JP2000343922A - Estimating device for relative velocity between parts above and below spring in vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate a relative velocity between parts above and below a spring even in time of turning of a vehicle. SOLUTION: In this device, a roll angular velocity θd of a vehicle body is calculated on the basis of a steering angle δand a vehicle velocity V (S20), while a stroke velocity Voi of each wheel is calculated by calculation of an observer on the basis of a vehicle model according to vertical accelerations Gbfl-Gbrr (S30). In the case of a turning state of a vehicle (S40), heave components Vhf, Vhr of the stroke velocities Voi of the front wheels and the rear wheels are calculated on the basis of the stroke velocities Voi (S50), while roll components Vsf, Vsr of the stroke velocities Voi of the front wheels and the rear wheels accompanying steering are calculated (S60). A relative velocity Vpi between parts above and below a spring is calculated on the basis of the heave components Vhf, Vhr and the roll components Vsf, Vsr (S70).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension for a vehicle such as an automobile, and more particularly to an apparatus for estimating a relative speed between a sprung portion and a unsprung portion of a vehicle.

[0002]

2. Description of the Related Art As one of devices for estimating a relative speed between a sprung portion and a unsprung portion of a vehicle, for example, Japanese Patent Application Laid-Open No. 9-30931 filed by the present applicant and another applicant is disclosed.
As described in Japanese Patent Publication No. 6 (1994), the vehicle has a means for detecting a vertical acceleration on a spring, a vehicle vibration model having a sprung mass, a spring and a shock absorber, and estimates the detected vertical acceleration on the spring. A device configured to calculate a deviation from a vertical acceleration on a spring and to estimate a relative speed between the sprung portion and the unsprung portion by vibration analysis means based on the deviation in accordance with a vehicle vibration model is conventionally known. .

According to the relative speed estimating apparatus according to the prior proposal, an acceleration sensor which is less expensive than a stroke sensor may be provided for each wheel. The relative speed estimating device can be configured at a lower cost than when the relative speed between the two is estimated.

[0004]

In general, a conventional relative speed estimating apparatus for estimating a relative speed between a sprung portion and a unsprung portion based on a vertical acceleration on a sprung portion, as shown in FIG. 100, spring 102 and shock absorber 10
4, and a relative speed is estimated based on a motion equation expressed by the following equation 1 based on the vehicle model. Equation 1 below
, M is the mass of the sprung mass 100, C is the damping coefficient of the shock absorber 104, and K is the mass of the spring 102.
Is the spring constant. Xtd is the second derivative of the displacement X of the sprung mass 100 relative to the absolute space, that is, the vertical acceleration of the sprung mass 100, and xd is the differential value of the relative displacement x between the sprung mass 100 and the unsprung mass 108, ie, the sprung mass. And the relative speed between the unsprung. MXtd + Cxd + Kx = 0 (1)

When the vehicle is traveling straight, the relative speed xd can be accurately calculated by Xtd detected by the vertical acceleration detecting means and the observer based on the above equation (1). As shown in the figure, the load on the vehicle is increased by 100
, A load F due to the load movement acts, and in this case, the actual equation of motion is as shown in the following Expression 2. MXtd + Cxd + Kx = F (2)

However, in the conventional relative speed estimating apparatus, since the relative speed xd is calculated according to the above equation 1 even when the vehicle turns, the relative speed during the turning of the vehicle cannot be calculated accurately.

The present invention has been made in view of the above-mentioned problems in a conventional relative speed estimating apparatus configured to estimate a relative speed between a sprung portion and a unsprung portion based on a vertical acceleration on a sprung portion. The main object of the present invention is to eliminate an error component caused by a lateral load shift of a vehicle accompanying the turning of the vehicle, so that even during the turning of the vehicle, the distance between the sprung portion and the unsprung portion is reduced. It is to estimate the relative speed with high accuracy.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided a motor vehicle comprising: a vertical acceleration detecting means on a spring provided for each wheel; Means for estimating the relative speed between sprung and unsprung for each wheel based on acceleration, means for extracting only the vertical component from the relative speed based on the vertical acceleration on the spring,
Means for detecting a roll state quantity on the spring; means for estimating a relative speed between sprung and unsprung by a roll on the spring based on the roll state quantity on the sprung; Means for calculating the relative speed between the sprung and unsprung portions of each wheel based on the relative speed of the rolls.

According to the configuration of the first aspect, the relative speed between the sprung portion and the unsprung portion is estimated for each wheel on the basis of the vertical acceleration on the sprung portion. Only the directional component is extracted, and the relative speed between the sprung and unsprung by the roll on the spring is estimated based on the roll state amount on the spring, and the vertical component of the relative speed based on the vertical acceleration on the spring and Since the relative speed between the sprung and unsprung portions is calculated for each wheel based on the relative speed due to the roll on the sprung, an error component caused by the lateral load movement accompanying the turning of the vehicle is eliminated, As a result, even when the vehicle is turning, the relative speed between the sprung portion and the unsprung portion can be estimated with high accuracy.

According to the present invention, in order to effectively achieve the above-mentioned main object, in the configuration of the first aspect, the roll state amount on the spring is a roll angular velocity on the spring. (The configuration of claim 2).

According to the second aspect of the present invention, the roll state quantity on the spring is the roll angular velocity on the spring, and the roll angular velocity on the spring is proportional to the relative velocity between the left and right sprung and unsprung. Therefore, the relative speed between the sprung portion and the unsprung portion due to the roll on the sprung portion is estimated with high accuracy.

[0012]

According to a preferred aspect of the present invention, in the configuration of the first aspect, the means for calculating the relative speed includes a means for detecting turning of the vehicle,
When the vehicle is substantially in a straight running state, the relative speed between the sprung and unsprung states of each wheel estimated based on the vertical acceleration on the sprung is defined as the relative speed, and when the vehicle is in a turning state, the vertical component And the relative speed between the sprung and unsprung portions is calculated for each wheel based on the relative speed of the roll on the sprung (preferred embodiment 1).

According to a preferred aspect of the present invention, in the configuration of the first aspect, the means for extracting only the vertical component is a relative speed estimated on the left and right wheels based on a vertical acceleration on a spring. Is calculated as the vertical component of the relative speed (preferred mode 2).

According to another preferred embodiment of the present invention, in the configuration of the above-mentioned preferred embodiment 2, the means for extracting only the up-down direction component extracts the up-down direction component for the front wheel side and the rear wheel side. (Preferred embodiment 3).

According to another preferred aspect of the present invention, in the configuration of the second aspect, the means for detecting the roll state amount on the spring detects the steering angle and the vehicle speed, and at least the steering angular speed and the vehicle speed. It is configured to calculate the roll angular velocity on the spring based on the vehicle speed (preferred mode 4).

According to another preferred embodiment of the present invention, in the configuration of the above-mentioned preferred embodiment 4, the means for detecting the roll state amount on the spring calculates a steering angular velocity based on the steering angle, and calculates the steering angle. It is configured to calculate the roll angular velocity on the spring based on the steering angular velocity and the vehicle speed (preferred mode 5).

According to another preferred embodiment of the present invention, the means for estimating the relative speed between the sprung and the unsprung by the roll is a front wheel side and a rear wheel. It is configured to estimate the relative speed between sprung and unsprung by the roll on the side (preferred embodiment 6).

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing a preferred embodiment of a vehicle sprung unsprung relative speed estimating apparatus according to the present invention.

In FIG. 1, 10FL and 10FR denote left and right front wheels of the vehicle, respectively, and 10RL and 10RR denote left and right rear wheels which are driving wheels of the vehicle, respectively. The left and right front wheels 10FL and 10FR, which are both driven wheels and steered wheels, are driven by rack and pinion type power steering devices 14 driven in response to steering of the steering wheel 12 by the driver via tie rods 16L and 16R. Steered.

A vertical acceleration sensor 20FL which detects vertical accelerations Gbfl and Gbfr of the vehicle body at portions corresponding to the left and right front wheels 10FL and 10FR, respectively, is provided on the vehicle body 18 as a sprung body.
And 20FR, respectively, and the vertical acceleration G of the vehicle body at a portion corresponding to the left and right rear wheels 10RL and 10RR, respectively.
Vertical acceleration sensors 20RL and 2 for detecting brl and Gbrr
0RR is provided. The steering column to which the steering wheel 12 is connected is provided with a steering angle sensor 22 for detecting a steering angle δ.

As shown in the figure, the vertical acceleration sensors 20FL-2
A signal indicating the vertical accelerations Gbfl to Gbrr of the vehicle body 18 at a position corresponding to each wheel detected by the 0RR and a signal indicating the steering angle δ detected by the steering angle sensor 22 are input to the arithmetic and control unit 24. Further, a signal indicating the vehicle speed V detected by the vehicle speed sensor 26 is also input to the arithmetic and control unit 24.

Although not shown in detail in the figure, the arithmetic and control unit 24 has, for example, a CPU, a ROM, a RAM, and an input / output port device, which are generally connected to each other by a bidirectional common bus. Microcomputer of various configurations. Vertical acceleration sensor 20FL-20RR
Is the vertical acceleration Gbi (i = fl,
fr, rl, rr), and the steering angle sensor 22 calculates the steering angle δ with the left turning direction of the vehicle as positive.

The arithmetic and control unit 24 calculates the roll angular velocity θd of the vehicle body based on the steering angle δ and the vehicle speed V according to a flowchart shown in FIG.
By calculating the observer based on the vehicle model based on Gbrr, the stroke speed Voi of each wheel (i = fl, fr, rl,
rr).

When the vehicle is in a substantially straight running state, the arithmetic and control unit 24 controls the relative speed Vpi (i = fl, fr, i) between the sprung portion and the unsprung portion at the portion corresponding to each wheel.
rl, rr) is set to the stroke speed Voi of each wheel obtained by the calculation of the observer. When the vehicle is in a turning state, the heave components Vhf and Vhr of the stroke speed for the front wheel side and the rear wheel side are determined based on the stroke speed Voi. The roll components Vsf and Vsr of the stroke speed accompanying the steering are calculated for the front wheel side and the rear wheel side, and the heave component Vh is calculated.
Based on f, Vhr and roll components Vsf, Vsr, the relative speed V between the sprung and unsprung portions at the portion corresponding to each wheel.
Calculate pi.

In the illustrated embodiment, the signal indicating the relative speed Vpi between the sprung portion and the unsprung portion at the portion corresponding to each wheel calculated by the arithmetic and control unit 24 as described above is, for example, The relative speed Vpi is input to the damping force control device 30 for controlling the damping force of the variable damping force type shock absorbers 28FL to 28RR provided for the respective wheels. The relative speed Vpi may be used for arbitrary control of the vehicle. The arithmetic and control unit 24 may be a part of a control unit that controls the vehicle using the relative speed Vpi, such as the damping force control unit 30.

Next, a relative speed calculation routine in the illustrated embodiment will be described with reference to the flowchart shown in FIG. The arithmetic control according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals.

First, at step 10, signals indicating the vertical accelerations Gbfl to Gbrr of the vehicle body 18 are read, and at step 20, a signal known in the art based on the steering angle δ and the vehicle speed V is read. The roll angular velocity θd of the vehicle body is calculated according to a function represented by the following equation 3. In the following formula 3, δd is a time differential value (steering angular velocity) of the steering angle δ. θd = f (δ, δd, V) (3)

In step 30, based on the vertical accelerations Gbfl to Gbrr of the vehicle body 18, the stroke speed Voi of each wheel (i = fl, i = fl,
fr, rl, rr) are calculated.

In step 40, it is determined whether or not the vehicle is in a turning state. When a negative determination is made, the process proceeds to step 80, and when an affirmative determination is made, the process proceeds to step 50. The determination as to whether the vehicle is in a turning state is made, for example, by the sum | θd | + | of the absolute value of the roll angular velocity θd of the vehicle body and the absolute value of the roll angle θ of the vehicle body calculated by the same equation as the above equation 3. The determination may be made by determining whether θ | is equal to or greater than the reference value.

In step 50, the heave components Vhf and Vhr of the stroke speed are calculated for the front wheels and the rear wheels on the basis of the stroke speeds Voi of the respective wheels according to the following equations 4 and 5, respectively. Vhf = (Vofl + Vofr) / 2 (4) Vhr = (Vorl + Vorr) / 2 (5)

In step 60, the coefficients for the front wheel side and the rear wheel side are Kf and Kr, respectively, and the following equation (6) is used.
The roll components Vsf and Vsr of the stroke speed are calculated for the front wheel side and the rear wheel side according to (7) and (7). Vsf = Kfθd (6) Vsr = Krθd (7)

In step 70, the heave component Vhf,
Based on Vhr and roll components Vsf, Vsr, the relative speed Vpi (i = fl, fr, rl, rr) between the sprung and unsprung portions at the portion corresponding to each wheel is calculated according to the following equation (8). . Vpfl = Vhf + Vsf Vpfr = Vhf-Vsf Vprl = Vhr + Vsr Vprr = Vhr-Vsr (8)

In step 80, the relative speed Vpi between the sprung portion and the unsprung portion at the portion corresponding to each wheel is set to the stroke speed Voi calculated by the observer.

In step 90, a signal indicating the relative speed Vpi calculated in step 70 or 80 is output to the damping force control device 30, and thereafter the process returns to step 10.

Thus, according to the illustrated embodiment, in step 20, the roll angular velocity θd of the vehicle body is calculated based on the steering angle δ and the vehicle speed V, and in step 30, the vehicle body 1
8, the stroke speed Voi of each wheel is calculated by the observer based on the vehicle model based on the vertical accelerations Gbfl to Gbrr.
Is calculated.

Then, in step 40, it is determined whether or not the vehicle is in a turning state. If it is determined that the vehicle is in a substantially straight running state, step 80 is executed.
In the above, the relative speed Vpi between the sprung portion and the unsprung portion at the portion corresponding to each wheel is set to the stroke speed Voi obtained by the operation of the observer.

On the other hand, when it is determined that the vehicle is in a turning state, the heave components Vhf and Vhr of the stroke speed for the front wheel side and the rear wheel side are determined in step 50 based on the stroke speed Voi of each wheel. In step 60, the roll components Vsf and Vsr of the stroke speed are calculated for the front wheel side and the rear wheel side, and in step 70, the heave components Vhf, Vhr and the roll component Vs are calculated.
Based on f and Vsr, the relative speed Vpi between the sprung portion and the unsprung portion at the portion corresponding to each wheel is calculated as the sum of the heave component and the roll component.

In general, the amount of load reduction on the turning inner wheel side and the amount of load increase on the turning outer wheel side due to the load movement accompanying the turning of the vehicle are equal. Heave component of stroke speed Vhf
And Vhr do not include an error component due to load movement. Further, the roll components Vsf and Vsr of the stroke speed on the front wheel side and the rear wheel side calculated based on the roll angular velocity θd of the vehicle body do not include an error component due to the load movement.

Therefore, according to the illustrated embodiment, the relative speed Vpi between the sprung portion and the unsprung portion at the portion corresponding to each wheel can be accurately calculated without being adversely affected by the load movement even when the vehicle turns. can do.

In particular, according to the illustrated embodiment, step 4
At 0, it is determined whether or not the vehicle is in a turning state, and when it is determined that the vehicle is not in a turning state, at step 80, the sprung mass at a portion corresponding to each wheel is determined. Since the relative speed Vpi between the unsprung portion and the unsprung portion is set to the stroke speed Voi obtained by the operation of the observer, the sprung portion and the spring during the straight running of the vehicle are compared with the case where steps 40 and 80 are omitted. It is possible to accurately calculate the relative speed Vpi between the lower position and the lower position.

According to the illustrated embodiment, the roll component of the stroke speed based on the roll angular velocity θd of the vehicle body is also calculated for each of the front wheel side and the rear wheel side, so that the roll component is calculated only for the entire vehicle. , The relative speed Vpi can be calculated accurately.

In the above, the present invention has been described in detail with respect to a specific embodiment. However, the present invention is not limited to the above embodiment, and various other embodiments are included in the scope of the present invention. It will be clear to those skilled in the art that is possible.

For example, in the above embodiment, whether the vehicle is in a turning state is determined by the roll angular velocity θd of the vehicle.
Is described based on the sum of the absolute value of the vehicle body and the absolute value of the roll angle θ of the vehicle body. However, the determination may be made based on the lateral acceleration or the yaw rate of the vehicle body, or the vehicle body may be estimated based on the steering angle and the vehicle speed. May be determined on the basis of the lateral acceleration or the yaw rate.

In the above-described embodiment, the roll component of the stroke speed accompanying the steering is the roll angular speed θ of the vehicle body.
Although it is calculated based on d, it may be calculated based on a turning state quantity other than the roll angular velocity θd, and the roll components of the stroke speed based on the roll angular velocity θd of the vehicle body may also be calculated on the front wheel side and the rear wheel side. Although the calculation is performed for each of them, the roll component may be modified to be calculated only for the entire vehicle.

[0046]

As is apparent from the above description, according to the first aspect of the present invention, an error component caused by a lateral load movement of the vehicle accompanying the turning of the vehicle is eliminated. The relative speed between the sprung portion and the unsprung portion can be estimated with high accuracy even during turning, and according to the configuration of claim 2, the relative speed between the sprung portion and the unsprung portion due to the roll on the sprung portion can be estimated. The relative speed can be estimated with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one preferred embodiment of a vehicle sprung unsprung relative speed estimation device according to the present invention.

FIG. 2 is a flowchart showing a sprung unsprung relative speed estimation routine in the illustrated embodiment.

FIG. 3 is an explanatory view showing a single-wheel vehicle model when the vehicle travels straight.

FIG. 4 is an explanatory view showing a single-wheel vehicle model when the vehicle is turning.

[Explanation of symbols]

 Reference Signs List 18 vehicle body 20FL-20RR vertical acceleration sensor 22 steering angle sensor 24 arithmetic control device 26 vehicle speed sensor 28FL-28RR shock absorber 30 damping force control device

Claims (2)

[Claims] 1. A vertical acceleration detection means on a spring provided for each wheel, and a means for estimating a relative speed between a sprung and unsprung state for each wheel based on the vertical acceleration on a spring. A means for extracting only a vertical component from a relative speed based on the vertical acceleration on the spring, a means for detecting a roll state amount on the spring, a sprung spring and a spring based on the roll state amount on the spring. Means for estimating the relative speed between the lower part and the means for calculating the relative speed between the sprung part and the unsprung part for each wheel based on the vertical component and the relative velocity of the roll on the sprung part; A sprung unsprung relative speed estimating device for a vehicle. 2. The apparatus according to claim 1, wherein the roll state quantity on the spring is a roll angular velocity on the spring.