Motion control method and apparatus for motorized window blinds and and the like

In a motion control system wherein a member is to be driven along a predetermined path of travel and motor drive means is provided for reversibly driving said driven member, said motor drive means being accelerated and decelerated in direct proportion to the width of motor drive pulses received, the improvement comprising:

• rotary speed sensing means connected to said driven member for rotation at a speed correlated with the speed of advancement of said driven member along said path of travel, and for generating electrical pulses at a rate corresponding to the rate of advancement of said driven member;
• motor drive pulse-generating means for generating the motor drive pulses of a width corresponding to the rate of advancement sensed by said speed sensing means and for driving said motor drive means;
• and
• comparator means electrically connected between said motor drive means and said pulse-generating means for comparing the rate of advancement of said driven member with a predetermined speed level and for adjusting the width of said motor drive pulses until the rate of advancement of said driven member corresponds with said predetermined speed level, said motor drive means including a DC motor drive, and speed control means for modulating power output to said motor drive over a fixed repeating time period in response to the rate of advancement of said member to be driven, said speed control means defined by a pulse width modulation circuit having a closed feedback loop connected to said speed sensing means, and said comparator means having upper and lower speed thresholds to define the boundaries of an acceptable speed range for either normal or reduced speeds.

A method of controlling the speed of advancement of a window shade between open and closed positions and for stopping the movement of the shade in the event of an obstruction, including a drive member for reversibly driving said shade, comprising the steps of:

• sensing the rate of advancement of said shade when said drive member is activated;
• establishing upper and lower normal speed levels within which said shade is to be advanced by said drive member;
• further establishing a minimum speed level below which said drive member is deactivated;
• comparing the rate of advancement of said shade with said upper and lower normal speed levels and adjusting the rate of advancement of said shade until it is between said upper and lower normal speed levels;
• and
• deactivating said drive member in the event that the rate of advancement is below said minimum speed level.