Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
2000-09-01
2001-09-25
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S069000, C701S041000, C180S446000
Reexamination Certificate
active
06295496
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to co-operative control systems for vehicles comprising a combination of a driving force or braking force distribution device which distributes the driving force or braking force between the right and left wheels or between the front and rear wheels and an electric power steering device which applies a steering assist torque to a steering system.
2. Description of the Relevant Art
There is a known technique for enhancing turning performance of a vehicle where the ratio by which the engine driving force is distributed between the right and left driven wheels is made variable, and the driving force distributed to the outer turning wheel is increased while the driving force distributed to the inner turning wheel is decreased so as to generate a yaw moment in the turning direction. In a vehicle having such a driving force distribution device, there is a disadvantage that when the driving forces distributed to the right and left driven wheels are varied, an undesirable steering force is produced in the right and left driven wheels which also serve as steered wheels (the torque steer phenomenon). Therefore, the present assignee has already made a proposal in which the torque steer phenomenon is lessened by utilizing an electric power steering device, which is provided in a vehicle and generates a steering assist torque in the electric power steering device so as to counteract the above-mentioned undesirable steering force (ref. Japanese Patent Application No. 9-302155).
Also, the present assignee has already made a proposal in which, with regard to a vehicle having an electric power steering device and in order to prevent an undesirable steering assist torque from being generated by an abnormality in the control means for the electric power steering device, when the actual motor current running in the motor of the electric power steering device and the steering torque detected by the steering torque detecting means are in a predetermined assist inhibition area, the drive of the motor of the electric power steering device is inhibited (ref. Japanese Patent Application No. 10-370099).
In the case where the vehicle has both of the previously proposed driving force distribution device and electric power steering device, the actual motor current of the electric power steering device includes a current component for assisting the steering operation of the driver and a current component for lessening the torque steer phenomenon. Therefore, if the value for the aforementioned assist inhibition area is looked up on the basis of the actual motor current, there is a possibility that, under the influence of the current component for lessening the torque steer phenomenon, the operation of the electric power steering device could be inhibited when its operation is necessary or the operation of the electric power steering device could be permitted when its operation is unnecessary.
The present assignee has, however, already made another proposal in which, with regard to a vehicle carrying out co-operative control of a driving force distribution device and an electric power steering device, the torque steer phenomenon can be effectively reduced by changing the aforementioned assist inhibition area according to the value of the current component for lessening the torque steer phenomenon so as to make the electric power steering device generate a steering torque in the opposite direction to that for assisting the steering operation (ref. Japanese Patent Application No. 11-63114).
When a vehicle carrying out co-operative control of a driving force distribution device and an electric power steering device travels in a straight line, both the current component for assisting the steering operation and the current component for lessening the torque steer phenomenon become zero. However, in the case where a current component for lessening the torque steer phenomenon is output due to a malfunction of the control means when the vehicle is travelling in a straight line and the torque steer phenomenon is not occurring, since the above-mentioned proposal described in Japanese Patent Application No. 11-63114 does not inhibit the output of the current component for lessening the torque steer phenomenon by using an assist inhibition area, an unexpected steering assist torque is produced and there is a possibility that the driver might experience a disagreeable sensation.
SUMMARY OF THE INVENTION
The present invention has been carried out in view of the above-mentioned circumstances, and it is an objective of the present invention to prevent the electric power steering device from generating a steering assist torque which gives a disagreeable sensation to the driver when the control means malfunctions in a co-operative control system for a vehicle which reduces the torque steer phenomenon by co-operatively controlling a driving force or braking force distribution device and an electric power steering device.
In order to achieve such objective, in accordance with a first characteristic of the present invention, a co-operative control system for a vehicle is proposed, with regard to a vehicle comprising force distribution device for distributing the driving force or braking force between spaced apart wheels, the vehicle co-operative control system comprising: a first control means for controlling the operation of the force distribution device; an electric power steering device having a motor for applying a steering assist torque to the vehicle steering system; and a second control means for calculating a motor control signal for driving the motor based on at least a steering torque signal detected by a steering torque detecting means and for inhibiting drive of the motor based on at least an actual motor current signal detected by a current detecting means and the steering torque signal; wherein the first control means calculates a correction signal for correcting the motor control signal based on an amount of control of the force distribution device and an offset current for correcting the actual motor current signal, and the second control means drives the motor based on a corrected motor control signal obtained by correcting the motor control signal with the correction signal and inhibits the drive of the motor based on a value obtained by correcting the actual motor current signal with the offset current and the steering torque signal, the offset current being set so as to be smaller than the correction signal.
In accordance with such co-operative control system for a vehicle, since a corrected motor control signal is calculated by correcting a motor control signal calculated by the second control means of the electric power steering device with a correction signal calculated by the first control means based on the amount of control of the force distribution device, and the second control means drives the motor of the electric power steering device based on the corrected motor control signal, it is possible to simultaneously assist the steering operation of the driver and lessen the torque steer phenomenon. Moreover, since the offset current for correcting the actual motor current signal is set so as to be smaller than the correction signal, when it is determined that the drive of the motor should be inhibited, if the first control means malfunctions so outputting an inadequate correction signal, it is possible to effectively inhibit the drive of the motor and prevent the electric power steering device from generating a steering assist torque which would give the driver a disagreeable sensation.
In accordance with a second characteristic of the present invention, in addition to the first characteristic described above, a co-operative control system for a vehicle is proposed, with regard to a vehicle having a force distribution device for distributing the driving force or braking force between spaced apart wheels, the co-operative control system comprising: a first control means for controlling the operation of the force distribut
Hori Masakatsu
Inagaki Hiromi
Iwazaki Akihiro
Kuribayashi Takashi
Okuma Shinji
Blackman William D.
Carrier Joseph P.
Carrier Blackman & Associates P.C.
Cuchlinski Jr. William A.
Honda Giken Kogyo Kabushiki Kaisha
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