Permanent magnet synchronous motor non-inductive control method

Abstract

The invention discloses a permanent magnet synchronous motor non-inductive control method, and belongs to the field of permanent magnet synchronous motor control. Comprising the following steps: firstly, selecting stator current in the permanent magnet synchronous motor, defining a system state equation and a mechanical motion equation of the permanent magnet synchronous motor, then designing an exponential sliding mode speed controller, and finally designing a hyperbolic tangent function-based super-spiral sliding mode observer to observe counter electromotive force. And obtaining the rotating speed of the motor by using an arc tangent function. According to the hyperbolic tangent function-based super-spiral sliding mode observer, smooth transition can be provided near a sliding mode surface, high-frequency switching caused by small interference is avoided, system buffeting is obviously reduced, the designed speed controller can quickly respond under the condition that the rotating speed is quickly changed or load disturbance is relatively large, and the system stability is improved. And meanwhile, the problem of integral saturation in a PI speed controller is avoided, the robustness of the system is improved, and the buffeting effect is inhibited.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a sensorless control method for a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motor (PMSM) has been widely used in electric vehicles, robotics and industrial automation due to its high efficiency, high power density and high dynamic response performance. However, traditional PMSM control systems rely on position sensors to obtain accurate rotor position information to achieve high-performance closed-loop control. Common sensors include rotary encoders, Hall sensors and resolvers, which can provide reliable position signals for control systems under various working conditions. The use of position sensors also brings several problems; first, the hardware cost of position sensors is high, especially in applications that require precise positioning, the quality and accuracy of the sensors directly affect the cost of the overall system. At the same time, the installation, calibration and maintenance of sensors increase the complexity of the system, bringing additional workload and cost to manufacturing and maintenance. Secondly, sensors are easily interfered by external factors in the actual working environment, such as extreme conditions such as high temperature, dust, vibration and humidity, which may cause sensor failure, so that the entire system loses accurate perception of the rotor position and affects the normal operation of the motor; in order to solve the cost and reliability issues related to sensors, in recent years, researchers have begun to explore position sensorless control technology to estimate the position and speed of the rotor through the electrical signals of the motor operation (such as stator current and voltage). However, the existing sensorless control technology still has many shortcomings. First, many existing methods have difficulty in accurately estimating the rotor position under low-speed or zero-speed conditions, which severely limits their scope of application. In addition, due to the presence of various nonlinear factors in actual motor systems, such as electromagnetic noise, parameter changes, and load disturbances, the accuracy of position estimation is difficult to guarantee.

[0003] Observers based on sliding mode control theory are widely used in position sensorless control technology. They have good anti-interference and robustness to model uncertainty. However, a major drawback of sliding mode controllers is the chattering phenomenon, that is, high-frequency oscillations occur in the control signal when switching, which not only reduces the control accuracy of the system, but also may cause mechanical wear in the motor system and affect its service life. Although some methods have attempted to reduce the chattering effect by filtering or adjusting the control algorithm, these improvements are often accompanied by a decrease in control response speed and system robustness, and cannot take both into account. Therefore, how to develop a position sensorless control technology that can work effectively in the full speed range without increasing hardware costs, especially to overcome the chattering problem in the sliding mode observer while maintaining the robustness and high precision of the system, is an important problem that needs to be solved in the current field of permanent magnet synchronous motor control. Summary of the invention

[0004] In order to solve the above technical problems, the technical solution of the present invention is a sensorless control method of a permanent magnet synchronous motor.

[0005] To implement the above technical solution, the specific steps are as follows:

[0006] A sensorless control method for a permanent magnet synchronous motor comprises the following steps:

[0007] S1. Establish a two-phase stationary coordinate system and obtain the stator current equation;

[0008] The stator current equation is as follows:

[0009]

[0010] In the formula, i α 、i β 、u α 、u β are the stator current and voltage of the α-axis and β-axis respectively; R and L are the stator resistance and stator inductance respectively; e α 、e β are the back electromotive force of α-axis and β-axis respectively;

[0011] S2. Establish the mechanical motion equation of the permanent magnet synchronous motor, which is as follows:

[0012]

[0013] Where, J is the moment of inertia; ω m is the rotor angular velocity; P n is the pole pair number; i q is the q-axis current; T L is the load torque, ψ f is the permanent magnet flux;

[0014] S3. Establish an exponential sliding film speed controller as the speed loop of the motor control system. The specific steps are as follows:

[0015] S3.1. Define the permanent magnet synchronous motor system state variables as:

[0016] x1=ω ref -ω m

[0017] In the formula, ω ref is the rotor reference angular velocity;

[0018] S3.2. In the permanent magnet synchronous motor system, an exponential sliding film speed controller is designed, a sliding surface is established, and an estimated value of the q-axis current is obtained according to the permanent magnet synchronous motor motion equation;

[0019] The expression of the exponential sliding film speed controller is:

[0020]

[0021] Where s is the sliding surface; sign(·) is the sign function; q' is the design parameter, and q'>0; ε represents the switching gain or the dithering gain;

[0022] The expression of the established sliding surface is as follows:

[0023] s=cx1+x2

[0024] In the formula, c is the integral coefficient, x1 is the system state variable, and x2 is the derivative of x1;

[0025] S3.3. According to the mechanical motion equation of the permanent magnet synchronous motor and the expression of the exponential sliding film speed controller, the estimated value of the q-axis current is obtained as follows:

[0026]

[0027] In the formula, t represents time; ε represents switching gain or jitter gain, that is, the larger the value, the stronger the sliding mode controller's ability to suppress disturbances, but the more violent the switching action, the greater the jitter;

[0028] S4, according to the hyperbolic tangent function, the synovial observer and the super-helical synovial observer algorithm, construct a super-helical synovial observer based on the hyperbolic tangent function to calculate the back electromotive force;

[0029] The expression of the hyperbolic tangent function is:

[0030]

[0031] In the formula, e x is an exponential function;

[0032] The expression of the synovial observer is as follows:

[0033]

[0034] In the formula, are the estimated current values ​​of the α-axis and β-axis respectively; k is the sliding mode gain coefficient; sign(·) is the sign function;

[0035] According to the expression of the sliding mode observer and the stator current equation of the two-phase stationary coordinate system, the current error state equation can be obtained as follows:

[0036]

[0037] In the formula, is the error of stator current in two-phase stationary coordinate system;

[0038] Furthermore, the expression of the superhelical synovial observer algorithm is:

[0039]

[0040] Where, k1 and k2 are the first gain coefficient and the second gain coefficient of the super-helical sliding mode, and x1 is the system state variable; Errors in system state variables;

[0041] The hyperbolic switching superhelix algorithm is obtained by combining the superhelix observer algorithm with the hyperbolic tangent function. Its expression is as follows:

[0042]

[0043] In the formula, h(.) represents the hyperbolic tangent function;

[0044] According to the current equation and the hyperbolic switching superhelical algorithm, the back electromotive force calculated by the superhelical sliding film observer of the hyperbolic tangent function is:

[0045]

[0046] In the formula, e α 、e β is the back electromotive force of α and β axes;

[0047] S5. Use the inverse tangent function to parse the motor's rotor speed and rotor position from the back electromotive force. The specific expressions are as follows:

[0048]

[0049] In the formula, is the estimated rotor position; is the rotor angular velocity;

[0050] S6. Input the motor rotor speed to the exponential sliding film speed controller to achieve a closed loop system.

[0051] Beneficial effects of the present invention:

[0052] Based on the original superhelix, the present invention changes the sign function into a hyperbolic tangent function. Compared with the sign function, the hyperbolic tangent function has continuity and can provide a smooth transition near the sliding surface, thereby effectively reducing the jitter of the system, avoiding high-frequency switching caused by slight interference, and improving the robustness of the system.

[0053] The present invention designs an exponential synovial film speed controller based on a hyperbolic tangent function super-helical synovial film observer. The speed controller can respond quickly when the speed changes rapidly or the load disturbance is large, while avoiding the integral saturation problem in the PI speed controller and improving the robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is a flow chart of the steps of the present invention;

[0055] Figure 2 This is the control block diagram of the permanent magnet synchronous motor principle;

[0056] Figure 3 The block diagram of the super spiral sliding mode observer for the hyperbolic tangent function;

[0057] Figure 4 This is a comparison chart of the zero-load speed of a permanent magnet synchronous motor;

[0058] Figure 5 This is a comparison chart of the permanent magnet synchronous motor's speed when a sudden load is applied. DETAILED DESCRIPTION

[0059] The present invention is further described in detail below in conjunction with specific embodiments.

[0060] like Figure 1 As shown, a method for controlling a permanent magnet synchronous motor without a sensor is shown in the block diagram. Figure 2 As shown, the specific steps include:

[0061] This embodiment is experimentally verified by building a simulation platform, and the parameters of the permanent magnet synchronous motor are selected as follows: rated power 200W, rated speed 3000r / min, rated torque 1.5N·m, pole pair number 5, permanent magnet flux linkage 0.15Wb, stator resistance 0.8Ω, and inductance 1.6mH.

[0062] S1. Establish a two-phase stationary coordinate system and obtain the stator current equation;

[0063] The current equation is as follows:

[0064]

[0065] In the formula, i α 、i β 、u α 、u β are the stator current and voltage of the α-axis and β-axis respectively; R and L are the stator resistance and stator inductance respectively; e α 、e β are the back electromotive force of α-axis and β-axis respectively;

[0066] S2. Establish the mechanical motion equation of the permanent magnet synchronous motor, which is as follows:

[0067]

[0068] Where, J is the moment of inertia; ω m is the rotor angular velocity; P n is the pole pair number; i q is the q-axis current; T L is the load torque, ψ f is the permanent magnet flux;

[0069] S3. Establish an exponential sliding film speed controller as the speed loop of the motor control system. The specific steps are as follows:

[0070] S3.1. Define the state variables of the permanent magnet synchronous motor system as:

[0071] x1=ω ref -ω m

[0072] In the formula, ω ref is the rotor reference angular velocity;

[0073] S3.2. In the permanent magnet synchronous motor system, an exponential sliding film speed controller is designed, a sliding surface is established, and an estimated value of the q-axis current is obtained according to the permanent magnet synchronous motor motion equation;

[0074] The expression of the exponential sliding film speed controller is:

[0075]

[0076] Where s is the sliding surface; sign(·) is the sign function; q' is the design parameter, and q'>0; ε represents the switching gain or the dithering gain;

[0077] The expression of the established sliding surface is as follows:

[0078] s=cx1+x2

[0079] In the formula, c is the integral coefficient, x1 is the system state variable, and x2 is the derivative of x1;

[0080] S3.3. According to the mechanical motion equation of the permanent magnet synchronous motor and the expression of the exponential sliding film speed controller, the estimated value of the q-axis current is obtained as follows:

[0081]

[0082] In the formula, t represents time; ε represents switching gain or jitter gain, that is, the larger the value, the stronger the sliding mode controller's ability to suppress disturbances, but the more violent the switching action, the greater the jitter;

[0083] S4, according to the hyperbolic tangent function, the synovial observer and the super-helical synovial observer algorithm, construct a super-helical synovial observer based on the hyperbolic tangent function to calculate the back electromotive force;

[0084] Figure 3 The block diagram of the super spiral sliding mode observer for the hyperbolic tangent function;

[0085] The expression of the hyperbolic tangent function is:

[0086]

[0087] In the formula, e x is an exponential function;

[0088] The expression of the synovial observer is as follows:

[0089]

[0090] In the formula, are the estimated current values ​​of the α-axis and β-axis respectively; k is the sliding mode gain coefficient; sign(·) is the sign function;

[0091] According to the expression of the sliding mode observer and the stator current equation of the two-phase stationary coordinate system, the current error state equation can be obtained as follows:

[0092]

[0093] In the formula, is the error of stator current in two-phase stationary coordinate system;

[0094] Furthermore, the expression of the superhelical synovial observer algorithm is:

[0095]

[0096] Where, k1 and k2 are the first gain coefficient and the second gain coefficient of the super-helical sliding mode, and x1 is the system state variable;

[0097] The hyperbolic switching superhelix algorithm is obtained by combining the superhelix observer algorithm with the hyperbolic tangent function. Its expression is as follows:

[0098]

[0099] According to the current equation and the hyperbolic switching superhelical algorithm, the back electromotive force calculated by the superhelical sliding film observer of the hyperbolic tangent function is:

[0100]

[0101] In the formula, e α 、e βis the back electromotive force of α and β axes;

[0102] S5. Use the inverse tangent function to parse the motor's rotor speed and rotor position from the back electromotive force. The specific expressions are as follows:

[0103]

[0104] In the formula, is the estimated rotor position; is the rotor angular velocity;

[0105] S6. Input the motor rotor speed to the exponential sliding film speed controller to achieve a closed loop system.

[0106] Figure 4 This is the experimental result of accelerating the motor from 0 to 1200 r / min when the motor is unloaded. It can be seen from the experimental results that the speed estimation of the method of the present invention can meet the speed regulation requirements of the system, and when the motor is running, there is almost no overshoot in the speed.

[0107] Figure 5 The experimental results show that the motor accelerates from 0 to 1200 r / min when it is unloaded and a 1N load is suddenly added in 0.1 second. It can be seen from the experimental results that the speed of the method of the present invention decreases after loading 1N·m, but the actual speed can still be tracked. The experimental results show that the system of the method of the present invention is stable when the motor is running and meets the speed regulation requirements of the system, which proves the feasibility of the present invention.

[0108] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A sensorless control method for a permanent magnet synchronous motor, characterized in that: The following steps are involved: S1. Establish a two-phase stationary coordinate system and obtain the stator current equation; S2. Establish the mechanical motion equation of the permanent magnet synchronous motor; S3, establishing an exponential sliding film speed controller as a speed loop of the motor control system; S4, according to the hyperbolic tangent function, the synovial observer and the super-helical synovial observer algorithm, construct a super-helical synovial observer based on the hyperbolic tangent function to calculate the back electromotive force; S5, using the inverse tangent function to parse the rotor speed and rotor position of the motor from the back electromotive force; S6. Input the motor rotor speed to the exponential sliding film speed controller to achieve a closed loop system.

2. A sensorless control method for a permanent magnet synchronous motor according to claim 1, characterized in that: The two-phase stationary coordinate system is established to obtain the stator current equation, and the formula of the stator current equation is as follows: In the formula, i α 、i β 、u α 、u β are the stator current and voltage of α-axis and β-axis respectively; R and L are stator resistance and stator inductance respectively; α 、e β are the back electromotive force of the α-axis and β-axis respectively.

3. The sensorless control method of a permanent magnet synchronous motor according to claim 1, characterized in that: The expression for establishing the mechanical motion equation of the permanent magnet synchronous motor is as follows: Where, J is the moment of inertia; ω m is the rotor angular velocity; P n is the pole pair number; i q is the q-axis current; T L is the load torque, ψ f is the permanent magnet flux.

4. The sensorless control method of a permanent magnet synchronous motor according to claim 1, characterized in that: The specific steps of establishing an exponential sliding film speed controller as the speed loop of the motor control system are as follows: S3.

1. Define the permanent magnet synchronous motor system state variables as: x1=ω ref -oh m In the formula, ω ref is the rotor reference angular velocity; S3.

2. In the permanent magnet synchronous motor system, an exponential sliding film speed controller is designed, a sliding surface is established, and an estimated value of the q-axis current is obtained according to the permanent magnet synchronous motor motion equation; The expression of the exponential sliding film speed controller is: Where s is the sliding surface; sign(·) is the sign function; q' is the design parameter, and q'>0; ε represents the switching gain or the dithering gain; The expression of the established sliding surface is as follows: s=cx1+x2 In the formula, c is the integral coefficient, x1 is the system state variable, and x2 is the derivative of x1; S3.

3. According to the mechanical motion equation of the permanent magnet synchronous motor and the expression of the exponential sliding film speed controller, the estimated value of the q-axis current is obtained as follows: Where, t represents time; ε represents switching gain or dithering gain.

5. The sensorless control method of a permanent magnet synchronous motor according to claim 1, characterized in that: According to the hyperbolic tangent function, the synovial observer and the super-helical synovial observer algorithm, a super-helical synovial observer based on the hyperbolic tangent function is constructed to calculate the back electromotive force. The expression of the hyperbolic tangent function is: In the formula, e x is an exponential function; The expression of the synovial observer is as follows: In the formula, are the estimated current values ​​of the α-axis and β-axis respectively; k is the sliding mode gain coefficient; sign(·) is the sign function; According to the expression of the sliding mode observer and the stator current equation of the two-phase stationary coordinate system, the current error state equation can be obtained as follows: In the formula, is the error of stator current in two-phase stationary coordinate system; The expression of the superhelical synovial observer algorithm is: Where, k1 and k2 are the first gain coefficient and the second gain coefficient of the super-helical sliding mode, and x1 is the system state variable; Errors in system state variables; The hyperbolic switching superhelix algorithm is obtained by combining the superhelix observer algorithm with the hyperbolic tangent function. Its expression is as follows: In the formula, h(.) represents the hyperbolic tangent function; According to the current equation and the hyperbolic switching superhelical algorithm, the back electromotive force calculated by the superhelical sliding film observer of the hyperbolic tangent function is as follows: In the formula, e α 、e β is the back electromotive force of the α and β axes.

6. The sensorless control method of a permanent magnet synchronous motor according to claim 1, characterized in that: The inverse tangent function is used to parse the rotor speed and rotor position of the motor from the back electromotive force. The specific expressions are as follows: In the formula, is the estimated rotor position; is the rotor angular velocity.

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