Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
2001-02-13
2002-12-17
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S043000, C180S446000
Reexamination Certificate
active
06496762
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automotive electric power steering controller that uses an electric motor to generate torque for assisting driver's steering force to thereby supplement the steering force supplied to the steering system. The invention also relates to a method of controlling this electric power steering controller.
2. Description of the Related Art
FIG. 14
is a block diagram showing the structure of the prior art electric power steering controller described, for example, in Japanese Patent Laid-Open No. 186994/1995. This controller has a steering torque detector
1
for detecting steering torque when the driver steers. A steering torque controller
2
calculates an assisting torque based on the output from the steering torque detector
1
and produces an output signal indicating the calculated assisting torque. A motor speed detector
3
detects the speed of an electric motor. A damping compensator
4
calculates and produces a damping compensation signal based on the motor speed detected by the motor speed detector
3
. A motor acceleration detector
5
detects the acceleration of the motor using the output from the motor speed detector
3
. An inertia compensator
6
calculates and produces an inertia compensation signal based on the motor acceleration detected by the motor acceleration detector
5
. A judging unit
7
makes a decision as to whether the output from the steering torque detector
1
and the output from the motor speed detector
3
are identical in sense and supplies the result of the decision to all of the steering torque controller
2
, the damping compensator
4
, and the inertia compensator
6
. A first adder
8
produces the sum of the assisting torque signal, the damping compensation signal, and the inertia compensation signal. This sum is referred to as the target torque. A motor current determiner
9
calculates and produces a target current signal from the target torque. The aforementioned motor is indicated by numeral
10
, produces a motor current value corresponding to an applied voltage, and generates an assisting torque that is roughly in proportion to the motor current value, thus driving the steering mechanism. A motor current detector
11
detects the current value of the motor
10
. A second adder
12
finds the difference between the target current signal produced by the motor current determiner
9
and the motor current value detected by the motor current detector
11
. A motor driver
13
determines a voltage applied to the motor
10
according to the error between the target current signal calculated by the motor current determiner
9
and the motor current value detected by the motor current detector
11
and applies the determined voltage to the motor
10
. A vehicle speed detector
14
detects the speed of the vehicle and sends a signal indicating the detected vehicle speed to all of the steering torque controller
2
, damping compensator
4
, and inertia compensator
6
.
The operation of the prior art electric power steering system constructed in this way is now described. When the driver of the automobile steers the steering wheel, the produced steering torque is measured by the steering torque detector
1
and sent to the steering torque controller
2
. This torque controller
2
calculates the assisting torque that is roughly in proportion to the output signal from the steering torque detector
1
and drives the motor
10
according to the assisting torque signal. In this way, the motor supplements the driver's steering torque. Consequently, the steering torque that the driver must produce is alleviated.
At this time, the judging unit
7
makes a decision as to whether the output from the steering torque detector
1
and the output from the motor speed detector
3
are identical in sense. If they are identical, neither the damping compensator
4
nor the inertia compensator
6
is operated; only the steering torque controller
2
is operated. The steering torque controller
2
determines the assisting torque signal according to both output from the steering torque detector
1
and vehicle speed signal from the vehicle speed detector
14
. The target torque is determined from this determined assisting torque signal. The motor current determiner
9
determines the motor driving current.
If they are not identical, the steering torque controller
2
is not operated; the damping compensator
4
and the inertia compensator
6
are operated. The target torque is determined from the output from the damping compensator
4
and from the output from the inertia compensator
6
. The motor current determination unit
9
determines the motor driving current. If the vehicle speed is low, the target torque is made identical in direction with the rotation of the motor. If the vehicle speed is high, the target torque is made opposite in direction to the rotation of the motor. Accordingly, when the driver is steering the steering wheel, the electric power steering system supplements the driver's steering torque to alleviate the torque necessary for the steering. When the driver is returning the steering wheel, if the vehicle speed is low, the electric power steering system assists the steering wheel to return to its center position. If the vehicle speed is high, the motor
10
is so controlled that the steering wheel is prevented from returning to its center position at an excessively high speed.
Generally, the driver steers when the vehicle turns round road curves or across road junctions and then the vehicle returns to straight-line driving. At this time, he or she returns the steering wheel by making use of spontaneous returning force of the steering wheel owing to reaction torque applied from the road surface through the tires. However, when the vehicle speed is low or the steering wheel is rotated through only a small angle during high-speed driving, the reaction torque applied from the road surface through the tires is weak and so the reaction torque is less than the frictional torque within the steering mechanism. Therefore, the steering wheel often does not return to its center position when the vehicle returns to straight-line driving. In this case, accordingly, the driver must apply torque to the steering wheel in returning the steering wheel. Consequently, the steering feeling deteriorates.
To cope with this problem, the prior art technique makes a decision as to whether the output from the steering torque detector
1
and the output from the motor speed detector
3
are identical in sense at low vehicle speeds. If they are not identical, the motor driving current is so set that the motor
10
is rotated in the forward direction. In this way, the returnability of the steering wheel at low vehicle speeds is improved.
In the prior art technique, when the driver steers while the reaction torque applied from the road surface through the tires is small as encountered when the vehicle turns a junction at a low speed or when turns a curve of a mildly winding road at a high speed, the steering wheel is kept stationary unless the driver applies torque in a direction to return the steering wheel. Hence, the motor
10
does not rotate. At this time, the judging unit
7
cannot judge whether the output from the steering torque detector
1
and the output from the motor speed detector
3
are identical or not. Consequently, the motor driving current cannot be so set that the motor is rotated in the forward direction. Hence, the returnability of the steering wheel cannot be improved.
Furthermore, in the prior art technique, the motor driving current is only allowed to be so set that the motor is rotated in the reverse direction. In consequence, the returnability of the steering wheel cannot be improved.
SUMMARY OF THE INVENTION
The present invention has been made to solve the foregoing problems.
It is an object of the present invention to provide an electric power steering controller which is for use in a vehicle and which permits the driver to return the steering w
Inoue Noriyuki
Inoyama Hisasi
Kurishige Masahiko
Nishiyama Ryoji
Wada Shunichi
Cuchlinski Jr. William A.
Leydig , Voit & Mayer, Ltd.
Marc-Coleman Marthe
LandOfFree
Electric power steering controller and method of controlling... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electric power steering controller and method of controlling..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electric power steering controller and method of controlling... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2992919