Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
1999-07-09
2001-03-27
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S041000, C340S465000, C180S400000, C180S402000, C180S422000, C180S427000, C180S442000, C180S446000
Reexamination Certificate
active
06208923
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention proceeds from an electromechanical steering actuator, in particular for steer-by-wire application in motor vehicles, with an electronic closed-loop/open-loop control system that generates steering signals for an electric servomotor, which acts via a gear unit on a steering control element. In particular the servomotor acts on a rack of a rack-and-pinion steering system. The closed-loop/open-loop control system comprising a process computer that delivers corrective signals to the servomotor via a drive unit.
Such a steering actuator is known, for example, from DE 195 40 956. In the known electromechanical steering actuator, the mechanical connection between the steering column and the rack of the rack-and-pinion steering system can be broken to permit steer-by-wire steering. In the event of a fault in the power-assisted or the automatic steering system, this additional system is shut down and the driver regains mechanical control over the wheels to be steered. The known steering actuators for an automatic steering mode are not completely fault-tolerant.
In a vehicle with a steer-by-wire system, where there is no longer a mechanical connection between the steering wheel and the gear unit, care must be taken to ensure that the steering actuator is fault-tolerant.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a fault-tolerant electromechanical steering actuator that permits a correct steer-by-wire steering function in the event of a fault, regardless of the subsystem in which it occurs.
Owing to the fact that, according to the present invention, the steering actuator is divided into two diversely redundant systems, the closed-loop/open-loop control system comprising two diversely redundant process computers each of which delivers the corrective signals, via a diversely redundant drive unit assigned to it, to two diversely redundant servomotors acting on the same steering shaft, the steering system remains fully available even in the event of a fault, regardless of the subsystem in which the fault occurs.
During normal operation, the first of the systems is operating and the second system is passive. Here, “passive” means that although the passive process computer is not generating any corrective signals for its assigned servomotor, it is still being powered by its assigned voltage supply device, i.e., it is in a standby mode, in which, however, it can still exchange information with the active process computer, receive information from the higher-level vehicle computer and receive position measurement signals from the position sensor.
The currently active process computer controls its assigned electric servomotor via the drive unit connected therebetween, exchanges information with the passive process computer, and receives position measurement signals from the position sensor and information from the higher-level vehicle computer. The currently active process computer further receives the phase voltages or phase currents from the other electric servomotor assigned to the passive process computer.
The two process computers constantly exchange their computed actual positions and fault information (watchdog function). In the event of a fault, the process computer of one system shuts down the other system via no-current-opening relays.
Two types of system-generated faults can occur:
Mode I: Here the position sensor is defective;
Mode II: In this case, any other subsystem in the two systems A or B is defective.
(It is assumed that all mechanical parts, such as shafts and gears, are designed and laid out so as to withstand normal loads and stress loads.)
When a fault of the Mode II class occurs, the system that has been passive becomes active and the system in which the fault occurred is shut down. If the system that has been passive fails, the active system naturally remains active. If the active system fails, on the other hand, the passive system becomes active.
Further objects and characteristics of the invention will be described in detail hereinbelow with reference to an exemplary embodiment of the electromechanical steering actuator according to the invention.
REFERENCES:
patent: 4869334 (1989-09-01), Marumoto et al.
patent: 4959787 (1990-09-01), Morishita et al.
patent: 5247441 (1993-09-01), Serizawa et al.
patent: 5327986 (1994-07-01), Saita
patent: 5335979 (1994-08-01), Nation et al.
patent: 5360077 (1994-11-01), Nishimoto et al.
patent: 5440487 (1995-08-01), Althoff et al.
patent: 5912539 (1999-06-01), Sugitani et al.
patent: 6018691 (2000-01-01), Yamamoto et al.
patent: 6032091 (2000-02-01), Noro et al.
patent: 6097286 (2000-08-01), Discenzo
patent: 6098296 (2000-08-01), Perisho, Jr. et al.
patent: 6138788 (2000-10-01), Bohner et al.
English Translation of Abstract Only.
Baker & Daniels
Cuchlinski Jr. William A.
Robert & Bosch GmbH
To Tuan C
LandOfFree
Fault-tolerant electromechanical steer-by-wire steering... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fault-tolerant electromechanical steer-by-wire steering..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fault-tolerant electromechanical steer-by-wire steering... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2492555