CN101078910A - AC position servo system interference observation and compensation method - Google Patents

Abstract

The invention discloses an observing and compensating method of disturbance in three-phase asynchronous motor complexor controlling slave system, which is characterized by the following: combining disturbance observer (DOB) and PID controlling method; inhibiting disturbance in the system; adopting di-closed-loop structure of position loop and electric current loop for slave system; designing disturbance observer (DOB) in the position loop faced to electric current loop; adopting PI to control for the electric current loop; adopting PD to control for the position loop. This invention possesses simple realization, simple method and easy control, which disturbance observer (DOB) possesses the advantages of quick response and separate adjustment.

Description

Observation of disturbing in a kind of AC position servo system and compensation method

Technical field

The present invention relates to the threephase asynchronous machine servo-drive system, particularly observation and the compensation method of disturbing in the vector control AC servo-drive system.

Background technology

In AC position servo system, interference is the principal element that causes system's servo performance to descend, and must be suppressed.In positional servosystem, disturb to mainly contain following source: the structural uncertain factor that the nominal model that (1) identification obtains and the error between actual controlled device, electromechanical servo system modeling process are ignored; (2) system in operational process, be subjected to such as external disturbance such as load changing, working environment variations; (3) loading moment interference that causes by static friction and static friction (non-linear friction) etc.

In traditional control system, adopt the PID control method that above-mentioned interference is suppressed usually, but that this method exists is poor to the adaptive faculty of load variations, a little less than the antijamming capability and be subject to weakness such as system parameter variations influence.Because the existence of integral element, PID and PI are bad to the inhibition effect that alternation disturbs, and limit cycle and low speed jerking motion etc. can occur again to static friction.If adopt simple PD control, step is disturbed can have static difference again, can't realize accurate position control.

Summary of the invention

The technical problem to be solved in the present invention is, above-mentioned defective at prior art, the method of disturbance-observer and compensation in a kind of AC position servo system is provided, to suppressing such as interference such as load changing, model uncertainty and non-linear frictions in the system, improve the antijamming capability and the robustness of system.

The technical solution adopted for the present invention to solve the technical problems is: comprise and adopt interference observer (DOB) in conjunction with the PID control method interference that exists in the system to be suppressed, servo-drive system adopts the double circle structure of position ring and electric current loop, in position ring, design interference observer (DOB) towards electric current loop, current loop controller adopts PI control, and position ring adopts PD control.

The invention has the beneficial effects as follows, the present invention has adopted interference observer (DOB) can the interference in the AC position servo system to be suppressed in conjunction with PID, interference observer (DOB) has the advantages that response is fast and can independently adjust, can effectively suppress to disturb, and system parameter variations is had stronger robustness, need not extra power or torque sensor, when design, can select parameters such as order, relative order and low-pass filter bandwidth, realize that simply method is flexible, be easy to control.

Description of drawings

Below in conjunction with the drawings and specific embodiments the present invention is described in further detail.

Fig. 1 is the basic structure block diagram of interference observer.

Fig. 2 is the equivalent construction block diagram of interference observer.

Fig. 3 is two closed loop positional servosystem structured flowcharts of vector controlled.

Fig. 4 is the current closed-loop theory diagram after simplifying.

Fig. 5 is the position closed loop theory diagram after simplifying.

Fig. 6 is for adopting the two closed loop positional servosystem structured flowcharts towards electric current loop DOB.

Embodiment

As shown in Figure 1, P (s) represents real system, P _n(s) represent nominal model, u is the outside input of system, and d is a distracter,

Be the estimated value of d, ξ is for measuring noise, and Q (s) is a low-pass filter, and its relative order is more than or equal to P _n(s) relative order.DOB is applied to nominal model to the interference of the difference of real system output and the output of nominal model as an equivalence.It estimates the interference of equivalence, and with its by way of compensation signal feedback to input end.

In order to understand principle based on the total system of interference observer, at first can make Q (s)=1, obtain $\widehat{\mathrm{\δ}}=\hat{d}=(1-\frac{P_n\left(s\right)}{P\left(s\right)})u+\frac{1}{P\left(s\right)}\mathrm{\ξ}+d.$ Under the ideal conditions, P _nEquate with P (s) that (s) then output can be expressed as $y=P\left(s\right)(u-\hat{d}+d)=P_n\left(s\right)u-\mathrm{\ξ}.$ As can be seen from Figure 2, y=G _Uy(s) u+G _Dy(s) d+G _Xy(s) ξ, wherein $G_{\mathrm{uy}}=\frac{P\left(s\right)P_n\left(s\right)}{P_n\left(s\right)+(P\left(s\right)-P_n\left(s\right))Q},$ $G_{\mathrm{dy}}=\frac{P\left(s\right)P_n\left(s\right)(1-Q\left(s\right))}{P_n\left(s\right)+(P\left(s\right)-P_n\left(s\right))Q},$ $G_{\mathrm{xy}}=\frac{P\left(s\right)Q\left(s\right)}{P_n\left(s\right)+(P\left(s\right)-P_n\left(s\right))Q\left(s\right)}.$

From above-mentioned equation, we as can be seen the design of interference observer mainly rely on Q (s), it is the important parameter of decision systems robustness and antijamming capability.

If Q (s) ≈ 1 can obtain G _Uy≈ P _n, G _Dy≈ 0, G _Xy≈-1 shows that interference observer makes real system similar to nominal model, has strengthened the robustness of control system simultaneously.If Q (s) ≈ 0 can obtain G _Uy≈ P G _Dy≈ P G _Xy≈ 0, shows that this moment, system approached open loop, do not have feedback element, also the existence of just not measuring noise.

In sum, the principle of design of wave filter Q (s) is: (1) can carry out real-Time Compensation to interference for making system, and the low frequency dynamic perfromance of Q (s) should approach 1, make after the dynamic process of DOB finishes, $\widehat{\mathrm{\δ}}\≈\hat{d}\≈d;$ (2) measure noise for suppressing, should make the High Frequency Dynamic of Q (s) approach zero, make system show the feature of open cycle system at high band.Therefore Q (s) is a low-pass filter.

In order to make contrary Q (s) P that is combined into of low-pass filter Q (s) and nominal model _n ^-1(s), physically can realize,, Fig. 1 equivalence can be deformed into form shown in Figure 2 simultaneously in order to suppress the measurement noise of high frequency.

As shown in Figure 3, the inventive method has designed two closed loop positional servosystems of being made up of position ring and electric current loop, adopts principle of vector control that threephase asynchronous machine is carried out position control.Can be seen that by Fig. 3 electric current loop is divided into torque current ring and exciting current ring, these two rings are identical on control mode.

(1) design of electric current loop

Fig. 4 is the current closed-loop theory diagram after simplifying.Electric current loop adopts PI control, and its controller is expressed as with transport function $G_i\left(s\right)=K_{p\_\mathrm{crt}}+\frac{K_{i\_\mathrm{crt}}}{s},$ Among the figure $a_{\_\mathrm{crt}}=\frac{1}{T_{\mathrm{el}}},b_{\_\mathrm{crt}}=\frac{1}{T_{\mathrm{el}}\·R_s},$ T _ElBe the electrical time constant of motor, R _sStator resistance for motor.Can know that thus the transport function of current closed-loop promptly can be expressed as $G_{\_\mathrm{crt}}\left(s\right)=\frac{K_{p\_\mathrm{crt}}{b}_{\_\mathrm{crt}}s+K_{i\_\mathrm{crt}}{b}_{\_\mathrm{crt}}}{s^2+(a_{\_\mathrm{crt}}+K_{p\_\mathrm{crt}}{b}_{\_\mathrm{crt}})s+K_{i\_\mathrm{crt}}{b}_{\_\mathrm{crt}}},$ If make ω _{_ crt}The electric current loop free-running frequency of expression expectation, ξ _{_ crt}The electric current loop damping ratio of expression expectation is by the characteristic ω of second-order system _{_ crt} ²=K _{I_crt}b _{_ crt}With 2 ω _{_ crt}ξ _{_ crt}=a _{_ crt}+ K _{P_crt}b _{_ crt}, select suitable free-running frequency and damping ratio, can obtain two parameters of current loop controller $K_{i\_\mathrm{crt}}=\frac{{{\mathrm{\ω}}_{\_\mathrm{crt}}}^2}{b_{\_\mathrm{crt}}}$ With $K_{p\_\mathrm{crt}}=\frac{2{\mathrm{\ω}}_{\_\mathrm{crt}}{\mathrm{\ξ}}_{\_\mathrm{crt}}-a_{\_\mathrm{crt}}}{b_{\_\mathrm{crt}}}.$

(2) design of position ring

When design, guarantee that the bandwidth of electric current loop is far longer than the bandwidth of position ring, the response time of whole electric current loop will be far smaller than the response time of outer shroud at this moment, actual torque current can be equal to reference current when analyzing, i.e. i _q=i _{Q_ref}

The equation of motion of asynchronous machine is $J\frac{\mathrm{d\ω}}{\mathrm{dt}}++\frac{B}{n_p}\mathrm{\ω}=T_e-T_L={\mathrm{Ki}}_q-T_L,$ Wherein J is the moment of inertia and the load rotating inertia sum of converting on the motor shaft of motor shaft; B is the viscous damping coefficient and the load viscous damping coefficient sum of converting on the motor shaft of motor shaft; n _pNumber of pole-pairs for motor; T _eBe electromagnetic torque; K is the moment constant; T _LBe loading moment, can be considered as a unknown disturbances of system.So in the asynchronous motor speed-regulating system, be first order inertial loop from the net torque to the rotating speed, can be expressed as with transport function $G_{\_\mathrm{crt}}\left(s\right)=\frac{\mathrm{\Ω}\left(s\right)}{I_{q\_\mathrm{ref}}}=\frac{K}{\mathrm{Js}+B}.$ In order to express conveniently, write as $G_{\_\mathrm{crt}}\left(s\right)=\frac{b_{\_\mathrm{spd}}}{s+a_{\_\mathrm{spd}}},$ A wherein _{_ spd}=B/J=0, b _{_ spd}=K/J.

With speed closed loop $G_{\_\mathrm{crt}}\left(s\right)=\frac{b_{\_\mathrm{spd}}}{s+a_{\_\mathrm{spd}}}$ As controlled device, the rate signal that records is carried out integration, feed back to the given side, position then, promptly constituted position closed loop, the output of positioner at this moment is the input of speed control.Fig. 5 adopts PD control for the position closed loop theory diagram after simplifying, position ring, and its controller is expressed as G with transport function _θ(s)=K _{P_pos}+ K _{D_pos}S, the transport function of then whole pair of closed loop positional servosystem is $G_{\_\mathrm{pos}}\left(s\right)=\frac{K_{d\_\mathrm{pos}}{b}_{\_\mathrm{spd}}s+K_{p\_\mathrm{pos}}{b}_{\_\mathrm{spd}}}{s^2+(a_{\_\mathrm{spd}}+b_{\_\mathrm{spd}}{K}_{d\_\mathrm{pos}})s+K_{p\_\mathrm{pos}}{b}_{\_\mathrm{spd}}}.$ Same, make ω _{_ pos}The free-running frequency of the double loop system of expression expectation, ξ _{_ pos}The damping ratio of the double loop system of expression expectation is according to the characteristic ω of second-order system _{_ pos} ²=K _{P_pos}b _{_ spd}With 2 ω _{_ pos}ξ _{_ pos}=a _{_ spd}+ K _{D_pos}b _{_ spd}, select suitable free-running frequency and damping ratio, can obtain two parameters of positioner $K_{p\_\mathrm{pos}}=\frac{{{\mathrm{\ω}}_{\_\mathrm{pos}}}^2}{b_{\_\mathrm{spd}}}$ With $K_{d\_\mathrm{pos}}=\frac{2{\mathrm{\ω}}_{\_\mathrm{pos}}{\mathrm{\ξ}}_{\_\mathrm{pos}}-a_{\_\mathrm{spd}}}{b_{\_\mathrm{spd}}}.$

(3) design of interference observer

Towards current closed-loop design interference observer, its schematic diagram as shown in Figure 6 in position ring.Controlled device is a current closed-loop shown in Figure 4, with P (s) expression, corresponding nominal model P _n(s) represent; Q (s) represents low-pass filter; θ _{_ ref}, θ, ω, d represent position set-point, physical location output, motor speed and distracter respectively.External disturbance such as the uncertainty of parameter and non-linear friction and load variations when distracter comprises modeling.

In the positional servosystem of two closed loops, during design DOB, electric current loop is considered as controlled device, it can be reduced to first order inertial loop, and this moment, the transport function of nominal model can be written as $P_n\left(s\right)=\frac{b_{\_\mathrm{spd}}}{s+a_{\_\mathrm{spd}}}.$ According to the principle of design of wave filter Q (s), Q (s) should select lower-order time as far as possible, and in order to guarantee that Q (s) physics can realize that its relative order must be taken all factors into consideration more than or equal to the relative order of controlled system again, selects low-pass first order filter among the design $Q\left(s\right)=\frac{1}{\mathrm{\τs}+1},$ Wherein, τ is a filter time constant, and size is 10 times of position ring sampling time.

Claims (5)

1, observation and the compensation method of disturbing in a kind of AC position servo system, comprise and adopt interference observer (DOB) interference that exists in the system to be suppressed in conjunction with the PID control method, it is characterized in that: servo-drive system adopts the double circle structure of position ring and electric current loop, in position ring, design interference observer (DOB) towards electric current loop, current loop controller adopts PI control, and position ring adopts PD control.

2, observation and the compensation method of disturbing in a kind of AC position servo system according to claim 1, it is characterized in that: the bandwidth of described electric current loop is much larger than the bandwidth of position ring, and the response time of whole electric current loop is much smaller than the response time of position ring.

3, observation and the compensation method of disturbing in a kind of AC position servo system according to claim 2, it is characterized in that: electric current loop is divided into torque current ring and exciting current ring, and these two rings all adopt the PI control mode.

4, observation and the compensation method of disturbing in a kind of AC position servo system according to claim 1, it is characterized in that: described interference observer comprises nominal model P _n(s) part insert real system P (s) partly, low-pass filter Q (s) end connects input end, the other end connects nominal model P _n(s) part, the relative order of low-pass filter Q (s) is more than or equal to nominal model P _n(s) relative order is with real system P (s) output and nominal model P _n(s) Shu Chu difference is applied to nominal model P as the interference of an equivalence _n(s), can estimate the interference of equivalence, and with its by way of compensation signal feedback to input end.

5, observation and the compensation method of disturbing in a kind of AC position servo system according to claim 4 is characterized in that: the low frequency dynamic perfromance of low-pass filter Q (s) is designed to approach 1, can makes servo-drive system that real-Time Compensation is carried out in interference; The High Frequency Dynamic of low-pass filter Q (s) is designed to approach zero, makes servo-drive system show the feature of open cycle system, suppress the measurement noise of system at high band.

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