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

Abstract

The invention discloses a motor non-inductive control method for avoiding dead zone influence at a low speed. The method comprises the following steps: S101, setting initial values of a motor angle and a speed as zero in a program; s102, a motor is started, and the whole foc vector control loop operates stably; and S103, judging whether the electrical angular velocity frequency is greater than 1khz or not, if so, entering the step S301, and if not, entering the following steps: S201, carrying out terminal voltage sampling by a hardware circuit to obtain a terminal voltage value, calculating and obtaining U alpha and U beta by terminal voltage software, and meanwhile, obtaining i alpha and i beta by a foc vector control loop. According to the invention, the actual terminal voltage of the motor is acquired through the hardware circuit, so that alpha and beta axis voltages are obtained, the actually sampled voltage does not contain the influence of a dead zone and can be directly input to the sliding mode observer, and the influence of the dead zone on the output of the sliding mode observer is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a motor sensorless control method for avoiding dead zone influence at low speed. Background Art

[0002] There are many existing sensorless control methods, such as sliding film observer, nonlinear flux observer, high-frequency injection, static voltage compensation model, etc., but they all have their limitations. Sensorless low-speed load has always been a difficult problem for sensorless control. For example, in the sliding film observer, in the motor vector control, the input of the sliding film 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 film observer includes the dead zone voltage. Due to 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 give the sliding film observer to estimate the real-time angle and speed of the motor will affect the final estimation accuracy, especially in the low-speed situation, the dead zone influence accounts for a larger proportion, and the angle and speed output by the sliding film observer cannot estimate the actual electrical angle and speed of the motor well, resulting in the motor easily losing step at low speed and difficulty in starting with load. Summary of the invention

[0003] The object of the present invention is to provide a motor sensorless control method that avoids the influence of dead zone at low speed, so as to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a motor sensorless control method for avoiding the influence of dead zone at low speed, comprising the following steps:

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

[0006] S102, start the motor, and the entire foc vector control loop runs stably;

[0007] S103, determine whether the electrical 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 software calculates and obtains U α and U β , while the foc vector control loop obtains i α and i β , the terminal voltage acquisition circuit first calculates the cut-off frequency of the low-pass filter:

[0009]

[0010] Where C is capacitance, R is resistance, C = 1nF, R || is a parallel resistor, MOTOR_U / MOTOR_V / MOTOR_W are the terminal voltages of the motor, which are the motor terminals to DC - The voltage of the terminal is converted to the phase voltage as follows:

[0011] A. Terminal voltage, phase voltage and DC - Voltage U to the motor center 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 is the sampled terminal voltage; U aO' , U bO' , U cO' is the motor phase voltage; U OO' , is the motor center point to DC - Voltage;

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

[0017] The sum of the three equations is equal to 0 according to the phase voltage amplitude, U aO' +U bO' +U cO' =0

[0018] Known U aO' +U bO' +U cO' =0, we get:

[0019]

[0020] Known U OO' The voltage of phases a, b, and c can be calculated:

[0021]

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

[0023] Clark coordinate transformation shows that:

[0024] U α =U aO'

[0025]

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

[0027] Calculate from B and C:

[0028]

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

[0030] S202. Will U α , U β and i α 、i β Sent to the synovial observer to estimate the angle θ and angular velocity ω e ;

[0031] S203, the estimated angle θ and angular velocity ω e Send it into the foc vector control loop to complete the motor angle and speed closed-loop control;

[0032] S301, current loop controller output U α 'and U β ', while the foc vector control loop obtains i α and i β ;

[0033] S302, U α , U β and i α 、i β Sent to the synovial observer to estimate the angle θ and angular velocity ω e ;

[0034] S303: The estimated angle θ and angular velocity ω e It is sent 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:

[0036] U α ′=U α +U dead

[0037] U β ′=U β +Udead # (1)

[0038] U α 'and U β ' is the calculated voltage output by the current loop PI controller, including the dead zone effect; U α and U β It is the voltage value actually obtained at the motor end.

[0039] The steps S202 and S303 also include analyzing the dead zone voltage for the calculated voltage U when the motor is at high and low speeds. α 'and U β 'Impact:

[0040]

[0041] From the above formula, we know that when the motor speed is high, and The value is relatively large, so U α and U β The value is large. According to formula (1), when U α and U β When the value is large, the dead zone voltage U dead For the calculated voltage U α 'and U β ' is relatively small, and has little impact on the true value. Similarly, when the motor angular frequency is low, U α and U β The value is small, the dead zone voltage U dead For the calculated voltage U α 'and U β ' accounts for a relatively large proportion.

[0042] In the steps S202 and S303, the synovial observer obtains the angle and angular velocity based on the following voltage equation:

[0043]

[0044] The input voltage U and input current i as well as the motor parameters are known: resistance R, inductance L and flux linkage Ψ r , according to the voltage equation, the motor rotor angle θ is estimated, and the angle is differentiated to obtain the speed ω e .

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The present invention collects the actual terminal voltage of the motor through a hardware circuit to obtain the alpha and beta axis voltages. The actually sampled voltage does not include the influence of the dead zone and can be directly input into the synovial observer, thus avoiding the influence of the dead zone on the output of the synovial observer and obtaining a higher precision angle and angular velocity. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a control flow diagram of the present invention;

[0048] Figure 2 This is the motor foc vector control block diagram of the present invention;

[0049] Figure 3 It is a schematic diagram of input and output of the synovial membrane observer of the present invention;

[0050] Figure 4 This is the circuit diagram of the terminal voltage collection of the present invention. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] See also Figure 1-4 The present invention provides a technical solution: a motor sensorless control method for avoiding the influence of dead zone at low speed, comprising the following steps:

[0053] S101, set the initial values ​​of the motor angle and speed to zero in the program;

[0054] S102, start the motor, and the entire foc vector control loop runs stably;

[0055] S103, determine whether the electrical 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:

[0056] S201, the hardware circuit samples the terminal voltage to obtain the terminal voltage value, and the terminal voltage software calculates and obtains U α and U β At the same time, the foc vector control loop obtains i α and i β ;

[0057] S202. Will U α , U β and i α 、i βSent to the synovial observer to estimate the angle θ and angular velocity ω e ;

[0058] S203, the estimated angle θ and angular velocity ω e Send it into the foc vector control loop to complete the motor angle and speed closed-loop control;

[0059] S301, current loop controller output u α 'and u β ', while the foc vector control loop obtains i α and i β ;

[0060] S302, U α 、u β and i α 、i β Sent to the synovial observer to estimate the angle θ and angular velocity ω e ;

[0061] S303: The estimated angle θ and angular velocity ω e It is sent into the foc vector control loop to complete the closed-loop control of the motor angle and speed.

[0062] Figure 4 For the terminal voltage acquisition circuit, first calculate the cutoff frequency of the low-pass filter:

[0063]

[0064] Where C is the capacitance, R is the resistance, C = 1nF, R || is a parallel resistor.

[0065] MOTOR_U / MOTOR_V / MOTOR_W are the terminal voltages of the motor, which are the voltages of the motor terminals to DC - voltage.

[0066] 1. The terminal voltage is converted to phase voltage and calculated as follows:

[0067] A. Terminal voltage, phase voltage and DC - Voltage U to the motor center OO' Relationship

[0068] U aO =U aO' +U OO'

[0069] U bO =U bO' +U OO'

[0070] U cO =UcO' +U OO'

[0071] Among them U aO , U bO , U cO is the sampled terminal voltage; U aO' , U bO' , U cO' is the motor phase voltage; U OO' , is the motor center point to DC - voltage.

[0072] B. Calculation of the relationship between phase voltage and terminal voltage

[0073] The sum of the three equations is equal to 0 according to the phase voltage amplitude, U aO' +U bO' +U cO' =0

[0074] Known U aO' +U bO' +U cO' =0, we can calculate:

[0075]

[0076] Known U OO' The voltage of phases a, b, and c can be calculated:

[0077]

[0078] C. Calculation of the relationship between phase voltage and alpha and beta axis voltages in the stationary coordinate system

[0079] Clark coordinate transformation shows that:

[0080] U α =U aO'

[0081]

[0082] D. Calculation of the relationship between phase voltage and terminal voltage

[0083] According to (2) and (3), we can calculate:

[0084]

[0085] From the above A to D, the relationship between the sampled terminal voltage and the alpha and beta axis voltages can be calculated.

[0086] 2. Relationship between the calculated voltage output by the current loop PI controller and the actual voltage of the motor:

[0087] U α ′=Uα +U dead

[0088] U β ′=U β +U dead #(1)

[0089] U α 'and U β ' is the calculated voltage output by the current loop PI controller, including the dead zone effect; U α and U β It is the voltage value actually obtained at the motor end.

[0090] 3. Analyze the dead zone voltage for the calculated voltage U when the motor is at high and low speed α 'and U β 'Impact:

[0091]

[0092] From formula (2), 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 larger. From formula (1), we can know that when U α and U β When the value is large, the dead zone voltage U dead For the calculated voltage U α 'and U β ' is relatively small, and has little impact on the true value. Similarly, when the motor angular frequency is low, U α and U β The value is small, the dead zone voltage U dead For the calculated voltage U α 'and U β ' accounts for a relatively large proportion.

[0093] 4. Analyze the influence of the voltage of the alpha axis and beta axis on the output accuracy of the synovial observer at high and low speeds of the motor:

[0094] The input of the non-sensing sliding film observer is the voltage and current of the alpha axis and the beta axis, and the output is the estimated angle and speed. The input accuracy of the sliding film observer directly affects the accuracy of its output angle and speed. The input voltage of the traditional non-sensing sliding film control method is the U output of the current loop PI controller. α 'and U β ', including the dead zone voltage, due to the low speed U α and U βThe value of is relatively small, and the dead zone accounts for a large proportion, which has a great impact on the output accuracy of the synovial observer. The method of the present invention samples the actual voltage at the motor end and calculates the two-phase stationary coordinate system voltage U α and U β , does not include the dead zone voltage, is the actual voltage at the motor end, and the input voltage of the synovial observer is the actual sampled U α and U β Voltage can improve output accuracy. At low speed, it can avoid the influence of dead zone on the accuracy of output angle and speed of the synovial observer.

[0095] 5. Turn off the terminal voltage sampling circuit at high speed:

[0096] Since the terminal voltage sampling circuit is actually a low-pass filter with a cut-off frequency of f=3.6khz, when the motor speed is close to the cut-off frequency, the sampled terminal voltage will have a phase lag, thus affecting U α and U β Therefore, when the motor electrical angular frequency is close to the cut-off frequency f = 3.6khz, it will cause the sampling voltage phase to lag. In order to avoid this problem, when the motor angular frequency reaches 1khz, it can be far away from the cut-off frequency f, turn off the terminal voltage sampling, and change the voltage input of the synovial observer from the original U α and U β Switch to the current loop PI controller output U α 'and U β '. α 'and U β 'At this time, the dead zone effect is still included. From the above analysis, it can be seen that when the motor speed is very high, the dead zone effect will account for a very small proportion and will have little effect on the output accuracy of the non-sensing sliding film observer.

[0097] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0098] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A motor sensorless control method for avoiding dead zone influence at low speed, characterized in that: The steps include: S101, set the initial values ​​of the motor angle and speed to zero in the program; S102, start the motor, and the entire foc vector control loop runs stably; S103, determine whether the electrical 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 software calculates and obtains U α and U β , while the foc vector control loop obtains i α and i β , the terminal voltage acquisition circuit first calculates the cut-off frequency of the low-pass filter: Where C is capacitance, R is resistance, C = 1nF, R || is a parallel resistor, MOTOR_U / MOTOR_V / MOTOR_W are the terminal voltages of the motor, which are the motor terminals to DC - The voltage of the terminal is converted to the phase voltage as follows: A. Terminal voltage, phase voltage and DC - Voltage U to the motor center 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 is the sampled terminal voltage; U aO' , U bO' , U cO' is the motor phase voltage; U OO' , is the motor center point to DC - Voltage; B. Calculation of the relationship between phase voltage and terminal voltage: The sum of the three equations is equal to 0 according to the phase voltage amplitude, U aO' +U bO' +U cO' =0 Known U aO' +U bO' +U cO' =0, we get: Known U OO' The voltage of phases a, b, and c can be calculated: C. Calculation of the relationship between phase voltage and alpha and beta axis voltages in the stationary coordinate system: Clark coordinate transformation shows that: IN α =U aO' D. Calculation of the relationship between phase voltage and terminal voltage: Calculate from B and C: The relationship between the sampled terminal voltage and the alpha and beta axis voltages is calculated from A, B, C and D above; S202. Will U α 、u β and i α 、i β Sent to the synovial observer to estimate the angle θ and angular velocity ω e ; S203, the estimated angle θ and angular velocity ω e Send it into the foc vector control loop to complete the motor angle and speed closed-loop control; S301, current loop controller output U α 'and U β ', while the foc vector control loop obtains i α and i β ; S302, U α , U β and i α 、i β Sent to the synovial observer to estimate the angle θ and angular velocity ω e ; S303: The estimated angle θ and angular velocity ω e It is sent into the foc vector control loop to complete the closed-loop control of the motor angle and speed.

2. The motor sensorless control method for avoiding dead zone influence at low speed 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: IN α '=U α +U dead IN β '=U β +U dead # (1) U α 'and U β ' is the calculated voltage output by the current loop PI controller, including the dead zone effect; U α and U β It is the voltage value actually obtained at the motor end.

3. The method for controlling a motor without a sense of dead zone at low speed according to claim 1, characterized in that: The steps S202 and S303 also include analyzing the dead zone voltage for the calculated voltage U when the motor is at high and low speeds. α 'and U β 'Impact: From the above formula, we know that when the motor speed is high, and The value is relatively large, so U α and U β The value is large. According to formula (1), when U α and U β When the value is large, the dead zone voltage U dead For the calculated voltage U α 'and U β ' is relatively small, and has little impact on the true value. Similarly, when the motor angular frequency is low, U α and U β The value is small, the dead zone voltage U dead For the calculated voltage U α 'and U β ' accounts for a relatively large proportion.

4. The method for controlling a motor without a sense of dead zone at low speed according to claim 1, characterized in that: In the steps S202 and S303, the synovial observer obtains the angle and angular velocity based on the following voltage equation: The input voltage U and input current i as well as the motor parameters are known: resistance R, inductance L and flux linkage Ψ r , according to the voltage equation, the motor rotor angle θ is estimated, and the angle is differentiated to obtain the speed ω e .

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