Motor vehicles – Steering gear – No mechanical connection between steering shaft and steering...
Reexamination Certificate
2002-01-22
2003-09-02
Morris, Lesley D. (Department: 3611)
Motor vehicles
Steering gear
No mechanical connection between steering shaft and steering...
C180S422000, C701S041000, C701S042000
Reexamination Certificate
active
06612392
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a steering wheel used in an indoor facility for driving practice, a reactive wheel of a game system and a steering wheel of a vehicle, and more particularly to a steer-by-wire system, which employs a brake using magneto-rheological fluid as an actuator to provide a driver with smooth feeling, and to escape improper and potentially dangerous acceleration of the steering wheel by the active actuator when driver's hands are released from steering wheel abruptly.
2. Description of the Prior Art
As well known to those skilled in the art, a driver is able to sense information on vehicle conditions and road surface conditions through a mechanical connection between a steering wheel and wheels of the vehicle. However, since a steer-by-wire system does not have any mechanical connection, an additional control is required to transmit suitable steering reaction force to the driver.
FIG. 1
shows a general structure of a steer-by-wire system using an active actuator of the prior art.
Referring to
FIG. 1
, in the steer-by-wire system of the prior art, there is no mechanical connection between a steering operator unit
700
and a steering actuator unit
710
. When the steering operator unit
700
receives a steering input from a steering wheel
600
, a motor of the steering actuator unit
710
turn the vehicle's wheels
660
accordingly.
In other words, the steering system has a first steering column which is connected to the steering wheel
600
and is rotated by the same, and a second steering column which is installed at a distance from the first steering wheel and rotatable in situ. A motor
610
for providing steering reaction force to the driver via the steering wheel
600
is coupled with the first steering column via a gear
630
. A motor
620
for steering the wheels
660
is engaged into the second steering column via a gear
630
.
Also, an angle sensor
640
for detecting a rotation angle of the steering wheel
600
and a torque sensor for detecting torque applied to the steering wheel
600
are provided at one end of the first steering column. A controller
650
controls the motor
620
in response to signals applied from the steering wheel angle sensor
640
so as to regulate a rotation angle of the vehicle wheels
660
. Also, the controller
650
controls the wheel steering motor
610
so that the steering wheel can be manipulated with a feeling similar to that in the mechanical steering system.
In the steer-by-wire system of the prior art configured as above, the steering wheel
600
is required to serve as a conventional steering wheel for changing the direction of the travel of a vehicle according to a steering input of the driver, and at the same time to make the driver feel a suitable amount of steering force. Therefore, in addition to the above steering wheel
600
, the steering system needs a rotation angle sensor for measuring an angle inputted by the driver and transmitting the same to the controller, and a steering wheel actuator for transmitting steering reaction force to the driver. Here, the steering wheel actuator is a very important component for influencing the controllability and stability of the steering wheel
600
, and employs a motor.
However, when a system with low impedance such as the steering wheel
600
of the steer-by-wire system is force-feedback controlled by using an active actuator such as the motor, the steering wheel
600
can be accelerated by the motor or the actuator at the moment that the steering input is removed. Then, the stability of the system cannot be ensured. Therefore, an active actuator such as the motor is not suitable for the steering wheel
600
of the steering system, where stability is important. Also, in using an active actuator such as a motor, an oscillatory torque is transmitted to the steering wheel
600
. Then, the driver feels vibration from the steering wheel that causes the driver to feel uncomfortable.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a steer-by-wire system using a semi-active actuator, in which a suitable amount of steering reaction force is supplied to a steering wheel by using a magneto-rheological brake as the semi-active actuator, by which stability can be promoted even if a driver input is removed, and a driver can feel smoothness in steering.
It is another object of the invention to provide a steer-by-wire system using a semi-active actuator which supplies steering reaction force to a steering wheel in response to driving conditions without a mechanical connection with wheels of a vehicle, and thus can be applied to the virtual reality system industry and the game industry.
In order to accomplish the above objects, the present invention provides a steer-by-wire system using a semi-active actuator, in which a wheel steering motor operates vehicle wheels when a steering wheel is rotated, the system comprising: a steering operator unit having a steering column with one end vertically connected to the center of the steering wheel, a torsion spring means connected between the other end of the steering column and a vehicle body via jigs mounted to both ends thereof, a magneto-rheological brake for providing steering reaction force according to the amount of current, a rotation angle sensor coupled with one end of the steering column for detecting rotation of the steering wheel, and a torque sensor coupled with one end of the steering column for detecting steering torque; a current regulator for controlling resistance force against rotation of the magneto-rheological brake; and a controller for controlling the current regulator according to torque data from the torque sensor, and controlling the wheel steering motor
110
according to rotational displacement data from the rotation angle sensor.
It is preferred that the magneto-rheological brake has a rotor fixed to the outer periphery of the steering column, a plurality of cores spaced apart from the rotor by a predetermined interval and wound with coils, and a housing spaced apart from the rotor by a predetermined interval for receiving the rotor and the plurality of cores, wherein the rotor, the plurality of cores and the housing define a space for containing a magneto-rheological fluid.
It is also preferred that the housing is fixed to the vehicle body to support rotation of the steering wheel, and the torsion spring means has a double structure of springs connected in parallel, in which one of the springs has diameter and spiral direction different from those of the other.
Also, it is preferred that the jigs are a pair shaped as a column, one of the jigs being centrally fixed to the steering wheel, and the other one of the jigs being fixed to the vehicle body.
In order to accomplish the above objects, the present invention further provides a steer-by-wire system using a semi-active actuator, in which a wheel steering motor operates vehicle wheels when a steering wheel is rotated, the system comprising: a steering operator unit having a first steering column vertically connected to the center of the steering wheel, a second steering column connected to the first steering column, a first torsion spring means connected between the first steering column and the second steering column via first jigs mounted to both ends thereof, a second torsion spring means connected between the second steering column and a vehicle body via second jigs mounted to both ends thereof, a first magneto-rheological brake for comparing torque by the first torsion spring means with the reference steering torque and providing resistance force to compensate for an error, a second magneto-rheological brake mounted to the second steering column for regulating torque by the first torsion spring means, a first rotation angle sensor coupled with one end of the first steering column for detecting angle displacement of the steering wheel,
Jung Inyong
Park Young-jin
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Korea Advanced Institute of Science and Technology
Lum L.
Morris Lesley D.
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