JPH0568642B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a steering angle detection device that can accurately detect a steering angle.

(b) Prior Art Conventionally, a travel guidance device has been proposed that calculates the current position of a vehicle based on the travel distance of the vehicle and the traveling direction and displays the result on a map. This type of travel guidance device uses a magnetic compass to detect the direction of the earth's magnetic field, but the earth's magnetic field may be affected by the proximity of railroad tracks or power lines carrying large currents, buildings, or other vehicles. There is a problem in that the detected direction is erroneous because the current position of the vehicle that is calculated and displayed is erroneous.

For example, in Japanese Patent Application Laid-Open No. 57-166513, when an error occurs in the detected azimuth based on the earth's magnetism, the azimuth of the vehicle is corrected by calculating the azimuth angle of the vehicle based on the steering angle of the steering wheel.

By the way, when using the steering angle to correct errors in the detected direction due to disturbances in the earth's magnetic field in the above-mentioned travel guidance system, it is necessary to know the absolute steering angle.
For example, when using a rotational displacement detection type sensor, it is necessary to provide a switch for detecting the neutral position on the actual steering side (i.e., the steering wheel) in order to detect the neutral position that is the reference (center) of the steering angle. However, because there are variations in the mounting position of the sensor and the gear ratio between the steering wheel and the actual steering wheel is about 15 to 20 times, it is not possible to accurately detect the neutral position with the actual steering wheel, and even at the same neutral position, the steering play may vary. Due to the inability to absorb errors in vehicle position detection, there has been a problem in that corrections when the earth's magnetic field is disturbed are not sufficient.

On the other hand, Japanese Patent Application Laid-open No. 57-41267 describes the property that when a vehicle is moving straight ahead at a certain speed or higher, the amplitude of the steering angle is within a certain range, and this state is maintained for a certain period of time. A method has been proposed in which a stable steering angle sensor is detected at all times by using a steering angle sensor, and by using this method, it is possible to determine whether the vehicle is traveling straight.

Therefore, it is conceivable to use the detection method of the steering angle sensor proposed in the above-mentioned Japanese Patent Application Laid-Open No. 57-41267 to determine whether the vehicle is running straight ahead, and to correct the detected azimuth error by combining it with the relative steering detection. When the vehicle is traveling at high speed around a gentle curve, it is determined that the vehicle is traveling straight, and there is a problem in that accurate direction cannot be detected. Further, when the vehicle is traveling on a sloped road, a similar problem occurs because the steering wheel is not in the neutral position even when the vehicle is traveling straight.

(c) Object and Structure of the Invention The present invention has been made in view of the above points, and has the object of accurately detecting the steering angle. The system is configured to determine whether the vehicle is traveling straight based on changes in the steering angle and changes in the steering angle.

FIG. 1 is a block diagram showing the overall configuration of the present invention, which includes a distance sensor that outputs distance data every time the vehicle travels a certain distance, a direction sensor that detects the direction of travel of the vehicle using geomagnetism, A steering angle sensor that detects a steering angle based on the rotation of the steering wheel is provided, and a change determination means determines changes in heading and changes in steering angle during a predetermined travel distance using distance data, and based on the determination result, The vehicle is configured to determine whether the vehicle is traveling straight by using a straight traveling determining means.

(d) Examples The present invention will be explained below based on the drawings.

FIG. 2 is a block diagram of an embodiment of the steering angle detection device according to the present invention.

In the figure, 1 is a steering angle sensor that detects the rotation angle of the steering wheel, 2 is a distance sensor that generates a pulse for each unit traveling distance, 3 is a geomagnetic sensor that detects the heading of the vehicle and outputs azimuth data, and 4 is the azimuth. This is a smoothing device that averages (moving average) data for each fixed distance traveled. Reference numeral 5 denotes a steering change determination device that determines a change in steering angle from the steering change from the steering angle sensor 1 and the travel distance from the distance sensor; 6 determines a change in the traveling direction from the moving averaged orientation data and the travel distance. 7 is a straight-ahead traveling discriminator that determines that the vehicle is traveling straight if there is no or little steering and there is no change in azimuth while traveling a predetermined distance according to the signals from the change discriminating devices 5 and 6; This is a neutral position setting device that resets a steering angle counter when the vehicle is traveling straight in response to a signal from the straight traveling reaction device 7.

Figure 3 shows a steering angle sensor built into the steering wheel, which includes a disc 1a with a slit inside the steering wheel 9 and two sets of photocouplers 1.
It is configured by providing a photo sensor 1b having bR and 1bL, and detects the left and right rotation angle of the steering wheel.

FIG. 4 is an example of a control circuit of a travel guidance device that uses the steering angle detection device according to the present invention to guide the travel of a vehicle by a microcomputer.

In the figure, the geomagnetic sensor 3 generates azimuth signal data (X, Y) according to the traveling direction of the vehicle using the geomagnetism.
The direction sensor outputs the direction signal data as A/
It is converted into a digital signal by a D converter 10.
Pulse signals from the steering angle sensor 1 and distance sensor 2 and signals from the A/D converter 10 are sent to the CPU 12 via the peripheral interface IC PIA 11.
transmitted to. The CPU 12 performs arithmetic processing to be described later. The arithmetic processing results in the CPU 12 are displayed on the display device 14 via the display device driving interface 13.

Next, the operation of the travel guidance device will be explained.

Figure 5 shows the basic process for the travel guidance device to perform the drive guide function, which starts when the power is turned on. First, in the initial processing routine, input devices such as peripheral interface ICs, counters, etc. are set, and furthermore, the steering counter _Ns for counting pulses from the steering angle sensor 1 is set to zero (F-100). Next, steering angle sensor 1, distance sensor 2, geomagnetic sensor 3
The current position of the vehicle is calculated based on the output data from the F-
101, F102).

FIG. 6 shows the processing step (F-
101) is a process for detecting the steering angle, and the pulse signal from the steering angle sensor 1 when the steering wheel 9 rotates in the normal direction.
Interrupt processing is performed at the rising edge of SEN1.
Pulse signals SEN1 and SEN2 generated when the steering wheel 9 rotates (a) in the forward direction and (b) in the reverse direction are the seventh pulse signals.
As shown in the figure, they are shifted by a quarter wavelength.
Therefore, first, the reverse rotation pulse signal at the rising edge of the forward rotation pulse signal SEN1 from the steering angle sensor 1.
Determine the level of SEN2 (F-200), and as shown in Figure 7, if it is at the “L (Low)” level,
Judging to be normal rotation, proceed to step (F-201) and press “H”.
(High)" level, it is determined that the rotation is in reverse and the process proceeds to step (F-202). When the steering wheel is rotating in the forward direction, the steering counter _Ns is counted up,
Steering counter when steering is reversed
Count down the _Ns .

FIG. 8 shows the process of resetting the steering counter _Ns in order to set the neutral position in the steering angle detecting device of the present invention, and the interrupt process is performed by a distance pulse output from the distance sensor 2 every time the vehicle travels a certain distance. It can be done.

When an interruption is made by a distance pulse, first, in step (F-300), the reference value N _B of the steering counter and the count value N _s calculated in FIG. If the difference is within one pulse, the process proceeds to step (F-301), and if it is two or more pulses, the process jumps to step (F-305). In step (F-301), in order to determine whether the traveling direction has changed or not, the reference direction data θ _B determined in the subsequent step (F-307) and the direction data from the geomagnetic sensor 3 are used. The average orientation data θ _AV averaged by the smoothing device 4
If the difference is within θ _a (for example, about 5 degrees), the process proceeds to the next step (F-302), and if it is greater than θ _a , the process proceeds to step (F-305).

When the conditions of steps (F-300, F-301) are satisfied, that is, when the steering is hardly performed and the heading does not change much, the traveling distance is counted up while driving straight (F-
302). Next, in step (F-303), the contents of the mileage counter CNT and a predetermined value A (for example, 100
m equivalent), and the contents of counter CNT are A.
If this is the case, proceed to the next step (F-304).
If it is less than A, proceed to return RTS. Therefore,
If the condition of CNT≧A is satisfied in step (F-303), that is, if the vehicle has traveled a predetermined distance or more with little steering change and direction change, the steering counter _Ns is cleared (reset) (F-303). 304), set the steering wheel to its neutral position. In this way, since the straight-ahead state can be confirmed over a relatively long travel distance, the neutral position can be detected with high accuracy. However, when resetting the neutral position, the heading of the vehicle cannot be determined from the steering angle, so it is necessary to reset as soon as possible, and it is better to set the initial reset conditions to be weak (i.e., the predetermined travel distance is short). .

Next step (F-305, F-306, F-
307), the conditions for performing the reset in step (F-304) are initially set. That is, clear the mileage counter CNT, set the reference value N _B of the steering counter, and set the reference direction data θ _B
Set. After that, the process returns to the process before the interrupt.

9 and 10 show flowcharts of two other embodiments for setting the neutral position in the steering angle detection device according to the present invention, and in these embodiments, steps with the same step numbers as in FIG. The objects perform the same processing.

Figure 9 is a processing program that increases the predetermined travel distance for determining whether the vehicle is traveling straight each time it is reset, and adds the processing shown in step (F-308) after the reset processing in step (F-304). It has been realized. The process of this step (F-308) is to add an additional distance B (for example, 50 m) to the predetermined traveling distance A.
The initial value of the predetermined travel distance A is assumed to be set in the initial processing (F-100) in FIG. 5 (for example, 50 m). Furthermore, the predetermined mileage A is
An initial value is set each time it is turned on from OFF, and it is also possible to set a maximum value (for example, 500 m) to set a limit.

Figure 10 shows a program that changes a predetermined mileage according to the traveling vehicle speed, and after the mileage count-up processing indicated by step (F-302), the steps (F-309 to F-312) surrounded by broken lines are executed. This is achieved by adding processing.

First, step (F-309) is a process to determine the running speed of the vehicle.
If the speed is less than h), go to the step (F-310), and if the speed is medium (for example, 30 to 60 km/h), go to the step (F-310).
-311), and if the speed is high (for example, 60 km/h or more), proceed to step (F-312). Here A ₁ ~ _{A 3}
For example, let A ₁ = 30 m, A ₂ = 80 m, and A ₃ = 150 m. In this case, the traveling vehicle speed is detected at the pulse interval of the distance pulse output from the distance sensor, that is, at the 9th pulse interval.
The time interval for processing the processing program shown in the figure can be detected and determined from the time in between. Also, by inserting the process shown in step (F-313) after step (F-304), once the reset is applied, the next condition will be a longer distance (however, the maximum length is A ₃ ). It's meant to be.

Incidentally, in the above embodiment, the change in the reset condition is determined by the change in travel distance, but the width of change in steering angle or the width of change in azimuth angle may be changed. Furthermore, on congested roads, vehicle speeds are low and driving is slow, so even if the road is a straight road, there are almost no steering changes and long distance driving is not common. Therefore, if the reset conditions are relaxed when the vehicle speed is low, the steering angle can be corrected at a relatively early stage. However, it is necessary to gradually tighten the reset conditions from the second time onward to perform a more accurate reset.

(E) Effects of the Invention As explained above, in the present invention, changes in the heading and steering angle are determined over a predetermined travel distance, and based on the determination results, the straight-ahead state of the vehicle is determined, and the straight-ahead state of the vehicle is determined. When it is determined that the vehicle is moving, the detected steering angle is reset, so that when the vehicle is traveling on a gentle curve, it will not be mistakenly judged as a straight line. In this case, the accurate neutral position can be detected without the need for a switch for detecting the neutral position of the steering wheel, so changes in the vehicle's orientation can be detected from the steering angle, and geomagnetic orientation data can be corrected accurately. Therefore, when the steering angle detection device according to the present invention is used in a vehicle travel guidance device to display the current position of the vehicle, accurate position display is possible. In addition, since the vehicle is reset repeatedly while driving, it is possible to absorb play in the steering due to road inclinations, etc. Furthermore, since the steering angle detection device of the present invention detects the neutral position using a distance sensor, a geomagnetic sensor, etc., when this device is incorporated into a device that detects the position of a vehicle using a geomagnetic sensor, There is no particular increase in cost, and highly accurate disturbance correction can be performed.

Further, in the present invention, the reset is performed within a relatively short distance after the power (ignition switch) is turned on, and the direction data can be corrected immediately, and thereafter it is possible to perform the reset again every longer distance traveled. Further, since the reset is applied according to the driving condition, the neutral position can be reset even in conditions where it is difficult to reset conventionally, such as during traffic jams, and the azimuth data can be corrected.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a steering angle detection device according to the present invention, FIG. 2 is a block diagram of a steering angle detection device according to the present invention, and FIG. 3 is a schematic diagram showing the installation state and configuration of a steering angle sensor. FIG. 4 is a block diagram of a control circuit of a travel guidance device that uses a steering angle detection device according to the present invention to guide vehicle travel by a microcomputer, and FIG. FIG. 6 is a flow chart of the steering angle detection process, FIG. 7 is a time chart of the steering pulse signal, and FIGS. 8, 9, and 10 are flow charts of the steering angle neutral position according to the present invention. Three different examples of reset processing flowcharts are shown. 1...Steering angle sensor, 2...Distance sensor, 3...
...Geomagnetic sensor, 5...Steering change discrimination device, 6...
...Azimuth change discrimination device, 7...Straight running discrimination device,
8... Neutral position setting device, 9... Steering wheel, 14... Display device.

Claims (1)

[Claims] 1. A distance sensor that outputs distance data every time the vehicle travels a certain distance, a direction sensor that uses geomagnetism to detect the direction of travel of the vehicle, and a steering angle sensor that detects the steering angle based on the rotation of the steering wheel.
a change determining means for determining a change in the traveling direction and a change in the steering angle during a predetermined travel distance from the distance data, the traveling direction and the steering angle; and determining whether the vehicle is traveling straight based on the determination result of the change determining means. A steering angle detection device comprising: straight-ahead determining means.