Technical session talks from ICRA 2012
TechTalks from event: Technical session talks from ICRA 2012
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Compliances of Symmetric Flexure Hinges for Planar Compliant MechanismsA general analytical compliance model is presented for symmetric flexure hinges formed of serial segments of known compliances and with thicknesses defined analytically. Serial combination, mirroring, and translation of individual segments yield the flexure compliances. As an illustration, the compliances of a right elliptical corner-filleted flexure hinge are studied. For an aluminum sample with dimensions of l = 0.0254 m, a = 0.006 m, b = 0.008 m, t = 0.0015 m, and w = 0.00635 m, experimental testing, finite element simulation, and analytical results are very close. Results of this study include plots of the rotary compliance in terms of geometric parameters.
Flexure Design Using Metal Matrix Composite Materials: Nanopositioning ExampleAdvanced metal matrix composite (MMC) materials combine a metal and at least another part, such as a ceramic, to form a material with enhanced mechanical properties compared to traditional materials. An aluminium silicon carbide metal matrix material is investigated for compliant flexure design for nanopositioning systems. The material is up to 60% stiffer than traditional aluminum alloy with little to no increase in density. It is shown that the dynamic response of flexure-guided stages can be more easily tailored using the MMC. A flexure-based nanopositioner is designed to exhibit low cross-coupling behavior at high frequencies using the MMC. Finite element analysis (FEA) is used to guide the design process, and a prototype stage is created and evaluated. The measured dynamic response agrees with the FEA modeling; particularly, by using the MMC the actuation mode of the stage can be designed to occur before the out-of-plane modes. The improvement in performance of using the MMC outweighs the disadvantages that include increase cost of the material and lower manufacturability compared to traditional aluminum alloys. The stage is characterized to demonstrate the advantages of the material.
Using Frequency-Weighted Data Fusion to Improve the Performance of a Digital Charge AmplifierPiezoelectric actuators are the most common among a variety of smart actuators due to their high resolution, low power consumption and wide operating frequency but they suffer hysteresis which affects linearity. In this paper a novel digital charge amplifier is presented which reduces hysteresis and linearizes the piezoelectric actuator. A frequency-weighted data fusion algorithm uses a non-linear ARX model to remove drift and increase the bandwidth of digital charge amplifier. Experimental results are presented.
A Z-Scanner Design for High-Speed Scanning Probe MicroscopyA major challenge in high-speed Atomic Force Microscopy is the low vertical bandwidth of the Z-scanner feedback loop. The maximum vertical feedback bandwidth is limited by the first Z-axis resonance frequency of the scanner. In this article, the design of a fast Z-scanner for high-speed Atomic Force Microscopy is presented. The Z-scanner consists of a piezoelectric stack actuator and a diaphragm flexure. The flexure provides the necessary preload to the actuator to prevent it from getting damaged during high-speed scans. A finite-element-analysis based optimization method is used to achieve a high resonance frequency of about 60 kHz. A counterbalance is added to the Z-scanner to minimize the inertial effect which tends to cause vibrations in the lateral axes of the device. This mechanical design enabled us to achieve a closed-loop vertical control bandwidth of 6.5 kHz. This is significantly higher than the closed loop bandwidth of the commercial AFM in which this stage was tested. AFM images of a test grating with sharp corners were recorded at a resolution of 200 x 200 pixels at 10 Hz, 100 Hz and 200 Hz line rates without noticeable image artifacts due to insufficient vertical bandwidth and vibrations.
Estimating the Resolution of Nanopositioning Systems from Frequency Domain DataMechanical and electrical noise in nanopositioning systems is unavoidable and dictates the maximum positioning resolution. The proper specification of resolution is critical for defining the smallest possible dimensions in a manufacturing processes or the smallest measurable features in an imaging application. This article defines a standard for the reporting of resolution and demonstrates how this parameter can be measured and predicted from frequency domain data.