JP3601354B2 - Position detection device - Google Patents

Description

【００３７】
但し、速度誤差推定部２０は、（１）式にて算出される速度誤差見積値Ｖｔｈが、上限値（本実施例では１［ｍ／ｓ］）より大きい場合には、速度誤差見積値Ｖｔｈを、この上限値に制限（即ち、０＜Ｖｔｈ≦１となる）し、また、測位演算に用いるＧＰＳ衛星の組合せや配置が変化する毎に、速度誤差見積値Ｖｔｈを繰り返し算出するように構成されている。
【００３８】
また、測位演算部２２及び速度ベクトル演算部２４は、受信回路部１２にて同じタイミングで受信された信号に基づき、測位位置データＰｇ及び速度ベクトルＶｇを、同じタイミングで繰り返し算出するように構成されている。
次に、測位演算部２２では、少なくとも３つ（好ましくは４つ以上）のＧＰＳ衛星との擬似距離を同時に検出し、この擬似距離を公知の測位演算に適用することにより、測位位置データＰｇを算出する。
【００３９】
また、速度ベクトル演算部２４では、（２）式を用いて求められる北方向速度Ｖｎ，及び東方向速度Ｖｅに基づき、これらを合成することで速度ベクトルＶｇを算出する。
【００４０】
【数１】

【００４１】
但し、Ｖｕは上方向速度、ＶＬＦは受信機の基準発振器のオフセットの速度換算値、ｎｉ，ｅｉ，ｕｉはＧＰＳ衛星ｉに向かう単位ベクトルの北，東，上方向余弦、Ｖｄｕｉ は衛星ｉからの電波（搬送波）のドップラーシフトの予測値（計算値）と受信回路部１２にて検出された搬送波の周波数変位の実測値との差を示している。なお、この速度ベクトル演算部２４における速度ベクトル演算は、測位演算部２２における測位演算と同様に公知のものである。
【００４２】
ここで、速度誤差推定部２０からの速度誤差見積値Ｖｔｈ，測位演算部２２からの測位位置データＰｇ，速度ベクトル演算部２４からの速度ベクトルＶｇに基づいて、演算部１４が行うフィルタリング処理を、図２に示すフローチャートに沿って説明する。
【００４３】
本処理は車両の運転開始後、周期的（本実施例では１［ｓ］周期）に繰り返し起動される。本処理が起動されると、まずＳ１１０では、速度誤差推定部２０，測位演算部２２，速度ベクトル演算部２４から、速度誤差見積値Ｖｔｈ，測位位置データＰｇ，速度ベクトルＶｇを入力し、続くＳ１２０では、本処理の今回の起動が、車両の運転開始後、最初の起動であるか否かを判断する。
【００４４】
そして、最初の起動であると判定された場合には、Ｓ１３０に移行して、Ｓ１１０にて読み込んだ測位位置データＰｇにより現在位置データＰ，及び推定位置データＰｅを初期化し、続くＳ１４０では、演算タイミングを表すパラメータｉを零に初期化（ｉ←０）して、Ｓ１７０に移行する。
【００４５】
以後、本処理の最初の起動を０回目として、本処理のｉ回目の起動時（以下、ｉ回目の演算タイミングという）にＳ１１０にて読み込まれるデータをＰｇ（ｉ），Ｖｇ（ｉ）、及び同じｉ回目の演算タイミングにて算出される現在位置データをＰ（ｉ）、更にＰ（ｉ）の算出に用いる推定位置データをＰｅ（ｉ）にて表すものとする。
【００４６】
一方、先のＳ１２０にて、本処理の今回の起動が最初の起動ではないと判定された場合にはＳ１５０に移行し、ビル等による電波遮断によって捕捉中のＧＰＳ衛星数が２以下となることにより、測位演算部２２及び速度ベクトル演算部２４による演算処理が中断されているか否かを判断する。
【００４７】
そして、測位演算が中断されることなく行われていれば、Ｓ１６０に移行して、次の（３）式に従って現在位置データＰ（ｉ）の算出を行う。即ち、先のＳ１２０にて読み込んだ測位位置データＰｇ（ｉ）と、前回の演算タイミングで後述のＳ１９０，Ｓ２４０，Ｓ２５０，Ｓ２６０のいずれかにて算出された推定位置データＰｅ（ｉ）との加重平均値を求めた後、Ｓ１７０に移行する。
【００４８】
【数２】

【００４９】
但し、ｍ＞０，ｎ＞０であり、例えば、ｍ＝９，ｎ＝１に設定する。なお、ｍの値をｎより大きくするほど、算出される現在位置データＰ（ｉ）のばらつきは小さくなる。
この加重平均値を求める処理は、測位位置データＰｇに対する速度ベクトルＶｇによるフィルタリングにて、現在位置データＰの軌跡が速度ベクトルＶｇにて規定される所定の範囲に入るように現在位置データＰを更新していくものであると考えることができる。
【００５０】
そして、Ｓ１７０では、Ｓ１３０又はＳ１６０にて設定，算出された現在位置データＰ（ｉ）を、ナビ演算部８に出力する。この時、ナビ演算部８では、ＧＰＳ受信機２からの現在位置データＰ（ｉ）に基づき、車両の現在位置および現在位置付近の道路地図を表示部６に表示させる。
【００５１】
続くＳ１８０では、Ｓ１１０にて読み込んだ速度誤差見積値Ｖｔｈを判定しきい値として、同じくＳ１１０にて読み込んだ速度ベクトルの大きさ｜Ｖｇ（ｉ）｜、即ち車両の移動速度が、速度誤差見積値Ｖｔｈより小さいか否かを判断する。
そして、速度ベクトルの大きさ｜Ｖｇ（ｉ）｜が速度誤差見積値Ｖｔｈ以上であると判定された場合には、車両は移動中であるものとしてＳ１９０に移行し、移動中の車両の速度・方向は短時間では急激に変化することはないことから、（４）式に示すように、現在位置データＰ（ｉ）と速度ベクトルＶｇ（ｉ）とを加算することにより、次回の演算タイミングでの推定位置データＰｅ（ｉ＋１）を求める。
【００５２】
Ｐｅ（ｉ＋１）＝Ｐ（ｉ）＋Ｖｇ（ｉ） （４）
一方、先のＳ１８０にて、速度ベクトルの大きさ｜Ｖｇ（ｉ）｜が速度誤差見積値Ｖｔｈより小さいと判定された場合には、車両は停止中であるものとしてＳ２００に移行し、今度は、測位位置と現在位置との距離｜Ｐｇ（ｉ）−Ｐ（ｉ）｜が、予め設定された上限距離Ｐｔｈより大きいか否かを判断し、肯定判定された場合、即ち、測位位置と現在位置との距離が許容範囲（上限距離Ｐｔｈ）を越えている場合にはＳ２１０に移行する。
【００５３】
Ｓ２１０では、予め設定された上限時間Ｔｔｈを計時するタイマが起動済みであるか否かを判断し、未だ起動していなければＳ２２０に移行して、タイマを起動後、Ｓ２５０に移行する。但し、タイマは、Ｓ１５０にて肯定判定された場合、及びＳ１８０にて否定判定された場合には、動作が停止され計時値もリセットされる。
【００５４】
一方、Ｓ２１０にてタイマが起動済みであると判定された場合には、Ｓ２３０に移行して、今度はタイマがタイムアウトしているか否かを判断し、タイムアウトしていればＳ２４０に移行して、（５）式に示すように、Ｓ１１０にて読み込んだ測位位置データＰｇ（ｉ）を、次回の推定位置データＰｅ（ｉ＋１）として設定する。
【００５５】
Ｐｅ（ｉ＋１）＝Ｐｇ（ｉ） （５）
また、先のＳ２００にて、測位位置と現在位置との距離｜Ｐｇ（ｉ）−Ｐ（ｉ）｜が上限距離Ｐｔｈ以下（即ち許容範囲内）である場合、又は、上限距離Ｐｔｈより大きくてもタイムアウトしていない場合には、Ｓ２５０に移行して、（６）式に示すように、今回の演算タイミングでの推定位置データＰｅ（ｉ）を、次回の演算タイミングでの推定位置データＰｅ（ｉ＋１）として設定する。
【００５６】
Ｐｅ（ｉ＋１）＝Ｐｅ（ｉ） （６）
また、先のＳ１５０にて、測位中断中であると判定された場合には、Ｓ２６０に移行して、（７）式に示すように、測位が中断される直前に最後に読み込まれた速度ベクトルＶｇ（ｉ０）を、現在位置データＰ（ｉ）に加算することにより、推定位置データＰｅ（ｉ＋１）を算出する。
【００５７】
Ｐｅ（ｉ＋１）＝Ｐ（ｉ）＋Ｖｇ（ｉＯ） （７）
ここで、ｉ０ は、最後に測位した時刻を示すパラメータを示す。つまり、測位中断中に車両の速度・方位が急激に変化しなければ、このような速度ベクトルＶ（ｉ０）に基づいて、次回以降の演算タイミングでの推定位置データＰｅ（ｉ＋１）を、ある程度正確に求めることができ、測位が再開された時には、その推定位置データＰｅによって現在位置をある程度正確に補正することができるのである。
【００５８】
そして、Ｓ１９０，Ｓ２４０，Ｓ２５０，Ｓ２６０のいずれかにて次回の推定位置データＰｅ（ｉ＋１）が算出されると、Ｓ２７０に移行して、パラメータｉをインクリメント（ｉ←ｉ＋１）して本処理を終了する。
即ち、本処理においては、各演算タイミング毎に、読み込んだ（Ｓ１１０）測位位置データＰｇ（ｉ）と、前回の演算タイミングにて求めた推定位置データＰｅ（ｉ）とにより、現在位置データＰ（ｉ）を求めている（Ｓ１６０）。
【００５９】
また、本処理においては、次回の演算タイミングで用いる推定位置データＰｅ（ｉ＋１）の算出を、場合に応じて次のように行っている。
即ち、車両が移動中（Ｓ１８０−ＮＯ）の場合は、車両の速度・方向が急激に変化することはないものとして、現在位置データＰ（ｉ）と速度ベクトルＶｇ（ｉ）とを加算することにより推定位置データＰｅ（ｉ＋１）を求め（Ｓ１９０）、一方、車両が停止中（Ｓ１８０−ＹＥＳ）の場合は、基本的には、推定位置データの更新を行わず、今回の推定位置データＰｅ（ｉ）をそのまま次回の推定位置データＰｅ（ｉ＋１）として設定（Ｓ２５０）している。
【００６０】
但し、本処理では、車両が停止しているか否かの判断を、速度ベクトルの大きさ｜Ｖｇ（ｉ）｜が速度誤差見積値Ｖｔｈより小さいか否かにより行っているため、車両が停止中であると判断しても、実際には、速度誤差見積値Ｖｔｈより小さい速度で低速移動している場合が考えられる。
【００６１】
この場合、推定位置データＰｅの更新が行われないことから、推定位置データＰｅ（ｉ）に基づいて算出される現在位置データＰ（ｉ）と、測位演算部２２にて算出される測位位置データＰｇ（ｉ）との間の誤差は、時間の経過に従って増大する。
【００６２】
そのため、この誤差、即ち、現在位置と測位位置との距離｜Ｐｇ（ｉ）−Ｐ（ｉ）｜が、許容範囲（上限距離Ｐｔｈ）を越えた場合（Ｓ２００−ＹＥＳ）には、推定位置データＰｅ（ｉ＋１）を測位位置データＰｇ（ｉ）により再初期化（Ｓ２４０）して、両データ間の誤差が小さくなるようにしている。
【００６３】
なお、現在位置と測位位置との距離｜Ｐｇ（ｉ）−Ｐ（ｉ）｜が許容範囲を越えるような状況は、車両の低速移動時に限らず、マルチパスが生じた場合にも発生する。但し、マルチパスは、ＧＰＳ衛星の移動により、一定時間が経過すると解消される可能性が高い。このため、上記状況が上限時間Ｔｔｈ以上継続した場合（Ｓ２１０−ＹＥＳ，Ｓ２３０−ＹＥＳ）にのみ、マルチパスの影響ではないものとして、上記再初期化（Ｓ２４０）を行うことにより、推定位置データＰｅ，ひいては現在位置データＰから、マルチパスの影響が排除されるようにしている。
【００６４】
ここで、図３は、フィルタリング処理により求められる現在位置データＰ（ｉ）および推定位置データＰｅ（ｉ）が変化する様子を表す説明図である。
なお、図３（ａ）〜（ｃ）のいずれも、演算タイミングｉ＝２までは、車両が速度誤差見積値Ｖｔｈ以上の速度で走行している場合を示している。
【００６５】
この時、測位位置データＰｇ（ｉ）と、よりバラツキの小さい速度ベクトルＶｇ（ｉ−１）に基づく推定位置データＰｅ（ｉ）との加重平均により算出される現在位置データＰ（ｉ）は、測位位置データＰｇ（ｉ）そのものよりもばらつきが小さくなる。
【００６６】
そして、図３（ａ）において、演算タイミングｉ＝３以降は、車両が実際に停止している場合を示しており、この場合、推定位置データＰｅ（ｉ）が固定され、速度ベクトルＶｇ（ｉ）に含まれる誤差の影響を全く受けないため、現在位置データＰ（ｉ）のばらつきが、より一層低減されることになる。
【００６７】
また、図３（ｂ）において、演算タイミングｉ＝３以降は、車両が速度誤差見積値Ｖｔｈより小さい速度で低速走行している場合を示している。ここでは、演算タイミングｉ＝４の時に、現在位置と測位位置との距離｜Ｐｇ（４）−Ｐ（４）｜が上限距離Ｐｔｈより大きくなり、その後、上限時間Ｔｔｈを経過した演算タイミングｉ＝Ｘ−１の時に、推定位置データＰｅの再初期化が行われている。
【００６８】
このように、低速走行を停止状態と判定してしまうと、測位位置データＰｇ（ｉ）と、推定位置データＰｅ（ｉ）との誤差が大きくなるが、再初期化を行うことで、現在位置に蓄積されるこの誤差が解消されることがわかる。
更に、図３（ｃ）において、演算タイミングｉ＝３以降は、車両は実際に停止しているがマルチパスが発生し、その後、演算タイミングｉ＝６にて、マルチパスが解消した場合を示している。つまり、速度ベクトルＶｇが速度誤差見積値Ｖｔｈより小さければ、推定位置データＰｅの更新が行われないため、マルチパスが発生して測位位置データＰｇが大きく変化したとしても、これに追従してしまうことがなく、マルチパスが解消された時に算出される現在位置データＰ（６）は、マルチパスが発生する以前に求められた現在位置データＰ（２）の近傍に復帰する。つまり、その後、車両が走行を再開した時に、マルチパスの影響が蓄積されていない現在位置データＰ（ｉ）が算出される。
【００６９】
そして、このようにして算出された現在位置データＰは、図２のフローチャートで説明したように、Ｓ１７０でナビ演算部８に出力される。そして、車両の現在位置が、その付近の道路地図と共に表示部６に表示される。図４に、実際に走行した場合の現在位置の走行軌跡を示す。図５に示した従来装置、即ち速度誤差見積値Ｖｔｈによる停止判定を行わない場合は、車両の停止時に算出される現在位置データＰのばらつきが大きいが、本実施例のＧＰＳ受信機２、即ち停止判定を行い、停止状態にあると判定すると推定位置データＰｅの更新を禁止する場合は、停止時における現在位置データＰのばらつきが大幅に減少し、安定した軌跡となっていることがわかる。
【００７０】
以上説明したように、本実施例のＧＰＳ受信機２によれば、現在位置データＰ（ｉ）と速度ベクトルＶｇ（ｉ）とに基づいて次の演算タイミングでの推定位置データＰｅ（ｉ＋１）を算出し、次の演算タイミングでは、この推定位置データＰｅ（ｉ＋１）と測位位置データＰｇ（ｉ＋１）とに基づいて、過去の測位位置データＰｇ（ｉ）をそのまま用いることなく、現在位置データＰ（ｉ＋１）を算出しているので、現在位置データＰを、時間遅れを生じさせることなく精度よく算出できる。
【００７１】
また、本実施例のＧＰＳ受信機２によれば、速度ベクトルの大きさ｜Ｖｇ（ｉ）｜が、測位に用いるＧＰＳ衛星の状態によって決まる速度誤差見積値Ｖｔｈより小さく、速度ベクトルＶｇ中の誤差成分による影響が大きい場合には、車両が停止中であると判定して、推定位置データＰｅ（ｉ）を固定し、速度ベクトルＶｇ（ｉ）による値の更新を行わないようにしているので、速度ベクトルＶｇ（ｉ）の誤差成分によって、停止中の現在位置データＰ（ｉ）がばらついてしまうことを確実に抑えることができる。
【００７２】
更に、本実施例のＧＰＳ受信機２では、車両が停止中である間に、測位位置と現在位置との距離｜Ｐｇ（ｉ）−Ｐ（ｉ）｜が、上限距離Ｐｔｈより離れた状態が、上限時間Ｔｔｈ以上継続した場合に、次回の演算タイミングでの推定位置データＰ（ｉ＋１）を、測位位置データＰｇ（ｉ）で再初期化するようにされている。
【００７３】
このため、停止中であると判定されているにも関わらず、実際には車両が速度誤差見積値Ｖｔｈより小さな速度で低速移動している場合に、これを検出して、低速移動により生じた誤差を解消できるだけでなく、マルチパスの影響により、測位位置と現在位置との距離が上限距離以上離れた状態が発生したとしても、上限時間Ｔｔｈ以上継続しなければ、測位位置データＰｇ（ｉ）による現在位置データＰ（ｉ）の再初期化を行わないため、マルチパスによる測位位置データＰｇ（ｉ）の異常が現在位置データＰ（ｉ）に蓄積されてしまうことを防止できる。
【００７４】
また、本実施例のＧＰＳ受信機２では、停止中であるか否かを判定するための速度誤差見積値Ｖｔｈを可変設定し、しかも、その上限値を制限するようにされている。
従って、測位に使用する人工衛星の組合せや配置により、刻々と変化する誤差に応じて、常に最適な速度誤差見積値Ｖｔｈを設定できるため、システムの性能を最大限に引き出すことができると共に、速度誤差見積値Ｖｔｈが必要以上に大きな値に設定されることにより、地図上に表示される現在位置の表示が、車両が動き始めているにも関わらずなかなか動き出さないといったような、不自然な動きとなることを確実に防止できる。
【００７５】
以上、本発明の一実施例について説明したが、本発明は上記実施例に限定されるものではなく、本発明の要旨を逸脱しない範囲において、様々な態様にて実施することができる。
例えば、上記実施例では、測位位置データＰｇ（ｉ）と推定位置データＰｅ（ｉ）とから現在位置データＰ（ｉ）を算出する際に、加重平均の重み付け係数ｍ，ｎを固定して用いているが、例えば、測位に使用するＧＰＳ衛星の組合せが変化する等して、測位精度が変化する毎に、この測位精度に応じて重み付け係数ｍ，ｎを変化させるようにしてもよい。具体的には、測位精度が高い時には、測位位置データＰｇ（ｉ）の重み付け係数ｎを大きくし、逆に測位精度が低い時には、推定位置データＰｅ（ｉ）の重み付け係数ｍを大きくすればよい。この場合、現在位置データＰ（ｉ）の精度及び安定性を向上させることができる。
【００７６】
また、実際の車両では加速度や回転が生じているため、車両の運動を一定速度と仮定して推定位置データＰｅ（ｉ）を算出している上記実施例では、推定位置データＰｅ（ｉ）に誤差が生じる。従って、一定速度から外れる車両の運動分を推定位置データＰｅ（ｉ）の誤差として考慮し、現在位置データＰ（ｉ）を算出する際の重み付け係数ｍ，ｎを決定するようにすれば、より精度良く現在位置データＰ（ｉ）を算出することができる。
【００７７】
また、上記実施例では、Ｓ１９０において、車両の運動を一定速度運動としてモデル化し、（４）式を用いて推定位置データＰｅ（ｉ＋１）を算出しているが加速度運動まで考慮し、（８）式を用いて推定位置データＰｅ（ｉ＋１）を算出するようにしてもよい。
【００７８】
Ｐｅ（ｉ＋１）＝Ｐ（ｉ）＋｛Ｖ（ｉ−１）＋Ｖ（ｉ）｝／２ （８）
更に、上記実施例では、Ｓ２４０において、推定位置データＰｅ（ｉ＋１）の再初期化を行う際に、測位位置データＰｇ（ｉ）をそのまま用いているが、タイマが起動してからタイムアウトするまでの間に、演算タイミング毎にＳ１１０にて読み込まれた複数の測位位置データＰｇに基づいて得られる平均化された測位位置データを用いるようにしてもよい。この場合の平均化処理としては、単純平均してもよいし、時系列に従って重み付け平均してもよいし、その時々の測位精度に応じて重み付け平均してもよい。
【００７９】
また、上記実施例では、停止状態を、速度ベクトルの大きさが予め設定された値より小さいか否かにより判定しているが、車速パルス等、車速を測定するために車載されている他の装置からの測定信号等に基づいて、直接停止状態を判定してもよい。
【００８０】
上記実施例において、ＧＰＳ受信機２が位置検出装置、アンテナ１０及び受信回路部１２が受信手段、速度誤差推定部２０が判定しきい値設定手段、測位演算部２２が疑似距離検出手段及び測位演算手段、速度ベクトル演算部２４が相対速度検出手段及び速度ベクトル演算手段、Ｓ１９０が位置推定手段、Ｓ１６０が現在位置更新手段、Ｓ１８０が停止判定手段、Ｓ２５０が禁止手段、Ｓ２１０〜Ｓ２４０が推定位置初期化手段に相当する。
【図面の簡単な説明】
【図１】実施例のＧＰＳ受信機を用いて構成されたナビゲーション装置の全体構成を表すブロック図である。
【図２】フィルタリング部にて実行されるフィルタリング処理の内容を表すフローチャートである。
【図３】フィルタリング処理により算出される現在位置データ及び推定位置データが変化する様子を表す説明図である。
【図４】地図上に表示された現在位置データの軌跡を示す説明図である。
【図５】従来装置による現在位置データの軌跡を示す説明図である。
【符号の説明】
２…ＧＰＳ受信機 ４…地図データ記憶媒体 ６…表示部
８…ナビ演算部 １０…アンテナ １２…受信回路部
１４…演算部 ２０…速度誤差推定部 ２２…測位演算部
２４…速度ベクトル演算部 ２６…フィルタリング部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a position detection device that receives a radio wave from an artificial satellite and detects the position of the reception point.
[0002]
[Prior art]
Conventionally, as this kind of device, a plurality of artificial satellites (hereinafter, referred to as GPS satellites) provided for GPS (Global Positioning System) are used to simultaneously receive radio waves from three or four GPS satellites, 2. Description of the Related Art There has been known a GPS receiver which obtains a pseudo distance from each GPS satellite using a C / A code superimposed on a radio wave, and calculates a position based on the pseudo distance to obtain a current position.
[0003]
Note that the pseudo distance is obtained by measuring a time required for a C / A code transmitted from a GPS satellite at a predetermined timing to reach a GPS receiver using a clock that operates according to a GPS reference time. Is multiplied by the propagation speed of the radio wave.
[0004]
By the way, in GPS, accuracy degradation (SA: Selective Availability) is introduced to control the detection accuracy, and the frequency of a carrier wave is intentionally fluctuated within a certain range. , Various measurement errors occur, and the positioning position obtained by the positioning calculation varies.
[0005]
As one of the methods for reducing the variation of such positioning positions, it is conceivable to average the latest positioning positions by past positioning positions (for example, by averaging the previous positioning position and the current positioning position). However, when this method is applied, there is a problem that the measured position obtained by the averaging is temporally delayed from the actual position.
[0006]
On the other hand, for example, Japanese Patent Application Laid-Open No. 8-68651 discloses that not only a positioning position is obtained from a pseudorange calculated based on a C / A code as in the conventional manner, but also that a carrier wave is determined according to a relative speed with respect to a GPS satellite. By using the Doppler shift that occurs, a speed vector indicating the moving speed and moving direction of the GPS receiving device (or the moving object equipped with the device) is obtained, and by using this speed vector, no time delay occurs. A device that suppresses variation in a positioning position by GPS is disclosed.
[0007]
In this device, an estimated position at the next measurement timing is obtained based on the current position and the velocity vector already calculated, and the weighted average value of the estimated position and the actually measured positioning position is calculated at the next measurement timing. The position is calculated.
[0008]
That is, the past (previous) positioning position is not used as it is, but is used for calculating an estimated position, and averaging is performed between the estimated position and the actually measured positioning position. Such a time delay does not occur, and the carrier has a higher resolution than the C / A code having a bit rate of 1 Mbps in the GPS receiver. Therefore, the current position is determined by combining the velocity vectors obtained using the carrier. In the case where the current position is obtained, the variation can be suppressed and the measurement accuracy is improved as compared with the case where the current position is obtained only by using the pseudo distance obtained using the C / A code.
[0009]
[Problems to be solved by the invention]
However, the fluctuation of the carrier frequency due to the SA cannot be distinguished from the frequency displacement due to the Doppler shift, and therefore, an error component corresponding to the magnitude of the fluctuation is superimposed on the velocity vector.
[0010]
When moving at high speed, the effect of the error component is small because the speed vector component generated by the movement is sufficiently large, but when stopping or traveling at low speed, the speed vector component generated by the movement becomes small, and the error component becomes relatively small. The effect is greater because of the larger size.
[0011]
As a result, when the above-mentioned GPS receiver is applied to a vehicular navigation device, a speed vector is detected even though the vehicle is actually stopped, and thus the current position on the map is determined. There is a problem that the display constantly changes and the display is difficult to see.
Further, for example, when the vehicle stops once at an intersection and starts moving again, if the current position during the stop varies due to an error component, the vehicle starts to move from a position different from the stopped position, as shown in FIG. Is displayed as if the vehicle were running on a cranked road. As a result, if the current position obtained by the GPS receiver is matched with the road on the map, there is a problem that the current position is displayed on an incorrect road in some cases.
[0012]
Furthermore, especially when traveling in an urban area, a multipath occurs in which radio waves reflected on buildings and the like are received. When this multipath occurs, the pseudorange to be detected becomes longer, so that correct positioning cannot be performed. However, if the vehicle is traveling, the surrounding conditions change in a short period of time, so the duration of the multipath condition is short, and there is almost no effect. In such a case, since the multipath state continues, the effect is large, and there is a problem that the current position displayed on the map of the navigation device becomes large and incorrect.
[0013]
Therefore, an object of the present invention is to improve the accuracy of a position detected during stoppage in a position detecting device using an artificial satellite in order to solve the above-mentioned problems.
[0014]
[Means for Solving the Problems]
In the position detecting device according to claim 1, which is an invention made to achieve the above object, the receiving means receives radio waves from a plurality of artificial satellites, and based on timing information superimposed on the received radio waves, Pseudo-distance detection means detects pseudo-ranges with the respective artificial satellites, and positioning calculation means repeatedly determines a positioning position at preset calculation timings based on the detected pseudo-distance.
[0015]
At the same time, the relative speed detecting means detects the relative speed between the device and each of the artificial satellites based on the frequency displacement of the radio wave received by the receiving means, and the speed vector calculating means detects the relative speed based on the detected relative speed. Thus, a velocity vector indicating the moving speed and moving direction of the device is repeatedly obtained for each calculation timing. That is, since the frequency of the radio wave is Doppler shifted according to the relative speed between the device and the artificial satellite, the relative speed can be obtained based on the frequency displacement caused by the Doppler shift.
[0016]
Then, the position estimating means obtains the estimated position of the device at the next calculation timing based on the speed vector obtained by the speed vector calculating means and the preset current position of the device, and updates the current position. The means updates the current position with a weighted average value of the measured position obtained by the position calculating means and the estimated position obtained by the position estimating means at the previous calculation timing.
[0017]
However, if the stop determination unit determines that the vehicle is in the stop state, the prohibition unit prohibits the update of the estimated position by the position estimation unit, and replaces the estimated position used at the current calculation timing with the next calculation timing. Set as the estimated position in.
According to the position detection device of the present invention configured as described above, the current position is obtained based on the measured position obtained using the timing information and the estimated position obtained using the velocity vector. The accuracy of the current position can be improved without causing a time delay as in a conventional device that uses a measured position to suppress variations.
[0018]
In addition, according to the position detection device of the present invention, the stop state is determined based on the moving speed of the device (or the moving body on which the device is mounted). Since the estimated position is not updated, it is possible to reliably prevent the current position from fluctuating due to an error component of the speed vector that becomes relatively large when the vehicle is stopped or running at low speed.
[0019]
Note that the speed vector calculation means may average the speed vector obtained at the previous calculation timing and the speed vector obtained at the current calculation timing as a speed vector to be supplied to the position estimation means.
In this case, when the speed vector is averaged, the estimated position is obtained more accurately because the acceleration of the speed vector is taken into account, so that the current position can be obtained more accurately.
[0020]
Note that when the stop state is determined by the stop determination unit, specifically, for example, the magnitude of the speed vector obtained by the speed vector calculation unit is determined by a predetermined determination threshold. It can be determined by comparing with a value. In this case, if the magnitude of the speed vector is smaller than the determination threshold, it may be determined that the vehicle is in the stopped state.
[0021]
By the way, when the vehicle is traveling at low speed such that the size of the speed vector is equal to or smaller than the determination threshold due to traffic congestion or the like, the estimated position is not updated even though the vehicle is actually moving. The estimated position greatly differs from the actual position, and as a result, the accuracy of the current position calculated based on the estimated position and the measured position may be reduced.
[0022]
Therefore, the claim 1 In the position detection device described above, during the stop state, the state where the measured position and the current position are separated by a predetermined upper limit distance or more continues for a predetermined upper limit time, the estimated position initialization means, The estimated position is initialized based on the measured position.
[0023]
In other words, if the device (moving body on which the device is mounted) is moving at a low speed equal to or less than the determination threshold, once a state in which the measured position is separated from the current position by the upper limit distance is detected, the determination is made. This state continues unless the movement at or above the threshold is started. For this reason, when continuing for more than the upper limit time, the apparatus considers that the low-speed movement is in the stopped state by performing initialization of the estimated position based on the positioning position, assuming that the apparatus is actually moving at a low speed. The error caused by this is eliminated.
[0024]
In addition, if a multipath occurs at the time of stoppage, the estimated position and the positioning position will also differ greatly, but after a certain period of time, the reception state will change due to the movement of the satellite and the multipath will be resolved. Often done. For this reason, if the upper limit time is set to a length long enough to increase the possibility that the multipath will be canceled, the movement is restarted without the effect of the multipath being accumulated at the current position. At times, an accurate current position from which the influence of multipath has been eliminated can be obtained.
[0025]
However, even if the radio waves from the satellite are normally received, the positioning positions obtained individually have relatively large errors. 3 As described, when the estimated position initializing means initializes the estimated position, it is desirable to use a position obtained by averaging a plurality of measured positions obtained during the stop state.
[0026]
The averaging may be a simple averaging of the positioning positions within a certain period, a weighted averaging in a time series, or a weighted averaging according to the positioning accuracy at each time.
By the way, the accuracy of the positioning position changes variously depending on the combination of artificial satellites used for positioning and the variation in accuracy of the artificial satellite itself, and accordingly, the range in which the error of the velocity vector varies also changes. In addition, even if the determination threshold value for determining whether or not the device is in the stopped state is set to be smaller than the variation in the error of the speed vector, an effective determination cannot be made.
[0027]
Therefore, the claim 4 As described above, it is preferable that the determination threshold value setting means is provided, and the determination threshold value used by the stop determination means is variably set based on the accuracy information superimposed on the radio wave received by the reception means. Thus, the optimum determination threshold can always be set according to the error that changes every moment depending on the combination and arrangement of the satellites used for positioning, so that the system performance can be maximized.
[0028]
However, if the judgment threshold value is variably set and this value becomes excessive, the estimated position is updated using the speed vector if the speed does not reach a certain high speed despite the movement being started. Therefore, when the update of the estimated position is started, the current position changes suddenly, and if the current position is displayed on a map such as a navigation device based on this, the display of the current position is unnatural. Would make a great move.
[0029]
Therefore, the claim 5 As described, the determination threshold value setting means calculates the determination threshold value by applying the institution information to a predetermined arithmetic expression, and if the calculated value is larger than a predetermined upper limit value, Is desirably limited to the upper limit.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating an overall configuration of a vehicle navigation device configured using the GPS receiver 2 of the present embodiment.
[0031]
As shown in FIG. 1, the vehicular navigation apparatus receives a radio wave from a GPS satellite and outputs a current position data P indicating a current position of the vehicle, and a map storing map data of a road map. Based on the data storage medium 4 and the map data from the map data storage medium 4 and the current position data P from the GPS receiver 2, a display unit 6 displays a road map of the running area of the vehicle centering on the current position of the vehicle. And a navigation operation unit 8 for displaying the information.
[0032]
Here, the GPS receiver 2 according to the present embodiment includes an antenna 10 for receiving radio waves from GPS satellites, and capture / tracking of a satellite signal, extraction of a carrier wave, and C / C based on a signal received from the antenna 10. A receiving circuit unit 12 for demodulating an A code, decoding data spread spectrum by a C / A code, extracting a frequency displacement amount of a carrier, measuring a transmission time of a C / A code, a CPU, a ROM, and a RAM; And an arithmetic unit 14 composed of a microcomputer mainly configured by a microcomputer.
[0033]
FIG. 1 shows a functional block of the arithmetic unit 14. As shown, the arithmetic unit 14 extracts accuracy information from the data decoded by the reception circuit unit 12, A speed error estimating unit 20 for calculating a speed error estimated value Vth as a determination threshold value based on the information, and a C / A code transmission time measured for each GPS satellite by the receiving circuit unit 12. A pseudo-range between the vehicle equipped with the navigation device and each GPS satellite is determined, and a positioning operation unit 22 that calculates positioning position data Pg representing a positioning position of the vehicle based on the pseudo-range and the reception circuit unit 12 extract the pseudo-range. The relative speed between each GPS satellite used for positioning calculation and the vehicle is obtained based on the obtained frequency displacement amount of the carrier, and the speed vector Vg representing the moving speed and the moving direction of the vehicle is obtained based on the relative speed. A degree vector operation unit 24, on the basis of the located position data Pg and velocity vector Vg obtained by the positioning calculation unit 22 and the velocity vector calculation unit 24, composed of the filtering unit 26 for calculating the present position data P.
[0034]
Among them, the speed error estimator 20 uses URA (User Range Accuracy) included in detailed orbit information (ephemeris) as accuracy information to be extracted from the decoded data, and an accuracy deterioration coefficient determined by the arrangement of GPS satellites used for positioning calculation. Using (DOP: Dilution Of Precision), an estimated speed error value Vth [m / s] is calculated according to the following equation (1).
[0035]
Vth = k × PMura × PMhdop (1)
Here, PMura is a parameter set based on URA, and as shown in Table 1, an average value of a range corresponding to URA, for example, if URA = 7, PMura = 36 is used. PMhdop is a horizontal precision deterioration coefficient (HDOP) obtained from the DOP, and k is a speed conversion of a measurement error of the Doppler shift generated by internal noise of the GPS receiver 2.
[0036]
[Table 1]

[0037]
However, when the estimated speed error value Vth calculated by the equation (1) is larger than the upper limit value (1 [m / s] in the present embodiment), the estimated speed error value Vth. Is limited to this upper limit (that is, 0 <Vth ≦ 1), and the velocity error estimation value Vth is repeatedly calculated every time the combination or arrangement of the GPS satellites used for the positioning calculation changes. Have been.
[0038]
Further, the positioning calculation unit 22 and the speed vector calculation unit 24 are configured to repeatedly calculate the positioning position data Pg and the speed vector Vg at the same timing based on the signals received by the reception circuit unit 12 at the same timing. ing.
Next, the positioning calculation unit 22 simultaneously detects at least three (preferably four or more) pseudoranges with the GPS satellites, and applies the pseudorange to a known positioning calculation to convert the positioning position data Pg. calculate.
[0039]
In addition, the speed vector calculation unit 24 calculates the speed vector Vg by synthesizing these based on the north direction speed Vn and the east direction speed Ve obtained using the equation (2).
[0040]
(Equation 1)

[0041]
Here, Vu is the upward speed, VLF is the speed converted value of the offset of the reference oscillator of the receiver, ni, ei, ui are the north, east, and upward cosine of the unit vector toward GPS satellite i, and Vdui is the value from satellite i. The figure shows the difference between the predicted value (calculated value) of the Doppler shift of the radio wave (carrier) and the actually measured value of the frequency displacement of the carrier detected by the receiving circuit unit 12. Note that the speed vector calculation in the speed vector calculation unit 24 is a known one, similarly to the positioning calculation in the positioning calculation unit 22.
[0042]
Here, the filtering process performed by the calculation unit 14 based on the estimated speed error value Vth from the speed error estimation unit 20, the positioning position data Pg from the positioning calculation unit 22, and the speed vector Vg from the speed vector calculation unit 24, This will be described with reference to the flowchart shown in FIG.
[0043]
This process is started periodically (1 [s] cycle in this embodiment) repeatedly after the start of the operation of the vehicle. When the present process is started, first, in S110, the estimated speed error value Vth, the measured position data Pg, and the measured speed vector Vg are input from the speed error estimating unit 20, the positioning operation unit 22, and the speed vector operation unit 24, and then in S120. Then, it is determined whether or not the current activation of this process is the first activation after the start of the vehicle operation.
[0044]
If it is determined that the activation is the first activation, the process proceeds to S130, in which the current position data P and the estimated position data Pe are initialized by the positioning position data Pg read in S110, and in subsequent S140, the calculation is performed. The parameter i representing the timing is initialized to zero (i ← 0), and the flow shifts to S170.
[0045]
Thereafter, assuming that the first activation of this processing is the 0th activation, the data read in S110 at the i-th activation of this processing (hereinafter referred to as the i-th computation timing) is represented by Pg (i), Vg (i), and The current position data calculated at the same i-th calculation timing is denoted by P (i), and the estimated position data used for calculating P (i) is denoted by Pe (i).
[0046]
On the other hand, if it is determined in S120 that the current activation of this process is not the first activation, the process proceeds to S150, in which the number of GPS satellites being captured becomes two or less due to radio wave blocking by a building or the like. Thus, it is determined whether or not the calculation processing by the positioning calculation unit 22 and the speed vector calculation unit 24 is interrupted.
[0047]
If the positioning calculation has been performed without interruption, the process proceeds to S160, and the current position data P (i) is calculated according to the following equation (3). That is, the weighting of the positioning position data Pg (i) read in S120 and the estimated position data Pe (i) calculated in any of S190, S240, S250, and S260 described later at the previous calculation timing. After calculating the average value, the process proceeds to S170.
[0048]
(Equation 2)

[0049]
However, m> 0 and n> 0, and for example, m = 9 and n = 1. Note that, as the value of m is larger than n, the variation in the calculated current position data P (i) becomes smaller.
In the processing for obtaining the weighted average value, the current position data P is updated by filtering the positioning position data Pg with the speed vector Vg such that the locus of the current position data P falls within a predetermined range defined by the speed vector Vg. Can be thought of as something to do.
[0050]
Then, in S170, the current position data P (i) set and calculated in S130 or S160 is output to the navigation operation unit 8. At this time, the navigation calculation unit 8 causes the display unit 6 to display the current position of the vehicle and a road map near the current position based on the current position data P (i) from the GPS receiver 2.
[0051]
In subsequent S180, the magnitude | Vg (i) | of the velocity vector also read in S110, that is, the moving speed of the vehicle is set to the estimated velocity error value, using the estimated velocity error value Vth read in S110 as a determination threshold value. It is determined whether it is smaller than Vth.
When it is determined that the magnitude | Vg (i) | of the speed vector is equal to or greater than the estimated speed error value Vth, the process proceeds to S190 assuming that the vehicle is moving, and the speed / speed of the moving vehicle is determined. Since the direction does not change suddenly in a short time, the current position data P (i) and the speed vector Vg (i) are added as shown in the equation (4), so that the direction is calculated at the next calculation timing. Of the estimated position data Pe (i + 1).
[0052]
Pe (i + 1) = P (i) + Vg (i) (4)
On the other hand, when it is determined in step S180 that the magnitude | Vg (i) | of the speed vector is smaller than the estimated speed error value Vth, the process proceeds to S200 assuming that the vehicle is stopped, and this time. , It is determined whether the distance | Pg (i) −P (i) | between the measured position and the current position is larger than a preset upper limit distance Pth, and when the determination is affirmative, that is, the measured position and the current position are determined. If the distance from the position exceeds the allowable range (upper limit distance Pth), the process proceeds to S210.
[0053]
In S210, it is determined whether or not a timer for measuring a preset upper limit time Tth has been started. If not, the process proceeds to S220. After the timer is started, the process proceeds to S250. However, when the affirmative determination is made in S150 and the negative determination is made in S180, the operation of the timer is stopped and the timer value is reset.
[0054]
On the other hand, if it is determined in S210 that the timer has been started, the process proceeds to S230, and it is determined whether the timer has timed out. If so, the process proceeds to S240, As shown in Expression (5), the positioning position data Pg (i) read in S110 is set as the next estimated position data Pe (i + 1).
[0055]
Pe (i + 1) = Pg (i) (5)
Also, in the previous S200, when the distance | Pg (i) -P (i) | between the measured position and the current position is equal to or less than the upper limit distance Pth (that is, within the allowable range), or is larger than the upper limit distance Pth. If the time has not timed out, the flow shifts to S250, where the estimated position data Pe (i) at the current operation timing is changed to the estimated position data Pe (i) at the next operation timing as shown in Expression (6). i + 1).
[0056]
Pe (i + 1) = Pe (i) (6)
If it is determined in S150 that the positioning is suspended, the process proceeds to S260, and the velocity vector last read immediately before the suspension of the positioning is performed as shown in Expression (7). The estimated position data Pe (i + 1) is calculated by adding Vg (i0) to the current position data P (i).
[0057]
Pe (i + 1) = P (i) + Vg (iO) (7)
Here, i0 indicates a parameter indicating the last positioning time. That is, if the speed / azimuth of the vehicle does not suddenly change during the suspension of the positioning, the estimated position data Pe (i + 1) at the next and subsequent calculation timings can be accurately corrected based on the speed vector V (i0). When the positioning is restarted, the current position can be corrected to some extent accurately by the estimated position data Pe.
[0058]
Then, when the next estimated position data Pe (i + 1) is calculated in any of S190, S240, S250, and S260, the process proceeds to S270, in which the parameter i is incremented (i ← i + 1), and the present process ends. I do.
That is, in this processing, at each calculation timing, the current position data P () is obtained based on the read (S110) positioning position data Pg (i) and the estimated position data Pe (i) obtained at the previous calculation timing. i) (S160).
[0059]
In this process, the calculation of the estimated position data Pe (i + 1) used at the next calculation timing is performed as follows depending on the case.
That is, when the vehicle is moving (S180-NO), the current position data P (i) and the speed vector Vg (i) are added assuming that the speed and direction of the vehicle do not change rapidly. , The estimated position data Pe (i + 1) is obtained (S190). On the other hand, when the vehicle is stopped (S180-YES), the estimated position data Pe (i) is basically not updated, and the current estimated position data Pe ( i) is directly set as the next estimated position data Pe (i + 1) (S250).
[0060]
However, in the present process, whether the vehicle is stopped is determined based on whether the magnitude | Vg (i) | of the speed vector is smaller than the estimated speed error value Vth. Even if it is determined that the speed is lower than the estimated speed error value Vth, the vehicle may be actually moving at a lower speed.
[0061]
In this case, since the estimated position data Pe is not updated, the current position data P (i) calculated based on the estimated position data Pe (i) and the positioning position data calculated by the positioning calculation unit 22 The error from Pg (i) increases over time.
[0062]
Therefore, if this error, that is, the distance | Pg (i) -P (i) | between the current position and the measured position exceeds the allowable range (upper limit distance Pth) (S200-YES), the estimated position data Pe (i + 1) is re-initialized with the positioning position data Pg (i) (S240) so that the error between the two data is reduced.
[0063]
The situation where the distance | Pg (i) -P (i) | between the current position and the measured position exceeds the allowable range occurs not only when the vehicle moves at low speed but also when a multipath occurs. However, there is a high possibility that the multipath will be canceled after a certain period of time due to movement of the GPS satellite. Therefore, only when the above situation continues for the upper limit time Tth or more (S210-YES, S230-YES), the re-initialization (S240) is performed assuming that it is not the influence of multipath, and the estimated position data Pe is obtained. , And hence the current position data P, so as to eliminate the influence of multipath.
[0064]
Here, FIG. 3 is an explanatory diagram showing how the current position data P (i) and the estimated position data Pe (i) obtained by the filtering process change.
Note that FIGS. 3A to 3C all show cases in which the vehicle is traveling at a speed equal to or higher than the estimated speed error value Vth until the calculation timing i = 2.
[0065]
At this time, the current position data P (i) calculated by the weighted average of the positioning position data Pg (i) and the estimated position data Pe (i) based on the speed vector Vg (i-1) having less variation is: The variation is smaller than the positioning position data Pg (i) itself.
[0066]
FIG. 3A shows the case where the vehicle is actually stopped after the calculation timing i = 3. In this case, the estimated position data Pe (i) is fixed, and the speed vector Vg (i ) Is not affected at all by the error included in the current position data P (i), so that the variation in the current position data P (i) is further reduced.
[0067]
FIG. 3B shows a case where the vehicle is traveling at a low speed at a speed smaller than the estimated speed error value Vth after the calculation timing i = 3. Here, when the calculation timing i = 4, the distance | Pg (4) -P (4) | between the current position and the positioning position becomes larger than the upper limit distance Pth, and thereafter, the calculation timing i = At the time of X-1, the re-initialization of the estimated position data Pe is performed.
[0068]
As described above, when the low-speed traveling is determined to be in the stop state, the error between the positioning position data Pg (i) and the estimated position data Pe (i) increases. It can be seen that this error accumulated in is eliminated.
Further, FIG. 3 (c) shows a case where the vehicle is actually stopped after the calculation timing i = 3, but a multipath occurs, and thereafter the multipath is resolved at the calculation timing i = 6. ing. In other words, if the speed vector Vg is smaller than the estimated speed error value Vth, the estimated position data Pe is not updated. Therefore, even if a multipath occurs and the positioning position data Pg greatly changes, the positioning position data Pg follows. Therefore, the current position data P (6) calculated when the multipath is eliminated returns to the vicinity of the current position data P (2) obtained before the occurrence of the multipath. That is, when the vehicle resumes running, the current position data P (i) in which the influence of the multipath is not accumulated is calculated.
[0069]
Then, the current position data P calculated in this manner is output to the navigation operation unit 8 in S170 as described in the flowchart of FIG. Then, the current position of the vehicle is displayed on the display unit 6 together with a nearby road map. FIG. 4 shows a traveling locus of the current position when the vehicle actually travels. In the case of not performing the stop determination based on the conventional apparatus shown in FIG. 5, that is, when the stop determination based on the estimated speed error value Vth is performed, the dispersion of the current position data P calculated when the vehicle stops is large, but the GPS receiver 2 of the present embodiment, When the stop determination is performed and the update of the estimated position data Pe is prohibited when it is determined that the vehicle is in the stop state, the variation of the current position data P at the time of the stop is greatly reduced, and it can be seen that the trajectory is stable.
[0070]
As described above, according to the GPS receiver 2 of the present embodiment, the estimated position data Pe (i + 1) at the next operation timing is calculated based on the current position data P (i) and the velocity vector Vg (i). At the next calculation timing, based on the estimated position data Pe (i + 1) and the positioning position data Pg (i + 1), the current position data P () is used without using the past positioning position data Pg (i) as it is. Since (i + 1) is calculated, the current position data P can be calculated accurately without causing a time delay.
[0071]
According to the GPS receiver 2 of the present embodiment, the magnitude | Vg (i) | of the velocity vector is smaller than the estimated velocity error value Vth determined by the state of the GPS satellite used for positioning, and the error in the velocity vector Vg When the influence of the component is large, it is determined that the vehicle is stopped, and the estimated position data Pe (i) is fixed, and the value is not updated by the speed vector Vg (i). Variations in the stopped current position data P (i) due to the error component of the velocity vector Vg (i) can be reliably suppressed.
[0072]
Further, in the GPS receiver 2 of the present embodiment, the state where the distance | Pg (i) -P (i) | between the measured position and the current position is larger than the upper limit distance Pth while the vehicle is stopped. When the time has continued for the upper limit time Tth or more, the estimated position data P (i + 1) at the next calculation timing is re-initialized with the positioning position data Pg (i).
[0073]
Therefore, when the vehicle is actually moving at a low speed at a speed smaller than the estimated speed error value Vth, it is detected that the vehicle is moving at a low speed even though it is determined that the vehicle is stopped. In addition to eliminating the error, even if the distance between the positioning position and the current position is longer than the upper limit distance due to the influence of multipath, if the distance does not continue for the upper limit time Tth, the positioning position data Pg (i) , The current position data P (i) is not reinitialized, so that it is possible to prevent abnormalities in the positioning position data Pg (i) due to multipath from being accumulated in the current position data P (i).
[0074]
Further, in the GPS receiver 2 of the present embodiment, the speed error estimated value Vth for determining whether or not the vehicle is stopped is variably set, and the upper limit is limited.
Therefore, the optimum speed error estimated value Vth can always be set according to the error that changes every moment depending on the combination and arrangement of the satellites used for positioning, so that the system performance can be maximized and the speed can be maximized. By setting the estimated error value Vth to a value larger than necessary, the display of the current position displayed on the map may cause an unnatural movement such that the vehicle does not easily start moving even though the vehicle is starting to move. Can be reliably prevented.
[0075]
As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, It can implement in various aspects in the range which does not deviate from the summary of this invention.
For example, in the above embodiment, when calculating the current position data P (i) from the positioning position data Pg (i) and the estimated position data Pe (i), the weighting coefficients m and n of the weighted average are fixed and used. However, the weighting coefficients m and n may be changed in accordance with the positioning accuracy each time the positioning accuracy changes, for example, when the combination of GPS satellites used for positioning changes. Specifically, when the positioning accuracy is high, the weighting coefficient n of the positioning position data Pg (i) is increased, and when the positioning accuracy is low, the weighting coefficient m of the estimated position data Pe (i) is increased. . In this case, the accuracy and stability of the current position data P (i) can be improved.
[0076]
In addition, since acceleration and rotation occur in the actual vehicle, the estimated position data Pe (i) is calculated assuming the movement of the vehicle at a constant speed. An error occurs. Therefore, by considering the motion of the vehicle deviating from the fixed speed as an error of the estimated position data Pe (i), the weighting coefficients m and n for calculating the current position data P (i) are determined. The current position data P (i) can be calculated with high accuracy.
[0077]
Further, in the above embodiment, in S190, the motion of the vehicle is modeled as a constant speed motion, and the estimated position data Pe (i + 1) is calculated using the equation (4). The estimated position data Pe (i + 1) may be calculated using an equation.
[0078]
Pe (i + 1) = P (i) + {V (i-1) + V (i)} / 2 (8)
Further, in the above embodiment, when re-initializing the estimated position data Pe (i + 1) in S240, the positioning position data Pg (i) is used as it is. In the meantime, averaged positioning position data obtained based on the plurality of positioning position data Pg read in S110 for each calculation timing may be used. In this case, the averaging process may be simple averaging, weighted averaging according to a time series, or weighted averaging according to the positioning accuracy at each time.
[0079]
In the above embodiment, the stop state is determined based on whether or not the magnitude of the speed vector is smaller than a preset value. However, other vehicle mounted to measure the vehicle speed, such as a vehicle speed pulse, is used. The stop state may be directly determined based on a measurement signal or the like from the device.
[0080]
In the above embodiment, the GPS receiver 2 is a position detecting device, the antenna 10 and the receiving circuit unit 12 are a receiving unit, the speed error estimating unit 20 is a determination threshold value setting unit, and the positioning calculating unit 22 is a pseudo distance detecting unit and a positioning calculation unit. Means, speed vector calculation unit 24 is relative speed detection means and speed vector calculation means, S190 is position estimation means, S160 is current position update means, S180 is stop determination means, S250 is inhibition means, and S210 to S240 are estimated position initialization. It corresponds to a means.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an overall configuration of a navigation device configured using a GPS receiver according to an embodiment.
FIG. 2 is a flowchart illustrating the content of a filtering process performed by a filtering unit.
FIG. 3 is an explanatory diagram showing how the current position data and the estimated position data calculated by the filtering process change.
FIG. 4 is an explanatory diagram showing a locus of current position data displayed on a map.
FIG. 5 is an explanatory diagram showing a locus of current position data by a conventional device.
[Explanation of symbols]
2 ... GPS receiver 4 ... Map data storage medium 6 ... Display unit
8 navigation operation unit 10 antenna 12 reception circuit unit
14 arithmetic unit 20 speed error estimating unit 22 positioning arithmetic unit
24: velocity vector calculation unit 26: filtering unit

Claims (5)

Receiving means for receiving radio waves from a plurality of artificial satellites;
A pseudo-range detecting unit configured to detect a pseudo-range with each of the artificial satellites based on timing information superimposed on a radio wave received by the receiving unit;
Based on the pseudo-range detected by the pseudo-range detecting means, a positioning calculating means for repeatedly obtaining a positioning position for each preset calculation timing,
A relative speed detection unit configured to detect a relative speed between the device and each of the artificial satellites based on a frequency displacement of a radio wave received by the reception unit;
Speed vector calculating means for repeatedly obtaining a speed vector indicating a moving speed and a moving direction of the device at each calculation timing based on the relative speed detected by the relative speed detecting means;
Position estimating means for obtaining an estimated position of the device at the next calculation timing based on the speed vector obtained by the speed vector calculating device and a preset current position of the device;
A current position updating means for updating the current position by a weighted average value of the positioning position obtained by the positioning operation means and the estimated position obtained by the position estimating means at the previous calculation timing;
In the position detecting device provided with
Stop determination means for determining a stop state of the position detection device,
Prohibiting means for prohibiting updating of the estimated position by the position estimating means when the stop judging means judges that the vehicle is in a stopped state;
During the stop state, if the state in which the positioning position and the current position are separated by a predetermined upper limit distance or more continues for a predetermined upper limit time or longer, the estimated position is initialized based on the positioning position. Estimated position initialization means,
A position detecting device comprising: The position detecting device according to claim 1,
The position detecting device according to claim 1, wherein said stop judging means judges a stop state when the magnitude of the speed vector obtained by said speed vector calculating means is smaller than a predetermined judgment threshold value. The position detecting device according to claim 1 ,
The position detection device according to claim 1, wherein the estimated position initialization means initializes the estimated position by a position obtained by averaging a plurality of positioning positions obtained during the stop state. The position detecting device according to any one of claims 1 to 3 ,
A position detecting device comprising: a determination threshold value setting unit that variably sets a determination threshold value used by the stop determination unit based on accuracy information superimposed on a radio wave received by the reception unit. The position detecting device according to claim 4 ,
The determination threshold value setting means calculates a determination threshold value by applying the accuracy information to a predetermined arithmetic expression, and when the calculated value is larger than a preset upper limit value, the determination threshold value is determined. Is limited to the upper limit.

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