JPH11161341A - Servo control method using pulse encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a servo control method which can obtain control precision higher than the resolution of the pulse encoder. SOLUTION: A dummy command pulse count value is found by multiplying a command pulse count value by a constant (c) and set in a deviation counter 3. A timer part 10 measures the encoder pulse interval ti-1 ,j of a rotary pulse encoder 7. A dummy pulse interval arithmetic part 11 finds a dummy pulse interval by dividing the measured encoder output pulse interval ti-1 ,j by the constant (c) and a pulse generation part 12 inputs a dummy encoder pulse to the deviation counter 3 at dummy pulse intervals to perform feedback control so that the dummy pulse count value becomes equal to the dummy command pulse count value. Each time an encoder pulse is inputted, the dummy pulse count value is corrected into the product of the number of encoder pulses and the constant to reduce a position decision error at the time of acceleration, deceleration, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control method using a pulse encoder.
The present invention relates to a servo control method capable of obtaining control accuracy higher than the resolution of a pulse encoder.

[0002]

2. Description of the Related Art Servo systems using a pulse encoder as a position or displacement sensor are used in various fields. For example, in the field of office equipment, a paper feed amount in a printer device is used. Optical rotary pulse encoders and linear pulse encoders are widely used for control and coordinate control of a pen head in a pen plotter. The pulse signal output from the pulse encoder connected to the drive system to be controlled is fed back to the control unit, and the position control based on the pulse count value and the speed control based on the pulse frequency are executed.

The control accuracy of a servo system using a pulse encoder often depends on the resolution of the pulse encoder. To put it simply, when a drive system is driven by control data of n pulses, n pulses are counted. The actual stop position of the control target when the drive system stops is within the range between the n-th slit and the (n + 1) -th slit of the pulse encoder, and has position control accuracy in slit interval units. That is, since the position control accuracy is determined by the interval between the slits, if the interval between the slits is large, the control accuracy will decrease and the position error will increase.

Therefore, when high control accuracy is required, a high-resolution pulse encoder having many slits and a narrow slit interval is used. However, a high-resolution pulse encoder requires precision machining and is extremely expensive. However, there is a problem that the cost of the servo system is significantly increased.

Therefore, there is a technical problem to be solved in order to provide a servo control method capable of obtaining a control accuracy higher than the resolution of the pulse encoder and to improve the performance while suppressing the system cost. It is an object of the present invention to solve the above problems.

[0006]

SUMMARY OF THE INVENTION The present invention proposes a servo control method using a pulse encoder as means for detecting a controlled variable of a controlled object. Means for calculating the pseudo target pulse number by multiplying by an integer constant, means for sequentially measuring the pulse interval output by the pulse encoder, and calculating the pseudo pulse interval by dividing the measured pulse interval by the constant. Means, while controlling the control amount to the target value by means of pseudo pulse counting for each pseudo pulse interval, at the time of encoder pulse input, the pseudo pulse count value is rounded down to the number of encoder pulses × the constant, or A servo control method using a pulse encoder that performs control by means for rounding up and correcting. .

When the reverse rotation of the pulse encoder is detected, the pseudo pulse count value between the encoder pulse at the time of detecting the reverse rotation and the immediately preceding encoder pulse is limited to an arbitrary number set to be equal to or less than the above-mentioned constant. The present invention provides a servo control method using a pulse encoder that executes control according to (1).

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram of a servo control circuit of a DC motor using a rotary pulse encoder. Servo control unit 2 that receives control data from CPU 1
The output of the deviation counter 3 is input to the analog control circuit 5 via the D / A converter 4, and the analog control circuit 5 controls the DC motor 6. The output of the rotary pulse encoder 7 interposed on the motor shaft of the DC motor 6 or the rotating shaft of the drive system driven by the motor shaft is fed back to the servo control unit 2.

The servo control section 2 is provided with a pseudo pulse count data calculation section 8 for multiplying the actual target pulse number data transferred from the CPU 1 by a preset integer constant c to calculate a pseudo target pulse number. The calculated pseudo target pulse number is transferred to the deviation counter 3.

[0010] The clock pulse of the clock pulse generator 9
The timer unit 10 that counts
Each time a coder 7 pulse is input,
Reset and start the time measurement based on
Thus, the immediately preceding encoder pulse interval t_{i-1, i}Measure
You. Then, the pseudo pulse interval calculation unit 11 calculates the measured
Encoder pulse interval t_{i-1, i}Divided by the constant c
Similar pulse interval st (st = t _{i-1, i}/ C) and pulse
The raw part 12 counts the clock pulse, and
Pseudo encoder pulse is input to deviation counter 3 at every interval st
I do.

The deviation counter 3 and the pulse generator 12 are controlled by the counter controller 13. When the next pulse is input from the rotary pulse encoder 7 before the deviation counter 3 counts the constant c or when the count is over. Corrects the pseudo encoder pulse count value of the deviation counter 3 up or down and corrects it to the value of (the number of actual encoder pulses × pulse division constant c) to correct the division error of the pseudo encoder pulse.

When the DC motor 6 rotates in the reverse direction beyond the target stop position when the motor is stopped, when the reverse rotation is detected by the actual encoder pulse, the deviation counter is set to the constant c or less according to the rotation direction. (The number is a preset number, for example, ± 3 when c = 10).

Next, the servo control method of the present invention will be described. First, for example, 1
When 000 pulse data is input, if the pulse division constant c of the pseudo pulse count data calculation unit 8 is 10, 1000 × 10 = 10000 pseudo target pulse data is set in the deviation counter 3 and the DC motor 6 Upon activation, the rotary pulse encoder 7 starts rotating.

At the same time as the start, the rotary pulse encoder 7
, The first encoder pulse is input, and the timer unit 10 starts counting the encoder pulse interval. However, the encoder pulse interval is unknown until the second pulse is input, so that the pseudo encoder pulse is not output. ,
When the second encoder pulse is input, the counter control unit 13 sets the count value of the deviation counter 3 to 10. At the same time, the encoder pulse interval t _0,1 is measured and the pseudo encoder pulse interval st = t _0,1 / 10 is calculated, and the pseudo encoder pulse is counted for each pseudo encoder pulse interval st. Each time a real encoder pulse i is input, the pseudo encoder pulse interval st = t _{i-1, i} /
By calculating 10 and counting the pseudo encoder pulses, the count value of the deviation counter 3 is updated.

When the DC motor 6 is started or stopped, the actual encoder pulse interval changes continuously during acceleration and deceleration. Therefore, the pseudo pulse interval st calculated based on the immediately preceding encoder pulse interval is used as the pseudo pulse interval st. When you count,
The time of pseudo pulse interval st × pulse division constant c does not coincide with the next actual encoder pulse interval, and a control error occurs. Therefore, when the input timing of the encoder pulse i does not match the count-up timing or count-down timing of the constant c (for example, when the constant c = 10, the pseudo pulse interval st × 8 or st × 12 When the next encoder pulse is input at the time of counting, the fraction of the constant c = 10 is rounded up or down from the count value of the deviation counter 3 and corrected to an integral multiple of the constant c. To prevent a position determination error from occurring.

As the cumulative value of the pseudo pulse count value approaches the target value, the DC motor 6 enters the deceleration region by the proportional control operation of the analog control circuit 5, and immediately before the edge of the 1001th slit of the rotary pulse encoder 7, The drive is stopped when the pseudo pulse count value matches the target value, and the error of the stop position is equal to the pseudo pulse interval st,
This is about 1/10 of the slit interval, and an accuracy of approximately c times (constant times) the position detection accuracy of the rotary pulse encoder 7 itself is obtained.

When the driving of the control object is stopped,
When the control target exceeds the target stop position due to disturbance such as inertia of the drive system, the DC motor 6 is driven in reverse by the pulse count value exceeding the target value, and the control target becomes 10
When passing through the front end of the 01th slit in the opposite direction, D
The C motor 6 is driven in reverse, so that the control object reciprocates in both the forward and reverse directions across the target stop position. However, since the rotation direction of the DC motor 6 is determined by the actual encoder pulse, the counter control unit 13 cannot detect the reverse rotation of the rotation direction when the DC motor 6 reversely rotates, and continues counting the pseudo pulses. Therefore, each time the control target reciprocates in both the forward and reverse directions across the slit at the target stop position, as described above, the deviation counter 3 sets the negative or positive division constant c (for example, -10 or When (+10) is set, the error of the set value of the deviation counter 3 with respect to the target position is large, and the analog controller 5 supplies the actual position deviation (less than the pseudo pulse interval st × 10).
Will be supplied. In this case, it takes time until the reciprocating motion of the control object converges, and if the loop gain of the control system is increased, oscillation occurs, the vehicle cannot be stopped, and a stop position error increases.

Therefore, in the servo control method of the present invention, the DC pulse is output from the output pulse of the rotary pulse encoder 7.
When the reverse rotation of the motor 6 is detected, the counter control unit 13
Sets an arbitrary number of pseudo pulses equal to or smaller than a constant c (for example, ± 3 when c = 10) in the deviation counter 3 in accordance with the rotation direction. Thereby, every time the control target receives an encoder pulse across the target stop position, the deviation counter 3 is set to the pseudo pulse number of 3 or -3, which is deviation data smaller than the actual encoder pulse interval,
The amplitude of the reciprocating motion of the controlled object is extremely reduced, and stops macroscopically immediately near the edge of the slit at the target position.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are possible within the technical scope of the present invention, and it goes without saying that the present invention extends to those modifications. is there.

[0020]

As described above, in the servo control method using the pulse encoder of the present invention, the pseudo pulse count is performed for each pseudo pulse interval obtained by dividing the output pulse interval of the pulse encoder by a constant, and the amount of movement and the position are determined. Therefore, control accuracy exceeding the resolution of the pulse encoder body can be obtained, which is effective in improving the cost-performance ratio of the servo control system.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a servo control circuit using a pulse encoder according to an embodiment of the present invention.

FIG. 2 is a timing chart showing a relationship between an encoder pulse and a pseudo encoder pulse.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU 2 Servo control part 3 Deviation counter 4 D / A converter 5 Analog control circuit 6 DC motor 7 Rotary pulse encoder 8 Pseudo pulse count data calculation part 9 Clock pulse generator 10 Timer part 11 Pseudo pulse interval calculation part 12 Pulse generation part 13 Counter control unit

Claims (2)

[Claims] 1. A servo control method using a pulse encoder as a control amount detection means of a control object, wherein the pulse encoder calculates a pseudo target pulse number by multiplying the target encoder pulse number by an integer constant. Means for sequentially measuring the pulse interval to be performed, means for calculating the pseudo pulse interval by dividing the measured pulse interval by the constant,
The control amount is made to coincide with the target value by means of pseudo pulse counting for each pseudo pulse interval, and at the time of encoder pulse input, the pseudo pulse count value is rounded down to the number of encoder pulses × the constant, or rounded up. A servo control method using a pulse encoder that executes control by means for correcting. 2. A servo control method using a pulse encoder as a control amount detection means for a control object, wherein the pulse encoder calculates a pseudo target pulse number by multiplying the target encoder pulse number by an integer constant. Means for sequentially measuring the pulse interval to be performed, means for calculating the pseudo pulse interval by dividing the measured pulse interval by the constant,
The control amount is made to coincide with the target value by means of pseudo pulse counting at each pseudo pulse interval, and when a reverse rotation of the pulse encoder is detected, the time between the encoder pulse at the time of reverse rotation detection and the immediately preceding encoder pulse is detected. A servo control method using a pulse encoder for executing control by means for limiting a pseudo pulse count value to an arbitrary number set in advance to the constant or less.