Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
2000-11-17
2001-08-28
Camby, Richard M. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C180S282000
Reexamination Certificate
active
06282471
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to active suspension systems for vehicles, and in particular to such systems which include active roll control.
BACKGROUND OF THE INVENTION
It can be a problem with active suspension control systems, particularly in off-road vehicles that they do not respond suitably when the vehicle is traversing a steep side slope. This is because, in conventional systems, the presence of a side slope cannot be detected and the system therefore responds to a side slope as if the vehicle were cornering. This can result in the consumption of a lot of power as the system tries to compensate for what can be the equivalent of severe vehicle roll but which can last for long periods of time. This is because the vehicle can continue to traverse the side slope for a considerable length of time whereas severe roll is generally only present for short periods.
It is known from EP 0 283 004 to provide a vehicle roll control system in which the roll control mechanism is modified in dependence on the speed of the vehicle. However, this system still does not address the problem of roll control on a side slope.
SUMMARY OF THE INVENTION
EP 0 689 116 discloses a system for detecting side slopes traversed by a vehicle using measurements of lateral acceleration and wheel speeds which in turn are used to determine vehicle speed and yaw rate.
DE 196 07 050 discloses a side slope detection system which uses a yaw sensor and wheel speed sensors.
DE 40 19 732 discloses a roll control system in which switches from an active to a passive state under high lateral accelerations so as to conserve energy and so as to reduce the power required from the system.
The present invention provides apparatus for detecting traversal of a side slope by a vehicle, the apparatus including an accelerometer arranged to produce an acceleration signal indicative of the lateral acceleration of the vehicle, speed measuring means arranged to produce a speed dependent signal dependent on the speed of the vehicle and control means, characterized in that the apparatus further comprises comparator means arranged to produce a difference signal indicative of the difference between the speed dependent signal and the acceleration signal, and integrating means arranged to integrate the difference signal over time and to produce a side slope detection signal if the integral reaches a predetermined value.
The speed dependent signal can vary only with the vehicle speed. Alternatively, if the vehicle includes a sensor for measuring steering angle the speed dependent signal can also be dependent on the steering angle.
Preferably the speed dependent signal is arranged to vary with the square of the vehicle speed. This gives the best indication of cornering acceleration because the cornering acceleration varies with the square of the speed of the vehicle.
The present invention further provides a vehicle suspension system including roll control means for controlling roll of the vehicle and apparatus according to the invention for detecting traversal of a side slope by a vehicle. Preferably the roll control means has active and passive modes and is arranged to respond to detection of a side slope by operating in the passive mode. Preferably the roll control means includes a hydraulic circuit including a pump which is arranged to provide hydraulic pressure for use in active roll control when the roll control means is in the active state but which can be turned off or operate at reduced power when the roll control means is in the passive state.
The roll control means may include a roll bar having two parts which can be moved relative to each other to control roll when the roll control means is in the active state and which can be locked together when the roll control system is in the passive state.
Preferably the roll control means is arranged to switch from the passive mode to the active mode if the vehicle speed exceeds a predetermined threshold speed while the roll control means is in the passive mode. This is because at higher speeds it can be assumed that the vehicle is no longer on a steep side slope and that normal roll control will be required.
Preferably the system further comprises means for producing a high speed signal when the vehicle speed exceeds said threshold speed, and wherein the high speed signal is input to the comparator means which is arranged to respond by altering the difference signal as if a speed signal indicative of a high vehicle speed or a lateral acceleration signal indicative of low lateral acceleration had been received.
REFERENCES:
patent: 40 19 732 A1 (1991-01-01), None
patent: 196 07 050 A1 (1997-08-01), None
patent: 196 15 311 A1 (1997-10-01), None
patent: 0 234 808 A2 (1987-09-01), None
patent: 0 234 552 A1 (1987-09-01), None
patent: 0 283 004 A3 (1988-09-01), None
patent: 0 689 116 A2 (1995-12-01), None
patent: 2 234 211 A (1991-01-01), None
Burdock William
Clare David Andrew
Camby Richard M.
Davis & Bujold P.L.L.C.
Land Rover Group Limited
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