JPH03189514A - Drift correction system for gyro sensor for automobile - Google Patents

Abstract

PURPOSE:To enable high-accuracy detection by handling the output of the gyro sensor as a drift when the variation quantity of the output signal of an azimuth sensor or the azimuth calculated from the output signal within a constant time is less than a constant value. CONSTITUTION:A frequency divider 34 divides the frequency of the output of an oscillator 37 by two and a primary coil 38 is driven through an amplifier 33. Consequently, secondary coils 31 and 32 generate secondary higher harmonics which differ in level according to the direction of the earth magnetism. The higher harmonic components are detected synchronously by synchronous detectors 35 and 36 to obtain a couple of DC voltages Vx and Vy which vary in level by the azimuth sensor 3 for the earth magnetism. Those voltages Vx and Vy are in sine-cosine relation and a CPU 1 finds the azimuth angle theta from theta=tan-<1>Vy/Vx. Then when the variation quantity of the output signal of the sensor 3 or the azimuth calculated from the output signal is less than the constant value, the output of the gyro sensor 4 is inputted to calculate an estimated drift quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drift correction device for a gyro sensor used in an automobile navigation device.

[Conventional technology]

This type of automobile navigation device uses a direction sensor (for example, a geomagnetic direction sensor) to detect changes in the direction of travel of the vehicle.

However, the earth's magnetic field is weak at around 0.4 Gauss.

For example, locations such as iron bridges, viaducts, and railroads are susceptible to external disturbances, and the magnetic field is disturbed and errors are likely to occur.

Therefore, consideration is being given to using a gyro sensor that is less susceptible to this disturbance. However, although this gyro sensor has good accuracy over a short period of time, its output characteristics tend to change depending on environmental temperature and the like. Therefore, if you drive for a long time,
There is an inconvenience that the direction is off, and even if you drive on a straight road, it will be detected as if you were driving in a large arc.

To solve this inconvenience, a conventional vehicle position detection device described in Japanese Patent Application Laid-open No. 64-3509 uses a vehicle speed sensor that detects the speed of the vehicle to detect the stopped state of the vehicle, and detects the stopped state of the vehicle. The gyro sensor output at the time is treated as a drift.

[Problem to be solved by the invention]

The conventional drift 1 correction device for automotive gyro sensors is configured as described above, so it is effective when the car stops relatively frequently, but it is effective when driving on a highway for a long time. If the condition exists, a problem occurs.

That is, as described above, the amount of drift (angular velocity) of the gyro sensor changes with changes in time, environmental temperature, etc., so if the vehicle is running for a long time without stopping, it is not possible to effectively correct the drift.

As a result, angular deviations will gradually occur in the detection results.

Furthermore, when a car rotates on a turntable in a parking lot or the like, there is a problem in that an extremely large detection error occurs.

The present invention has been made to solve the above-mentioned conventional problems, and provides a draft correction device that can effectively correct the drift 1 of a gyro sensor regardless of whether the vehicle is running or not. The purpose is to provide

[Means to solve the problem]

In order to achieve the above object, the present invention inputs and estimates the output of a gyro sensor when the output signal of the azimuth sensor or the amount of change in the azimuth calculated from the output signal within a certain period of time is within a certain value. It is equipped with arithmetic processing means for calculating the amount of drift.

[Effect]

The present invention treats the output of the gyro sensor as a drift when the output signal of the azimuth sensor or the amount of change in the azimuth calculated from the output signal within a certain period of time is within a certain value, thereby determining whether or not the vehicle is traveling. Regardless of the current situation, calculation of the draft amount of the gyro sensor can be continued, enabling highly accurate measurement.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, 1 is a microprocessor (MPU) as an arithmetic processing means, 2 is an analog/digital converter (ADC) provided on the input side of the microprocessor 1, and 3 is an orientation sensor such as a geomagnetic orientation sensor. sensor 3
is a core 30 made of magnetic material, a primary coil 38 and a set of 2
Secondary coils 31 and 32 are wound orthogonally, a frequency divider 34 is connected to this primary coil 38 via an amplifier 33, and a synchronous detector 35 and 36 is connected to a set of secondary coils 31 and 32. It is the composition. A gyro sensor 4 outputs a voltage signal W proportional to the speed (angular velocity) at which the direction of travel of the vehicle changes.

Next, the operation will be explained. The frequency divider 34 divides the output of the oscillator 37 into half, and drives the primary coil 38 via the amplifier 33. Therefore, second harmonics with different levels are generated in the secondary coils 31 and 32 depending on the direction of the earth's magnetism.

The output of the oscillator 37 is converted into this harmonic component by a synchronous detector 35,
When synchronous detection is performed at 36, for example, as shown in FIG. 2, a set of DC voltages I Vy whose levels change by the geomagnetic azimuth sensor is obtained.

This direct current voltage HVv has a sine-cosine relationship, and the azimuth angle 0 is determined by the following equation.

Also, depending on the direction of the secondary coils 31 and 32, the DC voltage v
X and V may be interchanged.

The microprocessor 1 reads the DC voltage VtVY via the analog-to-digital converter 2, and calculates the azimuth angle 0 using equation (1). Further, the microprocessor 1 can read the value of the voltage signal W output from the gyro sensor 4 via the analog-to-digital converter 2.

As shown in FIG. 3, the voltage signal W from the gyro sensor 4 exhibits a drift characteristic that changes with time even when the vehicle is stopped. Therefore, when tracing the travel trajectory of the vehicle using the output of the gyro sensor 4, an error occurs in the direction.

Therefore, in this embodiment, countermeasures are taken using software in the microprocessor 1. FIG. 4 shows a flowchart of the processing of the microprocessor 1. When the program starts, after necessary initialization, in step ST1, the signals V x , V
The value of y is taken in via the analog-to-digital converter 2.

Next, in step ST2, signal engineer 1 vy is stored as reference values VXR, V, , respectively, and step S
At T3, the azimuth O is calculated using the above equation (1) and stored as the geomagnetic azimuth MA.

Next, in step ST4, the gyro orientation (O
As the initial value of A), the above geomagnetic direction is substituted and stored as MA, and in step ST5, a timer (TIMER) is set.
It is determined whether the value of is 0 or not, and waits until rQJ is reached.

The timer may be a software 1 timer or a hard timer. Here, if a fixed value is set, the interrupt process shown in FIG. 5 is activated at fixed time intervals, and the timer clock is turned down from 1 to 1 until the timer clock reaches [O]. That is, in step 5T14, it is determined whether the timer is "0", and if it is not "o", step 5T15 is performed.
Decrease the timer value by 1 and return to the main program.

In any case, the processes after step ST6 need to be performed at regular intervals. When the timer reaches rQJ, the fixed time T is reset to the timer in step ST6.

In step ST7, the direction sensor signal yVy
and samples the gyro output W.

Next, in step ST8, it is determined whether the value of the signal Vx is within a certain value (D) from the previously sampled reference value (D), and if not, it is assumed that the direction has changed and a drift calculation is performed. Not performed.

If it is within a certain value, in step ST9, the signal V
The value for engineering is also constant compared to the standard value VYR.

Determine whether it is within the range. If the values of the signals V1 and VY are both within a certain value (Dx Dv) with respect to the reference value ■1 + VTR, it is assumed that the direction has not changed much, and a calculation is performed to estimate the drift amount WD in step 5TIO. .

FIG. 6 shows a flowchart for calculating the above-mentioned drift and amount WD.

This arithmetic processing implements the digital filter processing shown in FIG. Figure 6.

In FIG. 7, k is a constant greater than or equal to "O" and less than or equal to "1"; the larger k is, the greater the time constant of the filter becomes, and the output is suppressed to change slowly. 2" represents a delay. This delay scene is not constant and is similar to step 5T in FIG.
Equal to the interval at which IO is activated. In step 5T16 of FIG. 6, an intermediate variable AA is calculated. That is, the input W is multiplied by (1-k). In step 5T17, the variable AA is added to the previous value of the truffle Mwo multiplied by the coefficient k, and a new drift amount WL is obtained.
shall be. In general, drift NWD does not change quickly over time, but changes slowly. Therefore, if the constant is set to a large value of 0.9 or more, even if there is some noise (measurement error) in the input, it will be sufficiently removed.
A highly accurate estimated value drift amount Wa can be obtained. Although FIG. 7 shows a first-order type digital filter, the same applies to a higher-order type.

Next, in step 5TII, the gyro orientation GA is updated using the calculated drift ftwD using the following equation.

G A=G A+ (W Wo) ・TP Here, T is the same value as used in step ST6, and by subtracting the drift ffiwD from the input W and multiplying it by rP, the angle change and the previous gyro In addition to the orientation GA, the gyro orientation is updated.

In step 5T12, the geomagnetic azimuth (MA) is calculated, and in step 5T13, the reference values of the signal (2) and V (ma) R and VTR are updated, and the process returns to step ST5.

FIG. 8 shows another processing flowchart of the microprocessor 1. In the process of FIG. 4, as a condition for starting the drift amount calculation, the change in the signals V and Vo output from the direction sensor is set to a constant value. However, in the process shown in FIG. 8, the above condition is that the change in the geomagnetic direction is within a certain value.

First, in step 5T18, the signal VtVy output from the azimuth sensor is sampled, and in step 5T19, the geomagnetic azimuth (MA) is calculated. Step 5T20
In this case, the value of the geomagnetic direction MA is set as the reference value MAR. In step 5T21, the gyro orientation (O
Perform A) initialization. In step 5T22, the process waits until the timer value becomes "O". In step 5T23, a predetermined time 'rP is preset in the timer. In step 5T24, the signals VX, V, and input W are sampled, and in step 5T25, a new geomagnetic direction MA is calculated using the value of the signal IVY.

In step s'rz6, it is determined whether the difference from the reference value M A R is smaller than a constant value D2. If it is small, it is assumed that the change in direction was small in step 5T27,
The drift M (wD) is calculated. Next step 5
At T28, the gyro heading (GA) is updated, at step 5T29, the reference value M A R for the heading is updated, and the process returns to step 5T22.

Further, if the determination in step 5T26 is large, the process moves to step 5T28 and the gyro orientation is updated.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, when the output signal of the azimuth sensor or the variation type of the azimuth calculated from the output signal within a certain period of time is within a certain value, the output of the gyro sensor is Since the configuration is configured to calculate the estimated drift amount by inputting it, it is possible to continue calculating the drift amount of the gyro sensor regardless of whether the car is moving or not, and highly accurate measurement is possible. The effect is achieved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a sensor system according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing the angular characteristics of the azimuth sensor, FIG. 3 is a characteristic diagram explaining the drift characteristics of the gyro sensor, and FIG. Figure 4 is a flowchart for drift correction by the microprocessor, Figure 5 is a flowchart for explaining timer processing, Figure 6 is a flowchart for explaining drift area calculation processing, and Figure 7 is for explaining the contents of the digital filter processing in Figure 6. The block diagram shown in FIG. 8 is a flowchart illustrating another drift correction method. 1...Microprocessor (arithmetic processing means), 2...
Analog digital converter, 3. Direction sensor, 4. Gyro sensor. Part 1 Part 4 (2) Figure Figure Figure

Claims (2)

[Claims] (1) A gyro sensor that outputs the amount of drift and a direction sensor that detects the running direction of the vehicle, and the amount of change in the output signal of the direction sensor or the direction calculated from the output signal within a certain period of time is within a certain value. a calculation processing means for inputting the output of the gyro sensor to calculate an estimated drift amount; (2) The drift correction device for an automobile gyro sensor according to claim 1, wherein the arithmetic processing means is a digital filter.