JPH0117347B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brushless (non-contact) linear servo motor that enables extremely high precision speed control and position control. More specifically, the present invention relates to a non-contact type linear servo motor that directly linearly drives a controlled object and eliminates any contactor. Typical scopes of application of the present invention include pen block drive mechanisms of drawing machines such as XY plotters, pen block drive mechanisms of recorders such as XY recorders and strip chart recorders, and print head feeding mechanisms of printing machines such as line printers. This is a drive device that enables high-speed and highly accurate linear motion. Conventionally, the above-mentioned devices have adopted drive mechanisms that use rotary step motors or rotary servo motors to move the controlled object in a straight line through transmission members such as gears, rollers, pulleys, and wires. was the most common. However, when using such a drive mechanism, there is a certain limit to the performance that can be obtained, as described below, and if you try to exceed it, it will be difficult both technically and cost-wise. We were suddenly forced to face a difficult situation. The first problem is physical accuracy related to position accuracy, linearity, and reproducibility. For example, gears always have a constant backlash or dead zone, and pulleys have slip. Also, the longer the wire, the more its expansion and contraction will have a negative effect on accuracy. Since rotary step motors are not controlled in a closed loop (so-called open loop control), gear eccentricity has a subtle effect on linearity, and if you aim to increase speed, it is likely to cause step-out in transient conditions. There are also fatal problems. On the other hand, when using a rotary type servo motor, a linear potentiometer is often used at the point of action (control target) to achieve closed-loop control, which alleviates the accuracy deterioration factors caused by the transmission system. In this case, accuracy deterioration occurs due to the linear potentiometer. Linear potentiometers, which are currently widely used, consist of a wire-wound or conductive plastic resistor and a sliding brush.
Abrasion of the resistor largely controls accuracy. The second problem is reliability, such as durability and lifespan. The above-mentioned transmission system includes members that transmit force through frictional resistance, and uses rotating members such as rollers to bend the wire, so wear inevitably progresses in each part and causes deterioration. It is inevitable that something will happen. In addition, the probability of wire deterioration and disconnection accidents is particularly high. On the other hand, many rotary type servo motors are made from brushed DC motors, so there is a certain limit to their service life that must be taken into consideration. Furthermore, wear of the resistor of the potentiometer as described above is one of the factors that reduces reliability. The third problem is noise. As mentioned above, the conventional system transmits the rotational force of a rotary motor to the controlled object via a number of transmission members and drives it linearly, so there are many movable members and each part generates quite a lot of noise. In particular, the resonance noise of the wire and the rotation noise of the rollers are relatively loud. As a result, the quality of the equipment is often significantly impaired. Several attempts have been proposed to improve these shortcomings. One example is the application of linear step motors. This is an attempt to directly drive a pen block, etc., and can overcome many of the drawbacks mentioned above, but since it is a step motor, it is difficult to achieve complete closed-loop control, and as a result, speed increases. , which has the disadvantage of high acceleration. Also, although it is suitable for drawing machines such as XY plotters, it is not suitable for analog recorders such as XY recorders, and has the disadvantage that its range of applications is limited. The brushless linear servo motor of the present invention can solve all of the conventional problems as described above. Its characteristics are listed below. (1) A DC linear servo motor that directly linearly drives a controlled object (such as a pen block). (2) This is a brushless DC linear motor that has a built-in non-contact position sensor and uses this to configure an electronic commutator. (3) The potentiometer is an electronic linear potentiometer built into the motor and shared, so there is no need to provide an independent potentiometer. (4) The above built-in potentiometer is composed of an incremental encoder, sensor, and electronic circuit. (5) The sensor of the built-in potentiometer is shared with the non-contact position sensor of the electronic commutator, and all contacts such as brushes are eliminated. (6) The incremental encoder of the built-in potentiometer mentioned above is a scale with constant increments, and this is shared by the motor stator itself. (7) The stator, which is a component of the motor's magnetic circuit, has a large number of tooth-shaped irregularities made of a magnetic material with a constant pitch in its longitudinal direction, and can be used as the motor's electronic commutator and potentiometer. The sensor detects this tooth-like unevenness. (8) This linear servo motor has tooth-shaped irregularities made of magnetic material similar to the stator on the mover.
It has a so-called double slot structure. (9) This linear servo motor has a wide range of applications, including not only XY plotters but also XY recorders, analog recorders, line printers, etc., regardless of digital or analog control. (10) As mentioned above, it is extremely reliable because it does not have any contacts. (11) As mentioned above, since the controlled object is directly linearly driven, accuracy is high, and since there is no force transmission member, it has a long life and low noise. (12) As mentioned above, since parts are shared and integrated, it is advantageous in terms of cost and can be made smaller and lighter. As listed above, the brushless linear servo motor of the present invention has many features. The present invention will be explained below based on the drawings.
FIG. 1 shows an embodiment of the mechanical part of the brushless linear servo motor of the present invention. Fig. 1a is a perspective view of the main part, b is a sectional view taken along a plane perpendicular to the moving direction of the mover (cross-sectional view taken along line II), and c and d are sectional views taken along a plane parallel to the moving direction of the mover (- (a line cross-sectional view and a - line cross-sectional view). Common members in these drawings a to d are given the same numbers. 1 in the diagram
is a stator, which has a large number of tooth-shaped irregularities (hereinafter referred to as magnetic pole teeth) 2 made of a magnetic material at a constant pitch in the longitudinal direction (movement direction of the movable element).
3 is a movable element, and this movable element 3 includes a permanent magnet 4 magnetized in a plane direction perpendicular to the moving direction of the movable element;
Two yokes are stacked to sandwich this from both sides.
(A) 9A, yoke (B) 9B, and three 3-phase coils 10a, 10b, 10c wound around the yoke (A) and (B).
, three groups of magnetic pole teeth 5a, 5b, 5c are notched on the stator facing surface of the yoke (A), and three groups of magnetic pole teeth 6a, 6b, similarly notched on the yoke (B). 6c, a non-contact position detection sensor block 7, and guide means 8a, 8b such as rollers that maintain a constant slight gap between the stator 1 and the movable element 3 and smoothly guide the movable element. It consists of However, since this guide means would complicate the drawing, it is shown by broken lines only in FIG. 1b. In this embodiment, a large number of magnetic pole teeth 2 are provided on the stator 1 at a constant pitch in the longitudinal direction, whereas the yokes (A), (B) 9A, 9B on the movable side are
There are three groups of magnetic pole teeth each, for a total of six groups, and the pitch of the magnetic pole teeth within the same group is equal to the pitch of the stator, but the different groups are all sown that the phases are different. As mentioned above, FIGS. 1c and d are sectional views taken on two different planes parallel to the longitudinal direction, and in particular, FIG. 1c is a sectional view of a portion including the yoke (A) 9A; Diagram d is the yoke (B) 9B
FIG. As can be seen from the drawings c and d, the magnetic pole tooth groups 5a, 5b, and 5c incised on the yoke (A) 9A are out of phase with each other by 120 degrees.
Similarly, the magnetic pole tooth groups 6a, 6b, and 6c provided on the yoke (B) 9B are also different in phase from each other by 120 degrees. Furthermore, between yoke A and B, each
180° phase difference. That is, 5a, 6a, 5b
, 6b, 5c, and 6c are magnetic pole teeth with a 180° phase difference, respectively. Coils 10a, 10b,
10c are both wound around the yoke (A) 9A and the yoke (B) 9B. By sequentially applying current to the three three-phase coils, the movable element can be moved in the longitudinal direction on the stator. In particular, if the coils are sequentially energized electronically in accordance with the position information from the non-contact position detection sensor block 7, smooth and continuous movement can be achieved. Here, the magnetic circuit and the principle of driving force generation of the embodiment of the mechanical part of the brushless linear servo motor of the present invention shown in FIG. 1 will be explained. In order to explain this magnetic circuit, FIG. 2 is replaced with an electric circuit model. In the figure, 14 represents the permanent magnet as a battery, and the permeance 15a, 15b, 15c, 16a, 16
b, 16c are mover magnetic pole tooth groups 5a, 5, respectively.
b, 5c, 6a, 6b, 6c and the permeance of the air gap between the stator magnetic pole teeth 2. However, it is assumed here that the magnetic resistance of the yoke (A) 9A, the yoke (B) 9B, and the stator 1 is zero. 20a, 20b, 20
c is a model representation of three coils in three phases. Assuming that the permeance of the air gap between the stator magnetic pole teeth and each magnetic pole tooth group of the mover changes sinusoidally with respect to the moving direction of the mover, the moving direction of the mover is X, the pitch of the magnetic pole teeth is L, If the average value of each permeance is Po, permeance 15a, 15b, 15c16a, 16b,
The respective sizes of 16c P _a , P _b , P _c , P _a , P
_b and P _c can be approximated as follows. P _a = P _p + psin2π/LX P _b = P _p + psin (2π/LX-2/3π) P _c = P _p + psin (2π/LX-4/3π) P _a = P _p - psin2π/LX P _b = P _p -psin (2π/LX-2/3π) P _c =P _p -psin (2π/LX-4/3π) where p is the half-width value of the permeance change.
Here, Pa + Pb + Pc = 3Po, P _a + P _b + P _c = 3Po
Therefore, the total permeance of the magnetic circuit seen from the magnet can be considered to be constant (3/2Po) regardless of X. Furthermore, the magnetic potential difference between both ends of the permeance of each gap can also be considered to be constant regardless of X. Now, if the magnetomotive force of the magnet is F, the difference in magnetic potential between both ends of each permeance is F/2. Therefore, each permeance Pa,
Flux φa flowing through Pb, Pc, P _a , P _b , P _c ,
φb, φc, φ _a , φ _b , and φ _c can each be approximated as follows. φ _a =F/2・P _a =F/2 {Po+psin2π/LX} φ _b =F/2・P _b =F/2{Po+psin(2π/LX−2
/3π)} φ _c =F/2・P _c =F/2{Po+psin(2π/LX-4
/3π)} φ _a =F/2・P _a =F/2{Po−psin(2π/LX} φ _b =F/2・P _b =F/2{Po−psin(2π/LX−
2/3 π)} φ _c =F/2・P _c =F/2{Po−psin(2π/LX−
4/3 π)} Now, three phase three coils 20a, 20b, 20
The fluxes linked to c are φa, φ _a and φ _b , respectively.
and φ _b , φ _c and φ _c . Since φa and _φa are opposite in direction, the total flux _φA interlinking with the coil 20a is expressed as follows. Φ _A = φ _a - φ _a = F·psin2π/LX Similarly, the total fluxes Φ _B and Φ _C interlinking with the coils 20a and 20c are respectively expressed as follows. Φ _B = φ _b −φ _b = F・psin (2π/LX−2/3π) Φ _C = φ _c −φ _c = F・psin (2π/LX−4/3π) As can be seen from the above equation, Φ _A , Φ _B and Φ _C are each a function of X, and are sinusoidal functions having the period of the stator magnetic pole tooth pitch L and being shifted from each other by 120°. Therefore, a three-phase position detector (sensor) that can detect the pitch of the magnetic pole teeth of the stator or the irregularities of the teeth is provided, and the coils 20a, 20b, and 20c are sequentially energized based on the output of this sensor. This makes it possible to always generate driving force in one direction. In the present invention, the above-mentioned sensor is included in the non-contact position detection sensor block 7 shown in FIG. This sensor is configured to directly and non-contactly recognize the unevenness of the magnetic pole teeth of the stator. If the coils are sequentially energized electronically based on the output of this sensor, an electronic commutator motor without brushes or contacts can be created. In the present invention shown in FIG. 1, since the motor has three phases and three coils, the number of sensors included in the non-contact position detection sensor block 7 is also three, so that the irregularities of the stator magnetic pole teeth can be directly detected. , are positioned so that their phases differ by 120° with respect to their pitches L. FIG. 3 shows an embodiment of the non-contact position detection sensor block for the brushless linear servo motor of the present invention, which is shown laid down so that the surface facing the stator faces toward you. In the figure, 7 is a non-contact position detection sensor block, 31 is a screw hole for joining to the movable element, 32 is a stator facing surface, 33a,
34a is a pair of light emitting element and light receiving element attached to this stator facing surface 32, and the light emitting element 3
3a is a pair of light receiving elements 3 that emit light in a direction substantially perpendicular to the surface and reflect the light when it hits the stator.
4a. 33b,3
4b, 33c, and 34c are pairs of completely similar light emitting/light receiving elements, and there are three sets in total. With such a configuration, the unevenness of the stator magnetic pole teeth can be detected as a change in the amount of light reflected. The relative positional relationship of these three sets of light emitting and light receiving elements must be determined in relation to the pitch L of the magnetic pole teeth of the opposing stators. In the case of the embodiment shown in FIG. 3, a pair of light-emitting and light-receiving elements are attached at a distance of L/3 in the moving direction of the mover.
The two light-receiving elements are set so that they output waveforms that are shifted by 120° from each other in terms of position. In addition, since these three sets of light emitting/receiving elements need to play the role of electronic commutators for the three coils of the mover, their relative position with the mover magnetic pole tooth group is important, and they must be installed at a predetermined distance. Needless to say, it is necessary to FIG. 4 shows an example of the sensor output waveform of this non-contact position detection sensor block. The outputs of the three three-phase sensors (light receiving elements) have waveforms that are shifted by 120 degrees. Note that for reasons described later, each waveform must be as close to a sine wave as possible. The non-contact position detection sensor applicable to the present invention is not necessarily limited to the above-mentioned light emitting/light receiving element. For example, although not shown, it may be a Hall element. However, it is necessary to be able to directly and non-contact detect the irregularities of the stator magnetic pole teeth and to have a sine wave-like output with little distortion. The mechanical part of the brushless linear servo motor of the present invention has been explained above, but in particular, this motor has a stator,
One of the main constituent features of the present invention is that both the mover are made of magnetic material and have a structure (double slot structure) having a large number of tooth-like unevenness. Another similar requirement is that the stator has a structure consisting mainly of magnetic pole teeth made of magnetic material. A structure similar to this can be seen in step motors,
The reasons why such a structure is important and essential for the linear servo motor of the present invention are summarized as follows. (a) The motor of the present invention is a completely non-contact linear servo motor, the potentiometer is built into the motor, and the non-contact position detection sensor shared with the electronic commutator is fixed to the motor. Position detection is performed by regarding the child as a scale of a linear encoder. In order to make the resolution of a potentiometer finer, it is advantageous to have as fine a scale pitch as possible, even when interpolation is performed, and a double slot structure with finely pitched magnetic pole teeth is advantageous. is suitable. (b) The purpose can be achieved by using something like an optical grating with fine increments as a scale instead of such a stator, but the effect of sharing and integrating each component and the resulting cost reduction and miniaturization is This deviates from the gist of the present invention, which is one of the main points. (c) Instead of a stator with fine magnetic pole teeth,
In principle, it is possible to use a permanent magnet magnetized with a fine pitch as a stator (in this case, a permanent magnet is usually not needed on the mover side), but in reality, even with fine magnetization, a strong magnetic field cannot be generated. It is impossible to obtain this, and only a very weak driving force can be obtained. If pre-magnetized strip-shaped permanent magnets are alternately arranged in the longitudinal direction as a stator, the driving force will be slightly improved, but forming a stator with a length of several tens of centimeters to one meter is expensive from an accuracy standpoint. It's not realistic from any point of view. As mentioned above, the linear servo motor of the present invention can be applied to two-axis devices such as XY plotters and XY recorders. In the case of a general flat bed type, the Y motor, including its stator, serves as the movable element of the X motor, so the stator is required to be lightweight. In this respect, the motor stator structure of the embodiment shown in FIG. 1, which consists of only magnetic pole teeth and no permanent magnets, is very advantageous. From the above, the double slot structure in which the stator is composed only of magnetic pole teeth is an essential requirement for the present invention in terms of accuracy, cost, small size and light weight. Furthermore, in the above-described embodiments of the mechanical part of the brushless linear servo motor of the present invention, a so-called three-phase motor (therefore, the number of coils is three) is employed. In general, a two-phase motor has a simpler structure; for example, the number of sensor elements and coils of a non-contact position detection sensor block can be reduced, and the electric circuit section can also be simplified. However, as mentioned above, since the motor of the present invention has a double-slot type magnetic pole structure, if the number of phases is small, uneven magnetic force (so-called cogging force) peculiar to the magnetic circuit remains, causing noise and positioning servo errors. easy to become. Therefore, in the embodiment of the present invention, three phases were used. In fact, when comparing motors with similar dimensions and thrust experimentally, 3
The residual cogging force of the phase motor is 1/1 of that of the two-phase motor.
It was confirmed that the ratio would be 5 to 1/2. However, the present invention is not limited to the three-phase structure of the embodiment, and may be formed into a multi-phase structure depending on the application. Next, the electric circuit section of the brushless linear servo motor of the present invention will be explained. FIG. 5 is a block diagram of the electric circuit diagram of the brushless linear servo motor of the embodiment. 5 in the diagram
Reference numeral 0 designates a mechanical section of the motor, 51 a stator, 53 a movable element, and 57 a non-contact position detection sensor block. 58 is a roller bearing, 60
a, 60b, and 60c indicate three phase three coils.
Reference numerals 61a, 61b, and 61c are position signal amplifiers that amplify the three-phase position signals of the non-contact position detection sensor block 57, respectively. The output of this position signal amplifier is a sinusoidal wave output shifted by 120 degrees (shifted by L/3) with a period equal to the stator's magnetic pole tooth pitch L, and serves as a position signal for the electronic commutator. A three-phase motor drive circuit 62 sequentially energizes the three-phase motor coils in accordance with the position signals output from the position signal amplifiers 61a, 61b, and 61c.
The magnitude of that current is proportional to motor command voltage input 63. The non-contact electronic commutator is composed of the sensor and electronic circuit described above. Now, the position signal output of the position signal amplifier has the role of a potentiometer in addition to the role of the electronic commutator. The remaining portions of the block diagram shown in FIG. 5 mainly concern this potentiometer. This potentiometer is electronic rather than mechanical. This will be explained below. 64a,
64b and 64c are both modulation circuits that output high frequency carrier signals 65a and 65 using three sine wave outputs from position signal amplifiers 61a, 61b and 61c.
This is a type of multiplier that modulates signals b and 65c, respectively. However, the phases of these three carrier signals are shifted by 120 degrees. 66 is an adder circuit and the above 3
The modulated outputs of the three modulating circuits 64a, 64b, and 64c are added together. A low-pass filter 67 has the function of removing harmonic components of the modulated outputs added by the adder circuit 66 and extracting only the fundamental wave component. A waveform shaping circuit 68 converts the fundamental wave into a rectangular wave. The three sine wave outputs of the current position signal amplifiers 61a, 61b, and 61c are K ₁ (X), K ₂ (X), and K ₃ (X).
Suppose that it can be expressed as follows. K ₁ (X) = ksin2πX/L K ₂ (X) = ksin (2πX/L-2/3π) K ₃ (X) = ksin (2πX/L-4/3π) However, X is the displacement of the mover , L is the stator magnetic pole tooth pitch, and k is the half-width value of the amplitude. On the other hand, the carrier signals 65a, 65b, 65c
Assume that C ₁ (t), C ₂ (t), and C ₃ (t) can be expressed as follows. C ₁ (t)=sin(2πf _c t) C ₂ (t)=sin(2πf _c t-2/3π) C ₃ (t)=sin(2πf _c t-4/3π) (However, f _c Carrier frequency) If the result of modulation in the modulation circuits 64a, 64b, and 64c and addition in the addition circuit 66 is S(t,X), then S(t,X)=K ₁ (X)・C ₁ (t) +K ₂ (X)・C ₂ (
t)+K ₃ (X)・C ₃ (t) =k{sin(2πX/L)・sin(2πf _c t)+sin(2
πX/L-2/3π)・sin(2πf _c t-2/3π) +sin(2πX/L-4/3π)・sin(2πf _c t-4
/3π)}=3/2kcos(2πf _c t−2π/LX). This is applied to a carrier with a frequency of f _c ² 〓 _L
This means that the phase term is included. In other words, in S(t,X), position information X is converted into phase information. Therefore, S(t,
If the phase information of X) is demodulated, the movable element 53 of the motor
can recognize the location of Also, the mover 53
When is moving at speed v, X=vt, so the function S(t, v) with speed as a variable is expressed as follows. S(t, v) = 3/2kcos (2πf _c t-2π/Lvt) = 3/2kcos {2π(f _c - v/L)t} This means that the speed information v is the deviation from the carrier frequency f _c It means to be shown. Now f _c =
If 10KHz and L=1mm, then when the speed of v=±1m/s, v/L=±1KHz and S(t,v)
The frequencies of f _c =1KHz, that is, 9KHz, and 11KHz. From the above S(t,X), the conditions for accurately recognizing the position of the mover are position signals K ₁ (X), K ₂
The waveforms of (X) and K ₃ (X) are sine wave-like with little distortion with respect to position X. If the distortion is large, a potentiometer with many undulations and poor linearity will be created. Furthermore, the low-pass filter 67 functions to remove harmonic components contained in S(t,X). Generally, carrier signals 65a, 65b, and 65c are often used that have a large number of harmonics (for example, a rectangular wave), and in that case, a low-pass filter 67 is used.
is an essential element. Now, since the modulated and added signal S(t, In an embodiment of the present invention, a PLL (Phase Locked) including a frequency divider is used.
A demodulation method is used in which position information with high resolution is extracted by multiplying S(t,
The PLL circuit includes a phase comparator 69, a low-pass filter 70 that filters out the low frequency range of this output, and a VCO (voltage controlled oscillator) controlled by this output.
A voltage controlled oscillator) 71 and a frequency divider 72 that divides this frequency (denoted as _fv ) by 1/M (M is an integer). Note that the input of the phase comparator 69 is the waveform shaping circuit 6
8, and a frequency-divided version of the VCO 71 output (output of the frequency divider 72).
With this configuration, the output of the VCO 71 becomes the S
_{( t} , Here, a reference frequency generation circuit 73 is provided to generate a reference frequency such that f _p =M·f _c ,
By comparing this reference frequency f _p with the multiplied output of the VCO 71, only the phase information (2πMX/L) can be separated. A phase comparator 74, a low-pass filter 75, and a waveform shaping circuit 76 are used for this comparison and separation. The separated phase information (2πMX/L) is periodic with respect to X and can be expressed as 2πMX/L=2nπ (n is an integer). low pass filter 7
5. The phase information converted into a rectangular wave pulse by the action of the waveform shaping circuit 76 is X=n·(L/M), and the converted displacement amount of the movable element 53 per one pulse is L/M. As is clear from the above, the displacement of the movable element 53 is recognized in steps, and the minimum step L/M is the resolution. This is the pitch L of the stator magnetic pole teeth.
This means that the value is interpolated to 1/M at equal intervals. Therefore, in order to increase the resolution and obtain smooth position information, L should be made smaller and M should be made larger. 77
is a pulse separation circuit. Since the pulses output from the waveform shaping circuit 76 have no polarity, the direction cannot be determined even if the pulses are directly counted by a position counter. Therefore, based on the moving direction of the mover 53,
Separate into count pulse and down count pulse. 7
Reference numeral 8 denotes a position counter that increments the up count pulse and down count pulse and displays the current position of the movable element 53 in real time. Reference numeral 79 is an origin/initial reset input for the position counter 78. Note that 80 is a three-phase frequency divider, which divides the reference frequency f _p of the reference frequency generation circuit 73 by 1/M, and generates three-phase carrier signals 65a, 120 degrees apart from each other.
65b and 65c (frequency f _c ). With the above configuration, the position of the movable element 53 is digitally indicated on the position counter 78. Therefore, the output of the position counter 78 becomes the output of the potentiometer. The position control of the movable element 53 is as follows:
This is achieved by using an error amplification circuit 82 that amplifies the difference between the position command input 81 and the output of the position counter 78, and feeding the output to the three-phase motor drive circuit 62 as the motor command voltage input 63. be done. Next, some parts of the electric circuit section of the present invention will be explained in more detail. FIG. 6 shows the modulation circuits 64a, 64b, 6 of FIG.
This is an example of 4c. 101 is a position signal amplifier 6
This is the sine wave output (position signal) K(X) of 1a, 61b, or 61c. 102 is an inverting amplifier (gain 1). 103 is the carrier signal (frequency
f _c ) is a semiconductor switch controlled by 104. 105 is a modulated output. The semiconductor switch 103 has a carrier signal 104 at “H level”.
, the position signal K(X) 101 is transmitted as is, and when the carrier signal 104 is at "L level", the inverted position signal -K(X) is transmitted, as shown in the figure. A modulated output 105 is obtained. FIG. 7 shows an embodiment of the error amplifier 82 of FIG. 201 is the output of the position counter 78;
02 is a D/A converter that converts this into an analog value. 203 is a subtraction circuit that calculates the difference between the position command input 204 (analog input in this case) and the output of the D/A converter 202 (an analog signal indicating the current position of the movable element 53). 205
is an amplifier that amplifies the difference signal of the subtraction circuit 203.
06 is a lead-lag filter circuit for stabilizing the servo system by providing appropriate damping. Reference numeral 207 is the output of this lead-lag filter circuit 206 and serves as a motor command voltage input 63 to be applied to the three-phase motor drive circuit 62. The brushless linear servo motor of the present invention, which has been explained in detail above in terms of the mechanical part and the electric circuit part, has the following features: (1) Since it is a DC linear servo motor that linearly drives the controlled object directly, it is compatible with a rotary type motor. It is possible to ensure positional accuracy and reproducibility that could not be obtained in the conventional example using members. Moreover, noise can also be reduced. (2) It is a linear servo motor with a built-in non-contact position sensor, which is used to configure an electronic commutator and an electronic potentiometer, and eliminates any contact, so it is durable and reliable. high,
Also, it is free from brush hysteresis, bumpiness, etc. that occur with conventional potentiometers. (3) The sensor of the built-in potentiometer is shared with the sensor of the electronic commutator, and the scale of the encoder is a stator with tooth-like unevenness (magnetic pole teeth) in the longitudinal direction. , because they are shared, there is no need for an independent linear potentiometer, which is advantageous in terms of cost, and allows for reductions in size and weight. (4) The stator has a simple structure with a large number of magnetic pole teeth made of magnetic material at a constant pitch in the longitudinal direction, and it is lightweight because it does not include other magnetic circuit members such as permanent magnets. Footbed type XY printer and XY with reduced motor weight
It can be used as a Y motor (cursor motor) for a two-axis drawing device such as a recorder. (5) Compared to the conventional example, the number of parts for transmission members and movable members is significantly reduced, and the number of assembly steps can be greatly reduced. (6) Although it has a double slot magnetic pole tooth structure, it is a servo motor and not a step motor, so it has a wide range of applications, including not only plotters but also XY recorders and analog recorders. It has many excellent features and effects.

[Brief explanation of drawings]

FIG. 1 shows essential parts of an embodiment of the brushless linear servo motor of the present invention, in which a is a perspective view, b is a vertical cross-sectional view in one direction, c and d are vertical cross-sectional views in the other direction, and FIG. FIG. 1 is an explanatory diagram showing the magnetic circuit; FIG. 3 is a perspective view showing a non-contact position detection sensor block;
Fig. 4 is an output waveform diagram of the non-contact position detection sensor block, Fig. 5 is a block diagram of the electric circuit section of this embodiment, Fig. 6 is a circuit diagram showing the modulation circuit in the above electric circuit section, and Fig. 7 FIG. 2 is a circuit diagram showing an error amplifier in the electric circuit section. 1, 51... Stator, 2... Stator magnetic pole teeth,
3,53...Mover, 4...Permanent magnet, 5a,5
b, 5c, 6a, 6b, 6c... Mover magnetic pole tooth group, 7, 57... Non-contact position detection sensor block, 10a, 10b, 10c, 60a, 60b,
60c...Mover coil, 62...3-phase motor drive circuit, 64a, 64b, 65c...Modulation circuit,
66... Addition circuit, 69, 74... Phase comparator,
71...VCO (voltage controlled oscillator), 73...Reference frequency generation circuit, 78...Position counter, 82...
...Error amplification circuit.

Claims (1)

[Scope of Claims] 1. A stator made of a magnetic material having on its surface magnetic pole teeth consisting of a large number of tooth-like irregularities at a constant pitch in the longitudinal direction, and a stator facing the stator with a constant air gap therebetween. a guide means for maintaining and movable smoothly in the longitudinal direction along the stator; a permanent magnet disposed parallel to the longitudinal direction; and a permanent magnet disposed parallel to the longitudinal direction; The first and second
a movable element including a yoke, and a group of n (n is an integer) magnetic pole teeth each formed on the gap surface facing the stator of the first and second yokes,
In the same yoke, the arrangement of the n pieces is in the above-mentioned longitudinal direction, and the pitch of the teeth in the same group is the same for any magnetic pole tooth group, and the phases are mutual between different magnetic pole tooth groups in the same yoke. a plurality of magnetic pole tooth groups formed differently in the magnetic pole, and a magnetic flux generated by the permanent magnet that passes through the magnetic pole tooth group and reaches the stator magnetic body via the air gap portion. A plurality of coils of a movable element are wound around the yoke, and the irregularities of the magnetic pole teeth of the stator attached to the movable element are detected and converted into electrical signals, which generate approximately sine waves having different phases. a plurality of non-contact sensors for outputting position signals; electronic commutator means for sequentially energizing the plurality of coils in accordance with substantially sinusoidal position signals having mutually different phases; electronic potentiometer means for electrically recognizing the position of the movable element by demodulating phase information of a carrier signal modulated by substantially sinusoidal position signals having different phases; It comprises an error amplifier that amplifies the difference between the output of the meter means and the position command input, and a motor drive circuit that applies a current proportional to the magnitude of the output of the error amplifier to the plurality of coils and drives the movable element. A brushless linear servo motor characterized by: 2. The electronic potentiometer means includes a reference frequency generating circuit, a frequency dividing circuit that divides the output into 1/M (M is an integer) and generates a plurality of carrier signals having mutually different phases, and a frequency dividing circuit that divides the output into a plurality of carrier signals having mutually different phases. A plurality of modulation circuits modulated by the position signal, an addition circuit that adds the outputs of the modulation circuits, and a PLL circuit (Phase Locked Loop circuit) that multiplies the fundamental frequency component of the addition output of the addition circuit by M times. a phase comparator that compares the phase of the multiplied output of the voltage controlled oscillation circuit in the PLL circuit and the reference frequency output of the reference frequency generation circuit; a low-pass filter that filters low-frequency components of this output; A patent characterized in that it is configured to include a waveform shaping circuit that shapes the output of a filter to create a rectangular wave pulse, and a position counter that counts the rectangular wave pulse and digitally detects the position of the movable element. A brushless linear servo motor according to claim 1.