Electronic control for an automatic washing machine with a reversing PSC motor

Claims

What is claimed and desired to be secured by Letters Patent is:

1. A control system for an automatic washing machine having an agitation means and a motor with a first winding, said motor being coupled to said agitation means for drive said agitation means, said control system comprising:

means for cyclnig said motor off;

means for sensing the residual alternating current in said motor when said motor is cycled off and for providing a representation thereof; and

means for controlling the operation of said washing machine in response to said residual current representation, wherein said control means automatically controls the level of water in said washing machine in response to the duration of said residual current representation such that the smaller said duration representation, the higher said water level.

2. The control system of claim 1 including means responsive to the duration of said residual current representation for detecting an overload condition in said washing machine.

3. The control system of claim 1 including means for determining whether or not to cause said motor to agitate while increasing said water level.

4. The control system of claim 1 including means for summing the durations of said residual current representations over a predetermined number of agitator strokes to provide a representation of said sum, said water level control means controlling said water level such that the smaller said sum representation, the higher said water level.

5. The control system of claim 4 including means responsive to said sum representation for detecting an overload condition in said washing machine.

6. The control system of claim 1 wherein said motor is a permanent split capacitor motor wherein said means for sensing the residual alternating current comprises:

means for sensing zero crossings of alternating current in a motor winding when said motor is cycled off to provide a signal representative thereof; and

means for counting the number of sensed zero crossings to provide a sum, said sum being inversely related to the braking force on said motor.

7. The control system of claim 6 wherein said control means automatically controls the level of water in said washing machine in response to said sum representation such that the smaller said sum representation, the higher said water level.

8. The control system of claim 7 including means responsive to said sum representation for detecting an overload condition in said washing machine.

9. The control system of claim 7 including means for determining whether or not to cause said motor to agitate while increasing said water level.

10. The control system of claim 7 including means for adding said sum representations over a predetermined number of motor strokes to provide a total representation, said water level control means controlling said water level such that the smaller said total representation, the higher said water level.

11. The control system of claim 10 including means responsive to said total representation for detecting an overload condition in said washing machine.

12. The control system of claim 7 including means responsive to said sum representation for detecting an overload condition in said washing machine.

13. The control system of claim 6 wherein said control means includes means for controlling the stroke angle of said agitation means in response to said sum representation wherein the smaller said sum representation, the greater said stroke angle.

14. The control system of claim 6 wherein said washing machine includes means actuable by a user for selecting a cycle and providing a representation of said cycle selection, and wherein said control means includes means for controlling the stroke angle of said agitator in response to said sum representation and said cycle selection.

15. The control system of claim 6 wherein said control means is responsive to said sum representation to determine the duration of an agitation operation of said washing machine.

16. The control system of claim 1 wherein said control means includes means for controlling the stroke angle of said agitator in response to said residual current duration representation wherein the smaller said duration representation, the greater said stroke angle.

17. The control system of claim 1 wherein said washing machine includes means actuable by a user for selecting a cycle to provide a representation of said cycle selection and said control means includes means for controlling the stroke angle of said agitator in response to said residual current duration representation and said cycle selection representation.

18. The control system of claim 1 wherein said control means is responsive to said residual current duration representation to determine the size of the load in said washing machine during a water fill operation, an agitation operation, or a rinse operation.

19. The control system of claim 1 wherein said control means is responsive to said residual current duration representation to determine the duration of an agitation operation of said washing machine.

20. The control system of claim 19 wherein said washing machine includes means actuable by a user for selecting a cycle and providing a representation thereof, and wherein said duration determining means is further responsive to said cycle selection representation to determine said duration.

21. The control system of claim 20 wherein said washing machine includes means actuable by a user for selecting a temperature and providing a representation thereof, wherein said duration determining means is further responsive to said temperature selection representation to determine said duration.

22. An automatic washing machine comprising:

agitation means for agitating a load;

a reversible motor with first and second windings, said motor being coupled to said agitation means to drive said agitation means;

means for periodically energizing said motor for causing said motor alternately to rotate in opposite directions and for cycling said motor off between energization;

means for sensing the residual alternating current in said first and second motor windings when said motor is cycled off and for providing a representation thereof; and

means for controlling the operation of said washing machine in response to said residual current representation, wherein said means for controlling the operation of said washing machine in response to said residual current representation comprises means for controlling the stroke angle of said agitation means in response to said residual current.

23. The automatic washing machine in claim 22 wherein said motor is a permanent split capacitor motor.

24. The automatic washing machine of claim 23 wherein said means for sensing said residual current comprises:

means for counting the number of sensed zero crossings to provide a sum, said sum being inversely related to the braking force on said motor.

25. The automatic washing machine of claim 22 wherein said means for controlling the operation of said washing means in response to said residual current representation comprises means for controlling the duration of an agitation cycle of said automatic washing machine in response to said residual current.

26. The automatic washing machine of claim 22 wherein said means for controlling the operation of said washing machine in response to said residual current representation comprises means for controlling the level of water in said automatic washer in response to said residual current.

27. The automatic washing machine of claim 22 wherein said means for controlling the operation of said washing machine in response to said residual current representation comprises means for detecting an overload condition in said washer.

28. The automatic washing machine of claim 22 wherein said means for controlling the operation of said washing machine in response to said residual current representation comprises means for determining whether or not to operate said motor to drive said agitation means during a fill operation in response to said residual current representation.

29. The automatic washing machine of claim 22 further comprising means for sensing the load on the motor when the motor is operating under power and for providing a representation of said load, said controlling means controlling the operation of said washing machine in response to both said representation of said residual current and said representation of said load.

30. The automatic washing machine of claim 29 wherein:

said residual current sensing means comprises means for sensing and counting the number of zero crossings of alternating current when said motor is cycled off; and further wherein

said load sensing means ,comprises means for determining the motor phase angle and for detecting a characteristic increase in said motor phase angle representing the time when said motor attains full operating speed.

31. The automatic washing machine of claim 22 further comprising cycle selection means for selecting a cycle of operation for said washing machine, said controlling means controlling the operation of said washing machine in response to both said representation of said residual current and said representation of said cycle.

32. A method of washing clothes in an automatic washing machine having a rotatable laundering vessel, an agitator disposed within said vessel, a reversible permanent split capacitor motor coupled to said rotatable laundering vessel and said agitator to selectively drive said rotatable laundering vessel and said agitator, said motor having first and second windings and being powered by a power supply having an alternating line voltage, said method comprising the steps of:

periodically energizing said motor to effect agitation of said agitator and sensing zero crossings of alternating current in said first and second motor windings when said motor is cycled off between energizations thereof to provide a signal representative thereof;

counting the number of sensed zero crossings to provide a sum, said sum being inversely related to the braking force on said motor; and

controlling the operation of said washing machine in response to said braking force representation, wherein said step of controlling the operation of said washing machine in response to said braking force representation comprises controlling the stroke angle of said agitator in response to said braking force.

33. The method of claim 32 wherein said step of controlling the operation of said washing machine in response to said braking force representation comprises determining whether or not to operate said motor to drive said agitation means during a fill operation in response to said braking force representation.

34. The method of claim 32 wherein said step of controlling the operation of said washing machine in response to said braking force representation comprises:

controlling the stroke angle of said agitator in response to said braking force;

controlling the duration of an agitation cycle of said automatic washing machine in response to said braking force;

controlling the level of water in said automatic washing machine in response to said braking force; and

determining whether or not to operate said motor to drive said agitation means during a fill operation in response to said braking force representation.

35. A method of washing clothes in an automatic washing machine having a rotatable laundering vessel, an agitator disposed within said vessel, a reversible permanent split capacitor motor coupled to said rotatable laundering vessel and said agitator to selectively drive said rotatable laundering vessel and said agitator, said motor having first and second windings and being powered by a power supply having an alternating line voltage, said method comprising the steps of:

periodically energizing said motor to effect agitation of said agitator and sensing zero crossings of alternating current in said first and second motor windings when said motor is cycled off between energizations thereof to provide a signal representative thereof;

counting the number of sensed zero crossings to provide a sum, said sum being inversely related to the braking force on said motor; and

controlling the operation of said washing machine in response to said braking force representation, wherein said step of controlling the operation of said washing machine in response to said braking force representation comprises controlling the duration of an agitation cycle of said automatic washing machine.

36. The method of claim 35 wherein said step of controlling the operation of said washing machine in response to said braking force representation comprises determining whether or not to operate said motor to drive said agitation means during a fill operation in response to said braking force representation.

37. A method of washing clothes in an automatic washing machine having a rotatable laundering vessel, an agitator disposed within said vessel, a reversible permanent split capacitor motor coupled to said rotatable laundering vessel and said agitator to selectively drive said rotatable laundering vessel and said agitator, said motor having first and second windings and being powered by a power supply having an alternating line voltage, said method comprising the steps of:

periodically energizing said motor to effect agitation of said agitator and sensing zero crossings of alternating current in said first and second motor windings when said motor is cycled off between energizations thereof to provide a signal representative thereof;

counting the number of sensed zero crossings to provide a sum, said sum being inversely related to the braking force on said motor; and

controlling the operation of said washing machine in response to said braking force representation, wherein said step of controlling the operation of said washing machine in response to said braking force representation comprises controlling the level of water in said automatic washing machine in response to said braking force.

38. The method of claim 37 wherein said step of controlling the operation of said washing machine in response to said braking force representation comprises determining whether or not to operate said motor to drive said agitation means during a fill operation in response to said braking force representation.

39. A method of washing clothes in an automatic washing machine having a rotatable laundering vessel, an agitator disposed within said vessel, a reversible permanent split capacitor motor coupled to said rotatable laundering vessel and said agitator to selectively drive said rotatable laundering vessel and said agitator, said motor having first and second windings and being powered by a power supply having an alternating line voltage, said method comprising the steps of:

periodically energizing said motor to effect agitation of said agitator and sensing zero crossings of alternating current in said first and second motor windings when said motor is cycled off between energizations thereof to provide a signal representative thereof;

counting the number of sensed zero crossings to provide a sum, said sum being inversely related to the braking force on said motor; and

controlling the operation of said washing machine in response to said braking force representation, wherein said step of controlling the operation of said washing machine in response to said braking force representation comprises detecting an overload condition in said washing machine.

40. The method of claim 39 wherein said step of controlling the operation of said washing machine in response to said braking force representation comprises determining whether or not to operate said motor to drive said agitation means during a fill operation in response to said braking force representation.

41. An automatic washing machine powered by a supply having an alternating line voltage comprising:

an agitator;

a spin basket;

a permanent split capacitor motor coupled to said agitator and to said spin basket to selectively drive said agitator and spin basket, said motor having first and second windings;

means coupled to said motor for periodically energizing said first and second windings to cause said motor to effect agitation and for cycling said motor off between successive energizations to effect agitation of said agitator;

means for sensing zero crossings of alternating current in said first and second motor windings when said motor is on to provide a representation of said current zero crossings and, when said motor is cycled off, to provide a representation of residual current flowing through said first and second motor windings;

means responsive to said line voltage and said current zero crossing representation for determining a motor phase angle to provide a representation thereof; and

means for controlling various operations of said washing machine in response to said residual current representation and said motor phase angle representation, wherein said control means includes means for determining the optimal stroke angle of said agitator, said cycling means being responsive to said control means for cycling said motor off in accordance with said optimal stroke angle.

42. An automatic washing machine as recited in claim 41 wherein said control means includes means responsive to said residual current representation for automatically controlling the level of water in said washing machine in accordance with the size of the load in said washing machine.

43. An automatic washing machine as recited in claim 42 wherein said control means includes means responsive to said residual current representation for determining an overload condition while controlling the level of water in said washing machine.

44. An automatic washing machine as recited in claim 42 wherein said control means includes means responsive to said residual current representation for determining whether said motor should be cycled off to stop agitation while increasing the water level in said washing machine.

45. An automatic washing machine as recited in claim 41 wherein said control means includes means responsive to said residual current representation for determining the duration of an agitation operation of said washing machine.

46. An automatic washing machine as recited in claim 41 wherein said control means includes means responsive to said motor phase angle representation for determining the duration of a spin operation of said washing machine.

47. An automatic washing machine powered by a supply having an alternating line voltage comprising:

an agitator;

a spin basket;

a permanent split capacitor motor coupled to said agitator and to said spin basket to selectively drive said agitator and spin basket, said motor having first and second windings;

means coupled to said motor for periodically energizing said first and second windings to cause said motor to effect agitation and for cycling said motor off between successive energizations to effect agitation of said agitator;

means for sensing zero crossings of alternating current in said first and second motor windings when said motor is on to provide a representation of said current zero crossings and, when said motor is cycled off, to provide a representation of residual current flowing through said first and second motor windings;

means responsive to said line voltage and said current zero crossing representation for determining a motor phase angle to provide a representation thereof; and

means for controlling various operations of said washing machine in response to said residual current representation and said motor phase angle representation, wherein said control means includes means responsive to said motor phase angle representation for determining the amount of dither in said motor during a spin operation of said washing machine.

48. An automatic washing machine as recited in claim 41 wherein said control means includes means responsive to the determined amount of dither for determining an off balance condition during said spin operation.

49. An automatic washing machine as recited in claim 47 wherein said control means includes means for determining the optimal stroke angle of said agitator, said cycling means being responsive to said control means for cycling said motor off in accordance with said optimal stroke angle.

50. An automatic washing machine as recited in claim 47 wherein said control means includes means responsive to said residual current representation for automatically controlling the level of water in said washing machine in accordance with the size of the load in said washing machine.

51. An automatic washing machine as recited in claim 50 wherein said control means includes means responsive to said residual current representation for determining an overload condition while controlling the level of water in said washing machine.

52. An automatic washing machine as recited in claim 50 wherein said control means includes means responsive to said residual current representation for determining whether said motor should be cycled off to stop agitation while increasing the water level in said washing machine.

53. An automatic washing machine as recited in claim 47 wherein said control means includes means responsive to said residual current representation for determining the duration of an agitation operation of said washing machine.

54. An automatic washing machine as recited in claim 47 wherein said control means includes means responsive to said residual current representation for determining the duration of a spin operation of said washing machine.

CROSS REFERENCE TO RELATED APPLICATION

This application is related to an application entitled "ELECTRONIC CONTROL FOR AN AUTOMATIC WASHING MACHINE WITH A REVERSING PSC MOTOR," Ser. No. 07/392,473, filed concurrently herewith by the same inventor names in the present application, and now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control system for an apparatus having a permanent split capacitor (PSC) motor and more particularly to a control for an automatic washing machine having a reversing PSC motor wherein the operations of the washing machine are controlled in response to phase angles of the motor determined from sensed zero crossings of current flowing through the motor's windings when the motor is on and in response to the sensed zero crossings of residual motor generated current flowing through the motor's windings when the motor is off.

2. Description of the Prior Art

A control system for various appliances having an AC induction drive motor including an automatic washing machine is shown in my U.S. Pat. No. 4,481,786. That control system employs a ferrite core sensor having a primary winding that is formed of two turns of the drive motor's run winding, the sensor having a single turn secondary winding that forms a sense winding coupled to a motor phase monitoring circuit. The sense winding provides a signal representing a polarity change in the run winding current. The current polarity change signal is used by the motor phase monitoring circuit to provide a voltage compensated motor phase angle pulse to a microcomputer for the appliance to control various operations of the appliance. More particularly, a digital representation of the motor phase angle pulse is used by the microcomputer to monitor the starting of the drive motor by detecting a characteristic decrease in the motor phase angle representation. The motor phase angle representation is further used by the microcomputer of an automatic washing machine to determine the agitator torque which is in turn used by the microcomputer to automatically control the water level of the washing machine. An average motor torque number is also determined from the motor phase angle representation wherein the average motor torque number is used to provide an end of drain control for the washing machine.

The washer agitator torque routine (WATR) in FIG. 10 of U.S. Pat. No. 4,481,786 applies to washing machines which use a complex transmission to define the stroke angle and to convert the rotary motion of the motor into a back-and-forth, clockwise (CW) and counterclockwise (CCW) agitator motion. The motor of U.S. Pat. No. 4,481,786 rotates continuously and in a single direction during each clothes agitation period. The mid-stoke agitator torque is inferred by using the microcomputer to store the maximum and minimum motor phase number during each CW and CCW agitator stroke and compute the difference. The maximum motor phase number during each CW and CCW stroke occurs when the transmission gears are positioned such that the agitator is in hesitation. This number provides a base-line or reference motor phase number unaffected by agitator torque to which the minimum motor phase number or mid-stroke agitator torque can be compared.

The present invention applies to washing machines wherein each reversal of direction of the agitator is achieved by stopping and restarting the drive motor in the opposite direction. Washing machines of the present invention may use a transmission, but the transmission is relatively simple and provides a basic motor speed reduction and/or torque multiplication function. The direction of rotation of the motor determines the agitation direction and the angle of rotation of the motor shaft in conjunction with the transmission gear-ratio determines the agitation stroke angle. The present invention teaches how to use information from the motor electrical parameters to provide a closed-loop automatic water level control function in the absence of the above base-line or reference motor phase information as such information is not available with a washing machine having a simple, speed-reducing transmission. Also, the preferred embodiment pertains to a permanent split capacitor (PSC) drive motor as PSC motors are generally more amenable in applications requiring frequent starting, stopping and reversal of the motor rotational direction than split phase induction motors.

It has been found that automatic washing machines having reversing PSC drive motors cannot be as accurately controlled by the control system shown in U.S. Pat. No. 4,481,786 as washing machines having AC induction motors because the motor start time of a PSC motor varies not only with the size of the clothes load but with variations in the installation line voltage. More particularly, for a washing machine having a reversing PSC motor, the line voltage affects the motor start time more than the size of the clothes load. Further, the motor phase angle of a PSC motor does not change in the same manner as the motor phase angle of an AC induction motor since there is not a characteristic decrease in the phase angle of the PSC motor indicative of the motor reaching its operating speed. Another difference between washing machines having an AC induction motor and washing machines having a PSC motor is that the stroke angle and stroke rate of an agitator driven by an AC induction motor is fixed; whereas, the stroke angle and stroke rate of an agitator driven by a reversing PSC motor is variable.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a control system for a PSC motor that overcomes many of the disadvantages of the prior art control systems.

It is another object of the present invention to provide a method and apparatus for determining the braking force on a PSC motor by monitoring the residual current generated by the motor after the motor has been cycled off.

It is yet another object of the present invention to control various operations of a washing machine based on the braking force measured.

In accordance with the present invention, the disadvantages of prior control systems for automatic washing machines with reversing PSC motors have been overcome. The electronic control system of the present invention controls various operations of an automatic washing machine with a reversing PSC motor in response to a representation of the residual alternating current flowing through the motor windings when the motor is cycled off. It has been found that the residual alternating current is substantially unaffected by the installation line voltage because the PSC motor is disconnected from the line voltage when the PSC motor is cycled off during a hesitation period. It is during the hesitation period that the motor's braking action takes place. The duration of the residual alternating current during the hesitation period is inversely proportional to the braking force on the motor wherein the braking force is an indication of the size of the clothes load in the washing machine. Further, the motor's phase angle is analyzed in a manner particular to reversing PSC motors in order to determine the start time of the motor, i.e., the time at which the motor reaches its operating speed and further to control various operations of the washing machine not shown in U.S. Pat. No. 4,481,786.

The electronic control system of the present invention senses zero crossings of alternating current in at least one winding of the PSC motor when the motor is on to provide a representation thereof and when the motor is cycled off to provide a representation of residual current flowing through the motor winding. The residual current is generated by the motor which acts as a generator as it continues to rotate for a period of time after it has been de-energized. The control also detects zero crossings of the line voltage to provide a signal representative thereof wherein a motor phase angle representation is determined in response to the time from the voltage zero crossing signal to the current zero crossing signal.

In order to sense the zero crossings of alternating current in a winding of the PSC motor, a ferrite core transformer sensor is employed having a primary winding that includes at least one turn of a motor winding and a secondary winding at which the current zero crossing signal is generated. In the preferred embodiment, two ferrite core transformer sensors are employed wherein the primary winding of a first sensor includes at least one turn of a first motor winding and the primary winding of the second sensor includes at least one turn of a second motor winding. A sense winding extends through the first and second ferrite core transformers to form the secondary windings thereof wherein the polarity of the sense winding is such that the signals from each ferrite core transformer are additive when the motor is cycled off.

The electronic control of the present invention is responsive to the residual alternating current representation to determine the size of the load in the washing machine during water fill, agitation or rinse operations. The electronic control further automatically controls the water level in the washing machine in response to the residual alternating current representation. During the automatic water level control operation, the electronic control determines whether an overload condition exists from the residual alternating current representation and further determines whether to agitate or not while increasing the water level. The residual alternating current representation is further used to determine the optimal duration of a stroke, i.e., stroke angle, and the stroke rate of the washing machine's agitator such that the larger the load indicated by the residual alternating current representation, the greater the stroke angle or duration. The duration of agitation during wash and rinse cycles of the washing machine is further controlled in response to the water level which is in turn determined from the residual alternating current representation.

These and other objects, advantages and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and the drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1a is a schematic diagram of a control circuit for an automatic washing machine having a reversing permanent split capacitor motor and two ferrite core sensors;

FIG. 1b is a first alternative embodiment of the sensing portion of the circuit shown in FIG. 1a employing a single ferrite core sensor;

FIG. 1c is a second alternative embodiment of the sensing portion of the circuit shown in FIG. 1a employing a single ferrite core, sensor;

FIG. 1d is a third alternative embodiment of the sensing portion of the circuit shown in FI. 1a employing a single ferrite core sensor;

FIG. 2 is a schematic diagram illustrating the voltage regulator circuit shown in FIG. 1a;

FIG. 3 is a schematic diagram illustrating the volt pulse circuit shown in FIG. 1a;

FIG. 4 is a schematic diagram illustrating the current pulse circuit shown in FIG. 1a;

FIG. 5 is a schematic diagram illustrating the watchdog circuit shown in FIG. 1a;

FIG. 6 is a schematic diagram illustrating the triac driver circuit shown in FIG. 1a;

FIG. 7 is a schematic diagram illustrating the solenoid driver circuit shown in FIG. 1a;

FIG. 8a is a graphical representation of the voltage and current waveforms associated with the PSC motor shown in FIG. 1a;

FIG. 8b is a graphical representation of the output from the voltage regulator circuit shown in FIG. 1a;

FIG. 8c is a graphical representation of the output from the volt pulse circuit shown in FIG. 1a;

FIG. 8d is a graphical representation of the output of the ferrite core sensors with the dashed lines representing the auxiliary and main winding currents;

FIG. 8e is a graphical representation of the output of the current pulse circuit shown in FIG. 1a;

FIGS. 9a, 9c, 9e and 9g are graphical representations illustrating the PSC motor's main and auxiliary winding currents for clothes loads of various sizes ranging from no load in FIG. 9a to a full capacity load in FIG. 9g;

FIGS. 9b, 9d, 9f and 9h are graphical representations illustrating the output of the current pulse circuit shown in

FIG 1a generated in response to the sensor outputs for the motor winding currents respectively shown in FIGS. 9a, 9c, 9e and 9g;

FIG. 10 is a flow chart illustrating the main program MP for an automatic washing machine;

FIG. 11 is a flow chart illustrating the lagging phase monitoring routine LPMR;

FIG. 12 is a flow chart illustrating the PSC motor start routine MSR;

FIG. 13 is a flow chart illustrating the cycle routine CR;

FIG. 14 is a flow chart illustrating the agitate time routine ATR;

FIG. 15 is a flow chart illustrating the stroke routine SR;

FIG. 16 is a flow chart illustrating the residual pulse count routine RPCR;

FIG. 17 is a flow chart illustrating the agitate routine AR;

FIG. 18 is a flow chart illustrating the off-balance routine OBR;

FIG. 19 is a flow chart illustrating the spin routine SPNR; and

FIG. 20 is a perspective view of a vertical axis automatic clothes washing machine employing the control system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The control system of the present invention is used to control various operations of a vertical axis clothes washing machine 600 as shown in FIG. 20. The washing machine 600 includes a reversing permanent split capacitor (PSC) motor 10 that drives a spin basket 602 in one direction during a spin operation of the washing machine. The PSC motor 10 is also coupled to an agitator 604 for driving the agitator 604 in clockwise and counterclockwise directions wherein the PSC motor 10 includes a pair of motor windings which alternatively serve as the main motor winding and auxiliary motor winding upon each reversal of the PSC motor 10. The powered portion of each clockwise and counterclockwise agitator stroke occurs when the motor 10 is cycled on. Between each clockwise and counterclockwise stroke is a hesitation period during which time the PSC motor 10 is cycled off to allow the PSC motor 10 and the agitator 604 to come to a complete stop before the direction of the PSC motor 10 and the agitator 604 is reversed.

The control system of the present invention as shown in FIG. 1a and described in detail below senses the zero crossings of current flowing through the windings of the PSC motor 10 to provide current pulses 46 representative thereof. The system further generates volt pulses 45 representing the zero crossings of the alternating line voltage servicing the washing machine. The control system is responsive to the volt pulse and current pulse signals 45 and 46 to monitor the phase angle of the main and/or auxiliary windings of the PSC motor 10 during each line voltage half cycle when the motor is on to provide phase angle information. When the motor is cycled off, the control system of FIG. 1a is responsive to the current pulses 46 representing the zero crossings of the residual current flowing through the motor windings to provide residual current information.

The control system of the present invention utilizes various relationships between the motor's phase angle and motor torque and between the residual current and motor torque to control various operations of the washing machine. One such relationship is that the lagging phase angle of the main winding current of the PSC motor 10 is inversely related to the motor torque. Another such relationship is that the leading phase angle of the auxiliary winding current of the PSC motor 10 is directly related to the motor torque. A further relationship is that the duration of the residual alternating current flowing through the PSC motor windings when the motor is cycled off is inversely related to the motor torque.

More particularly, a microcomputer 50 shown in FIG. 1a is dedicated during a portion of each line half cycle to monitor timing relationships between the volt and current pulse signals 45 and 46 with crystal controlled clock cycles. Through the speed of the microcomputer 50, all data processing and/or decision making is completed before the arrival of any volt or current pulse information for the next line half cycle.

The microcomputer 50, when operating in accordance with the lagging phase monitoring routine LPMR, shown in FIG. 11, determines the lagging phase angle of the PSC motor 10 to provide a representation thereof. From the lagging phase angle of the PSC motor 10, the microcomputer 50 in accordance with the motor start routine MSR shown in FIG. 12 determines the starting time of the PSC motor 10 by detecting a characteristic increase in the lagging phase angle indicating that the PSC motor 10 has reached its operating speed.

From the motor start time, the microcomputer 50 determines the size of the clothes load in the washing machine 600 during a spin operation. More particularly, during a spin operation the PSC motor 10 drives the spin basket 602 of the washing machine 600 in one direction so that the motor start time represents the spin basket acceleration time, i.e., the time at which the spin basket reaches its operating or preferred spin speed. During the spin operation, the microcomputer 50, when operated in accordance with the off balance routine OBR 500 shown in FIG. 18, determines the amount of dither in the motor torque from the lagging phase angle of the motor and from the amount of dither determines whether an off balance condition exists. The microcomputer 50, operating in accordance with the spin routine SPNR shown in FIG. 19, further determines the duration of the spin operation from the motor start time and a cycle parameter.

The cycle parameter is calculated by the microcomputer 50 in accordance with the cycle routine CR (FIG. 13) in response to the cycle selection of the user. The user may select a delicate cycle, a permanent press cycle or a normal cycle by actuating a respective cycle selection button 603, 605 and 607 disposed on the washing machine 600. The user may further select the temperature of the wash cycle by actuating a temperature selection button 608, 609 and 611 respectively representing a hot water wash, warm water wash or cold water wash. The temperature selection parameters are utilized by the microcomputer 50 to determine the duration of agitation during the wash and deep rinse periods of the washing machine as discussed below.

When the PSC motor 10 is driving the agitator 604, for each agitator stroke, the motor start routine MSR is called to determine when the motor 10 reaches its operating speed. At this point, a stroke routine SR shown in FIG. 15 is called to complete the powered portion of the stroke. Following the powered portion of each clockwise and counterclockwise agitator stroke, the microcomputer 50 operates in accordance with the residual pulse count routine RPCR (FIG. 16) to count the number of current pulses 46 representing zero crossings of the residual alternating current flowing through the motor windings when the motor is cycled off. From the residual pulse count, the microcomputer 50 determines the size of the clothes load during the wash and rinse operations of the washing machine 600. The microcomputer 50, when operated in accordance with the stroke routine SR, determines the optimal duration of each agitator stroke, i.e. stroke angle, and the stroke rate in accordance with the residual pulse count from the previous stroke and the cycle parameter. For a given cycle parameter, the larger the size of the clothes load as indicated by a small residual p