Method and device for measuring automobile braking acceleration curve

Abstract

The invention discloses an automobile braking acceleration curve measuring method and device, and relates to the technical field of automobiles, and the method comprises the steps: collecting a space acceleration corresponding to a space inclination angle in a vehicle driving process; the friction acceleration borne by the vehicle is measured through a variable mass measuring method; measuring the wind resistance acceleration of the vehicle through a wind tunnel test; and linear superposition is conducted on the space acceleration, the friction acceleration and the wind resistance acceleration, and a set engine braking acceleration curve is obtained. The method comprises the following steps: acquiring a space acceleration corresponding to a space inclination angle in a vehicle driving process through a portable acceleration curve acquisition device; the space acceleration, the friction acceleration and the wind resistance acceleration are subjected to linear superposition, the influence of factors such as wind resistance and ground friction on the acceleration in the running process is eliminated, an acceleration curve of the fuel vehicle under the independent action of engine braking is obtained after setting, and therefore the method can be used for optimization of a regenerative braking control strategy of the electric vehicle.

Description

Technical Field

[0001] The present application relates to the field of automobile technology, and in particular to a method and device for measuring an automobile braking acceleration curve. Background Art

[0002] The measurement of the vehicle's acceleration G-value curve refers to recording the acceleration changes during the vehicle's driving process when the vehicle is accelerating and braking, and drawing a vehicle G-value curve to evaluate the vehicle's power performance and handling performance. In addition, in order to improve the vehicle's handling performance, automobile manufacturers are constantly exploring new technical means, including lightweighting the vehicle, improving the suspension and braking systems, and increasing engine power, all of which need to be verified and evaluated based on the measurement of the vehicle's G-value curve. At present, the measurement of the vehicle's G-value curve has become an indispensable technical means for evaluating vehicle performance.

[0003] However, the measurement of vehicle G-value curves often requires professional equipment and measurement procedures, and has a high degree of integration, and lacks portable data acquisition devices suitable for a variety of vehicle models. There is also a lack of effective description methods for the acceleration G-value curve under the action of engine braking alone. Summary of the invention

[0004] The main purpose of the present application is to provide a method and device for measuring a vehicle braking acceleration curve, aiming to solve the technical problems that the existing acceleration G-value curve measurement equipment under the action of engine braking alone is not portable enough and the G-value curve is not accurate enough.

[0005] To achieve the above purpose, the present application proposes a method for measuring a vehicle braking acceleration curve, the method comprising:

[0006] Collect the spatial acceleration corresponding to the spatial inclination of the vehicle during driving;

[0007] The friction acceleration generated by the friction force on the vehicle is measured by the variable mass measurement method;

[0008] The wind resistance acceleration generated by the wind resistance on the vehicle is measured through wind tunnel testing;

[0009] The spatial acceleration, the friction acceleration and the wind resistance acceleration are linearly superimposed to obtain a regulated engine braking acceleration curve.

[0010] In one embodiment, the step of collecting the spatial acceleration corresponding to the spatial inclination angle during the vehicle's driving process includes:

[0011] Collect acceleration information, angle information and magnetic value through IMU inertial unit;

[0012] The acceleration information, the angle information and the magnetic value are integrated through a nine-axis fusion algorithm to obtain a spatial inclination angle during vehicle driving;

[0013] The acceleration information is corrected according to the spatial inclination angle to obtain the spatial acceleration corresponding to the spatial inclination angle.

[0014] In one embodiment, the step of measuring the friction acceleration generated by the friction force applied to the vehicle by a variable mass measurement method comprises:

[0015] Determine the friction force relationship between the total mass of the vehicle and the dynamic friction coefficient in a preset number of experiments by a variable mass measurement method;

[0016] Determining the total force relationship between the total mass of the vehicle, the acceleration measurement values ​​in the predetermined number of experiments, the wind resistance, the friction force relationship and the engine braking force;

[0017] The friction acceleration is determined according to the friction force relationship and the total force relationship.

[0018] In one embodiment, the step of linearly superimposing the spatial acceleration, the friction acceleration and the wind resistance acceleration to obtain a regulated engine braking acceleration curve comprises:

[0019] Determining the acceleration relationship between the wind resistance acceleration and the engine braking acceleration according to the friction acceleration and the total force relationship;

[0020] An engine braking acceleration is determined according to the acceleration relationship, and a regulated engine braking acceleration curve is determined according to the engine braking acceleration.

[0021] In one embodiment, the step of determining the engine braking acceleration according to the acceleration relationship and determining a set engine braking acceleration curve according to the engine braking acceleration comprises:

[0022] determining an engine braking acceleration according to the acceleration relationship, and correcting the engine braking acceleration according to the spatial inclination angle to obtain a corrected engine braking acceleration;

[0023] The adjusted engine brake acceleration curve is determined according to the actual coordinate system conversion matrix and the corrected engine brake acceleration.

[0024] In one embodiment, before the step of determining the adjusted engine brake acceleration curve according to the actual coordinate system conversion matrix and the corrected engine brake acceleration, the method further includes:

[0025] Obtain the rotation angles of the vehicle in the X-axis, Y-axis and Z-axis directions in the preset coordinate system collected by the IMU inertial unit, and establish a theoretical coordinate system conversion matrix based on the rotation angles;

[0026] Obtain acceleration values ​​of the vehicle in the X-axis, Y-axis and Z-axis directions in a preset coordinate system collected by an IMU inertial unit, and determine an angular relationship between the acceleration value and the rotation angle;

[0027] The theoretical coordinate system conversion matrix is ​​converted according to the angular relationship to obtain an actual coordinate system conversion matrix.

[0028] In addition, to achieve the above-mentioned purpose, the present application also proposes a vehicle braking acceleration curve measuring device, the vehicle braking acceleration curve measuring device comprising:

[0029] The spatial acceleration acquisition module is used to acquire the spatial acceleration corresponding to the spatial inclination angle during the vehicle's driving process;

[0030] A friction acceleration measurement module, used to measure the friction acceleration generated by the friction force on the vehicle through a variable mass measurement method;

[0031] Wind resistance acceleration measurement module, used to measure the wind resistance acceleration generated by the wind resistance on the vehicle through wind tunnel testing;

[0032] The acceleration setting module is used to linearly superimpose the spatial acceleration, friction acceleration and wind resistance acceleration to obtain a set engine braking acceleration curve.

[0033] In addition, to achieve the above-mentioned purpose, the present application also proposes a vehicle braking acceleration curve measuring device, which includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the vehicle braking acceleration curve measuring method as described above.

[0034] In addition, to achieve the above-mentioned purpose, the present application also proposes a storage medium, which is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, the steps of the vehicle braking acceleration curve measurement method described above are implemented.

[0035] In addition, to achieve the above-mentioned purpose, the present application also provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the steps of the vehicle braking acceleration curve measurement method as described above are implemented.

[0036] The present application provides a method for measuring the braking acceleration curve of an automobile, by collecting the spatial acceleration corresponding to the spatial inclination angle during the driving process of the vehicle; measuring the friction acceleration generated by the friction force on the vehicle by the variable mass measurement method; measuring the wind resistance acceleration generated by the wind resistance on the vehicle by the wind tunnel test; linearly superimposing the spatial acceleration, friction acceleration and wind resistance acceleration to obtain a calibrated engine braking acceleration curve. The present application collects the spatial acceleration corresponding to the spatial inclination angle during the driving process of the vehicle through a portable acceleration curve acquisition device; linearly superimposes the spatial acceleration, friction acceleration and wind resistance acceleration to eliminate the influence of factors such as wind resistance and ground friction on the acceleration measurement results during driving, and obtains the acceleration curve of a fuel vehicle under the action of engine braking alone after calibration, which can be used to optimize the regenerative braking control strategy of electric vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0039] Figure 1 A schematic diagram of a flow chart of a first embodiment of a method for measuring a braking acceleration curve of an automobile of the present application;

[0040] Figure 2 This is the overall flow chart of the automobile braking acceleration curve measurement method of this application;

[0041] Figure 3 This is a hardware design block diagram of the acceleration acquisition device of this application;

[0042] Figure 4 A schematic diagram of the throttle (electric switch) release detection mechanism of the present application;

[0043] Figure 5 This is a schematic diagram of the mobile APP data display for this application;

[0044] Figure 6 A schematic diagram of the process of processing the JY901 sensor data set for this application;

[0045] Figure 7 A schematic diagram of a flow chart of a second embodiment of a method for measuring a braking acceleration curve of an automobile of the present application;

[0046] Figure 8This is a schematic diagram of the forces acting on the vehicle during braking in this application;

[0047] Fig. 9 A schematic diagram of a process flow provided for the third embodiment of the method for measuring the braking acceleration curve of an automobile of the present application;

[0048] Fig.10 This is a schematic diagram of the effect of the vehicle body inclination angle on acceleration in this application;

[0049] Fig.11 This is a force analysis diagram of the vehicle when the vehicle encounters an uneven road surface on the test road in this application;

[0050] Fig.12 This is a schematic diagram of the module structure of the vehicle braking acceleration curve measuring device according to an embodiment of the present application;

[0051] Fig.13 This is a schematic diagram of the device structure of the hardware operating environment involved in the automobile braking acceleration curve measurement method in the embodiment of the present application.

[0052] The purpose, features and advantages of this application will be further described in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0053] It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the present application and are not used to limit the present application.

[0054] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0055] The main solutions of the embodiments of the present application are: collecting the spatial acceleration corresponding to the spatial inclination angle during the vehicle's driving process; measuring the friction acceleration generated by the friction force exerted on the vehicle by a variable mass measurement method; measuring the wind resistance acceleration generated by the wind resistance exerted on the vehicle by a wind tunnel test; linearly superimposing the spatial acceleration, friction acceleration and wind resistance acceleration to obtain a regulated engine braking acceleration curve.

[0056] The measurement of the vehicle acceleration G-value curve refers to recording the acceleration changes during the vehicle's driving process by accelerating and braking the vehicle, and drawing a vehicle G-value curve to evaluate the vehicle's power performance and handling performance. In addition, in order to improve the handling performance of the vehicle, automobile manufacturers are constantly exploring new technical means, including lightweighting the vehicle, improving the suspension system and braking system, and increasing the engine power, all of which need to be verified and evaluated based on the measurement of the vehicle G-value curve. At present, the measurement of the vehicle G-value curve has become an indispensable technical means for evaluating vehicle performance. However, the measurement of the vehicle G-value curve often requires professional equipment and measurement procedures, and has a high degree of integration, and lacks portable collection devices suitable for a variety of vehicle models. There is a lack of an effective description method for the acceleration G-value curve under the action of engine braking alone.

[0057] The present application provides a solution, by collecting the spatial acceleration corresponding to the spatial inclination angle of the vehicle during driving; measuring the friction acceleration generated by the friction force on the vehicle through the variable mass measurement method; measuring the wind resistance acceleration generated by the wind resistance on the vehicle through wind tunnel testing; linearly superimposing the spatial acceleration, friction acceleration and wind resistance acceleration to obtain the adjusted engine braking acceleration curve. The present application collects the spatial acceleration corresponding to the spatial inclination angle of the vehicle during driving through a portable acceleration curve acquisition device; linearly superimposes the spatial acceleration, friction acceleration and wind resistance acceleration to eliminate the influence of factors such as wind resistance and ground friction on the acceleration measurement results during driving, and obtains the acceleration curve of the fuel vehicle under the action of engine braking alone after adjustment, which can be used to optimize the regenerative braking control strategy of electric vehicles.

[0058] It should be noted that the execution subject of the method of this embodiment can be a portable acceleration curve acquisition device with automobile braking acceleration curve measurement, network communication and program running functions; it can also be an automobile braking acceleration curve measurement device with the same or similar functions, or it can be a car equipped with the above-mentioned automobile braking acceleration curve measurement device. This embodiment and the following embodiments will be described by taking the automobile braking acceleration curve measurement device as an example.

[0059] Based on this, the embodiment of the present application provides a method for measuring a vehicle braking acceleration curve, referring to Figure 1 , Figure 1 This is a flow chart of the first embodiment of the vehicle braking acceleration curve measurement method of the present application.

[0060] In this embodiment, the vehicle braking acceleration curve measurement method includes steps S10 to S40:

[0061] Step S10, collecting the spatial acceleration corresponding to the spatial inclination angle during the vehicle's driving process.

[0062] It can be understood that this embodiment uses a portable acquisition device suitable for various vehicle models to obtain the acceleration curve of the vehicle after the accelerator pedal is released, processes the acceleration data collected by the sensor, and obtains the acceleration curve of the fuel vehicle under the action of engine braking alone after adjustment. The flow of the measurement method is explained with reference to the figure, Figure 2 This is the overall flow chart of the automobile braking acceleration curve measurement method of this application. In the development of the acquisition device, a throttle (electric switch) release detection mechanism is designed to use the release signal as the acquisition trigger signal of the angle sensor and the acceleration sensor to respectively collect the spatial inclination angle and the corresponding spatial acceleration during the vehicle's driving process, wherein the acceleration sensor needs to fully consider the influence of the sensor's fixed position and initial fixed angle. After saving the collected data, the acceleration value is adjusted, and the acceleration of the vehicle caused by ground friction is obtained by the variable mass measurement method. The wind resistance coefficient is obtained through wind tunnel testing, and then the acceleration of the vehicle caused by wind resistance is obtained. Combining the above contents, the adjusted engine braking acceleration curve is finally obtained according to the principle of linear superposition, so as to be used for the optimization of the regenerative braking control strategy of electric vehicles.

[0063] It should be noted that this embodiment provides a portable data acquisition device suitable for a variety of vehicle models. The appropriate sensor fixing position and angle are selected. Since the vibration and vehicle noise are large during the speed measurement process, it may affect the actual data. It is recommended to place it in the central position of the passenger compartment in the car. This can facilitate the calibration and testing of the device, and at the same time reduce the impact of the external environment on the speed measurement device, so that the sensor acquisition is as accurate as possible and the inaccurate measured value caused by angle deviation is reduced. The components of gravity acceleration in all directions at static state should also be measured to calculate the pitch angle and roll angle of the current inertial measurement unit to the road surface; a convenient and easy-to-use sensor triggering strategy should be designed to reduce the manual participation in the measurement process to reduce the error caused by human factors and make the measurement more accurate.

[0064] In the specific implementation, please refer to Figure 3 The hardware design block diagram of the acceleration acquisition device is used to illustrate the acceleration acquisition device. Among them, the single-chip microcomputer is responsible for data forwarding and data preprocessing, and communicates with the throttle (accelerator) sensor side through the Bluetooth module to accurately obtain the current throttle release time. The Bluetooth module communicates with the IMU inertial unit to obtain the real-time acceleration and angle information after the throttle is released. After obtaining the data, the real acceleration component is calculated in real time and the original data and fitting data are recorded. The fitting data is made more accurate by changing the vehicle body load. At the same time, the data is displayed on the observer's mobile phone in the form of a web page through the WiFi module, and the measurement results are displayed in real time.

[0065] It is understandable that the throttle sensor can use an infrared distance module, and by setting a threshold, it starts recording acceleration data when the distance exceeds the threshold and transmits it back to the microcontroller through the Bluetooth module. Figure 4 .

[0066] In addition, the mobile phone can also connect to the WiFi signal sent by the local microcontroller, enter the corresponding web page to view real-time data, or open the dedicated App to view the downloaded data. The mobile phone APP data display diagram can be referred to Figure 5 .

[0067] In a feasible implementation, step S10 may include steps S101 to S103:

[0068] Step S101, collecting acceleration information, angle information and magnetic value through the IMU inertial unit.

[0069] Step S102, fusing the acceleration information, the angle information and the magnetic value through a nine-axis fusion algorithm to obtain a spatial inclination angle during vehicle driving.

[0070] Step S103: correcting the acceleration information according to the spatial inclination angle to obtain the spatial acceleration corresponding to the spatial inclination angle.

[0071] It should be understood that the IMU inertial unit can use the JY901 sensor, which is a nine-axis sensor that integrates a three-axis velocity sensor, a three-axis acceleration sensor, and a three-axis magnetometer. The nine-axis fusion algorithm can be used to obtain accurate angle data. The accurate angle data can be used to correct the acceleration measurement error caused by installation errors and vehicle body tilt during movement. The specific data of this module is shown in Table 1 below. The JY901 sensor data set processing flow can be referred to Figure 6 .

[0072] Table 1 JY901 accelerometer parameters

[0073]

[0074]

[0075] In this implementation, acceleration information, angle information and magnetic value are collected by the IMU inertial unit, and accurate angle data is obtained using a nine-axis fusion algorithm. The accurate angle data can correct the acceleration measurement error caused by installation errors and vehicle body tilt during movement.

[0076] Step S20, measuring the friction acceleration generated by the friction force applied to the vehicle by a variable mass measurement method.

[0077] Step S30, measuring the wind resistance acceleration generated by the wind resistance on the vehicle through a wind tunnel test.

[0078] Step S40: linearly superimpose the spatial acceleration, friction acceleration and wind resistance acceleration to obtain a regulated engine braking acceleration curve.

[0079] It can be understood that the acceleration value can be adjusted after the collected data is saved, and the acceleration of the ground friction on the vehicle can be obtained by using the variable mass measurement method. The drag coefficient can be obtained through wind tunnel testing and then the acceleration of the wind resistance on the vehicle can be obtained. Combining the above contents and according to the principle of linear superposition, the adjusted engine braking acceleration curve can be finally obtained for future use in the optimization of electric vehicle regenerative braking control strategies.

[0080] This embodiment provides a method for measuring the braking acceleration curve of an automobile, which collects the spatial acceleration corresponding to the spatial inclination angle during the driving process of the vehicle; measures the friction acceleration generated by the friction force on the vehicle through the variable mass measurement method; measures the wind resistance acceleration generated by the wind resistance on the vehicle through a wind tunnel test; linearly superimposes the spatial acceleration, friction acceleration and wind resistance acceleration to obtain a calibrated engine braking acceleration curve. This embodiment collects the spatial acceleration corresponding to the spatial inclination angle during the driving process of the vehicle through a portable acceleration curve acquisition device; linearly superimposes the spatial acceleration, friction acceleration and wind resistance acceleration to eliminate the influence of factors such as wind resistance and ground friction on the acceleration measurement results during driving, and obtains the acceleration curve of a fuel vehicle under the action of engine braking alone after calibration, which can be used to optimize the regenerative braking control strategy of electric vehicles.

[0081] Based on the first embodiment of the present application, in the second embodiment of the present application, the same or similar contents as those in the above-mentioned embodiment 1 can refer to the above introduction, and will not be repeated later. Figure 7 , step S20, the vehicle braking acceleration curve measurement method further includes steps S201 to S203:

[0082] Step S201, determining the friction force relationship between the total mass of the vehicle and the dynamic friction coefficient in a preset number of experiments by a variable mass measurement method.

[0083] It is understandable that the acceleration data collected by the sensor can be processed in this embodiment to eliminate the influence of factors such as wind resistance and ground friction on the acceleration measurement results during driving, and the acceleration curve of the fuel vehicle under the engine braking alone can be obtained after adjustment. Factors such as wind resistance and ground friction will cause the measured acceleration to be not completely parallel to the road surface, resulting in inaccurate measurement data, and will also cause the measured acceleration to contain not only the acceleration of engine braking but also the acceleration caused by other resistances. Using inaccurate data on electric vehicles will cause the acceleration G value to be too large during deceleration. Therefore, by changing the mass of the vehicle body, measuring multiple times, etc., the influence of friction, wind resistance, etc. can be eliminated to obtain a more accurate engine braking acceleration G value.

[0084] It should be understood that the engine braking acceleration can be indirectly measured using the variable mass method. RB , wind resistance F w , friction resistance F f like Figure 8 When the vehicle load is changed, F f The wind resistance will also change accordingly, while the rolling friction is related to the tire material, contact surface conditions, etc., and has nothing to do with the load. Therefore, the resistance component in the measured acceleration can be eliminated.

[0085] In the specific implementation, two experiments are taken as examples for explanation. Let m1 and m2 be the total mass in the two experiments, μ be the kinetic friction coefficient, g be the gravitational acceleration, and the friction force relationship obtained from Newton's second law is as shown in formula (1):

[0086]

[0087] Step S202, determining the total force relationship between the total mass of the vehicle, the acceleration measurement values ​​in the preset number of experiments, the wind resistance, the friction force relationship and the engine braking force.

[0088] It should be noted that if the acceleration measurement values ​​in the two experiments are a1 and a2 respectively, F w is the wind resistance of the vehicle, F RB is the engine braking force of the vehicle, then the total force relationship can be obtained as shown in the following formula (2):

[0089]

[0090] Step S203: determining the friction acceleration according to the friction force relationship and the total force relationship.

[0091] It should be understood that by simplifying the above formulas (1) and (2), the friction acceleration can be obtained as shown in formula (3):

[0092]

[0093] In a feasible implementation, step S40 may include steps S401 to S402:

[0094] Step S401: determining the acceleration relationship between the wind resistance acceleration and the engine braking acceleration according to the friction acceleration and the total force relationship.

[0095] It can be understood that, according to the friction acceleration shown in the above formula (3) and the total force relationship shown in formula (2), the acceleration relationship between the wind resistance acceleration and the engine braking acceleration can be obtained as shown in formula (4):

[0096]

[0097] Among them, a w is the acceleration caused by wind resistance acting on the vehicle body, a RB It is the engine braking acceleration.

[0098] Step S402, determining the engine braking acceleration according to the acceleration relationship, and determining a calibrated engine braking acceleration curve according to the engine braking acceleration.

[0099] It should be understood that wind resistance does not change for the same vehicle, and rolling friction is related to the tire material, contact surface conditions, etc., and has nothing to do with the load, so the resistance component in the measured acceleration can be eliminated. Therefore, the wind resistance acceleration can be expressed as formula (5):

[0100]

[0101] Among them, a w Represents the acceleration of the vehicle body under the effect of wind resistance, C w represents the drag coefficient, ρ represents the air density, S represents the projection area of ​​the front of the vehicle, v represents the vehicle speed, and m represents the vehicle mass.

[0102] According to formula (5) and formula (4), the engine braking acceleration a can be obtained: RB As shown in formula (6):

[0103]

[0104] The engine braking acceleration is determined according to the acceleration relationship, and then a tuned engine braking acceleration curve is determined according to the obtained engine braking acceleration.

[0105] In this embodiment, the relationship between the wind resistance acceleration and the engine braking acceleration can be obtained by transforming the friction acceleration and the total force relationship, thereby eliminating the influence of factors such as wind resistance and ground friction on the acceleration measurement results during driving, thereby obtaining a more accurate engine braking acceleration.

[0106] In this embodiment, since the friction force will also change when the vehicle weight is changed, the mass of the vehicle is changed by the variable mass measurement method, and the total mass of the vehicle and the acceleration measurement value are combined with Newton's second law to calculate the friction acceleration.

[0107] Based on the first embodiment of the present application, in the third embodiment of the present application, the same or similar contents as those in the first embodiment can be referred to the above description, and will not be described in detail later. Fig. 9 , step S40, the vehicle braking acceleration curve measurement method further includes steps S403-S404:

[0108] Step S403, determining the engine braking acceleration according to the acceleration relationship, and correcting the engine braking acceleration according to the spatial inclination angle to obtain a corrected engine braking acceleration.

[0109] Step S404, determining a calibrated engine brake acceleration curve according to the actual coordinate system conversion matrix and the corrected engine brake acceleration.

[0110] It is understandable that when the vehicle engine brakes, the vehicle will tilt forward due to the backward resistance. The effect of the vehicle tilt angle on acceleration can be referred to Fig.10 , Fig.10 This is a schematic diagram of the effect of the vehicle body inclination angle on acceleration in this application. In the figure, g represents the vertical downward acceleration of the vehicle when stationary, g' is the measured gravity acceleration when the vehicle body is tilted forward, a represents the acceleration during engine braking, and a' represents the acceleration after the vehicle body is tilted during engine braking. At this time, the acceleration value a' measured by the nine-axis sensor will produce an error due to the existence of θ. The nine-axis sensor can measure this tiny pitch angle θ, so at this time, a can be corrected by known data.

[0111] a=a′cosθ (7)

[0112] In order to obtain accurate vehicle acceleration, it is usually necessary to ensure that the test road surface remains level throughout the entire process, without small ups and downs, to avoid the influence of gravity on vehicle acceleration. The influence of gravity on acceleration can be referred to Fig.11 , Fig.11 This is a schematic diagram of the effect of gravity on acceleration in this application. However, this approach is costly and inconvenient. When a vehicle passes uphill or downhill during driving, the nine-axis sensor can measure the pitch angle of the vehicle during this process. Then, the known data is corrected to eliminate the influence of gravity on acceleration, so as to obtain an accurate acceleration value. When the nine-axis sensor collects vehicle uphill data, the corresponding pitch angle is positive, and when it is downhill, it is negative, which is convenient for program processing.

[0113]

[0114] Based on the deceleration data obtained through processing and analysis, a deceleration model is developed to simulate the deceleration curve of the car. Based on the characteristics and rules of the deceleration data, a deceleration model is established by physical simulation or mathematical modeling, and the model is verified and optimized. Then, the adjusted engine brake acceleration curve is determined based on the actual coordinate system conversion matrix and the corrected engine brake acceleration.

[0115] In a feasible implementation manner, before step S404, steps A10 to A30 may also be included:

[0116] Step A10, obtaining the rotation angles of the vehicle in the X-axis, Y-axis and Z-axis directions in the preset coordinate system collected by the IMU inertial unit, and establishing a theoretical coordinate system conversion matrix according to the rotation angles.

[0117] It should be noted that the data collected by the IMU inertial unit is obtained, and the angular velocity of rotation in three directions is read by the JY901 sensor. Assume that the angle between the X-axis and the vehicle's forward direction or the direction horizontally perpendicular to the forward direction is α, the angle between the Y-axis and the vehicle's forward direction or the direction horizontally perpendicular to the forward direction is β, and the angle between the Z-axis and the vehicle's forward direction or the direction horizontally perpendicular to the forward direction is γ; where γ=0, the theoretical coordinate system conversion matrix is:

[0118]

[0119] Step A20, obtaining the acceleration values ​​of the vehicle in the X-axis, Y-axis and Z-axis directions in the preset coordinate system collected by the IMU inertial unit, and determining the angular relationship between the acceleration value and the rotation angle.

[0120] It can be understood that when the acceleration sensor is in a stable state, the acceleration values ​​detected by the acceleration sensor on the X-axis, Y-axis and Z-axis are respectively the components g of the gravity acceleration g x , g y and g z , then:

[0121]

[0122] Step A30, transforming the theoretical coordinate system transformation matrix according to the angle relationship to obtain an actual coordinate system transformation matrix.

[0123] It can be understood that, according to the angle relationship of the above formula (10) and the theoretical coordinate system transformation matrix of formula (9), the actual coordinate system transformation matrix can be obtained as:

[0124]

[0125] In this embodiment, when the vehicle engine brakes, the vehicle body will tilt forward due to the backward resistance. The engine braking acceleration is corrected according to the spatial tilt angle generated by the vehicle body tilting forward, and then the adjusted engine braking acceleration curve is obtained by combining the actual coordinate system conversion matrix.

[0126] It should be noted that the above examples are only used to understand the present application and do not constitute a limitation on the automobile braking acceleration curve measurement method of the present application. More simple transformations based on this technical concept are all within the protection scope of the present application.

[0127] This application also provides a vehicle braking acceleration curve measurement device, please refer to Fig.12 , the vehicle braking acceleration curve measuring device comprises:

[0128] The spatial acceleration acquisition module 10 is used to acquire the spatial acceleration corresponding to the spatial inclination angle during the vehicle's driving process;

[0129] The friction acceleration measurement module 20 is used to measure the friction acceleration generated by the friction force on the vehicle by a variable mass measurement method;

[0130] The wind resistance acceleration measurement module 30 is used to measure the wind resistance acceleration generated by the wind resistance of the vehicle through a wind tunnel test;

[0131] The acceleration setting module 40 is used to linearly superimpose the spatial acceleration, the friction acceleration and the wind resistance acceleration to obtain a set engine braking acceleration curve.

[0132] The automobile braking acceleration curve measuring device provided by the present application adopts the automobile braking acceleration curve measuring method in the above embodiment to solve the technical problem. Compared with the prior art, the beneficial effects of the automobile braking acceleration curve measuring device provided by the present application are the same as the beneficial effects of the automobile braking acceleration curve measuring method provided by the above embodiment, and other technical features in the automobile braking acceleration curve measuring device are the same as the features disclosed in the above embodiment method, which will not be repeated here.

[0133] The present application provides a vehicle braking acceleration curve measuring device, which includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the vehicle braking acceleration curve measuring method in the above-mentioned embodiment one.

[0134] Reference below Fig.13 , which shows a schematic diagram of the structure of a vehicle braking acceleration curve measuring device suitable for implementing the embodiment of the present application. The vehicle braking acceleration curve measuring device in the embodiment of the present application may include but is not limited to mobile terminals such as mobile phones, laptop computers, digital broadcast receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Descriptions), PMPs (Portable Media Players), vehicle-mounted terminals (such as vehicle-mounted navigation terminals), etc., and fixed terminals such as digital TVs, desktop computers, etc. Fig.13 The vehicle braking acceleration curve measuring device shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present application.

[0135] like Fig.13As shown, the automobile braking acceleration curve measuring device may include a processing device 1001 (such as a central processing unit, a graphics processing unit, etc.), which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM: Read Only Memory) 1002 or a program loaded from a storage device 1003 to a random access memory (RAM: Random Access Memory) 1004. In RAM1004, various programs and data required for the operation of the automobile braking acceleration curve measuring device are also stored. The processing device 1001, ROM1002 and RAM1004 are connected to each other through a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems can be connected to the I / O interface 1006: input devices 1007 including, for example, a touch screen, a touchpad, a keyboard, a mouse, an image sensor, a microphone, an accelerometer, a gyroscope, etc.; output devices 1008 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; storage devices 1003 including, for example, a magnetic tape, a hard disk, etc.; and communication devices 1009. The communication device 1009 can allow the automobile braking acceleration curve measurement device to communicate wirelessly or wired with other devices to exchange data. Although the figure shows an automobile braking acceleration curve measurement device with various systems, it should be understood that it is not required to implement or have all the systems shown. More or fewer systems may be implemented or have alternatively.

[0136] In particular, according to the embodiments disclosed in the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, the embodiments disclosed in the present application include a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes a program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network through a communication device, or installed from a storage device 1003, or installed from a ROM 1002. When the computer program is executed by the processing device 1001, the above-mentioned functions defined in the method of the embodiment disclosed in the present application are executed.

[0137] The automobile braking acceleration curve measuring device provided by the present application adopts the automobile braking acceleration curve measuring method in the above embodiment, which can solve the technical problem of automobile braking acceleration curve measuring. Compared with the prior art, the beneficial effect of the automobile braking acceleration curve measuring device provided by the present application is the same as the beneficial effect of the automobile braking acceleration curve measuring method provided by the above embodiment, and the other technical features in the automobile braking acceleration curve measuring device are the same as the features disclosed in the method of the previous embodiment, which will not be repeated here.

[0138] It should be understood that the various parts disclosed in this application can be implemented by hardware, software, firmware or a combination thereof. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0139] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0140] The present application provides a computer-readable storage medium having computer-readable program instructions (ie, computer programs) stored thereon, and the computer-readable program instructions are used to execute the vehicle braking acceleration curve measurement method in the above-mentioned embodiment.

[0141] The computer-readable storage medium provided in the present application may be, for example, a USB flash drive, but is not limited to electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, systems or devices, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this embodiment, the computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in combination with an instruction execution system, system or device. The program code contained on the computer-readable storage medium may be transmitted using any appropriate medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination of the above.

[0142] The computer-readable storage medium may be included in the vehicle braking acceleration curve measuring device; or may exist independently without being assembled into the vehicle braking acceleration curve measuring device.

[0143] The computer-readable storage medium carries one or more programs. When the one or more programs are executed by the automobile braking acceleration curve measuring device, the automobile braking acceleration curve measuring device: collects the spatial acceleration corresponding to the spatial inclination angle during the vehicle's driving process; measures the friction acceleration generated by the friction force exerted on the vehicle through a variable mass measurement method; measures the wind resistance acceleration generated by the wind resistance exerted on the vehicle through a wind tunnel test; and linearly superimposes the spatial acceleration, friction acceleration and wind resistance acceleration to obtain a calibrated engine braking acceleration curve.

[0144] Computer program code for performing the operations of the present application may be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0145] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the system, method and computer program product according to various embodiments of the present application. In this regard, each square box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the square box can also occur in a sequence different from that marked in the accompanying drawings. For example, two square boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each square box in the block diagram and / or flow chart, and the combination of the square boxes in the block diagram and / or flow chart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0146] The modules involved in the embodiments described in this application may be implemented by software or hardware, wherein the name of the module does not constitute a limitation on the unit itself in some cases.

[0147] The readable storage medium provided by the present application is a computer-readable storage medium, which stores computer-readable program instructions (i.e., computer programs) for executing the above-mentioned automobile braking acceleration curve measurement method, and can solve technical problems. Compared with the prior art, the beneficial effects of the computer-readable storage medium provided by the present application are the same as the beneficial effects of the automobile braking acceleration curve measurement method provided by the above-mentioned embodiment, and will not be repeated here.

[0148] The present application also provides a computer program product, including a computer program, which implements the steps of the above-mentioned vehicle braking acceleration curve measurement method when executed by a processor.

[0149] The computer program product provided by the present application can solve the technical problem. Compared with the prior art, the beneficial effects of the computer program product provided by the present application are the same as the beneficial effects of the automobile braking acceleration curve measurement method provided by the above embodiment, which will not be described in detail here.

[0150] The above descriptions are only some embodiments of the present application, and are not intended to limit the patent scope of the present application. All equivalent structural changes made using the contents of the present application specification and drawings under the technical concept of the present application, or direct / indirect applications in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A method for measuring a vehicle braking acceleration curve, characterized in that: The method includes: Collect the spatial acceleration corresponding to the spatial inclination of the vehicle during driving; The friction acceleration generated by the friction force on the vehicle is measured by the variable mass measurement method; The wind resistance acceleration generated by the wind resistance on the vehicle is measured through wind tunnel testing; The spatial acceleration, the friction acceleration and the wind resistance acceleration are linearly superimposed to obtain a regulated engine braking acceleration curve.

2. The method according to claim 1, characterized in that The step of collecting the spatial acceleration corresponding to the spatial inclination angle during the vehicle's driving process includes: Collect acceleration information, angle information and magnetic value through IMU inertial unit; The acceleration information, the angle information and the magnetic value are integrated through a nine-axis fusion algorithm to obtain a spatial inclination angle during vehicle driving; The acceleration information is corrected according to the spatial inclination angle to obtain the spatial acceleration corresponding to the spatial inclination angle.

3. The method according to claim 1, characterized in that The step of measuring the friction acceleration generated by the friction force applied to the vehicle by the variable mass measurement method comprises: Determine the friction force relationship between the total mass of the vehicle and the dynamic friction coefficient in a preset number of experiments by a variable mass measurement method; Determining the total force relationship between the total mass of the vehicle, the acceleration measurement values ​​in the predetermined number of experiments, the wind resistance, the friction force relationship and the engine braking force; The friction acceleration is determined according to the friction force relationship and the total force relationship.

4. The method according to claim 3, characterized in that The step of linearly superimposing the spatial acceleration, the friction acceleration and the wind resistance acceleration to obtain a regulated engine braking acceleration curve comprises: Determining the acceleration relationship between the wind resistance acceleration and the engine braking acceleration according to the friction acceleration and the total force relationship; An engine braking acceleration is determined according to the acceleration relationship, and a regulated engine braking acceleration curve is determined according to the engine braking acceleration.

5. The method according to claim 4, characterized in that The step of determining the engine braking acceleration according to the acceleration relationship and determining a set engine braking acceleration curve according to the engine braking acceleration comprises: determining an engine braking acceleration according to the acceleration relationship, and correcting the engine braking acceleration according to the spatial inclination angle to obtain a corrected engine braking acceleration; The adjusted engine brake acceleration curve is determined according to the actual coordinate system conversion matrix and the corrected engine brake acceleration.

6. The method according to claim 5, characterized in that Before the step of determining the adjusted engine brake acceleration curve according to the actual coordinate system conversion matrix and the corrected engine brake acceleration, the method further includes: Obtain the rotation angles of the vehicle in the X-axis, Y-axis and Z-axis directions in the preset coordinate system collected by the IMU inertial unit, and establish a theoretical coordinate system conversion matrix based on the rotation angles; Obtain acceleration values ​​of the vehicle in the X-axis, Y-axis and Z-axis directions in a preset coordinate system collected by an IMU inertial unit, and determine an angular relationship between the acceleration value and the rotation angle; The theoretical coordinate system conversion matrix is ​​converted according to the angular relationship to obtain an actual coordinate system conversion matrix.

7. A vehicle braking acceleration curve measuring device, characterized in that: The automobile braking acceleration curve measuring device comprises: The spatial acceleration acquisition module is used to acquire the spatial acceleration corresponding to the spatial inclination angle during the vehicle's driving process; A friction acceleration measurement module, used to measure the friction acceleration generated by the friction force on the vehicle through a variable mass measurement method; Wind resistance acceleration measurement module, used to measure the wind resistance acceleration generated by the wind resistance on the vehicle through wind tunnel testing; The acceleration setting module is used to linearly superimpose the spatial acceleration, friction acceleration and wind resistance acceleration to obtain a set engine braking acceleration curve.

8. A vehicle braking acceleration curve measuring device, characterized in that: The device comprises: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the vehicle braking acceleration curve measurement method according to any one of claims 1 to 6.

9. A storage medium, characterized in that: The storage medium is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, the steps of the vehicle braking acceleration curve measurement method according to any one of claims 1 to 6 are implemented.

10. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor, the steps of the vehicle braking acceleration curve measurement method according to any one of claims 1 to 6 are implemented.

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