Indirect Force Measurement for Hydraulic Walking Robot

Force sensing is an important issue for the control of legged robots. In this paper an indirect force measurement for hydraulic walking robots is presented. The test case is ROBOCLIMBER, a bulky, quadruped climbing and walking machine whose weighty legs enable it to carry out heavy-duty drilling operations. The paper shows how the placement of pressure transducers at both ends of the double effect hydraulic jacks allows measuring indirectly the contact forces between the feet and the ground. Several experiments are carried out to calibrate all sensors within their operational range of interest. Because of dynamic properties of hydraulic cylinders friction modelling is an important task to be carried out in order to determine at all times the true forces of the feet against the soil. After calibration and friction modelling, sensors are subjected to experimental performance evaluation.