JP2956222B2 - Body attitude control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle body attitude control apparatus having excellent responsiveness, which suppresses the roll of a vehicle body during a turning operation and keeps the vehicle flat.

[0002]

2. Description of the Related Art JP-A-61-18172 and JP-A-62-19851
In the vehicle body attitude control device disclosed in Japanese Patent Publication No. 1 (1993), a control force proportional to the lateral acceleration is applied to a hydraulic suspension mechanism to suppress a change in the vehicle body posture due to centrifugal force during turning, thereby keeping the vehicle body constant. However, there is a disadvantage that the vehicle body posture cannot be kept flat especially at the beginning of the turning movement due to a delay in detection of the lateral acceleration sensor, a delay in response of the hydraulic circuit, and the like.

[0003]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to perform attitude control based on a lateral acceleration predicted from a steering angular velocity and a vehicle speed in an initial stage of a turning motion, and to be proportional to an actual lateral acceleration in a steady state. Improve the responsiveness at the beginning of turning motion by performing the attitude control, and enable accurate attitude control even in marginal turning motion such as slipping tires,
An object of the present invention is to provide a vehicle body attitude control device.

[0004]

In order to achieve the above object, the present invention comprises a detecting means for detecting a steering angle, a vehicle speed, a lateral acceleration, and a longitudinal acceleration, respectively, and obtaining a predicted lateral acceleration from the steering angular speed and the vehicle speed. Lateral acceleration prediction means, moving load distribution means for calculating the ratio of the cornering force of the longitudinal axis from the steering angle and the vehicle speed and the detected lateral acceleration and longitudinal acceleration, the predicted lateral acceleration determined by the lateral acceleration prediction means and First roll control torque calculating means for calculating the roll control torque of the front-rear axis from the ratio of the cornering force; and the roll control torque of the front-rear axis based on the lateral acceleration detected by the detection means and the ratio of the cornering force. The second roll control torque calculating means to be determined, and the lateral acceleration detected by the detecting means and the ratio of the cornering force. Second roll control torque calculating means for calculating the roll control torque, and an oil for adjusting the oil amount of the hydraulic suspension mechanism of each wheel in accordance with the roll control torque obtained by the first and second roll control torque calculating means. An oil quantity control valve, wherein the oil quantity control valve is controlled in accordance with the roll control torque obtained from the first roll control torque calculating means at the beginning of the turning motion, and during the turning motion, The oil amount control valve is controlled according to the roll control torque obtained from the second roll control torque calculation means.

[0005]

In the initial stage of the turning motion, lateral acceleration is obtained by the lateral acceleration prediction means from the steering angle (steering wheel turning angle) speed and the vehicle speed, and cornering of the longitudinal axis by the moving load distribution means from the steering angle, the vehicle speed, the lateral acceleration and the longitudinal acceleration. Calculate the percentage of force. From the predicted lateral acceleration and the ratio of the cornering force, the roll control torque calculating means obtains the roll control torque of the front-rear axis. By adjusting the oil amount of the hydraulic suspension mechanism of each wheel in accordance with the roll control torque, roll control with excellent responsiveness can be performed during turning, especially at the beginning of turning motion, and the steering stability of the vehicle is improved. Is done.

[0006]

FIG. 1 is a block diagram of a vehicle body attitude control apparatus according to the present invention, and FIG. 2 is a hydraulic circuit diagram of a hydraulic suspension mechanism. As shown in FIG. 2, a hydraulic pump 4 driven by the engine sucks oil from an oil tank 2 and a check valve 6 from a pipe 5.
To the accumulator 8 of the pipe 7 Oil pressure monitoring means A is provided to keep the oil pressure to the pipe 7 at a predetermined value. That is, when the detection value of the oil pressure sensor 9 that detects the oil pressure of the pipe 5 exceeds a predetermined value, the pressure control valve 12 is switched, and a part of the pressure oil of the pipe 5 is changed to the pipe 10, the pressure control valve 12, The oil is returned to the oil tank 2 via the filter 27. When the oil pressure at the discharge port of the hydraulic pump 4 becomes abnormally high, a part of the pressure oil in the pipe 5 is returned to the oil tank 2 via the known relief valve 26 and the filter 27.

The hydraulic oil in the pipe 7 is supplied to each hydraulic suspension mechanism 19 of left and right front wheels and left and right rear wheels (only the left rear wheel is shown in FIG. 2). The hydraulic suspension mechanism 19 fits a piston 22 in a cylinder 23 and connects a rod 24 projecting upward from the piston 22 to the vehicle body 20, and a wheel 25 projecting downward from the cylinder 23 to a wheel 25.
It is connected to the knuckle. A spring 21 is interposed between the wall of the cylinder 23 and the vehicle body 20. A vehicle height sensor 28 that detects the amount of vertical displacement between the vehicle body 20 and the wheels 25 is disposed between the vehicle body 20 and the nuticle. The left and right front wheels,
When specifying each suspension mechanism 19 of the left and right rear wheels, FL, F
The subscripts R, RL, and RR will be added.

The pressure oil in the pipe 7 is supplied to a check valve 14, an oil amount control valve 1 comprising a general neutral position closed type electromagnetic proportional pressure control valve.
6. The pressure is supplied to the pressure accumulator 18 through the throttle 18a, and further supplied to the lower end chamber of the cylinder 23 through the rod 24 of the hydraulic suspension mechanism 19 and the internal passage of the piston 22. The oil pressure supplied to the lower end chamber of the cylinder 23 is detected by the oil pressure sensor 17. When the oil amount control valve 16 is switched, the oil in the lower end chamber of the cylinder 23 is returned to the oil tank 2 via the oil amount control valve 16, the check valve 15, the pipe 13, and the filter 27.

Each of the hydraulic suspension mechanisms 19 supporting the front and rear, left and right wheels is independently provided with check valves 14 and 15 and an oil amount control valve 1.
6, a throttle 18a, an accumulator 18, a hydraulic sensor 17, and a vehicle height sensor 28.

The roll amount (angle) of the vehicle body (spring), the pitch amount (angle) of the vehicle body, and the vertical position of the vehicle
2, θ2, x2, and the roll amount of the axle (unsprung), the pitch of the axle, and the vertical position of the axle (left and right center) are φ
Assuming that 1, θ1 and x1, the relative roll displacement Δφ, pitch displacement Δθ, and vertical displacement Δx between the vehicle body and the axle are expressed by the following equations.

Φ2 = φ1 + Δφ θ2 = θ1 + Δθ x2 = x1 + Δx The average vehicle height during stop is h, the detection value of the vehicle height sensor 28 of each wheel is hFL, hFR, hRL, hRR, and the change in vehicle height of each wheel is roll. Assuming that k11, k12, k21, and k22 are coefficients representing the degree of influence on the displacement amount Δφ and the pitch displacement amount Δθ, the roll displacement amount Δφ, the pitch displacement amount Δθ, and the vertical displacement amount Δx are expressed by the following equation (1).
become.

Δφ = kφ ｛k11 (hFL−hFR) + k12 (hRL−hRR)｝ Δθ = kθ ｛k21 (hFL + hFR) −k22 (hRL + hRR)｝ Δx = kx (hFL + hFR + hRL + hRR-4h) (Equation 1) kφ, kθ, and kx are gains. Each coefficient k1
1, k12, k21, and k22 are experimentally determined in consideration of the load on the front and rear shafts, the spring constant of the spring 21, and the like.

In general, the condition for keeping the vehicle body flat against road surface input is as follows: For extremely low frequency input, Δφ → 0 Δφ / φ1 → 0 Δθ → 0 Δθ / θ1 → 0 Δx → 0 Δx / x1 → 0 For a high frequency input, it can be considered that Δφ → −φ1 Δφ / φ1 → −1 Δθ → −θ1 Δθ / θ1 → −1 Δx → −x1 Δx / x1 → −1.

Therefore, a vibration control amount for keeping the vehicle body flat against road surface input, that is, a roll control torque F1
2. The pitch control torque F22 and the vertical control force F32

[0015]

(Equation 2) However, assuming that k1 to k6 are given by constants,
The following equation of motion holds.

[0016]

[Equation 2a] However, By transforming the above equation, Laplace transform, and expressing the Laplace operator by s, Equation 3 is obtained.

[0017]

(Equation 3) Here, the response to the extremely low frequency input corresponds to the case where s → 0 in the above transfer function, and the response to the high frequency input corresponds to the case where s → ∞ in the above transfer function. It turns out that the vehicle body satisfies the condition of being flat.

However, when the control is performed only by the equation 2, unless the values of the constants k1 to k6 are increased to some extent, the posture before and after the stop may not be maintained flat. On the other hand, if the values of the constants k1 to k6 are too large, there is a possibility that the ride comfort at low frequency input may be adversely affected.

Therefore, as represented by Equation 4, the steady-state error is removed by adding an integral term.

[0020]

(Equation 4) However, k7 to k9 are constants. If the feedback control described above is performed, the vehicle body can be kept flat against road surface input during straight running at a constant vehicle speed.

However, during turning and acceleration / deceleration, the response is not in time, and the posture of the vehicle changes. Therefore, the following proportional control corresponding to the lateral acceleration and the longitudinal acceleration is added. Assuming that the vehicle is traveling on a flat road surface with no unevenness, the following equation of motion holds for the roll and pitch of the vehicle body.

[0022]

(Equation 5) As shown in FIG. 3, the first term on the right side of the equation 5 is a moment in which lateral acceleration (longitudinal acceleration) acting on the center of gravity of the vehicle causes the body to roll (pitch), and the second term is a roll (pitch) of the body. ), The gravitational acceleration acting on the center of gravity of the car causes moments m · g and hR · s to roll (pitch) the car body.
The product of inφ (the product of mg · g and hP · sin θ).

Accordingly, the roll control torque F11 and the pitch control torque F21 for setting the roll and pitch of the vehicle body to 0 are expressed by the following equations.

−F11 = m · hR · GYS + m · g · hR · φ−kS1 · φ −F21 = m · hP · GXS + m · g · hP · θ−kS2 · θ There is no road surface input on a flat road surface without unevenness. Therefore, ignoring the vertical deflection of the tire and setting φ = Δφ and θ = Δθ, the roll control torque F11 and the pitch control torque F21 are
It is expressed by the following equation.

−F11 = m · hR · GYS + m · g · hR · Δφ−kS1 · Δφ −F21 = m · hP · GXS + m · g · hP · Δθ−kS2 · Δθ (Equation 5a) In this case, there is a case where the vehicle body cannot be kept flat at the beginning of the turning motion due to a response delay of the sensor, a response delay of the hydraulic circuit, and the like.

Thus, the present invention predicts the initial lateral acceleration of the turning motion. In other words, a predicted lateral acceleration is obtained by the lateral acceleration prediction means from the steering angular velocity and the vehicle speed at the beginning of the turning motion, a control amount for the roll of the vehicle body is obtained from the predicted lateral acceleration GYC obtained by the lateral acceleration prediction means, and the oil to the hydraulic suspension mechanism is obtained. Adjust the amount. Now, assuming that the roll of the vehicle body is negligibly small, the following equation of motion holds.

[0027]

(Equation 6) When the transfer function of the side slip angle β of the vehicle body with respect to the steering angular velocity dδH / dt is obtained from the above equation of motion, it is expressed by the following equation.

[0028]

Equation 7 GY = V (dβ / dt + r) = V · dβ / dt + V · r

[0029] Here, it is noted that V (dβ / dt) is dominant in the initial stage of the turning motion, and the transfer function G BE is approximated by a low-order equation as follows.

G BE = G ′ BE = GC (V) / {1 + s · TC (V)} where GC (V) is a function of the vehicle speed represented by the following equation 8,
C (V) is a function of the vehicle speed as shown in FIG.

[0031]

(Equation 8) As described above, the predicted lateral acceleration GYC at the beginning of the turning motion is obtained by the following equation.

GYC = GBE (dδ / dt) V + GYS Therefore, the roll control torque F11 at the beginning of the turning motion is
Equation 5a can be rewritten as follows.

−F11 = m · hR · GYC + m · g · hR · Δφ−kS1 · Δφ Here, if the roll control torque F11 is distributed to the ratio of the cornering force of the front-rear shaft to the front-rear shaft, an appropriate steering characteristic can be obtained. Is obtained.

Assuming that the vehicle speed at the beginning of the turning motion of the vehicle is constant and the steering angle δ is small, the yaw angular velocity r, the front wheel cornering force CF, and the rear wheel cornering force CR are given by:
It looks like this:

[0035] Holds. Here, the lateral acceleration GY is equal to the detection value GYS of the lateral acceleration sensor, that is, GY = GYS, but for the longitudinal acceleration GX, the detection value GXS of the longitudinal acceleration sensor includes an acceleration / deceleration component accompanying a change in vehicle speed. Therefore, GX does not become GXS.

The lateral acceleration GX is calculated by the following equation in consideration of the change rate dV / dt of the vehicle speed V.

GX = GXS-kG.dV / dt where kG is a ratio of the cornering force of the front and rear axes to the cornering force of the entire adjustment gain kCF, k
CR is as follows.

KCF = CF / (CF + CR) kCR = CR / (CF + CR) Accordingly, the roll control torque F11 for setting the roll of the vehicle body to 0 is obtained by the roll control torque F11F of the front shaft and the roll control torque of the rear shaft. When distributed to the ratio of the cornering force on the front-rear axis to F11R, the following equation is obtained.

F11F = kV6 · kCR · F11 F11R = kV7 · kCF · F11 (Equation 9) where kV6 and kV7 are roll control torques F11F and F11R obtained as above the adjustment gain. <F11R, the moving load of the rear shaft becomes larger than the moving load of the front shaft, and the vehicle tends to be oversteered. When the vehicle leaves a corner, the characteristics are opposite, and the vehicle tends to be understeered.

From the above results, the control amounts to be applied to the respective wheels (control oil amounts of the hydraulic suspension mechanism) VFL, VFR, VRL, VRR
Is represented by the following equation.

VFL = −kV1 · F12−kV2 · F22 + kV5 · F32 + F11F VFR = + kV1 · F12−kV2 · F22 + kV5 · F32 + F11F VRL = −kV3 · F12 + kV4 · F22 + kV5 · F32 + F11 + VF · + FV ++ FV + FV + · F12 + FV + FV + FV + FV +. However, kV1 to kV5 are constants.
As shown in FIG. 1, relative roll displacement and pitch displacement between the vehicle body (spring up) and the axle (unsprung) are calculated by the relative displacement calculating means 35 from the detection values of the vehicle height sensors 28 of the respective wheels. , The amount of vertical displacement, the steering angle sensor 30, the vehicle speed sensor 3
1. The ratio of the cornering force in the front-rear axis is calculated by the moving load distribution calculating means 33 from the detected values of the lateral acceleration sensor 32, and the predicted lateral acceleration is calculated by the lateral acceleration predicting means 42 from the detected values of the steering angle sensor 30 and the vehicle speed sensor 31. Seeking GYC,
Predicted lateral acceleration GYC, ratio of cornering force on longitudinal axis, detected value of lateral acceleration sensor 32, longitudinal acceleration sensor 2
9, the roll control torque calculating means 36, the pitch control torque calculating means 37, and the vibration control amount calculating means 39 determine the roll control torque, the pitch control torque, and the vertical control force from the detected value of No. 9, the roll displacement, the pitch displacement, and the vertical displacement. From the above results, the control oil amount shared by each wheel is obtained by the oil amount calculation means 40, and the oil amount control valve 16 is driven in accordance with the control oil amount, and the oil of the hydraulic suspension mechanism 19 of each wheel is obtained. Adjust the amount,
As a result, a change in the posture of the vehicle body due to centrifugal force during turning traveling is suppressed, and the posture of the vehicle body is kept substantially flat.

FIG. 5 is a flow chart of a control program for performing the above-mentioned control by an electronic control device comprising a micro computer. This control program is repeatedly executed at predetermined time intervals. p11 to p21 represent each step of the control program. A control program is started at p11, initialization is performed at p12, an interrupt program is started at p13, an output oil pressure pm of the hydraulic pump 4 is read by the oil pressure monitoring means A, and if the output oil pressure pm is larger than a predetermined value pc, When the output oil pressure pm is smaller than a predetermined value pc, the pressure control valve 12 is closed to open the output oil pressure p.
m is increased, thereby maintaining a predetermined value, and returning to this program.

At p14, the load of each wheel is obtained from the hydraulic sensor 17, the vehicle height of each wheel is obtained from the vehicle height sensor 28, the longitudinal acceleration is obtained from the longitudinal acceleration sensor 29, the lateral acceleration is obtained from the lateral acceleration sensor 32, and the vehicle speed is obtained from the vehicle speed sensor 31. , The steering angle is read from the steering angle sensor 30, and the lateral acceleration GYC is obtained by the lateral acceleration prediction means 42 from the steering angle and the vehicle speed at p15.

At p16, the relative roll displacement .DELTA..phi., Pitch displacement .DELTA.
θ and the vertical displacement Δx are obtained. At p17, the ratio kCF, kCR of the cornering force of the front-rear axis to the entire cornering force is calculated by the moving load distribution calculating means 33 from the steering angle, the vehicle speed, the lateral acceleration, and the longitudinal acceleration.

At p18, the lateral acceleration GYC, the cornering force ratio kCF, kCR, the lateral acceleration GY, the longitudinal acceleration GX,
Roll displacement Δφ, pitch displacement Δθ, vertical displacement Δx
The roll control torque calculating means 36, the pitch control torque calculating means 37, and the vibration control amount calculating means 39 determine the roll control torques F11F, F11 for keeping the vehicle body flat.
R, F12, pitch control torque F21, F22, vertical control force F
Ask for 32.

At p19, the oil amount calculating means 40 controls the control oil amounts VFL, VFR, VRL, VRR of the hydraulic suspension mechanism 19 for each wheel.
Ask for. At p20, the oil amount control valve 16 is driven based on the control oil amounts VFL, VFR, VRL, VRR, the oil amount of the hydraulic suspension mechanism 19 is adjusted, and the process ends at p21.

As shown in FIG. 6, actually, the oil amount signal applied to the hydraulic suspension mechanism 19 of each wheel (FIG. 6 shows the case of the left front wheel) is a DC voltage corresponding to the control oil amount. Alternatively, a pulse voltage having a duty ratio is applied to the electromagnetic coil of each oil amount control valve 16 to adjust the vehicle height. At this time, the hydraulic pressure p applied to the hydraulic suspension mechanism 19 of each wheel is detected by the hydraulic pressure sensor 17 and fed back to the electromagnetic coil of the oil amount control valve 16 as a voltage. In FIG. 6, kVL1
~ KVL3 is gain, kS is gain of oil pressure sensor 17, G
VL is a transfer function of the oil amount control valve 16 and GACT is a transfer function of the hydraulic suspension mechanism 19.

[0048]

As described above, the present invention provides a detecting means for detecting a steering angle, a vehicle speed, a lateral acceleration, and a longitudinal acceleration, a lateral acceleration predicting means for obtaining a predicted lateral acceleration from a steering angular velocity and a vehicle speed, A moving load distributing means for calculating a ratio of a cornering force on the longitudinal axis from the vehicle speed, the detected lateral acceleration and the longitudinal acceleration, and a longitudinal axis based on the predicted lateral acceleration determined by the lateral acceleration predicting means and the ratio of the cornering force. First roll control torque calculating means for obtaining the roll control torque of the first and second roll control torque calculating means for obtaining the roll control torque of the longitudinal axis from the lateral acceleration detected by the detecting means and the ratio of the cornering force. And a second row for obtaining a roll control torque of the front-rear axis from the lateral acceleration detected by the detection means and the ratio of the cornering force. A vehicle body comprising: a control torque calculating means; and an oil amount control valve for adjusting the oil amount of a hydraulic suspension mechanism of each wheel in accordance with the roll control torque obtained by the first and second roll control torque calculating means. In the attitude control device, the oil amount control valve is controlled in accordance with the roll control torque obtained from the first roll control torque calculating means in the initial stage of the turning motion, and is controlled by the second roll control torque calculating means during the turning motion. The oil amount control valve is controlled in accordance with the obtained roll control torque. Particularly, when shifting from straight running to turning, the roll control is performed based on the lateral acceleration predicted from the steering angular speed and the vehicle speed. In addition, the responsiveness to the change in the posture of the vehicle body due to the centrifugal force is excellent, and the steering stability is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a vehicle body attitude control device according to the present invention.

FIG. 2 is a hydraulic circuit diagram of a hydraulic suspension mechanism.

FIG. 3 is a rear view of the vehicle body for explaining a roll generated on the vehicle body during turning traveling.

FIG. 4 is a diagram showing a part of calculation contents of a lateral acceleration prediction means.

FIG. 5 is a flowchart of a control program of the attitude control device.

FIG. 6 is a block diagram of a feedback control mechanism provided in the hydraulic suspension mechanism of each wheel.

[Explanation of symbols]

16: oil amount control valve 19: hydraulic suspension mechanism 28: vehicle height sensor 29: longitudinal acceleration sensor 30: steering angle sensor
31: Vehicle speed sensor 32: Lateral acceleration sensor 33: Moving load distribution calculating means 35: Relative displacement amount calculating means 36:
Roll control torque calculation means 37: pitch control torque calculation means 39: vibration control amount calculation means 42: lateral acceleration prediction means

Claims (1)

(57) [Claims] 1. A detecting means for detecting a steering angle, a vehicle speed, a lateral acceleration, and a longitudinal acceleration, a lateral acceleration predicting means for obtaining a predicted lateral acceleration from a steering angular speed and a vehicle speed, and a steering angle, a vehicle speed, and a detected lateral acceleration. Moving load distribution means for calculating the ratio of the cornering force on the longitudinal axis from the longitudinal acceleration; and a first roll control torque for determining the roll control torque on the longitudinal axis from the predicted lateral acceleration determined by the lateral acceleration predicting means and the ratio of the cornering force. Roll control torque calculating means, a second roll control torque calculating means for obtaining a longitudinal axis roll control torque from the lateral acceleration detected by the detecting means and a ratio of the cornering force, Second roll control torque calculating means for obtaining a roll control torque of the front-rear axis from the lateral acceleration and the ratio of the cornering force, An oil amount control valve for adjusting the oil amount of the hydraulic suspension mechanism of each wheel in accordance with the roll control torque obtained by the second roll control torque calculating means; Initially, the oil amount control valve is controlled in accordance with the roll control torque obtained from the first roll control torque calculation means.
And controlling the oil amount control valve in accordance with the roll control torque obtained by the roll control torque calculating means.