Method for measuring the ice cornering characteristics of tires, system for generating data related to the ice cornering characteristics of tires, and program.

Abstract

To provide a technique for properly measuring cornering properties of a tire when mounted on a vehicle.SOLUTION: A measurement method of cornering properties of a tire includes: executing a measurement step of turning a vehicle, to which a sensor is fitted for detecting measurement values capable of deriving a vehicle lateral acceleration, an angular speed, a speed, a vehicle slip angle, and a steering angle, until the vehicle becomes a prescribed steering angle from a straight travel state, and detecting measurement values at multiple time points in turning by the sensor; calculating a slip angle of the tire at each time point, on the basis of the steering angle and the vehicle slip angle on each time point; calculating lateral force applied to a front wheel tire in each time point, on the basis of the speed, the vehicle lateral acceleration, the angular speed, and the slip angle of the tire in each time point; and generating data related to the cornering properties of the tire, on the basis of the lateral force and the slip angle of the tire in each of the multiple time points.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This disclosure relates to a method for measuring the ice cornering characteristics of a tire, a system for generating data related to the ice cornering characteristics of a tire, and a program. [Background technology]

[0002] Traditionally, vehicle cornering performance has been evaluated using subjective driver feedback. However, because subjective feedback relies on human perception, it is prone to variability in results, and the relationship between the evaluation results and the physical quantities to be evaluated is often ambiguous, making it difficult to utilize in tire design. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-147409 [Overview of the project] [Problems that the invention aims to solve]

[0004] Patent Document 1 describes a technique for determining an index indicating turning performance, including vehicle performance, based on the detected lateral acceleration and yaw rate of a vehicle that is turned at a constant radius on an icy road surface. However, although an index can be obtained, the index is not related to physical quantities, so it is not possible to obtain the cornering characteristics of the tire (for example, a cornering curve that shows the relationship between cornering force and tire slip angle).

[0005] On the other hand, one method for measuring the cornering characteristics of a tire is to use a bench test machine, which runs the tire on a stand. However, it is difficult to create a long-distance ice surface to reproduce ice cornering on a bench test machine and to take measurements. Furthermore, even if an ice surface is formed on the inner drum and measurements are taken, the contact surface is not flat but has a curved shape corresponding to the diameter of the drum, making it impossible to accurately measure the ice cornering characteristics of a tire when it is mounted on an actual vehicle.

[0006] Another method involves using a wheel-mounted force sensor with a 6-component force gauge, which allows for the measurement of forces acting on the tire. However, this requires changing the rim for each tire, and there is a risk that road conditions may change during the changeover, making it difficult to conduct tests under consistent conditions. Furthermore, the mass of the 6-component force gauge wheel itself and the mass of the amplifiers may cause the tire load and wheel alignment to differ from those when using a typical wheel.

[0007] This disclosure provides a technology that enables the appropriate measurement of the cornering characteristics of tires when they are mounted on an actual vehicle. [Means for solving the problem]

[0008] The method for measuring the cornering characteristics of a tire according to the present disclosure includes: performing a measurement step of turning a vehicle equipped with a sensor that can detect measured values ​​from which vehicle lateral acceleration, angular velocity, speed, vehicle slip angle and steering angle can be derived, from a straight-line driving state until a predetermined steering angle is reached, and detecting the measured values ​​at multiple points in time during the turn with the sensor; calculating the slip angle of the tire at each of the aforementioned points in time based on the steering angle and vehicle slip angle at each of the aforementioned points in time; calculating the lateral force acting on the front tire at each of the aforementioned points in time based on the speed, vehicle lateral acceleration, angular velocity and the slip angle of the tire at each of the aforementioned points in time; and generating data relating to the cornering characteristics of the tire based on the lateral force and the slip angle of the tire at each of the multiple points in time. [Brief explanation of the drawing]

[0009] [Figure 1] Block diagram showing the configuration of the system of the present embodiment. [Figure 2] Explanatory diagram in plan view of the sensor 3 attached to the vehicle 2. [Figure 3] Flowchart showing a method for measuring the cornering characteristics of a tire. [Figure 4] Graph showing the speed of the vehicle over time. [Figure 5] Graph showing the steering angle over time. [Figure 6] Graph showing the calculated slip angle of the front wheel tire over time. [Figure 7] Graph showing the calculated lateral force Ff of the tire over time. [Figure 8] Diagram showing a simplified vehicle model with four wheels divided into two front wheels and two rear wheels. [[ID=二十六]] [Figure 9] Diagram showing the lateral force Ff acting on the tire on the vertical axis and the slip angle of the tire on the horizontal axis.

Mode for Carrying Out the Invention

[0010] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0011] [System] The system of the present embodiment is used to measure the ice cornering characteristics of a tire. The ice cornering characteristics of a tire can be expressed, for example, by a cornering curve showing the relationship between the cornering force and the slip angle of the tire. As shown in FIG. 1, the system includes a processing unit 1 that processes the detection results of the sensor 3 attached to the vehicle 2. The processing unit 1 generates data related to the ice cornering characteristics of the tire based on the detection results of the sensor 3. The processing unit 1 may be implemented by one computer or by one or more computers in the cloud.

[0012] Figure 2 is a plan view diagram illustrating the sensor 3 attached to vehicle 2. In this embodiment, the sensor 3 is attached to vehicle 2, which is a truck (a four-wheeled vehicle), but it is not limited to this and may be attached to a passenger car. The measured values ​​detected by the sensor 3 can be any physical quantities from which the acceleration, angular velocity, speed, vehicle slip angle, and steering angle of vehicle 2 can be derived. Figure 2 shows a right turn state in which the front tires 20 are turned to the right, and schematically shows the position of the sensor 3 installed on vehicle 2. The sensor 3 in this embodiment includes an acceleration sensor 30, an angular velocity sensor 31, a steering angle meter 32, an optical vehicle slip angle meter 33, and two GPS devices (34) installed at the front and rear of the vehicle as speedometers. The acceleration sensor 30 provides the vertical, lateral (left-right), and longitudinal acceleration of vehicle 2. The angular velocity sensor 31 provides the vertical, lateral, and longitudinal angular velocity of vehicle 2. The steering angle meter 32 provides the steering angle, which is the rotation angle of the steering wheel. The vehicle slip angle is obtained from the vehicle slip angle meter 33. The vehicle speed is obtained from the GPS (34). Specific examples of the sensors 3 can be changed in various ways and are not limited to these combinations. The measured values ​​detected by the sensors 3 (each sensor 30-34) are stored in the recording device 35 installed in the vehicle 2. In this embodiment, there is no force sensor to detect the force acting on the rim (wheel) into which the tire 20 is incorporated, no force sensor to detect the force acting on the axle supporting the wheel, and no sensor to directly measure the force acting on the tire.

[0013] As shown in Figure 1, the system's processing unit 1 includes an acquisition unit 10, a slip angle calculation unit 11, a lateral force calculation unit 12, and a data generation unit 13. These units 10 to 13 are realized through the collaborative action of software and hardware, with the processor 1a executing the processing routines shown in Figure 2, which are pre-stored in a computer equipped with a processor 1a, memory 1b, various interfaces, etc. In this embodiment, a single processor 1a in one device realizes each unit, but this is not limited to this. For example, it may be configured so that multiple processors distribute the processing using a network and execute the processing of each unit. That is, one or more processors execute the processing. Memory 1b stores measurement values ​​at multiple time points detected by sensor 3, vehicle specifications (vehicle mass, yaw moment of inertia, distance from center of gravity to front axle, distance from center of gravity to rear axle, etc.), the slip angle of the tire calculated by the slip angle calculation unit 11, the lateral force acting on the tire calculated by the lateral force calculation unit 12, and data on the cornering characteristics of the tire generated by the data generation unit 13.

[0014] [Method for measuring the cornering characteristics of tires] Figure 3 will be used to explain the method for measuring the cornering characteristics of a tire.

[0015] In step ST1, the vehicle 2, to which the sensor 3 is attached, is turned on an icy surface from a straight-line driving state until it reaches a predetermined steering angle, and a measurement process is performed in which the sensor detects measurements at multiple points in time during the turn. In this embodiment, the vehicle 2, which is driving straight at a speed of approximately 8 km / h, is turned by turning the steering wheel so that the amount of change in the steering angle per unit time remains constant from 0 degrees to 720 degrees (approximately 2 turns of the steering wheel). Approximately 7.5 seconds elapsed until the steering angle reached the predetermined steering angle. Although the goal is to make the amount of change in the steering angle constant, it is not strictly constant because it is done manually. The sensor 3 takes measurements at multiple measurement points at 0.01-second intervals. In this embodiment, the vehicle 2 is turned on an icy surface during the measurement process.

[0016] In the next step, ST2, the system's acquisition unit 10 acquires measurement values ​​at multiple points in time detected by the sensor 3 during the turn. The acquired measurement values ​​are stored in memory 1b. The acquisition unit 10 may receive measurement values ​​from a recording device 35 connected to the system by the user, or it may be connected to the recording device 35 via a network so as to be able to communicate and acquire measurement values ​​automatically. Figure 4 is a graph showing the vehicle speed over time. Figure 5 is a graph showing the steering angle over time.

[0017] In the next step, ST3, the slip angle calculation unit 11 calculates the tire slip angle at each point in time based on the steering angle and vehicle slip angle at each point in time. The vehicle slip angle (vehicle slip angle at the center of gravity of vehicle 2) represents the angle β between the direction of the velocity vector at the center of gravity of vehicle 2 (direction of travel of vehicle 2) and the direction of vehicle 2 (forward), as shown in Figure 8. Since the direction of the tires relative to the vehicle is determined by the steering angle, the direction of the tires (angle) is identified (or calculated) from the steering angle based on data that has been pre-associated with the direction (angle) of the tires relative to the vehicle and the steering angle. Since the mounting position of the vehicle slip angle meter 33 is predetermined, the vehicle slip angle at the tire position can be determined from the measurement data of the vehicle slip angle meter 33 and the geometric relationship of circular turning in automotive engineering. Then, by calculating the slip angle at the front tire position and the direction of the tire (angle δ), the tire slip angle, which represents the angle between the direction of travel of the tire (which is also the direction of travel of the vehicle) and the direction of the tire, can be calculated. The calculated tire slip angle at each point in time is stored in memory 1b. Figure 6 is a graph showing the calculated front tire slip angle over time.

[0018] In the next step, ST4, the lateral force calculation unit 12 calculates the lateral force (cornering force) acting on the front tires at each point in time based on the velocity, vehicle lateral acceleration, angular velocity, and tire slip angle at each point in time. Lateral force F acting on the front tires f The calculation is performed using the vehicle's equation of motion (1).

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[0019] Equation (1) is derived from the lateral motion equation shown in Equation (2) and the rotational motion equation shown in Equation (3) based on the simplified vehicle model shown in FIG. 8. FIG. 8 is a diagram showing a simplified vehicle model with four wheels divided into two wheels, the front wheels and the rear wheels. In FIG. 8, the traveling direction of the vehicle is indicated by an arrow together with the speed V, the front wheels 20 are inclined at an angle δ to the right with respect to the direction of the vehicle, the angular velocity (yaw rate) at the center of gravity position G is indicated by γ, and the vehicle slip angle β is shown. The lateral force F f acting on the front wheels 20, the lateral force F r acting on the rear wheels 20', and the vehicle lateral acceleration A y are as shown in the figure. β’ in Equation (2) and γ’ in Equation (3) represent the differential values of the vehicle slip angle β and the yaw rate γ, respectively.

Number

[0020] In the next step ST5, the data generation unit 13 calculates the lateral force F acting on each tire at a plurality of time points fBased on the slip angle of the tire, data regarding the cornering characteristics of the tire is generated. As a specific example, the data generation unit 13 generates data on the lateral force F at each of multiple time points. f Furthermore, an approximate formula representing the relationship between the lateral force acting on the tire and the tire slip angle is fitted to the tire slip angle to obtain an approximate formula representing the tire's cornering curve. Specifically, the approximate formula using the magic formula shown in equation (4) is fitted to calculate coefficients A, B, C, and D. Since coefficient A relates to the maximum cornering force (CFMax value), it is possible to compare coefficient A for multiple tires. Coefficients B, C, and D are coefficients related to cornering stiffness, and these coefficients can explain how the force rises with respect to the tire slip angle.

number

[0021] Figure 9 shows the lateral force F acting on the tire on the vertical axis. f This figure shows the tire slip angle on the horizontal axis, with the measured values ​​at multiple points in time shown as points, and the dotted line representing the fitted approximation formula. In the example in Figure 9, the approximation formula is fitted to data collected in a single measurement process, but the approximation formula may also be fitted to data collected in multiple measurement processes. Doing so can improve accuracy.

[0022] [1] As described above, the tire cornering characteristics measurement method of this embodiment involves a vehicle 2 equipped with a sensor 3 that detects measurement values ​​from which vehicle lateral acceleration Ay, angular velocity γ, speed V, vehicle slip angle β, and steering angle can be derived, turning the vehicle 2 from a straight-line driving state until a predetermined steering angle is reached, and performing a measurement step of detecting measurement values ​​at multiple points in time during the turn with the sensor 3, calculating the tire slip angle at each point in time based on the steering angle and vehicle slip angle at each point in time, and calculating the speed V and vehicle lateral acceleration Ay at each point in time. yBased on the angular velocity γ and the tire slip angle, the lateral force F acting on the front tire at each point in time is calculated. f Calculating the lateral force F at each of the multiple time points. f This may include generating data on the cornering characteristics of the tire based on the tire slip angle.

[0023] Thus, even without using sensors that measure the forces acting on the tires, such as wheel force meters, if the vehicle's acceleration, angular velocity, speed, vehicle slip angle, and steering angle are measured using sensors, it is possible to calculate the lateral forces acting on the tires mounted on the actual vehicle and obtain a cornering curve.

[0024] [2] The method for measuring the cornering characteristics of a tire described in [1] above involves measuring the lateral force F at multiple points in time. f And the lateral force F acting on the tire with respect to the tire's slip angle. f This may further include fitting an approximate formula representing the relationship between the tire and the tire slip angle to obtain an approximate formula representing the tire's cornering curve. Since data composed of data at multiple points in time is discrete data, obtaining an approximation formula makes it easier to compare the cornering curves of multiple tires, thereby improving usability.

[0025] [3] In the method for measuring the cornering characteristics of a tire described in [2] above, the measurement step of measuring with the sensor 3 while turning the vehicle from a straight-ahead driving state until a predetermined steering angle is reached is performed multiple times, and the lateral force F acting on the tire is measured with respect to the measurement results obtained from the multiple measurement steps. f Alternatively, an approximate formula representing the relationship between the tire and the slip angle can be fitted to obtain an approximate formula representing the tire's cornering curve. By fitting the measurement results obtained from multiple measurement processes, it becomes possible to improve the accuracy of the resulting cornering curve.

[0026] [4] In the method for measuring the cornering characteristics of a tire described in [2] or [3] above, the approximation formula may be expressed as a magic formula. Alternatively, the approximation formula may be expressed by equation (4). Since coefficients A related to maximum cornering force (CFMax) and coefficients B, C, and D related to cornering stiffness are obtained, comparison with other tires becomes easier.

[0027] [5] The system that generates data on the cornering characteristics of the tires uses vehicle lateral acceleration A y A vehicle 2 equipped with a sensor 3 that detects measured values ​​from which angular velocity γ, speed V, vehicle slip angle β, and steering angle can be derived is turned from a straight-line driving state until a predetermined steering angle is reached, and an acquisition unit 10 acquires measured values ​​at multiple points in time detected by the sensor 3 during the turn, and a slip angle calculation unit 11 calculates the slip angle of the tires at each point in time based on the steering angle and vehicle slip angle β at each point in time, and the vehicle lateral acceleration A at each point in time y Based on the angular velocity γ and the tire slip angle, the lateral force F acting on the front tire at each point in time is calculated. f A lateral force calculation unit 12 calculates the lateral force F at each of multiple time points. f The system may also include a data generation unit 13 that generates data relating to the cornering characteristics of the tire based on the tire slip angle.

[0028] [6] The program is for vehicle lateral acceleration A y A vehicle 2 equipped with a sensor 3 that detects measured values ​​from which angular velocity γ, speed V, vehicle slip angle β, and steering angle can be derived is turned from a straight-line driving state until a predetermined steering angle is reached, and measured values ​​at multiple points in time detected by the sensor 3 during the turn are acquired, and the slip angle of the tires at each point in time is calculated based on the steering angle and vehicle slip angle β at each point in time, and the speed V and vehicle lateral acceleration A at each point in time are obtained. yBased on the angular velocity γ and the tire slip angle, the lateral force acting on the front tire at each point in time is calculated, as well as the lateral force F at each of the multiple point in time. f The process may involve generating data on the cornering characteristics of a tire based on the tire slip angle and having one or more processors perform this task.

[0029] Although embodiments of this disclosure have been described above with reference to the drawings, it should be understood that the specific configurations are not limited to these embodiments. The scope of this disclosure is indicated not only by the description of the embodiments above but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0030] The structures adopted in each of the above embodiments can be adopted in any other embodiment. The specific configuration of each part is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of this disclosure.

[0031] (A) The system may include a processing unit 1 but not sensor 3. Alternatively, the system may include sensor 3 and processing unit 1. If the system does not include sensor 3, a person may input the detection result of sensor 3 attached to vehicle 2 into the system.

[0032] (B) The approximation formula is not limited to formula (4) above, which is based on the magic formula. For example, other formulas based on the magic formula may be used. Alternatively, an approximation formula based on the brush model may be used instead of the magic formula.

[0033] (C) Sensor 3 is not limited to those described in the above embodiment. For example, the vehicle slip angle meter 33 in the above embodiment is an optical sensor that observes the road surface and detects the direction of travel of the vehicle, but is not limited to an optical sensor that detects the road surface. For example, a plurality of GPS sensors may be used to detect the direction of movement of each sensor, and the vehicle slip angle β may be derived based on the direction of movement of each sensor.

[0034] (D) In ​​the above embodiment, the data generation unit 13 fits an approximation formula to measurement data at multiple time points. However, since the measurement data at multiple time points itself is data relating to the cornering characteristics of the tire, it is also possible not to generate an approximation formula.

[0035] For example, the execution order of operations, procedures, steps, and stages in the devices, systems, programs, and methods shown in the claims, specifications, and drawings can be implemented in any order, as long as the output of a previous process is not used in a later process. Even if the flow in the claims, specifications, and drawings is described using terms such as "first," "next," etc., for convenience, it does not mean that the execution must be in that order.

[0036] Each component shown in Figure 1 is implemented by executing a predetermined program on one or more processors, but each component may also be configured with dedicated memory or dedicated circuitry. In the above embodiment, each component is implemented on the processor 1a of a single computer, but each component may be distributed and implemented on multiple computers or in the cloud. In other words, the above method may be executed on one or more processors.

[0037] The system includes a processor 1a. For example, the processor 1a may be a central processing unit (CPU), a microprocessor, or other processing unit capable of executing computer executable instructions. The system also includes memory 1b for storing system data. In one example, memory 1b includes computer storage media, such as RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, DVD or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other media that can be used to store desired data and that the system can access. [Explanation of Symbols]

[0038] 1... Processing unit, 10... Acquisition unit, 11... Slip angle calculation unit, 12... Lateral force calculation unit, 13... Data generation unit, 2... Vehicle, 3... Sensor.

Claims

1. A measurement process is performed in which a vehicle equipped with sensors that detect measured values ​​capable of deriving vehicle lateral acceleration, angular velocity, speed, vehicle slip angle, and steering angle is turned on an icy surface from a straight-ahead driving state until a predetermined steering angle is reached, and the measured values ​​at multiple points in time during the turn are detected by the sensors. Based on the steering angle and vehicle slip angle at each of the aforementioned time points, the slip angle of the tires at each of the aforementioned time points is calculated. Based on the speed, lateral acceleration, and angular velocity of the vehicle at each of the aforementioned time points, the lateral force acting on the front tires at each of the aforementioned time points is calculated. Based on the lateral force and the slip angle of the tire at each of the aforementioned multiple time points, data relating to the cornering characteristics of the tire is generated. Includes, A method for measuring the cornering characteristics of a tire, wherein the vehicle is not equipped with a force sensor that directly measures the force acting on the rim or axle.

2. A method for measuring the cornering characteristics of a tire according to claim 1, further comprising fitting an approximate formula representing the relationship between the lateral force acting on the tire and the slip angle of the tire to the lateral force and the slip angle of the tire at each of the multiple time points, in order to obtain an approximate formula representing the cornering curve of the tire.

3. A method for measuring the cornering characteristics of a tire according to claim 2, comprising: performing the measurement step of measuring with the sensor multiple times while the vehicle is turned from a straight-ahead driving state until it reaches a predetermined steering angle; and fitting an approximate formula representing the relationship between the lateral force acting on the tire and the slip angle of the tire to the measurement results obtained in the multiple measurement steps to obtain an approximate formula representing the cornering curve of the tire.

4. The method for measuring the cornering characteristics of a tire according to claim 2 or 3, wherein the approximation formula is expressed as a magic formula.

5. An acquisition unit that acquires the measured values ​​at multiple points in time detected by the sensors during a turn, while a vehicle equipped with sensors that detect measured values ​​capable of deriving vehicle lateral acceleration, angular velocity, speed, vehicle slip angle, and steering angle is turned from a straight-line driving state until a predetermined steering angle is reached. A slip angle calculation unit calculates the tire slip angle at each of the aforementioned time points based on the steering angle and the vehicle slip angle at each of the aforementioned time points, A lateral force calculation unit calculates the lateral force acting on the front tires at each of the aforementioned time points based on the speed, lateral acceleration, and angular velocity of the vehicle at each of the aforementioned time points, A data generation unit generates data relating to the cornering characteristics of a tire based on the lateral force and the slip angle of the tire at each of the aforementioned multiple time points. Equipped with, A system for generating data on the cornering characteristics of a tire, wherein the vehicle is not equipped with a force sensor that directly measures the force acting on the rim or axle.

6. A vehicle equipped with sensors that detect measured values ​​capable of deriving lateral acceleration, angular velocity, speed, vehicle slip angle, and steering angle is turned from a straight-line driving state until a predetermined steering angle is reached, and the measured values ​​at multiple points in time detected by the sensors during the turn are acquired. Based on the steering angle and vehicle slip angle at each of the aforementioned time points, the slip angle of the tire at each of the aforementioned time points is calculated; and based on the speed, vehicle lateral acceleration, and angular velocity at each of the aforementioned time points, the lateral force acting on the front tires at each of the aforementioned time points is calculated. Based on the lateral force and the slip angle of the tire at each of the aforementioned multiple time points, data relating to the cornering characteristics of the tire is generated. This is executed by one or more processors. The vehicle is not equipped with a force sensor that directly measures the force acting on the rim or axle, according to the program.

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