TechTalks from event: Technical session talks from ICRA 2012

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Compliant Nanopositioning

  • Compliances of Symmetric Flexure Hinges for Planar Compliant Mechanisms Authors: Lobontiu, Nicolae; Cullin, Matt; Ephrahim, Garcia; McFerran Brock, Jennifer; Ali, Muhammad
    A 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 Example Authors: Leang, Kam K.
    Advanced 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 Amplifier Authors: Bazghaleh, Mohsen; Grainger, Steven; Cazzolato, Benjamin Seth; Lu, Tien-Fu
    Piezoelectric 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 Microscopy Authors: Yong, Yuen Kuan; Moheimani, S. O. Reza
    A 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 Data Authors: Fleming, Andrew J.
    Mechanical 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.

Micro and Nano Robots I

  • Polymer-Based Wireless Resonant Magnetic Microrobots Authors: Tung, Hsi-Wen; Frutiger, Dominic R.; Pane, Salvador; Nelson, Bradley J.
    We present a class of Wireless Resonant Magnetic Microactuator (WRMMA) that integrates a polymer spring/body structure with electroplated ferromagnetic masses. The new devices, which we call PolyMites as they are derived from our previous MagMites, are simpler, faster and cheaper to fabricate than the MagMite. Like their predecessor, they are capable of moving on planar surfaces in dry and wet environments. Their improved biocompatibility also extends their potential for biological applications. PolyMites are 500 μm in diameter and 55 μm in height. In air they have attained a speed of 13 mm/s, approximately 26 body lengths per second. PolyMites are capable of micromanipulation on a surface, which is demonstrated by pushing and releasing micro-objects such as polystyrene beads in water.
  • Three-Dimensional Control of Engineered Motile Cellular Microrobots Authors: Kim, Dal Hyung; Kim, Paul; Julius, Agung; Kim, MinJun
    We demonstrate three-dimensional control with the eukaryotic cell Tetrahymena pyriformis (T. pyriformis) using two sets of Helmholtz coils for xy-plane motion and a single electromagnet for vertical motion. T. pyriformis is modified to have artificial magnetotaxis with internalized magnetite. Since the magnetic fields exerted by electromagnets are relatively uniform in the working space, the magnetite exerts only torque, without translational force, which enabled us to guide the cell’s swimming direction while the swimming force is exerted only by the cell’s motile organelles. A stronger magnetic force was necessary to steer cells to the z¬-axis, and, as a result, a single electromagnet placed just below our sample area is utilized for vertical motion. To track the cell’s positions in the z-axis, intensity profiles of non-motile cells at varying distances from the focal plane are used. During vertical motion along the z-axis, the intensity difference from the background decreases while the cell size increases. Since the cell is pear-shaped, the eccentricity is high during planar motion, but lowers during vertical motion due to the change in orientation. The three-dimensional control of the live organism T. pyriformis as a cellular robot shows great potential to be utilized for practical applications in microscale tasks, such as target transport and cell therapy.
  • Towards MR-Navigable Nanorobotic Carriers for Drug Delivery into the Brain Authors: Tabatabaei, Seyed Nasrollah; Sonia, Duchemin; Giouard, Hélène; Martel, Sylvain
    Magnetic Resonance Navigation (MRN) relies on Magnetic Nanoparticles (MNPs) embedded in microcarriers or microrobots to allow the induction of a directional propelling force by 3D magnetic gradients. These magnetic gradients are superposed on a sufficiently high homogeneous magnetic field to achieve maximum propelling force through magnetization saturation of the MNP. As previously demonstrated by our group, such technique was successful at maintaining microcarriers along a planned trajectory in the blood vessels based on tracking information gathered using Magnetic Resonance Imaging (MRI) sequences from artifacts caused by the same MNPs. Besides propulsion and tracking, the same MNPs can be synthesized with characteristics that can allow for the diffusion of therapeutic cargo carried by these MR-navigable carriers through the Blood Brain Barrier (BBB) using localized hyperthermia without compromising the MRN capabilities. In the present study, an external heating apparatus was used to impose a regional heat shock on the skull of a living mouse model. The effect of heat on the permeability of the BBB was assessed using histological observation and tissue staining by Evans blue dye. Results show direct correlation between hyperthermia and BBB leakage as well as its recovery from thermal damage. Therefore, the proposed navigable agents could be suitable for controlled opening of the BBB by hyperthermia and selective brain drug delivery.
  • Diamagnetically Levitated Robots: An Approach to Massively Parallel Robotic Systems with Unusual Motion Properties Authors: Pelrine, Ron; Wong-Foy, Annjoe; McCoy, Brian; Holeman, Dennis; Mahoney, Rich; Myers, Greg; Herson, Jim; Low, Thomas
    Using large numbers of microrobots to build unique macrostructures has long been a vision in both popular and scientific media. This paper describes a new class of machines, DiaMagnetic Micro Manipulator (DM3) systems, for controlling many small robots. The robots are diamagnetically levitated with zero wear and zero hysteresis, and driven using conventional circuits. Unusual motion properties have been reported in testing these systems, including exceptional open loop repeatability of motion (200 nm rms) and relative speeds (37.5 cm/s or 217 body lengths/s) [1]. A system using 130 micro robots as small as 1.7 mm with densities up to 12.5 robots/cm2 has been demonstrated. This paper reports initial data on robot trajectories, and shows that open loop trajectory repeatabilities on the order of 0.8 micrometers rms or better are feasible in a levitated state compared with 15 micrometers rms repeatability in a non-levitated state with surface contact. These results suggest an encouraging path to complex microrobotic systems with broad capabilities.
  • Magnetic Micro Actuator with Neutral Buoyancy and 3D Fabrication of Cell Size Magnetized Structure Authors: Yasui, Masato; Ikeuchi, Masashi; Ikuta, Koji
    We have developed two technologies for 3D magnetic microstructures, with a wide size range between 5&#956;m to 2mm. The first technology enables us to obtain density controlled 3D magnetic microstructures. The size is approximately 500&#956;m. In this scale, controlling density is vital for magnetic micro actuators, because the effect of gravity is strong. To adjust density, we developed the world’s first “density controllable magnetically photocurable (DMPC) polymer.” The DMPC polymer is a mixture of hollow microcapsules (density, 0.03 g/cm<sup>3</sup>), magnetic particles, and photocurable polymer. We can obtain desired relative density between 0.5 to 1.7 by adjusting the concentration of microcapsules. In addition, we succeeded in 3D velocity control of a screw-type magnetic micro actuator with neutral buoyancy in water. The delay time was 32msec. In addition, the actuator possessed 6 DOF. The second technology realized a 5&#956;m magnetic micro actuator, which is a combination of a 3D transparent structure and 2D magnetic structure. Various photocurable polymers can be applied as the 2D structure in this process, although we used magnetically photocurable polymer in this report. Furthermore, we have succeeded in driving a ferromagnetic micro actuator, whose diameter is as small as 1&#956;m. These two fabrication processes will become key technologies in both medical and life sciences field, because they can supply a wide variety of 3D micro structures with small effort.

Needle Steering

  • A New Hand-Held Force-Amplifying Device for Micromanipulation Authors: Payne, Christopher; Tun Latt, Win; Yang, Guang-Zhong
    Abstract— This paper presents a new hand-held device capable of amplifying delicate micromanipulation forces during minimal invasive surgical tasks. It relays force sensing to the user through a simple sliding feature that is coupled to the surgical tool, which translates relative to the casing of the device held by the operator. This forgoes the need of grounding frames or anchoring mechanisms to the body, allowing the device to be used in general surgical environments without affecting the workflow. The device uses a three-phase linear motor that is compact and capable of generating high forces that allow amplification factors of up to ×15. It features a closed-loop force control scheme to perform the required force amplification in which the force exerted on to the user is measured, forming the feedback in the control loop. The device permits interchangeability of instrumentation through a simple docking feature, and thus can be generalized to a range of surgical instruments for micromanipulation tasks. Detailed bench test and user trials have been performed to validate the accuracy and practical performance of the device. The results have shown a five times reduction of the minimum force threshold perceived by the subjects and ergonomically sound manipulation advantages.
  • An Optical Actuation System and Curvature Sensor for a MR-Compatible Active Needle Authors: Ryu, Seok Chang; Quek, Zhan Fan; Renaud, Pierre; Black, Richard J.; Daniel, Bruce; Cutkosky, Mark
    A side optical actuation method is presented for a slender MR-compatible active needle. The needle includes an active region with a shape memory alloy (SMA) wire actuator, where the wire generates a contraction force when optically heated by a laser delivered though optical fibers, producing needle tip bending. A prototype, with multiple side heating spots, demonstrates twice as fast an initial response compared to fiber tip heating when 0.8 W of optical power is applied. A single-ended optical sensor with a gold reflector is also presented to measure the curvature independently of temperature as a function of optical transmission loss. Preliminary tests with the sensor prototype demonstrate approximately linear response and a repeatable signal, independent of the bending history.
  • Semi-automatic needle steering system with robotic manipulator Authors: Bernardes, Mariana Costa; Adorno, Bruno Vilhena; Poignet, Philippe; Borges, Geovany Araujo
    This paper presents a semi-automatic system for robotically assisted 2D needle steering that uses duty-cycling to perform insertions with arcs of adjustable curvature radius. It combines image feedback manually provided by an operator with an adaptive path planning strategy to compensate for system uncertainties and changes in the workspace during the procedure. Experimental results are presented to validate the proposed platform.
  • Torsional Dynamics Compensation Enhances Robotic Control of Tip-Steerable Needles Authors: Swensen, John; Cowan, Noah J.
    Needle insertions serve a critical role in a wide variety of medical interventions. Steerable needles provide a means by which to enhance existing percutaneous procedures and afford the development of entirely new ones. Here, we present a new time-varying model for the torsional dynamics of a steerable needle, along with a new controller that takes advantage of the model. The torsional model incorporates time-varying mode shapes to capture the changing boundary conditions caused during insertion of the needle into the tissue. Extensive simulations demonstrate the improvement over a model that neglects torsional dynamics, and illustrates the possible effect of torsional model order on efficacy. Pilot feedback control experiments, conducted in artificial tissue (plastisol) under stereo image guidance, validate the overall approach: our results substantially out-perform previously reported experimental results on controlling tip-steerable needles.
  • The Impact of Interaction Model on Stability and Transparency in Bilateral Teleoperation for Medical Applications Authors: Sanchez Secades, Luis Alonso; LE, Minh-Quyen; Liu, Chao; Zemiti, Nabil; Poignet, Philippe
    An analysis of stability and transparency of a force feedback teleoperation system for cutting-edge robotic surgery is presented. Previous works in teleoperated robotic surgery do not consider the real behavior of the environment, which was supposed to be only elastic. However, new surgical procedures in which the environment dynamics plays a crucial role start emerging as a result of technological progress. In robotic assisted beating-heart surgery, for instance, the dynamics of the contact between surgical tools and soft tissues has an impact not only in the performance of the force control task but also in the performance of the teleoperation control scheme in terms of transparency and stability. Therefore, a more realistic description of the environment has to be adopted in order to safely operate during robot-patient interaction. For this purpose, a viscoelastic contact model is introduced into the bilateral teleoperation scheme, and a performance study is provided. The obtained results show the advantages of the selected approach when targeting teleoperated surgical interventions in which the interaction dynamics has become a significant issue.