SUMMARY

The dynamics of rigid body motion are defined by the inertial properties of the body - that is, the mass and moment of inertia. For complex systems, it may be necessary to derive these results empirically. Such is the case for manual wheelchairs, which can be modeled as a rigid body frame connected to four wheels. While 3D modeling software is capable of estimating inertial parameters, modeling inaccuracies and ill-defined material properties may introduce significant errors in this estimation technique. To that end, this thesis discusses the design of a device called the iMachine that determines the mass, location of the center of mass, and moment of inertia about the vertical (yaw) axis passing through the center of mass of a wheelchair. The iMachine is a spring-loaded rotating platform that freely oscillates about an axis passing through its center due to an initial angular velocity. The mass and location of the center of mass can be determined using a static analysis of a triangular configuration of load cells. An optical encoder records the dynamic angular displacement of the platform, and the natural frequency of free vibration is calculated using several techniques. The natural frequency can be related to the inertia by the dynamic equation of motion. In this thesis, test results are presented for the calibration of the load cells and springs. In addition, several objects with known mass properties were tested and comparisons are made between the analytical and empirical inertia results. Finally, the moment of inertia of a manual wheelchair is determined using the device, and conclusions are made regarding the reliability and validity of results. The results of this project will feed into energy calculations for the Anatomical Model Propulsion System (AMPS), a wheelchair-propelling robot used to measure the mechanical efficiency of manual wheelchairs.