Method for calculating maximum climbing angle of vehicle formation

Abstract

The invention relates to a method for calculating a maximum climbing angle of a vehicle formation. The method comprises the following steps: S1, calculating an air resistance coefficient when each vehicle runs in a formation state; s2, the maximum driving force and the driving resistance of the vehicles, the driving speed set by the vehicle formation and the weight of the vehicles are obtained; s3, calculating the maximum climbing angle when each vehicle runs in the formation state; and S4, calculating the maximum climbing angle of the vehicle formation. According to the calculation method, the maximum climbing angle of the whole vehicle formation (including the vehicles) during operation can be calculated, the influence of air resistance, climbing resistance, acceleration resistance and rolling resistance is fully considered, the calculation result is more accurate, and meanwhile, the method can be used for calculating the maximum climbing angle of the whole vehicle formation (including the vehicles) under the condition that the test site requirement is not high. And the reliable maximum gradeability of the vehicle formation can be rapidly obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle climbing angle calculation, and more specifically to a method for calculating the maximum climbing angle of a vehicle formation. Background Art

[0002] Vehicle platooning is a collaborative, safe driving behavior enabled by wireless communication that enables multiple autonomous vehicles to maintain a relatively stable geometric position and motion state in complex traffic environments, while meeting mission requirements and adapting to surrounding environmental constraints. Platooning can improve road efficiency, alleviate traffic pressure, reduce accident rates, and improve energy efficiency. While platooning holds significant significance for current road traffic, its full value cannot be realized without ensuring safety. Therefore, safety-focused platooning design is crucial.

[0003] In order to avoid the occurrence of "falling behind", sliding down the slope or even causing collision accidents during the process of vehicle formation formation due to the difference in the maximum climbing gradient caused by the driving force of the vehicles in the formation, the climbing angle is an important consideration in the optimization of vehicle formation driving performance. By measuring and optimizing the climbing angle, the string stability of the queue, that is, the performance of the formation, can be evaluated. Among them, the maximum climbing angle refers to the extreme slope that a vehicle can pass under a full load on a good road surface, and is expressed as a percentage of the vertical height of the slope to the horizontal distance. The maximum climbing gradient i is usually used. max Indicates that max =tanα×100%, unit is %, α is the slope angle.

[0004] Currently, in the field of vehicle detection, the existing methods for measuring the maximum climbing grade of a vehicle have the following problems:

[0005] 1) The existing method for measuring the maximum climbing gradient of a vehicle is based on the case of a single vehicle, and lacks research on the maximum climbing angle of multiple vehicles in a platoon.

[0006] 2) Vehicle platooning technology can effectively reduce wind resistance during platoon driving, thereby affecting the maximum climbing grade. Existing technologies fail to consider wind resistance when calculating the maximum climbing angle.

[0007] 3) In the field of vehicle testing, road tests and bench tests are commonly used to conduct maximum slope tests. For a platoon of multiple vehicles, different ramps and benches need to be built to conduct multiple tests, which has relatively high site requirements, time, and financial costs. Summary of the Invention

[0008] The object of the present invention is to provide a method for calculating the maximum climbing angle of a vehicle formation to solve the above-mentioned problem.

[0009] The present invention adopts the following technical solutions:

[0010] A method for calculating the maximum climbing angle of a vehicle formation, characterized by comprising the following steps:

[0011] Step S1, calculating the air resistance coefficient of each vehicle when traveling in a platoon;

[0012] Step S2: obtaining the maximum driving force, driving resistance, driving speed set for the vehicle formation, and vehicle weight of the vehicle;

[0013] Step S3: Calculate the maximum climbing angle of each vehicle when traveling in a platoon;

[0014] Step S4: Calculate the maximum climbing angle of the vehicle formation.

[0015] Furthermore, in step S1, the calculation formula for the air resistance coefficient of each vehicle when traveling in the platoon state is as follows:

[0016]

[0017] Where C is the air resistance coefficient when the i-th vehicle is traveling in a platoon. is the standard air resistance coefficient of the i-th vehicle when it is traveling as a free vehicle, ΔC d is the wake effect correction factor.

[0018] Furthermore, in step S2, the maximum driving force of the vehicle is the maximum driving force corresponding to the peak power of the motor used by the vehicle, and the maximum driving force is expressed as F t ;

[0019] The driving resistance can represent the total resistance ΣF experienced by the vehicle during driving. The calculation formula of the driving resistance is as follows:

[0020] ∑F=F i +F j +F f +F w

[0021] Among them, F i F is the component of gravity along the slope that the vehicle must overcome when traveling uphill on the slope; j F is the acceleration resistance that the vehicle needs to overcome when accelerating; f The rolling friction force that the vehicle overcomes on the ground is determined based on the vehicle's weight and rolling resistance coefficient; F w To overcome the air resistance from the air, it is determined according to the air resistance coefficient, air density, and the vehicle's frontal area and driving speed;

[0022] The driving speed set by the vehicle formation is the stable climbing speed of the vehicle formation traveling at a uniform speed; the driving speed set by the vehicle formation can be expressed as u;

[0023] The weight of the vehicle is the fully loaded mass of the vehicle, and the vehicle mass can be expressed as m.

[0024] Preferably, the maximum driving force can be obtained by the following formula:

[0025]

[0026] Where, F t The driving force for the wheels, is the engine output torque, i g is the transmission ratio, i o is the main reducer speed ratio, v T is the preset transmission efficiency, r is the effective wheel radius, and the data are measured using vehicle tests.

[0027] Preferably, the rolling resistance F f Determined based on vehicle weight and rolling resistance coefficient, the formula is as follows:

[0028] F f =mgf cosα

[0029] Where m is the mass of the vehicle, g is the acceleration of gravity, f is the rolling resistance coefficient, and α is the slope angle;

[0030] The air resistance is determined according to the air resistance coefficient, air density, and the frontal area and running speed of the vehicle, and the formula is as follows:

[0031]

[0032] Where C is the air resistance coefficient of the vehicle, A is the frontal area, and u is the stable climbing speed of the vehicle formation at a uniform speed;

[0033] The slope resistance formula is as follows:

[0034] F i =mg sinα

[0035] The acceleration resistance formula is as follows:

[0036]

[0037] Where u is the vehicle speed and δ is the vehicle rotation mass conversion coefficient.

[0038] Furthermore, in step S3, the climbing ability of the vehicle refers to the ability of the vehicle to overcome the F f and F wThe slope that can be climbed when all the remaining force is used to overcome the slope resistance. At this time, the vehicle is in a constant speed state, F j =0, and F t =F i +F f +F w ;

[0039] The maximum climbing angle of each vehicle when traveling in a platoon is:

[0040]

[0041] Among them, the medium α i is the maximum climbing angle of the i-th vehicle when traveling in a platoon, is the maximum driving force of the i-th vehicle when traveling in a platoon, m i is the gravity of the i-th vehicle, f i is the rolling resistance coefficient of the i-th vehicle, A i is the frontal area of the i-th vehicle, and u is the climbing speed of the platoon vehicles.

[0042] Furthermore, the formula for calculating the maximum climbing angle of the vehicle formation is as follows:

[0043] α max =min(α1, α2, ..., α n )

[0044] Among them, the maximum climbing grade i max Indicates that max =tanα max ×100%.

[0045] From the above description of the structure of the present invention, it can be seen that compared with the prior art, the present invention has the following advantages:

[0046] The calculation method of the maximum climbing angle of a vehicle formation of the present invention can calculate the maximum climbing angle of the entire vehicle formation (including each vehicle) during operation, and fully considers the influence of air resistance, climbing resistance, acceleration resistance and rolling resistance, so that the calculation result is more accurate. At the same time, this method can quickly obtain a reliable maximum climbing gradient of a vehicle formation under the condition that the test site requirements are not high. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a flow chart of the vehicle climbing ability calculation method of the present invention.

[0048] Figure 2 This is a force diagram of a vehicle climbing a slope according to the present invention.

[0049] Figure 3 This is a schematic diagram of the calculation parameters of the vehicle climbing ability of the present invention.

[0050] Figure 4 Schematic diagram of vehicle formation climbing in the present invention. DETAILED DESCRIPTION

[0051] The specific implementation of the embodiment of the present invention is described below with reference to the accompanying drawings.

[0052] Reference Figure 1 A method for calculating the maximum climbing angle of a vehicle formation comprises the following steps:

[0053] Step S1, calculating the air resistance coefficient of each vehicle when traveling in a platoon;

[0054] Step S2: obtaining the maximum driving force, driving resistance, driving speed set for the vehicle formation, and vehicle weight of the vehicle;

[0055] Step S3: Calculate the maximum climbing angle of each vehicle when traveling in a platoon;

[0056] Step S4: Calculate the maximum climbing angle of the vehicle formation.

[0057] Below, refer to Figures 1 to 4 , analyze each step in detail:

[0058] 1. Step S1, calculating the air resistance coefficient of each vehicle when traveling in a platoon.

[0059] When vehicles are traveling in a platoon, the wake of the leading vehicle significantly reduces the rear vehicle's drag coefficient. Factors influencing the wake effect include the distance between vehicles, driving speed, vehicle position, and the number of vehicles in the platoon. The shorter the distance between vehicles, the stronger the wake effect, and the more significantly the reduction in the rear vehicle's drag coefficient. Generally, the optimal distance between vehicles is 1 to 2 vehicle lengths. The faster the driving speed, the stronger the wake effect, and the more significant the reduction in the drag coefficient. As the number of vehicles in the platoon increases, the air resistance experienced by the following vehicles will gradually decrease, but will stabilize after reaching a certain number.

[0060] Therefore, the formula for calculating the air resistance coefficient of each vehicle when traveling in a platoon is as follows:

[0061]

[0062] Where C is the air resistance coefficient when the i-th vehicle is traveling in a platoon. is the standard air resistance coefficient of the i-th vehicle when it is traveling as a free vehicle, ΔC d This is a correction factor for the wake effect, determined by factors such as the relative position of the vehicles, their speed, and the distance between them. The actual correction value is usually determined through wind tunnel testing or computational fluid dynamics (CFD) simulations.

[0063] ΔC of the lead vehicle in the vehicle formation d The value is usually 0.1-0.2, and the following vehicle ΔC d The general value is 0.3-0.6, which needs to be estimated based on test data or simulation results for different vehicle models.

[0064] 2. Step S2: Obtain the maximum driving force, driving resistance, driving speed set by the vehicle formation, and vehicle weight of the vehicle.

[0065] The maximum driving force of a vehicle is the maximum driving force of the vehicle in a specific gear. The maximum driving force corresponding to the peak power of the motor is expressed as F t .

[0066] The maximum driving force can be obtained by the following formula:

[0067]

[0068] Where, F t The driving force for the wheels, is the engine output torque, i g is the transmission ratio, i o is the main reducer speed ratio, v T is the preset transmission efficiency, r is the effective wheel radius, and the data are measured using vehicle tests.

[0069] Reference Figure 2 The driving resistance can represent the total resistance ∑F encountered by the vehicle during driving. The driving resistance ∑F includes the slope resistance F i , rolling resistance F f , acceleration resistance F j and air resistance F w , the calculation formula of driving resistance is as follows:

[0070] ∑F=F i +F j +F f +F w

[0071] Among them, F i F is the component of gravity along the slope that the vehicle must overcome when traveling uphill on the slope; j F is the acceleration resistance that the vehicle needs to overcome when accelerating; f The rolling friction force that the vehicle overcomes on the ground is determined based on the vehicle's weight and rolling resistance coefficient; F w To overcome the air resistance from the air, it is determined based on the air resistance coefficient, air density, and the vehicle's frontal area and driving speed.

[0072] The above rolling resistance F fDetermined based on vehicle weight and rolling resistance coefficient, the formula is as follows:

[0073] F f =mgf cosα

[0074] Where m is the mass of the vehicle in kilograms (kg); usually 9.81 m / s 2 , f represents the rolling resistance coefficient, which is determined experimentally. The rolling resistance coefficient is related to the type of road surface, driving speed, and tire pressure. For example, the rolling resistance coefficient of a typical car on a good asphalt or concrete road surface is around 0.01-0.018. α is the slope angle.

[0075] The air resistance is determined according to the air resistance coefficient, air density, and the frontal area and running speed of the vehicle, and the formula is as follows:

[0076]

[0077] Where C is the drag coefficient of the vehicle, A is the frontal area in square meters, which is generally around 1.7-2.1 for a typical car, and u is the stable climbing speed of the vehicle formation at a uniform speed, in kilometers per hour (km / h).

[0078] The slope resistance formula is as follows:

[0079] F i =mg sinα

[0080] The acceleration resistance formula is as follows:

[0081]

[0082] Where u is the vehicle speed and δ is the vehicle rotation mass conversion coefficient.

[0083] The driving speed set for the vehicle formation is the stable climbing speed of the vehicle formation traveling at a uniform speed, expressed as u, in kilometers per hour (km / h).

[0084] The vehicle weight is the fully loaded mass of the vehicle, expressed as m, in kilograms (kg). The vehicle mass is calculated by adding the loaded mass (determined by the factory-specified model, with load distribution preferably uniform and secure) and the vehicle's maximum curb mass.

[0085] 3. Step S3, calculating the maximum climbing angle of each vehicle when traveling in a platoon.

[0086] Reference Figure 2 The climbing ability of a vehicle refers to the ability of the vehicle to overcome F f and F wThe slope that can be climbed when all the remaining energy is used to overcome the slope resistance, so At this time, the vehicle is in a constant speed state, so F j =0, therefore, F t =F i +F f +F w .

[0087] like Figure 3 The figure shows a schematic diagram of vehicle climbing ability calculation parameters according to the present invention.

[0088] The maximum climbing angle of each vehicle when traveling in a platoon is:

[0089]

[0090] Among them, the medium α i is the maximum climbing angle of the i-th vehicle when traveling in a platoon, is the maximum driving force of the i-th vehicle when traveling in a platoon, m i is the gravity of the i-th vehicle, f i is the rolling resistance coefficient of the i-th vehicle, A i is the frontal area of the i-th vehicle, and u is the climbing speed of the platoon vehicles.

[0091] 4. Step S4, calculating the maximum climbing angle of the vehicle formation.

[0092] like Figure 4 The formula for calculating the maximum climbing angle of the vehicle formation is as follows:

[0093] α max =min(α1, α2, ..., α n )

[0094] The gradeability of a vehicle refers to the maximum gradient that a vehicle can overcome when driving on a slope. max Indicates that max =tanα max ×100%, unit is %.

[0095] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A method for calculating the maximum climbing angle of a vehicle formation, characterized by: The following steps are involved: Step S1, calculating the air resistance coefficient of each vehicle when traveling in a platoon; Step S2: obtaining the maximum driving force, driving resistance, driving speed set for the vehicle formation, and vehicle weight of the vehicle; Step S3: Calculate the maximum climbing angle of each vehicle when traveling in a platoon; Step S4: Calculate the maximum climbing angle of the vehicle formation.

2. The method for calculating the maximum climbing angle of a vehicle formation according to claim 1, characterized in that: In step S1, the calculation formula for the air resistance coefficient of each vehicle when traveling in a platoon state is as follows: Among them, C i is the air resistance coefficient when the i-th vehicle is traveling in a platoon, is the standard air resistance coefficient of the i-th vehicle when it is traveling as a free vehicle, ΔC d is the wake effect correction factor.

3. The method for calculating the maximum climbing angle of a vehicle formation according to claim 1, characterized in that: In step S2, the maximum driving force of the vehicle is the maximum driving force corresponding to the peak power of the motor used by the vehicle, and the maximum driving force is expressed as F t ; The driving resistance can represent the total resistance ΣF experienced by the vehicle during driving. The calculation formula of the driving resistance is as follows: ∑F=F i +F j +F f +F w Among them, F i F is the component of gravity along the slope that the vehicle must overcome when traveling uphill on the slope; j F is the acceleration resistance that the vehicle needs to overcome when accelerating; f The rolling friction force that the vehicle overcomes on the ground is determined based on the vehicle's weight and rolling resistance coefficient; F w To overcome the air resistance from the air, it is determined according to the air resistance coefficient, air density, and the vehicle's frontal area and driving speed; The driving speed set by the vehicle formation is the stable climbing speed of the vehicle formation traveling at a uniform speed; the driving speed set by the vehicle formation can be expressed as u; The weight of the vehicle is the fully loaded mass of the vehicle, and the vehicle mass can be expressed as m.

4. The method for calculating the maximum climbing angle of a vehicle formation according to claim 3, characterized in that: The maximum driving force can be obtained by the following formula: Where, F t The driving force for the wheels, is the engine output torque, i g is the transmission ratio, i o is the main reducer speed ratio, v T is the preset transmission efficiency, r is the effective wheel radius, and the data are measured using vehicle tests.

5. The method for calculating the maximum climbing angle of a vehicle formation according to claim 4, characterized in that: The rolling resistance F f Determined based on vehicle weight and rolling resistance coefficient, the formula is as follows: F f =mgfcosα Where m is the mass of the vehicle, g is the acceleration of gravity, f is the rolling resistance coefficient, and × is the slope angle; The air resistance is determined according to the air resistance coefficient, air density, and the frontal area and running speed of the vehicle, and the formula is as follows: Where C is the air resistance coefficient of the vehicle, A is the frontal area, and u is the stable climbing speed of the vehicle formation at a uniform speed; The slope resistance formula is as follows: F i =mg sinα The acceleration resistance formula is as follows: Where u is the vehicle speed and δ is the vehicle rotation mass conversion coefficient.

6. The method for calculating the maximum climbing angle of a vehicle formation according to claim 5, characterized in that: The climbing ability of a vehicle refers to the ability of the vehicle to overcome the F f and F w The slope that can be climbed when all the remaining force is used to overcome the slope resistance. At this time, the vehicle is in a constant speed state, F j =0, and F t =F i +F f +F w ; The maximum climbing angle of each vehicle when traveling in a platoon is: Among them, the medium α i is the maximum climbing angle of the i-th vehicle when traveling in a platoon, F i t is the maximum driving force of the i-th vehicle when traveling in a platoon, m i is the gravity of the i-th vehicle, f i is the rolling resistance coefficient of the i-th vehicle, A i is the frontal area of the i-th vehicle, and u is the climbing speed of the platoon vehicles.

7. The method for calculating the maximum climbing angle of a vehicle formation according to claim 6, characterized in that: The formula for calculating the maximum climbing angle of the vehicle formation is as follows: a max =min(α1,α2,…,α n ) Among them, the maximum climbing grade i max Indicates that max =tan α max ×100%.

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