Traditional robots have rigid underlying structures that limit their ability to interact with their environment. For example, conventional robot manipulators have rigid links and can manipulate objects using only their specialised end effectors. These robots often encounter difficulties operating in unstructured and highly congested environments. A variety of animals and plants exhibit complex movement with soft structures devoid of rigid components. In this paper survey of literature related to continuum arm of robotic manipulator based on biological inspiration is carried out. It defines the fundamental difference between discrete, serpentine and continuum robot devices; presents the 'state of the art' of continuum robots and outlines their areas of application; and introduces some control issues. Finally some conclusions regarding the continued development of these devices are made.
Because of their potential for application in both civil and military sectors as well as the challenge in designing a tiny flying vehicle, micro aerial vehicles have attracted enormous attention. Several configurations of micro aerial vehicles are under development, namely fixed wing, rotary wing, and flapping wing. Under rotary-wing micro aerial vehicles, coaxial contrarotating configurations with a stabilizer bar seem to provide excellent stability behavior in pitch and roll degrees of freedom. This paper presents the results of an experimental study performed on a coaxial-contrarotor helicopter model to evaluate the performance of the rotor system using different rotor blades. The thrust and power of the rotors in independent and coaxial configurations were observed. The percentage thrust loss in the coaxial configuration was seen to be dependent on the ratio of the upper-and lower-rotor revolutions per minute as well as the spacing between the rotors. A theoretical analysis using a nonuniform inflow model was developed, which corroborated very well with the experimental data. Using low-Reynolds-number drag coefficients for the airfoil, the estimated power consumption of the rotors was found to match very well with the experimental data. A closed-form solution using a uniform inflow model to estimate the thrust performance of a coaxial rotor is proposed, which also matches with the experimental observations. Nomenclature a = lift curve slope a 0 , a 1 , a 2 = quadratic fit coefficientsof quadratic solution e = root offset K = nonuniform inflow rotor interaction factor k = uniform inflow rotor interaction factor R = radius of rotor r = radius of curvature of blade r = nondimensional radial location on blade T = thrust V = inflow velocity z = rotor separation distance α = angle of attack β = camber angle λ = nondimensional inflow velocity θ = circular-arc half-angle θ o = collective pitch angle θ o = nonuniform inflow equivalent collective pitch angle θ e = uniform inflow equivalent collective pitch angle σ = rotor solidity Ω = angular velocity of rotor Subscripts c = climb i = induced l = lower rotor u = upper rotor
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