JP2003264986A - Position controller for motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an accurate position controller without regulating by suppressing a positional deviation occurring at an accelerating or decelerating time of a motor to substantially zero. <P>SOLUTION: The position controller for the motor calculates at least twice to (n) times of incomplete differentiated value of a position command value, obtains a speed command estimated value by multiplying the calculated value by a constant, adds the speed command estimated value to the speed command value output from the controller to be corrected, and inputs a deviation of the speed detected value of the motor from the corrected speed command value to a speed controller so that the differentiated time constant is the same as a primary delay filter time constant. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position control device for an electric motor, which suppresses a position deviation (difference between a position command value and a position detection value) generated during acceleration / deceleration operation to substantially zero.

[0002]

2. Description of the Related Art Conventionally, as a position control method for an electric motor,
Programmable logic controller (hereinafter PL
Feed for calculating the speed command value by proportional control calculation based on the deviation (hereinafter referred to as position deviation) between the position command value given by a higher-level device such as C) and the detection value obtained from the position detector attached to the motor shaft.・ The back method is common. Such a feed back method is disclosed in JP-A-61-161.
It is disclosed in Japanese Patent No. 59509 and Japanese Patent Laid-Open No. 5-108164.

As another conventional technique, the change amount of the speed command value, which is the output value of the position control, is estimated in advance by the first-order incomplete differential calculation of the position command value, and the estimated value is output from the position controller. There is a feed-forward method in which a new speed command value is calculated by adding to the value. Such a feed-forward method is disclosed in JP-A-7-295652 and JP-A-2.
001-249720, JP 2001-3568A.
No. 22 publication.

[0004]

Although the feed back method can perform stable position control, a position deviation occurs during acceleration / deceleration operation and the entire path of the position is designated, for example, When applied to machine tools, process robots, etc., there was a problem that the machining accuracy of the machine deteriorates.

Further, even the feed-forward method cannot completely eliminate the position deviation during acceleration / deceleration operation, and it is necessary to finely adjust the position command value to adjust the machining accuracy. .

An object of the present invention is to provide a position control device which suppresses a position deviation occurring during acceleration / deceleration operation to substantially zero and realizes highly accurate machining without adjustment.

[0007]

A position controller for an electric motor according to the present invention inputs a power converter for driving the electric motor and a deviation between a position command value and a position detection value of the electric motor and outputs a speed command value. Position controller, a speed controller that outputs a torque current command value by inputting a deviation between the speed command value and a speed detection value of the motor, and an output current of the power converter is controlled according to the torque current command value. And a current controller for controlling the position command value, at least two or more incomplete differential values of the position command value are calculated, the calculated value is multiplied by a constant to obtain a speed command estimated value, and the speed command estimated value is calculated. Is corrected in addition to the speed command value output from the position controller, and the deviation between the corrected speed command value and the detected speed value of the electric motor is input to the speed controller.

The position control device for an electric motor according to the present invention corrects the position command value by adding an incomplete differential value of the position command value at least two times at least n times to the position command value and corrects the position command value. A deviation between the position command value and the position detection value of the electric motor is obtained, and the deviation is input to the position controller.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a structural example of a position control device for an electric motor according to this embodiment. In FIG. 1, 1 is an electric motor, 2 is a position detector for detecting a rotational position θ of the electric motor,
3 is a position controller for inputting a deviation signal between the position command θ ^* and the rotational position θ to calculate a position control output value N _fb ^* , 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.

Here, the speed command estimator 4 uses the position command θ
By inputting ^* , the speed command estimated value N _ff ^* is calculated and output.
In the position command θ ^* input to the speed command estimator 4, first, the differential time constant and the first-order lag filter time constant are both constant Ta.
Then, it enters the incomplete differential calculator 4a and outputs the signal Δθ ₁ ^* . The signal Δθ ₁ ^* is also input to the incomplete differential calculator 4b, which is equivalent to the incomplete differential calculator 4a.
The signal Δθ ₂ ^* calculated in b and the signal Δθ ₁ ^* are added by the adder 4
Input to c. The incomplete differential operation is repeated using the output of the adder 4c in the same manner as the incomplete differential operation unit 4b, and this incomplete differential operation is performed twice or more, n times, and Δ for each operation.
The addition value Δθ ^* is obtained by adding θ _n ^* and Δθ _n-1 ^* . Further, the added value Δθ ^* is multiplied by a constant (1 / Ta) to calculate the speed command estimated value N _ff ^* .

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 deviation signal between the speed command N ^* and the rotation speed N is input to the speed controller 7, and the torque current command Iq ^* is output. The current controller 8 calculates the 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 the voltage V proportional to the voltage command V ^* to drive the electric motor 1. To do. The current detector 10 detects the torque current value Iq of the power converter 9.

Next, referring to FIG. 2, an operation at the time of proportional control calculation using the above-mentioned conventional feedback method is shown as a comparative example. This comparative example corresponds to the case where the speed command estimated value N _ff ^* in FIG. 1 is set to zero (= 0). The position command θ ^* is set so that the speed command N ^* becomes a trapezoidal shape, and the points a to b in FIG. 2A are the acceleration section, the points b to c are the constant speed section,
The position deviation (θ ^* −θ) that occurs during operation is shown in FIG. 2B, where the points c to d are deceleration sections. As shown in FIG. 2B, the position deviation increases in the acceleration section (points a to b), reaches a maximum in the constant speed section (points b to c), and in the deceleration section (points c to d). Decrease.

Now, 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. Assuming that 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 given by the equation (1).

Θ / θ ^* = 1 / (1 + Ta · s) (Equation 1) In Equation (1), s is the Laplace operator, Ta is the position control response time constant [s] (1 / K _pp ). is there.

Considering the next positional deviation Δθ,
It becomes as shown in the equation (2).

Δθ = θ ^* −θ (Equation 2) By substituting the equation (1) into the equation (2) and rearranging Δθ, the following equation (3) is obtained.

Δθ = (Ta · s) / (1 + Ta · s) · θ ^* (Equation 3) That is, in the feedback method, the position deviation Δθ is the “first-order incomplete differential value” of the position command θ ^*. become.

Next, the conventional feed-forward method will be described. In the feed-forward method, the estimated value Δθ ^* of the position deviation is obtained by the following equation (4) based on the equation (3).

Δθ ^* = (Ta · s) / (1 + Ta · s) · θ ^* (Equation 4) Further, Δθ ^* is multiplied by a constant (1 / Ta) to obtain the speed command estimated value N _ff ^* ( _Equation 5). ) Formula.

N _ff ^* = s / (1 + Ta · s) · θ ^* (Equation 5) When the signal N _ff ^* obtained by the equation (5) is input to the adder 5 in FIG. The positional deviation Δθ '
It becomes as shown in the formula.

Δθ ′ = [(Ta · s) / (1 + Ta · s)] ² · θ ^* (Equation 6) In other words, the position deviation generated by the feed forward method is not expressed by the equation (3) but (Equation 6). ) It becomes the second-order incomplete differential value shown in the equation.

FIG. 3 shows a comparative example of the operation using the feed forward method. New position deviation (θ ^* −
θ) is the “second-order incomplete differential value” of the position command θ ^* , as shown in the equation (6). That is, the position deviation occurs only in the acceleration section (points a to b) and the deceleration section (points c to d).

In the present embodiment, the position deviation can be suppressed to substantially zero by the speed command estimator 4 shown in FIG. Less than,
This will be described. In this 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.

When the speed command estimator 4 is provided with, for example, up to two incomplete differential calculators 4b, the signal N _ff ^* is given by the equation (7).

N _ff ^* = 1 / Ta {Tas / (1 + Tas) + [Tas / (1 + Tas)] ² } θ ^* (Expression 7) (Signal of Expression 7) When N _ff ^* is added to the position control output value N _fb ^* and the speed command N ^* is calculated, the newly generated position deviation Δθ ″ becomes as shown in equation (8).

[0027] Δθ "= [(Ta · s ) / (1 + Ta · s)] 3 · θ * ... ( 8) (8) from equation, the position deviation Δθ of this case" is the position command θ ^* of the "three It is understood that it is the "incomplete differential value of the floor".

FIG. 4 shows the case of this embodiment. By providing the speed command estimator 4 of FIG. 1 with the incomplete differential calculator 4b (n = 2), the acceleration section (points a to b) and the deceleration section (points c to d) are also shown in FIG. As shown in b), the position deviation (θ ^* −θ) converges to almost zero. further,
When the number of incomplete differential calculators is increased to 4 (n = 4)
Then, inflection points of the position command are points a and b in FIG. 4B.
The position deviation can be further suppressed near the points, the points c and d.

In the present embodiment, at least two or more incomplete differential values are calculated from the position command θ ^* , and these n are calculated.
The position deviation can be reduced by adding the added value up to the number of times to the output value N _fb ^* of the position controller.

(Embodiment 2) FIG. 5 shows this embodiment. In this embodiment, instead of adding Δθ ^* ′ to the signal N _fb ^* , ΔΔ
θ ^* ′ is added to the signal θ ^* to calculate a new position command θ ^** .

In FIG. 5, reference numerals 1 to 3 and 6 to 10 denote
Since the constituent elements are the same as those in FIG. 1, description thereof will be omitted. In Figure 5,
4'is a position deviation estimator for estimating the position deviation during operation,
Reference numeral 5'denotes an adder that adds the position command θ ^* and the estimated value of the approximate position deviation and outputs a new position command θ ^** .

The position deviation estimator 4'will now be described in detail. A position command θ is given to the incomplete differential calculator 4a ′ whose differential time constant and first-order lag filter time constant are both constant Ta.
^* Is input and the signal Δθ ₁ ^* 'from the incomplete differential calculator 4a'
Is output. This signal Δθ ₁ ^* 'is the incomplete differential calculator 4
It is input to the incomplete differential calculator 4b 'equivalent to a'. Inexact differential calculator 4b 'with similarly operated signal [Delta] [theta] ₂ ^*' and 'an adder 4c' the signal [Delta] [theta] ₁ ^* input to. Using the output of the adder 4c ', the incomplete differential operation is repeated in the same manner as the incomplete differential operation unit 4b', and this incomplete differential operation is performed two or more times, n times, and 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 ^** .

Also in this embodiment, n = 2, as in the first embodiment.
When the relationship between the position command value θ ^* and the rotational position θ is examined for n = 4, the positional deviation Δθ is the same as in the first embodiment.
Could be suppressed to almost zero.

[0034]

According to the present invention, at least two or more incomplete differential values are calculated from the position command value, and the added value up to the n times is used to calculate the speed command value or the position. Since the command value is corrected, it is possible to provide a position control device that suppresses the position deviation during acceleration / deceleration operation to substantially zero and realizes highly accurate machining without adjustment.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a position control device for an electric motor according to a first embodiment.

FIG. 2 is an explanatory diagram of an operation during operation of the feed back method of the related art.

FIG. 3 is an explanatory diagram of an operation during operation of the 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 a position control device for an electric motor according to a second embodiment.

[Explanation of symbols]

1 ... 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.

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Claims (4)

[Claims] 1. A power converter for driving an electric motor, a position controller for inputting a deviation between a position command value and a position detection value of the electric motor to output a speed command value, the speed command value and the speed of the motor. In a position control device including a speed controller that inputs a deviation of a detected value and outputs 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, The incomplete differential value of the position command value is calculated at least two times more than n times, the calculated value is multiplied by a constant to obtain a speed command estimated value, and the speed command estimated value is output by the position controller. A position control device for an electric motor, which is modified in addition to the speed command value, and a deviation between the corrected speed command value and a detected speed value of the electric motor is input to the speed controller. 2. A power converter for driving an electric motor, a position controller for inputting a deviation between a position command value and a position detection value of the electric motor to output a speed command value, the speed command value and the speed of the motor. In a position control device including a speed controller that inputs a deviation from a detected value and outputs 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, The position command value is corrected by adding an incomplete differential value of at least two times, which is at least two times, to the position command value, and the deviation between the corrected position command value and the position detection value of the electric motor is calculated. A position control device for an electric motor, wherein the deviation is obtained and is input to the position controller. 3. The position control device for an electric motor according to claim 1, wherein a differential time constant used for the calculation of the incomplete fine value and a first-order lag filter time constant are:
A position control device for an electric motor having the same time constant. 4. The position control device for an electric motor according to claim 3, wherein the same time constant is an inverse number of the position controller gain.