Tire temperature dependence model correction method and apparatus therefor

Abstract

Provided are a tire temperature dependence model correction method and an apparatus therefor, whereby a tire temperature dependence model can be properly corrected. When a tire temperature dependence model obtained by modeling a tire maximum friction coefficient depending on a tire surface temperature of a tire (3) mounted on a wheel (2i) of a vehicle (1) is corrected by a processor (5), the tire surface temperature is calculated, the tire surface temperature, which is calculated according to temperature characteristics of the tire (3), is corrected, the tire maximum friction coefficient is calculated, the tire temperature dependence model is corrected using the corrected tire surface temperature and the calculated tire maximum friction coefficient, a target yaw rate of the vehicle is further calculated, a yaw rate difference between an actual yaw rate generated in the vehicle and the target yaw rate is calculated, a tire friction coefficient front-rear difference between front and rear wheels is calculated on the basis of the yaw rate difference and wheel loads of the front and rear wheels, and the tire temperature dependence model is corrected using the tire friction coefficient front-rear difference.

Description

Tire temperature dependence model correction method and apparatus therefor

[0001] This invention relates to a method and apparatus for correcting a tire temperature dependence model.

[0002] Patent Document 1 below discloses a technique for estimating the maximum friction coefficient according to individual tire specifications based on the tread distribution characteristics, contact area, and contact pressure distribution of the tire mounted on the wheel.

[0003] Japanese Patent Publication No. 2021-89163

[0004] However, the tire maximum friction coefficient estimation technique described in Patent Document 1 above assumes that the tire's tread compound characteristics and contact condition are known, and cannot be applied to unknown tires for which such specifications are unknown. On the other hand, there is a tire temperature dependence model that models the relationship between the tire surface temperature and the tire's maximum friction coefficient. This tire temperature dependence model differs depending on the type of tire. For example, in a new car, the tire temperature dependence model for the so-called original equipment tires is stored (installed), and if the tire temperature dependence model can be appropriately corrected to match the unknown tire when it is changed to an unknown tire (different type of tire), then it becomes possible to correctly determine the tire's maximum friction coefficient according to the tire's surface temperature. The present invention aims to provide a tire temperature dependence model correction method and apparatus that can appropriately correct the tire temperature dependence model.

[0005] One aspect of the present invention involves correcting a tire temperature dependence model, which models the maximum friction coefficient of a tire that depends on the surface temperature of the tire mounted on the wheel of a vehicle, using a computing device. This correction involves calculating the surface temperature of the tire, correcting the surface temperature of the tire calculated according to the temperature characteristics of the tire, calculating the maximum friction coefficient of the tire, correcting the tire temperature dependence model using the corrected surface temperature of the tire and the calculated maximum friction coefficient of the tire, calculating the target yaw rate of the vehicle, calculating the yaw rate difference between the yaw rate occurring in the vehicle and the target yaw rate, calculating the front-to-rear difference in the friction coefficient of the tire between the front and rear wheels based on the yaw rate difference and the wheel loads of the front and rear wheels, and further correcting the tire temperature dependence model using this front-to-rear difference in the friction coefficient of the tire.

[0006] According to one aspect of the present invention, even with an unknown tire whose specifications are unknown, the tire temperature dependence model can be corrected according to the tire's temperature characteristics, and furthermore, the tire temperature dependence model can be appropriately corrected based on the yaw rate difference during sports driving.

[0007] This is a system configuration diagram showing a tire temperature-dependent model correction system, which is one embodiment of the present invention. This is an explanatory diagram of the vertical load change amount for each wheel of the vehicle in Figure 1. This is an explanatory diagram of the heat generation and heat dissipation amount in the tire of the wheel. This is a flowchart of the calculation process performed in the tire temperature estimation unit in Figure 1. This is an explanatory diagram of the tire temperature-dependent model. This is an explanatory diagram of the tire surface temperature and tire internal temperature. This is a flowchart of the calculation process performed in the different tire type determination unit in Figure 1. This is a flowchart of the calculation process performed in the wheel load acquisition unit to the second model correction unit in Figure 1. This is an explanatory diagram of the correction of the tire temperature-dependent model performed in the second model correction unit in Figure 1.

[0008] Embodiments of the present invention will be described below with reference to the drawings. Note that the drawings are schematic and may differ from actual ones. The vehicle 1 of the embodiment shown in Figure 1 is an autonomous vehicle having four wheels 2i, similar to a typical passenger vehicle: a front right wheel 2FR, a front left wheel 2FL, a rear right wheel 2RR, and a rear left wheel 2RL. The vehicle 1 is also equipped with a driving control device 34 for autonomous driving the vehicle 1. The vehicle 1 is also equipped with a drive device for driving the vehicle 1, a braking device for braking the vehicle 1, and a steering device for steering the vehicle 1, and also has controllers for controlling each of these devices (none of which are shown). The vehicle 1 is also equipped with an environment recognition system for recognizing the surrounding environment, and a communication system for vehicle-to-infrastructure communication and vehicle-to-vehicle communication, and also has controllers for controlling each of these systems (none of which are shown).

[0009] The driving control device 34 for autonomously driving this vehicle 1, for example, based on control inputs such as surrounding environment information obtained from the environment recognition system and communication information obtained from the communication system, it manages the control state of the controlled objects in the drive system, braking system, and steering system, and outputs control commands to the drive controller, braking controller, and steering controller based on the driving action plan used in current autonomous driving logic of Level 3 or higher. As shown in Figure 3, each wheel 2i is fitted with a tire (pneumatic tire) 3. In this embodiment, an electric power steering system is provided as the steering system, and the driving control device 34 has a road surface friction coefficient calculation unit that calculates the road surface friction coefficient as the road surface friction coefficient from the magnitude of the road surface reaction force torque in this electric power steering system. The calculation of the road surface friction coefficient can also be performed by applying one of the various other methods that have been implemented.

[0010] Furthermore, this vehicle 1 is equipped with a tire temperature dependence model providing device 4 that provides the aforementioned driving control device 34 with a tire temperature dependence model that models the relationship between the surface temperature of the tire 3 of each wheel 2i and the maximum friction coefficient of the tire 3. The driving control device 34, for example as shown in Figure 5, uses the provided tire temperature dependence model to estimate the surface temperature T of the tire 3 of each wheel 2i, which is estimated by the tire temperature estimation unit 6 described later.ｉ From the maximum friction coefficient (tire maximum friction coefficient) μ of each wheel 2i ＴＭＡＸｉ is obtained, and using this maximum friction coefficient μ ＴＭＡＸｉ control commands to, for example, a drive controller, a brake controller, and a steering controller are calculated and set. In order to function this tire temperature dependency model providing device 4, the vehicle 1 includes a steering angle sensor 21, an acceleration sensor 22, a speed sensor 23, a driving force sensor 24, a road surface temperature sensor 25, an outside air temperature sensor 26, and a TPMS (Tire Pressure Monitoring System) 27. The steering angle sensor 21 detects the steering angle (steering angle) δ of the front wheels 2FR and 2FL which are the steered wheels of the vehicle 1. Further, the acceleration sensor 22 detects the acceleration a Ｘ in the longitudinal direction (front-back direction) and the acceleration a Ｙ in the width direction (lateral direction) of the vehicle 1. Further, the speed sensor 23 detects the traveling speed V of the vehicle 1. Further, the driving force sensor 24 detects the driving force and the braking force (driving / braking force) F ＸＴＴＬ of the vehicle 1. Further, the vehicle 1 includes a yaw rate sensor 28 that detects the yaw rate (actual yaw rate) γ generated in the vehicle 1.

[0011] The detection information detected by the steering angle sensor 21, the acceleration sensor 22, the speed sensor 23, and the driving force sensor 24 is acquired by a vehicle state acquisition unit 17 constructed in a processor 5 described later. Further, the road surface temperature sensor 25 detects the road surface temperature T ＲＯＡＤ [°C] of the road surface on which the vehicle 1 travels, and is composed of, for example, a non-contact type temperature sensor attached to the lower part of the vehicle body of the vehicle 1, and in that case, is arranged at a position facing the road surface on which the vehicle 1 travels. The road surface temperature T detected by this road surface temperature sensor 25 ＲＯＡＤ is acquired by a road surface temperature acquisition unit 18 constructed in a processor 5 described later. The outside air temperature sensor 26 detects the outside air temperature T ＡＩＲThe sensor detects the temperature in [°C], and in this embodiment, it is mounted on a part of the wheel well facing the inside of the vehicle 1. That is, the outside air temperature sensor 26 in this embodiment detects the temperature around the tire 3 of the wheel 2i inside the wheel well. The TPMS 27 detects the air pressure of the tire 3 of each wheel 2i, and also the internal temperature of the tire 3 (tire internal temperature) T ＩＮＲ It detects the temperature in [°C] and is attached to the wheel of each wheel 2i, for example. The ambient temperature T detected by the ambient temperature sensor 26 ＡＩＲ and the internal tire temperature T detected by TPMS27 ＩＮＲ This is obtained by the ambient temperature acquisition unit 19 built within the processor 5, which will be described later. Note that the tire internal temperature T ＩＮＲ This is used with the subscript i indicating the position of each wheel 2i.

[0012] The tire temperature dependence model providing device 4 has a processor 5 with advanced computational processing capabilities. The processor 5 includes a ROM (Read Only Memory) where the program is stored, a CPU (Central Processing Unit) which executes the program stored in the ROM, and a RAM (Random Access Memory) which functions as an accessible storage device. The processor 5 is equipped with a tire temperature estimation unit 6 and a tire temperature dependence model correction unit 7 as functional units. The tire temperature estimation unit 6 includes a vehicle state acquisition unit 17, a heat generation amount calculation unit 8, a previous temperature acquisition unit 20, a road surface temperature acquisition unit 18, an ambient temperature acquisition unit 19, a heat dissipation amount calculation unit 9, a temperature change amount calculation unit 10, and a surface temperature calculation unit 11. The heat dissipation amount calculation unit 9 further includes a first heat dissipation amount calculation unit 9a and a second heat dissipation amount calculation unit 9b. The tire temperature dependence model correction unit 7 includes a different tire type determination unit 12, a road surface friction coefficient acquisition unit 13, a tire friction coefficient calculation unit 14, a maximum tire friction coefficient calculation unit 15, and a first model correction unit 16, as well as a wheel load acquisition unit 29, a target yaw rate calculation unit 30, a yaw rate difference calculation unit 31, a front-to-rear difference in tire friction coefficient calculation unit 32, and a second model correction unit 33. These functional units operate when the CPU executes a program stored in ROM within the processor 5.

[0013] The following describes how the tire temperature estimation unit 6 estimates the surface temperature of the tire 3. The vehicle state acquisition unit 17 of the tire temperature estimation unit 6 acquires the steering angle δ of the vehicle 1 detected by the steering angle sensor 21 and the longitudinal acceleration (longitudinal acceleration) a of the vehicle 1 detected by the acceleration sensor 22. Ｘ and the acceleration (lateral acceleration) a in the width direction (lateral direction) of the vehicle 1 Ｙ The vehicle's travel speed V is detected by the speed sensor 23, and the braking force F is detected by the drive force sensor 24. ＸＴＴＬ The size is obtained. Then, the vehicle state acquisition unit 17 acquires this information, namely the steering angle δ of the vehicle 1 and the longitudinal acceleration a Ｘ , lateral acceleration a Ｙ Vehicle 1's travel speed V, braking force F ＸＴＴＬ The magnitude of the vehicle state information is output to the heat generation calculation unit 8. The heat generation calculation unit 8 calculates the heat generation of the tires 3 of each wheel 2i based on the vehicle state information input from the vehicle state acquisition unit 17. The heat generation is calculated as follows. First, the heat generation calculation unit 8 calculates the vertical load (wheel load) of each wheel 2i based on the vertical acceleration and lateral acceleration. In the calculation, as shown in Figure 2a, the vertical acceleration a Ｘ [m / s ２ Change in vertical load ΔF due to ] Ｚ－Ｘ [N] is calculated according to the following formula. In the formula, M [kg] is the mass of vehicle 1, L [m] is the wheelbase (farthest axle distance) of vehicle 1, and H ＣＧ [m] is the height of the center of gravity of vehicle 1. Similarly, as shown in Figure 2b, the lateral acceleration a Ｙ [m / s ２ Change in vertical load ΔF due to ] Ｚ－Ｙ [N] is calculated according to the following two formulas. In the formulas, D [m] is the tread of vehicle 1 (distance between the centers of the contact surfaces of the left and right wheels).

[0014]

[0015] Using these vertical load changes, the vertical load of each wheel 2i, i.e., the front right wheel load F, is calculated. ＺＦＲ [N], front left wheel load F ＺＦＬ [N], rear right wheel load F ＺＲＲ [N], rear left wheel load F ＺＲＬ [N] is calculated according to the following equations 3 to 6. Note that in the equations, LＲ [m] is the distance between the center of gravity of vehicle 1 and the rear axle, L Ｆ [m] is the distance between the center of gravity and the front axle of vehicle 1.

[0016]

[0017] Furthermore, the heat generation calculation unit 8 calculates the total lateral force F of the vehicle 1 (all wheels 2i). ＹＴＴＬ [N] is distributed to each wheel 2i, and the lateral force of each wheel 2i, i.e., the lateral force F of the front right wheel, is distributed in this manner. ＹＦＲ [N], front left wheel lateral force F ＹＦＬ [N], rear right wheel lateral force F ＹＲＲ [N], rear left wheel lateral force F ＹＲＬ [N] is calculated according to equations 7 to 10 below. Note that the total lateral force F of vehicle 1 ＹＴＴＬ [N] represents the mass M [kg] of vehicle 1 and the lateral acceleration a Ｙ [m / s ２ It is the product of ].

[0018]

[0019] Furthermore, the heat generation calculation unit 8 calculates the braking and driving force F of the vehicle 1 (all wheels 2i). ＸＴＴＬ [N] is distributed to each wheel 2i, and the longitudinal force of each wheel 2i, i.e., the front right wheel longitudinal force F, is distributed in this manner. ＸＦＲ [N], front left wheel longitudinal force F ＸＦＬ [N], rear right wheel longitudinal force F ＸＲＲ [N], rear left wheel longitudinal force F ＸＲＬ [N] is calculated according to the following formula 11. In the formula, DR is the ratio of braking and driving force distribution to each wheel 2i, and the subscript i represents the position of the wheel 2i, i.e., FR for front right, FL for front left, RR for rear right, and RL for rear left.

[0020]

[0021] The heat generation calculation unit 8 then calculates the vertical force F of each wheel 2i. Ｘｉ [N] and vertical load F Ｚｉ Based on [N], the longitudinal heat storage coefficient (which is also the heat capacity) W of the tire 3 of each wheel 2i is determined by referring to a pre-stored map. Ｘｉ The [N・m / ℃] is obtained. Similarly, the heat generation calculation unit 8 calculates the lateral force F of each wheel 2i. Ｙｉ [N] and vertical load F ＺｉBased on [N], the lateral heat storage coefficient (heat capacity) W of the tire 3 of each wheel 2i is determined by referring to a pre-stored map. Ｙｉ The [N・m / °C] value is obtained. The longitudinal heat storage coefficient of the tire 3 of each wheel 2i (hereinafter referred to as the tire longitudinal heat storage coefficient) W Ｘｉ and the lateral heat storage coefficient (tire lateral heat storage coefficient) W of the tire 3 of each wheel 2i Ｙｉ The map used to obtain the tire longitudinal heat storage coefficient W is a map created to reflect the fact that the heat generation QG of the tire 3 saturates when a large load (vertical load, longitudinal force and lateral force applied to the tire 3) greater than a predetermined value is applied to each tire 3. Therefore, the tire longitudinal heat storage coefficient W obtained by the heat generation calculation unit 8 is a map created to reflect the fact that the heat generation QG of the tire 3 saturates when a large load (vertical load, longitudinal force and lateral force applied to the tire 3) is applied to each tire 3. Ｘｉ and the lateral heat storage coefficient of the tire W Ｙｉ The heat generated by tire 3 QG increases with increasing load, but the rate of increase gradually decreases. ｉ (See Figure 3) This value is affected by the inflection point. Note that, if the tires 3 of each wheel 2i have clear and identical specifications, as described later with the original tires, then the longitudinal heat storage coefficient W of each tire 3 is... Ｘｉ and the lateral heat storage coefficient W Ｙｉ Although this is the same for all wheels 2i, as will be described later, in this embodiment, in order to deal with unknown tires (different types of tires) whose specifications for each wheel 2i are unknown, the longitudinal heat storage coefficient W of the tire 3 is used. Ｘｉ and the lateral heat storage coefficient W Ｙｉ The subscript i is assigned to each wheel 2i to indicate its position.

[0022] Next, the heat generation calculation unit 8 calculates the heat generation QG of the tires 3 of each wheel 2i. ｉ To calculate the longitudinal slip speed V of each wheel 2i (tire 3) from a two-wheeled model, based on the steering angle δ and travel speed V of vehicle 1. ＳＬＰＸｉ and lateral slip speed V ＳＬＰＹｉ The vertical slip velocity V is calculated as shown in Figure 3. ＳＬＰＸｉ and lateral slip speed V ＳＬＰＹｉ and the longitudinal force F of each wheel 2i (tire 3) Ｘｉ and lateral force F Ｙｉ and the longitudinal heat storage coefficient of the tire W Ｘｉ and the lateral heat storage coefficient of the tire W ＹｉUsing the following equation 12, the amount of heat generated between the tire 3 of each wheel 2i and the road surface (tire heat generation) QG is calculated. ｉ Calculate [°C / s]. Here, tire heat generation QG ｉ As is clear from the units, the calculated tire heat output QG ｉ This represents the increase in tire temperature 3 per unit time, or what can be called the tire temperature increase rate.

[0023]

[0024] Next, the previous temperature acquisition unit 20 shown in Figure 1, as will be described later, takes the surface temperature of the tire 3 of each wheel 2i calculated by the surface temperature calculation unit 11 and returns the previous surface temperature (previous tire surface temperature) T of the tire 3 of each wheel 2i. ０ｉ The temperature is obtained in [°C]. The previous temperature acquisition unit 20 is the ambient temperature T detected by the ambient temperature sensor 26 and acquired by the ambient temperature acquisition unit 19. ＡＩＲ The data from the previous tire surface temperature T ０ｉ The initial value is obtained via CAN. That is, the previous tire surface temperature T ０ｉ The initial value is the outside air temperature T ＡＩＲ This is the previous tire surface temperature T obtained by the previous temperature acquisition unit 20. ０ｉ Using this, the first heat dissipation amount calculation unit 9a in the heat dissipation amount calculation unit 9 calculates the first heat dissipation amount (first tire heat dissipation amount) QD1 of the tires 3 of each wheel 2i. ｉ Calculate the [°C / s]. First tire heat dissipation QD1 ｉ As shown in Figure 3, this represents the amount of heat dissipated from the tires 3 of each wheel 2i to the road surface, and the road surface temperature T is obtained by the road surface temperature acquisition unit 18. ＲＯＡＤ The following 13 equations are obtained using the formula. Note that the road surface heat dissipation coefficient κ is used in the equations. １ [1 / s] may be set to be larger as the road surface temperature decreases. Also, the second heat dissipation amount calculation unit 9b in the heat dissipation amount calculation unit 9 calculates the previous tire surface temperature T ０ｉ Using this, the second heat dissipation amount (second tire heat dissipation amount) QD2 of the tire 3 of each wheel 2i is calculated. ｉ Calculate the heat dissipation of this second tire QD2. ｉ This is the ambient temperature T obtained by the ambient temperature acquisition unit 19. ＡＩＲ and tire internal temperature T ＩＮＲｉObtained by the following formula (14), as shown in FIG. 3, it includes the heat dissipation amount QD21 (the first term on the right side of formula (14)) radiated from the tire 3 of each wheel 2i to the outside air and the heat dissipation amount QD22 (the second term on the right side of formula (14)) radiated from the tire 3 to the air inside the tire. Here, the outside air heat dissipation coefficient κ in the formula ２ is set to be larger as the outside air temperature T ＡＩＲ is smaller. Also, the internal heat dissipation coefficient κ in the formula ３ may be set to be larger as the internal temperature T of the tire ＩＮＲｉ is smaller.

[0025]

[0026] Here, the first tire heat dissipation amount QD1 ｉ and the second tire heat dissipation amount QD2 ｉ As is clear from the units of, the calculated first tire heat dissipation amount QD1 ｉ and the second tire heat dissipation amount QD2 ｉ are the temperature decrease amounts of the tire 3 per unit time, that is, what can be called the tire temperature decrease rate. Note that the difference value between the previous tire surface temperature T ０ｉ and the outside air temperature T ＡＩＲ multiplied by the outside air heat dissipation coefficient κ ２ , that is, only the first term on the right side of formula (14) may be used as the second tire heat dissipation amount QD2 ｉ . Similarly, the difference value between the previous tire surface temperature T ０ｉ and the internal temperature T of the tire ＩＮＲｉ multiplied by the internal heat dissipation coefficient κ ３ , that is, only the second term on the right side of formula (14) may be used as the second tire heat dissipation amount QD2 ｉ . Then, the temperature change amount calculation unit 10 subtracts the first tire heat dissipation amount QD1 ｉ and the second tire heat dissipation amount QD2 ｉ from the tire heat generation amount QG ｉ and calculates the temperature change amount (tire temperature change amount) dT ｉ / dt [°C / s] of the surface temperature of the tire 3 of each wheel 2i according to the following formula (15). Also, if formula (12) is substituted into the tire heat generation amount QG ｉ in formula (15), the following formula (16) is obtained. Here, as is clear from the unit of the tire temperature change amount dT ｉ / dt, the calculated tire temperature change amount dTｉ / dt represents the rate of change in tire temperature 3 per unit time, or the tire temperature change rate. The surface temperature calculation unit 11 in Figure 1 calculates the previous tire surface temperature T ０ｉ and tire temperature change dT ｉ Based on / dt, the surface temperature (tire surface temperature) T of the tire 3 of each wheel 2i ｉ Calculate.

[0027]

[0028] The calculation process in the above-mentioned functional unit is shown in the flowchart of Figure 4. In the calculation process according to this flowchart, first in step S1, the heat generation amount calculation unit 8 calculates the vertical load F of each wheel 2i according to equations 1 to 6 above. Ｚｉ Next, in step S2, the heat generation calculation unit 8 calculates the vertical force F of each wheel 2i according to equations 7 to 11 above. Ｘｉ and lateral force F Ｙｉ Next, in step S3, the heat generation calculation unit 8 calculates the vertical load F of each wheel 2i by referring to the map above. Ｚｉ and vertical force F Ｘｉ and lateral force F Ｙｉ The heat storage coefficient W of the tire 3 of each wheel 2i Ｘ , W Ｙ Next, in step S4, the heat generation calculation unit 8 calculates the slip speed V of each wheel 2i. ＳＬＰＸｉ , V ＳＬＰＹｉ Next, in step S5, the heat generation calculation unit 8 calculates the vertical force F of each wheel 2i according to the above equation 12. Ｘｉ and lateral force F Ｙｉ The heat storage coefficient W of the tire 3 of each wheel 2i Ｘ , W Ｙ , slip speed V of each wheel 2i ＳＬＰＸｉ , V ＳＬＰＹｉ The amount of tire heat generated by each wheel 2i according to QG ｉ Next, in step S6, the road surface temperature acquisition unit 18 calculates the road surface temperature T ＲＯＡＤ Next, in step S7, the ambient temperature acquisition unit 19 obtains the outside air temperature T ＡＩＲ Next, in step S8, the ambient temperature acquisition unit 19 obtains the internal tire temperature T of each wheel 2i. ＩＮＲｉThe process in steps S6 to S8 may be performed in any order, or simultaneously. Also, either step S7 or step S8 may be performed alone. Next, in step S9, the heat dissipation amount calculation unit 9 obtains the previous tire surface temperature T ０ｉ and road surface temperature T ＲＯＡＤ Using the above formula 13, the heat dissipation amount QD1 of the first tire of each wheel 2i ｉ In addition to calculating the previous tire surface temperature T ０ｉ and outside air temperature T ＡＩＲ and tire internal temperature T ＩＮＲｉ Using the above formula 14, the heat dissipation amount QD2 of the second tire of each wheel 2i ｉ The following is calculated. As mentioned above, the second tire heat dissipation QD2 ｉ This may be only the first term on the right-hand side of the above equation 14, or only the second term. Next, in step S10, the temperature change amount calculation unit 10 calculates the tire heat generation amount QG ｉ , First tire heat dissipation QD1 ｉ , and the heat dissipation amount of the second tire QD2 ｉ Using the above equations 15 to 16, the change in tire temperature dT of each wheel 2i ｉ / dt is calculated. Then, in step S11, the surface temperature calculation unit 11 calculates the previous tire surface temperature T of each wheel 2i. ０ｉ and tire temperature change dT ｉ Using / dt, tire surface temperature T ｉ Calculate.

[0029] The following describes the case where the tires 3 attached to each wheel 2i are not specific tires. Generally, when a vehicle 1 is sold as a so-called new car, specific tires are attached by the automobile manufacturer. These specific tires attached to new cars are widely called "original equipment tires," so in the following, the tires 3 initially attached to vehicle 1 will be referred to as original equipment tires. In contrast, it is also common for the owner of vehicle 1 to attach tires 3 different from the original equipment tires to each wheel 2i. These tires 3 different from the original equipment tires will be referred to as non-original tires. For example, as shown in Figure 5, tire 3 has a characteristic of maximum tire friction coefficient that depends on the tire surface temperature. If we define this characteristic of maximum tire friction coefficient as the tire temperature-dependent model, then, for example, when the driving control device 34 controls the braking force and steering state of vehicle 1, if we control the behavior (motion) of vehicle 1 by considering the maximum friction coefficient of each wheel 2i that depends on the tire surface temperature according to the tire temperature-dependent model, then it is clear that the former will yield behavior (motion) characteristics closer to the ideal. However, the tire temperature dependence model differs depending on the type of tire 3, or, to put it extremely, if tire 3 is different, then ideal vehicle behavior characteristics may not be obtained unless a tire temperature dependence model corresponding to that different tire is provided, for example, when tire 3 is changed from the original tire to a different type of tire. In other words, a different type of tire can be said to be an unknown tire with unknown specifications compared to the original tire. In this embodiment, as an example, the default (new car) tire temperature dependence model is set to that of the original tire, and when tire 3 is a different type of tire that is not the original tire, a tire temperature dependence model corresponding to that tire (different type of tire) is obtained and corrected. Note that although a different type of tire is an unknown tire that is not the original tire, all four wheels are assumed to be the same tire.

[0030] In the tire temperature dependence model correction unit 7 within the tire temperature dependence model providing device 4, the different tire determination unit 12 determines whether the tires 3 on each wheel 2i are different tires from the original tires. If the tires 3 on each wheel 2i are different tires, the road surface friction coefficient acquisition unit 13 obtains the road surface friction coefficient μ from the electric power steering device of the driving control device 34. Ｒ The road surface friction coefficient μ is obtained. The tire friction coefficient calculation unit 14 calculates this road surface friction coefficient μ. Ｒ Multiply this by a coefficient corresponding to the ratio of the wheel loads of each wheel 2i to obtain the friction coefficient (tire friction coefficient) μ of the tire 3 for each wheel 2i. Ｔｉ The tire maximum friction coefficient calculation unit 15 calculates, for example, the tire friction coefficient μ of each wheel 2i. Ｔｉ Based on the relationship between the slip ratio and the coefficient of friction, the maximum coefficient of friction μ of a typical tire 3 is determined at the slip ratio at which the coefficient of friction is maximized. ＴＭＡＸｉ This is calculated. In other words, for a typical tire 3, in the region where the slip ratio (absolute value) is small, the tire friction coefficient μ is calculated in accordance with the increase or decrease in the slip ratio (absolute value) by a proportionality coefficient (increase / decrease rate) corresponding to the grip force of each tire 3. Ｔｉ It also increases or decreases. On the other hand, as the slip ratio (absolute value) gradually increases, the tire friction coefficient μ at a certain slip ratio Ｔｉ When the coefficient of friction saturates, the tire friction coefficient μ is greater than the slip ratio (or its absolute value). Ｔｉ It gradually decreases. This is the tire friction coefficient μ Ｔｉ The slip ratio at which it saturates is approximately the same for a typical tire 3, therefore, the tire friction coefficient μ at the current slip ratio is Ｔｉ The rate of increase or decrease is calculated, and the tire friction coefficient μ is calculated using that rate of increase or decrease. Ｔｉ If we calculate the coefficient of friction at the slip ratio at which it saturates, we can obtain the maximum friction coefficient μ of each tire 3. ＴＭＡＸｉ Then, the first model correction unit 16 calculates the tire surface temperature T of each wheel 2i calculated by the surface temperature calculation unit 11. ｉ and the maximum friction coefficient μ of each wheel 2i ＴＭＡＸｉ The relationship is accumulated and the above tire temperature dependence model is corrected. Specifically, a new tire surface temperature T is added to the tire temperature dependence model in Figure 5. ｉ and the maximum friction coefficient μ of the tire ＴＭＡＸｉCorrect the point by re-plotting it.

[0031] Before explaining the calculation process for determining different types of tires performed by the different-type tire determination unit 12 described above, the principle for determining whether the tires 3 on each wheel 2i are different types of tires in this embodiment will be explained. Figure 6 shows the tire surface temperature T calculated by the surface temperature calculation unit 11. ｉ The dashed line represents the tire internal temperature T read from TPMS27. ＩＮＲｉ This is shown by a solid line. As is clear from Figure 6, the calculated tire surface temperature T ｉ This increases and decreases (fluctuations) in small increments. The calculated tire surface temperature T ｉ In this state, the internal tire temperature T ＩＮＲｉ Since the relationship is unclear, for example, the median tire surface temperature (median tire surface temperature T) can be calculated by integral processing using a digital filter. Ｃｉ When calculated, it exhibits the behavior shown by the dashed line in the figure. In particular, the median tire surface temperature T Ｃｉ In a state where the value continues to increase (rise), the delay time Δt is determined by the heat capacity of tire 3 (= heat storage coefficient: determined by the volume of the rubber part and the internal air part of tire 3). ０ｉ The internal temperature of the tire is T ＩＮＲｉ The median tire surface temperature is T Ｃｉ It follows the median tire surface temperature T. For example, when vehicle 1 starts moving after being stopped (parked) for a long time, Ｃｉ The temperature of the tire increases first, followed by the internal tire temperature T. ＩＮＲｉ Therefore, the different tire detection temperature T is set to a relatively low temperature (higher than room temperature). ＲＥＦ The median tire surface temperature T Ｃｉ The time when it reaches the surface temperature is called the surface temperature arrival time t. ｉ , tire internal temperature T ＩＮＲｉ The time when it reaches the internal temperature is called the internal temperature arrival time t. ＩＮＲｉ If tire 3 is the original tire, then there are two time t ｉ ,t ＩＮＲｉ Actual delay time Δt ｉ The delay time Δt corresponds to the original tires. ０ｉ This roughly matches. Conversely, if tire 3 is a different type of tire, then the two time t ｉ ,tＩＮＲｉ Actual delay time Δt ｉ The delay time Δt corresponds to the original tires. ０ｉ This does not match. Therefore, in this embodiment, the time t when the surface temperature is reached is not consistent. ｉ Median tire surface temperature T Ｃｉ (=T ＲＥＦ ) with delay time Δt ０ｉ Only a delay in the estimated internal tire temperature T ＥＩＮＲｉ [℃] (=T) ＲＥＦ ) is calculated, and this estimated tire internal temperature T ＥＩＮＲｉ and surface temperature arrival time t ｉ Delay time Δt ０ｉ The internal tire temperature T at the time elapsed ＩＮＲｉ The temperature difference ΔT inside the tire ＩＮＲｉ The internal temperature difference ΔT of the tire is calculated, and this is calculated. ＩＮＲｉ If (the absolute value of) is greater than or equal to the threshold, it is determined to be a different type of tire. If it is a different type of tire, the delay time Δt ０ｉ Actual delay time Δt ｉ The heat storage coefficient W of tire 3 in ratio Ｘｉ , W Ｙｉ This is corrected. Also, for example, the owner of vehicle 1 may replace one type of tire with yet another type of tire. Therefore, in this embodiment, each time a different type of tire is detected, a delay time Δt ０ｉ The actual delay time Δt ｉ The system was updated to allow for further detection of different types of tires. The criteria for detecting these different types of tires are based on the median tire surface temperature T. Ｃｉ The fact that the number is continuing to increase, and the internal temperature of the tire T ＩＮＲｉ The fact that the median tire surface temperature T is continuing to increase Ｃｉ Different tire type detection temperature T ＲＥＦ The tire internal temperature exceeds T ＩＮＲｉ Different tire type detection temperature T ＲＥＦ It exceeds the time t when the surface temperature is reached. ｉ Delay time Δt ０ｉ A sufficiently longer judgment start time Δt ＪThis is because a certain amount of time has elapsed. Therefore, the timing for determining different types of tires is the time (determination time) after a fairly long predetermined time has elapsed, after the vehicle 1 has stopped and started moving again, and a fairly short predetermined time has elapsed. Ｊ It is identified as such.

[0032] Next, the calculation process performed by the different tire type determination unit 12 will be explained using the flowchart in Figure 7. This calculation process is executed, for example, by a timer interrupt process with a predetermined sampling period. This calculation process starts, for example, when the vehicle 1 starts moving, and at the start of the calculation process, a flag F used during the process is set. １ F ２ F ３ All of them are reset. In this calculation process, first in step S21, the third flag F ３ Determine whether it is in a reset state of 0, and the third flag F ３ If it is in a reset state, the process proceeds to step S22; otherwise, it returns to the previous state. In step S22, the tire surface temperature T calculated by the surface temperature calculation unit 11 is ｉ The data is then read. Next, the process moves to step S23, where the median tire surface temperature T is obtained through the aforementioned digital filtering process. Ｃｉ Next, the process moves to step S24, and the internal tire temperature T obtained by the ambient temperature acquisition unit 19 is calculated. ＩＮＲｉ Read the first flag F. Next, proceed to step S25 and check the first flag F. １ Determine whether it is in a reset state of 0, and the first flag F １ If it is in a reset state, proceed to step S26; otherwise, proceed to step S29. In step S26, the median tire surface temperature T Ｃｉ Different tire type detection temperature T ＲＥＦ Determine whether or not the above is true, and the median tire surface temperature T Ｃｉ Different tire type detection temperature T ＲＥＦ If the above is true, proceed to step S27; otherwise, proceed to step S29. In step S27, the median tire surface temperature T Ｃｉ Different tire type detection temperature T ＲＥＦ The time when this occurs is the surface temperature reach time t. ｉAfter storing it as such, the process proceeds to step S28. In step S28, the first flag F １ Set to state 1 and then proceed to step S29.

[0033] In step S29, the second flag F ２ Determine whether it is in a reset state of 0, and check the second flag F ２ If the value is in a reset state, the process proceeds to step S30; otherwise, the process proceeds to step S33. In step S30, the internal tire temperature T ＩＮＲｉ Different tire type detection temperature T ＲＥＦ Determine whether or not the tire internal temperature T ＩＮＲｉ Different tire type detection temperature T ＲＥＦ If the above is true, proceed to step S31; otherwise, proceed to step S33. In step S31, the internal tire temperature T ＩＮＲｉ Different tire type detection temperature T ＲＥＦ The time when this occurs is the internal temperature reach time t. ＩＮＲｉ After storing it as such, the process proceeds to step S32. In step S32, the second flag F ２ The system is set to state 1 and then proceeds to step S33. In step S33, it is determined whether the aforementioned different tire determination condition is met according to individual calculation processes (not shown), and if the different tire determination condition is met, the system proceeds to step S34; otherwise, it returns to the previous state. In step S34, the third flag F ３ Set to state 1. Next, proceed to step S35 and store the stored delay time Δt. ０ｉ The data is then read. Next, the process moves to step S36, and as described above, the time t when the surface temperature is reached is read. ｉ Median tire surface temperature T Ｃｉ delay time Δt ０ｉ Estimated tire internal temperature T by delaying only ＥＩＮＲｉ Next, proceed to step S37 and calculate the time t when the surface temperature is reached. ｉ Delay time Δt ０ｉ The internal tire temperature T at the time elapsed ＩＮＲｉ The estimated internal tire temperature T was calculated as follows: ＥＩＮＲｉ The difference value is the internal tire temperature difference ΔT ＩＮＲｉThe calculation is performed as follows. Next, proceed to step S38, and calculate the internal tire temperature difference ΔT ＩＮＲｉ It is determined whether the absolute value of is greater than or equal to the threshold, and the internal tire temperature difference ΔT ＩＮＲｉ If the absolute value of is greater than or equal to the threshold, the process proceeds to step S39; otherwise, the process returns to normal, assuming that tire 3 has not been changed to a different type of tire since the last calculation. In step S39, the internal temperature arrival time t ＩＮＲｉ The surface temperature reaches time t from ｉ The actual delay time Δt is the time after subtracting the time. ｉ The calculation is performed as follows. Next, proceed to step S40, and calculate the tire longitudinal heat storage coefficient W. Ｘｉ and the lateral heat storage coefficient of the tire W Ｙｉ For each of these, the actual delay time Δt ｉ delay time Δt ０ｉ The tire heat storage coefficient W is calculated by multiplying by the coefficient obtained by dividing by . Ｘｉ , W Ｙｉ This corrects the tire heat storage coefficient W. Ｘｉ , W Ｙｉ The tire surface temperature T is the subsequent temperature. ｉ More specifically, tire heat generation QG ｉ This is used when calculating the delay time Δt. Next, the process moves to step S41, ０ｉ The actual delay time Δt ｉ Update and then return.

[0034] According to this calculation process, after a considerably long predetermined period of time when vehicle 1 has stopped, the median tire surface temperature T is calculated after the vehicle starts moving again. Ｃｉ Different tire type detection temperature T ＲＥＦ The time when this occurs is the time t when the surface temperature is reached. ｉ It is stored as such, and then the internal tire temperature T ＩＮＲｉ Different tire type detection temperature T ＲＥＦ The time when this occurs is the internal temperature reach time t. ＩＮＲｉ It is stored as follows. And when the different tire type determination condition is met, that is, when the surface temperature reaches time t ｉ From the start time of the determination Δt Ｊ The determination time t after the time has elapsed Ｊ Then, the time t when the surface temperature is reached ｉ Median tire surface temperature T Ｃｉ delay time Δt０ｉ The estimated internal tire temperature T is delayed. ＥＩＮＲｉ The following is calculated, and this estimated tire internal temperature T ＥＩＮＲｉ and surface temperature arrival time t ｉ Delay time Δt ０ｉ The internal tire temperature T at the time elapsed ＩＮＲｉ The difference value is the internal tire temperature difference ΔT. ＩＮＲｉ If the absolute value of is less than the threshold, tire 3 is determined to be unchanged since the last time a different tire type was detected. On the other hand, the internal tire temperature difference ΔT ＩＮＲｉ If the absolute value of is greater than or equal to the threshold, it is determined that tire 3 has been changed to a different type since the last time a different tire was detected, and in that case, the actual delay time Δt ｉ and delay time Δt ０ｉ The tire heat storage coefficient W Ｘｉ , W Ｙｉ This is corrected, and thereafter, that becomes the tire heat generation QG ｉ and tire surface temperature T ｉ It is used to calculate the tire surface temperature T. ｉ Tire internal temperature T ＩＮＲｉ The behavior of the tire, or in other words, the tire heat storage coefficient W, depends on the temperature characteristics of the tire. Ｘｉ , W Ｙｉ By correcting the tire surface temperature T ｉ It can be said that this is a tire surface temperature correction unit that corrects the tire heat storage coefficient W. Ｘｉ , W Ｙｉ It could also be described as an unknown tire detection unit that detects unknown tires.

[0035] The above describes the temperature characteristics of the tire, i.e., the internal temperature of the tire T ＩＮＲｉThis is a method for correcting the tire temperature dependence model based on the behavior of the tires, but there are cases where this tire temperature dependence model can be further corrected. Generally, in vehicle driving conditions called sports driving, for example, the driving speed is high, acceleration and deceleration are frequent and large, and steering is performed quickly and large, so the load on the front wheels is greater than the load on the rear wheels, and the tire surface temperature of the front wheels tends to be higher than that of the rear wheels. When the tire surface temperature of the front wheels is higher than that of the rear wheels, as is clear from the tire temperature dependence model in Figure 5, the maximum friction coefficient of the front wheels and the maximum friction coefficient of the rear wheels are clearly different. On the other hand, the yaw rate, which is the angular velocity of rotation of the vehicle, is a turning motion characteristic that can be assumed using the vehicle specifications, with the driving speed V and steering angle δ as variables. This yaw rate (yawing motion) is caused by the lateral force (cornering force) of the front and rear wheels. Therefore, when the tire surface temperature of the front wheel is higher than that of the rear wheel, and the maximum friction coefficient of the front wheel differs from that of the tire temperature-dependent model, a discrepancy will occur between the expected yaw rate and the actual yaw rate. Since this discrepancy in yaw rate is the difference between the front and rear wheels in the model of lateral force dependent on the friction force of the front and rear wheels, the difference in friction coefficients between the front and rear wheels can be determined from the discrepancy in yaw rate. Thus, in the wheel load acquisition unit 29 in Figure 1, the wheel load of the front wheel and the wheel load of the rear wheel are calculated from the vertical load of each wheel as described above, and in the target yaw rate calculation unit 30, the target yaw rate γ of the vehicle is calculated based on the travel speed V and steering angle δ. Ｔ The yaw rate difference calculation unit 31 calculates the target yaw rate γ. Ｔ The yaw rate difference Δγ is calculated from the difference in actual yaw rate γ detected by the yaw rate sensor 28, and the front-to-rear difference in tire friction coefficient calculation unit 32 calculates the difference in tire friction coefficients between the front and rear wheels (front-to-rear difference in tire friction coefficient) from this yaw rate difference Δγ. Then, the second model correction unit 33 corrects the tire temperature dependence model using this front-to-rear difference in tire friction coefficient.

[0036] To avoid the complexity of the explanation, prior to the calculation processing performed from the wheel load acquisition unit 29 to the second model correction unit 33, the target yaw rate γ of the vehicle is used. ＴThis will be explained. This target yaw rate γ Ｔ This is calculated using the travel speed V and steering angle δ according to the following equation 17. In the equation, M is the vehicle mass, I is the yaw radius of inertia, L is the wheelbase, L Ｆ L is the distance from the vehicle's center of gravity to the front axle 35F, which is the axle of the front wheels. Ｒ This is the distance from the vehicle's center of gravity to the rear axle 35R, which is the axle of the rear wheels. Ｆ The equivalent cornering power of the front wheels 2FR and 2FL is K Ｒ This represents the equivalent cornering power for the rear wheels 2RR and 2RL. Also, A, given in formula 17-3, is the stability factor.

[0037]

[0038] Next, the calculation process performed from the wheel load acquisition unit 29 to the second model correction unit 33 will be explained using the flowchart in Figure 8. This calculation process starts, for example, when the vehicle 1 starts running, and thereafter is executed, for example, by a timer interrupt process with a predetermined sampling period. In this calculation process, first, in step S51, the front-to-rear difference in tire surface temperature between the front wheel tire surface temperature and the rear wheel tire surface temperature is calculated. This front-to-rear difference in tire surface temperature is obtained, for example, as the difference between the average value of the tire surface temperatures of the two front wheels 2FR and 2FL and the average value of the tire surface temperatures of the two rear wheels 2RR and 2RL. Next, the process moves to step S52 to determine whether the front-to-rear difference in tire surface temperature is greater than or equal to a predetermined value. If the front-to-rear difference in tire surface temperature is greater than or equal to a predetermined value, the process moves to step S53; otherwise, it returns to the previous step. In this case, the predetermined value is a value corresponding to the temperature difference between the high-temperature front wheel tire surface temperature and the low-temperature rear wheel tire surface temperature that occur during the aforementioned sports driving. In step S53, the vertical loads of each wheel obtained according to equations 3 to 6 above are read, and these are used to calculate the wheel load of the front wheels and the wheel load of the rear wheels. The wheel load of the front wheels is, for example, the vertical load F of the two front wheels 2FR and 2FL. ＺＦＲ F ＺＦＬ The average value, the wheel load of the rear wheels, is the vertical load F of the two rear wheels (2RR, 2RL). ＺＲＲ F ＺＲＬ The average value is obtained. Next, proceeding to step S54, the target yaw rate γ of vehicle 1 is obtained using the travel speed V and steering angle δ according to equation 17 above. ＴNext, the process moves to step S55, where the actual yaw rate γ of the vehicle 1 detected by the yaw rate sensor 28 is read. Next, the process moves to step S56, where the target yaw rate γ is calculated. Ｔ The yaw rate difference Δγ is calculated from the difference between the actual yaw rate γ and the calculated yaw rate. Next, the process moves to step S57, where, according to individual calculation processes not shown in the diagram, the front-to-rear difference in tire friction coefficients is calculated from the yaw rate difference and the wheel loads of the front and rear wheels, as described above. That is, since the yaw rate difference is the model front-to-rear difference in lateral force of the front and rear wheels, which depends on the friction force of the front and rear wheels, which is the product of the wheel load and the tire friction coefficient, the difference in tire friction coefficients of the front and rear wheels is determined from the calculated yaw rate difference and the wheel loads of the front and rear wheels.

[0039] Next, the process moves to step S58, where the maximum tire friction coefficient of the front wheels is calculated by adding the front-to-rear difference in tire friction coefficients to the maximum tire friction coefficient of the rear wheels using the tire temperature dependence model corrected by the first model correction unit 16. That is, the maximum tire friction coefficients of the rear two wheels 2RR and 2RL are determined using the average values ​​of the tire surface temperatures of the two rear wheels 2RR and 2RL in the corrected tire temperature dependence model, and the maximum tire friction coefficients of the front two wheels 2FR and 2FL are obtained by adding the front-to-rear difference in tire friction coefficients to these maximum tire friction coefficients of the two rear wheels 2RR and 2RL. Next, the process moves to step S59, where the difference between the maximum tire friction coefficient of the front wheels in this tire temperature dependence model and the maximum tire friction coefficient of the front wheels calculated in step S58 is calculated using the tire temperature dependence model corrected by the first model correction unit 16. Specifically, the average values ​​of the tire surface temperatures of the two front wheels (2FR and 2FL) are used to determine the maximum friction coefficients of the two front wheels (2FR and 2FL) in the corrected tire temperature-dependent model. The difference in the maximum friction coefficients of the front wheels is then calculated from the difference between these maximum friction coefficients and the maximum friction coefficients of the two front wheels (2FR and 2FL) calculated in step S58. Next, the process moves to step S60 to determine whether the difference in the maximum friction coefficients of the front wheels calculated in step S59 is greater than or equal to a predetermined value. If the difference in the maximum friction coefficients of the front wheels is greater than or equal to the predetermined value, the process moves to step S61; otherwise, the process returns to the previous step. In step S61, the tire temperature-dependent model is corrected based on the front wheel tire surface temperature and the calculated maximum friction coefficients of the front wheels before returning to the previous step.

[0040] In this calculation process, if the difference in tire surface temperature between the front and rear tires is greater than or equal to a predetermined value that can be considered as being for sporty driving, that is, if the tire surface temperature of the front tires is greater than or equal to a predetermined value than the tire surface temperature of the rear tires, then a correction to the tire temperature dependence model based on the yaw rate difference will be performed. If the tire surface temperatures of the front and rear tires satisfy the conditions for sporty driving, the wheel load of the front and rear wheels will be calculated from the vertical load of each wheel, and the target yaw rate γ of vehicle 1 will be calculated using the driving speed V and steering angle δ. Ｔ We seek this target yaw rate γ ＴThe yaw rate difference Δγ of the actual yaw rate γ is calculated. Based on the principle that this yaw rate difference Δγ is based on the difference in lateral force between the front and rear wheels, the difference in tire friction coefficients between the front and rear wheels is calculated as the front-to-rear difference in tire friction coefficients. Then, the front-to-rear difference in tire friction coefficients is added to the maximum tire friction coefficient corresponding to the tire surface temperature of the colder wheel, i.e., the maximum tire friction coefficient of the rear wheel, to calculate the maximum tire friction coefficient of the front wheel. Since the tire surface temperature of the rear wheel is calculated by the surface temperature calculation unit 11, the maximum tire friction coefficient of the rear wheel corresponding to this rear tire surface temperature can be obtained from the tire temperature dependence model corrected by the first model correction unit 16. Figure 9a shows this corrected tire temperature dependence model. In this example, it is assumed that the tire surface temperature of the front wheel (Fr) is greater than the tire surface temperature of the rear wheel (Rr), so both the maximum tire friction coefficient of the front wheel (Fr) and the maximum tire friction coefficient of the rear wheel (Rr) corresponding to those tire surface temperatures can be obtained from the tire temperature dependence model. However, the maximum tire friction coefficient of the front wheels, calculated by adding the front-to-rear difference in tire friction coefficients to the maximum tire friction coefficient of the rear wheels, may deviate from the corrected tire temperature-dependent model. Figure 9b shows the case where the calculated maximum tire friction coefficient of the front wheels (Fr) is greater than the maximum tire friction coefficient of the front wheels in the tire temperature-dependent model. Conversely, Figure 9c shows the case where the calculated maximum tire friction coefficient of the front wheels (Fr) is greater than the maximum tire friction coefficient of the front wheels in the tire temperature-dependent model. In the case of Figure 9b, for example, the friction force of the front wheels is greater than the friction force inferred from the tire temperature-dependent model, and the actual yaw rate is considered to be above the target yaw rate. In the case of Figure 9c, for example, the friction force of the front wheels is smaller than the friction force inferred from the tire temperature-dependent model, and the actual yaw rate is considered to be below the target yaw rate. In such cases, the tire temperature-dependent model is corrected using the calculated maximum tire friction coefficient of the front wheels, as shown by the dashed lines in Figures 9b and 9c, respectively. In this way, when the tire surface temperature of the front wheels is greater than that of the rear wheels, the accuracy of the tire temperature-dependent model could be improved by correcting the maximum tire friction coefficient using the yaw rate difference.

[0041] Thus, in this embodiment, the tire surface temperature T of the tire 3 mounted on the wheel 2i of the vehicle 1 is ｉ The maximum friction coefficient μ of the tire depends on the tire. ＴＭＡＸｉ When the tire temperature dependence model, which models the tire surface temperature T, is corrected by the processor 5, ｉ The tire surface temperature T is calculated according to the temperature characteristics of tire 3. ｉ Correcting the maximum friction coefficient μ of the tire ＴＭＡＸｉ The corrected tire surface temperature and the calculated maximum tire friction coefficient μ are calculated. ＴＭＡＸｉ The tire temperature dependence model is corrected using this, and further the target yaw rate γ of the vehicle is determined. Ｔ The actual yaw rate γ generated in the vehicle and the target yaw rate γ are calculated. Ｔ The yaw rate difference Δγ is calculated, and the front-to-rear difference in tire friction coefficients between the front and rear wheels is calculated based on the yaw rate difference Δγ and the wheel loads of the front and rear wheels. This front-to-rear difference in tire friction coefficients is then used to correct the tire temperature dependence model. As a result, even with an unknown tire whose specifications are unknown, the tire temperature dependence model can be corrected according to the temperature characteristics of tire 3, and furthermore, the tire temperature dependence model can be appropriately corrected based on the yaw rate difference during sports driving.

[0042] Furthermore, by performing the correction of the tire temperature dependence model using the yaw rate difference when the front-to-rear difference in tire surface temperature between the corrected front and rear wheels exceeds a predetermined value, it becomes possible to define conditions in which the maximum tire friction coefficients of the front and rear wheels are different and appropriately correct the tire temperature dependence model. In addition, by calculating the maximum tire friction coefficient of the front wheel by adding the front-to-rear difference in tire friction coefficients between the front and rear wheels to the maximum tire friction coefficient of the rear wheel and then performing the correction of the tire temperature dependence model using the yaw rate difference, it becomes possible to appropriately correct the tire temperature dependence model during sports driving.

[0043] Furthermore, the calculated tire surface temperature T ｉ Estimated internal tire temperature T ＥＩＮＲｉ The internal tire temperature T detected at the same time is determined, and ＩＮＲｉ Estimated internal tire temperature T ＥＩＮＲｉFrom this, it is determined that it is an unknown tire with unknown specifications. This allows for proper determination of whether it is an unknown tire with unknown specifications. In addition, the calculated tire surface temperature T ｉ Tire internal temperature T ＩＮＲｉ Based on the delay state, the tire surface temperature T ｉ The tire heat storage coefficient W used in the calculation Ｘｉ , W Ｙｉ This corrects the tire surface temperature T, even for unknown tires with unknown specifications. ｉ This makes it possible to calculate the road surface friction coefficient μ of the road surface on which vehicle 1 travels. Ｒ Obtain this road surface friction coefficient μ Ｒ The tire friction coefficient μ of each wheel 2i Ｔｉ The coefficient of friction of the tire μ is calculated, and this tire friction coefficient μ Ｔｉ From the tire's maximum friction coefficient μ ＴＭＡＸｉ This calculates the appropriate tire surface temperature T. ｉ In conjunction with this, the tire temperature-dependent model can be properly corrected.

[0044] Although the tire temperature dependence model correction system according to the embodiment has been described above, the present invention is not limited to the configuration described in the above embodiment, and various modifications are possible within the scope of the gist of the present invention.

[0045] 1...Vehicle, 2i...Wheel, 3...Tire, 4...Tire temperature dependence model providing device, 5...Processor (arithmetic processing unit), 6...Tire temperature estimation unit, 7...Tire temperature dependence model correction unit, 8...Heat generation amount calculation unit, 9...Heat dissipation amount calculation unit, 10...Temperature change amount calculation unit, 11...Surface temperature calculation unit, 12...Different tire type determination unit, 13...Road surface friction coefficient acquisition unit, 14...Tire friction coefficient calculation unit, 15...Maximum tire friction coefficient calculation unit, 16...First model correction unit, 28...Yaw rate sensor, 29...Wheel load acquisition unit, 30...Target yaw rate calculation unit, 31...Yaw rate difference calculation unit, 32...Front-rear difference in tire friction coefficient calculation unit, 32...Second model correction unit

Claims

1. A tire temperature dependence model correction method for correcting a tire temperature dependence model that models the maximum friction coefficient of a tire that depends on the surface temperature of the tire mounted on the wheel of a vehicle, using a processing unit, comprising: a tire surface temperature calculation step for calculating the surface temperature of the tire; a tire surface temperature correction step for correcting the surface temperature of the tire calculated according to the temperature characteristics of the tire; a tire maximum friction coefficient calculation step for calculating the maximum friction coefficient of the tire; a first model correction step for correcting the tire temperature dependence model using the corrected tire surface temperature and the calculated maximum friction coefficient of the tire; a target yaw rate calculation step for calculating the target yaw rate of the vehicle; a yaw rate difference calculation step for calculating the yaw rate difference between the yaw rate occurring in the vehicle and the target yaw rate; a tire friction coefficient front-to-front difference calculation step for calculating the front-to-rear difference in the friction coefficient of the tire between the front and rear wheels based on the yaw rate difference and the wheel loads of the front and rear wheels; and a second model correction step for correcting the tire temperature dependence model using the front-to-rear difference in the friction coefficient of the tire.

2. The tire temperature dependence model correction method according to claim 1, characterized in that the correction of the tire temperature dependence model in the second model correction step is performed when the difference in the surface temperature of the corrected front and rear tires is greater than or equal to a predetermined value.

3. The tire temperature dependence model correction method according to claim 1, characterized in that the correction of the tire temperature dependence model in the second model correction step is performed by adding the difference between the front and rear tire friction coefficients to the maximum friction coefficient of the front or rear tire whichever is smaller, to calculate the maximum friction coefficient of the front or rear tire whichever is larger.

4. The tire temperature dependence model correction method according to claim 1, characterized in that the first tire surface temperature correction step comprises: an estimated tire internal temperature calculation step of estimating the internal temperature of the tire from the calculated tire surface temperature; and an unknown tire determination step of determining that the tire is an unknown tire with unknown specifications from the internal temperature of the tire detected at the same time and the estimated internal temperature of the tire.

5. The tire temperature dependence model correction method according to claim 4, characterized in that the first tire surface temperature correction step includes a tire heat storage coefficient correction step that corrects the heat storage coefficient of the tire used in calculating the tire surface temperature based on the delay state of the detected internal temperature of the tire with respect to the calculated surface temperature of the tire.

6. The tire temperature dependence model correction method according to claim 1, wherein the step for calculating the maximum tire friction coefficient comprises: a step for obtaining the friction coefficient of the road surface on which the vehicle travels; and a step for calculating the friction coefficient of the tire of the wheel from the obtained friction coefficient of the road surface, and the maximum friction coefficient of the tire is calculated from the calculated friction coefficient of the tire.

7. A tire temperature dependence model correction device that corrects a tire temperature dependence model, which models the maximum friction coefficient of a tire that depends on the surface temperature of the tire mounted on the wheel of a vehicle, using a calculation processing device, wherein the calculation processing device calculates the surface temperature of the tire, corrects the surface temperature of the tire calculated according to the temperature characteristics of the tire, calculates the maximum friction coefficient of the tire, corrects the tire temperature dependence model using the corrected surface temperature of the tire and the calculated maximum friction coefficient of the tire, calculates the target yaw rate of the vehicle, calculates the yaw rate difference between the yaw rate occurring in the vehicle and the target yaw rate, calculates the front-to-rear difference in the friction coefficient of the tires between the front and rear wheels based on the yaw rate difference and the wheel loads of the front and rear wheels, and further corrects the tire temperature dependence model using the front-to-rear difference in the friction coefficient of the tires.

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