SCREW THEORY-BASED FORCE CONTROL OF A PARALLEL PLANAR ROBOT FOR HANDLING HAZARDOUS MATERIALS

摘要

Screw theory-based force control was implemented for a parallel manipulator system targeted for use in hazardous environments such as aircraft arming and rearming, refueling, and combat turnaround missions. Screw theory was used to maintain validity and consistency between planar and spatial examples. The kinestatics were described using reciprocal screw systems to model the subspaces for the wrenches of constraint and twists of freedom. This enabled the geometric study of contact between two bodies, specifically referred to as the 'payload' and the 'target.' The research focused on commanding and controlling the contact interface between the payload and target, specifically how the two touching bodies applied constraint wrenches to each other as well as how the bodies freely twisted relative to each other. The specific objective of the research reported herein was to develop an assembly task supervisor using screw theory. The supervisor established a geometrically meaningful sequence of commands in real-time that maintained desirable contact and also 'steered' assembly towards a desirable completion. Additional research investigated an 'explicit kinestatic controller' which was a mid-level force controller, and a hydraulic-compliant-leg force controller, which was a low-level controller.