JP2639283B2 - Orientation sensor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direction sensor device,
Particularly, the present invention relates to a high-precision and inexpensive direction sensor device suitable for mounting on a vehicle.

[0002]

2. Description of the Related Art In a vehicle provided with a navigation system, there is a great demand for a direction sensor device that can be mounted with high accuracy and at low cost. 2. Description of the Related Art Conventionally, this type of azimuth sensor device has a configuration in which an analog output of an angular velocity sensor is converted into a digital signal at a fixed short period and the digital signal is integrated to obtain a vehicle azimuth as described in Japanese Patent Application Laid-Open No. 64-29707. There are many things.

[0003]

However, in the above-mentioned conventional configuration, since the rounding error of the minimum bit at the time of analog-to-digital (A / D) conversion is sequentially accumulated by digital integration, a relatively large azimuth error occurs as a result. There is a problem. On the other hand, if the resolution of the A / D converter is increased to avoid this, the number of bits of the A / D converter and the subsequent arithmetic circuit increases, which leads to an increase in price and a decrease in arithmetic speed.

[0004] The present invention solves such a problem.
It is an object of the present invention to provide a highly accurate and inexpensive azimuth sensor device without increasing the resolution of a / D converter.

[0005]

SUMMARY OF THE INVENTION According to the present invention, large angular velocities such as when a vehicle makes a right or left turn at an intersection are relatively short, while small angular velocities that occur on a gently curved road are relatively long. Focusing on the point of time, the configuration will be described. The azimuth sensor device includes an angular velocity sensor 1 that emits an analog signal corresponding to an angular velocity, and an analog integration sensor that integrates the analog signal and outputs an analog integration signal. Means 2 and an analog / digital (A / D) for converting the analog integrated signal into a digital signal and outputting the digital signal
Converting means 3 and digital integrating means 4 for integrating the digital signal every time the digital signal reaches a predetermined level
2 and a level detecting means 41 for resetting the analog integrating means 2 and outputting a digital integrated signal of the digital integrating means 42 as an azimuth signal.

[0006]

In the above configuration, the analog signal from the angular velocity sensor 1 is analog-integrated in advance, and the integrated signal is digitally integrated when the converted digital signal reaches a predetermined level. , The accumulation of the rounding error of the minimum bit is minimized, and high-precision azimuth detection can be performed at low cost without increasing the resolution of the A / D converter 3.

[0007]

FIG. 1 shows the configuration of a direction sensor device. The angular velocity sensor 1 is a vibrating gyroscope using a piezoelectric element (for example, Japanese Patent Laid-Open No. 2-266214), and generates an analog output voltage proportional to the angular velocity of the vehicle as shown in FIG.

The output signal of the angular velocity sensor 1 is input to an analog integrator 2 (to be described in detail later), and the integrated output is converted into a digital signal by an A / D converter 3. The digital signal is input to the arithmetic unit 4 and subjected to arithmetic processing to calculate the position of the own vehicle. The processing in the arithmetic unit 4 is performed by software, but the figure shows each processing in a block form. Hereinafter, the processing procedure of the arithmetic unit will be described with reference to the flowchart of FIG.

The A / D-converted digital signal is taken into a level detecting section 41 (step 101) and compared with a predetermined level Ds. When the digital signal reaches a predetermined level Ds, the digital integrating section 42 performs cumulative integration (step 102). , 10
3).

The azimuth calculating unit 45 calculates the vehicle azimuth based on the value of the digital integration (step 103). The own vehicle position calculating unit 46 calculates the map data based on the running distance obtained from the wheel rotation sensor 5 and the vehicle azimuth. The position on the map stored in the storage device 6 is determined and output to the display device 7. Next, a reset signal is output from the level detector 41, and the output of the analog integrator 2 is reset (step 1).
04).

During this processing, the offset calculating section 43
Receives the vehicle stop signal from the vehicle stop detection unit 44, calculates the offset amount of the angular velocity sensor 1, and corrects the integrated value in the digital integration unit 42.

FIG. 4 shows a detailed circuit of the analog integrator 2. The integrator 2 comprises an operational amplifier 21 constituting a buffer of an input section and an operational amplifier 22 constituting a bootstrap integration circuit of an output section. The "+" terminal of the operational amplifier 22 is provided with an integrating capacitor 24 and a reset in parallel therewith. FET switch 23 is connected.

The voltage output of the angular velocity sensor 1 is input to the terminal 2a of the analog integrator 2, charges the capacitor 24, and is integrated and converted into the voltage between both ends.
The signal is doubled by 5, 26 and output to the terminal 2b and input to the A / D converter 3 (FIG. 1) at the subsequent stage. The pulse reset signal from the arithmetic unit 4 is input to the terminal 2c, and the switch 23 is turned on to discharge the capacitor 24.

Now, in a vehicle, as shown in FIG.
An angular velocity having a large absolute value appears for a relatively short time when turning right or left at an intersection (x area in the figure), and a medium angular velocity appears for a longer time while traveling on a curved road or the like (y area in the figure). . Then, when traveling on a slowly curved road, a small angular velocity appears continuously for a long time (z region in the figure).

FIG. 6 shows the output voltage of the analog integrator 2 when a large angular velocity occurs. In this case, the output voltage of the angular velocity sensor 1 is large, and the digital signal obtained by digitally converting the integrated signal quickly reaches a predetermined level. Therefore, the digital integrating section 42 operates to integrate the digital signal and perform analog integration. Output is reset in a short period. However, when turning right or left at an intersection,
The azimuth signal, which is a digital integrated value, is changed quickly.

When the angular velocity is small, the output voltage of the angular velocity sensor 1 is small (FIG. 7), and the digital signal obtained by digitally converting the integrated signal reaches a predetermined level over time. Therefore, the digital integrator 42 is operated in a long cycle, and the output of the analog integrator 2 is also reset in a long cycle. In this case, the direction signal changes slowly, but there is no problem because the direction of a vehicle traveling on a gently curved road changes.

When the vehicle travels straight, the angular velocity is small and swings positively or negatively, but this is absorbed by the integrator and does not appear in the direction signal.

As described above, the output voltage of the angular velocity sensor 1 is integrated by the analog integrator 2 in advance, and digital integration is performed only when the digital signal obtained by converting the integrated signal reaches a predetermined level. The accumulation of the rounding error of the minimum bit at the time of conversion is minimized as compared with a conventional apparatus that frequently performs A / D conversion. Thus, high-accuracy azimuth detection can be performed at low cost without increasing the resolution of the A / D converter 3.

Further, the current angular velocity sensors 1 each have an inherent offset. In the configuration of the present invention, the offset is integrated by an analog integrator 2 and a digital signal obtained by converting the integrated signal is equal to or higher than a predetermined level. Since the digital integration is performed for the first time, the accumulated error caused by the A / D conversion of the offset can be suppressed to a small value.

In the above embodiment, if the digital signal input to the level detector 41 does not exceed the predetermined level for a certain period of time, digital integration is forcibly started.
The configuration may be such that the analog integrator 2 is reset.

[0021]

As described above, according to the azimuth sensor device of the present invention, high-accuracy azimuth detection can be performed at low cost, and the azimuth sensor device can be suitably used for a vehicle navigation system and the like.

[Brief description of the drawings]

FIG. 1 is an overall configuration block diagram of an apparatus.

FIG. 2 is an output characteristic diagram of an angular velocity sensor.

FIG. 3 is a processing flowchart of an arithmetic unit.

FIG. 4 is a circuit diagram of an integrator.

FIG. 5 is a graph showing a relationship between an angular velocity and a duration in a vehicle.

FIG. 6 is an output waveform diagram of an angular velocity sensor and an integrator.

FIG. 7 is an output waveform diagram of an angular velocity sensor and an integrator.

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 Angular velocity sensor 2 Analog integrator (Analog integration means) 3 A / D converter (A / D conversion means) 4 Computing device 41 Level detection part (Level detection means) 42 Digital integration part (Digital integration means) 44 Direction detection part 46 Own vehicle position calculation unit

Claims (3)

(57) [Claims] 1. An angular velocity sensor for emitting an analog signal according to an angular velocity, an analog integrating means for integrating the analog signal and outputting an analog integrated signal, and an analog / digital converter for converting the analog integrated signal into a digital signal and outputting the digital signal. Digital converting means, and level detecting means for operating the digital integrating means for integrating the digital signal each time the digital signal reaches a predetermined level, and resetting the analog integrating means. A direction sensor device that outputs a digital integration signal as a direction signal. 2. The analog integrating means includes at least
Features bootstrap integration circuit
The azimuth sensor device according to claim 1, wherein 3. The digital signal according to claim 2, wherein
Issue does not reach the specified level for a certain period of time
In this case, reset the analog integration means.
The azimuth sensor device according to claim 1, wherein: