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Abstract

A method and apparatus for measuring the mass of a dynamic load without being influenced by vibration caused by the apparatus itself or the environment. A dynamic load sensor that supports the dynamic load is periodically and continuously reciprocated in at least one predetermined direction. Within the dynamic load sensor, one end of a member comprising a spring system is fixed to a base of a non-spring system, the other end of the spring system is free. A load is applied to the free end of the spring system. The base is continuously and periodically agitated along with the spring system. A displacement of the base y.sub.1 and a displacement y.sub.2 of the free end of the spring mass system are continuously measured. By obtaining the first-order derivatives y.sub.1 and y.sub.2 and the second-order derivatives y.sub.1 and y.sub.2 from said displacements y, and y.sub.2 with respect to time, the mass of the load, m, can be calculated by the equation: m?y!=mg-?(mg+kf.sub.2 (y-y.sub.1 +y.sub.2))-f.sub.3 (y-y.sub.1 +y.sub.2)+f.sub.1 (my.sub.1,my.sub.2)! where the symbol ? ! represents a matrix whose determinant is (a number of degrees of member freedom.times.a number of data measurements), g is gravitational acceleration, kf.sub.2 (y-y.sub.1 +y.sub.2) is a material term of the component structure of the spring mass system, k is a spring constant, f.sub.3 (y-y.sub.1 +y.sub.2) is a damping term selected from the group consisting of: viscous friction, coulomb, hysteresis, fluid drag and fluid mass drag damping, and f.sub.1 (my.sub.1, my.sub.2) is a resultant time-varying forces term acting on the object having the mass m.

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