Force and Geometry Constraints in Robot Excavation

Abstract

One interest in this research effort was to develop and test an automatic control approach to adjust machine motions to the force conditions encountered during excavation - essentially constructing a robot which digs by feel. The problem is approached by supervisory control, consisting of discrete adjustments to the digging trajectory. A laboratory manipulator approximating a backhoe was configured with four actuated degrees of freedom, and an object-oriented programming environment was built to permit rapid prototyping of the supervisory control level. The object-oriented programming environment was also used to model spatial planning associated with excavation. The first approach applies to a Cartesian system and models the excavation volume as a rectangular prism, for decomposition into layers and further decomposition into unit cuboids forming an intended excavation plan. The work next addressed the mapping of an excavator in polar coordinates, typifying a backhoe at one fixed base position, to a prismatic excavation target.