ES2203002T3 - METHOD FOR DETERMINING TOTAL LOAD AND UNBALANCED LOAD IN A DRYER DRUM OF A WASHER. - Google Patents

Abstract

A method for determining unbalanced load and load in a washing machine that has a motor drive system to rotate the engine at an objective speed, characterized in that the motor drive system is provided with an auxiliary signal having a predetermined frequency spectrum and because the total load and the unbalanced load are determined by frequency spectrum analysis at different frequencies.

Description

Method to determine the total load and load unbalanced in a dryer drum of a washing machine.

The present invention relates to a method for determine the total load and unbalanced load in a washing machine which has a motor drive system to rotate the engine at a desired target speed. With the term washing machine We understand all types of devices that have a rotating drum whose speed can reach at least a value at which the clothes dirty sticks by centrifugal force against the side wall of drum. Washers / dryers are included in the term previous general.

The technical problem of determining the amount of dirty clothes loaded in a drum of a washing machine is well known in The technique. The known technical solutions are based on the amount of water absorbed by dry dirty clothes, the weather necessary to reach a predetermined target speed of drum or the current absorbed by the motor, EP-A-0143685 describes a method for determine the mass of dirty clothes from a torque measurement motor to drive the drum during an acceleration phase in constant acceleration This document does not teach how to calculate if the load is unbalanced or how much it is unbalanced (i.e. not evenly distributed on the side wall of the drum).

EP-A-71308 describes a method to calculate if there is a distribution unbalanced dirty clothes around the drum, with a tachometer monitoring the actual engine speed of the washing machine (if engine speed changes more than one quantity default, this means that dirty clothes are unbalanced).

The two previous methods do not solve the problem of detecting load and unbalanced load, and a machine that just using the two previous methods in combination would be too expensive since you would need an electronic device to detect the torque and an electronic device to detect the motor speed variation.

In US-A-5507054 a method is described that determines the load by stopping the system of motor drive and measuring the time needed to reach a predetermined lower speed. This document describes also an assessment of unbalanced load detecting the drum speed fluctuation, according to the previous EP-A-71308. Such valuations are carried out subsequently, therefore the duration of the cycle Washing is increased. In addition the different physical entities measured by the electronic circuit (speed fluctuation, time to reach a predetermined speed) make this one Ultimately quite expensive and complex, decreasing its reliability.

It is an objective of the present invention to avoid drawbacks mentioned above, providing a method and a control system that is cheap, reliable and that can lead to Perform both calculations in a very short time.

In addition, EP 0 903 845 describes a method and a washing machine according to the preamble of the claims 1 and 8, respectively.

According to a general aspect of the invention, providing a known signal that has a pattern or spectrum of default frequency added to the periodic control signal normal at constant speed (to keep the drum in the target speed), the system motor-drum-dirty clothes is excited so that by analyzing the speed feedback signal (for example by analyzing its frequency spectrum) is possible to calculate the total inertia (and therefore the mass of clothes dirty) and at the same time the unbalanced condition of the system. According to one aspect of the invention, a motor drive system that is equipped with a signal auxiliary that has a predetermined frequency spectrum, being determined the load and the unbalanced load by means of a frequency spectrum analysis at different frequencies.

Preferably, the auxiliary signal is a signal. periodic that has a different frequency than the frequency that corresponds to the engine's target speed. More preferably, the unbalanced load and the total load are determined by frequency spectrum analysis at a frequency that corresponds to the target speed and at a frequency that corresponds to said auxiliary signal respectively.

The main advantage of the method according to the present invention is that the detection of any condition of out of balance of the drum (and therefore its degree) and of the amount of dirty clothes in the drum both are obtained in a while very short "injecting" into the motor drive system the previous auxiliary signal and using the same spectrum analysis of frequency on two different frequencies.

Another advantage of the present invention is that provides a method to compensate the load friction of so that the selection of the inertia / mass of the load and of the speed of rotation, based on the moment of inertia loading and unbalanced load, are more accurate than with methods known.

The present method can be used to determine the inertia / mass of the dry load or wet load indifferently. The present method can be used to determine the burden of inertia / mass and the amount of unbalanced load that helps the Spin speed selection.

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Dynamic friction is caused by different components, for example the friction of the transmission system, the friction of ball bearings and, for shaft washers horizontal, friction of dirty clothes against the front door. In accordance with the present invention, use a search table of Data or Blurred Neural Logic system can compensate for Data derivation of frequency spectrum analysis. Such data search table or Blurred Neural Logic system is  determined by each type of washing machine as a result of tests experimental carried out in the washing machine with values Default total friction. From the compensated data from the frequency spectrum analysis, the compensated values of total load and unbalanced load, not such values being affected by dynamic friction.

An embodiment of the invention will now be described. with reference to the attached drawings, in which:

Figure 1 is a schematic mechanical model of the washing-machine;

Figure 2 is a block diagram of the system of control used in accordance with the present invention;

Figures 3a, 3b, 3c are diagrams of the frequency response of the system used in the agreement method with the present invention;

Figures 4a and 4b are parts of the organization chart of the control program used in the method according to the present invention;

Figures 5a and 5b are schematic diagrams. which show the correlation between frequency responses, frequency compensated responses and dynamic friction; Y

Figure 6 is an example of a logic control blurred for the inertia and imbalance detection system of according to the present invention.

Detailed description of a preferred embodiment

The method according to the invention is used for determine the inertia / mass and the unbalanced load of the clothes in a rotating drum for washer and dryer as well as for washer / dryer, and this can compensate, if desired, friction dynamics of the drum rotation system.

With reference to Figure 1 a Mechanical representation of a washer / dryer.

Motor M provides torque T m to the drum; motor rotation speed is transmitted to the drum through of a motion transmission system (not shown) and the speed is maintained / adjusted by a control system speed of known type (not shown). From now on we we will refer to the simple system shown in Figure 1, without considering The specific motor controller counts. According to the second law of dynamics, applied to the axis of the motor system, is you can say that a total torque equal to the sum of the torque is provided of inertia and friction torque

T = J \ text {*} \ frac {d \ omega} {dt} + \ gamma \ text {*} \ omega

where:

J is the total inertia applied to the drive shaft that includes drum and load torque,

γ is the coefficient of friction viscose,

T is the total torque given by the difference between the drive torque T_ {m} and resistant torque T_ {f},

\ omega is the speed of rotation of the drum in radians / second.

The Laplace transform allows the passage of time domain to frequency domain and equation Previous can be written as follows:

T (s) = s \ text {*} J \ text {*} \ Omega (s) + \ gamma \ text {*} \ Omega (s)

where s = j \ omega is the variable complex.

The transfer function between the total torque and The angular velocity of the drum is:

\ frac {\ Omega (s)} {T (s)} = \ frac {\ frac {1} {\ gamma}} {1 + s \ frac {J} {\ gamma}}

in which the gain G = is evidenced \ frac {1} {\ gamma} and the time constant \ tau = \ frac {J} {\ gamma} or the frequency pole \ overline {\ omega} = \ frac {\ gamma} {J}.

An additional step can be taken considering the torque proportional to the input signal of the system motor drive α_ {s} such as: T (s) = K_ {m} \ text {*} \ alpha_ {s} (s). The previous equation can be write as the following in which, simplifying, we assume K_ {m} = 1:

\ frac {\ Omega (s)} {\ alpha (s)} = H (s) = \ frac {\ frac {1} {\ gamma}} {1 + s \ frac {J} {\ gamma}}

If the load of clothes, during its revolutions of drum, not well distributed, an unbalanced load, with mass M_ {u} will generate a speed fluctuation that has a amplitude proportional to the M_ {u}.

If we call β the angle between the axis of imbalance and one set reference, you have to add a new torque term in the torque equilibrium equation. This pair It is due to the force of gravity g and its value is given by:

M_ {u} gr \ cos (β)

where r represents the distance between the center of gravity of the unbalanced load and the axis of rotation.

This additional pair can be taken into account a very simple way considering its effect when added to the speed that would be obtained if M_ {u} were zero. Using this reasoning, the angular velocity \ omega (t) measured becomes be:

\ omega (t) = \ omega_ {0} + M_ {u} gr | H (j \ omega_ {0}) | cos (\ omega_ {0} t)

where \ omega_ {0} is the system output obtained under the same unbalanced load conditions and | H (j \ omega_ {0}) | is the function module of H (s) transfer computed at the frequency \ omega_ {0}, to to know:

| H (j \ omega_ {0}) | = \ frac {\ frac {1} {\ gamma}} {\ sqrt {1 + \ frac {\ omega2 {0} J2} {\ gamma2}}}

The frequency spectrum of this function is shown in Figure 3a for a given value of the γ coefficient of friction (1 Nm s / rad) and for some values of moments of inertia J (0.4 and 0.8). As you can see, the amplitude of the spectrum frequency, computed at the frequency \ omega_ {0} depends on three variables: unbalanced load U, moment of inertia J and dynamic friction γ. In particular, the higher the inertia, the smaller the amplitude of the frequency spectrum.

In Figure 3b (where γ = 2 Nm s / rad), the great influence that friction has on the System under analysis.

In short, if there is an unbalanced load, the speed signal contains fluctuations whose amplitude is related to the unbalanced weight, the total inertia of the system and dynamic friction coefficient.

The applicant discovered that the problem of calculate the amount of imbalance and total inertia will solves in a surprisingly simple way by injecting into the system, as shown in Figure 2, a periodic signal with a known frequency \ omega_ {inj} (for example through a cosine wave signal) and analyzing the frequency spectrum of the controlled variable.

In Figure 2 the controlled system is considered complete instead of the open loop system shown schematically in Figure 1. All considerations made previously they can be repeated in the same way using, instead of the transfer function H (s) in open loop, that of loop closed H_ {c} (s) that depends on the actual control law of the speed control system. It should be noted that the Proposed approach works well whatever the type of controller since it is based on mechanical properties Structural system. Also, to simplify the explanation, we consider the target speed \ omega_ {t} constant whose value has to be above the speed at which clothes dirty sticks by centrifugal force against the side wall of drum.

With reference to Figure 2, the system of motor drive is energized by two components of speed, whose analytical value is given by:

\ alpha_ {s} = \ alpha_ {c} + A \ text {*} cos (2 \ pi \ t \ omega_ {inj})

Correspondingly, the measured speed is can divide into two different parts \ omega_ {t} and \ omega_ {inj}, so that the output \ omega is the speed resulting from the sum of the two component effects of the drives.

The first (\ alpha_ {c}) is determined by the error rate information and is triggered by the action of the speed controller. In case of balanced load, the term J * \ frac {d \ omega} {dt} is zero, and the torque provided by The engine is the one required to compensate for dynamic friction. In case of unbalanced loads, as shown before, the torque it has to be able to compensate the force of gravity of the load unbalanced during its spin phase and maintaining speed medium objective By doing this, a fluctuation of speed with an amplitude that depends on the imbalance itself. The speed fluctuation signal is generally used to evaluate the amount of imbalance but, due to the fact that if the inertial load increases the amplitude of the speed fluctuation decreases, known methods provide estimates approximate of the actual unbalanced load. The consequence with such known methods is that the turning speed is reduced to Avoid dangerous conditions. With the method according to the In the present invention, it is possible to calculate the actual value of the load unbalanced, thus allowing higher turning speeds if compared to known methods and systems, without any risk of mechanical failure of the washing machine.

The second component (\ omega_ {inj}) has the mission of "stressing" the system to emphasize the effect of load of inertia According to the invention, it is proposed and used the frequency spectrum analysis of the engine speed of so that, by means of two frequency components \ omega_ {t} and \ omega_ {inj}, the load of inertia (load total) and the unbalanced load are uniquely identified. While it is difficult to solve this issue mathematically in the time domain is, on the contrary, easily solvable in the frequency domain. Using the Laplace transform, you You can write the following equation:

\ Omega (s) = H_ {c} (s) \ \ text {*} \ \ alpha (s) = H_ {c} (s) \ \ text {*} \ (\ alpha_ {u} (s) + \ alpha_ {inj} (s))

Due to the frequency response theorem, the system steady state response to an input sine wave is a sine wave with the same frequency (as the wave of input) but with different amplitude and offset \ varphi. We can calculate the system output obtained after transitory as:

\ omega (t) = \ omega_ {t} + M_ {u} gr \ \ text {*} \ | H_ {c} (j \ omega_ {t}) | cos (\ omega_ {1} t) + A \ \ text {*} \ | H_ {c} (j \ omega_ {inj}) | cos (\ omega_ {inj} t + \ varphi)

The frequency response behavior, shown in Figure 3c (where γ = 1 Nm s / rad), explains how the system reacts in different loads of inertia. It is still very clear that the greater the inertia the greater the damping effect on speed fluctuations by looking at modules | H_ {c} (j \ omegat) | Y | H_ {c} (j \ omega_ {inj} t) | of the transfer function (see arrows at the target speed of 100 rpm, that is 1.66 Hz, in Figure 3c).

The previous equation can be written as follow:

\ omega (t) = \ omega_t + Au \ \ text {*} \ cos (\ omega_ {t} \ cdot t) + As \ \ text {*} \ cos (\ omega_ {inj} \ cdot t + \ varphi)

where the terms Au and As represent the transfer function modules (multiplied by constants M_ {u} gr and constants A) at frequencies \ omega_ {t} and \ omega_ {inj} respectively.

Each term can be computed as follows:

 (one) Au = \ frac {1} {NSamp} \ sqrt {\ left (\ sum \ limits_ {k = 1} ^ {Nsamp} \ overline {\ omega} \ \ text {*} \ cos (\ omega_ {t} \ cdot k \ cdot \ Delta t) \ right) ^ {2} + \ left (\ sum \ limits_ {k = 1} ^ {Nsamp} \ overline {\ omega} \ \ text {*} \ sen (\ omega_ {t} \ cdot k \ cdot \ Delta t) \ right) 2

 (two) As = \ frac {1} {NSamp} \ sqrt {\ left (\ sum \ limits_ {k = 1} ^ {Nsamp} \ overline {\ omega} \ \ text {*} \ cos (\ omega_ {inj} \ cdot k \ cdot \ Delta t) \ right) ^ {2} + \ left (\ sum \ limits_ {k = 1} ^ {Nsamp} \ overline {\ omega} \ \ text {*} \ sen (\ omega_ {inj} \ cdot k \ cdot \ Delta t) \ right) 2

where NSamp is the number of sampled data and \ overline {\ omega} = \ omega (\ upbar { T } + k \ Delta t ) where \ upbar { T } is the initial sampling time.

The injected signal type cos (\ omega_ {inj} t) has been selected only as a example and also with a view to its simple implementation, but the described method can be adopted with any type of signal injected (periodic or not) with a frequency spectrum known.

The load of inertia and the unbalanced load are they can now compute on the basis of these two values Au and As.

Experimental tests, made with different inertia and unbalanced loads allow implementation, in a micro controller, of a Neuronal Blurred Logic system. Alternatively, a table of search, in which, from the combination of the answer Au and As of the system, the inertia value and the imbalance.

As mentioned before, the method according to The present invention allows to compensate the friction in a way simple.

The following embodiment is based on the average of the output value of the speed control. Once it is designed speed control, ie PID parameters, (terms Proportional, Integral and Differential of the speed error respectively), a friction simulation can be done dynamic, mainly caused by the load plus the system speed transmission, through a controlled braking system. When a constant value of inertia is set, the value provided by the speed control system \ alpha_ {c} or differently \ alpha_ {s}, in state condition stationary, is proportional to friction. The estimate of such variable is thus computed by evaluating the mean of α_ {s}:

(Alpha_ {Medium}) (3) \ alpha_ {sMedia} = \ frac {1} {Nsamp} \ sum \ limits_ {k = 1} Nsamp} \ alpha_ {s} (k \ cdot \ Delta t)

At this point all the variables are known, the Amount of Inertia Load and Unbalanced Load can be estimate following the procedure scheme:

- Compute the Alpha_ {Medium}

- Compensate for As ^ {\ text {*}} = f TI ( As, Middle Alpha ) by compensating the term As.

- Compute the Unbalanced Load, Load Inertial = f_ {UL} Au, As ^ {\ text {*}} based on the As and Au values compensated

f_ {TI} and f_ {UL} are the search table for data or a system of Neuronal Blurred Logic, resulting from the experimental tests done.

Qualitative and simplified examples are shown of functions f_ {TI} and f_ {UL} in Figures 5a and 5b. The figure 5th shows the general correlation between the values of Alpha_ {Medium} and the offset values of As (ie As ^ {\ text {*}}), based on different curves of As and k. One time that As ^ {\ text {*}} has been determined from the diagram of the Figure 5a, such value is used in the diagram of Figure 5b, based in different curves of Au values, to determine the value offset of Au. It is clear that the diagrams in figures 5a and 5b are experimental diagrams determined for each type of washing machine for different known dynamic friction values. The data search table, the Fuzzy Logic system Neuronal or correlation diagrams can be stored advantageously in the central processing unit (microprocessor) that Control the washing machine.

The relationship found to compensate for the term As (shown in Figure 5a) has the following expression general:

As ^ {\ text {*}} = As \ left [1 + \ frac {k - Alpha_ {Medium}} {Alpha_ {Medium}} \ right]

where k depends on the characteristics of the engine and tough system torque mechanical.

An organization chart is shown in Figures 4a and 4b of the control algorithm. In Figure 4a the first block 10 is the initial phase in which the sample counter is reset. When the number of samples is equal to or greater than a predetermined number, then in Figure 4b blocks 12 and 14 compute the answer in frequency to calculate the total load and unbalanced load respectively. The values computed in blocks 12 and 14 feed block 16, together with the average Alpha value, indicative of dynamic friction, to compensate for this later. The values compensated for inertia load (total load) and load unbalanced are the output of the control algorithm and such values can be used by the central processing unit of the washing machine for different purposes, for example to set spin speeds or to set the amount of Clean water to use during rinsing.

Figure 6 shows a scheme of fuzzy rules taken in case of a blurred control solution. The rules blurred are of the following type

Rule 1 If As ^ {\ text {*}} is L and Au is M then J is H and U is H Ruler two If As ^ {\ text {*}} is M and Au is L then J is M and U is VL Rule 3 If As ^ {\ text {*}} is H and Au is VH then J is VL and U is H

Etc.

Claims (10)

1. A method for determining unbalanced load and load in a washing machine that has a motor drive system to rotate the engine at an objective speed, characterized in that the motor drive system is provided with an auxiliary signal having a frequency spectrum predetermined and because the total load and the unbalanced load are determined by frequency spectrum analysis at different frequencies. 2. A method according to claim 1, characterized in that said auxiliary signal is a periodic signal having a frequency different from the frequency corresponding to the target speed. 3. A method according to claim 2, characterized in that the total load and the unbalanced load are determined by analysis of the frequency spectrum at a frequency corresponding to said auxiliary signal and at a frequency corresponding to the target speed respectively. 4. A method according to any of the preceding claims, characterized in that it comprises compensation of total load and unbalanced load values taking into account dynamic friction, such compensation being based on experimental tests made on different and predetermined dynamic friction values. 5. A method according to claim 4, characterized in that said compensation is carried out by means of a data search table or a fuzzy logic system. 6. A method according to any of the preceding claims, characterized in that said frequency spectrum analysis is carried out by means of the Laplace transform. A method according to claim 6, characterized in that the module of the transfer function H (s) computed in the frequency \ 0 is of the following type: | H (j \ omega_ {0}) | = \ frac {\ frac {1} {\ gamma}} {\ sqrt {1 + \ frac {\ omega2 {0} J2} {\ gamma2}}} where: j \ omega_ {0} is the complex variable, γ is the coefficient of friction and J is the moment of inertia. 8. A washing machine comprising an electronic control system that includes a motor drive system for rotating the engine at a target speed, and a rotating drum driven by the engine through a transmission system, characterized in that the control system The electronic control system is capable of supplying the motor drive system with an auxiliary signal that has a predetermined frequency spectrum, the electronic control system being able to determine the total load and the unbalanced load by analyzing the frequency spectrum at different frequencies . 9. A washing machine according to claim 8, characterized in that the electronic control system is capable of supplying the motor drive system with a periodic signal having a frequency different from the frequency corresponding to the target motor speed. 10. A washing machine according to claim 9, characterized in that the electronic control system is capable of determining the total load and the unbalanced load by analyzing the frequency spectrum at a frequency corresponding to said auxiliary signal and at a corresponding frequency at the target speed respectively.