Motor speed control device and motor speed control method

Abstract

The motor speed control device of the embodiment includes a rotational speed estimation unit and a control unit. The rotational speed estimation unit generates an estimated value of the rotational speed of the motor using a result of FFT analysis of a speed detection signal ωFBK obtained based on a detection result of a resolver that detects the rotational speed of the motor, and the speed detection signal ωFBK. The control unit performs speed control in such a manner that a deviation between a speed command value for the speed control of the motor and the estimated value of the rotational speed is reduced.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to a motor speed control device and a motor speed control method. BACKGROUND

[0002] A resolver is one example of a "sensor (speed detector)" for detecting a rotational speed (angular speed) of a motor. Some motor speed control devices use a resolver to detect a rotational speed of a motor, and use a result of the detection to perform speed control of the motor. However, when a shaft of the resolver is eccentric with respect to a shaft of the motor, the result of the detection by the resolver has an error, and it is sometimes difficult to control the speed of the motor with high precision.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 10-23774 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] An object of the present application is to provide a motor speed control device and a motor speed control method that reduce the influence of eccentricity of a shaft of a resolver with respect to a shaft of a motor when a speed of the motor is detected by the resolver and speed control of the motor is performed.

[0008] MEANS FOR SOLVING THE PROBLEMS

[0009] A motor speed control device according to an embodiment has a rotational speed estimation section and a control section. The rotational speed estimation section generates an estimated value of a rotational speed of a motor using a result of FFT analysis of a speed detection signal ωFBK obtained based on a result of detection of a rotational speed of the motor by a resolver, and the speed detection signal ωFBK. The control section performs speed control in such a manner that a deviation between a speed command value for the speed control of the motor and the estimated value of the rotational speed is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a block diagram illustrating a motor drive system including a motor speed control device according to a first embodiment.

[0011] Figure 2 is a flowchart of speed estimation control based on an application condition according to the first embodiment.

[0012] Figure 3 is a flowchart of speed estimation control based on an application condition according to a second embodiment.

[0013] Figure 4 is a graph for explaining a speed feedback signal in a case where there is eccentricity in the 1st embodiment.

[0014] Figure 5 is a graph for explaining a result of performing FFT analysis processing on a speed feedback signal shown in Figure 4 .

[0015] Figure 6 is a graph for explaining a speed feedback signal shown in Figure 4 and a signal for eccentricity compensation.

[0016] Figure 7 is a graph for explaining a result of compensating a speed feedback signal shown in Figure 4 using the signal for eccentricity compensation. DETAILED DESCRIPTION

[0017] Hereinafter, a motor speed control device and a motor speed control method according to an embodiment will be described with reference to the drawings. Note that the drawings are schematic or conceptual diagrams and the allocation of functions to each part, and the like, are not necessarily the same as that of the actual situation.

[0018] Further, in the present application specification and each drawing, the same symbol is given to configurations having the same or similar functions. Then, sometimes, repeated description of these configurations is omitted.

[0019] In the embodiment, the so-called "connection" includes electrical connection. The so-called "based on XX" means "at least based on XX", and also includes a case where it is based on other elements in addition to XX. The so-called "based on XX" is not limited to a case where XX is directly used, and also includes a case where it is based on XX after being operated or processed. The so-called "XX or YY" is not limited to a case where either one of XX and YY is selected, and also includes a case where both of XX and YY are selected. This is the same in a case where the number of selection elements is three or more. "XX" and "YY" are arbitrary elements (for example, arbitrary information). The "inverter" is a power converter that outputs alternating current, and includes a DC / AC converter and the like. The "motor" is a rotary electric machine such as an induction motor that is driven by alternating current, and hereinafter, is simply referred to as a "motor". Sometimes, the "rotational speed of the motor" is simply referred to as the "speed of the motor".

[0020] (1st Embodiment)

[0021] Figure 1 is a block diagram illustrating a motor drive system 1 including the motor speed control device of the 1st embodiment. For example, the motor drive system 1 is provided with the motor speed control device 10.

[0022] The motor speed control device 10( Figure 1 described in the above is a control unit.) and the motor 2 (Figure 1 is described as a motor. ) and resolver 2A Figure 1 is described as SS. ) is connected. Motor speed control device 10 controls motor 2 in such a manner that the actual speed of motor 2 detected by resolver 2A coincides with a speed command value supplied additionally.

[0023] Motor 2 has a plurality of windings, each of which is connected to an output of inverter 8 described later. Inverter 8 is an example of a power converter. For example, inverter 8 converts direct-current electric power supplied from a direct-current power source (described as DC. in the figure) to drive motor 2. For example, when alternating current from inverter 8 flows into each winding, motor 2 rotates by electromagnetic action. For example, a shaft of resolver 2A is mechanically linked to a shaft of motor 2, and the shaft of resolver 2A rotates in conjunction with the rotation of the shaft of motor 2. Motor 2 and resolver 2A are adjusted so that the shaft (center of rotation) of the rotation of motor 2 coincides with the shaft (center of rotation) of the rotation of resolver 2A by adjusting the positions of motor 2 and resolver 2A with respect to each other, but sometimes do not completely coincide. A case where the shaft (center of rotation) of motor 2 and the shaft (center of rotation) of resolver 2A do not coincide is referred to as a state where eccentricity is generated. The eccentricity refers to, for example, a state where the center of gravity (center of mass) of a rotating body deviates from the center axis of rotation.

[0024] For example, motor speed control device 10 is a control device of inverter 8 that drives motor 2. Motor speed control device 10 includes phase speed detection section 3, rotational speed estimation section 4, speed control section 5, current control section 6, and PWM control section 7 (described as PWM. in the figure). In addition, speed control section 5, current control section 6, and PWM control section 7 are examples of control sections.

[0025] Speed control section 5 multiplies a speed deviation between a speed command value and a speed estimation value of motor 2 by a prescribed speed response gain to generate a command value of driving torque. The speed command value is supplied, for example, from a higher-level control device such as a programmable logic controller (PLC). The speed estimation value of motor 2 will be described later.

[0026] Current control section 6 is connected to the output of speed control section 5. Current control section 6 outputs a control amount generated in accordance with the difference between the command value of driving torque supplied from speed control section 5 and a torque current component supplied to motor 2.

[0027] PWM control section 7 is connected to the output of current control section 6 and is connected to inverter 8. PWM control section 7 controls inverter 8 by PWM control. Thus, PWM control section 7 can drive motor 2 by PWM control. PWM control section 7 preferably outputs a voltage and a current that drive motor 2 in accordance with the control amount generated by current control section 6.

[0028] For example, a current transformer that detects the phase current of each phase can also be provided on the wiring connected to the output of the inverter 8. The current transformer can also be provided on the wiring of at least two of the three phases of the three-phase alternating current. The current control section 6 can also perform current control based on the instantaneous value of the phase current detected by the current transformer.

[0029] The input of the phase speed detection section 3 is connected to the output of the resolver 2A. The phase speed detection section 3 samples the continuous-time series of speed detection signals ωFBK output from the resolver 2A at a predetermined period, and converts them to discrete-time data of quantized results (hereinafter, simply referred to as data of the speed detection signals ωFBK) by an A / D conversion section. The sampling is preferably performed at a period that enables reproduction of the signal of the frequency component of the object. The speed detection signals ωFBK are signals that are utilized as so-called speed feedback.

[0030] The rotational speed estimation section 4, for example, has an FFT analysis processing section 41 (FFT analysis in the drawing) and a speed compensation calculation section 42.

[0031] The FFT analysis processing section 41 performs FFT analysis of the speed detection signals ωFBK using the discrete-time data obtained based on the detection results of the resolver 2A.

[0032] For example, the input of the FFT analysis processing section 41 is connected to the output of the phase speed detection section 3. The FFT analysis processing section 41 acquires the data of the discrete-time system of the speed detection signals ωFBK output from the phase speed detection section 3, and converts the data of the speed detection signals ωFBK to data in the frequency domain by FFT (Fast Fourier Transform) analysis. The FFT analysis processing section 41 can be, for example, an FFT analyzer, or can be hardware that can perform equivalent or similar operation processing to the FFT analyzer. The number of data in the time domain, i.e., the length of the time window, can be determined according to the required accuracy of the analysis results in the frequency domain.

[0033] If the motor 2 is controlled at a constant speed, noise depending on the deviation is superimposed on the speed detection signals ωFBK as continuous repeating noise. Therefore, even at a certain time, as long as it is data of the speed detection signals ωFBK that is a result of sampling over a predetermined period, it is data that can reproduce the characteristics of the above-described noise.

[0034] The speed compensation calculation unit 42 uses the time-domain data obtained from the FFT analysis result (frequency-domain data) performed by the FFT analysis processing unit 41, and the data of the speed detection signal ωFBK (time-domain data), to generate and output an inferred value of the rotational speed of the motor 2. When generating time-domain data based on the FFT analysis result (frequency-domain data), a reverse FFT analysis method can be used. The speed compensation calculation unit 42 performs a reverse FFT analysis on the FFT analysis result (frequency-domain data) performed by the FFT analysis processing unit 41 to obtain time-domain data based on this.

[0035] For example, the speed compensation calculation unit 42 includes an eccentricity compensation calculation unit 421 (referred to as "eccentricity compensation" in the figure) and an adder 422. The input of the speed compensation calculation unit 42 (the input of the eccentricity compensation calculation unit 421) is connected to the output of the resolver 2A. The output of the speed compensation calculation unit 42 is connected to the first input of the adder 422. The second input of the adder 422 is connected to the output of the resolver 2A. The adder 422 adds the calculation result of the speed compensation calculation unit 42 supplied with its first input to the speed detection signal ωFBK output by the resolver 2A. Thus, the speed compensation calculation unit 42 uses the speed detection signal ωFBK supplied from the resolver 2A and the result of FFT analysis performed by the FFT analysis processing unit 41 to generate an estimated value of the rotational speed of the motor 2.

[0036] For example, the FFT analysis processing unit 41 generates the amplitude spectrum and phase spectrum of the speed detection signal ωFBK as the result of the FFT analysis of the speed detection signal ωFBK. Based on the amplitude spectrum of the speed detection signal ωFBK, the FFT analysis processing unit 41 extracts the amplitude components for each frequency of the speed detection signal ωFBK. The FFT analysis processing unit 41 can also extract the phase components for each frequency of the speed detection signal ωFBK based on the phase spectrum of the speed detection signal ωFBK. For example, the FFT analysis processing unit 41 can calculate the phase component of a signal at a specific frequency. In this case, the rotational speed inference unit 4 can correct the speed detection signal ωFBK based on its amplitude spectrum and phase spectrum to generate an inferred value of the rotational speed of the motor 2. Furthermore, the frequency component of a signal at a specific frequency, as described above, refers to the signal component within a defined frequency band based on the specific frequency as the center frequency.

[0037] For example, the eccentricity compensation calculation unit 421 of the speed compensation calculation unit 42 calculates specific frequency components and their magnitudes related to the rotational speed of the resolver 2A based on the amplitude spectrum. Based on the aforementioned phase spectrum, the eccentricity compensation calculation unit 421 calculates phase information of the specific frequency components relative to the reference phase. The eccentricity compensation calculation unit 421 generates a speed compensation amount based on the magnitude and phase information of the specific frequency components. The adder 422 of the speed compensation calculation unit 42 can use its speed compensation amount to correct the speed detection signal ωFBK, and generate the result of the correction as an inferred value of the rotational speed of the motor 2.

[0038] Furthermore, the motor speed control device 10 may include a processor such as a CPU, which executes a predetermined program to implement some or all of the functional units such as the rotation speed inference unit 4, speed control unit 5, current control unit 6, and PWM control unit 7. These functions may also be achieved through a circuit combination. The motor speed control device 10 may also utilize the storage area of ​​its internal storage unit to perform data transmission processing and analytical calculations by executing a predetermined program through the processor.

[0039] Reference Figure 2 The processing of velocity inference control under the application conditions (first application condition) of this embodiment will be explained. The first application condition of this velocity inference control is that the frequency, amplitude, and phase can be obtained through FFT analysis. Figure 2 This is a flowchart of speed inference control based on the application conditions (first application conditions) of the first implementation method.

[0040] After installing motor 2 and resolver 2A, the user sets the resolver 2A's shaft to be engaged with the motor 2's shaft so that the rotation of resolver 2A is linked to the rotation of motor 2's shaft. During this stage, the positional relationship between motor 2 and resolver 2A is adjusted in a manner that minimizes the aforementioned deviation.

[0041] The speed control unit 5 starts operation according to the speed command (speed command value) (step S11). The speed control unit 5 determines whether the speed estimation value of the motor 2 has reached the speed command (speed command value) (step S12), and repeats the process of step S12 until the speed estimation value reaches the speed command value. When the speed estimation value reaches the speed command value and the control state of constant speed operation is reached, the FFT analysis and processing unit 41 performs FFT analysis on the speed detection signal ωFBK (step S13) to obtain information on the frequency, amplitude, and phase of the speed detection signal ωFBK.

[0042] The speed compensation calculation unit 42 determines whether there is a higher harmonic of the fundamental frequency (called the operating frequency) of the motor 2 operating at a constant speed (step S15), and terminates a series of processes if the higher harmonic is not present.

[0043] In the presence of the aforementioned higher harmonics, the speed compensation calculation unit 42 generates an anti-phase signal of the signal component generated by eccentricity in the speed detection signal ωFBK (referred to as "speed FBK" in the figure) (step S16), adds the anti-phase signal to the speed detection signal ωFBK (referred to as "speed FBK" in the figure) (step S17), and ends the series of processes.

[0044] Thus, by obtaining the phase information of the signal components that overlap due to eccentricity based on the FFT analysis results, the rotational speed inference unit 4 can use the phase information obtained from the FFT analysis results of the speed detection signal ωFBK, and the phase information of the signal components that overlap due to eccentricity. Therefore, the rotational speed inference unit 4 can infer the speed of the motor 2 based on the speed detection signal ωFBK.

[0045] Figure 4 This is a diagram used to illustrate the speed feedback signal in the case of eccentricity in the first embodiment. Figure 4 The graph shown is a model of the results obtained by observing the output signal of resolver 2A over a specified period. The graph illustrates the relationship between the magnitude of the velocity (vertical axis) and the elapsed time (horizontal axis) obtained from the output signal of resolver 2A. This output signal is used as a velocity feedback signal.

[0046] In an ideal, non-eccentric state (comparative example), when motor 2 rotates at a constant speed, the value of the resolution result 2A, i.e., the speed, becomes constant. However, in the eccentric state as in the embodiment, even when motor 2 rotates at a constant speed, the amplitude of the resolution result 2A, i.e., the speed, can be observed to fluctuate periodically.

[0047] Figure 5 It is used to explain the Figure 4 The graph shows the result (amplitude spectrum) obtained by performing FFT analysis on the velocity feedback signal. Figure 5 The graph shown represents the amplitude spectrum relative to frequency (horizontal axis). Figure 4 The result of FFT analysis of the velocity feedback signal shown is as follows: Figure 5The amplitude spectrum is shown. The frequency frm is the frequency component corresponding to the rotational speed ωrm of the motor. According to the analysis results, it can be seen that in addition to the frequency frm, there is also a frequency component centered at a frequency fn that is N times the frequency frm (N is an integer greater than 2).

[0048] Reference Figure 6 This describes the signal used for eccentric compensation of overlapping frequency components in the output signal of such a resolver 2A. Figure 6 It is used for explanation Figure 4 The diagram shows the speed feedback signal and the signal used for eccentricity compensation.

[0049] The frequency component centered at frequency fn is extracted, and its phase relative to the variable components contained in the velocity feedback signal is adjusted. This is shown here as an eccentric compensation signal adjusted to have an out-of-phase relationship. Figure 6 The diagram shows a state where the DC level is matched so that the average value of the eccentricity compensation signal is consistent with the average value of the speed feedback signal.

[0050] Figure 7 This is used to illustrate the use of signal pairs for eccentricity compensation. Figure 4 The graph shows the result of compensating the speed feedback signal. Figure 7 The graph shown illustrates the relationship between the magnitude of velocity (vertical axis) and the passage of time (horizontal axis). This graph illustrates the result obtained by adding the variations in the eccentricity compensation signal and the velocity feedback signal.

[0051] According to the above implementation method, based on the FFT analysis results of the speed detection signal ωFBK, the frequency (N times the motor frequency), amplitude, and phase of the noise (variation) component caused by eccentricity can be clearly identified, and a signal for removing the noise (variation) caused by eccentricity can be output. The generated signal has the same frequency and amplitude as the noise component caused by eccentricity, but its phase is offset by 180 degrees, making it an inverse signal. By adding this signal to the speed detection signal ωFBK, the noise component caused by eccentricity can be removed.

[0052] (Second Implementation)

[0053] The second embodiment will be described. In the first embodiment, an example was described in which information about the frequency, amplitude, and phase of the noise (variation) component caused by eccentricity could be obtained from the FFT analysis of the velocity detection signal ωFBK. In this embodiment, a case is described in which the phase information described above cannot be obtained.

[0054] Reference Figure 3The processing of velocity inference control under the application conditions (second application conditions) of this embodiment will be explained. The second application condition of this velocity inference control is the case where the frequency and amplitude can be obtained through FFT analysis, but the phase cannot be obtained. Figure 3 This is a flowchart of speed inference control based on the second application condition.

[0055] After installing motor 2 and resolver 2A, set the resolver 2A shaft to be locked to the motor 2 shaft so that the shaft of resolver 2A is rotated in conjunction with the shaft of motor 2.

[0056] The speed control unit 5 starts operation according to the speed command (speed command value) (step S11). The speed control unit 5 determines whether the speed estimation value of the motor 2 has reached the speed command (speed command value) (step S12), and repeats the process of step S12 until the speed estimation value reaches the speed command value. When the speed estimation value reaches the speed command value and the motor enters a constant speed operation state, the FFT analysis processing unit 41 performs FFT analysis (step S13).

[0057] Next, the speed compensation calculation unit 42 sets the initial value of the phase (step S14).

[0058] The speed compensation calculation unit 42 determines whether there is a higher harmonic of the fundamental frequency (called the operating frequency) of the motor 2 operating at a constant speed (step S15), and terminates a series of processes if the higher harmonic is not present.

[0059] In the presence of the aforementioned higher harmonics, the speed compensation calculation unit 42 generates an anti-phase signal of the signal component generated due to eccentricity in the speed detection signal ωFBK (referred to as "speed FBK" in the figure) (step S16), and adds the anti-phase signal to the speed detection signal ωFBK (referred to as "speed FBK" in the figure) (step S17).

[0060] The speed compensation calculation unit 42 determines whether the wave height value of the inferred value of the speed detection signal ωFBK is the minimum value (step S18). If the wave height value of the inferred value of the speed detection signal ωFBK is the minimum value, it is regarded as the phase at that moment satisfying the anti-phase relationship, and a series of processes are ended.

[0061] If the wave height of the inferred value of the speed detection signal ωFBK is not the minimum value, the rotation speed inference unit 4 adds a predetermined amount to the phase, thereby determining the phase that is misaligned by the predetermined amount as a new phase (step S19), and repeats the process from step S16 onwards.

[0062] The reason why the inferred wave height of the velocity detection signal ωFBK can be considered to satisfy the phase-out relationship when it is at its minimum is that when there is a signal component due to eccentricity overlapping, the wave height of the velocity detection signal ωFBK will increase accordingly. By adding the signals in the opposite phase manner, such that the overlapping signal component disappears, the wave height of the inferred velocity detection signal ωFBK in this state will become minimum. Therefore, when the wave height of the inferred velocity detection signal ωFBK is detected to be at its minimum (minimum), the phase search is interrupted, thereby determining the optimal phase.

[0063] Thus, even if the phase information of the signal components that overlap due to eccentricity cannot be obtained from the FFT analysis results, the rotational speed inference unit 4 can infer the speed of the motor 2 based on the speed detection signal ωFBK.

[0064] In this case, by obtaining the phase information of the signal components (noise components) that overlap due to eccentricity based on the results of FFT analysis, the rotational speed inference unit 4 can use the phase information obtained from the FFT analysis of the speed detection signal ωFBK as the phase information of the signal components that overlap due to eccentricity. Thus, the rotational speed inference unit 4 can infer the speed of the motor 2 based on the speed detection signal ωFBK.

[0065] According to the above implementation method, based on the FFT analysis results of the speed detection signal ωFBK, the frequency (N times the motor frequency), amplitude, and phase of the noise (variation) component caused by eccentricity can be determined, and a signal for removing the noise (variation) caused by eccentricity is output. The generated signal has the same frequency and amplitude as the noise component caused by eccentricity, but its phase is offset by 180 degrees, becoming an inverted signal. By adding this signal to the speed detection signal ωFBK, the magnitude of the noise component caused by eccentricity can be reduced.

[0066] According to at least one embodiment described above, the electric motor speed control device includes a rotational speed estimation unit and a control unit. The rotational speed estimation unit generates an estimated value of the electric motor's rotational speed using the result of an FFT analysis of a speed detection signal ωFBK obtained based on the detection result of a resolver detecting the rotational speed of the electric motor, and the speed detection signal ωFBK. The control unit performs speed control in a manner that minimizes the deviation between the speed command value for electric motor speed control and the estimated value of the rotational speed.

[0067] The foregoing has described several embodiments of the present invention, but these embodiments are merely illustrative and not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and are also included within the scope of the invention as described in the claims and its equivalents.

[0068] Explanation of symbols

[0069] 1 Motor drive system, 2 Motor, 4 Rotation speed inference unit, 5 Speed ​​control unit, 6 Current control unit, 7 PWM control unit, 8 Inverter, 10 Motor speed control device, 41 FFT analysis and processing unit, 42 Speed ​​compensation calculation unit.

Claims

1. A motor speed control device, comprising: The rotational speed inference unit generates an inferred value of the rotational speed using the result of an FFT analysis of the speed detection signal ωFBK obtained from the detection result of a resolver that detects the rotational speed of the motor, and the speed detection signal ωFBK. The control unit performs speed control in a manner that minimizes the deviation between the speed command value for controlling the speed of the aforementioned motor and the estimated value for the rotational speed. The shaft of the aforementioned motor is connected to the shaft of the aforementioned resolver. When the aforementioned control unit controls the aforementioned motor at a constant speed, the speed detection signal ωFBK fluctuates due to the eccentricity of the shaft of the aforementioned resolver relative to the shaft of the aforementioned motor. The aforementioned rotational speed inference unit is, Based on the results of the FFT analysis of the velocity detection signal ωFBK and the initial value of the set phase, an inverse phase signal of the signal component in the velocity detection signal ωFBK caused by eccentricity is generated. The operation of adding the inverse phase signal to the velocity detection signal ωFBK is repeatedly performed. The phase when the wave height of the variable component caused by the eccentricity is at its minimum value is selected, and the inferred value of the rotational speed is generated.

2. The electric motor speed control device as described in claim 1, wherein, The aforementioned rotational speed inference unit includes: The FFT analysis and processing unit performs FFT analysis on the aforementioned velocity detection signal ωFBK; and The speed compensation calculation unit uses the results of the FFT analysis and the speed detection signal ωFBK to generate the inferred value of the rotational speed.

3. The electric motor speed control device as described in claim 2, wherein, The aforementioned FFT analysis and processing unit generates the amplitude spectrum and phase spectrum of the aforementioned velocity detection signal ωFBK, which are used as the result of the FFT analysis obtained through the aforementioned FFT analysis. The speed compensation calculation unit corrects the speed detection signal ωFBK based on the amplitude spectrum and the phase spectrum to generate the inferred value of the rotation speed.

4. The electric motor speed control device as described in claim 3, wherein, The aforementioned speed compensation calculation unit is, Based on the above amplitude spectrum, calculate the specific frequency components related to the rotational speed of the resolver, as well as the magnitude of these frequency components. Based on the aforementioned phase spectrum, the phase information of the specific frequency components is calculated. Based on the magnitude and phase information of the aforementioned specific frequency components, a velocity compensation amount is generated. The speed detection signal ωFBK is corrected using the speed compensation amount described above, and the result of the correction is used to generate the inferred value of the rotational speed.

5. The electric motor speed control device as described in claim 2, wherein, The aforementioned FFT analysis and processing unit generates the amplitude spectrum of the velocity detection signal ωFBK, which is used as the result of the FFT analysis obtained through the aforementioned FFT analysis. The speed compensation calculation unit corrects the speed detection signal ωFBK based on the amplitude spectrum and the adjusted phase, and generates the inferred value of the rotation speed.

6. The electric motor speed control device as described in claim 5, wherein, The aforementioned speed compensation calculation unit is, Based on the above amplitude spectrum, calculate the specific frequency components related to the rotational speed of the resolver, as well as the magnitude of these frequency components. Adjust the above phase, Based on the magnitude of the specific frequency components and the adjusted phase, a velocity compensation amount is generated. Using the aforementioned speed compensation amount, the speed detection signal ωFBK is corrected, and the result of the correction is used to generate the inferred value of the rotational speed.

7. The electric motor speed control device as described in claim 3, wherein, The control unit controls the rotational speed of the motor based on the speed command value related to the speed control of the motor and the modified speed detection signal ωFBK.

8. A method for controlling the speed of an electric motor, wherein, include: Using the FFT analysis results of the speed detection signal ωFBK obtained from the resolution of the motor's rotational speed detection, and the aforementioned speed detection signal ωFBK, an inferred value of the motor's rotational speed is generated. The speed control step is implemented in a way that reduces the deviation between the speed command value for the speed control of the aforementioned motor and the inferred value for the rotational speed. The shaft of the aforementioned motor is connected to the shaft of the aforementioned resolver. When the aforementioned motor is controlled at a constant speed, the speed detection signal ωFBK changes due to the eccentricity of the shaft of the aforementioned resolver relative to the shaft of the aforementioned motor. In this motor speed control method Based on the results of the FFT analysis of the velocity detection signal ωFBK and the initial value of the set phase, an inverse phase signal of the signal component in the velocity detection signal ωFBK caused by eccentricity is generated. The operation of adding the inverse phase signal to the velocity detection signal ωFBK is repeatedly performed. The phase when the wave height of the variable component caused by the eccentricity is at its minimum value is selected, and the inferred value of the rotational speed is generated.

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