New method for measuring inertial properties

A new, six-degree-of-freedom (DOF) force/moment sensor is being developed to measure all six components of dynamic force (three forces and three moments) applied at a point. This new sensor measures dynamic forces with extremely high resolution, even in the presence of very high static loads. Previously, this measurement capability was available only in low-resolution, strain-based force/moment sensors, which are not suitable for low dynamic force ranges. For the first time, test engineers can determine how accurate uniaxial force application assumptions actually are. This six DOF sensor is ideally suited for applications such as reaction force measurement, cutting force dynamometers, input force/noise path analysis, and general forced response input measurement. Advanced systems have already integrated the sensors to measure rigid body inertia properties (mass, center-of-gravity, moments of inertia) for structures as varied as full-scale aircraft, automobiles, and individual components such as automotive air conditioning compressors. Additionally, improved cutting force dynamometers utilizing these sensors can measure all six possible cutting forces (x, y, z force, torque, thrust, etc.) simultaneously, without setup restrictions such as requiring the tool be centered over the dynamometer. This paper describes the new six DOF sensor used in conjunction with a special multiple input calibration method that ultimately allows for a fast and precise determination of rigid body properties of automotive components. The paper focuses on the theory of operation along with practical application examples.