JP2010215061A - Control device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a control system at low cost capable of optimizing steering characteristics of a vehicle. <P>SOLUTION: A turning radius R of the vehicle is calculated from a steering angle SA of a steering wheel, a velocity V of the inner wheel out of rear wheels and the wheel base WB of the vehicle. An orbital velocity ωr of the vehicle is calculated from the velocity V of the inner wheel out of the rear wheels and the turning radius R. A rotation velocity ωs is calculated from the velocity difference ΔV between a velocity V+ΔV of the outer wheel out of the rear wheels and the velocity V of the inner wheel out of the rear wheels, and the tread tr of the vehicle. The vehicle is controlled so as to decrease the difference between the orbital velocity ωr and the rotation velocity ωs. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle control apparatus, and more particularly to a technique for controlling a vehicle steer characteristic so as to approach a neutral steer.

  Conventionally, in order to eliminate understeer or oversteer, various techniques for controlling the distribution of driving force between front and rear wheels or between left and right wheels have been proposed.

  Japanese Patent Laid-Open No. 2007-239819 calculates a target yaw rate based on a steering angle and a vehicle speed, and performs electronic control LSD according to a steering characteristic determined based on a difference between an actual yaw rate detected by a yaw rate sensor and a target yaw rate. A technique for controlling (Limited Slop Differential) is disclosed.

JP 2007-239819 A

  However, the technique described in Japanese Patent Application Laid-Open No. 2007-239819 requires a special sensor such as a yaw rate sensor for detecting the actual yaw rate. Therefore, there is room for further improvement in order to reduce the cost of the vehicle.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle control device that can reduce the cost of the vehicle.

  A vehicle control device according to a certain aspect is a vehicle control device in which only a front wheel of a front wheel and a rear wheel is steered by steering a steering wheel. The control device calculates the revolution speed of the vehicle from the steering angle of the steering wheel, the speed of the inner wheel of the rear wheel and the wheel base of the vehicle and the turning radius of the vehicle from the speed and the turning radius of the inner wheel of the rear wheel. Means for calculating, a means for calculating the rotational speed of the vehicle from the speed difference between the speed of the outer wheel of the rear wheel and the speed of the inner wheel of the rear wheel and the tread of the vehicle, and the revolution speed and the rotational speed Means for controlling the vehicle to reduce the difference.

  According to this configuration, the vehicle is controlled so as to reduce the difference between the revolution speed and the rotation speed of the vehicle. Thereby, the steering characteristic of the vehicle can be brought close to neutral steering. The revolution speed is calculated from the speed of the inner wheel of the rear wheel and the turning radius. The turning radius of the vehicle is calculated from the steering angle of the steering wheel, the speed of the inner wheel of the rear wheel, and the wheel base of the vehicle without using the yaw rate. The rotation speed is calculated from the speed difference between the speed of the outer wheel of the rear wheel and the speed of the inner wheel of the rear wheel and the tread of the vehicle without being detected using the yaw rate sensor. Accordingly, it is possible to realize a control system that can make the steering characteristic of the vehicle suitable without using a special sensor such as a yaw rate sensor. As a result, a vehicle control device that can reduce the cost of the vehicle can be provided.

It is a schematic block diagram which shows a vehicle. It is a functional block diagram of ECU. It is a figure which shows a neutral steer. It is a figure which shows oversteer. It is a figure which shows understeer. It is a figure which shows the area | region judged to be neutral steer. It is a figure which shows the area | region judged to be an oversteer. It is a figure which shows the area | region judged to be understeer. It is a figure which shows the control structure of the program which ECU performs.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  As shown in FIG. 1, a vehicle 100 in the present embodiment includes an engine 200, a torque converter 300, a transmission 400, a transfer 500, a front differential 600, a front wheel 700, a propeller shaft 800, an electronic control cup. A ring 900, a rear differential 1000, a rear wheel 1100, and an ECU (Electronic Control Unit) 2000 are included.

  The output torque of the engine 200 is a drive system (drive line) including a torque converter 300, a transmission 400, a front differential 600, a drive shaft 602, a transfer 500, a propeller shaft 800, an electronic control coupling 900, a rear differential 1000, and a drive shaft 1002. It is transmitted to the wheel via. Note that a motor may be used as a drive source instead of the engine 200.

  In the present embodiment, an FF-based four-wheel drive vehicle in which the front wheels 700 are main drive wheels and the rear wheels 1100 are auxiliary drive wheels will be described. However, the present invention is not particularly limited to this. For example, it may be an FR-based four-wheel drive vehicle in which the rear wheels are main drive wheels and the front wheels are auxiliary drive wheels.

  The transmission 400 is, for example, an automatic transmission that includes a planetary gear unit. CVT (Continuously Variable Transmission) may be used. A manual transmission may be used.

  Torque output from transmission 400 is distributed to front wheel 700 and rear wheel 1100 by transfer 500. Of the front wheels 700 and the rear wheels 1100, only the front wheels 700 are steered by the steering wheel 702 being driven by the driver.

  The front differential 600 is connected to the front wheel 700 via the drive shaft 602. A transfer 500 is connected to the transmission 400 via a case of the front differential 600. The transfer 500 is provided with a propeller shaft 800 that transmits the torque of the engine 200 to the rear wheel 1100 side. The end of the propeller shaft 800 on the rear wheel 1100 side is connected to the input side of the electronic control coupling 900. A rear differential 1000 is connected to the output side of the electronic control coupling 900. Rear differential 1000 is connected to rear wheel 1100 via drive shaft 1002.

  Torque generated in engine 200 is transmitted to front wheel 700 via transmission 400, front differential 600 and drive shaft 602. Torque generated in the engine 200 is transmitted to the rear differential 1000 through the transmission 400, the front differential 600, the transfer 500, the propeller shaft 800, and the electronic control coupling 900. Torque transmitted to the rear differential 1000 is transmitted to the rear wheel 1100 via the drive shaft 1002.

  The electronic control coupling 900 receives the torque transmitted from the propeller shaft 800 as an input, and adjusts the transmission amount of the torque output to the rear differential 1000. The electronic control coupling 900 is composed of, for example, a multi-plate clutch or the like, and the clutch pressing force is controlled based on a command current. That is, the electronically controlled coupling 900 controls the amount of torque transmitted between the transmission 400 and the rear wheel 1100 by being controlled between the clutch released state and the directly connected state. Thereby, the distribution of the driving force between the front wheel 700 and the rear wheel 1100 is controlled.

  The electronic control coupling 900 may be provided in the transfer 500. Further, instead of the electronic control coupling 900, an electronic control LSD may be provided as a center differential.

  Further, the electronic control LSD may be used for the front differential 600 and / or the rear differential 1000 to control the distribution of the driving force between the left and right wheels.

  Electronic control coupling 900 is controlled by ECU 2000. ECU 2000 is electrically connected to right rear wheel speed sensor 2100, left rear wheel speed sensor 2102 and steering angle sensor 2200.

  The right rear wheel speed sensor 2100 detects the rotational speed of the right rear wheel 1100. By multiplying the detected rotational speed by the circumference of the rear wheel 1100, the speed (vehicle speed) of the right rear wheel 1100 is calculated.

  The left rear wheel speed sensor 2102 detects the wheel speed of the left rear wheel 1100. By multiplying the detected rotational speed by the circumference of the rear wheel 1100, the speed (vehicle speed) of the left rear wheel 1100 is calculated.

  The steering angle sensor 2200 detects the steering angle SA and the steering direction of the steering wheel 702. Signals representing the detection results of these sensors are transmitted to ECU 2000.

  The function of ECU 2000 will be further described with reference to FIG. Note that the functions described below may be realized by software or hardware.

  ECU 2000 includes a turning radius calculation unit 2010, a revolution speed calculation unit 2020, a rotation speed calculation unit 2030, and a control unit 2040.

  The turning radius calculation unit 2010 calculates the turning radius R of the vehicle from the steering angle SA of the steering wheel 702, the speed V of the inner wheel of the rear wheel 1100, and the wheel base WB of the vehicle.

The rotation radius R is calculated by the following formula 1.
R = (1 + K0 × V ² ) × WB / (SA / GR) (1)
In Equation 1, “K0” is a constant. “GR” is a gear ratio (for example, a gear ratio between a rack and a pinion) in the steering device. The wheel base WB, the constant K0, and the gear ratio GR are stored in advance in a ROM (Read Only Memory) or the like.

  The revolution speed calculation unit 2020 calculates the revolution speed ωr of the vehicle from the speed V and the rotation radius R of the inner wheel of the rear wheel 1100.

The revolution speed ωr is calculated by the following equation 2.
ωr = V / R (2)
The rotation speed calculation unit 2030 calculates the vehicle rotation speed ωs from the speed difference ΔV between the speed V + ΔV of the outer wheel of the rear wheel 1100 and the speed V of the inner wheel of the rear wheel 1100 and the tread tr of the vehicle.

The rotation speed ωs is calculated by the following equation 3.
ωs = ΔV / tr (3)
The tread tr is stored in advance in a ROM or the like.

  The revolution speed ωr and the rotation speed ωs are used to determine the steering characteristic of the vehicle. For example, as shown in FIG. 3, when the revolution speed ωr and the rotation speed ωs are equal, it can be said that the steering characteristic is neutral steer.

  As shown in FIG. 4, when the rotation speed ωs is larger than the revolution speed ωr, it can be said that the steer characteristic is oversteer.

  As shown in FIG. 5, when the revolution speed ωr is larger than the rotation speed ωs, it can be said that the steering characteristic is understeer.

  Based on such a principle, in the present embodiment, when the revolution speed ωr and the rotation speed ωs are within a region indicated by hatching in FIG. 6, it is determined that the steering characteristic is neutral.

  If the revolution speed ωr and the rotation speed ωs are within the hatched area in FIG. 7, it is determined that the steering characteristic is oversteer.

  When the revolution speed ωr and the rotation speed ωs are in the region indicated by the oblique lines in FIG. 8, it is determined that the steering characteristic is understeer.

  Returning to FIG. 2, the control unit 2040 controls the vehicle so as to reduce the difference between the revolution speed ωr and the rotation speed ωs. For example, the electronic control coupling 900 is controlled so that the difference between the revolution speed ωr and the rotation speed ωs is reduced by changing the distribution of the driving force between the front wheels 700 and the rear wheels 1100. In addition, by controlling the output torque of the engine 200 or controlling the driving force distribution between the left and right wheels of the front wheel 700 or the rear wheel 1100 by electronically controlled LSD, the revolution speed ωr and the rotation speed ωs You may control a vehicle so that a difference may become small.

  When the steering characteristic is neutral steer, the control amount GAIN is zero. When the steering characteristic is oversteer, the control amount GAIN is calculated using the following equation 4 and a constant K1.

GAIN = K1 × (ωs−ωr) (4)
When the steering characteristic is understeer, the control amount GAIN is calculated using the following formula 5 and a constant K2.

GAIN = K2 × (ωs−ωr) (5)
The control amount GAIN is not limited to these.

  With reference to FIG. 9, a control structure of a program executed by ECU 2000 will be described.

  In step (hereinafter step is abbreviated as S) 100, ECU 2000 calculates vehicle turning radius R from steering angle SA of steering wheel 702, speed V of the inner wheel of rear wheel 1100, and wheel base WB of the vehicle.

  In S102, ECU 2000 calculates a revolution speed ωr of the vehicle from speed V and rotation radius R of the inner wheel of rear wheel 1100.

  In S104, ECU 2000 calculates vehicle rotation speed ωs from speed difference ΔV between speed V + ΔV at the outer wheel of rear wheel 1100 and speed V at the inner wheel of the rear wheel and vehicle tread tr.

  In S106, ECU 2000 determines whether or not the steering characteristic is neutral steering. If the steer characteristic is neutral steer (YES in S106), the process proceeds to S110. If not (NO in S106), the process proceeds to S108.

  In S108, ECU 2000 determines whether or not the steering characteristic is oversteer. If the steer characteristic is oversteer (YES in S108), the process proceeds to S112. If not (NO in S108), the process proceeds to S114.

  In S110, ECU 2000 sets control amount GAIN of electronic control coupling 900 to zero.

  In S112, ECU 2000 calculates control amount GAIN of electronic control coupling 900 by multiplying the difference between rotation speed ωs and revolution speed ωr by constant K1. That is, the control amount GAIN corresponding to the difference between the rotation speed ωs and the revolution speed ωr is calculated.

  In S114, ECU 2000 calculates control amount GAIN of electronic control coupling 900 by multiplying the difference between rotation speed ωs and revolution speed ωr by constant K2. That is, the control amount GAIN corresponding to the difference between the rotation speed ωs and the revolution speed ωr is calculated.

  In S116, ECU 2000 controls electronic control coupling 900 using calculated control amount GAIN so that the difference between revolution speed ωr and rotation speed ωs is reduced.

  A control mode of electronic control coupling 900 based on the structure and flowchart as described above will be described.

  When the vehicle is turning, the turning radius R of the vehicle is calculated from the steering angle SA of the steering wheel 702, the speed V of the inner wheel of the rear wheel 1100, and the wheel base WB of the vehicle (S100). Further, the revolution speed ωr of the vehicle is calculated from the speed V and the rotation radius R of the inner wheel of the rear wheel 1100 (S102). Therefore, the turning radius R and the revolution speed ωr are calculated without using the yaw rate.

  Further, the rotation speed ωs is not detected using the yaw rate sensor, but is calculated from the speed difference ΔV between the speed V + ΔV of the outer wheel of the rear wheel 1100 and the speed V of the inner wheel of the rear wheel and the tread tr of the vehicle ( S104).

  Thus, the revolution speed ωr and the rotation speed ωs that can be used to determine the steering characteristic of the vehicle can be calculated without using a special sensor such as a yaw rate sensor.

  If the steering characteristic is neutral steer (YES in S106), control amount GAIN of electronic control coupling 900 is set to zero (S110).

  If the steering characteristic is oversteer (YES in S108), the control amount GAIN of the electronic control coupling 900 is calculated by multiplying the difference between the rotation speed ωs and the revolution speed ωr by a constant K1 (S112).

  If the steering characteristic is understeer (NO in S108), the control amount GAIN of the electronic control coupling 900 is calculated by multiplying the difference between the rotation speed ωs and the revolution speed ωr by a constant K2 (S114).

  When the steer characteristic is oversteer or understeer, the revolution speed ωr and the rotation speed ωs are calculated using the calculated control amount GAIN in order to realize the driving force distribution between the front and rear wheels so that the steer characteristic approaches the neutral steer. The electronic control coupling 900 is controlled so as to reduce the difference between (S116).

  Accordingly, it is possible to realize a control system that can bring the vehicle steering characteristic closer to a suitable neutral steering without using a special sensor such as a yaw rate sensor.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100 Vehicle, 200 Engine, 300 Torque converter, 400 Transmission, 500 Transfer, 600 Front differential, 602 Drive shaft, 700 Front wheel, 702 Steering wheel, 800 Propeller shaft, 900 Electronic coupling, 1000 Rear differential, 1002 Drive shaft, 1100 Rear wheel, 2000 ECU, 2010 turning radius calculation unit, 2020 revolution speed calculation unit, 2030 rotation speed calculation unit, 2040 control unit, 2100 right rear wheel wheel speed sensor, 2102 left rear wheel wheel speed sensor, 2200 rudder angle sensor.

Claims (1)

A vehicle control device in which only a front wheel of a front wheel and a rear wheel is steered by steering a steering wheel,
Means for calculating a turning radius of the vehicle from a steering angle of the steering wheel, a speed of an inner wheel of the rear wheel and a wheel base of the vehicle;
Means for calculating the revolution speed of the vehicle from the speed of the inner wheel of the rear wheel and the turning radius;
Means for calculating the rotational speed of the vehicle from the speed difference between the speed of the outer wheel of the rear wheel and the speed of the inner wheel of the rear wheel and the tread of the vehicle;
A vehicle control device comprising: means for controlling the vehicle so as to reduce a difference between the revolution speed and the rotation speed.

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