Publications by Type: Journal Article

C. J. Walsh, Meskers, A. H. Slocum, and R. Gupta, “CT-Compatible Medical Drilling Stylet for Percutaneous Interventions,” ASME Journal of Medical Devices, vol. 6, no. 4, pp. 041001, 2012. Publisher's Version PDF
C. J. Walsh, et al., “Smaller and Deeper Lesions Increase the Number of Acquired Scan Series in CT-guided Lung Biopsy,” Journal of Thoracic Imaging, vol. 26, no. 3, pp. 196-203, 2011. PDF
G. Rothenhofer, C. J. Walsh, and A. H. Slocum, “Transmission Ratio Based Analysis and Robust Design of Mechanisms,” Precision Engineering, vol. 34, no. 4, pp. 790-797, 2010. Publisher's VersionAbstract

This paper proposes an analytical approach to the robust design of mechanisms, to achieve motion and accuracy requirements given a desired transmission ratio and allowable geometrical variations. The focus is on four-bar and slider-crank mechanisms, which are common elements for the transmission of rotary motion, especially over distances, which are too big for the use of conventional elements such as gears, and motion along a predefined guide-curve, which often is a straight line. For many power transmission applications, a constant relation between the motions of an input and corresponding output element is required. For a four-bar linkage, a value of 1 is the only possible constant transmission ratio—achieved when the mechanism has a parallelogram configuration. In the case of a slider-crank linkage a constant transmission ratio can be achieved with a properly designed circular guide-curve, which makes the slider-crank essentially equivalent to a four-bar. In practice, however, as a result of variations in link lengths due to manufacturing tolerances and load-induced or thermal deformations, the transmission ratio for a parallelogram four-bar linkage will deviate substantially from its ideal theoretical value of 1. Even small changes in link lengths due to deformations or joint backlash can cause unacceptable instantaneous transmission ratio variations. The concepts presented are not limited to the design of four-bars and slider-cranks but can also be applied universally in the design of other mechanisms.

C. J. Walsh, et al., “Women with Anorexia Nervosa: Finite Element and Trabecular Structure Analysis by Using Flat-Panel Volume CT,” Radiology, vol. 257, no. 1, pp. 167-174, 2010. PDF
C. J. Walsh, J. T. Heaton, J. B. Kobler, T. L. Szabo, and S. M. Zeitels, “Imaging of the Calf Vocal Fold with High Frequency Ultrasound,” The Laryngoscope, vol. 118, no. Oct. pp. 1894-1899, 2008. PDF
C. J. Walsh and C. K. Kearney, “Engineering, Science and Medicine: Transforming Healthcare,” Royal College of Surgeons in Ireland Student Medical Journal, vol. 1, no. 1, pp. 56-59, 2008. PDF
C. J. Walsh, N. C. Hanumara, A. H. Slocum, J. - A. Shepard, and R. Gupta, “A Patient-Mounted, Telerobotic Tool for CT-Guided Percutaneous Interventions,” ASME Journal of Medical Devices, vol. 2, no. 1, 2008. PDF
C. J. Walsh, K. Endo, and H. Herr, “Quasi-Passive Leg Exoskeleton for Load Carrying Augmentation,” International Journal of Humanoid Robotics, Special Issue: Active Exoskeletons, vol. 4, no. 3, pp. 487-506, 2007.Abstract

A quasi-passive leg exoskeleton is presented for load-carrying augmentation during walking. The exoskeleton has no actuators, only ankle and hip springs and a knee variable damper. Without a payload, the exoskeleton weighs 11.7kg and requires only 2 Watts of electrical power during loaded walking. For a 36kg payload, we demonstrate that the quasi-passive exoskeleton transfers on average 80% of the load to the ground during the single support phase of walking. By measuring the rate of oxygen consumption on a study participant walking at a self-selected speed, we find that the exoskeleton slightly increases the walking metabolic cost of transport (COT) as compared to a standard loaded backpack (10% increase). However, a similar exoskeleton without joint springs or damping control (zero-impedance exoskeleton) is found to increase COT by 23% compared to the loaded backpack, highlighting the benefits of passive and quasi-passive joint mechanisms in the design of efficient, low-mass leg exoskeletons.