CN114872695A - Active collision avoidance method and system and automobile - Google Patents
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- B60W30/08—Active safety systems predicting or avoiding probable or impending collision or attempting to minimise its consequences
- B60W30/09—Taking automatic action to avoid collision, e.g. braking and steering
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
- B60W30/08—Active safety systems predicting or avoiding probable or impending collision or attempting to minimise its consequences
- B60W30/095—Predicting travel path or likelihood of collision
- B60W30/0953—Predicting travel path or likelihood of collision the prediction being responsive to vehicle dynamic parameters
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- B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
- B60W2050/0001—Details of the control system
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- B60W2050/0028—Mathematical models, e.g. for simulation
- B60W2050/0037—Mathematical models of vehicle sub-units
- B60W2050/0039—Mathematical models of vehicle sub-units of the propulsion unit
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
- B60W2050/0001—Details of the control system
- B60W2050/0019—Control system elements or transfer functions
- B60W2050/0028—Mathematical models, e.g. for simulation
- B60W2050/0037—Mathematical models of vehicle sub-units
- B60W2050/0041—Mathematical models of vehicle sub-units of the drive line
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W2420/00—Indexing codes relating to the type of sensors based on the principle of their operation
- B60W2420/40—Photo, light or radio wave sensitive means, e.g. infrared sensors
- B60W2420/408—Radar; Laser, e.g. lidar
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W2520/00—Input parameters relating to overall vehicle dynamics
- B60W2520/10—Longitudinal speed
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W2554/00—Input parameters relating to objects
- B60W2554/40—Dynamic objects, e.g. animals, windblown objects
- B60W2554/404—Characteristics
- B60W2554/4042—Longitudinal speed
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
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Abstract
The invention provides an active collision avoidance method, an active collision avoidance system and an automobile, belongs to the technical field of intelligent traffic and unmanned driving, and simplifies a dynamic formula of an automobile transmission structure; an automobile longitudinal dynamics model of an engine model, a hydraulic torque converter model, an automatic transmission model and an entire automobile mass model; the method comprises the steps that information such as the relative distance, the relative speed, the speed and the acceleration of a rear vehicle, the speed and the acceleration of a front vehicle, the vehicle width and the transverse angle of the front vehicle and the rear vehicle is obtained through a radar sensor of the rear vehicle, and a safe distance model calculates the distance required to be kept between the front vehicle and the rear vehicle according to the information and compares the distance with the actual vehicle distance; when the actual vehicle distance is smaller than the safety distance in the collision avoidance system, the vehicle is in a dangerous condition and needs a driver to perform braking operation, and if the driver does not perform the braking operation, the active collision avoidance system directly closes a throttle valve of the vehicle and starts braking, so that the occurrence of rear-end accidents is avoided.
Description
Technical Field
The invention relates to the technical field of intelligent traffic and unmanned driving, in particular to an unmanned active collision avoidance method and system based on an automobile transmission structure and an automobile.
Background
The unmanned vehicle technology combines the technologies of a path navigation system, artificial intelligence, a radar, a GPS positioning system, a vehicle networking and the like, a vehicle-mounted sensor is arranged on a vehicle body, devices such as an accelerator, a brake and the like are connected with the internet, information of the unmanned vehicle is combined with other vehicles, pedestrians and roads, so that the unmanned vehicle has the capabilities of autonomous decision-making capability, control capability, environment perception and the like, the control of a driver on the vehicle is reduced, the comfort of the vehicle is further ensured, and the driving safety of the vehicle is also improved. For unmanned vehicles, the society of automotive engineers has defined six levels of vehicle automation, L0, L1, L2, L3, L4, L5. As the grade increases, the human driver will gradually relinquish control to the vehicle. When reaching the level L5, the vehicle can independently complete all driving operations by the intelligent system, and the unmanned vehicle can completely drive the vehicle to run in any scene.
However, the unmanned vehicle technology is still immature, and there is a problem in terms of safety. For example, No. 18/3/2018, an unmanned SUV of a certain model collides with a pedestrian on the road when conducting the unmanned test, has a speed of 64Km/h, and has no trace of deceleration. When a pedestrian goes out, the bicycle is pushed to cross the road, but the pedestrian does not walk on the crosswalk, and the test vehicle is provided with a plurality of cameras, wherein the cameras facing forwards are also opposite to a driver on the vehicle. Although having enough camera sensors can not avoid accidents, it is seen that there is still a need for improvement in collision avoidance systems for unmanned vehicles to avoid such accidents occurring again.
In the aspect of establishing the dynamic model, the vehicle model is constructed by starting from a kinematic model, wherein the vehicle is regarded as a point in the kinematic model, and the speed, the distance and the like are simply considered. Then, a two-degree-of-freedom kinematic model is proposed on the basis of the single mass point, wherein the two front wheels of the vehicle are regarded as one wheel, and the front wheels and the rear wheels have a certain corresponding relation in steering, and are not single mass points. When the acceleration is introduced into the vehicle model, the model is also converted from a kinematic model to a dynamic model, so that a two-degree-of-freedom moment-driven model appears, and the rear wheel of the model is driven by the moment, thereby generating the acceleration. To be more practical, the acceleration cannot meet the needs of the study simply by considering the external speed of the vehicle.
In the aspect of the controller, a control algorithm is involved in the collision avoidance function, and the use of the control algorithm determines whether the collision avoidance effect is good or bad, so the selection of the controller is particularly important. The PID controller, which is the most basic controller in the control theory, is used in the active collision avoidance function first. But the parameter setting is especially difficult due to the self limitation of the PID controller.
In the aspect of a collision avoidance model, like the conventional fixed safe distance model, when the distance between a front vehicle and a rear vehicle is reduced to a certain value, the rear vehicle is braked, but the distance model reduces the utilization rate of a road surface and does not consider the speed relation of the front vehicle and the rear vehicle.
Disclosure of Invention
The invention aims to provide an unmanned active collision avoidance method and system based on an automobile transmission structure and an automobile, wherein a complete vehicle dynamic model is constructed, a proper control algorithm is selected, an effective safe distance model is established, and the unmanned vehicle can be ensured to be actively prevented from collision, so that at least one technical problem in the background technology is solved.
In order to achieve the purpose, the invention adopts the following technical scheme:
in one aspect, the present invention provides an active collision avoidance method, including:
acquiring running environment information, wherein the running environment information comprises the relative distance between the vehicle and the front vehicle, the relative distance and the relative speed between the vehicle and the front vehicle, the running state information of the front vehicle, the vehicle type information of the front vehicle and the vehicle type information of the vehicle;
the method comprises the steps of utilizing a built vehicle longitudinal dynamics model, calculating a safe distance which needs to be kept between a front vehicle and a vehicle according to running environment information, comparing the safe distance with an actual vehicle distance between the vehicle and the front vehicle, when the actual vehicle distance is smaller than the safe distance, needing a driver to brake the vehicle, and if the driver does not execute the vehicle braking operation, directly closing a vehicle throttle valve to brake, so as to avoid rear-end accidents.
Optionally, based on three assumptions that the transmission shaft and the transmission gear are rigid, the slip ratio is not considered, and the automobile runs on a straight road surface in windless weather, a dynamic formula of the automobile transmission structure is simplified, and a longitudinal dynamic model of the automobile is constructed.
Optionally, the constructed vehicle longitudinal dynamics model comprises an engine model, a hydraulic torque converter model, an automatic transmission model and a whole vehicle mass model, and the accelerator and the brake are used as two mutually independent actuating mechanisms.
Optionally, the engine model is:
T e ＝f e (n e ,a)
under steady state conditions, the external and part load characteristics of the engine are non-linear functions related to engine opening and output speed, where T e For acceleration resistance, n e Is the engine speed, a is the throttle opening;
stabilizing the rotating speed of the engine at a fixed value to obtain a torque characteristic function of the engine; when the engine speed and the throttle opening are changed, the torque output characteristic of the engine can be regarded as a first-order linear model, namely the first-order linear model can be used as the output torque T of the engine ed With engine response lag time t e The relationship between the engine output torque and the engine torque is as follows:
from the torque transmission relationship between the engine and the torque converter, the relationship between the engine speed and the engine output torque can be obtained as shown in the following equation:
J e ω e ＝T ed -T p
in the formula T p For torque converter impeller torque, J e Effective moment of inertia for the rotating parts of the engine.
Optionally, the torque converter model is: characteristics of torque converters including torque characteristics and capacity characteristics, i.e. hydrodynamicTorque ratio tau and capacity factor K of torque converter tc . Pump speed omega of hydraulic torque converter p And turbine speed omega t The ratio of the torque to the torque; torque of pump impeller and turbine wheel respectively using T p And T t Represents; the torque characteristics and capacity characteristics are expressed as follows:
the obtained torque formula of the pump impeller of the hydraulic torque converter is as follows:
then, the formula for the turbine torque is:
the rotational speed and torque of the output shaft are respectively represented by omega 0 And T 0 Represents; for gear ratio determined according to gear g Represents; the transmission ratios corresponding to different gears are different, and the following two equations are established:
ω t ＝ω 0 R g
T 0 ＝T t R g 。
optionally, the automatic transmission model is: the gear clutch is automatically switched according to the speed of the vehicle and the opening degree of the throttle valve, the gear of the vehicle is automatically switched according to connection and release of the clutch, and smooth running of the vehicle is guaranteed.
Optionally, the vehicle mass model is as follows: when a vehicle driving system and a vehicle dynamic model are established, reasonable simplification and assumption are provided according to the real situation of vehicle running: the drive shaft and the transmission gear in the power transmission system are rigid; non-linear factors such as vehicle tires are not considered; the automobile is on a straight and horizontal road and runs in windless weather; during the driving process, the existing power and resistance relation is as follows:
F j ＝F t +F w +F f +F b
F j for acceleration resistance, F t As a driving force, F w As air resistance, F b For braking force, F f Is rolling resistance; wherein,
F t ＝T 0 i 0 η t /r
F w ＝0.5C d Aρv 2
F f ＝mgf
F b ＝K b P b
wherein, T e For engine torque, δ is the vehicle rotating mass conversion factor, i 0 Is the main reducer transmission ratio, K b For the brake pressure scaling factor, P b For brake pressure, f is the rolling resistance coefficient, C d The air resistance coefficient, a, windward area, ρ, air density.
Optionally, the safe distance is calculated as follows: in order to avoid rear-end collision, the actual longitudinal relative distance between the two vehicles is larger than the displacement difference of the two vehicles in the braking process; the safe distance d between the two vehicles is the difference of the driving distance between the two vehicles before and after the braking process; in an ideal state, when the actual longitudinal distance of the two vehicles reaches the critical safety distance, the two vehicles just collide:
wherein，S F Indicating the braking distance of the preceding vehicle, S L Indicating the braking distance, V, of the vehicle A Indicating the speed, theta, of the rear vehicle 1 Representing the included angle between the direction of the millimeter wave radar right ahead and the direction of the nearest target point; Δ v represents the speed difference between the two cars, a m Indicating the maximum deceleration of the host vehicle.
In a second aspect, the present invention provides an active collision avoidance system, comprising:
the system comprises an acquisition module, a storage module and a processing module, wherein the acquisition module is used for acquiring running environment information, and the running environment information comprises the relative distance between a vehicle and a front vehicle, the relative distance and the relative speed between the vehicle and the front vehicle, the running state information of the front vehicle, the vehicle type information of the front vehicle and the vehicle type information of the vehicle;
and the collision avoidance control module is used for calculating a safe distance required to be kept between the front vehicle and the vehicle according to the running environment information by using the constructed vehicle longitudinal dynamic model, comparing the safe distance with the actual vehicle distance between the vehicle and the front vehicle, when the actual vehicle distance is less than the safe distance, requiring a driver to perform braking operation on the vehicle, and if the driver does not perform braking operation on the vehicle, directly closing a throttle valve of the vehicle to perform braking, so as to avoid rear-end collision accidents.
In a third aspect, the present invention provides an unmanned vehicle comprising an active collision avoidance system as described above.
The invention has the beneficial effects that:
based on three assumptions that a transmission shaft and a transmission gear are rigid, the problem of slip rate is not considered, and an automobile runs on a straight road surface in windless weather, a dynamic formula of an automobile transmission structure is simplified;
the system comprises an engine model, a hydraulic torque converter model, an automatic transmission model and an automobile longitudinal dynamics model of an entire automobile mass model, wherein an accelerator and a brake are used as two mutually independent actuating mechanisms to jointly form a complete entire automobile longitudinal dynamics model;
in the active collision avoidance system, information such as relative distance, relative speed, rear vehicle speed and acceleration, front vehicle speed and acceleration, vehicle width and transverse angle of a rear vehicle and a front vehicle is obtained through a radar sensor of the rear vehicle, and a safety distance model calculates the distance required to be kept by the front vehicle and the rear vehicle according to the information and compares the distance with the actual vehicle distance; when the actual vehicle distance is smaller than the safety distance in the collision avoidance system, the vehicle is in a dangerous condition and needs a driver to perform braking operation, and if the driver does not perform the braking operation, the active collision avoidance system directly closes a throttle valve of the vehicle and starts braking, so that the occurrence of rear-end accidents is avoided.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flow chart of a vehicle power transmission from a throttle to the overall acceleration of the vehicle provided by an embodiment of the present invention;
FIG. 2 is a diagram of a longitudinal safe distance model according to an embodiment of the present invention;
fig. 3 is a flowchart illustrating a process of determining a dangerous condition by the autonomous collision avoidance system according to the embodiment of the present invention;
FIG. 4 is a diagram of a vehicle-mounted sensor acquiring real-time information of a vehicle operating condition according to an embodiment of the present invention;
FIG. 5 is a schematic block diagram of a lateral safe distance model according to an embodiment of the present invention;
FIG. 6 is a graph of vehicle braking acceleration under ideal conditions provided by the embodiment of the present invention;
fig. 7 is a structural diagram of an overall control system according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below by way of the drawings are illustrative only and are not to be construed as limiting the invention.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
For the purpose of facilitating an understanding of the present invention, the present invention will be further explained by way of specific embodiments with reference to the accompanying drawings, which are not intended to limit the present invention.
It should be understood by those skilled in the art that the drawings are merely schematic representations of embodiments and that the elements shown in the drawings are not necessarily required to practice the invention.
Example 1
In active collision avoidance systems, unmanned longitudinal dynamics models are also an essential part. The proposed active collision avoidance puts the considered emphasis on the safe distance model, so that the construction of the longitudinal dynamic model of the vehicle is too simple, the set parameters are few, the considered links are few, and the real practical application is not helped, so that the construction of the longitudinal dynamic model of the vehicle with complex parameters and various links is necessary.
Therefore, embodiment 1 of the present invention provides a dynamic modeling method based on an automobile transmission structure, a specific vehicle power transmission flow of which can be seen in fig. 1, and a vehicle dynamic model is formed by:
an engine model, a hydraulic torque converter model, an automatic transmission model and a whole vehicle mass model. The process from throttle to overall acceleration of the vehicle is shown in fig. 1 and shows the relevant characteristic parameters and the dynamic transmission relationship between them.
The whole collision avoidance process can be realized in an active collision avoidance system consisting of a sensor information acquisition module, a control operation module and a longitudinal dynamics module, in order to avoid existence of human factors, a complete longitudinal safe distance model is established by acquiring vehicle-mounted sensor information and evaluating the vehicle state, the safety constraint of the vehicle in the longitudinal collision avoidance process is analyzed, and a safe driving environment is provided for a driver and the vehicle. The information transfer of each module in this embodiment is shown in fig. 2.
After the whole system model is established, the dangerous working condition of the autonomous collision avoidance system needs to be judged according to the combination of the transverse safety distance model and the longitudinal safety distance model, the braking control system is triggered immediately when the dangerous condition is achieved, and once the braking control system is triggered, the unmanned vehicle is braked until the dangerous condition is relieved. The logic that should be followed by the determination process for hazardous conditions is shown in FIG. 3.
The safe distance model is established by acquiring real-time information of the running condition of the vehicle through a vehicle-mounted sensor, inputting the information acquired by the sensor into a control processor, obtaining a certain quantity capable of representing the current vehicle condition danger degree according to a pre-designed calculation method, and judging an emergency danger condition and triggering a vehicle autonomous braking measure or not through a threshold value method by a system ECU. The sensing area of the millimeter wave radar sensor is in a sector shape, danger judgment needs to be carried out from 2 aspects of the transverse direction and the longitudinal direction, and the braking system can be triggered when the automobile L and the front automobile F running in the same direction reach dangerous working conditions. Straight road driving state, as shown in fig. 4.
Wherein, W mea Representing the lateral distance between the millimeter-wave radar and the target vehicle; w 0 The safe distance which is required to be kept between the adjacent two sides of the self vehicle and the target vehicle is represented; w A Representing the width of the vehicle body; theta 1 Representing the included angle between the direction of the millimeter wave radar right ahead and the direction of the nearest target point; l is meal Representing the distance between the nearest target point and the millimeter wave radar; theta n Representing the included angle between the position and the direction of the millimeter wave radar right ahead and other target points; l is mean Indicating the distance between other target points and the millimeter wave radar.
When the own vehicle F is driving, the vehicle L is sensed, and since F has a certain length range, the radar detects a series of data about the position of the vehicle L, and the upper controller preferentially selects L from the data meal And theta 1 And (3) calculating to obtain the transverse distance between the target point and the millimeter wave radar sensor, as shown in the formula (1). To ensure driving safety, W mea The conditions to be satisfied are as shown in formula (2). And (3) a two-vehicle transverse safe distance simulation model, as shown in figure 5.
W mea ＝L meal sinθ 1 (1)
And calculating the longitudinal safety distance under the current driving condition according to the information such as the speed, the relative speed and the like of the vehicle, and further judging whether the longitudinal distance from the radar to the nearest target reaches an emergency state.
And establishing a longitudinal safe distance model according to the braking process of the vehicle and the vehicle pursuit problem based on the ideal state. The autonomous emergency braking system of the vehicle automatically takes braking measures independent of the driving consciousness of people, and the braking acceleration curve of the vehicle under the ideal state is shown in figure 6.
When t is from 0 to t 1 In the meantime, the pressure of a brake cylinder of the tire is gradually pressed on the tire, and the unmanned vehicle is in a brake deceleration increasing time period; when t is at t 1 To t 2 In between, the braking deceleration reaches a peak, i.e. the maximum vehicle deceleration that the ground can impart; when t is at t 2 To t 3 Meanwhile, the unmanned vehicle is in a safe environment, the purpose of collision avoidance is achieved, and the braking effect disappears.
In the autonomous emergency braking process of the automobile, the reaction time of the driver for subjectively judging the road condition is ignored, so that the automobile passes through a braking acceleration increasing stage and a braking acceleration maintaining stage until the automobile speed is 0. As shown in formula (3), the braking distance of the F vehicle is S F (ii) a As shown in formula (4), the braking distance of the L vehicle is S L 。
In the formula V A The rear vehicle speed (m/s) and Δ v are the relative speeds (m/s) of the two vehicles.
When the F vehicle is between 0 and t 1 In between, as in equation (5), the acceleration is a 1 。
In the formula a m Maximum deceleration (m/s) 2 )。
Thus, when F vehicle is between 0 and t 1 In between, the amount of change in speed is Δ v, as shown in equation (6).
Thus, it can be obtained that 1 The displacement between F and S F1 As shown in formula (7).
When the F vehicle is in, the speed of the F vehicle reaches V 1 As shown in formula (8).
When the F vehicle is at t 1 To t 2 In the middle, its acceleration a 2 Is constantly a m From 0 to t 1 The displacement between F and S F2 As shown in formula (9).
So at vehicle F at t 0 To t 2 In the middle, the total displacement S of the F vehicle F Is S F1 And S F2 And (4) the sum of formula (10).
In the above calculation, the time taken for the braking acceleration to rise is taken to be 0.2s, where t 1 The high-order term is negligibly small in value, so that the distance traveled by the vehicle in the braking process is shown as a formula (11).
When the F vehicle is at t 2 To t 3 In between, since the dangerous vehicle condition has been resolved, the vehicle deceleration can be regarded as 0. Time t required for braking of bicycle 2 As shown in formula (12).
When the L vehicle is at t 0 To t 2 In between, the total displacement of the L cars is S L As shown in formula (13).
Formula (14) can be obtained by bringing formula (12) into formula (13).
S L ＝V A (0.1+a m )-Δv·cosθ 1 (0.1+a m ) (14)
To avoid rear-end collisions, the actual longitudinal relative distance between the two vehicles should be greater than the difference in travel displacement between the two vehicles during braking. The longitudinal critical safety distance d between the self-vehicle F and the vehicle L is the difference of the driving distance between the front vehicle and the rear vehicle in the braking process. Ideally, when the actual longitudinal distance between the two vehicles reaches the critical safety distance, the two vehicles just collide.
From the equation (13), the threshold value of the longitudinal safe distance is continuously changed with the driving state of the vehicle, and the magnitude of the threshold value is related to the speed of the vehicle, the relative speed of the two vehicles, the azimuth angle, the maximum braking acceleration and other factors. And in the driving process of the automobile, comparing the actual longitudinal relative distance delta L between the automobile and the front obstacle with the safe distance at any time, and judging whether the automobile is possibly in rear-end collision danger or not.
ΔL＝L meal cosθ 1 (16)
As shown in equation (17), a dimensionless parameter epsilon is introduced to indicate the risk level of the vehicle that may be in collision, and a threshold value is set to indicate the critical state of the collision risk.
In an actual road, the braking process of an automobile is not ideal, errors exist in the effective reaction time of braking force and the maximum braking acceleration, a certain allowance is reserved on a longitudinal collision danger critical threshold, and the actual relative distance is 1.2 times of an ideal safety distance critical value. The threshold state of the parameter ε is ranked as follows:
when epsilon is more than 1, the safe vehicle distance state between the self vehicle and the front vehicle is kept;
when epsilon is more than 0.5 and less than or equal to 1, the vehicle has certain collision danger, but is not serious, and a driver needs to be kept alert;
when epsilon is more than 0.2 and less than or equal to 0.5, the vehicle is indicated to have larger collision danger, and the vehicle should send out an alarm to remind a driver to take braking measures;
when epsilon is less than or equal to 0.2, the vehicle is very close to the collision danger, and the system immediately uses the maximum braking force to perform autonomous emergency braking after detecting that the driver does not perform braking operation, so as to avoid collision injury or reduce collision loss.
Example 2
The embodiment 2 of the invention provides a dynamic modeling and active collision avoidance method based on an automobile transmission structure, and an algorithm and a device can well establish a vehicle longitudinal dynamic model. The longitudinal dynamic model of the vehicle is divided into four parts, namely an engine, a hydraulic torque converter, an automatic transmission and the whole vehicle mass, and the design of throttle control and braking force control switching logic is included, so that the structure of the longitudinal dynamic model is closer to that of the real vehicle. In the safe distance model part, a safe distance model based on the characteristics of a driver is adopted to ensure the driving safety of the vehicle.
In embodiment 2, the above dynamic modeling method based on an automobile transmission structure includes:
based on three assumptions that a transmission shaft and a transmission gear are rigid, the problem of slip ratio is not considered, and an automobile runs on a straight road surface in windless weather, the dynamic formula of the automobile transmission structure is simplified; the automobile longitudinal dynamics model is provided with an engine model, a hydraulic torque converter model, an automatic transmission model and an entire automobile mass model, and an accelerator and a brake are used as two mutually independent actuating mechanisms to jointly form a complete entire automobile longitudinal dynamics model.
After the model is established, an active collision avoidance system which accords with the characteristics of a driver is developed aiming at the problems of the driving characteristics of the driver and the lag of a vehicle transmission structure. In the active collision avoidance system, information such as relative distance, relative speed, rear vehicle speed and acceleration, front vehicle speed and acceleration, vehicle width and transverse angle of a rear vehicle and a front vehicle is obtained through a radar sensor of the rear vehicle, and a safety distance model calculates the distance required to be kept by the front vehicle and the rear vehicle according to the information and compares the distance with the actual vehicle distance. When the actual vehicle distance is smaller than the safety distance in the collision avoidance system, the vehicle is in a dangerous condition and needs a driver to perform braking operation, and if the driver does not perform the braking operation, the active collision avoidance system directly closes a throttle valve of the vehicle and starts braking, so that the occurrence of rear-end accidents is avoided.
In active collision avoidance systems, unmanned longitudinal dynamics models are also an essential part. The proposed active collision avoidance puts the considered emphasis on the safe distance model, so that the construction of the longitudinal dynamic model of the vehicle is too simple, the set parameters are few, the considered links are few, and the real practical application is not helped, so that the construction of the longitudinal dynamic model of the vehicle with complex parameters and various links is necessary.
A dynamic modeling method based on an automobile transmission structure is disclosed, wherein a specific vehicle power transmission flow can be seen in FIG. 1, and a vehicle dynamic model comprises the following components:
an engine model, a hydraulic torque converter model, an automatic transmission model and a whole vehicle mass model. The process from throttle to overall acceleration of the vehicle is shown in fig. 1 and shows the relevant characteristic parameters and the dynamic transmission relationship between them.
The whole collision avoidance process can be realized in an active collision avoidance system consisting of a sensor information acquisition module, a control operation module and a longitudinal dynamics module, in order to avoid existence of human factors, a complete longitudinal safe distance model is established by acquiring vehicle-mounted sensor information and evaluating the vehicle state, the safety constraint of the vehicle in the longitudinal collision avoidance process is analyzed, and a safe driving environment is provided for a driver and the vehicle. The information transmission of each module in the embodiment 2 is shown in fig. 2.
After the whole system model is established, the dangerous working condition of the autonomous collision avoidance system needs to be judged according to the combination of the transverse safety distance model and the longitudinal safety distance model, the braking control system is triggered immediately when the dangerous condition is achieved, and once the braking control system is triggered, the unmanned vehicle is braked until the dangerous condition is relieved. The logic that should be followed by the determination process for hazardous conditions is shown in FIG. 3.
The safe distance model is established by acquiring real-time information of the running condition of the vehicle through a vehicle-mounted sensor, inputting the information acquired by the sensor into a control processor, obtaining a certain quantity capable of representing the current vehicle condition danger degree according to a pre-designed calculation method, and judging an emergency danger condition and triggering a vehicle autonomous braking measure or not through a threshold value method by a system ECU. The sensing area of the millimeter wave radar sensor is in a sector shape, danger judgment needs to be carried out from 2 aspects of the transverse direction and the longitudinal direction, and the braking system can be triggered when the automobile L and the front automobile F running in the same direction reach dangerous working conditions. Straight road driving state, as shown in fig. 4.
Wherein, W mea Representing the lateral distance between the millimeter-wave radar and the target vehicle; w 0 The safe distance which is required to be kept between the adjacent two sides of the self vehicle and the target vehicle is represented; w A Represents the width of the vehicle body; theta 1 Representing the included angle between the direction of the millimeter wave radar right ahead and the direction of the nearest target point; l is meal Representing the distance between the nearest target point and the millimeter wave radar; theta n Representing the included angle between the position and the direction of the millimeter wave radar right ahead and other target points; l is mean Indicating the distance between other target points and the millimeter wave radar.
When the self-vehicle F is driven, the self-vehicle F senses the vehicle L, and since the self-vehicle F has a certain length range, the radar detects a series of data about the position of the vehicle L, and the upper-layer controller preferentially selects L from the data meal And theta 1 And (3) calculating to obtain the transverse distance between the target point and the millimeter wave radar sensor, as shown in the formula (1). To ensure driving safety, W mea The conditions to be satisfied are as shown in formula (2). And (3) a two-vehicle transverse safe distance simulation model, as shown in figure 5.
W mea ＝L meal sinθ 1 (1)
And calculating the longitudinal safety distance under the current driving condition according to the information such as the speed, the relative speed and the like of the vehicle, and further judging whether the longitudinal distance from the radar to the nearest target reaches an emergency state.
And establishing a longitudinal safe distance model according to the braking process of the vehicle and the vehicle pursuit problem based on the ideal state. The autonomous emergency braking system of the vehicle automatically takes braking measures independent of the driving consciousness of people, and the braking acceleration curve of the vehicle under the ideal state is shown in figure 6.
When t is from 0 to t 1 In the meantime, the pressure of a brake cylinder of the tire is gradually pressed on the tire, and the unmanned vehicle is in a brake deceleration increasing time period; when t is at t 1 To t 2 In between, the braking deceleration reaches a peak, i.e. the maximum vehicle deceleration that the ground can impart; when t is at t 2 To t 3 In the meantime, the unmanned vehicle is in a safe environment, the collision avoidance purpose is achieved, and the braking effect disappears.
In the automobileIn the autonomous emergency braking process, the reaction time of the driver for subjectively judging the road condition is ignored, so that the braking acceleration increasing stage and the braking acceleration maintaining stage are carried out until the vehicle speed is 0. As shown in formula (3), the braking distance of the F vehicle is S F (ii) a As shown in formula (4), the braking distance of the L vehicle is S L 。
In the formula V A The rear vehicle speed (m/s) and Δ v are the relative speeds (m/s) of the two vehicles.
When the F vehicle is between 0 and t 1 In between, as in equation (5), the acceleration is a 1 。
In the formula a m Maximum deceleration (m/s) 2 )。
Thus, when F vehicle is between 0 and t 1 In between, the amount of change in speed is Δ v, as shown in equation (6).
From this it can be obtained that, from 0 to t 1 The displacement between F and S F1 As shown in formula (7).
When F vehicle is in, its speed reaches V 1 As shown in formula (8).
When the F vehicle is at t 1 To t 2 In the middle, its acceleration a 2 Is constantly a m From 0 to t 1 The displacement between F and S F2 As shown in formula (9).
So that the vehicle is at t in F 0 To t 2 In the middle, the total displacement S of the F vehicle F Is S F1 And S F2 And (4) the sum of formula (10).
In the above calculation, the time taken for the braking acceleration to rise is taken to be 0.2s, where t 1 The high-order term is negligibly small in value, so that the distance traveled by the vehicle in the braking process is shown as a formula (11).
When the F vehicle is at t 2 To t 3 In between, since it is a dangerous vehicle condition that has been released, the vehicle deceleration can be regarded as 0. Time t required for braking of bicycle 2 As shown in formula (12).
When the L vehicle is at t 0 To t 2 In between, the total displacement of the L cars is S L As shown in formula (13).
Formula (14) can be obtained by bringing formula (12) into formula (13).
S L ＝V A (0.1+a m )-Δv·cosθ 1 (0.1+a m ) (14)
To avoid rear-end collisions, the actual longitudinal relative distance between the two vehicles should be greater than the difference in travel displacement between the two vehicles during braking. The longitudinal critical safety distance d between the self-vehicle F and the vehicle L is the difference of the driving distance between the front vehicle and the rear vehicle in the braking process. Ideally, when the actual longitudinal distance between the two vehicles reaches the critical safety distance, the two vehicles just collide.
From the equation (13), the threshold value of the longitudinal safe distance is continuously changed with the driving state of the vehicle, and the magnitude of the threshold value is related to the speed of the vehicle, the relative speed of the two vehicles, the azimuth angle, the maximum braking acceleration and other factors. And in the driving process of the automobile, comparing the actual longitudinal relative distance delta L between the automobile and the front obstacle with the safe distance at any time, and judging whether the automobile is possibly in rear-end collision danger or not.
ΔL＝L meal cosθ 1 (16)
As shown in equation (17), a dimensionless parameter epsilon is introduced to indicate the risk level of the car that may be collided with, and a threshold value is set to indicate the critical state of the collision risk.
In an actual road, the braking process of an automobile is not ideal, errors exist in the effective reaction time of braking force and the maximum braking acceleration, a certain allowance is reserved on a longitudinal collision danger critical threshold, and the actual relative distance is 1.2 times of an ideal safety distance critical value. The threshold state of the parameter ε is ranked as follows:
when epsilon is more than 1, the safe vehicle distance state between the self vehicle and the front vehicle is kept;
when epsilon is more than 0.5 and less than or equal to 1, the vehicle has certain collision danger, but is not serious, and a driver needs to be kept alert;
when epsilon is more than 0.2 and less than or equal to 0.5, the vehicle is indicated to have larger collision danger, and the vehicle should send out an alarm to remind a driver to take braking measures;
when epsilon is less than or equal to 0.2, the vehicle is very close to the collision danger, and the system immediately uses the maximum braking force to perform autonomous emergency braking after detecting that the driver does not perform braking operation, so as to avoid collision injury or reduce collision loss.
The method is characterized in that an automobile longitudinal dynamics model with complex parameters and various links is established, wherein the automobile longitudinal dynamics model comprises an engine model, a hydraulic torque converter model, an automatic transmission model and an entire automobile mass model, and an accelerator and a brake are used as two mutually independent executing mechanisms to jointly form a complete entire automobile longitudinal dynamics model, and an unmanned longitudinal dynamics model is an indispensable part in an active collision avoidance system. The proposed active collision avoidance puts the considered key on the safe distance model, so that the construction of the longitudinal dynamic model of the vehicle is too simple, the set parameters are few, the considered links are few, and the real practical application is not helped;
a control system capable of realizing parameter self-tuning is established, the system adopts a Simple Decomposition Fuzzy System (SDFS) to adjust parameters Kp, Ki and Kd of PID in real time, and the decomposition fuzzy theory and PID control are combined and applied to a vehicle dynamics model, so that the online automatic tuning of PID parameters is realized, the defect of common PID control regulation is made up, and the dynamic response to interference is accelerated;
a safe distance model is established, the safe distance model acquires real-time information of the running condition of the vehicle through a vehicle-mounted sensor, the information acquired by the sensor is input into a controller, a danger threshold value is obtained according to a pre-designed calculation method, the danger threshold value is a quantity representing the danger degree of the current vehicle condition, and the system can judge the emergency danger condition through a threshold value method and trigger whether autonomous braking measures of the vehicle are taken or not.
Firstly, an engine model, a hydraulic torque converter model, an automatic transmission model and a whole vehicle mass model are established, and the method comprises the following steps:
(1) an engine model:
T e ＝f e (n e ,a) (1)
under steady state operation, the external characteristic curve and the part load characteristic curve of the engine are nonlinear functions related to the opening degree and the output rotating speed of the engine, and T in the formula (1) e For acceleration resistance (N m), N e Is the engine speed (rpm) and a is the throttle opening (%).
The torque characteristic function of the engine can be obtained by stabilizing the rotation speed of the engine at a fixed value. When the engine speed and the throttle opening are changed, the torque output characteristic of the engine can be regarded as a first-order linear model, namely the first-order linear model can be used as the output torque T of the engine ed Dynamic characteristic of (in which the engine responds with a lag time t) e ) The relationship between the engine output torque and the engine torque is expressed by equation (2).
According to the torque transmission relationship between the engine and the torque converter, the relationship between the engine speed and the engine output torque can be obtained, as shown in equation (3).
J e ω e ＝T ed -T p (3)
In the formula T p For torque converter impeller torque (N m), J e Effective moment of inertia (kg · m) for the rotating parts of the engine 2 )。
(2) The hydraulic torque converter model:
the main component of the transmission is a hydraulic torque converter. The internal structure of the device is complex, and the transmission of the transmission device is ensured by the pump wheel, the turbine and the guide wheel blade. The characteristics of the torque converter include torque characteristics and capacity characteristics, i.e., torque ratio τ and capacity coefficient K of the torque converter tc Pump speed omega of a hydrodynamic torque converter p And turbine speed omega t The ratio is a torque ratio; pump impeller and turbine impellerMoments by T, respectively p And T t And (4) showing. The torque characteristic and the capacity characteristic are expressed by the formulas (4) and (5).
The torque converter impeller torque equation available from equation (5) is as equation (6).
By substituting equation (6) into equation (4), a turbine torque equation can be obtained, as shown in equation (7).
The rotational speed and torque of the output shaft are respectively represented by omega 0 And T 0 And (4) showing. Ratio R determined according to gear g And (4) showing. The transmission ratios corresponding to different gears are different, and the following two equations are established:
ω t ＝ω 0 R g (8)
T 0 ＝T t R g (9)
(3) automatic transmission model:
the transmission is a mechanical controller, also called an automatic gearbox, connected to the turbine. The gear clutch is automatically switched according to the speed of the vehicle and the opening degree of the throttle valve, and the gear of the vehicle is automatically switched according to the connection and the release of the clutch, so that the stable running of the vehicle is ensured. During the running of the vehicle, the throttle opening degree and the vehicle speed constitute a nonlinear function.
(4) The finished automobile mass model:
when a vehicle driving system and a vehicle dynamic model are established, reasonable simplification and assumption are provided according to the real situation of vehicle running: the drive shaft and the transmission gear in the power transmission system are rigid; non-linear factors such as vehicle tires are not considered; the car is on a straight and level road and is traveling in calm weather.
F j ＝F t +F w +F f +F b (10)
Equation (10) is the power and resistance present during travel, F j For acceleration resistance (N), F t As a driving force (N), F w Is the air resistance (N), F b To braking force (N), F f Is rolling resistance (N). Wherein, the specific expression formula of each symbol is shown as formula (11).
F t ＝T 0 i 0 η t /r
F w ＝0.5C d Aρv 2 (11)
F f ＝mgf
F b ＝K b P b
T in formula (11) e Is the engine torque (N m), delta is the vehicle rotating mass conversion factor, i 0 Is the main reducer transmission ratio, K b Is the proportional coefficient of brake pressure (N/Mpa), P b Is brake pressure (mpa), f is rolling resistance coefficient, C d Is the coefficient of air resistance, A is the frontal area (m) 2 ) ρ is the air density (Ns) 2 m -4 )。
After the whole vehicle model is built, an active collision avoidance system which accords with the characteristics of a driver is developed aiming at the driving characteristics of the driver and the problem of lagging of a vehicle transmission structure. During the running process of the vehicle, the safe distance model calculates the safe distance under the current working condition and compares the safe distance with the actual vehicle distance. When the actual vehicle distance is smaller than the safety distance in the collision avoidance system, the vehicle is in a dangerous condition and needs a driver to perform braking operation, and if the driver does not perform the braking operation, the active collision avoidance system directly closes a throttle valve of the vehicle and starts braking, so that the occurrence of rear-end accidents is avoided. The safety distance model in the active collision avoidance system must meet the requirements of various working conditions to ensure the safety of vehicle running. The road conditions required to be adapted by the safe distance model comprise urban highways, urban roads, expressways and the like, and the safe distance model has the advantages of wide application range, complex traffic conditions, good stability and low possibility of misoperation.
By acquiring information such as the relative distance, the relative velocity, the velocity and the acceleration of the rear vehicle, the velocity and the acceleration of the front vehicle, the vehicle width and the lateral angle of the rear vehicle and the front vehicle, the information is acquired by the radar sensor of the rear vehicle. The safe distance model calculates the distance to be kept between the front vehicle and the rear vehicle according to the information, and once the rear vehicle enters the distance, the rear vehicle directly enters an emergency braking state. The essence of the active collision avoidance system is the driving safety, and the method is to ensure the relatively safe distance between the front vehicle and the rear vehicle by decelerating the rear vehicle. Since the road passing rate is in direct proportion to the vehicle speed and in inverse proportion to the distance between vehicles, the too large inter-vehicle distance can cause low vehicle passing rate and low road surface utilization rate. The high-efficiency road passing rate and the driving safety are the key factors for the driving of the vehicle, and the safe distance model should be established by fully considering the two key factors, so that the safe distance model should have corresponding changes to meet the two factors under different working conditions. When a driver drives a vehicle, the judgment on the dangerous condition is different, but the safe distance model can also make the most reasonable judgment for the driver under the current condition while ensuring the safety of the vehicle driving, so that the safety of the vehicle and the driver is ensured, and the occurrence of safety accidents on the road is reduced.
In summary, the embodiment of the invention simplifies the dynamic formula of the automobile transmission structure based on three assumptions that the transmission shaft and the transmission gear are rigid, the problem of slip ratio is not considered, and the automobile runs on a straight road surface in windless weather; the parameters Kp, Ki and Kd of the PID are adjusted in real time by adopting simple decomposition fuzzy PID control, and the decomposition fuzzy theory and the PID control are combined and applied to a vehicle dynamics model, so that the online automatic setting of the PID parameters is realized, the defect of common PID control regulation is overcome, and the dynamic response to interference is accelerated; aiming at the driving characteristics of a driver and the problem of lagging of a vehicle transmission structure, an active collision avoidance system which accords with the characteristics of the driver is developed and comprises a complete longitudinal safe distance model and a control system of the collision avoidance system.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts based on the technical solutions disclosed in the present invention.
Claims (10)
1. An active collision avoidance method, comprising:
acquiring running environment information, wherein the running environment information comprises the relative distance between the vehicle and the front vehicle, the relative distance and the relative speed between the vehicle and the front vehicle, the running state information of the front vehicle, the vehicle type information of the front vehicle and the vehicle type information of the vehicle;
the method comprises the steps of utilizing a built vehicle longitudinal dynamics model, calculating a safe distance which needs to be kept between a front vehicle and a vehicle according to running environment information, comparing the safe distance with an actual vehicle distance between the vehicle and the front vehicle, when the actual vehicle distance is smaller than the safe distance, needing a driver to brake the vehicle, and if the driver does not execute the vehicle braking operation, directly closing a vehicle throttle valve to brake, so as to avoid rear-end accidents.
2. The active collision avoidance method of claim 1, wherein a vehicle longitudinal dynamics model is constructed by simplifying a dynamics formula of a vehicle transmission structure based on three assumptions that a transmission shaft and a transmission gear are rigid, a slip ratio problem is not considered, and a vehicle runs on a straight road surface in a windless weather.
3. The active collision avoidance method of claim 2 wherein the vehicle longitudinal dynamics models constructed include an engine model, a torque converter model, an automatic transmission model and a vehicle mass model, and throttle and brake are two independent actuators.
4. An active collision avoidance method according to claim 3 wherein the engine model is:
T e ＝f e (n e ,a)
under steady state conditions, the external and part load characteristics of the engine are non-linear functions related to engine opening and output speed, where T e For acceleration resistance, n e Is the engine speed, a is the throttle opening;
stabilizing the rotating speed of the engine at a fixed value to obtain a torque characteristic function of the engine; when the engine speed and the throttle opening are changed, the torque output characteristic of the engine can be regarded as a first-order linear model, namely the first-order linear model can be used as the output torque T of the engine ed With engine response lag time t e The relationship between the engine output torque and the engine torque is as follows:
from the torque transmission relationship between the engine and the torque converter, the relationship between the engine speed and the engine output torque can be obtained as shown in the following equation:
J e ω e ＝T ed -T p
in the formula T p For torque converter impeller torque, J e Effective moment of inertia for the rotating parts of the engine.
5. Active collision avoidance according to claim 4The method is characterized in that the hydraulic torque converter model is as follows: the characteristics of the torque converter include torque characteristics and capacity characteristics, i.e., torque ratio τ and capacity coefficient K of the torque converter tc Pump speed omega of a hydrodynamic torque converter p And turbine speed omega t The ratio is a torque ratio; torque of pump impeller and turbine wheel respectively using T p And T t Represents; the torque characteristics and capacity characteristics are expressed as follows:
the obtained torque formula of the pump impeller of the hydraulic torque converter is as follows:
then, the formula for the turbine torque is:
the rotational speed and torque of the output shaft are respectively represented by omega 0 And T 0 Represents; for gear ratio determined according to gear g Represents; the transmission ratios corresponding to different gears are different, and the following two equations are established:
ω t ＝ω 0 R g
T 0 ＝T t R g 。
6. the active collision avoidance method of claim 5, wherein the automatic transmission model is: the gear clutch is automatically switched according to the speed of the vehicle and the opening degree of the throttle valve, the gear of the vehicle is automatically switched according to connection and release of the clutch, and smooth running of the vehicle is guaranteed.
7. The active collision avoidance method of claim 6, wherein the vehicle mass model is: when a vehicle driving system and a vehicle dynamic model are established, reasonable simplification and assumption are provided according to the real situation of vehicle running: the drive shaft and the transmission gear in the power transmission system are rigid; non-linear factors such as vehicle tires are not considered; the automobile is on a straight and horizontal road and runs in windless weather; during the driving process, the existing power and resistance relation is as follows:
F j ＝F t +F w +F f +F b
F j for acceleration resistance, F t As a driving force, F w As air resistance, F b For braking force, F f Is rolling resistance; wherein,
F t ＝T 0 i 0 η t /r
F w ＝0.5C d Aρv 2
F f ＝mgf
F b ＝K b P b
wherein, T e For engine torque, δ is the vehicle rotating mass conversion factor, i 0 Is the main reducer transmission ratio, K b For the brake pressure scaling factor, P b For brake pressure, f is the rolling resistance coefficient, C d Is the air resistance coefficient, A is the frontal area, and ρ is the air density.
8. The active collision avoidance method of claim 1, wherein the safe distance is calculated as follows: in order to avoid rear-end collision, the actual longitudinal relative distance between the two vehicles is larger than the displacement difference of the two vehicles in the braking process; the safe distance d between the two vehicles is the difference of the driving distance between the two vehicles before and after the braking process; in an ideal state, when the actual longitudinal distance between the two vehicles reaches the critical safety distance, the two vehicles just collide:
wherein S is F Indicating the braking distance of the preceding vehicle, S L Indicating the braking distance, V, of the vehicle A Indicating the speed, theta, of the rear vehicle 1 Representing the included angle between the direction of the millimeter wave radar right ahead and the direction of the nearest target point; Δ v represents the speed difference between the two cars, a m Indicating the maximum deceleration of the host vehicle.
9. An active collision avoidance system, comprising:
the system comprises an acquisition module, a storage module and a processing module, wherein the acquisition module is used for acquiring running environment information, and the running environment information comprises the relative distance between a vehicle and a front vehicle, the relative distance and the relative speed between the vehicle and the front vehicle, the running state information of the front vehicle, the vehicle type information of the front vehicle and the vehicle type information of the vehicle;
and the collision avoidance control module is used for calculating a safe distance required to be kept between the front vehicle and the vehicle according to the running environment information by using the constructed vehicle longitudinal dynamic model, comparing the safe distance with the actual vehicle distance between the vehicle and the front vehicle, when the actual vehicle distance is less than the safe distance, requiring a driver to perform braking operation on the vehicle, and if the driver does not perform braking operation on the vehicle, directly closing a throttle valve of the vehicle to perform braking, so as to avoid rear-end collision accidents.
10. An unmanned vehicle comprising an active collision avoidance system according to claim 9.
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