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A Reconfigurable Multiplanar in Vitro Simulator for Real-time Absolute Motion with External and Musculotendon Forces

[+] Author and Article Information
Joshua T. Green

The University of Texas at El Paso College of Engineering Department of Metallurgical, Materials and Biomedical Engineering 500 W. University Ave. El Paso, TX 79968
jtgreen2@miners.utep.edu

Rena F. Hale

Mayo Clinic Orthopedic Biomechanics Laboratory 200 1st St. SW Rochester, MN 55905
hale.rena@mayo.edu

Jerome Hausselle

Oklahoma State University College of Engineering Architecture and Technology Mechanical & Aerospace Engineering 218 Engineering North Stillwater, OK 74078
jerome.hausselle@okstate.edu

Roger V. Gonzalez

The University of Texas at El Paso College of Engineering Department of Engineering Education and Leadership 500 W. University Ave. El Paso, TX 79968
rvgonzalez@utep.edu

1Corresponding author.

ASME doi:10.1115/1.4037853 History: Received October 13, 2016; Revised August 31, 2017

Abstract

Advancements in computational musculoskeletal biomechanics are constrained by a lack of experimental measurement under real-time physiological loading conditions. This paper presents the design, configuration, capabilities, accuracy, and repeatability of The University of Texas at El Paso Joint Load Simulator (UTJLS) by testing four cadaver knee specimens with 47 real-time tests including heel and toe squat maneuvers with and without musculotendon forces. The UTJLS is a musculoskeletal simulator consisting of two robotic manipulators and eight musculotendon actuators. Sensors include eight tension load cells, two force/torque systems, nine absolute encoders, and eight incremental encoders. A custom control system determines command output for position, force, and hybrid control and collects data at 2000 Hz. Controller configuration performed forward-dynamic control for all knee degrees of freedom except knee flexion. Actuator placement and specimen potting techniques uniquely replicate muscle paths. Accuracy and repeatability standard deviations across specimen during squat simulations were equal or less than 8 N and 5 N for musculotendon actuators, 30 N and 13 N for linear ground reaction forces, and 4.4 N m and 1.9 N m for ground reaction moments. The UTJLS is the first of its design type. Controller flexibility and physical design supports axis constraint to match traditional testing rigs, absolute motion, and synchronous real-time simulation of multiplanar kinematics, ground reaction forces, and musculotendon forces. System degrees of freedom, range of motion, and speed support future testing of faster maneuvers, various joints, and kinetic chains of two connected joints.

Copyright (c) 2017 by ASME
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