Method and system for speed limiting of autonomous vehicles

Abstract

The application is suitable for the automatic driving technical field, and particularly relates to an automatic driving vehicle speed limiting method and system, the method comprising: acquiring a vehicle driving speed and a throttle amount; acquiring environmental parameter information, and determining a whole vehicle speed limiting value according to the environmental parameter information; calculating a motor target torque value through a preset vehicle speed limiting algorithm according to the vehicle driving speed and the throttle amount; and controlling the motor according to the motor target torque value. The automatic driving vehicle speed limiting method provided by the application avoids the problem of frequent parameter adjustment, and can complete speed control through confirmation of each basic parameter of the vehicle at the beginning of design, so that frequent parameter adjustment is not needed, and development time and manpower cost are saved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of automatic driving, and particularly relates to an automatic driving vehicle speed limiting method and system. BACKGROUND

[0002] The vehicle speed is usually limited in an automatic driving vehicle to ensure the safety of the vehicle, and it is particularly important to limit the vehicle speed under the premise of no speed limit and no torque limit for a small automatic driving bus of L4 level and above.

[0003] At present, most of the algorithms used are PID control algorithms with motor torque as the controlled object and vehicle longitudinal speed as the feedback, but the PID algorithm needs to frequently adjust and calibrate the three coefficients of integral, differential and proportion. SUMMARY

[0004] The purpose of the embodiment of the application is to provide an automatic driving vehicle speed limiting method, which aims to solve the problem that the PID algorithm needs to frequently adjust and calibrate the three coefficients of integral, differential and proportion.

[0005] In the embodiment of the application, an automatic driving vehicle speed limiting method is provided, which comprises:

[0006] Obtaining the vehicle speed and the throttle amount;

[0007] Obtaining the environmental parameter information and determining the vehicle speed limit value according to the environmental parameter information;

[0008] According to the vehicle speed and the throttle amount, the motor target torque value is calculated through a preset vehicle speed limiting algorithm, and the function used by the vehicle speed limiting algorithm is:

[0009]

[0010] Wherein, c is the motor target torque value, the unit is Nm, c1 is the maximum value of the motor target torque, the unit is Nm, a is the vehicle speed value, the unit is km / h, b is the throttle amount, the range is [0, 100%], a1 is the vehicle speed limit value, the unit is km / h, and d1 is the motor target torque value of the automatic driving vehicle maintaining the speed limit value on the horizontal road, the unit is Nm.

[0011] According to the motor target torque value, the motor is controlled.

[0012] Preferably, the step of obtaining the environmental parameter information and determining the vehicle speed limit value according to the environmental parameter information specifically comprises:

[0013] Obtaining the vehicle positioning information and determining the road position where the vehicle is located according to the vehicle positioning information;

[0014] determining a maximum speed limit speed of the vehicle according to vehicle positioning information;

[0015] obtaining a driving speed of a nearby vehicle and a driving lane, and determining a whole vehicle speed limit value.

[0016] Preferably, the step of obtaining the driving speed of the nearby vehicle and the driving lane, and determining the whole vehicle speed limit value specifically comprises:

[0017] obtaining the driving speed of the nearby vehicle, and identifying other vehicles in each lane;

[0018] determining a driving speed of a front vehicle in a current lane, and determining whether the driving speed exceeds the maximum speed limit speed;

[0019] if the driving speed does not exceed the maximum speed limit speed, the driving speed is taken as the whole vehicle speed limit value, otherwise the maximum speed limit speed is taken as the whole vehicle speed limit value.

[0020] Preferably, a calculation formula of the motor target torque value of the autonomous vehicle maintaining the speed limit value on a horizontal road is:

[0021]

[0022] wherein, F 空 is an air resistance received when the vehicle reaches the speed limit value, in N, F 动 is a dynamic friction of the vehicle on a general road, is a basic parameter of the vehicle, in N, F 其他 is other resistance received when the vehicle drives at the speed limit value, in N, R is a tire radius of the vehicle, in meters, L1 is a gear ratio of a reducer, and W1 is a mechanical efficiency.

[0023] Preferably, in the calculation formula of the motor target torque value of the autonomous vehicle maintaining the speed limit value on the horizontal road,

[0024]

[0025] wherein, a is a wind resistance coefficient of the vehicle, which is obtained by wind tunnel test, p 空 is an air density at this time, in kg / m 3 , S is a windward projection area of a vehicle head, in m 2 , and V is a vehicle speed, in m / s.

[0026] Another purpose of the embodiment of the present application is to provide an autonomous vehicle speed limit system, which comprises:

[0027] a data acquisition module, configured to obtain a vehicle driving speed and a throttle amount;

[0028] The speed acquisition module is configured to acquire environmental parameter information and determine a vehicle speed limit value according to the environmental parameter information.

[0029] The output value calculation module is configured to calculate a motor target torque value according to a vehicle speed and an accelerator amount by using a preset vehicle speed limit algorithm, wherein a function used in the vehicle speed limit algorithm is as follows:

[0030]

[0031] wherein c is the motor target torque value, c1 is a maximum motor target torque value, a is the vehicle speed value, b is the accelerator amount, a1 is the vehicle speed limit value, and d1 is a motor target torque value for maintaining a speed limit value of the autonomous vehicle on a horizontal road.

[0032] The accelerator control module is configured to control the motor according to the motor target torque value.

[0033] Preferably, the speed acquisition module comprises:

[0034] The vehicle positioning unit is configured to acquire vehicle positioning information and determine a road position where the vehicle is located according to the vehicle positioning information.

[0035] The maximum speed determination unit is configured to determine a maximum speed limit speed of the vehicle according to the vehicle positioning information.

[0036] The speed limit speed determination unit is configured to acquire a driving speed of a nearby vehicle and a driving lane and determine the vehicle speed limit value.

[0037] Preferably, the speed limit speed determination unit comprises:

[0038] The vehicle identification subunit is configured to acquire a driving speed of a nearby vehicle and identify other vehicles in each lane.

[0039] The speed limit determination subunit is configured to determine a driving speed of a front vehicle in a current lane and determine whether the driving speed exceeds the maximum speed limit speed.

[0040] The determination result determination subunit is configured to take the driving speed as the vehicle speed limit value when the driving speed does not exceed the maximum speed limit speed, and otherwise take the maximum speed limit speed as the vehicle speed limit value.

[0041] Preferably, the calculation formula of the d1 is as follows:

[0042]

[0043] wherein F 空F is the air resistance received by the car when it reaches the speed limit value, unit is N, F 动 F is the dynamic friction of the car on the general road surface, F is the basic parameter of the car, unit is N, F 其他 F is the other resistance received by the car when it travels at the speed limit value, unit is N, R is the radius of the tire of the car, unit is meter, L1 is the gear ratio of the speed reducer, W1 is the mechanical efficiency.

[0044] Preferably, the calculation formula of the motor target torque value maintained by the automatic driving car on the horizontal road surface when the speed limit value is,

[0045]

[0046] Wherein, a is the wind resistance coefficient of the car, the parameter is obtained by wind tunnel test, p 空 is the air density at this time, unit is kg / m 3 , S is the windward projection area of the car head, unit is m 2 , V is the speed of the car, unit is m / s.

[0047] Another purpose of the embodiment of the application is to provide a computer device comprising a memory and a processor, the memory stores a computer program, and the computer program is executed by the processor to make the processor execute the steps of the automatic driving car speed limit method.

[0048] Another purpose of the embodiment of the application is to provide a computer readable storage medium, the computer readable storage medium stores a computer program, and the computer program is executed by the processor to make the processor execute the steps of the automatic driving car speed limit method.

[0049] The automatic driving car speed limit method provided by the embodiment of the application avoids the problem of frequent parameter adjustment, and can complete speed control through confirmation of each basic parameter of the vehicle at the beginning of design, without frequent parameter adjustment, thereby saving development time and manpower cost. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 The flow chart of the automatic driving car speed limit method provided by the embodiment of the application;

[0051] Figure 2 The architecture diagram of the automatic driving car speed limit system provided by the embodiment of the application. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the application more clear, the application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0053] It can be understood that the terms "first", "second", etc. used in the present application can be used herein to describe various elements, but unless specifically stated, these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first xx script can be referred to as the second xx script, and similarly, the second xx script can be referred to as the first xx script.

[0054] As shown in Figure 1 a flow chart of a speed limiting method for an autonomous vehicle provided by an embodiment of the present application, the method comprising:

[0055] S100, acquiring vehicle speed and throttle amount.

[0056] In the present embodiment, the vehicle speed and the throttle value are acquired, the vehicle speed being the current speed of the vehicle, and the throttle value being the current throttle value of the vehicle. When the speed limiting adjustment is performed, the current state of the vehicle is taken as the basis for adjustment.

[0057] S200, acquiring environmental parameter information, and determining the whole vehicle speed limit value according to the environmental parameter information.

[0058] In the present embodiment, this step specifically comprises acquiring vehicle positioning information, determining the road position where the vehicle is located according to the vehicle positioning information; determining the maximum speed limit speed of the vehicle according to the vehicle positioning information; acquiring the driving speed of nearby vehicles and the driving lane to determine the whole vehicle speed limit value; the step of acquiring the driving speed of nearby vehicles and the driving lane to determine the whole vehicle speed limit value specifically comprises: acquiring the driving speed of nearby vehicles, and identifying other vehicles in each lane; determining the driving speed of the vehicle in front of the current lane, and determining whether the driving speed exceeds the maximum speed limit speed; if the driving speed does not exceed the maximum speed limit speed, the driving speed is taken as the whole vehicle speed limit value, otherwise the maximum speed limit speed is taken as the whole vehicle speed limit value; when determining the whole vehicle speed limit value, the position of the vehicle is first identified, so as to determine the road currently driven according to the vehicle position, each road has a corresponding speed limit value, and the speed limit value is taken as the maximum speed limit speed. In order to ensure safety, the speed of the vehicle in front needs to be considered to avoid rear-end collision, so the size between the speed of the vehicle in front and the maximum speed limit speed needs to be determined, and when the driving speed does not exceed the maximum speed limit speed, the driving speed is taken as the whole vehicle speed limit value, otherwise the maximum speed limit speed is taken as the whole vehicle speed limit value.

[0059] S300, calculating the motor target torque value according to the vehicle speed and the throttle amount by using a preset vehicle speed limiting algorithm, the function used by the vehicle speed limiting algorithm being:

[0060]

[0061] Wherein, c is the motor target torque value, unit is Nm, c1 is the motor target torque maximum value, unit is Nm, a is the vehicle speed value, unit is km / h, b is the throttle amount, range is [0, 100%], a1 is the vehicle speed limit value, unit is km / h, d1 is the motor target torque value of the autonomous vehicle when maintaining the speed limit value on the horizontal road, unit is Nm.

[0062] In the embodiment, the motor target torque value is calculated by the preset vehicle speed limit algorithm according to the vehicle speed and the throttle amount; most of the existing technical solutions are PID speed regulation, that is, the PID control algorithm with the motor torque as the controlled object and the vehicle longitudinal speed as the feedback, that is,

[0063] u(t)=F p +F i +F d ,

[0064]

[0065] Wherein, u(t) is the current throttle target value, F p is the proportional part of the algorithm, Fi is the integral part of the algorithm, F d is the differential part of the algorithm, K p , K i , K d are the proportional coefficient, integral coefficient and differential coefficient of the algorithm respectively. Through the algorithm, reasonable throttle output corresponding to the limited speed can be obtained, so as to realize the limitation of the speed; due to the nature of the algorithm itself, K p , K i , K d Three parameters need to be obtained through multiple debugging and testing, and when the configuration of the vehicle changes, the three parameters need to be recalibrated, on the one hand, it is not conducive to the rapid development of the whole project, on the other hand, the parameters need to be frequently corrected according to the experience value, which greatly reduces the development efficiency; the embodiment provides a vehicle speed limit algorithm, which can obtain the three parameters through the algorithm.

[0066]

[0067]

[0068]

[0069] Wherein, the parameters are respectively:

[0070] c is the motor target torque value, unit is Nm;

[0071] a is the vehicle speed value, unit is km / h;

[0072] b represents the throttle position, ranging from [0, 100%];

[0073] a1 is the vehicle speed limit, in km / h;

[0074] c1 is the maximum target torque of the motor, in Nm;

[0075] d1 is the target torque value of the motor for maintaining the speed limit of the autonomous vehicle on a level road, in Nm;

[0076] F 空 The air resistance encountered by a car when it reaches the speed limit, measured in N;

[0077] F 动 This represents the kinetic friction force of a car on a normal road surface; it is a basic parameter of the car, and the unit is N.

[0078] F 其他 Other resistance encountered by a car when traveling at the speed limit, measured in N;

[0079] R is the radius of the car tire, in meters;

[0080] L1 is the gear ratio of the reducer;

[0081] W1 represents mechanical efficiency;

[0082] α is the drag coefficient of the car, which is obtained from wind tunnel testing;

[0083] ρ 空 This is the air density at this time, expressed in kg / m³. 3 ;

[0084] S represents the windward projected area of ​​the vehicle's front end, measured in meters (m²). 2 ;

[0085] V represents the vehicle's speed, measured in m / s.

[0086] The S400 controls the throttle according to the actual throttle output value.

[0087] like Figure 2 As shown, an embodiment of the present invention provides a speed limiting system for autonomous vehicles, the system comprising:

[0088] The data acquisition module 100 is used to acquire the vehicle's speed and throttle position.

[0089] In this module, the data acquisition module 100 acquires the vehicle's driving speed and throttle position. The vehicle's driving speed is the current driving speed of the vehicle, and the throttle position is the current throttle value of the vehicle. When adjusting the speed limit, the current state of the vehicle is used as the basis for adjustment.

[0090] The speed acquisition module 200 is configured to acquire environmental parameter information and determine a vehicle speed limit value according to the environmental parameter information.

[0091] In the module, the speed acquisition module 200 includes a vehicle positioning unit configured to acquire vehicle positioning information and determine a road position where the vehicle is located according to the vehicle positioning information; a maximum vehicle speed determination unit configured to determine a maximum speed limit speed of the vehicle according to the vehicle positioning information; and a speed limit speed determination unit configured to acquire a driving speed of a nearby vehicle and a driving lane and determine the vehicle speed limit value. The speed limit speed determination unit includes a vehicle identification subunit configured to acquire the driving speed of the nearby vehicle and identify other vehicles in each lane; a speed limit judgment subunit configured to determine a driving speed of a front vehicle in a current lane and judge whether the driving speed exceeds the maximum speed limit speed; and a judgment result determination subunit configured to take the driving speed as the vehicle speed limit value if the driving speed does not exceed the maximum speed limit speed, or take the maximum speed limit speed as the vehicle speed limit value. In the determination of the vehicle speed limit value, the position of the vehicle is identified first, so that the road currently driven is determined according to the vehicle position, each road has a corresponding speed limit value, and the maximum speed limit speed is taken as the speed limit value. In order to ensure safety, the speed of the front vehicle needs to be considered to avoid rear-end collision, so the size between the driving speed of the front vehicle and the maximum speed limit speed needs to be determined. When the driving speed does not exceed the maximum speed limit speed, the driving speed is taken as the vehicle speed limit value, or the maximum speed limit speed is taken as the vehicle speed limit value.

[0092] The output value calculation module 300 is configured to calculate a motor target torque value according to a vehicle driving speed and an accelerator amount by using a preset vehicle speed limit algorithm. The function used in the vehicle speed limit algorithm is:

[0093]

[0094] wherein c is the motor target torque value, with a unit of Nm, c1 is a maximum motor target torque value, with a unit of Nm, a is a vehicle speed value, with a unit of km / h, b is the accelerator amount, with a range of [0, 100%], a1 is the vehicle speed limit value, with a unit of km / h, and d1 is a motor target torque value of the autonomous vehicle when maintaining the speed limit value on a horizontal road, with a unit of Nm.

[0095] In the module, the output value calculation module 300 calculates the motor target torque value according to the vehicle driving speed and the accelerator amount by using the preset vehicle speed limit algorithm. Most of the existing technical solutions are PID speed regulation, that is, a PID control algorithm taking the motor torque as a controlled object and the vehicle longitudinal speed as a feedback, that is,

[0096] u(t)=F p +F i +F d ,

[0097]

[0098] Wherein, u(t) is the current throttle target value, F p is the proportional part of the algorithm, F i is the integral part of the algorithm, F d is the differential part of the algorithm, K p , K i , K d are the proportional coefficient, integral coefficient and differential coefficient of the algorithm respectively. Through the algorithm, reasonable throttle output corresponding to the limited speed can be obtained, so as to realize the limitation of speed; due to the nature of the algorithm itself, K p , K i , K d Three parameters need to be obtained through multiple debugging and testing, and when the configuration of the vehicle changes, the three parameters need to be recalibrated, on the one hand, it is not conducive to the rapid development of the overall project, on the other hand, the parameters need to be frequently corrected according to the experience value, which greatly reduces the development efficiency; the embodiment provides a kind of automobile speed limiting algorithm, through

[0099]

[0100]

[0101]

[0102] Wherein each parameter is as follows:

[0103] c is the target torque value of the motor, unit: Nm;

[0104] a is the vehicle speed value, unit: km / h;

[0105] b is the throttle, range: [0, 100%];

[0106] a1 is the vehicle speed limit value, unit: km / h;

[0107] c1 is the maximum target torque value of the motor, unit: Nm;

[0108] d1 is the target torque value of the motor when the automatic driving vehicle maintains the speed limit value on the horizontal road, unit: Nm;

[0109] F 空 is the air resistance received when the vehicle reaches the speed limit value, unit: N;

[0110] F 动 is the dynamic friction of the vehicle on the general road, which is the basic parameter of the vehicle, unit: N;

[0111] F 其他 For other resistance received by the car when driving at the speed limit value, unit: N;

[0112] R is the radius of the car tire, unit: meter;

[0113] L1 is the gear ratio of the reducer;

[0114] W1 is the mechanical efficiency;

[0115] α is the wind resistance coefficient of the car, which is obtained by wind tunnel test;

[0116] ρ 空 is the air density at this time, unit: kg / m 3 ;

[0117] S is the windward projection area of the car head, unit: m 2 ;

[0118] V is the speed of the car, unit: m / s;

[0119] The throttle control module 400 is used to control the throttle according to the actual throttle output value.

[0120] In one embodiment, a computer device is provided, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor implements the following steps when executing the computer program:

[0121] Obtain the vehicle speed and the throttle amount;

[0122] Obtain the environmental parameter information, and determine the vehicle speed limit value according to the environmental parameter information;

[0123] According to the vehicle speed and the throttle amount, calculate the motor target torque value through a preset vehicle speed limit algorithm, wherein the function used by the vehicle speed limit algorithm is:

[0124]

[0125] Wherein, c is the motor target torque value, unit: Nm, c1 is the maximum value of the motor target torque, unit: Nm, a is the vehicle speed value, unit: km / h, b is the throttle amount, range: [0, 100%], a1 is the vehicle speed limit value, unit: km / h, d1 is the motor target torque value of the autonomous vehicle when maintaining the speed limit value on the horizontal road, unit: Nm;

[0126] According to the motor target torque value, control the motor.

[0127] In one embodiment, a computer readable storage medium is provided, and the computer readable storage medium has stored thereon a computer program which, when executed by a processor, causes the processor to perform the following steps:

[0128] obtaining a vehicle speed and an accelerator amount;

[0129] obtaining environmental parameter information, and determining a vehicle speed limit value according to the environmental parameter information;

[0130] calculating a motor target torque value according to the vehicle speed and the accelerator amount by using a preset vehicle speed limit algorithm, wherein the function used by the vehicle speed limit algorithm is:

[0131]

[0132] wherein c is the motor target torque value, the unit is Nm, c1 is the maximum motor target torque value, the unit is Nm, a is the vehicle speed value, the unit is km / h, b is the accelerator amount, the range is [0, 100%], a1 is the vehicle speed limit value, the unit is km / h, and d1 is the motor target torque value of the autonomous vehicle maintaining the speed limit value on a horizontal road, the unit is Nm;

[0133] controlling the motor according to the motor target torque value.

[0134] It should be understood that although each step in the flowchart of each embodiment of the present application is displayed in sequence according to the arrow, these steps are not necessarily executed in sequence according to the arrow. Unless otherwise stated herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other sequences. Moreover, at least part of the steps in each embodiment can include multiple sub-steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution sequence of these sub-steps or stages is not necessarily sequential, but can be executed in rotation or alternation with at least part of other steps or sub-steps or stages of other steps.

[0135] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program. The program can be stored in a non-volatile computer readable storage medium, and when the program is executed, the processes of the above-mentioned embodiments of the methods can be included. Any reference to memory, storage, database, or other medium used in the embodiments provided in the present application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0136] Any combination of the technical features of the above-mentioned embodiments can be combined. In order to make the description simple, all possible combinations of the technical features in the above-mentioned embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0137] The above-mentioned embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the present application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

[0138] The above-mentioned is only the preferred embodiment of the present application, and does not limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for limiting the speed of an autonomous vehicle, characterized in that, The method includes: Obtain vehicle speed and throttle position; Obtain environmental parameter information and determine the vehicle speed limit based on the environmental parameter information; Based on the vehicle speed and throttle input, the target torque value of the motor is calculated using a preset vehicle speed limiting algorithm. The function used in the vehicle speed limiting algorithm is: Where c is the target torque value of the motor, in Nm; c1 is the maximum target torque value of the motor, in Nm; a is the vehicle speed, in km / h; b is the throttle position, ranging from [0, 100%]; a1 is the vehicle speed limit value, in km / h; and d1 is the target torque value of the motor for maintaining the speed limit value when the autonomous vehicle is on a level road, in Nm. The motor is controlled according to the target torque value.

2. The method for limiting the speed of an autonomous vehicle according to claim 1, characterized in that, The steps of acquiring environmental parameter information and determining the vehicle speed limit based on the environmental parameter information specifically include: Obtain vehicle location information and determine the vehicle's location on the road based on the vehicle location information; Determine the maximum speed limit of the vehicle based on the vehicle's location information; Obtain the speed and lane information of nearby vehicles to determine the speed limit for the entire vehicle.

3. The method for limiting the speed of an autonomous vehicle according to claim 2, characterized in that, The steps of obtaining the speed and lane information of nearby vehicles and determining the speed limit for the entire vehicle specifically include: Get the speed of nearby vehicles and identify other vehicles in each lane; Determine the speed of the vehicle ahead in the current lane and determine whether the speed exceeds the maximum speed limit; If the driving speed does not exceed the maximum speed limit, then the driving speed shall be used as the speed limit for the whole vehicle; otherwise, the maximum speed limit shall be used as the speed limit for the whole vehicle.

4. The method for limiting the speed of an autonomous vehicle according to claim 1, characterized in that, The formula for calculating the target torque value of the motor for maintaining the speed limit when the autonomous vehicle is on a level road is as follows: Among them, F 空 Air resistance when a car reaches the speed limit, measured in N and F. 动 This refers to the kinetic friction force of a car on a normal road surface, a basic parameter of the car, and its unit is N or F. 其他 The other resistances encountered by the car when driving at the speed limit are in N, R is the radius of the car tire in meters, L1 is the gear ratio of the reducer, and W1 is the mechanical efficiency.

5. The method for limiting the speed of an autonomous vehicle according to claim 4, characterized in that, In the formula for calculating the target torque value of the motor used to maintain the speed limit when an autonomous vehicle is on a level road, Where α is the drag coefficient of the car, which is obtained from wind tunnel testing, and ρ 空 This is the air density at this time, expressed in kg / m³. 3 S represents the windward projected area of ​​the vehicle's front end, in meters (m²). 2 V represents the vehicle speed, measured in m / s.

6. A speed limiting system for autonomous vehicles, characterized in that, The system includes: The data acquisition module is used to acquire vehicle speed and throttle position. The speed acquisition module is used to acquire environmental parameter information and determine the vehicle speed limit based on the environmental parameter information. The output value calculation module is used to calculate the target torque value of the motor based on the vehicle speed and throttle input, using a preset vehicle speed limiting algorithm. The function used in the vehicle speed limiting algorithm is: Where c is the target torque value of the motor, in Nm; c1 is the maximum target torque value of the motor, in Nm; a is the vehicle speed, in km / h; b is the throttle position, ranging from [0, 100%]; a1 is the vehicle speed limit value, in km / h; and d1 is the target torque value of the motor for maintaining the speed limit value when the autonomous vehicle is on a level road, in Nm. The throttle control module is used to control the motor according to the target torque value of the motor.

7. The speed limiting system for autonomous vehicles according to claim 6, characterized in that, The speed acquisition module includes: The vehicle positioning unit is used to acquire vehicle positioning information and determine the vehicle's location on the road based on the vehicle positioning information. The maximum speed determination unit is used to determine the maximum speed limit of a vehicle based on vehicle positioning information. The speed limit determination unit is used to obtain the speed of nearby vehicles and their driving lanes to determine the speed limit value for the entire vehicle.

8. The speed limiting system for autonomous vehicles according to claim 7, characterized in that, The speed limit determination unit includes: The vehicle recognition subunit is used to obtain the driving speed of nearby vehicles and identify other vehicles in each lane. The speed limit determination subunit is used to determine the speed of the vehicle ahead in the current lane and whether the speed exceeds the maximum speed limit. The determination result sub-unit is used to determine the vehicle speed limit when the driving speed does not exceed the maximum speed limit, and otherwise to determine the maximum speed limit.

9. The speed limiting system for autonomous vehicles according to claim 6, characterized in that, The formula for calculating the target torque value of the motor for maintaining the speed limit when the autonomous vehicle is on a level road is as follows: Among them, F 空 Air resistance when a car reaches the speed limit, measured in N and F. 动 This refers to the kinetic friction force of a car on a normal road surface, a basic parameter of the car, and its unit is N or F. 其他 The other resistances encountered by the car when driving at the speed limit are in N, R is the radius of the car tire in meters, L1 is the gear ratio of the reducer, and W1 is the mechanical efficiency.

10. The speed limiting system for autonomous vehicles according to claim 9, characterized in that, In the formula for calculating the target torque value of the motor used to maintain the speed limit when an autonomous vehicle is on a level road, Where α is the drag coefficient of the car, which is obtained from wind tunnel testing, and ρ 空 This is the air density at this time, expressed in kg / m³. 3 S represents the windward projected area of ​​the vehicle's front end, in meters (m²). 2 V represents the vehicle speed, measured in m / s.

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