A High-Fidelity Simulation Framework for Grasping Stability Analysis in Human Casualty Manipulation

TL;DR

This paper tackles the gap in robotic casualty manipulation by introducing a high-fidelity integrative simulation framework that couples rigid-body dynamics with finite element method (FEM) modeling to simulate soft-contact interactions with a high-detail digital human (CAVEMAN). It uses MB dynamics for efficient grasp planning and FEM for accurate biomechanical responses, including explicit FEM time integration and KKT-based contact constraints, to produce realistic deformation and injury-relevant insights. The authors demonstrate, through qualitative and quantitative comparisons against state-of-the-art multi-body simulations, that the FEM-enabled framework reveals significant differences in grasp stability and tissue deformation not captured by rigid-body models, highlighting biases in current SotA simulators. While the framework achieves higher biomechanical fidelity, it incurs substantial computational costs, prompting future work on surrogate models and real-time acceleration to enable field deployment. Overall, the work establishes a crucial step toward biomechanically informed planning and safer, effective robot-assisted casualty manipulation with potential impact on rescue robotics practice and safety assessments.

Abstract

Recently, there has been a growing interest in rescue robots due to their vital role in addressing emergency scenarios and providing crucial support in challenging or hazardous situations where human intervention is difficult. However, very few of these robots are capable of actively engaging with humans and undertaking physical manipulation tasks. This limitation is largely attributed to the absence of tools that can realistically simulate physical interactions, especially the contact mechanisms between a robotic gripper and a human body. In this letter, we aim to address key limitations in current developments towards robotic casualty manipulation. Firstly, we present an integrative simulation framework for casualty manipulation. We adapt a finite element method (FEM) tool into the grasping and manipulation scenario, and the developed framework can provide accurate biomechanical reactions resulting from manipulation. Secondly, we conduct a detailed assessment of grasping stability during casualty grasping and manipulation simulations. To validate the necessity and superior performance of the proposed high-fidelity simulation framework, we conducted a qualitative and quantitative comparison of grasping stability analyses between the proposed framework and the state-of-the-art multi-body physics simulations. Through these efforts, we have taken the first step towards a feasible solution for robotic casualty manipulation.

Figures (12)

• Figure 1: The prospect for using autonomous robot systems in casualty manipulation.
• Figure 2: A summary of current casualty extraction robots. (a) Valkyrie ValkyrieSBIR is one of the earliest investigations on using mobile robot for the recovery of battlefield casualties. (b) REX REXREVsbir approaches the victim with wheeled stretcher to load and drag the victim back to the larger combat medical vehicle (REV REXREVsbir) in (c). (d) The Battlefield Extraction Assist Robot (BEAR BEAR) is the first humanoid robot in robot assisted extraction and evacuation. It consists of a humanoid hydraulic torso and a mobile robot base, and it can carry the victim up to 500 pounds.
• Figure 3: A comparison of grasping in a SotA multi-body dynamics simulator (the rigid environment) and in an FE solver (soft environment). (a) (c) illustrate rigid point contacts, and (b) (d) demonstrate their soft environment counterparts. (e) is a simplified data flow diagram of the proposed simulation framework.
• Figure 4: Illustration of soft contact interactions in an FE solver, including definitions of nodes and elements.
• Figure 5: An illustrative example of a simulation done in the proposed integrative framework. A custom three-finger robotic hand grasps a rubber sphere. The left figure shows the Equilibrium State, and the right two figures show the Indented State with the maximum principal strain overlaid on the surface.