Load-independent control of a hydraulic excavator

The primary focus of this study is to investigate the control of excavation processes by applying load-independent hydraulic valves. This approach allows avoiding closed loop control system with sensors and transducers mounted on the excavator attachment. There are, then, no sensor cells mounted on the machine attachment. The considered system is composed,of two subsystems: a microcomputer and a hydraulic unit (a pump and load-independent valves). In the microcomputer unit, the bucket velocity vector is related to the oil flow into three cylinders through the application of inverse kinematics. Then, flows are transferred into the electric signals actuating the load-independent valves. Their motion is presented by applying transfer function. The performance of the system is verified by assuming an abrupt change of the oil flow into cylinders. The last part of the paper is devoted to the obtained experimental results. The first result deals with vertical drilling. The second result deals with an excavation along a horizontal trajectory. (C) 2002 Elsevier Science B.V All rights reserved.