The Effect of Freespace Properties on Unilateral Stiffness Classification

Virtual environments rendered through kinesthetic haptic devices have frequency-dependent dynamic properties that affect perception. Previous studies on the perception of virtual walls have suggested that the properties not only of the wall, but also of the freespace with which it is paired, influence the perceived wall stiffness (bias) and discrimination thresholds. In this work, two experiments were undertaken to examine the effect of mass and damping properties in freespace on virtual wall stiffness classification. The results suggest that there may be alterations to classification performance under large changes in freespace conditions, but that small changes in mass and damping do not appear to significantly affect performance. These results suggest that additional study is needed to fully understand the effects of freespace properties on wall stiffness classification, which may differ from their effects on discrimination or bias

Self-Powered Microgravity Resistance Exercise with Soft Pneumatic Exoskeletons

As preparations continue towards sending humans on a 3-year mission to Mars, space programs must find solutions to combat muscular atrophy experienced by astronauts during extended time in microgravity. One method currently used to combat muscle deterioration is daily resistance training sessions using an apparatus like the ARED or CEVIS exercise devices, but these daily exercise sessions are not expected to be enough to protect the muscles during longer missions. To help combat muscular atrophy, we propose self-resistance outside of the daily exercise sessions implemented through soft pneumatic exoskeletons that could be integrated into astronauts’ suits, augmenting the formal exercise regimen to improve astronaut health during lengthy missions. To test the effects of self-resistance on muscle activity, we developed an elbow-elbow soft exoskeleton which we pressurized with air and connected to a closed fluid circuit so that as the user flexed their elbows, they were forced to work against themselves (self-resistance) via this column of air. In order to determine the effect of self-resistance, bicep muscle activity (obtained via surface electromyography) was recorded during horizontal motions with self-resistance and during both vertical and horizontal motions without self-resistance. Peak muscle activity and its variability both increased when self-resistance was applied, and correspondence between peak muscle activity and pressure indicates that the level of resistance could be tuned to achieve loads comparable to gravity. This soft pneumatic exoskeleton has the potential for easy integration into astronauts’ suits and could reduce muscle deterioration in microgravity by engaging the muscles more consistently via self-resistance during daily tasks rather than only during specific exercise sessions

Vector Field Control Methods for Discretely Variable Passive Robotic Devices

Passive transmission-based robotic devices are capable of providing motion guidance while ensuring user safety and engagement. To circumvent some of the drawbacks associated with steering continuously variable transmissions based on rolling contacts, we are exploring a class of discretely variable devices, based on brakes and hydrostatic transmissions. Previously available control methods for discretely variable devices were built on velocity fields and only developed to stabilize a 1D target manifold. For n -DOF devices, methods to stabilize target manifolds of dimension 1 to n—1 are of interest. In this paper we contribute constraint field methods that stabilize n — 1 dimensional target manifolds while leaving the orthogonal subspace free to the control of the operator. We also contribute force-modulated SDOF velocity fields, which add between 1 and n— 2 virtual DOFs to the motion of devices whose physical constraints leave one DOF. Control performance is demonstrated in simulation for 3-DOF devices capable of imposing 1-D or 2-D constraints and in experiment for 2-DOF devices imposing 1-D constraints. Our experimental apparatus features digital hydraulic transmissions that are easily configured for n-dimensional space and capable of imposing constraints of any dimension, thus motivating the contributed methods

Effects of Dual-Frequency Environment Exploration on Stiffness Discrimination Thresholds

Previously, excitation frequency has been found to alter perceptual discrimination thresholds of stiffness, mass, and damping. Here, we explore how the blending of two frequencies could affect the just noticeable difference for stiffness. In a perceptual experiment based on the method of adjustments, we tested participants’ ability to match a reference stiffness moving at combinations of two frequencies to explore the effects on stiffness discrimination. As more of the lower frequency was added, participants’ ability to accurately match the reference was hampered. Results suggest that as two frequencies are excited, the resulting perceptual thresholds are blended between the levels for the individual frequencies

\u27Let Me See What I Could Do\u27: Students\u27 Epistemic Affect When Solving Open-Ended, Real-World Problems

This full research paper examines students’ epistemic affect, or their feelings about and within the doing of engineering, when encountering ill-defined problems in two of their first engineering science courses. Ill-defined problems are what students will encounter as professional engineers, but engineering students typically get little practice in their coursework at solving these types of problems. As students explained how they worked their way through the ill-defined and open-ended problems, we found evidence of both positive and negative feelings that arose, as well as descriptions of affective transitions, or shifts from one affect to another. Some of these transitions show evidence that students begin to regulate or anticipate these feelings as a result of repeated exposure to ill-defined problems. This work has implications for including the development of epistemic regulation as part of engineering students\u27 preparation for professional practice

Open-Ended Modeling Group Projects in Introductory Statics and Dynamics Courses

Traditionally, the types of problems that students see in their introductory statics and dynamics courses are well-structured textbook problems with a single solution [1]. These types of questions are often seen by students as being somewhat at-odds with the more “realistic” challenges that they may face in their design or lab courses. Additionally, in the pandemic-necessitated paradigm of emergency online instruction, methods of assessment beyond traditional exams have become more emphasized, both as a way of keeping students engaged by giving the material relevance and of ensuring that the work that they present is their own when so many solutions are available online

Toward Controllable Hydraulic Coupling of Joints in a Wearable Robot

In this paper, we develop theoretical foundations for a new class of rehabilitation robot: body powered devices that route power between a user’s joints. By harvesting power from a healthy joint to assist an impaired joint, novel bimanual and self-assist therapies are enabled. This approach complements existing robotic therapies aimed at promoting recovery of motor function after neurological injury. We employ hydraulic transmissions for routing power, or equivalently for coupling the motions of a user’s joints. Fluid power routed through flexible tubing imposes constraints within a limb or between homologous joints across the body. Variable transmissions allow constraints to be steered on the fly, and simple valve switching realizes free space and locked motion. We examine two methods for realizing variable hydraulic transmissions: using valves to switch among redundant cylinders (digital hydraulics) or using an intervening electromechanical link. For both methods, we present a rigorous mathematical framework for describing and controlling the resulting constraints. Theoretical developments are supported by experiments using a prototype fluid-power exoskeleton

Self-Powered Robots to Reduce Motor Slacking During Upper-Extremity Rehabilitation: A Proof of Concept Study

Background: Robotic rehabilitation is a highly promising approach to recover lost functions after stroke or other neurological disorders. Unfortunately, robotic rehabilitation currently suffers from motor slacking , a phenomenon in which the human motor system reduces muscle activation levels and movement excursions, ostensibly to minimize metabolic- and movement-related costs. Consequently, the patient remains passive and is not fully engaged during therapy. To overcome this limitation, we envision a new class of body-powered robots and hypothesize that motor slacking could be reduced if individuals must provide the power to move their impaired limbs via their own body (i.e., through the motion of a healthy limb). Objective: To test whether a body-powered exoskeleton (i.e. robot) could reduce motor slacking during robotic training. Methods: We developed a body-powered robot that mechanically coupled the motions of the user\u27s elbow joints. We tested this passive robot in two groups of subjects (stroke and able-bodied) during four exercise conditions in which we controlled whether the robotic device was powered by the subject or by the experimenter, and whether the subject\u27s driven arm was engaged or at rest. Motor slacking was quantified by computing the muscle activation changes of the elbow flexor and extensor muscles using surface electromyography. Results: Subjects had higher levels of muscle activation in their driven arm during self-powered conditions compared to externally-powered conditions. Most notably, subjects unintentionally activated their driven arm even when explicitly told to relax when the device was self-powered. This behavior was persistent throughout the trial and did not wane after the initiation of the trial. Conclusions: Our findings provide novel evidence indicating that motor slacking can be reduced by self-powered robots; thus demonstrating promise for rehabilitation of impaired subjects using this new class of wearable system. The results also serve as a foundation to develop more sophisticated body-powered robots (e.g., with controllable transmissions) for rehabilitation purposes

Consideration for Scaffolding Open-Ended Engineering Problems: Instructor Reflections After Three Years

This full research-to-practice paper is a collaboration between researchers and instructors to examine the scaffolding of open-ended problems. Most assigned homework problems are closed-ended with one correct answer and are unlike the ill-defined problems practicing engineers solve in the workplace. To begin bridging this gap, our research team of engineering education researchers and instructors have been designing and implementing ill-defined, open-ended homework problems for the past three years. This study presents instructor reflections on considerations for scaffolding open-ended problems, made after examining survey data from their own students. We present the results in six practices of scaffolding that better support students in their solving of the problems