Control of Contact Tasks in Autonomous and Human-Robot Collaborative Scenarios: A Dynamical System Approach

Robotic systems are more and more present in our daily life. Robots became indeed more economical, easy to program, safe and collaborative in their interaction with humans, versatile in performing different tasks and adaptive towards changes in the environment. Despite the recent advances in robotics, developing fully autonomous robots to achieve complex industrial or daily-life tasks is still very challenging. The human, due to his superior perception, understanding and reasoning skills, especially in uncertain environment, needs to be in the loop. Therefore, the ability of robots to collaborate with humans is of great interest in the robotics community. Human-Robot Collaboration usually implies robots that share the control of the tasks with humans, providing adjustable autonomy level and mutual adaptation. A field that can particularly benefits from such collaboration is assistive robotics surgery. The introduction of shared autonomy in surgical tasks has several advantages. In particular, it can provide higher accuracy, flexibility, control and efficiency during the operation, over longer time periods, relieve the surgeon during repetitive tasks and reduce his mental workload. However, it is not very clear how to best use shared control to assist a surgeon during the operation. As part of a research project (the "Surgical project"), in this thesis we would like to propose solutions to that problem by building a teleoperated shared control architecture for a laparoscopic surgery scenario. While laparoscopic surgery usually involves one surgeon and two human assistants to perform the surgery, the project aims to replace the assistants by two partially teleoperated robotic systems. The target shared control architecture would explore various strategies to ensure safety for both the patient and the surgeon, provide accuracy and stability in motion and force control of the tools attached to the robots, reduce the mental workload of the surgeon and adapt the level of assistance based on well-identified criteria. The first year was mainly devoted to the control of motion and force for contact tasks which is of great importance in the context of the project. Robot force control is traditionally achieved either explicitly through hybrid position/force control or implicitly using impedance control. We propose an approach leveraging the properties of dynamical systems (DS) for immediate re-planning and robustness to real-time perturbations by exploiting local modulation of the DS. Dynamical systems has been widely used as a tool to represent and generate motion in robotics application. Here the idea is to propose a DS formulation to generate contact force in addition to motion. First implementation and experiments to evaluate the effectiveness of the strategy were conducted in practice with a 7-DOF robotic arm (KUKA LWR IV+). So far we focused on contact tasks that were performed autonomously by one or two robots. Future work will improve and use the proposed DS approach to consider contact tasks in shared control scenarios where one human and one or two robots need to collaborate to successfully achieve the tasks. Because of the nature of the surgical project we will use teleoperation systems to introduce the human in the loop. The developed teleoperated shared control architecture will be evaluated on laparoscopic surgery related tasks