JP3349575B2 - Displacement speed detection method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a displacement speed of a detection object such as a rotating body or a linear moving body with high accuracy.

[0002]

2. Description of the Related Art In mobile machines such as OA equipment, industrial robots, machine tools, industrial machines, and vehicles, it is necessary to detect the displacement speed of these movable parts in order to perform various controls.

An object to be detected, such as a movable portion, makes a rotation or a linear motion. A rotary encoder or a linear encoder has been widely used in order to detect the displacement speed. These encoders determine the frequency of a pulse signal output for each predetermined displacement, and determine the displacement speed via an F / V converter.

[0004] It is also known to use a tachogenerator (finger speed generator, hereinafter abbreviated as tachogenerator). This tacho generator outputs a DC voltage corresponding to the rotation speed. Further, a method of obtaining a displacement speed from the output of a resolver is also known.

In this method using a resolver, the sine and cosine signals output from the resolver are input to an RD (resolver digital) converter to calculate the rotation angle. That is, the RD converter is formed of a PLL (Phase Locked Loop) device, and obtains an accurate phase with high resolution from a combination of a sine signal and a cosine signal.

[0006]

2. Description of the Related Art In the case of using the encoder, an output pulse is output for each predetermined amount of displacement of a detection target, so that an encoder having a high resolution is required to obtain a high-precision displacement speed. Become. Usually, 5 to 10 times the resolution required for position detection is required for this speed detection. Such an encoder would be very expensive. In addition, an inexpensive F / V converter has a slow response, and an F / V converter having a high response speed is very expensive.

[0007] The method using a taco generator requires regular maintenance due to the life of the brush of the taco generator itself, and is large and expensive. Although suitable for detecting a rotational speed, a mechanism for converting the linear motion into a rotary motion is also required for detecting the linear motion, and the size is increased.

In the method using a resolver and an RD converter, not only is the resolver large and expensive, but also the RD
There is a problem that the converter is also complicated and expensive.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a simple and compact structure, does not require the use of a high-resolution encoder, and provides a method for detecting a displacement speed having a high response speed. The primary purpose is to provide.
It is a second object of the present invention to provide a displacement velocity detecting device directly used for carrying out this method.

[0011]

According to the present invention, a first object is to provide a method for detecting a displacement speed of an object to be detected from an output signal of an encoder which outputs an analog sine signal and an analog cosine signal corresponding to the displacement of the object to be detected. , A. A / D converting the current values of the analog sine signal and analog cosine signal detected in a certain sampling period; b. Delay these digitized present values by one sampling period; c. Multiply the digitized current cosine signal and sine signal respectively by one sampling period delayed; d. Outputting the difference between these two multiplied values as a displacement speed; e. A digital computer is controlled so that the above-described steps a to d are repeated every predetermined sampling period. According to a second aspect of the present invention, there is provided a detection device for detecting a displacement speed of the detection target from an output signal of an encoder that outputs an analog sine signal and an analog cosine signal corresponding to the displacement of the detection target, comprising: a. First and second A / D converters for converting the analog sine signal and analog cosine signal into digital signals; b. First and second delay elements for delaying the digitized sine and cosine signals by one sampling period; c. First and second multiplying the current values of the sine signal and cosine signal output from the A / D converter by the cosine signal and sine signal one sampling period earlier output from the second and first delay elements, respectively A second multiplier; d. And a subtractor for obtaining the difference between the outputs of the two multipliers and outputting the difference as the displacement speed.

[0012]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is an operation flowchart. In Figure _1, φ _A, φ _B is the analog sine signal indicating an angular or displacement of the detection object (sin [theta)
And an analog cosine signal (cos θ), which are output from a magnetoresistive (MR) sensor, an optical sensor, or the like.

[0013] For example, the MR type sensors are opposed to each other by a permanent magnet embedded at regular intervals in a moving detection object.
Two are arranged with a phase difference of °. Further, two optical sensors are arranged with a phase difference of 90 ° from each other so as to face bar codes written on the moving body at regular intervals.

In FIG. 1, reference numerals 10 and 12 denote first and second A / D converters, 14 and 16 denote first and second delay elements each comprising a memory, and 18 and 20 denote first and second delay elements.
Are subtractors, and these are constituted by a CPU (digital computer). When a sampling pulse is transmitted from a clock (not shown), the CPU enters an interrupt process shown in FIG. 2 (step 100 in FIG. 2). A
The / D converters 10 and 12 read the input signals φ _A and φ _B at predetermined sampling periods (step 102 in FIG. 2), and A / D convert the read input signals φ _A and φ _B respectively. _Be the first and second delay elements 1 as A _n and B _n
4 and 16 (step 10 in FIG. 2).
4).

The CPU determines whether the data A _n and B _n are abnormal (step 106). For example, when the values of the data A _n and B _n become abnormally large or change suddenly, it is determined that there is an abnormality and the abnormality processing task is entered (step 1).
08).

If there is no abnormality in the data A _n and B _n , the outputs A _n−1 and B _n−1 one sampling cycle before and the current value A
_n, performs calculation of angular velocity ω by using the B _n (Step 1
10).

Here, the input signal sin θ,
Assume that the current value of the phase θ of cos θ is θ _n, and the phase one sampling cycle before this time is θ _n-1 . In this case, the delay elements 14 and 16 respectively have A _n-1 = sin
θ _n−1 , B _n−1 = cos θ _{n− 1} will be stored.

The first multiplier 18 is the first A / D converter 1
0 is multiplied by the current value of the sine signal A _n = sin θ _n and the cosine signal B _n-1 = cos θ _n-1 one sampling cycle earlier stored in the first delay element 16 to obtain sin θ _n
• Output cos θ _n-1 to the subtractor 22.

The second multiplier 20 has a current value B _n = cos θ _{n of} the cosine signal output from the second A / D converter 12,
Multiply by the sine signal A _n-1 = sin θ _n-1 one sampling cycle before stored in the second delay element 16 to obtain cos
θ _n · sin θ _n−1 is output to the subtractor 22 (step 104 in FIG. 2).

The subtractor 22 calculates the difference sin θ _n · c
os θ _n-1 -cos θ _n · sin θ _n-1 = sin (θ _n
−θ _n-1 ) is output (step 106 in FIG. 2). Here, since θ _n −θ _n−1 is very small, sin (θ _n −θ
_n-1 ) ?? _n- ? _{n -1} = ?? _n .
That is, the output △ theta _n of the subtracter 22 is equal to the angular velocity omega _n (step 110 in FIG. 2).

Since the current values A _n and B _n at that time are used as A _n-1 and B _{n-1 in the} next sampling period, the first and second delay elements 14 and 16 have A _n and B _n respectively.
_n-1 and B _n-1 are stored (step 112).

As described above, according to the present embodiment, the angular velocity ω _n
That is, the displacement speed of the detection target can be obtained by digital calculation for each sampling cycle. Therefore, extremely high responsiveness can be obtained without increasing the resolution of the encoder that supplies the input signals (sin θ _n , cos θ _n ).

Here, all the circuits including the A / D converters 10 and 12 can be constituted by a one-chip microcomputer or the like, and it is not necessary to use a particularly high-speed digital processor. For this reason, it is also possible to use a microcomputer used for other control to perform parallel processing with other control, and the hardware configuration is very simple, small, and inexpensive.

Note that the displacement speed ω _n =
If △ add adder for integrating theta _n, displacement amount from the reset time of the adder (Σ △ θ _n) can also be easily obtained. This results in a very simple and inexpensive configuration,
The displacement and displacement speed of the detection target can be obtained. Furthermore, it can be easily applied to a linear encoder.

[0025]

As described above, according to the first aspect of the present invention, the analog sine signal and the analog cosine signal are A / D-converted, and the sine signal and the cosine signal delayed by one sampling period are respectively converted into the digital cosine signal and the sine signal. The process of multiplying the signal and outputting the difference between these multiplied values as a displacement speed is repeatedly performed by a digital computer for each sampling cycle.

Therefore, the speed can be detected with high responsiveness and high accuracy without increasing the resolution of the encoder. Further, the circuit can be configured using a small digital processor such as a microcomputer, and the hardware can be simple and small, and it is inexpensive.

According to the second aspect of the present invention, there is provided an apparatus directly used for implementing the first aspect of the present invention.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a flow of operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 1st A / D converter 12 1st A / D converter 14 1st delay element 16 2nd delay element 18 1st multiplier 20 2nd multiplier 22 Subtractor

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01P 3/489 G01D 5/245 102

Claims (2)

(57) [Claims] 1. A method for detecting a displacement speed of a detection target from an output signal of an encoder that outputs an analog sine signal and an analog cosine signal corresponding to the displacement of the detection target, comprising: a. A / D converting the current values of the analog sine signal and analog cosine signal detected in a certain sampling period; b. Delay these digitized present values by one sampling period; c. Multiply the digitized current cosine signal and sine signal respectively by one sampling period delayed; d. Outputting the difference between these two multiplied values as a displacement speed; e. Controlling a digital computer so that the above steps a to d are repeated every predetermined sampling period; 2. A detection device for detecting a displacement speed of the detection target from an output signal of an encoder that outputs an analog sine signal and an analog cosine signal corresponding to the displacement of the detection target, comprising: a. First and second A / D converters for digitizing the analog sine signal and analog cosine signal; b. First and second delay elements for delaying the digitized sine and cosine signals by one sampling period; c. First and second multiplications of the current values of the sine and cosine signals output from the A / D converter with the cosine and sine signals one sampling period earlier output from the second and first delay elements, respectively. A second multiplier; d. And a subtractor for obtaining the difference between the outputs of the two multipliers and outputting the difference as the displacement speed.