@proceedings {082211289621, title = {Improved haptic fidelity via reduced sampling period with an FPGA-based real-time hardware platform (IMECE)}, volume = {9 PART B}, year = {2007}, note = {

Real Time Operating System (RTOS) control system;Proprietary control card;

}, pages = {1335 - 1342}, address = {Seattle, WA, United States}, abstract = {

Impedance based haptic interfaces face inherent challenges in displaying stiff virtual environments. Fidelity of a virtual environment is enhanced by stiff virtual walls combined with low damping and passive behavior of the interface. However, the stiffness of virtual walls displayed on an impedance based interface is limited by the damping inherent in the controller, the sampling rate of the control loop, and the quantization of the controller{\textquoteright}s position. Attempting to display a stiffness larger than this limiting value destroys the passivity of the interface, leading to active controller behavior and eventually closed loop instability. We propose a method of increasing the fidelity of a PHANToM Premium 1.0 commercial haptic interface by controlling it via a Field Programmable Gate Array (FPGA) both alone and with a Real Time Operating System (RTOS) control system. This custom controller enjoys several benefits over the standard control achieved via a proprietary control card in a Multitasking OS, including reduced system overhead and deterministic loop rate timing. The performance of the proposed FPGA/RTOS controller compares favorably with the performance of an FPGA/Multitasking OS controller. The FPGA/RTOS controller achieves control loop rates an order of magnitude greater than that of the proprietary controller, allowing virtual walls to be displayed with greatly increased stiffnesses, while retaining the passivity and low damping of the PHANToM interface. Copyright {\textcopyright} 2007 by ASME.

}, keywords = {Computer operating systems, Damping, Field programmable gate arrays (FPGA), Multitasking, Real time systems, Virtual reality}, attachments = {https://mahilab.rice.edu/sites/default/files/publications/56-IMECE2007-42085.pdf}, author = {Sevcik, Kevin S. and Kopp, E and O{\textquoteright}Malley, M.K.} } @proceedings {06169823803, title = {Virtual lab for system identification of an electromechanical system}, volume = {74 DSC}, number = {1 PART A}, year = {2005}, note = {

Virtual instrument (vi);Identification laboratory;Virtual Lab (VL);

}, pages = {705 - 712}, address = {Orlando, FL, United States}, abstract = {

A stand-alone virtual instrument (vi) has been developed to augment an experimental system identification laboratory exercise in a required mechanical engineering course on system dynamics. The Virtual Lab (VL) was used productively as a post-lab exercise in conjunction with an existing laboratory experiment for system identification. The VL can be formatted as a standalone file, which the students can download and access at their convenience, without the need for LabVIEW software. The virtual lab presented in this paper used the experimental identification of a transfer function for an xy recorder developed at Rose-Hulman Institute of Technology. In the original Rose-Hulman experiment, students view a video of the acquisition of frequency response data for an X-Y recorder. Then, students complete a detailed optimization procedure using Microsoft Excel in order to determine system parameters for two transfer function models. This paper describes using the Virtual Lab to extend the original lab exercise into an interactive mode. The students complete the Microsoft Excel part of the exercise, but then repeat the optimization using brute force via the LabVIEW based VL developed by the authors, rather than using the optimization toolbox in Excel. With the VL, students can see in real-time the effects of each unknown parameter on the frequency response plot, thus providing additional insight into the relationships between these parameters and the behavior of the electromechanical system. This feature is notably absent in the Microsoft Excel portion of the exercise. Although this exercise uses simple dynamic models, the combination of Excel and LabVIEW approaches provide an insightful introduction to experimental system identification. In this paper, details of the VL are presented, including the functionality of the VL and methodologies for disseminating the VL as a stand-alone piece of software. Finally some assessment results for the original (Excel version) and VL methods of presenting the laboratory exercise are discussed. Copyright {\textcopyright} 2005 by ASME.

}, keywords = {Computer software, Data acquisition, Mathematical models, Mechanical engineering, Real time systems, Students}, attachments = {https://mahilab.rice.edu/sites/default/files/publications/omalley2005asme.pdf}, author = {O{\textquoteright}Malley, M.K. and David M. McStravick} }