@inproceedings {1003, title = {Human and passive lower-limb exoskeleton interaction analysis: Computational study with dynamics simulation using nonlinear model predictive control}, booktitle = {The Society of Instrument and Control Engineers (SICE) Annual Conference}, year = {2023}, month = {09/2023}, publisher = {IEEE}, organization = {IEEE}, address = {Tsu, Japan}, keywords = {Balance control, Biomechanical analysis, Model-Based Design, Multibody model, Optimization}, doi = {https://doi.org/10.23919/SICE59929.2023.10354196}, author = {Naoto Haraguchi and Ali Nasr and Keaton A. Inkol and Kazunori Hase and John McPhee} } @inproceedings {921, title = {Model-based design and optimization of passive shoulder exoskeletons}, booktitle = {ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference}, year = {2021}, publisher = {ASME}, organization = {ASME}, abstract = {

To physically assist workers in reducing musculoskeletal strain or to develop motor skills for patients with neuromuscular disabilities, recent research has focused on Exoskeletons (Exos). Designing active Exos is challenging due to the complex human geometric structure, the human-Exoskeleton wrench interaction, the kinematic constraints, and the selection of power source characteristics. Because of the portable advantages of passive Exos, designing a passive shoulder mechanism has been studied here. The study concentrates on modeling a 3D multibody upper-limb human-Exoskeleton, developing a procedure of analyzing optimal assistive torque profiles, and optimizing the passive mechanism features for desired tasks. The optimization objective is minimizing the human joint torques. For simulating the complex closed-loop multibody dynamics, differential-algebraic equations (DAE)s of motion have been generated and solved. Three different tasks have been considered, which are common in industrial environments: object manipulation, over-head work, and static pointing. The resulting assistive Exoskeleton\’s elevation joint torque profile could decrease the specific task\’s human shoulder torque. Since the passive mechanism produces a specific torque for a given elevation angle, the Exoskeleton is not versatile or optimal for different dynamic tasks. We concluded that designing a passive Exoskeleton for a wide range of dynamic applications is impossible. We hypothesize that augmenting an actuator to the mechanism can provide the necessary adjustment torque and versatility for multiple tasks.

}, keywords = {Exoskeletons, Multibody System Dynamics, Optimization, Wearable Robotics}, author = {Ali Nasr and Spencer Ferguson and John McPhee} } @article {847, title = {Constrained Dynamic Optimization of Sit-To-Stand Motion Driven by B{\'e}zier Curves}, journal = {ASME Journal of Biomechanical Engineering}, year = {2018}, type = {Journal Article}, abstract = {

The purpose of this work is two-fold: first, to synthesize a motion pattern imitating sit-to-stand and second, to compare the kinematics and dynamics of the resulting motion to healthy sit-to-stand. Predicting sit-to-stand in simulation inspired the creation of three models: a biomechanical model, a motion model, and performance criteria as a model of preference. First, the human is represented as three rigid links in the sagittal plane. This model captures aspects of joint, foot, and buttocks physiology, which makes it the most comprehensive planar model for predicting sit-to-stand to date. Second, candidate sit-to-stand trajectories are described geometrically by a set of B{\'e}zier curves which seem well suited to predictive biomechanical simulations. Third, with the assumption that healthy people naturally prioritize mechanical efficiency, disinclination to a motion is described as a cost function of joint torques, and for the first time, physical infeasibility including slipping and falling. This new dynamic optimization routine allows for motions of gradually increasing complexity while the model\’s performance is improving. Using these models and optimal control strategy together has produced gross motion patterns characteristic of healthy sit-to-stand when compared with normative data from the literature.

}, keywords = {Biomechanics, Dynamics, Kinematics, Mechanical efficiency, Mechanics, Optimal Control, Optimization, Physiology, Preferences, Simulation}, doi = {10.1115/1.4041527}, url = {http://biomechanical.asmedigitalcollection.asme.org/article.aspx?articleid=2703965}, author = {V Norman-Gerum}, editor = {John McPhee} } @article {841, title = {Optimization-Based Motor Control of a Paralympic Wheelchair Athlete}, journal = {Sports Engineering}, volume = {21}, year = {2018}, abstract = {

The following research approximated how the central nervous system of Paralympic wheelchair athletes resolve kinematic redundancies during upper-limb movements. A multibody biomechanical model of a tetraplegic Paralympic athlete was developed using subject-specific body segment parameters. The angular joint kinematics throughout a specified Paralympic sport movement (i.e., wheelchair curling) were experimentally measured using inertial measurement units. The motor control system of the Paralympian was mathematically modelled and simulated using forward dynamics optimization. The predicted kinematics from different optimization objective functions (i.e., minimizing resultant joint moments, mechanical joint power, and angular joint velocities and accelerations) were compared with those experimentally measured throughout the wheelchair curling movement. Of the optimization objective functions under consideration, minimizing angular joint accelerations produced the most accurate predictions of the kinematic trajectories (i.e., characterized with the lowest overall root mean square deviations) and the shortest optimization computation time. The implications of these control findings are discussed with regards to optimal wheelchair design through predictive dynamic simulations.

}, keywords = {Forward Dynamics Modelling, Human Motor Control, Optimal Control, Optimization, Sports Biomechanics, Sports Engineering}, issn = {1460-2687}, doi = {10.1007/s12283-018-0265-2}, url = {https://link.springer.com/article/10.1007/s12283-018-0265-2}, author = {Brokoslaw Laschowski and Naser Mehrabi and John McPhee} }