Coaxial cooperative speed control method and system of double synchronous motor and fan simulation application

Abstract

The application discloses a coaxial collaborative speed control method and system of double synchronous motors and fan simulation application and belongs to the technical field of motor control and wind power test. By collecting speed and shaft current feedback signals, a system mechanical dynamic and motor mathematical model are constructed, a load torque estimator and a dynamic compensator are designed to suppress internal and external disturbances, total target electromagnetic torque is distributed based on a torque distribution coefficient, and an optimal control input is solved through a model predictive control to construct a cost function, so that double motor collaborative speed regulation is realized. A corresponding system comprises a signal acquisition unit, a model construction unit, a load estimation and dynamic compensation unit, a torque distribution and control unit, and can be applied to a fan main shaft simulation platform to reproduce the characteristics of large inertia and high load fluctuation. The application improves the dynamic response and coordination of double motors, simplifies the control structure, enhances the anti-disturbance ability, and is suitable for high-precision fan simulation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor control and wind power testing, in particular to a coaxial collaborative speed control method, system and fan simulation application of double synchronous motors. BACKGROUND

[0002] The main shaft system in the current wind power generation system has typical characteristics such as large inertia, high load fluctuation and strong nonlinearity. In the field of wind power control system development and testing, it is crucial to accurately reproduce the dynamic characteristics of the real main shaft by building a high-fidelity "fan main shaft simulation platform". The traditional scheme adopts a single high-power motor driving mode, but has inherent defects such as high equipment cost, large size and low energy efficiency. Therefore, the new solution of replacing a single motor with a double-motor coaxial driving structure has shown significant advantages in recent research and practical applications. It not only greatly improves the flexibility and economy of the system, but also provides a new technical path for accurately simulating the dynamic response of the main shaft under complex working conditions.

[0003] In the prior art, the double-motor collaborative control method still has many technical bottlenecks. The traditional double-motor driving scheme generally adopts a cascade control architecture of "speed loop + current loop". This structure has the following inherent defects: 1) complex control parameters: two sets of current loop controllers need to be designed independently, which requires a large amount of debugging work and makes parameter matching difficult; 2) limited dynamic response: the response time is added due to the double-loop structure, and the system bandwidth is difficult to further improve, making it difficult to meet the demand of high dynamic speed regulation of the fan main shaft. These technical bottlenecks restrict the application effect of the double-motor coaxial system in the field of fan main shaft simulation, and a more efficient and flexible control method is needed to improve the dynamic performance and adaptability of the system. SUMMARY

[0004] The purpose of the present application is to provide a coaxial collaborative speed control method, system and fan simulation application of double synchronous motors, which improves the dynamic performance and adaptability of the system.

[0005] To achieve the above-mentioned purpose, the present application provides a coaxial collaborative speed control method of double synchronous motors, comprising the following steps:

[0006] S1. Collecting the speed feedback signal and axle current feedback signal of the double synchronous motor coaxial system;

[0007] S2. Based on the speed feedback signal and axle current feedback signal, constructing a system mechanical dynamic model and a motor mathematical model to form a state space model;

[0008] S3. According to the state space model and the feedback signal, constructing a load torque estimator to estimate the external load disturbance, and constructing a dynamic compensator to suppress the internal disturbance of the motor;

[0009] S4. Based on the load torque estimation result and the given speed signal, the total target electromagnetic torque is calculated, and the total target electromagnetic torque is distributed to the two motors through a torque distribution coefficient to obtain the steady-state reference electromagnetic torque of each motor;

[0010] S5. According to the steady-state reference electromagnetic torque and the state space model, the steady-state reference current and voltage of each motor are determined;

[0011] S6. The system error dynamic equation is constructed, the cost function is constructed based on the model predictive control, and the optimal control input is solved to generate the motor control signal to realize the collaborative speed control of the double motors.

[0012] Preferably, in step S1, the speed feedback signal is calculated after the rotor position angle of the double motor spindle is collected by the encoder, the three-phase winding current of the two motors is collected by the current sensor, and the motor current feedback signal is calculated through the converter and converter.

[0013] Preferably, in step S2, the system mechanical dynamic model is constructed as follows:

[0014] ;

[0015] wherein, is the equivalent moment of inertia of the system, is the viscous friction coefficient; and are the electromagnetic torques generated by motor 1 and motor 2 respectively, is the external load disturbance;

[0016] The mathematical model of the two motors in the coordinate system is constructed:

[0017] ;

[0018] wherein, represents the motor; , are the axis and axis voltages of the motor respectively; , are the axis and axis currents of the motor respectively; is the flux linkage; and ​respectively shaft and shaft inductance is the number of pole pairs of the motor is the stator resistance , represents modeling error or motor internal disturbance

[0019] Preferably, in step S3, the load torque estimator is constructed according to the following expression:

[0020] ;

[0021] wherein, is the estimated value of the speed feedback signal is the estimated value of the load torque , is the estimated value of the load torque , is the parameter of the load torque estimator

[0022] Preferably, in step S4, the total target electromagnetic torque is calculated according to the following expression:

[0023] ;

[0024] wherein, is the target steady-state electromagnetic torque is the viscous friction coefficient

[0025] The expression of the torque distribution coefficient is as follows:

[0026] ;

[0027] wherein, represents the torque coefficient distributed to the motor is the rated torque of the motor , is the rated torque of the motor

[0028] A coaxial collaborative speed control system of a dual synchronous motor includes:

[0029] A signal acquisition unit is configured to acquire a speed feedback signal and a shaft current feedback signal of the coaxial system of the dual synchronous motor

[0030] A model construction unit is connected to the output end of the signal acquisition unit, and is configured to construct a system mechanical dynamic model, a motor mathematical model and a state space model based on the feedback signals

[0031] a load estimation and dynamic compensation unit, an input end of which is connected with an output end of the model construction unit and an output end of the signal acquisition unit, for constructing a load torque estimator to estimate external load disturbance and constructing a dynamic compensator to suppress internal disturbance of the motor;

[0032] a torque distribution unit, an input end of which is connected with an output end of the load estimation and dynamic compensation unit, for calculating total target electromagnetic torque based on the load torque estimation result and the given speed signal and distributing to the two motors through a torque distribution coefficient to obtain steady-state reference electromagnetic torque of each motor;

[0033] a control unit, input ends of which are respectively connected with an output end of the torque distribution unit and an output end of the model construction unit, for determining steady-state reference current and voltage according to the steady-state reference electromagnetic torque and the state space model, constructing a system error dynamic equation, and solving optimal control input based on model predictive control and generating motor control signals.

[0034] Preferably, the signal acquisition unit comprises an encoder, a current sensor, a signal conditioning circuit and an AD converter; the encoder is mechanically connected with a main shaft coaxial with the dual motor, and an output end thereof is connected with an encoding interface of a control chip; the current sensor is electrically connected with three-phase windings of the two motors, and an output end thereof is connected with a signal input interface of the control chip in sequence through the signal conditioning circuit and the AD converter, and the signal conditioning circuit is used for filtering and amplifying the current signal.

[0035] Preferably, the control unit comprises an error dynamic construction module, an optimal control solving module and a driving signal generation module; input ends of the error dynamic construction module are respectively connected with the steady-state reference value output by the torque distribution unit and the feedback signal output by the signal acquisition unit; an input end of the optimal control solving module is connected with an output end of the error dynamic construction module, and an output end thereof is connected with an input end of the driving signal generation module; an output end of the driving signal generation module is connected with inverters of the dual motor, for converting the optimal control input into a PWM driving signal.

[0036] Preferably, in step S6, the system error dynamic equation comprises a speed error, a shaft current error, a shaft current error and a voltage error; wherein the steady-state shaft reference current is , , the steady-state shaft reference voltage is , , and the given speed signal is ;

[0037] The system error dynamic equation is constructed as follows:

[0038] ;

[0039] wherein, , , , , respectively are speed error, two motor shaft current error and system voltage error.

[0040] Therefore, the application adopts the above-mentioned structure of a double synchronous motor coaxial collaborative speed control method, system and fan simulation application, has the following beneficial effects:

[0041] (1) The application introduces a torque distribution coefficient to achieve collaborative control according to the rated capacity of each motor, avoiding the passive following problem of traditional master-slave control mode, effectively improving the power coordination and energy efficiency of the double motor system.

[0042] (2) The application is based on a single-loop predictive control framework, which simplifies the control system structure, reduces the parameter setting workload, and enhances the convenience of engineering application; at the same time, it avoids the problem of dynamic response time superposition in the traditional double closed-loop structure, effectively improves the control bandwidth and dynamic response performance of the system, and is especially suitable for fan main shaft and other application scenarios with large inertia and high disturbance characteristics.

[0043] (3) The application designs a load estimator and a dynamic compensator structure, which can estimate the external load disturbance and motor internal modeling error in the coaxial system in real time, enhances the suppression ability of the system to unknown disturbances, and effectively improves the stability and precision of the control system.

[0044] (4) The optimal controller proposed in the application can derive an explicit analytical solution, avoiding the complex optimization solution problem in traditional model predictive control, with high calculation efficiency, easy to deploy on resource-limited embedded controllers, and good engineering application prospect.

[0045] (5) The control method of the application is suitable for double motor coaxial platform, which can simulate the dynamic response of the main shaft of the wind power system under variable working conditions, and meet the high precision and high dynamicity requirements of mechanical and electrical system testing and algorithm verification.

[0046] The technical solutions of the application will be further described in detail below with the help of the drawings and examples. DETAILED DESCRIPTION

[0047] Figure 1 is a schematic diagram of a double synchronous motor coaxial collaborative speed control system;

[0048] Figure 2 is a schematic diagram of a load torque estimator;

[0049] Figure 3Fig. 1 is a schematic diagram of a dynamic compensator for motor 1;

[0050] Figure 4 Fig. 2 is a schematic diagram of a dynamic compensator for motor 2;

[0051] Figure 5 Fig. 3 is a schematic diagram of system response curves under a step speed given signal; (a) is a response curve of motor speed under working condition 1; (b) is a response curve of q-axis current under working condition 1; (c) is a response curve of d-axis current under working condition 1;

[0052] Figure 6 Fig. 4 is a schematic diagram of system torque response under a step speed given signal; (a) is a response curve of motor 1 output torque under working condition 1; (b) is a response curve of motor 2 output torque under working condition 1; (c) is a response curve of total torque under working condition 1;

[0053] Figure 7 Fig. 5 is a schematic diagram of system response curves under a time-varying speed given signal; (a) is a response curve of motor speed under working condition 2; (b) is a response curve of q-axis current under working condition 2; (c) is a response curve of d-axis current under working condition 2;

[0054] Figure 8 Fig. 6 is a schematic diagram of system torque response under a time-varying speed given signal; (a) is a response curve of motor 1 output torque under working condition 2; (b) is a response curve of motor 2 output torque under working condition 2; (c) is a response curve of total torque under working condition 2. DETAILED DESCRIPTION

[0055] The technical solutions of the present application are further described below by means of the accompanying drawings and examples.

[0056] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the common meaning understood by one of ordinary skill in the art to which the present application pertains. The terms "first", "second", and similar terms used in the present application do not denote any order, quantity, or importance, but are merely used to distinguish different components. The terms "include", "contain", and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms do not mean physical or mechanical connection, but can include electrical connection, whether direct or indirect. The terms "upper", "lower", "left", "right", and the like merely indicate relative positional relationships, which can change when the absolute positions of the described objects change.

[0057] EMBODIMENT

[0058] The application realizes a double-motor coaxial collaborative speed control method and system and a fan main shaft simulation system by collecting speed feedback signals of a double-motor coaxial system and shaft current feedback signals of two motors , constructing a load torque estimator, a dynamic compensator, a load torque distribution mechanism and a single closed-loop speed controller. Figure 1 The design diagram is shown in the figure. The shaft current controller still adopts the proportional-integral (PI) control mode commonly used in the prior art, and the current reference value is calculated through the maximum torque per ampere (MTPA) strategy. The related technology has been disclosed in the existing published patents and is not the innovation content of the application.

[0059] The specific steps of the controller design are as follows:

[0060] Step S1: Collect the double-motor main shaft rotor position angle through the encoder, calculate the motor electrical angle and speed feedback signals , collect the three-phase winding currents , , of motor 1, calculate and shaft currents , , then calculate and shaft currents , , through the inverter, collect the three-phase winding currents , of motor 2, calculate and shaft currents , , then calculate and shaft currents , , through the inverter.

[0061] Step S2: Build the overall mechanical dynamics of the double-motor coaxial system:

[0062] ;

[0063] wherein, is the equivalent moment of inertia of the system, is the viscous friction coefficient. and are the electromagnetic torques generated by motor 1 and motor 2, respectively, is the external load disturbance;

[0064] Step S3: Construct the mathematical model of the two motors in the coordinate system:

[0065] ;

[0066] wherein, denotes the th motor; , denote the th motor's axis and axis voltage, respectively; , denote the th motor's axis and axis current, respectively; is the flux linkage; and are the axis and axis inductance, respectively; is the number of pole pairs of the motor; is the stator resistance; , denotes the modeling error or internal motor disturbance.

[0067] Step S4: According to the system mechanical equation obtained in step S2 and the mathematical model of the two motors in the coordinate system obtained in step S3, construct the state space model of the coaxial dual-motor system:

[0068] ;

[0069] wherein, , , , , , , , , , , .

[0070] Step S5: In order to realize dual-motor torque cooperation and improve the system's suppression ability to external disturbances, according to the system model obtained in step S4 and the speed feedback signal , construct the following speed estimator:

[0071] ;

[0072] wherein, is an estimate of the speed feedback signal , is an estimate of the load torque , , is a parameter of the load torque estimator.

[0073] Step S6: For motor 1, construct a dynamic compensator from the system model obtained in step S4, and the shaft current feedback signal and the given voltage signal as follows:

[0074] ;

[0075] wherein, is an estimate of the shaft current feedback signal of motor 1, is an estimate of the shaft current channel disturbance of motor 1, , is a parameter of the dynamic compensator.

[0076] Step S7: For motor 2, construct a dynamic compensator from the system model obtained in step S4, and the shaft current feedback signal and the given voltage signal as follows:

[0077] ;

[0078] wherein, is an estimate of the shaft current feedback signal of motor 2, is an estimate of the shaft current channel disturbance of motor 2, , is a parameter of the dynamic compensator.

[0079] Step S8: Calculate the total electromagnetic torque required to maintain steady state operation from the load torque estimate obtained in step S5, and the given speed signal , and the mechanical system dynamics equation derived in step S1 as follows:

[0080] ;

[0081] wherein, For the target steady-state electromagnetic torque, is the coefficient of viscous friction.

[0082] Step S9: To ensure that the two motors do not exceed their respective torque carrying capacity when operating within their rated speed range, a torque distribution coefficient is introduced to rationally coordinate their torque contribution based on the rated output capacity of the motors.

[0083] ;

[0084] in, Indicates allocation to the motor torque coefficient, For motor The rated torque.

[0085] Step S10: Based on the torque distribution coefficient obtained in step S9) Calculate the steady-state reference electromagnetic torque for each motor:

[0086] , ;

[0087] in, , These are the steady-state reference electromagnetic torques for motor 1 and motor 2, respectively.

[0088] Step S11: Based on the steady-state reference electromagnetic torque obtained in step S10 , Based on the system model obtained in step S4, calculate the steady-state condition of each motor. Shaft reference current:

[0089] ;

[0090] in, , These are the steady-state conditions of motor 1 and motor 2, respectively. Shaft reference current.

[0091] Step S12: Based on the steady state of each motor obtained in step S11 Shaft reference current , Based on the system model derived in step S4, calculate the steady-state performance of each motor. Shaft reference voltage:

[0092] ;

[0093] in, , These are the steady-state reference voltage commands for motor 1 and motor 2, respectively.

[0094] Step S13: According to the steady state obtained in step S11 axis reference current , and the steady state obtained in step S12 axis steady state reference voltage , and the given speed signal , the system error dynamic equation is constructed:

[0095] ;

[0096] where, , , , , are the speed error, the two motor axis current error and the system voltage error, respectively.

[0097] Step S14: According to the system error model obtained in step S13, the system error within the future prediction time length is estimated using Taylor expansion:

[0098] ;

[0099] where, is the prediction vector; is the speed error vector; and are the two motor axis current error vectors, respectively.

[0100] Step S15: In order to achieve optimal control performance, the speed tracking error of the system and the current tracking error of the two motors are comprehensively considered to construct the following cost function:

[0101] ;

[0102] where, , , is the weight factor, is the prediction step length.

[0103] Step S16: According to the cost function obtained in step S15, through further derivation, it can be equivalent to the following form:

[0104] ;

[0105] Step S17: According to the cost function obtained in step S16, the control variable , Calculate the partial derivatives separately and set them to zero to obtain the optimal control input. , The final analytical solution is of the following form:

[0106] ;

[0107] ;

[0108] ;

[0109] ;

[0110] , ;

[0111] Representation matrix The Line number The elements of the column.

[0112] Step S18: Based on the optimal control input matrix obtained in step S17 The error system constructed in step S12 and the system model obtained in step S3 can be used to obtain the optimal control voltage signals for each of the two motors:

[0113] ;

[0114] in, , These are motor 1 and motor 2 respectively. Shaft-given voltage signal.

[0115] The given design in steps S1-S18 shaft voltage signal , Under the influence of the two motors, The shaft current controller is working normally, and the dual-motor coaxial speed control system is asymptotically stable, meaning it stabilizes over time. The shift, speed deviation signal Gradually converges to 0, while the output torque of the two motors can be distributed according to the set distribution coefficient, that is, the output torque of motor 1 satisfies... The output torque of motor 2 satisfies .

[0116] Figures 2-4 The specific implementation block diagrams of the load torque estimator, the dynamic compensator of motor 1, and the dynamic compensator of motor 2 are given respectively. The load torque estimator, the dynamic compensator of motor 1, and the dynamic compensator of motor 2 can be implemented by reference.

[0117] In addition, the control parameter adjustment rule involved in the dual-motor coordinated speed controller of the application is as follows:

[0118] 1. Parameters in load torque estimator , for adjusting the estimation speed and accuracy of the load estimator, satisfying , , , wherein is the bandwidth of the estimator, and the parameter size is positively correlated with the estimation speed and accuracy.

[0119] 2. Parameters in motor 1 dynamic compensator , for adjusting the estimation speed and accuracy of the compensator for disturbance , satisfying , , , wherein is the bandwidth of the compensator, and the parameter size is positively correlated with the estimation speed and accuracy.

[0120] 3. Parameters in motor 2 dynamic compensator , for adjusting the estimation speed and accuracy of the compensator for disturbance , satisfying , , , wherein is the bandwidth of the compensator, and the parameter size is positively correlated with the estimation speed and accuracy.

[0121] 4. Dual-motor speed controller , , for weighing the importance of speed control and current control performance of the two motors, satisfying , , The parameter size is positively correlated with the importance of the related control performance, and by adjusting these coefficients, flexible balance between speed and current control accuracy can be achieved. for adjusting the prediction step of model prediction, satisfying The parameter size is negatively correlated with the response speed of the control performance.

[0122] Two working conditions are set to illustrate the effectiveness of the application:

[0123] 1. Set the step speed given signal rpm, initial load 1.5 Nm, torque distribution factor , , 0.25 s, 2 Nm load applied, 0.45 s removed.

[0124] 2, set the sinusoidal speed signal rpm, initial load 1.5 Nm, torque distribution factor , .

[0125] Figure 5 (a)-(c) and Figure 6 (a)-(c) gives the motor speed, shaft current, shaft current, motor 1 output torque, motor 2 output torque and total torque response curves under working condition 1. Figure 7 (a)-(c) and Figure 8 (a)-(c) gives the motor speed, shaft current, shaft current, motor 1 output torque, motor 2 output torque and total torque response curves under working condition 2. From the test results, it can be seen that the double-motor coaxial coordinated speed control method proposed by the application not only can realize fast and accurate tracking of the given speed reference signal, but also can real-time coordinate the output torque of the two motors, effectively improving the power coordination and dynamic response performance of the double-motor system.

[0126] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application rather than limit it, although the application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the application, and these modifications or equivalent replacements also cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the application.

Claims

1. A method of coaxial coordinated speed control of dual synchronous electric machines, characterized by: The method comprises the following steps: S1. Collecting speed feedback signals of the coaxial system of the dual synchronous motor and axial current feedback signals; S2. based on the speed feedback signal and axial current feedback signal, constructing a system mechanical dynamic model and a motor mathematical model, forming a state space model; S3. According to the state space model and the feedback signal, a load torque estimator is constructed to estimate external load disturbance, and a dynamic compensator is constructed to suppress motor internal disturbance; S4. Based on the load torque estimation result and the given speed signal, a total target electromagnetic torque is calculated, and the total target electromagnetic torque is distributed to the two motors through a torque distribution coefficient to obtain the steady-state reference electromagnetic torque of each motor; S5. determining steady-state reference electromagnetic torque and state space model for each motor based on the steady-state reference electromagnetic torque and state space model axle steady-state reference current and voltage; S6. Constructing system error dynamic equation, based on model predictive control, considering the speed tracking error of system and the shaft current tracking error of two motors, constructing cost function and solving optimal control input, generating motor control signal to realize double motor collaborative speed control. motor control signal to realize double motor collaborative speed control. In step S6, the system error dynamic equation includes the speed error, the shaft current error and the voltage error; wherein the steady-state shaft reference current is , the steady-state shaft reference voltage is , and the given speed signal is ; The system error dynamic equation is constructed as follows: ； wherein, , are the speed error, the two motor shaft current error and the system voltage error, respectively.

2. A method of co-axial coordinated speed control of dual synchronous electric machines as claimed in claim 1, wherein: In step S1, the speed feedback signal is calculated after the encoder collects the double-motor main shaft rotor position angle, The shaft current feedback signal is collected by the current sensor to collect the three-phase winding currents of the two motors, and the converter and converter is calculated.

3. A method of co-axial coordinated speed control of dual synchronous electric machines as claimed in claim 1, wherein: In step S2, the system mechanical dynamic model is constructed as follows: ； wherein, is the equivalent moment of inertia of the system, is the viscous friction coefficient; and are the electromagnetic torques generated by motor 1 and motor 2, respectively, is the external load disturbance; Construct the mathematical model of two motors in coordinate system: ； wherein, denotes the motor; denotes the motor; axis and axis voltage; denotes the motor; axis and axis current; is the flux linkage; and are the axis and axis inductances; is the number of pole pairs of the motor; is the stator resistance; denotes modeling errors or internal motor disturbances.

4. A method of co-axial coordinated speed control of dual synchronous electric machines as claimed in claim 3, wherein: In step S3, the expression for constructing the load torque estimator is as follows: ； in, It is a speed feedback signal The estimated value, It is the load torque The estimated value; These are parameters of the load torque estimator. The equivalent rotational inertia of the system, ,in The coefficient of viscous friction, for Shaft current feedback signal, for Shaft current feedback signal.

5. A method of co-axial coordinated speed control of dual synchronous electric machines as claimed in claim 1, wherein: In step S4, the expression for calculating the total target electromagnetic torque is as follows: ； wherein is the target steady state electromagnetic torque, is the viscous friction coefficient, is the load torque estimate; The expression for the torque distribution coefficient is as follows: ； wherein represents a torque coefficient assigned to the electric machine , is a rated torque of the electric machine .

6. A dual synchronous motor coaxial coordinated speed control system characterized by, The method comprises the following steps: The signal acquisition unit is used for acquiring the speed feedback signal and the shaft current feedback signal of the double-synchronous-motor coaxial system the shaft current feedback signal A model construction unit, an input end of which is connected with an output end of the signal acquisition unit, is used to construct a system mechanical dynamic model, a motor mathematical model and a state space model based on the feedback signal; A load estimation and dynamic compensation unit, an input end of which is connected with an output end of the model construction unit and an output end of the signal acquisition unit, is used to construct a load torque estimator to estimate external load disturbance, and a dynamic compensator to suppress motor internal disturbance; A torque distribution unit, an input end of which is connected with an output end of the load estimation and dynamic compensation unit, is used to calculate a total target electromagnetic torque based on the load torque estimation result and the given speed signal, and to distribute the total target electromagnetic torque to the two motors through a torque distribution coefficient to obtain the steady-state reference electromagnetic torque of each motor; a control unit, input ends of which are connected with output ends of the torque distribution unit and the model building unit respectively, for determining the steady-state reference current and voltage according to the steady-state reference electromagnetic torque and the state space model, building a system error dynamic equation, considering the speed tracking error of the system and the shaft current tracking error of the two motors based on model predictive control, and solving the optimal control input and generating the motor control signal; a control unit, input ends of which are connected with output ends of the torque distribution unit and the model building unit respectively, for determining the steady-state reference current and voltage according to the steady-state reference electromagnetic torque and the state space model, building a system error dynamic equation, considering the speed tracking error of the system and the shaft current tracking error of the two motors based on model predictive control, and solving the optimal control input and generating the motor control signal; The system error dynamic equation comprises a rotational speed error, a shaft current error and a voltage error; wherein the steady state shaft reference current is , the steady state shaft reference voltage is , and the given rotational speed signal is ; The system error dynamic equation is constructed as follows: ； wherein, , are the rotational speed error, the two motor shaft current error and the system voltage error, respectively.

7. A coaxial co-operating dual synchronous motor variable speed control system as claimed in claim 6, characterized in that: The signal acquisition unit comprises an encoder, a current sensor, a signal conditioning circuit and an AD converter; the encoder is mechanically connected with a main shaft coaxial with the double motor, and an output end thereof is connected with an encoding interface of the control chip; the current sensor is electrically connected with three-phase windings of the two motors, and an output end thereof is connected with a signal input interface of the control chip in sequence through the signal conditioning circuit and the AD converter, and the signal conditioning circuit is used to filter and amplify the current signal.

8. A coaxial co-operating dual synchronous motor speed control system as claimed in claim 6, characterized in that: The control unit comprises an error dynamic construction module, an optimal control solving module and a driving signal generation module; an input end of the error dynamic construction module is connected with the steady-state reference value output by the torque distribution unit and the feedback signal output by the signal acquisition unit respectively; an input end of the optimal control solving module is connected with an output end of the error dynamic construction module, and an output end thereof is connected with an input end of the driving signal generation module; an output end of the driving signal generation module is connected with an inverter of the double motor, and is used to convert the optimal control input into a PWM driving signal.

9. Use of a dual synchronous motor co-axial coordinated speed control in fan simulation, characterized in that, The system of claim 6 is applied to a fan main shaft simulation platform, and through the cooperative control capability of the system, the large inertia, high load fluctuation and strong nonlinear dynamic characteristics of the fan main shaft are reproduced, and high-fidelity simulation of the running state of the fan main shaft is realized.

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