A permanent magnet synchronous motor control method based on the combination of observer and adaptation

Abstract

This invention discloses a permanent magnet synchronous motor control method based on a combination of an observer and adaptation, comprising the following steps: S1, inputting a reference speed and actual speed into a fixed-time sliding mode controller for the speed loop; S2, obtaining the stationary coordinate system current through current conversion and inputting it into an adaptive state observer; and S3, obtaining motor speed information from the adaptive state observer. The invention first accurately models the permanent magnet synchronous motor; uses a super-helical sliding mode observer to estimate the motor's back electromotive force, thereby estimating the motor's speed and position using an inverse tangent function. Adaptive gain is introduced to enhance observer performance. A fixed-time convergent sliding mode controller is then designed to improve the controller's control performance.

Description

Technical Field

[0001] The present invention belongs to the field of sensorless speed control of permanent magnet synchronous motors, and relates to a permanent magnet synchronous motor control method based on the combination of an observer and adaptation. Background Art

[0002] Among nonlinear control methods, sliding mode control is considered one of the most effective approaches for handling uncertain nonlinear systems. Due to its fast response, high accuracy, and strong robustness, it has been widely used in the field of motor control. However, controller state information is often provided by sensors, which increases cost and system complexity. Furthermore, the settling time of typical controllers is dependent on the initial system state, making it difficult to accurately determine the upper bound on this time. Therefore, research is necessary to address these shortcomings in the existing technology and provide a solution. Summary of the Invention

[0003] To solve the above problems, the technical solution of the present invention is a permanent magnet synchronous motor control method based on the combination of observer and adaptation, comprising the following steps:

[0004] S1, inputs the reference speed and actual speed into the speed loop fixed time sliding mode controller;

[0005] S2, obtains the stationary coordinate system current through current conversion and inputs it into the adaptive state observer;

[0006] S3, the motor speed information is obtained by the adaptive state observer.

[0007] Preferably, the speed expression of the permanent magnet synchronous motor in S1 is:

[0008]

[0009] Where ω(t) is the motor speed, J is the moment of inertia, B is the damping coefficient, and T l (t) is the load torque, i q (t) is the q-axis current, P n is the number of motor pole pairs, ψ m is the motor flux strength;

[0010] The error model of velocity is thus:

[0011]

[0012] in, is the reference speed, e is the error between the reference speed and the actual speed of the motor. The reference speed and the state observer are input into the designed speed loop fixed-time sliding mode controller. The output equation of the controller is:

[0013]

[0014] in, m1>1, 0<m2<1, α1>0, β1>0; m3>1, 0<m4<1, α2>0, β2>0, k5 is greater than the upper bound of the interference, s is the designed sliding surface, and its expression is:

[0015]

[0016] The designed controller can make the motor speed error approach 0 within a fixed time, and the upper bound of its convergence time is independent of the initial state of the system, thereby realizing motor control.

[0017] Preferably, the current output by the fixed-time sliding mode controller in S2 is converted into the current of the stationary reference coordinate system after the coordinate system transformation and the SVPWM module; the converted current will serve as the input of the proposed adaptive state observer, which estimates the current of the stationary reference coordinate system based on the input, thereby inferring the speed and position information of the motor.

[0018] Preferably, the expression of the S3 adaptive state observer is:

[0019]

[0020] Among them, R is the resistance of the motor stator, L is the stator inductance, u α 、u β is the stator voltage, is the observed value of the current, is the observation error of the current, A1 and A2 are the parameters of the observer, which are adaptive parameters that change with the size of the estimation error. The adaptive law is a piecewise function:

[0021]

[0022] Where L1 is a positive integer, ω(t) is the motor speed, s is the designed sliding surface, This is the first time the system has reached the area time, ε is a small positive number, K b (s(t)) is the barrier function, which is defined as:

[0023]

[0024] in is a number greater than 0, and s is the designed sliding surface. The adaptive state observer estimates the current in the stationary reference coordinate system based on the current input, thereby obtaining the back electromotive force information, and then obtains the estimated values ​​of the motor speed and position based on the inverse tangent function.

[0025] The present invention has at least the following beneficial effects: in conventional permanent magnet synchronous motor speed control, the speed and position information required by the speed controller are all provided by sensors. However, the introduction of sensors will lead to increased costs and increase the structural complexity of the permanent magnet synchronous motor. When the sensor fails, it will also produce erroneous control results. Therefore, sensorless control of permanent magnet synchronous motors is extremely meaningful. The proposed state observer selects a sliding mode observer with excellent robustness and adopts adaptive parameters to improve the performance of the observer. In the controller design part, we designed a controller with fixed time stability properties. The upper bound of the controller's stability time is a quantity that is independent of the initial state and only related to the controller parameters. In this way, we can obtain an accurate upper bound of the motor speed stability time before using the motor.

[0026] The present invention first accurately models a permanent magnet synchronous motor. A super-helical sliding mode observer is used to estimate the motor's back electromotive force, which in turn uses the inverse tangent function to estimate the motor's speed and position. Adaptive gain is introduced to enhance the observer's performance. A fixed-time convergence sliding mode controller is then designed to improve the controller's control performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flowchart of a permanent magnet synchronous motor control method based on an observer and adaptive combination according to an embodiment of the present invention;

[0028] Figure 2 This is a system structure diagram corresponding to a permanent magnet synchronous motor control method based on a combination of observer and adaptation according to an embodiment of the present invention;

[0029] Figure 3 This is a block diagram of an adaptive observer algorithm in a permanent magnet synchronous motor control method based on a combination of observer and adaptation according to an embodiment of the present invention;

[0030] Figure 4 Graph showing the speed tracking performance of a controller at different initial speeds in a permanent magnet synchronous motor control method based on a combination of an observer and adaptation according to an embodiment of the present invention;

[0031] Figure 5 Graphs showing the speed tracking performance of three controllers under different reference speed conditions in a permanent magnet synchronous motor control method based on a combination of observer and adaptation according to an embodiment of the present invention;

[0032] Figures 6-11 Waveform diagram comparing an observer of a permanent magnet synchronous motor control method based on a combination of observer and adaptation (BF-STO) according to an embodiment of the present invention, a fixed parameter observer (CSTO) in the prior art, and a general adaptive observer (ASTO);

[0033] Figure 6 The current observation error diagram of the three observers at a stable reference speed (1000r / min);

[0034] Figure 7 The rotor speed and its estimation error diagram of the three observers at a stable reference speed (1000r / min);

[0035] Figure 8 The rotor position and estimation error diagrams of the three observers at a stable reference speed (1000r / min);

[0036] Figure 9 is the current observation error diagram of the three observers under the step reference speed;

[0037] Figure 10 The rotor speed and its estimation error diagram of the three observers under the step reference speed;

[0038] Figure 11 Figure 2 shows the rotor position and its estimation error of the three observers under step reference speed. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] On the contrary, the present invention covers any alternatives, modifications, equivalents, and solutions that fall within the spirit and scope of the present invention as defined by the claims. Furthermore, to facilitate a better understanding of the present invention, certain specific details are described in detail below in the detailed description of the present invention. Those skilled in the art will be able to fully understand the present invention without these details.

[0041] See also Figure 1 , is a flowchart of a permanent magnet synchronous motor control method based on an observer and adaptive combination according to an embodiment of the present invention, comprising the following steps:

[0042] S1, inputs the reference speed and actual speed into the speed loop fixed time sliding mode controller;

[0043] S2, obtains the stationary coordinate system current through current conversion and inputs it into the adaptive state observer;

[0044] S3, the motor speed information is obtained by the adaptive state observer.

[0045] S1, the speed expression of permanent magnet synchronous motor is:

[0046]

[0047] Where ω(t) is the motor speed, J is the moment of inertia, B is the damping coefficient, and T l (t) is the load torque, i q (t) is the q-axis current, P n is the number of motor pole pairs, ψ m is the motor flux strength.

[0048] The error model of velocity is thus:

[0049]

[0050] in, is the reference speed, and e is the error between the reference speed and the actual motor speed. The reference speed and the state observer are input into the designed speed loop fixed-time sliding mode controller, where the output equation of the controller is:

[0051]

[0052] in, m1>1, 0<m2<1, α1>0, β1>0; m3>1, 0<m4<1, α2>0, β2>0, k5 is greater than the upper bound of the interference, s is the designed sliding surface, and its expression is:

[0053]

[0054] The designed controller can make the motor speed error approach 0 within a fixed time, and the upper bound of its convergence time is independent of the initial state of the system, thereby achieving high-performance control of the motor.

[0055] In S2, the output current of the fixed-time sliding mode controller is converted to the current in the stationary reference frame after coordinate transformation and the SVPWM module. This converted current serves as the input to the proposed adaptive state observer, which estimates the current in the stationary reference frame based on the input and thus infers the motor's speed and position information.

[0056] S3, the expression of the adaptive state observer is:

[0057]

[0058] Among them, R is the resistance of the motor stator, L is the stator inductance, u α 、u β is the stator voltage, is the observed value of the current, is the observation error of the current, A1 and A2 are the parameters of the observer, which are adaptive parameters that change with the size of the estimation error. The adaptive law is designed as a piecewise function. The adaptive algorithm block diagram can be found in Figure 3 :

[0059]

[0060] Where L1 is a positive integer, ω(t) is the motor speed, s is the designed sliding surface, This is the first time the system has reached the area time, ε is a small positive number, K b (s(t)) is the barrier function, which is defined as:

[0061]

[0062] in is a number greater than 0, and s is the designed sliding surface. The observer estimates the current in the stationary reference frame based on the current input, thereby obtaining back EMF information. Using the inverse tangent function, we can obtain estimates of the motor's speed and position.

[0063] See also Figure 2 , which is the system structure diagram corresponding to the method of the present invention. The permanent magnet synchronous motor control system mainly consists of a speed loop and current loop controller, an SVPWM module, a current coordinate system conversion module, and an observer module. The current coordinate system conversion module includes: a Clark transformation module, which transforms the current from the natural coordinate system ABC to the stationary coordinate system; and a Park transformation module, which is responsible for transforming the current from the stationary coordinate system to the synchronous rotating coordinate system. The purpose of the current coordinate system conversion is to simplify the mathematical model of the three-phase PMSM in the natural coordinate system, thereby simplifying the controller design. The SVPWM module controls the load inverter. The SVPWM control strategy is a control strategy for controlling the converter based on the switching of the converter space voltage vector. It uses the switching of the inverter space voltage vector to obtain a quasi-circular rotating magnetic field. The current loop controller usually adopts a PID controller, whose function is to make the motor current follow the changes of the given current (speed loop output), which has an important impact on the rapidity and accuracy of the system response. The present invention designs a speed loop controller module and an observer module. The function of the speed loop controller is to make the motor speed tend to the reference speed. The function of the observer module is to observe the speed and position information of the permanent magnet synchronous motor, so that sensorless control can be performed in the absence of speed and position sensors.

[0064] See also Figure 4 and Figure 5 The waveform diagrams in the experiment show the speed of the permanent magnet synchronous motor under different reference speeds and disturbances. The diagrams show that compared to conventional sliding mode control algorithms, the fixed-time sliding mode controller designed in this invention performs better in the experiment. It has better convergence performance at both fixed and variable reference speeds, reaches the reference speed more quickly, and is highly robust to external disturbances.

[0065] To validate the effectiveness of the proposed method, experimental results are compared with conventional sliding mode control and general fixed-time sliding mode control. The convergence performance and robustness of the three controllers are compared under different reference speeds, including a steady reference speed and a step reference speed. Two experimental examples are used to illustrate the superior observation performance of the novel adaptive state observer of the present invention compared to existing state observers.

[0066] Figure 4 The figure shows the speed tracking performance of the proposed controller at different initial speeds. It can be seen that at different initial speeds, the controller can reach the reference speed in the same time, thus verifying the fixed-time convergence of the proposed controller. Figure 5 The speed tracking performance of the three controllers under different reference speed conditions is shown. As can be seen from the figure, whether under the conditions of stable reference speed (1000r / min) or step reference speed (from 500r / min to 1000r / min, and then from 000r / min to 500r / min), the controller proposed in the present invention can converge to the reference speed in a shorter time, indicating that the controller has better control performance. At the same time, we added a 4NM step load signal at 0.3s to verify the robustness of the controller. It can be seen that the proposed controller can recover to the reference speed in a faster time, indicating that the controller has better robustness.

[0067] In observer example 1, at a stable reference speed (1000r / min), we compare the proposed new adaptive state observer (BF-STO) with the fixed parameter observer (CSTO) and the general adaptive observer (ASTO). Figure 6-8 The observation effects and observation errors of the three observers for current, speed and position are shown respectively. Figure 6 As shown in Figure 3, the current observation errors of CSTO, ASTO and the invented method are 0.32mA, 0.19mA and 0.009mA respectively. The proposed observer has the smallest observation error. Figure 7The rotor speed and its estimation error are shown. When the speed is stable, the observation error of the present invention is 0.34 r / s, which is significantly smaller than 0.66 r / s of CSTO and 0.56 r / s of ASTO. Figure 8 The rotor position and its estimated error for the three observers are plotted. Despite phase compensation in the experiment, a large position error still exists. The error of the present invention is 0.000017 rad, which is smaller than that of CSTO (0.000488 rad) and ASTO (0.000303 rad). Furthermore, it can be seen that the present invention can also accurately estimate speed and position when the step torque is applied at 0.3 s and the estimation error is minimized.

[0068] To further verify the superior observation performance of the present invention, we again verified the observation performance of the three observers for current, speed, and position under the condition of a step reference speed (increasing from 500 r / min to 1000 r / min and then decreasing from 1000 r / min to 500 r / min). Figure 9-11 The observation effects and observation errors of the three observers for current, speed and position are shown respectively. Figure 9 The current observation error is shown. Obviously, the observation effect of CSTO is the worst, and its maximum estimated error is 0.38mA. The observation error of ASTO will increase with the increase of speed: the error is 0.03mA at 500R / s and 0.23mA at 1000R / s. The present invention has a stable and minimum observation error, that is, 0.009mA. At the same time, see Figure 10 , CSTO's speed observation performance is not good enough, and its maximum speed error is 1.05r / s. And ASTO's high-speed observation performance needs to be improved: at low speed, its error is 0.19r / s, and at high speed it is 0.62r / s. The present invention has the best performance, with an error of 0.12r / s at low speed and 0.4r / s at high speed. Figure 11 The rotor position and its observation errors are described in [1]. The position errors for CSTO, ASTO, and the present invention are 0.0008 rad, 0.0002 rad, and 0.00002 rad, respectively. The current, speed, and position estimation errors for the present invention are relatively stable, and the observed chattering problem is less severe than for CSTO and ASTO.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A permanent magnet synchronous motor control method based on the combination of observer and adaptation, characterized in that: The following steps are involved: S1, inputs the reference speed and actual speed into the speed loop fixed time sliding mode controller; S2, obtains the stationary coordinate system current through current conversion and inputs it into the adaptive state observer; S3, the motor speed information is obtained by the adaptive state observer; The expression of the S3 adaptive state observer is: Among them, R is the resistance of the motor stator, L is the stator inductance, u α 、u β is the stator voltage, is the observed value of the current, is the observation error of the current, A1 and A2 are the parameters of the observer, which are adaptive parameters that change with the size of the estimation error. The adaptive law is a piecewise function: Where L1 is a positive integer, ω(t) is the motor speed, s is the designed sliding surface, This is the first time the system has reached the area time, ε is a small positive number, K b (s(t)) is the barrier function, which is defined as: in is a number greater than 0, and s is the designed sliding surface. The adaptive state observer estimates the current in the stationary reference coordinate system based on the current input, thereby obtaining the back electromotive force information, and then obtains the estimated values ​​of the motor speed and position based on the inverse tangent function. The speed expression of the permanent magnet synchronous motor in S1 is: Where ω(t) is the motor speed, J is the moment of inertia, B is the damping coefficient, and T l (t) is the load torque, i q (t) is the q-axis current, P n is the number of motor pole pairs, ψ m is the motor flux strength; The error model of velocity is thus: in, is the reference speed, e is the error between the reference speed and the actual speed of the motor. The reference speed and the state observer are input into the designed speed loop fixed-time sliding mode controller. The output equation of the controller is: in, m1>1, 0<m2<1, α1>0, β1>0; m3>1, 0<m4<1, α2>0, β2>0, k5 is greater than the upper bound of the interference, s is the designed sliding surface, and its expression is: The designed controller can make the motor speed error approach 0 within a fixed time, and the upper bound of its convergence time is independent of the initial state of the system, thereby realizing motor control.

2. The method according to claim 1, characterized in that The current output by the fixed-time sliding mode controller in S2 is converted into the current of the stationary reference coordinate system after coordinate system transformation and SVPWM module; the converted current will serve as the input of the proposed adaptive state observer, which estimates the current of the stationary reference coordinate system based on the input, thereby inferring the speed and position information of the motor.

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