A current control system and method for a permanent magnet synchronous linear motor with multiple independent windings

Abstract

The present invention relates to a current control system and method for a permanent magnet synchronous linear motor with multiple movers and independent windings. The D-Q axis given current and a motor speed signal of a motor winding are obtained, and the D-Q axis given current is transformed to obtain a three-phase given current; the three-phase given current and a three-phase current signal output by an inverter are differentially input into a proportional resonant current controller, and the proportional resonant current controller performs parameter adjustment based on the motor speed signal and outputs a modulation wave; the modulation wave generates a digital switch quantity through sinusoidal pulse width modulation and is output to an inverter, and the inverter outputs a three-phase current signal to the motor, and current closed-loop control is performed on the motor; the single-phase current control method based on the proportional resonant current controller enables a controlled object to achieve error-free current tracking under high-speed conditions.

Description

Technical Field

[0001] The invention relates to a current control system and method for an independent winding permanent magnet synchronous linear motor, belonging to the technical field of linear motor current control. Background Art

[0002] Since linear motors eliminate the complex transmission mechanism of traditional linear motion devices, they are widely used in machine tools, intelligent equipment manufacturing, logistics and transportation.

[0003] In the field of long stroke, it is often required that the mover has no drag chain structure, and one or more movers can be set up for independent and flexible control. Therefore, a multi-motor permanent magnet synchronous linear motor system with magnetic steel as the mover and segmented armature as the stator is adopted.

[0004] The traditional permanent magnet synchronous linear motor adopts a three-phase structure, and the movers can be independent of each other or work together, which has good flexibility. However, the three-phase structure system usually needs to pre-conduct the next set of windings in the direction of movement during operation, which limits the minimum spacing between multiple movers. In some occasions where extremely small spacing is required, the three-phase multi-motor permanent magnet synchronous linear motor cannot meet the use requirements.

[0005] In order to reduce the constraints of the minimum spacing between movers, the armature of the permanent magnet synchronous linear motor system adopts a single-phase independent winding structure. The wire package of each winding is output separately, and there is no electrical connection and spatial coupling between any two phases. Combined with the single-phase current control method, the winding pre-conduction area can be reduced by two-thirds, thereby meeting the application requirements.

[0006] However, multi-motor permanent magnet synchronous linear motors generally use traditional single-phase current control methods for current control, which is based on proportional-integral control. For example, the single-phase current control method for multi-motor independent winding permanent magnet synchronous linear motors proposed in Patent 202210542179.8 is a single-phase current control method based on a proportional-integral controller. This method has a large current tracking error under high-speed operating conditions of the motor, which further causes the mover to be unable to reach the set acceleration, or even unable to reach the maximum operating speed of the system. Summary of the invention

[0007] In order to solve the problems existing in the prior art, the present invention provides a current control system and method for a permanent magnet synchronous linear motor with multiple movers and independent windings. The control method achieves a better current tracking effect under the condition of high-speed operation of the motor.

[0008] In order to achieve the above object, the technical solution proposed by the present invention is:

[0009] A current control method for a multi-motor independent winding permanent magnet synchronous linear motor, wherein the motor is controlled by an inverter, and the specific control method is:

[0010] Obtain the DQ axis given current and motor speed signal of the motor winding, and transform the DQ axis given current to obtain the three-phase given current;

[0011] The three-phase given current and the three-phase current signal output by the inverter are input into the proportional resonant current controller as a difference, and the proportional resonant current controller performs parameter adjustment based on the motor speed signal and outputs a modulation wave;

[0012] The modulation wave generates a digital switch quantity through sinusoidal pulse width modulation and outputs it to the inverter. The inverter outputs a three-phase current signal to the motor to perform current closed-loop control on the motor.

[0013] Among them, in the process of proportional resonant current controller parameter setting, the frequency domain design method is used to set the resonant frequency point open-loop gain G of the proportional resonant current controller. resonance and phase margin

[0014]

[0015] Where G0(s) is the open-loop transfer function of the proportional resonant current controller, ω openloop is the open-loop cut-off frequency;

[0016] The proportional coefficient K of the proportional resonant current controller is calculated by the following formula: p and the resonance coefficient K r To perform tuning:

[0017]

[0018] In the formula, G resonance is the resonance point gain; ω openloop is the open-loop cut-off frequency; is the phase margin; R is the motor resistance; L is the motor inductance; ω c is the resonance bandwidth; ω0 is the resonance frequency, which is obtained through the motor speed signal; t is a constant.

[0019] A further design of the above technical solution is as follows: the open-loop transfer function of the proportional resonant current controller is:

[0020]

[0021] Where s is the Laplace operator, T pwm is the equivalent inertia time constant of PWM modulation.

[0022] The proportional resonant current controller is discretized and the discretized form is:

[0023]

[0024] In the formula, y n is the output, a0, a1, a2, b0, b1 and b2 are all variables, T s is the sampling period.

[0025] The relationship between the resonant frequency ω0 and the motor speed v is as follows:

[0026] ω0=v·π / τ

[0027] Where τ is the motor pole pitch.

[0028] The direct axis current given I in the DQ axis given current of the motor winding d * is zero, the quadrature axis current is given by I q * for:

[0029]

[0030] In the formula, F e is the electromagnetic thrust, K f is the thrust coefficient.

[0031] The DQ axis given current is transformed into the three-phase ABC axis current given I by inverse Park transformation and inverse Clark transformation according to the following formula a * ,I b * and I c * :

[0032]

[0033] In the formula, θ e is the electrical angle, I0* is the zero-sequence current given.

[0034] Electrical angle θ e The relationship with the motor rotor position x is as follows:

[0035] θ e =x·π / τ.

[0036] A current control system of a multi-motor independent winding permanent magnet synchronous linear motor, comprising a multi-motor independent winding permanent magnet synchronous linear motor, a position speed feedback unit, a current conversion unit, a comparison unit, a proportional resonant current controller, a sinusoidal pulse modulation unit and an inverter;

[0037] The position speed feedback unit obtains the motor speed and mover position signal of the multi-motor independent winding permanent magnet synchronous linear motor, and feeds back the motor speed signal to the proportional resonant current controller, and feeds back the mover position signal to the current conversion unit. The current conversion unit is used to convert the DQ axis given current of the motor winding to obtain a three-phase given current, and send the three-phase given current to the comparison unit. The comparison unit is used to make a difference between the three-phase given current and the three-phase current signal output by the inverter, and input it to the proportional resonant current controller. The proportional resonant current controller uses the above parameter setting process to adjust the proportional coefficient K based on the motor speed signal. p and the resonance coefficient K r It is adjusted and used to output a modulation wave to the sinusoidal pulse modulation unit. The sinusoidal pulse modulation unit is used to generate a digital switching quantity and output it to the inverter. The inverter is used to generate a three-phase current signal according to the digital switching quantity and control the motor through the three-phase current signal.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention aims at a multi-motor independent winding permanent magnet synchronous linear motor system, and proposes a single-phase current control method based on a proportional resonant current controller and a parameter setting process thereof, so that the controlled object can basically achieve an error-free current tracking effect under high-speed conditions.

[0040] The present invention adopts a proportional resonant current controller to achieve accurate, fast and stable tracking of single-phase current; at the same time, a frequency domain design method is adopted to further derive the parameter setting equation of the proportional resonant current controller by designing the resonance point gain and phase margin of the proportional resonant system, thereby achieving accurate and fast controller parameter setting.

[0041] The single-phase current control system based on the proportional resonant current controller of the present invention realizes the characteristics of good tracking effect under proportional resonant current control, step speed response without any overshoot, and rapid tracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a block diagram of the proportional resonant single-phase current control structure of the independent winding system;

[0043] Figure 2 The closed-loop transfer function block diagram of the independent winding system based on proportional resonant current control;

[0044] Figure 3 This is the Q-axis current tracking effect diagram based on the proportional resonant current controller;

[0045] Figure 4 This is the D-axis current tracking effect diagram based on proportional resonant current controller;

[0046] Figure 5 This is the speed step response effect diagram based on proportional resonant current controller;

[0047] Figure 6 This is the Q-axis current tracking effect diagram based on proportional-integral current controller;

[0048] Figure 7 This is the D-axis current tracking effect diagram based on proportional-integral current controller;

[0049] Figure 8 This is the speed step response effect diagram based on proportional-integral current controller;

[0050] In the figure, 1-current conversion unit; 2-proportional resonant current controller; 3-sine pulse width modulation unit; 4-inverter; 5-multi-motor independent winding permanent magnet synchronous linear motor; 6-position speed feedback unit. DETAILED DESCRIPTION

[0051] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] Embodiment 1:

[0053] like Figure 1 As shown, the independent winding system of this embodiment adopts position-speed-current three-closed-loop control, and performs current closed-loop control of the independent winding through a proportional resonant current controller, specifically:

[0054] The motor DQ axis given current of the motor winding is obtained, and the DQ axis given current is converted by the current conversion unit 1 to obtain the three-phase given current.

[0055] Quadrature axis current given I q * The electromagnetic thrust is obtained by the output of the motor speed controller. The electromagnetic thrust is the output of the motor rotor closed-loop control. The electromagnetic thrust and the quadrature axis current given I q * The relationship is as follows:

[0056]

[0057] In the formula, F e is the electromagnetic thrust, K f is the thrust coefficient.

[0058] The DQ axis given current is converted into the three-phase ABC axis current given through inverse Park transformation and inverse Clarke transformation. The current transformation equation is as follows:

[0059]

[0060] In the formula, θ eis the electrical angle, obtained through the motor position signal; I d * is the direct axis current given, I0 * is the zero-sequence current given, I d * and I0 * Usually 0.

[0061] Then, the three-phase given current is input into the proportional resonant current controller 2 by comparing the difference with the feedback current; the feedback current is the three-phase current signal output by the inverter 4,

[0062] The proportional resonant current controller 2 outputs a modulation wave, which is then converted into a digital switch quantity through the sinusoidal pulse width modulation unit 3 and output to the inverter 4. The inverter 4 outputs a three-phase current signal to the multi-motor independent winding permanent magnet synchronous linear motor 5, thereby performing current closed-loop control on the multi-motor independent winding permanent magnet synchronous linear motor 5.

[0063] The multi-motor independent winding permanent magnet synchronous linear motor 5 collects motor speed and motor position information through the position speed feedback unit 6; the motor speed is converted into the resonant frequency ω0 to participate in the parameter setting of the proportional resonant current controller 2 to achieve speed closed-loop control; the motor position is converted into the electrical angle θ e It is used for transformation of the above given current to realize position closed-loop control.

[0064] The resonant frequency ω0 is obtained through the motor speed v, specifically:

[0065] ω0=v·π / τ

[0066] Where τ is the motor pole pitch.

[0067] Electrical angle θ e It is obtained by the motor rotor position x, specifically:

[0068] θe=x·π / τ.

[0069] In this embodiment, each winding of the motor can be controlled independently, and the control of any winding is not affected by the switching of other windings.

[0070] In this embodiment, the proportional resonant current controller is composed of a proportional term and a resonant term in parallel, and its frequency domain form is:

[0071]

[0072] In the formula, K p is the proportionality coefficient, K r is the resonance coefficient, ω c is the resonance bandwidth, ω0 is the resonance frequency, and s is the Laplace operator.

[0073] Combination Figure 2 , the proportional resonant single-phase current control method of this embodiment, its current loop open-loop transfer function is:

[0074]

[0075] Where R is the motor resistance, L is the motor inductance, T pwm is the equivalent inertia time constant of PWM modulation. Figure 2 in i Ref For a given current, i Fbk is the feedback current.

[0076] In order to ensure that the proportional resonant current controller can still track the signal of the specified frequency well when the system frequency fluctuates within a small range, this embodiment will c Set to 2, 5 or 10, at the same time, the proportional coefficient K of the proportional resonant current controller p and the resonance coefficient K r The tuning is achieved by setting the open-loop gain and phase margin at the resonant frequency of the system:

[0077]

[0078] In the formula, G resonance is the gain at the resonance point, ω openloop is the open-loop cut-off frequency, is the phase margin;

[0079] Due to T pwm Usually small, so it is set to 0, through G resonance and K can be obtained p and K r :

[0080]

[0081] In the formula, is a certain value.

[0082] Further, we can obtain:

[0083]

[0084] Substituting the set frequency domain parameters and the controlled object parameters into the above formula, the parameter tuning of the proportional resonant current controller can be completed.

[0085] Embodiment 2:

[0086] Based on the first embodiment, this example further discretizes the proportional resonant current controller for digital implementation, and derives its discretization form as follows:

[0087]

[0088] In the formula, y n is the output, a0, a1, a2, b0, b1 and b2 are all variables, T s is the sampling period.

[0089] Embodiment three:

[0090] like Figure 1 As shown, the current control system of the permanent magnet synchronous linear motor with multiple independent windings of the present invention implements the above control method. It includes a permanent magnet synchronous linear motor with multiple independent windings 5, a position and speed feedback unit 6, a current conversion unit 1, a comparison unit, a proportional resonant current controller 2, a sinusoidal pulse modulation unit 3 and an inverter 4;

[0091] The position and speed feedback unit 6 obtains the motor speed and mover position signals of the multi-motor independent winding permanent magnet synchronous linear motor, and feeds back the motor speed signal to the proportional resonant current controller 2, and feeds back the mover position signal to the current conversion unit 1. The current conversion unit 1 is used to convert the DQ axis given current of the motor winding to obtain a three-phase given current, and send the three-phase given current to the comparison unit. The comparison unit is used to subtract the three-phase given current from the three-phase current signal output by the inverter, and input it to the proportional resonant current controller. The proportional resonant current controller uses the parameter setting process described in claim 1 to adjust the proportional coefficient Kp and the resonance coefficient Kr based on the motor speed signal, and is used to output a modulation wave to the sinusoidal pulse modulation unit. The sinusoidal pulse modulation unit is used to generate a digital switching quantity and output it to the inverter. The inverter is used to generate a three-phase current signal according to the digital switching quantity, and control the motor through the three-phase current signal.

[0092] Test example:

[0093] This test example was experimentally verified on a 495mm long linear segment multi-motor independent winding permanent magnet synchronous linear motor. The motor has 33 sets of windings, four movers, a resistance of 0.4Ω, an inductance of 700μH, and a pole pitch of 18mm. The inverter adopts a full-bridge topology, and the controller consists of an MCU and an FPGA. The proportional resonant current controller described in the present invention is implemented in the FPGA, and the MCU is responsible for issuing current given instructions.

[0094] The following experiment is designed. When the mover moves at a high speed of 4m / s, the Q-axis current command input is the output of the speed loop, and the D-axis current command input is 0. At this time, the frequency of current change ω0 is 1396rad / s. Set ω c is 10rad / s, is 45°, and when it is substituted into the parameter setting equation, ω openloop 4500rad / s, Kp is 2, K r is 500.

[0095] The single-phase current control method of the permanent magnet synchronous linear motor with independent windings of the present invention and the single-phase current control method based on the proportional integral controller proposed in the invention patent 202210542179.8 were compared under the above working conditions. In the experiment, the open-loop cutoff frequency of the proportional integral controller was set to 222Hz, which is equal to the current change frequency at the maximum given speed.

[0096] Figure 3 and Figure 4 Based on the Q-axis and D-axis current control effect under the proportional resonance control of the present invention, thanks to the gain peak of the controller at the resonance point, the feedback current completely tracks the given current. Figure 6 and Figure 7 For the Q-axis and D-axis current control effects based on traditional proportional-integral control, since the proportional-integral control has a limited amplitude-frequency gain for the alternating signal, the feedback current cannot always fully track the given current, resulting in a current tracking error, which will further affect the control performance of the outer loop.

[0097] like Figure 5 and Figure 8 As shown in the figure, the speed control effects under the proportional resonance control of the present invention and the traditional proportional integral control are shown respectively. Thanks to the accurate and fast current tracking performance, Figure 5 The speed feedback in the system reaches the given speed quickly and without overshoot. Figure 8 The speed feedback in the tracking process has acceleration changes and overshoot, and ultimately takes more time to reach the given speed.

[0098] The above experiments show that the current control method of the multi-motor independent winding permanent magnet synchronous linear motor proposed in the present invention can not only realize fast and accurate zero-static current tracking, but also improve the outer loop control performance. This method has significant practicality and superiority.

[0099] The technical solutions of the present invention are not limited to the above-mentioned embodiments, and any technical solutions obtained by equivalent replacement methods fall within the scope of protection required by the present invention.

Claims

1. A current control method for a permanent magnet synchronous linear motor with multiple independent windings, wherein the motor is controlled by an inverter, characterized in that: Obtain the DQ axis given current and motor speed signal of the motor winding, and transform the DQ axis given current to obtain the three-phase given current; The three-phase given current and the three-phase current signal output by the inverter are differentially input into the proportional resonant current controller, and the proportional resonant current controller performs parameter adjustment based on the motor speed signal and outputs a modulation wave; The modulation wave generates a digital switch quantity through sinusoidal pulse width modulation and outputs it to the inverter. The inverter outputs a three-phase current signal to the motor to perform current closed-loop control on the motor. Among them, in the process of proportional resonant current controller parameter setting, the frequency domain design method is used to set the resonant frequency point open-loop gain G of the proportional resonant current controller. resonance and phase margin Where G0(s) is the open-loop transfer function of the proportional resonant current controller, ω openloop is the open-loop cut-off frequency; The proportional coefficient K of the proportional resonant current controller is calculated by the following formula: p and the resonance coefficient K r To perform tuning: In the formula, G resonance is the gain at the resonance point; ω openloop is the open-loop cut-off frequency; is the phase margin; R is the motor resistance; L is the motor inductance; ω c is the resonance bandwidth; ω0 is the resonance frequency, which is obtained through the motor speed signal; t is a constant.

2. The current control method of the multi-motor independent winding permanent magnet synchronous linear motor according to claim 1 is characterized in that: The open-loop transfer function of the proportional resonant current controller is: Where s is the Laplace operator, T pwm is the equivalent inertia time constant of PWM modulation.

3. The current control method of the multi-motor independent winding permanent magnet synchronous linear motor according to claim 2 is characterized in that: The proportional resonant current controller is discretized and the discretized form is: In the formula, y n is the output, a0, a1, a2, b0, b1 and b2 are all variables, T s is the sampling period.

4. The current control method of the multi-motor independent winding permanent magnet synchronous linear motor according to claim 3 is characterized in that: The relationship between the resonant frequency ω0 and the motor speed v is as follows: ω0=v·π / τ Where τ is the motor pole pitch.

5. The current control method of the multi-motor independent winding permanent magnet synchronous linear motor according to claim 1 is characterized in that: The direct axis current given I in the DQ axis given current of the motor winding d * is zero, the quadrature axis current is given by I q * for: In the formula, F e is the electromagnetic thrust, K f is the thrust coefficient.

6. The current control method of the multi-motor independent winding permanent magnet synchronous linear motor according to claim 5 is characterized in that: The DQ axis given current is transformed into the three-phase ABC axis current given I by inverse Park transformation and inverse Clark transformation according to the following formula a * ,I b * and I c * : Where θe is the electrical angle and I0* is the zero-sequence current reference.

7. The current control method of the multi-motor independent winding permanent magnet synchronous linear motor according to claim 6 is characterized in that: Electrical angle θ e The relationship with the motor rotor position x is as follows: i e =x·π / τ.

8. A current control system for a permanent magnet linear synchronous motor with multiple movers and independent windings based on the current control method according to any one of claims 1 to 7, characterized in that: It includes a permanent magnet synchronous linear motor with multiple independent windings, a position and speed feedback unit, a current conversion unit, a comparison unit, a proportional resonant current controller, a sinusoidal pulse modulation unit and an inverter; The position and speed feedback unit obtains the motor speed and mover position signals of the multi-motor independent winding permanent magnet synchronous linear motor, and feeds back the motor speed signal to the proportional resonant current controller, and feeds back the mover position signal to the current conversion unit. The current conversion unit is used to convert the DQ axis given current of the motor winding to obtain a three-phase given current, and send the three-phase given current to the comparison unit. The comparison unit is used to subtract the three-phase given current from the three-phase current signal output by the inverter, and input it to the proportional resonant current controller. The proportional resonant current controller uses the parameter setting process described in claim 1 to set the proportional coefficient Kp and the resonance coefficient Kr based on the motor speed signal, and is used to output a modulation wave to the sinusoidal pulse modulation unit. The sinusoidal pulse modulation unit is used to generate a digital switching quantity and output it to the inverter. The inverter is used to generate a three-phase current signal according to the digital switching quantity, and control the motor through the three-phase current signal. 9 . According to the current control system of the multi-motor independent winding permanent magnet synchronous linear motor of claim 8 , the current conversion unit comprises an inverse Park transformation and an inverse Clarke transformation.

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