Model-Based Estimation of the Gravity-Loaded Shape and Scene Depth for a Slim 3-Actuator Continuum Robot with Monocular Visual Feedback

Abstract

Fruitful developments on continuum robots have been witnessed in recent years due to their movements and manipulation capabilities in confined spaces. Due to the nature that a continuum robot has an infinite number of DoFs (Degrees of Freedom), majority of the existing systems deployed abundant actuators such that the robot can be controlled in separately modeled and actuated segments with constant or variable curvature. As the shape of a continuum robot is always jointly determined by its actuation and the interactions from the environment, it is hence worth exploring the opposite approach that how a task can be accomplished with a minimal number of actuators. This paper presents the first step of such an investigation where a slim 3-actuator continuum robot is actuated to reach different spatial locations under gravity. As the gravity greatly affects the robot's shape, a monocular camera, together with two UKFs (Unscented Kalman Filters), was used to concurrently estimate the robot's shape and the feature depth. Then the estimated shape can be used in updating the kinematics model of the robot to achieve motion control. Experiments were conducted to validate the effectiveness of the proposed shape estimation, which promises the motion control implementation in the near future work.