JP3812464B2 - Electric motor position control device - Google Patents

Description

（数７）式の信号Ｎ_ff ^* を位置制御出力値Ｎ_fb ^* に加算して、速度指令Ｎ^* を演算すると、新たに発生する位置偏差Δθ″は（数８）式に示すようになる。
【００２７】
Δθ″＝［（Ｔａ・ｓ）／（１＋Ｔａ・ｓ）］³・θ^* …（数８）
（数８）式より、この場合の位置偏差Δθ″は位置指令θ^* の「三階の不完全微分値」であることがわかる。
【００２８】
図４に、本実施例の場合を示す。図１の速度指令推定器４に不完全微分演算器４ｂを備えること（ｎ＝２）により、加速区間（ａ点からｂ点）および減速区間（ｃ点からｄ点）においても、図４(ｂ)に示すように位置偏差（θ^* −θ）が略零に収束する。さらに、不完全微分演算器の数を４つに増やした場合（ｎ＝４）では、位置指令の変極点である図４（ｂ）のａ点，ｂ点，ｃ点，ｄ点付近においても、さらに位置偏差を抑制できる。
【００２９】
本実施例では、位置指令θ^* から、少なくても２回以上のｎ回の不完全微分値を求め、それらのｎ回までの加算値を位置制御器の出力値Ｎ_fb ^* に加算して位置偏差を小さくできる。
【００３０】
（実施例２）
図５に本実施例を示す。本実施例では、Δθ^*′を信号Ｎ_fb ^*に加算する代わりに、Δθ^*′を信号θ^* に加算して、新たな位置指令θ^**を演算する。
【００３１】
図５において、符号１〜３，６〜１０は、図１と同一の構成要素であるので説明を省く。図５で、４′は運転時の位置偏差を推定する位置偏差推定器、５′は位置指令θ^* と概位置偏差の推定値を加算し、新たな位置指令θ^**を出値する加算器である。
【００３２】
ここで、位置偏差推定器４′の詳細な説明を行う。微分時定数および一次遅れフィルタ時定数が共に定数Ｔａである不完全微分演算器４ａ′に位置指令θ^* を入力し、不完全微分演算器４ａ′から信号Δθ₁ ^*′が出力される。この信号Δθ₁ ^*′は不完全微分演算器４ａ′と同等の不完全微分演算器４ｂ′に入力される。不完全微分演算器４ｂ′で同様に演算した信号Δθ₂ ^*′と前記信号Δθ₁ ^*′とを加算器４ｃ′に入力する。加算器４ｃ′の出力を用いて前記不完全微分演算器４ｂ′と同様に不完全微分演算を繰り返し、この不完全微分演算を２回以上、ｎ回行い、θ_n ^*′とθ_n-1 ^*′とを加え、加算値Δθ^*′を求める。この加算値Δθ^*′を、信号θ^* に加算し、新たな位置指令θ^**を演算する。
【００３３】
本実施例でも実施例１と同様に、ｎ＝２，ｎ＝４の場合について位置指令値θ^*と回転位置θとの関係を調べたところ、実施例１と同様に、位置偏差Δθを略零に抑制できた。
【００３４】
【発明の効果】
本発明によれば、位置指令値から、少なくても２回以上のｎ回の不完全微分値を算出し、それらｎ回までの加算値を用いて、速度指令値あるいは位置指令値を修正するので、加減速運転時における位置偏差を略零に抑制し、無調整で高精度な機械加工を実現する位置制御装置を提供できる。
【図面の簡単な説明】
【図１】実施例１の電動機の位置制御装置の構成図である。
【図２】従来技術のフィード・バック法の運転時の動作の説明図である。
【図３】別の従来技術であるフィード・フォワード法の運転時の動作の説明図である。
【図４】実施例１の運転時の動作の説明図である。
【図５】実施例２の電動機の位置制御装置の構成図である。
【符号の説明】
１…電動機、２…位置検出器、３…位置制御器、４…速度指令推定器、４′…位置偏差推定器、５，５′…加算器、６…速度演算器、７…速度制御器、８…電流制御器、９…電力変換器、１０…電流検出器。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device that suppresses a position deviation (difference between a position command value and a position detection value) generated during acceleration / deceleration operation to substantially zero in a position control device for an electric motor.
[0002]
[Prior art]
Conventionally, as a position control method for an electric motor, a deviation between a position command value given from a host device such as a programmable logic controller (hereinafter referred to as PLC) and a detection value obtained from a position detector attached to a motor shaft (hereinafter referred to as “position control value”). In general, a feedback method in which a speed command value is calculated by proportional control calculation based on the position deviation). Such a feedback method is disclosed in Japanese Patent Laid-Open No. 61-59509 and Japanese Patent Laid-Open No. 5-108164.
[0003]
As another conventional technique, the change in the speed command value, which is the output value of the position control, is estimated in advance by the first-order incomplete differentiation operation of the position command value, and the estimated value is added to the output value of the position controller. Thus, there is a feed-forward method for calculating a new speed command value. Such feed-forward methods are disclosed in Japanese Patent Application Laid-Open Nos. 7-295562, 2001-249720, and 2001-356822.
[0004]
[Problems to be solved by the invention]
The feedback method can perform stable position control. However, when the position deviation occurs during acceleration / deceleration operation and the entire path of the position is specified, such as a machine tool or a process robot, There was a problem that the machining accuracy of the machine deteriorated.
[0005]
Further, even with the feed-forward method, the position deviation during acceleration / deceleration operation cannot be made completely zero, and it is necessary to finely adjust the position command value to adjust the machining accuracy.
[0006]
An object of the present invention is to provide a position control device that suppresses a position deviation that occurs during acceleration / deceleration operation to substantially zero and realizes highly accurate machining without adjustment.
[0007]
[Means for Solving the Problems]
An electric motor position control device according to the present invention includes a power converter that drives an electric motor, a position controller that inputs a deviation between a position command value and a position detection value of the motor and outputs a speed command value, and the speed command A speed controller that outputs a torque current command value by inputting a deviation between the value and a detected speed value of the motor, and a current controller that controls an output current of the power converter according to the torque current command value, The position command value is calculated at least two times or more incomplete differential values, multiplied by a constant to obtain a speed command estimated value, and the position controller outputs the speed command estimated value. Correction is made in addition to the speed command value, and a deviation between the corrected speed command value and the detected speed value of the electric motor is input to the speed controller.
[0008]
The position control apparatus for an electric motor according to the present invention corrects a position command value by adding at least two incomplete differential values of the position command value to the position command value, and corrects the position command value. And the position detection value of the motor are obtained, and the deviation is input to the position controller.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0010]
Example 1
FIG. 1 shows a configuration example of a position control device for an electric motor according to the present embodiment. In FIG. 1, 1 is an electric motor, 2 is a position detector for detecting the rotational position θ of the electric motor, and 3 is inputted with a deviation signal between the position command θ ^* and the rotational position θ to calculate a position control output value N _fb ^* . A position controller, 4 is a speed command estimator, 5 is an adder, 6 is a speed calculator, 7 is a speed controller, 8 is a current controller, 9 is a power converter, and 10 is a current detector.
[0011]
Here, the speed command estimator 4 receives the position command θ ^* , and calculates and outputs the speed command estimated value N _ff ^* . The position command θ ^* input to the speed command estimator 4 first enters the incomplete differentiation calculator 4a whose differentiation time constant and first-order lag filter time constant are both constant Ta, and outputs a signal Δθ ₁ ^* . The signal Δθ ₁ ^* is also input to an incomplete differentiation operator 4b equivalent to the incomplete differentiation operator 4a, and the signal Δθ ₂ ^* calculated by the incomplete differentiation operator 4b and the signal Δθ ₁ ^* are added to the adder 4c. Is input. Using the output of the adder 4c, the incomplete differentiation operation is repeated in the same manner as the incomplete differentiation operation unit 4b, and this incomplete differentiation operation is performed twice or more and n times, and Δθ _n ^* and Δθ _{n− for} each operation. ₁ ^* is added to obtain the added value Δθ ^* . Further, a speed command estimated value N _ff ^* is calculated by multiplying the added value Δθ ^* by a constant (1 / Ta).
[0012]
The speed command estimated value N _ff ^* and the position control output value N _fb ^* are input to the adder 5 to obtain the speed command N ^* . The speed calculator 6 receives the rotational position θ and outputs the rotational speed N. The speed controller 7 receives a deviation signal between the speed command N ^* and the rotational speed N, and outputs a torque current command Iq ^* . The current controller 8 calculates a voltage command V ^* according to the deviation between the torque current command Iq ^* and the detected torque current value Iq, and the power converter 9 outputs a voltage V proportional to the voltage command V ^* to drive the motor 1. To do. The current detector 10 detects the torque current value Iq of the power converter 9.
[0013]
Next, the operation at the time of the proportional control calculation using the feedback method of the prior art will be shown as a comparative example with reference to FIG. This comparative example corresponds to the case where the speed command estimated value N _ff ^* in FIG. 1 is set to zero (= 0). A position command θ ^* is set so that the speed command N ^* is trapezoidal. From FIG. 2 (a), point a to point b are acceleration sections, point b to point c are constant speed sections, and point c to point d. FIG. 2B shows the positional deviation (θ ^* −θ) that occurs during operation, where is a deceleration zone. As shown in FIG. 2 (b), the positional deviation increases in the acceleration zone (from point a to b), becomes maximum in the constant speed zone (from point b to point c), and in the deceleration zone (from point c to point d). Decrease.
[0014]
Here, the relationship between the position command θ ^* and the position deviation Δθ (= θ ^* −θ) will be described using the transfer function of the position control system. When the magnitude of the proportional gain of the position controller 3 in FIG. 1 is K _pp , the closed loop transfer function θ / θ ^* from the position command θ ^* to the rotational position θ is as shown in the equation (1).
[0015]
θ / θ ^* = 1 / (1 + Ta · s) (Equation 1)
In Equation (1), s is a Laplace operator, and Ta is a position control response time constant [s] (1 / K _pp ).
[0016]
Considering the position deviation Δθ to be generated next, the following equation (2) is obtained.
[0017]
Δθ = θ ^* −θ (Expression 2)
Substituting equation (1) into equation (2) and rearranging Δθ, the following equation (3) is obtained.
[0018]
Δθ = (Ta · s) / (1 + Ta · s) · θ ^* (Equation 3)
That is, in the feedback method, the position deviation Δθ becomes the “first-order incomplete differential value” of the position command θ ^* .
[0019]
Next, the conventional feed-forward method will be described. In the feed-forward method, an estimated value Δθ ^* of the position deviation is obtained by the following equation (4) based on the equation (3).
[0020]
Δθ ^* = (Ta · s) / (1 + Ta · s) · θ ^* (Equation 4)
Further, Δθ ^* is multiplied by a constant (1 / Ta), and a speed command estimated value N _ff ^* is calculated by Equation (5).
[0021]
N _ff ^* = s / (1 + Ta · s) · θ ^* (Expression 5)
When the signal N _ff ^* obtained by the equation (5) is input to the adder 5 in FIG. 1, the newly generated position deviation Δθ ′ is as shown by the equation (6).
[0022]
Δθ ′ = [(Ta · s) / (1 + Ta · s)] ² · θ ^* (Equation 6)
That is, the position deviation generated by the feed-forward method is not the equation (3) but the second-order incomplete differential value shown in the equation (6).
[0023]
FIG. 3 shows a comparative example of operation using the feed-forward method. The newly generated position deviation (θ ^* −θ) is a “second-order incomplete differential value” of the position command θ ^* , as shown in the equation (6). That is, a positional deviation occurs only in the acceleration section (point a to b) and the deceleration section (point c to d).
[0024]
In the present embodiment, the position deviation can be suppressed to substantially zero by the speed command estimator 4 of FIG. This will be described below. In the present embodiment, at least two or more incomplete differential values are calculated from the position command value, and the signal N _ff ^* is estimated using the added value up to n times.
[0025]
When the incomplete differential calculator 4b, for example, up to two times is inserted into the speed command estimator 4, the signal N _ff ^* is as shown in (Expression 7).
[0026]

When the speed command N ^* is calculated by adding the signal N _ff ^{* in the} equation (7) to the position control output value N _fb ^* , the newly generated position deviation Δθ ″ is as shown in the equation (8). .
[0027]
Δθ ″ = [(Ta · s) / (1 + Ta · s)] ³ · θ ^* (Equation 8)
From the equation (8), it can be seen that the position deviation Δθ ″ in this case is the “third-order incomplete differential value” of the position command θ ^* .
[0028]
FIG. 4 shows the case of this embodiment. By providing the speed command estimator 4 of FIG. 1 with the incomplete differentiation calculator 4b (n = 2), the acceleration command (point a to point b) and the deceleration zone (point c to point d) are also shown in FIG. As shown in b), the position deviation (θ ^* −θ) converges to substantially zero. Further, when the number of incomplete differential calculators is increased to four (n = 4), even in the vicinity of points a, b, c, and d in FIG. Further, the position deviation can be suppressed.
[0029]
In the present embodiment, at least two or more incomplete differential values are obtained from the position command θ ^* , and the addition value up to n times is added to the output value N _fb ^* of the position controller. The position deviation can be reduced.
[0030]
(Example 2)
FIG. 5 shows this embodiment. In this embodiment, instead of adding Δθ ^* ′ to the signal N _fb ^* , Δθ ^* ′ is added to the signal θ ^* to calculate a new position command θ ^** .
[0031]
5, reference numerals 1 to 3 and 6 to 10 are the same components as those in FIG. In FIG. 5, 4 ′ is a position deviation estimator that estimates the position deviation during operation, and 5 ′ is an adder that adds the position command θ ^* and the estimated value of the approximate position deviation and outputs a new position command θ ^** . It is.
[0032]
Here, the position deviation estimator 4 'will be described in detail. The position command θ ^* is input to the incomplete differentiation calculator 4a ′ whose differentiation time constant and first-order lag filter time constant are both constant Ta, and the signal Δθ ₁ ^* ′ is output from the incomplete differentiation calculator 4a ′. This signal Δθ ₁ ^* ′ is input to an incomplete differentiation operator 4b ′ equivalent to the incomplete differentiation operator 4a ′. The signal Δθ ₂ ^* ′ calculated in the same manner by the incomplete differentiation calculator 4b ′ and the signal Δθ ₁ ^* ′ are input to the adder 4c ′. Using the output of the adder 4c ′, the incomplete differentiation operation is repeated in the same manner as the incomplete differentiation operation unit 4b ′, and this incomplete differentiation operation is performed n times or more twice to obtain θ _n ^* ′ and θ _n−1. ^* ′ Is added to obtain the added value Δθ ^* ′. This added value Δθ ^* ′ is added to the signal θ ^* to calculate a new position command θ ^** .
[0033]
In this embodiment, as in the first embodiment, when the relationship between the position command value θ ^* and the rotational position θ is examined in the case of n = 2 and n = 4, the position deviation Δθ is substantially reduced as in the first embodiment. It could be suppressed to zero.
[0034]
【The invention's effect】
According to the present invention, at least two or more incomplete differential values are calculated from the position command value, and the speed command value or the position command value is corrected using the added value up to n times. Therefore, it is possible to provide a position control device that suppresses the position deviation during acceleration / deceleration operation to be substantially zero and realizes highly accurate machining without adjustment.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a position control apparatus for an electric motor according to a first embodiment.
FIG. 2 is an explanatory diagram of an operation during operation of a conventional feedback method.
FIG. 3 is an explanatory diagram of an operation during operation of a feed-forward method, which is another conventional technique.
FIG. 4 is an explanatory diagram of an operation during operation of the first embodiment.
FIG. 5 is a configuration diagram of an electric motor position control apparatus according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electric motor, 2 ... Position detector, 3 ... Position controller, 4 ... Speed command estimator, 4 '... Position deviation estimator, 5, 5' ... Adder, 6 ... Speed calculator, 7 ... Speed controller , 8 ... current controller, 9 ... power converter, 10 ... current detector.

Claims (4)

A power converter that drives the motor, a position controller that inputs a deviation between the position command value and the position detection value of the motor and outputs a speed command value, and a deviation between the speed command value and the speed detection value of the motor. In a position controller comprising a speed controller that inputs and outputs a torque current command value, and a current controller that controls the output current of the power converter according to the torque current command value,
Obtain a speed command estimated value calculated n times incomplete derivative value least be twice or more of the position command value by multiplying a constant to the calculation value, and outputs the the speed command estimated value the position controller is A position control device for an electric motor which is corrected in addition to the speed command value and inputs a deviation between the corrected speed command value and a detected speed value of the motor to the speed controller. A power converter for driving the motor; a position controller for inputting a deviation between the position command value and the position detection value of the motor to output a speed command value; and a deviation between the speed command value and the speed detection value of the motor. In a position control device comprising: a speed controller that inputs a torque current command value and a current controller that controls an output current of the power converter according to the torque current command value;
Deviation between the position of least be inexact differential value of two or more n times the command value to correct the position command value in addition to the position command value, a position detection value of the motor and a position command value the modified And the deviation is input to the position controller.   3. The position control device for an electric motor according to claim 1, wherein the differential time constant used for the calculation of the incomplete differential value and the first-order lag filter time constant are the same time constant. An electric motor position control device.   4. The position control apparatus for an electric motor according to claim 3, wherein the same time constant is a reciprocal of the position controller gain.

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