Improved Measurement Method for the Identification of the Centre of Gravity Location and of the Inertia Tensor of Rigid Bodies

Abstract

The knowledge of the inertia properties of rigid bodies is of crucial importance for the correct simulation of complex mechanical systems. For this purpose at the Politecnico di Milano (Technical university of Milan) a series of test rigs have been constructed for the measurement of mass, centre of gravity location and inertia tensor of rigid bodies with masses ranging from 50 to 3500 kg. The test rigs are basically three or four bar pendulums carrying the body under investigation. The body is made to rotate around three axes passing nearby the body centre of gravity and the resulting highly non linear motion is recorded. A mathematical model simulating the motion of the body carried by the pendulum is used to identify the full inertia tensor by minimising the error between the computed and measured data. These test rigs are currently used for the identification of the mass properties of different cars, light farm tractors, engines, gearboxes and satellites. In this paper a new implementation of these test rigs is shown. By redesigning the instrumentation setup and with a new mathematical procedure for the identification, the test rigs can be used to identify the centre of gravity location and the inertia tensor with a single experimental test. In the new configuration the test rigs require a very short testing time and they are suitable for commercial development.