Permanent magnet synchronous motor speed control method based on improved load torque observer

Abstract

The application discloses a permanent magnet synchronous motor speed control method based on an improved load torque observer, and comprises the following steps: S1, acquiring a real-time measured mechanical angular velocity and an electromagnetic torque of the permanent magnet synchronous motor; S2, calculating a speed error between the measured mechanical angular velocity and an estimated mechanical angular velocity of the observer, and calculating an electromagnetic torque change rate; S3, based on the electromagnetic torque change rate, dynamically adjusting feedback gain parameters of the load torque observer, and the greater the electromagnetic torque change rate, the greater the selected values of the differential feedback gain and the proportional feedback gain; S4, according to the speed error, the adjusted feedback gain parameters of S3 and a differential term of the speed error introduced in the error feedback path of the observer, performing real-time calculation through a differential equation of the load torque observer, outputting and updating the load torque observation value; and S5, introducing the updated load torque observation value as a feedforward compensation into a permanent magnet synchronous motor control system to suppress speed fluctuation caused by load disturbance.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet synchronous motor technology, and in particular to a method for controlling the speed of a permanent magnet synchronous motor based on an improved load torque observer. Background Technology

[0002] In actual operation, due to the time-varying and unpredictable nature of load torque, it is difficult to effectively suppress speed fluctuations caused by load disturbances by relying solely on traditional PI regulators. Therefore, a compromise must be made on various performance indicators.

[0003] To improve the system's disturbance rejection performance, existing research indicates that using a state observer to observe the load torque is a good option, and applying a reduced-order load torque observer to a feedback control system has shown some effectiveness.

[0004] However, traditional reduced-order observers suffer from slow convergence speed, making it difficult to quickly track sudden changes in load torque. This results in significant speed overshoot and recovery time when the load changes, limiting their application in high-dynamic-performance applications.

[0005] Therefore, how to improve the dynamic response speed of the load torque observer and reduce the overshoot while ensuring the accuracy of the observation has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for controlling the speed of a permanent magnet synchronous motor based on an improved load torque observer, comprising the following steps: S1. Real-time acquisition of measured mechanical angular velocity and electromagnetic torque of permanent magnet synchronous motor; S2. Calculate the rotational speed error between the measured mechanical angular velocity and the mechanical angular velocity estimated internally by the observer, and calculate the electromagnetic torque change rate; S3. Based on the magnitude of the electromagnetic torque change rate, dynamically adjust the feedback gain parameters of the load torque observer, wherein the larger the electromagnetic torque change rate, the larger the values ​​of the differential feedback gain and the proportional feedback gain are selected. S4. Based on the speed error, the feedback gain parameter adjusted in S3, and the differential term of the speed error introduced in the observer error feedback path, the load torque observer performs real-time calculation through the differential equation of the load torque observer, and outputs and updates the observed load torque value. S5. The updated load torque observation value is introduced into the permanent magnet synchronous motor control system as a feedforward compensation value to suppress speed fluctuations caused by load disturbances.

[0007] Furthermore, the differential equation of the load torque observer is expressed as:

[0008] In the formula, For the estimated mechanical angular velocity, The measured mechanical angular velocity; The observed value of the load torque; This is the load torque; The coefficient of friction; J Let the system's rotational inertia be denoted by . The electromagnetic torque; , , , These are the feedback gain parameters.

[0009] Furthermore, the strategy for dynamically adjusting the feedback gain parameter of the load torque observer in S3 includes: The electromagnetic torque change rate obtained in real time | |With the preset first threshold Second threshold In comparison, among which, < ; Based on the comparison results, the proportional feedback gain is... and differential feedback gain Assign different combinations of parameters.

[0010] Furthermore, the differential feedback gain is determined based on the comparison results. and proportional feedback gain Different parameter combinations can be assigned, specifically including: When | |≤ At that time, , Assign the first parameter combination; when <| |< At that time, , Assign a second parameter combination, and in the second parameter combination The value is greater than that in the first parameter combination. value; When | |≥ At that time, , Assign a third parameter combination, and in the third parameter combination , The value is configured to maximize the dynamic response speed of the observer.

[0011] Furthermore, the feedback gain parameter The value is determined by debugging based on the actual dynamic response performance of the permanent magnet synchronous motor control system.

[0012] Furthermore, the feedback gain parameter The value was set to 0.

[0013] Furthermore, in step S5, the load torque observation value is fed forward to: The q-axis current reference path for the current loop; or, Torque setting channel for the speed loop.

[0014] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: Based on the reduced-order observer, this invention proposes a variable-parameter improved load torque observer, which incorporates a proportional-derivative element to adjust parameters according to the electromagnetic torque change rate. This enables the observer to prioritize and quickly track during severe disturbances and maintain stable accuracy during smooth operation, thereby improving the torque observation response speed and taking into account small overshoot. It effectively suppresses the speed fluctuation of permanent magnet synchronous motors caused by load disturbances during actual operation. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a block diagram of the torque observer disclosed in this invention; Figure 2 The above is a simulation comparison diagram of charging using a dual-winding motor, as disclosed in the embodiments of the invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention aims to provide a speed control method for permanent magnet synchronous motors based on an improved load torque observer. The design concept is to propose a variable parameter improved load torque observer based on a reduced-order observer, and to add a proportional-derivative element to dynamically adjust the parameters according to the actual effect, thereby improving the torque observation response speed while taking into account a small overshoot.

[0019] The speed control method of this permanent magnet synchronous motor is described in detail below.

[0020] S1. Real-time acquisition of the measured mechanical angular velocity and electromagnetic torque of the permanent magnet synchronous motor.

[0021] S2. Calculate the rotational speed error between the measured mechanical angular velocity and the mechanical angular velocity estimated internally by the observer, and calculate the electromagnetic torque change rate. |

[0022] S3, Based on electromagnetic torque change rate | |Size, dynamically adjusts the feedback gain parameter of the load torque observer, where the electromagnetic torque change rate| The larger the value, the greater the differential feedback gain. and proportional feedback gain The larger the selected value, the better.

[0023] In a further proposed approach, the strategy for dynamically adjusting the feedback gain parameter of the load torque observer includes: S31, The electromagnetic torque change rate calculated in real time | |With the preset first threshold Second threshold In comparison, among which, < ; S32. Based on the comparison results, determine the proportional feedback gain. and differential feedback gain Assign different combinations of parameters.

[0024] Specifically: (a) When | |≤ At that time, , Assign the first parameter combination; (b) When <| |< At that time, , Assign a second parameter combination, and in the second parameter combination... The value is greater than that in the first parameter combination. value; (c) When | When |≥, it is , Assign the third parameter combination, and in the third parameter combination , The value is configured to maximize the dynamic response speed of the observer.

[0025] In a further scheme, the feedback gain parameter The value is set to 0; feedback gain parameter The value is determined by debugging based on the actual dynamic response performance of the permanent magnet synchronous motor control system. .

[0026] S4. Based on the speed error, the feedback gain parameter adjusted in step S3, and the differential term of the speed error introduced in the observer error feedback path, the load torque observer performs real-time calculation through the differential equation of the load torque observer, outputs and updates the observed load torque value.

[0027] S5. The updated load torque observation value is introduced into the permanent magnet synchronous motor control system as a feedforward compensation value to suppress speed fluctuations caused by load disturbances.

[0028] Optionally, the load torque observation can be fed forward to the q-axis current reference channel of the current loop or the torque reference channel of the speed loop.

[0029] The following provides a further explanation of the implementation method of the variable parameter load torque observer provided by the present invention.

[0030] According to the principles of dynamics, the mechanical motion equations of a permanent magnet synchronous motor are:

[0031] In the formula, Electromagnetic torque; J Let the system's rotational inertia be denoted by . The measured mechanical angular velocity of the rotor; The coefficient of friction; This refers to the load torque (including no-load torque).

[0032] Among them, the measured mechanical angular velocity of the rotor Satisfying the expression:

[0033] In the formula, For mechanical angles.

[0034] When the sampling period is extremely small, it is assumed that the load torque is constant within one period, that is:

[0035] Solving the three formulas together, we can transform the equations into state equation form:

[0036] Wherein, the state vector Input quantity Output y = The matrix is ​​defined as , , .

[0037] The conventional design process for a reduced-order load torque observer is to ignore directly measurable parameters. ,reserve and For state variables, the reduced state vector Then the state equation simplifies to:

[0038] in, , Because conventional reduced-order load torque observers have a slow response, they cannot quickly track torque changes.

[0039] Therefore, a proportional and differential term for the error between the detected speed and the estimated speed is introduced into the reduced-order load torque observer to improve the convergence speed. The improved observer equation is as follows:

[0040] In the formula, This is the feedback matrix.

[0041] After substituting the parameters, the differential equation of the improved observer is:

[0042] In the formula, To estimate the mechanical angular velocity, To measure the mechanical angular velocity; This is the observed value of the load torque; This is the load torque; The coefficient of friction; J Let the system's rotational inertia be denoted by . Electromagnetic torque; , , , These are the feedback gain parameters.

[0043] The principle block diagram of the variable parameter load torque observer is as follows: Figure 1 As shown, the specific parameter adjustment process for this state observer is as follows: First design , ;Pick =0、 =0.

[0044] Add according to the dynamic response situation. ≠0、 Parameters ≠ 0; alternatively, one can consider obtaining different zero-pole configurations through tuning based on the transfer function, and then adjust according to the zero-pole configuration and dynamic response.

[0045] Based on simulation and experimental results, by taking different parameters at different stages according to the rate of change of electromagnetic torque, a method can be used to obtain a dynamic response that balances fast response and small steady-state error, such as... Figure 2 As shown, considering the rate of change of electromagnetic torque: When the rate of change exceeds a certain value At that time, take This is the value with the fastest dynamic response speed mentioned above.

[0046] When the rate of change exceeds a certain value At that time, take Appropriately increase The entire adjustment process is similar to the PI parameter tuning process.

[0047] After adjusting the above parameters, select appropriate values ​​based on the system's dynamic response. It can effectively improve system performance. The term represents the increase in the speed deviation differential, which can affect system stability and should be determined based on actual performance.

[0048] The technical principles of this invention can be summarized as follows: On the one hand, a differential term of the rotational speed error is introduced into the observer error feedback path. Because the differential term represents the "trend of change," it can provide an anticipatory correction. When the load changes abruptly and the speed error has just begun to change, the differential term can generate a strong correction signal, thereby greatly accelerating the initial response speed of the observer. This is a key means to solve the problem of slow convergence speed in traditional reduced-order load torque observers.

[0049] On the other hand, a variable parameter strategy is introduced, and its adjustment is based on the rate of change of electromagnetic torque. Due to the rate of change of electromagnetic torque It is a direct and sensitive reflection of the severity of load disturbances. When | A large gain indicates a drastic change in load. In this case, speed should be prioritized, so the gain should be increased. This makes the differential action stronger, forcing the observations to track quickly. When | A smaller gain indicates a stable or slowly changing load. In this case, stability should be prioritized and overshoot suppressed, so the gain is reduced to make the observation process smoother.

[0050] To verify the effectiveness of this invention, please refer to [link / reference]. Figure 2 The simulation diagram shown simulates the observation of rotational speed and load torque by loading a 50 Nm load in 0.3 s and unloading a 50 Nm load in 0.5 s.

[0051] Simulation results show that the rotational speed fluctuates during loading and unloading, and the observer can track the trend (since this invention focuses on evaluating torque observation, the speed tracking effect is not evaluated here). The dynamic response of the observers at different stages varies greatly. The torque overshoot of the variable parameter plus proportional adjustment proposed in this scheme is 11.5%, and the response time is 0.075s, which is an improvement in performance compared with other methods, proving the effectiveness of this method.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for speed control of a permanent magnet synchronous motor based on an improved load torque observer, characterized in that, Includes the following steps: S1. Real-time acquisition of measured mechanical angular velocity and electromagnetic torque of permanent magnet synchronous motor; S2. Calculate the rotational speed error between the measured mechanical angular velocity and the mechanical angular velocity estimated internally by the observer, and calculate the electromagnetic torque change rate; S3. Based on the magnitude of the electromagnetic torque change rate, dynamically adjust the feedback gain parameters of the load torque observer, wherein the larger the electromagnetic torque change rate, the larger the values ​​of the differential feedback gain and the proportional feedback gain are selected. S4. Based on the speed error, the feedback gain parameter adjusted in S3, and the differential term of the speed error introduced in the observer error feedback path, the load torque observer performs real-time calculations using its differential equation, outputs, and updates the observed load torque value; the differential equation of the load torque observer is expressed as: In the formula, For the estimated mechanical angular velocity, The measured mechanical angular velocity; The observed value of the load torque; This is the load torque; The coefficient of friction; J Let the system's rotational inertia be denoted by . The electromagnetic torque; , , , These are the feedback gain parameters; S5. The updated load torque observation value is introduced into the permanent magnet synchronous motor control system as a feedforward compensation value to suppress speed fluctuations caused by load disturbances.

2. The method for controlling the speed of a permanent magnet synchronous motor based on an improved load torque observer according to claim 1, characterized in that, The strategy for dynamically adjusting the feedback gain parameter of the load torque observer in S3 includes: The electromagnetic torque change rate obtained in real time | |With the preset first threshold Second threshold In comparison, among which, < ; Based on the comparison results, the proportional feedback gain is... and differential feedback gain Assign different combinations of parameters.

3. The method for controlling the speed of a permanent magnet synchronous motor based on an improved load torque observer according to claim 2, characterized in that, The result of the comparison is the differential feedback gain. and proportional feedback gain Different parameter combinations can be assigned, specifically including: When | |≤ At that time, , Assign the first parameter combination; when <| |< At that time, , Assign a second parameter combination, and in the second parameter combination The value is greater than that in the first parameter combination. value; When | |≥ At that time, , Assign a third parameter combination, and in the third parameter combination , The value is configured to maximize the dynamic response speed of the observer.

4. The method for controlling the speed of a permanent magnet synchronous motor based on an improved load torque observer according to claim 1, characterized in that, The feedback gain parameter The value is determined by debugging based on the actual dynamic response performance of the permanent magnet synchronous motor control system.

5. The method for controlling the speed of a permanent magnet synchronous motor based on an improved load torque observer according to claim 1, characterized in that, The feedback gain parameter The value was set to 0.

6. The method for controlling the speed of a permanent magnet synchronous motor based on an improved load torque observer according to claim 1, characterized in that, In step S5, the load torque observation value is fed forward to: The q-axis current reference path for the current loop; or, Torque setting channel for the speed loop.

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