Motor non-inductive control method for avoiding dead zone influence at low speed

Abstract

This invention discloses a sensorless motor control method to avoid dead zone effects at low speeds, comprising the following steps: S101, setting the initial values ​​of motor angle and speed to zero in the program; S102, starting the motor, and ensuring stable operation of the entire foc vector control loop; S103, determining whether the electric angular velocity frequency is greater than 1 kHz. If it is greater than 1 kHz, proceed to step S301; otherwise, proceed to the following step: S201, the hardware circuit samples the terminal voltage to obtain the terminal voltage value, and the terminal voltage is calculated by the software to obtain U. α and U β Meanwhile, the forc vector control loop acquires i α and i β This invention acquires the actual terminal voltage of the motor through hardware circuitry, thereby obtaining the alpha and beta axis voltages. The actual sampled voltages do not include the influence of the dead zone and can be directly input to the sliding diaphragm observer, thus avoiding the influence of the dead zone on the output of the sliding diaphragm observer.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, specifically to a sensorless motor control method that avoids the effects of dead zone at low speeds. Background Technology

[0002] There are many existing sensorless control methods, such as sliding mode observers, nonlinear flux observers, high-frequency injection, and static voltage compensation models, but they all have their limitations. Sensorless low-speed load control has always been a challenge. For example, in motor vector control, the input of the sliding mode observer is generally the output of the current loop PI controller. Due to the influence of the controller dead zone, the input voltage of the sliding mode observer includes the dead zone voltage. Because of the dead zone, the actual voltage at the motor end is not equal to the calculated voltage output by the current loop PI controller. Directly using the voltage output by the current loop PI controller to estimate the real-time angle and speed of the motor will affect the final estimation accuracy, especially at low speeds, where the dead zone effect is even greater. The angle and speed output by the sliding mode observer cannot accurately estimate the actual electrical angle and speed of the motor, leading to problems such as easy loss of synchronism at low speeds and difficulty in starting under load. Summary of the Invention

[0003] The purpose of this invention is to provide a sensorless motor control method that avoids the effects of dead zone at low speeds, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a sensorless motor control method to avoid the effects of dead zone at low speeds, comprising the following steps:

[0005] S101. The initial values ​​of the motor angle and speed are set to zero in the program;

[0006] S102. Start the motor, and the entire forc vector control loop will operate stably.

[0007] S103. Determine if the electric angular velocity frequency is greater than 1 kHz. If it is greater than 1 kHz, proceed to step S301. If it is not greater than 1 kHz, proceed to the following steps:

[0008] S201. The hardware circuit samples the terminal voltage to obtain the terminal voltage value, and the terminal voltage is calculated by the software to obtain U. α and U β Meanwhile, the forc vector control loop acquires i α and i β The terminal voltage acquisition circuit first calculates the cutoff frequency of the low-pass filter:

[0009]

[0010] Where C is capacitance and R is resistance, C = 1 nF. R || These are parallel resistors. MOTOR_U / MOTOR_V / MOTOR_W are the motor terminal voltages, which are the motor terminal voltages relative to DC. - The voltage, and the conversion of the terminal voltage to the phase voltage, are calculated as follows:

[0011] A. Terminal voltage, phase voltage, and DC - Voltage U at the center point of the motor OO′ Relationship:

[0012] U aO =U aO ′+U OO′

[0013] U bO =U bO′ +U OO′

[0014] U cO =U cO′ +U OO′

[0015] Among them, U aO U bO U cO U is the sampled terminal voltage; aO′ U bO′ U cO′ U is the phase voltage of the motor; OO′ , is the distance from the motor center point to DC - The voltage;

[0016] B. Calculation of the relationship between phase voltage and terminal voltage:

[0017] Adding the three equations together, according to the formula that the sum of the phase voltage amplitudes equals 0, U aO′ +U bO′ +U cO′ =0

[0018] Given U aO′ +U bO′ +U cO′ =0, calculated as follows:

[0019]

[0020] Given U OO′ The voltages of phases a, b, and c can be calculated:

[0021]

[0022] C. Calculation of the relationship between phase voltage and voltages along the alpha and beta axes of the stationary coordinate system:

[0023] According to the Clark coordinate transformation:

[0024] U α =U aO′

[0025]

[0026] D. Calculation of the relationship between phase voltage and terminal voltage:

[0027] Based on B and C, the following can be calculated:

[0028]

[0029] The relationship between the sampled terminal voltage and the alpha and beta axis voltages can be calculated from A, B, C, and D above.

[0030] S202. Will U α U β and i α i β The probe is fed into the synovial membrane observation device to estimate the angle θ and angular velocity ω. e ;

[0031] S203, calculate the estimated angle θ and angular velocity ω e The signal is fed into the forc vector control loop to complete the closed-loop control of the motor angle and speed;

[0032] S301, Current Loop Controller Output U α′ and U β′ Meanwhile, the forc vector control loop acquires i α and i β ;

[0033] S302, U α U β and i α i β The probe is fed into the synovial membrane observation device to estimate the angle θ and angular velocity ω. e ;

[0034] S303, calculate the angle θ and angular velocity ω e The signal is fed into the FOC vector control loop to complete the closed-loop control of the motor angle and speed.

[0035] In step S301, the relationship between the calculated voltage output by the current loop PI controller and the actual voltage of the motor is as follows:

[0036] U α ′=U α +U dead

[0037] U β ′=U β +U dead (1)

[0039] U α ′ and U β ′ is the calculated voltage output of the current loop PI controller, which includes the dead-time effect; U α and U β It is the actual voltage value obtained at the motor end.

[0040] Steps S202 and S303 further include analyzing the dead zone voltage and its effect on the calculated voltage U when the motor is at high and low speeds. α ′ and U β The impact of ′:

[0041]

[0042] From the above formula, we can see that when the motor speed is high, and The value is relatively large, so U α and U β The value is relatively large, and it can be known from formula (1) that when U α and U β When the value is large, the dead zone voltage U dead For calculating voltage U α ′ and U β The proportion of ′ is relatively small, so its impact on the true value is relatively small. Similarly, it can be seen that when the motor angular frequency is low, U α and U β The value is small, and the dead zone voltage U dead For calculating voltage U α ′ and U β The proportion of ′ is relatively large.

[0043] In steps S202 and S303, the synovial observer obtains the angle and angular velocity based on the following voltage equation:

[0044]

[0045] Given the input voltage U, input current i, and motor parameters: resistance R, inductance L, and flux linkage Ψ. r The rotor angle θ of the motor is estimated based on the voltage equation, and the speed ω is obtained by differentiating the angle. e .

[0046] Compared with the prior art, the beneficial effects of the present invention are:

[0047] This invention acquires the actual terminal voltage of the motor through hardware circuitry, thereby obtaining the alpha and beta axis voltages. The actual sampled voltages do not include the influence of the dead zone and can be directly input to the sliding diaphragm observer, avoiding the influence of the dead zone on the output of the sliding diaphragm observer and obtaining higher precision angles and angular velocities. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the control flow of the present invention;

[0049] Figure 2 This is a block diagram of the motor forc vector control of the present invention;

[0050] Figure 3 This is a schematic diagram of the input and output of the synovial membrane observer of the present invention;

[0051] Figure 4 This is a circuit diagram for acquiring the terminal voltage of the present invention. Detailed Implementation

[0052] 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.

[0053] Please see Figure 1-4 This invention provides a technical solution: a sensorless motor control method to avoid the effects of dead zone at low speeds, comprising the following steps:

[0054] S101. The initial values ​​of the motor angle and speed are set to zero in the program;

[0055] S102. Start the motor, and the entire forc vector control loop will operate stably.

[0056] S103. Determine if the electric angular velocity frequency is greater than 1 kHz. If it is greater than 1 kHz, proceed to step S301. If it is not greater than 1 kHz, proceed to the following steps:

[0057] S201. The hardware circuit samples the terminal voltage to obtain the terminal voltage value, and the terminal voltage is calculated by the software to obtain U. α and U β Meanwhile, the forc vector control loop acquires i α and i β ;

[0058] S202. Will U α U β and i α i βThe probe is fed into the synovial membrane observation device to estimate the angle θ and angular velocity ω. e ;

[0059] S203, calculate the estimated angle θ and angular velocity ω e The signal is fed into the forc vector control loop to complete the closed-loop control of the motor angle and speed;

[0060] S301, Current Loop Controller Output U α ′ and U β Meanwhile, the forc vector control loop obtains i α and i β ;

[0061] S302, U α U β and i α i β The probe is fed into the synovial membrane observation device to estimate the angle θ and angular velocity ω. e ;

[0062] S303, calculate the angle θ and angular velocity ω e The signal is fed into the FOC vector control loop to complete the closed-loop control of the motor angle and speed.

[0063] Figure 4 For the terminal voltage acquisition circuit, first calculate the cutoff frequency of the low-pass filter:

[0064]

[0065] Where C is capacitance and R is resistance, C = 1 nF. R || It is a parallel resistor.

[0066] MOTOR_U, MOTOR_V, and MOTOR_W are all the terminal voltages of the motor, which are the motor terminals relative to DC voltage. - The voltage.

[0067] 1. The calculation for converting terminal voltage to phase voltage is as follows:

[0068] A. Terminal voltage, phase voltage, and DC - Voltage U at the center point of the motor OO′ Relationship

[0069] U aO =U aO′ +U OO′

[0070] U bO =U bO′ +U OO′

[0071] U cO =UcO′ +U OO′

[0072] Among them U aO U bO U cO U is the sampled terminal voltage; aO′ U bO′ U cO′ U is the phase voltage of the motor; OO′ , is the distance from the motor center point to DC - The voltage.

[0073] B. Calculation of the relationship between phase voltage and terminal voltage

[0074] Adding the three equations together, according to the formula that the sum of the phase voltage amplitudes equals 0, U aO′ +U bO′ +U cO′ =0

[0075] Given U aO′ +Y bO′ +U cO′ =0 can be calculated to obtain:

[0076]

[0077] Given U OO′ The voltages of phases a, b, and c can be calculated:

[0078]

[0079] C. Calculation of the relationship between phase voltage and voltages along the alpha and beta axes of the stationary coordinate system

[0080] According to the Clark coordinate transformation:

[0081] U α =U aO′

[0082]

[0083] D. Calculation of the relationship between phase voltage and terminal voltage

[0084] Based on (2) and (3), we can calculate:

[0085]

[0086] The relationship between the sampled terminal voltage and the alpha and beta axis voltages can be calculated from A to D above.

[0087] 2. Relationship between the calculated voltage output of the current loop PI controller and the actual voltage of the motor:

[0088] U α ′=Uα +U dead

[0089] U β ′=U β +U dead (1)

[0090] U α ′ and U β ′ is the calculated voltage output of the current loop PI controller, which includes the dead-time effect; U α and U β It is the actual voltage value obtained at the motor end.

[0091] 3. Analyze the impact of dead-zone voltage on the calculated voltage U when the motor is at high and low speeds. α ′ and U β The impact of ′:

[0092]

[0093] From formula (2), it can be seen that when the motor speed is high, and The value is relatively large, so U α and U β The value is relatively large. From formula (1), it can be seen that when U... α and U β When the value is large, the dead zone voltage U dead For calculating voltage U α ′ and U β The proportion of ′ is relatively small, so its impact on the true value is relatively small. Similarly, it can be seen that when the motor angular frequency is low, U α and U β The value is small, and the dead zone voltage U dead For calculating voltage U α ′ and U β The proportion of ′ is relatively large.

[0094] 4. Analyze the impact of the voltages on the alpha and beta axes of the motor at high and low speeds on the output accuracy of the sliding diaphragm observer:

[0095] The input to a sensorless sliding diaphragm observer is the voltage and current along the alpha and beta axes, and the output is the estimated angle and velocity. The input accuracy of the sliding diaphragm observer directly affects the accuracy of its output angle and velocity. The input voltage of a traditional sensorless sliding diaphragm control method is the U output from a current-loop PI controller. α ′ and U β ′, which includes the dead zone voltage, due to the low speed U α and U βThe value is relatively small, and the dead zone accounts for a large proportion, thus having a significant impact on the output accuracy of the sliding diaphragm observer. The method of this invention samples the actual voltage at the motor terminals and calculates the two-phase stationary coordinate system voltage U. α and U β This does not include dead zone voltage; it is the actual voltage at the motor terminals. The input voltage of the sliding diaphragm observer is the actual sampled U. α and U β Voltage is increased to improve output accuracy. At low speeds, it avoids the impact of dead zones on the accuracy of the sliding diaphragm observer's output angle and speed.

[0096] 5. Shut down the terminal voltage sampling circuit at high speed:

[0097] Since the terminal voltage sampling circuit is actually a low-pass filter with a cutoff frequency of f = 3.6 kHz, when the motor speed approaches the cutoff frequency, the sampled terminal voltage will have a phase lag, thus affecting U. α and U β The value of this value leads to a decrease in the accuracy of the sensorless sliding diaphragm observer. Therefore, when the motor's electrical angular frequency approaches the cutoff frequency f = 3.6 kHz, it will cause a phase lag in the sampled voltage. To avoid this problem, when the motor's angular frequency reaches 1 kHz, it is far from the cutoff frequency f, and the terminal voltage sampling is turned off. The voltage input of the sliding diaphragm observer is changed from the original U... α and U β Switching to the output of the current loop PI controller U α ′ and U β ′。 U α ′ and U β At this point, the dead zone effect is still included. As can be seen from the previous analysis, when the motor speed is very high, the dead zone effect will account for a very small proportion and will not have a significant impact on the output accuracy of the sensorless sliding diaphragm observer.

[0098] 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.

[0099] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A sensorless motor control method to avoid dead zone effects at low speeds, characterized in that, Includes the following steps: S101. The initial values ​​of the motor angle and speed are set to zero in the program; S102. Start the motor, and the entire forc vector control loop will operate stably. S103. Determine if the electric angular velocity frequency is greater than 1 kHz. If it is greater than 1 kHz, proceed to step S301. If it is not greater than 1 kHz, proceed to the following steps: S201. The hardware circuit samples the terminal voltage to obtain the terminal voltage value, and the terminal voltage is calculated by the software to obtain U. α and U β Meanwhile, the forc vector control loop acquires i α and i β The terminal voltage acquisition circuit first calculates the cutoff frequency of the low-pass filter: Where C is capacitance and R is resistance, C = 1 nF. R || These are parallel resistors. MOTOR_U / MOTOR_V / MOTOR_W are the motor terminal voltages, which are the motor terminal voltages relative to DC. - The voltage, and the conversion of the terminal voltage to the phase voltage, are calculated as follows: A. Terminal voltage, phase voltage, and DC - Voltage U at the center point of the motor OO′ Relationship: IN aO =U aO′ +U OO′ IN bO =U bO′ +U OO′ IN cO =U cO′ +U OO′ Among them, U aO U bO U cO U is the sampled terminal voltage; aO′ U bO′ U cO′ U is the phase voltage of the motor; OO′ , is the distance from the motor center point to DC - The voltage; B. Calculation of the relationship between phase voltage and terminal voltage: Adding the three equations together, according to the formula that the sum of the phase voltage amplitudes equals 0, U aO′ +U bO′ +U cO′ =0 Given U aO′ +U bO′ +U cO′ =0, calculated as follows: Given U OO′ The voltages of phases a, b, and c can be calculated: C. Calculation of the relationship between phase voltage and voltages along the alpha and beta axes of the stationary coordinate system: According to the Clark coordinate transformation: IN α =U aO′ D. Calculation of the relationship between phase voltage and terminal voltage: Based on B and C, the following can be calculated: The relationship between the sampled terminal voltage and the alpha and beta axis voltages can be calculated from A, B, C, and D above. S202. Will U α U β and i α i β The probe is fed into the synovial membrane observation device to estimate the angle θ and angular velocity ω. e ; S203, calculate the estimated angle θ and angular velocity ω e The signal is fed into the forc vector control loop to complete the closed-loop control of the motor angle and speed; S301, Current Loop Controller Output U α ′ and U β Meanwhile, the forc vector control loop obtains i α and i β ; S302, U α U β and i α i β The probe is fed into the synovial membrane observation device to estimate the angle θ and angular velocity ω. e ; S303, The estimated angle θ and angular velocity ω e The signal is fed into the FOC vector control loop to complete the closed-loop control of the motor angle and speed.

2. The sensorless motor control method for avoiding dead zone effects at low speeds according to claim 1, characterized in that: In step S301, the relationship between the calculated voltage output by the current loop PI controller and the actual voltage of the motor is as follows: IN α ′=U α +U dead IN β ′=U β +U dead (1) U α ′ and U β ′ is the calculated voltage output of the current loop PI controller, which includes the dead-time effect; U α and U β It is the actual voltage value obtained from the motor terminal, U dead This is the dead zone voltage.

3. The sensorless motor control method for avoiding dead zone effects at low speeds according to claim 1, characterized in that: Steps S202 and S303 further include analyzing the dead zone voltage and its effect on the calculated voltage U when the motor is at high and low speeds. α ′ and U β The impact of ′: From the above formula, we can see that when the motor speed is high, and The value is relatively large, so U α and U β The value is relatively large, and it can be known from formula (1) that when U α and U β When the value is large, the dead zone voltage U dead For calculating voltage U α ′ and U β The proportion of ′ is relatively small, so its impact on the true value is relatively small. Similarly, it can be seen that when the motor angular frequency is low, U α and U β The value is small, and the dead zone voltage U dead For calculating voltage U α ′ and U β The proportion of ' is relatively large, where R is resistance, L is inductance, and Ψ is resistance. r Let ω be the magnetic flux linkage, θ be the rotor angle of the motor, and ω be the rotor angle. e ω is the angular velocity.

4. The sensorless motor control method for avoiding dead zone effects at low speeds according to claim 1, characterized in that: In steps S202 and S303, the synovial observer obtains the angle and angular velocity based on the following voltage equation: Given the input voltage U, input current i, and motor parameters: resistance R, inductance L, and flux linkage Ψ. r The rotor angle θ of the motor is estimated based on the voltage equation, and the speed ω is obtained by differentiating the angle. e .

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