KR20000008771A - Apparatus and methode for detecting speed of motor using alternate tacho-generator - Google Patents

Abstract

PURPOSE: An apparatus and a method for detecting a speed of a motor using an alternative tacho-generator is provided to reduce a time for a speed detection by using a linear operation element. CONSTITUTION: An apparatus and a method for detecting a speed of a motor using an alternative tacho-generator comprises: a tacho-generator(101); a first, a second, and a third amplifiers(102,103,104); a first, a second, and a third square multipliers(105,106,107); an adder(108); a fourth amplifier(109); a square root multiplier(110); and a fifth amplifier(111). The tacho-generator generates three-phase sine wave. The first, the second, and the third amplifiers amplify gains of a first, a second, and a third sine waves. The first, the second, and the third multipliers obtain a square multiplication for the signal. The adder adds the multiplied signal. The fourth amplifier amplifies the signal from the adder. The square root multiplier obtains the square root of the amplified signal. The fifth amplifier amplifies the gain of the signal.

Description

Motor speed detecting device and method using AC taco generator

The present invention relates to an apparatus and a method for detecting a motor speed using an alternating taco generator. Specifically, a sinusoidal AC tacho-generator of a two-phase or three-phase output is used to adjust the motor rotational speed with high accuracy. And a motor speed detecting apparatus and method using an alternating tachometer generator capable of detecting at high speed response.

In general, the motor driving field has recently come to estimate the speed close to the actual speed thanks to the high speed speed estimation theory and the spread of high speed digital computing devices.

The motor speed detection method using a sensor is roughly classified into a method using an encoder and a method using a taco generator. The method of using the pulse encoder which generates a pulse train according to the rotation is currently used most widely when the motor speed control is performed digitally. In this case, a method of converting pulse train information having a variable frequency proportional to speed into speed information is obtained by using a frequency to voltage converter, and obtaining speed information by counting the number of encoder pulses counted during a predetermined detection period. Technique (hereinafter referred to as M technique), technique of obtaining velocity information with a constant frequency clock number counted for a certain number of encoder pulse periods (hereinafter referred to as T technique), technique using both M technique and T technique simultaneously (Hereinafter referred to as M / T technique).

Since the method of using the F / V converter is using the RC circuit in principle, there is a problem that the pulsation occurs in the voltage magnitude to speed up the response, and the steady-state characteristics are poor when controlling the motor. Because of the change in the low speed, there is a problem that the response is slow at a high pulsation at a high speed and is not suitable as the speed information for the motor speed control.

The M or T technique is currently the most widely used speed detection method, but in the case of the M technique, the detection error increases toward the low speed region, and the speed detection itself is impossible at a speed below a certain limit, and the T technique is the opposite of the M technique. The detection error increases toward the high speed region, and at speeds above a certain limit, this also makes speed detection itself impossible.

In addition, both the M and T techniques use a digital calculator, but there is a problem that a low speed or high speed undetectable area occurs depending on the counting capability of the circuit. In addition, in the case of the M technique, since a long detection period is required to increase the speed detection degree, the problem of naturally varying the speed detection period occurs. Recently, the M / T technique has been widely used for high performance control of the motor in both low speed and high speed ranges. However, the speed detection delay and the complicated implementation of the speed detection method are complicated in this M / T technique. There are disadvantages.

Therefore, the instantaneous speed prediction technique is applied to compensate for the effect of the speed detection delay in the control of most high-accuracy motors, but it is also impossible to accurately predict the instantaneous speed when the speed fluctuates irregularly.

In the case of the speed detection method using a taco generator, there is a method using a single-phase AC taco generator and a method using a direct current taco generator. When using a single-phase AC taco generator, the magnitude and frequency of the output of the single-phase AC taco generator is proportional to the speed. As it is an AC waveform with a power converter, a converter that converts RMS of the sine wave into a DC value is used to obtain a constant speed information for controlling the motor. In this case, a F / V converter is used with a pulse encoder. Since the same problem occurs, it is actually used only for speed display using an AC voltmeter.

In case of using DC taco generator, the output of DC taco generator is DC voltage which is proportional to speed, so it is easy to use, but there is a problem that maintenance is necessary because of brush and commutator. Since there is a disadvantage in that a voltage is generated, it is necessary to filter the output of the DC taco generator, thereby causing a speed detection delay.

The present invention is to solve the above problems by using the sinusoidal AC taco generator of the two-phase or three-phase output having a phase difference of 90 degrees, so that the rotational speed of the motor can be detected with high accuracy and real time. It is an object of the present invention to provide an apparatus and method for detecting a motor speed using an alternating taco generator.

1 is a block diagram of a motor speed detection apparatus according to an embodiment of the present invention

2 is a block diagram of a motor speed detecting apparatus according to an embodiment of the present invention;

3 is a block diagram of a motor speed detecting apparatus according to a third embodiment of the present invention;

4 is a block diagram of a hardware device for implementing the motor speed detection method according to the present invention

5 is an output waveform diagram of a three-phase sine wave taco generator according to the present invention.

6 is a graph showing the M technique simulation results

7 is a graph showing the T technique simulation results

8 is a graph showing the simulation results of the M / T technique

9 is a graph showing the simulation results of 8-bit, 100 ㎲ A / D conversion after linear operation with the device according to the present invention.

10 is a graph showing a simulation result of 16-bit, 2㎲ A / D conversion after linear operation with the device according to the present invention.

11 is a graph showing the first result of the method according to the invention after asynchronous A / D conversion

12 is a graph showing the second result of the method according to the invention after asynchronous A / D conversion.

13 is a graph showing the first result of the method according to the invention after synchronous A / D conversion

14 is a graph showing the second result of the method according to the invention after synchronous A / D conversion.

In order to achieve the above object, the motor speed detecting apparatus using the AC taco generator according to the present invention, the taco generator for outputting a three-phase sine wave having a phase difference of 120 degrees corresponding to the rotation of the motor; First, second and third amplifiers for amplifying and outputting gains of the first, second and third sine waves from the taco generator; First, second, and third square multipliers for multiplying and outputting signals from the first, second, and third amplification units; An adder for adding and outputting respective signals from the first, second, and third square multipliers; A fourth amplifier for amplifying and outputting the gain of the signal from the adder; A square root multiplier for multiplying and outputting a signal from the fourth amplifier; And a fifth amplifier for amplifying the gain of the signal from the square root multiplication unit and outputting the signal as a signal representing the rotational speed of the motor.

The motor speed detecting apparatus using the AC taco generator according to the present invention includes a taco generator which outputs a three-phase sine wave having a phase difference of 120 degrees in response to rotation of the motor; First and second amplifiers for amplifying and outputting gains of the first and second sinusoidal waves from the taco generator; First and second square multipliers for multiplying and outputting signals from the first and second amplification units, respectively; A multiplier for multiplying and outputting the signal from the first amplifier and the signal from the second amplifier; An adder which adds and outputs each signal from the first and second square multipliers and the signal from the multiplier; A third amplifier for amplifying and outputting the gain of the signal from the adder; A square root multiplication unit for outputting a square root multiplication process for the signal from the third amplifier; And a fourth amplifier for amplifying the gain of the signal from the square root multiplication unit and outputting the signal as a signal representing the rotational speed of the motor.

In addition, a taco generator for outputting a two-phase sine wave having a phase difference of 90 degrees corresponding to the rotation of the electric motor; First and second amplifiers for amplifying and outputting gains of the first and second sinusoidal waves from the taco generator; First and second square multipliers for multiplying and outputting signals from the first and second amplification units, respectively; An adder which adds and outputs respective signals from the first and second square multipliers; A third amplifier for amplifying and outputting the gain of the signal from the adder, and a square root multiplier for multiplying and outputting the signal from the third amplifier; And a fourth amplifier for amplifying the gain of the signal from the square root multiplication unit and outputting the signal as a signal representing the rotational speed of the motor.

On the other hand, the motor speed detection method using the AC taco generator according to the present invention is a method of detecting the speed of the motor, the first 1,2,3 sine wave signals from the taco generator outputting a three-phase sine wave in response to the rotation of the motor Reading is inputted after being converted into first, second, and third digital signals E _U , E _V , E _W , respectively; Rotational angular velocity (ω) using the first, second, and third digital signal values (E _U , E _V , E _W ), the winding coefficient K _W of the taco generator, the number of turns n, and the magnetic flux Φ Ω = √ (2/3) × 1 / (K _W × n × Φ) × √ (E _U ² + E _V ² + E _W ² ) by calculating the relationship between .

In addition, as a method of detecting the motor speed, first and second sinusoidal signals from a taco generator that outputs a three-phase sine wave in response to rotation of the motor are converted into first and second digital signals E _U and E _V, respectively. Reading what is input; Rotational angular velocity ω is obtained by using the first and second digital signal values E _U and E _V , the winding coefficient K _W of the taco generator, the number of turns n, and the magnetic flux Φ. √3 × 1 / (K _W × n × Φ) × √ (E _U ² + E _V ² + (E _U × E _V )).

In addition, as a method of detecting the speed of the motor, the first and second sinusoidal signals from a taco generator that outputs a two-phase sine wave in response to the rotation of the motor are converted into first and second digital signals E _A and E _B, respectively. The rotational angular velocity by using the read-out step, the read-out first and second digital signal values E _A and E _B , the winding coefficient K _W of the taco generator, the number of turns n, and the magnetic flux Φ. (ω) for ω = 1 / characterized by yirueojim including the step of detecting by calculating the equation _{(K W × n × Φ)} × √ (E a 2 + E B 2).

The above objects and various advantages of the present invention will become more apparent from the preferred embodiments of the invention described below with reference to the accompanying drawings by those skilled in the art.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention detects the speed of an electric motor by using a two-phase tacho generator having a 90 degree phase difference or a three phase taco generator having a 120 degree phase difference.

In either case, it is useful to apply the output voltage waveform of the taco generator to a sine file. If harmonics are included, it should be noted that there is a pulsation even at a constant speed. Is taken offline and the harmonic content should be compensated for instantaneously according to the phase angle provided separately.

Compensation of the harmonic components is possible by the development of analysis and design techniques of electric devices using the recent finite element method, which makes it possible to manufacture taco generators with a full sine wave output. Motor: Permanent magnet type synchronous motor), so it can be applied as it is.

In particular, since the linear arithmetic element technology is at a considerable level, the implementation of the linear arithmetic element as in the following embodiment of the present invention has almost no speed detection time delay, and the micro like in other embodiments of the present invention described below. In the case of digital operation using a processor or the like, unlike the case of using a conventional pulse encoder, the speed detection cycle is not required, and thus, the speed detection delay factor other than the operation time does not occur, and the limit of the detection speed range other than the limit provided by the operation error Since it does not exist, it is very useful for high precision and high speed motor control.

Hereinafter, a process for calculating and detecting the motor speed using the sinusoidal AC tacho generator will be described.

First, the speed calculation using a three-phase tacho generator will be described.

When the phase voltage effective value of a three-phase tacho generator having a phase difference of 120 degrees is set to E, each phase voltage is represented by Equation 1.

If each side of the equation 1 is squared to add each side, then E can be summarized as Equation 2.

At this time, the effective value E of the sinusoidal organic electromotive force of the three-phase taco generator is expressed by Equation 3 when the winding factor is Kw, the rotational angular velocity is ω, the number of turns n, and the magnetic flux is Φ.

If Equation 3 is summarized for ω and substituted into Equation 2, Equation 4 is obtained.

In Equation 4, since K ₁ becomes a constant value, the speed of the motor can be calculated from the instantaneous value of the output voltage of the three-phase taco generator.

On the other hand, if the above-described Equation 4 is modified as shown in Equation 5, the operation can be performed only by the two-phase output having a phase difference of 120 degrees.

Next, the speed calculation process of the motor using the two-phase taco generator will be described.

When the effective value of the phase voltage of the two-phase tacho generator having a phase difference of 90 degrees is E, each phase voltage is expressed by the following equation.

In the same manner as in the three-phase case, the equation for the rotational angular velocity?

In Equation 7, K ₃ is a constant value, so that the speed of the motor can be calculated from the instantaneous value of the output voltage of the two-phase taco generator.

Next, a motor speed detecting apparatus and method using an AC taco generator according to the present invention to which the above-described speed calculation process of the motor is applied will be described with reference to the accompanying drawings.

1 is a block diagram illustrating a motor speed detection device using an AC taco generator constructed using a predetermined linear element according to an embodiment of the present invention, wherein a three-phase taco outputs a three-phase sine wave in response to rotation of the motor. Generator 101; First, second and third amplifiers 102, 103 and 104 for amplifying and outputting gains of the first, second and third sinusoidal signals output from the three-phase taco generator 101; First, second, third, and third square multipliers (105,106,107) for multiplying the phase voltage levels of the sinusoidal signals amplified by the first, second, third, and third amplifiers (103, 104, 105) by squares; An adder (108) for adding and outputting a sinusoidal signal having a voltage level multiplied by the first, second, and third square multipliers (105, 106, 107); A fourth amplifier 109 for amplifying and outputting a gain of the signal added and output from the adder 108; A square root multiplication unit (110) for outputting a square root multiplication process for the signal from the fourth amplifier (109); And a fifth amplifier 111 for amplifying and outputting the signal from the square root multiplication unit 110.

This configuration is for calculating the rotational angular velocity ω, which is the rotational speed of the motor, using a linear circuit element by using Equation 4 described above. The sine wave (E _U , E _V , E _W ) signals are multiplied by the first, second, and third square multipliers 105, 106, and 107, respectively, and added by the adder 108.

Next, the added signal is gain amplified by the fourth amplifier 109, and the amplified signal is multiplied by the square root multiplier 110 and amplified by the fifth amplifier 111 and output. The fifth amplifier 111 considers the constant K ₁ at the rotational angular velocity ω in Equation 4, so that the output signal can be used as the rotational speed of the motor.

In addition, the analog output signal is converted into a digital signal using an A / D converter (not shown) and can be used to control the rotational speed of the motor through the servo control means (not shown).

FIG. 2 is a block diagram of an electric motor speed detection device using an AC taco generator constructed by using a predetermined linear element according to the second embodiment of the present invention, and a two-phase sine wave of a three-phase tacho generator that outputs a three-phase sine wave. A three-phase taco generator 201 for outputting a three-phase sine wave in response to the rotation of the motor, in order to detect the rotational speed of the motor by using only; First and second amplifiers 202 and 203 for amplifying and outputting gains of the first and second sinusoidal signals output from the three-phase taco generator 201; First and second square multipliers 204 and 205 for multiplying the phase voltage levels of the sinusoidal signals amplified by the first and second amplifying units 202 and 203, respectively, and outputting the square voltages; A multiplier 206 for multiplying and outputting the phase voltage levels of the sinusoidal signals amplified by the first and second amplification units 202 and 203, respectively; An adder (207) for adding and outputting a sine wave signal having a voltage level multiplied by the first and second square multipliers (204, 205) and a signal from the multiplier (206); A third amplifier 208 for amplifying and outputting a gain of a signal added and output from the adder 207; A square root multiplication unit (209) for multiplying and outputting a signal from the third amplifying unit (208); And a fourth amplifier 210 for amplifying and outputting a signal from the square root multiplication unit 209.

This configuration is for calculating the rotational angular velocity?, Which is the rotational speed of the motor, by using a linear circuit element by using Equation 5 described above, and the first and second sinusoidal waves output from the first and second amplification units 202 and 203. The E _U , E _V ) signals are multiplied by the first and second square multipliers 204 and 205, respectively, and the first and second sinusoidal signals E _U and E _V are multiplied by the multiplier 206.

Next, the signal multiplied by the squares in the first and second square multipliers 204 and 205 and the signal multiplied in the multiplier 206 are added in the adder 207.

Then, the added signal is gain amplified by the third amplifier 208, the amplified signal is multiplied by the square root multiplier 209 and amplified by the fourth amplifier 210 and output. Since the constant K ₂ is considered in the rotational angular velocity ω in Equation 5 in the fourth amplifier 210, the output signal can be used as the rotational speed of the motor.

3 is a block diagram of an apparatus for detecting a motor speed using an alternating taco generator according to a third embodiment of the present invention, in order to detect a rotational speed of an electric motor by using a two-phase taco generator that outputs a two-phase sine wave. A two-phase tacho generator 301 which outputs two-phase sine waves in response to rotation of the motor; First and second amplifiers 302 and 303 for amplifying and outputting gains of the first and second sinusoidal signals output from the two-phase tacho generator 301, respectively; First and second square multipliers (304 and 305) for multiplying the phase voltage levels of the sinusoidal signals amplified by the first and second amplifiers (302 and 303), respectively, and outputting the square voltages; An adder (306) for adding and outputting a sinusoidal signal having a voltage level multiplied by the first and second square multipliers (304,305); A third amplifying unit 307 for amplifying and outputting a gain of the signal added and output from the adding unit 306; A square root multiplication unit (308) for multiplying and outputting a signal from the third amplifier (307) by square root multiplication; And a fourth amplifier 309 for amplifying and outputting a signal from the square root multiplication unit 308.

This configuration is for calculating the rotational angular velocity?, Which is the rotational speed of the motor, by using a linear circuit element by using Equation 7 described above, and the first and second sinusoidal waves output from the first and second amplification units 302 and 303. E _A , E _B ) signals are multiplied by the first and second square multipliers 304 and 305, respectively, and each square multiplied signal is added by the adder 306.

Then, the added signal is gain amplified by the third amplifier 307, the amplified signal is multiplied by the square root multiplier 308 and amplified by the fourth amplifier 309 and output. Since the fourth amplifier 309 considers the constant K ₃ at the rotational angular velocity ω in Equation 7, the output signal can be used as the rotational speed of the motor.

On the other hand, Figure 4 is a block diagram of a hardware device for implementing an electric motor speed detection method using the AC taco generator according to the present invention, the taco generator 401 for outputting a two-phase or three-phase sine wave due to the rotation of the motor Wow; First, second and third amplifiers 402, 403 and 404 for amplifying and outputting gains of respective sinusoidal signals from the taco generator 401; First, second, and third ADCs (405, 406, 407) for converting and outputting analog signals from the first, second, and third amplifiers (402, 403, 404) to digital signals; A value calculated by calculating the rotational angular velocity ω of the motor based on Equation 4, Equation 5, or Equation 7 by applying the digital values from the first, second, and third ADCs 405, 406, 407 to respective input ports. It becomes a value indicating the rotational speed of the electric motor, and includes a microprocessor 408 for applying this value to a servo control means (not shown) to control the rotational speed of the electric motor.

In such a configuration, the microprocessor 408 is the equation (4) or (5) or the above equation corresponding to whether the taco generator 401 is a taco generator having a three-phase sine wave output or a taco generator having a two-phase sine wave output. Based on Equation 7, the rotational angular velocity ω is calculated to detect the rotational speed of the motor.

Next, a simulation of the above-described speed detection method of the motor using a taco generator having a polyphase sine wave output according to the present invention was performed for the case of using a linear element and the case of digital calculation using a microprocessor. In order to simulate the M, T, and M / T techniques, which are the velocity detector method using the conventional pulse encoder, the simulation was also carried out with the actual implementation method.

The simulation time differs between the three-phase taco generator and the two-phase taco generator, but the characteristics will be the same. Therefore, the simulation is only performed for the three-phase taco generator. Was performed.

First, FIG. 5 shows a three-phase output waveform of a three-phase taco generator assuming four poles and the speed of the electric air calculated therefrom. When using a linear arithmetic element, the instantaneous speed is measured without time delay as shown in FIG. You can compute right away.

6 is a graph showing the percentage error between the actual speed and the detection speed and the speed when using the encoder generating 8000 pulses per revolution and using the M technique with a sampling time of 300 ms. Since the number of encoder pulses is small, it shows some error at low speed.

7 is a graph showing the detection speed and the percentage error when the T technique is used as an encoder generating a pulse of 1000 pulses per revolution using a clock of 1 MHz, and the number of clock pulses counted in one main period of the encoder pulse at high speed is small. It can be seen that there is an error. It can be seen that even at low speeds, the frequency of the encoder pulse is low, resulting in a large speed error as the detection delay occurs.

Fig. 8 is a graph showing the detection speed and the percentage error when the M / T method is used with a sampling time of 300 ms using a clock of 1 MHz and an encoder generating 2000 pulses per revolution. As the period gets longer, the error value becomes larger.

The reason why the simulation was performed by varying the number of pulses of the encoders in FIGS. 6 to 8 described above is a pulse suitable for the clock frequency and the sampling time in order to show an overall excellent case in the entire speed range due to the characteristics of the respective speed detection methods. I assumed a number.

9 is a graph showing the results of A / D conversion using the output of the three-phase sine wave taco generator according to the present invention and calculating the speed using a linear arithmetic element with an accuracy of 8 bits and a conversion time of 100 ms. , Compared with the results obtained using the M / T technique, shows better performance.

FIG. 10 is a graph showing the results of A / D conversion with a speed of 16 bits and a conversion time of 2 ms using a linear arithmetic circuit. It can be seen that there is no difference from the actual speed.

Fig. 11 is a graph showing the result of A / D conversion of the phase level voltage of the sine wave signal output from the three-phase taco generator and the speed calculation by the microprocessor. In addition to using the 8096, a general purpose 16-bit microprocessor with a conversion port, the calculation time is 50ms.

At this time, as shown in the figure, as a result of asynchronously converting the voltage of the three phases, it can be seen that the phase error occurs as much as the conversion time, and thus the calculated speed is pulsated.

FIG. 12 is a graph showing a result of using a high performance microprocessor using the same A / D converter as in FIG. 11 and having a DSP (Digital Signals Processor) class computation time of about 5 ms. It is small and it can be seen that there is a speed error only at very low speeds.

Next, FIG. 13 is a graph showing a result of applying synchronous A / D conversion in which A / D conversion is sequentially performed after latching a three-phase output voltage to a sample holder at the same time under the same conditions as in FIG. It can be seen that there is only a speed error due to the / D conversion time and the speed computation time delay.

In addition, FIG. 14 is a graph showing simulation results assuming the conversion time and the calculation time to the same extent as in FIG. 12, and it can be seen that the performance is very excellent when compared with the M / T method of FIG. .

From the above simulations, it can be seen that the speed detection method using the multi-phase sine wave AC taco generator according to the present invention is superior to other speed detection methods in terms of performance and practicality, and it takes less computation time when using the two-phase taco generator. It can be seen that even better.

As described above, the speed detection apparatus using the linear arithmetic element according to the present invention can substantially reduce the delay of the speed detection time, and the speed detection method using the microprocessor requires a speed detection period unlike the conventional pulse encoder. Therefore, speed detection delay factor other than operation time does not occur, and there is no limit of detection speed range except the limit that calculation error gives. Therefore, it is possible to detect the rotational speed of the motor with high accuracy and high speed response. There is an effect that can be performed more precisely.

Claims (6)

A taco generator 101 for outputting a three-phase sine wave having a phase difference of 120 degrees corresponding to the rotation of the motor; First, second and third amplifying units (102, 103, 104) for amplifying and outputting gains of the first, second, and third sine waves from the taco generator (101); First, second, third square multipliers (105, 106, 107) for outputting the squares of the signals from the first, second, third, and third amplification units (102, 103, 104) respectively; An adder (108) for adding and outputting respective signals from the first, second, and third square multipliers (105, 106, 107); A fourth amplifier 109 for amplifying and outputting the gain of the signal from the adder 108; A square root multiplication unit (110) for outputting a square root multiplication process for the signal from the fourth amplifier (109); And a fifth amplifying unit (111) for amplifying the gain of the signal from the square root multiplying unit (110) and outputting the signal as a signal representing the rotational speed of the electric motor. A taco generator 201 for outputting a three-phase sine wave having a phase difference of 120 degrees corresponding to the rotation of the electric motor; First and second amplifiers 202 and 203 for amplifying and outputting gains of the first and second sinusoidal waves from the taco generator 201; First and second square multipliers (204 and 205) for multiplying and outputting signals from the first and second amplifying units (202 and 203), respectively; A multiplier 206 for multiplying and outputting the signal from the first amplifier 202 and the signal from the second amplifier 203; An adder (207) for adding the respective signals from the first and second square multipliers (204, 205) and the signals from the multiplier (206) and outputting them; A third amplifier 208 for amplifying and outputting the gain of the signal from the adder 207; A square root multiplication unit (209) for multiplying and outputting a signal from the third amplifying unit (208); And a fourth amplifying part (210) for amplifying the gain of the signal from the square root multiplying part (209) and outputting the signal as a signal representing the rotational speed of the electric motor. A taco generator 301 for outputting a two-phase sine wave having a phase difference of 90 degrees corresponding to the rotation of the motor; First and second amplifiers 302 and 303 for amplifying and outputting gains of the first and second sinusoidal waves from the taco generator 301; First and second square multipliers 304 and 305 for multiplying and outputting signals from the first and second amplification units 302 and 303, respectively; An adder 306 for adding and outputting respective signals from the first and second square multipliers 304 and 305; A third amplifier 307 for amplifying and outputting a gain of the signal from the adder 306; A square root multiplication unit (308) for multiplying and outputting a signal from the third amplifier (307) by square root multiplication; And a fourth amplifier (309) for amplifying the gain of the signal from the square root multiply (308) and outputting the signal as a signal representing the rotational speed of the motor. As a method of detecting the rotational speed of the motor, The first, second, and third sinusoidal signals from the taco generator outputting the three-phase sine wave in response to the rotation of the motor are converted into the first, second, and third digital signals (E _U , E _V , E _W ), respectively. Steps; Rotation using the first, second, and third digital signal values E _U , E _V , E _W , the winding coefficient K _W of the taco generator, the number of turns n, and the magnetic flux Φ Calculating and detecting the angular velocity ω in a relation of ω = √ (2/3) × 1 / (K _W × n × Φ) × √ (E _U ² + E _V ² + E _W ² ) A motor speed detection method using an AC taco generator. As a method of detecting the rotational speed of the motor, Reading the first and second sinusoidal wave signals from the taco generator outputting the three-phase sine wave in response to the rotation of the motor being converted into the first and second digital signals E _U and E _V , respectively; Rotational angular velocity (ω) is obtained by using the first and second digital signal values (E _U and E _V ), the winding coefficient (K _W ), the number of turns (n), and the magnetic flux (Φ) of the taco generator. _and calculating and detecting in a relation ω = 2 / √3 × 1 / (K _W × n × Φ) × √ (E _U ² + E _V ² + (E _U × E _V )). Motor speed detection method using AC taco generator. As a method of detecting the rotational speed of the motor, Reading the first and second sinusoidal signals from the taco generator which outputs the two-phase sinusoidal waves corresponding to the rotation of the motor are converted into the first and second digital signals E _A and E _B , respectively; Using the first and second digital signal values E _A and E _B read in the above step, the winding coefficient K _W of the taco generator, the number of turns n and the magnetic flux Φ, the rotational angular velocity ω is obtained. An electric motor speed detection method using an AC taco generator, comprising the step of calculating and detecting in a relation of ω = 1 / (K _W × n × Φ) × √ (E _A ² + E _B ² ).