Inertia Tensor and Other Mass Properties Measurement for Automotive Applications

Massimiliano Gobbi; Giampiero Mastinu; Giorgio Previati

doi:10.4271/2014-01-0090

A method for the measurement of the full mass properties of vehicles and subsystems is presented.

The knowledge of the center of gravity location and of the inertia tensor of vehicles and subsystems is fundamental for performing accurate dynamic simulations, ranging from handling to durability.

The accurate estimation of the inertia tensor can be achieved primarily via experimental tests.

Given a rigid body and its mass, the proposed method allows to measure the center of mass location and the inertia tensor during a single test.

The proposed technique is based on the analysis of the free motion of a multi-cable pendulum to which the vehicle or the subsystem is connected. The body under test is made rotating around three axes passing nearby the body center of mass with a highly non linear motion. The motion of the pendulum and the forces acting on the system are recorded and the mass properties are identified by means of a proper mathematical procedure based on a least square estimation. After the vehicle or the component is positioned on the test rig, the full measurement procedure takes a few minutes. The natural frequencies of the pendulum and the accelerations involved are quite low, making this method suitable for full vehicle testing.

In the paper, the proposed method is described and two test rigs are presented: the first has been developed for road vehicles (up to 3500 kg) and the second for vehicles components i.e. engines, gearboxes, … (bodies up to 400 kg). A validation of the measurement method has been performed with satisfactory results. Both the center of gravity location and the inertia tensor components can be identified with very high accuracy. The test rigs hold a third part quality certificate according to ISO 9001 standard.

The system can be easily scaled up to measure the mass properties of large vehicles such as trucks, busses and even airpalnes.

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Inertia Tensor and Other Mass Properties Measurement for Automotive Applications 2014-01-0090

SAE MOBILUS