Region limiting excavation control system for construction machine

A region limiting excavation control system for a construction machine comprising a plurality of driven members including a plurality of front members which make up a multi-articulated type front device and are vertically movable, a plurality of hydraulic actuators for respectively driving said plurality of driven members, a plurality of manipulation means for instructing operation of said plurality of driven members, and a plurality of hydraulic control valves driven in accordance with control signals from said plurality of manipulation means for controlling flow rates of a hydraulic fluid supplied to said plurality of hydraulic actuators, wherein said system further comprises:

• region setting means for setting a region where said front device is movable;
• first detecting means for detecting status variables with regard to the position and posture of said front device;
• first calculating means for calculating the position and posture of said front device based on signals from said first detecting means;
• and
• first signal modifying means for, based on the control signals from the manipulation means of said plurality of manipulation means which are associated with particular front members and the values calculated by said first calculating means, modifying the control signals from the manipulation means for said front device so that, when said front device is moved within said set region to approach the boundary of said set region, a moving speed of said front device in the direction toward the boundary of said set region only is reduced from before said front device reaches the boundary of the set region whereby the movement of the front device is gradually changed to a direction along the boundary of said set region, and further said front device is moved in the direction along the boundary of said set region when the front device reaches the boundary of the set region.