Control device

Abstract

This control device comprises: a drive signal output unit that converts a γ-axis voltage command value V* γ and a δ-axis voltage command value V* δ into a drive signal and outputs the drive signal to an inverter; and an estimation unit 55 that calculates an estimated extended induced voltage that is generated in a motor on the basis of a γ-axis electric current value Iγ, a δ-axis electric current value Iδ, the γ-axis voltage command value V* γ, and the δ-axis voltage command value V* δ, and calculates an estimated position θ^re1 on the basis of the estimated extended induced voltage, wherein, when a restart request is received or when it is determined that the motor is rotating at a low speed, the drive signal output unit generates an upper arm short circuit drive signal or a lower arm short circuit drive signal, and the estimation unit 55 calculates the estimated position θ^re1 on the basis of a differential value of the γ-axis electric current value Iγ and the δ-axis electric current value Iδ that are converted by setting the estimated position θre1 to zero from an electric current flowing in the motor due to the upper arm short circuit drive signal or the lower arm short circuit drive signal.

Description

Control device

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

[0002] Position sensorless control of a motor using an extended electromotive force (EEMF) is known. For example, Non-Patent Document 1 describes a restart algorithm in which, immediately after restarting from a free-running state, a current command value is set to 0 for a certain period of time to estimate the excited EEMF, and signal superposition and polarity determination are performed in a low-speed stop region where the EEMF is insufficient, and position estimation is performed without signal superposition in a medium- to high-speed region where the EEMF is sufficient.

[0003] Takamasa Kozakura and Shinji Michiki, "Study on restart from free-run state in position sensorless control of permanent magnet synchronous motor using extended induced voltage," Institute of Electrical Engineers of Japan (Motor Drive / Rotating Machine / Automotive Joint Study Group), Institute of Electrical Engineers of Japan, May 30, 2021, pp. 63-68

[0004] The position estimation method described in Non-Patent Document 1 does not provide highly accurate position estimation under all conditions, and therefore, proposals for different position estimation methods are desired.

[0005] The present disclosure describes a control device that can improve the accuracy of position estimation.

[0006] A control device according to one aspect of the present disclosure is a control device that generates a drive signal for controlling an inverter that drives a motor, and includes: a current value converter 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 value output unit that outputs a specified γ-axis current value and a specified δ-axis current value; a γ-δ voltage command value calculator that calculates a specified γ-axis voltage value and a specified δ-axis voltage value based on the specified γ-axis current value, the specified γ-axis current value, the specified δ-axis current value, and the specified δ-axis current value; a drive signal output unit that converts the specified γ-axis voltage value and the specified δ-axis voltage value into drive signals and outputs them to the inverter; and an estimator that calculates an estimated extended electromotive force that is an estimate of an extended electromotive force generated in the motor based on the γ-axis current value, the δ-axis current value, the specified γ-axis voltage value, and the specified δ-axis voltage value, and calculates an estimated position that is an estimate of the position of the motor based on the estimated extended electromotive force. When a restart request is received or when it is determined that the motor is rotating at a low speed, the drive signal output unit generates an upper arm short-circuit drive signal that is a drive signal that simultaneously turns on the switching elements of the upper arms of the three phases of the inverter and simultaneously turns off the switching elements of the lower arms of the three phases of the inverter, or a lower arm short-circuit drive signal that is a drive signal that simultaneously turns off the switching elements of the upper arms of the three phases of the inverter and simultaneously turns on the switching elements of the lower arms of the three phases of the inverter.The estimator calculates an estimated position from the current flowing through the motor due to the upper arm short-circuit drive signal or the lower arm short-circuit drive signal, based on the differentiated values ​​of the γ-axis current value and the δ-axis current value converted by setting the estimated position to zero.

[0007] In this control device, when a restart request is received or when it is determined that the motor is rotating at a low speed, the control device simultaneously turns on the switching elements of the upper arms of the three phases of the inverter and simultaneously turns off the switching elements of the lower arms of the three phases of the inverter, or simultaneously turns off the switching elements of the upper arms of the three phases of the inverter and simultaneously turns on the switching elements of the lower arms of the three phases of the inverter. This allows the actual voltage value and the voltage command value to be zero, thereby eliminating voltage errors. In addition, since the estimated position is calculated based on the differential values ​​of the converted two-axis current values ​​with the estimated position set to zero, the influence of offset errors in the current sensors can be reduced. As a result, the accuracy of position estimation can be improved.

[0008] According to the present disclosure, the accuracy of position estimation can be improved.

[0009] Fig. 1 is a schematic configuration diagram of a control system including a control device according to an embodiment. Fig. 2 is a block diagram showing the functional configuration of a computing unit shown in Fig. 1. Fig. 3 is a flowchart showing an example of pre-restart processing performed by the control device of Fig. 1.

[0010] A control device according to an embodiment will be described in detail below with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0011] A schematic configuration of a control system including a control device according to one embodiment will be described with reference to FIG. 1 . FIG. 1 is a schematic configuration diagram of a control system including a control device according to one embodiment. The control system 1 shown in FIG. 1 is a system that performs position sensorless control of a motor (electric motor) M. The motor M is a position sensorless motor, such as a permanent magnet synchronous motor (PMSM). The motor M is mounted on a vehicle such as an electric forklift or a plug-in hybrid vehicle. The control system 1 includes an inverter circuit 2, a control device 3, and current sensors Se1, Se2, and Se3.

[0012] The inverter circuit 2 drives the motor M with DC power supplied from the DC power supply PS. The inverter circuit 2 includes a capacitor C and switching elements SW1, SW2, SW3, SW4, SW5, and SW6.

[0013] The capacitor C smoothes the voltage that is output from the DC power supply PS and input to the inverter circuit 2 .

[0014] The switching elements SW1 to SW6 are, for example, IGBTs (Insulated Gate Bipolar Transistors). Switching element SW1 is the switching element of the upper arm of the U phase. Switching element SW2 is the switching element of the lower arm of the U phase. Switching element SW3 is the switching element of the upper arm of the V phase. Switching element SW4 is the switching element of the lower arm of the V phase. Switching element SW5 is the switching element of the upper arm of the W phase. Switching element SW6 is the switching element of the lower arm of the W phase. One terminal of the capacitor C is connected to the positive terminal of the DC power supply PS and the collector terminals of the switching elements SW1, SW3, and SW5. The other terminal of the capacitor C is connected to the negative terminal of the DC power supply PS and the emitter terminals of the switching elements SW2, SW4, and SW6.

[0015] The connection point between the emitter terminal of switching element SW1 and the collector terminal of switching element SW2 is connected to the U-phase input terminal of motor M via current sensor Se1. The connection point between the emitter terminal of switching element SW3 and the collector terminal of switching element SW4 is connected to the V-phase input terminal of motor M via current sensor Se2. The connection point between the emitter terminal of switching element SW5 and the collector terminal of switching element SW6 is connected to the W-phase input terminal of motor M via current sensor Se3.

[0016] A drive signal is supplied to each gate of the switching elements SW1 to SW6 from the control device 3. Each of the switching elements SW1 to SW6 is turned on or off based on the drive signal supplied to the gate. By turning on or off each of the switching elements SW1 to SW6, the DC power output from the DC power supply PS is converted into three AC powers that are 120 degrees out of phase with each other, and these AC powers are input to input terminals of three phases (U phase, V phase, and W phase) of the motor M, causing the rotor of the motor M to rotate.

[0017] The current sensors Se1 to Se3 are configured by Hall elements or shunt resistors, etc. The current sensor Se1 detects a U-phase current value I ｕ The current sensor Se2 detects a V-phase current value I, which is the current value of the AC current flowing through the V-phase of the motor M, and outputs the detected value to the control device 3. ｖ The current sensor Se3 detects the W-phase current value I, which is the current value of the AC current flowing through the W-phase of the motor M, and outputs the detected value to the control device 3. ｗ and outputs the detected current to the control device 3. In this embodiment, the control system 1 includes three current sensors (current sensors Se1 to Se3), but may include two current sensors.

[0018] The control device 3 is a device that performs position sensorless control of the motor M. The control device 3 controls the inverter circuit 2 to drive the motor M. The control device 3 includes a drive circuit 4 and a computing unit 5.

[0019] The drive circuit 4 is configured by an IC (Integrated Circuit) or the like. The drive circuit 4 receives a U-phase voltage command value V ＊ ｕ , V-phase voltage command value V ＊ ｖ , and the W-phase voltage command value V ＊ ｗ The control circuit compares the signal with a carrier wave (such as a triangular wave, a sawtooth wave, or an inverse sawtooth wave), and outputs drive signals according to the comparison results to the gate terminals of the switching elements SW1 to SW6.

[0020] The computing unit 5 is an electronic control unit configured with a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. For example, a program stored in the ROM is loaded onto the RAM and executed by the CPU, thereby realizing various functions of the computing unit 5 shown in FIG.

[0021] Next, the functional configuration of the calculator 5 will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the functional configuration of the calculator shown in Fig. 1. As shown in Fig. 2, the calculator 5 includes, as functional components, a coordinate conversion unit 51, a γ-δ current command value output unit 52, a γ-δ voltage command value calculation unit 53, a coordinate conversion unit 54, and an estimation unit 55.

[0022] The coordinate conversion unit 51 converts the estimated position θ^ output from the estimation unit 55 ｒｅ１ Based on this, the U-phase current value I ｕ , V-phase current value I ｖ and W-phase current value I ｗ γ-axis current value I γ and the δ-axis current value I δ That is, the coordinate conversion unit 51 converts the current flowing through the motor M into a γ-axis current value I γ and the δ-axis current value I δ It functions as a current value converter that converts the estimated position θ ｒｅ１ is the rotor position θ of the motor M ｒｅ１ This conversion method is well known, so a detailed description will be omitted here. The coordinate conversion unit 51 converts the γ-axis current value I γ and the δ-axis current value I δ to the γ-δ voltage command value calculation unit 53 and the estimation unit 55. The coordinate conversion unit 51 outputs the U-phase current value I ｕ , V-phase current value I ｖ and W-phase current value I ｗ The current values ​​of two of the phases may be input, and the current value of the remaining phase may be calculated from the input current values ​​of the two phases.

[0023] In addition, "θ^ ｒｅ１ In the notation, "^" is located to the upper right of "θ", but in the notation "θ^" ｒｅ１" has the same meaning as the symbol written on the arrow pointing from the estimation unit 55 to the coordinate transformation unit 51 in FIG. 1. The same applies to other notations of "^". In this specification, the symbol "^" means an estimated value.

[0024] The γ-δ coordinate system is an estimated rotating coordinate system in which the axis equivalent to the d-axis of the d-q coordinate system is the γ-axis, and the axis equivalent to the q-axis is the δ-axis. The d-q coordinate system is a rotating coordinate system in which the direction of the north pole of the magnet of the motor M is the d-axis, and the direction perpendicular to the d-axis is the q-axis. The α-β coordinate system is a two-dimensional stationary coordinate system.

[0025] The γ-δ current command value output unit 52 receives an angular velocity command value ω ＊ and the estimated angular velocity ω^ output from the estimation unit 55 ｒｅ The angular velocity difference Δω is calculated, and the torque command value T ＊ Calculate the estimated angular velocity ω^ ｒｅ is the angular velocity ω of the rotor of the motor M ｒｅ The γ-δ current command value output unit 52 outputs the torque command value T ＊ γ-axis current command value I ＊ γ and the δ-axis current command value I ＊ δ The γ-axis current command value I ＊ γ and the δ-axis current command value I ＊ δ Since the method for generating the γ-axis current command value I is well known, a detailed description thereof will be omitted here. ＊ γ and the δ-axis current command value I ＊ δ is output to the γ-δ voltage command value calculation unit 53.

[0026] The γ-δ voltage command value calculation unit 53 calculates the γ-axis voltage command value V ＊ γ and the δ-axis voltage command value V ＊ δ The γ-δ voltage command value calculation unit 53 generates the γ-axis current command value I ＊ γ and γ-axis current value I γ The difference γ-axis current command value ΔI ＊γ and calculates the δ-axis current command value I ＊ δ and the δ-axis current value I δ The difference δ-axis current command value ΔI ＊ δ is calculated, and the differential γ-axis current command value ΔI ＊ γ and the differential δ-axis current command value ΔI ＊ δ is the γ-axis voltage command value V ＊ γ and the δ-axis voltage command value V ＊ δ That is, the γ-δ voltage command value calculation unit 53 converts the γ-axis current command value I ＊ γ and γ-axis current value I γ and the δ-axis current command value I ＊ δ and the δ-axis current value I δ Based on this, the γ-axis voltage command value V ＊ γ and the δ-axis voltage command value V ＊ δ The γ-axis voltage command value V ＊ γ and the δ-axis voltage command value V ＊ δ Since the method for generating the γ-δ voltage command value V is well known, a detailed description thereof will be omitted here. ＊ γ and the δ-axis voltage command value V ＊ δ to the coordinate transformation unit 54 and the estimation unit 55.

[0027] The coordinate conversion unit 54 converts the estimated position θ^ output from the estimation unit 55 ｒｅ１ Based on this, the γ-axis voltage command value V ＊ γ and the δ-axis voltage command value V ＊ δ is the U-phase voltage command value V ＊ ｕ , V-phase voltage command value V ＊ ｖ , and the W-phase voltage command value V ＊ ｗ This conversion method is well known, so a detailed description will be omitted here. The coordinate conversion unit 54 converts the U-phase voltage command value V＊ ｕ , V-phase voltage command value V ＊ ｖ , and the W-phase voltage command value V ＊ ｗ to the drive circuit 4. That is, the coordinate conversion unit 54 and the drive circuit 4 output the γ-axis voltage command value V ＊ γ and the δ-axis voltage command value V ＊ δ The inverter circuit 2 converts the voltage Vcc into a drive signal and outputs the converted voltage Vcc to the inverter circuit 2.

[0028] The estimation unit 55 estimates the estimated angular velocity ω^ ｒｅ and estimated position θ^ ｒｅ１ The estimation unit 55 calculates the γ-axis current value I γ , δ-axis current value I δ , γ-axis voltage command value V ＊ γ , δ-axis voltage command value V ＊ δ , the estimated angular velocity ω^ stored in a memory (not shown) ｒｅ , and motor parameters that can be estimated in advance. That is, the estimation unit 55 calculates an estimated extended electromotive force (EEMF) e, which is an estimated value of the extended electromotive force (EEMF) e generated in the motor M. γ , δ-axis current value I δ , γ-axis voltage command value V ＊ γ and the δ-axis voltage command value V ＊ δ It can be said that the estimated extended induced voltage e^, which is an estimated value of the extended induced voltage generated in the motor M, is calculated based on the γ-axis estimated extended induced voltage e^. Specifically, the estimating unit 55 calculates the estimated extended induced voltage e^ using an observer (motor model) shown in equation (1). The estimated extended induced voltage e^ is calculated based on the γ-axis estimated extended induced voltage e^. γ and the δ-axis estimated extended induced voltage e^ δ It contains and as vector components.

[0029] where p represents the time differential operator d / dt. The estimated winding resistance R^ and the d-axis estimated inductance L^ ｄ , and the q-axis estimated inductance L^ｑ are estimated values ​​of the motor parameters of the motor M to be controlled, and are estimated in advance by measurements using the motor M. The reason why the motor parameters of the motor M are estimated values ​​rather than actual values ​​is that the motor parameters vary depending on the current flowing through the motor M and the temperature.

[0030] Then, the estimation unit 55 calculates the position error Δθ^ based on the estimated expansion induced voltage e^. ｒｅ Specifically, the estimation unit 55 calculates the position error Δθ^ from the estimated extension induced voltage e^ using equation (2). ｒｅ Calculate.

[0031] Next, the estimation unit 55 calculates the position error Δθ^ ｒｅ Estimated angular velocity ω^ based on ｒｅ Specifically, the estimation unit 55 calculates, for example, the position error Δθ^ ｒｅ and a predetermined transfer function to obtain the estimated angular velocity ω^ ｒｅ Calculate.

[0032] Then, the estimation unit 55 estimates the angular velocity ω^ ｒｅ and position error Δθ^ ｒｅ Based on this, the estimated position θ ｒｅ１ Specifically, the estimation unit 55 calculates, for example, the estimated angular velocity ω^ ｒｅ The tentative estimated position θ^ obtained by integrating and the position error Δθ^ ｒｅ and a predetermined transfer function to obtain a corrected position error Δθ. ｒｅ１ The position error Δθ^ ｒｅ and a predetermined transfer function, it is not necessary to multiply by a predetermined transfer function. ｒｅ and estimated position θ^ ｒｅ１ is stored in memory, and the estimated angular velocity ω ｒｅ is output to the γ-δ current command value output unit 52, and the estimated position θ ｒｅ１ are output to the coordinate conversion unit 51 and the coordinate conversion unit 54.

[0033] Here, when the control device 3 receives a request to stop the motor M from the upper device, the control device 3 does not forcibly stop the motor M, but instead sets the U-phase voltage command value V ＊ ｕ , V-phase voltage command value V ＊ ｖ , and the W-phase voltage command value V ＊ ｗ Therefore, the motor M enters a free-running state where it rotates by inertia. After that, when the control device 3 receives a restart request for the motor M from the upper device, it restarts the motor M.

[0034] The pre-restart processing performed by the control device 3 will be described in detail below with further reference to Fig. 3. The pre-restart processing is processing performed by the control device 3 after receiving a restart request and before restarting. Fig. 3 is a flowchart showing an example of the pre-restart processing performed by the control device of Fig. 1. The series of processing shown in Fig. 3 is started when the control device 3 receives a restart request.

[0035] 3 , the control device 3 first controls the inverter circuit 2 so that the three-phase upper arm switching elements are simultaneously turned off and the three-phase lower arm switching elements are simultaneously turned on (step S11). Specifically, the coordinate conversion unit 54 controls the drive circuit 4 to output a lower arm short-circuit drive signal, which is a drive signal that simultaneously turns on the switching elements SW2, SW4, and SW6 and simultaneously turns off the switching elements SW1, SW3, and SW5. Note that the lower arm short-circuit drive signal in step 11 is output for a short period (e.g., several μs). Instead of the lower arm short-circuit drive signal, the coordinate conversion unit 54 may also control the drive circuit 4 to output an upper arm short-circuit drive signal, which is a drive signal that simultaneously turns on the switching elements SW1, SW3, and SW5 and simultaneously turns off the switching elements SW2, SW4, and SW6.

[0036] Next, the calculator 5 calculates whether the current flowing through the motor M due to the lower arm short-circuit drive signal is equal to or exceeds the threshold current value I ｔｈ It is determined whether the threshold current value I ｔｈ is the estimated position θ^ of the motor M based on the current value flowing through the motor M. ｒｅ１In other words, the current value flowing through the motor M is the threshold current value I ｔｈ If the current flowing through the motor M is smaller than the threshold current value I ｔｈ If it is determined that the γ-axis current value I is equal to or greater than the γ-axis current value I ≠ 0 (step S12: YES), the estimation unit 55 calculates the γ-axis current value I ≠ 0 based on the current value flowing through the motor M in step S11. γ , δ-axis current value I δ , γ-axis voltage command value V ＊ γ and the δ-axis voltage command value V ＊ δ is acquired (step S13).

[0037] Then, the estimation unit 55 estimates the acquired γ-axis current value I γ and the δ-axis current value I δ Using the estimated position θ ｒｅ１ (Step S14). Here, when the control device 3 receives a stop request, the estimated angular velocity ω^ stored in the memory is calculated. ｒｅ and estimated position θ^ ｒｅ１ is reset to zero. Therefore, immediately after the control device 3 receives the restart request, the estimated angular velocity ω^ ｒｅ is zero. The γ-axis voltage command value V ＊ γ and the δ-axis voltage command value V ＊ δ are all zero because the switching elements of the upper arms of the three phases are simultaneously turned off and the switching elements of the lower arms of the three phases are simultaneously turned on in step S13. Therefore, immediately after the control device 3 receives the restart request, the estimated extension induced voltage e^ is expressed by the following equation (3).

[0038] In a general voltage equation, the switching elements of the upper arms of the three phases are simultaneously turned off and the switching elements of the lower arms of the three phases are simultaneously turned on. ｄ , V ｑ = 0, and rearranging the current differential term yields the following equation (4). γ-axis current value I when a restart request is receivedγ and the δ-axis current value I δ Since the initial value of is 0, I ｄ , I ｑ = 0, so when substituted into the above formula (4), pI ｑ =-ωK Ｅ / L pLI ｑ =-ωK Ｅ Here, for motors with large magnet torque or motors in a free-running state, ωK Ｅ That is, pLI ｑ is sufficiently large. In other words, when the switching elements of the upper arm of the three phases are simultaneously turned off and the switching elements of the lower arm of the three phases are simultaneously turned on at the time of a restart request, the current differential term becomes dominant. Therefore, in the above equation (3), pL^ is larger than R^ × I. ｄ ×I is sufficiently large, so if we ignore R^×I, the phase of the extended induced voltage e^ is the current differential pI γ , pI δ The phase of the γ-axis current value I γ and the δ-axis current value I δ is the estimated position θ^ immediately after receiving the restart request. ｒｅ１ are set to zero, and the estimated rotating coordinate system (γδ coordinate system) and the stationary coordinate system (αβ coordinate system) coincide with each other, so the α-axis current value I α and β-axis current value I β The above property and the position error Δθ^ ｒｅ is the estimated position θ ｒｅ１ By utilizing the fact that the value of the vector .times. ... Using this, the γ-axis current value I γ and the δ-axis current value I δ Each differential value pI α , pI β Based on this, the estimated position θ ｒｅ１ Calculate.

[0039] On the other hand, in step S12, the current flowing through the motor M is equal to or exceeds the threshold current value I ｔｈIf it is determined that the difference is smaller than the reference value (step S12: NO), the coordinate conversion unit 54 again controls the three-phase upper arm switching elements included in the inverter circuit 2 to be simultaneously turned off and the three-phase lower arm switching elements to be simultaneously turned on (step S15), and then proceeds to step S13. The lower arm short circuit drive signal in step S15 is output for a longer period (e.g., several ms) than the lower arm short circuit drive signal in step S11. In step S15, the coordinate conversion unit 54 may cause the drive circuit 4 to output the upper arm short circuit drive signal instead of the lower arm short circuit drive signal.

[0040] In step S13 after step S15, the estimation unit 55 calculates the γ-axis current value I based on the current value flowing through the motor M in step S15. γ , δ-axis current value I δ , γ-axis voltage command value V ＊ γ and the δ-axis voltage command value V ＊ δ After that, step S14 is executed.

[0041] Subsequently, the estimation unit 55 receives the restart request and then calculates the estimated position θ^ ｒｅ１ It is determined whether the estimated position θ^ has been calculated twice (step S16). ｒｅ１ If the first estimated position θ^ has not been calculated twice (step S16; NO), ｒｅ１ When a predetermined time has elapsed since the calculation of the second estimated position θ^, the processing of steps S11 to S15 is repeated, and the estimation unit 55 calculates the second estimated position θ^ ｒｅ１ Calculate.

[0042] Then, the estimation unit 55 executes the process of step S14 twice to calculate the first estimated position θ^ ｒｅ１ and the second estimated position θ̂ ｒｅ１ and the value of the predetermined time which is the calculation time interval, the estimated angular velocity ω^ ｒｅ Furthermore, the estimation unit 55 calculates the estimated angular velocity ω^ ｒｅ and the second estimated position θ^ calculated in step S14. ｒｅ１ is stored in memory, and the estimated angular velocity ω ｒｅis output to the γ-δ current command value output unit 52, and the second estimated position θ ｒｅ１ to the coordinate transformation unit 51 and the coordinate transformation unit 54 (step S17). With this, the pre-restart process is completed.

[0043] This completes the series of processes shown in FIG.

[0044] In the control device 3 described above, when a restart request is received, the γ-axis voltage command value V ＊ γ and the δ-axis voltage command value V ＊ δ is set to zero, and the estimated position θ ｒｅ１ is set to zero, and the γ-axis current value I γ and the δ-axis current value I δ Each differential value pI α , pI β Based on this, the estimated position θ ｒｅ１ Therefore, the actual voltage value and the voltage command value can be set to zero, which eliminates the voltage error and improves the accuracy of position estimation. In particular, when the current value flowing through the motor M is equal to or exceeds the threshold current value I ｔｈ When the γ-axis current value I is smaller than γ, that is, when the motor M is rotating at a low speed, the S / N ratio deteriorates, which may result in a decrease in the accuracy of the position estimation. However, by eliminating the voltage error, it is possible to improve the accuracy of the position estimation even when the motor M is rotating at a low speed. In addition, γ and the δ-axis current value I δ Each differential value pI α , pI β Since the offset error in the current sensor is used, the influence of the offset error in the current sensor can be reduced, and the accuracy of the position estimation can be further improved.

[0045] In the control device 3, the estimation unit 55 calculates the estimated position θ^ using the above equation (5). ｒｅ１ In this case, the estimated position θ^ ｒｅ１ The calculation of the estimated position θ^ can be simplified. ｒｅ１ This can reduce the effect of offset errors in the current sensor.

[0046] In addition, in the control device 3, when a restart request is received, the estimation unit 55 calculates the first estimated position θ^ using the above equation (5). ｒｅ１ and calculate the first estimated position θ^ ｒｅ１ When a predetermined time has elapsed since the calculation of the second estimated position θ^, the second estimated position θ^ is calculated using the above formula (5). ｒｅ１ and calculate the first estimated position θ^ ｒｅ１ and the second estimated position θ̂ ｒｅ１ Estimated angular velocity ω^ based on ｒｅ In this case, the two estimated positions θ^ are calculated with high accuracy. ｒｅ１ Estimated angular velocity ω^ ｒｅ Therefore, the estimated angular velocity after restart is calculated as ω^ ｒｅ It is possible to improve the calculation accuracy of

[0047] Although one embodiment of the present disclosure has been described in detail above, the control device according to the present disclosure is not limited to the above embodiment.

[0048] Although the above embodiment relates to the pre-restart process, the present invention is not limited to this. When the motor M is rotating at a low speed, step S11 or step S15 may be executed, and the position of the motor M may be estimated based on the value of the current flowing through the motor M by executing step S11 or step S15. In other words, the calculator 5 may determine whether the motor M is rotating at a low speed, and when it is determined that the motor M is rotating at a low speed, the flow of FIG. 3 may be executed, or steps S15, S13, S14, S16, and S17 may be executed in order. For example, the calculator 5 may determine whether the value of the current flowing through the motor M is equal to or greater than the threshold current value I ｔｈ If the difference is smaller than , it is determined that the motor M is rotating at a low speed. When the position of the motor M is estimated while the motor M is rotating at a low speed, the S / N ratio deteriorates, which may result in a decrease in the accuracy of the position estimation. In contrast, by executing step S15, it is possible to eliminate the voltage error and improve the accuracy of the position estimation.

[0049] In this embodiment, the estimation unit sets the estimated position to zero and calculates the differential value of the converted γ-axis current value as pI α, the differential value of the δ-axis current value converted by setting the estimated position to zero is pI β In this case, the following equation (5) is satisfied: θ=tan －１ (-pI α / pI β ) (5) In this case, the calculation of the estimated position can be simplified, and the influence of offset errors in the current sensors on the calculated estimated position can be reduced.

[0050] When a restart request is received, the estimation unit may calculate a first estimated position using equation (5), calculate a second estimated position using equation (5) when a predetermined time has elapsed since the calculation of the first estimated position, and calculate an estimated angular velocity based on the first estimated position and the second estimated position. In this case, the estimated angular velocity is calculated from the two estimated positions calculated with high accuracy. Therefore, it is possible to improve the calculation accuracy of the estimated angular velocity after the restart.

[0051] 2... inverter circuit, 3... control device, 4... drive circuit (drive signal output unit), 51... coordinate conversion unit (current value conversion unit), 52... γ-δ current command value output unit, 53... γ-δ voltage command value calculation unit, 54... coordinate conversion unit (drive signal output unit), 55... estimation unit, M... motor, SW1 to SW6... switching elements

Claims

1. A control device that generates a drive signal for controlling an inverter that drives a motor, comprising: a current value 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 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 and a δ-axis voltage command value based on the γ-axis current value, the γ-axis current value, the δ-axis current value, and the δ-axis current command value; a drive signal output unit that converts the γ-axis voltage command value and the δ-axis voltage command value into the drive signal and outputs it to the inverter; and an estimator that calculates an estimated extended electromotive force, which is an estimate 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 calculates an estimated position, which is an estimate of the position of the motor, based on the estimated extended electromotive force, the drive signal output unit, when receiving a restart request or when it is determined that the motor is rotating at a low speed, generates an upper arm short-circuit drive signal that is the drive signal for simultaneously turning on upper arm switching elements of the three phases of the inverter and simultaneously turning off lower arm switching elements of the three phases of the inverter, or a lower arm short-circuit drive signal that is the drive signal for simultaneously turning off upper arm switching elements of the three phases of the inverter and simultaneously turning on lower arm switching elements of the three phases of the inverter, and the estimator calculates the estimated position based on differentiated values ​​of the γ-axis current value and the δ-axis current value converted from the current flowing through the motor by the upper arm short-circuit drive signal or the lower arm short-circuit drive signal while setting the estimated position to zero.

2. The estimation unit sets the estimated position to zero and calculates the differential value of the γ-axis current value as pI α , the differential value of the δ-axis current value converted by setting the estimated position to zero is pI β In this case, the following equation (5) is satisfied: θ=tan －１ (-pI α / pI β ) (5) The control device according to claim 1, wherein the estimated position is calculated by the following equation.

3. The control device described in claim 2, wherein when the restart request is received, the estimation unit calculates a first estimated position using equation (5), and when a predetermined time has elapsed since calculating the first estimated position, calculates a second estimated position using equation (5), and calculates an estimated angular velocity based on the first estimated position and the second estimated position.

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