JP2020011651A - Correction device, method and program for rotational speed of tire - Google Patents

Abstract

To calculate the rotational speed of a tire in which the impact of slip is cancelled.SOLUTION: A correction device acquires the rotational speeds of the first and second tires and calculates a comparison value comparing those rotational speeds, and also acquires a lateral acceleration applied to a vehicle and wheel torque. Further, the correction device calculates a linear parameter specifying a linear model which expresses the relation of the wheel torque with the comparison value and in which the inclination of the comparison value to the wheel torque depends on a lateral acceleration on the basis of the comparison value, lateral acceleration and wheel torque. Furthermore, the device calculates the rotational speed of the first tire in which the impact of slip is cancelled. One of the first and second tires is a front wheel tire and the other is a rear wheel tire, and the first tire is one to which a higher drive power than that of the second tire is applied.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a correction device, a method, and a program for correcting the rotation speed of one tire or a plurality of tires mounted on a vehicle.

  In order to make the vehicle run comfortably, it is important that the tire pressure is adjusted. This is because if the air pressure is lower than the appropriate value, there is a possibility that the ride comfort and the fuel efficiency may deteriorate. BACKGROUND ART Conventionally, a system (Tire Pressure Monitoring System; TPMS) for automatically detecting tire pressure reduction has been studied. The information that the tire is depressurized can be used, for example, for warning the driver.

  The method of detecting the pressure reduction of the tire includes a method of directly measuring the air pressure of the tire by attaching a pressure sensor to the tire, and a method of indirectly evaluating the pressure reduction of the tire using other index values. There is. As such a method, a Dynamic Loaded Radius (DLR) method or the like is known. The DLR method utilizes a phenomenon in which a reduced pressure tire is crushed during running, thereby reducing the dynamic load radius and rotating at a higher speed, and estimates the reduced pressure of the tire from the rotation speed of the tire (Patent Document 1 etc.).

Patent Document 1 discloses a detection device of the DLR system, and mentions three index values called DEL1 to DEL3 as decompression index values for evaluating decompression in the DLR system. In Patent Document 1, DEL1 to DEL3 are defined as follows. Here, V1 to V4 are the wheel speeds of the front left wheel, front right wheel, rear left wheel, and rear right wheel tire, respectively.
DEL1 = [(V1 + V4) / 2- (V2 + V3) / 2] / [(V1 + V2 + V3 + V4) / 4] × 100 (%)
DEL2 = [(V1 + V2) / 2- (V3 + V4) / 2] / [(V1 + V2 + V3 + V4) / 4] × 100 (%)
DEL3 = [(V1 + V3) / 2- (V2 + V4) / 2] / [(V1 + V2 + V3 + V4) / 4] × 100 (%)

  When the tire is depressurized, the rotation speed increases, so that decompression index values such as DEL1 to DEL3 also change. Accordingly, by setting the pressure reduction index value when the pressure reduction amount is reduced by the detection target as the threshold value, the pressure reduction can be detected.

Patent No. 4809199

  Meanwhile, the rotation speed of the tire for determining the above-described pressure reduction index value is affected by not only the pressure reduction of the tire but also the slip of the tire. Slip increases as wheel torque increases. That is, the rotation speed of the tire is not only affected by the pressure reduction, but also varied by the effect of the slip which changes according to the wheel torque. Therefore, depending on running conditions such as wheel torque, the accuracy of detecting reduced pressure based on the reduced pressure index value calculated from the rotation speed of the tire may be reduced. Therefore, it is desired to cancel the influence of the slip from the rotation speed of the tire. Note that canceling the influence of slip from the tire rotation speed is not only a case where tire pressure reduction is detected based on the pressure reduction index value, but also various controls based on tire rotation speed, such as a case where brake control is performed. It can also be desirable in situations where it takes place.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a correction device, a method, and a program for canceling an influence of a tire slip that changes according to a wheel torque and correcting a rotation speed of the tire.

  A correction device according to a first aspect of the present invention is a correction device that corrects a rotation speed of a first tire mounted on a vehicle, and includes a rotation speed acquisition unit, a comparison value calculation unit, and a lateral acceleration acquisition unit. , A torque obtaining unit, a linear relationship specifying unit, and a rotation speed correcting unit. The rotation speed obtaining unit obtains rotation speeds of the first tire and a second tire mounted on the vehicle. The comparison value calculation unit calculates a comparison value for comparing a rotation speed of the first tire with a rotation speed of the second tire. The lateral acceleration acquisition unit acquires a lateral acceleration applied to the vehicle. The torque obtaining unit obtains a wheel torque. The linear relationship identification unit is a linear model representing a relationship between the wheel torque and the comparison value based on the comparison value, the lateral acceleration, and the wheel torque, and includes a slope of the comparison value with respect to the wheel torque. Calculates a linear parameter that specifies a linear model and depends on the lateral acceleration. The rotation speed correction unit calculates a rotation speed of the first tire from which an influence of a slip on the comparison value caused by the wheel torque is canceled based on the rotation speed of the second tire and the linear parameter. One of the first tire and the second tire is a front wheel tire, the other is a rear wheel tire, and the first tire is a tire to which a greater driving force is applied than the second tire.

  The correction device according to a second aspect of the present invention is the correction device according to the first aspect, wherein the comparison value calculation unit determines, as the comparison value, two front tires and two rear wheels mounted on the vehicle. Among the tires, a first comparison value for comparing the rotation speed of one front wheel tire with the rotation speed of one rear wheel tire is calculated, and the rotation speed of the other front wheel tire and the rotation speed of the other rear tire are calculated. To calculate a second comparison value.

  A correction device according to a third aspect of the present invention is the correction device according to the first aspect or the second aspect, and further includes a decompression index value calculation unit. The decompression index value calculation unit may be any of four tires mounted on the vehicle based on the rotation speed of the second tire and the rotation speed of the first tire calculated by the rotation speed correction unit. Calculating a decompression index value, which is a comparison value for comparing the rotation speeds of the two wheels with the rotation speeds of the remaining two wheels, and comparing the decompression index value with a predetermined threshold value, thereby obtaining at least one of the tires. Detects the reduced pressure.

  The correction device according to a fourth aspect of the present invention is the correction device according to the third aspect, further including an alarm output unit that outputs a pressure reduction warning when a pressure reduction state of the tire is detected.

  A correction device according to a fifth aspect of the present invention is the correction device according to any one of the first to fourth aspects, wherein the comparison value is a rotation speed of the first tire and a rotation speed of the second tire. And the ratio.

  A correction device according to a sixth aspect of the present invention is the correction device according to any one of the first to fifth aspects, wherein the first tire is a driving wheel tire, and the second tire is a driven wheel. Tires.

A correction method according to a seventh aspect of the present invention is a correction method for correcting the rotation speed of a first tire mounted on a vehicle, and includes the following.
(1) Obtaining rotation speeds of the first tire and a second tire mounted on the vehicle.
(2) calculating a comparison value for comparing the rotation speed of the first tire with the rotation speed of the second tire;
(3) Obtaining lateral acceleration applied to the vehicle.
(4) Obtaining wheel torque.
(5) A linear model representing a relationship between the wheel torque and the comparison value based on the comparison value, the lateral acceleration, and the wheel torque, wherein a slope of the comparison value with respect to the wheel torque is equal to the lateral direction. Calculate linear parameters that specify a linear model that depends on acceleration.
(6) Based on the rotation speed of the second tire and the linear parameter, calculate the rotation speed of the first tire from which the influence of the slip on the comparison value due to the wheel torque is canceled.
Note that one of the first tire and the second tire is a front wheel tire, the other is a rear wheel tire, and the first tire is a tire to which a greater driving force is applied than the second tire.

A correction program according to an eighth aspect of the present invention is a correction program for correcting a rotation speed of a first tire mounted on a vehicle, and causes a computer to execute the following.
(1) Obtaining rotation speeds of the first tire and a second tire mounted on the vehicle.
(2) calculating a comparison value for comparing the rotation speed of the first tire with the rotation speed of the second tire;
(3) Obtaining lateral acceleration applied to the vehicle.
(4) Obtaining wheel torque.
(5) A linear model representing a relationship between the wheel torque and the comparison value based on the comparison value, the lateral acceleration, and the wheel torque, wherein a slope of the comparison value with respect to the wheel torque is equal to the lateral direction. Calculate linear parameters that specify a linear model that depends on acceleration.
(6) Based on the rotation speed of the second tire and the linear parameter, calculate the rotation speed of the first tire from which the influence of the slip on the comparison value due to the wheel torque is canceled.
Note that one of the first tire and the second tire is a front wheel tire, the other is a rear wheel tire, and the first tire is a tire to which a greater driving force is applied than the second tire.

  As the wheel torque increases, the slip of the tire increases, but the ease of slipping usually differs between the front tire and the rear tire. More specifically, in the case of a front-wheel drive vehicle or a rear-wheel drive vehicle, slip occurs in the drive wheel tire due to wheel torque. As a result, as the wheel torque increases, the balance between the rotational speed of the front wheel tires and the rotational speed of the rear wheel tires gradually changes, so that a linear relationship is established between the comparison value of the two and the wheel torque. obtain. In the case of a four-wheel drive vehicle, when a slip occurs due to wheel torque on a tire to which a larger driving force is applied, and when the torque distribution of the front and rear wheels is constant, a linear relationship can be established as described above. Further, the ease of slip varies between straight running and turning when the lateral acceleration applied to the vehicle is different. In other words, the influence of the wheel torque on the comparison value becomes greater as the lateral acceleration increases. This is modeled by expressing the slope of the comparison value with respect to the wheel torque as being dependent on the lateral acceleration in a linear model representing the relationship between the comparison value and the wheel torque. According to the present invention, such a linear model is specified, and the rotational speed of the tire is corrected based on the linear model. Therefore, it is possible to cancel the influence of the slip of the tire, which changes according to the wheel torque, from the rotation speed of the tire.

FIG. 1 is a schematic diagram illustrating a state in which a correction device according to an embodiment of the present invention is mounted on a vehicle. FIG. 2 is a block diagram showing an electrical configuration of the correction device. 9 is a flowchart illustrating a flow of a rotation speed correction process. The graph which plotted the wheel torque and the comparative value at the time of going straight. The graph which plotted the wheel torque and the comparative value at the time of going straight. The figure explaining load movement by lateral acceleration. The figure explaining load movement by lateral acceleration. The graph which plotted the wheel torque and the comparative value at the time of turning. The graph which plotted the wheel torque and the comparative value at the time of turning.

  Hereinafter, a correction device, a method, and a program according to an embodiment of the present invention will be described with reference to the drawings.

<1. Configuration of Correction Device>
FIG. 1 is a schematic diagram illustrating a state in which the correction device 2 according to the present embodiment is mounted on a vehicle 1. The vehicle 1 is a four-wheeled vehicle and includes a front left wheel FL, a front right wheel FR, a rear left wheel RL, and a rear right wheel RR. Tires T _FL , T _FR , T _RL , and T _RR are mounted on the wheels FL, FR, RL, and RR, respectively. The vehicle 1 according to the present embodiment is a front engine / front drive vehicle (FF vehicle), in which tires T _FL and T _FR as front wheel tires are driving wheel tires, and tires T _RL and T _{RR as} rear wheel tires. Is a driven wheel tire. Therefore, a greater driving force is applied to the tires T _FL and T _FR than to the tires T _RL and T _RR . The correction device 2 has a function of canceling the influence of the slip of the driving wheel tires T _FL and T _FR that changes according to the wheel torque, and correcting the measured rotation speed of the driving wheel tires T _FL and T _FR. I have. Further, the correcting device 2 determines the tires T _FL , T _FR , T _FR , based on the corrected rotation speeds of the drive wheel tires T _FL , T _FR and the measured rotation speeds of the driven wheel tires T _RL , T _RR . It has a function of detecting the pressure reduction of T _RL and T _RR . The correction device 2 is mounted on the vehicle 1 when a pressure reduction index value based on a dynamic load radius (DLR) method is calculated, and when the pressure reduction of the tires T _FL , T _FR , T _RL , and T _RR is detected based on the calculated value. An alarm to that effect is issued through the display 3 which is being displayed. Processing for detecting pressure reduction of the tires T _FL , T _FR , T _RL , and T _RR including processing for correcting the rotation speeds of the drive wheel tires T _FL , T _FR (hereinafter, sometimes referred to as rotation speed correction processing) (hereinafter, referred to as rotation speed correction processing). , May be referred to as pressure reduction detection processing) will be described later.

In the present embodiment, the reduced pressure state of the tires T _FL , T _FR , T _RL , and T _RR is detected based on the wheel speed (rotation speed). Wheel speed sensors 6 are attached to the tires T _FL , T _FR , T _RL , T _RR (more precisely, the wheels on which the tires T _FL , T _FR , T _RL , T _RR are mounted). The wheel speed sensor 6 detects the wheel speed information (that is, the tire rotation speed information) of the wheel to which the wheel is attached. The wheel speed sensors 6 are connected to the correction device 2 via the communication line 5, and wheel speed information detected by each wheel speed sensor 6 is transmitted to the correction device 2 in real time.

  As the wheel speed sensor 6, any device can be used as long as it can detect the wheel speed of the running wheels FL, FR, RL, RR. For example, a sensor of a type that measures wheel speed from an output signal of an electromagnetic pickup can be used, or a sensor that generates power using rotation like a dynamo and measures the wheel speed from a voltage at this time can be used. It can also be used. The mounting position of the wheel speed sensor 6 is not particularly limited, and may be appropriately selected according to the type of the sensor as long as the wheel speed can be detected.

  A wheel torque sensor (hereinafter, referred to as a WT sensor) 7 is attached to the left front wheel, which is one drive wheel FL of the vehicle 1. The WT sensor 7 detects a wheel torque WT of the vehicle 1. The WT sensor 7 is connected to the correction device 2 via the communication line 5, and information on the wheel torque WT detected by the WT sensor 7 is transmitted to the correction device 2 in real time.

  The structure and the mounting position of the WT sensor 7 are not particularly limited as long as the wheel torque of the driving wheel of the vehicle 1 can be detected. Various types of wheel torque sensors are commercially available, and their configurations are well-known, and thus detailed description is omitted here. Further, the wheel torque can be detected without using the WT sensor 7, and for example, the wheel torque can be estimated from the engine torque obtained from the engine control device.

  The vehicle 1 is provided with a lateral acceleration sensor 4 for detecting a lateral acceleration applied to the vehicle 1. The mounting position of the lateral acceleration sensor 4 is not particularly limited, and can be appropriately selected. The lateral acceleration sensor 4 is connected to the correction device 2 via a communication line 5. The information on the lateral acceleration detected by the lateral acceleration sensor 4 is transmitted to the correction device 2 in real time, like the wheel speed information and the information on the wheel torque WT.

  FIG. 2 is a block diagram illustrating an electrical configuration of the correction device 2. As shown in FIG. 2, the correction device 2 is a control unit mounted on the vehicle 1 as hardware, and includes an I / O interface 11, a CPU 12, a ROM 13, a RAM 14, and a non-volatile rewritable storage device. 15 are provided. The I / O interface 11 is a communication device for communicating with external devices such as the lateral acceleration sensor 4, the wheel speed sensor 6, the WT sensor 7, and the display 3. The ROM 8 stores a program 8 for controlling the operation of each part of the vehicle 1. The program 8 is written to the ROM 13 from a storage medium such as a CD-ROM or a writing device. The CPU 12 reads out and executes the program 8 from the ROM 13 to virtually execute the rotation speed acquisition unit 21, the torque acquisition unit 22, the lateral acceleration acquisition unit 23, the comparison value calculation unit 24, the linear relationship identification unit 25, the rotation speed It operates as the correction unit 26, the DEL calculation unit 27, and the alarm output unit 28. Details of the operation of each unit 21 to 28 will be described later. The storage device 15 is configured by a hard disk, a flash memory, or the like. The storage location of the program 8 may be the storage device 15 instead of the ROM 13. The RAM 14 and the storage device 15 are appropriately used for the operation of the CPU 12.

The display 3 can be realized in any mode, for example, a liquid crystal display element, a liquid crystal monitor, a plasma display, an organic EL display, and the like, as long as the user can be notified that the decompression is occurring. For example, the indicator 3 may be one in which four lamps respectively corresponding to the four-wheel tires T _FL , T _FR , T _RL , and T _RR are arranged in accordance with the actual arrangement of the tires. The mounting position of the display 3 can also be appropriately selected, but is preferably provided at a position that is easy for the driver to understand, such as on an instrument panel. When the control unit (correction device 2) is connected to a car navigation system, a monitor for car navigation can be used as the display 3. When a monitor is used as the display 3, the alarm may be an icon or text information displayed on the monitor.

<2. Decompression detection processing>
Hereinafter, with reference to FIG. 3, a decompression for detecting a decompression of the tires T _FL , T _FR , T _RL , and T _RR including a rotation speed correction process for correcting the rotation speeds of the drive wheel tires T _FL and T _FR. The detection process will be described. The process illustrated in FIG. 3 is repeatedly executed at a predetermined timing (for example, once every 10 minutes) while the electric system of the vehicle 1 is powered on. In the decompression detection process according to the present embodiment, it is specified which of the four tires _TFL , _TFR , _TRL , and _TRR is depressurized. More specifically, a reduced pressure tire can be detected in the following 14 patterns.
(1) _Reduced pressure only in T _FL (2) _Reduced pressure only in T _FR (3) _Reduced pressure only in T _RL (4) _Reduced pressure only in T _RR (5) _Reduced pressure only in T _FL and T _FR (6) _Reduced pressure only in T _FL and T _RL (7 ) Only T _FL , T _RR decompressed (8) Only T _FR , T _RL depressurized (9) Only T _FR , T _RR depressed (10) Only T _RL , T _RR depressed (11) Only T _FL , T _FR , T _RL Reduced pressure (12) _Reduced pressure only in T _FL , T _RL and T _RR (13) _Reduced pressure only in T _FL , T _FR and T _RR (14) _Reduced pressure only in T _FR , T _RL and T _RR

In step S1, the rotation speed acquisition unit 21 acquires V1 to V4. Here, V1 to V4 are the rotation speeds of the tires T _FL , T _FR , T _RL , and T _RR , that is, the wheel speeds of the wheels FL, FR, RL, and RR. The rotation speed acquisition unit 21 receives an output signal from the wheel speed sensor 6 during a predetermined sampling period ΔT, and converts the output signal into wheel speeds V1 to V4.

  In the following step S2, the torque obtaining unit 22 obtains the wheel torque WT of the vehicle 1. The torque obtaining unit 22 receives an output signal from the WT sensor 7 and converts the output signal into a wheel torque WT. Note that the output signal of the WT sensor 7 received at this time is data at the same time or substantially the same time as the output signal of the wheel speed sensor 6 received in the latest step S1.

  In the following step S3, the lateral acceleration acquisition unit 23 acquires the lateral acceleration α applied to the vehicle 1. The lateral acceleration acquisition unit 23 receives an output signal from the lateral acceleration sensor 4 and converts this into a lateral acceleration α. Note that the output signal of the lateral acceleration sensor 4 received at this time is data at the same time or substantially the same time as the output signal of the wheel speed sensor 6 received in the latest step S1.

In step S4, the comparison value calculation unit 24, the tire _{T FL, T FR, T RL} , from the rotational speed V1~V4 of T _RR, comparison value H1 of the rotational speed and the rotational speed of the rear wheel tires of the front wheel tires, Calculate H2. The comparison values H1 and H2 are values that decrease as the front wheel speed increases and increase as the rear wheel speed increases, or increase as the front wheel speed increases and increase as the rear wheel speed increases. It is a value that becomes smaller.

The comparison values H1 and H2 can be defined by various methods as long as they have the above characteristics. In the present embodiment, H1 and H2 are calculated according to the following equations. That is, in this embodiment, the comparison value H1 is the rotational speed V1 of the left front tire T _FL which is one of the driving wheel tires, in likewise driven wheel tires mounted on the left side of the vehicle 1 and the drive wheel tire T _FL This is a comparison value for comparing with the rotation speed V3 of a certain left rear wheel tire _TRL , and is expressed in the form of the ratio of the latter to the former. Comparison value H2, the other a rotational speed V2 of the right front tire T _FR is driven wheel tire, drive wheel tire T _FR Like right rear wheel tire T _RR is a driven wheel tires mounted on the right side of the vehicle 1 And a comparison value for comparing the rotation speed V4 with the rotation speed V4, and is expressed in the form of a ratio of the former to the latter.
H1 = V3 / V1
H2 = V4 / V2

In another embodiment, it can be defined as follows.
H1 = V3 ² / V1 ²
H2 = V4 ² / V2 ²

Alternatively, H1 and H2 can be defined as follows.
H1 = V4 / V1
H2 = V3 / V2

The comparison value H1 defined as described above is the rotation speed of one front tire and the rotation of one rear tire of the two front tires T _FL and T _FR and the two rear tires T _RL and T _RR. This is a comparison value for comparing with speed. Further, the comparison value H2 defined as described above is the rotation speed of the other front wheel tire and the other rear wheel tire of the two front wheel tires T _FL and T _FR and the two rear wheel tires T _RL and T _RR. This is a comparison value for comparing with the rotation speed of.

  The data sets of the wheel speeds V1 to V4, the wheel torque WT, the lateral acceleration α, and the comparison values H1 and H2 at or substantially at the same time acquired in steps S1 to S4 are stored in the RAM 14 or the storage device 15. . Steps S1 to S4 are repeatedly executed, and when the number of stored data sets becomes equal to or larger than the preset number N, the process proceeds to step S5.

  In step S5, the linear relationship specifying unit 25 determines the wheel torque WT and the comparison values H1, H2 based on the wheel torque WT, the lateral acceleration α, and the comparison values H1, H2, which are stored in the RAM 14 or the storage device 15. The linear models representing the relationship with are specified. Further, in the subsequent step S6, based on the linear model specified in step S5, it is possible to obtain the rotational speeds V1 'and V2' of the driving wheel tires from which the influence of the tire slip has been canceled. In the present embodiment, the rotation speeds V1 'and V2' obtained in this manner are used for detecting the pressure reduction of the DLR tire. By using the rotation speeds V1 'and V2', the decompression index values DEL1 to DEL3 canceling the influence of the tire slip can be obtained, so that the accuracy of detecting the decompression of the tire can be further improved.

  Hereinafter, the principle of steps S5 and S6 for canceling the influence of the slip from the rotation speed of the tire of the vehicle 1 will be described with reference to FIGS.

First, when the wheel torque WT is equal to or less than a certain value, it is considered that no or almost no slip occurs in the tire. However, as the wheel torque WT increases, the slip of the driving wheel tire increases. On the other hand, the driven wheel tire does not cause much slip. Therefore, when the wheel torque WT increases, the rotation speed of the driving wheel tire detected by the wheel speed sensor 6 increases, and the difference between this and the rotation speed of the driven wheel tire increases. Therefore, a linear relationship is established between the wheel torque WT and the comparison values H1 and H2 of the rotation speed of the driving wheel tire and the rotation speed of the driven wheel tire. FIG. 4A and FIG. 4B are experimental data of the vehicle 1 supporting this. FIGS. 4A and 4B are graphs respectively plotting the wheel torque WT and H1, H2 measured under the condition that the tire has the standard internal pressure. Here, H1 = V3 / V1, and H2 = V4 / V2. As shown in FIGS. 4A and 4B, the relationship between the acquired wheel torque WT and the comparison value H1 and the relationship between the wheel torque WT and the comparison value H2 are expressed by the following regression equations of the following straight lines M1 and M2, respectively. Can be.
M1: H1 = a1 × WT + b1
M2: H2 = a2 × WT + b2

However, when the vehicle 1 is turning, the ease with which the tires slip is changed. More specifically, as shown in FIGS. 5A and 5B, when the vehicle 1 turns, a lateral acceleration α is applied to the vehicle 1. As a result, the load moves on the left and right sides of the vehicle 1, the load applied to the tire inside the turn decreases, and the load applied to the outside tire increases. As a result, slip increases on the inner drive wheel tires and decreases on the outer drive wheel tires. For example, as shown in FIG. 5A, when the vehicle 1 turns left (turns left), the load moves from the left side to the right side of the vehicle 1, and the load applied to the left wheel tire inside the turn decreases, while turning. The load applied to the outer right wheel tire increases. As a result, the slip of the tire T _FL is increased, the slip of the tire T _FR is reduced. Conversely, as shown in FIG. 5B, when the vehicle 1 turns right, the load moves from the right side to the left side of the vehicle 1 and the load applied to the right wheel tire inside the turn decreases, while the left wheel outside the turn. The load on the tire increases. As a result, the slip of the tire T _FR is increased, the slip of the tire T _FL decreases. For this reason, it is considered that the linear relationship between the wheel torque WT and H1, H2 changes between when the vehicle 1 goes straight and when it turns.

FIG. 6 shows experimental data supporting this. 4A and 4B are based on data measured when the vehicle 1 is traveling straight. On the other hand, FIGS. 6A and 6B are graphs respectively plotting the relationship between the wheel torque WT measured under the same conditions as in FIG. 4 except that the vehicle 1 is turning left, and H1, H2. Comparing the graphs of FIGS. 6A and 6B with the graphs of FIGS. 4A and 4B, respectively, it can be seen that the regression line M1 slopes downward and to the right, and the regression line M2 changes so as to be more horizontal. That increases the slip of the tire T _FL in the left turning, this with V1 Gayori increases, because H1 is made smaller, M1 slope a1 is small (-5 × 10 ^-6 from -1 × 10 ^{- 5} ). On the other hand, the slip of the tire T _FR decreases, and accordingly, V2 becomes smaller and H2 becomes larger, so that the slope a2 of M2 becomes larger (from −5 × 10 ⁻⁶ to −2 × 10 ⁻⁶⁾ . change). Therefore, if the data is regressed without considering the influence of the lateral acceleration α applied to the vehicle 1, a regression error increases. As a result, the rotation speeds V1 and V2 may not be accurately corrected.

Therefore, the present inventor has modeled a linear model representing the relationship between the wheel torque WT and the comparison values H1 and H2, assuming that the slopes of the comparison values H1 and H2 with respect to the wheel torque WT depend on the lateral acceleration α. That is, the regression equation L1 of the wheel torque WT and H1 and the regression equation L2 of the wheel torque WT and H2 are newly defined by the following equations, respectively. The inclination of the wheel torque WT in the regression equations L1 and L2 includes an element that changes according to the lateral acceleration α. That is, it can be said that the regression equations L1 and L2 represent a linear relationship between the wheel torque WT and the comparison values H1 and H2 substantially independent of the lateral acceleration α. Strictly speaking, there is no linearity between the comparison values H1 and H2 and the wheel torque WT because the lateral acceleration α is taken into consideration. Therefore, the linear model here is an approximate linear model.
L1: H1 = (A1 × α + B1) × WT + C1
L2: H2 = (A2 × α + B2) × WT + C2

The comparison value H1 when the wheel torque WT is 0 (N · m), that is, the intercept C1 of the regression equation L1, is a comparison value H1 that is not affected by the wheel torque WT. Similarly, the comparison value H2 when the wheel torque WT is 0 (N · m), that is, the intercept C2 of the regression equation L2 is a comparison value H2 that is not affected by the wheel torque WT. The influence of the slip on the comparison values H1 and H2 by the wheel torque WT increases as the lateral acceleration α increases, but C1 and C2 are not affected by the lateral acceleration α. Thus, 'a wheel speed V2 of the tire T _FR influence of and slip is canceled' wheel speeds V1 of the tire T _FL influence of the slip is canceled, wheel speed V3 of the tire T _RL wheel speed of the tire T _RR V4 Is represented by the following equation.
V1 '= V3 / C1
V2 '= V4 / C2

Moreover, not only when the wheel torque WT is 0 (N · m), defines a small wheel torque value to the extent the slip of the tire does not occur no or hardly occur as a reference wheel torque WT _R, the reference wheel torque WT _R The wheel speeds V1 'and V2' can also be obtained from the comparison values H1 and H2. In this case, the wheel speeds V1 'and V2' are represented by the following equations.
V1 ′ = V3 / {(A1 × α + B1) × WT _R + C1}
V2 ′ = V4 / {(A2 × α + B2) × WT _R + C2}

  Based on the above principle, in step S5, the linear relation specifying unit 25 calculates the linear parameters A1, B1, C1, A2, B2, and C2 that determine the regression equations L1 and L2. To specify the regression equation, at least three (WT, H1, α) or (WT, H2, α) data sets are required. In the present embodiment, steps S1 to S4 are repeatedly executed until a predetermined number N of data sets is accumulated. Then, once the number of data sets exceeds N, each time a new data set is obtained, a linear relationship is specified using the latest predetermined amount of data sets. The method for specifying the linear parameter is not particularly limited. For example, a least squares method can be used, and a sequential least squares method or a Kalman filter can also be used for efficient computation. Thus, the linear relationship between the comparison values H1, H2 substantially independent of the lateral acceleration α and the wheel torque WT is specified.

In step S6, based on the regression equations L1 and L2 specified in step S5, the rotation speed correction unit 26 calculates the corrected rotation speeds V1 'and V2' of the tires T _FL and T _FR . Rotational speed V1 ', V2', as described above, the rotational speed V3, V4 of the driven wheel tire, comparison value when wheel torque WT is 0 when it is (N · m) or reference wheel torque WT _R It can be calculated from H1 and H2.

In the following step S7, the DEL calculation unit 27 calculates the decompression index values DEL1 to DEL3 for determining the decompression state of the tire. DEL1, DEL2, and DEL3 are index values having the following characteristics, respectively.
DEL1: an index value DEL2 that increases as wheel speeds V1 and V4 increase and decreases as wheel speeds V2 and V3 increase, or increases as wheel speeds V2 and V3 increase and decreases as wheel speeds V1 and V4 increase. : An index value DEL3 that increases as the wheel speeds V1 and V2 increases and decreases as the wheel speeds V3 and V4 increase, or increases as the wheel speeds V3 and V4 increase and decreases as the wheel speeds V1 and V2 increase. An index value that increases as the wheel speeds V1 and V3 increase and decreases as the wheel speeds V2 and V4 increase, or decreases as the wheel speeds V2 and V4 increase and decreases as the wheel speeds V1 and V3 increase.

As the tires T _FL , T _FR , T _RL , and T _RR decrease in pressure, the respective dynamic load radii decrease, and the respective wheel speeds V1 to V4 increase, and the values of the decompression index values DEL1 to DEL3 increase. Change. In the pressure reduction detection process according to the present embodiment, in step S8 described later, a change in the pressure reduction index values DEL1 to DEL3 from the reference value is detected, thereby detecting the tire pressure reduction state.

DEL1 to DEL3 can be defined by various methods as long as they have the above characteristics. In the present embodiment, DEL1 to DEL3 are calculated according to the following equations.
DEL1 = [(V1 + V4) / (V2 + V3) -1] * 100 (%)
DEL2 = [(V1 + V2) / (V3 + V4) -1] * 100 (%)
DEL3 = [(V1 + V3) / (V2 + V4) -1] * 100 (%)

In another embodiment, for example, as described in the section of the background art, the following definition can be made.
DEL1 = [[(V1 + V4) / 2- (V2 + V3) / 2] / (V1 + V2 + V3 + V4)] * 100 (%)
DEL2 = [[(V1 + V2) / 2- (V3 + V4) / 2] / (V1 + V2 + V3 + V4)] * 100 (%)
DEL3 = [[(V1 + V3) / 2- (V2 + V4) / 2] / (V1 + V2 + V3 + V4)] * 100 (%)

Alternatively, DEL1, DEL2, and DEL3 can be defined as follows.
DEL1 = (V1 ² + V4 ² )-(V2 ² + V3 ² )
DEL2 = (V1 ² + V2 ² )-(V3 ² + V4 ² )
DEL3 = (V1 ² + V3 ² )-(V2 ² + V4 ² )

  As described above, DEL1 is an index value that increases as the wheel speed of two wheels existing on one diagonal of the four wheels increases, and decreases as the wheel speed of two wheels existing on the other diagonal increases. is there. DEL3 is an index value that increases as the wheel speed of the left or right wheel of the four wheels increases, and decreases as the wheel speed of the remaining two wheels increases. On the other hand, DEL2 is an index value that increases as the wheel speeds of the two front wheels or the rear wheels of the four wheels increase, and decreases as the wheel speeds of the remaining two wheels increase.

When the calculation of DEL1 to DEL3 in step S7 is completed, the DEL calculation unit 27 determines the pressure reduction state (step S8). Specifically, the DEL calculating unit 27 first uses the DEL1 to DEL3 calculated in step S7 to perform one-wheel depressurization (1) to (4) and two-wheel depressurization among the above-described 14 reduced pressure tire patterns. (5) to (10) and three-wheel decompression (11) to (14) are detected. More specifically, it is determined whether each of DEL1 to DEL3 has increased by a threshold or more, decreased by a threshold or more, or the amount of change is equal to or less than a threshold, and according to a combination of these results, Determine whether the tire is depressurized. Table 1 shows, for example, the relationship between the change patterns of DEL1 to DEL3 and the patterns of the reduced pressure tires. Note that the upper threshold and the lower threshold used here are determined for each of DEL1 to DEL3 by an experiment or simulation using the vehicle 1, and are stored in the ROM 13 or the storage device 15 in advance.

  The DEL calculation unit 27 determines whether or not a reduced pressure is detected in any of the patterns (1) to (14). If no reduced pressure is detected in any of the patterns, the process returns to step S1. . On the other hand, if pressure reduction is detected in any of the patterns, the process proceeds to step S9.

  In step S <b> 9, the alarm output unit 28 outputs a decompression alarm via the display 3. At this time, the display unit 3 can give an alarm while distinguishing which tire is depressurizing, or can issue an alarm so as to show only that one of the tires is depressurizing. Further, the decompression warning can be executed in the form of audio output.

<3. Modification>
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to said Embodiment, A various change is possible unless it deviates from the meaning. For example, the following changes are possible. Further, the gist of the following modified examples can be appropriately combined.

<3-1>
The method for acquiring the data of the lateral acceleration α of the vehicle 1 is not limited to the method described in the above embodiment. For example, when the yaw rate sensor is mounted on the vehicle 1, the lateral acceleration α can be obtained from the output value of the yaw rate sensor.

<3-2>
In the above embodiment, the wheel speeds V1 'and V2' obtained in step S6 are used for the tire pressure reduction detection processing. However, the processing of steps S1 to S6 is not limited to the tire pressure reduction detection processing, and may be employed in various controls based on the rotation speed of the tire, for example, control of a vehicle brake.

<3-3>
In the above embodiment, H1 and H2 are calculated in step S4. However, only H1 or only H2 may be calculated according to the characteristics of the vehicle and the necessity. In this case, the wheel speed of either the tire _TFL or _TFR is corrected.

<3-4>
The function of correcting the rotation speed of the tire according to the present invention can also be applied to a rear wheel drive vehicle. In that case, the rotation speeds V3 and V4 of the rear wheel tires, which are the driving wheel tires, can be corrected by the same processing as in the above embodiment. In addition, the same function can be applied to a four-wheel drive vehicle, and can correct the rotation speed of a tire to which a greater driving force is applied among front wheel tires and rear wheel tires. Further, the function is not limited to a four-wheeled vehicle, but can be applied to a three-wheeled vehicle or a six-wheeled vehicle.

<3-5>
The comparison values H1 and H2 can also be defined as follows.
H1 = V1 / V3
H2 = V2 / V4
In this case, the corrected rotational speeds V1 'and V2' can be calculated according to the following equations.
V1 ′ = {(A1 × α + B1) × WT _R + C1} × V3
V2 ′ = {(A2 × α + B2) × WT _R + C2} × V4

Alternatively, the comparison values H1 and H2 can be defined as follows.
H1 = V1 / V4
H2 = V2 / V3
In this case, the corrected rotational speeds V1 'and V2' can be calculated according to the following equations.
V1 ′ = {(A1 × α + B1) × WT _R + C1} × V4
V2 ′ = {(A2 × α + B2) × WT _R + C2} × V3

Alternatively, the comparison values H1 and H2 have been described in the above embodiment, but may be defined as follows.
H1 = V4 / V1
H2 = V3 / V2
In this case, the corrected rotational speeds V1 'and V2' can be calculated according to the following equations.
V1 ′ = V4 / {(A1 × α + B1) × WT _R + C1}
V2 ′ = V3 / {(A2 × α + B2) × WT _R + C2}

<3-6>
The linear model representing the relationship between the wheel torque WT and the comparison values H1 and H2 is not limited to the one described in the above embodiment. For example, it can also be modeled by the following regression equation.
L1 ′: H1 = (A1 × α + B1) × WT + C1 + D1 × α
L2 ′: H2 = (A2 × α + B2) × WT + C2 + D2 × α

REFERENCE SIGNS LIST 1 vehicle 2 correction device 3 display 4 lateral acceleration sensor 6 wheel speed sensor 7 WT sensor 21 rotation speed acquisition unit 22 torque acquisition unit 23 lateral acceleration acquisition unit 24 comparison value calculation unit 25 linear relation identification unit 26 rotation speed correction unit 27 DEL calculation unit (decompression index value calculation unit)
28 Alarm output part FL Left front wheel FR Right front wheel RL Left rear wheel RR Right rear wheel T _FL Left front wheel tire T _FR Right front wheel tire T _RL Left rear wheel tire T _RR Right rear wheel tire V1-V4 Wheel speed α Lateral acceleration DEL1 ~ 3 Decompression index value

Claims (8)

A correction device for correcting a rotation speed of a first tire mounted on a vehicle,
A rotation speed acquisition unit that acquires a rotation speed of the first tire and a second tire mounted on the vehicle;
A comparison value calculation unit that calculates a comparison value for comparing the rotation speed of the first tire with the rotation speed of the second tire;
A lateral acceleration acquisition unit that acquires a lateral acceleration applied to the vehicle,
A torque acquisition unit that acquires wheel torque;
A linear model representing a relationship between the wheel torque and the comparison value based on the comparison value, the lateral acceleration, and the wheel torque, wherein a slope of the comparison value with respect to the wheel torque depends on the lateral acceleration. A linear relationship specifying unit that calculates a linear parameter that specifies a linear model;
A rotation speed correction unit that calculates a rotation speed of the first tire in which an influence of a slip on the comparison value is canceled by the wheel torque based on the rotation speed of the second tire and the linear parameter;
With
One of the first tire and the second tire is a front wheel tire, the other is a rear wheel tire, and the first tire is a tire to which a larger driving force is applied than the second tire.
Correction device. The comparison value calculation unit compares the rotation speed of one front wheel tire and the rotation speed of one rear wheel tire among the two front wheel tires and the two rear wheel tires mounted on the vehicle as the comparison value. Calculating a first comparison value, and calculating a second comparison value for comparing the rotation speed of the other front wheel tire with the rotation speed of the other rear wheel tire.
The correction device according to claim 1. Based on the rotation speed of the second tire and the rotation speed of the first tire calculated by the rotation speed correction unit, among the four tires mounted on the vehicle, the rotation speeds of any two wheels, Calculating a decompression index value, which is a comparison value for comparing the rotation speeds of the remaining two wheels, and detecting a decompression of at least one of the tires by comparing the decompression index value with a predetermined threshold value; The correction device according to claim 1, further comprising a value calculation unit. When a decompression state of the tire is detected, the apparatus further includes an alarm output unit that outputs a decompression alarm.
The correction device according to claim 3. The comparison value is a ratio between a rotation speed of the first tire and a rotation speed of the second tire.
The correction device according to claim 1. The first tire is a driving wheel tire, and the second tire is a driven wheel tire.
The correction device according to claim 1. A correction method for correcting a rotation speed of a first tire mounted on a vehicle,
Obtaining rotation speeds of the first tire and a second tire mounted on the vehicle;
Calculating a comparison value for comparing the rotation speed of the first tire with the rotation speed of the second tire;
Obtaining a lateral acceleration applied to the vehicle;
Getting the wheel torque,
A linear model representing a relationship between the wheel torque and the comparison value based on the comparison value, the lateral acceleration, and the wheel torque, wherein a slope of the comparison value with respect to the wheel torque depends on the lateral acceleration. Calculating a linear parameter identifying a linear model;
Based on the rotation speed of the second tire and the linear parameter, calculating the rotation speed of the first tire from which the influence of the slip on the wheel torque applied to the comparison value has been canceled;
Including
One of the first tire and the second tire is a front wheel tire, the other is a rear wheel tire, and the first tire is a tire to which a larger driving force is applied than the second tire.
Correction method. A correction program for correcting a rotation speed of a first tire mounted on a vehicle,
Obtaining rotation speeds of the first tire and a second tire mounted on the vehicle;
Calculating a comparison value for comparing the rotation speed of the first tire with the rotation speed of the second tire;
Obtaining a lateral acceleration applied to the vehicle;
Getting the wheel torque,
A linear model representing a relationship between the wheel torque and the comparison value based on the comparison value, the lateral acceleration, and the wheel torque, wherein a slope of the comparison value with respect to the wheel torque depends on the lateral acceleration. Calculating a linear parameter identifying a linear model;
Based on the rotation speed of the second tire and the linear parameter, calculating the rotation speed of the first tire from which the influence of the slip on the wheel torque applied to the comparison value has been canceled;
To the computer,
One of the first tire and the second tire is a front wheel tire, the other is a rear wheel tire, and the first tire is a tire to which a larger driving force is applied than the second tire.
Correction program.