Abstract: A control system for controlling quantity of hydraulic fluid of an excavator. The control system of this invention provides a method for controlling the quantity of the hydraulic fluid supplied to the swing motor in which in case of swinging operation for driving the swing motor in order to turn the upper frame with respect to the lower frame, the first hydraulic pump is automatically controlled by the controller in order to optimally output hydraulic fluid to timely correspond to starting of the practical swinging operation of the swing motor.

Abstract: A control system for automatically controlling the operation of a hydraulic system for heavy construction equipment. The system of this invention provides a controller optimally connected to sensors and to control devices on the hydraulic system so that it automatically and optimally preheats the engine coolant and the hydraulic fluid of the heavy construction equipment before a normal starting operation in order to reach to an optimal operating temperature in a relatively short time. The control system automatically checks the operating temperature of the engine coolant and the hydraulic fluid by temperature sensors, and alarms the operator to any overheat condition by an alarm device. The control system also automatically controls the operational mode in order to remove the overheat condition thus preventing the temperature of the engine coolant and the hydraulic fluid from rising above a predetermined temperature.