JPH0786418B2 - Azimuth detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention finds a current position in a moving body such as a car, displays the current position together with a road map around the vehicle, and searches for and guides a route to a destination. The present invention relates to an azimuth detecting device used for a vehicle-mounted navigation system.

2. Description of the Related Art As a conventional azimuth detecting device, for example, Japanese Patent Laid-Open No. 57-200813
It is shown in the publication.

As shown in this example, when a rate gyro that detects angular velocity is used as the azimuth sensor, the sensor output is integrated to calculate the azimuth change amount, which is successively added to the initial azimuth and the advancing azimuth of a moving body such as a vehicle is calculated. To calculate. However, since the zero drift (offset) of the rate gyro is not constant, when the traveling azimuth is calculated with the offset being a constant value, an error due to the integration of the offset is accumulated. In order to avoid it, in the above-mentioned conventional example, a means for detecting the stopped state of the vehicle is provided, the offset is recalculated from the sensor output while the vehicle is stopped, and the azimuth calculation is performed using the newly calculated offset in the traveling state thereafter. I was going to do it.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the case of correcting the offset of the rate gyro by the method as described above and calculating the traveling direction of the vehicle, it is effective when using the rate gyro with relatively high offset stability, When the stability of the offset is low, there is a drawback in that the azimuth error accumulates immediately during traveling.

An object of the present invention is to provide an azimuth detecting device that accurately calculates the traveling azimuth of a running vehicle even when a rate gyro having a relatively low offset stability is used in consideration of such a point.

Means for Solving the Problems The present invention provides a distance sensor for detecting a travel distance of a vehicle, a rate gyro for detecting a traveling direction, an elapsed time calculating means for measuring an elapsed time, the distance sensor and the rate gyro. Two offset measurement section detection means for detecting the stopped state or straight traveling state of the vehicle from the output, and two representative values of the output of the rate gyro when the vehicle is determined to be stopped or straight traveling by the offset measurement section detection means The representative value extracting means for extracting the above, the offset change rate for calculating the temporal change rate of the offset output from the time interval between the representative value selected by the representative value extracting means and the representative value measured by the elapsed time calculating means The rate gyro is turned off based on the outputs of the calculation means, the offset change rate calculation means, the representative value extraction means, and the elapsed time calculation means. An azimuth detecting device comprising: an offset estimating means for estimating a set output; and an azimuth detecting means for calculating a traveling azimuth of a vehicle from outputs of the rate gyro, the offset estimating means and the elapsed time calculating means. .

With the above-described structure, the present invention detects the stationary state or the straight running state of the vehicle by the offset measuring section detecting means, and the representative value extracting means selects the representative value of the offset from the rate gyro output at that time. Then, the temporal change tendency is calculated by the offset change rate calculating means, and the vehicle progresses while the offset estimating means measures the offset value of the rate gyro during running, which temporally changes using the calculated change tendency. Since the azimuth is calculated, it is possible to calculate the traveling azimuth with high accuracy even during traveling.

Embodiment 1 FIG. 1 is a block diagram of an azimuth detecting apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a distance sensor for detecting the traveling distance of the vehicle from the rotational speed of a vehicle tire or axle, and 2 is a rate gyro such as a vibration rate or a gas rate for detecting an angular velocity to calculate the traveling direction of the vehicle. Reference numeral 3 denotes an elapsed time calculating means such as a timer for measuring the elapsed time. Reference numeral 4 is an offset measuring section detecting means for judging the stopped state or straight traveling state of the vehicle from the output of the distance sensor 1 and the output of the rate gyro 2. 5 is an offset measuring section detecting means 4 for judging the stopped state or the straight traveling state. At this time, a representative value extracting means for extracting two or more representative values of the output of the rate gyro 2, 6 is an interval between the representative value of the offset extracted by the representative value extracting means 5 and the representative value measured by the elapsed time calculating means 3. The offset change rate calculating means for calculating the change rate of the offset of the rate gyro 2 over time, and the time change rate of the offset calculated by the offset change rate calculating means 6 and the representative value extracting means 5. Offset estimation means for estimating the offset of the rate gyro 2 from the representative value of the offset, and 8 is the azimuth calculation error amount due to the error of the offset estimation value. Calculating estimated direction error calculating means, 9 is the direction detecting means for calculating the traveling direction of the vehicle.

The operation of the azimuth detecting apparatus of the present embodiment configured as described above will be described below. The offset measurement section detecting means, the representative value extracting means, the offset change rate calculating means, the offset estimating means, the estimated azimuth error calculating means, and the azimuth detecting means can be configured by hardware, but here, they are realized by software using a microprocessor. The case will be described.

FIG. 2 is a flowchart showing the processing procedure. First, in step 201, an initial value is assigned to each variable. Next, at step 202, it is judged from the output of the distance sensor 1 whether or not the vehicle is traveling. If it is stopped, the processing proceeds to step 203, and if it is traveling, the processing proceeds to step 212.

If it is stopped, in step 203, the output V1 of the rate gyro 2 at the beginning of the current stop section is sampled. Subsequently, in step 204, it is determined whether or not there is a traveling section before the stop section. Step 20 if there is a running section
Go to step 5 otherwise Go to step 209. If there is a traveling section, the time interval Tr of the traveling section is calculated in Step 205, and the rate output V2 ′ at the end of the immediately preceding stopping section and the offset measured in the traveling section from V1 obtained in Step 203 are calculated. The time change rate dV 'is calculated by the following formula.

dV ′ = (V1−V2 ′) / Tr Then, in step 207, the azimuth error amount Δθ by the offset estimation is calculated by the following equation.

Δθ = n × (n + 1) × (dV−dV ′) × Ts ² / (2 × As) where Ts is the sampling interval (for example, 50 msec), As is the sensitivity of the rate gyro (for example, 50 mV / ° / sec), dV is the predicted time change rate of the offset used in the traveling section. Further, n indicates a time interval (Tr = n × Ts) of the traveling section when Ts is set as a unit time. This equation calculates the heading error amount from the difference from the predicted inclination dV, assuming that the true offset during traveling has changed with the newly obtained inclination of dV '. Using this azimuth error amount Δθ, in step 208, the azimuth error is corrected with θ = θ + Δθ 2. Here, θ indicates the current traveling direction.

Then, in step 209, the sensor output at the end of the current stop section is sampled and substituted into the representative value V2,
At 210, the time interval of the current stop section is substituted into the variable T.
Then, in step 211, the time change rate dV of the offset is calculated as dV = (V2-V1) / T, and the process proceeds to step 202. Step two
If it is determined in 02 that the vehicle is running, the process proceeds to step 22. In the travel section, first, in step 212, the elapsed time t from the end of the stop section is calculated, and in step 213, the offset Vz at that point is the time change rate dV of the offset obtained in the stop section and the offset value V2 at the end of the stop section. Therefore, linear prediction is performed using the calculation formula of Vz = V2 + dV × t. Using the offset value Vz calculated here, the traveling direction is calculated in the following step 214 using the following equation.

θ = θ ′ + (Vt−Vz) × Ts / As where Vt is the output of the current rate gyro,
θ'represents the traveling azimuth at the time of the previous sampling, and θ represents the traveling azimuth calculated this time. When the calculation of the traveling direction is completed in step 214, the process returns to the step before step 202 and the above operation is repeated.

In this flowchart, step 202 is an offset measurement section detecting means, steps 203 and 209 are representative value extracting means,
Steps 210 and 211 are offset change rate calculation means, steps 212 and 213 are offset estimation means, steps 204 and 205,
206 and 207 correspond to the estimated azimuth error calculating means, and steps 208 and 214 correspond to the azimuth detecting means.

As described above, in the present embodiment, the bearing calculation is not performed because the bearing does not change during the stop, and the sensor output is obtained at the beginning and end of the stopped section, and the time change rate of the offset is calculated from the sensor output. On the other hand, if it becomes a traveling section, the traveling direction is calculated while linearly predicting the offset from the sensor output at the end of the section calculated in the stop section and the time change rate of the offset. When a new stop section is reached, the time change rate of the offset is actually measured from the offset value before and after the traveling section, and the heading error amount by offset estimation is calculated and corrected. Therefore, it is possible to improve the traveling azimuth calculation accuracy as compared with the case where the azimuth is calculated while the offset is a constant value during traveling.

In the present embodiment, the two sensor outputs at the beginning and the end of the stop section were extracted as the representative value of the offset, and the time change rate was calculated. The rate of change with time may be calculated using any two of them as representative values. Further, two or more representative values may be sampled and the time change rate may be obtained as the time average thereof. Further, in the present embodiment, the reference value for the offset linear prediction during traveling is the sensor output at the end of the stop section, but this may not be the end value. Further, although the offset during traveling is linearly predicted, upper and lower limits of the offset may be set and the offset may be controlled to be a constant value when the predicted offset value exceeds the limit. Further, in the present embodiment, the heading error amount due to the offset estimation during the traveling section is obtained by assuming that the predicted value and the actual measured value of the offset are linear.
This does not need to be linear for both the predicted value and the measured value.

Further, in the present embodiment, the offset value and the time change rate are calculated only in the stop section, but for a rate gyro that calculates the yaw rate and the traveling azimuth, it can be regarded as equivalent to the stop section during traveling even in a straight line. Judging the straight running condition from the variation of sensor output or external information, the offset reference value and the time change rate are calculated in the straight running section in the same way as the stop section, and the offset is predicted only in the running status other than the straight running. You may calculate.

As described above, according to the present invention, when the traveling azimuth of the vehicle is calculated using the rate gyro, the traveling azimuth is calculated with a constant offset value using the value measured in the stopped state. Instead, the offset variation during traveling is predicted from the tendency of the offset variation during stoppage or straight traveling, and the traveling azimuth is calculated using the predicted offset value. Therefore, it is possible to improve the traveling azimuth calculation accuracy as compared with the case where the traveling azimuth is calculated with the offset being a constant value.

[Brief description of drawings]

FIG. 1 is a block diagram of an azimuth detecting apparatus according to an embodiment of the present invention, and FIG. 2 is a flow chart of the same embodiment. 1 ... distance sensor, 2 ... rate gyro, 3 ... elapsed time calculating means, 4 ... offset measuring section detecting means, 5
...... Representative value extracting means, 6 ... Offset change rate calculating means, 7 ... Offset estimating means, 8 ... Estimated heading error calculating means, 9 ... Heading detecting means.

Claims (2)

[Claims] 1. A distance sensor for detecting a traveling distance of a vehicle,
A rate gyro that detects a traveling direction, an elapsed time calculation unit that measures an elapsed time, an offset measurement section detection unit that detects a stopped state or a straight traveling state of the vehicle from the output of the distance sensor and the rate gyro, and the offset Representative value extracting means for extracting two or more representative values of the output of the rate gyro when it is determined that the vehicle is stopped or traveling straight ahead by the measurement section detecting means, and the representative value selected by the representative value extracting means and the above Offset change rate calculating means for calculating the temporal change rate of the offset output from the time interval of the representative values measured by the elapsed time calculating means, the offset change rate calculating means, the representative value extracting means, and the elapsed time calculating means. Offset estimation means for estimating the offset output of the rate gyro from the output of the rate gyro and the offset sensor. Azimuth detecting device characterized by comprising the azimuth detecting means for calculating the traveling direction of the vehicle from the output of the bets estimating means and the elapsed time calculating means. 2. An estimated azimuth error calculating means is provided, the azimuth error by offset estimation is calculated from the representative value extracting means and the elapsed time calculating means, and the azimuth error is corrected by the azimuth detecting means. The azimuth detecting device according to claim 1.