JP4128703B2 - Motor drive device - Google Patents

Description

ここで、Δω'は補正後の回転差分であり、α（α≧０）は実験的に求められた定数である。
【００３９】
その後、このように求めた補正した速度差分Δω'に補正ゲインＫを乗算して、基準デューティを補正するために使用される補正デューティΔＤ_n+2を求める（Ｓ１５）。この補正デューティΔＤ_n+2を所定のデューティ記憶部に格納する（Ｓ１６）。
【００４０】
次に、ＰＷＭデューティ制御部５において、基準デューティ値Ｄ₀を入力する（Ｓ１７）。位相が１８０°前に算出され、格納されていた補正デューティ値ΔＤ_nをデューティ記憶部から読み出す（Ｓ１８）。補正デューティ値ΔＤ_nと基準デューティ値Ｄ₀とから、次式により出力デューティＤ'を求める（Ｓ１９）。
Ｄ'＝Ｄ₀＋ΔＤ_n （７）
求めた出力デューティＤ'を、直流交流変換部２に出力する（Ｓ２０）。
【００４１】
このようにして求められた出力デューティ値と、基準デューティ値、補正デューティ値との関係を図６の（ａ）に示す。この図に示すように、本実施形態のモータ駆動装置では、周波数指令ω_sにより定まる基準デューティに対して補正デューティを用いて補正した出力デューティを用いて、直流交流変換部２のスイッチング素子の動作を制御する。これにより、図６の（ｂ）に示すような、負荷トルクに応じたモータの出力トルクを発生させることができ、安定した運転を可能とする。
【００４２】
すなわち、図６の（ｂ）に示すように、出力トルクと負荷トルクとがほぼ等しくなるように変化するため、式（１）の右辺の残差トルクは小さくなり、モータ１の回転速度ωの速度変動は小さくなる。
【００４３】
なお、上記説明では３相４極ブラシレスＤＣモータついて説明したが、本発明は、モータの回転速度及び速度差分を求める際に同一相における電機子巻線のゼロクロス情報から求められるように回転速度及び速度差分の範囲を設定すれば、他の極数のモータについても適用できる。
【００４４】
【発明の効果】
本発明に係るモータ駆動装置によれば、同一相のゼロクロス情報に基いて回転速度を求め、この回転速度に基いてデューティ値を制御する。これにより、位置検出手段の構成素子間のバラツキ、モータの巻線の相間公差の影響を排除でき、高い精度で回転速度の検出が可能となり、より精度の高いデューティ値の補正が可能となる。よって、高い精度で補正されたデューティ値を使用することにより、モータ駆動装置において、モータの出力トルクと機械系負荷トルクの差によって生ずる残差トルクをより小さく抑えることができ、機械系の音・振動を小さくし、機械系の防音、振動対策を簡略化できる。さらには、回路の製造コストも低減できる。
【００４５】
また、モータ駆動装置において、電機子巻線の誘起電圧のゼロクロス発生毎（（モータの回転角３０゜毎）に回転速度を求めてもよく、これにより残差トルクの制御をきめ細かく行うことができ、音・振動面での高性能化を図ることができる。
【００４６】
また、モータ駆動装置において、回転速度間の速度差分を検出してもよく、これにより、残差トルクの目安を知ることができ、速度制御性能の安定化を図ることができる。このとき、得られた回転速度の差分に対して、さらに、非線形演算処理を施してもよい。これにより、制御性安定度が一層増し、モータの乱調減少や、脱調のほとんどない動作信頼性の高いインバータシステムを提供できる。
【００４７】
また、モータ駆動装置において、回転角３０゜毎にデューティ値を更新してもよく、これにより、ＰＷＭデューティの制御を３０゜毎にきめ細かく行うことができ、音・振動面での高性能化を図ることができる。
である。
【００４８】
また、モータ駆動装置において、求めたデューティ値を、求めた時点から１８０°経過後に出力してもよい、これにより、モータの出力トルク位相と、負荷トルク位相を合致させることができるため、残差トルクを極力小さくでき、音・振動面での高性能化と、機械系の高信頼性化を図ることができる。
【００４９】
また、モータ駆動装置において、ブラシレスＤＣモータの回転速度制御用の基準デューティと、速度差分を制御用の補正デューティとの和で構成されるものである。これにより、モータの回転速度制御系は、速度変動・負荷変動に対して応答性の高い制御システムを構築できるので、速度サーボ運転などに適したインバータシステムを提供できる。
【図面の簡単な説明】
【図１】 本実施形態のモータ駆動装置の制御ブロック図。
【図２】 ＰＷＭデューティ制御部から出力される制御信号のベースパターンを説明した図。
【図３】 回転速度及び速度差分の検出を説明するための図。
【図４】 本実施形態におけるデューティ値の補正処理を示すフローチャート。
【図５】 速度差分ωの補正における非線形演算処理を説明した図。
【図６】 基準デューティ値と補正後のデューティ値の関係（ａ）、及び、出力トルクと負荷トルクの関係（ｂ）とを示した図。
【図７】 従来のモータ駆動装置の制御ブロック図。
【符号の説明】
１ ブラシレスＤＣモータ（ＢＤＭ）
２ 直流交流変換部
３ 磁極位置検出部
４ 速度差分検出部
５ ＰＷＭデューティ制御部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor drive device that controls the frequency of a brushless DC motor.
[0002]
[Prior art]
FIG. 7 shows a conventional 120 ° energization control (rectangular wave energization control) type motor driving device for controlling the rotation speed of the three-phase four-pole brushless DC motor 1. As shown in this figure, the motor driving device converts a DC voltage into a pseudo AC voltage and outputs it to a brushless DC motor (hereinafter abbreviated as “motor”) 1, and a rotor of the motor 1. And a magnetic pole position detector 3 for detecting the position. The PWM duty control unit 5 ′ outputs a duty signal for controlling the applied voltage, frequency, and phase for controlling the rotational speed of the motor 1. The DC / AC converter 2 includes six switching elements that open and close at high speed.
[0003]
As described above, in the motor driving apparatus configured as described above, the DC voltage is converted into a pseudo AC voltage having a variable frequency and phase by the DC / AC converter 2 and output to the brushless DC motor 1. The rotation speed of the brushless DC motor 1 is controlled by changing the frequency / phase (hereinafter referred to as “inverter frequency”) of the pseudo AC voltage output from the DC / AC converter 2. The inverter frequency is controlled by the PWM duty control unit 5 ′. A frequency command value ω _s is input to the PWM duty control unit 5 ′, and based on this value, the PWM duty control unit 5 ′ outputs six base patterns for opening and closing the switching elements of the DC / AC conversion unit 2. To do. When the switching elements are opened and closed by these base patterns, the inverter frequency output from the DC / AC converter 2 is controlled. Here, the inverse of one cycle of the base pattern is the inverter frequency.
[0004]
When changing the rotation speed of the motor 1, the PWM duty control unit 5 ′ changes the inverter frequency of the DC / AC conversion unit 2 based on the rotation phase information of the magnetic pole position detection unit 3 according to the change of the frequency command value ω _s. Then, the rotational speed of the brushless DC motor 1 is controlled.
[0005]
Here, the phase detection characteristic of the magnetic pole position detector 3 does not depend on the inverter frequency (phase) output from the DC / AC converter 2 or the voltage amplitude, but directly detects the induced voltage generated by the motor 1. The magnetic pole position is estimated and calculated.
[0006]
The PWM duty control unit 5 ′ outputs six types of base patterns based on the rotational phase information. The DC / AC converter 2 has six switching elements, and includes one switching element in the upper arm and one switching element in the lower arm for the U phase, the V phase, and the W phase, respectively.
[0007]
In motor driving by a conventional motor driving device, the rotational speed of the motor 1 is always constant when the load torque applied to the motor 1 is always constant. Therefore, the output angle of each base pattern PTNm (m = 1 to 6) is 30 ° in mechanical angle, and the output time is also constant. This is because the PWM duty width output from the PWM duty control unit 5 ′ is constant regardless of the rotation angle, and the output (generated) torque 17 generated by the motor 1 is also constant, so the output torque and load torque mismatch. This is because the residual torque generated by the above is always zero. For this reason, when the load torque is constant, the motor 1 can perform a substantially constant speed rotation operation and obtain good speed control performance.
[0008]
[Problems to be solved by the invention]
However, when a non-constant load torque is applied to the rotation angle of the motor, the rotational speed of the motor 1 changes every moment during one rotation due to the residual torque generated by the difference between the output torque and the load torque. Control becomes unstable. As a result, sound and vibration are generated from the motor 1 and the mechanical system, and the mechanical system must be rigidly configured to cope with this, resulting in a significant cost increase. In the worst case, the motor 1 and It had a big problem that led to the destruction of the load system.
[0009]
The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to reduce the sound and vibration of the mechanical system by suppressing the residual torque generated by the difference between the output torque and the load torque. It is another object of the present invention to provide a motor drive device that can simplify the soundproofing and vibration countermeasures of a mechanical system and further increase the circuit cost.
[0010]
[Means for Solving the Problems]
A motor driving device according to the present invention includes a switching element in a motor driving device that controls the number of revolutions of a three-phase n-pole (n is an even number of 4 or more) brushless DC motor, and opens and closes the switching element according to a control signal. The DC phase is converted into a desired pseudo AC voltage by the DC AC conversion means for outputting the pseudo AC voltage to the brushless DC motor, and the rotational phase obtained from the induced voltage of the three-phase armature winding of the brushless DC motor Position detecting means for detecting and outputting rotational phase information, and duty control means for outputting a control signal for PWM control of the opening / closing operation of the switching element of the DC / AC converting means. Further, the duty control means is obtained by dividing the control signal by a reference duty determining means for determining a reference duty value, which is a reference duty value, based on a frequency command, and dividing one rotation angle of the motor into n equal parts. It comprises a correction means for obtaining a rotation speed for each angle range, correcting the reference duty value based on the rotation speed, and an output means for outputting a control signal having the corrected duty value.
[0011]
The correction means of the duty control means is configured to change the rotation speed by the generation timing of one zero cross of the induced voltage of the armature winding and the zero cross in the armature winding in the same phase as the one zero cross. determined from the generation timing of the zero cross of after corner 180 °.
[0012]
Further, the correction means of the duty control means may determine the rotation speed every time zero crossing of the induced voltage in each phase of the armature winding occurs (every 30 ° rotation).
[0013]
The motor drive device may further include a speed difference detection unit that detects a difference between one rotation speed and a rotation speed after an electrical angle of 360 ° has elapsed after obtaining the rotation speed. At this time, the correction means of the duty control means corrects the duty value according to the difference.
[0014]
Further, the speed difference detection means may correct the difference by calculating a rotational speed difference and then applying a non-linear calculation process to the difference.
[0015]
Further, the duty control means may update the duty value every time the brushless DC motor rotates 60 degrees in mechanical angle and electrical angle .
[0016]
Further, the output means of the duty control means is configured such that the duty value corrected according to the rotational speed is a duty when 180 ° × (n−2) electrical angles have elapsed from the time when the rotational speed is obtained. You may make it output as a value.
[0017]
Further, the correction means of the duty control means may obtain a duty value to be output by adding a correction duty value determined according to the difference to the reference duty value.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a motor drive device according to the present invention will be described in detail with reference to the accompanying drawings.
[0019]
(Configuration of motor drive device)
FIG. 1 shows a configuration diagram of a motor drive device of the present embodiment. The motor driving apparatus shown in this figure controls the rotation speed of a three-phase four-pole brushless DC motor (hereinafter abbreviated as “motor”) 1 by 120 ° energization control (rectangular wave energization control). As shown in the figure, the motor drive device includes a DC / AC converter 2 that converts a DC voltage into a pseudo AC voltage and outputs the pseudo AC voltage, a magnetic pole position detector 3 that detects the position of the rotor of the motor 1, and a magnetic pole. A speed difference detection unit 4 that calculates the rotation speed from the rotor position of the motor 1 detected by the position detection unit 3 and a PWM duty signal that controls applied voltage, frequency, and phase for controlling the rotation speed of the motor 1 are output. And a PWM duty control unit 5 for performing the operation. The DC / AC converter 2 includes six switching elements 2u, 2v, 2w, 2x, 2y, and 2z that open and close at high speed.
[0020]
As described above, in the motor driving apparatus configured as described above, the DC voltage supplied from the DC power source is converted into a pseudo AC voltage having a variable frequency and phase by the DC / AC converter 2 and output to the motor 1. The number of revolutions of the motor 1 is controlled by changing the frequency / phase (hereinafter referred to as “inverter frequency”) of the pseudo AC voltage output from the DC / AC converter 2. This inverter frequency is controlled by the PWM duty controller 5. A frequency command value ω _s is input to the PWM duty control unit 5. The PWM duty control unit 5 outputs six types of base pattern signals for opening and closing the switching elements of the DC / AC conversion unit 2 based on this value. The inverter frequency output from the DC / AC converter 2 is controlled by opening and closing the switching elements by these base pattern signals.
[0021]
The commutation switching of each base pattern signal is performed based on the output signal of the magnetic pole position detector 3. The magnetic pole position detection unit 3 detects a zero-cross signal of the three-phase induced voltage of the motor 1 and outputs the detection signal to the speed difference detection unit 4. The zero cross signal is generated 12 times for three phases while the motor 1 makes one rotation. That is, if the motor 1 is rotating at a constant speed, the zero cross signal is generated at every 60 ° electrical angle . When the zero cross signal of the magnetic pole position detection unit 3 is input to the PWM duty control unit 5 via the speed difference detection unit 4, the PWM duty control unit 5 uses the base pattern signal based on the zero cross signal as a pattern PTN1 → pattern PTN2 → ... → Pattern PTN6 → Pattern PTN1. Further, the rotational speed can be determined from the zero cross signal. The phase change time constant and the torque value change time constant with respect to the rotation angle of the motor 1 are set to values that are at least twice as long as the motor 1 makes one rotation.
[0022]
(Base pattern)
The base pattern output from the PWM duty control unit 5 will be described. The base pattern is a pulse signal for driving the switching elements 2 u to 2 w and 2 x to 2 z of the DC / AC converter 2. The base pattern has six basic patterns in one cycle of the electrical angle of the output voltage of the DC / AC converter 2. The reciprocal of one cycle of the base pattern is the inverter frequency.
[0023]
FIG. 2 shows an example of the base pattern. As shown in the figure, the first pattern PTN1 makes the U-phase upper arm switching element 2u and the V-phase lower arm switching element 2y conductive. Second pattern PTN2 causes U-phase upper arm switching element 2u and W-phase lower arm switching element 2z to conduct. The third pattern PTN3 conducts the V-phase upper arm switching element 2v and the W-phase lower arm switching element 2z. The fourth pattern PTN4 conducts the V-phase upper arm switching element 2v and the U-phase lower arm switching element 2x. The fifth pattern PTN5 conducts the W-phase upper arm switching element 2w and the U-phase lower arm switching element 2x. The sixth pattern PTN6 conducts the W-phase upper arm switching element 2w and the V-phase lower arm switching element 2y.
[0024]
(Operation of motor drive device)
When the load torque applied to the motor 1 is always constant, the rotational speed of the motor 1 is always constant. Therefore, at this time, the pattern PTNm ′ (m ′ = 1 to 6) is output every time the rotor rotates 30 ° in mechanical angle, and the output time is also constant. This is because the PWM duty value output from the PWM duty control unit 5 is constant regardless of the rotation angle, so that the output torque (generated torque) generated by the motor 1 is also constant, and is the difference between the output torque and the load torque. This is because the residual torque is always zero. At this time, if the rotational speed of the motor 1 is ω and the combined moment of inertia of the motor 1 and the load machine system is Jm,
dω / dt = (output torque−load torque) / Jm = 0 (1)
The physical equation holds.
[0025]
However, if the load torque changes every moment under a constant output torque,
dω / dt = (output torque−load torque) / Jm ≠ 0 (2)
Thus, the rotational speed ω varies with time, and the motor 1 does not rotate at a constant speed.
[0026]
Even if the load torque changes every moment, the expression (1) needs to be satisfied in order for the rotational speed ω to be constant. That is, if the output torque is controlled so that the difference between the output torque and the load torque is small (substantially zero), the fluctuation in the rotational speed ω of the motor 1 is reduced. For this reason, in this motor drive device, the speed difference detector 4 detects this speed fluctuation, and controls the duty value so that the output torque and the load torque become equal.
[0027]
The rotational speed of the motor 1 is changed by controlling the duty value of the base pattern from the PWM duty control unit 5. That is, the rotational speed of the motor 1 increases as the PWM duty value of the base pattern increases, and the rotational speed decreases as the PWM duty value decreases. When the rotation speed is constant, increasing the PWM duty value increases the output torque of the motor 1. Thus, the PWM duty value is closely related to the rotation speed and the output torque.
[0028]
Therefore, in the motor drive device according to the present embodiment, a PWM for suppressing rotational fluctuation is determined with respect to a PWM duty (hereinafter referred to as “reference duty”) that is determined according to the frequency command ω _s and controls the speed. Duty (hereinafter referred to as “correction duty”) is added and corrected to obtain a duty for output (hereinafter referred to as “output duty”). Thereby, the output torque of the motor 1 is made equal to the load torque, and smooth motor driving is realized. The reference duty D ₀ is determined by the following equation.
D ₀ = D _s + K _D (ω _s −ω ₀ ) (3)
The predetermined duty value D _s is determined by the frequency reference, K _D is a constant, omega _s is the frequency command, omega ₀ is the average rotational speed of the motor.
[0029]
Hereinafter, the calculation of the correction duty and the correction of the PWM duty value using the correction duty will be described in detail.
[0030]
(Detection of motor rotation speed and speed fluctuation)
Considering the characteristics of the three-phase four-pole motor 1, it is preferable because accuracy can be improved by obtaining a speed fluctuation based on a zero cross signal for one of the U, V, and W phases. That is, when the speed fluctuation is obtained by using two or more types of zero-cross signals at the same time, the tolerance between phases (between U, V, and W phases) of the constituent elements of the magnetic pole position detector 3 and the electrical characteristics of the motor 1 This is because the speed fluctuation value with high accuracy cannot be obtained because it is greatly affected by the phase tolerance (those caused by the magnetization balance, rotor assembly tolerance, etc.). In order to eliminate these influences as much as possible, in the present embodiment, when the rotational speed and the fluctuations in the rotational speed are obtained, they are obtained based on zero-cross signals generated in the same type of phase.
[0031]
That is, since the motor 1 is a three-phase four-pole motor, the zero cross signal is generated four times in one phase while the rotor rotates once. That is, in one phase, a zero cross signal is generated every 90 ° (= 360 ° / 4). For this reason, in the present embodiment, the rotational speed ω of the motor 1 in the range of the rotational angle of 90 ° is obtained based on the zero cross signal of one phase generated every 90 ° (= 360 ° ÷ 4). Further, the speed difference Δω is obtained from the rotational speed ω _θ obtained at a certain time and the rotational speed ω _{θ +180} after the rotor has made a half rotation from that time (after the rotation angle of 180 ° has elapsed). That is, the speed difference Δω is obtained by the following equation.
Δω = ω _{θ +180} −ω _θ (4)
The rotational speed ω _θ and the rotational speed ω _{θ +180} after half rotation are both obtained using the same-phase zero-cross signal. That is, the speed difference (speed fluctuation) can be detected based on the zero-cross signal based on the induced voltage information for one phase.
[0032]
Hereinafter, the calculation of the speed difference will be specifically described with reference to FIG. Assume that base patterns PTN1, PTN2,... PTN6 are sequentially output as shown in FIG. Here, for convenience of explanation, the rotation speed is represented by ω _{n, m} . The subscript n at this time indicates the rotational speed at which the rotation speed is determined based on which area of each area when the rotation angle area of one rotation of the motor 1 is equally divided into four. The subscript m indicates the base point position (angle) in each region divided into four when calculating the rotation speed. That is, when m is 0, the first position of each area is shifted, when m is 1, the position shifted 30 degrees from the beginning of each area, and when m is 2, the position shifted 60 degrees from the beginning of each area. It shows that the rotational speed is calculated from the base point.
[0033]
For example, the rotational speed ωn shown in FIG. 3, 0 is a range of an electrical angle of 180 degrees between the up base pattern PTN1 base pattern PTN4 from is started output starts output was determined angle 0 ° as a reference point The rotation speed is shown. The rotational speed ω _{n, 0} is obtained from the output timing of the base pattern PTN1 and the output timing of the base pattern PTN4, both of which are given by the U-phase zero-cross signal.
[0034]
Hereinafter, the meaning of each rotation speed ω _{n, m} will be described with reference to FIG.
ω _{n, 0} → Rotational speed between pattern PTN1 output time and pattern PTN4 output time (determined by U-phase zero-cross signal)
ω _{n, 1} → Rotational speed between pattern PTN2 output time and pattern PTN5 output time (determined by zero-cross signal of W phase signal)
ω _{n, 2} → Rotational speed between the output time of pattern PTN3 and the output time of pattern PTN6 (determined by the zero-cross signal of the V-phase signal)
ω _{n + 1,0} → Rotational speed between pattern PTN4 output time and pattern PTN1 output time (determined by zero-phase signal of U-phase signal)
ω _{n + 1,1} → Rotational speed from pattern PTN5 output time to pattern PTN2 output time (determined from zero cross signal of W phase signal)
ω _{n + 1,2} → Rotational speed from the output time point of pattern PTN6 to the output time point of pattern PTN3
ω _{n + 2,0} → Rotational speed between pattern PTN1 output time and pattern PTN4 output time (determined by zero-phase signal of U phase signal)
ω _{n + 2,1} → Rotational speed from pattern PTN2 output time to pattern PTN5 output time (determined from zero-cross signal of W phase signal)
ω _{n + 2,2} → Rotational speed between pattern PTN3 output time and pattern PTN6 output time (determined by V-phase signal zero-cross signal)
ω _{n + 3,0} → Rotational speed from pattern PTN4 output time to pattern PTN1 output time (determined by zero-phase signal of U-phase signal)
ω _{n + 3,1} → Rotational speed between pattern PTN5 output time and pattern PTN2 output time (determined by zero-phase signal of W phase signal)
ω _{n + 3,2} → Rotational speed between pattern PTN6 output time and pattern PTN3 output time (determined by V-phase signal zero-cross signal)
[0035]
(Duty value correction)
As described above, the speed difference Δω _{n, m} is obtained every rotation angle of 30 °, and the speed difference Δω _{n, m} is multiplied by the correction gain K (> 0) to obtain the correction duty value. That is,
Correction duty = −KΔω _{n, m} (5)
[0036]
The speed difference Δω _{n, m} and the calculated correction duty value are stored in a speed storage unit and a correction duty storage unit, which are predetermined storage areas, respectively. For example, in FIG. 3, using the U-phase zero-cross signal, the rotation speed ω _{n + 2,0} is obtained at the start of pattern PTN4 output (270 ° position), and the rotation speed ω obtained 180 degrees before the rotation angle. _The correction duty value is calculated from _{n, 0,} and this value is stored in the correction duty storage unit. At this time, the stored correction duty value is used when a duty value used at that time is obtained after 180 ° rotation (details will be described later). In this way, the output torque of the motor 1 is controlled every 30 ° of rotation using the correction duty.
[0037]
(Control flowchart of motor drive device)
FIG. 4 is a flowchart showing the control of the motor driving apparatus showing the above-described operation.
[0038]
As shown in FIG. 4, when the base pattern PTNm ′ is output (S11), the rotational speed ω _{n, m} in the range from that point to the point 90 ° before the rotation angle is obtained (S12). A difference between the rotation speed ω _{n, m} and the rotation speed ω _{n-2, m} obtained 180 degrees before the rotation angle from that time is calculated to calculate a speed difference Δω _{n, m} (S13). At this time, since the speed difference Δω _{n, m} includes a calculation error and a detection error of the magnetic pole position detector 3, a predetermined correction is performed to minimize the influence of this error (S14). Specifically, correction is performed by a non-linear calculation process as shown in FIG. The process shown in FIG. 5 satisfies the following equation.

Here, Δω ′ is the corrected rotation difference, and α (α ≧ 0) is an experimentally determined constant.
[0039]
Thereafter, the corrected speed difference Δω ′ obtained in this way is multiplied by the correction gain K to obtain a correction duty ΔD _{n + 2} used for correcting the reference duty (S15). The correction duty ΔD _{n + 2} is stored in a predetermined duty storage unit (S16).
[0040]
Then, the PWM duty control section 5 inputs the reference duty value D ₀ (S17). The correction duty value ΔD _n calculated and stored 180 degrees before the phase is read from the duty storage unit (S18). From the corrected duty value ΔD _n and the reference duty value D ₀ , an output duty D ′ is obtained by the following equation (S19).
D ′ = D ₀ + ΔD _n (7)
The obtained output duty D ′ is output to the DC / AC converter 2 (S20).
[0041]
The relationship between the output duty value thus obtained, the reference duty value, and the corrected duty value is shown in FIG. As shown in this figure, in the motor drive device of the present embodiment, the operation of the switching element of the DC / AC converter 2 using the output duty corrected using the correction duty with respect to the reference duty determined by the frequency command ω _s. To control. As a result, the output torque of the motor according to the load torque as shown in FIG. 6B can be generated, and stable operation is possible.
[0042]
That is, as shown in FIG. 6B, since the output torque and the load torque change so as to be substantially equal, the residual torque on the right side of the equation (1) becomes small, and the rotational speed ω of the motor 1 Speed fluctuation is reduced.
[0043]
In the above description, the three-phase, four-pole brushless DC motor has been described. If the range of the speed difference is set, it can be applied to motors with other pole numbers.
[0044]
【The invention's effect】
According to the motor drive device of the present invention, the rotational speed is obtained based on the zero-cross information of the same phase, and the duty value is controlled based on the rotational speed. As a result, it is possible to eliminate the influence of the variation between the constituent elements of the position detection means and the phase tolerance of the motor winding, and the rotation speed can be detected with high accuracy, and the duty value can be corrected with higher accuracy. Therefore, by using the duty value corrected with high accuracy, the residual torque generated by the difference between the motor output torque and the mechanical system load torque can be further reduced in the motor drive device. Reduces vibration and simplifies mechanical soundproofing and vibration countermeasures. Furthermore, the manufacturing cost of the circuit can be reduced.
[0045]
Further, in the motor drive device, the rotation speed may be obtained every time zero crossing of the induced voltage of the armature winding occurs ((every motor rotation angle of 30 °), thereby making it possible to finely control the residual torque. High performance in terms of sound and vibration can be achieved.
[0046]
Further, in the motor drive device, the speed difference between the rotation speeds may be detected, so that a guideline for the residual torque can be known, and the speed control performance can be stabilized. At this time, non-linear calculation processing may be further performed on the obtained difference in rotational speed. As a result, the stability of controllability can be further increased, and an inverter system with high operational reliability can be provided with little motor turbulence reduction and almost no step-out.
[0047]
Also, in the motor drive device, the duty value may be updated every rotation angle of 30 °, so that the PWM duty can be finely controlled every 30 °, and the performance in terms of sound and vibration is improved. Can be planned.
It is.
[0048]
Further, in the motor drive device, the obtained duty value may be output after 180 ° has elapsed from the obtained time point, so that the output torque phase of the motor can be matched with the load torque phase. Torque can be reduced as much as possible, high performance in terms of sound and vibration, and high reliability of the mechanical system.
[0049]
In the motor drive device, the reference duty for controlling the rotational speed of the brushless DC motor and the sum of the speed difference and the correction duty for control are configured. As a result, the motor rotation speed control system can construct a control system having high responsiveness to speed fluctuations and load fluctuations, and thus an inverter system suitable for speed servo operation and the like can be provided.
[Brief description of the drawings]
FIG. 1 is a control block diagram of a motor drive device according to an embodiment.
FIG. 2 is a diagram illustrating a base pattern of a control signal output from a PWM duty control unit.
FIG. 3 is a diagram for explaining detection of a rotation speed and a speed difference.
FIG. 4 is a flowchart showing duty value correction processing in the present embodiment.
FIG. 5 is a diagram illustrating a nonlinear calculation process in correcting a speed difference ω.
FIG. 6 is a diagram showing a relationship (a) between a reference duty value and a corrected duty value, and a relationship (b) between an output torque and a load torque.
FIG. 7 is a control block diagram of a conventional motor driving device.
[Explanation of symbols]
1 Brushless DC motor (BDM)
2 DC / AC converter 3 Magnetic pole position detector 4 Speed difference detector 5 PWM duty controller

Claims (8)

In a motor drive device for controlling the rotation speed of a three-phase n-pole (n is an even number of 4 or more) brushless DC motor,
DC-AC conversion means including a switching element, converting the DC voltage to a desired pseudo AC voltage by opening and closing the switching element according to a control signal, and outputting the pseudo AC voltage to the brushless DC motor;
Position detecting means for detecting a rotational phase obtained from an induced voltage of the three-phase armature winding of the brushless DC motor and outputting rotational phase information;
Duty control means for outputting a control signal for PWM control of the switching operation of the switching element of the DC-AC conversion means,
The duty control means includes a reference duty determining means for determining a reference duty value, which is a reference duty value, based on a frequency command with respect to the control signal, and an angle obtained by equally dividing a rotation angle of the motor by n. obtains the rotation speed of each range, Ri Do from a correction means for correcting the reference duty value based on the rotational speed, and output means for outputting a control signal having a corrected duty value,
The correction means of the duty control means is configured to determine the rotation speed based on the generation timing of one zero cross of the induced voltage of the armature winding and the zero cross in the armature winding in phase with the one zero cross. motor driving apparatus according to claim Rukoto determined from the generation timing of the zero cross of after electrical angle of 180 ° from. The motor drive device according to claim 1,
n is 4, the motor drive device characterized by the above-mentioned. The motor drive device according to claim 1,
The motor drive apparatus according to claim 1, wherein the correction means of the duty control means obtains the rotational speed every time the induced voltage zero-cross occurs in each phase of the armature winding. In the motor drive device according to any one of claims 1 to 3,
A speed difference detecting means for detecting a difference between one rotation speed and a rotation speed after an electrical angle of 360 ° has elapsed after obtaining the one rotation speed;
The motor drive apparatus according to claim 1, wherein the correction means of the duty control means corrects the duty value according to the difference. The motor drive device according to claim 4, wherein
The speed difference detecting means, after calculating the difference in rotational speed, further corrects the difference by performing a non-linear calculation process. In the motor drive device according to any one of claims 1 to 5,
The duty control means updates the duty value every time the brushless DC motor rotates by 60 electrical degrees . In the motor drive unit according to any one of claims 1 to 6,
The output means of the duty control means outputs the duty value corrected according to the rotational speed as a duty value when an electrical angle of 180 ° × (n−2) has elapsed since the time when the rotational speed was obtained. The motor drive device characterized by the above-mentioned. In the motor drive unit according to any one of claims 4 to 7,
The motor drive apparatus according to claim 1, wherein the correction means of the duty control means obtains a duty value to be output by adding a correction duty value determined according to the difference to the reference duty value.

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