Hydraulic control systems have become increasingly popular as the means of actuation for human-scale legged robots and assistive devices. One of the biggest limitations to these systems is their run time untethered from a power source. One way to increase endurance is by improving actuation efficiency. We investigate reducing servovalve throttling losses by using a selective recruitment artificial muscle bundle comprised of three motor units. Each motor unit is made up of a pair of hydraulic McKibben muscles connected to one servovalve. The pressure and recruitment state of the artificial muscle bundle can be adjusted to match the load in an efficient manner, much like the firing rate and total number of recruited motor units is adjusted in skeletal muscle. A volume-based effective initial braid angle is used in the model of each recruitment level. This semi-empirical model is utilized to predict the efficiency gains of the proposed variable recruitment actuation scheme versus a throttling-only approach. A real-time orderly recruitment controller with pressure-based thresholds is developed. This controller is used to experimentally validate the model-predicted efficiency gains of recruitment on a robot arm. The results show that utilizing variable recruitment allows for much higher efficiencies over a broader operating envelope.

A novel, meso-scale hydraulic actuator characterization test platform, termed a linear hydraulic actuator characterization device, is demonstrated and characterized in this study. The linear hydraulic actuator characterization device is applied to testing McKibben artificial muscles and is used to show the energy savings due to the implementation of a variable recruitment muscle control scheme. The linear hydraulic actuator characterization device is a hydraulic linear dynamometer that can be controlled to enable a desired force and stroke profile to be prescribed to the artificial muscles. The linear hydraulic actuator characterization device consists of a drive actuator that is connected in series with the test muscles. Thus, the drive cylinder can act as a controlled disturbance to the artificial muscles to simulate various loading conditions. With the ability to control the loading conditions of the artificial muscles, the linear hydraulic actuator characterization device offers the ability to experimentally validate the muscles’ performance and energetic characteristics. For instance, the McKibben muscles’ quasi-static force–stroke capabilities, as well as the power savings of a variable recruitment control scheme, are measured and presented in this work. Moreover, the development and fabrication of this highly versatile characterization test platform for hydraulic actuators is described in this article, and the characterization test results and efficiency study results are presented.

The radiolysis mechanism of nitrous oxide adsorbed on magnesia has been studied at 77 K using e.s.r. spectroscopy and chromatography. The radiative decomposition of nitrous oxide is shown to take place not only during the dissociative capture of electrons, but also during the interaction of its molecules with magnesia exitons. At a monolayer coverage 0 < 0.75 the interaction of nitrous oxide with exitons of a solid involves both an ionic and a molecular mechanism, whereas at a monolayer coverage only a molecular mechanism is observed. In this case five magnesia exitons cause decomposition of seven nitrous oxide molecules. The transition from an ionic interaction between N,O molecules and exitons to a molecular one as a result of raising the irradiation temperature of nitrous oxide adsorbed on magnesia (0 = 0.5) has been revealed.An understanding of the mechanisms of radiolytic and photocatalytic heterogeneous processes requires a knowledge of how the transfer to an adsorbate of energy absorbed by a solid during irradiation of the whole system occurs. There are two models of energy transfer from a catalyst to an adsorbate that are usually considered in the literature.arising from applying ionizing radiation to the solid, emerge on the surface to interact with adsorbed molecules. This results in the formation of products and active particles capable of participating in further surface-chemical reactions.According to the second model the adsorbed molecule is a recombination centre of free charge carriers.8. Recombination of such charges on the adsorbed molecule evolves an energy equal to the width of the catalyst forbidden zone. If this energy is sufficient, decomposition of active particles of the adsorbed molecule will occur.Along with energy transfer from the adsorbent to the adsorbate, it may be expected that upon irradiation of a heterogeneous system energy transfer will take place at the expense of electronic excitation of the solid, as occurs upon irradiation of homogeneous systems.1°-12 In this case the energy of electron-excited molecules of the main substance is transferred to impurity molecules, thus resulting in their decomposition.Energy transfer from the solid to adsorbed molecules by electronic excitations of the solid was assumed2* when investigating radiolysis of nitrous oxide adsorbed on silicon oxide. This assumption is based on the fact that, on radiolysis of the N,O-SiO, heterogeneous system, the radiative-chemical yield of nitrogen in the presence of electron acceptors does not fall to zero. However, these experimental data are insufficient, and no additional experiments to confirm this hypothesis have been performed by the authors of ref.( 2 ) and (3).When studying the radiolysis of HCOOH adsorbed on NaA and CaA zeolites, the energy of the ionizing irradiation incident on the zeolite is also assumed13 to be transferred to adsorbed molecules of HCOOH through exitons.We have shown recentlyl4? l5 that nitrous oxide on alumina (Ssp 2 200 m2 g-l) partially decomposes owing to the interaction of its...

This work substantiates the technical solutions for ensuring high water speed of the future amphibious vehicle by the implementation of the movement regime based on the principle of hydrodynamic buoyancy. The conclusions obtained in the course of the search work are proved with the help of computational hydrodynamics modeling.