JP2009112104A - Sensorless controller of brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensorless controller of a brushless motor which can perform operational processing without using a high cost CPU, and does not require alteration of an operational processing program even if a brushless motor of control object is changed. <P>SOLUTION: The sensorless controller of a brushless motor comprises an angle control section 17 for calculating the correction angle of a rotor, speed calculation sections 18 and 19 for calculating the current speed of the rotor, an angle calculation section 20 for calculating the angle of the rotor, and a speed control section 11 for calculating the d-axis current command value and a q-axis current command value and outputting them to a current control section 12. The speed calculation sections 18 and 19 consist of a first speed calculation section 18 which determines the current speed ω of the rotor according to a formula ω=2π/T by using a time T required for a single revolution and outputs the current speed ω to the angle calculation section 20, and a second speed calculation section 19 which determines the current speed ω of the rotor from an angular variation S during a predetermined time Tk calculated at the angle calculation section according to a formula ω=S/Tk and outputs the current speed ω to the speed control section 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sensorless control device for a brushless motor.

  Conventionally, as a control device for controlling the driving of a brushless motor, a three-phase current value in a fixed coordinate system (a coordinate system consisting of a u-axis, a v-axis, and a w-axis that intersects each other at an angle of 120 °) is rotated. It is converted into a two-phase current (a d-axis current and a q-axis current) in a coordinate system (a coordinate system consisting of a d-axis indicating the magnetic flux direction of the field pole and a q-axis orthogonal thereto), and this two-phase current is used. A device that performs vector control is known.

A sensorless control device that estimates the rotor angle and speed without using a sensor for directly detecting the rotor angle of the brushless motor when performing vector control is also known, and such a brushless motor (1) As shown in FIG. 3, the sensorless control device (40) of the present invention is a speed control unit (41) for calculating a current command value in a two-axis coordinate system and a two-axis coordinate system based on the current command value in the two-axis coordinate system. A current control unit (42) for calculating a voltage command value in the coordinate system, a coordinate conversion unit (43) for calculating a three-phase voltage command value based on the voltage command value in the two-axis coordinate system, and a three-phase voltage command value PWM inverter (44) for supplying a DC drive current to the stator coil of the motor based on the current detection unit (45) for detecting the phase current flowing in the stator coil of the motor, and the phase detected by the current detection unit (45) 2 based on current An apparatus including a coordinate conversion unit (46) for calculating a current value in an axis coordinate system and a position / speed estimation unit (47) for obtaining a rotor angle and a rotor speed is known.
JP 2007-53829 A

  In the above conventional brushless motor sensorless control device, in order to estimate the rotor angle and speed of the brushless motor, the motor model is used to estimate the rotor angle from the inductance and resistance of the stator coil constituting the brushless motor. It is necessary to estimate the angle frequently by performing loop processing, and there is a problem that it is necessary to use a high-cost CPU having a large calculation load and high-performance calculation processing capability.

  In addition, since the motor models such as the inductance and resistance of the coil constituting the brushless motor are different for each brushless motor, it is necessary to change the arithmetic processing program for estimating the angle depending on the brushless motor to be controlled. There was also.

  An object of the present invention is to provide a brushless motor that can perform arithmetic processing without using a high-cost CPU and that does not need to change the arithmetic processing program even if the brushless motor to be controlled changes. It is to provide a sensorless control device.

  A sensorless control device for a brushless motor according to the present invention is a two-axis rotational coordinate system comprising a d-axis and a q-axis for a brushless motor having a stator having a multi-phase stator coil and a rotor having a permanent magnet. In a sensorless control apparatus that performs sensorless vector control using a current sensor, an angle control unit that calculates a correction angle of the rotor based on the current value and the command value of the d-axis current, and an angle change amount during a predetermined time from the current Calculates the current rotor angle using the speed calculator that calculates the rotor speed, the rotor angle obtained during the previous sampling, the correction angle obtained by the angle controller, and the speed obtained by the speed calculator. Subtracting ω calculated by the speed calculation unit from the commanded speed ω * input from the outside, and the subtraction result (ω * −ω) And a speed control unit that calculates a d-axis current command value and a q-axis current command value and outputs them to the current control unit, and the speed calculation unit uses the time T required for one rotation to Is obtained as ω = 2π / T, and the current speed ω of the rotor is calculated from the angle change amount S in the first speed calculation unit that outputs this to the angle calculation unit and the angle calculation unit during a predetermined time Tk. It is characterized by comprising a second speed calculation unit that obtains ω = S / Tk and outputs this to the speed control unit.

  In the speed control unit, the d-axis current command value and the q-axis current command value are calculated using the command speed ω * input from the outside and ω calculated by the speed calculation unit. A d-axis current value and a q-axis current value are obtained using the current command value and the q-axis current command value. The d-axis current value is detected (sampled) at a predetermined interval (sampling interval) Ts, and the rotor correction angle Δθ and the current rotor angle θ (current sampling) are calculated accordingly.

  The angle control unit calculates a correction angle Δθ for correcting the rotor angle θ so that the d-axis current value id converges to a command value id * (specifically, for example, 0). Angle deviation is corrected.

  The angle calculation unit obtains the current rotor angle θ (at the time of current sampling) from θ = θ ′ + ω × Ts + Δθ by using the rotor angle θ ′ and the speed ω obtained at the previous sampling for each sampling interval Ts. It is done.

  In the speed calculation unit, for example, the time T required for one rotation of the rotor can be obtained, and the current speed ω of the rotor can be obtained as ω = 2π / T.

  By calculating the current rotor angle θ based on the correction angle Δθ obtained by the angle control unit, the speed ω obtained by the speed calculation unit, and the rotor angle θ ′ obtained by the angle calculation unit, The rotor angle θ can be converged to the true angle of the rotor, and sensorless vector control can be performed with a simple calculation with a small calculation load without using a motor model. Further, since the calculation load is reduced and it is not necessary to use a high-performance and high-cost CPU, the cost can be reduced. Furthermore, since the rotor angle can be converged to the true rotor angle without using a motor model, there is no need to change the arithmetic processing program in correspondence with the brushless motor to be controlled, and highly versatile sensorless control. A device can be obtained.

  In the above, the current rotor speed ω is used in both the speed control unit and the angle calculation unit. The control using the d-axis current is performed at a sampling interval Ts that is shorter than the time T required for the rotor to make one revolution. Using the time T required for the rotor to make one revolution, ω = When the current rotor speed ω is obtained as 2π / T, the speed command value ω in the speed control unit is controlled during low-speed operation because the update timing is later than the control loop update timing and depends on the rotational speed. May become unstable. Therefore, it is preferable to obtain ω as ω = S / Tk from the angle change amount S in the angle calculation unit during the elapse of the predetermined time Tk as the rotor speed ω used in the speed control unit. The angle change amount S is constant by accumulating the change ΔK = K (n) −K (n−1) for each calculation cycle when θ = θ ′ + ω × Ts + Δθ where ω × Ts + Δθ is K (n). It is obtained as a value (angle counter value) obtained by integrating the time Tk.

  On the other hand, the speed of the rotor used in the angle calculation unit requires a certain time delay from the viewpoint that the rotor angle θ is obtained by θ = θ ′ + ω × Ts + Δθ and converged by changing Δθ. Yes, it is preferable to obtain it as ω = 2π / T.

  Therefore, in the sensorless control device of the present invention, the first speed calculation unit that outputs the rotor speed to the angle calculation unit receives a time counter value (time required for one rotation) T corresponding to an electrical angle of 2π from the angle calculation unit, The current speed ω of the rotor is determined as ω = 2π / T, and the second speed calculation unit that outputs the rotor speed to the speed control unit receives an angle counter value (during a predetermined time Tk elapses) from the angle calculation unit. The angle change amount) S is obtained, and the current rotor speed ω is obtained as ω = S / Tk. Thereby, the updated speed is input to the speed control unit in a short time, and stable speed control can be performed.

  According to the sensorless control device for a brushless motor of the present invention, sensorless vector control can be performed with a simple calculation with a small calculation load compared to the conventional one that estimates the angle and speed using a motor model. Therefore, it is not necessary to change the arithmetic processing program in correspondence with the brushless motor, and a sensorless control device with reduced cost and high versatility can be obtained. Then, the speed calculation unit is composed of the first and second speed calculation units, the rotor speed ω used in the angle calculation unit is obtained as ω = 2π / T, and the rotor speed ω used in the speed control unit is obtained. By obtaining as ω = S / Tk, stable speed control can be performed.

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

  FIG. 1 shows a sensorless control device for a brushless motor according to the present invention.

  The brushless motor is composed of a permanent magnet field synchronous motor (1) and a sensorless control device (2). The synchronous motor (1) includes a stator (4) having a stator coil (3) having a plurality of phases (three phases in this example) and a rotor (5) having a permanent magnet.

  The sensorless control device (2) performs sensorless vector control. The sensorless control device (2) calculates the d-axis / q-axis current command values id * and iq * in the two-axis coordinate system, and the two-axis coordinate system. a current control unit (12) for calculating the d-axis / q-axis voltage command values Vd *, Vq * in the two-axis coordinate system based on the d-axis / q-axis current command values id *, iq *; A three-phase coordinate converter (13) that calculates three-phase voltage command values Vu *, Vv *, Vw * based on the d-axis / q-axis voltage command values Vd *, Vq *, and a three-phase voltage command A PWM inverter (14) for supplying a DC drive current to the stator coil (3) of the motor (1) based on the values Vu *, Vv *, Vw *, and a phase current Iu, Iv flowing through the stator coil (3). Current detectors (15) for obtaining current values iu, iv, iw of the respective phases, and based on the phase current values iu, iv, iw. A two-phase coordinate conversion unit (16) for calculating d-axis / q-axis current values id and iq in a two-axis coordinate system, an angle control unit (17) for calculating a correction angle Δθ, and a speed ω. A first speed calculation unit (18) and a second speed calculation unit (19), and an angle calculation unit (20) for calculating the angle θ are provided.

  The angle control unit (17), the first speed calculation unit (18), the second speed calculation unit (19), and the angle calculation unit (20) are characteristic portions of the present invention and have been conventionally used due to their configuration. The position / speed estimation unit (see FIG. 3) is omitted.

  Each part (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) is stored in the ROM using a RAM having a working storage area. It operates by a CPU (not shown) that executes an arithmetic processing program and a control processing program.

  The speed control unit (11) subtracts ω calculated by the second speed calculation unit (19) from the command speed ω * input from the outside, and based on the subtraction result (ω * −ω), the d axis The current command value id * and the q-axis current command value iq * are calculated and output to the current control unit (12). In general, the d-axis current command value id * is 0.

  The current control unit (12) subtracts the d-axis current value id calculated by the two-phase coordinate conversion unit (16) from the d-axis current command value id *, and based on the subtraction result (id * -id). The d-axis voltage command value Vd * is calculated and output to the three-phase coordinate conversion unit (13), and the q-axis current command value iq * is calculated by the two-phase coordinate conversion unit (16). The q-axis current value iq is subtracted, and on the basis of the subtraction result (iq * −iq), the q-axis voltage command value Vq * is calculated and output to the three-phase coordinate conversion unit (13).

  The three-phase coordinate conversion unit (13) performs coordinate conversion on the d-axis voltage command value vd * and the q-axis voltage command value vq * using the angle θ calculated by the angle calculation unit (20). Then, three-phase voltage command values Vu *, Vv *, Vw * are created, and these voltage command values Vu *, Vv *, Vw * are output to the PWM inverter (14).

  The PWM inverter (14) is configured to apply a U-phase current Iu, a V-phase current Iv, and a W-phase so that voltages corresponding to the voltage command values Vu *, Vv *, and Vw * are applied to the three-phase stator coil (3). The phase current Iw is supplied to drive the motor (1).

  The current detector (15) samples the current supplied to the motor (1) by the PWM inverter (14) at an interval of the sampling time Ts, so that the phase current of three phases (U phase, V phase and W phase) is obtained. Current values iu, iv and iw are obtained and output to the two-phase coordinate conversion unit (16). The current detector (15) detects, for example, two-phase currents Iu and Iv, and calculates the current value iv of the third phase based on these two-phase current values iu and iv. However, the present invention is not limited to this. The sampling time Ts is shorter than the time required for the rotor (5) to make one rotation.

  The two-phase coordinate conversion unit (16) performs coordinate conversion on the current values iu, iv and iw of the phase current using the angle θ calculated by the angle calculation unit (20), thereby obtaining a d-axis. The current value id and the q-axis current value iq are calculated and output to the current control unit (12). Here, the d-axis current value id is also output to the angle control unit (17).

  Each time the d-axis current value id is input from the two-phase coordinate conversion unit (16), the angle control unit (17) calculates the correction angle Δθ based on the d-axis current value id. The calculated correction angle Δθ is output to the angle calculator (20) and used for controlling the angle θ of the rotor (5). PI control, PID control, or P control is used to calculate Δθ.

  When PI control (proportional / integral) is performed, the correction angle Δθ is calculated as follows: E: Deviation between d-axis current value id and predetermined command value d * (for example, 0), Cp: proportional gain of PI control, F: d-axis The accumulated value of E, which is the deviation between the current value id and the predetermined command value d *, is calculated as follows: Ci: PI control integral gain.

Δθ = Cp × E + Ci × F
The optimum values of Cp and Ci are determined based on the result of actually controlling the motor (1) by the control device (2). For this reason, the control device (2) can control the motor (1) without depending on the inductance and resistance of the stator coil (3) constituting the motor (1) to be controlled, and is highly versatile. It will be a thing.

  The first speed calculation unit (18) and the second speed calculation unit (19) obtain the rotor speed ω by mutually different equations using the rotor angle θ calculated by the angle calculation unit (20). The first speed calculator (18) outputs the obtained rotor speed ω to the angle calculator (20), and the second speed calculator (19) outputs the obtained rotor speed ω to the speed controller ( Output to 11).

  The first speed calculation unit (18) does not calculate the rotor speed at every sampling interval Ts, but determines whether the rotor (5) has rotated 360 ° or not, and this is necessary when it rotates 360 °. The obtained time T is obtained, and the rotor speed ω is obtained from 2π (= 360 °) / T.

  In the second speed calculation unit (19), ω is obtained as ω = S / Tk from the angle change amount S in the angle calculation unit during the elapse of the predetermined time Tk. Here, the angle change amount S is calculated by a change ΔK = K (n) −K (n−1) when θ = θ ′ + ω × Ts + Δθ is set to ω × Ts + Δθ = K (n). It is obtained as a value (angle counter value) obtained by integrating every period and integrating for a fixed time Tk.

  The angle calculation unit (20) calculates the correction angle Δθ calculated by the angle control unit (17) and the first speed every time the current values iu, iv and iw of the phase current are sampled (at the sampling time Ts interval). The rotor angle θ is calculated using the speed ω and the sampling time Ts calculated in the section (18). Specifically, using the rotor angle θk calculated at the previous sampling, the rotor angle θ (k + 1) at the current sampling (current) is calculated by the following equation.

θ (k + 1) = θk + ω × Ts + Δθ
Here, θ (k + 1) is a counter value corresponding to an electrical angle of 2π. When θ (k + 1) is 2π or more, 2π is subtracted, and the relationship of 0 ≦ θ (k + 1) <2π is satisfied.

  When the rotor (5) rotates in the direction of the arrow R in the figure as shown in FIG. 2 by the above calculation, the angle θn of the rotor (5) at a predetermined time n and the time during which the sampling interval Ts elapses. The angle θn + 1 of the current rotor (5) is obtained as the sum of the angle ω × Ts at which the rotor (5) rotates and the correction angle Δθ calculated by the angle control unit (17). Since the correction angle Δθ is included in the current angle θn + 1 of the rotor (5), the current angle θn + 1 of the rotor (5) can be converged to the actual angle of the rotor (5). The calculated angle θ is output to the coordinate conversion units (13) and (16).

  According to this control device, the current detection unit (15) determines the current values iu, iv and iw of each phase, and based on this, the coordinate conversion unit (16) to two phases converts the d-axis current value and A q-axis current value is calculated. Next, the correction angle Δθ is calculated by the angle control unit (17) using the d-axis current value. Next, the angle calculator (20) calculates the rotor angle θ after the sampling interval Ts. When the rotor rotates 360 °, the first speed calculator (18) calculates the rotor speed ω and updates the value of the rotor speed ω used in the angle calculator (20). The speed updated in a short time in the second speed calculator (19) is input to the speed controller (11).

  Thus, the control device (2) executes the arithmetic processing program and the control processing program, calculates the rotor angle θ without using the motor model, and adjusts the rotor angle so that the d-axis current converges to zero. The deviation is corrected. Since this control device (2) does not use a motor model when determining the rotor angle and speed, it is not necessary to change the arithmetic processing program in correspondence with the brushless motor to be controlled, and it is simple and has a small arithmetic load. Sensorless vector control can be performed with simple calculation. Then, the speed calculator is composed of the first speed calculator (18) and the second speed calculator (19), so that the rotor used in the angle calculator (20) and the speed controller (11), respectively. The speed ω can be made suitable for each, and stable speed control can be performed.

  The sensorless control device for the brushless motor can be applied to, for example, an electric pump, and sine wave sensorless drive for all other brushless motors.

FIG. 1 is a block diagram showing a sensorless control device for a brushless motor according to the present invention. FIG. 2 is a diagram illustrating angles calculated by the angle calculation unit. FIG. 3 is a block diagram showing a sensorless control device of a conventional brushless motor.

Explanation of symbols

(1) Motor
(2) Sensorless control device
(3) Stator coil
(4) Stator
(5) Rotor
(11) Speed controller
(12) Current controller
(17) Angle control unit
(18) First speed calculator
(19) Second speed calculator
(20) Angle calculator

Claims (1)

A sensorless control device that performs sensorless vector control using a two-axis rotational coordinate system composed of a d-axis and a q-axis for a brushless motor having a stator having a multi-phase stator coil and a rotor having a permanent magnet In
an angle control unit that calculates a correction angle of the rotor based on the current value and the command value of the d-axis current, a speed calculation unit that calculates a current rotor speed from an amount of change in angle during a predetermined time, and a previous sampling An angle calculator that calculates the current rotor angle using the rotor angle obtained at the time, the correction angle obtained by the angle controller and the speed obtained by the speed calculator, and the command speed input from the outside Speed control that subtracts ω calculated by the speed calculation unit from ω *, calculates a d-axis current command value and a q-axis current command value based on the subtraction result (ω * −ω), and outputs the command value to the current control unit Department and
The speed calculation unit uses the time T required for one rotation to determine the current rotor speed ω as ω = 2π / T and outputs this to the angle calculation unit, and a predetermined time Tk has elapsed. A brushless motor comprising: a second speed calculation unit that obtains the current rotor speed ω from ω = S / Tk from the angle change amount S in the angle calculation unit during the operation, and outputs this to the speed control unit Sensorless control device.

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