JP2526855B2 - Brushless motor controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor control device, and more particularly to a brushless motor control device that detects and controls the absolute position of a brushless motor rotor over a plurality of rotations.

[Prior Art] In recent years, various automatic controls have been widely performed, for example, machine tools that perform automatic numerical control, so-called NC machine tools, robots, and the like have become widespread. In equipment, the method and accuracy of feeding and positioning the controlled object are always a problem in every process such as processing, assembly and inspection. In order to respond to this, a highly reliable electric motor (hereinafter referred to as a motor) that has high efficiency and low cost and is easy to handle such as controlling the rotation speed.
In addition, there is a need for a low-cost detector that can detect the position or speed of a motor or a controlled object driven by the motor with high accuracy and reliability.

As an easily controllable motor, its equivalent inductance is small, the inertia of the rotor (hereinafter also referred to as the rotor) is small, the linearity of the correlation between torque and rotation speed is good, and the rotation speed is wide. It is necessary to satisfy the requirement of being able to control, and recently, DC drive coreless motors and brushless motors have been used. Among them, the brushless motor is, as its name suggests, excellent in durability and reliability without being a brush, and has features that it does not become a source of noise, so that it is widely used for precise control. However, since it is brushless, it is necessary to reverse the direction of the magnetic field excited by the current flowing through the fixed winding according to the position of the rotor that uses a permanent magnet. It is necessary to provide control to switch the direction of the exciting current depending on the position of the rotor that is detected.

On the other hand, various types of detectors for detecting the position and speed of the controlled object have been devised, but a well-known incremental encoder of the type that outputs a two-phase clock so as to detect forward / reverse rotation is the most popular. Widely used. An incremental encoder generates a pulse signal with a cycle that is synchronized with the rotation of the motor.Counting this number of pulses will detect the amount of rotation of the motor, but the amount of movement of the controlled object is the amount of rotation of the motor. As a result, the movement amount of the controlled object is detected. However, the incremental encoder only detects the amount of rotation of the motor and the amount of movement of the controlled object relative to each other, that is, as an amount from a certain reference point. It is possible to control the position only after performing a process such as resetting the origin or terminating the limit by, for example, sending the motor in a predetermined direction and hitting the limit switch when the system starts up. There wasn't. This means that the initialization process must be performed at each power failure, which is not preferable in terms of control safety. Also, when counting the output pulse of the incremental encoder, noise is added to the output pulse signal, or the rotation speed of the rotary shaft equipped with the incremental encoder is high, so the allowable response range of the incremental encoder or counter is temporarily increased. However, if it exceeds, it will cause an irrecoverable count mistake, which is a safety issue.

Further, considering the case of performing servo control using a brushless motor, as described above, in addition to the rotor position detector for switching the exciting current, a rotation speed detection means (tachogenerator) for detecting the rotation speed, Position (rotation amount)
There is a problem that an incremental encoder for detecting is required, and the detector has a complicated structure as shown in the schematic configuration of FIG. In the figure, 1
Is a brushless motor, 2 is a rotor position detector using a Hall element for detecting the position of a rotor (not shown) of the brushless motor 3, 3 is a tachogenerator for detecting the number of rotations of the rotor, and 4 is an incremental encoder. There is. Reference numeral 6 denotes a higher-level control device that commands a target position of a control target (not shown) according to a predetermined procedure. Reference numeral 8 denotes a position control means, which is a counter in which the target position of the control target instructed by the host controller 6 and the pulse signal from the incremental encoder 4 are accumulated.
The actual position of the controlled object detected by the output of 8a and the actual position of the controlled object are input to the amplifier 8b, and the target rotation speed of the brushless motor 1 is commanded. Reference numeral 10 denotes a speed control means, which inputs the target rotation speed instructed from the position control means 8 and the rotation speed (rotation speed) of the brushless motor 1 detected by the tachogenerator 3 to the amplifier 10a to make the brushless motor 1 The rotation speed control signal according to the current value to be output is output to the exciting current switching means 12. The excitation current switching means 12 responds to the output signal of the rotor position detector 2 in accordance with the polarity switching circuit 12a that inverts the polarity of the rotation speed control signal input from the speed control means and the rotor position of the brushless motor 1. It comprises a drive circuit 12b for inputting a rotation speed control signal whose polarity is switched, performing pulse width modulation (PWM), amplifying power, and then outputting a drive current to the brushless motor 1. Drive circuit 12b
Also detects the drive current to the brushless motor 1 and feeds it back to perform control such that a constant current output (constant output torque of the brushless motor) is obtained.

Although three types of detectors are used in the brushless motor control device configured as described above, the rotor rotation position detector 2 detects the absolute position of the rotor, and the tachogenerator 3 uses the analog voltage as the rotation speed. It is to be understood that a plurality of detectors having different meanings and formats of output are required, such as a type for detecting, and the incremental encoder 4 is a type which outputs two-phase pulses.

Providing a large number of detectors reduces the reliability of the device as a whole, and a servo controller using a resolver as a single detector has been proposed and implemented, but when a resolver is used, Since the motor control amount is detected as a phase difference, the phase locked loop (Phase Locked
Loop) control was proposed, and there was a problem that the control became complicated. Also, since the phase-locked loop using the output of the resolver is originally for speed control, if a signal for detecting the rotational position of the rotor or a signal equivalent to the incremental metal encoder is to be taken out, the configuration becomes extremely complicated. There was also a problem that high reliability could not be expected.

[Object of the Invention] The present invention has been made in view of the above points, and an object thereof is to provide a brushless motor control device having a simple detector configuration and high reliability.

[Configuration of the Invention] The configuration of the present invention made to achieve such an object is as follows:
As shown in FIG. 2, the drive position signal corresponding to the position of the driven object M2 driven by the brushless motor M1 is input, and the rotation amount of the brushless motor M1 is calculated based on the drive position signal and the target position. Position control means M3 for controlling and speed control means M4 for inputting a speed signal corresponding to the rotation speed of the brushless motor M1 and controlling the brushless motor M1 to the target rotation speed based on the speed signal and the target speed.
And a rotor position signal corresponding to the absolute position of the brushless motor M1 within one revolution of the rotor.
Excitation current switching means M5 for switching the direction of current flowing to the stator of M1, and a control signal output for detecting the rotation state of the brushless motor M1 and outputting the drive position signal, the speed signal, and the rotor position signal. In the brushless motor control device including the means M6, the control signal output means outputs the detection signal representing the absolute position of the rotor of the brushless motor M1 in accordance with the rotation position of the rotor. A position signal generating means M62 for generating the drive position signal from the absolute position of the rotor detected based on the detection signal from the absolute position detecting means M61, and the speed signal from the absolute position of the rotor. A brushless motor controller comprising: speed signal generating means M63; and rotor signal generating means M64 for generating the rotor position signal from the absolute position of the rotor. It is the gist of the apparatus.

[Operation] In the brushless motor control device of the present invention configured as described above, when the absolute position detection unit outputs a detection signal indicating the absolute position of the rotor of the brushless motor, the absolute position detection unit outputs the detection signal. The position signal generating means, the speed signal generating means, and the rotor signal generating means respectively generate three control signals necessary for controlling the brushless motor from the absolute position of the rotor detected based on the detection signals. That is, the position signal generation means generates a drive position signal corresponding to the position of the driven object driven by the brushless motor from the absolute position of the rotor, and the speed signal generation means generates the drive position signal of the brushless motor from the absolute position of the rotor. A speed signal corresponding to the rotation speed is generated, and the rotor signal generation means generates a rotor position signal for controlling the switching of the direction of the electric current supplied to the stator of the brushless motor from the absolute position of the rotor.

The position control means controls the rotation amount of the brushless motor based on the drive position signal generated by the position signal generation means and the target position, and the speed control means controls the rotation speed signal generated by the speed signal generation means. , The target rotation speed of the brushless motor is controlled based on the target rotation speed, and the excitation current switching means further supplies a current to the stator of the brushless motor based on the rotor position signal generated by the rotor signal generation means. The direction of is switched and controlled.

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

FIG. 3 is a block diagram showing a schematic configuration of the embodiment.
Here, as an example, a three-axis control device of a robot that performs three-axis control of XYZ will be taken up. In the figure, 20 is a host computer that controls the position of all three axes, 22 is an X-axis brushless motor, 24 is an absolute encoder that detects the absolute position of the brushless motor 22 over a plurality of revolutions, and 26 is an absolute encoder 24. The brushless motor control device for the X-axis, which takes in the output and outputs the excitation current switching signal ax and the rotation speed control signal bx to the servo amplifier 28, is shown. The Y-axis and Z-axis are also provided with exactly the same configuration, that is, 32 is a brushless motor for the Y-axis, 34 is an absolute encoder that detects the absolute position of the brushless motor 32 over a plurality of revolutions, and 36 is A brushless motor controller for the Y axis that takes in the output of the absolute encoder 34 and outputs an exciting current switching signal ay and a rotation speed control signal by to the servo amplifier 38, 42 is a brushless motor for Z axis, and 44 is a brushless motor 42. Absolute encoder that detects the absolute position of the encoder over multiple revolutions, 46 is a brushless motor controller for the Z axis that takes in the output of the absolute encoder 44 and outputs the excitation current switching signal az and the rotation speed control signal bz to the servo amplifier 48. Respectively. Each brushless motor controller 2
6, 36, 46 are configured to exchange data with the host computer 20 and control brushless motors 22, 32, 42 for each axis in accordance with commands from the host computer 20.

Since the configuration of each axis is the same, the following description will deal with the three axes as a representative of the X-axis device, if necessary.

Next, regarding each part constituting the three-axis control device of the robot of the embodiment, the absolute encoder 24 (34, 44),
Servo amplifier 28 (38,48), brushless motor controller 2
It will be explained in order of 6 (36, 46).

First, the principle of absolute position detection using the absolute encoder 24 and the structure of the absolute encoder 24 will be described with reference to FIGS. 4 to 7. FIG. 4 shows the conceptual configuration of the absolute encoder 24. The absolute encoder 24 is composed of three rotary encoders RE ₁ , RE ₂ , RE ₃ and gears that transmit the rotation of these rotary encoders. . Each of the rotary encoders RE ₁ , RE ₂ and RE ₃ divides one rotation into N and outputs a signal representing the rotational position of an internal rotary not shown in the drawing by an absolute position within one rotation. First rotary encoder
RE ₁ is connected to the spindle and detects the rotation of the spindle. The rotation to be detected is given from this main axis. The rotary shaft of the first rotary encoder RE ₁ is provided with a gear 51 having a number of teeth n−1 (where n is an arbitrary integer), and the gear 51 is provided on the rotary shaft of the _second rotary encoder RE _2. It meshes with a gear 52 having a number of teeth n. Further, the second encoder RE ₂ is provided with a gear 53 having a number of teeth n + 1, and this gear 53 meshes with a gear 54 having a number of teeth n provided on the rotation shaft of the third encoder RE ₃ .

Therefore, the main shaft is rotated 1, RE ₁ is one rotation, RE ₂ is (n-1) / n rotation, RE ₃ is (n-1) (n + 1) / n 2 rotates. Here, the rotational position (absolute position within one rotation) detected by each of the encoders RE ₁ , RE ₂ , RE ₃ is D ₁ , respectively.
Assuming D ₂ and D ₃ , the value of D ₁ when the main shaft makes one rotation is N, and D ₂ and D ₃ are as follows.

D ₁ = N In other words, the output D ₁ to D ₃ of each encoder RE ₁ to Re ₃ is
The main spindle mechanical displacement (rotational displacement over multiple rotations from the origin) changes in a predetermined cycle, and the main spindle mechanical displacement amount (rotation angle less than one rotation or more) corresponding to each cycle is The encoders RE ₁ , RE ₂ , and RE ₃ are different. That is, the mechanical displacement amount of the main shaft corresponding to one cycle of the first encoder RE ₁ , that is, the rotation angle is 2
Although it is π radians (that is, one rotation), the mechanical displacement amount of the main shaft, that is, the rotation angle corresponding to one cycle of the second encoder RE ₂ is 2π × n / (n−1) radians (that is, (n−
1) / n rotation), the mechanical displacement of the main shaft corresponding to one cycle of the third encoder RE ₃ , that is, the rotation angle is 2π × n ² /
(N-1) (n + 1) radians (that is, (n-1) (n
+1) / n ² rotations).

That is, each output signal D _{1 to} D ₃ always shows a value less than one cycle, but the mechanical displacement amount (rotation angle) of the main shaft corresponding to one cycle of each output signal D ₁ , D ₂ , D ₃ is respectively. Since they are different, the value of each output signal D ₁ , D ₂ , D ₃ represents a unique combination corresponding to the respective absolute position of the spindle. Specifically, how many rotations the output signal D _{1 of} the first encoder RE ₁ corresponding to the rotation of the main shaft corresponds from the origin (hereinafter, referred to as the number of cycles of D _1). ) Is uniquely determined by the unique combination of the values of each output signal D ₁ , D ₂ , D ₃ . In this decision, of course, not only the current value of the signal _{D 1, D 2, D 3} , the signal D ₁ that caused give rise to differences in each of these signals _{D 1, D 2, D 3} , Information related to the mechanical displacement of the spindle (or their difference) corresponding to one cycle of D ₂ and D ₃ respectively is also involved. The first encoder RE ₁ thus determined
The absolute position of the main axis can be specified by the combination of the number of cycles of the output signal D ₁ and the current value of the signal D ₁ .

The first number of periods of the output signal D ₁ of the encoder RE ₁ includes a current value of each signals D _1, D _2, D _3, of the signals D _1, D _2, the principal axis respectively corresponding to one period of the D ₃ It can be determined by an algebraic or mathematical method using information related to the amount of mechanical displacement (that is, information related to the degree of transmission of the mechanical interlocking of the main shaft to each encoder RE _{1 to} RE ₃ ). There are various possible calculation means for that purpose. Among them, the most efficient method in terms of calculation time and calculation circuit configuration is shown below. The rotary encoders RE ₁ , RE ₂ and RE ₃ can detect the absolute position by dividing one rotation of each rotor into N, and the number of teeth of the gears that connect the rotary encoders RE ₁ , RE ₂ and RE ₃ to each other is each n-1, n, since it is n + 1, one rotation of the brushless motor spindle, i.e. the rotary encoder RE ₁ per revolution of | D ₁ -D ₂ | variation of the n / n. Therefore, the output signal D ₁ and the rotary encoder RE output signal D ₂ the difference of the deviation value D _{1 2} of _{2 (D 1 2 = D 1} -D 2) of the rotary encoder RE _1, the number of cycles of the main shaft counted from the origin If (rotation number) is Rx, it can be calculated as Rx = D _{1 2} × n / N (2). Here, the origin is a position where the outputs D ₁ , D ₂ and D _{3 of the} rotary encoders RE ₁ , RE ₂ and RE ₃ are all zero.

As is clear from the formula (2), when the rotational speed Rx of the main spindle becomes n, the positional relationship between the rotary encoder RE ₁ and the other rotary encoder RE ₂ returns to the original position,
With only two rotary encoders, the absolute position can be detected over a plurality of rotations only at most n rotations.
Therefore, the detection range is further expanded by using the output signal D ₃ of the third rotary encoder RE ₃ .

That is, the deviation value a difference between the output signal D ₁ and the output signal D ₃ of the rotary encoder RE ₃ of the rotary encoder _{RE 1 D 1 3 = D 1} -
D ₃ ), the amount of change in the deviation value D _{1 3} per revolution of the spindle will be N / n ² , so if the rotation speed of the spindle from the origin exceeds Rx, the precision will be Rx. The absolute rotational speed Rx · ab ′ of the main axis from is calculated as Rx · ab ′ = D _{1 3} × n ² / N (3). If the value obtained by dividing the deviation value D _{1 3} by N / n is Ry (Ry = D _{1 3} × n / N), the absolute rotational speed of the spindle will eventually be Rx ・ ab
Is expressed as Rx · ab = n × Ry + Rx (4) The output signal D ₁ of the rotary encoder RE ₁ is added to this to represent the absolute position of the spindle over a plurality of revolutions. By taking into account the output D ₃ of the third rotary encoder RE ₃ , the detection range of the absolute position of the spindle is expanded from the origin to n ² rotations, as shown in the equation (3).

As described above, one method of detecting the rotational position of the main shaft of the brushless motor 22 by the absolute encoder 24 over a plurality of rotations has been shown. As an example, the number of divisions N per rotation of the rotary encoders RE ₁ , RE ₂ , RE ₃ is N. Is 1024, and an absolute encoder having 32 gear teeth for transmitting rotation to each of the rotary encoders RE ₁ , RE ₂ , and RE ₃ is taken, and an absolute encoder having such a configuration has 1024 minutes per rotation. It is possible to detect the absolute position of the spindle from the origin to the range of 1024 rotations with the accuracy of one rotation.

In the above description, the first and second rotary encoders RE ₁ , RE ₂
Between RE ₂ and RE ₃ , the speed is reduced at a ratio of "n-1 to n", and between RE ₂ and RE ₃ , the speed is increased at a ratio of "n + 1 to n".
_{Between 1} and RE _2, the speed is increased by the ratio of "n to n-1", and RE ₂ and R
Between E ₃ may be decelerated at a ratio of "n: n + 1". Even if the arithmetic expressions in that case are not exactly the same as the expressions (1) to (4), they can be easily derived in the same manner as those, and therefore the description thereof is omitted here. Further, the increase / decrease ratio among the encoders RE ₁ , RE ₂ and RE ₃ may be set to “n−a to n” or “n + a to n” instead of “n−1 to n” or “n + 1 to n”. Good. However, a is sufficiently smaller than n and is a divisor of n.

Next, the absolute encoder 24 used in this embodiment
The mechanical structure of will be described with reference to FIGS. 5, 6, and 7. FIG. 5 is an axial sectional view showing the structure of an absolute encoder equipped with the sensors VRE ₁ , VRE ₂ , and VRE ₃ , FIG. 6 is a schematic front view of the absolute encoder as seen from the gear mechanism side, and FIG. 7 is FIG. 5 is a cross-sectional view of _one sensor VRE ₁ . Here, the sensors VRE ₁ , VRE ₂ and VRE ₃ are respectively the fourth
It corresponds to the rotary encoders RE ₁ , RE ₂ and RE ₃ shown in the figure. In FIG. 5, the first sensor VRE ₁ and the second sensor VRE ₂ are shown in section, but the third sensor VRE ₃ is not shown. Reference numeral 77 is a central shaft to which the main shaft 78 to be detected is mounted, and a gear 81 is provided there, and the first shaft is coaxially arranged.
The sensor VRE _{1 of} is installed. Gears 82 and 83 are provided on the rotary shaft 79 of the second sensor VRE ₂ , and the gear 82 meshes with the gear 81. The gear 83 is the third as shown in FIG.
It meshes with the gear 84 of the sensor VRE ₃ . The number of teeth of each gear 81 to 84 is n-1, n, n + 1, n as in FIG. 90,91 are bearings, 92,93 are VRE ₁ and VRE ₂ stator cores, 94,95
Are VRE ₁ and VRE ₂ rotor cores, respectively.

As shown in FIG. 7, the sensor VRE ₁ has a plurality of poles A, B, C and D on the stator 92, and the primary coil 1 is provided on each pole A to D.
00A to 100D and secondary coils 102A to 102D are formed. The rotor 94 is, for example, an eccentric rotor, and has a shape that changes the reluctance of each pole according to the rotation angle. One of poles A, C and B, D that are diametrically paired
When the secondary coils 100A and 100C are excited with a sine wave signal and the other primary coils 100B and 100D are excited with a cosine wave signal, the following signal is obtained as a composite output Y ₁ of the secondary coils 102A to 102D. The other encoders VRE ₂ and VRE ₃ have the same structure,
The following signals are obtained as the next outputs Y ₂ and Y ₃ .

θ _1, θ _2, θ ₃ is the axis of rotation of the sensor VRE ₁ ~VRE ₃ 106,7
The rotation angles are 9,107, and the outputs Y ₁ and Y are obtained by phase-shifting the reference AC signal sinwt by the phase angle corresponding to each rotation angle.
₂ and Y ₃ are obtained respectively. Therefore, these output signals Y ₁ , Y
Absolute data showing the rotational position within one rotation by measuring the phase shifts θ ₁ , θ ₂ , and θ ₃ at ₂ and Y ₃ , respectively.
D ₁ , D ₂ , and D ₃ are obtained respectively.

Next, the structure and operation of the X-axis servo amplifier 28 for driving the X-axis brushless motor 22 will be described with reference to the block shown in FIG. In the figure, 121 is a power supply circuit for supplying the power supply Vs of the servo amplifier 28 and the drive power supplies + Vc and −Vc of the brushless motor 22 by receiving a power supply voltage Vp from the outside, and 122 is a brushless motor control device 26 for the X axis The speed amplifier that inputs and amplifies the rotation speed control signal bx, 125 is the rotation speed of the brushless motor 22 from the output of the speed amplifier 122 and the value of the current actually flowing in the brushless motor 22 detected by the current detector 127. , 129 is a polarity switching circuit that inverts the polarity of the rotation speed signal according to the excitation current switching signal ax, 131 is a rotation speed signal that gives the rotation speed of the brushless motor 22. PMW circuit that modulates to pulse width, 1
33 and 135 receive the output of the PMW circuit 131 and the power unit 137
The base driver circuits on the forward rotation side and the reverse rotation side, which switch power transistors for forward rotation and reverse rotation (not shown),
Respectively.

The operation of the PWM circuit 131 is well known and will be briefly described. 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, which is indicated by b from the brushless motor control device 26. When an analog signal designating the rotation speed of the brushless motor 22 is output, the PWM circuit 131 functions to provide the brushless motor 22 with a current output C having a pulse width corresponding to the magnitude of the analog signal. Since the pulse width modulation operates the output transistor of the power unit 137 in the saturation region, loss such as heat generation is small, the circuit can be simplified and downsized, and high reliability is realized. In FIG. 9, f indicates a region in which the pulse output for driving the brushless motor 22 is not output even if the actual speed of the brushless motor 22 and the target speed are deviated, that is, a so-called dead zone. Generally, the narrower the dead zone f, the higher the positioning accuracy. However, if the dead zone f is excessively narrow, the control tends to be unstable such that hunting may occur due to the response feed of the control system. Therefore,
The width is adjusted to an appropriate width based on the accuracy required for the robot three-axis control device and the stability of the control system.

Above, absolute encoder 24, servo amplifier 28
The detailed description was made for the host computer 2 in the configuration of the robot three-axis control device shown in FIG.
0, the brushless motor control device 26, the servo amplifier 28, the brushless motor 22, and the portion that controls the X-axis positioning control constituted by the absolute encoder 24 will be described with reference to the block diagram shown in FIG.

200 is a target position given from the host computer 20 and a signal D ₁ inputted from the absolute encoder 24,
A central processing unit (CPU) that inputs D ₂ and D ₃ and calculates these data to control the servo amplifier 28, and 202 is a read-on memory that stores control programs and initial data. (ROM), 204
Is a readable / writable random access memory (RAM) for temporarily storing data etc., 206 is a multi-bit register for the CPU 200 to exchange data with the host computer 20, and 208 is a clock generation that oscillates at a stabilized frequency. A circuit, 210 is a 10-bit counter for counting the clocks generated by the clock generation circuit 208, and 212 is a counter 210
The output of is output to the function generator 214 and the latches 216, 218, 220 1
0 bit parallel bus, 222 is output signal from _three sensors VRE ₁ , VRE ₂ and VRE ₃ of absolute encoder 24
Timing generation circuit for inputting D ₁ , D ₂ , D ₃ to generate a latch signal, 224 for digital output circuit for outputting excitation current switching signal ax, 226 for D / A conversion output circuit for outputting rotation speed control signal bx , 228 is CPU200, ROM202, RAM204, latch circuit 21
6,218,220, the digital output circuit 224, and the data bus interconnecting the D / A conversion output circuits are shown.

The function generator 214 includes a sine wave generator 214a and a cosine wave generator 2
14b is built in, 10-bit parallel data is received from the counter 210 via the parallel bus 212, and the value 0-1024 is set to 0-2 (pi) and a sine wave and a cosine wave are each output. The sine wave signal output from the sine wave generation circuit 214a is generated by the three sensors VR in the absolute encoder 24.
It is configured to be applied to the primary coils Ls ₁ , Ls ₂ , and Ls ₃ of E ₁ , VRE ₂ , and VRE ₃ , respectively. The primary coils Ls ₁ , Ls ₂ and Ls ₃ correspond to the primary coils 100A and 100C in FIG. Further, the cosine wave signal output from the cosine wave generating circuit 214b is similarly configured to be applied to the primary coils Lc ₁ , Lc ₂ , Lc ₃ (corresponding to the primary coils 100B and 100D in FIG. 7). There is. As a result, as described with reference to FIG. 7, the secondary coils L _{1 2} , L _{2 2} and L _{2 3 of the three} sensors VRE ₁ , VRE ₂ and VRE ₃ respectively.
A voltage is generated in the secondary coils 102A, 102B, 102C, and 102D in FIG. 7 according to the position of the rotor 94, and the combined output signals Y ₁ , Y ₂ , and Y ₃ are given by equation (5). Will be output according to
Three voltage comparison circuits 222 in the timing output generation circuit 222
The combined output signals Y ₁ , Y ₂ and Y ₃ are input to a, 222b and 222c, respectively,
By comparing with the reference voltage, the three sensors VRE ₁ ,
VRE ₂ and VRE ₃ rotation axes 106, 79 and 107 rotation angles θ ₁ , θ ₂ ,
The latch signal is generated at the timing according to θ ₃ . When the output of the counter 210 is stored in each latch circuit 216, 218, 220 by this latch signal, the latch circuit 216, 21
Data stored in 8,220 (count value of counter 210)
Are the output signals D ₁ , D ₂ , of the _three sensors VRE ₁ , VRE ₂ , VRE ₃ ,
Since this means D ₃ , the CPU 200 can calculate and detect the rotational position of the brushless motor 22 over 1024 rotations by applying the equations (1) to (4) using these data. .

Next, the processing and control of the CPU 200 performed in the X-axis positioning control system of the robot 3-axis control apparatus configured as described above will be described with reference to the flowchart of FIG.

The brushless motor control device 26
11 From the processing shown in FIG. A, the initialization step 290 is first executed to clear the internal register of the CPU 200 and the register 206.
Initialize and so on. When the brushless motor control device 26 is powered on, the clock generation circuit 208 generates a clock, and the counter 210, the function generator 214, and the timing generation circuit 222 are synchronized with the clock, and the latch circuits 216, 218, 220 at a predetermined timing. It works to repeat the operation of latching data. In steps 300, 310 and 320 subsequent to the initialization process in step 290, a signal representing the rotational position of the brushless motor 22 is output from the latch circuits 216, 218 and 220 as data D ₁ , D ₂ ,
The process of reading as D ₃ is performed. Step 300,310,
Using data D ₁ , D ₂ , and D ₃ read by 320, step 3
At 30, a process of calculating the rotational position of the brushless motor control device 22, that is, the absolute position La over a plurality of rotations of its main shaft (here, if n = 32, 1024 rotations) is performed. The above-mentioned equations (1) to (5) are used for this calculation. In step 330, after storing the absolute position La of the spindle of the brushless motor 22 obtained by the calculation in a predetermined area of the RAM 204, the process proceeds to step 340, and the absolute position obtained when the process of step 330 was performed last time (this The rotation speed vr of the brushless motor 22 is calculated from the difference between the previous value La ₋₁ ) and the absolute value La obtained in the immediately preceding step 330, and the interval (predetermined time t) at which this control routine is repeatedly executed. Calculation processing is performed. That is, with k as a constant, vr = k
The rotation speed vr can be obtained by × (La−La ₋₁ ) / t.
In this step 340, after obtaining vr, the previous absolute position La
_-1 update processing, ie, La _-1 = La processing and rotation speed vr
Is also stored in a predetermined area of the RAM 204.
In step 350, which follows step 340, the brushless motor
The process of obtaining the absolute position Ra of the rotor of 22 is performed. This processing can be directly obtained from the data D ₁ obtained from the output signal of the sensor VRE ₁ because the rotation axis of the sensor VRE ₁ also makes one rotation with respect to one rotation of the main shaft of the brushless motor 22. After obtaining the absolute position Ra of the rotor in step 350,
The process proceeds to step 360, where the current absolute rotor position Ra
Then, it is determined whether or not it is necessary to switch the direction of the drive current of the brushless motor 22. In the brushless motor 22, the direction of the current flowing through the stator winding is sequentially reversed with respect to the rotor (rotor) composed of permanent magnets, that is, the polarity of the magnetic field generated is reversed to continuously rotate the rotor. It has a mechanism to rotate it intentionally, and it is necessary to reverse the direction of the current supplied from the outside. Step 35
If the absolute position of the rotor obtained by 0 reaches the position where the direction of the drive current needs to be switched, the process is
Proceed to 370 and output its output via digital output circuit 224.
Is reversed. As a result, the direction of the drive current of the brushless motor 22 is reversed by the function of the exciting current switching circuit 129 of the servo amplifier 28 already described.
On the other hand, if the determination in step 360 is “NO”, step 370 is skipped and the process proceeds to step 380. In step 380, a process of reading the target rotation position Lm of the brushless motor 22 from the host computer via the register 206 is performed. Register 206 has host computer 20
More specifically, the latest rotational position of the brushless motor 22 corresponding to the position to be realized by the X axis as the three-axis control device of the robot is constantly written as the absolute position. Continued Step 39
At 0, the target position Lm read at step 380 and step 33
At 0, a process for obtaining a deviation value ΔL from the current rotational position La of the brushless motor 22 stored in a predetermined area of the RAM 204 is performed. At the next step 400, the deviation value ΔL obtained at step 390 and the current rotation speed vr of the brushless motor 22 stored in the predetermined area of the RAM 204 obtained at step 340.
Then, the processing for calculating the target rotation speed V is performed.
Various methods can be considered for the calculation of the target rotation speed V, but normally, the target rotation speed V is reduced as the actual position La approaches the target position Lm, that is, as ΔL becomes smaller, or The target rotation speed V is kept within a predetermined range of the current rotation speed vr, and the brushless motor 22 changes the rotation speed reasonably. In the following step 410, the target rotation speed V obtained in step 400
The process of outputting the rotation speed control signal bx corresponding to the servo amplifier 28 to the servo amplifier 28 is performed. The servo amplifier 28 receives the signal bx, controls the drive current of the brushless motor 22 by pulse width modulation as described above, and controls the rotation speed thereof.

After performing step 410, the process returns to step 300 to repeat the series of processes described above, steps 300 to 410.
By repeating the above, the rotational position of the brushless motor 22 is gradually controlled to the target position set by the host computer 20. Although only the X-axis position control of the robot three-axis control device has been described above, similar control is performed for the other two axes, and the host computer does not.
While being controlled by 20, precise control of position on the 3 axes is distributed and processed.

In the present embodiment configured as described above, the absolute encoder 24,3 that detects the rotational position of the brushless motor 22,32,42 as an absolute position over a plurality of rotations.
4,44, the output signals of the absolute encoders 24, 34, 44 are processed to switch the direction of the exciting current of the brushless motors 22, 32, 42 and control the rotation speed of the brushless motors 22, 32, 42 and its The rotation position is controlled over a plurality of rotations.

Therefore, it is not necessary to operate the origin setting one by one at the start of robot operation or when power is restored after a power failure, improving operability and providing all the information necessary for controlling the brushless motor in a single absolute. Since it is detected by the encoder, the device can be significantly downsized and simplified, and its reliability and safety are improved. Further, since the rotation 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, for example, three-axis control can be solved. In this embodiment, a so-called variable reluctance encoder is used as the absolute encoder, which is excellent in vibration resistance and heat resistance. For example, 70 ° C, which cannot normally be used with an optical absolute encoder
It operates without any problem even in the temperature range of ~ 100 ℃.

Although the variable reluctance type absolute encoder has been described in this embodiment, an optical encoder or any other absolute encoder capable of detecting the absolute position of the rotation of the motor over a plurality of rotations may be used. The same type can be used as well. The optical absolute encoder that outputs the absolute position with a code of multiple bits facilitates connection with the CPU and simplifies the configuration of the brushless motor control device.

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and it is needless to say that the present invention can be implemented in various modes without departing from the scope of the present invention.

[Effects of the Invention] As described in detail above, the brushless motor control device of the present invention detects only the absolute position of the rotor of the brushless motor, and controls the brushless motor from the detected absolute position of the rotor. Three necessary control signals, that is, a drive position signal, a speed signal, and a rotor position signal are generated, and the generated signals are used to switch the direction of the excitation current of the brushless motor and the rotation speed and rotation position of the brushless motor. Is controlled.

Therefore, according to the present invention, it is necessary to detect only the absolute position of the rotor by the single detecting means (absolute position detecting means) and control the brushless motor from the detected absolute position of the rotor. Since all the control signals are generated, the detection means can be greatly simplified compared to the conventional position in which the rotation state of the brushless motor is detected by a plurality of detection means, and the brushless motor is extended. The motor controller can be significantly downsized and simplified. Further, since the number of detecting means for detecting the state of the brushless motor is reduced, the device configuration is simplified and the wiring and the like are reduced, so that the reliability of the device can be improved. As a result, there is a secondary effect that the cost can be reduced.

Furthermore, according to the present invention, since the rotation state of the brushless motor is detected by a single detecting means, it is possible to obtain a high resolution in comparison with the space occupied by the detecting means. It is possible to obtain a highly accurate brushless motor control device even in a limited space. That is, in general, if an attempt is made to improve the resolution of the detection means, the detection means tends to increase in size. However, in the present invention, even if the detection means is increased in size to improve the resolution, only one detection means is provided. Therefore, as compared with an apparatus using a plurality of detecting means, the ratio of the occupied space of the detecting means to the increase in resolution is small.

Further, according to the present invention, since the absolute position detecting means detects the absolute position of the rotor of the brushless motor, no matter what position the rotor of the brushless motor is at the time of power-on or reset. Even if the rotor position is not mistakenly detected, safe and reliable control can be realized, and there is no need to perform rotor position adjustment processing such as origin reset and end limit, so control quickly. You can start.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a conventional brushless motor control device for explaining a conventional technique, FIG. 2 is a basic configuration diagram of the present invention, and FIG. 3 is a schematic configuration of a robot three-axis control device of an embodiment. 4 and 5 are explanatory views showing the principle of the absolute encoder, FIG. 5 is a sectional view in the width direction showing the structure of the absolute encoder, FIG. 6 is a front view of the same as seen from the gear mechanism side, and FIG. 7 is an absolute view. A cross-sectional view of the sensor VRE ₁ incorporated in the encoder, FIG. 8 is a block diagram showing the configuration of the servo amplifier, FIG. 9 is a graph for explaining pulse width modulation, and FIG. 10 is three-axis control of the robot of the embodiment. FIG. 11 is a block diagram showing an X-axis control system of the apparatus, and FIG. 11 is a flowchart showing an example of control of the embodiment. 22,32,42 …… Brushless motor 24,34,44 …… Absolute encoder 26,36,46 …… Brushless motor controller 28,38,48 …… Servo amplifier 131 …… PWM circuit 200 …… CPU 210 …… Counter 214 ... Function generator

Claims (1)

(57) [Claims] 1. 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 rotation speed of the brushless motor and controlling the brushless motor to the target rotation speed based on the speed signal and the target speed; Excitation current switching means for inputting the rotor position signal corresponding to the absolute position to switch the direction of the current flowing to the stator of the brushless motor, and detecting the rotation state of the brushless motor to detect the drive position signal and the speed. A control signal output means for outputting a signal and the rotor position signal, wherein the control signal output means is An absolute position detecting means for outputting a detection signal representing an absolute position of the rotor according to a rotational position of the rotor of the rackless motor; and an absolute position of the rotor detected based on a detection signal from the absolute position detecting means. Position signal generating means for generating a drive position signal, speed signal generating means for generating the speed signal from the absolute position of the rotor, and rotor signal generation for generating the rotor position signal from the absolute position of the rotor And a brushless motor control device.