%0 Journal Article %J IEEE Transactions on Biomedical Engineering %D 2018 %T Quantitative testing of fMRI-compatibility of an electrically active mechatronic device for robot-assisted sensorimotor protocols %A Farrens, A.J. %A Zonnino, A. %A Erwin,Andrew %A O'Malley, M.K. %A Johnson, C.L. %A Ress, D. %A Fabrizio Sergi %B IEEE Transactions on Biomedical Engineering %V 65 %P 1595-1606 %G eng %U http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8012485&tag=1 %R 10.1109/TBME.2017.2741346 %> https://mahilab.rice.edu/sites/default/files/publications/Farrens2018%20-%20Quantitative%20testing%20fMRI-comp.pdf %0 Journal Article %J Frontiers in Neurobotics %D 2017 %T Effects of assist-as-needed upper extremity robotic therapy after incomplete spinal cord injury: a parallel-group controlled trial %A John M. Frullo %A Jared Elinger %A Ali Utku Pehlivan %A Kyle Fitle %A Kathryn Nedley %A Gerard Francisco %A Fabrizio Sergi %A Marcia K. O'Malley %B Frontiers in Neurobotics %V 11 %G eng %> https://mahilab.rice.edu/sites/default/files/publications/fnbot-11-00026.pdf %0 Journal Article %J IEEE Transactions on Neural Systems and Rehabilitation Engineering %D 2017 %T Kinesthetic feedback during 2DOF wrist movements via a novel MR-compatible robot %A Erwin,Andrew %A O'Malley, M.K. %A Ress, D. %A Fabrizio Sergi %B IEEE Transactions on Neural Systems and Rehabilitation Engineering %V 25 %P 1489-1499 %G eng %U http://ieeexplore.ieee.org/document/7763863/ %R 10.1109/TNSRE.2016.2634585 %> https://mahilab.rice.edu/sites/default/files/publications/Erwin2017%20-%20MR%20SoftWrist_0.pdf %0 Journal Article %J IEEE/ASME Transactions on Mechatronics %D 2016 %T A Time-Domain Approach To Control Of Series Elastic Actuators: Adaptive Torque And Passivity-Based Impedance Control %A Dylan P. Losey %A Andrew Erwin %A Craig G. McDonald %A Fabrizio Sergi %A Marcia K. O'Malley %X

Robots are increasingly designed to physically interact with humans in unstructured environments, and as such must operate both accurately and safely. Leveraging compliant actuation, typically in the form of series elastic actuators (SEAs), can guarantee this required level of safety. To date, a number of frequency-domain techniques have been proposed which yield effective SEA torque and impedance control; however, these methods are accompanied by undesirable stability constraints. In this paper, we instead focus on a time-domain approach to the control of SEAs, and adapt two existing control techniques for SEA platforms. First, a model reference adaptive controller is developed, which requires no prior knowledge of system parameters and can specify desired closed-loop torque characteristics. Second, the time-domain passivity approach is modified to control desired impedances in a manner that temporarily allows the SEA to passively render impedances greater than the actuator's intrinsic stiffness. This approach also provides conditions for passivity when augmenting any stable SEA torque controller with an arbitrary impedance. The resultant techniques are experimentally validated on a custom prototype SEA.

%B IEEE/ASME Transactions on Mechatronics %V 21 %P 2085 - 2096 %G eng %U http://ieeexplore.ieee.org/abstract/document/7457670/ %R 10.1109/TMECH.2016.2557727 %> https://mahilab.rice.edu/sites/default/files/publications/Losey_TMECH.pdf %0 Conference Proceedings %B IEEE International Conference on Rehabilitation Robotics (ICORR) %D 2015 %T Development, control, and MRI-compatibility of the MR-SoftWrist %A Erwin,Andrew %A O'Malley, M.K. %A Ress, D. %A Fabrizio Sergi %B IEEE International Conference on Rehabilitation Robotics (ICORR) %I IEEE %C Singapore %P 187-192 %8 08/2015 %G eng %> https://mahilab.rice.edu/sites/default/files/publications/Erwin2015%20-%20MR%20SoftWrist.pdf %0 Journal Article %J IEEE/ASME Transactions on Mechatronics %D 2015 %T Interaction control capabilities of an MR-compatible compliant actuator for wrist sensorimotor protocols during fMRI %A Fabrizio Sergi %A Andrew Erwin %A Marcia K. O'Malley %K compliant actuators. %K Force control %K functional MRI (fMRI) %K MR-compatible robotics %X

This paper describes the mechatronic design and characterization of a novel MR-compatible actuation system designed for a parallel force-feedback exoskeleton for measurement and/or assistance of wrist pointing movements during functional neuroimaging. The developed actuator is based on the interposition of custom compliant elements in series between a non-backdrivable MR-compatible ultrasonic piezoelectric motor and the actuator output. The inclusion of physical compliance allows estimation of interaction force, enabling force-feedback control and stable rendering of a wide range of haptic environments during continuous scanning. Through accurate inner-loop

velocity compensation and force-feedback control, the actuator is capable of displaying both a low-impedance, subject-in-charge mode, and a high stiffness mode. These modes enable the execution of shared haptic protocols during continuous fMRI. 

The detailed experimental characterization of the actuation system is presented, including a backdrivability analysis, demonstrating an achievable impedance range of 22 dB, within a bandwidth of 4 Hz (for low stiffness). The stiffness control bandwidth depends on the specific value of stiffness: a bandwidth of 4 Hz is achieved at low stiffness (10% of the physical springs stiffness), while 8 Hz is demonstrated at higher stiffness. Moreover, coupled stability is demonstrated also for stiffness values substantially (25%) higher than the physical stiffness of the spring. Finally, compatibility tests conducted in a 3T scanner are presented, validating the potential of inclusion of the actuator in an exoskeleton system for support of wrist movements during continuous MR scanning, without significant reduction in image quality.

%B IEEE/ASME Transactions on Mechatronics %V 20 %P 2678-2690 %G eng %R 10.1109/TMECH.2015.2389222 %> https://mahilab.rice.edu/sites/default/files/publications/MR-compatible_actuator_v3.pdf %0 Conference Proceedings %B International Conference on Biomedical Robotics and Biomechatronics (BioRob) %D 2014 %T Compliant force-feedback actuation for accurate robot-mediated sensorimotor interaction protocols during fMRI %A Fabrizio Sergi %A Andrew Erwin %A Brian Cera %A Marcia K. O'Malley %B International Conference on Biomedical Robotics and Biomechatronics (BioRob) %I IEEE %8 08/2014 %G eng %> https://mahilab.rice.edu/sites/default/files/publications/Sergi2014%20-%201DOF%20MR%20devices.pdf %0 Conference Proceedings %B International Conference on Rehabilitation Robotics %D 2013 %T Design of a series elastic actuator for a compliant parallel wrist rehabilitation robot %A Fabrizio Sergi %A Melissa M. Lee %A Marcia K. O'Malley %B International Conference on Rehabilitation Robotics %8 06/2013 %G eng %> https://mahilab.rice.edu/sites/default/files/publications/Sergi_SEA_paper_2.pdf %0 Conference Proceedings %B 6th Annual ASME Dynamic Systems and Controls Conference %D 2013 %T Interaction control for rehabilitation robotics via a low-cost force sensing handle %A Andrew Erwin %A Fabrizio Sergi %A Vinay Chawda %A Marcia K. O'Malley %B 6th Annual ASME Dynamic Systems and Controls Conference %C Palo Alto, CA %G eng %> https://mahilab.rice.edu/sites/default/files/publications/Erwin2013%20-%20RiceWrist-Grip.pdf