This work focuses on the design, development, and testing of an inexpensive, low-profile, cartwheel flexure mechanism for torque measurement. It has been designed primarily for use in a rehabilitation and diagnostics instrument for the treatment of ankle injuries. The sensor is manufactured rapidly and at low-cost using an Omax™ abrasive waterjet machine. Strain gauges are bonded to the flexure beams to measure applied strain using a full wheatstone bridge circuit. Displacement, force, and torque are then calculated from the measured circuit voltage; power and velocity can also be determined if required by the application. Experimental results show that there exists a linear relationship between applied torque and output voltage of the wheatstone bridge for the nested cartwheel flexure design. Furthermore, results of preliminary tests of an ankle rehabilitation device show that it fulfills a need not currently satisfied by current rehabilitation and diagnostic technology in physical medicine and rehabilitation.

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