Method of evaluating the force controllability of the human finger

The ability of the human finger to control force against an impact load is determined by means of a novel practical method, which is a variation of the levitation mass method. In the method, a mass that is levitated with a pneumatic linear bearing and hence encounters negligible friction is made to collide with an object under test. During the collision, the Doppler frequency shift of a laser beam reflecting from the mass is accurately measured using an optical interferometer. The velocity, position, acceleration, and inertial force of the mass are calculated from the measured time-varying Doppler shift. The method is characterized by the fact that preparation for the test is easy, and measurement accuracy is high. The importance of visual information is also determined by means of conducting the tests under conditions in which the subject´s eyes are either opened or closed