Energy-efficient motion control of a hydraulic manipulator

In this paper a novel hydraulic closed-loop motion control system has been proposed, designed and implemented on a heavy-duty 2-DOF hydraulic manipulator. A new unconventional hydraulic drive is introduced to remove the complex nonlinear interconnection between cylinder pressure levels, supply pressure and load force. The remaining nonlinear coupling of force and velocity is then removed by nonlinear controller design. New hardware combined with this proposed controller design is able to improve the controllability of the load with lower supply pressure values than conventional controllers. This leads to improved energy efficiency and is therefore of great practical and economic importance. This is a significant result since energy efficiency of closed-loop controlled hydraulics is generally known to be very low and improvements very difficult to obtain.