Multiple-Contact Estimation for Tendon-Driven Continuum Robots with Proprioceptive Sensor Information by Contact Particle Filter and Kinetostatic Models

This paper presents a new approach to determine single and multiple simultaneous contact forces on a tendon-driven continuum robot (CR). The estimation is based solely on the proprioceptive tendon force and length sensors that are already present. Unlike for rigid-body robots, only indirect measurements of the external forces' deflection is available. The required full kinetostatic model, which is prone to local minima due to the unknown contacts, is solved with a particle filter. The method is validated by simulative studies and experimental investigations on a new robot setup for visual inspection of aircraft engines. The algorithm allows the estimation of single contacts with an error up to 4.43 mm or 2.9 % of the robot's length. Multiple contacts can only be correctly determined at the two distal of the three segments.

I. Introduction

As soon as a robot interacts with its environment, contact occurs that influences the robot's dynamics. While in human-robot collaboration (HRC) contact with the environment (as opposed to the human) should be avoided to prevent damage [1], in manipulation tasks contact is exploited to perform a task. Contact is required for legged or snake-like locomotion or for stabilizing the equilibrium e.g. of a humanoid robot with it's arms. Continuum robots are often used in confined unknown environments where intentional or unintentional contact with the environment occurs [2]. Before the contact situation can be exploited or avoided, it must be estimated.