A direct proportional control system for remotely controlling actuation of a tool. A well control system includes an actuator for a downhole well tool, the actuator including an actuator member which displaces to operate the well tool. A control system member is positioned at a remote location. A displacement...http://www.google.de/patents/US7240737?utm_source=gb-gplus-sharePatent US7240737 - Direct proportional surface control system for downhole choke
