Comparing "pick and place" task in spatial Augmented Reality versus non-immersive Virtual Reality for rehabilitation setting.

Introducing computer games to the rehabilitation market led to development of numerous Virtual Reality (VR) training applications. Although VR has provided tremendous benefit to the patients and caregivers, it has inherent limitations, some of which might be solved by replacing it with Augmented Reality (AR). The task of pick-and-place, which is part of many activities of daily living (ADL's), is one of the major affected functions stroke patients mainly expect to recover. We developed an exercise consisting of moving an object between various points, following a flash light that indicates the next target. The results show superior performance of subjects in spatial AR versus non-immersive VR setting. This could be due to the extraneous hand-eye coordination which exists in VR whereas it is eliminated in spatial AR.

Smart mug to measure hand's geometrical mechanical impedance.

A novel device, which looks like a mug, has been proposed for measuring the impedance of human hand. The device is designed to have convenient size and light weight similar to an ordinary coffee mug. It contains a 2-axis inertia sensor to monitor vibration and a small motor to carry an eccentric mass (m=100 gr, r=2 cm, rpm=600). The centrifugal force due to the rotating mass applies a dynamic force to the hand that holds the mug. Correlation of the acceleration signals with the perturbing force gives the geometrical mechanical impedance. Experimental results on a healthy subject shows that impedance is posture dependant while it changes with the direction of the applied perturbing force. For nine postures the geometrical impedance is obtained all of which have elliptical shapes. The method can be used for assessment of spasticity and monitoring stability in patients with stroke or similar problems.

Perturbation-based measurement of real and imaginary parts of human arm's mechanical impedance.

Mechanical impedance is a complex number and a system's property. Impedance of human arm is the control variable when the central nervous system coordinates a motion. This research proposes a new method for measuring the mechanical impedance as a complex number. Impedance is measured at the hand point while sinusoidal perturbation is applied. That helps extracting the real and imaginary part of the impedance. Simulations reveal how spring, mass, and damper contribute to the mechanical impedance. Despite the simulation results, our experiment shows that damping which is the real part of impedance is not frequency independent and imaginary part of mechanical impedance decreased with increasing frequency that in turn suggests the stiffness is increasing.