JP2007112367A - Vehicle tire state detection method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means and a device, measuring instantaneous braking stiffness or instantaneous cornering power of a tire in real time by extremely little arithmetic processing without requiring convergence calculation using a model or the like. <P>SOLUTION: Jerk of a vehicle, yaw angle jerk of the vehicle and a temporal change amount of control input to each the wheel tire of the vehicle are detected, and a change rate of force generated in each the wheel tire to the control input in each value instantaneous time can be calculated by a value obtained by dividing, by the temporal change amount of the control input, a value obtained by adding a value obtained by multiplying the jerk by a gain determined from vehicle specifications and a value obtained by multiplying the yaw angle jerk by a gain determined from the vehicle elements. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle tire grip state detection method and apparatus that change from moment to moment.

  Assuming that the vehicle is a single rigid body and considering planar motion, it can be described by translational motion and rotational motion. The force governing each is the force that the tire receives from the ground due to the relative movement of the tire attached to the vehicle and the ground, except for air resistance. In addition, a phenomenon has been formed in which the cause and the result are repeated one after another, such that the vehicle moves by the force and receives a new force.

  In order to control the movement of such a vehicle, it is necessary to grasp the situation of the force that the tire receives from the ground (hereinafter referred to as tire force). Moreover, it is necessary to evaluate the motion state of the vehicle using such information.

  As disclosed in Non-Patent Document 1, this tire force is dominated by the road surface friction coefficient, and in addition to this, the contact load, the slip ratio, and the wheel angle which is the angle formed by the tire traveling direction and the tire rotating surface is the same. Varies depending on the side slip angle. Further, when each parameter is small, the parameter changes linearly with respect to the parameter change, but each parameter becomes large. Specifically, in a region where the longitudinal acceleration and the lateral acceleration applied to the vehicle are large, the saturation / nonlinear characteristic becomes remarkable.

  Further, the stability of the vehicle tends to decrease in the high acceleration region, and various methods for estimating the tire force occurrence rate for each parameter in the nonlinear region have been proposed in order to construct a control device that corrects this.

  According to Patent Document 1, the vehicle body angular velocity according to the yaw rate of the vehicle body, the lateral acceleration, and the departure state of the vehicle body path is determined based on the steering angle, the vehicle speed, and the estimated cornering power of the front and rear wheels based on the vehicle body yaw rate, lateral acceleration, The calculation means for expanding the tire characteristics to the limit range where linear approximation cannot be performed in the region close to the maximum frictional force, the deviation between the calculated yaw rate and the actual yaw rate detected by the sensor, and the calculated lateral acceleration And a deviation calculating means for calculating the deviation of the actual lateral acceleration detected by the sensor, and a method of estimating the cornering power of the front and rear wheels by extending both of these deviations to the limit range. Specifically, the yaw rate γ and lateral acceleration Gy calculated by the calculation unit, the actual yaw rate γ ′ detected by the sensor and the actual lateral acceleration Gy ′ are input to the deviation calculating means, and the actual yaw rate γ ′ is calculated from the calculated yaw rate γ. Is subtracted to calculate the yaw rate deviation Δγ, and the lateral acceleration deviation ΔG is calculated by subtracting the actual lateral acceleration Gy ′ from the similarly calculated lateral acceleration Gy. When the actual lateral acceleration Gy ′ decreases and ΔG> 0, it is estimated that the cornering powers Kf and Kr of the front and rear wheels are both reduced by judging vehicle drift-out and spin in the limit region. When ΔG <0, it is estimated that the cornering powers Kf and Kr of the front and rear wheels are both increased by judging tuck-in or the like. When the actual yaw rate γ ′ decreases and Δγ> 0, it is estimated that drift-out is determined and the front wheel cornering power Kf decreases and the rear wheel cornering power Kr increases. When the actual yaw rate γ ′ increases and Δγ <0, it is estimated that the spin is judged and the front wheel cornering power Kf increases and the rear wheel cornering power Kr decreases.

  Moreover, in patent document 2, the detection part 1 detects acting force including the front-rear force Fx, the lateral force Fy, and the vertical force Fz which act on each wheel, and the specific part 2 is the friction between a wheel and a road surface. A method is disclosed in which the coefficient is specified and the estimation unit 6 estimates the cornering power ka of each wheel based on the acting force and the friction coefficient. If the longitudinal force Fx, lateral force Fy and vertical force Fz acting on the wheel, and the friction coefficient μ are known, the wheel slip angle βw is uniquely identified. When the wheel slip angle βw is specified, the cornering power ka of the wheel can be uniquely calculated based on the relationship between the wheel slip angle βw and the lateral force Fy.

  In Patent Document 3, the following cornering power estimation method is disclosed. The lateral acceleration estimating unit substitutes the vehicle body side slip angle differential value β ′ input from the side slip angle differential value calculating unit, the vehicle speed V and the yaw rate r, which are treated as constants, into the vehicle lateral acceleration formula, thereby estimating the vehicle. The lateral acceleration Gye is calculated and input to the subtracter. The subtractor calculates a deviation between the lateral acceleration Gy input from the lateral acceleration sensor and the estimated lateral acceleration Gye of the vehicle input from the lateral acceleration estimation unit, and outputs the deviation to the PID adjuster.

  The PID adjuster outputs an adjustment value that causes the deviation between the lateral acceleration Gy and the estimated lateral acceleration Gye of the vehicle to be zero by proportional / integral / differential (PID) operation, that is, output from the cornering power initial value input unit and skids. An adjustment value for adjusting a predetermined initial value for either one of the front wheel cornering power Kf or the rear wheel cornering power Kr input to the angular differential value calculation unit is calculated and input to the adder. That is, if the predetermined initial value for either one of the front wheel cornering power Kf or the rear wheel cornering power Kr input to the side slip angle differential value calculation unit is an appropriate value, the lateral acceleration Gy and the estimated lateral acceleration Gye of the vehicle Deviation is zero. For this reason, for example, when the estimated lateral acceleration Gye of the vehicle is larger than the detected lateral acceleration Gy, the front wheel cornering power Kf or the rear wheel cornering power Kr input to the side slip angle differential value calculation unit is reduced. An adjustment value is set. On the other hand, for example, when the estimated lateral acceleration Gye of the vehicle is smaller than the detected lateral acceleration Gy, an adjustment is made to increase the front wheel cornering power Kf or the rear wheel cornering power Kr input to the side slip angle differential value calculation unit. Value is set.

  Patent Document 4 discloses a method of estimating the gradient of the friction coefficient μ between the wheel and the road surface, that is, the road surface μ gradient value for each wheel based on the detected wheel speed. The road surface μ gradient estimation means includes, for example, a preprocessing filter that detects wheel speed vibration of each wheel as a response output of a wheel resonance system that receives road disturbance from the detected wheel speed, and detected wheel speed vibration. The transfer function identification means for identifying the transfer function of each wheel that satisfies the above-mentioned using the least square method, and the gradient of the friction coefficient μ between the tire and the road surface based on the identified transfer function for each wheel And a μ gradient calculating means for calculating.

Masato Abe “Automotive Movement and Control”, 1992 Sankaido Japanese Patent No. 3571370 JP 2005-3083 A JP 2003-146154 A JP 2003-291790 JP

  As described above, what is common to the four conventional technologies is that the cornering power or braking stiffness (road surface μ gradient) is estimated by the model, and the vehicle acceleration value calculated using that is actually mounted on the vehicle. A method of correcting an estimated value using a difference (error) from a value measured by a sensor is used. Such a method requires a complicated model and calculation in order to reduce the model error, and it takes time for the estimated value to converge when the road surface friction coefficient changes.

  The problem to be solved by the present invention is to provide means and apparatus for measuring the instantaneous cornering power and the instantaneous braking stiffness of a tire in real time with very little calculation processing, eliminating the need for convergence calculation using a model or the like. is there.

  In addition, the vehicle's motion is evaluated using the instantaneous cornering power and instantaneous braking stiffness of the tire measured in real time, and this is shown to the driver. When approaching an unstable state, an alarm is issued and the vehicle becomes unstable. It is a second problem to be solved by the present invention to provide a method and apparatus for adjusting the control input for stabilization.

In order to solve the above problem, the vehicle jerk, the vehicle yaw angle jerk,
The time change of the control input to each vehicle wheel tire is detected, and the value obtained by dividing the jerk by the time change of the control input multiplied by the first gain and the yaw angle jerk are the time change of the control input. The rate of change of the force generated by each wheel tire with respect to the control input for each moment may be calculated from the value obtained by adding the second gain to the value divided by.

Specifically, to calculate the instantaneous front wheel cornering power, the lateral jerk (J _y ) of the vehicle, the yaw angle jerk (J _r ) of the vehicle, and the time variation of the skid angle of each wheel tire on the front and rear wheels of the vehicle ( dβ _f / dt), the value obtained by dividing the lateral jerk by the time change of the skid angle (J _y / dβ _f / dt) _multiplied by the gain (m ・ l _r / 2l), and the yaw angle addition The value of tire cornering force for each side slip angle is calculated by adding the value obtained by dividing the acceleration by the time change of the side slip angle (J _r / dβ _f / dt) and the gain (I _z / 2l). The instantaneous cornering power (dY _f / dβ _f ), which is the rate of change, is calculated.
here,
Y _f : Cornering force generated by the front wheel β _f : Side slip angle of the front wheel
m: Vehicle inertial mass
l: Distance between front and rear wheels (wheelbase)
l _r : Distance from vehicle center of gravity to rear wheel
I _z : Yawing moment of inertia around the center of gravity of the vehicle. If the mathematical expression is displayed, the instantaneous cornering power of the front wheels is

Can be expressed as

Similarly,
Y _r : Cornering force generated by the rear wheel β _r : Side slip angle of the rear wheel
m: Vehicle inertial mass
l: Distance between front and rear wheels (wheelbase)
l _f : If the distance from the vehicle center of gravity to the front wheel, the instantaneous cornering power of the rear wheel is

Can be expressed as

  Further, as an evaluation method that represents, for example, vehicle motion characteristics, using these instantaneous cornering powers of the front and rear wheels, an apparent instantaneous static margin given by the following equation can be calculated momentarily.

  The original static margin is determined by dividing the neutral steer point, which is the point of application of the resultant force of the front and rear tires per unit side slip angle, by the wheelbase l with the load, slip ratio, running speed, etc. in a constant state (static). Defined as a dimensionless quantity. On the other hand, the amount of (Equation 3) is not static with constant load fluctuation, slip rate, travel speed, etc., but is also an amount that considers dynamic changes, so it is different from the original definition The word “pseudo” is used in a mixed sense. It remains a useful quantity for evaluating not only static states but also dynamic states.

  The steer characteristic of the vehicle can be evaluated from moment to moment, such as understeer if the apparent instantaneous static margin is positive, neutral steer if 0, and oversteer if negative.

  Therefore, by transmitting this information to the driver, it is possible to recognize the steer characteristic for each moment and to support the driving operation. It is also possible to control the vehicle motion by the controller using these values, for example, to control the yaw moment by independently controlling the left and right wheel driving force or braking force in order to stabilize the oversteered vehicle. is there.

  When the vehicle is moving at a high acceleration and the tire approaches a region that exhibits non-linear characteristics with respect to the control input, or when the road friction coefficient is lowered, the cornering power or braking stiffness of the front and rear wheels is significantly reduced. . Therefore, it is possible to support the driving operation by displaying this.

As described above, it is possible to provide means and apparatus for measuring the instantaneous cornering power and the instantaneous braking stiffness of a tire in real time with very little calculation processing without using a convergence calculation using a model or the like.
In addition, vehicle motion is evaluated using instantaneous cornering power and instantaneous braking stiffness measured in real time, and this is shown to the driver. When an unstable condition is approached, an alarm is issued. Techniques and apparatus for adjusting control inputs for stabilization can be provided.

  Hereinafter, the best mode for carrying out the present invention will be disclosed with reference to the drawings.

  FIG. 1 shows the overall configuration of the first embodiment of the present invention.

In the present embodiment, the vehicle 0 is a rear left wheel 53 by the engine 1, rear wheel drive vehicle is driven a right rear wheel 54: a (F ront Engine R ear Drive FR vehicle).

  The left front wheel 51, the right front wheel 52, the left rear wheel 53, and the right rear wheel 54 have brake rotors 61, 62, 63, 64, wheel speed detection rotors 81, 82, 83, 84, and wheel speeds on the vehicle side. Pickups 91, 92, 93, and 94 are mounted so that the wheel speed of each wheel can be detected. The wheel speed pickup may be a coil type or one that can measure to extremely low speed using a Hall element. The wheel speed signal of each wheel is subjected to an appropriate filtering process to determine the pseudo vehicle speed (V). For example, in the embodiment of the present invention, since it is a rear wheel drive vehicle, the front two wheels are driven wheels, and the simulated vehicle speed may be obtained from the average value. This pseudo vehicle speed calculation is performed by a brake controller 43 described later.

  The powertrain controller 42 controls a throttle, a fuel injection device, and the like (not shown) of the engine 1 in accordance with the depression amount of the accelerator pedal 11 of the driver. The output of the engine 1 is transmitted to the differential gear 4 via the electronic control transmission 2 and the propeller shaft 3 controlled by the power train controller 42. The differential gear 4 is connected to a left transfer unit 5 and a right transfer unit 6 including a clutch unit capable of controlling torque transmitted to each of the left rear wheel 53 and the right rear wheel 54. These left and right transfer units are controlled by a transfer controller 44.

  For example, when the vehicle is turning counterclockwise, the left transfer unit 5 and the right transfer unit are set so that the torque applied to the right rear wheel 54 is larger than the torque applied to the left rear wheel 53 when assisting the vehicle turning. Control 6 Further, when a yaw moment in the restoring direction is required for the vehicle turning, unlike the above-described direction, the left transfer unit 5 is set so that the torque applied to the left rear wheel 53 is larger than the torque applied to the right rear wheel 54. Control the right transfer unit 6. Further, even in a so-called engine brake state where the accelerator is not stepped on by the driver, this brake torque can be distributed and controlled to the left and right wheels.

Such mechanism to the central controller 40 calculates a yaw moment required to the vehicle motion by controlling the right and left transfer 5,6 from the transfer controller 44, direct control of the yaw moment applied to the vehicle (so-called D irect Y aw moment C ontrol) has become possible.

The steering system of the vehicle 0 is a front wheel steering device, and includes a power steering 7 including a variable gear mechanism and a steering angle sensor (both not shown), a steering 10, a driver steering angle sensor 31, and a steering controller 41. ing. In accordance with the gear ratio command of the central controller 40, the steering controller 41 has a rotational angle ratio between the actual steering angle (δ _f ) of the power steering 7 and the driver steering angle (δ _d ) measured by the driver steering angle sensor. Control that follows the command value from the controller 40 is performed. Here, when a command for a negative gear ratio is issued from the central controller 40, the actual steering angle is controlled in the reverse steering (countersteer) direction with respect to the driver steering angle.

  For such a mechanism, the central controller 40 calculates the lateral force or yaw moment required for the vehicle motion, and controls the power steering 7 by the steering controller 41, thereby controlling the lateral force applied to the vehicle and indirectly. However, the yaw moment can be controlled.

  Brake rotors 61, 62, 63, 64 are provided on the left front wheel 51, the right front wheel 52, the left rear wheel 53, and the right rear wheel 54, respectively, and the brake rotor is sandwiched between pads (not shown) on the vehicle body side. Accordingly, calipers 71, 72, 73, and 74 for reducing the speed of the wheels are mounted.

The caliper is a hydraulic type or an electric type having an electric motor for each caliper. Each caliper is basically controlled by the brake controller 43 in accordance with the amount of operation of the brake pedal 12 by the driver. Further, as described above, the wheel speed of each wheel is input to the brake controller 43, and the pseudo vehicle speed V is calculated. Further, the slip ratio as shown below is calculated from the simulated vehicle speed and the wheel speed of each wheel.
1) During braking

2) When driving

Where V is the simulated vehicle speed, R ₀ is the effective radius of the tire, and ω is the angular velocity of the tire.
Here, in the above equation, the pseudo vehicle speed V, that is, the speed of the vehicle center of gravity is applied as it is, but for each wheel, the speed component due to rotation around the center of gravity by applying the vehicle yaw rate to half of the tread (d _f / 2). May be considered.

  Each wheel is configured such that the above-described slip ratio can be controlled independently by the brake controller 43 in accordance with a driver's brake operation or a command from the central controller 40 described later. In general, the longitudinal force generated by a tire can be controlled by the slip ratio. Therefore, if the left and right wheels are controlled to have different slip ratios, the left and right wheels have different longitudinal forces, and this difference is multiplied by the tread. Can be generated. Also, according to the concept of the friction circle, the resultant force of the tire's longitudinal force and lateral force cannot be more than the vertical load W applied to the tire at that time multiplied by the friction coefficient μ, and the resultant force vector is the radius μW Stays within the circle (friction circle). Accordingly, in the vicinity of the grip limit, the lateral force can be indirectly controlled by controlling the longitudinal force by performing the slip ratio control during turning.

  For such a mechanism, the central controller 40 calculates the longitudinal force, lateral force, or yaw moment required for the vehicle motion, and controls the slip rate of each wheel from the brake controller 43, whereby the longitudinal force applied to the vehicle, Control of yaw moment and indirect but lateral force are possible.

  Next, a sensor group which is a main component of the present invention will be described.

As shown in FIG. 2, four acceleration sensors are arranged at dual positions across the center of gravity of the vehicle. Before the lateral acceleration sensor 21 is arranged at a position in front l _s from the center of gravity, the rear lateral acceleration sensor 22 is located from the center of gravity to the position of the rear l _s. Further, the left longitudinal acceleration sensor 23 is disposed at a position of the left d _s from the center of gravity, the right longitudinal acceleration sensor 24 is arranged at a position of the right l _s from the center of gravity point. Also, differentiating circuits 25, 26, 27, and 28 are provided which differentiate the outputs of the respective acceleration sensors to obtain jerk information. In the present embodiment, it is illustrated that each sensor is installed in order to clarify the existence of the differentiation circuit. However, in actuality, the acceleration signal is directly input to the central controller 40 and various calculation processes are performed, and then the differentiation process is performed. However, nothing essentially changes.

Next, the arrangement of each acceleration sensor and the physical quantities that can be detected will be described using mathematical expressions.
First, the vehicle motion physical quantity that can be measured at the right front / rear acceleration sensor 24 position (P) is examined (other sensors are not described in order to prevent complication).

  Here, the vehicle is considered as a planar vehicle model having no height direction. Consider X-Y-Z coordinates fixed in absolute space and coordinates x-y-z fixed at the center of gravity of a moving vehicle as shown in FIG. In this case, x is the traveling direction, y is the left direction, and z is the vertical upward direction.

In addition, as a general-purpose description method below,
{A-dot}: First-order time derivative of A {A-2dot}: Expressed as second-order time derivative of A.

If the position vector of the position P of the right longitudinal acceleration sensor 24 with respect to the xyz coordinates is ρ, and further the position vectors of the center of gravity C and the XY coordinates of the right longitudinal acceleration sensor 24 are R, r _p respectively,

It becomes. Here, when ρ is displayed as a component,

It becomes. The x-y-z coordinate system translates at an R-dot speed and rotates at an angular velocity of ω with respect to the X-Y-Z coordinate system.

Here, ρ _p is the relative velocity of point P to point C, and since point P is fixed to xyz coordinates, {ρ _p dot} = 0,

It becomes.
Here, if the vehicle velocity vector {R-dot} has a size in the x direction as u, a size in the y direction as v, a unit vector in the x direction as i, and a unit vector in the y direction as j,

It becomes. Also, since the angular velocity vector ω considers yaw motion around the Z axis,

Can be written. Where r is the yaw rate of the vehicle. Therefore,

Therefore,

Therefore, the acceleration vector {r-2dot} at point P is

Here, the derivative of the unit vector considered in the coordinate system fixed to the vehicle rotating at the yaw rate r is

Because

This value is a physical quantity that can be detected when an acceleration sensor is installed at point P. For example, if an acceleration sensor with sensitivity in the longitudinal direction is installed at point P, the product of the longitudinal acceleration of the vehicle ({u-dot} -vr), angular acceleration and the distance from the center of gravity (d _s · {r-dot} ) Can be detected. If an acceleration sensor with lateral sensitivity is installed at point P, the product of the vehicle's lateral acceleration ({v-dot} + ur), the square of the angular velocity and the distance from the center of gravity (d _s · r ^ 2 ) Can be detected.

  In addition, when the arrangement point of the left longitudinal acceleration sensor 23 is Q, the installation point of the front lateral acceleration sensor 21 is S, and the installation point of the rear lateral acceleration sensor 22 is R,

It becomes. Here, the underlined portions are physical quantities detected by the right longitudinal acceleration sensor 24, the left longitudinal acceleration sensor 23, the front lateral acceleration sensor 21, and the rear lateral acceleration sensor 22. If each of them is G _xr, G _xl, G _yf, G _yr ,

The vehicle longitudinal acceleration is Gx = {u-dot-v · r}, the vehicle lateral acceleration is Gy = {v-dot + u · r}, and the yaw angular acceleration is {r-dot}.

As described above, as shown in FIG. 2, when four acceleration sensors are arranged in a dual position across the vehicle center of gravity, the acceleration at the vehicle center of gravity can be detected from half of the sum of the outputs of the dual sensors. The angular acceleration at the vehicle center of gravity can be detected from the difference obtained by dividing the difference by the distance between the sensors. Accordingly, the longitudinal jerk J _x , lateral jerk J _y , and angular jerk J _r of the vehicle center of gravity can be described as follows.

Here, as shown in FIG. 2, each sensor has a differentiating circuit and linearly combines the values obtained by differentiating the acceleration signals or performs acceleration signal arithmetic processing, and after that, even if differentiation processing is performed, jerk and angle addition are performed. An acceleration signal can still be obtained. Therefore, in the following, the disclosure of the invention is advanced on the assumption that the differential processing is performed after the acceleration signal is captured.

  First, an invention will be disclosed in which lateral vehicle motion is expressed by a simplified model and instantaneous cornering power is detected.

FIG. 4 is a diagram showing an equivalent two-wheeled vehicle model of a four-wheeled vehicle. The left and right tires have the same side slip angle for both the front and rear wheels. If these are β _{f and} β _r ,

It becomes. Where β is the side slip angle of the vehicle center of gravity,

(U and v are the speed components in the xy direction of the aforementioned vehicle center of gravity), V is the vehicle speed, l _f is the distance between the vehicle center of gravity and the front axle, l _r is the distance between the vehicle center of gravity and the rear axle, r is the yaw angular velocity (yaw rate) of the vehicle.

As described above, considering a range in which the side slip angles of the left and right tires are equal, the value thereof is small, and the actual steering angle may be considered small is that of a vehicle traveling at a constant speed ignoring the roll of the vehicle body. When considering the movement of the horizontal plane, as shown in FIG. 4, the treads d _{f and} d _r of the vehicle are ignored, and the front and rear left and right wheels are equivalently concentrated at the intersections of the front and rear axes of the vehicle and the axles, respectively. This is equivalent to considering the movement of the vehicle.

If there is no difference in the characteristics of the left and right tires, there will be no difference in the cornering force that acts on the left and right tires, so this is calculated as a function of the side slip angles β _{f and} β _r of the front and rear wheels Y _f (β _f ), Y _r (β _r )

Can be written. And since this force can be regarded as acting in the y direction, the equation describing the lateral movement of the vehicle is

Here, m is the vehicle weight.

  Further, since the cornering force works as a yawing moment around the center of gravity, the yawing motion around the vertical axis passing through the center of gravity of the vehicle can be described by the following equation.

It becomes. Here, Iz is the yawing moment of inertia of the vehicle. If these two expressions are expressed as a matrix,

Therefore, if the front and rear cornering force is lf + lr = l (: wheelbase),

Gy and {r-dot} can be detected from the four acceleration sensors arranged as shown in FIG. 2 as described above, and the front and rear cornering forces can be detected.

  Next, the lateral jerk Jy and the angular jerk Jr of the vehicle are

If this is expressed as a matrix,

Therefore,

Therefore

It becomes.

Where K _iyf = dY _f (β _f ) / _{dβ f and} K _iyr = dY _r (β _r ) / dβ _r are the change in cornering force with respect to the change in the side slip angle of the front wheel and rear wheel for each moment. It can be considered as instantaneous cornering power. On the other hand, in the right side, the lateral jerk J _y and the yaw angle jerk J _r can be measured by differentiating the output signal using the four accelerometers as described above. {Β _f -dot} and {β _r -dot} can be expressed as follows.

As described above, the lateral acceleration G _y of the center of gravity can be measured from the sum of the measured values of the front lateral acceleration sensor 21 and the rear lateral acceleration sensor 22 shown in FIG. 3, and the yaw angular acceleration {r-dot} is measured from the difference. Is possible. Further, the actual steering angle (δ _f ) of the power steering 7 can be detected by the steering angle sensor in the power steering 7 as described above, and can be detected by time differentiation. Further, as described above, the vehicle speed V can be measured in the form of a simulated vehicle speed in the brake controller 43 from the wheel side sensor of each wheel.

  FIG. 5 is a block diagram showing a procedure for measuring the instantaneous cornering power of the front and rear wheels described above, and this logic is executed in the central controller 40.

Input measured value G _yr measurements G _yf and rear lateral acceleration sensor 22 before the lateral acceleration sensor 21, the pseudo vehicle speed V calculated in the brake controller 43 using the measured values of the wheel speed sensor, a power steering 7 It is (delta) detected by the inner rudder angle sensor. In this diagram, the differential processing is performed after obtaining the lateral acceleration and the yaw angular velocity from the measured values of the front lateral acceleration sensor 21 and the rear lateral acceleration sensor 22.

  As can be seen from FIG. 5, there is no tire model or vehicle motion model inside the logic. In addition, since there is no feedback loop, convergence calculation using a model or the like is unnecessary, and the instantaneous cornering power of the tire can be measured in real time with very little calculation processing.

FIG. 6 shows the relationship between the tire side slip angle and the lateral force. The increase in lateral force (dY / dβ) with respect to the unit side slip angle change can be considered as the cornering power. While the side slip angle is small (β <β ₄ ), the lateral force is proportional to the side slip angle (dY / dβ is a substantially constant value). However, when the side slip angle is increased, the lateral force is not proportional to the side slip angle. The above is the single characteristic of the tire, but when the vehicle is mounted, the sum of the lateral forces of the front and rear wheels becomes the lateral acceleration of the vehicle as shown in (Expression 37). Therefore, when the vehicle is turning, the lateral slip angle increases and the lateral force increases as the lateral acceleration increases. However, when the lateral acceleration increases and the side slip angle exceeds β ₄ , the cornering power decreases rapidly. Finally, at the side slip angle β ₆ , the lateral acceleration of the vehicle becomes a coefficient of friction between the road surface and the tire, and approaches the physical grip limit.

The approach to the grip limit can be evaluated by measuring the cornering power every moment as shown in the lower diagram of FIG. Since the instantaneous cornering power becomes zero at the tire side slip angle β ₆ and then reverses negative, a certain threshold value K _yth is determined in advance, and if the measured cornering power for each instantaneous moment is _greater than K _yth , the tire is still Is a linear region, for example, assuming that an indicator is displayed on the instrumental panel for the driver, it shows that it is safe in blue, and when it becomes smaller than _Kyth , it shows yellow, and when it is negative, it displays red By indicating the above, it is possible to present the grip level information to the driver and to improve safety. Further, this information presentation may be performed by an audio signal. For example, when the instantaneous cornering power becomes equal to or lower than _Kyth , a warning sound ( _radiation sound) starts to be heard, and the sound transmission interval may be shortened as the instantaneous cornering power decreases, so as to call attention. Further, like the sound, for example, tactile (tactile) information such as vibration may be input to the steering wheel, and the driver may be alerted by changing the intensity and frequency. By these, it can be expected that the driving operation of the driver is improved in the safe direction, and the possibility that the vehicle moves in the safe direction is increased.

  Next, a method for measuring braking stiffness according to the present invention will be described.

  FIG. 7 is a diagram showing an equivalent two-wheeled vehicle model in which the two front and rear wheels are regarded as one wheel while paying attention to the longitudinal motion and yaw motion of the four-wheeled vehicle.

  Fig. 7 shows a case where the actual rudder angle is small (nearly straight) and the slip ratio of the front and rear tires is small, and the movement of the horizontal plane of a vehicle traveling at a constant lateral speed ignoring the vehicle body pitch is considered. Thus, this corresponds to considering the movement of the vehicle in which the left and right front and rear wheels are equivalently concentrated at the intersections connecting the left and right axes of the vehicle and the front and rear wheels.

In this way, because there is no even difference longitudinal force acting on the front and rear tire if there is no difference in the characteristics of the front and rear of the tire itself, which slip rate s _l of the left and right wheels, s _r each X _l before and after as a function of (s _l ), X _r (s _r )

Can be written. And since this force can be considered to work in the X direction, the formula describing the longitudinal motion of the vehicle is

Here, m is the vehicle weight.

  Further, since the difference between the left and right braking / driving forces acts as a yawing moment around the center of gravity, the yawing motion around the vertical axis passing through the center of gravity of the vehicle can be described by the following equation.

It becomes. Here, I _z is the yawing moment of inertia of the vehicle. If these two expressions are expressed as a matrix,

Therefore,

G _x and {r-dot} can be detected from the four acceleration sensors arranged as shown in FIG. 2 as described above, and the front / rear braking / driving force can be detected. .

Next, the longitudinal jerk J _x and the angular jerk J _r of the vehicle are respectively

If this is expressed as a matrix,

Therefore,

Therefore,

Where K _ixl = dX _l (s _l ) / ds _l , K _ixr = dX _r (s _r ) / ds _r is the change in braking / driving force with respect to the change in slip ratio of the left wheel and right wheel for each moment, This can be thought of as instantaneous braking (driving) stiffness in a broad sense. By the way, the braking (driving) stiffness is the change when the slip rate is zero, so when considering the change rate at any slip rate every moment, it seems more appropriate to call it the instantaneous braking (driving) power .

Of the right side, and the longitudinal jerk J _x, the yaw angular jerk J _r can be measured by differential processing an output signal with four accelerometers as described above. The brake controller 43 can calculate the slip ratio of each wheel, and {s _l -dot} and {s _r -dot} can be measured by differentiating this signal.

  FIG. 8 is a block diagram showing a procedure for measuring the instantaneous braking (driving) power (stiffness) of the left and right wheels described above. The slip ratio calculation part is executed by the brake controller 43, while the other logic is executed by the central controller 40.

The inputs are the measured value G _xl of the left front / rear acceleration sensor 23, the measured value G _xr of the right front / rear acceleration sensor 24, the pseudo vehicle speed V calculated by the brake controller 43 using the measured value of each wheel speed sensor, and the left front / rear wheel And the average wheel speed of the right front and rear wheels. In this diagram, the differential processing is performed after obtaining the longitudinal acceleration and the yaw angular velocity from the measured values of the left longitudinal acceleration sensor 23 and the right longitudinal acceleration sensor 22.

  As can be seen from FIG. 8, there is no tire model or vehicle motion model inside the logic. In addition, since there is no feedback loop, convergence calculation using a model or the like is unnecessary, and the braking (driving) power (stiffness) of the tire can be measured in real time with very little calculation processing.

FIG. 9 shows the relationship between the tire slip ratio and braking / driving force. The increase (dX / ds) of the braking / driving force with respect to the unit slip ratio change can be considered as the braking (driving) power (stiffness). While the slip ratio is small (s <s ₄ ), the braking / driving force is proportional to the slip ratio (dX / ds is a substantially constant value). However, when the slip ratio increases, the braking / driving force is not proportional to the slip ratio. The above is a single characteristic of the tire. Considering when the vehicle is mounted, the sum of the braking / driving forces of the left and right wheels is the longitudinal acceleration of the vehicle as shown in (Formula 51). Therefore, a vehicle that is accelerating or decelerating increases the slip ratio and the braking / driving force when the longitudinal acceleration increases. However, when the longitudinal acceleration increases and the slip ratio exceeds s ₄ , the braking (driving) power (stiffness) decreases rapidly. Finally, at the slip ratio s ₆ , the longitudinal acceleration of the vehicle becomes the coefficient of friction between the road surface and the tire, and approaches the physical grip limit.

The approach to the grip limit can be evaluated by measuring the instantaneous braking (driving) power (stiffness) as shown in the lower diagram of FIG. The braking (driving) power (stiffness) becomes zero at tire slip ratio s ₆ and then reverses negative. Therefore, a certain threshold value K _xth is determined in advance, and the measured braking (driving) power for each moment. When (stiffness) is _greater than or _equal to K _xth , the tire is still in the linear region, so for example, assuming that the instrument panel displays an indicator for the driver, it is blue, indicating that it is safe and smaller than K _xth Then, it is possible to present the grip level information to the driver by displaying yellow to call attention, red display when reversed to negative, etc., and it is possible to improve safety. Further, this information presentation may be performed by an audio signal. For example, when the instantaneous braking (driving) power (stiffness) _falls below K _xth , a warning sound (transmitting sound) starts to sound, and as the instantaneous braking (driving) power (stiffness) decreases, the sound transmission interval is shortened. You may call attention. Similarly to sound, for example, tactile (tactile) information such as vibration may be input to the brake pedal to change the strength and frequency to give attention to the driver. Thereby, it can be expected that the driving operation of the driver is improved in the safe direction, and the possibility that the vehicle moves in the safe direction is increased.

  As described above, the time change of the longitudinal or lateral tire force is detected using the longitudinal or lateral jerk information and the angular jerk information when the vehicle is exercising, for example, the wheel Invention of a method for obtaining instantaneous cornering power and instantaneous braking (driving) power (stiffness) in a motion state by dividing a slip angle or a wheel slip ratio by a differential value of a so-called control input. Has been disclosed. The main invention part of this method is generalized and simplified and shown in FIG.

  According to the present invention, it is possible to provide means and apparatus for measuring the instantaneous cornering power and the instantaneous braking stiffness of a tire in real time with very little arithmetic processing without using a convergence calculation using a model observer or the like.

  In addition, the vehicle motion is evaluated using the instantaneous cornering power and instantaneous braking stiffness of the tire measured in real time, and this is shown to the driver, and a method and device for issuing an alarm when approaching an unstable state are provided. be able to.

FIG. 11 and FIG. 12 show the results of measuring the front wheel instantaneous cornering power (dY _f / dβ _f ) and the rear wheel instantaneous cornering power (dY _r / dβ _r ) using the method of the present invention for the actually traveling vehicle. Show. The vehicle speed is about 80 [km / h], and the lane is changed at a driver steering angle of 50 [deg]. In the range where {β-dot} is small (straight line and {β-dot} inversion point), noise is observed, but {β-dot} is more than an arbitrary threshold value (eg 0.02 (rad / s)) It is clear that the absolute value of can be measured sufficiently practically, and that the method of the present invention has engineering value. Of course, a convergence calculation that minimizes an error from the model output is unnecessary, and the instantaneous cornering power of the front and rear wheels can be independently measured in real time.

  Note that this method does not require a tire model (no need to estimate the road friction coefficient) and can measure the net instantaneous cornering power in any vehicle motion state, including roll steer and compliance steer. I want to be.

  The vehicle motion evaluation and control using the cornering power measured according to the present invention will be briefly described below.

Now, the lateral acceleration of the G _y, consider a small movement of the vehicle from the turning state of the yaw angular acceleration for small steering δ of G _r. The equation of motion at this time is

Can be described as follows. Here, since δ, β, r are very small,

Here, the lateral acceleration of the G _y, from the balance of the turning state of the yaw angular acceleration G _r,

Holds. Substituting these into (Equation 61) and (Equation 62) and rearranging results in the following equation.

This is an instantaneous equation of motion linearized based on the so-called micro disturbance theory. In other words, the instantaneous motion of the front and rear wheels at an arbitrary side slip angle is obtained by using the front wheel instantaneous cornering power (dY _f / dβ _f ) and the rear wheel instantaneous cornering power (dY _r / dβ _r ) that can be measured by the present invention. It can be described. At this time, when the formally apparent (pseudo) instantaneous stability factor (A _i ) is obtained,

Similarly, when an apparent instantaneous neutral steer point (l _Ni ), which is formally the instantaneous force of the front and rear wheel cornering forces, is obtained,

When this value is divided by the wheelbase l to obtain a non-dimensional apparent instantaneous static margin (SM _i ),

It becomes.

The quantity of-{l _f (dY _f / dβ _f ) -l _r (dY _r / dβ _r )} appearing in these values is an important quantity that affects the steer characteristic. Specifically, if this value is represented by an apparent static margin,
SM> 0 ………… Understeer (US)
SM = 0 ………… Neutral steer (NS)
SM> 0 ………… Oversteer (OS)
In the present invention, since the apparent instantaneous SM can be measured as described above, the instantaneous steer characteristic can be measured and evaluated. Therefore, it is possible to provide information to the driver or to control the vehicle as described below. The outline is shown below.

FIG. 12 is a diagram illustrating an applied point (neutral steer point: l _N ) of a resultant force of a lateral force generated when the center of gravity of the vehicle generates a side slip angle β. It is considered that the instantaneous steer characteristic changes from moment to moment depending on the position of the applied force point with respect to the position of the center of gravity. In a normal vehicle, in a static state, this l _N is often adjusted behind the center of gravity, that is, understeered. In this explanation, the apparent neutral steer point, not the apparent static margin, is used for discussion as a physical arm as a moment arm with an absolute value, not as a criterion for non-dimensionalized steer characteristics. This is to make sense.

  Next, the mechanism by which this apparent neutral steering point changes according to the driving operation of the driver and the motion state of the vehicle will be briefly described.

The instantaneous cornering powers dY _f / dβ _f and dY _r / dβ _r are load dependent. For this reason, it is considered that the driver controls these amounts by controlling loads on the front and rear wheels by braking or acceleration.

Specifically, just before starting cornering, the driver increases the load on the front wheel by braking and decreases the load on the rear wheel, so that dY _f / dβ _f is relatively compared to dY _r / dβ _r . To increase-{l _f (dY _f / dβ _f ) -l _r (dY _r / dβ _r )} (by bringing l _N closer to the center of gravity) to reduce the understeer tendency and to facilitate turning Yes. Also, when exiting the corner, the accelerator is turned on to transmit the driving force to increase the load on the rear wheel, and by reducing the load on the front wheel, dY _f / dβ _f is relatively compared to dY _r / dβ _r By increasing-{l _f (dY _f / dβ _f ) -l _r (dY _r / dβ _r )} (by keeping _Ni away from the center of gravity), the understeer tendency increases and vehicle stability increases. It is thought that it is secured.

Of course, the driver does not calculate-{l _f (dY _f / dβ _f ) -l _r (dY _r / dβ _r )} every moment. However, humans can experience jerk and angular jerk, and can recognize the relative position change between the target in the external world and the vehicle from visual information, and the side slip angle of the car body or its derivative. The value can also be considered sensitive. Furthermore, since the change in the rudder angle that you input can be recognized, using this information, information equivalent to-{l _f (dY _f / dβ _f ) -l _r (dY _r / dβ _r )} This is considered to be a reference for driving operation. Therefore, according to the present invention, − {l _f (dY _f / dβ _f ) −l _r (dY _r / dβ _r )} can be measured at any time, and the motion of the vehicle actually driving to accomplish a certain task It can be expected that the strategy for determining the driving operation of the driver for the task can be extracted.

Conversely, disturbances such as sudden changes in the friction coefficient of the road surface or when the assumed radius of curvature of the route is significantly smaller than the expected range may cause the vehicle yaw rate r or side slip angle β to become too large, resulting in tire sideways Even when the force characteristic becomes a non-linear region (for example, β _{6 in} FIG. 6), the neutral steer point approaches the center of gravity or is reversed negatively, and the vehicle may fall into the over steer characteristic. FIG. 13 shows this situation when the right corner is turned. If the applied force point is ahead of the center of gravity, in this case, a moment is generated that promotes counterclockwise yaw rate. If the concept of restoring moment that pulls the vehicle back to the stable side is used, the restoring moment is negative in this state, that is, it diverges unstablely and spins. It can be said that the restoring moment is too small or negative in the situation of spin generation.

According to the present invention, since it is capable of measuring the l _Ni every instant procedure fall into the spin conditions it can be measured. Therefore, it is possible to ensure the stability of the vehicle by giving a danger warning of the occurrence of spin to the driver and performing control to keep the restoring moment properly. FIG. 14 is an example in which this concept is shown most simply in a flowchart for each step. Each step is briefly described below.
0) Start 1) Measure the instantaneous cornering power of the front and rear wheels.
2) Calculate instantaneous neutral steer point l _Ni (i) 3) Compare l _Ni (i) with threshold level l _Nh
l When _Ni (i)> l _Nh , there is sufficient restoring moment → Return
l If _Ni (i) <l _Nh , there is a risk of oversteering → 4)
4) Warning occurrence (visual information, auditory information, tactile information)
5) Compare the current l _Ni (i) with the previous l _Ni (i-1)
l _Ni (i)> l _Ni (i-1), stability is recovering → Return
l If _Ni (i) <l _Ni (i-1), restoring yaw moment correction is required → 6)
6) Necessary restoration yaw moment calculation → 7)
7) Yaw moment distribution calculation (brake, accelerator, steer) → 8)
8) Comprehensive yaw moment calculation → 9)
9) Yaw moment error calculation
If | ΔM-ΣM | <ε _M , input appropriate moment → recovering stability → Return
| ΔM-ΣM | For> epsilon _M, among the excess and deficiency there → recalculation or more steps moment input, the threshold level l _Nh is it is necessary to vary depending on luck degree condition of the vehicle In the configuration of the present invention, since the operation input and the absolute value of the lateral force of each wheel have been measured, this can be realized by storing the map data in the central controller 40.

Further, in order to construct the yaw moment, although it is simply described in FIG. 15, steer: the steering angle is returned by δ _fc .

Central controller 40 → Steering controller 41
Brake: _Apply a braking force of F _{bfr to} the right (outer) front wheel and F _{brr to} the rear wheel.

Central controller 40 → Brake controller 43
Accelerator: _Apply F _trl driving force to the left (inner) rear wheel.

Central controller 40 → Powertrain controller 42
→ Left / right transfer controller 44
Thereby, the restored yaw moment shown in FIG. 15 can be obtained. Each distribution method can be considered in various ways, but we won't go into the details here. As another method for controlling the steer characteristic, it is conceivable to control the left and right load movements by changing the roll stiffness distribution of the suspensions of the front and rear wheels, instead of directly applying a moment. Specifically, it should be noted that by increasing the roll rigidity distribution of the front wheels, the instantaneous cornering power on the rear wheel side with relatively little load movement can be increased, and the steer characteristic can be changed in the understeer direction.

  As described above, as shown in FIG. 15, the vehicle regains stability, regains stability without spinning, and can continuously travel on the route. Here, it should be noted that it is not necessary to input the difference between the restored yaw moment with no control and the restored yaw moment because the original stability of the vehicle is exhibited by giving the restored yaw moment when unstable. I want to be. As described above, according to the present invention, since the procedure for transitioning the vehicle from the stable state to the unstable state can be measured instantaneously, it is possible to set the control intervention timing at an early stage, and to reduce the sense of incongruity. Since the original stability can be recovered at an early stage, the control amplitude of each actuator can be reduced.

  In addition, as a concept developed from the present invention, the static stability in the design of the vehicle is set strongly (the neutral steer point is set far away from the center of gravity to the rear), and at the initial turn, the same as described above. It is also conceivable to apply a method that gives a turning acceleration yaw moment instead of a restoring yaw moment, and stops the control when exiting the turning to bring out the inherent stability of the vehicle. With this configuration, normal turning performance can be achieved with an actuator with a small control amplitude, and where the road surface friction coefficient decreases, it can be stabilized by the original performance of the vehicle without applying energy to each actuator. It is. As a result, the actuator can be reduced in size and cost, and the fail-safe performance when the actuator fails can be improved.

  In any case, it is possible to evaluate the instantaneous steering stability when the driver is riding on the vehicle (man-machine system) by calculating the instantaneous neutral steering point by measuring the instantaneous cornering power. By appropriately controlling the actuator, the maneuverability and stability can be optimized. In addition, it can be expected that the driving operation of the driver will be improved in the safe direction by providing visual, auditory and tactile information as a warning to the driver based on the detected instantaneous neutral steer point before the control is turned on. The possibility of the vehicle moving in a safe direction is increased.

  The present invention has been described above with a focus on lateral motion. It has already been mentioned that instantaneous braking (driving) power (stiffness) can also be measured for longitudinal movement. By providing visual, auditory, and tactile information as warnings to the driver using these, it can be expected that the driving operation of the driver is improved in the safe direction, and the possibility that the vehicle moves in the safe direction is increased. At the same time, by controlling each wheel reading rate of braking / driving force, it is possible to greatly improve the maneuverability and stability when the driver is driving.

(Equipped with lateral acceleration sensor, longitudinal acceleration sensor, yaw rate sensor)
FIG. 16 is a diagram showing a second embodiment of the present invention in which a yaw rate sensor is mounted in addition to the longitudinal and lateral acceleration sensors. As shown in the figure, the lateral acceleration sensor 212, the longitudinal acceleration sensor 234, and the yaw rate sensor 200 are installed in the vicinity of the center of gravity (even if they are installed at positions away from the center of gravity, they are equivalent by changing the coordinates. In this case, the center of gravity is arranged in the vicinity of the center of gravity in order to avoid complications).

By arranging the sensors in this way and using four differentiating circuits, the lateral acceleration of the vehicle center of gravity: G _y
Lateral jerk: J _y
Longitudinal acceleration: G _x
Longitudinal jerk: J _x
Yaw angular velocity: r
Yaw angular acceleration: {r-dot}
Yaw angle jerk: J _r
It is the structure which can detect. Since the yaw rate can be directly measured as compared with the first embodiment, no integration circuit is required. These signals are input to the central controller 400.

  FIG. 17 is a block diagram showing a procedure for measuring the instantaneous cornering power of the front and rear wheels in the second embodiment of the present invention in which a yaw rate sensor is mounted in addition to the longitudinal and lateral acceleration sensors. Executed within.

The inputs are the measured value G _y of the lateral acceleration sensor 212, the measured value r of the yaw rate sensor 200, the simulated vehicle speed V calculated by the brake controller 43 using the measured values of the wheel speed sensors, and the steering angle in the power steering 7. Δ detected by the sensor. As can be seen from FIG. 17, there is no tire model or vehicle motion model inside the logic. In addition, since there is no feedback loop, convergence calculation using a model or the like is not required, and the cornering power of the tire can be measured in real time with very little calculation processing.

  FIG. 18 is a block diagram showing a measurement procedure of instantaneous braking (driving) power (stiffness) of the left and right wheels in the second embodiment of the present invention in which a yaw rate sensor is mounted in addition to the longitudinal and lateral acceleration sensors. is there. The slip ratio calculation part is executed by the brake controller 43, while other logic is executed by the central controller 400.

Input is the measured value G _x of the longitudinal acceleration sensor 234, the measured value r of the yaw rate sensor 200, the simulated vehicle speed V calculated by the brake controller 43 using the measured value of each wheel speed sensor, the left front wheel and the right front wheel The average wheel speed. As can be seen from FIG. 18, there is no tire model or vehicle motion model inside the logic. In addition, since there is no feedback loop, convergence calculation using a model or the like is not required, and instantaneous braking (driving) power (stiffness) of a tire can be measured in real time with very little calculation processing.

  As described above, in the second embodiment of the present invention in which the yaw rate sensor is mounted in addition to the longitudinal and lateral acceleration sensors, the instantaneous cornering power of the front and rear wheels and the instantaneous braking (driving) of the left and right wheels without any lack of information. It can be seen that the power (stiffness) can be measured and has the same engineering significance as the first embodiment of the present invention. Moreover, the sensor equivalent to the 2nd Example of this invention and its arrangement | positioning (FIG. 16) are the number of sensors and arrangement | positioning currently mounted in the passenger car currently marketed. In addition to this, the present invention can be realized with a small additional cost, that is, only differentiating means and logic calculations equivalent to those shown in FIGS.

(Equipped with lateral jerk sensor, longitudinal jerk sensor, angular jerk sensor)
FIG. 19 is equipped with a jerk sensor capable of directly detecting both acceleration and jerk and an angular jerk sensor capable of detecting angular acceleration and angular jerk to extract longitudinal and lateral acceleration and jerk information. It is a figure which shows the 3rd Example of this invention.
As shown in the figure, the lateral jerk sensor 2120, the longitudinal jerk sensor 2340, and the angular or acceleration sensor 2000 are installed in the vicinity of the center of gravity.

  Since the jerk sensor and the angular jerk sensor are described in detail in Japanese Patent No. 3417410, the detection principle is omitted here, and only the outline of the configuration is shown.

  As shown in FIG. 20, the jerk sensor includes a pendulum 201 attached to a casing 2010a so as to be able to move with one degree of freedom by a joint 2013, a coil 203 fixed to the pendulum 201, and a pendulum 201. A movable electrode 2041 attached in the direction of movement of the end side, a casing 2010 to which a magnet 202 is attached, a fixed electrode 2042 formed on the casing 2010 so as to face the movable electrode 2041, and a pendulum 201 A pendulum displacement detector 2040 that detects displacement from a balanced position, and a servo amplifier that is connected in series to the output side of the pendulum displacement detector 2040 and further wired so that the output side is connected to one side of the coil 203 205, and a reading resistor 206 wired so that one is grounded and the other is connected to the other of the coil 203. The detected acceleration information is extracted by a voltage drop (current value) in the reading resistor 206, and the jerk information is extracted as a terminal voltage of the coil 203.

  FIG. 21 is a diagram showing the overall configuration of the angular jerk sensor. The angular jerk sensor includes a rotating pendulum 1201, a coil 1202 fixed to the rotating pendulum 1201, a movable electrode 1204, a casing 1200, a magnet 1203 fixed to the casing 1200, a fixed electrode 1205, and a pendulum balance. A pendulum displacement detector 1206 for detecting displacement from the position, a servo amplifier 1207, and a reading resistor 1208 are included. The acceleration information is taken out by a voltage drop (current value) in the reading resistor 1208, and the angular jerk information is taken out as a terminal voltage of the coil 1202, as shown in FIG.

  With the above configuration, the third embodiment of the present invention can detect the lateral jerk and the angular jerk without using a differentiating circuit. However, since the yaw rate (angular velocity) cannot be directly detected as in the first embodiment, one integration circuit for integrating the yaw angular acceleration is required.

The sensor is arranged in this way, the lateral acceleration of the vehicle center of gravity: G _y
Lateral jerk: J _y
Longitudinal acceleration: G _x
Longitudinal jerk: J _x
Yaw angular velocity: r
Yaw angular acceleration: {r-dot}
Yaw angle jerk: J _r
It is the structure which can detect. These signals are input to the central controller 4000.

  FIG. 22 is equipped with a jerk sensor capable of directly detecting both acceleration and jerk and an angular jerk sensor capable of detecting angular acceleration and angular jerk for extracting longitudinal and lateral acceleration and jerk information. FIG. 10 is a block diagram showing a procedure for measuring instantaneous cornering power of front and rear wheels in a third embodiment of the present invention, and this logic is executed in the central controller 4000;

Inputs are lateral acceleration G _y and lateral jerk J _y which are measured values of lateral jerk sensor 2120, yaw angular acceleration {r-dot or Gr} and angular jerk J _r which are measured values of angular jerk sensor 2000, The pseudo vehicle speed V calculated by the brake controller 43 using the measured value of each wheel speed sensor, and δ detected by the steering angle sensor in the power steering 7. As can be seen from FIG. 22, there is no tire model or vehicle motion model inside the logic. In addition, since there is no feedback loop, convergence calculation using a model or the like is not required, and the cornering power of the tire can be measured in real time with very little calculation processing.

  FIG. 23 is equipped with a jerk sensor capable of directly detecting both acceleration and jerk and an angular jerk sensor capable of detecting angular acceleration and angular jerk for extracting longitudinal and lateral acceleration and jerk information. It is the block diagram which showed the measurement procedure of the instantaneous braking (driving) power (stiffness) of the left-right wheel in the 3rd Example of this invention. The slip ratio calculation part is executed by the brake controller 43, while the other logic is executed by the central controller 4000.

The input is the longitudinal acceleration G _x and longitudinal jerk J _x which are measured values of the longitudinal jerk sensor 2340, and the yaw angular acceleration {r-dot or G _r } and angular jerk which are measured values of the angular jerk sensor 2000. J _r is the simulated vehicle speed V calculated by the brake controller 43 using the measured value of each wheel speed sensor, and the average wheel speed of the left front and rear wheels and the right front and rear wheels. As can be seen from FIG. 23, there is no tire model or vehicle motion model inside the logic. In addition, since there is no feedback loop, convergence calculation using a model or the like is not required, and instantaneous braking (driving) power (stiffness) of a tire can be measured in real time with very little calculation processing.

  As described above, for extracting longitudinal and lateral acceleration and jerk information, a jerk sensor that can directly detect both acceleration and jerk, and an angular jerk sensor that can detect angular acceleration and angular jerk. The mounted third embodiment of the present invention can measure the instantaneous cornering power of the front and rear wheels and the instantaneous braking (driving) power (stiffness) of the left and right wheels without any lack of information. Or it turns out that it has the same engineering significance as Example 2. It should be noted that the arithmetic logic in the central controller 4000 is simplified by the differentiation circuit in the third embodiment of the present invention as compared with the other embodiments. In the third embodiment of the present invention, an example in which an electromagnetic servo type jerk sensor and an angular jerk sensor are employed has been described. However, the present invention is not limited to this. An acceleration sensor may be used.

  Finally, effects of the present invention will be briefly described through three embodiments of the present invention.

  It is possible to provide means and an apparatus that measure the instantaneous cornering power and braking stiffness of a tire in real time with very little arithmetic processing without using a convergence calculation using a model or the like.

  In addition, vehicle motion is evaluated using instantaneous cornering power and instantaneous braking stiffness measured in real time, and this is shown to the driver. When an unstable condition is approached, an alarm is issued. Techniques and apparatus for adjusting control inputs for stabilization can be provided.

The figure which shows the whole structure of 1st Example of this invention. The figure which shows sensor arrangement | positioning of 1st Example. Diagram showing a general description of vehicle motion Figure showing an equivalent (front and rear) two-wheeled vehicle model of a four-wheeled vehicle The figure which shows the instantaneous cornering power detection logic of 1st Example Diagram showing the relationship between wheel side slip angle and lateral force Diagram showing an equivalent (left and right) two-wheeled vehicle model of a four-wheeled vehicle The figure which shows the instantaneous braking power detection logic of 1st Example Diagram showing the relationship between wheel slip ratio and front / rear (braking / driving) force Conceptual diagram showing a general expression of the present invention The figure which shows the measurement result of the real vehicle to which this invention is applied Explanatory diagram showing neutral steer point (NSP) Diagram showing changes in vehicle characteristics, NSP, and restoring moment The figure which shows each step of detection of this invention, an alarm, and control The figure which shows the control effect of this invention The figure which shows sensor arrangement | positioning of 2nd Example of this invention. The figure which shows the instantaneous cornering power detection logic of 2nd Example. The figure which shows the instantaneous braking power detection logic of 2nd Example The figure which shows sensor arrangement | positioning of 3rd Example of this invention. Diagram showing jerk sensor Diagram showing angular jerk sensor The figure which shows the instantaneous cornering power detection logic of 3rd Example. The figure which shows the instantaneous braking power detection logic of 3rd Example

Explanation of symbols

0 ... vehicle, 1 ... engine, 2 ... electronic control mission, 3 ... propeller shaft, 4 ... differential gear, 5 ... left transfer unit, 6 ... right transfer unit, 7 ... power steering, 10 ... steering, 11 ... accelerator pedal, 12 ... Brake pedal, 21 ... Front lateral acceleration sensor, 22 ... Rear lateral acceleration sensor, 23 ... Left longitudinal acceleration sensor, 24 ... Right longitudinal acceleration sensor, 25,26,27,28 ... Differentiation circuit, 31 ... Steering angle sensor, 40 ... Central controller, 41 ... Steering controller, 42 ... Powertrain controller, 43 ... Brake controller, 44 ... Left / right transfer controller, 51 ... Left front wheel, 52 ... Right front wheel, 53 ... Left rear wheel, 54 ... Right rear wheel, 61 , 62, 63, 64 ... Brake rotor, 71, 72, 73, 74 ... Brake caliper, 81, 82, 83, 84 ... Wheel speed detection rotor, 91, 92, 93, 94 ... Wheel speed pickup, 200 ... Yaw rate Sensor, 212 ... lateral acceleration sensor, 234 ... longitudinal acceleration sensor, 512 ... front wheel of an equivalent (front and rear) two-wheeled vehicle model of a four-wheeled vehicle, 534 ... of an equivalent (front and rear) two-wheeled vehicle model of a four-wheeled vehicle Rear wheel, 513 ... 4-wheeled vehicle equivalent (left and right) 2-wheeled vehicle model left wheel, 524 ... 4-wheeled vehicle equivalent (left-right) 2-wheeled vehicle model right wheel, 2000 ... angular jerk sensor, 2120 ... lateral jerk sensor, 2340 ... longitudinal jerk sensor.

Claims (13)

  The vehicle jerk, the yaw angle jerk of the vehicle, and the time change of the control input to each wheel tire are detected, and the first gain is applied to the value obtained by dividing the jerk by the time change of the control input. The rate of change of the force generated by each wheel tire with respect to the instantaneous control input is obtained by adding the value obtained by dividing the value and yaw angle jerk by the time change of the control input to the value obtained by multiplying the second gain. A vehicle tire condition detection method characterized by calculating.   2. The vehicle tire condition detection method according to claim 1, wherein a lateral jerk of the vehicle is detected as jerk, and a time change of a side slip angle of each wheel tire is detected as a time change of a control input to each wheel tire of the vehicle. The vehicle tire condition is characterized in that the instantaneous cornering power, which is the rate of change of the cornering force of each wheel tire with respect to the instantaneous side slip angle, is calculated as the rate of change of the force generated by each wheel tire with respect to the instantaneous control input. Detection method. In the vehicle tire state detection method according to claim 2,
The value obtained by multiplying the detected vehicle lateral jerk by the vehicle inertial mass and the distance from the vehicle center of gravity to the rear wheel axle is divided by the distance between the front and rear wheel axles and the time change in the front wheel side slip angle. By multiplying the value obtained by multiplying the angular jerk of the vehicle by the yaw moment of inertia of the vehicle and dividing by the distance between the axles of the front and rear wheels and the time change in the side slip angle of the front wheel, the front wheel is halved. While calculating the instantaneous cornering power per one,
Detected from the value obtained by multiplying the detected vehicle lateral jerk by the vehicle inertia mass and the distance from the vehicle center of gravity to the front wheel axle, divided by the distance between the axles of the front and rear wheels and the time change in the side slip angle of the rear wheels. By subtracting the value obtained by multiplying the vehicle's angular jerk by the vehicle's yaw moment of inertia and dividing it by the distance between the front and rear axles and the time change in the side slip angle of the rear wheel, A vehicle tire condition detection method comprising calculating an instantaneous cornering power per wheel.   2. The vehicle tire condition detection method according to claim 1, wherein the longitudinal jerk of the vehicle is detected as jerk, and the peripheral speed of each vehicle wheel and the absolute vehicle speed of the vehicle are calculated as a time change of control input to each wheel tire of the vehicle. The difference in time is detected by dividing the difference by the circumferential speed of each vehicle wheel or the absolute vehicle speed of the vehicle, and the change rate of the force generated by each wheel tire with respect to the instantaneous control input A vehicle tire condition detection method for calculating an instantaneous braking stiffness, which is a rate of change of a longitudinal force of a wheel. Jerk detection means for detecting vehicle jerk, yaw angle jerk for detecting vehicle yaw angle jerk, and control input time change detection for detecting time change of control input to each wheel tire of vehicle Means and computing means,
In the arithmetic means, a value obtained by multiplying the jerk detected by the jerk detection means by the time change of the control input detected by the control input time change detection means and a gain multiplied by the yaw angle jerk means Each wheel tire for each momentary control input is calculated by adding a gain multiplied by the value obtained by dividing the yaw angle jerk generated by the control input time change detection means by the time change of the control input. A vehicle tire state detection device characterized by calculating a rate of change of force generated by the vehicle.   6. The vehicle tire condition detection device according to claim 5, wherein a lateral jerk detecting means for detecting a lateral jerk of the vehicle as a jerk detecting means, and a time change amount of a side slip angle of each wheel tire as a control input time change detecting means. And a change rate of a cornering force of each wheel tire with respect to an instantaneous skid angle as a rate of change of force generated by each wheel tire with respect to an instantaneous control input. A vehicle tire condition detecting device for calculating cornering power. In the vehicle tire state detection device according to claim 6,
The lateral jerk detecting means and the yaw angle jerk detecting means are grounded at an arbitrary distance forward from the vehicle center of gravity and are detected at an arbitrary distance backward from the vehicle center of gravity. It is composed of a second acceleration sensor that is grounded and detects lateral acceleration, and an arithmetic means.
The calculating means calculates the lateral acceleration of the vehicle from the sum of the outputs of the first and second acceleration sensors, calculates the lateral jerk by differentiating the calculated lateral acceleration, and outputs the first and second acceleration sensors. A vehicle tire condition detecting device that calculates a yaw angular jerk by calculating a yaw angular acceleration of a vehicle from a difference and differentiating the calculated yaw angular acceleration.   6. The vehicle tire condition detection device according to claim 5, wherein the longitudinal acceleration of the vehicle is detected as a jerk detection means, and the circumferential speed of each wheel of the vehicle is detected as a control input time change detection means. A slip rate time change detecting means for detecting a time change of the slip rate obtained by dividing the difference in absolute vehicle speed by the peripheral speed of each wheel of the vehicle or the absolute vehicle speed of the vehicle, A vehicle tire condition detection device that calculates an instantaneous braking stiffness, which is a rate of change of a longitudinal force of each wheel with respect to a slip rate of each moment as a rate of change of generated force. The vehicle tire state detection device according to claim 8, wherein the longitudinal jerk detecting means and the yaw angle jerk means are grounded at an arbitrary distance from the center of gravity of the vehicle to the right and detect acceleration in the longitudinal direction. A sensor, a second acceleration sensor that is grounded at an arbitrary distance from the center of gravity of the vehicle to the left and detects acceleration in the front-rear direction, and a calculation means,
The computing means computes the longitudinal acceleration of the vehicle from the sum of the outputs of the first and second acceleration sensors, computes the longitudinal jerk by differentiating the computed longitudinal acceleration, and calculates the first and second acceleration sensors. A vehicle tire condition detection apparatus that calculates a yaw angular acceleration by calculating a yaw angular acceleration of a vehicle from an output difference and differentiating the calculated yaw angular acceleration.   6. The vehicle tire condition detection device according to claim 5, wherein the device displays a change rate of the force generated by each wheel tire with respect to the calculated instantaneous control input to the driver, or the change rate is an arbitrary value. A vehicle tire condition detection device comprising a device that transmits to a driver as at least one of visual information, audio information, and tactile information when it is further lowered.   The vehicle tire condition detection device according to any one of claims 5 to 10, wherein the detected tire condition and vehicle speed, vehicle acceleration, vehicle jerk, vehicle yaw angular velocity, yaw angular acceleration, yaw angular jerk A vehicle tire condition detection device comprising a step of determining a tire control input using at least one of them. The vehicle tire condition detection device according to claim 6,
A device for displaying the calculated instantaneous cornering power to the driver, or when the instantaneous cornering power falls below an arbitrary value, it is transmitted to the driver as at least one of visual information, audio information or tactile information Equipped with a device to
Using the difference between the instantaneous cornering power of the front wheel multiplied by the distance from the center of gravity of the vehicle to the front axle and the value of the instantaneous cornering power of the rear wheel multiplied by the distance from the center of gravity of the vehicle to the rear axle. Vehicle tire condition detection comprising control means for executing at least one of a step of transmitting visual information, audio information, or tactile information to a driver or a step of determining a tire control input apparatus. The vehicle tire condition detection device according to any one of claims 5 to 11, wherein the jerk of the vehicle is directly detected by a jerk sensor, and the angular jerk of the vehicle is detected by an angular jerk sensor. A vehicle tire condition detection device.

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