative to lane line according to step 3.4 LY Thereby estimating the total time t required for the vehicle to leave the original lane and merge into the lane on the lane change side 2 The method comprises the steps of carrying out a first treatment on the surface of the Step 3.7:
different control methods are adopted for different situations:
a) For TC CR ＜t 2 +t s3 Adopting brake prohibition control;
b) For TC CF ＞t 2 +t s2 And TC is TC CR ＞t 2 +t s3 If so, recalculate the estimated time of collision with the following vehicle based on the brake intensity in step 3.5:
when TC CR ＞t 2 +t s3 Judging no danger, changing the road according to the braking strength in the step 3.5, and when TC CR ＜t 2 +t s3 When the channel changing process is forbidden, the channel changing process is performed;
c) For TC CF ＜t 2 +t s2 And TC is TC CR ＞t 2 +t s3 First, the braking strength z required for collision avoidance is calculated min2 Which satisfies the following conditions:
the required brake strength is then found to be z=max (z min1 ,z min2 ) The method comprises the steps of carrying out a first treatment on the surface of the Bringing this brake strength into the formula:
when TC CR ＞t 2 +t s3 Judging no danger, changing the braking strength according to the formula (9), and when TC CR ＜t 2 +t s3 Lane change is forbidden;
t s2 and t s3 Is a safe time threshold;
step 3.8, the collision risk analysis module transmits the obtained control result to the line control power distribution control module;
step 4:
the GPS inertial navigator of the state sensing module acquires the motion state information of the vehicle and transmits the motion state information to the line control power distribution control module;
step 5:
the linear control power distribution control module calculates and obtains the braking force control distribution strategy of each wheel by receiving the braking force target in the step 3 and the vehicle motion state obtained in the step 4 and combining the safety requirement of the lateral stability of the vehicle, and transmits the obtained braking force control target of each wheel to the linear control power distribution execution module;
the specific steps of the control and distribution strategy for the braking force of each wheel obtained by combining the safety requirements of the lateral stability of the vehicle are as follows:
1) Obtaining an ideal yaw rate value according to the steering angle of the steering wheel of the driver:
wherein L is the front-rear wheelbase;
2) Calculated yaw rate deviation e=γ d - γ, calculating an active yaw moment control amount by means of a sliding mode control algorithm:
in the middle ofEpsilon and k are slip form control parameters;
3) Comparing the braking strength control value obtained in the step 3 with the value obtained by the pedal stroke sensor, and taking the larger value of the braking strength control value and the value obtained by the pedal stroke sensor; meanwhile, the braking force of each wheel is obtained through optimization distribution by combining the active yaw moment control value, and the aim of the optimization distribution is as follows:
in which i= [ FL, FR, RL, RR ]]Four wheels of front left, front right, back left and back right are represented by F xi Representing the longitudinal force of the wheel, F yi Represents the lateral force of the wheel, mu represents the road adhesion coefficient, F zi Representing vertical wheel load, where F xi The following limitations are met for the optimization variables:
wherein c represents the wheel track; f in the formula yi The tire magic formula is used for solving the following steps:
F yi ＝Dsin{Carctan[Bα i -E(Bα i -arctanBα i )]} (14)
wherein B, C, D and E are tire model parameters, alpha i Is the wheel slip angle, wherein the front wheel slip angleRear wheel slip angle->
4) Outputting the obtained braking force distribution result of each wheel to a line control power execution module;
step 6:
the linear control power distribution execution module mobilizes each component of the linear control braking system to work according to the obtained braking force control target, provides accurate braking force for each wheel, and provides a safety auxiliary function for dangerous situations encountered by the vehicle in the lane changing process;
the vehicle brake-by-wire auxiliary safety system includes: the system comprises an environment sensing module, a driver input module, a vehicle ECU module, a state sensing module and an execution module;
the environment sensing module comprises a laser radar (2), a camera (3) and at least one millimeter wave radar (1); the laser radar (2), the camera (3) and the millimeter wave radar (1) respectively transmit acquired data to the collision risk analysis module (11);
the driver input module comprises a steering wheel (6), a steering column (5) connected with the steering wheel, a steering wheel angle and rotating speed sensor (4) arranged on the steering column, a brake pedal (8) and a pedal brake stroke sensor (7) connected with the brake pedal, wherein the steering wheel angle and rotating speed sensor (4) and the brake pedal stroke sensor (7) respectively transmit the obtained data to the collision risk analysis module (11);
the state sensing module comprises a GPS inertial navigator (10) and a GPS antenna (9) matched with the GPS inertial navigator; the state sensing module transmits the obtained data to the line control power distribution control module (12);
the vehicle ECU module includes a collision risk analysis module (11) and a line control power distribution control module (12) that are connected to each other.
2. The control method based on the vehicle brake-by-wire auxiliary safety system according to claim 1, wherein the GPS inertial navigator (10) is fixed inside the vehicle body, and the GPS antenna (9) is installed on the roof of the vehicle body.
3. Control method based on a vehicle brake-by-wire auxiliary safety system according to claim 1, characterized in that the lidar (2) and the camera (3) are each mounted to the roof of the vehicle body.
4. The control method based on the vehicle brake-by-wire auxiliary safety system according to claim 1, wherein the vehicle brake-by-wire auxiliary safety system comprises four millimeter wave radars (1) respectively installed at the front, rear, left and right sides of the vehicle body.
5. Control method based on a vehicle brake-by-wire auxiliary safety system according to claim 1, characterized in that the execution module comprises a brake sub-valve (13), an accumulator (14), a hydraulic pump (15) and wheels (18);
the brake sub valve (13), the energy accumulator (14) and the hydraulic pump (15) are connected in sequence; the brake (16) and the brake disc (17) are arranged on the wheel (18), and the brake (16) and the brake disc (17) are respectively connected with the brake sub-valve (13); the brake sub-valve (13) receives a control signal sent by the line control power distribution control module (12).
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| CN104442777A (en) * | 2014-11-27 | 2015-03-25 | 江苏理工学院 | Chassis wheel edge distributive type independent brake executing mechanism and chassis brake system |
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