Motor and control method and device thereof, storage medium and computer program product

Abstract

The invention discloses a motor and a control method and device thereof, a storage medium and a computer program product, and the method comprises the steps: enabling the actual q-axis current of the motor to be equal to the given q-axis current of the motor, employing a preset current-frequency starting mode, and controlling the open-loop starting of the motor in a speed loop; determining target switching time, switching point q-axis current and a target rotor angle of the motor according to the target torque, the set rotor angular speed and the actual rotor angle of the motor; and in combination with the given q-axis current of the motor, the switching point q-axis current, the target switching time, the actual rotor angle and the target rotor angle, adopting a preset sectional gentle reduction control strategy to control the given q-axis current of the motor to be reduced to the switching point q-axis current of the motor in a sectional manner, and switching from an open loop to a closed loop to realize stable starting of the motor. According to the scheme, the q-axis current is reduced in a three-section gentle slope mode, speed open-loop starting gentle slope smooth switching to closed-loop control is achieved, and the motor is started stably.

Description

Technical Field

[0001] The present invention belongs to the field of motor technology, and specifically relates to a motor control method, device, motor, storage medium and computer program product, and more particularly to a motor start open-loop smooth switching closed-loop control method, device, motor, storage medium and computer program product. Background Art

[0002] In the position sensorless control strategy of the motor (such as permanent magnet synchronous motor) of the related scheme, when the motor is at zero speed starting, the back electromotive force signal is weak and the accuracy of obtaining the rotor position information is limited, making it difficult to achieve a smooth start of the motor.

[0003] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0004] The object of the present invention is to provide a motor control method, device, motor, storage medium and computer program product to solve the problem that it is difficult to achieve smooth starting of the motor when the motor is at zero speed in the position sensorless control strategy of the motor (such as a permanent magnet synchronous motor), so as to achieve the effect of smoothly starting the motor by adopting a three-stage method to reduce the q-axis current in a gentle slope manner, realize the gentle slope smooth switching from the speed open-loop start to the closed-loop control, avoid the current fluctuation of the motor during the closed-loop switching, and make the motor start smoothly.

[0005] The present invention provides a control method for a motor, wherein the control system of the motor has a speed loop and a current loop; the control method for the motor comprises: making the actual q-axis current of the motor equal to the given q-axis current of the motor, and controlling the motor to start in the open loop of the speed loop by adopting a preset current-frequency starting mode; obtaining the target torque of the motor, obtaining the target speed of the motor, obtaining the set rotor angular velocity of the motor, and obtaining the actual rotor angle of the motor; determining the target rotor angle of the motor, the target switching time of the motor, and the switching point q-axis current of the motor according to the target torque of the motor, the target speed of the motor, the set rotor angular velocity of the motor, and the actual rotor angle of the motor; combining the given q-axis current of the motor, the switching point q-axis current of the motor, the target switching time of the motor, the actual rotor angle of the motor, and the target rotor angle of the motor, adopting a preset segmented smooth reduction control strategy, controlling the given q-axis current of the motor to be segmentedly reduced to the switching point q-axis current of the motor, and then controlling the motor to switch from the open loop of the speed loop to the closed loop of the current loop, so as to achieve smooth starting of the motor.

[0006] In some embodiments, the target rotor angle of the motor is determined according to the target torque of the motor, the target speed of the motor, the set rotor angular velocity of the motor, and the actual rotor angle of the motor, the target switching time of the motor is determined, and the switching point q-axis current of the motor is determined, including: determining the target rotor angle of the motor according to the target torque of the motor, the target speed of the motor, and the set rotor angular velocity of the motor; determining the time for the motor to switch from the open loop of the speed loop to the closed loop of the current loop according to the target rotor angle of the motor and the actual rotor angle of the motor, recorded as the target switching time of the motor; and determining the actual q-axis current variable of the motor when the motor switches from the open loop of the speed loop to the closed loop of the current loop, recorded as the switching point q-axis current of the motor.

[0007] In some embodiments, the preset segmented smooth reduction control strategy includes: a smooth reduction control strategy consisting of a first segment, a second segment, and a third segment; in combination with the given q-axis current of the motor, the switching point q-axis current of the motor, the target switching time of the motor, the actual rotor angle of the motor, and the target rotor angle of the motor, the preset segmented smooth reduction control strategy is adopted to control the given q-axis current of the motor to be segmentedly reduced to the switching point q-axis current of the motor, including: in the first segment, according to the given q-axis current of the motor, the switching point q-axis current of the motor, the target rotor angle of the motor, and the target rotor angle of the motor The switching time is controlled to reduce the given q-axis current of the motor in a cosine manner to a first given current variable, which is recorded as the first q-axis current of the motor; in the second section, according to the target switching time of the motor, the first q-axis current of the motor is controlled to be maintained; in the third section, according to the actual rotor angle of the motor and the target rotor angle of the motor, the first q-axis current of the motor is controlled to be linearly reduced to a second given current variable, which is recorded as the second q-axis current of the motor; until the second q-axis current of the motor reaches the switching point q-axis current of the motor, the given q-axis current of the motor is reduced in stages to the switching point q-axis current of the motor.

[0008] In some embodiments, in the first section, according to the given q-axis current of the motor, the switching point q-axis current of the motor, the target rotor angle of the motor, and the target switching time of the motor, the given q-axis current of the motor is controlled to be reduced to a first given current variable in a cosine manner, including: determining a first calculation coefficient times the target switching time of the motor to obtain a first duration; according to the given q-axis current of the motor, the switching point q-axis current of the motor, and the target rotor angle of the motor, calculating the first given current variable according to the following formula to control the actual q of the motor The shaft current is reduced and the duration is the first duration, so as to reduce the actual q-axis current of the motor to a first given current variable: Iq1*=Iq*×cosθ*+k1×(Iq*-Iqs); wherein Iq1* is the first given current variable, Iq* is the given q-axis current of the motor, that is, the target given q-axis current after the motor is started according to the preset current-frequency starting method, θ* is the target rotor angle reached by the motor within a certain period of time according to the given rotor angular velocity of the motor, k1 is the first calculation coefficient, and Iqs is the switching point q-axis current of the motor.

[0009] In some embodiments, in the second section, the power-angle self-balancing principle is utilized to control the first q-axis current of the motor to maintain according to the target switching time of the motor, including: determining a second calculation coefficient times the target switching time of the motor to obtain a second duration; utilizing the power-angle self-balancing principle to control the first q-axis current of the motor to maintain the second duration.

[0010] In some embodiments, in the third section, according to the actual rotor angle of the motor and the target rotor angle of the motor, the first q-axis current of the motor is controlled to be linearly reduced to a second given current variable, recorded as the second q-axis current of the motor; until the second q-axis current of the motor reaches the switching point q-axis current of the motor, the given q-axis current of the motor is reduced in stages to the switching point q-axis current of the motor, including: controlling the first q-axis current of the motor to be linearly reduced to the second q-axis current of the motor; determining the difference between the actual rotor angle of the motor and the target rotor angle of the motor, recorded as the rotor angle error of the motor; determining whether the rotor angle error of the motor is within a set error range; if it is determined that the rotor angle error of the motor is within the set error range, stopping the first q-axis current of the motor from being linearly reduced to the second q-axis current of the motor, and determining that the second q-axis current of the motor reaches the switching point q-axis current of the motor; if it is determined that the rotor angle error of the motor is not within the set error range, returning to continue controlling the first q-axis current of the motor to be linearly reduced to the second q-axis current of the motor.

[0011] Matching the above method, the present invention provides a control device for a motor on the other hand, wherein the control system of the motor has a speed loop and a current loop; the control device for the motor comprises: a control unit, configured to make the actual q-axis current of the motor equal to the given q-axis current of the motor, and adopt a preset current-frequency starting method to control the open-loop starting of the motor in the speed loop; an acquisition unit, configured to acquire the target torque of the motor, acquire the target speed of the motor, acquire the set rotor angular velocity of the motor, and acquire the actual rotor angle of the motor; the control unit is also configured to acquire the target torque of the motor, the target speed of the motor, the set rotor angular velocity of the motor, and the actual rotor angle of the motor according to the target torque of the motor, the target speed of the motor, and the current loop of the motor; The rotor angular velocity and the actual rotor angle of the motor are set, the target rotor angle of the motor is determined, the target switching time of the motor is determined, and the switching point q-axis current of the motor is determined; the control unit is also configured to combine the given q-axis current of the motor, the switching point q-axis current of the motor, the target switching time of the motor, the actual rotor angle of the motor, and the target rotor angle of the motor, and adopt a preset segmented smooth reduction control strategy to control the given q-axis current of the motor to be segmentedly reduced to the switching point q-axis current of the motor, and then control the motor to switch from the open loop of the speed loop to the closed loop of the current loop to achieve smooth starting of the motor.

[0012] In some embodiments, the control unit determines the target rotor angle of the motor, the target switching time of the motor, and the switching point q-axis current of the motor according to the target torque of the motor, the target speed of the motor, the set rotor angular velocity of the motor, and the actual rotor angle of the motor, including: determining the target rotor angle of the motor according to the target torque of the motor, the target speed of the motor, and the set rotor angular velocity of the motor; determining the time for the motor to switch from the open loop of the speed loop to the closed loop of the current loop according to the target rotor angle of the motor and the actual rotor angle of the motor, recorded as the target switching time of the motor; and determining the actual q-axis current variable of the motor when the motor switches from the open loop of the speed loop to the closed loop of the current loop, recorded as the switching point q-axis current of the motor.

[0013] In some embodiments, the preset segmented smooth reduction control strategy includes: a smooth reduction control strategy consisting of a first segment, a second segment, and a third segment; the control unit, in combination with the given q-axis current of the motor, the switching point q-axis current of the motor, the target switching time of the motor, the actual rotor angle of the motor, and the target rotor angle of the motor, adopts the preset segmented smooth reduction control strategy to control the given q-axis current of the motor to be segmentedly reduced to the switching point q-axis current of the motor, including: in the first segment, according to the given q-axis current of the motor, the switching point q-axis current of the motor, the target rotor angle of the motor, and the actual rotor angle of the motor According to the target switching time of the motor, the given q-axis current of the motor is controlled to be reduced to a first given current variable in a cosine manner, which is recorded as the first q-axis current of the motor; in the second section, according to the target switching time of the motor, the first q-axis current of the motor is controlled to be maintained; in the third section, according to the actual rotor angle of the motor and the target rotor angle of the motor, the first q-axis current of the motor is controlled to be linearly reduced to a second given current variable, which is recorded as the second q-axis current of the motor; until the second q-axis current of the motor reaches the switching point q-axis current of the motor, the given q-axis current of the motor is reduced to the switching point q-axis current of the motor in a segmented manner.

[0014] In some embodiments, the control unit, in the first section, controls the given q-axis current of the motor to be reduced to a first given current variable in a cosine manner according to the given q-axis current of the motor, the switching point q-axis current of the motor, the target rotor angle of the motor, and the target switching time of the motor, including: determining a first calculation coefficient times the target switching time of the motor to obtain a first duration; calculating the first given current variable according to the following formula according to the given q-axis current of the motor, the switching point q-axis current of the motor, and the target rotor angle of the motor, and controlling the motor The actual q-axis current of the motor is reduced and the duration is the first duration, so as to reduce the actual q-axis current of the motor to a first given current variable: Iq1*=Iq*×cosθ*+k1×(Iq*-Iqs); wherein Iq1* is the first given current variable, Iq* is the given q-axis current of the motor, that is, the target given q-axis current after the motor is started according to the preset current-frequency starting method, θ* is the target rotor angle reached by the motor within a certain period of time according to the given rotor angular velocity of the motor, k1 is the first calculation coefficient, and Iqs is the switching point q-axis current of the motor.

[0015] In some embodiments, the control unit, in the second section, utilizes the power-angle self-balancing principle to control the first q-axis current of the motor to maintain according to the target switching time of the motor, including: determining a second calculation coefficient times the target switching time of the motor to obtain a second duration; utilizing the power-angle self-balancing principle to control the first q-axis current of the motor to maintain the second duration.

[0016] In some embodiments, the control unit, in the third section, controls the first q-axis current of the motor to linearly decrease to a second given current variable, recorded as the second q-axis current of the motor, according to the actual rotor angle of the motor and the target rotor angle of the motor; until the second q-axis current of the motor reaches the switching point q-axis current of the motor, the given q-axis current of the motor is reduced to the switching point q-axis current of the motor in stages, including: controlling the first q-axis current of the motor to linearly decrease to the second q-axis current of the motor; determining the difference between the actual rotor angle of the motor and the target rotor angle of the motor, recorded as the rotor angle error of the motor; determining whether the rotor angle error of the motor is within a set error range; if it is determined that the rotor angle error of the motor is within the set error range, stopping the first q-axis current of the motor from linearly decreasing to the second q-axis current of the motor, and determining that the second q-axis current of the motor reaches the switching point q-axis current of the motor; if it is determined that the rotor angle error of the motor is not within the set error range, returning to continue controlling the first q-axis current of the motor to linearly decrease to the second q-axis current of the motor.

[0017] Matching the above device, the present invention further provides a motor, including: the control device of the motor described above.

[0018] In accordance with the above method, the present invention provides a storage medium on the other hand, wherein the storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the steps of the motor control method described above.

[0019] In accordance with the above method, the present invention further provides a computer program product, comprising a computer program, which implements the steps of the above motor control method when executed by a processor.

[0020] Therefore, the scheme of the present invention adopts a three-stage reduction method to reduce Iq* during the time when Iq* decreases to the closed-loop actual q-axis current variable Iqs when the motor starts and runs to the q-axis current Iq* given by the target open-loop current: the first stage first reduces it in a cosine manner, and the reduction time is 3 / 4Ts, and it is reduced to Iq1*; the second stage maintains the size of Iq1* for 1 / 8Ts; the third stage makes Iq1* linearly reduce, and when the rotor angle error is less than the set error (such as ±5%), Iq1* is reduced to Iq2*, that is, it is reduced from Iq* to Iqs, and then switched to closed-loop control; thus, when the motor starts and runs to the q-axis current given by the target open-loop current, in the process of switching from open loop to closed loop, the q-axis current is reduced in a gentle slope manner by adopting a three-stage method, so as to realize the smooth switching of the speed open-loop start-up gentle slope to the closed-loop control, avoid the current fluctuation of the motor during the switching of the closed loop, and make the motor start smoothly.

[0021] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic flow chart of an embodiment of a method for controlling a motor of the present invention;

[0024] Figure 2 A schematic flow chart of an embodiment of determining a target switching time of the motor, a switching point q-axis current of the motor, and a target rotor angle of the motor in the method of the present invention;

[0025] Figure 3 A schematic flow chart of an embodiment of controlling the given q-axis current of the motor to be reduced in stages to the switching point q-axis current of the motor in the method of the present invention;

[0026] Figure 4 A schematic flow chart of an embodiment of the method of the present invention for controlling the given q-axis current of the motor to be reduced to a first given current variable in a cosine manner;

[0027] Figure 5 A schematic diagram of a flow chart of an embodiment of controlling the first q-axis current of the motor to be maintained in the method of the present invention;

[0028] Figure 6 A flow chart of an embodiment of controlling the first q-axis current of the motor to be linearly reduced to a second given current variable in the method of the present invention;

[0029] Figure 7A schematic structural diagram of an embodiment of a control device for a motor of the present invention;

[0030] Figure 8 It is a flow chart of a novel three-stage open-loop gentle slope smooth switching closed-loop control method;

[0031] Fig. 9 It is a curve diagram of the change of the new three-stage open-loop gentle slope smooth switching closed-loop q-axis current;

[0032] Fig.10 It is a curve diagram of the angle change of the motor control rotating coordinate system (power-angle self-balancing);

[0033] Fig.11 This is a schematic diagram of the control principle of the speed loop open-loop gentle slope smooth switching current loop closed-loop control system.

[0034] In conjunction with the accompanying drawings, the reference numerals in the embodiments of the present invention are as follows:

[0035] 102 - acquisition unit; 104 - control unit. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. 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 making creative work are within the scope of protection of the present invention.

[0037] Considering that in the position sensorless control strategy of the motor (such as the permanent magnet synchronous motor), it is difficult to achieve a smooth start of the motor when the motor is at zero speed. Therefore, other methods are usually required to obtain the precise rotor position. The commonly used methods include I / F (i.e. current / frequency) start. The I / F control of the relevant scheme includes the open loop of the speed loop and the closed loop of the current loop. In the I / F start strategy, within a certain period of time when the speed loop open loop switches to the current loop closed loop, when the two values ​​are very different, if the algorithm does not handle this, it is very easy to cause violent oscillations in the speed and torque of the motor at the moment of switching, resulting in overshoot of the starting current and drastic changes in the speed, which in turn causes the motor to jitter and lose steps, which may eventually lead to motor start failure and even affect the service life of the chip (such as the chip in the motor controller) and the motor.

[0038] In the I / F starting strategy, the goal of the open-loop stage is to set the maximum output torque value of the motor and convert it into the maximum value of the q-axis current Iq*, which is used as the given value of the q-axis current to achieve the strong drag start of the motor. At the same time, the system presets the open-loop angular velocity ωr* and the time Ts for switching from open-loop to closed-loop control. When the motor reaches the preset closed-loop speed, the position observer can accurately detect the rotor angular position, and the system switches from open-loop control to closed-loop control. However, within a certain period of time when the speed loop switches from the open-loop to the current loop, since the rotation angle changes from the open-loop given angle to the observation angle of the position sensorless algorithm, when the open-loop switches to the closed-loop, Iq (i.e., the q-axis current) also switches from the given Iq* to the actual Iq of the closed loop. When the two values ​​differ greatly, if the algorithm does not handle this, it is very easy to cause violent oscillations in the speed and torque of the motor at the moment of switching, resulting in overshoot of the starting current and drastic changes in the speed, which in turn causes the motor to shake and lose steps, which may eventually lead to motor startup failure and even affect the service life of the chip (such as the chip in the motor controller) and the motor.

[0039] Some schemes propose a method for smooth start-up control of a position sensorless vector-controlled permanent magnet synchronous motor: when the actual steady-state speed V of the motor reaches the first target speed V_ref1, it enters the constant speed closed-loop control mode; in the constant speed closed-loop control stage, the q-axis current PI control loop is used to slowly converge the q-axis real-time detection current value Iq1 to Iq0; in the speed closed-loop control mode, the first target speed V_ref1 is raised to the maximum target speed V_max to control the motor operation, and then enters the constant torque control mode. However, this scheme does not design a method for reducing the open-loop given Iq, but mainly uses the Iq reduction method of the related scheme, taking the speed as a reference, and linearly reducing the size of the q-axis given current. Therefore, there is still a problem of a large difference between the given q-axis current and the actual q-axis current.

[0040] Therefore, the scheme of the present invention proposes a control method for a motor, specifically a control method for smoothly switching between open-loop and closed-loop at motor startup. During the period of switching between open-loop and closed-loop, a new three-stage control scheme of gently sloped and smoothly reducing the q-axis current is adopted, that is, the first stage uses a cosine method to reduce the given q-axis current Iq* to Iq1*, the second stage maintains Iq1*, and the third stage adopts a linear reduction strategy to achieve a smooth decrease of Iq1*. When the rotor angle error (that is, the error between the given rotor angle and the actual rotor angle) is within ±5%, it switches to closed-loop control to ensure the efficiency and stability of the entire process control system, so that the motor can smoothly and gently reduce the given q-axis current Iq* within the time of switching between the speed open-loop and the current loop closed-loop, so as to achieve the purpose of extremely small current and speed fluctuations when the motor starts, stable control system, and jitter-free startup, thereby achieving smooth starting of the motor.

[0041] The novel three-stage q-axis current reduction control strategy adopted in the scheme of the present invention is mainly aimed at reducing Iq* more smoothly in a short period of time when the open-loop switches to the closed-loop, without causing sudden changes in the system, and more accurately close to the actual Iq value, so as to achieve jitter-free starting of the motor. The open-loop reduction of the given q-axis current Iq* to the closed-loop q-axis current in the related scheme is usually linear, which may cause instability or oscillation of the control system due to the sudden change of Iq* because the drop is too fast. The scheme of the present invention adopts a novel three-stage reduction of the given q-axis current to achieve the stability of the control system during switching, and avoid the current fluctuation of the motor during the closed-loop switching, which may cause the motor to lose step or jitter, and make a lot of noise.

[0042] According to an embodiment of the present invention, a method for controlling a motor is provided. Figure 1 A flow chart of an embodiment of the method of the present invention is shown. The control system of the motor has a speed loop and a current loop; Fig.11 This is a schematic diagram of the control principle of the speed loop open-loop gentle slope smooth switching current loop closed-loop control system. Fig.11 In the example shown, the three-phase currents ia, ib, and ic of the motor are collected from the three-phase power supply line between the inverter and the motor. The three-phase currents ia, ib, and ic are transformed by Clark (i.e., the signals in the three-phase abc coordinate system are converted to the two-phase αβ coordinate system) to obtain the αβ axis currents iα and iβ. The αβ axis currents iα and iβ are transformed by Park to obtain the dq axis currents Id and Iq. The αβ axis currents iα and iβ are passed through the rotor and position estimation modules to obtain the speed ω and rotor angle θ. In the speed loop, Iq* and ωr* are obtained after the I / F control module, and ωr* is transformed by 1 / S (i.e., Laplace transformation) to obtain θ*. In the current loop, Iq*, Iq, ω are processed by the first comparator and the first PI module to obtain the q-axis voltage Vq, Id*=0, Id are processed by the second comparator and the second PI module to obtain the d-axis voltage Vd, Vd, Vq, θ are processed by the inverse Park transform and SVPWM (i.e., motor space vector control) to obtain the three-phase voltage Va, Vb, Vc and then input to the inverter. Among them, Park transform is to project the a, b, c three-phase current of the stator onto the direct axis (d axis) rotating with the rotor, the quadrature axis (q axis) and the zero axis (0 axis) perpendicular to the dq plane, thereby realizing the diagonalization of the stator inductance matrix and simplifying the operation analysis of the synchronous motor. Among them, ω is the mechanical speed, ωr is the electrical angular velocity, and ωr* is the given preset electrical angular velocity.

[0043] In the scheme of the present invention, Figure 1 As shown, the motor control method includes: step S110 to step S140.

[0044] In step S110, the actual q-axis current of the motor is set to be equal to the given q-axis current of the motor, and a preset current-frequency starting method is adopted to control the open-loop starting of the motor in the speed loop; wherein, the given q-axis current of the motor is such as Iq*, and the actual q-axis current of the motor is obtained such as Iq.

[0045] At step S120, when the motor is started by using a preset current-frequency start-up method in the open loop of the speed loop, the target torque of the motor is obtained, the target speed of the motor is obtained, the set rotor angular velocity of the motor (such as ωr*) is obtained, and the actual rotor angle of the motor (such as θ) is obtained. In addition, the load torque Tl is a fixed load value in the test and actual operation environment.

[0046] In step S130, the target switching time (such as Ts) of the motor is determined according to the target torque of the motor, the target speed of the motor, the set rotor angular velocity of the motor, and the actual rotor angle of the motor, the switching point q-axis current of the motor (such as Iqs) is determined, and the target rotor angle of the motor (such as the rotor angle θ* calculated in the open loop) is determined.

[0047] In some embodiments, the specific process of determining the target switching time (such as Ts) of the motor, determining the switching point q-axis current of the motor, and determining the target rotor angle (such as the rotor angle θ* calculated in the open loop) of the motor in step S130 is described in the following exemplary embodiment according to the target torque of the motor, the target speed of the motor, the set rotor angular velocity of the motor, and the actual rotor angle of the motor.

[0048] Combine the following Figure 2 The method of the present invention is shown as a flow chart of an embodiment of determining the target switching time of the motor, the q-axis current at the switching point of the motor, and the target rotor angle of the motor, further illustrating the specific process of determining the target switching time of the motor, the q-axis current at the switching point of the motor, and the target rotor angle of the motor in step S130, including: steps S210 to S220.

[0049] Step S210, determining the target rotor angle of the motor (such as the rotor angle θ* calculated in an open loop) according to the target torque of the motor, the target speed of the motor, and the set rotor angular velocity of the motor; the target rotor angle of the motor is the given rotor angle of the motor, and the initial value of the given rotor angle of the motor, that is, the initial position of the given rotor angle of the motor is θ* equal to 0.

[0050] Step S220, according to the target rotor angle of the motor and the actual rotor angle of the motor, determine the time (such as Ts) for the motor to switch from the open loop of the speed loop to the closed loop of the current loop, recorded as the target switching time (such as Ts) of the motor; and determine the actual q-axis current variable of the motor when the motor switches from the open loop of the speed loop to the closed loop of the current loop, recorded as the switching point q-axis current of the motor. Among them, the time to switch into the closed loop is determined when the error between the set rotor angular velocity θ* of the motor calculated according to the given parameters and the actual rotor angle θ of the motor calculated by the position observer is less than ±5%.

[0051] Specifically, Figure 8 As shown, the novel three-stage open-loop gentle slope smooth switching closed-loop control method includes: step 1, 1 / F open-loop strong drag start motor stage, set the rotor angular velocity to ωr; q-axis current: Iq = Iq*; d-axis current: Id = 0, rotor initial angle: θ = 0; according to the target torque and speed, set the speed open-loop switching closed-loop time to Ts, the closed-loop target q-axis current to Iqs (Iqs and Iq2* are related), and then perform step 2. The reduction time of the first stage is t1 (i.e. 3 / 4Ts), at this time, it decreases from Iq* to the value of Iq1*, Iq1* = Iq* × cosθ* + k1 × (Iq*-Iqs), such as Iq1* = Iq* × cosθ* + 3 / 4 × (Iq*-Iqs), θ* = ωr × t1, θ*∈(0,π / 2).

[0052] Figure 8 It is a flow chart of a new three-stage open-loop gentle slope smooth switching closed-loop control method. Fig.10 It is a curve diagram of the angle change of the motor control rotating coordinate system (power-angle self-balancing). In the scheme of the present invention, the adjustment of the q-axis current during the speed open-loop switching speed closed-loop adopts a new three-stage control strategy for reducing the q-axis current (i.e., three-stage reduction of Iq*). In the scheme of the present invention, the change of the q-axis current during the speed open-loop switching speed closed-loop is a gentle decrease of Iq* from the open-loop to the closed-loop time. The related schemes are basically switching directly or in a linear reduction switching mode. It can be seen that Fig. 9 It is shown that the scheme of the present invention is to reduce Iq* by cosine according to the rotor angle change calculated by the virtual coordinate system, and during the second stage of maintaining Iq1*, the motor's characteristic "power-angle self-balancing" is used to reduce the error of the rotor angle, and the speed is stable. The linear direct switching in the related scheme is performed. The difference is that the linear switching in the third stage is smaller than the linear switching of the related scheme, and the error between Iq* and the closed-loop Iqs is smaller, and the open-loop switching and closed-loop switching of the motor control system are more stable.

[0053] Fig. 9It is a curve diagram of the new three-stage open-loop gentle slope smooth switching closed-loop q-axis current change. Fig.11 The following is a general control diagram of a motor control system. Fig. 9 The schematic changes shown in the figure are as follows: the rotor angle information obtained by speed and position estimation is input into Fig.11 In the control system PID (i.e., in process control, control is performed according to the proportion P, integral I and differential D of the deviation) and inverse Park transformation shown, the virtual coordinate system rotor angle calculated by the given Iq* in the system open loop is compared with the calculated error. The calculation and conversion of various motor data can be carried out by the calculation means of the relevant scheme, and the motor control principle can be consulted. For example: the target current of the open-loop start-up is converted into the maximum value of the q-axis current as Iq* by converting the maximum output torque value of the motor, which can be obtained by calculation according to the motor control principle (such as the following formula).

[0054] Te = 1.5P × iq × Ψf;

[0055] Iq>(Tl+F×ω+Tf+J×dω / dt) / (1.5P×Ψf).

[0056] Among them, Te is the electromagnetic torque, P is the number of pole pairs, ψf is the magnetic flux of the motor, Tl is the load torque, F is the viscous damping, Tf is the static friction, and J is the motor moment of inertia.

[0057] At step S140, in combination with the given q-axis current of the motor, the switching point q-axis current of the motor, the target switching time of the motor, the actual rotor angle of the motor, and the target rotor angle of the motor, a preset segmented smooth reduction control strategy is adopted to control the given q-axis current of the motor to be reduced segmentally to the switching point q-axis current of the motor, and then the motor is controlled to switch from the open loop of the speed loop to the closed loop of the current loop to achieve smooth starting of the motor.

[0058] The scheme of the present invention proposes a three-stage gentle reduction control scheme for the q-axis current of the motor during the period of switching from open loop to closed loop, so that the q-axis current can be reduced in a gentle slope manner, and the motor can be started without jitter. In the scheme of the present invention, a new three-stage gentle slope control scheme for smoothly reducing the q-axis current is adopted, that is, the first stage cosine mode is used to reduce the given q-axis current Iq* to Iq1*, and the gentle slope reduction in the initial stage effectively avoids the sudden change of the system response; the second stage maintains Iq1* to provide a stable operating environment for the system; the third stage adopts a linear reduction strategy to achieve a smooth decline of Iq1*, and when the rotor angle error (that is, the error between the given rotor angle and the actual rotor angle) is ±5%, it switches to closed-loop control to ensure the efficiency and stability of the entire process control system, and realizes that the motor can smoothly and gently reduce the given q-axis current Iq* within the time of switching from speed open loop to current loop closed loop, so as to achieve the purpose of extremely small current and speed fluctuations when the motor starts, stable control system, and jitter-free start, and realize the smooth start of the motor. Thus, the stability and jitter of the system speed during motor startup are effectively optimized, providing a more stable and reliable control system for motor startup, achieving startup with minimal speed fluctuation and no jitter. In addition, the control strategy solves the problem of large difference between the given and actual q-axis current during the control system's open-loop switching to closed-loop control, resulting in current shock and high noise, thus avoiding motor startup failure and loss of motor service life.

[0059] In some embodiments, the preset segmented gentle reduction control strategy includes: a gentle reduction control strategy consisting of a first segment, a second segment, and a third segment. In step S130, in combination with the given q-axis current of the motor, the switching point q-axis current of the motor, the target switching time of the motor, the actual rotor angle of the motor, and the target rotor angle of the motor, the preset segmented gentle reduction control strategy is used to control the specific process of the given q-axis current of the motor to be segmentedly reduced to the switching point q-axis current of the motor, see the following exemplary description.

[0060] Combine the following Figure 3 The method of the present invention is shown as a flow chart of an embodiment of controlling the given q-axis current of the motor to be reduced in sections to the switching point q-axis current of the motor, further illustrating the specific process of controlling the given q-axis current of the motor to be reduced in sections to the switching point q-axis current of the motor in step S140, including: steps S310 to S330.

[0061] Step S310, in the first section, according to the given q-axis current of the motor, the switching point q-axis current of the motor, the target rotor angle of the motor, and the target switching time of the motor, the given q-axis current of the motor is controlled to be reduced to a first given current variable (such as Iq1*) in a cosine manner, which is recorded as the first q-axis current of the motor (such as Iq1*).

[0062] In some embodiments, in step S310, in the first section, the specific process of controlling the given q-axis current of the motor to be reduced to the first given current variable in a cosine manner according to the given q-axis current of the motor, the switching point q-axis current of the motor, the target rotor angle of the motor, and the target switching time of the motor is described in the following exemplary description.

[0063] Combine the following Figure 4 The method of the present invention is shown as a flow chart of an embodiment of controlling the given q-axis current of the motor to be reduced to the first given current variable in a cosine manner, further illustrating the specific process of controlling the given q-axis current of the motor to be reduced to the first given current variable in a cosine manner in step S310, including: steps S410 to S420.

[0064] Step S410, determining the first calculation coefficient times the target switching time of the motor to obtain a first duration; that is, the first duration is the first calculation coefficient times the target switching time of the motor. The target switching time of the motor is Ts, the first calculation coefficient is 3 / 4, and the second duration is t1=3 / 4Ts.

[0065] Step S420, according to the given q-axis current of the motor, the switching point q-axis current of the motor, and the target rotor angle of the motor, a first given current variable is calculated according to the following formula, and the actual q-axis current of the motor is controlled to decrease for a duration of the first duration, so as to reduce the actual q-axis current of the motor to the first given current variable:

[0066] Iq1*=Iq*×cosθ*+k1×(Iq*-Iqs);

[0067] Among them, Iq1* is the first given current variable, Iq* is the given q-axis current of the motor, that is, the target given q-axis current after the motor is started according to the preset current-frequency starting method, θ* is the target rotor angle reached by the motor within a certain time according to the given rotor angular velocity of the motor, that is, θ*=ωr×t1; k1 is the first calculation coefficient, and Iqs is the switching point q-axis current of the motor.

[0068] Specifically, Figure 8 As shown, the new three-stage open-loop gentle slope smooth switching closed-loop control method also includes: step 2, after the q-axis current Iq open-loop start-up is forcibly dragged to a given value Iq*, the first stage of the new three-stage open-loop smooth switching closed-loop control stage is entered, Iq* is gently reduced in a cosine manner, the reduction time is t1 (3 / 4Ts), the variable Iq1* is given in real time, and then step 3 is executed.

[0069] In step 2, the first section of the open-loop q-axis current Iq* cosine decreases.

[0070] In such Fig. 9 In the example shown, the speed loop open-loop I / F starts the motor for a period of time, and the q-axis current reaches the target open-loop current value Iq*. At this time, the Iq* of the relevant scheme will be directly linearly reduced according to the target closed-loop Iq, but this method is very prone to the problem of a large difference between the given q-axis current Iq* and the actual Iq. Therefore, in the scheme of the present invention, the first section Iq* is smoothly reduced to Iq1* in a cosine manner, and the cosine change angle is related to the given rotor angle change. The open-loop given angular velocity is ωr (θ=ωrT, T is time), and the reduction time of the first stage is t1 (i.e. 3 / 4Ts). At this time, the value from Iq* to Iq1* is Iq1*=Iq*×cosθ*+k1×(Iq*-Iqs), such as Iq1*=Iq*×cosθ*+3 / 4×(Iq*-Iqs), θ*=ωr×t1, θ*∈(0,π / 2). This cosine change control strategy can not only ensure the smooth decline of Iq* and avoid the uncertainty caused by large fluctuations, but also more accurately predict and track the change trend of the actual Iq, thereby significantly improving the stability and response speed of the motor system. Among them, when the motor is stationary, the back electromotive force signal is weak, and the accuracy of obtaining the rotor position information is limited. After the motor is started, the position observer can calculate the actual motor rotor position angle, and the actual q-axis current value, that is, Iqs, can be calculated according to the calculation formula of the motor control principle.

[0071] In the scheme of the present invention, when the q-axis current of the motor starts and reaches the given q-axis current Iq*, the open-loop control system enters the first stage of gentle slope smooth switching, and the given q-axis current Iq* decreases with the cosine amplitude, and the cosine reduction angle is related to the given rotor angle change. The angular velocity of the open-loop control is ωr*, and the actual rotor angle θ=ωr×T, where T represents time; and the reduction time t1 of the first stage is set to 3 / 4Ts. During this period, the q-axis current Iq of the motor will be smoothly reduced from the initial value Iq* to Iq1*, and the calculation formula is Iq1*=Iq*×cosθ*+k1×(Iq*-Iqs), such as Iq1*=Iq*×cosθ*+3 / 4×(Iq*-Iqs), where the open-loop rotor angle θ*=ωr×t1, and the value range of θ* is (0,π / 2). By designing the cosine variation of the Iq* value, it is possible to ensure that the motor system is adjusted in a smoother manner under open-loop control, thereby more closely matching the actual motor operating state. This method effectively avoids the problems of unstable motor speed, jitter caused by current mutations, and increased noise caused by large fluctuations in the given q-axis current Iq* value, and significantly improves the stability and efficiency of motor operation. Among them, Iqs is the closed-loop actual q-axis current variable, Ts is the time for switching from open-loop to closed-loop control, θ is the actual rotor angle monitored by the position observer, θ* is the rotor angle calculated in the open loop, ωr* is the angular velocity of the open-loop control, and ωr is the set rotor angular velocity.

[0072] Step S320: In the second section, controlling the first q-axis current of the motor to be maintained according to the target switching time of the motor.

[0073] In some implementations, in step S320, in the second section, the specific process of controlling the first q-axis current of the motor to maintain according to the target switching time of the motor is described in the following exemplary embodiment.

[0074] Combine the following Figure 5 The flowchart of an embodiment of controlling the maintenance of the first q-axis current of the motor in the method of the present invention further illustrates the specific process of controlling the maintenance of the first q-axis current of the motor in step S320, including: steps S510 to S520.

[0075] Step S510, determining a second calculation coefficient times the target switching time of the motor to obtain a second duration; wherein the target switching time of the motor is such as Ts, the second calculation coefficient is such as 1 / 8, and the second duration is such as t2=1 / 8Ts.

[0076] Step S520: utilizing the power-angle self-balancing principle to control the first q-axis current of the motor to maintain the second duration.

[0077] Specifically, Figure 8As shown, the new three-stage open-loop gentle slope smooth switching closed-loop control method also includes: step 3, at this time, Iq1* is reduced to close to the target closed-loop Iqs, and the second stage of the new three-stage open-loop smooth switching closed-loop control is entered, and the "power-angle self-balancing principle" of the motor is used to maintain the current Iq1* size for a time of 1 / 8Ts. During this period, the open-loop rotor calculation angle and the actual rotor angle are getting closer and closer, the motor speed slowly stabilizes, and the system is stable, and then step 4 is executed.

[0078] Among them, maintaining Iq1* utilizes the power-angle self-balancing principle, the purpose is to reduce the error between the rotor angle θ* of the speed open loop and the θ of the actual position observer in the motor control, and to switch the closed loop control more smoothly. The principle is: the q-axis current Iq* overcomes the load torque and static friction to start the motor rotation, and then the rotor angular velocity continues to increase due to the fixed acceleration, and the viscous resistance will continue to increase. Therefore, the torque required in the q-axis direction continues to increase, but the torque on the q* axis remains unchanged because of the given q-axis current Iq1*. Therefore, in order to achieve force balance, the power angle will continue to increase, thereby increasing the value of iq*cosθ* (* means a given value), that is, the open-loop rotor angle θ* is close to the actual rotor angle θ, the rotor error angle is reduced, and the system speed tends to be stable, thereby achieving the purpose of smooth motor start-up control.

[0079] In step 3, the magnitude of the second open-loop q-axis current Iq1* is maintained.

[0080] In such Fig. 9 In the example shown, when Iq* is reduced to Iq1* in a cosine manner through the control algorithm, if Iq1* is continued to be reduced by cosine, the q-axis current and rotor angle may change rapidly, causing fluctuations in the control system. Therefore, the second control algorithm is added at this time to maintain the size of Iq1* and use the "power-angle self-balancing principle" of the motor, such as Fig.10 In the figure, after the motor is started by I / F strong drag, according to the torque formula Te=Iq×cosθ×1.5P×Ψf, the q-axis current Iq* given by the open-loop control system overcomes the load torque and static friction and starts to rotate when the motor starts. After that, the rotor angular velocity continues to increase due to the fixed acceleration, and the viscous resistance will also continue to increase. Therefore, the torque required in the q-axis direction continues to increase, but the torque on the q* axis remains unchanged because the q-axis current does not change. Therefore, in order to achieve force balance, the power angle will continue to increase, thereby increasing the value of Iq*cosθ, that is, the open-loop rotor angle θ* is infinitely close to the actual rotor angle θ. At this time, the actual motor system control is close to the given control system, and the speed tends to be stable, which is conducive to providing a more efficient and reliable operating environment for closed-loop switching.

[0081] Among them, the power-angle self-balancing principle means that through the power angle self-balancing principle, the angle of the observer is constantly approaching the angle during open-loop strong drag, and finally the observer is cut into the control loop when the two are equal, so as to achieve stable operation of the system. The working mechanism of the power-angle self-balancing principle can be divided into two stages: the initial acceleration stage and the switching stage; in the initial acceleration stage, the speed is increased at a constant acceleration through open-loop strong drag; in the switching stage, relying on the power angle self-balancing principle, the angle of the observer is constantly approaching the angle during open-loop strong drag, and finally the observer is cut into the control loop when the two are equal, so as to achieve stable operation of the system.

[0082] In the scheme of the present invention, when the given q-axis current Iq* is reduced to Iq1* in a cosine manner through the control algorithm, if Iq1* is continuously reduced, it may cause system fluctuations and affect the starting stability of the motor. Therefore, the second stage control algorithm is designed to maintain the size of Iq1* and utilize the "power-angle self-balancing principle" of the motor to stabilize the speed of the motor control system. That is, after the motor is started by I / F strong drag, according to the torque formula Te=Iq×cosθ×1.5P×Ψf, Te is the electromagnetic torque, Iq is the actual q-axis current, P is the number of pole pairs, ψf is the magnetic flux of the motor, and θ is the actual rotor angle monitored by the position observer; when the motor just starts, the q-axis current Iq* given by the open-loop control system overcomes the load torque and static friction and starts to rotate, and then the rotor angular velocity continues to increase due to the fixed acceleration, and the viscous resistance will also continue to increase. Therefore, the torque required in the q-axis direction continues to increase, but the torque on the q-axis remains unchanged because the q-axis current. Therefore, in order to achieve force balance, the power angle will continue to increase, thereby increasing the value of Iq*cosθ, that is, the open-loop rotor angle θ* is close to the actual rotor angle θ, the rotor error angle is reduced, and the system speed tends to be stable, thereby achieving the purpose of smooth motor start-up control.

[0083] Step S330, in the third section, according to the actual rotor angle of the motor and the target rotor angle of the motor, the first q-axis current of the motor is controlled to be linearly reduced to a second given current variable (such as Iq2*), recorded as the second q-axis current of the motor (such as Iq2*); until the second q-axis current of the motor reaches the switching point q-axis current of the motor, the given q-axis current of the motor is reduced in segments to the switching point q-axis current of the motor.

[0084] like Figures 8 to 11As shown, the target current of the open-loop start is converted into the maximum q-axis current value Iq* by using the maximum output torque value of the motor, and the motor is started by open-loop strong drag with the value of Iq* being the given value of the q-axis current. The system presets the open-loop angular velocity ωr*, the time Ts for switching from open-loop to closed-loop control, and the closed-loop actual q-axis current variable is Iqs. When the motor starts and runs to the q-axis current Iq* given by the target open-loop current, a new three-stage control method for reducing Iq* is designed within the time when Iq* decreases to Iqs, so that when Iq* enters the closed loop, the first stage first decreases in a cosine manner, and the reduction time is 3 / 4Ts. The cosine reduction angle is related to the rotor position angle; the second stage maintains the current value of Iq*, that is, the size of Iq1*. By using the power-angle self-balancing principle, the motor speed tends to be stable, and the given calculated rotor angle is close to the actual rotor angle. Finally, entering the third stage, Iq1* decreases linearly. When the rotor angle error is less than ±5%, Iq1* is reduced to Iq2* at this time, and it is immediately switched to closed-loop control, realizing the smooth switching from the speed open-loop start to the closed-loop control with a gentle slope, avoiding the current fluctuation of the motor during the closed-loop switching, causing the motor to lose step or jitter, and reducing noise.

[0085] In some embodiments, in the third section in step S330, according to the actual rotor angle of the motor and the target rotor angle of the motor, the first q-axis current of the motor is controlled to be linearly reduced to a second given current variable, recorded as the second q-axis current of the motor; until the second q-axis current of the motor reaches the switching point q-axis current of the motor, the specific process of implementing the stepwise reduction of the given q-axis current of the motor to the switching point q-axis current of the motor is described in the following exemplary description.

[0086] Combine the following Figure 6 The flowchart of an embodiment of controlling the first q-axis current of the motor to be linearly reduced to a second given current variable in the method of the present invention is shown, further illustrating the specific process of controlling the first q-axis current of the motor to be linearly reduced to a second given current variable in step S330, including: steps S610 to S660.

[0087] Step S610 , controlling the first q-axis current of the motor to linearly decrease to the second q-axis current of the motor.

[0088] Step S620, determining a difference between the actual rotor angle of the motor and the target rotor angle of the motor, which is recorded as the rotor angle error (eg, Δθ) of the motor.

[0089] Step S630, determining whether the rotor angle error of the motor is within a set error range.

[0090] Step S640, if it is determined that the rotor angle error of the motor is within the set error range, stop the first q-axis current of the motor from linearly decreasing to the second q-axis current of the motor, and determine that the second q-axis current of the motor reaches the switching point q-axis current of the motor.

[0091] In step S650 , if it is determined that the rotor angle error of the motor is not within the set error range, the process returns to continue controlling the first q-axis current of the motor to linearly decrease to the second q-axis current of the motor.

[0092] Specifically, Figure 8 As shown, the novel three-stage open-loop gentle slope smooth switching closed-loop control method also includes: step 4, after the Iq1* changes in the first and second stages, Iq* is close to the closed-loop Iqs, and the rotor error angle is reduced. At this time, entering the third stage, Iq1* linearly decreases to Iq2*, and the change of the system q-axis current is not much different and can be reduced more smoothly, and then step 5 is executed.

[0093] In step 4, the third segment linearly decreases the q-axis current.

[0094] As Fig. 9 In the example shown, after maintaining Iq1* for a certain period of time (t1-t2, i.e. 1 / 8Ts), the motor system quickly adjusts the error between the given parameters and the actual parameters, the speed fluctuation is small and the rotor angle error is reduced, and the given Iq1* value is close to the actual motor q-axis current Iqs value; t1 here is the same as t1 in the first stage. At this time, entering the third stage, Iq1* linearly decreases to Iqs, such as Fig. 9 As shown, the linear reduction here is a direct reduction, from one value directly to another value; based on the reduction control of the previous two sections of the q-axis given current, the third section linearly reduces the given q-axis current Iq*, which can efficiently and stably achieve the switching of the given q-axis current to the closed-loop q-axis current. Fig.11 As shown, during the linear reduction, when the error between the actual rotor angle θ monitored by the position observer and the rotor angle θ* calculated by the open loop is within ±5%, the control system directly switches from the speed loop open-loop control to the current loop closed-loop control, thus completing the new three-stage control of reducing the given current of the q-axis and achieving stable speed, jitter-free, and low-noise starting of the motor.

[0095] Among them, Iqs closed-loop switching target current is a variable, which is determined according to the rotor error angle △θ. That is, when Iq1* is linearly reduced, once the control system calculates that △θ is already within the error range and meets the closed-loop switching conditions, the reduced real-time variable Iq2* is the closed-loop switching target current Iqs.

[0096] In the scheme of the present invention, after maintaining Iq1* for a certain period of time (t1~t2, i.e. 1 / 8Ts), the motor system speed fluctuation is small and the rotor error is small, the given Iq1* value is close to the actual motor q-axis current Iqs value, and the rotor angle error is reduced. At this time, the third stage Iq1* is linearly reduced to Iq*, which can efficiently and stably switch the given q-axis current to the closed-loop q-axis current. During the linear reduction period, when the error between the actual rotor angle θ monitored by the position observer and the rotor angle θ* calculated by the open loop is ±5%, the speed loop open-loop control is directly switched to the current loop closed-loop control, and the new three-stage control of reducing the given q-axis current is completed, achieving stable speed, no jitter, and low noise startup of the motor.

[0097] Step 5: Determine whether the △θ error range is ±5%: If yes, go to step 6; otherwise, return to step 4.

[0098] Step 6: Switch into current loop closed-loop control.

[0099] The scheme of the present invention realizes a control strategy of switching from an open-loop gentle slope to a closed-loop smoothly in the motor starting stage, adopts a new three-stage control scheme for reducing the q-axis current, and reduces the given q-axis current Iq* in a gentle slope manner. That is, when the motor starts and is strongly dragged to the given q-axis current Iq*, a control algorithm is added, and the given q-axis current Iq* is first reduced to Iq1* in a cosine change manner in the first stage; at this time, the second stage is entered, the Iq1* value is maintained, and the open-loop setting is slowly approached to the actual rotor angle by using the power-angle self-balancing principle, the rotor angle error is reduced, the motor speed is gradually stabilized, and the third stage Iq* is linearly reduced. When it is detected that the error between the given rotor angle and the actual rotor angle is ±5%, the reduced Iq2* at this time is close to the actual Iq, and Iq2* is regarded as the closed-loop Iqs. At this moment, the control system is smoothly switched from the open-loop gentle slope to the closed-loop control, thereby achieving extremely small fluctuations in current and speed, and switching to the closed-loop control in a gentle slope smoothly, achieving stable and jitter-free starting of the motor, and achieving smooth starting of the motor.

[0100] In the I / F startup strategy of the related scheme, when the loop is opened to Iq* (i.e., a given q-axis current is obtained according to various preset parameters), the motor has started to run, and the rotor angular position can be calculated according to the position observer, and then the actual q-axis current can be calculated. Therefore, when the rotor angle error is extremely small (i.e., the virtual coordinate system rotation angle and the position observer position angle error are extremely small), the Iqs calculated by the system and the given q-axis current Iq* can be considered to have a small error and can be switched directly. However, the actual Iqs changes all the time, and the switching between the two can easily cause the q-axis current to fluctuate in the motor control system current or speed at the moment of switching. The solution of the present invention is to add an algorithm to control Iq* during the switching time between the two, which can achieve smoother switching between the two, that is, to achieve smoother switching when the switch switches in a closed loop.

[0101] The solution of the present invention adopts a new three-stage control strategy for reducing the given q-axis current in the speed loop. When the motor speed is started in an open loop to a given q-axis current Iq*, a control algorithm is added so that Iq* is reduced to Iq1* in a cosine manner in the first stage during the period of entering the closed loop, so as to avoid large fluctuations in system speed, current, torque, etc. caused by direct linear reduction. When reducing to Iq1*, the parameters of each control controller of the system change smoothly. If Iq* is continuously reduced, it may cause system jitter, just like the linear reduction of Iq* in the related solution. At this time, the second q-axis current switching control scheme is designed to maintain the size of Iq1* and use the "power-angle self-balancing principle". During this period, the system speed gradually stabilizes and the given calculated rotor angle gradually approaches the actual rotor angle; based on the reduction amplitude of the previous given q-axis current Iq*, the third section of Iq1* is finally linearly reduced to Iq2*. The error between the two q-axis current values ​​is small. The linear change at this time can quickly and smoothly reduce the given q-axis current, thereby realizing rapid, gentle and smooth switching of the control system. When the rotor angle error is detected to be less than ±5%, it directly switches to closed-loop control, realizing a gentle and smooth switching from the speed open-loop to the current loop closed-loop control, thereby avoiding the problem of motor current fluctuations and high noise during the closed-loop switching, which may lead to loss of step or jitter when the motor starts.

[0102] By adopting the technical solution of this embodiment, when the motor starts and runs to the q-axis current Iq* given by the target open-loop current, a three-stage method is used to reduce Iq* during the time when Iq* is reduced to Iqs: the first stage is first reduced in a cosine manner, and the reduction time is 3 / 4Ts, until it is reduced to Iq1*; the second stage maintains the size of Iq1* for 1 / 8Ts; the third stage makes Iq1* linearly reduced, and when the rotor angle error is less than ±5%, Iq1* is reduced to Iq2*, that is, Iq* is reduced to Iqs, and then switched to closed-loop control; thus, when the motor starts and runs to the q-axis current given by the target open-loop current, in the process of switching from open loop to closed loop, a three-stage method is used to reduce the q-axis current in a gentle slope manner, so as to achieve a gentle and smooth switch from the speed open-loop start to the closed-loop control, thereby avoiding the current fluctuation of the motor during the switching of the closed loop, and making the motor start smoothly.

[0103] According to an embodiment of the present invention, a motor control device corresponding to the motor control method is also provided. Figure 7 The structure diagram of an embodiment of the device of the present invention is shown. The control system of the motor has a speed loop and a current loop; Fig.11 This is a schematic diagram of the control principle of the speed loop open-loop gentle slope smooth switching current loop closed-loop control system. Fig.11In the example shown, the three-phase currents ia, ib, and ic of the motor are collected from the three-phase power supply line between the inverter and the motor. The three-phase currents ia, ib, and ic are transformed by Clark (i.e., the signals in the three-phase abc coordinate system are converted to the two-phase αβ coordinate system) to obtain the αβ axis currents iα and iβ. The αβ axis currents iα and iβ are transformed by Park to obtain the dq axis currents Id and Iq. The αβ axis currents iα and iβ are passed through the rotor and position estimation modules to obtain the speed ω and rotor angle θ. In the speed loop, Iq* and ωr* are obtained after the I / F control module, and ωr* is transformed by 1 / S (i.e., Laplace transformation) to obtain θ*. In the current loop, Iq*, Iq, ω are processed by the first comparator and the first PI module to obtain the q-axis voltage Vq, Id*=0, Id are processed by the second comparator and the second PI module to obtain the d-axis voltage Vd, Vd, Vq, θ are processed by the inverse Park transform and SVPWM (i.e., motor space vector control) to obtain the three-phase voltage Va, Vb, Vc and then input to the inverter. Among them, Park transform is to project the a, b, c three-phase current of the stator onto the direct axis (d axis) rotating with the rotor, the quadrature axis (q axis) and the zero axis (0 axis) perpendicular to the dq plane, thereby realizing the diagonalization of the stator inductance matrix and simplifying the operation analysis of the synchronous motor.

[0104] In the scheme of the present invention, Figure 7 As shown, the motor control device includes: an acquisition unit 102 and a control unit 104.

[0105] The control unit 104 is configured to make the actual q-axis current of the motor equal to the given q-axis current of the motor, and adopt a preset current-frequency starting method to control the motor to start in the open loop of the speed loop; wherein the given q-axis current of the motor is such as Iq*, and the actual q-axis current of the motor is such as Iq. The specific functions and processing of the control unit 104 refer to step S110.

[0106] The acquisition unit 102 is configured to acquire the target torque of the motor, the target speed of the motor, the set rotor angular velocity (such as ωr*) of the motor, and the actual rotor angle (such as θ) of the motor when the motor is started in the open loop of the speed loop using a preset current-frequency starting method. The specific functions and processing of the acquisition unit 102 refer to step S120.

[0107] The control unit 104 is further configured to determine the target switching time (such as Ts) of the motor, the switching point q-axis current of the motor, and the target rotor angle (such as the rotor angle θ* calculated by the open loop) of the motor according to the target torque of the motor, the target speed of the motor, the set rotor angular velocity of the motor, and the actual rotor angle of the motor. The specific functions and processing of the control unit 104 are also shown in step S130.

[0108] In some implementations, the control unit 104 determines the target switching time (such as Ts) of the motor, the q-axis current at the switching point of the motor, and the target rotor angle (such as the rotor angle θ* calculated in an open loop) of the motor according to the target torque of the motor, the target speed of the motor, the set rotor angular velocity of the motor, and the actual rotor angle of the motor, including:

[0109] The control unit 104 is specifically further configured to determine the target rotor angle of the motor (such as the rotor angle θ* calculated in an open loop) based on the target torque of the motor, the target speed of the motor, and the set rotor angular velocity of the motor; the target rotor angle of the motor is the given rotor angle of the motor, and the initial value of the given rotor angle of the motor, that is, the initial position of the given rotor angle of the motor is θ* equal to 0.

[0110] The control unit 104 is also specifically configured to determine the time (such as Ts) for the motor to switch from the open loop of the speed loop to the closed loop of the current loop according to the target rotor angle of the motor and the actual rotor angle of the motor, recorded as the target switching time (such as Ts) of the motor; and determine the actual q-axis current variable of the motor when the motor switches from the open loop of the speed loop to the closed loop of the current loop, recorded as the switching point q-axis current of the motor. Among them, the time to switch into the closed loop, i.e., the target switching time of the motor, is determined when the error between the set rotor angular velocity θ* of the motor calculated according to the given parameters and the actual rotor angle θ of the motor calculated by the position observer is less than ±5%.

[0111] Specifically, Figure 8As shown, the novel three-stage open-loop gentle slope smooth switching closed-loop control method includes: step 1, 1 / F open-loop strong drag start motor stage, set the rotor angular velocity to ωr; q-axis current: Iq = Iq*; d-axis current: Id = 0, rotor initial angle: θ = 0; according to the target torque and speed, set the speed open-loop switching closed-loop time to Ts, the closed-loop target q-axis current to Iqs (Iqs and Iq2* are related), and then perform step 2. The reduction time of the first stage is t1 (i.e. 3 / 4Ts), at this time, it decreases from Iq* to the value of Iq1*, Iq1* = Iq* × cosθ* + k1 × (Iq*-Iqs), such as Iq1* = Iq* × cosθ* + 3 / 4 × (Iq*-Iqs), θ* = ωr × t1, θ*∈(0,π / 2).

[0112] Figure 8 It is a flow chart of a new three-stage open-loop gentle slope smooth switching closed-loop control method. Fig.10 It is a curve diagram of the angle change of the motor control rotating coordinate system (power-angle self-balancing). In the scheme of the present invention, the adjustment of the q-axis current during the speed open-loop switching speed closed-loop adopts a new three-stage control strategy for reducing the q-axis current (i.e., three-stage reduction of Iq*). In the scheme of the present invention, the change of the q-axis current during the speed open-loop switching speed closed-loop is a gentle decrease of Iq* from the open-loop to the closed-loop time. The related schemes are basically switching directly or in a linear reduction switching mode. It can be seen that Fig. 9 It is shown that the scheme of the present invention is to reduce Iq* by cosine according to the rotor angle change calculated by the virtual coordinate system, and during the second stage of maintaining Iq1*, the motor's characteristic "power-angle self-balancing" is used to reduce the error of the rotor angle, and the speed is stable. The linear direct switching in the related scheme is performed. The difference is that the linear switching in the third stage is smaller than the linear switching of the related scheme, and the error between Iq* and the closed-loop Iqs is smaller, and the open-loop switching and closed-loop switching of the motor control system are more stable.

[0113] Fig. 9 It is a curve diagram of the new three-stage open-loop gentle slope smooth switching closed-loop q-axis current change. Fig.11 The following is a general control diagram of a motor control system. Fig. 9 The schematic changes shown in the figure are as follows: the rotor angle information obtained by speed and position estimation is input into Fig.11 In the control system PID (i.e., in process control, control is performed according to the proportion P, integral I and differential D of the deviation) and inverse Park transformation shown, the virtual coordinate system rotor angle calculated by the given Iq* in the system open loop is compared with the calculated error. The calculation and conversion of various motor data can be carried out by the calculation means of the relevant scheme, and the motor control principle can be consulted. For example: the target current of the open-loop start-up is converted into the maximum value of the q-axis current as Iq* by converting the maximum output torque value of the motor, which can be obtained by calculation according to the motor control principle (such as the following formula).

[0114] Te = 1.5P × iq × Ψf;

[0115] Iq>(Tl+F×ω+Tf+J×dω / dt) / (1.5P×Ψf).

[0116] Among them, Te is the electromagnetic torque, P is the number of pole pairs, ψf is the magnetic flux of the motor, Tl is the load torque, F is the viscous damping, Tf is the static friction, and J is the motor moment of inertia.

[0117] The control unit 104 is further configured to combine the given q-axis current of the motor, the switching point q-axis current of the motor, the target switching time of the motor, the actual rotor angle of the motor, and the target rotor angle of the motor, and adopt a preset segmented smooth reduction control strategy to control the given q-axis current of the motor to be segmentedly reduced to the switching point q-axis current of the motor, and then control the motor to switch from the open loop of the speed loop to the closed loop of the current loop to achieve smooth starting of the motor. The specific functions and processing of the control unit 104 are also shown in step S140.

[0118] The scheme of the present invention proposes a three-stage gentle reduction control scheme for the q-axis current of the motor during the period of switching from open loop to closed loop, so that the q-axis current can be reduced in a gentle slope manner, and the motor can be started without jitter. In the scheme of the present invention, a new three-stage gentle slope control scheme for smoothly reducing the q-axis current is adopted, that is, the first stage cosine mode is used to reduce the given q-axis current Iq* to Iq1*, and the gentle slope reduction in the initial stage effectively avoids the sudden change of the system response; the second stage maintains Iq1* to provide a stable operating environment for the system; the third stage adopts a linear reduction strategy to achieve a smooth decline of Iq1*, and when the rotor angle error (that is, the error between the given rotor angle and the actual rotor angle) is ±5%, it switches to closed-loop control to ensure the efficiency and stability of the entire process control system, and realizes that the motor can smoothly and gently reduce the given q-axis current Iq* within the time of switching from speed open loop to current loop closed loop, so as to achieve the purpose of extremely small current and speed fluctuations when the motor starts, stable control system, and jitter-free start, and realize the smooth start of the motor. Thus, the stability and jitter of the system speed during motor startup are effectively optimized, providing a more stable and reliable control system for motor startup, achieving startup with minimal speed fluctuation and no jitter. In addition, the control strategy solves the problem of large difference between the given and actual q-axis current during the control system's open-loop switching to closed-loop control, resulting in current shock and high noise, thus avoiding motor startup failure and loss of motor service life.

[0119] In some embodiments, the preset segmented gentle reduction control strategy includes: a gentle reduction control strategy consisting of a first segment, a second segment, and a third segment. The control unit 104, in combination with the given q-axis current of the motor, the switching point q-axis current of the motor, the target switching time of the motor, the actual rotor angle of the motor, and the target rotor angle of the motor, adopts the preset segmented gentle reduction control strategy to control the given q-axis current of the motor to be segmentedly reduced to the switching point q-axis current of the motor, including:

[0120] The control unit 104 is further configured to control the given q-axis current of the motor to be reduced to a first given current variable (such as Iq1*) in a cosine manner according to the given q-axis current of the motor, the switching point q-axis current of the motor, the target rotor angle of the motor, and the target switching time of the motor in the first section, and record it as the first q-axis current of the motor (such as Iq1*). The specific functions and processing of the control unit 104 are also shown in step S310.

[0121] In some implementations, the control unit 104, in the first section, controls the given q-axis current of the motor to decrease to a first given current variable in a cosine manner according to the given q-axis current of the motor, the switching point q-axis current of the motor, the target rotor angle of the motor, and the target switching time of the motor, including:

[0122] The control unit 104 is further configured to determine a first calculation coefficient times the target switching time of the motor to obtain a first duration; that is, the first duration is the first calculation coefficient times the target switching time of the motor. The target switching time of the motor is Ts, the first calculation coefficient is 3 / 4, and the second duration is t1=3 / 4Ts. The specific functions and processing of the control unit 104 are also shown in step S410.

[0123] The control unit 104 is further configured to calculate a first given current variable according to the following formula based on the given q-axis current of the motor, the switching point q-axis current of the motor, and the target rotor angle of the motor, and control the actual q-axis current of the motor to decrease for the first duration, so as to reduce the actual q-axis current of the motor to the first given current variable:

[0124] Iq1*=Iq*×cosθ*+k1×(Iq*-Iqs);

[0125] Wherein, Iq1* is the first given current variable, Iq* is the given q-axis current of the motor, i.e., the target given q-axis current after the motor is started in a preset current-frequency starting mode, θ* is the target rotor angle reached by the motor within a certain period of time according to the given rotor angular velocity of the motor, i.e., θ*=ωr×t1; k1 is the first calculation coefficient, and Iqs is the switching point q-axis current of the motor. The specific functions and processing of the control unit 104 are also referred to step S420.

[0126] Specifically, Figure 8 As shown, the new three-stage open-loop gentle slope smooth switching closed-loop control method also includes: step 2, after the q-axis current Iq open-loop start-up is forcibly dragged to a given value Iq*, the first stage of the new three-stage open-loop smooth switching closed-loop control stage is entered, Iq* is gently reduced in a cosine manner, the reduction time is t1 (3 / 4Ts), the variable Iq1* is given in real time, and then step 3 is executed.

[0127] In step 2, the first section of the open-loop q-axis current Iq* cosine decreases.

[0128] In such Fig. 9 In the example shown, the speed loop open-loop I / F starts the motor for a period of time, and the q-axis current reaches the target open-loop current value Iq*. At this time, the Iq* of the relevant scheme will be directly linearly reduced according to the target closed-loop Iq, but this method is very prone to the problem of a large difference between the given q-axis current Iq* and the actual Iq. Therefore, in the scheme of the present invention, the first section Iq* is smoothly reduced to Iq1* in a cosine manner, and the cosine change angle is related to the given rotor angle change. The open-loop given angular velocity is ωr (θ=ωrT, T is time), and the reduction time of the first stage is t1 (i.e. 3 / 4Ts). At this time, the value from Iq* to Iq1* is Iq1*=Iq*×cosθ*+k1×(Iq*-Iqs), such as Iq1*=Iq*×cosθ*+3 / 4×(Iq*-Iqs), θ*=ωr×t1, θ*∈(0,π / 2). This cosine change control strategy can not only ensure the smooth decline of Iq* and avoid the uncertainty caused by large fluctuations, but also more accurately predict and track the change trend of the actual Iq, thereby significantly improving the stability and response speed of the motor system. Among them, when the motor is stationary, the back electromotive force signal is weak, and the accuracy of obtaining the rotor position information is limited. After the motor is started, the position observer can calculate the actual motor rotor position angle, and the actual q-axis current value, that is, Iqs, can be calculated according to the calculation formula of the motor control principle.

[0129] In the scheme of the present invention, when the q-axis current of the motor starts and reaches the given q-axis current Iq*, the open-loop control system enters the first stage of gentle slope smooth switching, and the given q-axis current Iq* decreases with the cosine amplitude, and the cosine reduction angle is related to the given rotor angle change. The angular velocity of the open-loop control is ωr*, and the actual rotor angle θ=ωr×T, where T represents time; and the reduction time t1 of the first stage is set to 3 / 4Ts. During this period, the q-axis current Iq of the motor will be smoothly reduced from the initial value Iq* to Iq1*, and the calculation formula is Iq1*=Iq*×cosθ*+k1×(Iq*-Iqs), such as Iq1*=Iq*×cosθ*+3 / 4×(Iq*-Iqs), where the open-loop rotor angle θ*=ωr×t1, and the value range of θ* is (0,π / 2). By designing the cosine variation of the Iq* value, it is possible to ensure that the motor system is adjusted in a smoother manner under open-loop control, thereby more closely matching the actual motor operating state. This method effectively avoids the problems of unstable motor speed, jitter caused by current mutations, and increased noise caused by large fluctuations in the given q-axis current Iq* value, and significantly improves the stability and efficiency of motor operation. Among them, Iqs is the closed-loop actual q-axis current variable, Ts is the time for switching from open-loop to closed-loop control, θ is the actual rotor angle monitored by the position observer, θ* is the rotor angle calculated in the open loop, ωr* is the angular velocity of the open-loop control, and ωr is the set rotor angular velocity.

[0130] The control unit 104 is further configured to control the first q-axis current of the motor to maintain according to the target switching time of the motor in the second section. The specific functions and processing of the control unit 104 are also shown in step S320.

[0131] In some implementations, the control unit 104, in the second section, controls the first q-axis current of the motor to maintain according to the target switching time of the motor by using the power-angle self-balancing principle, including:

[0132] The control unit 104 is further configured to determine a second calculation coefficient times the target switching time of the motor to obtain a second duration; wherein the target switching time of the motor is Ts, the second calculation coefficient is 1 / 8, and the second duration is t2=1 / 8Ts. The specific functions and processing of the control unit 104 are also shown in step S510.

[0133] The control unit 104 is further configured to control the first q-axis current of the motor to maintain the second duration by utilizing the power-angle self-balancing principle. The specific functions and processing of the control unit 104 are also shown in step S520.

[0134] Specifically, Figure 8As shown, the new three-stage open-loop gentle slope smooth switching closed-loop control method also includes: step 3, at this time, Iq1* is reduced to close to the target closed-loop Iqs, and the second stage of the new three-stage open-loop smooth switching closed-loop control is entered, and the "power-angle self-balancing principle" of the motor is used to maintain the current Iq1* size for a time of 1 / 8Ts. During this period, the open-loop rotor calculation angle and the actual rotor angle are getting closer and closer, the motor speed slowly stabilizes, and the system is stable, and then step 4 is executed.

[0135] In step 3, the magnitude of the second open-loop q-axis current Iq1* is maintained.

[0136] In such Fig. 9 In the example shown, when Iq* is reduced to Iq1* in a cosine manner through the control algorithm, if Iq1* is continued to be reduced by cosine, the q-axis current and rotor angle may change rapidly, causing fluctuations in the control system. Therefore, the second control algorithm is added at this time to maintain the size of Iq1* and use the "power-angle self-balancing principle" of the motor, such as Fig.10 In the figure, after the motor is started by I / F strong drag, according to the torque formula Te=Iq×cosθ×1.5P×Ψf, the q-axis current Iq* given by the open-loop control system overcomes the load torque and static friction and starts to rotate when the motor starts. After that, the rotor angular velocity continues to increase due to the fixed acceleration, and the viscous resistance will also continue to increase. Therefore, the torque required in the q-axis direction continues to increase, but the torque on the q* axis remains unchanged because the q-axis current does not change. Therefore, in order to achieve force balance, the power angle will continue to increase, thereby increasing the value of Iq*cosθ, that is, the open-loop rotor angle θ* is infinitely close to the actual rotor angle θ. At this time, the actual motor system control is close to the given control system, and the speed tends to be stable, which is conducive to providing a more efficient and reliable operating environment for closed-loop switching.

[0137] Among them, the power-angle self-balancing principle means that through the power angle self-balancing principle, the angle of the observer is constantly approaching the angle during open-loop strong drag, and finally the observer is cut into the control loop when the two are equal, so as to achieve stable operation of the system. The working mechanism of the power-angle self-balancing principle can be divided into two stages: the initial acceleration stage and the switching stage; in the initial acceleration stage, the speed is increased at a constant acceleration through open-loop strong drag; in the switching stage, relying on the power angle self-balancing principle, the angle of the observer is constantly approaching the angle during open-loop strong drag, and finally the observer is cut into the control loop when the two are equal, so as to achieve stable operation of the system.

[0138] In the scheme of the present invention, when the given q-axis current Iq* is reduced to Iq1* in a cosine manner through the control algorithm, if Iq1* is continuously reduced, it may cause system fluctuations and affect the starting stability of the motor. Therefore, the second stage control algorithm is designed to maintain the size of Iq1* and utilize the "power-angle self-balancing principle" of the motor to stabilize the speed of the motor control system. That is, after the motor is started by I / F strong drag, according to the torque formula Te=Iq×cosθ×1.5P×Ψf, Te is the electromagnetic torque, Iq is the actual q-axis current, P is the number of pole pairs, ψf is the magnetic flux of the motor, and θ is the actual rotor angle monitored by the position observer; when the motor just starts, the q-axis current Iq* given by the open-loop control system overcomes the load torque and static friction and starts to rotate, and then the rotor angular velocity continues to increase due to the fixed acceleration, and the viscous resistance will also continue to increase. Therefore, the torque required in the q-axis direction continues to increase, but the torque on the q-axis remains unchanged because the q-axis current. Therefore, in order to achieve force balance, the power angle will continue to increase, thereby increasing the value of Iq*cosθ, that is, the open-loop rotor angle θ* is close to the actual rotor angle θ, the rotor error angle is reduced, and the system speed tends to be stable, thereby achieving the purpose of smooth motor start-up control.

[0139] The control unit 104 is further configured to control the first q-axis current of the motor to linearly decrease to a second given current variable (such as Iq2*) in the third section according to the actual rotor angle of the motor and the target rotor angle of the motor, recorded as the second q-axis current of the motor (such as Iq2*); until the second q-axis current of the motor reaches the switching point q-axis current of the motor, the given q-axis current of the motor is reduced in sections to the switching point q-axis current of the motor. The specific functions and processing of the control unit 104 are also referred to step S330.

[0140] like Figures 8 to 11As shown, the target current of the open-loop start is converted into the maximum q-axis current value Iq* by using the maximum output torque value of the motor, and the motor is started by open-loop strong drag with the value of Iq* being the given value of the q-axis current. The system presets the open-loop angular velocity ωr*, the time Ts for switching from open-loop to closed-loop control, and the closed-loop actual q-axis current variable is Iqs. When the motor starts and runs to the q-axis current Iq* given by the target open-loop current, a new three-stage control method for reducing Iq* is designed within the time when Iq* decreases to Iqs, so that when Iq* enters the closed loop, the first stage first decreases in a cosine manner, and the reduction time is 3 / 4Ts. The cosine reduction angle is related to the rotor position angle; the second stage maintains the current value of Iq*, that is, the size of Iq1*. By using the power-angle self-balancing principle, the motor speed tends to be stable, and the given calculated rotor angle is close to the actual rotor angle. Finally, entering the third stage, Iq1* decreases linearly. When the rotor angle error is less than ±5%, Iq1* is reduced to Iq2* at this time, and it is immediately switched to closed-loop control, realizing the smooth switching from the speed open-loop start to the closed-loop control with a gentle slope, avoiding the current fluctuation of the motor during the closed-loop switching, causing the motor to lose step or jitter, and reducing noise.

[0141] In some implementations, the control unit 104 controls the first q-axis current of the motor to linearly decrease to a second given current variable, recorded as the second q-axis current of the motor, according to the actual rotor angle of the motor and the target rotor angle of the motor in the third section; until the second q-axis current of the motor reaches the switching point q-axis current of the motor, the given q-axis current of the motor is reduced in sections to the switching point q-axis current of the motor, including:

[0142] The control unit 104 is further configured to control the first q-axis current of the motor to linearly decrease to the second q-axis current of the motor. The specific functions and processing of the control unit 104 are also shown in step S610.

[0143] The control unit 104 is further configured to determine the difference between the actual rotor angle of the motor and the target rotor angle of the motor, which is recorded as the rotor angle error of the motor (eg, Δθ). The specific functions and processing of the control unit 104 are also shown in step S620.

[0144] The control unit 104 is further configured to determine whether the rotor angle error of the motor is within a set error range. The specific functions and processing of the control unit 104 are also shown in step S630.

[0145] The control unit 104 is further configured to, if it is determined that the rotor angle error of the motor is within a set error range, stop the linear reduction of the first q-axis current of the motor to the second q-axis current of the motor, and determine that the second q-axis current of the motor reaches the switching point q-axis current of the motor. The specific functions and processing of the control unit 104 are also shown in step S630.

[0146] The control unit 104 is further configured to return to continue controlling the first q-axis current of the motor to linearly decrease to the second q-axis current of the motor if it is determined that the rotor angle error of the motor is not within the set error range. The specific functions and processing of the control unit 104 are also shown in step S640.

[0147] Specifically, Figure 8 As shown, the novel three-stage open-loop gentle slope smooth switching closed-loop control method also includes: step 4, after the Iq1* changes in the first and second stages, Iq* is close to the closed-loop Iqs, and the rotor error angle is reduced. At this time, entering the third stage, Iq1* linearly decreases to Iq2*, and the change of the system q-axis current is not much different and can be reduced more smoothly, and then step 5 is executed.

[0148] In step 4, the third segment linearly decreases the q-axis current.

[0149] As Fig. 9 In the example shown, after maintaining Iq1* for a certain period of time (t1-t2, i.e. 1 / 8Ts), the motor system quickly adjusts the error between the given parameters and the actual parameters, the speed fluctuation is small and the rotor angle error is reduced, and the given Iq1* value is close to the actual motor q-axis current Iqs value; t1 here is the same as t1 in the first stage. At this time, entering the third stage, Iq1* linearly decreases to Iqs, such as Fig. 9 As shown, the linear reduction here is a direct reduction, from one value directly to another value; based on the reduction control of the previous two sections of the q-axis given current, the third section linearly reduces the given q-axis current Iq*, which can efficiently and stably achieve the switching of the given q-axis current to the closed-loop q-axis current. Fig.11 As shown, during the linear reduction, when the error between the actual rotor angle θ monitored by the position observer and the rotor angle θ* calculated by the open loop is within ±5%, the control system directly switches from the speed loop open-loop control to the current loop closed-loop control, thus completing the new three-stage control of reducing the given current of the q-axis and achieving stable speed, jitter-free, and low-noise starting of the motor.

[0150] In the scheme of the present invention, after maintaining Iq1* for a certain period of time (t1~t2, i.e. 1 / 8Ts), the motor system speed fluctuation is small and the rotor error is small, the given Iq1* value is close to the actual motor q-axis current Iqs value, and the rotor angle error is reduced. At this time, the third stage Iq1* is linearly reduced to Iq*, which can efficiently and stably switch the given q-axis current to the closed-loop q-axis current. During the linear reduction period, when the error between the actual rotor angle θ monitored by the position observer and the rotor angle θ* calculated by the open loop is ±5%, the speed loop open-loop control is directly switched to the current loop closed-loop control, and the new three-stage control of reducing the given q-axis current is completed, achieving stable speed, no jitter, and low noise startup of the motor.

[0151] Step 5: Determine whether the △θ error range is ±5%: If yes, go to step 6; otherwise, return to step 4.

[0152] Step 6: Switch into current loop closed-loop control.

[0153] The scheme of the present invention realizes a control strategy of switching from an open-loop gentle slope to a closed-loop smoothly in the motor starting stage, adopts a new three-stage control scheme for reducing the q-axis current, and reduces the given q-axis current Iq* in a gentle slope manner. That is, when the motor starts and is strongly dragged to the given q-axis current Iq*, a control algorithm is added, and the given q-axis current Iq* is first reduced to Iq1* in a cosine change manner in the first stage; at this time, the second stage is entered, the Iq1* value is maintained, and the open-loop setting is slowly approached to the actual rotor angle by using the power-angle self-balancing principle, the rotor angle error is reduced, the motor speed is gradually stabilized, and the third stage Iq* is linearly reduced. When it is detected that the error between the given rotor angle and the actual rotor angle is ±5%, the reduced Iq2* at this time is close to the actual Iq, and Iq2* is regarded as the closed-loop Iqs. At this moment, the control system is smoothly switched from the open-loop gentle slope to the closed-loop control, thereby achieving extremely small fluctuations in current and speed, and switching to the closed-loop control in a gentle slope smoothly, achieving stable and jitter-free starting of the motor, and achieving smooth starting of the motor.

[0154] In the I / F startup strategy of the related scheme, when the loop is opened to Iq* (i.e., a given q-axis current is obtained according to various preset parameters), the motor has started to run, and the rotor angular position can be calculated according to the position observer, and then the actual q-axis current can be calculated. Therefore, when the rotor angle error is extremely small (i.e., the virtual coordinate system rotation angle and the position observer position angle error are extremely small), the Iqs calculated by the system and the given q-axis current Iq* can be considered to have a small error and can be switched directly. However, the actual Iqs changes all the time, and the switching between the two can easily cause the q-axis current to fluctuate in the motor control system current or speed at the moment of switching. The solution of the present invention is to add an algorithm to control Iq* during the switching time between the two, which can achieve smoother switching between the two, that is, to achieve smoother switching when the switch switches in a closed loop.

[0155] The solution of the present invention adopts a new three-stage control strategy for reducing the given q-axis current in the speed loop. When the motor speed is started in an open loop to a given q-axis current Iq*, a control algorithm is added so that Iq* is reduced to Iq1* in a cosine manner in the first stage during the period of entering the closed loop, so as to avoid large fluctuations in system speed, current, torque, etc. caused by direct linear reduction. When reducing to Iq1*, the parameters of each control controller of the system change smoothly. If Iq* is continuously reduced, it may cause system jitter, just like the linear reduction of Iq* in the related solution. At this time, the second q-axis current switching control scheme is designed to maintain the size of Iq1* and use the "power-angle self-balancing principle". During this period, the system speed gradually stabilizes and the given calculated rotor angle gradually approaches the actual rotor angle; based on the reduction amplitude of the previous given q-axis current Iq*, the third section of Iq1* is finally linearly reduced to Iq2*. The error between the two q-axis current values ​​is small. The linear change at this time can quickly and smoothly reduce the given q-axis current, thereby realizing rapid, gentle and smooth switching of the control system. When the rotor angle error is detected to be less than ±5%, it directly switches to closed-loop control, realizing a gentle and smooth switching from the speed open-loop to the current loop closed-loop control, thereby avoiding the problem of motor current fluctuations and high noise during the closed-loop switching, which may lead to loss of step or jitter when the motor starts.

[0156] Since the processing and functions implemented by the device of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0157] According to an embodiment of the present invention, a motor corresponding to a control device of the motor is also provided. The motor may include: the control device of the motor described above.

[0158] Since the processing and functions implemented by the motor of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned device, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0159] According to an embodiment of the present invention, a computer program product corresponding to a motor is also provided, comprising a computer program, and when the computer program is executed by a processor, the steps of the motor control method described above are implemented.

[0160] Since the processing and functions implemented by the product of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned motor, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0161] According to an embodiment of the present invention, a storage medium corresponding to the motor control method is also provided, the storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the steps of the motor control method described above.

[0162] Since the processing and functions implemented by the storage medium of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0163] In summary, it is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0164] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A method for controlling a motor, characterized in that: The control system of the motor has a speed loop and a current loop; The control method of the motor comprises: The actual q-axis current of the motor is made equal to the given q-axis current of the motor, and a preset current-frequency starting mode is adopted to control the motor to start in the open loop of the speed loop; Obtaining a target torque of the motor, obtaining a target speed of the motor, obtaining a set rotor angular velocity of the motor, and obtaining an actual rotor angle of the motor; Determine a target rotor angle of the motor, a target switching time of the motor, and a switching point q-axis current of the motor according to a target torque of the motor, a target speed of the motor, a set rotor angular velocity of the motor, and an actual rotor angle of the motor; In combination with the given q-axis current of the motor, the switching point q-axis current of the motor, the target switching time of the motor, the actual rotor angle of the motor, and the target rotor angle of the motor, a preset segmented smooth reduction control strategy is adopted to control the given q-axis current of the motor to be reduced segmentally to the switching point q-axis current of the motor, and then the motor is controlled to switch from the open loop of the speed loop to the closed loop of the current loop to achieve smooth starting of the motor.

2. The motor control method according to claim 1, characterized in that: Determining a target rotor angle of the motor, a target switching time of the motor, and a switching point q-axis current of the motor according to a target torque of the motor, a target speed of the motor, a set rotor angular velocity of the motor, and an actual rotor angle of the motor, including: Determining a target rotor angle of the motor according to a target torque of the motor, a target rotation speed of the motor, and a set rotor angular velocity of the motor; According to the target rotor angle of the motor and the actual rotor angle of the motor, the time for the motor to switch from the open loop of the speed loop to the closed loop of the current loop is determined, which is recorded as the target switching time of the motor; and the actual q-axis current variable of the motor when the motor switches from the open loop of the speed loop to the closed loop of the current loop is determined, which is recorded as the switching point q-axis current of the motor.

3. The motor control method according to claim 1 or 2, characterized in that: The preset segmented gentle reduction control strategy includes: a gentle reduction control strategy consisting of a first segment, a second segment and a third segment; In combination with the given q-axis current of the motor, the switching point q-axis current of the motor, the target switching time of the motor, the actual rotor angle of the motor, and the target rotor angle of the motor, a preset segmented smooth reduction control strategy is adopted to control the given q-axis current of the motor to be segmentedly reduced to the switching point q-axis current of the motor, including: In the first section, according to the given q-axis current of the motor, the switching point q-axis current of the motor, the target rotor angle of the motor, and the target switching time of the motor, the given q-axis current of the motor is controlled to be reduced to a first given current variable in a cosine manner, which is recorded as the first q-axis current of the motor; In the second section, controlling the first q-axis current of the motor to be maintained according to the target switching time of the motor; In the third section, according to the actual rotor angle of the motor and the target rotor angle of the motor, the first q-axis current of the motor is controlled to be linearly reduced to a second given current variable, recorded as the second q-axis current of the motor; until the second q-axis current of the motor reaches the switching point q-axis current of the motor, the given q-axis current of the motor is reduced in sections to the switching point q-axis current of the motor.

4. The motor control method according to claim 3, characterized in that: In the first section, according to the given q-axis current of the motor, the switching point q-axis current of the motor, the target rotor angle of the motor, and the target switching time of the motor, controlling the given q-axis current of the motor to decrease to a first given current variable in a cosine manner includes: Determine a first calculation coefficient times the target switching time of the motor to obtain a first duration; According to the given q-axis current of the motor, the switching point q-axis current of the motor, and the target rotor angle of the motor, a first given current variable is calculated according to the following formula, and the actual q-axis current of the motor is controlled to decrease for the first duration, so as to reduce the actual q-axis current of the motor to the first given current variable: Iq1*=Iq*×cosθ*+k1×(Iq*-Iqs); Among them, Iq1* is the first given current variable, Iq* is the given q-axis current of the motor, that is, the target given q-axis current after the motor is started according to the preset current-frequency starting method, θ* is the target rotor angle reached by the motor within a certain time according to the given rotor angular velocity of the motor, k1 is the first calculation coefficient, and Iqs is the switching point q-axis current of the motor.

5. The motor control method according to claim 3, characterized in that: In the second section, the first q-axis current of the motor is controlled to be maintained according to the target switching time of the motor by utilizing the power-angle self-balancing principle, including: Determine a second calculation coefficient times the target switching time of the motor to obtain a second duration; By utilizing the power-angle self-balancing principle, the first q-axis current of the motor is controlled to maintain the second duration.

6. The motor control method according to claim 3, characterized in that: In the third section, according to the actual rotor angle of the motor and the target rotor angle of the motor, the first q-axis current of the motor is controlled to be linearly reduced to a second given current variable, which is recorded as the second q-axis current of the motor; until the second q-axis current of the motor reaches the switching point q-axis current of the motor, the given q-axis current of the motor is reduced in sections to the switching point q-axis current of the motor, including: Controlling the first q-axis current of the motor to linearly decrease to the second q-axis current of the motor; Determine a difference between an actual rotor angle of the motor and a target rotor angle of the motor, which is recorded as a rotor angle error of the motor; Determining whether the rotor angle error of the motor is within a set error range; If it is determined that the rotor angle error of the motor is within a set error range, the first q-axis current of the motor is stopped from linearly decreasing to the second q-axis current of the motor, and it is determined that the second q-axis current of the motor reaches the switching point q-axis current of the motor; If it is determined that the rotor angle error of the motor is not within the set error range, the process returns to continue controlling the first q-axis current of the motor to linearly decrease to the second q-axis current of the motor.

7. A control device for a motor, characterized in that: The control system of the motor has a speed loop and a current loop; the control device of the motor includes: A control unit is configured to make the actual q-axis current of the motor equal to the given q-axis current of the motor, and adopt a preset current-frequency starting method to control the motor to start in the open loop of the speed loop; an acquisition unit, configured to acquire a target torque of the motor, acquire a target speed of the motor, acquire a set rotor angular velocity of the motor, and acquire an actual rotor angle of the motor; The control unit is further configured to determine a target rotor angle of the motor, a target switching time of the motor, and a switching point q-axis current of the motor according to a target torque of the motor, a target speed of the motor, a set rotor angular velocity of the motor, and an actual rotor angle of the motor; The control unit is also configured to combine the given q-axis current of the motor, the switching point q-axis current of the motor, the target switching time of the motor, the actual rotor angle of the motor, and the target rotor angle of the motor, and adopt a preset segmented smooth reduction control strategy to control the given q-axis current of the motor to be reduced segmentally to the switching point q-axis current of the motor, and then control the motor to switch from the open loop of the speed loop to the closed loop of the current loop to achieve smooth starting of the motor.

8. A motor, characterized in that: include: The control device for a motor as claimed in claim 7.

9. A storage medium, characterized in that: The storage medium includes a stored program, wherein when the program is executed, the device where the storage medium is located is controlled to execute the motor control method according to any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method for controlling a motor according to any one of claims 1 to 6 are implemented.

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