Tire temperature dependence model correction method and device therefor

Abstract

Provided are a tire temperature dependence model correction method and a device therefor, whereby a tire temperature dependence model can be properly corrected. When using a processor (5) to correct a tire temperature dependence model obtained by modeling a tire maximum friction coefficient that is dependent on the tire surface temperature of a tire (3) mounted on a wheel (2i) of a vehicle (1), the tire surface temperature is calculated, the calculated tire surface temperature is corrected according to the temperature characteristics of the tire (3), the tire maximum friction coefficient is calculated, and the tire temperature dependence model is corrected using the corrected tire surface temperature and the calculated tire maximum friction coefficient.

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, described below, discloses a technique for estimating the maximum friction coefficient according to individual tire specifications based on the tread distribution characteristics, tire 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 computational processing unit. 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, and then correcting the tire temperature dependence model using the corrected surface temperature of the tire and the calculated maximum friction coefficient of the tire.

[0006] According to one aspect of the present invention, even for an unknown tire with unknown specifications, the tire temperature dependence model can be appropriately corrected according to the tire's temperature characteristics.

[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.

[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 31 for autonomous driving. 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 31 for autonomously driving this vehicle 1, for example, based on control inputs such as surrounding environment information obtained from an environment recognition system and communication information obtained from a 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 31 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 31 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 31, 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 then estimated by the tire temperature estimation unit 6 described later. ｉ The maximum friction coefficient (maximum tire friction coefficient) μ of each wheel 2i ＴＭＡＸｉ Obtain this maximum friction coefficient μ ＴＭＡＸｉ Using this, control commands to, for example, the drive controller, brake controller, and steering controller are calculated and set. In order for this tire temperature dependence model providing device 4 to function, the vehicle 1 is equipped with 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 (turning angle) δ of the front wheels 2FR and 2FL, which are the steering wheels of the vehicle 1. The acceleration sensor 22 detects the longitudinal acceleration a generated in the vehicle 1. Ｘ and the acceleration a in the width direction (lateral direction) of the vehicle 1 ＹIt is for detecting. Also, the speed sensor 23 is for detecting the traveling speed V of the vehicle 1. Also, the driving force sensor 24 is for detecting the driving force and braking force (driving and braking force) F generated in the vehicle 1 ＸＴＴＬ It is for detecting.

[0011] The detection information detected by these steering angle sensor 21, acceleration sensor 22, speed sensor 23, and driving force sensor 24 is acquired by a vehicle state acquisition unit 17 constructed in a processor 5 described later. Also, the road surface temperature sensor 25 is for detecting the road surface temperature T of the road surface on which the vehicle 1 travels ＲＯＡＤ [°C], and is composed of, for example, a non-contact temperature sensor attached to the lower part of the vehicle body of the vehicle 1. In that case, it 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 is for detecting the outside air temperature T outside the vehicle 1 ＡＩＲ [°C], and in this embodiment, it is attached to a part facing the inside of the wheelhouse of the vehicle 1. That is, the outside air temperature sensor 26 in this embodiment is for detecting the temperature around the tire 3 of the wheel 2i in the wheelhouse. The TPMS 27 detects the air pressure of the tire 3 of each wheel 2i and also detects the internal temperature of the tire (tire internal temperature) T ＩＮＲ [°C], and is attached to, for example, the wheel of each wheel 2i. The outside air temperature T detected by the outside air temperature sensor 26 ＡＩＲ and the tire internal temperature T detected by the TPMS 27 ＩＮＲ are acquired by an environmental temperature acquisition unit 19 constructed in a processor 5 described later. Note that the tire internal temperature T ＩＮＲ is used with the subscript i indicating the position of each wheel 2i attached.

[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 model correction unit 16. 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 (turning 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 ＸＴＴＬThe 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, L Ｒ [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 Ｚｉ Based 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 ＹｉThe 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, for example. 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 Ｙｉ Using 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, although it is called heat generation, the calculated tire heat generation 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 is obtained in [°C]. The previous temperature acquisition unit 20 uses the outside air temperature T detected by the outside air temperature sensor 26 and acquired by the environmental temperature acquisition unit 19 ＡＩＲ data as the initial value of the previous tire surface temperature T ０ｉ and obtains it through CAN. That is, the initial value of the previous tire surface temperature T ０ｉ is the outside air temperature T ＡＩＲ . Using the previous tire surface temperature T acquired by this previous temperature acquisition unit 20 ０ｉ , 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 ｉ of the tire 3 of each wheel 2i in [°C / s]. The first tire heat dissipation amount QD1 ｉ is, as shown in FIG. 3, the heat dissipation amount from the tire 3 of each wheel 2i to the road surface, and is obtained by the following equation (13) using the road surface temperature T acquired by the road surface temperature acquisition unit 18. Note that the road surface heat dissipation coefficient κ ＲＯＡＤ in the formula [1 / s] may be set to be larger as the road surface temperature is lower. Also, the second heat dissipation amount calculation unit 9b in the heat dissipation amount calculation unit 9 calculates the second heat dissipation amount (second tire heat dissipation amount) QD2 １ of the tire 3 of each wheel 2i in [°C / s] using the previous tire surface temperature T. This second tire heat dissipation amount QD2 ０ｉ is obtained by the following equation (14) based on the outside air temperature T acquired by the environmental temperature acquisition unit 19 and the tire internal temperature T, and as shown in FIG. 3, includes the heat dissipation amount QD21 (the first term on the right side of equation (14)) 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 equation (14)) from the tire 3 to the air inside the tire. Note that the outside air heat dissipation coefficient κ ｉ in the formula is set to be larger as the outside air temperature T is lower. Also, the internal heat dissipation coefficient κ ｉ in the formula may be set to be larger as the tire internal temperature T is lower. ＡＩＲ ＩＮＲｉ ２ ＡＩＲ ３ ＩＮＲｉ

[0025]

[0026] Here, the first tire heat dissipation amount QD1 ｉand the second tire heat dissipation amount QD2 ｉ As is clear from the unit of, although it is called the heat dissipation amount, the calculated first tire heat dissipation amount QD1 ｉ and the second tire heat dissipation amount QD2 ｉ is the temperature decrease amount of tire 3 per unit time, that is, what can be called the tire temperature decrease rate. Note that the previous tire surface temperature T ０ｉ and the outside air temperature T ＡＩＲ The value obtained by multiplying the difference value by the outside air heat dissipation coefficient κ ２ That is, only the first term on the right side of Equation 14 may be used as the second tire heat dissipation amount QD2 ｉ Similarly, the value obtained by multiplying the difference value between the previous tire surface temperature T ０ｉ and the tire internal temperature T ＩＮＲｉ by the internal heat dissipation coefficient κ ３ That is, only the second term on the right side of Equation 14 may be used as the second tire heat dissipation amount QD2 ｉ And 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 tire 3 of each wheel 2i according to the following Equation 15. Also, if Equation 12 is substituted into the tire heat generation amount QG ｉ in Equation 15, the following Equation 16 is obtained. Here, as is clear from the unit of the tire temperature change amount dT ｉ / dt, although it is called the change amount, the calculated tire temperature change amount dT ｉ / dt is the temperature change amount of tire 3 per unit time, that is, what can be called the tire temperature change rate. And the surface temperature calculation unit 11 in FIG. 1 calculates the surface temperature (tire surface temperature) T ０ｉ of tire 3 of each wheel 2i based on the previous tire surface temperature T ｉ and the tire temperature change amount dT ｉ / dt.

[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. ＩＮＲｉ The 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 ＡＩＲand 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 31 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 31. 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 (μ) is saturated, the tire friction coefficient (μ) is greater than the slip ratio (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 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 surface temperature 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 of tire 3 is W 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 detect and identify even more different types of tires. The criteria for identifying 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 a 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 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 The calculation error is also related to the tire's maximum friction coefficient μ. ＴＭＡＸｉ The calculation error was also kept within a small range, and the accuracy of the tire temperature dependence model improved compared to the case without correction. In contrast, the tire heat storage coefficient W was calculated without distinguishing between different types of tires. Ｘｉ , W Ｙｉ Tire surface temperature T when not corrected ｉ The calculation error and the maximum friction coefficient μ of the tire ＴＭＡＸｉ The calculation error was a relatively large value. That is, the different tire type determination unit 12 in this embodiment determines 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] 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 method. This allows the tire temperature dependence model to be appropriately corrected according to the temperature characteristics of tire 3, even for unknown tires with unknown specifications. In addition, 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 ＥＩＮＲｉ From 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. ｉIn conjunction with this, the tire temperature dependence model can be appropriately corrected. The tire temperature dependence model correction system according to the embodiment has been described above, but 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.

[0036] 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...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 a tire mounted on a vehicle's wheel, the method 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; and a model correction step for correcting the tire temperature dependence model using the corrected surface temperature of the tire and the calculated maximum friction coefficient of the tire.

2. The tire temperature dependence model correction method according to claim 1, characterized in that the 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.

3. The tire temperature dependence model correction method according to claim 2, characterized in that the 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 tire surface temperature.

4. 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 wheel's tire from the obtained friction coefficient of the road surface, and the maximum tire friction coefficient is calculated from the calculated tire friction coefficient.

5. 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 a tire mounted on a vehicle's wheel, by 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, and corrects the tire temperature dependence model using the corrected surface temperature of the tire and the calculated maximum friction coefficient of the tire.

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