The University of Massachusetts Amherst
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MIE Researchers Work on Revolutionary “Underwater Robot Gait Training System” to Assist Stroke and Injury Victims Regain Their Walking Gait

Frank Sup (left) and Yahya Modarres-Sadeghi (right)

Frank Sup (l) & Yahya Modarres-Sadeghi (r)

Principal Investigator Frank Sup and Co-Principal Investigator Yahya Modarres-Sadeghi of the Mechanical and Industrial Engineering (MIE) Department at the University of Massachusetts Amherst have been awarded a three-year, $749,043 grant (Award number: 2024409) from the National Science Foundation (NSF) National Robotics Initiative to study a pioneering “Underwater Robot Gait Training System.” The system is a robotic method for “natural and unconstrained gait training for persons recovering from stroke or injury by naturally assisting their gait using flow forces,” as the two researchers explain.

“This investigation will be conducted,” say Sup and Modarres-Sadeghi, “by focusing on the case of generating assistive forceful interactions on a person’s limbs produced by the wake of an upstream robot for rehabilitation purposes while walking on an underwater treadmill.”

What the two researchers are conceiving of is a robot that assists a rehabilitating person to walk through interactions between controlled vortices in an underwater treadmill and hydrofoil-shaped devices that will be attached to the patient’s leg.

Sup and Modarres-Sadeghi add that “Beyond health, extensions of this work can be applied to underwater robotic vehicle manipulation and in manufacturing to create new methods for fluid-based material handling and production processes.”

According to Sup and Modarres-Sadeghi, “With this approach, an underwater ‘cobot’ [or collaborative robot intended for direct human-robot interaction] gait-training system is created that can manipulate the power of the existing fluid flow to apply controlled forces to the lower limbs of a person [and assist him or her] while walking. The system is supported by new predictive simulations of underwater human gait with fluid-structure interaction dynamics to optimize the interconnected human-robot system.”

The researchers explain that cobots, in general, are designed to achieve their collaborative goals by being aware, responsive, compliant, and, in some cases, soft. However, an unexplored area of cobots is the opportunity to interact with persons without directly coming in to contact with them. Typically, cobots operate in low-density air under one atmosphere of pressure. However, this new underwater treadmill method offers opportunities for cobots to work with people in the water, a high-density fluid capable of transmitting momentum from one body to another.

According to Sup and Modarres-Sadeghi, one way of manipulating the motion of an object placed in an underwater flow is to place a second object upstream, thus creating a wake experienced by the object downstream. Exploiting the natural coupled system dynamics of these two objects in the wake can lead to a natural interaction approach between a person and a cobot without actually touching each other.
 
This concept enables the implementation of a new class of robotic power transmission that does not require a direct connection between the robot and the object being manipulated.

“In many existing robotic control problems, power is transferred through direct contact with the object to be manipulated,” say Sup and Modarres-Sadeghi. “This project focuses on the case of underwater manipulation, where the environment (water) has a significant impact on the overall system performance.”

Sup directs the Mechatronics and Robotics Research Laboratory, which focuses on human-centered mechatronic design in the development of rehabilitative technologies. The research topics focus on wearable robotics, such as intelligent prosthetics and exoskeletons, and advancing robotic design and control methodologies.

As Sup explains, “We strive to expand the boundaries in the research community while providing a hands-on learning environment in leading-edge science.”

Modarres-Sadeghi is the MIE graduate program director and heads the Fluid-Structure Interactions Lab, where he and his students use experimental, theoretical, and numerical tools to understand different fluid-structure interaction phenomena both from a fundamental point of view and with applications in several fields, including renewable energy and biomedical science.

In that context, Modarres-Sadeghi studies such topical subjects as fluid-structure interactions,  nonlinear dynamics, and chaos. (August 2020)