JPH0249109A - Vehicle azimuth detector - Google Patents

Abstract

PURPOSE:To derive the azimuth of a vehicle by catching an angular velocity of the vehicle as the function of car speed and a steering angle, leading out an angular velocity calculating expression corresponding to a characteristic of the vehicle, and applying a calculated angular velocity with time integration. CONSTITUTION:A vehicle azimuth detecting device 21 is constituted of an identifying device 22 for catching an estimated angular velocity omegae of a vehicle as the function of a car speed (v) and a steering angle thetas, updating a coefficient required for fixing this function expression by using data (v), thetas and omegad which are changed momentarily, and leading out an angular velocity calculating expression corresponding most to a characteristic of the vehicle, and an integrator 10 for bringing the angular velocity omegae which is estimated in accordance with the calculating expression obtained by this identifying device 22 to time integration, and deriving an azimuth thetac of the vehicle. In such a way, the output of an angular velocity sensor in which an error in a very small level is large is replaced with an estimated angular velocity by the calculating expression which is identified by using two pieces of variables of the car speed and the steering angle, and the error can be suppressed to the utmost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a vehicle orientation detection device that detects the orientation of a vehicle by time-integrating the angular velocity calculated from the vehicle speed and steering angle.

[Prior Art] In-vehicle navigation systems that use geomagnetism to measure vehicle heading are susceptible to changes in the output of the geomagnetic sensor due to the influence of strong disturbance magnetic fields formed around elevated tracks, railroad crossings, etc. ,
There is a high risk of incorrectly estimating the vehicle direction. Therefore, in order to avoid such erroneous estimations, it is recommended to use a method to check whether the vehicle has actually changed course by detecting the rotation angle (steering angle) of the vehicle's steering wheel. be.

The steering angle detection device 1 shown in FIG. 4 has a slit disk 4 fixed coaxially to the shaft 3 of a steering wheel 2.
The rotation angle of this slit disk 4 and the detection phase are set to 9
A pair of photo encoders 5 arranged with a difference of 0 degrees,
A steering angle sensor 8 connected to the photo encoder 5 and a rotation direction determination circuit 7 that receives outputs from both photo encoders 5 and 6 to determine the rotation direction, and a steering angle sensor 8 connected to the photo encoder 5 detects the steering angle θS.
It is configured to detect.

However, although this type of steering angle detection device l can detect the rotation angle and rotation direction of the steered wheel 2 with the accuracy of the photo encoder 5.6, if the steered wheel 2 moves slightly within the range of play, it cannot detect this. Since it is detected as a change in the steering angle, it can be detected when there is strong vibration from the road surface or strong wind pressure resistance.
There is a problem in that the vehicle tends to output erroneous information indicating that the vehicle has changed course even though it is traveling straight, and this has a negative effect on the course estimation of the on-vehicle navigation system.

Therefore, in an attempt to find the azimuth angle θC of the vehicle by time-integrating the angular velocity ωd of the vehicle, the present applicant prototyped a vehicle orientation detection device 11 that combines the angular velocity sensor 9 and the integrator IO shown in FIG. reached. The angular velocity sensor 9 used here includes a rotor 13 having a vibrator 12 that vibrates in the radial direction on a rotating surface, and a detection element 14 for detecting Coriolis force FC provided therein. A piezoelectric element is used as the detection element 14, and is attached perpendicularly to the attachment surface of the piezoelectric element 15 that drives the vibrator 12, and is attached to the rotor 1.
By receiving the Coriolis force Fc generated along the circumferential direction of 3, a voltage proportional to the force Fc is generated.

Generally, when an angular velocity ωd is given to an object with velocity V,
It is well known that a Coriolis force Fc, which is the mass m of an object multiplied by 2.omega.d, is generated. Strictly speaking, this Coriolis force Fc is expressed by the outer product of a velocity vector and an angular velocity vector, but when each vector is represented by a uniaxial component as in this example, it follows a simple scalar product, Fc. It can be expressed as c = 2 m V ωd. However, m is the effective mass of the vibrating portion of the vibrator 12, and ■ is the vibration speed of the vibrator 12. Needless to say, the angular velocity ωd can be determined using the above formula.

[Problems to be Solved by the Invention] The conventional vehicle orientation detection device 11 described above is configured to detect the vehicle azimuth θC by time-integrating the angular velocity ωd detected according to the principle of a gyro. The detection accuracy depends solely on the detection accuracy of the Coriolis force Fc, and the oscillator which is the proportionality constant! effective mass m of 2
The larger the vibration velocity V· is, the larger the detected Coriolis force Fc can be. However, there is a limit to the size of such a proportionality constant, so while it is fine if the angular velocity ωd is large to some extent, the smaller the angular velocity ωd, the lower the detection accuracy inevitably becomes. The azimuth angle θC also had the problem of lack of accuracy.

[Means for Solving the Problems] The present invention solves the above problems, and provides an identification device that captures the angular velocity of a vehicle as a function of vehicle speed and steering angle, and derives an angular velocity calculation formula that best matches the characteristics of the vehicle. and,
This identification device is characterized by comprising an integrator that time-integrates the angular velocity determined according to the calculation formula obtained by the identification device to determine the azimuth angle of the vehicle.

[Operation] This invention regards the angular velocity of a vehicle as a function of vehicle speed and steering angle, derives an angular velocity calculation formula that best matches the characteristics of the vehicle, and then integrates the angular velocity calculated according to the obtained calculation formula over time. Find the azimuth of the vehicle.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic configuration diagram showing an embodiment of the vehicle direction detection device of the present invention, and FIG. 2 is a flowchart for explaining the operation of the identification device shown in FIG. 1.

In FIG. 1, the vehicle orientation detection device 21 captures the estimated angular velocity ωe of the vehicle as a function of the vehicle speed V and the steering angle θS, and calculates the coefficients necessary for identifying this functional expression from the data V that changes from time to time.
, θS, and ωd to derive an angular velocity calculation formula that best matches the characteristics of the vehicle, and an identification device 22 that integrates the angular velocity ωe estimated according to the calculation formula obtained by this identification device 22 over time. , an integrator 10 for determining the azimuth angle θC of the vehicle. Since the identification device 22 shown in the embodiment performs two operations of identification and estimation simultaneously,
The estimation operation is performed based on the latest identification result obtained immediately before. The vehicle speed sensor 23 that detects the speed V of the vehicle is
Vehicle speed pulses synchronized with wheel rotation are counted, and vehicle speed is detected from the counted value per unit time. Further, the steering angle sensor 8 and the angular velocity sensor 9 are connected in parallel, and here, when the vehicle speed pulse obtained from the vehicle speed sensor 23 reaches a certain value, that is, when the vehicle travels a certain distance, Each time, the identification device 22 samples the steering angle θS and the angular velocity ωd.

By the way, the estimated angular velocity ωe of the vehicle can be calculated using the vehicle speed V and the steering angle θ.
When expressed as a function with two variables, ωe=f(v, θ
S), and when the two variables V and O5 of this functional formula are considered as mutually independent linear functions, ωe = a oV 10a + V + a 2 V
10...e1boθs + b rθs'+btθS-
It can be expanded as +-#-.

Note that the dash symbol represents time differentiation, and in consideration of estimation accuracy, finite terms up to the n-th aircraft are used,
By discarding higher-order differential terms, the coefficients a0 to a1 necessary for identifying the above relational expression are obtained. There are a total of 2 (n+1) −bns. Therefore, by collecting (n+1) sets of data V, θS, ωd and substituting them into the above equation (however, ωd is substituted into ωe) and solving the resulting simultaneous equations, the necessary coefficients a, ~a
This means that n and bo-bn can be identified.

However, the collected data is updated every moment, and more than (n+1) sets of data can be obtained in no time.

Therefore, after starting data collection in step (101) shown in FIG.
. -an.

~bn is determined and identified as the most reliable value at that time. Therefore, as the number of collected data increases, the identification error decreases, and the identification accuracy converges to extremely high accuracy.

On the other hand, the coefficient y thus identified. ~Yu. ,b.

~bn is immediately applied to the angular velocity calculation formula ωe=f(v, θS) as shown in step (103), and the estimated angular velocity ωe is calculated using the output V of the vehicle speed sensor 23 and the output θS of the steering angle sensor 8. It is offered to Therefore, the output ωd of the angular velocity sensor 9, which has a large error near zero, can be replaced with the angular velocity ωe estimated using two variables, the vehicle speed V and the steering angle O5. The risk of erroneous measurements due to this can be diluted.

That is, the step of time-integrating the estimated angular velocity ωe (l
The azimuth angle θC obtained in step 04) can be said to be the value with the least error, and the azimuth angle θC of the vehicle can be detected more accurately than when the output ωd of the angular velocity sensor 9 is directly integrated over time. Can be done.

In addition, in the above embodiment, the coefficient ao− of the angular velocity calculation formula
a n + b ob - b n is determined by the method of least squares, but if the first data obtained is rejected when more than (n+2) sets of data are collected, then Identification can be performed using only the latest (n+ 1) sets of data, in which case the unknown coefficient a0
~an. By solving the same number of equations as -b7, the solution can be uniquely determined, so the complicated calculation process required for the least squares method can be omitted.

In addition, in the embodiment, the identification device 22 always performs the two operations of identification and estimation in parallel, but the steps (
As shown in 201) to (207), a configuration in which identification and estimation are performed in a time-sharing manner is also possible.

In this case, identification is performed when appropriate data exceeding (n+1) sets are obtained, and after the identification is interrupted, the estimation operation is started. And for the estimated operation, (
When m sets of data sufficiently larger than n+1) are obtained, the process is once completed, and the identification is restarted in order to update the angular velocity calculation formula used up to that point. In this method, since the two operations of identification and estimation are performed in a time-sharing manner, the estimation accuracy is somewhat inferior compared to the above embodiment, but since identification and estimation do not need to be performed simultaneously, the identification device 22 The amount of work per unit time can be reduced.

Furthermore, the estimated angular velocity ωe is ωe−1゜10a I V + a 2 V ”+...
It is also possible to perform series expansion as +b0+blθs+btθs 2 + ---, and as for the method of expansion, it is preferable to adopt a method that is valid through experimentation or experience.

[Effects of the Invention] As explained above, the present invention regards the angular velocity of a vehicle as a function of vehicle speed and steering angle, derives an angular velocity calculation formula that best matches the characteristics of the vehicle, and further divides the angular velocity according to the obtained calculation formula. Since the azimuth angle of the vehicle is determined by time-integrating the output angular velocity, the output of the angular velocity sensor, which has a large error at a minute level, can be estimated using a calculation formula identified using two variables: vehicle speed and steering angle. By replacing it with angular velocity, errors can be suppressed as much as possible, and unlike the case where the output of an angular velocity sensor is simply integrated over time, it is possible to accurately detect the vehicle direction, so the steering wheel can be adjusted by the influence of vibrations from the road surface and wind pressure. The direction of the vehicle can be determined accurately even if the vehicle moves slightly within the range of play.By installing it in an on-vehicle navigation device that uses geomagnetism, the geomagnetic sensor can prevent errors in course judgment due to the influence of disturbances. This has excellent effects such as making it possible to strengthen the correction function in such cases.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the vehicle direction detection device of the present invention. FIG. 2 is a flowchart for explaining the operation of the identification device shown in FIG. A flowchart showing an operation method different from the flowchart shown in the figure, FIG. 4 is a schematic configuration diagram showing an example of a conventional steering angle detection device, and FIG. 5 is an example of a conventional vehicle orientation detection device using angular velocity. FIG. 809. Steering angle sensor, 9. ,,angular velocity senna. io, , integrator, 21. ,,Vehicle orientation detection device. 22., Identification device, 23. ,,vehicle speed sensor.

Claims (1)

[Claims] An identification device that captures the angular velocity of the vehicle as a function of vehicle speed and steering angle and derives an angular velocity calculation formula that best matches the characteristics of the vehicle, and an identification device that integrates the angular velocity calculated according to the calculation formula obtained by this identification device over time, and calculates the angular velocity of the vehicle. A vehicle direction detection device consisting of an integrator that determines the azimuth angle of the vehicle.