Testing and control of a compliant wrist

This report summarizes the evaluation of a controllable, instmmented compliant wrist. The design of th< wrist and the concept of a remote center of compliance (RCC) have been described in an earlier repoil (CMU-Rl-TR-82-9). The wrist is mounted on a large industrial robot used to load precisely machined parts int( jigs and fixtures on computer controlled machine tools. The robot and the machine tools form part of ai automated cell in which machined parts can be produced with a minimum of human intervention. Loadinj parts into machine tools is essentially an assembly operation in which the parts are slid into clamps or fixture and for this reason the RCC techniques that have been developed for assembly robots can also be applied to ; machining cell. The wrist employs spherical springs with an adjustable stiffness that varies between 33 and 450 lb/incl (5.8xlO and 7.9xlO N/m). This allows the center of compliance to be projected over a range from 1.0 to 6.: inches (25 to 157 mm) out from the upper platform of the wrist. The wrist has 5^ degrees of freedom, beinj compliant in each direction except axial extension. Deflections of ± 0.18 inches (4.6 mm) in the radial plan< and 0.20 inches (5.1 mm) in compression are possible. The accuracy of the sensors over this working range i within 0.001 inches (0.025 mm) for translational motions and within 0.001 radians for rotational motions.