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The generation of walking motion is one of the most vital functions of the human body because it allows us to be mobile in our environment. Unfortunately, numerous individuals suffer from gait impairment as a result of debilitating conditions like stroke, resulting in a serious loss of mobility. Our understanding of human gait is limited by the amount of research we conduct in relation to human walking mechanisms and their characteristics. In order to better understand these characteristics and the systems involved in the generation of human gait, it is necessary to increase the depth and range of research pertaining to walking motion. Specifically, there has been a lack of investigation into a particular area of human gait research that could potentially yield interesting conclusions about gait rehabilitation, which is the effect of surface stiffness on human gait. In order to investigate this idea, a number of studies have been conducted using experimental devices that focus on changing surface stiffness; however, these systems lack certain functionality that would be useful in an experimental scenario. To solve this problem and to investigate the effect of surface stiffness further, a system has been developed called the Variable Stiffness Treadmill system (VST). This treadmill system is a unique investigative tool that allows for the active control of surface stiffness. What is novel about this system is its ability to change the stiffness of the surface quickly, accurately, during the gait cycle, and throughout a large range of possible stiffness values. This type of functionality in an experimental system has never been implemented and constitutes a tremendous opportunity for valuable gait research in regard to the influence of surface stiffness. In this work, the design, development, and implementation of the Variable Stiffness Treadmill system is presented and discussed along with preliminary experimentation. The results from characterization testing demonstrate highly accurate stiffness control and excellent response characteristics for specific configurations. Initial indications from human experimental trials in relation to quantifiable effects from surface stiffness variation using the Variable Stiffness Treadmill system are encouraging.
ContributorsBarkan, Andrew Robert (Author) / Artemiadis, Panagiotis (Thesis director) / Santello, Marco (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2015-05
Description
The quality of life of many people is lowered by impediments to walking ability caused by neurological conditions such as strokes. Since the ankle joint plays an important role in locomotion, it is a common subject of study in rehabilitation research. Robotic devices such as active ankle-foot orthoses and powered exoskeletons have the potential to be used directly in physical therapy or indirectly in research pursuing more effective rehabilitation methods. This paper presents the LiTREAD, a lightweight three degree-of-freedom robotic exoskeletal ankle device. This novel robotic system is designed to be worn on a user's leg and actuate the foot position during treadmill studies. The robot's sagittal plane actuation is complemented by passive virtual axis systems in the frontal and transverse planes. Together, these degrees of freedom allow the device to approximate the full range of motion of the ankle. The virtual axis mechanisms feature locking configurations that will allow the effect of these degrees of freedom on gait dynamics to be studied. Based on a kinematic analysis of the robot's actuation and geometry, it is expected to meet and exceed its torque and speed targets, respectively. The device will fit either leg of a range of subject sizes, and is expected to weigh just 1.3 kg (2.9 lb.). These features and characteristics are designed to minimize the robot's interference with the natural walking motion. Pending validation studies confirming that all design criteria have been met, the LiTREAD prototype that has been constructed will be utilized in various experiments investigating properties of the ankle such as its mechanical impedance. It is hoped that the LiTREAD will yield valuable data that will expand our knowledge of the ankle and aid in the design of future lower-extremity devices.
ContributorsCook, Andrew James Henry (Author) / Lee, Hyunglae (Thesis director) / Artemiadis, Panagiotis (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Over the past decade, fall related injuries and death among individuals 65 and older due to osteosarcopenia have increased significantly. To reduce the risk of recurrent falls among the elderly caused by osteosarcopenia, a soft-body pneumatically stabilizing device is designed. A few different actuation methods are considered, both rigid and soft body actuators, before deciding the best fit for the design goals of the wearable assistive device. Much of the design is developed through numerically modeling and analyzing the human upper body as an inverted pendulum. Through this method, common characteristics of falling behavior are identified to develop a control system that counteracts falling motion with pneumatically produced forces. An emphasis on human-oriented design provides much of the framework for translating the numerical model of forces into a device that prioritizes user comfort without sacrificing assistive performance.
ContributorsJohansen, Max (Author) / Grewal, Anoop (Thesis director) / Marvi, Hamidreza (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2022-12
Description
This paper presents the design of a pneumatic actuator for a soft ankle-foot orthosis, called the Multi-material Actuator for Variable Stiffness (MAVS). This pneumatic actuator consists of an inflatable soft fabric actuator fixed between two layers of rigid retainer pieces. The MAVS is designed to be integrated with a soft robotic ankle-foot orthosis (SR-AFO) exosuit to aid in supporting the human ankle in the inversion/eversion directions. This design aims to assist individuals affected with chronic ankle instability (CAI) or other impairments to the ankle joint. The MAVS design is made from compliant fabric materials, layered and constrained by thin rigid retainers to prevent volume increase during actuation. The design was optimized to provide the greatest stiffness and least deflection for a beam positioned as a cantilever with a point load. The design of the MAVS took into account passive stiffness of the actuator when combining rigid and compliant materials so that stiffness is maximized when inflated and minimal when passive. An analytic model of the MAVS was created to evaluate the effects in stiffness observed by varying the ratio in length between the rigid pieces and the soft actuator. The results from the analytic model were compared to experimentally obtained results of the MAVS. The MAVS with the greatest stiffness was observed when the gap between the rigid retainers was smallest and the rigid retainer length was smallest. The MAVS design with the highest stiffness at 100 kPa was determined, which required 26.71 ± 0.06 N to deflect the actuator 20 mm, and a resulting stiffness of 1,335.5 N/m and 9.1% margin of error from the model predictions.
ContributorsHertzell, Tiffany (Author) / Lee, Hyunglae (Thesis director) / Sugar, Thomas (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05