Yingru Wang

The development of variably compliant haptic systems using magnetorheological fluids

In this study the authors develop haptic systems for telerobotic surgery. In order to model the full range of tactile force exhibited from an MR damper a microstructural, kinetic theory-based model of Magnetorheological (MR) fluids has been developed. Microscale constitutive equations relating flow, stress, and particle orientation are produced. The model developed is fully vectorial and relationships between the stress tensor and the applied magnetic field vector are fully exploited. The higher accuracy of the model in this regard gives better force representations of highly compliant objects. This model is then applied in force feedback control of single degree of freedom (SDOF) and two degrees of freedom (2DOF) systems. Carbonyl iron powders with different particle sizes mixed with silicone oils with different viscosities are used to make several sample MR fluids. These MR fluid samples are then used in three different designed MR dampers. A State feedback control algorithm is employed to control a SDOF system and tracking a 2-D profile path using a special innovative MR force feedback joystick. The results indicate that the MR based force feedback dampers can be used as effective haptic devices. The systems designed and constructed in this paper can be extended to a three degree of freedom force feedback system appropriate for telerobotic surgery.

Microstructural Analysis and Control of Magneto-Rheological Fluid

Characteristic phenomenological behavior of MR fluids is typically modeled by Bingham’s equation, which has no fundamental connection to the microstructure of MR fluid and the fully coupled mechanical-electrical-magnetic equations. In this paper microstructurally, kinetic theory-based model of MR fluids (consisting of micro-sized ferrous particles suspended in a Newtonian fluid) are developed. For modeling these composite systems, dumbbell models in which two beads joined by an elastic connector are investigated. In these models the distributed forces from the carrier fluid and from the magnetic field on the suspended particle are idealized as being localized on beads. Microscale constitutive equations relating flow, stress, and particle orientation are produced by integrating the coupled equations governing forces, flow, and orientation over a representative volume of particles and carrier fluid. Coefficients in the constitutive equations are specified not by a fit to macroscale experimental flow measurement but rather in terms of primitive measurements of particle microstructure, carrier fluid, viscosity and density, and temperature. These new models for MR fluids are three dimensional and applicable to any flow geometry, while the Bingham plastic model is in general applicable only to shear flow. The models in this paper reduce to forms similar to Bingham’s model in a simple shear flow, but with coefficients which arise from fundamental electromagnetic considerations and microstructural features such as geometrical, magnetic and mechanical characterization of the particles, quantities measured primitively from the carrier fluid, magnetic field and temperature.Copyright

Magnetorheological fluid based automotive steer-by-wire systems

The idea of this paper is to design a Magnetorheological (MR) fluid based damper for steer-by-wire systems to provide sensory feedback to the driver. The advantages of using MR fluids in haptic devices stem from the increase in transparency gained from the lightweight semiactive system and controller implementation. The performance of MR fluid based steer-by wire system depends on MR fluid model and specifications, MR damper geometry, and the control algorithm. All of these factors are addressed in this study. The experimental results show the improvements in steer-by-wire by adding force feedback to the system.

Characterization of Nanoparticle/Polymer Melt Composites

Two types of nanoparticles are studied: carbon nanofibers and nanoclays. These nanoparticles are incorporated into a polystyrene matrix using different techniques. For the carbon nanofiber/PS composite, solvent casting assisted with sonication and melt compounding methods are used. For nanoclay/PS system, exfoliated and intercalated composites are prepared using in‐situ polymerization and melt compounding methods, respectively. Dispersion of these nanoparticles in the PS matrix is studied using TEM, SEM and XRD. Rheological characterization of these composites is studied using the Rheometrics Mechanical Spectrometer (RMS800) for shear rheology and Rheometrics Melt Extensiometer (RME) for extensional rheology. Effects of the nanoparticle concentration and dispersion methods on the rheology are studied. The morphology of the composites is studied after the samples have been deformed in the rheometers at certain stage. The orientation of the nanoparticles is quantified based on TEM micrographs. Models are de...

Characterization and Modeling of Carbon Nanofiber Suspensions

The morphology and rheology of carbon nanofiber suspensions is studied. Untreated and acid‐treated vapor‐grown carbon nanofibers are dispersed in 90wt% glycerol water solutions. Microscopy analysis shows that the suspensions of the untreated fibers are poorly dispersed, containing some dispersed nanofibers, but also un‐dispersed nanofiber clumps that interact during flow to form continuous networks. In contrast, the treated fibers are observed to be well‐dispersed, and subsequent sonication further disperses the nanofibers, but with the cost of greatly shortening the nanofibers. The rheology of the CNF/glycerol‐water suspensions is found to be highly non‐Newtonian both in shear and extensional flows, with strong dependence on the dispersion, particle length, and concentration of the CNFs. We have developed kinetic theory‐based models for the carbon nanofiber suspensions from SEM measurements of their morphology, and through these models deduce the bulk rheological properties of the composite systems from ...