Patent ID: 7958585

Claim:
A method of determining the size of a load based on its inertia in a given washing machine having a rotatable drum driven by a variable speed motor, the method comprising the steps: 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, acceleration period, and deceleration period, measuring the power output of the motor during each period, calculating an average power output by averaging the power output at 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 value that estimates the total load size by applying the power fluctuation integral to a predetermined algorithm, storing the total load size value in a memory location, and sending a signal representative of the stored value whereby total load size is determined without regard for friction in the washing machine and the washing machine can use total load size in detecting imbalances.