Unlike traditional rigid linked robots, soft robotic manipulators can bend into a wide variety of complex shapes due to control inputs and gravitational loading. This paper presents a new approach for modeling soft robotic manipulators that incorporates the effect of material nonlinearities and distributed weight and payload. The model is geometrically exact for the large curvature, shear, torsion, and extension that often occur in these manipulators. The model is based on the geometrically exact Cosserat rod theory and a fiber reinforced model of the air muscle actuators. The model is validated experimentally on the OctArm V manipulator, showing less than 5% average error for a wide range of actuation pressures and base orientations as compared to almost 50% average error for the constant-curvature model previously used by researchers. Workspace plots generated from the model show the significant effects of self-weight on OctArm V.

Summary form only given. Continuum robots are biologically-inspired by the invertebrate organisms such as octopus arms and elephant trunks. These robots with a backbone-less structure offer a superior performance in unstructured and cluttered environments such as collapsed buildings, unknown geographical terrain, holes and tunnels. This video features OctArm, a continuum robot that demonstrates its capabilities in whole arm manipulation, biologically-inspired maneuvering, and grasping. The video also depicts a 3D graphical model of OctArm in that can be rendered in real-time in Matlab's real-time workshop.

Unlike traditional rigid-linked robots, soft robotic manipulators can bend into a wide variety of complex shapes due to control inputs and gravitational loading. This paper presents a new approach for modeling the dynamics of soft robotic manipulators that incorporates the effect of material nonlinearities and distributed and payload weight and is geometrically exact for the large curvature, shear, torsion and extension that often occur in these manipulators. The model is based on the general Cosserat theory of rods and a fiber reinforced model of air muscle actuators. The model is validated experimentally on the OctArm V manipulator, showing less that 5% average error for a wide range of actuation pressures and base orientations as compared to almost 50% average error for the constant curvature model previously used by researchers.

This paper describes the results of field trials and associated testing of the OctArm series of multi-section continuous backbone "continuum" robots. This novel series of manipulators has recently (Spring 2005) undergone a series of trials including open-air and in-water field tests. Outcomes of the trials, in which the manipulators demonstrated the ability for adaptive and novel manipulation in challenging environments, are described. Implications for the deployment of continuum robots in a variety of applications are discussed

In contrast to traditional robotic manipulators composed of rigid links, a continuum manipulator is a long, continuously flexible extremity that grasps objects usingthe entire length of the trunk. OctArm, a three-section continuum manipulator composed of 9 McKibben actuators, was mounted on tracked mobile platform and teleoperated in a series of field and laboratory experiments. Results from these experiments show its ability to grasp objects of many shapes and sizes, retain a solid hold despite vibration or changes in acceleration, cradle fragile objects reliably, and operate in extreme environments. This robust featureset shows the usefulness and strong potential of these manipulators.

Contact sensors can provide high-information-density object surface sensing in harsh and/or opaque environments. This paper describes the design, modeling, control, and data processing of a contact imager consisting of a flexible whisker mounted on a two-axis robot through a load cell. The whisker sweeps around and into contact with unknown objects, determining the three-dimensional location of contact points to within a specified position resolution. During contact, the whisker bends along the surface normal, producing large deflections. The joint angles and load cell signals are numerically processed to determine the whisker shapes. Comparison of whisker shapes during bending determines contact point location. Experimental results for several objects with wide ranging surface curvature and roughness demonstrate 1.51-cm resolution for a 45.5-cm whisker

Contact sensors can provide high information density object surface sensing in harsh and/or opaque environments. This paper describes the design, modeling, control, and data processing of a contact imager consisting of a flexible whisker mounted on a two-axis robot through a load cell. The whisker sweeps around and into contact with unknown objects, determining the 3-D location of contact points to within a specified position resolution. During contact, the whisker bends along the surface normal, producing large deflections. The joint angles and load cell signals are numerically processed using an elastica model to determine the whisker shapes. Comparison of whisker shapes during bending determines contact point location. Experimental results for several objects with wide ranging surface curvature and roughness demonstrate 1.51 cm RMS resolution for a 45.5 cm whisker.

Wound roll electroactive polymer actuators fabricated with dielectric elastomer (DE) materials provide high bandwidth actuation for robots, minipumps, loudspeakers, valves and prosthetic devices. In this paper, we develop a DE wound roll actuator fabrication process that produces high strain (13%), reliable (3480 cycles at maximum strain), and stiff (157 N/m) actuators. An axisymmetric finite element method (FEM) model with electrostatic and radial bulk modulus nonlinearity predicts actuator displacement and stress. The maximum compressive radial stress occurs at the center of the innermost active layer. This layer also has the thinnest material, indicating the most likely failure point. The nonlinear model predicts actuator displacement in response to applied voltage and load, and matches experiments to within 1 mm.

This paper introduces a novel continuum manipulator consisting of two flexible sections connected by rigid base plates. Each section uses 6-8 opposing contracting and extending McKibben actuators to provide two-axis bending. The contracting/extending actuator pairs are sized and positioned to provide matched rotation and torque. The experimental manipulator generates large rotation (30 - 35 degrees per section and 50 degrees for the entire manipulator) and load capacity (25 lb vertical lift) at 60 psi. With a large strength to weight ratio, this manipulator also is highly flexible, simple to manufacture, and is cost-effective.

Obstacle avoidance and object identification are important tasks for robots in unstructured environments. This paper develops an actuated whisker that determines contacted object profiles using a hub load cell. The shape calculation algorithm numerically integrates the elastica equations from the measured hub angle, displacement, forces, and torque until the bending moment vanishes, indicating the contact point. Sweeping the whisker across the object generates a locus of contact points that can be used for object identification. Experimental results demonstrate the ability to identify and differentiate square and curved objects at various orientations.

We focus on a class of robotic manipulators that utilize continuous backbone structures. Such manipulators, known as "continuum" robots, exhibit behavior similar to tentacles, trunks, and snakes. Specifically, we have previously discussed some of the mechanical and kinematic details of the Clemson -Tentacle Manipulator." This work examines the dynamic characteristics of this manipulator, proposing a vibration damping control strategy for configurations with the worst vibration characteristics. We begin by formulating the dynamics for one section of the Tentacle Manipulator. We then proceed to develop a vibration control strategy which incorporates a setpoint regulator. We supplement the theoretical developments with experimental results.

Presents a control strategy for the horizontal position control of a two degree-of-freedom overhead crane. The approach transforms the underactuated crane dynamics into a form similar to the well known ball-and-beam dynamics. A controller is then developed based on the work of Teel (1992, 1995) for the transformed dynamics using a saturation control design technique. The control approach is based on a crane model which includes the typically neglected, higher-order nonlinearities. The resulting controller provides for asymptotic positioning of the crane payload from a large set of initial conditions. Experimental trials demonstrate the performance of the proposed controller while a computer simulation is used to suggest the benefit of the proposed saturation controller over a standard linear controller.