Robotic Threading from a Gel-like Substance Based on Impedance Control With Force Tracking

Abstract

Gel-like matter is used extensively in a wide range of application fields including industrial applications such as the manufactory and assembly of garment and footwear products, soft macro/micro-robotics, medical diagnostics, and drug delivery. However, the manipulation of gel-like matter is very challenging, due to its high deformability, high viscosity, and fast phase changing. In this letter, we propose a novel biomimetic robotic fiber threading approach based on impedance control with force tracking. The highly integrated approach can control the impedance of the fiber during both threading and solidification of the fiber and characterize the mechanical properties of the fabricated fibers in the very same setup without changing parts. The impedance control method has also been adapted in this letter by adding a real-time estimator for continuously estimating the stiffness of the threading force for highly accurate control. The resulted fibers using the proposed approach demonstrates higher performances in all terms of toughness, stiffness, elongation and strength, compared to the traditional velocity controlled fiber fabrication approach.

Robotic Fiber Fabrication based on Solidification Force Control

“…To control the fiber fabrication process, we employed the impedance control with force tracking developed in [18]. The objective, as introduced in [26], is to provide a desired userspecified dynamical relationship, referred to as, target impedance between the manipulator (consisting of the precision positioner and the dispenser) position and the solidification force .…”

“…However, the stiffness of the Dextran changes continuously during fiber pulling. An online estimation method is used to estimate the stiffness during the whole threading process [18]. The Dextran stiffness is then estimated using the static part of the equation ( 1):…”

“…In this section, we investigate the impact of solidification force control using impedance control with force tracking [18], We use an experimental protocol as shown in Fig. 2 to conduct experiments and characterize the mechanical properties of the fabricated fibers, and investigate the repeatability of the experiments.…”

“…The produced fibers are one of the strongest and toughest biological materials, outperforming most synthetic polymers and even some metal alloys. In our recent work [18], a robotic gel fiber fabrication method based on impedance control with force tracking was proposed to control the pulling and solidification forces. The proposed method produced fibers with higher mechanical properties compared with fibers fabricated using open-loop pulling velocity regulation.…”

“…Here, we propose a novel approach that controls the mechanical properties of fiber by controlling the solidification force. We employ impedance control with force tracking developed in [18] to control the solidification force. The repeatability of the mechanical properties of the fabricated fibers has been studied and compared using three scenarios a) fiber fabrication without solidification force address:…”