This paper presents the design and experimental characterization of a continuously variable linear force amplifier based on the theory of capstans. In contrast to traditional capstan amplifiers, the design presented here uses an elastic cable, enabling a control actuator to not only continuously clutch output to a rotating drum but also passively declutch by releasing tension. Our experimental results demonstrate successful declutching at all force amplification ratios up to the limit of our experimental apparatus, 21 — significantly higher than previously published values. A system of distributed capstan amplifiers driven by a central torque source with cable engagement switched by lightweight, low torque actuators has potential to reduce the mass of distal actuators and enable more dynamic performance in robotic applications.

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The objective of this study is to evaluate the correlations between the quantitative MRI parameter, T 2 relaxation time, and the viscoelastic storage modulus for low concentrations of agarose gel. T 2 values were determined from MR image maps generated by a 3T scanner. The storage modulus was measured by dynamic mechanical analysis (DMA). It was found that the T 2 values decreased, while the storage modulus increased, with higher agarose concentrations.

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