A method for measuring human arm's mechanical impedance for assessment of motor rehabilitation

This research work aims to develop a new tool for assessment of human motor function with a focus on the upper limb. For that purpose, Simultaneous Sensing cum Actuating technology (SSA) will be used for measuring force, velocity, and especially mechanical impedance of the limb. Impedance measured at the hand point while the upper limb performing a motion task is a quality indicator of the limb's motor function. Conventional method of measuring mechanical impedance which requires a force and a motion sensor mounting on fixed base points is not applicable here. This method overcomes the difficulty. Here an electrical motor is used as sensor-actuator which carries a mechanical load (here human's limb); the motor plays the role of a sensor as well, so we calibrate the "transduction matrix" of the motor and will measure the mechanical impedance of the load through measuring the electrical impedance of the electrical motor. In this paper we explain how the appropriate apparatus was designed and tailored for this application and how the method was validated. At the end experimental result of measuring mechanical impedance of a human subject is presented.