CN113619580A - Lane keeping system and control method thereof - Google Patents

Lane keeping system and control method thereof Download PDF

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Publication number
CN113619580A
CN113619580A CN202111080846.7A CN202111080846A CN113619580A CN 113619580 A CN113619580 A CN 113619580A CN 202111080846 A CN202111080846 A CN 202111080846A CN 113619580 A CN113619580 A CN 113619580A
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vehicle
deviation
torque
control unit
steering
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靳立强
崔明萱
张奇祥
田梦杰
许杰
王凯
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Jilin University
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Jilin University
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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
    • B60W30/10—Path keeping
    • B60W30/12—Lane keeping
    • 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
    • B60W10/00—Conjoint control of vehicle sub-units of different type or different function
    • B60W10/20—Conjoint control of vehicle sub-units of different type or different function including control of steering systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
    • B62D5/046—Controlling the motor
    • B62D5/0463—Controlling the motor calculating assisting torque from the motor based on driver input

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  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Automation & Control Theory (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)
  • Control Of Driving Devices And Active Controlling Of Vehicle (AREA)

Abstract

The invention discloses a lane keeping system, comprising: a control unit; the output end of the measuring unit is connected with the input end of the control unit; the output end of the image acquisition unit is connected with the input end of the control unit; the steering motor system is electrically connected with the output end of the control unit; the driving motor system is electrically connected with the output end of the control unit; wherein the control unit is further electrically connected with a wheel of the vehicle. Through the matching of the control unit with the steering motor system and the driving motor system, the vehicle torque and the front and rear axle torque are distributed under different working conditions at present, and the vehicle offset posture and the vehicle steering insufficiency are improved. The invention also provides a control method of the lane keeping system, which is used for carrying out feedback control on the deviation of the actual yaw velocity and the ideal yaw velocity and controlling the power-assisted steering torque applied to the front wheels under different running conditions of the vehicle so as to ensure the track following capability of the running of the vehicle.

Description

Lane keeping system and control method thereof
Technical Field
The invention relates to a lane keeping system and a control method thereof, belonging to the field of vehicle safety.
Background
The decision model of the lane keeping system which carries out strategy calculation based on the current position (CCP) of the vehicle in the lane has low complexity, low cost and easy realization, thereby having wider application. The actuators of lane keeping systems are generally divided into three main categories: the actuating mechanism is a steering system and corrects the driving direction of the vehicle by controlling the steering wheel angle; the actuating mechanism is a braking system, and applies different braking forces, namely differential braking to wheels to enable the whole vehicle to generate a yaw moment and correct the driving direction of the vehicle; the actuating mechanism is a driving system, and the driving torque applied to the wheels is adjusted to generate a yaw moment on the whole vehicle so as to correct the driving direction of the vehicle.
Although a decision model based on the CCP has a road detection function, the curve detection efficiency is low, and since a general LKA system is executed by a steering motor based on the EPS, the EPS is prone to influence normal steering assistance due to the implementation of a vehicle holding function in a mode switching process of curve driving, thereby increasing potential safety hazards. In order to exert the steering assisting action of the EPS as much as possible, the actuating mechanism of the lane keeping system during turning can be adjusted to an inter-axle torque distribution device, the driving torque of the front axle and the rear axle is adjusted, so that the situation of vehicle deviation such as insufficient steering or excessive steering which is easy to occur during turning is improved, the EPS can normally exert the action while keeping the vehicle running at the center of a road, the steering of wheels is assisted if necessary, and the safety and the stability of the automobile are ensured.
Therefore, in order to ensure that the lane keeping system is easy to realize, easy to apply and low in complexity and has better reliability, efficiency, safety and stability, a distribution device capable of adjusting the driving torque of the front axle and the rear axle of the vehicle can be added on the basis that the steering system works as an actuating mechanism, the two actuating mechanisms are operated together to keep the correct running track of the vehicle, and the actuating mechanisms participating in control are different according to different running conditions, so that the efficiency and the reliability are greatly enhanced.
Disclosure of Invention
The invention designs and develops a lane keeping system, which realizes the distribution of vehicle torque and front and rear axle torque under different working conditions by the matching of a control unit, a steering motor system and a driving motor system, and improves the deviated posture of a vehicle and the insufficient steering of the vehicle.
The invention also designs and develops a control method of the lane keeping system, and the control method carries out feedback control on the deviation of the actual yaw velocity and the ideal yaw velocity and controls the power-assisted steering torque applied to the front wheels through a PID control algorithm under different running conditions of the vehicle so as to ensure the track following capability of the vehicle in running.
The technical scheme provided by the invention is as follows:
a lane keeping system comprising:
a control unit;
the output end of the measuring unit is connected with the input end of the control unit;
the output end of the image acquisition unit is connected with the input end of the control unit;
the steering motor system is electrically connected with the output end of the control unit;
the driving motor system is electrically connected with the output end of the control unit;
wherein the control unit is further electrically connected with a wheel of the vehicle.
It is preferable that: a steering wheel angle sensor, a vehicle yaw angle sensor, a yaw rate sensor, and an acceleration sensor.
A control method of a lane keeping system, using the lane keeping system, comprising:
the measuring unit is used for collecting a turn signal detected by the image collecting unit and a curvature signal of a lane line;
when the vehicle deviates from a lane and the curvature of a turn light signal and the curvature of a lane line are both 1 in a turning working condition, entering a steering rectification mode, controlling a driving motor system by a control unit, and adjusting the torque transmitted to a front shaft, wherein the vehicle runs in a normal track in the road;
when the steering signal is 0 under the straight-driving working condition, the distance L between the wheels and the center line of the lane is greater than the threshold value L of the distance L between the wheels and the center line of the lanethThe actual driver torque T is less than the actual driver torque threshold TthThe vehicle slip angle theta is smaller than the vehicle slip angle threshold thetathThen, entering a straight-going deviation rectifying mode; the control unit adjusts a steering angle through a steering motor system to enable the vehicle to keep running in a straight line at the center of a road;
otherwise, entering a safe mode;
wherein L isth＝0.4m、Tth＝1.5Nm、θth＝0.01rad。
Preferably, when entering the steer away mode,
setting the running mode of the vehicle as circular motion, establishing a single-point preview driver model, and obtaining the ideal yaw velocity of the vehicle as follows:
Figure BDA0003263935660000031
where Δ s is the preview deviation, vxThe speed of the vehicle in the longitudinal direction is taken as the speed, beta is the centroid slip angle of the vehicle, and delta t is the time when the ideal centroid position of the vehicle reaches the pre-aiming point on the target track;
feedback control of a deviation of an actual yaw rate from an ideal yaw rate by a PID control algorithm includes:
eωr＝sign(ωr)·(ωs-ωr)；
Figure BDA0003263935660000032
in the formula, ωrTo the actual yaw rate, ωsIdeal yaw rate, eωrIs the deviation of yaw angular velocity;
the torque value required to be transmitted between the shafts for realizing lane keeping is obtained as follows:
Mdyaw(t+Δt)＝Mdyaw(t)+ΔMdyaw；
in the formula, Mdyaw(t) is the value of torque delivered in the previous cycle, Mdyaw(t + Δ t) is the torque value, Δ M, of the next cycledyawIs the value of the torque change between the shafts between the adjacent periods;
wherein, the target torque value obtained by PID feedback control is as follows:
ΔMdyaw＝Kp·(eωr(t+Δt)-eωr(t))+Ki·eωr(t+Δt)；
in the formula, eωr(t) yaw rate deviation value of previous period, eωr(t + Δ t) is a yaw rate deviation value, Δ M, of the next cycledyawFor the change in transmitted torque of adjacent cycles, KpIs a scale factor, KiIs an integration factor.
Preferably, when entering the straight deviation rectifying mode:
LWR transverse control is carried out on the deviation of the lateral slip angle and the transverse displacement of the vehicle, and an expected front wheel corner is obtained;
establishing a two-degree-of-freedom model of the vehicle
Figure BDA0003263935660000041
Obtaining state equations of corresponding deviations of the four variables of the transverse displacement deviation, the transverse speed, the slip angle deviation and the slip angle speed:
Figure BDA0003263935660000042
wherein A, B, C is a coefficient matrix comprising:
Figure BDA0003263935660000043
Figure BDA0003263935660000044
Figure BDA0003263935660000051
where δ is the wheel angle, m is the vehicle mass, vxAs longitudinal velocity, /)fIs the distance from the center of mass of the vehicle to the front axle,/rIs the distance of the vehicle's center of mass to the rear axle, CfFor yaw stiffness of the front axle, CrFor cornering stiffness of the rear axle, IzIs the moment of inertia of the vehicle about the z-axis;
the control law of the expected turning angle of the system is as follows:
Figure BDA0003263935660000052
in the formula, deltasFor an ideal wheel angle, Δ L is the lateral displacement deviation,
Figure BDA0003263935660000053
is the lateral velocity, theta is the slip angle deviation,
Figure BDA0003263935660000054
is the slip angle velocity;
calculating an expected matrix K to obtain a characteristic value K of the matrix K1、K2、K3、K4Finally, a desired wheel turning angle δ is obtaineds；
The deviation of the actual value of the front wheel steering angle from the expected value is:
Δδ＝δ-δs；
through PID control, the power-assisted steering torque required to be applied to the front wheels to realize lane keeping is as follows:
Figure BDA0003263935660000055
in the formula, Kp、Ki、KdAre respectively a scale factor,Integral factor, differential factor.
The invention has the following beneficial effects:
the lane keeping system has low complexity, lower cost of structural components and the like and is easy to realize; the reliability is higher, the pertinence is stronger: the control unit can flexibly control the corresponding execution mechanism to act according to different running conditions of the vehicle, so that the purpose that the vehicle runs in the center of the lane is achieved; the efficiency is higher, the response is faster: the direct driving modes of the two executing mechanisms are both motor type, and the executing mechanisms can be controlled in time after the driving motor receives an instruction sent by the control unit.
Drawings
Fig. 1 is a schematic view of a vehicle on a lane according to the present invention.
Fig. 2 is a schematic view of the present invention for improving understeer condition.
FIG. 3 is a schematic diagram of the present invention for improving an oversteer condition.
Fig. 4 is a schematic structural diagram of the lane keeping system according to the present invention.
Fig. 5 is a control process diagram of the lane keeping system according to the present invention.
FIG. 6 is a schematic diagram illustrating the identification and operation of different modes according to the present invention.
Detailed Description
The present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.
As shown in fig. 1 to 6, the present invention provides a lane keeping system, which realizes the distribution of vehicle torque and front and rear axle torque under different working conditions by the cooperation of a control unit with a steering motor system and a driving motor system, and improves the vehicle offset attitude and the vehicle understeer, comprising:
control unit, measuring element, image acquisition unit, steering motor system and driving motor system, measuring element and image acquisition unit set up the head at the vehicle, and measuring element includes: the vehicle state information measuring device comprises a steering wheel angle sensor, a vehicle deflection angle sensor, a yaw velocity sensor and an acceleration sensor, wherein the output end of a measuring unit is connected with the input end of a control unit, the output end of an image acquisition unit is connected with the input end of the control unit, the image acquisition unit is used for acquiring images, and the measuring unit can obtain vehicle state information such as lane boundary line information, vehicle speed, yaw velocity, pedals, steering wheel angles and moments, steering lamp signals and the like. The control unit is an ECU (electronic control unit), the position and the state of the current vehicle in a road can be analyzed according to the state of the vehicle, the road environment and the state of a driver, whether the vehicle has the danger of deviating from a lane or not is judged, the vehicle enters a power-assisted deviation rectifying mode, a steering motor system and a driving motor system are execution mechanisms, the ECU sends an instruction to the execution mechanism, a steering motor in the steering motor system can apply torque to a steering wheel to rotate the steering wheel, and the vehicle is actively controlled to return to the center of the road; the driving motor for distributing the power of the front and rear shafts applies a certain axial force to the wet clutch through a set of structures such as helical gear transmission and the like, so that the main driving disc and the auxiliary driving disc are jointed or separated, the torque proportion distributed to the front and rear shafts is adjusted, the condition of understeer or oversteer when the vehicle turns is improved, and the vehicle is controlled to run in the center of a road.
The invention also provides a control method of a lane keeping system, which carries out feedback control on the deviation of the actual yaw velocity and the ideal yaw velocity and controls the power-assisted steering torque applied to the front wheels by a PID control algorithm under different running conditions of the vehicle so as to ensure the track following capability of the running of the vehicle, and comprises the following steps:
the method comprises the steps that the distance from wheels to the center line of a lane line in the driving process of a vehicle, the actual torque of a driver and the vehicle sideslip angle are collected through a measuring unit, and a turn light signal and a curvature signal of the lane line are detected through an image collecting unit;
when the vehicle deviates from a lane and the curvature of a turn light signal and the curvature of a lane line are both 1 in a turning working condition, entering a steering rectification mode, controlling a driving motor system by a control unit, and adjusting the torque transmitted to a front shaft, wherein the vehicle runs in a normal track in the road;
when the steering signal is 0 under the straight-driving working condition, the distance L between the wheels and the center line of the lane is greater than the threshold value L of the distance L between the wheels and the center line of the lanethThe actual driver torque T is less than the actual driver torque threshold TthThe vehicle slip angle theta is smaller than the vehicle slip angle threshold thetathThen, entering a straight-going deviation rectifying mode; the control unit adjusts a steering angle through a steering motor system to enable the vehicle to keep running in a straight line at the center of a road;
otherwise, entering a safe mode;
wherein L isth＝0.4m、Tth＝1.5Nm、θth＝0.01rad。
When the steering deviation correcting mode is entered, the steering deviation correcting mode is started,
setting the running mode of the vehicle as circular motion, establishing a single-point preview driver model, and obtaining the ideal yaw velocity of the vehicle as follows:
Figure BDA0003263935660000071
where Δ s is the preview deviation, vxThe speed of the vehicle in the longitudinal direction is taken as the speed, beta is the centroid slip angle of the vehicle, and delta t is the time when the ideal centroid position of the vehicle reaches the pre-aiming point on the target track;
feedback control of a deviation of an actual yaw rate from an ideal yaw rate by a PID control algorithm includes:
eωr＝sign(ωr)·(ωs-ωr)；
Figure BDA0003263935660000081
in the formula, ωrTo the actual yaw rate, ωsIdeal yaw rate, eωrAs deviation of yaw rate
The torque value required to be transmitted by the weekly building for realizing lane keeping is obtained as follows:
Mdyaw(t+Δt)＝Mdyaw(t)+ΔMdyaw；
in the formula, Mdyaw(t) is the value of torque delivered in the previous cycle, Mdyaw(t + Δ t) is the next periodTorque value of,. DELTA.MdyawIs the value of the torque change between the shafts between the adjacent periods;
wherein the PID feedback control obtains a target torque value of
ΔMdyaw＝Kp·(eωr(t+Δt)-eωr(t))+Ki·eωr(t+Δt)；
In the formula, eωr(t) yaw rate deviation value of previous period, eωr(t + Δ t) is a yaw rate deviation value, Δ M, of the next cycledyawFor the change in transmitted torque of adjacent cycles, KpIs a scale factor, KiIs an integration factor;
when entering the straight deviation rectifying mode:
LWR transverse control is carried out on the deviation of the lateral slip angle and the transverse displacement of the vehicle, and an expected front wheel corner is obtained;
establishing a two-degree-of-freedom model of the vehicle
Figure BDA0003263935660000082
Obtaining state equations of corresponding deviations of the four variables of the transverse displacement deviation, the transverse speed, the slip angle deviation and the slip angle speed:
Figure BDA0003263935660000091
wherein A, B, C is a coefficient matrix comprising:
Figure BDA0003263935660000092
Figure BDA0003263935660000093
Figure BDA0003263935660000094
delta is wheelCorner, m is the mass of the car, vxAs longitudinal velocity, /)fIs the distance from the center of mass of the vehicle to the front axle,/rIs the distance of the vehicle's center of mass to the rear axle, CfFor yaw stiffness of the front axle, CrFor cornering stiffness of the rear axle, IzIs the moment of inertia of the vehicle about the z-axis;
the control law of the expected turning angle of the system is as follows:
Figure BDA0003263935660000101
in the formula, deltasFor an ideal wheel angle, Δ L is the lateral displacement deviation,
Figure BDA0003263935660000102
is the lateral velocity, theta is the slip angle deviation,
Figure BDA0003263935660000103
is the slip angle velocity;
calculating an expected matrix K to obtain a characteristic value K of the matrix K1、K2、K3、K4Finally, a desired wheel turning angle δ is obtaineds；
The deviation of the actual value of the front wheel steering angle from the expected value is:
Δδ＝δ-δs；
through PID control, the power-assisted steering torque required to be applied to the front wheels to realize lane keeping is as follows:
Figure BDA0003263935660000104
in the formula, Kp、Ki、KdRespectively a proportional factor, an integral factor and a differential factor.
Under the straight-driving working condition, the lateral deviation value of the vehicle and the center line of the lane and the vehicle sideslip angle are detected through the image acquisition unit and the measurement unit, the vehicle speed, the steering wheel rotation angle and the steering lamp state signal are combined, the ECU performs LQR (Long Range response) optimization control on the basis of the lateral position deviation L and the sideslip angle theta of the vehicle according to the input signal, transmits an instruction to the steering motor system, and controls the steering wheel to rotate, so that the vehicle returns to the right and keeps running at the center of the lane.
Under the turning working condition, the measurement unit transmits the acquired signal to the ECU, the deviation is controlled to be optimal through calculation of PID + feedforward based on an ideal value and an actual value of the yaw velocity of the vehicle, then an instruction is transmitted to the driving motor, the engagement degree of a driving clutch piece and a driven clutch piece of the torque distribution device between the shafts is controlled, the torque distribution proportion of the front shaft and the rear shaft is correspondingly changed, the condition of insufficient or excessive steering of the vehicle is improved, and the vehicle runs in the center of a road along a normal track;
if the measuring unit detects that the vehicle is in a safe mode, the driver automatically controls the accelerator and the steering wheel to turn.
Lane monitoring is determined by processing image data in the forward facing camera within the image acquisition unit and making measurements for road lane markings. Under the turning working condition, when the vehicle deviates from the lane and the steering lamp signal and the curvature signal of the lane line are both 1, the vehicle is in the curve running working condition and is judged to be in the deviation rectifying mode during turning, and the ECU controls the torque transmission device between the shafts to increase or reduce the torque transmitted to the front shaft so that the vehicle runs in the road along a normal track. When the situation that the steering lamp is poor is monitored, the distance between the wheels and the center line of the lane is more than 0.4m, the actual torque of a driver is less than 1.5Nm, the lateral deviation angle of the vehicle is less than 0.01rad, the vehicle can be judged to be in a straight-going deviation rectifying mode, and the steering wheel rotates according to an ECU instruction, so that the vehicle keeps running in a straight line in the center of the road.
In the present invention, as a preferable mode, the distance threshold is 0.4 m;
in the present invention, as a preference, the driver's actual torque threshold is 1.5Nm,
in the present invention, it is preferable that the threshold value of the vehicle slip angle is 0.01 rad.
In other cases, the vehicle is deviated from the center of the road, but the deviation is not corrected because of the autonomous operation of the driver.
While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.

Claims (5)

1. A lane keeping system, comprising:
a control unit;
the output end of the measuring unit is connected with the input end of the control unit;
the output end of the image acquisition unit is connected with the input end of the control unit;
the steering motor system is electrically connected with the output end of the control unit;
the driving motor system is electrically connected with the output end of the control unit;
wherein the control unit is further electrically connected with a wheel of the vehicle.
2. The lane keeping system of claim 1, wherein the measurement unit comprises: a steering wheel angle sensor, a vehicle yaw angle sensor, a yaw rate sensor, and an acceleration sensor.
3. A control method of a lane keeping system using the lane keeping system according to any one of claims 1 to 2, characterized by comprising:
the method comprises the steps that the distance from wheels to the center line of a lane line in the driving process of a vehicle, the actual torque of a driver and the vehicle sideslip angle are collected through a measuring unit, and a turn light signal and a curvature signal of the lane line are detected through an image collecting unit;
when the vehicle deviates from a lane and the curvature of a turn light signal and the curvature of a lane line are both 1 in a turning working condition, entering a steering rectification mode, controlling a driving motor system by a control unit, and adjusting the torque transmitted to a front shaft, wherein the vehicle runs in a normal track in the road;
when the steering signal is 0 under the straight-driving working condition, the distance L between the wheels and the center line of the lane is greater than the threshold value L of the distance L between the wheels and the center line of the lanethThe actual driver torque T is less than the actual driver torque threshold TthThe vehicle slip angle theta is smaller than the vehicle slip angle threshold thetathThen, entering a straight-going deviation rectifying mode; the control unit adjusts a steering angle through a steering motor system to enable the vehicle to keep running in a straight line at the center of a road;
otherwise, entering a safe mode;
wherein L isth＝0.4m、Tth＝1.5Nm、θth＝0.01rad。
4. The control method of a lane keeping system according to claim 3, wherein when entering a steer away mode,
setting the running mode of the vehicle as circular motion, establishing a single-point preview driver model, and obtaining the ideal yaw velocity of the vehicle as follows:
Figure FDA0003263935650000021
where Δ s is the preview deviation, vxThe speed of the vehicle in the longitudinal direction is taken as the speed, beta is the centroid slip angle of the vehicle, and delta t is the time when the ideal centroid position of the vehicle reaches the pre-aiming point on the target track;
feedback control of a deviation of an actual yaw rate from an ideal yaw rate by a PID control algorithm includes:
eωr＝sign(ωr)·(ωs-ωr)；
Figure FDA0003263935650000022
in the formula, ωrTo the actual yaw rate, ωsIdeal yaw rate, eωrIs the deviation of yaw angular velocity;
the torque value required to be transmitted between the shafts for realizing lane keeping is obtained as follows:
Mdyaw(t+Δt)＝Mdyaw(t)+ΔMdyaw；
in the formula, Mdyaw(t) is the value of torque delivered in the previous cycle, Mdyaw(t + Δ t) is the torque value, Δ M, of the next cycledyawIs the value of the torque change between the shafts between the adjacent periods;
wherein, the target torque value obtained by PID feedback control is as follows:
ΔMdyaw＝Kp·(eωr(t+Δt)-eωr(t))+Ki·eωr(t+Δt)；
in the formula, eωr(t) yaw rate deviation value of previous period, eωr(t + Δ t) is a yaw rate deviation value, Δ M, of the next cycledyawFor the change in transmitted torque of adjacent cycles, KpIs a scale factor, KiIs an integration factor.
5. The control method of a lane keeping system according to claim 4, wherein when entering the straight deviation correcting mode:
carrying out LQR transverse control on the deviation of the lateral deviation angle and the transverse displacement of the vehicle to obtain an expected front wheel corner;
establishing a two-degree-of-freedom model of the vehicle
Figure FDA0003263935650000031
Obtaining state equations of corresponding deviations of the four variables of the transverse displacement deviation, the transverse speed, the slip angle deviation and the slip angle speed:
Figure FDA0003263935650000032
wherein A, B, C is a coefficient matrix comprising:
Figure FDA0003263935650000033
Figure FDA0003263935650000034
Figure FDA0003263935650000035
where δ is the wheel angle, m is the vehicle mass, vxAs longitudinal velocity, /)fIs the distance from the center of mass of the vehicle to the front axle,/rIs the distance of the vehicle's center of mass to the rear axle, CfFor yaw stiffness of the front axle, CrFor cornering stiffness of the rear axle, IzIs the moment of inertia of the vehicle about the z-axis;
the control law of the expected turning angle of the system is as follows:
Figure FDA0003263935650000041
in the formula, deltasFor an ideal wheel angle, Δ L is the lateral displacement deviation,
Figure FDA0003263935650000042
is the lateral velocity, theta is the slip angle deviation,
Figure FDA0003263935650000043
is the slip angle velocity;
calculating an expected matrix K to obtain a characteristic value K of the matrix K1、K2、K3、K4Finally, a desired wheel turning angle δ is obtaineds；
The deviation of the actual value of the front wheel steering angle from the expected value is:
Δδ＝δ-δs；
through PID control, the power-assisted steering torque required to be applied to the front wheels to realize lane keeping is as follows:
Figure FDA0003263935650000044
in the formula, Kp、Ki、KdRespectively a proportional factor, an integral factor and a differential factor.
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Cited By (1)

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Publication number Priority date Publication date Assignee Title
CN115891977A (en) * 2023-02-22 2023-04-04 北京易控智驾科技有限公司 Method and device for controlling understeer of unmanned mining vehicle, electronic equipment and storage medium

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