JPH07182046A - Position control system - Google Patents

Abstract

PURPOSE:To provide a position control system using an AC synchronous motor for simplifying a structure and lowering a cost. CONSTITUTION:A pole sensor 4 is attached to the AC synchronous motor 3 for linearly driving a table 1 and a linear encoder 5 for measuring the absolute position is provided under the table 1. The output of the linear encoder 5 is provided with a first arithmetic circuit 16 for computing and outputting the rotation angle of the motor 3 instead of a rotary encoder and a magnetic pole position detection circuit 15 detects the magnetic pole position of the motor 3 from the output of the arithmetic circuit 16 with the output of the pole sensor 4 as a reference. The output of the linear encoder 5 is provided with a second arithmetic circuit 17 for computing and outputting the rotation speed of the motor 3 and speed information obtained from it is defined as speed feedback signals instead of conventional rotary encoder output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position control system used for various machine tools and measuring machines, and more particularly to a position control system for performing servo control using an AC synchronous motor.

[0002]

2. Description of the Related Art In the conventional position control system using an AC synchronous motor, from the viewpoint of efficiently driving the AC synchronous motor, there are many methods (vector control method) for detecting the magnetic pole position of the motor and giving a torque current. Has been adopted. In current control of an AC synchronous motor, the model shown in FIG. 3 is usually used to coordinate-convert a three-phase AC model into a two-axis DC model that is easy to control. This conversion formula is expressed as follows. First, the following equation 1 is obtained using the angle variable θ in FIG.

[0003]

[Equation 1]

Here, Iu, Iv, and Iw are U, respectively.
Phase, V phase, and W phase armature currents, and Id and Iq are d-axis and q-axis armature currents of the two-axis DC model, respectively. By substituting the relationship of Iw = -Iu-Iv into the equation 1, the following equation 2 is obtained.

[0005]

[Equation 2]

The current feedback control amounts Id and Iq are obtained by performing the coordinate transformation of the equation (2). Further, in the current control loop, the d-axis obtained by adding the current command value and the current feedback amount,
Three-phase voltage command values Vu, Vv given to the power amplifier that actually drives the motor from the q-axis armature voltages Vd, Vq
The coordinate transformation for obtaining Vw is the inverse transformation of the equation 1, and the following equation 3
The conversion formula of is used.

[0007]

[Equation 3]

As is clear from the above current control algorithm, the angle variable θ, which is the magnetic pole position of the AC synchronous motor, is required to perform the coordinate conversion. Therefore, in such AC synchronous motor control, it is indispensable to measure the angle variable θ, and therefore a rotary encoder and a pole sensor for detecting a magnetic pole are usually used. That is, when the rotary encoder is of the incremental type, absolute angle position information cannot be obtained by this alone. Therefore, the pole sensor detects the magnetic pole at every 60 ° (electrical angle), and the output of the rotary encoder is used as a reference. The absolute counter is constructed to obtain the angle variable θ required for the above coordinate conversion.

[0009]

As described above, in the conventional position control system using the AC synchronous motor, the rotary encoder and the pole sensor are used. Further, in order to perform precise positioning of a controlled object such as a table, there are many systems provided with a linear encoder capable of absolute position detection in addition to the rotary encoder. For this reason, this type of system has a problem in that the configuration is complicated and a large amount of wiring space is required, so that the entire system becomes large and the cost becomes high.

The present invention has been made in view of such circumstances, and an object thereof is to provide a position control system using an AC synchronous motor, which is structurally simplified and reduced in cost.

[0011]

A first position control system according to the present invention includes an AC synchronous motor for linearly driving an object to be controlled, a pole sensor for detecting a magnetic pole of the AC synchronous motor, and the object to be controlled. A linear encoder for measuring the absolute position of the controlled object, a first computing means for computing and outputting the rotation angle of the AC synchronous motor from the output of the linear encoder, and an output of the pole sensor from the output of the first computing means. A magnetic pole position detecting means for detecting the magnetic pole position of the AC synchronous motor with reference to: and a second for calculating and outputting the rotational speed of the synchronous motor from the output of the linear encoder.
And a position control means for feeding back the position information output from the linear encoder with respect to a position command value from the outside to output a speed command value, and a speed command value output by the position control means. The speed control means for feeding back the speed information output from the second computing means to output a current command value, and the armature current of the AC synchronous motor with respect to the current command value from the speed control means. Current control means for feeding back a control current value obtained by coordinate conversion by the output of the magnetic pole position detection means to output a voltage command value, and coordinate conversion of the output of the current control means by the output of the magnetic pole position detection means. Motor drive means for controlling and driving the AC synchronous motor.

A second position control system according to the present invention is
An AC synchronous motor for linearly driving the controlled object, a linear encoder for measuring the absolute position of the controlled object, and a first arithmetic means for arithmetically outputting the rotation angle of the AC synchronous motor from the output of the linear encoder. And magnetic pole position detecting means for detecting the magnetic pole position of the AC synchronous motor based on the output of the first arithmetic means, and second arithmetic means for arithmetically outputting the rotational speed of the synchronous motor from the output of the linear encoder. A position control means for feeding back the position information output from the linear encoder with respect to a position command value from the outside to output a speed command value; and a position control means for the speed command value output by the position control means. The speed control means for feeding back the speed information which is the output of the second calculation means and outputting the current command value, and the AC synchronization with the current command value from the speed control means. Current control means for outputting a voltage command value by feeding back a control current value obtained by coordinate conversion of the armature current of the motor by the output of the magnetic pole position detection means, and the output of the current control means for detecting the magnetic pole position. And a motor drive unit for controlling and driving the AC synchronous motor by converting the coordinates according to the output of the unit.

[0013]

In the first position control system of the present invention, the rotary encoder conventionally mounted on the motor is not used, but the linear encoder for detecting the absolute position serves as an alternative. Since the relationship between the absolute position which is the output of the linear encoder and the rotation angle of the synchronous motor is known in advance, it can be easily converted into the rotation angle amount by multiplying the output of the linear encoder by a predetermined coefficient. Therefore, it is possible to perform this conversion by the first calculation means and detect the magnetic pole position θ by the magnetic pole position detection means in the same manner as in the conventional case, using the output of the pole sensor as a reference. Further, the time information is obtained from the calculation cycle (sampling cycle) for calculating the rotation speed information if the controller has a servo system configured by software calculation, and the controller may have a servo system configured by hardware. For example, since it is obtained from the oscillation circuit clock used in the rotation speed detection circuit, by using this and the output of the linear encoder, the information corresponding to the rotation speed information obtained from the conventional rotary encoder by the second computing means. Can be converted and output as the feedback amount for the speed command.

In the second position control system of the present invention, not only the rotary encoder but also the pole sensor is eliminated. In this case, the magnetic pole position can be detected only from the linear encoder output by checking the reference position information corresponding to the pole sensor output, for example, from the motor back electromotive force waveform and storing the reference absolute position of the machine. Is. Therefore, in the position control system of the present invention, the structure can be simplified by space saving and wire saving, and the cost can be reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a position control system according to an embodiment of the present invention. In this embodiment, the controlled object is the table 1. The table 1 is linearly driven by a pole screw 2 which is rotationally driven by an AC synchronous motor 3. A pole sensor 4 for detecting the magnetic pole is attached to the AC synchronous motor 3. Below table 1 is table 1
A linear encoder 5 is provided for precisely measuring the absolute position of the. At the output of the power amplifier 13 that controls and drives the AC synchronous motor 3, U of the three-phase armature current is output.
A current detection circuit 14 for detecting the phase- and V-phase armature currents Iu and Iv is provided.

The servo circuit for controlling the motor includes a position controller 6 which outputs a speed command value by adding a position command value from the outside and a position feedback signal from the linear encoder 5, and a speed command value obtained from this position controller 5. And a speed feedback signal to output a current command value, and a speed command by adding the q-axis current command value and the d-axis current command value (Id = 0) from this speed controller 7 and the current feedback signal. Current controllers 8 and 9 that output values
Is provided.

A magnetic pole position detection circuit 15 and coordinate conversion circuits 11 and 12 are provided to perform coordinate conversion for current control in the two-axis DC model. Magnetic pole position detection circuit 1
5 outputs the cosine value cos θ and the sine value sin θ of the angle variable θ indicating the magnetic pole position with the output of the pole sensor 4 as a reference. Therefore, the rotation angle of the AC synchronous motor 3 is output from the output of the linear encoder 5. A first arithmetic circuit 16 that arithmetically outputs is provided. Since the linear distance 1 indicated by the output of the linear encoder 5 and the rotation angle α of the AC synchronous motor 3 are in a proportional relationship and the proportional constant is uniquely determined, the first arithmetic circuit 16 is specifically Is a coefficient k (= α for the position information output from the linear encoder 5).
/ L) is applied to obtain the amount of rotation angle. The main body of the magnetic pole position detection circuit 15 is an absolute value counter, which calculates the magnetic pole position θ as a rotation angle from the output of the pole sensor 4 as a reference, and then sin
Outputs θ and cos θ.

A second arithmetic circuit 17 is provided to obtain the speed feedback amount from the output of the linear encoder 5. In order to obtain the rotation speed of the AC synchronous motor 3 from the distance information output from the linear encoder 5, time information is required. Therefore, if the second arithmetic circuit 17 is a controller in which a servo system is configured by calculation by software, time information obtained from a calculation cycle (sampling cycle) for calculating rotational speed information, and the servo system by hardware. If the controller is configured, the speed feedback amount is obtained from the time information obtained from the oscillation circuit clock used in the rotation speed detection circuit.

The coordinate conversion circuit 11 is a magnetic pole position detection circuit 1.
5 output sin θ, cos θ and current detection circuit 14 output Iu
, Iv, the current feedback amounts Id, Iq based on the above-mentioned equation 2 are calculated. Further, the coordinate conversion circuit 12
From the two-axis voltage command values Vd and Vq, the three-phase voltage command values Vu, Vv, and Vw are calculated based on the above equation 3. The non-interference controller 10 is for compensation of feedback control.

As described above, in this embodiment, the rotary encoder conventionally attached to the synchronous motor 3 is removed. Then, using the output of the linear encoder 5 instead of the rotary encoder, the first arithmetic circuit 1
6 and the second arithmetic circuit 17 are provided to obtain a control signal corresponding to the rotary encoder output. Therefore, space and wiring can be saved for the rotary encoder and its wiring.

FIG. 2 is a position control system according to another embodiment of the present invention. The parts corresponding to those in the embodiment of FIG. 1 are designated by the same reference numerals as those in FIG. 1 and their detailed description is omitted. In this embodiment, not only the rotary encoder but also the pole sensor is omitted. The reference signal corresponding to the pole sensor output can be obtained only from the linear encoder output by, for example, confirming from the back electromotive voltage waveform of the motor and storing the absolute position of the reference machine. Using this reference signal, the magnetic pole position detection circuit 15 can calculate the magnetic pole position θ as a rotation angle from the reference magnetic pole position as in the previous embodiment, and sin θ and cos θ can be output from this. According to this embodiment, structural simplification of the position control system is further achieved as compared with the previous embodiments.

[0022]

As described above, according to the present invention, there is provided a position control system using an AC synchronous motor, which is structurally simplified and reduced in cost by removing a rotary encoder and, if necessary, a pole sensor. be able to.

[Brief description of drawings]

FIG. 1 shows a position control system according to an embodiment of the present invention.

FIG. 2 shows a position control system according to another embodiment of the present invention.

FIG. 3 is a diagram for explaining an AC synchronous motor control system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Table (controlled object), 2 ... Pole screw, 3 ... AC synchronous motor, 4 ... Pole sensor, 5 ... Linear encoder, 6 ... Position controller, 7 ... Speed controller, 8, 9 ... Current controller, 10 ... Non-interference controller, 11 ... Coordinate conversion circuit, 12
... coordinate conversion circuit, 13 ... power amplifier, 14 ... current detector.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical indication H02P 21/00 6/06

Claims (2)

[Claims] 1. An AC synchronous motor for linearly driving a controlled object, a pole sensor for detecting a magnetic pole of the AC synchronous motor, a linear encoder for measuring an absolute position of the controlled object, and a linear encoder for the linear encoder. First calculation means for calculating and outputting the rotation angle of the AC synchronous motor from the output, and magnetic pole position detection for detecting the magnetic pole position of the AC synchronous motor based on the output of the pole sensor from the output of the first calculation means. Means, second computing means for computing and outputting the rotational speed of the synchronous motor from the output of the linear encoder, and speed command by feeding back position information output from the linear encoder to a position command value from the outside. The position control means for outputting a value and the speed information output by the second computing means are returned to the speed command value output by the position control means. And a speed control means for outputting a current command value, and control obtained by coordinate conversion of the armature current of the AC synchronous motor by the output of the magnetic pole position detection means with respect to the current command value from the speed control means. Current control means for feeding back a current value to output a voltage command value, and motor drive means for coordinate-converting the output of the current control means by the output of the magnetic pole position detection means to control and drive the AC synchronous motor. A position control system characterized by having. 2. An AC synchronous motor for linearly driving a controlled object, a linear encoder for measuring an absolute position of the controlled object, and a rotational angle of the AC synchronous motor calculated and output from an output of the linear encoder. First calculation means, magnetic pole position detection means for detecting the magnetic pole position of the AC synchronous motor based on the output of the first calculation means, and arithmetic output of the rotational speed of the synchronous motor from the output of the linear encoder. Second computing means, position control means for feeding back position information output from the linear encoder to a position command value from the outside to output a speed command value, and speed command value output by the position control means And a speed control means for feeding back the speed information output from the second computing means to output a current command value, and a current command value from the speed control means. A current control means for feeding back a control current value obtained by coordinate-converting the armature current of the AC synchronous motor by the output of the magnetic pole position detection means and outputting a voltage command value; and an output of the current control means. A position control system, comprising: a motor drive unit that controls and drives the AC synchronous motor by converting coordinates according to the output of the magnetic pole position detection unit.