CN116026609A - Method for estimating actual running resistance of vehicle - Google Patents
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Abstract
The invention relates to a method for estimating the actual running resistance of a vehicle, which is characterized by comprising the following steps: the vehicle is driven normally based on an actual road, and the vehicle speed, the engine rotation speed, the torque, the friction torque, the accelerator opening, the gear and the oil injection signal information are collected through a vehicle bus, an external instrument or a built-in sensor of the vehicle when the vehicle runs; the method comprises the steps of acquiring information of vehicle speed, acceleration, gradient and direction angle by adopting a GPS, a gyroscope and an accelerometer or utilizing a vehicle built-in inertial navigation system, estimating an actual road resistance curve coefficient value based on the information, and further combining gradient resistance and acceleration resistance calculation to estimate the actual road resistance. The beneficial effects are that: the method is suitable for the requirements of measuring and calculating the actual road resistance of the vehicle in all real scenes, and improves the testing efficiency; the obtained result represents the actual road resistance of the current condition, and can better meet the test requirement; based on the prior art of vehicles, the estimation and prediction of the road running resistance can be realized.
Description
Technical Field
The invention belongs to the technical field of automobile detection, and particularly relates to an estimation method of actual running resistance of a vehicle.
Background
The chassis dynamometer is used for carrying out test and evaluation on the dynamic performance, oil consumption, emission and the like of the vehicle, and is a test method commonly used in the design development and performance evaluation test of modern automobile products. The actual running resistance of the automobile can be accurately simulated on the chassis dynamometer by controlling the test conditions, and the test can be carried out on the basis of the actual running resistance, when the chassis dynamometer test is carried out, the road resistance curve of the automobile is firstly determined before the road running resistance is simulated so as to set the parameters of the chassis dynamometer, and because the experience value recommended by the rule standard is generally greatly different from the actual value, the relation curve between the actual resistance of the automobile and the speed of the automobile is mostly obtained by adopting a test method. Namely, the vehicle resistance value can be obtained by looking up a table according to the sliding resistance curve through the vehicle speed.
At present, a standard method for detecting running resistance of a vehicle mostly adopts a sliding method (such as related regulations in standards of GB18352-2016, GB/T27840-2021 and the like), in brief, in good weather conditions (a certain temperature and humidity range and insufficient wind speed for disturbing test results), after an automobile accelerates to a regulated speed on a special flat road test runway, a transmission is placed at a neutral position and slides to a low speed or even 0 speed, a data acquisition system with GPS positioning is used for synchronously recording the whole sliding process data, and a quadratic function relation between the resistance and the speed of the vehicle in the sliding process, namely F=A+B.V+C.V, is obtained through a standard calculation method 2 Where F is the coasting resistance, V is the vehicle speed, and A, B, C is the resistance coefficient, respectively.
By the method, a relatively accurate vehicle resistance curve can be obtained, and the method is suitable for standard laboratory regulation standard detection, but has certain limitation. First, the skid resistance curve cannot represent the skid resistance of other conditions due to the skid test performed at a specific test site and under specific temperature conditions with a fixed load for a specific test vehicle. Because the changes of the road property, altitude, load, temperature, vehicle condition and the like of the actual conditions all correspond to a specific resistance curve, if the test method required by the above rule standard is adopted to obtain the sliding resistance curve of all other conditions, it is not practical to obtain the approximate value only through some empirical parameter correction, such as temperature correction and altitude correction of the sliding resistance curve, but there is a problem that the correction value has larger error or cannot be corrected. Therefore, there are currently shortcomings in the technology and method for some development and test requirements to obtain the actual road sliding resistance curve.
With the development of vehicle technology, the vehicle energy-saving control technology based on model prediction needs to realize intelligent control of a power system according to actual resistance characteristics, and is also a solution for real-time vehicle traction prediction if a sliding resistance curve of an actual road can be obtained.
Disclosure of Invention
The invention aims to overcome the defects of the technology and provide an estimation method of the actual running resistance of the vehicle, which can be used for estimating and identifying the actual road resistance curve and predicting the actual road running traction of the vehicle required by a vehicle model control strategy.
The invention adopts the following technical scheme to realize the aim: a method for estimating the actual running resistance of a vehicle. The method is characterized in that: the vehicle is driven normally based on an actual road, and the vehicle speed, the engine rotation speed, the torque, the friction torque, the accelerator opening, the gear, the oil injection signal and other information are collected through a vehicle bus, an external instrument or a built-in sensor of the vehicle when the vehicle runs; the method adopts GPS, gyroscope and accelerometer, or utilizes the built-in inertial navigation system of the vehicle to collect information of speed, acceleration, gradient and direction angle, and based on the information, the coefficient value of the actual road resistance curve is estimated, and further, the actual road resistance can be estimated by combining gradient resistance and acceleration resistance calculation, and the specific steps are as follows:
judging traffic conditions, weather conditions and road conditions to meet the vehicle running environment conditions when the data acquisition is carried out;
judging the preheating state of the vehicle: selecting a medium-high speed running vehicle to enable the vehicle to reach a preheating requirement, and enabling the temperature of a cooling liquid of the vehicle and the temperature of engine oil to reach a stable state;
step three, driving requirements: the method comprises the steps of selecting a relatively straight actual road, driving a vehicle in a relatively stable driving behavior, avoiding rapid acceleration and deceleration as much as possible, and rapidly adjusting the driving behavior of a steering wheel (such as frequent lane change and steering), and recording the required vehicle operation data in real time. Corresponding data when rapid acceleration and deceleration, braking, gear shifting and steering actions occur need to be removed and are not adopted in subsequent calculation;
and step four, data acquisition. In the process of driving the vehicle, the relevant data of the vehicle during running is collected at the collection frequency not lower than 1Hz, and the vehicle speed V, the engine rotating speed n and the engine torque T are collected through the CAN bus of the OBD port of the vehicle tq Engine friction torque T m Throttle opening, gear and oil injection signal information; collecting information of vehicle speed, acceleration a, gradient theta or i and direction angle by adopting a GPS, a gyroscope and an accelerometer; selecting a constant-speed driving method or an actual driving speed fragment extraction method to complete data acquisition;
and fifthly, parameter estimation. And (3) carrying out data screening, processing and calculating according to the test data obtained in the step (IV) to obtain the resistance curve coefficient estimated value of the actual road of the vehicle.
Further, the judging of traffic conditions, weather conditions and road conditions is carried out under the conditions of no rain, no snow and no fog in the weather, and the relative humidity with the humidity of less than 95 percent and the altitude of less than 5000m are applicable at the temperature of-20 ℃ to 40 ℃; the road traffic index is less than or equal to 2; the wind speed is less than or equal to 2 levels, the ground average wind speed is less than or equal to 3m/s, and the gust is not more than 5m/s.
And step four, acquiring and calculating actual running data of the vehicle. Let F t Represents the driving force of the vehicle, T tq Representing engine torque, i g Representing variator ratio, i 0 Representing the final drive ratio, η representing the mechanical efficiency of the drive train, r representing the wheel radius, the driving force F t The method comprises the following steps:
if the vehicle slides with gears, the engine stops injecting oil and is in a reverse towing state, and the engine torque T tq Is negative and is set as T m Driving force F t The method comprises the following steps:
wherein the engine torque T tq And reverse torque T m The vehicle CAN bus information is acquired and recorded in real time, and the transmission gear ratio i of the transmission g And final drive ratio i 0 Acquiring information through a vehicle CAN bus; the wheel radius r selects the static radius value of the wheel.
The relation between the engine speed and the vehicle running speed is:
v is the running speed of the vehicle and is obtained in real time by GPS information or CAN bus information; n is the engine speed, and is obtained in real time by CAN bus information, and the driving force F of the vehicle t The relation with the engine speed, torque and vehicle speed is:
if the vehicle is in a reverse dragging sliding state with a gear, the formula is as follows:
when an automobile runs on a horizontal road at a constant speed, rolling resistance from the ground and air resistance from air need to be overcome; let the rolling resistance be F f Air resistance is F w When the vehicle runs on the slope, the slope resistance is F i When the vehicle is accelerating, the following steps are also neededAcceleration resistance F to be overcome j The vehicle running driving force Ft is the sum of the resistances, namely:
F t ＝F f +F w +F i +F j
wherein "F f +F w "is a quadratic function of the running speed of the vehicle, namely, is a quadratic function A+B.V+C.V of the standard sliding method 2 A resistance value determined by the A, B, C value in ";
ramp resistance F i The component force generated by the gravity of the vehicle along the ramp is smaller in normal condition when the vehicle runs on the ramp, for example, the maximum longitudinal slope of the micro-hills area of the expressway plain is 3% and the gradient of the mountain heavy hills area of the four-level highway is 9% according to the design rule of the highway route in China. Road grade is expressed as the ratio of the grade height h (in m) to the base length s (in m), namely:
therefore, if the gradient of the road is small, sin θ≡θ=i, then:
F i ＝M·g·sinθ
wherein M is the mass of the vehicle (unit kg), g is the gravitational acceleration (9.8M/s 2 ) The method comprises the steps of carrying out a first treatment on the surface of the θ is the road longitudinal grade angle; if the road is substantially straight, F i The value is approximately 0.
Acceleration resistance F j The inertial force of the vehicle is overcome when the vehicle accelerates and runs. The automobile mass is divided into a translation mass and a rotation mass, and when the automobile accelerates, the translation mass accelerates to generate inertia force, and the rotation mass generates inertia moment.
Wherein m is r The term "rotating mass" refers to the equivalent effective mass (unit kg) of all rotating parts and wheels on a vehicle, m r Can be obtained from a 3% estimate of the reference mass of the vehicle，
Is the running acceleration a (unit m/s 2 ) The derivation is made from the above formula:
F t ＝(A+B·V+C·V 2 )+M·g·sinθ+(M+m r ) A, combine with F t The calculation formula further obtains:
namely:
or, when the belt is in sliding:
further, the constant speed driving method of the fourth step is preferably selected as the method for determining the vehicle resistance coefficient A, B, C under relatively straight road conditions and good traffic conditions, in which the hill resistance Fi and the acceleration resistance F j May be approximately 0. The highest test speed is selected according to the actual speed limit of the road and the highest speed limit of the vehicle, the speed is gradually reduced from high speed to low speed according to the speed change of not more than 20km/h until the speed is lower than 20km/h, and the test data of 5 speed points are ensured at least for ensuring an effective fit resistance curve. At each vehicle speed point, the vehicle speed is held stationary for a period of time to obtain sufficient data. Screening the calculated data, wherein the selected vehicle speed is basically stable, and the stage data of the driver without sudden acceleration and deceleration, braking, gear shifting and great adjustment of the steering wheel driving behavior are used as the calculated data, so as to obtain a second-by-second quadratic function relation between the driving resistance and the vehicle speed V according to the formula (1). According to the least squares regression method, A, B, C values are obtained through analysis.
Further, in the fourth step, the actual driving speed segment extraction method comprises: in a section of test target road section, the vehicle drives normally according to the actual traffic condition, the running speed covers as much as possible all normal vehicle speed ranges lower than the speed limit of the vehicle, and the driving behavior of the steering wheel is prevented from rapid acceleration, rapid deceleration and greatly adjusted as much as possible. And judging the actual calculation data choice and the selected calculation formula according to the acquired data. The operation is selected to be relatively stable, the data of steering wheel and braking and gear shifting actions are not greatly adjusted, and the data of the speed lower than 15km/h are removed. If the gear-engaged sliding state occurs, selecting the formula (2), otherwise, selecting the formula (1) to obtain a second-by-second quadratic function relation between the running resistance and the vehicle speed V. According to the least squares regression method, A, B, C values are obtained through analysis.
After the A, B, C value is determined, if the vehicle is provided with a built-in vehicle-mounted inertial navigation system, in actual control of the vehicle, gradient information of a running road can be obtained in real time, further, road geographic information can be obtained through the Internet of vehicles, the vehicle can obtain gradient values of a front route in advance, actual road resistance can be estimated according to a formula (1), and therefore power requirements are predicted, and a solution is provided for predictive control of the vehicle.
The beneficial effects are that: compared with the prior art, the invention 1) is suitable for all the real scenes in need of measuring and calculating the actual road resistance of the vehicle, can be carried out at any time and any place without selecting a special test field, saves the test cost and improves the test efficiency; 2) The method is flexible and simple, can be repeatedly performed for a plurality of times according to the requirement, and the obtained result represents the actual road resistance of the current condition instead of the experience correction value, so that the test requirement can be better met; 3) Based on the prior art of vehicles, under the condition of not increasing hardware cost, the method can realize the estimation and prediction of the vehicle on the road running resistance based on the model control strategy, and meet the technical requirement of vehicle traction prediction control.
Drawings
Figure 1 is a flow chart of the overall process of the present invention.
Fig. 2 is a flowchart showing an implementation of the vehicle running resistance estimation method 1.
Fig. 3 is a flowchart showing an implementation of the vehicle running resistance estimation method 2.
Fig. 4 is a graph of sample point vehicle speed distribution for an example embodiment.
Fig. 5 (a) is a corresponding data map of actual running resistance and vehicle speed.
Fig. 5 (b) shows the result of routine running resistance curve fitting.
Detailed Description
The following describes the present invention in detail with reference to preferred embodiments.
Referring to the drawings in detail, the embodiment provides a method for estimating the actual running resistance of a vehicle, wherein the vehicle is driven normally based on an actual road, and information such as the speed, the engine speed, the torque, the friction torque, the accelerator opening, the gear, the oil injection signal and the like of the vehicle during running is collected through a vehicle bus, an external instrument or a built-in sensor of the vehicle; the method adopts GPS, gyroscope and accelerometer, or utilizes the built-in inertial navigation system of the vehicle to collect the information of speed, acceleration, gradient and direction angle, based on the data, the coefficient value of the actual road resistance curve is estimated, and the actual road resistance can be further estimated by combining gradient resistance and acceleration resistance calculation, and the specific steps are as follows:
step one, judging traffic conditions, weather conditions and road conditions.
Because it is the actual road resistance curve of test, so extreme weather conditions and congested traffic conditions are not possible. The method of the invention needs to be carried out under good weather conditions (no rain, snow or fog), and is applicable to common temperature and humidity conditions (such as-20 to 40 ℃ and relative humidity less than 95%) and altitude ranges (below 5000 m). The road traffic is guaranteed to be smooth, and the traffic index is not more than 2. To reduce the impact of wind speed on drag measurement, the wind speed is as small as possible, and it is recommended to choose wind conditions not higher than level 2 (breeze), typically requiring a ground average wind speed not higher than 3m/s and a gust not higher than 5m/s. If the traffic is smooth and the road is straight, the basic constant-speed driving can be ensured, and the constant-speed method is preferentially selected.
And step two, judging the vehicle preheating state. The temperature of the cooling liquid and the temperature of the engine oil of the vehicle reach a stable state, and if the preheating state is not good, the vehicle can be selected to run at a medium and high speed so as to reach the preheating requirement.
And step three, driving requirements. The data acquisition is completed by selecting the following method 1 or method 2. Generally, a relatively straight actual road is selected to drive a vehicle in a relatively stable driving behavior, so as to avoid rapid acceleration, deceleration and rapid adjustment of the driving behavior of a steering wheel (such as frequent lane change and steering) as much as possible, record the required vehicle running data in real time, and reject and avoid adoption of corresponding data when rapid acceleration, deceleration, braking, gear shifting and great adjustment of the driving behavior of the steering wheel occur in subsequent calculation.
Method 1: constant speed driving method. Because this method is relatively simple to calculate, if relatively straight road conditions and traffic conditions are desirable, it is preferable to select this method as the method of determining the vehicle resistance coefficient A, B, C. The highest test speed is selected according to the actual speed limit of the road and the highest speed limit of the vehicle, the speed is changed from high speed to low speed (or from low to high), the speed is gradually changed until the speed is lower than 20km/h, the speed is kept stable for a period of time at each speed point, sufficient data are ensured to be obtained, if continuous speed changing running conditions are not provided, the speed can be selected according to the actual conditions, and the data of all the required speed points can be completed gradually at different speed points.
Method 2: the method for extracting the actual driving speed segment. If the road and traffic conditions in the method 1 are not met, the method for normally driving the vehicle according to the actual traffic conditions can be adopted to acquire the required data. In a section of test target road section, the vehicle drives normally according to actual traffic conditions, the driving speed covers as much as possible all normal vehicle speed ranges lower than the vehicle speed limit, for example, the highest vehicle speed limit is 100, then the vehicle can drive according to the vehicle speed change not more than 20km/h, the vehicle speed is adjusted according to the actual traffic conditions, the stable driving state is not required to be maintained in the driving process, the speed change is not required to be increased or decreased, the driving operation of any vehicle speed can be carried out according to the actual requirements, the vehicle speed change is required to cover as much as possible the vehicle speed range of 20-100 km/h, the vehicle can drive reciprocally in the target road section, and the driving behavior of the steering wheel is prevented from being accelerated, decelerated suddenly and adjusted greatly as much as possible. After enough vehicle speed coverage data is acquired, data acquisition can be stopped, the actual calculation data choice is judged according to the acquired data, and a selected calculation formula is determined. And eliminating vehicle data when sudden acceleration, deceleration and braking, gear shifting and steering driving behaviors occur, eliminating data with the speed lower than 15km/h, eliminating other obvious abnormal data, intercepting actual running data covering various vehicle speed points, and judging the driving behaviors in a gear-shifting sliding state through an accelerator pedal, a gear and oil injection signals.
And step four, data acquisition. During driving of the vehicle, relevant data of the vehicle during running is collected at a collection frequency of not less than 1 Hz. The vehicle speed (V), the engine speed (n) and the engine torque (T) are collected through a CAN bus of the OBD port of the vehicle tq ) Engine friction torque (T) m ) Information such as throttle opening, gear, oil injection signals and the like; the GPS, the gyroscope and the accelerometer are adopted to collect information of vehicle speed, acceleration (a), gradient (theta or i) and direction angle, and if the vehicle is provided with a built-in inertial navigation system, the vehicle CAN bus CAN also be used for obtaining information of gradient, acceleration, steering angle and the like. The acceleration a can be obtained directly by an accelerometer or calculated by the vehicle speed V. The powertrain mechanical efficiency η may be provided by the vehicle manufacturer as a parameter value or as a theoretical recommendation. The vehicle mass M may be weighed or obtained by load calculation.
And fifthly, parameter estimation. And (3) screening data according to the test data obtained in the step four, and performing data processing calculation to obtain the resistance curve coefficient estimated value of the actual road of the vehicle. If the method 1 is adopted, according to the formula (1), a point-by-point quadratic function relation between the running resistance and the vehicle speed V in different vehicle speed stages is obtained. According to the least squares regression method, A, B, C values are obtained through analysis. If the method 2 is adopted, if the vehicle is in a gear-engaged sliding state, selecting the formula (2), otherwise, selecting the formula (1) to obtain a point-by-point quadratic function relation between the running resistance and different vehicle speeds V. According to the least squares regression method, A, B, C values are obtained through analysis.
After the A, B, C value is determined, if the vehicle is provided with a built-in vehicle-mounted inertial navigation system, in actual control of the vehicle, gradient information of a running road can be obtained in real time, further, road geographic information can be obtained through the Internet of vehicles, the vehicle can obtain gradient values of a front route in advance, and the actual road resistance can be estimated according to a resistance calculation formula, so that the power requirement is predicted, and a solution is provided for prediction control of the vehicle.
The resistance curve estimation algorithm is further described below in connection with a specific embodiment, taking the constant speed driving method as an example:
1) The highest speed of the test vehicle limits 100km/h, the speed change of 20km/h is used for selecting 20, 40, 60, 80 and 100km/h as speed selection points, the speed is kept basically stable for more than 60s at each speed point, the data of the vehicle when the acceleration, deceleration and braking, gear shifting and steering driving actions occur and other obvious abnormal data are finally adopted, only the data of relatively stable running of each speed point is intercepted, and finally the obtained data points are shown in figure 4, and the data of each speed point is about 400s. In the actual test process, the speed of the vehicle is from low to high and from high to low, if the traffic condition is limited, the vehicle can be segmented according to the actual situation, or the vehicle is driven by randomly selecting the speed point, so that the data of all the required speed points are completed.
2) Because it is a substantially straight road and the vehicle speed is substantially stable, the hill resistance Fi and the acceleration resistance F j Approximately 0, the calculation may be ignored. The mechanical efficiency eta of the transmission system adopts a theoretical experience recommended value of 0.84, and the actual running resistance F is finally calculated according to the formula (1) t As shown in fig. 5 (a), the resistance is densely distributed along with each vehicle speed point, taking into account that a certain vehicle speed fluctuation and resistance fluctuation exist in actual vehicle running, average value of data of each vehicle speed point can be obtained, quadratic term fitting can be performed on an average result curve, and an estimated value of a coefficient A, B, C can be obtained according to a least square regression method, as shown in fig. 5 (b), in this embodiment, the estimated value of the coefficient least square method of the actual road resistance curve is: a=909.42, b= -4.7921, c=0.179.
The method can be used for coefficient estimation of the actual road resistance curve of the vehicle under various environments and road conditions. On the basis, due toThe development of sensor technology, some vehicles are provided with built-in inertial navigation systems (including GPS, gyroscopes, accelerometers and the like), namely, more accurate information such as road gradient angle, acceleration, steering angle and the like can be obtained without depending on other instruments and equipment, and the development of the internet of vehicles also provides possibility for the vehicles to obtain the geographic information of the front road in real time, so that the invention can be also used for real-time prediction estimation calculation of the actual road resistance. I.e. according to the gradient information, the gradient resistance F is obtained i The traction force demand of the predicted vehicle can be calculated in real time by combining the acceleration and deceleration demands, the speed state of the vehicle and the real-time estimated resistance coefficient A, B, C value.
The above detailed description of a method for estimating an actual running resistance of a vehicle with reference to the embodiments is illustrative and not restrictive, and several embodiments can be listed in the defined scope, and therefore, variations and modifications without departing from the general inventive concept shall fall within the scope of protection of the present invention.
Claims (5)
1. A method for estimating the actual running resistance of a vehicle is characterized by comprising the following steps: the vehicle is driven normally based on an actual road, and the vehicle speed, the engine rotation speed, the torque, the friction torque, the accelerator opening, the gear and the oil injection signal information are collected through a vehicle bus, an external instrument or a built-in sensor of the vehicle when the vehicle runs; the method adopts a GPS, a gyroscope and an accelerometer, or utilizes a vehicle built-in inertial navigation system to collect information of vehicle speed, acceleration, gradient and direction angle, estimates the value of the actual road resistance curve based on the information, combines gradient resistance and acceleration resistance calculation, and estimates the actual road resistance, and comprises the following specific steps:
judging traffic conditions, weather conditions and road conditions to meet the vehicle running environment conditions for carrying out data acquisition;
and step two, judging the vehicle preheating state. Selecting a medium-high speed running vehicle to enable the vehicle to reach a preheating requirement, and enabling the temperature of a cooling liquid of the vehicle and the temperature of engine oil to reach a stable state;
and step three, driving requirements. Selecting a relatively straight actual highway, driving a vehicle by using relatively stable driving behaviors, avoiding rapid acceleration, deceleration and rapid adjustment of driving behaviors of a steering wheel (such as frequent lane change and steering) as much as possible, recording required vehicle operation data in real time, and eliminating corresponding data when the rapid acceleration, deceleration, braking, gear shifting and steering behaviors occur in subsequent calculation without adopting the data;
and step four, data acquisition. In the process of driving the vehicle, the relevant data of the vehicle during running is collected at the collection frequency not lower than 1Hz, and the vehicle speed V, the engine rotating speed n and the engine torque T are collected through the CAN bus of the OBD port of the vehicle tq Engine friction torque T m Throttle opening, gear and oil injection signal information; collecting information of vehicle speed, acceleration a, gradient theta or i and direction angle by adopting a GPS, a gyroscope and an accelerometer; selecting a constant-speed driving method or an actual driving speed fragment extraction method to complete data acquisition;
and fifthly, parameter estimation. And (3) carrying out data processing calculation according to the test data obtained in the step four to obtain the resistance curve coefficient estimated value of the actual road of the vehicle.
2. The method for estimating an actual running resistance of a vehicle according to claim 1, characterized in that: the first step of judging traffic conditions, weather conditions and road conditions is carried out under the conditions of no rain, no snow and no fog in weather, and the relative humidity with the temperature of-20 ℃ to 40 ℃ and the humidity of less than 95 percent and the altitude of less than 5000m are applicable; the road traffic index is less than or equal to 2; the wind speed is less than or equal to 2 levels, the ground average wind speed is less than or equal to 3m/s, and the gust is not more than 5m/s.
3. The method for estimating an actual running resistance of a vehicle according to claim 1, characterized in that: and step four, acquiring and calculating actual running data of the vehicle.
Let F t Represents the driving force of the vehicle, T tq Representing engine torque, i g Representing variator ratio, i 0 Representing the final drive ratio, η representing the mechanical efficiency of the drive train, r representing the wheel radius, the driving force F t The method comprises the following steps:
if the vehicle slides with gears, the engine stops injecting oil and is in a reverse towing state, and the engine torque T tq Is negative and is set as T m Driving force F t The method comprises the following steps:
wherein the engine torque T tq And reverse torque T m The vehicle CAN bus information is acquired and recorded in real time, and the transmission gear ratio i of the transmission g And final drive ratio i 0 Acquiring information through a vehicle CAN bus; the wheel radius r selects the static radius value of the wheel.
The relation between the engine speed and the vehicle running speed is:
v is the running speed of the vehicle and is obtained in real time by GPS information or CAN bus information; n is the engine speed, and is obtained in real time by CAN bus information, and the driving force F of the vehicle t The relation with the engine speed, torque and vehicle speed is:
if the vehicle is in a reverse dragging sliding state with a gear, the formula is as follows:
when the automobile runs on a horizontal road at a constant speed, the rolling resistance from the ground and the air are overcomeAir resistance; let the rolling resistance be F f Air resistance is F w When the vehicle runs on the slope, the slope resistance is F i Acceleration resistance F to be overcome when the vehicle is accelerating j The vehicle running driving force Ft is the sum of the resistances, namely:
F t ＝F f +F w +F i +F j
wherein "F f +F w "is a quadratic function of the running speed of the vehicle, namely, is a quadratic function A+B.V+C.V of the standard sliding method 2 A resistance value determined by the A, B, C value in ";
ramp resistance F i The component force generated by the gravity of the vehicle along the ramp is smaller in normal condition when the vehicle runs on the ramp, for example, the maximum longitudinal slope of the micro-hills area of the expressway plain is 3% and the gradient of the mountain heavy hills area of the four-level highway is 9% according to the design rule of the highway route in China. Road grade is expressed as the ratio of the grade height h (in m) to the base length s (in m), namely:
therefore, if the gradient of the road is small, sin θ≡θ=i, then:
F i ＝M·g·sinθ
wherein M is the mass of the vehicle (unit kg), g is the gravitational acceleration (9.8M/s 2 ) The method comprises the steps of carrying out a first treatment on the surface of the θ is the road longitudinal grade angle;
acceleration resistance F j The inertial force of the vehicle is overcome when the vehicle accelerates and runs. The automobile mass is divided into a translation mass and a rotation mass, and when the automobile accelerates, the translation mass accelerates to generate inertia force, and the rotation mass generates inertia moment.
Wherein m is r The term rotating mass means that, when the vehicle is traveling in neutral on the road,equivalent effective mass (unit kg), m of all rotating parts and wheels on the vehicle r Can be obtained from a 3% estimate of the reference mass of the vehicle,
the running acceleration a (unit m/s 2) of the vehicle. The derivation is made from the above formula:
F t ＝(A+B·V+C·V 2 )+M·g·sinθ+(M+m r ) A, combine with F t The calculation formula further obtains:
namely:
or, when the belt is in sliding:
4. the method for estimating an actual running resistance of a vehicle according to claim 1, characterized in that: the constant speed driving method in the fourth step is preferably selected as a method for determining the vehicle resistance coefficient A, B, C under relatively straight road conditions and good traffic conditions; the highest test speed is selected according to the actual speed limit of the road and the highest speed limit of the vehicle, the speed is changed gradually from high speed to low speed (or from low to high) with the speed not more than 20km/h until the speed is lower than 20km/h, and the speed is kept stable for a period of time at each speed point to ensure that enough data are acquired. The method comprises the steps of selecting stage data of which the vehicle speed is basically stable and the driver does not carry out rapid acceleration and deceleration, braking and gear shifting and greatly adjusts the driving behavior of the steering wheel as calculation data, obtaining corresponding data points of the vehicle resistance and the vehicle speed V in a second-by-second mode at different vehicle speed stages according to a formula (1), and obtaining a A, B, C value through analysis according to a least square regression method.
5. The method for estimating an actual running resistance of a vehicle according to claim 1, characterized in that: and step four, the actual driving speed fragment extraction method comprises the following steps: in a section of test target road section, the vehicle drives normally according to the actual traffic condition, judges the actual calculation data choice according to the collected data, selects the formula (1) and the formula (2), obtains the corresponding data points of the vehicle resistance and the vehicle speed V every second, and analyzes according to the least square regression method to obtain a A, B, C value.
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| CN117890128A (en) * | 2024-03-14 | 2024-04-16 | 中汽研汽车检验中心（天津）有限公司 | Method for testing running resistance of heavy vehicle under any load |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117890128A (en) * | 2024-03-14 | 2024-04-16 | 中汽研汽车检验中心（天津）有限公司 | Method for testing running resistance of heavy vehicle under any load |
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