Washing machine

A torque current component and an exciting current component of primary AC currents which are supplied to a stator of a three-phase induction motor are commanded independently of each other in accordance with a command rotational angular velocity and a rotational angular velocity of the three-phase induction motor rotating an agitator, and the rotational angular velocity of the three-phase induction motor is controlled by changing the magnitude and frequency of each of the primary AC currents. Furthermore, a test operation is carried out by giving the command angular velocity so as to make constant the angular velocity of the motor, and the laundry amount is estimated corresponding to an output torque of the motor in the test operation.

BACKGROUND OF THE INVENTION 
The present invention relates to a washing machine using a three-phase 
induction motor, or more in particular to a washing machine estimating the 
amount of laundry and detecting an unbalanced amount caused by uneven 
distribution of laundry in a rotatable drum. 
The motor for driving the agitator of the conventional washing machine is a 
single-phase induction motor in most cases. The single-phase induction 
motor drives the agitator by rotating at a constant rotational angular 
velocity determined by the power frequency and the reduction ratio of the 
reduction gear such as gears and belt. The single-phase induction motor 
has so small a torque in the range of low speeds that the amount of 
laundry that can be washed at a time and the washing system are limited. 
As a means for solving this problem, JP-A-7-255988 proposes a method for 
varying the rotational speed of the agitator using a DC brushless motor 
and an invertor circuit. 
On the other hand, JP-A-6-351292 proposes a method for varying the 
rotational speed of a three-phase induction motor by V/f control using an 
invertor circuit. 
A conventional washing machine estimating the amount of laundry in the 
rotatable drum is disclosed, for example, in JP-A-61-8094. In this prior 
art, the motor for driving the rotatable drum stops being driven at the 
time point when the rotational speed of the motor reaches a predetermined 
level wherein the amount of laundry is estimated based on the time from 
deenergization to of the motor to subsequent stop of the motor under 
rotation with inertia. On the other hand, JP-A-6-71085 proposes a method 
in which the voltage applied to the motor is maintained constant and the 
amount of laundry is estimated from the change in angular velocity 
information detected by an angular velocity sensor mounted on the motor. 
Further, JP-A-5-3990 discloses a method of estimating the amount of 
laundry from the current supplied to the motor. 
In a conventional washing machine disclosed in JP-A-3-70596 which detects 
an unbalanced amount due to the uneven distribution of laundry in the 
rotatable drum, a sensor for detecting the vibrations is mounted in the 
rotatable drum to detect an unbalance. Also, JP-A-5-103895 discloses a 
method for detecting an unbalanced state from the angular velocity 
information detected by an angular velocity sensor mounted on the motor. 
Further, JP-A-9-290089 discloses a method using a position sensor for 
detecting an unbalanced state of the rotatable drum and measuring the 
position of unevenly distributed laundry in the rotatable drum from the 
variations in the current flowing in the motor. 
The conventional method using a DC brushless motor has encountered a 
problem of high cost of the DC brushless motor in comparison with an 
induction motor. 
In the conventional method of controlling the angular velocity of a 
three-phase induction motor by invertor, a constant ratio V/f between the 
applied voltage and frequency of the motor must be maintained. However, 
the controllability of the three-phase induction motor is inferior to that 
of the DC motor. Especially, it is not easy to produce a large torque in 
low-speed ranges. Therefore the problem is that a large amount of laundry 
cannot be easily washed at a time. 
The method of estimating the amount of laundry such as the weight from the 
time during which the drive motor rotates under inertia has a low 
accuracy. Also, the method of estimating the amount of laundry based on 
the rotational angular velocity of the motor requires mounting of an 
angular velocity sensor on the motor. 
The above-mentioned methods of estimating the amount such as the weight of 
laundry in the rotatable drum has the problem of a low estimation 
accuracy, regardless of whether the amount of laundry is estimated from 
the change in the rotational angular velocity of the motor under a 
predetermined voltage applied thereto, or from the current supplied to the 
motor. 
The method for detecting the unbalanced amount in the rotatable drum, 
requires mounting of a sensor for detecting vibrations. On the other hand, 
detection of an unbalanced amount accurately from the change in rotational 
angular velocity requires a highly accurate angular velocity sensor, and 
therefore is expensive. Further, the method of detecting an unbalanced 
amount from the variations in the current supplied to an induction motor, 
poses the problem of a low detection accuracy. 
BRIEF SUMMARY OF THE INVENTION 
An object of the present invention is to provide a washing machine capable 
of washing a large amount of laundry at low cost, using a three-phase 
induction motor driven by invertor to attain a performance equivalent to a 
DC brushless motor. 
Another object of the invention is to provide a washing machine capable of 
estimating the amount of laundry accurately without using any velocity 
sensor. 
Still another object of the invention is to provide a washing machine, or 
especially a washing machine of drum type, which is capable of estimating 
the amount of laundry in the rotatable drum accurately and detecting an 
unbalanced amount due to an uneven distribution of laundry in the 
rotatable drum accurately. 
According to an aspect of the invention, there is provided a washing 
machine comprising a rotatable drum for washing and dewatering the 
laundry, a three-phase induction motor for rotating an agitator mounted in 
the rotatable drum, and an angular velocity estimator for estimating the 
rotational angular velocity from the value of at least one of the primary 
AC current and the primary AC voltage which are supplied to the stator of 
the three-phase induction motor, and from constants unique to the 
three-phase induction motor. In accordance with the command rotational 
angular velocity of the three-phase induction motor and the output value 
of the angular velocity estimator, the torque current component and the 
exciting current component of the primary AC current of each phase 
supplied to the stator of the three-phase induction motor are commanded 
independently of each other. Consequently, the magnitude and frequency of 
the primary AC current of each phase is changed to control the rotational 
angular velocity of the three-phase induction motor. 
According to another aspect of the invention, there is provided a washing 
machine further comprising a test operation means for determining, as the 
above-mentioned torque current component, the product of the difference 
between the command rotational angular velocity of the three-phase 
induction motor and the output value of the angular velocity estimator by 
a predetermined test operation constant. A test operation is conducted by 
supplying the same product as a command value to the three-phase induction 
motor. A laundry amount estimation means is included for estimating the 
amount of laundry in accordance with the output of the angular velocity 
estimator during the test operation. 
According to still another aspect of the invention, there is provided a 
washing machine comprising a motor for driving a rotatable drum, and a 
controller for controlling the rotational angular velocity of the motor. 
It further comprises a test operation controller for conducting a test 
operation of the motor by applying such a command angular velocity as to 
maintain a constant rotational angular velocity of the motor, and a 
laundry amount estimator for estimating the amount of laundry based on the 
output torque of the motor during the test operation. 
In the case where the motor is driven in response to such a command angular 
velocity as to maintain a constant rotational angular velocity, the output 
torque of the motor changes in accordance with the load. Under a heavy 
load, for example, the output torque increases. It is therefore possible 
to estimate the amount of laundry in the rotatable drum on the basis of 
the output torque. 
According to still another aspect of the invention, there is provided a 
washing machine comprising a motor for driving a rotatable drum, a 
controller for controlling the rotational angular velocity of the motor, a 
test operation controller for conducting a test operation by rotating the 
motor at a predetermined constant rotational angular velocity. It further 
comprises an unbalanced amount estimator for estimating the unbalanced 
amount in the rotatable drum due to an uneven distribution of laundry 
attached to the inner wall of the rotatable drum based on the output 
torque of the motor during the test operation. 
The motor is rotated at a predetermined rotational angular velocity and 
thus rotating the rotatable drum at a predetermined constant rotational 
angular velocity while the laundry is unevenly distributed in the 
rotatable drum. Consequently, the output torque of the motor undergoes 
variations in synchronism with the rotation. By determining the amount of 
variations of the output torque, therefore, the unbalanced amount of the 
rotatable drum can be estimated. 
According to still another aspect of the invention, there is provided a 
washing machine comprising an angular velocity estimator for estimating 
the rotational angular velocity of a three-phase induction motor for 
driving a rotatable drum or an agitator mounted in the rotatable drum 
based on at least one of the primary AC current value and the primary AC 
voltage value supplied to the stator of the three-phase induction motor, 
and based on constants unique to the three-phase induction motor. The 
angular velocity is estimated in accordance with the command rotational 
angular velocity of the three-phase induction motor and the output value 
of the angular velocity estimator. Based on the estimated angular velocity 
value, the torque current component and the exciting current component of 
the primary AC currents supplied to the stator of the three-phase 
induction motor are commanded independently of each other. Consequently, 
the rotational angular velocity of the three-phase induction motor is 
controlled by changing the magnitude and frequency of each of the primary 
AC currents, thereby realizing an inexpensive, high-performance washing 
machine. 
According to still another aspect of the invention, there is provided a 
washing machine further comprising a test operation controller for 
conducting a test operation of the three-phase induction motor in response 
to a command representing the above-mentioned torque current component 
given as the product of the difference between the command rotational 
angular velocity of the three-phase induction motor and the output of the 
angular velocity estimator by a predetermined test operation constant. It 
further comprises a laundry amount estimator, and the amount of laundry is 
estimated in accordance with the output of the angular velocity estimator 
during the test operation, thereby making it possible to realize a washing 
machine capable of estimating the laundry amount accurately. 
According to still another aspect of the invention, there is provided a 
washing machine comprising a motor for driving a rotatable drum, a 
controller for controlling the rotational angular velocity of the motor, a 
test operation controller for conducting a test operation of the motor in 
response to a command angular velocity associated with a constant angular 
acceleration of the motor. A laundry amount estimator is included for 
estimating the amount of laundry in accordance with the output torque of 
the motor during the test operation, thereby realizing a washing machine 
capable of estimating the laundry amount easily and accurately. 
According to still another aspect of the invention, there is provided a 
washing machine comprising a motor for driving a rotatable drum, a 
controller for controlling the rotational angular velocity of the motor, a 
test operation controller for conducting a test operation so as to attain 
a predetermined constant rotational angular velocity of the motor. An 
unbalanced amount estimator is included for estimating the unbalanced 
amount due to an uneven distribution of laundry closely attached to the 
rotatable drum in accordance with the output torque of the motor in the 
test operation, thereby realizing a washing machine capable of estimating 
the unbalanced amount of the rotatable drum accurately.

DETAILED DESCRIPTION OF THE INVENTION 
Preferred embodiments of the invention will be explained below with 
reference to FIG. 1 to FIG. 21. Hereinafter, the mark * on the right 
shoulder of each symbol indicating the current shows that the symbol 
involved is a command. A symbol of a physical amount lacking the mark *, 
on the other hand, indicates an actual value. A physical amount with a 
suffix "e" indicates an estimated value. 
First Embodiment 
FIG. 1 is a block diagram showing a configuration of a washing machine 
according to a first embodiment of the invention. 
In FIG. 1, the rotary shaft 110A of a three-phase induction motor 100 is 
coupled to the rotary shaft 102A of agitator 102 arranged in a rotatable 
drum 104 for washing and dewatering the laundry through a transmission 
mechanism 106. The output terminal of an angular velocity controller 110 
supplied with a command rotational angular velocity .omega..sub.m * for 
indicating the rotational angular velocity of the three-phase induction 
motor is connected to the respective input terminals of a slip frequency 
calculator 112 and a rotary/static coordinate converter 118. The other 
input terminals of the slip frequency calculator 112 and the rotary/static 
coordinate converter 118 are supplied with a command exciting current 
U.sub.1d *. The two output terminals of the rotary/static coordinate 
converter 118 are connected to the two input terminals of a 
two-/three-phase converter 120, respectively. The three output terminals 
of the two-/three-phase converter 120 are connected to the three input 
terminals, respectively, of a current controller 122. 
The three output terminals of the current controller 122 are connected to 
the three input terminals of a PWM invertor 124, respectively, and the 
three output terminals of the PWM invertor 124 are connected to the 
three-phase induction motor 100. The two input terminals of the PWM 
invertor 124 are connected through a converter 130 to a single-phase 100-V 
AC power supply. The three connection lines between the PWM invertor 124 
and the three-phase induction motor 100 are provided with current 
detectors 126a, 126b and 126c, respectively. The output terminals of the 
current detectors 126a, 126b, 126c are connected to the three control 
input terminals of the current controller 122, respectively. 
The three-phase induction motor 100 includes an angular velocity detector 
128 for detecting the rotational angular velocity. The output terminal of 
the angular velocity detector 128 is connected to the control input 
terminal of the angular velocity controller 110 and the input terminal of 
an amplifier 115. The output terminal of the amplifier 115 is connected to 
the input terminal of an adder 114. The other input terminal of the adder 
114 is connected to the output terminal of a slip frequency calculator 
112. The output terminal of the adder 114 is connected to the input 
terminal of an integrator 116. The output terminal of the integrator 116 
is connected to the other input terminal of the rotary/static coordinate 
converter 118. 
The operation of the washing machine configured as described above will be 
explained below with reference to FIG. 1. 
The laundry is washed by rotating the agitator 102 mounted in the rotatable 
drum 104 by the three-phase motor 100 through the transmission mechanism 
106. 
Generally, a three-phase induction motor can be considered as a two-phase 
model constituting a two-phase induction motor after three-/two-phase 
conversion. The fundamental equation for the two-phase induction motor is 
expressed in the following equation (1): 
##EQU1## 
where i.sub.1d, i.sub.1q are a d-axis current flowing in the stator 
constituting on the primary side and a q-axis current having a phase 
difference of 90 degree with the d-axis, respectively, and v.sub.1d, 
v.sub.1q a d-axis voltage and a q-axis voltage having a phase difference 
of 90 degree with the d-axis, respectively. .psi..sub.2d, .psi..sub.2q are 
secondary magnetic fluxes for the d-axis and the q-axis of the rotor on 
the secondary side, respectively. Also, R.sub.j, L.sub.j (j: 1 or 2) is a 
resistance and an inductance, respectively, on the j-order side. Again, M 
is a mutual inductance, .omega..sub.m a rotational angular velocity of the 
motor, and p is the number of pole pairs providing the number of pairs of 
N and S poles of the motor. 
As in the angular velocity control of the DC motor, the angular velocity 
controller 110 determines a command torque current I.sub.1q * specifying 
the torque current for generating a torque in accordance with equation (2) 
below, for example, from the command rotational angular velocity 
.omega..sub.m * and the value .omega..sub.m of the rotational angular 
velocity detected by the angular velocity detector 128. 
##EQU2## 
where K.sub.ps, K.sub.is are angular velocity control gains providing 
constants set in such a manner as to attain the desired response 
characteristic. 
The induction motor lacks a permanent magnet. In order to produce a 
magnetic field corresponding to the magnetic field created by a permanent 
magnet, therefore, a predetermined exciting current is supplied based on 
the command exciting current I.sub.1d *. Further, the slip frequency 
calculator 112 calculates the slip angular velocity .omega..sub.s using 
the command exciting current I.sub.1d * and the command torque current 
I.sub.1q * according to equation (3). 
##EQU3## 
The product of the rotational angular velocity .omega..sub.m and the number 
p of pole pairs of the three-phase induction motor is determined by the 
amplifier 115, and this product is added to the slip angular velocity 
.omega..sub.s at the adder 114. The result of addition is integrated by 
the integrator 116 thereby to determine the electrical phase angle 
.theta..sub.o shown in equation (4). 
##EQU4## 
Further, the rotary/static coordinate converter 118 makes calculations as 
shown in equation (5) using the command exciting current I.sub.1d *, the 
command torque current I.sub.1q * and the electrical phase angle 
.theta..sub.o in the same manner as if a permanent magnet is involved. 
##EQU5## 
As a result, the command exciting current I.sub.1d * and the command torque 
current I.sub.1q * are converted into command primary AC currents i.sub.1d 
*, i.sub.2q * indicating two-phase currents having a phase difference of 
90 degree. Then, the command primary AC currents i.sub.1d *, i.sub.1q * 
are converted by the two-/three-phase converter 120 into command primary 
AC currents i.sub.1a *, i.sub.1b *, i.sub.1c * indicating three-phase 
currents in accordance with equation (6). 
##EQU6## 
Once currents conforming with these command currents can be supplied, a 
three-phase induction motor having a performance equivalent to that of a 
DC motor is realized. 
Now, the operation of the current controller 122 will be explained. The 
actual primary AC currents i.sub.1a, i.sub.1b, i.sub.1c are controlled by 
feedback in such a manner as to follow the command primary AC currents 
i.sub.1a *, i.sub.1b *, i.sub.1c *, respectively. In the process, the 
actual primary AC currents are detected by the current detectors 126a, 
126b, 126c, and after making the calculations shown in equation (7), the 
command voltage v.sub.1z (z: a, b or c) is output. 
##EQU7## 
where K.sub.pc, K.sub.ic are current control gains which are constants set 
to follow a command value. In accordance with a signal having a pulse 
width corresponding to the command voltage V.sub.1z providing a control 
signal from the current controller 122, the PWM invertor 124 controls the 
DC voltage produced from a commercial power supply by the converter 130 by 
turning on or off internal transistors. As a result, the desired voltage 
is applied and the current is supplied to the three-phase induction motor 
100. 
Here, the sum of the primary AC currents i.sub.1a, i.sub.1b, i.sub.1c of 
the three phases supplied to the three-phase induction motor 100 is zero, 
as shown in equation (8). 
EQU i.sub.1a +i.sub.1b +i.sub.1c =0 (8) 
For detecting the primary AC current, the currents of two out of the three 
phases are detected, and the current of the remaining phase can be 
calculated from the two-phase current values detected. The above-mentioned 
operation can control the primary AC current supplied to the three-phase 
induction motor to the desired command value, so that the rotational 
angular velocity of the three-phase induction motor can be controlled to 
the desired angular velocity. 
The above-mentioned control system improves the controllability including 
the torque characteristic of a three-phase induction motor at the time of 
starting thereof, and a superior controllability like that of the DC motor 
can be obtained. Thus, a washing machine is easily realized in which a 
large amount of laundry can be washed at a time at the desired rotational 
angular velocity. 
According to the first embodiment, an example was explained in which the 
current is detected for current control. As an alternative, the voltage 
can be controlled by estimating the current from the constants unique to 
the three-phase induction motor and the fundamental equation (1). 
Also, although an example of a washing machine is shown for washing the 
laundry by rotating the agitator using a three-phase induction motor, the 
first embodiment is applicable to a washing machine of drum type with 
equal effect, for example, in which the agitator are not used and the 
rotatable drum is rotated directly. 
According to the first embodiment, an angular velocity detector such as an 
encoder is required for detecting the rotational angular velocity of a 
three-phase induction motor. A second embodiment of the invention will be 
explained with reference to a washing machine using a controller of a 
three-phase induction motor with a good controllability equivalent to the 
DC motor even without any angular velocity detector. 
Second Embodiment 
A washing machine according to a second embodiment of the invention will be 
explained below with reference to FIG. 2. 
FIG. 2 is a block diagram showing a configuration of a washing machine 
according to the second embodiment of the invention. 
In FIG. 2, the rotational shaft 100A of the three-phase induction motor 100 
is coupled to the transmission mechanism 106 for driving the rotational 
shaft 102A of the agitator 102 arranged in the rotatable drum 104. The 
output terminal of the angular velocity controller 110 supplied with the 
command rotational angular velocity .omega..sub.m * is connected to the 
respective input terminals of the slip frequency calculator 112 and the 
rotary/static coordinate converter 118. The other input terminal of the 
slip frequency calculator 112 and the rotary/static coordinate converter 
118 is supplied with the command exciting current I.sub.1d *. 
The two output terminals of the rotary/static coordinate converter 118 are 
connected to the input terminal of the two-/three-phase converter 120, and 
the three output terminals of the two-/three-phase converter 120 are 
connected to the three input terminals of the current controller 122, 
respectively. The three output terminals of the current controller 122 are 
connected to the three input terminals of the PWM invertor 124, 
respectively. The three output terminals of the PWM invertor 124 are 
connected to the three-phase induction motor 100. The two input terminals 
of the PWM invertor 124 are connected to an AC power supply of 100 V, 
single phase, through the converter 130. 
The three connection lines between the PWM invertor 124 and the three-phase 
induction motor 100 are provided with current detectors 126a, 126b, 126c, 
respectively. The output terminals of the current detectors 126a, 126b, 
126c are connected to the three control input terminals of the current 
controller 122. The output terminals of the current detectors 126a, 126b, 
126c are connected also to the three input terminals of the 
three-/two-phase converter 220, respectively. The two output terminals of 
the three-/two-phase converter 220 are connected to the two input 
terminals of a secondary magnetic flux estimator 224. Further, one of the 
two output terminals of the three-/two-phase converter 220 is connected to 
the input terminal of a first angular velocity estimator 226, and the 
other output terminal is connected to the input terminal of the second 
angular velocity estimator 228. 
The three output terminals of the current controller 122 are connected to 
the three input terminals of the three-/two-phase converter 222, 
respectively. The two output terminals of the three-/two-phase converter 
222 are connected to the other two input terminals of a secondary magnetic 
flux estimator 224, respectively. The two output terminals of the 
secondary magnetic flux estimator 224 are connected to the other two input 
terminals of the first angular velocity estimator 226, respectively. The 
other two output terminals of the secondary magnetic flux estimator 224 
are connected to the other two input terminals of a second angular 
velocity estimator 228, respectively. The output terminals of the first 
angular velocity estimator 226 and the second angular velocity estimator 
228 are connected to the two switching contacts of an estimated angular 
velocity switch 230, respectively. The common contact of the estimated 
angular velocity switch 230 is connected to the input terminals of the 
amplifier 115 and the angular velocity controller 115. 
The output terminal of the amplifier 115 is connected to one of the input 
terminals of the adder 114. The other input terminal of the adder 114 is 
connected to the output terminal of the slip frequency calculator 112. The 
output terminal of the adder 114 is connected to the input terminal of an 
integrator 116. The output terminal of the integrator 116 is connected to 
the other input terminal of the rotary/static coordinate converter 118. 
The operation of a washing machine configured as described above will be 
explained below with reference to FIG. 2. 
The agitator 102 mounted in the rotatable drum 104 are rotated through the 
transmission mechanism 106 by the three-phase induction motor 100 thereby 
to wash the laundry. 
The operation of the slip frequency calculator 112, the adder 114, the 
amplifier 115, the integrator 116, the rotary/static coordinate converter 
118, the two-/three-phase converter 120, the current controller 122, the 
PWM invertor 124 and the converter 130 is the same as that of the 
corresponding component parts in the first embodiment, and therefore the 
description is omitted. The angular velocity controller 110 determines the 
command torque current I.sub.1q * according to equation (9), for example, 
from the command rotational angular velocity .omega..sub.m * of the 
three-phase induction motor and the estimated angular velocity 
.omega..sub.me of the output of the angular velocity estimator 200. 
##EQU8## 
where K.sub.ps, K.sub.is are angular velocity gains which are constants 
set in such a manner as to attain the desired response characteristic. 
Once the angular velocity is correctly estimated, as in the first 
embodiment, a controllability equivalent to the DC motor can be realized. 
An example operation for estimating the rotary angular velocity of a 
three-phase induction motor will be explained below. 
The three-/two-phase converter 220 converts the respective detection 
outputs i.sub.1a, i.sub.1b, i.sub.1c of the current detectors 126a, 126b, 
126c, into the two-phase AC currents i.sub.1d, i.sub.1q by using equation 
(10). 
##EQU9## 
Then, the other three-/two-phase converter 222 converts three-phase command 
voltages v.sub.1z (z is a, b or c) into two-phase AC voltages v.sub.1d, 
v.sub.1q by using equation (11) . 
##EQU10## 
From these two-phase AC currents and the two-phase AC voltages, the 
secondary magnetic fluxes .psi..sub.2d, .psi..sub.2q can be estimated 
using equations (12) and (13) through the secondary magnetic flux 
estimator 224. 
##EQU11## 
From the fundamental equation (1) for the three-phase induction motor in a 
two-phase model, the following two equations are obtained for estimating 
the rotational angular velocity .omega..sub.me of the three-phase 
induction motor. 
##EQU12## 
In these two equations, the denominator may take the value of zero, in the 
neighborhood of where the estimation accuracy is deteriorated. In the 
state that the three-phase induction motor is driven, however, the 
secondary magnetic flux .psi..sub.2q representing the denominator of 
equation (14) and the secondary magnetic flux .psi..sub.2d representing 
the denominator of equation (15) change in sinusoidal forms having 90 
degrees of phase difference to each other. Therefore, it never occurs that 
both the denominators assume zero at the same time. 
A first angular velocity estimator 226 calculates an estimated angular 
velocity numerator section representing the numerator in accordance with 
equation (14). The estimated angular velocity numerator section is divided 
by a denominator representing the secondary magnetic flux .psi..sub.2q to 
estimate the rotational angular velocity of the three-phase induction 
motor. Then, a second angular velocity estimator 228 calculates an 
estimated angular velocity numerator section representing the numerator in 
accordance with equation (15). The estimated angular velocity numerator 
section is divided by the denominator representing the secondary magnetic 
flux .psi..sub.2d to estimate the rotational angular velocity of the 
three-phase induction motor. Then, the magnitude of the secondary magnetic 
fluxes .psi..sub.2d, .psi..sub.2q is measured and the one with the 
denominator not assuming a value in the neighborhood of zero is selected 
by an estimated angular velocity switch 230. As a result, the rotational 
angular velocity of the three-phase induction motor can be estimated 
always accurately. 
In the above-mentioned method, a large torque can be produced in a wide 
range of low to high speeds without using the angular velocity detector 
128 unlike in the first embodiment. A washing machine capable of washing a 
large amount of laundry can be realized easily. 
The two-/three-phase converter 120 forms the three-phase command primary AC 
current, and the three-phase primary AC current is compared with the 
three-phase command primary AC current in the current controller 122, so 
that the three-phase primary AC current is controlled. In another method, 
the three-phase primary AC current detected by the current detectors 126a, 
126b, 126c is converted into a two-phase primary AC current at the 
three-/two-phase converter 220. This two-phase current is compared with 
the two-phase command primary AC current before being applied to the 
two-/three-phase converter 120. Based on the result of comparison, the 
current is controlled, and the two-phase command voltage can be converted 
to a three-phase command voltage through the two-/three-phase converter. 
Also according to the second embodiment, a command voltage is used in place 
of the actual voltage. This leads to the advantage that a voltage detector 
is eliminated. In such a case, the accuracy of the command voltage is 
further improved if the affect of time delay or the like that occurs when 
the PWM invertor 124 is turned on is corrected. 
The second embodiment also represents an example of a washing machine for 
washing laundry by rotating agitator driven by a three-phase induction 
motor. This embodiment is applicable to a washing machine of drum type 
with equal effect, for example, in which the agitator are not used and a 
rotatable drum is directly rotated. 
Third Embodiment 
In the first and second embodiments, the exciting current for generating a 
magnetic field is controlled to a constant level in the same manner as if 
a permanent magnet is incorporated in the three-phase induction motor. In 
order to obtain a large torque in high rotational speed range, however, an 
increased exciting current is required, and therefore a high DC voltage is 
required. The DC voltage output from the converter 130, which is 
determined by the voltage of the commercial power supply, has a limited 
voltage value. 
As a third embodiment of the present invention, explanation will be made as 
to a washing machine comprising a controller for a three-phase induction 
motor which can produce a comparatively large torque by the voltage of the 
commercial power supply even in high rotational speed range such as when 
the laundry is dewatered. 
A washing machine according to the third embodiment is explained below with 
reference to FIG. 3. FIG. 3 is a block diagram showing a configuration of 
a washing machine according to the third embodiment of the invention. 
In FIG. 3, the rotary shaft 100A of the three-phase induction motor 100 is 
coupled to the rotary shaft 102A of the agitator 102 arranged in the 
rotatable drum 104 through the transmission mechanism 106. The output 
terminal of the angular velocity controller 110 supplied with a command 
rotational angular velocity .omega..sub.m * is connected to the respective 
input terminals of the slip frequency calculator 112 and the rotary/static 
coordinate converter 118. The input terminal of an exciting current 
converter 300 is connected to the input terminal of the angular velocity 
controller 110. 
The other input terminal of the slip frequency calculator 112 and the 
rotary/static coordinate converter 118 is connected to the output terminal 
of the exciting current converter 300. The two output terminals of the 
rotary/static coordinate converter 118 are connected to the two input 
terminals of a two-/three-phase converter 120. The three output terminals 
of the two-/three-phase converter 120 are connected to the three input 
terminals of the PWM invertor 124. The three output terminals of the PWM 
invertor 124 is connected to the three-phase induction motor 100. The two 
input terminals of the PWM invertor 124 are connected to an AC power 
supply of single phase, 100 V, through the converter 130. The three 
connection lines between the PWM invertor 124 and the three-phase 
induction motor 100 are provided with the current detectors 126a, 126b, 
126c, respectively. The output terminals of the current detectors 126a, 
126b, 126c are connected to the three input control terminals of the 
current controller 122, respectively, and to the three input terminals of 
the angular velocity estimator 200, respectively. 
The output terminal of the angular velocity estimator 200 is connected to 
the input terminal of the amplifier 115 and to the input terminal of the 
angular velocity controller 110. The output terminal of the amplifier 115 
is connected to one of the input terminals of the adder 114. The other 
input terminal of the adder 114 is connected to the output terminal of the 
slip frequency calculator 112. The other output terminal of the adder 114 
is connected to the input terminal of the integrator 116. The output 
terminal of the integrator 116 is connected to the other input terminal of 
the rotary/static coordinate converter 118. 
The operation of a washing machine configured as described above will be 
explained with reference to FIG. 3 below. 
Also in the third embodiment, the laundry is washed by rotating the 
agitator 102 which are mounted in the rotatable drum 104 and driven by the 
three-phase induction motor 100 through the transmission mechanism 106. 
The operation of the angular velocity controller 110, the slip frequency 
calculator 112, the adder 114, the amplifier 115, the integrator 116, the 
rotary/static coordinate converter 118, the two-/three-phase converter 
120, the current controller 122, the PWM converter 124, the converter 130 
and the angular velocity estimator 200 is the same as that of the 
corresponding units in the second embodiment, respectively, and therefore 
the description is omitted. 
In this embodiment, the washing machine further comprises an exciting 
current converter 300 supplied with a command rotational angular velocity 
.omega..sub.m * for outputting a command exciting current I.sub.1d *. In 
the case where the three-phase induction motor is driven at such a high 
speed as at the time of dewatering, the maximum control value of the 
primary AC voltage output from the current controller 122 exceeds a DC 
output voltage which is an output of the converter 130 determined by a 
source voltage. For this reason, the desired torque cannot be generated 
and the rotational angular velocity of the motor is reduced. 
At the time of dewatering, therefore, the command exciting current I.sub.1d 
* is reduced as compared with the time when the rotational angular 
velocity is low as at the time of washing. As a result, a comparatively 
large torque can be generated even in high speed range, thereby improving 
the dewatering capability. 
Although this embodiment represents an example of the washing machine for 
washing laundry by rotating the agitator by the three-phase induction 
motor, the embodiment is applicable also to a washing machine of drum type 
in which the agitator are not used, and the rotatable drum is rotated 
directly. 
Fourth Embodiment 
In the single-phase induction motor operated only at a predetermined 
angular velocity determined by the power frequency, the rise 
characteristic of the rotational angular velocity cannot be changed. 
In view of this, in a fourth embodiment of the invention, a washing machine 
will be explained below, which realizes an operation with low vibrations 
and low noises by alleviating the shocks when the agitator start rotating 
or reverse. 
The washing machine according to the fourth embodiment of the invention 
will be explained with reference to FIG. 4. 
FIG. 4 is a block diagram showing a configuration of the washing machine 
according to the fourth embodiment of the invention. 
In FIG. 4, the rotary shaft lOOA of the three-phase induction motor 100 is 
coupled to the rotary shaft 102A of the agitator 102 arranged in the 
rotatable drum 104 through the transmission mechanism 106. The output 
terminal of the command angular velocity generator 320 is connected to the 
input terminal of the angular velocity controller 110, and the command 
rotational angular velocity .omega..sub.m * is supplied to the angular 
velocity controller 110. The output terminal of the angular velocity 
controller 110 is connected to respective input terminals of the slip 
frequency calculator 112 and the rotary/static coordinate converter 118. 
The other input terminal of the slip frequency calculator 112 and the 
rotary/static coordinate converter 118 is supplied with the command 
exciting current I.sub.1d *. 
The two output terminals of the rotary/static coordinate converter 118 are 
connected to the two input terminals of the two-/three-phase converter 
120, respectively. The three output terminals of the two-/three-phase 
converter 120 are connected to the three input terminals of the current 
controller 122, respectively. The three output terminals of the current 
controller 122 are connected to the three input terminals of the PWM 
invertor 124, respectively, and to the three input terminals of the 
angular velocity estimator 200, respectively. The three output terminals 
of the PWM invertor 124 are connected to the three-phase induction motor 
100. The two input terminals of the PWM invertor 124 are connected to an 
AC power supply of single phase 100 V through the converter 130. 
Three connection lines between the PWM invertor 124 and the three-phase 
induction motor 100 are provided with the current detectors 126a, 126b, 
126c, respectively. The output terminals of the current detectors 126a, 
126b, 126c are connected to the three control input terminals of the 
current controller 122, respectively, and to the three input terminals of 
the angular velocity estimator 200, respectively. 
The output terminal of the angular velocity estimator 200 is connected to 
the input terminal of the amplifier 115 and the other input terminal of 
the angular velocity controller 110. The output terminal of the amplifier 
115 is connected to one of the input terminals of the adder 114. The other 
input terminal of the adder 114 is connected to the output terminal of the 
slip frequency calculator 112. The output terminal of the adder 114 is 
connected to the input terminal of the integrator 116. The output terminal 
of the integrator 116 is connected to the other input terminal of the 
rotary/static coordinate converter 118. 
The operation of the washing machine having the above-mentioned 
configuration will be explained below with reference to FIGS. 4 and 5. 
Also in the fourth embodiment, the laundry is washed by rotating the 
agitator 102 mounted in the rotatable drum 104 and driven by the 
three-phase induction motor 100 through the transmission mechanism 106. 
The operations of the angular velocity controller 110, the slip frequency 
calculator 112, the adder 114, the amplifier 115, the integrator 116, the 
rotary/static coordinate converter 118, the two-/three-phase converter 
120, the current controller 122, the PWM invertor 124, the converter 130 
and the angular velocity estimator 200 are the same as those of the 
corresponding component parts in the third embodiment, and therefore will 
not be described again. 
Assuming that the command rotational angular velocity .omega..sub.m * 
changing stepwise is applied to the three-phase induction motor in the 
conventional washing machine with the agitator 102 rotating at a constant 
angular velocity, the washing machine is operated with a shock due to 
transient response decided by the angular velocity control gain. 
Consequently, in order to rise the rotational angular velocity 
monotonously and smoothly without abrupt changes, the angular velocity 
control gain must be set to a low level. With the low level of angular 
velocity control gain, however, the disturbance suppression characteristic 
is deteriorated, when the laundry is caught in the agitator or otherwise. 
Another problem is that a rise time varies according to the amount of 
laundry. In view of this, a command rotational angular velocity 
.omega..sub.m *(t) is set by a time function of third order as expressed 
by equation (16) representing the curve of FIG. 5, for example. 
##EQU13## 
where T designates the rise time, and .omega..sub.mT designates a target 
rotational angular velocity. The command torque current I.sub.1q * is 
given in equation (17) below, for example, using the estimated angular 
velocity value .omega..sub.me. 
##EQU14## 
As a result, the desired transient response characteristic can be realized, 
and a washing machine of low vibrations and low noises is realized with 
the shock alleviated at the time of starting operation and reversing 
operation. 
Although the command rotational angular velocity .omega..sub.m *(t) is 
given by the time function of third order in this embodiment, a continuous 
function such as a sinusoidal function or a combination of a plurality of 
functions can also be employed. 
Also in the fourth embodiment, an example is shown of a washing machine in 
which the laundry is washed by rotating the agitator driven by the 
three-phase induction motor. Instead, this embodiment is also applicable 
to the washing machine of drum type, for example, in which the agitator 
are not used and the rotatable drum is rotated directly. 
Fifth Embodiment 
In a washing process, if a proper quantity of water is supplied in 
accordance with the amount of laundry, the problem of insufficient washing 
is solved or water consumption is reduced. For this purpose, the amount 
(e.g. weight) of laundry must be estimated accurately before water is 
supplied. 
As a fifth embodiment of the invention, a washing machine will be explained 
which can estimate the amount of laundry accurately by test rotating the 
agitator before water is supplied. 
FIG. 6 is a block diagram showing a configuration of a washing machine 
according to the fifth embodiment of the invention. 
In FIG. 6, the rotary shaft 100A of the three-phase induction motor 100 is 
coupled to the rotary shaft 102A of the agitator 102 arranged in the 
rotatable drum 104 through the transmission mechanism 106. The output 
terminals of the angular velocity controller 110 and a test operation 
controller 400 supplied with the command rotational angular velocity 
.omega..sub.m * are connected to two switching contacts of a switch 404, 
respectively. The common contact of the switch 404 is connected to the 
input terminals of the slip frequency calculator 112 and the rotary/static 
coordinate converter 118. The command exciting current I.sub.1d * is 
applied to the other input terminals of the slip frequency calculator 112 
and the rotary/static coordinate converter 118. The two output terminals 
of the rotary/static coordinate converter 118 are connected to the input 
terminals of the two-/three-phase converter 120. The three output 
terminals of the two-/three-phase converter 120 are connected to the three 
input terminals of the current controller 122, respectively. The three 
output terminals of the current controller 122 are connected to the three 
input terminals of the PWM invertor 124, respectively. The three output 
terminals of the PWM invertor 124 are connected to the three-phase 
induction motor 100. The two input terminals of the PWM invertor 124 are 
connected through the converter 130 to a single-phase AC power supply of 
100 V. 
The three connection lines between the PWM invertor 124 and the three-phase 
induction motor 100 are provided with the current detectors 126a, 126b, 
126c, respectively. The output terminals of the current detectors 126a, 
126b, 126c are connected to the three control input terminals of the 
current controller 122 and to the three input terminals of the angular 
velocity estimator 200. 
The output terminal of the angular velocity estimator 200 is connected to 
the input terminals of the amplifier 115, the angular velocity controller 
110, the test operation controller 400 and a laundry amount estimator 402. 
The output terminal of the amplifier 115 is connected to one of the input 
terminals of the adder 114. The other input terminal of the adder 114 is 
connected to the output terminal of the slip frequency calculator 112. The 
output terminal of the adder 114 is connected to the input terminal of the 
integrator 116. The output terminal of the integrator 116 is connected to 
the other input terminal of the rotary/static coordinate converter 118. 
The output terminal of the laundry amount estimator 402 is connected to 
the input terminal of a water level regulator 412 for regulating the 
amount of water in the rotatable drum 104. 
The operation of the washing machine having the above-mentioned 
configuration will be explained with reference to FIG. 6. 
In estimating the amount of laundry, as in washing the laundry, the 
agitator 102 mounted in the rotatable drum 104 are test operated through 
the transmission mechanism 106 by the three-phase induction motor 100. For 
example, estimation may be made after water is supplied into the rotatable 
drum 104. This method, however, has the disadvantage that the user has to 
wait until water is completely supplied. Therefore, estimation before 
water supply is desirable. However, when the agitator 102 is rotated 
before water supply in a similar manner to washing, estimation accuracy is 
deteriorated by undesirable raising and rolling up the laundry, or by 
hanging laundry with the agitator 102. Especially during the transient 
response, the effect of laundry being caught becomes more conspicuous and 
the estimation accuracy is further deteriorated. 
Before conducting a test operation for estimating the laundry amount, the 
first step is to turn the switch 404 to the test operation controller 400. 
In order to facilitate the estimation of the laundry amount, the test 
operation controller 400 controls the command torque current I.sub.1q * as 
represented by equation (18) below based on the command rotational angular 
velocity .omega..sub.m * of the three-phase induction motor and the 
estimated angular velocity .omega..sub.me output from the angular velocity 
estimator 200. 
EQU I.sub.1q *=K.sub.ps .multidot.(.omega..sub.m *-.omega..sub.me)(18) 
where K.sub.ps is the angular velocity control gain. The operation of the 
slip frequency calculator 112, the adder 114, the amplifier 115, the 
integrator 116, the rotary/static coordinate converter 118, the 
two-/three-phase converter 120, the current controller 122, the PWM 
invertor 124, the converter 130 and the angular velocity estimator 200 is 
the same as that of the corresponding component parts of the second 
embodiment, respectively, and therefore will not be explained again. 
In the case where the command torque current I.sub.1q * is given by 
equation (18), which includes no integration term unlike for washing. 
Consequently, the rotational angular velocity of the three-phase induction 
motor decreases with the increase in the amount of laundry providing the 
load. The amount of laundry, therefore, can be easily estimated from the 
magnitude of an estimated angular velocity output from the angular 
velocity estimator 200. 
In the case that the laundry amount is divided into five stages, for 
example, the laundry amount estimator 402 divides the estimated angular 
velocity .omega..sub.me and threshold values .omega.1 to .omega.4 
predetermined by test into equations (19), (20), (21), (22) and (23) for 
comparison. 
EQU .vertline..omega..sub.me .vertline..gtoreq..omega.1 (Laundry amount is very 
small) (19) 
EQU .omega.2.ltoreq..vertline..omega..sub.me &lt;.omega.1 (Laundry amount is 
small)(20) 
EQU .omega.3.ltoreq..vertline..omega..sub.me .vertline.&lt;.omega.2 (Laundry 
amount is medium) (21) 
EQU .omega.4.ltoreq..vertline..omega..sub.me &lt;.omega.3 (Laundry amount is 
large)(22) 
EQU .vertline..omega..sub.me .vertline.&lt;.omega.4 (Laundry amount is very 
large)(23) 
The control gain K.sub.ps in equation (18) is preferably set low in order 
that the rotational angular velocity of the three-phase induction motor 
may become sufficiently low in the case where the maximum laundry possible 
to wash is loaded. Also, the command rotational angular velocity 
.omega..sub.m * should not be set higher than the angular velocity for 
washing. Otherwise, the rotational angular velocity increases so large as 
to increase the probability of the laundry being rounded. 
After the amount of laundry is estimated, the water level regulator 412 
determines the amount of water to be supplied in the rotatable drum 104 in 
accordance with the estimated amount of laundry. Then, the switch 404 is 
turned to the angular velocity controller 110 and the washing is carried 
out as explained in the second embodiment. 
In this embodiment, the laundry amount is estimated from the magnitude of 
the estimated angular velocity. The estimated angular velocity is more 
varied with the increase in the laundry amount. In order to obviate this 
inconvenience, the test operation is conducted a plurality of times, and 
the resulting variation in the estimated angular velocity can be used to 
estimate the laundry amount. 
Also, instead of estimating the laundry amount from the magnitude of the 
estimated angular velocity as in the present embodiment, the torque 
current component can be used for estimation as in the method described 
below. 
First, in order to facilitate the estimation of the laundry amount in a 
test operation for estimating the laundry amount, the test operation 
controller 400 gives the command torque current I.sub.1q * from equation 
(24) below as in the angular velocity controller 110. The command torque 
current I.sub.1q * is based on the command rotational angular velocity 
.omega..sub.m * of the three-phase induction motor and the estimated 
angular velocity .omega..sub.me output from the angular velocity estimator 
200. 
##EQU15## 
where K.sub.pL, K.sub.iL are angular velocity control gains. The equation 
(24) contains the term of integration of angular velocity error. 
Therefore, when the command torque current I.sub.1q * is given by equation 
(24), the command torque current continues to increase until the estimated 
angular velocity comes to follow the command rotational angular velocity 
regardless of the laundry amount. In other words, the command torque 
current increases with the amount of laundry. Thus, the amount of laundry 
can be easily estimated not from the magnitude of the estimated angular 
velocity but from the command torque value. 
The change of the command torque current increases the slip angular 
velocity according to equation (3), thereby increasing the frequency of 
the primary AC current and the primary AC voltage. The amount of laundry, 
therefore, can be estimated also from the magnitude of frequency of these 
factors. 
Further, the response time from the time point of starting the test 
operation to the time point when the estimated angular velocity reaches 
the neighborhood of the command rotational angular velocity, i.e. the 
response time before the error between the estimated angular velocity and 
the command rotational angular velocity enters a predetermined error 
margin, increases with the increase in laundry amount. Therefore, the 
amount of laundry can also be estimated by measuring this response time. 
In this case, in order to improve the estimation accuracy of the laundry 
amount, the angular velocity control gains K.sub.pL, K.sub.iL can be 
decreased as compared with the time of washing operation. 
Also, the amount of laundry can be estimated by setting the command torque 
current at a predetermined constant value and measuring the time length 
from the time point when the test operation is started to the time point 
when the estimated angular velocity reaches a specified value. In this 
case, too, in order to improve the estimation accuracy of the laundry 
amount, the command torque current can be set at a value associated with a 
torque smaller than the one generated at the time of normal washing. 
Sixth Embodiment 
Equations (12) to (15) for estimating the rotational angular velocity of 
the three-phase induction motor or equation (3) for calculating the slip 
angular velocity use constants unique to the three-phase induction motor 
such as the resistance R.sub.j on j-order (j: 1 or 2) side, the inductance 
L.sub.j on j-order side and a mutual inductance M. These constants unique 
to the three-phase induction motor, however, are varied under the effect 
of such factors as variations in motor manufacture. 
In view of this, a washing machine according to a sixth embodiment of the 
invention will be explained, in which an always optimum washing operation 
can be performed by measuring the constants unique to the three-phase 
induction motor. 
A washing machine according to the sixth embodiment of the invention will 
be explained with reference to FIG. 7. 
FIG. 7 is a block diagram showing a configuration of a washing machine 
according to the sixth embodiment of the invention. 
In FIG. 7, the rotary shaft 100A of the three-phase induction motor 100 is 
coupled to the rotary shaft 102A of the agitator 102 arranged in the 
rotatable drum 104 through the transmission mechanism 106. The output 
terminal of the angular velocity controller 110 supplied with the command 
rotational angular velocity .omega..sub.m * is connected to respective 
input terminals of the slip frequency calculator 112 and the rotary/static 
coordinate converter 118. The other input terminal of the slip frequency 
calculator 112 and the rotary/static coordinate converter 118 is supplied 
with the command exciting current I.sub.1d *. 
The two output terminals of the rotary/static coordinate converter 118 are 
connected to the input terminals of the two-/three-phase converter 120. 
The three output terminals of the two-/three-phase converter 120 are 
connected to the three switching contacts of a three-circuit switch 452, 
respectively. The other three switching contacts of the switch 452 are 
connected to the three output terminals of a constant measurement current 
commander 450, respectively. The three common contact points of the switch 
452 are connected to the three input terminals of the current controller 
122, respectively. The three output terminals of the current controller 
122 are connected to the three input terminals of the PWM invertor 124, 
respectively. The three output terminals of the PWM invertor 124 are 
connected to the three-phase induction motor 100. 
Two input terminals of the PWM invertor 124 are connected through the 
converter 130 to an AC power supply of single phase, 100 V. Three output 
terminals of the current controller 122 are connected to the three common 
contacts of a three-circuit switch 456, respectively. The three connection 
lines between the PWM invertor 124 and the three-phase induction motor 100 
are provided with the current detectors 126a, 126b, 126c, respectively. 
The output terminals of the current detectors 126a, 126b, 126c are 
connected to the three control input terminals, respectively, of the 
current controller 122 on the one hand and to the three common terminals 
of the three-circuit switch 458 on the other hand. The three switching 
contacts of each of the switches 456, 458 are connected to the input 
terminals of the angular velocity estimator 200, and the other three 
switching contacts thereof are connected to the input terminals of a motor 
constant measurement device 454. 
The output terminal of the angular velocity estimator 200 is connected to 
the input terminals of the angular velocity controller 110 and the 
amplifier 115. The output terminal of the motor constant measurement 
device 454 is connected to the input terminals of the slip frequency 
calculator 112 and the angular velocity estimator 200. The output terminal 
of the amplifier 115 is connected to one of the input terminals of the 
adder 114. The other input terminal of the adder 114 is connected to the 
output terminal of the slip frequency calculator 112. The output terminal 
of the adder 114 is connected to the input terminal of the integrator 116. 
The output terminal of the integrator 116 is connected to the other input 
terminal of the rotary/static coordinate converter 118. 
The operation of the washing machine configured as described above will be 
explained with reference to FIG. 7. 
Also in this embodiment, the laundry is washed by rotating the agitator 102 
mounted in the rotatable drum 104 and driven by the three-phase induction 
motor 100 through the transmission mechanism 106. 
The operation of the angular velocity controller 110, the slip frequency 
calculator 112, the adder 114, the amplifier 115, the integrator 116, the 
rotary/static coordinate converter 118, the two-/three-phase converter 
120, the current controller 122, the PWM invertor 124, the converter 130 
and the angular velocity estimator 200 is identical to that of the 
corresponding component parts of the fifth embodiment, and therefore will 
not be described again. 
Now, the measurement of constants unique to the three-phase induction motor 
will be explained. 
A method of measuring constants unique to a three-phase induction motor in 
stationary state is described in the National Convention Record I.E.E. 
JAPAN Industry Applications Society, 1996, "Method of Measuring Constants 
of Induction Motor", pp.375-378, for example. In measuring the constants 
unique to the three-phase induction motor by this method, a current is 
supplied to the motor in stationary state from the constant measurement 
current commander 450 for a short length of time (say, several seconds) 
for making measurements. Therefore, the measurement cannot be carried out 
while the motor is running. 
According to the sixth embodiment, the input to the current controller 122 
is turned from the two-/three-phase converter 120 to the constant 
measurement current commander 450 by the switch 452 during the time when 
power is supplied to the motor or the motor is not running at the time of 
supplying water or dewatering. Further, the outputs of the current 
controller 122 and output of the current detectors 126a, 126b, 126c are 
turned from the angular velocity estimator 200 to the motor constant 
measurement device 454 by the switches 456, 458. Then, the constants 
unique to the three-phase induction motor are measured. After that, the 
constants unique to the three-phase induction motor used for the slip 
frequency calculator 112 and the angular velocity estimator 200 are 
changed. 
As a result, the manufacturing variations of individual motors are 
compensated. The effect of variations of the constants unique to the 
three-phase induction motor thus can be suppressed by measuring the 
variations of the resistance value due to an increased temperature of a 
running motor each time water is supplied or the laundry is dewatered. 
Thus, an always optimum washing operation can be carried out. 
Seventh Embodiment 
Among the constants unique to the three-phase induction motor, the 
self-inductance and the mutual inductance do not change during the motor 
operation. Thus, the values of the self-inductance and the mutual 
inductance, once measured, can be stored in a motor constant memory, and 
the motor can be controlled using the values stored in the motor constant 
memory. 
Even in the case where the constants unique to the three-phase induction 
motor are known in advance, the three-phase induction motor, once started, 
might increases in temperature causing a change in resistance R.sub.j. 
In order to obviate the above-mentioned problem, a washing machine will be 
explained below as a seventh embodiment of the invention. In the seventh 
embodiment, the resistance change with the temperature increase of the 
motor is corrected and an always optimum washing operation is performed. 
A washing machine according to the seventh embodiment of the invention will 
be explained with reference to FIG. 8. FIG. 8 is a block diagram showing a 
configuration of a washing machine according to the seventh embodiment of 
the invention. 
In FIG. 8, the rotary shaft 100A of the three-phase induction motor 100 is 
coupled to the rotary shaft 102A of the agitator 102 arranged in the 
rotatable drum 104 through the transmission mechanism 106. The output 
terminal of the angular velocity controller 110 supplied with the command 
rotational angular velocity .omega..sub.m * is connected to one of the 
switching contacts of the switch 404. The other switching contact of the 
switch 404 is connected to the output terminal of the test operation 
controller 400 supplied with the command rotational angular velocity 
.omega..sub.m *. The common contact of the switch 404 is connected to the 
respective input terminals of the slip frequency calculator 112 and the 
rotary/static coordinate converter 118. The other input terminals of the 
slip frequency calculator 112 and the rotary/static coordinate converter 
118 are supplied with the command exciting current I.sub.1d *. 
The two output terminals of the rotary/static coordinate converter 118 are 
connected to two input terminals of the two-/three-phase converter 120, 
respectively. The three output terminals of the two-/three-phase converter 
120 are connected to the three input terminals of the current controller 
122, respectively. The three output terminals of the current controller 
122 are connected to the three input terminals of the PWM invertor 124 on 
the one hand and to the three input terminals of the angular velocity 
estimator 200, on the other hand, respectively. The three output terminals 
of the PWM invertor 124 are connected to the three-phase induction motor 
100. The two input terminals of the PWM invertor 124 are connected through 
the converter 130 to a single-phase AC power supply of 100 V. The three 
connection lines between the PWM invertor 124 and the three-phase 
induction motor 100 are provided with the current detectors 126a, 126b, 
126c, respectively. The output terminals of the current detectors 126a, 
126b, 126c are connected to the three control input terminals of the 
current controller 122 on the one hand and to the other three input 
terminals of the angular velocity estimator 200 on the other hand, 
respectively. 
The output terminal of the angular velocity estimator 200 is connected to 
the input terminals of the angular velocity controller 110, the test 
operation controller 400, the laundry amount estimator 402 and the 
amplifier 115. The output terminal of the amplifier 115 is connected to 
one of the input terminals of the adder 114. The other input terminal of 
the adder 114 is connected to the output terminal of the slip frequency 
calculator 112. The output terminal of the adder 114 is connected to the 
input terminal of the integrator 116. The output terminal of the 
integrator 116 is connected to the other input terminal of the 
rotary/static coordinate converter 118. The output terminal of the laundry 
amount estimator 402 is connected to the input terminal of a resistance 
value curve selector 500. The output terminal of the resistance value 
curve selector 500 is connected to the input terminal of a resistance 
value compensator 504. The resistance value compensator 504 is connected 
also to a timer 502. The two output terminals of the resistance value 
compensator 504 are connected to the input terminals of the slip frequency 
calculator 112 and the angular velocity estimator 200, respectively. 
FIG. 9 is a graph showing the operation time and the temperature with the 
laundry amount as a parameter for the three-phase induction motor 
according to the invention. 
The operation of a washing machine configured as described above will be 
explained below with reference to FIGS. 8 and 9. 
Also in this embodiment, the laundry is washed by rotating the agitator 102 
mounted in the rotatable drum and driven by the three-phase induction 
motor 100 through the transmission mechanism 106. 
The operation of the angular velocity controller 110, the slip frequency 
calculator 112, the adder 114, the amplifier 115, the integrator 116, the 
rotary/static coordinate converter 118, the two-/three-phase converter 
120, the current controller 122, the PWM invertor 124, the converter 130, 
the angular velocity estimator 200, the test operation controller 400, the 
laundry amount estimator 402 and the switch 404 is identical to that of 
the corresponding component parts of the fifth embodiment, and therefore 
will not be described again. 
In the actual operation of washing, rinsing and dewatering, as shown in 
FIG. 9, the three-phase induction motor increases in temperature in 
accordance with the laundry amount and the operating time. With the 
increase in temperature, the primary resistor R.sub.1 (resistance of the 
stator winding) and the secondary resistor R.sub.2 (resistance of the 
rotor winding) change to an extent dependent on temperature. In accordance 
with the laundry amount estimated by the laundry amount estimator 402, the 
resistance value curve selector 500 selects a resistance increase curve 
set by previous measurement and stored in a ROM included in the resistance 
value curve selector 500. The operation time of the motor is measured by 
the timer 502. The primary resistor R.sub.1 and the secondary resistor 
R.sub.2 are derived at the particular time point by the resistance value 
compensator 504, thereby changing the constants used in the slip frequency 
calculator 112 and the angular velocity estimator 200. As a result, it is 
possible to suppress the effect of variations in the primary and secondary 
resistance values due to the temperature increase during the operation, 
thereby making it possible to secure an always optimum laundry condition. 
The temperature variations are more caused by the operation time than by 
the amount of laundry. It is therefore also effective to change the 
primary resistor R.sub.1 and the secondary resistor R.sub.2 based only on 
the operation time of the three-phase induction motor without taking the 
laundry amount into consideration. 
Eighth Embodiment 
FIG. 10 is a block diagram showing a configuration of the washing machine 
using a three-phase induction motor according to an eighth embodiment of 
the invention. 
In FIG. 10, the three-phase induction motor 100 is coupled through the 
transmission mechanism 106 to the rotatable drum 104 which washes, 
dewaters and dries the laundry. The output terminal of the command angular 
velocity generator 103 for outputting the command rotational angular 
velocity .omega..sub.m * commanding the rotational angular velocity of the 
three-phase induction motor is connected to the input terminal of the 
angular velocity controller 110. The output terminal of the angular 
velocity controller 110 is connected to the respective input terminals of 
the slip frequency calculator 112 and the rotary/static coordinate 
converter 118. The other input terminals of the slip frequency calculator 
112 and the rotary/static coordinate converter 118 are supplied with the 
command exciting current I.sub.1d *. 
The two output terminals of the rotary/static coordinate converter 118 are 
connected to the two input terminals of the two-/three-phase converter 
120, respectively. The three output terminals of the two-/three-phase 
converter 120 are connected to the three input terminals of the current 
controller 122, respectively. The three output terminals of the current 
controller 122 are connected to the three input terminals of the PWM 
invertor 124, respectively. The three output terminals of the PWM invertor 
124 are connected to the three-phase induction motor 100, respectively. 
The two input terminals of the PWM invertor 124 are connected through the 
converter 130 to an AC power supply. 
The three connection lines between the PWM invertor 124 and the three-phase 
induction motor 100 are provided with the current detectors 126a, 126b, 
126c, respectively. The output terminals of the current detectors 126a, 
126b, 126c are connected to the three input terminals of the 
three-/two-phase converter 220, respectively. The two output terminals of 
the three-/two-phase converter 220 are connected to a secondary magnetic 
flux estimator 224, an angular velocity estimator 226 and an output torque 
estimator 250. The three output terminals of the current controller 122 
are also connected to the input terminals of the three-/two-phase 
converter 222. The two output terminals of the three-/two-phase converter 
222 are connected to the secondary magnetic flux estimator 224. The output 
terminal of the secondary magnetic flux estimator 224 is connected also to 
the angular velocity estimator 226 and the output torque estimator 250. 
The output terminal of the angular velocity estimator 226 is connected to 
the input terminals of the amplifier 115 and the angular velocity 
controller 110. The output terminal of the output torque estimator 250 is 
connected to the input terminal of the laundry amount estimator 252. 
The output terminal of the amplifier 115 is connected to one of the input 
terminals of the adder 114. The other input terminal of the adder 114 is 
connected to the output terminal of the slip frequency calculator 112. The 
output terminal of the adder 114 is connected to the input terminal of the 
integrator 116. The output terminal of the integrator 116 is connected to 
the input terminal of the rotary/static coordinate converter 118. 
First, the basic operation of the washing machine configured as described 
above will be described below with reference to FIG. 10. The laundry in 
the rotatable drum 104 is washed by rotating the rotatable drum 104 by the 
three-phase induction motor 100 through the transmission mechanism 106. 
First, the operation of an angular velocity control unit 150 will be 
explained. 
As described above, the angular velocity control unit 150 includes the 
angular velocity controller 110, the slip frequency calculator 112, the 
adder 114, the amplifier 115, the integrator 116, the rotary/static 
coordinate converter 118 and the two-/three-phase converter 120. The 
angular velocity controller 110, like in the angular velocity control of a 
DC motor, gives a command torque current I.sub.1q * as indicated by 
equation (9), for example. The command torque current I.sub.1q * is formed 
from the command rotational angular velocity .omega..sub.m * of the 
three-phase induction motor output from the command angular velocity 
generator 103 and the estimated rotational angular velocity .omega..sub.me 
output from the angular velocity estimator 200 for estimating the 
rotational angular velocity of the three-phase induction motor described 
later. 
Once the rotational angular velocity is estimated correctly, the 
controllability equivalent to that of the DC motor can be realized. Since 
the induction motor has no permanent magnet, a predetermined exciting 
current for producing a magnetic field equivalent to that produced by a 
permanent magnet is applied to the exciting coil based on the command 
exciting current I.sub.1d *. The slip frequency calculator 112 calculates 
the slip angular velocity .omega..sub.s according to equation (3) using 
the command exciting current I.sub.1d * and the command torque current 
I.sub.1g *. 
The product of the actual rotational angular velocity .omega..sub.m 
obtained at the amplifier 115 and the number p of pole pairs of the 
three-phase induction motor is added to the slip angular velocity 
.omega..sub.s at the adder 114. The result of addition is integrated by 
the integrator 116, thereby producing an electrical phase angle 
.theta..sub.o given by equation (4). 
Further, by use of the rotary/static coordinate converter 118, equation (5) 
is calculated using the command exciting current I.sub.1d *, the command 
torque current I.sub.1q * and the electrical phase angle .theta..sub.o in 
the same manner as if in the presence of a permanent magnet magnetized in 
a predetermined direction. 
As a result, the command exciting current I.sub.1d * and the command torque 
current I.sub.1q * are converted into the primary command AC currents 
i.sub.1d * and i.sub.1q *, respectively, indicating the two-phase currents 
having 90 degrees of phase difference from each other. Then, the primary 
command AC currents i.sub.1d *, i.sub.1q * are converted into the primary 
command AC currents i.sub.1a *, i.sub.1b *, i.sub.1c * indicating the 
three-phase currents in accordance with equation (6) by the 
two-/three-phase converter 120. 
As far as currents can be supplied according to these command currents, the 
performance equivalent to that of the DC motor can be realized by the 
induction motor. 
Now, the operation of the current controller 122 will be explained. In the 
current controller 122, the actual primary AC currents i.sub.1a, i.sub.1b, 
i.sub.1c are controlled by feedback in such a manner as to follow the 
primary command AC currents i.sub.1a *, i.sub.1b *, i.sub.1c *, 
respectively. For example, the actual primary AC currents are detected by 
the current detectors 126a, 126b, 126c, and the command voltages v.sub.1z 
* (z: a, b, c) are output by the calculation according to equation (7). 
The PWM invertor 124 turns on/off, through transistors, a DC voltage 
produced from the commercial power supply by the converter 130 in 
accordance with the signal of a pulse width based on the command voltage 
provided from the current controller 122. In this way, the desired voltage 
is applied to supply a current to the three-phase induction motor 100. By 
the way, the sum of the primary AC currents i.sub.1a, i.sub.1b, i.sub.1c 
of three phases supplied to the three-phase induction motor 100 is zero, 
i.e., represents the relation shown by equation (8). 
In the current detection process, currents of any two of the three phases 
are detected, and the remaining phase of current can be calculated from 
the detected two phases of current value. In this way, the primary AC 
current supplied to the three-phase induction motor can be controlled to 
equal the desired command value, thereby making it possible to control the 
rotational angular velocity of the three-phase induction motor to the 
desired angular velocity. 
Next, explanation will be made as to the angular velocity estimator 200 for 
estimating the rotational angular velocity of the three-phase induction 
motor. The angular velocity estimator 200, includes a three-/two-phase 
converter 220, a three-/two-phase converter 222, a secondary magnetic flux 
estimator 224 and an angular velocity estimator 226. The three-/two-phase 
converter 220 converts the detection outputs i.sub.1a, i.sub.1b, i.sub.1c 
of the current detectors 126a, 126b, 126c into the two-phase AC currents 
i.sub.1d, i.sub.1q as shown in equation (10). The three-/two-phase 
converter 222, on the other hand, converts the three-phase command 
voltages v.sub.1z * (z: a, b, c) into the two-phase AC voltages v.sub.1d, 
v.sub.1q, as shown in equation (11). 
From the resulting two-phase AC current and two-phase AC voltage, the 
secondary magnetic flux estimator 224 makes calculations as shown in 
equations (12) and (13) thereby to estimate the secondary magnetic fluxes 
.psi..sub.2d, .psi..sub.2q, respectively. 
From the fundamental equation (equation 1) for the three-phase induction 
motor as a two-phase model, the following two equations (14) and (15) are 
obtained for determining the estimated rotational angular velocity 
.omega..sub.me of the three-phase induction motor. 
The denominators of these two equations may sometimes assume zero, in the 
neighborhood of which the estimation accuracy is low. In the case where 
the three-phase induction motor is driven, however, the. secondary 
magnetic flux .psi..sub.2q constituting the denominator of equation (14) 
and the secondary magnetic flux .psi..sub.2d making up the denominator of 
equation (15) take the form of sinusoidal waves 90 degree out of phase 
from each other. Therefore, both of them never assume zero at the same 
time. In view of this, the angular velocity estimator 226 checks the size 
of the secondary magnetic fluxes .psi..sub.2d, .psi..sub.2q, and selects 
the estimation equation (14) or (15), whichever has a denominator farther 
from zero than the other. Then, the rotational angular velocity of the 
three-phase induction motor can be always accurately estimated. In this 
way, the angular velocity of the three-phase induction motor can be 
controlled without using the angular velocity detector, and the operation 
conforming with the command angular velocity can thus be realized. 
A method of estimating the laundry amount in the rotatable drum 104 of a 
washing machine performing the above-mentioned operation will be explained 
below. The output torque .tau. of the three-phase induction motor can be 
expressed by equation (25) using the two-phase AC currents i.sub.1d, 
i.sub.1q and the secondary magnetic fluxes .psi..sub.2d, .psi..sub.2q, 
##EQU16## 
The output torque estimator 250 can calculate the output torque .tau. of 
the three-phase induction motor in accordance with equation (25). Also, 
the relation between the output torque of the three-phase induction motor 
and the rotational operation of the rotatable drum with the laundry placed 
therein is given by equation (26) below. 
##EQU17## 
where J is the moment of inertia of the rotatable drum, J.sub.L is the 
moment of inertia of the laundry, d.sub.1 is the disturbance such as 
friction, and r is the reduction ratio between the rotary shaft of the 
three-phase induction motor and the rotary shaft of the rotatable drum. In 
the process, when the angular acceleration A of the three-phase induction 
motor is constant, as shown in equation (27), the amount of laundry is 
constant. Then, the output torque .tau. of the three-phase induction motor 
becomes constant. 
##EQU18## 
Equation (26) shows that a change in the amount of laundry changes the 
output torque .tau. of the three-phase induction motor accordingly. The 
command rotational angular velocity of the three-phase induction motor 
output from the command angular velocity generator 103 is given in the 
form of a triangular wave as shown in FIG. 11(a). Consequently, the output 
torque is produced as a constant value in the time period of a constant 
angular acceleration as shown in FIG. 11(b). The estimation accuracy is 
improved if the minimum rotational angular velocity indicated by the 
triangular wave is set lower than the lowest angular velocity at which the 
laundry closely attaches to the rotatable drum. 
Also, in order to improve the estimation accuracy by avoiding the effect of 
the disturbance d.sub.1 such as friction, it is preferable to derive a 
torque difference between acceleration and deceleration. The angular 
acceleration in acceleration is represented by A and the angular 
acceleration in deceleration is represented by -A based on the command 
rotational angular velocity of a triangular wave. The difference 
.DELTA..tau. is determined between the maximum torque .tau.max in 
acceleration and the minimum torque .tau.min in deceleration. Then, the 
effect of the disturbance d.sub.1 can be eliminated. This state is shown 
in equation (28). 
EQU 2.multidot.(J+J.sub.L)A=.DELTA..tau./r.sup.2 (28) 
Equation (28) shows that the amount of laundry can be estimated from the 
output torque. The relation between the difference of the output torques 
and the amount of laundry is shown in FIG. 12. Based on the output of the 
output torque estimator 250, therefore, the laundry amount estimator 252 
can estimate the amount of laundry easily and accurately. In the case 
where the exciting current component and the torque current component are 
independently commanded in the three-phase induction motor as according to 
the present embodiment, the amount of laundry can be estimated also from 
the value of the torque current component such as the command torque 
current I.sub.1q * without using the output torque estimator 250 for 
estimating the output torque of the three-phase induction motor. 
Further, in the calculation of equation (11) in the eighth embodiment, 
since the command voltages v.sub.1z * (z: a, b, c) are used in place of an 
actual voltage, this avoids the need for a voltage detector. In this case, 
if the effect of the time delay or the like at the time of turning on the 
PWM invertor 124 is compensated, the voltage accuracy is improved. In the 
eighth embodiment, an angular velocity is commanded so as to maintain a 
constant angular acceleration in the rotation of the three-phase induction 
motor, and the laundry amount is estimated from the associated output 
torque. However, in the next embodiment, the laundry amount can 
alternatively be estimated from the rotational angular velocity by 
controlling the output torque to a constant level. 
Ninth Embodiment 
In a ninth embodiment of the present invention, a washing machine includes 
a laundry amount estimator for estimating the amount of laundry from the 
rotational angular velocity by controlling the output torque to a constant 
level. The washing machine according to the ninth embodiment is described 
with reference to FIG. 13. 
FIG. 13 is a block diagram showing a configuration of a washing machine 
according to the ninth embodiment of the invention. In FIG. 13, the 
three-phase induction motor 100 is coupled through the transmission 
mechanism 106 to the rotatable drum 104 for washing, dewatering and drying 
the laundry. The output terminal of a command torque generator 301 is 
connected to one of the input terminals of the torque controller 302. The 
command torque generated 301 outputs a command torque .tau.* for 
commanding the output torque of the three-phase induction motor. The other 
input terminal of the torque controller 302 and one of the input terminals 
of the slip frequency calculator 112 and the rotary/static coordinate 
converter 118 are supplied with the command exciting current I.sub.1d *. 
The output terminal of the torque controller 302 is connected to the other 
input terminal of the slip frequency calculator 112 and the rotary/static 
coordinate converter 118. The two output terminals of the rotary/static 
coordinate converter 118 are connected to the two input terminals of the 
two-/three-phase converter 120, respectively. The three output terminals 
of the two-/three-phase converter 120 are connected to the three input 
terminals of the current controller 122, respectively. The three output 
terminals of the current controller 122 are connected to the three input 
terminals of the PWM invertor 124, respectively. The three output 
terminals of the PWM invertor 124 are connected to the three-phase 
induction motor 100. The two input terminals of the PWM invertor 124 are 
connected to an AC power supply through the converter 130. 
The three connection lines between the PWM invertor 124 and the three-phase 
induction motor 100 are provided with the current detectors 126a, 126b, 
126c, respectively. The output terminals of the current detectors 126a, 
126b, 126c, are connected to the current controller 122, and also to the 
angular velocity estimator 200. The three output terminals of the current 
controller 122 are also connected to the angular velocity estimator 200, 
and the output of the angular velocity estimator 200 is connected to the 
input terminals of the amplifier 115 and the laundry amount estimator 304. 
The output terminal of the amplifier 115 is connected to one of the input 
terminals of the adder 114, and the other input terminal of the adder 114 
is connected to the output terminal of the slip frequency calculator 112. 
The output terminal of the adder 114 is connected to the input terminal of 
the integrator 116. The output terminal of the integrator 116 is connected 
to the input terminal of the rotary/static coordinate converter 118. 
The operation of the washing machine configured as described above will be 
explained with reference to FIG. 13. Also in this embodiment, like in the 
eighth embodiment, the laundry is washed by rotating the rotatable drum 
104 by the three-phase induction motor 100 through the transmission 
mechanism 106. The operation of the slip frequency calculator 112, the 
adder 114, the amplifier 115, the integrator 116, the rotary/static 
coordinate converter 118, the two-/three-phase converter 120, the current 
controller 122, the PWM invertor 124, the converter 130 and the angular 
velocity estimator 200 is the same as that of the corresponding component 
parts in the eighth embodiment. 
In this embodiment, a command torque generator 301 is comprised in place of 
the command angular velocity generator 103 of the eighth embodiment, and a 
torque controller 302 in place of the angular velocity controller 116. The 
operation of torque control will be explained. In the case where the 
actual current substantially coincides with the command current under 
current control, the output torque .tau. of the three-phase induction 
motor is represented by equation 29. Equation (25) can be transformed into 
equation (29) using the command exciting current I.sub.1d * and the 
command torque current I.sub.1q *. 
##EQU19## 
A command torque is output from the command torque generator 301, and in 
accordance with equation (29), the torque controller 302 generates the 
command torque current I.sub.1q *. The current controller 122 controls the 
current in compliance with the torque command current I.sub.1d * and thus 
makes it possible to output the desired output torque. 
Hereafter, an explanation will be given of a method of estimating the 
laundry amount in the rotatable drum 104 of the washing machine operating 
as described above. The relation between the output torque .tau. of the 
three-phase induction motor and the rotation of the rotatable drum 104 
with laundry placed therein is given by equation (26) as in the eighth 
embodiment. Upon application of a constant torque, therefore, the 
three-phase induction motor runs with isometric acceleration. Then, a 
command torque of a predetermined value is output from the command torque 
generator 301, and the corresponding rotational angular velocity of the 
three-phase induction motor is detected by the angular velocity estimator 
200. Next, the change in rotational angular velocity is checked by the 
laundry amount estimator 304 thereby to estimate the amount of laundry. 
In order to eliminate the effect of the disturbance d.sub.1 such as 
friction in equation (26) and to improve the estimation accuracy, a 
rectangular wave command torque is output and the angular velocity 
difference is taken between maximum angular velocity and minimum angular 
velocity. Consequently, the effect of the disturbance d.sub.1 can be 
eliminated. Alternatively, the amount of laundry can be estimated from the 
time required to reach a predetermined reference angular velocity from 
another predetermined reference angular velocity. 
In the example of a washing machine described above, the laundry closely 
attaches to the inner surface of the rotatable drum 104 due to the 
centrifugal force exerted in the dewatering process. The uneven 
distribution of the laundry attached to the inner wall leads to occurrence 
of a large vibration of the rotatable drum 104. As a tenth embodiment of 
the invention, therefore, a washing machine will be explained which 
includes an unbalanced amount estimator for estimating the unbalanced 
amount due to the uneven distribution of laundry. 
Tenth Embodiment 
A washing machine according to a tenth embodiment of the invention will be 
explained with reference to FIGS. 14 to 17. 
FIG. 14 is a block diagram showing a configuration of a washing machine 
according to the tenth embodiment of the invention. 
In FIG. 14, the three-phase induction motor 100 is coupled through the 
transmission mechanism 106 to the rotatable drum 104 for washing, 
dewatering and drying the laundry. The output terminal of a command 
angular velocity generator 401 for outputting the command rotational 
angular velocity .omega..sub.m * commanding the rotational angular 
velocity of the three-phase induction motor is connected to one of the 
input terminals of the angular velocity controller 150. The three output 
terminals of the angular velocity controller 150 are connected to the 
three input terminals of the current controller 122, respectively. The 
three output terminals of the current controller 122 are connected to the 
three input terminals of the PWM invertor 124, respectively. The three 
output terminals of the PWM invertor 124 are connected to the three-phase 
induction motor 100. The two input terminals of the PWM invertor 124 are 
connected through the converter 130 to an AC power supply. 
The three connection lines between the PWM invertor 124 and the three-phase 
induction motor 100 are provided with the current detectors 126a, 126b, 
126c, respectively. The output terminals of the current detectors 126a, 
126b, 126c are connected to three input terminals of the current 
controller 122, respectively. The output terminals of the current 
detectors 126a, 126b, 126c are also connected to the three input terminals 
of the three-/two-phase converter 220, respectively. The two output 
terminals of the three-/two-phase converter 220 are connected to the 
secondary magnetic flux estimator 224 on the one hand and to the angular 
velocity estimator 226 and the output torque estimator 250 on the other 
hand. 
The three output terminals of the current controller 122, on the other 
hand, are also connected to three input terminals of the three-/two-phase 
converter 222, respectively. The two output terminals of the 
three-/two-phase converter 222 are connected to the secondary magnetic 
flux estimator 224. The output terminals of the secondary magnetic flux 
estimator 224 are connected also to the angular velocity estimator 226 and 
the output torque estimator 250. The output terminal of the angular 
velocity estimator 226 is connected to the other input terminal of the 
angular velocity controller 150. The output terminal of the output torque 
estimator 250 is connected to the input terminal of an unbalanced amount 
estimator 403. 
The operation of the washing machine configured as described above will be 
described with reference to FIG. 14. According to this embodiment, like in 
the eighth embodiment, the rotatable drum 104 is rotated through the 
transmission mechanism 106 by the three-phase induction motor 100 to wash 
the laundry. The operation of the angular velocity controller 150, the 
current controller 122, the PWM invertor 124, the converter 130, the 
angular velocity estimator 200 and the output torque estimator 250 is the 
same as that of the corresponding component parts of the eighth 
embodiment, and therefore will not be described again. 
Mainly at the time of dewatering, the laundry attaches closely to the inner 
surface of the rotatable drum 104 due to the centrifugal force. First, 
explanation will be given of the unbalanced state caused by the uneven 
distribution of laundry closely attached so. FIG. 15 is a front view of 
the rotatable drum 104. As shown in FIG. 15, when the laundry 104A 
unevenly, closely attaches to the inner surface of the rotatable drum 104, 
the centrifugal force due to and the gravity of the laundry 104A are 
exerted on the rotatable drum 104. Especially, the centrifugal force 
increase with the rotational angular velocity of the rotatable drum 104 to 
such an extent as to cause a great vibration. Therefore, it is necessary 
to detect an unbalanced state before the rotational angular velocity 
increases after the rotatable drum 104 starts rotating at the time of 
dewatering or the like. Assuming that the clockwise rotation of the 
rotatable drum 104, i.e. the three-phase induction motor is the forward 
direction, and that the position of the unevenly distributed laundry 104A 
in the rotatable drum 104 is represented by an angle .phi., the equation 
of motion is given by equation (30). 
##EQU20## 
where J is the moment of inertia of the rotatable drum 104, J.sub.L is the 
moment of inertia of the laundry 104A, m is the unbalanced amount 
expressed in terms of mass of the unevenly distributed laundry 104A, g is 
the acceleration of gravity, R is the radius of the rotatable drum, 
d.sub.2 is the disturbance such as friction, and r is the reduction ratio 
between the rotary shaft of the three-phase induction motor and the rotary 
shaft of the rotatable drum. When the command angular velocity generator 
401 issues a predetermined command rotational angular velocity equal to or 
more than the rotational angular velocity at which the laundry 104A 
closely attaches to the inner surface of the rotatable drum 104 under the 
centrifugal force, the output torque generated by the three-phase 
induction motor changes as shown in FIG. 16. In the process, the variation 
range .DELTA..tau. of the difference between maximum torque and minimum 
torque generated by the three-phase induction motor is derived. 
Consequently, in equation (30), the terms of moment of inertia and 
disturbances are deleted, and the following equation (31) becomes 
effective. 
EQU .DELTA..tau.=2.multidot.mg.multidot.R.multidot.r (31) 
An example of relation between the unbalanced amount and a variation amount 
of torque is shown in FIG. 17. FIG. 17 shows that the unbalanced amount 
can be easily estimated from the variation amount of torque. In this way, 
the output torque .tau. of the three-phase induction motor can be 
estimated by the output torque estimator 250, while the three-phase 
induction motor is rotating at a predetermined rotational angular velocity 
following the command angular velocity .omega..sub.m * specified by the 
command angular velocity generator 401. Next, the difference between 
maximum torque and minimum torque constituting the output of the output 
torque estimator 250 is taken by the unbalanced amount estimator 403. By 
thus using the relation of FIG. 17, the unbalanced amount can be easily 
and accurately determined. 
In this way, the unbalanced amount can be measured before dewatering the 
laundry. In the case where the unbalanced amount increases beyond a 
predetermined amount, the dewatering operation can be suspended and 
resumed. Therefore, a large vibration can be prevented. 
In the case where the exciting current component and the torque current 
component are commanded independently of each other by use of the 
three-phase induction motor as in this embodiment, the amount of laundry 
can be estimated from the torque current component such as the command 
torque current I.sub.1q * without using the output torque estimator 250 
for estimating the output torque of the three-phase induction motor. 
Also, in conducting the estimation operation, the rotational angular 
velocity of the rotatable drum 104 is preferably selected to an angular 
velocity higher than the rotational angular velocity at which laundry 
attaches closely to the rotatable drum due to the centrifugal force, and 
lower than the rotational angular velocity at which the rotatable drum 
develops the primary resonance. This rotational angular velocity, though 
dependent on the structure of the washing machine, is 70 to 300 
revolutions per minute for the normal rotatable drum 104. 
In the above-mentioned configuration, when the estimated unbalanced amount 
is larger than a predetermined value, the dewatering operation is 
suspended and the whole operation restarted. In this way, large vibrations 
can be prevented. 
Now, explanation will be given below of a washing machine having the 
function of preventing the rotatable drum from easily losing the balance 
as an 11th embodiment of the invention. 
11th Embodiment 
A washing machine according to an 11th embodiment of the invention will be 
explained with reference to FIG. 18. FIG. 18 is a block diagram showing a 
configuration of a washing machine according to the 11th embodiment of the 
invention. 
In FIG. 18, the three-phase induction motor 100 is coupled through the 
transmission mechanism 106 to the rotatable drum 104 for washing, 
dewatering and drying the laundry. The output terminal of the command 
angular velocity generator 401 for outputting the command rotational 
angular velocity .omega..sub.m * is connected to one of the input 
terminals of the adder 501. The output terminal of the adder 501 is 
connected to one of the input terminals of the angular velocity controller 
150. The three output terminals of the angular velocity controller 150 are 
connected to the three input terminals, respectively, of the current 
controller 122. The three output terminals of the current controller 122 
are connected to the three input terminals of the PWM invertor 124, 
respectively, and the three output terminals of the PWM invertor 124 are 
connected to the three-phase induction motor 100. The two input terminals 
of the PWM invertor 124 are connected to an AC power supply through the 
converter 130. 
The three connection lines between the PWM invertor 124 and the three-phase 
induction motor 100 are provided with the current detectors 126a, 126b, 
126c, respectively. The output terminals of these current detectors 126a, 
126b, 126c are connected to the current controller 122. The output 
terminals of the current detectors 126a, 126b, 126c are connected also to 
the three input terminals of the three-/two-phase converter 220, 
respectively. The two output terminals of the three-/two-phase converter 
220 are connected to the secondary magnetic flux estimator 224 on the one 
hand and to the angular velocity estimator 226 and the output torque 
estimator 250 on the other hand. 
The three output terminals of the current controller 122 are also connected 
to the three input terminals of the three-/two-phase converter 222, 
respectively. The two output terminals of the three-/two-phase converter 
222 are connected to the secondary magnetic flux estimator 224. The output 
terminals of the secondary magnetic flux estimator 224 are connected to 
the input terminals of the angular velocity estimator 226 and the output 
torque estimator 250. The output terminal of the angular velocity 
estimator 226 is connected to the other input terminal of the angular 
velocity controller 150. The output terminal of the output torque 
estimator 250 is connected to the input terminals of an unbalanced amount 
estimator 403 and an unbalanced position estimator 503. The output 
terminals of the unbalanced amount estimator 403 and the unbalanced 
position estimator 503 are connected to two input terminals of a 
rotational angular velocity changer 505, respectively. The output terminal 
of the rotational angular velocity changer 505 is connected to the input 
terminal of the adder 501. 
The operation of a washing machine configured as described above will be 
explained with reference to FIG. 18. According to this embodiment, too, 
like in the eighth embodiment, the rotatable drum 104 is rotated through 
the transmission mechanism 106 by the three-phase induction motor 100 
thereby to wash the laundry. The operation of the angular velocity 
controller 150, the current controller 122, the PWM invertor 124, the 
converter 130, the angular velocity estimator 200 and the output torque 
estimator 250 is the same as that of the corresponding component parts of 
the eighth embodiment. The operation of the unbalanced amount estimator 
403 is the same as that of the corresponding component part of the tenth 
embodiment. 
According to the 11th embodiment, it is possible to detect the position of 
the laundry distributed unevenly by utilizing the method of measuring the 
magnitude of the unbalanced amount. First, explanation will be made about 
the operation of the unbalanced position estimator 503 for detecting the 
unbalanced position. 
In FIG. 15, the torque of the three-phase induction motor for rotating the 
rotatable drum 104 in the unbalanced state assumes a maximum value at an 
angle .phi. of 270 degrees and a minimum value at an angle .phi. of 90 
degrees in the drawing. It is therefore possible to detect the position 
where the laundry 104A closely attaches in the rotatable drum 104 from the 
maximum or minimum value of the output torque estimated by the output 
torque estimator 250. This makes it possible to improve the unbalanced 
state by dropping or displacing the laundry 104A closely attached to the 
inner surface of the rotatable drum 104 by suddenly changing the 
rotational angular velocity of the three-phase induction motor in 
accordance with the detected position. 
As an example, when the unbalanced position estimator 503 shows that the 
laundry 104A causing an unbalance is located at the upper portion 104B of 
the rotatable drum 104, i.e. the angle .phi. reaches the neighborhood of 
zero in FIG. 15, an angular velocity correction value is output from the 
rotational angular velocity corrector 505 thereby to decelerate the 
angular velocity of the rotatable drum 104. As a result of deceleration, 
when the gravity exceeds the centrifugal force exerted on the laundry 
104A, the laundry 104A comes off from the inner surface of the rotatable 
drum 104 and the unbalanced state is obviated. 
Another possible method is to suddenly increase or decrease the rotational 
angular velocity of the rotatable drum 104 and to displace the laundry 
104A by taking advantage of the energy of inertia. In this case, too, the 
position of laundry 104A closely attached unevenly to the inner surface of 
the rotatable drum 104 can be effectively displaced to correct the 
unbalanced state taking the relation between the position and gravity of 
the laundry 104A in unbalanced state into account. 
As described above, in the case where the unbalanced amount is larger than 
a predetermined value, the likelihood of an unbalanced state occurring 
again is considerably reduced by resuming the dewatering operation 
suspended to obviate the unbalanced state. This correcting operation is 
preferably performed in the neighborhood of a lowest rotational angular 
velocity at which the laundry 104A closely attaches to the inner surface 
of the rotatable drum 104 due to the centrifugal force in order to 
minimize the effect of the centrifugal force. 
12th Embodiment 
As a 12th embodiment of the invention, a washing machine having a rotatable 
drum which does not develop into the unbalanced state will be explained 
with reference to FIG. 19. FIG. 19 is a front view of a rotatable drum 204 
for explaining the operation of a washing machine according to the 12th 
embodiment of the invention. In FIG. 19, the rotatable drum 204 for 
washing, dewatering and drying the laundry has a plurality of protrusions 
550 for catching the laundry to be washed on an inner wall thereof. 
The operation of the washing machine having the above-mentioned 
configuration will be explained hereafter. In the washing machine having 
the rotatable drum 204 rotating about a substantially horizontal axis 204, 
the rotatable drum 204 is rotated in the direction of arrow for washing 
the laundry so as to hoist the laundry with the protrusions 550 and drop 
them at the next moment. At the time of dewatering, in order to avoid the 
unbalanced state of the rotatable drum 204 due to the uneven distribution 
of laundry, the laundry preferably attaches closely to the inner surface 
of the rotatable drum 204 uniformly by centrifugal force. 
As shown in FIG. 19, each protrusion 550 has a hook 570 configured 
rotationally asymmetric about a virtual plane 560 passing the protrusions 
550 and the rotational axis 204C. At the time of washing, the rotatable 
drum 104 is rotated in the direction of arrow in FIG. 19, so that the 
laundry thus hoisted by the hooks 570 of the protrusions 550 and are 
dropped from above. At the time of dewatering, on the other hand, a 
command rotational angular velocity of a negative value is output from the 
command angular velocity generator 401 of FIG. 18, for example, thereby to 
rotate the rotatable drum 204 in the direction opposite to the arrow. 
Then, the laundry is scarcely caught by the hooks 570 at the time of 
dewatering, and therefore, the rotatable drum 204 is not easily 
unbalanced. 
The above-described configuration makes it possible to realize a washing 
machine of which the rotatable drum 204 rarely becomes unbalanced. 
In view of this, a washing machine having the function of correcting the 
unbalanced state will be explained below as a 13th embodiment. 
13th Embodiment 
A washing machine according to the 13th embodiment of the present invention 
will be explained with reference to FIG. 20. FIG. 20 is a front view of a 
rotatable drum 334 of a washing machine according to the 13th embodiment. 
In FIG. 20, for example, 16 tanks 600 to 615 which can be filled with 
water are arranged around the rotatable drum 334 for washing, dewatering 
and drying the laundry. These tanks 600 to 615 rotate together with the 
rotatable drum 334. 
FIG. 21 is a block diagram showing a configuration of the washing machine 
according to the 13th embodiment. In FIG. 21, the output terminals of an 
unbalanced amount estimator 403 and an unbalanced position estimator 503 
are connected to two input terminals of the unbalanced amount corrector 
602, respectively. The output terminal of the unbalanced amount corrector 
602 is connected to switches 800 to 815 of electromagnets for selectively 
activating doors 700 to 715 for opening/closing the openings of the tanks 
600 to 615 by extending or retracting the movable pins (not shown) 
arranged radially outward of each door in parallel to a rotary shaft. 
The operation of the washing machine having the above-mentioned 
configuration will be explained with reference to FIGS. 20 to 21. First, 
all the tanks 600 to 615 are filled with water in advance. The rotatable 
drum 334 is rotated, and the unbalanced amount estimator 403 estimates the 
unbalanced amount of the rotatable drum 334 due to the uneven distribution 
of the laundry in the same manner as in the tenth embodiment. Further, the 
unbalanced position estimator 503 estimates the unbalanced position of the 
laundry in the rotatable drum 334 in the same manner as in the 11th 
embodiment. The unbalanced amount corrector 602 controls the switch 811 in 
such a manner as to open the door 711 of the tank 611 in the vicinity of 
the position of the unevenly distributed laundry 104A estimated by the 
unbalanced position estimator 503. As the door 711 opens, water is 
discharged from the tank 61 in accordance with the unbalanced amount 
estimated by the unbalanced amount estimator 403. As a result, the 
unbalanced state of the rotatable drum 334 due to the uneven distribution 
of the laundry 104A can be corrected and the dewatering operation becomes 
possible without causing a large vibration. 
In order to reduce the moment of inertia by reducing the weight of the 
rotatable drum 334, water is preferably left only in the tank 603 located 
symmetrically with respect to the unevenly distributed laundry 104A about 
the rotational center of the rotatable drum 334. In this case, water is 
discharged from the other tanks 600 to 602, 604 to 615 to correct the 
unbalance. The unbalanced state of the rotatable drum 334 can be easily 
corrected by this process. 
Each of the above-mentioned embodiments concerns a configuration using a 
three-phase induction motor. The motor for driving the rotatable drum, 
however, is not limited to such a configuration but other systems can also 
be employed. This invention of course is applicable with equal effect 
especially to a DC motor or a brushless motor of which the torque 
generated can be easily estimated. 
Although the present invention has been described in terms of the presently 
preferred embodiments, it is to be understood that such disclosure is not 
to be interpreted as limiting. Various alterations and modifications will 
no doubt become apparent to those skilled in the art to which the present 
invention pertains, after having read the above disclosure. Accordingly, 
it is intended that the appended claims be interpreted as covering all 
alterations and modifications as fall within the true spirit and scope of 
the invention.