JPH0472573A - Rotation speed detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a speed detection device for a rotating shaft of a motor used in a robot, machine tool, etc. The present invention relates to a rotational speed detection device capable of highly accurately detecting rotational speed from low-speed rotation to high-speed rotation based on the output of a detector.

[Conventional technology]

As is well known, encoders and resolvers are position sensors.

Conventionally, when detecting the rotational speed of a shaft using these position sensors, one of two methods has been used.

The first method is to count the amount of positional movement within a fixed sampling period. The second method measures the time interval required to move a certain amount.

[Invention or problem to be solved]

However, although the first method has high accuracy at high speed rotation, there is a problem in that the accuracy at low speed decreases as the speed decreases because the amount of positional movement within the sampling period decreases. On the other hand, the second method is highly accurate at low speed rotation, or as the speed increases, the time required to move a certain amount becomes shorter, so the accuracy at high speed decreases, and the accuracy decreases at low speed. The problem is that it takes a long time to move a certain amount, and it takes a long time to calculate the speed.

This invention has been made in view of the above circumstances, and is a rotation system that can detect speed with high accuracy over the entire speed range, and can also detect speed at fixed time intervals or at arbitrary times that require speed data. An object of the present invention is to provide a speed detection device.

[Means to solve the problem]

In this invention, in a rotational speed detection device that detects the speed of a rotational shaft using the output of a position detector attached to the rotational shaft, there is provided a rotational speed detection device that detects the speed of the rotational shaft using the output of a position detector attached to the rotational shaft. a memory means for accumulating and storing time data of the corresponding time measuring means; and a memory means for taking in the current position data of the position detector and the time data of the time measuring means when calculating the speed of the rotating shaft; A speed at which position data that differs by a predetermined amount or more from the current position data of the position detector and time data corresponding to the position data are read from the memory means, and the speed of the rotating shaft is calculated using these data. and calculation means.

Instead of the current position data of the position detector and the time data of the clock means used in the speed calculation means, the latest position data of the data stored in the memory means and the time data corresponding to the latest position data are used. It can also be used.

[Effect]

According to the configuration of the present invention, the time data T (k) is transmitted from the clock means at constant or arbitrary time intervals.
Position data P (k) at that time is taken in from a position detector such as a resolver or encoder, and these data are accumulated and stored in a memory means.

On the other hand, the position data of the position detector and the time data of the time measuring means are sequentially taken in at constant or arbitrary time intervals, and these are set as current position data P now and current time data T now.

Then, among the data stored in the memory means, position data P (i) which is more than a predetermined value ΔP away from the current position data P (i) and time data T (i) corresponding to the position data P (i) are stored. Extract these extracted data P
(i), T (i) and the current position data p now
Then, using the current time data T now, the rotational speed ω is calculated by differential processing as follows.

<IJ-C(Pnov-P(i))/(Tno
v −T (i) ) C is a constant determined by the unit of speed ω, the resolution of the timer, and the resolution of the position detector.

Here, the speed ω is the moving amount ΔP and the time required for this movement 4
When calculating the difference ω - △P / Δ using a knife, if the resolution of the movement measuring device is δP and the resolution of the time measuring device is 6, the accuracy of the speed ω (δω / ω) is δ ω / ω −δ P/Δ P −δ T/ΔT, so (δω/ω) is (δP/ΔP) and (δT/
△D).

In the configuration of the present invention, since the speed is calculated from the time required to move by a predetermined amount ΔP or more, δP is determined by the position detector, and δT is determined by the performance of the time measuring means used. Therefore, the accuracy of the speed ω is determined by ΔT.

In other words, the lower the speed, the larger ΔT becomes, so δT/ΔT becomes smaller.

The accuracy of is improved. Further, if ΔP is set to a large value, ΔT also becomes large and the accuracy of the speed ω improves, so by appropriately setting ΔP, any desired accuracy can be obtained.

In addition, in the present invention, past data P (i), T (i) stored in the memory and current data Pnow
Since the speed is calculated from ST now, the speed can be calculated at a fixed time regardless of the magnitude of ΔT or at any desired time when speed data is desired.

〔Example〕

Hereinafter, the present invention will be described in detail according to embodiments shown in the accompanying drawings.

FIG. 2 shows an embodiment of the present invention, in which a position detector 2 such as a rotary encoder or a resolver is attached to the rotating shaft of a motor 1. In this case, an incremental encoder is installed, and encoder 2 outputs pulse signals A and B with a 90@ phase shift, and 2 signals (
(generated for each rotation of the shaft) is output. The direction determining circuit 3 determines the rotational direction of the motor 1 from these input signals A and B, and manually inputs a count up signal UP to the up/down counter 4 when the motor is rotating in the forward direction, and a count down signal DOWN when the rotation is in the reverse direction. The up/down counter 4 receives a count up signal UP and a count down signal DOW.
By performing up/down counting according to N and resetting the count value using the Z signal, position data P of the rotating shaft of the motor 1 is output to the CPU 7.

The oscillator 6 generates a pulse signal with a predetermined period, and inputs the generated pulse signal to the free run counter 5. The free run counter 5 measures time by counting pulse signals from the oscillator 6, and the time data T is sent to the CPU 7.
Enter.

The CPU 7 calculates the rotational speed of the motor 1 based on the position data P from the up/down counter 4.
In this case, position data P from the up/down counter 4 is taken in periodically at a predetermined sampling period.

As shown in FIG. 3, the memory 8 has a memory capacity for storing n pieces of position data P of the up-down counter 4 and time data T of the free-run counter 5, respectively. and time data T are accumulated and stored. That is, the memory 8 stores the position data P and the time data T when the position data P is sampled. These position data P
and time data T corresponding to the position data are stored bare in the memory 8. In this case, first the memory 8
The paired data is stored until the memory capacity of the memory is full, and when the memory capacity is full, a data update operation is performed in which the latest data is stored in the address area corresponding to the oldest data.

The operation of the CPU 7 will be described in detail below with reference to the flowchart shown in FIG.

In this flowchart, the meaning of each symbol is as follows.

k: Address of memory 8 where the latest position data and time data are stored m: Variable value used to specify data in memory 8 used for speed calculation Pnow Current value of near down counter 4 Tnov:
Current value n of free run counter 5, maximum address CPT of memory 8: Number of pulses of counter 4 corresponding to one rotation of motor 1 t: Sampling period mass of position data P and time data T, CPU 7: Speed of motor 1 Prior to calculation, position data P and time data T are stored in the memory 8 until the memory 8 is full. That is, first, the CPU 7 sets the variable k to 1 and the variable m to 0 in step 100.
), the current position P now and the current time T now are read from the up/down counter 4 and the free run counter 5, respectively, and these are stored at the address k (-) of the memory 8.
1) is stored in storage areas P (k) and T (k) corresponding to (steps 110 and 120). From now on, cp
U7 increases address k by 1 (step 1
30), the current position fl P n at a predetermined sampling period
ow and the current time T now are sequentially read and stored in the memory 8(k) until the memory 8 is full (steps 110 to 140). As a result, n pieces of position data P and time data T are stored in the memory 8.

When the accumulation of this memory data is completed, the CPU 7 sets the variable n
is set to k (step 150), and then, at a predetermined sampling time, the CPU 7 calculates the current position P no from the up/down counter 4 and the free run counter 5.
w and the current time T now are respectively read (step 160).

Next, the CPU 7 inputs i- to -m (initially, k-n).

m-0) (step 170), and the calculated value i
An operation is performed to read the stored data P and T from the address area of the memory 8 corresponding to (step 170). That is, in this step 170, among the data stored in the memory 8, the mth stored data P from the newest one is
(i) and T(i) are read out. In the first stage, address area n is accessed.

However, if the procedure advances and i<1, then 1
n is added to the calculated value i+n, and the stored data P and T are read out from the address area of the memory 8 corresponding to the calculated value i+n. (Steps 1.80-190).

Next, the CPU 7 determines the difference PX (-Pnov-P(i)) between the current position P now read from the up-down counter 4 and the position data P(i) read from the memory 8.
) (step 200), and this value PX is further corrected taking into account the direction of rotation of the motor and rotations of the motor exceeding one revolution. That is, if PX is positive and time T no
If it is less than the limit value PL that allows forward rotation between w and T (i), then PX is used as the movement amount PM of the motor shaft (steps 220 and 240), and if PX is positive and larger than PL, the motor shaft is is rotating in the opposite direction, and the time T nOV and T
It is determined that the counter 4 has been reset by the Z signal during (i), and the value obtained by subtracting the value CPT (the number of pulses of the counter 4 corresponding to one revolution of the motor 1) from PX is set as the amount of movement PM of the motor shaft ( Step 220.250).

If px is negative and is less than the limit value NL that allows reverse rotation from time 11JTnov to T(1), then PX is set as the movement amount PM of the motor shaft and step 220.26
0), if PX is negative and smaller than NL, the motor shaft is rotating in the positive direction, and it is determined that the counter 4 was reset by the Z signal between time T now and T (i), and PX
The value obtained by adding the value CPT (the number of pulses of the counter 4 corresponding to one rotation of the motor 1) is set as the movement IPM of the motor shaft (steps 220 and 270).

Next, the CPU 7 calculates the motor movement I obtained in this way.
Compare PM with a predetermined movement amount ΔP, and
If MI≦ΔP, m is increased by +1 (step 290
), read out the stored data P(1) and T(i) of the m+1st (in this case, the 2nd address area from the newest, address area n-1) from the newest one.Step 17
0 to 190) Thereafter, the amount of movement PM is determined in the same manner as described above, and this amount of movement PM is again compared with the amount of movement ΔP. In this way, the above movement, i
Repeat the procedure to calculate iPM.

Note that even if IPMI>ΔP is not satisfied, when m−n is reached, the movement amount PM at this time is adopted.

Next, the CPU 7 uses the movement amount PM thus obtained, the current time T now, and the time data T (i) corresponding to the position data P (i) used to calculate the movement amount PM to calculate the following equation. First, calculate the rotational speed ω.

ω-C-PM/ (Tnov -T (i))...
(1) However, in the above equation (1), C is a constant value determined by the resolution of the encoder and the unit of speed.

Next, the CPU 7 adds 1 to k and stores the currently sampled position data P n in the address area (k+1) of the memory 8.
ow and time data T now (steps 320 and 350); if kin, then K-
1, and the currently sampled position data P now and time data T now are stored in the address area 1 of the memory 8.
is stored (steps 320 and 350). Note that when we first calculate the speed ω, it is −n, so
The value is set to -1 in step 340, and the currently sampled position data P now and time data T now are stored in the address area 1 of the memory 8 .

Next, the CPU 7 sets m to 0 again in step 36.
0), and the current time Tno from the free run counter 5.
ν is read, and when the time interval between this current time T no ν and the previous sampling time T (k) reaches a predetermined sampling period t (steps 370 to 380), the current position p now is read from the up/down counter 4 and the free run counter 5 again. and the current time T now, and repeats the same operation as described above.

Thus, in this embodiment, the predetermined sampling period t
The current position p now and the current time T now are calculated from the up/down counter 4 and the free run counter 5 every time.
are read respectively, and from among the past position data, the latest position data P (i) that is more than the current position P now and a predetermined movement amount ΔP set in advance and its time data T
(i) is selected and these data are subjected to differential processing according to the above equation (1) to obtain the motor rotation speed ω.

In the above embodiment, the sampling period for storing data in the memory 8 and the data sampling time for determining the current position P nov and the current time T now are made to match, and the sampling period for both is regular. The sampling period may be irregular, or the two sampling periods may be different.

For example, FIG. 4 shows a specific example in which the sampling period for storing data in the memory 8 and the data sampling period for determining the current position if P nov and the current time T now are different. P
When T nowl is sampled with novl as the current time, the current position Pn among the stored past data. The latest position data P(1) and its time data T(1) which are separated from vl by a predetermined movement amount ΔP or more are selected, and at this time the speed ω is as follows.

ω−C(P novl −P (1) )/(Tno
vl -T (1)) Also, P nov2 as the current position is T as the current time.
When nov2 is sampled, the latest position data P(3) which is separated from the current position P nov2 by more than a predetermined movement amount ΔP among the stored past data is selected, and this time data T(3) is selected. Sometimes the velocity ω is:

(,1-C(Pnov2-P (3) )/(Tno
v2-T (3)) By the way, in the above embodiment, when calculating the speed ω, data is taken in from the up/down counter 4 and the free run counter 5 at that point, and these data are used as the current position p now and the current time T now. However, when calculating the speed ω, the latest data among the data stored in the memory 8 at that time is used as the current position P.
It may also be used as data corresponding to the current time T now and the current time T now.

Furthermore, instead of storing the position data and time data at constant or arbitrary time intervals as in the above embodiment, a method of storing the position data and time data every time the position moves by a certain amount may be considered.

〔Effect of the invention〕

As explained above, according to the present invention, the speed is calculated from the time required to move a predetermined amount or more, so the lower the speed, the longer the above time becomes, and as a result, the lower the speed, the more accurate the speed. gets better. In addition, in the present invention, since the speed is calculated from past data and current data stored in the memory, the speed data is calculated at fixed time intervals or at any desired time regardless of the size of the above-mentioned time. It is possible to calculate As a result, in the present invention, the rotational speed is continuously calculated while always maintaining a constant accuracy, and high-precision speed control from high-speed rotation to low-speed rotation can be achieved in motor control of robots, NC machine tools, etc.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the operation of this embodiment of the invention.
FIG. 2 is a block diagram showing an embodiment of the invention, FIG. 3 is a diagram showing the contents of a memory, and FIG. 4 is a diagram showing a specific example of the embodiment. 1. Motor 2. Encoder 3. Direction discrimination circuit 4. A-band down counter 5. Free run counter 6. Oscillator 7
・CPU 8...Memory

Claims (2)

[Claims] (1) A rotational speed detection device that detects the speed of the rotating shaft using the output of a position detector attached to the rotating shaft, comprising: a timekeeping means for measuring time; and position data of the position detector and corresponding to the position data. a memory means for accumulating and storing time data of the time measuring means; when calculating the speed of the rotating shaft, the current position data of the position detector and the time data of the time measuring means are taken in, and the present time data of the data stored in the memory means is taken in; speed calculation means for reading out from the memory means position data whose position differs by a predetermined amount or more from the position data of the position detector and time data corresponding to the position data, and calculating the speed of the rotating shaft using these data; A rotation speed detection device comprising; (2) A rotational speed detection device that detects the speed of the rotating shaft using the output of a position detector attached to the rotating shaft, comprising: a timekeeping means for measuring time; and position data of the position detector and corresponding to the position data. a memory means for accumulating and storing time data of the time measuring means; when calculating the speed of the rotating shaft, the latest position data among the data stored in the memory means, the time data corresponding to the latest position data and the latest position data; reading position data whose position differs from the position data by a predetermined amount or more and time data corresponding to the position data from the memory means;
A rotational speed detection device comprising: speed calculation means for calculating the speed of a rotating shaft using the read data;