Method for calculating maximum climbing angle of vehicle platoon

Abstract

The present application relates to a kind of vehicle platoon maximum climbing angle calculation method, comprising the following steps: step S1, the air resistance coefficient of each vehicle when traveling in platoon state is calculated;Step S2, obtain the maximum driving force of vehicle, running resistance, vehicle platoon set speed and the weight of vehicle;Step S3, the maximum climbing angle of each vehicle when traveling in platoon state is calculated;Step S4, the maximum climbing angle of vehicle platoon is calculated.The present application calculation method can calculate the maximum climbing angle of entire vehicle platoon (including each vehicle) when running, and fully consider the influence of air resistance, climbing resistance, acceleration resistance and rolling resistance, so that the result of calculation is more accurate, meanwhile, the method can quickly obtain reliable vehicle platoon maximum climbing degree under the condition that test site requirement is not high.

Description

Technical Field

[0001] This invention relates to the field of vehicle climbing angle calculation technology, and more specifically to a method for calculating the maximum climbing angle of a vehicle platoon. Background Technology

[0002] Vehicle platooning is a cooperative and safe driving behavior that enables multiple autonomous vehicles to maintain relatively stable geometric posture and motion in complex traffic environments, while meeting mission requirements and adapting to environmental constraints, all through wireless communication. Vehicle platooning can improve road traffic efficiency, alleviate traffic congestion, reduce accident rates, and improve energy utilization. Vehicle platooning is of great significance to current road traffic, but all its value must be realized based on ensuring safety; therefore, the safety design of platooning is of paramount importance.

[0003] To avoid situations where differences in maximum gradeability due to the driving force of vehicles within a platoon lead to vehicles falling behind, rolling back, or even collisions during platooning, the gradeability angle is a crucial factor in optimizing platooning performance. Measuring and optimizing the gradeability angle allows for the evaluation of platoon stability, i.e., platooning performance. The maximum gradeability angle refers to the extreme gradient that vehicles can traverse on a good road surface under full load, expressed as a percentage of the vertical height to the horizontal distance of the gradient. It is typically represented by the maximum gradeability i. max In other words, i max =tanα×100%, where % is the slope angle.

[0004] Currently, existing methods for measuring a vehicle's maximum gradeability in the field of vehicle inspection have the following problems:

[0005] 1) Existing methods for measuring the maximum gradeability of vehicles are based on the case of a single vehicle, and there is a lack of research on the maximum gradeability of multiple vehicles in a platoon.

[0006] 2) Vehicle platooning technology can effectively reduce wind resistance during vehicle movement, thus affecting the maximum gradeability. Existing technologies lack consideration of wind resistance factors when calculating the maximum gradeability.

[0007] 3) In the field of vehicle testing, road tests and bench tests are commonly used to test the maximum gradient. For vehicle platoons with multiple vehicles, different slopes and benches need to be built for multiple tests, which has relatively high requirements for site, time and money. Summary of the Invention

[0008] The purpose of this invention is to provide a method for calculating the maximum climbing angle of a vehicle platoon, so as to solve the above-mentioned problems.

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

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

[0011] Step S1: Calculate the air resistance coefficient of each vehicle when it is traveling in convoy;

[0012] Step S2: Obtain the vehicle's maximum driving force, driving resistance, vehicle platoon setting speed, and vehicle weight;

[0013] Step S3: Calculate the maximum climbing angle for each vehicle when traveling in convoy;

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

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

[0016]

[0017] Where C is the air resistance coefficient of the i-th vehicle when it is traveling in platoon formation. Let ΔC be the standard air resistance coefficient of the i-th vehicle when it is traveling freely. d It is a wake effect correction factor.

[0018] Further, 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 be characterized by the sum of resistance ∑F experienced by the vehicle during driving. The formula for calculating 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 that a vehicle must overcome along the slope when traveling uphill; j F is the acceleration resistance that a vehicle must overcome when accelerating; f The coefficient of friction, F, is determined based on the vehicle's weight and the rolling resistance coefficient to overcome the rolling friction of the ground. w To overcome air resistance from the air, it is determined based on the air resistance coefficient, air density, and the vehicle's frontal area and speed.

[0022] The set speed of the vehicle formation is the stable climbing speed of the vehicle formation when the vehicle formation is moving at a constant speed; the set speed of the vehicle formation can be expressed as u.

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

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

[0025]

[0026] In the formula, F t For the driving force of the wheels, For engine output torque, i g For the gear ratio of the transmission, i o Main reducer speed ratio, v T The preset transmission efficiency is given by r, which represents the effective radius of the wheel, using vehicle test measurement data.

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

[0028] F f =mgf cosα

[0029] In the formula, m represents the mass of the vehicle, g is the acceleration due to gravity, f represents the rolling resistance coefficient, and α is the slope angle;

[0030] The air resistance is determined based on the air resistance coefficient, air density, and the vehicle's frontal area and operating speed, as shown in the following formula:

[0031]

[0032] In the formula, C is the air resistance coefficient of the vehicle, A is the frontal area, and u is the stable climbing speed of the vehicle convoy traveling at a constant speed.

[0033] The formula for slope resistance is as follows:

[0034] F i =mg sinα

[0035] The formula for acceleration resistance is as follows:

[0036]

[0037] In the formula, u is the vehicle speed, and δ is the vehicle rotational mass conversion factor.

[0038] Furthermore, in step S3, the vehicle's climbing ability refers to the vehicle's ability to overcome F f and F wAll remaining energy is used to overcome the gradient resistance to climb the slope, at which point the vehicle is at a constant speed. j =0, and F t =F i +F f +F w ;

[0039] The maximum climbing angle for each vehicle when traveling in convoy is:

[0040]

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

[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 gradient i max In other words, i max =tanα max ×100%.

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

[0046] The method for calculating the maximum climbing angle of a vehicle formation in this invention can calculate the maximum climbing angle of the entire vehicle formation (including each vehicle) during operation, and fully considers the effects of air resistance, climbing resistance, acceleration resistance and rolling resistance, making the calculation results more accurate. At the same time, this method can quickly obtain a reliable maximum climbing angle of the vehicle formation under conditions where the requirements of the test site are not high. Attached Figure Description

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

[0048] Figure 2 This is a schematic diagram of the forces acting on the vehicle climbing a slope according to the present invention.

[0049] Figure 3 This is a schematic diagram illustrating the calculation parameters for the vehicle's hill-climbing ability according to the present invention.

[0050] Figure 4 This is a schematic diagram of the vehicle platoon climbing uphill according to the present invention. Detailed Implementation

[0051] The specific implementation of the embodiments of the present invention will now be described with reference to the accompanying drawings.

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

[0053] Step S1: Calculate the air resistance coefficient of each vehicle when it is traveling in convoy;

[0054] Step S2: Obtain the vehicle's maximum driving force, driving resistance, vehicle platoon setting speed, and vehicle weight;

[0055] Step S3: Calculate the maximum climbing angle for each vehicle when traveling in convoy;

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

[0057] Below, refer to Figures 1 to 4 Each step will be analyzed in detail:

[0058] Step S1: Calculate the air resistance coefficient of each vehicle when it is traveling in a convoy.

[0059] When vehicles travel in platoons, the wake generated by the vehicle in front significantly reduces the drag coefficient of the following vehicle. The specific factors influencing the wake effect include the distance between vehicles, their speed, their position, and the number of vehicles in the platoon. The shorter the distance between vehicles, the stronger the wake effect and the more significant the reduction in drag coefficient for the following vehicle. Generally, the optimal distance between vehicles is 1 to 2 times the vehicle length. The faster the speed, the stronger the wake effect and the more pronounced the reduction in drag coefficient. As the number of vehicles in the platoon increases, the air resistance experienced by subsequent vehicles gradually decreases, but it tends to plateau after reaching a certain number.

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

[0061]

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

[0063] The lead vehicle ΔC of the vehicle formation d The value is generally taken as 0.1-0.2, and the subsequent vehicle ΔC d The value is generally taken as 0.3-0.6, and needs to be estimated based on test data or simulation results for different vehicle models.

[0064] 2. Step S2: Obtain the vehicle's maximum driving force, driving resistance, vehicle platoon setting speed, and vehicle weight.

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

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

[0067]

[0068] In the formula, F t For the driving force of the wheels, For engine output torque, i g For the gear ratio, i o Main reducer speed ratio, v T The preset transmission efficiency is given by r, which represents the effective radius of the wheel, using vehicle test measurement data.

[0069] Reference Figure 2 The driving resistance can be characterized by the sum of resistance ∑F experienced by the vehicle during driving, and the driving resistance ∑F includes the gradient resistance F. i Rolling resistance F f Acceleration resistance F j and air resistance F w The formula for calculating 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 that a vehicle must overcome along the slope when traveling uphill; j F is the acceleration resistance that a vehicle must overcome when accelerating; f The coefficient of friction, F, is determined based on the vehicle's weight and the rolling resistance coefficient to overcome the rolling friction of the ground. w To overcome air resistance, the parameters are determined based on the drag coefficient, air density, vehicle frontal area, and speed.

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

[0073] F f =mgf cosα

[0074] In the formula, m represents the mass of the vehicle, in kilograms (kg); it is usually taken as 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, vehicle speed, and tire pressure. For example, the rolling resistance coefficient of a typical sedan on a good asphalt or concrete road surface is around 0.01-0.018, and α is the slope angle.

[0075] The air resistance is determined based on the air resistance coefficient, air density, and the vehicle's frontal area and operating speed, as shown in the following formula:

[0076]

[0077] In the formula, C is the air resistance coefficient of the vehicle, A is the frontal area in square meters (typically around 1.7-2.1 for sedans), and u is the stable climbing speed of the vehicle convoy at a constant speed in kilometers per hour (km / h).

[0078] The formula for slope resistance is as follows:

[0079] F i =mg sinα

[0080] The formula for acceleration resistance is as follows:

[0081]

[0082] In the formula, u is the vehicle speed, and δ is the vehicle rotational mass conversion factor.

[0083] The vehicle platoon's set speed is the stable climbing speed of the vehicle platoon traveling at a constant speed, denoted as u, and the unit is kilometers per hour (km / h).

[0084] The weight of the vehicle is its full load mass, expressed in meters (m), and the unit is kilograms (kg). The vehicle mass can be obtained by adding the load mass (determined according to the manufacturer's specifications, with load distribution preferably uniform and securely fixed) and the vehicle's maximum curb weight.

[0085] 3. Step S3: Calculate the maximum climbing angle for each vehicle when traveling in convoy.

[0086] Reference Figure 2 A vehicle's climbing ability refers to its ability to overcome F f and F wAll remaining energy is used to overcome the slope resistance and climb the slope, so At this point, the vehicle is moving at a constant speed, so F j =0, therefore, F t =F i +F f +F w .

[0087] like Figure 3 The diagram shows the calculation parameters for the vehicle's climbing ability according to the present invention.

[0088] The maximum climbing angle for each vehicle when traveling in convoy is:

[0089]

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

[0091] Fourth, step S4: Calculate the maximum climbing angle of the vehicle platoon.

[0092] like Figure 4 The diagram shows a vehicle platoon climbing hill. The formula for calculating the maximum climbing angle of the vehicle platoon is as follows:

[0093] α max =min(α1, α2, ..., α) n )

[0094] A vehicle's climbing ability refers to the maximum gradient a vehicle can overcome when driving on a sloping road. It is usually expressed as the maximum gradeability (i). max In other words, i max =tanα max ×100%, in percentage.

[0095] The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the protection scope of the present invention.

Claims

1. A method for calculating the maximum climbing angle of a vehicle platoon, characterized in that: Includes the following steps: Step S1: Calculate the air resistance coefficient of each vehicle when it is traveling in convoy; In step S1, the formula for calculating the air resistance coefficient of each vehicle when traveling in convoy is as follows: ； in, Let be the air resistance coefficient of the i-th vehicle when it is traveling in platooning. Let be the standard air resistance coefficient of the i-th vehicle when it is traveling freely. It is a wake effect correction factor; Step S2: Obtain the vehicle's maximum driving force, driving resistance, vehicle platoon setting speed, and vehicle weight; 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: ; Driving resistance represents the total resistance experienced by a vehicle during driving. The formula for calculating driving resistance is as follows: ； in, This refers to the component of gravity that a vehicle must overcome along the slope when driving uphill on a ramp. The acceleration resistance that a vehicle must overcome when accelerating; The rolling resistance coefficient is determined based on the vehicle's weight and the rolling friction coefficient to help the vehicle overcome the rolling friction force on the ground. To overcome air resistance from the air, it is determined based on the air resistance coefficient, air density, and the vehicle's frontal area and speed. The set speed for the vehicle platoon is the stable climbing speed at which the vehicle platoon moves at a constant speed; the set speed for the vehicle platoon can be expressed as: ; The weight of a vehicle is its fully loaded mass, which can be expressed as: ; Step S3: Calculate the maximum climbing angle for each vehicle when traveling in convoy; A vehicle's climbing ability is its ability to overcome hills. and All remaining energy is used to overcome the gradient resistance to climb the slope, at which point the vehicle is at a constant speed. ,and ; The maximum climbing angle for each vehicle when traveling in convoy is: ； in, Let be the maximum climbing angle of the i-th vehicle when it is traveling in platoon formation. Let be the maximum driving force of the i-th vehicle when it is traveling in platoon formation. Let be the weight of the i-th vehicle. Let be the rolling resistance coefficient of the i-th vehicle. Let be the frontal area of ​​the i-th vehicle. The climbing speed of the convoy vehicles; Step S4: Calculate the maximum climbing angle of the vehicle platoon; the formula for the maximum climbing angle is as follows: ； Among them, the maximum gradient express, .

2. The method for calculating the maximum climbing angle of a vehicle platoon according to claim 1, characterized in that: The maximum driving force can be obtained by the following formula: ； In the formula, For the driving force of the wheels, For engine output torque, For the gearbox ratio, Main reducer speed ratio, To preset the transmission efficiency, Vehicle test measurement data is used to determine the effective radius of the wheel.

3. The method for calculating the maximum climbing angle of a vehicle platoon according to claim 2, characterized in that: Rolling resistance The formula is determined based on the vehicle weight and rolling resistance coefficient, as follows: ； In the formula, This refers to the mass of the vehicle. It is the acceleration due to gravity. Expressed as the rolling resistance coefficient, The slope angle; Air resistance is determined based on the drag coefficient, air density, vehicle frontal area, and operating speed, as shown in the following formula: ； In the formula, Let be the air resistance coefficient of the vehicle. For windward area, The stable climbing speed for vehicles to travel at a constant speed in platooning; The formula for slope resistance is as follows: ； The formula for acceleration resistance is as follows: ； In the formula, For vehicle speed, This is the conversion factor for the rotational mass of a vehicle.

Images