Impact-Aware Robotic Manipulation: Quantifying the Sim-To-Real Gap for Velocity Jumps

TL;DR

This work proposes an approach to generate and experimentally validate rigid impact maps from simulations with a physics engine, allowing to model impact scenarios of arbitrarily large complexity.

Abstract

Impact-aware robotic manipulation benefits from an accurate map from ante-impact to post-impact velocity signals to support, e.g., motion planning and control. This work proposes an approach to generate and experimentally validate such impact maps from simulations with a physics engine, allowing to model impact scenarios of arbitrarily large complexity. This impact map captures the velocity jump assuming an instantaneous contact transition between rigid objects, neglecting the nearly instantaneous contact transition and impact-induced vibrations. Feedback control, which is required for complex impact scenarios, will affect velocity signals when these vibrations are still active, making an evaluation solely based on velocity signals as in previous works unreliable. Instead, the proposed validation approach uses the reference spreading control framework, which aims to reduce peaks and jumps in the control feedback signals by using a reference consistent with the rigid impact map together with a suitable control scheme. Based on the key idea that selecting the correct rigid impact map in this reference spreading framework will minimize the net feedback signal, the rigid impact map is experimentally determined and compared with the impact map obtained from simulation, resulting in a 3.1% average error between the post-impact velocity identified from simulations and from experiments.

Figures (9)

• Figure 1: Depiction of the dual-arm robotic setup used throughout the validation approach presented in this work.
• Figure 2: Visualization of a grabbing motion performed using the simulation framework.
• Figure 3: Snapshots of the system for one of the hit-and-push experiments.
• Figure 4: Snapshots of the system for one of the grabbing experiments.
• Figure 5: Impact configuration for the set of hit-and-push experiments for the different ante-impact references. All three cases have identical impact position in Cartesian space, but the impact configuration in joint space is modified for case 3 to investigate its effective on the post-impact velocity.