JP4745838B2 - Control method and apparatus for electric actuator - Google Patents

Description

  The present invention relates to a control method and a control method for an electric actuator in which a stepping motor provided with an encoder is driven by a PWM (pulse width modulation) type power drive unit to operate the actuator.

  The electric actuator generally controls an AC servo motor or a stepping motor to drive the mechanical body. The AC servo motor drive is generally closed-loop vector current control, but has the disadvantage that current variation due to minute vibrations at the time of stoppage and speed-load fluctuation is large.

  In order to minimize the inductance of the motor coil as much as possible, there is a method of making the windings thicker. However, the input power increases and the current variation, which is also a drawback of the AC servo motor, causes the temperature margin of the device and the power supply outside the device. There are concerns about problems such as turbulence in the system.

  Compared to this, since the stepping motor has a large number of poles in structure, the stop system is high by the open loop control, and the resolution of the stop position can be further increased in the microstep. Conventional examples of performing open loop control of a stepping motor include Patent Document 1 (Japanese Patent Laid-Open No. 2004-320847) and Patent Document 2 (Japanese Patent No. 3503893).

  However, due to the advantage of the number of multipoles, for example, if the number of teeth is 50, the excitation frequency per rotation is about 10 times higher than that of the AC servo motor, and the motor command current and the motor phase current waveform are completely different at high speed. It becomes a different waveform and causes step-out.

  This can be explained with reference to the figure. FIG. 1 is a waveform diagram showing the relationship between the excitation current waveform for exciting the coil of the stepping motor and the generated torque τ. The phase current is output as a sin waveform for the A phase and a cosine waveform for the B phase. The vector phase angle, that is, the vector synthesis is the excitation angle θr, and the excitation angle is θr = 0 at sin 90 °. Under normal conditions, the excitation angle θr is 90 ° ahead of the rotor angle θm that is the angle of the rotor shaft of the stepping motor, and if the slip angle θ that is the difference between the excitation angle θr and the rotor angle θm is constant, the torque τ is It becomes a constant value.

  Such a relationship is established in the low speed range. However, in the middle speed range or higher (middle high speed range), the PWM duty ratio is saturated due to the increase of the back electromotive force of the motor, so that the current is distorted and the same as the low speed range. When the control is performed with such a command value, the current does not flow as desired, and the necessary torque cannot be obtained, and as a result, the speed cannot be increased to the middle / high speed range.

  FIG. 2 is a measured waveform of the command voltage VA (rectangular wave) at a speed of 12 rps and phase currents IA and IB of the A phase and the B phase. (A) is a slip angle θ of π / 2, that is, 90 °. In this case, (B) is (3/2) π, that is, 135 °, and the distortion of the phase currents IA and IB with respect to the command voltage VA is remarkable.

Therefore, Non-Patent Document 1 (2002 Annual Meeting of the Institute of Electrical Engineers, Industrial Applications Division, pages 131-134, “Open Loop Control of HB Stepping Motor in High Speed Range”) Control is proposed, but the purpose of the electric actuator is to efficiently control the combination pattern of force, acceleration, speed, and position of the mechanical body. This increases the complexity, size, and cost of the controller.
JP 2004-320847 A Japanese Patent No. 3503893 Proceedings of the 2001 IEEJ Industrial Application Division, pages 131-134 "Open loop control of HB type stepping motor in high speed range"

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electric actuator using a stepping motor with a simple circuit configuration and a simple algorithm so that the stable control of the mechanical body of the electric actuator is economically realized. The purpose is to make it possible to perform stable control easily and without difficulty in dividing into high-speed regions.

  In the electric actuator control method according to the present invention, the stepping motor provided with the encoder is driven by the pulse width modulation type power drive unit to operate the actuator, and the duty ratio of the pulse width modulation in the power drive unit is 100. Is determined in one excitation cycle, and the speed of the stepping motor is discriminated between the medium and high speed range and the low speed range, and the vector phase angle θi of the phase current of the A / B2 phase of the stepping motor and the encoder The slip angle θ, which is the phase difference from the rotor shaft phase angle θm obtained from the above, is obtained, and in the low speed range, when this slip angle θ is 30 ° or less, the phase current is changed in several steps at a rated ratio or less. , Change between 30 ° and 90 ° in several steps with the rated value, and when it is 90 ° or more, change it into several steps at a predetermined ratio or more of the rated value. In the middle and high speed range, the excitation angle for determining the two-phase phase current is advanced and controlled with respect to the power drive unit until the slip angle θ reaches 90 °.

In the low speed range, the vector phase angle θi of the phase currents of the A and B phases is converted from the count value of the current command for the stepping motor, and the slip angle θ, which is the phase difference from the rotor shaft phase angle θm, is obtained.
On the other hand, in the medium / high speed range, the phase currents of the A and B phases of the stepping motor are detected, and when the vector phase angle θi is 45 °, 135 °, 225 °, 315 °, the phase of the rotor shaft obtained from the encoder A slip angle θ, which is a phase difference from the angle θm, is obtained.

  The vector phase angle θi of 45 °, 135 °, 225 °, and 315 ° can be easily determined by logical operation based on the polarity when the detected two-phase phase currents are the same.

When changing the phase current in several steps in the low speed range, if the slip angle θ is 30 ° or less, the phase current is changed in several steps at less than 1/2 of the rating, and the rating is a number between 30 ° and 90 °. Change it in steps, and if it is 90 ° or more, change it in several steps at twice the rating.
When changing the phase current to several stages in the low speed region, the numerical values in the table calculated and stored in advance are referred to.
When the slip angle θ is 90 ° or more in the low speed range and the rating is the maximum rating, the command value of the angular velocity ω commanded to the power drive unit is decreased.
The step of changing the phase current in the low speed range may be about 2 to 5 steps.

  The control device for the electric actuator according to the present invention determines whether the duty ratio of the pulse width modulation in the power drive unit is 100% or not in one excitation cycle, and sets the speed of the stepping motor to the medium high speed range and the low speed range. Low-speed / medium / high-speed range discriminating means for discriminating, phase angle calculating means for obtaining the vector phase angle θi of the phase currents of the A and B phases of the stepping motor, the phase angle θi, and the phase angle of the rotor shaft obtained from the encoder a slip angle calculating means for obtaining a slip angle θ which is a phase difference with θm, and in a low speed range, when the slip angle θ is 30 ° or less, the phase current is changed in several steps at a predetermined ratio or less of the rated value, and from 30 ° The power drive unit is controlled so that it is changed in several steps while maintaining the rating during 90 °, and is changed in several steps at a predetermined ratio or more of the rating when it is 90 ° or more. Relative blanking unit, until the slip angle θ is 90 °, characterized in that a control means for controlling the flow proceeds excitation angle which determines the phase currents of two phases.

The present invention discriminates the speed of the stepping motor into a medium-high speed range and a low-speed range depending on whether the duty ratio of the pulse width modulation is 100%, and in the low speed range where no current distortion occurs, the slip angle θ Depending on whether the current is 30 ° or less, between 30 ° and 90 °, or 90 ° or more, the phase current is set to a predetermined ratio or less of the rated value, or remains at the rated value, or a predetermined ratio of the rated value. In either case, the phase current is changed in several stages, so that the vibration that tends to occur in the low speed range can be suppressed by the power drive unit itself, and smooth deceleration / acceleration can be performed.
On the other hand, in the medium / high speed region where current distortion occurs, the excitation angle that determines the two-phase current is forcibly advanced and controlled until the slip angle θ reaches 90 °. Speed up without any hindrance.

  When calculating the slip angle θ, in the low speed range, the vector phase angle θi of the phase currents of the A and B phases is converted from the count value of the current command for the stepping motor, and the slip is the phase difference from the rotor shaft phase angle θm. The angle θ is obtained, and in the middle and high speed range, the phase currents of the A and B phases of the stepping motor are detected, and the rotor obtained from the encoder when the vector phase angle θi is 45 °, 135 °, 225 °, 315 ° When the slip angle θ, which is the phase difference from the axis phase angle θm, is obtained, a simple algorithm (hardware and comparison) is used in both the low speed range and the medium / high speed range without performing special mathematical calculations. In the case of hardware processing, the slip angle θ can be obtained with a simple comparison circuit or simple logic circuit.

  When the phase current is changed in several steps in the low speed region, when the slip angle θ is 30 ° or less (θ <30 °), the phase current is changed in several steps at less than 1/2 of the rating, and the phase current is changed from 30 ° to 90 °. The interval (30 ° ≦ θ ≦ 90 °) is changed in several stages with the rating, and when it is 90 ° or more (θ> 90 °), it is changed in several steps at twice the rating. Control of the power drive unit can be simplified by determining values to be changed with reference to numerical values stored in a table obtained by calculation in advance.

  If the rating is the maximum rating when the slip angle θ is 90 ° or more in the low speed range, the speed can be changed quickly by decreasing the command value of the angular velocity ω commanded to the power drive unit.

  The operation and effect of the present invention will be described with reference to the drawings. FIG. 3 shows the relationship between the A-phase and B-phase command voltages of the two-phase stepping motor and the rotor angle (axis angle) in the magnetization direction in a polar coordinate system. In the low speed range, it looks like this figure. Assuming that the A-phase and B-phase currents are the a-axis and b-axis, and the rotor shaft is the d-axis, the combined vector of the phase currents of the A-phase and B-phase is the vector phase angle θi, and the rotor shaft angle with respect to the a-axis is the phase angle θm, and the q-axis component becomes the torque τ. The phase difference between the vector phase angle θi and the rotor shaft phase angle θm is the slip angle θ (θ = θi−θm).

  If the relationship between the slip angle θ and the torque τ is a waveform, it can be shown in FIG. When a clock signal of cw (clockwise rotation) or ccw (counterclockwise rotation) is given to the pulse width modulation type power drive unit, the power drive unit is rated for A phase and B phase. The phase current is made to flow by pulse width modulation so that the vector phase angle θi becomes.

  Since the stepping motor is driven at a slip angle θ such that the motor torque τ = external load torque τL, when the rated torque is indicated by a solid sin waveform in FIG. 4, when the external load torque τL becomes a low load, the torque Shift from the point a to 0, so that vibration at low speed becomes remarkable. For example, if the load is rated torque 1.0, it is point a, but if it is 0.5, point b. Here, since the slip angle at point b is 30 °, the command voltage to the motor for determining the phase currents of the A and B phases is set to ½ of the rating so as to obtain a sine waveform with a broken line. Vibration at low speed can be suppressed by the power drive unit itself. Also, the rated torque is maintained between 30 ° and 90 ° (30 ° ≦ θ ≦ 90 °), and when it is 90 ° or more (θ> 90 °), the required torque can be ensured by double the rating. It is possible to smoothly decelerate and accelerate in the low speed range while ensuring high speed.

  In the low speed range, the generated torque is thus determined by the slip angle θ which is the phase difference between the vector phase angle θi and the rotor shaft phase angle θm. The vector phase angle θi can be converted from the count value of the current command for the stepping motor, and the rotor shaft phase angle θm can be detected by counting the angle with a signal from the encoder.

However, above the medium speed range, as described above, the PWM duty ratio is saturated, the current is distorted, and the required torque cannot be obtained.
Therefore, the medium / high speed range and the low speed range are determined depending on whether the PWM duty ratio is saturated, that is, 100%. In the middle and high speed range, the slip angle θ cannot be obtained in the same manner as the low speed range. Therefore, the phase currents IA and IB of the stepping motors A and B are detected and the vector phase angle θi is obtained. When the slip angle θ is obtained by calculating the angle with respect to the angle, the processing becomes complicated and the load on the CPU (Central Processing Unit) increases. Therefore, the two-phase phase current is 1 due to the characteristics of the two-phase stepping motor. The excitation cycle is the same because the vector phase angle θi is every 90 ° of 45 °, 135 °, 225 °, and 315 °, and the polarity changes at that time. Judging from the polarity of the phase current of the phase, only the four points are simplified by obtaining the slip angle θ which is the phase difference from the phase angle θm of the rotor shaft.

  Since the polarity changes four times in one excitation cycle as described above, a ripple of the fourth harmonic is generated. However, since the sampling is synchronized, there is an effect that the detection fluctuation can be suppressed.

FIG. 5 detects the phase currents IA and IB of the A and B phases, calculates the vector phase angle θi therefrom (θi = tan ⁻¹ (IB / IA)), and the rotor shaft obtained from the encoder. It is a waveform showing the phase angle θm in correspondence with the command voltage VA when the speed is 12 rps. FIG. 5A shows that the slip angle θ, which is the difference between the excitation angle by the command voltage and the phase angle θm of the rotor shaft obtained from the encoder, is π / 2, that is, 90 °. The difference between the vector phase angle θi obtained by detecting the currents IA and IB and the phase angle θm of the rotor shaft is about 30 °, and the current phase is delayed. FIG. 5B shows that the slip angle θ, which is the difference between the excitation angle based on the command voltage and the phase angle θm of the rotor shaft obtained from the encoder, is 135 °, but the phase currents IA and IB of the A and B phases are The difference between the detected vector phase angle θi and the rotor shaft phase angle θm is about 90 °. In this case as well, the current phase is delayed.

  Therefore, in the medium and high speed range, the phase currents IA and IB of the A and B phases are detected, and the slip angle θ that is the difference between the vector phase angle θi calculated from the phase current θi and the phase angle θm of the rotor shaft is 90 °. Up to this point, the excitation angle for determining the two-phase phase current is advanced and controlled, and when the angle exceeds 90 °, the normal PWM control is performed, so that the speed can be increased while securing the necessary torque.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 6 shows an example of a system configuration when the present invention is applied. A plurality of electric actuators 1 are connected to a controller 3 via a connection cable 2, and a power source 4 and a power source 5 for control are connected to the controller 3. In addition to being connected via cables 8 and 9, the pluggable controller 6 and personal computer 7 as user equipment are connected via respective communication cables 10 and 11, and a plurality of electric actuators 1 are connected to one controller 3. The control apparatus according to the present invention is built in the controller 3.

  FIG. 7 is a block diagram in which the internal configuration of the controller 3 is divided into functions. The controller 3 includes an interface 12 for connecting to the pluggable controller 6 and the personal computer 7, and a user that stores the control position, speed, force, various parameters, initial setting values, and the like of the electric actuator 1 set by the user. A setting information storage unit 13; a control unit 14 including a control device according to the present invention; a power drive unit 15 that drives the stepping motor 20 of the electric actuator 1 by PWM (pulse width modulation); A sensing unit 16 that detects the angle of the rotor shaft based on a signal from an encoder 21 attached to the stepping motor 20 is provided.

  The electric actuator 1 decelerates the rotation of the stepping motor 20 by the speed reduction mechanism 22 and drives the main body mechanism portion 23 to position and grip the workpiece.

  FIG. 8 shows details of the control device according to the present invention, the power drive unit 15, and the sensing unit 16 included in the control unit 14.

  A user setting information storage unit 13 in FIG. 7 is secured in a memory in an MPU (Micro Processing Unit) 30 that is the center of the control unit 14. When the MPU 30 is given a command of the angular velocity ω for rotating the stepping motor 20, the MPU 30 converts the angular velocity ω into a phase angle by the angular velocity / phase angle conversion unit 31, and the speed of the stepping motor 20 is low. Depending on whether it is in the middle or high speed range, the speed-specific control units, that is, the low speed range control unit 32 and the medium and high speed range control unit 33 refer to the respective tables and perform separate processing in the low speed range and the medium and high speed range. I do. The low speed / medium / high speed region discriminating unit 34 determines whether the low speed region / medium / high speed region is the duty ratio of the pulse width modulation in the A phase / B phase PWM control unit 35A / 35B of the power drive unit 15 being 100%. Whether it is present or not is determined by one excitation cycle. If it is 100%, it is determined as a medium-high speed region, and if it is less than that, it is determined as a low-speed region.

  On the other hand, the rotor angle detector 36 of the sensing unit 16 counts and detects the phase angle θm of the rotor shaft from the A-phase, B-phase, and Z-phase signals from the encoder 21. This phase angle θm is given to the low speed region control unit 32 and the medium / high speed region control unit 33. In the respective tables of the low speed region control unit 32 and the medium / high speed region control unit 33, various values calculated in advance are stored according to the phase angle θm.

  FIG. 9 is a chart showing an example of the calculation and parameters. In this example, as shown in FIG. 10, the start / stop of the stepping motor 20 is commanded at an angular acceleration dω / dt, and the position L of the main body mechanism portion 23 of the electric actuator 1 is set to a constant speed operation state in the middle / high speed range. The case of moving linearly is assumed.

  The A-phase / B-phase PWM control units 35A and 35B of the power drive unit 15 are separately provided by the low-speed region control unit 32 in the low-speed region and separately in the medium-high speed region control unit 33 in the high-medium-speed region. Be controlled. In each of the A phase and the B phase, the A phase driver 37A and the B phase driver 37B of the power drive unit 15 cause the A phase and B phase currents to flow into the A phase coil 38A and the B phase coil 38B of the stepping motor 20, respectively. Each of these coils is supplied to excite these coils, and the rotor of the stepping motor 20 rotates. At that time, the currents IA and IB of the A and B phases are detected by the current sensors 39A and 39B of the A and B phases, respectively.

  The phase current vector angle detection unit 40 of the sensing unit 16 compares the A phase current IA and the B phase current IB detected by the current sensors 39A and 39B with a comparator, and inverts the output with an inverter to perform logic with an AND circuit. Through the logical processing of multiplying, it is detected that the vector phase difference θi of the phase currents of the A and B phases becomes 45 °, 135 °, 225 °, and 315 °. That is, the phase angle (vector phase difference θi) of these four points is detected from the polarities of the two-phase phase currents when the phase currents IA and IB of the A and B phases become the same (IA = IB). This is shown in Table 1 below.

  In the case of the low speed region, the low speed region control unit 32 counts the current command signal for the stepping motor 20 and converts the vector phase difference θi of the phase currents IA and IB of the A and B phases from the count value. Then, the slip angle θ is obtained as a difference between the converted vector phase difference θi and the rotor shaft phase angle θm from the rotor angle detector 36.

  On the other hand, in the middle / high speed range, the middle / high speed range control unit 33 slips as the difference between the vector phase difference θi from the phase current vector angle detection unit 40 and the rotor shaft phase angle θm from the rotor angle detection unit 36. Find the angle θ.

  The low-speed region control unit 32 and the medium / high-speed region control unit 33 give a current command to the A-phase / B-phase PWM control units 35A and 35B to determine the A-phase current and the B-phase current according to the slip angle θ. Although the phase current is changed, the mode of the change is also different.

  FIG. 11A shows a control routine in the case of the low speed region, and FIG. 11B shows a control routine in the case of the medium and high speed region. This is done by interruption based on the result of excitation cycle determination.

  When the determination result of the low speed / medium / high speed determination unit 34 is the low speed, the vector phase angle θi of the phase currents of the A and B phases is converted from the count value of the current command for the stepping motor 20 as described above. Then, the slip angle θ, which is the phase difference from the rotor shaft phase angle θm, is obtained. Actually, in step S1 of the control routine of FIG. 11A, a difference n3 between the count value n1 of the counter of the rotor angle detector 36 and the count value n2 of the current command counter is obtained, and the user setting information is obtained from this difference n3. With reference to the conversion formula stored in the storage unit 13, the slip angle θ converted into the excitation angle is obtained in step S2.

  In the next step S3, the slip angle θ is set to 30 ° with reference to the low speed control matrix stored in the table of the user setting information storage unit 13 as shown in the following Table 2 (θ-I table), for example. Different current command values are given in the following cases (θ <30 °), between 30 ° and 90 ° (30 ° ≦ θ ≦ 90 °), and 90 ° or more (θ> 90 °). The example in Table 2 is an example in which the rated current is changed in two stages of the maximum rating and a half thereof, and when the slip angle θ is 30 ° ≦ θ ≦ 90 °, the current is as it is rated. In the case of <30 °, when the rating is the maximum rating, it is ½ of the maximum rating (0.5 when the maximum rating is 1), and when the rating is ½ of the maximum rating, it is the same rating (1/1 of the maximum rating). 2). On the other hand, in the case of θ> 90 °, when the rating is the maximum rating, the angular velocity ω given to the angular velocity / phase angle conversion unit 31 in FIG. 8 is decreased, and when the rating is ½ of the maximum rating, the rating 2 Double (maximum rating).

  The following Table 3 shows that the rated current is the maximum rating, ½ (0.5 when the maximum rating is 1), ¼ (also 0.25), and ８ (also 0.125). It is an example in the case of changing to four stages.

  Since the present invention is intended to easily control the stepping motor 20 using the stepping motor 20 as a drive source of the electric actuator 1, the number of stages when the rated current is thus changed into several stages in the low speed range is as follows: About 2 to 5 steps are practical.

  As described above, since the vector current value determined according to the slip angle θ in the three stages in step S3 is distributed as the phase currents of the A phase and the B phase, assuming that this vector current value is I, in step S4, A value of I · sin θ is given to the A-phase PWM control unit 35A in FIG. 8, and a value of I · cos θ is given to the B-phase PWM control unit 35B.

  On the other hand, in the middle / high speed range of FIG. 11B, in step S11, the phases of the currents A and B are determined and stored, and the count value of the counter of the rotor angle detector 36 is stored. Then, in step S12, the rotor shaft phase angle θm obtained by converting the count value into the excitation angle is obtained from the conversion table stored in the user setting information storage unit 13.

  In the next step S13, only the four vector phase differences θi of 45 °, 135 °, 225 °, and 315 ° detected by the phase current vector angle detection unit 40 according to the above-described Table 1 are combined with the rotor. The slip angle θ, which is the difference from the axial phase angle θm, is calculated.

  Then, it is determined in step S14 whether or not this slip angle θ is 90 ° or less (θ ≦ 90 °), and until the slip angle θ reaches 90 ° (as shown in FIG. 12, the slip angle θ Until the excitation current I1 vector and the torque τ vector become the same) in step S15, the A phase / B phase PWM control units 35A, 35B The excitation angle for determining the two-phase phase current is advanced and controlled, and when 90 ° or more (θ> 90), normal PWM control is performed in step S16.

  In the above embodiment, an A / B two-phase stepping motor (bipolar winding) is taken as an example, but the present invention can also be applied to a two-phase unipolar winding stepping motor or a three-phase or more stepping motor.

It is a wave form diagram which shows the relationship between the exciting current waveform which excites the coil of a stepping motor, and the generate | occur | producing torque (tau). The command voltage VA (rectangular wave) when the speed of the stepping motor is 12 rps and the phase current actual measurement waveforms of the A phase and the B phase. (A) is when the slip angle θ is π / 2, (B) is (3 / 2) This is the case of π. It is a figure which shows the command voltage of A phase and B phase of a two-phase stepping motor, and the relationship between the rotor angle of a magnetization direction by a polar coordinate system. It is a wave form diagram which shows the relationship between slip angle (theta) and torque (tau). The phase currents of the A and B phases are detected, the vector phase angle θi is calculated therefrom, and the rotor shaft phase angle θm obtained from the encoder is shown in correspondence with the command voltage VA when the speed is 12 rps. In the waveform, (A) is the case where the slip angle θ is π / 2, and (B) is the case where (3/2) π. It is a figure which shows the system configuration example in the case of applying this invention. It is the block diagram which divided the internal structure of the controller of FIG. 6 into functions. It is a circuit diagram which shows the detail of the control apparatus by this invention contained in a control part, a power drive part, and a sensing part. It is a table | surface which shows the example of a calculation and parameter which are referred in a low speed area control part and a medium-high speed area control part. FIG. 5 is a timing chart assuming a case where the stepping motor is commanded to start / stop with an angular acceleration d and the position L of the body mechanism portion of the electric actuator is moved linearly in a constant speed operation state in a medium to high speed range. The flow in each case of the low speed region and the medium high speed region, (A) shows the control routine for the low speed region, and (B) shows the control routine for the medium high speed region. It is a figure which shows that slip angle (theta) becomes 90 degrees and the vector of exciting current I1 and the vector of torque (tau) become the same.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric actuator 2 Connection cable 3 Controller 4 Power supply 5 Power supply for control 6 Pluggable controller 7 Personal computer 8/9 Power cable 10/11 Communication cable 12 Interface 13 User setting information storage part 14 Control part 15 Power drive part 16 Sensing Part 20 Stepping motor 21 Encoder 22 Deceleration mechanism 23 Main body mechanism part 30 MPU
31 Angular velocity / phase angle conversion unit 32 Low speed region control unit 33 Middle / high speed region control unit 34 Low speed region / medium / high speed region discrimination unit 35A / 35B PWM control unit 36 Rotor angle detection unit 37A A phase driver 37B B phase driver 38A A phase coil 38B B-phase coil 39A / 39B Current sensor 40-phase current vector angle detector

Claims (13)

In an electric actuator that operates a stepping motor with an encoder driven by a pulse width modulation type power drive unit to operate the actuator,
Whether or not the duty ratio of the pulse width modulation in the power drive unit is 100% is determined by one excitation cycle, and the speed of the stepping motor is determined as a medium high speed range and a low speed range,
A slip angle θ, which is a phase difference between the vector phase angle θi of the phase currents of the A and B phases of the stepping motor and the phase angle θm of the rotor shaft obtained from the encoder,
In the low speed range, when the slip angle θ is 30 ° or less, the phase current is changed in several steps at a predetermined ratio or less of the rated value, and in the range between 30 ° and 90 °, the rated current is changed in several steps, and 90 ° or more. In the case of, it is changed in several steps at a predetermined ratio or more of the rating,
In the medium and high speed range, the excitation angle that determines the phase current of the two phases is advanced and controlled with respect to the power drive unit until the slip angle θ reaches 90 °.
A method for controlling an electric actuator. In the low speed range, the vector phase angle θi of the phase currents of the A and B phases is converted from the count value of the current command for the stepping motor, and the slip angle θ that is the phase difference from the rotor shaft phase angle θm is obtained.
In the middle and high speed range, the phase currents of the A and B phases of the stepping motor are detected, and when the vector phase angle θi is 45 °, 135 °, 225 °, 315 °, the phase angle θm of the rotor shaft obtained from the encoder The method of controlling an electric actuator according to claim 1, wherein a slip angle θ that is a phase difference between the first and second phases is obtained.   3. The electric actuator according to claim 2, wherein the vector phase angle θi of 45 °, 135 °, 225 °, and 315 ° is determined from the polarity when the detected phase currents of the two phases become the same. Control method.   When changing the phase current in several steps in the low speed range, if the slip angle θ is 30 ° or less, the phase current is changed in several steps at less than 1/2 of the rating, and the rating is a number between 30 ° and 90 °. The method for controlling an electric actuator according to any one of claims 1 to 3, wherein the electric actuator is changed in stages, and when the angle is 90 ° or more, the electric actuator is changed in several stages at twice the rating.   5. The method for controlling an electric actuator according to claim 1, wherein when changing the phase current to several stages in the low speed range, a numerical value of a table calculated and stored in advance is referred to. .   6. A command value of an angular velocity ω commanded to a power drive unit is reduced when the rating is the maximum rating when the slip angle θ is 90 ° or more in a low speed range. The control method of the electric actuator in any one of.   7. The method for controlling an electric actuator according to claim 1, wherein the phase current is changed in 2 to 5 steps in the low speed range. A control device for an electric actuator that drives an actuator by driving a stepping motor provided with an encoder with a power drive unit of a pulse width modulation method,
Deciding whether the duty ratio of pulse width modulation in the power drive unit is 100% or not in one excitation cycle, and discriminating the speed of the stepping motor into a medium / high speed region and a low / low speed region Means,
Phase angle calculation means for obtaining a vector phase angle θi of the phase currents of the A and B phases of the stepping motor;
A slip angle calculating means for obtaining a slip angle θ which is a phase difference between the phase angle θi and the phase angle θm of the rotor shaft obtained from the encoder;
In the low speed range, when the slip angle θ is 30 ° or less, the phase current is changed in several steps at a predetermined ratio or less of the rated value, and in the range between 30 ° and 90 °, the rated current is changed in several steps, and the phase current is changed to 90 ° or more. In some cases, the power drive unit is controlled to change in several steps at a predetermined ratio or more of the rated value, and in the middle / high speed range, the two-phase operation is performed until the slip angle θ reaches 90 ° with respect to the power drive unit. Control means for advancing and controlling the excitation angle for determining the phase current of
An electric actuator control apparatus comprising: In the low speed range, the phase angle calculation means converts the vector phase angle θi of the phase currents of the A and B phases from the count value of the current command for the stepping motor, and the slip angle calculation means is obtained from the encoder and the phase angle θi. Obtain the slip angle θ, which is the phase difference from the rotor shaft phase angle θm,
In the middle and high speed range, the phase angle calculation means detects the phase currents of the A and B phases of the stepping motor, determines the vector phase angle θi of 45 °, 135 °, 225 °, and 315 °, and the slip angle calculation means 9. The electric actuator control device according to claim 8, wherein a slip angle θ, which is a phase difference from the phase angle θm of the rotor shaft obtained from the encoder, is obtained for each vector phase angle θi.   The phase angle calculating means determines the vector phase angle θi of 45 °, 135 °, 225 °, 315 ° from the polarity when the detected phase currents of the two phases are the same. The control device for an electric actuator according to claim 9.   When the phase current is changed in several steps in the low speed range, the control means changes the phase current in several steps at less than 1/2 of the rating when the slip angle θ is 30 ° or less, and between 30 ° and 90 °. 10. The control device for an electric actuator according to claim 8 or 9, wherein: is changed in several steps as it is rated, and when it is 90 ° or more, it is changed in several steps at twice the rating.   12. The electric motor according to claim 8, wherein when the phase current is changed in several steps in the low speed region, the control means refers to a numerical value of a table calculated and stored in advance. Actuator control device. The slip angle calculation means determines 45 °, 135 °, 225 °, and 315 ° from the polarity when the detected phase currents of the two phases become the same as the phase angle θi of the combined vector of the A and B phases. The control device for an electric actuator according to any one of claims 10 to 12.

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