This article describes the design and fabrication of fiber-reinforced soft actuators for a worm-like robot designed to operate inside constrained tubes. The actuators include bending, extension and torsion. These actuators are experimentally characterised by measuring the deflection versus applied pressure. The results demonstrate that fiber wrapping pattern, geometry of cross-section and elastomer selection are the main determinants of performance. The actuators under consideration are employed to construct a soft worm-like robot capable of ascending a pipe. This class of applications includes steerable catheters, endoscopes and pipe inspection devices.
Piezoelectric and electrostatic based sensors are commonly used to measure pressure, acceleration, strain and force. These sensors can be modeled as a voltage source in series with a capacitive source impedance. There is a misconception that these sensors have infinitesimal resolution. This work describes the noise sources that contribute to the resolution of sensors with capacitive source impedances. The power spectral density (PSD) of each relevant noise source is derived in order to estimate the resolution. Expressions for the root-mean-square (RMS) and peak-to-peak noise are developed. These expressions are experimentally verified by estimating the resolution of a sensor with a 10 nF capacitance and 100 MΩ leakage resistance. The estimated resolution of 390 mV compares well with the measured resolution of 420 mV.
This chapter contains section titled: Product development in manufacturing The need for new product development (NPD) NPD activities NPD models NPD models Applying product development to construction: historical background Construction project process models Process development in construction Conclusion
The article describes a method for estimating the spectrum or RMS value of a low-level signal corrupted by noise. If two identical sensors can be employed simultaneously and the additive noise sources are uncorrelated, the cross power spectrum can recover the power spectrum of the underlying signal. When using the Welch method to estimate the cross power spectrum, the estimation process is shown to be biased but consistent, with a variance that is inversely proportional to the number of data sets. The proposed technique is demonstrated experimentally to recover the vibration spectrum of a piezoelectric cantilever. The dual sensor method reduces the effective noise floor by three orders of magnitude and recovers spectral features that were otherwise lost in noise.
Many soft robots are composed of soft fluidic actuators that are fabricated from silicone rubbers and use hydraulic or pneumatic actuation. The strong nonlinearities and complex geometries of soft actuators hinder the development of analytical models to describe their motion. Finite element modeling provides an effective solution to this issue and allows the user to predict performance and optimize soft actuator designs. Herein, the literature on a finite element analysis of soft actuators is reviewed. First, the required nonlinear elasticity concepts are introduced with a focus on the relevant models for soft robotics. In particular, the procedure for determining material constants for the hyperelastic models from material testing and curve fitting is explored. Then, a comprehensive review of constitutive model parameters for the most widely used silicone rubbers in the literature is provided. An overview of the procedure is provided for three commercially available software packages (Abaqus, Ansys, and COMSOL). The combination of modeling procedures, material properties, and design guidelines presented in this article can be used as a starting point for soft robotic actuator design.
Laser scanning lithography is a maskless method for exposing films of photoresist during semiconductor manufacturing. In this method a focused beam is scanned over a surface with varying intensity to create features in the photoresist. Given the shape of a desired feature, an exposure pattern must be found that approximates this shape in the developed photoresist. This can be cast as an optimization problem, which is complicated by the non-negative nature of the exposure function and the non-linear photochemistry of the film. In this article, a nonlinear programming approach is described that results in a tractable optimization problem which accounts for all of the practical constraints encountered in laser scanning lithography. This method is demonstrated to create a sub-wavelength feature which is verified by optical finite element simulation with a resolution of 20 nm.
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