JP2007333451A - Method for updating corrected value of incremental encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an incremental encoder capable of reducing errors in the computation of positional data when the power of the encoder is turned on. <P>SOLUTION: The incremental encoder includes an correction value change-over part 15 for outputting initial correction values 16a during the period from the power-on of the encoder to the output of correction value computation data 14a, changing over to the correction value computation data 14a after the period, and outputting it to a data correction part 13; an initial correction value control part 16 for controlling the initial correction values 16a; and a nonvolatile memory 18 for storing the initial correction values 16a. When the initial correction value control part 16 detects origin signals 11b outputted from a pulse detection part 11 after the power of the encoder is turned on, correction value data computed at a correction value operation part 14 is stored in the nonvolatile memory 18 as new initial correction values. The new initial correction values stored in the nonvolatile memory 18 are used when the encoder is activated next time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an incremental encoder used for motor control.

  In general, in an encoder that generates rotation angle information by digital calculation using digital data obtained by A / D converting a two-phase analog sine wave output signal having a phase difference of 90 degrees, an offset, amplitude fluctuation, Due to the phase shift, an error occurs in the position data calculation result, which adversely affects the position detection accuracy.

  Conventionally, in order to reduce the position data calculation error, the maximum value and the minimum value of the analog sine wave output signal are detected, and the detected value is used to calculate the offset amount, amplitude fluctuation amount, phase shift amount, etc., respectively. There has been proposed a method of reducing the occurrence of position data calculation errors by obtaining correction values and correcting digital data using the correction values (see, for example, Patent Document 1).

In addition, using a non-volatile memory, a correction value such as an offset amount stored in the non-volatile memory is constantly compared with a correction value calculated based on digital data, and the calculated correction value is stored. A method for automatically updating the nonvolatile memory when the correction value is different from the correction value is proposed (see, for example, Patent Document 2).
JP-A-8-35857 JP 2005-24290 A

  In the method of Patent Document 1, after the maximum value and the minimum value of the analog sine wave are detected, a correction value can be calculated from the detected value to correct the digital data. However, the correction value can be calculated in the maximum / minimum unconfirmed section in which the maximum value and the minimum value cannot be detected from the state in which the analog sine wave does not change immediately after startup until the analog sine wave is detected for one cycle. Can not. That is, the digital data cannot be corrected normally, and the position detection accuracy is significantly deteriorated.

  Furthermore, in order to suppress the fluctuation of the maximum value and the minimum value, when using the maximum value and the minimum value obtained by averaging the values for several cycles in the correction value calculation, the maximum / minimum unconfirmed section continues for several cycles, The section where the position detection accuracy deteriorates becomes large.

  In a device that uses a general incremental encoder, the origin signal output immediately after startup is used as the reference point of the device, and the operation is performed with position data calculated from an analog sine wave. When the origin signal is detected in the undetermined section, the reference point of the position data is greatly deviated from the accurate origin position, which causes a problem that the control position of the entire apparatus is deviated.

  In the method of Patent Document 2, when the calculated correction value is changed from the correction value stored in the non-volatile memory, the correction value is stored in the non-volatile memory. However, the actual correction value depends on the encoder eccentricity or temperature change. Since the number of rewrites of the non-volatile memory is limited in some cases, the number of rewrites exceeds the maximum number, and the correction value cannot be written normally.

SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide an incremental encoder capable of reducing a position data calculation error when an encoder power is turned on.

  In order to solve the above problems, the present invention provides a pulse detection unit that generates a pulse signal from an analog original signal generated according to a motor position, an analog detection unit that generates digital data according to the analog original signal, A correction value calculation unit that calculates and outputs correction value calculation data from the digital data, a data correction unit that corrects the digital data using correction value data output from the correction value calculation unit, and an output of the data correction unit In an incremental encoder including a position data calculation unit that calculates position data from data, an initial correction value is output during a period from when the encoder power is turned on until correction value calculation data is output, and thereafter the correction value calculation data And a correction value switching unit that outputs to the data correction unit and an initial correction value control that controls the initial correction value. And a non-volatile memory for storing the initial correction value, and when the initial correction value control unit detects an origin signal output from the pulse detection unit after the encoder power is turned on, the correction value calculation unit The calculated correction value data is stored in the non-volatile memory as a new initial correction value, and the correction value update of the incremental encoder that uses the new initial correction value stored in the non-volatile memory when the encoder is started next time Is the method.

  Further, the correction value control unit compares the new initial correction value with the initial correction value stored in the nonvolatile memory and updates the correction value not to be stored in the nonvolatile memory when the value does not change. .

  In addition, a temperature detection unit that detects the encoder temperature is further provided, and when the new initial correction value is stored in the nonvolatile memory, the correction value storage temperature detected by the temperature detection unit is also stored, and the temperature detection is performed at the next startup. This is a correction value update method in which the detected temperature from the unit is compared with the correction value storage temperature, and the initial correction value is corrected based on the comparison value.

  According to the incremental encoder correction value updating method of the present invention, the initial correction value used when the encoder power is turned on is updated using the correction value obtained when the origin signal is detected. Thus, the digital data can be appropriately corrected, and the position data calculation error can be reduced.

  Also, when the initial correction value is updated, it is compared with the initial correction value stored in the non-volatile memory, and if the correction value has not changed, the save operation is not performed, thereby preventing frequent rewriting of the non-volatile memory. be able to.

  In addition, temperature information is saved when the initial correction value is saved, and correction of the correction value due to temperature changes is suppressed by correcting the initial correction value based on the temperature information detected at the next startup and the stored temperature information. The position data calculation error can be effectively reduced.

  Therefore, even if the analog original signal fluctuates due to aging, etc., incremental encoder correction that can control without adversely affecting the reference point of the entire device by reducing the position data calculation error and detecting the correct origin position A value update method can be provided.

A pulse detector for generating a pulse signal from an analog original signal generated according to the motor position, an analog detector for generating digital data according to the analog original signal, and calculating and outputting correction value calculation data from the digital data A correction value calculation unit, a data correction unit for correcting the digital data using correction value data output from the correction value calculation unit,
In an incremental encoder including a position data calculation unit that calculates position data from output data of the data correction unit, an initial correction value is output during a period from when the encoder power is turned on until correction value calculation data is output, and thereafter Comprises a correction value switching unit that switches the correction value calculation data and outputs the data to the data correction unit, an initial correction value control unit that controls an initial correction value, and a nonvolatile memory that stores the initial correction value, When the initial correction value control unit detects an origin signal output from the pulse detection unit after the encoder power is turned on, the correction value data calculated by the correction value calculation unit is used as a new initial correction value. The new initial correction value stored in the non-volatile memory is used when the encoder is activated next time.

  The correction value updating method of the incremental encoder according to the present invention will be described with reference to the drawings.

  In FIG. 1, the position data generation unit of the incremental encoder includes an original signal generation unit 10, a pulse detection unit 11, an analog detection unit 12, a data correction unit 13, a correction value calculation unit 14, a correction value switching unit 15, and an initial correction value control. 16, a memory control unit 17, a nonvolatile memory 18, a position data calculation unit 19, a parallel-serial conversion unit 20, and a communication unit 21. Bidirectional serial communication with the servo amplifier 22 is performed by a communication unit 21 such as RS485. Do.

  The original signal generator 10 outputs a pulse signal 10a and an analog signal 10b corresponding to the rotational position of the motor. After sampling the pulse signal 10b, the pulse detector 11 outputs the two-phase pulse data 11a and the origin signal 11b necessary for calculating the position data 19a.

  The analog detector 12 samples the analog signal 10b, converts it into a format for calculating the position data 19a, and outputs the digital data 12a. The data correction unit 13 corrects the digital data 12a with the correction value 15a and outputs the corrected digital data 13a.

  The position data calculation unit 19 performs calculation based on the corrected digital data 13a, the two-phase pulse data 11a, and the origin signal 11b, thereby outputting position data 19a indicating the rotor position for each sampling period.

  The memory control unit 17 writes the initial correction value 16a and the parameter 20a representing the motor characteristics into the nonvolatile memory 18, and also reads out the in-memory initial correction value 17a and the in-memory parameter 17b from the nonvolatile memory when the encoder power is turned on. Do.

  Since the parameter 20a is uniquely determined by the motor to which the incremental encoder is connected, it is generally written only once at the time of factory shipment.

  The parallel-serial conversion unit 20 mutually converts serial data transmitted bi-directionally from the servo amplifier 22 via the communication means 21 and parallel data used inside the encoder, and uses the position data 19a or the in-memory parameter 17b as serial transmission data. The parameter 20a is output to the memory control unit 17 from the serial reception data from the servo amplifier.

  The correction value calculation unit 14 detects the offset, amplitude, and phase difference of the analog signal 10b from the digital data 12a and the two-phase pulse data 11a, and calculates the correction value calculation data 14a for digital correction by the data correction unit 13. The correction value calculation data 14a may include data necessary for digital correction in addition to the offset, amplitude, and phase difference.

  The correction value switching unit 15 outputs the initial correction value 16a as the correction value 15a from the time the encoder power is turned on until the analog signal can be detected in an arbitrary period, and the correction value calculation data 14a is corrected after the arbitrary period is detected. Output as value 15a. Further, the correction value switching unit 15 detects an arbitrary period of the analog signal by detecting the number of rises or falls of the two-phase pulse data 11a.

  The initial correction value control unit 16 writes the correction value calculation data 14a as the initial correction value write data 16b in the nonvolatile memory 18 via the memory control unit 17, and the initial correction value 17a in the memory is stored from the nonvolatile memory when the encoder power is turned on. Is output as an initial correction value 16a.

Next, the initial correction value 16a writing sequence of the initial correction value control unit 16 will be described with reference to the flowchart of FIG.
When the encoder power is turned on, the sequence is started, and correction value calculation data 14 a output from the correction value calculation unit 14 is acquired in the correction value acquisition processing 30. Next, in the origin detection determination process 31, it is determined whether the origin position is based on the origin signal 11b output from the pulse detector 11.

  If it is not the origin position, the process returns to the correction value acquisition process, and the correction value acquisition and the origin detection determination are repeated until the origin position is reached.

  When the origin position is reached in the origin detection determination process, the correction value fetched into the nonvolatile memory 18 via the memory control unit 17 in the correction value writing process 32 is written as the initial correction value 16a.

  This sequence may be executed not only once after power-on but also a plurality of times, or may be executed at arbitrary time intervals using a timer.

  In this way, by updating the initial correction value with the origin position, even if the original signal fluctuates due to aging, etc., control can be performed without adversely affecting the reference point of the entire apparatus by detecting the exact origin position. Yes.

  Hereinafter, Example 2 will be described with reference to FIG. The difference from the first embodiment is only the initial correction value 16a writing sequence of the initial correction value control unit 16, and the sequence will be described.

  In FIG. 3, the operations of the correction value fetch processing 30, the origin detection determination processing 31, and the correction value writing processing 32 are the same as the sequence of FIG.

  When the origin position is reached in the origin detection determination process 31, the in-memory initial correction value 17a is read from the nonvolatile memory 18 in the in-memory initial correction value reading process 33.

  Next, in the correction value update determination process 34, the correction value calculation data 14a is compared with the initial correction value 17a in the memory, and if the values are the same, the sequence ends without performing the correction value writing process, and the values are different. In the case, the correction value writing process is executed to update the correction value.

  As a result, the number of times of writing to the nonvolatile memory can be reduced to enable long-term use, and a more reliable incremental encoder can be obtained.

Hereinafter, Example 3 will be described with reference to FIG. The difference between the first embodiment and the second embodiment is that the temperature detection unit 23 is further provided, and the initial correction value control unit 16 writes and reads the initial correction value using the temperature data 23a output from the temperature detection unit 23. It is only the part which performs.

  In the initial correction value writing operation of the initial correction value control unit, the temperature data 23a is taken together with the correction value calculation data 14a in the correction value fetching process of FIGS. Write.

In the initial correction value reading operation, the in-memory initial correction value C _m and the in-memory temperature data T _m are read from the nonvolatile memory 18.

Next, the current temperature data T _n is read from the temperature detection unit 23, and a corrected correction value C _{c is obtained} by the following equation: C _c = G × (T _n −T _m ) + C _m Here, G is a fluctuation ratio of the correction value with respect to a predetermined temperature change of 1 ° C. The fluctuation ratio is determined by measuring the fluctuation of the correction value by changing the encoder temperature before shipment. Then, it outputs the correction value C _c of the corrected as an initial correction value 16a.

  Accordingly, the origin position can be detected more accurately by correcting the temperature change when the initial correction value is stored and when the initial correction value is used.

  The correction value update method of the present invention is also useful for an apparatus based on the origin of an incremental encoder.

1 is a block diagram of an incremental encoder according to a first embodiment of the present invention. Flowchart of initial correction value writing sequence in Embodiment 1 of the present invention Flowchart of initial correction value writing sequence in Embodiment 2 of the present invention Block diagram of the incremental encoder in Embodiment 3 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Original signal generation part 10a Pulse signal 10b Analog signal 11 Pulse detection part 11a Two-phase pulse data 11b Origin signal 12 Analog detection part 12a Digital data 13 Data correction part 13a Digital data after correction 14 Correction value calculation part 14a Correction value calculation data 15 Correction value switching unit 15a Correction value 16 Initial correction value control unit 16a Initial correction value 16b Initial correction value write data 17 Memory control unit 17a Initial correction value in memory 17b In-memory parameter 18 Non-volatile memory 19 Position data calculation unit 19a Position data 20 Parallel Serial Conversion Unit 20a Parameter 21 Communication Means 22 Servo Amplifier 23 Temperature Detection Unit 23a Temperature Data 30 Correction Value Acquisition Processing 31 Origin Detection Determination Processing 32 Correction Value Write Processing 33 In-Memory Correction Value Reading Processing 3 Correction value updating determination process

Claims (3)

A pulse detection unit that generates a pulse signal from an analog original signal generated according to the motor position, an analog detection unit that generates digital data according to the analog original signal, and an arithmetic output of correction value calculation data from the digital data A correction value calculation unit, a data correction unit that corrects the digital data using correction value data output from the correction value calculation unit, and a position data calculation unit that calculates position data from the output data of the data correction unit In an incremental encoder comprising: an initial correction value is output during a period from when the encoder power is turned on until correction value calculation data is output, and thereafter, the correction value calculation data is switched and output to the data correction unit A correction value switching unit, an initial correction value control unit for controlling the initial correction value, and a storage unit for storing the initial correction value. And when the initial correction value control unit detects an origin signal output from the pulse detection unit after the encoder power is turned on, the correction value data calculated by the correction value calculation unit is newly updated. A method for updating an incremental encoder correction value, wherein the initial correction value is stored in the non-volatile memory and the new initial correction value stored in the non-volatile memory is used when the encoder is activated next time. 2. The incremental encoder according to claim 1, wherein the correction value control unit compares a new initial correction value with an initial correction value stored in a nonvolatile memory, and does not store the new correction value in the nonvolatile memory when there is no change in the value. Correction value update method. A temperature detection unit for detecting the encoder temperature is further provided, and when the new initial correction value is stored in the nonvolatile memory, the correction value storage temperature detected by the temperature detection unit is also stored. 3. The incremental encoder correction value updating method according to claim 1, wherein the detected temperature is compared with the correction value storage temperature, and the initial correction value is corrected based on the comparison value.

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