JP6780855B2 - Servo actuator - Google Patents

Description

The present invention relates to a servo actuator.

In an actuator device in which a rotor pivotally supported rotatably and a stator that generates torque in the rotor are housed in a housing, a drive circuit that supplies a drive current to the stator and a control gain parameter given in advance are used. An actuator device is known in which a housing is provided with an arithmetic means for calculating a current command value given to a drive circuit (Patent Document 1).

A multi-pole magnet with a plurality of magnetic poles mounted coaxially with the rotation axis of the rotating body and arranged so as to face each of the multi-pole magnets, and detect a change in magnetic flux density according to the rotation of the multi-pole magnet. It is an absolute encoder equipped with a plurality of magnetic sensors, and each of the magnetic sensors outputs only one phase of A / B phase sinusoidal output having a phase difference of 90 degrees per number of magnetic poles according to the rotation of the multi-pole magnet. , A rotation detector, which is an absolute encoder in which the number of magnetic poles of a multi-pole magnet differs by only one pair, is also known (Patent Document 2).

JP-A-2002-199771 Japanese Unexamined Patent Publication No. 2012-08726

An object of the present invention is to provide a servo actuator capable of detecting the rotation position of a rotor with an absolute value while realizing high torque characteristics, and being compact and capable of saving wiring.

In order to solve the above problems, the servo actuator according to claim 1 is used.
A rotor with a permanent magnet field around the axis of rotation,
A stator having polar teeth arranged opposite to the permanent magnet field and arranged with a phase difference of 120 degrees, and a stator.
A coil connecting means in which a coil is provided on each pole tooth of the stator and is independently wired without connecting the phases.
A drive control unit that controls the rotation of the rotor by controlling the passing current of the coil independently by PWM (Pulse Width Modulation) switching.
The rotor sensor magnet attached eccentrically to the rotating shaft on the front end side opposite to the output shaft side of the rotor, and the drive control unit so as to face the rotor sensor magnet in the radial direction. A first rotation position sensor and a second rotation position sensor, which are arranged on a circle substantially concentric with the rotation axis with a first phase difference and detect the magnitude of the magnetic flux density, and the first rotation position sensor and It is arranged in the same direction as the second rotation position sensor by the second phase difference obtained by dividing the first phase difference by the number of magnetic poles of the rotor sensor magnet to detect the magnitude of the magnetic flux density. A rotation position detection unit composed of a third rotation position sensor and a fourth rotation position sensor, and detecting the rotation position of the rotor ,
A housing that integrally houses the drive control unit and the rotation position detection unit and rotatably supports the rotor around the rotation axis is provided.
It is characterized by that.

The invention according to claim 2 is the servo actuator according to claim 1 .
The rotation position of the rotor is detected based on the + sin signal output by the first rotation position sensor and the + cos signal output by the third rotation position sensor due to one rotation of the rotor sensor magnet . A sin signal obtained by adding a + sin signal output by the first rotation position sensor and a −sin signal output by the second rotation position sensor, a + cos signal output by the third rotation position sensor, and the first rotation position sensor. The absolute angle of one rotation of the rotor is calculated by detecting the rotation angle of the rotor based on the cos signal obtained by adding the −cos signals output by the rotation position sensor of 4 .
It is characterized by that.

According to the first aspect of the present invention, it is possible to provide a servo actuator that is compact and can save wiring while realizing high torque characteristics.

According to the second aspect of the present invention, it is possible to provide a low-cost, small-sized servo actuator capable of detecting a rotation position and a rotation angle of a rotor in a rotation direction and calculating an absolute rotation angle .

It is sectional drawing which shows the whole structure of the servo actuator which concerns on this embodiment. It is sectional drawing which shows the positional relationship of a rotor and a stator. (A) is a schematic cross-sectional view showing the configuration of the rotor and the sensor magnet, (b) is a schematic diagram showing the magnetic pole arrangement of the rotor, and (c) is a schematic diagram showing the magnetic pole arrangement of the sensor magnet. (A) is a schematic diagram showing the configuration of the control board, and (b) is a schematic diagram showing the arrangement of the sensor magnet and the first to fourth Hall elements. It is a schematic diagram which shows the positional relationship between a sensor magnet and the 1st to 4th Hall elements with rotation of a rotor shaft in a rotation position detection part. (A) is a schematic diagram showing the configuration of the rotation position detection unit, (b) is a characteristic curve diagram showing the waveform of the one-rotation absolute angle signal, and (c) is a characteristic curve diagram showing the waveform of the rotor shaft magnetic pole angle signal. is there. (A) is a schematic diagram showing the configuration of a power board, and (b) is a diagram showing the configuration of a coil drive circuit. It is a block diagram which shows the structure of a 1-chip microcomputer. (A) is a characteristic curve diagram showing a waveform of a one-turn absolute angle signal, and (b) is a characteristic curve diagram showing memory data. It is a flowchart which shows the flow of the process of calculating 1 rotation absolute angle. It is a figure which shows the structure of the feedback type trucking circuit for obtaining a rotation position from a rotor shaft magnetic pole angle signal. It is a timing chart which shows the transistor gate signal and the current command of a coil drive circuit. (A) is a diagram showing the relationship between the drive current and the torque ripple with respect to the current command in the servo actuator according to the present embodiment, and (b) is a diagram showing the relationship between the drive current and the torque ripple with respect to the current command in the servo actuator of the conventional example. is there.

Next, the present invention will be described in more detail with reference to the drawings below with reference to embodiments and specific examples, but the present invention is not limited to these embodiments and specific examples.
In addition, in the explanation using the following drawings, it should be noted that the drawings are schematic and the ratio of each dimension is different from the actual one, which is necessary for the explanation for easy understanding. Illustrations other than the members are omitted as appropriate.

(1) Overall configuration and operation of the servo actuator FIG. 1 is a schematic cross-sectional view showing the overall configuration of the servo actuator 1 according to the present embodiment, FIG. 2 is a schematic cross-sectional diagram showing the positional relationship between the rotor 11 and the stator 12, and FIG. (A) is a schematic cross-sectional view showing the configuration of the rotor 11 and the sensor magnet 231; (b) is a schematic diagram showing the magnetic pole arrangement of the rotor 11, and (c) is a schematic diagram showing the magnetic pole arrangement of the sensor magnet 231. 4A is a schematic diagram showing the configuration of the control board 210, FIG. 4B is a schematic diagram showing the arrangement of the sensor magnet 231 and the first to fourth Hall elements 232, and FIG. 5 is a rotation position detection unit. FIG. 6A is a schematic diagram showing the positional relationship between the sensor magnet 231 and the first to fourth Hall elements 232 accompanying the rotation of the rotor shaft 11a in 230, and FIG. 6A is a schematic diagram showing the configuration of the rotation position detection unit 230. , (B) is a characteristic curve diagram showing a waveform of a one-turn absolute angle signal, (c) is a characteristic curve diagram showing a waveform of a rotor shaft magnetic pole angle signal, and FIG. 7 (a) is a schematic diagram showing a configuration of a power substrate 220. , (B) is a diagram showing the configuration of the coil drive circuit 225.
Hereinafter, the overall configuration and operation of the servo actuator 1 will be described with reference to the drawings.

The servo actuator 1 includes a motor unit 10 that generates rotational torque, a control unit 20 that controls the rotation of the motor unit 10, and an output shaft 30 that outputs the rotational torque generated by the motor unit 10 without going through a speed reducer. , It is composed of a housing 40 that integrally accommodates these.

The motor unit 10 is provided with a rotor 11 as a rotor rotatably supported by rotary bearings 41 and 42 inside a housing 40 made of a conductive material such as metal (see FIG. 3A). .. As shown in FIG. 3B, the rotor 11 is formed by coaxially integrating a rotor magnet 11A, which is a permanent magnet magnetized in four poles, with a rotor shaft 11a.

Further, inside the housing 40, a stator 12 as a stator is arranged so as to surround the rotor 11. In the stator 12, six stator cores 12A to 12F having pole teeth 12a are fixed at equal intervals (60 degree intervals), and each of the stator cores 12A to 12F is wound and coil 13 (13A to 13F). ) Is formed.
Each of the stator cores 12A to 12F is divided in the circumferential direction thereof, and after the coils 13 are wound in an aligned manner on the outside, the stator 12 is formed by assembling the respective stator cores 12A to 12F (see FIG. 2). This enables high-density winding around the core and space saving of the servo actuator 1.

As a result, in the motor unit 10, the two coils 13A and 13D, 13B and 13E, 13C and 13F (three sets in total) facing 180 degrees are designated as U-phase, V-phase and W-phase, respectively, and these U-phase and V-phase are used. A drive current is applied to each of the phase and W phase coils 13 with a phase difference of 120 degrees to form a magnetic field, and a rotational torque of a magnitude corresponding to the current value of the drive current is generated via the rotor 11. It is designed to let you.

In the servo actuator 1 according to the present embodiment, the U-phase, V-phase, and W-phase coils 13 are independently wired without connecting the phases (hereinafter, referred to as a three-phase independent connection method). ) Is adopted, and the currents Iu, Iv, and Iw for each of the U-phase, V-phase, and W-phase coils 13 are controlled independently without mutual interference.

The control unit 20 is a control board 210 as a drive control unit that controls the rotation angle, rotation speed, rotation torque, etc. of the output shaft 30, and a power board that supplies a drive current to each coil 13 under the control of the control board 210. It is composed of 220 and a rotation position detection unit 230 that detects the absolute angle of one rotation and the position of the magnetic pole of the rotor 11, and is housed integrally with the motor unit 10 in the housing 40.

As shown in FIG. 4A, the control board 210 has a 1-chip microcomputer 211 mounted on one side of a printed wiring board formed in a rectangular shape in accordance with the housing 40, and a rotation position on the other side. It is configured by mounting the first to fourth Hall elements 232A, 232B, 232C, and 232D of the detection unit 230.

The rotation position detection unit 230 includes a sensor magnet 231 fixed to the front end side of the rotor shaft 11a opposite to the output shaft 30, and first to fourth Hall elements as rotation position sensors mounted on the control board 210. It is formed of 232A, 232B, 232C, and 232D.
As shown in FIG. 3C, the sensor magnet 231 is magnetized in the same four poles as the rotor magnet 11A of the rotor 11, and is eccentric to the rotor shaft 11a with a phase difference of 45 degrees from the rotor magnet 11A (eccentricity e). : It is fixed in the state shown in FIG. 4 (b)).

As shown in FIG. 4B, in the first to fourth Hall elements 232A, 232B, 232C, and 232D, the first Hall element 232A and the second Hall element 232B are 180 on a concentric circle with the rotor shaft 11a. The third Hall element 232C and the fourth Hall element 232D are positioned so as to be opposed to each other by 45 degrees in the same direction as the first to fourth Hall elements 232A, 232B, 232C, and 232D. It is mounted on the control board 210.

As described above, in the rotation position detection unit 230, since the sensor magnet 231 is fixed to the rotor shaft 11a in an eccentric state (eccentricity amount: e), when the rotor shaft 11a makes one rotation, it is shown in FIG. As described above, the distance between the sensor magnet 231 and the first to fourth Hall elements 232A, 232B, 232C, and 232D changes with the rotation of the rotor shaft 11a.
As a result, in the rotation position detection unit 230, the first to fourth Hall elements 232A, 232B, 232C, and 232D are arranged so that the rotational displacement of the rotor 11 is caused by the rotation of the sensor magnet 231 that rotates integrally with the rotor 11. It can be detected as a change in magnetic flux density at a position.

In the rotation position detection unit 230 shown in FIG. 6A, the rotational displacement of the rotor 11 is measured by the magnetic flux density Φ (the magnetic flux density Φ) at the arrangement positions of the first Hall element 232A and the third Hall element 232C accompanying the rotation of the rotor shaft 11a. It is detected as a change in θabs), and the detection results are used as the first and second absolute angle signals S1A and S1B of the waveforms given by SIN (θabs) and COS (θabs) as shown in FIG. 6B, respectively. It can be output.
Further, as shown in FIG. 6C, the outputs of the first Hall element 232A and the second Hall element 232B and the outputs of the third Hall element 232C and the fourth Hall element 232D are added, respectively. , 1st and 2nd rotor shaft pole angle signals S2A and S2B can be output.

Further, in the control board 210, the one-chip microcomputer 211 can communicate with the host device via the serial communication line via the host communication interface (I / F).

The one-chip microcomputer 211 includes the specified values of the rotation angle, rotation speed, or rotation torque of the output shaft 30 given by the host device (hereinafter, referred to as the designated rotation angle, the designated rotation speed, and the designated rotation torque, respectively), the first, and The second one-rotation absolute angle signals S1A and S1B, the first and second rotor shaft magnetic pole angle signals S2A and S2B, and the first to third drive current detection signals S3A to supplied from the power board 220 described later. Based on S3C, the current values of the drive currents to be applied to the U-phase, V-phase, and W-phase coils 13 (hereinafter referred to as the first to third current command values, respectively) are calculated, and these are calculated. The first to third current command values are sent to the power board 220.

As shown in FIG. 7A, a plurality of coil drive circuits 225 shown in FIG. 7B are formed on the power board 220 on one surface side of a printed wiring board formed rectangularly in accordance with the housing 40. The power FET 221 and the current detection resistor 222 of the above are mounted.
The power board 220 is a U-phase, V-phase, and W-phase coil 13 (13A to 13F) of the motor unit 10 based on the first to third current command values given by the one-chip microcomputer 211 of the control board 210. ), The rotor 11 of the motor unit 10 is rotationally driven by applying a drive current having a corresponding current value.

Further, the power substrate 220 detects the current value of the drive current applied to each of the U-phase, V-phase, and W-phase coils 13 by the current detection resistor 222, and the detection result is the first to third. The drive current detection signals S3A to S3C are sent to the control board 210.

In this way, in the servo actuator 1, the designated rotation angle, the designated rotation speed, or the designated rotation torque given by the host device by the control circuit including the one-chip microcomputer 211 of the control board 210 and the coil drive circuit 225 of the power board 220. The motor unit 10 is driven according to the above.

(2) Motor rotation control FIG. 8 is a block diagram showing the configuration of a one-chip microcomputer 211, FIG. 9 (a) is a characteristic curve diagram showing a waveform of an absolute angle signal of one rotation, and (b) is a characteristic curve diagram showing memory data. 10 is a flowchart showing the flow of processing for calculating the absolute angle of one rotation, FIG. 11 is a diagram showing the configuration of a feedback type trucking circuit for obtaining a rotation position from a rotor shaft magnetic pole angle signal, and FIG. 12 is a coil drive circuit. A diagram showing a timing chart showing a transistor gate signal of 225 and a current command, FIG. 13 (a) is a diagram showing the relationship between a drive current and a torque ripple with respect to a current command in the servo actuator 1, and FIG. 13 (b) is a conventional servo actuator. It is a figure which shows the relationship of the drive current and torque ripple with respect to a current command.
Hereinafter, the motor rotation control of the servo actuator 1 will be described with reference to the drawings.

As shown in FIG. 8, the one-chip microcomputer 211 includes a software servo unit 50, a rotor shaft position detection unit 51, a current control unit 52, a CPU, a ROM, a RAM, a register, and the like (not shown).
The current control unit 52 converts a current axis current command or a torque command into a current flowing through each phase coil 13 and controls the phase advance of each coil current with respect to the phase conversion-phase advance control unit 52A and each phase coil 13. A current command unit 52B that gives a command to flow the maximum current, and a PWM conversion unit 52C arranged for each coil so as to independently control the current of each coil based on the current command from the current command unit 52B. It is composed of.

(2.1) Rotor shaft position detection The rotor shaft position detection unit 51 digitally outputs the first and second absolute angle signals S1A and S1B output from the first Hall element 232A and the third Hall element 232C. The rotation position θabs of the rotor 11 is calculated from the first and second absolute angle data D1A and D1B obtained by conversion and stored in the register.

Since the sensor magnet 231 according to the present embodiment is magnetized to the same four poles as the rotor magnet 11A of the rotor 11 and is fixed in an eccentric state (eccentricity e: see FIG. 4) with respect to the rotor shaft 11a. When the rotor shaft 11a makes one rotation, the + SIN signals as the one-turn absolute angle signals S1A and S1B output from the first Hall element 232A and the third Hall element 232C arranged concentrically with the rotor shaft 11a (SIN (SIN). The magnitudes of the θabs)) and the + COS signal (COS (θabs)) change depending on the rotation angle of the rotor shaft 11a (see FIG. 9A).

The changing + SIN signal (SIN (θabs)) and + COS signal (COS (θabs)) are stored in advance in a memory (ROM: not shown) with respect to the rotation position (MSIN (θabs), MCOS (θabs): FIG. 9). By comparing with (see (b)), the rotation position θabs of the rotor 11 as one rotation absolute angle can be calculated.

The flowchart of FIG. 10 shows an example of a processing flow for calculating the rotation position θabs of the rotor 11 as one rotation absolute angle from the changing + SIN signal (SIN (θabs)) and + COS signal (COS (θabs)).
The one-chip microcomputer 211 detects SIN (θabs) and COS (θabs) output from the first Hall element 232A and the third Hall element 232C, and temporarily stores them in the RAM (S101).
Next, the data MSIN (θabs) and MCOS (θabs) of the rotation position θabs stored in the memory in advance are read out (S102) and compared with the detected SIN (θabs) and COS (θabs) (S103).

In step 103, when MSIN (θabs) and SIN (θabs) and MCOS (θabs) and COS (θabs) match (S103: Yes), the rotation position θabs of the rotor 11 is determined (S104).
In step 103, when MSIN (θabs) and SIN (θabs) and MCOS (θabs) and COS (θabs) do not match (S103: No), MSIN (θabs) and MCOS (θabs) with increased reference θabs are selected. It is read out (S105) and compared with the detected SIN (θabs) and COS (θabs) (S103). This process is repeated in step 103 until MSIN (θabs) and SIN (θabs) and MCOS (θabs) and COS (θabs) match (S103: Yes).

In this way, the rotation of the rotor 11 as one rotation absolute angle from the + SIN signal (SIN (θabs)) and + COS signal (COS (θabs)) output from the first Hall element 232A and the third Hall element 232C. The position θabs can be specified.

Here, θabs is one rotation angle from 0 to 2π (rad), and SIN (θabs) and COS (θabs) are the signals output from the first Hall element 232A and the third Hall element 232C in θabs. It is memory data whose size is digitally converted, and the resolution is determined by the resolution of an AD (analog-to-digital) converter. Specifically, when the AD converter has a resolution of 10 bits, 2π / 1024 has a resolution of θabs.

Further, the rotor shaft position detection unit 51 includes the output (+ SIN) of the first Hall element 232A, the output (-SIN) of the second Hall element 232B, the output (+ COS) of the third Hall element 232C, and the fourth. The first and second rotor axis magnetic pole angle signals S2A (SIN signal) and S2B (COS signal) obtained by adding the output (-COS) of the Hall element 232D of the above are digitally converted, and the first and second rotor shaft angle signals obtained are obtained. The rotor shaft pole angle data D2A and D2B of the above are input to the software servo unit 50 and the phase conversion-phase advance control unit 52A.

Since the sensor magnet 231 according to the present embodiment is fixed to the rotor shaft 11a in an eccentric state (eccentricity amount: e), when the rotor shaft 11a makes one rotation, the second Hall element 232B and the fourth Hall element 231 The Hall element 232D also outputs a −SIN signal and a −COS signal that change symmetrically with the + SIN signal and the + COS signal output from the first Hall element 232A and the third Hall element 232C, respectively.

Therefore, when the + SIN signal of the first Hall element 232A and the −SIN signal of the second Hall element 232B are added, the + COS signal of the third Hall element 232C and the −COS signal of the fourth Hall element 232D are added, respectively. , The change in the output signal due to the eccentric rotation can be canceled out to obtain the SIN signal and the COS signal (see FIG. 6C).

Then, the rotor shaft position detection unit 51 calculates the rotation position θm as the magnetic pole position of the rotor 11 based on the first and second rotor shaft pole angle data D2A and D2B, stores it in the register, and performs phase conversion-advance. It is sent to the phase control unit 52A.
The rotation position θm can be obtained by the feedback type tracking circuit shown in FIG. 11 as an example.

(2.2) The coil drive software servo unit 50 has the rotation position θabs as one rotation absolute angle of the rotor 11 stored in the register, the rotation position θm as the magnetic pole position of the rotor 11, and the designated rotation given by the host device. Based on the angle, the specified rotation speed, or the specified rotation torque, the target rotation torque (hereinafter referred to as the target rotation torque) T0 is calculated and stored in the register.

The phase conversion-phase advance control unit 52A has U-phase, V-phase, and W-phase coils based on the calculated target rotation torque T0 and the rotation position θm of the rotor 11 given by the rotor shaft position detection unit 51. The first to third current command values Iu-ref, Iv-ref, and Iw-ref, which represent the current values of the drive currents to be applied to 13, are calculated and sent to the current command unit 52B, respectively.

Further, the current control unit 52 receives the first to third drive currents obtained by digitally converting the first to third drive current detection signals S3A to S3C detected by the current detection resistor 222 of the coil drive circuit 225. Detection data D3A to D3C are given.

In this way, the current control unit 52 is based on the first to third current command values Iu-ref, Iv-ref, Iw-ref and the first to third drive current detection data D3A to D3C. PWM (Pulse Width Modulation) modulation is performed on the first to third current command values Iu-ref, Iv-ref, and Iw-ref, and the obtained first to third PWM signals S4A to S4C are used on the power board 220. It is sent to the coil drive circuit 225.

In the coil drive circuit 225, as shown in FIG. 7B, a circuit in which two transistors TR1 and TR2 are connected in opposite directions corresponding to each of the U-phase, V-phase, and W-phase coils 13 is used. Similarly, in a full bridge circuit including a circuit in which two transistors TR3 and TR4 are connected in opposite directions, an intermediate point between the transistors TR1 and TR2 and an intermediate point between the transistors TR3 and TR4 are connected by a U-phase coil 13. The V phase and the W phase are also configured by the same circuit.

As shown in FIG. 12, when the current command value Iu-ref is a positive value, the PWM pulse signal drives the base drive of the transistors TR1 and TR4, and the current command value Iu-ref is a negative value. At one time, the PWM pulse signal drives the base drive of the transistors TR2 and TR3.

As a result, in the coil drive circuit 225, the first to third PWM signals S4A to S4C are converted into drive currents Iu, Iv, and Iw for each of the U phase, V phase, and W phase, and these are supported respectively. It is designed to be applied to each of the U-phase, V-phase, and W-phase coils 13.

In the coil drive circuit 225, the magnitudes of the drive currents Iu, Iv, and Iw supplied to the U-phase, V-phase, and W-phase coils 13 are detected by the current detection resistors 222, and the detection results are obtained from the first to first. The drive current detection signals S3A to S3C of No. 3 are sent to the one-chip microcomputer 211.

The current control unit 52 gives a command to flow the maximum current to each of the U-phase, V-phase, and W-phase coils 13. Conventional 3-phase coil star-type or delta-type connection method In the coil connection method, the total current amount of U-phase, V-phase, and W-phase is zero (Kirchhoff's law), so the drive currents Iu, Iv, and Iw The maximum value is decided.
On the other hand, according to the three-phase independent connection method according to the present embodiment, since the coil current of each phase can be controlled independently, it is possible to give a current command to flow the maximum current to all the phases. As a result, a large current can flow on the current shaft during high-speed rotation.

Further, since such a three-phase independent connection method can be adopted to control each coil current independently, a current including harmonics can flow through the coils of each phase. FIG. 13 shows the relationship between the coil current waveform (U phase) and the motor torque according to the present embodiment in comparison with the conventional example (see FIG. 13B).
As shown in FIG. 13A, by configuring the coil 13 of the stator 12 in a three-phase independent wiring system, the harmonic current flowing due to the magnetic flux of the permanent magnet at the time of high-speed rotation is taken into consideration, and the coil 13 is harmonically tuned to each phase coil. A current including waves can be passed. That is, the correction torque can be generated by controlling the coil current, and the cogging torque and torque fluctuation caused by the magnetic distortion can be suppressed.

(3) Action / Effect of Servo Actuator In the servo actuator 1 according to the present embodiment, the U phase is used in the one-chip microcomputer 211 of the control board 210 based on the designated rotation angle, the designated rotation speed, or the designated rotation torque given by the host device. The current command values Iu-ref, Iv-ref, and Iw-ref of the drive currents Iu, Iv, and Iw to be applied to each of the V-phase and W-phase coils 13 are calculated, and the calculated current command values Iu-ref, The PWM signals S4A to S4C based on Iv-ref and Iw-ref are sent to the coil drive circuit 225 of the power board 220.
The coil drive circuit 225 generates drive currents Iu, Iv, and Iw based on the supplied PWM signals S4A to S4C, and applies these to the U-phase, V-phase, and W-phase coils 13 to rotate the rotor 11. Drive.
Then, the control board 210 and the power board 220 as the drive control unit for controlling the rotation of the rotor 11 are integrally housed inside the rotor 11, the stator 12 including the stator cores 12A to 12F and the coil 13, and the housing 40. Therefore, the amount of wiring to be connected to the outside can be reduced, and the wiring of the servo actuator 1 as a whole can be reduced.

Further, in the servo actuator 1, the rotation position detection unit 230 has a sensor magnet 231 fixed to the front end side of the rotor shaft 11a opposite to the output shaft 30, and first to fourth holes mounted on the control board 210. Formed from the elements 232A, 232B, 232C, and 232D, the sensor magnet 231 was magnetized to the same four poles as the rotor magnet 11A of the rotor 11 and eccentric to the rotor shaft 11a with a phase difference of 45 degrees from the rotor magnet 11A. It is fixed in the state.
In the first to fourth Hall elements 232A, 232B, 232C, and 232D, the first Hall element 232A and the second Hall element 232B face each other 180 degrees on a concentric circle with the rotor shaft 11a, and the third Hall element The 232C and the fourth Hall element 232D are mounted on the control board 210 so as to be located at positions shifted by 45 degrees in the same direction as the first to fourth Hall elements 232A, 232B, 232C, and 232D.

As a result, when the rotor shaft 11a makes one rotation, the + SIN signal (SIN (θabs)) and + COS signal (SIN (θabs)) and + COS signals output from the first Hall element 232A and the third Hall element 232C arranged concentrically with the rotor shaft 11a ( The size of COS (θabs)) changes depending on the rotation angle of the rotor shaft 11a.
One rotation by comparing the changing + SIN signal (SIN (θabs)) and + COS signal (COS (θabs)) with the values (MSIN (θabs), MCOS (θabs)) for the rotation position stored in the memory in advance. The rotation position θabs of the rotor 11 as an absolute angle can be calculated.

Further, when the + SIN signal of the first Hall element 232A and the −SIN signal of the second Hall element 232B, the + COS signal of the third Hall element 232C and the −COS signal of the fourth Hall element 232D are added, respectively, The SIN signal and the COS signal can be obtained by canceling the change in the output signal due to the eccentric rotation, and the rotation position θm as the magnetic pole position of the rotor 11 can be calculated.
This makes it possible to construct a servo actuator 1 provided with a rotation position detection unit 230 capable of detecting a small and inexpensive one rotation absolute angle.

In the servo actuator 1, each of the U-phase, V-phase, and W-phase coils 13 adopts a three-phase independent connection method in which the U-phase, V-phase, and W-phase coils are independently wired without connecting the phases. The currents Iu, Iv, and Iw with respect to the coil 13 are controlled independently without interfering with each other. Therefore, it is possible to give a current command to pass the maximum current to all phases. As a result, during high-speed rotation, a large current can flow on the current shaft, maximum torque can be generated, and miniaturization can be realized.
Further, in consideration of the harmonic current flowing due to the magnetic flux of the permanent magnet at the time of high-speed rotation, a current including harmonics can be passed through each phase coil 13, and correction by adding a harmonic component of magnetic flux which has not been used conventionally. It is possible to generate torque and suppress cogging torque and torque fluctuation caused by magnetic distortion.

Although the embodiments according to the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications are made within the scope of the gist of the present invention described in the claims. Is possible.

In the present embodiment, the case where the rotor magnet 11A is magnetized to 4 poles has been described, but the present invention is not limited to this, and for example, 8 poles or other poles may be magnetized. When the rotor magnet 11A is magnetized to 8 poles, the sensor magnet 231 also has the same number of 8 poles, and the Hall elements are arranged at 22.5 degrees to obtain a servo actuator with higher torque and less pulsation. be able to.

1 ... Servo actuator 10 ... Motor unit 11 ... Rotor 11A ... Rotor magnet 11a ... Rotor shaft 12 ... Stator 13 ... Coil 20 ... Control unit 210 ... Control Board 211 ... 1-chip microcomputer 220 ... Power board 221 ... Power FET
222 ... Current detection resistor 225 ... Coil drive circuit 230 ... Rotational position detector 231 ... Sensor magnet 232A, 232B, 232C, 232D ... Hall element 30 ... Output shaft 40 ...・ Housing

Claims (2)

A rotor with a permanent magnet field around the axis of rotation,
A stator having polar teeth arranged opposite to the permanent magnet field and arranged with a phase difference of 120 degrees, and a stator.
A coil connecting means in which a coil is provided on each pole tooth of the stator and is independently wired without connecting the phases.
A drive control unit that controls the rotation of the rotor by controlling the passing current of the coil independently by PWM (Pulse Width Modulation) switching.
The rotor sensor magnet attached eccentrically to the rotating shaft on the front end side opposite to the output shaft side of the rotor, and the drive control unit so as to face the rotor sensor magnet in the radial direction. A first rotation position sensor and a second rotation position sensor, which are arranged on a circle substantially concentric with the rotation axis with a first phase difference and detect the magnitude of the magnetic flux density, and the first rotation position sensor and It is arranged in the same direction as the second rotation position sensor by the second phase difference obtained by dividing the first phase difference by the number of magnetic poles of the rotor sensor magnet to detect the magnitude of the magnetic flux density. A rotation position detection unit composed of a third rotation position sensor and a fourth rotation position sensor, and detecting the rotation position of the rotor ,
A housing that integrally houses the drive control unit and the rotation position detection unit and rotatably supports the rotor around the rotation axis is provided.
Servo actuator characterized by that. The rotation position of the rotor is detected based on the + sin signal output by the first rotation position sensor and the + cos signal output by the third rotation position sensor due to one rotation of the rotor sensor magnet . A sin signal obtained by adding a + sin signal output by the first rotation position sensor and a −sin signal output by the second rotation position sensor, a + cos signal output by the third rotation position sensor, and the first rotation position sensor. The absolute angle of one rotation of the rotor is calculated by detecting the rotation angle of the rotor based on the cos signal obtained by adding the −cos signals output by the rotation position sensor of 4 .
The servo actuator according to claim 1.

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