V2SOM: A Novel Safety Mechanism Dedicated to a Cobot’s Rotary Joints

Younsse Ayoubi,Marc Arsicault,Said Zeghloul,Med Laribi

doi:10.3390/robotics8010018

Abstract

Unlike “classical” industrial robots, collaborative robots, known as cobots, implement a compliant behavior. Cobots ensure a safe force control in a physical interaction scenario within unknown environments. In this paper, we propose to make serial robots intrinsically compliant to guarantee safe physical human–robot interaction (pHRI), via our novel designed device called V2SOM, which stands for Variable Stiffness Safety-Oriented Mechanism. As its name indicates, V2SOM aims at making physical human–robot interaction safe, thanks to its two basic functioning modes—high stiffness mode and low stiffness mode. The first mode is employed for normal operational routines. In contrast, the low stiffness mode is suitable for the safe absorption of any potential blunt shock with a human. The transition between the two modes is continuous to maintain a good control of the V2SOM-based cobot in the case of a fast collision. V2SOM presents a high inertia decoupling capacity which is a necessary condition for safe pHRI without compromising the robot’s dynamic performances. Two safety criteria of pHRI were considered for performance evaluations, namely, the impact force (ImpF) criterion and the head injury criterion (HIC) for, respectively, the external and internal damage evaluation during blunt shocks.

Highlights

Robotics was introduced into industry at the beginning of the 1960s
A comparison between V2SOM and a constant stiffness (CS) variable stiffness mechanism (VSM) was performed through simulation of the HR collision model under Matlab/Simulink
An identical elastic deflection value was considered for CS and V2SOM deflection at 80% of Tmax

Summary

Introduction

Several industries (e.g., automobile, military and manufacture) improved their productivity rates thanks to the use of robots, taking advantage of their capabilities to execute repetitive tasks much faster than humans. Those classical industrial robots generally executed the production tasks in highly secured cells, out of the reach of human operators. The use of collaborative robots, known as cobots, emerges as a solution to improve the execution of those tasks where a human is required. Usually isolated to avoid physical contact with humans, cobots coexist with them in a shared common workspace and cooperate with them to accomplish the desired tasks. With the fourth industrial revolution, the number of cobots has increased [2] and they are being used more and more to assist well-experienced humans

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Conclusion