An approach to object-level stiffness regulation of hand-arm systems subject to under-actuation constraints

Abstract

When using a tool with a robotic hand-arm system, the stiffness at the grasped object plays a key role in the interaction with the environment, allowing the successful execution of the task. However, the rapidly increasing use of under-actuated hands in robotic systems due to their robustness and simplicity of control, pose limitations to the achievable object-level stiffness. Indeed, due to the serial coupling of the hand and the arm, the resulting object-level stiffness is determined by the most compliant of both elements. To address this problem, we propose a novel controller that takes into account the limited achievable geometry of the object stiffness ellipsoid given by a hand with under-actuation constraints, and exploits the contribution of the robotic arm in reshaping the final stiffness towards the desired profile. The under-actuation is illustrated by a coordinated stiffening of the hand fingers. The proposed method is experimentally validated by a hand-arm system performing a peg-in-hole task.

Modeling and Simulation of Robotic Grasping in Simulink Through Simscape Multibody

“… Katyara et al (2021) investigated the role of postural synergies in manipulation tasks and used SynGrasp to validate the proposed framework. Garate et al (2017 , 2018) exploited SynGrasp to implement in-hand manipulation strategies with a fully actuated hand based on Common-Mode Stiffness (CMS) and Configuration-Dependent Stiffness (CDS) principles, and to simulate control strategies for hand-arm systems subject to underactuation constraints ( Ruiz Garate and Ajoudani, 2020 ). Using SynGrasp, Almeida and Moreno (2020) further developed the concept of Potential Grasp Robustness ( Pozzi et al, 2017 ), devising new heuristics for managing computational load, and analysing the influence of uncertainties on its computation ( Almeida and Moreno, 2021 ).…”