Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
2001-08-20
2003-12-02
Camby, Richard M. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S072000, C701S083000
Reexamination Certificate
active
06658343
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and a device for stabilizing a vehicle equipped with a slip-controlled brake system.
BACKGROUND INFORMATION
A stabilization device for passenger vehicles is described in the article “FDR—Die Fahrdynamikregelung von Bosch”, published in the automotive engineering journal
ATZ Automobiltechnische Zeitschrift
, vol. 96, no. 11 (1994) pp. 674-689. With this stabilization device, the yaw rate and float angle of the vehicle are regulated by the control system. This is done by determining a control deviation between the actual values and the setpoint values for the float angle and the yaw rate. Starting with these setpoints, changes in setpoint slip which are implemented through appropriate engine control measures and/or brake control measures are determined. With the help of brake control measures, it is possible to increase or reduce the brake pressure on individual wheels according to the changes in setpoint slip.
A system for brake slip control is described in the article “Antiblockiersystem (ABS) f{dot over (u)}r Personenkraftwagen”, published in “Bosch Technische Berichte”, volume 7, (1980, no. 2, ISSN 006-789 X). In this system, the actual slip is compared with a setpoint slip during a braking operation, and as soon as the actual slip is equal to the setpoint slip, the brake pressure on the respective wheel is reduced.
For example, German Published Patent Application No. 2 112 669 describes an anti-lock device which controls wheel slip in such a way that maximum braking forces between the road surface and the tire are possible. This anti-lock device has a control device with which the anti-lock protection can be influenced when the longitudinal axis of the vehicle deviates from the direction of travel. This control device includes a final controlling element which automatically reduces wheel slip to a value at which lateral guidance of the wheel is improved significantly with hardly any noticeable reduction in brake pressure. The final controlling element reacts to the direction in which the vehicle travels along a curve. Among other things, this anti-lock device causes the braking force on the inside of the curve to be reduced and the braking force on the outside of the curve to be increased.
All the devices described above as belonging to the related art use wheel slip as a controlled variable to implement measures influencing the wheel.
SUMMARY OF THE INVENTION
The present invention provides a method and a device using an alternative controlled variable other than wheel slip so that measures to influence the wheels can be implemented on the basis of this alternative controlled variable.
The present invention provides a method for stabilizing a vehicle equipped with a slip-controlled brake system. In this method, wheel speeds are determined for the individual wheels of the vehicle. As an alternative to the slip, as a controlled variable, the wheel speed is used in the method according to the present invention. For this reason, a setpoint value for the wheel speed is determined for at least one wheel. A deviation quantity describing the deviation between the wheel speed determined for this wheel, and the setpoint value is determined for the at least one wheel. To stabilize the vehicle, the actuators assigned to the at least one wheel are controlled as a function of this deviation quantity.
Slip is a relative quantity; in other words, if slip is controlled by activating the actuators assigned to the wheel, then the wheel speed that will result after activating the actuators is not always known in advance. Wheel speed, however, is an absolute quantity. If wheel speed is regulated by activating the actuators assigned to the wheel, then the wheel speed which results after activating the actuators can be set at a desired level. Thus when traveling along curves, for example, the wheel speed resulting after activating the actuators can be adapted to the actual curve turned.
The method and device according to the present invention are to be used in vehicles equipped with an anti-lock control unit. This is not a restriction on the scope. Use in vehicles equipped with traction control or a form of slip control such as that described in the above-mentioned ATZ article is also possible.
Vehicles may also tend to oversteer during turning even in the partial braking range. If a vehicle is equipped with a brake slip control system, it can be stabilized with the help of the method according to the present invention. To stabilize the vehicle, pressure-modulating control measures which are not brake slip control measures per se can be implemented on the front axle.
In addition, due to the load reduction on the front wheel on the inside of the curve, vehicles equipped with a brake slip control system can be brought under brake slip control with this wheel very quickly. This can be perceptible in the pedal itself and from noises which constitute an impairment of driving comfort. The method according to the present invention can also prevent the front wheel on the inside of the curve from coming under brake slip control with even slight braking due to the load reduction at higher transverse accelerations. With the method according to the present invention, an improvement in both stability and comfort is achieved with brake slip control systems.
The slip-controlled brake system used with the device according to the present invention is one in which at least the brake slip of individual wheels of a vehicle can be controlled. The vehicle is in the partial braking range during this stabilization.
The at least one wheel whose actuators are activated as a function of the deviation quantity can be a wheel on the inside of the curve. In a further embodiment, it can be desired that the at least one wheel is the front wheel on the inside of the curve. The actuators are activated so that the braking effect prevailing on the wheel on the inside of the curve is reduced in comparison with the braking effect prevailing on the wheel on the same axle but on the outside of the curve. The following is achieved with the method of influencing the front wheel on the inside of the curve as described above. Since the method according to the present invention is designed primarily for a vehicle equipped with a slip-controlled brake system, only a control measure that reduces the braking effect and is to be implemented independently of the driver may be considered as a stabilizing control measure on the actuators assigned to the wheels. An increase in braking effect may not happen because such brake systems that operate by hydraulic or pneumatic means do not have any means for increasing pressure independently of the driver so that ultimately an increase in braking effect can be achieved. With the method according to the present invention, the tendency of the vehicle to oversteer is to be counteracted, so a yaw moment with an understeering effect must be produced. Since only a reduction in braking effect can be implemented independently of the driver, as mentioned above, it must be implemented on the wheels on the inside of the curve in order to achieve a yaw moment with an understeering effect. The front wheel on the inside of the curve is selected because due to the load distribution the transmission of force to this wheel on the inside of the curve can be more favorable than that to the rear wheel on the inside of the curve.
The setpoint for wheel speed as a function of the wheel speed of the wheel on the outside of the curve which is on the same axle as the wheel on the inside of the curve is used advantageously for the wheel speed. This type of determination is performed because the wheel on the outside of the curve is especially stable when traveling along curves because of the load distribution of the vehicle. It is likewise advantageous if the difference in wheel speeds which results when traveling along curves for wheels on the inside and outside of the curve is taken into account in determining the setpoint. This can be accomplished by determining
Diehle Stefan
Koch Matthaeus
Lah Oliver
Poggenburg Ruediger
Ullmann Steffen
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