JPH0334034B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vehicle position measuring device using a global positioning system (hereinafter abbreviated as GPS).

[Description of prior art]

In recent years, position measuring devices using GPS have come into use.

GPS uses satellites that transmit navigation data containing the three-dimensional position of each satellite on radio waves at predetermined timings, an antenna that receives the radio waves from these satellites, and a built-in clock that receives the data at predetermined timings. It consists of a computing device that analyzes navigation data from multiple satellites and calculates positions. Then, by using the satellite position information obtained from the navigation data and the measurement information of the propagation delay time based on the reception of the radio waves at a predetermined timing, a multidimensional simultaneous equation is established to obtain the position coordinates.

By the way, in the above multi-dimensional simultaneous equations, for example, when trying to find the position in three dimensions, the three unknowns related to the three-dimensional position include one of the deviations of the built-in clock from the atomic clock (hereinafter referred to as offset time).
In this case, the number of receivable satellites must be four or more. For example, when trying to determine the position two-dimensionally, the number of unknowns is 3 due to the above reasons, and the number of receivable satellites needs to be 3 or more (IEICE technical research report SANE84-11 "GPS receiver (See “Development and Measurement Experiment Results”).

However, the number of satellites that can be used for GPS is limited (currently 6), and the number of satellites that can be observed in a particular area is often 3 or less. In such a case, there is a problem that the three-dimensional position measurement described above becomes impossible.

In addition to cases where the number of observable satellites decreases depending on the time of day, there are also cases where the number of satellites that can be observed decreases depending on the time of day, and when the satellite is mounted on a vehicle and is driven through urban areas or mountainous areas, the shadows of buildings and mountains may obscure the satellite. There are cases where it becomes impossible to receive radio waves.

[Purpose of the invention]

This invention improves the above-mentioned problems, and when determining the position of a vehicle using a predetermined calculation method using a predetermined number of satellites, the number of observed satellites is at least one more than the predetermined number, and the calculation method is accurate and substantially the same. An object of the present invention is to provide a vehicle position measuring device that can determine the position of the vehicle.

[Structure of the invention]

As shown in FIG. 1, this invention to achieve the above object includes a receiving means 1 for receiving navigation data from a plurality of satellites, and a satellite for determining the number of receivable satellites from the reception results of the receiving means 1. a satellite number determining means 3 for determining whether the number of satellites detected by the satellite number determining means 3 is sufficient to perform a predetermined calculation; and a receiving means when the number of satellites detected by the satellite number determining means 3 is determined to be sufficient to perform a predetermined calculation. 1 to a predetermined number of satellites and calculates the vehicle position using a predetermined calculation method; and at least the vehicle position calculated by the first calculation means 5 from the center of the earth to the vehicle position. height position data storage means 7 for storing the distance of receiving height position data from the position data storage means 7, and receiving navigation data from one satellite less than the predetermined number from the receiving means 1, with the height position data being set as a constant value, substantially in accordance with the predetermined calculation method; a second calculation means 9 for calculating the position of the vehicle; and a first calculation means 5
and an output means 11 for appropriately outputting the vehicle position determined by the second calculation means 9.

[Explanation of Examples]

Examples of the present invention will be described below.

FIG. 2 shows a block diagram of a vehicle position measuring device used in combination with a route guidance device.

13 is an antenna that receives signals from a satellite; 1
5 is an RF front end that performs high frequency amplification, 17
is an IF amplifier that amplifies intermediate frequencies. Reference numeral 19 denotes a navigation data detection unit having four channels CH1, CH2, CH3, and CH4, and each channel includes a demodulation circuit 2 that performs spectrum despreading.
1, a low-pass filter 23, a PN generator 25, a synchronization circuit 27, and a navigation data detection circuit 29. 31 is the main computer,
33 indicates a route guidance device.

Comparing FIG. 1 and FIG. 2, the receiving means 1 is
It is formed by an antenna 13, an RF front end 15, an IF amplifier 17, and a navigation data detection device 19, and a satellite number determining means 3, first and second calculation means 5, 9, and height position data storage means 7. Both are formed within the main computer 31.
The calculation result output means 11 is an interface that provides the calculation results to the route guidance device 33 while appropriately utilizing the storage device of the main computer.
It is not directly shown in FIG. In FIG. 2, each channel CH1 to CH4 independently receives radio waves from each satellite and detects each navigation data. The detected navigation data is analyzed and calculated by the main computer 31 to determine the vehicle position.

FIG. 3 shows a flowchart of calculation processing using the convergence calculation method. These processes are performed within the main computer 31.

Prior to the start of calculation, an initial value is set in step 303. The initial value is an estimated value of the current position of the vehicle.
x', y', z' and the estimated value Δtu' of the offset time. Offset time is the error of the built-in clock relative to the absolute time (atomic clock). As the estimated value of the current position, the previous position data when the vehicle was stopped can be used as is. That is, when the vehicle is stopped, the vehicle position when the ignition switch is turned off is stored in the storage device of the main computer 31, and this stored position data can be used as is when the vehicle starts running next time. . Of course, manual input is also possible.

In step 305, the number of satellites is determined. In this example, the standard is to obtain a three-dimensional position using four satellites, and here the number of observable satellites is four.
It is determined whether there are 1 or 3, which is less than 1. If there are four, the process moves to step 311, and if there are three, the process moves to step 309 via step 307.

In step 311, calculation is performed by the first calculation means 5 shown in FIG. Here, an error in the estimated position is calculated using the convergence calculation method, and this error is evaluated in step 313.

Step 307 is a process that utilizes height position data. Here, a vehicle is something that normally travels on the surface of the earth, and compared to the displacement caused by traveling on the earth,
Since there are few changes in the height position, a large error will not occur even if the height position data is used.

The processing by the first calculation means in step 311 is based on four-dimensional simultaneous equations based on information from four satellites, whereas the processing by the second calculation means in step 309 is based on information from three satellites. In addition to the three equations, information that the height position data h is fixed,
That is, the only difference is that the equation x ² +y ² +z ² =h is added to form the above four-dimensional simultaneous equations. Note that the calculation is performed here using XYZ rectangular coordinates, but when calculating using spherical coordinates R, θ, ψ (θ corresponds to longitude and ψ corresponds to latitude), the center point is the center of the earth. In the two calculation means, the calculation is performed as R=h.

In step 313, evaluation is performed using an evaluation function. This is to evaluate how far the estimated positions x', y', and z' deviate from the actual positions.

In step 315, a convergence determination is made. That is, if the evaluation result in step 313 is good, that is, if the estimated position does not deviate greatly from the actual position, the process moves to step 319. If the evaluation result in step 313 is negative, that is, the estimated position deviates significantly from the actual position, the process moves to step 317.

In step 317, the estimated positions x', y', z' and the estimated offset time Δtu' are reselected, and the process is twice returned to step 305.
The processing from step 313 is step 3.
The process is repeated until it is determined in step 05 that the convergence situation is good.

If it is determined in step 315 that the convergence situation is good, the process moves to step 319, where the current position xyz of the vehicle and the offset time Δtu of the clock are determined, and the process ends in step 321.

The calculation results (vehicle position xyz) from the above processing are outputted from the output means 11 shown in FIG.
The location is displayed or used for other processing. Note that the height position data h resulting from the calculation is stored in the position data storage means shown in FIG. 1, but it is determined that it has been calculated by the first conversion means, and the previous value is updated only in this case. Alternatively, the previous position data may be updated and stored regardless of whether it is calculated by the first calculation means or the second calculation means. It is also conceivable to provide an altitude sensor in the vehicle and correct the altitude position data.

In the above embodiment, the offset time Δtu was taken as an unknown quantity, but this offset time may be reduced by using a highly accurate clock, or the previous measured value may be used for the offset time.

Alternatively, if it is not necessary to take this into consideration, it is sufficient to observe three satellites even in three-dimensional calculations. Therefore, in such a case, it is sufficient to determine 4 items as 3 items and 3 items as 2 items in the judgment in step 305 of the flowchart of FIG.

〔Effect of the invention〕

According to the invention described above, when determining the vehicle position using a predetermined calculation method using a predetermined number of satellites, the number of observed satellites is at least one more than the predetermined number, and the calculation method is accurate and substantially the same. It is possible to provide a vehicle position measuring device that can determine the position of the vehicle.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to claims of this invention, Figs. 2 and 3 show embodiments of this invention, Fig. 2 is a block diagram of a vehicle position measuring device, and Fig. 3 is arithmetic processing performed by a microcomputer. This is a flowchart. 1... Receiving means, 3... Satellite number determining means, 5...
...First calculation means, 7...Height position data storage means, 9...Second calculation means, 11...Output means, 1
9...Navigation data detection device, 31...Main computer, 33...Route guidance device.

Claims (1)

[Claims] 1. Receiving means for receiving navigation data from a plurality of satellites, and satellite number determining means for determining the number of receivable satellites from the reception results of the receiving means and determining whether the number of satellites is sufficient to perform a predetermined calculation. , when the number of satellites detected by the satellite number determining means is determined to be sufficient to perform a predetermined calculation, a step of receiving navigation data from a predetermined number of satellites from the receiving means and calculating the position of the vehicle using a predetermined calculation method; a height position data storage means for storing at least the height position data of the vehicle position calculated by the first calculation means; and a height position data storage means for storing at least the height position data of the vehicle position calculated by the first calculation means; When it is determined that one satellite is missing, height position data is received from the height position data storage means, navigation data from one satellite less than the predetermined number is received from the receiving means, and the height position data is used to calculate the predetermined number of satellites. A vehicle position comprising: second calculation means for calculating the position of the vehicle substantially according to a calculation method; and output means for appropriately outputting the vehicle position determined by the first calculation means and the second calculation means. Measuring device.