Induction motor flux estimator/controller

Claim 3

The method of control of an induction motor as claimed in claim 6, wherein: said step of computing the currents to be supplied to the stator of the induction motor to achieve the commanded speed includes calculating a quadrature axis stator current employing said measured rotor speed, the commanded rotor speed and a prior calculated direct axis stator current, calculating a direct axis stator current employing a prior calculated stator frequency, calculating a slip frequency employing said calculated quadrature axis stator current and said calculated direct axis stator current, calculating a stator frequency employing said measured rotor speed and a prior calculated slip frequency, calculating a rotor flux angle error employing said calculated rotor quadrature flux and said calculated rotor direct flux, and said step of calculating said rotor quadrature flux and said rotor direct flux in said rotating coordinate system employs said calculated stator quadrature voltage, said calculated stator direct voltage, said calculated stator quadrature axis current, said calculated stator direct axis current, said calculated slip frequency, said measured rotor speed, the prior calculated rotor quadrature flux and the prior calculated rotor direct flux, said step of calculating said estimated rotor flux angle is achieved by integration of said stator frequency, said step of calculating said corrected rotor flux angle includes subtraction of said calculated rotor flux angle error employing said uncorrected rotor flux angle, said step of calculating said currents to be supplied to the stator employs said calculated quadrature axis stator current, said calculated direct axis stator current and said corrected rotor flux angle.

Claim 4

The method of control of an induction motor as claimed in claim 2, wherein: said step of calculating said direct axis stator current employs a stored chart relating stator frequency to direct axis stator current.

Claim 5

The method of control of an induction motor as claimed in claim 2, wherein: said step of calculating said slip frequency employs the equation ##EQU10## where W sl is the slip frequency to be calculated, iqs is the prior calculated quadrature axis stator current, ids is the prior calculated direct axis stator current and Tr is the rotor time constant which is the ratio of the rotor inductance to the rotor resistance.

Claim 6

The method of control of an induction motor as claimed in claim 2, wherein: said step of calculating said stator frequency employs the sum of the measured rotor speed and the prior calculated slip frequency.

Claim 7

The method of control of an induction motor as claimed in claim 2, wherein: said step of calculating said rotor quadrature flux and said rotor direct flux employs the equation ##EQU11## where +qr(k+1) is said rotor quadrature flux to be calculated, λdr(k+1) is said rotor direct flux to be calculated, k is an index variable for counting said computing repetitions, T is the time interval between said repetitions, Tr is the is the rotor time constant which is the ratio of the rotor inductance to the rotor resistance, ω sl is said calculated slip frequency, λqr(k) is said prior calculated rotor quadrature flux, λdr(k) is said prior calculated rotor direct flux, Lm is the mutual inductance between rotor and stator, iqs(k) is said prior calculated quadrature axis stator current, ids(k) is said prior calculated direct axis stator current, Ls' is the stator transient inductance given by ##EQU12## Lr is the rotor inductance, Ls is the stator inductance, Vqs(k) is said prior calculated stator quadrature voltage, Vds(k) is said prior calculated stator direct voltage, the matrix L is given by ##EQU13## ##EQU14## ω r is the rotor frequency, λ 1 and λ 2 are eigenvalue constants selected from the range of 0.87 to 0.95, b is a constant given by -(r s +Lm/(Lr*Tr)), and ω e is the stator frequency.

Claim 8

The method of control of an induction motor as claimed in claim 2, wherein: said step of calculating said currents to be supplied to the stator employs the equations I.sub.a =iqs*cos θ.sub.rf +ids*sin θ.sub.rf I.sub.b =(=1/2iqs+0.866 ids)*cos θ.sub.rf +(0.866 iqs-1/2ids)*sin θ.sub.rf I.sub.c =-(I.sub.a +I.sub.b) where iqs is said calculated quadrature axis stator current, ids is said calculated direct axis stator current, and θ rf is said calculated rotor position.

Claim 11

The method of control of an induction motor to a commanded rotor speed as claimed in claim 8, wherein: said step of computing the currents to be supplied to the stator of the induction motor are repetitively performed via a digital processor.