In this paper, we propose and investigate a new approach to modeling variable curvature continuum robot sections, based on Euler spirals. Euler spirals, also termed Clothoids, or Cornu spirals, are those curves in which the curvature increases linearly with their arc length. In this work, Euler spirals are applied to the kinematic modeling of continuum robots for the first time. The approach was evaluated using the sections of numerous continuum robots, including two novel parallel continuum robots. Each robot consists of three parallel sections, each with three thin, long McKibben actuators. These sections are poorly modeled by the widely used constant curvature kinematic model. The constant curvature and Euler spiral models were compared and the Euler spiral method was seen to be a significantly better match for a wide range of configurations of the robot hardware.

We describe the design and physical realization of a novel branching continuum robot, aimed at inspection and cleaning operations in hard-to-reach environments at depths greater than human arm lengths. The design, based on a hybrid concentric-tube/tendon actuated continuum trunk core, features two pairs of fully retractable continuum branches. The retractable nature of the branches allows the robot to actively change its topology, allowing it to penetrate narrow openings and expand to adaptively engage complex environmental geometries. We detail and discuss the realization of a physical prototype of the design, and its testing in a simulated glove box environment.

In this paper, we describe a novel nonlinear control strategy for the closed-loop control of extensible continuum robots. Previous attempts at controlling continuum robots have proved difficult due to the complexity of their system dynamics. Taking advantage of a previously developed dynamic model for a three-section, planar, continuum manipulator, we develop an adaptation-based control law. We present simulation results of a set-point tracking between a rigid-link control device and an extensible continuum manipulator. Experimental results of the controller implemented on a six degree-of-freedom continuum robot are also presented.

In this paper, we show how structures and strategies employed by thin-stemmed plants can be adapted to improve robot access to unstructured and congested environments. Specifically, we show how the use of vine-inspired movement strategies can enhance long thin continuum robot exploration and inspection operations. We introduce a new theoretical plant growth-inspired approach for modeling and motion generation of continuum robot backbones. The approach is demonstrated in numerous experiments including inspection within a high fidelity, full-scale mock-up of the International Space Station at NASA Johnson Space Center, using novel robot tendril hardware.

We present a novel approach to teleoperation of continuum robots. In contrast to previous approaches restricted to three Degree-of-Freedom (DoF) joysticks, a six degree-of-freedom rigid-link manipulator is used as the input device. Mappings from the rigid-link arm to the continuum robot are synthesized and analyzed, focusing on their potential for creating a more intuitive operational interface. The approach was implemented using a six degree-of-freedom rigid-link manipulator as input device for teleoperation of a three section, nine degree-of-freedom continuum robot. Tests were conducted across a range of planar and spatial tasks, using fifteen participant operators. The results demonstrate the feasibility of the approach, and suggest that it can be effective independent of the prior robotics, gaming, or teleoperative experience of the operator.

This paper details closed-loop control experiments that were conducted on an extensible continuum manipulator, the OctArm. The performance of three controllers are shown here. The controllers can be classified into two categories: Closed-loop configuration-space control and closed-loop task-space teleoperation. Two controllers were tested in the configuration-space control experiments: a proportional-derivative (PD) controller and a nonlinear sliding-mode controller. The third controller is also shown in which the redundant extensible continuum manipulator tip tracks the motion of a kinematically-dissimilar non-redundant rigid-link master system. The results of these experiments confirm the ability of the control strategies to effectively control continuum robot hardware.

While the field of continuum manipulators has been the subject of increasing attention from the robotics community, knowledge of their inherent capabilities is still limited. Controllers have been proposed that exploit the null-space of redundant continuum manipulators, however studies of the nature of continuum robot null-spaces have not yet been done. In this paper, we first develop a convenient set of extensible, continuum manipulator forward kinematics and resolved-motion rate inverse kinematics. This allows us to analyze the null-space of 2-section, planar, extensible, redundant continuum manipulators to consider the underlying structure of general continuum robot self-motions and discuss their importance to real-world examples and applications.

A continuum manipulator, such as a multi-section trunk/tentacle robot, is promising for deft manipulation of a wide range of objects of different shapes and sizes. Given an object, a continuum manipulator tries to grasp it by wrapping tightly around it. Autonomous grasping requires realtime determination of whether an object can be grasped after it is identified, and if so, the feasible whole-arm wrapping around configurations of the robot to grasp it, which we call grasping configurations, as well as the path leading to a grasping configuration. In this paper, we describe the process for autonomous grasping from object detection to executing the grasping motion and achieving force-closure grasps, with a focus on a general analysis of all possible types of planar grasping configurations of a three-section continuum manipulator. We further provide conditions for existence of solutions and describe how to find a valid grasping configuration and the associated path automatically if one exists. Experimental results with the OctArm manipulator validate our approach, and shows that the entire process to determine an autonomous grasping operation, which includes automatic detection of the target object and determination of a grasping configuration and a path to the grasping configuration that avoids obstacles, can take just a small fraction of a second. Once a grasping configuration is reached, the manipulator can lift the object stably, i.e., a force-closure grasp can be achieved.

In this paper, teleoperated control of a kinematically redundant, continuum slave manipulator with a non-redundant, rigid-link master system is considered. This problem is novel because the self-motion of the redundant robot can be utilized to achieve secondary control objectives while allowing the user to concentrate on controlling only the tip of the slave system. To that end, feedback linearizing controllers are proposed for both the master and slave systems, whose effectiveness is demonstrated using numerical simulations for the case of singularity avoidance as a subtask.

In this paper, we present a new approach towards the control of continuous backbone (continuum) “trunk and tentacle” robots. Development of model-based control algorithms for this new and emerging class of robots has been relatively slow due to the inherent complexity of their mathematical models. Based on the recently developed kinematics, velocity Jacobian and full dynamic model, a simple nonlinear task-space controller, established for rigid-link robots, is adapted and extended for continuum manipulators for the regulation of its tip or any location along its backbone in the task-space. This approach is applicable to all continuum robots with extension/contraction and bending capabilities. Simulation results are shown using a three-section, six degree-of-freedom planar continuum robot.

We discuss disciplinary barriers which have traditionally prevented robotics from significantly impacting the built (architectural) environment we inhabit. Specifically, we describe the implementation of, and lessons learned from, a multidisciplinary graduate-level course in Architectural Robotics. The results from class interactions and projects provide insight into novel ways in which robotics expertise can be effectively leveraged in architecture. Conversely, our outcomes suggest ways in which the knowledge and perspective of architects could stimulate significant innovations in robotics.