CN113401366B - A strong anti-disturbance composite control method to overcome the influence of periodic moving parts - Google Patents

Abstract

The invention relates to a strong anti-interference composite control method for overcoming the influence of periodic moving parts, belonging to the field of spacecraft attitude control; the method comprises the steps of estimating periodic interference by comprehensively utilizing Fast Fourier Transform (FFT) and an Extended State Observer (ESO), designing an equivalent feedforward compensation law according to the angular momentum conservation principle on the basis, adjusting a feedforward compensation moment value of interference moment by utilizing a fuzzy logic system, and dynamically adjusting the gain of a PID controller according to whether the interference moment is in a feedforward compensation period or not. Compared with the prior art, the method does not need system identification and excessive model prior knowledge, and realizes better anti-interference effect by a simple control law; the invention is used for controlling the satellite attitude with periodic interference, and can effectively improve the attitude control precision and the attitude stability of the system. The whole method has strong systematicness, clear process and easy realization.

Description

A strong anti-disturbance composite control method to overcome the influence of periodic moving parts

technical field

The invention belongs to the field of spacecraft attitude control, and relates to a strong anti-disturbance composite control method for overcoming the influence of periodic moving parts.

Background technique

Large and long-lived satellites usually carry many different types of payloads, and the satellite dynamics are complex and control requirements are high. For imaging payloads, the attitude stability of the satellite platform is an important technical indicator. Under the influence of various interference factors such as flexible vibration, liquid sloshing, and component movement, it is difficult to improve the stability of the star's attitude. Among the many interference sources on the satellite, the low-frequency motion interference of periodic moving parts is common and has a significant impact. Common periodic moving parts on the star include scanning cameras, scanning antennas, solar windsurfing drive mechanism (SADA) and so on. Especially SADA, which is an important component required by almost all 3-axis stabilized satellites. SADA is usually driven by a stepper motor, and the step disturbance torque during stepping is significant. In high-stability remote sensing satellites, subdivision driving is often used to reduce the single-step motion interference of SADA. This requires special design on the hardware, and the system cost is relatively high. Therefore, for periodic motion disturbance, it is necessary to improve the control method to improve its ability to resist motion disturbance as much as possible.

For unknown periodic interference, the existing control methods are mainly divided into three categories: 1) When the interference cannot be measured, but the period is known, the repetitive control based on the internal model principle is generally used, which is a kind of feedback control, but there are large When the dynamics are not modeled, the system stability is not easy to guarantee; 2) When the disturbance can be directly measured or known in advance (these conditions are usually difficult to meet in engineering), the control method based on feedforward is generally used, including inverse dynamics method and finite impulse response method, etc.; 3) For satellite attitude control with unknown (unknown period or unknown amplitude) deterministic interference, the existing literature mainly uses the system identification method to establish the interference model, and the uncertainty of the model parameters is passed. Improve the robustness of the feedback control law to ensure.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, a strong anti-disturbance composite control method is proposed to overcome the influence of periodic moving parts, which can be used in satellite attitude control with periodic interference and can effectively improve the attitude of the system Control accuracy and attitude stability. The whole method is systematic, the process is clear, and it is easy to implement.

The technical solution of the present invention is:

A strong anti-disturbance composite control method for overcoming the influence of periodic moving parts, comprising the following steps:

Step 1. Set the angular velocity measurement period as h, and the time series as t ₁ , t ₂ ,…,t _k ,…; the current angular velocity measurement value is ω(k);

Step 2: Take the satellite angular velocity measurement sequence ω(k-N+1), ... ω(k-1), ω(k) as the input, and use the fast Fourier transform method to output the first harmonic of the periodic motion interference frequency f _d , and calculate the motion disturbance period Δt _d ;

Step 3, calculate the estimated value z ₂ (k) of angular acceleration at the current moment; calculate the amplitude T _d (k) of the periodic disturbance torque; and obtain the maximum amplitude T _d,max of the periodic disturbance torque;

Step 4. Denote the moment when the amplitude T _d (k) of the periodic disturbance torque rises from 0 to 0.1*T _d,max as _ts , and within the same motion disturbance period Δt _d , the amplitude of the periodic disturbance torque T _d (k) The moment when T _d,max drops to 0.1*T _d,max is denoted as t _f ; calculate the feedforward compensation duration Δt _c in each dynamic disturbance period Δt _d ; calculate the number of sampling points N _d of the disturbance period and the the number of sampling points N _c in the feed compensation duration;

Step 5: Calculate the feedforward control amount _Tc according to the number of sampling points Nd in the disturbance period and the number of sampling points _Nc in the _feedforward compensation duration;

Step 6, according to the angular velocity measurement sequence ω(k-N+1), ... ω(k-1), ω(k), utilize the extreme value method to obtain the maximum amplitude ω _max of the angular velocity error;

Step 7: Calculate the time value Δt _lead of the feedforward compensation of the disturbance torque according to the maximum magnitude T _d,max of the estimated value of the disturbance torque and the maximum magnitude ω _max of the angular velocity error; and calculate the delay value relative to the start time of the current calculation cycle Δt _lag ;

Step 8. The feedforward control rate is composed of three parameters, the delay value Δt _lag relative to the start time of the current calculation cycle, the feedforward compensation duration Δt _c , and the feedforward control amount T _c , that is, the Δt _lag after the start of the current calculation cycle. During the period of ~Δt _lag +Δt _c , the feedforward control amount T _c is output, and the feedforward compensation flag S _c is set to 1; in the time outside the period of Δt _lag ~Δt _lag +Δt _c , the feedforward control amount T _c is set. Set to 0, and set the feedforward compensation flag S _c to 0;

Step 9: Adjust the feedback control law according to the value of the feedforward compensation flag S _c ;

Step 10: Add the control quantity output by the feedback control law and the control quantity output by the feedforward control rate to obtain a final composite control quantity, and use the composite control quantity to control the satellite.

In the above-mentioned strong anti-disturbance composite control method for overcoming the influence of periodic moving parts, in the second step, the fast Fourier transform method is a radix-2 type fast Fourier transform algorithm selected by time; motion disturbance The calculation method of period Δt _d is:

Δt _d =1/f _d .

In the above-mentioned strong anti-disturbance composite control method for overcoming the influence of periodic moving parts, in the step 3, the calculation method of the angular acceleration estimated value z ₂ (k) at the current moment is:

where e(*) is the observer error;

z ₁ (*) is the first-order state quantity of the observer;

h is the angular velocity measurement period;

ω(k-1) is the measured value of angular velocity;

β ₁ is the first preset gain coefficient;

u(k) is the closed-loop control quantity;

J is the uniaxial moment of inertia of the star;

β ₂ is the second preset gain coefficient;

fal(x,α,δ) is a nonlinear function;

The calculation formula of the nonlinear function fal(x,α,δ) is:

where α and δ are preset coefficients.

In the above-mentioned strong anti-disturbance composite control method for overcoming the influence of periodic moving parts, in the step 3, the calculation method of the amplitude T _d (k) of the periodic disturbance moment is:

T _d (k)=u(k)-Jz ₂ (k)

And the maximum amplitude T _d,max of the periodic disturbance torque is obtained by the extreme value judgment method.

In the above-mentioned strong anti-disturbance composite control method for overcoming the influence of periodic moving parts, in the step 4, the calculation method of the feedforward compensation duration Δt _c is:

Δt _c = _{t f} -ts .

In the above-mentioned strong anti-disturbance composite control method for overcoming the influence of periodic moving parts, in the step 4, the calculation method of the sampling point number N _d of the disturbance period is:

In the formula, Z(*) is rounded off;

The calculation method of the number of sampling points N _c in the feedforward compensation period is:

In the above-mentioned strong anti-disturbance composite control method for overcoming the influence of periodic moving parts, in the step 5, the calculation method of the feedforward control amount T _c is:

In the above-mentioned strong anti-disturbance composite control method to overcome the influence of periodic moving parts, in the seventh step, the calculation method of the time value Δt _lead of the disturbance torque feedforward compensation is: establishing a fuzzy logic system; input variables of the fuzzy logic system is the maximum amplitude T _d,max of the periodic disturbance torque and the maximum amplitude ω _max of the angular velocity error, and the output variable is the time value Δt _lead of the disturbance torque feedforward compensation; the rules of fuzzy logic are shown in Table 1:

Table 1

In the table, S means small; M means medium; B means large; S1 means small; S2 means small; B1 means large; B2 means large;

The domain of discourse of the maximum amplitude T _d,max of the periodic disturbance torque is [0, 0.15];

The domain of discourse of the maximum magnitude ω _max of the angular velocity error is [0, 0.01];

The domain of the disturbance torque feedforward compensation moment value Δt _lead is [0, 4.3].

In the above-mentioned strong anti-disturbance composite control method for overcoming the influence of periodic moving parts, in the step 7, the calculation method of the delay value Δt _lag relative to the starting moment of the current calculation cycle is:

Δt _lag =Δt _d -Δt _lead

In the formula, Δt _d is the motion disturbance period.

In the above-mentioned strong anti-disturbance composite control method for overcoming the influence of periodic moving parts, in the step 9, the feedback control law adopts the PID control rate, and the specific method for adjusting the PID control law is:

When S _c =0, that is, during the non-feedforward compensation period, the PID control law with normal gain is adopted; when S _c =1, that is, during the feedforward torque compensation, the PID control law with higher gain is adopted, that is, on the basis of the normal value Properly increase the proportional coefficient and differential coefficient of the PID control law.

The beneficial effects of the present invention compared with the prior art are:

(1) The present invention does not require system identification, and does not require too much prior knowledge of the model;

(2) The present invention realizes precise compensation and suppression of the periodic motion disturbance of the moving parts on the satellite, and has a better anti-disturbance effect.

Description of drawings

Fig. 1 is the strong anti-interference compound control flow chart of the present invention;

FIG. 2 is a schematic structural diagram of a strong disturbance immunity composite control system provided by an embodiment of the present invention.

Detailed ways

The present invention will be further elaborated below in conjunction with the examples.

Aiming at the influence of periodic moving parts on the satellite, a novel feedforward + feedback composite control method with strong anti-disturbance capability is proposed. The method comprehensively utilizes Fast Fourier Transform (FFT) and Extended State Observer (ESO) estimation Periodic disturbance. On this basis, the equivalent feedforward compensation law is designed according to the principle of angular momentum conservation, and the fuzzy logic system is used to adjust the time value of the disturbance torque feedforward compensation, and dynamically adjust the PID controller according to whether it is in the feedforward compensation period. gain. Compared with the existing method, the method does not need to perform system identification and does not need too much prior knowledge of the model, and achieves a better anti-disturbance effect with a concise control law.

The strong anti-disturbance composite control method to overcome the influence of periodic moving parts, as shown in Figure 1, specifically includes the following steps:

Step 1: Set the angular velocity measurement period as h, and the time series as t ₁ , t ₂ ,…,tk,…; the current angular velocity measurement value is ω(k).

Step 2: Take the satellite angular velocity measurement sequence ω(k-N+1), ... ω(k-1), ω(k) as the input, and use the fast Fourier transform method to output the first harmonic of the periodic motion interference frequency f _d , and calculate the motion disturbance period Δt _d ; the fast Fourier transform method is a radix-2 fast Fourier transform algorithm selected by time; the calculation method of the motion disturbance period Δt _d is:

Δt _d =1/f _d .

Step 3, calculate the estimated value z ₂ (k) of angular acceleration at the current moment; calculate the amplitude T _d (k) of the periodic disturbance torque; and obtain the maximum amplitude T _d,max of the periodic disturbance torque; estimate the angular acceleration at the current moment The value z ₂ (k) is calculated as:

where e(*) is the observer error;

z ₁ (*) is the first-order state quantity of the observer;

h is the angular velocity measurement period;

ω(k-1) is the measured value of angular velocity;

β ₁ is the first preset gain coefficient;

u(k) is the closed-loop control quantity;

J is the uniaxial moment of inertia of the star;

β ₂ is the second preset gain coefficient;

fal(x,α,δ) is a nonlinear function;

The calculation formula of the nonlinear function fal(x,α,δ) is:

where α and δ are preset coefficients.

The calculation method of the amplitude T _d (k) of the periodic disturbance moment is:

T _d (k)=u(k)-Jz ₂ (k)

And the maximum amplitude T _d,max of the periodic disturbance torque is obtained by the extreme value judgment method.

Step 4. Denote the moment when the amplitude T _d (k) of the periodic disturbance torque rises from 0 to 0.1*T _d,max as _ts , and within the same motion disturbance period Δt _d , the amplitude of the periodic disturbance torque T _d (k) The moment when T _d,max drops to 0.1*T _d,max is denoted as t _f ; calculate the feedforward compensation duration Δt _c in each dynamic disturbance period Δt _d ; calculate the number of sampling points N _d of the disturbance period and the The number of sampling points N _c in the feed-forward compensation duration; the calculation method of the feed-forward compensation duration Δt _c is:

Δt _c = _{t f} -ts .

The calculation method of the number of sampling points N _d of the interference period is:

In the formula, Z(*) is rounded off;

The calculation method of the number of sampling points N _c in the feedforward compensation period is:

Step 5: Calculate the feedforward control amount _Tc according to the number of sampling points N _d of the disturbance period and the number of sampling points N _c in the feedforward compensation duration; the calculation method of the feedforward control amount T _c is:

Step 6: According to the angular velocity measurement sequence ω(k-N+1), ... ω(k-1), ω(k), use the extreme value method to obtain the maximum magnitude ω _max of the angular velocity error.

Step 7: Calculate the time value Δt _lead of the feedforward compensation of the disturbance torque according to the maximum magnitude T _d,max of the estimated value of the disturbance torque and the maximum magnitude ω _max of the angular velocity error; and calculate the delay value relative to the start time of the current calculation cycle Δt _lag ; the calculation method of the time value Δt _lead of the disturbance torque feedforward compensation is: establish a fuzzy logic system; the input variables of the fuzzy logic system are the maximum amplitude T _d,max of the periodic disturbance torque and the maximum amplitude ω _max of the angular velocity error , the output variable is the moment value Δt _lead of the disturbance torque feedforward compensation; the rules of fuzzy logic are shown in Table 1:

Table 1

In the table, S means small; M means medium; B means large; S1 means small; S2 means small; B1 means large; B2 means large;

The domain of discourse of the maximum amplitude T _d,max of the periodic disturbance torque is [0, 0.15];

The domain of discourse of the maximum magnitude ω _max of the angular velocity error is [0, 0.01];

The domain of the disturbance torque feedforward compensation moment value Δt _lead is [0, 4.3].

The calculation method of the delay value Δt _lag relative to the start time of the current calculation cycle is:

Δt _lag =Δt _d -Δt _lead

In the formula, Δt _d is the motion disturbance period.

Step 8. The feedforward control rate is composed of three parameters, the delay value Δt _lag relative to the start time of the current calculation cycle, the feedforward compensation duration Δt _c , and the feedforward control amount T _c , that is, the Δt _lag after the start of the current calculation cycle. During the period of ~Δt _lag +Δt _c , the feedforward control amount T _c is output, and the feedforward compensation flag S _c is set to 1; in the time outside the period of Δt _lag ~Δt _lag +Δt _c , the feedforward control amount T _c is set. Set to 0, and set the feedforward compensation flag S _c to 0;

Step 9: Adjust the feedback control law according to the value of the feedforward compensation flag S _c ; the feedback control law adopts the PID control rate, and the specific method for adjusting the PID control law is:

When S _c =0, that is, during the non-feedforward compensation period, the PID control law with normal gain is adopted; when S _c =1, that is, during the feedforward torque compensation, the PID control law with higher gain is adopted, that is, on the basis of the normal value Properly increase the proportional coefficient and differential coefficient of the PID control law.

Step 10: Add the control quantity output by the feedback control law and the control quantity output by the feedforward control rate to obtain a final composite control quantity, and use the composite control quantity to control the satellite.

Example

Taking a satellite with a flywheel as an executive component as an example, the specific implementation of the present invention will be introduced. Take satellite pitch axis control as an example to illustrate. Assuming that the inertia of the satellite pitch axis is 5000kg.m2, the maximum combined moment of the flywheel group on the pitch axis is 0.2Nm. The moving part on the star is SADA, which is driven by a stepper motor through a reduction gear. Its motion period Δt _d = 4.32s, the maximum torque T _d,max acting on the star is about 0.1Nm, and the dynamic process of single-step motion is about 1s. The controller sampling period h=0.1s. The following technical points and calculation formulas are realized by the onboard software and calculated in real time. FIG. 2 is a schematic structural diagram of a strong disturbance immunity composite control system provided by an embodiment of the present invention. In this system,

(1) Using the fast Fourier transform, the periodic interference frequency is estimated from the angular velocity measurement information.

A conventional decimation by time radix-2 FFT algorithm is used. The data length (number of sequence points) N is 128. The input of the FFT algorithm module is the satellite angular velocity measurement information sequence ω(k-N+1), ...ω(k-1), ω(k), and the output is the first harmonic frequency (fundamental frequency) f of the periodic motion interference _d . After f _d is obtained by the FFT algorithm, the period value of the motion disturbance is obtained according to the following formula:

Δt _d =1/f _d

(2) Design a second-order expansion state observer, obtain the estimated value of the star acceleration from the satellite angular velocity measurement information, and further calculate the amplitude of the periodic disturbance torque.

Design a nonlinear discrete second-order extended state observer to obtain the estimated value of angular acceleration z ₂ (k) at the current moment. The formula is as follows:

where e(*) is the observer error;

z ₁ (*) is the first-order state quantity of the observer;

h is the angular velocity measurement period;

ω(k-1) is the measured value of angular velocity;

β ₁ is the first preset gain coefficient;

u(k) is the closed-loop control quantity;

J is the uniaxial moment of inertia of the star;

β ₂ is the second preset gain coefficient;

fal(x,α,δ) is a nonlinear function;

The relevant design coefficients are selected as follows: β ₁ =30, β ₂ =110.

According to the output result of the extended state observer, the amplitude T _d (k) of the periodic disturbance torque is further calculated, and the formula is as follows:

T _d (k)=Jz ₂ (k)-u(k)

According to the disturbance torque data accumulated for a period of time (in this example, it is taken as 5Δt _d ), the maximum magnitude of the periodic disturbance torque is calculated by using the conventional extreme value judgment method (in this example, the simplest sequence comparison method is used) value T _d,max .

(3) Calculate the equivalent disturbance torque feedforward compensation value in each compensation period.

3.1) The time from 0 to 0.1*T _d,max is recorded as _ts , and the time from T _d,max to 0.1*T _d,max is recorded as t _f . Let Δt _c =t _f -t _s be the feedforward compensation duration in each disturbance period Δt _d . Calculate the number of sampling points in the interference period and compensation time respectively, the formula is as follows:

In the formula, Z(*) represents the rounding operation.

3.2) Calculate the feedforward control amount, the formula is as follows:

(4) Design a two-dimensional fuzzy logic system to adjust the moment value of the disturbance torque feedforward compensation.

The design steps of fuzzy logic system are as follows:

4-1) Determine the universe of input and output variables and define the corresponding fuzzy sets

The domains of input and output variables are:

T _d,max =[0,0.15](Nm), ω _max =[0,0.01](°/s), Δt _lead =[0,4.3](s);

The fuzzy sets are:

T _d,max ={S2,S1,M,B1,B2}

ω _max ={S,M,B}

Δt _lead = {S2, S1, M, B1, B2}

4-2) Establish a fuzzy rule base

The fuzzy rule base is described in the form of fuzzy rule table, as shown in Table 1.

4-3) Determine the membership function of each variable

In the present invention, there is no special requirement for the membership function of each variable, so the same membership function is adopted. The membership function adopts a triangular membership function. Its expression is as follows:

In the formula, x _i is the input quantity, c _i is the value of the i-th average point in the universe of discourse, and b _i is an adjustable parameter.

4-4) Establish a fuzzy system using single-value fuzzer, Mamdani inference engine, and center-average defuzzifier

In the fuzzy inference engine, the inference type adopts the Mamdani fuzzy implication minimum operation method, and (and) operation adopts the intersection method (take the small method), or (also/or) operation adopts the union method (take the large method), and the synthesis uses the largest method. - Minimum method.

(5) Implement feedforward torque compensation according to the moment value of disturbance torque feedforward compensation.

The feedforward compensation time value Δt _lead given by the fuzzy logic system is converted into a delay value relative to the start time of the current calculation cycle, and the conversion formula is:

Δt _lag =Δt _d -Δt _lead

(6) Dynamically adjust the gain of the PID feedback control law according to whether it is in the feedforward compensation period.

The feedback control law adopts the most commonly used PID control law.

During non-feedforward compensation, the PID control law with normal gain is used. For this example, the normal parameters of the PID control law are as follows: K _p =30, K _i =0.3, K _d =40. During the feedforward torque compensation, a higher gain PID control law is adopted, that is, the proportional coefficient and differential coefficient of the PID control law are appropriately increased on the basis of the normal value. For this example, K _p =50, K _i =0.3, K _d =65 during feedforward torque compensation.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can use the methods and technical contents disclosed above to improve the present invention without departing from the spirit and scope of the present invention. The technical solutions are subject to possible changes and modifications. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention belong to the technical solutions of the present invention. protected range.

Claims (10)

1. a strong anti-disturbance composite control method that overcomes the influence of periodic moving parts, is characterized in that, comprises: Step 1. Set the angular velocity measurement period as h, and the time series as t ₁ , t ₂ ,…,t _k ,…; the current angular velocity measurement value is ω(k); Step 2: Take the satellite angular velocity measurement sequence ω(k-N+1), ... ω(k-1), ω(k) as the input, and use the fast Fourier transform method to output the first harmonic of the periodic motion interference frequency f _d , and calculate the motion disturbance period Δt _{d according to the f d ;} Step 3: Calculate the estimated angular acceleration value z ₂ (k) at the current moment according to the angular velocity measurement value ω(k-1); calculate the amplitude T _d (k) of the periodic disturbance moment; and obtain the maximum amplitude of the periodic disturbance moment T _d,max ; Step 4. Denote the moment when the amplitude T _d (k) of the periodic disturbance torque rises from 0 to 0.1*T _d,max as _ts , and within the same motion disturbance period Δt _d , the amplitude of the periodic disturbance torque T _d (k) The moment when T _d,max drops to 0.1*T _d,max is denoted as t _f ; calculate the feedforward compensation duration Δt _c in each dynamic disturbance period Δt _d ; calculate the number of sampling points N _d of the disturbance period and the the number of sampling points N _c in the feed compensation duration; Step 5: Calculate the feedforward control amount _Tc according to the number of sampling points Nd in the disturbance period and the number of sampling points _Nc in the _feedforward compensation duration; Step 6, according to the angular velocity measurement sequence ω(k-N+1), ... ω(k-1), ω(k), utilize the extreme value method to obtain the maximum amplitude ω _max of the angular velocity error; Step 7: Calculate the time value Δt _lead of the feedforward compensation of the disturbance torque according to the maximum magnitude T _d,max of the estimated value of the disturbance torque and the maximum magnitude ω _max of the angular velocity error; and calculate the delay value relative to the start time of the current calculation cycle Δt _lag ; Step 8. The feedforward control law is composed of three parameters, the delay value Δt _lag relative to the start time of the current calculation cycle, the feedforward compensation duration Δt _c , and the feedforward control amount T _c , that is, the Δt _lag after the start of the current calculation cycle. During the period of ~Δt _lag +Δt _c , the feedforward control amount T _c is output, and the feedforward compensation flag S _c is set to 1; in the time outside the period of Δt _lag ~Δt _lag +Δt _c , the feedforward control amount T _c is set. Set to 0, and set the feedforward compensation flag S _c to 0; Step 9: Adjust the feedback control law according to the value of the feedforward compensation flag S _c ; Step 10: Add the feedback control quantity output by the feedback control law and the feedforward control quantity to obtain a final composite control quantity, and use the composite control quantity to control the satellite. 2. method according to claim 1, is characterized in that, in described step 2, fast Fourier transform method is the radix-2 type fast Fourier transform algorithm of decimation by time; Calculate according to described f _d The motion disturbance period Δt _d includes: Δt _d =1/f _d . 3. method according to claim 1, is characterized in that, in described step 3, the calculation method of current moment angular acceleration estimated value z ₂ (k) is:

where e(*) is the observer error; z ₁ (*) is the first-order state quantity of the observer; h is the angular velocity measurement period; ω(k-1) is the measured value of angular velocity; β ₁ is the first preset gain coefficient; u(k) is the closed-loop control quantity; J is the uniaxial moment of inertia of the star; β ₂ is the second preset gain coefficient; fal(x,α,δ) is a nonlinear function; The calculation formula of the nonlinear function fal(x,α,δ) is:

where α and δ are preset coefficients. 4. method according to claim 3, is characterized in that: in described step 3, the calculation method of the amplitude T _d (k) of periodic disturbance moment is: T _d (k)=u(k)-Jz ₂ (k) And the maximum amplitude T _d,max of the periodic disturbance torque is obtained by the extreme value judgment method. 5. The method according to claim 4, characterized in that: in the step 4, the calculation method of the feedforward compensation duration Δt _c is: Δt _c = _{t f} -ts . 6. method according to claim 5, is characterized in that: in described step 4, the calculation method of sampling point number N _d of interference period is:

In the formula, Z(*) is rounded off; The calculation method of the number of sampling points N _c within the feedforward compensation period is:

7. The method according to claim 6, wherein: in the step 5, the calculation method of the feedforward control amount T _c is:

8. The method according to claim 7, wherein: in the step 7, the calculation method of the time value Δt _lead of the disturbance torque feedforward compensation is: establishing a fuzzy logic system; the input variable of the fuzzy logic system is periodic disturbance The maximum magnitude of the torque T _d,max and the maximum magnitude of the angular velocity error ω _max , the output variable is the time value Δt _lead of the disturbance torque feedforward compensation; the rules of fuzzy logic are shown in Table 1: Table 1

In the table, S means small; M means medium; B means large; S1 means small; S2 means small; B1 means large; B2 means large; The domain of discourse of the maximum amplitude T _d,max of the periodic disturbance torque is [0, 0.15]; The domain of discourse of the maximum magnitude ω _max of the angular velocity error is [0, 0.01]; The domain of the disturbance torque feedforward compensation moment value Δt _lead is [0, 4.3]. 9. The method according to claim 8, wherein: in the step 7, the calculation method of the delay value Δt _lag relative to the start time of the current calculation cycle is: Δt _lag =Δt _d -Δt _lead In the formula, Δt _d is the motion disturbance period. 10. The method according to claim 9, characterized in that: in the step 9, the feedback control law adopts a PID control rate, and the specific method for adjusting the PID control law is: When S _c =0, that is, during the non-feedforward compensation period, the PID control law with normal gain is adopted; when S _c =1, that is, during the feedforward torque compensation, the PID control law with higher gain is adopted, that is, on the basis of the normal value Properly increase the proportional coefficient and differential coefficient of the PID control law.

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