JPS60219988A - Controller for brushless motor - Google Patents

Abstract

PURPOSE:To eliminate the necessity of processing such as resetting of an origin by detecting the absolute position of a rotor over a plurality of rotations of a brushless motor to control the switching of the direction of an exciting current and controlling the rotating speed and position. CONSTITUTION:Absolute encoders 24, 34, 44 for detecting the rotating positions of brushless motors 22, 32, 42 over a plurality of rotations are respectively provided in the motors 22, 32, 42, the output signals of the encoders 24, 34, 44 are processed by a host computer 20, and the computer 20 performs the switching of the directions of the exciting currents of the motors 22, 32, 42, the rotating speeds of the motors 22, 32, 42, and the rotating positions over a plurality of rotations. Accordingly, when a robot starts operating or at recovering time after the power interruption, it is not necessary to operate the setting of the origin at every time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brushless motor control device, and more particularly to a brushless motor control device that performs control by detecting the absolute position of the end of rotation of a brushless motor over multiple rotations. .

[Prior art] In recent years, various types of automatic control have come to be performed on floor holes, such as the widespread use of automatic numerical control (NG machine tools, so-called NG machine tools, robots, etc.). In devices to which such automatic control is applied, the method and accuracy of feeding and positioning the controlled object are always issues in all processes such as processing, assembly, and inspection. , a highly reliable electric motor (hereinafter referred to as a motor) that is easy to handle, such as controlling the rotational speed, and a low-speed electric motor that can detect the position and speed of the motor or the controlled object driven by the motor with high precision and high reliability. A low cost detector is required.

As a motor that is easy to control, its equivalent inductance is small, the inertia of the rotor (hereinafter also referred to as rotor) is small, and the correlation with the rotation speed from 1 to
It is necessary to satisfy the requirements of being able to control the rotational speed over a wide range, and recently DC-driven coreless motors and brushless motors have been used. Among these, brushless motors are widely used for precise control because, as the name suggests, they do not have brushes, are highly durable and reliable, and do not cause noise.

However, since it is brushless, it is necessary to maintain the direction of the magnetic field excited by the 7 J current flowing through the fixed winding for a long time, so a detector is installed to detect the rotor position, and the magnetization is adjusted according to the detected rotor position. Control is required to switch the direction of the current.

On the other hand, various types of detectors have been devised to detect the position and speed of an object, but the well-known incremental・Encoders are the most widely used. Incremental encoders generate pulse signals with a period synchronized with the rotation of the motor, and by counting the number of pulses, the amount of rotation of the motor can be detected. Since the movement m of the controlled object corresponds to the amount of rotation of the motor, the amount of movement of the controlled object is detected as a result.However, the incremental encoder does not detect the amount of rotation of the motor or the amount of movement of the controlled object. Since it is only detected relatively, that is, as b) from a certain LTP point, in an office control system using this, when the system starts up, such as when the power is turned on, the motor is moved in a predetermined direction. and set the limit switch to 1, c.
You can reset the origin, set the end limit, etc. by
[The position could only be controlled after processing. This means that initialization must be performed every time there is a power outage, which is not desirable in terms of control safety. Also, when counting the output pulses of the incremental encoder, noise may be added to the output pulse signal, or the rotational speed of the rotating shaft to which the incremental encoder is attached may be high, causing the allowable response range of the incremental encoder or counter to be temporarily exceeded. If the value exceeds 0, it will cause a counting error that cannot be recovered, posing a safety problem.

Furthermore, considering the case where servo flil control is performed using a brushless motor, in addition to the rotor position detector for switching the excitation current as described above, there is also a rotation speed detector fi (tacho generator) that detects the rotation speed. ),position(
An incremental encoder for detecting the rotation (m) is required, and there is a problem in that the configuration of the detector becomes complicated, as shown in FIG. In the figure, 1 is a brushless motor, 2 is a rotor position detector using a Hall element that detects the position of a rotor (not shown) of the brushless motor 1, 3 is a tacho generator that detects the rotation speed of the rotor, and 4 is an incremental rotor.] Each represents two encoders. Reference numeral 6 denotes a higher-level control device, which commands the target position of a control object (not shown) according to a predetermined procedure. Reference numeral 8 denotes a position control means which controls the actual position of the controlled object, which is commanded by the upper control device 6 and detected by the target position of the object IC1tilI11 and the output of the counter 8a where the pulse signals from the incremental encoder 4 are accumulated. The target rotational speed of the brushless motor 1 is commanded by inputting the position into the amplifier 8b. 10 is a speed control means, and position I11 m means 8
The target rotational speed commanded by and the rotational speed (rotational speed) of the brushless motor 1 detected by the tacho generator 3
is input to the amplifier 10a, and the brushless motor 1 (-
It is configured to output a rotational speed decrease signal to the excitation current switching means 12 in accordance with the current value to be output. encouragement j1
1 current switching means 12 selects the four rotation speed I input from the speed aJ control means in accordance with the output signal of the rotor position detector 2.
+IJ111 Inverts the polarity of the signal J- Polarity switching circuit 12
A and a rotation speed control signal whose polarity is switched according to the position of the brushless motor 1 are input, pulse width modulation (PWM) is performed, power is amplified, and a drive current is output to the brushless motor 1. and a drive circuit 12b. The drive circuit 12b detects the drive current to the brushless motor 1, applies feedback, and performs control such that a constant current output (output torque of the brushless motor is constant).

In the brushless motor control device configured as described above, 3
Although various types of detectors are used, the rotor rotational position detector 2 detects the absolute position of the rotor.
Nereku 3 detects the rotation speed using an analog voltage, and incremental encoder 4 is a type that outputs two-phase pulses. Multiple detectors with different output meanings and formats are required. I can see that it is being done.

Providing a large number of detectors will reduce the reliability of the entire device, and although servo control using a resolver as a single detector has been proposed and implemented, In this case, the motor control amount is detected as a phase difference, so a phase locked loop (P h
This method is based on i-control based on (Loop), and there is a problem in that the control becomes complicated. In addition, since the phase-locked loop using the output of the resolver is originally for speed control, the configuration would be extremely complicated if you tried to extract a signal for detecting the rotational position of the rotor or a signal equivalent to 5 for an incremental encoder. [Objective of the Invention 1] The present invention has been made in view of the above points, and its purpose is to simplify the configuration of the detector and to achieve a high reliability. An object of the present invention is to provide a reliable brushless motor fiIIJ control device.

[Configuration of the Invention] The configuration of the present invention made to achieve the above object is as shown in FIG. 2, in which a driven object M2 driven by a brushless motor M1
a position control means M3 that receives a drive position signal corresponding to the position of the brushless motor M1 and controls the rotation of the brushless motor M1 based on the drive position signal and the target position; and a speed signal that corresponds to the rotational speed of the brushless motor M1. speed control means M for controlling the brushless motor M1 to a target rotational speed based on the speed signal and the target speed.
4, and excitation current switching means M5 that receives a rotor position signal corresponding to the absolute position within one revolution of the rotor of the brushless motor M1 and switches the direction of the current that energizes the stator of the brushless motor M1. , an absolute position detection means M6 for detecting the absolute position of the rotor over multiple rotations of the brushless motor M1, and generating the drive position signal from the detected absolute position of the rotor. A brushless motor control device comprising: generating the speed signal and outputting it to the speed control means M4; generating the rotor position signal and switching the excitation current. The gist is:

[Examples] Examples of the present invention will be described in detail below based on the drawings.

FIG. 3 is a block diagram showing the general structure of the embodiment. Here, as an example, we will take up a three-axis crime prevention device for a robot that performs three-axis x-y-z control.

In the figure, 20 is a host computer that controls the position of the three-wheel metal body, 22 is a brushless motor for the X axis, and 24
26 is an absolute encoder that detects the absolute position of the brushless motor 22 over multiple rotations, and 26 is an absolute encoder that takes in the output of the absolute encoder 24 and outputs it to the servo amplifier 2.
8 respectively represent an X-axis peripheral brushless motor control device that outputs an excitation current switching signal aX and a rotational speed control signal bx.

Exactly the same configurations are prepared for the Y-axis and the Z-axis, namely, 32 is a brushless motor around the Y-axis, 34 is an absolute encoder that detects the absolute position of the brushless motor 32 over multiple rotations, and 36 is an absolute encoder that detects the absolute position of the brushless motor 32 over multiple rotations. Takes the output of absolute encoder 34 and connects it to servo amplifier 3 with lυ
8 to excitation current switching signal 'ja'1. Rotation speed control signal by
Brushless motor control device around the Y axis, 42
is a brushless motor around the Z axis, 44 is an absolute F encoder that detects the absolute position of the brushless motor 42 over multiple rotations, and 46 is an absolute encoder 4
The brushless motor control device around the Z-axis receives the output of No. 4 and outputs an excitation current switching signal aZ and a rotational speed control signal bz to the servo amplifier 48. Each brushless motor control device 26, 36, 46 exchanges data with the host computer 2o, and according to instructions from the host computer 2o, the brushless motor 22 of each axis is controlled.
．． 32.42.

Since the configuration of each axis is the same, in the following, the three axes will be represented by the X-axis device as necessary.

Next, the absolute encoder 24 (34, 4
4>, the servo amplifier 28 (38, 48), and the brushless motor control device 26 (36, 46).

First, the principle of absolute position detection using the absolute encoder 24 and the structure of the absolute encoder 24 will be explained using FIGS. 4 to 7. FIG. 4 shows a conceptual configuration of the absolute encoder 24, which consists of three rotary encoders RE+, RE2. It is composed of REa and gears that transmit the rotation of these rotary encoders.

Each row encoder RE+, RE2. REa divides one revolution into N parts and outputs a signal representing the rotational position of an internal rotor (not shown) as an absolute position within one revolution. 1st
The rotary encoder RE+ is connected to the main shaft and detects rotation of the main shaft. The rotation to be detected is given from this main axis. A gear 51 with the number of teeth n-1 (where n is an arbitrary integer) is provided on the rotating shaft of the first low-return encoder RE+, and this gear 51 is connected to the second
The rotary encoder RE2 is meshed with a gear 52 having n teeth provided on the rotating shaft of the rotary encoder RE2. Furthermore, a second encoder R
Ez is provided with a gear 53 having n+1 teeth, and this gear 53 meshes with a gear 54 having n teeth provided on the rotating shaft of the third encoder REa.

Therefore, when the main shaft rotates once, RE+ rotates once and RE2
is (n-1)/n rotation, REa is (n-1)(I)+1
)/n” rotations. Here, each encoder RE+
, RE2. If the rotational position detected by REa (absolute position within one rotation) is D+, Dz, and D3, the value of Dl when the main shaft makes one rotation is N, and D2.03 is as follows.

D+ -N In other words, the output D1~ of each encoder RE+~RE3
D3 is a rotation angle that changes at a predetermined period according to the mechanical displacement of the main shaft (rotational displacement over multiple rotations from the origin), and is less than one rotation or more than one rotation, and the mechanical displacement of the main shaft corresponding to each period is measured. ) is each encoder RE+, RE
2. Each REa is different. In other words, the amount of mechanical displacement of the main shaft corresponding to one period of the first encoder RE1, that is, the rotation angle is 2π radian (that is, one rotation), but the mechanical displacement of the main shaft corresponding to one period of the second encoder RE2 The quantity, that is, the rotation angle is 2π゛xn/(n-1
> radians (that is, (n-1)/n rotations), and the mechanical displacement of the main shaft corresponding to 1 vJ of one revolution of the third encoder RE3, that is, the rotation angle is 2πXn''/ (n -1> (
n +1 > radians (that is, (n −1) (n +
1 >/n rotations).

That is, each output signal D1 to D3 always shows a value less than one cycle, but each output signal DI, D2. Since the mechanical displacement M (rotation angle) of the spindle corresponding to one period of Da is different, each output signal D corresponds to each absolute position of the spindle.
The values of +, Dz, and Ds each represent a unique combination. Specifically, how many rotation mills the output signal D1 of the first encoder RE+, which corresponds one-to-one to the rotation of the main shaft, corresponds to from the origin (hereinafter referred to as the period number of Dl) is It is determined uniquely by the unique combination of values of each output signal D+, D2.DB.In this determination, of course, not only the current value of the output signal D+D2.D3 but also each of these signals D+, D2.DB is determined. Also involved is information related to the amount of mechanical displacement of the spindle (or the difference thereof) corresponding to one period of each signal D+, D2.Ds, which is a factor that causes a difference between the signals D+ and D2.Ds.

The output signal D of the first encoder RE+ determined in this way
The absolute position of the main axis can be specified by the combination of the period number 1 and the current value of the signal D1.

The number of cycles of the output signal D1 of the first encoder RE+ is different from that of each signal D+, D2 . The current value of Da and each signal D+, D
2. Algebraic or mathematical It can be determined by the method. Various calculation methods can be considered for this purpose, but among them, the most efficient method in terms of calculation time and calculation circuit configuration will be described below. Row reencoder RE+.

RE2. REa can detect the absolute position by dividing one rotation of each rotor into N parts, and each rotary encoder RE+
, RE2. Since the number of teeth of the gears connecting REa to each other is n-i, n, n + 1, respectively, one rotation of the main shaft of the brushless motor, that is, the rotation encoder R
The change in ID1-D21 per revolution of E+ is N/n. Therefore, the output signal D of the low reencoder RE+
1 and the output signal D2 of the rotary encoder RE2 is the deviation value DI2 (D+z-D+-D2), and the number of cycles (rotation speed) of the co-axis counted from the origin is RX.
It can be expressed as Rx = D+ 2 Xn /N - (2). Note that the origin here means each row encoder RE+, RE2. Each output D+, D2 . of REa. Da
This is the position where both are zero.

As is clear from equation (2), when the rotational speed R× of the spindle becomes 0, the positional relationship between the row reencoder RE+ and the other rotary encoder RE2 returns to the original, so only the two row reencoders are used. In this case, absolute position detection over multiple rotations can only be performed up to n rotations at most. Therefore, the detection range is further expanded using the output signal D3 of the third rotary 1 encoder REa.

That is, t between the output signal D1 of the rotary encoder RE+ and the output signal D3 of the rotary encoder RE3 is defined as the deviation value D.
+ 3 (D+ s=D+ Da), then 1 of the main axis
Since the change in deviation value D+a per rotation is N/11, if the rotation speed of the main shaft from the origin exceeds Rx,
If the accuracy is RX, then the absolute rotation speed of the main shaft from the origin is Rx
-ab- is Rx -ab--D+ Bxn'L/N
−= (3) How can I be punished? Deviation 1eD+a is N/n
The value divided by is written as Ry (RY = D1a x11/
N>, after all, the absolute rotational speed Rx-ab of the main shaft is Rx -
It will be expressed as ab-n xRy +Rx -=-(4). Adding the output signal D1 of the rotary encoder RE+ to this represents the absolute position of the main shaft over a plurality of rotations. By considering the output D3 of the third rotary encoder REa, Equation (3)
As shown in , the detection range of the absolute position of the spindle is n from the origin.
'L rotation.

Above, the method of detecting the rotational position of the main shaft of the brushless motor 22 over multiple rotations using the absolute encoders 2 and 4 has been described. The number of divisions N per rotation of REa is 1024, and each row encoder RE+
, RE2. The number of teeth of the gear that transmits rotation to REa is 32.
If we take up the absolute encoder of 2015, an absolute encoder with such a configuration can detect the absolute position of the spindle within a range of 1024 revolutions from the origin with an accuracy of 1/1024 revolution per revolution. .

In the above description, the first and second rotary encoders RE+,
It decelerates between RE2 at a ratio of rn-i to 0, and REz
Between REa, the speed increases at a ratio of [n+1 to nJ (7), but on the contrary, between RE+ and RE2, the speed increases at a ratio of n to n-1.
The speed increases at a ratio of ``n to n+1'' between RE2 and REa.
The speed may be reduced at a ratio of . Although the arithmetic expressions in that case are not exactly the same as the above-mentioned expressions (1) to (4), they can be easily derived in the same way as these, so they will be omitted here. In addition, each encoder RE+, RE2゜R
The increase/decrease ratio between Ea is "n-1 to 1)" or "n+1
instead of “n-a vs. n” or “n+a vs. n”
”. However, it is assumed that a is sufficiently smaller than n and is a divisor of 0.

Next, the absolute encoder 24 used in this example
The mechanical structure of this will be explained with reference to FIGS. 5, 6, and 7. Figure 5 shows sensor VRE+.

VRE2. FIG. 6 is a schematic front view of the absolute encoder as seen from the gear mechanism side, and FIG. 7 is a cross-sectional view of one sensor VRF+. Here, sensors VRE+, VRE2. VREII is the fourth
The D-tary encoders RE+, RE2. R.E.
This corresponds to a. In FIG. 5, the first sensor VR
E+ The second sensor VRE2 is shown in cross section, but the third sensor VREa is not shown. 77 is the central shaft to which the main shaft 78 to be detected is attached, and the gear 81 is attached thereto.
is provided, and a first sensor VRE+ is attached coaxially. Gears 82 and 83 are provided on the rotating shaft 79 of the second sensor VREz, and the gear 82 is connected to the gear 8.
It meshes with 1.

The gear 83 meshes with the gear 84 of the third sensor VRE3, as shown in FIG. The number of teeth of each gear 81 to 84 is ll-1, n, n+1°n as in FIG. 4. 90.
91 is the bearing, 92.93 is each/? VRE1, VRE
z stator core, 94.95 are VRE+ and VR respectively
This is the E2 rotor core.

Primary coils 100A-100D and secondary coils 102A-102D are formed in each type A-D.

The rotor 94 is, for example, an eccentric rotor, and has a shape that changes various types of slip roughtance depending on the rotation angle.

Exciting the primary coils 100A and 100C of one of the poles A, C and B and D, which are paired in the diametrical direction, with a sine wave signal,
When the other primary coils 100B and 100D are excited with a cosine wave signal, the combined output Y of the secondary coils 102A to 1020
1, the following signal is obtained. Other encoders VRE
2°VRFa has a similar structure, and the secondary output Y2. Y3
The following signal is obtained.

θ1. θ2, 03 is the rotation angle of the rotation shaft 106, 79, 107 of each sensor VRE+ to VREa, and outputs Y+, Y2 . Y3 is brought forward respectively.

Therefore, these output signals Y+.

Y2. 1 in Y3. ll phase shift θ1. θ2. By measuring θ3, absolute value data D+, D2 . Da is determined respectively.

Next, the configuration and function of the X-axis servo amplifier 28 that drives the X-axis brushless morph 22 will be explained with reference to the block shown in FIG.

In the figure, 121 is a power supply circuit which receives power supply voltage Vp from the outside and supplies power supply VS for the entire servo amplifier 28 and drive power supplies +Vc and -Vc for the brushless morph 22;
122 is a speed amplifier that manually amplifies the rotational speed control signal bx from the brushless morph control device 26 outputting from the X axis;
25 is an amplifier that outputs a rotational speed belief that controls the rotational speed of the brushless morph 22 to be constant based on the output of the speed amplifier 123 and the value of the current actually flowing through the brushless morph 22 detected by the current detector 127; 129 encourages the polarity of the rotation speed signal! 1 current cut I9! 131 is a PWM circuit that modulates the rotation speed signal giving the rotation speed of the brushless motor 22 into a pulse width; 133° 135 is a PMW circuit 131
1 and 2, respectively, represent pace driver circuits on the forward rotation side and the reverse rotation side, which switch the forward rotation and reverse rotation power transistors (not shown) of the power unit 137 in response to the output of the power unit 137.

Since the operation of the PWM circuit 131 is well known, it will be briefly explained. FIG. 9 shows the relationship between the rotation speed signal bx input to the servo amplifier 28 and the current output actually output to the brushless motor 22, but the brushless morph control device M26 is not shown in the diagram. When an analog signal specifying the rotational speed of the brushless motor 22 is output, a current ratio IC with a pulse width corresponding to the magnitude of the analog signal is applied to the brushless motor 22 by the function of the WM circuit 131. . Since pulse width modulation operates the output transistor of the power unit 137 in the saturation region, losses such as heat generation are small, the circuit can be simplified and miniaturized, and high reliability is also achieved. In FIG. 9, [ indicates a so-called dead zone, which is a region where a pulse output for driving the brushless motor 22 is not output even if the actual speed of the brushless motor 22 differs from the target speed. In general, the narrower the dead zone f, the better the positioning accuracy will be, but if it is too narrow, control tends to become unstable, such as hunting or the like due to poor response of the control system. Therefore, the width is adjusted to an appropriate width based on the accuracy required for a robot's three-axis control device and the stability of the control system.

Above, absolute encoder 24, servo amplifier 2
8 has been explained in detail, but next, 3. of the robot shown in FIG. 3 has been explained in detail. Of the configuration of the axis-based TA11 device, the post computer 20. Brushless morph control wave @26. Servo amplifier 28. The part that controls the positioning of the X-axis, which is comprised of the brushless motor 22 and the absolute encoder 24, will be explained using the block diagram shown in FIG.

200 is the target position given from the host computer 20 and the signal D1.200 inputted from the absolute encoder 24. Dz and D3 are input and these data are operated to drive the servo amplifier 28 to a read-on memory (ROM) in which -9 etc. are stored, and 204 is a read/write random access memory (ROM) which temporarily stores data etc. RAM
), 206 are registers with multiple pins 1 to 2 for the CPU 200 to exchange data with the host computer 20.
08 is a clock generation circuit that oscillates at a stabilized frequency; 210 is a 10-bit counter that counts the clock generated by the clock generation circuit 208; and 212 is a function generator 214. latch 216,
218. Outputs to 220, 10 pins 1~ parallel bus, 222 is the three sensors VRE+ of the absolute encoder 24.

VR [E2. (7) Output signals D+, Dz from VREa.

224 is a digital output circuit that outputs excitation current switching signal aX; 226 is D that outputs rotational speed control signal bx;
/A conversion output horn circuit, 228 is CPU200. ROM2
02. RAM204. Latch circuits 216, 218, 22
0. Each represents a data bus connecting the digital output circuit 224.0/A conversion output circuit to phase n.

The function generator 214 has a built-in sine wave generator 214a and a cosine wave generator 2141), receives 10-bit parallel data from the counter 210 via the parallel bus 212, and outputs the IUs O to 1024 to O. A sine wave and a cosine wave are respectively output as ~2π. The sine wave signal output from the sine wave generating circuit 214a is t? of 3') in the absolute encoder 24. /suVRj+ ,VR[
E 2 , each primary coil LS+ of VRE a, Is
2. It is configured to be applied to Ls3. Primary coil LS+, l.

S2. LSa is the primary coil 100A in Fig. 7,
It corresponds to 100C. Moreover, the cosine wave generation circuit 214b
Similarly, the cosine wave signal output from the primary coil Let,
LCz, LCa (primary carp in Figure 7/1,100B, 1
4M is applied so that it is applied to the voltage (equivalent to 00D). As a result, as explained using FIG. 7, three sensors VRE+, VRE2. Each secondary coil L+ of VREB
2.122゜12g (Figure 17 (7) Secondary coil 102A
, 102B.

1020.102D), a voltage is generated depending on the position of the rotor 94, and the combined output signals Y+, Y2.
Since Y:l is output according to equation (5), the three voltage comparison circuits 222a in the timing output generation circuit 222
, 222b, 222c are combined output signals Y+, Y2
．． Y9 respectively) and compare the reference voltages, the three sensors VRE+, VRE2 . VREa (7
) Rotation angle θ1 of rotation axis 106, 79°107. θ2.
A latch signal is generated at a timing corresponding to θ3. When the output of the counter 210 is stored in each latch circuit 216, 218, 220 using this latch signal, the data stored in the latch circuits 216, 218, 220 (the count (direct) of the counter 210 is
+, VR[E2. VREa output signals D+, D2.
Since this means DB, the CPU 200 can calculate and detect the rotational position of the brushless motor 22 over 1024 rotations by using these data and applying equations (1) to (4).

Next, the CPU which is executed in the positioning control system around the X-axis of the robot 3-axis control device configured as above.
The processing and control of 200 will be explained using the flowchart of FIG.

When the brushless motor control device 26 is powered on, it starts processing from FIG.
0 is executed to clear the internal registers of the CPU 200, initialize the registers 206, etc. When the brushless mode control device 26 is powered on, the low clock generation circuit 208 generates a clock, and the counter 210 . The function generator 214 and the timing generation circuit 222 operate in synchronization with the clock to repeatedly latch data in the latch circuits 216, 218, and 220 at predetermined timings.

Step 300 follows initialization processing in step 290
, 310, 320, the latch circuits 216, 218, 2
20 represents the rotational position of the brushless motor 22, and a process is performed in which signals are read as data DI and D2°DB. Data D+ read in steps 300, 310, and 320.

D2. Using the DB, in step 330, the brushless [
A process is performed to calculate the rotational position of the control device 22, that is, the absolute position La over multiple rotations of its main shaft (here, 1024 rotations if n = 32).This calculation is performed using the above-mentioned formula ( 1) to (5) are used. In step 330, the absolute position La of the main shaft of the brushless motor 22 determined by the calculation is stored in a predetermined area of the RAM 204, and then the process proceeds to step 340, where the previous step 330 is used. The absolute position obtained when processing , the difference between the previous time (referred to as lIILa-1) and the absolute value La obtained in the immediately preceding step 330, and the interval at which this control routine is repeatedly executed (a predetermined time t) ), a process for calculating the rotational speed vr of the brushless motor 22 is performed.

That is, vr=kx(La −La−1) where k is a constant
The rotational speed Vl' can be set by /l. In this step 340, after setting vr, the previous absolute position 1 a-+
A process of updating 1a-+ = 1a and a process of storing the rotational speed vr in a predetermined area of the RAM 204 are also performed. Step 350 following step 340
Then, processing for determining the absolute position Ra of the rotor of the brushless motor 22 is performed. This process is performed by brushless motor 2.
The rotation axis of sensor VRE+ also rotates 1 for each rotation of the main axis of 2.
Since the rotor rotates, the output of the sensor VRIE+ (which can be directly determined from the data D1 obtained from the It is determined whether or not it is necessary to switch the direction of the drive current of the brushless motor 22 from the absolute position Ra of the motor. It uses a mechanism that continuously rotates the rotor, reversing the IJ direction of the flowing current one after another, and in other words, reversing the polarity of the generated magnetic field. If the absolute position of the rotor determined in step 350 is at a position where it is necessary to switch the direction of the drive current, the process proceeds to step 370, where the rotor is output via the digital output circuit 224. A process of reversing the output aX is performed. As a result, the direction of the drive current of the brushless motor 22 is reversed by the movement of the excitation current switching circuit 129 of the servo amplifier 28 described above.On the other hand, the determination at step 360 is rNOJ. If so, the process skips step 370 and proceeds to step 380. In step 380, a process is performed to read the target rotational position LII of the brushless motor 22 from the host computer via the register 206. 20, the latest rotational position of the brushless motor 22 corresponding to the position to be realized by the X-axis as a three-axis control device of the robot is constantly written as an absolute position.Continuing step 39
0, a process is performed to calculate the deviation value ΔL between the target position LIl read in step 380 and the current rotational position [La of the brushless motor 22 stored in a predetermined area of the RAM 204 in step 330. next.

In step 400, the deviation value ΔL obtained in step 390 is
and the current rotational speed V of the brushless motor 22 stored in the predetermined area of the RAM 204 determined in step 340.
From this, a process is performed to calculate the target rotational speed (2).

Various methods can be used to calculate the target rotational speed (■) performed here, but usually, as the actual position 1a approaches the target position [Lm, that is, as ΔL becomes smaller, the target rotational speed V is also reduced. Also, the target rotation speed ■ is the current rotation speed iv
r is held within a predetermined range, and the brushless motor 22 is configured to change its rotation speed without difficulty. In the subsequent step 410, a process is performed in which a rotational speed control signal bx corresponding to the target rotational speed V determined in step 400 is output to the servo amplifier 28. The servo amplifier 28 receives the signal bx and controls the drive current of the brushless motor 22 by pulse width modulation as described above,
Control its rotation speed.

After executing step 410, the process returns to step 300 and performs the series of processes described above, from step 300 to step I! 110 is repeated to move the brushless motor 22 to the target position set by the controller 20.
The rotational position of will be gradually controlled. Also, above,
Although only the X-axis position i1i control of the robot's 3-axis control limb has been explained, similar control is performed for the other two axes, and the position on the 3 axes can be precisely controlled while being controlled by the host computer 20. are processed in a distributed manner.

In this embodiment configured as described above, the brushless motors 22, 32, 42 are provided with absolute encoders 24, 34, 44 for detecting the rotational position as an absolute position over multiple rotations. ~En・
The output t@ of the rotor 24, 34.44 is processed to switch the direction of the excitation current of the brushless motor 22, 32.42, control the rotational speed of the brushless motor 22, 32.42, and rotate it over multiple rotations. Position 1ilJ Ill is being carried out.

Therefore, there is no need to set the origin every time the robot starts operating or when the power is restored after a power outage.
In addition to improved operability, all the information necessary to control the brushless motor is detected by a single absolute encoder, which allows the device to be significantly smaller and smaller.
It can be simplified, and its reliability and safety are also improved. Furthermore, since the rotational speed can be changed by software, the speed of approach to the target position can be easily controlled, and the problem of interference with other objects in three-axis control, for example, can be solved. Further, in this embodiment, a so-called variable magnetic resistance type absolute encoder is used, and its vibration resistance and heat resistance are inferior. For example, 70°C to 10°C, which cannot normally be used with an optical Absoligo 1 encoder.
It operates without any problems even in the temperature ffJ range of 0''C.

Although this embodiment has been explained using a variable magnetic resistance type absolute encoder, any absolute encoder that can detect the absolute rotational position of the motor over multiple rotations may be used, such as an optical type or any other type. Similar models can also be used. A 16-type optical absolute encoder that outputs the absolute position as a multi-bit code can be easily connected to a CPU, and the configuration of the brushless motor control device can be simplified.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way (it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention.

[Effects of the Invention] As described in detail above, the brushless motor control device of the present invention detects the absolute position of the rotor over multiple rotations of the brushless motor, and adjusts the excitation current of the brushless motor based on the detected absolute position. , and controls the rotational speed and rotational position of the brushless motor.

Therefore, when controlling the rotational position over multiple rotations,
There is no need to perform processing such as resetting the origin each time, and the actual position can be immediately known and control can be executed, and various information necessary for controlling the brushless motor can be obtained from the detected absolute position and control can be performed. This has the excellent effect of making the brushless motor control device significantly smaller and simpler, and increasing its reliability and safety.As a result, costs can also be reduced. It also has secondary effects.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a conventional brushless motor control device for explaining the prior art, Fig. 2 is a basic configuration diagram of the present invention, and Fig. 3 is a schematic diagram of a three-axis control device for a robot according to an embodiment. 4 is an explanatory diagram showing the principle of the absolute encoder, FIG. 5 is a width direction view showing the structure of the absolute encoder, and FIG. 6 is a front view similarly seen from the gear mechanism side. Figure 7 is a cross-sectional view of the sensor VRE1 incorporated in the absolute encoder, Figure 8 is a block diagram showing the configuration of the servo amplifier, Figure 9 is a graph explaining pulse width modulation, and Figure 10 is a diagram of the robot of the example. FIG. 11 is a block diagram showing the X-axis control system of the three-axis control device, and is a flowchart showing an example of control in the embodiment. 22.32.42... Brushless motor 24.34.
44...Absolute encoder 26.36.46
...Brushless motor control device 28.38.48...
・Servo amplifier 131...PWM circuit 200-J-CP U 210...Counter 214...Function generator agent Patent attorney Tsutomu Sadachi and 1 other person Figure 1 Figure 4 @ 5 Figure 90 24 93 No. 6 Figure 7 RE7 2

Claims (1)

[Scope of Claims] Position control means for inputting a drive position signal corresponding to the position of a driven object driven by a brushless motor and controlling the amount of rotation of the brushless motor based on the drive position signal and a target position. a speed control means for inputting a speed signal corresponding to the rotational speed of the brushless motor and controlling the brushless motor to a target rotational speed based on the speed signal and the target speed; and one revolution of the rotor of the brushless motor. In a brushless motor IIJ all apparatus, the brushless motor IIJ all device includes: excitation a current switching means for inputting a rotor position signal corresponding to the absolute position of the brushless motor and switching the direction of the current flowing to the stator of the brushless motor; Absolute position detection means for detecting the absolute position of the rotor over a plurality of rotations; and from the detected absolute position of the rotor, generating the drive position signal and outputting it to the position control means, generating the speed signal. A brushless motor control device comprising: control signal output means for generating the rotor position signal and outputting it to the speed control means, and generating the rotor position signal and outputting it to the excitation current switching means.