Anti-disturbance control method for permanent magnet direct-drive motor based on extended sliding mode disturbance observer

Abstract

The present invention discloses an anti-disturbance control method for a permanent magnet direct-drive motor based on an extended sliding mode disturbance observer. A new PI speed controller is adopted in the speed loop, and a proportional integral link is introduced in the feedback channel to improve the dynamic response and anti-disturbance capabilities. An extended sliding mode disturbance observer is adopted to estimate in real time the system disturbance term that cannot be accurately measured, and the observed load torque value is feed-forward compensated to the current regulator, thereby effectively reducing the thrust fluctuation of the motor and improving the dynamic response speed of the system.

Description

Technical Field

[0001] The present invention relates to the field of motor control, and more specifically, to an anti-disturbance control method for a permanent magnet direct-drive motor based on an extended sliding mode disturbance observer. Background Art

[0002] Compared with induction motors and reluctance motors, permanent magnet direct-drive motors with high magnetic energy product permanent magnet excitation have advantages such as high power density, high efficiency, and high power factor, and are very suitable for direct-drive traction systems. Direct-drive traction motors have a complex working environment. They not only need to switch frequently between a variety of operating conditions, but also face frequent load disturbances caused by various factors. This requires the control system to have fast dynamic response capabilities and strong anti-interference capabilities.

[0003] Since the traditional PI controller is a passive anti-disturbance control that uses error feedback to eliminate errors, for multivariable, nonlinear, and strongly coupled permanent magnet synchronous motor systems, the system speed response based on PI speed control is slow, the anti-disturbance ability is weak, the decoupling is incomplete, and it is difficult to obtain satisfactory dynamic response performance.

[0004] In actual operation, since the motor load is time-varying and unpredictable, the PI regulator alone cannot effectively suppress the speed fluctuation caused by load disturbance. To address this problem, a torque sensor can be used to directly measure the motor load torque and perform real-time compensation, but this will increase the system cost, and the sensor accuracy and response speed will affect the actual measurement accuracy. Summary of the invention

[0005] The purpose of the present invention is to observe the load torque value of the motor in real time, and feed-forward the observed value to the current regulator, while adopting a new PI controller to improve the robustness of the system, and provide a permanent magnet direct drive motor anti-disturbance control method based on an extended sliding mode disturbance observer, which specifically includes the following steps:

[0006] Step 1: In the dual closed-loop vector control of the permanent magnet synchronous motor, the three-phase current and speed signals of the sampled motor are sent to the extended sliding mode disturbance observer to observe the load torque value of the motor in real time.

[0007] Step 2: The new PI speed controller is based on the given speed n ref Perform control calculation with the actual motor speed n to obtain the speed controller output;

[0008] Step 3: Obtain the observed value of load torque by estimation Calculate the q-axis compensation current i qc ;

[0009] Step 4: Output control voltage u through current loop controller α 、u βThe SVPWM module controls the inverter to drive the motor.

[0010] In the step 1, the motor load torque value is observed in real time The specific method is:

[0011] Based on load torque observer

[0012]

[0013] in, is the estimated value of the motor load torque, is the estimated motor angular velocity, n p is the number of motor pole pairs, J is the rotor moment of inertia, B is the damping coefficient, ψ m is the permanent magnet flux, i q is the q-axis current, Z is the sliding mode control law, and q and l are the sliding mode control coefficients.

[0014] The sliding surface of the observer is defined as The sliding mode reaching law is set as:

[0015]

[0016] Where α (α>1) and β (0<β<1) are control coefficients, k is the sliding mode gain, sgn() is the sign function, and η is defined as:

[0017]

[0018] The sliding mode control law is defined as:

[0019]

[0020] In step 2, the specific control method of the new PI speed controller is:

[0021] Adding a proportional-integral link to the feedback channel of the traditional PI speed controller yields the system transfer function:

[0022]

[0023] where k p , k i are the proportional and integral control coefficients on the forward channel, k pf , k if are the proportional and integral control coefficients on the feedback channel, k T is the torque coefficient of the motor.

[0024] In step 3, the q-axis compensation current i qc The specific calculation method is:

[0025]

[0026] Where the control gain b = 3n p ψ m / 2J.

[0027] The permanent magnet direct drive motor anti-disturbance control method based on the extended sliding mode disturbance observer is implemented by a permanent magnet synchronous motor double closed-loop control system, which includes a new PI speed controller, a load torque observer, a dq axis current controller, a coordinate transformation module, an SVPWM module and a three-phase inverter.

[0028] The beneficial effect of the present invention is that a new PI speed controller is used to output a given value of the q-axis current, so that the motor speed can quickly track the given speed when the speed changes frequently, thereby effectively improving the dynamic response performance of the motor. A load torque observer is used to estimate the motor load torque value in real time, and the observed value is feed-forward compensated to the current regulator. Sufficient current changes can be generated to offset the influence of disturbances such as load disturbances and motor parameter changes without the need for the speed controller to output a large change, thereby effectively reducing the speed fluctuation of the motor. The load torque observer adopts an extended sliding mode observer and a variable power sliding mode approach law, which effectively weakens the system jitter while maintaining a fast convergence speed. When the load torque changes, the observation error of the load torque can be quickly eliminated, which improves the observation effect of the load torque, and further improves the robustness of the motor control through current feed-forward compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the system block diagram of the double closed-loop control of the permanent magnet synchronous motor;

[0030] Figure 2 The block diagram of load torque observer based on extended sliding mode observer;

[0031] Figure 3 This is the block diagram of the new PI speed controller;

[0032] Figure 4 This is the speed response simulation result when the motor speed changes suddenly;

[0033] Figure 5 This is the speed response simulation result when the motor load changes suddenly. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0035] Figure 1 Block diagram of permanent magnet synchronous motor vector control system to realize the anti-disturbance control method of permanent magnet direct drive motor based on extended sliding mode disturbance observer.

[0036] Considering the non-salient polarity of the motor, i d =0 vector control mode, establish the mathematical model of the motor, and its magnetic flux equation is:

[0037]

[0038] The voltage equation of the dq rotating coordinate system is:

[0039]

[0040] The electromagnetic torque equation of the motor is:

[0041]

[0042] The equation of motion for the motor is:

[0043]

[0044] In formula (1), (2), (3), (4), ψ d , q are dq axis flux respectively; L d , L q They are the dq axis inductance; m is the permanent magnet flux; u d 、u q are dq axis voltage respectively; R is the motor stator resistance; ω is the motor angular velocity; i d 、i q are dq axis current respectively; T e is the electromagnetic torque of the motor; n p is the number of motor pole pairs; ω is the angular velocity of the motor; J is the rotor moment of inertia; T L is the motor load torque; B is the damping coefficient.

[0045] Taking into account the load disturbance and parameter perturbation, the motion equation of the motor can be expressed as:

[0046]

[0047] Where f(t) is the total disturbance.

[0048] The load torque observer can be designed as:

[0049]

[0050] in is the estimated motor angular velocity; is the estimated value of the load disturbance; Z is the sliding mode control; q and l are the sliding mode control coefficients.

[0051] Select the sliding surface as:

[0052]

[0053] Based on the traditional exponential reaching law, a new sliding mode reaching law is designed as follows:

[0054]

[0055] Where α (α>1) and β (0<β<1) are control coefficients, k is the sliding mode gain, sgn() is the sign function, and η is defined as:

[0056]

[0057] When the system state is far away from the sliding surface or close to the sliding surface, different terms in the reaching law take effect, which can effectively reduce the system chattering while accelerating the convergence speed.

[0058] The sliding mode control law can be designed as:

[0059]

[0060] The difference between the estimated disturbance and the actual disturbance can be calculated as:

[0061]

[0062] It can be seen that when the appropriate control coefficient is selected, the estimated disturbance value can quickly track the actual disturbance value. The estimated load torque value is feed-forwarded to the current regulator:

[0063]

[0064] Figure 2 This is the block diagram of the load torque observer based on the extended sliding mode observer.

[0065] In the new PI speed controller, a proportional-integral link is added to the feedback channel to obtain the system transfer function:

[0066]

[0067] where k p , k i are the proportional and integral control coefficients on the forward channel, k pf , k if are the proportional and integral control coefficients on the feedback channel, k T is the thrust coefficient of the motor.

[0068] Figure 3 This is the block diagram of the new PI speed controller. By properly setting the k in the feedback channel pf , k ifThe value of can further reduce the speed overshoot and improve the system's anti-disturbance capability while ensuring fast dynamic response.

[0069] Example

[0070] The permanent magnet direct drive motor anti-disturbance control method based on the extended sliding mode disturbance observer of the present invention is simulated and verified:

[0071] The speed loop of the control strategy adopts a new PI controller and uses an extended sliding mode observer to estimate the motor load torque in real time, and feeds the estimated value into the current regulator in real time to improve the dynamic response capability and load disturbance resistance of the motor. In order to verify the effectiveness of the control method of the present invention, a simulation model of the control method of the present invention is built in MATLAB / Simulink. The simulation results are shown in Figure 2. Figure 4 and Figure 5 shown.

[0072] In the simulation model, the permanent magnet synchronous motor parameters are set as follows: permanent magnet flux is 0.1827Wb, AC and DC axis inductance is 12mH, stator resistance is 0.95Ω, pole pair number is 4, and moment of inertia is 0.003kg·m 2 , the damping coefficient is 0.008N·m·s, and the DC side voltage is 311V.

[0073] Figure 4 The speed response simulation results when the motor speed suddenly changes. The motor starts at a given speed of 500rpm, and after running for 0.3s and 0.6s, the given speed suddenly changes to 1000rpm and 1500rpm respectively. The motor load torque is 0 during the entire operation. It can be seen that during the speed mutation process, the overshoot of the motor speed is 0, and the adjustment time is within 0.03s.

[0074] Figure 5 The simulation results of the speed response when the motor load suddenly changes. The motor runs at a given speed of 1000 rpm, and the load is suddenly increased by 10 Nm and reduced by 10 Nm at 0.2s and 0.5s respectively. It can be seen that when the motor load suddenly changes, the motor speed will fluctuate, but it can run stably at 1000 rpm again in a short time.

[0075] according to Figure 4 and Figure 5 It can be seen that the permanent magnet direct-drive motor anti-disturbance control method based on the extended sliding mode disturbance observer disclosed in the present invention can operate stably under conditions such as sudden changes in speed and load, and has good dynamic response capability and load disturbance resistance capability, thereby verifying the effectiveness of the permanent magnet direct-drive motor anti-disturbance control method based on the extended sliding mode disturbance observer disclosed in the present invention.

[0076] In addition to the technical features described in the specification, other technologies involved in the present invention are conventional technologies mastered by those skilled in the art, such as PI current controller module, coordinate transformation module and SVPWM module.

[0077] The present invention has many specific application paths. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principle of the present invention. These improvements should also be regarded as the protection scope of the present invention.

Claims

1. A permanent magnet direct drive motor anti-disturbance control method based on an extended sliding mode disturbance observer, characterized in that: The control method uses an extended sliding mode disturbance observer to estimate the load torque value of the permanent magnet synchronous motor in real time, feeds the load torque value forward to the IP speed controller, obtains a system transfer function with an added proportional integral link, and controls the permanent magnet synchronous motor according to the system transfer function; The control method comprises the following steps: Step 1: In the dual closed-loop vector control of the permanent magnet synchronous motor, the three-phase current and speed signals of the sampled motor are sent to the extended sliding mode disturbance observer to estimate the load thrust observation value of the permanent magnet synchronous motor in real time. Step 2: PI speed controller sets the speed n ref and the actual motor speed n to perform control calculation to obtain the output of the PI speed controller; Step 3: Obtain the observed value of load thrust by estimation Calculate the q-axis compensation current i qc ; Step 4: Output control voltage u through current loop controller α 、u β , the SVPWM module controls the inverter to drive the motor; In the step 1, the load thrust observation value of the permanent magnet synchronous motor is estimated in real time The specific method is: The load torque value of the motor is observed in real time based on the extended sliding mode disturbance observer: in, is the estimated value of the motor load torque, is the estimated motor angular velocity, n p is the number of motor pole pairs, J is the rotor moment of inertia, B is the damping coefficient, ψ m is the permanent magnet flux, i q is the q-axis current, Z is the sliding mode control law, q and l are the sliding mode control coefficients; The sliding surface of the observer is defined as The sliding mode reaching law is set as: Among them, α and β are control coefficients, k is the sliding mode gain, sgn() is the sign function, and η is the control gain value The sliding mode control law is defined as: Where J is the motor's moment of inertia.

2. The anti-disturbance control method for a permanent magnet direct-drive motor based on an extended sliding mode disturbance observer according to claim 1, characterized in that: The control gain value η is defined as:

3. The anti-disturbance control method for a permanent magnet direct-drive motor based on an extended sliding mode disturbance observer according to claim 1, characterized in that: The output of the PI speed controller in step 2 is specifically: where k p , k i are the proportional and integral control coefficients on the forward channel, k pf , k if are the proportional and integral control coefficients on the feedback channel, k T is the thrust coefficient of the motor, and s is the complex frequency.

4. The method for controlling the permanent magnet direct drive motor against disturbances based on the extended sliding mode disturbance observer according to claim 1, characterized in that: In step 3, the q-axis compensation current i qc The specific calculation method is: Where the control gain b = 3n p ψ m / 2J.

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