From the view of the human engineering, it is useful to study the torsional acceleration of the wrist under various actions of the arm Using cross-spring torsional pendulum, three kinds of torsional vibration pickup (T. V. P) of high natural frequency are made. The theoretical natural frequency f_nt of the T. V. P is as follows. f_nt=1/(2π){(32bt^3)/(WD^2l)((r^2)/(l^2)E+k_2G)・g}^1/2 in which E; the Young modulus of plate spring, G; the rigidity of plate spring, W; the weight of the pendulum of circular disc, D, the diameter of the pendulum, g; the acceleration of gravity, r; the distancc from center of the pendulum to that of plate spring, k_2 ; the shape factor of plate spring, and b,t,1; width, thickncss, length of the plate spring respectively. The experimental values of natural frequency f_nof the three kinds of T.V.P agrce very well with the theoretical ones f_nt. Under various actions of the arm, the time variations of the torsional acceleration of the wrist are obtained by the present T.V.P, Rlnd they are discussed respectively in this Paper
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