JP2887207B2 - Drift correction method for gyro sensor for automobile - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drift correction device for a gyro sensor used in an automobile navigation device.

[Conventional technology]

2. Description of the Related Art An azimuth sensor (for example, a geomagnetic azimuth sensor) is used in a navigation apparatus for an automobile of this type to detect a change in the traveling direction of the vehicle.

However, since the geomagnetism is weak, about 0.4 Gauss, it is susceptible to disturbances in places such as railway bridges, viaducts, and railways.
The magnetic field is disturbed and errors easily occur.

Therefore, use of a gyro sensor that is less susceptible to this disturbance has been studied. However, this gyro sensor has good accuracy in a short period of time, but its output characteristics are liable to change due to environmental temperature and the like. For this reason, if the vehicle travels for a long time, the azimuth will be out of order, and there is a problem that even if the vehicle travels on a straight road, it is detected that the vehicle travels in a large arc.

As a solution to this inconvenience, conventionally, for example, a vehicle position detection device described in Japanese Patent Application Laid-Open No. 64-3509 uses a vehicle speed sensor that detects the speed of a vehicle to detect the stop state of the vehicle, and stops the vehicle. The gyro sensor output at the time is treated as drift.

[Problems to be solved by the invention]

The conventional drift correction device for a car gyro sensor is configured as described above, and is effective when the vehicle stops relatively frequently. In some cases, problems arise.

That is, as described above, the drift amount (angular velocity) of the gyro sensor changes with changes in time, environmental temperature, and the like. Therefore, if the vehicle is running for a long time without stopping, drift correction cannot be effectively performed.

As a result, the detection result gradually shifts in angle.

Further, when the car rotates on a turntable such as a parking lot, there is a problem that an extremely large detection error occurs.

SUMMARY An advantage of some aspects of the invention is to provide a drift amount correction device capable of effectively performing drift correction of a gyro sensor regardless of whether or not the vehicle is traveling. The purpose is to provide.

[Means for solving the problem]

In order to achieve the above object, the present invention calculates an estimated drift amount used for drift correction of a gyro sensor that is mounted on a vehicle and detects an angular velocity of the vehicle, and uses the estimated drift amount to correct drift of the gyro sensor. In the drift correction device that implements, the azimuth sensor that detects the traveling azimuth of the vehicle, and detects the output of the azimuth sensor every predetermined time, and compares the output value detected this time with the output value detected last time. By determining whether the difference is within a predetermined range, a determination unit that determines the stability of the traveling azimuth, and each time the determination unit determines that the traveling azimuth is stable, Estimated drift amount calculating means for calculating the estimated drift amount from the output of the gyro sensor detected in the, azimuth sensor,
The apparatus further comprises two magnetic field detectors for detecting magnetic field strengths in two directions orthogonal to each other, wherein the determination means detects each output from the two magnetic field detectors at predetermined time intervals, and detects the current time. The stability of the traveling azimuth is determined by determining whether the difference between the output value and the previous output value is within a predetermined range.

[Action]

The present invention treats the output of the azimuth sensor or the azimuth calculated from the output signal within a certain period of time when the amount of change is within a certain value. Regardless, the calculation of the drift amount of the gyro sensor can be continued,
Enables highly accurate measurement.

〔Example〕

Hereinafter, 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 arithmetic processing means, 2 is an analog / digital converter (ADC) provided on the input side of the microprocessor 1, and 3 is a direction sensor such as a geomagnetic direction sensor. In the sensor 3, a primary coil 38 and a set of secondary coils 31, 32 are wound orthogonally around a core 30 made of a magnetic material, and a frequency divider 34 is connected to the primary coil 38 via an amplifier 33. One set of secondary coils 31,3
2 is a configuration in which synchronous detectors 35 and 36 are connected. 4 is a voltage signal W proportional to the speed (angular speed) at which the traveling direction of the vehicle changes.
This is a gyro sensor that outputs.

Next, the operation will be described. The frequency divider 34 divides the output of the oscillator 37 by half, and drives the primary coil 38 via the amplifier 33. Therefore, second harmonics having different levels are generated in the secondary coils 31 and 32 in accordance with the direction of terrestrial magnetism.

This harmonic component is output from the oscillator 37 to the synchronous detectors 35 and 36.
As shown in FIG. 2, for example, as shown in FIG.
V _X and V _Y are obtained.

The DC voltages V _X and V _Y have a sine and cosine relationship, and the azimuth θ is obtained by the following equation.

Further, the direction of the secondary coil 31 and 32, the DC voltage V _X and V
_Y may be exchanged.

The microprocessor 1 reads the DC voltages V _X and V _Y via the analog-to-digital converter 2 and calculates the azimuth θ using the above equation (1). Further, the microprocessor 1 can read the value of the voltage signal W output from the gyro sensor 4 via the analog / digital converter 2.

As shown in FIG. 3, the voltage signal W from the gyro sensor 4 has a drift characteristic that changes with time even when the vehicle stops. Therefore, this gyro sensor 4
When the traveling locus of the vehicle is traced using the output of the above, an error occurs in the bearing.

Therefore, in this embodiment, the microprocessor 1
Measures are taken by software in. Figure 4 is shows a flowchart of processing of the microprocessor 1, the program starts, after the required initialization, in step ST1, signal V _X, the value of V _Y via an analog digital converter 2 Take in.

Next, in step ST2, the signal V _X, relative to V _Y each value V _XR, stored as V _YR, in step ST3, the
The azimuth angle θ is calculated by the equation (1) and stored as the geomagnetic azimuth MA.

Next, in step ST4, the above geomagnetic direction is substituted for MA as an initial value of the gyro direction (GA) and stored.
In step ST5, it is determined whether or not the value of the timer (TIMER) is 0, and the process waits until it becomes "0".

The timer may be a soft timer or a hard timer. Here, if a constant value is set, the interrupt processing shown in FIG. 5 is started at regular intervals, and the countdown is performed until the timer value becomes “0”. That is, in step ST14, it is determined whether or not the timer is "0". If not, the timer value is decremented by "1" in step ST15 and the process returns to the main program.

In any case, the processing after step ST6 needs to be performed at regular intervals. When the timer reaches "0", in step ST6, and re-set for a certain period of time T _P to the timer.

In step ST7, samples the signal V _X, V _Y, and gyro output W of the azimuth sensor. Then step ST8
At which the value of the signal V _X is equal to the previously sampled reference value V _XR
Is determined to be within a predetermined value (D _X ). If not, it is determined that the azimuth has changed, and no drift calculation is performed.

If it is within a predetermined value, in step ST9, the signal V _Y
For determining whether within a predetermined value D _Y to the reference value V _YR also. If the values of the signals V _X and V _Y are both within a fixed value (D _X D _Y ) with respect to the reference values V _XR and V _YR , it is determined that the azimuth has not changed much, and the drift amount W _D is determined in step ST10. An estimating operation is performed.

A flow for calculating the drift amount W _D shown in Figure 6.
This arithmetic processing realizes the processing of the digital filter shown in FIG. In FIGS. 6 and 7, k
Is a constant not less than "0" and not more than "1".
The time constant of the filter increases, and the output is suppressed to a slow change. Z ^-1 represents the delay. This delay amount is not constant, and is equal to the interval at which step ST10 in FIG. 4 is activated. In step ST16 of FIG. 6, an intermediate variable AA is calculated. That is, for the input W, (1-
multiply by k). In step ST17, a variable AA is added to the value obtained by multiplying the value of the previous drift amount W _{D by} the coefficient k to obtain a new drift amount W _D. In general drift amount W _D is not time varying fast, indicating the slow changes. So if in the constant to a value of more than 0.9, even if there is some noise (measurement error) to the input, is sufficiently removed, high estimation value drift amount W _D with accuracy. FIG. 7 shows a temporary digital filter.
The same applies to higher order ones.

In next step ST11, performs the following equation to update the gyro azimuth GA using the calculated drift amount W _D.

GA = GA + (W-W D) · T P where, T _P is the same as the value used in step ST6,
Pull the drift amount W _D from the input W, multiplied by T _P, Motomari angle variation, and updates the gyro azimuth in addition to the previous gyro heading GA.

Calculating a geomagnetic direction (MA) in step ST12, in step ST13, the signal V _X, V _Y of the reference value V _XR, updates the V _YR, the flow returns to step ST5.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, when the output signal of the azimuth sensor or the change amount of the azimuth calculated from the output signal within a certain time is within a certain value,
Since the estimated drift amount is calculated by inputting the output of the gyro sensor, the calculation of the drift amount of the gyro sensor can be continued irrespective of whether the vehicle is running or not, and high accuracy can be achieved. The effect that measurement becomes possible is achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a sensor system according to one embodiment of the present invention, FIG. 2 is a waveform diagram showing an angle characteristic of an azimuth sensor, FIG. 3 is a characteristic diagram for explaining a drift characteristic of a gyro sensor, FIG. 4 is a flowchart for drift correction by the microprocessor, FIG. 5 is a flowchart for explaining timer processing, FIG. 6 is a flowchart for explaining drift amount calculation processing, and FIG. 7 is a diagram for explaining the contents of the digital filter processing in FIG. FIG. DESCRIPTION OF SYMBOLS 1 ... Microprocessor (arithmetic processing means), 2 ... Analog-digital converter, 3 ... Direction sensor, 4 ... Gyro sensor.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-182519 (JP, A) JP-A-61-181912 (JP, A) Jpn.

Claims (1)

(57) [Claims] 1. A drift correction device mounted on a vehicle, calculating an estimated drift amount used for drift correction of a gyro sensor for detecting an angular velocity of the vehicle, and performing drift correction of the gyro sensor using the estimated drift amount. An orientation sensor that detects a traveling orientation of the vehicle, an output of the orientation sensor is detected at predetermined time intervals, and a difference between an output value detected this time and an output value detected last time is in a predetermined range. Determining whether the traveling azimuth is stable by determining whether the traveling azimuth is stable. Each time the traveling azimuth is determined to be stable by the determining means, the Estimated drift amount calculating means for calculating the estimated drift amount from the output of the gyro sensor, wherein the direction sensor has two directions orthogonal to each other. The apparatus further comprises two magnetic field detectors for detecting a magnetic field intensity, wherein the determination unit detects each output from the two magnetic field detectors at predetermined time intervals, and outputs an output value detected this time and a previous output value. A drift correction device for a gyro sensor for an automobile, wherein the stability of the traveling azimuth is determined by determining whether a difference between the driving direction and the driving direction is within a predetermined range.