Method for monitoring and influencing an electric motor

A system for monitoring and controlling an electric motor operable for being driven by motor current to move a movable object, the system comprising:

• a pulse generator for generating a sequence of rectangular-pulse signals as a function of motor speed;
• a motor current sensor for measuring a value of the motor current simultaneously with a specified slope of each respective rectangular-pulse signal;
• a memory register for storing the measured motor current values;
• a processor for calculating a reference value Iref as a function of the motor current value I(t−N) measured N (N>1) rectangular-pulse signal slopes prior to a currently measured motor current value I(t0);
• wherein the processor compares the currently measured motor current value I(t0) to the reference value Iref and compares the currently measured motor current value I(t0) to an immediately preceding measured motor current value I(t−1);
• wherein the processor increments a first counter if the currently measured motor current value I(t0) is greater than the immediately preceding measured motor current value I(t−1), increments a second counter if the currently measured motor current value I(t0) is less than or equal to the immediately preceding measured motor current value I(t−1), and resets the first counter when the second counter exceeds a stored second threshold value;
• and
• wherein the processor generates at least one of a stopping and a reversing signal for the motor if the currently measured motor current value I(t0) exceeds the reference value Iref and the first counter simultaneously exceeds a stored first threshold value.