Novel design of a soft lightweight pneumatic continuum robot arm with decoupled variable stiffness and positioning

Soft robot arms possess unique capabilities when it comes to adaptability, flexibility and dexterity. In addition, soft systems that are pneumatically actuated can claim high power to weight ratio. One of the main drawbacks of pneumatically actuated soft arms is that their stiffness cannot be varied independently from their end-effector position in space. The novel robot arm physical design presented in this paper successfully decouples its end-effector positioning from its stiffness. An experimental characterisation of this ability is coupled with a mathematical analysis. The arm combines the light weight, high payload to weight ratio and robustness of pneumatic actuation with the adaptability and versatility of variable stiffness. Light weight is a vital component of the inherent safety approach to physical human-robot interaction. In order to characterise the arm, a neural network analysis of the curvature of the arm for different input pressures is performed. The curvature-pressure relationship is also characterised experimentally

Design, fabrication and control of soft robots

Conventionally, engineers have employed rigid materials to fabricate precise, predictable robotic systems, which are easily modelled as rigid members connected at discrete joints. Natural systems, however, often match or exceed the performance of robotic systems with deformable bodies. Cephalopods, for example, achieve amazing feats of manipulation and locomotion without a skeleton; even vertebrates such as humans achieve dynamic gaits by storing elastic energy in their compliant bones and soft tissues. Inspired by nature, engineers have begun to explore the design and control of soft-bodied robots composed of compliant materials. This Review discusses recent developments in the emerging field of soft robotics.National Science Foundation (U.S.) (Grant IIS-1226883

Conductivity, XRD, and FTIR Studies of New Mg2+-ion-conducting Solid Polymer Electrolytes: [PEG: Mg(CH3COO)2]

Solid polymer electrolytes based on poly (ethylene glycol) (PEG) doped with Mg(CH3COO)2 have been prepared by using the solution-casting method. The X-ray diffraction patterns of PEG with Mg(CH3COO)2 salt indicated a decrease in the degree of crystallinity with increasing concentration of the salt. The complexation of Mg(CH3COO)2 salt with the polymer was confirmed by using Fourier transform infrared spectroscopy (FTIR) studies. The ionic conductivity was measured for the [PEG: Mg(CH3COO)2] system in the frequency range 50 Hz - 1 MHz. The addition of Mg salt was found to improve the ionic conductivity significantly. The 15-wt-% Mg(CH3COO)2-doped system had a maximum conductivity of 1.07 ?10 126 S/cm at 303 K. The conductance spectrum shows two distinct regions: a dc plateau and a dispersive region. The temperature dependence of the ionic conductivity reveals the conduction mechanism to be an Arrhenius-type thermally activated process

The effect of a synthetic double layer hydroxide on the rate of II→I phase transformation of poly(1-butene)

Perkalite is an unusual clay in the domain of polymer-based nanocomposites. In this paper, the use of perkalite as a filler for poly(1-butene) was investigated. Particular attention was posed on the study of the effect of this particular kind of clay on the rate of II→I phase transition of the matrix. Wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) were used to determine the structure and morphology of the samples, the degree of dispersion of the filler and to follow the kinetics of the phase transition of poly(1-butene). Mechanical properties were moreover measured. Perkalite was found to increase the rate of II→I phase transition with respect to the neat matrix, because it affected the free energy of the crystalline phase, by decreasing the perfection of the crystals. Rather than the disruption of the regular ordering at a crystalline cell level, the effect on the lamellar morphology seems to be preponderant. The fragility of perkalite layers and the substantial reduction of the tactoids did not allow to influence the entropic factor to the phase diagram of poly(1-butene), because the filler was not able to locally increase the pressure on the nascent crystalline domains. Perkalite was therefore not able to achieve a direct formation of the phase I of poly(1-butene) directly from the melt. The reduction of the size of perkalite tactoids confirmed that poly(1-butene) is very efficient in homogeneously dispersing the filler, thereby justifying the use of the materials produced in the present study as viable masterbatches for the production of polyolefin-based nanocomposites

Structure-Property Relationships in Heterophasic Thermoplastic Elastomers Filled with Montmorillonite

Polypropylene (PP)/ethylene-propylene rubber (EPR)/Montmorillonite ternary nanocomposites with a phase separated morphology were studied in this work. Wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to investigate the samples. One of the aim of this work was to separate the effects of rubber and clay content on the structure, morphology and mechanical properties of the samples. The presence of clay favored the formation of phase and disrupted the lamellar framework. Clay had moreover a major role in shaping thephase separated morphology of the samples. Atomic Force Microscopy showed that the shearexerted by the clay layers was key for inducing a shish kebab morphology in the polymer matrix. Rubber content decreased the degree of crystallinity at a crystalline cell level and induced the formation of a double population of lamellar stacks. The mechanical properties of the samples primarily depended on rubber content, and they were secondarily tuned by the effect of clay. This synergistic effect allowed to obtain composites with increased stiffness, ductility and toughness, oppositely to what is frequently found

Poly(epsilon-caprolactone) filled with electrospun nylon fibres: A model for a facile composite fabrication

Electrospun fibres are very rarely used as reinforcing agents in polymer-based composites. A fabrication approach is presented that allows to easily prepare composites based on polycaprolactone (PCL) filled with nylon 6 electrospun fibres by compression moulding. At very low filler contents (3%), the obtained composites exhibited improved stiffness with a simultaneous increase in ductility, differently from what is usually found in PCL nanocomposites with a variety of fillers, in which increases in modulus happen at the expense of elongation at break. The presence of fibres with a very small diameter, typical of the products of electrospinning, favoured a good interfacial adhesion between matrix and filler. Being of a similar order of magnitude than polymer lamellae, electrospun fibres can be used to shape the morphology of lamellar stacks, and therefore the final properties of the composites