A method for online identification of rotational inertia and torque disturbance compensation sliding mode control

Abstract

The application belongs to the technical field of permanent magnet synchronous motor speed control of electric aircraft, and discloses a method for online identification of rotational inertia and compensation of torque disturbance of sliding mode control, which comprises the following steps: step 1: according to the motor speed, electromagnetic torque and load torque of the motor driving system at a certain moment, the rotational inertia is identified through recursive least squares method; step 2: the load torque change of the motor driving system is observed by using a disturbance observer, and the motor speed is estimated and compensated; step 3: the motor speed is accurately controlled by a sliding mode speed controller, so that the actual value of the motor speed approaches the given value. The method for online identification of rotational inertia and compensation of torque disturbance of sliding mode control can identify the motor rotational inertia and compensate the load disturbance, solves the problem of inaccurate motor speed response, and improves the reliability of the operation of the electric aircraft.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of permanent magnet synchronous motor speed control of electric aircraft, and particularly relates to a rotational inertia online identification and torque disturbance compensation sliding mode control method. BACKGROUND

[0002] Due to the influence of rotational inertia perturbation and external disturbance, the speed response of the permanent magnet synchronous motor driving system of the electric aircraft is often inaccurate, which affects the safety of the electric aircraft operation.

[0003] In order to improve the operation quality of the driving system and the reliability of the electric aircraft, in view of the problem that the speed response of the permanent magnet synchronous motor is inaccurate due to the change of the rotational inertia of the system and the change of the load, online identification of the rotational inertia and estimation and compensation of the load change are mainly adopted to solve the problem. Since the rotational inertia of the permanent magnet synchronous motor changes with the working state during operation, the speed response is inaccurate. Meanwhile, the change of the load also affects the speed response, which further affects the reliability of the electric aircraft operation.

[0004] Therefore, in view of the fact that the permanent magnet synchronous motor of the electric aircraft is easily affected by the rotational inertia perturbation and the load disturbance during operation, and the speed response is negatively affected, a sliding mode control method for online identification and torque compensation of the permanent magnet synchronous motor of the electric aircraft is proposed. SUMMARY

[0005] In view of this, the application discloses a rotational inertia online identification and torque disturbance compensation sliding mode control method to solve the safety problem caused by the inaccurate speed response of the electric aircraft during operation.

[0006] The technical scheme provided by the application is specifically a rotational inertia online identification and torque disturbance compensation sliding mode control method, which comprises the following steps:

[0007] Step 1: according to the speed, electromagnetic torque and load torque of the motor driving system at a certain moment, the rotational inertia is identified by using the recursive least square method;

[0008] Step 2: the load torque change of the motor driving system is observed by using a disturbance observer, and the speed is estimated and compensated according to the rotational inertia;

[0009] Step 3: according to the obtained rotational inertia and compensated speed, the motor speed is accurately controlled by using a sliding mode speed controller, so that the actual value of the motor speed approaches the given value.

[0010] Further, the least square method with a forgetting factor is used to identify the rotational inertia in step 1, and the rotational inertia is calculated by the following formula:

[0011] Further, the least square method with a forgetting factor is used to identify the rotational inertia in step 1, and the rotational inertia is calculated by the following formula:

[0012] Let c=aT L (k);

[0013] Let φ(k) T =[T e (k-1),-ω m (k-1),-1], θ=[a,b,c] T , we get: ω r (k) = φ T (k)·θ

[0014] The iterative process of recursive least squares method is as follows:

[0015]

[0016]

[0017] Where Te is the electromagnetic torque; T L is the load torque; b m is the viscous friction coefficient; ω r is the motor speed; J is the moment of inertia, λ is the forgetting factor, T s is the sampling time, is the estimated value of the kth iteration, is the correction term, P(K) is a three-dimensional covariance matrix.

[0018] Further, in step 2, the estimated compensation speed is calculated using the following formula:

[0019]

[0020] Te is the electromagnetic torque; T L is the load torque; b m is the viscous friction coefficient; ω r is the motor speed; J is the moment of inertia; ω c is the estimated motor speed after compensation by the observer; T LC is the observed torque.

[0021] Further, the step 3 specifically includes the following steps:

[0022] Step 3.1: According to the mechanical motion equation of the surface-mounted PMSM:

[0023]

[0024] Te is the electromagnetic torque; T L is the load torque; b m is the viscous friction coefficient; ω c is the estimated motor speed after compensation by the observer; J is the moment of inertia.

[0025] Step 3.2: define the error between the given speed and the compensated speed as x1 by the moment of inertia and the compensation speed;

[0026]

[0027] The sliding mode surface is designed as:

[0028]

[0029] s is the sliding mode surface state vector;

[0030] Step 3.3: update the q-axis current by using the sliding mode controller with an asymptotic approach rate, as follows:

[0031]

[0032]

[0033] In the formula, ε, c, k, δ, σ1, σ2 are all sliding mode speed controller parameters; T L is the load torque; b m is the viscous friction coefficient; J is the moment of inertia.

[0034] The online moment of inertia identification and torque disturbance compensation sliding mode control method provided by the application can identify the moment of inertia online and compensate the load disturbance, solve the problem of inaccurate speed response, and improve the reliability of the electric aircraft operation.

[0035] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the disclosure of the application. BRIEF DESCRIPTION OF DRAWINGS

[0036] The accompanying drawings incorporated in the specification and constituting a part hereof illustrate embodiments consistent with the application and serve to explain the principles of the application together with the specification.

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0038] Figure 1 The flowchart of the online moment of inertia identification and torque disturbance compensation sliding mode control method provided by the disclosed embodiment is shown in the figure.

[0039] Figure 2A control logic schematic diagram of a method for online identification of rotational inertia and torque disturbance compensation sliding mode control is provided for the disclosed embodiment of the application.

[0040] Figure 3 A schematic diagram of a comparison of speed response based on the method provided by the application and the traditional PI algorithm during operation of an electric aircraft. DETAILED DESCRIPTION

[0041] The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, the same numbers are used to designate the same elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not meant to represent all embodiments consistent with the application. Rather, they are merely examples of systems consistent with some aspects of the application as detailed in the appended claims.

[0042] To solve the problems of electric aircraft permanent magnet synchronous motor working process is susceptible to rotational inertia perturbation and load disturbance, etc., the present embodiment provides a method for online identification of rotational inertia and torque disturbance compensation sliding mode control, comprising

[0043] Considering that the rotational inertia will change during the operation of the motor, step 1 is taken: according to the motor speed, electromagnetic torque and load torque of the motor drive system at a certain time, the rotational inertia is identified by recursive least squares method; wherein the certain time can be the speed, electromagnetic torque and load torque at the current state;

[0044] The least squares method with forgetting factor is used to identify the rotational inertia, which is calculated by the following formula:

[0045]

[0046] Let c=aT L (k);

[0047] Let φ(k) T =[T e (k-1),-ω m (k-1),-1],θ=[a,b,c] T , we get: ω r (k)=φ T (k)·θ

[0048] The iterative process of recursive least squares method is as follows:

[0049]

[0050]

[0051] Wherein, Te is electromagnetic torque; T L is load torque; b m is viscous friction coefficient; ω r is motor speed; J is moment of inertia, λ is forgetting factor, T s is sampling time, is the estimated value of the kth iteration, is the correction term, P(K) is a three-dimensional covariance matrix.

[0052] Step 2: Through the moment of inertia, the load torque change of the motor drive system is observed by using the disturbance observer, and the speed is estimated and compensated;

[0053] The estimated and compensated speed is calculated by the following formula:

[0054]

[0055] Te is electromagnetic torque; T L is load torque; b m is viscous friction coefficient; ω r is motor speed; J is moment of inertia; ω c is the motor speed estimated and compensated by the observer; T LC is the observed torque.

[0056] Step 3: According to the obtained moment of inertia and compensated speed, the motor speed is accurately controlled by the sliding mode speed controller, so that the actual value of the motor speed approaches the given value.

[0057] Step 3 specifically includes the following steps:

[0058] Step 3.1: According to the surface-mounted PMSM mechanical motion equation:

[0059]

[0060] Te is electromagnetic torque; T L is load torque; b m is viscous friction coefficient; ω c is the motor speed estimated and compensated by the observer; J is moment of inertia;

[0061] Step 3.2: Through the moment of inertia and the compensated speed, define the error between the given speed and the compensated speed as x1;

[0062]

[0063] The sliding surface is designed as:

[0064]

[0065] s is the sliding plane state vector;

[0066] Step 3.3: update q-axis current by using sliding mode controller with asymptotic reaching law, as follows:

[0067]

[0068]

[0069] wherein ε, c, k, δ, σ1, σ2 are sliding mode speed controller parameters; T L is load torque; b m is viscous friction coefficient; J is moment of inertia.

[0070] As Figure 1 shown in the flow chart of the identification method of the method for online identification of moment of inertia and torque disturbance compensation sliding mode control.

[0071] As Figure 2 shown in the control logic diagram using the above control method.

[0072] Figure 3 A set of simulation data using the method provided by the present application compared with the original PI control method is shown, and the research object is a permanent magnet synchronous motor with a rated power of 35kW, and the resistance, inductance and flux of the motor are 0.9 ohm, 0.85mH and 0.187Wb respectively. As Figure 3 shown in the speed response curve of the simulation of the aircraft from take-off to cruising stage, the given speed is 2400r / min which is reduced to 2000r / min at a certain time. From the simulation results, it can be seen that in terms of PMSM speed response, the PI controller produces large overshoot, slow response speed and large fluctuation; the control method provided by the present embodiment has faster response speed, smooth response curve and smaller fluctuation.

[0073] Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses or adaptive changes of this application following in general the principles of the application and including such steps that are readily apparent to those skilled in the art and including those not specifically shown or described herein. The specification and examples are to be regarded as exemplary and not restrictive, and the true scope and spirit of the application is indicated by the claims.

Claims

1. A sliding mode control method for online identification of rotational inertia and compensation of torque disturbance, characterized in that, include Step 1: Based on the motor speed, electromagnetic torque, and load torque of the motor drive system at a certain moment, identify the moment of inertia using the recursive least squares method; Step 2: Using the moment of inertia, observe the load torque change of the motor drive system with a disturbance observer, and estimate and compensate for the motor speed. Step 3: Based on the obtained motor moment of inertia and compensated speed, the motor speed is precisely controlled by a sliding mode speed controller so that the actual value of the motor speed is close to the given value; In step 2, the compensation speed is estimated using the following formula: ； T e T is the electromagnetic torque. L b is the load torque; m ω is the coefficient of viscous friction; r ω is the motor speed; J is the moment of inertia; c Estimate the compensated motor speed for the observer; T LC To observe the torque; Step 3 specifically includes the following steps: Step 3.1: Based on the mechanical motion equations of the surface-mounted PMSM: ； T e T is the electromagnetic torque. L b is the load torque; m ω is the coefficient of viscous friction; c The observer estimates the compensated motor speed; J is the motor's moment of inertia. Step 3.2: Define the error between the given speed and the compensated speed as x1 by using the moment of inertia and the compensated speed; ； The sliding surface is designed as follows: ； s is the sliding mode plane state vector; Step 3.3: Update the q-axis current using a sliding mode controller that utilizes the asymptotic approach rate, as shown in the following equation: ； In the formula, ε, c, k, δ, σ1, and σ2 are all parameters of the sliding mode speed controller; T L b is the load torque; m is the coefficient of viscous friction; J is the moment of inertia.

2. The sliding mode control method for online identification of moment of inertia and compensation of torque disturbance according to claim 1, characterized in that, In step 1, the least squares method with a forgetting factor is used to identify the moment of inertia, which is calculated using the following formula: ； make , , ; make , ,get: ; The identification iterative process using the recursive least squares method is as follows: ； ； Among them, T e T is the electromagnetic torque. L b is the load torque; m ω is the coefficient of viscous friction; r T is the motor speed; J is the motor moment of inertia; λ is the forgetting factor; T s Sampling time, This is the estimated value for the k-th iteration. P(K) is the correction term, and P(K) is the three-dimensional covariance matrix.

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