CN112721846B - Front bumper active protection method for safe electric car in rear-end collision - Google Patents
Front bumper active protection method for safe electric car in rear-end collision Download PDFInfo
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- B60R19/40—Arrangements for mounting bumpers on vehicles adjustably or movably mounted, e.g. horizontally displaceable for securing a space between parked vehicles in the direction of an obstacle before a collision, or extending during driving of the vehicle, i.e. to increase the energy absorption capacity of the bumper
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Abstract
The invention particularly relates to a safe front bumper active protection method for an electric car in rear-end collision. The protection method comprises a driving monitoring step and a judging step; an execution step; when the running speed V of the vehicle is higher than a certain speed and the braking acceleration signal a is higher than a certain value, the control unit sends a signal to the execution unit, and the execution unit raises the front bumper by delta H to make the distance H between the front bumper and the ground consistent with the height H0 of the front bumper when the vehicle stops or runs at a constant speed; when the electric car is emergently braked under the condition of a certain speed, the front bumper rises by a certain height, the height reduction of the front bumper of the car during the emergency braking is compensated, so that the front bumper of the car is positioned at the correct height when the car and the front car collide with each other, the energy absorption function of the bumper is exerted, and the safety of the car in the rear-end collision accident is greatly improved.
Description
The application has the following application numbers: 202010264030.9, filing date: 2020-04-07, the patent name "method and device for actively protecting front bumper when rear-end collision occurs in electric car".
Technical Field
The invention relates to an active protection system of an electric car, in particular to a safe active protection method and device for a front bumper of the electric car during rear-end collision.
Background
The existing unmanned automobile is becoming a new direction of automobile field development, for example, a ternary lithium battery driven electric vehicle, the design of the front bumper face shield position is obviously different from the traditional automobile, the traditional automobile must be provided with an air inlet grille for radiating heat of a radiator behind the air inlet grille, the power source of the electric automobile is a battery and a motor system, and the requirement for radiating heat is low, so that most of electric automobiles usually select a closed face shield in order to reduce the air resistance coefficient of an automobile body, for example, a tesla model 3 car, the front face shield of the automobile body is closed, an auxiliary air inlet with a small size is reserved below the face shield, other parts are not arranged behind the face shield at the front part of the electric automobile except the bumper, and the position near the bumper is relatively open.
On the other hand, for the current automobile rear-end collision accident investigation, and by referring to relevant accident identification data, common modes of the rear-end collision accident include a brake lag type, a starting error type and a driving line change type, wherein when the brake lag type and the brake lag type rear-end collision occur, the speed of a rear-end collision automobile is higher in part, according to the investigation on the rear-end collision accident in Lin Yang (japan), the rear-end collision automobile usually adopts emergency braking before the rear-end collision, so that the front bumper of the rear-end collision automobile is lowered in height and is drilled under the rear bumper of the collided automobile, and the front part of the automobile body of the rear-end collision automobile is directly arranged at the rear part of the collided rear bumper, so that the rear-end collision automobile is more easily damaged obviously; that is, even if the front and rear vehicles have the same bumper height, the rear-end vehicle often slightly or significantly digs into the vehicle because the front bumper height of the rear-end vehicle is lowered after the rear-end vehicle is braked, which increases with the difference in height between the two bumpers and the difference in speed between the two vehicles.
Devices capable of achieving front bumper lifting have appeared, for example, a lifting type front bumper structure proposed in patent CN201810378039, which comprises a vehicle chassis, a front bumper, a control unit and an execution unit; a front bumper raisably and lowerably provided on a vehicle chassis; the control unit is used for automatically identifying the pedestrian, sending an instruction to the execution unit before the vehicle collides with the pedestrian, and lifting or dropping the front bumper through the execution unit; however, the bumper structure and the protection method only aim at protecting pedestrians when a vehicle collides with a pedestrian in front, and how a front bumper is controlled when the vehicle collides with the vehicle in front of the vehicle is not considered, so that the rear-end collision vehicle can be better protected, and the bumper structure and the protection method cannot be applied to the problem that the safety of the rear vehicle is reduced due to the reduction of the height of the front bumper when the rear vehicle is braked in the vehicle-vehicle rear-end collision accident.
Disclosure of Invention
The invention aims to provide an active protection device and a protection method for a front bumper of an electric car in rear-end collision, which improve the safety of the car in rear-end collision with a front vehicle.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows: the method for actively protecting the front bumper when the safe electric car knocks into the rear comprises the following steps of: a driving monitoring step and a judging step; an execution step;
the running monitoring step comprises the following steps: the control unit receives a vehicle running speed signal V and a vehicle braking acceleration signal a, and then enters a judging step:
the judging step is as follows:
d. when the vehicle running speed V is greater than a certain speed V0, entering the step b;
e. when the braking acceleration signal a is larger than a certain value a0, the step c is carried out:
the execution steps are as follows:
f. the control unit sends a signal to the execution unit, and the execution unit raises the front bumper by delta H to ensure that the distance H between the front bumper and the ground is consistent with the height H0 of the front bumper when the automobile stops or runs at a constant speed;
the method for calculating the delta H is calculated according to the following (1-1),
d. the control unit continuously receives the value a, and when a is smaller than a0 again, the control unit controls the execution unit to lower the front bumper and restore the initial position;
in the above formula, k 1 Is the rigidity coefficient, L, of the front suspension of the electric car 1 The distance between the mass center and the front end of the electric car is defined, m is the mass of the electric car, a is the acceleration value generated by braking the car, and h is the height between the mass center of the electric car and the ground.
Preferably, in the method for calculating Δ H, Δ H is also calculated according to the formula (1-2) 2 And will be Δ H 1 ，ΔH 2 The larger value of the two is taken as the value Δ H:
ΔH＝Max(ΔH 1 ，ΔH 2 )
in the above formula, k 2 Is the rigidity coefficient of the rear suspension of the electric car 2 Is the distance from the center of mass to the rear axle, L 2 The distance between the position center of mass and the rear end of the electric car.
Preferably, the V0 is 50km/h or 60km/h or 70km/h or 80km/h, and the a0 is 5.0-6.2m/s 2 。
Preferably, in the monitoring step, the control unit of the electric car further receives image information T in front of the vehicle, and determines that the object in front of the vehicle is a vehicle or a pedestrian according to the image information T in front of the vehicle;
in the judging step b, when the front image information T shows that the front object is a vehicle and the braking acceleration signal a is greater than a fixed value a0, the process proceeds to step c.
Preferably, in the monitoring step, the control unit of the electric car further receives the distance L between the vehicle and the front vehicle and the rotation speed n of the front wheel of the vehicle;
in the judging step b, when the braking acceleration signal a is greater than a certain value a0, the current minimum braking distance Lmin of the vehicle is calculated according to the following formula and is greater than L, and then the step C is carried out;
in the above formula, mu is the friction coefficient between the tire and the ground;
the value method of mu is as follows: the control unit of the electric car also receives a front wheel slip rate parameter s, and the slip rate s is calculated according to the following formula:
s＝V-Rβ/V (1-10)
β＝n·2·π/60 (1-11)
in the above formula, R is the effective radius of the tire, beta is the rotation angular velocity of the tire, and n is the rotation speed of the tire;
when s is less than or equal to 0.15, mu is 0.5;
when s is more than 0.15 and less than or equal to 0.3, mu is 0.8;
when s is more than 0.3, mu is 0.6-0.7;
the active bumper protection device corresponding to the active front bumper protection method during rear-end collision of the safe electric car is characterized in that: the active protection device comprises a bumper which is arranged at the front end of the electric car and is horizontally arranged relative to the transverse direction of the car; the bumper is detachably connected with the energy absorption box behind the bumper, and moves up and down in the vertical direction of the car relative to the energy absorption box; the energy absorption box and the engine compartment longitudinal beam are detachably connected; the up-and-down movement of the bumper is driven by the execution unit; the control line of the execution unit is connected with the I/O port of the control unit, and the I/O port of the control unit is also respectively connected with the signal lines of a vehicle speed sensor, a vehicle body acceleration sensor and an electric car front wheel speed sensor; the method comprises the following steps that a vehicle speed sensor acquires a vehicle speed V, a vehicle body acceleration sensor acquires a braking acceleration a, and a front wheel speed sensor of a front wheel of the electric car acquires a front wheel rotating speed n; and power lines of the execution unit, the control unit, the vehicle speed sensor, the vehicle body acceleration sensor and the front wheel speed sensor are respectively connected with a storage battery or a battery power supply lead of the electric car.
Preferably, the bumper is a hollow rectangular steel pipe or a hollow circular steel pipe or a hollow oval steel pipe, the outer side surfaces of two ends of the bumper are respectively in bolted connection or welded connection with the outer side surface of a sliding block, the sliding block is arranged on a vertically arranged guide rail and slides up and down relative to the guide rail, the side surfaces of the upper end and the lower end of the guide rail are respectively connected with the upper end and the lower end of the front end of a horizontally arranged connecting support with an H-shaped section through flange bolts or bolts, the H-shaped framework of the connecting support is connected with the front end of the energy absorption box through bolts at the inner side groove part towards the car cab direction, and the rear end of the energy absorption box is connected with the front end of the engine longitudinal beam through bolts;
the execution unit comprises two electric push rods which are symmetrically arranged along the left and right of the automobile, and the electric push rods are vertically arranged or obliquely arranged between the bumper and the connecting bracket along the longitudinal direction of the automobile; the rod end of a piston rod of the electric push rod is connected with the bumper through a bolt or a hinge, and the base of the electric push rod is connected with the front end of the connecting bracket through a bolt or a hinge.
Preferably, the vehicle speed sensor is mounted on the output shaft of the transmission or the inner side wall of the axle housing of the drive axle in a bolt or buckle or bonding mode; the vehicle body acceleration sensor is arranged on a seat cushion at the bottom of a driver seat or on the outer side surface of a bumper in a bolt or buckle or bonding mode; the front wheel speed sensor is arranged on a steering knuckle on the inner side of a front wheel hub of the automobile in a bolt or buckle or bonding mode.
Preferably, the vehicle speed sensor is a Yujie MsZD vehicle speed sensor or an XH96563 transmission vehicle speed sensor of Zhongcheng corporation or a vehicle speed sensor used by other companies or cars, the vehicle body acceleration sensor is an MPU-6050 GY-521 three-axis gyroscope or a GY-362ADXL362 three-axis acceleration sensor module or an acceleration sensor of other models, and the wheel speed sensor is an 8E0927803A front wheel speed sensor of Hunter corporation or a wheel speed sensor of GAK corporation or a wheel speed sensor of Tesla electric cars or a wheel speed sensor of other models produced by Town corporation; the control unit is an FSD processor of Tesla, a DriveXavier processor of England, a Nuvo-5095G of Baidu open source, an AT89C52 single chip microcomputer or a PLC control panel; the electric push rod is a stepping 50 electric push rod of the dragon company, a 12V/24V electric telescopic rod of the Pofeld company, a high-speed pen type electric push rod of the health worker company or electric push rods of other types.
The invention has the following beneficial effects: when the electric car is emergently braked under the condition of a certain speed, the front bumper of the electric car rises by a certain height, the front depression of the car in emergency braking is compensated, and the height of the front bumper is reduced, so that the front bumper of the electric car is positioned at the correct height when the car and the front car collide with each other, the energy absorption function of the bumper is exerted, and the safety of the car in the collision accident is greatly improved.
Drawings
FIG. 1 is a front view of an active bumper guard;
FIG. 2 is a top view of the active bumper guard;
FIG. 3 is a schematic diagram of a circuit connection of the control unit;
FIG. 4 is a pin diagram of an AT89C52 single chip microcomputer;
FIG. 5 is a schematic view of a front wheel speed sensor of the front-drive electric car;
FIG. 6 is a schematic illustration of the vehicle speed sensor mounted on the transmission;
FIG. 7 is a schematic diagram of the calculation of the height reduction of the front bumper when the car is braked.
Detailed Description
As shown in fig. 1-7, the method for actively protecting the front bumper when a safe electric car knocks into the rear includes the following steps in sequence: a driving monitoring step and a judging step; an execution step;
the first embodiment is as follows:
when the unmanned level of the electric car is lower than the L2 level, the electric car is generally not equipped with an environment identification module, or the environment identification module is a simple ultrasonic radar or an infrared radar, in this case, the electric car cannot identify the specific information of the environment in front of the vehicle, whether an obstacle exists in front and the distance of the obstacle can be measured, but whether the obstacle is the vehicle or the pedestrian cannot be identified, in order to adapt to the electric car, the protection method comprises the following steps:
the running monitoring step comprises the following steps: the control unit receives a vehicle running speed signal V and a vehicle braking acceleration signal a, and then enters a judging step:
the judging step is as follows:
a. when the vehicle running speed V is greater than a certain speed V0, entering the step b;
b. when the braking acceleration signal a is larger than a certain value a0, the step c is carried out:
the execution steps are as follows:
c. the control unit sends a signal to the execution unit, and the execution unit raises the front bumper by delta H to ensure that the distance H between the front bumper and the ground is consistent with the height H0 of the front bumper when the automobile stops or runs at a constant speed;
when the vehicle speed is low, the vehicle is often driven in urban roads, pedestrians and other vehicles exist in the collision accident in front of the vehicle, when the collision accident is with pedestrians, the bumper is not suitable to be lifted in view of safety, when the collision accident is with other vehicles, because the vehicle speed is low and the vehicle deformation is not too large, the embodiment one is more suitable for the occasions with high vehicle speed, such as an expressway or a closed road, the V0 value is set to be a certain speed, the speed limit value is generally 50-60km/h in reference to the main road of China, when a passenger vehicle collides, the collision test speed in consideration of the body strength of the passenger vehicle is generally 50km/h, the lower limit value of the V0 value is suitably set to be 50km/h, of course, when the vehicle is often used for long-distance driving or expressway driving, the V0 value can be adjusted to be 60km/h or 70km/h or 80km/h, when the vehicle speed is high, after a driver steps on the brake pedal before the front vehicle rear end collision, the vehicle can be set to be corresponding to be a corresponding deceleration value or a corresponding to be set to be a corresponding standard or a corresponding deceleration value of the method, and the method is set to be used for the automobile braking test speed under reference for the acceleration test speed of 50km/h, and the automobile, and the acceleration test speed of the method is set to be taken as a reference for the case of the method, and the method is set to be taken as a reference for the method, and the method is taken as the method is taken 2 。
In order to calculate the height Δ H of the bumper which needs to be compensated when the vehicle brakes, calculation can be performed according to a calculation model shown in fig. 7, the height Δ H1 of the front end of the vehicle which descends when the vehicle brakes is calculated according to (1-1), and Δ H is taken as Δ H1, and it can also be considered that the distances between the center of gravity of the vehicle and the front and rear wheels are different because the rigidity k1 and k2 of the front and rear suspension of the vehicle are different, so the values of Δ H1 and the height Δ H2 of the rear end of the vehicle which descends when the vehicle brakes are different, and simplified calculation is performed to ensure that the height of the bumper which ascends is enough, and the larger value of the two is taken as Δ H;
ΔH＝Max(ΔH 1 ，ΔH 2 )
Δ H1 and Δ H2 calculated in the formulae (1-1) and (1-2) are derived from the following formulae:
tanα＝Δ 1 /l 1 (1-3)
tanα＝Δ 2 /l 2 (1-4)
ΔH 1 ＝tanα·L 1 (1-5)
ΔH 2 ＝tanα·L 2 (1-6)
in the above formula, k 1 Is the rigidity coefficient, k, of the front suspension of the electric car 2 The rigidity coefficient of the rear suspension of the electric car; l is a radical of an alcohol 0 For the wheelbase of an electric car, | 1 Is the distance from the center of mass to the front axle of the electric car 2 The distance from the center of mass to the rear axle of the electric car, L is the total length of the car, L 1 Is the distance L between the center of mass and the front end of the electric car 2 The distance between the center of mass and the rear end of the electric car, m is the mass of the electric car, a is the acceleration value generated by the braking of the car, g is the gravity acceleration, and 9.8m/s is taken 2 H is the height of the center of mass of the electric car from the ground, and alpha is the front depression angle of the electric car during braking; delta 1 is the vertical compression of the front suspension, and delta 2 is the vertical extension of the rear suspension;
the transfer amount of vertical force on the front wheel and the rear wheel caused by inertia force during vehicle braking is as follows:
therefore, the front suspension compression amount and the rear suspension compression amount can be simply calculated according to Hooke's law:
then combining the formulas (1-3) to (1-6) to obtain the formulas (1-1) and (1-2);
d. and the control unit continuously receives the value a, and when the driver controls the braking process of the vehicle to be finished, namely the vehicle is decelerated to a safe speed or is stopped, a is smaller than a0, the control unit controls the execution unit to lower the front bumper by delta H and restore the initial position.
When the electric car is braked emergently at a certain speed, the front bumper rises to a certain height, the height reduction of the front bumper of the car during emergency braking is compensated, the front bumper of the car is positioned at the correct height when the car and the front car collide with each other, the energy absorption function of the bumper is exerted, and the safety of the car in the rear-end accident is greatly improved.
In order to realize the protection method, the corresponding active bumper protection device comprises a bumper 1 which is arranged at the front end of the electric car and is horizontally arranged relative to the transverse direction of the car; the bumper 1 is detachably connected with the energy absorption box 7 behind the bumper 1, and moves up and down in the vertical direction of the car relative to the energy absorption box 7; the energy absorption box 7 and the engine compartment longitudinal beam are detachably connected; the up and down movement of the bumper 1 is driven by the execution unit; the control line of the execution unit is connected with the I/O port of the control unit, and the I/O port of the control unit is also respectively connected with the signal lines of a vehicle speed sensor 21, a vehicle body acceleration sensor 22 and an electric car front wheel speed sensor 23; the method comprises the following steps that a vehicle speed sensor 21 acquires a vehicle speed V, a vehicle body acceleration sensor 22 acquires a braking acceleration a, and a front wheel speed sensor 23 acquires a front wheel rotating speed n of the electric car; the power lines of the execution unit, the control unit, the vehicle speed sensor 21, the vehicle body acceleration sensor 22 and the electric car front wheel speed sensor 23 are respectively connected with a storage battery or a battery power supply lead of the electric car; the vehicle speed sensor 21 is arranged on an output shaft of a transmission or the inner side wall of a drive axle housing in a bolt or buckle or bonding mode; the vehicle body acceleration sensor 22 is arranged on a cushion at the bottom of the driver seat or on the outer side surface of the bumper 1 in a bolt or buckle or bonding mode; the front wheel speed sensor 23 is mounted on the steering knuckle inside the front wheel hub of the automobile in a bolt or a buckle or bonding mode.
The bumper is characterized in that the bumper 1 is a hollow rectangular steel pipe or a hollow circular steel pipe or a hollow oval steel pipe, the outer side surfaces of two ends of the bumper 1 are respectively in bolted connection or welded connection with the outer side surface of a sliding block 3, the sliding block 3 is installed on a vertically arranged guide rail 4 and can slide up and down relative to the guide rail 4, the side surfaces of the upper end and the lower end of the guide rail 4 are respectively in bolted connection or bolt connection with the upper end and the lower end of the front end of a horizontally arranged H-shaped connecting bracket 6, the H-shaped inner side of the connecting bracket 6 is connected with the front end of an energy absorption box 7 through bolts, and the rear end of the energy absorption box 7 is connected with the front end of an engine longitudinal beam 8 through bolts;
the execution unit comprises two electric push rods 5 which are symmetrically arranged along the left and right of the automobile, and the electric push rods 5 are vertically arranged or obliquely arranged between the bumper and the connecting bracket 6 along the longitudinal direction of the automobile; the rod end of a piston rod of the electric push rod 5 is connected with the bumper 1 through a bolt or a hinge, and the base of the electric push rod 5 is connected with the front end of the connecting bracket 6 through a bolt or a hinge;
the vehicle speed sensor 21 is a Yujie MsZD vehicle speed sensor or an XH96563 transmission vehicle speed sensor of Zhongcheng corporation or a vehicle speed sensor used by other companies or cars, the vehicle body acceleration sensor 22 is an MPU-6050-GY-521 triaxial gyroscope or a GY-362-ADXL362 triaxial acceleration sensor module or an acceleration sensor of other models, and the wheel speed sensor 23 is an 8E0-927-803-A front wheel speed sensor of Hunter corporation or a wheel speed sensor of GAK corporation or a wheel speed sensor for Tesla electric cars or a wheel speed sensor of other models produced by Town corporation; the control unit is an AT89C52 singlechip or a PLC control panel; the electric push rod 5 is a stepping 50 electric push rod of the dragon company, a 12V/24V electric telescopic rod of the Pofeld company, a high-speed pen type electric push rod of the Corp company or an electric push rod of other types.
Example two:
if the road is an urban road when the vehicle collides with the front, the collision situations are vehicle-vehicle collision and vehicle-human collision respectively, in the vehicle-human collision situation, for the safety of pedestrians, the collision point should be as low as possible, so that the injury to the pedestrians can be effectively reduced, and in the vehicle-vehicle rear-end collision situation, the height of the bumper should be kept, so that a better implementation mode is as follows: in the monitoring step, the control unit of the electric car also receives image information T in front of the vehicle, and simultaneously judges that an object in front of the vehicle is a vehicle or a pedestrian according to the image information T in front of the vehicle;
in the judging step b, when the front image information T shows that the front object is a vehicle and the braking acceleration signal a is greater than a fixed value a0, the process proceeds to step c.
After the image information T is used for judging that the front obstacle is a pedestrian or a vehicle, when the image information T at the front displays that the front object is the pedestrian, the front bumper is not subjected to height compensation operation, so that the safety of the pedestrian is effectively protected, and the scheme can be better suitable for urban roads.
According to the method for identifying the object in the image as the vehicle or the pedestrian according to the image information T, the existing technology can be used, for example, an environment identification module of an unmanned electric car with automatic driving levels of L3 and above L3 can identify the surrounding environment, for example, an automatic pilot automatic driving system carried by Tesla model 3, and the system comprises a complete hardware device sensor, an image processing module, a central processing unit and control algorithm software which are required by the unmanned driving process; for example, the unmanned system used in ES8 electric SUV of the company of nei, which can photograph, process and identify the image information of the environment in front of the vehicle, so as to distinguish whether the obstacle in front of the vehicle is a pedestrian or a vehicle, for example, the open-source unmanned system disclosed by the company of hundredths, which can directly recognize the environment of the vehicle without special technology, and can be directly realized by the technical personnel in the field of unmanned driving of the vehicle. In order to realize the acquisition, processing and judgment process of the image information on the hardware equipment, the control unit can be an FSD processor of Tesla, a Drive Xavier processor of Invada or a Nuvo-5095G processor of a Baidu open source, the control unit is also in communication connection with an environment recognition module, and the environment recognition module sends the image information T in front of the automobile to the control unit; the environment recognition module comprises an environment recognition sensor, the environment recognition sensor is in communication connection with the image processor or the image processing module, and the image processor or the image processing module is in communication connection with the control unit; the environment recognition sensor is a laser radar which is arranged on the roof of the car through a bolt or a buckle or a camera which is arranged on a front bumper of the car;
if a laser radar is adopted, the laser radar can coaxially rotate for 360 degrees, so that a circle of point cloud information around the laser radar is provided, and the information is processed by an image processor matched with the laser radar and then sent to a control unit; if the camera is adopted, light rays of the camera pass through a lens and an optical filter to reach a CMOS or CCD integrated circuit at the rear section, optical signals are converted into electric signals, the electric signals are converted into digital image signals in standard formats of RAW, RGB or YUV through an image processor ISP, and the digital image signals are transmitted to the control unit through a data transmission interface.
Example three:
in order to reduce the rising times of the front bumper and avoid excessively frequent rising and falling, a better implementation mode is as follows: in the monitoring step, the control unit of the electric car also receives the distance L between the vehicle and the front vehicle; the distance L can be acquired by an environment identification module or a radar or an infrared distance sensor;
in the step b, when the braking acceleration signal a is greater than a certain value a0, the current minimum braking distance Lmin of the vehicle calculated according to the following formula is greater than L, and the step C is carried out;
in the above formula, mu is the friction coefficient between the tire and the ground, and mu is 0.5-0.8 during calculation.
The value taking method of the mu comprises the following steps: the control unit of the electric car also receives a front wheel slip rate parameter s, and the slip rate s is calculated according to the following formula:
s＝V-Rβ/V (1-10)
β＝n·2·π/60 (1-11)
in the above formula, R is the effective radius of the tire, beta is the rotation angular velocity of the tire, and n is the rotation speed of the tire;
when s is less than or equal to 0.15, mu is 0.5;
when s is more than 0.15 and less than or equal to 0.3, mu is 0.8;
when s is more than 0.3, mu is 0.6-0.7;
the braking distance of the vehicle in the current braking deceleration state can be accurately calculated according to the formulas 1-9 to 1-11, so that whether the vehicle collides with the front vehicle in the rear-end collision mode or not is judged in advance, and only when Lmin is larger than L, namely the vehicle still collides with the front vehicle in the rear-end collision mode after braking, the step c is carried out, and the front bumper is lifted.
In practical use, the protection method of the second embodiment and the protection method of the third embodiment may be combined, lmin is calculated while the object in front of the vehicle is determined to be a pedestrian or a vehicle, and when the object in front is a vehicle and Lmin > L, the step c is performed.
The protection method in the first embodiment, the second embodiment and the third embodiment can be independently applied to the car, and can also be designed into a plurality of selection modes by using programming software, and the selection modes are adaptively selected by a driver or an unmanned system according to the environment where the vehicle is located.
Claims (4)
1. The method for actively protecting the front bumper when the safe electric car knocks into the rear is characterized in that: the protection method comprises the following steps which are carried out in sequence: a driving monitoring step and a judging step; an execution step;
the running monitoring step comprises the following steps: the control unit receives a vehicle running speed signal V and a vehicle braking acceleration signal a, and the control unit of the electric car also receives image information T in front of the vehicle and judges that an object in front of the vehicle is a vehicle or a pedestrian according to the image information T in front of the vehicle; then entering a judging step:
the judging step is as follows:
a. when the vehicle running speed V is greater than a certain speed V0, entering the step b;
b. when the braking acceleration signal a is larger than a certain value a0 and the front image information T shows that the front object is a vehicle, the method proceeds to step c:
the execution steps are as follows:
c. the control unit sends a signal to the execution unit, and the execution unit raises the front bumper by delta H to ensure that the distance H between the front bumper and the ground when the vehicle brakes is consistent with the height H0 between the front bumper and the ground when the vehicle stops or runs at a constant speed;
the calculation method of the delta H calculates the delta H according to (1-1) 1 Calculating Δ H according to the formula (1-2) 2 And will be Δ H 1 ，ΔH 2 Comparing the sizes of the two, and taking the larger value of the two as delta H;
ΔH＝Max(ΔH 1 ，ΔH 2 )
d. the control unit continuously receives the value a, and when a is smaller than a0 again, the control unit controls the execution unit to lower the front bumper and restore the initial position;
in the above formula, k 1 Is the rigidity coefficient, L, of the front suspension of the electric car 1 Is the distance between the center of mass and the front end of the electric car, i 1 Is the distance of the center of mass from the front axle, L 0 The distance between the axle and the ground is the axle base of the electric car, m is the mass of the electric car, a is the acceleration value generated by braking the car, and h is the height between the mass center of the electric car and the ground; k is a radical of 2 Is the rigidity coefficient of the rear suspension of the electric car 2 Is the distance from the center of mass to the rear axle, L 2 The distance between the mass center and the rear end of the electric car.
2. The method for actively protecting the front bumper when the safe electric car knocks into the rear according to claim 1, is characterized in that: the V0 is 50km/h or 60km/h or 70km/h or 80km/h, and the a0 is 5.0-6.2m/s 2 。
3. The method for actively protecting the front bumper of the safe electric car during the rear-end collision according to claim 1, is characterized in that: in the monitoring step, the control unit of the electric car also receives the distance L between the vehicle and the front vehicle and the rotating speed n of the front wheel of the vehicle;
in the judging step b, when the braking acceleration signal a is greater than a fixed value a0, the current minimum braking distance Lmin of the vehicle is calculated according to the following formula (1-9) and is greater than L, and then the step C is carried out;
in the above formula, mu is the friction coefficient between the tire and the ground; v is the vehicle speed; g is gravity acceleration, and is 9.8m/s 2 ；
The value method of mu is as follows: the control unit of the electric car also receives a front wheel slip rate parameter s, and the slip rate s is calculated according to the following formula:
s＝(V-Rβ)/V (1-10)
β＝n·2·π/60 (1-11)
in the formula, R is the effective radius of the tire, beta is the rotation angular velocity of the tire, n is the rotation speed of the tire, the rotation speeds of the left front wheel and the right front wheel are respectively measured during measurement, and the average value of the rotation speeds of the left front wheel and the right front wheel is taken as the rotation speed of the tire;
when s is less than or equal to 0.15, mu is 0.5;
when s is more than 0.15 and less than or equal to 0.3, mu is 0.8;
when s is greater than 0.3, mu is 0.6-0.7.
4. The active bumper protection device corresponding to the active front bumper protection method in the rear-end collision of the safe electric car according to claim 1, 2 or 3, wherein the active bumper protection device comprises a bumper (1) which is arranged at the front end of the electric car and horizontally arranged relative to the transverse direction of the car, the bumper (1) is detachably connected with an energy absorption box (7) behind the bumper, and the bumper moves up and down relative to the energy absorption box (7) in the vertical direction of the car; the energy absorption box (7) is detachably connected with the longitudinal beam of the engine compartment; the up-and-down movement of the bumper (1) is driven by an execution unit; the control line of the execution unit is connected with the I/O port of the control unit, and the I/O port of the control unit is also respectively connected with the signal lines of a vehicle speed sensor (21), a vehicle body acceleration sensor (22) and an electric car front wheel speed sensor (23); the method comprises the following steps that a vehicle speed sensor (21) collects a vehicle speed V, a vehicle body acceleration sensor (22) collects a braking acceleration a, and a front wheel speed sensor (23) of an electric car collects a front wheel rotating speed n; and power lines of the execution unit, the control unit, the vehicle speed sensor (21), the vehicle body acceleration sensor (22) and the front wheel speed sensor (23) are respectively connected with a storage battery or a battery power supply lead of the electric car.
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| CN202010264030.9A CN111439228B (en) | 2020-04-07 | 2020-04-07 | Method and device for actively protecting front bumper during rear-end collision of electric car |
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| CN202110039390.3A Active CN112693413B (en) | 2020-04-07 | 2020-04-07 | Front bumper active protection device for rear-end collision of electric car |
| CN202010264030.9A Active CN111439228B (en) | 2020-04-07 | 2020-04-07 | Method and device for actively protecting front bumper during rear-end collision of electric car |
| CN202110039401.8A Active CN112693414B (en) | 2020-04-07 | 2020-04-07 | Method for protecting active lifting of front bumper during rear-end collision of electric car |
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| CN202110039401.8A Active CN112693414B (en) | 2020-04-07 | 2020-04-07 | Method for protecting active lifting of front bumper during rear-end collision of electric car |
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| CN112721846B (en) * | 2020-04-07 | 2022-11-08 | 西华大学 | Front bumper active protection method for safe electric car in rear-end collision |
| CN113147648B (en) * | 2021-03-03 | 2022-07-01 | 西华大学 | Dot-matrix airbag popping judgment system and judgment method for unmanned vehicle |
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| CN112693413B (en) | 2022-08-26 |
| CN112693414A (en) | 2021-04-23 |
| CN112693413A (en) | 2021-04-23 |
| CN111439228B (en) | 2021-02-23 |
| CN112721846A (en) | 2021-04-30 |
| CN112693414B (en) | 2022-08-09 |
| CN111439228A (en) | 2020-07-24 |
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