Efficient Collision Detection Method for Flexure Mechanisms Comprising Deflected Leafsprings

When designing and optimizing spatial flexure mechanisms, it is hard to predict collision due to 3D motion and large deformations, which compromises the utilization of spatial freedom. A computationally efficient collision test is desirable to assure that feasible mechanism designs are found when algorithmically optimizing the shape of elastic mechanisms, which are prone to collision. In this paper, a method is presented to test for collision specifically suited for flexure mechanisms by taking advantage of the typical slender aspect ratio and shape of the elastic members. Hereby, an efficient collision test is obtained that allows for the computation of a quantitative value for the severeness of collision. This value can then be used to efficiently converge to collision free solutions without excluding good mechanism designs leading to improved mechanisms, which utilize the maximum spatial design freedom

3D-printed flexure-based finger joints for anthropomorphic hands

Flexure-based finger joints for prosthetic hands have been studied, but until now they lack stiffness and load bearing capacity. In this paper we present a design which combines large range of motion, stiffness and load bearing capacity, with an overload protection mechanism. Several planar and non-planar hinge topologies are studied to determine load capacity over the range of motion. Optimized topologies are compared, in 30 degrees deflected state, in terms of stresses by deflection and grasping forces. Additionally, support stiffnesses were computed for all hinges in the whole range of motion (45 degrees). The Hole Cross Hinge presented the best performance over the range of motion with a grasping force up to 15 N while deflected 30 degrees. A new concept, the Angle Three-Flexure Cross Hinge, provides outstanding performance for deflections from 17.5 up to 30 degrees with a 20 N maximum grasping force when fully deflected. Experimental verification of the support stiffness over the range of motion shows some additional compliances, but the stiffness trend of the printed hinge is in line with the model. The presented joints power grasping capability outperform current state flexure-base hands and are comparable to commercial non-flexure-based prosthetic hands. In the event of excessive loads, an overload protection mechanism is in place to protect the flexure- hinges

Inverted curved flexure hinge with torsional reinforcements in a printed prosthetic finger

Flexure-based finger joints for prosthetic hands have been studied, but until now they lack stiffness and load capacity. In this paper we present a design which combines large range of motion, stiffness and load capacity, with a torsional overload protection mechanism. Five design considerations which increase grasp force and limit the stress values are presented: (1) Due to the inverted flexure attachment, the flexures are loaded mainly in tension, avoiding buckling of flexures. (2) Curved flexures have been used of which one straightens out at large deflection angles to improve load capacity at large deflections. (3) To achieve high torsional loads, one of the flexures is outfitted with triangular torsional stiffeners, which increase the out-of-plane stiffness significantly, while only slightly increasing the actuation stiffness. (4) The entire joint is rotated by 20˚ so the combination of actuation and contact forces lead to mainly axial forces in the curved leaf spring, avoiding excessive internal bending. The presented prosthetic flexure-based finger joint is able to achieve 20N of contact force with an additional 5N of out of plane load over the entire 80˚ range of motion, which is a major improvement over existing prosthetic flexure-based finger designs

Contrasting phenotypes of putative proprioceptive and nociceptive trigeminal neurons innervating jaw muscle in rat

BACKGROUND: Despite the clinical significance of muscle pain, and the extensive investigation of the properties of muscle afferent fibers, there has been little study of the ion channels on sensory neurons that innervate muscle. In this study, we have fluorescently tagged sensory neurons that innervate the masseter muscle, which is unique because cell bodies for its muscle spindles are in a brainstem nucleus (mesencephalic nucleus of the 5(th )cranial nerve, MeV) while all its other sensory afferents are in the trigeminal ganglion (TG). We examine the hypothesis that certain molecules proposed to be used selectively by nociceptors fail to express on muscle spindles afferents but appear on other afferents from the same muscle. RESULTS: MeV muscle afferents perfectly fit expectations of cells with a non-nociceptive sensory modality: Opiates failed to inhibit calcium channel currents (I(Ca)) in 90% of MeV neurons, although I(Ca )were inhibited by GABA(B )receptor activation. All MeV afferents had brief (1 msec) action potentials driven solely by tetrodotoxin (TTX)-sensitive Na channels and no MeV afferent expressed either of three ion channels (TRPV1, P2X3, and ASIC3) thought to be transducers for nociceptive stimuli, although they did express other ATP and acid-sensing channels. Trigeminal masseter afferents were much more diverse. Virtually all of them expressed at least one, and often several, of the three putative nociceptive transducer channels, but the mix varied from cell to cell. Calcium currents in 80% of the neurons were measurably inhibited by μ-opioids, but the extent of inhibition varied greatly. Almost all TG masseter afferents expressed some TTX-insensitive sodium currents, but the amount compared to TTX sensitive sodium current varied, as did the duration of action potentials. CONCLUSION: Most masseter muscle afferents that are not muscle spindle afferents express molecules that are considered characteristic of nociceptors, but these putative muscle nociceptors are molecularly diverse. This heterogeneity may reflect the mixture of metabosensitive afferents which can also signal noxious stimuli and purely nociceptive afferents characteristic of muscle