A method for generating an excitation signal and maintaining the amplitude of a feedback signal stable

Abstract

The application discloses a method for generating excitation signals and keeping feedback signal amplitude stable, and relates to the technical field of signal amplitude processing. The method for generating excitation signals and keeping feedback signal amplitude stable comprises the following steps: generating a positive sine excitation signal; inputting the positive sine excitation signal into a positive sine signal tracking sensor and feeding back a positive sine signal. The input excitation voltage of the PI control sensor can control the stability of two-phase voltage sampling point voltage output by the sensor, so that the two-phase voltage sampling point voltage is stabilized at a value close to a quantized reference voltage, random errors of an angle can be reduced, the excitation signal and the output signal are in linear relationship, and thus the operation of an electromechanical actuator can be ensured. In addition, the SVPWM modulation mode with high output voltage amplitude, flexible phase and amplitude modulation, fast response is adopted, when compared with single-phase SPWM modulation, high excitation voltage is kept when the sensor connection line is increased, line voltage drop is compensated, and other interference factors are compensated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of signal amplitude processing, in particular to a method for generating excitation signals and keeping feedback signal amplitude stable. BACKGROUND

[0002] The sine-cosine encoder and the rotary transformer are widely used in various electromechanical systems such as motor drive control systems as a rotating machine position (angle) detection device. This kind of sensor uses a sine signal for excitation, and the amplitude and phase relationship of the feedback of the two output orthogonal sine signals (two-phase signals) is detected, and the required rotation angle value can be obtained through further digital signal processing.

[0003] When the electromechanical actuator is running normally, the feedback voltage value detected by the sensor output should be linearly related to the excitation signal. When the feedback voltage value cannot be stabilized at a value close to the quantization reference voltage, the angle obtained will have random errors, resulting in non-linear errors, which will have adverse effects on the operation of the electromechanical actuator. SUMMARY

[0004] Technical problems to be solved

[0005] In view of the deficiencies of the prior art, the present application provides a method for generating excitation signals and keeping feedback signal amplitude stable, which solves the problem that the output of the detection sensor is difficult to stabilize at a value close to the quantization reference voltage, and the angle has random errors, which has adverse effects on the operation of the electromechanical actuator.

[0006] Technical scheme

[0007] To achieve the above purpose, the present application is implemented by the following technical scheme: a method for generating excitation signals and keeping feedback signal amplitude stable, comprising the following steps:

[0008] Step 1: generate a sine-cosine excitation signal;

[0009] Step 2: input the sine-cosine excitation signal into a sine-cosine signal tracking sensor and feedback a sine-cosine signal;

[0010] Step 3: the configuration amount of the sine-cosine excitation signal output is a reference signal of PI control, and the feedback sine-cosine signal is a feedback signal of PI control, and the input excitation voltage of the sine-cosine signal tracking sensor is controlled to stabilize the voltage amplitude of the two-phase voltage sampling points output by the sine-cosine signal tracking sensor

[0011] Further, the sine excitation signal in the first step is a two-phase voltage, and the SVPWM signal generated by the processor or control logic.

[0012] Further, the SVPWM signal adopts two-phase output to constitute the excitation signal pair corresponding to excitation, and the calculation formula of the undistorted voltage amplitude is:

[0013] V = V dc × 0.866 × 1.732 / 1.5,

[0014] Wherein, V dc is the voltage to be modulated.

[0015] Further, the calculation formula of the peak value E1 of the driving voltage of the sine signal tracking sensor in the second step is as follows:

[0016]

[0017] Where R is the equivalent input resistance of the sine signal tracking sensor, and I is the driving current.

[0018] Further, the output of the sine signal tracking sensor is a quadrature sine voltage, and the two-phase voltage values are respectively: e1 = E0sinω t sinθ1, e2 = E0sinω t cosθ1, wherein E0 is the voltage amplitude, ω t is the excitation voltage frequency.

[0019] Further, the specific steps for controlling the input excitation voltage of the sine signal tracking sensor in the third step include:

[0020] S1, sampling the two-phase instantaneous value E2 of the feedback sine signal, and calculating the sine signal amplitude E3 according to the sampled instantaneous value;

[0021] S2, taking the sine signal amplitude calculated in S1 as the feedback value, taking the peak-to-peak value of the sine excitation signal input into the sine signal tracking sensor as the reference value, and controlling the output duty ratio and output voltage increase through the PI calculation formula;

[0022] S3, repeating S1 and S2 to make the input excitation voltage of the sine signal tracking sensor stable to the reference value.

[0023] Further, the two-phase instantaneous value E2 of the feedback sine signal in S1 is obtained by quantizing the two-phase returned signals, and the sampling mode is the ADC sampling of the MCU embedded processor.

[0024] Further, the process of calculating the sine signal amplitude E3 in S1 includes:

[0025] S11, calculating θ2 of E3sinθ1cosθ2-E3cosθ1sinθ2=0, that is, calculating θ2 of E3sin(θ1-θ2)=0;

[0026] S12. θ1 is calculated by E3sinθ1=E3cosθ1=E2, and θ2 in S11 is obtained from this.

[0027] S13. The amplitude of the sine and cosine signals E3 can be calculated using E3sinθ1=E3cosθ2=E2.

[0028] Furthermore, the E3 = E0sinω t Where E0 is the voltage amplitude, ω t The frequency of the excitation voltage.

[0029] Furthermore, the PI calculation formula is as follows:

[0030] Out=(Ref-fb)KP+Int(Ref-fb)KI

[0031] Where Out is the output, Ref-fb is the reference value minus the feedback value, KP is the proportional coefficient, Int(Ref-fb) is the integral operation, KI is the integral coefficient, and both KP and KI are positive numbers.

[0032] Beneficial effects

[0033] The present invention has the following beneficial effects:

[0034] (1) The method of generating and maintaining the amplitude of the excitation signal and the feedback signal is to control the stability of the voltage of the two-phase voltage sampling point of the sensor output by controlling the input excitation voltage of the sensor through PI control, so that they are stabilized at a value close to the quantization reference voltage, which can reduce the random error of the angle and make the excitation signal and the output signal linearly related, thereby ensuring the operation of the electromechanical actuator.

[0035] (2) The method of generating and maintaining the stable amplitude of the excitation signal is to adopt the SVPWM modulation method with high output voltage amplitude, flexible phase and amplitude modulation and fast response. Compared with single-phase SPWM modulation, it maintains a high excitation voltage when the sensor connection is increased, compensates for line voltage drop, and compensates for other interference factors.

[0036] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0037] Fig. 1 This is the signal flow diagram of the present invention;

[0038] Fig. 2 This is a flowchart of the amplitude stabilization method of the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] In the description of this invention, it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inner", "around", etc., which indicate orientation or positional relationship, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this invention.

[0041] Please see Figs. 1-2 This invention provides a technical solution: a method for generating an excitation signal and maintaining a stable feedback signal amplitude, comprising the following steps:

[0042] The first step is to generate sine and cosine excitation signals;

[0043] The second step involves inputting sine and cosine excitation signals into a sine and cosine signal tracking sensor and receiving back sine and cosine signals.

[0044] The third step is to configure the output of the sine and cosine excitation signals as the reference signals for PI control, and the feedback sine and cosine signals as the feedback signals for PI control, thereby controlling the input excitation voltage of the sine and cosine signal tracking sensor to stabilize the voltage amplitude at the two-phase voltage sampling points of the sine and cosine signal tracking sensor.

[0045] Specifically, the sinusoidal excitation signal in the first step is a two-phase voltage, which is an SVPWM signal generated by the processor or control logic;

[0046] The SVPWM signal uses two-phase outputs to form the excitation signal corresponding to the excitation, and the formula for calculating the undistorted voltage amplitude is as follows:

[0047] V = V dc ×0.866×1.732 / 1.5,

[0048] Among them, V dc The voltage to be modulated;

[0049] Specifically, the formula for calculating the peak value E1 of the driving voltage of the sine and cosine signal tracking sensor in the second step is as follows:

[0050]

[0051] Where R is the equivalent input internal resistance of the sine and cosine signal tracking sensor, and I is the driving current;

[0052] The output of the sine and cosine signal tracking sensor is a quadrature sine and cosine voltage, and its two-phase voltage values ​​are: e1=E0sinω t sinθ1,e2=E0sinω t cosθ1, where E0 is the voltage amplitude, ω t The frequency of the excitation voltage.

[0053] In this implementation scheme, the SVPWM signal uses a two-phase output to form the excitation signal corresponding to the excitation, and the undistorted voltage amplitude it generates is V = V dc ×0.866×1.732 / 1.5, although single-phase SPWM modulation can also generate the required sinusoidal excitation voltage, the undistorted voltage amplitude it produces is V1=V dc ×0.866, which shows that the SPWM method has a larger voltage output, and is therefore more conducive to excitation control.

[0054] Specifically, the third step of controlling the input excitation voltage of the sine and cosine signal tracking sensor includes the following steps:

[0055] S1, sample and feedback the instantaneous values ​​of the two phases of the sine and cosine signals E2, and calculate the amplitude of the sine and cosine signals E3 based on the sampled instantaneous values;

[0056] S2. Using the amplitude of the sine and cosine signals calculated in S1 as the feedback value, and the peak-to-peak value of the sine and cosine excitation signals input by the sine and cosine signal tracking sensor as the reference value, the output duty cycle and output voltage increase are controlled by the PI calculation formula.

[0057] S3. Repeat S1 and S2 to stabilize the input excitation voltage of the sine and cosine signal tracking sensor to a reference value.

[0058] The instantaneous two-phase values ​​E2 of the feedback sine and cosine signals in S1 are obtained by quantizing the two-phase returned signals, and the sampling method is ADC sampling of the MCU embedded processor.

[0059] In this implementation scheme, the amplitude of the sine and cosine signals E3 is calculated based on the sampled two-phase instantaneous values ​​E2 and used as the feedback value of the PI control. At the same time, the peak-to-peak value of the sine and cosine excitation signals input by the sine and cosine signal tracking sensor is used as the reference value to adjust the duty cycle and output voltage of the control output, so that the input excitation voltage of the sine and cosine signal tracking sensor is stabilized as the reference value, thereby keeping the excitation signal and the output signal in a linear relationship.

[0060] Specifically, the process of calculating the amplitude E3 of the sine and cosine signals in S1 includes:

[0061] S11. Calculate θ2 for E3sinθ1cosθ2-E3cosθ1sinθ2=0, that is, calculate θ2 for E3sin(θ1-θ2)=0;

[0062] S12. θ1 is calculated by E3sinθ1=E3cosθ1=E2, and θ2 in S11 is obtained from this.

[0063] S13. The amplitude of the sine and cosine signals E3 is calculated by E3sinθ1=E3cosθ2=E2;

[0064] The E3 = E0sinω t Where E0 is the voltage amplitude, ω t The frequency of the excitation voltage.

[0065] In this implementation scheme, the amplitude of the sine and cosine signals, E3, which is the feedback value, can be calculated using E2 according to the above calculation formula.

[0066] Specifically, the PI calculation formula is as follows:

[0067] Out=(Ref-fb)KP+Int(Ref-fb)KI

[0068] Where Out is the output, Ref-fb is the reference value minus the feedback value, KP is the proportional coefficient, Int(Ref-fb) is the integral operation, KI is the integral coefficient, and both KP and KI are positive numbers.

[0069] In this implementation scheme, when Ref-fb is positive, Out is positive, the SVPWM output duty cycle D1 increases, the output voltage increases, and the feedback sine and cosine signals increase.

[0070] Fig. 1 The signal flow graph is shown below, where:

[0071] SVPWM stimulus this method: SVPWM sinusoidal excitation signal generation;

[0072] The SVPWM signal is generated by the MCU or processing logic.

[0073] Two-phase signal: The sinusoidal excitation signal consists of two-phase voltages;

[0074] PI control loop (this method): PI control loop;

[0075] SPWM (single phase) SIN stimulus (other methods): SPWM (single phase) SIN excitation signal;

[0076] Ref+stimulus+Ref-stimulus-: Positive or negative input excitation signal for sine and cosine sensors;

[0077] SIN feedbackout, COS feedbackout: The sensor outputs sine and cosine signals.

[0078] Both single-phase SPWM modulation and two-phase SVPWM can generate the required sinusoidal excitation voltage. The formula for calculating the undistorted voltage amplitude generated by single-phase SPWM modulation is V1 = V dc ×0.866, while SVPWM uses two-phase output to form the excitation signal corresponding to the excitation, and its formula for calculating the undistorted voltage amplitude is V2=V dc ×0.866×1.732 / 1.5, V in both formulas dc The voltage to be modulated. Therefore, it can be seen that using SVPWM results in a larger voltage output, which is more beneficial for excitation control.

[0079] Sine and cosine encoders and rotary transformers are widely used in various electromechanical systems such as motor drive control systems as devices for detecting the position (angle) of rotating machinery. These sensors are excited by sinusoidal signals. By detecting the amplitude and phase relationship of two quadrature sinusoidal signals (two-phase signals) fed back from the sensor output, the required rotation angle value can be obtained through further digital signal processing.

[0080] The input to the sine / cosine signal tracking sensor is a sinusoidal signal with a typical frequency of 10kHz and a drive current of 10-20mA. Its peak drive voltage can be determined by... The calculation shows that R is the equivalent input resistance of the sine / cosine signal tracking sensor, and I is the drive current. For example, when the equivalent input resistance of the sine / cosine signal tracking sensor is 150 ohms and the drive current is 10mA, the peak drive voltage is E1 = 2.12V, and its output is a quadrature sine / cosine voltage, with the two-phase voltages being e1 = E0sinω. t sinθ1,e2=E0sinω t cosθ1, where E0 is the voltage amplitude, ω t The frequency of the excitation voltage.

[0081] Assume E0sinω tIf the value is a, then the detected two-phase voltages are asinθ1 and acosθ1, respectively. The voltage values ​​of the two-phase output can be quantized by the signals returned by the two phases and sampled using the ADC of the MCU embedded processor. Assuming that the sampled values ​​at the same time are a1 and a2, if the sampling quantization error is very small, then a1 = a2, that is, asinθ1 = acosθ1. Therefore, the smaller the quantization error, the higher the confidence of the sampled data, and the more accurate it is.

[0082] If we introduce a θ2, then asinθ1cosθ2-acosθ1sinθ2 can be expressed as asin(θ1-θ2). When θ1=θ2, sin(θ1-θ2) is 0. Therefore, θ2 that makes asinθ1cosθ2-acosθ1sinθ2=0 is the θ1 we need to find. This can be understood as substituting different values ​​of sinθ2 and cosθ2 to find θ1. By observing this angle detection method, we can see that when the local a remains a relatively constant large value, that is, close to the sampled reference voltage value, we can have a1 and a2 with higher confidence. Here, a is the amplitude of the sine and cosine signals generated by the excitation signal after passing through the sine and cosine detection signal device. In this way, the excitation signal and the output signal have a linear relationship.

[0083] To better understand the above, assume that a equals the reference voltage and the quantization range is 0-b. Then a is b or b-1, where 1 is the quantization error. The maximum deviation between a1 and a2 is b-(b-1)=1.

[0084] If a is half of the reference voltage, then theoretically a1 is a2 is The maximum deviation between a1 and a2 is 2, which is significantly greater than the previous assumption. At the same time, asinθ1cosθ2-acosθ1sinθ2 shows that as a decreases, a deviates further from the ideal value. The ratio of a to its ideal value is less than 1. The deviations of asinθ1 and acosθ1 in asinθ1cosθ2-acosθ1sinθ2 from the actual value are greater, and when the two deviate in opposite directions, the calculated θ1 will have random errors. If a, i.e., the feedback voltage value, is not controlled, the error will also be nonlinear, which will have an adverse effect on the operation of the electromechanical actuator.

[0085] By controlling the input excitation voltage of the sine and cosine signal tracking sensor, the stability of the two-phase voltage sampling points of the sensor output can be controlled, and they can be stabilized at a value close to the quantization reference voltage (a relatively large value). The SVPWM modulation method with high output voltage amplitude, flexible phase and amplitude modulation, and fast response is adopted. When the sensor connection is increased, a high excitation voltage is maintained to compensate for line voltage drop and other interference factors.

[0086] Because the two-phase signal detection device is physically coupled, most of the common-mode interference between the two phases cancels each other out in subsequent processing. Only one phase signal needs to be detected. The peak-to-peak value of this single-phase signal is used as the feedback signal, and the configuration value of the sine / cosine SVPWM excitation signal output is used as the reference signal. A PI control loop controls the SVPWM duty cycle modulation, thus controlling the SVPWM output, which is called the automatically adjusted excitation signal. Therefore, regardless of changes in operating conditions, the signal generated by the sine / cosine encoder under test remains stable. Fig. 2 As shown, the specific steps include:

[0087] S1, sample and feedback the instantaneous values ​​of the two phases of the sine and cosine signals E2, and calculate the amplitude of the sine and cosine signals E3 based on the sampled instantaneous values;

[0088] S2. Using the amplitude of the sine and cosine signals calculated in S1 as the feedback value, and the peak-to-peak value of the sine and cosine excitation signals input by the sine and cosine signal tracking sensor as the reference value, the output duty cycle and output voltage increase are controlled by the PI calculation formula.

[0089] S3. Repeat S1 and S2 to stabilize the input excitation voltage of the sine and cosine signal tracking sensor to the reference value.

[0090] S1 includes:

[0091] S11. Calculate θ2 for E3sinθ1cosθ2-E3cosθ1sinθ2=0, that is, calculate θ2 for E3sin(θ1-θ2)=0;

[0092] S12. θ1 is calculated by E3sinθ1=E3cosθ1=E2, and θ2 in S11 is obtained from this.

[0093] S13. The amplitude of the sine and cosine signals E3 can be calculated using E3sinθ1=E3cosθ2=E2.

[0094] Example 1

[0095] Assuming the amplitude of the sine / cosine signal tracking sensor excitation signal is 2V peak-to-peak value, used as a reference value, the SVPWM control duty cycle is D1:

[0096] For example, if the sampled values ​​of the feedback sine and cosine signals are both 0.707V instantaneous values ​​in both phases, then θ2, where E3sinθ1cosθ2 - E3cosθ1sinθ2 is 0, is the θ1 to be found, and E3 = E0sinω t Where E0 is the voltage amplitude, ω tTo determine the excitation voltage frequency, i.e., E3sinθ1=E3cosθ2=0.707, we can calculate that θ2 is 45°. At this time, the peak-to-peak value of the E3sinθ1 signal can be obtained from E3sinθ1=E3cos45°=0.707, and we can get E3=1.

[0097] The PI control reference value is 2, the feedback value is E3 = 1, and the PI calculation formula is:

[0098] Out=(Ref-fb)KP+Int(Ref-fb)KI

[0099] Where Out is the output, Ref-fb is the reference value minus the feedback value, KP is the proportional coefficient, Int(Ref-fb) is the integral operation, and KI is the integral coefficient. KP and KI are both positive numbers, so Ref-fb = 2 - 1 = 1, therefore Out is positive. As the SVPWM output duty cycle D1 increases, the output voltage increases, and the feedback sine and cosine signals increase. The above PI control loop is repeated, and the feedback sine and cosine signals track the sensor excitation voltage, stabilizing at a peak-to-peak value of 2V.

[0100] Taking the feedback value of 0.707 as an example, if PI control is not used, the reference voltage of the sampling reference circuit is 3.3V, and the ADC resolution is 12 bits, then the sampling error Verror = 3.3 / 4096 = 0.0008V. The sampling error between the two phases is random. Therefore, from asinθ1cosθ2 - acosθ1sinθ2, one possibility for the maximum error is that asinθ1 introduces a positive sampling error, and acosθ1 introduces a negative sampling error. Substituting the sampled value and the estimated error... The difference is (0.707+0.0008)cosθ2-(0.707-0.0008)sinθ2. Calculate θ2. If θ2 is required to be 45°, its actual upper limit is 45.065°. If PI control is used, the angle calculation formula, based on the original calculation conditions, is (2*0.707+0.0008)cosθ2-(2*0.707-0.0008)sinθ2, and the upper limit of θ2 is calculated to be 45.033°. Comparative analysis shows that PI control has higher accuracy.

[0101] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0102] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for generating an excitation signal and maintaining a stable feedback signal amplitude, characterized in that: Includes the following steps: The first step is to generate sine and cosine excitation signals; The second step involves inputting sine and cosine excitation signals into a sine and cosine signal tracking sensor and receiving back sine and cosine signals. The third step is to configure the output of the sine and cosine excitation signals as the reference signals for PI control, and the feedback sine and cosine signals as the feedback signals for PI control, so as to control the input excitation voltage of the sine and cosine signal tracking sensor and stabilize the voltage amplitude of the two-phase voltage sampling points of the sine and cosine signal tracking sensor. The sinusoidal excitation signal in the first step is a two-phase voltage, an SVPWM signal generated by a processor or control logic; the SVPWM signal uses two-phase outputs to form an excitation signal corresponding to the excitation, and the formula for calculating the undistorted voltage amplitude is as follows: V=V dc ×0.866×1.732 / 1.5, Among them, V dc The voltage to be modulated; The specific steps for controlling the input excitation voltage of the sine and cosine signal tracking sensor in the third step include: S1, sample and feedback the instantaneous values ​​of the two phases of the sine and cosine signals E2, and calculate the amplitude of the sine and cosine signals E3 based on the sampled instantaneous values; S2. Using the amplitude of the sine and cosine signals calculated in S1 as the feedback value, and the peak-to-peak value of the sine and cosine excitation signals input by the sine and cosine signal tracking sensor as the reference value, the output duty cycle and output voltage increase are controlled by the PI calculation formula. S3. Repeat S1 and S2 to stabilize the input excitation voltage of the sine and cosine signal tracking sensor to a reference value. The process of calculating the amplitude E3 of the sine and cosine signals in S1 includes: S11. Calculate θ2 for E3sinθ1cosθ2-E3cosθ1sinθ2=0, that is, calculate θ2 for E3sin(θ1-θ2)=0; S12. θ1 is calculated by E3sinθ1=E3cosθ1=E2, and θ2 in S11 is obtained from this. S13. The amplitude of the sine and cosine signals E3 can be calculated using E3sinθ1=E3cosθ2=E2.

2. The method for generating an excitation signal and maintaining a stable feedback signal amplitude according to claim 1, characterized in that: The formula for calculating the peak value E1 of the driving voltage of the sine and cosine signal tracking sensor in the second step is as follows: Where R is the equivalent input internal resistance of the sine and cosine signal tracking sensor, and I is the drive current.

3. The method for generating an excitation signal and maintaining a stable feedback signal amplitude according to claim 2, characterized in that: The output of the sine and cosine signal tracking sensor is a quadrature sine and cosine voltage, and its two-phase voltage values ​​are: e1=E0sinω t sinθ1,e2=E0sinω t cosθ1, where E0 is the voltage amplitude, ω t The frequency of the excitation voltage.

4. The method for generating an excitation signal and maintaining a stable feedback signal amplitude according to claim 1, characterized in that: The instantaneous two-phase values ​​E2 of the feedback sine and cosine signals in S1 are obtained by quantizing the two-phase returned signals, and the sampling method is ADC sampling of the MCU embedded processor.

5. The method for generating an excitation signal and maintaining a stable feedback signal amplitude according to claim 1, characterized in that: The E3 = E0sinω t Where E0 is the voltage amplitude, ω t The frequency of the excitation voltage.

6. The method for generating an excitation signal and maintaining a stable feedback signal amplitude according to claim 1, characterized in that: The formula for calculating PI is as follows: Out=(Ref-fb)KP+Int(Ref-fb)KI Where Out is the output, Ref-fb is the reference value minus the feedback value, KP is the proportional coefficient, Int(Ref-fb) is the integral operation, KI is the integral coefficient, and both KP and KI are positive numbers.

Images