Parameter estimation and actuator friction analysis for a mini excavator

Gravitational and friction terms play an important role in achieving high performance control of heavy-duty hydraulic machines, such as excavators. In this paper, a new approach for decoupled estimation of the gravitational parameters is presented. Static experiments are carried out with an instrumented computer-controlled mini excavator to estimate the gravitational parameters. Load pins are used for indirect measurement of the joint torques from cylinder reaction forces. It is investigated via experiments that bucket payload can be estimated with a 5% accuracy. Furthermore, direct measurement of the actuators´ friction shows that considerable amount of static friction exists inside the cylinders that cannot be neglected