JPS63103912A - Controller for motor - Google Patents

Abstract

PURPOSE:To improve the accuracy of commutation control over a brushless motor by providing arrays of n1 and n2 light transmission slit in two stages to a code disk and setting the number of teeth of the motor to n1-n2. CONSTITUTION:The two stages of the light transmission arrays are provided in the circumferential direction of the code disk 1 which rotates integrally with the output shaft M of the motor; and n1 slits 2 are in the outside array and n2 slits 3 are in the inside array. Light passed through slits 2 and 3 is detected by photodiode arrays 8 and 9 (formed by arraying, for example, eight photodiodes within one pitch of respective slits) and their detection signals are processed 10 to obtain the phase difference phi=(n1-n2)theta (theta: angle of rotation of the disk 1) between both signals. In this case, n1-n2 is the number of teeth of the motor, so the phase difference phi corresponds to the deviation in the electric angle between the teeth of the rotor and stator of the motor. The position relation between both teeth is detected based on it to perform the commutation control over the motor according to the position relation. Namely, many slits are provided to reduce the angular resolution, so the detection accuracy of displacement is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a motor control system that uses light to detect the rotational position of a brushless motor.

[Prior Art] An optical displacement converter projects light onto transparent slits formed on a code plate at a predetermined pitch, and detects the light passing through the transparent slits with a light receiving element. It uses light to determine the displacement of the code plate.

Conventionally, as such a displacement transducer, for example, there has been a "displacement transducer" disclosed in Japanese Patent Application No. 58-13951 filed by the present applicant.

In this displacement transducer, the angular resolution is (number of transparent slits)
It is determined by × (the number of 1lTi in 1 pitch of the transparent slit). For example, when the number of slits is 160 and the number of interpolations is 4096, the angular resolution is 360/655360 degrees.

[Problems to be solved by the invention] This displacement converter is a brushless DD'U: Dir.
ect Drive Motor), it is not only used as a displacement transducer, but also detects the position of the teeth provided on the rotor and stator of the DD motor, and flows excitation current of 2-phase, 3-phase, etc. to the coil of the motor. Zui! It is also used to provide a signal that is to be used after IllI sin (hereinafter referred to as commutation control). For this reason, it has conventionally been necessary to make the number of light-transmitting slits of the motor equal to the number of teeth of the motor.

Therefore, the following problems arose.

■Accuracy is poor because the number of slits in the code plate cannot be increased.

Since the slit is larger than ■■, a larger light source is required.

■Since the radius of the slit cannot be made large, the hole in the center of the code plate cannot be made large, making it difficult to pass the motor and displacement converter wires through.

The present invention was made to solve the above-mentioned problems, and by using an optical displacement converter, commutation control is possible even when the number of transparent slits is larger than the number of teeth of the motor. The purpose is to realize a T11 system for Tanabata.

[Means for Solving the Problems] The present invention includes: attaching a code plate in which transparent slits are formed in a predetermined array to the rotor of a brushless motor; projecting light onto the transparent slits; In the motor control device for determining the positional relationship between the teeth of the rotor and stator of the motor based on the transmitted light, the code plate is provided with a two-stage slit row with a number of light-transmitting slits of n and 02, nl n2 (nl>n2) is set to the number of teeth of the motor, and the positional deviation between the teeth of the motor's rotor and stator is determined from the phase difference between the detection signals of the light that has passed through the n and n2 translucent slits. This is a motor control device characterized by comprising a signal processing section for determining the following.

[Sien example] It is a block diagram of an Example.

In the figure, reference numeral 1 denotes a disc-shaped code plate, on which two rows of light-transmitting slits are arranged at a predetermined pitch in the circumferential direction. The outer slit row is provided with n+ translucent slits 2, and the inner translucent slit row is provided with n+ translucent slits 2.
Two transparent slits 3 are provided. These light-transmitting slits 2 and 3 are provided to detect misalignment between the teeth of the motor rotor and stator. code board 1
A slit S is provided outside the slit 2 as a slit for detecting the rotational position of the slit. This code plate 1 rotates together with the output shaft M of the motor.

4.5 is a light source, and 6 and 7 are lenses for converting the light beams from the light sources 4 and 5 into parallel beams.

The light that has passed through lens 6 hits slits 2 and S, and the light that has passed through lens 7 hits slit 3.

8, Dl, and D2 are image sensors that receive light (slit image) passing through the light-transmitting slit 2. The photodiode array 8 includes, for example, eight photodiodes 81 to 81.
88 are arranged in an array.

Reference numeral 9 denotes an image sensor that receives the light (slit image) that has passed through the light-transmitting slit 3. For example, eight photodiodes 91 to 9 are arranged in an array.

These photodiodes are arranged within one pitch P of the light-transmitting slit, as shown in FIG.

10 is a signal processing unit which calculates the positional relationship between the rotor of the motor and the teeth of the stator based on the detection signals of the photodiodes 81-8 and 91-9.

A specific example of the configuration of such a control III device is shown in FIG. Components in FIG. 3 that are the same as those in FIG. 1 are given the same reference numerals. The same applies to the figures below.

In FIG. 3, SW1 to SW8 are photodiodes 8, to 8.
8d9. This is a switch that sequentially takes out the signals from ~98 at a fixed timing.

11.12 is an OP amplifier, and each switch SW1 to S
Amplify the signal applied via W8.

The outputs of the OP amplifiers 11 and 12 have a stepped waveform. The height of the waveform corresponds to the number of photodiodes that detected light.

13 and 14 are low-pass filters, and OP amplifier 11
．． 12 low frequency signal components are extracted.

The outputs of the OP amplifiers 11 and 12 are passed through the low-pass filter 13.
．． 14, the waveform becomes a periodic function.

15.16 is a comparator and low pass filter 1
3. Shape the signals f+(j) and f2(1) from 14 into waveforms.

17 is a phase difference counter, which detects the signal f+ (i> and "2 (1)" based on the timing of the counting clock CLK.
Count the phase difference. The signal f+ (i) is used to reset the counter value, and the signal nf2 (j>) is used to strobe the counter.

If you want to divide one period of these signals by 1024, set the frequency fc of the coefficient clock CLK to 1024fs (fs
is the frequency of the signal j3ft (t), f2 (t)>.

18 is a ROM in which the values of sin and COS are stored.

Phase m s of phase difference θe given from 7J counter 17
The in value and the cosl value are read from the ROM 18.

19.20 is a cylindrical D/A converter (digital-to-analog converter), and sinθ read from ROM18
11f1 of e's (direct and cos θC) is transformed by D7'Δ.

These transducers are given a motor torque specification.

21.22 is a constant current amplifier, and the multiplication Th'! D
//Based on the signals from the A converters 19 and 20, a constant current is applied to the coils L+ and L2 of the D D motor 23. J024 detects the rotational position of the code plate 1 (12Vy'I detection circuit The specific configuration of this circuit is shown in FIG.

In FIG. 4, 31 is a shift register, and switch SW
Turn on SW1 to SW8 in sequence.

32 is a timing generation circuit, switch fsW8 at the 8th port
At the timing when is turned on, (J number f1<1> is given to the take-in counter 33 and the latch circuit 34.
is the phase shift of the signal f1 (t) from the clock generator 35
Count at the same timing. The clock generator 35 generates a clock signal of 12MI-(z, for example. The latch circuit 34 latches the count 1 of the counter 33.

36 is a frequency dividing circuit, which divides the clock signal of the clock generator 35 into, for example, 11512, and divides the clock signal of the clock generator 35 into 11512,
is applied as a timing signal for turning on the switches SW1 to SW8 (A).

37 is a microprocessor which uses the 1 from the latch circuit 34 as a signal to determine the rotational position of the code plate.

The output signals of the diodes D1 and D2 are sent to the amplifier 3.
After being amplified by 8, a buffer of 13 is given to the microprocessor 37. This signal becomes the reference position signal (exit signal).

Next, the operation of the ill 1211B will be explained.

The skin frequency of the switches SW1 to SW8 is set to 8rs.

The light passing through the outer light-transmitting slit 2 is detected by a photodiode array 8, and the light passing through the inner light-transmitting slit 3 is detected by a photodiode array 9. When the detection signals of these photodiode arrays are scanned at a frequency of 8'f's, the signals f+(j) and f2(1) that have passed through the low-pass filters 13 and 14 are as follows.

f+ (j)−△, s i n (ωt+n, θ)
■f2 (j)=△2Sin(ωt+-n20) ■
△1. Δ2: constant, θ: rotation angle of sign ω−2π[S Here, the phase difference φ between both signals is φ−(n+n2)θ ■left.

Here, the relationship between the phase tφ and the rotation angle θ of the code plate will be explained.

For example, the number of outer slits n1 is 8 and the number of inner slits n2 is 61 [! 31. Regarding the case of a.

In this case, the motor lflam is set to 2 from 8-6.

In this case, the relationship between the detection signals of the A togiode arrays 8 and 9 and the rotation angle of the motor is as shown in FIGS. 5(a> and 5(b)).

As shown in the figure, the deviation (electrical angle) of these detection signals is proportional to the rotation angle 0 (mechanical angle) and becomes φ1. It increases as φ2...

The deviation φ between both detection signals when the code plate rotates by θ is as follows from equation 0.

φ-(8-6)θ On the other hand, when the code plate rotates by θ, the rotor of the motor also rotates by θ. Since the number of teeth of the motor is two, the teeth of the rotor and stator of the motor are angularly shifted by 2θ in electrical angle. That is, the phase difference detected by the code plate corresponds to the electrical angle difference between the teeth of the motor's rotor and stator. Based on this, the positional relationship between the teeth of the motor's rotor and stator (separate width angle) is detected, and the motor is commutated and controlled based on this positional relationship.

Next, let's talk about the correction operation for errors caused by eccentricity of the code plate!
Qll.

Now, if the number of pulses according to the position of the code plate (hereinafter referred to as the number of position pulses) obtained from the signals gf+(j> and f2 (j) is N+Jj and N2, e: true rotation angle, δ:
@center i1n, fl+: The mounting of the photodiode A-door array 8 is a radius, R2: The mounting of the photodiode array 9 is a radius. From the formula 0.0, the true rotation angle θ is, here, △−N
l +N2, B=NI N2. Errors due to eccentricity are corrected by finding e using the equation 0.

Such error correction calculations are performed by a separately provided microprocessor.

In addition, in the embodiment, the case where the motor is a two-phase motor has been described, but the present invention is not limited to this, and the motor may be a three-phase motor. In this case, the phase of the current signal flowing through each coil is θe, θe 120°.

It becomes θe+120'.

[effect] According to the present invention, the following effects (q) can be obtained.

In other words, the number of slits is set so that the difference between the number of transparent slits on the outside and inside of the two-stage transparent slit row is the number of poles of the motor. Can be installed.

This improves displacement detection accuracy because the angular resolution can be reduced. Furthermore, since the pitch of the light-transmitting slits can be reduced, the light source can also be made smaller. From Figure 6,
) A diode array PD△ is installed with an error Δ in radius R.
The error E caused in the detection signal by is equal to the number of nnislits. (2) From the formula, the smaller n and R are, the smaller the error [is.

Furthermore, since the number of light-transmitting slits can be increased, the radius of attachment of the slits can be increased. This allows a large hole to be formed in the center of the code plate, allowing the wiring of the motor and displacement converter to pass through easily.

In addition to this, the detection accuracy can also be improved because it is configured to compensate for errors due to eccentricity of the code plate based on the detection signals of the two photodiode arrays.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of a motor control device according to the present invention, FIG. 2 is a diagram showing the arrangement relationship between a photodiode and a light-transmitting slit, and FIGS. A diagram showing a specific configuration example of the control device, FIG. 5 is an explanatory diagram of the operation of the control device in FIG. 1, and FIG. 6 is a diagram for explaining errors occurring in the control device shown in FIG. 1. . 1... Code plate, 2.3... Translucent slit, 4.5.
...Light source, 8, 9...Photodiode array, 10
...Signal processing section. Figure 1 Figure 2 Figure 4

Claims (1)

[Scope of Claims] A code plate on which transparent slits are formed at a predetermined pitch is attached to the rotor of a brushless motor, and light is projected onto the transparent slits, and based on the light passing through the transparent slits, In a motor control device that determines the positional relationship between the teeth of the motor rotor and stator, two-stage slit rows with the numbers of light-transmitting slits n_2 and n_2 are provided on the code plate, and n_1-n_2 (n_1>n_2).
) is set to the number of teeth of the motor, and n_1 is set to the number of teeth of the motor.
What is claimed is: 1. A motor control device comprising: a signal processing section that calculates a positional deviation between teeth of a rotor and a stator of a motor from a phase difference between detection signals of light that has passed through n_2 and n_2 light-transmitting slits.