Dual Arm Impact-Aware Grasping through Time-Invariant Reference Spreading Control

TL;DR

This paper introduces a novel dual-arm robotic grasping method that leverages impact-aware control with time-invariant reference spreading to improve speed and robustness in simultaneous impacts.

Contribution

It proposes a new impact-aware control framework using reference spreading and a synchronization task, validated through simulations on realistic robot models.

Findings

Effective impact synchronization reduces control effort.

Robustness against impact timing mismatch demonstrated.

Simulation results show improved grasping speed and reliability.

Abstract

With the goal of increasing the speed and efficiency in robotic dual arm manipulation, a novel control approach is presented that utilizes intentional simultaneous impacts to rapidly grasp objects. This approach uses the time-invariant reference spreading framework, in which partly-overlapping ante- and post-impact reference vector fields are used. These vector fields are coupled via the impact dynamics in proximity of the expected impact area, minimizing the otherwise large velocity errors after the impact and the corresponding large control efforts. A purely spatial task is introduced to strongly encourage the synchronization of impact times of the two arms. An interim-impact control phase provides robustness in the execution against the inevitable lack of exact impact simultaneity and the corresponding unreliable velocity error. In this interim phase, a position feedback signal is derived from the ante-impact velocity reference, which is used to enforce sustained contact in all contact points without using velocity error feedback. With an eye towards real-life implementation, the approach is formulated using a QP control framework, and is validated using numerical simulations on a realistic robot model with flexible joints and low-level torque control.