DIMLab Stander Symposium Projects

2018

Development and Actuation of a Shape-changing Rigid-body Human Foot Prototype

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This project focuses on the actuation of a multi-segment rigid body foot prototype capable of matching the change in profile of a human foot during gait. Previous work has focused on the design of the prototype using methods of shape-changing kinematic synthesis. In order to actuate the prototype, a tendon-based actuation scheme was conceived and partially implemented. The current prototype includes a series of paired cables, each connected to a separate segment of the foot. Tension in the cables counteracts the force of torsional springs implemented at the joints keeping the segments positioned in a neutral configuration, allowing each segment to achieve appropriate plantar- and dorsiflexion to match gait-derived configurations. Current work focuses on implementing active elements to drive the cables, as well as refinement of joint stiffness to increase the functionality and biomechanical accuracy of the prototype.


Design of a Self-Orienting Solar Array for Small Low-Earth Orbit Satellites

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As electronics have become increasingly smaller and more capable, small satellites called cubesats are deployed in missions that would have taken much larger spacecraft 30 years ago. To power these satellites while in orbit, a novel solar array design is proposed by which these small satellites may harvest energy. With the inspiration of a sunflower that autonomously faces the sun as it passes overhead, a solar array possessing similar characteristics is desirable. The proposed design could generate more energy during the craft's time in the sunlight by continuously adjusting to face the sun. More energy gathered corresponds to an enhancement of the capability of these cubesats due to the ability to accomplish missions with greater scope than those currently in use.

Spatial Morphometric Analysis Using Shape-Changing Rigid-Body Chains

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Morphometry is the quantitative comparison of shapes, primarily curves. As an alternate to classical methods of spatial morphometry, this work investigates a kinematic synthesis methodology for designing a spatial chain of rigid-bodies to match arbitrary spatial curves. The goal is to find a single set of spatial bodies that can be moved to approximately align with any given set of spatial curves. Previous rigid-body shape-change morphometry work focused on mechanisms composed of rigid planar links connected by prismatic and revolute joints to approximate planar curves. Open space curves are the current focus of the research. The primary advantage of this method is its capacity to describe the difference in space curves with a limited number of parameters

Displacement Analysis and Rigid Body Guidance in Spherical Linkages Using SU(2) and Homotopy Continuation

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This work seeks to efficiently and systematically model and solve the equations associated with the class of design problems arising in the study of spherical kinematics. To accomplish this, the group of special unitary matrices, SU(2), is utilized. SU(2) is used to analyze and synthesize the kinematics of a variety of systems including the three-roll wrist, the spherical four-bar mechanism, and the spherical Watt I linkage. Two methods of formulating the synthesis problem are considered. Specifically, the five orientation synthesis of a spherical four-bar mechanism and the eight orientation task of the Watt I linkage are solved using both the loop closure equations and an approach derived from the dot product that recognizes physical constraints within the linkage. Finally, using SU(2) readily allows for the use of a homotopy-continuation-based solver, in this case Bertini. The use of Bertini is motivated by its capacity to calculate every solution to a design problem.

Validating the Location and Tracking of a Human’s Center of Mass Using a Statically Equivalent Serial Chain
This project seeks to validate the use of a statically equivalent serial chain (SESC) in locating and tracking a human’s center of mass (CoM). The statically equivalent serial chain used in this project is comprised of 13 parameters, each roughly corresponding to a portion of the human body. Given these 13 parameters, the SESC points directly at a person’s CoM. Every individual has a unique set parameters to calculate their SESC. These parameters are determined by capturing poses and using the body segment length and position information, as well as the center of pressure reading, acquired from the different poses. A Wii Balance Board and Xbox Kinect were used in this study as inexpensive force plate and motion capture systems. There are other methods for calculating a person’s center of mass, but these require expensive equipment and more complex computational processes. The method proposed here is a low cost, fast, and easy way to accurately predict a person’s CoM. In order to determine the feasibility of the SESC model, subjects of varying body types were tested, and SESC predictions for the CoM were checked for both accuracy and repeatability. A minimum number of poses required to achieve an accurate CoM prediction was determined by figuring out where subject’ parameters converged, which increases time efficiency of the process. Additionally, it was found that the number of frames required to capture a pose could be decreased from 30 to 15 frames without sacrificing accuracy. This resulted in a total testing and setup time of 30 minutes per subject, opposed to one hour previously. Thus, validating the SESC method as a fast, easy, and fairly accurate solution for predicting a human’s CoM

Dynamic Analysis of Alternative Mechanical Press Linkages 
The goal is this project is to compare the dynamic characteristics of alternative linkages for a mechanical press. Mechanical presses are the most common machine used in the mass production of sheet metal parts. Forming sheet metal parts, such as a car door or a tin can, involves striking a flat piece of metal with a die that shapes the part and punctures holes. A conventional press uses a slider-crank linkage and flywheel to provide a high energy strike for a short time period. A motor delivers torque to a flywheel that in turn, provides the rated capacity (tonnage) during the strike. Certain operations, such as deep drawing, require a longer dwell time than is possible with the slider-crank design. Various alternative linkages are proposed that have the ability to provide long dwell times. A dynamic analysis of each linkage is essential to understand motor demands, joint loads, and efficient design options. The linkage analyses are performed using SolidWorks multi-body dynamic simulation software.

Experimental Validation and Reliability Testing for Center of Mass Body Tracking
 

Determining and then tracking the center of mass is difficult for a connected system of segments, such as a human, animal, or humanoid robot. Available techniques to perform these operations are complicated, time-consuming, or expensive. The technique known as Statically Equivalent Serial Chain (SESC) modeling promises to be inexpensive, using only an Xbox Kinect and a Wii Balance Board for equipment, and quick because only a modest number of subject poses are needed. Although SESC models have previously proven to reasonably estimate the center of mass (CoM) of systems of bodies from a limited number of experiments, recent validation testing shows the capacity for significant improvement. This research aimed to improve upon current testing protocols, reduce sensor error through improved calibration, and refine the algorithm employed to produce more meaningful parameters. As the CoM is an important parameter in gait analysis, SESC methods are prominent when considering in-home rehabilitation techniques that are versatile enough to improve potentially offset CoM problems for people of differing body types and sizes. Due to this significance, the research performed continued the development of the SESC technique toward its use in individualized rehabilitation protocols.

Steady-State Modeling of Condensing Units with an Economizer Loop


This work presents an engineering model that simulates the steady-state operation of air-cooled condensing units. Packaged, air-cooled, condensing units includes a compressor, condensing coil, tubing, and fans, fastened to a base or installed within an enclosure. To increase capacity, leading-edge condensing units are being equipped with a brazed-plate heat exchanger for an economizer loop, configured in either upstream or downstream extraction schemes. Results from simulation are shown to favorably compare with experimentation.
Subpages (1): stander symposium 2017