Control device

Abstract

If position estimation is not possible during the start-up of a motor (M) or during sensorless control, an upper branch short-circuit drive signal is generated to simultaneously switch on three-phase upper branch switching elements (SW1, SW3, SW5) of an inverter (2) and to simultaneously switch off three-phase sub-branch switching elements (SW2, SW4, SW6) or a sub-branch short-circuit drive signal is generated to simultaneously switch off the upper branch switching elements (SW1, SW3, SW5) and to simultaneously switch on the sub-branch switching elements (SW2, SW4, SW6).

Description

Technical field

[0001] The present invention relates to a control device for a motor. State of the art

[0002] There is a motor control device that estimates the position (electrical angle) of a motor rotor using an extended electromotive force estimated based on a voltage command value, and controls the operation of each of the switching elements of an inverter by means of a voltage command value generated based on the position. Patent literature 1 discloses a related technique.

[0003] If the on / off times of the switching elements vary due to individual differences or differences in temperature characteristics between the switching elements, an error occurs between the voltage command value and a true value. Furthermore, the magnitude of the error is constant regardless of the rotor's angular velocity.

[0004] As a result, since the augmented electromotive force decreases when the rotor's angular velocity is relatively low (in a low-speed range), the error is relatively large, leading to a deterioration in the signal-to-noise ratio of the augmented electromotive force and a deterioration in the estimation accuracy of the rotor's position. Therefore, the estimation accuracy of the rotor's position deteriorates when the motor's rotor angular velocity is relatively low during start-up, increasing the possibility that the motor may enter a step-out state and cannot be restarted. List of patent literature

[0005] Patent literature 1: JP 2022 - 85 227 A Summary of the invention: Technical problem

[0006] One objective according to an embodiment of the present invention is to suppress a state of falling out of step when a motor is started. Solution to the problem

[0007] A control device according to an embodiment of the present invention is a control device that generates a drive signal for controlling an inverter that drives a motor and that comprises: a current conversion unit that converts a current flowing through the motor into a γ-axis current value and a δ-axis current value; a γ-δ current command output unit that outputs a γ-axis current command value and a δ-axis current command value; a γ-δ voltage command calculation unit that calculates a γ-axis voltage command value based on the γ-axis current value and the γ-axis current command value and calculates a δ-axis voltage command value based on the δ-axis current value and the δ-axis current command value; a drive signal conversion unit that converts the γ-axis voltage command value and the δ-axis voltage command value into the drive signal; an estimation unit,a calculating an estimated position, which is an estimated value of the motor's position; and a first determination unit that determines whether or not a position estimation of the motor is possible by the estimating unit, wherein an upper branch short-circuit drive signal or a lower branch short-circuit drive signal is generated when the motor is started or when the first determination unit determines that a position estimation of the motor is not possible, wherein the upper branch short-circuit drive signal is the drive signal for simultaneously switching on three-phase upper branch switching elements of the inverter and simultaneously switching off three-phase lower branch switching elements of the inverter, wherein the lower branch short-circuit drive signal is the drive signal for simultaneously switching off the three-phase upper branch switching elements of the inverter and simultaneously switching on the three-phase lower branch switching elements of the inverter.and the estimation unit is the estimated position, which is the estimated value of the motor's position, calculated based on the current flowing through the motor when the upper branch short-circuit drive signal or the lower branch short-circuit drive signal is generated.

[0008] The control device may have a second determination unit, and the second determination unit may be configured to determine, based on the current flowing through the motor due to the upper branch short-circuit drive signal or the lower branch short-circuit drive signal, whether or not the position estimation of the motor is possible.

[0009] As described above, since the upper branch short-circuit drive signal or the lower branch short-circuit drive signal is generated when the motor is started, or when it is determined that position estimation is not possible, it is possible to prevent an error between a voltage command value and a true value by varying the on / off states of the switching elements. As a result, even if the angular velocity of the motor is relatively low, it is possible to suppress a deterioration in the estimation accuracy of a rotor's position and to prevent a state of out-of-position fall-out.

[0010] Furthermore, the control device can be configured to generate the drive signal to supply a three-phase alternating current to the motor when the second determination unit determines that position estimation of the motor is possible.

[0011] Furthermore, the control device can be configured to start a timer and generate the drive signal to ensure that the current flowing through the motor has a constant value when the second determining unit determines that a value of the current flowing through the motor is less than a threshold current and position estimation of the motor is possible, and to generate the upper branch short-circuit drive signal or the lower branch short-circuit drive signal after a first predetermined time has elapsed.

[0012] Furthermore, the estimation unit can be configured to calculate an estimated extended electromotive force, which is an estimated value of an extended electromotive force generated in the motor, based on the γ-axis current value, the δ-axis current value, the γ-axis voltage command value, and the δ-axis voltage command value, and to calculate the estimated position, which is the estimated value of the position of the motor, based on the estimated extended electromotive force, and the first determination unit can be configured to determine that position estimation is not possible if the estimated extended electromotive force is less than a threshold value, and to generate the upper branch short-circuit drive signal or the lower branch short-circuit drive signal. Advantageous effects of the invention

[0013] According to the present invention, it is possible to suppress a state of falling out of step when the engine is started. Brief description of the drawings Fig. Figure 1 shows a representation illustrating an example of a control system according to an embodiment. Fig. Figure 2 shows a flowchart illustrating the operation of a computing unit during the restart of an engine. Fig. Figure 3 shows a representation illustrating an example of an actual angular velocity and an angular velocity command value during a restart of the engine. Description of exemplary implementations

[0014] An exemplary embodiment is described in more detail below with reference to the drawings.

[0015] Fig. Figure 1 shows a representation illustrating an example of a control system according to the embodiment.

[0016] A in Fig. 1 Illustrated control system 1 includes, for example, a motor M mounted in a vehicle such as an electric forklift or a plug-in hybrid vehicle, an inverter 2 that drives the motor M, and a control device 3 that outputs a drive signal to the inverter 2.

[0017] Motor M, for example, is a surface magnet synchronous motor or a synchronous motor with embedded magnets.

[0018] Inverter 2 drives motor M using power supplied from a power source P and includes a capacitor C, switching elements SW1 to SW6 (for example, insulated-gate bipolar transistors (IGBTs)), and current sensors Se1 to Se3. One terminal of capacitor C is connected to a positive terminal of the power source P and the collector terminals of switching elements SW1, SW3, and SW5 (upper branch switching elements), while the other terminal of capacitor C is connected to a negative terminal of the power source P and the emitter terminals of switching elements SW2, SW4, and SW6 (lower branch switching elements). A connection point between an emitter terminal of switching element SW1 and a collector terminal of switching element SW2 is connected to a U-phase input terminal of motor M via current sensor Se1.A connection point between an emitter terminal of switching element SW3 and a collector terminal of switching element SW4 is connected to a V-phase input terminal of motor M via the current sensor Se2. A connection point between an emitter terminal of switching element SW5 and a collector terminal of switching element SW6 is connected to a W-phase input terminal of motor M via the current sensor Se3.

[0019] The capacitor C smooths a voltage that is output from the power source P and applied to the inverter 2.

[0020] Switching element SW1 is switched on or off based on a drive signal S1 output from control device 3. Switching element SW2 is switched on or off based on a drive signal S2 output from control device 3. Switching element SW3 is switched on or off based on a drive signal S3 output from control device 3. Switching element SW4 is switched on or off based on a drive signal S4 output from control device 3. Switching element SW5 is switched on or off based on a drive signal S5 output from control device 3. Switching element SW6 is switched on or off based on a drive signal S6 output from control device 3.When each of the switching elements SW1 to SW6 is switched on or off, a DC voltage output from the power source P is converted into three AC voltages having phases that differ from each other by 120 degrees, the AC voltages being applied to the U-phase, V-phase and W-phase input terminals of the motor M, causing a rotor of the motor M to rotate.

[0021] Current sensor Se1 comprises a Hall effect sensor, a shunt resistor, or the like, detects a U-phase current value Iu flowing through a U-phase of motor M, and outputs this U-phase current value to the control device 3. Current sensor Se2 also comprises a Hall effect sensor, a shunt resistor, or the like, detects a V-phase current value Iv flowing through a V-phase of motor M, and outputs this V-phase current value Iv to the control device 3. Current sensor Se3 also comprises a Hall effect sensor, a shunt resistor, or the like, and detects a W-phase current value Iw flowing through a W-phase of motor M, and outputs this W-phase current value Iw to the control device 3. It should be noted that according to the present embodiment, three current sensors Se1 to Se3 are provided; however, any two of the three can be provided instead of all three.

[0022] The control device 3 comprises a storage unit 4, a drive circuit 5, and a calculation unit 6. The control device 3 drives the motor M by controlling the inverter 2.

[0023] Memory unit 4 includes random access memory (RAM), read-only memory (ROM), or the like.

[0024] The drive circuit 5 includes an integrated circuit (IC) or the like, compares a voltage value of a carrier shaft (triangular shaft, sawtooth shaft or reverse sawtooth shaft or the like) with a U-phase voltage command value Vu*, a V-phase voltage command value Vv* and a W-phase voltage command value Vw*, which are output from the calculation unit 6, and outputs the drive signals S1 to S6 according to the comparison result to gate terminals of the switching elements SW1 to SW6.

[0025] For example, drive circuit 5 outputs the drive signal S1 at a high level and outputs the drive signal S2 at a low level when the U-phase voltage command value Vu* is equal to or greater than the voltage value of the carrier shaft, and outputs the drive signal S1 at a low level and outputs the drive signal S2 at a high level when the U-phase voltage command value Vu* is less than the voltage value of the carrier shaft. Furthermore, drive circuit 5 outputs the drive signal S3 at a high level and outputs the drive signal S4 at a low level when the V-phase voltage command value Vv* is equal to or greater than the voltage value of the carrier shaft, and outputs the drive signal S3 at a low level and outputs the drive signal S4 at a high level when the V-phase voltage command value Vv* is less than the voltage value of the carrier shaft.Furthermore, the drive circuit 5 outputs the drive signal S5 at a high level and outputs the drive signal S6 at a low level when the W-phase voltage command value Vw* is equal to or greater than the voltage value of the carrier shaft, and outputs the drive signal S5 at a low level and outputs the drive signal S6 at a high level when the W-phase voltage command value Vw* is less than the voltage value of the carrier shaft.

[0026] The calculation unit 6 includes a microcomputer or the like, and includes a current value conversion unit 7, an estimation unit 8, a subtraction unit 9, a torque command value calculation unit 10, a γ-δ current command value output unit 11, a subtraction unit 12, a subtraction unit 13, a voltage command value calculation unit 14, switches 15 and 16, a voltage command value conversion unit 17, and a determination unit 18. For example, the current value conversion unit 7, the estimation unit 8, the subtraction unit 9, the torque command value calculation unit 10, the γ-δ current command value output unit 11, the subtraction unit 12, the subtraction unit 13, the voltage command value calculation unit 14, the switch 15, the switch 16, the voltage command value conversion unit 17 and the determination unit 18 are configured such that the microcomputer executes a program stored in the memory unit 4.

[0027] The current conversion unit 7 converts the U-phase current value Iu, the V-phase current value Iv, and the W-phase current value Iw into a y-axis current value Iγ and a δ-axis current value Iδ, using an estimated position θ^ of the rotor output by the estimation unit 8. That is, the current conversion unit 7 converts a current flowing through the motor M into the γ-axis current value Iγ and the δ-axis current value Iδ. The current conversion unit 7 can perform a function of taking input current values ​​of two phases under the U-phase current value Iu, the V-phase current value Iv, and the W-phase current value Iw, and calculating a current value of the remaining phase based on the input current values ​​of the two phases.

[0028] It should be noted that a γ-δ coordinate system is an estimated rotating coordinate system, and a coordinate system in which an axis corresponding to a d-axis of a dq coordinate system is a γ-axis, and an axis corresponding to a q-axis is a δ-axis. The dq coordinate system is a rotating coordinate system in which an N-pole direction of a magnet of motor M is the d-axis, and a direction orthogonal to the d-axis is the q-axis. Furthermore, the estimated position θ^ is an estimated value of a position θ of the rotor of motor M.

[0029] For example, the current value conversion unit 7 converts the U-phase current value Iu, the V-phase current value Iv and the W-phase current value Iw into the y-axis current value Iγ and the δ-axis current value Iδ using a transformation matrix C1, which is expressed by the following equation 1. [Mathematical expression 1] C1=23[cos θ cos(θ−2π / 3)cos(θ+2π / 3)−sin θ −sin(θ−2π / 3)−sin(θ+2π / 3)

[0030] The subtraction unit 9 calculates an angular velocity difference Δω between an estimated angular velocity ω^ output from the estimation unit 8 and an angular velocity command value ω* entered from outside.

[0031] The torque command value calculation unit 10 calculates a torque command value T* using the angular velocity difference Δω output from the subtraction unit 9. For example, the torque command value calculation unit 10 accesses (not illustrated) information stored in the memory unit 4, in which angular velocities of motor M are linked to torques of motor M, and obtains a torque associated with an angular velocity equal to the angular velocity difference Δω as the torque command value T*.

[0032] The γ-δ current command output unit 11 outputs a γ-axis current command value Iγ* and a δ-axis current command value Iδ* using the torque command value T*. For example, the γ-δ current command output unit 11 accesses (not illustrated) information stored in the memory unit 4, in which the torques of motor M are associated with the γ-axis current command values ​​Iγ* and the δ-axis current command values ​​Iδ*, and obtains the γ-axis current command value Iγ* and the δ-axis current command value Iδ* associated with the torque corresponding to the torque command value T*. It should be noted that the γ-δ current command value output unit 11 can be configured to output the γ-axis current command value Iγ* and the δ-axis current command value Iδ* using the externally input torque command value T*.In such a configuration, the subtraction unit 9 and the torque command value calculation unit 10 are omitted.

[0033] The subtraction unit 12 calculates a difference γ-axis current command value ΔIγ between the y-axis current command value Iγ* output from the γ-δ current command output unit 11 and the y-axis current value Iγ output from the current conversion unit 7.

[0034] The subtraction unit 13 calculates a difference γ-axis current command value ΔIγ between the γ-axis current command value Iγ* output from the γ-δ current command output unit 11 and the y-axis current value Iγ output from the current conversion unit 7.

[0035] The voltage command value calculation unit 14 converts the differential delta-axis current command value ΔIδ output from the subtraction unit 12 and the differential delta-axis current command value ΔIδ output from the subtraction unit 13 into a delta-axis voltage command value Vγ* and a delta-axis voltage command value Vδ*. For example, the voltage command value calculation unit 14 calculates the delta-axis voltage command value Vγ* by calculating the following equation 2 and calculates the delta-axis voltage command value Vδ* by calculating the following equation 3.It should be noted that Kp denotes a constant of a proportional term of a PI control, Ki denotes a constant of an integral term of the PI control, ω^ denotes an estimated angular velocity calculated by the estimation unit 8 in a previous control period, Ld denotes a d-axis inductance component of the motor M, Lq denotes a q-axis inductance component of the motor M, and KE denotes an induced voltage constant. VY*=KpΔIY+∫(KiΔIY)−ωLqIY Vδ*=KpΔIδ+∫(KiΔIδ)+ωLdIδ

[0036] This means that the subtraction unit 12 and 13 and the voltage command value calculation unit 14 function as a γ-δ voltage command value calculation unit, which calculates the γ-axis voltage command value Vγ* based on the γ-axis current value Iγ and the γ-axis current value Iγ* and calculates the δ-axis voltage command value Vδ* based on the δ-axis current value Iδ and the δ-axis current command value Iδ*.

[0037] Switch 15 is configured to be able to select whether a γ-axis voltage command value Vγ*'' (an upper branch short-circuit drive signal or a lower branch short-circuit drive signal, which are described later) is to be output to the voltage command value conversion unit 17 as a γ-axis voltage command value Vγ*' for the purpose of performing three-phase short-circuit control, which is described later, or whether the γ-axis voltage command value Vγ* calculated by the voltage command value calculation unit 14 is to be output to the voltage command value conversion unit 17 as the γ-axis voltage command value Vγ*'.Furthermore, the switch 16 is configured to be able to select whether a δ-axis voltage command value Vδ*'' (the upper branch short-circuit drive signal or the lower branch short-circuit drive signal, which are described later) is to be output to the voltage command value conversion unit 17 as a δ-axis voltage command value Vδ*' for the implementation of the three-phase short-circuit control described later, or whether the δ-axis voltage command value Vδ* calculated by the voltage command value calculation unit 14 is to be output to the voltage command value conversion unit 17 as the δ-axis voltage command value Vδ*'.

[0038] The voltage command value conversion unit 17 converts the γ-axis voltage command value Vγ*' and the δ-axis voltage command value Vδ*' into the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw*, respectively, using the estimated position θ^ output from the estimation unit 8. For example, the voltage command value conversion unit 17 converts the γ-axis voltage command value Vγ*' and the δ-axis voltage command value Vδ*' into the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw*, respectively, using a transformation matrix C2 expressed by the following equation 4. [Mathematical expression 2] C2=23[cos θ −sin θ cos(θ−2π / 3)−sin(θ−2π / 3)cos(θ+2π / 3)−sin(θ+2π / 3)]

[0039] The voltage command value conversion unit 17 outputs the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* to the drive circuit 5. This means that the voltage command value conversion unit 17 and the drive circuit 5 function as a drive signal conversion unit, which converts the γ-axis voltage command values ​​Vγ* and the δ-axis voltage command value Vδ* into a drive signal and outputs the drive signal to the inverter 2.

[0040] The determination unit 18, as a first determination unit, determines whether a position estimation of the motor M by the estimation unit 8 is possible or not. This determination is made in step S10 during normal sensorless control, as in step S9 of a flowchart. Fig. 2, which illustrates the operation of the computing unit 6 during a restart of the engine M, as described later.

[0041] The estimation unit 8 has a function for calculating the estimated angular velocity ω^ and the estimated position θ^. For example, a method for calculating the estimated angular velocity ω^ and the estimated position θ^ could be a procedure that uses an extended electromotive force. Example of a method using an extended electromotive force

[0042] The estimation unit 8 calculates an estimated extended electromotive force e^, which is an estimated value of an extended electromotive force (EEMF) e generated in the motor M, based on the γ-axis current value Iγ, the δ-axis current value Iδ, the γ-axis voltage command value Vγ*', the δ-axis voltage command value Vδ*', the estimated angular velocity ω^ stored in the memory unit 4, and motor parameters that can be estimated in advance. This means that it can be said that the estimation unit 8 calculates the estimated extended electromotive force e^, which is the estimated value of the extended electromotive force e generated in the motor M, on the basis of the γ-axis current value Iγ, the δ-axis current value Iδ, the γ-axis voltage command value Vγ*' and the δ-axis voltage command value Vδ*'.In particular, the estimation unit 8 calculates the estimated extended electromotive force e^ using an observer (motor model) expressed by the following equation 5. The estimated extended electromotive force e^ has an estimated extended electromotive γ-axis force eγ^ and an estimated extended electromotive δ-axis force eδ^ as vector components. [Mathematical expression 3] [eγeδ]=[Vγ* 'Vδ* ']−[R +p L d ω L q ω L q R +p L d ][IγIδ]

[0043] It should be noted that p denotes a time derivative operator d / dt. A winding resistance value R^, a d-axis inductance Ld^, and a q-axis inductance Lq^ are estimated values ​​of motor parameters of the motor M to be controlled and are estimated beforehand by measurement or the like using the motor M. The reason why the estimated values ​​are used instead of the actual values ​​of the motor parameters of motor M is that the motor parameters vary depending on the temperature and the current flowing through the motor M.

[0044] The estimation unit 8 then calculates a position error Δθ^ based on the estimated extended electromotive force e^. In particular, the position error Δθ^ is calculated from the estimated extended electromotive force e^ by the following equation 6. [Mathematical expression 4] Δθ=tan−1(−e γ e δ )

[0045] The estimating unit 8 then obtains the estimated angular velocity ω^ based on the position error Δθ^. Specifically, the estimating unit 8 calculates the estimated angular velocity ω^, for example, by multiplying the position error Δθ^ by a predetermined transfer function. The estimating unit 8 then calculates the estimated position θ^ based on the estimated angular velocity ω^ and the position error Δθ^. Specifically, for example, the estimating unit 8 calculates the estimated position θ^ by adding a temporary estimated position, obtained by integrating the estimated angular velocity ω^, and a corrected position error, obtained by multiplying the position error Δθ^ by the predetermined transfer function.It should be noted that the position error Δθ^ is multiplied by the predetermined transfer function, but it is not necessary to multiply it by the predetermined transfer function. Afterwards, the estimation unit 8 stores the calculated estimated angular velocity ω^ and the estimated position θ^ in the storage unit 4, outputs the estimated angular velocity ω^ to the subtraction unit 9 and the voltage command value calculation unit 14, and outputs the estimated position θ^ to the current value conversion unit 7 and the voltage command value conversion unit 17.

[0046] When a request to stop motor M is received from a host device, the control device 3 stops the output of the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* without forcibly stopping motor M. Therefore, motor M is in a freewheeling state, rotating due to inertia. Subsequently, when a request to restart the motor is received from the host device, the control device 3 restarts motor M.

[0047] Fig. Figure 2 shows the flowchart illustrating the operation of the computation unit 6 during a restart of the motor M. It should be noted that a case in which the determination unit 18 determines that, in normal operation except at the time of restarting, position estimation based on the extended electromotive force (equation 8, described later) is not possible, is the same as a case in which, in the step S10 described later, a "yes" is determined, and thus these are described together.

[0048] First, the calculation unit 6 sets a time T of a timer to zero and starts the timer (step S1).

[0049] The calculation unit 6 then performs the three-phase short-circuit control to carry out a control such that the switching elements SW1, SW3 and SW5 of the upper three-phase branches contained in the inverter 2 are switched off simultaneously and the switching elements SW2, SW4 and SW6 of the lower three-phase branches are switched on simultaneously (step S2).

[0050] In particular, switch 15 is switched to output the γ-axis voltage command values ​​Vγ*'' to the voltage command value conversion unit 17 for the implementation of three-phase short-circuit control, and switch 16 is switched to output the δ-axis voltage command values ​​Vδ*'' to the voltage command value conversion unit 17 for the implementation of three-phase short-circuit control.

[0051] As a result, the U-phase voltage command value Vu*, the V-phase voltage command value Vv* and the W-phase voltage command value Vw* are output from the voltage command value conversion unit 17 for the implementation of the three-phase short-circuit control, and the sub-branch short-circuit drive signal, which is a drive signal for the implementation of the three-phase short-circuit control, is output from the drive circuit 5 to the inverter 2.

[0052] It should be noted that the sub-branch short-circuit drive signal is output in step S2 for a short duration (e.g., a few microseconds). Furthermore, instead of the sub-branch short-circuit drive signal, the upper-branch short-circuit drive signal, which is a drive signal for simultaneously switching on the switching elements SW1, SW3, and SW5 and simultaneously switching off the switching elements SW2, SW4, and SW6, can be output from drive circuit 5 to inverter 2.

[0053] Subsequently, the calculation unit 6 calculates a γ-δ-axis current value Iγδ using the following equation 7, based on the γ-axis current value Iγ and the δ-axis current value Iδ, which are calculated from a value of the current flowing through the motor M via the sub-branch short-circuit drive signal. The determination unit 18, as a second determination unit, then determines whether the calculated γ-δ-axis current value Iγδ is equal to or greater than a first current threshold value I0 (step S3). The first current threshold value I0 is, for example, a minimum value of the γ-δ-axis current value Iγδ if the estimated position Φ^ can be calculated with the required estimation accuracy, assuming that this can be obtained beforehand through an experiment, a simulation, or the like.It should be noted that the current flowing through motor M increases with increasing rotor speed, thus increasing the accuracy of the estimated position Φ^ to be calculated and reducing the probability of a step-out. Therefore, the required estimation accuracy refers, for example, to an accuracy that makes a step-out less likely, even when using sensorless control. [Mathematical expression 5] I γδ=I γ 2+I δ 2

[0054] In step S3, if the γ-δ-axis current value Iγδ is less than the first current threshold value I0 (step S3: No), the processing proceeds to step S4.

[0055] In step S4, it is determined whether the γ-δ-axis current value Iγδ is equal to or greater than a second current threshold value I1. The second current threshold value I1 is, for example, a value that is smaller than the first current threshold value I0, and is a minimum value of the γ-δ-axis current value Iγδ from which the estimated position Φ^ can be calculated, and it is assumed that it is obtained beforehand through an experiment, a simulation, or the like.

[0056] In step S4, if the γ-δ-axis current value Iγδ is equal to or greater than the second current threshold value I1 (step S4: Yes), the timer is started after the timer time T has been set to zero, and the estimated position Φ^ is calculated from the estimated extended electromotive force e^, which is calculated to zero by setting the expression that has Vγ*', Vδ*' and ω^ in equation 5, from the γ-axis current value Iγ and the δ-axis current value Iδ, which are calculated from a value of the current flowing through the motor M due to the sub-branch short-circuit drive signal (step S5). This means that if the γ-δ-axis current value Iγδ is equal to or greater than the second current threshold value I1, the determination unit 18 determines as the second determination unit that position estimation is possible, and effects a transition from three-phase short-circuit control to current control.

[0057] Then, the control device 3 performs the current control using the estimated position θ^ calculated in step S5 (step S6). In the current control, the control device 3 performs an on / off control of the switching elements SW1 to SW6 such that the current flowing through the motor M has a constant value for a preset predetermined time, thereby increasing the angular velocity of the rotor. For example, the switching elements SW1 to SW6 are repeatedly switched on and off by setting the δ-axis current command value Iδ*, described later, to a constant value (for example, a maximum value). According to the present embodiment, the switching elements SW1 to SW6 are controlled to be switched on and off such that the current flowing through the motor M has a constant value.

[0058] It should be noted that during current control, the control device 3 only needs to perform control such that the current flowing through the motor M has a constant value for the pre-set predetermined time, and can then perform control such that the current flowing through the motor M varies.

[0059] Then, the calculation unit 6 determines whether the time T is equal to or longer than the first predetermined time T1 (step S7).

[0060] In step S7, current control is performed continuously if time T is shorter than the first predetermined time T1 (step S7: No), and processing returns to step S1 if time T is equal to or longer than the first predetermined time T1 (step S7: Yes). The first predetermined time T1 is the time required to increase the γ-δ-axis current value Iγδ by increasing the rotor speed by a predetermined current value, and this is assumed to be obtained beforehand through an experiment, simulation, or the like.

[0061] Furthermore, if the γ-δ-axis current value Iγδ is equal to or greater than the first current threshold I0 (step S3: Yes), the calculation unit 6 calculates the estimated angular velocity ω^ and the estimated position θ^ based on the estimated extended electromotive force e^, which is calculated using all parameters of equation 5 based on the γ-axis current value Iγ and the δ-axis current value Iδ, which are calculated from a value of the current flowing through the motor M via the sub-branch short-circuit drive signal (step S8). That is, if the γ-δ-axis current value Iγδ is equal to or greater than the first current threshold I0, the determination unit 18, as the second determination unit, determines that position estimation is possible and effects a transition from three-phase short-circuit control to sensorless control.

[0062] The control device 3 then performs sensorless control using the estimated angular velocity ω^ and the estimated position θ^ calculated in step S8 (step S9). During sensorless control, the control device 3 generates a drive signal to supply three-phase alternating current to the motor M. In other words, the control device 3 performs on / off control of the switching elements SW1 to SW6 such that the motor M rotates at a desired speed.

[0063] Furthermore, the calculation unit 6 determines whether an extended electromotive γ-δ axis force eγδ, calculated by the following equation 8 on the basis of the estimated extended electromotive force e^, which is the estimated value of the extended electromotive force e generated by the drive signal to supply the three-phase alternating current to the motor M, is equal to or greater than a threshold value th (step S10). [Mathematical expression 6] e γδ=(e γ )2+(e δ )2

[0064] Sensorless control is then performed continuously if, in step S10, it is determined that the extended electromotive force γ-δ-axis eγδ is equal to or greater than the threshold th (step S10: No), and processing returns to step S1 if the extended electromotive force γ-δ-axis eγδ is less than the threshold th (step S10: Yes). For example, the threshold th is assumed to be a minimum value of the extended electromotive force γ-δ-axis eγδ in a case where sensorless control can be performed, and is obtained beforehand through an experiment, simulation, or the like.This means that the determination unit 18, as the first determination unit, determines that velocity estimation and position estimation can be performed by the estimation unit 8 and causes sensorless control to continue if the extended electromotive γ-δ-axis force eγδ is equal to or greater than the threshold th, and determines that position estimation by the estimation unit 8 is not possible and causes a transition from sensorless control to three-phase short-circuit control if the extended electromotive γ-δ-axis force eγδ is less than the threshold th.

[0065] Furthermore, if the γ-δ-axis current value Iγδ is less than the second threshold value I1 (step S4: No), the calculation unit 6 terminates the drive control of motor M (step S11). That is, if the γ-δ-axis current value Iγδ is less than the second current threshold value I1, the determination unit 18, as the second determination unit, determines that a state in which at least position estimation is possible has not been achieved, even though the three-phase short-circuit control is carried out, and the drive control of motor M is terminated.

[0066] This shows Fig. Figure 3 shows a representation illustrating an example of an actual angular velocity and the angular velocity command value ω* when restarting the motor M. It should be noted that the horizontal axis of two-dimensional coordinates, which in Fig. Figure 3 illustrates the time, and the vertical axis indicates the angular velocity. Furthermore, there is a solid line that... Fig. Figure 3 shows the actual angular velocity, and a dashed line indicates the angular velocity command value ω*.

[0067] Initially, at time t1, the angular velocity command value ω* of ω1 becomes zero, the drive control of the motor M is stopped, and then the actual angular velocity gradually decreases.

[0068] Then, when at time t2, when the motor M is restarted, the angular velocity command value ω* is switched from zero to ω1, the three-phase short-circuit control is carried out. In a case where the γ-δ-axis current value Iγδ, calculated based on the γ-axis current value Iγ and the δ-axis current value Iδ, which are calculated from a value of the current flowing through the motor M via the three-phase short-circuit control, is less than the first current threshold value I0, and the γ-δ-axis current value Iγδ is equal to or greater than the second current threshold value I1, the current control and the three-phase short-circuit control are repeated alternately until the γ-δ-axis current value Iγδ is equal to or greater than the first current threshold value I0, thus increasing the angular velocity of the rotor. In the Fig. In the illustrated example 3, it is assumed that the current control is performed three times until the γ-δ-axis current value Iγδ is equal to or greater than the first current threshold value I0. It should be noted that the current control can only be performed once according to the γ-δ-axis current value Iγδ during the restart of the motor M.

[0069] Then, when the γ-δ-axis current value Iγδ becomes equal to or greater than the first current threshold value I0 at time T3, a transition is made from three-phase short-circuit control to sensorless control.

[0070] As described above, the control device 3 is configured according to the exemplary embodiment to perform the three-phase short-circuit control when the determination unit 18, as the first determination unit, determines that the position estimation is not possible due to a relatively low extended electromotive force when starting the motor M or during sensorless control or after performing current control for a certain period of time, so that the estimation accuracy of the estimated position θ^ can be improved.In general, in normal sensorless control (PWM control), when the motor M is started or when the augmented electromotive force is relatively low (when the rotor angular velocity is relatively low), the error (dead-time error) between a true value and each of the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* is relatively larger when the augmented electromotive force is lower. This then degrades the signal-to-noise ratio of the augmented electromotive force and the accuracy of the rotor position estimation.Therefore, compared to normal sensorless control (PWM control), the influence of dead-time error can be eliminated by implementing three-phase short-circuit control when the motor M is started or when the extended electromotive force is relatively low and the determination unit 18 determines that position estimation is not possible, as in the present embodiment. This makes it possible to improve the signal-to-noise ratio of the extended electromotive force and the estimation accuracy of the estimated position θ^. As a result, even when the angular velocity of the motor M is relatively low, it is possible to suppress the deterioration in the estimation accuracy of the rotor position and to prevent out-of-step fall-out.

[0071] Furthermore, in the control device 3 according to the exemplary embodiment, the actual angular velocity can be increased by performing current control when the γ-δ axis current value Iγδ is less than the first current threshold value I0 and the y-δ axis current value Iγδ is equal to or greater than the second current threshold value I1, so that a transition to sensorless control can be carried out in a relatively short time after the start of the motor M.

[0072] Furthermore, in the control device 3 according to the exemplary embodiment, the drive control of the motor M is terminated when the γ-δ-axis current value Iγδ is less than the first current threshold value I0 and the γ-δ-axis current value Iγδ is less than the second current threshold value I1. This makes it possible to suppress a state of out-of-control in the sensorless control.

[0073] It should be noted that the present invention is not limited to the embodiment described above, and that various modifications or changes can be made without departing from the idea of ​​the present invention.

[0074] For example, one of the first current threshold values ​​I0 and the second current threshold value I1 can be used without both being provided. In this case, current control can be omitted, and it can be selected whether to perform sensorless control or drive control of the motor M.

[0075] Furthermore, the determination unit 18, as the second determination unit, determines whether position estimation is possible based on the current flowing through motor M via the three-phase short-circuit control. However, position estimation in step S5 or S8 can be performed without this determination, i.e., by omitting the second determination unit. In this case, position estimation may fail, and the control may, for example, terminate if position estimation fails a predetermined number of times.

[0076] Furthermore, the unit of determination 18 has both the function as the first unit of determination and the function as the second unit of determination, but both can be provided separately.

[0077] Furthermore, it can be configured such that it includes both the observer expressed by equation 5 and an observer obtained by excluding the term containing Vγ*', Vδ*' and ω^ from equation 5.

[0078] Furthermore, in steps S3 and S4, the determination can be carried out on the basis of the magnitude of the γ-axis current value Iγ or the δ-axis current value Iδ instead of the magnitude of the γ-δ-axis current value Iγδ.

[0079] Furthermore, examples of the procedure for calculating the estimated angular velocity ω^ and the estimated position θ^ are shown.<Verfahren, das einen Nulldurchgangszeitpunkt der induzierten Spannung verwendet> ,<ein Verfahren, das eine elektromotorische Geschwindigkeitskraft verwendet,> and a<Verfahren, das Magnetfluss verwendet> in addition to the method described above [which uses an enhanced electromotive force], the method is not particularly limited. Example of the<Verfahren, das einen Nulldurchgangszeitpunkt der induzierten Spannung verwendet>

[0080] First, the estimating unit 8 obtains the estimated position θ^ based on a phase of an induced voltage generated during a no-current phase under the U-phase, V-phase, and W-phase of motor M at a zero-crossing time when the voltage of the no-current phase becomes a midpoint potential (a voltage of 1 / 2 of the voltage of power source P) of the voltage of power source P. It should be noted that a method for calculating the estimated angular velocity ω^ from the estimated position θ^ is similar to the<Verfahren, das die erweiterte elektromotorische Kraft verwendet> , which has been described above, therefore a further description is omitted.Furthermore, in a case where the<Verfahren, das eine Nulldurchgangszeitpunkt der induzierten Spannung verwendet> When the procedure of calculating the estimated angular velocity ω^ and the estimated position θ^ is applied, the calculation unit 6 calculates the induced voltage during the zero crossing time based on the input U-phase current value Iu, the input V-phase current value Iv, and the input W-phase current value Iw.

[0081] Furthermore, in the case where the<Verfahren, das einen Nulldurchgangszeitpunkt der induzierten Spannung verwendet> When the procedure for calculating the estimated angular velocity ω^ and the estimated position θ^ is applied, the calculation unit 6 returns to step S1 and performs the three-phase short-circuit control when the motor M is started, or when the induced voltage of any phase is less than a threshold value th' in step S10 of Fig. 2 is (Step S10: Yes). It should be noted that if it is determined that the induced voltage of any phase is equal to or greater than the threshold th' (Step S10: No), the computation unit 6 continuously performs sensorless control. For example, the threshold th' is assumed to be a minimum value of the induced voltage of any phase in a case where sensorless control can be performed, and is obtained beforehand through an experiment, simulation, or the like.This means that the determining unit 18, as the first determining unit, determines that the estimating unit 8 is in a state where it can perform velocity and position estimation when the induced voltage of any phase is equal to or greater than the threshold th', and causes sensorless control to continue; and, when the induced voltage of any phase is less than the threshold th', determines that the estimating unit 8 is in a state where it is unable to perform velocity and position estimation, and causes a transition from sensorless control to three-phase short-circuit control.

[0082] As described above, the three-phase short-circuit control is carried out when the motor M is started or when the induced voltage is relatively low, and the determination unit 18, as the first determination unit, determines that position estimation is not possible, even in the case where the<Verfahren, das einen Nulldurchgangszeitpunkt der induzierten Spannung verwendet> when the method of calculating the estimated angular velocity ω^ and the estimated position θ^ is applied, so that the estimation accuracy of the estimated position θ^ can be improved.In general, in normal sensorless control (PWM control), when the motor M is started or when the induced voltage is relatively low (when the angular velocity of the rotor is relatively low), the current flowing through the motor M is relatively small, so that the zero-crossing time of the induced voltage is unclear, the signal-to-noise ratio of the induced voltage deteriorates, and the estimation accuracy of the rotor position deteriorates.Therefore, in comparison to a normal sensorless control (PWM control), the current flowing through the motor M can be increased by performing three-phase short-circuit control as in the present embodiment when the motor M is started or when the induced voltage is relatively low and the determining unit determines that position estimation is not possible, thus making it possible to clarify the zero-crossing time of the induced voltage and to improve the estimation accuracy of the estimated position θ^. Example of the<Verfahren, das eine elektromotorische Geschwindigkeitskraft verwendet>

[0083] First, the estimating unit 8 calculates an electromotive force eM generated in the motor M, based on the γ-axis current value Iγ, the δ-axis current value Iδ, the γ-axis voltage command value Vγ*', the δ-axis voltage command value Vδ*', the estimated angular velocity ω^ stored in the memory unit 4, and the motor parameters, which can be estimated in advance. Specifically, the estimating unit 8 calculates the electromotive force eM using the following equation 9. Note that P denotes a time derivative operator d / dt, and KE denotes an induced voltage constant. A winding resistance value R^, a d-axis inductance Ld^ and a q-axis inductance Lq^ are estimated values ​​of motor parameters of the motor M to be controlled, and are estimated in advance by measurement or the like using the motor M.The reason why estimated values ​​are used instead of the actual values ​​of the motor parameters of motor M is that the motor parameters vary depending on the temperature and the current flowing through motor M. [Mathematical expression 7] [Vγ* 'Vδ* ']−[R+pLd−ωLq−ωLqR+pLd][iγiδ]+[0eM×KE]

[0084] Then the estimating unit 8 obtains an estimated value of the current flowing through the motor M and an actual current based on the calculated electromotive velocity force eM and calculates the estimated angular velocity ω^ and the estimated position θ^ based on a current error between the estimated value and the actual value.

[0085] Furthermore, in a case where the<Verfahren, das die elektromotorische Geschwindigkeitskraft verwendet> when the method of calculating the estimated angular velocity ω^ and the estimated position θ^ is applied, similar to the case where the<Verfahren, das einen Nulldurchgangszeitpunkt der induzierten Spannung verwendet> When the procedure for calculating the estimated angular velocity ω^ and the estimated position θ^ is applied, the calculation unit 6 returns to step S1 and performs the three-phase short-circuit control when the motor M is started or when the induced voltage of any phase in step S10 exceeds the specified value. Fig. 2 is less than the threshold th' (step S10: Yes). Note that if it is determined that the induced voltage of any phase is equal to or greater than the threshold th' (step S10: No), the computation unit 6 continuously performs sensorless control.This means that the determining unit 18, as the first determining unit, determines that the estimating unit 8 is in a state in which it is able to perform velocity and position estimation, and causes sensorless control to continue if the induced voltage of any phase is equal to or greater than the threshold th', and determines that the estimating unit 8 is in a state in which it is unable to perform velocity and position estimation, and causes the transition from sensorless control to three-phase short-circuit control if the induced voltage of any phase is less than the threshold th'.

[0086] As described above, even in the case where the [method using the estimated electromotive velocity force] is applied as the method for calculating the estimated angular velocity ω^ and the estimated position θ^, three-phase short-circuit control is performed when the motor M is started or when the induced voltage is relatively low and the determining unit 18, as the first determining unit, determines that position estimation is not possible, so that the estimation accuracy of the estimated position θ^ can be improved.In general, in normal sensorless control (PWM control), when the motor starts or when the induced voltage is relatively low (when the rotor angular velocity is relatively low), the error (dead-time error) between the true value and each of the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* is relatively larger when the induced voltage is lower. Thus, the signal-to-noise ratio of the induced voltage deteriorates, and the accuracy of the rotor position estimation deteriorates.Therefore, in comparison to normal sensorless control (PWM control), the influence of the dead time error can be removed by performing three-phase short-circuit control when the motor M is started or when the induced voltage is relatively low and the determination unit 18 determines that position estimation is not possible, as in the present embodiment, so that it is possible to improve the signal-to-noise ratio of the induced voltage and improve the estimation accuracy of the estimated position θ^. Example of the<Verfahren, das Magnetfluss verwendet>

[0087] First, the estimating unit 8 calculates an o-axis magnetic flux λa and a β-axis magnetic flux λβ based on the γ-axis current value Iγ, the δ-axis current value Iδ, the γ-axis voltage command value Vγ*', the δ-axis voltage command value Vδ*', and the motor parameters, which can be estimated beforehand. Specifically, the estimating unit 8 calculates the α-axis magnetic flux λα and the β-axis magnetic flux λβ using the following equation 10. It should be noted that the following equation 10 is obtained from the following equations 11 to 13. That is, if the definition as in the following equation 12 is applied in an observer (engine model) that is expressed by the following equation 11, the following equation 11 is expressed as the following equation 13.Subsequently, when the following equation 13 is transformed into an α-β-axis system (a system with fixed coordinates), the following equation 10 is obtained. It should be noted that an α-axis voltage Vα corresponds to the γ-axis voltage command value Vγ*' in the fixed coordinate system, a β-axis voltage Vβ corresponds to the δ-axis voltage command values ​​Vδ*' in the fixed coordinate system, an α-axis current iα corresponds to the γ-axis current value Iγ in the fixed coordinate system, and a β-axis current iβ corresponds to the δ-axis current value Iδ in the fixed coordinate system. Furthermore, λd denotes a d-axis magnetic flux and λq denotes a q-axis magnetic flux. [Mathematical expression 8] [VαVβ]=[R+pLd00R+pLd][iαiβ]+p[λαλβ] [Mathematical expression 9] [Vγ* 'Vδ* ']−[R+pLd−ωLdωLdR+pLd][iγiδ]+[0p(Lq−Ld)iδ]+ω[⋅(Lq⋅Ld)iδKE] [Mathematical expression 10] λ=[λdλq]=[KE(Lq−Ld)iδ] [Mathematical expression 11] [Vγ* 'Vδ* ']−[R+pLd−ωLdωLdR+pLd][iγiδ]+p[λdλq]+ω[−λqλd]

[0088] The estimation unit 8 then inserts the calculated o-axis magnetic flux λα and the calculated β-axis magnetic flux λβ into the following equation 14 to calculate the estimated position θ^. It should be noted that a method for calculating the estimated angular velocity ω^ from the estimated position θ^ is similar to the method described above [using an extended electromotive force], and therefore a description of this method is omitted. [Mathematical expression 12] θ = tan−1λβλα

[0089] Furthermore, in a case where the<Verfahren, das einen Magnetfluss verwendet> When the procedure for calculating the estimated angular velocity ω^ and the estimated position θ^ is applied, the calculation unit 6 returns to step S1 and performs the three-phase short-circuit control when the motor M is started, or when the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is less than a threshold value th'' in step S10 of Fig.2 is (Step S10: Yes). It should be noted that if it is determined that the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is equal to or greater than the threshold th'' (Step S10: No), the computation unit 6 continuously performs sensorless control. For example, the threshold th'' is assumed to be a minimum value of the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' in a case where sensorless control can be performed, and is obtained beforehand through an experiment, simulation, or the like.This means that the determining unit 18, as the first determining unit, determines that when the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is equal to or greater than the threshold th'', the estimating unit 8 is in a state in which it is able to perform velocity and position estimation, and causes sensorless control to continue; and determines that when the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is less than the threshold th'', the estimating unit 8 is in a state in which it is unable to perform velocity and position estimation, and causes the transition from sensorless control to three-phase short-circuit control.

[0090] As described above, this also applies in the case where the<Verfahren, das Magnetfluss verwendet> When the procedure for calculating the estimated angular velocity ω^ and the estimated position θ^ is applied, the three-phase short-circuit control is performed when the motor M is started or when the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is relatively small and the determination unit 18, as the first determination unit, determines that position estimation is not possible, so that the estimation accuracy of the estimated position θ^ can be improved.In general, in normal sensorless control (PWM control), when the motor M is started or when the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is relatively small (when the rotor angular velocity is relatively low), the error (dead-time error) between the true values ​​of the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* is relatively larger when the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is smaller.

[0091] Thus, the signal-to-noise ratio of the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' deteriorates, and the estimation accuracy of the rotor position deteriorates. Therefore, compared to normal sensorless control (PWM control), the influence of the dead-time error can be eliminated by implementing three-phase short-circuit control, as in the present embodiment, when the motor M is started or when the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is relatively small and the determination unit 18 determines that position estimation is not possible. This makes it possible to improve the signal-to-noise ratio of one phase voltage of the motor M and thus improve the estimation accuracy of the estimated position θ^.It should be noted that instead of the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*', the determination can be carried out using the γ-axis current value Iγ, the γ-axis voltage command value Vγ*', the δ-axis current value Iδ and the δ-axis voltage command value Vδ*'. Reference symbol list 1 Control system 2 inverters 3 Control device 4 storage units 5 Drive circuit 6 units of calculation 7 Current value conversion unit 8 Estimation unit 9 subtraction unit 10 Torque command value calculation unit 11 γ-δ current command value output unit 12 subtraction unit 13 Subtraction unit 14 Voltage command value calculation unit 15,16 switches 17 Voltage command value conversion unit 18 Unit of identification (first unit of identification, second unit of identification) P Power source C capacitor Se1 current sensor Se2 current sensor Se3 current sensor QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2022 - 85 227 A

[0005]

Claims

[1] Control device which generates a drive signal for controlling an inverter which drives a motor, wherein the control device comprises: a current value conversion unit that converts a current flowing through the motor into a y-axis current value and a δ-axis current value, a γ-δ current command value output unit that outputs a γ-axis current command value and a δ-axis current command value, a γ-δ voltage command value calculation unit that calculates a γ-axis voltage command value based on the γ-axis current value and the γ-axis current command value, and calculates a δ-axis voltage command value based on the δ-axis current value and the δ-axis current command value, a drive signal conversion unit that converts the γ-axis voltage command value and the δ-axis voltage command value into the drive signal, an estimation unit that calculates an estimated position, which is an estimated value of a position of the engine, and a first determination unit that determines whether or not a position estimation of the motor is possible by the estimation unit, wherein an upper branch short-circuit drive signal or a lower branch short-circuit drive signal is generated when the motor is started or when the first determination unit determines that the position estimation of the motor is not possible, wherein the upper branch short-circuit drive signal is the drive signal for simultaneously switching on three-phase upper branch switching elements of the inverter and simultaneously switching off three-phase lower branch switching elements of the inverter, wherein the lower branch short-circuit drive signal is the drive signal for simultaneously switching off the three-phase upper branch switching elements of the inverter and simultaneously switching on the three-phase lower branch switching elements of the inverter, and, When the upper branch short-circuit drive signal or the lower branch short-circuit drive signal is generated, the estimation unit calculates the estimated position, which is the estimated value of the motor's position, based on the current flowing through the motor. [2] Control device according to claim 1, comprising a second determination unit, wherein the second determination unit determines, on the basis of the current flowing through the motor due to the upper branch short-circuit drive signal or the lower branch short-circuit drive signal, whether the position estimation of the motor is possible or not. [3] Control device according to claim 2, wherein the drive signal for supplying a three-phase alternating current to the motor is generated when the second determination unit determines that the position estimation of the motor is possible. [4] Control device according to claim 3, wherein, If the second determination unit determines that a value of the current flowing through the motor is less than a current threshold value and the position estimation of the motor is possible, a timer is started, and the drive signal is generated to cause the current flowing through the motor to have a constant value, and the upper branch short-circuit drive signal or the lower branch short-circuit drive signal is generated after a first predetermined time has elapsed. [5] Control device according to claim 3, wherein The estimated unit is an estimated extended electromotive force, which is an estimated value of an extended electromotive force generated in the motor, calculated on the basis of the γ-axis current value, the δ-axis current value, the γ-axis voltage command value, and the δ-axis voltage command value; and the estimated position, which is the estimated value of the motor's position, calculated on the basis of the estimated extended electromotive force. The first determination unit determines that position estimation is not possible if the estimated extended electromotive force is less than a threshold value, and generates the upper branch short-circuit drive signal or the lower branch short-circuit drive signal.

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