JP4104409B2 - Servo mechanism - Google Patents

Description

【００４１】
で表される。ただし、０＜ζ_fk＜１、ｈは振動モードの数である。
【００４２】
この負荷３の特性１／Ｇ_fに対して、負荷速度制御ループＲ２の実現したい支配特性（ノミナル特性）を１／Ｇ_nと表すとき、１／Ｇ_nの相対次数を１／Ｇ_fと等しく、かつ、１次または２次で表されるような非振動的な特性に設定する。このようなノミナル特性１／Ｇ_nを多項式で表すと、
【００４３】
【数２】

【００４４】
で表される。ただし、１≦ζ_np、ｈは振動モードの数である。ここで、ω_npはω_fkよりも大きく設定し、例えば、ω_fkの２倍程度に設定される。また、ζ_npは１に近似した値に設定することが例示される。
【００４５】
ここで、負荷速度特性補償要素１３の伝達特性１／βを
１／β＝Ｇ_f／（Ｇ_n−１）
と設定する。すると、負荷速度特性補償要素１３の伝達特性１／βの相対次数をゼロに設定することができる。このとき、負荷速度制御ループＲ２の一巡伝達特性の相対次数が低くなることにより、振動的な応答を抑えて制御系を安定化することができる。つまり、負荷速度制御ループＲ２の伝達特性である指令速度Ｖ_rと負荷速度Ｖ₀の比をノミナル特性１／Ｇ_nに実現することができる。すなわち、負荷速度制御ループＲ２の応答を非振動的とし、負荷３を安定に制御することができる。
さらに、負荷速度制御ループＲ２を安定化することができるので、負荷速度制御ループＲ２のゲインを大きくすることができる。すると、外乱の影響を低減することができる。
【００４６】
また、負荷３の特性１／Ｇ_fを正確に把握できない場合がある。負荷３の特性１／Ｇ_fを正確に把握できない場合は、負荷３の伝達特性の近似特性１／Ｇ_mを設定する。
【００４７】
負荷３の近似特性１／Ｇ_mを設定するにあたっては、まず、負荷３の特性のパラメータである減衰係数ζ_fおよび固有角周波数ω_fの変動幅を見積もる。固有角周波数に関しては、変動幅を見積もった固有角周波数よりも小さい値、例えば７０％ぐらいの固有角周波数で固定して負荷３の近似特性の固有角周波数とする。減衰係数に関しては、ある一定範囲で定められる推奨値で固定する。このようにして設定される負荷３の近似特性１／Ｇ_mを多項式で表すと、
【００４８】
【数３】

【００４９】
となる。ただし、０＜ζ_mk＜１、ｈは振動モードの数である。
【００５０】
この負荷３の近似特性１／Ｇ_mに対して、負荷速度制御ループＲ２の実現したい支配特性（ノミナル特性）１／Ｇ_nを、相対次数を１／Ｇ_mと等しく、かつ、非振動的な特性に設定する。ここで、ω_npはω_mkよりも大きく設定され、例えば、ω_mkの２倍程度に設定される。また、ζ_npは１に近似した値に設定することによって支配特性１／Ｇ_nが非振動的になることがが例示される。
【００５１】
この負荷３の近似特性１／Ｇ_mを用いて、負荷速度特性補償要素の特性１／βを設定し、
１／β＝Ｇ_m／（Ｇ_n−１）
とする。すると、負荷３の特性が正確に把握できず一意に決定できない場合であっても、負荷速度特性補償要素１３の特性１／βを設定することができる。
【００５２】
このとき、負荷３の近似特性１／Ｇ_mを定めるにあたり、固有角周波数を、少なくとも見積もった変動幅の最悪値である最小値よりも小さい値とするので、最悪の場合であってもこの近似特性１／Ｇ_mで十分対応できる。
ノミナル特性１／Ｇ_nと負荷３の近似特性１／Ｇ_mの次数は等しいので、負荷速度特性補償要素１３の特性１／βの相対次数をゼロとすることができる。よって、負荷速度制御ループＲ２の応答をノミナル特性１／Ｇ_nとすることができる。その結果、負荷速度制御ループＲ２の応答を非振動的とし、負荷３を安定に制御することができる。
【００５３】
負荷３の構造が複雑であって、負荷３が非常に高次の振動モードを有する場合がある。このような場合は、負荷３の近似特性１／Ｇ_mを見積もるに当たって、負荷３の高次振動モードを正確に把握することが困難である。このような場合には、負荷３の高次の振動モードについては捨象して、低次の振動モードに対応して負荷３の近似特性１／Ｇ_mを設定してもよい。一般に、低次の振動モードのゲイン特性は大きいのに対し高次振動モードのゲインは小さいため、高次振動モードを捨象して近似しても高次振動モードの影響は小さいからである。このように高次振動モードを捨象して設定する近似特性１／Ｇ_mを利用して負荷速度特性補償要素１３の伝達特性１／βを求めると、計算量を少なくできる。その結果、制御周期を短縮することができ、制御のリアルタイム性能を向上させることができる。
【００５４】
負荷３の近似特性１／Ｇ_mを設定するに際して負荷３の高次の振動モードを捨象した場合に、捨象した高次振動モードの影響が現れることもありうる。このような場合には、負荷速度特性補償要素１３の特性にゲインＫ_αを加味して、負荷速度制御ループＲ２のゲイン余有を調整する。
【００５５】
図７に、負荷速度特性補償要素１３にゲインＫ_αを加味して、負荷速度特性補償要素１３の特性をＫ_α／βと表した場合のブロック図を示す。なお、モータ速度制御ループＲ３の特性をまとめて１／Ｇνβと表す。
【００５６】
ここで、ゲインＫ_αを小さく設定することにより、もともとゲインの小さい高次振動モードの影響をさらに小さく設定することができる。ゲインＫ_αの値としては、例えば、１に近い値に設定することが例示される。
【００５７】
次に、負荷速度特性補償要素１３の特性Ｋα／βの具体的な設計ついて、負荷３の振動モードが２（ｈ＝２）である場合を例示して説明する。
負荷３の特性1／Ｇ_fはｈ＝２の場合、次のように表される。
【００５８】
【数４】

【００５９】
ここで、ω_f1＜ω_f2、０＜ζ_f1＜１、０＜ζ_f2＜１であり、１／Ｇ_fは０＜ζ_f1＜１、０＜ζ_f2＜１のとき振動的特性となる。
【００６０】
モータ速度制御ループＲ３の特性１／Ｇ_νβについて、次に示す2重根（−１／ω_νβ）をもつ特性となるように図１のモータ速度特性補償要素１４の特性Ｋ_νＧ_νの設計を行う。
【００６１】
【数５】

【００６２】
ただし、ω_νβはモータ速度制御ループＲ３の応答固有角周波数である。
このとき、指令負荷速度Ｖ_mrから負荷速度Ｖ₀までの負荷速度制御ループの一巡伝達関数は次のようになる。
【００６３】
【数６】

【００６４】
つまり、負荷速度Ｖ₀と指令速度Ｖ_mrの比であるＶ₀／Ｖ_mrを規範となるノミナルモデル（実現したい設計モデル）１／Ｇ_nとするための負荷速度特性補償要素１３の伝達特性Ｋ_α／βを求める。このためには、次の式が成り立つ負荷速度特性補償要素Ｋ_α／βを求める。
【００６５】
【数７】

【００６６】
これより、負荷速度特性補償要素１３の特性Ｋ_α／βは次のように求めることができる。
【００６７】
【数８】

【００６８】
ここで、負荷３の特性１／Ｇ_fおよびノミナル特性Ｇ_nを具体的に定めれば、負荷速度特性補償要素１３の特性Ｋ_α／βを求めることができる。
そこで、次に、負荷３の特性１／Ｇ_fおよびノミナル特性Ｇ_nの定め方について説明する。
【００６９】
負荷３の特性１／Ｇ_fは正確に求めることは困難である場合があり、代わりに負荷３の近似特性のモデル１／Ｇ_mを設定する。
【００７０】
【数９】

【００７１】
固有角周波数ω_m1、ω_m2の設定は、負荷の特性１／Ｇ_fの各振動モードに対応した固有角周波数よりも低い固有角周波数を持つパラメータとする。つまり、ω_m1＜ω_f1＜ω_m2＜ω_f2とする。すると 負荷の近似特性１／Ｇ_mは次のようになる。
【００７２】
【数１０】

【００７３】
ここで、ｚ₄、ｚ₃、ｚ₂、ｚ₁、ｚ₀は次の通りである。
ｚ₄＝１
ｚ₃＝２（ζ_m1ω_m1＋ζ_m2ω_m2）
ｚ₂＝ω_m1 ²＋４ζ_m1ζ_m2ω_m1ω_m2＋ω_m2 ²
ｚ₁＝２（ζ_m1ω_m2＋ζ_m2ω_m1）ω_m1ω_m2
ｚ₀＝ω_m1 ²ω_m2 ²
【００７４】
次に、ノミナルモデル１／Ｇ_nは１／Ｇ_mに対応して、次のように2次標準形の積で構成する。
【００７５】
【数１１】

【００７６】
ここで、ノミナルモデル１／Ｇ_nの右辺第1項をノミナルモデルの主応答の特性とする。したがって、固有角周波数はω_n1＜ω_n2となり、ω_n1は負荷速度制御ループのマイナーループであるモータ速度制御ループＲ３の応答角周波数ω_νβに対して、ω_n1＜ω_νβの範囲で設定する。また、減衰係数ζ_n1は振動的挙動を招かないために１以上とする。
右辺第2項についてはノミナルモデルの主応答である第1項に影響がないようにω_νβ＜ω_n2とする。
したがって、１／（Ｇ_n−１）は次のようになる。
【００７７】
【数１２】

【００７８】
ここで、ｐ₄、ｐ₃、ｐ₂、ｐ₁、ｐ₀は次の通りである。
ｐ₄＝１、
ｐ₃＝２（ζ_n1ω_n1＋ζ_n2ω_n2）
ｐ₂＝ω_n1 ²＋４ζ_n1ζ_n2ω_n1ω_n2＋ω_n2 ²
ｐ₁＝２（ζ_n1ω_n2＋ζ_n2ω_n1）ω_n1ω_n2
ｐ０＝０
【００７９】
よって、負荷速度特性補償要素Ｋ_α／βは次のようになる。
【００８０】
【数１３】

【００８１】
ここで、このままでは分子の次数（＝6次）＞分母の次数（＝4次）となり、プロパー（分子の次数が分母の次数以下）とならず、非振動的な特性補償を行うことができない。そこで、次の要素を付加することにより、分子の次数（＝6次）＝分母の次数（＝6次）として、相対次数を0とする補償要素を構成する。
【００８２】
【数１４】

【００８３】
ここでｃは定数であり、モータ速度応答角周波数ω_νβに対して、ｃ＝５程度とすればＫ_α／βの特性へ与える影響は小さい。このとき、負荷速度特性補償要素１３の特性Ｋ_α／βは次のようになる。
【００８４】
【数１５】

【００８５】
ただし、ω_m1＜ω_f1＜ω_m2＜ω_f2＜ω_n1＜ωνβ＜ω_n2である。
（式３）の基本形を基にして相対次数がゼロを保つように補償要素を負荷速度特性補償要素１３に付加することにより、さらに特性改善を行うことができる。例えば、システムゲインＫ_sに相当する周波数ω＝Ｋ_s（ｒａｄ／ｓ）におけるゲインを高めて、負荷速度制御ループＲ２の特性（ゲインの低下と位相遅れ）を改善したい場合は、次の要素を追加する。
【００８６】
【数１６】

【００８７】
これは、位置制御ループＲ１を構成したときの位置制御ループＲ１の応答においてオーバーシュートを発生させないために有効となる。
このとき、負荷速度特性補償要素１３の特性Ｋ_α／βは次のようになる。
【００８８】
【数１７】

【００８９】
この場合、ωがＫ_sから１０Ｋ_s（ｒａｄ／ｓ）におけるゲイン特性が−４０ｄＢ／ｄｅｃとなりω＝Ｋ_s（ｒａｄ／ｓ）におけるゲインを１０倍程度高めることができる。
【００９０】
以上、このような構成によれば、次の効果を奏することができる。
（１）負荷３の制御対象部３４に加速度検出器５３を設けて、加速度検出器５３で検出された加速度の積分値を検出ヘッド５２で検出された負荷本体３２の移動速度に加味する。すると、真に制御したい対象部である制御対象部３４の駆動速度を正確に検出することができる。この正確に検出された制御対象部３４の駆動速度をフィードバックすることにより、制御対象部３４の精密な制御が可能となる。
【００９１】
（２）モータ速度制御ループＲ３と、負荷速度制御ループＲ２と、位置制御ループＲ１とをそれぞれ独立したループとする。このとき、モータ速度特性補償要素１４と負荷速度特性補償要素１３とに同じ伝達関数を含まない。よって、それぞれのループを完全に独立したものとし、各ループにおいて最適の補償要素を設けることができる。つまり、モータ２と負荷３との慣性比などに関係なく、それぞれに最適の補償要素を設けることができる。特に、負荷速度制御ループＲ２の安定性について、負荷速度特性補償要素１３の伝達特性（１／βまたはＫ_α／β）を負荷３の特性とノミナル特性とから設計的に設定することができる。つまり、負荷速度制御ループＲ２の伝達特性の相対次数を下げ、負荷速度制御ループＲ２の一巡伝達特性を実現したい非振動的なノミナル特性とすることができる。よって、負荷速度特性補償要素１３の特性を定めるにあたり、試行錯誤的な方法をとる手間を省くことができる。
【００９２】
（３）負荷３の特性１／Ｇ_fが正確に求められない場合であっても、負荷３の近似特性１／Ｇ_mを用いることにより、負荷３を制御することができる。負荷３の近似特性１／Ｇ_mを定めるに当たって、負荷３の固有角周波数の変動幅における最小値よりも小さい固有角周波数を近似特性の固有角周波数とする。よって、最悪の場合であっても、負荷の制御を安定して行うことができる。
【００９３】
（４）負荷３が複雑であり高次の振動モードを有する場合は、高次の振動モードを捨象して負荷３の近似特性１／Ｇ_mを設定する。すると、制御系の計算負担を軽くすることができる。よって、制御周期を短縮することができ、制御のリアルタイム性能を向上させることができる。
【００９４】
（５）負荷３の近似特性１／Ｇ_mを設定するに当たって高次振動モードを捨象したことにより、振動的な応答が生じる場合であっても、負荷速度特性補償要素１３の伝達特性のゲインＫ_αを調整することにより、高次振動モードによる影響を低減することができる。
【００９５】
（６）負荷速度特性補償要素１３の伝達特性（１／βまたはＫ_α／β）を、負荷の特性１／Ｇ_fまたは近似特性１／Ｇ_mとノミナル特性１／Ｇ_nとから設計的に決定することができる。よって、負荷３の構造が複雑で試行錯誤的な方法では調整できない場合であっても、負荷３の制御を行うことができる。
【００９６】
（７）負荷速度制御ループＲ２の相対次数を低くするように負荷速度特性補償要素１３の特性を設定することにより、負荷速度制御ループＲ２のゲインを大きくすることができる。すると、外乱Ｔ_dの影響を小さくしてより精密な制御を行うことができる。
【００９７】
尚、本発明のサーボ機構は、上記実施形態にのみ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内において種々変更を加え得ることは勿論である。例えば、負荷としてはリニアモータの移動要素であってもよい。このような場合、低剛性負荷を、リニアモータの移動要素（負荷本体）と、この移動要素に連結され制御対象部を有する付属部とで構成する。さらに、制御対象部の移動速度を検出する負荷速度検出手段を設ける。この負荷速度検出手段としては、リニアモータの固定要素側に設けられ移動要素の移動方向に検出要素を有するスケールと、移動要素に設けられスケールに対する単位時間当たりの移動量を検出する検出ヘッドと、検出ヘッドと制御対象部との間に設けられ制御対象部の基準位置からのずれ量を検出するずれ量検出手段とを備えて構成してもよい。
【００９８】
また、負荷としては、上記実施形態に限らず、モータとの連結部分や負荷自身に低剛性部を有し制御対象部の位置、速度、加速度等が振動的な応答を示すものであれば特に限定されることなく、本発明のサーボ機構により安定に制御される。
【００９９】
【発明の効果】
以上、説明したように本発明のサーボ機構によれば、単一または複数の振動モードを有する低剛性負荷の振動的挙動と外乱の影響を抑制し、低剛性負荷の移動と位置決めを精密に、かつ、速やかに行うことができるという優れた効果を奏し得る。
【図面の簡単な説明】
【図１】本発明のサーボ機構にかかる一実施形態のブロック図である。
【図２】前記実施形態において、モータと負荷とのモデルを示す図である。
【図３】従来のサーボ機構のブロック図を等価変換した図である。
【図４】従来のサーボ機構のブロック図を等価変換した図である。
【図５】従来のサーボ機構のブロック図を等価変換した図である。
【図６】従来のサーボ機構のブロック図を等価変換した図である。
【図７】前記実施形態において、負荷速度特性補償要素にゲイン定数Ｋ_αを加味した図である。
【図８】従来のサーボ機構のブロック図である。
【符号の説明】
１ サーボ機構
２ モータ
３ 負荷
４ モータ速度検出器
５ 負荷速度検出手段
６ モータ速度比較器
７ 駆動力伝達部
８ 負荷速度比較器
９ 積分要素
１０ 位置検出器
１１ 位置比較器
１２ システムゲイン設定要素
１３ 負荷速度特性補償要素
１４ モータ速度特性補償要素
１５ 速度比較器
３１ テーブル
３２ 負荷本体
３３ 付属部
３４ 制御対象部
５１ スケール
５２ 検出ヘッド
５３ 加速度検出器
７６１ 低剛性部分
７６２ 低剛性部分
Ｒ１ 位置制御ループ
Ｒ２ 負荷速度制御ループ
Ｒ３ モータ速度制御ループ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a servo mechanism. For example, the present invention relates to a servo mechanism that drives and controls a low-rigidity load driven by a motor or the like.
[0002]
[Background]
In a servomechanism that controls the position and driving speed of a load that is a driving body driven by a motor, the displacement, speed, and acceleration that occur when the motor is driven by a motor with a low-rigidity part connected to the motor is a vibration response There is one that drives and controls a low-rigidity load.
In such a servomechanism, a servomechanism that suppresses vibrations generated in a low-rigidity load and suppresses disturbance caused by friction or non-linearity of the mechanism is known (for example, Non-Patent Document 1 and Patent Document 1). ).
[0003]
FIG. 8 shows a conventional servo mechanism 100 that performs drive control of a low-rigidity load.
The servo mechanism 100 includes a motor 2 and a low rigidity load 3 driven by the motor 2 and having a low rigidity portion. A motor speed detector 4 that detects the driving speed of the motor 2 is provided between the motor 2 and the low rigidity load 3. The driving speed of the low-rigidity load 3 is detected by the load speed detector 5, and the load displacement P, which is an integral amount of the load speed (integration element 9).₀Is detected by the position detector 10 and output to the position comparator 11. The position comparator 11 is a command position P set and inputted from the outside._cAnd load displacement P₀To the system gain setting element 12 that determines the main value of the response time constant. The system gain setting element 12 is a command speed V of the low rigidity load 3_rIs output to the speed comparator 15.
A first coupling element 161 is connected to the load speed detector 5, and a second coupling element 162 is connected to the motor speed detector 4. The relative order of the transfer functions of the first coupling element 161 and the second coupling element 162 is set to zero. Outputs from the first coupling element 161 and the second coupling element 162 are combined by the combiner 163 and then output to the speed comparator 15. The speed comparator 15 receives the command speed V from the system gain setting element 12._rAnd the output value from the synthesizer 163 are compared, and the difference is output to the speed characteristic compensation element 164. The speed characteristic compensation element 164 outputs the command speed of the motor 2 and inputs it to the motor 2.
In such a configuration, the command position P set and inputted to the position comparator 11_cThe displacement P of the low-rigidity load 3 by the motor 2 according to₀Is feedback controlled.
Here, a position control loop is constituted by a loop in which the output of the position detector 10 is fed back to the position comparator 11 from the position comparator 11 through the motor 2, the low rigidity load 3, and the like. A speed control loop is constituted by a loop in which the output of the synthesizer 163 is fed back to the speed comparator 15 from the speed comparator 15 via the motor 2, the low rigidity load 3, and the like.
[0004]
In such a configuration, the relative order when the characteristic of the low-rigidity load 3 to be controlled is expressed by a transfer function is generally negative from −2 to, for example, −2, −3, and −4. At this time, if the relative degree of the compensation element is negatively large, for example, -1, -2, or -3, the stability of the control system is impaired.
That is, as a compensation element for suppressing vibration, it is desirable that the relative order of the transfer function is zero, and the relative orders of the characteristics of the first coupling element 161 and the second coupling element 162 are set to zero. Then, at this time, the gain constant K of the speed characteristic compensation element 164_νCan be set sufficiently high. Furthermore, the gain constant K_νCan be set to a characteristic determined by the characteristics of the first compensation element 161 and the second compensation element 162.
That is, the dominant characteristic 1 / G of the speed control loop_nCan be determined by the characteristics of the first coupling element 161, the second coupling element 162 and the load 3,
G_n= Α + βG_f
And gain constant K_νIs larger, the command speed V_rAnd load speed V₀Ratio V₀/ V_rIs
V₀/ V_r→ 1 / G_n  (K_ν→ ∞) (Formula 1)
It can be.
At this time, the dominant characteristic 1 / G of the speed control loop_nIs set as a non-vibrating value so that the command speed V_rLoad speed V₀The transmission characteristic of the non-vibration characteristic can be made.
The transfer function of the second coupling element is V₀/ V_rTransfer characteristic of 1 / G_nAnd when
1 / β = α + βG_f    (Formula 2)
Can be determined.
[0005]
[Non-Patent Document 1]
Transactions of the Society of Instrument and Control Engineers, Vol. 27, No. 5, 562/568 (1991)
[Patent Document 1]
Patent Publication No. 2707149
[0006]
[Problems to be solved by the invention]
In the above configuration, when the inertia ratio between the motor 2 and the low-rigidity load 3 is relatively small, the gain constant K_νIs effective because it can be raised sufficiently. Gain constant K_νThis is because the speed control loop can be designed non-vibrating according to (Equation 1) and the characteristic β of the second compensation element 162 can be determined according to (Equation 2). Furthermore, the gain constant K_νBy increasing the value, the influence of disturbance can be reduced.
[0007]
However, when the inertia ratio between the motor 2 and the low-rigidity load 3 is large, the gain constant K of the speed characteristic compensation element 164 of the speed control loop._νCannot be set large. This is because if the gain is increased when the inertia ratio between the motor 2 and the low-rigidity load 3 is large, the instability of the control system increases. Gain constant K_νCannot be increased, the approximate expression of (Expression 1) cannot be used.₀/ V_r1 / G_nThere arises a problem that it is difficult to match the above. In this case, the design of the characteristic β of the second coupling element 162 that is the compensation element cannot be determined by (Equation 2), so that there is a problem that β must be obtained by trial and error. Furthermore, since the gain constant cannot be increased, there arises a problem that the influence of disturbance cannot be reduced.
Further, the conventional configuration can be applied to the case where the low-rigidity load 3 has one vibration mode, but cannot be applied to the case where the low-rigidity load 3 has a plurality of vibration modes such as two or three. There's a problem.
[0008]
The object of the present invention is to solve the conventional problems, suppress the vibrational behavior and disturbance of a low-rigidity load having a single or a plurality of vibration modes, precisely move and position the low-rigidity load, and It is an object of the present invention to provide a servo mechanism that can be performed promptly.
[0009]
[Means for Solving the Problems]
  The servo mechanism according to claim 1, wherein a motor speed control loop having a motor and a motor speed detecting means for detecting a driving speed of the motor, and a load speed detection for detecting a load speed of a low-rigid load driven by the motor. A load speed control loop having a means and a position control loop having a position detection means for detecting the position of the low-rigidity load, and the load speed control loop performs forward compensation for the characteristics of the load speed control loop. The characteristic 1 / β of the control characteristic compensation element is expressed as 1 / Gn, where the transfer characteristic of the low rigidity load is 1 / Gf and the dominant characteristic of the load speed control loop is a non-vibrating characteristic. , Gn and Gf are set equal to each other, 1 / β = Gf / (Gn-1).
  The servo mechanism according to claim 2 is a motor speed control loop having a motor and a motor speed detecting means for detecting a driving speed of the motor, and a load speed detection for detecting a load speed of a low-rigid load driven by the motor. A load speed control loop having a means and a position control loop having a position detection means for detecting the position of the low-rigidity load, and the load speed control loop performs forward compensation for the characteristics of the load speed control loop. A characteristic compensation element, wherein the characteristic 1 / β of the control characteristic compensation element is an approximate characteristic of the transfer characteristic of the low-rigid load 1 / G m The dominant characteristic of the load speed control loop is 1 / G as a non-vibrating characteristic. n And G n And G m When the orders of are set equal, 1 / β = G m / (G n -1).
[0010]
According to such a configuration, the motor speed control loop, the position control loop, and the load speed control loop become independent loops. At this time, in each loop, it is possible to independently provide compensation elements for compensating the characteristics of each loop. For example, by providing a motor characteristic compensator and a load speed compensation element in each of the motor speed control loop and the load speed control loop, a stable control system can be designed without depending on the inertia ratio of the motor and the low rigidity load. be able to. In particular, by providing a load speed control loop, a compensator for load characteristics can be provided independently. Therefore, if the load speed control loop is provided with a control characteristic compensation element that makes the relative order zero corresponding to the vibration mode of the load speed, the relative order of the loop transfer characteristic of the load speed control loop is reduced, and the load of low rigidity load is reduced. Speed can be a non-vibrating characteristic with fast response.
In addition, if the gain is set large in each loop, the influence of disturbance entering each loop can be reduced. In particular, the load disturbance can be suppressed more than before by providing the load speed control loop independently. .
[0013]
In such a configuration, when the characteristic 1 / β of the control characteristic compensation element is determined by the above formula, the relative order of 1 / β becomes zero. At this time, the dominant characteristic of the load speed control loop is set as a non-vibrating characteristic._nCan be. For example, 1 / G in which the characteristics of the load speed control loop are set as primary or secondary non-vibration characteristics_nIt can be designed to the characteristics represented by Then, the response of the load speed control loop can be made non-oscillating, and a low-rigidity load can be controlled stably.
[0014]
Here, the relative order means (order of the s polynomial in the numerator) − (degree of the s polynomial in the denominator) in the transfer function representing the characteristics of the control system. If this relative order becomes negatively large, particularly -3 or more (-3, -4, ...), control becomes impossible (oscillation state). Since the relative order of the low-rigidity load is generally -2, -3, -4, etc., if the relative order of the compensation element itself is as large as -1, -2, -3,. Becomes oscillating.
[0015]
Therefore, the transfer characteristic 1 / G of the low rigidity load required experimentally or analytically._fThe characteristic of the load speed control loop to be realized (nominal characteristic) 1 / G_nThe order of 1 / G_fSet equal to
1 / β = G_f/ (G_n-1)
Thus, the characteristic 1 / β of the control characteristic compensation element is determined. Then, the relative order of 1 / β becomes zero. At this time, the transfer characteristic of the load speed control loop can be set freely to some extent. For example, the non-vibrating 1 / G expressed by the primary or secondary characteristic_nCan be. That is, the response of the load speed control loop can be made non-vibrating, and a low-rigidity load can be controlled stably.
[0016]
Here, the transfer characteristic 1 / G of the low rigidity load_fIn some cases, parameters such as the natural angular frequency and the damping coefficient that determine the transfer characteristics of a low-rigid load fluctuate or cannot be accurately grasped. Therefore, the range of parameter fluctuations such as the natural angular frequency and damping coefficient of the low-rigidity load is estimated, and the transfer characteristic 1 / G fixed at a natural angular frequency lower than the natural angular frequency corresponding to each vibration mode of the low-rigidity load._mSet. This 1 / G_mAgainst
1 / β = G_m/ (G_n-1)
Thus, the characteristic 1 / β of the control characteristic compensation element is set. Then, even if the transfer characteristic of the low-rigidity load is not uniquely determined, the response of the load speed control loop can be made non-vibrating and the low-rigidity load can be stably controlled.
[0017]
According to a fourth aspect of the present invention, in the servo mechanism according to the third aspect, the approximate characteristic of the transfer characteristic of the low-rigid load is 1 / G._m, 1 / G_fG_mThe order of is G_fIt is characterized by being less than the order of.
[0018]
The servo mechanism according to claim 5 is the servo mechanism according to any one of claims 1 to 4, wherein a gain K is added to the characteristic 1 / β of the control characteristic compensation element._αK_α/ Β, and a gain margin with respect to a higher-order vibration mode in the transfer characteristic of the low-rigidity load is adjusted.
[0019]
Low rigidity load 1 / G_fIf the structure of is complicated, 1 / G_fIt is difficult to accurately grasp the higher order vibration modes. In such a case, the resonance and anti-resonance frequencies of the higher-order vibration modes have high values, but in this frequency band, 1 / G_fThe gain characteristic is usually smaller than 1. So, 1 / G_mAnd 1 / G_nThe order of 1 / G_fEven if the lower order is set and the higher order vibration mode is not considered, it is possible to avoid the appearance of the higher order vibration mode with a low rigidity load. 1 / G_m, 1 / G_nThe order of 1 / G_fBy setting the order lower than the order, the burden of control calculation can be reduced. Then, the control cycle can be shortened and the real-time performance of the control can be improved.
[0020]
1 / G_nWhen the higher-order vibration mode is not taken into consideration, the higher-order vibration mode may become apparent and a vibrational response may appear. In this case, for example, the control characteristic compensation element 1 / β and the gain K_αThis gain K_αBy adjusting this, the low-rigidity load can be controlled in a non-vibrating manner. For example, by reducing the gain, it is possible to reduce the influence of the vibrational response due to the higher-order vibration mode.
While adjusting the gain, no change is made to the value of 1 / β, so the nominal characteristic 1 / G of the load speed control loop_nWhile maintaining the characteristics of the control characteristic compensation element set so as to realize the above, it is possible to cope with the influence of higher-order vibration modes.
[0021]
The servo mechanism according to claim 6 is the servo mechanism according to any one of claims 1 to 5, wherein the low-rigidity load is movably provided on a fixed base and is driven by the motor. A load main body and an appendage unit connected to the load main body and having a control target part are provided, and load speed detection means for detecting a moving speed of the control target part is provided, and the load speed detection means includes the A scale provided on the base side and having a detection element in the movement direction of the load body; a detection head provided on the load body for detecting a movement amount per unit time relative to the scale; and provided in the control target unit And an acceleration detection means for detecting the acceleration of the control target portion.
[0022]
According to such a configuration, the load main body is driven on the base by driving the motor. Then, the attachment part is moved together with the load main body. At this time, the movement speed per unit time of the load main body is detected by the detection head on the load main body on the amount of movement per unit time with respect to the scale on the base side. Further, the acceleration generated in the control target part is detected by the acceleration detecting means. By calculating the speed information generated in the control target part by the integration process from the acceleration information detected by the acceleration detection means and adding it to the movement speed of the load main body detected by the detection head, the precise movement speed of the control target part is obtained. That is, it is possible to detect the load speed that is the control target. For example, if the attachment portion is low in rigidity, the attachment portion behaves like a vibration, so that the movement speed of the control target portion does not match the movement speed of the load body. However, according to the present invention, since the acceleration detection means is provided in the control target part and the movement speed of the control target part obtained from the acceleration generated in the control target part is taken into account, the movement speed (load speed) of the control target part is determined. You can know precisely. By accurately detecting the load speed and performing feedback control based on the detected value, it is possible to precisely drive and control the load, particularly the control target part.
[0023]
A servo mechanism according to a seventh aspect is the servo mechanism according to any one of the first to fifth aspects, wherein the low-rigidity load is connected to a load main body constituted by a moving element of a linear motor, and the load main body. And a load speed detecting means for detecting a moving speed of the control target section, and the load speed detection means is provided on a fixed element side of the linear motor. A scale having a detection element in the movement direction of the load body; a detection head provided on the load body for detecting a movement amount per unit time relative to the scale; and provided between the detection head and the control target unit. It is characterized by comprising deviation amount detecting means for detecting the deviation amount from the reference position of the control target part.
[0024]
According to such a configuration, the load main body is driven with respect to the fixed element of the linear motor by the motor thrust of the linear motor. Then, the attachment part is moved together with the load main body. At this time, the moving speed per unit time of the load main body is detected by the detection head on the load main body on the amount of movement per unit time with respect to the scale on the fixed element side. When the load main body is moved, elastic deformation occurs according to the rigidity of the load main body and the attachment portion, and the control target portion is deviated from the reference position by the elastic deformation. This deviation amount is detected by deviation amount detection means. As the deviation amount detection means, for example, a strain gauge provided between the detection head and the control target unit can be used.
The amount of deviation detected by the deviation amount detection means is differentiated to calculate speed information generated in the control target part, and by adding to the moving speed of the load main body detected by the detection head, the precise movement of the control target part is performed. The speed, that is, the load speed to be controlled can be detected. For example, if the attachment portion is low in rigidity, the attachment portion behaves like a vibration, so that the movement speed of the control target portion does not match the movement speed of the load body. However, according to the present invention, since the acceleration detection means is provided in the control target part and the movement speed of the control target part obtained from the acceleration generated in the control target part is taken into account, the movement speed (load speed) of the control target part is determined. You can know precisely.
By accurately detecting the load speed and performing feedback control based on the detected value, it is possible to precisely drive and control the load, particularly the control target part.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of the servo mechanism of the present invention.
The servo mechanism 1 has a motor 2 and a load 3 as a driving body driven by the motor 2 and having a low rigidity portion. Transfer characteristic of motor 2 is 1 / G_rAnd the transfer characteristic of load 3 is 1 / G_fRepresented by Between the motor 2 and the load 3, a motor speed detector 4 is provided as a motor speed detecting means for detecting the driving speed of the motor 2. The load 3 is provided with load speed detecting means 5 for detecting the driving speed of the load 3.
[0026]
FIG. 2 shows models of the motor 2, the motor speed detector 4, the load 3, and the load speed detection means 5.
The motor 2 is a coil motor that includes a drive amplifier 21 and includes a rotor 22 that rotates according to a command value of the current amplified by the drive amplifier 21. A motor speed detector 4 that detects the rotational speed of the rotor 22 is directly connected to the rotor 22 of the motor 2. The motor driving speed detected by the motor speed detector 4 is output to the motor speed comparator 6 (see FIG. 1).
The driving force of the motor 2 is transmitted to the load 3 by the driving force transmission unit 7. The drive force transmission unit 7 is moved by a drive shaft 71 directly connected to the rotor 22 of the motor 2 via the motor speed detector 4 and a rotation / linear motion conversion mechanism 72 that converts rotation of the drive shaft 71 into linear motion. And a connecting portion 75 that connects the moving member 74 and the load 3. A low-rigidity portion 761 such as a spring exists in the middle of the drive shaft 71. The connecting portion 75 has a low-rigidity portion 762 such as a spring or a dashpot, for example.
[0027]
The load 3 is slidable in one direction on a table 31 that is a fixed base, and the table 3 is parallel to the paper surface in FIG. 2 by the driving force of the motor 2 transmitted by the driving force transmission unit 7. A load main body 32 to be driven and an attachment 33 connected to the load main body 32 and having a control target portion 34 at the tip thereof are configured. At the tip of the attachment portion 33, for example, a measuring element 341 as a control object that is moved along the surface of the object to be measured is provided, and the measuring machine is driven by the load 3 and the servo mechanism 1 that drives and controls the load 3. It is configured.
The load 3 is provided with load speed detecting means 5 for detecting the moving speed of the load 3. The load speed detecting means 5 includes a scale 51 provided on the table 31 side and having a detection element in the moving direction of the load main body 32, and a detection head 52 provided on the load main body 32 and detecting a movement amount per unit time with respect to the scale 51. And an acceleration detector 53 as an acceleration detecting means provided in the control target unit 34 for detecting the acceleration of the control target unit 34.
[0028]
The scale 51 and the detection head 52 constitute, for example, a photoelectric, capacitive or magnetic linear encoder, and detect the amount of movement of the load body 32 per unit time relative to the table 31, that is, the driving speed. To do. The acceleration detector 53 detects acceleration generated in the control target unit 34. The acceleration information of the control target section 34 detected by the acceleration detector 53 is integrated and converted into speed information, and then added to the driving speed of the load main body 32 detected by the detection head 52. Then, the exact drive speed of the control target unit 34, that is, the load speed V₀Is calculated.
[0029]
Load speed V detected by the load speed detecting means 5₀Information is branched, one is output to the load speed comparator 8, and the other is the load displacement information P which is the integral amount of the load speed (integration element 9).₀Is output to the position detector 10. The position detector 10 receives load displacement information P₀Is output to output means such as an external monitor or printer, while load displacement information P₀Is output to the position comparator 11.
[0030]
The position comparator 11 receives command position information P that is set and input from the outside and commands the position of the load 3._cAnd load displacement information P from the position detector 10₀And compare. The position comparator 11 outputs this comparison result to the system gain setting element 12 (transfer characteristic Ks) that determines the main value of the response time constant. Transfer characteristic K of system gain setting element 12_sIs the command position P_cTo load position P₀Is a parameter that determines the time constant of the response until the position P of the load 3₀Is the command position P_cIs set not to overshoot.
The system gain setting element outputs the command speed Vr of the load 3 to the load speed comparator 8.
[0031]
The load speed comparator 8 receives the command speed V from the system gain setting element 12._rAnd load speed information V output from the load speed detecting means 5₀And the difference is output to a load speed characteristic compensation element 13 (transfer characteristic 1 / β) as a control characteristic compensation element. The command speed V of the motor 2 from the load speed characteristic compensation element 13_mrIs output to the motor speed comparator 6.
[0032]
The motor speed comparator 6 receives the motor command speed V from the load speed characteristic compensation element 13._mrAnd the motor speed V from the motor speed detector 4_mIs compared with the motor speed characteristic compensation element 14 (transfer characteristic K_νG_ν). The output from the motor speed characteristic compensation element 14 is input to the motor 2 as a command current value.
Further, between the load 3 and the load speed detecting means 5, there is a disturbance T caused by friction and non-linearity of the mechanism._dWill be added.
[0033]
In such a configuration, the position control loop R1 is configured by a loop from the position comparator 11 and the system gain setting element 12 to the position detector 10 and returning to the position comparator 11 again.
A load speed control loop R2 is configured by a loop from the load speed comparator 8 and the load speed characteristic compensation element 13 to the load speed detecting means 5 and again to the load speed comparator 8.
A motor speed control loop R3 is constituted by a loop from the motor speed comparator 6 and the motor speed characteristic compensation element 14 to the motor speed detector 4 and again to the motor speed comparator 6.
[0034]
In such a configuration, the setting of the transmission characteristic 1 / β of the load speed characteristic compensation element 13 and the transmission characteristic KνGν of the motor speed characteristic compensation element 14 that reduce the vibration response due to the low rigidity of the load 3 will be described. .
[0035]
First, the transfer characteristic K of the motor speed characteristic compensation element 14_νG_νThe setting of will be described.
Equivalent conversion is performed from the block diagram of FIG. 8 described in the background art to separate the first coupling element 161 and the second coupling element 162 (see FIG. 3). Further, when the second coupling element 162 and the first coupling element 161 are converted from the feedback element to the forward compensation element (see FIGS. 4 and 5), the block diagram shown in FIG. 5 is obtained. Here, when the characteristic α of the first coupling element 161 is set to 1, the block diagram shown in FIG. 6 is obtained.
[0036]
In the block diagram of FIG. 6, at first glance, the motor speed control loop, the load speed control loop, and the position control loop appear to be controlled independently, but the same transfer function β is used for the motor speed control loop and the load speed control loop. It is a problem that appears.
Further, the transfer function β is inversely related between the load speed control loop and the motor speed control loop. Therefore, if the transfer function β is set so that the characteristic compensation of the motor 2 is performed in the motor speed control loop, the characteristic compensation of the load 3 cannot be performed, and the characteristic compensation of the load 3 is performed in the load speed control loop. When the transfer function β is set, the characteristic compensation of the motor 2 cannot be performed. That is, in the conventional state (FIG. 8), it can be understood that characteristics of both the motor 2 and the load 3 cannot be compensated.
[0037]
Here, in the motor speed control loop, the compensator 141 that compensates the characteristics of the motor 2 does not directly compensate the characteristics of the load 3. Therefore, the compensator 164 of the motor 2 does not need to include the transfer function β in the motor speed control loop, and simply the gain constant K_νIncluding K_νG_νIt is good. Then, the block diagram of FIG. 1 of this embodiment is obtained.
[0038]
According to such a configuration, the position control loop R1, the load speed control loop R2, and the motor speed control loop R3 are completely independent loops. Therefore, in each loop, it is possible to provide compensation elements for compensating the characteristics of each loop independently. In particular, since the load speed control loop R2 becomes independent, the load speed characteristic compensation element 13 can be provided independently as a compensator for the load characteristics.
[0039]
Next, the setting of the characteristic 1 / β of the load speed characteristic compensation element 13 that suppresses the vibration characteristic of the load 3 will be described.
First, the characteristic 1 / G of the load 3 to be controlled_fIs determined experimentally or analytically. s is the Laplace operator, ω_fThe natural angular frequency of the vibration of the load, ζ_fIs the damping coefficient, and h is the number of vibration modes, the characteristics of the load 3 are
[0040]
[Expression 1]

[0041]
It is represented by However, 0 <ζ_fk<1, h is the number of vibration modes.
[0042]
Characteristics of load 3 1 / G_fFor the load speed control loop R2, the dominant characteristic (nominal characteristic) to be realized is 1 / G._n1 / G_nThe relative order of 1 / G_fAnd a non-vibration characteristic as expressed in the first or second order. Such nominal characteristics 1 / G_nIs represented by a polynomial expression:
[0043]
[Expression 2]

[0044]
It is represented by However, 1 ≦ ζ_np, H is the number of vibration modes. Where ω_npIs ω_fkLarger than, for example, ω_fkIs set to about twice as large. Also, ζ_npIs set to a value approximate to 1.
[0045]
Here, the transfer characteristic 1 / β of the load speed characteristic compensation element 13 is
1 / β = G_f/ (G_n-1)
And set. Then, the relative order of the transfer characteristic 1 / β of the load speed characteristic compensation element 13 can be set to zero. At this time, the relative order of the one-cycle transfer characteristic of the load speed control loop R2 is lowered, so that the control system can be stabilized while suppressing the vibrational response. That is, the command speed V which is the transfer characteristic of the load speed control loop R2._rAnd load speed V₀Ratio of nominal characteristics 1 / G_nCan be realized. That is, the response of the load speed control loop R2 can be made non-vibrating and the load 3 can be controlled stably.
Furthermore, since the load speed control loop R2 can be stabilized, the gain of the load speed control loop R2 can be increased. Then, the influence of disturbance can be reduced.
[0046]
Also, the characteristic 1 / G of the load 3_fMay not be accurately grasped. Characteristics of load 3 1 / G_fIs not accurately grasped, approximate characteristic 1 / G of the transfer characteristic of load 3_mSet.
[0047]
Approximate characteristic of load 3 1 / G_mFirst, the damping coefficient ζ, which is a parameter of the characteristics of the load 3, is set._fAnd the natural angular frequency ω_fEstimate the fluctuation range. With respect to the natural angular frequency, the natural angular frequency of the approximate characteristic of the load 3 is fixed at a value smaller than the natural angular frequency at which the fluctuation range is estimated, for example, a natural angular frequency of about 70%. The attenuation coefficient is fixed at a recommended value determined within a certain range. Approximate characteristic 1 / G of the load 3 set in this way_mIs represented by a polynomial expression:
[0048]
[Equation 3]

[0049]
It becomes. However, 0 <ζ_mk<1, h is the number of vibration modes.
[0050]
Approximate characteristic 1 / G of this load 3_mIn contrast, the dominant characteristic (nominal characteristic) 1 / G to be realized by the load speed control loop R2_n, Relative order 1 / G_mAnd set to non-vibrating characteristics. Where ω_npIs ω_mkFor example, ω_mkIs set to about twice as large. Also, ζ_npIs set to a value approximating 1 to control characteristics 1 / G_nIs non-vibrating.
[0051]
Approximate characteristic 1 / G of this load 3_mTo set the characteristic 1 / β of the load speed characteristic compensation element,
1 / β = G_m/ (G_n-1)
And Then, even if the characteristic of the load 3 cannot be accurately grasped and cannot be determined uniquely, the characteristic 1 / β of the load speed characteristic compensation element 13 can be set.
[0052]
At this time, the approximate characteristic 1 / G of the load 3_mSince the natural angular frequency is set to a value that is at least smaller than the minimum value that is the worst value of the estimated fluctuation range, this approximate characteristic 1 / G is obtained even in the worst case._mCan handle enough.
Nominal characteristic 1 / G_nAnd approximate characteristic 1 / G of load 3_mTherefore, the relative order of the characteristic 1 / β of the load speed characteristic compensation element 13 can be made zero. Therefore, the response of the load speed control loop R2 is expressed as a nominal characteristic 1 / G._nIt can be. As a result, the response of the load speed control loop R2 can be made non-vibrating and the load 3 can be controlled stably.
[0053]
The structure of the load 3 may be complicated, and the load 3 may have a very high order vibration mode. In such a case, the approximate characteristic 1 / G of the load 3_mIt is difficult to accurately grasp the higher-order vibration mode of the load 3 when estimating. In such a case, the higher-order vibration mode of the load 3 is discarded, and the approximate characteristic 1 / G of the load 3 corresponding to the lower-order vibration mode._mMay be set. In general, the gain characteristics of the low-order vibration mode are large while the gain of the high-order vibration mode is small. Therefore, even if the high-order vibration mode is omitted and approximated, the influence of the high-order vibration mode is small. Approximation characteristics 1 / G set by discarding higher-order vibration modes in this way_mIf the transfer characteristic 1 / β of the load speed characteristic compensation element 13 is obtained by using, the amount of calculation can be reduced. As a result, the control cycle can be shortened and the real-time performance of the control can be improved.
[0054]
Approximate characteristic of load 3 1 / G_mWhen the higher-order vibration mode of the load 3 is discarded when setting, the influence of the discarded higher-order vibration mode may appear. In such a case, the gain K is added to the characteristics of the load speed characteristic compensation element 13._αIn consideration of the above, the gain margin of the load speed control loop R2 is adjusted.
[0055]
FIG. 7 shows the gain K in the load speed characteristic compensation element 13._α, The characteristic of the load speed characteristic compensation element 13 is_αA block diagram when represented as / β is shown. The characteristics of the motor speed control loop R3 are collectively expressed as 1 / Gνβ.
[0056]
Where gain K_αBy setting small, it is possible to further reduce the influence of the high-order vibration mode having a small gain. Gain K_αAs the value of, for example, setting to a value close to 1 is exemplified.
[0057]
Next, a specific design of the characteristic Kα / β of the load speed characteristic compensation element 13 will be described by exemplifying a case where the vibration mode of the load 3 is 2 (h = 2).
Load 3 characteristics 1 / G_fIs expressed as follows when h = 2.
[0058]
[Expression 4]

[0059]
Where ω_f1<Ω_f2, 0 <ζ_f1<1, 0 <ζ_f2<1, 1 / G_fIs 0 <ζ_f1<1, 0 <ζ_f2When <1, vibration characteristics are obtained.
[0060]
Characteristics of motor speed control loop R3 1 / G_νβFor the following double root (-1 / ω_νβ) Of the motor speed characteristic compensation element 14 of FIG._νG_νDo the design.
[0061]
[Equation 5]

[0062]
Where ω_νβIs the response natural angular frequency of the motor speed control loop R3.
At this time, the command load speed V_mrTo load speed V₀The loop transfer function of the load speed control loop up to is as follows.
[0063]
[Formula 6]

[0064]
That is, the load speed V₀And command speed V_mrIs the ratio of V₀/ V_mrNominal model (design model to be realized) 1 / G_nThe transmission characteristic K of the load speed characteristic compensation element 13 for_α/ Β is obtained. For this purpose, a load speed characteristic compensation element K for which the following equation holds:_α/ Β is obtained.
[0065]
[Expression 7]

[0066]
Thus, the characteristic K of the load speed characteristic compensation element 13_α/ Β can be obtained as follows.
[0067]
[Equation 8]

[0068]
Here, the characteristic 1 / G of the load 3_fAnd nominal characteristic G_nIs specifically determined, the characteristic K of the load speed characteristic compensation element 13_α/ Β can be obtained.
Therefore, next, the characteristic 1 / G of the load 3_fAnd nominal characteristic G_nExplain how to define.
[0069]
Characteristics of load 3 1 / G_fMay be difficult to obtain accurately, and instead, approximate model 1 / G of load 3_mSet.
[0070]
[Equation 9]

[0071]
Natural angular frequency ω_m1, Ω_m2Is the load characteristic 1 / G_fA parameter having a natural angular frequency lower than the natural angular frequency corresponding to each vibration mode. That is, ω_m1<Ω_f1<Ω_m2<Ω_f2And Then approximate load characteristics 1 / G_mIs as follows.
[0072]
[Expression 10]

[0073]
Where z_Four, Z_Three, Z₂, Z₁, Z₀Is as follows.
z_Four= 1
z_Three= 2 (ζ_m1ω_m1+ Ζ_m2ω_m2)
z₂= Ω_m1 ²+ 4ζ_m1ζ_m2ω_m1ω_m2+ Ω_m2 ²
z₁= 2 (ζ_m1ω_m2+ Ζ_m2ω_m1) Ω_m1ω_m2
z₀= Ω_m1 ²ω_m2 ²
[0074]
Next, nominal model 1 / G_nIs 1 / G_mCorresponding to, it consists of the product of the secondary standard form as follows.
[0075]
[Expression 11]

[0076]
Where the nominal model 1 / G_nThe first term on the right side of is the characteristic of the main response of the nominal model. Therefore, the natural angular frequency is ω_n1<Ω_n2And ω_n1Is the response angular frequency ω of the motor speed control loop R3, which is a minor loop of the load speed control loop._νβFor ω_n1<Ω_νβSet within the range. Also, the damping coefficient ζ_n1Is 1 or more so as not to cause vibrational behavior.
For the second term on the right side, ω so that the first term, which is the main response of the nominal model, is not affected._νβ<Ω_n2And
Therefore, 1 / (G_n-1) is as follows.
[0077]
[Expression 12]

[0078]
Where p_Four, P_Three, P₂, P₁, P₀Is as follows.
p_Four= 1,
p_Three= 2 (ζ_n1ω_n1+ Ζ_n2ω_n2)
p₂= Ω_n1 ²+ 4ζ_n1ζ_n2ω_n1ω_n2+ Ω_n2 ²
p₁= 2 (ζ_n1ω_n2+ Ζ_n2ω_n1) Ω_n1ω_n2
p0 = 0
[0079]
Therefore, load speed characteristic compensation element K_α/ Β is as follows.
[0080]
[Formula 13]

[0081]
In this case, the order of the numerator (= 6th order)> the order of the denominator (= 4th order) does not become proper (the order of the numerator is less than the order of the denominator), and non-vibration characteristic compensation cannot be performed. . Therefore, by adding the following elements, a compensation element is formed in which the relative order is 0, where the numerator order (= 6th order) = denominator order (= 6th order).
[0082]
[Expression 14]

[0083]
Where c is a constant and the motor speed response angular frequency ω_νβOn the other hand, if c = about 5, K_αThe effect on / β characteristics is small. At this time, the characteristic K of the load speed characteristic compensation element 13_α/ Β is as follows.
[0084]
[Expression 15]

[0085]
Where ω_m1<Ω_f1<Ω_m2<Ω_f2<Ω_n1<Ωνβ <ω_n2It is.
By adding a compensation element to the load speed characteristic compensation element 13 so as to keep the relative order zero based on the basic form of (Expression 3), the characteristics can be further improved. For example, system gain K_sIs equivalent to the frequency ω = K_sWhen it is desired to improve the characteristics of the load speed control loop R2 (gain reduction and phase delay) by increasing the gain at (rad / s), the following elements are added.
[0086]
[Expression 16]

[0087]
This is effective in preventing overshoot from occurring in the response of the position control loop R1 when the position control loop R1 is configured.
At this time, the characteristic K of the load speed characteristic compensation element 13_α/ Β is as follows.
[0088]
[Expression 17]

[0089]
In this case, ω is K_sTo 10K_sThe gain characteristic at (rad / s) becomes −40 dB / dec and ω = K_sThe gain at (rad / s) can be increased by about 10 times.
[0090]
As described above, according to such a configuration, the following effects can be obtained.
(1) The acceleration detector 53 is provided in the control target part 34 of the load 3, and the integrated value of the acceleration detected by the acceleration detector 53 is added to the moving speed of the load main body 32 detected by the detection head 52. Then, it is possible to accurately detect the driving speed of the control target unit 34 that is a target unit that is truly desired to be controlled. By accurately feeding back the detected driving speed of the control target unit 34, the control target unit 34 can be precisely controlled.
[0091]
(2) The motor speed control loop R3, the load speed control loop R2, and the position control loop R1 are independent loops. At this time, the motor speed characteristic compensation element 14 and the load speed characteristic compensation element 13 do not include the same transfer function. Therefore, each loop can be made completely independent, and an optimal compensation element can be provided in each loop. That is, an optimum compensation element can be provided for each of them regardless of the inertia ratio between the motor 2 and the load 3 or the like. In particular, regarding the stability of the load speed control loop R2, the transfer characteristic (1 / β or K_α/ Β) can be set by design from the characteristics of the load 3 and the nominal characteristics. In other words, the relative order of the transfer characteristic of the load speed control loop R2 can be lowered, and a non-vibration nominal characteristic for realizing the one-round transfer characteristic of the load speed control loop R2 can be obtained. Therefore, in determining the characteristics of the load speed characteristic compensation element 13, it is possible to save the trouble of taking a trial and error method.
[0092]
(3) Load 3 characteristics 1 / G_fEven if it is not accurately obtained, the approximate characteristic 1 / G of the load 3_mThe load 3 can be controlled by using. Approximate characteristic of load 3 1 / G_mIs determined, the natural angular frequency smaller than the minimum value in the fluctuation range of the natural angular frequency of the load 3 is set as the natural angular frequency of the approximate characteristic. Therefore, even in the worst case, the load can be controlled stably.
[0093]
(4) When the load 3 is complicated and has a higher-order vibration mode, the higher-order vibration mode is discarded and the approximate characteristic 1 / G of the load 3_mSet. Then, the calculation burden on the control system can be reduced. Therefore, the control cycle can be shortened and the real-time performance of the control can be improved.
[0094]
(5) Approximate characteristic 1 / G of load 3_mEven when a vibration response occurs due to the removal of the higher-order vibration mode in setting, the gain K of the transfer characteristic of the load speed characteristic compensation element 13_αBy adjusting, the influence of the higher-order vibration mode can be reduced.
[0095]
(6) Transfer characteristic of the load speed characteristic compensation element 13 (1 / β or K_α/ Β) is the load characteristic 1 / G_fOr approximate characteristics 1 / G_mAnd nominal characteristics 1 / G_nAnd can be determined by design. Therefore, even when the structure of the load 3 is complicated and cannot be adjusted by a trial and error method, the load 3 can be controlled.
[0096]
(7) The gain of the load speed control loop R2 can be increased by setting the characteristics of the load speed characteristic compensation element 13 so as to lower the relative order of the load speed control loop R2. Then, disturbance T_dIt is possible to perform more precise control by reducing the influence of.
[0097]
The servo mechanism of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the scope of the present invention. For example, the load may be a moving element of a linear motor. In such a case, the low-rigidity load is constituted by a moving element (load body) of the linear motor and an attached part that is connected to the moving element and has a control target part. Furthermore, a load speed detecting means for detecting the moving speed of the control target part is provided. As the load speed detection means, a scale provided on the fixed element side of the linear motor and having a detection element in the moving direction of the moving element, a detection head provided on the moving element and detecting a moving amount per unit time with respect to the scale, A displacement amount detection unit that is provided between the detection head and the control target unit and detects a shift amount from the reference position of the control target unit may be provided.
[0098]
In addition, the load is not limited to the above-described embodiment, and in particular, if the portion connected to the motor or the load itself has a low-rigidity portion and the position, speed, acceleration, etc. of the control target portion show a vibration response. Without being limited, it is stably controlled by the servo mechanism of the present invention.
[0099]
【The invention's effect】
As described above, according to the servo mechanism of the present invention, the vibration behavior and disturbance of a low-rigidity load having a single or a plurality of vibration modes are suppressed, and the movement and positioning of the low-rigidity load are precisely controlled. And the outstanding effect that it can perform rapidly can be show | played.
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment according to a servo mechanism of the present invention.
FIG. 2 is a diagram illustrating a model of a motor and a load in the embodiment.
FIG. 3 is a diagram obtained by equivalently converting a block diagram of a conventional servo mechanism.
FIG. 4 is a diagram obtained by equivalently converting a block diagram of a conventional servo mechanism.
FIG. 5 is a diagram obtained by equivalently converting a block diagram of a conventional servo mechanism.
FIG. 6 is a diagram obtained by equivalently converting a block diagram of a conventional servo mechanism.
FIG. 7 shows a gain constant K as a load speed characteristic compensation element in the embodiment._αFIG.
FIG. 8 is a block diagram of a conventional servo mechanism.
[Explanation of symbols]
1 Servo mechanism
2 Motor
3 Load
4 Motor speed detector
5 Load speed detection means
6 Motor speed comparator
7 Driving force transmission part
8 Load speed comparator
9 Integration elements
10 Position detector
11 Position comparator
12 System gain setting elements
13 Load speed characteristics compensation element
14 Motor speed characteristic compensation factor
15 Speed comparator
31 tables
32 Load body
33 Attachment
34 Controlled part
51 scale
52 Detection head
53 Acceleration detector
761 Low rigidity part
762 Low rigidity part
R1 position control loop
R2 load speed control loop
R3 Motor speed control loop

Claims (6)

A motor speed control loop having a motor and motor speed detecting means for detecting the driving speed of the motor;
A load speed control loop having load speed detection means for detecting a load speed of a low rigidity load driven by the motor ;
; And a position control loop having a position detecting means for detecting a position of the low rigidity load,
The load speed control loop is:
A control characteristic compensation element for forward-compensating the characteristic of the load speed control loop is provided,
The characteristic 1 / β of the control characteristic compensation element is
When the transfer characteristic of the low-rigidity load is represented as 1 / G f and the dominant characteristic of the load speed control loop is represented as 1 / G n as a non-vibration characteristic, the orders of G n and G f are set equal to 1 / Β = G f / (G n −1) . A motor speed control loop having a motor and motor speed detecting means for detecting the driving speed of the motor;
A load speed control loop having load speed detection means for detecting a load speed of a low rigidity load driven by the motor ;
; And a position control loop having a position detecting means for detecting a position of the low rigidity load,
The load speed control loop is:
A control characteristic compensation element for forward-compensating the characteristic of the load speed control loop is provided,
The characteristic 1 / β of the control characteristic compensation element is
When the approximation characteristic of the transmission characteristic of the low-rigidity load is 1 / G m , the dominant characteristic of the load speed control loop is 1 / G n as a non-vibration characteristic, and the orders of G n and G m are set equal 1 / β = G m / (G n −1) . The servomechanism according to claim 2,
When the approximate characteristic of the transfer characteristic of the low rigidity load is 1 / Gm and the transfer characteristic of the low rigidity load is expressed as 1 / Gf,
A servo mechanism characterized in that the order of Gm is equal to or less than the order of Gf. The servomechanism according to any one of claims 1 to 3,
A servo mechanism characterized in that a gain Kα is added to a characteristic 1 / β of the control characteristic compensation element to obtain a Kα / β, and a gain margin for a higher-order vibration mode in a transmission characteristic of the low-rigid load is adjusted. The servomechanism according to any one of claims 1 to 4,
The low-rigidity load is configured to include a load main body that is movably provided on a fixed base and is driven by the motor, and an attachment that is connected to the load main body and has a control target portion.
A load speed detecting means for detecting a moving speed of the control target unit is provided;
The load speed detection means includes a scale provided on the base side and having a detection element in the moving direction of the load main body, a detection head provided on the load main body and detecting a movement amount per unit time with respect to the scale, A servo mechanism comprising: an acceleration detection unit provided in the control target unit for detecting an acceleration of the control target unit. The servomechanism according to any one of claims 1 to 4,
The low-rigidity load is configured to include a load main body configured by a moving element of a linear motor, and an attachment unit connected to the load main body and having a control target unit,
A load speed detecting means for detecting a moving speed of the control target unit is provided;
The load speed detecting means is a scale provided on the fixed element side of the linear motor and having a detection element in the moving direction of the load main body, and a detection provided for detecting the amount of movement per unit time relative to the scale provided in the load main body. A servo mechanism comprising: a head; and a deviation amount detection unit that is provided between the detection head and the control target unit and detects a shift amount of the control target unit from a reference position. .

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