A Fully Pneumatic Soft Manipulator With Proximally Generated, Body-Transmitted Roll for Closed-Loop 6-DoF Pose Regulation

Abstract

Most soft manipulators lack independently controllable roll about the end-effector’s longitudinal axis, leaving the complete pose unregulated. Roll can instead be generated at the arm base and transmitted through the deformable body, avoiding both a distal rotary actuator and a routed transmission element—a route so far demonstrated at surgical scale and at mN<inline-formula><tex-math notation="LaTeX">$\cdot$</tex-math></inline-formula>m torque levels. We extend it to a manipulation-scale, fully pneumatic platform in which a base-mounted pneumatic rotary actuator drives rotation and coordinated deformation of a torsionally stiff honeycomb arm converts it into end-effector roll. At this scale the architecture becomes markedly harder to control. We therefore develop a spherical-joint-approximation model with explicit passive torsion coordinates and a progress-based kinematic synchronization (PBKS) strategy. Across 30 workspace targets under four control configurations, the full framework satisfied 2 mm / <inline-formula><tex-math notation="LaTeX">$1^\circ$</tex-math></inline-formula> at <inline-formula><tex-math notation="LaTeX">$t=30$</tex-math></inline-formula> s at every target, whereas a torsion-free model failed on <inline-formula><tex-math notation="LaTeX">$16/30$</tex-math></inline-formula> targets and disabling synchronization raised the mean position overshoot from 8 to 212 mm. The arm tracked a <inline-formula><tex-math notation="LaTeX">$180^\circ$</tex-math></inline-formula>end-effector roll while regulating the remaining five DoFs, and delivered 6 –10.5 N<inline-formula><tex-math notation="LaTeX">$\cdot$</tex-math></inline-formula>m of blocked-output roll torque. Door unlocking, lightbulb installation, and water pouring illustrate task feasibility in the tested quasi-static regime.