JP2009095154A - Motor controller and its speed detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller which can detect exact speed over the entire speed control range by detecting the speed based on the detection of position and the time required for change of position when it is above a certain speed, and by detecting the speed based on the change of position during sampling time when it is below a certain speed, and to provide its speed detection method. <P>SOLUTION: An encoder 3 outputs time data, i.e. measurements of time required for change of positional data during the sampling time. A speed calculation section 15 defines the positional data as first positional data, generates second positional data by decimating predetermined amount of the first positional data, and generates third positional data by decimating predetermined amount of the second positional data, and then calculates the motor speed based on the second and third positional data. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor control device that drives a machine or the like with a servo motor and a speed detection method thereof.

  The first prior art is “related to a method for detecting the speed of a servo drive that detects the speed from an encoder pulse”, and is “accurate even when pulse input is lost during sampling due to a decrease in the rotational speed of the motor. The object is to provide a speed detection method of a servo driver capable of smoothly controlling the rotational speed of a motor by estimating the speed ", and" the means for storing the data when there are no encoder pulses PA and PB during sampling " In this case, the speed at the time of sampling is estimated by a fixed arithmetic expression using the speed detection data at the time of sampling from a plurality of times stored in (see, for example, Patent Document 1).

  The second prior art is “related to a servo motor control device such as a digital servo control device”. “Even if there is an encoder pulse interval error, the motor speed is accurately estimated to control the speed at a low speed. The purpose is to provide a servo motor control device in which the motor does not stop even when the command speed is not 0 when the estimated speed is used to control the speed. 4 calculates the detection speed of the servo motor 1 from the output pulse of the encoder 2, and calculates the estimated load torque from the motor current detected by the current detector 11 by the estimated load torque calculation unit 6 and the detected speed every time the output pulse is generated. And the average estimated load torque is calculated by averaging the estimated load torque n times for each occurrence of the output pulse by the n-time averaging unit 12. When the speed control unit 9 performs speed control so that the detected speed becomes a speed command at a predetermined control cycle and the detected speed cannot be calculated in the speed control cycle section, the estimated speed calculation unit 7 performs the average estimation. An estimated speed is calculated from the load torque and the motor current, and speed control is performed so that the estimated speed becomes the speed command (see, for example, Patent Document 2).

Further, the third prior art relates to “a method for improving speed characteristics in a servo that enables speed control with high stability in the entire speed range and a servo system improved in speed characteristics”. To provide a speed characteristic improvement method in a servo system and a servo system with improved speed characteristics, capable of high-accuracy speed detection in the entire speed range, and capable of realizing highly stable speed control in the entire speed range. Measure the feedback pulse detected by the incremental encoder at a certain sampling time asynchronous to the feedback pulse, count the number of feedback pulses N _FBP between sampling times, and by counting the reference clock generated at intervals T _CLK, a total of the feedback pulse number N _FBP Obtains a reference clock number N _CLK in the period taken to, the time interval T _CLK, a feedback pulse number N _FBP, the reference clock number N _CLK and the resolution of the feedback pulse [Delta] D, the velocity V of the controlled object by the following equation Based on the calculated speed, V = N _FBP * ΔD / (N _CLK * T _CLK ), the speed of the controlled object, or the speed and position are controlled ”(see, for example, Patent Document 3).

Thus, in the first and second prior arts, when estimating the speed, the speed detection data at the time of sampling a plurality of times before is used, and the average estimated load torque and the motor current are used. In the third prior art, the period required to count the feedback pulse number N _FBP by counting the feedback pulse number N _FBP between sampling times and the reference clock N _CLK generated at a predetermined time interval T _CLK The speed V is calculated based on the number of reference clocks N _CLK and the resolution ΔD of the feedback pulse (V = N _FBP × ΔD / (N _CLK × T _CLK )).
JP 11-038884 A (page 3-4, FIG. 1) JP 09-172793 A (6th page, FIG. 1) JP 06-325441 A (page 4-6, FIG. 1)

In the first prior art, when there are no encoder pulses PA and PB during sampling, that is, in the case of extremely low speed rotation, the speed is estimated by weighting the speed detection data at the time of sampling a plurality of times before. However, there is a problem in that high-accuracy speed cannot be detected, and therefore, speed responsiveness is deteriorated.
In the second prior art, since the speed is estimated based on the average estimated load torque and the motor current, only an averaged speed can be obtained, and a highly accurate speed cannot be detected. There was also the problem of getting worse.
In the third prior art, since the speed is detected based on the reference clock N _CLK and the feedback pulse resolution ΔD, the speed resolution is the feedback pulse number N _FBP , the reference clock number N _CLK , and the feedback pulse resolution. There is also a problem that the resolution cannot be obtained more than the resolution of the feedback pulse because it is determined by the resolution ΔD.
The present invention has been made in view of such a problem, and detects a speed by a time required for position detection and a change in the position at a certain speed or more, and a position at a certain sampling time at a certain speed or less. It is an object of the present invention to provide a motor control device and a speed detection method thereof that can detect a speed from a change in the speed and detect an accurate speed in the entire speed control range.

In order to solve the above problem, the present invention is configured as follows.
The invention according to claim 1 includes a speed calculation unit that inputs position data output by an encoder connected to a motor at a constant sampling time, and calculates a motor speed based on the position data and the sampling time. In the motor control device that drives the motor based on a position or speed command, the encoder outputs time data obtained by measuring a time required for the change of the position data within the sampling time, and the speed A calculation unit sets the position data as first position data, generates the second position data by subtracting the first position data for a predetermined amount, and subtracts the second position data for a predetermined amount. Three-position data is generated, and the motor speed is calculated based on the first and second position data.

  The invention according to claim 2 requires the change amount of the second position data and the change of the second position data when the speed calculation unit according to the invention of claim 1 is equal to or higher than a certain motor speed. The motor speed is calculated based on the time data, and if the motor speed is less than the certain motor speed, the motor speed is calculated based on the first position data and the sampling time.

  According to a third aspect of the present invention, the time data in the first aspect of the invention is the time required for the change of the second position data to be greater than the minimum resolution.

  According to a fourth aspect of the present invention, when the speed calculation unit according to the first aspect of the invention has no change in the first position data, the direction of the motor speed is the same as the motor speed at the previous sampling time. The motor speed is calculated assuming that the minimum resolution of the first position data has changed at the beginning or the middle of the next sampling time.

  According to a fifth aspect of the present invention, when the speed calculation unit according to the first aspect of the present invention has no change in the first position data, the direction of the motor speed is the same as the motor speed at the previous sampling time. The motor speed is calculated assuming that the minimum resolution of the first position data has changed at the beginning or middle of the next sampling time, and if the motor speed is less than a certain motor speed, the motor speed Is 0.

  The invention described in claim 6 includes a speed calculation unit that inputs position data output by an encoder connected to the motor at a constant sampling time, and calculates a motor speed based on the position data and the sampling time. In a speed detection method of a motor control device that drives the motor based on a position or speed command, the encoder outputs time data obtained by measuring a time required for the change of the position data within the sampling time. The speed calculation unit sets the position data as the first position data, generates the second position data by subtracting the first position data for a predetermined amount, and further determines the second position data in advance. The third position data is generated by subtracting the minute, and the motor speed is calculated based on the first and second position data.

  The invention according to claim 7 requires the change amount of the second position data and the change of the second position data when the speed calculation unit according to the invention of claim 6 is equal to or higher than a certain motor speed. The motor speed is calculated based on the time data. If the motor speed is less than the certain motor speed, the motor speed is calculated based on the first position data and the sampling time.

  According to an eighth aspect of the invention, the time data in the sixth aspect of the invention is the time required for the change of the first position data to be greater than or equal to the minimum resolution.

  According to a ninth aspect of the present invention, when the speed calculation unit according to the sixth aspect of the invention has no change in the first position data, the direction of the motor speed is the same as the motor speed at the previous sampling time. The motor speed is calculated on the assumption that the minimum resolution of the first position data is changed at the beginning or the middle of the next sampling time.

  According to a tenth aspect of the present invention, when the speed calculation unit according to the sixth aspect of the invention has no change in the first position data, the direction of the motor speed is the same as the motor speed at the previous sampling time. The motor speed is calculated assuming that the minimum resolution of the first position data has changed at the beginning or middle of the next sampling time, and if the motor speed is less than a certain motor speed, the motor speed Is set to 0.

  According to the first to tenth aspects of the present invention, the speed is detected based on the position detection and the time required to change the position above a certain speed, and the speed is detected based on the position change at a certain sampling time below the certain speed. In addition, an accurate speed can be detected in the entire speed control range. In addition, since the speed is calculated when the first position data changes beyond the minimum resolution, the influence of noise and the like can be reduced, and the speed can be calculated with a stable resolution (second position data). In addition, an accurate speed can be detected even when there is no change in the first position data within the sampling time.

  Hereinafter, specific examples of the method of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a motor control device according to Embodiment 1 of the present invention. In the figure, 1 is a motor control device, 2 is an electric motor (motor), 3 is a position detector such as an encoder, 11 is a position or speed control unit, 12 is a current control unit, 13 is an inverter unit, 14 is an input circuit unit, Reference numeral 15 denotes a speed signal calculation unit. A configuration in which a position command or a speed command is input and the electric motor 2 is driven according to the command and the position detection signal or the speed detection signal (the electric motor 2, the position detector 3, the position or speed control unit 11, the current control unit 12). The inverter unit 13 and the input circuit unit 14) have a configuration obtained by a well-known technique, and a detailed description thereof will be omitted.
The part where the present invention is different from the prior art is a part provided with a speed calculation unit 15 for executing a speed detection method described later.
The speed calculation unit 15 detects the speed based on the change amount of the position detection value and the time required for the change above a certain speed, and detects the speed based on the change amount of the position detection value at the sampling time below the certain speed.

FIG. 2 is a schematic block diagram of the encoder 3. In the figure, 31 is a light emitter, 32 is a rotating disk having a slit, 33 is a light receiver, 34 is an amplifier, 35 is an A / D converter, 36 is a position conversion circuit, and 37 is a counter.
The encoder 3 outputs position data and time data necessary for speed calculation in the speed calculation unit 15, and a method of outputting position data and time data in the encoder 3 will be described.

First, the light receiver 33 receives light from the light emitter 31 through the slits A and B having a phase difference of 90 degrees of the rotating disk 32 and outputs a corresponding signal.
Next, this signal is amplified by the amplifier 34 to obtain output waveforms of Aφ and Bφ. Here, the output waveforms of Aφ and Bφ are sinusoidal signals depending on how light passes through the slits of the rotating disk 32.
Next, the A / D converter 35 receives the sinusoidal signals Aφ and Bφ, converts them into digital values with fine resolution, and outputs them to the position conversion circuit 36.

Next, the position conversion circuit 36 obtains an angle within one pulse of the encoder 3 based on the output of the A / D converter 35 and converts it into a position (for example, the sine wave signals Aφ and Bφ are A / D converted). Then, it is converted into a pulse position based on the voltage, amplitude, and phase relationship), and position data with fine resolution is output.
Next, the counter 37 always counts the output of the position conversion circuit 36 (position data with fine resolution), and when the output changes, the change is latched and the time required for the change is expressed by a clock of a fixed period. Counting is performed, and time data required for changing the encoder signal input circuit unit 14 is output at every sampling time. Since the output of the position conversion circuit 36 (position data with a fine resolution) is likely to be shaken due to the influence of noise or the like, it took time to change when the position changed 2 to 4 times the minimum resolution of the position data. Use time data.
In this way, position data with resolution within one pulse of the encoder 3 and time data required when the position changes can be output.

  FIG. 3 is a diagram for explaining position data which is an output of the position conversion circuit 36. (A) is a sine wave signal of Aφ or Bφ output from the amplifier 34 in FIG. (B) and (b1) to (b-3) are sine wave signals obtained by enlarging the dotted line portion of the sine wave signal of (a), and position data for obtaining the speed detection signal and the position detection signal in FIG. Yes, (b-1) is the position data used for the position detection signal, and (b-2) is the position data with a resolution that is stable at rest throughout the entire rotation of the encoder 3 (if the position is fixed, it will not fluctuate). (B-3) shows the position data used for the speed detection signal (the resolution at which several pulses fluctuate depending on the location in one full rotation of the encoder 3). The position data with a fine resolution output from the position conversion circuit 36 in FIG. 2 corresponds to (b-3).

In the figure, position data is detected by three methods, and the position resolution is the highest (fine) position (b-3) in the relationship of (b-1) ≦ (b-2) ≦ (b-3). It becomes resolution. The position data (b-2) having a resolution of about 1/2 to 1/4 of the position data (b-1) used for the position detection signal is the resolution position data (b-2) which is stable at rest during the entire rotation of the encoder 3. Further, the position data (b-3) having a resolution of about 1/2 to 1/4 of the position data (b-2) having a resolution that is stable at rest during one rotation of the encoder 3 is used as the position data (b-3). (In FIG. 3, position data in which the position data (b-1) used for the position detection signal is 1/4 each is shown). It should be noted that what position resolution is to be determined may be determined in advance by measurement (for example, any resolution that is stable when stationary over the entire rotation of the encoder 3).
For these three kinds of position data, (b-3), which is the highest (fine) position resolution, is subtracted for a predetermined amount or masked several bits to (b-2), and (b-2) Is subtracted for a predetermined amount, or a few bits are masked to obtain (b-1).

The reason why there are three types of position data is as follows.
Since (b-3) output from the position conversion circuit 36 in FIG. 2 is likely to be shaken by noise or slight vibrations, it is difficult to obtain time data when the position data changes and the amount of change in the position data. Prone to vibration. Therefore, (b-3) is position data for calculating a speed detection signal from a difference between position data changed within a certain sampling time.
Also, (b-2) is unstable due to the phase relationship between Aφ and Bφ, slit error, disc shake, A / D converter error, etc. when stopped, but stable over a certain speed. Yes. Therefore, (b-2) is position data for calculating the time data when the position data changes and the amount of change of the position data.
Also, (b-1) is position data used as a position detection signal because the resolution is low among the three kinds of position data and the influence of noise and slight vibration is low and stable.

  Next, regarding the first speed calculation method in the speed calculation unit 15 in FIG. 1, the position data (b-3) used for the speed detection signal and the position data with resolution that is stable when stationary over the entire rotation of the encoder 3 ( The speed calculation method based on b-2) will be described. This speed calculation method is performed at regular sampling times, and the finally calculated speed is used for the speed detection signal in FIG.

(Step 1) Position data (b-3) in FIG. 3 with fine resolution output from the position conversion circuit 36 of the encoder 3 in FIG. 2 and time data required for the change in the position data output from the counter 37 are: Input to the speed calculation unit 15 via the input circuit unit 14 in FIG.
(Step 2) The speed calculation unit 15 in FIG. 1 calculates the amount of change in position data in one sampling time as the difference between the current and previous position data, and calculates the speed divided by the sampling time (known speed calculation) Method) and go to step 3.

(Step 3) It is determined whether or not the speed calculated in Step 2 is equal to or higher than a certain speed level. If the speed is equal to or higher than a certain speed level, the process proceeds to Step 4.
Since the resolution of the A / D converter 35 for position detection is fine and is easily shaken by noise or slight vibration, it is difficult to obtain the time data and the amount of change of the position data when the position data changes, and even if it is obtained, the vibration Therefore, the position data ((b-2) in FIG. 3) is detected at a resolution of about 2 to 4 pulses / sampling time of the position data ((b-3) in FIG. 3). That is, the speed level is set to a constant speed that is not vibrational as described above.
(Step 4) The change amount of the position data ((b-2) in FIG. 3) obtained by masking the position data obtained in Step 1 ((b-3) in FIG. 3) by several bits is calculated as the current position and the previous position. It is calculated as the difference between the data, and it is divided by the time data required for the position change to calculate the speed.

FIG. 4 is a diagram showing the timing of detecting position data. In the figure, T1 is the time at the sampling time from the time when the previous position (X2) changed, T2 is the time from the time when the current position (X4) is changed to the sampling time, Ts is the sampling time, and T is the previous position Assuming time data required for the change of (X2) and the current position (X4), T can be calculated as T = Ts + T1-T2.
Thus, at a certain speed level or higher, the position data ((b-3) in FIG. 3) obtained by masking the position data obtained in Step 1 ((b-3) in FIG. 3) by several bits as in Step 4 described above (( The amount of change in b-2)) is calculated as the difference between the current position data and the previous position data, and an accurate speed can be detected from the time data required for the position change.

Next, a speed calculation method based on only the position data (b-3) used for the speed detection signal will be described as the second speed calculation method in the speed calculation unit 15 in FIG. Note that this speed calculation method is performed at regular sampling times, and the finally calculated speed is used for the speed detection signal in FIG. 1 and replaces the above-described first speed calculation method. Is.
(Step 11) Position data with a fine resolution ((b-3) in FIG. 3) output from the position conversion circuit 36 of the encoder 3 in FIG. 2 and time data required for the change of the position data output from the counter 37 are: 1 is input to the speed calculation unit 15 via the input circuit unit 14 in FIG. 1, and the process proceeds to Step 12 (the same as Step 1 described above).
(Step 12) The speed calculation unit 15 in FIG. 1 calculates the change amount of the position data in one sampling time as the difference between the current and previous position data, and calculates the speed divided by the sampling time (known speed calculation) Then go to step 13 (same as step 2 above).

(Step 13) It is determined whether or not the difference in position data in step 12 is zero. When the position data difference is 0, the process proceeds to step 14, and when the position difference is not 0, the time T in step 14 is set to 0 and the speed calculation process is terminated.
(Step 14) The sampling time Ts is added to the time data of the position data difference (calculation of the time T).
(Step 15) The speed is calculated by dividing the position data difference in Step 12 by the time T calculated in Step 14. Note that the speed direction is the speed direction at the time of the previous sampling.
Further, when half the sampling time Ts is added to the time difference between the position data differences, the speed can be calculated on the assumption that the position data in step 11 has changed in the middle of the next sampling.

(Step 16) It is determined whether the speed calculated in Step 15 is below a certain speed level. Below a certain speed level, the process proceeds to step 17. On the other hand, if the speed is above a certain speed level, the speed calculated in step 12 is used as the speed calculation value.
The speed level is set to a constant speed that does not become vibrational as described above. For example, the speed level is set to be slightly larger than the resolution of the speed to be obtained. That is, if the speed level is set too low infinitely, there will be no zero, and there will be no stable region that is neither positive nor negative. Therefore, since the speed resolution itself has a margin for numerical calculation, it needs to be increased to some extent, and is set to be slightly larger than the required speed resolution depending on the relationship with the positioning resolution.
(Step 17) The speed is set to 0 and the speed calculation process is terminated.
As described above, even when the velocity calculation at which the position data difference becomes zero becomes zero, the velocity can be detected by measuring the position difference time by adding the sampling time.

1 is a schematic configuration diagram of a motor control device according to a first embodiment of the present invention. Schematic configuration block diagram of the encoder 3 The figure explaining the position data which is the output of the position conversion circuit 36 Diagram showing timing of position data detection

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor control apparatus 2 Motor 3 Encoder 11 Position or speed control part 12 Current control part 13 Inverter part 14 Input circuit part 15 Speed calculation part 31 Light emitter 32 Rotary disk 33 Light receiver 34 Amplifier 35 A / D converter 36 Position conversion Circuit 37 counter

Claims (10)

A position calculating unit configured to input position data output by an encoder connected to the motor at a constant sampling time and calculate a motor speed based on the position data and the sampling time; In the motor control device that drives
The encoder outputs time data obtained by measuring a time required for the change of the position data within the sampling time;
The speed calculation unit sets the position data as first position data, generates the second position data by subtracting the first position data for a predetermined amount, and subtracts the second position data for a predetermined amount. To generate third position data,
A motor control device that calculates the motor speed based on the first and second position data. When the speed calculation unit is equal to or higher than a certain motor speed, the motor speed is calculated based on a change amount of the second position data and time data required for the change of the second position data,
2. The motor control device according to claim 1, wherein when the motor speed is lower than the certain motor speed, the motor speed is calculated based on the first position data and the sampling time.   The motor control device according to claim 1, wherein the time data is a time required for the change of the second position data to be equal to or greater than a minimum resolution.   When the speed calculation unit does not change the first position data, the direction of the motor speed is the direction of the motor speed at the previous sampling time, and the magnitude of the motor speed is at the beginning or middle of the next sampling time. The motor control device according to claim 1, wherein the motor speed is calculated assuming that a minimum resolution of the first position data is changed. When the speed calculation unit does not change the first position data, the direction of the motor speed is the direction of the motor speed at the previous sampling time, and the magnitude of the motor speed is at the beginning or middle of the next sampling time. Calculating the motor speed as a change in the minimum resolution of the first position data;
The motor control device according to claim 1, wherein the motor speed is set to 0 when the motor speed is lower than a certain motor speed. A position calculating unit configured to input position data output by an encoder connected to the motor at a constant sampling time and calculate a motor speed based on the position data and the sampling time; In the speed detection method of the motor control device that drives
The encoder outputs time data obtained by measuring a time required for the change of the position data within the sampling time;
The speed calculation unit sets the position data as first position data, generates the second position data by subtracting the first position data for a predetermined amount, and subtracts the second position data for a predetermined amount. To generate third position data,
A speed detection method for a motor control device, wherein the motor speed is calculated based on the first and second position data. When the speed calculation unit is equal to or higher than a certain motor speed, the motor speed is calculated based on a change amount of the second position data and time data required for the change of the second position data,
The speed detection method of the motor control device according to claim 6, wherein the motor speed is calculated based on the first position data and the sampling time when the motor speed is lower than the certain motor speed.   The speed detection method of the motor control device according to claim 6, wherein the time data is a time required for a change of the second position data exceeding a minimum resolution.   When the speed calculation unit does not change the first position data, the direction of the motor speed is the direction of the motor speed at the previous sampling time, and the magnitude of the motor speed is at the beginning or middle of the next sampling time. The speed detection method of the motor control device according to claim 6, wherein the motor speed is calculated assuming that a minimum resolution of the first position data has changed. When the speed calculation unit does not change the first position data, the direction of the motor speed is the direction of the motor speed at the previous sampling time, and the magnitude of the motor speed is at the beginning or middle of the next sampling time. Calculating the motor speed as a change in the minimum resolution of the first position data;
The speed detection method of the motor control device according to claim 6, wherein the motor speed is set to 0 when the motor speed is lower than a certain motor speed.

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