Continuous models for peristaltic locomotion with application to worms and soft robots.

A continuous model for the peristaltic locomotion of compressible and incompressible rod-like bodies is presented. Using Green and Naghdi's theory of a directed rod, incompressibility is enforced as an internal constraint. A discussion on muscle actuation models for a single continuum is included.

Mechanics-based model for the cooking-induced deformation of spaghetti.

In this article, we propose a minimal model for the cooking-induced deformation of spaghetti and related food products. Our approach has parallels to the use of rod theories for the mechanics of slender bodies undergoing growth and is inspired by a wealth of experimental data from the food science literature. We use our model to investigate the cooking of a single strand of spaghetti confined to a pot and reproduce a curious three-stage deformation sequence that arises in the cooking process.

On Planar Discrete Elastic Rod Models for the Locomotion of Soft Robots.

Modeling soft robots that move on surfaces is challenging from a variety of perspectives. A recent formulation by Bergou of a rod theory that exploits new developments in discrete differential geometry offers an attractive, numerically efficient avenue to help overcome some of these challenges. Their formulation is an example of a discrete elastic rod theory.

Dynamical analysis and development of a biologically inspired SMA caterpillar robot.

With the goal of robustly designing and fabricating a soft robot based on a caterpillar featuring shape memory alloy (SMA) actuators, analytical and numerical models for a soft robot were created based on the forward crawling motion of the Manduca sexta caterpillar. The analytical model features a rod theory and the mechanics of undulation were analyzed using a motion pattern based on the 'Witch of Agnesi' curve. Complementing these models, experiments on a SMA actuator sample were performed in order to determine its flexural rigidity and curvature as a function of the actuation voltage.

A Kinect-based movement assessment system: marker position comparison to Vicon.

Accurate movement analysis systems are prohibitive in cost and size to be accessible to the general population, while commercially available, affordable systems lack the accuracy needed for clinical relevance. To address these limitations, we developed a Depth Camera Movement Assessment System (DCMAS) featuring an affordable, widely available depth camera (e.g.

The roles of impact and inertia in the failure of a shoelace knot.

The accidental untying of a shoelace while walking often occurs without warning. In this paper, we discuss the series of events that lead to a shoelace knot becoming untied. First, the repeated impact of the shoe on the floor during walking serves to loosen the knot.

Verifying the equivalence of representations of the knee joint moment vector from a drop vertical jump task.

Biomechanics software programs, such as Visual3D, Nexus, Cortex, and OpenSim, have the capability of generating several distinct component representations for joint moments and forces from motion capture data. These representations include those for orthonormal proximal and distal coordinate systems and a non-orthogonal joint coordinate system. In this article, a method is presented to address the challenging problem of evaluating and verifying the equivalence of these representations.

On representations for joint moments using a joint coordinate system.

In studies of the biomechanics of joints, the representation of moments using the joint coordinate system has been discussed by several authors. The primary purpose of this technical brief is to emphasize that there are two distinct, albeit related, representations for moment vectors using the joint coordinate system. These distinct representations are illuminated by exploring connections between the Euler and dual Euler bases, the "nonorthogonal projections" presented in a recent paper by Desroches et al.

A musculoskeletal model for the lumbar spine.

A new musculoskeletal model for the lumbar spine is described in this paper. This model features a rigid pelvis and sacrum, the five lumbar vertebrae, and a rigid torso consisting of a lumped thoracic spine and ribcage. The motion of the individual lumbar vertebrae was defined as a fraction of the net lumbar movement about the three rotational degrees of freedom: flexion-extension lateral bending, and axial rotation.

Interclinician and intraclinician variability in the mechanics of the pivot shift test for posterolateral rotatory instability (PLRI) of the elbow.

Hypothesis: Posterolateral rotatory instability (PLRI) of the elbow results from injury to the lateral collateral ligament complex from trauma or iatrogenic injury. The lateral pivot-shift test (PST) is standard for diagnosing PLRI, but its subjectivity affects diagnosis and makes it difficult to train young surgeons. A well-controlled investigation has not been done to quantify interclinician and intraclinician variability in PST mechanics in the intact and unstable elbow.

On the stiffness matrix of the intervertebral joint: application to total disk replacement.

The traditional method of establishing the stiffness matrix associated with an intervertebral joint is valid only for infinitesimal rotations, whereas the rotations featured in spinal motion are often finite. In the present paper, a new formulation of this stiffness matrix is presented, which is valid for finite rotations. This formulation uses Euler angles to parametrize the rotation, an associated basis, which is known as the dual Euler basis, to describe the moments, and it enables a characterization of the nonconservative nature of the joint caused by energy loss in the poroviscoelastic disk and ligamentous support structure.

Curve encirclement and protein structure.

A method of measuring the extent to which space curves encircle one another is introduced. The method provides a family of sets which characterize encircling curves, allowing curve pairs that engage (and also single curves that self-engage) to be distinguished. The method is applied to the backbone chains of protein molecules.