Abstract: A pressure control valve of a hydraulic control system of automatic transmissions has reducing pressure PR supplied from a reducing valve by duty control of a pressure control solenoid valve controlled by a transmission control unit thereby changing line pressure PL supplied from a manual valve into the control pressure and supplying the control pressure to the friction element. The valve comprises a valve spool operated by the duty-controlled reducing pressure, a valve body in which the valve spool linearly moves, and a feedback line which communicates the control pressure with one side of the valve body thereby reducing the deviation of the control pressure.

Abstract: The present invention relates to an automatic system for controlling the steering of a non-railed transfer crane travelling along a lane indicant. The system comprises a vision sensor for continuously photographing the condition of a crane's actual travelling direction with respect to lanes represented by the lane indicant, and outputting predetermined deviations (distance as well as angle) showing off-centered degrees between the crane's actual travelling direction and the lanes based on the photographed image signal, and a deviation processor for outputting a control signal to a motor driver so that the crane can travel toward removing the deviation distance. By properly changing a rotative velocity of the crane's wheels, the present invention prevents the crane's travelling direction from being off-centered from the lanes.