JP2005168260A - Device for calculating vehicular item variations of electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve high precision behavior control at a low cost by obtaining the variations of vehicular items used for controlling the behavior of an electric vehicle, without providing a plurality of sensors. <P>SOLUTION: By driving front wheels and rear wheels of the electric vehicle in a stop state at the same phase in a reverse direction to each other, up and down vibrations are caused to occur to a car body via the elasticity of suspension devices and the vibration frequency is made to change within a range from 1 Hz to dozens of Hz to obtain a peak gain frequency f1 from its transmission characteristics (frequency characteristics) A, when the gain of the up and down vibrations of the car body peaks. While a peak gain frequency f0 is obtained in advance from the transmission characteristics (frequency characteristics) B, which is caused to occur in the similar manner as above under a reference vehicle weight (the vehicle weight when only a driver is on board), a vehicle weight variation Δm is obtained by the operation of Δm=äk/(2π)<SP>2</SP>}ä(1/fl<SP>2</SP>)-(1/f0<SP>2</SP>)} from the difference between f0 and f1, using the spring constant k of the suspension devices. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention, when performing behavior control such as yaw rate control of an electric vehicle, changes according to the vehicle condition change amount required for obtaining the target behavior of the electric vehicle, in particular, the vehicle weight and the front and rear weight distribution. The present invention relates to a device for calculating a vehicle specification change amount of an electric vehicle.

Conventionally, for example, as disclosed in Japanese Patent Application Laid-Open No. 2004-133826, vehicle specifications that change according to traveling conditions such as vehicle weight and front / rear weight distribution and control the yaw rate of the vehicle based on these are known.
This yaw rate control device can optimize the vehicle's target yaw rate under many different conditions and with sufficient consideration of many disturbances so that it can be accurately optimized under these conditions and disturbances. The aim is to achieve highly accurate yaw rate control.

  In recent years, various vehicle behavior control devices such as a post-differential limiting control device and a driving force distribution control device mounted on a vehicle have been used. The amount of control is determined according to the motion state (motion equation) of the vehicle. When determining to achieve the target yaw rate set in, there is a problem that the response and accuracy related to the detection (estimation) of the road surface friction coefficient are not sufficient, and the driving conditions that can be detected (estimated) For example, changes in road surface friction coefficient, vehicle response to quick steering wheel operation (steering), vehicle behavior non-linearity, vehicle behavior non-linearity when the steering wheel is operated greatly, vehicle loading conditions, etc. There is a problem that the detection (estimation) accuracy and responsiveness of the changing vehicle weight and the front and rear weight distribution are not sufficient.

Since it is difficult to optimize the target yaw rate due to restrictions related to these problems, the yaw rate control technique described in Patent Document 1 estimates the motion state of the vehicle and calculates the target yaw rate based on this,
The stability factor is calculated based on at least one of the difference in vehicle behavior characteristics between right steering and left steering, the estimated current vehicle weight, and the estimated current vehicle front-rear weight distribution. The target yaw rate is calculated based on the stability factor.

Specifically, the target yaw rate is calculated in consideration of the vehicle weight, front / rear weight distribution ratio, front / rear axle weight, front / rear axis-center of gravity distance, front / rear wheel equivalent cornering power, and actual front wheel steering angle. In addition, the target yaw rate is calculated by setting different steady yaw rate gains for the left and right steering directions.
Further, when calculating the reference yaw rate in consideration of the vehicle dynamic characteristics, the delay time constant of the yaw rate response to the steering is changed based on the estimated value of the road surface friction coefficient to calculate the reference yaw rate.
In addition, when the vehicle is in a spin state, the correction speed of the correction with respect to the reference yaw rate by the target yaw rate correction coefficient is set at a first-order lag cutoff frequency that follows the actual yaw rate, and is reduced or prohibited, and the target yaw rate becomes excessive. It is to prevent becoming.
Japanese Patent Laid-Open No. 2002-316546

However, in order to accurately control the yaw rate of the vehicle by distributing the driving force, it is necessary to fully consider the disturbance. Among the disturbances, the change in the weight of the vehicle and the distribution of the weight in the front / rear direction are significant disturbance factors when performing the yaw rate control. .
Particularly in the electric vehicle targeted by the present invention, each wheel can be independently driven and controlled by an individual motor, and the yaw rate control of a vehicle with good responsiveness can be performed by this wheel independent driving control. Therefore, how to consider the disturbance in the vehicle model is a big issue.

  By the way, when trying to take into account disturbances such as vehicle weight changes and front and rear weight distribution changes in yaw rate control, multiple sensors such as front and rear acceleration sensors and brake fluid pressure sensors are required to detect and estimate these changes. This causes a problem of increasing costs.

In the case of an electric vehicle, at least the front wheels and the rear wheels can be motor-driven independently, and depending on the driving mode of the front and rear wheels, the vehicle body can be vibrated up and down via the elastic support structure of the wheels by the suspension device, In addition, it is recognized that changes in vehicle specifications such as changes in vehicle weight and changes in weight distribution in the front and rear that need to be obtained in order to satisfy the above requirements for accuracy in vehicle behavior control appear as changes in the vertical vibration. Based on
It is possible to calculate the vehicle specification change amount from the vertical vibration change and provide it to the vehicle behavior control, so that only the installation of the acceleration sensor for detecting the vertical vibration can be performed without using a plurality of sensors. It is an object of the present invention to propose a vehicle specification change amount calculation device for an electric vehicle that can realize high accuracy of vehicle behavior control without causing the above-mentioned cost problem.

For this purpose, the vehicle behavior change calculating device for an electric vehicle according to the present invention is constructed as described in claim 1.
First, the vehicle as a premise is an electric vehicle in which the front wheels and the rear wheels suspended from the vehicle body via a suspension device are independently motor-driven.
Motor drive control means for generating vertical vibrations for generating vertical vibrations in the vehicle body by driving at least one of the front wheels and rear wheels back and forth with the contact point of the other wheel as a reaction force;
Vertical vibration detection means for detecting vertical vibration of the vehicle body generated by the means;
Vehicle specification change amount calculating means is provided for calculating the amount of change in the vehicle specification that affects the appearance of the vehicle body vertical vibration from the vehicle body vertical vibration detected by this means.

According to the vehicle specification change amount calculating device of the present invention, the motor drive control means for generating vertical vibrations drives at least one of the front wheels and the rear wheels back and forth with the ground contact point of the other wheel as a reaction force receiver, A vertical vibration is generated in the vehicle body, this vertical vibration is detected by the vertical vibration detection means, and the vehicle specification change calculation means is used to detect various vehicle effects that affect the output of the vertical vibration from the detected vehicle vertical vibration. To calculate the original amount of change,
The vehicle specification change amount can be calculated from the vehicle body vertical vibration change and provided to the vehicle behavior control. For this reason, as a sensor, only an acceleration sensor (vertical vibration detection means) for detecting the vehicle vertical vibration is installed. High accuracy of vehicle behavior control can be realized without using a plurality of sensors, and thus without causing the cost problem.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 is a diagrammatic side view of an electric vehicle including a vehicle specification change amount calculating device according to an embodiment of the present invention.
The electric vehicle includes a front wheel 3F and a rear wheel 3R suspended on the vehicle body 1 via suspension devices 2F and 2R, and motors 4F and 4R are individually coupled to the front wheel 3F and the rear wheel 3R by driving and coupling the front wheels 3F and 3R. The rear wheels 3R can be driven individually.

  The motor 4F may be common to the left and right front wheels 3F, or may be provided individually to the left and right front wheels 3F.The motor 4R may be common to the left and right rear wheels 3R, and the left and right rear wheels 3R. It may be provided individually.

A common energy supply device 5 for supplying drive energy to the motors 4F and 4R is mounted on the vehicle, and this is composed of a battery 5a and an inverter 5b.
The drive energy supply to the motors 4F and 4R is performed by the controller 6 supplying the electric power from the battery 5a to the motors 4F and 4R under the control of the inverter 5b, and the motors 4F and 4R respond to such energy supply. The electric vehicle is driven with the driving force requested by the driver by operating the accelerator pedal by driving the wheels.

Incidentally, the controller 6 performs not only the vehicle driving control described above but also the calculation processing of the vehicle specification change amount which is the object of the present invention. Built-in original variation calculation means.
The former motor drive control means for generating the vertical vibration is, for example, via the inverter 5b so as to drive the front wheel 3F and the rear wheel 3R back and forth in the same phase and in opposite directions as indicated by arrows α and β in FIG. By supplying the electric power of the battery 5a to the motors 4F and 4R, the vertical vibration γ is generated in the vehicle body 1 through the elasticity of the suspension devices 2F and 2R, and the vibration frequency is sequentially within a range of about 1 Hz to several tens of Hz. To change.
If the motor 4F is provided separately for the left and right front wheels 3F, or if the motor 4R is provided separately for the left and right rear wheels 3R, the motors 4F related to the left and right front wheels 3F are driven in the same direction synchronously, It goes without saying that both motors 4R related to the left and right rear wheels 3R are driven in the same direction in synchronization.

In order to detect the vehicle body vertical vibration γ at the center of gravity G of the vehicle body 1, a vertical vibration detection means 7 that enables an acceleration sensor is provided.
The vehicle specification change amount calculation means (not shown) in the controller 6 changes the vibration gain (the magnitude of vibration) with respect to the frequency detected by the means 7 as illustrated by A in FIG. Based on the detection result of the vertical vibration of the vehicle body, a change amount (vehicle weight change amount) of the vehicle weight, which is one of the vehicle specifications, is calculated from the transfer characteristic (frequency characteristic) A of the vertical vibration γ based on this detection result.

In calculating the amount of change in vehicle weight, the transmission shown in FIG. 2 of the vertical vibration of the vehicle body generated in the same manner as described above based on the reference vehicle weight (for example, the vehicle weight when only the driver is on board). From the characteristic (frequency characteristic) B, the peak gain frequency f0 when the vehicle body vertical vibration gain reaches its peak is obtained in advance.
Then, from the transmission characteristic (frequency characteristic) A shown in FIG. 2 of the vehicle vertical vibration γ detected this time, a peak gain frequency f1 when the vehicle vertical vibration gain reaches its peak is obtained, and a reference peak gain frequency f0 is obtained. From the difference from the inherent peak gain frequency f1 detected this time, the vehicle weight change amount Δm is obtained by the following calculation using the spring constant k of the suspension devices 2F and 2R.
Δm = {k / (2π) ² } {(1 / f1 ² )-(1 / f0 ² )}

  The controller 6 calculates a new current vehicle yaw inertia moment according to the vehicle weight change based on the vehicle weight change amount Δm calculated as described above, and calculates the corrected yaw inertia moment according to the vehicle weight change. A target yaw rate is obtained by reflecting it in a vehicle model (vehicle motion equation) for vehicle yaw rate control, and the controller 6 sends the target yaw rate to each motor 4F, 4R from the energy supply device 5 so that the target yaw rate is achieved during the travel control. A predetermined yaw rate control is performed by controlling the electric power.

  In the above description, the controller 6 calculates the vehicle weight change amount Δm related to the vehicle yaw moment of inertia as the vehicle specification change amount, and this is used for the yaw rate control. For the purpose of further improving the yaw rate control accuracy, A configuration in which the vehicle front-rear weight distribution change amount related to the vehicle yaw inertia radius is also obtained as the vehicle specification change amount, and this is also used for the yaw rate control will be described below.

In this case, the above-described motor drive control means (not shown) for generating vertical vibrations in the controller 6 is in a stopped state, with the front wheel 3F braked, or with the rear wheel 3R braked on the other wheel. A longitudinal moment is applied to the vehicle body 1 by driving the 3R or 3F back and forth, and the longitudinal vibration is generated in the vehicle body 1 by the elasticity of the suspension devices 2F and 2R due to the longitudinal moment.
This vertical vibration of the vehicle body is detected by the vertical vibration detection means 7.

The vehicle specification change amount calculation means (not shown) in the controller 6 estimates the current vehicle front-rear weight distribution from the magnitude (transmission characteristics) of the vehicle body vertical vibration detected by the means 7,
The size of the vehicle vertical vibration generated in the same manner as described above based on the reference longitudinal weight distribution (front and rear weight distribution when only the driver is on board) and the vehicle vertical motion detected by the means 7 The amount of change in the vehicle front-rear weight distribution is calculated from the ratio to the magnitude of vibration, and contributes to the vehicle yaw rate control as follows.

That is, the controller 6 changes the vehicle yaw inertia moment after correction according to the vehicle weight change amount Δm from the vehicle yaw inertia radius change amount obtained from the ratio of the vehicle body vertical vibration magnitude (the yaw at the reference front-rear weight distribution). The amount of deviation from the inertia radius is further corrected, and the re-corrected yaw inertia moment is reflected in a vehicle model (vehicle motion equation) for vehicle yaw rate control to obtain a target yaw rate. Predetermined yaw rate control is performed by controlling the power from the energy supply device 5 to the motors 4F and 4R so that the target yaw rate is achieved during the control.
As a result, it is possible to eliminate the influence of both the change in the vehicle weight and the change in the front / rear weight distribution, which is a disturbance when performing the yaw rate control, and it is possible to further improve the yaw rate control accuracy.

The calculation of the vehicle specification change amount and the correction of the yaw moment of inertia based on the calculation are based on the assumption that the vehicle body 1 is stable in a horizontal state, but in reality, the suspension devices 2F, 2R, etc. There is a possibility that the vehicle body 1 is inclined due to the difference in friction. In this case, the above-described effect is halved.
In order to avoid this, before the calculation of the vehicle specification change amount and the correction of the yaw inertia moment based on the above-mentioned calculation, the controller 6 causes the vehicle body 1 due to the non-uniform strokes of the suspension devices 2F and 2R. It is preferable to drive the front wheel 3F and the rear wheel 3R back and forth in the same phase in opposite directions so that the inclination of the vehicle body 1 is eliminated so that the posture of the vehicle body 1 is stabilized.

  In FIG. 1, one acceleration sensor for detecting the vertical vibration at the center of gravity G of the vehicle body 1 is provided as the vertical vibration detecting means 7, but a stroke sensor for detecting the stroke amount is already provided in the suspension devices 2F and 2R. If it is, the vertical vibration of the vehicle body may be calculated from the detection values of these stroke sensors.

In any case, according to the configuration of this embodiment, at least one of the front wheel and the rear wheel is driven back and forth using the contact point of the other wheel as a reaction force receiver, thereby generating vertical vibrations in the vehicle body. Because it contributes to the high accuracy of vehicle yaw rate control by calculating the amount of change in vehicle specifications from the change in vibration,
As a sensor, only one vertical vibration detecting means 7 that enables an acceleration sensor is provided, and a plurality of sensors are not used, or the existing suspension stroke sensor is used as described above and no sensor is installed. Therefore, high accuracy of vehicle yaw rate control can be realized at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view showing an electric vehicle including a vehicle specification change amount calculating device according to an embodiment of the present invention. It is a characteristic view showing the frequency characteristic of the upper limit vibration generated in the vehicle body by the same phase reverse drive of the front and rear wheels.

Explanation of symbols

1 body
2F front wheel suspension system
2R rear wheel suspension system
3F front wheel
3R rear wheel
4F front wheel drive motor
4R Rear wheel drive motor 5 Energy supply device
5a battery
5b Inverter 6 Controller (Motor drive control means for generating vertical vibration: vehicle specification change calculation means)
7 Vertical vibration detection means (acceleration sensor)

Claims (5)

In an electric vehicle comprising a front wheel and a rear wheel suspended from a vehicle body via a suspension device, and driving the front and rear wheels independently of each other,
Motor drive control means for generating vertical vibrations for generating vertical vibrations in the vehicle body by driving at least one of the front wheels and rear wheels back and forth with the contact point of the other wheel as a reaction force;
Vertical vibration detection means for detecting vertical vibration of the vehicle body;
And a vehicle specification change amount calculating means for calculating a change amount of the vehicle specification affecting the way of the vehicle vertical vibration from the vehicle vertical vibration detected by the means. A vehicle specification change calculation device for automobiles. In the vehicle specification change amount calculation device according to claim 1,
The motor drive control means for generating vertical vibrations generates vertical vibrations in the vehicle body by driving the front wheels and rear wheels back and forth in opposite directions in the same phase,
The vehicle specification change amount calculation device for an electric vehicle, wherein the vehicle specification change amount calculation means calculates a vehicle weight change amount from a transmission characteristic of the vertical vibration of the vehicle body. In the vehicle specification change amount calculation device according to claim 2,
The vertical vibration generating motor drive control means vibrates the vehicle body so that the frequency changes sequentially,
The vehicle specification change amount calculation means calculates a vehicle weight change based on a difference between a peak gain frequency when the vehicle body vertical vibration gain reaches a peak and a peak gain frequency obtained in advance based on a reference vehicle weight. A vehicle specification change amount calculation device for an electric vehicle, characterized in that the amount is calculated. In the vehicle specification change amount calculation device according to claim 1,
The vertical vibration generating motor drive control means generates vertical vibration in the vehicle body by driving the other wheel back and forth while braking one of the front wheels and the rear wheels,
The vehicle specification change amount calculating means calculates the magnitude of the vertical vibration of the vehicle body and the magnitude of the vertical vibration of the vehicle body that has been obtained in advance by the motor drive control means for generating vertical vibrations based on the reference front-rear weight distribution. A vehicle specification change amount calculation device for an electric vehicle, characterized in that the change amount of the vehicle front-rear weight distribution is calculated by comparison. In the vehicle specification change amount calculation device according to any one of claims 1 to 4,
Prior to the calculation of the vehicle specification change amount, the front wheels and the rear wheels are driven back and forth in opposite phases in the same phase so that the inclination of the vehicle body caused by the uneven stroke of the suspension device is eliminated. A vehicle specification change calculation device for an electric vehicle.

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