Design, development and testing of a balance board with variable torsional stiffness and time delay

Denise Renee Cruise, Purdue University

Abstract

The ability to balance and maintain upright posture can decline for a variety of reasons, such as aging and neuromuscular impairment. As the ability to balance declines, the risk of falling increases. Falls are a major cause of injury, and often lead to a dramatic decline in quality of life. Currently, to alleviate balance deficiencies, people participate in balance training, which most commonly refers to standing on an unstable balance board; the most common boards used are either passive wobble boards, or more advanced commercial systems such as the Biodex System SD® or the Neurocom SMART Balance Master®. Balance training has been shown to improve both static posture and dynamic balance; however, the current methodologies only utilize stiffness and force control. It has been shown that there are two distinct mechanisms of loss of postural instability: forward/back leaning, arising from insufficient postural stiffness or decreased neuromuscular gain, and limit cycle oscillations, which arise from excessive time delay in the neuromuscular system. We have created a balance board able to elicit both mechanisms of instability, which can be achieved through two controllable parameters: torsional stiffness and haptic feedback time delay. In addition to building a functional balance board, a safety platform was also fabricated which ensures both user safety and comfort. After careful calibration of the balance board and the systems used to gather data, initial human testing was performed. Three major tests were completed: discrete step stiffness, linear ramping stiffness, and variable time delay. These tests confirmed that the balance board system is capable of utilizing both mechanisms of instability; both forward/backward leaning and limit cycle oscillations we observed in all participants. These initial results are promising, and lead directly into a variety of different options for testing on the balance board. The board can be used to test various populations including athletes, older adults, and people with neuromuscular disorders. The ultimate goal of this balance board would be to create a balance score that can be compared among populations, to use the board for training, and to convert this balance board to a robotic platform that creates individualized training plans for users. This novel balance board system has created a large range of possibilities for the future of balance studies and training.

Degree

M.S.E.

Advisors

Raman, Purdue University.

Subject Area

Mechanical engineering|Kinesiology

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