JP4421130B2

JP4421130B2 - Vibration isolation method and apparatus

Info

Publication number: JP4421130B2
Application number: JP2001089264A
Authority: JP
Inventors: 毅水野
Original assignee: Japan Science and Technology Agency; National Institute of Japan Science and Technology Agency
Current assignee: Japan Science and Technology Agency; National Institute of Japan Science and Technology Agency
Priority date: 2000-06-30
Filing date: 2001-03-27
Publication date: 2010-02-24
Anticipated expiration: 2021-03-27
Also published as: JP2002081498A

Description

【０００１】
【発明の属する技術分野】
本発明は、機器の除振に係り、地動外乱の絶縁を目的とするパッシブ除振のみならず、ばね上の外乱にも対処できるアクティブ除振をも可能とする除振方法およびその装置に関するもので、ＮＣ機械、マシニングセンター等の工作機械からＩＣ業界のステッパーに代表される各種機器にまで採用され、加工テーブル等を外乱から絶縁して高精度加工を達成せんとするものである。
【０００２】
【従来の技術】
現在、半導体デバイス製造システムや極微小領域計測システム等では、急速に高精度化、高性能化してきており、これらのシステムでは、振動等の外乱を除去する除振、防振装置の重要性が増大している。除振装置で除去すべき振動外乱は、設置床からの振動に起因する地動外乱と、装置のばね上に入力される直動外乱とに大別でき、前者には低剛性の機構が適しており、後者には高剛性の機構が適している。図１１は、地動外乱を絶縁して除振する従来のパッシブ除振システムを示すのもので、床３６からの振動伝達率を低くするためにばね定数ｋを小さくしてばね剛性を小さくすると、除振テーブル３２（質量ｍ）上の質量変化Δｍや除振テーブル３２に作用する荷重の変化等のばね上での外乱に対して弱くなってしまう。逆に、ばね上での外乱に対してはある程度ばね剛性を大きくする必要がある。このような外乱吸収のための低剛性機構と、位置、姿勢保持のための高剛性機構という相反する特性が要求される。
【０００３】
一般に、正のばね定数ｋ₁、ｋ₂を有する２つのばね３５−１、３５−２を直列に結合して１つの除振機構を構成すると、そのばね定数は次式で求められる。
ｋ_c＝ｋ₁ｋ₂／（ｋ₁＋ｋ₂）（１）
つまり、通常の正のばね定数を有するばねを直列に結合すると、結合してできたばね定数は、結合前のばね定数より必ず小さくなるものである。したがって、これら従来のばねのみを使用した除振装置では、質量変化や振動等のばね上での外乱に対して高い剛性を確保することが極めて困難であることから、アクティブ除振制御装置が提案された。
【０００４】
図１２は、一般的なアクティブ除振制御装置の原理を示したもので、除振台１１０上に設置された加速度センサ１１４による検出信号に基づいてコントローラ１１５によって除振台１１０の振動を抑制する制御入力を計算し、求められた制御入力によって、ばね１１１および減衰器１１２と並列に設置されたアクチュエータ１１３を動作させることによって除振制御を行う。
【０００５】
【発明が解決しようとする課題】
しかしながら、このようなアプローチは、除振台や床の振動が正確に検出されることを前提としており、実現化されるには、低周波の振動まで感度良く検出できるサーボ型加速度センサを用いる必要があるために高価格になる上、採用されるサーボ型加速度センサによっては、直動外乱に対する剛性が未だ充分とは言い難く、完全な振動絶縁性能を確保するには不充分であった。
【０００６】
そこで本発明では、前記従来の除振方法およびその装置の課題を解決して、地動外乱に対する振動絶縁性能を損なうことなく、直動外乱に対する高い剛性を確保して、高い除振機能を発揮して精密加工等を可能にする除振方法およびその装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
このため、本発明が採用した技術解決手段は、
床と第１部材との間には所定の正のばね定数を有するばねを配設し、第１部材に対向して配置された第２部材との間には第１部材に向けて第２部材を引き上げるべく作用する永久磁石と電磁石とからなる負のばね定数を構成する磁気浮上機構を配設し、永久磁石は永久磁石の吸引力のみで第２部材を支持し、電磁石は第２部材に外力が加わると負のばね定数で第１部材と第２部材とのギャップを狭くするよう制御され、また、前記正と負のばね定数の大きさは等しくかつ第２部材で発生する直動外乱に対して略無限の剛性を有するようにすることにより、床から第１部材に伝わる振動を絶縁するとともに、第１部材から第２部材に伝わる振動を絶縁することを特徴とする除振方法である。
また、床に支柱を立設し、この支柱と第１部材との間には、第１部材を引き上げるべく作用する永久磁石と電磁石とからなる負のばね定数を構成する磁気浮上機構を配設し、永久磁石は永久磁石の吸引力のみで第１部材を支持し、電磁石は第２部材に外力が加わると負のばね定数で支柱と第１部材とのギャップを狭くするよう制御され、前記第１部材に対向して配置した第２部材と第１部材との間には所定の正のばね定数を有するばねを配設し、
前記正と負のばね定数の大きさは等しくかつ第２部材で発生する直動外乱に対して略無限の剛性を有するようにすることにより、床から第１部材に伝わる振動を絶縁するとともに、第１部材から第２部材に伝わる振動を絶縁することを特徴とする除振方法である。
また、前記第１部材は中間部材であり、前記第２部材は除振テーブルであることを特徴とする除振方法である。
また、床と、所定の正のばね定数を有するばねと、そのばねによって前記床上に支持されるとともに床からの振動が絶縁される第１部材と、第１部材に対して対向して配置され負荷を載置するための第２部材とを備え、第１部材と第２部材との間には、第１部材に向けて第２部材を引き上げるべく作用する永久磁石と電磁石とからなる負のばね定数を構成する磁気浮上機構を配設し、前記永久磁石は永久磁石の吸引力のみで第２部材を支持し、電磁石は前記第２部材に外力が加わると負のばね定数で第１部材と第２部材とのギャップを狭くするよう制御され、前記正と負のばね定数の大きさは等しくかつ第２部材で発生する直動外乱に対して略無限の剛性を有するようにするように構成したことを特徴とする除振装置である。
また、床に立設した支柱と、支柱に対向して配置した第１部材と、第１部材に対して対向して配置され負荷を載置するための第２部材と、第１部材と第２部材との間に配置される正のばね定数を有するばねとを備え、支柱と第１部材との間には支柱に向けて第１部材を引き上げるべく作用する永久磁石と電磁石とからなる負のばね定数を構成する磁気浮上機構を配設し、永久磁石は永久磁石の吸引力のみで第２部材を支持し、電磁石は第２部材に外力が加わると負のばね定数で支柱と第１部材とのギャップを狭くするよう制御され、前記正と負のばね定数の大きさは等しくかつ第２部材で発生する直動外乱に対して略無限の剛性を有するようにするように構成したことを特徴とする除振装置である。
また、前記磁気浮上機構は、前記第１部材に設けた電磁石と、前記第２部材に設けた永久磁石とで構成し、前記第１部材に設けた電磁石の吸引力を前記第２部材へ作用する荷重の増減に応じて増減させるように構成したことを特徴とする除振装置である。
また、前記磁気浮上機構は、前記第１部材に設けた永久磁石と、前記第２部材に設けた電磁石とで構成し、前記第２部材に設けた電磁石の吸引力を前記第２部材へ作用する荷重の増減に応じて増減させるように構成したことを特徴とする除振装置である。
また、前記磁気浮上機構は、前記支柱側に設けた永久磁石と、前記第１部材に設けた電磁石とで構成し、前記第１部材に設けた電磁石の吸引力を前記第１部材へ作用する荷重の増減に応じて増減させるように構成したことを特徴とする除振装置である。
また、前記磁気浮上機構は、前記支柱側に設けた電磁石と、前記第１部材に設けた永久磁石とで構成し、前記支柱側に設けた電磁石の吸引力を前記第１部材へ作用する荷重の増減に応じて増減させるように構成したことを特徴とする除振装置である。
また、前記第１部材は中間部材であり、前記第２部材は除振テーブルであることを特徴とする除振装置である。
また、前記ばねと併設して所定の減衰率の減衰装置を設置したことを特徴とする除振装置である。
また、前記永久磁石に併設して強磁性体を設け、前記電磁石の吸引力を第２部材に作用する荷重の増減に応じて増減させるように構成したことを特徴とする除振装置である。
【０００８】
以下、本発明の除振方法およびその装置の実施の形態を図面に基づいて説明する。本発明は、正のばね特性を有する支持機構と、負のばね特性を有する支持機構とを直列に接続することによって、装置上で発生する直動外乱に対して略無限大の剛性を有せしめるとともに、床に対する振動を絶縁することを特徴とするもので、先ず、負のばね特性を有する支持機構として、ゼロパワー特性を有する磁気浮上機構を用いた実施の形態について説明する。図１は本発明の除振方法およびその装置の第１実施の形態を示すもので、本発明は、床６と中間台である第１部材１との間にばね５を配設して床６から第１部材１に伝わる振動を絶縁するとともに、前記第１部材１と除振テーブルである第２部材２との間に永久磁石３と電磁石４とから構成されるゼロパワー特性を有する磁気浮上機構を配設することによって、前記第１部材１から第２部材２に伝わる振動を絶縁することを特徴とする。本実施の形態では、床６に対して所定の正のばね定数ｋ_Pのばね５によって支持された中間台１と、該中間台１に対して永久磁石３と電磁石４とから構成されて所定の負のばね定数ｋｓのゼロパワー特性を有する磁気浮上機構によって支持された除振テーブル２とから構成され、図示の例では、中間台１に設けられた電磁石４の吸引力を永久磁石３が設けられた除振テーブル２の質量増加等に起因する荷重の増減に応じて増減させるように適宜の制御装置（図示省略）により制御するように構成したものである。
【０００９】
なお、図２（Ａ）に示すように、磁石による吸引力を増加させるために、永久磁石３と併用して強磁性体７を除振テーブル２側に配置してもよい。あるいは、図２（Ｂ）に示すように、永久磁石３を電磁石４の鉄心に埋め込んで複合磁石とし、除振テーブル２側には強磁性体７だけを設置してもよい。また、電磁石と永久磁石との配置を逆、すなわち除振テーブル２側に電磁石４を、中間台１側に永久磁石３を設け、電磁石４の吸引力を除振テーブル２に作用する荷重の増減に応じて増減させるように構成してもよい。この場合も、図２（Ｃ）に示すように、永久磁石３と併用して強磁性体７を中間台１側に設置してもよい。あるいは、図２（Ｄ）に示すように、永久磁石３を電磁石４の鉄心に埋め込んで複合磁石とし、中間台１側には強磁性体７だけを設置してもよい。
【００１０】
次に、図３および図４を用いて本発明における中間台と除振テーブルとの間にて採用されるゼロパワー磁気浮上制御系について説明する。ゼロパワー制御は、電磁石と永久磁石とを組み合わせて構成された吸引型磁気浮上系で、図３に示すように、浮上対象物である除振テーブル１２の重量を永久磁石１３の吸引力のみで支持するとともに、支持固定側１１における電磁石１４のコイル電流を定常的にゼロに保持する制御方法である。ａの静止状態では、除振テーブル１２は力が釣り合った状態にて静止位置に停まっているが、ｂの荷重時に示すように、除振テーブル１２に下向きの一定の外力（質量増加Δｍ等）が加わると、電磁石１４のコイルに電流を流して除振テーブル１２を引き上げようとする吸引力を発生させ、前記永久磁石１３による吸引力と下向きの力が釣り合うように制御され、ｃに示すように、ギャップが狭くなる位置で電磁石１４に流れる電流がゼロとなり静止状態となる。上記のような作用をする制御系は、図１では省略されているが、ｄに示すように、浮上対象物である除振テーブル１２の支持固定側（図１の装置では中間台）に対する位置を検出する変位センサ２１、該センサ２１の出力信号に基づいて電磁石１４のコイル電流を定常的にゼロに保持しながら除振テーブル１２を浮上保持するための制御信号を生成する制御回路２２と、該制御回路２２の出力にしたがって電磁石１４のコイルに所定の電流を流す電力増幅器２３等から構成される制御装置２０を用いて実現される。
【００１１】
図４は通常のばね系との比較を説明するもので、図面左側に示すように、通常のばね系では、所定の正のばね定数のばねにより支持された質量ｍ２２が質量増加Δｍを生じると、質量増加（荷重）方向に移動する、いわゆるパッシブ除振制御がなされる。これに対して、ゼロパワー制御では、図面右側に示すように、質量増加Δｍが生じると、前記ばね系とは逆方向に質量ｍ１２が上方に移動してギャップを狭くするように電磁石１４が制御される。そのため、見かけ上は負のばね定数を有するかのような挙動を示す。このゼロパワー制御によって実現される負のばね定数の性質を利用し、本発明では、通常の正のばね定数によるパッシブ除振制御と組み合わせることによって、ばね上での質量変化が生じても、質量ｍすなわち除振テーブル等が変位を生じないように構成したものである。
【００１２】
すなわち、図１（ｂ）に示すように、除振テーブル２に質量増加Δｍ等によって下向きの一定外力Ｆ₀（＝Δｍｇ）が加わると、ゼロパワー制御の作用によって、中間台１に設置された電磁石４と除振テーブルとの距離はＦ₀／ｋ_sだけ短くなる（ｋ_sはゼロパワー制御によって実現される負のばね定数）。したがって、ｋ_s＝ｋ_Pなる関係を満たすように除振装置が設計されていれば、除振テーブルは全く変位しないことになる。前記数式（１）ｋ_c＝ｋ₁ｋ₂／（ｋ₁＋ｋ₂）を用いて説明すると、ゼロパワー制御によってｋ₁＝−ｋ₂なる関係を満たす負のばね定数が実現できると、
｜ｋ_c｜＝＋∞ （２）
なるばね定数が得られる。すなわち、ばね定数の大きさが等しい正のばねと負のばねとを結合することによって、ばね定数が無限大のばねが得られる。これはコンプライアンスがゼロとなることを意味している。
【００１３】
以下に、図１に示した本発明の除振制御系について理論解析を行う。
＜基本方程式＞
本解析では各質量および床の垂直方向の変位のみを扱う。この系の運動方程式は次式のように求められる。

ここで、
ｘ₁、ｘ₂：中間台、除振テーブルの平衡点からの変位
ｘ₀：床の振動変位
ｋ_P：床から中間台を支持するばねのばね定数
ｆ_c：磁石の吸引力の動作点からの変動分
ｆ_d：除振テーブルに作用する直動外乱
また、ｃ_Pは、図１には示されていないが、ばね５と並列に設置された減衰装置の減衰係数である。減衰装置がない場合はｃ_P＝０とすればよい。磁石の吸引力の変動分は、近似的に次のように表される。
ｆ_c＝ｋ_s（ｘ₂−ｘ₁）＋ｋ_iｉ（６）
ここで、
ｋ_s：磁石の変位・吸引力係数
ｋ_i：磁石の電流・吸引力係数
ｉ：制御電流
【００１４】
＜ゼロパワー制御系＞
ここでは、中間台と除振テーブルの相対変位から制御入力を構成する。この場合、ゼロパワー制御を達成する制御入力は一般に次のように表すことができる。
Ｉ（ｓ）＝−ｃ₂（ｓ）ｓ（Ｘ₂（ｓ）−Ｘ₁（ｓ））（７）
ここで、ｃ₂（ｓ）はゼロを極に持たない強プロパーな伝達関数で、制御系が安定になるように選定される。中間台のダイナミクスが無視できる場合には、２以上の次数を持つ制御器によって安定化が可能となる。
【００１５】
＜基本特性の解析＞
簡単のため初期条件をゼロと仮定してラプラス変換すると、式（４）〜（７）から次式が求められる。

【００１６】
各変数のラプラス変換は、対応する大文字で表している。直動外乱に対する剛性を評価するために、
Ｆ_d＝Ｆ₀／ｓ（Ｆ₀：ｃｏｎｓｔ）（１３）
とする。床の振動の影響を無視すると（ｘ₀＝０）、除振テーブルの定常変位ｘ₂（∞）は、次のように求められる。

したがって、
ｋ_P＝ｋ_s （１５）
を満たすように除振装置が設計されていれば、
ｘ₂（∞）／Ｆ₀＝０（１６）
となる。これは、コンプライアンスがゼロ、すなわち剛性が無限大となることを意味する。また、中間台の変位ｘ₁（∞）および電磁石と除振テーブルとのギャップの変動量（ｘ₁（∞）−ｘ₂（∞））は、それぞれ次のように求められる。
ｘ₁（∞）／Ｆ₀＝１／ｋ_P （１７）
（ｘ₁（∞）−ｘ₂（∞））／Ｆ₀＝１／ｋ_s （１８）
したがって、除振テーブルに下向きの力（Ｆ₀＜０）が作用するとき、中間台は下向きに変位するのに対し、除振テーブルは中間台に近づくように上向きに変位することが確認できた。このように、ゼロパワー磁気浮上機構を利用した除振装置では、中間台を支持する機械式ばねのばね定数と磁石の変位・吸引力係数の大きさを等しく設定することによって、直動外乱に対する剛性が無限大となることが理論的に示された。
【００１７】
図５は本発明の除振方法およびその装置の基礎実験装置を示すもので、図５（Ａ）は実験装置の正面図、図５（Ｂ）はその側面図である。床に固定されたベース１０から立設されたリニアシャフト９ａ、９ｂに嵌挿されたばね５ａ、５ｂを介設して中間台１が設置され、前記リニアシャフト９ａ、９ｂを嵌合して中間台１に設置されたリニアブッシュ８ａ、８ｂによって、中間台１の運動が垂直方向の１自由度の並進運動に拘束される。一方、除振テーブル２の下部両側に設置されたガイドブロック１５ａ、１５ｂが、ベース１０に立設されたガイドレール１６ａ、１６ｂに係合し、除振テーブル２の運動を垂直方向の１自由度の並進運動に拘束する。除振テーブル２の下端部には上方に向いた永久磁石３、３が設置され、対向する中間台１の下部には電磁石４が設置される。除振テーブル２の中間台１に対する相対変位はセンサ１７が検出し、ベース１０に対する中間台１の相対変位はセンサ１８が検出するように構成される。
【００１８】
次に、図６および図７により、前記試作した基礎実験装置を用いて行った実験結果について説明する。図６はゼロパワー磁気浮上系の負のばね特性についての実験結果で、中間台１を固定して、除振テーブルの質量を１７００ｇ、１３１０ｇ、７００ｇについて付加質量Δｍを増大させていった場合のテーブルの変位量を測定したもので、どの質量でも線型的にテーブル変位は上昇しており、ゼロパワー制御が線型的な負のばねとして動作していることがわかった。また、ゼロパワー制御の持つばね定数は除振テーブルの質量を操作することで、様々な値に設定することができることもわかる。
【００１９】
図７は中間台をばねによって支持した状態での除振テーブルの床に対する変位についての実験結果で、正のばね定数は６．８２５（ｋＮ／ｍ）で、正と負のばね定数がほぼ一致するところは、テーブル質量が１３００ｇ付近を基準として、１２８０ｇ〜１４００ｇの範囲と推定できる。因みに１３１０ｇのときの負のばね定数は約７ｋＮ／ｍである。図によれば、テーブル質量が１３８０ｇのとき除振テーブル変位量は２０μｍで、テーブル位置はほぼ初期位置を保持したまま、良好な動作をしていることがわかる。この１３８０ｇという値は実験前に推測した範囲内の値で、また正と負のばね定数の差が大きくなるにつれて動作性能が低下することもわかる。
【００２０】
こららの関係から、先に示した理論解析の有効性が確認できた。ゼロパワー磁気浮上機構とばね機構を組み合わせたゼロコンプライアンス機構は、式の上では除振テーブルの床に対する変位をゼロにするとともに直動外乱に対する無限大のテーブル剛性を可能にしている。実測された範囲ではテーブルの床に対する最大剛性は約４９０ｋＮ／ｍで、このとき、除振テーブルの床に対する変位も最小値を示している。これは、ゼロパワー磁気浮上機構とばねを組み合わせることにより、コンプライアンスをほぼゼロとすることができ、これによって、直動外乱に対する剛性をきわめて大きくできることが確認できた。
【００２１】
図８は本発明の除振方法およびその装置の第２実施の形態を示すもので、床２０６に設置された支柱２０７に対して永久磁石２０３と電磁石２０４とから構成されて所定の負のばね定数Ｋ_Sを持つゼロパワー特性を有する磁気浮上機構によって支持された中間台２０１と、該中間台２０１に所定の正のばね定数Ｋ_Pのばね２０５によって支持された除振テーブル２０２とから構成され、図示の例では、支柱２０７に設けられた電磁石２０４の吸引力を永久磁石２０３が設けられた中間台２０１への荷重の増減に応じて増減させるように適宜の制御装置（図示省略）により、電磁石２０４と中間台２０１との距離を制御するように構成したものである。
【００２２】
このような構成によって、除振テーブル２０２に質量増加Δｍ等により下向きの一定外力Ｆ₀（＝Δｍｇ）が加わると、除振テーブル２０２を支持するばね２０５はＦ₀／Ｋ_Pだけ圧縮されて短くなる。同時に、ばね２０５の反力によって中間台２０１にも下向きの外力Ｆ₀が加わることになり、ゼロパワー制御の作用によって、電磁石２０４と中間台２０１との距離はＦ₀／Ｋ_Sだけ短くなり、中間台２０１はこの分だけ上向きに変位することになる。したがって、Ｋ_S＝Ｋ_Pなる関係を満たすように除振装置が設計されていれば、除振テーブル２０２は全く変位しないことになる。これは、コンプライアンスがゼロ、すなわち剛性が無限大になることを意味している。つまり、図８に示された除振装置は前記図１に示された除振装置と同じ除振性能を有していることが理解される。
【００２３】
図９は本発明の除振方法およびその装置の第３実施の形態を示すもので、床３００に所定の正のばね定数Ｋ_Pのばね３０１および減衰装置３０２によって支持された中間台３０３と、該中間台３０３に対して永久磁石３０４と電磁石３０５とから構成され所定の負のばね定数Ｋ_Sを持つゼロパワー特性を有する磁気浮上機構と、床３００に所定の正のばね定数Ｋ_P’のばね３１１および減衰装置３１２によって支持された中間台３１３と、該中間台３１３に対して永久磁石３１４と電磁石３１５とから構成され所定の負のばね定数Ｋ_S’を持つゼロパワー特性を有する磁気浮上機構とによって支持された除振テーブル３２０とから構成されたものである。
【００２４】
このような構成において、Ｋ_S＝Ｋ_PおよびＫ_S’＝Ｋ_P’なる関係を満たすように除振装置が設計されていれば、除振テーブル３２０の左側（中間台３０３側）および右側（中間台３１３側）においてコンプライアンスがゼロすなわち剛性が無限大となるので、除振テーブル３２０上のどの位置に垂直方向の一定外力が作用しても、除振テーブル３２０は全く変位しない。このような特性から、除振テーブル３２０上に可動ステージ３２１を設置した場合、移動負荷３２２がどの位置にあっても除振テーブル３２０は変位せず、その姿勢を水平に保つことができる。
【００２５】
図１０は本発明の除振方法およびその装置の第４実施の形態を示すもので、床４００に、垂直方向には所定の正のばね定数Ｋ_P ¹のばね４０１および減衰装置４０２、水平方向には所定の正のばね定数Ｋ_P ²のばね４０３および減衰装置４０４によって支持された中間台４０５と、該中間台４０５に対して、垂直方向には永久磁石４０６と電磁石４０７とから構成された所定の負のばね定数Ｋ_S ¹を持つゼロパワー特性を有する磁気浮上機構、水平方向には永久磁石４０８と電磁石４０９とから構成された所定の負のばね定数Ｋ_S ²を持つゼロパワー特性を有する磁気浮上機構によって支持され、さらに、床４００に、垂直方向には所定の正のばね定数Ｋ_P ³のばね４１１および減衰装置４１２、水平方向には所定の正のばね定数Ｋ_P ⁴のばね４１３および減衰装置４１４によって支持された中間台４１５と、該中間台４１５に対して、垂直方向には永久磁石４１６と電磁石４１７とから構成された所定の負のばね定数Ｋ_S ³を持つゼロパワー特性を有する磁気浮上機構、水平方向には永久磁石４１８と電磁石４１９とから構成された所定の負のばね定数Ｋ_S ⁴を持つゼロパワー特性を有する磁気浮上機構によって支持された除振テーブル４２０とから構成されたものである。
【００２６】
このような構成において、Ｋ_S ¹＝Ｋ_P ¹、Ｋ_S ²＝Ｋ_P ²、Ｋ_S ³＝Ｋ_P ³およびＫ_S ⁴＝Ｋ_P ⁴なる関係を満たすように除振装置が設計されていれば、除振テーブル４２０の左側（中間台４０５側）および右側（中間台４１５側）においてコンプライアンスがゼロすなわち剛性が無限大となり、同時に除振テーブル４２０上の水平方向のコンプライアンスもゼロとなるので、除振テーブル４２０のどの位置に垂直方向および水平方向の一定外力が作用しても、除振テーブル４２０は全く変位しない。
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【００５１】
以上、本発明の除振方法および装置の実施の形態を説明してきたが、本発明の趣旨の範囲内で、中間台および除振テーブルの形状、形式、電磁石および永久磁石の形状、形式およびそれらの配設形態（電磁石を中間台あるいは除振テーブルに設置するか、永久磁石を除振テーブルあるいは中間台に設置するか、永久磁石に加えて強磁性体を併設するか、もしくは永久磁石を電磁石の鉄心に組み込んで除振テーブルあるいは中間台のいずれか一方にのみ設置し、他方には強磁性体を設置するように構成してもよい）、ばねおよび減衰装置の形状、形式およびその中間台への配設形態（床と中間台との間にはばねに加えて適宜の減衰装置を併設してもよい）、ゼロパワー制御手段、除振の方向（前述の各実施の形態では、主として垂直方向の除振について説明したが、水平方向の除振、あるいは垂直方向および水平方向を同時に除振するように構成できることは言うまでもない。）等については適宜選定できる。
【００５２】
【発明の効果】
以上、詳細に説明したように、本発明では、正のばね特性を有する支持機構と、負のばね特性を有する支持機構とを直列に接続することによって、装置上で発生する直動外乱に対して略無限大の剛性を有せしめるとともに、床に対する振動を絶縁することによって、除振テーブル等の装置が床に対して、正のばね特性を有する支持機構と負のばね特性を有する支持機構とを介して配設されるので、床からの地動外乱に対する振動絶縁性能を損なうことなく、装置上で発生する直動外乱に対する高い剛性が確保され、高い除振機能を発揮して精密加工等を可能にする。
【００５３】
また、床と第１部材との間にばねを配設して床から第１部材に伝わる振動を絶縁するとともに、前記第１部材と第２部材との間に永久磁石と電磁石とから構成されるゼロパワー特性を有する磁気浮上機構を配設することによって、比較的制御が簡便な磁力制御のみにより、前記第１部材から第２部材に伝わる振動を絶縁して、除振テーブルの地動外乱に対する振動絶縁性能を損なうことなく、直動外乱に対する高い剛性を確保して、高い除振機能を発揮して精密加工等を可能にする。
【００５４】
また、床と第１部材との間にばねを配設して床から第１部材に伝わる振動を絶縁するとともに、前記第１部材と第２部材との間にアクチュエータと制御装置からなる負のばね特性を付与することによって、前記第１部材から第２部材に伝わる振動を絶縁するように構成した場合、前記第１部材から第２部材に伝わる振動を絶縁して、除振テーブルの地動外乱に対する振動絶縁性能を損なうことなく、直動外乱に対する高い剛性を確保して、高い除振機能を発揮して精密加工等を可能にすることは無論のこと、負のばね特性を得るために種々のアクチュエータの採用が可能となって設計の自由度が向上する。
【００５５】
また、前記床と中間台との間に、前記ばねと併設して所定の減衰率の減衰装置を設置した場合は、共振の発生を抑制して全体としてより高い除振機能を発揮させることができる。さらに、前記中間台に設けられた電磁石の吸引力を永久磁石が設けられた除振テーブルへ作用する荷重の増減に応じて増減させるように構成した場合、あるいは前記中間台に設けられたアクチュエータの伸びを除振テーブルへ作用する荷重の増減に応じて増減させるように構成した場合は、除振テーブルへの配線を避けることができるので、制御設備が簡素化される。
【００５６】
また、前記中間台に設けられた電磁石と永久磁石から構成される複合磁石の、強磁性体が設けられた除振テーブルに対する吸引力を除振テーブルへ作用する荷重の増減に応じて増減させるように構成した場合には、除振テーブルへの配線を避けることができると同時に、強磁性体だけが設置される除振テーブルの製作が容易になる。さらにまた、前記除振テーブルに設けられた電磁石の、永久磁石が設けられた中間台に対する吸引力を除振テーブルへ作用する荷重の増減に応じて増減させるように構成した場合は、永久磁石のみが設置される中間台の構成を簡素化できる。また、前記除振テーブルに設けられた電磁石と永久磁石から構成される複合磁石の、強磁性体が設けられた中間台に対する吸引力を除振テーブルへ作用する荷重の増減に応じて増減させるように構成した場合には、強磁性体だけが設置される中間台の製作が容易になる。
【００５７】
また、床と第１部材との間にゼロパワー特性を有する磁気浮上機構を配設した場合、あるいは床に対してアクチュエータと制御装置から構成されて所定の負のばね特性を有する支持機構によって支持された中間台と、該中間台に所定の正のばね定数を有するばねによって支持された除振テーブルとから構成された場合は、磁気浮上機構の磁力制御、あるいはアクチュエータの制御が静止側である床との間にて行えるので、配線等の取りまわしが簡素化される。さらに、前記中間台と除振テーブルとの間に、前記アクチュエータと併設して所定のばね定数のばねおよび所定の減衰率の減衰装置を設置した場合は、ばねで除振テーブルの重量を支持することによりアクチュエータのエネルギ消費を低減し、さらに除振系の共振を避けて減衰特性を改善することができる。
かくして、本発明によれば、地動外乱に対する振動絶縁性能を損なうことなく、直動外乱に対する高い剛性を確保して、高い除振機能を発揮して精密加工等を可能にする除振方法およびその装置が提供される。
【図面の簡単な説明】
【図１】本発明の除振装置のゼロパワー特性を有する磁気浮上機構を用いた第１実施の形態を示す説明図である。。
【図２】同、第１実施の形態の変形例を示す図である。
【図３】本発明で使用されるゼロパワー制御系の特徴の説明図である。
【図４】ばね系とゼロパワー制御系の動作比較図である。
【図５】本発明の除振装置の基礎実験装置を示す図である。
【図６】ゼロパワー磁気浮上系の負のばね特性の実験結果図である。
【図７】除振テーブルの床に対する変位の実験結果図である。
【図８】本発明の除振装置の第２実施の形態を示す説明図である。
【図９】本発明の除振装置の第３実施の形態を示す説明図である。
【図１０】本発明の除振装置の第４実施の形態を示す説明図である。
【図１１】従来のばね系の除振システム図である。
【図１２】従来のアクティブ除振装置の説明図である。
【符号の説明】
１中間台（第１部材）
２除振テーブル（第２部材）
３永久磁石
４電磁石
５ばね
６床
７強磁性体
１９減衰装置[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to vibration isolation of equipment, and to a vibration isolation method and apparatus capable of active vibration isolation that can cope with disturbance on a spring as well as passive vibration isolation for the purpose of isolating ground disturbance. Therefore, it is used for machine tools such as NC machines and machining centers, as well as various devices typified by steppers in the IC industry, to insulate processing tables from disturbances and achieve high-precision machining.
[0002]
[Prior art]
At present, semiconductor device manufacturing systems and ultra-small area measurement systems are rapidly increasing in accuracy and performance, and in these systems, the importance of vibration isolation and vibration isolation devices that remove disturbances such as vibrations is important. It is increasing. Vibration disturbances to be removed by the vibration isolation device can be broadly classified into ground disturbances caused by vibrations from the installation floor and linear motion disturbances that are input on the springs of the device. For the latter, a highly rigid mechanism is suitable. FIG. 11 shows a conventional passive vibration isolation system that insulates and isolates ground disturbance, and in order to reduce the vibration transmissibility from the floor 36, if the spring constant k is decreased and the spring rigidity is decreased, It becomes weak against disturbance on the spring such as mass change Δm on the vibration isolation table 32 (mass m) and load change acting on the vibration isolation table 32. On the contrary, it is necessary to increase the spring rigidity to some extent against disturbance on the spring. The contradictory characteristics of such a low-rigidity mechanism for absorbing disturbance and a high-rigidity mechanism for maintaining position and posture are required.
[0003]
In general, positive spring constant k₁, K₂When two vibration springs 35-1 and 35-2 having the above are coupled in series to constitute one vibration isolation mechanism, the spring constant is obtained by the following equation.
k_c= K₁k₂/ (K₁+ K₂(1)
That is, when a spring having a normal positive spring constant is coupled in series, the spring constant formed by the coupling is necessarily smaller than the spring constant before the coupling. Therefore, with these conventional vibration isolation devices that use only springs, it is extremely difficult to ensure high rigidity against disturbances on the spring, such as mass changes and vibrations, so an active vibration isolation control device is proposed. It was done.
[0004]
FIG. 12 shows the principle of a general active vibration isolation control device. The controller 115 suppresses the vibration of the vibration isolation table 110 based on a detection signal from the acceleration sensor 114 installed on the vibration isolation table 110. The control input is calculated, and the vibration isolation control is performed by operating the actuator 113 installed in parallel with the spring 111 and the attenuator 112 according to the obtained control input.
[0005]
[Problems to be solved by the invention]
However, this approach is based on the premise that vibrations from the vibration isolation table and floor are accurately detected. To realize this approach, it is necessary to use a servo-type acceleration sensor that can detect even low-frequency vibrations with high sensitivity. Therefore, depending on the servo type acceleration sensor employed, the rigidity against the direct acting disturbance is still not sufficient, and it is insufficient to ensure complete vibration insulation performance.
[0006]
Therefore, the present invention solves the problems of the conventional vibration isolation method and the device thereof, secures high rigidity against linear motion disturbance without damaging the vibration insulation performance against ground motion disturbance, and exhibits a high vibration isolation function. It is an object of the present invention to provide a vibration isolation method and apparatus that enable precision machining and the like.
[0007]
[Means for Solving the Problems]
For this reason, the technical solution means adopted by the present invention is:
A spring having a predetermined positive spring constant is disposed between the floor and the first member,2nd member arranged facing the 1st memberBetween1st memberPermanent magnet and electromagnet acting to pull up the second member towardA magnetic levitation mechanism that constitutes a negative spring constant consisting ofThe permanent magnetThe second member is supported only by the attraction force of the permanent magnet, and the electromagnet is controlled to narrow the gap between the first member and the second member with a negative spring constant when an external force is applied to the second member.,In addition, the positive and negative spring constants are equal in magnitude and have substantially infinite rigidity against the direct acting disturbance generated in the second member, thereby insulating the vibration transmitted from the floor to the first member. And the first memberThe vibration isolation method is characterized in that the vibration transmitted to the second member is insulated.
In addition, a column is erected on the floor, and acts between the column and the first member to pull up the first member.A magnetic levitation mechanism comprising a negative spring constant consisting of a permanent magnet and an electromagnet is provided.,The permanent magnet supports the first member only by the attractive force of the permanent magnet, and the electromagnet is controlled to narrow the gap between the support column and the first member with a negative spring constant when an external force is applied to the second member.AboveBetween the second member and the first member arranged to face the first memberIsA spring having a predetermined positive spring constant is provided.And
Insulating vibration transmitted from the floor to the first member by making the positive and negative spring constants equal and having almost infinite rigidity against the linear motion disturbance generated in the second member, 1st memberThe vibration isolation method is characterized in that the vibration transmitted to the second member is insulated.
The first member is an intermediate member, and the second member is a vibration isolation table.
Further, the floor, a spring having a predetermined positive spring constant, a first member supported on the floor by the spring and insulated from vibrations from the floor, are disposed to face the first member. A second member for placing a load, and acts between the first member and the second member to lift the second member toward the first member.A magnetic levitation mechanism that constitutes a negative spring constant composed of a permanent magnet and an electromagnet is disposed,AboveThe permanent magnet supports the second member only by the attractive force of the permanent magnet,AboveWhen an external force is applied to the second member, the gap between the first member and the second member is controlled to be narrow with a negative spring constant.,An anti-vibration device characterized in that the positive and negative spring constants are equal in magnitude and have substantially infinite rigidity against a linear motion disturbance generated in the second member.is there.
In addition, the pillars erected on the floor,PropA first member disposed opposite to the1st memberA second member for placing a load disposed opposite to the first member, and a spring having a positive spring constant disposed between the first member and the second member,A magnetic levitation mechanism that constitutes a negative spring constant composed of a permanent magnet and an electromagnet acting to pull up the first member toward the column is disposed between the column and the first member. The second member is supported only by the attraction force, and the electromagnet is controlled to narrow the gap between the column and the first member with a negative spring constant when an external force is applied to the second member.,An anti-vibration device characterized in that the positive and negative spring constants are equal in magnitude and have substantially infinite rigidity against a linear motion disturbance generated in the second member.is there.
The magnetic levitation mechanism includes an electromagnet provided on the first member and a permanent magnet provided on the second member, and acts on the second member by the attraction force of the electromagnet provided on the first member. The vibration isolator is configured to increase / decrease in accordance with increase / decrease of load to be applied.
The magnetic levitation mechanism includes a permanent magnet provided on the first member and an electromagnet provided on the second member, and acts on the second member by the attraction force of the electromagnet provided on the second member. The vibration isolator is configured to increase / decrease in accordance with increase / decrease of load to be applied.
The magnetic levitation mechanism is composed of a permanent magnet provided on the support column side and an electromagnet provided on the first member, and acts on the first member by the attraction force of the electromagnet provided on the first member. The vibration isolator is configured to increase or decrease in accordance with an increase or decrease in load.
The magnetic levitation mechanism includes an electromagnet provided on the support column side and a permanent magnet provided on the first member, and a load that applies an attractive force of the electromagnet provided on the support column side to the first member. The vibration isolator is configured to increase / decrease according to increase / decrease.
The first member is an intermediate member, and the second member is a vibration isolation table.
Further, the vibration isolator is provided with an attenuator having a predetermined attenuation factor in combination with the spring.
Further, the vibration isolator is configured such that a ferromagnetic material is provided alongside the permanent magnet, and the attraction force of the electromagnet is increased or decreased according to the increase or decrease of the load acting on the second member.
[0008]
Embodiments of the vibration isolation method and apparatus of the present invention will be described below with reference to the drawings. In the present invention, a support mechanism having a positive spring characteristic and a support mechanism having a negative spring characteristic are connected in series, thereby providing almost infinite rigidity against a linear motion disturbance generated on the apparatus. In addition, an embodiment using a magnetic levitation mechanism having zero power characteristics as a support mechanism having negative spring characteristics will be described first. FIG. 1 shows a first embodiment of a vibration isolation method and apparatus according to the present invention. In the present invention, a spring 5 is disposed between a floor 6 and a first member 1 which is an intermediate platform. 6 which insulates the vibration transmitted from the first member 1 to the first member 1 and has a zero power characteristic composed of a permanent magnet 3 and an electromagnet 4 between the first member 1 and the second member 2 which is a vibration isolation table. By providing a levitation mechanism, the vibration transmitted from the first member 1 to the second member 2 is insulated. In the present embodiment, a predetermined positive spring constant k with respect to the floor 6_PThe intermediate stand 1 supported by the spring 5 and the permanent magnet 3 and the electromagnet 4 with respect to the intermediate stand 1 and supported by a magnetic levitation mechanism having a zero power characteristic with a predetermined negative spring constant ks. In the example shown in the figure, the attraction force of the electromagnet 4 provided on the intermediate stand 1 is adjusted according to the increase or decrease in load caused by the mass increase of the vibration isolation table 2 provided with the permanent magnet 3. It is configured to be controlled by an appropriate control device (not shown) so as to increase or decrease.
[0009]
As shown in FIG. 2A, the ferromagnetic material 7 may be arranged on the vibration isolation table 2 side in combination with the permanent magnet 3 in order to increase the attractive force by the magnet. Alternatively, as shown in FIG. 2B, the permanent magnet 3 may be embedded in the iron core of the electromagnet 4 to form a composite magnet, and only the ferromagnetic material 7 may be installed on the vibration isolation table 2 side. Further, the arrangement of the electromagnet and the permanent magnet is reversed, that is, the electromagnet 4 is provided on the vibration isolation table 2 side, the permanent magnet 3 is provided on the intermediate stand 1 side, and the load applied to the vibration isolation table 2 is increased or decreased. You may comprise so that it may increase / decrease according to. Also in this case, as shown in FIG. 2C, the ferromagnetic material 7 may be installed on the intermediate table 1 side in combination with the permanent magnet 3. Alternatively, as shown in FIG. 2D, the permanent magnet 3 may be embedded in the iron core of the electromagnet 4 to form a composite magnet, and only the ferromagnetic body 7 may be installed on the intermediate platform 1 side.
[0010]
Next, a zero power magnetic levitation control system employed between the intermediate platform and the vibration isolation table in the present invention will be described with reference to FIGS. Zero power control is an attraction type magnetic levitation system configured by combining an electromagnet and a permanent magnet. As shown in FIG. 3, the weight of the vibration isolation table 12 that is a levitating object is determined only by the attraction force of the permanent magnet 13. This is a control method in which the coil current of the electromagnet 14 on the support fixing side 11 is constantly maintained at zero while being supported. In the stationary state “a”, the vibration isolation table 12 stays at the stationary position in a state where the forces are balanced, but as shown in the load “b”, the vibration isolation table 12 has a constant downward external force (mass increase Δm, etc.). ) Is applied to generate a suction force for pulling up the vibration isolation table 12 by passing a current through the coil of the electromagnet 14, and the suction force by the permanent magnet 13 and the downward force are controlled to be balanced, as shown in c As described above, the current flowing through the electromagnet 14 becomes zero at a position where the gap becomes narrow, and the stationary state is established. Although the control system that performs the above operation is omitted in FIG. 1, as shown in d, the position relative to the support and fixing side of the vibration isolation table 12 that is a floating object (the intermediate platform in the apparatus of FIG. 1). A control circuit 22 for generating a control signal for levitating and holding the vibration isolation table 12 while constantly holding the coil current of the electromagnet 14 at zero based on an output signal of the sensor 21; This is realized by using a control device 20 including a power amplifier 23 and the like for supplying a predetermined current to the coil of the electromagnet 14 according to the output of the control circuit 22.
[0011]
FIG. 4 illustrates a comparison with a normal spring system. As shown on the left side of the drawing, in the normal spring system, a mass m22 supported by a spring having a predetermined positive spring constant causes a mass increase Δm. In other words, so-called passive vibration isolation control that moves in the direction of mass increase (load) is performed. On the other hand, in the zero power control, as shown on the right side of the drawing, when the mass increase Δm occurs, the electromagnet 14 is controlled so that the mass m12 moves upward in the opposite direction to the spring system to narrow the gap. Is done. Therefore, it behaves as if it has a negative spring constant. By utilizing the property of the negative spring constant realized by this zero power control, in the present invention, even if the mass change on the spring occurs by combining with the passive vibration isolation control by the normal positive spring constant, the mass m, that is, the vibration isolation table or the like is configured so as not to be displaced.
[0012]
That is, as shown in FIG. 1B, a constant external force F is applied downward on the vibration isolation table 2 due to a mass increase Δm or the like.₀When (= Δmg) is added, the distance between the electromagnet 4 installed on the intermediate table 1 and the vibration isolation table is F by the action of zero power control.₀/ K_sOnly shorter (k_sIs a negative spring constant realized by zero power control). Therefore, k_s= K_PIf the vibration isolator is designed to satisfy the relationship, the vibration isolation table will not be displaced at all. Formula (1) k_c= K₁k₂/ (K₁+ K₂) Is used to explain k by zero power control.₁= -K₂If a negative spring constant that satisfies the relationship
｜ k_c| = + ∞ (2)
A spring constant is obtained. That is, by combining a positive spring and a negative spring having the same spring constant, a spring having an infinite spring constant can be obtained. This means zero compliance.
[0013]
Hereinafter, a theoretical analysis is performed on the vibration isolation control system of the present invention shown in FIG.
<Basic equation>
In this analysis, only the vertical displacement of each mass and floor is dealt with. The equation of motion of this system is obtained as follows:

here,
x₁, X₂: Displacement from the equilibrium point of the intermediate platform and vibration isolation table
x₀: Vibration displacement of the floor
k_P: Spring constant of the spring that supports the intermediate platform from the floor
f_c: Fluctuation from the operating point of the magnet's attractive force
f_d: Linear motion disturbance acting on the vibration isolation table

C

_P1 is a damping coefficient of a damping device that is not shown in FIG. C if there is no damping device_P= 0. The fluctuation of the magnet attractive force is approximately expressed as follows.
f_c= K_s(X₂-X₁) + K_ii (6)
here,
k_s: Magnet displacement / attraction force coefficient
k_i: Magnet current / attraction force coefficient
i: Control current
[0014]
<Zero power control system>
Here, the control input is constituted by the relative displacement between the intermediate platform and the vibration isolation table. In this case, the control input to achieve zero power control can generally be expressed as:
I (s) =-c₂(S) s (X₂(S) -X₁(S)) (7)
Where c₂(S) is a strong proper transfer function having no zero at the pole, and is selected so that the control system becomes stable. If the dynamics of the intermediate stage can be ignored, stabilization can be achieved by a controller having an order of 2 or more.
[0015]
<Analysis of basic characteristics>
For simplicity, assuming that the initial condition is zero and performing Laplace transform, the following equations are obtained from equations (4) to (7).

[0016]
The Laplace transform of each variable is represented by the corresponding capital letter. To evaluate the stiffness against linear motion disturbance,
F_d= F₀/ S (F₀: Const) (13)
And Ignoring the effects of floor vibration (x₀= 0), steady displacement x of vibration isolation table₂(∞) is obtained as follows.

Therefore,
k_P= K_s                                                (15)
If the vibration isolation device is designed to satisfy
x₂(∞) / F₀= 0 (16)
It becomes. This means that the compliance is zero, that is, the stiffness is infinite. Also, the displacement of the intermediate platform₁(∞) and the fluctuation amount of the gap between the electromagnet and the vibration isolation table (x₁(∞) -x₂(∞)) is obtained as follows.
x₁(∞) / F₀= 1 / k_P                                (17)
(X₁(∞) -x₂(∞)) / F₀= 1 / k_s                (18)
Therefore, a downward force (F₀When <0) acted, it was confirmed that the intermediate table was displaced downward, whereas the vibration isolation table was displaced upward so as to approach the intermediate table. As described above, in the vibration isolator using the zero power magnetic levitation mechanism, the spring constant of the mechanical spring supporting the intermediate base and the magnitude of the displacement / attraction force coefficient of the magnet are set to be equal to each other to prevent direct acting disturbance. It has been theoretically shown that the stiffness is infinite.
[0017]
FIG. 5 shows a vibration isolation method and a basic experimental apparatus for the apparatus of the present invention. FIG. 5 (A) is a front view of the experimental apparatus, and FIG. 5 (B) is a side view thereof. An intermediate platform 1 is installed via

springs

5a and 5b fitted and inserted into

linear shafts

9a and 9b standing from a base 10 fixed to the floor, and the

linear shafts

9a and 9b are fitted into the intermediate platform. The

linear bushes

8a and 8b installed at 1 restrain the motion of the intermediate platform 1 to translational motion with one degree of freedom in the vertical direction. On the other hand, the guide blocks 15a and 15b installed on both sides of the lower part of the vibration isolation table 2 engage with the

guide rails

16a and 16b provided upright on the base 10, and the motion of the vibration isolation table 2 is one degree of freedom in the vertical direction. Restrained to translational movement.

Permanent magnets

3, 3 facing upward are installed at the lower end of the vibration isolation table 2, and an electromagnet 4 is installed at the lower part of the facing intermediate platform 1. The sensor 17 detects the relative displacement of the vibration isolation table 2 with respect to the intermediate base 1, and the sensor 18 detects the relative displacement of the intermediate base 1 with respect to the base 10.
[0018]
Next, with reference to FIG. 6 and FIG. 7, the results of experiments conducted using the prototype basic experimental apparatus will be described. FIG. 6 is a result of an experiment on the negative spring characteristic of the zero power magnetic levitation system. In the case where the intermediate stand 1 is fixed and the mass of the vibration isolation table is increased to 1700 g, 1310 g, and 700 g, the additional mass Δm is increased. The displacement of the table was measured, and the table displacement increased linearly at any mass, and it was found that zero power control was operating as a linear negative spring. It can also be seen that the spring constant of zero power control can be set to various values by manipulating the mass of the vibration isolation table.
[0019]
Fig. 7 shows the experimental results of the displacement of the vibration isolation table against the floor with the intermediate stand supported by the spring. The positive spring constant is 6.825 (kN / m), and the positive and negative spring constants are almost the same. It can be estimated that the table mass is in the range of 1280 g to 1400 g based on the vicinity of 1300 g. Incidentally, the negative spring constant at 1310 g is about 7 kN / m. According to the figure, it can be seen that when the table mass is 1380 g, the vibration isolation table displacement amount is 20 μm, and the table position is operating well while maintaining the initial position. This value of 1380 g is a value within the range estimated before the experiment, and it can also be seen that the operating performance decreases as the difference between the positive and negative spring constants increases.
[0020]
From these relationships, the effectiveness of the theoretical analysis shown above was confirmed. The zero-compliance mechanism, which combines the zero-power magnetic levitation mechanism and the spring mechanism, makes the displacement of the vibration isolation table relative to the floor zero and allows infinite table rigidity against linear motion disturbance. In the actually measured range, the maximum rigidity of the table with respect to the floor is about 490 kN / m. At this time, the displacement of the vibration isolation table with respect to the floor also shows the minimum value. It was confirmed that by combining the zero power magnetic levitation mechanism and the spring, the compliance can be made almost zero, and thereby the rigidity against the direct acting disturbance can be extremely increased.
[0021]
FIG. 8 shows a second embodiment of the vibration isolation method and apparatus according to the present invention, which is composed of a permanent magnet 203 and an electromagnet 204 with respect to a column 207 installed on a floor 206, and a predetermined negative spring. Constant K_SAn intermediate table 201 supported by a magnetic levitation mechanism having zero power characteristics, and a predetermined positive spring constant K on the intermediate table 201_PIn the illustrated example, the attraction force of the electromagnet 204 provided on the support column 207 is changed according to the increase or decrease of the load on the intermediate table 201 provided with the permanent magnet 203. The distance between the electromagnet 204 and the intermediate base 201 is controlled by an appropriate control device (not shown) so as to increase or decrease the distance.
[0022]
With such a configuration, a constant external force F that is downward is applied to the vibration isolation table 202 due to a mass increase Δm or the like.₀When (= Δmg) is applied, the spring 205 supporting the vibration isolation table 202 is F₀/ K_POnly compressed and shortened. At the same time, a downward external force F is exerted on the intermediate table 201 by the reaction force of the spring 205.₀The distance between the electromagnet 204 and the intermediate base 201 is F due to the action of zero power control.₀/ K_SAccordingly, the intermediate table 201 is displaced upward by this amount. Therefore, K_S= K_PIf the vibration isolator is designed so as to satisfy the relationship, the vibration isolation table 202 is not displaced at all. This means that the compliance is zero, that is, the stiffness is infinite. That is, it is understood that the vibration isolation device shown in FIG. 8 has the same vibration isolation performance as the vibration isolation device shown in FIG.
[0023]
FIG. 9 shows a third embodiment of the vibration isolation method and apparatus according to the present invention. The floor 300 has a predetermined positive spring constant K._PThe intermediate base 303 supported by the spring 301 and the damping device 302, and the intermediate base 303 includes a permanent magnet 304 and an electromagnet 305, and has a predetermined negative spring constant K._SA magnetic levitation mechanism having zero power characteristics and a predetermined positive spring constant K on the floor 300_PThe intermediate table 313 supported by the spring 311 and the damping device 312, and a permanent magnet 314 and an electromagnet 315 with respect to the intermediate table 313, and a predetermined negative spring constant K_SAnd a vibration isolation table 320 supported by a magnetic levitation mechanism having zero power characteristics having '.
[0024]
In such a configuration, K_S= K_PAnd K_S'= K_PIf the vibration isolation device is designed so as to satisfy the relationship ', the compliance is zero, that is, the rigidity is infinite on the left side (intermediate base 303 side) and the right side (intermediate base 313 side) of the vibration isolation table 320. No matter which position on the vibration isolation table 320 is applied with a constant external force in the vertical direction, the vibration isolation table 320 is not displaced at all. From such characteristics, when the movable stage 321 is installed on the vibration isolation table 320, the vibration isolation table 320 is not displaced regardless of the position of the moving load 322, and the posture can be kept horizontal.
[0025]
FIG. 10 shows a fourth embodiment of the vibration isolation method and apparatus of the present invention. The floor 400 has a predetermined positive spring constant K in the vertical direction._P ¹Spring 401 and damping device 402 in the horizontal direction with a predetermined positive spring constant K_P ²And a predetermined negative spring constant K composed of a permanent magnet 406 and an electromagnet 407 in the vertical direction with respect to the intermediate table 405._S ¹A magnetic levitation mechanism having zero power characteristics having a predetermined negative spring constant K composed of a permanent magnet 408 and an electromagnet 409 in the horizontal direction_S ²Is supported by a magnetic levitation mechanism having zero power characteristics and has a predetermined positive spring constant K in the vertical direction on the floor 400._P ^ThreeSpring 411 and damping device 412, a predetermined positive spring constant K in the horizontal direction_P ^FourThe intermediate base 415 supported by the spring 413 and the damping device 414, and a predetermined negative spring constant K composed of a permanent magnet 416 and an electromagnet 417 in a direction perpendicular to the intermediate base 415._S ^ThreeA magnetic levitation mechanism having zero power characteristics having a predetermined negative spring constant K composed of a permanent magnet 418 and an electromagnet 419 in the horizontal direction_S ^FourAnd a vibration isolation table 420 supported by a magnetic levitation mechanism having zero power characteristics.
[0026]
In such a configuration, K_S ¹= K_P ¹, K_S ²= K_P ², K_S ^Three= K_P ^ThreeAnd K_S ^Four= K_P ^FourIf the vibration isolator is designed to satisfy the following relationship, the compliance is zero, that is, the rigidity is infinite on the left side (intermediate base 405 side) and the right side (intermediate base 415 side) of the vibration isolation table 420, and at the same time the vibration isolation Since the horizontal compliance on the table 420 is also zero, the vibration isolation table 420 is not displaced at all regardless of the position of the vibration isolation table 420 where a constant external force in the vertical and horizontal directions is applied.
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[0051]
The embodiments of the vibration isolation method and apparatus of the present invention have been described above, but within the scope of the present invention, the shape and type of the intermediate platform and the vibration isolation table, the shape and type of the electromagnet and the permanent magnet, and those (Electric magnets are installed on an intermediate stand or vibration isolation table, permanent magnets are installed on an anti-vibration table or intermediate stand, or a ferromagnetic material is added to the permanent magnet,Alternatively, a permanent magnet may be incorporated in the iron core of the electromagnet and installed only on one of the vibration isolation table or the intermediate table, and a ferromagnetic material may be installed on the other), the shape of the spring and the damping device, Type and arrangement form on the intermediate platform (an appropriate damping device may be provided in addition to the spring between the floor and the intermediate platform), zero power control means, direction of vibration isolation (each of the above-mentioned implementations) In the form ofAlthough the vertical vibration isolation has been mainly described, it goes without saying that it can be configured to perform horizontal vibration isolation, or vibration isolation in the vertical and horizontal directions simultaneously. ) Etc. can be selected as appropriate.
[0052]
【The invention's effect】
As described above in detail, in the present invention, a support mechanism having a positive spring characteristic and a support mechanism having a negative spring characteristic are connected in series to prevent a linear motion disturbance generated on the apparatus. A support mechanism having a positive spring characteristic and a negative spring characteristic for a device such as a vibration isolation table with respect to the floor by isolating the vibration with respect to the floor. Therefore, high rigidity against linear motion disturbance generated on the equipment is ensured without impairing vibration insulation performance against ground motion disturbance from the floor, and high vibration isolation function is demonstrated to perform precision machining, etc. enable.
[0053]
In addition, a spring is disposed between the floor and the first member to insulate vibration transmitted from the floor to the first member, and is configured by a permanent magnet and an electromagnet between the first member and the second member. By providing a magnetic levitation mechanism having zero power characteristics, the vibration transmitted from the first member to the second member is insulated only by magnetic force control, which is relatively easy to control, and against the ground motion disturbance of the vibration isolation table. Without sacrificing vibration isolation performance, high rigidity against linear motion disturbance is ensured and high vibration isolation function is demonstrated to enable precision machining.
[0054]
Further, a spring is disposed between the floor and the first member to insulate vibration transmitted from the floor to the first member, and between the first member and the second member, a negative composed of an actuator and a control device. By providing spring characteristics, the vibration transmitted from the first member to the second member is insulated.If configured,Insulates the vibration transmitted from the first member to the second member, and ensures high rigidity against linear motion disturbance without damaging the vibration insulation performance against ground motion disturbance of the vibration isolation table, and exhibits a high vibration isolation function Needless to say, precision machining or the like is possible, and various actuators can be used to obtain negative spring characteristics, thereby improving the degree of freedom in design.
[0055]
In addition, when a damping device having a predetermined damping rate is installed between the floor and the intermediate platform in combination with the spring, it is possible to suppress the occurrence of resonance and exhibit a higher vibration isolation function as a whole. it can. Furthermore, when it is configured to increase or decrease the attractive force of the electromagnet provided on the intermediate table in accordance with the increase or decrease of the load acting on the vibration isolation table provided with the permanent magnet, or the actuator provided on the intermediate table In the case where the elongation is increased or decreased according to the increase or decrease of the load acting on the vibration isolation table, wiring to the vibration isolation table can be avoided, so that the control equipment is simplified.
[0056]
Further, the attraction force of the composite magnet composed of the electromagnet and the permanent magnet provided on the intermediate table to the vibration isolation table provided with the ferromagnetic material is increased or decreased according to the increase or decrease of the load acting on the vibration isolation table. In this case, wiring to the vibration isolation table can be avoided, and at the same time, it becomes easy to manufacture the vibration isolation table in which only the ferromagnetic material is installed. Furthermore, when the electromagnet provided on the vibration isolation table is configured to increase / decrease the attraction force with respect to the intermediate table provided with the permanent magnet according to the increase / decrease of the load acting on the vibration isolation table, only the permanent magnet is provided. It is possible to simplify the configuration of the intermediate platform on which is installed. Further, the attraction force of the composite magnet composed of the electromagnet and the permanent magnet provided on the vibration isolation table to the intermediate base provided with the ferromagnetic material is increased or decreased according to the increase or decrease of the load acting on the vibration isolation table. In this case, it becomes easy to manufacture an intermediate stand on which only a ferromagnetic material is installed.
[0057]
Further, when a magnetic levitation mechanism having zero power characteristics is disposed between the floor and the first member, or supported by a support mechanism having a predetermined negative spring characteristic that is configured of an actuator and a control device for the floor. And a vibration isolation table supported by a spring having a predetermined positive spring constant on the intermediate table, the magnetic force control of the magnetic levitation mechanism or the control of the actuator is on the stationary side. Since it can be performed between floors, wiring and the like are simplified. Further, when a spring having a predetermined spring constant and a damping device having a predetermined damping rate are installed between the intermediate platform and the vibration isolation table in combination with the actuator, the weight of the vibration isolation table is supported by the spring. As a result, the energy consumption of the actuator can be reduced, and the damping characteristics can be improved by avoiding resonance of the vibration isolation system.
Thus, according to the present invention, a vibration isolation method that ensures high rigidity against linear motion disturbance without sacrificing vibration isolation performance against ground motion disturbance, and exhibits high vibration isolation function and enables precision machining and the like. An apparatus is provided.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a first embodiment using a magnetic levitation mechanism having zero power characteristics of a vibration isolation device of the present invention. .
FIG. 2 is a diagram showing a modification of the first embodiment.
FIG. 3 is an explanatory diagram of features of a zero power control system used in the present invention.
FIG. 4 is an operation comparison diagram between a spring system and a zero power control system.
FIG. 5 is a diagram showing a basic experimental apparatus for a vibration isolation device of the present invention.
FIG. 6 is an experimental result diagram of negative spring characteristics of a zero power magnetic levitation system.
FIG. 7 is an experimental result diagram of displacement of the vibration isolation table with respect to the floor.
FIG. 8 is an explanatory diagram showing a second embodiment of the vibration isolation device of the present invention.
FIG. 9 is an explanatory view showing a third embodiment of the vibration isolator of the present invention.
FIG. 10 is an explanatory view showing a fourth embodiment of the vibration isolator of the present invention.
FIG. 11 is a diagram of a conventional spring system vibration isolation system.
FIG. 12 is an explanatory diagram of a conventional active vibration isolator.
[Explanation of symbols]
1 Intermediate stand (first member)
2 Vibration isolation table (second member)
3 Permanent magnet
4 Electromagnet
5 Spring
6 floors
7 Ferromagnetic material
19 Attenuator

Claims

A spring having a predetermined positive spring constant is disposed between the floor and the first member, and the second member is disposed toward the first member between the second member disposed opposite the first member . A magnetic levitation mechanism that constitutes a negative spring constant composed of a permanent magnet and an electromagnet acting to pull up the member is disposed , the permanent magnet supports the second member only by the attraction force of the permanent magnet, and the electromagnet is the second member. When an external force is applied, the gap between the first member and the second member is controlled to be narrowed by a negative spring constant, and the positive and negative spring constants are equal in magnitude and are generated by the second member. By isolating the vibration transmitted from the floor to the first member and by isolating the vibration transmitted from the first member to the second member by having substantially infinite rigidity against disturbance. .

A magnetic levitation mechanism that constitutes a negative spring constant composed of a permanent magnet and an electromagnet acting to pull up the first member is disposed between the column and the first member. The permanent magnet supports the first member only with the attraction force of the permanent magnet, and the electromagnet is controlled to narrow the gap between the column and the first member with a negative spring constant when an external force is applied to the second member . A spring having a predetermined positive spring constant is disposed between the second member and the first member arranged facing the member, and the magnitudes of the positive and negative spring constants are equal and the second member is By having substantially infinite rigidity against the generated linear motion disturbance, the vibration transmitted from the floor to the first member is insulated and the vibration transmitted from the first member to the second member is insulated. Vibration isolation method.

3. The vibration isolation method according to claim 1, wherein the first member is an intermediate member, and the second member is a vibration isolation table.

A floor, a spring having a predetermined positive spring constant, a first member supported on the floor by the spring and insulated from vibrations from the floor, and disposed opposite to the first member to apply a load A negative spring constant comprising a permanent magnet and an electromagnet that act to pull up the second member toward the first member, between the first member and the second member. The permanent magnet supports the second member only by the attraction force of the permanent magnet, and the electromagnet has a negative spring constant when the external force is applied to the second member. The gap between the two members is controlled to be narrow, and the positive and negative spring constants are equal in magnitude and configured to have substantially infinite rigidity against the linear motion disturbance generated in the second member. A vibration isolator characterized by that.

A column erected on the floor, a first member arranged opposite to the column , a second member arranged opposite to the first member for mounting a load, a first member and a second member And a negative spring comprising a permanent magnet and an electromagnet that act to pull up the first member toward the support between the support and the first member. A magnetic levitation mechanism that constitutes a constant is provided, the permanent magnet supports the second member only by the attraction force of the permanent magnet, and the electromagnet has a negative spring constant when the external force is applied to the second member, The positive and negative spring constants are equal to each other, and are configured to have substantially infinite rigidity against the linear motion disturbance generated in the second member. The vibration isolator.

The magnetic levitation mechanism is composed of an electromagnet provided on the first member and a permanent magnet provided on the second member, and a load that applies an attractive force of the electromagnet provided on the first member to the second member The vibration isolation device according to claim 4, wherein the vibration isolation device is configured to increase or decrease in accordance with the increase or decrease of.

The magnetic levitation mechanism is composed of a permanent magnet provided on the first member and an electromagnet provided on the second member, and a load that applies the attractive force of the electromagnet provided on the second member to the second member The vibration isolation device according to claim 4, wherein the vibration isolation device is configured to increase or decrease in accordance with the increase or decrease of.

The magnetic levitation mechanism is composed of a permanent magnet provided on the support column side and an electromagnet provided on the first member, and a load acting on the first member by an attractive force of the electromagnet provided on the first member. The vibration isolator according to claim 5, wherein the vibration isolator is configured to increase or decrease in accordance with the increase or decrease.

The magnetic levitation mechanism is composed of an electromagnet provided on the support column side and a permanent magnet provided on the first member, and an increase / decrease in the load acting on the first member by the attractive force of the electromagnet provided on the support column side. The vibration isolator according to claim 5, wherein the vibration isolator is configured to increase or decrease in accordance with the frequency.

The vibration isolator according to any one of claims 4 to 9, wherein the first member is an intermediate member, and the second member is a vibration isolation table.

The vibration isolator according to any one of claims 4 to 10, wherein an attenuator having a predetermined attenuation rate is installed along with the spring.

12. The structure according to claim 4, wherein a ferromagnetic material is provided adjacent to the permanent magnet, and the attraction force of the electromagnet is increased or decreased according to an increase or decrease of a load acting on the second member. The vibration isolator described in 1.