Low-moment-of-inertia axial magnetic field permanent magnet synchronous motor system without position sensor

Abstract

The invention discloses a position-sensorless axial magnetic field permanent magnet synchronous motor system with low rotational inertia, which comprises an axial magnetic field permanent magnet synchronous motor and a position-sensorless control system, and is characterized in that the axial magnetic field permanent magnet synchronous motor comprises a static rotor magnet yoke, a stator and a rotor, and the rotor is arranged on a motor shaft; the rotor is located between the static rotor magnet yoke and the stator, air gaps are formed between the rotor and the static rotor magnet yoke and between the rotor and the stator, the rotor comprises a plurality of magnetic steels, magnetic conductive patches and a rotor core, the magnetic conductive patches are attached to the surfaces of the magnetic steels, the contact surfaces of the magnetic conductive patches and the magnetic steels are arc-shaped, and the magnetic conductive patches are in a middle concave shape. The magnetic steel is attached to or embedded into the surface of the rotor iron core at equal intervals, and the position-sensorless control system is used for achieving driving control over the axial magnetic field permanent magnet synchronous motor. The high-permeability patches are attached to the surfaces of the rotor permanent magnets, and the salient pole effect of the motor is remarkably improved by enhancing the magnetic permeability of a magnetic circuit, so that the rotor position estimation precision is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous motors, and particularly to a sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia. Background Art

[0002] Axial magnetic field permanent magnet synchronous motors are widely used in new energy vehicles, industrial drives and other fields due to their high efficiency, high power density and reliability. Traditional permanent magnet synchronous motor control relies on mechanical position sensors (such as encoders or resolvers) to obtain rotor position information. However, the sensors increase the system cost, complexity and maintenance requirements, and their reliability decreases especially in harsh environments such as high temperature, high humidity or strong magnetic fields. Therefore, sensorless control technology has become a research hotspot. When the motor is running at high speed, the rotor position information is calculated by the back electromotive force-based control method, which fails under zero-speed or low-speed operating conditions due to the weak back electromotive force signal. The high-frequency signal injection method extracts the rotor position information by injecting high-frequency signals into the motor windings and utilizing the saliency effect of the motor, and has become an effective solution at zero speed or low speed. Generally, due to the symmetry of the magnetic circuit design of the axial magnetic field permanent magnet synchronous motor, such as the uniform distribution of permanent magnets, the consistent air gap thickness and the symmetric structure of the rotor core, the magnetic circuit characteristics of the direct axis and the quadrature axis are almost the same, resulting in equal direct axis inductance and quadrature axis inductance and lack of saliency. Especially when the motor is running at zero speed or low speed, this characteristic of equal inductance makes it difficult to generate a strong enough high-frequency current response when applying the sensorless control technology of the high-frequency signal injection method to the motor, the signal amplitude is weak, the signal-to-noise ratio is low, and it is easily affected by noise, and the accuracy and robustness of rotor position estimation will be significantly reduced. Therefore, it is not suitable for directly applying sensorless technology. Summary of the Invention

[0003] The object of the present invention is to provide a sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia. By thinning the permanent magnet and attaching a high-permeability iron core to enhance the saliency effect, when the motor is running at zero speed or low speed, a high-frequency voltage signal is injected into the direct axis in the direct and quadrature axis coordinate system to form a pulsating voltage signal in the stationary coordinate system, and a position tracking observer is combined to achieve high-precision rotor position estimation at zero speed or low speed. At high speed, the rotational speed and position information are solved by the back electromotive force, reducing the system complexity and noise influence.

[0004] The technical solution for the purpose of the present invention is: a sensorless axial magnetic field permanent magnet synchronous motor system with low rotational inertia, including an axial magnetic field permanent magnet synchronous motor and a sensorless control system. The axial magnetic field permanent magnet synchronous motor includes a stationary rotor yoke, a stator, and a rotor. The rotor is arranged on the motor shaft, located between the stationary rotor yoke and the stator, and there are air gaps between the rotor and both the stationary rotor yoke and the stator. The rotor includes a plurality of permanent magnets, magnetic conductive patches, and a rotor core. The magnetic conductive patches are attached to the surfaces of the permanent magnets, the contact surfaces between the magnetic conductive patches and the permanent magnets are arc-shaped, and the magnetic conductive patches are recessed in the middle. The permanent magnets are mounted or embedded on the surface of the rotor core at equal intervals. The sensorless control system is used to achieve the drive control of the axial magnetic field permanent magnet synchronous motor.

[0005] Compared with the prior art, the present invention has the following remarkable advantages:

[0006] (1) By thinning the permanent magnets and attaching high magnetic conductivity patches, the present invention enhances the salient pole effect of the axial magnetic field motor and overcomes the limitation of equal inductance between the d-axis and the q-axis.

[0007] (2) The high magnetic conductivity patches in the present invention are flexibly designed, and the thickness and shape can be adjusted to adapt to various working conditions, improving the versatility.

[0008] (3) The present invention improves the signal-to-noise ratio of the high-frequency signal injection method when the motor operates at low speed or zero speed, and enhances the rotor position estimation accuracy and robustness.

[0009] (4) By combining the phase-locked loop and the back electromotive force method, the present invention realizes full-speed-range rotor position tracking and ensures stability and reliability at different speeds.

[0010] (5) The present invention does not require a mechanical position sensor, reducing the system complexity and cost, while maintaining high performance and reliability. Brief Description of the Drawings

[0011] Figure 1 is a block diagram of the sensorless axial magnetic field permanent magnet synchronous motor system with low rotational inertia of the present invention;

[0012] Figure 2 is an exploded schematic view of the axial magnetic field permanent magnet synchronous motor of the present invention.

[0013] Figure 3 is a schematic diagram of the implementation principle of rotor position estimation by injecting a pulsating high-frequency voltage signal based on a position tracking observer when the motor of the present invention operates at zero speed or low speed.

[0014] Figure 4 is a simulation result of rotor position estimation by injecting a pulsating high-frequency voltage signal based on a position tracking observer when the motor of the present invention operates at zero speed or low speed.

[0015] Figure 5 It is the implementation principle block diagram of the rotor position estimation of the sliding mode observer based on the phase-locked loop when the motor in the present invention operates at high speed.

[0016] Figure 6 It is the simulation result of the rotor position estimation of the sliding mode observer based on the phase-locked loop when the motor in the present invention operates at high speed. Specific implementation manners

[0017] The present invention will be further described below with reference to the accompanying drawings.

[0018] A sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia and its control method enhance the salient polarity by thinning the permanent magnets and attaching high-permeability iron cores on the surfaces, so that it has the ability of high-precision rotor position estimation in the full-speed operation scenario. The contact surface between the magnetic flux conducting patch and the permanent magnet is arc-shaped, and the magnetic flux conducting patch is concave in the middle to increase the reluctance of the direct axis, thereby reducing the inductance of the direct axis and enhancing the salient pole effect of the direct and quadrature axis inductances to improve the magnetic field response during high-frequency signal injection at zero speed or low speed, enabling the motor to generate stronger position-related signals and being applicable to sensorless control. Meanwhile, the rotor position information can still be estimated using the established back electromotive force at high speed.

[0019] As Figure 1 shown, a sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia includes an axial magnetic field permanent magnet synchronous motor and a sensorless control system. As Figure 2 shown, the axial magnetic field permanent magnet synchronous motor includes a stationary rotor yoke 11, a stator 12, a rotor 13 and an air gap 14. The rotor 13 is arranged on the motor shaft, located between the stationary rotor yoke 11 and the stator 12, and there are air gaps 14 between the rotor 13 and both the stationary rotor yoke 11 and the stator 12. The rotor 13 includes a plurality of permanent magnets 131, magnetic flux conducting patches 133 and a rotor core 132. The permanent magnets 131 and the magnetic flux conducting patches 133 are mounted or embedded on the surface of the rotor core 132 at equal intervals. The stationary rotor yoke 11 includes a yoke 111 and a yoke core 112. The stator 12 includes a stator core 121 and a plurality of stator windings 122. The permanent magnets 131 are thinned, and magnetic flux conducting patches 133 with stronger magnetic conductivity are attached to their surfaces. The contact surface between the magnetic flux conducting patches 133 and the permanent magnets 131 is arc-shaped, and the magnetic flux conducting patches are concave in the middle to increase the reluctance of the direct axis, correspondingly reducing the inductance of the direct axis and enhancing the salient pole effect of the direct and quadrature axis inductances to improve the magnetic field response during high-frequency signal injection.

[0020] The sensorless control system is used to calculate the rotor position information of the motor and realize the drive of the axial-flux permanent magnet synchronous motor. The specific functions include: when the axial-flux permanent magnet synchronous motor operates at zero speed or low speed, a high-frequency voltage signal is injected into the d-axis of the axial-flux permanent magnet synchronous motor, and the q-axis current of the axial-flux permanent magnet synchronous motor is extracted. After calculation, the rotor position information of the axial-flux permanent magnet synchronous motor is obtained. At the same time, the rotor position information is fed back to the axial-flux permanent magnet synchronous motor to form a control closed-loop as feedback; when the axial-flux permanent magnet synchronous motor operates at high speed, the back electromotive force established during the operation of the axial-flux permanent magnet synchronous motor is extracted. After calculation, the rotor position information of the axial-flux permanent magnet synchronous motor is obtained. At the same time, the rotor position information is fed back to the axial-flux permanent magnet synchronous motor to form a control closed-loop as feedback.

[0021] In a further embodiment, by thinning the thickness of the permanent magnet 131 and attaching a high-permeability patch 133, the thickness of the permanent magnet 131 is 60% to 80% of the original thickness (the original thickness of the permanent magnet is 10 mm), and the thickness of the permeable patch 133 is 1.0 mm to 3.0 mm. The permanent magnet 131 is cut into a middle bulge, while the permeable patch 133 is in the shape of a middle depression and fits tightly with the permanent magnet 131. Since the permeability of the permanent magnet 131 is less than that of the high-permeability iron core 133, the direct-axis magnetic resistance is larger than the quadrature-axis magnetic resistance, and the direct-axis inductance is smaller than the quadrature-axis inductance L d < L q , enhancing the salient-pole effect of the direct and quadrature-axis inductances to improve the magnetic field response during high-frequency signal injection, so that the motor can generate stronger position-related signals.

[0022] In a further embodiment, the magnetization directions of the permanent magnet 131 and the permeable patch 133 are the same and alternate in the axial direction.

[0023] In a further embodiment, the material of the permeable patch 133 is a soft magnetic alloy.

[0024] In a further embodiment, the rotor core 132 includes two rings, which are connected by rotor spokes.

[0025] In a further embodiment, the rotor 13 is in a non-magnetic yoke form. A number of permanent magnets 131 and permeable patches 133 are embedded in the spokes of the rotor core 132, and the total thickness of the permanent magnet 131 and the attached permeable patch 133 is equal to the thickness of the spokes.

[0026] In a further embodiment, the system has two operating modes, namely: when the motor operates at zero speed or low speed, the rotor position is estimated by injecting a pulsating high-frequency voltage signal based on a position tracking observer, including injecting a high-frequency voltage signal into the d-axis of the stator winding 122, collecting the q-axis current in the stator winding 122, and using a position tracker to estimate the rotor position information; when the motor operates at high speed, the rotor position is estimated based on the back electromotive force generated by the electrical signals related to the rotational speed in a three-phase permanent magnet synchronous motor based on a fundamental wave mathematical model, collecting the back electromotive force in the stator winding 122, and using a sliding mode observer based on a phase-locked loop to estimate the rotor position information.

[0027] In a further embodiment, when the motor operates at zero speed or low speed, a high-frequency voltage signal is injected into the d-axis of the axial flux permanent magnet synchronous motor, and the q-axis current of the axial flux permanent magnet synchronous motor is extracted. A rotor synchronous rotating coordinate system is established. The axis is the estimated rotor synchronous rotating coordinate system, and the direct and quadrature axes are the actual rotor synchronous rotating coordinate systems. is the two-phase stationary coordinate system. is the estimated rotor position angle. is the actual rotor position angle, and the rotor estimation error angle is calculated. is:

[0028]

[0029] As Figure 3 shown, the voltage equation of the permanent magnet synchronous motor in the direct and quadrature axis synchronous rotating coordinate system can be expressed as:

[0030]

[0031] In the formula: 、 are the direct and quadrature axis components of the stator voltage respectively; 、 are the direct and quadrature axis components of the stator current respectively; R is the resistance of the stator; 、 are the direct and quadrature axis components of the stator flux linkage respectively; is the electrical angular velocity; 、 are the direct and quadrature axis inductance components respectively; is the permanent magnet flux linkage.

[0032] The frequency of the high-frequency injection signal is generally much higher than the fundamental wave frequency of the motor. , since the resistance is much smaller than the reactance at high frequencies, it can be ignored. At this time, the voltage equation of the three-phase permanent magnet synchronous motor under high-frequency excitation can be simplified as:

[0033]

[0034] In the estimated rotor synchronous rotating coordinate system, the relationship between the high-frequency voltage and current is as follows:

[0035]

[0036] wherein, and as well as and are respectively the high-frequency voltage and current components of the axis and the axis in the estimated rotor synchronous rotating coordinate system . is the average inductance, and is the half-difference inductance.

[0037] In a further embodiment, a high-frequency voltage signal is injected into the d-axis of the stator winding 122 based on the estimated rotor synchronous rotating coordinate system:

[0038]

[0039] wherein, is the amplitude of the high-frequency voltage signal, and is the frequency of the high-frequency voltage signal.

[0040] In a further embodiment, the q-axis current in the stator winding 122 is collected. After the above derivation, the injected high-frequency voltage signal on the d-axis is substituted into the high-frequency voltage and current equations in the estimated rotor synchronous rotating coordinate system, and through integration, the following can be obtained:

[0041]

[0042] When , in the estimated rotor synchronous rotating coordinate system, the amplitude of the high-frequency current component on the axis is related to the rotor position estimation error angle . As shown in Figure 2 , thinning the permanent magnet 131 and attaching the high-permeability patch 133 can significantly increase the difference between the direct-axis inductance and the quadrature-axis inductance , making the high-frequency current signal easier to extract.

[0043] In a further embodiment, a position tracker is used to estimate the rotor position information:

[0044] (1) A band-pass filter (BPF) is used to extract the high-frequency current signal containing the rotor position information, filtering out the fundamental current and high-frequency carrier current in the motor current signal;

[0045] (2) The high-frequency current signal containing rotor position information is passed through a low-pass filter (LPF) to obtain a rotor position error signal, and the error signal is linearized, i.e.:

[0046]

[0047] where, is the error signal coefficient.

[0048] (3) Adjust the PI parameter gains in the position tracking observer so that approaches zero, then the rotor position angle estimation error also approaches zero, and the estimated value of the rotor position converges to the actual value of the rotor position.

[0049] (4) The estimated rotor speed is obtained through position tracking observation, (using a phase-locked loop structure), and the speed calculation formula is:

[0050]

[0051] where, k p , k i are the proportional and integral gain coefficients of the PI regulator in the position tracking observer, and t is the integral time variable.

[0052] Integrate the obtained estimated rotor speed to obtain the estimated rotor position . Feed the obtained rotor position information back to the servo control system of the axial permanent magnet synchronous motor to form a control closed loop.

[0053] In a further embodiment, the proposed pulsating high-frequency voltage signal injection model based on a position tracking observer is built in a simulation software, Figure 4 showing the actual position and the estimated position of the rotor. Due to the certain lag of the simulation system compared with the actual system, there is a position mutation during the position period switching, but the error remains within a very small range during the entire stable operation period. This reflects that the improved axial permanent magnet synchronous motor can apply the sensorless control technology based on high-frequency signal injection at zero speed or low speed due to the increased saliency ratio.

[0054] In a further embodiment, as Figure 5 shown, when the motor operates at high speed, according to the equivalent control principle of sliding mode control, the back electromotive force in the voltage of the stator winding (122) collected is separated and extracted to keep it on the sliding surface. The voltage equation of the permanent magnet synchronous motor in the stationary coordinate system is:

[0055]

[0056] where, , is the stator voltage; and is the stator current; is the extended back electromotive force, and satisfies:

[0057]

[0058] All the information of the motor rotor position and speed is included in the extended back electromotive force. A sliding mode observer is used to observe the extended back electromotive force. Generally, the sliding mode observer is designed as:

[0059]

[0060] In the formula, is the observed value of the stator current, is the control input of the observer.

[0061] Rewriting the voltage equation in the stationary coordinate system into the state equation of current and taking the difference with the above formula, the stator current error equation can be obtained as:

[0062]

[0063] In the formula: is the current observation error. The sliding mode control law is designed as:

[0064]

[0065] In the formula:

[0066] When the state variable of the observer reaches the sliding mode surface After that, the observer state will always remain on the sliding mode surface.

[0067] In a further embodiment, the separated back electromotive force is processed by a sliding mode and then passed through a low-pass filter to obtain a back electromotive force signal containing rotor position information. According to the equivalent control principle of sliding mode control, the control quantity at this time can be regarded as the equivalent control quantity, and we can get:

[0068]

[0069] Since the actual control quantity is a discontinuous high-frequency switching signal, in order to extract a continuous back electromotive force estimated value, a low-pass filter needs to be added additionally:

[0070] In the formula, and are the actual discontinuous back electromotive force control quantities, and The continuous back electromotive force signal is obtained by passing the discontinuous back electromotive force control quantity after the sliding mode processing through a low-pass filter. is the time constant of the low-pass filter.

[0071] In a further embodiment, after the output angle generated by the phase-locked loop is fed back, it is compared with the back electromotive force signal including the input angle to obtain the rotor position error angle, and the signal including the rotor position error angle information is linearized.

[0072] Assume , when it is considered that holds, then:

[0073]

[0074] In the formula, , is the back electromotive force signal including the rotor position information obtained by passing the back electromotive force control quantity after the sliding mode processing through a low-pass filter.

[0075] In a further embodiment, the PI parameter gain in the phase-locked loop is adjusted so that the linearized error signal is less than the error value. As the input of the PI regulator of the phase-locked loop, by adjusting the PI parameter gain in the phase-locked loop, tends to zero, so that the estimated rotor position converges to the actual rotor position . At the same time, the error signal passes through the proportional-integral link to obtain the estimated rotor speed , and the integral of the obtained estimated rotor speed is taken to obtain the estimated rotor position . The obtained rotor position information is fed back to the servo control system of the axial permanent magnet synchronous motor to form a control closed loop.

[0076] In a further embodiment, the error signal passes through the proportional-integral link in the phase-locked loop to obtain the estimated rotor speed :

[0077]

[0078] In the formula, k p , k i are the proportional and integral gain coefficients of the PI regulator in the phase-locked loop, and t is the integral time variable. The present invention identifies the rotor position based on the electrical model during the operation of the motor, so as to realize sensorless control. High-frequency signal injection is required at zero speed or low speed to track the rotor salient pole caused by the difference between the direct-axis and quadrature-axis inductances, so as to calculate the rotor salient pole position. At high speed, since the back electromotive force of the motor has been established, high-frequency signal injection is no longer required.

[0079] In a further embodiment, the proposed sliding mode observer model based on the phase-locked loop is built in the simulation software in the present invention. Figure 6 The actual position of the rotor and the estimated position of the rotor are shown. Since there is a certain lag in the simulation system compared with the actual system, there is a sudden change in position during the position period switching. However, the error fluctuates within a very small range during the entire stable operation period. This verifies the feasibility of estimating the rotor position by using the electrical signals (induced back electromotive force) related to the rotational speed in a three-phase permanent magnet synchronous motor based on the fundamental wave mathematical model at high speeds.

[0080] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention.

Claims

1. A sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia, characterized in that, It includes an axial - field permanent - magnet synchronous motor and a sensorless control system. The axial - field permanent - magnet synchronous motor includes a stationary rotor yoke (11), a stator (12), and a rotor (13). The rotor (13) is arranged on the motor shaft, located between the stationary rotor yoke (11) and the stator (12), and there are air gaps (14) between the rotor (13) and both the stationary rotor yoke (11) and the stator (12). The rotor (13) includes a number of permanent magnets (131), magnetic conductive patches (133), and a rotor core (132). The magnetic conductive patches (133) are attached to the surfaces of the permanent magnets (131). The contact surface between the magnetic conductive patches (133) and the permanent magnets (131) is arc - shaped, and the magnetic conductive patches (133) are recessed in the middle. The permanent magnets (131) are mounted or embedded on the surface of the rotor core (132) at equal intervals. The sensorless control system is used to achieve the drive control of the axial - field permanent - magnet synchronous motor.

2. The sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia according to claim 1, characterized in that The specific method for the sensorless control system to achieve the drive control of the axial - field permanent - magnet synchronous motor is as follows: When the operating speed of the axial - field permanent - magnet synchronous motor is lower than the set threshold, a high - frequency voltage signal is injected into the d - axis of the axial - field permanent - magnet synchronous motor, and the q - axis current of the axial - field permanent - magnet synchronous motor is extracted. After calculation, the rotor position information of the axial - field permanent - magnet synchronous motor is obtained. At the same time, the rotor position information is fed back to the axial - field permanent - magnet synchronous motor to form a control closed - loop. When the operating speed of the axial - field permanent - magnet synchronous motor is not lower than the set threshold, the back - electromotive force established during the operation of the axial - field permanent - magnet synchronous motor is extracted. After calculation, the rotor position information of the axial - field permanent - magnet synchronous motor is obtained. At the same time, the rotor position information is fed back to the axial - field permanent - magnet synchronous motor to form a control closed - loop.

3. The sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia according to claim 2, wherein When the operating speed of the axial - field permanent - magnet synchronous motor is lower than the set threshold, the specific method for extracting the q - axis current of the axial - field permanent - magnet synchronous motor and obtaining the rotor position information of the axial - field permanent - magnet synchronous motor after calculation is as follows: A band - pass filter is used to extract the high - frequency current signal containing the rotor position information, and filter out the fundamental current and high - frequency carrier current in the motor current signal. The high - frequency current signal containing the rotor position information passes through a low - pass filter to obtain a rotor position error signal, and the error signal is linearized. Adjust the PI parameter gains in the position tracking observer so that the linearized error signal is less than the error threshold. The estimated rotor speed is obtained through a position tracking observer , and the specific formula is as follows: ； where k p , k i are the proportional and integral gain coefficients of the PI regulator in the position tracking observer, respectively, is the rotor position estimation error angle, is the error signal coefficient, and t is the integral time variable; Integrate the obtained estimated rotor speed to obtain the estimated rotor position .

4. The sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia according to claim 3, characterized in that The linearized error signal is specifically: ； Wherein, is the high-frequency component of the current on the axis in the estimated rotor synchronous rotating coordinate system, is the frequency of the high-frequency voltage signal, is the amplitude of the high-frequency voltage signal, and are the direct-axis and quadrature-axis inductance components respectively.

5. The sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia according to claim 2, wherein When the operating speed of the axial - field permanent - magnet synchronous motor is not lower than the set threshold, the specific method for extracting the back - electromotive force established during the operation of the axial - field permanent - magnet synchronous motor and obtaining the rotor position information of the axial - field permanent - magnet synchronous motor after calculation is as follows: According to the equivalent control principle of sliding - mode control, the back - electromotive force in the voltage of the stator winding (122) collected is separated and extracted to keep the back - electromotive force on the sliding surface. The separated back - electromotive force is processed by sliding - mode and then passes through a low - pass filter to obtain a back - electromotive force signal containing the rotor position information. The output angle feedback generated by the phase - locked loop is compared with the back - electromotive force signal to obtain a signal containing the rotor position error information, and the signal containing the rotor position error information is linearized. Adjust the PI parameter gain in the phase-locked loop so that the linearized error signal is less than the error threshold; The estimated rotor speed is obtained through a phase-locked loop , and the specific formula is as follows: ； where k p , k i are the proportional and integral gain coefficients of the PI regulator in the phase-locked loop, is the rotor position angle, is the estimated rotor position angle, t is the integral time variable, and k is the error signal coefficient; Integrate the obtained estimated rotor speed to obtain the estimated rotor position .

6. The sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia according to claim 5, wherein The specifically linearized error signal is: ； Wherein, and are the back electromotive force signals obtained after the back electromotive force control quantity after the synovial membrane treatment passes through a low-pass filter.

7. The sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia according to claim 1, wherein The thickness of the permanent magnet (131) is 6 mm to 8 mm, and the thickness of the magnetic conductive patch (133) is 1.0 mm to 3.0 mm.

8. The sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia according to claim 1, characterized in that, The magnetization directions of the permanent magnet (131) and the magnetic conductive patch (133) are the same and alternate in the positive and negative directions along the axis.

9. The sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia according to claim 1, wherein The material of the magnetic conductive patch (133) is soft magnetic alloy.

10. The sensorless axial magnetic field permanent magnet synchronous motor system with low moment of inertia according to claim 1, characterized in that, The rotor core (132) includes two circular rings, which are connected by rotor spokes.

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