Patent ID: 7739764

Claim:
A method of determining the magnitude of a load imbalance and total load size in a given washing machine having a rotatable drum driven by a variable speed motor, the method comprising: establishing a speed profile for the washing machine comprising a period of constant speed, an acceleration period, and a deceleration period; operating the motor to rotate the drum, sequentially, at the period of constant speed, the acceleration period, and the deceleration period, measuring the power output of the motor in more than one sample during each period, calculating an average power output by averaging the power output over the number of samples during the period of constant speed, calculating a power fluctuation integral by summing the integral area above the average power output for the acceleration period with the integral area below the average power output for the deceleration period, calculating a total load size value by multiplying the static imbalance power fluctuation integral with a first predetermined constant and summing the result with a second predetermined constant, applying the power fluctuation integral and total load size value to a predetermined algorithm to obtain a magnitude of static load imbalance value, and storing the magnitude of static load imbalance value and total load size value in a memory location; and sending a signal representative of the stored values, whereby the washing machine drum can operate at an optimum spinning speed or the load can be rearranged depending on the magnitude of the static load imbalance.