JPH05322909A - Rotation speed detector - Google Patents

Abstract

(57) [Summary] [Purpose] Minimize speed detection variations due to encoder variations. A plurality of sensors for detecting rotation angles of a plurality of phases, and a multiplication phase conversion for generating a forward / reverse rotation pulse 1 by multiplying the A phase detection pulse among the phase detection pulses from each sensor by 1. The circuit 3 and the speed detection counter 7 for detecting the speed by counting the number of fixed-cycle sampling pulses 8 between the forward / reverse rotation pulse 1 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation speed detecting device using an encoder.

[0002]

2. Description of the Related Art Encoders with high resolution are expensive and
In order to obtain the same position detection accuracy with an inexpensive encoder, it is common to use the encoder by multiplying it by 2 or 4. As a method of quadrupling, as shown in FIG.
The forward / reverse rotation pulse 32 is generated by the multiplication phase conversion circuit 31 from the rising and falling edges of the pulses from the phase and B phase sensors. The position detection is performed by reading the pulse 32 with the position detection counter 61.
For speed detection, the speed detection counter 71 inputs the constant period pulse 8 at the sampling frequency f [Hz] between (and between) the forward / reverse rotation pulses 32, and counts to calculate the speed. If the count number of the fixed-cycle pulse at this time is n [PLS], speed = f / n [PLS / s
ec].

[0003]

As shown in FIG. 3, the structure of the encoder is such that slits (transmission holes) 13 are formed at equal intervals along the circumference of the rotating body 12 (provided in the motor or the like), The sensors 10 and 11 for the A phase and the B phase are provided at a position where the light from the light source 9 is received through the slit 13, and a gap is created between the A phase and the B phase sensors 10 and 11 to form 90 °. Has a phase difference of. Originally 3
Based on the detection pulses from the A-phase and B-phase sensors 10 and 11, the normal rotation (reverse rotation) pulses 4 as shown in FIG. However, the phase difference between the A-phase and B-phase detection pulses of the actual encoder is not 90 °, and if the accuracy is low, there is a deviation of nearly 30% (Fig. 4). Therefore, the forward (reverse) pulse 4 as shown in FIG.
There is a problem in that there is variation between the two and the rate of generation from this also varies. Therefore, as a result, despite trying to rotate the motor at the target speed, it is recognized that the speed deviates from the target,
You will drive out of your goal.

Ideal phase difference between A and B phases (cycle)
T ₀ Actual encoder phase shift ± α (0 ≦ α ≦ 1.0) Sampling pulse frequency f (the number of sampling pulses at this time is f · T ₀ , (1 ± α) f · T ₀ ) Ideal Speed detected at phase difference = f / n = f / f
T ₀ = 1 / T ₀ Detected speed in actual encoder = f / n = f /
When (1 ± α) · f · T ₀ = 1/1 ± α · 1 / T ₀ α = ± 20%, the actual speed takes a value of 83% to 125% with respect to the ideal value of 100%. ..

Therefore, an object of the present invention is to provide a rotation speed detecting device which solves the above problems.

[0006]

Basically, the variation of the encoder is only between the A phase and the B phase, and there is almost no variation between the A phase and the next A phase (B phase to the next B phase). Don't have Also, pay attention to the two points that it can be regarded as stopped (speed = 0) if the next A phase is not input after the input of the A phase, and ignore the variation of the encoder by performing the calculation. The present invention has been made based on the finding that it is possible to provide a plurality of sensors for detecting rotation angles of a plurality of phases, and a detection pulse of any one phase among the phase detection pulses from each sensor. And a means for generating a forward / reverse rotation pulse and a means for detecting the speed by counting the number of fixed-cycle sampling pulses between the forward / reverse rotation pulses.

[0007]

According to the present invention, there is absolutely no variation in the encoder phase, for example, between the A phase and the next A phase (or B phase).
Sampling is performed between the phase and the next B phase), and the calculation is performed between the A phase and the B phase as if the sampling was performed to detect the speed.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

As shown in FIG. 1, the detection pulses from the A-phase and B-phase sensors are input to a multiplication phase conversion circuit 3, where the forward / reverse rotation pulse 1 is multiplied by 4 from both input pulses.
And the forward / reverse rotation pulse 2 which is obtained by multiplying only the A phase detection pulse by 1.
And create. The pulse 1 multiplied by 4 is input to the position detection counter 6 to detect the position, and the pulse 2 and the fixed period pulse 8 which are multiplied by 1 are input to the speed detection counter 7. The number of samplings between the pulses 2 of the pulse 8 is counted by the counter 7 to detect the speed.

When the sampling frequency is f and the number of sampling pulses is n ', the speed is f / (n' / 4) = 4f / n 'The number of sampling pulses at this time is the number of pulses from the A phase to the next A phase. ..

Considering the period from the A phase to the next A phase as 4T ₀ , n ′ = 4f · T ₀ Velocity detected from an actual encoder = 4f / f · 4T
₀ = 1 / T ₀ .

That is, it matches the speed detected at the ideal phase difference. It has been confirmed that the encoder to which the present invention is applied to the encoder having the 20% shift between the A phase and the B phase can achieve the same speed control as the conventional example using the encoder having the 5% shift between the A phase and the B phase.

[0013]

As described above, according to the present invention, it is possible to minimize variations in speed detection due to variations in encoders.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example of the present invention.

FIG. 2 is a diagram illustrating a conventional example.

FIG. 3 is a diagram illustrating an operation of an encoder.

FIG. 4 is a diagram showing operation pulses in an actual encoder.

[Explanation of symbols]

 1 Multiplying phase conversion circuit 6 Position detection counter 7 Speed detection counter

Claims (1)

[Claims] 1. A plurality of sensors for detecting rotation angles of a plurality of phases, and a detection pulse of any one phase among the detection pulses of each phase from the respective sensors is multiplied to generate a forward / reverse rotation pulse. A rotation speed detecting device comprising: a means and a means for detecting the speed by counting the number of constant-cycle sampling pulses between the forward / reverse rotation pulses.