JPH1054838A - Position detection apparatus and speed detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a correct position and a correct speed of a motor by counting pulse signals output from pulse clocks which generate the pulse signals wish a smaller cycle than that of pulse signals output from an encoder. SOLUTION: An error operation part 4 compares a target value stored in a memory 3 with position or speed information of a motor M operated at a position or speed operation part 11, and calculates a difference. A compensation operation part 5 operates an adjustment amount based on the difference, and a pulse width modulation(PWM) generator 6 controls the motor M via an amplifier A on the basis of the adjustment amount. A pulse clock 81 from a pulse generation circuit 8 generates a pulse signal with a smaller cycle than that of an output pulse from an encoder E. Output pulses from the pulse clock 81 are counted by a counter circuit 82 after the pulse signal output from the encoder E first rises before a sampling period terminates. A position or speed of the motor M is calculated at the operation part 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device and a speed detecting device for detecting a position and a speed of a rotating body based on an output signal from an encoder connected to the rotating body.

[0002]

2. Description of the Related Art In a conventional position detecting device and speed detecting device, a predetermined calculation is performed based on a signal from an encoder edge attached to a rotating body such as a motor to detect the position and speed of the rotating body. .

For example, speed information is obtained by counting the number of high-speed pulse signals from the rising edge of the encoder to the next rising edge. The position is detected by counting the number of encoder edges.

[0004] In detecting the position and speed of a rotating body using such an encoder, a practical method suitable for maximizing the sampling period is 6 to 1 per cycle.
It is considered that it is better to sample 0 times (Morikita Publishing Co., Ltd., GF Franklin, JD Powell, Digital Control of Dynamic System, p. 98)
reference).

In addition, it is known that at least 10 encoder pulses are required in a sampling period, and in this case, even if the encoder pulses are rotated at the same speed, an error of 10% occurs depending on the reading timing ( Corona, Yasuhiko Dote, Fumio Harashima, Motion Control, p.42).

[0006]

However, in the position detecting device and the speed detecting device using such an encoder, the position and the speed are determined by the number of high-speed pulse signals from the rising of the first pulse to the rising of the last pulse in the sampling period. Since the speed is detected, even if an encoder signal of at least 10 pulses is obtained in the sampling period, a maximum error of 10% occurs.

In order to reduce this error, it is conceivable to obtain a large number of encoder signals in a sampling period. However, this requires an encoder having a high number of teeth, which makes the device difficult to manufacture.

[0008]

SUMMARY OF THE INVENTION The present invention is directed to a position detecting device and a speed detecting device for solving such a problem. In other words, the position detection device of the present invention includes an encoder that is connected to the rotating body and outputs a plurality of pulse signals during one rotation of the rotating body, and a pulse generator that generates a pulse signal with a period smaller than the pulse signal output by the encoder. Means, counting means for counting the number of pulse signals output from the pulse generation means, from the first rise of the pulse signal output from the encoder within a preset sampling period, until the end of the sampling period, Position calculating means for calculating the position of the rotating body based on the number of pulse signals counted by the counting means.

Further, in addition to the configuration of the above-described position calculating device, the speed detecting device of the present invention further comprises a first position calculating unit which calculates the first position calculated by the position calculating means.
And speed calculation means for calculating the speed of the rotating body based on the position information, the second position information after a lapse of a certain time, and the certain time.

In the present invention, the number of pulse signals output from the pulse generating means is counted from the first rise of the pulse signal output from the encoder within the preset sampling period to the end of the sampling period. Therefore, accurate counting can be performed within a sampling period as compared with the case where the number of pulse signals from the pulse generating means from the rising of the first pulse to the rising of the last pulse is counted.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a position detecting device and a speed detecting device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining the present embodiment, and shows an example in which a position detecting device and a speed detecting device in the present embodiment are applied to a control device 1 of a motor M.

The control device 1 includes a target value setting unit 2, a memory 3, an error calculation unit 4, a compensation calculation processing unit 5, a PWM (Puls
e Width Modulation) generator 6, an edge detection circuit 7 for detecting an edge of a pulse signal sent from the encoder fetch circuit T, a pulse signal generation circuit 8, including a pulse clock 81 and a counter circuit 82, an edge counter circuit 9, a memory 10, position or speed calculation unit 11
Is constituted by a one-chip microcomputer, and a control signal is sent to the motor M via the amplifier A from now on.

In the control device 1, the target speed setting and control target speed and position are set by the target value setting unit 2 and stored in the memory 3. The error calculation unit 4 compares the target value stored in the memory 3 with the information on the position or speed of the motor M calculated by the position or speed calculation unit 11 and calculates the difference. The compensation calculation processing unit 5 calculates the adjustment amount based on the difference between the actual position or speed of the motor M calculated by the error calculation unit 4 and the target value. In the PWM generator 6,
A pulse width signal is generated based on the adjustment amount, and the motor M is controlled via the amplifier A.

The position detecting device according to the present embodiment comprises an encoder E, a pulse signal generating circuit 8, a position or speed calculating unit 11,
The pulse clock 81 is counted by the counter circuit 82 from the first rising edge of the pulse signal output from the encoder E to the end of the sampling period, particularly at the sampling interrupt edge S specifying the sampling period. The feature is that it is.

Further, in the speed detecting device of the present embodiment, in the configuration of the above-described position detecting device, based on the calculated first position information, the second position information after a lapse of a certain time, and the certain time. The position or speed calculator 11 calculates the speed of the motor M.

Next, a specific control method will be described with reference to the flowchart of FIG. 2 and the timing chart of FIG. First, the control is started by the start of the sampling interrupt, and in step S1, a pulse value x is input. This pulse value x is the number of high-speed pulse signals from the last rise of the encoder output signal of the sampling period (k-1 to k) in the timing chart shown in FIG. 3 to the sampling interrupt k.

Next, in step S2, a pitch (movement amount) C per encoder pulse is input, and in the next step S3, a value A obtained by subtracting 1 from the number of rising edges of the encoder in the sampling period is input. FIG.
In the example shown in FIG. 6, since there are three rising edges in the sampling period, A = 3-1 = 2 in this example.

Next, in step S4, a process of obtaining B by dividing x by the number of pulses per target frequency is performed. That is, the number of pulses per target frequency is, for example, the high-speed pulse signal m '' between the first rising edge and the next rising edge in the sampling period, and the high-speed pulse signal m from the rising edge to the next rising edge. '''Etc.

Therefore, according to the calculation in step S4,
The number of pulses (fraction less than 1) of the encoder output from the last rising edge of the sampling period shown in FIG. 3 to the sampling interrupt k can be obtained.

For example, if the number x of high-speed pulses from the last rising edge of the encoder to the sampling interrupt k is 1000 pulses and the number of pulses per target frequency is 2500 pulses, B = 1000 /
2500 = 0.4.

Next, in step S5, a process of calculating a detection position from A, B, and C obtained earlier is performed. That is, the detection position is calculated by (A + B) * C.

For example, A = 2, B = 0.4, C = 50μ
m, the detection position is (2 + 0.4) * 50 μm
= 0.12 mm. Thus, in the present embodiment,
Conventionally, the position is detected by counting the number of high-speed pulses from the last rising edge of the encoder in the sampling period to the sampling interrupt k, and converting this to the number of pulses (fraction less than 1) of the encoder. This means that the part that has not been performed is taken into account, so that highly accurate position detection can be performed.

Next, in step S6, it is determined whether or not the position control is to be performed. If the position control is to be performed, the process proceeds to steps S7 to S8. That is, in step S7, position error = reference position−detected position is calculated, and in step S8, position compensation is performed from the value of the position error. As a result, the motor M is corrected to the correct position.

In the case of speed control, steps S9 to S9 are executed.
The process proceeds to S12. In step S9, it is determined whether or not to perform speed control. If speed control is to be performed, in step S10, detected speed = 検 出 (detected position (current) −
The detection position (one sample before) / one sample elapsed time 計算 is calculated. That is, in this calculation, how much the motor M has moved from the detection position one sample before to the present is calculated.

By calculating the amount of movement of the motor M, it is possible to obtain how much the motor M has moved in one sampling period. Therefore, by dividing the amount of movement by the time of one sampling period, the speed can be obtained. Can be detected.

That is, speed = {position (current sample time) -position (one sample before)} / sampling period is calculated. For example, if the position (current sample time) is 0.1
If 8 mm, the position (one sample before) is 0.12 mm, and the sampling period is 1.0 ms, the speed is
(0.18 mm-0.12 mm) / 1 ms = 60 mm /
Seconds.

Next, in step S11, speed error = reference speed-detected speed is calculated, and in step S12, speed compensation is performed from the value of the speed error. As a result, the motor M is controlled to an accurate speed.

After performing the position control and the speed control, as shown in step S13, the data is replaced with the current detection position as the detection position of one sample before, and the current detection speed is changed to the detection speed of one sample before. To replace the data.

As described above, in the position detecting device and the speed detecting device according to the present embodiment, since the sampling period takes into account the odd number of pulses between the last rising edge of the encoder and the sampling interrupt, accurate position detection is performed. The position can be detected, and an accurate speed can be detected based on the detected position.

[0030]

As described above, the position detecting device and the speed detecting device of the present invention have the following effects. That is, in the present invention, since the sampling period considers the odd number of pulses from the last rising edge of the encoder to the sampling interrupt, accurate position detection and speed detection can be performed.

Also, by taking into account the above odd number of pulses, the detection error is small even if the number of pulses in the sampling period is small, and the position detection and speed detection can be performed without using an encoder having a large number of teeth. Can be performed. This makes it possible to reduce the size of the encoder, easily configure the control device, and reduce the size of the device.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment.

FIG. 2 is a control flowchart.

FIG. 3 is a timing chart illustrating a control example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 control device 2 target value setting unit 4 error calculation unit 5 compensation calculation processing unit 6 PWM generator 7 edge detection circuit 8 pulse signal generation circuit 9 edge counter circuit 11 position or speed calculation unit E encoder M also S sampling interrupt edge T Encoder capture circuit

Claims (2)

[Claims] 1. A position detecting device for detecting a position of a rotating body according to the number of rotations of the rotating body, wherein the position detecting apparatus is connected to the rotating body and outputs a plurality of pulse signals during one rotation of the rotating body. An encoder that generates a pulse signal with a period finer than the pulse signal output by the encoder; and a sampling period from a first rising edge of the pulse signal output from the encoder within a preset sampling period. Counting means for counting the number of pulse signals output from the pulse generating means, and calculating the position of the rotating body based on the number of pulse signals counted by the counting means. And a means for detecting a position. 2. A speed detecting device for detecting a speed of a rotating body based on a position detected according to a rotation speed of the rotating body within a predetermined time, wherein the speed detecting apparatus is connected to the rotating body, An encoder that outputs a plurality of pulse signals during rotation; a pulse generating unit that generates a pulse signal with a period finer than the pulse signal output by the encoder; and a pulse signal output from the encoder within a preset sampling period. Counting means for counting the number of pulse signals output from the pulse generating means during the period from the first rising edge of the sampling period to the end of the sampling period, and based on the number of pulse signals counted by the counting means. Position calculating means for calculating the position of the rotating body, first position information calculated by the position calculating means, second position information after a predetermined time has elapsed, Speed detecting apparatus characterized by and a speed calculation means for calculating a speed of the rotating body based on the time and the.