United States Patent (19)
`Hirata
`
`54 on-BOARD VEHICLE POSITION
`DETECTOR
`(75) Inventor: Seiichiro Hirata, Sanda, Japan
`73) Assignee: Mitsubishi Denki K.K., Tokyo, Japan
`(21) Appl. No.: 757,421
`(22
`Filed:
`Sep. 10, 1991
`30)
`Foreign Application Priority Data
`Sep. 12, 1990 (JP)
`Japan .................................. 2-239929
`Sep. 12, 1990 (JP
`Japan .................................. 2-239930
`51) Int. Cl.............................................. G06F 15/50
`52 U.S. C. .................................... 364/449; 364/450;
`342/357
`(58) Field of Sesirch ............... 364/443, 449, 450, 453,
`364/454; 342/357, 358, 451; 73/178 R
`References Cited
`U.S. PATENT DOCUMENTS
`4,459,667 7/1984 Takeuchi............................. 364/450
`4,688,176 8/1987 Hirata .................................. 364/449
`4,731,613 3/1988 Endo et al. .......................... 364/450
`4,899,285 2/1990 Nakayama et al. ................. 342/357
`4,903,212 2/1990 Yokouchi et al. .................. 364/449
`4,949,268 8/1990 Nishikawa et al. ................. 364/450
`
`56)
`
`US005257195A
`11) Patent Number:
`(45) Date of Patent:
`
`5,257,195
`Oct. 26, 1993
`
`5,087,919 2/1992 Odagawa et al.................... 364/450
`FOREIGN PATENT DOCUMENTS
`379198 7/1990 European Pat. Off. .
`2013906 10/1970 Fed. Rep. of Germany.
`3227547 2/1984 Fed. Rep. of Germany.
`3310111 9/1984 Fed. Rep. of Germany .
`Primary Examiner-Gary Chin
`Attorney, Agent, or Firn-Sughrue, Mion, Zinn,
`Macpeak & Seas
`ABSTRACT
`57
`An on-board vehicle position detector includes a dead
`reckoning position detector 4 and a GPS receiver 6, the
`outputs of which are stored in the dead reckoner data
`memory unit 8 and the GPS data memory unit 7, respec
`tively, at a predetermined sampling period. Usually, the
`position of the vehicle is determined on the basis of the
`data obtained via the GPS receiver 6. When, however,
`the vehicle travel distance between two successive sam
`pling times as determined via the GPS receiver 6 be
`comes abnormally large, the position data of the dead
`reckoning position detector 4 is selected.
`
`5 Claims, 5 Drawing Sheets
`
`
`
`
`
`2
`
`
`
`3
`
`DISTANCE
`SENSOR
`
`DIRECTION
`SENSOR
`
`DATA PROCESSING UNIT
`la
`
`b
`
`COMPARATOR
`
`SWITCHER
`
`GPS
`DATA
`MEMORY
`
`DEAD
`RECKONER
`DATA
`MEMORY
`
`
`
`
`
`
`
`
`
`
`
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`U.S. Patent
`
`Oct. 26, 1993
`
`Sheet 1 of 5
`
`5,257,195
`
`5
`
`N/
`
`FIG. I
`
`2
`
`3
`
`DISTANCE
`SENSOR
`
`DIRECTION
`SENSOR
`
`6
`
`.
`
`GPS
`RECEIVER
`
`DEAD
`RECKONER
`
`4.
`
`
`
`DATA PROCESSING UNIT
`
`la
`
`b
`
`COMPARATOR
`
`SWITCHER
`
`7
`
`GPS
`DATA
`MEMORY
`
`Ricker
`DATA
`MEMORY
`
`8
`
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`U.S. Patent
`
`Oct. 26, 1993
`
`Sheet 2 of 5
`
`5,257,195
`
`F. G. 2
`
`
`
`
`
`
`
`
`
`S22
`
`POSITION S1
`VIA GPS
`DETERMINED
`
`
`
`READ OUT
`PRECEDING
`POSITION S2
`
`S23
`
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`U.S. Patent
`
`Oct. 26, 1993
`
`Sheet 3 of 5
`
`5,257,195
`
`F. G. 3
`
`
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`U.S. Patent
`
`Oct. 26, 1993
`
`Sheet 4 of 5
`
`5,257,195
`
`F. G. 4
`
`2
`
`3
`
`DSTANCE
`SENSOR
`
`DIRECTION
`SENSOR
`
`5
`
`V/
`
`6
`
`GPS
`RECEIVER
`
`DEAD
`RECKONER
`
`4.
`
`
`
`DATA PROCESSING UNIT
`
`1
`
`la
`
`1b.
`
`H-COMPARATOR
`V-COMPARATOR
`
`SWITCHER
`
`7
`
`GPS
`DATA
`MEMORY
`
`DEAD
`RECKONER
`DATA
`MEMORY
`
`8
`
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`U.S. Patent
`
`Oct. 26, 1993
`
`Sheet 5 of 5
`
`5,257,195
`
`FIG. 5
`
`
`
`POSITION
`DETERMINED
`VA GPS
`
`READ OUT
`GPS
`H- & V-DATA
`
`
`
`S57
`
`OUTPUT POSITION
`VIA GPS
`
`OUTPUT POSITION
`VIA DEAD RECKONER
`
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`

`ON BOARD VEHICLE POSITION DETECTOR
`
`10
`
`15
`
`BACKGROUND OF THE INVENTION
`This invention relates to on-board vehicle position
`detectors, and more particularly to those utilized in
`automobile navigation systems.
`The Global Positioning System (GPS) is attracting
`attention as a means for detecting and determining the
`position of moving objects, such as ships, airplanes, and
`automobiles. For example, an article by T. Itoh et al.,
`“Navigation System Using GPS for Vehicles', SAE
`(Society of Automotive Engineers, Inc.) Technical
`Paper Series 861360, 1986, describes an automotive
`application of the GPS navigation system.
`The position detector utilizing Global Positioning
`System (GPS) determines the current position of a vehi
`cle (moving object) on the basis of radio waves received
`from a plurality of satellites. Generally, the Global Posi
`tioning System (GPS) position detector (receiver) re
`ceives clock signals from three or more GPS satellites.
`The clock data from a plurality of satellites are com
`pared with the clock of the vehicle, and the distances
`from the vehicle to the respective satellites are deter
`25
`mined on the basis of the differences of the clock on the
`vehicle and those of the satellites. The current position
`of the vehicle is determined from the distances to the
`respective GPS satellites.
`The GPS position detectors are capable of determin
`ing the position the vehicle accurately, to within about
`30
`30 meters. However, for the determination of the posi
`tion of the vehicle, the GPS position detectors are in
`need of clock signals from GPS satellites. If signals from
`GPS satellites are not available, the GPS position detec
`tors cease functioning. On the other hand, the self-con
`35
`tained or independent type position detectors (the dead
`reckoning type position detectors) are capable of deter
`mining the current position of vehicles solely on the
`basis of the data obtained by themselves. However, they
`are not as accurate as the GPS position detectors.
`Thus, a GPS and a dead reckoning position detector
`are usually combined and used together in a single ve
`hicular on-board position detector unit. In such case,
`when signals from three or more GPS satellites are
`available, the position is determined on the basis of the
`45
`information obtained via the GPS position detector
`system. When, on the other hand, such condition is not
`satisfied, the position of the vehicle is determined on the
`basis of data obtained via the dead reckoning position
`detector.
`This combined type position detector, however, still
`has the disadvantage that position data obtained via the
`GPS position detector system may sometimes contain a
`large error due to the so-called multi-path effect.
`Namely, when the vehicle is running in a mountain or
`55
`city area, the GPS radio waves from the satellites may
`reach the vehicle after being reflected by mountains or
`buildings. Then, the paths of the GPS radio waves from
`the satellites to the vehicle are longer than the proper
`direct paths from the GPS satellites to the vehicle.
`60
`Under such circumstances, the position of the vehicle
`obtained on the basis of the GPS measurement data
`contains a large error, and an abnormal position may
`thus be displayed by the position detector.
`SUMMARY OF THE INVENTION
`It is therefore an object of this invention to provide a
`combined type on-board vehicle position detector in
`
`5,257,195
`2
`cluding the GPS receiver and the self-contained type
`detector systems, which is capable of determining the
`current position of the vehicle accurately even when, in
`particular, the vehicle is running in a region such as a
`mountain or city area where the multi-path effect is
`conspicuous.
`The above project is accomplished in accordance
`with the principle of this invention by a vehicle position
`detector which comprises: a GPS receiver for receiving
`GPS signals from GPS satellites and for determining at
`a predetermined period a current position of the vehicle
`on the basis of GPS signals received from the GPS
`satellites; a dead reckoning position detector for deter
`mining a current position of the vehicle at a predeter
`mined period cycle on the basis of data obtained by
`sensors mounted on the vehicle; a first memory means
`for storing position data obtained via the GPS receiver
`means; a second memory means for storing position
`data obtained via the dead reckoning position detector
`means; a comparator means for comparing a position of
`the vehicle as determined by the GPS receiver means at
`a current determination cycle with a position of the
`vehicle as determined by the GPS receiver means at an
`immediately preceding determination cycle, said com
`parator means calculating a distance between the posi
`tion of the vehicle determined at the current determina
`tion cycle and the position of the vehicle determined at
`the immediately preceding determination cycle; and a
`switcher means for switching a current output of the
`vehicle position detector in accordance with a result of
`comparison via comparator means, wherein said
`switcher means selects as the current output of the
`vehicle position detector a position obtained via dead
`reckoning position detector means when said distance
`exceeds a predetermined reference value, said compara
`tor means otherwise selecting a position obtained via
`the GPS receiver means.
`Thus, usually, the position of the vehicle is deter
`mined on the basis of the data obtained via the GPS
`receiver. When, however, the vehicle travel distance
`between two successive sampling times as determined
`via the GPS receiver becomes abnormally large, the
`position data of the dead reckoning position detector is
`selected.
`Alternatively, the GPS receiver may determine at a
`predetermined period a current height and a velocity, as
`well as a planar position of the vehicle on the basis of
`GPS signals received from the GPS satellites. Then, the
`comparator means determines whether or not the
`height and velocity determined via the GPS receiver
`means fall within respective predetermined ranges.
`Switcher means then switches a current output of the
`vehicle position detector in accordance with the result
`of the determination by the comparator means, wherein
`the switcher means selects as the current output of the
`vehicle position detector a position obtained via the
`GPS receiver when both the height and velocity deter
`mined via the GPS receiver means fall within the re
`spective predetermined ranges, the switcher means
`otherwise selecting a position obtained via the dead
`reckoning position detector.
`BRIEF DESCRIPTION OF THE DRAWINGS
`The features which are believed to be characteristic
`of this invention are set forth with particularity in the
`appended claims. The structure and method of opera
`tion of this invention itself, however, will be best under
`
`SO
`
`65
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`O
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`15
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`5,257,195
`3
`4.
`stood from the following detailed description, taken in
`At step S22, judgement is made whether or not a
`conjunction with the accompanying drawings, in
`position determination of the vehicle position S1 by
`means of the information from satellites has been made
`which:
`FIG. 1 is a block diagram showing the organization
`for the current position determination cycle. If the re
`sult of the judgment at step S22 is negative, the execu
`of a first embodiment of this invention;
`tion proceeds to step S25, where the position informa
`FIG. 2 is a flowchart showing the position detection
`tion obtained from dead reckoning position detector 4 is
`procedure of the vehicle position detector of FIG. 1;
`FIG. 3 is a diagram showing the operation character
`output.
`On the other hand, when the result of judgment at
`istics of the vehicle position detector of FIG. 1;
`step S22 is affirmative, the execution proceeds to next
`FIG. 4 is a block diagram showing the organization
`step S23, where the position S2 of the vehicle deter
`of a second embodiment of this invention; and
`mined at the immediately preceding position determina
`FIG. 5 is a flowchart showing the position detection
`tion cycle is read out from the GPS data memory unit 7.
`procedure of the vehicle position detector of FIG. 4.
`Further, at step S24, judgment is made by the compara
`In the drawings, like reference numerals represent
`tor means 1a of the data processing unit 1 whether or
`like or corresponding parts or portions.
`not the distance between S1 and S2 (the distance trav
`DETAILED DESCRIPTION OF THE
`eled by the vehicle) is greater than a predetermined
`PREFERRED EMBODIMENTS
`reference value K:
`Referring now to the accompanying drawings, the
`20
`preferred embodiments of this invention are described.
`FIG. 1 is a block diagram showing the organization
`of a first embodiment of this invention. The vehicle
`position detector of FIG.1 mounted on a vehicle (auto
`mobile) includes a data processing unit 1 which receives
`25
`data from a dead reckoning position detector (i.e., inde
`pendent or self-contained type position detector) 4 and
`a Global Positioning System (GPS) position detector 6.
`The dead reckoning position detector 4 is supplied data
`from a distance sensor 2 and a direction sensor 3 which
`30
`determine the traveling distance and direction, respec
`tively, of the moving vehicle by means of a velocity
`sensor and a geomagnetic sensor, respectively. The
`dead reckoning position detector 4 determines at a pre
`determined period the current position of the vehicle on
`35
`the basis of the data supplied from the distance sensor 2
`and the direction sensor 3. The GPS receiver 6 is fed
`from the output of an antenna 5 which receives radio
`waves from GPS satellites. The GPS receiver 6 deter
`mines at a predetermined period the current position of
`40
`the vehicle on the basis of the clock signals obtained
`from three or more GPS satellites.
`The data processing unit 1, which is supplied data
`from the dead reckoning position detector 4 and the
`GPS receiver 6, includes a comparator means 1a and a
`45
`switcher means 1b. The successive positions of the vehi
`cle determined by the GPS receiver 6 and the dead
`reckoning position detector 4, respectively, are stored
`via the data processing unit 1 in a GPS data memory
`unit 7 and a dead reckoner data memory unit 8, respec
`50
`tively, which are connected to the data processing unit
`1.
`The operation of the vehicle position detector of
`FIG. 1 is as follows.
`FIG. 2 is a flowchart showing the position detection
`55
`procedure of the vehicle position detector of FIG.1. At
`the start step S21, the driver of the vehicle starts the
`vehicle position detector by hitting, for example, a start
`key on the key input board of the vehicle position detec
`tor. Thus, the GPS receiver 6 and the dead reckoning
`position detector 4 begin to determine the present or
`current position of the vehicle at a predetermined per
`iod, and the data processing unit 1 stores the respective
`position data successively in the GPS data memory unit
`7 and the dead reckoner data memory unit 8, respec
`65
`tively. When, however, clock signals from three or
`more GPS satellites are not available, the GPS receiver
`6 ceases to determine the position of the vehicle.
`
`If the result of judgment at step S24 is affirmative, the
`execution proceeds to next step S25, where the current
`position information obtained from the dead reckoning
`position detector 4 is output. On the other hand, when
`the result of judgment at step S24 is negative, the execu
`tion proceeds to step S26, where the current position
`information based on data from the GPS receiver 6 is
`output. The switcher means 1b of the data processing
`unit 1 switches the output between the position data as
`determined via GPS information and the position data
`as determined via dead reckoning position detector, in
`accordance with the result of judgment at step S24.
`Thus, usually, the position of the vehicle is deter
`mined on the basis of the data obtained via the GPS
`receiver 6. When, however, the vehicle travel distance
`between two successive sampling times as determined
`via the GPS receiver 6 becomes abnormally large, the
`position data of the dead reckoning position detector 4
`is selected.
`FIG. 3 is a diagram showing the operation character
`istics of the vehicle position detector of FIG. 1. The
`moving vehicle is plotted in the X-Y plane. Two dotted
`lines 31 and 32 are drawn at 45 degrees on both side of
`the latest position S1 determined via GPS data. The
`judgment at step S24 may be effected by determining
`whether or not the vehicle position S2 determined at
`the preceding determination cycle is outside of the re
`gion between the two lines 31 and 32.
`FIG. 4 is a block diagram showing the organization
`of a second embodiment of this invention. The GPS
`receiver 6 of the position detector of FIG. 4 outputs at
`a predetermined period the height (altitude) and the
`velocity, as well as the planar position, of the vehicle.
`Alternatively, the data processing unit 1 may calculate
`the velocity of the vehicle from the successive positions
`supplied from the GPS receiver 6. The data processing
`unit 1 stores the successive GPS data in the GPS data
`memory unit 7. Further, the comparator means 1a of the
`data processing unit 1 includes a height comparator unit
`(H-comparator) and velocity comparator unit (V-com
`parator). Otherwise, the organization of the position
`detector is similar to that of FIG. 1.
`The operation of the vehicle position detector of
`FIG. 4 is described by referring to FIG. 5.
`FIG. 5 is a flowchart showing the position detection
`procedure of the vehicle position detector of FIG. 4. At
`the start step S51, the driver of the vehicle starts the
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`5,257,195
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`6
`vehicle position detector by hitting, for example, a start
`1. A vehicle position detector mounted on a vehicle,
`comprising:
`key on the key input board of the vehicle position detec
`GPS receiver means for receiving GPS signals from
`tor. Thus, the dead reckoning position detector 4 begins
`GPS satellites and for determining at a predeter
`to determine the position of the vehicle at a predeter
`mined cycle a current position of the vehicle on the
`mined period. Further, the GPS receiver 6 begins to
`basis of said GPS signals received from the GPS
`determine the height and the velocity, as well as the
`satellites;
`planar position, of the vehicle at a predetermined per
`dead reckoning position detector means for determin
`iod. When, however, clock signals from three or more
`ing a current position of the vehicle at a predeter
`GPS satellites are not available, the GPS receiver 6
`mined cycle on the basis of data obtained by sen
`10
`ceases to determine these values. The data processing
`sors mounted on the vehicle;
`unit 1 stores the respective data obtained by the GPS
`first memory means for storing position data obtained
`receiver 6 and the dead reckoning position detector 4,
`by the GPS receiver means;
`successively, in the GPS data memory unit 7 and the
`second memory means for storing position data ob
`dead reckoner data memory unit 8, respectively.
`tained by the dead reckoning position detector
`At step S52, judgment is made whether or not the
`means;
`position determination of the vehicle by means of the
`comparator means for comparing, exclusively, a posi
`information from satellites has been made for the cur
`tion of the vehicle as determined by the GPS re
`rent position determination cycle. Namely, judgment is
`ceiver means at a current determination cycle with
`made whether or not the GPS receiver 6 has output
`a position of the vehicle as determined by the GPS
`20
`data for the current period.
`receiver means at an immediately preceding deter
`If the result of the judgment at step S52 is negative,
`mination cycle, said comparator means calculating
`the execution proceeds to step S57, where the position
`a distance between the position of the vehicle de
`information obtained from dead reckoning position
`termined at the current determination cycle and
`detector 4 is output.
`the position of the vehicle determined at the imme
`On the other hand, when the result of judgment at
`diately preceding determination cycle; and
`step S52 is affirmative, the execution proceeds to next
`switcher means for switching a present output of the
`step S53, where the height data H and the velocity data
`vehicle position detector esclusively in accordance
`V of the vehicle determined at the preceding cycle is
`with a result of said comparison by the comparator
`read out from the GPS data memory unit 7. Further, at
`means, wherein said switcher means selects as the
`30
`step S54, judgment is made whether or not the height H
`present output of the vehicle position detector a
`falls between a predetermined minimum reference value
`position obtained by the dead reckoning position
`H1 and a predetermined maximum reference value H2:
`detector means when said distance exceeds a pre
`determined reference value, said comparator
`HCHCH2
`means otherwise selecting a position obtained by
`the GPS receiver means.
`2. A vehicle position detector as claimed in claim 1,
`wherein said dead reckoning position detector means
`determines the present position of the vehicle on the
`basis of outputs of a distance sensor and a direction
`sensor mounted on the vehicle.
`3. An on-board vehicle position detector mounted on
`a vehicle, comprising:
`GPS receiver means for receiving GPS signals from
`GPS satellites and for determining at a predeter
`mined cycle a present height, velocity and a planar
`position of the vehicle on the basis of said GPS
`signals received from the GPS satellites;
`dead reckoning position detector means for determin
`ing a present position of the vehicle at a predeter
`mined cycle on the basis of data obtained by sen
`sors mounted on the vehicle;
`GPS data memory unit means for storing data ob
`tained by the GPS receiver means;
`dead reckoner data memory unit means for storing
`position data obtained by the dead reckoning posi
`tion detector means;
`comparator means for determining, exclusively,
`whether or not the height and velocity determined
`by the GPS receiver means fall within respective
`predetermined ranges; and
`switcher means for switching a present output of the
`vehicle position detector exclusively in accordance
`with a result of said determination by the compara
`tor means, wherein said switcher means selects as
`the present output of the vehicle position detector
`a position obtained by the GPS receiver means
`when both the height and velocity determined by
`
`50
`This judgment at step S55 is effected by the V-com
`parator within the comparator means 1a of the data
`processing unit 1.
`If the result of judgment at step S55 is negative, the
`execution proceeds to step S57, where the position
`information obtained from dead reckoning position
`detector 4 is output. If the result of judgment at step S55
`is affirmative, the execution proceeds to next step S56,
`where the current position information based on data
`from the GPS receiver 6 is output.
`The switcher means 1b of the data processing unit 1
`switches the output between the position data as deter
`mined via GPS information and the position data as
`determined via dead reckoning position detector, in
`65
`accordance with the result of judgments at steps S54
`and S55.
`What is claimed is:
`
`35
`This judgement at step S54 is effected by the H-com
`parator of the comparator means 1a of the data process
`ing unit 1.
`If the result of judgement at step S54 is negative, the
`execution proceeds to step S57, where the position
`information obtained from dead reckoning position
`detector 4 is output.
`If the result of judgement at step S54 is affirmative,
`the execution proceeds to step S55, where a further
`45
`judgment is made whether or not the velocity V falls
`between a predetermined minimum reference value V1
`and a predetermined maximum reference value V2:
`
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`receiver at an immediately preceding determination
`the GPS receiver means fall within the respective
`cycle fall within said respective predetermined ranges.
`predetermined ranges, said switcher means other
`5. A vehicle position detector as clained in claim 3,
`wise selecting a position obtained by the dead reck
`wherein said dead reckoning position detector means
`oning position detector means.
`determines the present position of the vehicle on the
`4. A vehicle position detector as claimed in claim 3,
`basis of outputs of a distance sensor and a direction
`wherein said comparator means determines whether or
`sensor mounted on the vehicle.
`not the height and velocity determined by the GPS
`k
`k
`k
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`k
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