JP3047467B2 - Body attitude control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pitch (forward and backward tilting) of a vehicle body during acceleration and deceleration of a vehicle.
The present invention relates to a posture control device for a vehicle body that suppresses the vehicle body posture and keeps the vehicle body posture substantially flat.

[Prior Art] The vehicle body posture control device disclosed in Japanese Patent Application Laid-Open No. 61-181714 discloses a vehicle body attitude control device that suppresses the forward movement of the vehicle body during acceleration (quote) and the forward movement of the vehicle body during deceleration (dive). The amount of oil proportional to the longitudinal acceleration is supplied to or discharged from the hydraulic suspension mechanisms for the front and rear wheels, respectively, so that the vehicle body attitude is kept substantially flat.

In the above body posture control device, there is no problem if the longitudinal acceleration sensor for detecting longitudinal acceleration is installed at the same height as the longitudinal tilt center of the vehicle, but as shown in FIG.
In a normal vehicle, the longitudinal center O of the vehicle body is located below the road surface, so that it is impossible to arrange the longitudinal acceleration sensor at the same height as the pitch center of the vehicle body.

Therefore, when the longitudinal acceleration sensor is provided above the center of the pitch of the vehicle body, the longitudinal acceleration component g1 due to the pitch of the vehicle body is obtained.
Is also added and detected. Therefore, if the oil amount of each hydraulic suspension mechanism is adjusted based on the detection value of the longitudinal acceleration sensor, the ride comfort is adversely affected.

[Problems to be Solved by the Invention] In view of the above-described problems, an object of the present invention is to reduce the adverse effect caused by disposing the longitudinal acceleration sensor at a position higher than the pitch center of the vehicle body. Provided is a vehicle body posture control device that corrects a detection value of a longitudinal acceleration sensor during high middle-speed running, adjusts the oil amount of each hydraulic suspension mechanism based on the corrected longitudinal acceleration, and suppresses the vehicle body pitch. It is in.

[Means for Solving the Problem] In order to achieve the above object, a configuration of the present invention comprises a relative displacement amount calculating means for obtaining a pitch displacement amount based on a signal from a vehicle height sensor for detecting a vehicle height of each wheel; A longitudinal acceleration correcting means for obtaining a longitudinal acceleration multiplied by a correction coefficient which takes a value of 0 at low speed and high speed and 1 or less at medium speed from a signal of the vehicle speed sensor and the longitudinal acceleration sensor, and a relative displacement amount at medium speed; A vibration control amount calculating means for obtaining a pitch control torque for keeping the vehicle body flat based on signals from the calculating means and the longitudinal acceleration correcting means; and a control oil amount of the hydraulic suspension mechanism based on a signal from the vibration control amount calculating means. It is characterized by comprising an oil amount calculating means to be obtained, and an oil amount control valve for adjusting the oil amount of each hydraulic suspension mechanism based on a signal from the oil amount calculating means.

[Action] Focusing on the fact that the pitch of the vehicle body does not adversely affect the riding comfort at extremely low speeds and the fact that there is little road surface input that causes the vehicle body to pitch at high speeds, the detection value of the longitudinal acceleration sensor is used as it is. The amount of oil in each of the front and rear hydraulic suspension mechanisms is adjusted.

In middle-speed running, the detection value of the longitudinal acceleration sensor is multiplied by an appropriate correction value, and the amount of oil applied to the front and rear hydraulic suspension mechanisms is controlled based on the corrected longitudinal acceleration so as to suppress the pitch.

According to the present invention, the longitudinal acceleration component applied to the longitudinal acceleration sensor due to the pitch of the vehicle body is removed from the detection values of the longitudinal acceleration sensor, and the longitudinal acceleration component acting on the vehicle body due to the road surface change or the acceleration / deceleration of the vehicle is removed. The oil amount is added to the hydraulic suspension mechanism, and the vehicle body attitude returns to the flat more quickly without the adverse effect of the conventional excessive oil amount control.

FIG. 1 is a block diagram of an attitude control device for a vehicle body according to the present invention, and FIG. 2 is a hydraulic circuit diagram of a hydraulic suspension mechanism. Second
As shown in the figure, a hydraulic pump 4 driven by the engine
Sucks oil from the oil tank and supplies the oil from the pipe 5 to the accumulator 8 of the pipe 7 via the check valve 6. 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 for detecting the oil pressure of the pipe 5 exceeds a predetermined value, the hydraulic control valve 12 is switched, and a part of the pressure oil of the pipe 5
10. The oil is returned to the oil tank 2 via the hydraulic control valve 12, the pipe 13, and 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 through a known relief valve 26 and a filter 27.

The pressure oil in the pipe 7 is supplied to each hydraulic suspension mechanism 19 of the 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 the piston 22 in the cylinder 23 and connects the rod 24 projecting upward from the piston 22 to the vehicle body 20, while connecting the rod projecting downward from the cylinder 23 to the nut of the wheel 25. Become. 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 provided between the vehicle body 20 and a nut of the vehicle body 20. When specifying the suspension mechanisms 19 for the left and right front wheels and the left and right rear wheels, F
L, FR, RL, RR will be appended.

The pressure oil in the pipe 7 is supplied to an accumulator 18 through a check valve 14, an oil amount control valve 16 composed of a general neutral position closed type electromagnetic proportional pressure control valve, and a throttle 18a. It is supplied to the lower end chamber of the cylinder 23 through the internal passage of the rod 24 and 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 changed to the oil amount control valve 16,
The oil is returned to the oil tank 2 through the check valve 15, the pipe 13, and the filter 27.

Each hydraulic suspension mechanism 19 supporting the front, rear, left and right wheels is independently provided with check valves 14, 15, oil quantity control valve 16, throttle 18a, pressure accumulator 1
8, a hydraulic sensor 17 and a vehicle height sensor 28 are provided.

The roll amount (angle) of the body (spring), the body pitch (angle), and the vertical position of the vehicle center of gravity are φ2, θ2, x2, respectively, the roll amount of the axle (unsprung), the pitch of the axle, the axle (left and right) Assuming that the vertical position of (center) is φ1, θ1, x1, respectively, the relative roll displacement Δφ, pitch displacement Δθ, and vertical displacement Δx of the axle between the vehicle body and the axle are expressed by the following equations.

φ2 = φ1 + Δφ θ2 = θ1 + Δθ x2 = x1 + Δx h is the average vehicle height during stop, hFL, hFR, hRL, hRR is the detection value of the vehicle height sensor 28 of each wheel, and the vehicle height change of each wheel is the roll displacement amount Δφ And k11, k12, k21 and k22 as coefficients representing the degree of influence on the pitch displacement .DELTA..theta., The roll displacement .DELTA..phi., The pitch displacement .DELTA..theta.

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

Generally, the condition for keeping the vehicle 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 High frequency input On the other hand, it can be considered that Δφ → −φ1 Δφ / φ1 → −1 Δθ → −θ1 Δθ / θ1 → −1 Δx → −x1 Δx / x1 → −1.

Therefore, the vibration control amounts for keeping the vehicle body flat against the road surface input, that is, the roll control torque F12, the pitch control torque F22, and the vertical control force F32 are given by -F12 = -k1, .DELTA..phi.-k2..DELTA..phi .'- F22 =- k3 · Δθ−k4 · Δθ′−F32 = −k5 · Δx−k6 · Δx ′ (2) However, assuming that k1 to k6 are given by constants, the following equation of motion is established.

IX ・ φ2 ″ = − k1 ・ Δφ−k2 ・ Δφ ′ IY ・ θ2 ″ = − k3 ・ Δθ−k4 ・ Δθ ′ m2 ・ x2 ″ = − k5 ・ Δx−k6 ・ Δx ′ where IX: inertia to the body roll Moment IY: Moment of inertia with respect to vehicle pitch m2: Vehicle mass The above equation is transformed, Laplace transform is performed, and the Laplace operator is represented by s, and the following equation is obtained.

Δφ / φ1 = -1 + (k1 + k2 · s) / (k1 + k2 · s + IX · s 2) Δθ / θ1 = -1 + (k3 + k4 · s) / (k3 + k4 · s + IY · s 2) Δx / x1 = -1 + (k5 + k6 · s ) / (K5 + k6 · s + m2 · s ² ) (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 is the above transfer. Since this corresponds to the case where s → ∽ in the function, when s → 0 Δφ / φ1 → −1 + 1 → 0 Δθ / θ1 → −1 + 1 → 0 Δx / x1 → −1 + 1 → 0 When s → ∽ Δφ / φ1 → −1 + 0 → −1 Δθ / θ1 → −1 + 0 → −1 Δx / x1 → −1 + 0 → −1, indicating that the vehicle body satisfies the condition of being flat.

However, when control is performed only by equation (2), the constant
If the values of k1 to k6 are not increased to some extent, the posture when the vehicle is stopped may not be able to 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. That is, -F12 = -k1 · Δφ -k2 · Δφ'-k7 · ∫Δφdt -F22 = -k3 · Δθ -k4 · Δθ'-k8 · ∫Δθdt -F32 = -k5 · Δx -k6 · Δx'-k9 .DELTA..DELTA.xdt (4) where k7 to k9 are constants If the above-described feedback control is performed, the vehicle body can be kept flat against road surface input during straight running at a constant vehicle speed.

However, the response is not enough for the lateral acceleration during turning and the longitudinal acceleration during acceleration / deceleration, and the posture of the vehicle body 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.

IX · φ ″ = m2 · hR · GYS + m2 · g · hR · φ + F11 −kS1 · φ IX · θ ″ = m2 · hP · GXS + m2 · g · hP · θ + F21 −kS2 · θ (5) where hR: vehicle weight center And the center of the roll hP: Height difference between the center of gravity of the vehicle and the center of the pitch F11: Roll control torque F21: Pitch control torque kS1: Roll stiffness coefficient of spring 21 kS2: Pitch stiffness coefficient of spring 21 GYS: Detection value of lateral acceleration sensor GXS: Detected value of longitudinal acceleration sensor As shown in FIG. 4 for the case of the pitch of the vehicle centering on the pitch center O, in the equation (5), the first value on the right side
The term is a moment in which lateral acceleration (longitudinal acceleration) acting on the center of gravity of the vehicle causes the vehicle body to roll (pitch), and the second term is a gravitational acceleration acting on the center of gravity of the vehicle accompanying the roll (pitch) of the vehicle body, causing the body to roll (pitch). Moment m2 · g and h
The product of R · sin φ (the product of m2 · g and hP · sin θ).

Accordingly, the roll control torque F11 and the pitch control torque F21 for setting the roll and the pitch of the vehicle body to 0 respectively are set.
Is represented by the following equation.

-F11 = m2 · hR · GYS + m2 · g · hR · φ-kS1 · φ -F21 = m2 · hP · GXS + m2 · g · hP · θ-kS2 · θ Since there is no road surface input on a flat road surface without unevenness, tires Neglecting the vertical deflection of, approximately φ = Δφ, θ = Δθ
In other words, roll control torque F11, pitch control torque F12
Is represented by the following equation.

-F11 = m2 · hR · GYS + m2 · g · hR · Δφ-kS1 ·
Δφ-F21 = m2 · hP · GXS + m2 · g · hP · Δφ-kS2 ·
Δθ -F11 = k13 · GYS + k14 · Δφ-kS1 · Δφ -F21 = k23 · GXS + k24 · Δθ-kS2 · Δθ (6) However, K13, K14, K23, and K24 are constants, and the roll control torque F11 is described later. By distributing to the front and rear shafts as described above, good steering characteristics can be obtained.

Assuming that the vehicle is turning at a constant vehicle speed and the steering angle is small, the yaw angular velocity r and the front wheel cornering force C
F, rear wheel cornering force CR is as follows.

r = GY / V−βs where −β = GX / GY CF = −kF (β + 1F · r / V−δ) CR = −kR (β−1R · r / V) where V: vehicle speed β: vehicle body Side slip angle GX: longitudinal acceleration due to turning GY: lateral acceleration due to turning kF: front wheel cornering power kR: rear wheel cornering power 1F: distance between front wheel and vehicle weight center 1R: distance between rear wheel and vehicle weight center δ: actual steering angle The lateral acceleration is approximately GY = GYS, but the longitudinal acceleration is corrected because the detected value GXS of the longitudinal acceleration sensor includes the longitudinal acceleration component when the vehicle is accelerated / decelerated, and does not become GX = GXS. There is a need. Therefore, the longitudinal acceleration GX due to the turning travel is calculated by the vehicle speed V
As a function of the rate of change V ′.

GX = GXS-kG.V 'where kG is the adjustment gain. The ratios kCF and kCR of the front and rear axle cornering forces to the entire cornering force are as follows.

kCF = CF / (CF + CR) kCR = CR / (CF + CR) Therefore, the roll control torque F11 for setting the roll of the vehicle body to 0 is distributed to the roll control torque F11F of the front shaft and the roll control torque F11R of the rear shaft. Then, the following equation is obtained.

F11F = kV6 ・ kCR ・ F11 F11R = kV7 ・ kCF ・ F11 (7) However, kV6 ・ kV7 is equal to or more than the adjustment gain, so that the roll control torque becomes F11F <F11R at the start of cornering (at the time of corner entry), and The moving load of the shaft becomes larger than the moving load of the front shaft, and the vehicle tends to be oversteered. At the end of turning (when leaving a corner), the vehicle tends to be understeered.

By the way, when pitch control is performed by the above equation (6),
It interferes with control by road surface input and adversely affects the riding comfort.

Therefore, the present invention focuses on the fact that the road surface input that causes pitching of the vehicle body is small during high-speed running, and that there is little adverse effect on the vibration riding comfort at extremely low speed running. By controlling the posture with the output of the longitudinal acceleration sensor being weighted, and performing the posture control with the change rate V 'of the output of the vehicle speed sensor at the middle speed, the adverse effect on the vibration and ride comfort control is minimized. It is to suppress. That is, as shown in FIG. 3, a function f (V) is set such that kGX = 0 at V = 0, kGX = kGXC at V = VC1 (0 <kGXC ≦ 1), and kGX = 0 at V = VC2. GXS '= k12 {kGX.V' + (1-kGX) GXS} -F21 = m2.hP.GXS '+ m2.g.hP..DELTA..theta.-kS2..DELTA..theta. , And distribute appropriately to the front and rear axes.

F21F = kV8 · F21 F21R = kV9 · F21 (9) Here, kV8 and kV9 are adjustment gains. From the above results, the control amount (control oil amount of the hydraulic suspension mechanism) applied to each wheel VFL, VFR / VRL, VRR is expressed by the following equation.

VFL = -kV1 / F12-kV2 / F22 + kV5 / F32 + F11F-F
21F VFR = + kV1 / F12-kV2 / F22 + kV5 / F32 + F11F-F
21F VRL = −kV3 · F12 + kV4 · F22 + kV5 · F32 + F11R + F
21R VRR = + kV3 · F12 + kV4 · F22 + kV5 · F32 + F11R + F
21R (10) where kV1 to kV5 are constants. According to the above principle, the relative pitch displacement between the vehicle body and the axle is calculated from the vehicle height of each wheel by the relative displacement calculating means, and the longitudinal acceleration is calculated. The detection value of the longitudinal acceleration sensor is corrected by the correcting means in relation to the vehicle speed, and the pitch control torque is obtained by the vibration control amount calculating means from the pitch displacement and the corrected longitudinal acceleration, and the oil amount is controlled in accordance with the pitch control torque. The valve is driven to adjust the vehicle height by adjusting the amount of oil in the hydraulic suspension mechanism of each wheel, thereby keeping the vehicle body attitude substantially flat.

FIG. 5 is a flow chart of a control program for performing roll control and up / down control in addition to the above-described vehicle body pitch control by an electronic control device including a microcomputer. This control program is repeatedly executed at predetermined time intervals. p11
Pp21 represents the steps of the control program. The control program is started at p11, initialization is performed at p12, and the output hydraulic pressure pm of the hydraulic pump 4 is read by the hydraulic pressure monitoring means A at p13. If the output hydraulic pressure pm is larger than the predetermined value pc, the hydraulic control valve 12
When the output hydraulic pressure pm is smaller than the predetermined value pc, the hydraulic pressure control valve 12 is closed to increase the output hydraulic pressure pm and maintain the output hydraulic pressure pm at the predetermined value.

In p14, 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, and the lateral acceleration is obtained from the lateral acceleration sensor.
32, the vehicle speed from the vehicle speed sensor 31, and the steering angle from the steering angle sensor 30
, The relative displacement calculating means 35 calculates the relative roll displacement Δφ, pitch displacement Δθ, and vertical displacement Δx between the vehicle body and the axle at p15.

In step p16, the longitudinal acceleration correcting means 34 calculates the longitudinal acceleration multiplied by a correction coefficient which takes a value of 0 or less at low and high speeds and 1 or less at medium speeds in relation to changes in vehicle speed from the signals of the vehicle speed sensor 31 and the longitudinal acceleration sensor 29. . Moving load distribution calculation means 3 in p17
The ratios kCF and kCR of the cornering forces of the front and rear axes with respect to the entire cornering force are determined by 3.

In p18, the roll control torques F11F, F11R, F12, pitch control torques F21F, F21R, F22, and vertical control force F32 for keeping the vehicle body flat are obtained by the vibration control amount calculation means 39. p19
Then, the control oil amount VFL, VFR / VRL, VRR of each hydraulic suspension mechanism 19 is obtained by the oil amount calculating means 40. Control oil volume VFL, VFR with p20
-Based on VRL and VRR, each oil amount control valve 16 is driven, the oil amount of each 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 or a DC voltage corresponding to the control oil amount. 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. 6, kVL1 to kVL3 are gains, kS is the gain of the oil pressure sensor 17, GVL is the oil amount control valve 16
GACT is the transfer function of the hydraulic suspension mechanism.

[Effects of the Invention] As described above, the present invention provides a relative displacement calculating means for calculating a pitch displacement based on a signal from a vehicle height sensor for detecting a vehicle height of each wheel, and signals from the vehicle speed sensor and the longitudinal acceleration sensor. A longitudinal acceleration correction means for obtaining a longitudinal acceleration multiplied by a correction coefficient which takes a value of 1 or less in relation to a change in vehicle speed at low and high speeds, and a relative displacement amount calculating means and a longitudinal acceleration correcting means. A vibration control amount calculating means for obtaining a pitch control torque for keeping the vehicle body flat based on the signal; an oil amount calculating means for obtaining a control oil amount of the hydraulic suspension mechanism based on a signal from the vibration control amount calculating means; Since an oil amount control valve for adjusting the oil amount of each hydraulic suspension mechanism based on the signal of the amount calculating means is provided, the posture of the vehicle body is accurately detected,
The vehicle body posture can be kept almost flat at all times, and the ride comfort and steering stability are improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device of a body attitude control device according to the present invention, FIG. 2 is a hydraulic circuit diagram of a hydraulic suspension mechanism, and FIG. 3 shows a relationship between a vehicle speed and a correction coefficient for multiplying a longitudinal acceleration. FIG. 4 is a side view showing the pitch state of the vehicle body, and FIG.
FIG. 6 is a flowchart of a control program of the attitude control device, and FIG. 6 is a block diagram of a feedback control mechanism provided in a hydraulic suspension mechanism of each wheel. 16: oil amount control valve, 19: hydraulic suspension mechanism, 28: vehicle height sensor, 2
9: longitudinal acceleration sensor, 31: vehicle speed sensor, 33: moving load distribution calculation means, 34: longitudinal acceleration correction means, 35: relative displacement amount calculation means, 39: vibration control amount calculation means, 40: oil amount calculation means

Claims (1)

(57) [Claims] A relative displacement calculating means for obtaining a pitch displacement based on a signal from a vehicle height sensor for detecting a vehicle height of each wheel;
A longitudinal acceleration correction means for obtaining a longitudinal acceleration multiplied by a correction coefficient that takes a value of 0 at low speed and high speed and 1 or less at medium speed in relation to a change in vehicle speed from the signals of the vehicle speed sensor and the longitudinal acceleration sensor; Vibration control amount calculating means for obtaining a pitch control torque for keeping the vehicle body flat based on signals from the amount calculating means and the longitudinal acceleration correcting means, and a control oil amount for the hydraulic suspension mechanism based on a signal from the vibration control amount calculating means. And a hydraulic control valve for adjusting the hydraulic flow of each hydraulic suspension mechanism based on a signal from the hydraulic flow calculation means.