Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
1999-09-29
2001-08-21
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C180S197000, C180S233000, C180S404000, C180S442000, C180S443000, C180S446000, C280S735000, C318S052000, C318S432000, C318S489000, C318S587000
Reexamination Certificate
active
06278922
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for controlling the steering angle of a vehicle, which automatically controls the rotational angle (steering angle) of a steering shaft to assume a target value. More particularly, the invention relates to a device for controlling the steering angle of a vehicle, which features improved control precision over a wide range of steering angles.
2. Prior Art
There has heretofore been known a device for automatically controlling the steering angle of a radio-controlled vehicle for use exclusively in yard (hereinafter referred to as “radio-controlled vehicle”) to assume a target angle in an attempt to improve productivity and operation efficiency by saving manpower as taught in, for example, Papers of Academic Lectures, 944, Japanese Technological Association of Automobiles, Oct., 1991.
To control the steering angle of the radio-controlled vehicle of this kind, the rotational angle of the steering shaft must be detected as an absolute value. At present, a voltage detected by a potentiometer is converted into a digital value through an A/D converter and is used as a detected angular value (hereafter an angle detection value).
Similar automatic control devices have also been taught, such as a radio-controlled device for vehicles disclosed in Japanese Unexamined Patent Publication (Kokai) No. 258822/1997 and a steering angle detecting device for vehicles disclosed in Japanese Unexamined Patent Publication (Kokai) No. 13106/1986.
However, the conventional devices disclosed in the above-mentioned publications are still not satisfactory with respect to precision for controlling the steering angle and the control response. When applied to an automatic operation controller used on an automobile road such as an expressway, for example, control performance is not-obtained to a satisfactory degree and it becomes difficult to maintain travelling within a lane.
In order to improve the steering angle control precision and the control response, furthermore, the precision for detecting the steering angle must be heightened. When it is attempted to heighten the resolution of the A/D converter by using a potentiometer, however, the device tends to become susceptible to noise making, after all, and it is difficult to improve the detection precision to a sufficient degree.
Because of lack of steering angle control precision and control response, therefore, the conventional devices for controlling steering angle of the vehicle could not be applied to automatically operating the vehicles on an automobile road.
Besides, when it is attempted to enhance the detection precision of the potentiometer by enhancing the resolution of the A/D converter from the standpoint of improving steering angle control precision and response performance, the device tends to become susceptible to noise making, and it is difficult to improve the steering angle detection precision to a sufficient degree.
SUMMARY OF THE INVENTION
The present invention was accomplished in order to solve the above-mentioned problems, and its object is to provide a device for controlling the steering angle of a vehicle, which features improved control precision over a wide range, by using angle detection values of a first potentiometer in a first angular range corresponding to the whole steering angles and by using angle detection values of a second potentiometer having a high resolution in a narrow second angular range near the neutral point of the steering angles.
A device for controlling the steering angle of a vehicle according to the present invention comprises:
a steering drive means for rotatably driving a steering shaft;
a steering angle detection means for producing the rotational angle of said steering shaft as an angle detection value; and
a target torque operation means for operating a target torque to be applied to said steering shaft based on a deviation between a target angle of said steering shaft and a steering angle based on said angle detection value, wherein
said target torque is applied to said steering shaft through said steering drive means so that said steering angle is brought into agreement with said target angle;
wherein said steering angle detection means includes:
a first potentiometer that produces a second detected angular value (hereafter a first angle detection value) proportional to a-rotational position over a first angular range in which said steering shaft can be turned; and
a second potentiometer that produces a second detected angular value (hereafter a second angle detection value) proportional to a rotational position over a second angular range which includes a neutral point of said steering shaft and is narrower than said first angular range; and
wherein said target torque operation means includes an angle operation unit for operating said steering angle based on said first and second angle detection values; and
wherein said angle operation unit produces said first angle detection value as said steering angle when said first angle detection value lies outside said second angular range, and produces said second angle detection value as said steering angle when said first angle detection value lies within said second angular range.
The angle operation unit includes a weighing/synthesizing means for weighing and synthesizing said first and second angle detection values and wherein, the output value of said weighing/synthesizing means is produced as said steering angle in a range close to an angular position where said first and second angle detection values are changed over, said weighing/synthesizing means uses a first weighing coefficient and a second weighing coefficient which gradually change in a complementary manner in said close range, and produces values obtained by multiplying said first and second angle detection values by said first and second weighing coefficients, said first weighing coefficient being set to 1 outside said second angular range and being set to 0 within said second angular range, and said second weighing coefficient being set to 0 outside said second angular range and being set to 1 within said second angular range.
The angle operation unit includes an offset error operation means for operating an offset error between said first potentiometer and said second potentiometer based on a deviation between said first angle detection value and said second angle detection value, and a correction means for correcting at least either said first angle detection value or said second angle detection value by using said offset error.
The offset error operation means includes a histogram operation means for operating a histogram of a deviation in the detection value, and produces, as an offset error, a deviation in the detection value that appears most frequently in said histogram.
The offset error operation means includes a filtering means, and uses a first filtering coefficient and a second filtering coefficient that are set in a complementary manner, and produces, as said offset error, the values obtained by multiplying the deviation in the detection value of this time and the deviation in the detection value of the previous time by said first filtering coefficient and said second filtering coefficient, respectively.
The offset error operation means produces the offset error of the previous time when a difference between the deviation in the detection value of this time and the deviation in the detection value of the previous time is larger than a permissible value.
The offset error operation means produces said offset error based on said deviation in the detection value when said first angle detection value lies within said second angular range, and produces said deviation in the detection value of the previous time as said offset error when said first angle detection value lies outside said second angular range.
The second potentiometer produces the second angle detection value in a manner to repeat the same value for every turn of said second potentiometer.
A device for controlling the steering
Cuchlinski Jr. William A.
Mancho Ronnie
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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