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Passive Gravity-Balanced Assistive Device for Sit-to-Stand Tasks Inventors:

Serial Number: Filing Date:

Agrawal, Sunil K.; Fattah, Abbas; Catlin, Glenn; Hamnett, John 60/748,429

Docket Number: UD06-12

December 8, 2005

Sit-to-stand (STS) is one of the most common daily activities, which is also a pre-requisite for other functional movements that require ambulation. STS activity is mechanically demanding, and it is estimated that, in the United States, more than two million people over age 64 have difficulty in rising from a chair.

Passive Swing-Assist Exoskeletons for MotorIncomplete Spinal-Cord Injury Patients Inventor:

Serial Number: Filing Date:

Agrawal, Sunil K. Provisional Filed

Docket Number: UD07-20

April 6, 2007

This patent application describes the design of a passive swing-assist orthosis for gait training of spinalcord injury patients. Through simulation of a swinging leg, spring parameters on the exoskeleton are optimized so that it provides the propulsion force required by a subject during walking. Experiments have been performed with healthy subjects walking on a treadmill. In the coming months, this passive orthosis will be used for gait learning of spinal cord injury patents.

A machine is said to be gravity balanced if joint actuator torques are not needed to keep the system in equilibrium in any configuration. Gravity balancing is often used in industrial machines to decrease the required actuator efforts during motion. A number of methods have been proposed for gravity balancing that include counterweights, springs, and auxiliary parallelograms that determine the center of mass. However, these concepts have rarely been applied to rehabilitation machines, which generally require externally supplied power to function and thereby pose increased risk to the user.

Intelligent Powered Mobility for Special Needs Children

STS motion is primarily a planar activity, and gravity balancing is a useful principle that can assist a user in this activity. A gravity-balancing apparatus does not require power and keeps the human body in neutral equilibrium during the entire range of motion, enabling a person to stand up from a chair without significant effort.

Our current mobile robot prototype, the “UD1” uses a commercial robot, adapted to seat an infant with a joystick. The UD1 is equipped with an on-board computer, odometry to record its movements, an array of sensors on its periphery to determine the obstacle-free area around it, and a wireless communication link to a host computer to continuously transfer position data. Using joysticks, UD1 can be either manually driven by the infant or a caregiver. In addition, using in-house developed intelligent software, it can be autonomously or semi-autonomously driven safely while avoiding obstacles. Our current data collection with UD1 only utilizes the manual drive capability of the robot. Our next generation prototypes will have additional capabilities to enhance training and assessment of infant learning, such as: 1. Semi-autonomous navigation of the robot to respond to infant joystick commands and obstacles in the environment; 2. Development of a force-field joystick to train an infant to navigate within a cluttered environment; 3. “Virtual leash” to allow the robot to autonomously follow a parent within a selected leash radius while navigating in an indoor or outdoor environment.

According to one exemplary embodiment, the present invention provides a passive gravity-balancing assist device for sit-to-stand motion. The design combines the use of auxiliary parallelograms to determine the center of mass along with springs connecting the center of mass to an inertially fixed frame so that the total potential energy of the system is constant during sit-to-stand motion. The passive gravity-balancing assistive device minimizes risk to the user and may be employed as a rehabilitative aid, a training device, an evaluation tool for the study of sit-to-stand motion, or other related uses.


INVENTIONS - Technologies Available for Licensing


Serial Number: Filing Date:

Agrawal, S. K.; Galloway, J.; Ryu, J.-C. Provisional Filed October 3, 2007

Docket Number: UD08-15

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