JP2004297901A - Control device for brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a brushless motor that can stably drive the brushless motor at all times, even if load torque abruptly changes. <P>SOLUTION: The control device comprises a motor control device 5 and can stably drive the brushless motor 51 in accordance with the load torque by commutation operation, on the basis of a torque current estimate value, when the load torque abruptly changes. The motor control device 5 is constituted of a current detection circuit 4, that converts a current flowing to an armature winding of the brushless motor 51 to a voltage, and detects it; a sample hold means 23 that sample-holds a detected DC current value and outputs the torque current estimated value; a commutation target current value operation means 24 that operates a commutation target current value, based on the torque current estimation value; a commutation command output means 25 that outputs a commutation command, when the DC current value detected at the current detection circuit 4 exceeds the commutation target current value; a sample-time operation means 26 that sets a time for sample-detecting the post commutation-command DC current value; and a timer means 27 that outputs, at each sample-detecting time, a current sample command for sample-holding with the DC current value outputted from the current detection circuit 4, at the set time as the torque current estimated value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４３】
ここで、
ｉ：Ａ／Ｄ変換器２１から出力する数値（Ｄ）にて算出した直流電流値Ｉｄｃ
Ｋ：Ａ／Ｄ変換器２１において電流を電圧に変換する場合の比例定数
Ｖｍａｘ：フルスケール時の入力電圧
Ｄｍａｘ：フルスケール値
【００４４】
前記電機子電流算出手段２２は、［数１］に示す〔１〕式に、Ａ／Ｄ変換器２１から出力される数値Ｄを求める場合に使用した各データ、即ち、段落番号［００４０］に記載した数値を代入して演算処理することにより、Ａ／Ｄ変換器２１から出力される数値Ｄに対応する直流電流値Ｉｄｃを算出するものである。
【００４５】
【数２】

【００４６】
となり、前記電機子電流算出手段２２にて算出された直流電流値Ｉｄｃ（４Ａ）が、後述するサンプルホールド手段２３に入力される。
【００４７】
つづいて、前記サンプルホールド手段２３の役割について説明する。このサンプルホールド手段２３は前記のように、Ａ／Ｄ変換器２１から順次出力される数値に基づき演算処理して算出した直流電流値Ｉｄｃを、所定のサンプル時刻ｔｓ毎に保持・記録するための手段で、前記サンプル時刻毎に保持する直流電流値Ｉｄｃをトルク電流推定値Ｉｑとする。前記サンプリングの時刻ｔｓは、前回の電機子巻線に流れる電機子電流の通電相切換周期（以下、転流周期Ｔという）Ｔ_ｎ−１から演算処理して決定するものである。
【００４８】
即ち、本発明においてサンプル時刻ｔｓの設定は、ひとつ前（前回）の転流周期Ｔ_ｎ−１に、サンプリング係数Ｋｔを乗じて決定している。なお、サンプリング係数Ｋｔは、０＜Ｋｔ＜１の範囲で対象となる電動機の特性によって決定すればよく、サンプル時刻ｔｓの算出は次式〔２〕の［数３］によって算出する。
【００４９】
【数３】

【００５０】
ここで、
ｎ：転流回数
Ｋｔ：サンプリング係数
前記［数３］に示す〔２〕式によってサンプル時刻ｔｓを算出し、ｔ＝ｔｓとなった時点でのＡ／Ｄ変換器２１から出力される数値により演算処理して算出した直流電流値Ｉｄｃをトルク電流推定値Ｉｑとしてサンプルするものである。ここで、ｔは電機子巻線の所定の通電相における転流周期Ｔが終了した時刻を示すものである。前記トルク電流推定値Ｉｑは、電機子巻線の通電相の転流周期Ｔ毎に発せられる転流指令の時点から、前記サンプル時刻ｔｓ後の直流電流値Ｉｄｃの大半がトルク寄与成分になると推定してサンプルした電流値Ｉｑを表わしている。
【００５１】
次に転流目標電流値演算手段２４について説明する。この演算手段２４は、前記サンプルホールド手段２３によって保持・記憶した直流電流値Ｉｄｃにおけるトルク電流推定値Ｉｑを定数倍して、これを定常時転流目標電流値Ｉｓｆの初期値とする機能と、前記初期値を時間の経過とともに順次低減する機能とを備えており、この転流目標電流値演算手段２４によりトルク電流推定値Ｉｑをベースにして、前記定常時転流目標電流値Ｉｓｆを［数４］に示す次式により求めるものである。
【００５２】
【数４】

【００５３】
ここで、
Ｋｓ：速度の関数
Ｉｑ：トルク電流推定値
τｄ：低減時定数
ｔａ：サンプル時刻からの時間
但し、サンプル時刻の度にｔａ＝０にリセットする。
前記［数４］に示す〔３〕式で算出した定常時転流目標電流値Ｉｓｆは、常時電機子電流算出手段２２にて算出された直流電流値Ｉｄｃと、次に説明する転流指令出力手段２５にて比較される。
【００５４】
前記した転流指令出力手段２５は、ブラシレスモータ５１の電機子巻線に通電される電機子電流の通電相を切換える機能、即ち、各通電相の転流周期Ｔを設定して転流指令を出力するものである。これは、ブラシレスモータ５１の電機子巻線の各通電相への通電をタイミングよく切換えることにより、ブラシレスモータ５１の駆動を良好に継続させる。そして、前記所定通電相の転流周期Ｔは、定常時転流目標電流値Ｉｓｆと、電機子電流算出手段２２から転流指令出力手段２５に入力される直流電流値Ｉｄｃとが一致したとき、あるいは、直流電流値Ｉｄｃが定常時転流目標電流値Ｉｓｆを上回ったとき、電機子巻線の通電相を切換（転流）えるものである。
【００５５】
サンプル時刻演算手段２６は、ブラシレスモータ５１の電機子巻線の通電相を切換えたときの転流周期Ｔ、即ち、前回の転流周期Ｔ_ｎ−１にサンプリング係数を乗じてサンプル時刻ｔｓを演算処理（算出）する機能を備えており、この演算処理により得られたサンプル時刻ｔｓ毎に、電機子電流算出手段２２から出力される直流電流値Ｉｄｃをサンプルホールド手段２３によりサンプルホールドするものである。なお、サンプル時刻ｔｓの演算処理は前記した［数３］にて行われるため、その説明は重複するので割愛する。
【００５６】
タイマ手段２７は、前記サンプル時刻演算手段２６により演算処理して算出された時刻ｔｓ毎に、サンプルホールド手段２３に直流電流値Ｉｄｃをサンプルホールドする指令を出力する機能を備えており、このタイマ手段２７の存在によってサンプルホールド手段２３は、事前に設定した時刻ではなく、常に、各通電相における最適な切換周期（転流周期Ｔ）毎において、確実に直流電流値Ｉｄｃをホールドして転流目標電流値演算手段２４に出力させることができるので、各通電相における転流指令は最適な時刻を選定して行うことができる。なお、前記タイマ手段２７には、電流サンプル指令を出力する毎に、タイマ手段２７をゼロリセットするゼロリセット手段（図示せず）が具備されている。
【００５７】
つづいて、回転数算出手段２８は、電機子電流算出手段２２から出力された直流電流値Ｉｄｃをベースとして算出するもので、図４に電機子電流算出手段２２から順次出力される電流波形図にて示す如く、直流電流値Ｉｄｃの周期をカウント手段（図示せず）にてカウントし、このカウント数値から１周期の時間を、例えば、ｔ秒とすることによってブラシレスモータ５１の現時点における回転数（回転速度）を算出するもので、その算出式は［数５］に示す式を用いる。
【００５８】
【数５】

【００５９】
ここで、
Ｐ：ブラシレスモータの極数
ｔ：出力波形の１周期の時間（秒）
前記［数５］に示す算出式によってブラシレスモータ５１の毎分の回転速度を算出するものである。
【００６０】
次に定電流・回転数制御手段２９について説明する。この定電流・回転数制御手段２９は、前記回転数算出手段２８により算出したブラシレスモータ５１の回転速度と、事前に設定した回転速度（速度指令値）とを比較し、常にブラシレスモータ５１の回転速度を速度指令値と一致させるように電機子巻線に通電される電機子電流の指令電流値ｉ０を制御するように構成されている。
【００６１】
また、前記定電流・回転数制御手段２９においては、ブラシレスモータ５１の駆動中に負荷トルクが変動して電機子巻線の各通電相に流れる電機子電流が増加し、この結果、電機子巻線の温度が上昇し、所定の設定温度を超えたような場合に発生する電機子巻線の焼損や回転子に設けた永久磁石の脱磁現象を防ぐために、事前に電機子巻線に流れる電機子電流の最大値を設定し、電機子電流算出手段２２から出力される直流電流値Ｉｄｃが最大電流値を超えないように定電流制御を行うように構成されている。
【００６２】
従って、電機子巻線に通電される電機子電流が、負荷の増大により急上昇するような場合は、未然に回転子の回転速度を速度指令値より低下させて、電機子巻線に通電される電機子電流の増大を阻止して定電流制御が行えるように設けられている。この結果、ブラシレスモータ５１の運転中に負荷トルクが急変した場合でも、前記定電流・回転数制御を行うことにより、ブラシレスモータ５１を常に所定の回転速度で円滑に駆動制御させることが可能となる。
【００６３】
ＰＷＭ制御手段３０は、転流指令出力手段２５からの出力によって作動し、かつ、前記定電流・回転数制御手段２９からの出力（電圧指令値Ｖｑ）によってパルス幅を変調し、この変調したパルス幅の信号をＰＷＭ制御信号としてインバータ回路７に出力し、インバータ回路７の所要のトランジスタｕ〜ｚのベースを、所要パルス幅に整定されたパルス信号によってオン・オフ動作を制御することにより、ブラシレスモータ５１を任意の速度指令値により駆動制御させるものである。
【００６４】
始動時補償手段３１は、ブラシレスモータ５１の始動時に、ブラシレスモータ５１が充分な始動トルクが得られるように設けたものである。ブラシレスモータ５１は定常時のセンサレス駆動方式においては、定常時転流目標電流値Ｉｓｆを定めることができず、この結果、始動させることが不可となる。このため、ブラシレスモータ５１においては、その始動時のみ始動時転流目標電流値Ｉｓｂを用いてこれを転流目標値とする。即ち、ブラシレスモータ５１においては、その始動時に強制的に始動時転流目標電流値Ｉｓｂ（負荷によって個々に異なるものの、ブラシレスモータ５１に通電される最大電流値を目安に設定することは云うまでもない）に基づく電流を電機子巻線に通電してブラシレスモータ５１を起動させるものである。なお、前記始動時転流目標電流値Ｉｓｂは、時間の経過とともに低減し、定常時の転流目標電流値Ｉｓｆが始動時転流目標電流値Ｉｓｂを上回ったとき、定常時におけるセンサレス駆動方式に切換えるように構成されている。
【００６５】
次に、前記のように構成されたブラシレスモータ駆動回路１の動作について説明する。最初に、ブラシレスモータ５１の始動について説明する。ブラシレスモータ５１の駆動は、転流周期Ｔをベースにして算出したサンプル時刻ｔｓ後にサンプルホールド手段２３にて保持・記憶する直流電流値Ｉｄｃをトルク電流推定値Ｉｑとみなして転流目標電流値Ｉｓを決定する方式においては、最初の通電モードにおける前記転流目標電流値Ｉｓが不定、即ち、始動時におけるサンプル時刻ｔｓが不定となり、この結果、転流目標電流値Ｉｓを設定することができず、ブラシレスモータ５１は始動不能となる。
【００６６】
本発明においては、前記の回避策として時間経過に伴い暫時電流値が低下する始動電流指令値（始動時転流目標電流値Ｉｓｂ）を設定して、ブラシレスモータ５１の始動初期における転流（電機子巻線の通電相切換）を行うようにした。前記始動時転流目標電流値Ｉｓｂは、始動時の負荷条件によって事前に設定するもので、本件発明では、図２に示すモータ制御装置５に具備した始動時補償手段３１がその役目を担っている。
【００６７】
図５、７において、ブラシレスモータ５１の始動処理について説明する。始動に際しては、図２に示すＰＷＭ制御手段３０において、ＰＷＭのキャリア周波数、通電比率（デューティサイクル）を初期値として設定するとともに、始動時補償手段３１においては、転流目標電流値Ｉｓとして始動時転流目標電流値Ｉｓｂを代入（設定）した後、通電を開始する（図７のステップＳ１〜Ｓ３参照）。
【００６８】
これは、始動時において、キャリア周波数、デューティサイクルを低く設定することにより、電流を滑らかに、かつ、順次増加させてブラシレスモータ５１のソフトスタートを実現するためのものである。また、始動時転流目標電流値Ｉｓｂを設けて始動初期の転流を行うことは、負荷に大きな負担、例えば、ブラシレスモータをポンプの駆動源に使用した場合、水の抵抗、ゴミ等の存在によりインペラに大きな負荷が加えられていたり、あるいは、エアコンの室外機を駆動する場合、ファンに逆風等の外乱が加わり負荷が必要以上に増加している場合を想定してのことである。
【００６９】
通電が開始されると、交流電源１０が整流・平滑回路２を介して制御電源回路３とインバータ回路７に通電される。制御電源回路３からは、５Ｖの直流電源がモータ制御装置５をはじめ、各回路に供給される。前記モータ制御装置５は直流電源（５Ｖ）の通電に伴い作動し、始動時補償手段３１によって設定された始動時転流目標電流値Ｉｓｂにより転流指令手段２５→ＰＷＭ制御手段３０を経てインバータ回路７にＰＷＭ制御信号を出力し、インバータ回路７の、例えば、トランジスタｕ、ｙをオンし、ブラシレスモータ５１の電機子巻線のＵ相からＶ相へ電機子電流が通電される。この結果、ブラシレスモータ５１の駆動が開始される。
【００７０】
前記ブラシレスモータ５１に通電された電機子電流は、電流検出回路４のシャント抵抗４ａに検出され、電圧変換されてモータ制御装置５のＡ／Ｄ変換器２１に出力される。電流検出回路４によって検出された直流電流値Ｉｄｃは、Ａ／Ｄ変換器２１によってデジタル値に変換されるとともに、前記デジタル値に変換された数値は電機子電流算出手段２２に出力され、前記Ａ／Ｄ変換器２１にて設定された数値をベースにして電機子電流算出手段２２は、［数１］により演算処理して直流電流値Ｉｄｃを算出し、この直流電流値Ｉｄｃをサンプルホールド手段２３と転流指令手段２５に出力する。
【００７１】
サンプルホールド手段２３に入力された直流電流値Ｉｄｃは、サンプル時刻演算手段２６により［数３］に示す〔２〕式により演算処理して算出したサンプル時刻ｔｓが、タイマ手段２７から電流サンプル指令が出力される毎に保持・記憶する。このサンプルホールド手段２３は前記記憶・保持される直流電流値Ｉｄｃをトルク電流推定値Ｉｑとしてサンプルするものである。なお、タイマ手段２７は、前記電流サンプル指令の出力後ゼロリセット手段（図示せず）により、一旦リセットされて次の電流サンプル指令の出力に備えている。
【００７２】
前記サンプルホールドされたトルク電流推定値Ｉｑは次の転流目標電流値演算手段２４に出力され、この演算手段２４によって始動時転流目標電流値Ｉｓｂを求める。そして、前記転流目標電流値演算手段２４により求めた始動時転流目標電流値Ｉｓｂが、電機子電流算出手段２２から転流指令出力手段２５に出力される直流電流値Ｉｄｃと比較し、Ｉｓｂ＜Ｉｄｃでなければ、転流指令出力手段２５は転流指令をＰＷＭ制御手段３０に出力しない。この場合は、再度始動時転流目標電流値Ｉｓｂ及び定常時転流目標電流値Ｉｓｆの演算処理を行うことは云うまでもない。
【００７３】
前記とは逆に、Ｉｓｂ＜Ｉｄｃとなれば、転流指令出力手段２５よりＰＷＭ制御手段３０に転流指令が出力され、ＰＷＭ制御手段３０からは、インバータ回路７のオンされていたトランジスタｕ、ｙに代って、トランジスタｕ、ｚをオンさせるＰＷＭ制御信号を出力し、電機子巻線のＵ相からＶ相に流れていたブラシレスモータ５１の電機子電流がＵ相からＷ相へ転流される（図７のステップＳ４〜Ｓ６参照）。
【００７４】
図５は前記したブラシレスモータ５１の始動時における転流タイミングの状況を示す波形図で、図５から判明するように、始動時転流目標電流値Ｉｓｂは時間の経過とともに減衰するように構成されている。そして、転流目標電流値Ｉｓは、始動時転流目標電流値Ｉｓｂと定常時転流目標電流値Ｉｓｆのいずれか大きな値が選択されるものの、一度定常時転流目標電流値Ｉｓｆが始動時転流目標電流値Ｉｓｂを上回った時点でＩｓ＝Ｉｓｆとなる。しかし、前記したように、ブラシレスモータ５１の始動時における定常時転流目標電流値Ｉｓｆは不定のため、始動時転流目標電流値Ｉｓｂが転流目標電流値Ｉｓとなる。
【００７５】
そして、転流指令（転流周期Ｔ）は、転流目標電流値Ｉｓ（始動時転流目標電流値Ｉｓｂ）と直流電流値Ｉｄｃとが転流指令出力手段２５により比較され、直流電流値Ｉｄｃが転流目標電流値Ｉｓに達した時点で転流処理が行われる。この結果、前記のように、直流電流値Ｉｄｃが転流目標電流値Ｉｓを超えるまでの間は、図５に示す波形図の如く、繰返し始動時転流目標電流値Ｉｓｂと定常時転流目標電流値Ｉｓｆを計算し、いずれか大きな値が選択される。なお、転流周期Ｔは転流の都度タイマ手段２７によってＴ＝０にリセットされ、始動時転流目標電流値Ｉｓｂは通電開始からの時間によって計算されることは云うまでもない（図７のステップＳ６〜Ｓ１２参照）。
【００７６】
図５において、定常時転流目標電流値Ｉｓｆが始動時転流目標電流値Ｉｓｂと同等もしくは上回ったとき、即ち、図７のステップＳ８において、Ｉｓｆ≧Ｉｓｂとなった時点でブラシレスモータ５１は始動時の運転状態から、定常時の運転状態に移行するものである（図７のステップＳ８、Ｓ１３参照）。
【００７７】
このように、ブラシレスモータ５１はその始動時、事前に設定した始動時転流目標電流値Ｉｓｂをベースにして転流周期Ｔを設定し、かつ、ＰＷＭ制御手段３０においては、そのキャリア周波数を低く設定して電機子巻線に通電する電機子電流を徐々に滑らかに増加させ、しかも、通電比率は通電開始が定常運転に至る間に０から徐々に増大させて駆動させるようにしたので、負荷トルクに対応して円滑に始動させることができる。
【００７８】
次に、ブラシレスモータ５１の定常運転状態を図６、８において説明する。前記したように、ブラシレスモータ５１の始動運転時から定常運転時に移行した場合においても、基本的には定常時転流目標電流値Ｉｓｆを算出して転流周期を設定することにより、速度指令値にて設定した回転速度（回転数）を維持させてブラシレスモータ５１の駆動を行うものである。
【００７９】
図８において、定常時転流目標電流値Ｉｓｆと直流電流値Ｉｄｃとを比較し、直流電流値Ｉｄｃが定常時転流目標電流値Ｉｓｆに達した時点で転流を行い、電機子巻線の通電相を切換える（図８のステッＳ２２参照）。この場合、直流電流値Ｉｄｃが定常時転流目標電流値Ｉｓｆに達していない場合は、定常時転流目標電流値Ｉｓｆを再度計算し、直流電流値Ｉｄｃと定常時転流目標電流値Ｉｓｆとの比較を繰り返す（図８のステップＳ２０、Ｓ２１参照）。前記の状況は図６の（ａ）〜（ｅ）に示す転流タイミングの波形図によって明らかである。
【００８０】
転流後、図８のステップＳ２３、Ｓ２４によって次の電流サンプル指令までのタイマ時間を、［数３］に示す〔２〕式を用いて算出する。そして、前記サンプル時刻ｔｓに到達したら、図８のステップＳ２５に移行してトルク電流推定値Ｉｑをベースにして［数４］に示す〔３〕式により定常時転流目標電流値Ｉｓｆを設定する。このフローチャートに従い転流指令を出力し、電機子巻線の通電相の切換を行うもので、これらの説明については、既に、［数３］、［数４］に示す〔２〕、〔３〕の式によってサンプル時刻ｔｓ、定常時転流目標電流値Ｉｓｆを演算処理して算出するところで説明したので、詳細な説明は省略するが、本発明においては、単に定常時転流目標電流値Ｉｓｆを算出して転流タイミングを設定するのではなく、前記の転流タイミングは、常に電機子巻線に通電される電機子電流が回転トルクに寄与している最適な時刻に、トルク電流推定値Ｉｑとして前記通電電流をサンプルし、このトルク推定電流値Ｉｑをベースにして定常時転流目標電流値Ｉｓｆを算出して、ブラシレスモータ５１の転流タイミングを設定することができるようにしたので、ブラシレスモータ５１は常に負荷の変動に対応して速度指令値の回転速度（回転数）を維持して駆動することができる。
【００８１】
この結果、図８のステップＳ２６において、ブラシレスモータ５１の電機子巻線に通電される電機子電流が事前に設定した最大電流値に比べて大きいか、小さいかを比較し、図８のステップＳ２７において大きい場合は（負荷の増加）、図３に示す定電流・回転数制御手段２９に設定した定電流制御手段が作動して、電機子巻線に通電される電機子電流を抑制し、電機子巻線が過電流によって焼損するのを未然に阻止する。この場合、通電電流が抑制されるため、ブラシレスモータ５１の回転速度（回転数）は制御された電流によって制限されることは云うまでもない。
【００８２】
また、図８のステップＳ２６において、電機子巻線に通電される電流が最大電流値より小さい場合は、ステップＳ２８に移行し、図３に示す回転数算出手段２８にて算出した回転数を、速度指令値にて事前に設定した回転数に一致させるべく、定電流・回転数制御手段２９に設定した回転数制御手段が作動して、速度指令値に設定した回転速度が得られるように電流を通電制御させて電機子巻線に通電するように構成されているため、ブラシレスモータ５１は常に負荷トルクに対応して所定の速度指令値の回転速度で円滑に駆動させることができる。
【００８３】
次に、前記したブラシレスモータ５１の定電流・回転数制御処理の詳細は、図９に示すフローチャートに記載した通りのものである。前記の定電流・回転数制御の基本は、本発明のブラシレスモータ駆動回路１が電流波形規範形センサレスドライブ方式を採用している関係上、インバータ回路７の接地側に挿設した電流検出回路４のシャント抵抗４ａにより検出した検出電流が、ブラシレスモータ５１の回転子の回転位置検出に係る唯一の情報源としているので、ブラシレスモータ５１における回転速度（回転数）検出も電機子巻線の通電相を切換えるための転流周期Ｔから算出している。
【００８４】
この結果、図３に示すように、例えば、負荷（井戸用ポンプ等）が最大定格出力以下で運転しているような場合は、回転数算出手段２８を有する回転速度制御ループにより負荷の定速運転を実施し、また、負荷の運転中に最大定格出力を超えた場合には、ブラシレスモータ５１の保護を図るために、電機子電流算出手段２２を有する定電流制御（定出力制御）のみを用いた電流制御ループによって、ブラシレスモータ５１の運転を実施している。
【００８５】
前記における定電流・回転数制御処理を図９によって説明する。図９のステップＳ３０において、ブラシレスモータ５１の転流周期Ｔをベースにして回転子の回転数ｒｐｍを［数５］に示す〔４〕式によって算出する。前記算出した回転数ｒｐｍをステップＳ３１において、ＰＷＭ制御手段３０のキャリア周波数変更閾値と同等（大きい）か、否かを比較し、同等の場合は、ＰＷＭ制御手段３０のキャリア周波数を上昇させ、否の場合はキャリア周波数を引下げる。
【００８６】
次に、図９のステップＳ３４に移行し、速度指令値ｒｐｍ０と現在の回転速度（回転数）ｒｐｍとの差における回転数偏差値ｒｐｍｅを算出する。そして、この回転数偏差値ｒｐｍｅから現在の指令電流値ｉ０をステップＳ３５にて算出する。この指令電流値ｉ０はＰＩ制御によって算出する。即ち、比例要素と積分要素とを含む演算によって前記指令電流値ｉ０を算出するものである。
【００８７】
この指令電流値ｉ０はステップＳ３６により最大電流値（最大定格出力）ｉｍａｘと比較し、指令電流値ｉ０が最大電流値ｉｍａｘと同等か超える場合は、前記指令電流値ｉ０を最大電流値ｉｍａｘとする。この時点で、結果的に定電流制御を実行することになる（図９のステップＳ３７参照）。この後、ステップＳ３８に移行し、指令電流値ｉ０と現在のトルク電流推定値Ｉｑ（電機子電流算出手段２２にて算出）との差を求め、その求めた値を電流偏差ｉｅとする。
【００８８】
前記ステップＳ３８により算出した電流偏差ｉｅによって、ＰＷＭ制御手段３０から出力されるパルス信号（ＰＷＭ通電幅）のＰＷＭ通電幅指令値ｖｄ０をステップＳ３９により算出する。そして、前記ステップＳ３９にて算出して得られたＰＷＭ制御手段３０から出力されるＰＷＭ通電幅指令値ｖｄ０と、ＰＷＭ制御手段３０から出力される事前に設定したＰＷＭ通電幅最大値ｖｄｍａｘとをステップＳ４０により比較し、ＰＷＭ通電幅指令値ｖｄ０がＰＷＭ通電幅最大値ｖｄｍａｘと同等か、あるいは、大きい場合、ＰＷＭ制御手段３０からは、ＰＷＭ通電幅最大値ｖｄｍａｘを限度、即ち、ＰＷＭ通電幅最大値ｖｄｍａｘをＰＷＭ通電指令値ｖｄ０としてステップＳ４１においてＰＷＭ制御信号を出力し、インバータ回路７の所要トランジスタｕ〜ｚを所定時間オン・オフ制御させて、ブラシレスモータ５１の回転速度（回転数）を速度指令値に適合させるように構成されている。この後、ステップＳ４１により、前記電機子巻線に流れる電機子電流を通電制御しながら、回転子の回転速度値を個々に調整して、ブラシレスモータ５１を所定の速度指令値にて回転を継続させるものである。
【００８９】
以上説明したように、本発明において定電流・回転数制御手段２９は、図３に示すように、電流検出回路４によって検出した電機子巻線に流れる電機子電流をベースにして、これをモータ制御装置５にプログラム設定した電流制御プログラムと、速度制御プログラムにて作動する電機子電流算出手段２２と、回転数制御手段２８とにより算出した指令電流値ｉ０や現在の回転速度（回転数）ｒｐｍを、それぞれ事前に設定した最大電流値ｉｍａｘ、回転数目標値（速度指令値）ｒｐｍ０と適応させるべく制御可能に構成されているので、ブラシレスモータ５１は、負荷変動に対応して回転数を回転数目標値ｒｐｍ０に一致させるように制御し、かつ、指令電流値ｉ０が最大電流値ｉｍａｘを超えようとした場合は、指令電流値ｉ０を最大電流値ｉｍａｘの範囲内に保持することができるため、負荷トルクが急変する場合においても、適切に定電流・回転数制御が行い得、ブラシレスモータ５１を安定して駆動することができる。
【００９０】
また、前記したモータ制御装置５においては、図１０のフローチャートで示すように、ブラシレスモータ５１の異常検知の処理機能（始動停止手段）も具備されている。この異常検知によってブラシレスモータ５１の始動を停止させる始動停止手段は、主にブラシレスモータ５１の起動時に発生する不測の事態を未然に回避するために設けられている。
【００９１】
以下、始動停止手段を有する異常検知処理の内容を図１０のフローチャートによって説明する。なお、ブラシレスモータ５１の始動処理は、既に図７によって詳細に説明したので省略する。ブラシレスモータ５１を図１０のステップＳ５１により始動させ電機子巻線の通電相を切換えるための転流周期Ｔ（時間）を、ステップＳ５２により転流指令が出力される毎に計測し、前記転流指令に要する時間が、ブラシレスモータ５１の最高回転速度時における転流周期Ｔの時間より小さいか、大きいかを次のステップＳ５３に判断する。
【００９２】
図１０のステップＳ５３にて始動時の転流周期Ｔが最高回転速度時の転流周期Ｔより小さいと判断されたときはステップＳ５４に移行し、始動処理は一旦停止する。一方、始動時の転流周期Ｔが最高回転速度時の転流周期Ｔより大きい場合、即ち、ブラシレスモータ５１の始動時は負荷が停止している関係上図５に示すように、始動時転流目標電流値Ｉｓｂにて起動させているため、その転流周期Ｔは必然的に大きく（電機子巻線の通電相切換には時間を要する）なる。しかし、ブラシレスモータ５１は定常時運転に変換されると回転速度も速くなる結果、転流周期Ｔ（電機子巻線の通電相の切換時間は早くなる）は当然小さくなる。
【００９３】
前記により始動時の転流周期Ｔが最高回転数の転流周期Ｔより大きいときは、ステップＳ５５に移行してトルク電流推定値Ｉｑを検出する。このトルク電流推定値Ｉｑは、ブラシレスモータ５１の始動時においては、実質的に始動時転流目標値Ｉｓｂに相当し、このトルク電流推定値Ｉｑと事前に設定した最大トルク電流推定値（最大電流値Ｉｍａｘ）とをステップＳ５６にて比較する。
【００９４】
ステップＳ５６により比較した結果、トルク電流推定値Ｉｑが小さいときは、次のステップＳ５７、Ｓ５８に移行し、ブラシレスモータ５１をセンサレス制御して始動させるとともに、始動後において定常時転流目標電流値Ｉｓｆが始動時転流目標電流値Ｉｓｂを上回った時点で、定常運転に移行し、ブラシレスモータ５１は定電流・回転数制御手段２９により駆動制御されて回転を継続する。逆にトルク電流推定値Ｉｑが最大トルク電流値を上回るようなときは、過電流値に達したと判断し、ステップＳ５４に移行する。
【００９５】
即ち、ステップＳ５３、Ｓ５６にて否と判定された場合は、ステップＳ５４に移行し、ブラシレスモータ５１は起動せず、停止状態にある。この場合は、モータ制御装置５の始動停止手段に設けた図示しないリトライ制御手段を操作し、再始動処理を実行する。この場合、リトライ制御手段の操作を例えば、３回繰り返してブラシレスモータ５１が始動すれば問題ない。しかし、リトライ制御手段を３回操作してもブラシレスモータが再始動できない場合は、ステップＳ６１にて異常と判断しブラシレスモータ５１の始動を中止する。
【００９６】
この始動中止は、ブラシレスモータ５１の故障か、あるいは、負荷に問題があって始動処理が行えないもので、この異常判断によってブラシレスモータ５１の始動時に無理に通電を行うことにより、ブラシレスモータ５１が焼損するという問題を未然に回避することができる。なお、前記モータ制御装置５のプログラムで対応できない瞬間的な過電流に対しては、ブラシレスモータ駆動回路１に設けた過電流検出回路８にてこれを検出し、直ちにモータ制御装置５と通電制御回路６に過電流検出信号を出力して動作中の処理を停止するように構成されているので、ブラシレスモータ５１が過電流によって検知するのを良好に回避することができる。
【００９７】
【発明の効果】
本発明は以上説明したように、ブラシレスモータをセンサレスにて駆動制御するモータ制御装置は、ブラシレスモータの電機子巻線における転流指令を、電流検出回路にて検出した直流電流値をモータ制御装置においてトルク電流推定値として転流目標電流値に演算処理し、これを電流検出回路にて検出された直流電流値と比較処理することにより瞬時に出力される結果、最適な転流タイミングにより転流指令を出力することが可能となり、ブラシレスモータの電機子巻線に流れる電機子電流の通電相切換は常に最適な時期で円滑に行い得、これにより、ブラシレスモータの回転制御を円滑・良好に、かつ、高効率で行うことができる。従って、ブラシレスモータの運転中に負荷トルクが急変した場合においても、適切なタイミングで転流指令を出力することができるので、ブラシレスモータを常に所定の回転速度にて安定した状態で駆動させることができる。
【００９８】
また、本発明においては、モータ制御装置に定電流・回転数制御手段を採用するようにしたので、ブラシレスモータは、自体の回転速度と事前に設定した回転速度の速度指令値とを常に比較して、ブラシレスモータの回転速度を速度指令値と一致させるように回転数制御を行い、しかも、負荷の増大により通電電流が増加して、ブラシレスモータの温度を上昇させたり、ブラシレスモータの回転子に設けた永久磁石が脱磁する等の問題を回避するために、電機子巻線に通電される最大電流値を事前に設定し、電流検出回路にて検出される直流電流値が前記最大電流値を超過するのを阻止して定電流制御を行うようにしたので、ブラシレスモータは、その運転中に負荷トルクの急変によりトルク変動が生じたとしても、適切な転流作用により、常に所定の回転速度で安定した状態での駆動を実現することができる。
【００９９】
更に、本発明においては、始動時の転流指令を出力させる始動時補償手段がモータ制御装置に具備されているので、ブラシレスモータはその始動時、始動トルクを発生させるために充分な電機子電流を電機子巻線に通電させることができるため、始動時においてもブラシレスモータを始動トルクに対応して適確に、かつ、ソフト的に始動させることができる。しかも、ブラシレスモータの始動時においては、負荷トルク等の関係から始動時転流目標電流値が最大電流値を超えるような場合は、異常と判断してブラシレスモータの始動を停止させるとともに、異常状態が解消されれば、リトライ操作によって即座に始動操作が行い得るため、この種センサレス駆動方式のブラシレスモータを常に迅速・確実に、かつ、スムースに始動させることができるという利点も備えている。
【図面の簡単な説明】
【図１】本発明のブラシレスモータ駆動回路を示す回路図である。
【図２】本発明のブラシレスモータ駆動回路に設けたモータ制御装置の構成を示すブロック図である。
【図３】定電流・回転数制御手段の構成を概略的に示すブロック図である。
【図４】電流検出回路の出力電流波形を示す波形図である。
【図５】ブラシレスモータの始動運転時において、電機子巻線に流れる電流波形を示す図である。
【図６】ブラシレスモータの定常運転時において、各手段の出力電流波形を示す図である。
【図７】ブラシレスモータの始動時の運転処理を説明するフローチャートである。
【図８】同じくブラシレスモータの定常の運転処理を説明するフローチャートである。
【図９】ブラシレスモータの定電流・回転数処理を説明するフローチャートである。
【図１０】ブラシレスモータの異常状態における処理を説明するフローチャートである。
【符号の説明】
１ ブラシレスモータ駆動回路
４ 電流検出回路
５ モータ制御装置
６ 通電制御回路
７ インバータ回路
８ 過電流検出回路
２１ Ａ／Ｄ変換器
２２ 電機子電流算出手段
２３ サンプルホールド手段
２４ 転流目標電流値演算手段
２５ 転流指令出力手段
２６ サンプル時刻演算手段
２７ タイマ手段
２８ 回転数算出手段
２９ 定電流・回転数制御手段
３０ ＰＷＭ制御手段
３１ 始動時補償手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is, for example, when starting the electric equipment such as a well pump, or even when the torque suddenly changes during the operation of the electric equipment, always smoothly in response to a predetermined torque, and in a stable state The present invention relates to an improvement in a control device of a brushless motor that enables continuation of constant speed operation.
[0002]
[Prior art]
2. Description of the Related Art Today, brushless DC motors have come to be used in various electric appliances such as home electric appliances in consideration of high efficiency, variable speed, small size and light weight. Conventional brushless DC motors (hereinafter referred to as "motors") have a built-in magnetic pole position detection sensor for detecting the rotational position of the rotor, but have the following problems. For example, when a stator core (stator) for distributed winding of an armature winding is formed by distributed winding of an armature winding on the stator core, an armature winding portion is formed from both ends of the stator core in the axial direction. The coil end protrudes outward. For this reason, the mounting position of the magnetic sensor for detecting the magnetic pole position of the rotor is necessarily restricted by the coil end, so that the rotor extends the axial length dimension to the vicinity of the coil end, and the magnetic sensor And a small permanent magnet for detecting the magnetic pole position is attached to the end of the rotor shaft of the rotor, and a magnetic sensor is placed outside this permanent magnet. The method of detecting the position of the magnetic pole of the rotor has been generally put to practical use.
[0003]
However, in the former, there is a problem that the motor itself becomes larger and its price increases as the amount of magnets provided on the outer periphery of the rotor increases, and in the latter, the magnetic poles of the rotor and the magnetic poles increase. Since it is necessary to surely perform alignment with the permanent magnet for position detection, there has been a problem that the number of steps for assembling the motor and the like increase. In addition, in both of the above methods, a method is adopted in which a magnetic sensor is attached outside the coil end, so that it is difficult to avoid enlarging the size of the motor, and the manufacturing cost of the motor itself is increased. Included.
[0004]
In order to solve the above-mentioned problem, the use of the magnetic sensor itself and its attachment are not required by eliminating the magnetic sensor and realizing the sensorless operation. The number of points and man-hours can be reduced, and the size and cost of the motor can be easily reduced. In a sensorless drive system generally used today, for example, a sensorless drive system using a speed electromotive force generated in an armature winding of a motor as a sole information source, such as a 120-degree conduction voltage inverter drive system. Since there is no need for a sensor board or a harness member for signal transmission at all, the operating temperature of the magnetic sensor itself, the environmental resistance to noise, etc., and the advantages in terms of manufacturing costs are extremely large, but at the time of starting the motor. In addition, instability remains in the rotation performance of the motor itself in the low-speed operation region, and there is a problem that the inertia torque is specified and the motor can be used only for special purposes.
[0005]
That is, the sensorless drive circuit in this type of motor focuses on the correlation between the speed electromotive force generated in the armature winding of the rotating motor and the position of the field, and determines the commutation timing of the motor based on the speed electromotive force. Was. When the motor is started, the motor is forcibly commutated at a preset frequency and voltage as a synchronous motor or a stepping motor, and the load is increased to a rotation region where sufficient speed electromotive force for field position detection is generated. It was configured to gradually accelerate while maintaining the balance with the torque.
[0006]
However, in the sensorless drive circuit of the motor, the acceleration time after starting the motor is inevitably long, and it is difficult to start the motor at low rotation and high torque. That is, it is difficult to perform rapid acceleration control due to the instability of the speed torque characteristic, and there are two modes, a forced commutation mode (so-called self-control operation) and a synchronous inverter operation mode (feedback control operation) based on feedback of estimated position information. There was only a method of having two modes and gradually accelerating while always maintaining the balance with the inertia of the power system including the motor and the load torque. The commutation timing is determined by the speed electromotive force. Since the speed electromotive force is detected by using the voltage of the armature winding of the motor, the armature current accompanying the energization switching at the time of a high load torque is obtained. Since the commutation spike voltage due to the recirculation of the motor increases, a large error occurs in the speed electromotive force information that can be detected. As a result, a large error occurs in the estimation result of the field pole position, and it is very difficult to determine the commutation action at an appropriate commutation timing.
[0007]
In view of the above problems, the present applicant has invented, for example, a sensorless drive circuit for a brushless motor described in Japanese Patent Application Laid-Open No. 9-37586. The sensorless drive circuit focuses on the waveform characteristics common to each waveform block forming the armature current waveform of each phase of the motor as shown in FIG. Among the two remarkable current increase areas A and B appearing in each block of the energization area in (2) (see FIG. 11), the second current increase area B is detected and the commutation timing is reached (commutation timing). And commutation control is performed. The detection of the second current increase region B is performed based on the fact that the armature current flowing through the armature winding of the motor has become a predetermined multiple (for example, 1.2 times) of the average value of the current. (Hereinafter referred to as “average method”) (for example, refer to Patent Document 1).
[0008]
[Patent Document 1]
JP-A-9-37586
[0009]
However, in the sensorless drive circuit of the brushless motor, since the averaging process of the armature current requires a predetermined time, such an average value method is applied to a load such as a pump for a well or a fan for an outdoor unit of an air conditioner. There has been a problem that it cannot be used as a motor for a drive source of an electric device whose torque changes suddenly due to a disturbance. That is, the average value of the armature current cannot be changed in response to a sudden change in the load torque. Therefore, at the time of such a sudden change, the second current increase region B is erroneously detected, so that the commutation operation cannot be performed at an appropriate commutation timing, and the motor may be vibrated or the synchronous escape may occur. There is a risk that stable driving may not be possible due to the stoppage.
[0010]
In view of the various problems described above, the present invention provides a motor that controls a brushless motor to operate at a constant speed by following a sudden change in load torque even when the load torque suddenly changes due to disturbance or the like during operation of the brushless motor. An object of the present invention is to provide a control device for a brushless motor including the control device.
[0011]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an inverter circuit having a plurality of switching elements for sequentially supplying a DC voltage to a plurality of armature windings of a brushless motor, and turning on / off the plurality of switching elements of the inverter circuit. A current detection circuit that converts an armature current flowing through an armature winding of the brushless motor into a voltage and detects the voltage, and a current detection circuit that includes a current control circuit that rotates the brushless motor. Sample-hold means for sample-holding the DC current value detected by the circuit and outputting a torque current estimated value; and commutation target current value calculating means for calculating and processing a commutation target current value based on the torque current estimated value. A commutation finger that outputs a commutation command when the DC current value detected by the current detection circuit exceeds the commutation target current value. Output means, sample time calculating means for calculating and setting the time at which the DC current value after outputting the commutation command is sampled, and output from the current detection circuit at the time set by the sample time calculating means The motor control device is characterized by comprising timer means for outputting a current sample command for sampling and holding a DC current value as a torque current estimated value at each time.
[0012]
According to the first aspect of the present invention, the armature current flowing through the armature winding of the brushless motor is voltage-converted and detected by the current detection circuit, and the detected DC current value is appropriately converted by the sample-and-hold means of the motor control device. The sampled and held value is output to the commutation target current value calculating means as an estimated torque current value. Based on the estimated torque current value, a steady state commutation target current value is obtained by the commutation target current value calculating means. A constant commutation target current value is compared with the DC current value detected by the current detection circuit, and when the DC current value exceeds the steady-state commutation target current value, a commutation command is output. The command is output from the PWM control means to the inverter circuit via the power supply control circuit. In the inverter circuit, the switching element is controlled to be turned on / off by a command from an energization control circuit, the motor control device is configured to control the commutation of the brushless motor, and to drive and control the brushless motor without a sensor. The commutation command to the DC current value detected by the current detection circuit in the motor control device, as a torque current estimated value, based on the torque current specified value based on this, to calculate the steady-state commutation target current value, Is instantaneously output by comparing the DC current value detected by the current detection circuit with the DC current value. As a result, a commutation command can be output at an optimum commutation timing, and the armature winding of the brushless motor can be output. The switching of the energized phase of the armature current flowing through the motor can always be performed smoothly at the optimum commutation timing. As a result, even when the load torque suddenly changes, the rotation speed control of the brushless motor can be performed smoothly, favorably, and with high efficiency. Therefore, even when the load torque suddenly changes during the operation of the brushless motor, the commutation command can be appropriately output by following the suddenly changed torque, and the brushless motor is always driven at a predetermined rotational speed in a stable state. Can be done.
[0013]
According to a second aspect of the present invention, there is provided an inverter circuit having a plurality of switching elements for sequentially supplying a DC voltage to a plurality of armature windings of a brushless motor, and turning on / off the plurality of switching elements of the inverter circuit. A current detection circuit that converts an armature current flowing through an armature winding of the brushless motor into a voltage and detects the voltage, and a current detection circuit that includes a current control circuit that rotates the brushless motor. Sample-hold means for sample-holding the DC current value detected by the circuit and outputting a torque current estimated value; and commutation target current value calculating means for calculating and processing a commutation target current value based on the torque current estimated value. A commutation finger that outputs a commutation command when the DC current value detected by the current detection circuit exceeds the commutation target current value. Output means, sample time calculating means for calculating and setting the time at which the DC current value after outputting the commutation command is sampled, and output from the current detection circuit at the time set by the sample time calculating means Timer means for outputting a current sample command for sampling and holding a DC current value as a torque current estimation value at each of the times, and further, a maximum current value set in advance for an armature current flowing through an armature winding of the brushless motor. A motor control device comprising a constant current / rotation speed control means for controlling the rotation speed of the brushless motor, or the armature current flowing through the armature winding of the brushless motor, by judging whether the rotation is large or small. It is characterized by the following.
[0014]
According to the second aspect of the present invention, the armature current flowing through the armature winding of the brushless motor is voltage-converted and detected by the current detection circuit, and the detected DC current value is appropriately converted by the sample-and-hold means of the motor control device. The sampled and held value is output to the commutation target current value calculating means as an estimated torque current value. Based on the estimated torque current value, a steady state commutation target current value is obtained by the commutation target current value calculating means. A constant commutation target current value is compared with the DC current value detected by the current detection circuit. If the DC current value exceeds the steady-state commutation target current value, a commutation command is output. Is output from the PWM control means to the inverter circuit via the conduction control circuit, and the switching element of the inverter circuit is turned on / off by a command from the conduction control circuit, The motor control device is configured to control the commutation of the brushless motor and control the drive of the brushless motor without a sensor. The motor control device further includes an armature current flowing through the brushless motor that has a preset maximum current. The constant current / rotation speed control means for controlling the rotation speed of the brushless motor and the armature current supplied to the armature winding is always provided by grasping the magnitude of the value and the magnitude thereof. In the motor control device of the present invention, the DC current value detected by the current detection circuit is used as the estimated torque current value, and the steady-state commutation target current value is calculated based on the estimated torque current value. As a result of instantaneously outputting a commutation command to the brushless motor by comparing the DC current value detected in It is possible to output a command, it is possible to properly perform the energization phase switching of the armature current flowing in the armature winding of the brushless motor is always optimal commutation timing. As a result, the rotation speed control of the brushless motor can be performed smoothly and satisfactorily at the time of a sudden change in load torque, and can be performed with high efficiency. , Which always compares the rotation speed of the brushless motor with the speed command value of the rotation speed set in advance corresponding to the load torque, and controls the energization voltage so that the rotation speed of the brushless motor matches the speed command value. In addition to controlling the number of motors, the current flowing through the armature windings increases due to the increase in load torque, and the temperature of the brushless motor rises, causing burnout or demagnetizing the permanent magnet provided on the rotor of the brushless motor. In order to avoid such a problem as before, a maximum current value supplied to the armature winding is set, and the DC current value detected by the current detection circuit is the maximum current value. In order to prevent the above-mentioned problem, the above-mentioned problem is solved by performing the constant current control, so that the brushless motor has an appropriate commutation even if the torque fluctuates due to a sudden change in the load torque during the operation. In addition, it is possible to always drive the motor in a stable state at a predetermined rotation speed, and to satisfactorily avoid problems such as burning and demagnetization of the brushless motor.
[0015]
According to a third aspect of the present invention, in the control device for a brushless motor according to the second aspect, the constant current / rotational speed control means determines a commutation period of the armature current flowing in the energized phase of the armature winding of the brushless motor. It is characterized by comprising a motor speed calculating means for detecting and calculating the speed of the brushless motor.
[0016]
According to the third aspect of the present invention, the rotation speed of the brushless motor is calculated and calculated by the constant current / rotation speed control means based on the commutation period of the armature current flowing in the energized phase of the armature winding. In the brushless motor, the rotation speed (rotation speed) of the brushless motor is changed from the rotation speed (rotation speed) to the rotation speed set in advance, and the delay / speed is immediately changed. As a result, by immediately controlling the armature current flowing through the armature winding, even if the rotation speed changes suddenly according to the load torque, the rotation speed can be corrected by the constant current / rotation speed control means. It is convenient because it can be easily performed. In addition, the detection of the motor rotation speed can be performed simply by counting the commutation period of the armature current flowing in the energized phase of the armature winding and performing an arithmetic process, so that a detection means such as a rotation speed detection sensor is specially provided. Therefore, the rotation speed of the brushless motor can be controlled accurately and economically.
[0017]
According to a fourth aspect of the present invention, in the control device for a brushless motor according to the second aspect, the constant current / rotational speed control means includes an armature of the brushless motor based on a DC current value detected by the current detection circuit. An armature current calculating means for calculating an armature current flowing through the winding is provided.
[0018]
According to the fourth aspect of the present invention, an electric machine detects an armature current that is applied to each energized phase of an armature winding in each commutation cycle by performing an arithmetic process on a DC current value detected by a current detection circuit. Since the armature current calculation means is provided in the constant current / rotational speed control means, even if the armature current supplied to the armature winding changes abruptly due to a change in load torque, the supplied current is determined by the armature current calculation. If the rotation speed of the brushless motor suddenly changes in accordance with the calculated DC current value with respect to the rotation speed (rotation speed) set in advance as a speed command value, the armature winding is immediately performed. The motor speed can be returned to the value of the speed command value by controlling the armature current supplied to the motor, and even if the motor speed rapidly decreases due to the load torque, the constant current Control means Since the control is performed so that the maximum current value does not exceed the preset maximum current value, the problem that the armature current flowing through the armature windings due to the fluctuation of the load torque exceeds and adversely affects the armature windings is ensured. This is convenient because it can be avoided.
[0019]
According to a fifth aspect of the present invention, in the control device for a brushless motor according to the first or second aspect, when the brushless motor is started, the current value is increased with time from a current value sufficient to generate a starting torque of the brushless motor. It is characterized by comprising a start-up compensation means for outputting a commutation command at the time of starting the brushless motor from the commutation command output means using the start-up commutation target current value at the time of the attenuating start-up.
[0020]
According to the fifth aspect of the present invention, when starting the brushless motor, the DC current value detected by the current detection circuit cannot be used as the estimated torque current value to set the commutation target current value. Cannot rotate. For this reason, at the time of starting the brushless motor, a commutation command at the time of starting is output by a starting commutation target current value in which the current value attenuates as time elapses from a current value required to generate a starting torque. Since the motor control device is provided with a start time compensation means for starting the brushless motor, a sufficient armature current to overcome the load torque can be supplied to the armature winding at the time of the start, so that the brushless motor can be started. Even at this time, the brushless motor can be started accurately and softly in accordance with the starting torque. That is, the start-time commutation target current value can be set by the load torque condition at the start by the start-time compensating means, so that the brushless motor of the sensorless drive system can be set to correspond to the load torque even at the time of the start. It can be started quickly and reliably. At the time of the start, the commutation target current value at the start is attenuated as time elapses, and when the commutation target current value at the time of steady operation exceeds the commutation target current value at the start, the brushless It goes without saying that the motor is switched to the sensorless drive system in a steady state.
[0021]
According to a sixth aspect of the present invention, in the control device for a brushless motor according to the first aspect, when the commutation target current value at the time of starting exceeds a maximum current value supplied to the brushless motor, And a start / stop unit for stopping the start of the brushless motor.
[0022]
In the invention according to claim 6, when starting the brushless motor, the starting commutation target current value is supplied by the starting compensation means to start the brushless motor, and the starting commutation target current value is a predetermined maximum. If the current exceeds the current value, the brushless motor is determined to be abnormal and the start / stop means is activated to forcibly stop the start of the brushless motor. Problems such as damage by energization can be reliably avoided.
[0023]
According to a seventh aspect of the present invention, in the control device for a brushless motor according to the sixth aspect, the start / stop unit includes a retry control unit for executing a restart operation a predetermined number of times.
[0024]
In the invention according to claim 7, when the starting operation of the brushless motor is determined to be abnormal due to an increase in load torque or the like at the time of starting, the restart operation is performed using the retry control means, so that the brushless motor is configured. Is designed to check the load etc. and restart operation by the retry control means if it is determined that the operation is abnormal at the start, so that the operation of the brushless motor at the start can be performed quickly, reliably and efficiently. This is convenient.
[0025]
According to an eighth aspect of the present invention, in the control device for a brushless motor according to the first or second aspect, the timer means includes zero reset means for resetting the timer means to zero each time after outputting the current sample command. It is characterized by having done.
[0026]
In the invention described in claim 8, after the time counted up to the time when the DC current value output from the current detection circuit is detected as a sample by the timer means is once returned to zero, the next current sample is detected. Since the zero reset means is provided, the sampling timing of the torque current estimated value can be accurately set from the previous commutation cycle. It has the advantage that it can be performed smoothly and satisfactorily in response to sudden changes in
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. The circuit diagram shown in FIG. 1 is a drive circuit (hereinafter, referred to as a brushless motor drive circuit) 1 used in a sensorless DC brushless motor shown as an embodiment in which a control device for a brushless motor of the present invention is implemented.
[0028]
The above-described brushless motor drive circuit 1 is used as a sensorless drive circuit of a brushless motor used as a well pump for pumping well water or a drive device of an electric device such as an outdoor fan of an air conditioner whose load torque changes suddenly. Is a so-called surface magnet type brushless motor in which a permanent magnet field is a rotor and a three-phase armature winding is a stator, and an embedded magnet type in which a permanent magnet is embedded in a rotor. And the brushless motor drive circuit 1 is used as drive control means for each of the brushless motors 51.
[0029]
Next, the configuration of the brushless motor drive circuit 1 will be described. In FIG. 1, the brushless motor drive circuit 1 is roughly divided into a rectifying / smoothing circuit 2, a control power supply circuit 3, a current detection circuit 4, a motor control device 5, a conduction control circuit 6, an inverter circuit 7, , An overcurrent detection circuit 8 and a reset circuit 9.
[0030]
Subsequently, each circuit and device constituting the brushless motor drive circuit 1 will be described. First, the rectifying / smoothing circuit 2 is configured to rectify and smooth the AC power supply 10 by the diode bridge 2a and the smoothing capacitor 2b, and to supply, for example, 140 V DC power to the control power supply circuit 3 and the inverter circuit 7. ing. The control power supply circuit 3 includes, for example, a ringing choke converter type switching power supply 3a. The control power supply circuit 3 supplies a control power supply (for example, 5V) for driving the circuits and devices to drive these circuits. Supply.
[0031]
The current detection circuit 4 is a circuit that converts an armature current flowing through an armature winding (not shown) of the brushless motor 51 into a voltage and detects the voltage, and is inserted and connected between the output terminal of the rectification / smoothing circuit 2 and the inverter circuit 7. Shunt resistor 4a and an amplifier circuit 4b for amplifying a voltage detected by the shunt resistor 4a to a predetermined voltage. An armature current flowing through the armature winding is detected by the shunt resistor 4a. Is output to the motor control device 5 with the DC current amplified by the amplifier circuit 4b as a DC current value. FIG. 4 shows an output waveform of a DC current value output from the current detection circuit 4 during a steady operation of the brushless motor 51. The DC current value is used to switch an energized phase of an armature winding. It is used as a base for determining the commutation period and controlling the constant current and the number of revolutions.
[0032]
The motor control device 5 includes, for example, a 16-bit single-chip microcomputer. The one-chip large-scale integrated circuit includes a brushless motor 51 such as an 8-bit A / D converter and various control means. Various functions necessary for drive control are incorporated. These control functions are, for example, a sensorless control program, a current control program, a speed control, and the like for performing software processing of the various control means (described later). Drive control is performed by a control program and an abnormality detection program.
[0033]
The energization control circuit 6 is a circuit for distributing the output from the motor control device 5 to the inverter circuit 7 and outputting it. The energization control circuit 6 is configured using a predetermined number of AND circuits. The output from the motor control device 5 is sequentially distributed to the inverter circuit 7 for output, and an overcurrent value equal to or greater than the maximum current value determined by the maximum rating of the brushless motor is input to an overcurrent detection circuit 8 described later. When an overcurrent is detected, the overcurrent detection circuit 8 outputs an output stop command to the motor control device 5 and the conduction control circuit 6 instantaneously from its output terminal, thereby preventing the overcurrent from flowing through the inverter circuit 7. .
[0034]
Next, the inverter circuit 7 will be described. The inverter circuit 7 is a circuit for sequentially supplying and switching, for example, a DC voltage of 140 V to each of the three-phase (U-phase, V-phase, and W-phase) armature windings of the brushless motor 51 for each phase. . The collector terminals of three transistors u, v, w are connected to the positive input terminal of the rectifying / smoothing circuit 2 of the inverter circuit 7, respectively. , The emitter terminals of three transistors x, y, z are connected to each other, and these transistors u, v, w, x, y, z form three arms corresponding to a three-phase armature winding. Have been. Each of the transistors u to z is connected to a required output terminal of the conduction control circuit 6, and is configured to be able to perform on / off control according to an output from the conduction control circuit 6. In addition, between the collector and the emitter of each of the transistors u to z, a current due to a back electromotive force generated in the armature winding of the brushless motor 51 when the transistors u to z are turned on / off is not shown. A required number of diodes are respectively connected in anti-parallel.
[0035]
The overcurrent detection circuit 8 includes an amplifier circuit 8a having one connected to the output terminal of the shunt resistor 4a of the current detection circuit 4 and the other grounded, and a latch circuit 8b having an input terminal connected to the output terminal of the amplifier circuit 8a. The armature current flowing through the armature winding of the brushless motor 51 is detected by the shunt resistor 4a of the current detection circuit 4, and the detected DC current value reaches a preset overcurrent value. In this case, this is detected and held by the latch circuit 8b, and the output signals output from the motor control device 5 and the power supply control circuit 6 are transmitted from the latch circuit 8b to the motor control device 5 and the power supply control circuit 6, respectively. It outputs an overcurrent signal for instantaneously stopping the output to the circuit 7 to prevent the overcurrent from flowing through the armature winding. That is, the operation of the brushless motor 51 is forcibly stopped to prevent the brushless motor 51 from being damaged by an overcurrent.
[0036]
The reset circuit 9 includes, for example, an analog switch 9a and a reset IC element 9b. When the overcurrent detection circuit 8 operates, the motor control device 5 and the conduction control circuit 6 input an overcurrent signal. When the overcurrent disappears and the brushless motor drive circuit 1 returns to a normal state when the output is stopped by the above, a reset signal is output to the motor control device 5 and the energization control circuit 6, respectively. The microcomputer of the device 5 is initialized so that it can deal with the next re-drive of the brushless motor 51.
[0037]
Next, the configuration of the motor control device 5 will be described with reference to FIGS. As described above, the motor control device 5 is configured to perform drive control of the brushless motor 51 by activating each control unit that forms a control function according to the motor control program described above. The prerequisite motor control program roughly comprises the following program.
[0038]
(1) Sensorless control program
This program determines the commutation period for switching each energized phase based on the armature current waveform flowing in the energized phase of the armature winding of the brushless motor 51, and smoothly controls the rotation of the brushless motor 51. is there.
(2) Current control program
This program drives the brushless motor 51 with a predetermined current, and determines a PWM conduction width command value (PWM control signal) based on a current deviation (a difference between a command current value and a current supplied to an armature winding). To do.
(3) Speed control program
This program operates the brushless motor 51 in accordance with a speed command value set in advance. The program obtains a command current value from a rotation speed deviation (difference between the speed command value and the motor rotation speed), and uses this command current value to perform PWM. An energization width command value (a PWM control signal is determined, and the brushless motor 51 is always driven and controlled by a preset speed command value.
(4) Abnormality detection program
This program detects an operation abnormality when a preset speed command value (number of rotations) of the brushless motor 51 and a command current value for maintaining the speed command value exceed a preset maximum current value. The current supply to the brushless motor 51 is immediately stopped.
[0039]
Subsequently, each control means and the like constituting the control function of the motor control device 5 will be described. First, in FIG. 2, the A / D converter 21 of the motor control device 5 converts the DC current value detected by the current detection circuit 4 into a digital value. 4 can be obtained based on the voltage output from the amplifier circuit 4b.
[0040]
In other words, the current input to the amplifier circuit 4b is, for example, 4 A, and the A / D converter 21 (8 bits) has a full-scale value of 255. In this case, the proportional constant K when converting the current into the voltage in the A / D converter 21 is set to K = 0.2. When the output voltage from the amplifier circuit 4b is obtained based on the above data, V = 0.2 × 4 = 0.8V. When this output voltage 0.8V is divided by the input voltage (5V) at the time of full scale, 0.8 (V) / 5 (V) = 0.16. When the numerical value of 0.16 is multiplied by the full-scale value 255, 0.16 × 255 = 40.8, and the value obtained by rounding down the decimal point of 40.8, that is, the numerical value of 40 is the A / D converter. 21.
[0041]
Based on the numerical value (40) output from the A / D converter 21, the current value held and stored by the armature current calculating means 22 in the sample and hold means 23, which will be described later, is represented by the following equation [Equation 1]. Calculate using
[0042]
(Equation 1)

[0043]
here,
i: DC current value Idc calculated by numerical value (D) output from A / D converter 21
K: Proportional constant when converting current to voltage in A / D converter 21
Vmax: input voltage at full scale
Dmax: Full scale value
[0044]
The armature current calculating means 22 calculates the data used for obtaining the numerical value D output from the A / D converter 21 in the equation [1] shown in [Equation 1], that is, in the paragraph number [0040]. A DC current value Idc corresponding to the numerical value D output from the A / D converter 21 is calculated by substituting the described numerical values and performing arithmetic processing.
[0045]
(Equation 2)

[0046]
The DC current value Idc (4A) calculated by the armature current calculation means 22 is input to a sample and hold means 23 described later.
[0047]
Next, the role of the sample and hold means 23 will be described. As described above, the sample and hold means 23 holds and records the DC current value Idc calculated by performing arithmetic processing based on the numerical values sequentially output from the A / D converter 21 at predetermined sample times ts. By means, the DC current value Idc held at each sample time is set as a torque current estimated value Iq. The sampling time ts is equal to the current-period switching period (hereinafter, referred to as a commutation period T) T of the armature current flowing through the previous armature winding. _n-1 Is determined by arithmetic processing from
[0048]
In other words, in the present invention, the setting of the sampling time ts is determined by the immediately preceding (previous) commutation period T _n-1 Is multiplied by a sampling coefficient Kt. The sampling coefficient Kt may be determined in the range of 0 <Kt <1 depending on the characteristics of the target electric motor, and the sampling time ts is calculated by [Equation 3] of the following equation [2].
[0049]
[Equation 3]

[0050]
here,
n: Number of commutation
Kt: sampling coefficient
The DC current value Idc calculated by calculating the sample time ts by the equation [2] shown in the above [Equation 3] and performing arithmetic processing on the numerical value output from the A / D converter 21 at the time when t = ts. Is sampled as the estimated torque current value Iq. Here, t indicates the time when the commutation period T in the predetermined energized phase of the armature winding ends. The estimated torque current value Iq is estimated that most of the DC current value Idc after the sample time ts becomes a torque contributing component from the time of the commutation command issued every commutation period T of the energized phase of the armature winding. Represents the sampled current value Iq.
[0051]
Next, the commutation target current value calculation means 24 will be described. The calculating means 24 multiplies the torque current estimated value Iq at the DC current value Idc held and stored by the sample and hold means 23 by a constant, and sets this as an initial value of the steady state commutation target current value Isf; A function of sequentially reducing the initial value with the passage of time. The commutation target current value calculation means 24 calculates the steady-state commutation target current value Isf based on the torque current estimated value Iq by [number 4] by the following equation.
[0052]
(Equation 4)

[0053]
here,
Ks: function of speed
Iq: estimated torque current
τd: Reduction time constant
ta: time from sample time
However, ta = 0 is reset at each sampling time.
The steady-state commutation target current value Isf calculated by the equation [3] shown in the above [Equation 4] is calculated based on the DC current value Idc calculated by the armature current calculation means 22 and the commutation command output described below. The comparison is made by means 25.
[0054]
The commutation command output means 25 has a function of switching the energized phase of the armature current supplied to the armature winding of the brushless motor 51, that is, sets the commutation period T of each energized phase and issues a commutation command. Output. This allows the drive of the brushless motor 51 to be favorably continued by switching the energization of the armature windings of the brushless motor 51 to each energizing phase with good timing. The commutation cycle T of the predetermined energized phase is determined when the steady-state commutation target current value Isf and the DC current value Idc input from the armature current calculation means 22 to the commutation command output means 25 are: Alternatively, when the DC current value Idc exceeds the steady state commutation target current value Isf, the energized phase of the armature winding is switched (commutation).
[0055]
The sample time calculating means 26 calculates the commutation period T when the energized phase of the armature winding of the brushless motor 51 is switched, that is, the previous commutation period T _n-1 Is multiplied by a sampling coefficient to calculate (calculate) a sample time ts. The DC current value Idc output from the armature current calculation unit 22 is calculated for each sample time ts obtained by the calculation process. The sample and hold means 23 performs sample and hold. Since the calculation process of the sample time ts is performed by the above-described [Equation 3], the description thereof will be omitted because it is duplicated.
[0056]
The timer means 27 has a function of outputting a command to sample and hold the DC current value Idc to the sample and hold means 23 at each time ts calculated by the arithmetic processing by the sample time calculation means 26. Due to the presence of 27, the sample-and-hold means 23 reliably holds the DC current value Idc at every optimal switching cycle (commutation cycle T) in each energized phase, not at the time set in advance, and always sets the commutation target. Since the current value calculation means 24 can output the commutation command, the commutation command in each energized phase can be performed by selecting an optimal time. The timer means 27 is provided with a zero reset means (not shown) for resetting the timer means 27 to zero each time a current sample command is output.
[0057]
Subsequently, the rotation speed calculation means 28 calculates the DC current value Idc output from the armature current calculation means 22 as a base, and FIG. 4 shows a current waveform diagram sequentially output from the armature current calculation means 22. As shown in the figure, the cycle of the DC current value Idc is counted by a counting means (not shown), and the time of one cycle is set to, for example, t seconds from the count value, to thereby determine the current rotational speed of the brushless motor 51 ( (Rotational speed), and the calculation formula uses the formula shown in [Equation 5].
[0058]
(Equation 5)

[0059]
here,
P: Number of poles of brushless motor
t: Time of one cycle of output waveform (second)
The rotation speed per minute of the brushless motor 51 is calculated by the calculation formula shown in [Equation 5].
[0060]
Next, the constant current / rotation speed control means 29 will be described. The constant current / rotation speed control unit 29 compares the rotation speed of the brushless motor 51 calculated by the rotation speed calculation unit 28 with a preset rotation speed (speed command value), and constantly rotates the brushless motor 51. A command current value i0 of the armature current supplied to the armature winding is controlled so that the speed matches the speed command value.
[0061]
Further, in the constant current / rotation speed control means 29, the load torque fluctuates during the driving of the brushless motor 51, so that the armature current flowing through each energized phase of the armature winding increases. In order to prevent burnout of the armature winding and demagnetization of the permanent magnet provided on the rotor, which occurs when the temperature of the wire rises and exceeds a predetermined set temperature, it flows through the armature winding in advance. The maximum value of the armature current is set, and the constant current control is performed so that the DC current value Idc output from the armature current calculation means 22 does not exceed the maximum current value.
[0062]
Therefore, when the armature current supplied to the armature winding suddenly increases due to an increase in the load, the rotation speed of the rotor is reduced from the speed command value beforehand and the armature winding is supplied to the armature winding. It is provided so that constant current control can be performed while preventing an increase in the armature current. As a result, even when the load torque suddenly changes during the operation of the brushless motor 51, it is possible to constantly and smoothly drive the brushless motor 51 at a predetermined rotation speed by performing the constant current / rotation speed control. .
[0063]
The PWM control means 30 is operated by the output from the commutation command output means 25, and modulates the pulse width by the output (voltage command value Vq) from the constant current / rotation speed control means 29. By outputting a signal having a width as a PWM control signal to the inverter circuit 7 and controlling the bases of required transistors u to z of the inverter circuit 7 on / off by a pulse signal settled to a required pulse width, a brushless operation is performed. The drive of the motor 51 is controlled by an arbitrary speed command value.
[0064]
The starting compensation means 31 is provided so that the brushless motor 51 can obtain a sufficient starting torque when the brushless motor 51 starts. In the steady state sensorless drive system, the brushless motor 51 cannot determine the steady state commutation target current value Isf, and as a result, cannot be started. For this reason, in the brushless motor 51, the commutation target current value Isb is used as the commutation target value only at the time of starting the motor. That is, in the brushless motor 51, the starting commutation target current value Isb is forcibly set at the time of the start (although it depends on the load, it is needless to say that the maximum current value supplied to the brushless motor 51 is set as a guide). Is supplied to the armature winding to start the brushless motor 51. The starting commutation target current value Isb decreases with the passage of time, and when the steady-state commutation target current value Isf exceeds the startup commutation target current value Isb, the sensorless driving method in the steady state is used. It is configured to switch.
[0065]
Next, the operation of the brushless motor drive circuit 1 configured as described above will be described. First, the starting of the brushless motor 51 will be described. The brushless motor 51 is driven by considering the DC current value Idc held and stored by the sample and hold means 23 after the sampling time ts calculated based on the commutation period T as the estimated torque current value Iq and the commutation target current value Is Is determined, the commutation target current value Is in the first energization mode is indefinite, that is, the sample time ts at the time of starting becomes indefinite. As a result, the commutation target current value Is cannot be set. , The brushless motor 51 cannot be started.
[0066]
In the present invention, the starting current command value (the starting commutation target current value Isb) at which the current value temporarily decreases with the passage of time is set as the avoidance measure, and the commutation (electric (Switching of the current-carrying phase of the slave winding). The starting commutation target current value Isb is set in advance according to a load condition at the time of starting. In the present invention, the starting compensation means 31 provided in the motor control device 5 shown in FIG. I have.
[0067]
5 and 7, the start-up process of the brushless motor 51 will be described. At the start, the PWM control means 30 shown in FIG. 2 sets the PWM carrier frequency and the duty ratio (duty cycle) as initial values, and the start time compensation means 31 sets the commutation target current value Is as the starting time. After substituting (setting) the commutation target current value Isb, energization is started (see steps S1 to S3 in FIG. 7).
[0068]
This is to realize a soft start of the brushless motor 51 by setting the carrier frequency and the duty cycle to be low at the time of starting, thereby increasing the current smoothly and sequentially. Further, providing commutation target current value Isb at start and performing commutation at the initial stage of the start is a heavy burden on a load. For example, when a brushless motor is used as a drive source of a pump, the presence of water resistance, dust, etc. Therefore, it is assumed that a large load is applied to the impeller, or when the outdoor unit of the air conditioner is driven, a disturbance such as a back wind is applied to the fan and the load is increased more than necessary.
[0069]
When the energization is started, the AC power supply 10 is energized to the control power supply circuit 3 and the inverter circuit 7 via the rectification / smoothing circuit 2. From the control power supply circuit 3, a DC power of 5 V is supplied to each circuit including the motor control device 5. The motor control device 5 is operated in accordance with the energization of the DC power supply (5V), and the commutation command means 25 → the PWM control means 30 through the commutation command means 25 → PWM control means 30 according to the commutation target current value Isb set by the start compensation means 31. 7, a PWM control signal is output to the inverter circuit 7, and for example, the transistors u and y of the inverter circuit 7 are turned on, so that an armature current flows from the U-phase to the V-phase of the armature winding of the brushless motor 51. As a result, the driving of the brushless motor 51 is started.
[0070]
The armature current supplied to the brushless motor 51 is detected by the shunt resistor 4a of the current detection circuit 4, converted into a voltage, and output to the A / D converter 21 of the motor control device 5. The DC current value Idc detected by the current detection circuit 4 is converted into a digital value by an A / D converter 21, and the numerical value converted into the digital value is output to an armature current calculation means 22. The armature current calculation means 22 calculates the DC current value Idc by performing arithmetic processing based on [Equation 1] based on the numerical value set by the / D converter 21, and the DC current value Idc is sampled and held by the sample-and-hold means 23. To the commutation command means 25.
[0071]
The DC current value Idc input to the sample-and-hold means 23 is calculated by the sample time ts calculated by the sampling time calculating means 26 according to the equation [2] shown in [Equation 3]. Hold and store each time it is output. The sample and hold means 23 samples the DC current value Idc stored and held as an estimated torque current value Iq. The timer means 27 is reset once by the zero reset means (not shown) after the output of the current sample command, and prepares for the output of the next current sample command.
[0072]
The sampled and held torque current estimated value Iq is output to the next commutation target current value calculation means 24, and the calculation means 24 obtains the starting commutation target current value Isb. Then, the starting commutation target current value Isb obtained by the commutation target current value calculation means 24 is compared with the DC current value Idc output from the armature current calculation means 22 to the commutation command output means 25, and Isb If not <Idc, the commutation command output means 25 does not output the commutation command to the PWM control means 30. In this case, it is needless to say that the calculation process of the starting commutation target current value Isb and the steady-state commutation target current value Isf is performed again.
[0073]
Conversely, if Isb <Idc, a commutation command is output from the commutation command output means 25 to the PWM control means 30, and from the PWM control means 30, the transistors u, for which the inverter circuit 7 has been turned on, Instead of y, a PWM control signal for turning on the transistors u and z is output, and the armature current of the brushless motor 51 flowing from the U phase to the V phase of the armature winding is commutated from the U phase to the W phase. (See steps S4 to S6 in FIG. 7).
[0074]
FIG. 5 is a waveform diagram showing the state of the commutation timing at the time of starting the brushless motor 51 described above. As is apparent from FIG. 5, the starting commutation target current value Isb is configured to attenuate as time elapses. ing. As the commutation target current value Is, a larger one of the starting commutation target current value Isb and the steady-state commutation target current value Isf is selected, but once the steady-state commutation target current value Isf is When the current value exceeds the commutation target current value Isb, Is = Isf. However, as described above, the steady-state commutation target current value Isf at the time of starting the brushless motor 51 is indeterminate, and thus the start-time commutation target current value Isb becomes the commutation target current value Is.
[0075]
The commutation command (commutation cycle T) is obtained by comparing the commutation target current value Is (starting commutation target current value Isb) with the DC current value Idc by the commutation command output means 25, and the DC current value Idc Commutation processing is performed at a time point when has reached the commutation target current value Is. As a result, as described above, until the DC current value Idc exceeds the commutation target current value Is, as shown in the waveform diagram of FIG. The current value Isf is calculated, and a larger value is selected. Note that the commutation cycle T is reset to T = 0 by the timer means 27 each time commutation is performed, and it is needless to say that the commutation target current value Isb at the time of starting is calculated based on the time from the start of energization (FIG. 7). Steps S6 to S12).
[0076]
In FIG. 5, when the steady-state commutation target current value Isf is equal to or greater than the start-time commutation target current value Isb, that is, when Isf ≧ Isb in step S8 of FIG. 7, the brushless motor 51 starts. The operation state shifts from the operating state at the time to the operating state at the steady state (see steps S8 and S13 in FIG. 7).
[0077]
As described above, the brushless motor 51 sets the commutation period T based on the start-time commutation target current value Isb set in advance at the time of the start, and the PWM control means 30 lowers the carrier frequency. Since the armature current flowing through the armature winding is set to gradually increase, and the energization ratio is gradually increased from 0 during the period from the start of energization to the steady operation, the motor is driven. It can be started smoothly according to the torque.
[0078]
Next, the steady operation state of the brushless motor 51 will be described with reference to FIGS. As described above, even when the brushless motor 51 shifts from the start operation to the steady operation, the speed command value is basically calculated by calculating the steady state commutation target current value Isf and setting the commutation cycle. The brushless motor 51 is driven while maintaining the rotation speed (number of rotations) set in.
[0079]
In FIG. 8, the steady state commutation target current value Isf is compared with the DC current value Idc, and commutation is performed when the DC current value Idc reaches the steady state commutation target current value Isf. The energized phase is switched (see step S22 in FIG. 8). In this case, if the DC current value Idc has not reached the steady state commutation target current value Isf, the steady state commutation target current value Isf is calculated again, and the DC current value Idc and the steady state commutation target current value Isf are calculated. Are repeated (see steps S20 and S21 in FIG. 8). The above situation is apparent from the waveform diagrams of the commutation timings shown in FIGS.
[0080]
After the commutation, the timer time until the next current sample command is calculated in steps S23 and S24 of FIG. 8 by using the equation [2] shown in [Equation 3]. When the sampling time ts has been reached, the process proceeds to step S25 in FIG. 8 to set the steady-state commutation target current value Isf based on the estimated torque current value Iq according to [3] shown in [Equation 4]. . A commutation command is output in accordance with this flowchart, and the energized phase of the armature winding is switched. The description of these has already been given in [Equation 3] and [Equation 4] [2] and [3]. In the present invention, the steady-state commutation target current value Isf is simply calculated by calculating the sample time ts and the steady-state commutation target current value Isf by calculating the following formula. Rather than calculating and setting the commutation timing, the commutation timing is always set at the optimal time when the armature current flowing through the armature windings contributes to the rotational torque. Since the commutation current is sampled, the steady-state commutation target current value Isf is calculated based on the estimated torque current value Iq, and the commutation timing of the brushless motor 51 can be set. Brushless motor 51 can always be driven to maintain the rotational speed of the speed command value in response to variation of the load (speed).
[0081]
As a result, in step S26 of FIG. 8, it is determined whether the armature current supplied to the armature winding of the brushless motor 51 is larger or smaller than a preset maximum current value. Is large (increase in load), the constant current control means set in the constant current / rotation speed control means 29 shown in FIG. 3 operates to suppress the armature current flowing through the armature winding, This prevents the child winding from being burnt out due to overcurrent. In this case, since the energizing current is suppressed, it goes without saying that the rotation speed (the number of rotations) of the brushless motor 51 is limited by the controlled current.
[0082]
If the current supplied to the armature winding is smaller than the maximum current value in step S26 in FIG. 8, the process proceeds to step S28, and the rotation speed calculated by the rotation speed calculating unit 28 shown in FIG. In order to match the rotation speed set in advance with the speed command value, the rotation speed control means set in the constant current / rotation speed control means 29 is operated so that the rotation speed set in the speed command value is obtained. The brushless motor 51 can be smoothly driven at a rotational speed of a predetermined speed command value always corresponding to the load torque since the armature winding is energized by controlling the energization of the motor.
[0083]
Next, the details of the constant current / rotation speed control processing of the brushless motor 51 are as described in the flowchart shown in FIG. The constant current / rotation speed control is based on the fact that the brushless motor drive circuit 1 of the present invention employs a current waveform reference type sensorless drive system, and therefore, the current detection circuit 4 inserted on the ground side of the inverter circuit 7. The detection current detected by the shunt resistor 4a is the only information source related to the detection of the rotational position of the rotor of the brushless motor 51. Therefore, the rotation speed (rotation speed) of the brushless motor 51 is also detected by the energized phase of the armature winding. Is calculated from the commutation period T for switching.
[0084]
As a result, as shown in FIG. 3, for example, when the load (a well pump or the like) is operating at or below the maximum rated output, the rotation speed control loop having the rotation speed calculation means 28 controls the load at a constant speed. When the operation is performed and the maximum rated output is exceeded during the operation of the load, in order to protect the brushless motor 51, only the constant current control (constant output control) having the armature current calculation means 22 is performed. The operation of the brushless motor 51 is performed by the used current control loop.
[0085]
The above-described constant current / rotation speed control processing will be described with reference to FIG. In step S30 in FIG. 9, the rotational speed rpm of the rotor is calculated by the equation [4] shown in [Equation 5] based on the commutation period T of the brushless motor 51. In step S31, the calculated rotation speed rpm is compared with a carrier frequency change threshold value of the PWM control means 30 to determine whether it is equal (larger) or not. If so, the carrier frequency of the PWM control means 30 is increased. In the case of, lower the carrier frequency.
[0086]
Next, the process proceeds to step S34 in FIG. 9 to calculate a rotation speed deviation value rpme at a difference between the speed command value rpm0 and the current rotation speed (rotation speed) rpm. Then, the current command current value i0 is calculated from the rotational speed deviation value rpme in step S35. This command current value i0 is calculated by PI control. That is, the command current value i0 is calculated by an operation including a proportional element and an integral element.
[0087]
This command current value i0 is compared with the maximum current value (maximum rated output) imax in step S36. If the command current value i0 is equal to or exceeds the maximum current value imax, the command current value i0 is set to the maximum current value imax. . At this point, as a result, the constant current control is executed (see step S37 in FIG. 9). Thereafter, the process proceeds to step S38, in which a difference between the command current value i0 and the current torque current estimated value Iq (calculated by the armature current calculating means 22) is obtained, and the obtained value is set as a current deviation ie.
[0088]
The PWM current width command value vd0 of the pulse signal (PWM current width) output from the PWM control means 30 is calculated in step S39 based on the current deviation ie calculated in step S38. Then, the PWM conduction width command value vd0 output from the PWM control means 30 obtained by the calculation in step S39 and the preset PWM conduction width maximum value vdmax output from the PWM control means 30 are stepped. If the PWM conduction width command value vd0 is equal to or larger than the PWM conduction width maximum value vdmax, the PWM control means 30 will limit the PWM conduction width maximum value vdmax, that is, the PWM conduction width maximum value. A PWM control signal is output in step S41 with vdmax as a PWM energization command value vd0, and required transistors u to z of the inverter circuit 7 are turned on and off for a predetermined time, so that the rotation speed (rotation speed) of the brushless motor 51 is controlled. It is configured to match the value. Thereafter, in step S41, while controlling the energization of the armature current flowing through the armature winding, the rotation speed values of the rotor are individually adjusted, and the brushless motor 51 continues rotating at a predetermined speed command value. It is to let.
[0089]
As described above, in the present invention, the constant current / rotational speed control means 29 uses the armature current flowing through the armature winding detected by the current detection circuit 4 as a base as shown in FIG. The command current value i0 and the current rotation speed (rotation speed) rpm calculated by the current control program set in the control device 5, the armature current calculation means 22 operated by the speed control program, and the rotation speed control means 28. Are adapted to be adapted to a preset maximum current value imax and a rotation speed target value (speed command value) rpm0, respectively, so that the brushless motor 51 rotates the rotation speed in response to a load change. When the control is performed so as to match the numerical target value rpm0 and the command current value i0 is going to exceed the maximum current value imax, the command current value i0 is set to the maximum current value. It is possible to hold in the range of imax, when the load torque suddenly changes also performed by the appropriate constant current and rotational speed control to obtain, can be stably driving a brushless motor 51.
[0090]
Further, the motor control device 5 described above is also provided with a processing function (start / stop means) for detecting an abnormality of the brushless motor 51, as shown in the flowchart of FIG. The start / stop means for stopping the start of the brushless motor 51 based on this abnormality detection is provided in order to avoid an unexpected situation mainly occurring when the brushless motor 51 is started.
[0091]
Hereinafter, the contents of the abnormality detection processing having the start / stop means will be described with reference to the flowchart of FIG. The startup process of the brushless motor 51 has been described in detail with reference to FIG. The commutation cycle T (time) for starting the brushless motor 51 in step S51 of FIG. 10 and switching the energized phase of the armature winding is measured every time a commutation command is output in step S52. It is determined in the next step S53 whether the time required for the command is smaller or larger than the time of the commutation cycle T when the brushless motor 51 is at the maximum rotation speed.
[0092]
When it is determined in step S53 of FIG. 10 that the commutation period T at the time of starting is smaller than the commutation period T at the time of the maximum rotation speed, the process proceeds to step S54, and the starting process is temporarily stopped. On the other hand, when the commutation period T at the start is larger than the commutation period T at the maximum rotation speed, that is, when the brushless motor 51 is started, the load is stopped as shown in FIG. Since the commutation is started at the current target current value Isb, the commutation period T is necessarily large (it takes time to switch the energized phase of the armature winding). However, when the brushless motor 51 is converted to the steady-state operation, the rotation speed also increases, and as a result, the commutation period T (the switching time of the current-carrying phase of the armature windings increases) naturally decreases.
[0093]
When the commutation cycle T at the time of starting is larger than the commutation cycle T at the maximum rotation speed, the process proceeds to step S55 to detect the estimated torque current value Iq. When starting the brushless motor 51, the estimated torque current value Iq substantially corresponds to the commutation target value Isb at the start, and the estimated torque current value Iq and the preset maximum torque current estimated value (maximum current Value Imax) in step S56.
[0094]
As a result of the comparison in step S56, when the estimated torque current value Iq is small, the process proceeds to the next steps S57 and S58, the brushless motor 51 is started by sensorless control, and after the start, the steady-state commutation target current value Isf When the current exceeds the commutation target current value Isb at the time of start, the operation shifts to a steady operation, and the brushless motor 51 is driven and controlled by the constant current / rotation speed control means 29 to continue rotating. Conversely, when the estimated torque current value Iq exceeds the maximum torque current value, it is determined that the overcurrent value has been reached, and the process proceeds to step S54.
[0095]
That is, when it is determined in steps S53 and S56 that it is not, the process proceeds to step S54, in which the brushless motor 51 does not start and is in a stopped state. In this case, the retry control means (not shown) provided in the start / stop means of the motor control device 5 is operated to execute the restart processing. In this case, if the operation of the retry control means is repeated three times, for example, and the brushless motor 51 starts, there is no problem. However, if the brushless motor cannot be restarted even after operating the retry control means three times, it is determined that there is an abnormality in step S61, and the start of the brushless motor 51 is stopped.
[0096]
This stoppage of the start is due to the failure of the brushless motor 51 or a problem with the load that the start process cannot be performed. The problem of burning out can be avoided beforehand. Incidentally, an instantaneous overcurrent that cannot be handled by the program of the motor control device 5 is detected by an overcurrent detection circuit 8 provided in the brushless motor drive circuit 1 and immediately connected to the motor control device 5 by the power supply control. Since the configuration is such that the overcurrent detection signal is output to the circuit 6 and the processing during operation is stopped, the detection of the brushless motor 51 by the overcurrent can be satisfactorily avoided.
[0097]
【The invention's effect】
As described above, the present invention relates to a motor control device that drives and controls a brushless motor without a sensor. The motor control device detects a commutation command in an armature winding of the brushless motor and a DC current value detected by a current detection circuit. Calculates the commutation target current value as the estimated torque current value, compares it with the DC current value detected by the current detection circuit, and instantaneously outputs the result. It is possible to output a command, and the energized phase switching of the armature current flowing through the armature winding of the brushless motor can be smoothly performed at the optimal time, whereby the rotation control of the brushless motor can be smoothly and smoothly performed. In addition, it can be performed with high efficiency. Therefore, even when the load torque suddenly changes during the operation of the brushless motor, the commutation command can be output at an appropriate timing, so that the brushless motor can always be driven in a stable state at a predetermined rotation speed. it can.
[0098]
Further, in the present invention, the constant current / rotation speed control means is employed in the motor control device, so that the brushless motor always compares its own rotation speed with a preset speed command value of the rotation speed. Control the rotational speed of the brushless motor so that it matches the speed command value.In addition, the increase in the load increases the energizing current and raises the temperature of the brushless motor. In order to avoid such a problem that the provided permanent magnet is demagnetized, the maximum current value to be supplied to the armature winding is set in advance, and the DC current value detected by the current detection circuit is the maximum current value. , And the constant current control is performed so that the brushless motor has an appropriate commutation even if the torque fluctuates due to a sudden change in the load torque during the operation. It is possible to realize the driving of a stable state at a predetermined rotational speed.
[0099]
Further, in the present invention, since the motor control device is provided with a start time compensating means for outputting a commutation command at the time of starting, the brushless motor has a sufficient armature current for generating a starting torque at the time of starting. Can be supplied to the armature winding, so that even at the time of starting, the brushless motor can be started accurately and softly in accordance with the starting torque. In addition, when starting the brushless motor, if the commutation target current value at the time of starting exceeds the maximum current value due to load torque and the like, it is determined that there is an abnormality, and the brushless motor is stopped and the abnormal state is determined. Is eliminated, the starting operation can be performed immediately by the retry operation, so that the sensorless drive type brushless motor can be started quickly, reliably, and smoothly at all times.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a brushless motor drive circuit according to the present invention.
FIG. 2 is a block diagram showing a configuration of a motor control device provided in the brushless motor drive circuit of the present invention.
FIG. 3 is a block diagram schematically showing a configuration of a constant current / rotation speed control unit.
FIG. 4 is a waveform diagram showing an output current waveform of a current detection circuit.
FIG. 5 is a diagram illustrating a waveform of a current flowing through an armature winding during a start-up operation of the brushless motor.
FIG. 6 is a diagram showing output current waveforms of each means during a steady operation of the brushless motor.
FIG. 7 is a flowchart illustrating an operation process at the time of starting the brushless motor.
FIG. 8 is a flowchart illustrating a steady operation process of the brushless motor.
FIG. 9 is a flowchart illustrating a constant current / rotation speed process of the brushless motor.
FIG. 10 is a flowchart illustrating a process in an abnormal state of the brushless motor.
[Explanation of symbols]
1 Brushless motor drive circuit
4 Current detection circuit
5 Motor control device
6 Energization control circuit
7 Inverter circuit
8 Overcurrent detection circuit
21 A / D converter
22 Armature current calculation means
23 Sample holding means
24 Commutation target current value calculation means
25 Commutation command output means
26 Sample time calculation means
27 Timer means
28 Revolution calculation means
29 Constant current / rotation speed control means
30 PWM control means
31 Start-up compensation means

Claims (8)

An inverter circuit having a plurality of switching elements for sequentially applying a DC voltage to a plurality of phase armature windings of the brushless motor, and an energization for turning on and off the plurality of switching elements of the inverter circuit to rotate the brushless motor. A control circuit for controlling a brushless motor, comprising: a current detection circuit that converts an armature current flowing through an armature winding of the brushless motor into a voltage and detects the voltage; and a DC current value detected by the current detection circuit. Sample-and-hold means for sample-holding and outputting a torque current estimation value, commutation target current value calculation means for calculating and processing a commutation target current value based on the torque current estimation value, and detection by the current detection circuit. A commutation command output means for outputting a commutation command when the detected DC current value exceeds the commutation target current value; Sample time calculation means for calculating and setting the time at which the DC current value after the command output is detected as a sample, and torque current estimation based on the DC current value output from the current detection circuit at the time set by the sample time calculation means. A brushless motor control device comprising: a motor control device including timer means for outputting a current sample command for sampling and holding as a value at each time. An inverter circuit having a plurality of switching elements for sequentially applying a DC voltage to a plurality of phase armature windings of the brushless motor, and an energization for turning on and off the plurality of switching elements of the inverter circuit to rotate the brushless motor. A control circuit for controlling a brushless motor, comprising: a current detection circuit that converts an armature current flowing through an armature winding of the brushless motor into a voltage and detects the voltage; and a DC current value detected by the current detection circuit. Sample-and-hold means for sample-holding and outputting a torque current estimation value, commutation target current value calculation means for calculating and processing a commutation target current value based on the torque current estimation value, and detection by the current detection circuit. A commutation command output means for outputting a commutation command when the detected DC current value exceeds the commutation target current value; Sample time calculation means for calculating and setting the time at which the DC current value after the command output is detected as a sample, and torque current estimation based on the DC current value output from the current detection circuit at the time set by the sample time calculation means. Timer means for outputting a current sample command for sampling and holding as a value at each time, and furthermore, setting an armature current flowing through an armature winding of the brushless motor to a value larger or smaller than a preset maximum current value. A brushless motor comprising: a constant current / rotational speed control means for judging and controlling the rotation speed of the brushless motor or the armature current flowing through the armature winding of the brushless motor; Control device. The constant current / rotation speed control unit includes a motor rotation speed calculation unit configured to detect a commutation period of the armature current flowing in the energized phase of the armature winding of the brushless motor and calculate the rotation speed of the brushless motor. 3. The control device for a brushless motor according to claim 2, wherein The constant current / rotation speed control means includes an armature current calculation means for calculating an armature current flowing through an armature winding of the brushless motor based on a DC current value detected by the current detection circuit. 3. The control device for a brushless motor according to claim 2, wherein: When starting the brushless motor, the brushless motor uses a commutation target output current value at start-up when the current value attenuates with time from a current value sufficient to generate the starting torque of the brushless motor. 3. The brushless motor control device according to claim 1, further comprising a start-time compensation means for outputting a commutation command at the time of starting the motor. The motor control device may further include a start / stop unit configured to determine that an abnormality has occurred and stop the start of the brushless motor when the start-time commutation target current value exceeds a maximum current value supplied to the brushless motor. The control device for a brushless motor according to claim 1, wherein 7. The brushless motor control device according to claim 6, wherein the start / stop unit includes a retry control unit for executing a restart operation of the stopped brushless motor a predetermined number of times. 3. The brushless motor control device according to claim 1, wherein said timer means includes a zero reset means for temporarily resetting the timer means to zero each time a current sample command is output.

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