Patent ID: 7019476

Claim:
A method for recognizing an obstructed situation of a movable element being driven by a motor, the method comprising: evaluating values of a variable indicative of rotational speed of a motor at successive time points as the motor is driving a movable element; starting from a current time point, determining changes between a sequence of the variable values determined at immediately preceding time points over a given time interval; comparing the changes between the sequence of the variable values over the given time interval with a variable value change range for the given time interval, wherein the variable value change range for the given time interval represents a behavior of the variable value changes expected to occur during the given time interval when the element is in an obstructed situation; determining that the element is in an obstructed situation if the changes between the sequence of the variable values for the given time interval fall within the variable value change range for the given time interval; and determining that the element is in a non-obstructed situation if the changes between the sequence of the variable values for the given time interval fall outside of the variable value change range for the given time interval.