JP2018115912A - Signal processing device, measurement device, industrial machine, and article manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal processing device advantageous in cost and accurate measurement.SOLUTION: A signal processing device 140 that processes a periodic signal which is obtained through a scale with motion of an object due to a motor comprises a processing unit 142 that obtains a rotation angle or a position of the object on the basis of a phase of the periodic signal, and the processing unit 142 obtains a predicted value of the rotation angle or the position on the basis of the rotation angle or the position, a command signal Iref to the motor, and a transfer characteristic of the motor, and obtains the rotation angle or the position on the basis of the predicted value and a phase of the periodic signal corresponding thereto.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a signal processing device, a measuring device, an industrial machine, and an article manufacturing method.

  A motor included in an industrial machine such as a laser processing device (galvanomirror device) or a robot can be controlled based on the rotation angle of the motor measured using a rotary encoder. As the rotary encoder, for example, an optical incremental encoder can be used. In general, measurement of the rotation angle of a motor using the encoder needs to count pulses obtained by binarizing the output signal of the encoder head. From the viewpoint of cost, a signal processing device is known in which a circuit for binarization and counting is omitted (Patent Document 1).

Japanese Patent No. 5409882

  The signal processing apparatus disclosed in Patent Document 1 utilizes the fact that the motor can be regarded as rotating at a constant speed in a short period of time. However, in the industrial machine as described above, there may be a case where the rotational speed of the motor cannot be considered constant, for example, by rotating the motor with a large acceleration. In such a case, accurate measurement may be difficult with the signal processing device of Patent Document 1.

  An object of the present invention is to provide a signal processing apparatus that is advantageous in terms of cost and accurate measurement, for example.

  In order to solve the above-described problems, the present invention is a signal processing apparatus that processes a periodic signal obtained through a scale in accordance with the movement of an object by a motor, and based on the phase of the periodic signal, the rotation angle of the object Or a processing unit that obtains a position, and the processing unit obtains a predicted value of the rotational angle or position based on the rotational angle or position, a command signal to the motor, and the transmission characteristics of the motor, and the predicted value and the corresponding period The rotation angle or position is obtained based on the phase of the signal.

  According to the present invention, for example, it is possible to provide a signal processing device that is advantageous in terms of cost and accurate measurement.

It is a block diagram which shows the structure of the galvano apparatus containing the signal processing apparatus which concerns on 1st Embodiment. It is a block diagram which shows the relationship between a feedback control part and a galvano apparatus. It is a block diagram which shows the structure of the galvano apparatus containing the signal processing apparatus which concerns on 2nd Embodiment. It is a figure which shows the structural example of the laser processing apparatus as an example of an industrial machine. It is a figure which shows the structural example of the 6-axis arm type robot as an example of an industrial machine.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram illustrating a configuration of a galvano device (drive device) including a signal processing device according to the present embodiment. The galvano device 100 includes a motor 110, an encoder 120, a current amplifier 130, a signal processing device 140, and an object (for example, a mirror) rotated by the motor 110. The galvano device 100 can also be a measuring device that measures the rotation angle or position of the motor 110, that is, the rotation angle or position of an object rotated by the motor 110. In the following description, the description related to the rotation angle of the motor 110 can be replaced with the description related to the position of the motor 110 and the rotation angle or position of the object rotated by the motor 110. The signal processing device 140 includes an A / D (analog / digital) conversion unit 141 and a processing unit 142. Note that the A / D converter 141 may be included in the encoder 120. FIG. 2 is a block diagram illustrating a relationship between the feedback control unit 200 and the galvano device 100. The feedback control unit 200 performs feedback control so that the rotation angle y of the motor 110 calculated by the signal processing device 140 matches the target rotation angle at a predetermined time interval (predetermined timing).

  A current command Iref is input to the current amplifier 130 from the feedback control unit 200 shown in FIG. The current command Iref is a command signal that commands the rotation of the motor 110. The current amplifier 130 supplies a current to the motor 110 based on the current command Iref. The motor 110 rotates with a torque generated according to the current. The encoder 120 is a detection unit that detects the rotation angle θ of the motor 110. For example, the encoder 120 outputs an A-phase signal and a B-phase signal of analog signals corresponding to periodic signals having phases different from each other by 90 degrees to the A / D converter 141. For example, the A phase signal may be a Sin wave signal and the B phase signal may be a Cos wave signal. The phase shift is not limited to 90 degrees, and the number of signals is not limited to two.

  In the present embodiment, a transmissive optical encoder may be used as the encoder 120. The encoder 120 has a scale provided with a slit through which light passes, and the scale rotates around the rotation axis of the motor 110. During rotation, the scale is irradiated with light from the light emitting element, and the light transmitted through the slit is detected by the light receiving element. The A-phase signal and the B-phase signal having phases different from each other by 90 degrees can be obtained, for example, by shifting the arrangement of the light receiving elements.

The A / D conversion unit 141 is an output unit that converts the A-phase signal and the B-phase signal from analog signals to digital signals and outputs the signals to the processing unit 142. The processing unit 142 calculates an arc tangent value of the ratio between the A phase signal and the B phase signal converted into a digital signal, that is, tan ⁻¹ (B / A).

  On the other hand, the current command value Iref is also input to the processing unit 142. The processing unit 142 obtains a predicted angle y ′ that is a predicted value of the rotation angle of the motor 110 by a Kalman filter based on the current command value Iref and the rotation angle y of the motor 110 output by the signal processing device 140 last time. The Kalman filter takes into consideration a dynamic characteristic model obtained by modeling the dynamic characteristic of the motor 110. The dynamic characteristic of the motor 110 is, for example, an input of the motor 110 indicating how long the motor 110 reaches the predetermined rotational speed with respect to the current command value Iref for setting the motor 110 to the predetermined rotational speed. It means the response characteristic to current (also referred to as transfer characteristic). The rotation angle y used by the Kalman filter is the rotation angle previously calculated by the processing unit 142. When the predicted angle y ′ is calculated for the first time after the driving of the motor 110 is started, the predicted angle y ′ is calculated by setting the rotation angle y to zero. .

で表される。ここで、ｓはラプラス演算子、ｋ０は定数である。
離散時間カルマンフィルタを適用するために、上式を離散化し、システム雑音、観測雑音を考慮した状態方程式は次式のように示される。

υ（ｋ）はシステム雑音、ω（ｋ）は観測雑音である。
また、事前状態推定値は

事前誤差共分散行列は、

カルマンゲインは、

状態推定値は、

事後誤差共分散行列は、

となる。システム雑音の標準偏差をσｖ、観測雑音の標準偏差をσωとする。ここで、本実施形態において、入力ｕ（ｋ）は、電流指令値Ｉｒｅｆであり、事前状態推定値は予測角度ｙ´に相当する。また、観測値ｙは回転角度ｙに相当する。 The Kalman filter will be described. The dynamic characteristic model (transfer function) P (s) of the motor 110 is

It is represented by Here, s is a Laplace operator, and k0 is a constant.
In order to apply the discrete-time Kalman filter, the above equation is discretized, and the state equation in consideration of system noise and observation noise is expressed as follows.

υ (k) is system noise and ω (k) is observation noise.
The prior state estimate is

The prior error covariance matrix is

Kalman gain is

The state estimate is

The posterior error covariance matrix is

It becomes. The standard deviation of system noise is σv, and the standard deviation of observation noise is σω. Here, in the present embodiment, the input u (k) is the current command value Iref, and the prior state estimated value corresponds to the predicted angle y ′. The observed value y corresponds to the rotation angle y.

In the measurement of the rotation angle using an optical encoder, the phase obtained from tan ⁻¹ (B / A) and the phase obtained from the up / down count value of one of the A phase signal and the B phase signal. Is added to obtain the rotation angle. The phase is obtained from the count value by dividing the count value by the number K of slits provided on the scale and multiplying the result by 2π. In this embodiment, an estimated value of the count value (hereinafter referred to as a count estimated value) is obtained without using a counting unit that counts up and down of the signal and means for binarizing the signal.

The estimated count value n is obtained as follows. First, an arctangent tan ⁻¹ (B / A) calculated based on the A-phase signal and the B-phase signal converted into a digital signal, that is, an actual measurement value is subtracted from the predicted angle y ′. The subtraction result is multiplied by 2 / π to convert the unit, approximated to an integer value by a round function, and multiplied by π / 2 to obtain the estimated count value n. This approximation is performed in order to remove the influence of disturbances such as dynamic characteristic modeling errors and electrical noise on the subtraction result. In the present embodiment, the up-counting and the down-counting are performed every π / 2.

The rotation angle y of the motor 110 is obtained by dividing the estimated count value n by the number of slits K and adding 2π and the inverse tangent tan ⁻¹ (B / A). The obtained rotation angle y is input to the Kalman filter and used for calculation of the rotation angle y by the next current command Iref. The elements necessary for estimating the count value are the current command value Iref, the motor 110 dynamic characteristic model, the actually measured value of the arctangent tan ⁻¹ (B / A), and the rotation angle y of the motor 110 obtained last time. It is not necessary to assume that the rotation speed of the motor is constant.

  As described above, according to the processing unit 142 of the present embodiment, even if the motor 110 is accelerated or decelerated, it is possible to reduce the counting unit and the binarizing means and detect the rotation angle of the motor 110 with high accuracy. .

(Second Embodiment)
In the first embodiment, the count value is approximated using the round function. However, depending on the magnitude of disturbance such as a dynamic characteristic modeling error or electrical noise, the error of the approximate value can be large. The present embodiment includes a configuration for determining whether or not the error of the approximate value is large. FIG. 3 is a block diagram showing a configuration of the galvano device including the signal processing device according to the present embodiment. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

The calculation unit 242 of the signal processing device 240 according to the present embodiment further includes an encoder model 243, an A-phase comparison unit 244, and a B-phase comparison unit 245 in addition to the configuration of the processing unit 142 of the first embodiment. The encoder model 243 outputs estimated signals obtained by estimating the A-phase signal and the B-phase signal based on the predicted angle y ′ output by the Kalman filter. The A phase comparison unit 244 compares the estimated A phase signal with the A phase signal output from the A / D conversion unit 141. Similarly, the B-phase comparison unit 245 compares the estimated B-phase signal with the B-phase signal output from the A / D conversion unit 141. As a result of the comparison, when the phase difference of each signal does not fall within a predetermined allowable range, it is determined that the obtained rotation angle y has a large error. If the error is large, measures such as resetting the equation representing the dynamic characteristic model of the motor 110 are taken so that the error falls within a predetermined range. The magnitude of the error may be determined by comparing the arc tangent tan ⁻¹ (B / A), that is, the phase of each signal. According to the present embodiment, the detection accuracy of the rotation angle of the motor can be adjusted in the signal processing device in which the counting unit and the binarizing means are reduced.

(Application examples for industrial machinery)
The galvano device (drive device) of the above embodiment can be used in a laser processing device such as a laser drilling device, a laser trimmer device, or a laser repair device. FIG. 4 is a diagram showing a configuration of a laser processing apparatus 400 using a galvano apparatus. The laser processing apparatus 400 irradiates an object W to be processed with laser light, and performs processing such as cutting, drilling, and welding of the object W to manufacture an article. The laser processing apparatus 400 includes a light source 410 and a lens 420. The laser processing apparatus 400 according to the present embodiment scans the laser light emitted from the light source 410 in the X direction and the Y direction on the XY plane parallel to the surface of the object W. The galvano devices 430 and 440 are arranged one by one in the X direction and the Y direction, respectively, and irradiate the object W by reflecting the laser beam with a mirror. The mirror which is a movable part is driven by a motor, and the rotation of the motor is controlled by a control unit such as the feedback control unit 200 based on the measurement result of the rotation angle of the motor by the galvano devices 430 and 440.

  The drive device of the above embodiment can also be used for an industrial robot such as a 6-axis arm type robot. FIG. 5 is a diagram showing a configuration of the six-axis arm type robot 600. Driving devices (galvano devices) 610 to 660 are provided in each joint portion. Each joint which is a movable part is driven by a motor, and the rotation of the motor is controlled by a control unit such as the feedback control unit 200 based on the measurement result of the rotation angle of the motor by the galvano devices 610 to 660. The drive of the arm type robot 600 is controlled. The 6-axis arm type robot 600 holds an object with a gripping portion provided at the tip, and moves it such as translation or rotation. Further, by assembling (assembling) an object to other parts by the six-axis arm type robot 600, an article composed of a plurality of parts, for example, an electronic circuit board or a machine can be manufactured. Further, an article can be manufactured by processing (processing) the moved object.

  By applying the galvano device or drive device having the signal processing device described in the above embodiment to an industrial machine, it can contribute to the cost reduction of the entire device. The industrial machine can be used in an article manufacturing method. The article manufacturing method of the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article as compared with the conventional method.

  In the above-described embodiment, the galvano device having the signal processing device has been mainly described. However, the signal processing device of the above-described embodiment can also be applied to control of a driving device including other motors such as a DC motor and an AC motor. In the above embodiment, the count value estimation means using the Kalman filter is used, but other estimation means such as an H∞ filter may be used. The motion generated in the object by the motor is not limited to the rotational motion, and may be a linear motion, for example.

  When the A / D conversion unit 141 is included in the encoder 120, signal degradation between the signal processing device 140 and the encoder 120 can be suppressed, which can be advantageous in terms of detection accuracy of the rotation angle.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

100 Galvano device (drive device)
110 Motor 120 Encoder 130 Current Amplifier 140 Signal Processing Device 141 A / D Converter (Output Unit)
142 processor

Claims (12)

A signal processing device for processing a periodic signal obtained through a scale in accordance with the movement of an object by a motor,
A processing unit for obtaining a rotation angle or position of the object based on a phase of the periodic signal;
The processor is
Based on the rotation angle or position, a command signal to the motor, and the transmission characteristics of the motor, obtain a predicted value of the rotation angle or position,
Based on the predicted value and the phase of the periodic signal corresponding thereto, the rotation angle or position is obtained.
A signal processing apparatus. The processor is
Determining whether a difference between a phase calculated from the predicted value and a phase of the periodic signal corresponding to the predicted value is within an allowable range, and setting the transfer characteristic based on a result of the determination The signal processing apparatus according to claim 1.   The signal processing apparatus according to claim 1, wherein the processing unit includes a Kalman filter for obtaining the predicted value.   4. The method according to claim 1, wherein the processing unit obtains the rotation angle or position based on a value obtained by subtracting a phase of the periodic signal corresponding to the predicted value from the predicted value. 2. The signal processing device according to item 1.   The signal processing apparatus according to claim 1, wherein the periodic signal includes a plurality of periodic signals having different phases.   The signal processing apparatus according to claim 1, wherein the transfer characteristic includes a transfer function. An output unit that outputs a periodic signal obtained through a scale in accordance with the movement of an object by a motor;
The signal processing device according to any one of claims 1 to 6, which processes the periodic signal;
A measuring device comprising:   The measurement apparatus according to claim 7, wherein the output unit outputs the periodic signal as a digital signal. A motor that causes the movement of the object;
A measuring device according to claim 7 or 8,
A control unit for controlling the motor based on a measurement result of the measurement device;
An industrial machine characterized by including.   The industrial machine according to claim 9, wherein the object includes a mirror.   The industrial machine according to claim 9, wherein the object includes a robot.   An article manufacturing method comprising: processing an object using the industrial machine according to any one of claims 9 to 11 to manufacture an article.

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