JPS62138716A - Signal processing circuit for azimuth sensor - Google Patents

Abstract

PURPOSE:To perform high-precision azimuth detection by averaging an azimuth sensor signal normally and removing small fluctuations, and outputting the azimuth sensor signal as it is during a period wherein the azimuth sensor signal varies greatly. CONSTITUTION:The azimuth sensor signal A outputted by an azimuth sensor is averaged by an averaging process circuit 1, which outputs an average by a differentiation circuit 2, whose output signal C is inputted to a window comparator 3, and a signal selection control signal D is outputted by comparators 3b and 3d and a OR gate 3e unless the level of the output signal C is within a predetermined range. Then, a signal selecting circuit 4 selects the averaged signal B normally or the azimuth sensor signal A when the signal selection control signal D is generated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a circuit that processes an output signal of a direction sensor mounted on a vehicle to detect the direction of travel of the vehicle, and in particular to a circuit that processes an output signal of a direction sensor that is mounted on a vehicle and detects the direction of travel of the vehicle. The present invention relates to a direction sensor signal processing circuit for reliably and quickly extracting only changes in the direction of travel along a road.

[Prior art]

In recent years, with the rapid development of electronic technology, in-vehicle navigation devices have been developed. This in-vehicle navigation device automatically displays the current location and direction of travel of the vehicle to guide the vehicle to its destination.

Here, the in-vehicle navigation device includes a direction detection section that detects the running direction of the vehicle, a vehicle speed detection section that detects the running speed of the vehicle from the rotation of the wheels, a direction signal generated from the direction detection section, and a direction signal generated from the direction detection section and the vehicle speed. It consists of a calculation part that calculates the current position of the vehicle by inputting and calculating the vehicle speed signal generated from the detection part, and a display part that displays the current position determined by this calculation part along with the driving direction. .

Here, the orientation sensor used in the orientation detection section detects the orientation using earth's magnetism, and consists of two types of coils wound in different directions, each having a level corresponding to the orientation. Direction signal X.

Y is taken out, and the azimuth in the vehicle's traveling direction is determined from the phase relationship and level of these two direction signals.

[Problem that the invention seeks to solve]

However, when an azimuth sensor is mounted on a car to detect the azimuth in the direction of travel, subtle fluctuations occur in the output signal of the azimuth sensor even when driving on a straight road. In other words, even when driving on a straight road, the driver uses delicate steering wheel operations to ensure that the vehicle continues to travel in a straight line, even if the vehicle is drifting left or right.This slight left and right movement of the vehicle causes fluctuations in the direction sensor. This is what appears in the output signal. If fluctuation occurs in the output signal of this direction sensor, an error will occur in the calculation of the current position and the direction of travel.

On the other hand, slight changes have been removed by supplying the output signal of the direction sensor to an averaging processing circuit and applying averaging processing, but if the vehicle actually changes its direction of travel, Since the averaging process is also applied to the signal in the case of a vehicle, the output signal waveform becomes dull and a change in the running direction cannot be detected quickly.

[Means for solving problems]

The orientation sensor signal processing circuit according to the present invention normally averages and extracts the output signal of the orientation sensor to obtain the orientation signal, and if the level of the differential signal obtained by differentiating the output signal of the orientation sensor exceeds the set range, The output signal of the direction sensor is directly extracted as a direction signal.

[For production]

In the azimuth sensor signal processing circuit configured in this way, the azimuth sensor signal is normally averaged and extracted, so subtle fluctuations in the azimuth sensor signal are prevented when driving in a straight line, and a stable azimuth signal is obtained. You will get it. If the level of the differential signal that differentiates the output signal of the direction sensor exceeds the negotiated value, it is determined that the direction of travel of the vehicle has changed along the road, and during this period, the output signal of the direction sensor is directly extracted. This prevents signal delays caused by the averaging circuit and prioritizes prompt detection of changes in travel direction.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of an orientation sensor signal processing circuit according to the present invention. In the figure, reference numeral 1 denotes an averaging processing circuit, which integrates the azimuth sensor signal output from an azimuth sensor (not shown) to extract an averaged signal B from which minute changes have been removed. 2 is a differentiation circuit that differentiates the direction sensor signal A and extracts a differential signal C corresponding to the amount of change; 3 is a differentiation circuit that determines the period in which the level of the differential signal C exceeds a set range, and controls the signal selection control signal. A comparator 3b which is a window comparator that outputs and detects a period in which the differential signal C exceeds the upper limit reference value V□ set by the variable resistor 3a, and a comparator 3b which detects the period in which the differential signal C exceeds the lower limit reference value VL set by the variable resistor 3c. It is comprised of a comparator 3b that detects a period in which the signal decreases beyond that level, and an OR gate 3e that takes out the output signals of both comparators 3b and 3d as a signal selection control signal. Reference numeral 4 denotes a signal selection circuit, which normally selects the averaged signal supplied from the averaging processing circuit 1 to the input terminal 6 to output it as an azimuth signal E, and controls signal selection to be output from the window comparator 3. When the signal RI is inverted to "H", the azimuth signal E is selected by selecting the azimuth sensor signal A supplied to the input terminal a only during the "H" period.
It is configured to output as .

In the direction sensor signal processing circuit configured in this way,
For example, when the azimuth sensor signal A in the state shown in FIG.
By applying averaging processing using an integrating circuit, etc.,
Averaged signal B shown in Fig. 2(b) in which minute changes have been absorbed
is output. On the other hand, the differentiating circuit 2 receives the direction sensor signal A
By differentiating , the differential signal C shown in Fig. 2 [C] is obtained.
is output and supplied to the window comparator 3. Here, the comparator 3b constituting the window comparator 3
Since the differential signal C is supplied to the positive input terminal and the upper limit reference value Vll set by the variable resistor 3a is supplied to the negative input terminal, the differential signal C is set to the upper limit reference value shown in FIG. 2 (C1). When the value VH is exceeded, this comparator 3b
The output of is inverted and an "H" signal is output. This "I" signal is output as a signal selection control signal by the OR gate 3e. In other words, for the differential signal C shown in FIG.
, -zt.

A signal selection control signal is output in between.

Here, the signal selection circuit 4, which is switched and controlled by the signal selection control signal, operates at time 1. During the period up to this point, the level of the differential signal C output from the differentiating circuit 2 is between the upper limit reference value □ and the lower limit reference value VL, and the signal selection control signal is “L”. Averaged signal B shown in figure (b)
is selected and outputted as the azimuth signal E shown in FIG. 2(d). Therefore, during the period up to this point L1, a stable signal from which the fluctuations included in the azimuth sensor signal A have been removed is output as the azimuth signal E. Next, Figure 2(c)
Between time points tI+LZ shown in FIG. 2, since the differential signal C output from the differentiating circuit 2 is greater than the upper limit reference value VH, the window comparator 3 generates an "H" level signal selection control signal. When the signal selection control signal is generated, the signal selection circuit 4 selects the azimuth sensor signal supplied to the input terminal a, and outputs this as the azimuth signal E. That is, in response to a large change in the direction sensor signal A, the direction sensor signal A is taken out as it is and used as the direction signal E, thereby preventing a signal delay.

Here, the signal will contain fluctuations during the period from the time when the differential signal C reaches its maximum to time t2, but this period is quite short and does not pose any problem. It is more effective to be able to detect the direction quickly. Next, after time L2 shown in FIG.
The signal selection circuit 4 outputs the differential signal B, which is stabilized with the fluctuation removed, as the orientation signal E as shown in FIG. 2 (dl).In other words, in this orientation sensor signal processing circuit, If the direction sensor signal fluctuates slightly, it is determined that the vehicle is traveling in a straight line, and the direction sensor signal A is stabilized by averaging processing and outputted as the direction signal E. On the other hand, when the direction sensor signal changes significantly and the direction of travel changes, by outputting the direction sensor signal A as it is, priority is given to stabilizing the direction of travel rather than stabilizing the signal. Therefore, by performing various arithmetic processing using the azimuth signal output from this azimuth sensor signal processing circuit, it is possible to determine the current position and traveling direction with high precision, and to quickly determine changes therein. It becomes possible.

Note that if the running direction changes significantly in the direction opposite to the case described above, the level of the direction sensor signal A will drop rapidly, so the differential signal C output from the differentiator circuit 2 will
will change significantly in the negative direction, but since the window comparator 3 is provided with a comparator 3d that compares the input signal with the lower limit reference value , in this case as well, as in the case described above, The signal selection circuit 4
directly selects and outputs the azimuth sensor signal A, thereby speeding up the detection of azimuth changes.

〔Effect of the invention〕

As explained above, the azimuth sensor signal processing circuit according to the present invention normally averages and extracts the azimuth sensor signal to remove small fluctuations and obtain a stable azimuth signal.
During a period in which the direction sensor signal changes significantly, the direction sensor signal is output as it is as a direction signal. For this reason, under normal conditions, highly accurate direction detection can be performed by removing signal fluctuations and creating a stable direction signal.
It also has the excellent effect of quickly detecting the direction when the running direction changes.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the azimuth sensor signal processing circuit according to the present invention, and FIG. 2 is a waveform diagram showing the operation of each part for explaining the operation of the circuit diagram shown in FIG. 1. 1...Averaging processing circuit, 2...Differentiating circuit, 3...
Window comparator, 4...signal selection circuit. Applicant: NEC Home Electronics Co., Ltd.>
Kujishiku＞ ◆History 0 Rei

Claims (1)

[Claims] an averaging processing circuit that averages the orientation sensor signals output from the orientation sensor and outputs an averaged signal; a differentiation circuit that differentiates the orientation sensor signal; A window comparator that outputs a signal selection control signal when the user is located at An azimuth sensor signal processing circuit comprising: a signal selection circuit that outputs an azimuth signal upon selection.