Kinematically optimal hyper-redundant manipulator configurations

“Hyper-redundant” robots have a very large or infinite degree of kinematic redundancy. This paper develops new methods for determining “optimal” hyper-redundant manipulator configurations based on a continuum formulation of kinematics. This formulation uses a backbone curve model to capture the robot's essential macroscopic geometric features. The calculus of variations is used to develop differential equations, whose solution is the optimal backbone curve shape. We show that this approach is computationally efficient on a single processor, and generates solutions in O(1) time for an N degree-of-freedom manipulator when implemented in parallel on O(N) processors. For this reason, it is better suited to hyper-redundant robots than other redundancy resolution methods. Furthermore, this approach is useful for many hyper-redundant mechanical morphologies which are not handled by known methods

Discrete Cosserat Approach for Multi-Section Soft Robots Dynamics

In spite of recent progress, soft robotics still suffers from a lack of unified modeling framework. Nowadays, the most adopted model for the design and control of soft robots is the piece-wise constant curvature model, with its consolidated benefits and drawbacks. In this work, an alternative model for multisection soft robots dynamics is presented based on a discrete Cosserat approach, which, not only takes into account shear and torsional deformations, essentials to cope with out-of-plane external loads, but also inherits the geometrical and mechanical properties of the continuous Cosserat model, making it the natural soft robotics counterpart of the traditional rigid robotics dynamics model. The soundness of the model is demonstrated through extensive simulation and experimental results for both plane and out-of-plane motions.Comment: 13 pages, 9 figure

Trunk Robot for Extended Environments

We describe the design and physical realization of a novel type of large-scale continuum robot. The design, based on a hybrid concentric-tube/tendon actuated structure, is realized at a significantly larger scale than previous concentric tube continuum robots, with an extended length well over one meter. While operation at this scale opens up new types of potential applications, realization at this scale presents interesting challenges. We detail and discuss the associated issues via the prototyping and testing of the physical system with the help of experiments

A disposable continuum endoscope using piston-driven parallel bellow actuator

This paper presents a novel low cost disposable continuum endoscope based on a piston-driven parallel bellow actuator design. The parallel bellow actuator achieves motion by being pressurized via displacement-controlled pistons. The displacements are generated by rack-and-pinion mechanisms using inexpensive stepper motors. The design concept provides a potential alternative solution to upper gastrointestinal (UGI) diagnosis. The modularity and the use of inexpensive components allow for low fabrication costs and disposability. The use of robotic assistance could facilitate the development of an easier interface for the gastroenterologists, avoiding the nonintuitive manipulation mapping of the traditional UGI endoscopes. We adapt existing kinematic solutions of multi-backbone continuum robots to model continuum parallel bellow actuators. An actuation compensation strategy is presented and validated to address the pneumatic compressibility through the transmission lines. The design concept was prototyped and tested with a custom control platform. The experimental validation shows that the actuation compensation was demonstrated to significantly improve orientation control of the endoscope end-effector. This paper shows the feasibility of the proposed design and lays the foundation toward clinical scenarios

Continuum Robots for Space Applications Based on Layer-Jamming Scales with Stiffness Capability

Continuum robots, which have continuous mechanical structures comparable to the flexibility in elephant trunks and octopus arms, have been primarily geared toward the medical and defense communities. In space, however, NASA projects these robots to have a place in irregular inspection routines. The inherent compliance and bending of these continuum arms are especially suitable for inspection in obstructed spaces to ensure proper equipment functionality. In this paper, we propose a new solution that improves on the functionality of previous continuum robots, via a novel mechanical scaly layer-jamming design. Layer-jamming assisted continuum arms have previously required pneumatic sources for actuation, which limit their portability and usage in aerospace applications. This paper combines the compliance of continuum arms and stiffness modulation of the layer jamming mechanism to design new hybrid layer jamming continuum arms. The novel designs use an electromechanical actuation which eliminates the previous need for pneumatic actuation therefore making the hardware compact and portable

Modeling and Verification of a Multi-section Continuum Robot

Continuum robots mimic the principle of a special biological structure known as the muscular hydrostat. These robots have an ability to bend at any location on along its backbone and have potential applications in disaster relief, medical surgeries and nuclear waste disposal. This thesis presents the modeling and verification of a multi-section continuum robot by applying the Cosserat theory of rods. Next, 2D verification is performed on a continuum robot based on a backbone composed of a nickel titanium alloy. In addition, the thesis develops the theoretical foundations for a cable-driven continuum robot by studying the effects of cable guide mass which cause additional deformation of the robot The results of this thesis show that the multi-section model is accurate within 3.4% in predicting the Cartesian tip coordinates, and the model with the cable guides accurate within 1.26% error in predicted versus the observed Cartesian tip coordinates of the backbone

Dynamics for variable length multisection continuum arms

Variable length multisection continuum arms are a class of continuum robotic manipulators that generate motion by structural mechanical deformation. Unlike most continuum robots, the sections of these arms do not have (central) supporting flexible backbone, and are actuated by multiple variable length actuators. Because of the constraining nature of actuators, the continuum sections can bend and/or elongate (compress) depending on the elongation/contraction characteristics of the actuators being used. Continuum arms have a number of distinctive differences with respect to traditional rigid arms namely: smooth bending, high inherent compliance, and adaptive whole arm grasping. However, due to numerical instability and the complexity of curve parametric models, there are no spatial dynamic models for multisection continuum arms. This paper introduces novel spatial dynamics and applies these to variable length multisection continuum arms with any number of sections. An efficient recursive computational scheme for deriving the equations of motion is presented. This is applied in a general form based on structurally accurate and numerically well-posed modal kinematics that assumes circular arc deformation of continuum sections without torsion. It is shown that the proposed modal dynamics are highly scalable, producing efficient and accurate numerical results. The spatial dynamic simulation results are experimentally validated using a pneumatic muscle actuated multisection prototype continuum arm. For the first time this enables investigation of spatial dynamic effects in this class of continuum arms