JP4487130B2 - Wheel lateral force calculation method and wheel lateral force calculation device - Google Patents

Description

  The present invention relates to a wheel lateral force calculation method and a wheel lateral force calculation device that calculate, for each wheel, a lateral force applied to each wheel during turning of the vehicle for a vehicle having a plurality of wheels.

  The turning characteristics (cornering characteristics) of automobile vehicles are particularly important for the handling stability of automobile vehicles, and the evaluation of cornering characteristics of automobile vehicles is also important for the design of automobile vehicles with higher handling stability. It is. The cornering characteristics of an automobile equipped with wheels with tires mounted on the wheels are related to various factors such as the characteristics of the vehicle structure (weight balance, etc.), suspension characteristics, tire characteristics, and road surface conditions. ing. In cornering of an automobile, the sum of the forces (cornering forces) generated on the ground contact surfaces of the front and rear tires and the centrifugal force of the vehicle are in a balanced state. The size of the cornering force depends on the force (wheel lateral force) in the direction perpendicular to the equator plane of each tire generated on the ground contact surface of each tire. The magnitude of this lateral force generated during cornering varies depending on the automobile vehicle, tires, and running conditions. Evaluating the magnitude of the wheel lateral force of each wheel under various conditions is particularly important for evaluating the cornering characteristics of automobile vehicles.

For example, as a method for evaluating the lateral force generated in a specific tire, a method using a known indoor cornering tester can be given. In such an indoor cornering tester, for example, the specific tire is brought into contact with the virtual road surface while a load is applied to the specific tire. Then, the virtual road surface and the specific tire are moved relative to each other to roll the specific tire, and the lateral force generated on the contact surface of the specific tire is measured. However, as with the cornering characteristics described above, various factors such as the characteristics of the vehicle structure (weight balance, etc.), the characteristics of the suspension, the characteristics of the tire, and the road surface condition are involved in the lateral force generated in the vehicle tire. ing. Also, during actual vehicle travel, changes in the load on each wheel frequently occur due to changes in the attitude of the vehicle. For this reason, in a known indoor cornering tester, a tire is actually attached to a vehicle, and a state (the load state applied to the tire and the rolling state of the tire) when the vehicle actually travels on the road surface is reproduced. Is limited in its reproducibility, and it is impossible to accurately measure the lateral force generated on the contact surface of the specific tire when the specific tire is actually attached to the vehicle. On the other hand, as a method for evaluating the lateral force generated in the tire actually mounted on the vehicle, in Patent Document 1, the torsional deformation of the tire side wall is measured by a sensor, and the generated torsional deformation is generated from the measured twisting deformation. A system for predicting tire force that estimates lateral force to be described is described.
JP 2001-512207 A

  However, in the system for predicting the force of the tire described in Patent Document 1, it is necessary to grasp the relationship between the tire deformation and the force generated during the deformation in advance. It takes a lot of labor to grasp the relationship between the tire deformation and the force generated during the deformation. By only using the relationship between the tire deformation and the force generated in the deformation, as grasped in advance, various states when the vehicle actually travels on the road surface (the load state applied to the tire and the rolling of the tire) In the state), the lateral force generated on the ground contact surface of the tire cannot be accurately measured. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for easily and accurately calculating a lateral force generated on each of a plurality of wheels actually mounted on a vehicle.

In order to solve the above-mentioned problems, the present invention relates to a vehicle having a plurality of wheels, a method for calculating the lateral force applied to each wheel during the turning of the vehicle, A centrifugal force deriving step for obtaining a magnitude of a centrifugal force in a direction substantially perpendicular to the vehicle traveling direction; a ground contact length deriving step for obtaining a contact length of each of the plurality of wheels during turning of the vehicle; A lateral force calculating step of calculating a lateral force applied to each wheel based on a ratio of a contact length of each wheel to a total sum of the contact lengths of the respective wheels and a magnitude of the centrifugal force. A wheel lateral force calculation method is provided.
In the lateral force calculation step, it is preferable that the lateral force applied to each wheel is calculated for each wheel by multiplying the magnitude of the centrifugal force and the ratio of the contact length of each wheel.

  Further, the wheel includes a tire, and prior to the contact length deriving step, an acceleration for acquiring time-series acceleration data of a predetermined portion of the tire generated when the rolling tire receives an external force from the road surface Preferably, the method includes a data acquisition step, and the contact length derivation step uses the tire time-series acceleration data acquired in the acceleration data acquisition step to determine the contact length of each of the plurality of wheels.

  In the contact length deriving step, time-series acceleration data based on tire deformation is extracted from the time-series acceleration data, and the time of the second floor is extracted from the time-series acceleration data based on the tire deformation. It is preferable to calculate an amount of deformation at a predetermined portion of the tire by performing integration to obtain displacement data, and calculate the contact length using the amount of deformation at the predetermined portion of the tire.

  The acceleration data acquired in the acceleration data acquisition step is at least one of radial acceleration data orthogonal to the tire circumferential direction and tire circumferential acceleration data. The deformation amount of the predetermined portion of the tire calculated in the length deriving step is preferably a radial deformation amount and a circumferential deformation amount or a radial deformation amount of the tire.

  The centrifugal force deriving step calculates a rotational angular velocity of each wheel using time-series acceleration data of a predetermined part of the tire for each of the plurality of wheels, and based on the rotational angular velocity of each wheel, the vehicle An estimated value of the turning radius of the vehicle and the traveling speed of the vehicle, and the centrifugal force is calculated based on the turning radius of the vehicle, the estimated value of the traveling speed of the vehicle, and the weight information of the vehicle acquired in advance. preferable.

  The centrifugal force deriving step calculates the moving speed of each wheel using the rotational angular velocity of each wheel, and the ratio of the moving speeds of the left and right wheels provided on at least one axle of the vehicle. May be used to derive the turning radius of the vehicle.

  The centrifugal force deriving step includes the magnitude of acceleration approximately perpendicular to the traveling direction of the vehicle and the weight of the vehicle, measured by a vehicle acceleration sensor provided in the vehicle, during the turning of the vehicle. Based on the above, it is preferable to derive the magnitude of the centrifugal force.

  Note that the present invention is an apparatus for calculating lateral force applied to each wheel during turning of the vehicle with respect to a vehicle having a plurality of wheels, with respect to the vehicle traveling direction applied to the vehicle during turning. Centrifugal force deriving means for determining the magnitude of centrifugal force in a substantially vertical direction, ground contact length deriving means for determining the contact length of each of the plurality of wheels during turning of the vehicle, and the contact length of each of the plurality of wheels A wheel lateral force calculation device comprising lateral force calculation means for calculating the lateral force applied to each wheel based on the ratio of the contact length of each wheel with respect to the sum of the sum and the magnitude of the centrifugal force. Also provided. The lateral force calculating means preferably calculates the lateral force applied to each wheel for each wheel by multiplying the magnitude of the centrifugal force and the ratio of the contact length of each wheel.

  Further, the wheel is a wheel provided with a tire, and is provided at a predetermined portion of the tire, and the time-series acceleration of the predetermined portion of the tire is generated when the rolling tire receives an external force from the road surface. It is preferable to have an acceleration sensor that acquires data, and the contact length deriving unit obtains the contact length of each of the plurality of wheels by using time series acceleration data of the tire measured by the acceleration sensor. .

  The contact length deriving means extracts time-series acceleration data based on tire deformation from the time-series acceleration data, and performs second floor time with respect to the time-series acceleration data based on the tire deformation. By calculating the displacement data by performing integration, a deformation amount calculation unit that calculates a deformation amount at a predetermined portion of the tire, and a contact length calculation unit that calculates the contact length using the deformation amount at the predetermined portion of the tire. It is preferable to have it.

  The acceleration data measured by the acceleration sensor is at least one of radial acceleration data orthogonal to the tire circumferential direction and tire circumferential acceleration data, and the contact length derivation is performed. The deformation amount of the predetermined portion of the tire calculated by the means is preferably a radial deformation amount and a circumferential deformation amount or a radial deformation amount of the tire.

  In addition, the centrifugal force deriving means, based on the rotational angular velocity, an angular velocity calculating unit that calculates a rotational angular velocity of each wheel using time-series acceleration data of a predetermined portion of the tire for each of the plurality of wheels, A turning radius calculation unit for obtaining a turning radius of the vehicle, a speed estimation value calculation unit for obtaining an estimated value of the traveling speed of the vehicle based on the rotational angular velocity, a turning radius of the vehicle, an estimated value of the traveling speed of the vehicle, and It is preferable to include a centrifugal force calculation unit that calculates the centrifugal force based on the weight information of the vehicle acquired in advance.

  Further, the turning radius calculation unit calculates the moving speed of each wheel using the rotational angular velocity of each wheel, and the ratio of the moving speeds of the left and right wheels provided on at least one axle of the vehicle. It is preferable to derive the turning radius of the vehicle using the value of.

  In addition, the vehicle includes a vehicle acceleration sensor that measures the magnitude of vehicle acceleration in a direction substantially perpendicular to the vehicle traveling direction during the turning of the vehicle, and the centrifugal force deriving means includes It is preferable to derive the magnitude of the centrifugal force based on vehicle acceleration and information on the weight of the vehicle.

  In addition, it is preferable that a plurality of the acceleration sensors are provided in the circumferential direction of the tire, and it is also preferable that a plurality of the acceleration sensors are provided in the width direction of the tire.

  According to the wheel lateral force calculation method and the wheel lateral force calculation device of the present invention, the lateral force generated on each of a plurality of wheels actually mounted on the vehicle during the turning of the vehicle is simply and accurately calculated. be able to.

  Hereinafter, a wheel lateral force calculation method and a wheel lateral force calculation device according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

  FIG. 1 is a schematic configuration diagram illustrating a wheel lateral force calculation device 10 (device 10), which is an example of a wheel lateral force calculation device according to the present invention. The device 10 is provided in a vehicle 12 provided with four wheels 14a to 14d. These four wheels 14a to 14d are wheels formed by mounting the same type of tires (tires having the same tire size, tire rim width, belt structure, tire filling air pressure, etc.) 15a to 15d, respectively. is there. The apparatus 10 includes sensor units 16a to 16d, a data processing unit 20, and a display 34. The sensor units 16a to 16d are respectively provided on the four wheels 14a to 14d. When the vehicle 12 travels on the road surface, the tire 15 of each wheel is generated by receiving an external force from the road surface. The acceleration information of a predetermined part is acquired and transmitted by a radio signal. Further, the data processing unit 20 receives the radio signals transmitted from the sensor units 16a to 16d, derives the ground contact length of each wheel and the centrifugal force acting on the vehicle 12 from the deformation acceleration information of each wheel, Using the centrifugal force and the contact length, the magnitude of the lateral force generated on each of the four wheels 14a to 14d is calculated. The display 34 displays the contact length and centrifugal force derived in the data processing unit 20 and the calculation result of the lateral force generated in each of the wheels 14a to 14d. In the example shown in FIG. 1, the data processing unit 20 is disposed on the vehicle 12, but the data processing unit 20 is portable and is not limited to being disposed on the vehicle 12.

  FIG. 2 is a diagram illustrating the sensor unit 16a and the data processing unit 20 in the wheel lateral force calculation device 10 shown in FIG. Since the sensor units 16a to 16d have the same configuration, only the sensor unit 16a and the wheel 14a provided with the sensor unit 16a are illustrated here. The data processing unit 20 includes a receiver 3, an amplifier (AMP) 4, processing means 21, a CPU 23, and a memory 27. The data processing unit 20 is a computer equipped with a receiver 3 and an AMP 4 in which each unit, which will be described later, of the processing means 21 functions when the CPU 23 executes a program stored in the memory 27. In the memory 27, the wheel base L of the vehicle 12, the vehicle tread width K, the vehicle weight M, the length of the outer circumference of the wheels 14 a to 14 d, that is, the tires of the tires 15 a to 15 d, which are input by input means (not shown) or the like. The value of the length of the outer periphery (all the wheels 14a to 14d are the same) is stored. Each parameter is appropriately called by each unit described later of the processing unit 21. Each parameter will be described later.

  The processing means 21 includes a tire acceleration data acquisition unit 22 that acquires measurement data of acceleration in the tread portions of the tires 15a to 15d constituting the wheels 14a to 14d, and a signal processing unit 24 that processes the tire acceleration data. The ground contact length deriving unit 40 for deriving the ground contact lengths of the wheels 14a to 14d using the acceleration data, and the centrifugal force deriving unit for deriving the centrifugal force applied to the vehicle 12 during turning using the acceleration measurement data. 50, the ground contact length of each of the wheels 14a to 14d derived from the ground contact length deriving unit 40 (the ground contact length of each of the tires 15a to 15d mounted on each of the wheels 14a to 14d), and the centrifugal force deriving unit 50 The ground contact surface of each of the wheels 14a to 14d using the centrifugal force applied to the vehicle 12 derived in Wheel 14a~ wheel 14d is mounted to each, consisting of lateral force calculating section 70. for calculating the magnitude of the lateral force generated in the ground surface) of each of the tires 15 a to 15 d. Details of the configuration of the processing means 21 will be described later.

  The present invention uses the contact length of each of the wheels 14a to 14d (the contact length of each of the tires 15a to 15d) and the magnitude of the centrifugal force applied to the vehicle 12 derived by the centrifugal force deriving unit 50, so that the wheels 14a to 14 It is characterized in that the magnitude of the lateral force generated on each of the contact surfaces 14d (the contact surfaces of the tires 15a to 15d) is calculated. According to the present invention, for example, when the vehicle 12 travels on a general road at a speed (normal speed) that complies with laws and regulations (in the case of normal travel), it occurs on the ground plane of each of the wheels 14a to 14d. The magnitude of the lateral force can be calculated easily and with high accuracy. Hereinafter, the characteristics of the present invention will be described by taking as an example a case where the vehicle 12 turns while the vehicle 12 is traveling normally. FIGS. 3A and 3B are diagrams for explaining the forces applied to the vehicle 12 and the wheels 14a to 14d when the vehicle 12 is turning (cornering). FIG. 3A is a view of the vehicle that is turning. 12 is a schematic diagram for explaining the centrifugal force applied to the vehicle 12 and the lateral force generated on each wheel 14a to 14d of the vehicle 12. FIG. FIG. 3B is an enlarged view of one wheel (wheel 14a) of the vehicle 12, and is a view of the wheel 14a as viewed from the road surface side.

  As shown in FIG. 3A, while the vehicle is turning (cornering), the vehicle 12 is subjected to centrifugal force F acting in the direction of pushing the vehicle 12 to the outside of the corner. Cornering forces (CFa to CFd) acting against the centrifugal force F are generated on the wheels 14a to 14d, respectively. During cornering, the centrifugal force F and the sum of the lateral forces CFa to CFd generated on the wheels 14a to 14d are balanced. With reference to FIG.3 (b), the outline of the force which acts on a grounding surface of the wheel 14a which is a right front wheel, for example during cornering is demonstrated. The wheel 14a rolls on the road surface with the tire 15a in contact with the road surface, as indicated by the hatched area in FIG. 3B. During cornering, the contact length of the tire 15 at the intersection of the tire equator plane and the road surface is CLa. During cornering, the equator plane of the tire 15a constituting the wheel 14a has an angle (slip angle) with respect to the traveling direction of the vehicle. When this slip angle is small, the wheel lateral force (SFa) acting perpendicularly to the tire equatorial plane and acting toward the inside of the corner is almost the same as the cornering force CFa (SFa≈CFa) (FIG. 3 (b) ) Exaggerated slip angle). That is, when the vehicle 12 travels on a general road in accordance with legal regulations (in the case of normal travel), the slip angle is relatively small (particularly very small at the rear wheels), and the total wheel lateral force (SFa to SFd). And the centrifugal force F are balanced (F = SFa + SFb + SFc + SFd).

  In addition, when the slip angle is small, a constant load is applied to a wheel equipped with an arbitrary pneumatic tire, and this wheel is grounded to a specific road surface (a road surface in which the road surface state does not change while the wheel is rolling). It is well known that the wheel lateral force (SF) generated in this wheel is proportional to the slip angle. That is, when the slip angle is small, the gradient of the change in the wheel lateral force with respect to the change in the slip angle (so-called cornering power; CP) is constant. In addition, the four wheels 14a to 14d provided in the vehicle 12 have almost no slip angle for any of the wheels, and the slip angles of the four wheels 14a to 14d are substantially the same. That is, it can be said that the magnitude of the wheel lateral forces SFa to SFd applied to each of the four wheels 14a to 14d can be expressed by the magnitude of the cornering power CP of each wheel.

  Here, when the vehicle cornering power CP is determined according to the physical quantity related to the wheel 14a during the turning of the vehicle 12, the magnitude of the cornering power CP of each wheel is determined according to the physical quantity. That is, the wheel lateral forces SFa to SFd of each wheel can be obtained. As described above, when a constant load is applied to a wheel equipped with an arbitrary pneumatic tire and the wheel is in contact with a specific road surface, the contact length of the wheel (the contact length of the tire) is always constant. It has become. That is, in a state where the slip angle is small, the gradient of the change in the wheel lateral force with respect to the change in the slip angle (cornering power; CP) is constant when the contact length of the wheel is constant. In the case of normal traveling, due to a change in the posture of the vehicle 12 during traveling, the load applied to each of the plurality of wheels 14a to 14d provided on the vehicle 12 also frequently occurs, and the ground contact length CLa to each of the wheels 14a to 14d. CLd varies in various ways.

  4A to 4C are graphs showing the relationship between the ground contact length of each wheel and the cornering power CP for a plurality of different wheels. Each wheel is loaded with a load having a different magnitude. It is a graph which shows the measurement result which measured the cornering power CP of each wheel about when each is grounded on a specific road surface. FIG. 4A shows the size of the cornering power CP of each tire when two types of tires A and B having different rim widths (rim sizes) are used and different loads are applied to the respective tires. Yes. Both the tire A and the tire B are tires of the same tire size (tire size 205 / 65R15), and each is filled with the same air pressure (200 kPa). As can be determined from FIG. 4A, even if the rim width is different, the contact length of the tire and the cornering power of the tire are in a linear relationship (proportional relationship). 4 (b) uses tire A and tire B in FIG. 4 (a), and each tire is filled with an air pressure (300 kPa) different from that shown in FIG. 4 (a), and is different for each tire. The magnitude of the cornering power CP of each tire in a state where a load is applied is shown. As can be determined by comparing FIG. 4A and FIG. 4B, the tire contact length and the tire cornering power are in a linear relationship (proportional relationship) even if the air pressure is different. FIG. 4C shows the tire C and the tire D different from both the tire A and the tire B used in FIGS. 4A and 4B in a state where different loads are applied to the respective tires. The size of the cornering power CP of each tire is shown. The tire C and the tire D have different belt structures. However, both the tire C and the tire D are tires having the same tire size (tire size 215 / 45ZR17) and the same rim size (17 × 7JJ), and each is filled with the same air pressure (230 kPa). As can be judged from FIG. 4 (c) and by comparing FIGS. 4 (a) to 4 (c), even if the tire belt structure or the tire size is different, the tire contact length and the tire cornering power Is in a linear relationship (proportional relationship).

  Thus, regardless of the tire size, tire rim width, belt structure, and tire filling air pressure, the contact length and the tire cornering power (CP) are in a linear relationship for any tire. That is, it can be said that the cornering power CP of the tire and the contact length of the tire have a linear relationship regardless of the type of each tire, and the cornering power CP of the tire is determined according to the contact length of the tire. That is, it can be said that the wheel lateral force SF is determined in accordance with the tire contact angle SA in addition to the tire slip angle SA.

  The tires 15a to 15d mounted on the four wheels 14a to 14d provided in the vehicle 12 are all the same type of tire (the tire size, the tire rim width, the belt structure, and the tire filling air pressure are substantially the same). In addition, the slip angles of the wheels 14a to 14d during the turning are substantially the same (almost no slip angle is generated for any of the wheels). That is, when the plurality of wheels provided in the vehicle are all the same type in normal traveling, the wheel lateral forces SFa to SFd generated on the wheels are respectively equal to the ground contact lengths CLa to CLd of the wheels 14a to 14d. It is determined according to each.

As described above, the wheel lateral forces SFa to SFd of each wheel are generated against the centrifugal force applied to the vehicle 12, and the sum of the wheel lateral forces (the sum of SFa to SFd) and the centrifugal force F are balanced. (F = SFa + SFb + SFc + SFd). The magnitudes of the wheel lateral forces SFa to SFd generated on the wheels 14a to 14d respectively correspond to the contact lengths CLa to CLd of the wheels 14a to 14d. That is, the wheel lateral forces SFa to SFd generated on the respective wheels use the ratio of each wheel to the sum of the contact lengths CLa to CLd of the four wheels 14a to 14d and the magnitude of the centrifugal force, It can obtain | require by following formula (1-1)-Formula (1-4).

  According to the invention of the present application, in particular, for example, when the vehicle 12 travels on a general road at a normal speed according to the regulations (in the case of normal travel), the lateral generated on the ground contact surface of each of the wheels 14a to 14d. The magnitude of the force can be calculated easily and with high accuracy. In the present invention, even when the vehicle travels normally, for example, if necessary processing such as correcting the magnitude of the lateral force calculated according to the slip angle of each wheel is performed, The wheel lateral force generated on each wheel can be calculated using the centrifugal force and the length of the contact length of each wheel.

  In the processing means 21 shown in FIG. 1, the tires of the respective wheels that are turning are converted into the ground contact lengths CLa to CLd of the wheels 14 a to 14 d and the centrifugal force F necessary for calculating the wheel lateral forces SFa to SFd. It calculates based on the measurement data of the acceleration of each predetermined part of 15a-15d. The acceleration measurement data used here is detected by the acceleration sensor 2 fixed to the inner peripheral surface of the tire cavity region of each of the transmission units 16a to 16d provided on each wheel, and the transmitter 17 of each transmission unit. Is transmitted to the receiver 3 and amplified by the amplifier 4. Note that the transmitter 17 may not be provided, and for example, the acceleration sensor 2 may be separately provided with a transmission function and transmitted from the acceleration sensor 2 to the receiver 3. Each transmitter 17 provided on each of the wheels 14a to 14d has identification information (ID) that enables identification, and the transmitter 17 measures acceleration measured by a corresponding acceleration sensor. An ID is transmitted together with the data.

As the acceleration sensor 2, for example, a semiconductor acceleration sensor disclosed in Japanese Patent Application No. 2003-134727 filed earlier by the applicant of the present application is exemplified. Specifically, the semiconductor acceleration sensor includes a Si wafer having a diaphragm formed in the outer peripheral frame portion of the Si wafer, and a pedestal for fixing the outer peripheral frame portion, and a weight is provided at the center of one surface of the diaphragm. And a plurality of piezoresistors are formed on the diaphragm. When acceleration is applied to the semiconductor acceleration sensor, the diaphragm is deformed, and the resistance value of the piezoresistor changes due to the deformation. A bridge circuit is formed so that this change can be detected as acceleration information.
By fixing this acceleration sensor to the tire inner peripheral surface, the acceleration acting on the tread portion during tire rotation can be measured.
In addition to this, the acceleration sensor 2 may be an acceleration pickup using a piezoelectric element, or a strain gauge type acceleration pickup combined with a strain gauge.

  FIG. 5 is a block diagram for explaining the processing means 21. The processing means 21 includes the tire acceleration data acquisition unit 22, the signal processing unit 24, the contact length deriving unit 40, the centrifugal force deriving unit 50, and the lateral force calculating unit 70 as described above. The contact length calculation unit 40 includes a deformation amount calculation unit 42 and a contact length calculation unit 44, and the centrifugal force derivation unit 50 includes a rotation angular velocity calculation unit 52 and a wheel movement amount calculation. The unit 54, the simulated vehicle speed calculation unit 56, the turning radius calculation unit 58, and the centrifugal force calculation unit 62 are configured.

  The tire acceleration data acquisition unit 22 is a part that acquires, as input data, acceleration measurement data for at least one rotation of the tire amplified by the amplifier 4. Data supplied from the amplifier 4 is analog data, which is sampled at a predetermined sampling frequency and converted into digital data. In addition, the data acquisition part 22 is based on the above-mentioned ID transmitted from each transmitter 15, and the measurement data of the acceleration transmitted from each wheel is the measurement data of the tire acceleration of which wheel (wheels 14a to 14a). Which wheel of the wheels 14d is determined). Thereafter, each processing performed in each part of the signal processing unit 24, the contact length deriving unit 40, and the centrifugal force deriving unit 50 is performed in parallel for each measurement data of the tire of each wheel.

  The signal processing unit 24 is a part that extracts time-series data of acceleration based on tire deformation from digitized acceleration measurement data. The signal processing unit 24 smoothes the acceleration measurement data, calculates an approximate curve for the smoothed signal to obtain the background component 1, and smoothes the background component 1 By removing from the acceleration measurement data, time series data of acceleration based on tire deformation is extracted. The acquired time series data of acceleration based on the deformation of the tire is sent to the contact length deriving unit 40 and the centrifugal force deriving unit 50, respectively. Specific processing in the signal processing unit 24 will be described later.

  The deformation amount calculation unit 42 of the contact length deriving unit 40 calculates the deformation amount of the tire by obtaining the displacement data by performing second-order time integration on the time series data of the acceleration based on the extracted tire deformation. It is a part to do. Second-order integration with respect to time is performed on time series data of acceleration based on tire deformation, and then an approximate curve is calculated for the data obtained by second-order integration to obtain background component 2, and this background The amount of deformation of the tire is calculated by removing component 2 from the displacement data obtained by second-order integration. Further, after that, a second-order differential with respect to time is performed on the calculated tire deformation amount data to obtain acceleration data corresponding to the tire deformation amount, that is, the acceleration based on the tire deformation not including the noise component. Calculate time-series data. Specific processing will be described later.

  The contact length calculation unit 44 is a part that calculates the contact length of each tire of each of the wheels 14a to 14d from the calculated tire deformation amount and acceleration time series data based on the tire deformation. Information on the calculated contact length of each tire is output to the lateral force calculation unit 70.

  The centrifugal force deriving unit 50 uses the time series data of the acceleration based on the tire deformation received from the signal processing unit 24 to calculate various parameters representing the vehicle behavior during the turning of the vehicle 12, and uses these parameters. The centrifugal force F acting on the vehicle 12 is calculated. FIG. 6 is a diagram illustrating various parameters that are calculated by the centrifugal force deriving unit 50 and that represent the behavior of the vehicle 12 during turning. In the example shown in FIG. 6, the slip angles of the wheels 14c and 14d as the rear wheels are sufficiently smaller than the slip angles of the wheels 14a and 14b as the front wheels. The case where the turning center of is located is shown. The centrifugal force deriving unit 50 calculates the magnitude of the centrifugal force F related to the vehicle 12 based on a model as shown in FIG.

  The rotational angular velocity calculation unit 52 determines, from the time series data of acceleration based on the deformation of the tire, a point O (FIG. 2) that faces the center position of the tire contact surface as shown in FIG. 2 for each of the wheels 14a to 14d. The timing at which the rotation angle φ of the installation position of the acceleration sensor 2 provided in each tire is 180 °, 540 °, 900 °. And based on the extracted timing, the rotational angular velocity (rotation angle (phi) per unit time (refer FIG. 2)) of each wheel 14a-14d around the time-series axle is derived | led-out. The processing in the rotational angular velocity calculation unit 52 will be described in detail later.

Of the wheels 14a to 14d calculated by the rotation angular velocity calculation unit 52, the wheel movement amount calculation unit 54 determines the rotation angular velocity around the respective axles and the wheels 14a and 14b. Wheel outer circumferential length (that is, the length of the outer circumference of each tire 15a to 15d in the tire rotation direction), and the wheel center position of each of the wheels 14a and 14b (the equatorial plane of each wheel (tire), and each The wheel movement amount (L _FR and L _FL shown in FIG. 6), which is the movement amount per unit time, of the intersection point with the axle that is the rotation center of the wheel is calculated. The processing in the wheel movement amount calculation unit 54 will be described in detail later.

  The pseudo vehicle speed calculation unit 56 calculates an estimated value (pseudo vehicle speed V) of the moving speed with respect to the road surface of the vehicle 12 based on the wheel moving amount that is the moving amount per unit time of the wheel 14a and the wheel 14b. The calculated simulated vehicle speed V is sent to the centrifugal force calculator 62.

Turning radius calculating unit 58, using the wheel movement amount _{L FR} and _{L FL} wheel 14a and the wheel 14b, a wheel base L of the vehicle 12, the vehicle tread width K, and calculates the turning radius R of the vehicle 12. Here, the wheel base L is the distance between the axles of the front wheels 14a and 14b and the axles of the rear wheels 14c and 14d (the front wheel center position and the rear wheel center). The distance between the vehicle and the vehicle 12 in the front-rear direction). The vehicle tread width K is the distance between the equator plane of the wheel 14c as the rear wheel and the equator plane of the wheel 14d (the wheel center position of the wheel mounted on the left side of the vehicle 12 and the right side of the vehicle 12 mounted). This is the distance in the left-right direction of the vehicle 12 from the center position of the wheel). The processing in the simulated vehicle speed calculation unit 56 will be described in detail later. The position of the center of gravity of the vehicle 12 includes a dividing line that divides the distance between the axles of the front wheels 14a and 14b and the rear wheels 14c and 14d into two equal parts, and the rear wheels 14c. This is the intersection of the equator plane and the equator plane of the wheel 14d with a split plane that bisects the distance. The motion of the vehicle 12 can be represented by a mass point model in which the total weight M of the vehicle 12 is concentrated at the center of gravity.

  The centrifugal force calculation unit 62 calculates the magnitude of the centrifugal force F acting on the vehicle 12 that is turning by using the calculated turning radius R, the simulated vehicle speed V, and the total weight M of the vehicle 12. . The calculated centrifugal force magnitude F is output to the lateral force calculator 70.

  In the processing device 21, the ground contact length deriving unit 40 derives the ground contact lengths CLa to CLd of the wheels 14 a to 14 d, and the centrifugal force deriving unit 50 derives the centrifugal force F applied to the vehicle 12. And in the lateral force calculation part 70, using each formula of said Formula (1-1)-Formula (1-4), the magnitude | size of the lateral force which generate | occur | produces on each contact surface of each wheel 14a-14d, Calculate for each wheel. The calculated value of the lateral force generated on each wheel is displayed on the display 34.

  The display 34 is a known image display unit that displays and outputs the magnitude of the lateral force generated in each of the wheels 14 a to 14 d calculated by the lateral force calculation unit 70. The display 34 is not limited to the magnitude of the lateral force generated on each wheel calculated by the lateral force calculation unit 70, and is handled by the processing device 21 such as the waveform of the acquired acceleration data and various calculated parameters. Various data and calculation results can be displayed sequentially.

  FIG. 7 is a flowchart showing the wheel lateral force calculation method of the present invention, which is implemented in such an apparatus 10. 8 to 12 show an example of a result obtained by each process in the apparatus 10. All of these results are obtained by measuring acceleration in the radial direction (radial direction) of the tire with the acceleration sensor 2. Hereinafter, the wheel lateral force calculation method implemented in the apparatus 10 will be described in detail.

  First, the measurement data of acceleration of each wheel amplified by the amplifier 4 is supplied to the data acquisition unit 22, sampled at a predetermined sampling frequency, and digitized measurement data as shown in FIG. Is acquired (step S102). At this time, as described above, the data acquisition unit 22 is based on the above-mentioned ID transmitted from each transmitter 15, and the acceleration measurement data transmitted from each wheel is the measurement data of the acceleration of the tire of which wheel. It is determined whether there is any wheel (wheel 14a to wheel 14d).

  Next, the acquired measurement data is supplied to the signal processing unit 24, and first, smoothing processing using a filter is performed (step S104). As shown in FIG. 8A, since the measurement data supplied to the signal processing unit 24 includes a lot of noise components, the smoothing processing results in smooth data as shown in FIG. 8B. For example, a digital filter having a predetermined frequency as a cutoff frequency is used as the filter. The cut-off frequency varies depending on the rolling speed and noise components. For example, when the rolling speed is 60 (km / hour), the cut-off frequency is set to 0.5 to 2 (kHz). In addition, a smoothing process may be performed using a moving average process, a trend model, or the like instead of the digital filter.

  Next, the signal processing unit 24 removes the low-frequency background component 1 from the smoothed acceleration measurement data (step S106). The background component 1 of radial acceleration includes an acceleration component and centrifugal acceleration component of centrifugal force (centripetal force) during rolling of the tire (note that these components are also included in the background component of circumferential acceleration). In FIG. 8B, the waveform of the background component 1 is shown. The extraction of the low frequency component is performed by further performing a smoothing process on the waveform data after the smoothing process obtained in step 104. For example, a digital filter having a predetermined frequency as a cutoff frequency is used. For example, when the rolling speed is 60 (km / h), the cutoff frequency is set to 0.5 to 2 (kHz). In addition, a smoothing process may be performed using a moving average process, a trend model, or the like instead of the digital filter. Further, in the waveform data after the smoothing process, for example, a plurality of nodes are provided at predetermined time intervals, and a first approximate curve is obtained by a least square method using a predetermined function group, for example, a cubic spline function. You may obtain | require by calculating. The node means a constraint condition on the horizontal axis that defines the local curvature (flexibility) of the spline function. The signal processing unit 24 subtracts the background component 1 extracted in this way from the acceleration measurement data smoothed in step S104, so that the acceleration component and the gravitational acceleration component based on the rotation of the tire from the measurement data. Is removed. FIG. 8C shows time-series data of acceleration after removal. Thereby, the component of acceleration based on the ground deformation of the tread portion of the tire (time series data of acceleration based on the deformation of the tire) can be extracted.

  The signal processing unit 24 further determines the timing at which the rotation angle φ is 180 °, 540 °, 900 °,... From the time series data of acceleration based on tire deformation acquired in this way. Each is extracted (step S108). In the signal processing unit 24, in the graph of the time series data of the acceleration based on the tire deformation, the timing at which the acceleration based on the tire deformation takes the minimum value, the rotation angle φ is φ = 180 °, 540 °, 900 °. Extracted as the timing of. That is, the timing of these minimum values is extracted as the timing at which the acceleration sensor 2 fixed on the inner peripheral surface of the tire cavity region arrives (closest) to the center position of the tire contact surface as shown in FIG. In the tire contact area, the position of the tire outer peripheral surface in the direction perpendicular to the road surface is defined by the road surface. In the contact area, the road surface deforms the tire outer peripheral surface, which is originally curved, on a flat surface, so that the tire deforms in the thickness direction. As a result, the position of the inner peripheral surface of the tire cavity region fluctuates in the tire thickness direction (direction perpendicular to the road surface) in the ground contact region. The deformation in the thickness direction of the tire is minimized at the center position of the contact surface. The timing at which the acceleration based on the deformation of the tire obtained by the acceleration sensor arranged on the inner peripheral surface of the tire cavity region is minimized is such that the rotation angle φ is 180 °, 540 °, 900 °,. It can be said that Each process from step S104 to step S108 is performed on the acceleration measurement data of each of the wheels 14a to 14d acquired in step S102.

  Next, using the processing result of the data processing unit, the centrifugal force deriving unit 50 calculates the magnitude F of the centrifugal force applied to the vehicle 12 that is turning. First, the rotational angular velocity calculation unit 52 calculates the time-series angular velocities of the wheels 14a to 14d (step S110). FIGS. 9A and 9B are diagrams for explaining the signal waveforms obtained by the processing in step S <b> 110, and are graphs acquired by the time series calculation unit 52. The rotational angular velocity calculation unit 52 creates a scatter diagram representing the correspondence between each timing and the rotational angle, using the timings at which the rotational angle φ is 180 °, 540 °, 900 °, etc. extracted in step S108. Based on this scatter diagram, an approximate curve representing a time-series rotation angle is generated for each of the wheels 14a to 14d. FIG. 9A shows the correspondence between the approximate curve generated for one wheel and each timing and rotation angle extracted in step S108. Then, for each wheel, the time-series rotational angle represented by the approximate curve is time-differentiated to derive the time-series rotational angular velocity of each wheel. FIG. 9B is a graph of the rotational angular velocity in time series of the one wheel obtained from the approximate curve shown in FIG. In step S110, such a time-series rotational angular velocity is derived for each of the wheels 14a to 14d.

Next, the wheel movement amount calculation unit 54 calculates the wheel movement amount in a predetermined time range for each of the wheels 14a to 14d (step S112). The wheel movement speed of each wheel can be obtained by multiplying the rotation speed of each wheel by the length of the wheel outer diameter. That is, the time-series wheel moving speed of each wheel is calculated by multiplying the time-series rotational angular velocity of each wheel (for example, the graph shown in FIG. 9A) by the length of the wheel outer diameter. The wheel movement speed of this time series is integrated in a predetermined time range, and the wheel movement amount of each wheel is calculated. The wheel movement amount calculation unit 54 may calculate the wheel movement amount L _FR and the wheel movement amount L _FL in a predetermined unit time for at least the wheel 14 a and the wheel 14 b that are the front wheels of the vehicle 12.

  Next, the simulated vehicle speed calculation unit 56 calculates an estimated value (simulated vehicle speed V) of the moving speed of the vehicle 12 with respect to the road surface from the moving amount of each wheel per predetermined unit time (step S114). In the simulated vehicle speed calculation unit 56, first, the wheel movement amount per unit time (wheel movement speed of each wheel) of each wheel is obtained from the wheel movement amount of the angular wheel in a predetermined time range. Then, an average value of the wheel moving speeds of the wheels 14 a to 14 d may be calculated as the simulated vehicle speed V of the vehicle 12. In the present invention, the pseudo vehicle speed V may be, for example, an average value of wheel movement speeds of the two wheels 14c and 14d on the rear wheel side of the vehicle 12, and a detailed calculation method of the pseudo vehicle speed V is limited. Not.

  Next, the turning radius calculation unit 36 calculates the turning radius R during turning of the vehicle 12 (step S116). Hereinafter, calculation of the turning radius R in the turning radius calculation unit 36 will be described with reference to FIG. Hereinafter, as shown in FIG. 6, a case where the vehicle 12 moves by the turning angle θ around the turning radius in the predetermined time range will be described. It is assumed that the turning angle θ in the predetermined time range is sufficiently small.

さらに、旋回角θは充分に小さいので、下記式（４）および下記式（５）が成り立ち、下記式（６）が導出される。

In FIG. 6, since the turning angle θ is sufficiently small, the following expressions (2) and (3) are established.

Further, since the turning angle θ is sufficiently small, the following formula (4) and the following formula (5) are established, and the following formula (6) is derived.

Substituting Equation (2) and Equation (3) into Equation (6) and solving for R yields Equation (7) below.

  In this manner, the turning radius calculation unit 36 derives the turning radius R. The calculated value of the turning radius R is sent to the centrifugal force calculator 62.

遠心力の導出は、このように行なわれる。 The centrifugal force calculation unit 62 uses the calculated turning radius R, the simulated vehicle speed V, and the total weight M of the vehicle 12 to determine the magnitude of the centrifugal force F acting on the vehicle 12 that is turning as follows. It calculates using Formula (8) (step S118). The calculated centrifugal force magnitude F is output to the lateral force calculator 70.

The centrifugal force is derived in this way.

Next, using the processing result by the data processing unit, the contact length deriving unit 40 calculates the contact lengths CLa to CLd that are the contact lengths of the wheels 14a to 14d of the vehicle 12 that is turning. First, the deformation amount calculation unit 42 calculates a distribution of deformation amounts based on the ground deformation of the tread portion from the time series data of acceleration based on the ground deformation (step S120). FIGS. 10A to 10C are graphs schematically showing the processing results performed by the deformation amount calculation unit 42 in step S120. In the deformation amount calculation unit 42, first, time integration data of acceleration based on ground deformation is subjected to second-order time integration to generate displacement data. FIG. 10A shows a result of second-order integration with respect to time of time series data of acceleration from which the first background component has been removed in the data processing unit. As shown in FIG. 7A, it can be seen that the displacement increases with time. This is because the time series data of acceleration to be integrated includes a noise component and is integrated by integration. In general, when the amount of deformation or displacement of a point of interest in a tread portion of a tire that rolls in a steady state is observed, a periodic change is shown with the rotation period of the tire as a unit. Therefore, it is usually not possible for the displacement to increase with time.
Therefore, the following processing is performed on the displacement data so that the displacement data obtained by performing the second-order time integration shows a periodic change in units of the tire rotation cycle.

  That is, the noise component included in the displacement data is calculated as the background component 2 in the same manner as the method for calculating the background component 1. At this time, the deformation amount during rolling of the tire in the region including the contact area with the road surface can be obtained with high accuracy by using the time-series rotation angle obtained in the derivation of the centrifugal force. More specifically, the area on the circumference of the tire is divided into a first area including a contact area with the road surface and a second area other than this, and the first area is larger than θ = 90 degrees 270. An area of less than 85 degrees, greater than 450 degrees and less than 720 degrees, greater than 810 degrees and less than 980 degrees, and the second area is θ = 0 to 90 degrees and 270 degrees to 360 degrees, 360 degrees to 450 degrees And 630 degrees to 720 degrees, 720 degrees to 810 degrees, and 980 degrees to 1070 degrees. The background component 2 uses the plurality of circumferential positions (time corresponding to θ or θ) in the second region as nodes, and uses a predetermined function group, and the first region and the second region It calculates | requires by calculating a 2nd approximation curve with the least squares method with respect to the data of an area | region. The node means a constraint condition on the horizontal axis that defines the local curvature (flexibility) of the spline function. In FIG. 10B, a second approximate curve representing the background component 2 is indicated by a dotted line. In the example of FIG. 10B, the position indicated by “Δ” in FIG. 10B, that is, θ = 10, 30, 50, 70, 90, 270, 290, 310, 330, 350, 370, 390. , 410, 430, 450, 630, 650, 670, 690, 710, 730, 750, 770, 790, 810, 990, 1010, 1030, 1050, 1070 degrees.

By performing function approximation on the displacement data shown in FIG. 10A with a cubic spline function passing through the data points of the nodes, a second approximate curve indicated by a dotted line in FIG. 10B is calculated. Is done. When performing function approximation, there are no nodes in the first region, function approximation is performed using only a plurality of nodes in the second region, and the weighting factor of the second region used in the least square method performed in function approximation is used. The processing is performed with 1 being set to 1, and the weighting coefficient of the first region being set to 0.01. Thus, when calculating the background component 2, the first weighting factor is reduced and the node is not defined in the first region. The background component 2 is calculated mainly using the displacement data in the second region. It is to do. In the second region, deformation due to contact of the tread portion is small and the deformation changes smoothly on the circumference, so that the amount of deformation of the tire is small on the circumference and the change is also extremely small. On the other hand, in the first region, the tread portion of the tire is greatly displaced and rapidly changes based on the ground deformation. For this reason, the amount of deformation based on ground deformation is large and rapidly changes on the circumference. That is, the deformation amount of the tread portion in the second region is substantially constant as compared with the first deformation amount. Thus, by calculating the first approximate curve mainly using the displacement data obtained by the second order integration of the second area, the first area including not only the second area but also the ground contact area with the road surface is obtained. The amount of deformation during rolling of the tire in the region can be obtained with high accuracy.
In FIG. 10B, the second approximate curve calculated mainly using the displacement data of the second region is indicated by a dotted line. In the second region, the second approximate curve substantially matches the displacement data (solid line).

  Then, the approximate curve calculated as the background component 2 is subtracted from the displacement data, and the distribution of the deformation amount based on the ground deformation of the tread portion is calculated. FIG. 10 (c) shows the distribution of deformation based on the ground deformation of the tread portion, which is calculated by subtracting the second approximate curve (dotted line) from the displacement signal (solid line) shown in FIG. 10 (b). Show. FIG. 10C shows a distribution of deformation amounts for three rotations (three times of ground contact) when a predetermined measurement position on the tread portion rotates around the circumference and is displaced. It can be seen that the amount of deformation changes with each contact. The deformation amount calculated by such a method coincides with the deformation amount when the simulation is performed using the tire finite element model with high accuracy.

  Then, the contact length calculation unit 28 calculates the contact length (step S122). First, the time-series data of the deformation amount in the tread portion shown in FIG. 10C is subjected to second order differentiation with respect to time, so that the noise component is removed from the acceleration shown in FIG. , That is, acceleration time series data that does not include a noise component based on the ground deformation of the tread portion is calculated.

FIG. 11A shows a method for obtaining the grounding region and the grounding length. First, in the time series data of acceleration not including a noise component based on the ground deformation of the tire tread portion extracted in step S122, two points where acceleration changes rapidly and crosses zero are obtained. Next, the positions in the displacement data corresponding to the two obtained points are obtained, and these positions are set as the positions of the front end and the rear end as shown in FIG. The portion where the time series data of acceleration changes greatly in this way can be defined as the ground contact front end and the ground back end when the tread portion rotates and comes into the ground region, or when it comes out of the ground region. This is because the tire deforms rapidly. Further, it is possible to clearly determine the position where the time series data of acceleration crosses zero.
The lower graph in FIG. 11A is a graph written by changing from a polar coordinate system expressed in the radial direction and circumferential direction of the tire to an orthogonal coordinate system expressed in the vertical direction and the front-rear direction of the tire. It is a graph which shows the deformation | transformation shape of the tire which has existed and deform | transformed by the grounding. On this graph, the contact length can be evaluated by determining the positions of the front end and the rear end.
The contact length calculated by such a method coincides with the contact length accurately when a simulation is performed using a finite element model of a tire.

Further, in place of the method shown in FIG. 11A, the ground region and the ground length can be obtained by the method shown in FIG. Specifically, FIG. 11 (b) shows the normalization by dividing the position in the front-rear direction of the tire by the outer diameter C of the tread portion of the tire when the ground contact center position of the tire is the origin. It is the graph which expressed the deformation | transformation shape of the tire by dividing the position of an up-down direction by the outer diameter C, and normalizing. As shown in FIG. 11 (b), in the deformed shape of the tire, a position crossing a straight line that is a certain distance δ upward from the lowest point in the vertical direction corresponds to a standardized position corresponding to the ground contact front end and a ground rear end Standardized position. By obtaining the normalized positions and multiplying them by the outer diameter C, the positions of the front contact end and the rear contact end can be determined, whereby the contact area and the contact length of the tire can be determined. The fixed distance δ used for determining the front end position and the rear end position is preferably in the range of 0.001 to 0.005, for example. In addition, the position where the square value of the distance when the tread portion is separated upward from the lowest point crosses a predetermined value can be set as the ground contact front end and the ground contact rear end. For example, the predetermined value is in the range of 0.00002 (cm ² ) to 0.00005 (cm ² ), and preferably 0.00004 (cm ² ). It has been confirmed that the measurement results obtained by variously examining the contact length by changing the load applied to the stationary tire and the result of the contact length obtained by the above method show extremely high correlation.
FIG. 12 shows an example of the contact area and contact length obtained by the above method. A thick line portion in FIG. 12 indicates a grounding region.

  As described above, the deformation amount of the tread portion of the tire can be calculated in any of the radial direction, the circumferential direction, and the width direction, and the deformed shape and trajectory of the rolling tire can be obtained. Further, by providing a plurality of acceleration sensors on the inner peripheral surface of the tread portion on the circumference, it is possible to simultaneously acquire the ground contact state at the circumferential position of the tread portion. Furthermore, by providing a plurality of acceleration sensors in the width direction of the tire and obtaining the contact length in the width direction and the distribution of the contact area, the contact shape of the rolling tire can be acquired.

  Such derivation of the contact area (step S120 and step S122) is performed for each time series data of acceleration based on tire deformation of each wheel 14a to 14d, and the vehicle 12 of each wheel 14a to 14d is determined. The ground contact lengths CLa to CLd during turning are calculated. The calculated contact lengths CLa to CLa are output to the lateral force calculation unit 70.

  The lateral force calculation unit 71 uses the magnitude R of the centrifugal force applied to the vehicle 12 that is turning and the ground contact lengths CLa to CLd of the wheels 14a to 14d calculated in step S118, and the above formula (1 ), Wheel lateral forces SFa to SFd generated in the wheels 14a to 14d are calculated (step S124). The calculated wheel lateral forces SFa to SFd are displayed on the display 34.

  As described above, by providing a plurality of acceleration sensors on the inner peripheral surface of the tread portion on the circumference, it is possible to acquire the lateral force distribution in the circumferential direction of the tread portion that occurs in the ground contact area of the wheel. Furthermore, by providing a plurality of acceleration sensors in the width direction of the tire, the lateral force distribution in the width direction generated in the ground contact area of the wheel can be obtained.

  In the present embodiment, the centrifugal force applied to the vehicle 12 is calculated using acceleration data acquired by an acceleration sensor provided in the tire. In the present invention, the magnitude of the centrifugal force applied to the vehicle during turning is derived by arranging the vehicle acceleration sensor in the vehicle so that the magnitude of acceleration in a direction substantially perpendicular to the vehicle traveling direction can be measured. May be. For example, a vehicle acceleration sensor arranged in the vehicle measures the magnitude of vehicle acceleration in a direction substantially perpendicular to the traveling direction of the vehicle while the vehicle is turning, and the centrifugal acceleration is performed based on the vehicle acceleration and the vehicle weight. The magnitude of the force may be derived. The centrifugal force deriving method in the present invention is not particularly limited.

  As described above, the tire lateral force calculation method and the tire lateral force calculation method of the present invention have been described in detail. However, the present invention is not limited to the above embodiment, and various improvements and modifications can be made without departing from the gist of the present invention. Of course.

It is a schematic block diagram explaining an example of the wheel lateral force calculation apparatus of this invention. It is a figure explaining the sensor unit and the data processing unit in the wheel lateral force calculation apparatus shown in FIG. (A) And (b) is a figure explaining the force concerning a vehicle or a wheel at the time of turning of a vehicle. (A)-(c) is a graph which shows the relationship between the contact length of each wheel, and cornering power about several different wheel, respectively. It is a block diagram explaining the process means in the wheel lateral force calculation apparatus shown in FIG. It is a figure explaining the various parameters showing the behavior of the vehicle in the turning driving | running | working calculated in the centrifugal force derivation | leading-out part of the wheel lateral force calculation apparatus shown in FIG. It is a flowchart which shows an example of the wheel lateral force calculation method of this invention. (A)-(c) is a graph which shows the signal waveform obtained by the wheel lateral force calculation method of this invention. (A) And (b) is a graph which shows the signal waveform obtained by the wheel lateral force calculation method of this invention. (A)-(c) is a graph which shows the signal waveform obtained by the wheel lateral force calculation method of this invention. (A) And (b) is a figure explaining the calculation method of the contact length performed by the wheel lateral force calculation method of this invention. It is a figure which shows an example of the contact length calculated with the wheel lateral force calculation method of this invention.

Explanation of symbols

2 Acceleration sensor 3 Receiver 4 Amplifier (AMP)
DESCRIPTION OF SYMBOLS 10 Wheel lateral force calculation apparatus 21 Processing apparatus 22 Tire acceleration data acquisition part 23 CPU
24 Signal processing unit 27 Memory 34 Display 40 Ground contact length deriving unit 42 Deformation amount calculating unit 44 Ground contact length calculating unit 50 Centrifugal force deriving unit 52 Rotational angular velocity calculating unit 54 Wheel movement amount calculating unit 56 Pseudo vehicle speed calculating unit 58 Turning radius calculating unit 62 Centrifugal force calculator 70 Lateral force calculator

Claims (18)

For a vehicle having a plurality of wheels, a method of calculating a lateral force applied to each wheel during the turning of the vehicle,
A centrifugal force deriving step for obtaining a magnitude of a centrifugal force in a direction substantially perpendicular to the vehicle traveling direction, which is applied to the vehicle that is turning;
A contact length derivation step for determining a contact length of each of the plurality of wheels during turning of the vehicle;
A lateral force calculation step of calculating a lateral force applied to each wheel based on a ratio of a contact length of each wheel to a total sum of the contact lengths of each of the plurality of wheels and a magnitude of the centrifugal force. Wheel lateral force calculation method.   The lateral force calculating step calculates the lateral force applied to each wheel for each wheel by multiplying the magnitude of the centrifugal force and the ratio of the contact length of each wheel, respectively. 1. The wheel lateral force calculation method according to 1. The wheel comprises a tire;
Prior to the contact length derivation step, there is an acceleration data acquisition step for acquiring time-series acceleration data of a predetermined portion of the tire, which is generated when the rolling tire receives an external force from the road surface,
The contact length deriving step calculates the contact length of each of the plurality of wheels using the time-series acceleration data of the tire acquired in the acceleration data acquisition step. Wheel lateral force calculation method.   The contact length deriving step extracts time-series acceleration data based on tire deformation from the time-series acceleration data, and performs second-order time integration on the time-series acceleration data based on the tire deformation. 4. The wheel lateral direction according to claim 3, wherein the displacement data is calculated to calculate a deformation amount at a predetermined portion of the tire, and the contact length is calculated using the deformation amount at the predetermined portion of the tire. Force calculation method. The acceleration data acquired in the acceleration data acquisition step is at least one data of radial acceleration data orthogonal to the tire circumferential direction and tire circumferential acceleration data,
The wheel according to claim 4, wherein the deformation amount of the predetermined portion of the tire calculated in the contact length deriving step is a radial deformation amount and a circumferential deformation amount or a radial deformation amount of the tire. Lateral force calculation method.   The centrifugal force deriving step calculates a rotational angular velocity of each wheel using time-series acceleration data of a predetermined portion of the tire for each of the plurality of wheels, and turns the vehicle based on the rotational angular velocity of each wheel. An estimated value of a radius and a traveling speed of the vehicle is obtained, and the centrifugal force is calculated based on a turning radius of the vehicle, an estimated value of the traveling speed of the vehicle, and weight information of the vehicle acquired in advance. The wheel lateral force calculation method according to any one of claims 3 to 5.   The centrifugal force deriving step calculates the moving speed of each wheel using the rotational angular velocity of each wheel, and the value of the ratio of the moving speeds of the left and right wheels provided on at least one axle of the vehicle The wheel lateral force calculation method according to claim 6, wherein a turning radius of the vehicle is derived by using.   In the centrifugal force deriving step, an acceleration magnitude approximately perpendicular to a vehicle traveling direction and a weight of the vehicle measured during the turning of the vehicle measured by a vehicle acceleration sensor provided in the vehicle are used. The wheel lateral force calculation method according to any one of claims 1 to 5, wherein the centrifugal force is derived based on the magnitude. For a vehicle having a plurality of wheels, a device that calculates the lateral force applied to each wheel during the turning of the vehicle,
Centrifugal force deriving means for determining the magnitude of centrifugal force in a direction substantially perpendicular to the vehicle traveling direction, which is applied to the vehicle that is turning.
A contact length deriving means for determining a contact length of each of the plurality of wheels during turning of the vehicle;
Lateral force calculation means for calculating the lateral force applied to each wheel based on the ratio of the contact length of each wheel to the sum of the contact lengths of each of the plurality of wheels and the magnitude of the centrifugal force. Wheel lateral force calculation device.   The lateral force calculation means calculates the lateral force applied to each wheel for each wheel by multiplying the magnitude of the centrifugal force and the ratio of the contact length of each wheel, respectively. Item 10. The wheel lateral force calculation device according to Item 9. The wheel is a wheel provided with a tire,
An acceleration sensor that is provided at a predetermined portion of the tire and that generates time-series acceleration data of the predetermined portion of the tire that is generated when the rolling tire receives an external force from the road surface;
11. The wheel according to claim 9, wherein the contact length deriving unit obtains a contact length of each of the plurality of wheels using time-series acceleration data of the tire measured by the acceleration sensor. Lateral force calculation device. The contact length deriving means includes
Extracting time-series acceleration data based on tire deformation from the time-series acceleration data, and obtaining displacement data by performing second-order time integration on the time-series acceleration data based on the tire deformation. The deformation amount calculation unit for calculating the deformation amount in a predetermined portion of the tire,
The wheel lateral force calculation device according to claim 11, further comprising: a contact length calculation unit that calculates the contact length using a deformation amount at a predetermined portion of the tire. The acceleration data measured by the acceleration sensor is at least one of radial acceleration data orthogonal to the tire circumferential direction and tire circumferential acceleration data,
The wheel according to claim 12, wherein the deformation amount of the predetermined portion of the tire calculated by the contact length deriving unit is a radial deformation amount and a circumferential deformation amount of the tire, or a radial deformation amount. Lateral force calculation device. The centrifugal force deriving means includes, for each of the plurality of wheels, an angular velocity calculating unit that calculates a rotational angular velocity of each wheel using time-series acceleration data of a predetermined portion of the tire;
A turning radius calculation unit for obtaining a turning radius of the vehicle based on the rotational angular velocity;
A speed estimated value calculation unit for obtaining an estimated value of the traveling speed of the vehicle based on the rotational angular velocity;
And a centrifugal force calculation unit that calculates the centrifugal force based on the turning radius of the vehicle, the estimated value of the traveling speed of the vehicle, and the weight information of the vehicle acquired in advance. The wheel lateral force calculation device according to any one of claims 11 to 13. The turning radius calculation unit calculates the moving speed of each wheel using the rotational angular velocity of each wheel,
15. The wheel lateral force calculation device according to claim 14, wherein a turning radius of the vehicle is derived using a value of a ratio of the moving speeds of left and right wheels provided on at least one axle of the vehicle. . A vehicle acceleration sensor provided on the vehicle for measuring the magnitude of vehicle acceleration in a direction substantially perpendicular to the vehicle traveling direction during the turning of the vehicle;
The wheel according to any one of claims 9 to 13, wherein the centrifugal force deriving means derives the magnitude of the centrifugal force based on the vehicle acceleration and information on the weight of the vehicle. Lateral force calculation device.   The wheel lateral force calculation device according to any one of claims 11 to 16, wherein a plurality of the acceleration sensors are provided in a circumferential direction of the tire.   17. The wheel lateral force calculation device according to claim 11, wherein a plurality of the acceleration sensors are provided in a width direction of the tire.

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