CN114179806B - Control method and system for hill start of automatic driving vehicle - Google Patents

Control method and system for hill start of automatic driving vehicle Download PDF

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Publication number
CN114179806B
CN114179806B CN202111528453.8A CN202111528453A CN114179806B CN 114179806 B CN114179806 B CN 114179806B CN 202111528453 A CN202111528453 A CN 202111528453A CN 114179806 B CN114179806 B CN 114179806B
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vehicle
hill
hill start
control system
driving force
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CN114179806A (en
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胡杰
张敏超
陈瑞楠
朱令磊
钟鑫凯
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Wuhan University of Technology WUT
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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
    • B60W30/18—Propelling the vehicle
    • B60W30/18009—Propelling the vehicle related to particular drive situations
    • 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
    • B60W30/18—Propelling the vehicle
    • B60W30/18009—Propelling the vehicle related to particular drive situations
    • B60W30/18054—Propelling the vehicle related to particular drive situations at stand still, e.g. engine in idling state
    • 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
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/02—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to ambient conditions
    • B60W40/06—Road conditions
    • B60W40/076—Slope angle of the road
    • 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
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/10—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to vehicle motion
    • B60W40/105—Speed
    • 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
    • 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
    • B60W2552/00—Input parameters relating to infrastructure
    • B60W2552/15—Road slope, i.e. the inclination of a road segment in the longitudinal direction

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Regulating Braking Force (AREA)
  • Control Of Transmission Device (AREA)
  • Control Of Driving Devices And Active Controlling Of Vehicle (AREA)

Abstract

The invention provides a control method and a system for hill start of an automatic driving vehicle, wherein the hill start process of the automatic driving vehicle is divided into a parking state, a hill start state, a sliding state and a normal running state, the current state of the vehicle is judged by acquiring the current sensor signals of the automatic driving vehicle and track information issued by a planning module in real time, and the vehicle is controlled by a vehicle control system. The invention solves the problem of slope sliding of the automatic driving vehicle in the process of hill start, so that the automatic driving vehicle starts stably on the hill, and has wide practicability and strong adaptability.

Description

Control method and system for hill start of automatic driving vehicle
Technical Field
The invention belongs to the technical field of automatic driving of vehicles, and relates to a hill start control method and system.
Background
Currently, a control module in an automatic driving vehicle generally adopts various closed-loop control methods to coordinate and control an actuator of the vehicle so as to accurately follow a track issued by a planning module. However, various problems that can not be eliminated exist in actual vehicles, such as sensor errors, controller delays, actuator delays and the like, and the problems can cause errors when the vehicles perform motion control, and the output of the upper controller can be regulated in real time through a control method in the normal running process so as to reduce the errors and realize accurate following of a planned track. However, under the working condition of hill start, if the output driving force has an accuracy error or delay, the vehicle may slide, and at this time, the comfort of the passengers and the safety of the vehicle may be seriously affected.
Disclosure of Invention
In order to solve the problems in the background art, the invention provides a control method and a system for hill start of an automatic driving vehicle.
The invention provides a control method for hill start of an automatic driving vehicle, which comprises the following steps:
s1, after a vehicle is started, a vehicle control system jumps to a parking state, hill information is obtained in real time, and hill start driving force is calculated;
s2, the vehicle control system acquires vehicle state information in real time and judges whether the vehicle is ready to start: when the vehicle is not ready to start, the vehicle control system maintains a stopped state; when the vehicle is ready to start, entering the next step;
s3, analyzing the ramp information acquired in the S1, judging whether the vehicle starts on a ramp, and jumping the vehicle control system to a normal running state when the vehicle does not start on the ramp; when the vehicle is in a hill start state, the vehicle control system jumps to a hill start state, performs hill start control on the vehicle, and applies the hill start driving force calculated in the step S1;
s4, when the vehicle is started on a slope, the vehicle control system acquires vehicle speed information in real time and judges whether the vehicle slides on the slope: when the vehicle does not slide down a slope, the vehicle control system jumps to a normal running state; when the vehicle slides, the vehicle control system jumps to a sliding state, the vehicle is controlled to slide and the hill start driving force is increased until the vehicle does not slide, and the vehicle control system jumps to a normal running state again;
s5, acquiring vehicle speed and vehicle state information in real time in a normal running state of the vehicle, and judging whether the vehicle is ready to stop or not: when the vehicle is not ready to stop, the vehicle control system maintains a normal running state; when the vehicle is ready to park, the vehicle speed drops to zero and the vehicle control system jumps to a park condition.
Further, in S1, the hill start driving force is:
T t ＝(mgsinθ+mgcosθf)×α+β，
wherein T is t Representing current hill startThe required driving force, m is the mass of the whole vehicle, g is the gravitational acceleration, θ is the road gradient angle, f is the rolling resistance coefficient of the ramp road, and α and β are two adjustment coefficients; the method for determining the alpha and beta is that the vehicle is stopped on the slopes with different gradients, the output driving force of the system when the vehicle starts on the slopes with different gradients with constant acceleration a is recorded, and then a curve fitting method is adopted to fit T t - θ curve, determining α, β as two adjustment coefficients.
Further, in the step S2, the method for determining whether the vehicle is ready to start is as follows: when the gear of the vehicle is in the P gear, the speed of the vehicle is smaller than the speed threshold value x, and the request speed in the track information sent by the vehicle planning module is greater than zero within a period of time t in the future, the vehicle is ready to start, otherwise, the vehicle is not ready to start; wherein the speed threshold x depends on the magnitude of the speed sensor value fluctuation when the vehicle is stationary.
Further, in the step S3, the method for determining whether the vehicle is started on a hill is as follows: if the gradient angle of the road on which the vehicle is positioned is larger than the gradient threshold value i, the vehicle is started on a hill, otherwise, the vehicle is not started on a hill; the calculation method of the gradient threshold i comprises the following steps: i=f, where f is the rolling resistance coefficient of the ramp road.
Further, in the step S3, the method for performing the hill start control on the vehicle and applying the hill start driving force calculated in the step S1 at a proper time includes: firstly, setting the output value of a brake of a vehicle to be the maximum value, then switching the gear of the vehicle to the D gear, then closing an electronic parking brake system, then controlling an accelerator pedal to enable the vehicle to output the hill start driving force calculated in the step S1, and finally setting the output value of the brake to be zero.
Further, in the step S4, the method for controlling the vehicle to slip and increasing the hill start driving force in the step S4 includes: firstly setting the output value of a brake of a vehicle to be the maximum value, then switching the gear of the vehicle to the P gear, and then applying increased hill start driving force; the increased hill start driving force is as follows:
T t ′＝(mgsinθ+mgcosθf)×α+β+ma，
wherein T is t ' represents increased hill start driving force, m is the mass of the whole vehicle, g is the gravitational acceleration, θ is the estimated road gradient angle, f is the rolling resistance coefficient of the hill road, α, β are two adjustment coefficients, a is the absolute value of the longitudinal acceleration when the vehicle is running downhill; the method for determining the alpha and beta is that the vehicle is stopped on the slopes with different gradients, the output driving force of the system when the vehicle starts on the slopes with different gradients with constant acceleration a is recorded, and then a curve fitting method is adopted to fit T t - θ curve, determining α, β as two adjustment coefficients.
Further, in the step S5, the method for determining whether the vehicle is ready to stop is as follows: if the gear of the vehicle is in the P gear, the speed of the vehicle is smaller than the speed threshold value x, and the request speed in the track information sent by the vehicle planning module is equal to zero within a period of time t in the future, the vehicle is ready to park, otherwise, the vehicle is not ready to park; wherein the speed threshold x depends on the magnitude of the speed sensor value fluctuation when the vehicle is stationary.
The invention also provides a control system for hill start of the automatic driving vehicle, which comprises a parking control module, a hill start control module, a hill slip control module and a normal running control module.
The parking control module is used for: the method is used for judging whether the vehicle is ready to start or not and sending out corresponding instructions: when the vehicle is not ready to start, the vehicle control system is instructed to maintain the vehicle in a stopped state; when the vehicle is ready to start, the vehicle control system is instructed to enter the hill start control module.
The hill start control module is used for: the method is used for judging whether the vehicle is started on a hill and sending out corresponding instructions: when the vehicle is not in the hill start state, the vehicle control system is instructed to jump to the normal running control module; when the vehicle is hill start, the vehicle control system is instructed to perform hill start control on the vehicle and apply hill start driving force.
The landslide control module is characterized in that: the method is used for acquiring the speed information in real time to judge whether the vehicle slides on a slope: when the vehicle does not slide down a slope, the vehicle control system is instructed to jump to a normal running control module; when the vehicle slides, the vehicle control system is instructed to control the vehicle to slide and increase the hill start driving force until the vehicle does not slide, and then the vehicle control system jumps to the normal running control module.
The normal running control module is used for: the method is used for acquiring the vehicle speed and vehicle state information in real time and judging whether the vehicle is ready to stop or not: when the vehicle is not ready to stop, the vehicle control system is instructed to maintain a normal running state; when the vehicle is ready to park, the vehicle control system is instructed to park by reducing the vehicle speed to zero, and the vehicle control system enters the park control module.
The invention divides the hill start process of the automatic driving vehicle into a parking state, a hill start state, a sliding state and a normal running state, judges the current state of the vehicle by acquiring the existing sensor signals of the automatic driving vehicle and track information under a planning module in real time, and instructs a vehicle control system to control the vehicle through a hill start control system. The invention solves the problem of slope sliding of the automatic driving vehicle in the process of hill start, so that the automatic driving vehicle starts stably on the hill, and has wide practicability and strong adaptability.
Drawings
FIG. 1 is a flow chart of a method of controlling hill start of an autonomous vehicle.
Fig. 2 is an effect graph of curve fitting.
FIG. 3 is a schematic diagram of a control system for hill start of an autonomous vehicle.
Detailed Description
The following detailed description of the invention, taken in conjunction with the accompanying drawings, is not intended to limit the invention, but is made merely by way of example, and the advantages of the invention will be more clearly understood. All modifications directly derived or suggested to one skilled in the art from the disclosure of the present invention should be considered as being within the scope of the present invention. Other parts of the examples not described in detail are prior art.
Fig. 1 is a flowchart of a control method for hill start of an automatically driven vehicle, and a detailed description will be given below of a control process for hill start of an automatically driven vehicle in connection with a specific embodiment.
1. After the automatic driving vehicle is started, the vehicle control system jumps to a parking state, the ramp information is acquired in real time, and the hill start driving force is calculated.
Specifically, the vehicle control system acquires the vehicle speed and the longitudinal acceleration information from the sensor, and there are various methods of estimating the road gradient angle, and in this embodiment, the road gradient angle is estimated by using the kalman filter method, and the driving force required for the hill start on the current hill is calculated from the estimated road gradient angle.
The method for estimating the road gradient angle by adopting Kalman filtering comprises the following steps:
first, a state variable at the time of k of the vehicle control system is defined: x (k) = [ v (k) a ] sen (k)sinα(k)] T ,
Wherein v (k) is the speed of the speed sensor on the automatic driving vehicle at time k, a sen (k) For the longitudinal acceleration of the acceleration sensor on the autonomous vehicle at time k, sin α (k) is the sine value of the road ramp angle at time k.
In one period T, the state equation of the vehicle control system is:
x(k)＝A×x(k-1)+w(k)，
wherein x (k-1) is a state variable at time k-1, A is a process matrix, and the value isw (k) is the process noise and its covariance matrix is Q.
The process noise represents the deviation between the state space equation of the vehicle control system and the actual process, and the covariance Q of the process noise can be obtained through a comparison experiment.
The observation equation for the vehicle control system is:
z(k)＝H×x(k)+v(k)，
Z(k)＝H×x(k)+v(k)，
wherein H is an observation matrix, and the value of H isv (k) is observation noise, and the covariance matrix is R.
The measurement noise represents the accuracy error of the sensor, and the covariance R is the measurement variance obtained by long-term probability statistics of the sensor measurement data.
The predicted next periodic state equation is:
the predicted next cycle error covariance is: p (P) - (k)＝AP(k-1)A T +Q。
The Kalman filter gain is: k (K) =p - (k)H T [HP - (k)H T +R] -1
So that the error covariance can be updated as: p (K) = [ I-K (K) H]P - (k)
The state variable estimated value updated according to the measured value is:
thus, the estimated road gradient angleWherein->Estimate value +.>Is a third row element of (c).
Thus hill start driving force T t The method comprises the following steps:
T t ＝(mgsinθ+mgcosθf)×α+β，
wherein T is t Represents the driving force required by the current hill start, m is the mass of the whole vehicle, g is the gravitational acceleration, θ is the road gradient angle, fThe rolling resistance coefficient of the ramp road is the rolling resistance coefficient, and alpha and beta are two adjustment coefficients.
The method for determining the alpha and beta as two adjustment coefficients comprises the steps of stopping the vehicle on slopes with different gradients, recording output driving force of a system when the vehicle starts on the slopes with different gradients at constant acceleration a, and fitting T by adopting a curve fitting method t - θ curve, determining α, β as two adjustment coefficients.
In the following, a specific example of hill start for an autonomous vehicle is described.
The parameters of the hill start of the autonomous vehicle are shown in table 1.
TABLE 1 parameters for hill start for an autonomous vehicle
The specific confirmation method of the adjustment coefficients alpha and beta comprises the following steps: stopping the vehicle on the slopes with different gradients, and testing the acceleration of the vehicle on the slopes with different gradients by 1m/s 2 The magnitude of the hill start driving force output by the vehicle at the start is shown in table 2 as specific data of the test.
Table 2 slope angle and hill start driving force value correspondence table
Slope angle θ (rad) Hill start driving force T t (N)
0.174(10°) 4287.534186299495
0.261(15°) 6721.648966662501
0.348(20°) 8913.275048967099
0.435(25°) 9345.863164866276
0.522(30°) 9456.843647519458
0.609(35°) 12232.54679509844
The data in table 2 are subjected to curve fitting by a least square method, and the fitted curve formula is as follows: t (T) t The effect graph of fitting = (mgsinθ+mgcos θf) ×α+β is shown in fig. 2, and α= 1.02364349 and β= 1596.32547272 can be obtained.
When the actual ramp angle is 30 degrees, the vehicle is stopped on the ramp, and enters a ramp starting state, and the formula T is utilized t = (mgsinθ+mgcos θf) ×α+β, the hill start driving force output from the vehicle is calculated as 10529.88N.
When the actual ramp angle is 15 degrees, the vehicle is stopped on the ramp, and enters a ramp starting state, and the formula T is utilized t = (mgsinθ+mgcos θf) ×α+β, and the hill start driving force output from the vehicle is calculated as 6398.90N.
2. The vehicle control system acquires vehicle state information in real time and judges whether the vehicle is ready to start: when the vehicle is not ready to start, the vehicle control system maintains a parking state and ends; when the vehicle is ready to start, the next step is entered.
Specifically, the method for judging whether the automatic driving vehicle has a starting intention is as follows:
(1) The gear of the vehicle is in the P gear;
(2) The speed of the vehicle is less than a speed threshold x, which depends on the magnitude of the speed sensor value fluctuation when the vehicle is stationary;
(3) The request speed in a period of time t in the future is greater than zero in the track information sent by the vehicle planning module.
When all the three conditions are met, the automatic driving vehicle is judged to be ready for starting, otherwise, the vehicle is not ready for starting.
3. Analyzing the acquired hill information, judging whether the vehicle starts on a hill, and jumping to a normal running state by a vehicle control system when the vehicle is not in the hill start state; when the vehicle is hill start, the vehicle control system jumps to a hill start state, performs hill start control on the vehicle, and applies a hill start driving force T t 。
Specifically, the method for judging whether the vehicle is started on a hill is as follows: if the gradient angle of the road on which the vehicle is positioned is larger than the gradient threshold value i, the vehicle is started on a hill, otherwise, the vehicle is not started on a hill; the calculation method of the gradient threshold i comprises the following steps: i=f, where f is the rolling resistance coefficient of the ramp road.
Specifically, the method of performing the hill start control for the vehicle and applying the hill start driving force Tt is as follows:
(1) Setting the output value of the brake to be the maximum value, namely locking the brake;
(2) Delay 0.2 seconds;
(3) Switching the vehicle gear to the D gear;
(4) Delay 0.2 seconds;
(5) Closing the electronic parking brake system;
(6) Delay 0.2 seconds;
(7) Controlling an accelerator pedal to enable the vehicle to output a hill start driving force Tt;
(8) Delay 0.5 seconds;
(9) Setting the brake output value to zero, i.e. releasing the brake.
The steps are carried out according to the above steps.
When the actual ramp angle isAt 30 deg. the vehicle outputs a hill start driving force of 10529.88N, at which time the vehicle will be at 1.6m/s as known from sensors on the vehicle 2 Is used for ramp-up.
When the actual ramp angle is 15 degrees and the vehicle outputs a hill start driving force of 6398.90N, the vehicle will take a speed of 0.813m/s as known from the sensors on the vehicle 2 Is used for ramp-up.
4. When the vehicle starts on a slope, the vehicle control system acquires vehicle speed information in real time to judge whether the vehicle slides on the slope: when the vehicle does not slide down a slope, the vehicle control system jumps to a normal running state; when the vehicle slides, the vehicle control system jumps to a sliding state, the vehicle is controlled to slide, the hill start driving force is increased until the vehicle does not slide, and the vehicle control system jumps to a normal running state again.
Specifically, the method for judging whether the automatic driving vehicle slides on a slope in the process of hill starting comprises the following steps: whether the vehicle speed signal is negative. If the vehicle speed signal is negative, judging that the automatic driving vehicle is in a sliding slope, otherwise, not in a sliding slope.
The method for controlling the vehicle to slide and increasing the hill start driving force comprises the following steps:
(1) Setting the output value of the brake to be the maximum value, namely locking the brake;
(2) Delay 0.2 seconds;
(3) Shifting vehicle gear to P gear
(4) Delay 0.2 seconds;
(5) Applying increased hill start driving force T t ′；
(6) Delay for 2 seconds;
(7) Jump to hill start condition
The steps are carried out according to the above steps.
Wherein the increased hill start driving force T t ' is:
T t ′＝(mgsinθ+mgcosθf)×α+β+ma，
wherein T is t ' represents increased hill start driving force, m is the mass of the whole vehicle, g is the gravitational acceleration, θ is the estimated road gradient angle, and f is the slopeThe rolling resistance coefficient of the road, α, β, is two adjustment coefficients, a is the absolute value of the longitudinal acceleration of the vehicle when a hill slip occurs, and this value is read from the sensor.
The method for determining the alpha and beta as two adjustment coefficients comprises the steps of stopping the vehicle on slopes with different gradients, recording output driving force of a system when the vehicle starts on the slopes with different gradients at constant acceleration alpha, and fitting T by adopting a curve fitting method t - θ curve, determining α, β as two adjustment coefficients.
5. Under the normal running state of the vehicle, acquiring the vehicle speed and vehicle state information in real time, and judging whether the vehicle is ready to stop or not: when the vehicle is not ready to stop, the vehicle control system maintains a normal running state; when the vehicle is ready to park, the vehicle speed drops to zero and the vehicle control system jumps to a park condition.
Specifically, the method of judging whether the vehicle is ready to stop is:
(1 gear is in P gear;
(2) The speed of the vehicle is less than a speed threshold x, which depends on the magnitude of the speed sensor value fluctuation when the vehicle is stationary;
(3) The request speed in the future period t in the track information sent by the vehicle planning module is equal to zero.
When all the three conditions are met, the automatic driving vehicle is judged to be ready for parking, otherwise, the vehicle is not ready for parking.
FIG. 3 is a schematic diagram of a control system for hill start of an autonomous vehicle, the control system being comprised of a park control module, a hill start control module, a hill run control module, and a normal travel control module, each interconnected with the vehicle control system.
The parking control module is used for judging whether the vehicle is ready to start or not and sending out corresponding instructions: when the vehicle is not ready to start, the vehicle control system is instructed to maintain the vehicle in a stopped state; when the vehicle is ready to start, the vehicle control system is instructed to enter the hill start control module.
The hill start control module is used for judging whether the vehicle starts on a hill and sending out corresponding instructions: when the vehicle is not in the hill start state, the vehicle control system is instructed to jump to the normal running control module; when the vehicle is hill start, the vehicle control system is instructed to perform hill start control on the vehicle and apply hill start driving force.
The landslide control module is used for acquiring vehicle speed information in real time to judge whether the vehicle slides on a slope: when the vehicle does not slide down a slope, the vehicle control system is instructed to jump to a normal running control module; when the vehicle slides, the vehicle control system is instructed to control the vehicle to slide and increase the hill start driving force until the vehicle does not slide, and then the vehicle control system jumps to the normal running control module.
The normal running control module is used for acquiring vehicle speed and vehicle state information in real time and judging whether the vehicle is ready to stop or not: when the vehicle is not ready to stop, the vehicle control system is instructed to maintain a normal running state; when the vehicle is ready to park, the vehicle control system is instructed to park by reducing the vehicle speed to zero, and the vehicle control system enters the park control module.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings and specific examples, but the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solutions of the present invention within the scope of the technical concept of the present invention, and all the simple modifications belong to the protection scope of the present invention.

Claims (5)

1. A control method for hill start of an autonomous vehicle, comprising the steps of:
s1, after a vehicle is started, a vehicle control system jumps to a parking state, hill information is obtained in real time, and hill start driving force is calculated;
s2, the vehicle control system acquires vehicle state information in real time and judges whether the vehicle is ready to start: when the vehicle is not ready to start, the vehicle control system maintains a stopped state; when the vehicle is ready to start, entering the next step;
the method for judging whether the vehicle is ready to start comprises the following steps: when the gear of the vehicle is in the P gear, the speed of the vehicle is smaller than the speed threshold value x, and the request speed in the track information sent by the vehicle planning module is greater than zero within a period of time t in the future, the vehicle is ready to start, otherwise, the vehicle is not ready to start; wherein the speed threshold x depends on the magnitude of the speed sensor value fluctuation when the vehicle is stationary;
s3, analyzing the ramp information acquired in the S1, judging whether the vehicle starts on a ramp, and jumping the vehicle control system to a normal running state when the vehicle does not start on the ramp; when the vehicle is in a hill start state, the vehicle control system jumps to a hill start state, performs hill start control on the vehicle, and applies the hill start driving force calculated in the step S1;
the method for judging whether the vehicle starts on a hill is as follows: if the gradient angle of the road on which the vehicle is located is greater than the gradient threshold valueThe vehicle is hill-started, otherwise the vehicle is not hill-started; the gradient threshold ∈>The calculation method of (1) is as follows: />Wherein->The rolling resistance coefficient of the ramp road;
the method for performing hill start control on the vehicle and timely applying the hill start driving force calculated by the S1 comprises the following steps: firstly, setting a brake output value of a vehicle to be the maximum value, then switching a vehicle gear to a D gear, then closing an electronic parking brake system, then controlling an accelerator pedal to enable the vehicle to output the hill start driving force calculated in the step S1, and finally setting the brake output value to be zero;
s4, when the vehicle is started on a slope, the vehicle control system acquires vehicle speed information in real time to judge whether the vehicle slides on the slope: when the vehicle does not slide down a slope, the vehicle control system jumps to a normal running state; when the vehicle slides, the vehicle control system jumps to a sliding state, the vehicle is controlled to slide and the hill start driving force is increased until the vehicle does not slide, and the vehicle control system jumps to a normal running state again;
the method for controlling the vehicle to slide and increasing the hill start driving force comprises the following steps: firstly setting the output value of a brake of a vehicle to be the maximum value, then switching the gear of the vehicle to the P gear, and then applying increased hill start driving force; the increased hill start driving force is as follows:
，
wherein,indicates increased hill start driving force, +.>Is the whole car quality->Is acceleration of gravity>For the estimated road gradient angle +.>For the rolling resistance coefficient of the ramp road, +.>、/>For two adjustment coefficients +.>The absolute value of the longitudinal acceleration when the vehicle is running on a slope; said->、/>Method for determining two adjustment factors, in order to stop the vehicle on a slope of different grade, the vehicle is recorded with constant acceleration +.>The output driving force of the system when the hill start is performed is then fitted by curve fitting>-/>Curve, determine->、/>Two adjustment coefficients;
s5, acquiring vehicle speed and vehicle state information in real time in a normal running state of the vehicle, and judging whether the vehicle is ready to stop or not: when the vehicle is not ready to stop, the vehicle control system maintains a normal running state; when the vehicle is ready to park, the vehicle speed drops to zero and the vehicle control system jumps to a park condition.
2. A control method for hill start of an autonomous vehicle according to claim 1, wherein: in the step S1, the hill start driving force is:
，
wherein,represents the driving force required for the current hill start, +.>Is the whole car quality->Is acceleration of gravity>For the estimated road gradient angle +.>For the rolling resistance coefficient of the ramp road, +.>、/>Two adjustment coefficients; said->、/>Method for determining two adjustment factors, in order to stop the vehicle on a slope of different grade, the vehicle is recorded with constant acceleration +.>The output driving force of the system when the hill start is performed is then fitted by curve fitting>-/>Curve, determine->、/>Two adjustment coefficients.
3. A control method for hill start of an autonomous vehicle according to claim 2, wherein: in the step S5, the method for determining whether the vehicle is ready to stop is as follows: if the gear of the vehicle is in the P gear, the speed of the vehicle is smaller than the speed threshold value x, and the request speed in the track information sent by the vehicle planning module is equal to zero within a period of time t in the future, the vehicle is ready to park, otherwise, the vehicle is not ready to park; wherein the speed threshold x depends on the magnitude of the speed sensor value fluctuation when the vehicle is stationary.
4. A control system for hill start of an autonomous vehicle, characterized by: the system comprises a parking control module, a hill start control module, a hill sliding control module and a normal running control module which are interconnected with a vehicle control system;
the parking control module is used for: the method is used for judging whether the vehicle is ready to start or not and sending out corresponding instructions: when the vehicle is not ready to start, the vehicle control system is instructed to maintain the vehicle in a stopped state; when the vehicle is ready to start, the vehicle control system is instructed to enter a hill start control module; the method for judging whether the vehicle is ready to start comprises the following steps: when the gear of the vehicle is in the P gear, the speed of the vehicle is smaller than the speed threshold value x, and the request speed in the track information sent by the vehicle planning module is greater than zero within a period of time t in the future, the vehicle is ready to start, otherwise, the vehicle is not ready to start; wherein the speed threshold x depends on the magnitude of the speed sensor value fluctuation when the vehicle is stationary;
the hill start control module is used for: the method is used for judging whether the vehicle is started on a hill and sending out corresponding instructions: when the vehicle is not in the hill start state, the vehicle control system is instructed to jump to the normal running control module; when the vehicle is hill start, the vehicle control system is instructed to perform hill start control on the vehicle and apply hill start driving force; the method for judging whether the vehicle starts on a hill is as follows: if the gradient angle of the road on which the vehicle is located is greater than the gradient threshold valueThe vehicle is hill-started, otherwise the vehicle is not hill-started; the gradient threshold ∈>The calculation method of (1) is as follows: />Wherein->The rolling resistance coefficient of the ramp road; the method for performing hill start control on the vehicle and timely applying the hill start driving force calculated by the S1 comprises the following steps: firstly, setting a brake output value of a vehicle to be the maximum value, then switching a vehicle gear to a D gear, then closing an electronic parking brake system, then controlling an accelerator pedal to enable the vehicle to output the hill start driving force calculated in the step S1, and finally setting the brake output value to be zero;
the landslide control module is characterized in that: the method is used for acquiring the speed information in real time to judge whether the vehicle slides on a slope: when the vehicle does not slide down a slope, the vehicle control system is instructed to jump to a normal running control module; when the vehicle slides on a slope, the vehicle control system is instructed to control the slope on the vehicle and increase the hill start driving force until the vehicle does not slide on the slope, and the vehicle control system jumps to the normal running control module again; the increased hill start driving force is:
，
wherein,indicates increased hill start driving force, +.>Is the whole car quality->Is acceleration of gravity>For the estimated road gradient angle +.>For the rolling resistance coefficient of the ramp road, +.>、/>For two adjustment coefficients +.>The absolute value of the longitudinal acceleration when the vehicle is running on a slope; said->、/>Method for determining two adjustment factors, in order to stop the vehicle on a slope of different grade, the vehicle is recorded with constant acceleration +.>The output driving force of the system when the hill start is performed is then fitted by curve fitting>-/>Curve, determine->、/>Two adjustment coefficients;
the normal running control module is used for: the method is used for acquiring the vehicle speed and vehicle state information in real time and judging whether the vehicle is ready to stop or not: when the vehicle is not ready to stop, the vehicle control system is instructed to maintain a normal running state; when the vehicle is ready to park, the vehicle control system is instructed to park by reducing the vehicle speed to zero, and the vehicle control system enters the park control module.
5. A control system for hill start of an autonomous vehicle as claimed in claim 4, wherein: in the hill start control module, the hill start driving force is as follows:
，
wherein,represents the driving force required for the current hill start, +.>Is the whole car quality->Is acceleration of gravity>For the estimated road gradient angle +.>For the rolling resistance coefficient of the ramp road, +.>、/>Two adjustment coefficients; said->、/>Method for determining two adjustment factors, in order to stop the vehicle on a slope of different grade, the vehicle is recorded with constant acceleration +.>The output driving force of the system when the hill start is performed is then fitted by curve fitting>-/>Curve, determine->、/>Two adjustment coefficients.
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