Permanent magnet motor predictive control torque ripple suppression method and system and medium

Abstract

The invention provides a permanent magnet motor predictive control torque ripple suppression method and system and a medium, and relates to the technical field of permanent magnet motor control, and the method comprises the steps: obtaining two-phase current, rotating speed and rotor position measured by a permanent magnet motor in real time; converting the two-phase current into d-axis current and q-axis current according to the rotor position, and converting seven groups of alternative voltage vectors of an inverter into seven groups of d-axis voltage and q-axis voltage; constructing a deadbeat current prediction model, and predicting seven groups of current state values in the future; constructing a sliding-mode observer to estimate a load torque; determining an estimated torque pulsation value according to the estimated load torque; constructing a cost function; and determining an alternative voltage vector corresponding to the minimum value of the cost function in the seven groups of current state values and the estimated torque pulsation values in the future as an optimal voltage vector, and generating a control signal for controlling the permanent magnet motor according to the switching state corresponding to the optimal voltage vector. According to the method, the torque ripple of the permanent magnet motor can be effectively suppressed.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet motor control, and in particular to a method, system and medium for suppressing torque pulsation in predictive control of a permanent magnet motor. Background Art

[0002] As an advanced control strategy, model predictive control is widely used in the control of permanent magnet motors for robots due to its ability to handle multivariable control systems and optimize dynamic performance. Model predictive control maximizes the dynamic response and stability of the motor system by optimizing the control input in real time. However, due to the existence of torque pulsation, model predictive control cannot completely eliminate this fluctuation when applied to permanent magnet motors. Especially in fields such as robots that require extremely high smooth control, torque pulsation will cause control errors and affect the precise motion and stability of the robot.

[0003] In order to solve the problem of torque pulsation in permanent magnet motors, traditional methods are mostly focused on optimizing the motor structure design and improving the control algorithm. First, structural improvements such as optimizing the winding design and adjusting the pole shape can effectively reduce torque pulsation. For example, Gao Jian et al. reduced the cogging effect by changing the structural design of the stator and rotor in the patent "A method for suppressing the cogging torque pulsation of a permanent magnet synchronous motor", thereby reducing the torque pulsation. Secondly, the optimization of the control algorithm is also widely used. For example, Qiu Xin et al. introduced a torque and flux observer in the patent "A method for controlling the torque and flux linkage of a permanent magnet synchronous motor", dynamically compensated for the torque fluctuation, and improved the output stability of the motor. Although these methods have alleviated the problem of torque pulsation to a certain extent, due to the limitations of the structure and algorithm, the control accuracy in a dynamic environment is low, and it is still difficult to meet the needs of precision application scenarios such as robots that have high requirements for smooth control. Summary of the invention

[0004] To solve the above problems, the present invention provides a method for suppressing torque pulsation in predictive control of a permanent magnet motor. The method is based on a sliding mode observer, estimates the load torque in real time, extracts the torque pulsation signal, and integrates it into the cost function of the model predictive control, thereby effectively suppressing the torque pulsation. Compared with the traditional method, the present invention improves the dynamic control accuracy and is particularly suitable for application scenarios such as robots that have high requirements for smooth control, providing a reliable torque pulsation control solution.

[0005] To achieve the above object, the present invention provides the following technical solutions.

[0006] The present invention provides a method for suppressing torque pulsation of a permanent magnet motor by predictive control, comprising the following steps:

[0007] Obtain the real-time measured two-phase current, speed and rotor position of the permanent magnet motor; convert the two-phase current into d and q axis currents according to the rotor position, and convert the seven sets of alternative voltage vectors of the inverter into seven sets of d and q axis voltages;

[0008] Construct a deadbeat current prediction model, and predict the future seven sets of current state values ​​according to the current motor speed, d, q axis currents and seven sets of d, q axis voltages through the deadbeat current prediction model;

[0009] Constructing a sliding mode observer to estimate the speed of the permanent magnet motor, determining the difference between the estimated speed and the real-time measured speed, and determining the estimated load torque according to the difference; determining the estimated torque pulsation value according to the estimated load torque;

[0010] A cost function is constructed using the difference between the actual current and the expected current, and the difference between the estimated torque pulsation value and the expected torque pulsation value; an alternative voltage vector corresponding to the minimum value of the cost function among the future seven groups of current state values ​​and estimated torque pulsation values ​​is determined as the optimal voltage vector, and a control signal for controlling the permanent magnet motor is generated according to the switching state corresponding to the optimal voltage vector.

[0011] Preferably, the two-phase current is converted into d-axis and q-axis current according to the rotor position, as shown in the following formula:

[0012]

[0013] Among them, i d (k) and i q (k) is the d,q axis current of the permanent magnet motor; i a (k) and i b (k) is the a and b phase currents of the permanent magnet motor; θ(k) is the rotor position.

[0014] Preferably, the seven groups of candidate voltage vectors of the inverter are converted into seven groups of d and q axis voltages, as shown in the following formula:

[0015]

[0016] Among them, u d (k) and u q (k) is the d,q axis voltage; 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 .

[0017] Preferably, the deadbeat current prediction model is as shown in the following formula:

[0018]

[0019] Among them, i d (k+1) and i q (k+1) is the current state value of the next seven groups; i d (k) and i q (k) is the d,q axis current of the permanent magnet motor; ω m (k) is the motor speed; p is the number of motor pole pairs; T s is the control period; f is the permanent magnet flux, R s is the motor resistance, L d and L q are the d and q axis inductances respectively.

[0020] Preferably, determining the estimated torque pulsation value according to the estimated load torque comprises the following steps:

[0021] Construct a sliding mode observer:

[0022]

[0023] Among them, J is the motor moment of inertia; B is the friction coefficient; k1 is the observer coefficient, and its value is 4 times the rated torque of the motor. is the estimated speed ω of the sliding mode observer m * (k) and the actual motor speed ω m (k), For the following function:

[0024]

[0025] The motor load torque value T estimated by the sliding mode observer l * (k) is:

[0026]

[0027] The future current state value i d (k+1) and i q (k+1) and the motor load torque value T l * (k) Substitute into the following formula to calculate the torque ripple value |T rip(k)|:

[0028] |T rip (k)|=1.5p((L d -L q )i d (k)i q (k)+Ψ f i q (k))-Bω m (k)-T l * (k).

[0029] Preferably, the cost function is as follows:

[0030]

[0031] Among them, i d_ref ,i q_ref is the current reference value, T rip_ref is the expected torque ripple value.

[0032] The present invention also provides a permanent magnet motor predictive control torque pulsation suppression system, the system comprising:

[0033] processor;

[0034] a memory having stored thereon a computer program executable on the processor;

[0035] Wherein, when the computer program is executed by the processor, the steps of the permanent magnet motor predictive control torque pulsation suppression method are implemented.

[0036] The present invention also provides a computer-readable storage medium, on which a data processing program is stored. When the data processing program is executed by a processor, the steps of the permanent magnet motor predictive control torque pulsation suppression method are implemented.

[0037] Beneficial effects of the present invention:

[0038] The present invention proposes a method, system and medium for suppressing torque pulsation in predictive control of a permanent magnet motor. The present invention first constructs a sliding mode load torque observer to accurately estimate the load torque. Then, the torque pulsation signal is extracted by observing the difference between the load torque and the electromagnetic torque. Finally, the torque pulsation signal is integrated into the cost function of the predictive control, thereby achieving effective suppression of torque pulsation while optimizing the control process. It is particularly suitable for precision application scenarios such as robots that have high requirements for smooth control, and significantly improves the stability and precision control level of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1is a flow chart of a method for suppressing torque pulsation in predictive control of a permanent magnet motor according to an embodiment of the present invention;

[0040] Figure 2 It is a principle block diagram of a sliding mode observer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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.

[0042] Example 1

[0043] Permanent magnet motors for robots are widely used in model predictive control, but there is a problem of torque pulsation. Traditional solutions mainly reduce torque pulsation by optimizing the motor structure design or improving the control algorithm. However, these methods are limited by the limitations of structure and algorithm, and it is difficult to completely eliminate torque pulsation in high-precision application scenarios. The present invention proposes a method for suppressing torque pulsation of predictive control through a sliding mode observer. First, by constructing a sliding mode observer, the load torque of the motor is accurately estimated in real time, and the actual torque pulsation signal is extracted. Secondly, the signal is integrated into the cost function of the model predictive control, and the optimal control voltage vector is dynamically selected by optimizing the control strategy. Finally, the control strategy is used to effectively suppress torque pulsation and improve the dynamic response and control accuracy of the motor system.

[0044] The present invention proposes a method for suppressing predictive control torque pulsation by using a sliding mode observer. Figure 1 As shown, the electrical parameters of the permanent magnet motor in this embodiment are as follows: the inductance is L d =L q =0.3mH, resistance is R s =0.5Ω, rotor flux is ψ f =0.083Wb, the number of permanent magnet pairs is p=3, the rated speed is 300rad / s, and the control period is T s =0.0002s, motor moment of inertia J =0.0001, friction coefficient B =0.0022. The method specifically includes the following steps:

[0045] S1: State measurement. Measure the a and b phase currents of the permanent magnet motor and record them as i a (k) and i b (k), motor speed ω m (k) and rotor position θ(k).

[0046] S2: Coordinate transformation. 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):

[0047]

[0048] S3: Control voltage calculation. 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 voltages u using the following formula: d (k) and u q (k):

[0049]

[0050] 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 .

[0051] S4: Predict the future state of the current. Set the motor pole number p = 3 and the control period T s =0.0002, permanent magnet flux ψ f =0.083, d,q axis inductance L d =L q =0.0003, d,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:

[0052]

[0053] The future seven sets of current state values ​​i can be predicted d (k+1) and i q (k+1) is:

[0054]

[0055] S5: Use sliding mode observer to estimate load torque. The schematic diagram of sliding mode observer is as follows: Figure 2 As shown. Motor moment of inertia J = 0.0001, friction coefficient B = 0.0022, permanent magnet flux ψ f = 0.083, the number of motor pole pairs p = 3, the observer coefficient k1 = 4, the d, q axis current i d (k) and i q (k) Substitute the following sliding mode observer:

[0056]

[0057] You can get:

[0058]

[0059] in, is the estimated speed ω of the sliding mode observer m * (k) and the actual motor speed ω m (k), For the following function:

[0060]

[0061] The motor load torque value T estimated by the sliding mode sensor l * (k) is:

[0062]

[0063] S6: Extract the torque ripple value. d (k+1) and i q (k+1) and estimated load torque T l * (k) Substitute into the following formula to calculate the torque ripple value |T rip (k)|:

[0064]

[0065] S7: Construct a cost function. Considering the current and torque ripples, construct the following cost function J1:

[0066]

[0067] Among them, i d_ref ,i q_ref is the current reference value, T rip_ref is the expected torque ripple value.

[0068] S8 selects the optimal voltage vector and generates a control signal

[0069] The expected torque ripple value T rip_ref and estimated torque ripple value |T rip (k) |, seven sets of current future states corresponding to seven sets of alternative voltage vectors i d (k+1), i q (k+1) and current reference value i d_ref ,i q_ref Substitute the cost function J1 respectively, compare the seven groups of cost function values, and sort them from small to large. The alternative voltage vector that minimizes the cost function value is used as the optimal voltage vector, and a control signal is generated according to the switch state corresponding to the optimal voltage vector to control the motor.

[0070] The above is a method for suppressing torque pulsation of a permanent magnet motor by predictive control provided by an embodiment of the present embodiment. Based on the same idea, the present embodiment also provides a corresponding system for suppressing torque pulsation of a permanent magnet motor by predictive control. The specific definition of the system for suppressing torque pulsation of a permanent magnet motor by predictive control can be found in the definition of the method for suppressing torque pulsation of a permanent magnet motor by predictive control mentioned above, which will not be repeated here. Each module in the above-mentioned system for suppressing torque pulsation of a permanent magnet motor by predictive control can be implemented in whole or in part by software, hardware and a combination thereof. Each of the above-mentioned modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute the operations corresponding to each of the above-mentioned modules.

[0071] This embodiment also provides a computer-readable storage medium, which stores a computer program, which can be used to execute the above Figure 1 A method for suppressing torque ripple in predictive control of a permanent magnet motor is provided.

[0072] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0073] The above are only preferred embodiments of the present invention and are 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 protection scope of the present invention.

Claims

1. A method for suppressing torque pulsation in predictive control of a permanent magnet motor, characterized in that: The following steps are involved: Obtain the real-time measured two-phase current, speed and rotor position of the permanent magnet motor; convert the two-phase current into d and q axis currents according to the rotor position, and convert the seven sets of alternative voltage vectors of the inverter into seven sets of d and q axis voltages; Construct a deadbeat current prediction model, and predict the future seven sets of current state values ​​according to the current motor speed, d, q axis currents and seven sets of d, q axis voltages through the deadbeat current prediction model; Constructing a sliding mode observer to estimate the speed of the permanent magnet motor, determining the difference between the estimated speed and the real-time measured speed, and determining the estimated load torque based on the difference; determining an estimated torque pulsation value according to the estimated load torque; A cost function is constructed using the difference between the actual current and the expected current, and the difference between the estimated torque pulsation value and the expected torque pulsation value; an alternative voltage vector corresponding to the minimum value of the cost function among the future seven groups of current state values ​​and estimated torque pulsation values ​​is determined as the optimal voltage vector, and a control signal for controlling the permanent magnet motor is generated according to the switching state corresponding to the optimal voltage vector.

2. The method for suppressing torque ripple in predictive control of a permanent magnet motor according to claim 1, characterized in that: The two-phase current is converted into d and q axis current according to the rotor position, as shown in the following formula: Among them, i d (k) and i q (k) is the d,q axis current of the permanent magnet motor; i a (k) and i b (k) is the a and b phase currents of the permanent magnet motor; θ(k) is the rotor position.

3. The method for suppressing torque ripple in predictive control of a permanent magnet motor according to claim 1, characterized in that: The seven groups of alternative voltage vectors of the inverter are converted into seven groups of d and q axis voltages, as shown in the following formula: Among them, u d (k) and u q (k) is the d,q axis voltage; 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 .

4. The method for suppressing torque ripple in predictive control of a permanent magnet motor according to claim 1, characterized in that: The deadbeat current prediction model is shown in the following formula: Among them, i d (k+1) and i q (k+1) is the current state value of the next seven groups; i d (k) and i q (k) is the d,q axis current of the permanent magnet motor; ω m (k) is the motor speed; p is the number of motor pole pairs; T s is the control period; ψ f is the permanent magnet flux, R s is the motor resistance, L d and L q are the d and q axis inductances respectively.

5. The method for suppressing torque ripple in predictive control of a permanent magnet motor according to claim 1, characterized in that: Determining the estimated torque pulsation value according to the estimated load torque comprises the following steps: Construct a sliding mode observer: Among them, J is the motor moment of inertia; B is the friction coefficient; k1 is the observer coefficient, and its value is 4 times the rated torque of the motor. is the estimated speed ω of the sliding mode observer m * (k) and the actual motor speed ω m (k), For the following function: Motor load torque value estimated by sliding mode observer for: The future current state value i d (k+1) and i q (k+1) and the motor load torque value Substitute the following formula to calculate the torque ripple value |T rip (k)|:

6. The method for suppressing torque ripple in predictive control of a permanent magnet motor according to claim 1, characterized in that: The cost function is shown as follows: Among them, i d_ref ,i q_ref is the current reference value, T rip_ref is the expected torque ripple value.

7. A permanent magnet motor predictive control torque pulsation suppression system, characterized in that: The system comprises: processor; a memory having stored thereon a computer program executable on the processor; Wherein, when the computer program is executed by the processor, the steps of the method for suppressing torque pulsation of predictive control of a permanent magnet motor as claimed in any one of claims 1 to 6 are implemented.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a data processing program, and when the data processing program is executed by a processor, the steps of the method for suppressing torque pulsation in predictive control of a permanent magnet motor according to any one of claims 1 to 6 are implemented.

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