A power system control method for a pure electric bus

Abstract

The application provides a power system control method of a pure electric bus, comprising the following steps: obtaining driving control information or braking control information; switching to a corresponding mode according to the value of the driving or braking pedal change rate, and outputting the driving or braking pedal opening curve in the corresponding mode to a corresponding torque control module; calculating the vehicle driving torque value or the target braking torque value through the driving or braking pedal opening curve, and outputting the corresponding torque control instruction to a motor controller. The application identifies the driving intention by recognizing the speed of the driving or braking pedal change rate of the driver, switches different driving or braking modes in real time, realizes the acceleration and torque control of the pure electric bus under different driving or braking conditions, meets the power demand of the driver under various complex conditions, improves the followability and stability of the driving or braking torque, and more effectively ensures the vehicle power and driving safety.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle power system technology, specifically to a power system control method for a pure electric bus. Background Technology

[0002] Existing control methods for pure electric bus power systems typically map the opening of the drive or brake pedal directly to the motor torque during driving or braking, thus outputting torque control commands to the motor. However, due to differences in driving feel, habits, and comfort between electric and traditional vehicles, existing torque control commands cannot reflect the driver's intentions in real time, resulting in poor torque responsiveness and significant fluctuations, which substantially impacts the driving range of electric vehicles.

[0003] In addition, since the operating conditions of pure electric buses consist of different working states, such as driving and regenerative braking, different control methods need to be developed for different driving conditions in order to improve the energy utilization and transmission efficiency of pure electric vehicles, so that pure electric buses can be adapted to different operating conditions.

[0004] Chinese invention patent application CN 201910397396.0 discloses a pure electric vehicle drive motor control method based on driver acceleration intention recognition. The method includes: the electric vehicle controller allocates a reference output torque and a dynamic compensation torque to the motor, and the total output torque of the drive motor is obtained by adding the two. This scheme obtains the reference output torque of the motor by linearly looking up a table based on the pedal opening degree, and obtains the dynamic compensation torque by linearly looking up a table based on the pedal opening change rate. The combined torque of the reference output torque and the dynamic compensation torque is then applied to the vehicle. However, this scheme uses a simple linear correlation to determine the torque relationship and does not consider vehicle information such as speed and acceleration. Therefore, the obtained combined output torque of the motor cannot accurately reflect actual needs. Furthermore, this scheme does not consider factors such as wind resistance and rolling resistance, and does not switch corresponding modes in real time based on the pedal opening change rate, making it difficult to reflect the driver's acceleration needs, such as rapid acceleration, normal driving, and gentle driving, and thus failing to meet the driver's power requirements under various complex conditions.

[0005] The vehicle dynamics equations (see: Yu Zhisheng, *Automotive Theory* [M], Machinery Industry Press, 2009) represent the dynamic behavior of a vehicle, that is, the relationship between the vehicle's acceleration, total traction force, and total mass. Furthermore, the basic vehicle dynamics equations also represent the relationship between the vehicle's driving force and its driving resistance. The driving force is equal to the sum of four resistances: rolling resistance, gradient resistance, air resistance, and acceleration resistance. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the prior art by providing a power system control method for a pure electric bus, which can switch between different driving and braking modes in real time to achieve acceleration and torque control of the pure electric bus under different driving and braking conditions, thereby meeting the power needs of the driver under various complex conditions.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for controlling the power system of a pure electric bus includes the following steps:

[0009] Step 1: Obtain drive control information or braking control information;

[0010] Step 2: When drive control information is obtained, switch to power mode, standard mode or economy mode according to the value of drive pedal change rate K, and output the drive pedal opening curve of the corresponding mode.

[0011] When braking control information is obtained, the system switches to emergency braking mode or standard braking mode according to the value of brake pedal change rate K1, and outputs the brake pedal opening curve for the corresponding mode.

[0012] The drive pedal opening curve is a set curve showing the correspondence between the target drive pedal opening and the input drive pedal opening, and the brake pedal opening curve is a set curve showing the correspondence between the target brake pedal opening and the input brake pedal opening. Both are pre-downloaded to the vehicle controller and called by the vehicle controller when controlling the vehicle to drive.

[0013] Step 3: Obtain the target drive pedal opening using the drive pedal opening curve, and calculate the vehicle drive torque value T. 合 The target brake pedal opening is obtained from the brake pedal opening curve, and the target braking torque value T is calculated. 目标1 ;

[0014] Step 4: Based on the vehicle drive torque value T 合 Or the target braking torque value T 目标1 It outputs the corresponding torque control command to the motor controller.

[0015] This invention identifies driving intentions and judges the rate of change of the driver's drive and brake pedals, switching between different drive and brake modes in real time. This can truly reflect the driver's actual needs and realize the acceleration and torque control of pure electric buses under different drive and brake conditions. It meets the driver's power needs under various complex conditions, improves the following and stability of drive and brake torque, and more effectively ensures vehicle power and driving safety.

[0016] Furthermore, in step 2, when the drive control information is obtained, if the rate of change of the drive pedal K is greater than or equal to the set threshold α, it is determined to be the power mode; if the rate of change of the drive pedal K is greater than the set threshold β and less than the set threshold α, it is determined to be the standard mode; if the rate of change of the drive pedal K is less than the set threshold β, it is determined to be the economy mode.

[0017] When braking control information is obtained, if the brake pedal change rate K1 is greater than or equal to the set threshold α1, it is determined to be an emergency braking mode; if the brake pedal change rate K1 is less than the set threshold α1, it is determined to be a standard braking mode.

[0018] This invention, tailored to the characteristics of pure electric buses, sets thresholds to define different driving and braking modes to meet the driver's needs. Compared to the traditional method of mapping torque to the pedals, it achieves recognition of driving intentions and assessment of driving modes, thus better meeting driving requirements.

[0019] Furthermore, the process of obtaining the drive pedal opening curve includes: (a) obtaining historical data during different drivers' driving processes, wherein the historical data includes: drive pedal opening and drive pedal opening change rate; (b) classifying the historical data into power mode, standard mode, and economy mode according to the drive pedal opening change rate; (c) in each mode, using the two-dimensional interpolation of the drive pedal opening change rate and the drive pedal opening as input, and the target drive pedal opening as output, performing visualization processing using Matlab to obtain the drive pedal opening curve corresponding to each mode;

[0020] The process of obtaining the brake pedal opening curve includes: (a1) obtaining historical data during different drivers' driving processes, wherein the historical data includes: brake pedal opening and brake pedal opening change rate; (b1) classifying the historical data into emergency braking mode and standard braking mode according to the brake pedal opening change rate; (c1) in each mode, using the two-dimensional interpolation of the brake pedal opening change rate and the brake pedal opening as input, and the target brake pedal opening as output, performing visualization processing using Matlab to obtain the brake pedal opening curve corresponding to each mode.

[0021] Preferably, in step 3, the vehicle driving torque value T 合 The calculation formula is:

[0022] T 合 =U T (t)+T 目标 ;

[0023] Among them, U T (t) represents the drive torque compensation value, T 目标 The target driving torque value.

[0024] Furthermore, the target driving torque value T 目标 The calculation formula is:

[0025] T 目标 ·i g ·i o ·η T / r=δ·ma set +mg·f+C w ·A·V 2 act / 21.15;

[0026] Among them, a set The target acceleration value is empirically calibrated and obtained from a two-dimensional interpolation table of the target drive pedal opening and vehicle speed; δ is the rotational mass coefficient; a direct drive scheme i is adopted. g =1; i o Main reduction ratio; η T Transmission efficiency; r is the rolling radius; m is the vehicle weight; g is the acceleration due to gravity; f is the rolling resistance coefficient; C w V is the drag coefficient; act A represents the vehicle's actual speed; A represents the frontal area.

[0027] The driving torque compensation value U T The formula for calculating (t) is:

[0028]

[0029] Where t = kTs, T s e represents the discrete data sampling period. a (t)=a set -a act (t) represents the target acceleration a. set and actual acceleration a act The deviation signal, K PT K is the proportionality coefficient. IT K is the integral coefficient. DT is the differential coefficient.

[0030] This invention fully considers resistances such as wind resistance and rolling resistance. It obtains the target acceleration through the mode opening curve and calculates the target driving torque value by combining the vehicle dynamics equation, which is more in line with the actual situation of the vehicle. At the same time, it uses the actual acceleration as input and calculates the compensation torque through the PID algorithm. When the planned acceleration is much greater than the actual acceleration, the compensation torque is calculated according to the acceleration deviation. The resulting motor torque is in line with the actual situation of the vehicle and meets the actual needs of dynamic balance.

[0031] Preferably, in step 3, the target braking torque value T 目标1The calculation formula is:

[0032] T 目标1 ·i g ·i o ·η T / r=mg·f+C w ·A·V 2 act / 21.15+δ·ma set1 ;

[0033] Among them, a set1 The empirically calibrated target deceleration value is obtained from a two-dimensional interpolation table of the target brake pedal opening and vehicle speed; δ is the rotational mass coefficient; a direct drive scheme i is adopted. g =1; i o Main reduction ratio; η T Transmission efficiency; r is the rolling radius; m is the vehicle weight; g is the acceleration due to gravity; f is the rolling resistance coefficient; C w V is the drag coefficient; act A represents the vehicle's actual speed; A represents the frontal area.

[0034] This invention employs an open-loop control structure, calculates the target braking torque using vehicle dynamics equations, and takes into account various resistances. It can respond to braking demands in a timely manner, greatly improving the following performance and stability of the braking torque, and more effectively ensuring the vehicle's power and safety. It can also respond promptly to the driver's driving needs.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) This invention addresses the characteristics of pure electric buses by identifying the rate of change of the drive and brake pedals in real time to determine the driver's driving intentions. During driving, it can switch between power mode, standard mode, and economy mode in real time; during braking, it can switch between emergency braking mode and standard braking mode in real time, thereby enabling acceleration and torque control of pure electric buses under different driving and braking conditions. This meets the driver's power needs under various complex conditions, improves the following and stability of drive and braking torque, and more effectively ensures vehicle power and safety.

[0037] (2) This invention combines PID algorithm and vehicle dynamics equations to obtain the vehicle's driving torque; it adopts an open-loop control structure to obtain the target braking torque, which can respond to braking demands in a timely manner. This invention greatly improves the following performance and stability of driving and braking torques, more effectively ensures the vehicle's power and safety, and can respond to the driver's driving needs in a timely manner. Attached Figure Description

[0038] Figure 1This is a flowchart of the power system control method for a pure electric bus according to an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the power system drive method for a pure electric bus according to an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of the braking method of the power system of a pure electric bus according to an embodiment of the present invention. Detailed Implementation

[0041] Example 1

[0042] like Figure 1 As shown in the figure, this embodiment 1 provides a power system control method for a pure electric bus, and the specific steps are as follows:

[0043] Step 1: After the vehicle is connected to high voltage, the vehicle control unit (VCU) obtains drive control information by judging the motor drive status and the driver's pedal operation. If the motor is in drive mode and the driver is pressing the drive pedal to drive the vehicle, drive control is initiated.

[0044] Step 2: Based on the drive control information obtained in Step 1, the vehicle control unit (VCU) switches to power mode, standard mode or economy mode according to the value of the drive pedal change rate K, and outputs the drive pedal opening curve of the corresponding mode to the drive torque control module.

[0045] When drive control information is obtained, if the drive pedal changes very rapidly, and the rate of change of the drive pedal K is greater than or equal to the set threshold α, it can be inferred that the driver's driving intention is strong, and the vehicle controller (VCU) determines it to be in power mode; if the drive pedal changes moderately, and the rate of change of the drive pedal K is greater than the set threshold β and less than the set threshold α, the vehicle controller (VCU) determines it to be in standard mode; if the drive pedal changes slowly, and the rate of change of the drive pedal K is less than the set threshold β, the vehicle controller (VCU) determines it to be in economy mode.

[0046] It should be noted that in this embodiment 1, thresholds α and β are set based on the time it takes for the pedal opening to change from 0% to 100%, that is, based on the time it takes for the pedal to change from its natural state to its maximum driving state. Here, α represents a 95% change in pedal opening per second, and β represents a 55% change in pedal opening per second.

[0047] When switching to Power mode, the output drive pedal opening curve is the same as the Power mode's pedal opening curve; when switching to Standard mode, the output drive pedal opening curve is the same as the Standard mode's pedal opening curve; and when switching to Eco mode, the output drive pedal opening curve is the same as the Eco mode's pedal opening curve. The drive pedal opening curve is a pre-set curve representing the target input drive pedal opening versus the input drive pedal opening. This curve is pre-downloaded to the vehicle controller and is used by the vehicle controller when controlling vehicle movement.

[0048] To make it easier to understand, let's take an example: when the driver's pedal opening is n%, and the pedal opening change rate is 96% per second, it is determined that the driver has a strong driving intention and enters the power mode. Based on the pedal opening curve of the power mode, the target driving pedal opening of m% (m>n) is obtained, and subsequent calculations are performed.

[0049] In this embodiment 1, a large amount of historical data from different drivers' driving processes is obtained through CAN message data or a host computer. This historical data includes: vehicle speed, motor torque, drive pedal opening, and drive pedal opening change rate. Based on the drive pedal opening change rate, the historical data is categorized into power mode, standard mode, and economy mode. In each mode, the two-dimensional interpolation of the drive pedal opening change rate and the drive pedal opening is used as input, and the target drive pedal opening is used as output. The visualization is performed using Matlab to obtain the pedal opening curve corresponding to each mode.

[0050] Step 3: After receiving the drive pedal opening curve, the drive torque control module obtains the target drive pedal opening based on the curve, and calculates the target drive torque value T by combining it with the vehicle dynamics equations of the motor. 目标 The drive torque compensation value U is calculated using a PID algorithm. T (t), the driving torque compensation value U T (t) and the target driving torque value T 目标 The combined forces are integrated to obtain the vehicle driving torque value T. 合 .

[0051] It should be noted that, in practice, the torque can be directly mapped by looking up the motor speed in a table, or the target driving torque can be directly calculated by the motor drive and pedal opening.

[0052] like Figure 2 As shown, in this embodiment 1, the target driving torque value T is calculated using the vehicle dynamics equations of the electric motor. 目标 The drive torque compensation value U is calculated using a PID algorithm. T (t), and the resultant force of the two is taken as the vehicle driving torque value T. 合 The specific implementation process is as follows:

[0053] The target driving torque value T is calculated using the vehicle dynamics equations of the electric motor. 目标 :

[0054] T 目标 ·i g ·i o ·η T / r=δ·ma set +mg·f+C w ·A·V 2 act / 21.15;

[0055] Among them, a set The target acceleration value is empirically calibrated and obtained from a two-dimensional interpolation table of the target drive pedal opening and vehicle speed; δ is the rotational mass coefficient; a direct drive scheme i is adopted. g =1; i o Main reduction ratio; η T Transmission efficiency; r is the rolling radius; m is the vehicle weight; g is the acceleration due to gravity; f is the rolling resistance coefficient; C w V is the drag coefficient; act A represents the vehicle's actual speed; A represents the frontal area.

[0056] The PID algorithm controls the system based on the proportional, integral, and derivative components of the deviation. It is one of the most widely used algorithms in industrial applications, enabling automatic, accurate, and rapid correction of the control system in closed-loop systems.

[0057] The drive torque compensation value U is calculated using a PID algorithm. T (t):

[0058] The input is the target acceleration a. set and actual acceleration a act Deviation signal:

[0059] e a (t)=a set -a act (t);

[0060] Since the data acquired by the CAN bus has a period of Ts and is discrete, it needs to be discretized into a time interval of t = kTs. In this embodiment 1, the sampling period is 20ms, and 1s = 50 multiplied by 20ms.

[0061] Corresponding drive torque compensation U T The function of (t) can be written as:

[0062]

[0063] Among them, K PT K is the proportionality coefficient. IT K is the integral coefficient. DT T is the differential coefficient. s For discrete data sampling periods.

[0064] Step 4: Based on the calculated vehicle drive torque value T 合 The vehicle control unit (VCU) outputs corresponding torque control commands to the motor controller, thereby driving the vehicle.

[0065] Example 2

[0066] like Figure 1 As shown in the figure, this embodiment 2 provides a power system control method for a pure electric bus, and the specific steps are as follows:

[0067] Step S1: After the vehicle is connected to high voltage, the vehicle control unit (VCU) identifies the driving intention by judging the motor braking status and the driver's pedal action. If the motor is in braking status, the driver presses the brake pedal to brake, and braking control is initiated.

[0068] Step S2: Based on the braking control information obtained in Step 1, the vehicle control unit (VCU) switches to emergency braking mode or standard braking mode according to the value of the brake pedal change rate, and sends the brake pedal opening curve corresponding to the mode to the brake torque control module.

[0069] When braking control information is received, if the brake pedal changes extremely rapidly and the brake pedal change rate K1 is greater than or equal to the set threshold α1, the driver urgently needs to brake, and the vehicle controller (VCU) determines it to be in emergency braking mode; if the brake pedal changes moderately and the brake pedal change rate K1 is less than the set threshold α1, the vehicle controller (VCU) determines it to be in standard braking mode.

[0070] It should be noted that in this embodiment 2, a threshold α1 is set based on the time it takes for the pedal opening to change from 0% to 100%, that is, based on the time it takes for the pedal to change from its natural state to its maximum braking state. Here, α1 is the pedal opening changing by 75% per second.

[0071] When switching to emergency braking mode, the output brake pedal opening curve is the brake pedal opening curve for emergency braking mode; when switching to standard braking mode, the output brake pedal opening curve is the brake pedal opening curve for standard braking mode. The brake pedal opening curve is a curve showing the correspondence between the set target brake pedal opening and the input brake pedal opening. This brake pedal opening curve is pre-downloaded to the vehicle controller and is then called upon by the vehicle controller when controlling vehicle movement.

[0072] For example: when the driver's brake pedal opening is n1% and the brake pedal opening change rate is 76% per second, it is determined that the driver has a strong braking intention and enters emergency braking mode. Based on the pedal opening curve of emergency braking mode, the target brake pedal opening of m1% (m1>n1) is obtained and subsequent calculations are performed.

[0073] In this embodiment 2, a large amount of historical data from different drivers during driving is collected through CAN message data or a host computer. The historical data includes: vehicle speed, motor torque, brake pedal opening, and brake pedal opening change rate. Based on the brake pedal opening change rate, the historical data is classified into emergency braking mode and standard braking mode. In each mode, the two-dimensional interpolation of the brake pedal opening change rate and the brake pedal opening is used as input, and the target brake pedal opening is used as output. The visualization is performed using Matlab to obtain the pedal opening curve corresponding to each mode.

[0074] Step S3: After receiving the brake pedal opening curve, the braking torque control module obtains the target brake pedal opening based on the curve, and calculates the target braking torque value T using the vehicle dynamics equations of the motor. 目标1 .

[0075] like Figure 3 As shown, this embodiment 2 employs an open-loop control structure, calculating the target braking torque T using the vehicle dynamics equations of the motor. 目标1 The specific implementation process is as follows:

[0076] T 目标1 ·i g ·i o ·η T / r=mg·f+C w ·A·V 2 act / 21.15+δ·ma set1 ;

[0077] Among them, a set1 The planned target deceleration value is obtained from an empirically calibrated two-dimensional interpolation table of the target brake pedal opening and vehicle speed.

[0078] Step S4: Based on the calculated target braking torque value T 目标1 The vehicle control unit (VCU) outputs torque control commands to the motor controller, thereby braking the vehicle.

[0079] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not limiting. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the scope of protection of the present invention.

[0080] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0081] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A power system control method for a pure electric bus, characterized in that, Includes the following steps: Step 1: Obtain drive control information or braking control information; Step 2: When drive control information is obtained, switch to power mode, standard mode or economy mode according to the value of drive pedal change rate K, and output the drive pedal opening curve of the corresponding mode. When braking control information is obtained, the system switches to emergency braking mode or standard braking mode according to the value of brake pedal change rate K1, and outputs the brake pedal opening curve for the corresponding mode. The drive pedal opening curve is a set curve showing the correspondence between the target drive pedal opening and the input drive pedal opening, and the brake pedal opening curve is a set curve showing the correspondence between the target brake pedal opening and the input brake pedal opening. Both are pre-downloaded to the vehicle controller and called by the vehicle controller when controlling the vehicle to drive. Step 3: Obtain the target drive pedal opening using the drive pedal opening curve, and calculate the vehicle drive torque value T. 合 ; The target brake pedal opening is obtained from the brake pedal opening curve, and the target braking torque value T is calculated. 目标1 ; Step 4: Based on the vehicle drive torque value T 合 Or the target braking torque value T 目标1 It outputs the corresponding torque control command to the motor controller; In step 2, when drive control information is obtained, if the rate of change of the drive pedal K is greater than or equal to a set threshold α, it is determined to be a power mode; if the rate of change of the drive pedal K is greater than a set threshold β and less than a set threshold α, it is determined to be a standard mode; if the rate of change of the drive pedal K is less than a set threshold β, it is determined to be an economy mode. When braking control information is obtained, if the brake pedal change rate K1 is greater than or equal to the set threshold α1, it is determined to be an emergency braking mode; if the brake pedal change rate K1 is less than the set threshold α1, it is determined to be a standard braking mode. The process of obtaining the drive pedal opening curve includes: (a) obtaining historical data during different drivers' driving processes, wherein the historical data includes: drive pedal opening and drive pedal opening change rate; (b) classifying the historical data into power mode, standard mode, and economy mode according to the drive pedal opening change rate; (c) in each mode, using the two-dimensional interpolation of the drive pedal opening change rate and the drive pedal opening as input, and the target drive pedal opening as output, performing visualization processing using Matlab to obtain the drive pedal opening curve corresponding to each mode; The process of obtaining the brake pedal opening curve includes: (a1) obtaining historical data during different drivers' driving processes, wherein the historical data includes: brake pedal opening and brake pedal opening change rate; (b1) classifying the historical data into emergency braking mode and standard braking mode according to the brake pedal opening change rate; (c1) in each mode, using the two-dimensional interpolation of the brake pedal opening change rate and the brake pedal opening as input, and the target brake pedal opening as output, performing visualization processing using Matlab to obtain the brake pedal opening curve corresponding to each mode.

2. The power system control method according to claim 1, characterized in that, In step 3, the vehicle driving torque value T 合 The calculation formula is: T 合 =U T (t)+T 目标 ; Among them, U T (t) represents the drive torque compensation value, T 目标 The target driving torque value.

3. The power system control method according to claim 2, characterized in that, The target driving torque value T 目标 The calculation formula is: ； Among them, a set The empirically calibrated target acceleration value is obtained from a two-dimensional interpolation table of target drive pedal opening and vehicle speed; δ The rotational mass coefficient is used; a direct drive scheme is adopted. i g =1; i o Main reduction ratio; η T For transmission efficiency; r The rolling radius; m For vehicle weight; g It is the acceleration due to gravity; f This is the rolling resistance coefficient; C w This refers to the drag coefficient; V act The actual speed of the vehicle; A For windward area; The driving torque compensation value U T The formula for calculating (t) is: ； Where t=kT s T s e represents the discrete data sampling period. a (t)=a set -a act (t) represents the target acceleration a. set and actual acceleration a act The deviation signal, K PT K is the proportionality coefficient. IT K is the integral coefficient. DT is the differential coefficient.

4. The power system control method according to claim 1, characterized in that, In step 3, the target braking torque value T 目标1 The calculation formula is: ； Among them, a set1 The empirically calibrated target deceleration value is obtained from a two-dimensional interpolation table of the target brake pedal opening and vehicle speed; δ The rotational mass coefficient is used; a direct drive scheme is adopted. i g =1; i o Main reduction ratio; η T For transmission efficiency; r The rolling radius; m For vehicle weight; g It is the acceleration due to gravity; f This is the rolling resistance coefficient; C w This refers to the drag coefficient; V act The actual speed of the vehicle; A This refers to the windward area.

Images