JP2011079419A - Tire-state estimator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire-state estimator capable of accurately estimating a tire-state. <P>SOLUTION: The tire-state estimator includes: a tire-slip-angle estimating means 500 for estimating a tire slip angle; and a tire-force-maximum-value estimating means 300 for estimating a tire force maximum-value according to a previous value of the tire slip angle, a tire slip rate, and tire longitudinal force. The tire-slip-angle estimating means 500 estimates the tire slip angle based on the tire force maximum value, the tire slip rate, the tire longitudinal force, and a vehicle state measuring value. Thereby, a tire state can be accurately estimated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a tire state estimation device applied to an automobile.

  As a conventional technique for estimating a tire state, a technique described in Patent Document 1 is known. In Patent Document 1, a tire state is estimated using a map derived from tire characteristics from a self-aligning torque (hereinafter referred to as SAT) detection value, a lateral state quantity, and a longitudinal state quantity. Here, the tire state is a dimensionless quantity called a grip degree representing a margin until the tire force reaches a limit. The SAT is a torque around the turning center of the tire due to a deviation between the turning center of the tire and the point where the tire lateral force is applied. The lateral state quantity indicates, for example, a tire slip angle or a tire lateral force, and the front-rear direction quantity indicates a tire longitudinal force.

  In Patent Document 1, a sensor for detecting SAT and an electronic circuit corresponding to the sensor are required, which increases the vehicle cost. For example, in order to detect SAT, it is conceivable to install an axial force sensor for detecting the axial force acting on the tie rods of steered wheels (steering wheels). Leads to an increase. Further, in Patent Document 1, a tire slip angle or a tire lateral force is required as a lateral state quantity in order to estimate the tire state. In order to detect these, a sensor or tire for detecting the tire slip angle is required. An expensive sensor such as a lateral force sensor is required.

Japanese Patent No. 4213994

  Here, the axial force acting on the tie rod of the steered wheel (steering wheel) can be estimated from the output torque (assist torque) of the assist motor of the electric power steering, for example, if the vehicle is equipped with the electric power steering or the like. Is possible. However, the SAT of a wheel that does not have a steering mechanism (non-steered wheel) such as a rear wheel of a commercially available vehicle is detected without using a special sensor such as an axial force sensor or a lateral force sensor. It is particularly difficult to do so, and there is a possibility that the tire condition cannot be accurately estimated. For this reason, for example, when vehicle motion control is performed based on the estimated tire state, if the estimation accuracy cannot be sufficiently ensured, the control performance may be reduced, and the ride quality of the automobile may be deteriorated.

  Therefore, the tire condition estimation device of the present invention estimates the tire force maximum value according to the previous value of the tire slip angle, the tire slip rate and the tire longitudinal force, and the tire force maximum value, the tire slip rate, the tire longitudinal The tire slip angle is estimated based on force and vehicle state measurement values.

  According to the present invention, since it is possible to accurately estimate the tire state of a wheel that is difficult to detect SAT, such as a wheel that does not have a steering mechanism (non-steering wheel), an improvement in vehicle motion control performance can be expected. The ride comfort is expected to improve. Further, the vehicle state necessary for estimating the tire state can be detected by an existing sensor, and a special sensor for detecting a tire slip angle, a tire lateral force, or the like is not required, so that an increase in vehicle cost can be suppressed.

Explanatory drawing which shows the vehicle structure to which 1st Embodiment of the tire state estimation apparatus which concerns on this invention is applied. The block diagram which shows the calculation content of the tire state estimation in 1st Embodiment of the tire state estimation apparatus which concerns on this invention. Explanatory drawing which shows a tire force maximum value typically using a tire force. The block diagram which shows the calculation content in the tire force maximum value estimation means of FIG. Explanatory drawing which shows the vehicle structure to which 2nd Embodiment of the tire state estimation apparatus which concerns on this invention is applied. The block diagram which shows the calculation content of the tire state estimation in 2nd Embodiment of the tire state estimation apparatus which concerns on this invention. Explanatory drawing which shows typically the front-wheel tire force maximum value in a tire lateral direction using a rear-wheel tire force. It is a characteristic view which shows the tire force maximum value estimation result of each wheel in the tire state estimation apparatus of 2nd Embodiment, (a) is a characteristic view which shows the tire force maximum value of a left front wheel, (b) is a tire of a right front wheel. A characteristic diagram showing a maximum force value, (c) a characteristic diagram showing a tire force maximum value of a left rear wheel, and (b) a characteristic diagram showing a tire force maximum value of a right rear wheel. Explanatory drawing which shows the vehicle structure to which 3rd Embodiment of the tire state estimation apparatus which concerns on this invention is applied. The block diagram which shows the calculation content of the tire state estimation in 3rd Embodiment of the tire state estimation apparatus which concerns on this invention. Explanatory drawing which shows the vehicle structure to which 4th Embodiment of the tire state estimation apparatus which concerns on this invention is applied. The block diagram which shows the calculation content of the tire state estimation in 4th Embodiment of the tire state estimation apparatus which concerns on this invention. Explanatory drawing which shows the vehicle structure to which 5th Embodiment of the tire state estimation apparatus which concerns on this invention is applied. The block diagram which shows the calculation content of the tire state estimation in 5th Embodiment of the tire state estimation apparatus which concerns on this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  In the first embodiment, the tire state estimation device of the present invention is applied to a vehicle configuration in which four wheels are driven independently.

  FIG. 1 shows a vehicle configuration of the first embodiment. This vehicle is provided with a left front wheel drive motor 40FL, a right front wheel drive motor 40FR, a left rear wheel drive motor 40RL, and a right rear wheel drive motor 40RR as drive force generation sources, and the drive motor output shafts are respectively for the wheels 2FL, 2FR, It is connected to 2RL and 2RR. The drive motors 40L and 40R are three-phase synchronous motors in which permanent magnets are embedded in the rotor. The drive circuit 41 drives the four drive motors 40FL, 40FR, 40RL, and 40RR with electric power from the lithium ion battery 42 so that the drive motor output torque matches the torque command value received from the integrated controller 30. The drive circuit 41 detects the output torque of each drive motor 40FL, 40FR, 40RL, 40RR and a rotational position sensor (not shown) attached to the motor rotation shaft of each drive motor 40FL, 40FR, 40RL, 40RR. Each motor rotation speed is transmitted to the integrated controller 30.

  The front wheels 2FL and 2FR are mechanically steered via the steering gear 12 by the rotational movement of the steering wheel 11 operated by the driver.

  The integrated controller 30 includes each drive motor current, an accelerator opening signal APO detected by an accelerator pedal sensor 23, and a steering wheel rotation angle signal STR detected by a steering angle sensor 21 attached to the rotation shaft of the steering wheel 11. And a yaw rate signal γ detected by the yaw rate sensor 8, a lateral acceleration signal ay (vehicle lateral acceleration ay) detected by the acceleration sensor 28 attached to the position of the center of gravity, and attached to each wheel 2FL, 2FR, 2RL, 2RR. Respective wheel speeds (wheel angular speeds) ωfl, ωfr, ωrl, and ωrr detected by a rotation sensor (not shown) are input.

  FIG. 2 is a block diagram showing calculation details of tire state estimation in the first embodiment. The tire slip rate estimating means 100 in FIG. 2 detects the tire slip rate from each wheel speed. The tire slip ratio s (i, j) during driving is obtained based on the vehicle speed Vx (vertical speed) and the wheel speed ω (i, j) from the definition of the tire slip ratio using Formula (1).

  Here, the vehicle speed Vx is calculated based on, for example, the slowest wheel speed among the wheels. The tire slip rate s (i, j) during braking is defined by Equation (2).

  Here, the vehicle speed Vx is calculated based on, for example, the fastest wheel speed among the wheels. Alternatively, an observer may be configured from the vehicle dynamics and the vehicle speed Vx may be estimated based on the vehicle state (“Nonlinear State and Tire Force Estimate for Advanced Vehicle Control”, Laura R. Ray, Tranaction control ration). Vol.3, No.1, 1995).

  The tire longitudinal force detection means 200 in FIG. 2 detects the tire longitudinal force from the drive motor current and the drive wheel speed. At the time of driving, the tire longitudinal force is obtained based on the driving motor current and the wheel speed. As shown in Equation (3), the drive torque Td (i, j) is proportional to the drive motor current it (i, j) with the torque constant Kt as a proportional constant.

  Here, the subscripts i and j define the physical quantity of each ring as described above. For each wheel, the equation of motion expressed by Equation (4) is established.

  Here, Fx (i, j) is a tire longitudinal force, ω ′ (i, j) is a wheel acceleration, Rw is a tire effective radius, and Iw is an inertia moment of each wheel. Therefore, the tire longitudinal force Fx (i, j) is expressed by the following equation (5) from the equations (3) and (4), and the drive motor current it (i, j) and the wheel acceleration ω ′ (i, j). Based on.

  At the time of braking, for example, the relationship between the brake pressure, the wheel speed ω (i, j), and the tire longitudinal force Fx (i, j) is mapped in advance so that the left and right rear wheel longitudinal forces are converted into the left and right rear wheel speeds. And the left and right rear wheel brake pressures. When the cooperative regenerative brake is used, the tire longitudinal force Fx (i, j) may be obtained based on the signal of the control unit that controls the brake.

  In the tire force maximum value estimating means 300 of FIG. 2, the tire slip ratio s (i, j) detected by the tire slip ratio detecting means 100 and the tire longitudinal force Fx (i, j) detected by the tire longitudinal force detecting means 200 are used. ) To estimate the maximum tire force. The tire force maximum value estimated here is the maximum value of the tire force in the direction in which the tire force is generated (FIG. 3).

  The tire force maximum value estimating means outputs a nominal value (predetermined value) when the tire slip rate s (i, j) is smaller than a preset tire slip rate threshold, and when the tire slip rate is larger than the tire slip rate threshold. As will be described later, the tire force maximum value estimated using the tire model from the tire slip rate and the tire longitudinal force is output. Here, the nominal value is, for example, a static wheel load (wheel load when the vehicle is stationary) obtained from the vehicle weight and the position of the vehicle center of gravity. The reason for setting the tire slip ratio threshold is that when the tire slip ratio is extremely small, the sensitivity to the tire force maximum value of the tire longitudinal force decreases, and it becomes difficult to estimate the tire force maximum value using the tire model. . The tire slip ratio threshold value is set to the minimum tire slip ratio at which an estimation error is kept within a predetermined error range in estimating a tire force maximum value using a tire model described later.

  When the tire slip rate s (i, j) is larger than the threshold value (tire slip rate threshold value), the tire force maximum value is estimated based on the following calculation. FIG. 4 shows a block diagram showing the calculation contents in the tire force maximum value estimating means 300 of FIG. 4 converts the tire longitudinal force Fx (i, j) into the tire force F (i, j) using Equation (6).

  However, θ (i, j) is an angle formed by the tire contact surface longitudinal direction and the tire force. In the brush tire model, the tire slip ratio s (i, j) is used and is expressed by Expression (7).

  Here, the parameter λ (i, j) is the tire slip rate s (i, j) detected by the tire slip rate detecting means 100 in FIG. 2 and the tire slip angle αi (estimated by the tire slip angle estimating means 500 in FIG. (Previous value) is used to define the equations (8) and (9). At the time of the initial calculation, since the tire slip angle αi is not calculated by the tire slip angle estimating means 500 (since there is no previous value), a preset value (for example, zero) is used as the tire slip angle αi. Yes.

  Here, α is a tire slip angle, s is a tire slip rate, FX is a tire longitudinal force, and Fy is a tire lateral force.

  And tire force F (i, j) is calculated using numerical formulas (10) and (11) from numerical formulas (6), (7), (8), and (9).

  4 calculates the tire force adhesion ratio from the tire force F (i, j), the tire slip rate s (i, j), and the tire slip angle αi (previous value). At the time of the initial calculation, since the tire slip angle αi is not calculated by the tire slip angle estimating means 500 (since there is no previous value), a preset value (for example, zero) is used as the tire slip angle αi. Yes.

  According to the brush model, the tire force F (i, j) is expressed by the following equation (12) (according to “Tire and Vehicle Dynamics”, Pacejka, Butterworth Heinemann).

  Here, ξ (i, j) is a dimensionless tire adhesion area length. Therefore, when the ratio of the tire force F (i, j) and the tire force maximum value μ (i, j) Fz (i, j) is a non-dimensionalized tire force Fn (i, j), Equation (13) Can be expressed.

  On the other hand, if the adhesion length margin ξm (i, j) is defined by the difference between 1 and the dimensionless adhesion area length ξ (i, j), it can be expressed as Equations (14) and (15).

  Here, the parameter λ (i, j) is defined by equations (8) and (9). Further, the tire force adhesion ratio Pf (i, j) is defined by the ratio between the dimensionless tire force Fn (i, j) and the adhesion length margin ξm (i, j). Then, the adhesion length margin ξm (i, j) is calculated using the following formulas (16) and (17) from the formulas (13), (14), and (15), and the tire force F (i, j) and the tire slip. It is calculated from the rate s (i, j) and the tire slip angle αi (previous value).

  The dimensionless tire force calculation unit 330 in FIG. 4 calculates the dimensionless tire force from the tire force adhesion ratio Pf (i, j). The tire force adhesion ratio is defined by the following formulas (16) and (17) and the formulas (14) and (15) which are the definition formulas of the adhesion length margin ξm (i, j) and the non-dimensionalized tire based on the brush model. From Expression (13), which is a defining expression of force Fn (i, j), it can be expressed as Expression (18).

  On the other hand, the dimensionless tire force Fn (i, j) is expressed by the brush model as shown in Equation (13). Therefore, the relationship between the tire force adhesion ratio Pf (i, j) and the non-dimensional tire force Fn (i, j) is described by a mapping Z expressed by Expression (19).

  Here, the adhesion zone length ξ (i, j) is a parameter. In actuality, in order to obtain the dimensionless tire force Fn (i, j) from the tire force adhesion ratio Pf (i, j), for example, this mapping may be mapped in advance, or the Newton method may be used. You may solve this equation numerically.

  4 calculates the tire force maximum value Fp (i, j) from the tire force F (i, j) and the dimensionless tire force Fn (i, j). Since the tire force maximum value Fp (i, j) is given by the product of the road surface friction coefficient of each wheel and the wheel load, it can be calculated using Expression (20).

  Note that the tire force maximum value Fp (i, j) estimated here is the generation limit of the tire force in the direction θ (i, j) in which the tire force F (i, j) occurs (see FIG. 3). ). In the case where the tire friction circle is not a perfect circle and the tire lateral force estimation means 400 of FIG. 2 requires a tire force generation limit in the lateral direction or the longitudinal direction, the formula (20) is considered in consideration of the shape of the tire friction circle. It is necessary to convert the given tire force maximum value Fp (i, j). In the present embodiment, when the tire lateral force is estimated by the tire lateral force estimating means 400 of FIG. 2 using the brush model, the generation limit of the tire force in the direction in which the tire force F (i, j) is generated is required. There is no need to do this conversion.

  Conventionally, as a method of estimating the maximum tire force value, it has been common to estimate the road friction coefficient and wheel load separately and to estimate them from the product of them, but both the road friction coefficient and wheel load are increased. It was difficult to estimate the accuracy, leading to a deterioration of the tire force maximum value estimation accuracy. On the other hand, the present method is characterized in that the tire force maximum value Fp (i, j) can be directly estimated using the characteristics of the brush model, and the tire force maximum value Fp (i, j) can be accurately estimated. . That is, even when there is anisotropy in the tire friction circle, the tire state can be estimated with high accuracy, and when this estimated value is used for vehicle motion control, control with better riding comfort is possible.

  In the tire lateral force estimating means 400 of FIG. 2, the tire force maximum value estimated by the tire force maximum value estimating means 300 and the tire slip angle and tire slip rate detecting means 100 estimated by the tire slip angle estimating means 500 are detected. The tire lateral force is estimated from the tire slip rate. For example, when a brush tire model is used, the tire lateral force Fy () is calculated from the tire slip rate s (i, j), the tire force maximum value Fp (i, j), and the tire slip angle estimated value αi (previous value). i, j) is estimated. At the time of the initial calculation, since the tire slip angle αi is not calculated by the tire slip angle estimating means 500 (since there is no previous value), a preset value (for example, zero) is used as the tire slip angle αi. Yes.

  At the time of driving, the tire lateral force Fy (i, j) can be calculated by Expression (21).

  Here, ξ (i, j) in Equation (21) is expressed by Equation (22).

  At the time of braking, the tire lateral force Fy (i, j) can be calculated by Expression (23).

  Here, ξ (i, j) in Equation (23) is expressed by Equation (24).

  A tire model that can calculate the tire lateral force from the tire slip angle, the tire slip rate, and the tire force maximum value can be used without being limited to the brush model.

  In the tire slip angle estimating means 500 of FIG. 2, the tire lateral force estimated by the tire lateral force estimating means 400, the tire longitudinal force detected by the tire longitudinal force detecting means 200, the yaw rate detected in advance, the vehicle lateral acceleration, and the longitudinal direction. The tire slip angle is estimated from the speed.

  First, the derivation of this observer is shown. The vehicle dynamic characteristics in the vertical direction and the horizontal direction when the driving force is taken into consideration are expressed by Expression (25) and Expression (26), respectively.

  Here, m is the vehicle weight, Vy is the lateral speed, and γ is the yaw rate. The vehicle body slip angle β is an angle formed by the vertical speed Vx and the horizontal speed Vy, and is represented by Expression (27).

It is expressed. Differentiating both sides of Equation (27) yields Equation (28).

It is. Considering that Vy = βVx is established when the vehicle dynamic characteristics represented by Equation (25) and Equation (26) are substituted into Equation (28) and the vehicle body slip angle β is sufficiently small, Equation (29) )

  Based on the above results, an observer for estimating the vehicle slip angle β is configured so that the difference between the estimated lateral force and the actual lateral force becomes zero (Equation 30).

  Here, K is an observer gain, Fyr is an estimated rear wheel lateral force value estimated using equations (21) and (23) (estimated value of total left and right rear wheel lateral forces), and Fyrmes is a rear wheel lateral force. This is the force detection value (the detection value of the total lateral force of the left and right rear wheels). In the present embodiment, the rear wheel lateral force detection value is detected by calculating from the vehicle lateral acceleration ay and the yaw rate using Formula (31), which is a balance relational expression between the front wheel lateral force and the rear wheel lateral force of the next vehicle. To do.

  Therefore, Equation (30) is the difference between the lateral force Fyrmes detected by calculating from the yaw rate and the vehicle body lateral acceleration using Equation (31) and the lateral force Fyr estimated using Equations (21) and (23). The observer is configured to decrease.

  Further, using the relationship of the following equations (32) and (33), the front tire slip angle αf and the rear tire slip angle are calculated from the estimated vehicle slip angle β and the detected yaw rate γ and front wheel turning angle δf. αr is obtained.

  The front tire slip angle thus estimated is used in the tire force maximum value estimation means 300 and the tire lateral force estimation means 400 shown in FIG. In this way, by configuring the observer for estimating the vehicle slip angle β so that the difference between the estimated lateral force and the actual lateral force becomes zero, the tire slip angle and other tire states can be estimated with high accuracy.

  The estimated amount obtained by this algorithm can be used for control for stabilizing the vehicle behavior, for example. In general, if the vehicle speed is kept constant and the turning angle is continuously increased, the tire lateral force eventually exceeds the maximum lateral force and the vehicle behavior becomes unstable. Therefore, based on the tire lateral force and the tire force maximum value obtained by this estimation algorithm, for example, if control is performed to reduce the front wheel turning angle before the tire lateral force exceeds the tire force maximum value, the vehicle behavior is It can be kept stable.

  In such a 1st embodiment, in estimating a tire state, a sensor for detecting SAT (self-aligning torque) and an electronic circuit corresponding to it are unnecessary, and a vehicle cost can be reduced. Further, the vehicle state necessary for estimating the tire state can be detected by an existing sensor, and a special sensor for detecting a tire slip angle, a tire lateral force, or the like is not required, so that the vehicle cost can be reduced. Furthermore, since it is possible to accurately estimate the tire condition even when it is difficult to detect SAT in a wheel that does not have a steering mechanism (non-steering wheel), it can be expected to improve the performance of vehicle motion control, and the ride quality of the vehicle Improvement is expected.

  In addition, a tire force adhesion ratio calculation unit that calculates a tire force adhesion ratio from the previous value of tire slip ratio and tire slip angle and tire longitudinal force, and a tire that obtains a maximum tire force value from the tire force adhesion ratio and tire longitudinal force Since the tire force maximum value estimation means having the force maximum value calculation unit is provided, it is possible to estimate the tire force maximum value with high accuracy, and when this estimated value is used for vehicle motion control, it is possible to perform control with better riding comfort. Become.

  Furthermore, since the tire slip angle is estimated using not only the maximum tire force value but also the previous values of the tire lateral force and tire slip angle, if this estimated value is used for vehicle motion control, it is more comfortable to ride. Better control.

  And when the tire slip rate exceeds a predetermined value, the tire force maximum value is estimated, and when it does not exceed the predetermined value, a value estimated based on a static wheel load is output. Even when acceleration / deceleration is not performed, the tire state can be estimated with a certain accuracy.

  Hereinafter, although other embodiment of this invention is described, the same code | symbol is attached | subjected about the component same as 1st Embodiment mentioned above, and the overlapping description is abbreviate | omitted suitably.

  Next, a second embodiment of the present invention will be described. In the second embodiment, the tire state estimation device of the present invention is applied to a vehicle configuration in which rear wheels 2RL and 2RR are driven independently on the left and right sides and front wheels 2FL and 2FR are driven wheels. FIG. 5 shows a vehicle configuration of the second embodiment. This vehicle includes a left rear wheel drive motor 40RL and a right rear wheel drive motor 40RR as driving force generation sources, and is directly connected to the left rear wheel 2RL and the right rear wheel 2RR, respectively. Each drive motor 40RL, 40RR is a three-phase synchronous motor in which a permanent magnet is embedded in a rotor. The drive circuit 41 drives the left and right drive motors 40RL, 40RR with the electric power from the lithium ion battery 42 so that the drive motor output torque matches the torque command value received from the integrated controller 30. The drive circuit 41 then integrates the output torque of each drive motor 40RL, 40RR and the motor rotation speed detected by a rotation position sensor (not shown) attached to the motor rotation shaft of each drive motor 40RL, 40RR, respectively. Send to.

  The front wheels 2FL and 2FR are mechanically steered mechanically via the steering gear 12 by the rotational movement of the steering wheel 11 operated by the driver.

  The integrated controller 30 includes an accelerator opening signal APO detected by an accelerator pedal sensor 23, a steering wheel rotation angle signal STR detected by a steering angle sensor 21 attached to the rotation shaft of the steering wheel 11, and a yaw rate sensor 8. Detected by a yaw rate signal γ to be detected, a lateral acceleration signal ay (vehicle lateral acceleration ay) detected by the acceleration sensor 28 attached to the center of gravity position, and a rotation sensor attached to each wheel 2FL, 2FR, 2RL, 2RR. Each wheel speed (wheel angular speed) ωfl, ωfr, ωrl, ωrr is input.

  FIG. 6 is a block diagram showing the calculation contents of the tire state estimation in the second embodiment.

  In the tire slip ratio detecting means 100 of FIG. 6, the rear wheel tire slip ratio is detected from each wheel speed by the same calculation as the first embodiment (the same calculation as the tire slip ratio detection means 100 of the first embodiment). . In the first embodiment, four wheels are detected, but in this second embodiment, the tire slip rate is detected only for the left and right rear wheels.

  In the tire longitudinal force detection means 200 of FIG. 6, the rear wheel tire is calculated from the drive motor current and the drive wheel speed by the same calculation as the first embodiment (the same calculation as the tire vertical force detection means 200 of the first embodiment). Detects longitudinal force.

  The rear wheel tire force maximum value estimation means 300 in FIG. 6 performs the same calculation as the tire force maximum value estimation means 300 in FIG. 2 in the first embodiment, thereby rear wheel tire slip ratio, rear wheel tire longitudinal force, and tire slip angle. The rear wheel tire force maximum value is estimated from the rear wheel tire slip angle estimated by the estimating means 800 (described later).

  The rear wheel tire lateral force estimating means 400 in FIG. 6 estimates the rear wheel tire force maximum value, the rear wheel tire slip ratio, and the tire slip angle by the same calculation as the tire lateral force estimating means 400 in FIG. 2 in the first embodiment. The rear wheel tire lateral force is estimated from the rear wheel tire slip angle estimated by means 800 (described later).

  In the rear wheel tire force maximum value estimating means 300 and the rear wheel tire lateral force estimating means 400 of FIG. 6, the tire slip angle estimating means 800 (described later) calculates the rear wheel tire slip angle αr at the time of the initial calculation. Since there is no value (since there is no previous value), a preset value (for example, zero) is used as the rear wheel tire slip angle αr.

  The front wheel tire force maximum value estimation means 600 in FIG. 6 estimates the front wheel tire force maximum value from the rear wheel tire longitudinal force and the rear wheel tire force maximum value. First, attention is paid to the relationship between the longitudinal force acting on the vehicle body, the lateral force, and each wheel load, which is derived from the balance of moments in the roll pitch direction of the vehicle.

  Here, Fz (f, l) is the left front wheel load, Fz (f, r) is the right front wheel load, Fz (r, l) is the left rear wheel load, Fz (r, r) is the right rear wheel load, hcg. Is the height from the ground to the center of gravity of the vehicle, and lt is the tread width. Further, Fxall and Fyall are the total values of longitudinal force or lateral force acting on the entire vehicle, and the total longitudinal force value Fxall is the sum of the left and right rear wheel longitudinal forces estimated by the tire longitudinal force detecting means 200 of FIG. It can be calculated with That is, the longitudinal force total value Fxall is calculated using the mathematical formula (38).

  Further, the road surface friction coefficient μrr of the left rear wheel and the road surface friction coefficient μrr of the right rear wheel in the direction in which the tire force acts are calculated using Expression (39), respectively.

  However, as in the first embodiment, the subscript j corresponds to l: left wheel or r: right wheel.

  Furthermore, assuming that the road surface friction coefficient μ is the same between the front and rear wheels, the road surface friction coefficient of the left and right wheels is calculated using Equation (40).

  Further, the maximum tire force values for the left and right front wheels can be written as shown in Equation (41).

  From Formula (34) to Formula (41), the maximum tire force value Fp (f, j) for the left and right front wheels can be expressed as Formula (42).

  The mathematical formula (42) is derived as follows.

  After all, the left and right front wheel tire force maximum values Fp (f, j) are the left and right rear wheel tire force maximum values Fp (r, l), Fp (r, r) and the left and right rear wheel longitudinal forces Fx (r, l), Fx. It can be calculated from (r, r).

  Fp (f, j) estimated here is a generation limit of the front wheel tire force in the direction θ (r, j) in which the rear wheel tire force is generated. On the other hand, what is required for calculating the front wheel tire lateral force by the front wheel tire lateral force estimating means 700 in FIG. 6 is the limit of occurrence of the front wheel tire force (cornering force) in the tire lateral direction in which the front wheel tire force acts. . Therefore, the generation limit of the front tire force in the direction in which the rear wheel tire force is generated is converted into the generation limit in the tire lateral direction (FIG. 7).

  When the tire force generation direction θ (r, j) is changed from 0 to 360 degrees, the corresponding distribution of the maximum tire force value is expressed, for example, as an ellipse (the tire friction circle has anisotropy). When there is, the tire force maximum value Fp (f, j) in the direction in which the rear wheel tire force is generated is converted to the front wheel tire force maximum value Fpy (f, j) in the tire lateral direction by Expression (44).

  Here, Rμ is a coefficient indicating the flatness of the ellipse representing the tire force maximum value, and is defined by Expression (45) from the longitudinal road surface friction coefficient μx and the lateral road surface friction coefficient μy.

  Θ (r, j) is a direction in which the rear wheel tire force is generated, and is calculated from the rear wheel tire slip rate s (r, j) and the rear wheel tire slip angle αr using Equation (7).

  In the front wheel tire lateral force estimating means 700 of FIG. 6, the front wheel tire force maximum value (front wheel tire force maximum value in the tire lateral direction) estimated by the front wheel tire force estimating means 600 and the tire slip angle estimating means 800 are estimated. The front wheel tire lateral force is estimated from the tire slip angle (previous value). At the time of the initial calculation, since the front wheel tire slip angle αf is not calculated by the tire slip angle estimating means 800 (since there is no previous value), a value (for example, zero) set in advance as the front wheel tire slip angle αf is used. Used.

  For estimating the front wheel tire lateral force Fy, for example, a model formula based on the following Fiara theory ("Automobile motion and control" written by Masato Abe, published on March 10, 2007, published by Sankai-do) is used. Hereinafter, this model formula is referred to as a fiara model.

  Here, Ψ (f, j) is expressed by Expression (47).

  In equation (47), αf is the front tire slip angle. A tire model that can calculate the tire lateral force from the tire slip angle and the maximum tire force can be used without being limited to the filar model.

  In the tire slip angle estimating means 800 of FIG. 6, the rear wheel tire longitudinal force detected by the tire longitudinal force detecting means 200 and the rear wheel tire lateral force and the front wheel tire lateral force estimated by the rear wheel tire lateral force estimating means 400 are estimated. The front and rear wheel tire slip angles are estimated from the front wheel tire lateral force estimated by means 700. Similar to the first embodiment, an observer of the following expression regarding the vehicle slip angle β is derived from the vehicle dynamic characteristics in consideration of the braking / driving force.

  Further, similarly to the first embodiment, the front tire slip angle αf and the rear tire slip angle αr are obtained from the vehicle slip angle β, the yaw rate γ, and the vehicle speed Vx using the equations (32) and (33).

  FIG. 8 shows a tire force maximum value estimation result using the present embodiment when an acceleration circle turn is performed by computer simulation. Since the tire force maximum value estimated value matches the true value for each wheel, it can be seen that the present example is operating properly.

  In such a second embodiment, the same operational effects as those of the first embodiment described above can be obtained. In the second embodiment, the tire condition of each wheel can be accurately estimated even when driven wheels are present.

  Next, a third embodiment of the present invention will be described. In the third embodiment, the tire state estimation device of the present invention is applied to a vehicle configuration in which front wheels 2FL and 2FR are driven independently on the left and right sides and rear wheels 2RL and 2RR are driven wheels.

  FIG. 9 shows a vehicle configuration of the third embodiment. This vehicle includes a left front wheel drive motor 40FL and a right front wheel drive motor 40FR as driving force generation sources, which are directly connected to the left front wheel 2FL and the right front wheel 2FR, respectively. Each drive motor 40FL, 40FR is a three-phase synchronous motor in which a permanent magnet is embedded in a rotor. The drive circuit 41 drives the left and right drive motors 40FL, 40FR with electric power from the lithium ion battery 42 so that the drive motor output torque matches the torque command value received from the integrated controller 30. Then, the drive circuit 41 transmits the output torque of the drive motors 40FL and 40FR and the motor rotation speed detected by a rotation position sensor (not shown) attached to the motor rotation shaft of the drive motors 40FL and 40FR to the integrated controller 30, respectively. To do.

  The front wheels 2FL and 2FR are mechanically steered mechanically via the steering gear 12 by the rotational movement of the steering wheel 11 operated by the driver.

  The integrated controller 30 includes an accelerator opening signal APO detected by an accelerator pedal sensor 23, a steering wheel rotation angle signal STR detected by a steering angle sensor 21 attached to the rotation shaft of the steering wheel 11, and a yaw rate sensor 8. The yaw rate signal γ to be detected and the respective wheel speeds (wheel angular speeds) ωfl, ωfr, ωrl, and ωrr detected by the rotation sensors attached to the wheels 2FL, 2FR, 2RL, and 2RR are input.

  Further, in the third embodiment, as will be described later, since the observer is configured to perform error correction of the tire slip angle estimated value based on the yaw rate, the acceleration sensor 28 differs from the first and second embodiments described above. Is not required.

  FIG. 10 is a block diagram showing the calculation contents of the tire state estimation in the third embodiment.

  The tire slip ratio detecting means 100 in FIG. 10 detects the front wheel tire slip ratio from each wheel speed in the same manner as the tire slip ratio detecting means 100 in FIG. 2 in the first embodiment.

  The tire longitudinal force detection means 200 of FIG. 10 detects the front wheel tire longitudinal force from the drive motor current and the drive wheel speed in the same manner as the tire longitudinal force detection means 200 of FIG. 2 in the first embodiment.

  The front wheel tire force maximum value estimation means 300 in FIG. 10 performs the same calculation as the tire force estimation means 300 in FIG. 2 in the first embodiment, thereby calculating the front wheel tire longitudinal force, the front wheel tire slip ratio, and the tire slip angle estimation means 1000 (described later). ) Estimate the maximum value of the front wheel tire force from the front wheel tire slip angle.

  The front wheel tire lateral force estimating means 400 of FIG. 10 performs the same calculation as the tire lateral force estimating means 400 of FIG. 2 in the first embodiment, thereby calculating the front wheel tire maximum force value, the front wheel tire slip ratio, and the tire slip angle estimating means 1000 ( The front wheel tire lateral force is estimated from the front tire slip angle estimated in (below).

  In the front wheel tire force maximum value estimation means 300 and the front wheel tire lateral force estimation means 400 in FIG. 10, the tire slip angle estimation means 1000 (described later) does not calculate the front wheel tire slip angle αf at the time of the initial calculation ( Since there is no previous value), a preset value (for example, zero) is used as the front tire slip angle αf.

  The rear wheel tire force maximum value estimation means 600 in FIG. 10 estimates the rear wheel tire force maximum value from the front wheel tire longitudinal force and the front wheel tire force maximum value. In the same manner as in the second embodiment, when considering the balance between the roll acting on the vehicle and the moment in the pitch direction, the left and right rear wheel tire force maximum value Fp (r, j) is the front wheel tire force maximum value Fp (f, j). Is estimated using Equation (49).

  Fp (r, j) estimated here is the limit of generation of the rear wheel tire force in the direction θ (f, j) in which the front wheel tire force is generated.

  On the other hand, what is necessary for the estimation of the rear wheel tire lateral force by the rear wheel tire lateral force estimating means 900 in FIG. 10 is the generation limit of the rear wheel tire force in the tire lateral direction, which is the direction in which the rear wheel tire force is generated. . Therefore, the generation limit of the rear wheel tire force in the direction in which the front wheel tire force is generated is converted to the limit in the tire lateral direction by the same calculation as in the second embodiment. When the tire force generation direction is changed from 0 to 360 degrees, when the corresponding tire force distribution is expressed by an ellipse, for example, this conversion can be realized by Expression (50).

  Here, Rμ is a coefficient representing the flatness of the tire force maximum ellipse, and is defined by Equation (45). Θ (f, j) is the direction in which the front wheel tire force is generated, and is defined from the front wheel tire slip rate s (f, j) and the front wheel tire slip angle αf using Equation (7).

  In the rear wheel tire lateral force estimating means 900 of FIG. 10, the rear wheel tire force maximum value (the rear wheel tire force maximum value in the tire lateral direction) and the rear wheel tire slip angle αr estimated by the tire slip angle estimating means 1000 are used. The rear wheel tire lateral force Fy (r, j) is estimated. When the Fiara model is used as a tire lateral force model, the rear wheel tire lateral force is estimated by Expression (51).

  Here, Ψ (r, j) is expressed by Equation (52).

  A tire model that can calculate the tire lateral force from the tire slip angle and the maximum tire force can be used without being limited to the filar model.

  In the tire slip angle estimating means 1000 of FIG. 10, the front wheel tire lateral force estimated by the front wheel tire lateral force estimating means 400, the rear wheel tire lateral force estimated by the rear wheel tire lateral force estimating means 900, the detected yaw rate and Estimate the tire slip angle of the front and rear wheels from the longitudinal speed. Unlike the first and second embodiments, since the observer is configured without using the vehicle lateral acceleration, the acceleration sensor 28 can be omitted, the vehicle cost can be reduced, and estimation by noise mixed in the acceleration sensor 28 can be performed. The adverse effects on the system can be eliminated.

  In order to derive this observer, the fact that Formula (53) holds for the vehicle body slip angle β from the vehicle dynamic characteristics in the vertical direction and the horizontal direction is used.

  Further, from the vehicle dynamic characteristics of the rotational motion, the mathematical formula (54) is established for the yaw rate γ.

  Here, I is the vehicle yaw moment of inertia, and lt is the tread width. In the above two formulas, particularly in the present embodiment, Fxrl = Fxrr = 0. Further, the state vector x, the input u of the vehicle motion system, and the output y are determined as follows.

  If f (.) is a state equation and h (.) is an output equation, the vehicle motion system can be expressed by the following equation from equations (53) and (54).

  Therefore, the observer for estimating the state vector x can be designed by the following equation.

  In the above equation (59), K is an observer gain vector, and y is a yaw rate detection value detected by the yaw rate sensor 8. Therefore, the observer is configured so that an error between the detected yaw rate value and the estimated yaw rate value is reduced by designing the observer as in Expression (59). From the vehicle body slip angle β included in the state vector x thus estimated, the front wheel tire slip angle αf and the rear wheel tire slip angle αr are estimated using the relationship between the slip angle, the yaw rate, and the vehicle speed. Further, the estimated front wheel tire slip angle αf is used by the front wheel tire maximum force estimating means 300 and the front wheel tire lateral force estimating means 400, and the rear wheel tire slip angle αr is used by the rear wheel tire lateral force estimating means 900.

  Next, a fourth embodiment of the present invention will be described. As shown in FIG. 11, the fourth embodiment has substantially the same vehicle configuration as the second embodiment described above, but the vehicle can detect the self-aligning torque (SAT) of the front wheels (steering wheels). It has a configuration. Thus, the tire condition can be estimated even when the road surface friction coefficient μ is not equal between the front and rear wheels.

The front wheels 2FL, 2FR are not only mechanically steered mechanically via the steering gear 12 by the rotational movement of the steering wheel 11 operated by the driver, but are also auxiliary steered by assist torque by the auxiliary steering motor 24. A driver torque is detected by a torque sensor 22 attached to the steering shaft, and an input current of the auxiliary steering motor 24 is detected and transmitted to the integrated controller 30.
Since other configurations are the same as those of the second embodiment, description thereof is omitted.

  Also in the third embodiment, the same operational effects as those of the second embodiment described above can be obtained.

  FIG. 12 is a block diagram showing the calculation contents of the tire state estimation in the fourth embodiment.

  In the tire slip ratio detecting means 100 of FIG. 12, the rear wheel tire slip ratio is detected from each wheel speed by the same calculation as the second embodiment (the same calculation as the tire slip ratio detecting means 100 of the second embodiment). .

  In the tire longitudinal force detection means 200 of FIG. 12, the rear wheel tire is calculated from the drive motor current and the drive wheel speed by the same calculation as in the second embodiment (the same calculation as in the tire vertical force detection means 200 of the second embodiment). Detects longitudinal force.

  In the rear-wheel tire force maximum value estimation means 300 in FIG. 12, the rear-wheel tire slip rate is calculated by the same calculation as in the second embodiment (the same calculation as in the rear-wheel tire force maximum value estimation means 300 in the second embodiment). The maximum value of the rear wheel tire force is estimated from the rear wheel tire longitudinal force and the rear wheel tire slip angle estimated by the tire slip angle estimating means 1400 (described later).

  In the rear wheel tire lateral force estimating means 400 of FIG. 12, the rear wheel tire maximum force value and the rear are calculated by the same calculation as that of the second embodiment (the same calculation as that of the rear wheel tire lateral force estimation means 400 of the second embodiment). The rear wheel tire lateral force is estimated from the wheel tire slip rate and the rear wheel tire slip angle estimated by the tire slip angle estimating means 1400 (described later).

  In the rear wheel tire force maximum value estimation means 300 and the rear wheel tire lateral force estimation means 400 in FIG. 12, the rear wheel tire slip angle αr is calculated by a tire slip angle estimation means 1400 (described later) at the time of initial calculation. Since there is no value (since there is no previous value), a preset value (for example, zero) is used as the rear wheel tire slip angle αr.

  The self-aligning torque (SAT) detecting means 1100 in FIG. 12 detects the front wheel SAT from the electric power steering assist torque and the electric power steering driver torque. From the driver torque Tstr detected by the torque sensor 21 having the configuration shown in FIG. 11 and the assist torque Tass calculated from the input current of the auxiliary steering motor 24, the average value of the SAT of each of the left and right wheels is calculated as the self-aligning torque of the front wheels. Estimated as Tsat. That is, the front wheel SAT is obtained by the equation (60).

  The front wheel tire force maximum value estimation means 1200 in FIG. 12 estimates the front wheel tire force maximum value from the front wheel SAT and the front wheel tire slip angle estimated by the tire slip angle estimation means 1400 (described later) in FIG. For example, according to the fiara model, SAT is expressed as shown in Equation (61).

  Here, Fpf is a front wheel tire force maximum value, αf is a front wheel tire slip angle, and lc is a tire contact surface length. The front wheel tire maximum force Fpf can be obtained by substituting the front wheel tire slip angle and the front wheel SAT into this equation and solving the cubic equation.

  The front wheel tire lateral force estimating means 1300 in FIG. 12 estimates the front wheel tire lateral force from the front wheel tire maximum force value and the front wheel tire slip angle. For example, when a fiara tire model is used, the front wheel tire lateral force Fyf is estimated by the following equation.

  Here, ψf is expressed by Equation (63).

It is. Any tire model capable of calculating the tire lateral force from the tire slip angle and the maximum tire force can be used without being limited to the filar tire model.

  The tire slip angle estimating means 1400 in FIG. 12 detects the rear wheel tire lateral force estimated value estimated by the rear wheel tire lateral force estimating means 400 and the front wheel tire lateral force estimated by the front wheel tire lateral force estimating means 1300. The front and rear tire slip angles are estimated from the yaw rate, longitudinal speed, and vehicle lateral acceleration.

  Unlike the previous embodiments, the front wheel tire lateral force estimated by the front wheel tire lateral force estimating means 1300 of the present embodiment is the average value of the lateral forces generated on the left and right wheels. When the observer is derived by the same operation as the form, the following equation is obtained.

  Based on the vehicle slip angle β estimated from this equation, the front wheel tire slip angle αf and the rear wheel tire slip angle αr are estimated in the same manner as in the first embodiment.

  Also in the fourth embodiment, since the tire state can be accurately estimated, the performance improvement of the vehicle motion control can be expected, and the ride comfort of the automobile is expected to be improved.

  Next, a fifth embodiment of the present invention will be described. As shown in FIG. 13, the fifth embodiment has substantially the same configuration as the second embodiment described above, but the driving force generation source of the vehicle is changed from a motor to an internal combustion engine such as an engine.

  In FIG. 13, reference numeral 50 denotes an internal combustion engine such as an engine, which supplies driving force. Reference numeral 51 in FIG. 13 denotes a transmission, which selects an appropriate gear and transmits a driving force to the axle via the gear. Information on the selected gear is transmitted to the integrated controller 30. Although not shown in the figure, a rotation sensor is attached to each wheel, and the detected wheel speeds (wheel angular speeds) ωfl, ωfr, ωrl, and ωrr are input to the integrated controller 30.

  FIG. 14 is a block diagram showing the calculation contents of the tire state estimation in the fifth embodiment.

  In the tire slip ratio detection means 100 of FIG. 14, the rear wheel tire slip ratio is detected from each wheel speed by the same calculation as the second embodiment (the same calculation as the tire slip ratio detection means 100 of the second embodiment). .

  14 detects the rear wheel tire longitudinal force from the driving torque and the driving wheel speed. For example, mathematical expression (65) is used to detect the rear wheel tire longitudinal force.

  Td (r, j) is a driving torque generated in the rear wheel, and is estimated from, for example, a selected gear ratio and the rotational speed of the internal combustion engine, using a map that shows these relationships created in advance.

  Further, rear wheel tire force maximum value estimation means 300, rear wheel tire lateral force estimation means 400, front wheel tire force maximum value estimation means 600, front wheel tire lateral force estimation means 700, and tire slip angle estimation means 800 in FIG. Each estimated value is obtained by the same calculation content as in the second embodiment.

  Also in the fifth embodiment, it is possible to obtain the same effects as those of the second embodiment described above.

2FL ... Left front wheel 2FR ... Right front wheel 2RL ... Left rear wheel 2RR ... Right rear wheel 11 ... Steering hole 30 ... Integrated controller

Claims (10)

Tire slip angle estimating means for estimating tire slip angle;
Tire force maximum value estimating means for estimating the tire force maximum value according to the previous value of the tire slip angle, the tire slip rate and the tire longitudinal force,
The tire slip angle estimation means estimates a tire slip angle based on the tire force maximum value, the tire slip rate, the tire longitudinal force, and a vehicle state measurement value.   The tire force maximum value estimating means includes a tire force adhesion ratio calculation unit for calculating a tire force adhesion ratio from the previous value of the tire slip angle, the tire slip ratio and the tire longitudinal force, and the tire force adhesion ratio. The tire condition estimation device according to claim 1, further comprising a tire force maximum value calculation unit that obtains a tire force maximum value from the tire longitudinal force.   The tire condition estimating device according to claim 1 or 2, wherein the tire force maximum value estimating means estimates a tire force maximum value in consideration of anisotropy of a tire friction circle.   When the tire slip rate exceeds a predetermined tire slip rate threshold value, the tire force maximum value estimating means is configured to calculate a value estimated based on the previous value of the tire slip angle, the tire slip rate, and the tire longitudinal force. The tire force maximum value is a value estimated based on a static wheel load when the tire slip ratio does not exceed the tire slip ratio threshold value. The tire state estimation apparatus according to claim 1.   The tire according to claim 4, wherein the tire slip ratio threshold is determined such that an estimation error of the tire force maximum value when the tire slip ratio threshold is exceeded is within a desired error range. State estimation device. Tire lateral force estimation means for estimating tire lateral force from the tire tire maximum value and the previous value of the tire slip angle;
The tire according to any one of claims 1 to 5, wherein the tire slip angle estimating means estimates the tire slip angle from the estimated tire lateral force, the tire longitudinal force, and the vehicle state measurement value. State estimation device. Driving wheel tire lateral force estimating means for estimating driving wheel tire lateral force; and driven wheel tire lateral force estimating means for estimating driven wheel tire lateral force;
The tire slip angle estimating means estimates the tire slip angle of the driving wheel and the tire slip angle of the driven wheel using the estimated driving wheel tire lateral force, the estimated driven wheel tire lateral force and the vehicle state measurement value. To do,
The tire force maximum value estimating means includes driving wheel tire force maximum value estimating means for estimating the tire force maximum value of the driving wheel, and driven wheel tire force maximum value estimating means for estimating the tire force maximum value of the driven wheel. Have
The driving wheel tire force maximum value estimating means estimates the driving wheel tire force maximum value according to the previous value of the tire slip angle of the driving wheel, the driving wheel tire slip rate and the tire longitudinal force of the driving wheel,
The driven wheel tire force maximum value estimating means estimates the driven wheel tire force maximum value according to the driving wheel tire force maximum value and the tire longitudinal force of the driving wheel,
The drive wheel tire lateral force estimating means estimates the drive wheel tire lateral force from the previous value of the drive wheel tire slip angle, the drive wheel tire maximum value and the drive wheel tire slip rate,
The driven wheel tire lateral force estimating means estimates the driven wheel tire lateral force from the previous value of the driven wheel tire slip angle and the maximum value of the driven wheel tire. The tire state estimation device described.   The tire condition estimating device according to claim 7, wherein the driven wheel tire lateral force estimating means estimates the driven wheel tire lateral force in consideration of anisotropy of a tire friction circle.   The tire state estimation device according to claim 1, wherein the vehicle state measurement value includes a yaw rate.   The tire state estimation device according to claim 1, wherein the vehicle state measurement value includes a yaw rate and a vehicle lateral acceleration.

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