Motor control device

Abstract

To lessen a switching shock during shift to a position sensorless mode.SOLUTION: A control circuit (100) provided in a motor control device (3) includes: an axis error derive unit (112) that derives an axis error between a rotation axis synchronized wit rotation of a rotor provided in a permanent magnet synchronization motor and an estimated axis of the rotation axis; and a speed estimation unit (114) that estimates a rotation speed of the rotor by using a difference between the axis error and an axis error command value or the axis error as an input error. The control circuit shifts to a position sensorless mode of driving the motor on the basis of the estimated rotation speed via a synchronous operation mode of increasing the rotation speed of the rotor in accordance with a speed command value without depending on the axis error. The control circuit derives the axis error in each of the synchronous operation mode and the position sensorless mode, and sets an initial parameter of the speed estimation unit in the position sensorless mode on the basis of the axis error and the speed command value immediately before the shift from the synchronous operation mode to the position sensorless mode.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a motor control device.

Background Art

[0002] Among vector controls for permanent magnet synchronous motors, vector control performed without using a position sensor for rotor position detection is called sensorless vector control or the like. To execute sensorless vector control, it is necessary to increase the rotational speed of the motor until a necessary induced voltage is generated. Therefore, generally, the rotational speed is increased in an open loop until a necessary induced voltage is generated, and then it is often shifted to a mode for realizing sensorless vector control.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] [Summary] When shifting from a mode of increasing the rotational speed in an open loop to a mode for realizing sensorless vector control, a phenomenon called a switching shock may occur. The switching shock causes rapid speed or current fluctuations and has an adverse effect on quietness and the like. A technique for suppressing the switching shock is required.

[0005] A motor control device according to an aspect of the present disclosure includes an axis error derivation unit configured to derive an axis error between a rotation axis synchronized with the rotation of a rotor provided in a permanent magnet synchronous motor and an estimated axis of the rotation axis, and a speed estimation unit configured to estimate the rotation speed of the rotor using a difference between the axis error and an axis error command value or the axis error as an input error. The control circuit includes a control circuit that increases the rotation speed of the rotor according to a speed command value regardless of the axis error through a synchronous operation mode, and shifts to a sensorless position mode in which the motor is driven based on an estimated rotation speed by the speed estimation unit. The control circuit derives the axis error in each of the synchronous operation mode and the sensorless position mode, and sets initial parameters of the speed estimation unit in the sensorless position mode based on the axis error and the speed command value immediately before shifting from the synchronous operation mode to the sensorless position mode.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

[0007] [Detailed Description] Hereinafter, examples of embodiments of the present disclosure will be specifically described with reference to the drawings. In each of the drawings referred to, the same parts are denoted by the same reference numerals, and redundant descriptions regarding the same parts are omitted in principle. In this specification, for the sake of simplicity of description, by indicating symbols or signs referring to information, signals, physical quantities, functional units, circuits, elements, or components, etc., the names of the information, signals, physical quantities, functional units, circuits, elements, or components, etc. corresponding to the symbols or signs may be omitted or abbreviated. For example, the γ-axis voltage command value referred to by the symbol Vγ * hereinafter (see FIG. 3) may be denoted as the γ-axis voltage command value Vγ * or may be abbreviated as the voltage command value Vγ * or the command value Vγ * but they all refer to the same thing. Also, in this specification, the connection between a plurality of parts forming a circuit, such as any circuit element, wiring, node, etc., may be understood to refer to an electrical connection unless otherwise specified.

[0008] FIG. 1 is a schematic block diagram of a motor drive system SYS according to an embodiment of the present invention. The motor drive system SYS in FIG. 1 includes a motor 1, an inverter 2 which is a PWM inverter, a motor control device 3, a host device 4, and a current sensor 5. PWM is an abbreviation for "Pulse Width Modulation". A DC power supply 10 is connected to the inverter 2. The DC power supply 10 is connected to wirings WL and WH. The DC power supply 10 outputs a positive DC voltage with respect to the wiring WH based on the potential of the wiring WL.

[0009] The motor 1 is a three-phase permanent magnet synchronous motor, and includes a rotor 6 provided with permanent magnets, and a stator 7 provided with armature windings 7u, 7v, and 7w of the U-phase, V-phase, and W-phase. The motor 1 may be an embedded magnet synchronous motor or a surface magnet synchronous motor. The armature windings 7u, 7v, and 7w are Y-connected with the neutral point 11 as the center. In the armature windings 7u, 7v, and 7w, the non-connected ends on the opposite side of the neutral point 11 are respectively connected to the terminals 12u, 12v, and 12w. That is, one ends of the armature windings 7u, 7v, and 7w are commonly connected at the neutral point 11, and the other ends of the armature windings 7u, 7v, and 7w are respectively connected to the terminals 12u, 12v, and 12w.

[0010] The inverter 2 is a power converter including half-bridge circuits for the U-phase, V-phase, and W-phase. Each half-bridge circuit has a pair of switching elements. In each half-bridge circuit, the pair of switching elements are connected in series between the wirings WH and WL, and a DC voltage output from the DC power supply 10 is applied to each half-bridge circuit.

[0011] The half-bridge circuit for the U-phase is composed of a high-potential side switching element 8u (hereinafter also referred to as the upper arm 8u) and a low-potential side switching element 9u (hereinafter also referred to as the lower arm 9u). The half-bridge circuit for the V-phase is composed of a high-potential side switching element 8v (hereinafter also referred to as the upper arm 8v) and a low-potential side switching element 9v (hereinafter also referred to as the lower arm 9v). The half-bridge circuit for the W-phase is composed of a high-potential side switching element 8w (hereinafter also referred to as the upper arm 8w) and a low-potential side switching element 9w (hereinafter also referred to as the lower arm 9w). Incidentally, a diode (free wheel diode) with a forward direction from the wiring WL to the wiring WH may be connected in parallel to each of the switching elements 8u, 8v, 8w, 9u, 9v, and 9w.

[0012] The connection points of the upper arm 8u and the lower arm 9u connected in series, the connection points of the upper arm 8v and the lower arm 9v connected in series, and the connection points of the upper arm 8w and the lower arm 9w connected in series are connected to the terminals 12u, 12v, and 12w, respectively. In FIG. 1, although field effect transistors are shown as each switching element, they can also be replaced with IGBTs (insulated gate bipolar transistors) or the like.

[0013] The inverter 2 generates AC power (three-phase AC power) from the DC power from the DC power supply 10 under the control of the motor control device 3 and supplies it to the motor 1. More specifically, the DC voltage from the DC power supply 10 supplied to the inverter 2 (the output DC voltage of the DC power supply 10) is PWM modulated (pulse width modulation) by the switching operation of each switching element in the inverter 2, thereby being converted into a three-phase AC voltage. When the three-phase AC voltage is supplied to the motor 1, currents corresponding to the three-phase AC voltage flow through each armature winding (7u, 7v, and 7w), and the motor 1 is driven. Incidentally, ignoring the dead time for preventing the upper arm and the lower arm of the same phase from being turned on simultaneously, in each half-bridge circuit, when the upper arm is on, the lower arm is off, and when the upper arm is off, the lower arm is on. Unless otherwise specified, the following description will be made ignoring the above dead time.

[0014] The three-phase AC voltage applied to the motor 1 by the inverter 2 consists of the U-phase voltage Vu representing the voltage applied to the armature winding 7u of the U-phase, the V-phase voltage Vv representing the voltage applied to the armature winding 7v of the V-phase, and the W-phase voltage Vw representing the voltage applied to the armature winding 7w of the W-phase. The overall applied voltage to the motor 1, which is the combined voltage of the U-phase voltage Vu, the V-phase voltage Vv, and the W-phase voltage Vw, is called the motor voltage (motor terminal voltage), and is represented by the symbol Va.

[0015] When a motor voltage Va is applied, the U-phase component, V-phase component, and W-phase component of the current supplied from the inverter 2 to the motor 1 are respectively referred to as the U-phase current Iu, V-phase current Iv, and W-phase current Iw. The U-phase current Iu is supplied to the armature winding 7u through the terminal 12u, the V-phase current Iv is supplied to the armature winding 7v through the terminal 12v, and the W-phase current Iw is supplied to the armature winding 7w through the terminal 12w. The total supply current to the motor 1, which is the combined current of the U-phase current Iu, V-phase current Iv, and W-phase current Iw, is called the motor current (armature current) and is represented by the symbol Ia.

[0016] The current sensor 5 detects any two or more of the U-phase current Iu, V-phase current Iv, and W-phase current Iw and provides the detection results to the motor control device 3.

[0017] The motor control device 3 can provide a PWM signal for realizing desired vector control to the inverter 2 while based on the detection results of the current sensor 5 and the like. The motor control device 3 is connected to the upper device 4 via the bus 13. The bus 13 consists of a plurality of communication wirings. Bidirectional communication is possible between the motor control device 3 and the upper device 4 via the bus 13. The bus 13 may be a serial bus or a parallel bus. When the bus 13 is a serial bus, the bidirectional communication between the motor control device 3 and the upper device 4 may be, for example, I 2 C (Inter-Integrated Circuit) communication, or communication by SPI (Serial Peripheral Interface).

[0018] The upper-level device 4 is an external device (external circuit) provided outside the motor control device 3, and can transmit various commands to the motor control device 3 via the bus 13. The motor control device 3 operates according to the commands from the upper-level device 4. The command is, for example, a signal instructing to rotate the motor 1 at a desired rotational speed. Note that the rotation of the motor 1 specifically means the rotation of the rotor 6. The upper-level device 4 may be connected to the motor control device 3 through a signal line other than the bus 13, and the upper-level device 4 may supply various command signals to the motor control device 3 through the signal line. The motor control device 3 operates according to the command signal. For example, the upper-level device 4 can instruct the motor control device 3 to start the rotation of the motor 1 or specify the rotational speed of the motor 1 by the command signal. At this time, a speed command value ω * described later is generated according to the command signal. More specifically, for example, the command signal may be an analog voltage signal from 0V to 4V. In this case, a command signal having a voltage value of 1V or more instructs the start of rotation of the motor 1. When the command signal has a voltage value of 1V or more, as the voltage value of the command signal increases from 1V to 4V, an increase in the rotational speed of the motor 1 is instructed. Also, for example, the command signal may be a rectangular wave signal. In this case, the start of rotation of the motor 1 or the specification of the rotational speed of the motor 1 can also be performed according to the duty or frequency of the rectangular wave signal.

[0019] The motor control device 3 is an electronic component including a semiconductor chip having a semiconductor integrated circuit formed on a semiconductor substrate, a housing that houses the semiconductor chip, and a plurality of external terminals exposed from the housing to the outside of the motor control device 3. The motor control device 3 is formed by encapsulating the semiconductor chip in a housing made of resin. Each circuit in the motor control device 3 is formed in the semiconductor integrated circuit.

[0020] Here, it is assumed that the inverter 2 is provided outside the motor control device 3, but the inverter 2 can be built in the motor control device 3 (the inverter 2 and the motor control device 3 can both be built in the above-mentioned electronic component).

[0021] Figures 2 and 3 are the analytical model diagrams of the motor 1. In Figure 2, the U-phase axis, V-phase axis, and W-phase axis (i.e., the stator winding fixed axes of the U-phase, V-phase, and W-phase) which are fixed axes are shown. 6a represents the permanent magnet provided on the rotor 6 of the motor 1. In the rotating coordinate system that rotates at the same speed as the rotational speed of the magnetic flux created by the permanent magnet 6a, the axis along the direction of the magnetic flux created by the permanent magnet 6a is called the d-axis, and the control rotational axis corresponding to the d-axis is called the γ-axis. The direction of the d-axis coincides with the direction of the magnetic flux created by the permanent magnet 6a. Also, as shown in Figure 3, the axis that is phase-advanced by 90 electrical degrees from the d-axis is called the q-axis, and the axis that is phase-advanced by 90 electrical degrees from the γ-axis is called the δ-axis. In Figures 2 and 3, the counterclockwise direction corresponds to the phase-advancing direction.

[0022] The d-axis and the γ-axis are rotational axes, and the γ-axis corresponds to the d-axis estimated within the motor control device 3 (i.e., corresponds to the estimated axis of the d-axis). Similarly, the q-axis and the δ-axis are rotational axes, and the δ-axis corresponds to the q-axis estimated within the motor control device 3 (i.e., corresponds to the estimated axis of the q-axis). Hereinafter, the d-axis and the q-axis are collectively referred to as the dq-axis. The γ-axis and the δ-axis are collectively referred to as the γδ-axis. The dq-axis is a rotational axis that rotates in synchronization with the rotation of the rotor 6, and the γδ-axis is a control rotational axis corresponding to the estimated axis of the dq-axis.

[0023] The rotational speed of the dq-axis is represented by ω. The rotational speed of the γδ-axis is represented by ωc. The angle (phase) of the d-axis when looking at the d-axis in the phase-advancing direction with the U-phase axis as the reference is represented by θ. Similarly, the angle (phase) of the γ-axis when looking at the γ-axis in the phase-advancing direction with the U-phase axis as the reference is represented by θc. The angles represented by θ and θc are angles in the electrical angle, and they are generally also called the rotor position or the pole position. The rotational speeds represented by ω and ωc are angular velocities in the electrical angle. The difference Δθ between the phase θ of the d-axis and the phase θc of the γ-axis is called the axis error and is represented by "Δθ = θ - θc".

[0024] Hereinafter, θ or θc is referred to as the rotor position, and ω or ωc is referred to as the rotational speed. In particular, θ can also be referred to as the actual rotor position, and ω can also be referred to as the actual rotational speed. Also, the γ-axis and δ-axis, which are the axes of rotation in control, are also called the control axes. When the rotor position and rotational speed are derived by estimation, the γ-axis and δ-axis can be called the estimated axes in control.

[0025] Symbols involved in the control of the motor drive system SYS are defined as follows. The d-axis component, q-axis component, γ-axis component, and δ-axis component of the motor voltage Va are respectively called the d-axis voltage, q-axis voltage, γ-axis voltage, and δ-axis voltage, and are represented by the symbols Vd, Vq, Vγ, and Vδ. The d-axis component, q-axis component, γ-axis component, and δ-axis component of the motor current Ia are respectively called the d-axis current, q-axis current, γ-axis current, and δ-axis current, and are represented by the symbols Id, Iq, Iγ, and Iδ. Ld and Lq respectively represent the d-axis inductance (d-axis component of the inductance of the armature winding) and q-axis inductance (q-axis component of the inductance of the armature winding) in motor 1. Ra represents the resistance value of the armature winding per phase of motor 1. Ld, Lq, and Ra belong to the motor parameters according to the electrical characteristics of motor 1.

[0026] The target values of the γ-axis voltage Vγ and δ-axis voltage Vδ that the γ-axis voltage Vγ and δ-axis voltage Vδ should follow are respectively the γ-axis voltage command value Vγ * and the δ-axis voltage command value Vδ * as represented by. The target values of the γ-axis current Iγ and δ-axis current Iδ that the γ-axis current Iγ and δ-axis current Iδ should follow are respectively the γ-axis current command value Iγ * and the δ-axis current command value Iδ * as represented by. The target values of the U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw that the U-phase voltage Vu, V-phase voltage Vv, and W-phase voltage Vw should follow are respectively the U-phase voltage command value Vu * , the V-phase voltage command value Vv * and the W-phase voltage command value Vw * as represented by. The command value Vu * , Vv *and Vw * A three-phase voltage command value is formed by

[0027] In addition, in this specification, Iγ can also be used as a symbol representing the value of the γ-axis current. That is, the value of the γ-axis current may be denoted as the γ-axis current value Iγ. The same applies to symbols representing physical quantities or state quantities other than Iγ.

[0028] FIG. 4 shows the internal configuration and peripheral configuration of the motor control device 3. The motor control device 3 includes a control circuit 100 and a memory 150. The motor control device 3 is driven based on a power supply voltage supplied from a voltage source (not shown). In addition to the control circuit 100 and the memory 150, an internal power supply circuit that generates one or more internal power supply voltages from the power supply voltage, a communication interface that realizes communication with the host device 4, and an abnormality detection circuit that detects various abnormalities (none of which are shown) are provided in the motor control device 3.

[0029] The memory 150 has a volatile memory such as a RAM (Random Access Memory) and a non-volatile memory such as a flash memory. The volatile memory may have a storage unit classified as a register. The control circuit 100 is composed of a combination of hardware and software. That is, the control circuit 100 is composed of hardware such as a DSP (Digital Signal Processor) and a microcomputer that executes a program, and the program is stored in the non-volatile memory in the memory 150. For example, the speed control unit 118 described later can be realized by a microcomputer. However, the control circuit 100 may be realized only by hardware or only by software.

[0030] The control circuit 100 includes each part referred to by reference numerals 111 to 128 and 130. Each part in the motor control device 3 can freely use each value and each signal input to the motor control device 3 and each value and each signal generated within the motor control device 3. Each part in the motor control device 3 derives, sets, or outputs a command value (Iγ * Iδ * Vγ* and Vδ * and Vu * and Vv * and Vw * and ω * and Δθ * (including) or the state quantities (Iu, Iv, Iγ, Iδ, Δθ, Δθ IN , θc, ωe, ωc) are updated, and the command value or state quantity to be derived, set, or output by itself is derived, set, or output using the latest command value or state quantity given to itself. Further, motor parameters corresponding to the electrical characteristics of the motor 1 are given in advance to the motor control device 3, and the motor control device 3 can perform various calculations using the motor parameters.

[0031] As control modes of the control circuit 100, there are a positioning mode, a synchronous operation mode, and a sensorless position mode. The synchronous operation mode can also be referred to as a synchronous drive mode. The motor control device 3 can perform sensorless vector control of the motor 1 (that is, perform vector control of the motor 1 without using a sensor for detecting the rotor position θ). To realize sensorless vector control, it is necessary to increase the rotational speed ω until the induced voltage required for the motor 1 is generated. Therefore, when starting the motor 1 (that is, in the process of increasing the rotational speed ω of the rotor 6 from the state where the rotor 6 is stopped toward the rotational speed specified from the host device 4), the control circuit 100 shifts its control mode from the positioning mode through the synchronous operation mode to the sensorless position mode, and then maintains it in the sensorless position mode. In FIG. 4, the states of the changeover switches 116 and 121 in the positioning mode or the synchronous operation mode are illustrated. In FIG. 5, the states of the changeover switches 116 and 121 in the sensorless position mode are illustrated. The details of the significance of these respective modes will be described later, and the operations and functions of each part in FIG. 4 or FIG. 5 will be explained.

[0032] In the configuration example of FIG. 4, the current sensor 5 detects the values of the U-phase current Iu and the V-phase current Iv, and supplies the detected U-phase current value Iu and V-phase current value Iv to the coordinate conversion unit 111.

[0033] The coordinate conversion unit 111 derives and outputs the γ-axis current value Iγ and the δ-axis current value Iδ by performing coordinate conversion of the U-phase current value Iu and the V-phase current value Iv on the γδ axis based on the rotor position θc. The rotor position θc is supplied from the integrator 127 to the coordinate conversion unit 111.

[0034] The axis error derivation unit 112 derives the axis error Δθ using all or part of the γ-axis current value Iγ and the δ-axis current value Iδ from the coordinate conversion unit 111, the voltage command values Vγ * and Vδ * , and the rotational speed ωc from the changeover switch 116. Various methods have been proposed as methods for deriving the axis error Δθ, and the axis error Δθ may be derived by any derivation method including known derivation methods in the axis error derivation unit 112. For example, the axis error Δθ may be derived using the following formula (1A).

[0035]

Equation

[0036] The subtractor 113 receives the axis error Δθ and the axis error command value Δθ * , and the subtractor 113 derives their difference (Δθ * -Δθ). The axis error command value Δθ * represents the value that the axis error Δθ should follow, that is, the target value of the axis error Δθ. The axis error command value Δθ * is input from the axis error command unit 128 to the subtractor 113. The axis error command value Δθ * is usually set to zero. It may be fixed at “Δθ * = 0”, and in this case, the axis error command unit 128 can be omitted from the control circuit 100.

[0037] The difference (Δθ * -Δθ) derived by the subtractor 113 is supplied to the PLL control unit 114 as the input error Δθ IN . “Δθ IN = Δθ * -Δθ”, but when fixed at “Δθ * = 0”, the axis error Δθ itself becomes the input error ΔθIN is used. The PLL control unit 114 is a speed estimation unit that operates significantly only in the position sensorless mode. The control circuit 100 may stop the operation of the PLL control unit 114 in the positioning mode and the synchronous operation mode. In the position sensorless mode, the PLL control unit 114 estimates the rotational speed ω from the input error Δθ IN using proportional-integral control, and derives and outputs an estimated rotational speed ωe which is the estimated rotational speed ω. As will be described later, in the position sensorless mode, the estimated rotational speed ωe is treated as the rotational speed ωc of the control axis. In the position sensorless mode, the PLL control unit 114 cooperates with each part in the control circuit 100 to realize PLL (Phase Locked Loop) control, and estimates the rotational speed ω so that the input error Δθ IN converges to zero (in other words, so that the input error Δθ IN approaches zero), and derives the estimated rotational speed ωe.

[0038] The speed command unit 115 sets and outputs a speed command value ω * . The speed command value ω * represents the value that the rotational speeds ω and ωc should follow, that is, the target values of the rotational speeds ω and ωc.

[0039] The switch 116 selectively outputs either the output of the PLL control unit 114 or the output of the speed specifying unit 115 as the rotational speed ωc. In the positioning mode and the synchronous operation mode, the speed command value ω * is selected by the switch 116 and becomes "ωc = ω * " (see FIG. 4), and in the position sensorless mode, the estimated rotational speed ωe is selected by the switch 116 and becomes "ωc = ωe" (see FIG. 5).

[0040] The subtractor 117 derives a speed error (ω * - ωc) which is the difference between the speed command value ω * and the rotational speed ωc output from the switch 116. The speed error (ω * - ωc) derived by the subtractor 117 is input to the speed control unit 118.

[0041] The speed control unit 118 operates significantly only in the sensorless position mode. The control circuit 100 may stop the operation of the speed control unit 118 in the positioning mode and the synchronous operation mode. In the sensorless position mode, the speed control unit 118 uses proportional-integral control or the like so that the speed error (ω * - ωc) converges to zero (in other words, so that the speed error approaches zero), and derives and outputs the δ-axis current command value Iδ * .

[0042] The current command unit 119 sets and outputs the γ-axis current command value Iγ * . The current command unit 120 functions significantly only in the positioning mode and the synchronous rectification mode, and sets and outputs the δ-axis current command value Iδ * in the positioning mode and the synchronous rectification mode.

[0043] The changeover switch 121 selectively outputs either the output of the current command unit 120 or the output of the speed control unit 118 to the subtracter 123. In the positioning mode and the synchronous operation mode, the δ-axis current command value Iδ * output from the current command unit 120 is input to the subtracter 123 via the changeover switch 121 (see FIG. 4). In the sensorless position mode, the δ-axis current command value Iδ * output from the speed control unit 118 is input to the subtracter 123 via the changeover switch 121.

[0044] The subtracter 122 derives the current error (Iγ * - Iγ) which is the difference between the γ-axis current command value Iγ * from the current command unit 119 and the γ-axis current value Iγ from the coordinate conversion unit 111. The current error (Iγ * - Iγ) derived by the subtracter 122 is input to the current control unit 124.

[0045] The subtracter 123 derives the current error (Iδ * - Iδ) which is the difference between the δ-axis current command value Iδ * input through the changeover switch 121 and the δ-axis current value Iδ from the coordinate conversion unit 111. The current error (Iδ* -Iδ) is input to the current control unit 124. In the positioning mode and the synchronous operation mode, the δ-axis current command value Iδ output from the current command unit 120 * and the difference between the δ-axis current value Iδ output from the coordinate conversion unit 111 is the current error (Iδ * -Iδ), which is derived by the subtractor 123 (see FIG. 4). In the position sensorless mode, the δ-axis current command value Iδ output from the speed control unit 118 * and the difference between the δ-axis current value Iδ output from the coordinate conversion unit 111 is the current error (Iδ * -Iδ), which is derived by the subtractor 123 (see FIG. 5).

[0046] The current control unit 124 performs current feedback control using proportional-integral control or the like so that the current errors (Iγ * -Iγ) and (Iδ * -Iδ) both converge to zero. At this time, non-interference control for eliminating interference between the γ-axis and the δ-axis is used, and the γ-axis voltage command value Vγ * -Iγ) and (Iδ * -Iδ) both converge to zero so as to derive * the γ-axis voltage command value Vγ * and the δ-axis voltage command value Vδ * -Iγ) and (Iδ * -Iδ) to zero, any derivation method including known methods can be used as the derivation method of the command values Vγ * and Vδ * When deriving the command values Vγ * and Vδ * , the rotational speed ωc and the current values Iγ and Iδ may also be referred to. The command values Vγ * and Vδ * derived by the current control unit 124 are input to the coordinate conversion unit 125.

[0047] The coordinate conversion unit 125 coordinates the command values Vγ * and Vδ * on the three-phase fixed coordinate axes based on the rotor position θc, thereby obtaining the command values Vu * , Vv* and Vw * to derive a three-phase voltage command value composed of these and output it to the PWM conversion unit 126.

[0048] The PWM conversion unit 126 generates a PWM signal according to the three-phase voltage command values Vu * , Vv * and Vw * and drives the inverter 2 based on the PWM signal. The PWM signal is such that the values of the U-phase, V-phase, and W-phase voltages Vu, Vv, and Vw respectively match the command values Vu * , Vv * and Vw * . For this reason, the inverter 2 generates a three-phase AC voltage (and thus three-phase AC power) from the output DC voltage (and thus output DC power) of the DC power supply 10 by pulse width modulation so that the values of the U-phase, V-phase, and W-phase voltages Vu, Vv, and Vw respectively match the command values Vu * , Vv * and Vw * , and supplies the generated three-phase AC voltage to the motor 1. In the inverter 2, the switching elements 8u, 8v, 8w, 9u, 9v, and 9w are controlled to be on / off according to the PWM signal, so that AC power according to the three-phase voltage command values Vu * , Vv * and Vw * is supplied to the motor 1.

[0049] The integrator 127 derives the rotor position θc by integrating the rotational speed ωc from the changeover switch 116. The rotor position θc derived by the integrator 127 is supplied to the coordinate conversion units 111 and 125.

[0050] The shaft error command unit 128 sets and outputs a shaft error command value Δθ * . The shaft error command unit 128 can also set a shaft error command value Δθ * other than zero, but as described above, basically it may be fixed to “Δθ * = 0”.

[0051] The startup control unit 130 sets and switches the control mode of the control circuit 100. When starting the motor 1 (i.e., in the process of increasing the rotational speed ω of the rotor 6 from a state where the rotor 6 is stopped towards the rotational speed specified by the host device 4), the startup control unit 130 shifts the control mode of the control circuit 100 from the positioning mode, through the synchronous operation mode, to the sensorless mode, and then maintains it in the sensorless mode hereinafter. Hereinafter, the control mode of the control circuit 100 is simply referred to as the control mode.

[0052] The startup control unit 130 has a function of controlling the states of the changeover switches 116 and 121, and with the change of the states of the changeover switches 116 and 121, the transition from the synchronous operation mode to the sensorless mode is realized. When the control mode is the positioning mode and the synchronous operation mode, as shown in FIG. 4, the startup control unit 130 controls the changeover switch 116 so that "ωc = ω" * and controls the changeover switch 121 so that the d-axis current command value Iδ output from the current command unit 120 is supplied to the subtracter 123 through the changeover switch 121. When the control mode is the sensorless mode, as shown in FIG. 5, the startup control unit 130 controls the changeover switch 116 so that "ωc = ωe" and controls the changeover switch 121 so that the d-axis current command value Iδ * output from the speed control unit 118 is supplied to the subtracter 123 through the changeover switch 121. Further, when starting the motor 1, the startup control unit 130 controls the speed command unit 115 and the current command units 119 and 120 so that the command values ω * , Iγ * , and Iδ * are set as shown below. *

[0053] FIG. 6 is a schematic diagram showing the transition of the control mode when starting the motor 1. As time elapses, it is assumed that times t1, t2, and t3 are visited in this order. The control mode is the positioning mode from time t1 until just before time t2, switches from the positioning mode to the synchronous operation mode at time t2, and then switches from the synchronous operation mode to the position sensorless mode at time t3. Time ta is a time after time t2 and before time t3 (the meaning of time ta will be described later). Just before time t1, a command is transmitted from the host device 4 to the motor control device 3 to instruct the rotor 6 to rotate at a rotational speed ωx, and in response to the reception of the command, control by the control circuit 100 is executed from time t1. In FIG. 6, the δ-axis current command value Iδ when the control mode is the positioning mode and the synchronous operation mode * is output by the current command unit 120, and the δ-axis current command value Iδ when the control mode is the position sensorless mode * is output by the speed control unit 118.

[0054] <Positioning mode> The positioning mode is a control mode that fixes the rotor position θ (and θc) at a predetermined initial position θ INITIAL . In the positioning mode, the control circuit 100 gradually supplies a direct current to any one of the stator windings of a specific phase (that is, any one of the stator windings 7u, 7v, and 7w). More specifically, in the positioning mode, the current command unit 119 gradually increases the γ-axis current command value Iγ * from zero to a positive predetermined value Iγ0 * , while the current command unit 120 fixes the δ-axis current command value Iδ * at zero. In the positioning mode, since direct current power is supplied to the motor 1, the speed command value ω * is fixed at zero (the start control unit 130 controls the speed command unit 115 so that “ω * = 0”). After time t1, the time when the γ-axis current command value Iγ * reaches the predetermined value Iγ0 * corresponds to time t2. The start control unit 130, after time t1, when the γ-axis current command value Iγ * reaches the predetermined value Iγ0* When reaching this point, switch the control mode from the positioning mode to the synchronous operation mode.

[0055] <Synchronous operation mode> The synchronous operation mode is a control mode in which the motor 1 is driven in synchronization with the rotor position θc obtained by integrating the speed command value ω * In the synchronous operation mode, the control circuit 100 drives the inverter 2 through the generation and output of the three-phase voltage command values Vu * based on the detection results (Iu, Iv) of the current sensor 5 and the speed command value ω * , Vv * and Vw * to control the motor 1. In the synchronous operation mode, under the control of the startup control unit 130, the speed command unit 115 gradually increases the speed command value ω * from zero to a predetermined reference speed command value ω1 * . As a result, the rotational speeds ω and ωc increase following the increase in the speed command value ω * . In the synchronous operation mode, since "ωc = ω * " (see Fig. 4), the control circuit 100 controls the motor 1 so that the rotational speeds ω and ωc increase according to the speed command value ω * regardless of the shaft error Δθ. The integrator 127 regards the rotor position θc at the timing of shifting from the positioning mode to the synchronous operation mode as coinciding with the initial position θ INITIAL , and thereafter derives the rotor position θc by integrating the rotational speed ωc.

[0056] The reference speed command value ω1 * is determined by the set data stored in the memory 150. The host device 4 can give the set data for determining the reference speed command value ω1 * to the motor control device 3 and store it in the memory 150. In the synchronous operation mode, the γ-axis current command value Iγ * is fixed at a predetermined value Iγ0 * and the δ-axis current command value Iδ * is fixed at zero. However, in the synchronous operation mode, the γ-axis current command value Iγ *It is also possible to vary it (for example, gradually decrease it from a predetermined value Iγ0 * ), and it is also possible to vary the δ-axis current command value Iδ * (for example, gradually increase it from zero). After time t2, when the speed command value ω * reaches the reference speed command value ω1 * , the corresponding time is time t3. The startup control unit 130 switches the control mode from the synchronous operation mode to the sensorless mode when the speed command value ω * reaches the reference speed command value ω1 * .

[0057] <Sensorless mode> In the sensorless mode, the rotational speed ω is estimated so that the shaft error Δθ matches the shaft error command value Δθ * (that is, the estimated rotational speed ωe is derived), and the motor 1 is driven based on the estimated rotational speed ωe. In the sensorless mode, the estimated rotational speed ωe is used as the rotational speed ωc of the control axis (see FIG. 5). Also, considering that the shaft error command value Δθ * is zero, in the sensorless mode, the control circuit 100 can make the estimated rotational speed ωe follow the speed command value ω * (in other words, reduce the error between the estimated rotational speed ωe and the speed command value ω * to zero) and control the motor 1 so that the shaft error Δθ converges to the shaft error command value Δθ * or zero. Specifically, the control of the motor 1 by the control circuit 100 is realized by the control circuit 100 driving the inverter 2 through the generation and output of the three-phase voltage command values Vu * , Vv * and Vw * . In the sensorless mode, since the estimated rotational speed ωe represents an estimated value of the actual rotational speed ω, the actual rotational speed ω follows the speed command value ω * .

[0058] In the sensorless mode, the current error (Iγ * - Iγ), and the δ-axis current command value Iδ output from the speed control unit 118 *Based on the current error (Iδ * -Iδ), the motor 1 is driven and controlled through the generation of voltage command values (Vγ * , Vδ * , Vu * , Vv * and Vw * ) such that both converge to zero.

[0059] After shifting from the synchronous operation mode to the sensorless position mode, the current command unit 119 may gradually decrease the γ-axis current command value Iγ * from a predetermined value Iγ0 * towards zero as shown in FIG. 6, and may fix the γ-axis current command value Iγ * at zero after the γ-axis current command value Iγ * reaches zero. In the example of FIG. 6, after “Iγ * =0 ” ”, the speed command value ω * gradually increases from the reference speed command value ω1 * towards the speed command value ω2 * corresponding to the rotational speed ωx, and thereafter, is maintained at “ω * =ω2 * ”. The speed command value ω2 * is greater than the reference speed command value ω1 * . After shifting to the sensorless position mode, the speed command value ω * is adjusted within the range where “ω *” >ω1 * ” is satisfied so as to obtain the rotational speed ω according to the command from the host device 4. In the sensorless position mode, the speed control unit 118 adjusts the δ-axis current command value Iδ * so as to reduce the speed error (ω * -ωc), and thus so as to reduce the speed error (ω * -ωe). Note that the γ-axis current command value Iγ * in the sensorless position mode may be non-zero depending on the content of the vector control to be realized.

[0060] Incidentally, when switching from the synchronous operation mode to the sensorless position mode, a phenomenon generally called switching shock may occur in some cases. In the switching shock, a rapid and large change occurs in the rotational speed ω, and a rapid and large change also occurs in the amplitude of each phase current. The switching shock becomes prominent immediately after switching from the synchronous operation mode to the sensorless position mode when the deviation between the rotational speed ωc(ωe) of the control axis and the actual rotational speed ω is large. When the usage environment of the motor 1 is fixed, such as when the load of the motor 1 is constant, by setting the command values (Iγ * 、Iδ * 、ω * ) in the synchronous operation mode to appropriate values according to the usage environment, (Δθ * -Δθ) can be made zero immediately after switching to the sensorless position mode, and as a result, the switching shock can be sufficiently suppressed. However, when the usage environment of the motor 1 is uncertain, the above appropriate values also become uncertain. Therefore, it is necessary to devise a way to make (Δθ * -Δθ) zero immediately after switching to the sensorless position mode.

[0061] In the synchronous operation mode, the motor 1 is controlled in an open loop using the speed command value ω * as the rotational speed ωc of the control axis. For this reason, in a general reference motor control device different from the motor control device 3, the calculation for deriving the shaft error Δθ is not performed in the synchronous operation mode.

[0062] Fig. 7 schematically shows the waveform of the rotational speed ωc’ in the vicinity where the switching from the synchronous operation mode to the sensorless position mode is performed in the reference motor control device. The rotational speed ωc’ corresponds to the rotational speed ωc of the control axis in the reference motor control device. In the reference motor control device, a rapid change in the rotational speed due to the switching shock occurs. Although not particularly shown, in the reference motor control device, a rapid fluctuation also occurs in the current command value immediately after switching to the sensorless position mode.

[0063] In order to suppress the switching shock, in the motor control device 3 according to the present embodiment, the axial error Δθ is derived not only in the sensorless mode but also in the synchronous operation mode. That is, the axial error derivation unit 112 always derives the axial error Δθ in the sensorless mode and the synchronous operation mode. However, the axial error derivation unit 112 may derive the axial error Δθ for all of the period during which the control mode of the control circuit 100 is set to the sensorless mode and a part of the period during which the control mode of the control circuit 100 is set to the synchronous operation mode. That is, the axial error derivation unit 112 may stop deriving the axial error Δθ during the period from time t2 to time ta, and always derive the axial error Δθ after time ta. The axial error Δθ is not derived in the positioning mode.

[0064] <Configuration of PLL control unit (speed estimation unit)> FIG. 8 shows the internal configuration of the PLL control unit 114. As described above, in the sensorless mode, the PLL control unit 114 estimates the rotational speed ω from the input error Δθ IN using proportional-integral control, and derives and outputs the estimated rotational speed ωe which is the estimated rotational speed ω. To achieve this, the PLL control unit 114 includes a proportional calculator 114a, an integral calculator 114b, and an adder 114c.

[0065] The proportional calculator 114a derives and outputs the product (Kp·Δθ IN ) obtained by multiplying the input error Δθ by a predetermined proportional gain Kp. The integral calculator 114b integrates the input error Δθ using the integral gain Ki to derive and output the value (Ki·Δθ IN / s). The adder 114c derives and outputs the sum of the output value (Kp·Δθ IN ) of the proportional calculator 114a and the output value (Ki·Δθ IN / s) of the integral calculator 114b. The output value of the adder 114c is represented by (Kp·Δθ IN +Ki·Δθ IN / s), and the output value of the adder 114c corresponds to the estimated rotational speed ωe. Hereinafter, the output value (Kp·Δθ IN ) of the proportional calculator 114a IN and the output value (Ki·Δθ IN) may be referred to as the proportional term, and the output value (Ki·Δθ IN / s) of the integrator 114b may be referred to as the integral term. Note that "s" in the expressions representing the output values of the integrator 114b and the adder 114c represents the Laplace operator.

[0066] The proportional calculator 114a only needs to multiply the input error Δθ in a certain noted control cycle by the proportional gain Kp in the noted control cycle. IN On the other hand, the integrator 114b needs to determine its output value taking into account the integration result of the input error Δθ before a certain noted control cycle in the noted control cycle. That is, the integrator 114b needs to obtain its output value by adding the current input error Δθ to the integration result of the past input error Δθ. IN Therefore, in the control cycle immediately after the transition from the synchronous operation mode to the position sensorless mode, with the initial parameter corresponding to the integration result of the past input error Δθ set in the integrator 114b, it is necessary to add the current input error Δθ to the initial parameter. The initial parameter corresponds to the initial value of the integral value of the integral term in the position sensorless mode. IN to the integration result of the past input error Δθ IN In order to suppress the switching shock, it is crucial to set an appropriate value for the initial parameter. The startup control unit 130 according to this embodiment sets the above initial parameter (the initial parameter of the speed PLL control unit 114) based on the axis error Δθ and the speed command value ω IN immediately before the transition from the synchronous operation mode to the position sensorless mode. Briefly speaking, when transitioning to the position sensorless mode, based on the input error Δθ IN and the speed command value ω

[0067] immediately before the transition to the position sensorless mode, the integration value of the integral term that makes the output value (Kp·Δθ * +Ki·Δθ IN / s) of the adder 114c match the reference speed command value ω1 * is obtained by inverse calculation, and the obtained integration value is set as the above initial parameter. IN +Ki·Δθ IN / s) is made to match the reference speed command value ω1 * by inverse calculation, and the obtained integration value is set as the above initial parameter.

[0068] The method for setting initial parameters will be described in more detail. Hereinafter, the integral value of the integral term is referred to as the integral value IV. The operations in the control circuit 100 are performed based on the instantaneous values of each command value or each state quantity discretized at a predetermined control period. Now, assume that the control period at which the calculation of the axis error Δθ starts is the first control period, and at the same time, assume that the control period immediately before the control mode shifts from the synchronous operation mode to the position sensorless mode is the m-th control period. m represents an arbitrary integer of 2 or more. The command value or state quantity derived or set in the i-th control period is represented by a symbol with [i]. Therefore, for example, Δθ, Δθ IN , ω * , ωe, ωc, IV are represented by Δθ[i], Δθ IN [i], ω * [i], ωe[i], ωc[i], IV[i], respectively. Also, the i-th control period is referred to as the control period P[i]. i represents an arbitrary natural number. FIG. 9 shows some command values and state quantities in a plurality of control periods. It is assumed that the axis error command value Δθ * is fixed to a constant value (for example, zero).

[0069] In the position sensorless mode, the integral calculator 114b obtains its latest output value by multiplying the sum of the currently held integral value IV and the latest input error Δθ IN by the integral gain Ki. Therefore, when the control period P[i] belongs to the control period of the position sensorless mode (that is, when "i > m"), the estimated rotational speed ωe[i] is represented by the following formula (2A). ωe[i]=(Kp×Δθ IN [i]) +(Ki×(IV[i - 1]+Δθ IN [i])) ···(2A)

[0070] Here, IV[i - 1] is the integral value IV held by the integral calculator 114b in the control period P[i] before obtaining the output value of the integral calculator 114b in the control period P[i], and is the input error Δθ up to the control period P[i - 1] INrepresents the cumulative value. The integrator 114b in the control cycle P[i] multiplies the sum obtained by adding the latest input error Δθ IN [i] to the integration value IV[i - 1] by the integration gain Ki to obtain its output value (the integral term which is the second term on the right side of Equation (2A)). The proportional calculator 114a in the control cycle P[i] multiplies the latest input error Δθ IN [i] by the proportional gain Kp to obtain its output value (the proportional term which is the first term on the right side of Equation (2A)).

[0071] When “i = m + 1”, Equation (2A) is equivalent to Equation (2B). Similarly, when “i = m + 2”, Equation (2A) is equivalent to Equation (2C). The same applies to the case of “i > m + 2”. ωe[m + 1]=(Kp×Δθ IN [m + 1]) +(Ki×(IV[m]+Δθ IN [m + 1])) ···(2B) ωe[m + 2]=(Kp×Δθ IN [m + 2]) +(Ki×(IV[m + 1]+Δθ IN [m + 2])) ···(2C)

[0072] The integration value IV[m] is the integration value IV initially set when deriving the estimated rotational speed ωe in the position sensorless mode, that is, the initial value of the integration value in the position sensorless mode (in other words, the integration value of the integral term immediately after the transition from the synchronous operation mode to the position sensorless mode), and corresponds to the above-mentioned initial parameters.

[0073] The startup control unit 130 obtains the integration value IV[m] as follows. The startup control unit 130 assumes that the following (3A) is satisfied in the control cycle P[m]. IV VIRTUAL represents a virtual integration value. The virtual integration value IV VIRTUAL represents the cumulative value of the input error Δθ IN up to the control cycle P[m - 1], and is a value virtually set. Δθ IN [m] is the final input error Δθ in the synchronous operation mode INis the input error Δθ immediately before shifting from the synchronous operation mode to the sensorless position mode IN is ω * [m] is the final speed command value ω in the synchronous operation mode * and is the speed command value ω immediately before shifting from the synchronous operation mode to the sensorless position mode * The speed command value ω * [m] may coincide with the reference speed command value ω1 * (see Fig. 6). ω * [m] = (Kp × Δθ IN [m]) + (Ki × (IV VIRTUAL + Δθ IN [m])) ···(3A)

[0074] The startup control unit 130 obtains the virtual integration value IV * by solving the expression (3A) based on the speed command value ω IN [m] and the input error Δθ VIRTUAL [m] for the virtual integration value IV VIRTUAL . That is, the virtual integration value IV VIRTUAL satisfying the expression (3A) is obtained. Then, the startup control unit 130 sets the sum of the obtained virtual integration value IV VIRTUAL and the input error Δθ IN [m] as the integration value IV[m]. That is, the startup control unit 130 sets the integration value IV[m] according to the following expression (3B). IV[m] = IV VIRTUAL + Δθ IN [m] ···(3B)

[0075] As a result, the integration value IV[m] corresponds to the cumulative value of the input error Δθ IN up to the control period P[m]. By setting the value (IV VIRTUAL + Δθ IN [m]) satisfying the expression (3A) as the integration value IV[m], the integration value IV[m] becomes the final speed command value ω * (ω *[m]) has a value that conforms to this. Therefore, the deviation between the rotational speed ωc (ωe) of the control axis and the actual rotational speed ω immediately after switching from the synchronous operation mode to the sensorless position mode becomes small, and thus the switching shock is suppressed.

[0076] As can be seen from Equation (2A), the PLL control unit 114 (speed estimation unit) derives the estimated rotational speed ωe[i] as follows at any specific control cycle P[i] in the sensorless position mode. That is, at any specific control cycle P[i] in the sensorless position mode, the PLL control unit 114 (speed estimation unit) calculates the input error Δθ IN [i] of the control cycle P[i] by multiplying it by the proportional gain Kp (deriving the value of the first term on the right side of Equation (2A)), and derives the integral term of the control cycle P[i] by multiplying the value (IV[i - 1]+Δθ IN [i]) by the integral gain Ki (deriving the value of the second term on the right side of Equation (2A)), and derives the estimated rotational speed ωe[i] of the control cycle P[i] by obtaining the sum of the proportional term of the control cycle P[i] and the integral term of the control cycle P[i] (deriving the value on the left side of Equation (2A)).

[0077] Here, the value (IV[i - 1]+Δθ IN [i]) is the cumulative addition of the input error Δθ IN up to the control cycle P[i] in the sensorless position mode to the above initial value (i.e., the integral value IV[m]). That is, for example, if "i = m + 2", the value (IV[i - 1]+Δθ IN [i]) is equal to the value (IV[m + 1]+Δθ IN [m + 2])=(IV[m]+Δθ IN [m + 1]+Δθ IN [m + 2]), which is the cumulative addition of the input error (Δθ IN [m + 1]+Δθ IN [m + 2]) up to the control cycle P[m + 2] in the sensorless position mode to the above initial value (i.e., the integral value IV[m]). Also, for example, if "i = m + 3", the value (IV[i - 1]+Δθ IN [i]) is the value (IV[m + 2]+Δθ IN [m + 3])=(IV[m + 1]+ΔθIN [m + 2] + Δθ IN [m + 3]) = (IV[m] + Δθ IN [m + 1] + Δθ IN [m + 2] + Δθ IN [m + 3]) is equal to, and the input error (Δθ IN [m + 1] + Δθ IN [m + 2] + Δθ IN [m + 3]) is the cumulative addition of the above initial value (i.e., the integral value IV[m]).

[0078] Figure 10 schematically shows the waveform of the rotational speed ωc in the vicinity where the motor control device 3 switches from the synchronous operation mode to the sensorless position mode. In the motor control device 3, the fluctuation of the rotational speed ωc at the time of switching to the sensorless position mode is sufficiently smaller than that of the above-described reference motor control device (see FIG. 7), that is, the rapid change in the rotational speed due to the switching shock is suppressed. Although not particularly shown, in the motor control device 3, a rapid change is also unlikely to occur in the current command value immediately after switching to the sensorless position mode.

[0079] For example, even if the starting conditions of the motor 1 are indefinite, such as when the load of the motor 1 varies variously, it is possible to smoothly shift from the synchronous operation mode to the sensorless position mode without causing a large current change. Even if the motor 1 is a mass-produced motor and the motor 1 is started under the same conditions every time, the manufacturing variations of the motor 1 may cause various current changes during the shift to the sensorless position mode. Even in such a situation, the switching shock can be reduced. Also, in the technology according to the present disclosure, the process for reducing the switching shock can be completed in a short time, and there are great advantages compared to a method (see the above Patent Document 1) in which after the synchronous operation mode, a shift to the sensorless position mode is made after undergoing some adjustment process.

[0080] <Modification, etc.> The current sensor 5 provided in the motor drive system SYS of FIG. 1 is a sensor that detects the output current from the inverter 2 to the motor 1. In the configuration of FIG. 4, an example is given in which the current sensor 5 detects the U-phase current Iu and the V-phase current Iv as the output current of the inverter 2. However, in the motor drive system SYS, instead of the current sensor 5, as shown in FIG. 11, a current sensor 5a that detects the current flowing between the DC power supply 10 and the inverter 2 may be provided. The current flowing between the DC power supply 10 and the inverter 2 is referred to as the bus current Idc. The bus current Idc refers to the current flowing through the wiring WH or WL. In the configuration of FIG. 11, the current flowing through the wiring WL is detected by the current sensor 5a, but the current flowing through the wiring WH may be detected by the current sensor 5a. A signal representing the bus current value Idc detected by the current sensor 5a is supplied to the motor control device 3.

[0081] When the current sensor 5a is used instead of the current sensor 5, in the control circuit 100, based on the three-phase voltage command values Vu * , Vv * and Vw * and the bus current value Idc, the U-phase current value Iu and the V-phase current value Iv are derived. A known method can be used as the derivation method. Specifically, a phase current detection unit (not shown) is provided in the control circuit 100. The phase current detection unit determines two sampling timings for detecting the bus current Idc based on the three-phase voltage command values Vu * , Vv * and Vw * , and based on the bus current value Idc detected at each sampling timing and the high / low results between the voltage command values Vu * , Vv * and Vw * , the U-phase current value Iu and the V-phase current value Iv are derived and output. At this time, if necessary, the relational expression of Iu + Iv + Iw = 0 is used.

[0082] Embodiments of the present disclosure can be appropriately modified in various ways within the scope of the technical idea shown in the claims. The above embodiments are merely examples of the embodiments of the present disclosure, and the meanings of the terms of the present disclosure or each constituent element are not limited to those described in the above embodiments. The specific numerical values shown in the above description are merely examples, and of course, they can be changed to various numerical values.

[0083] <Addendum> An addendum is provided for the present disclosure in which specific configuration examples are shown in the above embodiments.

[0084] A motor control device (3) according to one aspect of the present disclosure includes an axis error derivation unit (112) configured to derive an axis error (Δθ) between a rotation axis (dq axis) synchronized with the rotation of a rotor (6) provided in a permanent magnet synchronous motor (1) and an estimated axis (γδ axis) of the rotation axis, and a speed estimation unit (114) configured to estimate the rotation speed of the rotor using a difference between the axis error and an axis error command value or the axis error as an input error (Δθ IN ), and includes a control circuit (100). The control circuit increases the rotation speed of the rotor according to a speed command value (ω * ) regardless of the axis error through a synchronous operation mode, and then shifts to a sensorless mode in which the motor is driven based on an estimated rotation speed (ωe) by the speed estimation unit. The control circuit derives the axis error in each of the synchronous operation mode and the sensorless mode, and sets initial parameters of the speed estimation unit in the sensorless mode based on the axis error and the speed command value immediately before shifting from the synchronous operation mode to the sensorless mode (first configuration).

[0085] Thereby, a switching shock that may occur when shifting from the synchronous operation mode to the sensorless mode can be suppressed.

[0086] In the motor control device according to the first configuration, in the sensorless mode, the speed estimation unit includes a proportional term (Kp·Δθ) proportional to the input errorIN ) and derive the estimated rotational speed through the derivation of the integral term (Ki·Δθ IN / s) due to the integral of the input error, and the initial parameter may be a configuration (second configuration) that is the initial value of the integral value of the integral term in the sensorless position mode.

[0087] In the motor control device according to the second configuration, the control circuit determines a virtual integral value (IV VIRTUAL ) such that the sum of the first term and the second term is equal to the speed command value immediately before the transition from the synchronous operation mode to the sensorless position mode. The first term is a term obtained by multiplying the proportional gain by the input error immediately before the transition from the synchronous operation mode to the sensorless position mode (the first term on the right side of Equation (3A)), and the second term is a term obtained by multiplying the integral gain by the sum of the input error and the virtual integral value immediately before the transition from the synchronous operation mode to the sensorless position mode (the second term on the right side of Equation (3A)). The initial value is the integral value (IV[m]) of the integral term immediately after the transition from the synchronous operation mode to the sensorless position mode. The control circuit sets the sum of the input error (Δθ IN [m]) and the virtual integral value (IV VIRTUAL ) immediately before the transition from the synchronous operation mode to the sensorless position mode for the initial value (the left side of Equation (3B)). This may be a configuration (third configuration).

[0088] In the motor control device according to the third configuration, in each control cycle in the sensorless position mode, the axial error and the estimated rotational speed are derived by the axial error derivation unit and the speed estimation unit, and the speed estimation unit is configured to multiply the input error in the specific control cycle in the sensorless position mode by the proportional gain to derive the proportional term in the specific control cycle, and multiply the value obtained by cumulatively adding the input error up to the specific control cycle in the sensorless position mode to the initial value by the integral gain to derive the integral term in the specific control cycle, and derive the estimated rotational speed in the specific control cycle by obtaining the sum of the proportional term and the integral term in the specific control cycle (a fourth configuration) may be used.

[0089] In the motor control device according to any one of the first to fourth configurations, in the synchronous operation mode, the control circuit gradually increases the speed command value and controls the permanent magnet synchronous motor so that the rotational speed of the rotor increases according to the speed command value regardless of the axial error, and in the sensorless position mode, the control circuit controls the permanent magnet synchronous motor so that the estimated rotational speed follows the speed command value and the axial error converges to the axial error command value or zero (a fifth configuration) may be used.

[0090] In the motor control device according to the fifth configuration, the motor control device includes an inverter (2) configured to generate AC power from DC power and supply the AC power to the permanent magnet synchronous motor, and a current sensor (5, 5a) configured to detect an output current (two or more of Iu, Iv, Iw) from the inverter to the motor or a bus current (Idc) flowing between a DC power source (10) that supplies the DC power to the inverter and the inverter. Connected thereto, in the synchronous operation mode, the control circuit controls the permanent magnet synchronous motor by driving the inverter based on the detection result of the current sensor and the speed command value, and in the sensorless position mode, the control circuit drives the inverter based on the detection result of the current sensor, the estimated rotational speed, and the speed command value to control the permanent magnet synchronous motor (sixth configuration).

[0091] In the motor control device according to any one of the first to sixth configurations, the control circuit fixes the position of the rotor by supplying current to the armature winding of a specific phase in the permanent magnet synchronous motor, and then shifts to the synchronous operation mode. When the speed command value reaches the reference speed command value (ω1 * ) in the synchronous operation mode, it may shift to the sensorless position mode (seventh configuration).

[0092] In the motor control device according to any one of the first to seventh configurations, the control circuit derives the shaft error throughout the period in which the control circuit operates in the sensorless position mode and also derives the shaft error in at least a part of the period in which the control circuit operates in the synchronous operation mode (eighth configuration).

Explanation of Signs

[0093] SYS Motor drive system 1 Motor 2 Inverter 3 Motor control device 4 Host device 5, 5a Current sensor 6 Rotor 6a Permanent magnet 7 Stator 7u, 7v, 7w Armature winding 8u, 8v, 8w, 9u, 9v, 9w Switching element 10 DC power supply 11 Neutral point 12u, 12v, 12w Terminals 13 Bus WH, WL Wiring 100 Control circuit 111, 125 Coordinate conversion unit 112 Axis error derivation unit 113, 117, 122, 123 Subtractor 114 PLL control unit 114a Proportional calculator 114b Integral calculator 114c Adder 115 Speed command unit 116, 121 Switching switch 118 Speed control unit 119, 120 Current command unit 124 Current control unit 126 PWM conversion unit 127 Integrator 128 Axis error command unit 130 Start control unit 150 Memory Iu U-phase current Iv V-phase current Iγ γ-axis current Iδ δ-axis current Iγ * γ-axis current command value Iδ * δ-axis current command value Vγ * γ-axis voltage command value Vδ * δ-axis voltage command value Vu * U-phase voltage command value Vv * V-phase voltage command value Vw * W-phase voltage command value Δθ Axis error Δθ* Axis error command value Δθ IN Input error ω * Speed command value ωe Estimated rotational speed ωc Rotational speed θc Rotor position Idc Bus current

Claims

1. An axis error derivation unit configured to derive an axis error between a rotation axis that synchronizes with the rotation of a rotor provided in a permanent magnet synchronous motor and an estimated axis of the rotation axis, and a speed estimation unit configured to estimate the rotation speed of the rotor using a difference between the axis error and an axis error command value or the axis error as an input error, and a control circuit having the same, the control circuit shifts to a sensorless mode of driving the motor based on an estimated rotation speed by the speed estimation unit through a synchronous operation mode of increasing the rotation speed of the rotor according to a speed command value regardless of the axis error, the control circuit derives the axis error in each of the synchronous operation mode and the sensorless mode, and sets initial parameters of the speed estimation unit in the sensorless mode based on the axis error and the speed command value immediately before shifting from the synchronous operation mode to the sensorless mode , a motor control device.

2. In the sensorless mode, the speed estimation unit derives the estimated rotation speed through derivation of a proportional term proportional to the input error and an integral term obtained by integrating the input error, the initial parameter is an initial value of an integrated value of the integral term in the sensorless mode , the motor control device according to claim 1.

3. The control circuit obtains a virtual integral value such that the sum of Item 1 and Item 2 becomes equal to the speed command value immediately before shifting from the synchronous operation mode to the sensorless mode, Item 1 is a term obtained by multiplying a proportional gain by the input error immediately before shifting from the synchronous operation mode to the sensorless mode, Item 2 is a term obtained by multiplying an integral gain by the sum of the input error and the virtual integral value immediately before shifting from the synchronous operation mode to the sensorless mode, the initial value is an integrated value of the integral term immediately after shifting from the synchronous operation mode to the sensorless mode, the control circuit sets, for the initial value, the sum of the input error and the virtual integral value immediately before shifting from the synchronous operation mode to the sensorless mode , the motor control device according to claim 2.

4. In each control cycle in the sensorless mode, the axis error and the estimated rotation speed are derived by the axis error derivation unit and the speed estimation unit, The speed estimation unit derives the proportional term for the specific control period by multiplying the input error for the specific control period by the proportional gain in the specific control period in the position sensorless mode, and multiplies the value obtained by cumulatively adding the input error up to the specific control period in the position sensorless mode to the initial value by the integral gain to derive the integral term for the specific control period, and derives the estimated rotational speed for the specific control period by obtaining the sum of the proportional term for the specific control period and the integral term for the specific control period. The motor control device according to claim 3.

5. In the synchronous operation mode, the control circuit gradually increases the speed command value and controls the permanent magnet synchronous motor so that the rotational speed of the rotor increases according to the speed command value regardless of the shaft error. In the position sensorless mode, the control circuit controls the permanent magnet synchronous motor so that the estimated rotational speed follows the speed command value and the shaft error converges to the shaft error command value or zero. The motor control device according to any one of claims 1 to 4.

6. The motor control device is connected to an inverter configured to generate AC power from DC power and supply it to the permanent magnet synchronous motor, and a current sensor configured to detect an output current from the inverter to the motor or a bus current flowing between a DC power source that supplies the DC power to the inverter and the inverter. In the synchronous operation mode, the control circuit controls the permanent magnet synchronous motor by driving the inverter based on the detection result of the current sensor and the speed command value. In the position sensorless mode, the control circuit controls the permanent magnet synchronous motor by driving the inverter based on the detection result of the current sensor, the estimated rotational speed, and the speed command value. The motor control device according to claim 5.

7. The control circuit supplies current to the armature winding of a specific phase in the permanent magnet synchronous motor to fix the position of the rotor, then shifts to the synchronous operation mode, and when the speed command value reaches the reference speed command value in the synchronous operation mode, shifts to the position sensorless mode. The motor control device according to any one of claims 1 to 4.

8. The control circuit derives the axis error throughout the entire period during which the control circuit operates in the position sensorless mode, and also derives the axis error at least in part of the period during which the control circuit operates in the synchronous operation mode. The motor control device according to any one of claims 1 to 4.

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