Magnetorheological Device Development and Testing: Student Projects Augmenting Research

Journal of Engineering Technology, Spring 2004 by Vavreck, Andrew N

Program Impact and Future Plans

The impact of this research in the Penn State Altoona electromechanical ET (EMET) program is found primarily in capstone design projects incorporating MR technology. Currently, a 1-credit hour preparation course is taught on a pilot basis in the fall semester of the senior year, and a 3credit hour capstone design course is taught in the spring semester of the senior year. With guidance from faculty, student teams develop project ideas and preliminary designs in the prep course, then refine and track project plans through the detailed design, testing, fabrication, and reporting required by the capstone course.7 The project management software Microsoft Project is used in both courses to help students organize, schedule, and monitor project phases. Usually, projects are funded internally, but on occasion industrial support is secured. The EMET program does not aggressively pursue industry-based projects, owing to concerns about industry schedules, liability, contractual complications, funding uncertainties, and a dearth of large industrial concerns in the school's disciplines. However, projects that support faculty research are deliberately pursued. The opportunity to merge faculty teaching and research interests provides much needed efficiency, given the heavy teaching load at an undergraduate campus.

The MR damper test bed has inspired several other student projects involving MR device design. For example, one student team designed and built a rotary MR brake tester, which uses a servomotor and gearbox to actuate a MR brake while a potentiometer and torque cell capture angular displacement and torque data. The brake includes the element of backlash, an interesting part of the parameter estimation. Inspired by the rotary brake team's work, another student team developed a nonreversible MR coupling for use in on-demand, four-wheel drive systems, as shown in figure 17.

This coupling uses permanent magnets mounted on a rotor to vary the magnetic field in a tube through which MR fluid flows. The MR fluid also passes through a hydraulic pump that shares a shaft with the rotor. The magnets are arranged on curved flexible vanes attached to the rotor, and pass through a high viscosity liquid as the rotor turns. The vanes spread open when the rotor turns in one direction, solidifying and impeding the fluid being pumped and increasing torque, and collapse when the rotor turns in the opposite direction, reducing the magnetic field, pumping resistance, and torque. The action duplicates the function of viscous couplings in four-wheel-drive systems, which must disengage in reverse to not interfere with antilock brake operation.8

Another project involved the introduction of MR fluid into a rodless pneumatic cylinder. Especially challenging was the small volume available to introduce an iron core and coil, given the need for passage of the cylinder's sealing bands. The rodless cylinder was successfully converted into a linear brake which that more than quadrupled the static braking force.