KR100340209B1 - The vehicle navigation device including temperature-compensation function and the method thereof - Google Patents

Abstract

The present invention relates to a non-contact vehicle navigation apparatus using an acceleration sensor, a gyro sensor, etc., to effectively remove the bias error of the sensor according to the temperature change to enable accurate vehicle position and safe navigation.

Description

Non-Contact Vehicle Navigation System with Temperature Compensation and Temperature Compensation Method {THE VEHICLE NAVIGATION DEVICE INCLUDING TEMPERATURE-COMPENSATION FUNCTION AND THE METHOD THEREOF}

The present invention relates to a non-contact vehicle navigation apparatus having a temperature correction function, which is car interface free.

In general, a vehicle navigation apparatus is used in a transportation device such as a vehicle so as to determine a current position and predict a route and a required time to a destination. The vehicle equipped with the vehicle navigation apparatus includes a GPS (Global Positioning System) receiver, so that information such as latitude, longitude, and altitude transmitted from a plurality of satellites belonging to the GPS is detected from various sensors installed in the vehicle. The current position of the vehicle is calculated based on the information, and the calculated current position of the vehicle is displayed on a map on the monitor. The vehicle navigation apparatus calculates and displays various information necessary for driving the vehicle, such as the driving direction of the vehicle, the distance to the destination, the moving speed, and the shortest distance to the destination.

1 is a block diagram showing a vehicle navigation apparatus according to the prior art. The GPS receiver 8 shown in FIG. 1 simultaneously receives radio waves from a plurality of GPS satellites, calculates the absolute position by longitude and latitude, and provides it to the positioning means 9. The acceleration sensor 1 detects the acceleration in the traveling direction of the vehicle, and the azimuth gyro sensor (also called yaw gyro) 2 detects the rotational angular velocity of the vertical axis rotation with respect to the road surface of the vehicle, and the tilt gyro sensor (pitch) 3) detects the rotational angular velocity of the shaft rotation perpendicular to both the direction of travel of the vehicle and the vertical axis relative to the road surface. The acceleration sensor 1 and the gyro sensors 2 and 3 have the characteristic that the sensitivity coefficient of the output value at rest, that is, the bias value or the actually displayed output value changes irregularly with temperature or time. In addition, vibrations accompanying driving of the vehicle may generate noise in the sensor output signal, resulting in inaccurate calculation data. Such irregular errors are corrected by the random error correction means 4. Next, the distance calculating means 5 calculates the moving distance of the vehicle on the basis of the outputs of the error-corrected acceleration sensor 1 and the gradient gyro sensor 3. In addition, the azimuth calculating means 6 calculates a moving direction of the vehicle on the basis of the error-corrected azimuth gyro sensor 2, and the relative position means 7 calculates the moving distance calculated by the distance calculating means 5 and The relative position of the vehicle is calculated on the basis of the moving bearing calculated by the bearing calculating means 6. Next, the positioning means 9 reads the relative position calculated by the relative position calculating means 7 and the absolute position calculated by the GPS receiver 8 and the map data stored in the map storage means 10 to position the vehicle. Is finally determined, and such location information is displayed on the display means 11 together with the map data.

Unlike the contact navigation system which disassembles the inside of the car and connects the navigation device to the vehicle speed sensor, the parking brake line, the back lamp line, and the like, the non-contact navigation device does not use the vehicle speedometer as described above. In addition, since no separate wiring is required and only power is supplied from a cigar lighter, device movement between vehicles is easy. However, there is a disadvantage that the speed and position error of the device becomes large due to the error of the inertial sensor that changes with time and temperature. Therefore, a technique for automatically correcting the error of the inertial sensor is necessary, and in the related art, all bias errors due to temperature changes are regarded as random errors, and the correction is performed after estimating the error using a Kalman filter. The bias error could not be effectively eliminated until the sensor ambient temperature in the device was maintained at an arbitrary temperature (saturation temperature). Thus, such errors continue to accumulate, which not only degrades the performance of the device significantly, but such inertial sensors alone do not allow accurate navigation.

An object of the present invention is to effectively remove the bias error of the sensor according to the temperature change to enable accurate vehicle position display and safe vehicle navigation.

1 is a block diagram of a non-contact vehicle navigation apparatus according to the prior art.

2 is a block diagram of a non-contact vehicle navigation apparatus according to the present invention.

3 is a diagram showing an example of bias error caused by temperature change.

4 is a diagram illustrating division and characteristics of a bias error.

5 is a diagram illustrating an example of correcting a normal bias error.

6 is a diagram illustrating an example of a sensor coefficient download program screen.

7 is a diagram illustrating an example of a sensor coefficient correction program screen.

※ Explanation of code about main part of drawing ※

1: acceleration sensor 2: bearing gyro sensor

3: tilt gyro sensor 4: random error correction means

5: distance calculating means 6: azimuth calculating means

7: relative position calculation means 8: GPS receiver

9: positioning means 10: map storage means

11 display means 12 temperature sensor

13: Normal error correction means

Vehicle navigation apparatus according to the present invention for achieving the above object is a GPS receiver for receiving positioning data from a plurality of GPS satellites to obtain positioning data; Sensor means comprising an acceleration sensor for measuring the acceleration in the traveling direction of the vehicle, an orientation gyro sensor for measuring the angular velocity in the azimuth direction and the inclination angle direction, and an inclination gyro sensor; Temperature detection means for measuring a temperature around the sensor means; Normal error correction means for correcting a bias error caused by a temperature change of the sensor means; Distance calculating means for calculating a moving distance of the vehicle based on the error-corrected acceleration sensor output; Azimuth calculation means for calculating a moving direction of the vehicle based on the error-corrected gyro sensor output; Relative position calculating means for calculating a relative position of the vehicle based on the movement distance calculated by the distance calculating means and the movement bearing calculated by the azimuth calculating means; Map storage means for storing map data; Position determination means for finally determining the position of the vehicle by reading the relative position calculated by the relative position calculating means, the absolute position calculated by the GPS receiver, and map data stored in the map storage means; And means for displaying location information together with the map data.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of a non-contact vehicle navigation apparatus according to the present invention will be described in detail.

2 is a block diagram showing the configuration of a vehicle navigation apparatus according to the present invention, which is a temperature sensor 12 for detecting a temperature around a sensor inside the apparatus and a normal for correcting a bias error of a sensor generated according to a change in temperature. Except for the error correcting means 13, since it is similar to the block diagram in FIG. 1, the description of the components of the same reference numeral is omitted.

Looking at the operation principle of the non-contact vehicle navigation apparatus according to the present invention configured as described above in detail as follows.

As described above, the acceleration sensor and the gyro sensors have the characteristic that the sensitivity coefficient of the output value at the stop, that is, the bias value or the actually displayed output value varies irregularly with temperature or time. Therefore, it is necessary to correct the bias error of the sensor generated by the change of temperature. The bias error correction of the sensor according to such a temperature change is performed by the normal error correction means 13, and then the irregular error caused by the noise on the sensor output caused by the vibration during driving of the vehicle as already mentioned above. Is corrected by the random error correction means 4.

As shown in FIG. 4, the bias error may be classified into three types, such as a constant error (ie, a certain amount of error), an error caused by temperature change, and a random error. When an input is applied to the gyro 2 or 3 or the acceleration sensor 1, the sensor output is usually output as a voltage value between 0 and 5V. Therefore, in order to obtain signed angular velocity and acceleration information, a reference value indicating a state in which an input is "0" is required, which may be defined as a bias. The ideal bias is 2.5V, which is the middle of the input range, but the true value of the bias is not 2.5V due to problems with the input voltage or the sensor itself. Therefore, in order to increase the accuracy of navigation, the error of such bias must be corrected.

There are various causes of the error in the bias, but mainly due to temperature change and instability of the reference voltage. An example of bias error due to temperature change is shown in FIG. 3. As already mentioned, in the case of an inertial sensor such as a gyro or an acceleration sensor, the bias error is divided into a constant error, an error due to temperature change, and a random error. First, the constant error is an error including a deterministic error having a repetitive characteristic and a random constant error that varies with each driving, and this error component is assumed to remain constant for a short time. In the case of the acceleration sensor, since the gravity acts under the influence of the inclination angle, this constant error cannot be calculated even during the stop. In other words, since zero speed correction is impossible, the bias change rate and the reference temperature for the temperature are obtained, The bias is determined using the difference between the measured temperature and the reference temperature. However, the gyro sensor can be zero speed corrected. When the complete stop condition is satisfied, the average value of the gyro output is set again as a deterministic bias, and the reference temperature is changed to this temperature. Then, while driving, the bias is determined using the difference between the bias change rate and the reference temperature and the measured temperature.

Specifically, the normal bias error can be obtained by the following equation.

Azimuth Gyro Sensor Normal Bias (HGyroDBias) =

Where Hn is the azimuth gyro output and N is the sampling number.

Inclined Gyro Sensor Normal Bias (PGyroDBias) =

Where Pn is the slope gyro output value and N is the sampling number.

If the error caused by the temperature change is corrected only for the constant error described above, the bias is changed during long driving, and thus the accurate angular velocity and acceleration cannot be obtained. The biggest cause of bias changes during driving is temperature change, and these temperature characteristics are different for each product, and it is cumbersome that experiments should be performed for all products, but the temperature correction process is a necessary step when using a low-grade inertial sensor. By using the temperature change amount from the initial temperature, a method of predicting and correcting the bias change amount is used.

Specifically, the bias error can be expressed by the following equation.

Azimuth Gyro Sensor Bias (HGyroBias) = H_SLOPE × (Measured Temperature-Initial Temperature)

Inclined Gyro Sensor Bias (PGyroBias) = P_SLOPE × (Measured Temperature-Initial Temperature)

Accelerometer Bias (AccelBias) = A_SLOPE × (Measured Temperature-Reference Temperature)

Here, the temperature coefficient for each sensor, that is, H_SLOPE, P_SLOPE, A_SLOPE depends on each product characteristic, and can be determined by a product shipment test.

The random error occurs when the error of the bias is corrected by using the constant error component and the error component of temperature change described above. However, the accurate sensor output may not be obtained. Becomes large. Therefore, it is necessary to estimate the bias by averaging the sensor itself data, for example, a Kalman filter or the like is used. Since the random error is applied in most navigation devices, the detailed description is omitted.

An example of correcting the error due to the constant error and the temperature change is shown in FIG. 5. When the EPROM is used as a conventional method for storing programs and data in the navigation device, since the regular bias and the temperature coefficient described above need to be changed to a new one, it is cumbersome to disassemble the device and input a new program in the ROM. In order to prevent such a hassle, in the present invention, by using a flash memory, it is possible to download and rewrite a program or use only this value by downloading a necessary value into a small memory such as a serial EPROM without changing the program. .

FIG. 6 shows an example of a program screen capable of downloading sensor coefficients from a personal computer to a navigation device, and FIG. 7 shows an example of the configuration of a screen for correcting detailed items and corresponding values of the sensor coefficients.

First, since the bias error of the sensor according to the temperature change can be eliminated even in a season where the temperature difference is severe, such as summer or winter season, accurate position display and safe vehicle navigation are possible.

Second, since the bias error due to the temperature change and the reference voltage instability can be eliminated in advance, it is possible to improve the estimation accuracy of the random error appearing while driving.

Third, since the sensor coefficient for temperature compensation can be downloaded from an external device, it is possible to prevent the hassle of disassembling and replacing the device after rewriting the program in the ROM after the correction of the sensor coefficient.

Fourth, since it can be implemented only by adding a temperature sensor and software to the existing configuration, there is an advantage that it is economically cheap.

Claims (3)

A GPS receiver for receiving radio waves from a plurality of GPS satellites to obtain positioning data; Sensor means comprising an acceleration sensor for measuring the acceleration in the traveling direction of the vehicle, an orientation gyro sensor for measuring the angular velocity in the azimuth direction and the inclination angle direction, and an inclination gyro sensor; Temperature detection means for measuring a temperature around the sensor means; Normal error correction means for correcting a bias error caused by a temperature change of the sensor means; Distance calculating means for calculating a moving distance of the vehicle based on the error-corrected acceleration sensor output; Azimuth calculation means for calculating a moving direction of the vehicle based on the error-corrected gyro sensor output; Relative position calculating means for calculating a relative position of the vehicle based on the movement distance calculated by the distance calculating means and the movement bearing calculated by the azimuth calculating means; Map storage means for storing map data; Position determination means for finally determining the position of the vehicle by reading the relative position calculated by the relative position calculating means, the absolute position calculated by the GPS receiver, and map data stored in the map storage means; And And a means for displaying location information together with the map data. The method of claim 1, The normal error correction means is as follows: Azimuth Gyro Sensor Bias (HGyroBias) = H_SLOPE × (Measured Temperature-Initial Temperature) Inclined Gyro Sensor Bias (PGyroBias) = P_SLOPE × (Measured Temperature-Initial Temperature) Acceleration sensor bias (AccelBias) = A_SLOPE × (measurement temperature-reference temperature) is used to correct the bias change using the temperature change from the initial temperature, where the temperature coefficients (H_SLOPE, P_SLOPE, A_SLOPE) for each sensor are Non-contact vehicle navigation apparatus, which varies according to each product characteristic and can be determined by a pre-shipment test. The method of claim 1, wherein the normal error correcting means further comprises a flash memory or a small amount of computer readable memory means for downloading a normal bias and sensor coefficients calculated by an experiment from an external computer device. Contactless vehicle navigation system.