JP6485295B2 - Vehicle center of gravity height estimation device - Google Patents

Description

  The present invention relates to a vehicle center-of-gravity height estimation device that estimates the height of the center of gravity of a vehicle.

  Conventionally, a method for estimating the height of the center of gravity of a vehicle by measuring a roll angular velocity on a spring of the vehicle and specifying a roll resonance frequency based on the measured sprung roll angular velocity of the vehicle is known. Patent Document 1 discloses a method for specifying the roll resonance frequency based on the frequency characteristics of the sprung roll angular velocity.

Japanese Patent No. 4517107

  However, when the roll resonance frequency is estimated using only the roll angular velocity on the spring, there is a problem that it is easily influenced by the state of the road surface on which the vehicle travels. For example, the tendency of the vehicle to swing differs depending on the unevenness of the road surface, so that when the road surface state changes, the frequency spectrum of the roll angular velocity on the spring changes, and the estimation accuracy of the roll resonance frequency decreases. There was a problem. As a result, the accuracy of estimating the height of the center of gravity of the vehicle has also decreased.

  Therefore, the present invention has been made in view of these points, and an object of the present invention is to provide a vehicle center-of-gravity height estimation device that can improve the estimation accuracy of the center of gravity of the vehicle.

  A vehicle center-of-gravity height estimation device according to the present invention includes a weight specifying unit that specifies a sprung weight, a rigidity specifying unit that specifies a vehicle roll stiffness, a sprung angular velocity measuring unit that measures a sprung angular velocity, and an unsprung angular velocity. An unsprung angular velocity measuring means for measuring, a resonance frequency identifying means for identifying a roll resonance frequency on the spring based on a frequency component of a transfer function indicating a relationship between the unsprung angular velocity and the unsprung angular velocity; Estimating means for estimating the height of the center of gravity based on the weight, the vehicle roll rigidity, and the roll resonance frequency specified by the resonance frequency specifying means. In this way, the vehicle center-of-gravity height estimation device can remove the influence of the state of the road surface on which the vehicle travels, and therefore can estimate the center-of-gravity height of the vehicle with high accuracy.

  The resonance frequency specifying means, for example, based on the frequency component of the transfer function obtained by dividing the cross spectral density function of the unsprung angular velocity and the unsprung angular velocity by the power spectral density function of the unsprung angular velocity, Specify the roll resonance frequency. By doing in this way, the vehicle center-of-gravity height estimation device can effectively remove the influence of the state of the road surface on which the vehicle travels.

  The resonance frequency specifying means may specify the frequency having the largest frequency component of the transfer function as the roll resonance frequency. By doing in this way, the vehicle center-of-gravity height estimation device can easily estimate the center-of-gravity height of the vehicle in which the influence of the road surface state is suppressed.

  The sprung angular velocity measuring means is provided, for example, on a vehicle body frame, and the unsprung angular velocity measuring means is provided on the axle closest to the sprung angular velocity measuring means. By arranging the sprung angular velocity measuring means and the unsprung angular velocity measuring means in this way, it is possible to reduce the influence of the difference in roll motion between the front part and the rear part of the vehicle due to the twisting of the vehicle.

  According to the present invention, it is possible to improve the estimation accuracy of the height of the center of gravity of the vehicle.

It is a mimetic diagram of the state which looked at vehicles S concerning this embodiment from back. It is a figure which shows the structure of a gravity center height estimation apparatus. It is a figure which shows the frequency characteristic of a transfer function. It is a figure which shows the frequency characteristic of a sprung angular velocity.

[Overview of this embodiment]
FIG. 1 is a schematic diagram of the vehicle S according to the present embodiment as viewed from behind. The vehicle S is, for example, a truck whose position of the center of gravity changes depending on the state of the load. The vehicle S has a vehicle body chassis 1 and a load portion 2 on a spring. The load part 2 accommodates a load carried by the vehicle S. Further, the vehicle S includes an axle (axle) 3, a differential (differential device) 4, and tires 5 (right tire 5 </ b> R and left tire 5 </ b> L) under the spring.

  Air suspensions 11 (11R, 11L) are provided between the sprung and unsprung parts. The vehicle body chassis 1 is provided with a sprung angular velocity measuring unit 12, and the axle 3 or the differential 4 is provided with an unsprung angular velocity measuring unit 13. The sprung angular velocity measuring unit 12 is an angular velocity sensor that measures the roll angular velocity of the sprung portion. The unsprung angular velocity measuring unit 13 is an angular velocity sensor that measures the roll angular velocity of the unsprung portion.

  The sprung angular velocity measuring unit 12 and the unsprung angular velocity measuring unit 13 are provided at substantially the same position in the traveling direction of the vehicle S, that is, in the direction orthogonal to the vehicle body width. For example, the unsprung angular velocity measuring unit 13 is provided on the axle 3 or the differential 4 closest to the position where the unsprung angular velocity measuring unit 12 is provided.

The “synthetic centroid point” in FIG. 1 indicates the position of the centroid when the main body of the vehicle S and the load accommodated in the load portion 2 are combined. In this specification, represents the height of the combined center of gravity point H1, the height of the roll center H _rc, the distance from the roll center to combined center of gravity point and h = H1-H _rc.

ここで、Ｋ_φｔは車両Ｓのロール剛性である。ロール剛性とは、ロール角を単位角だけ変化させるために必要なローリングモーメントの大きさである。 _Assuming that the mass m on the spring is concentrated on the composite barycentric point, the roll resonance frequency _fφx is expressed by the following equation (1).

Here, K _φt is the roll rigidity of the vehicle S. Roll rigidity is the magnitude of the rolling moment required to change the roll angle by a unit angle.

When the above formula (1) is developed, the distance h from the roll center to the composite barycentric point is obtained from the following formula (2).

The vehicle roll stiffness K _φt can be calculated as a value unique to the vehicle S that is not affected by the loading state. The sprung mass m can be estimated based on the air spring internal pressure of the air suspension 11 or the like. Therefore, if the roll resonance frequency _fφx is known, h can be calculated, and the vehicle center-of-gravity height can be estimated by adding the height H _rc of the roll center to h.
Hereinafter, the configuration and operation of the center-of-gravity height estimation apparatus 10 that estimates the center-of-gravity height of the vehicle S will be described in detail.

[Configuration and Operation of Center of Gravity Height Estimation Device 10]
FIG. 2 is a diagram illustrating the configuration of the center-of-gravity height estimation apparatus 10.
The center-of-gravity height estimation device 10 includes an air suspension 11, an unsprung angular velocity measurement unit 12, an unsprung angular velocity measurement unit 13, a storage unit 14, and a control unit 15. The storage unit 14 is a storage medium such as a ROM, a RAM, and a hard disk, for example. The storage unit 14 stores a program executed by the control unit 15, data used for the control unit 15 to estimate the height of the center of gravity of the vehicle, and the like. The storage unit 14 stores, for example, the vehicle roll rigidity _Kφt in association with the type or model name of the vehicle S.

  The control unit 15 is a CPU, for example. The control unit 15 estimates the vehicle height based on information input from the air suspension 11, the sprung angular velocity measuring unit 12, and the unsprung angular velocity measuring unit 13 by executing the program stored in the storage unit 14. To do. The storage unit 14 and the control unit 15 are mounted on a printed circuit board, and the control unit 15 is connected to the air suspension 11, the sprung angular velocity measuring unit 12, and the unsprung angular velocity measuring unit 13 by a cable or wirelessly.

The control unit 15 functions as a weight specifying unit 151, a rigidity specifying unit 152, a resonance frequency specifying unit 153, and an estimating unit 154 by executing a program.
The weight specifying unit 151 specifies the weight on the spring based on the internal pressure value of the air spring input from the air suspension 11. For example, the weight specifying unit 151 specifies the weight on the spring by referring to a weight calculation table stored in the storage unit 14 and associated with the internal pressure value and the weight.
The stiffness specifying unit 152 specifies the roll stiffness of the vehicle S by reading the vehicle roll stiffness K _φt stored in the storage unit 14.

  The resonance frequency specifying unit 153 specifies the roll resonance frequency on the spring based on the frequency component of the transfer function indicating the relationship between the sprung angular velocity and the unsprung angular velocity. The resonance frequency specifying unit 153 can calculate the transfer function by dividing the cross spectral density function of the unsprung angular velocity and the unsprung angular velocity by the power spectral density function of the unsprung angular velocity. In addition to the spectral density function, the resonance frequency specifying unit 153 may use, for example, a time series analysis method (AR method) or an Eigensystem Realization Algorithm (ERA method) using an autoregressive process.

  The resonance frequency specifying unit 153 can remove a road surface state that affects both the sprung angular velocity and the unsprung angular velocity by specifying the roll resonance frequency based on the transfer function. Therefore, the resonance frequency specifying unit 153 can specify the roll resonance frequency determined based on the characteristics of the vehicle S and the state of the load with high accuracy regardless of the road surface state.

  FIG. 3 is a diagram illustrating the frequency characteristics of the transfer function. In FIG. 3, the horizontal axis indicates the frequency, and the vertical axis indicates the magnitude of the transfer function. As shown in FIG. 3, one peak appears in the frequency characteristic of the transfer function. The frequency at which this peak occurs, that is, the frequency at which the frequency component of the transfer function is maximized corresponds to the roll resonance frequency. Therefore, the resonance frequency specifying unit 153 can specify the roll resonance frequency by specifying the peak frequency having the largest frequency component in the frequency characteristic of the transfer function.

The estimating unit 154 estimates the height of the center of gravity based on the sprung weight, the vehicle roll rigidity, and the calculated roll resonance frequency. Specifically, the estimation unit 154 calculates the sprung weight acquired by the weight specifying unit 151, the vehicle roll rigidity acquired by the stiffness specifying unit 152, and the resonance frequency specifying unit 153 in the above equation (2). By substituting the roll resonance frequency, the distance h from the roll center to the composite barycentric point is calculated. Then, the center of gravity height is estimated by adding the height H _rc of the roll center to the distance h.

  The estimation unit 154 may output information based on the estimated center-of-gravity height to the driver's seat monitoring device. For example, when the height of the center of gravity is larger than a predetermined height, the estimation unit 154 can alert the driver by outputting warning information to the monitor device.

[Comparative example]
FIG. 4 is a diagram illustrating the frequency characteristics of the sprung angular velocity. The horizontal axis in FIG. 4 indicates the frequency, and the vertical axis indicates the rolling amplitude (roll angular velocity) on the spring. In FIG. 4, the solid line indicates the rolling amplitude when the vehicle S travels on the road surface A, and the broken line indicates the rolling amplitude when the vehicle S travels on the road surface B. In the conventional method, the roll resonance frequency is specified using the frequency characteristics of the rolling amplitude shown in FIG.

While the vehicle S is traveling on the road surface A, the roll angular velocity frequency at which the rolling amplitude becomes maximum is _fφx1 . On the other hand, while the vehicle S is traveling on the road surface B, the roll angular velocity frequency at which the rolling amplitude becomes maximum is _fφx2 . If unevenness of the road surface B is finer than the unevenness of the road surface A, the rolling amplitude at high frequencies f _Faiekkusu2 than f _Faiekkusu1 is considered to be greatest. Therefore, when the conventional method is used, the frequency at which the rolling amplitude becomes maximum varies depending on the road surface condition, and it is difficult for the resonance frequency specifying unit 153 to specify the roll resonance frequency with high accuracy.

[Effect in this embodiment]
As described above, in the center-of-gravity height estimation device 10 according to the present embodiment, the resonance frequency specifying unit 153 is based on the frequency component of the transfer function indicating the relationship between the sprung angular velocity and the unsprung angular velocity. The roll resonance frequency is specified. Then, the estimating unit 154 estimates the height of the center of gravity based on the vehicle roll rigidity, the sprung weight, and the roll resonance frequency specified by the resonance frequency specifying means. By doing in this way, since the influence of the state of the road surface on which the vehicle S travels can be removed, the estimation unit 154 can estimate the height of the center of gravity of the vehicle S with high accuracy.

  The sprung angular velocity measuring unit 12 is provided in the vehicle body chassis 1, and the unsprung angular velocity measuring unit 13 is provided on the axle closest to the sprung angular velocity measuring unit 12. Since the sprung angular velocity measuring unit 12 and the unsprung angular velocity measuring unit 13 are arranged in this manner, the influence of the difference in roll motion between the front part and the rear part of the vehicle due to the twisting of the vehicle can be reduced. The unit 153 can calculate a transfer function with higher accuracy.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  For example, in the above description, the case where the air suspension 11 is provided between the sprung portion and the unsprung portion has been described. However, another type of suspension may be provided.

  Further, in the above description, the case where the unsprung angular velocity measuring unit 13 measures the roll angular velocity of the unsprung portion using the angular velocity sensor has been described. However, the unsprung angular velocity measuring unit 13 uses other means, The roll angular velocity of the unsprung portion may be measured. For example, the unsprung angular velocity measuring unit 13 may measure the roll angular velocity of the unsprung portion using height sensors (sensors for detecting the height) provided on the left and right of the vehicle S. In this case, the unsprung angular velocity measurement unit 13 uses the left and right height sensors to measure the change in the distance between the spring upper part (frame) and the unsprung part (axle 3), and between the measurement result and the left and right height sensors. Based on the distance, the unsprung roll angular velocity can be measured.

DESCRIPTION OF SYMBOLS 1 Car body chassis 2 Loading part 3 Axle 4 Differential 5 Tire 10 Center of gravity height estimation apparatus 11 Air suspension 12 Unsprung angular velocity measurement part 13 Unsprung angular velocity measurement part 14 Storage part 15 Control part 151 Weight specific part 152 Stiffness specific part 153 Resonance frequency Specific part 154 Estimation part S Vehicle

Claims (4)

A weight identifying means for identifying the sprung weight;
Rigidity specifying means for specifying vehicle roll rigidity;
Sprung angular velocity measuring means for measuring sprung angular velocity;
Unsprung angular velocity measuring means for measuring unsprung angular velocity;
A resonance frequency specifying means for specifying a roll resonance frequency on the spring based on a frequency component of a transfer function indicating a relationship between the sprung angular velocity and the unsprung angular velocity;
Estimating means for estimating the height of the center of gravity based on the sprung weight, the vehicle roll rigidity, and the roll resonance frequency specified by the resonance frequency specifying means;
A vehicle center-of-gravity height estimation device. The resonance frequency specifying means is based on a frequency component of the transfer function obtained by dividing a cross spectral density function of the unsprung angular velocity and unsprung angular velocity by a power spectral density function of the unsprung angular velocity. Identify the frequency,
The vehicle center-of-gravity height estimation apparatus according to claim 1. The resonance frequency specifying means specifies the frequency having the largest frequency component of the transfer function as the roll resonance frequency.
The vehicle center-of-gravity height estimation apparatus according to claim 1 or 2. The sprung angular velocity measuring means is provided on the vehicle body chassis,
The unsprung angular velocity measuring means is provided on an axle closest to the unsprung angular velocity measuring means;
The vehicle center-of-gravity height estimation apparatus according to any one of claims 1 to 3.

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