Permanent magnet synchronous motor model prediction speed control method based on additive state decomposition
Technical Field
The invention belongs to the field of motor control, and in particular relates to a permanent magnet synchronous motor model predictive speed control method based on additive state decomposition.
Background
The permanent magnet synchronous motor (PERMANENT MAGNET synchronous motor, PMSM) has the characteristics of simple structure, high power density, reliable operation and the like, and is widely applied to the fields of aerospace, electric automobiles, numerical control machine tools, robot control and the like. The PMSM speed regulation system in practical application is inevitably influenced by uncertain factors such as unmodeled dynamics, parameter perturbation, external load disturbance and the like, and satisfactory control precision is difficult to achieve by adopting conventional PID control. Therefore, the research designs an advanced control method to effectively inhibit the internal and external interference in the PMSM speed regulation system, and the realization of high-precision control of the advanced control method has important scientific significance and application value.
With the continuous development of control theory, various novel nonlinear control technologies are sequentially proposed and applied to a PMSM speed regulation system, such as sliding mode control, self-adaptive control, H ∞ robust control and the like. However, the above methods have certain disadvantages, for example, the suppression of disturbance and external disturbance of system parameters by the conventional sliding mode control is at the cost of generating high-frequency buffeting, which may excite the unmodeled characteristics of the system, so that the performance of the PMSM system is greatly compromised. The method reduces the sensitivity of disturbance in the output channel of the system by improving the robustness of the controller, and has the problems of compromise between nominal performance and robustness, tracking control and disturbance suppression performance.
Model predictive control (Model predictive control, MPC) was born in the 70 s of the last century as an optimization control theory, when the MPC is applied to a PMSM speed regulation system, the MPC directly takes the rotating speed as a control target to be added into a cost function, predicts the rotating speed at the next moment according to a mechanical motion equation of a motor, and obtains the optimal control quantity by minimizing the cost function. MPC has faster dynamic performance, but this approach cannot directly cope with external load disturbances and is more sensitive to model uncertainty. In addition, the MPC calculation amount increases exponentially with the increase of the prediction step, and the application of the MPC calculation amount in a PMSM speed regulation system is limited by the excessive calculation amount.
Disclosure of Invention
Aiming at the defects or improvement demands of the prior art, the invention provides a permanent magnet synchronous motor model prediction speed control method based on an additive state decomposition (ADDITIVE STATE d) technology, which is used for decomposing the speed tracking problem of a disturbed PMSM into the tracking control problem of a nominal main system and the disturbance suppression problem of an uncertain auxiliary system. And respectively designing a model prediction controller and a state feedback controller based on disturbance estimation and compensation aiming at a main system and an auxiliary system with independent control tasks, and fusing the controllers to obtain a final speed loop composite control law, so that the PMSM still has higher rotating speed tracking precision under the conditions of parameter perturbation, unmodeled dynamic and external load interference.
In order to achieve the above object, according to one aspect of the present invention, there is provided a permanent magnet synchronous motor model predictive speed control method based on additive state decomposition, including:
S1, establishing a mathematical model of a surface-mounted PMSM under a dq synchronous rotation coordinate system;
S2, equivalently decomposing the speed subsystem into a nominal main system and an auxiliary system containing uncertainty by using an additive state decomposition technology;
s3, designing an exponential convergence type model prediction controller aiming at the main system, so that the tracking error of the main system output to the given reference rotating speed gradually converges to be near 0 in an exponential form;
S4, aiming at an auxiliary system, designing a generalized proportional integral observer (Generalized proportional integral observer, GPIO) to estimate the total disturbance of the speed subsystem on line, and on the basis, designing a state feedback control law based on disturbance active compensation to inhibit the influence of disturbance on the output of the auxiliary system;
s5, fusing control inputs of the main system and the auxiliary system to obtain a speed loop composite control law.
The surface-mounted PMSM mathematical model in step S1 is built as follows:
Wherein R and L are stator resistance and stator inductance, p is the pole pair number of the motor, J is the rotor moment of inertia, B is the viscous damping coefficient, ψ f is the rotor permanent magnet flux linkage, i d and i q are the d and q axis currents, u d and u q are the d and q axis voltages, ω is the rotor angular velocity, ω e =pω is the rotor electrical angular velocity, and T L is the load torque.
The decomposition of the speed subsystem in step S2 comprises the sub-steps of:
S201, dividing a speed subsystem into a main system and an auxiliary system according to an additive state decomposition idea, so as to simplify the control problem; the main system (nominal system) is noted as:
Wherein ω p is the main system state and i qp is the main system control input; the main system control targets are: designing i qp such that when time t→infinity, ω p-ωr →0, where ω r is a given reference input speed;
s202, defining:
Wherein i qr is a speed loop composite control law, omega s and i qs are respectively used as the state and control input of an auxiliary system, and an auxiliary system state equation is established:
Order the The above auxiliary system is further noted as:
the control targets of the auxiliary system are as follows: i qs is designed such that when time t→infinity, ω s →0.
Preferably, the design of the exponential convergence model predictive controller of the host system in step S3 comprises the sub-steps of:
s301, setting a speed ring discrete period as T s, and discretizing a main system by using a forward Euler method to obtain the following steps:
ωp(k+1)=ωp(k)+Tsbiqp(k);
Defining a main system speed tracking error:
the first order derivative is obtained and then discretized by a forward Euler method to obtain:
assume that e p converges exponentially to 0, i.e
Wherein the method comprises the steps ofFor the exponential convergence factor, the above formula is discretized by forward euler method:
s302, selecting the following cost function:
In the middle of Is a weight coefficient;
S303, order
Recording deviceAnd (3) obtaining:
Through the calculation, the method has the advantages that, Thus, whenIn this case, the cost function in step S302 takes a minimum value.
Preferably, the controller design of the secondary system in step S4 comprises the following sub-steps:
s401 is provided with Taking f s and its i-th derivative f s (i) (i=1, 2,., n) as the expansion state variables, building an n+2-th order augmentation system state space model corresponding to the auxiliary system:
Wherein the state variables Control input u=i qs, output y=ω s, coefficient matrix:
S402, the GPIO pair ω s、fs and its i-th derivative f s (i) (i=1, 2, online estimation n):
Wherein the method comprises the steps of Representing an estimate of the state x, M is the observer gain matrix to be designed, which can be found by pole configuration. Discretizing the GPIO by using a forward Euler method to obtain the product:
Wherein I (n+2) represents an (n+2) x (n+2) th order identity matrix;
s403, obtaining a total disturbance estimated value based on the discrete form GPIO in the step S402 The following auxiliary system control laws are designed:
wherein K x is the state feedback gain, which can be obtained by the pole allocation method, The gain is compensated for the disturbance.
Preferably, the speed ring composite controller in step S5 is designed as follows:
In general, the above technical solutions conceived by the present invention have mainly the following advantages compared with the prior art:
(1) The invention utilizes the additive state decomposition technology to decompose the problems of rotation speed tracking and disturbance suppression of the permanent magnet synchronous motor into independent control problems of two subsystems, so that the controller design has higher degree of freedom and flexibility;
(2) The model predictive controller of the main system can be designed and operated offline, and the real-time calculation amount and the calculation complexity of the digital controller can be effectively reduced during practical application;
(3) The auxiliary system is used for solving the problem of speed loop disturbance suppression, and the GPIO is used for estimating the total disturbance of the system on line, so that the GPIO has stronger time-varying disturbance estimation performance compared with a conventional linear extended state observer;
(4) The method provided by the invention does not depend on an accurate model, when the system has parameter perturbation and unmodeled dynamic, the parameter perturbation and unmodeled dynamic can be used as a part of total disturbance to be estimated and compensated, and the system has strong robustness and is suitable for complex environments and severe working conditions;
(5) The method provided by the invention is applied to a PMSM speed regulation control system, has excellent system dynamic and steady state performance, can realize high-precision tracking of a constant value and a time-varying reference rotating speed, and meets the application requirements of the PMSM speed regulation control system in the field of high-performance servo.
Drawings
FIG. 1 is a schematic diagram of a PMSM control system according to the method of the present invention disclosed in an embodiment of the present invention;
FIG. 2 is a schematic flow chart of the method of the present invention;
FIG. 3 is an equivalent exploded schematic view of the speed ring subsystem;
FIG. 4 is a schematic diagram of a speed controller according to the present invention;
Fig. 5 is a waveform diagram of motor output signals when the reference rotational speed ω r =1000 rpm is set;
FIG. 6 is a graph of tracking error versus the present method and conventional MPC method when the reference speed ω r =1000 rpm is set;
fig. 7 is a waveform diagram of motor output signals when the reference rotational speed ω r =500 sin (20pi t) rpm is set;
Fig. 8 is a graph of tracking error versus the present method and conventional MPC method when the reference rotational speed ω r =500 sin (20pi t) rpm is set.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Fig. 1 is a block diagram of a PMSM control system employing the method of the present invention. The speed loop adopts the model predictive controller based on the additive state decomposition, and the given reference rotating speed is omega r. The speed loop control signal i qr is used as a reference value of q-axis current, the reference value of d-axis current is i dr =0, the current loop control period is T c, and the tracking of d-axis current and q-axis current on the reference current is realized by adopting a conventional PID control strategy.
Fig. 2 is a flow chart of a method for controlling a model prediction speed of a permanent magnet synchronous motor based on additive state decomposition according to an embodiment of the present invention, where the method shown in fig. 2 includes the following steps:
S1, under the dq synchronous rotation coordinate system, establishing a mathematical model of the surface-mounted PMSM as follows:
Wherein R and L are stator resistance and stator inductance, p is the pole pair number of the motor, J is the rotor moment of inertia, B is the viscous damping coefficient, ψ f is the rotor permanent magnet flux linkage, i d and i q are the d and q axis currents, u d and u q are the d and q axis voltages, ω is the rotor angular velocity, ω e =pω is the rotor electrical angular velocity, and T L is the load torque.
S2, FIG. 3 is an equivalent system decomposition schematic diagram, and the speed subsystem is divided into a main system and an auxiliary system according to an additive state decomposition idea, so that the control problem is simplified. The main system (nominal system) is noted as:
Where ω p is the main system state and i qp is the main system control input. The main system control targets are: i qp is designed such that when time t→infinity, ω p-ωr →0.
Definition:
Wherein i qr is a speed loop composite control law, omega s and i qs are respectively used as the state and control input of an auxiliary system, and an auxiliary system state equation is established:
Order the The above auxiliary system is further noted as:
the control targets of the auxiliary system are as follows: i qs is designed such that when time t→infinity, ω s →0.
S3, setting a speed ring discrete period as T s, and discretizing a main system by using a forward Euler method to obtain the product:
ωp(k+1)=ωp(k)+Tsbiqp(k).
Defining a main system speed tracking error:
the first order derivative is obtained and then discretized by a forward Euler method to obtain:
assume that e p converges exponentially to 0, i.e
Wherein the method comprises the steps ofThe index convergence coefficient is obtained by discretizing the above formula by using a forward Euler method:
selecting the following cost function:
In the middle of Is a weight coefficient.
Order the
Recording deviceAnd (3) obtaining:
Through the calculation, the method has the advantages that, Thus, whenAnd when the cost function is the minimum value.
S4, designing a state feedback control law based on disturbance estimation and compensation, and inhibiting influence of disturbance on output of an auxiliary system. Is provided with Taking f s and its i-th derivative f s (i) (i=1, 2,., n) as the expansion state variables, building an n+2-th order augmentation system state space model corresponding to the auxiliary system:
Wherein the state variables Control input u=i qs, output y=ω s, coefficient matrix:
The following GPIO was designed to make an online estimate of ω s、fs and its i-derivative f s (i) (i=1, 2,., n):
Wherein the method comprises the steps of Representing an estimate of the state x, M is the observer gain matrix to be designed, which can be found by pole configuration. Discretizing the GPIO by using a forward Euler method to obtain the product:
Wherein I (n+2) represents an (n+2) × (n+2) th order identity matrix.
Total disturbance estimated value based on the above discrete form GPIOThe following auxiliary system control laws are designed:
wherein K x is the state feedback gain, which can be obtained by the pole allocation method, The gain is compensated for the disturbance.
S5, the structure of the permanent magnet synchronous motor model prediction speed control system based on the additive state decomposition is shown in fig. 4. And (3) performing controller fusion on control inputs of the main system and the auxiliary system of the speed loop, and designing the following speed loop composite control law:
In order to test the control performance of the permanent magnet synchronous motor model predictive speed control method based on the additive state decomposition, the method is applied to a PMSM speed regulation system, and motor parameters are given in table 1. The set load torque is:
TABLE 1
Fig. 5 (a) - (d) are respectively a reference input and output rotational speed waveform, a q-axis current reference value i qr waveform, an a-phase current i a waveform, and an electromagnetic torque T e waveform when the reference rotational speed ω r =1000 rpm is set. Fig. 6 is a comparison of motor speed tracking error for the method provided by the present invention and a conventional MPC method. As can be seen from fig. 5 and fig. 6, the method provided by the invention can effectively estimate and compensate the total disturbance in the speed regulating system of the permanent magnet synchronous motor, inhibit the influence of load mutation, time-varying load and the like on the motor rotation speed, realize high-precision tracking of the motor output rotation speed on a given reference rotation speed, and has stronger robustness compared with the conventional MPC speed controller.
In fig. 7, (a) - (e) are the reference input and output rotational speed waveforms, the rotational speed tracking error waveform, the q-axis current reference value i qr waveform, the a-phase current i a waveform, and the electromagnetic torque T e waveform, respectively, when the reference rotational speed ω r =500 sin (20pi T) rpm is set. Fig. 8 is a comparison of motor speed tracking error for the method provided by the present invention and a conventional MPC method. As can be seen from fig. 8, the method provided by the invention has strong robustness to load abrupt change, time-varying load and the like, and has higher tracking precision to time-varying reference signals.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.