A concept for actuating and controlling a leg of a novel walking parallel kinematic machine tool

The scope of this paper is to present a novel method of actuating the legs of a walking parallel kinematic machine tool (WalkingHex) such that the upper spherical joint can be actively driven while walking and remain a free, passive joint while performing machining operations. Different concepts for the number of Degrees of Freedom (DoF) and methods for actuating the chosen concept are presented, leading to a description of a three-wire actuated spherical joint arrangement. The inverse kinematics for the actuation mechanism is defined and a control methodology that accounts for the redundantly actuated nature of the mechanism is explored. It is demonstrated that a prototype of the system is capable of achieving a motion position accuracy within 5.64% RMS. Utilising the concept presented in this paper, it is possible to develop a walking robot that is capable of manoeuvring into location and performing precision machining or inspection operations

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Mechanical function generators with potentiometer as sensing elemen

Extendible-retractable electric field measurement antenna for IMP J

An antenna dispenser mechanism for the IMP J spacecraft was designed, fabricated, and tested. Upon command the mechanism deploys or retracts a conductor for use as a receiving antenna for an electric field measurement experiment. Five identical units were fabricated and tested to the IMP H & J environmental test specification. Of these, four are designated for flight on the IMP J spacecraft and one as a prototype flight spare. The testing program was successfully completed although certain design modifications were required as problems were uncovered by the testing; particularly thermal vacuum operation. The antenna mechanism functions well under the expected environmental and loading conditions. The wear life and load capability of the dry molybdenum disulphide lubricant originally used on the heavily loaded worm and gear pair were disappointing and a substitute material was applied. The lubricant finally applied performed well; although other problems were generated

Protein disulfide isomerase acts as an injury response signal that enhances fibrin generation via tissue factor activation

The activation of initiator protein tissue factor (TF) is likely to be a crucial step in the blood coagulation process, which leads to fibrin formation. The stimuli responsible for inducing TF activation are largely undefined. Here we show that the oxidoreductase protein disulfide isomerase (PDI) directly promotes TF-dependent fibrin production during thrombus formation in vivo. After endothelial denudation of mouse carotid arteries, PDI was released at the injury site from adherent platelets and disrupted vessel wall cells. Inhibition of PDI decreased TF-triggered fibrin formation in different in vivo murine models of thrombus formation, as determined by intravital fluorescence microscopy. PDI infusion increased — and, under conditions of decreased platelet adhesion, PDI inhibition reduced — fibrin generation at the injury site, indicating that PDI can directly initiate blood coagulation. In vitro, human platelet–secreted PDI contributed to the activation of cryptic TF on microvesicles (microparticles). Mass spectrometry analyses indicated that part of the extracellular cysteine 209 of TF was constitutively glutathionylated. Mixed disulfide formation contributed to maintaining TF in a state of low functionality. We propose that reduced PDI activates TF by isomerization of a mixed disulfide and a free thiol to an intramolecular disulfide. Our findings suggest that disulfide isomerases can act as injury response signals that trigger the activation of fibrin formation following vessel injury

Exploding wire initiation and electrical operation of a 40-kV system for arc-heated drivers up to 10 feet long

Exploding wire initiation and electrical operation of 40 kV system for arc heated drivers up to 10 feet lon