JP2574761B2 - Vehicle suspension control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable suspension control method for a vehicle, and more particularly to a suspension control method suitable for improving ride comfort by reducing a change in attitude.

[Conventional technology]

Conventionally, the suspension control method is usually a soft suspension, as described in Automotive Technology Vol. 39, No. 1 (1985), and a hard suspension is used only when a change in attitude or a decrease in steering performance occurs. Is controlled. However, no consideration has been given to the effect of changes in the natural frequency of the vehicle due to changes in the load weight and changes in the input frequency component from the road surface on ride comfort.

Further, vehicle control and damping force control / spring constant control were performed independently.

Nissan Motor: Super Sonics Suspension (Preprint of the Automotive Engineering Academic Lectures May 1985)
As described in, the ultrasonic wave is radiated from the lower part of the car body, and the reflected wave from the road surface is detected to know the unevenness of the road surface, and adjust the damping force of the suspension according to the unevenness state Things.

[Problems to be solved by the invention]

In the prior art, firstly, there is a problem that the change in the natural frequency of the vehicle due to the change in the loaded weight and the influence on the ride comfort due to the change in the input frequency component from the road surface are not considered.

Second, there is a problem in that cooperative control is not taken into consideration at the time of anti-roll, anti-dive, anti-squat and the like.

Thirdly, there is a problem in that no consideration is given to the effects of crosswinds and changes in wind pressure when a car exits a tunnel or when a car is about to be cut through.

It is an object of the present invention to achieve an improvement in ride comfort by adapting to changes in the loaded weight of a vehicle and changes in road surface conditions, and to changes in the posture during roll and pitch movements, and furthermore, the vehicle may pass through a tunnel or a cut-through. It is an object of the present invention to provide a suspension control method for detecting in advance the timing of departure from the vehicle and automatically adjusting the characteristics of the suspension beforehand so as to cope with an expected cross wind or wind pressure change.

[Means for solving the problem]

Conventional suspension control lacks consideration of changes in the natural frequency of the vehicle and changes in the input frequency component from the road surface to the vehicle. The present invention compensates for this by changing the vehicle gross weight, damping coefficient and spring constant (vehicle center of gravity motion displacement).
Attention is paid to the sensitivity of the transfer function of / (input from the road surface).

In addition, the suppression of roll and pitch movements in the conventional suspension control only controls the sensibility and the spring constant, and does not perform control in coordination with the vehicle height adjustment function. The basic concept of the present invention devised is to predict the rotational motion from the steering wheel steering angle and the vehicle speed, and perform attitude control, spring constant and damping coefficient control based on the predicted value.

Further, in the present invention, the intensity and frequency (spectrum) intensity distribution of the sound of the vehicle traveling sound reflected from an object around the road (front and rear, left and right and up and down directions) are determined by the vehicle when the geometric shape and material of the reflecting object are determined. The phenomenon that some change is made when approaching the vicinity of the changing boundary is used. The reflected sound mainly from the front and side is collected by a microphone attached to the automobile, and the signal is analyzed by a general statistical processing means for time series events to detect the change of the reflected sound. If a change is detected, it is assumed that there is a high possibility of crosswind or wind pressure change in the front of the changing boundary such as the geometrical shape of the reflecting object, and the change is made before the vehicle reaches the boundary. Adjust the suspension characteristics so that they are not strongly affected by crosswinds or wind pressure changes.

[Action]

In the present invention, by focusing on the sensitivity of the transfer function,
The center of gravity of the vehicle is moderated, the amount of rotational displacement is suppressed by controlling the spring constant and the like in accordance with the rotational movement predicted from the steering wheel angle and the vehicle speed. By adjusting, it becomes possible to cope with a situation change at a tunnel exit or the like.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to FIG.

For simplicity of description, the vertical movement of the vehicle will be taken as an example. The same can be realized when considering suppression of pitching and rolling.

In FIG. 1, the sensor 1, the actuator 3, and the computer mounted on the vehicle are written outside the vehicle 2 in order to make the explanation easy to understand. In fact, they are mounted on the vehicle.

Based on the gross vehicle weight based on the height 11 of the four-wheel springs at the time of starting the vehicle, and transfer function change information of (vehicle center of gravity road height) / (input from road surface) with respect to the gross vehicle weight change in FIG. , And estimate the transfer function by linear interpolation. During traveling, input time series data from the road surface is calculated based on the time series data of the height of the sprung parts of the four wheels, and the input time series data is subjected to FFT (Fast Fourier Transform) at frequencies 1/2,
The components of 1,2,4,8,16 (Hz) are calculated and estimated. Let them be β
_{1/2, β 1, β 2,} β 4, β 8, represented by beta _16. Next, based on FIG. 3 (transfer function change diagram due to damping coefficient change) and FIG. 4 (transfer function change diagram due to spring constant change), gain G _i , And these are Can be approximated. Here, j (= 1,..., 4) represents each wheel portion, and G ₁゜: reference weight reference spring constant K _j゜, reference damping coefficient C _j゜, j = 1,
... 4, transfer function gain at frequency i, ΔW: the amount of change in the vehicle weight from the reference value, ΔK _j : the amount of change in the spring constant of the j wheel portion from the reference value, and ΔC _j : the amount of change in the damping coefficient of the j wheel portion from the reference value. Here, the next evaluation function PI, within the range achievable by the actuator, α _i : A weight for each frequency, a spring constant and a damping coefficient for minimizing are determined by a linear programming method with respect to a constraint, and this is set as an operation amount. Based on this operation amount, the actuator 3 is operated to obtain a desired spring constant,
Realize the damping coefficient.

Since the manipulated variable is obtained by the linear programming method from Equations (1) and (2), the manipulated variable that minimizes the evaluation function can be obtained in the same manner even when the evaluation function includes a term for suppressing pitching or rolling. . In this case, however, the sensitivity of each frequency to the (pitch angle) / (pitch torque input), (roll angle) / (roll torque inlet) spring constant, damping coefficient, roll moment and pitch moment (second to second).
(Corresponding to Fig. 4), and the frequency components of the pitch torque and the roll torque from the road surface are estimated from the change in the vehicle speed and the change in the sideslip angle. Estimate the change.

If the actuator is not continuous but has only discrete values, the optimal operation amount is calculated by the combination optimization calculation.

Next, another embodiment of the present invention will be described with reference to FIG.

For simplicity, only the anti-roll control will be described. Anti-dive and anti-squat control can be realized in a similar manner.

The details of the functions of the computer 4 are as follows. The roll motion predicting unit predicts that a roll motion will occur if α · VT ₀ (judgment reference value) (3) based on detailed information on the steering wheel steering angle α and the vehicle speed V, and determines the right and left of the wheel stroke due to the roll motion. The difference δ ′ is predicted by linear interpolation from the relationship shown in FIG. However, the difference between right and left wheel stroke [delta] by the change in the steering angle α and the vehicle speed so that changes every moment, using the maximum value [delta] _max of this value, it calculates an operation amount of Sasupenshiyon. In the manipulated variable calculation unit, if α · VT ₁ (judgment reference value) (4), the manipulated variable is determined so that the spring constant K and the damping coefficient C are hardened, and from the time when the equation (3) holds, Turn on the vehicle height control on each wheel. However, if there was Setsutsu the handle to the left (right), lower left (right) side of the vehicle only δmm / 2, the right (left) side so as to lower only [delta] _max / 2. For this purpose, the reference operation time T _N of the actuator is shown in FIG.
T _N = f ⁻¹ (δ) (5) However, since the response time of the all motion changes depending on the angular velocity of the steering angle, the actual operation time T of the vehicle height control device is: It is. T ₀ , T ₁ , and β in Equations (3), (4), and (6) are design parameters of this control system, and should be set for each vehicle type. If the roll motion returns and the roll angle has the opposite sign for a certain period of time or longer, the anti-roll vehicle height control is released, the left and right vehicle heights are made equal, and the spring constant and damping coefficient are set to normal. It is a thing to return. If the roll motion returns within the time T during the vehicle height control, cancellation of the vehicle height control has priority.

Another embodiment of the present invention will be described with reference to FIG.
This embodiment includes a microphone 81, a reflected sound change detection unit 82, a storage unit 83, a suspension control unit 84, and a vehicle speed detector 88.

In this embodiment, the microphone 81 is connected to the vehicle body 6.
, And collects traveling reflection sounds mainly from the front and side, and sends a signal 811 thereof to the reflection sound change detection unit 82. At 82, the signal 811 is input to the storage unit 83 via the signal line 812, and the past reflected sound signals stored in the storage unit 83 are extracted via the signal line 812, and the intensity and / or Alternatively, a statistical comparison is made from the viewpoint of frequency intensity distribution, and if there is a difference exceeding a predetermined reference in the comparison result in consideration of the vehicle speed signal 815 input from the vehicle speed detector 88, the suspension control unit 84 is informed accordingly. Is transmitted via the signal line 13.

When the suspension control unit 84 receives the information that the temporal change of the reflected sound is equal to or more than the reference, it sends a control signal 814 to the variable suspension 85 that connects the axle 87 and the vehicle body 86,
Change the characteristics of the suspension so that it is more resistant to crosswinds and changes in wind pressure.

When the time change of the reflected sound is equal to or less than the reference, the suspension control unit 84 sends a control signal 814 to the variable suspension 85 so as to change the characteristics of the suspension so as to improve the riding comfort.

According to the present embodiment, when the microphone is mounted on the upper part of the vehicle body, the ratio of the reflected sound (indirect sound) from the structure on the side of the road or in front of the road is higher than the direct sound of the running sound emitted from the tire, and the entrance and exit of the tunnel or through , Etc., has the effect of increasing the detection capability.

In addition, since the vehicle speed detector is provided, the time change of the reflected sound can be detected in consideration of the vehicle speed, and it is possible to roughly estimate the boundary position where the geometrical shape of the reflecting object changes, so that the time timing of the control can be reduced. This has the effect of making it easier to take.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, since the vibration control of the vehicle weighted according to frequency can be performed by adapting to the natural vibration characteristic change of the vehicle and the change of the input frequency component from the road surface to the vehicle, there is an effect of improving the riding comfort.

In addition, since not only the change in the spring constant and the damping coefficient but also the vehicle height of each wheel can be controlled at the same time, there is little change in the posture and there is an effect of improving the riding comfort.

In addition, since the vehicle can detect tunnels, cut-throughs, bridges, etc. before the vehicle reaches them, the adverse effect on the steering stability of cross wind and wind pressure changes at the exit of tunnels, cut-off entrances, etc. There is an effect that control can be avoided in advance.

In addition, the method according to the present invention is simpler than a method of detecting a forward tunnel or a cut-through by performing pattern recognition from an obtained image by providing an optical vision to a vehicle, and is faster and cheaper than the method of detecting a vehicle. This has the effect of being strong against noise such as vibration.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of the suspension control method of the present invention, and FIG. 2 is a gain curve diagram of a transfer function of (vertical displacement of vehicle center of gravity) / (input from road surface) corresponding to three types of vehicle weights. 3 and 4 are gain curve diagrams of the same transfer function for three types of damping coefficients and three types of spring constants, respectively. FIG. 5 is an explanatory diagram of the suspension control method of the present invention, and FIG. Fig. 7 shows the relationship between the steering angle and the vehicle speed during the steady circular turning of the car and the difference between the left and right wheel strokes. Fig. 7 shows the relationship between the expansion and contraction of the vehicle height control actuator and the required time under the reference vehicle load. FIG. 1 is a configuration diagram when an embodiment of a suspension automatic control method according to the present invention is applied to an automobile. 21 …… (0.8 × reference vehicle weight) gain curve, 22 ……
Gain curve at reference vehicle weight, 23 …… (1.2 × reference vehicle weight), gain curve, 31… (0.5 × reference damping coefficient)
Gain curve at the time, 32 ... gain curve at the reference attenuation coefficient,
33 …… (1.5 × reference attenuation coefficient) gain curve, 41 ……
Gain curve when (0.5 x reference spring constant), 42 ... Gain curve when reference spring constant, 43 ... (1.5 x reference spring constant)
Time gain curve.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-37511 (JP, A) JP-A-57-160707 (JP, A) JP-A-60-203517 (JP, A) JP-A-62 61811 (JP, A)

Claims (2)

(57) [Claims] 1. A method for measuring a change amount of a characteristic for determining a motion state of a vehicle from a reference amount in advance and obtaining a gain curve indicating a relationship between a gain and a frequency for each predetermined amount of characteristics, When the vehicle is in a running state, time-series data representing the motion state of the vehicle is measured, and from the time-series data, input time-series data for the vehicle from the road surface is calculated.From the input time-series data, A plurality of frequency components are extracted, and the gain for each frequency component is changed from the reference amount of the gain, the gain curve, and the previously measured characteristic when the characteristic is a reference amount and the corresponding frequency component is used. A suspension control method for the vehicle, wherein the suspension is controlled based on the determined gain and the extracted frequency component. 2. The suspension control method for a vehicle according to claim 1, wherein the characteristics that determine the motion state of the vehicle include a weight of the vehicle, a damping force of the suspension, a spring constant of the suspension, A suspension control method for a vehicle, comprising at least one of a roll moment of the vehicle and a pitch moment of the vehicle.