David T. Branson

Shape function-based kinematics and dynamics for variable length continuum robotic arms

This paper presents a new three dimensional kinematic and dynamic model for variable length continuum arm robotic structures using a novel shape function-based approach. The model incorporates geometrically constrained structure of the arm to derive its deformation shape function. It is able to simulate spatial bending, pure elongation, and incorporates a new stiffness control feature. The model is validated through numerical simulations, based on a prototype continuum arm, that yields physically accurate results.

Design, modeling and control of a pneumatically actuated manipulator inspired by biological continuum structures

Biological tentacles, such as octopus arms, have entirely flexible structures and virtually infinite degrees of freedom (DOF) that allow for elongation, shortening and bending at any point along the arm length. The amazing dexterity of biological tentacles has driven the growing implementation of continuum manipulators in robotic systems. This paper presents a pneumatic manipulator inspired by biological continuum structures in some of their key features and functions, such as continuum morphology, intrinsic compliance and stereotyped motions with hyper redundant DOF. The kinematics and dynamics of the manipulator are formulated and identified, and a hierarchical controller taking inspiration from the structure of an octopus nervous system is used to relate desired stereotyped motions to individual actuator inputs. Simulations and experiments are carried out to validate the model and prototype where good agreement was found between the two.

Novel modal approach for kinematics of multisection continuum arms

This paper presents a new three dimensional (3D) kinematic model based on mode shape functions (MSF) for multisection continuum arms. It solves the singularity problems associated with previous models and introduces a novel approach for intuitively deriving exact, singularity-free MSFs, thus avoiding mode switching schemes and simplifying error models. The model is able to simulate spatial bending, pure elongation/contraction, and introduces inverse orientation kinematics for the first time to multisection continuum arms. Also, it carefully accounts for physical constraints in the joint space to provide enhanced insight into practical mechanics, and produces correct results for both forward and inverse kinematics. The model is validated through simulations, based on a prototype continuum robotic arm. Proposed approach is applicable to a broad spectrum of continuum robotic arm designs.

Dynamic model of a hyper-redundant, octopus-like manipulator for underwater applications

The octopus arm is a unique tool that combines strength and flexibility. It can shorten, elongate and bend at any point along its length. To model this behavior, a hyper-redundant manipulator composed of multiple segments is proposed. Each segment is a parallel robotic mechanism with redundant actuation. The kinematics and dynamics of this manipulator are analyzed and simulated utilizing a modular computational modeling method. Simulation results for some primitive movements are presented, and the effect of hydrodynamic forces is included.

Dynamic modeling and control of an octopus inspired multiple continuum arm robot

This paper proposes a dynamic model for a multiple continuum arm robot inspired by live octopuses. The kinematics and dynamics for a single arm are analyzed and formulated including the longitudinal muscles, radial muscles, isovolumetric constraints, and interaction between suckers and an object. The single arm model is then expanded to a multiple arm system that is capable of generating archetypal locomotion patterns such as crawling and swimming. A hierarchical controller based on octopus neurophysiology is used to achieve simple and reliable control of the multiple continuum arm system. Simulations for single arm movements and multiple arm locomotions are presented. The results of this work can be used in the study of control schemes for multiple continuum arm robots and live octopuses.

Dynamic continuum arm model for use with underwater robotic manipulators inspired by octopus vulgaris

Continuum structures with a very high or infinite number of degrees of freedom (DOF) are very interesting structures in nature. Mimicking this kind of structures artificially is challenging due to the high number of required DOF. This paper presents a kinematic and dynamic model for an underwater robotic manipulator inspired by Octopus vulgaris. Then, a prototype arm inspired by live octopus is presented and the model validated experimentally. Initial comparisons of simulated and experimental results show good agreement.

Pneumatic muscle actuated continuum arms: Modelling and experimental assessment

This paper presents an improved mode shape function-based 3D dynamic model for pneumatic muscle actuated continuum arms, and validates the model and simulation results through experimental testing. The model also facilitates the direct control of pneumatic muscle actuated continuum arms through the use of input pressure. This is achieved without additional intermediary transformations and does not have singularity problems present in previous models. The proposed arm model uses a new pneumatic muscle actuator (PMA) dynamic model with hysteresis that is capable of modelling both extending and contracting PMAs. The proposed hysteric model is simple, easily adaptable, and validated experimentally. The PMA model can be applied to dynamically model any PMA based system as well as PMA actuated continuum arms utilizing different actuator configurations.

Dynamics for biomimetic continuum arms: A modal approach

This paper presents an improved 3D dynamic model based on mode shape functions for biomimetic continuum robotic arms intended for underwater operation. It is an extension to the dynamic model proposed in the authors previous work to incorporate angular moments and hydrodynamic forces such as buoyancy, lift, and drag. The proposed model is based on an accurate kinematic model and gives an enhanced insight into practical mechanics. Also, it can be generalized for any variable length continuum arm to include external forces. A feedback control structure in the joint space is also implemented for increased performance of the continuum arm. Numerical results demonstrate underwater effects for spatial bending and pure elongations/contractions. The model carefully accounts for mechanical constraints in the joint space to yield physically accurate results.

A 3D dynamic model for continuum robots inspired by an octopus arm

Continuum robotic arms are based on non-rigid components that result in a nearly infinite number of degrees of freedom (DOF). Due to this reason it can be very complex to establish mathematical models for continuum robotic arms. This paper presents a 3D dynamic model of an arm based on octopus anatomy that utilizes 4 longitudinal and 4 radial muscles. The arm is composed of a multi-segment structure having distributed stiffness and damping to represent the muscles. The simulations are applied to a multi-segment arm, and results mimic several typical octopus arm motions.

Timing-based control via echo state network for soft robotic arm

Soft robots are difficult to control because of their compliant and elastic body dynamics compared with robots made of rigid bodies. In this paper, we present a control scheme inspired by the octopus called timing-based control for soft robotic arms. This control scheme is motivated to positively exploit the natural dynamics of the soft body. We demonstrate a scheme for controlling an object-reaching task by using an echo state network on a 3D physical soft robotic arm simulator and show that this network can successfully perform the task. Detailed analyses and evaluations of the generalization capacity of the network and the performances to the reaching task are presented.