Permanent magnet motor torque ripple estimation and suppression method based on priority ranking

Abstract

The permanent magnet motor torque ripple estimation and suppression method based on priority ranking has the main advantages that the high dynamic response of the motor is kept, the torque ripple is effectively suppressed, and the steady-state performance of a system is remarkably improved. Firstly, electromagnetic torque and torque pulsation can be accurately estimated by measuring key parameters such as current, rotating speed and torque, an optimal voltage vector is selected through priority ranking, suppression of the torque pulsation is achieved, and a control algorithm is simplified. And secondly, the method avoids the problem of complex weight factor adjustment in the traditional method, so that the system has better adaptability under different working conditions. According to the method, a universal and efficient solution is provided for torque ripple suppression of the permanent magnet motor, and a reliable technical means is provided for improving the dynamic performance and the steady-state precision of a motor system.

Description

Technical Field

[0001] The invention belongs to the field of permanent magnet motor torque pulsation suppression, and in particular relates to a permanent magnet motor torque pulsation estimation and suppression method based on priority sorting. Background Art

[0002] Permanent magnet motors are widely used in high-precision equipment such as robots and CNC machine tools due to their high power density, high torque output and compact structure. In order to give full play to the performance advantages of permanent magnet motors, advanced control technology must be equipped. At present, finite control set model predictive control has gradually become an effective solution to replace traditional proportional integral control because it does not require a modulator and has the advantages of fast dynamic response. However, although finite control set model predictive control performs well in improving dynamic performance, it easily introduces high-frequency noise, further aggravating the torque pulsation problem. Torque pulsation is a key factor affecting the performance of permanent magnet motors, which can cause speed fluctuations, vibrations and noise, especially in high-precision application scenarios. Therefore, how to effectively suppress torque pulsation while maintaining high dynamic response has become a key technical challenge to improve the overall performance of the motor.

[0003] Traditional methods for suppressing torque pulsation of permanent magnet motors mainly include solutions based on cost function optimization and modulation technology. For example, Zhao Haiyan et al., in the patent "Permanent Magnet Synchronous Motor Model Prediction-Direct Torque Control Method", took torque pulsation as part of the cost function and suppressed torque fluctuations by optimizing switch selection. However, this method requires different weight factors to be assigned to multiple control targets, resulting in a complex weight adjustment process and difficulty in adapting to different working conditions. Hua Wei et al. proposed a hybrid control method based on space vector modulation in the patent "Permanent Magnet Synchronous Motor Weightless Model Prediction Torque Control System and Method", which reduces torque pulsation by increasing the number of control vectors. However, the main disadvantage of this method is that the computational complexity is significantly increased, which brings great challenges to practical applications. Although the above methods are effective in suppressing torque pulsation, their complex weight adjustment and computational burden limit their wide application under variable working conditions.

[0004] The present invention proposes a method for estimating and suppressing torque pulsation of a permanent magnet motor based on priority sorting, and its main principles are as follows: First, the current, speed and load torque of the motor are measured to estimate the electromagnetic torque and torque pulsation of the motor. Then, by calculating the influence of seven groups of alternative voltage vectors on current and torque, priority sorting is performed, and finally the optimal voltage vector that can minimize the cost function and torque pulsation is selected for control. This method simplifies the algorithm, can effectively suppress torque pulsation, and improve the steady-state performance of the motor. It is particularly suitable for application scenarios with high precision and high dynamic response. Summary of the invention

[0005] In order to effectively estimate and suppress the torque pulsation of the permanent magnet motor and improve the dynamic and steady-state performance of the system, the present invention proposes a method for estimating and suppressing the torque pulsation of the permanent magnet motor based on priority sorting. This method estimates the electromagnetic torque and torque pulsation values ​​and introduces a priority sorting mechanism, which can effectively suppress the torque pulsation without using complex weighting factors. This scheme not only simplifies the control algorithm, but also significantly improves the steady-state performance of the system, and is particularly suitable for application scenarios with high precision and high dynamic response.

[0006] A method for estimating and suppressing torque pulsation of a permanent magnet motor based on priority sorting, characterized by the following steps:

[0007] Step 1: Measure current, load torque, position and speed: Use a current sensor to measure the current of the permanent magnet motor phase a and phase b, denoted as i a (k) and i b (k), using the torque sensor to measure the load torque T l (k), using the position sensor to detect the motor speed ω m (k) and rotor position θ(k);

[0008] Step 2: Calculation of d-axis and q-axis currents: According to the rotor position θ(k), the phase current i is converted into a (k) and i b (k) is converted into d, q axis current i d (k) and i q (k):

[0009]

[0010] Step 3: Calculation of d and q axis control voltages: According to the rotor position θ(k), the seven sets of alternative voltage vectors of the inverter are converted into seven d and q axis control voltages u using the following formula: d (k) and u q (k):

[0011]

[0012] Among them, U dc is the system DC bus voltage, [s a , s b , s c ] T are the switching states corresponding to the seven sets of alternative voltage vectors of the inverter, which are [0, 0, 0] T , [1, 0, 0] T , [1, 1, 0] T , [0, 1, 0] T , [0, 1, 1] T, [0, 0, 1] T , [1, 0, 1] T ;

[0013] Step 4: Predict the future state of current: transform the d and q axis current i d (k) and i q (k), seven groups of d, q axis control voltage u d (k) and u q (k) Motor speed ω m (k) Substitute the following permanent magnet motor current prediction model to predict the future seven sets of current state values ​​i d (k+1) and i q (k+1):

[0014]

[0015] Among them, L d , L q , R s , ψ f and p are electrical parameters, representing d-axis inductance, q-axis inductance, resistance, rotor flux and permanent magnet pole pair number, respectively. s To control the cycle;

[0016] Step 5: Determine the control voltage priority according to the cost function: The seven future states i corresponding to the seven sets of candidate voltage vectors are d (k+1), i q (k+1) and current reference value i d_ref ,i q_ref Substitute the following cost functions respectively:

[0017]

[0018] Compare the seven groups of cost function values ​​and sort them from small to large. The candidate voltage vector with the smallest cost function J is marked as 1, the second smallest is marked as 2, and so on. The priorities of other candidate voltage vectors are marked as 3, 4, 5, 6, and 7 in turn.

[0019] Step 6: Electromagnetic torque estimation: According to the seven sets of current state values ​​i d (k+1) and i q (k+1), use the following formula to estimate the seven sets of electromagnetic torque T of the motor e (k+1):

[0020]

[0021] Step 7: Torque ripple estimation: Based on seven sets of electromagnetic torques T e (k+1), load torque T l(k) and motor speed ω m (k), use the following formula to estimate the motor torque ripple T r (k+1):

[0022]

[0023] Step 8: Determine the control voltage priority according to the torque pulsation: Compare the seven groups of torque pulsation values ​​and sort them from small to large, which will make the torque pulsation T r The (k+1) smallest candidate voltage vector priority is marked as 1, the second smallest is marked as 2, and so on, and the priorities of other candidate voltage vectors are marked as 3, 4, 5, 6, and 7 in turn;

[0024] Step 9: Select the optimal voltage vector and generate a control signal: Multiply the priorities corresponding to the same alternative voltage vectors in step 5 and step 8, and compare the sizes of the seven groups of products. Select the alternative voltage vector that minimizes the product as the optimal voltage vector, and use the switch state corresponding to the voltage vector as the control signal to control the motor.

[0025] The beneficial effects of the present invention are as follows: the present invention proposes a method for estimating and suppressing torque pulsation of a permanent magnet motor based on priority sorting, the main advantage of which is that while maintaining the high dynamic response of the motor, the torque pulsation is effectively suppressed, and the steady-state performance of the system is significantly improved. First, by measuring key parameters such as current, speed and torque, the electromagnetic torque and torque pulsation can be accurately estimated, and the optimal voltage vector is selected by priority sorting to suppress the torque pulsation, thereby simplifying the control algorithm. Secondly, the method avoids the complex weight factor adjustment problem in the traditional method, so that the system has better adaptability under different working conditions. The method provides a general and efficient solution for the suppression of torque pulsation of permanent magnet motors, and provides a reliable technical means for improving the dynamic performance and steady-state accuracy of the motor system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of a method for estimating and suppressing torque pulsation of a permanent magnet motor based on priority sorting of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The present invention includes but is not limited to the following embodiments.

[0028] The torque pulsation of a permanent magnet motor is a key factor affecting its performance, especially in high-precision equipment such as robots and CNC machine tools. Torque pulsation can cause vibration, noise and speed fluctuations, thereby affecting the operating accuracy of the equipment. Traditional torque pulsation suppression methods, such as cost function optimization and methods based on modulation technology, have problems such as complex calculations and difficulty in adjusting weight factors, which limit their application in practice. The present invention proposes a method for estimating and suppressing torque pulsation of a permanent magnet motor based on priority sorting. First, the current, speed and load torque of the motor are measured in real time, and the changing trend of the torque pulsation is accurately captured through electromagnetic torque estimation and torque pulsation calculation. Then, through the priority sorting mechanism, the optimal voltage vector that can comprehensively minimize the torque pulsation and cost function is selected to control the operation of the motor. This method does not require complex weight adjustment, simplifies the control algorithm, and effectively suppresses torque pulsation in the full speed range, thereby improving the steady-state performance and dynamic response of the motor. The process of the method for estimating and suppressing torque pulsation of a permanent magnet motor based on priority sorting proposed by the present invention is as follows Figure 1 In this embodiment, the electrical parameters of the permanent magnet motor are as follows: inductance is 3 mH, resistance is 0.5 Ω, rotor flux is 0.083Wb, permanent magnet logarithm is 3, rated speed is 300 rad / s, control period is 0.0002 s, and the implementation process of the permanent magnet motor torque pulsation estimation and suppression method based on priority sorting is as follows:

[0029] Step 1: Measure current, load torque, position and speed

[0030] The current sensor is used to measure the current of the permanent magnet motor phase a and phase b, which is recorded as i a (k) and i b (k), using the torque sensor to measure the load torque T l (k), using the position sensor to detect the motor speed ω m (k) and rotor position θ(k).

[0031] Step 2: Calculation of d and q axis currents

[0032] According to the rotor position θ(k), the phase current i is converted into a (k) and i b (k) is converted into d, q axis current i d (k) and i q (k):

[0033]

[0034] Step 3: Calculation of d and q axis control voltages

[0035] According to the rotor position θ(k), the seven sets of alternative voltage vectors of the inverter are converted into seven d and q axis control voltages u using the following formula:d (k) and u q (k):

[0036]

[0037] Among them, U dc is the system DC bus voltage, [s a , s b , s c ] T are the switching states corresponding to the seven sets of alternative voltage vectors of the inverter, which are [0, 0, 0] T , [1, 0, 0] T , [1, 1, 0] T , [0, 1, 0] T , [0, 1, 1] T , [0, 0, 1] T , [1, 0, 1] T ;

[0038] Step 4: Predict the future state of current

[0039] The d and q axis current i d (k) and i q (k), seven groups of d, q axis control voltage u d (k) and u q (k) Motor speed ω m (k) Substitute the following permanent magnet motor current prediction model to predict the future seven sets of current state values ​​i d (k+1) and i q (k+1):

[0040]

[0041] The inductor L d = L q = 0.003, resistance R s = 0.5, magnetic flux ψ f = 0.083, number of pole pairs p = 3 and control period T s =0.0002 s is substituted into the above formula to obtain the predicted current calculation formula of the motor in the embodiment:

[0042]

[0043] Step 5: Predict the future state of current

[0044] Determine the control voltage priority according to the cost function: The seven groups of future states i corresponding to the seven groups of candidate voltage vectors d (k+1), i q(k+1) and current reference value i d_ref ,i q_ref Substitute the following cost functions respectively:

[0045]

[0046] Compare the seven groups of cost function values ​​and sort them from small to large, mark the priority of the candidate voltage vector that makes the cost function J the smallest as 1, the second smallest as 2, and so on, and mark the priorities of other candidate voltage vectors as 3, 4, 5, 6, and 7. In this embodiment, it is assumed that the first candidate voltage vector is marked with a priority of 2 in this step, the second candidate voltage vector is marked with a priority of 4, the third candidate voltage vector is marked with a priority of 7, the fourth candidate voltage vector is marked with a priority of 1, the fifth candidate voltage vector is marked with a priority of 3, the sixth candidate voltage vector is marked with a priority of 5, and the seventh candidate voltage vector is marked with a priority of 6.

[0047] Step 6: Electromagnetic Torque Estimation

[0048] According to the seven groups of current state values ​​i d (k+1) and i q (k+1), use the following formula to estimate the seven sets of electromagnetic torque T of the motor e (k+1):

[0049]

[0050] Step 7: Torque ripple estimation

[0051] According to the seven groups of electromagnetic torque T e (k+1), load torque T l (k) and motor speed ω m (k), use the following formula to estimate the motor torque ripple T r (k+1):

[0052]

[0053] Step 8: Determine control voltage priority based on torque ripple

[0054] Comparing the seven groups of torque pulsation values ​​and sorting them from small to large will make the torque pulsation T rThe (k+1) smallest candidate voltage vector priority is marked as 1, the second smallest is marked as 2, and so on, and the priorities of other candidate voltage vectors are marked as 3, 4, 5, 6, and 7. In this embodiment, it is assumed that the first candidate voltage vector priority is marked as 4 in this step, the second candidate voltage vector priority is marked as 2, the third candidate voltage vector priority is marked as 3, the fourth candidate voltage vector priority is marked as 5, the fifth candidate voltage vector priority is marked as 1, the sixth candidate voltage vector priority is marked as 7, and the seventh candidate voltage vector priority is marked as 6.

[0055] Step 9: Select the optimal voltage vector and generate control signals

[0056] By multiplying the priorities corresponding to the same alternative voltage vectors in step 5 and step 8, seven groups of products in this embodiment can be obtained as follows: the priority product of the first alternative voltage vector is 8, the priority product of the second alternative voltage vector is 8, the priority product of the third alternative voltage vector is 21, the priority product of the fourth alternative voltage vector is 5, the priority product of the fifth alternative voltage vector is 3, the priority product of the sixth alternative voltage vector is 35, and the priority product of the seventh alternative voltage vector is 36.

[0057] The sizes of the seven groups of products are compared. Since the fifth candidate voltage vector has the smallest priority product, it is selected as the optimal voltage vector, and the switch state corresponding to the voltage vector is used as a control signal to control the motor.

Claims

1. A method for estimating and suppressing torque pulsation of a permanent magnet motor based on priority sorting, characterized in that Here are the steps: Step 1: Measure current, load torque, position and speed: Use a current sensor to measure the current of the permanent magnet motor phase a and phase b, denoted as i a (k) and i b (k), using the torque sensor to measure the load torque T l (k), using the position sensor to detect the motor speed ω m (k) and rotor position θ(k); Step 2: Calculation of d-axis and q-axis currents: According to the rotor position θ(k), the phase current i is calculated using the following formula: a (k) and i b (k) is converted into d, q axis current i d (k) and i q (k): ； Step 3: Calculation of d and q axis control voltages: According to the rotor position θ(k), the seven sets of alternative voltage vectors of the inverter are converted into seven d and q axis control voltages u using the following formula: d (k) and u q (k): ， Among them, U dc is the system DC bus voltage, [s a , s b , s c ] T are the switching states corresponding to the seven sets of alternative voltage vectors of the inverter, which are [0, 0, 0] T , [1, 0, 0] T , [1, 1, 0] T , [0, 1, 0] T , [0, 1, 1] T , [0, 0, 1] T , [1, 0, 1] T ; Step 4: Predict the future state of current: transform the d and q axis current i d (k) and i q (k), seven groups of d, q axis control voltage u d (k) and u q (k) Motor speed ω m (k) Substitute the following permanent magnet motor current prediction model to predict the future seven sets of current state values ​​i d (k+1) and i q (k+1): ； Among them, L d , L q , R s , ψ f and p are electrical parameters, representing d-axis inductance, q-axis inductance, resistance, rotor flux and permanent magnet pole pair number, respectively. s To control the cycle; Step 5: Determine the control voltage priority according to the cost function: The seven future states i corresponding to the seven sets of candidate voltage vectors are d (k+1), i q (k+1) and current reference value i d_ref ,i q_ref Substitute the following cost functions respectively: ； Compare the seven groups of cost function values ​​and sort them from small to large. The candidate voltage vector with the smallest cost function J is marked as 1, the second smallest is marked as 2, and so on. The priorities of other candidate voltage vectors are marked as 3, 4, 5, 6, and 7 in turn. Step 6: Electromagnetic torque estimation: According to the seven sets of current state values ​​i d (k+1) and i q (k+1), use the following formula to estimate the seven sets of electromagnetic torque T of the motor e (k+1): ； Step 7: Torque ripple estimation: Based on seven sets of electromagnetic torques T e (k+1), load torque T l (k) and motor speed ω m (k), use the following formula to estimate the motor torque ripple T r (k+1): ； Step 8: Determine the control voltage priority according to the torque pulsation: Compare the seven groups of torque pulsation values ​​and sort them from small to large, which will make the torque pulsation T r The (k+1) smallest candidate voltage vector priority is marked as 1, the second smallest is marked as 2, and so on, and the priorities of other candidate voltage vectors are marked as 3, 4, 5, 6, and 7 in turn; Step 9: Select the optimal voltage vector and generate a control signal: Multiply the priorities corresponding to the same alternative voltage vectors in step 5 and step 8, and compare the sizes of the seven groups of products. Select the alternative voltage vector that minimizes the product as the optimal voltage vector, and use the switch state corresponding to the voltage vector as the control signal to control the motor.

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